Patent Publication Number: US-6335403-B1

Title: Process for producing a polymer by polymerization of a monomer having an ethylenic double bond

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a process for producing a polymer by polymerizing in a polymerization vessel a monomer having an ethylenic double bond, and particularly a process that can prevent polymer scales from adhering to polymerization vessel inner wall surfaces and others and can produce polymers having a good quality. 
     2. Description of the Prior Arts 
     As known in processes for producing polymers by polymerizing monomers in polymerization vessels, there is a problem that polymers may adhere to polymerization vessel inner wall surfaces and others in the form of scales. 
     Such polymer scales having adhered to polymerization vessel inner wall surfaces and others may cause a decrease in yield of polymers, a decrease in cooling capacity of polymerization vessels, and a lowering of product quality when polymer scales having adhered come off to mix into polymer products, and also may bring about a disadvantage that much labor and time must be taken to remove the polymer scales. 
     Moreover, since the polymer scales contain unreacted monomers, there is a possibility that operators are exposed to them to cause physical disorder. 
     Accordingly, in the polymerization of monomers having ethylenic double bonds, in order to prevent polymer scales from adhering to polymerization vessel inner wall surfaces and others, various methods are known in which the polymerization vessel inner wall surfaces, stirrers and so forth are coated with a polymer scale preventive agent (hereinafter “scale preventive agent”) by one-liquid coating to form coating films (hereinafter “one-liquid coating method”). As the scale preventive agent, usable are, e.g., a polar organic compound such as an amine compound, a quinone compound or an aldehyde compound or a dye or pigment (Japanese Patent Publications (kokoku) Nos. 45-30343 and 45-30835), a polar organic compound or dye treated with a metal salt (Japanese Patent Publication (kokoku) No. 52-24953, a mixture of an electron-donating compound and an electron-accepting compound (Japanese Patent Publication (kokoku) No. 53-28347), a condensation reaction product of 1-naphthol with formaldehyde (Japanese Pre-examination Patent Publication (kokai) No. 57-164107), a condensation reaction product of a phenol compound with formaldehyde (Japanese Pre-examination Patent Publication (kokai) No. 57-192413), a polyaromatic amine (Japanese Patent Publication (kokoku) No. 59-16561), a self-condensation product of a polyhydric phenol or a self-condensation product of a polyhydric naphthol (Japanese Pre-examination Patent Publication (kokai) No. 54-7487), a condensation reaction product of a ketone resin with a phenol compound (Japanese Pre-examination Patent Publication (kokai) No. 62-236804), a condensation reaction product of an aromatic amine with an aromatic nitro compound and a material obtained by making the compound basic (Japanese Patent Publication (kokoku) No. 60-30681), and a condensation reaction product of an aromatic amine with a quinone compound (Japanese Pre-examination Patent Publication (kokai) No. 61-7309). 
     In the case of polymer scale preventive coating films obtained by such one-liquid coating methods, scales tend to adhere to the vicinity of a gas-liquid boundary surface in the polymerization vessel during polymerization, or, depending on the composition of a polymerization reaction mixture, scales tend to adhere to the whole wall surface. Accordingly, to prevent this, it is known to mix in a coating liquid containing the scale preventive agent a water-soluble polymeric compound such as an anionic polymeric compound, an amphoteric polymeric compound, a cationic polymeric compound or a hydroxyl-group-containing polymeric compound; an inorganic colloid; or a substance having no affinity for monomers, as exemplified by an inorganic salt such as an alkali metal salt (hereinafter “scale preventive auxiliary agent”). These one-liquidcoating methods are effective for preventing the adhesion of polymer scales when monomers having ethylenic double bonds are polymerized in polymerization vessels. 
     In instances where no sufficient polymer scale prevention effect can be obtained by the one-liquid coating method, a method of forming coating films by coating two types of coating liquids through two stages (hereinafter “two-liquid two-stage coating method”) is proposed, which comprises a) coating a coating liquid containing the scale preventive agent as described above, to form a first layer, and b) coating further thereon a coating liquid containing the above polymer scale preventive auxiliary agent, to form a second layer (Japanese Pre-examination Patent Publication (kokai)Nos. 3-74404, 2-80403, 2-80402, 2-80401 and 2-47102). 
     In both the above one-liquid coating method and two-liquid two-stage coating method for preventing the adhesion of polymer scales, spray coating is usually used as a coating process in view of productivity including operability. 
     In the one-liquid coating method of coating the scale preventive agent by spray coating, the coating film is formed by a process comprising the following steps 1 to 3. 
     Step 1: A coating liquid containing the scale preventive agent is coated on the polymerization vessel inner wall surface and other surfaces with which monomers come into contact. 
     Step 2: The coated surfaces are dried to form a dry film. 
     Step 3: The surface of the coating film thus formed is washed to remove any excess coating liquid. 
     In the two-liquid two-stage coating method comprising coating the scale preventive agent and coating the polymer scale preventive auxiliary agent both by spray coating, the coating film formation comprising the same steps 1 to 3 as the above is operated also in the second-stage coating. 
     When the above spray coating is used, the surfaces of baffles and stirring blades that face polymerization vessel inner wall surfaces stand within the dead angle from a spray nozzle. Since it is hard for the coating liquid to reach the surfaces of such portions standing blind or hidden from the spray nozzle, the scale preventive agent can not be coated thereon in the same way as on the surfaces not standing blind. Thus, it is difficult to form a uniform coating film over the surfaces standing blind and the surfaces not standing blind. If a coating film in a quantity effective enough to prevent the adhesion of polymer scales is intended to be formed also on the blind surfaces, it is inevitable to use a coating liquid containing the scale preventive agent in a larger quantity than that for the other surfaces. It follows that an unnecessarily excess preventive agent is applied on the surfaces not standing blind. Hence, the coating film thus formed have had an uneven coating thickness and the coating film have had a larger thickness locally than is necessary. 
     The formation of polymer scale preventive coating films by spray coating has also had the following problems. 
     (1) Usually, the coating film comprising the scale preventive agent is formed previously for each polymerization batching. Since it is common for the scale preventive agent to have a color, the scale preventive agent is repeatedly coated as the polymerization is batched repeatedly in a larger number, so that the coating film may have a large thickness at some part. The part having such a thick coating film may come off to become included into the reaction mixture, or the scale preventive agent may be coated on polymer scales having already adhered to the polymerization vessel inner wall surfaces and others and may come off together with a part of the scales to mix into the resultant polymerization products. This may cause colored particles or fish eyes brought in their formed products or may cause a low product quality such as a high initial discoloring of formed products, disadvantageously. 
     (2) As stated above, the effect of preventing scales at the surfaces standing blind or hidden in the polymerization vessel, standing within the dead angle from the spray nozzle, can not be said to be so much sufficient, considering the scale preventive agent applied in a fairly larger quantity than that on other surfaces. 
     (3) The spray coating requires a drying step of drying the coated surfaces, and takes a time necessary for forming the coating film of the scale preventive agent. Accordingly, in respect of an improvement of productivity, it is sought to shorten the time necessary for forming the coating film. 
     As a measure for eliminating the above disadvantages in the spray coating, a method is proposed in which a coating liquid containing a scale preventive agent is coated using steam as a carrier (hereinafter “wsteam coating”) (Japanese Patent Publication (kokoku) No. 1-5044). As the coating liquid in this method, used is a coating liquid comprised of the scale preventive agent alone or a coating liquid to which the scale preventive auxiliary agent is further added. 
     This steam coating has the following advantages. 
     (1) A thin and uniform coating film of the scale preventive agent, necessary for preventing the adhesion of scales effectively can be formed using the coating liquid in a small quantity. 
     (2) The coating film of the scale preventive agent, necessary for achieving the scale prevention effect can be formed using the coating liquid in a small quantity, also on the portions standing blind or hidden in the polymerization vessel, standing within the dead angle from the spray nozzle. Thus, the polymer scale prevention effect can be attained also on these portions. 
     (3) The drying step is unnecessary in the coating film forming step, so that the time necessary for forming the coating film of the scale preventive agent can be shortened. 
     Incidentally, in the steam coating, the coating liquid and steam are mixed so that the coating liquid is carried by the steam and can be applied to the polymerization vessel inner wall surfaces and others. Accordingly, the concentration of the scale preventive agent in the coating liquid is set taking account of the fact that the solution is diluted with steam. Usually, the concentration of the scale preventive agent in the coating liquid for steam coating is set 4 to 40 times that of the one for spray coating, although the amount of a scale preventive agent necessary in steam coating is approximately equivalent to that necessary in spray coating. 
     In contrast to the advantages, the steam coating has problems on the following points. 
     (1) Although the steam coating enables uniform coating in a polymerization vessel, the deposition of scale can be prevented insufficiently around the interface between the gas-liquid phases. 
     (2) As the result of the insufficient prevention of scale deposition around the interface between gas-liquid phases, the polymer scale deposition will grow around the interface with repetition of polymerization runs. A part of the grown deposited scale may peel off the inner surfaces of the polymerization vessel during polymerization and be incorporated into a polymer product to cause formation of fisheyes. 
     (3) A scale preventive agent is coated on the inner surfaces of a polymerization vessel repeatedly as polymerization runs are repeated. Consequently, the layer of the scale preventive agent become thicker gradually. A part of the thick layer of the agent may peel off during polymerization and be incorporated into polymer products to cause colored particles. The colored particles will lower anti-initial discoloration properties, particularly luminosity index L, of polymer products. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a process for producing a polymer by polymerizing a monomer having an ethylenic double bond, which can shorten the time for forming coating films of scale preventive agents to improve productivity, can improve the effect of preventing scales, can make colored particles less mix into polymer products obtained by this process, can lessen fish eyes and initial discoloring of formed products and can improve the quality of polymeric products and their formed or molded products. 
     The above subject can be settled by a process for producing a polymer by polymerizing in a polymerization vessel a monomer having an ethylenic double bond, wherein 
     the polymerization vessel has a polymer scale preventive coating film on its inner wall surfaces and other surfaces with which the monomer comes into contact during polymerization; 
     the coating film being formed by coating a first coating liquid containing a compound selected from the group consisting of an aromatic compound having 5 or more conjugated  bonds and a heterocyclic compound having 5 or more conjugated  bonds and a second coating liquid containing at least one hydrophilic compound selected from the group consisting of a water-soluble polymeric compound, an inorganic colloid, an inorganic salt and an acid; the first coating liquid and the second coating liquid being simultaneously coated by means of steam as a carrier. 
     According to the polymerization process of the present invention, the time for forming coating films of scale preventive agents can be shortened to improve productivity, and also, when monomers having an ethylenic double bond are polymerized, polymer scales can be prevented effectively from adhering to not only wall surfaces at the liquid-phase portion in the polymerization vessel but also stirrers, baffle surfaces facing the wall surface, and the vicinity of the boundary surface between the gaseous phase and the liquid phase. Hence, the quality of polymer products can be improved and the colored particles can be made very less mix into polymers, and also formed products obtained by forming the polymers into sheets can be made to have very less fish eyes and also have good anti-initial discoloring. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings, 
     FIG. 1 schematically illustrates the arrangement in a polymerization apparatus; and 
     FIG. 2 schematically illustrates the arrangement in another polymerization apparatus. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Scale prevention coating films used in the method of the present invention are formed on the surfaces of polymerization vessel inner walls and so forth. The coating films are formed of a mixture of components contained in the first coating liquid and second coating liquid. Here, the components contained in both the coating liquids may at least react in part to form a reaction product. Hence, stated more exactly, the coating films are formed of a mixture and/or reaction product of the components contained in both the coating liquids. 
     The scale prevention effect attributable to the present invention is brought out by cooperation of components of the first coating liquid and second coating liquid, and it is difficult to distinguish which components are contributory. Especially in the coating films formed, the both components have been made uniform and in some cases have reacted, and it is difficult to state separately what components are contributory to the effect. In the following description, however, the compound having conjugated  bonds of the first coating solution is often called the “scale preventive agent” and the hydrophilic compound of the second coating solution the “scale preventive auxiliary agent” for the sake of convenience. 
     First Coating Liquid 
     The aromatic compound and heterocyclic compound used in the first coating liquid each have 5 or more conjugated  bonds. In the present specification, the term “ bonds” is meant to be double bonds and triple bonds, including, e.g., C═C, C≡C, N═N, C═N, C═S and C═O, and the term “conjugated  bond” is meant to be a series of  bonds wherein each pair of adjacent  bonds are connected to each other through a single bond and all of the  bonds have a mutually conjugated relationship with each other. The aromatic compound having 5 or more conjugated  bonds and the heterocyclic compound having 5 or more conjugated  bonds are herein called together generically as “conjugated  bond compound” in some cases. The 5 or more  bonds are present in the conjugated  bond compound may form a single conjugation group or two or more conjugation groups. 
     Aromatic compound having 5 or more conjugated  bonds: 
     The aromatic compound having 5 or more conjugated  bonds may include benzene derivatives, naphthalene derivatives, polynuclear aromatic compounds, quinones, non-benzene type aromatic compounds, and aromatic compound condensation products having a weight-average molecular weight, which term herein means weight-average molecular weight in terms of polystyrene as measured by gel permeation chromatography, of 500 or more. 
     First, as benzene derivatives, there may be included: 
     phenols and derivatives thereof, such as 3,7-dihydroxy-10-methylxanthene and hydroxyanthraquinone; 
     aromatic amines and derivatives thereof, such as quinoline, carbazole, o-phenanthroline, p-phenanthroline, 3,6-diaminoacridine, 3-aminophenothiazine, 2-aminophenazine, phenothiazine, 2-hydroxy4-methyl-quinoline; 
     nitro and nitroso derivatives, such as phenazine, phenazine oxide, 1-phenylazo-2-naphthol, triphenyldioxadine and 4-nitroxanthone; 
     aromatic aldehydes, such as benzoflavin; 
     benzene derivatives having further one substituent other than aldehyde group, such as 1-hydroxy-2,4-methyl-fluorone, 3-phenylcoumarone, ethyl coumarine-3-carboxylate, 3-acetylcoumarine, 5-chloro-3-(4-hydroxyphenyl)anthranyl and 3-nitroacridone; 
     benzene derivatives having further one substituent other than acyl group, such as xanthone, 2-benzoylxanthone, xanthene and fluorene; 
     benzene derivatives and toluene derivatives having three or more different substituents, such as 7-acetoxy-8-methoxy-3-(2-nitrophenyl)carbostyryl; 
     aralkyl compounds, such as 9-benzylacridine; and 
     diazo compounds and azo compounds, such as 1,1′-azonaphthalene and azoxyphenol. 
     Next, as naphthalene derivatives, there may be included: 
     alkyl, alkenyl and phenylnaphthalenes, such as 2-methylnaphthalene, 1-ethyl-naphthalene, 2-ethylnaphthalene and 1,2-dimethylnaphthalene; 
     dinaphthyls, such as 1,1′-dinaphthyl, 1,2′-dinaphthyl and 2,2′-dinaphthyl; 
     naphthylarylmethanes, such as 1-benzylnaphthalene, 2-benzylnaphthalene, 1-(α,α-dichlorobenzyl)naphthalene, diphenyl-α-naphthyl-methane, diphenyl-β-naphthylmethane and di-α-naphthylmethane; 
     naphthylarylethanes, such as 1,2-di-α-naphthylethane and 1,2-di-β-naphthylethane; 
     hydronaphthalenes such as 1,2-dihydronaphthalenes, 1,4-dihydronaphthalene and 1,2,3,4-tetrahydronaphthalene; 
     nitronaphthalenes and derivatives thereof, such as nitromethyl-naphthalene, nitroalkylnaphthalene, nitrophenyl-naphthalene, halo-nitronaphthalene, halo-dinitro-naphthalene, nitrosonaphthalene, diaminonaphthalene, triaminonaphthalene and tetraaminonaphthalene; 
     halogenated naphthalenes, such as 1-fluoro-naphthalene, 1-chloronaphthalene and 1-chloro-3,4-dihydronaphthalene; 
     naphthylhydroxylamines, naphthylpyrazines and naphthylureas, such as α-naphthylhydroxylamine, β-naphthylthiohydroxyl-amine, N-nitroso-α-naphthylhydroxylamine, α-naphthylhydrazine and 1,2-dibenzocarbazole; 
     naphthalene-based aralkyl compounds, such as dibenzoanthracene, acenaphthene, diphenyl-naphthylchloromethane and nitromethylnaphthalene; 
     naphthoaldehydes and derivatives thereof, such as α-naphthoaldehyde and 2-(2,4-dinitrophenyl)-1-(α-naphthyl)-ethylene; 
     acetonaphthenes and benzoylnaphthalenes, such as 1,2;5,6-dibenzanthracene, 2′-methyl-2,1′-dinaphthyl ketone, 2-methyl-1,1′-dinaphthyl ketone and styryl-2-naphthyl ketone. 
     As the polynuclear aromatic compounds, there may be included: 
     anthracenes and derivatives thereof, such as anthracene, 1,2-dihydroanthracene, 1-chloroanthracene, 1,4-dichloroanthracene, 1-nitroanthracene, 9,10-dinitroanthracene, 1-aminoanthracene, 2-dimethyl-aminoanthracene, 2-anilinoanthracene, 9-methylamino-anthracene, 1,4-diaminoanthracene; 
     phenanthrenes and derivatives thereof, such as phenanthrene, 9,10-dihydrophenanthrene, 1,2,3,4-tetrahydrophenanthrene and 1-chlorophenanthrene; 
     phenanthrenequinones, such as phenanthrene-1,2-quinone and phenanthrene-1,4-quinone; and 
     polynuclear aromatic compounds and derivatives thereof, such as pentacene, hexacene, benzophenanthrene, benzo[a]anthracene, pyrene and coronene. 
     As quinones and derivatives thereof, there may be included: 
     naphthoquinones and derivatives thereof, such as 1,2-naphthoquinone, 3-hydroxy-2,2′-binaphthyl-1,4;3′,4′-diquinone, 5,6-benzoquinoxaline, 1,2-benzophenazine, 2-benzoazo-1-naphthol, 4-(2,4-dihydroxyphenyl)-1,2-dihydroxynaphthalene, 4-(3,4,5-trihydroxyphenyl)-1,2-dihydroxynaphthalene and 1,4-naphthol; and 
     anthraquinones and derivatives thereof, such as 1,2-anthraquinone, 2,3-anthraquinone, 1,4-anthraquinone, alizarin, quinizarin, chrysazin, hystazarin, anthraflavin, isoanthraflavin, anthragallol, purpurin, hydroxyanthrarufin, hydroxychrysazin, hydroxyflavopurpurin, quinazarin and alizarinpentacyanine. 
     Further, as the non-benzene aromatic compounds, there may be included, for example, azulene, cyclodecapentane, cyclotetradecaheptane, cyclooctadecanonaene, cyclotetracosadodecaene, heptalene, fulvalene, sesquiflulvalene, heptafluvalene and perinaphthene. 
     The aromatic compound condensation products having a molecular weight of 500 or more may suitably be aromatic compound condensation products having preferably a weight-average molecular weight of from 500 to 70,000, and more preferably from 1,500 to 30,000. 
     Preferred aromatic compound condensation products include the compounds below, for instance. 
     Aldehyde Compound/aromatic Hydroxyl Compound Condensation Products 
     The aldehyde compound/aromatic hydroxyl compound condensation product is a condensation product of an aldehyde compound with an aromatic hydroxyl compound. The use of such aldehyde compound/aromatic hydroxyl compound condensation products in scale preventive agents are disclosed in, for example, Japanese Pre-examination Patent Publication (kokai) No. 57-192413, Japanese Patent Publication (kokoku) No. 6-62709, Japanese Pre-examination Patent Publication (kokai) No. 57-164107 and WO098/24820. 
     The aldehyde compounds include, for example, formaldehyde, acetaldehyde, propionaldehyde, butylaldehyde, acrolein, crotonaldehyde, benzaldehyde, furfural, phenylacetaldehyde, 3-phenylpropionaldehyde and 2-phenylpropionaldehyde. From industrial and economical viewpoints, formaldehyde and acetaldehyde are advantageous. 
     The aromatic hydroxyl compounds include, for example, dihydroxybiphenyl compounds, naphthol compounds, phenol compounds, tannins and dimeric compounds of 2,3-dihydroxynaphthalene. 
     Examples of the dihydroxybiphenyl compounds include 2,2′-dihydroxybiphenyl, 2,2′-dihydroxy-5,5′-dimethylbiphenyl, 2,2′-dihydroxy-4,4′,5,5′-tetramethylbiphenyl, 2,2′-dihydroxy-5,5′-dichlorobiphenyl, 2,2′-dihydroxy-5,5′-dichlorohexylbiphenyl and 2,2′-dihydroxy-5,5′-di-tert-butylbiphenyl. In particular, from an industrial viewpoint, 2,2′-dihydroxybiphenyl is preferred. 
     Examples of the naphthol compounds include 1-naphthol, 2-naphthol, 1,3-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,7-dihydroxynaphthalene, 6-hydroxy-2-naphthoic acid, 2-hydroxy-1-naphthoic acid, 1-hydroxy-2-naphthoic acid and 1-hydroxy-8-naphthoic acid. 
     Examples of the phenol compounds include phenol, cresol, pyrogallol, hydroxyhydroquinone, resorcin, catechol, hydroquinone, bisphenol-A, hydroxybenzoic acid, dihydroxybenzoic acid, 2-hydroxy-5-methoxybenzoic acid and salicylic acid. 
     Examples of the tannins include tannic acid, Chinese gallotannin, Turkish gallotannin, sumac tannin, quebracho tannin, and tannin of persimmon (shibuol). 
     The dimeric compounds of 2,3-dihydroxynaphthalene include, for example, 2,3,2′,3′-tetrahydroxybinaphthyl. 
     The above condensation product of an aldehyde compound with an aromatic hydroxyl compound can be produced by reacting these reactive components in a suitable medium in the presence of a catalyst, usually at room temperature to 200° C. for 2 to 100 hours, preferably at 30 to 150° C. for 3 to 30 hours. Each of the aromatic hydroxyl compound and the aldehyde compound can be used singly or in combination of two or more kinds. 
     The medium in which the above condensation reaction is carried out includes, for example, water; and organic solvents, such as alcohols, ketones and esters. The organic solvents include, for example, alcohols, such as methanol, ethanol and propanol; ketones, such as acetone and methyl ethyl ketone; and esters, such as methyl acetate and ethyl acetate. 
     The medium in which the above condensation reaction is carried out has a pH in the range of usually from 1 to 13, and pH adjusters may be used without any particular limitations. 
     The catalyst used in the above condensation reaction includes, for example, acidic catalysts, such as sulfuric acid, hydrochloric acid, perchloric acid, p-toluenesulfonic acid, methanesulfonic acid and trifluoromethanesulfonic acid; and basic catalysts, such as NaOH, KOH and NH 4 OH. 
     The ratio of the aldehyde to the aromatic hydroxyl compound used when the condensation reaction is carried out depends on the types of the aldehyde compound, aromatic hydroxyl compound, solvent and catalyst used, the reaction time, the reaction temperature and so forth. Generally, it is preferable to use from 0.1 to 10 mols of the aldehyde compound per mol of the aromatic hydroxyl compound. 
     Pyrogallol/acetone Condensation Products 
     The pyrogallol/acetone condensation product is a condensation product of pyrogallol with acetone, the molar ratio of the pyrogallol to the acetone being in the range of usually from 1/0.1 to 1/10, and the melting point thereof being usually from 100 to 500° C. The melting point increases with an increase in molecular weights. For example, melting points of from 160 to 170° C. correspond to molecular weights of from 1,450 to 1,650; and melting points of from 200 to 220° C., to molecular weights of from 2,600 to 4,000. The use of such pyrogallol/acetone condensation products in scale preventive agents is disclosed in, for example, Japanese Pre-examination Patent Publication (kokai) No. 4-328104. 
     The pyrogallol/acetone condensation product can be produced by dissolving pyrogallol in acetone, and condensing them in the presence of a condensation catalyst. The pyrogallol is used in an amount of usually from 1 to 100 parts by weight per 100 parts by weight of the acetone. As the condensation catalyst, for example, phosphorus oxychloride is used. The reaction may be carried out at room temperature to 100° C. 
     Polyhydric Phenol Self-condensation Products and Polyhydric Naphthol Self-condensation Products 
     Polyhydric phenols are exemplified by catechol, resorcinol, chlororesorcinol, hydroquinone, phloroglucinol and pyrogallol; dihydroxytoluene and dihydroxyxylene; trihydroxytoluene and trihydroxyxylene; ethyl-, propyl-, butyl- or pentyl-di- or tri-hydroxybenzene; and trihydroxybenzene. Polyhydric naphthols are exemplified by naphthol derivatives, such as 1,3-, 1,4-, 1,5- or 1,7-dihydroxynaphthalene. The use of such polyhydric phenol self-condensation products and polyhydric naphthol self-condensation products in scale preventive agents is disclosed in, for example, Japanese Pre-examination Patent Publication (kokai) No. 54-7487. 
     The polyhydric phenol self-condensation product or polyhydric naphthol self-condensation product can be produced by heating polyhydric phenol or polyhydric naphthol in an inert atmosphere, such as nitrogen, argon or the like, at a temperature ranging from 200 to 350° C. for 4 to 100 hours. In this reaction, various catalysts may be used, as exemplified by zinc chloride, aluminum chloride and sodium hydroxide. 
     Aromatic Amine Compound Condensation Products 
     The aromatic amine compound condensation products include, for example; 
     (1) a self-condensation product of an aromatic amine compound; 
     (2) a condensation product of an aromatic amine compound with a phenol compound; 
     (3) a condensation product of an aromatic amine compound with an aromatic nitro compound; and 
     (4) a basic product obtained by making basic a condensation product of an aromatic amine compound with an aromatic nitro compound by the use of an alkali metal salt or an ammonium compound. 
     The use of such aromatic amine compound condensation products in scale preventive agents is disclosed in, for example, Japanese Patent Publication (kokoku) Nos. 59-16561 and 60-30681. 
     The aromatic amine compounds are exemplified by aniline, o-, m- or p-phenylenediamine, o-, m- or p-aminophenol, o-, m- or p-chloroaniline, p-aminobenzene, 2,4-diaminoazobenzene, p-aminoacetanilide, o-, m- or p-methylaniline, N,N-dimethyl-p-phenylenediamine, 4-chloro-o-phenylenediamine, 4-methoxy-o-phenylenediamine, 2-amino-4-chlorophenol, 2,3-diaminotoluene, 2,4-diaminophenol, and diphenylamines such as 4-aminodiphenylamine, 2-aminodiphenylamine, 4,4′-diaminodiphenylamine, 4-amino-3′-methoxydiphenylamine and 4-amino-4′-hydroxydiphenylamine. 
     The phenol compounds are specifically exemplified by phenol, hydroquinone, resorcinol, catechol, hydroxyhydroquinone, pyrogallol, o-, m- or p-chlorophenol, o-, m- or p-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid and 2,5-, 2,6- or 3,5-dihydroxytoluene. 
     The aromatic nitro compounds are exemplified by nitrobenzene, o-, m- or p-hydroxynitrobenzene, o-, m- or p-nitroanisole, o-, m- or p-nitrophenetole, o-, m- or p-chloronitrobenzene, o-, m- or p-aminonitrobenzene, o-, m- or p-nitrobenzoic acid, o-, m- or p-nitrobenzenesulfonic acid, o-, m- or p-nitroaniline, 2-nitro-p-phenylenediamine, 2-amino-4-nitrophenol, 2-amino-5-nitrophenol and 4-amino-2-nitrophenol. 
     In order to carry out the self-condensation reaction of an aromatic amine compound alone, the condensation reaction of an aromatic amine compound with a phenol compound and the condensation reaction of an aromatic amine compound with an aromatic nitro compound, a mineral acid and a condensation catalyst are used. The mineral acids are exemplified by hydrochloric acid, nitric acid, hydrobromic acid, phosphoric acid and sulfuric acid. 
     Preferable condensation catalysts are exemplified by permanganic acid and salts thereof, such as permanganic acid and potassium permanganate; chromic acid-related compounds, such as chromium trioxide, potassium dichromate and sodium chlorochromate; metal nitrates, such as silver nitrate and lead nitrate; halogens, such as iodine and bromine; peroxides, such as hydrogen peroxide, sodium peroxide, benzoyl peroxide, potassium persulfate, ammonium persulfate, peracetic acid, cumene hydroperoxide, perbenzoic acid and p-menthane hydroperoxide; oxygen acids or oxygen acid salts, such as iodic acid, potassium iodate and sodium chlorate; metal salts, such as ferrous chloride, ferric chloride, copper sulfate, cuprous chloride, cupric chloride and lead acetate; ozone; and oxides, such as copper oxide, mercury oxide, cerium oxide, manganese dioxide and osmic acid. It is also effective to use hydrogen peroxide and ferrous chloride in combination. 
     The self-condensation reaction of an aromatic amine compound alone, the condensation reaction of an aromatic amine compound with a phenol compound and the condensation reaction of an aromatic amine compound with an aromatic nitro compound may be carried out in the presence of a condensation catalyst at 100 to 350° C. for 2 to 100 hours. 
     The ratio of an aromatic amine compound to a phenol compound or an aromatic nitro compound, which are used in the condensation reaction of an aromatic amine compound with a phenol compound and the condensation reaction of an aromatic amine compound with an aromatic nitro compound, depends on the types of the aromatic amine compounds, phenol compounds and aromatic nitro compounds and catalysts used, the reaction time, the reaction temperature and so forth. Generally, it is preferable to use from 0.1 to 10 mols of the phenol compound or the aromatic nitro compound per mol of the aromatic amine compound. 
     In order to make basic a condensation product of an aromatic amine compound with an aromatic nitro compound by the use of an alkali metal salt or an ammonium compound, for example, 100 parts by weight of the condensation product of an aromatic amine compound with an aromatic nitro compound is dispersed in water, 10 to 20 parts by weight of an alkaline or ammonium compound, such as NaOH, KOH, Na 2 CO 3 , NH 4 OH or (NH 4 ) 2 CO 3  is added thereto, and the mixture obtained is heat treated at 90 to 140° C. The alkali or ammonium compound may be used in an amount sufficient to neutralize the mineral acid used at the time of the condensation reaction. 
     Quinone Compound Condensation Products 
     The quinone compound condensation products include, for example, (A) a self-condensation product of a quinone compound, and (B) a condensation product of a quinone compound with at least one compound selected from the group consisting of an aromatic hydroxyl compound and an aromatic amine compound. The use of such quinone compound condensation products in scale preventive agents is disclosed in, for example, Japanese Pre-examination Patent Publication (kokai) Nos. 5-112603 and 6-56911. 
     The quinone compounds include, for example, benzoquinones and derivatives thereof, such as o-, m- or p-benzoquinone, tolu-p-quinone, o-xylo-p-quinone, thymoquinone, 2-methoxybenzoquinone, gentisyl quinone, polyporic acid and ubiquinone-n; naphthoquinones and derivatives thereof, such as 6-methyl-1,4-naphthoquinone, 2-methyl-1,4-naphthoquinone, α-naphthoquinone, juglone, lawsone, plumbagin, alkannin, echinochrome A, vitamin k 1 , vitamin k 2 , shikonin, β,β′-dimethyl acrylshikonin, β-hydroxyisovaleroshikonin and teracrylshikonin; anthraquinones and derivatives thereof, such as tectoquinone, 3-hydroxy-2-methylanthraquinone, anthraquinone, 2-hydroxyanthraquinone, alizarin, xanthopurpurin, rubiadin, munjistin, crysophanic acid, carminic acid, kermesic acid and laccaic acid A; and phenanthrenequinones such as phenanthrenequinone. 
     The aromatic amine compounds are specifically exemplified by aniline, o-, m- or p-phenylene-diamine, o-, m- or p-chloroaniline, o-, m- or p-methylaniline, N,N-dimethyl-p-phenylenediamine, 4-chloro-o-phenylenediamine, 4-methoxy-o-phenylenediamine, 2-amino-4-chlorophenol, 2,3-diaminotoluene, 4-amino-2-aminophenol, o-, m- or p-aminophenol, o-, m- or p-aminobenzoic acid, 2,3-, 2,4-, 2,5-, 2,6-, 3,4-, 3,5- or 4,6-diaminobenzoic acid, 3- or 4-aminophthalic acid, 2-, 4- or 5-aminoisophthalic acid, 4,6-diaminoisophthalic acid, 2,5- or 2,6-diaminoterephthalic acid, 3-, 4- or 5-aminosalicylic acid, 4-hydroxyanthranilic acid, o-, m- or p-aminobenzenesulfonic acid, 2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-diaminobenzenesulfonic acid, 2-amino-1-phenol-4-sulfonic acid and 6-amino-4-chloro-1-phenol-2-sulfonic acid, α-naphthylamine, β-naphthylamine, 1,5-diaminonaphthalene, 1-amino-5-hydroxynaphthalene, 1,8-diaminonaphthalene, 2,3-diminonaphthalene, 4-amino-1-naphthol, 1-amino-5-naphthol, 1,2-naphthylenediamine-7-carboxylic acid, 1,5-naphthylenediamine-2-carboxylic acid, 1,5-naphthylenediamine-4-carboxylic acid, 1,6-naphthylenediamine-4-carboxylic acid, 1,8-naphthylenediamine-4-carboxylic acid, 1,2-naphthylenediamine-3-sulfonic acid, 1,2-naphthylenediamine-4-sulfonic acid, 1,2-naphthylenediamine-5-sulfonic acid, 1,2-naphthylenediamine-6-sulfonic acid, 1,2-naphthylenediamine-7-sulfonic acid, 1,3-naphthylenediamine-5-sulfonic acid, 1,3-naphthylenediamine-6-sulfonic acid, 1,4-naphthylenediamine-2-sulfonic acid, 1,4-naphthylenediamine-7-sulfonic acid, 1,5-naphthylenediamine-2-sulfonic acid, 1,5-naphthylenediamine-4-sulfonic acid, 1,5-naphthylenediamine-7-sulfonic acid, 1,6-naphthylenediamine-2-sulfonic acid, 1,6-naphthylenediamine-4-sulfonic acid, 1,6-naphthylenediamine-7-sulfonic acid, 1,8-naphthylenediamine-4-sulfonic acid, 1,8-naphthylenediamine-3,6-disulfonic acid, 1,8-naphthylenediamine-4,5-disulfonic acid, α-amino-β-naphthalenepropionic acid, α-amino-β-naphthalenecarboxylic acid, 2-naphthylamine-1-sulfonic acid, 8-naphthylamine-1-sulfonic acid, 5-naphthylamine-1-sulfonic acid, 1-amino-2-naphthol-4-sulfonic acid, 2-amino-8-naphthol-6-sulfonic acid (γ-acid), 2-amino-5-naphthol-7-sulfonic acid (J-acid) and 1-amino-8-naphthol-3,6-disulfonic acid (H-acid), and diphenylamines, such as 4-aminodiphenylamine, 2-aminodiphenylamine, 4,4′-diaminodiphenylamine, 4-hydroxydiphenylamine, 4-amino-3′-methoxydiphenylamine, 4-amino-4′-hydroxydiphenylamine, 4-carboxydiphenylamine, 4-amino-4′-carboxydiphenylamine, 4-sulfodiphenylamine and 4- amino-4′-sulfodiphenylamine. 
     The aromatic hydroxyl compounds are exemplified by phenols and derivatives thereof, such as phenol, hydroquinone, resorcinol, catechol, hydroxyhydroquinone, pyrogallol, o-, m- or p-chlorophenol, o-, m- or p-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid and 2,5-, 2,6- or 3,5-dihydroxytoluene. 
     In addition, they are exemplified by naphthols and derivatives thereof, such as α-naphthol, β-naphthol, 1,3-, 1,4-, 1,5-, 2,3-, 2,6- or 2,7-dihydroxynaphthalene, 1-hydroxy-2-naphthoic acid and 3-hydroxy-2-naphthoic acid. 
     The self-condensation of a quinone compound or the condensation of a quinone compound with an aromatic hydroxyl compound and/or an aromatic amine compound is carried out in an organic solvent medium, optionally in the presence of a condensation catalyst. The organic solvent medium has a pH within the range of from 1 to 13, preferably from 4 to 10, and pH adjusters may be used without any particular limitations. The pH adjusters used include acidic compounds, for example, phosphoric acid, sulfuric acid, phytic acid and acetic acid; and alkali compounds, for example, alkaline metal compounds or ammonium compounds, such as LiOH, KOH, NaOH, Na 2 CO 3 , Na 2 SiO 3 , Na 2 HPO 4  and NH 4 OH; and organic amine compounds, such as ethylenediamine, monoethanolamine and triethanolamine. 
     As the medium for the condensation reaction, organic solvents as exemplified by alcohols, ketones and esters, or mixed solvents of water and organic solvents miscible with water are preferred. Usable organic solvents miscible with water include, for example, alcohols, such as methanol, ethanol and propanol; ketones, such as acetone and methyl ethyl ketone; and esters, such as methyl acetate and ethyl acetate. 
     The condensation catalyst may be optionally used which is exemplified by azo catalysts such as α,α′-azobisisobutylonitrile and α,α′-azobis-2,4-dimethylvaleronitrile; elementary or molecular single halogens, such as iodine, bromine and chlorine; peroxides, such as hydrogen peroxide, sodium peroxide, benzoyl peroxide, potassium persulfate, ammonium persulfate, peracetic acid, cumene hydroperoxide, perbenzoic acid and p-menthane hydroperoxide; oxygen acids or oxygen acid salts, such as iodic acid, periodic acid, potassium periodate and sodium perchlorate. Incidentally, since the quinone compound acts as a condensation catalyst, the condensation reaction takes place even in the absence of a condensation catalyst. 
     The condensation reaction may be generally carried out at room temperature to 200° C. for 0.5 to 100 hours. 
     When (a) a quinone compound and (b) an aromatic hydroxyl compound and/or an aromatic amine compound are condensed, the proportion of both reactive components used depends on the types of the aromatic amine compounds, quinone compounds and aromatic hydroxyl compounds, the reaction temperature and the reaction time. It is preferable to use from 0.01 to 10.0 mols of the component (b) per mol of the component (a). 
     Sulfide Compounds of Aromatic Hydroxyl Compounds 
     Sulfide compounds of aromatic hydroxyl compounds refer to condensation products of aromatic hydroxyl compounds with sulfur chlorides such as sulfur monochloride and sulfur dichloride. Use of such sulfide compounds of aromatic hydroxyl compounds in the scale preventive agent is disclosed in, e.g., Japanese Pre-examination Patent Publication (kokai) Nos. 4-311702, 4-339801, 5-155905 and 6-9711. 
     The aromatic hydroxyl compounds may include aromatic hydroxyl compounds of naphthol compounds described above, phenol compounds and the like. 
     To obtain the sulfide compounds, various methods are available. For example, a method is available in which the above phenols and sulfur chlorides such as sulfur monochloride and sulfur dichloride are subjected to condensation reaction. This reaction is carried out in an organic solvent inert to sulfur chlorides, in which a polyhydric phenol has been dissolved. Such an organic solvent may include, e.g., aromatic hydrocarbons such as toluene, xylene and chlorobenzene, and ethylene dichloride, chloroform and ethyl acetate. The phenol and the sulfur chloride may be in such a ratio that the latter is from about 0.5 to 2 mols, and preferably from about 0.9 to 1.2 mols, per mole of the former. The reaction may be carried out at a temperature of from about 50° C. to about 150° C. Hydrogen chloride formed as a by-product may be volatilized, or, in a closed system, a dehydrochlorinating agent such as triethylene-amine may be used. After the reaction has been completed, in an instance where the reaction product stand dissolved in the solvent, the solvent may be removed by evaporation to take out the reaction product. In an instance where the reaction product stand deposited, solid-liquid separating operation such as filtration may be carried out to take out the reaction product. 
     As another method for obtaining the sulfide compound, a method is available in which a polyhydric phenol and a small amount of an alkali hydroxide are heated and melted, sulfur powder is added thereto little by little and further the temperature is raised to about 150° C. to about 200° C., where the reaction is carried out while releasing to the outside of the system the hydrogen sulfide being formed, the reaction mixture is cooled and thereafter dissolved in the solvent described later, followed by filtration to collect the insoluble matter, which is then neutralized with a dilute acid, and the aqueous phase is removed to obtain the compound in the form of a solution. 
     Heterocyclic compound having 5 or more conjugated  bonds: 
     The heterocyclic compounds having 5 or more conjugated  bonds include, for example, oxygen-containing heterocyclic compounds, nitrogen-containing heterocyclic compounds, sulfur-containing heterocyclic compounds, dicyclic compounds having a nitrogen atom possessed in common by the two rings, and alkaroids. 
     First, as the oxygen-containing heterocyclic compounds, there may be included: 
     benzofuran, isobenzofuran, dibenzofuran and derivatives thereof, such as furano-[2′,3′-7,8]flavone, 9-phenylanthracene, o-hydroxymethyltriphenylcarbinol, 3,3′-diphenylphthalide, rubrene, α-sorinine and phenazone; 
     pyran derivatives and pyrone derivatives, such as 2-p-hydroxyphenyl-4,6-diphenylpyrylium ferrichloride, anhydrobase, benzopyran and 6-phenylcoumarin; 
     chromenol derivatives and chromene derivatives, such as 6-methyl-2,3-diphenylchromone, 6-methyl-2,3-diphenyl-4-(p-tolyl)-1,4-benzopyran-4-ol, chromanol, γ-chromene, hydroxychmarone, chromene, cyanizine chloride, fisetin, chrysinidine, apigenidin and rotoflavinidine; 
     flavone, flavonol and isoflavon derivatives, such as flavonol, flavone, fukugetin; 
     coumarin, its derivatives, isocoumarin and its derivatives, such as 7-hydroxy-3,4-benzocoumarin, dicoumarol, angelicin, psoralen, bergapten, bergaptol, xanthotoxin, xanthotoxal, isopimpinellin, pimpinellin, oroselol, oroselone, peucedanin, hydroxypeucedanin, ostruthol, medakenine, nodakenetin, seselin, xanthyletin, xanthoxyletin; and 
     xanthone and related compounds; such as dixanthylene, 9-phenylxanthene, isoxanthone, 1,2,7,8-dibenzoxanthene, 3,9-diphenylxanthene, 9,9-diphenylxanthene, and the like. 
     Next, the nitrogen-containing heterocyclic compounds may include: 
     indoles, such as indolo[3,2-c]quinoline, indolo[1,2-c]quinazoline, 2-(1-naphthyl)-3-triphenylmethylindole, 2-(2-naphthyl)-3-triphenylmethylindole, 3,3′-diindolyl and 3,2′-diindolyl; 
     oxoderivatives of indole, such as 3-(4-ethoxy-1-naphthyl)hydroxyindole and indophenine; 
     carbazoles, such as 1-phenyl-1,2,3-benzotriazole, 2,2′-diaminodiphenyl, 1,1′-dicarbazole; 
     porphyrins, such as porphyrazine, magnesium octamethyltetraazaporphyrin, azadipyromethine, diazacoproporphyrin, porphine and mesotetraphenylporphyrin; 
     oxazoles, such as phenanthrooxazole; 
     thiazoles, such as α-naphthothiazole, β-naphthothiazole, naphtho[1,2]thiazole, 2-methyl[1,2]thiazole, 2-phenylnaphtho[1,2]thiazole, 2-methylnaphtho[2,1]-thiazole, 2-hydroxynaphtho[2,1]thiazole, 2-aminonaphtho[1,2]thiazole and 2-mercaptonaphtho[1,2]-thiazole; 
     oxadiazoles, such as naphtho[1,2]furazane; 
     quinoline and related compounds, such as quinoline, quinaldine, quinaldine-N-oxide, ethylquinoline, 2-phenylquinoline, 3-methylquinoline, 4-phenylquinoline, 6-methylquinoline and 2,4-dimethylquinoline; 
     isoquinoline and related compounds, such as 1-methylisoquinoline, 1-phenylisoquinoline, 4-phenylisoquinoline, 1,1′-biisoquinoline and 5,5′-biisoquinoline; 
     acridine and related compounds, such as acridine, 1-methylacridine, 9-phenylacridine, 9-(3-pyridinyl)acridine, 2-acridinol, acridine-3,6-diol, 4-methoxyacridine, 9-phenoxyacridine, 1-nitroacridine, 4-aminoacridine, 1-aminoacridine, 9-phenylaminoacridine, 9-hydroxyacridine and 3,6-diamino-4,5-dimethylacridine; 
     phenanthridines, such as 3,4-benzoquinoline, 6-methylphenanthridine, 6-aminomethylphenanthridine and 6-phenylphenanthridine; 
     anthrazolines, such as pyrido[2,3-g]quinoline, 2,7-diphenyl[2,3-g]quinoline, 2,8-diphenylpyrido[3,2-g]-quinoline; 
     phenanthroline and related compounds, such as 1,7-phenanthroline and 1,10-phenanthroline; 
     pyridoindoles, such as 1,9-pyridoindole, 2,9-pyridoindole and 4,9-pyridoindole; 
     naphthylidine and related compounds, such as 1,5-naphthylidine, 1,7-naphthylidine, 1,8-naphthylidine, 3-amino-1,5-naphthylidine, 2-amino-1,5-naphthylidine and 2-hydroxy-1,7-naphthylidine; 
     oxazine and related compounds such as phenoxazinone and resazurin; 
     thiazine and related compounds, such as phenothiazine, nitrophenothiazine, 4-amino-4′-anilinodiphenyl disulfide, 2-chloro-10-(3-dimethylaminopropyl)phenothiazine, 10-[1-methyl-3-piperidylmethyl)phenothiazine and 2-acetyl-10-(3-dimethylaminopropyl)phenothiazine; 
     pyridazine and related compounds, such as cinnoline, 3-methylcinnoline, 4-chlorocinnoline, 3-bromocinnoline, 4-cinnolinol, 4-aminocinnoline, phthalazine, 4-ethyl-2-phenylphthalazinone and phthalazine thiol; 
     pyrimidine and related compounds, such as sulfadiazine, sulfisomidine, pteridine, 2,4-pterine diol, 2-amino-6-methyl-4-pteridinol, xanthopterine, quinazoline, 2,4-dichloroquinazoline and 2,3-diphenyl-4-quinazoline; 
     pyrazine related compounds, such as quinoxaline and 2-methylquinoxaline; 
     tri- and tetra-hetero six-membered cyclic compounds, such as 1,2,4-benzotriazine and 1,2,4-benzotriazine-3-ol; 
     Further, the sulfur-containing heterocyclic compounds may include: 
     fused thiophene compounds, such as dihydronaphtho[2,1-b]-thianaphthene, 1,3-diphenylisothianaphthene and dibenzothiophene; 
     five-membered monocyclic compounds containing 2 hetero atoms, such as 3,4-dihydronaphtho-2,1-trithione, thiaflavone, thiacoumarin, thiaxanthene, thiaxanthohydrol, thiaxanthone, Milacil D, and bisthiaxanthylene; 
     six-membered cyclic compound having two or more hetero atoms, such as thianthrene, 2,7-dimethylthianthrene, 1-thianthrenyl lithium, 1-chlorothianthrene and phenoxathine. 
     Further, other useful compounds may include: 
     dicyclic compounds having a nitrogen atom possessed in common by the two rings, such as 2:3-benzopyrrocoline, 1,5,8-trimethyl-2:3-benzopyrrocoline and 1-ethyl-5,8-dimethyl-2:3-benzopyrrocoline; and 
     alkaroids, such as casimiroin, 2-penthylquinoline, 4-hydroxy-2-pentylquinoline and 4-methoxy-2-pentylquinoline. 
     Of the conjugated  bond compounds, it is preferable to use those which are condensation products of aromatic compounds and have a weight-average molecular weight of 500 or more. 
     Of the condensation products of aromatic compounds, aldehyde compound/aromatic hydroxyl compound condensation products and quinone compound condensation products are particularly preferred. 
     The first coating liquid is prepared by dissolving the conjugated  bond compound in a proper solvent. The solvent includes, for example, water; alcohol solvents, such as methanol, ethanol, propanol, butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 3-methyl-1-butanol, 2-methyl-2-butanol and 2-pentanol; ketone solvents, such as acetone, methyl ethyl ketone and methyl isobutyl ketone; ester solvents, such as methyl formate, ethyl formate, methyl acetate, ethyl acetate and methyl acetoacetate; ether solvents, such as 4-methyldioxolane and ethylene glycol diethyl ether; furans; and non-protonic solvents, such as dimethylformamide, dimethyl sulfoxide and acetonitrile. The solvents may be appropriately used singly or as a mixed solvent of two or more thereof. 
     Among the above solvents, preferred are water and a mixed solvent of water and an organic solvent miscible with water. Among the above organic solvents, organic solvents miscible with water include alcohol solvents, such as methanol, ethanol and propanol; ketone solvents, such as acetone and methyl ethyl ketone; and ester solvents, such as methyl acetate and ethyl acetate. Particularly, it is preferred that alcohol solvents are used. In the case where a mixed solvent of water and an organic solvent miscible with water is used, the organic solvent is preferably contained in such an amount that there is no danger of inflammation, evaporation and the like and there is no problem on safety in handling, for example, on toxicity. Specifically, the amount is preferably 50% by weight or less, more preferably 30% by weight or less. 
     The pH of the first coating liquid is selected appropriately depending on the kind of the conjugated  bond compound. For example, for pyrogallol/acetone condensation products, polyhydric phenol self-condensation products and polyhydric naphthol self-condensation products, a pH of 2.0 to 6.5 is preferred. For this pH adjusters used for adjustment of the pH include, for example, hydrochloric acid, sufuric acid, phosphoric acid, pyrophosphoric acid and nitric acid. For the condensation products of aldehyde compound/aromatic hydroxyl compound, condensation products of an aromatic amine compound, and condensation products of a quinone compound, a pH of 7.5 to 13.5 is preferred, and a pH of 8.0 to 12.5 is more preferred. For that case, alkaline compounds used for pH adjustment include, for example, alkali metal compounds or ammonium compounds, such as LiOH, NaOH, KOH, Na 2 CO 3 , Na 2 HPO 4  and NH 4 OH; and organic amine compounds, such as ethylenediamine, monoethanolamine, diethanolamine and triethanolamine. 
     The conjugated  bond compound in the first coating liquid may preferably be in a concentration ranging from 1.0 to 25.0% by weight, more preferably from 2.5 to 15.0% by weight, and still more preferably from 4 to 10% by weight. If they are in too low a concentration, a difficulty may occur such that the steam must be used in a large quantity in order to form the first layer in an effective quantity. If they are in too high a concentration, the coating liquid may become unstable to cause a precipitate during storage in a storage tank, or coating solution feed lines and coating nozzles may clog with precipitates of deposits, making it difficult to coat the coating solution. As the result, this causes a lowering of the scale prevention effect. 
     To the first coating liquid, an anticorrosive agent, an antifungal agent and so forth may optionally be added as long as the effect of the present invention is not damaged. 
     Second Coating Liquid 
     As the second coating liquid, a coating liquid containing at least one hydrophilic compound selected from the group consisting of a water-soluble polymeric compound, an inorganic colloid, an inorganic salt and an acid is used. 
     Water-soluble Polymeric Compound 
     The water-soluble polymeric compound includes, for example, water-soluble hydroxyl group-containing polymeric compounds, water-soluble amphoteric polymeric compounds, water-soluble anionic polymeric compounds and water-soluble cationic polymeric compounds. 
     The water-soluble hydroxyl group-containing polymeric compounds include, for example, starches such as amylose, amylopectin, dextrin and oxidized starch; animal viscous liquid materials such as chitin; cellulose derivatives such as methyl cellulose, glycol cellulose, ethyl methyl cellulose, hydroxyethyl cellulose, and hydroxyethyl methyl cellulose; hemicelluloses such as xylan, mannan, arabogalactan, galactan, and araban; lignins such as alcohol lignin, dioxane lignin, phenol lignin, hydrotropic lignin, mercaptolignine, alkali lignin, thioalkali lignin, acid lignin, cuproxam lignin, and periodate lignin; and partially saponified polyvinyl alcohols and polyvinyl alcohols. Among these, preferred are amylopectin, dextrin, methyl cellulose, glycol cellulose, mannan, galactan, alcohol lignin, dioxane lignin, alkali lignin, and acid lignin. The water-soluble amphoteric polymeric compounds include, for example, glue, gelatin, casein, albumin, ribonucleic acids, deoxyribonucleic acids, and chitosan. The water-soluble anionic polymeric compounds include, for example, anionic polymeric compounds having a carboxyl group or sulfonic acid group in their side chain as exemplified by sulfomethylated compounds of polacrylamide, polyacrylic acid, alginic acid, an acrylamide/vinylsulfonic acid copolymer, polymethacrylic acid and poystyrenesulfonic acid, carboxymethyl starch, pectic acid, pectinic acid, protopectinic acid, carragheenin, hyaluronic acid, chondroitin sulfuric acid, heparin, keratosulfuric acid, thioglycollic acid, lignin sulfonic acid, styrene-maleic anhydride copolymers, acrylic acid-maleic anhydride copolymers, and carboxymethyl cellulose. The water-soluble cationic polymeric compounds include cationic polymeric electrolytes having nitrogen atoms on the side chains, the nitrogen atoms having positive charges, as exemplified by polyethylene-imine, polyvinyl amine, polyacrylamide, an N-vinyl-2-pyrrolidone/acrylamide copolymer, a cyclized polymer of dimethyldiamylammonium chloride, a cyclized polymer of dimethyldiethylammonium bromide, a cyclized polymer of diallylamine hydrochloride, a cyclized copolymer of dimethyldiallylammonium chloride with sulfur dioxide, polyvinyl pyridine, polyvinyl pyrrolidone, polyvinyl carbazole, polyvinyl imidazoline, polydimethylaminoethyl acrylate, polydiethylaminoethyl acrylate, polydiethylaminoethyl methacrylate, and derivatives or modified products of any of these polymeric compounds, as exemplified by partially cross-linked products, copolymers, graft copolymers, and these polymeric compounds into which a functional group such as —OH, —NH 2 , —COOH or —SO 3 H has been introduced. 
     Of the water-soluble polymeric compounds exemplified above, preferred are methyl cellulose, hydroxyethyl cellulose, hydroxyethylmethyl cellulose, polyvinyl alcohol, partially saponified polyvinyl alcohol, glue, casein, gelatin, chitosan, polyacrylic acid, alginic acid, polymethacrylic acid, pectic acid, carragheenin, hyaluroic acid, carboxymethyl cellulose, polyvinyl pyrrolidone and a styrene-maleic anhydride copolymer. 
     Inorganic Colloid 
     The inorganic colloids include, for example, colloids of oxides or hydroxides of metals selected from aluminum, thorium, titanium, zirconium, antimony, tin, iron and so forth; colloids of tungstic acid, vanadium pentoxide, selenium, sulfur, silica, gold or silver; and silver iodide sol. Among them, preferred are colloids of oxides or hydroxides of metals selected from aluminum, titanium, zirconium, tin and iron; and colloidal silica. These inorganic colloids may be those obtained by any production processes on which there are no particulate limitations. For example, particulate colloids produced by a dispersion process using water as a dispersion medium or an agglomeration process are available. The colloidal particles have a size of preferably 1 to 500 nm. 
     Inorganic Salt 
     The inorganic salts include, for example, alkaline metal silicates and inorganic salts of alkaline-earth metals. 
     The alkaline metal silicate include, for example, metasilicates (M 2 SiO 3 ), orthosilicates (M 4 SiO 4 ), disilicates (M 2 Si 2 O 3 ), trisilicates (M 3 Si 3 O 7 ) and sesquisilicates (M 4 Si 3 O 10 ) wherein in these formulae, M represents an alkaline metal, such as lithium, sodium or potassium, of alkaline metals; and water glass. 
     The inorganic salts of alkaline earth metals include, e.g., silicates, carbonates, phosphates, sulfates, nitrates, borates, acetates, hydroxides, oxides or halides of alkaline earth metals such as magnesium, calcium and barium. Of these alkaline earth metal compounds, particularly preferred are magnesium carbonate, calcium carbonate, magnesium phosphate, calcium phosphate, calcium pyrophosphate, calcium dihydrogenpyrophosphate, barium phosphate, calcium sulfate, calcium borate, magnesium hydroxide, calcium hydroxide, barium hydroxide, magnesium chloride and calcium chloride. 
     Acid 
     The acid may include inorganic acids such as phosphoric acid, pyrophosphoric acid, polyphosphoric acid, phosphomolybdenic acid, silicomolybdenic acid, phosphotungstic acid, silicotungstic acid, molybdic acid and tungstic acid; and organic acids such as terephthalic acid, 1,12-dodecanedicarboxylic acid, 1-dodecanedisulfonic acid, benzoic acid, lauric acid, sulfanilic acid, p-styrene sulfonic acid, propionic acid, salicylic acid, copper phthalocyanine tetrasulfonic acid, urocanic acid, L-asciorbic acid, D-isoasciorbic acid, chlorogenic acid, caffeic acid, p-toluenesulfonic acid, sorbic acid, β-naphthoquinone 4-sulfonic acid, phytic acid and tannic acid. 
     Of the above hydrophilic compounds, water-soluble polymeric compounds, inorganic colloids and inorganic salts are preferred, and water-soluble polymeric compounds are particularly preferred. 
     The second coating liquid is prepared by dissolving at least one selected from the above hydrophilic compounds in a suitable solvent. As the solvent, water or a mixed solvent of water and a hydrophilic organic solvent having an affinity for water may be used. Of the above solvents, the hydrophilic organic solvent may include alcohol type solvents such as methanol, ethanol and propanol; ketone type solvents such as acetone and methyl ethyl ketone; and ester type solvents such as methyl acetate and ethyl acetate. In addition, of the above solvents, it is preferable to use alcohol type solvents. In the case when the mixed solvent of water and the hydrophilic organic solvent is used, the hydrophilic organic solvent may preferably be used in such a content that there is no danger of combustion or explosion and there is no problem on the safety in handling such as toxicity. Stated specifically, the hydrophilic organic solvent may preferably be in a content of 50% by weight or less, and more preferably 30% by weight or less. Preferably, all of the solutes are completely dissolved and colloidal particles are completely uniformly dispersed in a solvent to form the second coating liquid in a uniform solution. 
     In the second coating solution, a pH adjuster such as NaOH or ethylenediamine may also optionally be used. An anticorrosive agent, an antifungal agent and so forth may further be added as long as the effect of the present invention is not damaged. 
     The hydrophilic compound in the second coating liquid may preferably be in a concentration ranging from 0.01 to 20% by weight, more preferably from 0.1 to 15% by weight. 
     Carrier Steam 
     According to the process of the present invention, the coating film is formed by applying the first and second coating liquids simultaneously on the polymerization vessel inner wall by means of steam as a carrier. The steam used may be steam usually available or superheated steam, and may preferably be steam having a pressure of from 2 to 35 kgf/cm 2 ·G (0.20 to 3.43 MPa·Gauge), and more preferably one having a pressure of from 2.8 to 20 kgf/cm 2 ·G (0.27 to 1.96 MPa·Gauge). The steam may preferably have a temperature of from 120 to 260° C., and more preferably from 130 to 200° C. 
     The pressure and temperature of the steam described above are the values measured before the mixing of the steam with the coating solutions, for example, in the interior of a steam feed line  6  as shown in FIG. 1 described below. 
     Formation of Coating Film 
     The coating film formed by the method of the present invention will be described with reference to a coating apparatus shown in FIG. 1, which illustrates the arrangement in a polymerization apparatus. 
     Step 1. (Pre-heating of Polymerization Vessel Inner Wall Surfaces and Others by Steam) 
     Hot water or the like is passed through a jacket  2  attached to a polymerization vessel  1  to pre-heat the polymerization vessel inner wall surfaces to a temperature of 50° C. or above (preferably from 50 to 95° C.). At the upper part of this polymerization vessel, a coating ring  4  is provided which is formed of a ring-shaped pipe and has upward nozzles  3   b  and downward nozzles  3   a . To the coating ring  4 , a line  5  is connected through which the steam and the coating liquid are fed from the outside of the polymerization vessel  1 . To line  5  are connected a steam feed line  6 , the first coating liquid feed line  7  and the second coating liquid feed line  8  through the respective valves. If necessary, the steam (usual steam or superheated steam) may be blown into the vessel from the coating nozzles  3   a  and  3   b  of this coating ring  4  to pre-heat also baffles (not shown) and stirring blades (not shown). In this apparatus, the steam is fed to the coating ring  4  from a steam feeder  9  via a flowmeter  10  through lines  6  and  5 . 
     Step 2. (Coating) 
     The steam is fed to the coating ring  4 , and the first coating liquid held in a first coating liquid tank  11  is fed to the coating ring  4  through lines  7  and  5  by means of a pump  12  or an aspirator valve (not shown). P denotes a pressure gauge. Substantially at the same time, the second coating liquid held in a second coating liquid tank  13  is fed likewise to the coating ring  4  through lines  8  and  5  by means of a pump  14 . 
     The first and second coating liquids are carried by the steam and is, in the state of mist, applied to and coated on polymerization vessel inner wall surfaces and surfaces with which polymers come into contact during polymerization, such as baffle surfaces and stirring blade surfaces. Simultaneously with this coating, a mixture and/or reaction product of the first and second coating liquids coated on these surfaces is dried (simultaneous drying), so that the coating film is formed. Hence, it is unnecessary to make any particular operation for the drying. 
     The steam (G) and the total of the first and second coating liquids (L) may preferably be in a mixing ratio (L/G) of from 0.005 to 0.8, and more preferably from 0.01 to 0.2, as flow rate ratio on the basis of weight. 
     The first coating liquid (L 1 ) and the second coating liquid (L 2 ) may be mixed in a proportion (L 1 /L 2 ) appropriately adjusted in accordance with the concentration of the respective coating liquids. Their proportion may preferably be so adjusted that the conjugated--bond-containing compound in the first coating liquid and the hydrophilic compound in the second coating liquid are in a weight ratio ranging from 0.01 to 100, and more preferably ranging from 0.20 to 30. In accordance with the concentration of the both coating liquids, the flow rate ratio (weight-based) of the L 1  and L 2  may preferably be so adjusted to 0.1 to 10.0, and more preferably 0.2 to 5.0, that such a solid matter component ratio can be attained. 
     Step 3. (Water washing) 
     After the feeding of the steam and the coating liquid are stopped, the inside of the polymerization vessel is washed with cleaning water held in a water tank  15 . The cleaning water is fed into the polymerization vessel  1  from nozzles  18  through a line  17  by means of a pump  16 . However, water washing is unnecessary if the coating liquid does not so affect the product quality. 
     The coating film thus formed may preferably have a dried coating weight of from 0.001 to 5 g/m 2 , and more preferably from 0.001 to 2 g/m 2 . 
     Polymerization 
     The process of the present invention is applied to the polymerization of a monomer having an ethylenically unsaturated double bond. Examples of the monomer include vinyl halides such as vinyl chloride; vinyl esters such as vinyl acetate andvinyl propionate; acrylic acid, methacrylic acid and their esters or salts; maleic acid, fumaric acid and their esters or anhydrides; diene monomers such as butadiene, chloroprene and isoprene; styrene; acrylonitrile; vinylidene halides; and vinyl ether. 
     Examples particularly suitable for practicing the process of the present invention include the production of polymers of vinyl halides, such as vinyl chloride, vinylidene halides, or a monomeric mixture comprised primarily of them by suspension polymerization or emulsion polymerization in an aqueous medium. The coating film formed by the process of the present invention has a high durability even for monomers, such as α-methylstyrene, acrylic acid esters, acrylonitrile and vinyl acetate, which have a high solvency power for the conventional coating film, so that the process can be carried out suitably even for the production of polymer beads and latex comprised of polystyrene, polymethacrylate, polyacrylonitrile, etc.; the production of synthetic rubbers such as SBR, NBR, CR, IR, IIR, etc.(these synthetic rubbers are generally produced by emulsion polymerization); and the production of ABS resin. 
     In the polymerization of one or more of these monomers, an object of preventing scale can be effectively accomplished irrespective of polymerization types, such as suspension polymerization, emulsion polymerization, bulk polymerization and solution polymerization, even in the presence of any of additives such as emulsifiers, stabilizers, lubricants, plasticizers, pH adjusters and chain transfer agents. For example, in the case of suspension polymerization or emulsion polymerization of a vinyl monomer, various additives are optionally added, as required. The additives include, for example, suspending agents such as partially saponified polyvinyl alcohol and methyl cellulose; anionic emulsifiers such as sodium lauryl sulfate; nonionic emulsifiers such as sorbitan monolaurate and polyoxyethylene alkyl ether; stabilizers such as tribasic lead sulfate, calcium stearate, dibutyltin dilaurate and dioctyltin mercaptide; chain transfer agents such as trichloroethylene and mercaptans; and pH adjusters. According to the present process, deposition of scale is effectively prevented in the presence of any of the additives above. 
     The remarkable polymer scale deposition preventive effect of the invention is exhibited without being affected by the kind of polymerization catalysts even when any of catalysts is used. Specifically, the catalysts include, for example, t-butyl peroxyneodecanoate, bis(2-ethylhexyl)peroxydicarbonate, 3,5,5-trimethylhexanoyl peroxide, α-cumylperoxyneodecanoate, cumenehydroperoxide, cyclohexanone peroxide, t-butyl peroxypivarate, bis(2-ethoxyethyl)peroxydicarbonate, benzoyl peroxide, diisopropylbenzene hydroperoxide, lauroyl peroxide, 2,4-dichlorobenzoyl peroxide, diisopropyl peroxydicarbonate, α,α′-azobisisobutylonitrile, α,α′-azobis-2,4-dimethylvaleronitrile, di-2-ethylhexyl diperoxyisophthalate, potassium persulfate and ammonium persulfate. 
     Other conditions for polymerization may be those which are conventionally used, and there are no limitations unless the effects of the present invention are impaired. In the following, taking the cases of suspension polymerization, solution polymerization and bulk polymerization as examples, typical conditions of polymerization will be described. 
     First, in the suspension polymerization, water and a dispersant are charged into a polymerization vessel, and then a polymerization initiator is charged therein. Subsequently, the polymerization vessel is evacuated to reduce the initial pressure to a value of 0.1 to 760 mmHg (0.01 to 101 kPa), and a monomer or monomers are then charged, whereupon the internal pressure takes usually a value of 0.5 to 30 kgf/cm 2 ·G (150 to 3,040 kPa). Thereafter, polymerization is carried out at a reaction temperature of 30 to 150° C. During the polymerization, one or more materials selected from water, a dispersant and a polymerization initiator are, optionally, added. Reaction temperature during the polymerization is different depending on the kind of a monomer to be polymerized. For example, in the case of polymerizing vinyl chloride, polymerization is carried out at 30 to 80° C., while in the case of polymerizing styrene, polymerization is carried out at 50 to 150° C. The polymerization may be judged to be completed when the pressure inside the polymerization vessel has dropped to a value of 0 to 7 kgf/cm 2 ·G (100 to 790 kPa) or when there has been observed substantially no difference between the inlet temperature and outlet temperature of a cooling water flowing into and out of a jacket provided circumferentially of the polymerization vessel (i.e., when liberation of heat due to the polymerization reaction has subsided). The amounts of the water, dispersant and polymerization initiator are generally 20 to 500 parts by weight, 0.01 to 30 parts by weight, and 0.01 to 5 parts by weight, respectively, per 100 parts by weight of the monomer. 
     In solution polymerization, an organic solvent, such as toluene, xylene and pyridine, is used as the polymerization medium, in place of water. If necessary, a dispersant may be used. The other conditions for polymerization are generally the same as those described for suspension polymerization. 
     In bulk polymerization, after a polymerization vessel is evacuated to a pressure of about 0.01 to 760 mmHg (0.001 to 101 kPa), a monomer and a polymerization initiator are charged into the polymerization vessel, and then polymerization is carried out at a reaction temperature of −10 to 250° C. For example, the reaction temperature is 30 to 80° C. for the polymerization of vinyl chloride, and is 50 to 150° C. for the polymerization of styrene. 
     EXAMPLES 
     The present invention will now be described below in greater detail by giving Examples. In the following, “part(s)” refers to “part(s) by weight”. In tables, “auxlliary agents” refers to “polymer scale preventive auxiliary agent”. 
     Production of Condensation Products 
     In the following Production Examples, the weight-average molecular weight of each condensation product obtained was measured in the following way. 
     Measurement of Weight-average Molecular Weight 
     Weight-average molecular weight in terms of polystyrene was measured by gel permeation chromatography (GPC) under the following measurement conditions. 
     Columns: 
     Guard column: 
     Trade name: Shim-pack GPC-800DP, manufactured by Shimadzu Corporation. 
     Analytical columns: 
     Trade name: shim-pack GPC-803D, 802D, manufactured by Shimadzu Corporation. 
     Mobile phase: 10 mM LiBr/DMF 
     Flow rate: 1.0 ml/min 
     Detector: RI 
     Temperature: 60° C. 
     Production Example 1 
     Production of Condensation Product No. 1 
     Into a pressure-resistant reaction vessel, 30,000 mols (960 kg) of methanol, 100 mols (15.8 kg) of 1,8-diaminonaphthalene, 50 mols (5.4 kg) of p-benzoquinone and 250 mols (31.5 kg) of pyrogallol were charged, and the temperature was raised to 70° C. with stirring. After the reaction was carried out at 70° C. for 10 hours, the reaction mixture was cooled to obtain a methanol solution of a condensation product (Condensation Product No. 1). The Condensation Product No. 1 had a weight-average molecular weight of 3,500. 
     Production Example 2 
     Production of Condensation Product No. 2 
     With reference to Production Example 3 disclosed in Japanese Patent Publication (kokoku) No. 6-62709, a scale preventive agent was produced. 
     Into apressure-resistant reaction vessel, 30 mols (5.59 kg) of 2,2′-dihydroxybiphenyl, 30 mols (0.948 kg) of paraformaldehyde with a purity of 95%, 0.19 kg of paratoluenesulfonic acid and 10 liters of ethylene glycol dimethyl ether were charged, and the temperature was raised to 130° C. with stirring. After the reaction was carried out at 130° C. for 17 hours, the reaction mixture was cooled to 50° C. and then put into 50 liters of water. The resin separated by putting said mixture into water was filtered off and then washed with water, followed by drying to obtain 5.1 kg of a 2,2′-dihydroxybiphenyl-formaldehyde condensation resin (Condensation Product No. 2). The Condensation Product No. 2 had a weight-average molecular weight of 5,400. 
     Production Example 3 
     Production of Condensation Product No. 3 
     With reference to Production Example 1 disclosed in Japanese Pre-examination Patent Publication (kokai) No. 57-164107, a polymer scale preventive agent was produced. 
     Into a pressure-resistant reaction vessel, 250 mols (36.0 kg) of 1-naphthol and 180 liters of 1N-NaOH aqueous solution (containing 180 mols or 7.2 kg of NaOH) were charged, and the temperature was raised to 70° C. with stirring. Next, to the reaction mixture, formaldehyde (19.75 liters of 38 w/v % aqueous solution, 250 mols) was dropwise added over a period of 1.5 hours. During the addition, the internal temperature of the reaction vessel was controlled so as not to exceed 80° C. Then, the reaction mixture was cooled to 60° C. over a period of 3 hours with the stirring kept. Next, the temperature of the reaction mixture was raised to 98° C. to carry out the reaction at 98° C. for 1.5 hours. Thereafter, the reaction mixture was cooled to obtain an alkaline solution of a condensation product (Condensation Product No. 3). The Condensation Product No. 3 had a weight-average molecular weight of 2,400. 
     Production Example 4 
     Production of Condensation Product No. 4 
     With reference to Coating Compound Synthesis 2 disclosed in Japanese Pre-examination Patent Publication (kokai) No. 57-192413, a scale preventive agent was produced. 
     Into a pressure-resistant reaction vessel, 100 mols (12.6 kg) of pyrogallol and 100 liters of water were charged, and the pyrogallol was dissolved in the water. Next, to the solution obtained, 200 mols (21.2 kg) of benzaldehyde and 300 mols (29.4 kg) of phosphoric acid were added, and the mixture thereof was reacted at 95° C. for 10 hours. As a result, a water-insoluble reddish brown product was obtained. This water-insoluble product was washed with ether, followed by extraction with methanol to extract a methanol-soluble matter from the water-insoluble product. Then, the methanol was removed from the extract by drying to obtain Condensation Product No. 4 (pyrogallol-benzaldehyde condensate), as a residue, which had a weight-average molecular weight of 4,500. 
     Production Example 5 
     Production of Condensation Product No. 5 
     With reference to Production Example I disclosed in Japanese Patent Publication (kokoku) No. 59-16561, a scale preventive agent was produced. 
     Into a pressure-resistant reaction vessel, 100 mols (10.8 kg) of m-phenylenediamine, 200 mols (22.0 kg) of resorcinol and 1.04 kg of 35% hydrochloric acid (10 mols as HCl) as a catalyst were charged, and the temperature was raised to 305° C. Immediately after the mixture in the reaction vessel reached 305° C., it was cooled. The water vapor evolved in the course of the raise in temperature and the reaction was removed, and the internal pressure was kept at 150 kPa or below. After cooling, the resulting m-phenylenediamine/resorcinol condensate was pulverized, followed by washing with water, filtering and drying, to obtain Condensation Product No. 5 which had a weight-average molecular weight of 4,000. 
     Production Example 6 
     Production of Condensation Product No. 6 
     With reference to Production Example VI disclosed in Japanese Patent Publication (kokoku) No. 59-16561, a scale preventive agent was produced. 
     Into a pressure-resistant reaction vessel, 100 mols (10.9 kg) of p-aminophenol and 0.99 kg of 30% hydrochloric acid (9.5 mols as HCl) were charged, and the temperature was raised to 169° C. Immediately after the reaction mixture reached 169° C., 18 liters of xylene was slowly added. The xylene was added so that the water formed during the condensation reaction was removed as an azeotropic mixture. Next, the temperature of the reaction mixture was raised to 222° C., and the reaction was carried out at 222° C. for 3 hours. The xylene-water mixed vapor evolved during the reaction was removed, and the internal pressure was kept at 150 kPa or below. After the reaction was carried out for 3 hours, the reaction mixture was cooled. The reaction product (Condensation Product No. 6) obtained was solid. Next, the reaction product was pulverized into fine particles, and thereafter washed with water, followed by filtration and then drying to obtain the Condensation Product No. 6 which had a weight-average molecular weight of 2,500. 
     Production Example 7 
     Production of Condensation Product No. 7 
     With reference to Production Example 1 disclosed in Japanese Pre-examination Patent Publication (kokai) No. 54-7487, a scale preventive agent was produced. 
     Into a reaction vessel, 200 mols (22.0 kg) of resorcinol was charged, and then heated in a nitrogen atmosphere. The temperature of resorcinol was raised to 300° C., and the reaction was carried out at 300° C. for 8 hours, followed by cooling. The solid self-condensed resorcinol thus obtained was pulverized to obtain Condensation Product No. 7 which had a weight-average molecular weight of 1,700. 
     Production Example 8 
     Production of Condensation Product No. 8 
     (1) Synthesis of a 2,3-dihidoroxynaphthalene dimer compound: 
     Into a flask having an inner capacity of 3 liters provided with a reflux condenser, 1350 mL of methanol was charged and then 144 g (0.9 mol) of 2,3-dihydoroxynaphthalene was dissolved therein. After the dissolution, the temperature was raised to 65° C., and 243 g (0.9 mol) of ferric chloride hydrate(FeCl 3 ·6H 2 O) dissolved in 450 mL of methanol was added dropwise to the solution obtained under reflux over 30 minutes. After the addition, reaction was continued under reflux for 5 hours. Subsequently, the reaction solution was transferred into 4.5 liters of a diluted hydrochloric acid and then the resulting mixture was stirred for 12 hours, to produce a dimer compound of 2,3-dihydroxynaphthalene. The reaction solution thus obtained was filtered to remove the solvents, and thereafter the residual matter was washed with two liters of pure water for two hours. The solution was filtered again to remove the ferric chloride hydrate(FeCl 3 ·6H 2 O). 
     The dimer compound of 2,3-dihydroxynaphthalene obtained was dried in a dryer at 40° C. 
     (2) Into a 3 liter-flask provided with a reflux condenser, one liter of pure water was charged, and then 5 g of sodium hydroxide and 50 g of the 2,3-dihydroxynaphthalene dimer compound obtained as above were charged. Subsequently, after the temperature was raised to 70° C., 12.75 g of 37% aqueous formaldehyde solution dissolved in 237.3 g of distilled water, was added dropwise over 30 minutes. After the addition, reaction was continued at the same temperature for five hours, and then the temperature was raised to 95° C. and reaction was continued for further two hours, thereby Condensation Product No. 8 being obtained. Incidentally, the reactions were all carried out in N 2  atmospheres. 
     After the completion of the reactions, Condensation Product No. 8 was cooled to 25° C., and then preserved in an N 2  atmosphere. The weight-average molecular weight was 22,000. 
     Production Examnple 9 
     Production of Condensation Product No. 9 
     Into a reaction vessel having an inner capacity of 2 liters provided with a reflux condenser, a mixed solvent of methanol (450 g) with water (450 g) was charged and subsequently 100 g of α-naphthoquinone and 10 g of sodium hydroxide were charged. Then, the internal temperature of the reaction vessel was raised to 50° C. and the mixture in the reaction vessel was reacted at 50° C. for 24 hours, followed by cooling the same to room temperature. Thus, a solution of Condensation Product No. 9 was obtained. The Condensation Product No. 9 had a weight-average molecular weight of 3,000. 
     Production Example 10 
     Production of Condensation Product No. 10 
     In a 20 L internal volume reaction vessel having a reflux condenser, 1.5 kg of 1-naphthol and 7.5 L of toluene were put, and the mixture obtained was heated with stirring until the toluene became refluxed. Under reflux at this temperature, 930 ml of sulfur monochloride was added dropwise over a period of 6 hours, and thereafter the mixture obtained was kept for 1 hour at that temperature. After the reaction mixture was cooled, 5 L of hexane was added with stirring to cause the reaction product to precipitate. Thereafter, the reaction product was filtered, and then dried to obtain Condensation Product No. 10. The Condensation Product No. 10 had a weight-average molecular weight of 1,200. 
     Production Example 11 
     Production of Condensation Product No. 11 
     In a 20 L internal volume reaction vessel having a reflux condenser, 6.7 L of water, 1,786 g (9.5 mols) of 6-hydroxy-2-naphthoic acid, 55 g (0.5 mol) of resorcinol and 620 g (15.5 mols) of NaOH were put, and thereafter the mixture obtained was heated to 50° C. with stirring. At the time it reached 50° C., 1.0 L of an aqueous 30 w/v % formaldehyde solution (formaldehyde: 10 mols) was added dropwise over a period of 1 hour. During the addition, the internal temperature of this reaction vessel was so controlled not to become higher than 55° C. Next, the reaction mixture thus obtained was heated to 85° C., and was allowed to react at 85° C. for 3 hours. Thereafter, the reaction mixture obtained was cooled to obtain an alkaline solution of a condensation product (Condensation Product No. 11). The Condensation Product No. 11 had a weight-average molecular weight of 2,200. 
     Preparation of First Coating liquid 
     Preparation of first coating liquid Nos.101-114 
     Using a conjugated  bond compound, pH adjuster and solvent shown in Table 1, first coating liquids were so prepared as to meet the conditions shown in Table 1 [conjugated  bond compound (A), auxiliary agent (B), pH adjuster, (A)/(B) weight ratio, (A)+(B) total concentration, solvent composition, and pH]. In the table, the coating liquid No. 102 is a coating liquid containing a scale preventive agent in a low concentration, to be used for spray coating. 
     Preparation of coating liquid Nos. 115-119 
     The following compounds I to V were used as a conjugated  bond compound. 
     I: phenanthrene-1,4-quinone 
     II: quinizarine 
     III: 1,5-diaminonaphthalene 
     IV: 1,4-diaminoanthrathene 
     V: 1,2-naphthoquinone 
     Using a compound above, a pH adjuster and a solvent shown in Table 2, first coating liquids were so prepared as to meet the conditions shown in Table 2 [conjugate  bond compound (A), auxiliary agent (B), pH adjuster, (A)/(B) weight ratio, (A)+(B) total concentration, solvent composition, and pH]. 
     In the following table, the condensation product is simply called “CP”. For example, “CP 9” stands for “Condensation Product No. 9”. 
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                   
                   
                 (A) + (B) 
                   
                   
               
               
                   
                   
                   
                   
                   
                 Coating 
               
               
                 First 
                 Conjugated 
                   
                   
                 (A/B) 
                 liquid 
               
               
                 coating 
                 π bond 
                 Auxiliary 
                 pH 
                 (weight 
                 concentration 
                   
                 Coating 
               
               
                 liquid No. 
                 compound (A) 
                 agent (B) 
                 adjuster 
                 ratio) 
                 (wt %) 
                 Solvent 
                 liquid pH 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 101 
                 CP9 
                 None 
                 NaOH 
                 — 
                 6 
                 water 
                 12.5 
               
               
                 102 
                 CP9 
                 Colloidal silica 
                 NaOH 
                 100/100 
                 0.5 
                 water 
                 10.5 
               
               
                 103 
                 CP1 
                 None 
                 NaOH 
                 — 
                 4 
                 water/methanol 70/30 
                 12.5 
               
               
                 104 
                 CP2 
                 none 
                 KOH 
                 — 
                 4 
                 Water 
                 13.0 
               
               
                 105 
                 CP3 
                 none 
                 NaOH 
                 — 
                 4 
                 water 
                 12.5 
               
               
                 106 
                 CP4 
                 none 
                 ethylenediamine 
                 — 
                 4 
                 water/methanol 80/20 
                 9.0 
               
               
                 107 
                 CP5 
                 none 
                 NaOH 
                 — 
                 3.5 
                 water 
                 13.0 
               
               
                 108 
                 CP6 
                 none 
                 KOH 
                 — 
                 3.5 
                 water 
                 12.0 
               
               
                 109 
                 CP7 
                 none 
                 nitric acid 
                 — 
                 5 
                 water 
                 4.5 
               
               
                 110 
                 CP8 
                 none 
                 NaOH 
                 — 
                 5 
                 water 
                 12.5 
               
               
                 111 
                 CP9 
                 none 
                 ethylenediamine 
                 — 
                 5 
                 water 
                 11.0 
               
               
                 112 
                  CP10 
                 none 
                 NaOH 
                 — 
                 4 
                 water 
                 12.0 
               
               
                 113 
                  CP11 
                 none 
                 NaOH 
                 — 
                 4 
                 water 
                 12.5 
               
               
                 114 
                  CP10 
                 none 
                 none 
                 — 
                 4 
                 N-methyl-2-pyrrolidone 
                 — 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                   
                   
                   
                 (A) + (B) 
                   
                   
               
               
                   
                   
                   
                   
                   
                 Coating 
               
               
                 First 
                 Conjugated 
                   
                   
                 (A/B) 
                 liquid 
               
               
                 coating 
                 π bond 
                 Auxiliary 
                 pH 
                 (weight 
                 concentration 
                   
                 Coating 
               
               
                 liquid No. 
                 compound (A) 
                 agent (B) 
                 adjuster 
                 ratio) 
                 (wt %) 
                 Solvent 
                 liquid pH 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 115 
                 I 
                 none 
                 ethylenediamine 
                 — 
                 4 
                 water 
                 13.0 
               
               
                 116 
                 II 
                 none 
                 NaOH 
                 — 
                 4 
                 water 
                 12.5 
               
               
                 117 
                 III 
                 none 
                 none 
                 — 
                 4 
                 methanol 
                 — 
               
               
                 118 
                 IV 
                 none 
                 none 
                 — 
                 4 
                 mehtanol 
                 — 
               
               
                 119 
                 V 
                 none 
                 none 
                 — 
                 4 
                 N-methyl-2-pyrrolidone 
                 — 
               
               
                   
               
            
           
         
       
     
     Preparation of Second Coating liquid 
     Preparation of second coating liquid Nos.201-218 
     Using an auxiliary agent (B), a pH adjuster and a solvent shown in Tables 3 and 4, second coating liquids were so prepared as to meet the conditions shown in Tables 3 and 4 [auxiliary agent (B), weight ratio of (1)/(2), (3) or (4), total concentration of auxiliary agent (B), solvent, pH adjuster, and pH]. In the Table 3, the coating liquid No. 202 is a comparative coating liquid containing a scale preventive agent in a relatively low concentration, to be used for spray coating. In coating liquids making use of a water-soluble polymeric compound, when the water-soluble polymeric compound (B) was soluble with difficulty, the solvent was heated to about 70° C. to effect dissolution. 
     
       
         
           
               
               
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                   
                 Auxiliary agent (B) 
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 Second 
                 Water- 
                   
                   
                   
                 Weight ratio 
                 Total 
                   
                   
                   
               
               
                 coating 
                 soluble 
                 Inorganic 
                 Inorganic 
                 Acid 
                 of (1)/(2), 
                 concentration 
                   
                 pH 
                 Coating 
               
               
                 liquid 
                 polymer (1) 
                 colloid (2) 
                 salt (3) 
                 (4) 
                 (3) or (4) 
                 of (B) (wt %) 
                 Solvent 
                 adjuster 
                 liquid pH 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 201 
                 polyvinyl 
                 — 
                 — 
                 — 
                 — 
                 1.5 
                 water 
                 none 
                 7.5 
               
               
                   
                 pyrrolidone 
               
               
                 202 
                 polyvinyl 
                 colloidal 
                 — 
                 — 
                 100/50 
                 0.6 
                 water 
                 none 
                 8.5 
               
               
                   
                 pyrrolidone 
                 silica 
               
               
                 203 
                 — 
                 colloidal 
                 — 
                 — 
                 — 
                 3.0 
                 water 
                 none 
                 9.5 
               
               
                   
                   
                 silica 
               
               
                 204 
                 — 
                 — 
                 water 
                 — 
                 — 
                 1.5 
                 water 
                 none 
                 12.5 
               
               
                   
                   
                   
                 glass 
               
               
                 205 
                 — 
                 — 
                 — 
                 phitic 
                 — 
                 2.0 
                 water/methanol 70/30 
                 none 
                 1.3 
               
               
                   
                   
                   
                   
                 acid 
               
               
                 206 
                 polyvinyl 
                 — 
                 — 
                 — 
                 — 
                 2.0 
                 water 
                 none 
                 7.5 
               
               
                   
                 pyrrolidone 
               
               
                 207 
                 gelatin 
                 — 
                 — 
                 — 
                 — 
                 1.0 
                 water 
                 N a OH 
                 8.5 
               
               
                 208 
                 pectin acid 
                 — 
                 — 
                 — 
                 — 
                 1.5 
                 water 
                 none 
                 7.0 
               
               
                 209 
                 casein 
                 — 
                 — 
                 — 
                 — 
                 3.5 
                 water/ethanol 90/10 
                 KOH 
                 7.5 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                   
                 Auxiliary agent (B) 
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 Second 
                 Water- 
                   
                   
                   
                 Weight ratio 
                 Total 
                   
                   
                   
               
               
                 coating 
                 soluble 
                 Inorganic 
                 Inorganic 
                 Acid 
                 of (1)/(2), 
                 concentration 
                   
                 pH 
                 Coating 
               
               
                 liquid 
                 polymer (1) 
                 colloid (2) 
                 salt (3) 
                 (4) 
                 (3) or (4) 
                 of (B) (wt %) 
                 Solvent 
                 adjuster 
                 liquid pH 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 210 
                 polyvinyl 
                 colloidal silica 
                 — 
                 — 
                 100/50 
                 1.5 
                 water 
                 ethylenediamine 
                 9.0 
               
               
                   
                 pyrrolidone 
               
               
                 211 
                 polyvinyl 
                 — 
                 pyrophosphoric 
                 — 
                 100/10 
                 1.1 
                 water 
                 none 
                 7.0 
               
               
                   
                 pyrrolidone 
                   
                 acid calcium 
               
               
                 212 
                 polyvinyl 
                 — 
                 — 
                 phitic acid 
                  100/100 
                 2.0 
                 water 
                 none 
                 1.5 
               
               
                   
                 pyrrolidone 
               
               
                 213 
                 polyvinyl 
                 — 
                 — 
                 sulfuric acid 
                 100/50 
                 1.5 
                 water 
                 none 
                 1.0 
               
               
                   
                 pyrrolidone 
               
               
                 214 
                 gelatin 
                 colloidal silica 
                 — 
                 — 
                  100/100 
                 1.0 
                 water 
                 N a OH 
                 9.0 
               
               
                 215 
                 gelatin 
                 — 
                 — 
                 phosphoric acid 
                 100/50 
                 1.5 
                 water 
                 none 
                 1.5 
               
               
                 216 
                 polyacrylic 
                 — 
                 pyrophosphoric 
                 — 
                 100/20 
                 1.2 
                 water 
                 none 
                 2.5 
               
               
                   
                 acid 
                   
                 acid calcium 
               
               
                 217 
                 polyacrylic 
                 — 
                 — 
                 tannic acid 
                  100/100 
                 2.0 
                 water 
                 none 
                 1.0 
               
               
                   
                 acid 
               
               
                 218 
                 pectic acid 
                 — 
                 — 
                 phosphomolybdic 
                 100/50 
                 1.5 
                 water 
                 none 
                 1.0 
               
               
                   
                   
                   
                   
                 acid 
               
               
                   
               
            
           
         
       
     
     Example 1 
     FIG. 2 schematically illustrates the arrangement of a polymerization apparatus. In respect to a polymerization vessel, the same elements as in FIG. 1 are denoted with the same numerals. The following experiments were made using a polymerization apparatus shown in FIG.  2 . In FIG. 2, a 2 m 3  internal volume polymerization vessel  1  made of SUS 316L stainless steel is equipped with a stirrer  21  having stirring blades  20  (a stirring motor is not shown), a heating-cooling jacket  2 , a manhole  22 , a baffle  23  and other fittings (not shown) usually providing for polymerization vessels for polymerizing vinyl chloride. A line  24  connected to the upper part of the polymerization vessel  1  is a line for charging materials. To the line  24 , branch lines such as a vinyl chloride monomer (VCM) charging line  24   a , a catalyst solution charging line  24   b , a suspending agent charging line  24   c  and a pure-water charging line  24   d  are connected as shown in FIG.  2 . This charging lines  24  and  24   a - 24   d  are provided with valves V 1 , V 2 , V 3 , V 4  and V 5  at the positions shown in the drawing. A line  25  also connected to the upper part of the polymerization vessel  1  is provided in order to evacuate the inside of the polymerization vessel  1  and to recover monomers, and is led to a gas holder  27  through a line  26  branched from the line  25 . A monomer recovery line  28  is led out of the gas holder  27 , and a line  29  led out of the gas holder  27  is connected to the line  25  so as to be used in pressure equalization described later. These lines  25 ,  26 ,  28  and  29  are provided with valves V 6 , V 7 , V 8 , V 9 , V 10 , V 11 , V 12  and V 13 . The line  26  is branched into a line  26   a  provided with a vacuum pump  30  so that monomers can be recovered and a line  26   b  with no pump, and thereafter the branched lines are joined together to form a single line which is connected to the gas holder  27 . To the upper part of the polymerization vessel  1 , a line  31  is also connected in order to wash the inside of the polymerization vessel with water. The line  31  is provided with valves  14  at the position shown in the drawing and has a nozzle  32  at the end introduced inside the vessel. To the upper part of the polymerization vessel  1 , a first coating liquid feed line  34  and a second coating liquid feed line  35  are connected to a coating liquid feed line  33  through valves V 17  and V 18 , respectively, as shown in the drawing. Further, to the line  33  a steam feed line  36  is connected via a valve V 19 . The line  33  is provided at its end located inside the vessel with a coating ring  4  to which coating nozzles  3   a ,  3   b  are attached. This line  33  is provided with valves V 15  and V 16  at the positions shown in the drawing. To the bottom of the polymerization vessel  1 , a line  37  is connected, which is branched into a line  38   a  through which polymer slurry is led to a blow-down tank and a line  38   b  through which the coating liquids or washing water is discharged. The lines  38 ,  38   a  and  38   b  are provided with valves V 20 , V 21  and V 22  at the positions shown in the drawing. 
     In each experiment, the coating liquids were previously coated on the polymerization vessel inner wall surfaces and others in the manner as described below, followed optionally by drying to form a coating film. In the polymerization vessel, vinyl chloride monomers were polymerized in the manner as described below. 
     (1) Coating and drying: 
     The coating film is formed on the inner wall surfaces and others of the polymerization vessel of the polymerization apparatus shown in FIG. 2, by a method of a), b), c) or d) below. Methods a), b) and c) are methods of comparative examples. In the initial stage of each method, all of the valves are closed. 
     a) One-liquid spray coating and drying: 
     Hot water is passed through the jacket  2  to keep the polymerization vessel  1  inner wall surfaces heated to a temperature of 70° C. (Time for preheating with the jacket: 10 minutes). The valves V 17 , V 16 , V 15 , V 20  and V 22  are opened, and the first coating liquid containing a scale preventive agent is coated at a flow rate of 5 L (liter)/min for 1.5 minutes. The valves V 17 , V 16 , V 15 , V 20  and V 22  are closed, and then the valves V 6 , V 8 , V 13 , and V 9  are opened, where the vacuum pump  30  is actuated to evacuate the inside to 8.0 kPa (−700 mmHg and the wet coating is dried (drying is necessary; drying time: 25 minutes) to form a coating film. Thereafter, the vacuum pump is stopped and the valves V 8 , V 13 , and V 9  are closed. Next, the valves V 7  and V 10  are opened to make the internal pressure of the polymerization vessel  1  equal to the internal pressure of the gas holder  27 . Thereafter, the valves V 6 , V 7  and V 10  are closed. The feeding of hot water to the jacket  2  is stopped. 
     b) Two-liquid two-stage spray coating and drying: 
     Hot water is passed through the jacket  2  to keep the polymerization vessel  1  inner wall surfaces heated to a temperature of 70° C. (Time for preheating with the jacket: 10 minutes). The valves V 17 , V 16 , V 15 , V 20  and V 22  are opened, and the coating liquid containing a scale preventive agent (for under coating) is coated at a flow rate of 5 L/min for 1.5 minutes. The valves V 17 , V 16 , V 15 , V 20  and V 22  are closed, and then the valves V 6 , V 8 , V 13 , and V 9  are opened, where the vacuum pump  30  is actuated to evacuate the inside to 8.0 kPa (−700 mmHg) and the wet coating is dried (drying is necessary; drying time: 25 minutes) to form a first layer. Thereafter, the vacuum pump is stopped and the valves V 8 , V 13 , and V 9  are closed. Next, the valves V 7  and V 10  are opened to make the internal pressure of the polymerization vessel  1  equal to the internal pressure of the gas holder  27 . Thereafter, the valves V 6 , V 7  and V 10  are closed. Next, the valves V 18 , V 16 , V 15 , V 20  and V 22  are opened, and the coating liquid containing a polymer scale preventive auxiliary agent (for top coating) is coated on the above first layer at a flow rate of 5 L/min for 1.5 minutes. The valves V 18 , V 16 , V 15 , V 22  and V 20  are closed, and then the valves V 6 , V 8 , V 13 , and V 9  are opened, where the vacuum pump  30  is actuated to evacuate the inside to −700 mm Hg and the wet coating is dried (drying is necessary; drying time: 25 minutes) to form a second layer. Thereafter, the vacuum pump is stopped and the valves V 8 , V 13 , and V 9  are closed. Next, the valves V 7  and V 10  are opened to make the internal pressure of the polymerization vessel  1  equal to the internal pressure of the gas holder  27 . Thereafter, the valves V 6 , V 7  and V 10  are closed. The feeding of hot water to the jacket  2  is stopped. 
     c) One-liquid steam coating (and simultaneous drying): 
     Hot water is passed through the jacket  2  to keep the polymerization vessel  1  inner surfaces heated to a temperature of 70° C. (Time for preheating with the jacket: 10 minutes). The valves V 19 , V 22 , V 20 , V 15  and V 16  are opened, and 392 kPa·Gauge (4 kgf/cm 2 ·G) (143° C.) of steam is blown into the polymerization vessel at a flow rate of 240 kg/Hr for 3 minutes. After the inside of the vessel is pre-heated, the valve V 17  is opened, and the coating liquid containing a scale preventive agent is coated and dried simultaneously at a flow rate of 0.2 L/min for 2 minutes while utilizing the steam as a carrier. Thereafter, the valves V 19 , V 22 , V 20 , V 15 , V 16  and V 17  are closed. The feeding of hot water to the jacket  2  is stopped. 
     d) Two-liquld one-stage steam coating (and simultaneous drying): 
     (1) Coating and drying 
     Hot water is passed through the jacket  2  to keep the polymerization vessel  1  inner wall surfaces heated to a temperature of 70° C. (Time for preheating with the jacket: 10 minutes). The valves V 9 , V 22 , V 20 , V 15  and V 16  are opened, and 392 kPa·Gauge (4 kgf/cm 2 ·G) (143° C.) of steam is blown into the polymerization vessel  1  at a flow rate of 240 kg/Hr for 3 minutes. After the inside of the vessel is pre-heated, the valve V 17  is opened and, substantially at the same time when the valve  17  is opened, the valve  18  is opened, where the first coating liquid containing a scale preventive agent and the second coating liquid containing an auxiliary agent are coated and dried simultaneously at a flow rate of 0.2 L/min for 2 minutes and at a flow rate of 0.1 L/min for 2 minutes, respectively, while utilizing the steam as a carrier, to form a coating film. Thereafter, the valves  17  and  18  are closed. Further thereafter, the valves V 19 , V 22 , V 20 , V 15  and V 16  are closed. The feeding of hot water to the jacket  2  is stopped. 
     (2) Second water washing for inside of the vessel: 
     The valves V 14 , V 20 , V 22 , V 6 , V 7  and V 10  are opened to wash the inside of the polymerization vessel with water, and the wash water is discharged to a waste water tank. The valves V 14 , V 20  and V 22  are closed. 
     The time for washing with water is four (4) minutes when the method a) or b) is used, and it is one (1) minute when the method c) or d) is used. 
     (3) Charging: 
     The valves V 1 , V 2  and V 3  are opened, and 200 parts by weight of pure water, 0.022 part by weight of partially saponified polyvinyl alcohol and 0.028 part by weight of hydroxymethyl cellulose are charged into the polymerization vessel  1 . The valves V 1 , V 2 , V 3 , V 6 , V 7  and V 10  are closed. 
     Next, the valves V 1  and V 5  are opened, and 100 parts by weight of vinyl chloride monomer (VCM) is charged. Then the valve V 5  is closed. Next, with the charged materials being stirred, the valve V 4  is opened, and 0.03 part by weight of t-butyl peroxyneodecanate is charged. Then the valves V 1  and V 4  are closed. 
     (4) Polymerization: 
     Hot water is passed through the jacket  2  to raise the temperature while stirring the materials charged. At the time the internal temperature has reached 52° C., cooling water is passed through the jacket  2  to maintain the internal temperature at 52° C., where the polymerization is carried out. At the time the internal pressure has dropped to 490 kPa·Gauge (5 kgf/cm 2 ·G), the polymerization is terminated. 
     (5) Gas discharging: 
     The valves V 6 , V 8 , V 12  and V 9  are kept open, and gas is discharged to the gas holder  27  until the internal pressure returns to substantially the atmospheric pressure. Thereafter, the valves V 12 , V 8  and V 9  are closed. Then the valves V 11  and V 10  are opened, and monomers recovered in the gas holder  27  is sent to the step of recovering the VCM through line  28 . Thereafter, the valves V 11  and V 10  are closed. 
     (6) Pressure equalization: 
     The valves V 7  and V 10  are opened, and the internal pressure of the polymerization vessel  1  and the internal pressure of the gas holder  27  are made equal (pressure equalization). 
     (7) Slurry withdrawing: 
     The valves V 20  and V 21  are opened, and polymerization slurry is withdrawn out of the vessel to the blow-down tank (not shown). The polymerization slurry withdrawn to the blow-down tank is thereafter dehydrated and dried to become a vinyl chloride polymer product. 
     (8) Vessel-inside first washing: 
     The valve V 14  is opened. The inside of the polymerization vessel  1  is washed with water, and the wash water is sent to the blow-down tank. Thereafter, the valves V 14 , V 20 , V 21 , V 6 , V 7  and V 10  are closed. During this washing of the inside of the vessel, hot water is passed through the jacket  2  to keep the temperature of the polymerization vessel wall surfaces at 70° C. 
     The coating solution and coating film forming method used in each experiment are shown in Table 5. 
     In each experiment, the operation from the (1) coating and drying up to the (8) first washing after completion of polymerization is set as one batching. The like operation was repeated by the number of batching as shown in Table 7. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                   
                   
                 First 
                 Second 
               
               
                   
                   
                 coating 
                 coating 
               
               
                 Experiment 
                   
                 liquid 
                 liquid 
               
               
                 No. 
                 Coating film forming method 
                 No. 
                 No. 
               
               
                   
               
             
            
               
                 101 
                 d)two-liquid one-stage steam coating 
                 101 
                 201 
               
               
                  102* 
                 c)one-liquid steam coating 
                 101 
                 none 
               
               
                  103* 
                 a)one-liquid spray coating 
                 102 
                 none 
               
               
                  104* 
                 a)one-liquid spray coating 
                 none 
                 202 
               
               
                  105* 
                 b)two-liquid spray coating 
                 102 
                 202 
               
               
                 106 
                 d)two-liquid one-stage steam coating 
                 111 
                 203 
               
               
                 107 
                 d)two-liquid one-stage steam coating 
                 111 
                 204 
               
               
                 108 
                 d)two-liquid one-stage steam coating 
                 111 
                 205 
               
               
                 109 
                 d)two-liquid one-stage steam coating 
                 111 
                 206 
               
               
                 110 
                 d)two-liquid one-stage steam coating 
                 111 
                 207 
               
               
                 111 
                 d)two-liquid one-stage steam coating 
                 111 
                 208 
               
               
                 112 
                 d)two-liquid one-stage steam coating 
                 103 
                 209 
               
               
                 113 
                 d)two-liquid one-stage steam coating 
                 104 
                 210 
               
               
                 114 
                 d)two-liquid one-stage steam coating 
                 105 
                 211 
               
               
                 115 
                 d)two-liquid one-stage steam coating 
                 106 
                 212 
               
               
                 116 
                 d)two-liquid one-stage steam coating 
                 107 
                 213 
               
               
                 117 
                 d)two-liquid one-stage steam coating 
                 108 
                 214 
               
               
                 118 
                 d)two-liquid one-stage steam coating 
                 109 
                 215 
               
               
                 119 
                 d)two-liquid one-stage steam coating 
                 110 
                 216 
               
               
                 120 
                 d)two-liquid one-stage steam coating 
                 111 
                 217 
               
               
                 121 
                 d)two-liquid one-stage steam coating 
                 112 
                 218 
               
               
                 122 
                 d)two-liquid one-stage steam coalting 
                 113 
                 211 
               
               
                 123 
                 d)two-liquid one-stage steam coating 
                 114 
                 211 
               
               
                 124 
                 d)two-liquid one-stage steam coating 
                 105 
                 212 
               
               
                 125 
                 d)two-liquid one-stage steam coating 
                 105 
                 215 
               
               
                 126 
                 d)two-liquid one-stage steam coating 
                 115 
                 215 
               
               
                 127 
                 d)two-liquid one-stage steam coating 
                 116 
                 216 
               
               
                 128 
                 d)two-liquid one-stage steam coating 
                 117 
                 217 
               
               
                 129 
                 d)two-liquid one-stage steam coating 
                 118 
                 218 
               
               
                 130 
                 d)two-liquid one-stage steam coating 
                 119 
                 215 
               
               
                   
               
               
                 (Remarks) *Comparative Example  
               
            
           
         
       
     
     &lt;Evaluation&gt; 
     In each experiment, measurement was made on the following items to make evaluation. The results are shown in Tables 6, 7 and 8. 
     Time required to form coating films 
     The time taken for the formation of coating films in Examples and Comparative Examples is shown in Table 6. 
     Measurement of the amount of polymer scale deposited 
     In each experiment, after the final batching was completed, polymer scale built-up at the liquid-phase portion in the polymerization vessel and polymer scale built-up on the surfaces of stirring blades and baffles and on and in the vicinity of the boundary between the gas-phase portion and the liquid-phase portion were determined in the following way. 
     The scale deposited in an area of 10 cm×10 cm at a surface to be measured was scraped off with a spatula as completely as can be confirmed with the naked eye, and then the scraped scale was weighed on a balance. The measured value was multiplied by 100 to obtain the amount of the deposited polymer scale per area of 1 m 2 . The results are given in Table 7. 
     Measurement of fish eyes 
     Fish eyes produced when a polymeric product obtained at the final batching in each experiment is formed into sheet, were measured by the method below. 
     A hundred (100) parts by weight of a polymer obtained, 50 parts by weight of dioctyl phthalate (DOP), 1 part by weight of dibutyltin dilaurate, 1 part by weight of cetyl alcohol, 0.25 part by weight of titanium oxide and 0.05 part by weight of carbon black were mixed. The resulting mixture was kneaded at 150° C. for 7 minutes with 6 inch rolls, and then formed into a sheet 0.2 mm thick. The obtained sheet was examined for the number of fish eyes per 100 cm 2  by light transmission. The results are given in Table 8. 
     Measurement of luminosity index (L value) 
     Measurement of luminosity index (L value) of a sheet formed from a polymer obtained in each experiment was carried out, according to the method below. The results are given in Table 8. 
     A hundred (100) parts by weight of an obtained polymer, 1 part by weight of a dibutyltin laurate stabilizing agent (TS-101, product of Akisima Chemical Co.) and 0.5 part by weight of a cadmium organic complex stabilizing agent (C-100J, product of Katsuta Kako Co.), and 50 parts by weight of dioctyl phthalate as a plasticizer were kneaded at 160° C. for 5 minutes with a twin roll mill, and then formed into a sheet 1 mm thick. Subsequently, this sheet was placed in a molding frame measuring 4×4×1.5 cm, heated at 160° C. under a pressure of 6.37 to 6.87 MPa·Gauge (65 to 70 kgf/cm 2 ·G) to prepare a test specimen. This test specimen was measured for luminosity index L in the following way. 
     First, the stimulus value Y of XYZ color system is determined by the photoelectric tristimulus colorimetry using the standard light C, photoelectric colorimeter (Color measuring color difference meter Model Z-1001DP, product of Nippon Denshoku Kogyo K.K.) in accordance with JIS Z 8722. As the geometric condition of illumination and light reception, the condition d defined in section 4.3.1 of JIS Z 8722 is adopted. 
     Next, from the stimulus value Y obtained, the L value is calculated based on the Hunter&#39;s color difference equation: L=10Y ½  described in JIS Z 8730 (1980). The greater the value of L, the higher the whiteness is evaluated, namely, the better the initial anti-discoloration properties are. 
     Examination of colored particles: 
     A mixture of 100 parts by weight of the polymer obtained in each experiment after the final batching was completed, 2 parts by weight of a stabilizer TVS N-2000E (available from Nitto Kasei Co., Ltd.) and 20 parts by weight of a plasticizer dioctyl phthalate was thoroughly kneaded and thereafter put in a molding frame of 160 mm×130 mm×3 mm, and was subsequently pressure-molded at a temperature of 175° C. and a pressure of 3.43 MPa·Gauge (35 kgf/cm 2 ·G) to obtain a sample for examination. Samples thus obtained were examined visually on the number of colored particles. The results are shown in Table 8. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 6 
               
             
            
               
                   
                   
               
               
                   
                 Spray coating 
                 Steam coating 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 b) Two- 
                   
                 d) Two- 
               
               
                   
                   
                 liquid 
                   
                 liquid 
               
               
                   
                 a) One- 
                 two- 
                 c) One- 
                 one- 
               
               
                   
                 liquid 
                 stages 
                 liquid 
                 stage 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Jacket pre-heating time (min) 
                 10.0 
                 10.0 
                 10.0 
                 10.0 
               
               
                 Steam pre-heating time (min) 
                 0 
                 0 
                 3.0 
                 3.0 
               
               
                 First-liquid coating time (min) 
                 1.5 
                 1.5 
                 2.0 
                 2.0 
               
               
                 First-liquid drying time (min) 
                 25.0 
                 25.0 
                 0 
                 0 
               
               
                 Second-liquid coating time (min) 
                 0 
                 1.5 
                 0 
                 2.0 
               
               
                 Second-liquid drying time (min) 
                 0 
                 25.0 
                 0 
                 0 
               
               
                 Water washing time (min) 
                 4.0 
                 4.0 
                 1.0 
                 1.0 
               
               
                 (second washing) 
               
               
                 Total time (min) 
                 40.5 
                 67.0 
                 16.0 
                 16.0 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                   
                 TABLE 7 
               
             
            
               
                   
                   
               
               
                   
                 Scale build-up (g/m2) 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                   
                 Liquid 
                 Vicinity of 
                   
                   
               
               
                 Experiment 
                 Number of 
                 phase 
                 gas-liquid 
                 Stirring 
               
               
                 No. 
                 batches 
                 portion 
                 interface 
                 blade 
                 Baffle 
               
               
                   
               
               
                 101 
                 250 
                 0 
                 0 
                 0 
                 3 
               
               
                  102* 
                 250 
                 0 
                 45  
                 8 
                 10  
               
               
                  103* 
                 250 
                 0 
                 0 
                 85  
                 120  
               
               
                  104* 
                  20 
                 26  
                 185  
                 270  
                 335  
               
               
                  105* 
                 250 
                 0 
                 0 
                 51  
                 65  
               
               
                 106 
                 250 
                 0 
                 0 
                 0 
                 7 
               
               
                 107 
                 250 
                 0 
                 0 
                 0 
                 6 
               
               
                 108 
                 250 
                 0 
                 0 
                 0 
                 4 
               
               
                 109 
                 250 
                 0 
                 0 
                 0 
                 5 
               
               
                 110 
                 250 
                 0 
                 0 
                 0 
                 4 
               
               
                 111 
                 250 
                 0 
                 0 
                 0 
                 6 
               
               
                 112 
                 250 
                 0 
                 0 
                 0 
                 5 
               
               
                 113 
                 250 
                 0 
                 0 
                 0 
                 7 
               
               
                 114 
                 250 
                 0 
                 0 
                 0 
                 7 
               
               
                 115 
                 250 
                 0 
                 0 
                 0 
                 4 
               
               
                 116 
                 250 
                 0 
                 0 
                 0 
                 5 
               
               
                 117 
                 250 
                 0 
                 0 
                 0 
                 5 
               
               
                 118 
                 250 
                 0 
                 0 
                 0 
                 4 
               
               
                 119 
                 250 
                 0 
                 0 
                 0 
                 7 
               
               
                 120 
                 250 
                 0 
                 0 
                 0 
                 5 
               
               
                 121 
                 250 
                 0 
                 0 
                 0 
                 7 
               
               
                 122 
                 250 
                 0 
                 0 
                 0 
                 7 
               
               
                 123 
                 250 
                 0 
                 0 
                 0 
                 6 
               
               
                 124 
                 250 
                 0 
                 0 
                 0 
                 5 
               
               
                 125 
                 250 
                 0 
                 3 
                 2 
                 7 
               
               
                 126 
                 250 
                 0 
                 4 
                 2 
                 8 
               
               
                 127 
                 250 
                 0 
                 3 
                 3 
                 8 
               
               
                 128 
                 250 
                 0 
                 3 
                 3 
                 7 
               
               
                 129 
                 250 
                 0 
                 4 
                 3 
                 9 
               
               
                 130 
                 250 
                 0 
                 3 
                 2 
                 7 
               
               
                   
               
               
                 (Remarks) *Comparative Example  
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 8 
               
             
            
               
                   
               
               
                 Scale build-up and quality 
               
            
           
           
               
               
               
               
            
               
                 Experiment 
                 Fish eyes 
                 Luminosity index 
                 Colored particles 
               
               
                 No. 
                 (number) 
                 (L value) 
                 (number) 
               
               
                   
               
               
                 101 
                 1 
                 73.0 
                 3 
               
               
                  102* 
                 19  
                 72.0 
                 25  
               
               
                  103* 
                 32  
                 72.0 
                 76  
               
               
                  104* 
                 110  
                 72.0 
                 82  
               
               
                  105* 
                 11  
                 72.0 
                 31  
               
               
                 106 
                 2 
                 73.0 
                 3 
               
               
                 107 
                 1 
                 73.0 
                 2 
               
               
                 108 
                 2 
                 73.0 
                 4 
               
               
                 109 
                 1 
                 73.0 
                 2 
               
               
                 110 
                 1 
                 73.0 
                 3 
               
               
                 111 
                 1 
                 73.0 
                 2 
               
               
                 112 
                 1 
                 73.0 
                 2 
               
               
                 113 
                 2 
                 73.0 
                 4 
               
               
                 114 
                 2 
                 73.0 
                 4 
               
               
                 115 
                 1 
                 73.0 
                 3 
               
               
                 116 
                 2 
                 73.0 
                 5 
               
               
                 117 
                 2 
                 73.0 
                 3 
               
               
                 118 
                 1 
                 73.0 
                 3 
               
               
                 119 
                 1 
                 73.0 
                 3 
               
               
                 120 
                 1 
                 73.0 
                 3 
               
               
                 121 
                 1 
                 73.0 
                 4 
               
               
                 122 
                 2 
                 73.0 
                 5 
               
               
                 123 
                 2 
                 73.0 
                 5 
               
               
                 124 
                 2 
                 73.0 
                 4 
               
               
                 125 
                 7 
                 73.0 
                 9 
               
               
                 126 
                 5 
                 73.0 
                 8 
               
               
                 127 
                 6 
                 73.0 
                 10  
               
               
                 128 
                 6 
                 73.0 
                 9 
               
               
                 129 
                 5 
                 73.0 
                 7 
               
               
                 130 
                 7 
                 73.0 
                 10  
               
               
                   
               
               
                 (Remarks) *Comparative Example