Method for polymerizing vinyl monomers in a coated reactor

Abstract: A process for producing a polymer by polymerizing in a polymerization vessel a monomer having an ethylenic double bond is provided. In this process, 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 is formed by coating a coating liquid containing (A) a compound selected from the group consisting of an aromatic compound having 5 or more conjugated π bonds and a heterocyclic compound having 5 or more conjugated π bonds, and (B) a compound selected from the group consisting of an inorganic colloid, a chelate reagent, a metal compound that produces a metal ion capable of forming a complex having at least two coordination numbers, and an acid; the coating liquid being coated by means of steam as a carrier. This process can shorten the time for forming coating films of scale preventive agents to improve productivity, can improve the effect of preventing polymer scales, can make colored particles less which mix into polymer products, can lessen fish eyes and initial discoloring of formed products and can improve the quality of polymeric products and their formed or molded products.

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-liquid coating methods are effective for preventing the adhesion of polymer scales when monomers having ethylenic double bonds are polymerized in polymerization vessels. 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. 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 "steam 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. Accordingly, as a means for achieving the above object, the present invention provides 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 coating liquid containing: (A) a compound selected from the group consisting of an aromatic compound having 5 or more conjugated π bonds and a heterocyclic compound having 5 or more conjugated π bonds; and (B) at least one compound selected from the group consisting of an inorganic colloid, a chelate reagent, a metal compound that produces a metal ion capable of forming a complex having at least two coordination numbers, and an acid; the coating liquid being 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 The present invention will be described below in detail. In the following, the polymer scale preventive agent is called "scale preventive agent". [Component (A)] The aromatic compound and heterocyclic compound used in the first coating liquid each have 5 or more conjugated π bonds. In the present specification, the term "π 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 π bonds" is meant to be a series of π bonds wherein each pair of adjacent π bonds are connected to each other through a single bond and all of the πbonds have a mutually conjugated relationship with each other. The aromatic compound having 5 or more conjugated π bonds and the heterocyclic compound having 5 or more conjugated π bonds are herein called together generically as "conjugated π bond compound" in some cases. The 5 or more π bonds are present in the conjugated π bond compound may form a single conjugation group or two or more conjugation groups. - Aromatic compound having 5 or more conjugated π bonds: The aromatic compound having 5 or more conjugated π 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-methylquinoline; 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-methylfluorine, 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, halodinitro-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, diphenylnaphthylchloromethane 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-dimethylaminoanthracene, 2-anilinoanthracene, 9-methylaminoanthracene, 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 WO98/24820 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. 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 π bonds: The heterocyclic compounds having 5 or more conjugated πbonds 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-acridine 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 π 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. [Component (B)] The component (B) used in the coating liquid will be described below. The component (B) is at least one compound selected from the group consisting of an inorganic colloid, a chelate reagent, a metal compound that produces a metal ion capable of forming a complex having at least two coordination numbers, and an acid. These compounds are described below in order. 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, silver and silver iodide. 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. Chelate reagent The chelate reagent may preferably include (a) compounds not having any acidic coordination group, as exemplified by cationic chelate reagents having a coordination group such as an -NH 2 group (primary amines, amides and hydrazine), an =NH group (secondary amines and hydrazine), an ≡N group (tertiary amines), an -N=N- group (azo compounds and heterocyclic compounds), an -NO 2 group (nitro compounds), an -N=O group (nitroso compounds), a =C=N group (Schiff bases and heterocyclic compounds), a =C=NH group (aldehydes, ketoimines and enamines), an -S- group (thioethers), a =C=S group (thioketones and thioamides), an ≡S group (heterocyclic compounds), an -SCN group (thiocyanato and isothiocyanato), a =C=O group (aldehydes, ketones and quinones), an -O- group (ethers), a -COOR group (esters), an -N=O group (nitroso compounds), and an ≡N→O group (N-oxides); and (b) compounds having an acidic coordination group, as exemplified by anionic chelate reagents having a coordination group such as an -OH group (alcohols), a -COOH group (carboxylic acids), an -SO 2 H group (sulfonic acids), an =N-OH group (oximes), an -SH group (thiols), and a group represented by the formula: (thiocarboxylic acids). These may specifically include the following examples. Diethylenetriamine, triethylenetetramine, triaminotriethylamine, tetrakis(β-aminoester)ethylenediamine, N,N'-dimethylethylenediamine, N,N'-tetramethylethylenediamine, 1,3-diaminorpopane, 1,2-diaminorpopane, bipyridine, terpyridine, o-phenanthroline, thiourea, gluoxazalbis(methylimine), acetylacetone, thenoyltrifluoroacetone, purine, piperidine, histamine, imidazole, 2,2'-diquinolyl, 4,7-diphenyl-1,10-phenanthroline, o-phenylenediamine, 3,3'-diaminobenzidine, diphenylcarpazide, diphenylcarpazone, benzoylmethane, dithizone, diphenyl thiocarodiazone, isonicotinic acid hydrazide, N-dihydroxyethylglycine, iminodiacetic acid, nitrilotriacetic acid, N-hydroxyethyliminodiacetic acid, ethylenediaminetetraacetic acid, N,N'-ethylenediaminediacetic acid, N-hydroxyethylethylenediaminetriacetic acid, diethdylenetriaminepentaacetic acid, 1,2-cyclohexanediaminetetraacetic acid, trimethylenediaminetetraacetic acid, ethylenebis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid, ethylenediaminetetrapropionicdiacetic acid, ethylenediaminedipropionic acid, β-aminoethylphosphonic-N,N-diacetic acid, aminomethylphosphonic-N,N'-diacetic acid, 2,3-dimethylmercaptopropanol, sodium diethyldithiocarbamate, 8-hydroxyquinoline, dimethylglyoxime, glycine, aspartic acid, N,N'-dihydroxyethylethylenediamine, triethanolamine, α-furyldioxime, 1,2-dimercaptopropanol, α-benzoineoxime, thiooxine, and 2-mercaptobenzothiazole. Metal compound that produces metal ion capable of forming complex having at least two coordination numbers The metal compound that produces a metal ion capable of forming a complex having at least two coordination numbers is exemplified by metal compounds that produce metal ions having two coordination numbers such as Cu(I), Ag(I), Hg(I) and Hg(II), metal ions having four coordination numbers such as Be(II), B(III), Zn(II), Cd(II), Hg(II), Al(III), Co(II), Ni(II), Cu(II), Ag(II), Au(III), Pd(II) and Pt(II), metal ions having six coordination numbers such as Ca(II), Sr(II), Ba(II), Ti(IV), V(III), V(IV), Cr(III), Mn(II), Mn(III), Fe(II), Fe(III), Co(II), Co(III), Ni(II), Pd(IV), Cd(II), Al(III), Sc(III), Y(III), Si(IV), Sn(II), Sn(IV), Pb(II), Pb(IV), Ru(III), Rh(III), Os(III), Ir(III) and lanthanoids, metal ions having eight coordination numbers such as Zr(IV), Hf(IV), Mo(IV), W(IV), U(IV) and actinoids, as exemplified by halides, nitrates, sulfates, hydroxides, oxides and organic acid salts (such as oxalates and acetates) of any of these metallic elements. Acid The acid may include inorganic acids such as phosphoric acid, pyrophosphoric acid and polyphosphoric 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, 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. The above component (B) may more preferably be used in combination of two or more types. For example, preferred are use in combination of the chelate reagent with the metal compound that produces a metal ion capable of forming a complex having at least two coordination numbers and use in combination of the chelate reagent with the acid. [Coating Liquid] The coating liquid is prepared by dissolving the above components (A) and (B) 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, acetonitrile, N-methyl-2-pyyrolidone and 1,3-dimethyl-2-imidazolidinone. 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; ester solvents, such as methyl acetate and ethyl acetate; and non-protonic solvents, such as N-methyl-2-pyyrolidone and 1,3-dimethyl-2-imidazolidinone. Particularly, it is preferred that alcohol solvents and non-protonic 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 coating liquid is selected appropriately depending on the kind of the compound used. When the adjustment of pH is required, an acid or an alkali compound may appropriately be used as a pH adjuster. The acid is exemplified by hydrochloric acid, sulfuric acid and nitric acid. The alkali compound is exemplified by alkali metal compounds such as LiOH, NaOH, KOH, Na 2 CO 3 , Na 2 HPO 4 and NH 4 OH. The component (A) in the coating liquid may preferably be in a concentration ranging from 0.5 to 20.0% by weight, and more preferably from 1.0 to 10.0% by weight. If this component is 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 coating film in an effective quantity. If it is in too high a concentration, the coating liquid may become unstable to cause a precipitate during storage in a storage tank, and the coating film formed by coating the coating liquid on the inner wall surfaces and others may have uneven coatings to cause a lowering of the scale preventive effect. The proportion of the component (B) to the component (A) may preferably be 1 to 500 parts by weight, and more preferably 10 to 300 parts by weight, based on 100 parts by weight of the component (A). The component (A) and the component (B) may preferably be in a total concentration ranging from 1.0 to 25.0% by weight, and more preferably from 1.5 to 15.0% by weight. To the coating liquid, in addition to the components (A) and (B), a water-soluble polymeric compound, a surface-active agent, a cross-linking agent and so forth may be added in such an extent that storage stability, adhesion to wall surfaces and uniform-film-forming properties of the coating liquid are not damaged or the effect of the present invention is not damaged. [Carrier Steam] According to the process of the present invention, the coating film is formed by applying the coating liquid 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 form 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 liquid, 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 3b and downward nozzles 3a. 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 the line 5, a steam feed line 6 and the coating liquid feed line 7 are connected through the respective valves. If necessary, the steam (usual steam or superheated steam) may be blown into the vessel from the coating nozzles 3a and 3b 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 8 via a flowmeter 9 through lines 6 and 5. Step 2 . (Coating of coating liquid) The steam is fed to the coating ring 4, and the coating liquid held in a coating liquid tank 10 is fed to the coating ring 4 through lines 7 and 5 by means of a pump 11 or an aspirator valve (not shown). P denotes a pressure g auge. The coating liquids is 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 coating liquid (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 in terms of flow rate ratio on the basis of weight. 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 12. The cleaning water is fed into the polymerization vessel 1 from nozzles 15 through a line 14 by means of a pump 13. 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 0.0005 to 3 g/m 2 , and more preferably from 0.0005 to 1 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 and vinyl 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-cumyl peroxyneodecanoate, cumene hydroperoxide, 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, "auxiliary agent" 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: With reference to Production Example 3 disclosed in Japanese Patent Publication (kokoku) No. 6-62709, a scale preventive agent was produced. Into a pressure-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. 1). The Condensation Product No. 1 had a weight-average molecular weight of 5,400. Production Example 2 Production of Condensation Product No. 2: 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. 2). The Condensation Product No. 2 had a weight-average molecular weight of 2,400. Production Example 3 Production of Condensation Product No. 3: 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. 3 (pyrogallol-benzaldehyde condensate), as a residue. The Condensation Product No. 3 had a weight-average molecular weight of 4,500. Production Example 4 Production of Condensation Product No. 4: 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 (Condensation Product No. 4) thus obtained was pulverized. The Condensation Product No. 4 had a weight-average molecular weight of 1,700. Production Example 5 Production of Condensation Product No. 5: (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 144g (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. 5 being obtained. Incidentally, the reactions were all carried out in N 2 atmospheres. After the completion of the reactions, Condensation Product No. 5 was cooled to 25° C, and then preserved in an N 2 atmosphere. The weight-average molecular weight was 22,000. Production Example 6 Production of Condensation Product No. 6: 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. 6 was obtained. The Condensation Product No. 6 had a weight-average molecular weight of 3,000. Production Example 7 Production of Condensation Product No. 7: 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. 7. The Condensation Product No. 7 had a weight-average molecular weight of 1,200. Production Example 8 Production of Condensation Product No. 8: 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. 8). The Condensation Product No. 8 had a weight-average molecular weight of 2,200. - Preparation of Coating liquids - Preparation of coating liquid Nos.101-129 : Using a conjugated π bond compound, an inorganic colloid, a chelate reagent, a metal compound that produces a metal ion capable of forming a complex having at least two coordination numbers, an acid, a pH adjuster and a solvent which are shown in Tables 1 A and 1 B and Tables 2 A and 2 B, coating liquids were so prepared as to meet the conditions shown in Tables 1 A and 1 B and Tables 2 A and 2 B [conjugated π bond compound (A), auxiliary agent (B), pH adjuster, (A)/(B)-i/(B)-ii/(B)-iii/(B)-iv weight ratio, (A)+(B) total concentration, solvent composition, and pH]. Incidentally, the coating liquid No. 102 is a coating liquid containing a scale preventive agent in a low concentration, to be used for spray coating. Coating liquids Nos. 103, 104, 105, 106, 107, 108, 109 and 110 are coating liquids containing a conventional steam coating scale preventive agent to which the component (B) is not added. Preparation of coating liquid Nos. 130-134: The following compounds I to V were used as a conjugated π bond compound. I: 3,6-Diaminoacrydine II: Phenanthrene-1,4-quinone III: Quinizarine IV: 1,8-Diaminoanthrathene V: Flavonol Using a compound above, a pH adjuster and a solvent shown in Tables 2 A and 2 B, coating liquids were so prepared as to meet the conditions shown in Tables 2 A and 2 B [conjugated π bond compound (A), auxiliary agent (B), pH adjuster, (A)/(B)-i/(B)-ii/(B)-iii/(B)-iv weight ratio, (A)+(B) total concentration, solvent composition, and pH]. In the following table, the condensation product is simply called "CP". For example, "CP1" stands for "Condensation Product No. 1". Experiment No. Conjugated π bond compound (A) Auxiliary agent(B) Inorganic colloid (1) Chelate agent (2) Metal compound that produces metal ion capable of forming complex having at least two coordination numbers (3) Acid (4) 101 CP6 none thiourea calcium pyrophosphate phitc acid 102* CP6 colloidal silica none none none 103* CP1 - - - - 104* CP2 - - - - 105* CP3 - - - - 106* CP4 - - - - 107* CP5 - - - - 108* CP6 - - - - 109* CP7 - - - - 110* CP8 - - - - 111 CP1 colloidal silica - - - 112 CP6 - diethylenetriamine - - 113 CP3 - - pyrophosphoric acid calcium - 114 CP4 - - - pyrophosphoric acid 115 CP5 colloidal silica imidazole - - 116 CP6 colloidal silica - nickel choride - 117 CP7 colloidal silica - - polyphosphoric acid 118 CP8 colloidal silica - - - Experiment No. (A)/(B)-i/(B)-ii/(B)-iii/(B)-iv Weight ratio (A)+(B) Total concentra-tion (wt%) Solvent pH adjuster pH 101 100-/10//10/10 5.0 water/methanol/(60/40) NaOH 12.0 102* 100/100/-/-/- 0.5 water NaOH 10.5 103* 100/- 5.0 water NaOH 12.0 104* 100/- 5.0 water NaOH 12.0 105* 100/- 5.0 water NaOH 12.0 106* 100/- 5.0 water NaOH 12.0 107* 100/- 5.0 water NaOH 12.5 108* 100/- 5.0 water NaOH 12.5 109* 100/- 5.0 water NaOH 12.5 110* 100/- 5.0 water NaOH 12.5 111 100/100/-/-/- 4.0 water NaOH 12.5 112 100/-/30/-/- 5.0 water /ethanol(60/40) KOH 12.0 113 100/-/-/20/- 3.0 water KOH 12.0 114 100/-/-/50 4.0 water - 3.0 115 100/100/30/-/- 6.5 water NaOH 9.0 116 100/100/-/30/- 5.0 water NaOH 8.0 117 100/100/-/-/50 8.5 water/methanol (70/30) - 2.5 118 100/50/-/-/- 5.0 n-methyl-2-pyrrolidone - - Auxiliary agent(B) Experiment No. Conjugated π bond compound (A) Inorganic colloid (1) Chelate agent (2) Metal compound that produces metal ion capable of forming complex having at least two coordination numbers (3) Acid (4) 119 CP1 - dithizone - tannic acid 120 CP2 - 8-hydroxyquinoline - phitic acid 121 CP3 - - titanium sulfate - 122 CP4 - - calcium phosphate phitic acid 123 CP5 - imidazole - terephthalic acid 124 CP6 - triethylenetetramine copper sulfate sulfunilic acid 125 CP7 - 1,3-diaminopropane cobalt chloride - 126 CP8 - thiourea - polyphosphoric acid 127 CP6 - - calcium carbonate salicylic acid 128 CP6 - thiooxine boron oxide - 129 CP6 - triethylenetetramine ferric sulfate - 130 I - thiourea calcium pyrophosphate - 131 II - triethylenetetramine ferric sulfate - 132 III - imidazole - phitic acid 133 IV - diethylenetriamine - phitic acid 134 V - 1.3-diaminopropane - pyrophosphoric acid Experiment No. (A)/(B)-i/(B)-ii/(B)-iii/(B)-iv Weight ratio (A)+(B) Total concentra-tion (wt%) Solvent pH adjuster pH 119 100/-/10/-/10 2.0 water/ methanol/(60/40) - 6.0 120 100/-/10/-/20 5.5 water NaOH 11.0 121 100/-/-/5/- 4.0 water KOH 7.5 122 100/-/-5/5 5.0 water sulfate 4.0 123 100/-/5/-/40 5.0 water NaOH 12.0 124 100/-/5/10/5 5.0 water KOH 11.0 125 100/-/10/20/- 5.0 water KOH 11.0 126 100/-/30/-/10 5.0 water NaOH 10.0 127 100/-/-/10/20 7.0 N-methyl-2-pyyrolidone - - 128 100/-/10/20/- 7.5 water NaOH 11.5 129 100/-/20/10/- 5.0 water NaOH 11.0 130 100/-/20/5/- 5.0 water NaOH 9.5 131 100/-/50/5/- 5.0 water/ methanol(60/40) NaOH 12 132 100/-/20/-/10 5.0 water NaOH 12 133 100/-/20/-/20 5.0 N-methyl-2-pyyrolidone - - 134 100/-/10/-/30 5.0 water - 2.5 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 24a, a catalyst solution charging line 24b, a suspending agent charging line 24c and a pure-water charging line 24d are connected as shown in Fig. 2. This charging lines 24 and 24a-24d are provided with valves V1, V2, V3, V4 and V5 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 V6, V7, V8, V9, V10, V11, V12 and V13. The line 26 is branched into a line 26a provided with a vacuum pump 30 so that monomers can be recovered and a line 26b 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 a valve 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 coating liquid feed line 34 is connected to a coating liquid feed line 33 through a valve V17 as shown in the drawing. Further, to the line 33 a steam feed line 35 is connected via a valve V18. The line 33 is provided at its end located inside the vessel with a coating ring 4 to which coating nozzles 3a, 3b are attached. The line 33 is provided with valves V15 and V16 at the positions shown in the drawing. To the bottom of the polymerization vessel 1, a line 36 is connected, which is branched into a line 37a through which polymer slurry is led to a blow-down tank and a line 37b through which the coating liquids or washing water is discharged. These lines 36, 37a and 37b are provided with valves V19, V20 and V21 at the positions shown in the drawing. Reference Nos. of coating liquids used in each experiment are shown in Tables 4 and 5. 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 V17, V16, V15, V19 and V21 are opened, and the coating liquid is coated at a flow rate of 5 L(liter)/min for 1.5 minutes. The valves V17, V16, V15, V19 and V21 are closed, and then the valves V6, V8, V13, and V9 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 V8, V13, and V9 are closed. Next, the valves V7 and V10 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 V6, V7 and V10 are closed. The feeding of hot water to the jacket 2 is stopped. b) 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 V18, V21, V19, V15 and V16 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 V17 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 V18, V21, V19, V15, V16 and V17 are closed. The feeding of hot water to the jacket 2 is stopped. (2) Second water washing for inside of the vessel: The valves V14, V19, V21, V6, V7 and V10 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 V14, V19 and V21 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 V1, V2 and V3 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 V1, V2, V3, V6, V7 and V10 are closed. Next, the valves V1 and V5 are opened, and 100 parts by weight of vinyl chloride monomer (VCM) is charged. Then the valve V5 is closed. Next, with the charged materials being stirred, the valve V4 is opened, and 0.03 part by weight of t-butyl peroxyneodecanate is charged. Then the valves V1 and V4 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 490kPa·Gauge (5 kgf/cm 2 ·G), the polymerization is terminated. (5) Gas discharging: The valves V6, V8, V12 and V9 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 V12, V8 and V9 are closed. Then the valves V11 and V10 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 V11 and V10 are closed. (6) Pressure equalization: The valves V7 and V10 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 V19 and V20 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 V14 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 V14, V19, V21, V6, V7 and V10 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 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 Tables 4 and 5. <Evaluation> Time required to form coating films The time taken for the formation of coating films in Examples and Comparative Examples is shown in Table 3. 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 x 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 Tables 4 and 5. 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. The results are given in Tables 5 and 6. 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. 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 Tables 5 and 6. 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 x 4 x 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's color difference equation: L=10Y 1/2 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 x 130 mm x 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 Tables 5 and 6. a) Spray coating b) Steam coating Jacket pre-heating time (min) 10.0 10.0 Steam pre-heating time (min) 0 3.0 Coating time (min) 1.5 2.0 Drying time (min) 25.0 0 Water washing time (min) (second washing) 4.0 1.0 Total time (min) 40.5 16.0 Experiment No. Coating film formation Coating liquid No. Number of batches Scale build-up (g/m 2 ) Liquid phase portion Vicinity of gas-liquid interface Stirring blade Baffle 101 b) Steam coating 101 300 0 0 0 0 102* a) Spray coating 102 300 0 0 125 135 103* b) Steam coating 103 300 0 126 28 30 104* b) Steam coating 104 300 0 111 18 21 105* b) Steam coating 105 300 0 108 17 20 106* b) Steam coating 106 300 0 122 21 25 107* b) Steam coating 107 300 0 124 24 27 108* b) Steam coating 108 300 0 105 17 19 109* b) Steam coating 109 300 0 116 20 24 110* b) Steam coating 110 300 0 127 25 29 111 b) Steam coating 111 300 0 0 2 4 112 b) Steam coating 112 300 0 0 5 10 113 b) Steam coating 113 300 0 0 2 5 114 b) Steam coating 114 300 0 0 2 5 115 b) Steam coating 115 300 0 0 4 7 116 b) Steam coating 116 300 0 0 3 7 117 b) Steam coating 117 300 0 0 2 4 118 b) Steam coating 118 300 0 0 4 8 Experiment No. Coating film formation Coating liquid No. Number of batches Scale build-up (g/m 2 ) Liquid phase portion Vicinity of gas-liquid interface Stirring blade Baffle 119 b) Steam coating 119 300 0 0 0 0 120 b) Steam coating 120 300 0 0 0 0 121 b) Steam coating 121 300 0 0 0 0 122 b) Steam coating 122 300 0 0 0 0 123 b) Steam coating 123 300 0 0 0 0 124 b) Steam coating 124 300 0 0 0 0 125 b) Steam coating 125 300 0 0 0 0 126 b) Steam coating 126 300 0 0 0 0 127 b) Steam coating 127 300 0 0 0 0 128 b) Steam coating 128 300 0 0 0 0 129 b) Steam coating 129 300 0 0 0 0 130 b) Steam coating 130 300 0 6 3 12 131 b) Steam coating 131 300 0 7 5 15 132 b) Steam coating 132 300 0 9 4 10 133 b) Steam coating 133 300 0 8 4 13 134 b) Steam coating 134 300 0 8 3 11 Experiment No. Fish eyes (number) Luminosity index (L value) Colored particles (number) 101 1 73.0 4 102 61 72.0 73 103 19 72.0 58 104 16 72.0 50 105 14 72.0 49 106 18 72.0 52 107 18 72.0 51 108 13 72.0 44 109 17 72.0 56 110 19 72.0 61 111 3 73.0 7 112 3 73.0 7 113 4 73.0 9 114 3 73.0 6 115 4 73.0 8 116 4 73.0 9 117 3 73.0 7 Experiment No. Fish eyes (number) Luminosity index (L value) Colored particles (number) 118 3 73.0 6 119 1 73.0 4 120 1 73.0 5 121 2 73.0 6 122 1 73.0 5 123 2 73.0 4 124 1 73.0 5 125 1 73.0 4 126 1 73.0 5 127 2 73.0 6 128 1 73.0 5 129 1 73.0 4 130 6 72.5 7 131 6 72.5 7 132 5 72.5 6 133 6 72.5 5 134 7 72.5 6

Claims: A process for producing a polymer by polymerizing in a polymerization vessel a monomer having an ethylenic double bond, wherein said 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; said coating film being formed by coating a coating liquid comprising: (A) an aromatic compound condensation product having a weight-average molecular weight of 500 or more, which is selected from the group consisting of aldehyde compound/aromatic hydroxyl compound condensation products and quinone compound condensation products, said aromatic hydroxyl compound being at least one compound selected from the group consisting of a dihydroxybiphenyl compound, a naphthol compound, and a dimeric compound of 2,3-dihydroxynaphthalene; and (B) at least one compound selected from the group consisting of a chelate reagent, and a metal compound that produces a metal ion capable of forming a complex having at least two coordination numbers; said coating liquid being coated by means of steam as a carrier. The process of Claim 1, wherein said aromatic hydroxyl compound is a dihydroxybiphenyl compound. The process of Claim 1, wherein said aromatic hydroxyl compound is a naphthol compound. The process of Claim 1, wherein said aromatic hydroxyl compound is a dimeric compound of 2,3-dihydroxynaphthalene. The process of Claim 1, wherein said coating liquid is a solution containing a compound selected from the group consisting of condensation products of aldehyde compound/aromatic hydroxyl compound, and condensation products of a quinone compound in water or a mixed solvent of water with a hydrophilic organic solvent miscible with water, and having a pH of 4 to 13.0. The process of Claim 1, wherein the component (B) is a combination of the chelate reagent with the metal compound that produces a metal ion capable of forming a complex having at least two coordination numbers. The process of Claim 1, said component (B) further comprising an inorganic colloid or an acid or both of them. The process of Claim 1, wherein the component (B) comprises a cationic chelate compound having a coordination group selected from the group consisting of an -NH 2 group, an =NH group, an =N group, an -N=N- group, an -NO 2 group, an -N=O group, a =C=N group, a =C=NH group, an -S- group, a =C=S group, an ≡S, an -SCN group, a =C=O group, an -O- group, a -COOR group, an -N=O group and an ≡N→O group . The process of Claim 1, wherein the component (B) comprises an anionic chelate compound having a coordination group selected from the group consisting of an alcoholic hydroxyl group, a -COOH group, an -SO 2 H group, an =N-OH group, an -SH group and a group represented by the formula: The process of Claim 7, wherein the component (B) comprises an inorganic colloid, and the inorganic colloid is selected from the group consisting of colloids of oxides or hydroxides of metals selected from aluminum, thorium, titanium, zirconium, antimony, tin and iron; colloids of tungstic acid, vanadium pentoxide, selenium, sulfur, silica, gold, silver and silver iodide. The process of Claim 1, wherein the component (B) comprises a metal compound that produces a metal ion capable of forming a complex having 2, 4, 6 or 8 coordination number. The process of Claim 7, wherein the component (B) contains at least one of an inorganic acid and an organic acid. The process of Claim 1, wherein the component (B) is present in an amount of 1 to 500 parts by weight based on 100 parts by weight of the component (A). The process of Claim 1, wherein the component (A) in said coating liquid is in a concentration ranging from 0.5 to 20.0% by weight. The process of Claim 1, wherein said steam used in the application of said coating liquid has a temperature of 120 to 260°C and a pressure of 0.20 to 3.43 MPa·Gauge (2 to 35 kgf/cm 2 ·G) The process of Claim 1, wherein, in the application of said coating liquid, the coating liquid (L) and the steam (G) are mixed in a ratio (L/G) of from 0.005 to 0.8 in terms of flow rate ratio on the basis of weight.

Inventors: NOGUKI GENJI, SHIMIZU TOSHIHIDE, WATANABE MIKIO, NOGUKI, GENJI, SHIMIZU, TOSHIHIDE, WATANABE, MIKIO, Noguki, Genji, c/o Enbi Gijutsu Kenkyusho, SHIMIZU, TOSHIHIDE, C/O ENBI GIJUTSU KENKYUSHO, WATANABE, MIKIO, C/O ENBI GIJUTSU KENKYUSHO
Applicants: SHINETSU CHEMICAL CO, SHIN-ETSU CHEMICAL CO., LTD.
Application year: 2000
Main classification: C08F2
IPC codes: C08F2, C08F14