PROCESS FOR PRODUCTION OF VINYL CHLORIDE POLYMER

Abstract: This process is a process for production of a vinyl chloride polymer by suspension polymerization or emulsion polymerization of vinyl chloride monomer or a mixture of vinyl chloride monomer with a vinyl monomer copolymeriz­ able with said vinyl chloride monomer in an aqueous medium, characterized in that the polymerization is carried out in a polymerizer, the inner wall surface and portions of the auxiliary equipment thereof which may come into contact with the monomer during polymerization being previously coated with a scaling preventive comprising at least one selected from dyes, pigments and aromatic or heterocyclic compounds having at least 5 conjugated π bonds, while controlling the chloride ion concentration in the reaction mixture to not higher than 100 ppm. According to said process, scaling onto the inner wall surface of a polymerizer, etc. during polymerization can be prevented effectively and surely.

Description: This invention relates to a process for producing a vinyl chloride polymer, particularly to improvement of scaling prevention on the inner wall surface of a polymerizer and so on in the course of polymerization of vinyl chloride, etc. In processes for suspension polymerization or emulsion polymerization of vinyl chloride monomer of a mixture of vinyl chloride monomer and other vinyl monomers in the presence of a polymerization catalyst, there is involved the problem that polymer scales stick to the inner wall surface of the polymerizer or the portions of the auxiliary equipment of the polymerizer which may come into contact with the monomer, such as stirrer, during polymerization Scales sticking to the inner wall of the polymerizer, etc. will result in a lower polymer yield and cooling capacity of the polymerizer, and may also cause so called fish eyes formed by the adhering scales peeling off the inner wall of the polymerizer and mixing in with the product, thereby lowering the quality of the product. Further, the removal of the adhering scales requires enormous amount of labor and time; in addition, untreated monomers (vinyl chloride, etc.) are absorbed into the scales which may involve disadvantageously the danger of bringing about hazards to the human body. As the method for preventing scaling of polymer, it is known in the art to apply a coating of a chemical reagent (hereinafter referred to as "scaling preventive") on the inner wall surface of the polymerizer; various such scale preventives have been proposed. Among the various known methods, there is known a particularly good method in which a dye and/or a pigment is used as the scaling preventive (Japanese Patent Publication No. 30835/1970). However, this method is not always effective and sure in preventing scaling, and thus is not always satisfactory. Accordingly, an object of the present invention is to provide a process for production of a vinyl chloride polymer which can surely prevent scaling in the course of polymerization of vinyl chloride monomer or a mixture of vinyl chloride monomer with other vinyl monomers. The present inventors in attempting to improve on the method disclosed in Japanese Patent Publication No. 30835/1970 have consequently found that scaling can be prevented effectively and surely by use of a dye, or a pigment in combination with an inorganic compound, and also by controlling the chloride ions (Cl⁻) in the reaction mixture during polymerization. According to the present invention, there is provided a process for production of a vinyl chloride polymer by suspension polymerization or emulsion polymerization of vinyl chloride monomer or a mixture of vinyl chloride monomer with a vinyl monomer copolymerizable with said vinyl chloride monomer in an aqueous medium, characterized in that the polymerization is carried out in a polymerizer, the inner wall surface and portions of the auxiliary equipment thereof which may come into contact with the monomer during polymerization being previously coated with a scaling preventive comprising at least one member selected from the group consisting of dyes and pigments and an inorganic compound, while controlling the chloride ion concentration in the reaction mixture to not higher than 100 ppm. According to the process of the present invention, the scaling preventing action possessed by the above scaling preventive can be induced surely and potently, whereby scaling can effectively be prevented. Accordingly, no labor or time is required for scale removal, enabling continuous use of the polymerizer and improved running efficiency. Also, the cooling capacity of the polymerizer can be maintained constantly, without any fear of entrainment of the scales into the product, whereby the quality of the product polymer can be improved. Generally, the chloride ion concentration in the reaction mixture during polymerization of vinyl chloride monomer or a vinyl monomer mixture containing vinyl chloride monomer will increase abruptly at the initial stage of polymerization, thereafter tending to be increased slightly or remain at the same level until completion of polymerization. The concentration of the chloride ions may be considered to be influenced by various factors such as the contents of methyl chloride and hydrochloric acid contained in the vinyl monomer used as the starting material, the temperature of the water used in charging, the degree of vacuum after charging, etc. The present inventors have found that the scaling preventing action possessed by dyes, and pigments can be surely induced by using them in combination with an inorganic compound and controlling said chloride ion concentration in the reaction mixture throughout the polymerization procedure to 20 ppm or less, to accomplish the present invention as mentioned above. If the chloride ion concentration in the reaction mixture during polymerization exceeds 20 ppm, even if the aforesaid scaling preventive may be applied on the inner wall surface of the polymerizer, etc., its effect as the scale preventive cannot fully be exhibited, whereby scaling cannot effectively be prevented. According to the present invention, one or more compounds selected from dyes and pigments may be used singly or in combination. However, it is preferable to use an azine dye. The dyes and pigments which can be used as the scaling preventive in the process of the present invention may be exemplified by: azo dyes such as monoazo and polyazo dyes and pigments, metal complex azo dyes and pigments, stilbene azo pigments and thiazole azo dyes; anthraquinone dyes and pigments such as anthraquinone derivatives, anthrone derivatives and the like; indigoid dyes and pigments such as indigo derivatives and thioindigo derivatives; phthalocyanine dyes and pigments; carbonium dyes and pigments such as diphenylmethane dyes, triphenylmethane dyes and pigments, xanthene dyes, and macridine dyes; quinoneimine dyes such as azine dyes, oxazine dyes and thiazine dyes; methine dyes such as polymethine or cyanine dyes; quinoline dyes; nitro dyes; benzoquinone and naphthoquinone dyes; naphthalimide dyes and pigments; perinone dyes; sulfide dyes; fluorescent dyes; azoic dyes; and reactive dyes. These can be used either singly or in any desired combination of two or more compounds. Of these dyes and pigments as exemplified above, particularly preferred are azine dyes, as mentioned above. More specifically typical examples of these dyes and pigments are enumerated below. Azo dyes and pigments include the following compounds. Exemplary monoazo and polyazo dyes are Basic Yellow 32, 34 and 36; Basic Orange 2, 32, 33 and 34; Basic Red 17, 18, 22, 23, 24, 32, 34, 38, 39 and 40; Basic Violet 26 and 28; Basic Blue 58, 59, 64, 65, 66, 67 and 68; Basic Brown 1, 4, 11 and 12; Basic Black 8, Azoic Diazo Component 4, 21, 27 and 38; Disperse Yellow 3, 4, 5, 7, 8, 23, 50, 60, 64, 66, 71, 72, 76, 78 and 79; Disperse Orange 1, 3, 5, 13, 20, 21, 30, 32, 41, 43, 45, 46, 49, 50 and 51; Disperse Red 1, 5, 7, 12, 13, 17, 43, 52, 54, 56, 58, 60, 72, 73, 74, 75, 76, 80, 82, 84, 88, 90, 97, 99, 101, 103, 113, 117, 122, 125, 126, 128 and 129; Disperse Violet 10, 24, 33, 38, 41, 43 and 96; Disperse Blue 85, 92, 94 and 106; Disperse Brown 3 and 5; Disperse Black 1, 2, 10, 26, 27, 28, 29, 30 and 31; Solvent Yellow 2, 6, 14, 15, 16, 19, 21 and 56; Solvent Orange 1, 2, 5, 6, 14 and 45; Solvent Red 1, 3, 23, 24, 25, 27 and 30; Solvent Brown 3, 5 and 20; Solvent Black 3; Pigment yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 65, 73 and 83; Pigment Orange 1, 2, 5, 13, 14, 15, 16, 17, 24 and 31; Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 60, 63, 64, 68, 112, 114 and 163; Pigment blue 25; Pigment Green 10; Pigment Brown 1 and 2; Pigment Black 1; Direct Yellow 1, 8, 11, 12, 24, 26, 27, 28, 33, 44, 50, 58, 85, 86, 87, 88, 89, 98, 100 and 110; Direct Orange 1, 6, 8, 10, 26, 29, 39, 41, 49, 51, 57, 102 and 107; Direct Red 1, 2, 4, 13, 17, 20, 23, 24, 28, 31, 33, 37, 39, 44, 46, 62, 63, 75, 79, 80, 81, 83, 84, 89, 95, 99, 113, 197, 201, 218, 220, 224, 225, 226, 227, 228, 229, 230 and 231; Direct Violet 1, 7, 9, 12, 22, 35, 51, 63, 90, 94 and 98; Direct Blue 1, 2, 6, 8, 15, 22, 25, 71, 76, 77, 78, 80, 120, 123, 158, 160, 163, 165, 168, 192, 193, 194, 195, 196, 203, 207, 225, 236, 237, 246, 248 and 249; Direct Green 1, 6, 8, 28, 30, 31, 33, 37, 59, 63, 64 and 74; Direct Brown 1A, 2, 6, 25, 27, 44, 58, 59, 101, 106, 173, 194, 195, 209, 210 and 211; Direct Black 17, 19, 22, 32, 38, 51, 56, 71, 74, 75, 77, 94, 105, 106, 107, 108, 112, 113, 117, 118, 132, 133 and 146; Acid Yellow 11, 17, 19, 23, 25, 29, 36, 38, 40, 42, 44, 49, 61, 70, 72, 75, 76, 78, 79, 110, 127, 131, 135, 141, 142, 164 and 165; Acid Orange 1, 7, 8, 10, 19, 20, 24, 28, 33, 41, 43, 45, 51, 56, 63, 64, 65, 67 and 95; Acid Red 1, 6, 8, 9, 13, 14, 18, 26, 27, 32, 35, 37, 42, 57, 75, 77, 85, 88, 89, 97, 106, 111, 114, 115, 117, 118, 119, 129, 130, 131, 133, 134, 138, 143, 145, 154, 155, 158, 168, 249, 252, 254, 257, 262, 265, 266, 274, 276, 282, 238, and 303; Acid Violet 7, 11, 97 and 106; Acid Blue 29, 60, 92, 113, 117 and 120; Acid Green 19, 20 and 48; Acid Brown 2, 4, 13, 14, 20, 53, 92, 100, 101, 236, 247, 266, 268, 276, 277, 282, 289, 301 and 302; Acid Black 1, 7, 24, 26, 29, 31, 44, 76, 77, 94, 109 and 110; Mordant Yellow 1, 3, 5, 23, 26, 30, 38 and 59; Mordant Orange 1, 4, 5, 6, 8, 29 and 37; Mordant Red 7, 9, 17, 19, 21, 26, 30, 63 and 89; Mordant Violet 5 and 44; Mordant Blue 7, 13, 44, 75 and 76; Mordant Green 11, 15, 17 and 47; Mordant Brown 1, 14, 15, 19, 21, 33, 38, 40, 52 and 87; Mordant Black 1, 3, 7, 9, 11, 17, 26, 32, 38, 43, 44, 51, 54, 65, 75, 77, 84, 85, 86 and 87; Food Yellow 3 and 4; Food Red 7 and 9; exemplary metal complex azo dyes are Solvent Yellow 61 and 80; Solvent Orange 37, 40 and 44; Solvent Red 8, 21, 83, 84, 100, 109 and 121; Solvent Brown 37; Solvent black 23; Acid Black 51, 52, 58, 60, 62, 63, 64, 67, 72, 107, 108, 112, 115, 118, 119, 121, 122, 123, 131, 132, 139, 140, 155, 156, 157, 158, 159 and 191; Acid Yellow 59, 98, 99, 111, 112, 114, 116, 118, 119, 128, 161, 162 and 163; Acid Orange 74, 80, 82, 85, 86,87, 88, 122, 123 and 124; Acid Red 180, 183, 184, 186, 194, 198, 199, 209, 211, 215, 216, 217, 219, 256, 317, 318, 320, 321 and 322; Acid Violet 75 and 78; Acid Blue 151, 154, 158, 161, 166, 167, 168, 170, 171, 175, 184, 187, 192, 199, 229, 234 and 236; Acid Green 7, 12, 35, 43, 56, 57, 60, 61, 65, 73, 75, 76, 78 and 79; Acid Brown 19, 28, 30, 31, 39, 44, 45, 46, 48, 224, 225, 226, 231, 256, 257, 294, 295, 296, 297, 299 and 300; Direct Yellow 39; Direct Violet 47 and 48; Direct Blue 90, 98, 200, 201, 202 and 226; Direct Brown 95, 100, 112 and 170; an exemplary stilbene azo dye is Direct Black 62 and exemplary thiazole azo dyes are Direct Red 9 and 11. Anthraquinone dyes and pigments include the following compounds. Exemplary anthraquinone derivatives are Basic Violet 25; Basic Blue 21, 22, 44, 45, 47, 54 and 60; Azoic Diazo Component 36; Vat Yellow 2, 3, 10, 20, 22 and 33; Vat Orange 13 and 15; Vat Red 10, 13, 16, 31, 35 and 52; Vat Violet 13 and 21; Vat Blue 4, 6, 8, 12, 14, 64, 66, 67 and 72; Vat Green 8, 13, 43, 44 and 45; Vat Brown 1, 3, 22, 25, 39, 41, 44, 46, 57, 68, 72 and 73; Vat Black 8, 14, 20, 25, 27, 36, 56, 59 and 60; Disperse Orange 11; Disperse Red 4, 9, 11, 15, 53, 55, 65, 91, 92, 100, 104, 116 and 127; Disperse Violet 1, 4, 8, 23, 26, 28, 30 and 37; Disperse Blue 1, 3, 5, 6, 7, 20, 26, 27, 54, 55, 56, 60, 61, 62, 64, 72, 73, 75, 79, 81, 87, 90, 91, 97, 98, 99, 103, 104 and 105; Disperse Yellow 51; Solvent Violet 13 and 14; Solvent Blue 11, 12, 35 and 36; Solvent Green 3; Pigment Red 83 and 89; Pigment Blue 22; Acid Violet 31, 34, 35, 41, 43, 47, 48, 51, 54, 66 and 68; Acid Blue 23, 25, 27, 40, 41, 43, 45, 54, 62, 72, 78, 80, 82, 112, 126, 127, 129, 130, 131, 138, 140, 142, 143, 182, 183, 203, 204 and 205; Acid Green 25, 27, 28, 36, 40, 41 and 44; Acid Brown 27; Acid Black 48 and 50; Mordant Red 3 and 11; Mordant Blue 8 and 48; Mordant Black 13; Pigment Violet 5; exemplary anthrone derivatives are Vat Yellow 1 and 4; Vat orange 1, 2, 3, 4 and 9; Vat Violet 1, 9 and 10; Vat Blue 18, 19 and 20; Vat Green 1, 2, 3 and 9; Vat Black 9, 13, 29 and 57; Vat Red 13; Acid Red 80, 82 and 83. Indigoid dyes and pigments include the following compounds. Exemplary indigo derivatives are Vat Blue 1, 3, 5, 35 and 41; Reduced Vat Blue 1; Pigment Violet 19 and 122; Acid Blue 74 and 102; Solubilized Vat Blue 5 and 41; Solubilized Vat Black 1; Food Blue 1; exemplary thioindigo derivatives are Vat orange 5; Vat Red 1, 2 and 61; Vat Violet 2 and 3; Pigment Red 87 and 88; Vat Brown 3. Phthalocyanine dyes and pigments may include, for example, Solvent Blue 55; Pigment Blue 15, 16 and 17; Pigment Green 36, 37 and 38; Direct Blue 86 and 199; Mordant Blue 58. Carbonium dyes and pigments include the following compounds. An exemplary diphenylmethane dye is Basic Yellow 2; exemplary triphenylmethane dyes are Basic Red 9; Basic Violet 1, 3 and 14; Basic Blue 1, 5, 7, 19, 26, 28, 29, 40 and 41; Basic Green 1 and 4; Solvent Violet 8; Solvent Blue 2 and 73; Pigment Violet 3; Pigment Blue 1, 2 and 3; Pigment Green 1, 2 and 7; Direct Blue 41; Acid Violet 15 and 49; Acid Blue 1, 7, 9, 15, 22, 83, 90, 93, 100, 103 and 104; Acid Green 3, 9 and 16; Mordant Violet 1; Mordant Blue 1, 29 and 47; Food Violet 2; Food Blue 2; Food Green 2; exemplary xanthene dyes are Basic Red 1; Solvent Red 49; Pigment Red 81 and 90; Pigment Violet 1, 2 and 23; Acid Red 51, 52, 87, 92 and 94; Mordant Red 15 and 27; Food Red 14; exemplary acridine dyes are Basic Orange 14 and 15. Quinoimine dyes include the following compounds. Exemplary azine dyes are Basic Red 2; Basic Black 2; Solvent Black 5 and 7; Acid Blue 59; Acid Black 2; exemplary oxiazine dyes are Basic Blue 3; Direct Blue 106 and 108; exemplary thiazine dyes are Basic Yellow 1; Basic Blue 9, 24 and 25. Methine dyes include the following compounds. Exemplary polymethine (or cyanine) dyes are Basic Yellow 11, 13, 14, 19, 21, 25, 28, 33 and 35; Basic Orange 21 and 22; Basic Red 12, 13, 14, 15, 27, 29, 35, 36 and 37; Basic Violet 7, 15, 21 and 27. Quinoline dyes may be exemplified by Basic Green 6; Disperse Yellow 54 and 56; Solvent Yellow 33; Acid Yellow 3. Nitro dyes may be exemplified by Disperse Yellow 1, 33, 39, 42, 49 and 54; Acid Yellow 1. Benzoquinone and naphthoquinone dyes may be exemplified by Disperse Blue 58 and 108; Acid Brown 103, 104, 106, 160, 161, 165 and 188. Naphthalimide dyes and pigments may be exemplified by Pigment Red 123; Vat Violet 23 and 39; Acid Yellow 7. Perinone dyes may be exemplified by Vat Orange 7 and 15. Sulfide dyes may include, for example, Solubilized Sulfur Yellow 2; Sulfur Yellow 4; Sulfur Orange 3, Sulfur Red 2, 3, 5 and 7; Solubilized Sulfur Blue 15; Sulfur Blue 2, 3, 4, 6, 7, 9 and 13; Sulfur Green 2, 3, 6, 14 and 27; Solubilized Sulfur Brown 1 and 51; Sulfur Brown 7, 12, 15 and 31; Sulfur Black 1, 2, 5, 6, 10, 11 and 15; Vat Yellow 35, 42 and 43; Vat Blue 43 and 56. Fluorescent dyes may include, for example, fluorescent brightening agents 14, 22, 24, 30, 32, 37, 45, 52, 54, 55, 56, 84, 85, 86, 87, 90, 91, 104, 112, 121, 134, 135, 153, 162, 163, 164, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176 and 177. Azoic dyes may include, for example, Azoic Diazo Component 17, 20, 22, 24, 26, 31, 35, 41, 47, 48, 109 and 121; Azoic Coupling Component 2, 3, 4, 5, 7, 8, 10, 11, 12, 14, 15, 16, 17, 18, 19, 20, 23, 26, 28, 29, 35, 36, 37, 41 and 108; Azoic Brown 2, 7, 11 and 15; Azoic Black 1 and 5; Azoic Yellow 1 and 2; Azoic Orange 2, 3 and 7; Azoic Red 1, 2, 6, 9, 16 and 24; Azoic Violet 1, 2, 6, 7, 9 and 10; Azoic Green 1. Reactive dyes may include, for example, Reactive Yellow 1, 2, 3, 4, 6, 7, 11, 12, 13, 14, 15, 16, 17, 18, 22, 23, 24, 25, 26, 27, 37 and 42; Reactive Orange 1, 2, 4, 5, 7, 13, 14, 15, 16, 18, 20, 23 and 24; Reactive Red 1, 2, 3, 4, 5, 6, 7, 8, 11, 12, 13, 15, 16, 17, 19, 20, 21, 22, 23, 24, 28, 29, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 45, 46, 49, 50, 58, 59, 63 and 64; Reactive Violet 1, 2, 4, 5, 8, 9 and 10; Reactive Blue 1, 2, 3, 4, 5, 7, 8, 9, 13, 14, 15, 17, 18, 19, 20, 21, 25, 26, 27, 28, 29, 31, 32, 33, 34, 37, 38, 39, 40, 41, 43, 44 and 46; Reactive Green 5, 6, 7 and 8; Reactive Brown 1, 2, 5, 7, 8, 9, 10, 11, 14 and 16; Reactive Black 1, 3, 4, 5, 6, 8, 9, 10, 12, 13, 14 and 18. Further, pigments may be exemplified by inorganic pigments such as Chrome Yellow, Zinc Yellow, ZTO type zinc chromate, red lead, iron oxide powder, zinc white, aluminum powder and zinc powder. In the process of the present invention, the scaling preventive to be used in the present invention further contains, in addition to at least one of dyes, and pigments, at least one of inorganic compounds. Although an inorganic compound per se has no scaling preventive action, the scaling preventive action possessed by dyes and pigments has unexpectedly been found to be enhanced when it is combined with dyes or the like. It has also been found that this effect can surely be exhibited, if the chloride ion concentration in the reaction mixture is controlled to 20 ppm or less. At a level of the chloride ion concentration in excess of 20 ppm, the scaling preventive effect is not enough to prevent effectively scaling. When a mixture of a dye and/or a pigment with an inorganic compound is to be applied by coating on the inner wall surface of a polymerizer, etc., the proportion of the both components may preferably be 0.1 to 2000 parts by weight of the inorganic compound, more preferably 1 to 1000 parts by weight, per 100 parts by weight of the dye, pigment or conjugated π bond compound. Such inorganic compounds may include silicic acids or silicates, such as orthosilicic acid, metasilicic acid, mesodisilicic acid, mesotrisilicic acid, mesotetrasilicic acid, sodium metasilicate, sodium orthosilicate, sodium disilicate, sodium tetrasilicate, potassium metasilicate, potassium hydrogen disilicate, lithium orthosilicate, hexalithium orthodisilicate, water glass, 12-silicotungstic acid, iso-12-silicotungstic acid, 10-silicotungstic acid, potassium 12-silicotungstate, potassium iso-12-silicotungstate, potassium 10-silicotungstate, sodium 12-silicotungstate, sodium iso-12-silicotungstate, silicomolybdic acid, potassium silicomolybdate and sodium silicomolybdate; metal salts such as oxyacid salts, acetates, nitrates, hydroxides or halides of metals selected from alkaline earth metals such as magnesium, calcium, barium, aluminum family metals such as aluminum, tin family metals such as titanium, tin, iron family metals such as iron, nickel, chromium family metals such as chromium, molybdenum, manganese family metals such as manganese, copper family metals such as copper, silver, platinum family metals such as platinum, inorganic colloids prepared by mechanical crushing, irradiation of ultrasonic wave, electrical dispersion or chemical methods, such as gold colloid, silver colloid, sulfur colloid, colloid of ferric hydroxide, colloid or stannic acid, colloid or silicic acid, colloid of manganese dioxide, colloid of molybdenum oxide, colloid of barium sulfate, colloid of vanadium pentoxide, colloid of aluminum hydroxide and colloid of lithium silicate. Among the above inorganic compounds, silicates, silicic acid colloid and ferric hydroxide colloid are particularly preferred. For coating of the scaling preventive on the inner wall of a polymerizer, it can be applied as such or as a coating solution prepared by dissolving or dispersing in an appropriate solvent. The concentration of the scaling preventive in the coating solution is generally preferred to be 0.01% by weight or higher. The solvent which may be used in preparation of the coating solution may be water or various organic solvents, including, for example: aliphatic hydrocarbons such as gasoline, petroleum, benzine, mineral spirit, petroleum naphtha, V.M.&P. naphtha, decalin, tetralin, p-cymene, and the like; aromatic hydrocarbons such as benzene, toluene, and xylene; halogenated hydrocarbons such as trichloroethylene, perchloroethylene, chloroform, carbon tetrachloride, ethylene trichloride, benzene monobromide, benzene monochloride and benzene dichloride; alcohols such as amyl alcohol, ethyl alcohol, isopropyl alcohol, 2-ethylbutyl alcohol, 2-ethylhexyl alcohol, cyclohexanol, methyl alcohol, methylamyl alcohol, benzyl alcohol and butyl alcohol; ketones such as acetone, acetonylacetone, diisobutyl ketone, diethyl ketone, dipropyl ketone, methyl amyl ketone, methyl butyl ketone, methylcyclohexanone, methyldipropyl ketone, methyl ethyl ketone, methyl n-hexyl ketone, methyl isobutyl ketone, methyl propyl ketone and mesityl oxide; esters such as acetates, butyrates, propionates, and formates; alcohol esters such as butyl lactate, isopropyl lactate, ethyl lactate, ethyl oxypropionate and diethyl maleate; ketone esters such as ethyl acetoacetate and ethyl pyruvate; ethers such as isopropyl ether, ethyl ether, diethyl carbitol, diethyl cellosolve and butyl ether; ketone alcohols such as acetonylmethanol, diacetone alcohol, dihydroxyl acetone and pyruvyl alcohol; ether alcohols such as isopropyl cellosolve, carbitol, glycidol, cellosolve, glycol ether, benzyl cellosolve, butyl carbitol, butyl cellosolve, methyl carbitol, methyl cellosolve and triethyleneglycol monoethyl ether; ketone ethers such as acetal ethyl ether, acetonyl-methanol ethyl ether and methyl ethoxyethyl ether; ester ethers such as butylcarbitol acetate, butyl cellosolve acetate, carbitol acetate, cellosolve acetate, 3-methoxybutyl acetate, methylcarbitol acetate and methyl cellosolve® acetate. When organic solvents highly compatible with water are employed, water may be added to the coating solution in an amount within the range which does not impair solubility or dispersibility of the scaling preventive, whereby the coating solution can be improved in economy and safety during transportation and storage. Such solvents includes: alcohols such as methyl alcohol, ethyl alcohol, allyl alcohol, n-propyl alcohol and isopropyl alcohol; ketones such as acetone, acetonylacetone and diacetone alcohol; esters such as ethyleneglycol monomethyl ether acetate, diethyleneglycol methyl ether acetate and monoethyl ether acetate; ethers such as dioxane, ethyleneglycol monomethyl ether and ethyleneglycol monoethyl ether; furans such as tetrahydrofuran and furfuryl alcohol; aprotic solvents such as acetonitrile, N,N-dimethylformamide and N,N-dimethylacetamide. When the scaling preventive to be used is a water-soluble sulfonic acid type or carboxylic acid type dye having sulfonic acid groups or carboxylic acid groups in the form of an alkali salt or ammonium salt, water can be used as the solvent in which the preventive is to be dissolved, as disclosed in Japanese Patent Publication No. 5442/1981, whereby there is the advantage in safety and hygiene that the solvent is non-toxic and harmless. If water is used as the solvent as described above, wettability of the coating solution for the inner wall of a polymerizer, can be enhanced by addition of alcohols, preferably C₃₋₆ monohydric alcohols, such as n-propyl alcohol, n-butyl alcohol, iso-butyl alcohol, sec-butyl alcohol, t-butyl alcohol, n-amyl alcohol, t-amyl alcohol, iso-amyl alcohol, sec-amyl alcohol, sec-hexyl alcohol, as disclosed in Japanese Patent Publication No. 5444/1981. Also, as disclosed in Japanese Patent Publication No 5442/ 1981, for the purpose of making drying of the coating solution after coating easier, an organic solvent compatible with water such as alcoholic solvents, ester solvents, ketone solvents, may be added to the coating solution. In carrying out coating of the coating solution containing the scaling preventive on the inner wall of a polymerizer, etc. according to the process of the present invention, various fixing agents can be used for enhancement of the fixing characteristic, if desired. The fixing agent may be used according to various methods, for example, the method in which it is incorporated in the coating solution containing the scaling preventive, the method in which the fixing agent or a solution thereof is previously applied on the wall surface prior to coating of the scaling preventive, followed by overlaying of the scaling preventive thereon, and the suitable method may be selected depending on the kind of the scaling preventive and the kind of the fixing agent. Such fixing agents may include the polymeric compounds as shown below: olefin polymers, such as polyethylene, polyethylene sulfonic acid, polypropylene, poly(1-butene), polyisobutene, polycyclopentene, polycyclopentylethylene, polycyclohexylethylene, poly(3-cyclohexyl-1-propene), poly(4-cyclohexyl-1-butene), poly(5-cyclohexyl-1-pentene), poly(cyclotrifluoroethylene), poly(tetrafluoroethylene); diene polymers, such as polyallene, polybutadiene, polyisoprene, polychloropyrene, poly(1-methoxybutadiene), poly(2-tert-butyl-1,3-butadiene), poly(cyclopentadiene), poly(1,3-cyclohexadiene), poly(dimethylfulvene), poly(4-vinyl-1-cyclohexane), poly(1,5-hexadiene), poly(1,5-cyclooctadiene), poly(bicyclo-[2,2,1 ]-hepta-2,5-diene), poly(5,7-dimethyl-1,6-octadiene), poly(diallylphthalate), poly(diallylmethylsilane), poly(diallylphenylphosphineoxide); acetylene polymers, such as polyacetylene, poly(cyanoacetylene), poly(hydroxymethyl)acetylene), poly(butoxyacetylene), poly(phenylacetylene), poly(diphenyldiacetylene), poly(pyridylacetylene); aliphatic vinyl polymers and vinylidene polymers, such as polyvinyl alcohol, polyallyl alcohol, poly(vinylformal), poly(vinylacetal), poly(vinylbutyral), poly(vinylisobutyral), poly(vinylcyclohexanoneketal), poly(vinyl acetate), poly(vinylchloroacetate), poly(vinyl isobutyrate), poly(vinyl pivalate), poly(vinyl n-caproate), poly(vinyl caprylate), poly(vinyl laurate), poly(vinyl palmitate), poly(vinyl benzoate), poly(vinyl sulfate), poly(vinyl chloride), poly(vinylidene chloride), poly(vinyl bromide), poly(vinyl methyl ether), poly(vinyl ethyl ether), poly(vinyl n-propyl ether), poly(vinyl isopropyl ether), poly(vinyl n-butyl ether), poly(vinyl isobutyl ether), poly(vinyl tert-butyl ether), poly(vinyl neopentyl ether), poly(vinyl carbomethoxymethyl ether), poly(vinyl-2-methoxyethyl ether), poly(vinyl-2-chloroethyl ether), poly(vinyl 2,2,2-trifluoroethyl ether), poly(vinyl benzyl ether), poly(vinyl methyl ketone), poly(methyl isopropenyl ketone), poly(1-nitropropylene), poly(vinylsulfofluoride), poly(vinylsulfonic acid), poly(vinyl diphenylphosphineoxide), poly(vinyl diphenylphosphinesulfide), poly(dimethyl-2-cyano-2-propene-1-phosphonate), poly(diethyl-2-cyano-2-propene-1-phosphonate), poly(maleic anhydride); aromatic vinyl polymers, such as polystyrene, poly(α-methylstyrene), poly(4-chlorostyrene), poly(4-bromostyrene), poly(dichlorostyrene), poly(4-methoxystyrene), poly(2,5-dimethoxystyrene), poly(vinylbis(1-ethoxyethyl)hydroquinone), poly(4-vinyl-phthalic acid), poly(4-vinylphenylboric acid), poly(diphenyl-4-styrylphosphine oxide), poly(diphenyl-4-styrylphosphine sulfide), poly(9-vinylanthracene), poly(4-vinylbiphenyl), poly(acenaphthylene), polyindene; heterocyclic vinyl polymers, such as poly(N-vinylcarbazole), poly(9-Δ⁵-pentenylcarbazole, poly(9-Δ⁵-hexenylcarbazole), poly(N-vinylpyrrolidone), poly(2-vinylpyridine), poly(4-vinylpyridine), poly(2-methyl-2-vinylpyridine), poly(2,4-dimethyl-6-vinyl-S-triazine), poly(N-vinyl-1,2,4-triazine), poly(N-vinylbenztriazole), poly(N-morpholinone-(3)), polycoumarone; acrylic and methacrylic polymers, such as polyacrylic acid, polymethacrylic acid, poly(methyl acrylate), poly(ethyl acrylate, poly(butyl acrylate), poly(5-cyano-3-thia-phenylacrylate), poly(methyl methacrylate), poly(ethyl methacrylate), poly(n-propyl methacrylate), poly(n-butyl methacrylate), poly(isobutylmethacrylate), poly(n-hexyl methacrylate), poly(2-ethylbutyl methacrylate), poly(n-octyl methacrylate), poly(n-laury methacrylate), poly(4-(tert-butyl)phenyl methacrylate), poly(bornyl methacrylate), poly(β-(N-carbazyl)ethyl methacrylate), poly(tert-butyl crotonate), polyacrylonitrile, polymethacrylonitrile, polyacrylamide, poly(N,N-dimethylacrylamide), poly(N-(1,1-dimethyl-3-oxobutyl)acrylamide, poly(acrylopiperidine), poly(acrylomorpholide), poly(9-acryloylcarbazole), polymethacrylamide, polyacrolein, poly(α-methylacrolein), poly(diacryloylmethane), poly(acrylic anhydride), poly(methacrylic anhydride); polyethers, such as polyformaldehyde, polyacetaldehyde, poly(mono-chloroacetaldehyde), polychloral, polypropionaldehyde, polyacrolein, poly(2-formyl-Δ⁵-dihydropyrane), poly(trans-1,2-cyclohexanedicarboxyaldehyde), poly(glutardialdehyde), poly(β-methylglutardialdehyde), poly(β-phenylglutardialdehyde), poly(dimethylketene), polyacetone, poly(monobromoacetone), poly(7-oxa-bicyclo[2,2,1]heptane), poly(3-phenoxylene), poly(2,6-xylenol), poly(ethylene oxide), poly(propylene oxide), poly(cyclopentene oxide), poly(cyclohexene oxide), poly(phenylglycidyl ether), poly(1,2-di(epoxyethyl)benzene), poly(3,3-bis(chloromethyl)ocetane), poly(tetrahydrofuran); polysulfides, polysulfones, such as poly(thiocarboxylfluoride), poly(ethylenedichloride-sodium tetrasulfide), poly(dichlorodiethyl ether-sodium disulfide), poly(dichlorodiethyl ether-sodium tetra-sulfide), poly(phenylenesulfide), poly(ethylenesulfone), poly(propylenesulfone), poly(1-butenesulfone), poly(5-norbornenesulfone), poly(styrenesulfone), poly(1-pentylsulfone), poly(1-hexylsulfone), poly(1-heptylsulfone), poly(butadienesulfone), poly(isoprenesulfone), poly(dimethylbutadienesulfone), poly(1,5-hexadienesulfone), poly(cis,cis-cyclooctadienesulfone), poly(norbornadienesulfone); various addition polymers, such as poly(methylene diisocyanate), poly(ethylene diisocyanate), poly(trimethylene diisocyante), poly(tetramethylene diisocyanate), poly(5-iminohydantoin), poly(perfluoroglutarodinitrile), poly(1-(perfluorobutyryl)aziridine); formaldehyde resins, such as phenol-formaldehyde resin, melamine-formaldehyde resin, urea-formaldehyde resin, aniline-formaldehyde resin, p-toluenesulfonamide-formaldehyde resin; polyesters, such as poly(11-oxyundecanoate), poly(hexamethylene succinate), poly(hexamethylene sebacate, poly(hexadecamethylene sebacate), poly(hexamethylene-α,α′-dibutylsebacate), poly(octamethylene cis-hexahydroterephthalate), poly(octamethylene transhexahydroterephthalate), poly(hexamethylene maleate), poly(hexamethylene fumarate), poly(hexamethylene acetylenedicarboxylate), poly(ethylene terephthalate), poly(p-phenylene isophthalate), poly(4,4′-biphenylene isophthalate), poly(hexamethylene carbonate), poly(p-phenylene carbonate), poly(m-phenylene carbonate), poly(4,4′-isopropylidenediphenylene carbonate), poly(4,4′-(2-pentylene)diphenylene carbonate), poly(1,2-bis(hydroxymethyl)carborane-adipic acid), poly(allylsulfonate), poly(hydroquinone-aryloxyphosphoryl dichloride), poly(hydroquinone-(chloromethyl)phosphoryl dichloride), poly(hydroquinone-(N-dimethyl)phosphoramidic acid)dichloride; polyamides, such as poly(isocyanate), poly(vinylisocyanate), poly(butylisocyanate), poly(3-aminopropionic acid), poly(6-aminopropionic acid), poly(11-aminoundecanoic acid), poly(hexamethylene adipamide), poly(decamethylene adipamide), poly(3,3′-(methylimino)bistrimethylene adipamide), poly(benzidine-isophthalic acid), poly(pyrromelliticdianhydride-aromatic diamine), poly(1,6-hexamethylenebis(carboxyethyl)sulfide), poly(1,6-hexamethylenediamine-benzene-1,3-bis-sulfonic acid chloride), poly(trans-2,5-dimethyl-piperazine-4,4′-sulfonyl-dibenzoyl chloride), poly(bis(3-aminopropyl)phenylphosphine-adipic acid), poly(bis(3-aminopropyl)phenylphosphine-terephthalic acid), poly(bis(3-aminopropyl)methylphosphine oxide-adipic acid), poly(bis(3-aminopropyl)n-octylphosphine-adipic acid), poly(bis (3-aminopropyl)phenylphosphine oxide-adipic acid), poly(hexamethylenediamine-bis(2-carboxyethylene)phenylphosphine oxide), poly(hexamethylenediaminebis(p-carboxyphenyl)phenylphosphine oxide), poly(piperazine-bis(2-carboxyethyl)phenylphosphine oxide); polyureas, polyurethanes, such as polyureas, poly(1,10-decamethylenediamine-1,6-hexamethylenebisethylurethane), poly(diphenylmethane-4,4′-diisocyanate-4,4′-diphenylmethane), poly(toluene-2,4-diisocyanate-N,N′-bis(trimethylsilyl-p,p′-diaminodiphenyl ether, polyurethane, polyurethane poly(propyleneoxide) basis; various linear condensed polymers, such as poly(diethylcarbodiimide), poly(diallylcarbodiimide), poly(di-n-butylcarbodiimide), methylisopropylcarbodiimide), poly(di-n-hexylcarbodiimide), poly(diphenylcarbodiimide), poly(4,4′-diphenylenemethanecarbodiimide), poly(hexamethylenecarbodiimide), poly(1,3-xylylenecarbodiimide ), poly(3-methyl-1,4-phenylenecarbodiimide), poly(2,2′-dimethyl-biphenylenecarbodiimide), poly(2,2′-dimethoxy-biphenylenecarbodiimide), poly( 1,5-naphthylenecarbodiimide), poly(adipyldihydrazide-succinoyl chloride), poly(adipyldihydrazide-isophthaloyl chloride), poly(isophthalicdihydrazide-terephthaloyl chloride), poly(2,5-dimethylbenzylene), poly(p-xylylene), poly(2,5-dimethylxylylene), poly(2,5-dimethoxy-p-xylylene), poly(p-xylylidene), poly(α-cyano-m-xylylidine), poly(α-cyano-p-xylylidine), poly(nitrophenylene), poly(tetramethyl-p-phenylenedimethylene), poly(2,5-dihydroxy-p-phenylenedimethylene), poly(4,4′-oxydiphenylenedimethylene), poly(2,5-dimethoxy-p-phenylenedimethylene); heterocyclic condensed polymers, such as poly(benzoimidazole), poly(alkylene-5,5′-dibenzoimidazole) poly(allylene-5,5′-dibenzoimidazole), poly(pyromellitimide), poly(benzooxazole), poly(oxadiazole), poly(oxadiazolidine), poly(dithiazole), poly(benzothiazole), poly(1,4-xylenyl)-2-methylpiperazine), poly(quinoxaline), poly(S-triazinyleneimide); natural polymers, modified natural polymers, such as natural rubber, cyclized rubber hydrochloric acid rubber, chlorinated rubber, guttapercha, cellulose, methyl cellulose, ethyl cellulose, propyl cellulose, butyl cellulose, allyl cellulose, benzyl cellulose, hydroxyethyl cellulose, carboxylmethyl cellulose, cyanoethyl cellulose, cellulose triformate, cellulose acetate, cellulose triacetate, cellulose tripropionate, cellulose tributyrate, cellulose tricaproate, cellulose tricarbanilate, cellulose nitrate, cellulose trinitrate, starch, amylose, amylose acetate, amylose carbanilate, amylopectin, alginic acid, chitin, glycogen, gum arabic, gum tragacanth, heparine, pectin, rosin, kopal, shellac, casein, collagen(calf-skin), collagen(ichthyocol), gelatin, peanut-protein, soybean-protein, nucleic protein (calf thymus), nucleic protein (sperm of sea urchin), sarcosine), sericin, silk, wool, zein, polyadenylic acid, deoxyribonucleic acid, ribonucleic acid); polysiloxanes, such as polysiloxane, polydimethylsiloxane; organic metal polymers, such as poly(bis(imidazolate)-metal(II)), poly(aluminumtriisopropylateethylenediamine); and inorganic polymers such as polymetaphosphate, and so on. In the process of the present invention, the above-mentioned scaling preventive is applied on the inner wall surface of a polymerizer and the portions of the auxiliary polymerizer equipment where scales may be sticked, namely the portions which monomers may come into contact with during polymerization (including portions which monomers can possibly contact), for example, stirring blades, stirring shaft, condenser, header, baffles, search coil, bolts, nuts, etc. Preferably, the scaling preventive is further applied on the portions of recovery system of unreacted monomers where scales may be sticked, for example, the inner surfaces of monomer distillation columns, condensers, monomer storage tanks, valves, etc. The materials of the above polymerizer and portions of the axuiliary polymerizer equipment are not particularly limited, but such a material as stainless steel or a material applied with glass lining may be available. These portions where coating is to be applied should preferably have a surface roughness (Rmax as defined by JIS B 0106) of 10 µm or less, more preferably 5 µm or less. The method for applying the scaling preventive on the inner surface of a polymerizer, etc. as mentioned above is not particularly limited, and may be inclusive typically of the brush coating, spray coating, the method of filling the polymerizer with a coating solution followed by withdrawal thereof, and otherwise the automatic coating methods as disclosed in Japanese Laid-open Patent Publication (Kokai) Nos. 61001/1982, 36288/1980, Japanese Laid-open Patent Publication (Kohyo) Nos. 501116/1981, 501117/ 1981 and Japanese Laid-open Patent Publication (Kokai) No. 11303/1984. The process of the present invention is applicable for homopolymerization of vinyl chloride monomer and copolymerization of vinyl chloride monomer with other vinyl monomers in an aqueous medium. The system of polymerization may be either suspension polymerization or emulsion polymerization. Vinyl monomers which can be provided for copolymerization may be exemplified by vinyl esters such as vinyl acetate, vinyl propionate, acrylic acid, methacrylic acid or their esters or salts, maleic acid or fumaric acid, and their esters of anhydrides, diene monomers such as butadiene, chloroprene or isoprene, further styrene, acrylontrile, vinylidene halide, and vinyl ether,. In the suspension and emulsion polymerizations, the polymerization catalysts generally employed are, for example, organic peroxides such as t-butylperoxyneodecanate, di-2-ethylhexylperoxydicarbonate, 3,5,5-trimethylhexanoylperoxdide, α-cumylperoxyneodecanoate, cumene hydroperoxide, cyclohexanoneperoxide, t-butylperoxypivalate, di-2-ethoxyethylperoxydicarbonate, benzoyl peroxide, lauroyl peroxide, 2,4-dichlorobenzoyl peroxide, diisopropylperoxydicarbonate and acetylcyclohexylperoxide, azo catalysts such as α-α′-azobisisobutyronitrile, α-α-azobis-2,4-dimethylvaleronitrile, water soluble persulfates such as potassium persulfate and ammonium persulfate,. Also, as a dispersant, there may be employed, for example, suspending agents such as natural or synthetic polymeric compounds, e.g., partially saponified product of polyvinyl acetate, polyacrylic acid, copolymer of vinyl acetate and maleic anhydride, celulose derivative such as hydroxypropylmethyl cellulose and gelatin; emulsifiers as exemplifed by nonionic emulsifiers such as sorbitane monolaurate, sorbitane trioleate, anionic emulsifiers such as sodium laurylsulfonate, sodium alkylbenzenesulfonate. As other additives, fillers such as calcium carbonate, titanium oxide, etc., stabilizers such as tribasic lead sulfate, calcium stearate, dibutyltin laurate, dioctyltin mercaptide, etc., lubricants such as lice wax, stearic acid, cetyl alcohol, etc., plasticizers such as DOP, DBP, etc., chain transfer agents such as trichloroethylene, mercaptans, etc. and pH controllers may be added into the polymerization system. According to the process of the present invention, irrespectively of which catalysts, dispersants or additives may be employed, scaling can effectively be prevented in any polymerization system. The present invention is described in more detail below by referring to the following Examples, by which the scope of the present invention is not limited. (Note: In the following Examples, Experiment Nos. 218 to 300 are skipped.) Example 1 As shown in Table 1, for each experiment, a dye or a pigment was dissolved or dispersed in a solvent, with the addition of an inorganic compound and optionally a polymeric compound as shown in the same Table to prepare a coating solution. The formulation ratio of the inorganic compound the polymeric compound, and optionally the concentration of the dye or pigment in the coating solution are also shown in Table 1. The coating solution was applied on the polished inner wall surface of a stainless steel polymerizer of an inner volume of 1000 liters and the portions which may contact with monomers such as stirrer, dried at 80°C for 10 minutes and then thoroughly washed with water. Next, the thus coated polymerizer was charged with 200 Kg of vinyl chloride monomer, 400 Kg of deionized water, 44 g of partially saponified Poval®, 56 g of hydroxypropylmethyl cellulose and 60 g of t-butylperoxyneodecanate, and polymerization was carried out at 52°C for 7 hours. After completion of polymerization, the polymer was taken out and the polymerizer was washed internally with water at a flow rate of 0.1 m³/m²hr as shown in Table 1. The above operations from coating and charging to washing with water were conducted for each batch and this was repeated for a maximum of 200 batches. The chloride ion concentration in the reaction mixture during polymerization in each experiment was controlled by changing the contents of the methyl chloride and hydrochloric acid components contained in the starting vinyl chloride monomer, the temperature of the charged deionized water (in the range of from 10 to 80°C) and the degree of vacuum after charging of deionized water and the suspending agent (-750 to -100 mmHg). Various starting vinyl monomer materials with different contents of methyl chloride and hydrochloric acid were prepared by mixing two kinds of vinyl chloride monomers, namely (1) one containing 40 to 50 ppm of methyl chloride and 0 to 2 ppm of hydrochloric acid and (2) the other containing 1000 to 3000 ppm of methyl chloride and 1 to 10 ppm of hydrochloric acid at various weight ratios within the range of from 80: 100 to 20:0. After completion of polymerization of each batch, the chloride ion concentration in the slurry was measured according to the method defined by JIS K 0102 (1974). The average value and the maximum and minimum values of their measured values are shown for each experiment in Table 1. Also, scaling after completion of each batch of the 10th, 30th, 50th, 100th, 150th and 200th batch was evaluated by visually according to the standards shown below, and the amount of scales adhering (g/m²) was also measured after completion of thue final batch. The results are also shown in Table 1. A: no sticking of scale B: several percent sticking of sandy scales C: scales sticking thinly over part of the surface (about 10% sticking percentage) D: scales sticking thickly over part of the surface (about 10% sticking percentage) E: scales sticking thinly over part of the surface (about 50% sticking percentage) F: scales sticking thickly over part of the surface (about 50% sticking percentage) G: scales sticking thinly over the entire surface H: scales sticking thickly over the entire surface In Table 1, the Experiment numbers marked with an asterisk (*) indicate Comparative examples. In particular, Experiment Nos. 1 and 2 are examples in which the inner wall surface of the polymerizer was subjected to no treatment with any compound. Also, the coating solution employed in Experiment Nos. 33 and 34 was prepared by dissolving one part of sodium sulfide in 100 parts of water and adding 0.5 part of a dye to the resultant solution, followed by heating at 80°C for 30 minutes. Example 2 As shown in Table 2, for each experiment, a dye or a pigment was dissolved or dispersed in a solvent, with the addition of an inorganic compound and optionally a polymeric compound as shown in the same Table to prepare a coating solution. The formulation ratio of the inorganic compound and optionally the polymeric compound and the concentration of dye or pigment in the coating solution are also shown in Table 2. The coating solution was applied on the polished inner wall surface of a stainless steel polymerizer of an inner volume of 1000 liters and the portions which may contact with monomers such as stirrer, dried at 70°C for 20 minutes and then thoroughly washed with water. Next, the thus coated polymerizer was charged with 200 Kg of vinyl chloride monomer, 400 Kg of deionized water, 2.2 Kg of sodium lauryl sulfate, 3.2 Kg of cetyl alcohol and 300 g of α,α′-azobis-2,4-dimethylvaleronitrile, and polymerization was carried out at 50°C for 10 hours. After completion of polymerization, the polymer was taken out and the polymerizer was washed internally with water at a flow rate of 0.1 m³/m²hr, as shown in Table 2. The above operations from coating and charging to washing with water were conducted for each batch and this was repeated for a maximum of 200 batches. The chloride ion concentration was controlled and the scaling was evaluated similarly as described in Example 1. The conditions and the results are shown in Table 2. In Table 2, the Experiment numbers marked with an asterisk (*) indicate Comparative Examples. In particular, Experiment Nos. 91 and 92 are examples in which the inner wall surface of the polymerizer was subjected to no treatment with any compound. Also, the coating solution employed in Experiment Nos. 104 and 149 was prepared by dissolving one part of sodium sulfide in 100 parts of water and adding 0.5 part of a dye to the resultant solution, followed by heating at 80°C for 30 minutes. Example 3 As shown in Table 3, for each experiment, a dye or a pigment was dissolved or dispersed in a solvent, with the addition of an inorganic compound and, optionally a polymeric compound as shown in the same Table to prepare a coating solution. The formulation ratio of the inorganic compound and optionally the polymeric compound and the concentration of the dye or pigment in the coating solution are also shown in Table 3. The coating solution was applied on the polished inner wall surface of a stainless steel polymerizer of an inner volume of 1000 liters and the portions which may contact with monomers such as stirrer, dried at 70°C for 20 minutes and then thoroughly washed with water. Next, the thus coated polymerizer was charged with 160 Kg of vinyl chloride monomer, 40 Kg of vinyl acetate monomer, 400 Kg of deionized water, 600 g of gelatin, 2 Kg of Triclene® and 350 g of lauroyl peroxide, and polymerization was carried out at 70°C for 6 hours. After completion of polymerization, the polymer was taken out and the polymerizer was washed internally with water at a flow rate of 0.1 m³/m²hr, as shown in Table 3. The operations from coating and charging to washing with water were conducted for each batch and this was repeated for a maximum of 200 batches. The chloride ion concentration was controlled and the scaling was evaluated similarly as described in Example 1. The conditions and the results are shown in Table 3. In Table 3, the Experiment numbers marked with an asterisk (*) indicate Comparative Examples. In particular, Experiment Nos. 158 and 159 are examples in which the inner wall surface of the polymerizer was subjected to no treatment with any compound. Also, the coating solution employed in Experiment No. 195 was prepared by dissolving one part of sodium sulfide in 100 parts of water and adding 0.5 part of a dye to the resultant solution, followed by heating at 80°C for 30 minutes. Example 4 As shown in Table 4, for each experiment, a dye or a pigment was dissolved or dispersed in a solvent, with the addition of an inorganic compound and, optionally a polymeric compound as shown in the same Table to prepare a coating solution. The formulation ratio of the inorganic compound and, optionally the polymeric compound and the concentration of the dye or pigment in the coating solution are also shown in Table 4. The coating solution was applied on the polished inner wall surface of a stainless steel polymerizer of an inner volume of 1000 liters and the portions which may contact with monomers such as stirrer, dried at 80°C for 10 minutes and then thoroughly washed with water. Next, the thus coated polymerizer was charged with 200 Kg of vinyl chloride monomer, 400 Kg of deionized water, 40 g of a partially saponified polyvinyl alcohol, 60 g of hydroxypropylmethyl cellulose and 80 g of di-2-ethylhexylperoxycarbonate, and polymerization was carried out at 57°C for 7 hours. After completion of polymerization, the polymer was taken out and the polymerizer was washed internally with water at a flow rate of 0.1 m³/m²hr, as shown in Table 4. The above operations from coating and charging to washing with water were conducted for each batch and this was repeated for a maximum of 200 batches. The chloride ion concentration was controlled and the scaling was evaluated similarly as described in Example 1. Also, the numbers of fish eyes in the products obtained from the polymers produced in the 10th, 30th, 50th, 100th, 150th and 200th batches in each experiment were measured as follows. A mixture of 100 parts by weight of a polymer obtained by dehydrating and drying the slurry after polymerization, 50 parts by weight of DOP, 1 part by weight of dibutyltin laurate, 1 part by weight of cetyl alcohol, 0.25 part by weight of titanium oxide and 0.05 part by weight of carbon black was kneaded between two rolls at 150°C for 7 minutes and then formed into a sheet with a thickness of 0.2 mm. The number of fish eyes per 100 cm² contained in the sheet was examined according to the light transmission method. The conditions and the results are shown in Table 4. In Table 4, the Experiment numbers marked with an asterisk (*) indicate Comparative examples. In particular, Experiment Nos. 200 and 201 are examples in which the inner wall surface of the polymerizer was subjected to no treatment with any compound. Example 5 As shown in Table 5, for each experiment, a conjugated π bond compound was dissolved or dispersed in a solvent, optionally with the addition of an inorganic compound or a polymeric compound as shown in the same Table to prepare a coating solution. The formulation ratio of the inorganic compound or the polymeric compound and the concentration of the conjugated π bond compound in the coating solution are also shown in Table 5. The coating solution was applied on the polished inner wall surface of a stainless steel polymerizer of an inner volume of 1000 liters and the portions which may contact with monomers such as stirrer, dried at 70°C for 20 minutes and then thoroughly washed with water. Next, the thus coated polymerizer was charged with 200 Kg of vinyl chloride monomer, 400 Kg of deionized water, 44 g of a partially saponified polyvinyl alcohol, 56 g of hydroxypropylmethyl cellulose and 60 g of t-butylperoxyneodecanate, and polymerization was carried out at 52°C for 7 hours. After completion of polymerization, the polymer was taken out and the polymerizer was washed internally with water at a flow rate of 0.1 m³/m²hr, as shown in Table 5. The above operations from coating and charging to washing with water were conducted for each batch and this was repeated for a maximum of 200 batches. The chloride ion concentration was controlled and the scaling was evaluated similarly as described in Example 1. The conditions and the results are shown in Table 5. In Table 5, the Experiment numbers marked with an asterisk (*) indicate Comparative Examples. In particular, Experiment Nos. 301 and 302 are examples in which the inner wall surface of the polymerizer was subjected to no treatment with any compound. Also, the coating solution employed in Experiment Nos. 333 and 334 was prepared by dissolving one part of sodium sulfide in 100 parts of water and adding 0.5 part of a dye to the resultant solution, followed by heating at 80°C for 30 minutes. Example 6 As shown in Table 6, for each experiment, a conjugated π bond compound was dissolved or dispersed in a solvent, optionally with the addition of an inorganic compound or a polymeric compound as shown in the same Table to prepare a coating solution. The formulation ratio of the inorganic compound or the polymeric compound and the concentration of the conjugated π bond compound in the coating solution are also shown in Table 6. The coating solution was applied on the polished inner wall surface of a stainless steel polymerizer of an inner volume of 1000 liters and the portions which may contact with monomers such as stirrer, dried at 70°C for 20 minutes and then thoroughly washed with water. Next, the thus coated polymerizer was charged with 200 Kg of vinyl chloride monomer, 400 Kg of deionized water, 0.25 Kg of hydroxypropylmethyl cellulose, 0.25 Kg of sorbitane monolaurate and 50 g of α,α′-azobis-2,4-dimethylvalelonitrile, and polymerization was carried out at 57°C for 10 hours. After completion of polymerization, the polymer was taken out and the polymerizer was washed internally with water at a flow rate of 0.1 m³/m²hr, as shown in Table 6. The above operations from coating and charging to washing with water were conducted for each batch and this was repeated for a maximum of 200 batches. The chloride ion concentration was controlled and the scaling was evaluated similarly as described in Example 1. The conditions and the results are shown in Table 6. In Table 6, the Experiment numbers marked with an asterisk (*) indicate Comparative examples. In particular, Experiment Nos. 413 and 414 are examples in which the inner wall surface of the polymerizer was subjected to no treatment with any compound. Example 7 As shown in Table 7, for each experiment, a conjugated π bond compound was dissolved or dispersed in a solvent, optionally with the addition of an inorganic compound or a polymeric compound as shown in the same Table to prepare a coating solution. The formulation ratio of the inorganic compound or the polymeric compound and the concentration of the conjugated π bond compound in the coating solution are also shown in Table 7. The coating solution was applied on the polished inner wall surface of a stainless steel polymerizer of an inner volume of 1000 liters and the portions which may contact with monomers such as stirrer, dried at 60°C for 20 minutes and then thoroughly washed with water. Next, the thus coated polymerizer was charged with 160 Kg of vinyl chloride monomer, 40 Kg of vinyl acetate monomer, 400 Kg of deionized water, 600 g of gelatin, 2 Kg of Triclene® and 350 g of lauroyl peroxide, and polymerization was carried out at 70°C for 6 hours. After completion of polymerization, the polymer was taken out and the polymerizer was washed internally with water at a flow rate of 0.1 m³/m²hr, as shown in Table 7. The above operations from coating and charging to washing with water were conducted for each batch and this was repeated for a maximum of 200 batches. The chloride ion concentration was controlled and the scaling was evaluated similarly as described in Example 1. The conditions and the results are shown in Table 7. In Table 7, the Experiment numbers marked with an asterisk (*) indicate Comparative examples. In particular, Experiment Nos. 467 and 468 are examples in which the inner wall surface of the polymerizer was subjected to no treatment with any compound. Example 8 As shown in Table 8, for each experiment, a conjugated π bond compound was dissolved or dispersed in a solvent, optionally with the addition of an inorganic compound or a polymeric compound as shown in the same Table to prepare a coating solution. The formulation ratio of the inorganic compound or the polymeric compound and the concentration of the conjugated π bond compound in the coating solution are also shown in Table 8. The coating solution was applied on the polished inner wall surface of a stainless steel polymerizer of an inner volume of 1000 liters and the portions which may contact with monomers such as stirrer, dried at 80°C for 10 minutes and then thoroughly washed with water. Next, the thus coated polymerizer was charged with 200 Kg of vinyl chloride monomer, 400 Kg of deionized water, 40 g of a partially saponified polyvinyl alcohol, 60 g of hydroxypropylmethyl cellulose and 80 g of di-2-ethylhexylperoxycarbonate, and polymerization was carried out at 57°C for 7 hours. After completion of polymerization, the polymer was taken out and the polymerizer was washed internally with water at a flow rate of 0.1 m³/m²hr, as shown in Table 8. The above operations from coating and charging to washing with water were conducted for each batch and this was repeated for a maximum of 200 batches. The chloride ion concentration was controlled and the scaling was evaluated similarly as described in Example 1. Also, the numbers of fish eyes in the products obtained from the polymers produced in the 10th, 30th, 50th, 100th, 150th and 200th batches in each experiment were measured similarly as in Example 4. The conditions and the results are shown in Table 8. In Table 8, the Experiment numbers marked with an asterisk (*) indicate Comparative examples. In particular, Experiment Nos. 507 and 508 are examples in which the inner wall surface of the polymerizer was subjected to no treatment with any compound.

Claims: A process for production of a vinyl chloride polymer by suspension polymerization or emulsion polymerization of vinyl chloride monomer or a mixture of vinyl chloride monomer with a vinyl monomer copolymerizable with said vinyl chloride monomer in an aqueous medium, characterized in that the polymerization is carried out in a polymerizer, the inner wall surface and portions of the auxiliary equipment thereof which may come into contact with the monomer during polymerization being previously coated with a scaling preventive comprising at least one member selected from the group consisting of dyes and pigments, and an inorganic compound, while controlling the chloride ion concentration in the reaction mixture to not higher than 20 ppm. A process according to Claim 1, wherein said scaling preventive comprises an azine dye. A process according to Claim 2, wherein said azine dye is selected from the group consisting of Basic Red 2, Basic Black 2, Solvent Black 5, Solvent Black 7, Acid Blue 59 and Acid Black 2. A process according to any one of Claims 1 to 3, wherein said inorganic compound is at least one member selected from the group consisting of silicic acids, silicates; salts of alkaline earth metals, zinc family metals, aluminum family metals, tin family metals, iron family metals, chromium family metals, manganese family metals, copper family metals and platinum family metals; and colloids of silica and ferric hydroxide. A process according to Claim 4, wherein said inorganic compound is a silicate, a silicic acid colloid or a ferric hydroxide colloid. A process according to any one of preceding Claims, wherein a fixing agent is used for enhancement of the fixing characteristic of said scaling preventive. A process according to Claim 6, wherein said fixing agent is at least one selected from olefin polymers, diene polymers, acetylene polymers, aliphatic vinyl or vinylidene polymers, aromatic vinyl polymers, heterocyclic vinyl polymers, acrylic or methacrylic polymers, polyethers, polysulfides, polysulfones, addition polymers, polyesters, polyamides, polyureas, polyurethanes, linear condensed polymers, heterocyclic condensed polymers, natural polymers, modified natural polymers, polysiloxanes, organic metal polymers and inorganic polymers. A process according to any of the preceding Claims, wherein the portions of recovery system of unreacted monomers where scales may stick are further previously coated with the scaling preventive.

Inventors: KANEKO, ICHIRO, KITAMURA, HAJIME, KOYANAGI, SHUNICHI, SHIMIZU, TOSHIHIDE
Applicants: SHIN-ETSU CHEMICAL CO., LTD.
Application year: 1985
Main classification: C08F2
IPC codes: C08F2, C08F4, C08F14