IE42459B1 - Method for the polymerization of vinyl chloride - Google Patents

Abstract

In the polymerisation of monomeric vinyl chloride, alone or mixed with one or more olefinically unsaturated, copolymerisable monomers, in the presence of a polymerisation initiator, the deposition of polymer crusts is prevented, and the quality and the productivity increased, if, before the polymerisation, the surfaces of the inside wall and other parts of the polymerisation vessel which come into contact with the monomer or the monomers are each treated with at least one compound selected from a) polar organic compounds, including polar organic dyes, and b) halides, hydroxides, oxides, and carboxylates of metals, oxygen acids of elements from the second to the sixth period of groups IIB and III to VII of the Periodic Table, and inorganic salts of these oxygen acids. The compounds a) and b) are applied separately or simultaneously, using conventional techniques.

Description

This invention relates to a method, for polymerizing vinyl chloride monomer or a monomeric mixture composed mainly of vinyl chloride and, more particularly, to a method for preventing deposition of polymer scale on the inner wall of the polymerization vessel concerned and other surfaces in contact with the monomer or monomeric mixture.

In any known types of polymerization, such as, suspension polymerization, emulsion polymerization, ' solution polymerization, gas phase polymerization and hulk polymerization, the deposition of polymer scale on the inner wall of a polymerization vessel and other surfaces in contact with a monomer or monomers has been a serious problem for the following reasons. Firstly, the polymer scale deposition causes decreases in the yield of polymer product and the cooling efficiency of the polymerization vessel. Secondly, any scale coming the off the surfaces possibly becomes mixed in/polymer product,, resulting in the deterioration cf its quality.

Thirdly, the removal of scale deposition, or the descaling of the surfaces, requires much labour and time, resulting in the reduction of productivity.

Lastly and as a matter of very great importance of late, the descaling operation usually carried out following every polymerization run involves a health problem to workers owing to any unreacted monomer or monomers that have been adsorbed on the scale. -24248a For the prevention of polymer scale deposition on the various surfaces, there have been proposed some methods which comprise coating those surfaces with polar organic compounds, such as, amine compounds, quinone compounds and aldehyde compounds, dyes and pigments. (See Japanese Patent Publications Nos. 30343/1970 and 30835/1970). However, the prior art techniques have not been found effective in a polymerization process in which vinyl chloride is polymerized in the presence of emulsifying agents or in combination with a comonomer or comonomers, or the polymerization mixture contains peroxides such as benzoyl peroxide or lauroyl peroxide or higher carboxylic acids such as 1 auric acid or stearic acid or salts thereof.

Further according to the prior art techniques, the effect of scale prevention can hardly be maintained for repeated polymerization runs.

British Patent Specification No. 1,521,058 discloses and claims a method for the polymerization of vinyl chloride monomer or a mixture of monomers composed mainly of vinyl chloride in the presence of a polymerization initiator in a polymerization vessel, in which a layer comprising a metal complex with at least one organic compound which is a polar compound and/or a dye is formed at least on the inner surfaces of the polymerization vessel which come into contact with the monomer or monomer mixture, said metal complex being formed by treating said organic compound with a metal compound in a ratio of from 100:5 to 100:300 by weight respectively.

According to the present invention, in a method for the polymerization of vinylchloride monomer or a mixture of monomers composed mainly of vinylchloride in the presence of a polymerization initiator in a polymerization vessel, the surfaces of the vessel coming into contact with the monomer or monomers are treated, prior to polymerization, with (a) an organic compound which is a polar compound and/or a dye and (b) a compound which is a metal halide, hydroxide, oxide or carboxylate, or an oxyacid, or an inorganic salt thereof, of an element of the second to sixth period of group IXB or sub-group A or B of Groups III to VII of the Periodic Table. - 3 42453 The polar organic compounds of group (a) are selected from the group consisting of Nitrogen-containing organic compounds, sulphurcontaining organic compounds, oxygen-containing organic compounds, phosphorus-containing organic compounds, tars, pitches, rosins and waxes Nitrogen-containing organic compounds, for example those having an amino, azo, nitro, nitroso or azomethine group or an azine ring and amine, imine quarternary ammonium compounds, e.g. azomethane, azobenzene, nitrobenzene, nitrosobenzene, monoaminomononitroazobenzene, pyrazine, pyridine, thiazine, aniline, oxazines e.g. benzal aniline, EDTA, Nigrosine Black, Oil Black, Spirit Black, diami nonaphthalenes, diphenylamine, hydrazine, Ν,Ν-dimethylaniline, urea, laurylamine, cetyl trimethyl ammonium chloride, polyamides and polyethylene imines.

Sulfur-containing organic compounds, for example those having a thiocarbonyl, thioether and thioalcohol group, e.g., thioglycolic acid, thiourea, thiocarbanilic acid, thiocarbamic acid, thiobenzoic acid, dialkyl thioethers (as represented by the formula R-S-R' where R and - 4 42458 R’, which may be the same or different, each represent an alkyl group) such as dimethylsulfide and ethylmethylsulfide, alkyl and /nercaptans such as propylmercaptan and butylmercaptan, polysulfides, polysulfones and sulfonic acids such as p-toluensulfonic acid, cyclohexylsulfonic acid, «f-naphthal ene sulfonic acid, anthraquinonesulfonic acid, metanilic acid, dodecylbenzenesulfonic acid, and e.g. salts thereof,/with alkali metals such as sodium and potassium.

Oxygen-containing organic compounds such as, for example, quinones, ketones, aldehydes, ethers, alcohols and alkali salts thereof, esters, carboxylic acids and salts thereof, sulfoxides and oximes, e.g., p-benzoquinone, anthraquinone, benzophenone, acetophenone, diisopropylketone, formaldehyde, acetaldehyde, benzaldehyde, octyl alcohol, cetyl alcohol, benzyl alcohol, phenol, cresol, hematein, propargyl alcohol, hydroquinone, fluorescein, ethylene glycol, pentaerythritol, glucose, sucrose, polyvinyl alcohol, diisopropyl ether, diphenyl ether, ι ι cellulose ethers, amylacetate, ethylbenzoate, stearic acid, benzoic acid, salicylic acid, - 5 42453 maleic acid., oxalic acid, tartaric acid, Rochelle salt, succinic-acid, malic acid, isonicotinic acid, phenylglycine, 3-oxy-2naphthoic acid, gallic acid, polyacetals and polyacrylic aeid.

Phosphorus-containing organic compounds such as, for example, phosphoric and polyphosphoric acid esters and alkali metal or ammonium salts thereof, e.g., monolauryl phosphate, sorbitan hexametaphosphate, polyoxyethylene sorbitan ’ triphosphate and phytic acid.

The tars, pitches, rosins and waxes with a poorly defined chemical structure.

Further, the organic dyes of group (a) are exemplified by the following.

Azo dyes such as monoazo dyes, polyazo dyes, metal-containing azo dyes, naphthol dyes (azoic dyes and inactive dyes) and dispersed azo dyes; anthraquinone dyes such as anthraquinone acid dyes, anthraquinone vat dyes, anthrone vat dyes, alizarin dyes and dispersed anthraquinone dyes; indigo dyes such as Brilliant Indigo B, Threne Red Violet RH and Threne Printing Black B; 2g sulfide dyes such as Sulfur Blue PBB and Sulfur Black B and Sudan B; phthalocyanine dyes - 6 42459 such as copper and metal-free phthalocyamne and also compounds,/ diphenyImethane or tripheny Imethane dyes, nitro dyes, nitroso dyes, thiazole dyes, xanthene dyes, acridine dyes, azine dyes, oxazine dyes, thiazine dyes, benzoquinone and naphthoquinone dyes, and cyanine dyes; and water-soluble organic dyes,-such as Direct Brilliant Yellow G (direct dye), Acid Light Yellow 2G (acid dye), Levafix Yellow 4G (reactive dye), Procion Brilliant Orange G (reactive dye), Direct Past Scarlet GS (direct dye), Direct Bordeaux NS (direct dye), Brilliant Scarlet 3R (acid dye), Acid Alizarine Red B (acid mordant dye), Direct Turkish Blue Gl (direct dye), Cibacron Blue 30 (reactive dye), Blankophor B (acid dye), Nigrosine (acid dye), Sirius G (direct dye), Chrysamine G (direct dye), Direct Past Yellow GG (direct dye), Chrome Yellow G (acid mordant dye), Chrome,Yellow ME (acid mordant dye), Eosine G (acid dye), Basic Plavin 8G (basic dye), Astrazon Yellow 3G (basic dye), Rhodamine 6GCP (basic dye), Safranine T (basic dye), Rhodamine B (basic dye), Daitophor AN (basic dye), Auramine Cone (basic dye), Chrysoidine (basic dye) and Bismarck Brown BG (basic dye). - 7 42453 The polar organic compounds and organic dyes can be used alone or in combination.

The compounds of group (b) useful in the method of the present invention include metal halides, oxides, hydroxides and lower carboxylates. Suitable metals are exemplified by alkali metals such as sodium and potassium, alkaline earth metals such as magnesium, calcium and barium, metaTs of the zinc group such as zinc metals of the aluminium group such as aluminium metals of the tin group such as titanium and tin, metals of the iron group such as iron and nickel, metals of the chromium group such as chromium and molybdenum, metals of the manganese group such as manganese, metals of the copper group such as copper and silver and metals of the platinum group such as platinum. Illustrative of these compounds are sodium fluoride, sodium acetate, ferrous chloride, calcium chloride, potassium chloride, sodium tartrate, sodium chloride, calcium acetate, titanium dioxide, sodium oxalate, aluminium chloride, cupric chloride, manganese dioxide, iron octoate and stannic chloride.

Other suitable compounds of group (b) are the oxyacids of the elements belonging to the second to sixth periods of groups IIB and III to VII of the Periodic Table and inorganic salts of the oxyacids.

References in this specification to the Periodic Table of the elements are to be construed in the light of the table given in General and Inorganic Chemistry by J. R. Partington, 3rd Edition, Macmillan (1958). Thus the elements which can form the oxyacids for the purposes of this invention are the following: B, C, N, 0, F, Al, Si, P, S, Cl, Sc, Τι, V, Cr, Mn, Zn, Ga, Ge, As, Se, Br, Y, Zr, Nb, Mo, Tc, Cd, In, Sn, Sb, Te, I, the rare earths, Hf, Ta, W, Re, Hg, TI, Pb, Bi, Po and At. The elements from which the oxyacids for use in this invention will generally be formed are zinc, boron, - 8 4 2459 aluminium, carbon, silicon, tin, titanium, nitrogen, phosphorus, sulfur, chromium, molybdenum, tungsten, chlorine and manganese.

Illustrative oxyacids and salts thereof are as follows. Zincic acid, boric acid, aluminic acid, carbonic acid, silicic acid, stannic acid, titanic acid, phosphoric acids (including dehydrated and condensed phosphoric acids, such as, metaphosphoric acid, pyrophosphoric acid and tripolyphosphoric acid), nitric acid, sulfuric acid, chromic acid, molybdic acid, tungstic acid, manganic acid, chloric acid permanganic aoid , dichromic acid in higher oxidation nitrous, hyponitrous, phosphorous, hypophosphoric and hypophosphorous acids , and salts of the above oxoacids with ammonium, alkali metals or alkaline earth metals.

In carrying out the method of the present invention, it is advantageous that compounds (a) and (b) are dissolved or dispersed separately or in combination in a solvent prior to application. Suitable solvents are water, alcohols, ester5» ketones, hydrocarbon5 and chlorinated hydrocarbons. - 9 _ 42453 There are three preferred ways of carrying out the treatment of the surfaces of the polymerisation vessel in accordance with the invention.

In the first of the three embodiments, the surfaces are coated with a solution or dispersion of the organic compound and the thus-coated surfaces are then contacted with a solution or dispersion of the compound of group (b). Preferably, the coated surfaces are heated at a temperature of from 50 to 1OO°C for more than ten minutes in contact with the second solution or dispersion. The second solution or dispersion may then be removed from the reactor and the polymerisation procedure carried out.

However, if the polymerisation mixture is aqueous, as is the case in, for example, suspension or emulsion polymerisation, and if the solvent used to form the second solution or dispersion is water, then it is not necessary to remove the heated aqueous solution or dispersion.

In the second preferred manner of carrying out the treatment, a solution or dispersion of the compounds of groups (a) and (b) dissolved or dispersed in a solvent is heated at a temperature of from 50 to 100°C for more than 10 minutes, and the surfaces are coated with the heated solution or dispersion. Preferably, the solution or dispersion is prepared by the dropwise addition of a solution or dispersion of the organic compound in a suitable solvent to a solution or dispersion of the compound of group (b) in the same or a different solvent. After coating the surfaces, they may, if desired, be washed with water.

The third preferred way of carrying out the treatment is to coat the surfaces alternately with a solution or dispersion of the organic compound and with a solution or dispersion of the compound of group (b).

Either solution or dispersion may be applied before the other and the alternate coating operations may be carried but one or more times. The solutions or dispersions may be prepared in the same or different solvents. Preferably, after the surfaces have been coated with both solutions or dispersions, they are heated at a temperature of from 50 to 100°C for more than ten minutes, preferably by passing hot water through a jacket or by blowing hot air into the reactor. Most preferably, the application of the solutions or dispersions is completed by passing hot water through the jacket and simultaneously blowing hot air into the reaction vessel at each coating operation. - 10 434 59 In any of the above embodiments it is advantageous that compounds (a) and (b) are brought into contact with each other at an elevated temperature higher than 5O°C.

If such temperature is lower, no satisfactory result is obtained and more than 10 hours are required for the treatment.

The ratio of compound (b) to compound (a) used in accordance with the method of the present invention may vary depending on the kinds of compounds used and the type of polymerization concerned. Specifically in the above-described first embodiment in which compound (b) has a low concentration in an aqueous phase and in the third embodiment in which compounds with (a) and (b) do not mix well/each other, the ratio of compound (b) to compound (a) is preferred to be relatively large or, generally, from 0.1:1 to 500:1 by weight. In the second embodiment in which the heated mixture of compounds (a) and (b) is applied, the ratio of compound (b) to compound (a) can be relatively small, say, from 0.01:1 to 50:1 by weight.

In accordance with the present invention, the amount of compound (a) or (b) or the mixture thereof to be used for coating the surfaces of the inner wall and Other parts of the reactor may be more or less the same as in case where conventional coating materials are used according to the prior art techniques. For example, sufficient prevention of polymer scale deposition can be accomplished with an amount of at least 0.001 g/m2. - 11 42450 The three treatment procedures described above may be employed singly, or at least two of them may be employed in combination. For example, the surfaces may first be coated with a mixed solution of compounds (a) and (b) followed by heating as in the second embodiment, the thus-coated surfaces then being further coated with a solution of compound (a) and a solution of compound (b) in succession, followed by heating, as in the third embodiment.

When more than one organic compound of group (a) is used, it is possible in some cases to obtain better results by selecting one water-soluble and one water-insoluble compound of group (b).

Further, it is useful, in order to attain good scaleprevention, to add at least one of the compounds of groups (a) and (b) to the polymerisation mixture. For example, the compound, or a mixed and heated solution or dispersion of compounds of groups (a) and (b), may be added to the polymerisation mixture in an amount not exceeding 100 ppm based on the weight of the monomer or monomers. Amounts higher than 100 ppm may cause adverse effects on the polymeric product. - 12 4 2 4 53 In order to further enhance the prevention of scale deposition in accordance with the present invention, it is proposed to add to the polymerization mixture an alkaline substance, though not in conformity with the definition of compound (b), such as, oxides, hydroxides, carbonates, phosphates, bicarbonates, silicates and acetates of alkali metals, alkaline earth metals and ammonium. However, it is important that the alkaline substance should be added in an amount such θ that will not work to deteriorate ifae resulting polymer.

The suitable amount is, for example, up to 1 # by weight based on the monomer or monomeric mixture.

The method of the present invention can be applied to all types of polymerization, i.e., suspension I5 polymerization, emulsion polymerization, solution polymerization· and bulk polymerization, of vinyl chloride monomer or a monomeric mixture composed mainly of vinyl chloride. Further, the method of the invention does not place any limitations on the kinds of various add?θ itives, such as, suspending agents, emulsifiers and chain transfer agents, polymerization initiators, polymerization temperature and the velocity of agitation.

The method of the invention may be applied 2g effectively to not only homopolymerization of vinyl chloride but also copolymerization of vinyl chloride - 13 i. -3 4 SO with a copolymerizahle monomer or monomers. As the copolymerizahle monomers, there can he mentioned., for example, vinyl esters, vinyl ethers, acrylic and methacrylic acids, esters thereof, maleic and fumaric acids, esters thereof, maleic anhydride, aromatic vinyl monomers, vinyl halides other than vinyl chloride, vinylidene halides, olefins, acrylonitrile and methacrylonitrile.

This invention will further be illustrated hy the following examples.

Example 1.

For the purpose of this Example, 2-liter stainless steel autoclaves, each equipped with a turbine agitator were provided. The surfaces of the inner wall of each autoclave and the agitator blades were coated with a 0.1$ solution in toluene of each of the various organic dyes as indicated under heading Compound A in Table I in an amount of about 0.05 g/m (as solid), and the coated surfaces were dried at 70°C for 60 minutes, whereupon a 1% aqueous solution of each of the various oxoacids or salts thereof as indicated under heading Compound B in the same table was applied over the coated and dried surfaces in an amount of about 0.05 g/m2 (as solid), followed by drying at 70°C for 60 minutes. Then, into each autoclave thus coated were - 14 4 2 4 5 3 put 900g of water, 0.4g of methylcellulose and. 0.8g of polyvinyl alcohol. After the autoclave was evacuated of air and filled with nitrogen instead, 600g of vinyl chloride monomer and 0.21g of «t,^’-azobisdimethyl valeronitrile were charged and the mixture was subjected to suspension polymerization at an agitating velocity of 1,000 r.p.m. and a temperature of 57°C for about 6 hours. The polymerization runs were continuously repeated with each autoclave till scale deposition exceeded 1 g/m2, the numbers of such repeated polymerization runs being mentioned in Table I under the heading No. of Runs.

The No. of Runs means, in other words, that scale deposition was effectively prevented during those repeated polymerization runs. The details and results are set out in Table I.

For comparative jfurposes, tests using Compound A or B alone, not in combination, were carried out in and under similar manners and conditions, obtaining the results as set out in the same table. - 15 434S3 Table I Compounds A and B Compound A Compound B Compound A Compound B Test No. No. of Runs Test No. No. of Runs Test No. No. of Runs Nigrosine Black Sodium silicate 1 18 13 12 25 2 Spirit Black Potassium nitrite 2 12 14 9 26 2 Oil Black Boric acid 3 10 15 7 27 1 Threne Grey E Silicic acid 4 5 16 3 28 2 Aniline Black Potassium dichromate 5 6 17 4 29 1 Alizarine Yellow R Tripoly- phosphoric 6 6 18 2 30 2 acid Fast Light Magnesium Yellow G carbonate 7 4 19 3 31 1 Threne Golden Yellow RK Stannic acid ? 3 20 2 32 1 Pyrazolone Red Sodium molybdate 9 3 21 2 33 2 Permanent Orange GTR Titanic acid 10 3 22 2 34 1 Phthalocyanine Blue Permanganic acid 11 2 23 1 35 1 Naphthol Yellow S Sodium borate 12 3 24 2 36 1 Note: Tests numbered 13-36 are controls. - 16 42453 Example 2.

The same autoclaves as used, iri Example 1 were coated, with Compounds A and B in combination as indicated in Table H and, for comparative purposes, with compound A or B alone as indicated in the same table, in and under the same manner and conditions as in Example 1. Into each of the coated autoclaves were charged 900g of water, 6g of sodium lauryl sulfonate, 1g of potassium persulfate and 600g of vinyl chloride, to carry out emulsion polymeriza10 tion at 48°C for 10 hours. The details and results of these tests are tabulated as follows.

Table II No. of Test No. Compound A Compound B Runs 37 Nigrosine Black Tripolyphosphoric acid 5 38 Spirit Black Sodium molybdate 3 39 Oil Black Sodium nitrite 2 40 Nigrosine Black Sodium silicate 5 41 Spirit Black Boric acid · 3 42 Nigrosine Black -- 3 43 Spirit Black — 2 44 — Sodium silicate 1 45 — Sodium nitrite 1 46 — Phosphoric acid 1 Note: Tests numbered 42-46 are controls. - 17 43 4.50 Example 3.

The same autoclaves as used in Examplo 1 were coated with Compounds A and B In combination as indicated in Table IH and, for comparative purposes, with compound A or B alone as indicated in same table, in and under the same manner and conditions as in Example 1. Into each of the coated autoclaves were charged 900g of water, 0.4g of methyl cellulose, 0.8g of polyvinyl alcohol, 600g of vinyl chloride, 60g of a comonomer, i.e., vinyl acetate or vinylidene chloride, and 0.21 g of isopropyl peroxydicarbonate were charged, to carry out suspension polymerization at 52°C for about 6 hours. The details and results of those are set out in Table Kt. - 18 ' ΐ Table IK Test No. Comonomer Compound A Compound B No. of Runs 47 Vinyl acetate Nigrosine Black Silicic acid 8 48 If Oil Black Tripolyphosphoric acid 5 5 49 II Nigrosine Black . Potassium nitrite 7 50 II Oil Black Boric acid 4 51 Vinylidene chloride Nigrosine Black Phosphoric acid 8 52 II Spirit Black Sodium molybdate 5 53 II Nigrosine Black Potassium silicate 8 10 54 Vinyl acetate Nigrosine Black — 5 55 II Oil Black — 3 56 II — Silicic acid 1 57 II 1 Tripolyphosphoric acid 1 58 Vinylidene chloride Nigrosine Black , — 5 15 59 II Spirit Black — 3 60 ll — Sodium molybdate 1 Note: Teste.numbered 54-60 are controls. - 19 4 2459 Example 5· The same autoclaves as used in Example 1 was coated with Compounds A and B in combination as indicated in Table V in and under the same manner and conditions as in Example 4. With each of the coated autoclaves, emulsion polymerization similar to that of Example 2 was carried out. The details and results of these tests are set out in Table V. Table V Test No. Compound A Compound B No. of Runs 73 Nigrosine Black Tripolyphosphoric acid i 4 74 Spirit Black Sodium molybdate 2 75 Oil Black Sodium nitrite 2 76 Nigrosine Black Sodium silicate 4 77 Spirit Black Boric acid 2 - 21 42453 Example 6.

The same autoclaves as used in Example 1 were coated with Compounds A and B in combination as indicated in Table VI in and under the same manner and conditions as in Example 4. With each of the coated autoclaves, suspension polymerization or copolymeriza- tion substantially similar to that’ of Example 3 was carried out. The details and results of the tests are set out in Table VI. Table VI Test No. Compound A Compound B No. of Runs 78 Nigrosine Black Silicic acid 7 79 Oil Black Tripolyphosphoric acid 5 80 Nigrosine Black Potassium nitrite 7 81 Oil Black Boric acid 4 82 Nigrosine Black Phosphoric acid 6 83 Spirit Black Sodium molybdate . 5 84 Nigrosine Black. Potassium silicate 6 Note: Test Nos. 78—81 are of the homopolymerization of vinyl chloride.

Test Nos. 82-84 are of the copolymerization of vinyl'chloride and vinylidene chloride. - 22 42 4»rp Example 7* The same autoclaves as used in Example 1 were coated with a solution of Nigrosine Black in ethanol or toluene in the varied amounts as indicated in Table VB, followed by drying at 70°C for 60 minutes, and, thereupon, a 1$ aqueous solution of sodium silicate was applied over the coated-and dried surfaces rt in an amount of 0.05 e/m (as solid), followed by drying at 70°C for 60 minutes. Then, with each of the coated autoclaves, the suspension polymerization of vinyl chloride was carried out in and under the same manner and coxiditions as in Example 1 to test for scale deposition. The details and results are set out in Table VIL Table VB Test No. Amount of Nigrosine Black applied, g/m^ No. of Runs 8510 2 86 2 3 87 1 4 88 0.5 5 89 0.05 5 90 0.005 3 91 0.0005 2 92 0.5 2 93 0.5 6 94 0.01 3 - 23 42450 Notes: 1) Solutions of Nigrosine Black used . in Test Nos. 85-91 were in ethanol, while those used m Test Nos. 92-94 were in toluene. 2j In Test No. 93, the surfaces of the Nigrosine Black coatings were lightly wiped with a piece of ethanol impregnated cotton gauze after drying.

Example 8.

The same coating, and polymerization procedure as taken in Test No. 88 of Example 7 was repeated except that 5% hy weight, 0.1% hy weight or 0.0001% by weight, based on vinyl chloride, of sodium silicate was added to the polymerization mixture before the polymerization reaction was commenced. As a result, the numbers of polymerization runs during which scale deposition was prevented were 9, 7 and 5, respectively.

Example 9· The same procedure as taken in Test No. 61 of Example 4 was repeated except that the coated surfaces were additionally coated with Nigrosine Black and sodium silicate in and under the same fashion and conditions as in Test No. 1 of Example 1. The number of scale preventing runs of polymerization was 25.

Example 10.

For the purpose of this example, 1,000-liter stainless steel polymerization vessels each equipped with an agitator of the paddle type, having blades 600 mm in diameter, were used. The surfaces of the inner wall of the vessels and the agitator blades and shaft were coated with a 0.5# solution in methanol of a mixture of Sudan B and Nigrosine in the varied mixing ratios hy weight as indicated in Table VIE in an amount of 0.05 Λ O Ιθ g/nr (as solid), the coated surfaces totalling to 4 a .

Into each of the thus coated polymerization vessel were charged 500 kg of water, in which one of the various metal salt3 as indicated in· Table VIE was dissolved, was charged, followed by treatment at a temperature yg shown in the same table under agitation at a rate of 110 r.p.m. for 30 minutes, and cooling. Thereupon, 2.2 kg of sodium lauryl sulfate, 3 kg of cetyl alcohol, 200 g of dimethyl valeronitrile and 200 kg of vinyl chloride were charged to carry out suspension poly20 meri2ation at 50°C for 7 hours in accordance with a conventional method. After the reaction was over, the coated surfaces were washed with water and dried, and then the amounts of scale deposition were determined, as set out in Table VIE.

For comparative purposes, similar tests were conducted with Sudan B or Nigrosine alone and not in combination or without any metal salt. The results are also shown in the table. - 25 4 2-159 Table VIH Test No. Mixing Ratio Sudan B/Nigroane Temper- ature Metal Salt Amount of Scale (g/m2) 95* 100 / 0 90°C Sodium Silicate, 10 g 520 96 100 / 10 tt tl 5 97 100 / 50 tt • It- 0 98 100 / 100 ft It 0 99 100 / 500 tt II 0 100 wo / 1000 tt It 20 101* 0 / 100 It tt 780 102 100 / 100 70°C tt 3 103 100 / 100 50°C tl 10 104 tt 90°C Sodium bicarbonate, 20 g 0 105 tt tl Calcium 0 primary phosphate, 20 g 106 tt tt Sodium 0 acetate, 20 g 107 tt tf Ferrous 0 chloride, 20 g 108 It fl Calcium 0 chloride, 20 g 109 ft ft Potassium 0 sulfate, 20 g 110 ft 1t Allan, 20 g 0 111 tf ft Sodium 0 carbonate, 10 g 112* 0 / 0 (None) 1,800 113* 100 / 0 ** (None) 960 114* 0 / 100 ** (None) 1,250 Notes: *Control.

**No heat treatment. - 26 42453 Example 11.

The same polymerization vessels as used in Exanple 10 were coated in a similar fashion with a 1% solution or dispersion in one of the solvents as indicated in Table IX, of a polar organic compound or an organic dye alone or in combination and with a metal salt as indicated in the same table, which had been heated at 90°C for 30 minutes. After the coated surfaces were washed with water, 100 kg of vinyl chloride, 200kg ]θ of water, 0.05 kg of diisopropyl peroxydicarbonate, 1 kg Of sodium dodecylbenzenesulfonate and 1.5 kg of cetyl alcohol were charged in each polymerization vessel, followed by emulsion polymerization at an elevated temperature, say, 45°C, under agitation at a rate of 110 r.p.m. for 8 hours. After completion of the reaction, the amounts of scale deposition was examined and determined. The results are set out in Table IX. - 27 Table IX Test No. Polar Organic Compd/ Dye/ffietal Salt Mixing Ratio Solvent Amount of Scale 115* (None) (None) (g/m2) 1,600 116* Sudan B — Toluene 550 117* Diaminonaphthalene — Methanol 630 118* Nigrosine Base — Mixed* ** 480 119* EDTA-2Na ___ Water 1,100 120* Phytic acid — Methanol 980 121* Methylene Blue — tt 690 122* Nigrosine --- · Water 1,300 123 Sudan B/Nigrosine/ NaoSiO/ 100/ 5/100 Ethanol- 23 124 »1 ’ 100/ 50/100 tt 0 125 (1 .100/ 100/100 It 0 126 1» 100/1000/100 tt 10 127 Diaminonaphthalene/ 100/ 100/100 tt 0 128 Nigrosine/NaHCQ·} Nigrosine Base/ «1 II 0 129 Nigrosine/NaHCO^ Methylene Blue/ tl tt 30 130 Nigrosine/PeCl2 Sudan B/Phytic acid/ tt It 63 131 NaHCO3 tf -Naphthylamine/ tl Water 81 132 EDTA-2Na/Na2SO4 Induline/p-t oluene- tt Mixed*** 53 133 sulfonic acid/NaCl Oil Brown BB/ tr It 49 134 Daitophor AN/GaC03 Spirit Black/ It tt 0 • Rochelle salt/Na-jSiO^ Notes; * Control.

** Toluene and methanol.

*** Ethanol and methylene chLoride. - 28 10 424S3 Example 12.

The same polymerization vessels as used in Example 10 were coated in a similar fashion with the same material as used in Test No. 126 of Example 11 in rt an amount of 0.1 g/πι (as solid). Into each of the coated vessels were charged 100 kg of vinyl chloride, 200 kg of water together with the varied initiators, suspending agents and/or other additives or comonomers as shown in Table X, followed by suspension polymerization at an elevated temperature, say, 57°C, under agitation at a rate of 100 r.p.m. for 10 hours.

After completion of the reaction, the amounts of scale deposition was examined and determined. The results are set out in Table X.

As controls, similar polymerization using the same additives or comonomers as above was carried out • with the polymerization vessels which had been coated with a single dye, say, Nigrosine. Base or not coated at all. The resulting scale deposition was shown in the same Table X.

In Table X, PVA is for polyvinyl acetate; HPMC is for hydroxypropylmethyl cellulose; IBP is for di-isopropyl peroxydicarbonate; LPO is for lauroyl peroxide; and BPO is for benzoyl peroxide. - 29 Table X Test No. Polymer- ization Initiator Suspending Agent Additive/ Comonomer Amount of Scale Present Invention Control (g/m2) (g/m2) 135 Dimethylvaleronitrile, 0.03 kg Partially saponified PVA, 0.1 kg Vinyl acetate, 15 kg 0 190 136 II If 1 Vinyl acetate, 5 kg 0 130 5 137 11 BPMC, 0.1 kg Sorbitan monolaurate 0.1 kg 0 f 230 138 It ir Sodium 2-etbylhexylsulfosuccinate, 0.1 kg 0 290 139 IPP, 0.02 kg Partially saponified PVA, 0.1 kg (None), 0 210 140 IPO 0.5 kg II (None) 0 330 141 BPO, 0.7 kg tl (None) 0 310 10 142* Dimethylvaleronitrile, 0.3 kg ft (None) 1,200 Note: * Control. No coating. - 30 4 2 4 5 3 Example 13.

The same coating materials as used in Test No. 129 of Example 11, were applied over the surfaces of the inner wall and other parts in combined ve33el3 for bulk polymerization, the first vessel being of a 2-lifcer stainless steel vertical type and the second vessel being of a 4-liter stainless steel'horizontal type.

Then all the coated surfaces were washed with water and dried. Into the first vessel were charged 800g of vinyl 1q chloride and 0.4g of dimethyl valeronitrile, followed by bulk polymerization at 60°C under agitation at a rate of 900 r.p.m. for 2 hours. The reaction mixture was transferred into the second vessel whioh had been charged with 800g of vinyl chloride and 0.4g of dimethyl valeroy5 nitrile, Polymerization was conducted at 57°C under agitation at a rate of 100 r.p.m. for 10 hours. After completion of the polymerization, polymer scale deposition was examined with respect to each polymerization vessel.

For comparison, a similar test was carried out without any coating treatment or with coating with only Nigrosine Base.

The results of the above tests are set out in Table XI. - 31 42459 Table XI Test Amount of Scale No. Coating Material 1st Vessel mm Vessel 143 Same as Test No. 125 (g/m2) 0 (g/m2) 0 144 Same as Test No. 129 0 0 145 Same as Test No. 136 • -0 0 146* (None) 1,400 2,040 147* Nigrosine Base 70 18O Note: * Control.

Example 14.

With the same polymerization vessel as coated and used in Test No. 126 of Example 11, suspension polymerization was carried out in the same maimer and with the same additives as in Test No. 137 of Example 12 for Ϊ0 hours, except that in some tests the coating material of Test No. 126 was separately added to the polymerization mixture in the varied amounts as indicated in Table XII and in the other tests an alkaline substance, say, sodium hydroxide, calcium hydroxide or sodium acetate was added as indicated in the Table. This polymerization 2o run was repeated to observe the deposition of scale by naked eyes or in the same fashion as in Example 1. The results are set out in Table XII. - 32 4 24 63 Table XII Test No. Amount of Coating Material Added Alkaline Substance & Amount Added Time of addition* No. of Runs (p.p.m.) 148 (None) (None) — 3 149 10 (None) — 4 150 50 (None) — 6 151 100 (None) — 8 152 (None) NaOH 0.01 0 8 153 (None) NaOH 0.01 1 hr. 6 154 (None) NaOH 0.01 2 hrs. 5 155 (None) NaOH . 0.01 3 hrs. 4 156 (None) NaOH 0.05 0 10 157 (None) NaOH 0.1 0 13 158 (None) Ca(0H)2 0.05 1 hr. 8 159 50 CHjCOONa 0.1 1 hr. 16 Notes: The amounts in p.p.m. or $ are based on the weight of vinyl chloride monomer.

* Number of hour or hours lapsed from the start of each polymerization run.

Claims (27)

1. A method for the polymerisation of vinyl chloride monomer or a mixture of monomers cohiposed mainly of vinyl chi or ide in the presence of a polymerisation initiator· in a polymerisation vessel, in which the surfaces of the vessel coming into contact with the monomer or monomers are treated, prior to polymerisation, with (a) an organic compound which is a polar compound and/or a dye and (b) a compound which is a metal halide, hydroxide, oxide or carboxylate, or an oxyacid, or an inorganic salt thereof, of an element of the second to sixth period of group IIB or sub-group A or B of Groups III to VII of the Periodic Table.

2. A method according to Claim 1 in which the treatment comprises coating the surfaces with a solution or dispersion of the said organic compound and contacting the thus-coated surfaces with a solution or dispersion of the compound of group (b).

3. A method according to Claim 1 in which the treatment comprises heating a solution or dispersion of the compounds of groups (a) and (b) dissolved or dispersed in a solvent, at a temperature of from 50 to 100°C for more than 10 minutes, and coating the surfaces with the heated solution or dispersion.

4. A method according to Claim 1 in which the treatment comprises coating the surfaces alternately with a solution or dispersion of the said organic compound and with a solution or dispersion of the compound of group (b). 5. Polyoxyethylene sorbitan triphosphate or phytic acid.

5. A method according to Claim 2 in which the coated surfaces are heated at a temperature of from 50 to 100°C for more than 10 minutes in contact with the solution or dispersion of the compound of group (b).

6. A method according to Claim 4 in which the surfaces, having been coated with solutions or dispersions of compounds of both groups (a) and (b), are heated at a temperature of from 50 to 100°C for more than

7. A method according to Claim 1 in which the treatment comprises at least two of the precedures defined in Claims 2 to 4. - 34 4S453

8. A method according to Claim 3 in which the weight ratio of the compound of group (b) to the said organic compound is from 0.01:1 to 50:1.

9. A method according to Claim 4 in which the weight ratio of the compound of group (b) to the said organic compound is from 0.1:1 to 500:1. 10. Dioxide, iron octoate or stannic chloride.

10. A method according to any preceding claim in which both a water-soluble and a water-insoluble compound of group (b) are used. 10 minutes.

11. A method according to any preceding claim in which at least one of the compounds of groups (a) and (b) is also added to the polymerisation mixture.

12. A method according to any preceding claim in which a compound of group (a) or (b), or a mixed and heated solution or dispersion of compounds of groups (a) and (b), is added to the polymerisation mixture in an amount not exceeding 100 ppm based on the weight of the monomer or monomers.

13. A method according to any preceding claim in which the polar organic compound contains a nitrogen, sulphur, oxygen or phosphorus atom, or is a tar, pitch, rosin or wax.

14. A method according to any preceding claim in which the organic dye is selected from azo dyes, anthraquinone dyes, indigo dyes, sulfide dyes, phthalocyanine dyes, diphenylmethane dyes, triphenylmethane dyes, nitro dyes, nitroso dyes, thiazole dyes, xanthene dyes, acridine dyes, azine dyes, oxazine dyes, thiazine dyes, benzoquinone dyes, naphthoquinone dyes, and cyanine dyes. 15. Acid, tungstic acid, manganic acid, chlorid acid, permanganic acid, dichromic acid, nitrous acid, hyponitrous acid, phosphorous acid, hypophosphoric acid and hypophosphorous acid.

15. A method according to any preceding claim in which the organic dye is selected from Direct Brilliant Yellow G, Acid Light Yellow 2G, Levafix Yellow 4G, Procion Brilliant Orange G, Direct Fast Scarlet GS, Direct Bordeaux NS, Brilliant Scarlet 3R, Acid Alizarine Red B, Direct Turkish Blue GL, Cibacron Blue 3G, Blankophor B, Nigrosine, Sirius G, Chrysamine G, Direct Fast Yellow GG, Chrome Yellow G, Chrome Yellow ME, Eosine G, Basic Flavin 8G, Astrazon Yellow 3G, Rhodamine 6GCP, Safranine T, Rhodamine B, Daitophor AN, Auramine Cone, Chrysoidine and Bismarck Brown BG. - 35 4 24 53

16. A method according to Claim 13 in which the nitrogen-containing organic compound is selected from compounds having an amino, imino, azo, nitro, nitroso or azomethine group or an azine ring, and quarternary ammonium compounds.

17. A method according to Claim 13 in which the sulfur-containing organic compound has a thiocarbonyl, thioether or thioalcohol group.

18. A method according to Claim 13 in which the oxygen-containing organic compound is selected from quinones, ketones, aldehydes, ethers, alcohols and alkali salts thereof, esters, carboxylic acids and salts thereof, sulfoxides and oximes.

19. A method according to Claim 13 in which the phosphoruscontaining organic compound is selected from esters of phosphoric and polyphosphoric acid and alkali metal or ammonium salts thereof.

20. A method according to Claim 13 in which the nitrogen-containing organic compound is selected from azomethane, azobenzene, nitrobenzene, nitrosobenzene, monoaminomononitroazobenzene, pyrazine, pyridine, thiazine, aniline, oxazines, benzal aniline, EDTA, «- and β -naphthyl ami nes, ethanolamine, diethanolamine, toluidine, Methylene Blue, Nigrosine Black, Oil Black, Spirit Black, diaminonaphthalenes, diphenyl amine, hydrazine, Ν,Ν-dimethylaniline, urea, laurylamine, cetyl trimethyl ammonium chloride, polyamides and polyethylene imines.

21. A method according to Claim 13 in which the sulfur-containing organic compound is selected from thioglycolic acid, thiourea, thiocarbanilic acid, thiocarbamic acid, thiobenzoic acid, dialkyl thioethers, alkylmercaptans, polysulfides, polysulfones and sulfonic acids and salts thereof.

22. A method according to Claim 13 in which the oxygen-containing organic compound is selected from jj-benzoquinone, anthraquinone, benzophenone, acetophenone, di isopropyl ketone, formaldehyde, acetaldehyde, benzaldehyde, octyl alcohol, cetyl alcohol, benzyl alcohol, phenol, cresol, hematein, propargyl alcohol, hydroquinine, fluorescein, ethylene glycol pentaerythritol, glucose, sucrose, polyvinyl alcohol, diisopropyl ether, diphenyl ether, cellulose ethers, amylacetate, ethyl benzoate, stearic acid, benzoic acid, salicylic acid, maleic acid, oxalic acid, tartaric acid, Rochelle salt, - 36 succinic acid,malic acid, isonicotinic acid, phenylglycine, 3-oxy-2-naphthoic acid, gallic acid, polyacetals and polyacrylic acid.

23. A method according to Claim 19, in which the phosphoric or polyphosphoric acid ester is monolauryl phosphate, sorbitan hexametaphosphate,

24. The method according to any preceding claim in which the compound of group (b) is sodium fluoride, sodium acetate, ferrous chloride, calcium chloride, potassium chloride, sodium tartrate, sodium chloride, calcium acetate, titanium dioxide, sodium oxalate, aluminium chloride, cupric chloride, manganese

25. A method according to any of Claims 1 to 23 in which the oxyacid is selected from zincic acid, boric, acid, aluminic acid, carbonic acid, silicic acid, stannic acid, titanic acid, phosphoric acid, dehydrated phosphoric acids, condensed phosphoric acids, nitric acid, sulfuric acid, chromic acid, molybdic

26. A method according to Claim 1 substantially as described in any of the Examples. 2o

27. A vinyl chloride homopolymer or copolymer when prepared by a method according to any preceding claim.