CA1057896A - Method for the polymerization of vinyl chloride - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Vinyl chloride monomer or a monomer mixture composed mainly of vinyl chloride is polymerized in a polymerization reactor whose inner walls and agitator and other surfaces coming into contact with the monomer or monomers are coated with a coating material containing at least one electron-donor compound and at least one electron-acceptor compound. By this method, the deposition of polymer scale on those surfaces is greatly reduced, and high quality polymer can be produced.

Description

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This invention relates to a method for the polymerization of vinyl chloride or a mixture of monomer or monomers composed mainly of vinyl chloride in the presence of a polymerization initiator in a polymerization reactor, in which the deposition of polymer scale on the inner walls of the polymerization reactor and the surfaces of an agitator and other parts in contact with the monomer or monomers can be effectively inhibited.
Known methods for the production of vinyl chloride polymer include suspension polymerization, emulsion polymerization, solution polymerization, gas-phase polymerization and bulk polymerization. These conventional polymerization methods have ;~
a defect that polymer scale is deposited on the surfaces of the walls of the polymerization reactor and other parts including agitating blades in contact with the monomer, resulting in the reduction of the yield of polymer product and the cooling i efficiency of the polymerization reactor. Further, the scale deposited on the surfaces tends to come off and enter the polymer product, resulting in a lowering of the product quality. Further-more, all scale deposited on the surfaces has to be removed 20 following each polymerization run, this requires much labor and ;~
time, and results in a reduction of productivity. Besides, the ;~
scale-removing operations involve a health problem due to the ~;
fact that monomeric vinyl chloride has a carcinogenic property.
In order to prevent such unwanted polymer scale deposition on the inner walls and other surfaces within the polymerization reactor, it has been proposed to coat those surfaces uith an amine compound, a quinone compound, an aldehyde compound or other polar organic compound (see U.S. Patent 3,669,946). Although this is useful for suspension polymerization, it is not so for ~
30 the other types of polymerization. Even in suspen~ion ~ -~. ' ' ~`.~ , ..
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polymerization this process is effective only for the homopoly-merization of vinyl chloride where the polymer scale preventive effect can be maintained through a considerably large number of repeated polymerization runs. Furthermore, generally speaking, this process has disadvantages:
~1) when a copolymerization of vinyl chloride with one or more copolymerizable monomer or monomers is intended,

(2) when an emulsifier is added to the polymerization mixture as the dispersing assistant, 10 (3~ when an acyl peroxide, such as benzoyl peroxide or lauroyl ;
peroxide, is used as the polymerization initiator, and (4~ when the polymerization is carried out in the presence of certain processing additives, such as lubricants and ~tabilizers, e.g., lauric acid, stearic acid, lauryl sulfonate, stearyl sul~onate and salts thereof.
According to the present invention there is provided a method for the polymerization of vinyl chloride or a mixture of monomers composed mainly of vinyl chloride in the presence of a polymerization initiator in a polymerization reactor, the method comprising coating the inner walls of said polymerization reactor and other surfaces coming into contact with the monomer or monomers with a coating material containing at least one electron-donor compound and at least one electron-acceptor compound and polymerizing the polymerization mixture in the thus coated polymerization reactor.
Such a method permits the polymerization of vinyl chloride or a mixture of monomer or monomers composed mainly of vinyl chloride in the presence of a polymerization initiator in a polymerization reactor substantially without deposition of polymer scale on the inner walls of the polymerization reactor and other surfaces in contact with the monomer or monomers, 1~S7~
regardless of the type of polymerization. Furthermore, the method enables high quality vinyl chloride polymer to be produced with an improved production efficiency. `~
The invention will be further understood from the following description by way of example of embodiments thereof.
According to the method in accordance with a preferred ;-embodiment of the present invention, the deposition of polymer scale on the inner walls of the polymerization reactor, agitator blades and other parts in contact with monomer or monomers can be substantially eliminated. Further, advantageously, this method is effective in any type of polymerization, i.e., suspen-sion polymerization, emulsion polymerization, solution polymeriza-tion or bulk polymerization and also in the copolymerization of a monomer mixture composed mainly of vinyl chloride as well as in the homopolymerization of vinyl chloride.
The prevention of polymer scale deposition is presumed to follow the mechanism wherein a mixture of an electron-donor compound and an electron-acceptor compound forms a charge-transfer complex which is effective for this purpose, different from the customarily employed coating compounds, such as amines, - quinones and aldehydes. More specifically, the surface over which the thus formed charge-transfer complex has been applied is made to have the state such that the same surface does not absorb scale-forming molecules present in the polymerization mixture.
The electron-donor compounds useful in the method of the present invention include ~ -electron-donor compounds, ~ -electron-donor compounds and n-electron-donor compounds. More specifically, there can be mentioned, for example, aromatic compounds, such as benzene, naphthalene, anthracene, phenanthrene, fluoracene, pyrene/ azul~ne, fluorene, diphenylmethane, triphenylmethane, naphthacene and chrysene; olefinically unsaturated compounds,

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such as dienes and polyenes; nitrogen-containing organic compounds other than nitro compounds such as aminonaphthalene, diphenyl-amine, phenazine, carbazole, acr.idine, o-phenanthroline, higher aliphatic amines, benzidine, azobenzene, hydrazobenzene, aniline, o-toluidine, pyridine, morpholine, nicotine, 8-hydroxyquinoline, indole, skatole, pyrimidine, piperazine, ethylamine, diethylamine, triethylamine, ethylene diamine, guanidine, trimethylene diamine, hydrazine derivatives, hexamethylene diamine, ethanolamine, diethanolamine and triethanolamine; sulfur-containing organic compounds, such as phenothiazine, dibenzophenothiazine, mercaptobenzothiazole, thioethers, mercaptans, diphenylthiourea, thiourea, polysul~ides, thiocresol and thiophenol; oxygen containing organic compounds, such as ~ -naphthol, phsnol,

4-chlorophenol, resorcinol, pyrogallol, pyrocatechol, glucose, maltose, cellulose ethers, phenoxazine, diphenyl.ene oxide and other aromatic ethers; halogens, such as iodine and bromine;
basic quinoneimine dyes containing an azine, oxazine or thiazine ring, such as Methylene Blue, Safranine, Nigrosine Base, Spirit Black, Induline, Nile ~lue and Aniline Black; basic azo dyes containing a monoazo-, bisazo- or polyazo structure, such as Bismarck Brown R and Yellow AB; diphenylmethane dyes, such as :.
Auramine JD; triphenylmethane dyes, such as Magenta and Malachite Green; oil-soluble, amino-containing azo dyes, such as Sudan `
Black B, Oil Scarlet SN and Oil Yellow; basic xanthene dyes, such ~ . :
as Rhodamine B; other basic or electron-donating group containing .
thiazole dyes, basic stilbene dyes, phthalocyanine dyes and cyanine dyes; and pigments, such as Spirit Blue.
The electron-acceptor compounds useful in the present invention include ~ -electron-acceptor compounds and ~ -electron-acceptor compo~lnds. More specifically, there can be mentioned,for example, quinone compounds, such as benzoquinone, S7~

naphthoquinone, anthraquinone, diphenoquinone, chloranil, and fluoranil; sulfonic acids and their sodium, potassium and ammonium salts, such as ~ -naphthalenesulfonic acid, anthraquinone-sulfonic acid, sodium dodecylbenzenesulfonate, metanilic acid, ~;~
cyclohexylsulfonic acid and p-toluenesulfonic acid; halogenated hydrocarbons; carboxylic acids, such as 3-hydroxy-2-naphthoic acid, naphthalene-carboxylic acid, diphenylcarboxylic acid, picric acid, thioglycolic acid, benzoic acid/ maleic acid and ascorbic acid, their anhydrides and their sodium, potassium and ammonium salts; nitro compounds, such as ~ -nitronaphthalene, nitrobenzene and trinitrobenzene; cyano compounds, such as ~ -cyanonaphthalene and tetracyanoethylene; phosphoric acids, such as tripolyphosphoric acid and phytic acid, and their sodium, potassium and ammonium salts; acid azo dyeq, such as ~ -Naphthol orange, ~maranth, Acid Brown ~X, Acid Cyanine GR, Acid Light Yellow and Milling Black VLG; acid mordant azo dyes, such a3 Chrome Black PB; direct azo dyes, such aq Direct Brown M, Congo Red and Direct Blue; anthraquinone dyes, such as anthraquinone mordant dyes (e.g, Alizarine), anthraquinone acid dyes (e.g.
Anthraquinone Violet JD), anthraquinone vat dyes (e.g. Indanthrene~
naphthoquinone and benzoquinone vat dyes, such as Indanthrene ID-6GD; Indigosol and Anthrasol dyes; indigo dyes, such as Brilliant Indigo B; nitro dyes, such as Naphthol Yellow S;
nitroso dyes; sulfide dyes7 acidic triphenylmethane dyes, such as Acid Milling Green J and Acid Violet 4BN; acidic quinoneimine dyes containing an azine, oxazine or thiazine ring, such as Nigrosine and Brilliant Alizaline Blue 3K; oil-soluble, amino-free ~-azo dyes, such as Solar Brown RKX, Oil Red RR, Oil Red SA, Oil Scarlet 308 and Vari Fast Black 3804; acid xanthene dyes, such 30 as Rhodamine B Base; reactive dyes, such as Brilliant Orange GS, ;~

Brilliant Blue RS, Quinoline dyes; parazolone dyes, such as ~'' ,.~ ~.

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Xylene Fast Yellow 2G; acid stilbene dyes, such as Chrysophenine;
and thiazole dyes, such as Diaresin Rose BD.
At least one electron-donor compound and at least one electron-acceptor compound are mixed conveniently by dissolving or dispersing them together in a suitable medium. It is e~en possible to dissolve or disperse them separately, the resulting two dissolutions or dispersions then being mixed. Such dissolving or dispersing operations are carried out usually at room tempera-ture or, sometimes, below 0C. or above S0C., optionally under irradiation with light. The light used in general is visible or ultra-violet light from a fluorescent or mercury lamp. ` ;
Illustrative of the media in which the electron-donor and electron-acceptor compounds are dissolved or dispersed are water;
ethers, such as tetrahydrofuran and diisopropyl ether; alcohols, such as methanol, ethanol and propanol; esters, such as methyl acetate and ethyl acetate; ketones, sùch as acetone and ~
methylethylketone; hydrocarbons, such as benzene, toluene, ~ ~-xylene and hexane; chlorinated hydrocarbons, such as methylene chloride, carbon tetrachloride and trichloroethylene; and aprotic solvents, such as dimethylformamide, dimethylacetamide, dimethylsulfoxide and acetonitrile. 1'hese individual media can be used alone or in combinations.
A good effect of preventing the deposition of polymer scale is attained when the mixing ratio of the electron-donor compound and the electron-acceptor compound is between 1:20 and 20:1, preferably between 1:5 and 5:1, by weight.
The amounts of the mixture of the electron-donor and electron-acceptor compounds applied on the inner walls of the polymerization reactor and other parts coming in contact with ~;
the monomer or monomers are unchanged from those adopted in the prior art methods using conventional coating materials~ In other i'~ .

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words, a sufficient effect of preventing polymer scale deposition can be obtained when the mlxtuxe is applied on the surfaees in an amount of at least 0.001 g per m of coated area. It is recommended, however, that the thus coated surfaces are washed with water to remove any excessive coatings which would even ually come off and enter the polymer product.
Further, the effect of preventing the cleposition of polymer scale can be enhanced by adding one or more alkaline sub~
stances, such as oxides, hydroxides, carbonates, phosphates, bicarbonates, silicates and carboxylates of alkali metals, alkaline earth metals and ammonium to the polymerization mixture. ~;
In this case, however, it is preferred that the amount of such additives is always smaller than 1% by waight based on the monomer or monomers so that the quality of the resulting polymer should not be degraded and the polymerization reaetion is not `
disturbed.
The method is effective to all types of polymerization of vinyl ehloride ineluding suspension, emulsion, solution and bulk polymerization. Further, the method is not limited by ~ ;
polymerization conditions, such as polymerization temperatures and agitation conditions, or by the kinds of additives to the polymerization mixture, for example suspendin~ agents, sueh as partially saponi~ied polyvinyl aleohol and methyleellulose, anionie emulsifiers, sùch as sodium lauryl sulfate, sodium dodeeyl benzene sulfonate and sodium dioetyl sulfosuccinate, nonionic emulsifiers, such as sorbitan mon~laurate and polyoxyethylene alkyl ether, chain transfer agents, such as trichloroethylene and mereaptans, `
and initiators, such as diisopropyl peroxydicarbonate, lauroyl peroxide and dimethyl valeronitrile. The effect of the method is not affected by the presenee of eertain proeessing additives, such as fillers (e.g. calei~ carbonate and titanium dioxide), ~
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stabilizers (e.g. tribasic lead sulfate, calcium stearate and dibutyltin laurate), lubricants (e.g. rice wax and stearic acid) and plasticizers (e.g. dioctyl phthalate and dibutyl phthalate).
Furthermore, an excellent effect can be attained not only in the homopolymerization of vinyl chloride but also in the copolymerization of vinyl chloride with one or more monomers copolymerizable with vinyl chloride, for example vinyl esters, vinyl ethers, acrylonitrile, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters, maleic acid, maleic acid esters, maleic anhydride, fumaric acid, fumaric acid esters, aromatic vinyl monomers, vinyl halides other than vinyl chloride, vinylidene halides, and olefins. ~ -The present invention will now be further illustrated by the following ~xamples.

Various coating solutions were prepared by mixing the electron-donor compounds and the electron-acceptor compounds in the solvents, as set forth in Table I, at room temperature with agitation for 3 hoursr followed by filtration, to have a concen-tration of 1% by weight based on the solvent.
Each coating solution thus obtained was applied to thesurfaces of the inner walls of a l,000-liter stainless steel polymerization reactor in an amount of 0.1 g/m2 (as solid). The surfaces so treated were then dried and washed with water.
Thereupon, 500 kg of deionized water, 0.5 kg of hydroxy-propylmethylcellulose, 0.5 kg of sorbitan monolaurate, 200 g of dimethyl valeronitrile and 200 kg of vinyl chloride were charged in the polymerization reactor, followed by polymerization at 57C.
for 10 hours. After completion of the polymerization, the amount of polymer scale deposited on the surfaces was determinPd with the results as given in the same table.

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Table I
Exp. El~ctron-donor Electron-ac- 5cal~
No. compound 5~E~L~o~y~¦ Solvent 1* Nigro~lne Base None (~) 250 ~-2* Diaminonaphthalene None (b) 310 3* None Oil Scarlet ~oa (b) 3 4* None Rhodamine Ba~e (b) 410

5 Nigrosine Base Nigrosine (b)

6 Oil Scarlet SN Nigrosine ~b) O

7 Diaminonaphthalene Acid Brown GR (b) O

8 Ethylenediamine Chrome Black ~B (b) O

9 Malachite Green Oil Scarlet 308 ~b) O ..
tO Spirit Black p-Benzoquinone (b) 11 Induline Amaranth (c) O
12 Azulene Rhodamine Ba~ (b) o :
1~ Nigro~ine Base Opr~ Red RR(b) o 14 Thiophenol Nlgro~ine. ~b) O
15 Sudan Black B/ Nigroslne(b) o ~Ethylenediamine~
16 Diaminonaphthalene/ Nigrosine(b) O
ethanolamine**
17 Nigrosine Ba~e Diphenoqulnone/ (b) O ~ ~;
p~enol** ~:
18 Nigrosine Ba~e Oil Scarlet 308 (d) o 19* Nigrosine Base/ None (b~ 280 .: :
Sudan Black B**
20* Diaminonaphthalene/ None (b) 260 morpholine*~
21* None Rhodamine Ba~e/ (b) 320 Nigro~ine*~ : :
22* None Opras Red M / (b) 350 Diphenyl acid*.*
23* None p-Benzoquinone/ (b) 250 Acid Brown GR** -~
24* Induline/ None (b) 300 :
~plrit Black** .
* Control ** Mixing ratio: 1:1 br weight olvent: a : Mixed ~olvent of toluene and methanol b : Me~hanol .(c): Dimethylformamide d : Methylene chloride . ,.. ,, . . : .

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Example 2.
Coating solution were prepared by mixlng ~udan ~lQck B ~s tha elec~ron donor and Nlgro~ine ~ the electron acceptor ln the v~rious proportlon~ ~by w~ight) ln certain solvents under specific-cGnditlons, ~8 ~et rorth in T~ble II, followed by filtration, to h~ w a concen~
tration of 1~ by weight based on ~h~ solvent~
Each ooating solutlon thu~ obtalned w~l~ appliod ts the surfaces Or the lnner W~113 o~ ça~! lOOO~liter stainless steel polymerization reactor and the agltator blades ln an amount o~ 0.1 g/m2 (aa solld). m~ sur~ace~
80 treatsd were then driad and wa~h~d wlth w~t~r.
Thereupon, 500 kg of deionized water, 0,5 k~ o~ partially ~aponified polyvlnyl alcohol, 100 ~ of dllso~ropyl peroxydicarbonate and 200 kg of vinyl chlorido were charged ln the polymerization reactor, follow0d by polymerization ~t 57C ~or 10 hours with aglt~tion at 100 r.p.~. After completion Or the polymerlzatlon, the :
amount o~ polymer scale deposited on the surface~ was~ .
: .
determined with the re~ultq as given in the table,

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Table II
Exp. Sudan Nigro- Sc~1 No. ~lack ~ sine Solvent Conditions 25* None None None per-se 13tO
26* 100 None Methanol per-se 420 27* None 100 Methonol per-se 460 28 100 100 Methanol (a) 0 29 100 100 Methanol (b) 0 100 100 Methanol ~c) 1 31 100 100 Methanol (d) 5 3 100 100 Methanol (e) 0 33 100 5 Methanol (a) 85 lo 34 100 20 Methanol ~a) 15 100 50 Methanol (a) 0 36 5 100 Methanol (a) 60 37 20 100 Methanol (a) ~2 38 50 100 Methanol (a~ 0 39 100 100 E-thylene- (~)0 ~ diamine~*

* Control ** This solvent served also a~ an electron-donor compound.
Condition ~a): Both compounds were together in the solvent with agitation ~or 3 hours at room temperature.
(b): The same as (a) above except the temperature was 0C.
(c): The same as (a) above except the temperature was 90C.
(d): Each compound was formed into a solution in the solvent with agitation for 3 hours at room temperature, and the resulting two solutions were mixed together.
(e): The same as (a) above except irradiation of ultraviolet light was added.
(f): me q~me as (a) above except the agitat~o~
period was I hour.

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~AMPLE 3 The coating solution of Experiment No. 28 of Example 2 was applied to the surfaces of the inner walls of a l,000-liter stainless steel polymerization vessel and an agitator having paddle-type blades 600 mm in diameter in an amount of 0.1 g/m2 (as solid). The surfaces so treated were then dried and washed with water.
Thereupon, 100 kg of vinyl chloride, 200 kg of deionized water and the certain amounts of the processing additives together with the certain amounts of the polymerization initiator and the dispersing agent, as set forth in Table III, were charged in the polymerization reactor, followed by polymerization at 57C. for 10 hours with agitation at 100 r.p.m. After completion of the polymerization, the amount of polymer scale deposited on the sur~aces was determined with the results as given in the table under the heading "Present Invention".
For comparison, the same procedure as above was repeated except that the coating solution was a solution of Nigrosine Base alone, and the amount of polymer scale was determined with the results as given in the same table under the heading "Control".
For another comparison, Experiment No. 52 shown in the table was conducted in a similar manner except no coating solution was used. As a result, the amount of polymer scale deposition in this test is given in the column of "Scale, g/m2"
in the same table.

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Table III
., :' Processing Pre~ient Exp . Initiator Dispersing additive ( ~ ) ln-No. (k~ a~ent (k~ , yQ~ Control DVN(0.03~ PVA(0.1) Stearic acid ~0.1) 0 310 41 -do- -do- Calcium stearEiite O 300 (O.1) 42 -do- -do- Zinc oleate (O.t) 0 230 :.
43 -do- -do- _ 0 170 44 -do- -do- - O 130 45 -do- HPMC (0.1) Sodium 2-ethyl- 0 330.
hexyl-sulfo- .
succinate (0.1) 46LPO(0.5~PVA (0.1) - 0 330 47BPO(0.7) -do- _ 0 300 48IPP(0.02) -do- Trlbasic lead 0 360 ~tearate (1.2) Calciumi carbonate(3.0) DOP (2.0) Stearic acid (0.5) Calciumi stearate (O.7) Titaniumi dioxide(t.5) ~ ~ -49 -do- -do- Dibasic lead G 4tO
stearate (0.7) Tribasic lead ~tearate (1.0) Polyethylene wax~O.5) .:
Lead s-teara-te (1.4) :~
Barium stearate(O.2) ~
Stearic acid (0.1) ~ .
50 -do- -do- Calciumi 0 390 stearate (1.0) Rice wax (1.2) Octyl mercaptide(O.7) Polyethylene wax (0.1) ~-51 DVN(0.03) S.L.S.(1.0) - 27 450 :
C.A. (1.5) 52 -do- P~A (0.1) - - 1200 ,, ,,, , , , , . - :

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Note~
(1) In Exp. No.4~, there wa~ u~ed a monomer mixture consisting of 85 kg o~ vinyl chlorlde and 15 kg o~ vinyl acetate, instead of vinyl chloride as used in other experiments. -(2) In Exp. No.44, there was used a monomer miXture consi~ting of. 95 kg of vinyl chloride and 5 ~g ::
of vinyl acetate.

(3) In Exp. No.51, the agitat~on qpeed was 30 r.p.m.
S4) In the table, DVN is for dimethylvaleronltrile; . ~ :
LP0 is for lauroylperoxide; BP0 i~ ~or benzoylperoxide; IPP i9 for diisopropylpe~o~
dicarbonate; PVA is for partially saponi~ied polyvinyl alcohol; HPMC is for hydroxypropyl-methylcellulose; S.L.S. i8 for s~dium lauryl sulfate; C.A. is for cetyl alcohol; and ~:
DOP is for dioctylphthalate. -~

''''`'~ ~ '~; ' Example 4.
The coating solution of Exp. No.28 o~ Example 2. ~.
~0 :
wa~ applied to the surfaces of the inner walls o~ a 5-liter stainles3 steel polymerizatlon reactor and the agitation blades in an amount o~ 0.1 g/m2, ~nd the ~ur~ace~ so treated were dried and then washed with water. Thereupon, 1,B00 g of vinyl chloride, 2,700 g 'of deionized water, 0.1 g Or partially saponified polyvinyl ' ~ S'7~

alcohol,. 0.1 g of ~odium ~tearate and 0.03 g of dimethyl-valeronitrile were charged in the polymeri~ation reactor and ~ubJected to polymerization at 57C in the pre~ence of a certain alkaline substance which wa~ added in :
amounts and at tlme~ as indicated in Table IV. Run~ of such polymerization were repeated with the 3~m~ poly-merization reactor ~ntil polymer scale depo~itin~ on the coated surfaces was found to exceed 1 g/m2 or observed with the nak~d eye. The number of runs Ju3t prior to that run where tha polymer scale deposition was 80 found or observed were countcd. The re8ult8 are given in the table, . Table IV
Exp. Alkallne Amount, Addit~on Time, No. of No. Substance wei~ht % _ hours* Runs 53 None 54 Sodium hydr~xide 0.01 0 - do - 0.01 2 5 56 - do - 0.01 4 3 57 - do - 0.1 0 12 58 Sodium acetate 0 j o 9 59 - do - 0.1 2 7 Calcium hydroxide 0.05 0 10 * Number of hours after start of the polymerization.

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Example 5.
The coating ~olution of Exp. No.~8 of Example 2 was applied to the ~ur~aces of inner walls o~ two polymeri-zation reactors, one being a vertic~l-type 2~-liter ~tainless steel reactor and the other being El horizontal- -type 4-liter stainless steel reactor and oth~3r part~
coming into contact with monomer, in an ~mount of 0.1 g/m2.
The coated surfac~s were drled and then washed with water. Thereupon, 800 g of vinyl ehloride ~nd 0.4 g o~ dimethylvaleronitrile were charged into tho ~ir3t 2-liter polymerization reactor, i~ollowed by polymeri-zation at 60C for 2 hours with agitation At 900 r.p.m. ;~
m e r,esulting reaction mixture wa9 tran8i~erred to the second 4-liter polymerization reactor which had been charged with 800 g of vinyl chloride and 0.4 g of ;
dimethylvaleronitrile, to carry out a further polymeri-zation at 57C for 10 hours with agitation at 100 r.p.m. ~ ~

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Polymer scale deposition on the sur~aces of each polymerization reactor wa~ determined as given in Table V.

For comparison, a qimilar test was carried out without use of the coatlng solution or wlth use of a coating solution consi~ting of Nigro~ine Base alone.
The results are ~hown in the ~ame table.

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Table V

No, Coatin~ solution _ _ irst rsactor econd reactor 61 Same a~ Exp. 28 0 0 62 None 1400 2040 63 Nigrosine Base 70 ~0 ..

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Claims (12)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for the polymerization of vinyl chloride or a mixture of monomers composed mainly of vinyl chloride in the presence of a polymerization initiator in a polymerization reactor, the method comprising coating the inner walls of said polymerization reactor and other surfaces coming into contact with the monomer or monomers with a coating material containing at least one electron-donor compound and at least one electron-acceptor compound and polymerizing the polymerization mixture in the thus coated polymerization reactor.

2. The method of claim 1 wherein said coating material contains said electron-donor compound and said electron-acceptor compound in a ratio ranging from 1:20 to 20:1 by weight.

3. The method of claim 1 wherein said coating material contains said electron-donor compound and said electron-acceptor compound in a ratio ranging from 1:5 to 5:1 by weight.

4. The method of claim 1, 2 or 3 wherein the amount of said coating material is at least 0.001 g per m2 as solid.

5. The method of claim 1, 2 or 3, wherein said polymerization mixture contains at least one processing additive.

6. The method of claim 1 wherein the coated surface within said polymerization reactor is washed with water prior to the polymerization.

7. The method of claim 1, 3 or 6 wherein said coating material comprises a solution of said electron-donor compound and said electron-acceptor compound in a solvent selected from the group consisting of water, alcohols, esters, ketones, hydrocarbons, chlorinated hydrocarbons and aprotic solvents.

8. The method of claim 1, 3 or 6 wherein said electron-donor compound is at least one selected from the group consisting of aromatic compounds, olefinically unsaturated compounds, nitrogen-containing organic compounds other than nitro compounds, sulfur-containing organic compounds, oxygen-containing organic compounds, halogens, basic quinoneimine dyes, basic azo dyes, diphenylmethane dyes, triphenylmethane dyes, oil-soluble amino-containing azo dyes, basic xanthene dyes, thiazole dyes, basic stilbene dyes, phthalocyanine dyes and cyanine dyes.

9. The method of claim 1, 3 or 6 wherein said electron-acceptor compound is at least one selected from the group consisting of quinone compounds, sulfonic acids and their salts, halogenated hydrocarbons, carboxylic acids and their anhydrides and salts, nitro compounds, cyano compounds, phosphonic acids and their salts, acid azo dyes, acid mordant azo dyes, direct azo dyes, anthraquinone dyes, naphthoquinone and bezoquinone vat dyes, Indigosol and Anthrasol dyes, Indigo dyes, nitro dyes, nitroso dyes, sulfide dyes, acidic triphenylmethane dyes, acidic quinoneimine dyes, oil-soluble amino-free azo dyes, acid xanthene dyes, reactive dyes, quinoline dyes, pyrazolone dyes, acid stilbene dyes and thiazole dyes.

10. The method of claim 1, 3 or 6 wherein said polymerization mixture is a dispersion of said monomer or monomers in an aqueous medium alkalified by addition of an alkaline substance.

11. The method of claim 1, 3 or 6 wherein said electron-donor compound is at least one selected from the group consisting of Nigrosine Base, diaminonaphthalene, Oil Scarlet SN, ethylene-diamine, Malachite Green, Spirit Black, Induline, Azulene, Thio-phenol, Sudan Black B, ethanolamine and morpholine.

12. The method of claim 1, 3 or 6 wherein said electron-acceptor compound is at least one selected from the group consisting of Oil Scarlet 308, Rhodamine Base, Nigrosine, Acid Brown GR, Chrome Black PB, p-benzoquinone, Amaranth, Opras Red RR, diphenoquinone, phenol and diphenyl acid.