CA1280532C - Process for the production of polyvinyl chloride of low vinyl chloride content - Google Patents

Abstract

ABSTRACT

The invention relates to a novel process for the production of polyvinyl chloride having a low vinyl chloride monomer content, the latter being removed from a slurry or latex which result from polymerization of vinyl chloride in aqueous media. In the novel process vinyl chloride is removed from a slurry or latex that contains from about 1000 parts to 15,000 parts by weight of vinyl chloride per million parts by weight of the slurry or latex and from 5% to 50% by weight of a polymer selected from the group consisting of polyvinyl chloride and copolymers of vinyl chloride with at least one mono-mer copolymerizable therewith that comprises a) heating said slurry or latex at a temperature in the range of 70°C. to 125°C.or contacting the slurry or latex with at least one organic liquid at a temperature in the range of 25°C. to 125°C.and b) removing vinyl chloride vapor from the slurry or latex.
The resultant aqueous slurry or latex and final polymer product has reduced carcinogenicity.

Description

Case 3233-F 128053Z
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, PROCESS FOR THE PRODUCTION OF POLYVINYL
CHLORIDE OF LOW VINYL CHLORIDE CONTENT
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¦ This invention relates to a process for the production of ~polyvinyl chloride of low vinyl chloride content by the removal of unreacted monomer from the slurry or latex resulting from aqueous ¦processes for the production of polyvinyl chloride. It further ¦relates to a slurry or latex of low vinyl chloride content and to polyvinyl chloride containing very little or no detectiblemonomer.
When vinyl chloride is polymerized in an aqueous medium by suspension or emulsion polymerization techniques, there is obtain-ed a slurry or latex that contains from 5% to 50% by weight and in most cases 20% to 45% by weight of polyvinyl ahloride. It also~
contains up to 5% by weight of unreacted vinyl chloride. Most of the unreacted monomer is usually removed by heating the slurry or latex under reduced pressure to about 65C. As it is ordinarily ¦ practiced, this stripping procedure reduces the monomer content of the slurry or latex to about 1000 parts to 15,000 parts by weight I of vinyl chIoride per million parts by weight of the slurry or ¦ latex. Further processing yields dried products that may contain ¦
¦ 500 ppm or more of monomer.
¦ In view of recently-developed safety standards that requir~
¦that the amount of vinyl chloride in polyvinyl chloride and in the ¦atmosphere that workers breathe be maintained at very low levels, ¦it is necessary that the monomer content of the slurry or latex be ¦sufficiently reduced so that these requirements can be met.
¦ In accordance with this invention, it has been found that I
¦the monomer content of aqueous slurries and latexes of vinyl ~chlorlde hom polymero and copoly ers can be sub6tantially reduced .~ ' ', 'i,.:;,, , I

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by either heating the slurry or latex at a temperature in the range of 70 C to 12S C to remove the vinyl chloride from it or contacting the slurry or latex with at least one organic liquid at a temperature in the range of 25 C to 125 C and removing the vinyl chloride from it.
Thus, in accordance with the present invention there is provided the process for the removal of vinyl chloride from a slurry or latex that contains from about 1000 parts to 15,000 parts by weight of vinyl chloride per million parts by weight of the slurry or latex and from S~ to 50~ by weight of a polymer selected from the group consisting of polyvinyl chloride and copolymers of vinyl chloride with at lsast one monomer copolymerizable therewith that comprises a) heating said slurry or latex at a temperature in the range of 70 C to 125 C or contacting the slurry or latex with 0.5a to 20~
by weight, based on the weight of the slurry or latex, of a compound selected froM the group consisting of vinyl acetate, methylene chloride, di-tert-butyl-p-cresol, and mixtures thereof, at a temperature in the range of 25C to 125C and then b) removing vinyl chloride vapor from the slurry or latex.
Aqueous slurries and latexes of the very low VCM content described herein are unique and have not been required in conventional PVC processes for the preparation of PVC resin in the past. The recently-discovered potential carcinogenicity of vinyl chloride now demonstrates the need for slurries or latexes of very low monomer content from which dried PVC resin of significantly reduced VCM content to the point of no detectible VCM by gas chromatography can be produced.
An advantage of slurries and latexes of this invention is that, upon further dewatering and drying as conventionally practiced in the PVC industry, such slurries or latexes release significantly less vinyl chloride into the wor~ing areas of such plants.
The aqueous slurrieæ and latexes that are treated by the process of this invention are prepared by the conventional suspension or emulsion ~LZ80~;3~
polymerization processes. In the suspension polymerization process, vinyl chloride or a mixture of vinyl chloride with at least one comonomer is suspended in water by the use of suspending agents and agitation. The polymerization is started by means of a free radical generating polymeriza-tion initiator, such as lauroyl perixide, benzoyl perixide, diisopropyl peroxydicarbonate, tertiary butyl peroxypivalate, azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, combinations of dialkyl peroxydicarbonates and lauroyl peroxide, sulfonyl peroxides and the like. Suspending agents such as methylcellulose, hydroxy-_ 2a -Lb~i ~Z8053'~
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methylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellu-lose, hydrolyzed polyvinyl acetate, gelatin, methyl vinyl ether-maleic anhydride copolymers and combinations of the above are included in the reaction mixtures.
In the emulsion polymerization process, vinyl chloride homopolymers and copolymers are prepared by conventional emulsion Ipolymerization techniques. Free radical initiators, such as j'lhydrogen peroxide, organic peroxides, persulfates, and redox ¦Isystems are used. Surface active agents, such as alkyl sulfates, j~alkane sulfonates, alkylaryl sulfonates and fatty acid soaps, are ¦~employed to emulsify the vinyl chloride monomer and comonomers, l~if any. An alternate method of dispersion resin preparation is described in U.S. Patent No. 2,981,722 to Enk et al., granted April 25, 1961.
When copolymers are prepared, vinyl chloride is polymerize~
with a copolymerizable monomer to form a product that contains up to 30% by weight of the comonomer. Among the monomers that can be copolymerized with vinyl chloride are acrylic acid, acrylonitrile, n-butyl acrylate, diallyl maleate, dibutyl maleate, diethyl fuma-l rate, dimethyl itaconate, ethyl acrylate, ethylene, isobutylene, ¦ maleic anhydride, methacrylic acid, methacrylonitrile, methyl acrylate, methyl vinyl ether, 2-ethylhexyl acrylate, propylene, triallyl cyan~rate, triallyl isocyanurate, trimethylolpropane, trimethacrylate, vinyl acetate, N-vinyl carbazole, vinylidene chloride, vinyl isobutyl ether, N-vinylpyrrolidone, and mixtures thereof. I
¦ Further details concerning the production of vinyl chloride ¦homopolymer and copolymers by suspension and emulsion polymeriza-I ¦tion processes are set forth in Kirk-Othmer, "Encyclopedia of ¦Chemical Technology", Second Edition, Volume 21, pages 373-379.

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In a preferred embodiment of the invention, a slurry or latex that contains from 5% to 50% by weight of a vinyl chloride polymer and from 1000 ppm to 15,000 ppm of vinyl chloride is ,Iheated at a temperature in the range of 70C. to 125C., and 'i~preferably in the range of 85C. to 125C. to remove vinyl chloride from it. The heating may be carried out under atmos-~pheric or subatmospheric pressure. In this way there is obtained ¦a slurry or latex that contains not more than 50 ppm and in most ~¦cases 10 ppm or less of vinyl chloride. The dried polymer pro-¦duced by dewatering the slurry or latex has a very low vinyl ~chloride content and can be further processed without creating ~health hazards in the work area.
The processing of vinyl chloride polymers at elevated temperatures to reduce their monomer content is contrary to the ~l teachings of the art, since the art teaches that such heating 'i decomposes these polymers.
In another preferred embodiment of the invention, a slurry or latex that contains from 5% to 50% by weight of a vinyl chloride polymer and from 1000 ppm to 15,000 ppm of vinyl chloride ! is contacted with an organic liquid, which is preferably vinyl acetate, before, during, or following normal residual monomer recovery, and vinyl chloride is removed from it by the stripping techniques practiced in the art, preferably at a temperature in ¦ the range of 25C. to 125C. Because the treated slurry or latex has a substantially reduced monomer content, its subsequent processing does not constitute a health hazard in the operating work areas,and the dried polymer obtained after dewatering also has a very low monomer content.
The organic liquids that can be used in this process include esters such as vinyl acetate, vinyl propionate, n-butyl _ 4 _ 1, `.

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acrylate, dibutyl maleate, diethyl fumarate, dimethyl itaconate, ~ethyl acrylate, methyl methacrylate, octyl acrylate, ethyl acetate, di-2-ethylehxylphthalate~and di-n-octylphthalate; hydrocarbons l~such as pentane, heptane, white oil, cyclohexane, methylcyclo-,pentane, benzene, toluene, xylene, ethylbenzene, styrene, pentene, lhexene, heptene, butadiene, isoprene; alcohols such as methyl llalcohol, ethyl alcohol, isopropyl alcohol, butanol, 2-ethylhexanol~
,¦dodecanol, cetyl alcohol, ethylene glycol, propylene glycol, and butylene glycol; phenols such as phenol, di-tertiary butyl para-Icresol, styrenated phenols, butylated phenols and bisphenol A;
¦~ethers such as diethyl ether, methyl vinyl ether and low molecular~weight polyethers; nitrogen-containing compounds such as triethyl-~amine, triethanolamine, aniline, dimethylaniline, morpholine, ', pyridine, pyrrole, acetonitrile, acrylonitrile, methacrylonitrile,l acetamide, dimethylacetamide, dimethylformamide, caprolactam, N-vinylcarbazole and N-vinylpyrrolidone; nitro compounds such as itromethane, nitroethane and nitrobenzene; halogen-containing compounds such as methylchloride, methylene chloride, chloroform, carbon tetrachloride, ethylene dichloride, ethyl chloride, . vinylidene chloride, chlorobenzene, and fluorinated methanes and ethanes; carboxylic acids such as formic acid, acetic acid, acrylic acid, methacrylic acid, lauric acid, stearic acid and oleic acid; aldehydes such as propionaldehyde, butyraldehyde and benzaldehyde; ketones such as acetone, methyl ethyl ketone, methyl ¦isobutyl ketone, benzoin, benzophenone, methyl vinyl ketone and ¦cyclohexanone; carboxylic acid anhydrides such as maleic anhydride ¦and phthalic anhydride; acid chlorides such as acetyl chloride, ¦benzoyl chloride and phthaloyl chloride; sulfur-containing com-.. ¦pounds such as carbon disulfide, ethyl mercaptan, dodecyl mercap-¦tan, dimethyl sulfoxide, dimethyl sulfone, tetramethylene sulfone, ~ _ 5 _ , ` iZ8053Z~`
,, thioglycolic acid and thiophene; cyclic ethers such as dioxane, Itrioxane, furan, tetrahydroguran, propylene oxide and butylene ¦oxide; conventional diester and polymeric plasticizers for PVC
,~such as phthalates, maleates and adipate diesters, phosphate esters and polyesters; dimethyl silicones; and liquid stabilizers ¦for PVC such as dialkyl tin dilaurates including dibutyl tin dilaurate. A single organic liquid or a mixture of two or more l¦organic liquids can be used.
¦l In general the amount of organic solvent added to the slurry or latex will be from about 0.5% to about 20% by weight, ¦based upon the weight of the slurry or latex, although smaller and~
larger amounts can also be used.
Those skilled in the art will understand that when the organic liquid used is of relatively low boiling point, such as vinyl acetate or methylene chloride, the liquid is essentially l separated from the resin when the process of this invention is ¦ carried out. ~n the other hand, when the organic liquid used is l relatively high boiling, such as di-2-ethylhexyl phthalate, the J ¦ organic liquid used essentially remains with the resin. This can be a further advantage of our invention, when the organic liquid is a conventional additive to vinyl chloride homopolymers and copolymers, as when the organic liquid is a commonly known stabilizer, lubricant, plasticizer, antioxidant, antifoam, I
antistatic agent, etc.
; The invention is further illustrated by the following ~examples.
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I Examples 1-15 In each of Examples 1-15 (Table I), an aqueous slurry containing about 30 percent by weight of polyvinyl chloride was heated and agitated at the temperature and pressure for the time stated with the vinyl chloride monomer evolved being removed.
l Resins A, B and C were prepared using a mixture of lauroyl ,Iperoxide and di-2-ethylhexylperoxydicarbonate as the initiator and ~methyl cellulose as the suspension agent. Resin D was prepared ~¦using the initiator used in preparing Resin A, hydroxypropylmethylf ~¦cellulose as the suspension agent, and trichloroethylene as a ¦~chain transfer agent. Resin E was prepared using the initiator ~and the suspension agent used in preparing Resin D.
¦ In Table I, each of the Examples, with the exception of ¦Example 10, relates to a laboratory treatment in which the samples of slurry that were treated ranged from about 500-1000 grams.
Example 10 represents a pilot plant run in which about 30 gallons of the slurry was treated. In each Example, except 10 and 15, the slurry was a commercial slurry produced by conventional low temperature and vacuum treatment to remove unreacted vinyl chloride monomer (VCM).
In Table I, the VCM concentrations are concentrations of vinyl chloride monomer in ppm, based upon the weight of the resin.
Comparison of the results obtained shows the advantage of the prese4t vention.

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Examples 16-21 In each of Examples 16-21,an aqueous slurry of a copolymer of vinyl chloride and vinyl acetate (vinyl acetate content about ll8-16 percent by weight) was heated and agitated at the temperature ,iand pressure for the time stated with vinyl chloride monomer evolved being removed. The slurry contained about 30 percent by weight of the copolymer.
i~ Resin F was prepared using a mixture of lauroyl peroxide and di-2-ethylhexylperoxydicarbonate as the initiator and hydroxy-propylmethylcellulose as the suspension agent. Resin G wàs pre-pared using lauroyl peroxide as the initiator, gelatin as the suspension agent, and trichloroethylene as a chain transfer agent.l Examples 16-21 were laboratory experiments in which the amount of slurry treated was between 500 and 1000 grams. In each ¦
of Examples 16-21, the slurry treated was a commercial slurry produced by conventional low temperature and vacuum treatment to remove vinyl chloride.
In Table II, the VCM concentrations are concentrations of vinyl chloride in ppm, based upon the weight of the resin.
Examples 22-28 In each of Examples 22-28, to an aqueous slurry containing about 30 percent by weight of polyvinyl chloride was added five ¦percent by weight of vinyl acetate, based upon the initial weight ~of the slurry; from the mixture, vinyl chloride was removed by ¦vaporization. The temperatures, pressures, vaporization times and ¦results obtained are set forth in Table III.
In Table III, the VCM concentrations are concentrations ~of vinyl chloride in ppm (weight/weight), based upon the weight of the resin. Resins H and J were prepared using a mixture of lauroy peroxide and di-2-ethylhexylperoxydicarbonate as the initiator and _ g _ I

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il Examples 29-36 il ¦! In each of Examples 29-36, an aqueous slurry of a copoly-~mer of vinyl chloride and vinyl acetate (vinyl acetate content (, ¦¦about 8 to 16 percent by weight) was heated and agitated at the temperature and pressure for the time stated with vinyl chloride monomer evolved being removed. I
Resin K was prepared using the initiator of Resin H and the suspension agent of Resin I. Resin L was prepared using lauroyl peroxide as the initiator, gelatin as the suspension agent and trichloroethylene as a chain transfer agent. Examples 29-36 were laboratory experiments in which the amount of slurry treated j was 500 grams.
In Table IV, the VCM concentrations have the same meaning as in Table III. In Examples 29-36, the added vinyl acetate was essent1ally moved from the res1n.

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Example 37 About 550 grams of a latex containing about 30 percent by weight of a homopolymer of vinyl chloride was agitated in a one liter, three neck flask. The latex had been prepared using the linitiator of Resin H and the ammonium salt of oxidized oleic acid las the suspension agent. The latex contained 5052 ppm VCM, based ,'on the weight of the resin.
,I Twenty-five grams of vinyl acetate was added dropwise.
¦A vacuum of 100 mm Hg was applied for two hours at room temperature.
The latex then contained 888 ppm VCM, based on the weight of the resin.
After heating for 40 minutes at 55-60C. at 250 mm Hg ~vacuum, the latex contained 4.2 ppm VCM, based on the weight of ~the resin.
¦I Example 38 Seven hundred fifty grams of a latex containing about 30 ¦¦percent by weight of a copolymer prepared from vinyl chloride and ~vinyl aGetate (vinyl acetate content about one to six percent by weight) was agitated in a one liter, three neck flask along with 35 grams of di-2-ethylhexylphthalate. The latex contained 264 ppm~
,~ VCM, based upon the weight of the copolymer.
The mixture was stirred for 15 minutes under a vacuum of 630 mm Hg. Still under vacuum, the mixture was heated at 75C.
for one-half hour. The latex then contained 45 ppm VCM based upon ¦the weight of the copolymer. Continuing the heating and stirring ¦at the same temperature and with the same vacuum for a further ¦period of one-half hour, the latex then contained 9 ppm VCM, ¦based upon the weight of the copolymer. The bulk of the added ~, dl-Y-ethylhe~ ylphthslate essent i ally rems~ ned wJ th the res~n .

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Example 39 A slurry (about 30 percent solids by weight) of vinyl chloride-vinyl acetate copolymer made with lauroyl peroxide as the initiator and gelatin as the suspending agent and containing trichloroethylene as the chain transfer agent that weighed 344 pounds was charged to a 50 gallon, glass-lined reactor. The slurry, which contained about 3000 ppm VCM, based upon the weight ¦
of the resin, was heated to 60C. Then 10.32 lbs. of vinyl aceta$e ,was added, and the reactor was sealed. When the slurry had been heated to 74C. with agitation, a vacuum of 250 mm Hg was applied to recover the VCM. The resulting slurry contained no VCM detecti ble by gas chromatography.
Example 40 ~ The resin used was a dried commercial homopolymer of i~vinyl chloride prepared by the suspension process using a combi-nation of lauroyl peroxide and di-2-ethylhexylperoxydicarbonate as the initiator and hydroxypropylmethylcellulose as the suspending agent that had a VCM content of 145 parts per million (ppm).
The homopolymer was mixed with 400 ml. of water in a one 1, literjflask to form a slurry containing 35 percent by weight of solids. To the slurry 50 ml. of methylene chloride was added.
The mixture was steam-stripped to remove all the methylene chloridè, following which the resin was separated by filtration and dried at~
40C. overnight. The dried resin had a vinyl chloride monomer ¦content not detected by gas chromatography.
Example 41 An aqueous slurry containing 65 percent by weight of a ¦commerical vinyl chloride homopolymer was prepared by the suspen-~sion process using the initiator system and the suspending agent of Example 40. The slurry contained about 9,000 ppm of vinyl chloride monomer, based upon the weight of the homopolymer.

,1 ~280~32 . . , To 450 grams of the slurry was added 50 ml. of methylene chloride. The mixture was stirred for one-half hour at room ~temperature, after which a vacuum was applied for a period of two 'Ihours by means of a water aspirator. The slurry was then filter~ed ;iand dried overnight at 50C. Vinyl chloride monomer could not be detected by means of gas chromatography ll Example 42 ¦1 The procedure of Example 23 was repeated, but in this llexample the 25 grams of vinyl acetate added had previously been ¦Imixed with 5 grams of di-tert-butyl-para-cresol. Results similar ¦~to those obtained in Example 23 were obtained with respect to the VCM concentration (ppm). Those skilled in the art will understand that upon further processing the slurry to produce solid resin the di-tert-butyl-para-cresol will remain in the resin and serve as ¦an anti-oxidant.
Example 43 Two hundred grams of a slurry that contained 35 percent by weight of polyvinyl chloride and 9000 ppm of vinyl chloride was heated and agitated at 80C. for 3 hours. I
¦ Samples which were taken at the end of one, two, and three¦
¦hours were dried overnight at 50C. These dried samples contained ¦13 ppm, 7 ppm, and less than 5 ppm of vinyl chloride, respectively~i ¦ Example 44 `
¦ An aqueous slurry containing 30 percent by weight of a ¦commercial vinyl chloride homopolymer ~as prepared by the suspen- ¦
¦sion polymerization process using a mixture of lauroyl peroxide ¦and di-2-ethylhexylperoxydicarbonate as the initiator, hydroxy-propylmethylcellulose as the suspending agent, and trichloro-ethylene as a chain transfer agent. The slurry contained 1,212 pp~
of vinyl chloride, based upon the weight of the homopolymer.
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~,..;, ~80~;~2 A sample of the slurry waS heated and agitated at 85C. for four hours in a one liter round bottom flask fitted with an air ~condenser. The slurry was then filtered and dried overnight at ~50C. The dried resin had a VCM content of 8 ppm.
Example 45 The procedure of Example 44 was repeated, but at a tempera-ture of 75C. rather than 85C. and with a homopolymer prepared with the initiator system of Example 40 and with hydroxymethyl-'cellulose as the suspension agent. Samples taken at the end of one, two, three and four hours, after drying overnight at 50C. had VCM contents of 9 ppm, 7 ppm, not detected, and not detected, ,respectively.
,, When the slurry was heated and agitated at 85C., samples taken at the end of one and two hours had VCM contents of 7 and 3 ppm, respectively, after drying at 50C. overnight.
l Example 46 l An aqueous slurry containing about 30 percent by weight of a commercial vinyl chloride-vinyl acetate copolymer (about 10 percent by weight vinyl acetate) was prepared by the suspension ~process using the initiator and the suspending agent of Example 40 ¦fWhen a portion of the slurry was filtered and the resin was dried overnight at 50C., the dried resin had a VCM content of 83 ppm.
A 500 gm. sample of the slurry was placed in a one-liter, Iffthree_neck, round bottom flask at ambient temperature along with ,i50 gm. of vinyl acetate. After one-half hour of stirring, vacuum ,was applied (28 mm of' mercury) with continued stirring. Samples ~were taken at the end of one and two hours. The dried products showed no detectible monomer content.
The procedure of the preceding paragraph was repeated, but this time the slurry was heated to 45C. with a vacuum of 100 mm of ', lf ~ 280~3Z

~mercury after the one-half hour of stirring. Again the final ;sample showed no detectible VCM content.
Example 47 A water slurry of a commercial homopolymer of vinyl chloride prepared using lauroyl peroxide and di-2-ethylhexylper-oxydicarbonate as the initiator and methyl cellulose as the :suspending agent was heated and agitated in a three-necked, round bottom flask at 80C. while maintaining a vacuum of 400 mm Hg.
The vinyl chloride concentration of the starting slurry was 4663 ppm based on the weight of the slurry. Samples of the slurry were withdrawn from the flask after heating as described above after one, two and three hours,and these slurry samples had VCM contents of 20 ppm, none detected, and none detected, respectively.
Example 48 To 2000 gm. of a polyvinyl chloride dispersion resin latex ~(resin content about 40 percent by weight) that had a vinyl llchloride content of 12,955 ppm, based on the weight of the resin, i~as prepared by the process of U. S. Patent No. 2~981,722 to Enk llet al., granted April 25, 1061, was added 300 ml. of a one percent j~by weight aqueous magnesium sulfate solution. The batch was ~¦brought to 90C. and maintained and agitated at this temperature ¦~for one hour. The dispersion latex that was obtained had a monomer content of less than one ppm. The dispersion latex was l¦cooled, filtered and dried in an oven overnight at 45C. The ¦dried resin had no detectible ~CM content.
Example 49 To 500 grams of a polyvinyl chloride dispersion latex (resin content about 40 percent by weight) having a vinyl chloride ~. ~tcontent of 5898 ppm as prepared by the process of U. S. Patent I ~No. 2,981,722 to Enk et al., granted April 25, 1961, was added ,1.

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250 grams of water. The batch was brought to 90C. and maintained and agitated for one hour at this temperature. The dispersion latex and the dried resin prepared from it had no detectible VCM
content.

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Claims (13)

1. The process for the removal of vinyl chloride from a slurry or latex that contains from about 1000 parts to 15,000 parts by weight of vinyl chloride per million parts by weight of the slurry or latex and from 5% to 50% by weight of a polymer selected from the group consisting of polyvinyl chloride and copolymers of vinyl chloride with at least one monomer copolymerizable therewith that comprises a) heating said slurry or latex at a temperature in the range of 70°C to 125°C and then b) removing vinyl chloride vapor from the slurry or latex.

2. The process of claim 1 wherein the latex is heated at a temperature in the range of 85°C to 125°C.

3. The process of claim 1 wherein the removal of vinyl chloride is continued until the vinyl chloride content of the slurry or latex is not more than 50 parts per million, based on the weight of polymer in the slurry or latex.

4. The process of claim 1 wherein the removal of vinyl chloride is continued until the vinyl chloride content of the slurry or latex is not more than 10 parts per million, based on the weight of polymer in the slurry or latex.

5. The process of claim 1 wherein the polymer in the slurry or latex is polyvinyl chloride.

6. The process of claim 1 wherein the polymer in the slurry or latex is a copolymer containing vinyl chloride and up to 30% by weight of vinyl acetate.

7. An aqueous slurry or latex that contains from 5% to 50% by weight of a polymer selected from the group consisting of polyvinyl chloride and copolymers of vinyl chloride with at least one copolymerisable monomer and not more than 50 ppm of vinyl chloride.

8. An aqueous slurry or latex as set forth in claim 7 that contins 20% to 45% by weight of said polymer.

9. An aqueous slurry or latex as set forth in claim 7 that contains an amount of vinyl chloride that is not detectible by gas chromatography.

10. The process for the removal of unconverted vinyl chloride from an aqueous polymer dispersion that contains 1,000 parts to 15,000 parts by weight of vinyl chloride per million parts by weight of the dispersion and from 5% to 50% by weight of a polymer selected from the group consisting of polyvinyl chloride and copolymers of vinyl chloride with at least one monomer copolymerizable therewith that comprises:
a) heating said dispersion at a temperature in the range of 80°C to 100°C and b) removing vinyl chloride vapor from the dispersion wherein the removal of vinyl chloride is continued until the vinyl chloride content of the dispersion is not more than 50 parts per million based on the weight of polymer in the dispersion.

11. The process of claim 10 wherein the polymer in the dispersion is polyvinyl chloride.

12. The process of claim 10 wherein the polymer in the dispersion is a copolymer containing vinyl chloride and up to 30% by weight of vinyl acetate.

13. The process of claim 10 wherein the aqueous vinyl chloride polymer dispersion is an aqueous dispersion obtained by polymerization in aqueous suspension.