CA1111176A - Method of preparing vinyl halide polymers and copolymers with polyolefins - Google Patents

Abstract

¦ ABSTRACT
Polymers of excellent impact strength, reduced particle size, and enhanced proportions of fines are obtained in the bulk polymerization of a vinyl halide or mixture thereof with comonomer(s) in the presence of a high molecular weight polyolefin added to the polymerization mass upon conversion of 0 to about 20% by weight of monomer(s) to polymer, by removing from the polymerization mass during the thick paste state thereof sufficient vinyl halide to adjust the effective concentration of polyolefin to above about 3.5% based on vinyl halide. The resultant product which contains an enhanced proportion of fines and is devoid of massive agglomerates, requires less mechanical work in combustion or shorter heating in melting in subsequent conventional processing steps.

Description

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This invention relates to an improvement in the preparation of polymers of high impact strength and enhanced processability. More particularly the invention relates to an improvement in the bulk polymerization of vinyl halide or vinyl haLide-comonomer mixtures in the presence of high concentrations of high molecular weight polyolefins. It is especially concerned with a novel improvement in said poly-merization which diminishes formation of product agglomerates and provides a more finely divided, more homogeneous, and more easily processed particulate polymer.
It is known to polymerize a vinyl halide, e.g.
vinyl chloride, or up to about 50 weight percent of mixture thereof with a compatible comonomer in bulk in the presence of a polyolefin to obtain a vinyl halide polymer of improved impact strength and processability. Thus, according to U.S.
Patent 4,071,582, issued January 31, 197~3 of A. Takahashi vinyl halide or a vinyl halide-comonomer mixture can be polymerized in a single or two stage bulk reaction in the presence of about 0.05 to about 20% of a polyolefin rubber of weight molecular weight ranging from about 50,000 to 1,000,000 or higher to produce a polyvinyl halide product ;
containing both free, i.e. dispersed, and grafted polyolefin of excellent impact strength, and other desirable properties such as reduced melt viscosity. It is now found, however, that polymers of especially excellent high impact strengths :

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of the order of about lO to 20 ft/lbs. per square inch or gredter, are obtained as a general result in the reference process when the ~mount of polyolefin charged is above about 3.5 weight percent, preferably above about 5.3 weight percent based on the vinyl halide concentration. However, it is also found that use of such high concentrations of polyolefin, especially of polyolefins of molecu-lar weight above l50,000 incurs difficulties ln mixing the reaction mass, and results in a product having a relatively low proportion of finely divided particles and a substantial number of relatively massive lumps or agglomerates. In the reference polymerization, as soon as the agitated reaction mixture is warmed up to initiate polymerization, the polymerization mass proceeds fram a substan-tially clear solution or dispersion of polyolefin in vinyl halide or vinyl halide-comonomer mixture to a milky, opaque emulsion. Af-ter about one hour, the reaction becomes a paste, and after about 1.5 hours of reaction, corresponding to about 25 to 30% conversion of vinyl halide to polymer, the reaction isotherm sho~ls a rapid increase, with concurrent thickening of the paste, i.e. develop-ment of a "thick paste state" in the reaction mass. After about 40 to 45% conversion of the vinyl halide monomer to polymer, the thick paste becomes, in the main, a fine non-viscous powder. When high concentrations of polyolefin are charged to the reaction in order to obtain the aforementioned polymer of exceptionably good impact strength, the thick paste state of the reaction mixture is so viscous, i.e. of consistency substantially similar to unbaked dough, that the a~itation of the mixture provides little mixing effect in the polymerization mass. In other words the reaction ~; mixture consists of several large dough-like agglomerates, or in the extreme cases, a single dough-like lump, adhering to, and ~; 30 revolving or rotating upon the agitator or stirrer. When the reaction is carried to completion from the aforementioned thick paste state, the product contains a relatively small proportion .
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` 1~11~76 of evenly shaped finely divided particles compared to the proportion of such fines obtained when the polyolefin is charged at low concen-trations, i.e. at 5.3% by weight or less or especially at 3.5% by weight or less based on the vinyl halide employed. The product also contains, one or several massive irregularly shaped agglomerates which agglomerate or agglomerates can in extreme cases comprise a major or a predominant part of ~he polymer product. The particu-late product of the reference process normally has hard fused sur-faces and generally large particles therein must be comminuted, e.g. by grinding or equivalent pulverization process, to make them suitable for conventional polymer processing steps. The latter operations generally entail handling the polymer in a fluid melted state. ~ccordingly, polymer processing of the aforementioned large particles or massive agglomerates entails undesirable, costly ex-penditure of mechanical energy in pulverization of the particles.
Alternative direct melting or fusion of the products containing the massive agglomerates and a large proportion of relatively large particles also generally requires prolonged heating of the product which can affect deleteriously the polymer color and~or degrade the polymer. The large product particles and agglomérates obtained by employing the aforementioned relatively high amounts of polyolefin in the reference process are generally less homogeneous than small product particl~s since high local concentrations of monomer, poly-ole~in and reaction initiator build up wlthin the large particles and especially within the massive agglomerates absent effective mixing within these large particles during their formation in the thick paste state. Additionally, poor heat transfer from within ~ the relative massive body of these particles deleteriously affects ;~ the homogeneity of the polymer within the particle.
The reference process generally prescribes agitation of the polymerization mass, but as pointed out above and as illustrated .~ : , ,, . . . . -., .. . . . . . .

'76 in Example 2 below such agitation does not prevent formation of product agglomerates and undesir~bly large proportions of large particles in the product when the aforementioned large concentra-tions of polyolefin are employed in the polymerization. Moreover, increasing the speed of the agitation in the reaction would not be a feasible method of overcoming the aforementioned disadvant~ges of the reference process, since in the thick paste state of the polymerization wherein the undesirable agglomerates and large par-ticles arise, the dough-like reaction mass collects upon, and re-volves with, the rotating or revolving agitator or stirrer.Accordingly, increasing the speed of the agitation would not in-crease the internal mixing in the agglomerated reaction mass and might, especially at extremely high agitation spee`ds, damage the agitator or the agitator motor.
15According to the invention, the disadvantages associated with the prior art process are overcome by an improvement in the process ;~ ~ for preparation of a vinyl halide polymer which comp~ises polymer-izing in bulk a vinyl halide monomer, in liquid phase, either alone or in combination with up to about ~0% by weight of another ethylen-ically unsaturated monomer copolymerizable therewith in the initial presence of more than about 1.8% by weight based on said vinyl halide monomer of a polyolefin or mixture of polyolefins having a wèight average molecular weigh~ of at least about 50,000. This improvement comprises removing from the polymerizatiorl mass during the thick paste state thereof a sufficient amount of the vinyl ha-lide in the polymerization mass to raise the effective concentra-tion of said polyolefin to abbve about 3.5 weight percent based on vinyl halide remaining in said mass after said removal of vinyl halide, whereby polymerization mass agglomerates are broken up and a more finely divided particulate product of high impact strength is obtained. ~ -, , :::
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: ~ - , . : ' 1111~76 In general the present process permits-relatively high effective concentrations of the polyolefin to be employed in the prior ~rt vinyl halide polymerization process of aforementioned US Patent No. 4,071,582 to obtain finely divided polymer products of a relatively great concentration of grafted polyolefin, e.g.
above about 6.0%, usually above about 8%, based on the weight of the product, and hence an improved impact strength, e.g. about 10 to 20 ft/lbs per inch as measured by the Notched Izod Impact Test.
~ASTM D-256). The removal of vinyl hal;de monomer in accord with the invention provides a substantially more finely divided product than when such removal is omitted, i.e., the proportion of smaller size particles, e.g. particles of cross-sectional width less than about 1.2 mm, in the product is substantially increased, typically by about 200% or more, and the maximum product particle size is greatly diminished, typically twenty-fold or more, as illustrated by a comparison of the results of Examples 1 and 2 below. Accord-ingly, to obtain homogeneously pulverized polymer suitable for Corl-ventional polymer processing, substantially less mechanical work ~s re~u~red for conlminution of the present polymer products than is required for comparable agglomerated polymers obtained by the prior art process. Alternatively, if it is desired to process the pre-sent polymers without a preceding comminution step, the present finely divided polymers are found to require, in genera1, shorter heating for melting than is the case with the comparable reference process products containin~ massive agglomerates and substantially greater proportions of larger particles. Thus on melting, the present polymer products are exposed to extrenle temperatures for shorter periods thereby diminishing the deleterious effect that such temperatures may have upon polymer stability and color.
Since the present product contains a substantially greater pro-~ ~ portion of smaller size particles and is devoid of .~, ~r !~

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''- '' ' '. ,"'.,'''. .'. . ' "'';','' -,. ''.'"'"' ' ',' '' ' ',' ' ' ' ', ` ' ' . ' . '' ',' "'' "'' the massive produc~ agglomerates obtained in the prior art process when effective polyolefin concentrations a~ove about 3.5% or especially above about 5.3% are employed, the parti-culate product of the invention is also of a more homogeneous constitution than the reference product~
It was highly surprising to discover tha~ vinyl halide monomer removal in accordance with the invention was effective in breaking up reaction mixture agglomerates since, in general, the prior art associated with vinyl halide bulk polymerization has taught such removal to be undesirable or has prescribed addition of vinyl halide to the polymerization mass to break up agglomerates.` Thus U.S. 2,230,240 to H.L.
Gerhart which is directed to bulk polymerization of a vinyl compound, e.g. vinyl halide, and a maleic anhydride comonomer requires the reaction to be carried out under a sufficient reaction pressure to prevent escape of the vinyl monomer since such removal by venting causes ebullition of the poly-merization mass which impairs the homogeniety of the product.
Moreover, U.S. 2,961,432 to H. Fikenscher et al which contem~
plates bulk polymerization of a vinyl compound, e.g. vinyl halide, in the presence of a polymer thereof teaches (see col. 3, lines 15-21) that is especially desirable to add vinyl monomer in vapor form to the agitated polymerization mass to avoid agglomeration in the reaction mixture, which teaching contradicts the improvement step of the present invention.
Except for the above-defined improvements of the invention, the reactants and reaction conditions, e.g.
reaction temperature and pressure, are substantially the same as those of the polymerization disclosed in the afore-mentioned U.S. Patent 4,071,582.

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~lli76 The vinyl halide utilized in the present process is preferably vinyl chloride, although other vinyl halides such as vinyl fluoride and vinyl bromide can be employed also.
In carrying out the present improved process the vinyl halide monomer can be removed from the thick paste state of ~he agitated polymerization reaction mass in any suitable way. For example tne liquid monomer may be filtered from the bul~ reaction mass, e.g.
by passage through a pressure filter. lhe filtrate is then dis- -tilled outside the reaction vessel with the distillation residue containing initiator and unreacted polyolefin being returned to the reaction vessel. Ho~ever, since the pol~neriz~tion is general-ly carried out under at least autogeneous superatomospheric pres-sure, especially when vinyl chloride is employed as the vinyl halide reactant, removal of the vinyl halide is preferably achieved by venting the reaction mixture of a pressure zone, e.g. the atmos-phere, wherein the pressure is substantially below the reaction pressure. RemovQl by venting is especially desirable since it pro-~ motes rapid removal of heat from the reaction mass. Vinyl halide ; monomer removal is commenced during the above-described thick paste ZO state of the reaction, the duration of which corresponds to conver-sion to polymer of about Z5% to about 45%, more typically about 30%
to about 40% by weight of vinyl halide, based on vinyl halide charged. The onset of the thick paste state is generally accom-panied by ~ rapid increase in the heat evolved from the reaction, ~; 25 i.e. by a rapid increase in the reaction isotherm as ev~denced by a sharp increase in reaction pressure. Preferably, vinyl halide removal in accordance with the invention is commenced about 5 minutes to about 15 minutes after beginning of the thick paste state of the polymerization. The venting of vinyl halide from the reaction mass according to the preferred mode of removal of vinyl halide may be carried out in continuous fashior" or alter-natively ~nd desirably, in intermittent but regular fashion with X

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~L1 1 1~L7 6 the reaction mass being restor~d, after each release of vinyl halide, substantially to the temperature and pressure prevailing in the reaction mass prior to each release of the monomer. The polymerization vessel is desirably equipped with a conven~ional adjustable valve to facilitate venting.
The amount of vinyl halide monomer which is removed during the thick paste state of the polymerization reaction in order to avoid product agglomerates according to the invention is generally a minor proportion of the vinyl halide employed in the polymeriza-tion, i.e. less than about 50 weight percent of the vinyl halide charged. Preferably, however, to retain substantially all of the benefits and advantages of the prior art polymerization process of aforementioned US Patent No. 4,071,582, no more than about 40 weight percent, typically no more than about 30 weight percent, of the vi-nyl halide charged to the polymerization is removed in the present process. While some improvement in obtaining finely divided poly-mer product of small maximum particle size can be achieved by re-moving only small amounts, say 2 to 3% by weight, of vinyl halide during the thick paste state of the polymerization~ it is preferred to remove at least about 5 weight percent of the vinyl halide charged in the practice of the invention. Preferably the percent-age of vinyl halide removed can vary from about 8 to l5% up to about 25 to 35% and is more preferably about l5 to 35% based on the vinyl halide charged.
The rate of removal of vinyl halide by venting or other removal technique can be varied over a wide range but usually is about 0.1%
to about 1.5% preferably about 0.15% to about 1.2% per m;nute based on the weight of vinyl halide charged. An especially good result is generally obtained when the vinyl halide is removed from the polymerization mass at a rate which can range from about 0.3% to about 0.8% up to about 1.0% or even up to about 1.2% by weight per minute.
~ The proportion of vinyl halide and polyolefin charged initially `;~': ' .
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- to the polymerization may vary over a wide range but should be sufficient to provide, after vinyl halide removal in the thick paste state, an effective polyolefin concentration of from aboYe about 3.5% to about 20% by weight, preferably at least above about 5.3% and especially is about 5.5% to about 10% by weight computed on the amount of vinyl halide remaining after removal of vinyl ha-lide according to the invention, i.e. on the amount of vinyl halide charged minus the amount of vinyl halide removed in the thick paste state of the polymerization. An especially good result is general-ly obtained when the intial charge of polyolefin and vinyl halide and the amount of vinyl halide removed in the thick paste state of the reaction are sufficient to provide an effectiYe polyolefin con-centration of about 6 to about 8% or even up to about 9% by weight.
Usually the initial concentration of polyolefin and vinyl halide in lS the polymerization are such as to provide a reaction mixture con-taining before venting or other removal of the vinyl halide, above about 1.8% and desirably at least about 3%, typically about 3.5%
or greater of polyolefin based on the weight of vinyl halide charged.
While the exact chemical nature of the polymer formed by the process of the present invention is not known, it is believed that a graft copolymer is formed in which the vinyl halide polymer forms upon the polyolefin polymer. To obtain a maximum reduction in melt viscosity which is a standard measure of processability, the poly-mer used as the trunk polymer in graft polymerization should be incompatible with the vinyl halide polymer formed. During the pro-cessing of a polymer of a vinyl halide such as in molding, the physical propèrties of the polymer change during the processing ; as the result of the polymer being held at high temperatures for ~ long periods of combina~ion with the internal heat built up as a ;; . :
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result of shear forces produced by the processing machinery. Thus, the physical properties of a graft polymer having a trunk polymer which is compatible with the vinyl halide polymer can change during processir,g as the result of solubilization of the trunk polymer into S the polyvinyl halide. In such a case, the impact strength would de-crease during the processing. Therefore, the compositions of the present invention are directed to graft copolymers having a polyole-fin backbone polymer which is incompatible with the vinyl halide polymer formed thereon. With such an incompatible polymer backbone, the physical properties of the graft copolymer do not change during processing, since the incompatibility prevents the solubilization of the trunk polymer in the polyvinyl halide. The melt viscosity is reduced by the choice of a graft copolymer and is not affected by the usual subsequent processing conditions.
The melt viscosity of the graft copolymer formed also depends upon the molecular weight of the trunk polymer, as well as the vi-nyl halide polymer formed thereon. A maximum reduction of melt viscosi~ty can~be expected frorn the graft copolymer where the trunk polymer is chosen so as to have low molecular weight, e.g. a weight average molecular weight of 50,000 to 150,000 and the vinyl halide monomer is polymérized so as to have a reasonably low molecular weight also, such low molecular weight olefin polymers being pre-; ferred~for especially easy processing in the molteli~state. Prefer-ab1y to;produce~polymer products of excellent impact strength, i.e.
25~ of high graft pdlyolefin content or high grafting efficiency, the weight average molecular weight of the polyolefin may range from about 150,000 to about l,000,000 or higher and is especially about 150,000 to about 400,000.
While~vinyl~ chloride is the preferred vinyl halide reactant of the invention, other suitable vinyl halide monomers useful in the 1nvent1On are~the alpha-halo-subst1tuted ethylenically unsaturated ' ' . . . . . ', .
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` ~ 1111176 compourlds which like vinyl chloride are capable of entering into an addition polymerization reaction, for example, vinyl fluoride, vinyl bromide, vinyl iodide, vinylidene fluoride, vinylidene chloride, vi- -nylidene bromide, vinylidene iodide and the like. The polymers of the present invention can be formed of the same or different alpha-halo-substituted ethylenically unsaturated materials and, thus, the invention includes homopolymers, copolymers, terpolymers, and inter-polymers formed by addition polymerization. Illustrative o~ these copolymers is a copolymer of vinyl chloride and vinylidene chloride.
While it is preferred that the monomer composition be comprised totally of vinyl halide monomer, e.g. vinyl chloride, alone, the present invention is also intended to include copolymers formed by the free-radical addition polymerization of a monomer composition containing a predominant amount, e.g. at least 50 percent of vinyl halide and a minor amount, e.g., less than 50% by weight of another ethylenically unsaturated monomer composition copolymerizable there with. Preferably, the other ethylenically unsaturated monomer is used in amounts of 20% or less by weight and more preferably in amounts o~ 10% or less by weight of the total monomer used in pre paring the polymer. Suitable ethylenically unsaturated compounds which can be used to form copolymers, terpolymers, tetrapolymers, interpolymers and the like, are illustrated by the following mono-olefinic hydrocarbons, i.e. monomers containing only carbon and hydrogen~ including such materials as ethylene, propylene, 3-methyl-butene-l, 4-methylpentene-1, pentene-l, 3,3-dimethylbutene-1, 4,4-dimethylbutene-l, octene-l,~decene-l, styrene and its nuclear alpha-;~ ~ alkyl or aryl substituted derivatives, e.g. o-, m-, or p-methyl, ethyl, propyl or butyl styrene; alphamethyl, ethyl, propyl or butyl styrene; phenyl styrene, and halogenated styrenes such as alpha-30 ~ chlorostyrene; monoolefinically unsaturated esters including vinyl ~.

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~1~1176 esters, e.g. vinyl acetate, vinyl propionate, vinyl butyrate, vinyl stearate, vi~yl benzoate, vinyl-p-chlorobenzoates, alkyl methacryl-ates, e.g. methyl, ethyl, propy1 and butyl methacrylate; octyl methacrylate, alkyl crotonates, e.g. octyl; alkyl acrylates, e.g.
methyl, ethyl, propyl, butyl, 2-ethyl hexyl, stearyl, hydroxyether and tertiary butylamino acrylates, isopropenyl esters, e.g. isopro-penyl acetate, isopropenyl propionate, isopropenyl butyrate and isopropenyl isobutyrate; isopropenyl halides, e.g. isoproperlyl chloride; vinyl esters of halogenated acids, e.g. vinyl alpha-chloroacetate, vinyl alpha-chloropropionate and vinyl alpha-bromo-propionate, allyl and methallyl esters, e.g. allyl chloride, allyl cyanide; allyl chlorocarbonate, allyl nitrate, allyl formate and allyl acetate and the corresponding methallyl compounds; esters of alkenyl alcohols, e.g. beta-ethyl allyl alcohol and beta-propyl lS allyl alcohols halo-alkyl acrylates, e.g. methyl alpha-chloroacryl-ate and ethyl alpha-chloroacrylate, methyl alpha-chloroacrylate and ethyl alpha-chloroacrylate, methyl alpha-bromoacrylate, ethyl alpha- ~ -bromoacrylate, methyl alpha-fluoroacrylate, ethyl alpha-fluoroacryl-ate, methyl alpha-iodoacrylate and ethyl alpha-iodoacrylate; alkyl alpha-cyanoacrylates, e.g. methyl alpha-cyanoacrylate and ethyl alpha-cyanoacrylate and alkyl alpha-cyanoacrylates, e.g. methyl alpha-cyanoacrylate and ethyl alphacyanoacrylate; maleates, e.g.
; monomethyl maleate, monoethyl maleate, dimethyl maleat, diethyl ;;~ maleate; and fumarates, e.g. nlonomethyl fumarate, monoethyl fu-~: 25 marate, dimethyl fumarate, diethyl fumarate; and diethyl gluta-conate; monoolefinically unsaturated organic nitriles including, for example, fumaronitrile, acrylonitrile, methacrylonitrile, ethacrylonitrile, l,l-dicyanopropene-l, 3-octeneitrile, crotonî-trlle and oleonitrile; monoolefinically unsaturated carboxylic acids including for example, acrylic acid, methacrylic acid, cro-~1 tonic acid, 3-butonoic acid, cinnamic acid, maleic, fumaric .. . . .

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: : ~ ~ . .: ~ : . . : -and itaconic acids, maleic anhydride and the like. Amides of these acids, such as acrylamide, are also useful. Vinyl alkyl ethers and vinyl ethers, e.g. vinyl methyl ether, vinyl ethyl ether, vinyl pro-pyl ether, vinyl n-butyl ether, vinyl isobutyl ether, vinyl ~-ethyl-hexyl ether, vinyl 2-chloroethyl ether, vinyl propyl ether, vinyl n-butyl ether, vinyl isobutyl ether, vinyl 2-ethylhexyl ether, vinyl

2-chloroethyl ether, vinyl cetyl ether and the like; and vinyl sul-fides, e.g. vinyl beta-chloroethyl sulfide, vinyl beta-ethoxyethyl sulfide and the like can also be included. Diolefinically unsatura-ted hydrocarbons containing two olefinic groups in conjugated rela-tion and the halogen derivatives thereof, e.g. butadiene-1,3i 2-methyl-butadiene-1,3; 2,3-dimethylbutadiene-1,3; 2-methyl-butadiene-1,3; 2,3-dimethyl-butadiene-1,3; 2-chloro-butadiene-1,3; 2,3-dichlro-butadiene 1,3; and 2-bromo-butadiene-1,3 and the like can also be used.
~; Specific monomer compositions for forming copolymers can be illustrated by vinyl chloride and/or chloride and vinyl acetate, vinyl chloride and/or vinylidene chloride and Maleic or fumaric acid esters, vinyl chloride and/or vinylidene chloride and acryl-20 ate or methacrylate ester, vinyl chloride and/or vinylidene chlor-ide and vinyl alkyl ether. These are given as illustrative of the numerous combinations of monomers possible for the formation of copolymers. The present invention includes all such combinations.
The free radical bulk polymeriz~tion of the monomer composi-25 tion is conducted in the presence of an olefin homopolymer, co-polymer, terpolymer, or tetrapolymer and halogenated derivatives thereof. The olefin polymers can also contain a diene as a mono-mer unit.
i Suitable monomers are propene, butene-l, isobutenel pentene,:
30 hexenej heptane, octene, 2-methylpropene-1, 3-methylbutene-1, 4-- ~ methylpentene-l, 4-methylhexene-1, 5-methylhexene-1.

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- ~L1~L~L~L'~ 6 Suitable comonomers are those utilized to prepare homopolymers as listed above such as propene or butene-l with ethene or isobutyl-ene with isoprene ethene with vinylacetate, ethene with ethyl acryl-ate, and the like. Suitable termonomers are those utilized to prepare homopolymers and copolymers as disclosed above such as pro-pene, ethene and the like containing up to 15% preferably up to about 6% by weight of a diene such as dicyclopentadiene, butadiene, cyclooctadiene and other non-conjugated dienes with 1inear or cyclic chains.
The polyolefins used are characterized by being soluble, p~r-tially soluble or dispersible at normal room temperature and pres-sure in vinyl chloride monomer and if a homopolymer having monomeric units with 2 to 8 carbon atoms; if copolymers, having monomeric units with 2 to 8 carbon atoms, and if a halogenated polymer, having mono-meric units with 2 to 8 carbon atoms. Suitable halogenated polyole-fins are the chlorinated, brominated or fluorinated polyolefins.
The weight average molecular weight of the olefin polymers, copoly- -mers, terpolymers and tetrapolymers can vary from about 50,000 to about 1,00~,000 and higher as described above.
;~ ~ 20 The free radical bulk polymerization can take place in accord-ance with the process of the invention at temperature between about 25 and about 90, preferably about 40 to about 80, and especially about 50 to about 75C. The polymerization reaction is conducted in the presence of a small initiating amount of a free radical inia-tor for the reaction. Useful free-radical initiators are organic ;~ ~ or lnorganic peroxides, persulfates, oxonides, hydroperoxides, per-acids and percarbonates, diazonium salts, diazotates, peroxysulfon-ates, tr~alkyl borane-oxygen systems, amine oxides, and azo com-pounds such as 2,2'-azo-bis-isobutyronitrile and 2,2'-azo-bis-2, 4-dimethyl valeronitrile. Preferably an azo compound or an organic peroxy compound~,~especially an organic peroxide, is used as the in-itiator. The initiator is used in a concentration rang1ng from - . , , - , , - ~. . :

~L1~L~L1 7 6 about O.Ol to about l.O% and preferably about 0.05 to about 0.5%
based on the total weight of all monomers in the react;on mixture.
Organic initiators which have particularly good soiubility in the bulk polymerization mass as disclosed in aforementioned US Patent 4,071,~82, and hence, are especially useful in the practice of the inventors include the following representative examplesi lauroyl peroxide, benzoyl peroxide, diacetyl peroxide, azobisisobutyroni-trile, diisopropyl peroxydicarbonate, azo-bis-isobutyramidine hy-drochloride, t-butyl peroxypivalate, 2,4-dichloro-benzoyl peroxide, and 2,2'-azo-bis-(2,4-dimethyl valeronitrile). These and other suitable initiators are more particularly described by J. Brandrup and E.H. Im~nergut, Editors "Polymer Handbook", Interscience Publishersg 1966, Chapter II entitled "Decomposition of Organic Free Radical Initiators", the pertinent disclosure whereof is in-corporated herein by reference. Advantageously, the initiator which is used is chosen from a group of initiators known in the prior art as the "hot catalysts" or those which have a high degree of free-radical initiating activity. Initiators with a lower de-gree of activity are less desirable in that they require longer polymerization times. Alsos long polymerization times may cause preliminary product degradation evidenced by color problems, e.g.
pinking.
The present process is preferably carried out in a single stage bulk operation but, if conven~ent or desired, the reaction can be effected in a two stage reaction confiyuration in which high speed, high shear agitation is used during a first stage, and low speed, low shear agitation is used in a second stage. Two stage bulk polymerization processes for vinyl halide and vinyl halide-comonomer mixtures which are useful in the practice of the inven-tion are described in aforementioned US Patent No. 4,07l,582 as ~ .

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well as British Patent 1,047,489 and US Patent 3,522,227, to Thomas.
In the following abbreviated descript~on of a typical t~Jo stage reaction configuration for carrying out the present process, for the sake of simplicity, the initial stage of the polyrnerization or copolymerization will be referred to as first stage reaction and the vessel in which this initial stage of polymerization is carried out will be referred to as "Prepolyrnerizer". The final or oomple-mentary stage of the polymerization will be called simply second stage reaction and the vessel in which it is carried out, the "Polymerizer".
In the first stage reactor, the means chosen to agitate the monomer or monomers is of a type capable of providing high shear agitation and is commonly referred to as a "radical turbine type"
agitator. At the start of the first stage reaction, the Prepoly-merizer is charged with a monorner composition to which an initia-tor has been added. Any polymerization generally used in bulk polymerization methods, that is, those hereinabove described, can be used to~an extent which is usual for bulk polymerization pro-cesses. After addition of the vinyl chloride monomer to the first stage reactor, a small amount of monomer is vented in the process of removing the air from the first stage reactor vessel. The speed of~the turbine type agitator generally lies between 500 and 2,000 revolutions per minute or a tip speed of about 2 to 7 meters per second in the first stage reactor. A tip speed of at least about 0.1, and preferably, about 0.5 to about 2 meters per second is used in the second s~tage reactor. These figures should not be regarded as limiting values. As soon as a conversion of at least about 3 to about 20% of the monomer composition has been obtained in the first stage reactor, the contents of the vessel are transferred to a ,, ~. , ; 30 ~ second stage polymerizer vessel equipped to provide slow speed, low shear agitation;~so as to insure proper temperature control of the reaction medium. Preferably, the conversion in the first stage - reactor is about 3 to about l5% and is especially about 7 to about l5%. The reaction temperature in both first and second stage re-actors generally ranges between about 25C. to about 90C., prefer-ably about 40 to about 80C. The reaction pressure in the first stage reactor is also at least an autogeneous superatmospheric pres-sure generally in the range between about 8q to about ~lO pounds per square inch, and preferably, between about 90 to about l90 pounds per square inch.
Since the minimum conversion (e.g. about 25-30%) of vinyl halide corresponding to onset of the thick paste state of the poly-merization invariably occurs in the second reaction stage of the above-described two stage reaction configuration, vinyl halide mon-omer is always removed from the second stage of the two stage reac-tion process in accordance with the invention. Moreover, as will lS be evident to those skilled in the art, the conditions of tempera-ture,ppressure and agitation of the second stage are sl~bstantially similar to, and hence, typify those used when carrying out the Pre-sent improved polymerization in a single reaction stage.
The improved polymerization product of the invention is recovered from the polymerization reaction vessel in conventional fashion, e.g. by expelling unreacted monomers by venting. The pre-sent finely divided products are easily ground or otherwise comminu-ted to a homogeneous powder for admixture with conventional inert additives such as fillers, dyes, and pigments. In addition, the po1ymerization products can be admixed with plasticizers, lubri-cants, thermostabilizers and ultraviolet and light stabilizers as desired. If desired the present product can be directly melted for combinat~on with the aforementioned additives and subsequent molten processing, such as molding and extrusion. The melting or fusion of the present polymers which contain predominantly, finely . ,.:

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divided part;cles, occurs so rapidly as to avoid any serious decom-position or color-degradation caused by exposure to eleYated teni-perature during the melting of fusion operation.
The exact mechanism by which the present process effectively breaks up reaction mixture agglomerates is not understood completely, but while the invention is not bound to any theory it is surmised that removal of vinyl halide in accord with the inventi~n increases the ratio of solid phase, i.e. polymer, to liquid phase, i.e. vinyl halide monomer containing dissolved or dispersed polyole~in in the reaction mass and hence rapidly advances the reaction mass out of the thick paste state into the fluid powder state described hereinabove.
In order to further illustrate the invention, but without being limited thereto, the following examples are given. In this specification and claims, unless otherwise indicated, parts, per-centages and proportions are by weight and temperatures are in degrees cent;grade.

A two liter cylindrical glass reaction vessel is equipped with a beaker bar agitator operating at about 200 revolutions per minute at a tip speed of about 0.1 meters per second, a pressure sensor, and a venting valve and is surrounded by a jacket contain-ing aqueous constant temperature heating bath. The reactor is charged with 45.0 g. of a polyolefin mixture of aVerage weight average molecular weight of 330,000 which is a 3:4 mixture of 19.3g. of Epsyn*~7006 (an ethylene propylene copolymer of weight average molecular weight of 22~,000 manufac~ured by Copolymer Corp.) and 25.7g. of SK43A** (an ethylene propylene copolymer of weight average molecular weight of 420,000 manufactured by Copolymer Corp.) and 0.7g. of lauroyl peroxide initiator. The reaction vessel is *tradeln~rk **Supplier's Designation , . . . .. . ., - - . . ..

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checked for leaks by pressurization with nitrogen, evacuated to a subatmospheric pressure of about 5mm, and charged with 745g. of vinyl chloride. After the vessel is sealed, about 80g. of the vi-nyl chloride is vented from the reaction vessel to remove entrapped 5 air thereby providing a net charge of vinyl chloride of about 665g.
and an initial polyolefin concentration of about 6.77% based on the weight of the vinyl chloride. The reaction mass is heated with agi-tation to a temperature of about 90-72 under an autogenous pressure of about 170-175 psig to initiate the polymerization. The polymer-10 ization mass changes from a substantially clear solution or disper-sion, to an opaque slurry. After about 1.5 hours, there is a sharp increase in the reaction exotherm, i.e. in the heat evolved from the reaction mass as evidenced by a rise in reaction pressure. At about the same time, the consistency of the reaction mixture be-15 comes similar to that of dough indicating the onset of the thickpaste state of the polymerization. After about 5 minutes from the exotherm increase, the venting valve of the reactor is opened in-termittently but regularly over â period of 30 minutes to vent about 8% of the vinyl chloride (based on net vinyl chloride changed) 20 to an exhaust at atmospheric pressure at an average rate of about 0.267 percent per minute so that the effective concentration of polyolefin is about 7.37% (based on net vinyl chloride charged less vinyl chloride vented). On completion of the venting operation the polymerization rapidly advances to the powder state of polymer-25 ization, i.e. the polymerization mass changes from a highly viscousdough-like paste to substantially fine, non-viscous powder. The reaction is allowed to proceed under the foregoing conditions of temperature, pressure and agitation until no more liquid monomer ~; ~ is observed in the reaction vessel and the pressure therein begins 30 to drop indicating the end of the polymerization. The duration of the polymerization from inception of initiation is about 2.9 hours.

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The polymerization vessel is vented to the atmosphere to remove residual vinyl chloride. The particulate pol~ner in the reaction vessel (313 g.) together with scrapings from the reactor bottom and walls and the agitator, i.e. bottom cake, wall scale and stirrer deposit (61 g. about 16.3 total product) amount ot a product yield of 374 g. of which about 12.3% is polyolefin in both grafted and free dispersed form so that the amount of pol~ner obtained from vi-nyl chloride is 329 g. corresponding to a conversation of about 50%
based on net vinyl chloride cl~arged to the reaction.
The particulate portion of the product is then passed through a No. 16 mesh sieve (US standard sieve size). The amourlt of parti-culate polymer fines, i.e. particles of average cross-sectional width of about 1.2mm or less, which passes through the sieve is 108g. (about 29% of total polymer product). The amount of par-ticulate polymer retained on the sieve, i.e. polymer particles of average cross-sectional width greater than about 1.2mm, is 205g.
(55%) of which about 114g. is substantially evenly shaped granular polymer of average cross-sectional width of about 1.2mm to about lU~n, about 49g. is globular polymer of average cross-sectional width o~ about 10 to about 2~mm and about 42g. is in the form of three irregular agglomerates or lumps having an average cross-sectional width (measured across their widest dimension) of about 30mm.
The above-mentioned particulate fraction of the product is tested for impact strength by the Notched Izod Impact Test, accord-ing to the procedure of ASTM-D256. Samples for use in this test are prepared by mixing together 100 parts of the polymer, 5 parts of Acryloid* K120-ND (an acrylic polymer processing aid manufac-tured by Rohm and Haas Co.) and 2 parts Thermolite* 31 Cdi-n-butyl tin S,S,'-bis(isooctyl mercapto-acetate) thermal stabilizer, manu-factured by M and T Chemicals, Inc.]. The mixture is milled on a ~; ~ two roll Farrell mill for 5 minutes at about 188 and compression *trademark : :

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~111176 monomer during the thick paste state in accordance with the invention provides a vinyl chloride-polyolefin polymer of high impact strength with improved small particle size, i.e. a greater proportion of the product is particulate polymer having an average cross-sectional width of less than about 1.2mm while the average cross-sectional width of the largest polymer particle is reduced from about 700mm (as in control Example 2) to about 30inm (as in Example 1).
From comparison of the results of control Example 6 with those of Examples 1-5, it is also apparent that a satisfactory excellent impact strength as measured by the highly discriminating Notched Izod Impact Strength Test. ;s obtained when the percentage of grafted polyolefin in the polymer product is greater than about 6 percent.
Control Example 6 illustrates that whereas an initial concen-lS tration of 5.3% polyolefin in the polymerization reaction massprovides a polymer product of desirably small particle size such a smal1 concentration of polyolefin in the reaction mixture, when it remains the effective polyolefin reaction concentration by omission of the monomer removal step of the invention, produces 20 polymer product of low graft polyolefin content, i.e. 6% or less, and, hence, of unsatisfactory, inferior impact strength compared to that of the products of corresponding Examples 3-5. In the latter Examples, the polymerization masses have initial polyole-fin concentrations of about 5.3% as ~n Example 6 but monomer re-moval in accord with the invention in these Examples raises theeffective polyolefin reaction concentration to about 6.9% to ~ about 7.6% resulting in products of enhanced impact strength.

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~111176 The procedure of Example 1 is repeated substantia11y as described except that the net charge of vinyl chloride is 670g., the polyolefin is 42.5g. of a mixture (average wieght average molecular weight, 390,0-00) of lOg. of Epsyn* 7006 and 32,5g. of SK43A** corresponding to an initial polyolefin concentration of 6.34% based on net vinyl chloride charged, vinyl chloride removal by venting is commenced about 10 minutes after the increase in the reaction exotherm which indicates the beginning of the thick paste state of the polymerization, venting of vinyl chloride is continued for 15 minutes to remove about 10% of the vinyl chloride charged.(providing an effective polyolefin concentration of about 7.05%) at an average rate of about 0.33% per minute and the dura-tion of reaction is 2.~ hours. The particulate polymer in the re-action vessel (321g.) together with cake from the reactor bottom (41g.), reactor wall scale (16g.) and deposit on the agitator (50g.) amounts to a product yield of 371g. of which about 11.5% is polyole-fin in grafted and free dispensed form so that the conversion of vinyl chloride to polymer is 328g. (58%). On screening the par-ticulate portion (321g., 71% of the total product), 98g. (26%) is of average particle cross-sectional width less than about 1.2mmi 166g. (45%) is of average cross-sectional width greater than about 1.2mm. of which 89g. is substantially evenly shaped granular poly-mer of average cross-sectional width of about 1.2mm to about 5mm and 77g. is globular agglomerates of average cross-sectional width greater than about 5mm; the maximum cross-sectional width of such agglomerates being about 15mm. The particles of width of less than about 1.2mm. and those of width between about 1.2 and about 5mm have a 10% total polyolefin content with the percentage graft-ing being about 90% (corresponding to about 9% graft polyolefin in the product) and a Notched Izod Impact strength of about 16 ft/lbs.
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Example 8 To a vertical type first stage reactor of 2.5 gallon capacity and stainless steel construction, equipped with a radial turbine-type agitation a pressure sensor and a Yenting valve, there is added 6.~1 kg. vinyl chloride monomer, 1.26 9. of dicyclohexyl peroxydicarbonate polymerization ~initiator sold under the tradename "Lupersol 229" and 0.75 9. of a 50%
.
methanol solution of "Gelva" (a densifying agent which is a 2:1 copolymer of vinyl acetate and crotonlc acid manufactured by Monsanto Co.). About 0.908 kg. of vinyl chloride monomer are vented from the reactor in order to remove entrapped air. The reaction mass is heated to about 70 under an autogeneous reaction pressure of about 167 psig. with the agitator operating at about 1500 rpm and agitated at these conditions of temperature and pressure for about 25 minutes after which period the conversion of vinyl chloride to Yinyl chloride polymer is about 8% and the reaction mixture is ready for transfer to the second stage reactor as described hereinbelow.
Meanwhile into the second stage reactor, which is a 5 gallon stainless steel vessel equipped with a $piral agitator operating at a speed of about 63 rp~, a pressure sensor and a ~enting Yalve, there is charged at 0~, ~08.63 9 of Epsyn 40A (an ethylene propylene-modiFied terpolynler oF about 160,000 weight avera3e molecular weight, wherein the ethylene-propylene ratio is about 55/45 and the diene is ethylidene norbornene present in an amount of 3+ 0.5 percent, manufactured by the Copolymer Corp.) which has been finely shredded and dusted with 58.38 9. of pulverulent bulk polymerized vinyl chloride polymer (to prevent aggolmeration and promote dissolution of the polyolefin in the reaction mixture) and 0.4 9 of 2,6d;-t-butyl paracresol antioxidant color, stabilizer. The mixture is freed of air by drawing a vacuum of about 29 inchesof mercury in the reaction vessel and thereafter flooding the vessel with nitrogen. After repetition of the air removal treatment, 3.75 9. of the "Luper-sol 229" initiator and abo~t 7.72 kg. of additional vinyl chloride monomer . - . . , . .. : ... .. . . ... . . . . .

are charged to the reactor thereby providing a proportion of polyolefin based on monomer of about 3%. After the reaction vessel is sealed, the reaction mixture is heated under agitation to about 40 and the first stage reaction mixture described hereinabove is added. The reaction mass is then maintained at the reaction temperature of about 58 under an autogeneous reaction pressure of abDut 130 psig~ for about two hours to reach the thick paste stage of the polymerization reaction. About 4.54 kg. of vinyl chloride monomer are then vented from the agitated reaction mixture over a period of about 40 minutes to provide an effect;ve polyolefin concentration of 4.5%, with the pressure and tempera-ture of the reaction vessel dropping to about 90 psig. and about 47, respectively~ during the venting operation. On completion of the venting operation, the agitated reaction mixture is heated over a period of 35 minutes to a temperature of about58~ and a pressure of about 130 psig. and is ma;ntained at the latter conditionsof temperature and pressure for about 40 minutes. At the end of the latter time period a drop in the pressure in the reaction vessel indicates that the polymerization reaction is substantially complete. The reaction vessel is heated to about 70 and any unreacted vinyl chloride monomer in the vessel is vented therefrom over a 45 minute period. To insure as complete as possible removal of yinyl chloride monomer residue from the product, the product is degassed in vacuo at 85 for about 4 hours and subsequently at about 0 for about one hour and then is discharged from the reactor.
A pulverulent polymer product oF excellent impact strength is obtained in a yie~d of about 7.36 kg. (corresponding to a conversion of monomer to ;
polymer of about 77% based on monomer charged to the polymerization which does not include the monome~ vented during the thick paste state in the second reaction stage.) About 90.1% portion of the product passes through a 10 mesh screen (U.S.Standard Sieve Series). The latter portionjof the product contains only about 47 parts per million of residual vinyl chloride monomer.
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1~11176 Example 9 (Control) The procedure of Example 8 is repeated substantially as described except that the amount of vinyl halide monomer and initiator charged at the beginning of the second reaction stage is 3.18 kg. and 5.0 9., respectively,and the monomer removal step of the invention is omitted so that the proportion of polyolefin based on monomer in the second stage is substantially the same as that in Example 8 above subsequent to the monomer removal step, i.e. ab~ut 4.5%. ~he product which has satisfactory impact resistance is obtained in a yield of 7.72 kg. (corresponding to a conversion of monomer to polymer of about 80% based on monomer charged to the polymeri-zation). Only about 60% of the product ;s capable of passing through the 10 mesh screen described in E~ample 8. The amount of residual vinyl chloride monomer in the product fraction which passed through the 10 mesh screen is about900 ppm. Comparison of the results of this example with that of Example 8 -15 above illustrates that the process of the invention effects a substantial enhancement of the proportion of small size product particles obtained and a substantial diminution of residual vinyl chloride monomer therein even when, as shown in Example 8, the effective concentration of the polyolefin subsequent to the monomer removal step is substantially below the preferred value of above about 5.3%.
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1 ~L1 1 1 7 6 In the foregoing Examples l,3-5, 7 and 8 which are illustrative of the invention it will be apparent that many process changes can be made without departing from either the spirit or the scope of the invention. For example, if desired, a portion, e.g. about lO% of the vinyl chloride reactant, may be replaced by a compatible comonomer, e.g. methyl acrylate, to obtain an excellent finely divided particulate vinyl chloride-methyl acrylate-polyolefin polymer. Also, advantageously the vinyl chloride which is~
allowed to escape in the aforementioned illustrative examples can be collected by venting the vinyl chloride to a cooled receiYer at atmospheric pressure or to a compressor for liquification. The resultant recovered vinyl chloride can be reserved for later polmerization. Fu~thermore, excellent results are obtained in the aforementioned illustratiYe examples when the ethylene propylene polyolefin reactant is replaced by the following olefin polymers: polyethylene, polypropylene and ethylene propylene diene-modified lS terpolymer having an ethylene/propylene ratio of 55/45 and containing l,4-hexadiene as the diene in an amount of 3 + 0.5 percent, a l-butene -ethylene copolymer containing 5% ethylene and chlorinatèd polyethylene sold under the trademark "Tyrin".
Moreover, instead of adding the polyolefin reactant directly to the polymerization as described in the above Examples, the polyolefin can be m1xed with all, or more conveniently, a portion of the vinyl halide monomer reactant and dissolved, partially dissolved or dispersed in said monomer with heating and/or agitation, as desired, Prior to addit;on to the reaction vessel. While the addition of the polyolefin to the polymerization reaction mixture according to the invention can be carried out at the beginning of polymerization reaction~ i.e. at 0% conversion by weight of monomer to ~he polymer, it is desirable that the polyolefin be added immediately after some of the monomer, i.e. up to about~20%, has been converted to polymer, preferably after about l% to about l5%, more preferably about 3 : .- 28-,, :
.. .: ' 11~117~i .-to 15% conversion of monomer to polymer. When the polymerization isoperated as a two stage process in accordance with the aforementioned techniques of British Patent 1,047,4~9 and U.S. Patent 3,522,227, the polyolefin is added to the polymerization substantially immediately after the completion of the first stage, i.e. after preferably about 3% to 15%
by weight and more preferably about 7% to about 15% of the monomer has been converted to polymer. Conveniently, in carrying out the polymerization in the two stage reaction configuration, the polyolefin is added to the second stage so as to be present in the second stage reaction vessel prior to occurrence of any substantial polymerization therein.
The addition of the polyolefin reactant subsequent to initiation of the polymerization as described above provides in conjunction with the monomer venting procedure of the invention, in general, a faster poly~
merization reaction, a lower concentration of residual vinyl halide monomer in the polymerization product, and especially, a particularly excellent distribution of product particle size, i.e. the product is characterized by an especially narrow distribution of product particle size and contains an :. .
especially large, generally predominant, fraction of the most minute particles.
Such improved product particle size distribution is of especial advantage in many uses of the prpduct such as injection molding and extrusion of .
articles such as pipe and siding.
According to another preferred mode of carrying out the invention, ~t is advantageous when operating the polymerization according to the aforementioned two stage configuration to add to the f;rst reaction stage ; 25 only a portion, of the`monomer or monomers used in the process with thebalance~bèing added~so as to be present in the second reaction stage prior to the thick paste state venting operation which in the two stage reactlon ~ . . . .
configuration is carriled out in the second reaction stagç. Generally at - . .-~.. :~ : :

3L~L~L1 1 7 6 least about 50% by weight or more of the monomer reactant (corresponding to at least about 60% by weight or more.of the monomer reactant when the amount of monomer vented in the thick paste state is discounted from the amount of monomer used in the polymerization) is added to the first reaction stage with the balance being added at about the beginning of the second reaction stage (so that it is present prior to the venting operation of the invention). Preferably about 50% to about 60% by weight of the monomer reactant is addèd in the first reaction stage (corresponding to addition of a,bout 60% to about 70% of the monomer reactant when the monomer .
reactant wh;ch is vented is discounted as described above).
This preferred mode.of charging monomer br monomers in carrying out the polymerization in the aforementioned two reaction stage configuration --, permits use of a first stage reaction vessel of smaller size than that used in the second reacti'on stage and also in general, assists in providing a product of excellent particle size distributlon.
: Whlle this invention has been described with reference to certainspecific embodiments, it will be recognized by those skilled in the art that many variations are possible (as illus.trated above) without departing from the sp;rit and scope of the invention.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

In the process for the preparation of a vinyl halide polymer which comprises po1ymerizing in bulk a vinyl halide monomer, in the liquid phase, either alone or in combination with up to about 50%
by weight of another ethylenically unsaturated monomer copolymer-izable therewith, in the initial presence of more than about 1.8%
by weight based on said vinyl halide monomer of a polyolefin or mix-ture of polyolefins having a weight average molecular weight of at least about 50,000, the improvement which comprises removing from the polymerization mass during the thick paste state thereof from about 2% to less than about 50% by weight of the vinyl halide charged to the polymerization mass, the effective concentration of said polyolefin or mixture of polyolefins after said vinyl halide removal being above about 3.5 weight percent based on vinyl halide remaining in said polymerization mass after said removal of vinyl halide whereby a more finely divided particulate product of high impact strength is obtained.

The process of Claim l wherein the polymer present is a vinyl halide homopolymer, the polymerization is carried out in a single stage, and the polyolefin is selected from the group consisting of:
(l) halogenated polyolefins;
(2) olefin homopolymers;
(3) olefin copolymers and terpolymers;
said polymers having 2 to 8 carbon atoms in the monomeric units thereof and a weight average molecular weight of about 150,000 to 1,000,000 and the amount of vinyl halide monomer removed is about 5% to about 40% of the vinyl halide monomer charged to the polymerization.

The process of Claim 2 wherein the initial concentration of polyolefin or mixture of polyolefins is at least about 3% by weight halide monomer and the effective concentration of said polyolefin or mixture of polyolefins after said vinyl halide removal is above about 5.3 weight percent based on vinyl halide remaining in the polymerization mass after said removal of vinyl halide.

The process of Claim 3 wherein said vinyl halide monomer is vinyl chloride, the polymerization is a single stage bulk polymer-ization carried out at a temperature of about 25° to about 90°C.
under at least autogeneous superatomspheric pressure in the pre-sence of an initiating amount of a free radical initiator for the reaction, the thick paste state of the polymerization mass corre-sponds to a conversion of vinyl chloride to polymer of about 30%
to about 40% by weight, and about 8% to 35% by weight of the vinyl chloride is removed by venting from said pressurized polymeriza-tion mass and said polyolefin terpolymers contain a diene as a monomeric unit.

The process of Claim 4 wherein the vinyl chloride is vented from the polymerization mass at a rate of about 0.1 to 1.5% by weight vinyl chloride per minute based on vinyl chloride charged to the polymerization, the polymerization temperature is from about 40° to about 80°C. at autogenous superatmospheric pressure, the diene of the polyolefin terpolymer is selected from the group consisting of dicyclopentadiene, 1,3-butadiene and non-conjugated dienes with linear or cyclic chains and is present in said ter-polymer in a proportion up to about 15% by weight of said terpoly-mer and the effective concentration of polyolefin in the polymer-ization mass is about 5.5% to about 10% by weight.

The process of Claim 5 wherein the diene of the polyolefin terpolymer is present in said terpolymer in a proportion up to about 6% by weight of said terpolymer.

The process of Claim 6 wherein the polymerization temperature is from about 50° to about 75° centigrade, the initiator is an organic peroxy-or azo compound added to the polymerization mass in a concentration of about 0.01% to about 1.0% based on the weight of vinyl chloride the effective concentration of polyolefin is about 6% to about 9% by weight based on vinyl chloride and the vinyl chloride is vented from the poly-merization mixture at a rate of about 0.15% to 1.2% per minute, said venting commencing about 5 to about 15 minutes after onset of the thick paste state in the polymerization mass.

The process of Claim 7 wherein the average weight average molecular weight of the polyolefin is about 150,000 to about 400,000, the initiator is an organic peroxide, and the vinyl chloride is vented from the poly-merization mixture at a rate of about 0.3% to about 1.2% per minute.

The process of Claim 8 wherein the polyolefin reactant is an olefin copolymer or terpolymer.

The process of Claim 9 wherein the polyolefin is ethylene-propylene ethylidene norbornene terpolymer.

The process of Claim 9 wherein the polyolefin is an ethylene-propylene 1,4-hexadiene terpolymer.

The process of Claim 9 wherein the polyolefin is an ethylene-propylene copolymer.

The process of Claim 9 wherein the polyolefin is a butene-l-ethylene copolymer.

The process of Claim 8 wherein the polyolefin is an olefln homopolymer.

The process of Claim 14 wherein the olefin homopolymer is polyethylene.

The process of Claim 14 wherein the olefin homopolymer is polypropylene.

The process of Claim 8 wherein the polyolefin is a halogenated polyolefin.

the process of Claim 17 wherein the halogenated polyolefin is chlorinated polyethylene.

The process of Claim 1 comprising carrying out the polymerization in a first stage wherein the reaction mixture is subjected to high speed agitation until about 3 to about 20% by weight of said monomer or monomers have been converted to polymers and further polymerizing the resultant reaction mixture together with additional monomer or monomers in a second stage during which the reaction mixture is subjected to low speed agitation until polymerization has been completed so that the thick paste state of the polymerization and the removal therein of vinyl halide takes place in said second reaction stage.

The process of Claim 19 wherein a portion, amounting to at least about 50% by weight, of the monomer or monomers charged to the polymerization reaction are added in the first stage, the balance of the monomer or the monomers being added at about the beginning of the second stage.

The process of Claim 20 wherein there is added in the first stage about 50% to about 60% by weight of the monomer or monomers charged to the polymerization reaction.

The process of Claim 21 wherein about 3% to about 15% by weight of the monomer or monomers is converted to polymer in the first reaction stage.

The process of Claim 22 wherein about 7% to about 15% of monomer or monomers is converted to polymer in the first reaction stage.

The process of Claim 23 wherein the monomer reactant is vinyl chloride.

In the process for the preparation of a vinyl halide polymer which comprises polymerizing in bulk a vinyl halide monomer, in the liquid phase, either alone or in combination with up to about 50% by weight of another ethylenically unsaturated monomer copolymerizable therewith, in the initial presence of more than about 1.8% by weight based on said vinyl halide monomer of a polyolefin or mixture of polyolefins having a weight average molecular weight of at least about 50,000, said polyolefin or mixture of polyolefins beign present during the polymerization only during the period which commences at 0% to about 20% conversion of the monomer or monomers to polymer and concludes with the end of the polymerization, the improvement which comprises removing from the polymerization mass during the thick paste state thereof from about 2% to less than about 50% by weight of the vinyl halide changed to the polymerization mass, the effective concentration of said polyolefin or mixture of polyolefins after said vinyl halide removal being above about 3.5 weight percent based on vinyl halide remaining in said polymerization mass after said removal of vinyl halide whereby a more finely divided particulate product of high impact strength is obtained.

The process of Claim 25 wherein the polymer present is a vinyl halide homopolymer, the polymerization is carried out in a single stage, and the polyolefin is selected from the group consisting of:
(1) halogenated polyolefins (2) olefin homopolymers;
(3) olefin copolymers and terpolymers;
said polymers having 2 to 8 carbon atoms in the monomeric units thereof and a weight average molecular weight of about 50,000 to 1,000,000 and the amount of vinyl halide monomer removed is about 5% to about 40% of the vinyl halide monomer charged to the polymerization mass.

The process of Claim 26 wherein the olefin polymer is present in the polymerization after about 1% of the monomer or monomers have been converted to polymer.

The process of Claim 27 wherein the olefin polymer is present in the polymerization after about 3% to about 15% by weight of the monomers have been converted to polymer.

The process of Claim 28 wherein the initial concentration of polyolefin or mixture of polyolefins is at least about 3% by weight based on said vinyl halide monomer and the effective concentration of said polyolefin or mixture of polyolefins after said vinyl halide removal is above about 5.3 weight percent based on vinyl halide remaining in the polymerization mass after said removal of vinyl halide.

The process of Claim 29 wherein said vinyl halide monomer is vinyl chloride, the polymerization is a single stage bulk polymerization carried out at a temperature of about 25° to about 90° centigrade under at least .

autogeneous superatmospheric pressure in the presence of an initiating amount of a free radical initiator for the reaction, the thick paste state of the polymerization mass corresponds to a conversion of vinyl chloride to polymer of about 30% to about 40% by weight, and about 8% to 35% by weight of the vinyl chloride is removed by venting from said pressurized poly-merization mass and said polyolefin terpolymers contain a diene as a monomeric unit.

The process of Claim 30 wherein the vinyl chloride is vented from the polymerization mass at a rate of about 0.1 to 1.5% by weight vinyl chloride per minute based on vinyl chloride charged to the polymerization, the polymerization temperature is from about 40° to about 80° centigrade at autogeneous superatmospheric pressure, the diene of the polyolefin ter-polymer is selected from the group consisting of dicyclopentadiene, 1,3-butadiene and non-conjugated dienes with linear or cyclic chains and is present in said terpolymer in a proportion up to about 15% by weight of said terpolymer and the effective concentration of polyolefin in the poly-merization mass is about 5.5% to about 10% by weight.

The process of Claim 31 wherein the diene of the polyolefin terpolymer is present in said terpolymer in a proportion up to about 6% by weight of said terpolymer.

The process of Claim 32 wherein the polymerization temperature is from about 50° to about 75° centigrade, the initiator is an organic peroxy- or azo compound added to the polymerization mass in a concentration of about 0.01%
to about 1.0% based on the weight of vinyl chloride, the effective concent-ration of polyolefin is about 6% to about 9% by weight based on vinyl chloride and the vinyl chloride is vented from the polymerization mixture at a rate of about 0.15% to 1.2% per minute, said venting commencing about 5 to about 15 minutes after onset of the thick paste state in the polymerization.

The process of Claim 33 wherein the initiator is an organic peroxide, and the vinyl chloride is vented from the polymerization mixture at a rate of about 0.3% to about 1.2% per minute.

The process of Claim 34 wherein the polyolefin is an olefin copolymer terpolymer.

The process of Claim 35 wherein the polyolefin is ethylene-propylene ethylidene norbornene terpolymer.

The process of Claim 35 wherein the polyolefin is an ethylene-propylene 1,4-hexadiene terpolymer.

The process of Claim 35 wherein the polyolefin is an ethylene-propylene copolymer.

The process of Claim 35 wherein the polyolefin is a butene-l-ethylene copolymer.

The process of Claim 34 wherein the polyolefin is an olefin homopolymer.

The process of Claim 40 wherein the olefin homopolymer is polyethylene.

The process of Claim 40 wherein the olefin homopolymer is polypropylene.

The process of Claim 34 wherein the halogenated polyolefin is chlorinated poly olefin.

The process of Claim 43 wherein the halgenated polyolefin is chlorinated polyethylene.

The process of Claim 25 comprising carrying out the polymerization in a first stage, wherein the reaction mixture is subjected to high speed agitation until about 3 to about 20% by weight of said monomer or monomers have been converted to polymers and further polymerizing the resultant reaction mixture together with additional monomer or monomers in a second stage during which the reaction mixture is subjected to low speed agitation until polymerization has been completed, said polyolefin or mixture of poly-olefins being introduced to the reaction mixture at the beginning of the second reaction stage so that the thick paste state-of the polymerization and the removal therein of vinyl halide takes place in said second reaction stage.

The process of Claim 45 wherein a portion, amounting to at least about 50% by weight, of the monomer or monomers charged to the polymerization reaction are added in the first stage, the balance of the monomer or monomers being added at about the beginning of the second stage.

The process of Claim 45 wherein there is added in the first stage about 50% to about 60% by weight of the monomer or monomers charged to the polymerization reaction.

The process of Claim 47 wherein about 3% to about 15% by weight of the monomer or monomers is converted to polymer in the first reaction stage.

The process of Claim 48 wherein about 7% to about 15% of monomer or monomers is converted to polymer in the first reaction stage.

The process of Claim 49 wherein the monomer reactant is vinyl chloride.

The process of Claim 26 wherein the weight average molecular weight of the polyolefin reactant is about 50,000 to about 150,000.

The process of Claim 26 wherein the weight average molecular weight of the polyolefin reactant is about 150,000 to about 1,000,000.

In the process for the preparation of a vinyl halide polymer which comprises polymerizing in bulk a vinyl halide monomer, in the liquid phase, either alone or in combination with up to about 50% by weight of another ethylenically unsaturated monomer copolymerizable therewith in the initial presence of more than about 1.8% by weight based on said vinyl halide monomer of a polyolefin or mixture of polyolefins having a weight average molecular weight of at least about 50,000, said polyolefin or mixture of polyolefins being present during the polymerization only during the period which commences at 0% to about 20% conversion of the monomer or monomers to polymer and concludes with the end of the polymerization, said poly-merization being carried out in a first stage wherein the reaction mixture is subjected to high speed agitation until about 3% to about 20% by weight of said monomer or monomers have been converted to polymer, and further polymerizing the resultant reaction mixture together with additional monomer or monomers in a second stage during which the reaction mixture is subjected to low speed agitation until the polymerization has been completed, the improvement which comprises removing from the polymerization mass during the thick paste state thereof from about 2% to less than about 50% by weight of the vinyl halide charged to the polymerization mass, the effective con-centration of said polyolefin or mixture of polyolefins after said vinyl halide removal being above about 3.5 weight percent based on vinyl hailde remaining in said polymerization mass after said removal of vinyl halide whereby a more finely divided particulate product of high impact strength is obtained.

A high impact strength polyvinyl halide prepared by the process of Claim 1.

A high impact strength polyvinyl halide prepared by the process of Claim 25.

A high impact strength polyvinyl halide prepared by the process of Claim 53.

In the process for the preparation of a vinyl halide polymer which comprises polymerizing in bulk a vinyl halide monomer, in liquid phase, either alone or in combination with up to about 50%
by weight of another ethylenically unsaturated monomer copolymer-izable therewith in the initial presence of more than about 3.5%
by weight based on said vinyl halide monomer of a polyolefin or mixture of polyolefins having a weight average molecular weight of at least about 50,000, the improvement which comprises removing from the polymerization mass during the thick paste state thereof from about 2% to less than about 50% by weight of the vinyl halide charged to the polymerization mass, the effective concentration of said polyolefin after said vinyl halide removal being above about 5.3 weight percent based on vinyl halide remaining in said polym-erization mass after said removal of vinyl halide whereby a more finely divided particulate product of high impact strength is obtained.

The process of Claim 57 wherein the polymer present is a vinyl halide homopolymer, the polymerization is carried out in a single stage, and the polyolefin is selected from the group consisting of:
(1) halogenated polyolefins;
(2) olefin homopolymers;
(3) olefin copolymers and terpolymers, said polymers having 2 to 8 carbon atoms in the monomeric units thereof and a weight average molecular weight of about 150,000 to 1,000,000 and the amount of vinyl halide monomer removed is about 5% to about 30% of the vinyl halide monomer charged to the polymerization mass.

The process of Claim 58 wherein said vinyl halide monomer is vinyl chloride, the polymerization is a single stage bulk polymer-ization carried out at a temperature of about 25° to about 90° C.
under at least autogenous superatmospheric pressure in the presence of an initiating amount of a free radical initiator for the reac-tion, the thick paste state of the polymerization mass corresponds to a conversion of vinyl chloride to polymer of about 30 to about 40% by weight, and about 8 to 25% by weight of the vinyl chloride is removed by venting from said pressurized polymerization mass and said polyolefin terpolymers contain a diene as a monomeric unit.

The process of Claim 59 wherein the vinyl chloride is vented from the polymerization mass at a rate of about 0.1 to 1.5% by weight vinyl chloride per minute based on vinyl chloride charged to the polymerization, the polymerization temperature is from about 40° to about 80°C. at autogeneous superatmospheric pressure,the diene of the polyolefin terpolymer is selected from the group consisting of dicyclopentadiene, 1,3-butadiene and non-conjugated dienes with linear or cyclic chains and is present in said terpoly-mer in a proportion up to about 6% by weight of said terpolymer and the effective concentration of polyolefin in the polymerization mass is about 5.5% to about 10% by weight.

The process of Claim 60 wherein the polyolefin is selected from the group consisting of ethylene-propylene copolymers, ethyl-ene-propylene diene-modified terpolymers, propylene homopolymer, butene-l-ethylene copolymer and chlorinated polyolefin, the poly-merization temperature is from about 50° to about 75° C., the initiator is an organic peroxy- or azo compound added to the polymerization mass in a concentration of about 0.01% to about 1.0% based on the weight of vinyl chloride, the effective concen-tration of polyolefin is about 6% to about 8% by weight based on vinyl chloride and the vinyl chloride is vented from the polymer-ization mixture at a rate of about 0.15% to 1.2% per minute, said venting commencing about 5 to about 15 minutes after onset of the thick paste state in the polymerization mass.

The process of Claim 61 wherein the average weight average molecular weight of the polyolefin is about 150,000 to about 400,000, the initiator is an organic peroxide, and the vinyl chloride is vented from the polymerization mixture at a rate of about 0.8% to about 1.0% per minute.

The process of Claim 62 wherein the polyolefin is ethylene-propylene ethylidene norbornene terpolymer.

The process of Claim 62 wherein the polyolefin is an ethylene-propylene 1,4-hexadiene terpolymer.

The process of Claim 62 wherein the polyolefin is an ethylene-propylene copolymer.

A high impact strength polyvinyl halide of improved small particle size prepared by the process of Claim 57.

The process of Claim 57 comprising polymerization in two stages in which, during â first stage, the reaction mixture is subjected to high speed agitation until about 3 to about 20% by weight of said monomer or monomers have been converted to polymers and further polymerizing the resultant reaction mixture together with additional monomer or monomers in a second stage during which the reaction mixture is subjected to low speed agitation until polymerization has been completed so that the thick paste state of the polymerization and the removal therein of vinyl halide takes place in said second reaction stage.

The process of Claim 45 wherein the olefin polymer is intro-duced to the polymerization reaction in admixture with a portion of the monomer or monomers used in the polymerization reaction.

The process of Claim 68 wherein about 50% to about 60% of the monomer or monomers charged to the polymerization are added in the first stage with the balance being added at about the beginning of the second stage.