CA1079434A - Thermoplastic polyblends - Google Patents

Abstract

A polyblend is disclosed which comprises 20%-90% by weight of at least one rigid plastic, about 10-60% by weight of an emulsion polymer of an acrylate which has been over-polymerized with a vinyl chloride suspension polymer, about 1-30% by weight of an interpolymer containing a suspension polymer of polyvinyl chloride over-polymerized with a methacrylate containing component, and from about 0-30% by weight polyvinyl chloride. If desired, up to about 10% of a conventional flame retardant can be included to confer flame retardancy on the polyblend. The polyblend has good impact resistance, as well as good rigidity, hardness, and tensile strength.

Description

Technical Description of the Invention Rigid thermoplastics, such as styrene-acrylonitrile copolymers, are strong, hard plastics. In order to improve the impact resistance of such plastics, these copolymers have been blended with preformed elastomers. The elastomer modified plastics comprise uniformly dispersed and stable elastomer particles with-in a continuous, rigid plastic matrix or phase. The elastomers ) which have been used include the following monomers: butadiene, butadiene-styrene, butadienë-acrylonitrile and alkyl acrylate esters. Graft copolymers of the aforementioned elastomers with styrene-acrylonitrile are commonly employed. When such elastomers or grafted-elastomers are incorporated into a styrene-arrylonitrile matrix, the impact resistance and toughness of the resulting plastic is enhanced as demonstrated typically by an increase of notched izod impact (ASTM D~256) and appearance of a yield point in the stress-strain curve in the testing of a fabricated specimen (ASTM-638). Generally for such modified thermoplastics, however, : ; .

. . ', ' ! ' :: ' ' ' 4i. ~ . ' ;
' 34~

there is a decrease in tensile strength (ASTM D-638~, hardness (ASTM D-2583), rigidity (ASTM D-790), and deflection temperature under load (ASTM D-648), as compared to the unmodified thermo-plastic. Since these decreases are related to ihe elastomer content of the polymer, high impact resistance grades generally have substantially lower values for these properties relative to unmodified styrene-acrylonitrile copolymers.
The present invention is a polyblend containing a rigid, low-impact resistance copolymer as described above, having excep-0 tional impact resistance and toughness with generally good tensile strength, hardness, rigidity and deflection temperatures under load as compared to high impact resistance grades of elastomer modified styrene-acrylontrile copolymers known to the prior art.
A further embodiment of the invention is the additive blend of impact resistance improving additives itself, which is to be blended with the described rigid plastic or copolymer.
The polyblend of this invention comprises: (a) from about 20-90% by weight, preferably about 50-70%, of at least one rigid plastic; (b) from about 10-60% by weight, preferably about 15% to '0 45%, of an emulsion polymer of an acrylate, e.g., polybutyl acrylate, which has been over-polymerized by a vinyl chloride suspension polymer; (c) about 1-30~ by weight, preferably about 5-20% by weight, of an interpolymer comprising particles of poly-vinyl chloride (PVC) which have been over-polymerized with a !5 methacrylate cont~;n;ng component, preferably a mixture of methyl methacrylate and butyl acrylate; and (d~ about 0-40% by weight, preferably about 15-25%, of suspension grade polyvinyl chloride.
The inclusion of a few percent, e.g. up to about 10% by weight, of a inorganic flame retardant to the polyblend provides an ~ exceptionally tough and impact resistant flame retarded thermo-plastic.

/
, ~2-~ , 1~7~'~3'~ C-3535/3923 The polyhlend of additives which are responsible for the impact resistance improvement of the rigid plastic and which is to be added to the selected rigid plastic comprises about (a) 20%-90%, by weight, of polyacrylate over-polymerized with suspension PVC, (b) about 10-75% by weight polyvinyl chloride which has been over-polymerized with a polvmethacrylate containing component, and (c) about 0-35% by weight of polyvinyl chloride. About 0-20%
of a conventional flame retardant can also be present. These percentages are based on the total weight of the additives in I the polyblend which is to be added to the rigid plastic.
The presence of the polyacrylate which has been over-polymerized with vinyl chloride suspension polymer in the rigid plastic provides elastomer particles which enhance the impact re-sistance characteristics of the rigid plastic-containing polyblend.
i The use of the interpolymer of polyvinyl chloride which has been over-polymerized with the methacrylate containing component in small amounts dramatically improves the impact resistance of such a polyblend without the further addition of large amounts of elastomer to the blend. The addition of polyvinyl chloride has also been found to enhance the impact resistance characteristics of the rigid plastic-containing polyblend.
- Each of the components of the polyblend can be formed separately. The emulsion polymer of acrylate having the over-polymerized vinyl chloride suspension polymer, the interpolymer of , suspension grade polyvinyl chloride with the over-polymerized methacrylate component, and the optional polyvinyl chloride com-ponent, if desired, are then blended with the rigid plastic by any method known to persons of ordinary skill in the art. For example, the rigid plastic and the individual components, either in resinous or powder form, may be blended in a conventional ., ,~,, ~ .

c-3s3s/3g23 ~7~3~

mixer, and the powder blend can be fed directly into the fabric-ating machinery for conversion into finished parts. Alternatively, the dry blended mixture of resins may first be converted into pellets by extrusion into rod form with cutting to appropriate lengths. These pellats can then be fed into fabricating machinery for conversion into the finished part. Alternatively, the rigid plastic in pellet or diced form can be mixed with pellets which contain the other components, and the mixture of pellets can be extruded and chopped inta pellets on suitable equipment for subsequent fabrication into finished products. If desired, the rigid plastic in pellet form can be mixed with previously formed pellets which contain the other components and the admixture of - pellets can be fed directly into the fabricating machinery. The opportunity to prepare a mixture via the final method listed above is particularly desirable for manufacturing operations because - it m;n;m; zes the number of intermediate blending and storage operations. In addition, it allows the processor a very wide latitude of range within which to blend the rigid plastic with the components of this invention.
The blends of rigid plastic with those of the com-ponents of this invention may be fabricated by any conventional `~ plastic fabricating technique. The blends may be calendered into film and sheet, injection or compression molded into simple or complex shape and extruded into film and sheet or profile sh~pes.

' 1~7~3~
Rigid Plastic The term "rigid plastic" as used herein is intended to include styrene-acrylonitrile copolymers and styrene-acrylonitrile copolymers which are modified with elastomers. Examples of ; preferred rigid plastics for use herein are:
(1) copolymers of a styrene, e.g., styrene, alphamethyl styrene and/or tertiary butyl styrene, with an acrylonitrile, e.g., acrylonitrile and methacrylonitrile, commonly known as "SAN"
polymers;

(2) acrylonitrile-butadiene-styrene resins, commonly referred to as "ABS" resins, which generally comprise either a mixture of a 60 to 80: 40 to 20 styrene:acrylonitrile copolymer with from about 10 to 40%, by weight, of a 5 to 40:95 to 60 acrylonitrile-butadiene copolymer or a mixture of a 60 to 80:~0 to 20 styrene:acrylonitrile copolymer with from about 10 to 40%, by weight, of a graft of the latter copolymer onto polybutadiene;

(3) the acrylate:styrene:acrylonitrile resins, com-monly referred to as "ASA" resins, which comprise copolymers containing a major proportion of a C2-C8 alkyl acrylate ester elastomer upon which is grafted ahout 65 to 45~, by weight of the latter copolymer, of a 70-80:30-20 styrene:acrylonitrile - copolymer;

(4) the methacrylate:butadiene:styrene resins, com-monly referred to as the "~BS" resins, which comprise a minor proportion of a methyl methacrylate:styrene:acrylonitrile ter-polymer grafted and/or blended with either polybutadiene or a copolymer of butadiene and minor proportions of such comonomers, for example as styrene and acrylonitrile; and

(5) the styrene-acrylonitrile copolymers which have been modified with EPDM,an ethylene-propylene-diene modified rubber.

7~

Elastomeric Polyacrylic PvC Copolymer Component This component is prepared by means of a process which comprises the suspension polymerization of vinyl chloride, or a mixture of vinyl chloride with a minor proportion of one or more comonomers, in the presence of an aqueous emulsion of an poly-acrylate, e.g., polybutyl acrylate, which in a preferred embodi-ment is crosslinked. Microscopic ex~ ;nation of the "suspension-emulsion interpolymer" (SEI) particles formed herein reveals that the polymer of the suspension polymerized vinyl monomer, i.e., the polyvinyl chloride, is intimately admixed with the elastomer particles. This phenomenon apparently results from the fact that the vinyl chloride monomer, which is used for the final suspension polymerization step, has partially swollen the elastomer part-icles prior to polymerizing. The resulting particles, having been prepared by means of a suspension process, are in the -~ form of agglomerates which have a particles size that is sub-stantially greater than that of the original rubber emulsion particles utilized in their preparation.
In greater detail, now, the elastomer particles which ` 20 are utilized in preparing the elastomeric polyacrylic - PVC
copolymer particles which are used in the polyblend of this invention are made by means of conventional aqueous emulsion - procedures well known to those skilled in the art using emulsi-fiers and water soluble catalysts.

.~ .
`: :

.;, !
.', ' ~)79~34 Thus, in conducting the aqueous emulsion polymerization of the elastomeric polyacrylic - PVC copolymer particles, there is first prepared a monomer charge comprising an aqueous emulsion containing about 10-50% by weight, of one or more monomers which will be described in detail hereinbelow. From about 0.05-2.0%, by weight of the monomer mixture, of a water soluble catalyst such as, for example, ammonium, sodium or potassium persulfate, hydrogen peroxide or a redox system, such as a mixture of a persulfate with an alkali metal bisulfite, thiosul-fate or hydrosulfite, is introduced and the mixture is then heated at a temperature of from about 40C. to 95C. for a period of about 0.5 to 8 hours. The emulsion should also contain from about 0.2 - 2.0%, by weight of the total monomer charge, of any of the well known surfactants, or blends of such surfactants, which will produce elastomer particles of about 0.05 to 15 microns, preferably 0.1 to 0.8 micron. Included within this class of surfactants are the common soaps, the salts of long-chain carboxylic and sulfonic acids, the alkylated aromatic sulfonic acids and the salts of long-chain amines.

~7~

Moreover, it has been found that regardless of the particular emulsifier being utilized in preparing the elasto-mer latex, its polymerization in large scale commercial equip-ment is greatly facilitated by introducing the monomer charge to the system in about three equal portions over a period of from about 1 to 3 hours. Thus, where this is not done and the total m~n~_ -r charge is introduced in one portion, the resulting exothermic polymerization reaction often becomes virtually un-controllable leading to overheating which, in turn, may set up, i.e., coagulate, the resulting polymer latex. However, by dividing the monomer charge and introducing it in about three equal portions, the resulting polymerization reaction remains controllable and overheating and coagulation can be prevented.
The polyacrylic elastomer particles used in preparing the elastomeric polyacrylic - PVC copolymer particles used in the - polyblend of this invention comprise an polyacrylic copolymer hav-ing a Tg, i.e., a glass transition temperature, of less than about 25C. This acrylic polymer is formed by free radical initiated emulsion polymerization of at least one C2-Cpj alkyl acrylate in-cluding n-butyl acrylate, 2-ethylhexyl acrylate, and ethyl acrylate Included within the terminology "acrylic polymer" are those copolymers of the above-mentioned acrylate monomers with minor proportions, e.g., up to about 25-30~ of one or two of such vinyl monomers as styrene, acrylonitrile, vinyl acetate, benzyl acrylate, and methyl methacrylate; ethylenically unsaturated carboxylic acids such as, acrylic, methacrylic, itaconic and maleic acids;
isoprene; chloroprene; ethylene and other common vinyl monomers.
These polyacrylic elastomer particles are preferably crosslinked so that they can retain their size and shape during subsequent polymer processing steps. This cross-linking can be achieved during the .
' i -8-., .

r~

polymerization of the acrylic monomers if at least one poly-ethylenically unsaturated monomer is included in the polymerization recipe. As used in this disclosure the term "crosslinked" denotes a polymer which at ambient temperatures is substantially in-soluble in such organic solvents as tetrahydrofuran or cyclo-hexanone.
Crosslinking is effected by the presence of small quantities, i.e., 0.05-10% (based on the weight of the acrylate monomers) of a poly- ethylenically unsaturated monomer, i.e., a L0 monomer containing at least two ethylenically unsaturated groups, such as, for example, allyl methacrylate, divinyl benzene, ` diethylene glycol dimethacrylate, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, methylene-bis-acrylamide, diethylene glycol diacrylate, ethylene glycol diacrylate, divinyl L5 ether, diallyl umarate, diallyl phthalate, divinyl sulfone, divinyl carbitol, triethylene glycol dimethacrylate, trimethylene - glycol diacrylate, butylene glycol diacrylate, pentamethylene ; glycol diacrylate, glyceryl triacrylate, octylene glycol di-acrylate, trimethylolpropane triacrylate, the tetraacrylate ester of pentaerythritol and various diallyl phosphonates. Preferred for this purpose however, is 1,3-butylene glycol diacrylate.
The next step in the process of preparing the elastomeric polyacrylic-PVC copolymer particles involves the suspension poly-merization of a monomer charge comprising vinyl chloride in the presence of the aqueous emulsion of elastomer particles whose prep-aration has been described hereinabove. In addition to vinyl chloride, one may also use a monomer charge comprising a mixture of vinyl chloride with a minor proportion of one or more additional vinyl monomers other than vinyl chloride, including the vinyl esters, such as vinyl acetate, the vinyl phosphonates, such as bis(beta-chloroethyl) vinylphosphonate, the vinylidene halides, _g_ C-3535/3~23 the olefins, the alkyl vinyl ethers and the ethylenically un-saturated dicarboxylic acids, their anhydrides and their Cl- C18 mono- and dialkyl esters. It is preferred to employ vinyl chloride as the sole monomer during this suspension polymeriza-tion step.
The polyvinyl chloride either with or without a minor proportion of vinyl comonomer is preferably admixed with a stabilizer and lubricant. The amount of stabilizer can range between about 0.1~ and 10% based upon the weight of polyvinyl chloride, and the amount of lubricant can range between about 0.1% to 10%. Examples of suitable lubricants are stearic acid and its barium, calcium and lead salts, petroleum or paraffin based waxes, oils, low molecular weight polyethylene waxes, stearamides, montan wax, modified montan wax, synthetic waxes, and stearic acid esters such as glyceryl monostearate. Examples of suitable stabilizers are the phenyl salicylates; benzophenones;
benzotriazoles; basic lead compounds such as dibasic lead phos-phate, dibasic lead stearate, lead sulfate, lead chlorosilicate and dibasic lead phthalate; organo tin compounds such as dibutyl tin maleate, dibutyltin dilaurate, di(n-octyl) tin maleate polymer, n-butyl stannoic acid, thiollauric acid or its anhydride, dibutyl-tin lauryl mercaptide, dibutyltin isoctyl thioglycollate, dibutyltin mercaptopropionate and di(n-octyl) tin S,S'bis(isoctylmercapto-; acetate); organic acid salts of barium, cadmium, calcium or zinc such as barium 2-ethylhexoate, barium nonylphenate, cadmium 2-ethyl-hexoate, zinc 2-ethylhexoate, and the laurates and stearates of barium, cadmium, calcium or zinc, polyols such as pentaerythritol and sorbital; nitrogen compounds such as melamine, benzog~l~n~;ne and dicyandiamide; epoxies such as epoxidized soya oil, epoxidized ~- 30 linseed oil, epoxidized tall oil esters and butyl and octyl epoxy stearate; organic phosphites such as diphenyldecyl phosphite, phenyl didecy] phosphite and trisnonylphenyl phosphite; ~n~, -.; , 4~

liquid phenolics such as butylated hydroxytoluene, etc. For a more complete listing of lubricants, stabilizers and other functional additives, one may consult "Polyvinyl Chloride" by H. A. Sarvetnick published by Van Nostrand Reinhold Co., New York, N.Y. in 1969.
In conducting the suspension polymerization, the vinyl chloride or the mixture of vinyl chloride with one or more comonomers is added to the previously prepared aqueous emulsion of the elastomer polymer particles in a concentration of about 20 to 90%, by weight, of the latter elastomer part-icl~s. Also required to be admixed with the aqueous emulsion of the elastomer polymer particles is a concentration of from about 0.01 to 5~, preferably about 0.05-1%, as based on the total weight of the vinyl chloride monomer or monomer mixture which has been added to the aqueous emulsion of the elastomer particles, of a suspending agent such as, for example methyl cellulose, hydroxy-ethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, talc, clay, polyvinyl alcohol, gelatine and the like. Preferred for this purpose is hydroxypropyl methyl cellulose which should, preferably have a viscosity of at least about 3,000 and, pre-ferably, about 15,000 cps. as determined, at 20C., with a 2~, by weight, aqueous solution of the polymer in a Ubbelohde visco-meter according to ASTM Procedures D-1347-64 and D-2363-65T.
The use of the latter suspending agent has been found to provide for an extremely clean reaction system.
More particularly, the use, as a suspending agent, of hydroxypropyl methyl cellulose having the above-specified molecular weight requirements is found to substantially reduce the phenomenon of plate out in the suspension polymer-ization step of this process whereas the use of other sus-pending agents often leads to a significant degree of plate , --11--:~

~75~

out. Thus, as is known to those skilled in the art "plate out" refers to the undesirable formation of a skin or film of polymer on the reactor wall. Needless to say, this skin presents a serious problem since it must be removed prior to any subsequent usage of the reactor inasmuch as it interferes with proper heat transfer during polymerization.
In addition, the use of the above-described grade of hy-droxypropyl methyl cellulose results in the attA;nm~nt of a satis-factory bulk density and particle size distribution on the part of the resulting elastomeric polyacrylic-PVC copolymer particles.
A monomer soluble catalyst or initiator such, for example, as azobisisobutyronitrile, lauroyl peroxide, benzoyl peroxide or isopropylperoxy dicarbonate should also be present in a concentration of from about 0.01 to 3%, by weight, prefer-ably about 0.2-1%, of the vinyl chloride monomer or monomer mix-ture that has been added to the elastomer emulsion. It has also been found that adjusting the pH of the polymer latex to a level within the range of from about 3-9 has the effect of improving its mechanical stability and also serves to produce a clean re-action during the subsequent suspension polymerization step.
This pH adjustment may be readily accomplished by the addition, to the emulsion, of the requisite quantity of a basic solution such, for e~ample, as an aqueous solution of sodium carbonate of bicarbonate or of sodium hydroxide.
Polymerization may then be initiated by heating the above-described recipe at a temperature in the range of from about 45 to 75C. and for a period of from about 2 to 12 - hours with agitation being applied throughout the course of the reaction. The resulting product is an aqueous suspension s, i~ -12-of elastomeric polyacrylic - PVC copolymer particles wherein the supernatant fluid is completely devoid o~ any of the original rubber polymer emulsion. The total particle solids content of these suspensions will be in the range of from about 20 to 50%, by weight. Each of these elastomeric polyacrylic-PVC copolymer particles comprise, in effect, a particle of an elastomer prepared by means of an emulsion polymerization procedure having a vinyl chloride suspension polymer which has been polymerized onto the elastomer particles by means of a suspension polymerization step so that it surrounds and~or is homogeneously dispersed throughout the mass of the crosslinked acrylic elastomer emulsion polymer particle. The extent to which this vinyl chloride suspension i polymer will surround and/or be dispersed within the mass of the crosslinked polyacrylic elastomer emulsion polymer particie will, of course, be determined hy the particular monomers which are util-ized in the suspension polymerization step as well as by the parti-cular polymer which comprises the crosslinked polyacrylic elastomer polymer fraction.
Thus, in these elastomeric p~lyacrylic - PVC copolymer particles, the ~polyacrylic elastomer emulsion polymer nay be pre-sent in a concentration of from 2.0 to ~0%, by weight, said elas-tomer particles having the suspension polymer surrounding and/or homogeneously dispersed therein, the latter proportions being based on the total weight of the elastomeric polyacryli~ - PVC
copolymer particles. Preferred products should contain about 30 to 55%, by weight of a crosslinked polyacrylic elastomer emulsion polymer and about 55 to 70%, by weight, of the vinyl chloride suspension polymer surrounding and/or homogeneously dispersed throughout the mass of said elastomer emulsion polymer.

-~7~3~

The elastomeric polyacrylic - PVC copolymer particles resulting from the process should desirably have a particle size in the range of from about 10 to 200 microns and can, therefore, be readily recovered, as by fil~ration on a Buchner funnel or similar apparatus, and thereupon simply air dried. There is no need for the use of a costly and time-consuming spray drying or coagulation procedure as is usually required for the isolation, on a large scale commercial basis, of the rubber polymer particles from which these elastomeric polyacrylic - PVC copolymer particles are themselves prepared. These particles should also have a bulk density of at least about 0.2 and preferably about 0.3-0.4 gm/cm2 as determined, for example, by ASTM D-1895.
PVC/Methacrylate Interpolymer This component as designated above is an interpolymer of polyvinyl chloride (PVC) and a polymethacrylate containing com-ponent which comprises methyl methacrylate, and if desired, an-`~ other acrylate. The use of the terms "methacrylate" and "polymeth-acrylate" in describing the methacrylate containing portion of the interpolymer is intended to cover both methyl methacrylate alone ~- 20 as well as methyl methacrylate-cont~in;ng copolymers.
: .
The interpolymer is formed by a preferred process which comprises suspension polymerizing vinyl chloride under conditions whereby polyvinyl chloride is obtained in a certain particle size range by means of a conventional, free radical initiated, suspension polymerization at a controlled rate of agitation and in the presence of a specified concentration of a suspend-ing agent; removing unreacted vinyl chloride from the system after polymerization is at least 60% complete; adding to the , .
system an effective concentration of a chain transfer agent, a minor proportion, i.e., up to about 50% by total solids :.

C-3535/3~23 ~7~34~

weight of a methacrylate ester monomer charge comprising methyl methacrylate (~A) and up to about 25% by its weight of one or more optional comonomers, as hereinafter defined, and an initiator;
continuing the polymerization until the thus added methyl methacrylate, and any optional comonomers added therewith are polymerized in and/or on the particles of the previously poly-merized PVC; and, separatina the polymethacrylate-modified poly-vinyl chloride interpolymer thereby obtained. Apparently, the thus added methacrylate ester monomer, i.e., the methyl methacry-0 late and any optional comonomers, are absorbed by and polymerized in and/or on the initially prepared polyvinyl chloride particles so as to thereby produce a polymethacrylate-modified PVC resin.
According to the preferred embodiment of the process, the methacrylate ester monomer, i.e., the ~A and any optional monomers, is introduced into the system in a con-~centration of from about 20-lnO%, and preferahly from about 25-66%, by weight, of the previously polymeri7.ed PVC. Thus, from about 10-60%, and preferably about 20-~0%, hy weight, of the resulting polymethacrylate-modified polyvinyl chloride pro-~o duct will comprise moieties derived from the methacrylate ester monomer, i.e.,from the ~ ~ and any optional monomers, while the polyvinyl chloride comprises from about 40 to 90%, and preferably about 60-80%, by weight, of the total weight of this product. It is important that the methacrylate ester monomer ~5 which is employed should comprise from about 80 to 100%, by weight, of MMA but, as a minor monomer ingredient together with the MMA, it is preferred that up to about 20% by weight of the total methacrylate ester monomer weight, should be comprised of one or more optional monomers.

:: .

C~3535/3923 ~7~3~

In other words, the polYmethacrylate e.ster moieties of the polymethacrylate modified polyvinyl chloride may comprise poly-methyl methacrylate or, more preferahly, copolymers of methyl methacrylate with up to about 20~, hy weight, of at least one i ethylenically unsaturated, i.e. vinyl, comonomer. And, as previously noted, these polymethacrylate ester moieties, which should preferably comprise a methyl methacrylate copolymer, are present in the polymethacrylate overpolymerized polyvinyl chloride particles in a concentration of from about 10-60%, and -0 preferably about 20-40%, as based on the weight of the polyvinyl chloride moiety of the interpolymer particles.
The vinyl comonomers which can he used, together with methyl methacrylate, in forming the preferred polymethacrylate ester moieties of these particles may be selected from the group .5 consisting of the C2-C3 alkyl methacrylates, e.g. ethyl, n-propyl and isopropyl methacrylate; the glycidyl esters of acrylic and methacrylic acid, e.g.,glycidyl methacrylate and glycidyl .- acrylate; and, preferably, the Cl-C12 alkyl acrylates wherein J the alkyl group may be straight or branched, e.g. methyl, n-propyl, '0 n-butyl, iso-butyl, tertbutyl, hexyl, 2-ethylhexyl, decyl and dodecyl acrylate; or, mixtures of any two or more of the latter optional monomers. Especially preferred is the polymethacrylate-modified PVC interpolymer wherein the respective particles comprise - about 60-80%, by weight, of polyvinyl chloride and ahout 40-20%, 'S by weight, of a polymethacrylate ester moiety which comprises a copolymer containing ahout 86%-93%, by weight, of methyl meth-acrylate and 7%-14~, by weight, o n-butyl acrylate.
- The process for forming the interpolymer comprises adding the appropriate amount o.f methacrylate ester monomer, com-~0 prising methyl methacrylate with or without one or more :.

:: .

~7~

optional comonomers~ to a previously polymerized, aqueous sus-pension of polyvinyl chloride, parti~ularly PVC obtained by means of a suspension polymerization process. The PVC may con-tain any of the lubricants and stabilizers mentioned before in connection with the elastomeric ~olyacrylic - PVC copolymer component. In conducting such a suspension polymerization process for the preparation of PVC, the vinyl chloride monomer, or a mixture of vinyl chloride with a minor proportion of an appropriate comonomer, such as vinyl acetate or a lower alkyl acrylate, is admixed with a concentration of from about 0.01 to 5.0%, as based on the weight of the total monomer mixture, of a suspending agent such, for example, as methyl cellulose, hydroxyethyl cellulose, hydroxypropvl cellulose, carboxy-methyl cellulose, talc, clay, polyvinyl alcohol, gelatine and the like. The particle size of the resulting PVC part-icles has been found to be affected hy the concentration of the suspending agent that is present in the system. Thus, ~` it is necessary to utilize a concentration of the selected suspending agent which is within the above stated limits.
For example, if the latter maximum limit for the concentra-tion of the suspending agent is suhstantially exceeded, the resulting PVC particles will be well below the required `- particle size range which is in the range of from ahout 5 to 150 microns. Conversely, if the lower limit of this range is not met, the resulting PVC particles will be far too large.
In addition, a monomer-soluble, free radical catalyst or initiator such, for example as 2,2'-azobisisobutyronitrile, lauroyl peroxide, benzoyl peroxide or isopropylperoxy dicar-bonate should be present in the system in a concentration of from about 0.01 to 3~, by weight, of the total monGmer charge being utilized for the polymerization of the PVC or vinyl chloride copolymer.

., ,, : . .

~07~
Polymerization of the subsequently added methacrylate ester monomer is initiated by a standard monomer soluble, i.e., oil-soluble, free radical initiating catalyst. Suitable cata-lysts include, 2,2'-azobisisobutyronitrile, lauroyl peroxide, benzoyl peroxide, t-butyl peroxy pivalate and isopropylperoxy dicarbonate. The catalyst can either be premixed with the meth-acrylate prior to addition to the warm sus~ension PVC medium, - as described in Kraft et al. U. S. Patent 3,928,500 issued Dec. 23, 1975 or by addition of both methacrylate and o non-premixed catalyst to the PVC suspension when the latter is cool as described in Dyer et al. U. S. Patent 3,919,137 issued November 11, 1975 followed by the application of heat to the suspension medium. The former procedure for adding meth-acrylate and initiator is the preferred method.
, Chain transfer agents are used during the polymerization of the methacrylate, and any optional monomers, in order to further control the properties, e.g., melt flow properties, of the resulting methacrylate modified PVC particles which are to be used in the poly~lend. These chain transfer agents, can be selected from the group consisting of:
(1) chlorinated aliphatic hydrocarbons such as carbon tetrachloride, chloroform, methylene chloride, butyl chloride, methyl chloroform, propylene chloride and trichloro-ethylene;
i ~2) aromatic hydrocarbons such as toluene, xylene, ., mesitylene, cume~e, ethyl benzene, t-butyl benzene and ~hloro-benzene;
(3) aldehydes, such as acetaldhyde, propionaldehyde, `~- benzaldehyde and crotonaldehyde;
'"

` : _ '~ ' ' , , - ' ' , ~7~

(4) aliphatic and cyclic ketones, such as methyl ethyl ketone, acetone, diethyl ketones, methyl isobutyl ketone and cyclohexanone methyl ethyl ketone;
(5) cyclic ethers, such as dioxane and tetrahydrofuran;

(6) alkyl esters of aliphatic carboxylic acids, such as methyl isobutyrate and e~hyl acetate;

(7) aliphatic alcohols, such as sec-butyl alcohol, n-butyl alcohol, isobutyl alcohol and t-butyl alcohol;

(8) aliphatic carboxylic acids, such as acetic acid;

(9) cyclic hydrocarbons, such as methyl cyclohexane;
and, most preferably;

(10) mono- di- and polymercaptans including monomer-captans such as methyl mercaptan; ethyl mercaptan; propyl mer-captan; n-butyl mercaptan; n- and t-butyl mercaptan; n- and t-phenyl mercaptan; hexyl mercaptan; n- and t-heptyl mercaptan;
n- and t-octyl mercaptan; n- and t-decyl mercaptan; n-dodecyl, i.e., lauryl, and t-dodecyl mercaptan; n- and t-tetradecyl mercaptan; n- and t-hexadecyl mercaptan; n- and t-octadecyl mercaptan; n- and t-eicosyl mercaptan; n- and t-pentacosyl mercaptan; n- and t-octacosyl mercaptan, n- and t-triconyl mercaptan and blends thereof. From this group of mono-mer-captans, it is preferred to use lauryl mercaptan.
-! Other operable monomercaptans include thioacetic acid; l-mercapto-2-butanone; methyl mercaptoacetate; ethyl mercaptothioacetate; 1-mercapto-2-ethoxyethane; diethyl mer-captoethyl phosphorotrithioate; 2-mercaptoethyl acetamide;
dimethyl aminomethyl mercaptan; cysteamine; mercaptomethyl-thiopropane; monomercaptocyclohexane; benzyl mercaptan;
cysteine; and, mercaptoethanol.
:-., r, ~:
'~' ~ ' -19--~7~3~

Suitable dim~rcaptan chain transfer agents can be illustrated by ethanedithiol; 2,3 dimercaptopropanol; decan-edithol-1,10 and the like.
Suitable polymercaptan chain transfer agents having more than three mercaptan groups per molecule can be illustrated by pentaerythritol tetra(7-mercaptoheptanoate); mercaptoacetic acid triglyceride; pentaerythritol tri(beta-mercaptopropionate);
pentaerythritol tetra(beta-mercaptopropionate); cellulose tri-(alpha-mercaptoacetate); 1,2,3-propane-trithiol; 1,2,3,4-neopentane tetrathiol; 1,2,3,4,5,6-mercaptopoly(ethyleneoxy) ethyl(sorbitol); l,l,l-trimethyl propane tri(alpha-mercapto-acetate); dipentaerythritol hexa(3-mercaptopropionate); 1,2, 3-tris(alpha-mercaptoacetypropane); thiopentaerythritol tetra(alpha-mercaptoacetate); 1,6,10-trimercaptocyclododecane, 1,2,3,4,5,6-hexamercaptocyclohexane; N,N', N"N'''-tetra (2-mercaptoethyl)py,o.~,ellitamide; tri-(2-mercaptoethyl) nitrilotriacetate; pentaerythritol tri(alpha-mercapto-acetate); pentaerythritol tetra(alpha-mercaptoacetate);
tri(p-mercaptomethylphenyl)methane; 2,2,7,7-tetrakis(mer-captomethyl)-4,5-dimercapto-octane; 5,5,5-tri(mercaptoethyl) phosphorotrithioate; xylitol penta(beta-mercaptopropionate~;
and, the like.
Illustrative of low molecular weight polymeric materials having at least 3 pendant mercaptan groups per ; 25 molecule are homopolymers and copolymers of vinyl thiol, e.g., polyvinyl thiol. Other polymeric thiols, such as glycerol/ethylene glycol polyether polymercaptan can also ; be used as chain transfer agents in the process of this invention.
,:

~ .

From the above group, optimum results are, however obtained by the use of low molecular weight polymercaptans having from 3-5 mercaptan groups per molecule as illustrated by pentaerythritol tetrathioglvcolate; pentaerythritol tetra (3-mercaptopropionate); trimethylolethane tri(3-mercaptopro-pionate); xylitol penta(beta-mercaptopropionate); trimethylole-thane trithioglycolate, trimethylolpropane tri(3-mercaptopro-prionate); and, trimethylolpropane trithioglycolate. ~he use of the latter polymercaptans are preferred since they are most efficient with respect to the rate of polymerization which is attainable in the system wherein they are utilized.
With respect to the amount of chain transfer which is used in forming the polyvinyl chloride/meth(acrylate) interpolymer this will largely be determined by the particular chain transfer - 15 agent that is selected. However, in most instances they may be utilized in a concentration of from about 0.025-7.5%, as based on the total weight of the methacrylate ester monomer charge, i.e., on the total weight of the M~ and any of the above-identified optional monomers present in the monomer system. In general, mercaptans, and particularly polymercaptans, are more efficient and may be used in concentrations at the lower end of the latter range whereas less efficient chain transfer agents, such as the aromatic hydrocarbons, will be used in concen-` trations at the upper end of this range.
By utilizing a chain transfer agent in forming the interpolymer particles used in this invention, it is possible to exercise a greater degree of control upon the molecular weight, which is higher than the maximum value in the below stated range, of that portion of the final polymeric product :
.':

' :
,. . .

which is derived from the ~ ~ and any optional comonomers which may have been introduced together therewith. This, in turn, affects the molecular weight of the product as a whole.
Thus, it may be here stated that the PVC/meth(acrylate) inter-polymers should, preferably, have a molecular weight, as expressed in terms of their Relative Viscosity, as determined in a 1%, by weight, solution of the polymer in cyclohexanone at 25C., of from about 1.50 - 2.80 and, preferably, from ahout 2.30 - 2.60.
Thus, it has been found that those products having a Relative Viscosity within this range will display optimum character-istics. As is known to those skilled in the art, Relative Viscosity is calculated by the use of the following formula:
Relative Viscosity = Tl where Tl= the time required for the passage of a standard volume of the polymer solution throu~h an orifice in a viscometer and T2= the time required for the passage of a standard volume of the solvent through the orifice in the identical viscometer.
The polymerization of the methacrylate ester monomer, i.e., of the ~DMA and of any optional comonomers which may have - been introduced into the system therewith, is conducted by heating the system, i.e., the selected chain transfer agent, the previously prepared PVC host polymer and the mixture of the catalyst with the MMA and any optional comonomers, at a temperature of from about 40to lOnC. for a time sufficient to completely polymerize the ~MA, and any optional comonomers in and/or on the host PVC particles. It is to be pointed out that it is not ordinarily necessary to introduce any fresh suspending agent into the system since a sufficient quantity will already be present from the initial polymerization of the PVC.

.
:

y ~ ~
lV7~3'~

The particular catalyst, temperature, reaction time and other operating conditions chosen are, of course, interde-pendent and may be those ordinarily employed in the polymeri-zation of MMA. Other variations in polymerization technique will suggest themselves to those skilled in the art.
The process used herein is particularly satisfac-tory when conducted with polyvinyl chloride homopolymers as the initially prepared vinyl chloride host polymer. However, as has already been brief 1Y noted, there can also be employed the usual copolymers of vinyl chloride with minor proportions of one or more ethylenically unsaturated, i.e., vinyl, comono-mers provided that the resulting vinyl chloride copolymers are within the above specified particle size and Relative Viscosity ranges.
Illustrative of these vinyl comonomers which can be used in preparing the vinyl chloride conta~n;ng host polymer of the meth-acrylic modified polyvinyl chloride component of this invention include alpha-olefins such as ethylene, propylene and butylene;
- vinyl esters of carboxylic acids such as vinyl acetate, vinyl propionate, vinyl butyrate, and viny] stearate; Cl-C20 alkyl esters of acrylic and methacrylic acid such as methyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate and lauryl acrylate; aryl, halo- and nitro substituted benzyl esters of acrylic and methacrylic acid such as benzyl acrylate and 2-chlorobenzyl acrylate; ethylenically unsaturated monocarboxylic acids such as acrylic and methacrylic acids;
ethylenically unsaturated dicarboxylic acids, their anhydrides ~- and their Cl-C20 mono- and dialkyl esters such as aconitic acid, fumaric acid, maleic acid, itaconic acid, citraconic acid, maleic anhydride, dibutyl fumarate and mono- diethyl maleate;
amides of ethylenically unsaturated carboxylic acids such as .~
~ -23-:
,, , ~7~3~

acrylamide and methacrylamide; vinyl aryl compounds such as styrene and alpha-methyl styrene; nitriles of ethylenically unsaturated carboxylic acids such as acrylonitrile and meth-acrylonitrile; vinyl pyrrolidones such as N-vinyl-2-pyrroli-; done; Cl-C20 alkyl vinyl ethers such as methyl vinyl ether, ethyl vinyl ether and stearyl vinyl ether; dienes such as isoprene and butadiene; and, glycidyl esters of acrylic and methacrylic acid such as glycidyl acrylate and glycidyl methacrylate, etc.
L0 In this process the PVC, or vinyl chloride copolymer, is first polymerized by the suspension technique until the re-action is at least 60% complete and preferably 80% or more com-plete. Unreacted vinyl chloride must then be removed when the system is vented before the MMA and any optional comonomers are subsequently added and polymerized. If this is not done, the , r~ -;n;ng vinyl chloride monomer will undergo an undesirable copolymerization with the subsequently added MMA leading to non-reproducible results and to the preparation of a soft, rubbery product which often hardens before it can be removed from the reactor. This feature of sequential polymerization, i.e, of first polymerizing the vinyl chloride and then the MMA, is an important step in the process of forming the methacrylate modified poly-vinyl chloride to be used in the polyblend.
The methacrylate ester polymerization, i.e., the poly-, 25 merization of the MMA with or without one or more optional monomers, may be carried out in the same vessel immediately - after the initial vinyl chloride suspension polymerization has been completed or the PVC may have been performed, i.e., previously polymerized, stoxed and used at a later date in carrying out this second step of the process. If the methacrylate . . .

:

3,~

ester monomer polymerization is carried out in situ as soon as the original PVC polymerization system has been vented and un-reacted monomer removed, then it may not be necessary to add any additional catalyst.
Formation of Optional PVC Component Suspension grade polyvinyl chloride should be selected for use as the optional polyvinyl chloride component of the poly-blend. Processes for its formation are well known. As used herein in the term "polyvinyl chloride" is intended to include polyvinyl chloride containing up to about 25% of one of the well known com-pounds which copolymerized well with vinyl chloride, e.g., the vinyl esters, vinyl phosphonates, vinylidene halides, olefins and the like. The suspension polymerization is performed by adding the monomer to an aqueous medium containing about 0.01 to 5% by weight based on the weight of monomer, preferably about 0.05 - 1%, of a suspending agent, such as methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, talc, clay, polyvinyl alcohol, gelatine and the like, and from about 0.01 to 3.0% by weight, based upon the weight of monomer, preferably about 0.2 - 1%, of a monomer soluble catalyst such as azobisisobutyro-nitrile, lauroyl peroxide, benzoyl peroxide or isopropylperoxy dicarbonate. Polymerization is initiated by heating the mixture at 45-75C. for about 2 to 12 hours. The optional PVC component can contain any of the lubricants or stabilizers described above.
Flame Retardant As mentioned before the rigid plastic containing poly-blend of the present invention can contain any conventional inor-ganic or organometallic flame retardant if a flame retardant poly-blend is desired.

', ,.
!

Preferred for use are antimony oxide, barium metaborate, zinc borate, magnesium borate, blends of antimony oxide and one of the boarates, and conventional metallocene flame retardants, e.g., ferrocene, (C2~s)2Fe. The amount of flame retardant that should be added to the polyblend cont~ining the rigid plastic ranges up to about 10~ by weight of that polyblend. The amount in the blend of additives to be added to the rigid plastic should be up to about 20% by weight of the blend of additives.
The polyblend formed by the present invention has good .0 impact resistance with good maintenance of rigidity as demon-strated by its flexural modulus. The processability characteris-tics of the rigid plastic are unexpectedly retained in view of the presence of the polyvinyl chloride contAi n; ng additives which would be expected to provide less acceptable heat stability. The .5 nclusion of substantial amounts of methacrylate elastomer in the polyblend rather than the conventional butadiene or butadiene copolymer additives enhances the weatherability characteristics of the resulting polyblend.
The following Examples will further illustrate certain ro preferred embodiments of this invention. In these Examples, all parts gLven are by weight, unless otherwise noted:
EXAMPLE I
About 2393 lbs. of distilled water, 1738 grams of the bis(tridecyl)ester of sodium sulfosuccinic acid (Aeroso ~TR-70), '5 1250 grams of potassium persulfate and 500 grams of sodium bicar-bonate were charged into a 500 gallon reacter fitted for moderate agitation. Butylene glycol diacrylate (22 lbs, 5 oz) and butyl - acrylate (1100 lbs) were mixed and 200 lbs of the mix were charged . ~

~ -26-.

c-3s3s/3g23 ~7~3~

into the reactor. The reactor was closed and was warmed to 70C.
As soon as the ensuing exothermic reaction began to subside, the remainder of the mix was pumped into the reactor just fast enough to maintain an exothermic reaction. The temperature was held at 70C. for 30 minutes after all monomer had been added, and the reactor was allowed to cool down to room temperature. The latex was strained into a receiver and had a solids content of 31~.
Two additional batches were run to supply the required amount of latex for the suspension step described below.
To a 4000 gallon reactor was added 6500 lbs of the latex from the above procedure. Fourteen pounds of methyl cellulose suspending agent (Methocel HG 9~ - 15,000 cps) was dissolved in a portion of a 15,865 lb water charge and was added to the reactor along with the remainder of the water charge. Azoisobutyronitrile 15 (Vazo 6~) was added (5 lbs) and the reactor was closed. Evacuation of the reactor to 15-20 in. Hg was performed and this pressure was maintained for 15 minutes. The reactor pressure was allowed to rise to atmospheric pressure by the addition of gaseous vinyl chloride monomer. Evacuation was repeated for five minutes and 20 a total of 6300 lbs of vinyl chloride monomer was added. With agitation the mixture was warmed to 140F. and was held at this temperature until the reactor pressure had decreased by 38 psia.
At this point, 5.5 lbs of butylated hydroxytoluene was added and the unreacted vinyl chloride monomer was vented off. The mixture -~ 25 was allowed to 30C., and the product was recovered.
EXAMPLE II
The ingredients listed in Table II, with the exception of NaHSO3, were charged into a polymerization reactor:
I

;~:
, -27-:
~- ' - ,' ~07943~

REAGE~TAMOUNT(Parts by Weight) Butyl acrylate 100 Butylene glycol diacrylate 2 Distilled wat~r 730 Aerosol TR-7~(bis[tridecyl]
ester of sodium sulfosuccinic acid) 32 Potassium persulfate 0.42 NaHCO3 0.2 NaHSO3 0.2 - FeSO4 0-004 The reactor was evacuated to a pressure of 26 in.Hg and the vacuum was broken with nitrogen. The evacuation and nitrogen purge was repeated. The reactor was heated to 30C. with stirring and the NaHSO3 was added. The temperature was raised to 50C. and was maintained at this temperature until polymerization was completed.
The reactor was cooled to 30C.,was opened and was charged with 277 parts by weight of distilled water, 45 parts by weight of Methocel 1242 suspending agent and 0.16 parts by weight of lauroyl peroxide. The reactor was closed, vacuum was applied for 10 minutes and 158 parts by weight of vinyl chloride monomer was added. The reaction mixture was stirred and warmed to 60C. The -; temperature was maintained at this level until the pressure in the reactor decreased by 35 psia. About 11 parts by weight of butylated hydroxytoluene was added, unreacted vinyl chloride monomer was vented and the reactor was cooled to room temperature in order to recover the granular resin.
EXAMPLE III
About 0.089 parts by weight Methocel 1242 methylcellulose - 30 suspending agent was dissolved in a portion of 248 parts by weight water and was added to a polymerization reactor with the rPmA;n~er of the water and 0.038 parts by weight of Vazo 64 azobisisobut~L~nitrile initiator. The reactor was cooled and ' :~

~ -28-~ ' .
.~
, ~ . .

~7~

evacua~ed, and the vacuum was broken with nitrogen. The reactor was reevacuated and 100 parts of vinyl chloride monomer was charged. The mixture was heated to 71C. with vigorous agitation, and the temperature was held until the pressure gauge showed a 20 psia decrease. Unreacted vinyl chloride monomer was vented j off and the reactor was cooled to 25C. An additional 0.081 parts of Vazo 64 was charged into the reactor at this point. About 0.005 parts by weight of lauryl mercaptan was dissolved in 29.6 parts by weight of methyl methacrylate, and this mixture was charged to the reactor along with about 4.96 parts by weight of butyl acrylate. The mixture was heated to 75C. and was held at this temperature for 4 hours, was cooled, and the resin was re-covered.
EXAMPLE IV
The Table set forth below, Table I, shows three separate polyblends of the present invention formed from a commercially available ABS plastic and the components made in Examples I-III along with the physical characteristics of these blends:

., ., , , '~ ' ' : .

TABLE I
COMPONENT % BY WEIGHT TEST PROCEDURE
ABS (Cycolac DH-1000)* 50 70 70 Example I 40 -- --Example II -- 20 25 Example III 10 10 5 o Tensile Str., Yield (lb/in2)6900 6900 6600 ASTM D-638 ~G
% Elongation, Yield 7 7 7 ASTM D-638 Tensile Str., Break (lb/in,2) 5300 5300 5200 ASTM D-638 % Elongation at Break 53 39 34 ASTM D-638 Izod Impact 1/8"(ft-lb/in) 14.3 4.7 5.4 ASTM D-256 Tensile Impact (ft-lb/in) 190 150 150 ASTM D-1822 Tensile Modulus (lb/in2x 10-5) 1.13 1.17 1.14 ASTM D-638 : Flexural Modulus(lb/in2x 10-5) 2.94 2.90 2.70 ASTM D-790 DTL (C., 1/4" specimen at 264 psi fiber stress) 82.5 85.585.5 ASTM D-648 -* sold by Borg-Warner Corp. I

w N

- , .

~79439~

EXAMPLE V
The procedure described in Example III was utilized with the exception that the following amounts of reagent were used in the first polymerization:
REAGENT AMOUNT(Parts by Weight) Vinyl chloride monomer 100 Distilled water 257 Methocel 1242~ 0.093 Vazo 64~nitiator 0.022 The following reagents were used in the second polymerization:
REAGENT AMOUNT(Parts by Weight) Methyl methacrylate 36.9 vazo 64g~nitiator 0.11 - Lauryl mercaptan 0.05 EXAMPLE VI
, A series of polyblends were fabricated utilizing a commercially available ABS resin, the elastomeric acrylic - PVC
copolymer component formed in Example I and the PVC/meth(acrylate) interpolymer formed in Example IV. Table 2 sets forth the blends ` which were formed and the results which were obtained.

.

:. -;.` ~

~, :
.

, .............................................................. :
; -31-., ~, . ~ : .

~ l)7g~3'~

EXAMPLE VII
All the reagents listed in the Table were charged into a 4000 gallon reactor with the sodium bisulfite being added last:
REAGENTAMOUNT(Parts by Weight) Butyl acrylate 2490 lbs 2-ethylhexyl acrylate1070 lbs Butylene glycol diacrylate 70 lbs Distilled water1730 gallons Aerosol TR-70@~bis[tridecyl]
ester of sodium sulfosuccinic acid~ ~ 12 lbs*
Aerosol ~ (dihexyl ester of sodium sulfosuccinic acid) 10.5 lbs*
Potassium persulfate 22.5 lbs Sodium bisulfite10~1/8 lbs Ferrous sulfate 40 grams Sodium biscarbonate 6.75 lbs * Aerosol TR-70 and MA were dissolved in 250 gallons of distilled water.
~20 The reactor was evacuated twice and was broken each time with nitrogen. The agitator was turned on, and the reaction medium was warmed to 113F. and was held at this temperature until ;
polymerization was completed about 3-1/2 hours later. The reactor was cooled to 85F. with agitation about 20.5 lbs of Methacel HG~
90 suspending 680 gallons of deionized water was added to the latex formed above. The agitator was stopped and 2.75 lbs of Vazo 64 initiator was added. The reactor was closed and evacuated at 20 in. Hg for 10 minutes. The reaction mixture was brought to ; atmospheric pressure with nitrogen and the evacuation was re-peated for 5 min. Vinyl chloride monomer (4240 lbs~ was charged into the reactor and the mixture was agitated and warmed to 140F.
The temperature was held at 140F. until an 80 psia drop in pres- ;
-~ sure occurred in the reactor. About 6 lbs of butylated hydroxy-toluene was added and unreacted vinyl chloride was vented from the reactor. The reactor was opened and 14.75 lbs of aluminum sulfate was added. After cooling the product was recovered.

`

:'` ' . .

~7~4~

EXAMPLE VIII
Two polyblends were formed comprising a commercially available ABS resin, the component of Example VII, the component of Example III, and a commercially available PVC suspension resin (SCC-616 sold by Stauffer Chemical Co.). Flame retardants (Sb203 and hydrated zinc borate) were also utilized. Table 3 sets forth the compositions and Table 4 gives the physical characteristics of the two polyblends.

~' !~
-, ,' ;
`' COMPONENT I II
ABS(Cyclolac DH-1000~ 52 48 Example VI 33 30 Example III 2 5 PVC (SCC-616) 8 13 Sb2O3* 2 8 Hydrated zinc borate** 1.5 2*** 1.5 _ * White Star 101-1 ~ `~
**Humphrey 2B-112 *k*du Pont R-900 Both were non-burning by the ASTM D-635 procedure.

I** I** II**
MIXED PELLETS PREPELLETIZED MIXED PELLETS
FR-ABS* UNANN~ALED uNANNEALEn ANNEALED UNA~RALED ANNEALED
Tensile 9tr at Yield (lb/in2) 6900 6600 6600 6900 6800 7000 Tensile Str at Break (lb/in ) 4600 5200 5200 5700 5300 5600 %Elongation at Yield 6 7 7 7 7 7 %Elongation at Break 21 34 32 28 41 30 Fluxural Modulus X 10-5 2.27 2.04 2.09 2.09 2.18 2.63 Impact - Izod 1/8" 2.6 5.9 6.5 5.0 8.1 6.5 Impact - Tensile 121 150 144 141 198 168 DTL 1/4" (C.) 82.5 86 85.0 102.5 83.5 99.5 * Borg Warner Cyclolac KJB used in th~ fire retardant AB9.
** See Table 3 for the composition - , . . .

~7~

The scope of protection sought is set forth in the appended claims.

:, ~:, _36-:

Claims (16)

What is Claimed is:

1. A thermoplastic polyblend having improved impact resistance comprising:
(a) about 20 to 90% by weight of a rigid plastic;
selected from the group consisting of acrylonitrile-butadiene-styrene resins, copolymers of a styrene with an acrylonitrile, the acrylate:styrene:acrylonitrile resins, meth-acrylate:butadiene:styrene resins, and styrene-acrylonitrile compolymers modified with ethylene-propylene-diene modified rubber;
(b) about 10 to 60% by weight of a copolymer comprising an acrylate which is overpolymerized by a vinyl chloride suspension polymer;
(c) about 1 to 30% of an interpolymer comprising a polyvinyl chloride suspension polymer overpolymerized with a methacrylate component, and (d) about 0 to 40% by weight of polyvinyl chloride;

2. A polyblend as claimed in Claim 1 wherein the rigid plastic is present at about 50% to 70% by weight.

3. A polyblend as claimed in Claim 1 wherein the copolymer of (b) comprises from about 15% to 45% by weight of the polyblend.

4. A polyblend as claimed in Claim 1 wherein the interpolymer of (c) comprises about 5% to 20% by weight of the polyblend.

5. A polyblend as claimed in Claim 1 wherein the acrylate copolymer in the copolymer in (b) is crosslinked with a monomer containing more than one ethylenically unsaturated group.

6. A polyblend as claimed in Claim 5 wherein the crosslinked acrylate has a glass transition temperature of less than about 25°C.

7. A polyblend as claimed in Claim 6 wherein the acrylate in the copolymer comprises at least one C2-C8 alkyl acrylate.

8. A polyblend as claimed in Claim 1 wherein the vinyl chloride suspension polymer in the copolymer of the inter-polymer of (b), (c) and in component (d) is selected from the group consisting of polyvinyl chloride and copolymers of vinyl chloride with a minor proportion of at least one other vinyl monomer.

9. A polyblend as claimed in Claim 1 wherein the amount of component (d) is about 15-25% by weight of the poly-blend.

10. A polyblend as claimed in Claim 1 wherein the interpolymer of (c) comprises about 60-80%, by weight, polyvinyl chloride and about 40-20%, by weight, of the methacrylate component.

11. A polyblend as claimed in Claim 1 wherein the meth-acrylate component in (c) comprises methyl methacrylate and n-butyl acrylate.

12. A polyblend as claimed in Claim 11 wherein the methacrylate component comprises about 86-93%, by weight, of methyl methacrylate and about 7-14%, by weight, of n-butyl acrylate.

13. A polyblend as claimed in Claim 1 which further comprises about 0-10% of a flame retardant.

14. A polyblend as claiméd in Claim 13 wherein the flame retardant is selected from the group consisting of antimony trioxide, barium metaborate, zinc borate, magnesium borate, blends of the borates or metaborates with antimony trioxide, and metallocenes.

15. A polyblend as claimed in Claim 1 which further comprises in the polyvinyl chloride about 0.1% to about 10% of a lubricant based upon the weight of the polyvinyl chloride.

16. A polyblend as claimed in Claim 1 which further comprises in the polyvinyl chloride about 0.1% to 10% of a stabil-izer based upon the weight of the polyvinyl chloride.