CA1253641A - Processing aid compositions - Google Patents

Abstract

- i-PATENT APPLICATION
of ISMAIL SAMY RABINOVIC
HUBERT THOMANN
GERARD GUTH and WILLIAM EARL CARTER
for IMPROVED PROCESSING AID COMPOSITIONS
DN 83-36 MSA:plb ABSTRACT OF DISCLOSURE

This invention is directed to improved processing aid compositions for vinylchloride polymers. The improved processing aid compositions are formed from an intimate admixture of a conventional processing aid for vinylchloride polymers and a dispersion aid polymer.
The dispersion aid polymer acts to disperse the processing aid polymer in the vinylchloride polymer, reducing the tendency of the processing aid to form lumps or gels in the vinylchloride polymer. The weight ratio of the processing aid polymer to the dispersion aid polymer in the improved processing aid composition ranges from 99.5 to 0.5 to 90 to 10. The vinylchloride polymer contains from about 0.5 to 5 parts by weight of the improved processing aid composition to 99.5 to 95 parts of vinylchloride polymer.

Description

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~ FIELD OF THE INVENTION
: ThiQ lnvention relates to proces~lng ald~ ~or vlnylchlorlde polymers, and more particularly to improved proces~qing aid composltions ~or vlnylGhlorlde ; polymers containing a dispersion aid polyme~ for the improved disper~lon o~ ¢onventional proce~sing aids ln the ~lnylchloride polymer.

Pol~meric processlng alds are widely used ln the o productlon o~ polyvlnylchloride (PVC) articles to improve the proce~sing performance Or P~C during extrus~on, inJection and/or thermoformlng operations.
Proce~slng aid~ act to reduce the temperature requlred for ~uslon o~ PVC, promote homogeneity and hot strength o~ th~ PVG~ reduce melt fraGture, reduce plateout ~; durlng processlng~ ~nd impart better ductllity to the rlnished product. Lowerlng the tempera~ure o~ ~u~lon ;~ results ln prolonged heat stability for PVC, allows for a margin o~ ~afety when using regrlnd materlal, and 0 decreases the proce~sing tlme. Greater hot strength and reduced melt fracture allows a processor to extrude ` or calender the PVC at a faster rate wlth improved sur~ace quallty. Reductlon or elim1nation of plateout allows ~or extended proces~lng runs without re~ects due ~.~
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to plateout markoff and without time-consumlng shutdowns ~or cleaning out deposits that would lnterfere with melt flow and contribute to PVC
degradation. The homogenizing effect of processing aids is very important in providing products having signiflcantly improved ductillty and thermo-formability. The uniformity of the temperature dependent properties of PVC obtained with the inclusion of processing aids improves the overall ability o~
processors to operate their equipment.
Processing aids generally also improve the tensile ; strength~ modulus and, to a smaller extent, the heat distortion temperature of PVC but do not improve impact strength and can actually reduce the impact strength of PVC when added at high levels.
Various types of polymeric processing aids have been deve~oped for use with PVC. These processing aid polymers include acrylic polymers and copolymers, such as hlgh molecular weight polymethyl methacrylate with weight average molecular weights ranging from about 750,000 to about 7 million, copolymers formed predominantly ~rom methyl methacrylate and minor amounts of alkyl acrylates, and copolymers of acrylics and styrene, styrene and acrylonitrile, and poly(alphamethyl-styrene). These processlng aid polymers may be homopolymers, single stage or multiple stage copolymers, or graft copolymers.
~ Not all conventional processing aids are alike in - their balance of properties or efficiencies under different operating conditions. The composition, structure and/or staging, molecular weight, and concentration of the processing aid in PVC all contribute to their performance properties.
With the notable exception of poly(alphamethyl-styrene) processing aids~ processing aids typically are thermodynamically miscible or compatible with P~C such ; - 2 -:~:

that when blended at small levels wlth PVC, the modi~ied PVC exhibits a slngle glass transitlon temperature (Tg). While the processing aids are typically compatlble with PVC, they have Tg's that are much higher than the Tg of PVC. For example, PVC is relatlvely soft, having a Tg of about 70C, whlle polymethyl methacrylate type processing aids have Tgs on the order of about 95C to about 105C. Processlng aid~q and PVC also exhiblt dlfferences in viscosity which also makes it difflcult to obtain homogeneous blend~ of proces~lng aids in PVC. Obtaining well disper~ed proce~slng aids throughout the PVC matrlx is desirable ~or aesthetic and physlcal reasons For instance, if the processing ald is not weli dlspersed ln PVC, the processing ald partlcles will lump together forming gels in the PVC. These gels produce a PVC
product having an undesirable, lrregular or bumpy, appearance. In addltlon, these gels or lumps also act as stress concentratlon points ln the PVC promoting ~ fracture initiation and propagation and reducing the lmpact resistance of PVC.
Improvements in the dispersion of processlng aids in PVC have been attempted by modifying the proce~sing conditions to break down the~e gels or by modifying the structure of the processing ald polymer itself. Higher shearlng conditions durlng processing have been used to attempt to improve the dlsperslon of processing aids in PVC, however, these higher shear condition~ reduce the output of PVC product that can be achleved. In 3 addltion, attempts to break down the gels, by applylng more worklng energy to the modified PVC elther by increasing the internal friction temperature or shearing condltions by reducing the operating temperature of the machinery~ have also been attempted but have been found to be less than completely ~' , - , ~i;36~

adequate. Other attempts to modify the composltlon and/or structure o~ the processlng ald lt~el~, for example, by formulating ~ multi-~tage proces3ing ald where the first stage has a Tg equal to or le3~ than 60C and where the amount of the ~lrst stage 18 equal to or le~s than 25 percent by weight of the total processlng ald (U.S. Patent 3,833,686) have also been developed.
DeRplte the wide recognltion of the problem o~
dlspersing proce~sing aids in PVC, no generally adequate solutlon for dispersing processing aids, that otherwise exhlbit poor dlsper~ion or lead to a hiBh level of gel~ in PVC, ha~ been available. -It is, there~ore~ an obJect o~ this lnventlon to - -provlde an improved processlng ald composltion that ls well dispersed ln PVC reducing the tendency of the processlng ald to ~orm gels in the modlfied PVC.
U.SO Patent No. 4,440,905 entltled Dunkelspersers i8 believed to be most relevant to the present lnvention. ~hls patent 13 dlrected to the use of dlspersant "dunkelsperser" polymer~ to dl~perse elastomeric impact modifiers in rlgld thermopla~tic matrlx polymers including PVC. Elastomeric impact modl~lers are structurally dl~ferent from, and ~unction quite dlf~erentlg ln PYC than, proces~lng aids.
Elastomerlc impact modiflers are u~ually core-shell or multlple stage rubbery polymers such a~ methacrylate-butadlene-styrene (MBS), acrylonltrile-butadiene-styrene (ABS) and others such as ~or example those 3 descrlbed in U.S. Patents 2,802,809, 2,943,074, 3~251~904J 3~678,133, 3,793,402 and 3,899,547; or llnear or crosslinked, ~lngle ctage rubbery polymers such as polybutadiene, butadiene/styrene acrylonitrlle, llnear ethylene-propylene copolymers; segmented block copolymer~ such as butanediol-polytetrameth~lene ~, ,' ' , i ~

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etherdiol terephthalate ester; or polymers modlfied to impart elastomeric behavior ~uch as chlorlnated polyethylene. Other examples of elastomeric lmpact modifiers are disclosed in U.S Patent 4,440,905.
Impact modlfiers are synthesized to be elastomeric-ba~ed toughening agents for thermoplastics. They are insoluble in thermoplastics and their function can be analogized to the actlon of rubber balls suspended in a polymer matrix. When impact modifiers are added to PVC a two phase system, exhibiting multiple glass transition temperatures~ is formed. In order to obtain uniform toughness and 5 impact efficiency Por the modified thermoplastic polymer, these lmpact modifiers, or rubbery spheres, must be uniformly distributed throughout the polymer ; matrix. Because of the dlfferent criterla requlred to synthesize impact modifier compositions, and the different mechanlsm by which impact modiflers function in thermoplastics compared to processing aids, lt was completely unexpected to those in the art of PVC
additl~es that "dunkelsperser" polymers could be useful as dispersion aid polymers in combinatlon with conventional processing aids for PVC.
SUMMARY OF THE INVENTION
Broadly, the lmproved processing aid compositions of the invention are blends of conventlonal PVC
processing aid polymers (a) and di~perslon aid polyme-rs (b), and more partlcularly the lnvention is directed to lmproved processing ald compositions where the processing aid polymers (a) are formed from methyl methacrylate and from O to 50 weight percent of a (Cl-C4 alkyl)-acrylate, and where the dlspersion ald polymers (b) are homopolymers or copolymers ~ormed from at lea~t 50 welght percent of one or more of the followlng monomers: (Cl-C8 alkyl)-acrylates, (C~-Cg cycloalkyl)-acrylates, ethylene, propylene, ' `~'`'1 ?`~.,5 . ' ' .
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vinylacetate and butadlene, and where the welght ratio of processing ald polymer (a) to dlspersion ald polymer (b) i8 ~rom 39~5 to ~.5 ~o 90 to 10, and preferably from 99 to 1 to 95 to 5; the remainder of the monomers of said copolymers being methacrylate and/or styrene monomPrs.
The lnventlon al~o lc dlrectsd to PVC compositions containing the lmproved processlng ald composltions, and to method~ for for~ulatlng the lmproved processlng ald and modlfled PVC compositlons.
. DETAILED DESCRIPTION OF THE INVENTION
The processlng ald polymer (a), that ls dispersed in PVC by the dlsperslon ald polymers (b), may be a conventlonal slngle or multlple stage polymer as disclosed ln U.S. Patent 3,833,686 of R.J. Grochowski et al., issued Sep~ember 3, 1974r or as disclosed in British Patents 1,511,683 and 981,116.
The dlsperslon ald polymer (b) is a homopolymer or copolymer formed from at least 50 welght percent o~ one ` or more of the following monomers: (Cl-C8 alkyl)-acrylates, (C6-Cg cycloalkyl)-acrylates, ethylene, ; propylene, vlnylacetate and butadlene. Pre~erably, the dispersion aid polymer (b) is one o~ the ~ollowing polymers: poly(butyl acrylate), poly(ethyl acrylate), polybutadiene, poly(ethyl acrylate/styrene), poly(butylacrylate/styrene), poly(butyl acrylate/methyl methacrylate), poly(ethylacrylate/butyl methacrylate) J
poly(butadlene/styrene) and poly(butylacrylate/
styrene/methyl methacrylate). These polymers are prepared ~rom less than 50 welght percent methacrylate 3 and/or styrene monomer. Other suitable dispersion polymers (b) include poly(vinylacetate) and poly(ethylene/vinylacetate).
The molecular welght range o~ suitable disperslon aid polymers (b) is wlde, ranging from about 15,000 to about 100,000 weight average molecular welght. The dispersion aid polymers (b) may be cros~linked and/or graft llnked, preferably to a maxlmum extent of 5 i ~ - 6 -percent by weight crosslinker or graft-linker units.
This crosslinking and/or graft-linking makes the deter-mination of the molecular weight of the final dispersion aid polymer (b) difficult.
The dispersion aid polymer (b) is generally a single stage polymer, but it may be a multiple stage polymer. When the dispersion aid polymer (b) is a multiple stage polymer, the overall monomer composition used to form the polymer and the composition of the outermost stage must conform to the composition parameters specified above, namely that these stages are formed from less than 50 weight percent methacrylate and/or styrene monomer, even if earlier stages do not so conYorm. The dispersion aid polymer (b) should not be confused with any polymer that might ; adventitiously be formed during the preparation of a multiple stage processlng aid polymer (a)~ since such an adventitious polymer would not function as a dispersion aid polymer (b) in the invention.
The dispersion aid polymer (b) is intimately blended with the processing aid polymer (a) to form the improved processing aid composition of the invention.
Any method of making a very thorough, intimate mixture of dispersion aid polymer (b) and processing aid polymer (a) is sultable, however, simple admixture o~ a polymeric processing aid powder and a dispersion aid ` polymer will typically be insu~icient unless intimate ~i thorough mixing is achieved. One metho~ of forming the ; improved processing aid compositions of the invention is to form the dlspersion aid polymer (b) by emulsion polymerizing the dispersion aid monomers in the presence of a latex of the processing aid polymer (a) also havlng been formed by emulsion polymerization.
The presently preferred method is to separately prepare emulsions of processing aid polymer (a) and dispersion ` aid (b), mix the emulsions together, and then coisolate , .

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the two polymers as by spray drying or coagulation.
Spray Drying, An Introductlon to Principles, Operational Practices, and Applications, K. Masters, CRC Press, Cleveland, Ohio (1972), describes spray drying in detail. Coagulation or salting out the stabllizing surface active agent from the emulsion by slowly adding the polymer emulsion to, for example, twice its volume o~ electrolyte solution containing any one of the ~ollowing salts and/or acids such as NaCl, ,10 KCl, CaCl2, Na2SO4, MgSO4, acetic acid, oxalic acid, HCl, HNO3, H2SO4 and H3PO4 can be used. The polymers may then be separated by filtration, washed several times with fresh water to remove excess electrolyte, and drled.
The processlng aid polymer (a) and dispersion aid polymer (b) can also be isolated from the emulsion mixture by evaporation or ~reeze drying.
When following the preferred preparation and isolation methods, it is important that the two emulsions be compatible so that they will not precipitate prior to the coisolation, or pre~erably the coagulation, step. For instance, the surfactants used to prepare the t~o emulsions should be the same or of similar type, i.e. o~ the same ionic ~pecies and of similar water solubility or hydrophilic-lipophilic balance.
The welght ratio of the processing aid polymer (a) ~ to the dispersion aid polymer (b) ranges from 99.5 to ; 0.5 to 90 to 10, and pre~erably from 99 to 1 to 95 to 3 5. Most preferably the weight ratio of the processing aid (a) to dispersion aid polymer (b) ranges ~rom about 98 to 2 to about 96 to 4.
The vinylchlorlde polymers, to be modi~ied using the improved processing aid compositions (a plus b) of the invention, include polyvinylchloride and copolymers ~ormed from at least 50 weight percent vinylchloride ~3~
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monomer and less than or equal to 50 weight percent o~
at least one other monomer such as vlnylacetate and/or ethylvinylacetate.
The weight ratio o~ the vinylchloride polymer to the lmproved processing aid composition may be the same aæ currently used with vinylchlorlde polymers and conventional processing alds. Normally this welght ratio ranges ~rom 90 to 10 to 99.5 to 0.5 vlnylchlorlde polymer to improved processing aid polymer composition, and more typically ~rom g5 to 5 to 99 to 1 by welght.
Other standard addltlves may be used to make up the vinylchloride polymer formulation. For example, impact modi~iers, colorants, pigments, plasticizers, stabilizers and lubricants may al~o be added to the formulatlon.
A~ter the PVC formulatlon is prepared, the formulation may be processed by standard methods such as blow moldlng, calendering, inJectlon molding and extruslon molding to ~orm a ~ubstantially gel ~ree acticle.
Some preferred embodiment~ o~ the lnvention are provlded in the illustrative examples that follow.
These examples are intended to illustrate the invention and should not be construed as limltlng the scope o~
the lnventlon. Comparatlve tests are also provided utllizing conventional processing aids and compounds that were lnitially thought to be potentially sultable as dispersion ald polymers tb). The3e examples clearly show that some o~ these polymers ~all the dispersabllity rating test and do not, there~ore, ~all within the scope o~ the lnvention.
This dlsper abllity ratlng test involved the preparation of a PVC masterbatch containing conventional addltives. Two parts of conventlonal processing aid (a) was added to the PVC masterbatch and mill-stretched control str~p3 were prepared. A rating o~ 100 was set as belng equal to a control strip that _ 9 _ 3~

wa~ completely unsultable because it contained many undispersed particles (gels). It was, however, also found later in the experiments that the PVC masterbatch plus 2 parts processing aid (a) could actually result ln even a less sultably dlspersed (more gels) mill-stretched strip than the inltial strlps used as the control ~or examples 1 16. Examples 17-19 compare the effect of two improved processing ald composition~ of the in~ention ~or dispersing the processing aid polymer (a) in the second PVC control formulation having a dispersability rating greater than 100.
The following presents a general procedure used to prepare the dlsperslon aid polymers (b) and the PVC
master batch. All parts and percentages are by weight unless otherwi~e indicated.
Dis~ersion Ald Polymer Dlspersion aid polymers (b) were prepared in an aqueous emulsion uslng the following lngredlents and procedure.
Charges ~ Parts A - Delonized water at PH greater than 7 u~lng a base 397.5 B - Sodium lauryl ~ulfate (SLS) or sodium stearate 0.26 Bl - Sodium lauryl 3ulfate (SLS) or sodlum stearate 1.49 C - Moncmer(s) to fonn dispe~ion aid polymer (b) 212.6 D - t-dodecyl mercaptan as chain transfer agent or varied butylene glYCol dlacrylate (B~A) as difunctlonal mDno~er E - Potassium persul~ate (KPS) in water as free 1.1 radical initiator Ihe theoretical solld~ con~ent was calculated to be 32.4%
Prodedure The delonized water (A) was charged to a one liter Pour-neck flask fitted with a stirrer, thermometer, nitrogen inlet and condenser. The water was heated to 65C water and stlrred for lO minutes. me KPS
initiator (E~ was then added followed by 15% of the .~

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monomer(s) (C) and chain transfer agent and/or BDA
difunctional monomer (D), and the temperature was maintained at 65C until an exotherm was observed.
At thls point, the second emulsifier charge (Bl) was added followed by the gradual addition of the balance of the monomer(s) C and chain transfer agent and/or BDA difunctional monomer (D) over a one hour period. After the completion of the addition of the monomer(s), and chain transfer and/or difunctional monomer, the batch was maintained at 65C for 15 minutes and then cooled to room temperature.
PVC Masterbatch A PVC masterbatch formulation without the processing aid composition of the invention was prepared from the following ingredients:
Parts PVC (K-58) Resin 100 Sulfur-c-ontaining organic tin stabilizer 2.0 Plastlcizer-dioctylphthalate (DOP) 5.0 Lubricant System:
Stearic acid 1.0 and Rohm and Haas Company Acryloid~ K-175 3.0 PVC Plus Processin~ Aid Two parts of conventional proces ing aid and 2 parts o~ the improved processing aid compositions of the invention were separately added as powders to PVC
masterbatch formulations and mixed homogeneously in a high intensity Prodex-Henschel blender to form the final PVC plus processlng aid samples.
Each final formulation was milled on a two-roll Schwabenthan mill having two chrome polished rolls.
The dimenslon of the rolls are 35 centimeters in length (30 centimeters in working length) and 15 centimeters in diameter. The two-roll mill was run at a temperature of 190C and at a speed of 26/20 rpm (front/rear rolls). Once the film was formed on the :

~ront roll and after the standard practice of obtaining a homogeneous film was concluded, ~he mill was stopped and horizontal strips measuring approximately 4 to 5 centlmeters in width were cut at the full length o~ the roll, taken ~rom the roll, and stretched immediately to twice their length U9 ing a gulde o~ the appropriate length. Each stip was held in the stretched position until cool.
Each milled and stretched strip was rated for the amount o~ undispersed processing aid particles (gels) using a rating system of 0 to 100 (except ~or examples 17-19 as explained previously), with 0 being equal to a strip having no undispersed particles (no gels) and 100 being equal to the standard control (PVC plu~
conventional processing aid (a) only) strip having many undispersed processlng aid particles (gels). In each series o~ PVC dispersion evaluations, at least one sample o~ a conventional processing aid (a) without a dispersion aid (b) was run as the control. A material, rated at lO0 or more (control ~or examples 17-19) contalns an unacceptable number o~ gels. A
dispersability rating of between 40 and 50, based on lO0 as the control, ls considered to be very gOodg whereas anything above 70, based on 100, has a commercially unacceptable number of undlspersed gels.
In examples 17-19, where the control was rated poorer than 100, a rating o~ 90 or less constituted a-considerable improvement in processing aid dlspersion.
In order to determine whether a given processing aid composition is ef~ective to substantially reduce gel colonies of processing aid (a) in polyvlnylchloride formulations a reduction of at least about 30 units ~rom a control (rated as 100) is requlred. Pre~erred dispersion aids (b) gave a reduction of at least 45 units from the control formulation rated as lO0.

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Methyl methacrylate = MMA
Butyl methacrylate = BMA
Styrene = St Methyl acrylate = MA
Ethyl acrylate = EA
Butyl acrylate . = BA
Butadiene = Bd o EXAMPLES 1-8 In these examples, reported in Table I, varlous disperslon aid polymers (b) were prepared in aqueous emulsion using 4% t-DDM (D) based on monomer(s~ (C) ~ollowing above-described proc0dure. The dispersion aid emulsion was mlxed with an emulsion of a conventional methyl methacrylate-ethyl acrylate processing aid (a) such that the weight ratio of polymer (b) to polymer (a) was 3 to 97. The mixed emulsions were then i olated by spray drying. The ratio of the improved processing aid composition (a plus b) to PVC in the masterbatch was 2 parts to 100 ; parts PVC.
TABLE I
Dispersed Dispersion Product Dispe~ion Aid Rating Acceptable/
ExamplePo~r (b) 0-100_ Not acceptable ~ 1 Control PVC plus Conventional 100 Not acceptable : ~ processing aid (a) only:
no dispersion aid (b)

2 EA 65Acceptable

3 BA 55Acceptable

4 BA/St: 55/45 40Acceptable BA/St: 70/30 60Acceptable ~ ~ 35 6 MMA 90Not acceptable : 7 St 85Not acceptable 8 MMA/EA: 90/10 75Not acceptable , ' ~' ~, : - 13 -:

. . . .

These examples illustrate that methyl methacrylate, styrene and a 90/10 copolymer of methyl methacrylate and ethyl acrylate are unacceptable disperslon aid polymers (b) for use ln the processing aid composition . of the invention, while polyethyl acrylate, butyl acrylate and butyl acrylate-styrene copolymers formed from less than 50 percent styrene, are ef~ective dispersion aid polymers (b) processing alds in PVC.

These examples explored the relationship between the composition of the dispersion ald polymer (b) and its molecular weight. A series of low and high molecular weight dispersion aid polymers (b) were prepared using 4% and 0% t-dodecyl mercaptan chain trans~er agents, respectively. The molecular weight of the low molecular weight dispersion aid polymers (b) ; ranged from 19,000 to 38,000, while the molecular weight of the hlgh molecular weight dispersion aid polymeræ (b) ranged from 137JOOO to 3,890,000. In each example, the ratio of dispersion aid polymer (b) to processlng aid polymer (a) was 3 to 97 by weight and - the processing aid compositions (a plus b) were present at 2 parts to 100 parts by weight PVC. Dispersability :. ratings were obtained in accordance with the gensral procedure as used with examples 1-80 The results are presented in Table II.

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The low molecular weight and high molecular welght polybutylacrylate and polyethylacrylate dispersion aid polymers (b) (examples 10 and 9) are effective in dispersing processing aid polymers (a) in PVC. The effectiveness of these dispersing aids diminished very slightly wlth decreaslng molecular weight but did not diminish significantly to the point that they are not effective dispersion aid polymers (b). Polymethyl methacrylate and polystyrene are not ef~ective dispersion aid polymers (b) ~or processing aids at either high or low molecular weights.

The dispersion aid polymers (b) from examples 2 and 4 were examined to determine the e~fect o~ the ratio of processing aid polymer (a) to dispersion aid polymer (b) ln the emulsion mixture on the dispersion o~ processing aid (a) in PVC.
Exa~ples 14-16 examined a butylacrylate/styrene (55:45) dispersion aid copolymer (b) in processing aid compositions where the ratio of (a) to (b) was 98.5 to 1.5 and 97 to 3, respectively. Polymethyl methacrylate, not a suitable dispersion aid (b) as indicated by example 6, was also evaluated at these levels. Examples 17-19 examined an ethylacrylate dispersion aid polymer a~d a butyl acrylate~styrene (55:45) dispersion aid copolymer (b), where the ratio o~ (a) to (b) was 97.5 to 2.5 and 95 to 5. Note, howéver, that the PVC processlng aid control used in thls test (Example 17) was much poorer than the previously prepared controls that had been given a diæpersability rating o~ 100. The results are shown in Table III.

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Example 15 to the Ba~St (55:45) dispersion aid copolymer (b) was found to be acceptable as a dispersion aid polymer ~or processing aid (a) at 1.5%
additive level as well as~at the higher 3% additlve level. The MMA sample (example 16) is not acceptable as a dispersion aid polymer (b) at 1.5% or 3% additive levels.
In examples 17-19 the EA and Ba/St dispersion aid polymers (b) were found to result in acceptably ; 10 improved dispersion in a very poorly dispersed PVC
control sample having a dispersability rating greater than 100. The control sample example 17 was much worse in gel formation than any o~ the previous control sample~, and rating o~ 90 or less exhibited a slgnificant improvement even though such absolute numbers would not have been acceptable with a PVC
control sample rated at 100. The conclusion reached ~rom examples 14-19 is that as the concentration o~
dlspersion aid polymer (b) is increased relative to processing aid polymer (a), between 1.5 and 5%, the disperslon of the processing aid was lmproved.

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Claims (9)

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

1. An improved processing aid polymer composition for vinylchloride polymers comprising a processing aid polymer (a) and a dispersion aid polymer (b) where the weight ratio of (a) to (b) ranges from 99.5 to 0.5 to 90 to 10, and where said dispersion aid polymers are homopolymers or copolymers formed from at least 50 percent by weight of at least one of the monomers selected from the group consisting of (C1-Ca alkyl)-acrylates, (C6-C9 cycloalkyl)-acrylates, ethylene, propylene, vinyl acetate and butadiene, the remainder of the monomers being methacrylate and/or styrene monomers.

2. The improved processing aid polymer composition of claim 1 where the weight ratio of processing aid polymer (a) to dispersion aid polymer (b) ranges from 98 to 2 to about 96 to 4.

3. The improved processing aid polymer composition of claim 1 wherein said dispersion aid polymer (b) comprises at least one of the polymers selected from the group consisting of polybutyl acrylate, polyethyl acrylate, polybutadiene, and copolymers of ethyl acrylate and styrene, butyl acrylate and styrene, butadiene and styrene, butyl acrylate and methyl methacrylate, ethyl acrylate and butyl methacrylate, and butyl acrylate, styrene and methyl methacrylate, where the polymer is formed from less than 50 percent by weight methacrylate or styrene monomers.

4. A vinyl chloride polymer composition comprising from about 0.5 to 5 parts by weight of the improved processing aid polymer composition of claim 1 and from about 99.5 to 95 parts by weight vinyl chloride polymer.

5. The vinyl chloride polymer composition of claim 4 comprising from about 2 to 3 parts by weight of the improved processing aid polymer composition and from about 98 to 97 parts by weight vinylchloride polymer.

6. An improved processing aid polymer composition for vinylchloride polymers comprising a processing aid polymer (a) formed from at least 50 weight percent methyl methacrylate and from 0 to 50 weight percent of a (C1-C4) alkyl acrylate, and a dispersion aid polymer (b) selected from the group consisting of polybutyl acrylate, polyethyl acrylate, polybutadiene, and copolymers of ethyl acrylate and styrene, butyl acrylate and styrene, butadiene and styrene, butyl acrylate and methyl methacrylate, ethyl acrylate and butyl methacrylate, and butyl acrylate, styrene and methyl methacrylate, wherein the styrene and or methacrylate is less than 50% of the dispersion aid polymer (b) and wherein the ratio of (a) to (b) ranges from 98 to 2 to about 96 to 4.

7. A process for dispersing a processing aid polymer in a vinyl chloride polymer comprising intimately blending from about 99.5 to about 90 parts by weight of said processing aid polymer with from about 0.5 to about 10 parts by weight of a dispersion aid polymer (b) selected from the group consisting of polybutyl acrylate, polyethyl acrylate, polybutadiene, and copolymers of ethylacrylate and styrene, butylacrylate and styrene, butadiene and styrene, butyl acrylate and methyl methacrylate, ethyl acrylate and butyl methacrylate, and butylacrylate, styrene and methyl methacrylate where the polymer is formed from less than 50 percent by weight methacrylate or styrene monomers.

8. The process of claim 7 further comprising preparing said processing aid polymer (a) and said dispersion aid polymer (b) separately by standard aqueous emulsion polymerization techniques, mixing the emulsions, coisolating the polymers, and intimately blending said coisolated polymers with the vinyl chloride polymer.

9. The improved processing aid polymer composition of claim 6 where said dispersion aid polymer (b) is selected from the group consisting of polyethyl acrylate, polybutyl acrylate, and copolymers of butyl acrylate and styrene formed from less than 50 weight percent styrene monomer.