Polymeric compositions
v I United States Patent 1191 1111 3,875,260 Patel et al. 1 Apr. 1, 1975 [5 POLYMERIC COMPOSITIONS 1495090 1/1969 Germany 260/880 R 1002.902 9/1965 United Kingdom 260/880 R [75] &#39;l l Goverdhfinbha&#39; Faieh 6.513.552 4/1967 Netherlands 260/880 R Dunkmfield; Thomas Orr Craig, Mottram, both of England OTHER PUBLICATIONS [73] Assignee; Sterling Moulding Materialsq Encyclopedia of Polymer Science and Technology,  
  Stabs/bridge, Cheshire England Vol. 12, p. 288. lnterscience, New York (1970). 22 Filed: Dec. 7, 1971 ASTM D 7 [21] Appl. No.: 205,695 Primary E.\an1inerJoseph L. Schofer Assistant E.\&#39;aminerA. Holler [30] Foreign Application Priority Data Attorney, Agent. or FirmWenderoth. Lind &amp; Ponack D 17,1970 0 &#39;tB&#39;tz&#39; 60078 70 cc rea r1 nn [57] I ABSTRACT [52] US. Cl. 260/878 R, 260/880 R A polymer composition, eg a high-impact polysty- [51] Int. Cl. C08f 15/00 rene, having novel morphological structure comprises [58] Field of Search 260/878 R, 880 R a polymeric matrix. e.g. polystyrene. in which there are dispersed particles of a second polymer. e.g. an [56] References Cited ethylene-propylene terpolymer. The particles of sec- U IT ST S P S 0nd polymer contain occlusions of matrix polymer and 3 488 743 1 1970 Bacr et al 260/878 R the occlusions also contain sub&#39;occ&#39;usions of third 3:538:190 11/1970 Meredith Ct al. 260/878 R Polymeric 1 98- Polybumdienfl which is more 3538.192 11/1970 Bishop, Sr 260/878 R Specific IO grafting with the monomeric constituents of 3.694.522 9/1972 Tsuruta et 211.... 260/878 R the matrix polymer than is the second polymer spe- 3,696.172 10/1972 Kaiho ct al 260/880 R cies. The compositions are tough and have good oxi- FOREIGN PATENTS oR APPLICATIONS 6,714,754 5/1968 Netherlands 260/880 R 7 Claims, 7 Drawing Figures Poi rsTrR/v- ISTYRENE CONTINUOUS PHASE I [PT STYRENE DROPLET.  
 POL YSTYRE/VE STYREN&#39; OCCLUS/ON.  
 &#39; POL YBUTADIENE -sTrRE/v suaoccws orvs,  
 PATENTEDA R H975 3,875,260  
 sum 1 OF 3 FIG. 75  
 POL YBUTA D/ENE STYRENE G EPT-STYRENE CONTINUOUS PHASE PATENTEU 3,875,280  
  SHEET 2 BF 3 Fla. 2  
  [PT-STYRE/M POL YBUTADIENE CONTINUOUS -STYRNE PHASE DROP/.57  
 POL YSTYRENE- S TYRE NE DROPLE T COMPOSITE DROPLT 0F POLYBUTADIENE- STYRENE ENVELOPED WITH/N POLYSTYRENE- ST YRENE F103 EPT STYRE/VE CONTINUOUS PHASE PATENTEU 1 1575 3, 875,260  
 SHEET 3 [If 3 P01 ISTYRE/VE- STYRENE CONTINUOUS PHASE I EPT-STYRENE DROPLEZ&#39; POL YSTYRE/VE STYRENE OCCLUS/ON.  
 POL YBUTAD/ENE STYRENE SUB OCCLUSIONS.  
 1000K PHOTOGRAPH 0F SYSTEM AFTER PHASE INVERSION.  
  POLYMERIC COMPOSITIONS This invention relates to composite polymeric materials of novel morphological structure, and to a process for producing them.  
 paring such a polymer composition, which process comprises:  
  providing a solution of a first polymer P,- in a monomeric solvent which is polymerisable to polymer his well known that the incorporation of natural or 5 P,,,, said solution containing a dispersed phase of P synthetic rubbers in glassy polymers such as polystyin the solvent, said disperse phase containing ocrene or styrene copolymers improves the toughness of clusions of a modified polymer P the latter 0] mers. It is also well known that b dissolving a atd ral or synthetic rubber such as pol yisoand g g p-olym-ensafilon of the Solvent to Sald polyp&#39;rene, polybutadiene, rubbery copolymers of butadi- E r e vlscislty&#39;o the PS Solvent phase bemg d t f th 1 d l t 1g ert an thato the P -solvent phase at the moment erisearrinoslgrrlfgrtzazrdothin ypegijrigrisprrgpy znzg f iphase lnversion takes place and the P,,,-solvent phase ecomes continuous.  
 graft copolymers can be produced, and that the resulting toughened polymer has a two phase structum I According to one embodiment of the process of the When the polymerisation is conducted in a suitably agia 9 i g syitem g gg l g by tated reactor, the rubber is dispersed in the polystyrene V1 a f e 1 ymer; R t mono matrix as particles sized from about 1,u. to a. The menc so vent e v0 O t e vent phase phase Changes which Occur during Such polymerisa should be less than that of the P -solvent phase. Prefertions are well reported. Furthermore, an explanation E3 corcentranon of polymer Pg 15 less than that has been provided for the formation of occlusions of 0 p0 ymer I polystyrene which can be seen within the elastomer The P y System y also be formed by mlxmg particles in a finished high-impact polystyrene compotogether a Solutlon of P y m the monomer? i i solvent containing a dispersed phase of modified poly- For the preparation of such a composition, for exammer Pa elther I pie high impact polystyrene ps it is usual to a. a solution of the polymer P, in the monomeric solsolve an unsaturated rubber in the polymerisable, monvent I omeric solvent, and to polymerise the solvent by an agia f l of Polymer P m the monomenc 9 tation polymerisation technique. The elastomers emcomammg a dlsperse phase of Polymer m the ployed generally have sufficient unsaturation to ensure I U f I that grafting of the elastomer by the polymerising solways p055 exdrgp prepaae vent occurs, since it is known that such grafting ena Impact p0 ystyrene w 16 com mest. e toug h&#39;ances toughness by providing adhesion between the F lmparied by unsaturated elastomer Wlth the OX- dispersed elastomer phase and the continuous polysty ldanon reslstance lmparted y a saiurated l rene matrix However the use of unsaturated elasto Furthermore, the HIPS of this invention exhibits better mers renders the HIPS susceptible to oxidative embrittiaughness than a HIPS ldentlcalphemlcal flemem under Certain conditions tion made by mechanically blending two species of fwh&#39; b mad b ase a- Previous attempts in the art to overcome this disad- HIPS i P i e d vantage by using saturated elastomers such as ethylene rate ymensdtlon 0 g unon t g fi g me o w ic e propylene rubbers, whilst being successful In provid- 40 $22 gi i gg g gi of the 1 ing oxidation resistant types of HIPS have resulted in rated elasgmyer in monomer mammals havng i t9uglhness when Fompared Thus according to a feature of this invention there is T e equwa em amount 0 an unsat provided a polymeric composition comprising a matrix ura e e as omer.  
 We have found that it is possible to produce a class glass 85 3222 32 yg gig fi :832:32?  
  at f unsaturate monomer, sai matrix avmg isperse mer matrix are occluded and SUb-OCCUldd Wlth matrix therethrough particles of a Saturated elastomer, said Polymer and Pther dIffeFPnt elast?n ler Parncles- These saturated elastomer particles containing occlusions of new l b cpmposfltlons exlnblt useful and unex&#39; the matrix material, said occlusions being sub-occluded pecte Com &#34;muons O Propemeswith particles of a modified unsaturated elastomen In accordance i this inYefltlon {her}? is Provided a It should be understood that the terms saturated P y composltlon comprlslng a mamx Ofa P y and unsaturated used herein to describe the elastom having dispersed therein Particles of a yf s mers refer to the relative susceptibilities of the elastosaid dispersed particles containing occlusions 0 matrix mers to undergo fti b h l i i monomaterial, said occlusions containing sub-occlusions of meric Solvent 8 modified p y g wherein h p ym g more The novel attributes of HIPS prepared in accordance susceptible to grafting with the monomer c constituents with this invention are qualitatively compared with the of polymer P,, than is polymer P properties of related materials known in the art in the The present invention also provides a process for prefollowing Table.  
  HlPS (A) HIPS (B) Novel structure containing containing Mechanical containing the Property saturated unsaturated blend of saturated and unelastomer elastomer (A) &amp; (B) saturated elastomers Toughness Poor Good Poor Good Oxidation resistance Good Poor Fair Good Although a large number of polymers can have the novel morphological structure, the invention is particularly applicable to polymer systems in which the matrix is a polymer of a monovinyl or monovinylidenic hydrocarbon and the invention will be explained in greater detail with reference to a polystyrene polybutadiene EPT (Ethylene-Propylene Terpolymer) system in which P,, is polystyrene, P,, is polybutadiene and P is EPT. The ethylene-propylene terpolymer will be regarded as being saturated in comparison with the butadiene, since the unsaturated third monomer is present in it to only a minor extent. Thus, EPT contains less than 3 carbon-carbon double bonds per thousand car- 7 bon atoms whereas polybutadiene contains 250 carbon-carbon double bonds per thousand carbon atoms.  
  As applied to the preparation of HIPS, the process of this invention thus involves providing a mixture in which a continuous phase of EPT dissolved in styrene contains a disperse phase of polystyrene in styrene; wherein the disperse phase itself contains a further disperse phase of polybutadiene-styrene, which further disperse phase may optionally contain occlusions of polystyrene in styrene. There are various ways of reaching this system, of which three may be mentioned as follows:  
  A. The EPT and polybutadiene are dissolved in monomeric styrene and the system subjected to polymerisation conditions. This is the preferred procedure, and is described in more detail below.  
  B. Instead of dissolving polybutadiene in monomeric styrene (as in A), the polybutadiene may be provided in the form of inclusions in a polystyrene matrix by using a conventional HIPS. This HIPS is added, in proportion to provide the required amount of polybutadiene, to a solution of EPT in styrene, which is then polymerised as before.  
  C. Instead of adding the conventional HIPS to a solution of EPT in monomeric styrene (as in B), the conventional HIPS may be added to an EPT styrene that is in the process of polymerisation. The important requirement is that the polystyrene in the EFT-styrene system should be in the disperse phase at the time of addition of conventional HIPS.  
  The EPT polymers may be prepared in solution using heterogeneous catalysts. Ethylene and propylene are the main constituents in a ratio of about 60 to 40 parts. Small amounts of di-functional monomers are frequently copolymerised such as di-cyclopentadiene or -ethylidene-2-norbornene. The Mooney viscosity of EPT may range from 200. The EPT elastomers are known to possess better ageing properties than the commonly used elastomers in toughened polystyrene or A.B.S.  
  The polybutadiene rubbers are synthesised using a wide variety of catalysts, such as Ziegier or butyl lithium. The structure is predominantly 1,4 addition but the cis content may differ widely according to the catalysts; from percent to 95 percent, the remainder being trans, with small amounts of the vinyl structure. :I&#39;ge Mooney viscosity varies normally between 25 and The optimum concentration of the EFT polymer is 5-7 percent and of the polybutadiene is 0.5-2 percent. The total content of EPT and polybutadiene preferably should not be less than 4.5 percent by weight of the total solution.  
 The monovinyl or monovinylidene monocyclic aromatic hydrocarbon is preferably styrene but other hydrocarbons such as vinyl toluene and alphamethyl styrene may be used in .admixture with each other or with styrene. Examples of monomers which may be copolymerised with such hydrocarbons are acrylonitriles, vinyl esters of aliphatic monocarboxylic acids and aliphatic or alicyclic esters of monoethylenically unsaturated acids.  
  Polymerisation of the solution of the rubbers in the monomer or mixture of monomers is preferably initiated by decomposition of one or more free radical precursors chosen in accordance with the temperature at which it is desired to conduct the polymerisation. Such radical precursors as benzoyl peroxide, lauroyl peroxide, tertiary butyl peracetate, di-tertiary butyl peroxide and dicumyl peroxide may be used. A normal concentration range of one of these would be 0.005 0.5 percent. The polymerisation may also be initated by the action of heat alone.  
  The reaction mixture may also contain various chain transfer agents such as tert-dodecyl mercaptan, tertbutylmercaptan or the unsaturated dimer of alpha methyl styrene.  
  Lubricants such as stearic acid or white mineral oils; .may be incorporated as is well known in the art. Minor amounts of inert diluents such as ethylbenzene, toluene and diethylbenzene may also be incorporated into the reaction mixture.  
 The reaction is normally carried out using an agitated mass polymerisation process, at least until 20 percent of the monomer or monomers has polymerised, the reaction temperature during the first step belng from C to C. The second step may also be carried out polybutadiene feedstock showing the continuous phase of EFT-styrene and the disperse phase which is droplets of polybutadiene-styrene;  
  FIG. 1B is an explanatory diagram of the feedstock shown in FIG. 1A;  
  FIGS. 2 and 3 are respectively, an explanatory diagram and photgraph (IOOOX) showing the morphology of the polymerisation system at about 5% conversion;  
  FIG. 4 is a diagram schematically representing the formation of a polybutadiene-styrene occlusion within a polystyrene-styrene droplet;  
  &#39;FIGS. 5 and 6 are respectively an explanatory diagram and a photograph (IOOOX) showing the morphology of the system after phase inversion.  
  The changes which occur during polymerisation and phase inversion may be explained as follows.  
  The dissolution of 6 percent EPT and 1 percent polybutadiene together in styrene monomer yields a twophase system (the EFT-polybutadiene content exceeds 4.5 percent of the total solution); when suitably agitated, the system consists of a discrete phase of ous phase of EFT-styrene solution as shown in FIGS.  
 1A and 1B. Polymerisation of such a system leads to the formation of polystyrene, which in an agitated reactor separates as a second discrete phase of polystyrenestyrene solution. The morphology of the system of 5 percentconversion is shown in FIG. 2 and FIG. 3. An unusual feature of the system at this stage of conversion is that some of the polystyrene-styrene droplets contain smaller droplets of what appear from their refractive index to be polybutadiene-styrene solution. This phenomenon is shown diagrammatically in FIG. 3.- The OC- currence of such morphology can be rationalised as fol-- lows.  
  During polymerisation of the styrene monomer, growing polystyryl radicals undergo chain transfer with polybutadiene and hence grafting of polystyrene to polybutadiene takes place. The EPT, on the other hand, presents a structure which is less susceptible to grafting. All polybutadiene-styrene droplets will consequently, after a time, contain some amount of a second polymeric species, namely poly(styrene-g-butadiene). This species, like the non-grafted polybutadiene, will also be incompatible with the continuous EPT-styrene phase.  
  Consider a polybutadiene-styrene droplet, marked A in FIG. 4, which will contain poly(styrene-gbutadiene). The interface between such a droplet and&#39; the EPT-styrene continuous phase in which it is sus-. pended is characterised by an interfacial tension, T if the polybutadiene-styrene droplet were relocated within a polystyrene-styrene droplet the resultant interfacial tension at its surface, T would be lower than T since the grafted species present in the polybutadiene-styrene droplet would now have their polystyrene segments arrayed in a compatible environment. We have observed that collision of a polystyrenestyrene droplet with a polybutadiene-styrene droplet leads to the latter being enveloped by the former, thereby generating the arrangement of phases shown in FIG. 2 and FIG. 3. This phenomenon, encountered in v a real polymerisation, can be observed also in agitated simulations of partially polymerised system at e.g. 5 percent conversion. These systems are generated by mixing polystyrene, polybutadiene, EPT and styrene monomer in the requisite proportions until all the polymers dissolve. Small amounts of styrene-butadiene volume of polystyrene-styrene phase/volume of EPT-styrene phase l to be exceeded, the following events are observed.&#39; Areas of the EPT-styrene solution begin to undergo dispersion to form the discrete phase, but due to the viscosity of the EPT-styrene solution, some polystyrenestyrene droplets are trapped within it and are thus prevented from becoming part of the incipient continuous phase. However, some polystyrene-styrene droplets contain polybutadiene-styrene within them as described above. As a result of this state, established prior to phase inversion, the composite&#39;fluid system now has the morphology shown in FIG. 5 and FIG. 6.  
  The invention will be illustrated by the following Examples.  
 EXAMPLE 1 Procedure (a) 1,288 grams of styrene monomer, together with 84 grams of EPT elastomer [a terpolymer of ethylene and propylene with 3-4 percent ethylidene norbornene having a Mooney viscosity (ML 1+4 at C) of 60-65] and 14 grams of the polybutadiene [Mooney viscosity (ML 1+4 at 100C) of 45] shown in the Table were charged to a 2-litre flask fitted with a reflux condenser, thermometer, nitrogen inlet and an anchor type impeller. The contents of the flask were agitated at 120 rpm until no dissolved material remained. A catalyst combination consisting of 0.7 grams tertiary-butyl peracetate, 0.28 grams di-tertiary-butyl peroxide and 0.07 grams dicumyl peroxide dissolved in 14 grams mineral oil was added. The mixture was heated at 92C for 3 hours, 95C for 6 hours, C for 6 hours and 180C for 6 hours. Agitation at rpm was maintained until microscopy of samples withdrawn from the mixture indicated that the polystyrene-styrene solution had become the continuous phase whereupon 0.14 of n-lauryl mercaptan was added and the mixture transferred into glass screw-cap bottles, 5 inches tall and 1 /2 inches diameter; polymerisation was then completed according to the above temperature cycle in an oil-bath. The polymer billets were granulated and injection moulded. The resulting composite polymeric structure had a high impact strength as measured by the lzod test, and when examined under an electron microscope at 2,000 showed the novel morphology.  
 By way of comparison, a polymeric composite mate- .rial was prepared in such a manner as to have the same chemical composition as the material prepared by Procedure (a) but lacking the novel morphology. This latter polymeric material was prepared as follows: Procedure (b) A solution of 7 percent by weight of the same EPT elastomer as used in Procedure (a) was prepared in styrene monomer, and then polymerised using the same catalyst system, agitation regime and temperature cycle as given under Procedure (a).  
 A solution of 7 percent by weight of the same polybu- P-71, P-70, P-73 and P-83 were made by Procedure (a) y and all have the novel structure described above; they are pairs of replicate runs made to indicate repeatability. Run P-80 contains 7 percent EPT rubber only, while run P-82 contains &#39;7 percent polybutadiene. A physical blend of these polymers was made to provide a comparison between polymers having the same chemical composition, but not both having the novel phase structure described above. Thus, Table 1 shows the properties of a 6/1 blend of P-80 with P-82 which may be compared with the properties of P-73 and/or P-83. The improved impact strength of the polymer containing the novel structure is evident, in comparison Table 3 Property Retention upon Oven Ageing with the impact strength of the polymer having the Po] mer from Com 1 same chemical composition butlacking the novel mor- Erlum le 2 Poly iii e r phology. Furthermore, Table 1 indicates that the polyr mer containing 6 percent of the oxidation resistant, sat- 5225 30 18 urated elastomer, present as part of the novel structure 92 Elongation has an impact strength as good as that of the polymers i P 3] 8 containing the less oxidation resistant polybutadiene.  
 Table 1 Polymer No. P-7l P-70 P-73 P-83 P-80 P-82 6 l Blend of a P 80/P-82 7r EPT 6 6 6 6 7 6 7r polybutadiene 1 1 l 1 7 1 Type of Polyhutadicnc 55 55 45 45 45 45 Elongation l0 l8 l6 l9 6 10 Yield Stren th PSI 5600 5090 5280 5250 5900 6000 Ult. Strcngt PS1 5240 4540 4640 4800 5150 .5150 Izod Impact Strength ft. lbs/in. notch 1.6 1.8 1.5 2.0 0.7 1.8 1.1  
 EXAMPLE 2 EXAMPLE 3 The apparatus described in Example 1 was charged with the following: 1,288 grams of styrene monomer, 14 grams of the polybutadiene of Example 1, and 84 grams of an EPT rubber designated lntolan 140A. Agitation was maintained till no rubber remained undissolved. As internal lubricants, 21 grams of Shell Risella oil and 1.4 grams of zinc stearate were added, followed by a catalyst which consisted of 1.19 grams of di-tertbutyl peroxide. The mixture was heated with agitation at 120 rpm for 4.5 hours at 96C. When polystyrenestyrene had become the continuous phase (as shown by microscopy of samples), 1.4 grams of 1,2-dimethyl-l,2-  
 diethyl-1,Z-diphenylethane and 0.14 grams of lauryl mercaptan were added. At the end of the 4.5 hour period, the mass was transferred into 4-ounce&#39;bottles and heated as follows: 6 hours at 1 10C, 6 hours at 120C, 6 hours at 130C, 6 hours at 180C and 0.25 hours at 280C. The product was cooled, granulated and injection moulded. The properties are shown in Table 2. To demonstrate the superior retention of toughness of the material upon ageing, a commercially available impact polystyrene made using approximately 7 percent by weight of polybutadiene was taken, moulded, and the test pieces exposed in an air oven at 70C for 14 days together with those from the material made in Example 2. A comparison between the polymers of this invention and the commercial polybutadiene modified HIPS are set forth in Table 3.  
  The apparatus described in Example 1 was charged with 1288 grams of styrene, 14.0 grams of the polybutadiene of Example 1, 14 grams of Shell Risella oil, and 84 grams of EPT rubber, Nordel 1040 (a product of Du Pont). Nordel 1040 is a rubbery terpolymer of approximately equimolar amounts of ethylene and propylene, together with 3-4 wt percent of hexa-1,4-diene; it has a Mooney viscosity (ML 1+4) at 121C of 40. The vessel contents were agitated till no more rubber remained undissolved. The temperature was raised to C and 1.26 grams of di-tert.-butyl peroxide added. Agitation was maintained at 120 rpm. The temperature cycle followed was: 4.25 hours at 95C, 6 hours at C, 6 hours at C, 6 hours at C, 5.25 hours at C and 0.25 hours at 280C. When the polystyrene-styrene phase had become continuous, 1.4 grams of 1,2- dimethyl-1,2-diethyl-1,Z-diphenylethane and 0.14 grams lauryl mercaptan were added. At the end of the initial 4.25 hour period the polymerising mass was poured into 4 ounce bottles for the remainder of the polymerisation cycle. The final product was granulated and injection moulded and had the properties: Izod impact strength 1.3 ft. lbs/in. notch, 3,960 psi tensile yield strength, 3,920 psi tensile strength at break, elongation at break 33 percent.  
 EXAMPLE 4 I The procedure of Example 3 was used to polymerise a system prepared by dissolving 14 grams of polybutadiene (lntene 45) and 84 grams of Esso Vistalon 6505 rubber 1288 grams of styrene. Vistalon 6505 is a rubbery terpolymer of ethylene and propylene in approximately equimolar proportions together with 9-12 percent of ethylidene norbornene. It has a Mooney viscosity (ML 1+8 at 127C) of 50. The resulting polymer had the following properties: Izod impact strength (ft. lbs/in. notch) 1.5 tensile yield strength (psi) 3600, ultimate tensile strength (psi) 4240, elongation at break (percent) 26.  
  Although&#39;the Examples here presented have been confined to the polystyrene-polybutadiene-EPT- styrene system, the number of such systems which may be generated is large, since the conditions necessary fortheir creation are:  
 a. monomer or monomers (M M M in which all polymeric species (both inid. that the volume of the P,,-monomer(s) phase be less than the volume of the P -monomefls) phase. Under these conditions it may be found that small amounts of the polymer P are present in the P monomer(s) phase, or vice versa. and  
 e. that the viscosity of the P -monomefls) solution at phase inversion be higher than the viscosity of the solution of polymer or interpolyiners formed from monomer(s) M,, M .M in those monomer(s).  
  Clearly these requirements can be met by a large number of combinations of materials.  
 We claim:  
  1. A process for the production of a polymer composition comprising a matrix of polystyrene having disposed therein particles of an ethylene-propylene terpolymer (EPT) having a Mooney Viscosity of from 20 to 200, said dispersed particles containing occlusions of matrix material, said occlusions containing subocclusions of a modified polybutadiene having a Mooney Viscosity (ML-l 4 at 100C) of from 25 to 70, which process comprises providing a solution of EPT having a Mooney Viscosity of from 20 to 200 and polybutadi ene having a Mooney Viscosity (ML 1 4 at lC) of from 25 to 70 in monomeric styrene, the concentrations of EPT and polybutadiene being from Sto 7 percent and from 0.5 to 2 percent by weight, respectively, based on the weight of the total composition and the volume of the polybutadiene-styrene phase being less than that of the EPT-styrene phase and effecting polymerization by an agitated mass polymerization techcosity of from to 200 in a styrene monomer&#39;soivent which is polymerizable to polystyrene, said solution containing a disperse phase of polystyrene in the sol-&#39; propylene terpolymer and modified polybutadiene in g the monomeric styrene solvent, the volume of the modmer to polystyrene.  
 nique until at least 20 percent of the styrene has poly- =ethylene propylene terpolymer having a &#34;Mooney Viscosity of from 20 to 200, said dispersed particles containing occlusions of polystyrene, said occlusions containing sub-occlusions of a modifiedv polybutadiene having a Mooney Viscosity (ML 1 4 at l00C)&#39;of from 25 to a&#39;nd, said modified polybutadienebeing moresu sceptible to grafting&#39;with a styrene monomer than is the ethylene-propylene terpolymer.  
  3. A process for the production of a polymer compo- I I sition comprising a matrix of polystyrene having dispersed therein particles of an ethylene-propylene ter,  
 polymer having a Mooney Viscosity of from 20 to 200, said dispersed particles containing occlusions of polystyrene. said occlusions containing sub-occlusions of a modified polybutadiene having a Mooney Viscosity (ML 1 4 at C) of from 25 to 70 and, said modifiedpolybutadiene being more susceptible to grafting ethylene-propylene terp&#39;olymerihavingva Mooney Vis vent, said disperse phase containing occlusions of a modified polybutadiene polymer having a Mooney Viscosity (ML 1 4 at l00C) of from 25 to 70. and effecting the polymerization of the monomeric styrene solvent to polystyrene.  
  4. A process according to claim 3 wherein the solu tion is formed by providing a solution of the ethyleneified polybutadiene solvent phase being less than that of the ethylene-propyiene terpolymer-solvent phase, and effecting the polymerization of the styrene monotion is formed by mixing-together I l. a polystyrene polymericontaining inclusions of the said modified polybu&#39;tadiene. and r 2. a solution of the saida-ethylene-propylene terpolymer in the monomericistyrene solvent containing a disperse phase of polystyrene in the styrene solvent. 7. A process according to claim 3 wherein the ethylene propylene terpolymer-is present in an amount of from 5 to 7 percentby-fwjeight, based upon the weight 1 of the total compositionand theimodified polybutadiene is present in an amount of from 0.5 to 2 percent .by  
 weight of the total composition.  
 I an t I claim 3 wherein the solu