POLYCARBONATE/AROMATIC POLYESTER BLENDS CONTAINING AN OLEFINIC MODIFIER

Abstract: A polycarbonate blend of good impact and flexural strength, good heat distortion and weldline properties, and good solvent resitance prepared by admixing with polycarbonate an aromatic polyester, an olefinic epoxide-containing modifier (such as ethylene/vinyl acetate/glycidyl methacrylate terpolymer), and, optionally, a thermoplastic elastomer (such as a styrene/butadiene/styrene block copolymer), a rubber-modified styrene/acrylonitrile copolymer, and/or less than 5 wt percent of a graft polymer of the core-shell type (such as methacrylate/butadiene/styrene copolymer).

Description: POLYCARBONATE/AROMATIC POLYESTER BLENDS CONTAINING AN OLEFINIC MODIFIER This invention relates to compositions containing polycarbonate blended with other polymers, " and relates particularly to polycarbonate compositions having both improved solvent resistance and improved impact and flexural strength- Polycarbonate has found many uses because, in general, it combines a high level of heat resistance and dimensional stability with good insulating and non- corrosive properties, and it is easily molded. It does, however, suffer from a tendency to craze and crack under the effects of environmental stress, especially contact with organic solvents such as gasoline. Polycarbonate which has crazed is, undesirably, more likely to experience brittle rather than ductile failure. This disadvantage has been somewhat relieved by the practice of blending polycarbonate with substances such as various olefin polymers. These added substances are capable of improving the resistance of polycarbonate to solvents, but they tend to delaminate and cause an offsetting reduction in the toughness, impact resistance and weldline strength of the blended high gloss polycarbonate composition. It would accordingly be desirable if substances admixed with polycarbonate for the purpose of improving its environmental stress failure resistance, for example resistance to organic solvents, did not also deleteriously affect its toughness and impact and weldline strength, and cause delamination as evidenced by peeling or splintering. In Chung, U.S. Pat. No. 4,554,315, a system to promote the level of mechanical properties of polycarbonate is described wherein polycarbonate is 10 blended with a polyester, an epoxide-containing modifier (preferably containing styrene and methyl methacrylate), and 5-30 percent of a core-shell, impact modifiying graft polymer. However, no recognition exists therein - - of the possibility of strengthening polycarbonate while maintaining a useful level of solvent resistance by employing a graft polymer in the system at levels below 5 percent , or by employing none at all, or by employing in place of the graft polymer a thermoplastic elastomer 20 or a rubber-modified sytrene/acrylonitrile copolymer. This invention involves a composition of matter containing, in admixture, (a) an aromatic carbonate polymer, (b_) an aromatic polyester, and (c_) an epoxide- 25 containing modifier having a glass transition temperature ("T g ") less than 0°C, and, optionally, one or more of the following: (d)(_i) a thermoplastic elastomer, (d)(ϋ) a rubber-modified sytrene/acrylonitrile copolymer containing less than 40 30 percent rubber, (d) (iii) less than 5 percent (by weight of the total composition) of a core-shell graft polymer containing more than 40 percent rubber. This invention also involves a method of molding polycarbonate whereby polycarbonate which has been admixed with at least an aromatic polyester and an epoxide-containing modifier having a T g less than 0°C is molded. Further, this invention involves a method of strengthening, or reducing the notch sensitivity to imnpact loading of, a polycarbonate by blending it with at least an aromatic polyester and an epoxide-containing modifier having a T g less than 0°C. Blending a polycarbonate/polyester composition with at least an epoxide-containing modifier having a g less than 0°C is also a method of providing an improved polycarbonate/polyester composition. It has been found that a composition prepared by blending or admixing polycarbonate with at least an aromatic polyester and an epoxide-containing modifier having a T g less than 0°C possesses not only desirable levels of solvent resistance, but possesses as well physical strength which is superior to that of a composition of said three components which also contains a core-shell graft polymer containing more than 40 percent rubber at a level of 5 percent or more (by weight of the total composition). The compositions of this invention are useful, for example, in the production of films, fibers, extruded sheets, multi-layer laminates and molded or shaped articles of virtually all varieties, especially appliance and instrument housings, automobile body panels and other components for use in the automotive and electronics industries. The methods of this invention are useful for preparing compositions and molded articles having applications which are the same as or similar to the foregoing. The compositions of this invention are those in which (a) polycarbonate has been admixed in a blended composition with (b) an aromatic polyester, and (c_) an epoxide-containing modifier having a glass transition temperature ("Tg") less than 0°C, and, optionally, one or more of the following: (d)(i.) a thermoplastic elastomer, (d.)(i L ) a rubber-modified sytrene/acrylonitrile copolymer containing less than 40 percent rubber by weight, (d)(iii) less than 5 percent (by weight of the total composition) of a core-shell graft polymer containing more than 40 percent rubber by weight. Suitable ranges of content for components (a), (b) and (c) in the compositions of this invention, expressed in parts by weight, are as follows: (a) polycarbonate from 5 parts to 95 parts, and preferably from 10 parts to 85 parts, (b) aromatic polyester from 5 parts to 95 parts, and preferably from 10 parts to 70 parts, and (c) epoxide-containing modifier from 0.1 - part to 20 parts, and preferably from 1 parts to 15 parts. When one or more of optional components (d)(i), (d)(ii), (d)(iii) are utilized in the compositions of this invention, they may be present, respectively, in the following amounts, expressd as a percent of the total weight of all components present in the composition, (d)(i) thermoplastic elastomer up to twenty- five percent (25 percent ), and preferably up to fifteen percent (15 percent ) , (d)(ii) rubber-modified styrene/acrylonitrile copolymer, up to twenty-five percent (25 percent ), and preferably up to fifteen percent (15 percent ), and (d)(iii) core-shell graft polymer, less than five percent (5 percent ), and preferably up to four percent (4 percent ) . Compositions prepared within the above ranges of content possess not only desirable levels of environmental stress failure resistance, but possess as well impact and flexural strength and heat distortion properties which are superior to those of compositions which contain a core-shell graft polymer at a level of 5 wt percent or more. Preparation of the compositions of this invention can be accomplished by any suitable mixing means known in the art. Typically the substances to be admixed with polycarbonate are dry blended in particulate form with sufficient agitation to obtain thorough distribution thereof within the polycarbonate. If desired, the dry-blended formulation can further, but need not, be melt mixed in an extruder. Mixing rolls, a dough-mixer or a Banbury mixer can also be used in the blending. Alternatively, a master batch formulation can be prepared containing polycarbonate or polyester and the substances to be admixed or blended with it, wherein the polycarbonate (or polyester) is present in only a minor proportion, e.g. 20 percent . The master batch is then available for storage or shipment in commerce, and can be diluted with additional polycarbonate (or polyester) at the time of use. The compositions of this invention can be formed or molded using conventional techniques such as compression, injection, calendering, vacuum forming, extrusion and/or blow molding techniques, alone or in combination. The compositions can also be formed into films, fibers, multi-layer laminates or extruded sheets on any machine suitable for such purpose. (a) Polycarbonate. The aromatic polycarbonates suitable for use in the present invention are produced by any of the conventional processes known in the art for the manufacture of polycarbonates. Generally, aromatic polycarbonates are prepared by reacting an aromatic dihydric phenol with a carbonate precursor, such as phosgene, a haloformate or a carbonate ester. A preferred method for preparing suitable polycarbonates involves the use of a carbonyl halide, such as phosgene, as the carbonate precursor. This method involves passing phosgene gas into a reaction mixture containing an activated dihydric phenol, or a nonactivated dihydric phenol and an acid acceptor, such as pyridi e, dimethyl aniline, quinoline and the like. The acid acceptor may be used undiluted or diluted with inert organic solvents, such as methylene chloride, chlorobenzene or 1 ,2-dichloroethane. Tertiary amines are advantageous since they are good solvents as well as acid acceptors during the reaction. The temperature at which the carbonyl halide reaction proceeds may vary from below 0°C to 100°C. The reaction proceeds satisfactorily at temperatures from room temperature to 50°C. Since the reaction is exothermic, the rate of phosgene addition may be used to control the temperature of the reaction. The amount of phosgene required will generally depend upon the amount of dihydric phenol present. Generally speaking, one mole of phosgene will react with one mole of dihydric phenol to form the polycarbonate and two moles of HC1. The HC1 is in turn taken up by the acid acceptor. Another method for preparing the aromatic polycarbonates useful in this invention involves adding phosgene to an alkaline aqueous suspension of dihydric phenols. This is preferably done in the presence of inert solvents such as methylene chloride, 1,2- dichloroethane and the like. Quaternary ammonium compounds may be employed to catalyze the reaction. Yet another method for preparing such aromatic polycarbonates involves the phosgenation of an agitated suspension of an anhydrous alkali salt of an aryl diol in a nonaqueous medium such as benzene, chlorobenzene or toluene. The reaction is illustrated by the addition of phosgene to a slurry of the sodium salt of, for example, Bisphenol A in an inert polymer solvent such as chlorobenzene. Generally speaking, a haloformate such as the bis-haloformate of Bisphenol A may be used in place of phosgene as the carbonate precursor in any of the methods described above. When a carbonate ester is used as the carbonate precursor in the polycarbonate-forming reaction, the materials are reacted at temperatures in excess of 100°C for times varying from 1 to 15 hours. Under such conditions, ester interchange occurs between the carbonate ester and the dihydric phenol used. The ester interchange is advantageously consummated at reduced pressures on the order of from 10 to 100 millimeters of mercury, preferably in an inert atmosphere such as nitrogen or argon. Although the polymer-forming reaction may be conducted in the absence of a catalyst, one may, if desired, employ a typical ester exchange catalyst, such as metallic lithium, potassium, calcium or magnesium. The amount of such catalyst, if used, is usually small, ranging from 0.001 percent to 0.1 percent , based on 0 the weight of the dihydric phenols employed. In the solution methods of preparation, the aromatic polycarbonate emerges from the reaction in either a true or pseudo solution depending on whether an 15 aqueous base or pyridine is used as an acid acceptor. The copolymer may be precipitated from the solution by adding a polymer nonsolvent, such as heptane or isopropanol. Alternatively, the polymer solution may be 0 heated, typically under reduced pressure, to evaporate the solvent. The methods and reactants described above for preparing carbonate polymers suitable for use in ?c - the practice of this invention are discussed in greater detail in Schnell, US Pat. No. 3,028,365; Campbell, US Pat. No. 4,384,108; Glass, US Pat. No. 4,529,791; and Grigo, US Pat. No. 4,677,162. 30 A preferred aromatic polycarbonate is characterized by repeating units corresponding to the general formula: wherein X is a linear or cyclic, divalent C- ] -C2 Q hydrocarbon radical, a single bond, -0-, -S-, -S2~ > -SO-, -Sθ2~ > or -CO-. Each aromatic ring may additionally contain, instead of hydrogen, up to four substituents such as C- j —C^ alkyl hydrocarbon or alkoxy radicals, aryl or aryloxy radicals, or halo radicals. Although the polycarbonates mentioned above, such as those derived from 2,2-bis(4- hydroxyphenyl)propane ("Bisphenol-A" or "Bis-A") or from 1 , 1-bis(4-hydroxyphenyl)-1-phenyl ethane ("Bisphenol-A- P" or "Bis-A-P"), can each be employed in this invention as a homopolymer, the carbonate polymers used herein can also be derived from two or more bisphenols, or two or more acid- or hydroxy-terminated reactants such as dicarboxylic acids or alkylene glycols, or from two or more different dihydroxy compounds, or mixtures of any of the foregoing, in the event a carbonate copolymer or interpolymer, such as a copolyester/carbonate is desired, rather than a homopolymer. Copolymers can be formed, for example, when a bisphenol is reacted with a carbonic acid derivative and a polydiorganosiloxane containing α,ω-bishydroxyaryloxy terminal groups to yield a siloxane/carbonate block copolymer (as are discussed in greater detail in Paul, USP 4,569,970), or when a bisphenol is reacted with a bis(ar-haloformylaryl) carbonate to yield an alternating copolyestercarbonate. The bis(ar-haloformylaryl) carbonate is formed by reacting a hydroxycarboxylic acid with a carbonic acid derivative under carbonate forming conditions, such copolyestercarbonates being discussed in greater detail in Swart, USP 4,105,533. The term "polycarbonate" as used herein, and in the claims appended hereto, should therefore be understood to include carbonate homopolymers, carbonate copolymers (as described above), and/or blends of carbonate homopolymers and/or carbonate copolymers. (b) Polyester. The aromatic polyester used in this invention may be made by a variety of methods. Although the self-esterification of hydroxycarboxylic acids is known, direct esterification, which involves the reaction of a diol with a dicarboxylic acid with the resulting elimination of water, is a more frequently used method for commercial production, giving an -[-AABB-]- polyester. Although the presence of a catalyst such as p-toluene sulfonic acid, a titanium alkoxide or a dialkyltin oxide is helpful, the primary driving force behind the direst esterification reaction is heat. Temperatures applied exceed the melting points of the reactants and typically approach the boiling point of the diol being used, and usually range from 150°C to 280°C. An excess of the diol is typically used, and once all of the acid has reacted with diol, the excess diol is removed by distillation with the application of additional heat under reduced pressure. The ester of the diacid initially formed from the diol, having -OH end groups, undergoes alcoholysis and polymerization to form polymeric esters and the diol is split out as a byproduct and removed from the reaction zone. The reaction is typically carried out in the presence of an inert gas. Alternatively, but in like manner, ester- forming derivatives of a dicarboxylic acid can be heated with a diol to obtain polyesters in an ester interchange reaction. Suitable acid derivatives for such purpose are esters, halides, salts or anhydrides of the acid. When a bis ester of the diacid is used for purposes of 10 the interchange reaction, the alcohol from which the ester is formed (the alcohol to be displaced) should be lower boiling than the diol to be used for formation of polyester (the displacing alcohol). The reaction can then be conveniently run at a temperature at or below 15 the boiling point of the displacing alcohol but well above that of the displaced alcohol, and is usually run in a temperature range similar to that for direct esterification. The ester interchange reaction is typically run in the presence of a diluent, for example, 20 an inert organic solvent such as chloroform or tetrachloroethane, and in the presence of a base, for example a tertiary organic base such as pyridine. Typical catalysts used when ester interchange involves ?c - alcoholysis are weak bases such as carbonates or alkoxides of sodium, lithium, zinc, calcium, magnesium or aluminum, whereas catalysts such as antimony oxide, titanium butoxide or sodium acetate are often used when acidolysis occurs in the interchange reaction. Diol 30 derivatives such as an acetate can be used effectively when it is desired to conduct acidolysis. Maintenance of high temperature is an important aspect of esterification, particularly toward the end of the reaction. As a consequence, thermal ester scission competes with polymer growth as the prevailing result of the process, which places an upper limit on the molecular weight which can be achieved through the use of melt polymerization. The molecular weight of polyester can be increased by adding a chain coupling agent, such as diphenyl carbonate, to the melt reaction mixture just prior its completion. Or, to achieve higher weight by solid state polymerization, polyester product of intermediate weight can be heated in a vacuum or stream of inert gas, first to a temperature where it crystallizes and then to a temperature close to its melting point. Polyesters can also be produced by a ring- opening reaction of cyclic esters or lactones, for which organic tertiary bases and alkali and alkaline earth metals, hydrides and alkoxides can be used as initiators. Advantages offered by this type of reaction are that it can be run at lower temperatures, frequently under 100°C, and there is no need to remove a condensation product from the reaction. Whether a polyester is crystalline or amorphous is typically a function of the symmetry of the starting materials from which it is made. When one or more hydrogens on the diol and/or the diacid (or derivative) which are reacted to form a polyester are replaced by larger radicals such as alkyl or halogen, the intermolecular spacing of the resulting molecules may be disrupted if the presence of the substituent creates assymetric or irregularly shaped molecules. The component containing the substituent may also be combined into the polyester molecule in random orientation, resulting in structural irregularity in the polymer chain. Factors which can influence crystallization of ring-containing polyesters are the directionality of the ester groups, the stereochemistry of the rings and variations in symmetry where the rings are bridged. For example, a poly(alkylene isophthalate) crystallizes only with difficulty, and a polyester prepared from phthalic acid typically does not crystallize at all. However, where the amount of monomer containing the asymmetry is small in relation to the remainder of the starting materials, the portion of the resulting polyester molecule which suffers from structural irregularity will also be small, and crystallization will typically not be impeded. A crystalline material may be identified by the endotherm it displays on a differential scanning calorimeter. Suitable reactants for making the polyester used in this invention, in addition to hydroxycarboxylic acids, are diols and dicarboxylic acids either or both of which can be aliphatic or aromatic. A polyester which is a poly(alkylene alkanedicarboxylate) , a poly(alkylene phenylenedicarboxylate) , a poly(phenylene alkanedicarboxylate), or a poly(phenylene phenylenedicarboxylate) is therefore appropriate for use herein. Alkyl portions of the polymer chain can be substituted with, for example, halogens, alkoxy groups or alkyl side chains and can contain divalent heteroatomic groups (such as -0-, -S- or -SO2-) in the paraffinic segment of the chain. The chain can also contain unsaturation and non-aromatic rings. Aromatic rings can contain substituents such as halogens, alkoxy or alkyl groups, and can be joined to the polymer backbone in any ring position and directly to the alcohol or acid functionality or to intervening atoms. Typical alkylene diols used in ester formation are the C 2 -C 10 glycols, such as ethylene-, propylene-, and butylene glycol. Alkanedicarboxylic acids frequently used are oxalic acid, adipic acid and sebacic acid. Diols which contain rings can be, for example, a 1 ,4-cyclohexylenyl glycol or a 1 ,4-cyclohexane- dimethylene glycol, resorcinol, hydroquinone, 4,4'- thiodiphenol, bis-(4-hydroxyphenyl)sulfone, a dihydroxynaphthalene, a xylylene diol, or can be one of the many bisphenols such as 2,2-bis-(4- hydroxyphenyl)propane. Aromatic diacids include, for example, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyletherdicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid. In addition to polyesters formed from one diol and one diacid only, the term "polyester" as used herein includes random, patterned or block copolyesters, for example those formed from two or more different diols and/or two or more different diacids, and/or from other divalent heteroatomic groups. Mixtures of such copolyesters, mixtures of polyesters derived from one diol and diacid only, and mixtures of members from both of such groups, are also all suitable for use in this invention, and are all included in the term "polyester". For example, use of cyclohexanedimethylol together with ethylene glycol in esterification with terephthalic acid forms a clear, amorphous copolyester ("PETG") of particular interest. Also contemplated are PCTG; liquid crystalline polyesters derived from mixtures of 4- hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid; or mixtures of terephthalic acid, 4-hydroxybenzoic acid and ethylene glycol; or mixtures of terephthalic acid, 4- hydroxybenzoic acid and 4,4'-dihydroxybiphenyl. Aromatic polyesters such as the poly(alkylene phenylenedicarboxylates) polyethylene terephthalate and polybutylene terephthalate, or mixtures thereof, are particularly useful in this invention. Methods and materials useful for the production of polyesters, as described above, are discussed in greater detail in Whinfield, US Pat. No. 2,465,319, Pengilly, US Pat. No. 3,047,539 and Russell, US Pat. No. 3,756,986. (c) Epoxide-containing modifier. The epoxide-containing modifier used in this invention is a terpolymer which has a glass transition temperature ("T g ") less than 0°C. Tg is the temperature or temperature range at which a polymeric material shows an abrupt change in its physical properties, including, for example, mechanical strength. T g can be determined, for example, by differential scanning calorimetry. The epoxide- containing modifier of this invention is formed as a terpolymer from (i) (A) at least one olefin monomer such as ethylene, propylene, isopropylene, butylene orisobutylene, or at least one conjugated diene such as butadiene, and the like, or mixtures thereof, or (B) a copolymer of one or more olefin monomers, such as described above, with other vinyl monomer(s), but containing a sufficient amount of the olefin monomer(s) to impart a T g of less than 0°C to the epoxide- containing modifier; (ii) at least one vinyl ( i.e. olefinically unsaturated, including vinylidene) or olefin monomer carrying at least one epoxide group; and (iii) at least one vinyl ( i.e. olefinically unsaturated, including vinylidene) monomer not carrying an epoxide group. Representative vinyl ( i.e. olefinically unsaturated, including vinylidene) monomers useful as component (c)(iii) in forming the terpolymer epoxide- containing modifier of this invention include the following: vinyl compounds (especially when they bear a polar, electronegative group or functionality) such as vinyl toluene, alphamethyl styrene, halogenated styrene; those containing nitrile groups such as copolymers of acrylonitrile, methacrylonitrile or alpha-halogenated acrylonitrile; a C^C g alkyl acrylate such as ethyl acrylate, butyl acrylate, hexyl acrylate or hydroxy ethyl acrylate; a C^C g alkyl methacrylate such as mehtyl methacrylate or hexyl methacrylate; others containing ester groups such as derivatives of acrylic or methacrylic acids, for example esters of said acids and any of the C.-C 6 aliphatic or cycloaliphatic alcohols, especially the C j -C 4 aliphatic or cycloaliphatic alcohols; an acrylic or methacrylic acid; the vinylidene monomers, especially when they bear a polar, electronegative group or functionality such as a halogen group, or an organic group having a double or triple bond such as phenyl, carboxy, cyano or the like; vinyl esters or vinyl ethers; alkenyl-aromatic compounds such as styrene and substituted derivatives thereof; maleimides; mononitriles having alpha-beta-olefinic unsaturation and lower alkyl or halogen substituents; esters of olefinically unsaturated carboxylic acids; aliphatic vinyl compounds such as vinyl chloride, vinylidene chloride, acrylic and methacrylic acid esters, amides and nitriles, vinyl acetate, vinyl propionate and vinyl benzoate; vinyl-methyl-ether, vinyl-ethyl-ether and vinyl-isobutyl-ether; and aromatic vinyl compounds such as styrene, alpha -methyl styrene, vinyl toluene, p-ethylstyrene, 2,4-dimethyl styrene, o-chlorostyrene and 2,5-dichlorostyrene; vinyl 10 esters; vinyl ethers; alpha-olefins; vinyl toluenes; vinyl xylenes; the maleates; the fumarates; and the like; or mixtures of two or more of any of the foregoing. In general, vinyl and vinylidene monomers from groups such as the vinyl and vinylidene -esters, - 15 ethers, -organic acids, -aromatics, -alcohols, - anhydrides, -halides, -nitriles and -amides; or mixtures of any of the foregoing may be used. Additionally, any one or more of the foregoing monomers may be copolymerized with carbon monoxide. 20 Vinyl monomers such as the foregoing may also be copolymerized as part of the olefin copolymer described above as component (c)(i)(B); or, when p ,- carrying an epoxide group, may be used as the component (c)(ii). Or, the epoxide group may be carried on an olefin monomer. Suitable olefinically unsaturated monomers 30 containing epoxide groups for use as component (c)(ii) of the terpolymer modifier include, for example, glycidyl esters of unsaturated carboxylic acids (glycidyl methacrylate); glycidyl ethers of unsaturated alcohols (allyl-glycidyl-ether) and of alkenylphenols (isopropenylphenyl-glycidylether) ; and vinyl and allyl esters of epoxycarboxylic acids (vinyl esters of epoxidized oleic acid). In general, all compounds which contain both a polymerizable unsaturated group and reactive epoxide groups in the molecule can be used for the manufacture of the modifier of the invention. Copolymers of 1-25 percent (by weight) of glycidyl methacrylate, 40-95 percent of ethylene, and 4-40 percent of vinyl acetate are particularly suitable for use herein as the terpolymer modifier. Copolymers containing epoxide groups may be obtained according to known processes, for example by radical polymerization in chlorobenzene at 8θ°C in 50 percent strength solution. For instance, monomers such as listed above are dissolved in an appropriate solvent, such as benzene, chlorobenzene or toluene, and polymerized at a temperature of 8θ°C by adding azobisisobutyronitrile, whereby oxygen is excluded. After the monomers have been reacted, the solvent used is distilled off (e.g., chlorobenzene at 100°C and 20 torr) and the residue is dried in vacuum at 100°C and then powdered. The terpolymer modifier of this invention can also be prepared in gas phase under conditions suitable for polymerizing an olefin. For example, the terpolymer can be made in either a tubular reactor or a stirred autoclave, where heated, pressurized feed streams of olefin or vinyl monomer gas, peroxide free-radical initiator and chain transfer agent are injected into the reaction device. The reaction of formation usually occurs at 1,500-3,000 atm (152-304 MPa) and at a temperature usually not exceeding 300°C, as known in the art. The molecular weight of the epoxide-containing terpolymer modifier is typically between 10,000 and 500,000, preferably between 30,000 and 200,000, and it typially contains 5 to 1,000, preferably 20 to 500, epoxide groups per macromolecule. (d)(i) Thermoplastic Elastomer. The thermoplastic elastomers useful in this invention are those which have a Tg less than 0°C. These thermoplastic elstomers are characterized, for example, in that they can be melted, for mixing or other purposes, and recooled without undergoing any change in properties; and they also retain their properties after having been dissolved and reformed upon removal of the solvent. The thermoplastic elastomers suitable for use herein are further characterized by the randomness of the shape and size they take on when mixed by shearing forces with the other components making up the compositions of this invention, especially when heat is applied during such mixing. Because the thermoplastic elastomer is typically a long chain molecule, segments of thermoplastic elastomer in the polymer composition matrix are generally elongated, linear ribbons or bands. However, chain coiling can yield globule-shaped segments of thermoplastic elastomer in the matrix. The random shape and size assumed in the polymer compositon matrix by a thermoplastic elastomer may be distinguished from the shape and size assumed by component (d)(iii), the core-shell graft polymer. The core-shell graft polymer is uniformly present in the polymer matrix in a bead shape both before and after mixing by application of shearing forces, whether heat is used or not, and is typiclly present in a rather narrow size range, for example 0.05- 0.8 microns. The retention of this core-shell, or spherical, shape by the graft polymer, even after heating and mixing, results from the fact that the outer layers, which surround the core, are formed by grafting appropriate monomers onto the core. A core-shell graft polymer such as is used a component (d)(iii) typically cannot be melted and recooled without a change in properties because the graft polymer will tend to 10 decompose or crosslink, and the bead-shaped segments of graft polymer will tend to agglomerate upon melting, making dispersion of them by mixing very difficult. The thermoplastic elastomers useful in this - - invention are based generally on an olefininc backbone, and include mixtures of more than one of such thermoplastic elastomers. Representative examples of a few olefin-based rubbers which are suitable for use herein, individually or in a mixture, as thermoplastic 20 elastomers are as follows: Butyl rubber is the product of copolymerizing isobutylene and isoprene where the isoprene typically makes up no more than 2.5 mole percent of the copolymer, 25 Although the solution process is used to manufacture butyl rubber, most of it is made by a precipitation (slurry) method wherein the monomers are copolymerized in methyl chloride diluent using a catalyst such as aluminum chloride. 30 In EPM (ethylene/propylene copolymer) rubber, the ratio of ethylene to propylene is from 50/50 to 75/25. A diene can be added to the copolymer to furnish a pendant group containing an addition polymerizable C=C bond. The diene, which can be straight chain or cyclic, is typically not conjugated, and the two C=C bonds typically have different activities with respect to polymerization. When a diene is copolymerized with ethylene and propylene, the product is known as EPDM rubber. EPM/EPDM rubbers can also be copolymerized or grafted with vinyl monomers such as styrene and acrylonitrile. Formation of neoprene rubber by polymerization of 2-chloro-1 ,3-butadiene can result from addition involving both of the double bonds, or through just one of the two leaving the other as a pendant group. Neoprene rubber is typically made by free radical batch emulsion polymerization, but can also be made in a continuous process. Nitrile rubber, which is polymerized from 1,3- butadiene and acrylonitrile, typically has 15-50 percent acrylonitrile content. It is usually preferred to make nitrile rubbers by emulsion in an aqueous system. As with rubbers involving derivatives of butadiene, formation of polybutadiene can be by either 1,4 or 1,2 (vinyl) addition of the butadiene molecule. 1,4 products are either cis or trans , and vinyl products are classified as to tacticity. Polybutadiene rubber is typically manufactured by solution polymerization, using organic lithium compounds or coordination catalysts containing metals in reduced valence states. Polyisoprene, with its pendant methyl group on what would otherwise be a butadiene unit, also polymerizes in cis-1,4, trαras- 1 , 4 or 1,2 (vinyl) form. Ziegler catalysts are frequently used in the polymerization of polyisoprene. Polyether rubbers include epichlorohydrin elastomers, which can be prepared either by a coordination polymerization mechanism using an aluminum alkyl-water catalyst in a hydrocarbon solvent, or in solution using benzene, toluene or methylene chloride as the solvent. Propylene oxide elastomers can also be 0 prepared in solution, by copolymerization with allyl glycidyl ether, using a coordination catalyst such as diethyl zinc water. An SBR rubber is a copolymer of styrene and 15 butadiene which typically contains 23 percent styrene. Of the butadiene content, 18 percent of it is cis, 65 percent is trans and 17 percent is vinyl. The monomers themselves can be randomly dispersed along the backbone, or blocks of each monomer can be randomly dispersed. 0 Thermoplastic elastomers also include A-B-A or A-B block copolymers which have a rigid block "A" having a T g above room temperature (approximately 23-25°C) and pc - a rubbery block "B" having a Tg below room temperature. Examples of typical pairings of materials to form the respective A and B blocks of a block copolymer thermoplastic elastomer are shown in Table I. 30 Table I Block Copolymer Pairings Block copolymer thermoplastic elastomers can be prepared, for example, by anionic polymerization using an alkyl-lithium initiator. Hydrogenated styrene/ethylene-butylene/styrene block copolymers, such as that available from Shell Oil Co. as Kraton™ G-1651 rubber, are preferred. (d)(ii) Styrene/ Acrylonitrile Copolymer. The styrene/acrylonitrile copolymer ("SAN") suitable for use in this invention is that which is rubber-modified. An example of a rubber-modified styrene/acrylonitrile copolymer which can be advantageously used in this invention is an elastomeric-thermoplastic composite such as an acrylonitrile/butadiene/styrene copolymer ("ABS"). The elastomeric portion of such composite is usually dispersed as discrete particles in a matrix made up of the thermoplastic portion. ABS is typically formed by the grafting of an SAN copolymer onto a polybutadiene substrate latex. The polybutadiene forms particles of rubber - the elastomeric component - which are dispersed as a discrete phase in a thermoplastic matrix formed by the SAN. The rubber content of the rubber-modified styrene/acrylonitrile copolymer used in this invention is less than 40 percent by weight. This structural aspect of ABS - the dispersion of rubber particles in a compatible thermoplastic phase or matrix - is more important than the precise monomer content. The composite can be manufactured from nothing other than acrylonitrile, butadiene and styrene, or other monomers can be substituted or mixed in with them. Some of the monomers which are frequently substituted for or intermixed with acrylonitrile, butadiene and styrene are mentioned below in connection with the three usual methods of manufacturing ABS. What is set forth below concerning methods of making the elastomeric/thermoplastic composite used as a rubber- modified styrene/acrylonitrile copolymer in this invention from acrylonitrile, butadiene and styrene applies equally to the other forms of said elastomeric/thermoplastic composite which result from variation in the monomer mix. The elastomeric/thermoplastic composite used as a rubber- modified styrenic thermoplastic resin in this invention can be made from any of the various monomers, and can be made by any of the various methods, which are included below in the discussion relating specifically to the manufacture of ABS. One method for making ABS resin is emulsion polymerization wherein the first step is the production of a rubber substrate latex in an aqueous emulsion. The substrate results from polymerization, which can be initiated by organic peroxides, persulfates, iron, sugar, or peroxide redox systems, of 1 ,3-butadiene alone or in combination with other monomers. Butadiene can be copolymerized with either styrene or acrylonitrile to form the substrate, but numerous other comonomers yield equivalent results. In general, any mixture containing a butadiene-1 ,3 hydrocarbon and a copolymerizable compound containing a single olefinic double bond, in proportions such that an unsaturated elastomeric copolymer - a rubber - is formed on polymerization of the mixture in aqueous emulsion, is appropriate. For example, there may be used mixtures containing a predominant amount of butadiene-1 ,3, isoprene, 2,3- dimethyl butadiene-1 ,3 or piperylene, or a combination of two or more of these and a lesser amount of one or more of the following monomers: styrene, alpha-methyl styrene, p-methoxy styrene, p-chloro styrene, dichloro styrene, vinyl naphthalene and other alkenyl substituted aromatic compounds of the formula R Ar-C=CH 2 wherein Ar is an aromatic radical having its connecting valence on a ring carbon atom with R being as follows: hydrogen or alkyl; acrylonitrile, methacrylonitrile, ethacrylonitrile, alphachloro acrylonitrile, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, methyl acrylate, propyl acrylate, butyl acrylate, octyl acrylate, methyl alpha-chloro acrylate, methacrylamide, acrylamide, N.N-diethyl acrylamide and other nitriles, amides and alkyl esters of alpha-methylene aliphatic monocarboxylic acids; substituted aromatic maleimides such as N-phenyl maleimide; diethyl fumarate, diethylchloromaleate, vinylidene chloride, methyl vinyl ketone, methyl isopropenyl ketone, vinyl pyridines, vinyl furan, vinyl carbazole, isobutylene, ethylene, and the like. It is preferred that, in the preparation of the rubber latex, the proportion of butadiene to other monomers be in the range of 2/1 to 15/1. After formation of the rubber latex substrate, the rubber latex substrate and styrene and acrylonitrile monomers are subjected to further aqueous emulsion wherein the rubber latex substrate makes up from 4 percent to less than 40 percent of the rubber-monomer mass charged to the reactor. The concentration of styrene is usually 1.5 to 3.5 times that of acrylonitrile. However other monomers such as 0 methacrylonitrile, divinylbenzene, α-methyl styrene, p- methyl styrene, methyl methacrylate, N-phenyl maleimide, chlorinated and brominated styrenes, and methyl-, ethyl- or n-butylacrylate, or mixtures thereof, may also be in conjunction with styrene and acrylonitrile. Organic 15 peroxides, azo compounds, persulfates, or redox systems are usually used to initiate polymerization. SAN is formed, some of which is grafted to the rubber latex substrate, and some of which is free. The latex containing both the grafted rubber and the free SAN is 20 then mixed with a coagulant solution, heated and agitated to produce discrete particles of ABS resin. The slurry containing those particles is dewatered in a centrifuge, and the resin is dried. Methods for making pc - ABS resin by emulsion polymerization, as described above, are discussed in greater detail in Childers, USP 2,820,773 and Calvert, USP 3,238,275. When ABS is made by suspension polymerization, 30 a pre-formed elastomeric component ( i.e. a rubber), usually a polybutadiene or a butadiene/styrene copolymer, is dissolved in a mixture of styrene and acrylonitrile. The rubber component may be one of the several mentioned above with respect to emulsion polymerization of ABS, or may be polyisoprene, polycyclopentadiene, natural rubber, chlorinated rubber or copolymers of butadiene with isobutylene. However, the preferred rubber component is a linear 1,4 polybutadiene having a 35 percent to 50 percent cis content. The preferred ratio of styrene to acrylonitrile in the styrene-acrylonitrile solution is 90/10 to 60/40, and in the preferred recipe the rubber component 10 constitutes from 4 percent to less than 40 percent of the product. As with the emulsion process described above, numerous substances will function in a manner equivalent to that of styrene and may be substituted therefor, to-wit: alphamethyl styrene, or other 15 substituted vinyl aromatics such as vinyl-toluene, vinylxylene, vinylethyl benzene or vinylchloro benzene. Methacrylonitrile is another alkenyl cyanide monomer which will serve in the place of acrylonitrile. 20 The rubber component, monomers and initiator are charged to the reaction vessel and polymerization ensues until a conversion rate of 15 percent to 30 percent is reached, resulting in the production of a p ,- prepolymer. Phase inversion occurs, and the rubber precipitates from solution and becomes the discontinuous phase dispersed as particles ranging from 0.5 to 5 μm in size. The prepolymer is then placed in a suspension reactor in an aqueous solution containing a suspending 30 agent, initiator and chain transfer agent. Typical suspending agents are carboxymethyl cellulose, polyvinyl alcohol, methyl cellulose, sulfonated polystyrenes, polyglycol ethers and hydroxyethyl cellulose. Typical initiators for the polymerization which occurs during suspension are t-butyl perbenzoate, di-t-butyl peroxide, dibenzoyl peroxide, t-butyl peracetate or t-butylperoxy isopropyl carbonate. Agitation of the solution helps complete the polymerization. The process is completed by dewatering the slurry in a centrifuge, and moisture content is further reduced by flash drying. Manufacture of ABS by the suspension process, as described above, is discussed in greater detail in Carrock, USP 3.515,692 and Ackerman, USP 4,151,128. In bulk or mass polymerization, ABS is formed by dissolving an elastomeric component ( i.e. a rubber) in the monomer mix, which contains styrene, acrylonitrile, an initiator and, frequently, a chain transfer agent such as a mercaptan or a terpinolene. The reaction can, however, be thermally initiated. The styrene and acrylonitrile monomers polymerize, some grafting to the rubber component, but most forming a monomer-polymer solution. As the relative volume of the monomer-SAN polymer phase increases, discrete rubber particles become dispersed in the matrix resulting from the monomer-SAN polymer phase. The rubber particles are stabilized by being grafted to SAN polymers at the interface between the particles and the SAN polymer matrix. Additional stabilization is furnished when monomer becomes occluded, and polymerizes, within the rubber particles. Because polymerization occurs completely within a monomer/polymer medium, viscosity increases as conversion increases. To allow continued agitation of the reaction mixture despite such increasing viscosity, diluents such as methyl ethyl ketone and ethylbenzene are added to the reactor. Upon the completion of polymerization, the melt is devolatilized using equipment such as a devolatilizing extruder or a flash evaporator, and vacuum is applied to remove unreacted monomers and diluents. As is true of ABS made by the emulsion or suspension method, numerous substances can be used in the bulk method in place of, or conjunction with, styrene, examples of such substances being as follows: alpha-alkyl monovinylidene monoaromatic compounds, e.g. alpha-methylstyrene, alpha-ethylstyrene, alpha- methylvinyltoluene; ring-substituted alkyl styrenes, e.g. vinyl toluene, o-ethylstyrene, p-ethylstyrene, 2,4- dimethylstyrene; ring-substituted halostyrenes, e.g., o- chlorostyrene, p-chlorostyrene, o-bromostyrene, 2,4- dichlorostyrene; ring-alkyl, ring-halo-substituted styrenes, e.g. 2-chloro-4-methylstyrene and 2,6-dichloro- 4-methylstyrene; methacrylates such as methyl methacrylate; maleic acid and its esters and anhydrides; substituted aromatic maleimides such as N-phenyl maleimide; and mixtures of the foregoing. If so desired, mixtures of such monovinylidene aromatic monomers may be employed. Methacrylonitrile can also be used in combination with acrylonitrile. Bulk methods for the preparation of ABS, as described above, are discussed in greater detail in Kruse, USP 4,187,260, Simon, USP 4,252,911 and Weber, USP 4,526,926. Another form which the rubber-modified styrene/acrylonitrile copolymer used in this invention can take is an AES (acrylonitrile/EPDM/styrene) copolymer. This is obtained when SAN is grafted to a substrate made up of an EPDM (ethylene/propylene/non- conjugated diene copolymer) rubber, as in the case of Rovel ® weatherable polymers, which are discussed in greater detail in Henton, USP 4,766,175 and are available from The Dow Chemical Company. SAN can also be crosslinked to an acrylate elastomer to form a rubber-modified styrenic thermoplastic resin, as in the case of an ASA (acrylonitrile/styrene/acrylate) copolymer, which is discussed in greater detail in Yu, USP 3,944,631. Although mixtures of the various copolymers described above can serve as the rubber-modified 0 styrenic thermoplastic resin of this invention, the preferred rubber-modified styrenic thermoplastic resin is ABS. (d)(iii) Core-shell Graft Polymer. The graft polymers 15 suitable in this invention are of the core-shell type, contain more than 40 percent rubber, and are characterized in that their structure comprises an elastomeric core based substantially on either a diene or an acrylate, and a rigid grafted phase. These 0 polymers are further characterized in that the glass transition temperature of the elastomeric phase is below 0°C, and the elastomeric phase may optionally be at least partially crosslinked. The grafted phase typically pc - comprises at least one monomer selected from acrylic esters of saturated aliphatic alcohols, methacrylic esters of saturated aliphatic alcohols, vinyl acetate, acrylonitrile, styrene and alkyl styrene. 30 A diene rubber contains a substrate latex, or core, which is made by polymerizing a diene, preferably a conjugated diene, or by copolymerizing a diene with a mono-olefin or polar vinyl compound, such as styrene, acrylonitrile, or an alkyl ester of an unsaturated carboxylic acid such as methyl methacrylate. The substrate latex is typically made up of 40-85 percent diene, preferably a conjugated diene, and 15-60 percent of the mono-olefin or polar vinyl compound. The elastomeric core phase should have a glass transition temperature ("T g ") of less than 0°C, and preferably less than -20°C. A mixture of monomers is then graft polymerized to the substrate latex. A variety of monomers may be used for this grafting purpose, of which the following are exemplary: vinyl compounds such as 10 vinyl toluene or vinyl chloride; vinyl aromatics such as styrene, alpha-methyl styrene or halogenated styrene; acrylonitrile, methacrylonitrile or alpha-halogenated acrylonitrile; a C.-C 8 alkyl acrylate such as ethyl acrylate or hexyl acrylate; a C j -C 8 alkyl methacrylate 15 such as methyl methacrylate or hexyl methacrylate; acrylic or methacrylic acid; and the like or a mixture of two or more thereof. The grafting monomers may be added to the 20 reaction mixture simultaneously or in sequence, and, when added in sequence, layers, shells or wart-like appendages can be built up around the substrate latex, or core. The monomers can be added in various ratios to -,- each other although, when just two are used, they are frequently utilized in equal amounts. A typical weight ratio for methyl methacrylate/butadiene/styrene copolymer ("MBS" rubber) is 60-80 parts by weight substrate latex, 10-20 parts by weight of each of the 30 first and second monomer shells. A preferred formulation for an MBS rubber is one having a core built up from 71 parts of butadiene, 3 parts of styrene, 4 parts of methyl methacrylate and 1 part of divinyl benzene; a second phase of 11 parts of styrene; and a shell phase of 11 parts of methyl methacrylate and 0.1 part of 1,3-butylene glycol dimethacrylate, where the parts are by weight of the total composition. A diene- based, core-shell graft copolymer elastomer and methods for making same, as described above, are discussed in greater detail in Saito, USP 3,287,443, Curfman, USP 3,657,391, and Fromuth, USP 4,180,494. An acrylate rubber has a first phase forming an elastomeric core and a second phase forming a rigid 0 thermoplastic phase said elastomeric core. The elastomeric core is formed by emulsion or suspension polymerization of monomers which consist of at least 50 weight percent alkyl and/or aralkyl acrylates having up to fifteen carbon atoms, and, although longer chains may 15 be used, the alkyls are preferably C 2 -C 6 , most preferably butyl acrylate. The elastomeric core phase should have a Tg of less than 25°C, and preferably less than 0°C. 0 The rigid thermoplastic phase of the acrylate rubber is formed on the surface of the elastomeric core using suspension or emulsion polymerization techniques. The monomers necessary to create this phase together p j- with necessary initiators are added directly to the reaction mixture in which the elastomeric core is formed, and polymerization proceeds until the supply of monomers is substantially exhausted. Monomers such as an alkyl ester of an unsaturated carboxylic acid, for 30 example a C.-C 8 alkyl acrylate like methyl acrylate, hydroxy ethyl acrylate or hexyl acrylate, or a C j -C 8 alkyl methacrylate such as methyl methacrylate or hexyl methacrylate, or mixtures of any of the foregoing, are some of the monomers which can be used for this purpose. Either thermal or redox initiator systems can be used. Because of the presence of the graft linking agents on the surface of the elastomeric core, a portion of the chains which make up the rigid thermoplastic phase are chemically bonded to the elastomeric core. It is preferred that there be at least 20 percent bonding of the rigid thermoplastic phase to the elastomeric core. A preferred acrylate rubber is made up of more than 40 percent to 95 percent by weight of an 10 elastomeric core and 60 percent to 5 percent of a rigid thermoplastic phase. The elastomeric core can be polymerized from 75 percent to 99.8 percent by weight C.-C 6 acrylate, preferably n-butyl acrylate. The rigid thermoplastic phase can be polymerized from at least 50 15 percent by weight of C^C g alkyl methacrylate, preferably methyl methacrylate. Acrylate rubbers and methods for making same, as described above, are discussed in greater detail in Owens, USP 3,808,180 and Witman, USP 4,299,928. 20 A variety of additives may be used in the compositions of this invention for protection against thermal, oxidative and ultra-violet degradation. Such p j- additives may be included in the composition at any point during the processing, and the choice as to which additive is employed, if any, is not critical to this invention. Representative of the thermal and oxidative stabilizers which can advantageously be utilized are 30 hindered phenols, hydroquinones, phosphites, including substituted members of those groups and/or mixtures of more than one thereof. A preferred phenolic anti- oxidant is Irganox™ 1076 anti-oxidant, available from Ciba-Geigy Corp. Ultra-violet stabilizers such as various substituted resorcinols, salicylates, benzotriazoles, benzophines, hindered amines and hindered phenols can also be usefully included in the compositions of this invention, as can be lubricants, colorants, fillers such as talc, clay or mica, pigments, ignition resistant additives and mold release agents, and reinforcement agents such as fiberglass. Additives and stabilizers such as the foregoing, and many others which have not been mentioned, are known in the art, and the decision as to which, if any, to use is not critical 0 to this invention. However, such additives, if used, typically do not exceed 5 percent by weight of the total composition, except fillers or reinforcing agents, which may constitute up to 40 percent of the composition. 15 Illustrative Embodiments. To illustrate the practice of this invention, examples of several preferred embodiments are set forth below. It is not intended, however, that these examples (Examples 1-8) should in 20 any manner restrict the scope of this invention. Some of the particularly desirable features of this invention may be seen by contrasting the characteristics of Examples 1-8 with those of controlled formulations pc - (Control A-D) which do not possess the features of, and are not therefore embodiments of, this invention. The polycarbonate compositions prepared in Controls A-D and Examples 1-8 are made by dry blending 30 the ingredients thereof and agitating same in a paint shaker for 7 minutes. The dry blended formulations are then melt mixed in a vented 30mm Werner-Pfleiderer co- rotating, twin screw extruder using a 270°C set temperature and 250 rpm. Each extruded composition is passed through a water bath, chopped into granules and collected for molding. Granules are thoroughly dried in a circulated air oven at 115°C for six hours prior to molding. All samples are prepared by injection molding on a 75 ton (6.8 x 10 4 kg) Arburg molding machine. Molding temperatures for the barrel and mold are set at 280°C and 190°F (88°C), respectively. The formulations of the polycarbonate compositions of Controls A-D and Examples 1-8 are given 10 below in Table II in parts by weight. In Table II: "(1) PC 300-10" is Calibre ® 300-10 polycarbonate resin, a 10 melt flow value polycarbonate resin available from The Dow Chemical Company; "(2) PET 9506" is polyethylene terephthalate 15 having 0.95 inherent viscosity (measured in accordance with ASTM Designation D 4603-86), available as Traytuf™ polyester from Goodyear Tire and Rubber Co.; "(3) SMMAGMA" is a terpolymer, containing 60 parts styrene, 20 parts methyl methacrylate and 20 parts 20 glycidyl methacrylate, which has a T g greater than 0°C and has a weight-average molecular weight of approximately 30,000; "(4) EVAGMA" is a terpolymer containing p ,- ethylene, vinyl acetate and glycidyl methacrylate (available from Sumitomo Chemical America), which has a weight-average molecular weight of approximately 100,000; "(5) GRC 120" is a core-shell graft polymer 30 containing approximately 50 percent rubber, wherein styrene and acrylonitrile are grafted onto a butadiene core; "(6) Kraton τu G 1651" is a hydrogenated styrene/butadiene block thermoplastic elastomer copolymer from Shell Oil Company; "(7) PA-2130" is a core-shell graft polymer containing 75 percent rubber (available from M&T Chemical Co.), wherein styrene and methyl methacrylate are grafted onto a butadiene core; "(8) Vistalon™ 3708" is an EPDM thermoplastic elastomer available from Exxon Corp.; "(9) ABS 941" is acrylonitrile/butadiene/styrene copolymer containing less than 30 percent rubbber, available from The Dow Chemical Company; and "(10) EVA" is ethylene/vinyl acetate copolymer containing approximately 85 wt percent ethylene and 15 wt percent vinyl acetate, such as Elvax™ 3152 copolymer available from DuPont. Table II Content of Controls A-D and Examples 1-8 in parts by weight The results of tests performed on the blended polycarbonate compositions of Controls A-D and Examples 1-8 are shown below in Table III. Impact resistance is measured by the Izod test according to ASTM Designation D 256-84 (Method A). The notch is 10 mils (0.254 mm) in radius. An inverted T (±) indicates that the notch is cut so that the 0 flexural shock caused by the striking nose of the pendulum is propagated parallel to the direction of flow taken by the molten extrudate during formation of the sample. Vertical parallel lines (||) indicate that the notch is cut so that the flexural shock caused by the 15 striking nose of the pendulum is propagated perpendicular to the direction of flow taken by the molten extrudate during formation of the sample. The result is stated first in ft-lb/in and then in J/m, and is sometimes referred to below as the "Izod value". 20 Weldline Izod strength is also measured according to ASTM Designation D 256-84 (Method A), but with respect to a sample which has been formed with a pe - butt weld in a double gated mold. The sample is unnotched, and it is placed in the vise so that the weld is coincident with the top surface of the vise jaws. The result is stated first in ft-lb/in and then in J/m, and is sometimes referred to below as the "weldline Izod 30 value". Flexural modulus is measured in accordance with ASTM Designation D 790-84a. The result is stated first in psi x 10 5 and then in MPa. Deflection temperature under load ("DTUL") is measured in accordance with ASTM Designation D 648-82 at 66 psi. The result is stated first in psi and then in MPa. Tensile strength at break and percent elongation at break are both measured in accordance with ASTM Designation D 638-84 with respect to samples which have, before testing, been (a) heated in a forced air oven at 250°F for 30 minutes, (b) cooled at room temperature for 24 hours, (c) placed under 0.5 percent strain while submerged in a bath of 60 wt percent isooctane and 40 wt percent toluene for 5 minutes, and (d) allowed to dry for 24 hours. Specular gloss is measured according to ASTM Designation D 523-85 using a Dr. Bruno Lange Reflectometer RB. The beam axis angle is 20°. Table III Test Results of Controls A-D and Examples 1-8 It can be seen from these test results that, when a composition is formed from (a) a polycarbonate, (b) an aromatic polyester and (c) an epoxide-containing modifier having a Tg less than 0°C, such as in Examples 1 and 2, the resulting composition shows marked improvements in strength over that obtained when, as in Control B, an epoxide-containing modifier having a Tg greater than 0°C is used as the component (c) instead. In particular, the Izod values are all noticeably higher for Examples 1 and 2 than for Control B. Moreover, it can be seen, by comparing Controls A and B, that the presence of the epoxide-containing modifier having a Tg greater than 0°C in Control B gives no improvement in the Izod values over Control A, which contains polycarbonate and polyester alone. When a composition is formed from (a) a polycarbonate, (b) an aromatic polyester and (c) an epoxide-containing modifier having a Tg less than 0°C, such as in Examples 1 and 2, the resulting composition shows marked improvements in strength over that obtained when, as in Control C, a core-shell graft polymer is additionally admixed therewith at a level exceeding 5 wt percent . In particular, the weldline and room temperature Izod values, the flexural modulus and the DTUL are all noticeably higher for Examples 1 and 2 than for Control C. When a composition is formed from (a) a polycarbonate, (b) an aromatic polyester and (c) an epoxide-containing modifier having a T g less than 0°C, such as in Examples 1 and 2, the resulting composition shows marked improvements in strength over that obtained when, as in Control D, the olefinic modifier does not contain an epoxide. In particular, the weldline Izod values are all noticeably higher for Examples 1 and 2 than for Control D, and the room temperature Izod values are all noticeably higher for Example 1 than for Control D. In addition, Control D exhibits quite high gloss and suffers from severe delamination of the skin layer on repeated bending of the molded part. When a composition is formed from (a) a polycarbonate, (b) an aromatic polyester, (c) an epoxide-containing modifier having a Tg less than 0°C, and (d)(i) a thermoplastic elastomer, the resulting composition shows marked improvements in strength over that obtained when, as in Control C, a core-shell graft polymer is used therein at a level exceeding 5 wt percent rather than a thermoplastic elastomer. In particular, the Izod values at room temperature and at low temperatures, the flexural modulus, the DTUL and the tensile strength are all noticeably higher for Examples 3 and 4 than for Control C. When a composition is formed from (a) a polycarbonate, (b) an aromatic polyester, (c) an epoxide-containing modifier having a T g less than 0°C, (d)(i) a thermoplastic elastomer and (d)(iii) a core- shell graft polymer at a level below 5 wt percent , the resulting composition shows marked improvements in strength over that obtained when, as in Control C, a graft polymer is used therein at a level exceeding 5 wt percent without the addition of a thermoplastic elastomer. In particular, the weldline Izod value, the Izod values at room temperature and at low temperatures, the flexural modulus and the DTUL are all noticeably higher for Examples 5 and 6 than for Control C. Despite containing more than twice as much polyester as Control C, Example 7 also has Izod values, flexural modulus and tensile strength which are noticeably higher than those for Control C. When a composition is formed from (a) a polycarbonate, (b) an aromatic polyester, and (c) an epoxide-containing modifier having a T g less than 0°C, and (d)(ii) a rubber-modified styrene/acrylonitrile 0 copolymer, the resulting composition shows marked improvements in strength over that obtained when, as in Control C, a core-shell graft polymer is used therein at a level exceeding 5 wt percent rather than a rubber- modified styrene/acrylonitrile copolymer. In 5 particular, despite containing more than twice as much polyester as Control C, Example 8 has Izod values, flexural modulus and tensile strength which are noticeably higher than those for Control C. 0 Contrary to expectation based on the art, these results show that it is not necessary to employ a core- shell graft polymer at levels over 5 wt percent in a composition containing at least a polycarbonate, a p ,- polyester and an epoxide-containing modifier to achieve a good balance of impact and flexural strength and DTUL, as well as strength, such as tensile strength, after solvent soaking. For example, the use of a core-shell graft polymer at 15 wt percent , as in Control C, 30 actually lowers the room temperature Izod values, the flexural modulus and DTUL of the resulting composition as compared to all the examples, and lowers the low- temperature Izod values as compared to all examples but Examples 1 and 2, which contain no additional impact modifiers. It is within the skill in the art to practice this invention in numerous modifications and variations in light of the above teachings. It is, therefore, to be understood that the various embodiments of this invention described herein may be altered without departing from the spirit and scope of this invention as defined by the appended claims.

Claims: Claims: 1. A composition of matter comprising, in admixture, (a) an aromatic polycarbonate, (b) an aromatic polyester, (c) a terpolymer, having a glass transition temperature ("T g ") less than 0°C, comprising (i_) (A) an olefin monomer, or (B) a copolymer containing a sufficient amount of an olefin monomer to impart a Tg of less than 0°C to the terpolymer; (ϋ) at least one vinyl monomer carrying at least one epoxide group; and (iii) at least one vinyl monomer not carrying an epoxide group, and (d) one or more members of the group consisting of (d)(i) a thermoplastic elastomer in an amount of up to 25 percent by total weight of all components of the composition; (d)(ii) a rubber-modified styrene/acrylonitrile copolymer in an amount of up to 25 percent by total weight of all components of the composition; and (d)(iii) a graft polymer of the core-shell type in an amount less than 5 percent by total weight of all components of the composition. 2. The composition of Claim 1 wherein the component (c)(ii) is a glycidyl ester of an unsaturated carboxylic acid. 3. The composition of Claim 2 wherein the glycidyl ester of an unsaturated carboxylic acid is 0 glycidyl methacrylate. 4. The composition of Claim 1 wherein the thermoplastic elastomer, component (d)(i), is an A-B-A block copolymer containing a rigid block "A" having a 5 glass transition temperature above 25°C and a rubbery block "B" having a glass transition temperature below 25°C. 5. The composition of Claim 4 wherein the 0 block "A" is polymerized from a vinyl aromatic compound and the block "B" is polymerized from an olefin or diene. ι - 6. The composition of Claim 4 wherein the block copolymer is hydrogenated, and the block "A" is polymerized from styrene and the block "B" is polymerized from butadiene. 0 7. The composition of Claim 1 wherein the rubber-modified styrnene/acrylonitrile copolymer is acrylonitrile/butadiene/styrene copolymer. 8. The composition of Claim 1 wherein the core-shell graft polymer is characterized in that (a) it has greater than 40 percent by weight rubber, (b) its core comprises a conjugated diene or a C.-C 15 acrylate, said core having a glass transition temperature below 0°C, and (c) its grafted phase comprises a carboxylic acid ester of a saturated aliphatic alcohol, acrylic or methacrylic acid, a vinyl nitrile compound, a vinyl aromatic compound, or a mixture 0 thereof. 9. The composition of Claim 8 wherein the grafted phase of said core-shell graft polymer is formed from an acrylic or methacrylic acid ester of a C χ -C 6 5 aliphatic alcohol, styrene, acrylonitrile, or a mixture thereof. 10. A composition of matter comprising, in admixture, 0 (a) an aromatic polycarbonate, (b) a poly(alkylene terephthalate), (c) ethylene/vinyl acetate/glycidyl methacrylate terpolymer, and pc (d) one or more members of the group consisting of a hydrogenated styrene/butadiene/styrene block copolymer, acrylonitrile/butadiene/styrene copolymer, a methacrylate/butadiene/styrene core-shell rubber in an amount less than 5 30 percent by total weight of all components including said core-shell rubber, an ethylene/propylene/diene copolymer, and a grafted ethylene/propylene/diene copolymer. 11. The composition of Claim 1 or 10 in the form of a molded article. 12. A method of molding an aromatic polycarbonate comprising (i) forming a composition comprising (a) said aromatic polycarbonate, (b) an aromatic polyester, (c) a terpolymer, having a glass transition - jQ temperature ("Tg") less than 0°C, comprising (I_) (A) an olefin monomer, or (B) a copolymer containing a sufficient amount of an olefin monomer to impart a Tg of less than 0°C to the terpolymer; (I_I_) at least 15 one vinyl monomer carrying at least one epoxide group; and (III) at least one vinyl monomer not carrying an epoxide group, and (d) one or more members of the group consisting 0 of (d)(1) a thermoplastic elastomer; (d)(II) a rubber-modified styrene/acrylonitrile copolymer; and 5 (d)(III) a graft polymer of the core-shell type in an amount less than 5 percent by total weight of all components of the composition including said core-shell graft polymer; and 0 (ϋ) molding said composition. 13. A method of decreasing the notch sensitivity to impact loading of a composition of an aromatic polycarbonate and an aromatic polyester, as measured by ASTM Designation 256-84 (Method A), comprising blending with said composition (a) a terpolymer, having a glass transition temperature ("T g ") less than 0°C, comprising (_i) (A) an olefin monomer, or (B) a copolymer containing a sufficient amount of an olefin monomer to impart a Tg of less than 0°C to the terpolymer; (Li) at least one vinyl monomer carrying at least one epoxide group; and (iii) 0 at least one vinyl monomer not carrying an epoxide group, and (b) one or more members of the group consisting of (i) a thermoplastic elastomer; (ii) a rubber-modified styrene/acrylonitrile 15 copolymer; and (iii) a graft polymer of the core-shell type in an amount less than 5 percent by total weight of all components of the composition including said core-shell graft polymer. 0 14. The method of Claim 12 or 13 wherein the core-shell graft polymer is characterized in that it has greater than 40 percent by weight pc rubber, its core comprises a conjugated diene or of a C.-C 15 acrylate, said core having a glass transition temperature below 0°C, and its grafted phase comprises a carboxylic acid 30 ester of a saturated aliphatic alcohol, acrylic or methacrylic acid, a vinyl nitrile compound, a vinyl aromatic compound, or a mixture thereof.

Inventors: LAUGHNER MICHAEL K, LAUGHNER, MICHAEL, K.
Applicants: DOW CHEMICAL CO, THE DOW CHEMICAL COMPANY
Application year: 1991
Main classification: C08L67
IPC codes: C08L21, C08L23, C08L25, C08L33, C08L51, C08L55, C08L67, C08L69, C08L87