EP0305514A1

EP0305514A1 - Impact modified polyester compositions with improved heat resistance

Info

Publication number: EP0305514A1
Application number: EP88904732A
Authority: EP
Inventors: Charles Franklyn Pratt
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1987-03-19
Filing date: 1988-03-09
Publication date: 1989-03-08
Also published as: JPH01500600A; AU1792588A; WO1988007065A1; CA1333731C; AU613376B2

Abstract

Des compositions de moulage de polyesters thermoplastiques modifiés par impact par des caoutchoucs d'EPDM (monomère de diène éthylènepropylène) greffés par du méthacrylate de glycidyle présentent une meilleure resistance à la chaleur avec l'addition de polymères vitreux, c'est-à-dire des polymères thermoplastiques ayant des températures de transition de verre amorphe supérieures à environ 100°C, par exemple, le poly(styrène-acrylonitrile), le poly(sulfone) aromatique, le poly(phénylène éther) et/ou le poly(carbonate) aromatique, sans diminuer de manière significative la résistance à l'impact ni les caractéristiques des lignes de jonction.Molding compositions of thermoplastic polyesters modified by impact with EPDM (ethylene propylene monomer) rubbers grafted with glycidyl methacrylate show improved heat resistance with the addition of vitreous polymers, i.e. thermoplastic polymers having amorphous glass transition temperatures greater than about 100°C, for example, poly(styrene-acrylonitrile), aromatic poly(sulfone), poly(phenylene ether) and/or poly(carbonate) aromatic, without significantly diminishing the impact resistance or the characteristics of the joining lines.

Description

"IMPACT MODIFIED POLYESTER COMPOSITIONS WITH IMPROVED HEAT RESISTANCE"

This invention relates to heat resistant impact modified thermoplastic molding compositions and, more par¬ ticularly, to glycidyl methacrylate or glycidyl acrylate grafted EPDM impact modifiers for thermoplastic polyester, copolyester and polyblend molding compositions that also include glassy polymers to improve heat resistance.

BACKGROUND OF THE INVENTION High molecular weight linear polyesters and copoly- esters of glycols and terephthalic or isophthalic acid have been available for a number of years. These are described inter alia in Whinfield et al., U.S. 2,465,319, and in Pengilly, U.S. 3,047,539. These patents disclose that the polyesters are particularly advantageous as film and fiber formers. With the development of molecular weight control, the use of nucleating agents and two-step molding cycles, poly(ethylene terephthalate) or PET has become an important constituent of injection moldable compositions. Further, poly(l,4-butylene terephthalate) or PBT, because of its very rapid crytallization from the melt, is uniquely useful as a component in such compositions. Work pieces molded from such polyester resins, in comparison with other thermoplastics, offer a high degree of surface hardness and abrasion resist¬ ance, high gloss and lower surface friction. Furthermore, in particular, poly(1,4-butylene tere¬ phthalate) is much simpler to use in injection molding tech^¬ niques than poly(ethylene terephthalate). For example, it is possible to injection mold poly(1,4-butylene terephthalate) at low mold temperatures of from about 30° to 60°C. to pro- duce highly crystalline, dimensionally stable moldings in short cycle times. Because of the high rate of crystalliza¬ tion, even at low temperatures, no difficulty is encountered in removing the moldings from the molds. Additionally, the dimensional stability of poly(l,4-butylene terephthalate) in¬ jection moldings is very good even at temperatures near or well above the glass temperature of poly(1,4-butylene tere¬ phthalate) . However, the impact resistance of unmodified poly¬ esters is relatively low at room temperature and below. Thus for many applications, it is desirable to have polyesters which are impact resistant at relatively high and relatively low ambient temperatures. Yet, the other mechanical proper- ties such as modulus of elasticity, tensile strength at yield and at break should be impaired either not at all or only to an acceptable degree.

It has been recommended in various places to im¬ prove the impact resistance of polyesters by adding other polymers including rubbery interpolymers and copolymers. Specifically, the impact strength of thermoplastic linear crystalline polyesters, including poly(l,4-butylene tereph¬ thalate) , has been .improved by the incorporation therein of an ethylenepropylene nonconjugated diene rubbery terpolymer (EPDM) . Although EPDM is capable of impact-modifying PBT polyester compositions, e.g., Coran et al._f U.S. 4,141,863 and Tanaka et al., U.S. 4,290,927, such compositions often suffer from "incompatibility" resulting in streaks or delamination of molded or extruded parts. In Hepp, European Patent Application 0 149 192, published July 24, 1985, there is disclosed a thermoplastic molding composition consisting of a thermoplastic resin, e.g., polyester, copolyester or block copolyester and a rubbery polymer comprising EPDM epoxidized with, e.g., m- chloroperoxy-benzoic acid and, optionally, a second non- rubbery, glassy thermoplastic polymer, e.g., aromatic poly¬ carbonate, to enhance surface characteristics and/or capability. The examples given by this reference in Tables 1, 2 and 3 do not, however, exhibit a combination of good impact strength and acceptable knit-line characteristics nor is there any indication that heat reistance is in any way enhanced by the addition of the polycarbonate.

Epstein, U.S. 4,172,859, discloses the use of glassy random copoly ers, e.g., polycarbonate with PET or PBT which contain various polar monomers. He also alludes to the use of materials grafted with various polar monomers, e.g., glycidyl methacrylate (GMA) , to impact modify thermoplastic polyesters including PBT and PET, and polycarbonate. How¬ ever, this patent does not deal with and therefore fails to recognize one factor that is critical to the function of EPDM-g-GMA materials as impact modifiers for PBT and poly¬ carbonate systems. It does not recognize the benefits of reactive glycidyl ( eth)acrylates as graft monomers over non-reactive polar monomers such as maleic anhydride or n-vinyl pyrrolidone.

In the prior .disclosures of Olivier, U.S. Patent Application, Serial No. 690,613, filed January 11, 1985,

Pratt et al., U.S. Patent Application Serial No. , filed , Attorney's Docket No. 337-1997 (8CT-4294), and McHale et al. , U.S. Patent Application Serial

No. , filed , Attorney's Docket

No. 337-2022 (8CT-4612), there are taught rubbery glycidyl methacrylate (GMA) grafted EPDM impact modifiers for poly¬ ester resins. In the specific examples, materials are described with high impact strengths. Good results are obtained with GMA contents of above 1% by weight in the rubbery modifier. However, no hint or suggestion is given in such prior disclosures that other thermoplastic resins, especially glassy resins, can be added to improve properties such as heat resistance.

It has now been surprisingly discovered that thermo¬ plastic polymers having an amorphous glass transition temper¬ ature above about 100°C. can be incorporated in relatively small amounts into thermoplastic polyester compositions comprising glycidyl methacrylate grafted EPDM (EPDM-g-GMA) impact modifiers, and that such compositions will exhibit improved heat resistance as measured conveniently by heat distortion, despite the fact that a major proportion of the composition comprises polyesters having a relatively low glassy transition temperature, e.g., below about 80°C. and especially below about 75°C. At the same time, the advan¬ tageous effect on heat resistance is obtained without dimin¬ ishing significantly the impact strength and knit-line characteristics of such compositions. While not intending to be bound by any particular theory underlying this invention, it is believed that the improved heat resistance of these impact-modified polyester compositions may be due to the reinforcing effect of small regions of glassy polymer in the matrix, offsetting the tend- ency of the polyester, e.g., PET or PBT, to soften at temper¬ atures above their relatively low amorphous glass transition temperatures, which for PET is about 73°C. and for PBT is about 59°C.

SUMMARY OF THE INVENTION In accordance with the present invention are pro¬ vided heat resistant impact modified reinforced thermoplastic compositions comprising:

(a) a high molecular weight thermoplastic poly¬ ester resin having an amorphous glass transition temperature of below about 80°C,

(b) an effective amount of an impact improving rubbery polymer comprising an EPDM terpolymer grafted with glycidyl methacrylate or glycidyl acrylate or a mixture thereof, alone, or grafted in further combination with a C,-C_lfl alkyl methacrylate or acrylate or a mixture thereof; and

(c) a small, effective amount of a heat resistance improving thermoplastic polymer having an amorphous glass transition temperature above about 100°C. Preferred features of the invention are composit- ions as defined above wherein component (a) comprises an amount of from about 30 to about 90 parts by weight, compon¬ ent (b) comprises an amount of from about 10 to about 55 parts by weight and component (c) an amount of from about 0.5 to about 15 parts by weight, based on a total composition of 100 parts by weight of (a), (b) and (c) combined.

Particularly preferred are compositions as defined above wherein component (c) is selected from the group com¬ prising poly(styrene-acrylonitrile) , aromatic poly(sulfone) pol (phenylene ether), aromatic poly(carbonate) or a mixture of any of the foregoing.

DETAILED DESCRIPTION OF THE INVENTION The high-molecular weight linear polyesters used as component (a) in the practice of the present invention are polymeric glycol esters of terephthalic acid and isophthalic acid. They are available commercially or can be prepared by known techniques, such as by the alcoholysis of esters of phthalic acid with a glycol and subsequent polymerization, by heating glycols with free acids or with halide derivatives thereof, and similar processes. These are described in U.S. 2,465,319 and U.S. 3,047,539, and elsewhere.

Although the glycol portion of the polyester can contain from 2 to 10 carbon atoms, it is preferred that it contain from 2 to 4 carbon atoms in the form of linear methylene chains.

Preferred polyesters will be of the family consisting of high molecular weight, polymeric glycol terephthalates or isophthalates having repeating units of the general formula:

wherein n is a whole number of from 2 to 4 , and mixtures of such esters, including copolyesters of terephthalic and iso¬ phthalic acids of up to about 30 mole percent isophthalic units.

Especially preferred polyesters are poly(ethylene terephthalate) and poly(l,4-butylene terephthalate) .

Illustratively, high molecular weight polyesters will have an intrinsic viscosity of at least about 0.7 deci¬ liters/gram and, preferably, at least 0.8 deciliters/gram as measured in a 60:40 phenol-tetrachloroethane mixture at 30°C. At intrinsic viscosities of at least about 1.0 deciliters/ gram, there is a further enhancement of toughness of the present compositions.

Copolyesters useful for the invention are preferably prepared from terephthalic acid and/or isophthalic acid and/or a reactive derivative thereof and one or more glycols, which may be a straight or branched chain aliphatic/cycloaliphatic glycol. Illustratively, the glycol will be ethylene glycol; 2-methyl-l,3-propanediol, 1,4-butanediol; 1,5-pentanediol; 1,6-hexanediol; 1,9-nonanediol; 1,10-decanediol; neopentyl- glycol; 1,4-cyclohexanediol; 1_r4-cyclohexanedimethanol; a mixture of any of the foregoing, or the like. Illustrative of suitable aliphatic dicarboxylic acids for the mixed aromatic/aliphatic embodiments ar suberic, sebacic, azelaic, and adipic acids and the like.

The copolyesters may be prepared by ester inter¬ change in accordance with the standard procedures. The co- polyesters may preferably be derived from at least 50% butylene terephthalate units.

The block copolyesters useful in the composition of this invention are prepared by the reaction of terminally re¬ active poly(l,4-butylene terephthalate), preferably of low molecular weight, and a terminally reactive copolyester or aliphatic polyester or both in the presence of a catalyst for transesterification, such as zinc acetate, manganese acetate, titanium esters, and the like. The terminal groups can com¬ prise hydroxyl, carboxyl, carboalkoxy, and the like, includ- ing reactive derivatives thereof. After initial mixing, polymerization is carried out under standard conditions, e.g., 220° to 280°C, in a high vacuum, e.g., 0.1 to 2 mm Hg, to form the block copolymer of minimum randomization in terms of distribution of chain segments. The result of reaction between two terminally reactive groups, of course, must be an ester linkage. These copolyesters are described in a German Patent application P 27 56 167.7.

The copolyester designated component of these block copolyesters may be terminally reactive segments of copoly- esters as described above. These copolyesters are most pre¬ ferably derived from an aliphatic glycol and a mixture of aromatic and aliphatic dibasic acids in which the mole ratio concentration of aromatic to aliphatic acids is from between 1 to 9 to about 9 to 1, with an especially preferred range being from about 3 to 7 to about 7 to 3.

The terminally reactive aliphatic polyester compon¬ ent of these block copolyesters will contain substantially stoichiometric amounts of the- aliphatic diol and the alipha¬ tic dicarboxylic acid. In addition to their ease of formation by well known procedures, both the aforementioned aromatic/aliphatic copoly¬ esters and aliphatic polyesters are commercially available. One source for such materials is the Ruco Division/Hooker Chemical Company, Hicksville, New York, which designates its compounds as "Rucoflex".

The block copolyesters used in the invention prefer¬ ably comprise from about 95 to about 50 parts by weight based on the block copolyester of. poly(1,4-butylene terephthalate) segments. The pol (1,4-butylene terephthalate) blocks-, before incorporation into the block copolyesters, will preferably have an intrinsic viscosity of about 0.1 dl./g. and, prefer¬ ably, between about 0.1 and about 0.5 dl./g., as measured in a 60:40 mixture of phenol-tetrachloroethane at 30°C. The balance 50 to 5 parts by weight of the copolyester will com- prise blocks of the aforementioned aromatic/aliphatic copolyesters and/or aliphatic polyesters.

As will be understood by those skilled in the art, the poly(l,4-butylene terephthalate) block can be straight chain or branched, e.g., by use of a branching component, e.g., from about 0.05 to about 1 mole percent, based on tere¬ phthalate units of a branching component which contains at least 3 ester-forming groups. This can be a polyol, e.g., pentaerythritol, trimethylol-propane, and the like or a poly- basic acid compound, e.g., trimethyl tri estate, and the like. Blends of the foregoing homopolymers, copolymers and/or block copolymers or derivatives thereof are also use¬ ful for the invention.

The glycidyl ester grafted terpolymer additives used in the rubbery polymeric impact modifier (b) in this invention may be prepared from any of the well known EPDM terpolymer rubbers. EPDM terpolymers useful for preparing the grafted materials used in the invention are commercially available, e.g., Copolymer Corp. (EPSYN* 55) _r or may be pre¬ pared using a Ziegler-type catalyst. The preparation of typical EPDM terpolymers is described, for example, in Gresham et al., U.S. 2,933,480; Tarney, U.S. 3,000,866; Guglielminp et al., U.S. 3,407,158; Gladding, U.S. 3,093,621 and U.S. 3,379,701. These terpolymers are characterized by the absence of chain or backbone unsaturation and the pres- ence of sites of unsaturation in- groups which are pendant to or are in cyclic structures outside of the main polymer chain.

Useful EPDM terpolymers for the production of the glycidyl ether grafted terpolymers used in this invention comprise ethylene, a C, to C-,_g straight or branched chain alpha-olefin, preferably propylene, and a non-conjugated di- olefin. Satisfactory nonconjugated dienes that may be used as the third monomer in the terpolymer include straight chain dienes such as 1,4-hexanediene, cyclic dienes such as cyclo- octadiene and bridged cyclic dienes such as ethylidene norbornene.

Preferred EPDM terpolymers are comprised of about 10-95, preferably 45-70 mole percent, by weight ethylene, about 5 to 90, preferably 30-55 mole percent polypropylene and a minor amount of diene monomer, most preferably a poly- unsaturated bridged ring hydrocarbon or halogenated deriva¬ tive thereof, most preferably 5-ethylidene-2-norbornene. These EPDM terpolymers have a melt ^"index of approximately 79 g/10 in., a Mooney viscosity of approximately 78 and a gram molecular weight of about 21,600.

The backbone rubber is subsequently graft modified with a graft monomer of epoxy functional acrylate or meth¬ acrylate. Although grafting may occur by various reaction mechanisms at practically any point on the backbone rubber, generally, the grafting takes place at an unreacted point of unsaturation on the polyene. For this reason, it is desir¬ able to make use of an ethylene, mono-olefin, polyene back¬ bone rubber having at least two unsaturated carbon-to-carbon linkages per 100 carbon atoms and little additional benefit is derived from the use of unsaturated backbone rubber having more than 20 carbon-to-carbon double bonds per 1000 carbon atoms. In the preferred practice of this invention, use is made of an unsaturated rubber having from 4-10 carbon-to- ^■ carbon double bonds per 1000 carbon atoms. The point of ethylenic unsaturation on the epoxy functional graft monomer must be sufficiently reactive to react directly with the unsaturation of the polyene; or to react with a graft chain originating at, or for combination with, the polyene unsaturation. Such levels of reactivity require the alpha-beta situation of the ethylenic unsatura¬ tion as found in, for example, an epoxy functional esters of acrylic acid or alkyl acrylic acid. A free radical initia¬ tor, such as a dialkyl peroxide may be used to promote the graft reaction. Such initiator is generally used in an amount within the range of 1-5 parts per 100 parts by weight of the unsaturated rubber, and preferably in an amount within the range of 1-2 percent by weight.

Preferred as the graft monomer herein is glycidyl methacrylate (GMA) .

The graft chain formed by the grafting process on the backbone rubber need not be a homopolymer or even be of entirely epoxy functional graft monomers. For example, com¬ binations of the two above-mentioned epoxy functional graft monomers may be used as well as combinations of either or both with other C, -C,_g alkyl acrylates or methacrylates, wherein C,-C,_a may be straight chain or branched, e.g., methyl, ethyl, isopropyl, 2-ethyl-hexyl, decyl, ri-octodecyl, and the like. Particularly useful such comonomer grafts are grafts of glycidyl acrylate and/or glycidyl methacrylate and methyl methacrylate.

It is preferred in the present invention that the gel content of the elastomeric material be controlled either during polymerization or in subsequent processing to achieve a value of greater than about 10% by weight and less than 80%. With a gel content too low impact strength is high, but knit line strength is low. With a gel content too high, both impact strength and knit line strength not as high as desirable.

Gel content in an especially convenient analysis, according to ASTM D-3616, is measured by the weight percent of remaining elastomeric material after extraction in hexane or toluene. Gel content is an indication of the degree of cross-linking in the elastomeric material. Of course, per¬ sons skilled in the art are familiar with a variety of ways to control the degree of cross-linking and thus the gel con¬ tent can be determined by numerous other methods. The cross¬ link reaction may be a direct rubber backbone to rubber back¬ bone joining, an epoxy functionality to epoxy functionality or rubber backbone joining, or a graft chain free radical addition to a second graft chain or to a rubber backbone. Further, cross-linking may be achieved by the addition of a cross-linking agent to effectively achieve any of the above reactions. Thus, any of several steps to control gel content may be taken. Thermal aging will increase gel content. In- creasing the amount of epoxy functional graft monomer will increase gel content. Increasing the amount of polyene mono- ene monomer in the rubber backbone will increase gel content. The addition of a cross-linking agent will increase gel con¬ tent. The use of graft monomers with greater tendency to cross-link will increase gel content, for example, a homo- polymer graft of glycidyl acrylate will cross-link more readily than a homopolymer graft of glycidyl methacrylate or a copolymer graft of glycidyl acrylate and methyl meth¬ acrylate. As stated above, gel content of the elastomeric material used in this invention should range up to no higher than about 80%. Although cross-linking can be carried on well past this level, as has been mentioned, high levels of cross-linking diminish the dispersibility of the elastomeric material and lead to non-uniform mixing. Also, such high levels of localized cross-linking will create brittle areas within the elastomeric material which will decrease rubbery character. It is apparent that cross-linking should be uni¬ formly dispersed throughout the elastomeric material. It is preferred in the present invention that the elastomeric material have an epoxy functionality of at least 2.5 epoxy functionalities per 1000 carbon atoms, and prefer¬ ably between about 5.0 and 13 epoxy functionalities per 1000 carbon atoms. Epoxy functionality means those epoxy sites which remain in the impact modifier resin after the loss of such functionalities as may react in the cross-linking reac¬ tion. In the instance of the use of GMA or GA as the epoxy functional graft monomer, a graft level of above about 1.0%, preferably above about 1.5%, and most preferably, above about 2% by weight is necessary to provide the minimum level of epoxy as shown above. The maximum is not particularly criti¬ cal, e.g., up to 10-15% by weight can be used, although no particular advantage is achieved above about 10% by weight.

The grafting reaction may be carried out in solvent solution with the unsaturated rubber backbone present in a concentration which may range from 10-30 percent by weight, with constant stirring, at an elevated temperature within the range of 125-200°C. for a time ranging from 1/2 to 2 hours. The reaction condition can be varied depending somewhat upon the type and amount of catalyst and temperature conditions, - as is well known to those skilled in the art. Where high amounts of graft monomer are to be attached to the backbone rubber, it has been found to be advantageous to carry out the graft reaction in the melt state of the backbone rubber, i.e., extruder grafting. This process is simply performed by feed¬ ing the backbone rubber, an excess of graft monomer, and an appropriate catalyst to a melt extruder and mixing and react¬ ing the feed components at an elevated temperature.

The heat resistance improving thermoplastic polymers useful as component (c) in the practice of this invention comprise a range of materials that are well known to those skilled in this art. Generally these heat resistance improv¬ ing polymers, also known as "glassy" polymers, have amorphous glass transition temperatures preferably above about 100°C, more preferably above about 110°C. Suitable as component (c) are such polymers including but not limited to polyphenylene oxides alone, or in combination with styrene resins, amorphous polyamides, polyamide-imides, polyaryl ethers, polycarbonates, polyetherimides, polyimides, styrene copolymers such as styrene-acrylonitrile (SAN), polysulfones, and thermoplastic polyurethanes. Especially preferred are SAN copolymers, polysulfones, pol (polyphenylene ethers) and polycarbonates available respectively under the tradenames TY IL*880 (Dow Chemical), UDEL* 2100 (Union Carbide), PPO* and LEXAN*131 (General Electric Company) . The glass transition tempera- tures (Tg) for these preferred glassy polymers are all above 100°C, e.g., Poly-SAN, 110°C; polysulfone, 190°C; poly- (phenylene ether), 110-135°C; and poly(bisphenol A carbon¬ ate), 150°C. Unsuitable as component (c) herein are crystal- line polymers such as crystalline nylons and crystalline poly(phenylene sulfides) . Also unsuitable polymers include acrylics, polyacrylonitrile (PAN), polystyrenes, styrene- methyl-methacrylate copolymers, and polyvinyl chloride poly¬ mers and copolymers. The latter all have amorphous glass transition temperatures of below about 100°C. and will not be suitable.

In general, the quantity of the glassy polymer com¬ ponent (c) will not be substantial in comparison to the rest of components (a) and (b). Typically, only a heat resistance improving amount of the glassy polymer is required. Generally, the polyester component (a) will comprise an amount of from about 30 to about 90 parts by weight, the rubbery polymer of component (b) will comprise an amount of from about 10 to about 55 parts by weight, and component (c) will comprise an amount of from about 0.5 to about 15 preferably 1 to 10 parts by weight, based on a total composition of 100 parts by weight of (a), (b) and (c) combined. In certain embodiments of this invention, the rubbery polymer of component (b) may comprise a "preblend" of EPDM grafted with glycidyl methacrylate and the -polyester resin, e.g., PBT in a ratio of from about 1:1 to about 10:1 of the impact modifier to the polyester. As will be exemplifed in the next section, this impact modifying "pre¬ blend" can comprise EPDM-g-GMA and PBT in a ratio of 3:1 respectively. The above described elastomeric material is physical¬ ly dispersed in a thermoplastic polymer melt to form discrete particles of rubbery polymer in a continuous phase of a thermo¬ plastic matrix resin or blend. At least an impact strength improving amount of elastomeric material is dispersed in the matrix resin. Generally, this requires that the elastomeric material constitute at least 1.5 percent by weight, preferably 3-5 to 80 percent, most preferably 10 to 55 percent, by weight based on total thermoplastic content, including elastomeric material, of the molding composition. It will be apparent that, while the indicated composition range is optimum for making toughened rigid plastic articles, acceptable molding materials can still be made from mixtures with rubber con¬ tents much higher than this range. Thermoplastic elastomer type molding compounds are produced when the elastomer con- tent exceeds 55 weight percent, and even mixtures above the phase inversion composition, i.e., those in which the thermo¬ plastic resin phase is sem^όr noncontinuously interdispersed in a rubbery polymer matrix can be used to make flexible molded articles with excellent properties. 80 weight percent elastomer is a typical upper limit. Compounding of the rubber, thermoplastic resin and reinforcing agent is carried out by standard techniques, for ^'example, by simple melt blending or dry mixing and melt extruding at an appropriate elevated temperature for any given thermoplastic matrix. The resultant admixture is then molded into a thermoplastic piece of specific dimensions or further extruded into a film or sheet product.

It is important to the final properties of molded parts containing elastomeric material that there is suffici- ent mixing in the extrusion of the resin melt. Herein, several reactions have been taught or suggested to take place in the extruder and such are, of course, effected by mixing as well as residence time in the extruder. Thus, thorough mixing of the polymer melt is suggested and, depending upon the equipment employed, two successive extrusions of the melt may be required.

As has been mentioned, in preferred compositions the particle size of the rubber grafted with glycidyl esters will be selected to provide that at least 60 weight percent of such particles, and preferably more than 70 weight percent of them are greater than 1 micron in diameter. Such composi¬ tions combine optimum notched Izod impact strength, with knit-line strength, and these are vastly superior to those obtained with compositions wherein, for example, only about 50 weight percent of the particles exceed 1 micron in dia¬ meter. Particle size can be measured in any of the ways known in this art, but an especially convenient way is to use a computerized particle size analyzer to measure photomicro¬ graphs of scanning electron microscopy (SEM) images. Compounding can be carried out in conventional • equipment. For example, after pre-drying the thermoplastic polyester resin, e.g., at 125°C. for 4 hours, a single screw extruder is fed with a dry blend of the polyester, glassy polymer and the additive ingredients, e.g., antioxidant and/ or stabilizer, the screw employed having a long transition and metering section to insure melting. On the other hand, a twin screw extrusion machine, e.g., a 28 mm or 30 mm or even 90 mm Werner Pfleiderer machine can be fed with resin and additives at the feed port. In either case, a generally suitable machine temperature will be about 450°F. to 570°F. The compounded composition can be extruded and cut up into molding components such as conventional granules, pellets, etc., by standard techniques.

The compositions of this invention can be molded in any equipment conventionally used for thermoplastic composi¬ tions. For example, with poly(l,4-butylene terephthalate) good results will be obtained in an injection molding machine, e.g., of the Newbury type or a Cincinnati 75 ton type with conventional cylinder temperature, e.g., 450°F. and conven- . tional mold temperatures, e.g., 150°F.

It is to be understood that the foregoing composi¬ tions may contain other additives known in the art, includ¬ ing, but without limitation, mold release agents, flow pro¬ moters, antioxidants , coloring agents, coupling agents, and stabilizers including transesterification stabilizers. The elastomeric containing molding compositions of this invention may be used as molding pellets and may contain pigments, dyes, stabilizers, plasticizers, and the like. One may readily determine which are necessary and suitable for a particular application.

DESCRIPTION OF TEE PREFERRED EMBODIMENTS The following examples illustrate the preferred in¬ vention. The claims are not to be construed to be limited by them in any manner whatsoever. EXAMPLES 1-3

Impact modified PBT compositions in accordance with the present invention were blended and suitable workpieces were molded for testing. The impact modifier was used as a 75/25 w/w concentrate in PBT. Blends were tumble-mixed and extruded on a WP-30 twin screw extruder. The materials were subsequently dried and molded on a 75 ton Cincinnati injec¬ tion molding machine. Compositions and results are set forth in Table 1.

TABLE 1: Thermoplastic Compositions PBT/ EPDM-g-GMA Terpolymers/Glassy Polymers

Example 1A* _1 _2 3_

Composition (parts by weight)

Poly(l,4-butylene terephthalate)³ 82.75 78 78 78

EPDM-g-GMA^b 17.25 EPDM-g-GMA^C 18 18 18

Poly(styrene-acrylonitrile) 4 — — —

Polysulfohe^e — — 4

Poly(bisphenol A carbonate)^f — — — 4

Hindered Phenol Antioxidant . 0.3 0.3 0.3 Hindered Phenol Antioxidant/ . — — — (0.3/

Stabilizer 0.95)

1.25

Notched Izod, ft.lb./in. 15.5 14.5 12.4 13.8

Unnotched Izod, ft.lb./in. 21.3 16.1 21.7 31.1 TABLE 1 : ( CONTINUED )

Heat Distortion Temperature

66 psi, °C 95 134 136 127

°F 203 273 277 261 * Control a VALOX*315, General Electric Company b Prepared from Copolymber Rubber Co. EPSYN*4906 EPDM rubber and glycidyl methacrylate using dicu yl peroxide initia¬ tor, 6.4% GMA content. c Prepared from Copolymber Rubber Co. EPSYN*55 EPDM rubber and glycidyl methacrylate using 2 ,5-dimethyl-2 ,5-di( t- butyl peroxy) hexane initiator, 7.5% GMA content, d TYRIL*880, Dow Chemical Company e UDEL*2100, Union Carbide Company f LEXAN*131, General Electric Company

The results above indicate that the heat resistance of EPDM-g-GMA impact modified polyester compositions is im¬ proved with the addition of a glassy polymer in accordance with this invention. The above patents, applications and/or publications are incorporated herein by reference.

Many variations will suggest themselves to those skilled in the art in light of the above, detailed descrip¬ tion. For example, instead of using poly( 1 ,4-butylene tere- phthalate) as component (a) , other polyester resins can be used, such as poly( ethylene terephthalate) or copolyesters derived from one or more aliphatic and/or aromatic dicarboxy- lic acids and one or more straight or branched chain alipha¬ tic or cycloaliphatic glycols including random or block copolyesters. Instead of injection molding, blow molding, including injection blow molding can be used. Instead of glycidyl methacrylate, a mixture of glycidyl methacrylate and methyl methacrylate, a mixture of glycidyl acrylate and methyl methacrylate or a mixture of glycidyl methacrylate and octadecyl methacrylate can be used. Instead of poly- (styrene-acrylonitrile) , polysulfone or polycarbonate as glassy polymers, other thermoplastic polymers such as poly- (2,6-dimethyl-l,4-phenylene ether) resin can be added in effective amounts to improve heat resistance. Furthermore, other additives known to those skilled in the art may be added in conventional amounts to the impact modified composi¬ tions herein including but without limitation, antioxidants, nucleating agents, mold release agents, flow promoters, coloring agents, flame retardants, coupling agents and stabilizers.

All such obvious variations are within the full intended scope of the appended claims.

Claims

CLAIMS :

1. A heat resistant impact-modified thermoplastic composition comprising:

(a) a high molecular weight thermoplastic polyester resin having an amorphous glass transition temper¬ ature of below about 80°C;

(b) an effective amount of an impact improving rubbery polymer comprising an EPDM terpolymer grafted with glycidyl methacrylate or glycidyl acrylate or a mixture thereof, alone, or grafted in further combination with .a C,-C,g alkyl methacrylate or acrylate or a mixture thereof; and

(c) a small, effective amount of a heat resis¬ tance improving thermoplastic polymer having an amorphous

^'glass transition temperature above about 100°C.

2. A composition as defined in Claim 1 wherein the amorphous glass transition temperature of component (c) is above about 110°C.

3. A composition as defined in Claim 1 wherein said polyester is selected from the group comprising poly- (1,4-butylene terephthalate), pol (ethylene terephthalate), copolyesters or any combination thereof.

4. A composition as defined in Claim 1 wherein said polyester is poly(1,4-butylene terephthalate).

5. A composition as defined in Claim 1 wherein the thermoplastic polyester resin (a) is a copolyester derived from one or more aliphatic and/or aromatic dicarboxylic acids and one or more straight or branched chain aliphatic or cycloaliphatic glycols.

6. A composition as defined in Claim 3 wherein the copolyester is a random copolyester.

7. A composition as defined in Claim 3 wherein the copolyester is a block copolyester.

8. A composition as defined in Claim 3 wherein the thermoplastic polyester resin (a) is a polyblend of poly(l,4- butylene terephthalate) and poly(ethylene terephthalate) .

9. A composition as defined in Claim 1 wherein the grafted EPDM terpolymer is derived from approximately 45 to 70 mole percent ethylene, approximately 30-55 mole percent propylene and a minor amount of 5-ethylidene-2-norbornene.

10. A composition as defined in Claim 1 wherein the EPDM-glycidyl ester grafted terpolymer is present in an amount of approximately 1.5 to 80 percent by weight based on the total composition.

11. A composition as defined in Claim 1 wherein the grafted EPDM terpolymer is present in an amount of approximately 10 to 55 percent by weight based on the total composition.

12. A composition as defined in Claim 4 wherein component (b) comprises a preblend of EPDM grafted with glycidyl methacrylate and poly(l,4-butylene terephthalate) in a ratio of from about 1:1 to about 10:1 of the former to the latte .

13. A composition as defined in claim 1 wherein said heat resistance improving thermoplastic polymer (c) is selected from the group comprising poly(styrene-acrylo¬ nitrile) , aromatic poly(sulfone) , poly(phenylene ether), aromatic pol (carbonate) or a mixture of any of the foregoing.

14. A composition as defined in Claim 1 wherein said component (a) comprises an amount of from about 30 to about 90 parts by weight, component (b) comprises an amount of from about 10 to about 55 parts by weight, and component (c) an amount of from about 0.5 to about 15 parts by weight, based on a total composition of 100 parts b weight of (a), (b) and (c) combined.

15. A process for producing impact modified heat resistant thermoplastic molding composition comprising melt blending:

(b) an effective amount of an impact improv¬ ing amount of a rubbery polymer comprising an EPDM terpolymer grafted with 2% or more by weight based on said terpolymer of glycidyl methacrylate or glycidyl acrylate or a mixture thereof, alone, or grafted in further combination with a C,-C,_g alkyl methacrylate or acrylate or a mixture thereof; and

(c) a small, effective amount of a heat resistance improving thermoplastic polymer having an amorphous glass transition temperature above about 100°C.

16. A process as defined in Claim 15 wherein the amorphous glass transition temperature of component (c) is above about 110°C.

17. A process as defined in Claim 15 wherein said polyester is selected from the group comprising poly(l,4- butylene terephthalate), poly(ethylene terephthalate), copolyesters or any combination thereof.

18. A process as defined in Claim 17 wherein said polyester is polyd,4-butylene terephthalate).

19. A process as defined in Claim 1 wherein the grafted EPDM terpolymer is derived from approximately 45 to 70 mole percent ethylene, approximately 30-55 mole percent propylene and a minor amount of 5-ethylidene-2-norbornene«

20. A process as defined in Claim 1 wherein the EPDM-glycidyl ester grafted terpolymer is present in an amount of approximately 1.5 to 80 percent by weight based on the total composition.

21. A process as defined in Claim 15 wherein the grafted EPDM terpolymer is present in an amount of approx¬ imately 10 to 55 percent by weight based on the total composition.

22. A process as defined in Claim 15 wherein com¬ ponent (b) comprises a preblend of EPDM grafted with glycidyl methacrylate and poly(l,4-butylene terephthalate) in a ratio of from about 1:1 to about 10:1 of the former to the latter.

23. A process as defined in Claim 15 wherein said heat resistance improving thermoplastic polymer (c) is selected from the group comprising poly(styrene-acrylo¬ nitrile) , aromatic poly(sulfone) , poly(phenylene ether) , aromatic poly(carbonate) or a mixture of any of the foregoing.

24. A process as defined in Claim 15 wherein com¬ ponent (a) comprises an amount of from about 30 to about 90 parts by weight, component (b) comprises an amount of from about 10 to about 55 parts by weight and component (c) com¬ prises from about 0.5 to about 15 parts by weight, based on a total composition of 100 parts by weight of (a), (b) and (c) combined.

25. An article of manufacture thermoformed from an impact modified thermoplastic composition as defined in Claim 1.