POLYESTER COMPOSITIONS CONTAINING AN IMPACT MODIFIER Field of the Invention This invention pertains to certain, novel polyester compositions which exhibit improved toughness. More specifically, this invention pertains to novel polyester compositions comprising (i) at least one polyester containing diol residues comprising ethylene glycol residues and diacid residues comprising terephthalic acid residues, 2,6-naphthalenedicarboxylic acid resides or a mixture thereof, and containing antimony residues; (ii) certain epoxy-containing impact modifiers and (iii) at least one phosphorus compound or residues of at least one phosphorus compound.

Background of the Invention Polyesters such as poly (ethyiene terephthalate) (PET) are engineering thermoplastics used in a wide variety of end use applications such as fibers, films, automotive parts, food and beverage containers and the like. They can be processed by a variety of techniques including injection molding, compression molding, extrusion, thermoforming, blow molding, and combinations thereof. Sometimes, it is desirable to add impact modifiers to improve the toughness of polyesters used in the manufacture of molded parts such as those used in automotive, appliance, cookware or food storage applications. U. S. Patent 4,172,859 discloses that polymeric materials that serve well as impact modifiers should (i) possess a modulus 1/10 that of the polyester matrix material, (ii) be well dispersed within the matrix material in discrete phases of 0.01 micron to 3.0 micron in size, and (iii) be well bonded to the matrix.

Low modulus polymers commonly used as impact modifiers fall into several general classes. The first class comprises rubbers based on butadiene or isoprene, e. g., polybutadiene, polyisoprene, natural rubber,

styrene-butadiene (SBR) j acrylonytrile-butadiene (ABN or nitrile rubber), styrene-butatene-styrene (SBS) or hydrogenated SBS (styrene-ethylene- butene-styrene) block copolymers (SEBS), or acrylonytrile-butadiene- styrene (ABS) polymers containing high levels of butadiene. Butadiene- based rubbers generally have lower glass transition temperatures (Tg's) which help to improve low temperature toughness, but they may not be stable under the high temperatures at which polyesters are processed. The second major class of impact modifiers comprise elastomers based on polyethylene, e. g., ethylene-propylene rubbers (EPR) or EPRs with a small amount of side chain diene moiety (EPDM), ethylene-acrylate copolymers such as ethylene/methyl acrylate, ethylene/ethyl acrylate, ethylene/butyl acrylate and ethylene/methylacrylate/glycidyl methacrylate, or ethylene- vinyl acetate copolymers (EVA). A third group of impact modifiers consists of core-shell impact modifiers such as those that contain a poly (methyl methacrylate) (PMMA) hard shell with either a butadiene methcrylate- butadiene-styrene (MBS) or butyl acrylate (acrylic) core, e. g., PARALOID manufactured by Rohm & Haas Company. Core-shell impact modifiers based on ABS (acrylonitrile-butadiene-styrene) also are commercially available, e. g., BLENDEX manufactured by GE Specialty Chemicals).

Other elastomers that may serve as impact modifiers include polyesters, e. g., HYTRELI manufactured by E. I. duPont de Nemours Company and ECDEL manufactured by Eastman Chemical Company, and polyurethanes, e. g., PELLETHANE manufactured by Dow Chemical Company, or silicone rubbers.

By properly matching the melt viscosities of the matrix and impact modifier at the temperatures of melt processing, a fine discrete impact modifier phase can be created by the shearing forces obtained during melt processing. A mixing screw must be designed properly to create the appropriate shear fields during a compounding/extrusion process.

However, impact modifiers dispersed by purely mechanical action may re- coalesce during a later stage of processing where shear may be reduced.

Alternatively, impact modifiers can be manufactured to an inherently small size using latex or other polymerization processes. Impact modifiers manufactured in this way often contain a stiff shell of harder polymer and are, therefore, often referred to as core-shell impact modifiers. These impact modifiers can be made in 0.2-0.5 micron sizes ideally suited for impact modification of nylons, polycarbonates and polyesters. Nonetheless, these core-shell impact modifiers also must be dispersed by shearing action during melt processing, and are prone to re-coalesce during later stages of molding or compounding.

The introduction of functional groups into the impact modifier that either are highly soluble in the matrix polymer or will react with the matrix polymer is one means of enhancing dispersion and preventing coalescence. Interaction between these functional groups and the matrix during compounding creates a thin interlayer of material that make the impact modifier and matrix more energetically compatible. Compatibility related to these functional groups leads to good mixing and good dispersion of the impact modifier. The enhanced compatibility also will reduce the possibility that the impact modifier phases will re-coalesce later during processing. Therefore, impact modifiers containing functional groups that react rapidly with the matrix polymer produce well-dispersed impact modifier phases of small particle size See"Rubber Toughened Engineering Plastics", A. A. Coller, Chapman & Hall, London, 1994]. The incorporation of functional groups into the impact modifier also will ensure a good bond between the impact modifier and matrix, i. e. interfacial adhesion between these immiscible phases.

Impact modifiers can be functionalized with a variety of reactive or non-reactive monomers. These functional monomers can be incorporated into the impact modifier directly during preparation of the impact modifier or

subsequently by means of a grafting polymerization step. Non-reactive impact modifiers (for example an EPDM-grafted-SAN) compatibilize themselves to the matrix through a closer matching of solubility parameters, without actually bonding to the matrix polymer. The reactive groups of reactive impact modifiers chemically bond to the matrix polymer but, to be effective, they must do so in the limited time available in the extruder during compounding.

U. S. Patent 4,172,859 lists a variety of functional groups which can be grafted or copolymerized onto ethylene-based elastomers for use with polyesters and nylons. In practice, maleic anhydride (MAH) functionalized impact modifiers work well for nylons, and there are many commercial products available, e. g., EPR-MAH, EVA-MAH, and SEBS-MAH. However, the reaction between maleic anhydride and polyesters is not fast enough for significant compatibilization in the timescales encountered during normal compounding. A functional group that reacts particularly well with polyesters is the monosubstituted oxirane, or epoxy, group such as is present in glycidyl methacrylate (GMA), glycidyl acrylate, allyl glycidyl ether, and 3,4-epoxy-1-butene (EpB). This patent describes thermoplastic compositions comprising blends of polyesters and epoxy-functionalized, random ethylene copolymers.

The following patent documents also describe polyester compositions which contain epoxy-containing, ethylene-based polymeric materials. U. S. Patent 4,284,540 describes the use of ethylene/GMA copolymers as a toughening agent for polyesters when combined with 0.1 to 5 weight percent of an added barium catalyst. U. S. Patent 4,753,980 discloses that polyester compositions containing 3-40 weight percent of either ethylene/ethyl acrylate/GMA terpolymer or ethylene/butyl acrylate/GMA terpolymer superior possess low temperature toughness when compared to analogous polyester compositions which contain an ethylene/methyl acrylate/GMA terpolymer.

U. S. Patents 5,098,953,5,086,119,5,086,118,5,086,116, and 5,068,283 disclose that the toughness of polyester compositions containing ethylene/GMA copolymers or ethylene/alkyl acrylate/GMA terpolymers can be improved by adding a functional crosslinking agent in the compositions.

The functional crosslinking agent contains, in one molecule, at least two functional groups having reactivity with epoxy group, carboxyl group or hydroxyl group.

U. S. Patent 5,206,291 describes compositions comprising a polyester containing 1,4-cyclohexanedimethanol residues and an ethylene/GMA copolymer. U. S. Patent 5,436,296 discloses that an ethylene/GMA copolymer may be used to compatibilize blends of polyethylene and polyester. European Patent Publication EP 481,471 B1 and Penco et al., Journal of Applied Polymer Science, 57,329 (1995) disclose compositions comprising a polyester, a linear low density polyethylene, an ethylene/ethyl acrylate/GMA terpolymer and 0.5% to 1 % of an amine for the opening of an epoxy ring.

U. S. Patents 5,483,001,5,407,999, and 5,208,292 and Die Angewandte Makromolekulare Chemie, p. 89, disclose polyester _ compositions having improved toughness which contain an ethylene/alkyl acrylate/GMA terpolymer, an ethylene/alkyl acrylate/maleic anhydride terpolymer, and a catalyst such as dimethylstearylamine which accelerates the reaction between the functional groups of the two terpolymers. U. S.

Patent 5,652,306 and European Patent Publication EP 737,715 A2 disclose polyester compositions containing MBS or acrylic-type core-shell impact modifiers and small amounts of ethylene/alkyl acrylate/GMA terpolymers.

While several of the preceding patents discuss the use of added catalysts to promote a reaction between epoxy-containing ethylene polymers and polyesters, in none of these patents is there any direct disclosure that the toughness of the blend is affected by the presence of residues of catalysts used in the preparation of the polyester. Polyesters

typically are prepared using metal catalysts that remain in the polyester product. Examples of these catalysts include organic and inorganic compounds of arsenic, cobalt, tin, antimony, zinc, titanium, magnesium, gallium, germanium, sodium, lithium and the like. Antimony compounds frequently are used in the preparation of PET.

There is reference in U. S. Patent 4,284,540 and in Stewart et al.

Polymer Engineering and Science., 33 (11), 675 (1993), that certain residual catalysts present in PET can significantly affect the rate of reaction of epoxy functional polymers with PET. U. S. 4,284,540 notes that, among the above mentioned residual polyester polymerization catalysts, antimony catalyst residues are preferred for promoting the reaction between polyester and an epoxy group. The patent does not, however, provide any toughness data related to the presence of these catalyst residues. Stewart et al. quantified the rate of reaction between PET and a copolymer of ethylene and glycidyl methacrylate (E/GMA) by monitoring the rise in torque of a mixture of these two components in an instrumented mixing bowl (also known as a torque rheometer). According to Stewart et al., torque rheometry provides a simple and straightforward method for monitoring the viscosity of polymer blends as a function of blending time. The rheometer continuously measures the torque required to turn the rotor blades that shear and mix the sample within the mixing bowl. For a given material and set of processing conditions, the torque measured is approximately a linear function of the viscosity of the sample. Any change in viscosity with time is in turn related to such effects as changes in molecular weight of the sample (for example, an increase due to a reaction or a decrease due to degradation) or the formation of grafts, branches or crosslinks in the sample. The work by Stewart et al. shows that mixtures of E/GMA with PET containing antimony catalyst residues gave rise to significant increases in torque with mixing time. This led to the conclusion that PET containing antimony catalyst residues accelerated the reaction between the PET and

the E/GMA. PET containing residual antimony catalyst was found to produce a more rapid increase in torque than PET containing other residual catalysts. It is often implied by those knowledgeable in the art that a rapid reaction between the E/GMA and the PET containing residual antimony catalyst should lead to better dispersion of the E/GMA (i. e., a smaller particle size) and better bond to the PET. This superior dispersion should, in turn, lead to improved toughness in the resultant blend. Furthermore, since the PET containing residual antimony catalyst reacts faster than the PET containing other catalysts, it is implied that the use of PET containing antimony catalyst residues should lead to tougher blends with epoxy containing ethylene copolymers.

Contrary to the teachings of the prior art discussed above, we have discovered that the toughness of blends of polyesters with epoxy-containing ethylene polymers is strongly affected by the presence of residues of catalysts used in the manufacture of the polyesters. Indeed, when epoxy- containing ethylene polymers are blended with polyesters containing antimony catalyst residues, the resulting polyester composition exhibits surprisingly low toughness values. Nonetheless, it has been found that superior toughness values are obtained when a phosphorus compound is added to this blend during compounding. Although we do not wish to be bound by any technical theories, it is believed that the antimony catalyst residues present in a polyester accelerates an epoxy-epoxy reaction within the epoxy-containing ethylene copolymer. For example, subsequent work using the same mixing bowl experiment as performed by Stewart et al. has shown that a similar increase in torque with time can be obtained when antimony acetate is added directly into an epoxy-containing copolymer with no PET present. The resultant epoxy-containing ethylene copolymer is highly crosslinked, suggesting that the catalyst is highly active in promoting reactions within the impact modifier itself. Transmission electron microscope images of blends of antimony-catalyzed PET with epoxy-

containing ethylene copolymers show that the impact modifier has formed into large phases, many greater than 1 micron in size. These phases are too large to produce maximum toughness in the PET. It is believed that the phosphorus compound deactivates the residual antimony catalyst, disabling the epoxy-epoxy reaction and allowing the epoxy-PET reaction.

The following patents address the use of phosphorus compounds in polyesters. None of these patents address the use of these compounds to control the morphology of epoxy-containing ethylene polymers when in the presence of residues of catalysts used in the manufacture of the polyesters so to maximize the toughness of the resultant blends.

U. S. Patent 4,845,169 describes a thermoplastic blend of PET, a polyester elastomer, and 2 to 6 weight percent of an alkyl-aryl phosphite to allow grafting between the two polyesters. We have found this amount of phosphite to be excessive and detrimental to the toughness of our systems.

U. S. Patent 5,194,468 discloses the use of a mixture of two aromatic phosphites to transesterify a polyester elastomer to another polyester and improve compatibility to a high density polyethylene.

U. S. Patent 5,411,999 discloses compositions comprising a polycarbonate, an epoxy-functionatized polyester, a rubbery impact modifier and a catalyst quencher such as sodium dihydrogen phosphate to inhibit transesterification between the polycarbonate and the polyester. Sodium acid pyrophosphate gave the best hydrolytic stability. An alkyl phosphite was found to give very poor hydrolytic stability. U. S. Patent 5,541,244 teaches that certain phosphates, in particular zinc dihydrogen phosphate, are good transesterification inhibitors that"do not negatively influence the impact strength"of a mixture of two polyesters. No impact modifiers containing an epoxide functionality are disclosed.

None of these patents discuss the use of a phosphorus compound to improve the toughness of a polyester blended with an epoxy-containing ethylene polymer.

Brief Summary of the Invention It now has been discovered that compositions comprising certain polyesters containing antimony residues and certain epoxy-containing impact modifiers exhibit improved toughness when a phosphorus compound is included in the compositions. The polyester utilized typically contains up to about 400 parts per million by weight (ppmw) antimony metal, e. g., antimony residues resulting from the use of an antimony catalyst in the manufacture of the polyester. The polyester compositions provided by the present invention comprise: I. about 75 to 98 weight percent of a thermoplastic polyester comprised of: (A) diacid residues comprising at least 85 mole percent terephthalic acid residues, 2,6-napthalenedicarboxylic acid residues or a mixture of terephthalic acid and 2,6-naph- thalenedicarboxylic acid residues; (B) diol residues comprising at least 85 mole percent ethylene glycol residues; and _ (C) at least 50 parts per million by weight (ppmw) of antimony metal; II. about 25 to 2 weight percent of an impact modifying polymer comprised of about 0.5 to 15 weight percent of epoxy-containing residues derived from monomers selected from glycidyl methacrylate, glycidyl acrylate, allyl gycidyl ether, 3,4-epoxy-1- butene, or a mixture of any two or more of such monomers; and III. a phosphorus compound ; wherein the amount of phosphorus compound present gives a P: Sb atomic ratio of 1: 1 or greater and the weight percentages are based on the total weight of components I and 11.

Detailed Description of the Invention The polyester component of our novel compositions are commercially available and/or may be prepared by batch or continuous processes using conventional melt phase or solid state condensation procedures well known in the art. Also, the polyester component may be obtained from post consumer waste, e. g., recycled polyester. Polyesters useful in the present invention are comprised of diacid residues comprising at least 85 mole percent terephthalic acid residues, 2,6-napthalenedicar- boxylic acid residues or a mixture of terephthalic acid and 2,6-naphthalene- dicarboxylic acid residues; (B) diol residues comprising at least 85 mole percent ethylene glycol residues; and (C) at least 50 ppmw of antimony metal wherein the polyester is made up of 100 mole percent diacid residues and 100 mole percent diol residues. Up to 15 mole percent of the diacid component of the polyesters may be derived from diacids other than terephthalic and 2,6-napthalenedicarboxylic acid residues. For example, up to 15 mole percent of the diacid residues may be residues derived from dicarboxylic acids containing about 4 to about 40 carbon atoms such as succinic, glutaric, adipic, pimelic, suberic, azelic, sebacic, terephthalic, isophthalic, sulfodibenzoic, sulphoisophthalic, maleic, fumaric, 1,4-cyclo- hexanedicarboxylic (cis-, trans-, or cis/trans mixtures), and the like. The diacid residues may be derived from the dicaroxylic acids, esters and acid chlorides thereof, and, in some cases, anhydrides thereof.

Similarly, up to 15 mole percent of the diol residues may be derived from diols other than ethylene glycol. Examples of other diols which may be used in the preparation of the polyester component include those containing 3 to about 10 carbon atoms such as propylene glycol, 1,3-pro- panediol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, neopentyl glycol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, diethylene glycol, 1,4-cyclohexane- dimethanol (cis, trans, or cis/trans mixtures) and the like. Small amounts, e. g., up to 2 mole percent, of a branching agent such as trimellitic

anhydride, pyromeliitic dianhydride, glyceroi, pentaerythritol, polyvinyl alcool, styrene-maleic anhydride (SMA) and the like may be may be included in the polyester if desired.

The polyester component of the compositions of the present invention should have an inherent viscosity (IV) in the range of about 0.4 to about 1.4 dL/g, preferably about 0.55 to 0.95 dL/g, measured at 25°C using 0.50 g of polyester per 100 mL of a solvent consisting of 60 weight percent phenol and 40 weight percent tetrachloroethane. The polyester component preferably is unmodified PET having an IV of about 0.55 to 0.95 dL/g.

The polyester component of our novel compositions contains at least 50 ppmw of antimony metal, typically about 50 to 400 ppmw Sb and preferably about 100 to 300 ppmw Sb. The antimony metal may be introduced to the polyester by using an antimony compound, e. g., antimony acetate or oxide, as a catalyst in the preparation of the polyester. It is also possible to introduce the antimony into the polyester subsequent to the preparation of the polyester.

The second component of the compositions of the present invention is an impact modifying polymer comprised of about 0.5 to 20 weight percent of epoxy-containing residues derived from monomers selected from glycidyl methacrylate, glycidyl acrylate, allyl gycidyl ether, 3,4-epoxy-1-butene, or a mixture of any two or more of such monomers. These epoxy-containing monomers may be introduced into the impact modifier during polymerization, or they may be subsequently grafted onto the impact modifier. Such epoxy-containing, impact modifier polymers are well known in the art and are available from a plurality of manufactures.

Impact modifiers that may be modified with a functional epoxy group include, but are not restricted to, polyethylene; polypropylene; polybutene; ethylene based copolymers and terpolymers containing vinyl acetate, alkyl acrylate, alkyl methacrylate where the alkyl group could be methyl, ethyl, butyl or ethylhexyl; ethylene-propylene copolymers (EPR); ethylene-

propylene-diene (EPDM); natural rubber; polybutadiene; polyisoprene; acrylonitrile-butadiene (nitrile rubber); styrene-butadiene (SBR); styrene- butadiene-styrene (SBS); styrene-ethylene-butene-styrene (SEBS); acrylonitrile-butadiene-styrene (ABS); methyl methacrylate-butyl acrylate (acrylic core-shell); methyl methacrylate-butadiene-styrene (MBS core- shell); organic silicone rubbers; elastomeric fluorohydrocarbons; elastomeric polyesters; polyurethanes; or combinations thereof. Of these materials, those based on polyethylene are preferred.

Preferred epoxy-containing impact modifiers include copolymers and terpolymers having the respective general formulas E/Y and E/X/Y wherein: X represents residues derived from wherein R'is alkyl of up to about 8 carbon atoms, preferably alkyl of 1 to 4 carbon atoms, and R2 is hydrogen, methyl or ethyl, preferably hydrogen or methyl, and X constitutes about 10 to 40 weight percent, preferably 15 to 35 weight percent, and most preferably 20 to 35 weight percent, of terpolymer E/X/Y; Y represents residues derived from glycidyl methacrylate, glycidyl acrylate, allyl glycidyl ether and 3,4-epoxy-1-butene which constitute about 0.5 to 20 weight percent, preferably about 2 to 10 weight percent, of copolymer E/Y and terpolymer E/X/Y; and E represents ethylene residues that constitute the remainder of the composition.

Of these, copolymers based on ethylene-GMA (E/GMA) containing about 2 to 10 weight percent GMA residues, and terpolymers based on ethylene-methyl acrylate-GMA, ethylene-ethyl acrylate-GMA and ethylene- butyl acrylate-GMA containing about 20 to 35 weight percent alkyl acrylate residues and about 2 to 10 weight percent GMA residues are particularly preferred. The concentration of the epoxy-containing impact modifiers in

the compositions of the present invention preferably is about 10 to 25 weight percent, based on the total weight of components I and il, for injection molding uses and about 2 to 15 weight percent, based on the total weight of components I and 11, for compositions intended for extrusion into sheet or film or for use in thermoforming applications.

The third component of our novel compositions is at least one phosphorus compound which is present in an amount which gives a P: Sb atomic ratio of at least 1 : 1. The particular phosphorus compound is not critical and may be selected from a wide variety of phosphorus-containing compounds such as organo-phosphorus compounds, e. g., phosphite esters such as trihydrocarbyl phosphites, phosphonate esters such as dihydro- carbyl phosphonates, phosphate esters such as trihydrocarbyl phosphates, phosphines such as trihydrocarbyl phosphines, phosphine oxides such as trihydrocarbylphosphine oxides and and the like, wherein the hydrocarbyl groups may be selected from alkyl, cycloalkyl and aryl groups containing up to about 20 carbon atoms. A preferred phosphorus compound is bis (2,4-t-butylphenyl) pentaerythritol diphosphite available under the tradenames Ultranox 626 and Alkanox P-24. Additional examples of specifc organo-phosphorus compounds include distearylpentaerythritol diphosphite available under the tradenames Weston 618 and Mark 5060, tetrakis (2,4-di- t-butylphenyl) 4,4'-biphenylenediphosphonite available under the trade- names Sandostab P-EPQ and Alkanox 24-44, triphenyl phosphate, triphenyl phosphite, and dimethylphosphonate available under the trade- names Antiblaze 1045 and Amgard P-45. Phosphorus acids such as phosphorous acid, phosphoric acid, pyrophosphoric acid, polyphosphoric acid and their respective salts also may be sued. All of these phosphorus compounds are believed to be effective in slowing the epoxy-epoxy reaction due to a phosphorus-induced inactivation of the residual antimony catalyst. Inactivation of the antimony permits a selective reaction between

the epoxy portion of the impact modifying polymer and the polyester which results in a better dispersion and thus, better impact modification.

The amount of phosphorus compound present in the polyester compositions of our invention normally should be an amount which gives a P: Sb atomic ratio of 1: 1 or greater, e. g., a P: Sb atomic ratio in the range of about 1: 1 to 5: 1, preferably in the range of 2: 1 to 3: 1. The inclusion of excessive amounts of phosphorus compounds in the polyester compositions can result in compositions having poor impact properties even though the impact modified is present as small dispersions. Excessive phosphorus compounds (of various oxidation states) can form strong acids by combination with trace amounts of water present in even the most thoroughly dried polyester. Such strong acids are detrimental to polyester molecular weight (Mw) upon which toughness depends directly. Strong acids also can catalyze epoxy-epoxy reactions which may lessen adhesion to the matrix.

The phosphorus compound normally is added to the molten polyester simultaneously with or prior to the addition of the epoxy- containing impact modifier. The phosphorous compound also may be added to the polyester during its manufacture although adding the phosphorus compound during polyester preparation may have a negative effect on the rates of polymerization and/or solid stating. Thus, addition of a phosphorus compound during polymerization is a not a preferred method of addition.

The impact modifier and polyester may be pellet blended before extrusion or they may be fed from separate streams. These reactive impact modifiers also may be combined with non-reactive impact modifiers of similar composition. The polyester compositions of this invention can be readily prepared by conventional compounding technology, such as the use of single or twin screw extruders. The resultant blends are readily extruded

into film or sheeting and injection molded, compression molded or thermoformed into desired shapes or objects.

Other additives normally used in polyesters such as stabilizers, antioxidants, pigments, colorants, plasticizers, flame retardants, mold release agents, slip agents and the like may be used as desired. Glass fibers or other inorganic fillers can also be included. Although not required, small amounts of nucleating agents such as polyethylene, polypropylene, talc and the like may be used.

A particularly preferred embodiment of the invention consists of a polyester composition comprising : I. about 75 to 98 weight percent of a thermoplastic polyester comprising poly (ethylene terephthalate) having an inherent viscosity of about 0.55 to 0.95 dL/g, measured at 25°C using 0.50 g of polyester per 100 mL of a solvent consisting of 60 weight percent phenol and 40 weight percent tetrachloroethane, containing about 100 to 300ppmw Sb ; II. about 25 to 2 weight percent of an impact modifying polymer selected from ethylene/methyl acrylate/glycidyl methacrylate terpolymers containing about 20 to 35 weight percent methyl acrylate residues and about 2 to 10 weight percent glycidyl methacrylate residues; and III. a phosphorus compound; wherein the amount of phosphorus compound present gives a P: Sb atomic ratio of about 2: 1 to 3: 1 and the weight percentages are based on the total weight of components I and 11. Alternatively, up to 50% of the amount of component 11 may consist of an ethylene/methyl acrylate copomlymer containing about 20 to 35 weight percent methyl acrylate residues.

Examples The novel polyester compositions provided by the present invention are further illustrated by the following examples wherein all percentages given are by weight unless otherwise specified. Percentage concentrations

of phosphorus compounds are based on the combined weight of the polyester and impact modifier components. The following polyesters, prepared using conventional polycondensation procedures and the catalyst specified, were used in the examples: Polyester A: Poly (ethylene terephthalate) having an IV of 0.72 prepared from ethylene glycol and terephthalic acid using 200 ppmw antimony catalyst provided as antimony triacetate.

Polyester B: Poly (ethylene terephthalate) modified with 1,4-cyclohexane- dimethanol residues having an IV of 0.72 prepared from terephthalic acid and a mixture of 96.5 mole percent ethylene glycol with 3.5 mole percent cyclohexanedimenthanol using 200 ppmw antimony catalyst to an IV of 0.72 provided as antimony triacetate.

Impact Modifier 1: An ethylene/methyl acrylate/glycidyl methacrylate terpolymer containing 24% methyl acrylate residues and 8% glycidyl methacrylate residues, available from Elf Atochem under the name"Lotader AX8900"and having a melt flow of 6.5 g/10 minutes measured by ASTM D1238 at 190°C using a 2.16 kg weight.

Impact Modifier 2: An ethylene/methyl acrylate copolymer containing 24% methyl acrylate residues, available from Elf Atochem under the name"Lotryl 24MA07"having a melt flow of 8 g/10 minutes measured by ASTM D1238 at 190°C using a 2.16 kg weight. IM-2 is similar to IM-1 but contains no epoxy functionality.

ImPact Modifier 3: An ethylene/glycidyl methacrylate copolymer containing 8% glycidyl methacrylate residues, available from Elf Atochem under the name"Lotader AX8840"and having a melt flow of 5 g/10 minutes measured by ASTM D1238 at 190°C using a 2.16 kg weight.

The polyester compositions of the examples were prepared by feeding the polyester, impact modifier and phosphorus compound through separate feeders into the main hopper of a 30 mm twin-screw, compounding extruder. The extruder barrel temperatures was set at 290°C

(554°F), screw speed was 300 revolutions per minute and the throughput rate was 11.4 kg (25 pounds) per hour. Test bars 3.2mm thick by 12.8mm wide by 125mm long were molded on a ToyoA molding machine using a chilled-4°C (25°F) mold. The test bars thus prepared contained essentially amorphous polyester. The test bars then were crystallized in an air oven at 120°C for 3 hours. Test bars were machined into notched Izod test coupons and tested in accordance with ASTM D256.

Morphology was examined using either TEM (transmission electron microscopy) or SEM (scanning electron microscopy). Specimens for TEM examination were cut using a cryomicrotome. Specimens for SEM examination were freeze fractured in liquid nitrogen. The particle sizes listed represent the diameters of the most common large particles of the impact modifier phases present in the SEM or TEM photo.

COMPARATIVE EXAMPLE 1 The polyester composition of Comparative Example 1 consisted of 80% Polyester A containing about 200 ppmw antimony and 20% Impact Modifier 1. This composition has a 23°C (72°F) Notched Izod value of 354 Joules per meter (6.62 foot-pounds per inch). The TEM particle size of the impact modifier was 2 microns.

COMPARATIVE EXAMPLE 2 The polyester composition of Comparative Example 2 consisted of 80% Polyester B containing about 200 ppmw antimony and 20% Impact Modifier 1. This composition has a 23°C (72°F) Notched Izod value of 373 Joules per meter (6.98 foot-pounds per inch). The TEM particle size of the impact modifier was 2 microns.

COMPARATIVE EXAMPLE 3 The polyester composition of Comparative Example 3 consisted of 80% Polyester A containing about 200 ppmw antimony and 20% Impact Modifier 2. This composition has a 23°C (72°F) Notched Izod value of 45 Joules per meter (1.12 foot-pounds per inch). The TEM particle size of the impact modifier was 0.84 microns. The particle size is good but there is no bonding.

COMPARATIVE EXAMPLE 4 The polyester composition of Comparative Example 4 consisted of 80% Polyester A containing about 200 ppmw antimony and 20% Impact Modifier 3. This composition has a 23°C (72°F) Notched Izod value of 243 Joules per meter (4.54 foot-pounds per inch). The TEM particle size of the impact modifier was 2 microns.

EXAMPLE 1 The polyester composition of Example 1 consisted of 80% Polyester A containing about 200 ppmw antimony, 20% Impact Modifier 1 and 0.05% of bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite (Ultranox 626,50 ppmw phosphorus). This composition has a 23°C (72°F) Notched Izod value of"No Break". A"No Break"result indicates that the material did not completely fracture under the indicated conditions with an Izod value of greater than 1000 Joules per meter (534.5 foot-pounds per inch). The TEM particle size of the impact modifier was 0.5 microns.

EXAMPLE 2 The polyester composition of Example 2 consisted of 80% Polyester B containing about 200 ppmw antimony, 20% Impact Modifier 1 and 0.05% of bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite (Ultranox 626,50 ppmw phosphorus). This composition has a 23°C (72°F) Notched Izod

value of No Break. The TEM particle size of the impact modifier was 0.5 microns.

EXAMPLE 3 The polyester composition of Example 3 consisted of 80% Polyester A containing about 200 ppmw antimony, 10% Impact Modifier 1,10% Impact Modifier 2 and 0.05% of bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite (Ultranox 626). This composition has a 23°C (72°F) Notched Izod value of 501 Joules per meter (9.37 foot-pounds per inch). The TEM particle size of the impact modifier was 0.5 microns.

EXAMPLE 4 The polyester composition of Example 4 consisted of 80% Polyester A containing about 200 ppmw antimony, 20% Impact Modifier 3 and 0.05% of bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite (Ultranox 626,50 ppmw phosphorus). This composition has a 23°C (72°F) Notched Izod value of"No Break". A"No Break"result indicates that the material did not completely fracture under the indicated conditions with an Izod value of greater than 1000 Joules per meter (534.5 foot-pounds per inch). The TEM particle size of the impact modifier was 0.5 microns.

EXAMPLES 5-15 AND COMPARATIVE EXAMPLE 5 Examples 5-15 show the effect that different types of organic and inorganic phosphorus compounds have on the 72°F (23°C) and 32°F (0°C) Notched Izod toughness of blends of comprising 80% Polyester A and 20% Impact Modifier 1. The concentration of each of the phosphorus compounds was 0.3%. All of the phosphorus compounds had a favorable effect on the 23°C (72°F) Notched Izod toughness. Example 13 shows that 0.3% Ca3 (PO4) 2 also improves the 32°F (0°C) notched Izod toughness of the blend. The phosphorus compounds used in each example were :

Example 5: Bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite Example 6: Distearylpentaerythritol di phosphite Example 7: Tetrakis (2,4-di-t-butylphenyl) 4,4"-biphenylenediphosphonite Example 8: Triphenyl phosphate Example 9: Triphenyl phosphite Example 10: Dimethylphosphonate Example 11: Na2H2P207 Example 12: CaHPO4 Example 13: Ca3(PO4)2 Example 14: Na2HP04 Example 15: NaH2PO4 Comparative Example 5 (C-5) shows the 23°C (72F) and 0°C (32°F) Notched Izod toughness of a blend of comprising 80% Polyester A and 20% Impact Modifier 1 which contains no phosphorus compound. The 23°C (72°F) and 0°C (32°F) Notched Izod Values for the compositions of Examples 5-15 and Comparative Example 5 are set forth in Table I wherein the values given are joules per meter and (foot-pounds per inch).

TABLE I Example Notched Izod Values No. 23°C (72°F) 0°C (32°F) 5 610 (11.40) 195 (3.65) 6 793 (14.83) 164 (3.07) 7 325 (6.08) 122 (2.28) 8 514 (9.61) 176 (3.29) 9 487 (9.11) 153 (2.86) 10 720 (13.46) 239 (4.47) 11 877 (16.40) 275 (5.14) 12 877 (16.40) 292 (5.46) 13 933 (17.45) 744 (13.91) 14 672 (12.57) 266 (4.97) 15 654 (12.23) 466 (8.71) C-5 257 (4.81) 195 (3.65)

EXAMPLES 16-21 AND COMPARATIVE EXAMPLES 6 AND 7 Examples 16-21 show the effect that varying concentrations of bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite have on particle size and and 0°C (32°F) Notched Izod toughness of polyester compositions containing 80% Polyester A and 20% Impact Modifier 1. The 0°C (32°F) Notched Izod values are more sensitive to differing concentrations of phosphorus than are the 23°C (72°F) Notched Izod values. The distribution of impact modifier particles sizes, measured from SEM images, narrows dramatically to a dense population of very uniform, small particles with 0.05% of the phosphorus compound added. It is apparent that excessive levels of phosphorus causes impact toughness to drop, despite the small particle sizes. The 0°C (32°F) Notched Izod values reported in Examples 5-15 presumably are low because of the higher levels of phosphorus compound used in those examples. It is apparent from Example 13 that the Ca3PO4 can be used in higher concentrations than the other phosphorus compounds evaluated.

The compositions of Comparative Examples C-6 and C-7 consist of 80% Polyester A and 20% impact Modifier 1 and no phosphorus compound. The 0°C (32°F) Notched Izod Values for the compositions of Examples 16-21 and Comparative Examples C-6 and C-7 are set forth in Table II wherein the values given are joules per meter and (foot-pounds per inch). Table II also reports the particle sizes (microns) of the impact modifier phase determined by SEM for the compositions of Examples 16-21 and Comparatives Examples C-6 and C-7. The values given for Concentration of Phosphorus Compound are the weight/weight concentrations of bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite based on the total weight of the polyester and the impact modifier.

TABLE II Concentration Notched Example of Phosphorus Izod Values Particle No. Compound 0°C (32°F) Size 16 0.01 243 (4.54) 2 17 0.02 486 (9.09) 1.5 18 0.05 781 (14.61) 0.7 19 0.10 639 (11.95) 0.7 20 0.20 444 (8.30) 0. 5 21 0.30 240 (4.49) 0.6 C-6 0 296 (5.53) 3 C-7 0 304 (5.68) 4 The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.