Blends of polyarylates, polyesters and a thermoplastic polymer

Abstract: The invention deals with blends of polyarylates, polyes­ ters and a thermoplastic polymer. The molding compositions according to the invention comprise a blend of a polyarylate, a polyester, and at least one thermoplastic polymer selected from the group consisting of a polyurethane, a vinyl chloride polymer, a poly(aryl ether), a copolyetherester block polymer or a polyhydroxyether. These blends have excellent compatability and can be molded into a variety of articles.

Description: This invention is directed to a molding composition comprising a blend of a polyarylate a polyester, and at least one thermoplastic polymer selected from the group consisting of a polyurethane, a vinyl chloride polymer, a poly(aryl ether), a copolyetherester block polymer or a polyhydroxyether. Polyarylates are aromatic polyesters derived from a dihydric phenol, particularly, 2,2-bis-(4-hydroxyphenyl)-propane (also identified as Bisphenol-A) and an aromatic dicarboxylic acid, particularly mixtures of terephthalic and isophthalic acids. Polyarylates are high temperature, high performance thermoplastic polymers with a good combination of thermal and mechanical properties. They have a high continuous use temperature of about 130°C, and good unnotched toughness, with a pendulum impact value of greater than 0.82 × 10⁵Pa (300 ft.lbs./in.³). Additionally, polyarylates have inherent flammability and combustion resistance as well as good weatherability. The polyarylates have good melt stability at high temperatures and good color retention. They also have good processability which allows them to be molded into a variety of articles. Polyarylates have been blended with other resin systems such as ABS resin (U.S. Patent 3,792,118), polycarbonate resins (U.S. Patent 3,792,115), polyurethane resins, methyl methacrylate resins, etc. The blending of resins is often used to cover a defect of one resin with another resin. For example, a resin having a low heat distortion temperature may be blended with a resin having a high heat distortion temperature. However, this method is generally accompanied by unfavorable effects on other properties such as deterioration of mechanical properties or an inferior surface of the resulting injection molded resin. Specifically, when polyarylates are blended with resins such as thermoplastic polyurethanes, vinyl chloride polymers, methyl methacrylate resins, etc. several problems result. Polyarylates have high viscosities which require a high molding temperature which exceeds the temperature stability limit of the other resin which is blended with the polyarylate. Thus, when this blend is molded deterioration of the resin occurs. This is observed particularly with blends of polyarylate and vinyl chloride polymers. Additionally, when there is an extreme viscosity difference between the high viscosity polyarylate and the other polymer severe surface irregularities (e.g. jetting) are observed when these blends are injection molded. This is observed especially when polyarylate is blended with, for example, ABS resins and poly(methyl methacrylate) resins. Further, the extremely high viscosity of polyarylates prevents a uniform product from being obtained when the polyarylate is blended with a resin having a lower viscosity by conventional polymer mixing techniques, i.e., extrusion or Banbury type melt mixing. The non-uniform blend will not weather as well as a uniform blend of the resins nor will it have an acceptable balance of properties. It has now been found that the addition of a polyester derived from an aliphatic or cycloaliphatic diol, or mixtures thereof, and an aromatic dicarboxylic acid to a blend of a polyarylate and at least one thermoplastic polymer selected from the group consisting of a vinyl chloride polymer, a copolyetherester block polymer or a polyhydroxyether, produces a blend which has excellent surface appearance and can be easily molded without deterioration. Additionally, it has been found that the addition or polyarylate to a blend of the polyester and the thermoplastic polymer improves the weatherability of the blend, i.e., the mechanical properties of the blends are retained after exposure to conditions of ultraviolet light and moisture. The presence of the polyester resin in the blend provides a uniform blend and the resins can be blended using conventional polymer mixing techniques. The presence of the polyester resin in the blend does not interfere with the improving effect the polyarylate has on the weatherability of the blend. The blends of the present invention have excellent mechanical properties, better than the properties of a binary blend of polyarylate and a thermoplastic polymer. This is unexpected and allows heretofore unusable binary systems of polyarylate resin and thermoplastic polymer to be molded into articles. According to the present invention there is provided a molding composition comprising a blend of: (a) 4 to 80 weight percent of a polyarylate derived from at least one dihydric phenol and at least one aromatic dicarboxylic acid consisting from 95 to 0 mole percent of terephtalic acid and 5 to 100 moles percent of isophtalic acid; (b) 4 to 60 weight percent of a polyester having an intrinsic viscosity of 0.04 to 0.2m³/kg derived from an aliphatic or cycloaliphatic diol, or mixtures thereof containing from 2 to 10 carbon atoms, and at least one aromatic dicarboxylic acid, and (c) 10 to 92 weight percent of at least one thermoplastic polymer selected from the group consisting of a polyurethane, a vinyl chloride polymer, a copolyetherester block polymer or a polyhydroxyether. Polyarylates The polyarylates of this invention are derived from a dihydric phenol and an aromatic dicarboxylic acid. A particularly desirable dihydric phenol is of the following formula: wherein Y is selected from alkyl groups of 1 to 4 carbon atoms, chlorine or bromine, z has a value of from 0 to 4, inclusive, and R' is a divalent saturated aliphatic hydrocarbon radical, particularly alkylene and alkylidene radicals having 1 to 3 carbon atoms, and cycloalkylene radicals having up to and including 9 carbon atoms. The preferred dihydric phenol is Bisphenol-A. The dihydric phenols may be used individually or in combination. Additionally, said dihydric phenols can be used in combination with a dihydric phenol of the following formula: wherein Y and z are as previously defined. Suitable aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acids, and mixtures thereof, as well as alkyl substituted homologs of these carboxylic acids wherein the alkyl groups contain from 1 to about 4 carbon atoms, and acids containing other inert substituents such as halides, alkyl or aryl ethers, and the like. The polyarylates contain from 95 to 0 mole percent of terephthalic acid and from 5 to 100 mole percent of isophthalic acid. More preferably, the polyarylates contain a mixture of from 30 to 70 mole percent of terephthalic acid and from 70 to 30 mole percent of isophthalic acid. A polyarylate containing a mixture of 50 mole percent of terephthalic acid and 50 mole percent of isophthalic acid is most preferred. The polyarylates of the present invention can be prepared by any of the well known prior art polyester forming reactions, such as the reaction of the acid chlorides of the aromatic dicarboxylic acids with the dihydric phenol, the reaction of the diaryl esters of the aromatic dicarboxylic acids with the dihydric phenols, and the reaction of the aromatic diacids with diester derivatives of the dihydric phenol. These processes are described in, for example, U.S. Patents 3,317,464; 3,948,856; 3,780,148; 3,824,213 and 3,133,898. These polyarylates have a reduced viscosity of from about 0.4 to about 1.0 as measured in p-chlorophenol at 49°C (2 kg/m³). Polyesters The polyesters which are suitable for use herein are derived from an aliphatic or cycloaliphatic diol, or mixtures thereof, containing from 2 to 10 carbon atoms and at least one aromatic dicarboxylic acid. The polyesters which are derived from an aliphatic diol and an aromatic dicarboxylic acid have repeating units of the following general formula: wherein n is an integer of from 2 to 4. The preferred polyester is poly(ethylene terephthalate). Also contemplated herein are the above polyesters with minor amounts, e.g., from 0.5 to about 2 percent by weight, of units derived from aliphatic acids and/or aliphatic polyols, to form copolyesters. The aliphatic polyols include glycols such as poly(ethylene glycol). These can be made following the teachings of, for example, U.S. Patents 2,465,319 and 3,047,539. Among the units which can be present in the copolyesters are those derived from aliphatic dicarboxylic acids, e.g., of up to about 50 carbon atoms, including cycloaliphatic straight and branched chain acids, such as adipic acid, cyclohexanediacetic acid, dimerized C₁₆-C₁₈ unsaturated acids (which have 32 to 36 carbon atoms), trimerized acids, and the like. In addition, there can be minor amounts of units derived from aliphatic glycols and polyols, e.g., of up to about 50 carbon atoms preferably from 2 to about 20 carbon atoms and these include, among others, propylene glycol, glycerol, diethylene glycol, triethylene glycol and the like. The polyesters which are derived from a cycloaliphatic diol and an aromatic dicarboxylic acid are prepared by condensing either the cis- or trans-isomer (or mixtures thereof) of, for example, 1,4-cyclohexanedimethanol with the aromatic dicarboxylic acid so as to produce a polyester having recurring units having the following formula: wherein the cyclohexane ring is selected from the cis- and trans-isomers thereof and R represents an aryl radical containing 6 to 20 carbon atoms and which is the decarboxylated residue derived from an aromatic dicarboxylic acid. Examples of aromatic dicarboxylic acids indicated by R in formula II, include isophthalic or terephthalic acid 1,2-di(p-carboxyphenyl) ethane, 4,4'-dicarboxydiphenyl ether, etc., and mixtures of these. All of these acids contain at least one aromatic nucleus. Fused rings can also be present such as in 1,4- or 1,5-naphthalene-dicarboxylic acids. The preferred dicarboxylic acid is terephthalic acid or mixtures of terephthalic and isophthalic acid. A preferred polyester may be derived from the reaction of either the cis- or trans-isomer (or a mixture thereof) of 1,4-cyclohexanedimethanol with a mixture of iso- and terephthalic acids. These polyesters have repeating units of the formula: Another preferred polyester is a copolyester derived from a cyclohexane dimethanol, an alkylene glycol and an aromatic dicarboxylic acid. These copolyesters are prepared by condensing either the cis- or trans-isomer (or mixtures thereof) of, for example, 1,4-cyclohexane-dimethanol and an alkylene glycol with an aromatic dicarboxylic acid so as to produce a copolyester having repeating units of the following formula: wherein the cyclohexane ring is selected from the cis- and trans-isomers thereof, R is as previously defined, n is an integer of 2 to 4, the x units comprise from about 10 to about 90 percent by weight and the y units comprise from about 10 to about 90 percent by weight. The preferred copolyester may be derived from the reaction of either the cis- or trans-isomer (or mixtures thereof) of 1,4-cyclohexanedimethanol and ethylene glycol with terephthalic acid in a molar ratio of 1:2:3. These copolyesters have repeating units of the following formula: wherein x and y are as previously defined. The polyesters as described herein are either commercially available or can be produced by methods well known in the art such as those set forth in, for example, U.S. Patent 2,901,466. The preferred polyesters are poly (1,4-cyclohexanedimethanol tere/iso-phthalate) and a copolyester of 1,4-cyclohexanedimethanol, ethylene glycol and terephthalic acid and poly(ethylene terephthalate) as previously described. The polyesters used herein have an intrinsic viscosity of 0.04 to 0.2m³/kg. measured in a 60:40 phenol/tetrachloroethane mixture or similar solvent at 23-30°C. The intrinsic viscosity is defined by the following relationship. wherein ηSP = specific viscosity, and C = the concentration in m³/kg × 10⁻¹. Thermoplastic Polymers The thermoplastic polymers suitable for use in this invention are selected from the group consisting of a polyurethane, a vinyl chloride polymer, a poly(aryl ether), a copolyetherester block polymer, a polyhydroxyether, or mixtures thereof. A. Polyurethanes These thermoplastic polyurethanes may be synthesized by methods disclosed in U.S. Pat. No. 3,214,411. A particularly useful polyester resin used as a starting material for the thermoplastic polyurethane are those produced from adipic acid and a glycol having at least one primary hydroxyl group. The adipic acid is condensed with a suitable glycol or mixture of glycols which have at least one primary hydroxyl group. The condensation is stopped when an acid number of from about 0.5 to about 2.0 is reached. The water formed during the reaction is removed simultaneously therewith or subsequently thereto such that the final water content is from about 0.01 to about 0.2%, preferably from about 0.01 to 0.05%. Any suitable glycol may be used in reaction with the adipic acid such, as, for example, ethylene glycol, propylene glycol, butylene glycol, hexanediol, bis- (hydroxymethylcyclohexane), 1,4-butanediol, diethylene glycol, 2,2-dimethyl propylene glycol, 1,3-propylene glycol and the like. In addition to the glycols, a small amount of trihydric alcohol of up to about 1% may be used along with the glycols such as, for example, trimethylolpropane, glycerol, hexanetriol and the like. The resulting hydroxyl polyester has a molecular weight of at least about 600, a hydroxyl number of about 25 to about 190 and preferably between about 40 and about 60, and acid number of between about 0.5 and about 2 and a water content of 0.01 to about 0.2%. The organic diisocyanate to be used in the preparation of the elastomer is preferably 4,4'-diphenylmethane diisocyanate. It is desired that the 4,4'-diphenylmethane diisocyanate contain less than 5% of 2,4'-diphenylmethane diisocyanate and less than 2% of the dimer of diphenylmethane diisocyanate. It is further desired that the acidity calculated as HCl is from about 0.0001 to about 0.02%. The acidity calculated as percent HCl is determined by extracting the chloride from the isocyanate in a hot aqueous methanol solution or by literating the chloride on hydrolysis with water and titrating the extract with a standard silver nitrate solution to obtain the chloride ion concentration present. Other diisocyanates may be used in preparing the thermoplastic processable polyurethanes such as ethylene diisocyante, ethylidene diisocyanate, propylene diisocyanate, butylene diisocyanate, cyclopentylene-1,3-diisocyanate, cyclohexylene-1,4-diisocyanate, cyclohexylene-1,2-diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2-diphenylpropane-4,4'-diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, xylylene diisocyanate, 1,4-naphthylene diisocyanate, 1,5-naphthylene diisocyanate, diphenyl-4,4'-diisocyanate, azobenzene-4,4'-diisocyanate, diphenyl sulfone-4,4'-diisocyanate, dichlorohexamethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 1-chlorobenzene-2,4-diisocyanate, furfurylidene diisocyanate and the like. Any suitable chain extending agent having active hydrogen containing groups reactive with isocyanate groups may be used such as, for example, diols including ethylene glycol, propylene glycol,1,4-butanediol, butenediol, butynediol, xylylene glycols, amylene glycols, 1,4-phenylene-bis-β-hydroxy ethyl ether, 1,3-phenylene-bis-β-hydroxy ethyl ether, bis-(hydroxy-methyl-cyclohexane), hexanediol, thiodiglycol and the like; diamines including ethylene diamine, propylene diamine, butylene diamine, hexamethylene diamine, cyclohexylene diamine, phenylene diamine, tolylene diamine, xylylene diamine, 3,3'-dichlorobenzidine, 3,3'-dinitrobenzidine and the like; alkanol amines such as, for example, ethanol amine, aminopropyl alcohol, 2,2-dimethyl propanol amine, 3-aminocyclohexyl alcohol, p-aminobenzyl alcohol and the like. The difunctional chain extenders mentioned in U.S. Pat. No. 2,620,516, 2,621,166 and 2,729,618 incorporated herein by reference may be used. If desirable, a small amount of polyfunctional material may be utilized. This polyfunctional chain extender, however, should not be present in an amount greater than about 1% by weight. Any suitable polyfunctional compound may be used in this application such as, for example, glycerol, trimethylolpropane, hexanetriol, pentaerythritol and the like. In accordance with the process of this invention, the polyester, the organic diisocyanate and the chain extender may be individually heated preferably to a temperature of from about 60° to about 135°C. and then the polyester and chain extender are substantially simultaneously mixed with the diisocyanate. Of course, to increase the rate of reaction, any suitable catalyst may be added to the reaction mixture such as tertiary amines and the like as set forth in U.S. Pat. Nos. 2,620,516, 2,621,166 and 2,729,618. Although adipate polyesters are preferred, polyesters may be used which are based on succinic acid, suberic acid, sebacic acid, oxalic acid, methyl adipic acid, glutaric acid, pimelic acid, azelaic acid, phthalic acid, terephthalic acid, isophthalic acid and the like. Polyesters based on ε-caprolactone are also preferred. A polyether may be used instead of the polyester in the preparation of the thermoplastic polyurethane and preferably polytetramethylene glycol having an average molecular weight between about 600 and 2000 and preferably about 1000. Other polyethers such as polypropylene glycol, polyethylene glycol and the like may be used providing their molecular weight is above about 600. The above and other thermoplastic polyurethanes such as disclosed in U.S. Pat. Nos. 2,621,166, 2,729,618, 3,214,411, 2,778,810, 3,012,992 Canadian Pat. Nos. 754,233, 733,577 and 842,325 may be used to produce the thermoplastic polyurethanes. B. Vinyl Chloride Polymers Vinyl chloride polymers for the purpose of this invention are polyvinyl chloride and copolymers of vinyl chloride with olefinically unsaturated polymerisable compounds which contain at least 80 percent by weight of vinyl chloride incorporated therein. Olefinically unsaturated compounds which are suitable for copolymerisation are, for example, vinylidene halides, such as vinylidene chloride and vinylidene fluoride, vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl chloroacetate, vinyl benzoate, acrylic and α-alkyl-acrylic acids and their alkyl esters, amides and nitriles, methacrylic acid, methyl methacrylate, ethyl acrylate, 2-ethyl-hexylacrylate, butyl methacrylate, acrylamide, N-methyl acrylamide, acrylonitrile and methacrylonitrile, aromatic vinyl compounds such as styrene and vinyl naphthalene and olefinically unsaturated hydrocarbons such as ethylene, bicyclo-[2,2,1]-hept-2-ene and bicyclo-[2,2,1]-hepta-2,5-dienes. These vinyl chloride polymers are known and can be prepared by the usual methods of emulsion, suspension, bulk or mass polymerisation. Vinyl chloride polymers which have molecular weights of 40,000 to 60,000 are preferred. D. Copolyetherester Block Copolymer The polyetheresters consist essentially of a multiplicity of recurring intralinear long chain and short chain ester units connected head-to-tail through ester linkages, said long chain ester units being represented by the following structure: and said short chain ester units being represented by the following structure wherein: G is a divalent radical remaining after removal of terminal hydroxy groups from a poly(alkylene oxide) glycol having a molecular weight of about 400-3500; D is a divalent radical remaining after removal of hydroxyl groups from a low molecular weight diol having a molecular weight less than about 250; and R₂ is a divalent radical remaining after removal of carboxyl groups from a dicarboxylic acid having a molecular weight less than about 300; with the provisos that the short chain ester units constitute about 25-65% by weight of the copolyester, at least about 70% of the R₂ groups must be 1,4-phenylene radicals, at least about 70% of the D groups must be the 1,4-butylene radicals. and the sum of the percentages of the R₂ groups which are not 1,4-phenylene radicals and of the D groups which are not 1,4-butylene radicals cannot exceed about 30%. The term "long chain ester units" as applied to units in a polymer chain refers to the reaction product of a long chain glycol with dicarboxylic acid. Such "long chain ester units", which are a repeating unit in the copolyesters of this invention correspond to the Formula a above. The long chain glycols of the instant invention are poly(alkylene oxide) glycols having a molecular weight between about 400 and 3500, preferably between about 600 and 2000. Copolyesters prepared from poly(alkylene oxide) glycols having a molecular weight of about 600-2000 are preferred because they exhibit useful properties over a wide range of temperature, combined with limited water swell. Copolyesters prepared from poly(alkylene oxide) glycols having a molecular weight in excess of about 3500 may crystallize and lose their elastomeric character and good low temperature properties. Copolyester prepared from glycols having molecular weights below about 400 have useful properties only within a narrow temperature range and are less suited for injection molding and extrusion because of a slower rate of crystallization of the resultant block copolymer. The long chain glycols contain a major proportion of tetramethylene oxide units. In a preferred embodiment of the instant invention the long chain glycols will be entirely poly(tetramethylene oxide) glycol. In some instances it may be desirable to use random or block copolymers of tetramethylene oxide containing minor proportions of a second alkylene oxide. Typically the second monomer will constitute less than about 40 mole percent of the poly(alkylene oxide) glycols and preferably less than 20 mole percent. Representative examples of the second monomer include 1,2- and 1,3- propylene oxides, 1,2-butylene oxide and ethylene oxide. The term "short chain ester units" as applied to units in a polymer chain refers to low molecular weight compounds or polymer chain units having molecular weights less than about 550. They are made by reacting a low molecular weight diol (below about 250) with a dicarboxylic acid to form ester units represented by Formula (b) above. Included among the low molecular weight diols (other than 1,4-butanediol) which react to form short chain ester units are acyclic, alicyclic and aromatic dihydroxy compounds. Preferred are diols with 2-15 carbon atoms such as ethylene, propylene, isobutylene, tetramethylene, pentamethylene, 2,2-dimethyltrimethylene, hexamethylene and decamethylene glycols, dihydroxy cyclohexane, cyclohexane dimethanol, resorcinol, hydroquinone, 1,5-dihydroxy naphthalene, etc. Especially preferred are aliphatic diols containing 2-8 carbon atoms. Included among the bisphenols which can be used are bis(p-hydroxy) diphenyl, bis(p-hydroxyphenyl) methane, and bis(p-hydroxyphenyl) propane. Equivalent esterforming derivatives of diols are also useful (e.g., ethylene oxide or ethylene carbonate can be used in place of ethylene glycol). The term "low molecular weight diols" as used herein should be construed to include such equivalent ester-forming derivatives: provided, however, that the molecular weight requirement pertains to the diol only and not to its derivatives. Dicarboxylic acids (other than terephthalic acid) which are reacted with the foregoing long chain glycols or low molecular weight diols to produce the copolyesters of this invention are aliphatic, cycloaliphatic or aromatic dicarboxylic acids of a low molecular weight. The term "dicarboxylic acids" as used herein, includes acid equivalents of dicarboxylic acids having two functional carboxyl groups which perform substantially like dicarboxylic acids in reaction with glycols and diols in forming copolyester polymers. These equivalents include esters and ester-forming derivatives, such as acid halides and anhydrides. The molecular weight requirement pertains to the acid and not to its equivalent ester or ester-forming derivative. Thus, an ester of a dicarboxylic acid having a molecular weight greater than 300 or an acid equivalent of a dicarboxylic acid having a molecular weight greater than 300 are included provided the acid has a molecular weight below about 300. The dicarboxylic acids can contain any substituent groups or combinations which do not substantially interfere with the copolyester polymer formation and use of the polymer in the elastomeric compositions of this invention. Aliphatic dicarboxylic acids, as the term is used herein, refers to carboxylic acids having two carboxyl groups each attached to a saturated carbon atom. If the carbon atom to which the carboxyl group is attached is saturated and is in a ring, the acid is cycloaliphatic. Aliphatic or cycloaliphatic acids having conjugated unsaturation often can not be used because of homopolymerization. However, some unsaturated acids, such as maleic acid, can be used. Aromatic dicarboxylic acids, as the term is used herein, are dicarboxylic acids having two carboxyl groups attached to a carbon atom in an isolated or fused bezene ring. It is not necessary that both functional carboxyl groups be attached to the same aromatic ring and where more than one ring is present, they can be joined by aliphatic or aromatic divalent radicals such as -O- or -SO₂-, alkylene, alkylidene, etc. Representative aliphatic and cycloaliphatic acids which can be used for this invention are sebacic acid, 1,3-cyclohexane dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid, adipic acid, glutaric acid, succinic acid, carbonic acid, oxalic acid, azelaic acid, diethylmalonic acid, allylmalonic acid, 4-cyclohexane-1,2-dicarboxylic acid, 2-ethylsuberic acid, 2,2,3,3-tetramethylsuccinic acid, cyclopentanedicarboxylic acid, decahydro-1,5-naphthylene dicarboxylic acid, 4,4-bicyclohexyl dicarboxylic acid, decahydro-2,6-naphthylene dicarboxylic acid, 4,4-methylenebis-(cyclohexyl) carboxylic acid, 3,4-furan dicarboxylic acid, and 1,1-cyclobutane dicarboxylic acid. Preferred aliphatic acids are cyclohexane-dicarboxylic acids and adipic acid. Representative aromatic dicarboxylic acids which can be used include phthalic, terephthalic and isophthalic acids, substituted dicarboxy compounds with two benzene nuclei such as bis(p-carboxyphenyl) methane, p-carboxyphenyl/oxybenzoic acid, ethylene-bis (p-oxybenzoic acid) 1,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, phenanthrene dicarboxylic acid, anthracene dicarboxylic acid, 4,4'-sulfonyl dibenzoic acid and C₁-C₁₂ alkyl and ring substituted derivatives thereof, such as halo, alkoxy, and aryl derivatives. Hydroxy acids such as p(β-hydroxyethoxy) benzoic acid can also be used providing an aromatic dicarboxylic acid is also present. Aromatic dicarboxylic acids are a preferred class for preparing the copolyester polymers useful for compositions of this invention. Among the aromatic acids, those with 8-16 carbon atoms are preferred, particularly the phenylene dicarboxylic acids, i.e., terephthalic and isophthalic acids. It is essential that at least about 70 mole percent of the dicarboxylic acid incorporated into the polymer be terephthalic acid and at least about 70 mole percent of the low molecular weight diol incorporated into the polymer be 1,4-butanediol. Thus, at least 70% of the R₂ groups in Formulae a and b above are 1,4-phenylene radicals and at least about 70% of the D groups in Formula b above are 1,4-butylene radicals. A further requirement in making the polymers of this invention is that the sum of the percentages of the R₂ groups which are not 1,4-phenylene radicals and of the D groups which are not 1,4-butylene radicals cannot exceed about 30%. For example, if 30% of the low molecular weight diol molecules incorporated into the polymer are other than 1,4-butanediol, then all of the dicarboxylic acid used must be terephthalic acid, or if 10% of the low molecular weight diol molecules are other than 1,4-butanediol, then at least about 80% of the dicarboxylic acid used must be terephthalic acid. The D and R units which are not 1,4-butylene and 1,4-phenylene, respectively, can be derived from any of the low molecular weight diols or dicarboxylic acids named above. The dicarboxylic acids or their derivatives and the polymeric glycol are incorporated into the final product in the same molar proportions as are present in the reaction mixture. The amount of low molecular weight diol actually incorporated corresponds to the difference between the moles of diacid and polymeric glycol present in the reaction mixture. When mixtures of low molecular weight diols are employed, the amounts of each diol incorporated is largely a function of the amounts of the diols present, and relative reactivities. The total amount of glycol incorporated is still the difference between moles of diacid and polymeric glycol. The copolyesters of this invention contain about 25-65% by weight of short chain ester units corresponding to Formula (b) above, the remainder being long chain ester units corresponding to Formula a above. When the copolyesters contain less than about 25% by weight short chain units, the tear strength and solvent resistance of the copolyesters fall to undesirably low levels and when the copolyesters contain more than about 65% short chain units, the low temperature properties worsen and the copolyesters become less elastomeric. The preferred balance of properties is obtained when the short chain ester content is about 55-62%. The most preferred copolyesters of this invention are those prepared from dimethylterephthalate, 1,4-butanediol and poly (tetramethylene oxide) glycol having a molecular weight from about 600-1500. The polymers described herein can be made conveniently by a conventional ester interchange reaction. A preferred procedure involves heating the dimethyl ester of terephthalic acid with a long chain glycol and a molar excess of a butanediol in the presence of a catalyst at 150 to 260°C. followed by distilling off methanol formed by the interchange. Heating is continued until methanol evolution is complete. Depending on temperature, catalyst and glycol excess, this polymerization is complete within a few minutes to a few hours. The procedure results in the preparation of a low molecular weight prepolymer which can be carried to a high molecular weight copolyester of this invention by the procedure described below. Such prepolymers can also be prepared by a number of alternate esterification or ester interchange processes; for example, the long chain glycol can be reacted with a high or low molecular weight short chain ester homopolymer or copolymer is the presence of catalyst until randomization occurs. The short chain ester homopolymer or copolymer can be prepared by ester interchange from either the dimethyl esters and low molecular weight diols, as above, or from the free acids with the diol acetates. Alternatively, the short chain ester copolymer can be prepared by direct esterification from appropriate acids, anhydrides or acid chlorides, for example, with diols or by other processes such as reaction of the acids with cyclic ethers or carbonates. Obviously the prepolymer might also be prepared by running these processes in the presence of the long chain glycol. The resulting prepolymer is then carried to high molecular weight by distillation of the excess of short chain diol. This process is known as "polycondensation". Additional ester interchange occurs during the distillation to increase the molecular weight and to randomize the arrangement of the copolyester units. Best results are usually obtained if this final distillation or polycondensation is run at less than 1 mm. Hg pressure and 240-260°C. for less than 2 hours in the presence of antioxidants such as sym-di-beta-naphthyl-p-phenylene-diamine and 1,3,5-trimethyl-2,4,6-tris[3,5-ditertiary butyl-4-hydroxybenzyl] benzene. Most practical polymerization techniques rely upon ester interchange to complete the polymerization reaction. In order to avoid excessive hold time at high temperatures with possible irreversible thermal degradation, it is advantageous to employ a catalyst for ester interchange reactions. While a wider variety of catalysts can be used, organic titanates such as tetrabutyl titanate used alone or in combination with magnesium or calcium acetates are preferred. Complex titanates, such as Mg[HTi(OR₃)₆] 2' derived from alkali or alkaline earth metal alkoxides and titanate esters are also very effective. Inorganic titanates, such as lanthanum titanate, calcium acetate/antimony trioxide mixtures and lithium and magnesium alkoxides are representative of other catalysts which can be used. These polyetheresters are described in, for example, U.S. Patents 3,784,520 and 3,766,146. E. Polyhydroxyether The thermoplastic polyhydroxyethers in the present invention have the general formula [D-O-E''-O wherein D is the radical residuum of a dihydric phenol, E'' is a radical residuum of an epoxide selected from mono- and diepoxides and contains from 1 to 2 hydroxyl groups and n is an integer which represents the degree of polymerization and is at least 30 and preferably is above about 80. In general, thermoplastic polyhydroxyethers are prepared by contacting under polymerization conditions a dihydric phenols and an epoxide containing from 1 to 2 epoxide groups in substantially equimolar amounts. The product produced by the reaction between bisphenol-A and epichlorohydrin has the repeating unit and can be termed a poly(monohydroxyether) of bisphenol-A. The product produced by the reaction between hydroquinone and butadiene dioxide has the repeating unit and can be termed a poly(dihydroxyether) of hydroquinone. By the use of both a monoepoxide and a diepoxide poly(hydroxy-dihydroxyethers) can be obtained, the relative amounts of mono- and diepoxide determining the final concentration of the mono- and dihydroxy containing repeating units E'' in the polymer. Any dihydric phenol can be used in forming polyhydroxyethers. Illustrative dihydric phenols are mononuclear dihydric phenols such as hydroquinone, resorcinol, and the like as well as the polynuclear phenols which are preferred. The dihydric polynuclear phenols have the general formula: wherein: Ar is an aromatic divalent hydrocarbon radical such as naphthylene and phenylene with phenylene being preferred for the thermoplastic polyhydroxyethers used in this invention; B and B₁ which can be the same or different are alkyl radicals such as methyl, n-propyl, n-butyl, n-hexyl, n-octyl and the like, preferably alkyl radicals having a maximum of 4 carbon atoms; or halogen atoms, i.e., chlorine, bromine, iodine, or fluorine; or alkoxy radicals such as methoxy, methoxymethyl, ethoxy, ethoxyethyl, n-butyloxy, amyloxy and the like, preferably an alkoxy radical having a maximum of 4 carbon atoms, a and a₁ are independently integers of 0 to 4, R' is alkylene, alkylidene, cycloalkylene or a saturated divalent group. Particularly preferred are dihydric polynuclear phenols having the general formula: wherein B, B₁, a and a₁ are as previously defined, and R₃ is an alkylene or alkylidene group, preferably having from 1 to 3 carbon atoms inclusive or cycloalkylene or R₃ is a saturated divalent group such as is obtained from compounds such as vinylcyclohexene and dipentene or its isomers by reaction with two moles of phenol per mole of the compound. R₃ preferably contains from 1 to 9 carbon atoms. Diepoxides useful for the preparation of polyhydroxyethers can be represented by the formula wherein R₄ is representative of a bond between adjacent carbon atoms or a divalent inorganic or organic radical such as an aliphatic, aromatic, homocyclic, heterocyclic or acyclic arrangement of atoms. By the term "diepoxide" is meant a compound containing two epoxide groups i.e. groups containing an oxirane oxygen atom bonded to two vicinal aliphatic carbon atoms. Saturated diepoxides in which both the oxirane oxygen atoms are bonded to carbon atoms of a saturated aliphatic hydrocarbon chain are particularly preferred. The term "saturated diepoxides" refers to diepoxides which are free of ethylenic unsaturation, i.e. -C=C- and acetylenic unsaturation, i.e. -C≡C-. Diepoxides which contain solely carbon, hydrogen and oxygen atoms are especially preferred. The oxygen atoms can be (in addition to oxirane oxygen), ether oxygen, i.e. -O- oxacarbonyl oxygen, i.e. and the like. A single diepoxide or a mixture of at least two diepoxides can be employed in preparing the polydihydroxyethers of the present invention and the term "diepoxide" is intended to include a mixture of at least two diepoxides. Other diepoxides which can be mentioned include those wherein the two oxirane groups are linked through an aromatic ether i.e. compounds having the grouping wherein R₄ is a divalent organic radical, W is a divalent aromatic radical residuum of a dihydric phenol such as those listed above in the description of dihydric phenols, and d is an integer from 0 to 1 inclusive. Still other diepoxides include ethers wherein the oxirane groups are connected to vicinal carbon atoms at least one pair of which is a part of a cycloaliphatic hydrocarbon. These polyhydroxy ethers are prepared by methods well known in the art such as those detailed in, for example, U.S. Patent 3,238,087; 3,305,528; 3,294,747 and 3,277,051. Ordinarily from 0.985 to 1.015 moles and preferably one mole of the epoxide is employed per mole of dihydric phenol. Polymerization occurs at room temperature (25°C.) and lower but only slowly, hence ordinarily, an elevated temperature e.g. 40°C. to 250°C. or more preferably from 80 to 125°C. is used to ensure a rapid rate of polymerization. Pressure is not at all critical, with polymerization being successfully effected at atmospheric, subatmospheric, or superatmospheric pressure with or without an inert gas such as nitrogen in the reaction vessel. The polyarylate is used in amounts of from about 4 to about 80, preferably from about 40 to about 60 weight percent. The polyester is used in amounts of from about 4 to about 60, preferably from about 10 to about 45 weight percent. The thermoplastic polymer is used in amounts of from about 10 to about 92, preferably from about 30 to 60 weight percent. The compositions of this invention are prepared by any conventional mixing methods. For example, a preferred method comprises mixing the polyarylate, polyester, and thermoplastic polymer in powder or granular form in an extruder and extruding the mixture into strands, chopping the strands into pellets and molding the pellets into the desired article. It should, of course, be obvious to those skilled in the art that additives may be included in the present compositions. These additives include plasticizers; pigments; flame retardant additives, particularly, decabromodiphenyl ether and triarylphosphates, such as triphenylphosphate; reinforcing agents, such as glass fibers; thermal stabilizers; ultraviolet light stabilizers processing aids, impact modifiers and the like. The impact modifiers which can be used are described in U.S. Patent Application Serial No. 049,131 of L. M. Robeson, titled "Impact Modified Polyarylate Blends", filed June 18, 1979. These impact modifiers are a graft copolymer of a vinyl aromatic, an acrylate, an unsaturated nitrile, or mixtures thereof, grafted onto an unsaturated elastomeric backbone and having a tensile modulus (as measured by ASTM D-638, except that the test piece is compression molded to a 0.5 mm thickness) of less than about 7 × 10⁸ Pa, and preferably from about 1.05 × 10⁸ to less than about 7 × 10⁸ Pa. The unsaturated elastomeric backbone may be polybutadiene, poly(butadiene-co-styrene), poly(butadiene-co-acrylonitrile), or poly(isoprene). In each of the polymers there is sufficient butadiene to give the polymer a rubbery character. The constituents which are grafted onto the unsaturated elastomeric backbone are selected from a vinyl aromatic, such as styrene, a-methylstyrene, alkylstyrene, or mixtures thereof; an acrylate such as the acrylic ester monomers, such as methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, or mixtures thereof, an unsaturated nitrile such as acrylonitrile, methacrylonitrile, or mixtures thereof. It will be understood that the vinyl aromatic, acrylate and acrylonitrile may be used individually or in any combinations in grafting onto the unsaturated elastomeric backbone. These impact modifiers are free-flowing powders and are commercially available as impact modifiers for poly(vinyl chloride) as described in, for example, V. Shakaypal, in "Developments in PVC Technology", edited by J. H. L. Hensen and A. Whelan, Applied Science Publishers Ltd., New York, 1973. The grafted constituents of the impact modifier will comprise from about 20 to about 60 percent by weight of said constituents such that their tensile modulus does not exceed about 7 × 10⁸ Pa, and is preferably, between about 1.05 × 10⁸ to less than about 7 × 10⁸ Pa. Examples The following examples serve to give specific illustrations of the practice of this invention but they are not intended in any way to limit the scope of this invention. Control A A polyurethane (Pellethane 2102-80A sold by Upjohn Company and having the mechanical properties described in Table 10) was injection molded into ASTM test bars (at 200°C) using a Newbury 35 × 10⁻⁶ m³ screw injection molding machine. The test bars were measured for the following properties: tensile strength and modulus according to ASTM D-638, and elongation at break according to ASTM D-638. The results are shown in Table 1. Preparation of blend of polyacrylate and poly(ethyleneterephthalate): 60 weight percent of polyarylate (Ardel D-100 sold by Union Carbide Corporation and prepared from Bisphenol-A and a mixture of 50 mole percent each of terephthalic and isophthalic acid chlorides, by conventional methods, having a reduced viscosity of 0.66 as measured in p-chlorophenol at 49°C, 2 kg/m³) was blended with 40 weight percent of poly(ethylene terephthalate) having an intrinsic viscosity of 0.064 as measured in a 60/40 1,1,2,2-tetrachloroethane/phenol mixture at 25°C. This blend was prepared by extrusion blending the components at about 270°C into pellets in a single screw 25 mm diameter extruder with L/D=36/1. Example 1 20 weight percent of the blend of polyarylate and poly(ethylene terephthalate) described above was blended with 80 weight percent of the polyurethane, Pellethane 2102-80A, described in Control A. The blend was prepared by extrusion blending the components at about 210-220°C in a single screw 25 mm diameter extruder with L/D=36/1. The extrudate was chopped into pellets. The pelletized product was molded into test bars and tested by the procedures as described in Control A. The results are shown in Table 1. Example 2 The procedure of Example 1 was exactly repeated except that 40 weight percent of the blend of polyarylate and poly(ethylene terephthalate) and 60 weight percent of the polyurethane were used. The results are shown in Table 1. Control B A polyurethane (Texin 355 DXH sold by Mobay Chemical Co. and having the mechanical properties described in Table 1) was injection molded into test bars and tested by the procedures as described in Control A. The results are shown in Table 1. Example 3 20 weight percent of the blend of polyarylate and poly(ethylene terephthalate) described above was blended with 80 weight percent of the polyurethane, Texin 355 DXH, described in Control B. The blend was prepared by extrusion blending the components at aboutt 210-220°C in a single screw 25 mm diameter extruder with L/D = 36/1. The extrudate was chopped into pellets. The pelletized product was molded into test bars and tested by the procedures as described in Control A. The results are shown in Table 1. Example 4 The procedure of Example 3 was exactly repeated except that 40 weight percent of the blend of polyarylate and poly(ethylene terephthalate) and 60 weight percent of the polyurethane were used. The results are shown in Table 1. Control C A thermmoplastic polyurethane (Pellethane 2102-55D sold by Upjohn Company and having the mechanical properties described in Table 1) was injection molded into test bars and tested by the procedures as described in Control A. The results are shown in Table 1. Example 5 40 weight percent of the blend of polarylate and poly(ethylene terephthalate) described above was blended with 60 weight percent of the polyurethane, Pellethane 2102-55D, described in Control C. The blend was prepared by extrusion blending the components at about 200-210°C in a single screw 25 mm diameter extruder with L/D = 36/1. The extrudate was chopped into pellets. The pelletized product was molded into test bars and tested by the procedures as described in Control A. The results are shown in Table 1. The data in Table 1 shows that the addition of polyarylate/poly(ethylene terephthalate) blends to thermoplastic polyurethanes yields higher modulus products while retaining good strength and ultimate elongation. This method of polymeric reinforcement offers distinct advantages over inorganic filler or fiber reinforcement. Commercially, the maximum tensile modulus of unreinforced thermoplastic polyurethanes is 1.4 × 10⁸ Pa. The ternary blend of this invention yields improved load bearing properties including lower creep and lower deformation under load. Control D A thermoplastic polyurethane (Pellethane 2102-55D sold by Upjohn Company and having the mechanical properties described in Table 11; was compression molded into samples at 210°C in a 100 × 100 × 5 mm inch mold cavity into test samples. These samples were exposed in an artificial weathering unit for 500, 1000 and 2000 hours by the procedure as described in ASTM D-1499. From the exposed specimens, 3.175 mm wide specimens were shear cut to determine the tensile strength according to a procedure similar to ASTM D-638. The initial tensile strength after molding is shown in Table 2 and the percent of the retention of the tensile strength of the samples is reported after 500, 1000 and 2000 hours of exposure in the weathering unit (Weatherometer). The results are shown in Table 2. Preparation of blend of polyarylate and poly(ethylene terephthalate) As described on page 12, lines 11-18 in connection with Control A. Example 6 10 weight percent of the blend of polyarylate and poly(ethylene terephthalate) described above was blended with 90 weight percent of the polyurethane, Pellethane 55D, described in Control D. The blend was prepared by mixing the components in a Brabender blender at about 210-230°C. The product was tested by the procedure of Control D. The results are shown in Table 2. Example 7 The procedure of Example 6 was exactly repeated except that 20 weight percent of the blend of polyarylate and poly(ethylene terephthalate) and 80 weight percent of the polyurethane were used. The results are shown in Table 2. The data in the Table show improved retention of tensile strength after artificial weathering exposure with addition of low levels of polyarylate. The addition of the polyarylate/poly(ethylene terephthalate) blend to the thermoplastic polyurethane did not detract from the excellent tensile strength exhibited by the thermoplastic polyurethane. Control E A poly(ether-ester) (AB) n block copolymer (Hytrel 5555 sold by E. I. du Pont Company and having the mechanical properties listed in Table 3) was injection molded into ASTM test bars (at 220-230°C) using a Newbury 35 × 10⁻⁶m³ screw injection molding machine. The test bars were measured for the following properties: tensile strength and modulus according to ASTM D-638, and elongation at break according to ASTM D-638. The results are shown in Table 3. Preparation of blend of polyarylate and poly(ethylene terephthalate) As described on page 12, lines 11-18 in connection with Control A. Example 8 20 weight percent of the polyarylate/poly(ethylene terephthalate) blend prepared above was blended with 80 weight percent of the block copolymer (Hytrel 5555) described in Control E. The blend was prepared by extrusion blending the components into pellets at 220-230°C in a single screw 25 mm diameter extruder with L/D = 36/1. The pellets were injection molded into ASTM test bars and tested by the procedures described in Control E. The results are shown in Table 3. Example 9 Example 8 was exactly repeated except that 40 weight percent of the polyarylate/poly(ethylene terephthalate) blend and 60 weight percent of the block copolymer (Hytrel 5555) was used. The results are shown in Table 3. Control F A poly(butylene terephthalate)-polytetrahydrofuran (AB) n block (Hytrel 6345 sold by E. I. du Pont Company and having the mechanical properties listed in Table 3) was injection molded into ASTM test bars and tested by the procedures described in Control E. The results are shown in Table 3. Example 10 20 weight percent of the polyarylate/poly(ethylene terephthalate) blend prepared above was blended with the block copolymer (Hytrel 6345) described in Control F. The blend was prepared by extrusion blending the components into pellets at 220-230°C in a single screw 25 mm diameter extruder with L/D = 36/1. The pellets were injection molded into ASTM bars and tested by the procedures described in Control E. The results are shown in Table 3. Example 11 Example 10 was exactly repeated except that 40 weight percent of the polyarylate/poly(ethylene terephthalate blend and 60 weight percent of the block copolymer (Hytrel 6345) were used. The results are shown in Table 3. The data in the Table show that addition of the polyarylate/poly(ethylene terephthalate) blend to the block copolymer results in a significant increase in modulus while maintaining the excellent tensile strength inherent in these block copolymers. The increased modulus will improve the resistance to deformation under load. Control G A poly(ether-ester) (AB) n block copolymer, Hytrel 5555, described in Control AA was compression molded at 230°C in a 100 × 100 × 5 mm mold cavity to form 0.5 mm samples. These samples were exposed in an artificial weathering unit for 500 and 1000 hours by the procedure as described in ASTM D-1499. From the exposed specimens, 3.175 mm wide specimens were shear cut to determine the tensile strength according the procedure of ASTM D-638. The initial tensile strength after molding is shown in Table 4 and the percent of the retention of the tensile strength of the samples is reported after 500 and 1000 hours of exposure in the weathering unit (Weatherometer). The results are shown in Table 4. Preparation of a blend of polarylate and poly(ethylene terephthalate) As described on page 12, lines 11-18 in connection with Control A. Example 12 10 weight percent of the polyarylate/poly(ethylene terephthalate) blend prepared above was blended with 90 weight percent of the block copolymer (Hytrel 5555) described in Control G. The blend was prepared by mixing the components in a Brabender blender at 220-230°C. The blend was then tested by the procedures described in Control G. The results are shown in Table 4. Example 13 Example 12 was exactly repeated except that 20 weight percent of the polyarylate/poly(ethylene-terephthalate) blend and 80 weight percent of the block copolymer (Hytrel 5555) was used. The results are shown in Table 4. Control H A poly(butylene terephthalate)-polytetrahydrofuran (AB) n block copolymer, Hytrel 6345, described in Control BB was compression molded and tested by the procedure described in Control G. The results are shown in Table 4. Example 14 10 weight percent of the polyarylate/poly(ethylene terephthalate) blend prepared above was blended with 90 weight percent of the block copolymer (Hytrel 6345) described in Control H. The blend was prepared by mixing the components in a Brabender blender at 220-230°C. The blend was then tested by the procedure described in Control G. The results are shown in Table 4. Example 15 Example 14 was exactly repeated except that 20 weight percent of the polyarylate/poly(ethylene-terephthalate) blend and 80 weight percent of the block copolymer (Hytrel 6345) was used. The results are shown in Table 4. The results in the Table show that the block copolymers degrade very rapidly under the test conditions. The addition of a blend of polyarylate/poly(ethylene-terephthalate) to the block copolymer results in improved tensile strength retention of the poly(ether-ester) block copolymer after weathering. Control I 100 weight percent of poly(vinyl chloride) having an inherent viscosity of 0.78 (as measured by ASTM-D1243, Method A) (QSAH-7 sold by Union Carbide Corporation) was mixed with 4 parts by weight of an organo tin thermal stabilizer (TM-181 sold by Cincinnati Milacron). This mixture was compression molded at 180°C in a 100 × 100 × 5 mm mold cavity to form 0.5 mm samples. These samples were exposed to an artificial weathering unit for 500 and 1000 hours by the procedure as described in ASTM D-1499. From the exposed specimens, 3.175 mm wide specimens were shear cut to determine the tensile strength according to the procedure of ASTM D-638. The initial tensile strength after molding is shown in Table 5 and the percent of the retention of the tensile strength of the samples is reported after 500 and 1000 hours of exposure in the weathering unit (Weatherometer). The color of the sample after 1000 hours of exposure is also shown. The results are shown in Table 5. Preparation of a blend of polyarylate and poly(ethylene terephthalate) As described on page 12, lines 11-18 in connection with Control A. Example 16 10 parts by weight of the polyarylate/poly(ethylene terephahalate) blend prepared above was blended with the mixture of 100 parts by weight of the poly(vinyl chloride) and 4 parts by weight of the stabilizer as described in Control I. The blend was prepared by blending the two premixed blends on a two roll mill at 170-180°C roll temperature. The blend was then tested by the procedure described in Control I. The results are shown in Table 5. Example 17 Example 16 was exactly repeated except that 20 parts by weight of the polyarylate/poly(ethylene terephthalate) blend was used. The results are shown in Table 5. Control J 100 parts by weight of the poly(vinyl chloride) (QYSA sold by Union Carbide Corporatiion) having an inherent viscosity of 0.63 (as measured by ASTM D-1243, Method A) was mixed with 4 parts by weight of a thermal stabilizer (TM-181) described in Control I. The mixture was compression molded and tested by the procedure described in Control I. The results are shown in Table 5. Example 18 20 parts by weight of the polyarylate/poly(ethylene terephalate) blended prepared above was blended with a mixture of 100 parts by weight of poly(vinyl chloride) and 4 parts by weight of the stabilizer as described in Control I. The blend was prepared by blending the two premixed blends on a two roll mill at 170-180°C roll temperature. The blend was then tested by the procedure described in Control I. The results are shown in Table 5. The results in the Table show that the ternary blends of polyarylate/poly(ethylene terephthalate) and poly(vinyl chloride), according to this invention having improved retention of tensile strength and also exhibit lower discoloration after exposure of 1000 hours in comparison to the poly(vinyl chloride). Example 19 50 weight percent of poly(hydroxy ether) having a reduced viscosity of 0.41 as measured in methylene chloride (Phenoxy PKHH sold by Union Carbide Corporation) was blended with 33.5 weight percent of polyarylate, Ardel D-100, and 16.5 weight percent of a copolyester, PETG-6763 (a copolyester prepared by the reaction of cyclohexanedimethanol and ethylene glycol with terephthalic acid, in a molar ratio of 1:2:3. This polyester has a M n of about 26,000 and is sold by Tennessee Eastman Company). The blend was prepared by extrusion blending the components at 265°C in a single screw 25 mm diameter extruder with L/D = 36/1. The extrudate was chopped into pellets. The pelletized product was injected molded into ASTM test specimens (250-265°C) using a Newbury 35 × 10⁻⁶m³ screw injection molding machine. The test specimens were measured for the following properties: tensile strength and modulus according to ASTM D-638; elongation at break according to ASTM D-638; and notched izod impact strength according to ASTM D-256. The results are shown in Table 6 as follows: Blends of poly(hydroxy ether) and polyarylate are very difficult to prepare and injection mold due to the potential of crosslinking due to transesterification. However, the addition of a copolyester to the poly(hydroxy ether) and polyarylate allows for sufficient blending and fabrication lattitude for forming injection molded articles. The ternary blend has good mechanical properties. Example 20 40 weight percent of a polyarylate, Ardel D-100 was blended with 20 weight percent of a copolyester of cyclohexanedimethanol, ethylene glycol and terephthalic acid (PETG-6763 a copolyester prepared by the reaction of cyclohexanedimethanol and ethylene glycol with terephthalic acid, in a molar ratio of 1:2:3. This polyester has a M n of about 26,000 and is sold by Tennessee Eastman Company), 30 weight percent of a poly(methyl methacrylate) grafted into butadiene based rubber (Pexiglas DR sold by Rohm & Haas Company having a tensile modulus of 1,694 × 10⁶ Pa, a tensile strength of 40.5 × 10⁶ Pa, an elongation of 48 percent, a flexural modulus of 1,939 × 106 Pa, flexural strength of 65.7 × 10⁶ Pa a notched izod impact strength of 1.29 J/25 mm of Notch, a tensile impact strength of 88 × 10³ Pa × m and a heat distortion temperature of 70°C.), and 10 weight percent of a styrene/acrylate/butadiene terpolymer (KM-611 a styrene/acrylate/butadiene terpolymer having a tensile modulus of 305 × 10⁶ Pa and sold by Rohm & Hass Company). This blend was prepared by extrusion blending the components at about 270°C in a 25 mm diameter extruder with L/D = 36/1. The extrudate was chopped into pellets. The pellets were molded into ASTM test specimens (at 270-300°C) using a Newbury 35 × 10⁻⁶m³ screw injection molding machine. The test specimens were measured for the following properties: tensile strength and modulus according to ASTM D-638; elongation at break according to ASTM D-638; notched izod impact strength according to ASTM D-256; tensile impact strength according to ASTM D-1822; heat distortion temperature measured at 1.85 × 10⁶ Pa on a 3.175 mm unannealed test bar according to ASTM D-635. The results are shown in Table 7. Example 21 52.5 weight percent of a polyarylate, Ardel D-100, 17.5 weight percent of a copolyester, PETG-6763 (described in Example 20), 10 weight percent of a styrene/acrylate/butadiene terpolymer (KM-611 described in Example 20) and 20 weight percent of a poly(methyl methacrylate) (XT-375 sold by American Cyanamid). The blend was prepared as in Example 20 molded into test samples and tested by the procedures as described in Example 20. The results are shown in Table 7. Example 22 Example 21 was exactly repeated except that 20 weight percent of a poly(methyl methacrylate) (XT-250 sold by American Cyanamid) was substituted for the XT-375 poly(methyl methacrylate). The results are shown in Table 7.

Claims: A molding composition comprising a blend of: (a) 4 to 80 weight percent of a polyarylate derived from at least one dihydric phenol and at least one aromatic dicarboxylic acid consisting from 95 to 0 mole percent of terephthalic acid and 5 to 100 moles percent of isophthalic acid; (b) 4 to 60 weight percent of a polyester having an intrinsic viscosity of 0.04 to 0.2 m³/kg derived from an aliphatic or cycloaliphatic diol, or mixtures thereof containing from 2 to 10 carbon atoms; and at least one aromatic dicarboxylic acid; and (c) 10 to 92 weight percent of at least one thermoplastic polymer selected from the group consisting of a polyurethane, a vinyl chloride polymer, a copolyetherester block copolymer, and a polyhydroxyether. A composition as defined in claim 1 wherein the dihydric phenol is of the formula: wherein Y is selected from alkyl groups of 1 to 4 carbon atoms, chlorine or bromine, z independently has a value from 0 to 4, inclusive, and R' is a divalent saturated aliphatic hydrocarbon radical selected from alkylene and alkylidene radicals having from 1 to 3 carbon atoms, and cycloalkylene radicals having up to and including 9 carbon atoms. A composition as in claim 1 wherein the polyester has repeating units of the general formula: wherein n is an integer of from 2 to 4. A composition as in claim 1 wherein the polyester has recurring units of the following formula: wherein the cyclohexane ring is selected from the cis- and trans-isomer thereof, and R is an aryl radical containing 6 to 20 carbon atoms and which is the decarboxylated residue derived from an aromatic dicarboxylic acid, or, the polyester is a copolyester having repeating units of the following formula: wherein the cyclohexane ring is selected from the cis- and trans-isomers thereof, R is an aryl radical containing 6 to 20 carbon atoms and which is the dicarboxylated residue derived from an aromatic dicarboxylic acid, n is an integer of 2 to 4, x units comprise from 10 to 90 percent by weight and the y units comprise from 10 to 90 percent by weight. A composition as in claim 1 wherein the polyester has recurring units of the following formula or the polyester is a copolyester having repeating units of the following formula wherein x and y are as defined in claim 4. A composition as defined in claim 1 having improved retention of tensile strength after weathering wherein (c) is a polyurethane, which is derived from a polyester resin having a molecular weight of at least 600, an organic diisocyanate, and a low molecular weight chain extender having active hydrogen containing groups reactive with isocyanate or which is derived from a polyether, an organic diisocyanate, and a low molecular weight chain extender having active hydrogen containing groups reactive with isocyanate, the said polyether being selected from polytetramethylene glycol having an average molecular weight between about 600 and 2000, polypropylene glycol having a molecular weight above 600 and polyethylene glycol having a molecular weight above 600. A composition as defined in claim 1 having improved retention of tensile strength after weathering wherein (c) is a poly(vinyl chloride) polymer or a copolymer of vinyl chloride with an olefinically unsaturated polymerisable compound which contains at least 80 percent by weight of vinyl chloride incorporated therein. A composition as defined in claim 1 having improved retention of tensile strength after weathering wherein (c) is a copolyetherester block copolymer, which consists essentially of multiplicity of recurring intralinear long chain and short chain ester units connected head-to-tail through ester linkages, said long chain ester units being represented by the following structure: and said short chain ester units being represented by the following structure: wherein: G is a divalent radical remaining after removal of terminal hydroxy groups from a poly(alkylene oxide) glycol having a molecular weight of 400-3500; D is a divalent radical remaining after removal of hydroxyl groups from a low molecular weight diol, having a molecular weight less than 250; and R₂ is a divalent radical remaining after removal of carboxyl groups from a dicarboxylic acid having a molecular weight less than 300; with the provisos that the short chain ester units constitute 25-65% by weight of the copolyester, at least 70% of the R₂ groups must be 1,4-phenylene radicals, at least 70% of the D groups must be the 1,4-butylene radicals, and the sum of the percentages of the R₂ groups which are not 1,4-phenylene radicals and of the D groups which are not 1,4-butylene radicals cannot exceed 30%. A composition as defined in claim 1 wherein (c) is a polyhydroxyether, wherein the polyhydroxyether has the general formula [D-O-E''-O wherein D is the radical residuum of a dihydric phenol, E'' is a radical residuum of an epoxide selected from mono- and diepoxides and contains from 1 to 2 hydroxyl groups and n is an integer which represents the degree of polymerization and is at least 30. A composition as defined in claim 1 which contains from 40 to 60 weight percent of the polyarylate a), from 10 to 45 weight percent of the polyester b) and from 30 to 60 weight percent of the thermoplastic polymer c).

Inventors: ROBESON LIOYD MAHLON, ROBESON, LIOYD MAHLON
Applicants: AMOCO CORP, AMOCO CORPORATION
Application year: 1980
Main classification: C08L67
IPC codes: C08L27, C08L67, C08L71, C08L101, C08L33, C08L1, C08L75, C08G18, C08L81