COPOLYETHERESTER MOLDING COMPOSITIONS Nan-I Liu and Surrendra Agarwal The present invention relates to novel thermo¬ plastic elastomeric molding compositions having excel¬ lent stress-strength properties, particularly low temperature impact resistance, while retaining low flexural modulus and excellent physical appearance. Specifically, the compositions of the present inven¬ tion consist essentially of one or more thermoplastic copolyetherester elastomers in random or block form, and a property improving modifier combination therefor consisting of a) a poly(butylene terephthalate)polyester b) a irtonoalkenyl arene-conjugated diene copoly- er or copoly er composition and, optionally, c) clay.

BACKGROUND Copolyetheresters are well known and have enjoyed continued and increasing commercial success. They are available from several sources including the Hytrel ^* ^ resins from E.I. duPont and the GAFLEX-^ resins from GAF Corporation and are described in U.S. Patent Nos. 3,023,192; 3,651,014; 3,763,109; 3,766,146; 3,784,520; 3,801,547; 4,156,774; 4,264,761 and 4,355,155, among others, all incorporated herein by reference. While these copolyetheresters have a number of desirable properties including excellent tear strength, flex life, toughness, and general elastomeric stress-strain characteristics, their use is limited by their low flexural characteristics, primarily flexural modulus and flexural strength, as well as their generally low melt-viscosities. Depending upon their specific form¬ ulation, copolyetheresters suitable for molding appli¬ cations vary from very soft elastomers to semi-rigid elastomers. However, many molding applications

require that the molding compositions be rigid at least to the extent that molded parts therefrom are able to maintain their structural integrity and resist deformation upon low energy impact. Further, certain molding processes, e.g. shape forming by blow molding or profile-extrusions require the molding composition to have a moderate to fairly high melt-viscosity in order to avoid draw down of the melt resin.

It is suggested in the foregoing references that the modulus of elasticity of copolyetheresters may be increased by incorporating therein various reinforcing fillers such as glass and mica. More recently, it has been alleged that the flexural modulus as well as other physical properties may be enhanced by blending with copolyetheresters one or more thermoplastic poly¬ esters. For example, Brown et al (US Pat. No. 3,907,926) have prepared copolyetherester compositions having alleged improved Young's modulus combined with good flexibility and low temperature impact strength by creating a uniform blend of poly(butylene tere¬ phthalate) and a copolyetherester. Additionally, Perry et al (UK 1,431,916) have prepared blends of a polyester, particularly poly(alkylene terephthalates) , and a copolyetherester allegedly having improved im- pact strength, stiffness and processability. Finally, Charles et al (US Pat. No. 4.469,851) have prepared blends of poly(butylene terephthalate) and a copoly¬ etherester derived from butanediol, butenediol, di ethylterephthalate and poly(tetramethylene ether) glycol which allegedly have improved melt stability. It has also been suggested that the problems associated with draw down of the melt resin in shape forming can be overcome by admixing with the copoly¬ etherester an APS resin (terpolymer of acrylonitrile, butandiene and styrene) or an MBS resin (terpolymer of methyl ethacrylate, butadiene and styrene) . However,

such ^" compositions suffer from defects in surface characteristics, most noticeably the occurrence of roughness and fish-eyes. Yusa et al. overcomes this problem by the use of a specific graft copolymer characterized as consisting essentially of a cross-linked styrene/methylmethacrylate shell grafted on a cross-linked butadiene or alkyl acrylate core.

While the addition of polyester or rubbery copolymer to copolyetheresters improves impact strength an /or flexural properties and draw down, respectively, each is not without problems. With respect to blends of polyester and copolyetherester, while flexural modulus and strength increase sharply as the polyester level increases, there is an equally dramatic loss of tensile elongation. Further, where low temperature impact is desired, the amount of polyester needed to provide an appreciable increase in low temperature impact is such that the flexural modulus may be too high for the application. With respect to blends of the rubbery copolymer with copolyetheresters, as mentioned, except for a small class of graft copolymers, rubbery copolymers induce, fish-eyes and other detrimental physical, particularly surface, characteristics to the polymer. The addition of the highly cross-linked graft copolymer of Yusa et al. significantly lessens the problems with appearance, but at the loss of physical properties, most notably tensile strength and stress elongation. It has now been found that copolyetheresters having excellent low temperature impact strength, excellent flexural properties and superior surface characteristics may be prepared by admixing therewith a modifier combination of a poly(butylene terephthal¬ ate) and a monoalkenyl arene-conjugated diene copolymer.

Summary In accordance with the present invention there are provided improved thermoplastic elastomeric compo¬ sitions having excellent flexibility and low tempera- ture stress-strength properties combined with superior surface characteristics consisting essentially of:

A) one or more thermoplastic elastomeric copoly¬ etheresters and

B) from about 10 to about 60 percent by weight, based on the combined weight of (A) & (B) , of a modifier combination consisting essentially of: i) one or more poly(butylene terephtha¬ late) homopolyesters or copolyesters; ii) a onoalkenyl arene-conjugated diene rubbery copolymer selected from the group consisting of a) a ^" block copolymer comprising at least two monoalkenyl arene polymer end blocks A and at least one hydrogenated partially hydrogenated or non-hydrogen- ated conjugated diene polymer mid block B, said block copolymer having an 8 to 55 percent by weight monoalkenyl arene polymer block content, each polymer block A having an average molecular weight of between 5,000 and 125,000, and each polymer block B having an average molecular weight of between about 10,000 and about 300,000, and b) a core-shell graft copolymer com¬ prising a predominatel -conjugated diene polymer core to which is grafted a shell polymerized from one or more monomers at least one of which is a monoalkenyl arene; and

iii) optionally, clay; wherein a) the poly(butylene terephthalate) com¬ prises from about 5 to about 50, preferably from about 10 to about 25, percent by weight of the total composition, b) the monoalkenyl arene-con- jugated diene copolymer comprises from about 5 to about 30, preferably from about 10 to about 15, percent by weight of the total composition and c) the clay, if present, is used in an amount up to about 25, preferably 20 weight percent, based on the total composition.

In the most preferred compositions, the poly- (butylene terephthalate) (B) (i) is poly(1,4-butylene terephthalate) and the monoalkenyl arene-conjugated diene copolymer is selected from non-hydrogenated block copolymers of polystyrene-polybutadiene-poly- styrene. and graft copolymers of a polybutadiene core with a •polymethylmethacrylate/polystyrene shell. Finally it is especially desirable to pre-compound the graft copolymer with some or all of the poly(butylene terephthalate) prior to admixing with the copoyetherester.

DETAILED DESCRIPTION OF THE INVFNTION Suitable thermoplastic copolyetheresters (A) include both random and block copolymers. In general these are prepared by conventional esterification/polycon- densation processes from (a) one or more dicls, (b) one or more dicarboxylic acids, (c) one or more long chain ether glycols, and, optionally, (d) one or more caprolartones or polycaprolaotones.

Diols(a) which can be used in the preparation of the copolyetheresters include both saturated and unsaturated aliphatic and cycloaλiphatic dihydroxv compounds as well as aromatic dihydroxv compounds. These diolε are preferably of a low molecular weight, i.e. having a molecular weight of about 300 or less.

When used herein, the term "diols" and "low molecular weight diols" should be construed to include.equiv¬ alent ester forming derivatives thereof, provided, however, that the molecular weight requirement per- tains to.the diol only and not to its derivatives. Exemplary of ester forming derivatives there may be given the acetates of the diols as well as, for example, ethylene oxide or ethylene carbonate for ethylene glycol. Preferred saturated and unsaturated aliphatic and cycloaliphatic diols are those having from about 2 to 19 carbon atoms. Exemplary of these diols there may be given ethylene glycol; propanediol? butanediol; pentanediol; 2-methyl propanediol; 2,2-dimethyl pro- panediol; hexanediol; decanediol; 2-octyl undecane- diol; 1,?.-, 1,3- and 1,4- dihydroxy cyclohexane; 1,2-, 1,3- and 1,4-cyclohexane dimethanol; butenediol; hex- enediol, etc. Especially preferred are 1 ,4-butanediol and mixtures thereof with hexanediol or butenediol. Aromatic diols suitable for use in the prepara¬ tion of the thermoplastic elastomers are generally those having from 6 to about 19 carbon atoms. In¬ cluded among the aromatic dihydroxy compounds are resorcinol; hydroσuinone; 1,5-dihydroxy naphthalene; 4,4'-dihydroxy diphenyl; bis(p-hydroxy phenyl)methane and 2,2-bis (p-hydroxy phenyl) propane.

Fspecially preferred diols are the saturated ali¬ phatic diols, mixtures thereof and mixtures of a saturated diol(s) with an unsaturated diol(s), wherein each diol contains from ? to about 8_carbon atoms.

Where more than one diol is employed, it is preferred that at least about 60 mole %, most preferably at least 80 mole %, based on the total diol content, be the same diol. As mentioned above, the preferred thermoplastic elastomers are those in which 1,4- butanediol is present in a predominant amount.

Dicarboxylic acids (b) which are suitable for use in the preparation of the copolyetheresters include aliphatic, cycloaliphatic, and/or aromatic dicar¬ boxylic acids. These acids are preferably of a low molecular weight, i.e., having a molecular weight of less than about 350; however, higher molecular weight dicarboxylic acids, especially dimer acids, may also be used. The term "dicarboxylic acids" as used here¬ in, includes equivalents of dicarboxylic acids having two functional carboxyl groups which perform substan¬ tially like dicarboxylic acids in reaction with gly- cols and diols in forming polyester polymers. These equivalents include esters and ester-forming deriva¬ tives, such as acid halides and anhydrides. Addition- --- ^■ ly, the dicarboxylic acids may contain any substi- tuent group (s) ,or combinations which do not substan¬ tially interfere with the polymer formation and use of the polymer in ^* the practice of this invention.

Aliphatic dicarboxylic acids, as the term is used herein, refers to carboxylic acids having two carboxyl groups each of which is 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. Aromatic dicarboxylic acids, as the term is used herein, are dicarboxylic acids having two carboxyl groups each of which is attached to a carbon atom in an isolated or fused benzene ring system. It is not necessary that both functional carboxyl groups be attached to the same aromatic ring and where more th?n one ring is present, they can be joined by aliphatic or aromatic divalent radicals or divalent radicals such as -0- or -SO--.

Representative aliphatic and cycloa." iphatic acids which can be used are sebacic acid, 1 ,2-cyclohexane dicarboxylic acid, 1 ,3-cyclohexane dicarboxylic acid,

1,4-σyclohexane dicarboxylic acid, adipic acid, glut¬ aric acid, succinic acid, oxalic acid, azelaic acid, diethylmalorjc acid, allylmalonic acid, dimer acid, 4-cyclohexene-l ,2- dicarboxylic acid, 2-ethylsuberic acid, tetramethylsuccinic acid, cyclopentane dicar¬ boxylic acid, decahydro-l,5-naphthalene dicarboxylic acid, 4,4'- bicyclohexyl dicarboxylic acid, decahydro- 2,6-naphthalene dicarboxylic acid, 4,4 ethylenebis- (cyclohexane carboxylic acid) , 3,4-furan dicarboxylic acid, and 1 ,1-cyclobutane dicarboxylic acid. Pre¬ ferred aliphatic acids are cyclohexane dicarboxylic acids,sebacic acid, dimer acid, glutaric acid, azelaic acid and adipic acid.

Representative aromatic dicarboxylic acids which can be used include terephthalic, phthalic and iso- phthalic acids, bi-benzoic acid, substituted dicarboxy compounds with two benzene nuclei such as bis (p-carb- oxyphenyl) methane, oxybis (benzoic acid) , ethylene- 1 ,2-bis- (p-oxybenzoic acid) , 1,5-naphthalene dicarb- oxylic acid, 2,6-naphthalene dicarboxylic acid, 2,7- naphthalene dicarboxylic acid, phenanthrene dicarb¬ oxylic acid, anthracene dicarboxylic acid, 4,4'- sulfonyl diher∑oic: ac d, and halo and C--C. - alkyl, alkoxy, and aryl ring substitution derivatives there- of. Hydroxy acids such as p( μ> -hydroxyethoxv)benzoic acid can also be used provided an aromatic dicar¬ boxylic acid is also present.

Preferred dicarboxylic acids for the preparation of the po_yetheriτnide esters are the aromatic dicarh- oxvlic acids, mixtures thereof and mixtures of one or more dicarboxylic acid with an aliphatic and/or cyclo¬ aliphatic dicarboxylic acid, most preferably the aro¬ matic dicarboxylic acid?. Among the aromatic acids, those with R-16 carbon atoms are pre ^f erred, part cu- larly the brnzene dicarboxylic acids, i.e., phthalic, ter<=phthalic and isophthalic acids and their dimethv.

derivatives. Especially preferred is dimethyl terephthalate.

Finally, where mixtures of dicarboxylic- acids are employed, it is preferred that at least about 60 mole %, preferably at least about 80 mole %, based on 100 mole *■ of dicarboxylic acid (b) be of the same dicar¬ boxylic acid or ester derivative thereof. As men¬ tioned above, the preferred copolyetheresters are those in which di ethylterephthalate is the predominant dicarboxylic acid.

Suitable long chain ether glycols (c) which can be used in the preparation of the thermoplastic elast¬ omers are preferably poly (oxyalkylene) glycols and copoly (oxvalkylene) glycols of molecular weight of from about 400 to 12000. Preferred, poly (oxyalkylene) units are derived from long chain ether glycols of from about 900 to about 4000 molecular weight and having a carbon-to-oxygen ratio of from about 1.8 to about 4.3, exclusive of any side chains. Representative of suitable poly(oxyalkylene) - glycols there may be given poly (ethylene ether) glycol; poiy (propylene ether) glycol) poly(tetramethylene ether) glycol; random or block copolymers of ethylene oxide and propvlene oxide, including ethylene oxide end capped poly (propylene ether) glycol and predom¬ inately poly(ethylene ether) backbone, copoly (propy¬ lene ether-ethylene ether)glycol; and random or block copolymers of tetrahydrofuran with minor amounts of a second monomer such as ethylene ^' oxide, propylene oxide, or ethyltetrahydrofuran (used in proportions such that the carbon-to-oxygen ratio does not exceed about 4.3) . Polyfor al σlycols prepared by reacting formaldehyde with diols such as 1 ,4-butanediol and 1 , 5-pentanediol are also useful. Especially preferred poly (oxyalkylene) glycols are poly (propylene ether) - glycol, poly (tetramethylene ether) glycol and predom-

inately poly (ethylene ether) backbone copoly(propylene ether-ethylene ether)glycol.

Optionally, these copolyetheresters may have incorporated therein one or more caprolactones or polycaprolactones. Such caprolactone modified copolyetheresters are disclosed in copending U.S. Pat. application Serial No. 643,985 filed August 24, 1984, herein incorporated by reference.

Caprolactones (d) suitable for use herein are widely available commercially, e.g.. Union Carbinde Corporation and Aldrich Chemicals. ^' While epsilon caprolactone is especially preferred, it is also poss¬ ible to use substituted caprolactones wherein the epsilon caprolactone is substituted by a lower alkyl group such as a methyl or ethyl group at the alpha, beta, gamma, delta or epsilon positions. Addition¬ ally, it is possible to use polycaprolactone, includ¬ ing homopolymers and copolymers thereof with one or more components, as well as hydroxy terminated poly- caprolactone, as block units in the novel copolyether¬ esters of the present invention. Suitable polycapro¬ lactones and processes for their production are described in, for example, U.S. Pat. Nos. 3,761,511; 3,767,627, and 3,806,495 herein incorporated by reference.

In general, suitable copolyetherester elastomers (A) are those in which the weight percent of (c) . org chain ether glycol component or the combined weight percent of (c) long chain ether glycol component and (d) caprolactone component in _he copolyetherester is from about 5 to about 70 weight percent. Preferred, composition are those wherein the weight percent of (c) or (c) and (d) is from about 10 to about 50 weight percent. Where both (c) long chain ether glycol and (d) caprolactone are present, each will comprise from about 2 to about 50 percent by weight , preferrably

fro -about 5 to about 30 percent by weight, of the copolyetherester.

As described above, the copolyetheresters may be prepared by conventional esterification/condensation reactions for the production of polyesters. Exemplary of the processes that may be practiced are as set forth in, for example, U.S. Pat. Nos. 3,023,192; 3,763,109; 3,651,014; 3,663,653 and 3,801,547, herein incorporated by reference. Additionally, these compo- sitions may be prepared by such processes and other known processes to effect random copolymers, block copolymers or hybrids thereof wherein both random and block units are present. For example, it is possible that any two or more of the foregoing monomers/reac- tants may be prereacted prior to polymerization of the final copolyetheresters. Alternatively a two part synthesis may be employed where in two different diols and/or dicarboxylic acids are each prereacted in separated reactors to form two low molecular weight prepolymers which are then combined with the long chain ether glycol to form the final tri-block copoly- _$ etherester. Further exemplification of various copolyetheresters will be set forth below in the examples. The foregoing thermoplastic elastomers (A) are modified in accordance with the teachings of the in¬ stant invention by admixing therewith a modifying amount of a combination (B) of (i) one or more thermo¬ plastic poly (butylene terephthalate) homopoly er or copolymer, (ii) one or more monoalkenyl arene- -conjugated diene rubbery copolymer and (iii) optionally, clay filler.

While poly (1 , 4-butylene terephthalate)homopoly- ester is the preferred poly (butylene terephthalate) polymer, copolyesters thereof are also suitable. Such copolyesters generally comprise at least about 70 mole

percent, preferably at least 80 mole percent, based on total monomer content, of butylene and terephthalate units. The comonomer may be either a dicarboxylic acid or diol or a combination of the two. Suitable dicarboxylic acid comonomers include the C _fi to C. , aromatic dicarboxylic acids, especially the benzene dicarboxylic acids, i.e. phthalic and isophthalic acids and their alkyl, e.g. methyl, derivatives and C. to C. , aliphatic and cycloaliphatic dicarboxylic acids including for example sebacic acid; glutaric acid; azelaeic acid; tetramethyl succinic acid; 1,2-, 1,3- and 1, -cyclohexane dicarboxylic acids and the like, as mentioned above. Suitable diol comonomers include but are not limited to C_ to C _R aliphatic and cyclo- aliphatic diols, e.g. ethylene glycol, hexanediol, butanediol and 1,2-, 1,3- and 1,4- cyclohexanedi- methanol. Other suitable diols are as mentioned above for the preparation of the copolyetherester elastomer. The monoalkenyl arene-conjugated diene copolymers suitable for use in the present invention are selected from ABA type block copolymers and core-shell type copolymers. Further, the term "monoalkenyl arene- -conjugated diene" copolymers is intended to include copolymers having additional comonomers therein as long as both monoalkenyl arene monomers and conjugated diene monomers are each present in an amount of at least about 10 mole percent based on total monomer content of the copolymer.

As stated above, suitable block copolymers (B)- (ii) (a) comprise at least two monoalkenyl. arene poly¬ mer end blocks A and at least one hydrogenated, par¬ tially hydrogenated or non-hyrogenated conjugated diene polymer m block B, said block copolymer having an 8 to 55 percent by weigh monoalkenyl arene polymer block content, each polymer block A having an average molecular weight o* between about 5,000 and about

]25_,0.00, and each polymer block B having an average molecular weight of between about 10,000 and about 300,000.

These block copolymers may have a variety of geometrical structures, since the invention does not depend on any specific geometrical structure, but rather upon the chemical constitution of each of the polymer blocks. Thus, the structures may be linear, radial or branched so long as each copolymer has at least two polymer end blocks A and at least one poly¬ mer mid block B as defined above. The specific struc¬ ture of the polymers is determined by their methods of polymerization. For example, linear polymers re¬ sult by sequential introduction of the desired mono- mers into the reaction vessel when using such initiators as lithium-alkyls or dilithiostilbene and the like, or by coupling a two segment block copolymer with a difuntional coupling agent. Branched struc¬ tures, on the other hand, may be obtained by the use of suitable coupling agents having a functionality with respect to the polymers or precursor polymers where hydrogenation of the final block polymer is desired, of three or more. Coupling may be effected, with multi-funtional coupling agents such as dihalo- alkanes or dihaloalkenes and divinyl benzene as well as certain polar compounds such as silicon halides, siloxanes or esters of monohydric alcohols with car- boxylic acids. The presence of any coupling residues in the polymer may be ignored for an adequate descrip- tion of the polymers forminc a part of the co posi- tions of this invention. Likewise, in the generic sense, the specific structures also may be ignored.

Various methods, including those as mentioned above, for the preparation of the block copolyir-ers are known in the art. For example, such polymers, includ¬ ing processes for the hydrogenation thereof, where

desired, are disclosed in U.S. Patent Numbers 3,149,182; 3,595,942; 3,694,523; 3,287,333; 3,231,635 and 3,842,029, all incorporated herein by reference. In such processes, particular preference is made to the use of lithium based catalysts and especially lithium alkyls for the preparation of the block polymers.

Exemplary of typical species of block copolymers there may be given: polystyrene-polybutadiene-polyεtyrene (SBS) polystyrene-polyisoprene-polystyrene (SIS) poly (alpha-methylstyrene) -polybutadiene-poly- (alpha-methylstyrene) and poly(alpha-methylstyrene) -polyisoprene-poly- (alpha-methystyrene)

It will be understood that both blocks A and B may be either hompolymer or random copolymer blocks as long as each block predominates in at least ^' one class of the monomers characterizing the blocks and as long as the A blocks individually predominate in mono¬ alkenyl arenes and the B blocks individually predom¬ inate in dienes. The term "monoalkeny arene" will be taken to include especially styrene and its analogs and homologs including alpha-methylstyrene and ring- substituted styrenes, particularly ring-methylated sytrenes. The preferred monoalkenyl arenes are styrene and alpha-methylstyrene, and styrene is par¬ ticularly preferred. The B blocks may comprise homo- polymers of butadiene or isoprene and copolymers of one of these two dienes with a monoalkenyl arene as long as the B blocks predominate in conjugated die e units. When the monomer employed is butadiene, it is preferred that between about 35 and about 55 mole per¬ cent of the condensed butadiene units in the butadiene polymer block have 1 , ? configuration. Thus, when a hydrogenated or partially hydrogenated block copolymer

is desired, it is or has segments which are or resemble a regular copolymer block of ethylene and butene-1 (EB) . If the conjugated diene employed is isoprene, the resulting hydrogenated product is or resembles a regular copolymer block of ethylene and propylene (EP) .

When hyrogenation of the block copolymer is de¬ sired, it may be and is preferably effected by use of a catalyst comprising the reaction products of an aluminum alkyl compound with nickel or cobalt carboxylates or alkoxides under such conditions as to preferably substantially completely hydrogenate at least 80% of the aliphatic double bonds while hydrogenating no more than about 25% of the alkenyl arene aromatic double bonds. Preferred hydrogenated block copolymers are those where at least 99% of the aliphatic double bonds are hydrogenated while less than 5% of the aromatic double bonds are hydrogenated. The average molecular weights of the individual blocks may vary within certain limits. In most instances, the monoalkenyl arene blocks will have number average molecular weights in the order of 5,000-125,000 preferably 7,000-60,000 while the conjugated diene blocks either before or after hydro- genation will have average molecular weights in the order of 10,000-300,000, preferably 30,000-150,000. The total average molecular weight of the block co¬ polymer is typically in the order of 25,000 to about 350,000, preferably from about 35,000 to about 300,000. These molecular weights are most accuratelv determined by tritium counting methods or osmotic pressure measurements.

The proportion of the monoalkenyl arene blocks should be between about 8 and 55% by weight of the block copolymer, preferably between about 10 ar.d 30% by weight.

The second class of monoalkenyl arene-conjugated diene copolymers (B) (ii) are of the core-shell type. In general these are characterized as having a pre¬ dominately conjugated diene rubbery core and one or m.ore shells graft polymerized thereon and derived from monoalkenyl arene monomers alone or, preferably, in combination with other vinyl monomers.

More particularly, the first or core phase of the core-shell copolymer comprises polyermized conjugated diene units of one or more conjugated dienes alone or copolymerized with units of a vinyl monomer or mixture of vinyl monomers. Suitable conjugated dienes for use in said core phase include butadiene, isoprene, 1,3- pentadiene and the like. Illustrative of the vinyl monomers copolymerizeable therewith include the vinyl aromatic compounds such as sytrene, alpha-methyl¬ styrene, vinyl toluene, para-methylstyrene and the like; esters of acrylic and methacrylic acid, includ¬ ing for example methyl aerylate, ethyl acrylate, butyl acrvlate, methyl methacrvlate and ethyl methacrylate; and unsaturated aliphatic nitriles such as acrylo- nitrile, methacrylonitrile and the like. The core of said copolymer should comprise at least about 50 per¬ cent by weight of the conjugated diene. Preferred grafted core-shell copolymers for use herein comprise a core of polybutadiene homopolymer or a styrene-buta- diene copolymer comprising about 10 to 50% by weight styrene and about 90 to 50% by weight of butadiene, havinσ a molecular weight of from about 150,000 to about 500,000. The core phase may also include a cross-linking monomer, more particularly described below.

The final or shell phase of the copolymer com¬ prises polymerized units of a monoalkenyl arene alonn or copolymerized with one or more other vinyl monomers wherein at least 10 mole percent of the graft compcn-

- 17 - ent-is derived from the monoalkenyl arene monomer. Preferred monoalkenyl arene monomers are styrene, alpha-methylstyrene, para-methylstyrene and the like, •most preferably styrene. Additional monomers that may be copolymerized therewith in an amount up to 90 mole % include the esters of acrylic and methacrylic acid including for example, ethyl acrylate, methyl acryl- ate, butyl acrylate, methyl methacrylate, ethyl meth- acrylate, butyl methacrylate and the like; unsaturated aliphatic nitrile such as acrylonitrile and methacrylo- nitrile and vinyl halides such as vinyl chloride and vinyl bromide. Especially preferred shells are those derived from polymerized units of styrene and methyl methacrylate wherein each is present in an amount of from 10 to 90 mole %. Additionally, these shells may also have copolymerized therewith a minor amount, pre¬ ferably less than 10 mole % of one or more of the other aforementioned monomer units. As with the core, the shell phase may also include a cross-linking monomer as discussed more fully below.

Optionally, the core-shell copolymers may further comprise one or more cross-linked or non-cross-linked intermediate layers which is grafted to the core and upon which the final shell layer is grafted, comprised. of one or more polymerized vinyl monomer. Suitable vinyl monomers for one in these intermediate layers include but are not limited to those mentioned above, especially polystyrene. Where such intermediate layers are present in the core-shell copolymer and are derived from at least 10 mole % of a monoalkenyl arene monomer, the final or shell phase may comprise up to and including 100 mole % monomer units which are not monoalkenyl arene units. Especially preferred in such instances are multi-phase copolymers wherein the intermediate phase comprises polystyrene and the final stage comprises polymethyl.methacrylate.

- As mentioned each of the individual stages of the core-shell copolymers may contain a cross-linking monomer which may serve not only to cross-link the units of the individual layers but also graft-link the shell to the core. As the cross-linking agent for use in preparation of the core-shell copolymers, those which copolymerize smoothly with the monomer in the respective stages of the reaction should be selected. Representative cross-linking agents include, but are not limited to aromatic polyfunctional vinyl compounds such as divinyl benzene, trivinyl benzene, divinyl toluene and the like; di and tri- methacrylates and di and triacrylates of polyols represented by monoethyl- e e-, diethylene- and tr ethylene glycols, 1,3- butanediol and glycerin allyl esters of unsaturated aliphatic carboxylic acid such as allyl acrylate, allyl methacrylate. and the like and di- and triallyl compounds such as diallyl phthalate, diallyl sebacate, triallytriazine and the like are mentioned. While the amount of cross-linking agent employed is from about 0.01 to 3.0% by weight based on the monomer charge for each stage of the reaction, gener¬ ally, the total amount of cross-linking agent in the final graft copolymer will preferably be less than 3.0 weight percent.

The core-shell copolymers suitable for use herein generally compr se from about 50 to about 90 weight percent of the core and from about 10 up to 50 weight percent of the graft or shell phase. Where an inter- mediate phase or layer is present in the graft copoly¬ mer the shell and intermediate phase will each com¬ prise from about 5 to about 25 weight percent of the copolymer.

The core-shell graft copolymers for use in the present invention are prepared by the conventional, method of emulsion polymerization, however, in an

alternative method, graft copolymerization may be carried out after suitably coagulating the latex of cross-linked trunk polymer for adjusting the size of the latex particles of the trunk polymer. Also, during polymerization the monomeric com¬ ponents used in the graft copolymerization may be brought into reaction in one step, or in multiple steps while supplying them in portions of suitable ratio of the present invention between the components. Specific examples of suitable core-shell graft copolymers and the production thereof are disclosed in for example U.S. Patent Numbers 4,180,494 and 4,292,233; herein incorporated by reference. Commer¬ cially available grafted core-shell copolymers for use herein include the KM653 and KM611 from Rohm and Haas Chemical Company.

Optionally, the modifier combination (B) may further comprise clay filler. Clays are well known and widely available commercially. Preferred clays are the crystalline and paracrystalline clays. Espe¬ cially preferred are the crystalline clays, most pre¬ ferably the Kaolin clays. The clays, particularly the Kaolin clays, may be in the hydrous form or in the calcined, anhydrous form. Exemplary of commerically available, suitable clays there may be given the clays available under the tradenames Whitex and Translink from Freeport Kaolin.

Additionally, it is preferred, although not re¬ quired, to utilize clay fillers which have been treated with a titanate or silane coupling agent.

Exemplary of such coupling agents there may be given vinyl tris 2-methoxy ethoxy silane and gamma-a ino- propyl triethyoxy silane (A-1100, Union Carbide) .

The modifier combination (B) comprises from about 10 to about 60 weight percent, preferably from about

20 to about 40 weight percent, based on the total com-

position. Individually, the modifiers comprising the modifier combination will each be present as ^' follows:

- the poly (butylene terephthalate) (B) (i) com¬ prises from about 5 to about 50, preferably from about 10 to about 25, percent by weight of the total composition

- the monoalkenyl arene-conjugated diene copoly¬ mer (B) (ii) comprises from about 5 to about 30, preferably from about 10 to about 15, percent by weight of the total composition.

- the clay filler, if present, comprises up to about 25, preferably up to about 20 weight percent based on the total composition.

In a most preferred embodiment, where a core- shell copolymer is employed as the monoalkenyl arene- -conjugated diene copolymer (B) (ii) , it is desirable to precompound the core-shell copolymer with the poly- (butylene terephthalate) or a portion thereof. As identified by Yusa et al. (U.S. 4,442,262) , the use of core-shell copolymers in general with copolyether¬ esters results in the occurrence of surface roughness and fisheyes. Applicant has now surprisingly found that otherwise unsuitable core-shell copolymers may be employed without the occurrence of fisheye if the core- shell copolymer is pre-compounded with the poly(buty¬ lene terephthalate) . Equally surprising is the find¬ ing that the use of the pre-compounded core-shell copolymer results in composition having unexpectedly improved physical properties as compared to those comp- ositions wherein the poly(butylene terephthalate) and core-shell copolymers were not precompounded. In practice most any ratio of core-shell copolymer to poly (butylene terephthalate) may be used; however, it is preferred that the ratio of 4:1 to 1:4, most pre- ferably 3:2 to 2:3, be employed to provide greater diεpersibility of the core-shell copolymer in the final composition.

Finally, while the foregoing is concerned with precompounding of the core-shell copolymer, the con¬ cept of precompounding is equally applicable to the block copolymer. Similarly, it is anticipated that the precompounding of the block copolymer with the poly (butylene terephthalate) will result in enhanced physical properties due to the improved dispersibility thereof.

While the compositions of this invention possess many desirable properties, it is sometimes advisable and pre ^f erred to further stabilize certain of the compositions against thermal or oxidative degradation as well as degradation due to ultraviolet light. This can be done by incorporating stabilizers into the blend compositions. Satisfactory stabilizers comprise phenols and their derivatives, amines and their derivatives, compounds containing both hydroxy1 and amine groups, hydroxyazines, oxi es, polymerrc phenolic esters and salts of multivalent metals in which the metal is in its lower state.

Representative phenol derivatives useful as stabilizers include 3,5-di-tert-butyl-4-hydroxy hydro- cinnamic triester with 1 ,3 ,5-tris- (2-hydroxyethyl-s- triazine-2,4,6-(lH, 3H, 5H) trione; 4,4'-bis (2,6- ditertiary-butylphenyl) ; 1 ,3,5-trimethyl-2,4, 6-tris- (3, 5-ditertiary-butyl-4-hydroxylbenzyl)benzene and 4,4 '-butylidene-bis (6-tertiary-butyl-m-cresol) . Various inorganic metal salts or hydroxides can be used as well as organic complexes such as nickel di- butyl dithiocarbamate, manganous salicylate and copper 3-phenyl-sal cylate. Typically amine stabilizers in¬ clude N,N'-bis (beta-naphth l) -p-phenylenediamine; N, '-bis (1-methylheptyl) -p-phenylenediamine and either ph^nyl-beta-napththyl amine or its reaction products with aldehydes. Mixtures of hindered phenols with esters of thiodipropionic acid, mercaptides and phos-

phit.e esters are particularly useful. Additional stabilization to ultraviolet light can be obtained by compounding with various UV absorbers such as substi¬ tuted benzophenones and/or benzotriazoles. The compositions of the present invention may be prepared by any of the well known techniques for pre¬ paring polymer blends or admixtures, with extrusion blending being preferred. Suitable devices for the blending include single screw extruders, twin screw extruders, internal mixers such as the Bambury Mixer, heated rubber mills (electric or oil heat) or Farrell continuous mixers. Injection molding equipment can also be used to accomplish blending just prior to molding, but care must be taken to provide sufficient time and aggitation to insure uniform blending prior to molding.

Alternatively, the ingredients may be dry blended prior to extrusion or injection ^" molding. Finally, as mentioned above the modifier combination, including the clay, if present, may be precompounded prior to compounding with the copolyesterester. The polymer compositions prepared in accordance with the present invention are suitable for a broad range of molding applications. These compositions manifest excellent physical attributes making them especially suited for applications requiring excellent stress-strength characteristics and low temperature impact strength yet good flexiblity. Furthermore, parts prepared from these compositions have excellent surface character- istics and appearance in spite of their use of other¬ wise unsuitable core shell copolymers. Finally, these compositions are found to also exhibit unexpectedly improved flex life.

PET-AILED DESCRIPTION OF TPr PREFERRED EMBODIMENTS The following examples are presented as illustrative of the present invention and are not to be construed as limiting thereof.

The following copolyetheresters were used in exemplifying the present invention:

Polymers A and B Polymers A and B are random copolyetheresters derived from 25 parts butanediol, 14 parts hexanediol, 48 parts dimethyl terephthalate and 13 parts poly- (tetra ethylene ether) glycol (MW 1000 and 2000) , respectively.

Polymers C and D Polymers C and D are random copolyetheresters derived from 22 parts butanediol, 12 parts hexanediol, 42 parts dimethyl terephthalate and 24 parts poly- (tetramethylene ether) glycol (MW 1000 and 2000) , respectively. Polymers E and F

Polymer E and F are random copolyetherester derived from butanediol, butenediol, dimethyl-tere- phthalate and poly (tetramethylene ether) glycol (MW 1000) and available from GAF Corporation as GAFLEX* ⁵ " 555 and 547. The latter having a higher weight per¬ cent of ether glycol.

Polymer G Polymer G is a block copolyetherester derived from butanediol, dimethyl terephthalate and poly- (tetramethylene ether) glycol (MW 1000) and is avail¬ able from E.I. du Pont as Hytrel^ 7246.

Pol mers H and I Polymers H and I are triblock copolyetheresters derived from about 60 parts by weight poly {butylene terephthalate) prepolymer, about 30 parts by weight poly (tetramethylene ether) glycol (MW 1000) and about 15 parts by weight of poly (butylene hexahydrophthal- ate) prepolymer and poly (hexa ethylene hexahydrcphthnl- ate) prepolymer, respectively. All compositions were prepared by melt blending on a si.ngle screw Prodex*^ extruder. Physical proper-

ties of these compositions were determined in accord¬ ance with ASTM methods as follows:

Notched Izod ASTM D256 Unnotched Izod ASTM P256

Flexural Strength ASTM P790

Tensile Elongation ASTM D638

Tensile Strength ASTM

Other physical properties were determined in accor- dance with procedures known and accepted in the art. Pynatup is a measure of stress-strength properties of the composition and is expressed as Emax/Etotal where¬ in Emax is the maximum energy the standard part can withstand under deflection before permanent deforma- tion (i.e. non-recoverable deflection) and Etotal is the total energy the part can withstand before mix¬ ture. Finally all compositions contained less than about 2 parts by weight, generally, from 0.3 to 1.6 parts by weight phenolic and/or amine stabilizers typical for such compositions.

Examples 1 and 2, Comparative Example A-D Two series of compositions employing two differ¬ ent modulus copolyetheresters were prepared. Fach series demonstrates the copolyetherester modified with a polyester as taught by the prior art for improved modulus and impact and the copolyetheresters of the present invention modified with a combination of polv- ester and a monoalkenyl arene-conjugated diene copolymer modifier resin. The specific compositions and the physical properties thereof were as shown in Table 1.

A review of either se of examples, i.e. A and P with 1 or C and D with 2 demonstrates the marked improvement in low temperature impact strength by the composition of the present invention as compared to the minor improvement in the polyester modified

copolyetheresters. Furthermore, in addition to the much low temperature impact strength, the composition of the present invention retained, for the most part, great flexibility wherein the polyester modified copolyetheresters tended to be very rigid in com¬ parison, as evident by their much higher flexural modulus.

Table 1

Polymer P 100 65 65

Polymer D — — — 100 65 70

PP ^ — 35 20 — 35 20

KM Conc. ^b — — - 15 — — 10

Notched Izod, Ft. lb/ n. NB NB NB NB NB NB Notched Izod, -30°C,

Ft. lb/ in. 0.85 0.95 1.3 — 1.2 1.6

Unnotched Izod, -30°C

Ft. lb/in. — — — — — NB

Flexural Modulus, psi x 10 18.3 83.4 49.1 12.6 86 53.7 Tensile strength, psi 4160 2688 3600 3030 3500 3072 τ ^* pnsile Elongation, * 640 475 445 840 450 424

a. poly(butylene terephthalate) available from General Electric Company as VALOX"*' 295 resin b. Concentrate of butadiene based core-shell impact modifier Rohm & Haas KM653 in A OX^ 315 polv (butylene terephthalate) resin from GE, (45:55, wt/wt).

Examples 3 and 4 Comparative Examples E and F A series of compositions were prepared to scope out the breadth of the present invention. Consequent¬ ly several monoalkenyl arene and conjugated diene co- polymers were tried in the formulation of the compo¬ sitions of the present invention. The specific compo¬ sitions and the physical properties thereof were as shown in Table 2.

The results presented in Table 2 clearly demon- strate the specificity of the beneficial properties to those compositions employing copolymer modifier resins having both monoalkenyl arene and conjugated diene monomers or units. Other known rubbery copolymers, spcifically the EPDM rubbers and the acrylate based core-shell copolymers did not demonstrate the marked improvement in low temperature notched izod and equally importantly, they were found to have poor dynatup properties.

TAB F 2

E

Polymer B 75 60 65 65

PBT ^a 15 25 20 20

KM Core ^b 10

SBS ^C 15

K-EEA Con ^a 15 EPDM Conc. ^e — — -- 15

Notched Izod, ft.lb/in. NB NB NB 3.2 to

Notched Izod, -30°C, Ft. lb/in. 1.2 2.4 1.0 0.95 00

3 Flexural Modulus, 10 , psi 52 51 44 46

Tensile Elongation,% 490 430 440 320

Dynatup, -30°C 22/34 20/35 8/8 14/15

Ema /F.total

a+b - see footnotes table 1 c. Styrene-Butadiene-Styrene triblock copolymer from Shell d. Concentrate of Acrylic based core-shell copolymer (KM330) in ethylene e p.

Examples 5-8 A series of compositions were prepared demon¬ strating the broad scope of the present invention. The specific formulations of the compositions and the physical properties thereof are shown in Table 3. As is evident from these examples, the percent by weight of the individual components of the present invention may vary widely and still the beneficial properties thereof are retained. Examples 9-16

To further demonstrate the breadth of the present invention, a series of compositions were prepared with¬ in the scope of the present invention demonstrating its applicablity to a broad spectrum of random and block copolyetherester elastomers. The formulations of each example and the physical properties thereof were as presented in Table 4.

Table 3

Polymer B 90 70 40 70

PBT I ^a — — 20

PBT II ^b — 30 —

KM Conc ^C 10 30 30 9.5

Na-St ^a — — 0.5

Notched Tzod, ft. lb/in NB NB NB 10

Unnotched Izod-30°C. ft. lb/in NB NB NB NB

Flexural Modulus, PFT x 10 ³ 29 42 123 52

Tensile Strength, psi 51R0 3480 4670 2800

Tensile Elongation, % 750 395 398 280

Dynatup 20/35 12/22 22/41 19/31

».max. /Etotal

a . see note a Tabel 1 b. Poly (butylene terephthalate) available from General Electric Company as LOX- 315 resin. c. See note b Table 1 d. Sodium s. arate nucleating agent

TABLE" 4

10 11 12 13 14 15 16

Polymer A R C D E G H I

Amount 65 65 70.5 70.5 64 70 65 65

PRT I ^a 20 20 20 20 ___-__. 10

PPT II ^b 5 5

KM. Conc° 15 15 9.5 9.5 36 20 30 30

Notched Izod, ft. lb/in. NB NB NB NB NB 1.2 NB NB

Notched Izod, -30°C. 3.9 1.3 5.7 2 . 2 4.2 4.2 __ ft. lb/in. ϋnnotched Izod, -30°C. ft. lb/in. NB NB 19 NB NB

3 Flexural Modulus psixlO 41.7 49.1 46.9 36.6 107 47.3 41.3

Tensile Elongation % 400 445 443 328 340 376 328

a.b.c. - see footnotes a,b,c Table 3

Examples 17 and 18 An additional series of examples within the scope of the present invention were prepared to demonstrate the unexpected improvement in both physical properties and surface appearance by precompounding the core- shell graft copolymer with at least a portion of the poly (butylene terphthalate) prior to incorporating into the compositions of the present invention.

The two formulations and the properties thereof are presented in Table 5. Clearly, the composition in which the core-shell copolymer was precompounded manifested greatly superior low temperature impact strength as well as Ross flex or flex life. More importantly, the surface appearance of parts molded from the precompounded core-shell copolymer were essentially free of surface defects, particularly fisheyes and roughness, as compared to the composition in which precompounding had not take place.

TABLE 5 17 18

Polymer D 65 64

PBT ^a 20 —

KM powder 15 —

KM Conc. ^c — 36

Notched Izod. Ft lb/in NB NP

Notched Izod -30°C,

Ft lb/in 2.3 4.2

Unnotched Izod, -30°C,

Ft lb/in NB NB

Ross Flex (cut) 206 2967

Ross Flex (no cut) 4500 160S0 fisheyes yes no a. see footnote a Table 1 b. butadiene based core- -shell copolymer from Rohm Haas yy 653

* c. see footnote b Table 1

Examples 19-24, Comparative Examples G-J A final series of examples were prepared demon¬ strating the benefit of the present invention to comp¬ osition further including clay in order to reduce heat sag. The specific formulations and the physical properties thereof are set forth in Table 6. As is evident from the examples, the composition of the present invention exhibit improved impact strength, both notched izod and dynatup while retaining the low heat sag benefit of clay. These examples again, further demonstrate the breadth of the present inven¬ tion to compositions in which the formulation .of each of the components varies widely.

Table 6

19 20 21 22 23 2 it

Polymer F _l5 50 -i 2 37 32 -ι2

Polymer F -- -- <ι5 50 _»0 50

PBT I ^a ?0 35 30 35 33 28 23 23

PBT H ^b 25 35 —

KM Conc. ^C 10 -- 10 -- 20 — — 10 20 20

Clay 15 15 15 15 15 15 25 25 25 15

Notched Izod ft lb/in 3.1-> 3.02 3.90 3.78 NB 7.1(2NB) 1.11 .25 1.1* 1.28

Notched Izod -30°C, ft lb/in. 1.01 0.66 1.«ι6 1.25 2.36 3.0-t 2.0Θ 3.60

Unnotched lzod,-30°C ft. lb/in. 37.6(3NB) 1-t.2(2NB)21.6(3NB) 3_t.β(3NB) NB NB 29.7 33.2(3NB) 21.7 NB

Tensile Elongation, % 112 162 137 H2 13,2 111

Heat Sag 290°F,

1 hr/mm 22 22 33 33 _»1 -»1 17 20 16 2_t

Dynatup E /E _t . , 2-1/31 7/7 33Λ6 3<»/_t9 25/38 27/39 max total

a,b,and c - see footnotes a,b,c, Table 3