FIELD OF THE INVENTION The present invention relates to a method for increasing the molecular weight of a polymer composition by melt mixing a composition composed of a polymer having at least one isocyanate reactive group and a therrnoplastic polyurethane.

BACKGROUND OF THE INVENTION There is a growing need for producing high molecular weight copolymers. In particular, high molecular weight polyesters and copolyesters can be used in a number of different applications. For example, high molecular weight polyesters can be used as reinforcing agents in rubber articles. Additionally, high molecular weight polyesters can be extruded and molded into a wide variety of useful articles. A problem associated with the production of high molecular weight polyesters is the amount of time it takes to produce a polymer with the desired molecular weight. Upon extended heating, the polymer can undergo thermal degradation, which ultimately reduces the molecular weight of the polymer.

One approach for increasing the molecular weight of a polymer involves the addition of a compound that is capable of reacting with the polymer. This is referred to in the art as "chain extension." U.S. Patent No. 4.071,503 to Thomas el al. discloses

the reaction between a polycarbodiimide and a polyester in order to increase the molecular weight and melt strength. U.S. Patent No. 4,568,720 to Aharoni et al. and Jacques et al. (Polomes; Vol. 37, No. 7, pp 1189-1200, 1996) disclose the use of phosphite compounds as chain extenders. Cardi et al. (J. Applied Po4'iiier Science Vol. 50, pp 1501-1509, 1993) discloses the chain extension of poly(ethylene terephthalate) with 2,2'-bis(2-oxazoline). U.S. Patent No. 4,857,603 to Akkapeddi et al. discloses the chain extension of poly(ethylene terephthalate) with polylactams.

Bikiaris et al. (Jour-rlal of polol7zez Science: Part A: Polymer Chemistry, Vol. 34, 1 337- 1342, 1996) investigated the combination ofdiimidodiepoxides with poly(ethylene terephthalate) and poly(butylene terephthalate) in order to increase the molecular weight of the polyester. None of these references, however, disclose the use of a thermoplastic polyurethane as a chain extender.

The prior art discloses the combination of polyurethanes and polymers in order to increase the mechanical properties of the resultant blend. U.S. Patent No. 5,519,094 to Tseng et al. and U.S. Patent No. 5,258 ,445 to Sperk et al. disclose the combination of a thermoplastic polyurethane, a polyester, and a glass fiber to produce a molding composition. International Patent No. WO 95/26432 to Wagner et al. disclose the preparation of an abrasion resistant polyester blend composed of a thermoplastic polyester, a thermoplastic polyurethane, and optionally, nonpolymeric additives that exhibits improved processing safety. Canadian Patent No. 1,111,984 (hereafter CA '111) discloses a poly(butylene terephthalate)/polyurethane molding composition.

Tseng et al., Sperk et al., Wagner el al., and CA '111 teach one of ordinary skill in the art to use a higher amounts of polyurethane in order to increase or enhance the mechanical properties of the blend. These references are not concemed with increasing the molecular weight of a polymer.

In light of the above it would be very desirable to have a method for increasing the molecular weight polymer that does not require the use of toxic or hazardous materials that can react with the polymer.

SUMMARY OF THE INVENTION In accordance with the purpose(s) of this invention, as embodied and broadly described herein, this invention, in one aspect, relates to a method for making a polymer composition, comprising melt mixing a composition comprising a polymer having at least one isocyanate reactive group and a thermoplastic polyurethane, wherein the thermoplastic polyurethane is less than 5% by weight of the composition, wherein the polymer is not a polyamide.

The invention further relates to a polymer composition produced by the present invention.

The invention further relates to an article comprising the polymer composition produced by the present invention.

Additional advantages ofthe invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. it is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

DETAILED DESCRIPTION OF TIlE INVENTION The present invention may be understood more readily by reference to the following detailed description of preferred embodiments of the invention and the Examples included therein.

Before the present methods are disclosed and described, it is to be understood that this invention is not limited to specific synthetic methods or to particular formulations, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. in this specification and in the claims which fellow, reference will be made to a number of terms which shall be defined to have the following meanings: The singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise.

"Optional" or "optionally" means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.

The term "isocyanate reactive group" is any group that can react with an isocyanate moiety as shown in Equation I. Examples of isocyanate reactive groups include, but are not limited to a hydroxyl group, an amino group, a carbonate group, or a carboxyl group.

A "carbonyl compound" is any carboxylic acid, ester, acid halide, or anhydride The tenn "dicarbonyl compound" is any dicarboxylic acid, diester, diacid halide, or dianhydride.

The term "glycol" is any compound that possesses at least two hydroxyl groups.

Additionally, a glycol can be any precursor compound that is readily converted to a compound possessing two hydroxyl groups. An example of such a compound is hydroquinone (I), which can be converted to biphenol (II) using techniques known in the art.

In accordance with the purpose(s) of this invention, as embodied and broadly described herein, this invention, in one aspect, relates to a method for making a polymer composition, comprising melt mixing a composition comprising a polymer having at least one isocyanate reactive group and a thermoplastic polyurethane, wherein the thenoplastic polyurethane is less than 5% by weight of the composition, wherein the polymer is not a polyamide.

The polymer used in the present invention has at least one isocyanate reactive group. The role of the isocyanate reactive group with respecl to producing a polymcr composition will be discussed below. In one embodiment, the polymer comprises a polyester. a liquid crystalline polymer, a polycarbonate, or a combin3tion thereof.

In one embodiment, toe polymer comprises a polyester. Polyesters useful in tlle present invention comprise the reaction product between (1) at least one first glycol

component comprising an aliphatic glycol, a cycloaliphatic glycol, an aromatic glycol, or a combination thereof, and (2) at least one first dicarbonyl component comprising an aliphatic dicarbonyl compound, a cycloaliphatic dicarbonyl compound, an aromatic dicarbonyl compound, or a combination thereof.

In one embodiment, the first glycol component comprises a first glycol compound comprising ethylene glycol; propylene glycol; 1,3-propanediol; 1,4- butanediol; 1 ,6-hexanediol; 1,8-octanediol; 1,1 0-decanediol; 2,2-dimethyl- 1,3- propanediol; 1,4-cyclohexanedimethanol; diethylene glycol; polyethylene glycol; polypropylene glycol; polytetramethylene glycol, or a combination thereof. In one embodiment, the first glycol compound comprises ethylene glycol; 1,3-propanediol; 1,4-butanediol, or 1,4-cyclohexanedimethanol. In another embodiment, the first glycol compound has from 2 to 10 carbon atoms. In another embodiment, the first glycol component further comprises a second glycol compound, wherein the second glycol compound comprises glycerol, trimethyolpropane, pentaerythritol, or a combination thereof. In this embodiment, the second glycol component behaves as a branching agent, which forms branches off the polymer backbone.

Examples of first dicarbonyl compounds that can react with the glycol component to produce the polyester include, but are not limited to, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, or a combination thereof. In one embodiment, the first dicarbonyl component comprises terephthalic acid, cyclohexanedicarboxylic acid, or naphthalenedicarboxylic acid. Any of the isomers of naphthalenedicarboxylic acid and cyclohexanedicarboxylic acid are useful in the present invention. For example, the cis-, tra,is-, or cis/tialis isomers of cyclohexanedicarboxylic acid can be used. In one embodiment, the 2,6-isomer of naphthalenedicarboxylic acid can be used. in another embodiment, the polyester further comprises the reaction product of a second dicarbonyl compound comprising a C4 to C40 dicarbonyl compound. The

second dicarbonyl is a modifying dibasic acid. In one embodiment, the second dicarbonyl compound comprises succinic acid, glutaric acid, adipic acid, sebacic acid, dimer acid, or a combination thereof. Dimer acid comprises the dimerization product of unsaturated fatty acids, wherein the fatty acid has from 14 to 24 carbon atoms. In one embodiment, the first dicarbonyl component comprises at most 65 mole % of the second dicatonyl compound, wherein the sum of the dicarbonyl compounds of the first dicarbonyl component equals 100 mole %.

In another embodiment, the first dicarbonyl component further comprises a third dicarbonyl compound, wherein the third dicarbonyl compound comprises trimellitic acid, trimellitic anhydride, pyromellitic anhydride, or a combination thereof. The third dicarbonyl compound can also behave as a branching agent as described above.

In one embodiment, the polyester has an inherent viscosity of from 0.2 to 1.5 dL/g, preferably from 0.3 to 1.2 dL/g as determined in 60/40 phenol/tetrachloroethane.

Examples of polyesters useful in the present invention include, but are not limited to, poly(butylene terephthalate), poly(propylene terephthalate), poly(ethylene terephthalate), poly(ethylene naphthalate), poly(cyclohexanedimethylene terephthalate), or a combination thereof. In one embodiment, the polyester is poly(ethylene-2,6- naphthalate) or poly(l ,4-cyclohexanedimethylene terephthalate). In a preferred embodiment, the polyester comprises poly(ethyelene terephthalate) or poly(butylene terephthalate). ln another embodiment, the polymer can be a copolyester. Any combination of the glycols and dicarbonyl compounds described above can be used to prepare copolyesters useful in the present invention. In one embodiment, the copolyester is the condensation product between poly(ethylene terephthalate) and polyethylene glycerol.

In another embodiment, the polymer comprises a liquid crystalline polymer.

Any ofthe liquid crystalline polymers disclosed in U.S. Patent Nos. 4,169,933 and

4,1617,470 are useful in the present invention, which are hereby incorporated by reference in their entirety.

In one embodiment, the liquid crystalline polymer comprises the reaction product benveen a second glycol component and a first carbonyl component. In one embodiment, the second glycol component comprises hydroquinone, biphenol, cyclohexanedimethanol, or a combination thereof. In one embodiment, the first carbonyl component comprises p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, p- acyloxybenzoic acid, 2,6-naphthalenedicarboxyl ic acid, terephthalic acid, isophthalic acid, or a combination thereof, preferably p-hydroxybenzoic acid, 2,6- naphthalenedicarboxylic acid, or terephthalic acid. In one embodiment, the liquid crystalline polyester has a molecular weight of from 5,000 to 25,000.

A variety of polycarbonates can be used in the present invention. In one embodiment, the polycarbonate comprises bisphenol A polycarbonate.

Any thermoplastic polyurethane known in the art is useful in the present invention. Examples of thermoplastic polyurethanes than can be used in the present invention are disclosed in U.S. Patent Nos. 4,822,827; 4,376,834, and 4,567,236, which are incorporated by reference in their entirety. The thermoplastic polyurethanes of the present invention can be both rigid and elastomeric.

In one embodiment, the thermoplastic polyurethane comprises the reaction product between a polyisocyanate and a diol component. Examples of polyisocyanates include, but are not limited to, a methylenebis(phenyl isocyanate), a cycloaliphatic diisocyanate. a cyclohexylene diisocyanate, or a combination thereof. In one embodiment. any of the 4,4-isomer, the 2A'-isomer, or combinations thercof of methylenebis(phenyl isocyanate) can be used. Examples of other metllylenebis(phenyl isocyanates) include, but are not limited to, W?- and p-phenylene diisoeyanates; chlorophenylene diisocyanates; cc, a'-xylylene diisocyanate: 2.4- and 26-toluene

diisocyanate and mixtures of these latter two isomers; toluidine diisocyanate, hexamethylene diisocyanate; 1 ,5-naphthalene diisocyanate, or isophorone diisocyanate.

In one embodiment, the methylenebis(cyclohexyl isocyanate) is the 4,4'-isomer, the 2,4'-isomer and mixtures thereof. Any of the geometric isomers including tra)lsltrans, cisltrazls, cislcis and mixtures thereof can be used. Examples of cycloaliphatic diisocyanates include, but are not limited to, cyclohexylene diisocyanates (1,2-; 1,3-; or 1,4-), l-methyl-2,5-cyclohexylene diisocyanate, 1 -methyl-2,4-cyclohexylene diisocyanate, 1 -methyl-2,6-cyclohexylene di isocyanate, 4,4'-isopropylidenebis(cyclohexyl isocyanate), or 4,4'-diisocyanatodicyclohexyl.

In another embodiment, the isocyanate is a modified form of methylenebis(phenyl isocyanate). These isocyanates have been reacted with an aliphatic glycol or a mixture of aliphatic glycols, such as described in U.S. Pat. Nos.

3,394,164: 3,644,457; 3,883,571; 4,031,026; 4,115,429; 4,118,411; and 4,299,347, which are hereby incorporated by reference in their entirety.

In one embodiment, the diol component comprises at least one cycloaliphatic diol and at least one diol extender. In one embodiment, the cycloaliphatic diol comprises 1 ,3-cyclobutanediol; 1,3-cyclopentanediol; 1 2-cyclohexanediol; 1 ,3-cyclohexanediol; 1 ,4-cyclohexanediol, 2-cyclohexene- 1 ,4-diol; 2-methyl- 1 ,4-cyclohexanediol; 2-ethyl- 1 ,4-cyclohexanediol; 1 ,3-cycloheptanediol; 1 ,4-cycloheptanediol; 2-methyl- 1 ,4-cycloheptanediol; 4-methyl- 1 ,3-cycloheptan edi o 1 1 ,3-cyclooctanediol; 1 ,4-cyclooctanediol; 1 ,5-cyclooctanediol, 5-methyl-l .4-cyclooctanediol; 5-ethyl- 1 4-cyclooctanediol; 5-propyl-l 4-cyclooctanediol; 5-butyl- 1 4-cyclooctanediol; 5 -hexyl - I 4-cyclooctanediol; 5-heptyl - 1 ,4-cyclooctaned jol; 5-octyl- 1 ,4-cyclooctanedio I; 4,4'-methylenebis(cycloheanol); 4,4'-methylenebis(2-methylcyclobexanol): 4,4'-methylenebis(3-methylcyclohexanol); 3,3'-methplenebis(cyclohertanol); 4'-ethylenebis(cyc lohexanol );

4,4'-propylenebis(cyclohexanol); 4,4'-butylenebis(cyclohexanol); 4,4'-isopropylidenebis(cyclohexanol); 4,4'-isobutylenebis(cyclohexanol); 4,4'-dihydroxydicyclohexyl; 4,4'-carbonylbis(cyclohexanol); 3,3'-carbonylbis(cyclohexanol); 4,4'-sulfonylbis(cyclohexanol), 4,4'-oxybis(cyclohexanol), or a combination thereof.

In one embodiment, the diol extender comprises ethylene glycol; 1 ,3-propanediol; 1,4-butanediol; 1,5-pentanediol; 1,6-hexanediol; 1,2-propanedio]; 1,3-butanediol; 2,3-butanediol; 1,3-pentanediol; 1,2-hexanediol; 3-methylpentane- 1 ,5-diol; 1,9-nonanediol; 2-methyloctane- 1 ,8-diol; 1 ,4-cyciohexanedimethanol; hydroquinone bis(hydroxyethyl)ether; diethylene glycol; dipropylene glycol; tripropylene glycol; ethanolamine; N-methy]-diethanolamine; N-ethyldiethanolamine, or a combination thereof.

In one embodiment, the diol component can be an ester diol formed by esterifying an aliphatic dicarboxylic acid with an aliphatic diol listed above. Examples of aliphatic dicarboxylic acids include, but are not limited to, adipic acid, azelaic, acid, or glutaric acid. In one embodiment, from about 0.01 to about 0.8 mole of dicarboxylic acid per mole of diol are reacted to produce the ester diol. in one embodiment, the diol component is the reaction product between an aliphatic diol or triol and a lactone. In one embodiment, 0.01 to 2 moles of lactone per mole of diol or triol are reacted with one another to produce the diol component.

Examples of aliphatic diols in this embodiment include, but are not limited to, 1 ,4-cyclohexanedimethanol, neopentyl glycol, hexalle-l,6-diol, ethylene glycol, butane-1,4-diol, ortrimethylolpropane. Examples of aliphatic triols include, but are not limited to, glycerol or trimethylolpropane. In one embodiment, the lactone is epsilon- caprolactone.

In one embodiment, the cycloaliphatic diol is from 1 0 to 90% by weight of tulle

diol component and the diol extender is from 10 to 90% by weight of the diol component, wherein the sum of the weight percentages of the cycloaliphatic diol and diol extender is equal to 100%.

In another embodiment, a polyol is used to prepare the tlermoplastic polyurethane. Examples of polyols include, but are not limited to, a polyether polyol. a polyester polyol, a hydroxy-terminated polycarbonate, a hydroxy-terminated polybutadiene, a hydroxy-terminated polybutadiene-acrylonitrile copolymer, a hydroxy-terminated copolymer of a dialkyl siloxane and alkylene oxide, or a combination thereof. In one embodiment, the molecular weight of the polyol is from about 1,250 to about 10,000, preferably, from about 2,000 to about 8,000.

Examples of polyether polyols include, but are not limited to, polyoxyethylene glycol or polyoxypropylene glycol. In one embodiment, polyoxyethylene glycol or polyoxypropylene glycol can be capped with 1) ethylene oxide residues; 2) random and block copolymers of ethylene oxide and propylene oxide; 3) propoxylated tri- and tetrahydric alcohols such as glycerine, trimethylolpropane, or pentaerythritol; 4) polytetramethylene glycol, or 5) random and block copolymers of tetrahydrofuran and ethylene oxide and/or propylene oxide. In one embodiment, the polyether polyol is a random and block copolymer of ethylene and propylene oxide or polytetramethylene glycol. Other examples of polyether polyols useful in the present invention include, but are not limited to vinyl reinforced polyether polyols, such as the polymerization product between styrene and/or acrylonitrile and the polyether polyol.

In one embodiment, a polyether ester can be prepared by reacting a polyethcr polyol described above with a di- or trifunctional aliphatic or aromatic carboxylic acid Examples of useful carboxylic acids include, but are not limited to, adipic acid, azelaic acid, glutaric acid, isophthalic acid, terephthalic acid, or trimellitic acid. In one embodiment, the polyester polyol is the polymerization product between epsilon-caprolaclone and ethylene glycol or ethanolamine. ln one embodiment. the

polyester polyol is prepared by the esterification of a polycarboxylic acid such as phthalic acid, terephthalic acid, succinic acid, glutaric acid, adipic acid, or azelaic acid and with a polyhydric alcohol such as ethylene glycol, butanediol, glycerol, trimethylolpropane, 1,2,6-hexanetriol, or cyclohexanedimethanol and the like. In one embodiment, the polyester polyol is prepared by esterifying a dimeric or trimeric fatty acid, optionally mixed with a monomeric fatty acid such as oleic acid, with a long chai aliphatic diol such as hexane-1,6-diol.

In one embodiment, a polyether diamine useful in the present invention is JEFFAM1NE6, which is manufactured by Jefferson Chemical Company.

In one embodiment, polycarbonates used to make the thermoplastic polyurethanes of the present invention containing hydroxyl groups useful in the present invention are prepared by reacting a diol, such as propane-1,3-diol, butane-1,4-diol, hexan-1,6-diol, diethylene glycol, triethylene glycol, or dipropylene glycol, with a diarylcarbonate (e.g. diphenylcarbonate) or with phosgene.

In one embodiment, silicon-containing polyethers useful in the present invention are copolymers of alkylene oxides with dialkylsiloxanes such as dimethylsiloxane. The silicon-containing polyethers disclosed in U.S. Pat. No.

4,057,595, which is hereby incorporated by reference in its entirety, can be used in the present invention.

In one embodiment, hydroxy-terminated poly-butadiene copolymers sold under the tradename POLY BDQÇ Liquid Resins manufactured by Arco Chemical Company are useful in the present invention. In one embodiment, hydroxy- and amine-terminated butadiene/acrylonitrile copolymers sold under the tradename HYCARZ hydroxyl-terminated (HT) Liquid Polymers and amine-terminated (AT) Liquid Polymers, respectively, can be used in the present ins entioll.

In one embodiment, the thermoplastic polyurethane is ISOPLASTs, which is manufactured by the Dow Chemical Company. There are a number of different thermoplastic polyurethanes sold under the tradename ISOPLAST; however, these thermoplastic polyurethanes are typically the reaction product between methylenebis(phenyl isocyanate) and a number of different glycols. In one embodiment, the thermoplastic polyurethane is ISOPLASTs 301, which is the reaction product between methylenebis(phenyl isocyanate), 1,6-hexanediol, cyclohexanedimethanol, and polytetramethylene glycerol.

In one embodiment, the thermoplastic polyurethane is from 1 to 4%, preferably from 1 to 3%, more preferably from 1 to 2%, or even more preferably from 1 to 1.5% by weight of the mixture, wherein the sum of the weight percentages of the thermoplastic polyurethane and the polymer is equal to 100 %.

One advantage of the present invention is that only a small amount of thermoplastic polyurethane is required to increase the molecular weight of the polymer.

Moreover, by using higher amounts of thermoplastic polyurethane, which is disclosed in the prior art, the viscosity of the resultant composite also increases. The higher the viscosity, the more difficult it is to extrude the composite. The present invention avoids these processing problems by using only a small amount of thermoplastic polyurethane.

In one embodiment, the polymer is poly(butylene terephthalate) and the thermoplastic polyurethane is ISOPLASTX 301.

Other additives known in the art can be added to tlle polymer composition.

Examples of additives include, but are not limited to. a colorant, a filler, a processing aid, a plasticizer, a nucleating compound, a stabilizer. an antioxidant, a mold release agent, a flame retardant, a reinforcing agent, an epoxy compound, or a combination thereof. in one embodiment, the reinforcint2 agent comprises glass fiber, carbon fiber, calcium carbonate, taic, iron oxide, mica, montn'orillo!ite, clay, kaolin, wollastonite, or

a combination thereof. In one embodiment, the additive can be melt mixed with the polymer and the thermoplastic polyurethane.

The polymer of the present invention and the thermoplastic polyurethane can be melt mixed using a number of techniques known in the art. In one embodiment, melt mixing can be performed by a Brabender Plastograph, Haake plastograph melt mixer (Rheocord 90), a single screw extruder, or a twin screw extruder (such as Werner Pfleiderer equipment). The temperature and lime required to melt mix the polymer and thermoplastic polyurethane depend upon the the polymer and thermoplastic polyurethane selected; however, one of ordinary skill in the art can deduce these parameters. In one embodiment, melt mixing can be reactive extrusion. A number of prior art techniques extrude two or more components merely to blend the components.

This is not the case with reactive extrusion, which involves chemically reacting the components in order to produce a new compound. This is one reason why low amounts of thermoplastic polyurethane are required in the present invention when compared to prior art methods. The present invention is not concerned with the formation of a simple blend.

The invention further relates to the polymer compositions produced by the present invention.

Not wishing to be bound by theory, it is believed that during melt mixing, the thermoplastic polyurethane depolymerizes to produce an isocyanate intermediate i)1 sits(. The polymer, which has at least one isocyanate reactive group, reacts with the isocyanate intermediate. This ultimately rcsulls in the chain extension of the polymer. which increases the molecular weight of the polymer. Additionally, the process of the present invention does not use toxic and hazardous isocyanates, which are disclosed in the art as chain extenders, to increase the molecular weight of the polymer.

In one embodiment, if two or more polymers are melt mixed 'vith tic

thermoplastic polyurethane, then a copolymer is formed. In this embodiment, the copolymer composition can be a block and/or graft copolymer. The formation of the block and/or graft copolymers depends upon the location of the isocyanate reactive group on the polymer.

Any of the polymer composites of the present invention can be melt processed and extruded as pellets or chips. The polymer composites can also be molded or shaped to produce a desired article by using extrusion, pultrusion, injection molding, or compression molding techniques.

EXAMPLES The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the methods and compositions of matter claimed herein are made and evaluated, and are intended to be purely exemplary of the invention and are not intended to limit the scope of what the inventors regard as their invention. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.) but some errors and deviations should be accounted for. Unless indicated othenvise, parts are parts by weight, temperature is in "C or is at room temperature and pressure is at or near atmospheric.

All of the following examples were prepared using poly(butylene terephthalate) (PBT) having an initial molecular weight of 1 5,000 as determined by gel permeation chromatography against poly(ethylene terephthalate) standards. The thermoplastic polyurethane utilized in these examples was lSOPLAST 301, which is manufactured by Dow Chemical. Melt processing was done by mixing on a twin screw extruder with a set point of 240 "C. A feed rate of 50 lbs/hr was utilized providing a residence time of 90 seconds. The examples were extruded into a cold water bath and pellctizcd. All compositions are reported on a weight % basis. All formulations contain 2.25 wt (¼) "additives" which consist of antioxidants, stabilizers and processing aids. Molecular

weight was obtained by gel permeation chromatography (GPC).

Examples 1-3 Example 1 is a comparative example that does not contain a thermoplastic polyurethane additive of this invention. In Example I, the molecular weight of poly(butylene terephthalate) decreased in the absence of thermoplastic polyurethane (from 15,000 to 14,500). Examples 2 and 3 are representative examples of this invention containing 1.5 and 3 wt% of the thermoplastic polyurethane respectively.

Examples 2 and 3 are of higher molecular weight than the control, which indicates that chain extension occurred during the melt processing of the thermoplastic polyurethane and PBT. The data in Table 1 demonstrate that the addition of a small amount of thermoplastic polyurethane increases the molecular weight of the polymer.

Table 1: Molecular Weight of Thermoplastic Polyurethane Chain Extended Polyesters Example # 1 2 3 Matrix Resin PBT PBT PBT Matrix Resin (%) 97.75 96.25 94.75 Additives (%) 2.25 2.25 2.25 Polyurethane (%) 0 1.5 3 Mn 14,500 16,300 16,200 Mw 32,800 38,800 39,200 Throughout this application, various publications are referenced. The disclosures of these publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art to which this invention pertains.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.