FOAMABLE POLYESTER COMPOSITIONS HAVING A LOW LEVEL OF UNREACTED BRANCHING AGENT

Abstract: This invention relates to a process for preparing foamable branched polyester compositions having increased melt viscosity and melt strength, and a reduced level of unreacted monomeric branching agent. The process involves melt blending (A) a composition containing a polyolefin and branching agent, (B) a nucleating agent either in powder form or (B') in the form of a composition containing a polyolefin and nucleating agent, and a polyester.

Description: FOAMABLE POLYESTER COMPOSITIONS HAVING A LOW LEVEL OF UNREACTED BRANCHING AGENT Field of the Invention This invention relates to a process for preparing foamable branched polyester compositions having increased melt viscosity and melt strength, and a reduced level of unreacted branching agent. Background of the Invention Many polymeric materials are foamed to provide low density articles such as films, cups, food trays, decorative ribbons, and furniture parts. For example, polystyrene beads containing low boiling hydrocarbons such as pentane are formed into lightweight foamed cups for hot drinks such as coffee, tea, hot chocolate, and the like. Polypropylene can be extruded in the presence of blowing agents such as nitrogen or carbon dioxide gas to provide decorative films and ribbons for package wrappings. Also, polypropylene can be injection molded in the presence of blowing agents to form lightweight furniture such as lightweight chairs and table legs. Polyesters such as poly(ethylene terephthalate) typically have a much higher density (e.g. about 1.3 g/cc) than other polymers. Therefore, it would be desirable to be able to foam polyester materials to decrease their weight for use in making molded parts, films, sheets, food trays, and the like. Such foamed articles also have better insulating properties than unfoamed parts. However, it is difficult to foam such polyester materials because of the low melt viscosity and low melt strength of typical poly(ethylene terephthalate) and related polyester polymers. The low melt viscosity and low melt strength of the polyesterε is a problem because the polymer melt will not adequately retain the bubbles of an expanding gas during molding or extrusion operations. It would be desirable therefore to be able to provide polyester polymers which could be foamed with conventional foaming systems. One approach to providing polyesters with acceptable melt viscosities involves treating preformed polyesters with monomeric branching agents such aε multifunctional carboxylic acids, anhydrides or polyols to provide branched polyesters. Such compositions are disclosed in U.S. Patent Nos. 3, 553,157, 4,132,707, 4,145,466, 4,999,388, 5,000,991, 5,110,844, 5,128,383, 5,134,028, and 5,288,764. The branching agents used include tri— and tetracarboxylic acids and anhydrides such as trimesic acid, pyromellitic acid, and pyromellitic dianhydride (PMDA) or polyols such as trimethylolpropane and pentaerythritol. U.S. Patent No. 5,288,764 discloses a process for preparing a foamed polyester resin which involves forming a molten mixture containing two separate polyester resins with at least one of the polyester resins containing a branching agent, adding a blowing agent to the molten mixture, and extruding the resultant mixture to obtain a foam. To promote the reaction between the branching agent and the polyester, U.S. Patent No. 5,288,764 teach the addition of an organic or inorganic Group I, II or III metal compound. Moreover, U.S. Patent No. 5,288,764 teaches that poor quality foam is obtained when a polyolefin is substituted for the polyester as the carrier resin of the branching agent. U.S. Patent No. 5,000,991 discloses a process for preparing a polyester foam which involves melting a polyester resin and a branching agent, mixing the molten resin with a blowing agent and extruding the mixture. To promote the reaction between the branching agent and the polyester, U.S. Patent No. 5,000,991 teaches the addition of an organic or inorganic compounds from Group I, II or III metals of the Periodic Table. Moreover, U.S. Patent No. 5,000,991 teaches away from using polyolefins as a carrier of the branching agent. The disadvantage associated with the aforementioned patents to produce polyester foam is that the level of free or unreacted monomeric branching agent, for example pyromellitic dianhydride (PMDA) , is unacceptably high for most food packaging applications. Summary of the Invention The process of the present invention is used to prepare a foamable branched polyester composition having a reduced level of unreacted monomeric branching agent. The foamable branched polyester composition displays increased melt viscosity and melt strength during extrusion, and is prepared by a process comprising melt blending: (A) a composition consisting essentially of: (1) 50 to 99 weight % of a polyolefin having a repeat unit selected from the group consisting of ethylene, propylene, butene, and combinations thereof, provided the ethylene polymers have a melt index of 0 to 100 at 190°C as measured by ASTM D1238-56T, and the propylene and butene polymers have a melt flow rate of 0 to 100 at 230°C as measured by ASTM D1238-56T; and (2) 1 to 50 weight % of a monomeric branching agent having a molecular weight of 50 to 5000 selected from the group consisting of a carboxylic acid having at least two carboxyl groups, and an anhydride having at least one anhydride group, and combinations thereof, provided a reactive compound of a Group I, II, or III metal is not included in composition (A) ; (B) at least one nucleating agent in powder form; and (C) a polyester having an inherent viscosity of 0.4 to 1.1 dL/g comprising repeat units from (a) a dicarboxylic acid selected from the group consisting of aromatic dicarboxylic acids having 8 to 14 carbon atoms, saturated aliphatic dicarboxylic acids having 4 to 12 carbon atoms, and cycloaliphatic dicarboxylic acids having 8 to 12 carbon atoms, and combinations thereof; and (b) a diol selected from the group consisting of cycloaliphatic diols having 6 to 20 carbon atoms, aliphatic diols having 3 to 20 carbon atoms, and combinations thereof, wherein the foamable branched polyester composition comprises 0.1 to 20 weight % of (A), 0.01 to 10 weight % of (B) , 80 to 99.9 weight % of (C) , based on the total weight of (A) , (B) , and (C) . In the alternative, the nucleating agent may be added in the form of a composition (B' ) consisting essentially of: (3) 50 to 99 weight % of a polyolefin having a repeat unit selected from the group consisting of ethylene, propylene, butene, and combinations thereof, provided the ethylene polymers have a melt index of 0 to 100 at 190°C, and the propylene and butene polymers have a melt flow rate of 0 to 100 at 230°C; and (4) 1 to 50 weight % of at least one nucleating agent, provided a reactive compound of a Group I, II, or III metal is not included in composition (B) , wherein the foamable branched polyester composition comprises 0.1 to 20 weight % of (A), 0.02 to 20 weight % of (B'), 80 to 99.9 weight % of (C) , based on the total weight of (A), (B'), and (C) . Description of the Invention The process of the present invention is used to prepare a foamable branched polyester composition having increased melt viscosity and melt strength, and a reduced level of unreacted monomeric branching agent, preferably less than 50 parts per million (ppm) , more preferably less than 5ppm, of unreacted monomeric branching agent. Component (A) is a composition containing a polyolefin and a monomeric branching agent. The polyolefin is added in an amount of 50 to 99 weight percent, preferably 70 to 95 weight percent, based on the weight of the polyolefin and monomeric branching agent. The polyolefin is selected from linear low density polyethylene, conventional low density polyethylene, high density polyethylene, ethylene copolymers with α—olefins containing 2 to 10 carbon atoms, polypropylene, propylene copolymers with a—olefins containing 2 to 10 carbon atoms, poly—1— butene, butene copolymers with α-olefins containing 2 to 10 carbon atoms, poly—4—methyl—1—pentene, 4— ethyl—1— pentene copolymers with α—olefins containing 2 to 10 carbon atoms and the like. The ethylene polymers have melt index values as measured by ASTM Method No. D1238- 56T of 0 to 100 at 190°C, preferably 0.1 to 20. Propylene and butene polymers have melt flow rate values as measured by ASTM Method No. D1238-56T of 0 to 100 at 230°C, preferably 0.1 to 20 at 230°C. The olefin polymers are readily prepared by conventional methods. The polyolefin is melt blended with a monomeric branching agent in an amount of l to 50 weight percent, preferably 5 to 30 weight percent, based on the amount of polyolefin. The monomeric branching agent has a molecular weight of 50 to 5000, preferably, 100 to 1000. The monomeric branching agent is selected from a carboxylic acid having at least two carboxyl groups, and an anhydride having at least one anhydride group. Suitable carboxylic acid monomeric branching agents also include polycarboxylic acids. Preferably, the carboxylic acid monomeric branching agents are used in the form of their lower alkyl esters or as their cyclic anhydrides. Suitable monomeric branching agents, for example, are trimesic acid, pyromellitic acid, pyromellitic dianhydride, trimellitic anhydride, benzenetetra carboxylic anhydride, benzophenone tetracarboxylic anhydride, hemimellitic acid, trimellitic acid, trimesic acid, pyromellitic acid, 1,1,2,2—ethanetetracarboxylie acid, 1,1,2—ethanetricarboxylic acid, 1,3,5— pentanetricarboxylic acid, and 1,2,3,4— cyclopentanetetracarboxylic acid. Preferably, the monomeric branching agent iε selected from pyromellitic dianhydride (PMDA) , trimellitic anhydride, benzenetetra carboxylic anhydride, and benzophenone tetracarboxylic anhydride. Combinations of monomeric branching agents may also be used. Composition (A) is prepared by melt blending the polyolefin and the monomeric branching agent in an extruder, Branbury mixer or other conventional melt mixing device until a homogeneous blend is obtained which is extruded and pelletized. The nucleating agent is added to the foamable polyester composition either as a powder (B) and/or in the form of a composition (B' ) . In the case the nucleating agent is added in powder form, the nucleating agent is present in the foamable branched polyester composition in an amount of 0.01 to 10 weight %, preferably 0.1 to 2 weight %, based on the total weight of (A) , (B) , and (C) . The nucleating agent may alternatively be added in the form of a composition (B') which contains a polyolefin and a nucleating agent. In the case the nucleating agent is added in the form of a composition, the nucleating agent composition is present in the foamable branched polyester composition in an amount of 0.02 to 20 weight %, preferably 1 to 10 weight %, more preferably 2 to 5 weight %, based on the total weight of (A), (B'), and (C) . The nucleating agent composition (B') contains a polyolefin and a nucleating agent. The polyolefin is added in an amount of 50 to 99 weight percent, preferably 60 to 80 weight percent, based on the weight of the polyolefin and nucleating agent. The polyolefin is melt blended with 1 to 50 weight percent, preferably 10 to 20 weight percent, of the nucleating agent. The polyolefin is selected from linear low density polyethylene, conventional low density polyethylene, high density polyethylene, ethylene copolymers with a—olefins containing 2 to 10 carbon atoms, polypropylene, propylene copolymers with α—olefins containing 2 to 10 carbon atoms, poly—1—butene, 1—butene copolymers with α—olefins containing 2 to 10 carbon atoms, poly—4—methyl—1—pentene, 4—methyl—1—pentene copolymers with α—olefins containing 2 to 10 carbon atoms and the like. The ethylene polymers have melt index values aε measured by ASTM Method No. D1238-56T of 0 to 100 at 190°C, preferably 0.1 to 20. Propylene and butene polymers have melt flow rate values as measured by ASTM Method No. D1238-56T of 0 to 100 at 230°C, preferably 0.1 to 20 at 230°C. The olefin polymers are readily prepared by conventional methods. Any nucleating agent may be used as long as the nucleating agent is capable of providing a nucleation site. Suitable nucleating agents include, for example, titanium dioxide, talc, chopped fiber glass, alumina, clay, and fumed silica. A combination of nucleating agents may also be added. Optionally, other additives known to those skilled in the art to be used with polyolefins and polyesters may be included in the composition of (B'). Such additives include, for example, stabilizers; antioxidants, such as IRGONOX 1010 and ETHANOX 330; buffers; flame retardants; lubricants; extenders; colorants; and pigments such as carbon black and dyes. It is important to note, however, that a reactive compound of a Group I, II, or III metal, such as sodium carbonate, must not be included in compositions (A) or (B'). The present inventors have determined that the use of reactive compounds of Group I, II or III metals has an adverse effect on the amount of unreacted or free monomeric branching agent in the final polyester product. While not wishing to be bound by any particular mechanism or theory, the present inventors believe that the presence of any organic or inorganic compounds of Group I, II or III metals result in conversion of the monomeric branching agent to its metallic salt form which is unable to react with the polyester. The polyester (C) is melt blended with composition (A) and either the nucleating agent (B) and/or composition (B'). A wide range of polyesters may be used. The polyester is present in an amount of 80 to 99.9 weight percent, preferably 95 to 99 weight percent, based on the weight of the compositions (A) and (B' ) . The polyester has an inherent viscosity of 0.4 to 1.1 dL/g as measured at 23°C. using 0.50 grams of polymer per 100 ml of a solvent consisting of 60% by weight phenol and 40% by weight tetrachloroethane. When the polyester is melt blended with composition (A) and the nucleating agent at elevated temperatures, the monomeric branching agent reacts with the polyester to provide branching and thus to increase the melt viscosity and the melt strength of the polyester. A compound of a Group I, II, or III metal in an amount of 0.001 to 1 weight % may be melt blended with the polyester, if desired, to modify the physical characteristics of the foam product. The polyester contains repeat units from 100 mole percent dicarboxylic acid and 100 mole percent diol. Dicarboxylic acids useful in the present invention include aromatic dicarboxylic acids preferably having 8 to 14 carbon atoms, saturated aliphatic dicarboxylic acids preferably having 4 to 12 carbon atoms, and cycloaliphatic dicarboxylic acids preferably having 8 to 12 carbon atoms. Specific exampleε of dicarboxylic acids are: terephthalic acid, phthalic acid, isophthalic acid, naphthalene—2,6—dicarboxylic acid, cyclohexanedicarboxylic acid, cyclohexanediacetic acid, diphenyl—4,4'—dicarboxylic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, and sebacic acid. Preferably, the dicarboxylic acid is selected from terephthalic acid, isophthalic acid, naphthalene¬ dicarboxylic acid, and cyclohexanedicarboxylic. The polyester may be prepared from one or more of the above dicarboxylic acids. It should be understood that use of the corresponding acid anhydrides, esterε, and acid chlorides of theεe acids is included in the term "dicarboxylic acid". Diols useful in the present invention include cycloaliphatic diols preferably having 6 to 20 carbon atoms or aliphatic diols preferably having 3 to 20 carbon atoms. Specific examples of diols are: 1,4—cyclohexanedimethanol, ethylene glycol, diethylene glycol, triethylene glycol, propane—1,3—diol, butane—1,4—diol, pentane—1,5-diol, hexane—1,6—diol, 3—methylpentanediol—(2,4) , 2—methylpentanediol—(1,4) , 2,2,4—trimethylpentane—diol—(1,3) , 2—ethylhexanediol-(1,3), 2,2-diethylpropane—diol—(1,3) , hexanediol—(1,3) , 1,4—di—(hydroxyethoxy)—benzene, 2,2—bis—(4—hydroxycyclohexy1)—propane, 2,4— ihydroxy—1,1,3,3—tetramethyl—cyclobutane, 2,2—bis—(3—hydroxyethoxyphenyl)-propane, and 2,2— is—(4—hydroxypropoxyphenyl)—propane. Preferably the diol is selected from ethylene glycol, 1,4—butanediol, and 1,4—cyclohexane—dimethanol. The polyester may be prepared from one or more of the above diols. The polyester is prepared by conventional melt phase or solid state polycondensation techniques well known in the art. Optionally, the polyester may include an antioxidant in an amount up to two percent by weight of the polyester. Preferably, the amount of antioxidant iε 0.1 to 1 percent by weight of the polyester. The antioxidant may be added with the monomers prior to the formation of the polyester or, if desired, added to the molten polymer after polymerization has been completed. The antioxidant may alεo be melt blended with the polyeεter. Preferably, the antioxidant is added with the monomers before polymerization of the polyester is initiated. The polyeεter may alεo contain an additive. Additives εuch as nucleating agents, for example, titanium dioxide, talc, chopped fiber glass, alumina, clay, and fumed silica, stabilizers, antioxidants, such as IRGONOX 1010 and ETHANOX 330, buffers, flame retardants, lubricantε, extenders, colorants, and pigmentε εuch aε carbon black and dyeε, normally used with polymers may be used if desired. Such additives, their amounts, and their use are well known in the art. For example, improvement in light stability is possible by the addition of small amounts of pigmentε or the incorporation of a light stabilizer, such aε ultraviolet light absorbers. The polyester compositions prepared by the process of the present invention are dried in a conventional or vacuum oven and are extruded or molded by conventional techniques. The polyester compositions are useful in a variety of end useε including the manufacture of films, tubeε, foams, blow molded objects, extrusion coated materials, food packaging containers, injection molded parts and the like. While the polyester compositions can be used in many molding or extrusion applicationε, for example, injection molding, injection blow molding, extrusion, extrusion blow molding, etc. , to form non- foamed products, the polyester compositions are preferably used to prepare foamed articles particularly for use in the food packaging industry. The foam articles prepared from the polyester compositionε are in compliance with European Union (EU) regulations for global (total) migration, antimony migration, and PMDA migration into food simulating εolventε. In addition, the foam articles are within the Food and Drug Adminiεtration (FDA) quidelineε (1988 Recommendationε for Chemiεtry Data for Indirect Additive Petitions) for evaluation of PMDA migration into food simulating solventε. Foaming polymers is a process well known in the art. Extrusion techniques common to those skilled in the art can be used to foam the polyester and composition of the present invention, preferably to densities less than 1.1 g/cc, more preferably, densities of lesε than about 0.2 g/cc are achieved. In a typical foam extrusion procesε, the basic apparatus comprises a single extruder (preferably a length to diameter ratio of at least about 30:1), a liquid injection pump or gas cylinder with injector valves, a die to form the desired object, a cooling devise and a devise to collect the expanded, extruded product. In such a process a two—stage screw is typically used but is not critically necessary. The polyester and composition are preferably added to the extruder feed hopper (or hoppers) and fed to the feed section of the screw. The polyester and composition are melted in the transition section of the screw and the blowing agent added either in the transition section of the screw or near the beginning of the metering section. Suitable blowing agents include inert gases, such aε nitrogen and carbon dioxide, hydrocarbonε boiling about —40°C to about 45°C, such as propane, butane and pentane; hydrofluorcarbons εuch as 1,1—difluoroethane and 1,1,1,2—tetrafluoroethane; and hydrochlorofluorocarbons; and gas liberating chemical blowing agents, such as sodium bicarbonate, a combination of citric acid and sodium bicarbonate, a combination of citric acid and sodium carbonate, azodicarbonamide and various endothermic blowing agents which release C0 2 and/or N 2 . Mixtures of blowing agents can also be used. Blowing agents are used in amounts of about 0.01 to about 20% (by weight based upon the weight of the polyester and blowing agent) to obtain the desired high expansion ratios. Concentrations of about 0.1 to about 5 wt percent are typical. The reεin melt containing diεsolved and/or dispersed blowing agent is metered by the screw to the die. Upon exiting the die, the melt is expanded, optionally shaped, cooled and collected. The temperature profile on the extruder and die is adjusted to melt the polyester in the extruder prior to the injection of the blowing agent and adequately cool the melt/blowing agent composition to allow for expansion without coalescence. Another typical foam extrusion procesε employε two extruderε operating in tandem. In thiε process the polyester is mixed, melted and the blowing agent injected in the first extruder. The melt/blowing agent composition is transferred by means of a conventional transfer tube to the feed section of the second extruder which is uεed to tranεfer the melt blend to the die and to bring the melt temperature and preεεure in the die to the values necessary for optimum foam formation. Typically the two extruders are of different sizeε. The tandem extruder process allows for excellent control of process variables. Various screw configurations and designs can be used to prepare foamed polyesterε. Mixerε can be added to the εcrew or aε independent componentε to diεperse additives, nucleation agents, and blowing agents. Twin screw extruders or satellite extruders may also be used. Satellite extruders may be used for cc—extrusion of a thin, solid, nonfoamed, polymer layer on the foamed polyester εheet. Additionally, thin nonfoamed layers of polymers may also be applied on the foamed εheet through a εeparate lamination proceεε. The materialε and Testing Procedures used for the results shown herein are as follows: I. Analysis of Total PMDA in Polyolefin Composition This method to measure the total amount of PMDA compounded in polyolefin compoεition batch is based on a hydrolysis procedure. The samples were dissolved in hot p—xylene and appropriate amounts of trifluoroacetic acid and water were added to hydrolyze PMDA to its acid form, pyromellitic acid (PMA) . The PMA produced was measured by a reversed phase liquid chromatography procedure using an UV (absorption at 255 nm) detection method. The quantitation was performed by calibrating the detector using standards of PMA that have been prepared similarly as the samples of polyolefin compositionε. Detailε of the procedure are aε followε: Liquid Chromatograph: WATERS 510 Detector: WATERS Lambda Max 451 UV-Visible, operating at 255 nm. Autosampler: Perkin Elmer LC—600. Data Processing Software: ACCESS*CHROM Chromatography Data System. Calculation type: Multilevel (3) with benzoic acid aε internal standard. Column: BDS-Hypersil C-18, 250x4.6 mm with 120 micron particle εize. Injection: 5 microliters Elution: Linear gradient (see below for description of mobile phases) Initial 1.5 100 0 12 1.5 40 60 13 1.5 0 100 19 1.5 0 100 20 1.5 100 0 25 1.5 100 60 Reagentε: a) p—Xylene. b) Reagent Grade Water (e.g. water produced by a Millipore Milli—Q™ purification system) . c) Reagent grade trifluoroacetic acid. d) Diluting solution. This is a solution of 50/50 (v/v) of THF/Acetonitrile containing benzoic acid as an internal standard with a concentration of 0.1 g/L. e) Acetonitrile used as mobile phase. Designated as mobile phase B. f) 0.1 % phosphoric acid in water used as mobile phase. Deεignated as mobile phase A. g) PMA (pyromellitic acid) . Sample Preparation: a) Weight about 0.15 g of polyolefin composition to four decimal places. b) Transfer to a culture tube (The tube needs to be the kind that haε a teflon lined εcrew cap) . c) Add 10 ml of p—xylene. d) Add 1 ml of trifluoroacetic acid. Measured with a graduate cylinder e) Add 0.2 ml of water, measured with an appropriate syringe or pipette. f) Add a 1 inch magnetic stirring bar. g) Cap the tube and heat to 120°C for one hour while stirring. h) After the heating period, cool the tubes to room temperature. Open the tubes and add 10 ml of the diluting solution, i) Transfer the mixture to a 250—ml volumetric flask, j) Wash the tube two more timeε with 10 ml of the diluting solution and transfer the washing to the volumetric flask. Fill to the mark with the same diluting solution, k) Tranεfer an aliquot from the 250—ml volumetric flaεk to a syringe equipped with a 0.45 micron PTFE filter. Filter the sample and collect the filtrate in a LC vial. 1) The sample iε ready for analyεiε. Calibration Standard Preparation: a) Three different standardε are prepared. Weigh the appropriate amount of PMA (described below) to four decimal places and transfer to a 250—ml volumetric flask, b) Add 10 ml of p—xylene and 1 ml of TFA. c) Add 100 ml of the diluting solution and dissolve the sample. d) Fill the flask to the mark with the diluting solution. e) Transfer an aliquot from the 250—ml volumetric flask to a LC vial. f) Standard 1: 0.0400 g, Standard 2: 0.0200 g, Standard 3: 0.0100 g. Precision and Accuracy: The precision was determined from five replicate analyεeε of two different samples shown below. The accuracy has not been rigorously evaluated due to the lack of a standard of known concentration, but recovery studies performed yielded resultε in the 98—100%. Sample Mean Standard RSD(%) 80%PP - 20% PMDA 20.1034 0.1934 0.9622 90%PP - 10% PMDA 9.9732 0.3071 3.0794 II. Analvεis of "Active" PMDA in Polyolefin Composition. This method to measure active PMDA (i.e. the amount of PMDA which waε not hydrolyzed to acid—anhydride or the PMA during the compounding) in the polyolefin composition was based on making a derivative with diethylamine. The samples were dissolved in hot p—xylene and an appropriate amount of diethylamine was added. The samples were heated to 120°C for 1 hour to allow for the derivatization reaction to occur. The diethylamine derivatives of PMDA were measured by a reversed phase liquid chromatography procedure using a UV (absorption at 255 nm) detection method. The detector was calibrated using standardε prepared from pure PMDA and treated in an identical faεhion aε the polyolefin compoεition. Details of the procedure were as follows: Liquid Chromatograph: WATERS 510 Detector: WATERS Lambda Max 451 UV—Visible. Operating at 255 nm. Autosampler: PERKIN ELMER LC-600. Data Procesεing Software: ACCESS*CHROM Chromatography Data System. Calculation type: Single point calculation. Column: BDS—Hypersil C—18, 250x4.6 mm with 120 micron particle size. Injection: 5 microliters Elution: Linear gradient (see a description of the mobile phaεes below) Initial 1.5 100 0 12 1.5 40 60 13 1.5 0 100 19 1.5 0 100 20 1.5 100 0 25 1.5 100 0 Reagents a) p—Xylene. b) Anhydrous Diethylamine: Reagent can be obtained from Aldrich Chemicals. c) (Cat.No. 38645-6) . d) Reagent grade trifluoroacetic acid. e) Diluting solution: This is a solution of 50/50 (v/v) of THF/Acetonitrile. f) Acetonitrile used as mobile phase. Designated as mobile phase B. g) 0.1 % phosphoric acid in water used as mobile phaεe. Designated as mobile phase A. h) Pyromellitic dianhydride: Reagent can be obtained from Aldrich (Cat.No. B402-3) . Sample Preparation: a) Weigh 0.15 grams of εample (to the fourth decimal place) into a 25 n x 150 m culture tube. b) Add 10 ml of p—xylene. c) Add 2 ml of diethyl amine. d) Cap and heat for at 120°C for l hour. e) Let the teεt tubes cool to room temperature. f) Add 10 ml of the diluting solution and shake. g) Add 3.5 ml of trifluoroacetic acid. h) Transfer to a 250 ml volumetric flask. i) Continue to wash out the culture tube with the diluting solution into the volumetric flask, j) Fill the 250-ml flask to the mark with the diluting solution. k) Filter approximately 1.5 ml of sample through a 0.45 micron filter onto a LC auto sampler vial. Calibration Standard Preparation. a) Weigh 0.02 grams of pure pyromellitic dianhydride to the fourth decimal place. b) Add 10 ml of p—xylene. c) Add 2 ml of diethyl amine. d) Cap and heat for at 120 °C for 1 hour. e) Let the test tubes cool to room temperature. f) Add 10 ml of the diluting solution and shake. g) Add 3.5 ml of trifluoroacetic acid. h) Transfer to a 250 ml volumetric flask. i) Continue to wash out the culture tube with the diluting solution into the volumetric flask. j) Fill the 250— l flask to the mark with the diluting solution, k) Filter approximately 1.5 ml of sample through a 0.45 micron filter onto a LC auto sampler vial. Precision and Accuracy: The precision waε determined from eight replicate analyεeε of one sample. The accuracy has not been rigorously evaluated due to the lack of a standard of known concentration, but recovery studies performed yielded resultε in the 95-100%. III. Analysis of Total PMDA in the Polyester Blend This analysiε of total PMDA in the polyester blend was based on an hydrolysiε procedure. The polyester sample was hydrolyzed in a εolution of potassium hydroxide in a mixture of methanol and dimethyl sulfoxide. The polyeεter was hydrolyzed back to the monomeric components. Any unreacted and reacted PMDA is therefore in solution and in the form of the tetracarboxilic acid, PMA. The PMA is analyzed by a anion exchange liquid chromatography procedure using an UV (absorption at 210 nm) detection method. The detector was calibrated with standards prepared from pure PMA. Details of the procedure were as follows: Liquid Chromatograph: HEWLETT PACKARD 1090 Detector: APPLIED BIOSYSTEMS 783A operating at 210 nm Autosampler: HEWLETT PACKARD 1090. Data Processing Software: ACCESS*CHROM Chromatography Data System. Calculation type: Multilevel (3) Column: WHATMAN PARTSIL-SAX, 100 mm x 4.6 mm. Injection: 20 microliters Elution: Isocratic run at 1.0 ml minute Reagents: a) KH 2 P0 4 : Reagent can be obtained from Mallinckrodt. b) Phosphoric acid. c) NaH 2 P0 4 : Reagent can be obtained from Mallinckrodt. d) Na 2 HP0 4 : Reagent can be obtained from Mallinckrodt. e) Trifluoroacetic acid. f) Reagent Grade Water (e.g. water produced by a Millipore Milli—Q™ purification system) g) Mobile Phase: l) Weigh 20.4135 g of KH 2 P0 4 into a plastic weighing boat and transfer to l liter volumetric flask. 2) Add 500 ml of water and dissolve the KH 2 P0 4 . 3) Add 150 ml of Acetonitrile to the volumetric flask and fill to the mark with Water. 4) Transfer to a 1 Liter Wheaton Bottle and adjust the pH to 2.6 by adding cσmpositiond phosphoric acid dropwise. a) Pyromellitic acid (PMA) : Reagent can be obtained from Aldrich. Sample Preparation: a) Weigh 0.15 g of sample to the fourth decimal place. b) Transfer to a culture test tube and add 10 ml of 0.5N KOH in methanol: DMSO (50/50) c) Heat the sampleε to 120°C for 30 minuteε. d) Transfer hydrolyzed sample to a 100 ml volumetric flask with the 90:10 solution of 0.2 M KH 2 P0 4 in acetonitrile. e) Mix and place in a ultrasonic bath for 5 minutes. f) Filter 1.5 ml of the solution from the 100—ml flask through a 0.45 microm filter and receive the filtrate in a LC vial. Calibration Standard Preparation: a) Prepare a stock solution of PMA by weighing 0.0500 grams to the fourth decimal place. b) Transfer the PMA to a 50 ml volumetric flaεk. c) Add 2 ml of 2.5 N KOH in methanol. d) Add 20 ml of water and place in a εonicating bath for 10 minuteε. e) Fill the flask to the mark with water. f) Make a 0.1 to 100 dilution of the stock solution to give an approximate concentration of IE—3 g/L. g) Make a 0.25 to 100 dilution of the stock εolution to give an approximate concentration of 2.5E—3 g/L. h) Make a 1.0 to 100 dilution of the stock solution to give an approximate concentration of IE—2 g/L. i) The diluting solution to prepare the standardε (steps h to i) is a 90:10 solution of 0.2 M KH 2 P0 4 in acetonitrile. Precision and Accuracy: The precision was determined from 8 replicate analyses of one sample. The accuracy has not been rigorously evaluated due to the lack of a standard of known concentration, but recovery studieε performed yielded reεultε in the 95—100%. IV. Analysis of "Unreacted" or "Free" PMDA in the Polyester Blend This analysiε of the unreacted PMDA in the polyester blend was based on a dissolution of the sample followed by a hydrolysis procedure to convert PMDA to PMA. The samples were dissolved in trifluoroacetic acid and the polymer was subsequently precipitated by adding appropriate amounts of chloroform, acetone and water. The sample was filtered. The pH of the filtrate that contains the PMA is adjusted. The analysis of PMA is accomplished by a anion exchange liquid chromatography method. PMA was measured by an UV (absorption at 210 nm) detection method. The detector was calibrated using standards prepared from pure PMA. Details of the procedure were as followε: Liquid Chromatograph: HEWLETT PACKARD 1090 Detector: APPLIED BIOSYSTEMS 783A operating at 210 nm Autosampler: HEWLETT PACKARD 1090. Data Processing Software: ACCESS*CHROM Chromatography Data System. Calculation type: Multilevel (3) Column: WHATMAN PARTSIL-SAX, 100 mm x 4.6 mm. Injection: 20 microliters Elution: Isocratic run at l.o ml minute Reagents: a) KH 2 P0 4 : Reagent can be obtained from Mallinckrodt. b) Phosphoric acid. c) NaH 2 P0 4 : Reagent can be obtained from Mallinckrodt. c) Na 2 HP0 4 : Reagent can be obtained from Mallinckrodt. e) Trifluoroacetic acid. f) Chloroform. g) Reagent Grade Water (e.g. water produced by a Millipore Milli—Q™ purification system) h) Acetone . i) Ammonium Hydroxide. j) Mobile Phaεe: 1) Weigh 20.4135 g of KH 2 P0 4 into a plastic weighing boat and transfer to 1 liter volumetric flask. 2) Add 500 ml of water and dissolve the KH 2 P0 4 . 3) Add 150 ml of acetonitrile to the volumetric flask and fill to the mark with Water. 4) Transfer to a 1 Liter Wheaton Bottle and adjuεt the pH to 2.6 by adding compositiond phosphoric acid dropwise. k) Filtrate wash solution: 1) Weigh 1.8455 gramε of Na 2 HP0 4 into a plaεtic weighing pan. Transfer to a 1 liter volumetric flask. 2) Weigh 0.9659 grams of NaH 2 P0 4 into a plastic weighing pan. Transfer to a 1 liter volumetric flask. 3) Add approximately 500 ml of reagent grade water and place in a εonic bath until dissolved. 4) Fill to the mark with reagent grade water. 1) Pyromellitic acid (PMA) . Reagent can be obtained from Aldrich Chemicals (Cat.No. 41228—7) . Sample Preparation: a) Weigh 2 grams (to the 4th decimal place) of sample into a 250 ml Erlenmeyer flask. Record the weight. b) Add a 2 inch stir bar and place on a hot plate heated to 60°C. c) Add 20 ml of trifluoroacetic acid to diεεolve the polymer. d) Stir for 1 hour (one hour iε typically long enough for ground samples that pass through a 3 mm screen. ) e) After the sample has completely dissolved, remove from the heat and place in an ice and water bath for 15 minutes. During the addition of the additional chemicals, the εample needε to remain in the bath. f) Add 35 ml of chloroform. g) Using a separatory funnel, add 10 ml of acetone dropwise. h) Using the same εeparatory funnel, add dropwiεe 35 ml of reagent grade water, i) Add 25 ml of ammonium hydroxide (approximately 37%) dropwiεe. j) Remove from the ice and water bath and heat at 60°C for 1 hour. Let cool for 15 minutes, k) Filter the samples under vacuum using a course fritted funnel. 1) Wash the flask, filter, and filtrate with reagent grade water, m) Wash the flask, filter, and filtrate again using 50 ml of the filtrate wash εolution. n) After washing, use a Pasteur pipet to remove the chloroform layer from the bottom of the flask. o) Adjust the pH of the sample to a value between 6.4 to 6.5 using compositiond phosphoric acid, p) Transfer the sample to a 250 ml volumetric flask using reagent grade water to wash out the Erlenmeyer flask. q) Fill to the mark with reagent grade water, r) Filter approximately 1.5 ml of the sample through a 0.45 micron syringe filter into a LC auto sampler vial. Calibration Standard Preparation: a) Prepare a stock solution of PMA by weighing 0.0500 grams to the fourth decimal place. b) Transfer the PMA to a 50—ml volumetric flask. c) Add 2 ml of 2.5 N KOH in methanol. d) Add 20 ml of water and place in a sonicating bath for 10 minutes. e) Fill the flask to the mark with water. f) Make a 0.1 to 100 dilution of the stock solution to give an approximate concentration of IE—3 g/L. g) Make a 0.25 to 100 dilution of the stock solution to give an approximate concentration of 2.5E—3 g/L. h) Make a 1.0 to 100 dilution of the stock solution to give an approximate concentration of 1E-2 g/L. i) The diluting solution to prepare the standardε (εteps h to i) is a 90:10 solution of 0.2 M KH 2 P0 4 in acetonitrile. Precision and Accuracy: The precision was determined from five replicate analyses of a sample. Sample Mean Std. Dev. RSD % Polyester Blend 1391ppm 80 5.75 The accuracy of the method has not been rigorously evaluated due to the lack of a standard of known concentration, but recovery studies of spiked solutionε of pyromellitic acid (PMA) with concentrationε between 4 X IO -3 g/L (800 ppm in a polymer sample, see sample preparation section) and 2 X IO -3 g/L (400 ppm in a polymer εample) . yielded recoveries in the 92 to 100% range. The detection limit of the method was evaluated by preparing standards of PMA to concentrations as low as 2.5 X 10 -5 g/L (5 ppm in a polymer sample) . It was determined that 2.5 X 10 -5 g L was the lowest concentration that gives a signal for PMA that is detected but not easily quantitated. V. Extractions and Analyses for Micrration and Compliance Testing of Foam Samples Extractions: a) Foam trays (three) were filled with 100 ml of 3% acetic acid/water and covered with a sheet of Teflon. A temperature probe was added to one tray. The trays were placed in a pressure cooker with a 15 psi preεεure regulator until the temperature reached 100°C. The regulator waε then removed and the temperature maintained for 2 hours at 100°C. After 2 hours, the samples were removed from the pressure cooker, cooled to room temperature, and poured into clean rinsed flasks. b) Teflon presεure cellε were uεed for the 8% ethanol/water extractions. The bottom part from four foam trays were cut into 1/2 dm 2 (7.75 in. 2 ) sections. The 1/2 dm 2 sections were cut into 8 stripε of about 1 in. 2 , placed in preεsure cells with wire spacers, and filled with 50 ml of solvent. The pressure cells were placed in a pressure cooker with a 15 psi pressure regulator. After the pressure reached 15 psi (250°F) , the samples were heated for 2 hours, removed from the oven, cooled to room temperature and poured into clean rinsed flasks. c) Foam trays (four) filled with 100 g of HB 307 oil were placed in an oven at 175°C. It took about 2 hours for the oven temperature to recover to 175°C. The samples were then heated for 2 hours, removed from the oven, and the oil poured into flasks. Area of Trayε Expoεed to Solvents: The area of the trays exposed to 100 ml of solventε were determined by cutting a εection of trays expoεed to 100 ml, weighing and comparing to the weight of a 4 in. 2 εection of the tray. For strips cut from trays for the 8% Ethanol extractions in (b) above, both sideε of the stripε were uεed in calculating the area of exposure. Total Migration Into Food Simulants Total migration of polymer specieε into the food εimulantε waε determined by UV/VIS analyεeε of the extracts. PMDA and TPA in Food Stimulants The migration of PMDA and TPA into the food stimulantε waε determined by HPLC uεing a UV detector. Note: During the extractionε, pyromellitic dianhydride (PMDA) getε hydrolyzed to itε acid form, pyromellitic acid (PMA) , and iε determined as such. Antimony in Food Stimulants Antimony migration into the food stimulant was determined by ICP/MS. VI. Melt Strength Melt Strength was determined according to ASTM D3835 measured at 280°C by extruding the molten polyester downward through a die 0.1 inch in diameter and 0.25 inches long at a shear rate of 20 εecond -1 using an Instron rheometer and allowing the extrudate to fall freely. The diameter of the end of a six inch length of extrudate, measured from the orifice of the die, is measured. The percent Melt Strength is determined from the formula: wherein D is the diameter, in inches, of the extrudate supporting a six inch length of extrudate. If D is less than 0.1 inch, the Melt Strength is a negative number since there is no increase in the diameter of the extrudate. If D is greater than 0.1 inch, the Melt Strength is a positive number. VII. Melt Viscoεitv Melt viεcosity was measured according to ASTM D4440 at zero shear and 280°C. VIII. Molecular Weight Molecular weight was measured by gel permeation chromatography (GPC) . This invention will be further illustrated by a consideration of the following examples, which are intended to be exemplary of the invention. All parts and percentages in the examples are on a weight basis unless otherwise stated. Example 1 Preparation of 20 wt% PMDA composition based on polypropylene. A PP/PMDA composition waε prepared by melt blending in a 30 mm Werner and Pfleiderer twin screw extruder (400-430 c F), 80 lb of polypropylene (melt flow rate 4) and 20 lb of pyromellitic dianhydride (PMDA) . The extrudate in the shape of a rod (2—3 mm in diameter) was quenched by passing it in a cold water trough, and then chopped into pellets (2—3 mm long) and air dried. This composition was tested according to Test Procedures I and II and shown to contain 20 wt% PMDA. Example 2 Preparation of 15 wt% PMDA composition based on polypropylene. The procedure of Example 1 waε repeated except that 85 lb of polypropylene and 15 lb of PMDA were used. Example 3 Preparation of 10 wt% PMDA composition based on polypropylene The procedure of Example 1 was repeated except that 90 lb of polypropylene and 10 lb of PMDA were used. Example 4 Preparation of 40 wt% Talc composition based on polypropylene. A PP/Talc composition was prepared by melt blending in a 30 mm Werner and Pfleiderer twin screw extruder (400—430°F) , 60 lb of Polypropylene (melt flow rate 4) and 40 lb of Talc (Polar Minerals, Inc., Product #9102, median particle size 2—3 microns) . The extrudate in the shape of a rod (2—3 mm in diameter) was quenched by passing it through a cold water trough, and chopped into pellets (2—3 mm long) and air dried. Example 5 Preparation of 30 wt% Talc composition based on polypropylene. The procedure of Example 4 was repeated except that 70 lb of polypropylene and 30 lb of Talc were used. Example 6 Preparation of 20 wt% Talc composition based on polypropylene. The procedure of Example 4 was repeated except that 80 lb of polypropylene and 20 lb of Talc were used. Example 7 Preparation of 40 wt% Ti0 2 composition based on polypropylene. The procedure of Example 4 is repeated except that 60 lb of polypropylene and 40 lb of Ti0 2 were used. Example 8 Preparation of 20 wt% Tiθ 2 , 20 wt% Talc composition based on polypropylene. The procedure of Example 4 was repeated except that 60 lb of polypropylene, 20 lb of Talc and 20 lb of Ti0 2 were used. Example 9 Preparation of 39.75 wt% Talc, 0.25 wt% Ethanox 330 antioxidant composition based on polypropylene. The procedure of Example 4 was repeated except that 60 lb of polypropylene, 39.75 lb of Talc and 0.25 lb of Ethanox 330 was used. Example 10 Preparation of 39.90 wt% Talc, 0.10 wt% Irganox 1076 antioxidant composition based on polypropylene. The procedure of Example 4 was repeated except that 60 lb of polypropylene, 39.90 lb of Talc and 0.10 lb of Irganox 1076 were used. Example 11 Preparation of 39.70 wt% Talc, 0.20 wt% stabilizer, 0.10 wt% Irganox 1010 antioxidant composition based on polypropylene. The procedure of Example 4 was repeated except that 60 lb of polypropylene, 39.70 lb of Talc, 0.20 lb of dilauryl thiodipropionate and 0.10 lb of Irganox 1010 were uεed. The latter two compounds are present as heat stabilizers and antioxidants. Example 12 Preparation of 39.70 wt% Ti0 2 , 0.20 wt% stabilizer, 0.10 wt% Irganox 1010 antioxidant compoεition based on a polypropylene copolymer. The procedure of Example 4 was repeated except that 60 lb of propylene copolymer containing 5 mole % of l-butene (melt flow rate 3.5), 39.70 lb of Ti0 2 , 0.20 lb of dilauryl thiodipropionate and 0.10 lb of Irganox 1010 was used. Example 13 Preparation of 10 wt% PMDA, 20 wt% Talc composition based on polypropylene. The procedure of Example l was repeated except that 70 lb of polypropylene, 10 lb of PMDA, and 20 lb of Talc (Polar Minerals, Product # 9102) was used. Example 14 Preparation of 10 wt% PMDA, 30 wt% Talc, 5 wt% Na 2 C0 3 composition based on polypropylene. The procedure of Example 1 was repeated except that 55 lb of polypropylene, 10 lb of PMDA, 30 lb of Talc (Polar Minerals, # 9102) and 5 lb of anhydrous Na 2 C0 3 (Rhone—Poulenc) was used. Example 15 Preparation of 40 wt% Talc, 10 wt% Na 2 C0 3 composition based on polypropylene. The procedure of Example 4 was repeated except that 50 lb of polypropylene, 40 lb of Talc (Polar Minerals, # 9102) and 10 lb of anhydrous Na 2 C0 3 (Rhone-Poulenc) was used. Example 16 Poly (ethylene terephthalate), PET 12440 (IV 0.70), supplied by Eastman Chemical Company, was dried at 300°F for 6 hours (to a dew point of —40°C) in a Conair desiccant dryer. It was fed through the main feed hopper of a 3.5" Prodex single εcrew extruder (L/D = 24/1) equipped with a helical static mixer and an EDI 30" flex lip die having a 3 mm land length. The extruder was heated as noted below: Heat zone 1 540°F Heat zone 2 560°F Heat zone 3 560°F Heat zone 4 520°F Die Adapter 500°F Die 500°F The composition pellets from Example 1 and 4 were dry blended manually in a 50:50 ratio (and labeled aε Blend—1,4) and fed into the feed throat of the extruder using a Colormate additive feeder attached to the bottom of the PET feed hopper. This additive feeder was calibrated for the above composition blend such that any desired level of the blend could be dialed in by simply turning the control knob on the feeder. The following experimental runs were completed using different levels of the above composition blend, and the extruder screw speed; and the PET/Composition blend extrudate samples were collected at the extruder die; these samples were analyzed for free PMDA by the analytical procedure described in Test Procedure IV. SAMPLE SCREW SPEED FREE PMDA PET/2.50% Cone. Blend-1,4 30 rpm None Detected PET/1.75% Cone. Blend-1,4 45 rpm None Detected PET/1.00% Cone. Blend-1,4 30 rpm None Detected PET/2.50% Cone. Blend-1,4 45 rpm None Detected These results indicate that none of the four samples had any detectable levels of free PMDA. Comparison Example 17 The procedure of Example 16 was repeated except that the composition prepared in Example 13 was used instead of the composition blend-1,4 (50:50 mix of compositions of Example 1 and 4) . The extruder temperature profile was the same aε in the Example 16 above. Uεing a pre—calibrated additive feeder aε deεcribed above, the following experimental runs were completed using different levels of the composition of Example 13, and the extruder screw speed; the PET/Composition extrudate samples were collected at the extruder die, and were analyzed for Free PMDA by the analytical procedure described in Test Procedure IV. SAMPLE SCREW SPEED FREE PMDA PET/2.50% Cone. Ex. 13 30 rpm 29 ppm PET/1.75% Cone. Ex. 13 45 rpm 23 ppm PET/1.75% Cone. Ex. 13 30 rpm 24 ppm PET/1.00% Cone. Ex. 13 45 rpm 19 ppm These results indicate that the extrudates have significant levels of free PMDA. Comparison Example 18 The procedure of Example 16 was repeated except that a 50:50 dry blend of the composition pellets from Examples 1 and 15 was used instead of the 50:50 dry blend of the compositions from Examples 1 and 4. The extruder temperature profile was the same as in the Example 16 above. The blend of compositions of Examples 1 and 15 was added to the PET melt using an additive feeder at a rate of 1.7 wt % (based upon the PET output rate) . A sample of the PET/Composition blend extrudate was collected at the extruder die, and analyzed for Free PMDA by Test Procedure IV. This sample was shown to contain 0.0045 wt % (or 45 parts per million) of Free PMDA present in it (recall that the total amount of PMDA used to make this PET blend sample was 0.17 wt %) . Example 19 Poly (ethylene terephthalate), PET 12440 (IV 0.70), supplied by Eastman Chemical Company, was dried at 300°C for 6 hourε (to a dew point of —40°C) in a Conair desiccant dryer. It was then fed through the main feed hopper of a Battenfeld Gloucester tandem 2" primary/2.5" secondary foam extrusion line equipped with a 2 7 / 8 " diameter annular die and a Movacolor additive feeder attached to the feed throat of the primary extruder. Both 2" and 2.5" extruders have a 30/1 L/D ratio. Near the end of the primary extruder there is located an injection port capable of injecting a blowing agent under high pressure into the polymeric melt. The primary and the secondary extruders are connected through a well known low pressure crosεover zone. The blowing agent used in this example is an environmentally friendly hydrofluorocarbon gas, 1,1—difluoroethane (DuPont, 152A) . The extruders, the crosεover zone and the annular die are heated through their entire length as noted below: Primary 2" Extruder Zone 1 520°F Primary 2" Extruder Zone 2 550°F Primary 2" Extruder Zone 3 550°F Primary 2" Extruder Zone 4 550°F Primary 2" Extruder Zone 5 553°F Croεεover Zone 6 545°F Croεεover Zone 7 539°F Seal Zone 8 305°F Secondary 2.5" Extruder Zone 9 497°F Secondary 2.5" Extruder Zone 10 499°F Secondary 2.5" Extruder Zone 11 494°F Secondary 2.5" Extruder Zone 12 490 C F Annular Die Zone 13 489°F Annular Die Zone 14 495°F Annular Die Zone 15 480°F Annular Die Melt Temperature 488°F The polypropylene/PMDA compoεition from Example 1 and the polypropylene/Talc composition from Example 4 were dry blended manually in a 50:50 ratio and fed into the feed throat of the primary extruder using the Movacolor additive feeder attachment at a rate of 1.5 wt % (based upon the output of the PET extrudate) - this then gave a final composition of the PET extrudate as one containing 0.15 wt % PMDA, 0.30 wt % Talc and 1.05 wt % polypropylene. Other relevant extrusion conditions and parameters are as follows: Pressures (psi) 2" extruder 3690 Crossover zone 2640 Die 1280 Blowing agent injection pressure 2400 Drive Conditionε 2" extruder 95 rpm/23 ampε 2.5" extruder 23 rpm/19 ampε Polymer output 83 lb/hr Blowing agent injected 0.38 lb/hr The foam coming from the annular die had a dry hand and good melt strength so that it can be readily stretched over a 7" diameter water cooled mandrel. The foam was slit and collected as a sheet 22" wide. The thickness and density of the foam respond well to changes in the line—speed and blowing gas level. The foam produced had a density of 0.20 g/cc at a thickness of 65 mils. It had an IV of 0.805 dl/g and a GPC weight average molecular weight of 85690 and a Mz Mn ratio of 10.78. It alεo had a crystallinity of 15.9% as measured by DSC. Scanning Electron Microscopy showed the cell structure to be well formed with all cells being closed and of approximately 200 micron diameter in size. This foam sample produced above was analyzed for the level of unreacted or free PMDA according to Test Procedure IV, and it was shown to contain no detectable free PMDA. The above sample was also subjected to an extraction test using 8% ethanol in water at 250°F for 2 hours inside a pressure cooker as deεcribed in Test Procedure V. The extract was then analyzed using a Liquid Chromatograph (HPLC) and the presence of any PMDA in this food stimulant was not detected. To test the accuracy of this analysis, the extract was spiked with PMDA at 32 parts per billion (ppb) (this was below the regulatory limits) and checked for % recovery. It had an average recovery of 102%. Similarly good foaming reεults were achieved using compositions of Examples 2 and 5 which were mixed at a ratio of 50:50 and the mixture fed through the feeder at the rate of 2.0 wt %. Similarly good reεults were also obtained when isopentane, nitrogen or carbon dioxide gaε waε uεed instead of the hydrofluorocarbon (152A) gas as the blowing agent. Similarly good foaming results were alεo achieved when a combination of a chemical blowing agent and a gas blowing agent were used. Thus, the polyester was dusted with 0.5 wt % of the chemical blowing agent, azodicarbonamide, prior to the extrusion process, and then the isopentane blowing agent was used during the extrusion process as deεcribed above. Similarly good foaming reεultε were alεo achieved when 0.05 weight % of the chemical blowing agent, HYDROCEROL HK 40B, was fed into the extruder along with the polyester and the composition blend, and then a gas blowing agent, for example, 1,1—difluoroethane or nitrogen) was used during the extrusion process as described above. Example 20 Poly (ethylene terephthalate), PET 12440 (IV 0.70), supplied by Eastman Chemical Company, waε dried at 300°F for 6 hours (to a dew point of —40°C) in a portable Walton Stout desiccant dryer. It was then fed through the main feed hopper of a Battenfeld Gloucester tandem 3.5" primary/4.5" secondary foam extrusion line equipped with a 3.5" diameter annular die at the end of the secondary extruder , an additive (pellet form) feeder, and a powder additive feeder attached to the feed throat of the primary extruder. Both 3.5" and 4.5" extruders have a 30/1 L/D ratio. Near the end of the primary extruder there is located an injection port capable of injecting a blowing agent under high pressure into the polymeric melt. The primary and the secondary extruders are connected through a well known low pressure crossover zone. The blowing agent used in this example is an environmentally friendly hydrofluorocarbon gas, 1,1—difluoroethane (DuPont, 152A) . The extruders, the crossover zone and the annular die are heated through their entire length aε noted below: Primary 3.5" Extruder Zone 1 445°F Primary 3.5" Extruder Zone 2 544°F Primary 3.5" Extruder Zone 3 538°F Primary 3.5" Extruder Zone 4 529°F Primary 3.5" Extruder Zone 5 518°F Primary 3.5" Extruder Zone 6 510°F Screen Changer Body 503°F Screen Changer Slide 504°F Crossover 563°F Secondary Seal 174°F Secondary 4.5" Extruder Zone 1 478°F Secondary 4.5" Extruder Zone 2 480°F Secondary 4.5" Extruder Zone 3 481°F Secondary 4.5" Extruder Zone 4 477°F Annular Die Zone 1 489°F Annular Die Zone 2 484°F Annular Die Adapter 479°F Annular Die Melt Temperatuurree 472°F The polypropylene/PMDA composition from Example 1 was fed—in into the feed throat of the primary extruder using the pellet additive feeder attachment at a rate of 1.0 wt % (based upon the output of the PET extrudate). Powder talc (Polar Mineralε Inc., Product # 9102, median particle size 2—3 microns) was also fed into the feed throat of the primary extruder using the powder feeder attachment at a rate of 0.3 wt % (based upon the output of the PET extrudate) . The final PET extrudate compoεition was therefore one containing 0.20 wt % PMDA, 0.30 wt % Talc and 0.80 wt % polypropylene. Other relevant extrusion conditionε and parameterε are aε followε: Preεεureε (psi) 3.5" Extruder 2000-2200 Crossover zone 2000 4.5" Extruder 1600 Blowing agent injection pressure 3630 Drive Conditions 3.5" Extruder 62 rpm/84 amps 4.5" Extruder 12.4 rpm/29 ampε Polymer output 316 lb/hour Blowing agent injected 1.0 lb/hour Under these conditions, the PET/Composition/Talc composition deεcribed above extrudeε with the deεired characteristics needed to produce good foam. The foam coming out of the annular die has a dry hand and good melt strength so that it can be readily stretched over a 16 1 / 4 " diameter water cooled mandrel (70°F) . The foam is slit, and the sheet is trimmed to 48" width and collected. The thickness and density of the foam respond well to changes in the line—speed and blowing gas level. The foam produced has a density of 0.26 g/cc at a thicknesε of 45 milε. It has an IV of 0.76 dl/g and a GPC weight average molecular weight of 76130 and a Mz/Mn ratio of 10.38. It also has a crystallinity of 4.56% aε meaεured by DSC. Scanning electron microscopy show the cell structure to be well formed with all cells being closed. The average cell εize was approximately 200—500 microns in diameter in the machine direction and 100—200 microns in diameter in the transverse direction. This foam PET sheet produced above was thermoformed into foam trays using an Irwin thermoformer equipped with a heated matched mold. Typical forming conditions were as given below: Oven Temperatures: Top 495 491 491 492°F Bottom 491 491 491 491°F Top/Bottom Near Side 550/500°F Top/Bottom Far Side 591/513°F Top/Bottom Radd 581/510°F Top/Bottom Pre-heat 500/522°F Line speed: 10.9 cycles per minute A sample of the foam tray produced was analyzed by DSC and it showed a % cryεtallinity of 28.6%; the weight average molecular weight and Mz/Mw ratio obtained by GPC were 74714 and 9.20 respectively. A sample of the foam trays produced was analyzed for the level of unreacted or free PMDA according to Test Procedure IV, and it was shown to contain no detectable free PMDA. These foam trayε were also subjected to a complete extraction test protocol for evaluation of compliance with European Union (EU) regulations for global (total) migration (TM) , antimony migration, and PMDA migration into food simulating solvents. PMDA migration into food simulating solvents was also evaluated using testε conεistent with FDA guidelines (1988 Recommendations for Chemistry Data for Indirect Additive Petitions) . These trays complied with all limits and no migration of PMDA was detected in any of the extracts. The data is summarized in the following table: 3% Acetic Acid HB 307 Oil 8% EtOH (100°C/2h) (175°C/2h) (250°F/2h) TM . Sb PMDA TM Sb PMDA PMDA < mg/kg < mg/kg > mg/kg Foam Trays .11 .00 .00 13 .00 .00 .00 EU LIMITS .60 .01 05 60 01 .05 Not Regul¬ ated Notes: 1) TM = terephthaloyl moieties determined by UV was uεed aε a meaεure of total (global) migration. Sb = Antimony determined by ICP MS. PMDA = pyromellitic dianhydride determined aε the acid by HPLC. 2) The 3% acetic acid and HB 307 extractions were obtained by adding 100 ml solvent to the trays with a contact area of 1.8 dm 2 . The 8% ethanol extractions were obtained by exposing 1/2 dm 2 strips to 50 ml solvent with wire spacers in pressure cells in the pressure cooker. A contact area of 1 dm 2 (double side) was used in the 8% ethanol calculations. 3) Trace amounts of antimony were found in the 3% and HB 307 oil extracts but it was leεε than 0.01 mg/kg. 4) No PMDA was detected in the extracts. The extracts were spiked with PMDA at levels below the limits and the % recoveries of the spikeε determined: HB307 oil = Spiked at 0.033 mg/kg (EU guidelineε, 6 dm 2 /Kg of food εtimulant) and 35 ppb in—food (FDA guidelines, 10 grams of food stimulant per square inch) with an average recovery of 98%. 3% Acetic acid = Spiked at 0.033 mg/kg (EU guidelines, 6 dm 2 /Kg of food stimulant) and 36 ppb in—food (FDA guidelines, 10 grams of food stimulant per square inch) with an average recovery of 86%. 8% Ethanol = Spiked at 0.03 mg/kg (EU guidelines, 6 dm 2 /Kg of food stimulant) and 32 ppb in—food (FDA guidelines, 10 grams of food stimulant per square inch) with an average recovery of 102%. Similarly good foaming results are achieved using composition of Example 3 at a feed rate of 2.0 wt %, and powder Ti0 2 at a feed rate of 0.4 wt %. Similarly good foaming results are achieved using compositions of Examples 1 and 6 which are mixed at a ratio of 33:66 and the mixture fed through the feeder at the rate of 1.0 wt %. Similarly good foam resultε are achieved uεing compositionε of Exampleε l and 8 which are mixed at a ratio of 50:50 and fed at the rate of 1.0 wt %. Similarly good foaming results are achieved using isopentane or nitrogen gas as the blowing agent. Similarly good foaming resultε are achieved when a combination of a chemical blowing agent (e.g. 5—phenyl tetrazole or azodicarbona ide) or a sodium bicarbonate/citric acid based chemical blowing agent, and a gas blowing agent (e.g. isopentane) was used. Similarly good foaming resultε are achieved uεing compositions of Example 1 and 7 which are each fed into the extruder using two separate feederε at the rates of 1.0 wt %. Similarly good foaming resultε are achieved using composition of Example 1 at a feed rate of 1.0 wt %, and either one of the compositionε of Examples 9, 10, 11 or 12 alεo being fed into the extruder at the εame rate of 1.0 wt %. Compariεon Example 21 The procedure of Example 20 was repeated except that the composition of Example 14 was used instead of the composition of Example 1 and powder talc. The extruder drive, pressure and temperature profiles were the same aε in Example 20. The composition of Example 14 was used at a rate of 2.0 wt %; thuε the final PET extrudate composition was one containing 0.20 wt % PMDA, 0.60 wt % Talc, 0.10 wt % anhydrous Na 2 C0 3 and 1.10 wt % polypropylene. This composition extruded with the desired characteristics needed to produce good foam. The foam coming out of the annular die haε a dry hand and good melt strength so that it can be readily stretched over a 16 1 / 4 " diameter water cooled mandrel (70°F) . The foam sheet is collected in the form of a 48" wide roll as described in Example 20. The foam produced has a denεity of 0.30 g/cc at a gauge thickneεε of 100 milε. It haε an IV of 0.78 dl/g and a GPC weight average molecular weight of 73739 and a Mz/Mn ratio of 14.96. Scanning Electron Microscopy show the cell structure to be well formed with all cells being closed and of approximately 210 micron diameter in size. A sample of this foam sheet produced was analyzed for the level of unreacted or free PMDA according to the analytical procedure deεcribed in Teεt Procedure IV, and it waε shown to contain 0.048 wt % (or 480 parts per million) of free PMDA (recall that the total amount of PMDA used to make this foam sample was 0.20 wt %) . Comparison Example 22 The procedure of Example 20 was repeated except that the additives PMDA, Talc and Na 2 C0 3 were all added in the powder form uεing powder additive feeder attachmentε. The levelε that the powder additiveε were added-in were εuch that the final compoεition of the PET extrudate waε one containing 0.15 wt % PMDA, 0.45 wt % Talc and 0.10 wt % Na 2 C0 3 . Under these conditions, although we were able to produce PET foam of good physical appearance and cell size, when we analyzed a sample of thiε foam for the level of unreacted or free PMDA according to the analytical procedure deεcribed in Test Procedure IV, we found that it contained as much aε 0.0155 wt % (or 155 parts per million) of free PMDA. The foamed compositions of Example 16, 19 and 20 were prepared according to the teachings of the present invention and display less than 5 ppm of unreacted or free monomeric branching agent. Moreover these foam compositionε have improved melt viεcoεity and melt εtrength. For example, a 0.9 IV PET has a melt viscoεity of about 19,000 poiεe at 280°C, and a melt εtrength of —51% at 280°C. When branched with 0.2% pyromellitic dianhydride from the composition, the melt viscosity is about 117,000 poise at 280°C, and the melt strength is about +40% at 280°C. It is clear from the examples that the use of any organic or inorganic compounds of Group I, II or III metals in the procesε of the preεent invention has an adverse effect on the amount of unreacted or free monomeric branching agent in the final polyester product. Example 13 describes the preparation of a composition in which the additive, talc, has been added together with PMDA into the polypropylene carrier. In Example 17, the composition of Example 13 was used to prepare a PET/composition blend which contained εignificant levelε of free or unreacted PMDA (19—29 ppm depending upon the level of composition used) . In contrast, a blend was prepared in Example 16 which did not contain any unreacted PMDA branching agent using a 50:50 mixture of the PP/PMDA and PP/Talc compositions prepared in Examples 1 and 4, respectively. In Example 15, a composition was prepared in which both talc and Na 2 C0 3 were compounded together into the polypropylene carrier. Example 18 incorporated the composition prepared in Example 15 to into a PET/1.7 weight percent composition blend which contained 45 ppm of free or unreacted PMDA. In contrast, the PET/1.75 weight percent composition blend prepared in Example 17, which did not contain any Na 2 C0 3 , was determined to contain only 23 ppm of free or unreacted PMDA present. A similar situation is found when comparing Examples 19 and 20 which have no detectable unreacted or free PMDA to Examples 21 and 22 which have 480 ppm and 155 ppm, respectively, of free and unreacted PMDA. The foam trayε produced in Example 20 were alεo subjected to a complete extraction test protocol for evaluation of compliance with European Union (EU) regulations for global (total) migration, antimony migration, and PMDA migration into food simulating solvents. The test protocol also provided for evaluation of PMDA migration into food simulating solvents consiεtent with Food and Drug Adminiεtration (FDA) guidelineε (1988 Recommendationε for Chemiεtry Data for Indirect Additive Petitionε) . No migration of PMDA was detected in any of the extracts. The calibration limit for the test of extractable PMDA in food simulating solventε was 15 parts per billion (ppb) . The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variationε and modificationε can be effected within the εpirit and εcope of the invention.

Claims: WHAT IS CLAIMED IS: 1. A process for preparing a foamable branched polyester composition having a reduced level of unreacted monomeric branching agent, comprising melt blending: (A) a composition consiεting eεsentially of: (1) 50 to 99 weight % of a polyolefin having a repeat unit selected from the group consisting of ethylene, propylene, butene, and combinationε thereof, provided the ethylene polymers have a melt index of 0 to 100 at 190°C as measured by ASTM D1238—56T, and the propylene and butene polymers have a melt flow rate of 0 to 100 at 230°C as measured by ASTM D1238-56T; and (2) l to 50 weight % of a monomeric branching agent having a molecular weight of 50 to 5000 selected from the group consisting of a carboxylic acid having at least two carboxyl groups, and an anhydride having at least one anhydride group, and combinations thereof, provided a reactive compound of a Group I, II, or III metal is not included in composition (A) ; (B) at least one nucleating agent in powder form; end (C) a polyester having an inherent viscosity of 0.4 to 1.1 dL/g comprising repeat units from (a) a dicarboxylic acid selected from the group consiεting of aromatic dicarboxylic acids having 8 to 14 carbon atoms, saturated aliphatic dicarboxylic acids having 4 to 12 carbon atoms, and cycloaliphatic dicarboxylic acids having 8 to 12 carbon atoms, and combinations thereof; and (b) a diol selected from the group consisting of cycloaliphatic diols having 6 to 20 carbon atoms, aliphatic diols having 3 to 20 carbon atoms, and combinationε thereof, wherein the foamable branched polyeεter compoεition comprises 0.1 to 20 weight % of (A), 0.01 to 10 weight % of (B) , 80 to 99.9 weight % of (C) , baεed on the total weight of (A) , (B) , and (C) . 2. A procesε for preparing a foamable branched polyeεter compoεition having a reduced level of unreacted monomeric branching agent, compriεing melt blending: (A) a compoεition conεisting essentially of: (1) 50 to 99 weight % of a polyolefin having a repeat unit selected from the group consiεting of ethylene, propylene, butene, and combinationε thereof, provided the ethylene polymerε have a melt index of 0 to 100 at 190°C as measured by ASTM D1238—56T, and the propylene and butene polymers have a melt flow rate of 0 to 100 at 230°C as measured by ASTM D1238-56T; and (2) 1 to 50 weight % of a monomeric branching agent having a molecular weight of 50 to 5000 selected from the group consisting of a carboxylic acid having at least two carboxyl groups, and an anhydride having at leaεt one anhydride group, and combinationε thereof, provided a reactive compound of a Group I, II, or III metal iε not included in composition (A) ; (B') a composition consiεting essentially of : (3) 50 to 99 weight % of a polyolefin having a repeat unit selected from the group consisting of ethylene, propylene, butene, and combinations thereof, provided the ethylene polymers have a melt index of 0 to 100 at 190°C, and the propylene and butene polymers have a melt flow rate of 0 to 100 at 230°C; and (4) 1 to 50 weight % of at least one nucleating agent, provided a reactive compound of a Group I, II, or III metal is not included in composition (B'); and (C) a polyester having an inherent viscoεity of 0.4 to l.l dL/g comprising repeat units from (a) a dicarboxylic acid selected from the group consiεting of aromatic dicarboxylic acids having 8 to 14 carbon atoms, saturated aliphatic dicarboxylic acids having 4 to 12 carbon atoms, and cycloaliphatic dicarboxylic acids having 8 to 12 carbon atoms, and combinations thereof; and (b) a diol selected from the group consiεting of cycloaliphatic diolε having 6 to 20 carbon atoms, aliphatic diols having 3 to 20 carbon atoms, and combinationε thereof, wherein the foamable branched polyeεter compoεition comprises 0.1 to 20 weight % of (A), 0.02 to 20 weight % of (B'), 80 to 99.9 weight % of (C) , based on the total weight of (A), (B'), and (C) . 3. A procesε for preparing a foamable branched polyeεter compoεition having a reduced level of unreacted monomeric branching agent, compriεing melt blending: (A) a composition consisting essentially of: (1) 70 to 95 weight % of a polyolefin having a repeat unit selected from the group consisting of ethylene, propylene, butene, and combinations thereof, provided the ethylene polymers have a melt index of 0 to 100 at 190 C C as measured by ASTM D1238—56T, and the propylene and butene polymers have a melt flow rate of 0 to 100 at 230°C as measured by ASTM D1238-56T; and (2) 5 to 30 weight % of a monomeric branching agent having a molecular weight of 50 to 5000 selected from the group consisting of a carboxylic acid having at least two carboxyl groups, and an anhydride having at least one anhydride group, and combinations thereof, provided a reactive compound of a Group I, II, or III metal iε not included in composition (A) ; (B') a composition consisting essentially of : (3) 60 to 80 weight % of a polyolefin having a repeat unit selected from the group consiεting of ethylene, propylene, butene, and combinationε thereof, provided the ethylene polymerε have a melt index of 0 to 100 at 190°C, and the propylene and butene polymerε have a melt flow rate of 0 to 100 at 230°C; and (4) 20 to 40 weight % of at least one nucleating agent, provided a reactive compound of a Group I, II, or III metal is not included in composition (B'); and (C) a polyester having an inherent viscosity of 0.4 to 1.1 dL/g comprising repeat units from (a) a dicarboxylic acid selected from the group consisting of aromatic dicarboxylic acids having 8 to 14 carbon atoms, saturated aliphatic dicarboxylic acids having 4 to 12 carbon atoms, and cycloaliphatic dicarboxylic acids having 8 to 12 carbon atoms, and combinations thereof; and (b) a diol selected from the group consiεting of cycloaliphatic diols having 6 to 20 carbon atoms, aliphatic diols having 3 to 20 carbon atoms, and combinations thereof, wherein the foamable branched polyester composition comprises 1 to 10 weight % of (A) , 1 to 10 weight % of (B'), 80 to 98 weight % of (C) , based on the total weight of (A), (B'), and (C) . 4. The process of Claim l wherein the nucleating agent is added in an amount of 0.1 to 2 weight %, based on the total weight of (A) , (B) , and (C) . 5. The process of Claim l wherein the polyolefin, component (1) , is selected from the group conεisting of polyethylene and polypropylene. 6. The process of Claim 2 wherein the polyolefin, component (3), is selected from the group consiεting of polyethylene and polypropylene. 7. The procesε of Claim 1 wherein the monomeric branching agent, component (2) , iε selected from the group consisting of trimesic acid, pyromellitic acid, pyromellitic dianhydride, trimellitic anhydride, benzenetetra carboxylic anhydride, benzophenone tetracarboxylic anhydride, hemimellitic acid, trimellitic acid, trimesic acid, pyromellitic acid, 1,1,2,2—ethanetetracarboxylie acid, 1,1,2— ethanetricarboxylic acid, 1,3,5—pentanetricarboxylic acid, 1,2,3,4—cyclopentanetetracarboxylic acid, and combinations thereof. 8. The procesε of Claim 7 wherein the monomeric branching agent iε εelected from the group conεiεting of pyromellitic dianhydride, trimellitic anhydride, benzenetetra carboxylic anhydride, and benzophenone tetracarboxylic anhydride. 9. The process of Claim 1 wherein the nucleating agent is selected from the group consisting of titanium dioxide, talc, chopped fiber glass, alumina, clay, and fumed silica. 10. The process of Claim 9 wherein the nucleating agent is talc. 11. The process of Claim 1 wherein the dicarboxylic acid component of the polyester is selected from the group consisting of terephthalic acid, phthalic acid, isophthalic acid, naphthalene—2,6—dicarboxylic acid, cyclohexanedicarboxylic acid, cyelohexanediacetic acid, and combinationε thereof. 12. The process of Claim 11 wherein the dicarboxylic acid is terephthalic acid. 13. The process of Claim 1 wherein the diol component of the polyester is selected from the group consisting of 1,4—cyclohexanedimethanol, ethylene glycol, diethylene glycol, triethylene glycol, propane—l,3-diol, butane—1,4—diol, pentane—1,5—diol, hexane—1,6—diol, 3-methylpentanediol-(2,4) , 2-methylpentanediol-(l,4) , 2,2,4—trimethylpentane— iol—(1,3), 2—ethylhexanediol—(1,3), 2,2-diethylpropane-diol—(1,3), hexanediol—(1,3) , 1,4-di—(hydroxyethoxy)—benzene, 2,2—bis—( — ydroxycyclohexy1)—propane, 2,4-dihydroxy—1,1,3,3—tetramethy1-cyclobutane, 2,2—bis—(3—hydroxyethoxyphenyl)-propane, and 2,2—bis—(4—hydroxypropoxyphenyl)—propane. 1 . The procesε of Claim 13 wherein the diol component of the polyeεter is ethylene glycol. 15. The process of Claim 1 wherein the polyester additionally contains 0.1 to 10 weight percent of at least one additive selected from the group consisting of titanium dioxide, talc, chopped fiber glass, alumina, clay, fumed silica, stabilizerε, antioxidants, buffers, flame retardants, lubricants, extenders, colorants, pigments, carbon black, dyes, and nucleating agents. 16. The process of Claim l wherein the polyester contains an antioxidant in an amount up to two percent by weight of the polyester. 17. The process of Claim 16 wherein the antioxidant is present in an amount of 0.1 to 1 percent by weight of the polyester. 18. The process of Claim 1 wherein the foamable branched polyester composition has less than 50 parts per million (ppm) of unreacted monomeric branching agent. 19. The procesε of Claim 18 wherein the foamable branched polyester composition has lesε than 5 parts per million (ppm) of unreacted monomeric branching agent. 20. The process of Claim 2 wherein the foamable branched polyester composition has lesε than 50 parts per million (ppm) of unreacted monomeric branching agent. 21. The procesε of Claim 20 wherein the foamable branched polyeεter compoεition haε leεε than 5 parts per million (ppm) of unreacted monomeric branching agent. 22. The process of Claim 1 wherein the foamable branched polyester composition iε extruded into a εheet and formed into an article. 23. The process of Claim 1 wherein the foamable branched polyester composition is melted inside an extruder, injected with a gas blowing agent, extruded into a foamed sheet and formed into an article. 24. The procesε of Claim 1 wherein a chemical blowing agent iε added to the foamable branched polyeεter composition and the composition is melted inside an extruder, injected with a gas blowing agent, extruded into a foamed sheet and formed into an article. 25. The process of Claim 1 wherein a chemical blowing agent is added to the foamable branched polyester composition and the compoεition iε melted inside an extruder, extruded into a εheet and formed into an article.

Inventors: BOONE GARY DARREL, JUAREZ-GARCIA CARLOS HUMBERTO, KHEMANI KISHAN CHAND, BOONE, GARY, DARREL, JUAREZ-GARCIA, CARLOS, HUMBERTO, KHEMANI, KISHAN, CHAND
Applicants: EASTMAN CHEM CO, EASTMAN CHEMICAL COMPANY
Application year: 1996
Main classification: C08L67
IPC codes: C08J9, C08L67