MXPA97008603A - Foamed brass polyesters with ethylene copolymers - Google Patents

Abstract

Branched polyester compositions having an I.V. are described. of at least about 0.7 dl / g and a sufficiently high melt viscosity to allow foaming during extrusion or molding operation. These branched polyesters are easily foamable with a wide range of foaming agents to provide low density shaped articles, films and sheets. The branched polyesters comprise from about 80 to about 99.9% by weight of a polyester and from about 0.1 to about 20% by weight of an ethylene copolymer containing repeating units of ethylene and of a monomer selected from the group consisting of acrylic acid, methacrylic acid, alkyl acrylate, alkyl methacrylate and vinyl alcohol. The polyester comprises repeating units of about 75 to 100% mol of a dibasic acid having from 6 to 40 carbon atoms and 0 to about 25 mol% of a dibasic acid modifier and repeating units of from about 75 to 100 mol% of a glycol from 2 to 10 carbon atoms, 0 to about 25 mol% of a modifying glycol and 0 to about 25 mol% of a modifying compound selected from the group comprising amino alcohols, diamines and lactam

Description

FOAMED POLYESTERS BRANCHED WITH CQPQLIMERP-? Pfi KTII.KWQ DESCRIPTION OF THE INVENTION This invention relates to high molecular weight polyester compositions having high melt viscosity and melt strength and which can be foamed with a wide range of foaming agents. More particularly, this invention relates to polyesters containing branching agents of ethylene copolymers and foamed articles produced therewith. Many polymeric materials are foamed to provide low density articles such as films, cups, food trays, decorative ribbons and furniture parts. For example, polystyrene strips containing low boiling hydrocarbons such as pentane, are formed into lightweight foamed cups for hot beverages 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 wraps. Also, polypropylene can be injection molded in the presence of these blowing agents, to form lightweight furniture parts such as table legs and to form lightweight chairs.

Polyesters such as poly (ethylene terephthalate) have much higher density (for example about 1.3 g / cm 3) than other polymers. Therefore, it would be convenient to be able to foam polyester materials to decrease their weight to use in producing molded parts, films, sheets, food trays and the like. These foaming articles also have better insulating properties than the non-foamed parts. However, it is difficult to foam these polyester materials due to the low melt viscosity and low melting strength of the typical poly (ethylene terephthalate) and related polyester polymers. The low melt viscosity and low melting strength of the polyesters is a problem because the polymer melt will not adequately retain the bubbles of an expanding gas during molding or extrusion operations. It would therefore be convenient to be able to provide polyester polymers which can be foamed with conventional foaming systems. One approach to providing polyesters having high melt viscosities involves treating preformed polyesters with monomeric materials which are multifunctional carboxylic acids or polyols, to provide branched polyesters. These compositions are described in U.S. Pat. US. 4,132,707; 4,145,466;, 4,999,388; 5,000,991; 5,110,844;, 5,128,383; and 5,134,028. The branching agents employed include tri- and tetracarboxylic acids and anhydrides such as trimesic acid, pyromellitic acid and pyromellitic dianhydride or polyols such as trimethylolpropane and pentaerythritol. These monomeric branching agents will provide polyesters with increased melt viscosities and melting strengths but their use is often disadvantageous. The usual method of adding the branching agent is to fuse the polyester in an extruder and add the branching agent to the melt in the barrel of the extruder. however, it is difficult to control the amount of branching agent employed and to obtain adequate mixing and reaction before the melt leaves the matrix. To solve the aforementioned problems and provide polyesters with sufficient melt strength which are easy to foam and result in excellent foaming properties, U.S. Pat. No. 5,399,595 issued to Sublett, discloses the incorporation of small amounts of a sulfonomer of dicarboxylic acid such as sulfoisophthalic acid into a polyester composition of essentially repeating units of terephthalic acid or naphthalenedicarboxylic acid and an aliphatic or cycloaliphatic glycol. These foamable polyesters are prepared by a combination of solid state polymerization and melting phase to result in a polyester composition that is easy to foam. To solve the aforementioned problems of the prior art, the inventors of the present invention additionally provide a branched polyester, which has increased melt viscosity and melt strength for use in producing a foamed article of excellent foaming properties, the foamed article of the branched polyester has an I.V. of at least 0.7 dl / g, and a sufficiently high melt viscosity to allow foaming during extrusion or molding operations. The branched polyester comprises: (A) about 80 to about 99.9% by weight based on the total weight of (A) and (B) of a polyester comprising: (1) repeating units of about 75 to 100% mol of a dibasic acid having 6 to 40 carbon atoms and 0 to about 25 mol% of a modifying dibasic acid, and (2) repeating units of about 75 to 100 mol% of a glycosl having 2 to 10 carbon atoms , 0 to about 25 mol% of a modifying glycol and to about 25 mol% of a modifying compound selected from the group comprising amino alcohols, diamines and lactams,% mol is based on 100% in mol of (l) and 100% in mol of (2); (B) about 0.1 to about 20% by weight based on the total weight of (A) and (B) of an ethylene copolymer containing repeating units of ethylene and of a monomer selected from the group consisting of acrylic acid, methacrylic acid , alkyl acrylate, alkyl methacrylate and vinyl alcohol. According to another embodiment of the invention, there is provided a process for preparing a foamed article of a branched polyester comprising the steps of: (a) preparing a polyester comprising (1) repeating units of about 75 to 100% mol of a dibasic acid having 6 to 40 carbon atoms and 0 to about 25 mol% of a modifying dibasic acid, and (2) repeating units of about 75 to 100 mol% of a glisol having 2 to 10 carbon atoms , 0 to about 25 mol% of a modifying glycol and to about 25 mol% of a modifying compound selected from the group comprising amino alcohols, diamines and lactams,% mol is based on 100 mol% of (1) and 100% in mol of (2); (b) preparing an ethylene copolymer comprising repeating units of ethylene and a comonomer selected from the group comprising acrylic acid, methacrylic acid, alkyl acrylate, alkyl methacrylate and vinyl alcohol; (c) drying the polyester and ethylene copolymer; (d) forming a melt comprising about 80 to about 99.9% by weight of the dry polyester and about 0.1 to about 20% by weight of the dry ethylene copolymer; (e) cooling and transforming the melt into solid particles; (f) polysondensate the particles in the solid state until a branched polyester having an I.V. of at least about 0.70 is obtained; (g) melting the branched polyester particles; (h) adding a blowing agent to the branched polyester melt; e (i) extruding the composition of step (h) through a matrix. Certain polymeric materials containing multiple hydroxyl, carboxylic acid or ester groups have now been found useful as branching agents for polyesters and polyesteramides to cause an increase in their melt viscosity and melt strength resulting in improved foamability. Suitable polymeric materials include copolymers of ethylene with monomers of either acrylic acid, methacrylic acid, alkyl acrylates, alkyl methacrylates or vinyl alcohol. The concentration of the ethylene copolymer branching agents is generally in the range of about 0.1 to about 2 weight percent (wt%) based on the total weight of the ethylene copolymer and the polyester composition. An ethylene copolymer content of less than 10% by weight is preferred. The content of the monomers of acrylic acid, methacrylic acid, alkyl acrylates and alkyl metasylates in the ethylene copolymers is generally in the range of about 0.5 to about 40% by weight and preferably less than 20% by weight. These ethylene copolymers have melt index values of about 0.1 to about 200 g / 10 min. (ASTM D-1238-56T). For ethylene copolymers containing alkyl acrylates or alkyl methacrylates, the alkyl groups will generally contain 1 to 4 carbon atoms. For the vinyl alcohol / ethylene copolymer, the content of the vinyl alcohol is in the range of about 1 to about 95% by weight. This copolymer is easily prepared by the hydrolysis of ethylene / vinyl acetate copolymers and it is desirable that the residual acetate portions be quite low (for example, less than about 1 or 2% by weight). The melt index of this copolymer will generally be in the range of about 0.1 to about 200 gm / 10 min. Ethylene copolymers are typically stabilized using small amounts of antioxidants. For example about 0.05 to about 0.1% by weight of Irganox (brand) 1010, Irganos 1075, Ethanox (brand) 330 and the like can be used. In addition, small amounts of other stabilizers such as dilauryl thiodipropionate and Weston 619 can be employed in combination with the stabilizers mentioned above. A wide range of polyester polymers are useful in this invention and include polyesters derived from dibasic acids containing 6 to 40 carbon atoms and glycols containing 2 to 10 carbon atoms. These polyesters in general will have inherent viscosity (I.v.) with values in the range of about 0.4 to about 0.70 (measured in a phenol / tetrachloroethane 60/40 solution) and are generally crystallizable. The polyesters can be in any form including homopolymers, copolymers, modified polymers, branched polymers and mixtures. Preferred dibasic acids for preparing the polyesters include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid and the like or their alkyl esters. When naphthalenedicarboxylic acid is used, it can be any of the various isomers, but preferred ones include 2,6-, 2,7-, 1,5- and 1,6-isomers. Mixtures of the various isomers can also be used. The preferred isomers of cyclohexanedisarboxylic acids are the 1,3- or 1,4-isomers, and may be cis-, trans- or a mixture of cis / trans isomers. Preferred glycols include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like. when cyclohexanedimethanol is used, it may be the 1,3- or 1,4-isomeric isomers or it may be cis-, trans- or a mixture of cis / trans isomers. Polyester copolymers, ie copolyesters, can contain up to about 25 mol% of other dibasic acids or glycols. Modifying dibasic acids (in addition to those named above) include oxalic, succinic, glutaric, adipic, sebacic, suberic, dimer, sulfoisophthalic, or its metal salts and the like. When any of the aforementioned acids are listed, it will be understood that the use of their corresponding acid anhydrides, esters and acid chlorides is included. Modifying glycols, (in addition to those previously named) include 1,6-hexanediol, n-glypentyl glycol, 2,2,4,4-tetramethyl-l, 3-slclobutandiol, and the like. Polyesteramides can also be employed in the practice of this invention. These polymers will contain the dibasic acid and glycol portions as recited above. In addition, the glycol portion will contain up to about 25 mol% of a modifying compound of an amine alcohol, a diamine, and / or a lactam. Some convenient compounds include 4-aminomethylcyclohexane-methanol, hexamethylenediamine, caprolactam and the like. The polyesters in their various forms, polyester amides and ethylene copolymers, are easily prepared by conventional polymerization techniques well known in the art. A combination of melt formulation and solid state polycondensation is used to accomplish the branching reactions of the ethylene copolymers with the polyesters forming polymeric branched polyesters which exhibit increased melt viscosity and melt strength relative to polyesters that have not been branched with polymeric materials. The effect of branching is to provide polyesters with significant improved foamability and blow molding characteristics. In the preferred embodiment of the process, the ethylene copolymer is dry blended with the polyester, dried in vacuum or convection ovens and then melt formulated in an extruder at temperatures in the range of about 260 ° C to about 300 °. C. Optionally, the ethylene and polyester copolymer can be dried separately and fed to the extruder. The extrudate is formed into solid and dry particles. Any forms of particles can be employed including nodes, granules, powders or chips or platelets. The particles are then processed in a solid-state poly-condensation unit while circulating or blowing an inert gas, such as nitrogen, through the nodules at temperatures in the range of about 200 * C to about 230 ° C. This polycondensation reaction in the solid state is continued until the inherent viscosity of the polymer mixture reaches a value of at least about 0.70 dl / g and preferably a value of about 0.90 dl / g. The combination of fusion formulation and polycondensation in the solid state is employed because the polymerization in the melting phase to high molecular weight polyesters is significantly limited by the substantial increase in melt viscosity of the branched polyesters. The melt eventually reaches a melt viscosity that is difficult to handle. In addition, in conventional extruders used to formulate extrusion in reaction time is limited due to the size of the extruder. In general, there is not enough time to allow sufficient branching reactions to occur. The resulting polymer is a ready-to-use branched polyester, which is in a convenient form for processing foamed final products. The branched polyester can be added directly to an extruder to fuse and mix with a blowing agent or first dry mix with other ingredients before blending to improve the performance properties of the final products. A variety of end uses are contemplated including the manufacture of films, tubes, blow molded objects, extrusion coated materials, food packaging containers and injection molded parts.

The branched polyester has a melt viscosity above 500 Pa.s (5000 poises) at 280 * C and a melt strength above -50%, which are typically values for certain unbranched polyesters such as poly (ethylene terephthalate) (PET) . Preferably, the melt viscosity is in the range of approximately 2,000 to 20,000 Pa.s (approximately 20,000 to 200,000 poises) at 280 ° C and the melting strength is in the range of approximately -25 to + 60%, these being excellent properties for foaming. Both melt viscosity and melt strength are measured at 280 ° C. A wide variety of methods for foaming branched polyester are available. These include injecting an inert gas such as nitrogen or carbon dioxide into the melt during extrusion or molding operations. Inert hydrocarbon gases such as methane, ethane, propane, butane and pentane or chlorofluorocarbons, hydroslorofluorocarbons and the like, may also be employed, another method involves the dry blending of organic blowing agents with the branched polyester and then extruding or molding the compositions to provide foamed articles. During the extrusion or molding operation, an inert gas such as nitrogen is released from the blowing agents and provides the foaming action. Typical blowing agents include azodicarbonamide, hydrazocarbonamide, dinitrosopentamethylentet mina, p-toluenesulfonyl hydrazodicarboxylate, 5-phenyl-3,6-dihydro-l, 3,4-oxadia2in-2-one, sodium borohydride, sodium bicarbonate, 5-phenyltetrazole , p, p'-oxybis (benzenesulfonylhydrazide) and the like »Yet another method involves the mixing of sodium carbonate or sodium bicarbonate with a portion of the branched polyester particles, the mixing of an organic acid such as citric acid with another portion of branched polyester particles and then a mixture of the two types of particles is extruded or molded at elevated temperatures. Carbon dioxide gas evolved from the interaction of sodium carbonate and citric acid provide the action of foaming in the melt. In particular, when ethylene copolymers of alkyl acrylates or alkyl methacrylates are used as the branching agent, the lower alkyl groups are released as volatile alcohols during foaming. This further improves the desired foaming action. Patents describing various foaming methods and equipment include US Patents. Nos. 5,116,881; 5,134,028; 4,626,183; 5,128,383? 4,746,478; 5,110,844; 5,000,991 and 4,761,256. Other background information regarding foaming technology can be found in Kirk-Othmer's Encyclopaedia of Chemical Technology, Third Edition, Volume 11, pages 82-145 (1980), John Wiley and Sons, Inc., New York, NY, and the Encyclopedia of Polymer Science and Engineering, Second Edition, Volume 2, pages 434-446 (1985), John Wiley and Sons, Inc., New York, NY. Many ingredients that can be added to the branched polyesters to improve their performance properties include buffers, antioxidants, metal deactivators, colorants, phosphorus stabilizers, impact modifiers, nucleating agents, ultraviolet and heat stabilizers, and the like. All these additives and their use is well known in the art and does not require extensive discussion. Therefore, only a limited number will be referred, it being understood that any of these compounds can be employed as long as they do not impede the performance of the branched polyesters. In many cases, nucleating agents such as talc, Ti03 or small amounts of polyolefin materials such as polyethylene, polypropylene, ethylene or propylene copolymers and the like, are beneficial additives for the foamable branched polyester compositions. Certain nucleating agents are important for creating bubble initiation sites and for influencing the cell size of the foamed sheet or foamed object. Other suitable additives include impact modifiers and antioxidants. Examples of typical commercially available impact modifiers well known in the art and useful in this invention, include ethylene / propylene terpolymers, styrene-based block polymers, and various core-type / acrylate-type impact modifiers. The impact modifiers can be used in conventional amounts from 0.1 to 25 weight percent of the total composition and preferably in amounts of 0.1 to 10 weight percent of the composition. Examples of typical commercially available antioxidants useful in this invention include, but are not limited to, hindered phenols, phosphites, diphosphites, polyphosphites, and mixtures thereof. Combinations of aromatic and aliphatic phosphite compounds may also be included. This invention will also be illustrated by a consideration of the following examples, which are intended as examples of the invention. All parts and percentages of the examples are a weight basis unless otherwise stated. The test materials and procedures employed for results illustrated herein in the examples are as follows: Inherent viscosity (IV) is measured at 25 * C using 0.50 gram of polymer per 100 ml of solvent consisting of 60 wt.% Phenol and 40 wt. % by weight of tetrasloroethane. Fusion Strength and Matrix Swelling are determined in accordance with ASTM D3835 measured at 280 ° C by extruding the molten polyester down through a 0.254 cm (0.1 inch) diameter and 0.625 cm (0.25 inch) long matrix. Shear rate of 20 seconds "1 using an Instron rheometer and allowing the extrudate to fall freely.Matrix inflation is determined by measuring the diameter of the extrudate immediately outside the hole and dividing by the diameter of the hole. as Matrix Swell in percent The end diameter of a length of 15.24 sm (six inches) of extrudate, measured from the orifice of the matrix, is measured.The percent Melt Strength is determined from the formula: P r, Q * 2S4 100 0.254 where D is the diameter, in centimeters of extrudate that supports an extruded length of 15.24 cm (six inches), if D is less than 0.254 cm (0.1 inch), the Strength of Fusi It is a negative number since there is no increase in the diameter of the extrudate. If D is greater than 0.254 cm (0.1 inch), the Fusion Resistance is a positive number. The melt viscosity is measured according to ASTM D4440 at zero shear and 280 ° C. The mole percentages of the diol and acid residues are determined by gas chromatography or NMR. Example i Dry poly (ethylene terephthalate) nodules (PET) (I.V. 0. 60), dry nodules of ethylene / vinyl alcohol copolymer (EVOH) (32% by weight of ethylene, 0.7 melt index) and talc, are thoroughly mixed in a stainless steel vessel to provide a mixture containing 5% by weight of EVOH and 0.5% by weight of talc. The nodule mixture is fed to an extruder and added in the melt at 275 β C. The melt is extruded through a rod matrix and the rod is cut into 0.3175 cm (1/8 inch) nodules. These dry nodules are then presented under polycondensation conditions in solid state in a glass column with a diameter of 3.175 cm (1.25 inches). The column is veneered to allow solvents to reflux thereby providing heat to the column. The temperature of the column ee maintained at 198 ° C using ethylene glycol at reflux. The bottom of the column has a surface of frosted glass to allow inert gases to pass upwards through the column. Nitrogen is passed through the column nodules at a rate of 1.22 ra (4 cubic feet) per hour to remove the ethylene glycol and other volatile components released, as the I.V. of the polymer. At 18 hours, the polymer sample has an I.V. from 0.81. The melting strength of this sample is -16.5%, matrix swelling is + 29.5%, and the melt viscosity is 5,800 Pa.s (58,000 poise) at 280 ° C. The starting poly (ethylene terephthalate) sample has a melt strength of -105%, a matrix swelling of -30% and a melt viscosity of 500 Pa.s (5.00 poise) at 280 ° C. A large batch of a branched polyester similar to the above is made in a solid state unit properly scaled.

Samples of the mixture now converted to a branched polyester are fed to a tandem extruder consisting of a 5.08 cm (2 inch) primary extruder which is capable of injecting a high pressure gas blowing agent into the polymer melt, an extruder secondary 6.35 cm (2.5 inches) that allows the melt to froth under reduced pressure and an annular die with a] 7.62 cm (3 inches) in diameter] located at the end of the second extruder through which the extrudate passes. The two extruders are connected through a well-known low-pressure crossing zone. The gaseous blowing agent used is isopentane. The extruders, the crossover zone and annular die are heated between 260"C and 274 ° C through their entire length as noted above: Primary Extruder 5.08 cm (2 inches) = 260 ° C Crossover Zone = 260 ° C Secondary extruder 6.35 cm (2.5 inches) = 260ßC Annular matrix of 7.62 cm (3 inches) - 274 ° C Other conditions and relevant extrusion parameters are as follows: Pressure ks / cm2 f if Extruder 5.08 sm (2 inches) 393.7 a 421.8 (5600-6000) Crossing area 262.9 to 271.36 (3740-3860) Extruder 6.35 cm (2.5 inches) 155.4 to 156.8 (2210-2230) Isopentane injection 228.5 to 393.7 (3250-5600) v occluses < ae Extrusion Extrusion 5.08 cm (2 inches) 87 rpm Extruder 6.35 cm (2.5 inches) 16.4 rpm Output polymer 29.937 kg (66 Ib.) / hour Isopentane injected 0.726 kg (1.6 Ib.) / hour Under these conditions, the composition of Branched PET described above is extruded with the desired characteristics required to produce good foam. The foam coming from the annular die has good dry hand feel and good melting strength so that it can be easily stretched on a water cooled mandrel. The foam is slotted and collected as a sheet with a width of 0.9144 meter (36 inches). The thickness and density of the foam respond well to changes in the linear velocity and the level of isopentane. The foam produced has a density of 0.21 g / cm3 at a thickness of 1.49 mm (59 mils), an I.V. of 0.80 and a crystallinity of 15.3% as measured by DSC. Scanning electron microscopy and confocal light microscopy showed the well-formed cell structure with all cells closed and 100-200 μm diameter in size. The foam exhibits the following good post-expansion properties: (a) A small piece of the foam produced above is immersed in boiling water for 2 minutes and then cooled to room temperature. Its thickness is measured using a FOWLER micrometer at several points on the surface of the foam and the average thickness is 2.31 mm (91 mils), which is an increase of 54% from the foam as it was produced. The density of this post-expanded foam is measured as 0.11 g / cm3. It has a crystallinity of 31.26% as measured by DSC. Scanning Electron Microscopy and Confocal Light microscopy show the cell structure that is well formed with all cells closed and of diameter 200-400 μm in size, (b) A small piece of the foam is also post-expanded in an oven with conventional air at 175 ° C for 3 minutes. This foam has an average thickness of 1.9 mm (75 mils) and a density of 0.16 g / cm3. It has a crystallinity of 31.53% as measured by DSC. The Electron Microscopy of Exploration and Confocal Light Microscopy show the cellular structure that is well formed with all the cells closed and of diameter 200-300 μm in size. similarly, good foaming results are achieved with the following modifications to the example described above: (a) PET / EVOH mixtures are used which contain 0.3, 1, 3 and 5% by weight of the EVOH copolymer. (b) Carbon dioxide or nitrogen gas are used instead of isopentane as the blowing agent. (c) The branched PET is sprinkled with 2% by weight of the azodicarbonamide chemical blowing agent before the extrusion process instead of using the isopentane blowing agent. (d) A combination of a chemical blowing agent and a gas blowing agent is used when sprinkling the branched PET with 0.5% by weight of the chemical blowing agent azodicarbonamide before the extrusion process and then using the isopentane blowing agent during the extrusion process. The extrusion process as described above. Similarly, good results are achieved using 5% by weight of an ethylene / acrylic acid copolymer containing 8% by weight of asyric acid (CAS No. 910-77-9) instead of the EVOH copolymer. Example 2 The procedure of Example 1 is repeated using a branched polyester of poly (ethylene terephthalate) containing 0.3 mol% trimellitic anhydride (IV 0.68), 1 wt% EVOH copolymer of Example 1 and 0.5 wt% Ti02 . The foam produced had good dry hand feeling and good cellular structure. Similarly, good results are achieved when the foamed branched poly (ethylene terephthalate) copolyester containing 0.2 mol% of triraelitic acid or pyromellitic dianhydride with the EVOH copolymer.

Use 3 The procedure of Example 1 is repeated using a poly (ethylene terephthalate) copolyester containing 3.5% mol of 1,4-cyclohexanedimethanol (IV 069), 5% by weight of an EVOH copolymer (95% by weight of ethylene, melt index 4.2), 1.0% by weight of sodium carbonate and 0.5% by weight of talc. The foam produced had good dry hand feel and good uniform cell structure. Example 4 The procedure of Example 1 is repeated using poly (1,4-cyclohexylenedimethylene terephthalate) (I, V, 0.68), 3% by weight of an ethylene / methyl acrylate copolymer (20% by weight of methyl acrylate; 6.0 melt) and 1% by weight of talc. The foam produced had good dry feel at hand and a good uniform cellular structure. Similarly, good results are achieved when 0.5% by weight of the ethylene / methyl acrylate copolymer is used. Example 5 The procedure of Example 1 is repeated using a copolyester of poly (ethylene terephthalate) containing 9% mol of 1,4-cyclohexanedimethanol (IV 0.55), 2% by weight of an ethylene / methyl methacrylate copolymer (15%) by weight of methyl methacrylate, melt index 10.1) and 0.5% by weight of TiOa. The foam produced has a uniform, good cell structure and imparts a dry feeling to the hand. Similarly, good results are obtained using copolyesters of poly (ethylene terephthalate) containing 17% mol of diethylene glycol (I.V. 0.65). EXAMPLE 6 The procedure of Example 1 is repeated using a poly (1, 4-cyclohexylenedimethylene terephthalate) polyester polyol, containing 15% by mol of ethylene glycol (IV 0.68), 1% by weight of an ethylene / acrylic acid copolymer (88). % by weight of ethylene, melt index 7.2), 0.5% by weight of sodium carbonate and 0.5% by weight of Ti02. The foam produced has a good uniform cellular structure and dry feeling at hand. Similarly, good results are achieved when copolymers of poly (1,4-cyclohexylenedimethylene terephthalate) contain 5 mol% isophthalic acid (IV 0.69), 17 mol% isophthalic acid (IV 0.67) or 10 mol% acid 2 , 6-naphthalenedicarboxylic (Iv 0.65) are used, as well as when copolyesteramide of poly (ethylene terephthalate) containing 5% by mol of 4-aminomethylcyclohexane methanol is used. The procedure of Example 1 is repeated using a poly (ethylene 2,6-naphthalene icarboxylate) (IV 0.68), 5% by weight of an EVOH copolymer (90% by weight of ethylene, melt index 1.3) and 2% by weight of talc. The foam produced has good uniform cellular structure and dry feeling at hand. Similarly, good foaming results are achieved when the branched polyester is dusted with 2% by weight azodicarbonamide chemical blowing agent prior to the extrusion process instead of using the isopentane blowing agent. The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications may be made within the spirit and scope of the invention.

Claims (37)

1. CLAIMS 1. Foamed article of a branched polyester having an I.V. of at least 0.7 dl / g and a sufficiently high melt viscosity to allow foaming during extrusion or molding operations, the branched polyester comprises: (A) from about 80 to about 99.9% by weight based on the total weight of (A) and (B) of a polyester comprising: (1) repeating units of about 75 to 100% mol of a dibasic acid having from 6 to 40 carbon atoms and about 25% mol of a modifying dibasic acid, and (2) ) repeating units of about 75 to 100% mol of a glycol having from 2 to 10 carbon atoms, or from about 0 to about 25 mol% of a modifying glycol and about 25 mol% of a modifying compound selected from the group comprising amino alcohols, diamines and lactams,% mol is based on 100% mol of (1) and 100% mol of (2), and (B) about 20% by weight based on the total weight of (A) and (B) of an ethylene copolymer containing a Repetitive amounts of ethylene and of a monomer selected from the group comprising acrylic acid, methacrylic acid, alkyl asrilate, alkyl methacrylate and vinyl alcohol.
2. 2. The foamed article according to claim 1, wherein the dibasic acid of the polyester is selected from the group comprising terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid and alkyl esters and mixtures thereof.
3. 3. The foamed article according to claim 2, wherein the naphthalenedicarboxylic acid is selected from the group of isomers comprising 2,6-, 2,7-, 1,5- and 1,6-naphthalene dicarboxylic acid and mixtures thereof.
4. 4. The foamed article according to claim 2, wherein the cyclohexanedicarboxylic acid is selected from the group of isomers comprising 1,3-, 1,4-, cis- and trans-cyclohexanedicarboxylic acids and mixtures thereof.
5. 5. The foamed article according to claim 1, wherein the polyester glycol is selected from the group comprising ethylene glycol, 1,4-butanediol and 1,4-cyclohexanedimethanol.
6. 6. The foamed article according to claim 1, wherein the polyester-modifying dibasic acid is selected from the group comprising terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, oxalic acid, succinic acid, glutaric acid, adipic acid, sebasic acid, suberic acid, dimer acid, sulfoisophthalic acid and mixtures thereof.
7. The foamed hinge according to claim 1, wherein the polyester modifying glycol is selected from the group comprising ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, neopentyl glycol, 2 , 2,4,4, -tetramethyl-l, 3-cislobutanediol and their mixtures.
8. 8. The foamed article according to claim 1, wherein the polyester modifying compound is selected from the group comprising 4-aminomethylcyclohexanmethanol, hexamethylenediamine and caprolactam.
9. 9. The foamed article according to claim 1, wherein the branched polyester contains less than 10% by weight of ethylene copolymer.
10. 10, The foamed article according to claim 1, wherein the ethylene copolymer contains from about 0.5 to about 40% by weight of the comonomer selected from the group comprising acrylic acid, methacrylic acid, alkyl acrylate and alkyl methacrylate,
11. 11. The foamed joint according to claim 10, wherein the ethylene copolymer contains less than 20% by weight of the comonomer.
12. 12. The foamed article according to claim 1, wherein the ethylene copolymer contains about 1 to about 95% by weight of vinyl alcohol.
13. The foamed article according to claim 12, wherein the ethylene copolymer has a residual acetate portion of less than about 1 to about 2% before preparation by hydrolysis of ethylene / vinyl acetate copolymers.
14. 14. The foamed article according to claim 1, wherein the alkyl acrylates and alkyl methacrylates contain alkyl groups having 1 to 4 carbon atoms.
15. 15. The foamed article according to claim 1, wherein the ethylene copolymers are stabilized by the addition of an antioxidant.
16. 16. The foamed hinge according to claim 1, wherein the polyester further comprises monomeric branching agents.
17. 17. A branching agent for increasing the melt viscosity and melting strength of a polyester composition for improving foamability, comprising repeating units of ethylene and a comonomer selected from the group comprising acrylic acid, methacrylic acid, alkyl acrylate, alkyl methacrylate and vinyl alcohol.
18. 18. The branching agent as described in claim 17, characterized in that the weight percent of the somonomer selected from the group comprising acrylic acid, methacrylic acid, alkyl acrylate and alkyl methacrylate is from about 0.5 to about 40.
19. 19. The branching agent as described in claim 18, characterized in that the weight percent of the comonomer is less than
20. 20. The branching agent as described in claim 17, characterized in that the percent of the vinyl alcohol is about 1 to about 95.
21. 21. The branching agent as described in claim 17, characterized in that the branching agent is added to the polyester composition in an amount from about 0.1 to about 20% by weight, based on the percent by total weight of the branching agent and the polyester.
22. 22. A process for preparing a foamed article of a branched polyester comprising the steps of: (a) preparing a polyester, comprising (1) repeating units of about 75 to 100 mol% of a dibasic acid having 6 to 40 carbon atoms and 0 to about 25 mol% of a modifying dibasic acid, and (2) repeating units of about 75 to 100 mol% of a glycol having from 2 to 10 carbon atoms, or about 25 mol% of a glycol modifier and 0 to about 25% by mol of a modifier compound selected from the group comprising amino alcohols, diamines and lactams,% mol based on 100% mol of (1) and 100% mol of ( 2); (b) preparing an ethylene copolymer comprising repeating units of ethylene and of a comonomer selected from the group comprising acrylic acid, methacrylic acid, alkyl acrylate, alkyl methacrylate, and vinyl alcohol; (c) drying the polyester and ethylene copolymer; (d) forming a melt comprising about 80 to about 99.9% by weight of the dry polyester and about 0.1 to about 20% by weight of the dry ethylene copolymer; (e) cooling and transforming the melt into solid particles; (f) polycondensing the particles in the solid state until a branched polyester containing an I.V. of at least about 0.70 is obtained; (g) melting the branched polyester particles; (h) adding a blowing agent to the branched polyester melt; e (i) extruding the composition of step (h) through a matrix.
23. Method according to claim 22, characterized in that in step (a) the polyester is prepared with dibasic acid selected from the group comprising terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid and alkyl esters and mixtures thereof.
24. Method according to claim 23, characterized in that in step (a) the polyester is prepared with the naphthalene dicarboxylic acid selected from the group of isomers comprising 2,6-, 2,7-, 1,5-, acid and 1,6-naphthalene-dicarboxylic acid and mixtures thereof.
25. 25. Method according to claim 23, characterized in that in step (a) the polyester is prepared with cyclohexanedicarboxylic acid selected from the group of isomers comprising 1,3-, 1,4-, cis- and trans- cyclohexanedicarboxylic acid and its mixtures.
26. 26. Process according to claim 22, characterized in that in step (a) the polyester is prepared with the glycol selected from the group comprising ethylene glycol, 1,4-butanediol and 1,4-cyclohexanedimethanol.
27. Method according to claim 22, characterized in that in step (a) the polyester is prepared with the dibasic acid modifier selected from the group comprising terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, oxalic acid, succinic acid, glutaric acid, adipic acid, sebasic acid, suberic acid, dimer acid, sulfoisophthalic acid and mixtures thereof,
28. 28. Method of conformity with claim 22, characterized in that in step (a) the polyester is prepared with the glycol modifier selected from the group comprising ethylene glycol, 1,4-butanediol, 1,4-cislohexanedimethanol, 1,6-hexanediol, neopentyl glycol, 2,4,4,4-tetramethyl-l, 3-cyclobutanediol and mixtures thereof.
29. 29. Process according to claim 22, characterized in that in step (a) the polyester is prepared with the modifier compound selected from the group comprising 4-aminomethylcyclohexamethoxy, hexamethylenediamine and caprolactam.
30. 30. Process according to claim 22, characterized in that in step (a) the ethylene copolymer is prepared, containing from about 0.5 to about 40% by weight of the comonomer selected from the group comprising acrylic acid, methacrylic acid, alkyl acrylate and alkyl methacrylate.
31. 31. Method according to claim 30, characterized in that in step (b) the ethylene copolymer is prepared containing less than 20% by weight of comonomer.
32. 32. Conformity procedure with claim 22, characterized in that in step (b) the ethylene copolymer is prepared containing from about 1 to about 95% by weight vinyl alcohol.
33. 33. Method according to claim 22, characterized in that in step (b) the ethylene copolymer is prepared with the alkyl acrylates and alkyl ratethacrylates containing alkyl groups having 1 to 4 carbon atoms.
34. 34. Method according to claim 22, characterized in that in step (d) the melt comprising less than 10% by weight of the ethylene copolymer is formed.
35. 35. Method according to claim 22, characterized in that in step (f) the polycondensation in the solid state continues until the branched polyester has an I.V. of at least 0.90.
36. 36. Process according to claim 22, characterized in that in step (g) the branched polyester is melted, having a melt viscosity of about 500 Pa.s (5,000 poise) and an envelope melting strength (-50) per cent, both measured at 280 ° C.
37. 37. Method according to claim 36, characterized in that in step (g) the branched polyester is melted having a melt viscosity of from about 2,000 to about 20,000 Pa.s (about 20,000 to about 200,000 poise) at 280PC and a melting strength of approximately (-25) to approximately (+60) percent, both measured at 280 ° C.