MXPA00010287A - Sheets formed from polyesters including isosorbide - Google Patents

Abstract

A sheet made of a polyester which includes monomer units of terephthaloyl moieties, ethylene glycol moieties and isosorbide moieties is described. The polyester has an inherent viscosity of at least about 0.35 dL/g when measured as a 1%(weight/volume) solution of said polyester in o-chlorophenol at a temperature of 25°C. The present invention also relates to a method of making the polyester sheet described above and a method of thermoforming the sheet into articles.

Description

LAMINATES CONFORMED WITH POLYESTERS INCLUDING ISOSORBIDE FIELD OF THE INVENTION The invention relates to a sheet formed of a polyester, methods for making the polyester and articles made of the sheet. More specifically, this description relates to sheets made of a polyester having a portion of isosorbide, a portion of terephthaloyl and a portion of ethylene glycol, methods for making the same and articles made therefrom.

BACKGROUND OF THE INVENTION Polymeric sheets have various uses, such as in signage, glass placement, thermoforming articles, advertisements and substrates for advertisements, for example. For many of these uses, the heat resistance of the sheet is an important factor. Therefore, a higher melting point and glass transition temperature (Tg) are desirable in order to provide better heat resistance and greater stability. In addition, it is desired that the sheets have resistance to ultraviolet radiation (UV) and scraping, good tensile strength, optical clarity Ref: 123442 high and good impact resistance, particularly at low temperatures. Various polymeric compositions have been used in an attempt to satisfy all of the foregoing criteria. In particular, polyethylene terephthalate (PET) has been used to form sheets at low cost, for many years. However, these PET sheets have a low temperature impact resistance, a low vitreous transition temperature (Tg) and a high crystallization rate. Therefore, the PET sheets can not be used at low temperatures due to the danger of rupture and can not be used at high temperatures because the polymer crystallizes, which reduces optical clarity. Polycarbonate sheets can be used in applications where a low temperature impact resistance is required, or a high service temperature is required. In this regard, the polycarbonate sheets have high impact forces at low temperatures, as well as a high Tg which allows them to be used in high temperature applications. However, polycarbonate has a poor solvent resistance, so its use is limited in certain applications, and it is susceptible to stresses that induce fracture. Polycarbonate sheets are also provided with greater impact resistance than is needed for certain applications, making them expensive and inefficient for use. Therefore, there is a need for a sheet material that offers: (1) high impact strength at low temperature, (2) higher service temperature, (3) good solvent resistance, and (4) a high speed low crystallization. The diol 1,4: 3,6-dianhydro-D-sorbitol, hereinafter referred to as isosorbide, the structure of which is illustrated below, is easily manufactured from renewable resources, such as sugars and starches. For example, isosorbide can be made from D-glucose by hydrogenation followed by acid-catalyzed dehydration.

Isosorbide has been incorporated as a monomer in polyesters that also include terephthaloyl moieties. See, for example, R. Storbeck et al, Makromol. Chem .. Vol. 194, pp. 53-64 (1993); R. Storbeck et al, Polymer, Vol. 34, p. 5003 (1993). However, it is generally considered that secondary alcohols such as isosorbide have little reactivity and are sensitive to acid catalyzed reactions. See, for example D. Braun et al., J. Prakt. Chem .. Vol. 334, pp. 298-310 (1992). As a result of the poor reactivity, polyesters made with an isosorbide monomer and the terephthalic acid esters are expected to have a relatively low molecular weight. Ballauff et al, Polyesters (Derived from Renewable Sources), Polymeric Materials Encyclopedia, Vol. 8, p. 5892 (1996). Copolymers containing portions of isosorbide, portions of ethylene glycol and portions of terephthaloyl have been reported only rarely. A copolymer containing these three portions, in which the ratio and moles of ethylene glycol to isosorbide is about 90:10, are reported in published German patent application No. 1,263,981 (1968). The polymer is used as a minor component (approximately 10%) of a combination with polypropylene to improve the dyeability of the polypropylene fiber. It is made by melt polymerization of dimethyl terephthalate, ethylene glycol and isosorbide, but the conditions which are described are only mentioned in general terms in the publication, and a polymer having a high molecular weight is not provided.

Copolymers of these same three monomers are newly described again, where it has been observed that the vitreous transition temperature (Tg) of the copolymer is increased with an isosorbide monomer content of up to about 200 ° C for the terephthalate homopolymer of isosorbide. The polymer samples are made by reacting terephthaloyl dichloride in solution with the diol monomers. This method provides a copolymer with a molecular weight that is apparently higher than that obtained in the German patent application described above but still relatively low in comparison to other polyester polymers and copolymers. In addition, these polymers are manufactured by solution polymerization and are therefore free of diethylene glycol portions as a polymerization product. See R. Storbeck, Dissertation, Universitát Karlsruhe (1994); R. Storbeck, et al., J. Ap l. Polvmer Science. Vol. 59, pp. 1199-1202 (1996). U.S. Patent 4,418,174 describes a process for the preparation of polyesters useful as raw materials in the production of aqueous baked lacquers. The polyesters are prepared with an alcohol and an acid. One of the many preferred alcohols is dianhydrosorbitol. However, the average molecular weight of the polyesters is from 1,000 to 10,000, and a polyester containing a portion of dianhydrosorbitol is not actually produced.

U.S. Patent 5,179,143 describes a process for the preparation of compression molded materials. In addition, polyesters containing hydroxyl are disclosed therein. These hydroxyl-containing polyesters are listed to include polyhydric alcohols including 1,4: 3,6-dianhydrosorbitol. However, again, the highest molecular weights reported are relatively low, that is, from 400 to 10,000 and in fact a polyester containing the 1, 4: 3, 6-dianhydrosorbitol portion is not made. Published PCT applications WO 97/14739 and WO 96/25449 disclose cholesteric and nematic liquid crystalline polyesters including portions of isosorbide as monomer units. Such polyesters have relatively low molecular weights and are not isotropic.

BRIEF DESCRIPTION OF THE INVENTION Contrary to the teachings and hopes that have been published in the prior art, isotropic, ie semicrystalline and amorphous or non-liquid crystalline copolyesters containing terephthaloyl moieties, ethylene glycol moieties, isosorbide moieties and, optionally, portions of diethylene glycol , they are easily synthesized in molecular weights that are suitable for manufacturing manufactured products such as sheets, on an industrial scale.

The process conditions for producing a polyester sheet, particularly the amounts of monomers used in the polyester, are desirably chosen so that the final polymer product used for sheet making has the desired amounts of the various monomer units, preferably with equimolar amounts of monomer units derived from a diol and a diacid. Due to the volatility of some of the monomers, including isosorbide, and depending on the method of making the polyester, some of the monomers are desirably included in excess at the start of the polymerization reaction and are removed as the reaction proceeds. This is particularly true for ethylene glycol and isosorbide. The polyester can be formed by any method known in the art. However, preferably, the polyester is formed by solvent or melt polymerization. The choice of method can be determined by the desired amount of diethylene glycol in the final product. In a preferred embodiment, the number of terephthaloyl moieties in the polymer is in the range of about 25% to about 50 mole% (moles% of the total polymer). The polymer may also include amounts of one or more aromatic diacid portions such as, for example, those derived from isophthalic acid, 2,5-furanodicarboxylic acid, 2,5-thiophenedicarboxylic acid, 2,6-naphthalene dicarboxylic acid, , 7-naphthalenecarboxylic acid and 4,4'-benzoic acid at combined concentrations of up to about 25 mol% (moles% of the total polymer). In a preferred embodiment, units of ethylene glycol monomers are present in amounts of about 5 mol% to about 49.75 mol%. The polymer may also contain portions of diethylene glycol. Based on the manufacturing method, the amount of diethylene glycol portions is in the range of about 0.0 mole% to about 25 mole%. In a preferred embodiment, the isosorbide is present in the polymer in amounts in the range of about 0.25 mol% to about 40 mol%. One or more different diol monomer units may also be included, in amounts up to a total of about 45 mole%. The polyester has an inherent viscosity, which is an indicator of molecular weight, of at least about 0.35 dl / g, measured in a 1% (w / v) solution of the polymer in o-chlorophenol at a temperature of 25 ° C. . A higher inherent viscosity, such as for example about 0.40 dl / g, preferably at least about 0.50 dl / g, is desired for optimum formation of a sheet. Further processing of the polyester can generate inherent viscosities of up to about 1.0 dl / g. The polyester sheets of the present invention are manufactured by any method known in the art and are suitable for use in various applications, such as glass placement, signage, advertisements, and advertising substrates. The sheets demonstrate good impact resistance at low temperature, high Tg resulting in increased maximum service temperature and decreased crystallinity, thus providing greater optical transparency. In addition, the present invention relates to a method for making a polyester article by thermoforming the polyester sheet described above.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES INVENTION The isotropic polyester sheets and the method for their preparation are described in detail in the following. In particular, a method for making the polyester comprising portions of terephthaloyl, portions of ethylene glycol and portions of isosorbide is the process described, as well as the processes for forming sheets from such a polymer.

In a preferred embodiment, the ethylene glycol monomer units are present in the polymer in amounts of about 33 mole% to about 49.9 mole%, preferably 37 mole% up to about 45 mole%, although larger amounts can be included as necessary for get the desired results The polymer composition may also contain diethylene glycol monomer units. Depending on the manufacturing method, the amount of diethylene glycol monomer units is in the range of from about 0.0 mole% to about 5.0 mole%, preferably from 0.25 mole% to about 5.0 mole%, although higher amounts can be included as needed to obtain the desired results. Diethylene glycol can be made as a byproduct of the polymerization process, or it can be added directly to the composition to help accurately regulate the amount of diethylene glycol monomer units that are in the polymer. In the preferred embodiments, portions of isosorbide are present in the polymer in amounts in the range of about 0.25 mole% to about 30 mole%, preferably from about 0.25 mole% to about 2.0 mole%, most preferably about 1.0. moles% to about 6.0 moles% although larger amounts may be included as necessary to obtain the desired results. One or more monomer units of another diol may optionally be included in amounts up to a total of about 2.0 mole%, preferably less than 1.0 mole%. The amount of other diols included, however, may be greater than necessary to obtain the desired results. Examples of the optional units or other diol units include aliphatic alkylene glycols having 3-12 carbon atoms and having the empirical formula HO-CnH2n-OH, where n is an integer of 3-12, including branched diols such as 2,2-dimethyl-1,3-propanediol; cis or trans-1,4-cyclohexanedimethanol and mixtures of cis and trans isomers; triethylene glycol; 2, 2-bis [4- (2-hydroxyethoxy) phenyl] -panole; 1,1-bis [4 - (2-hydroxyethoxy) phenyl] cydohexane; 9, 9-bis [4- (2-hydroxyethoxy) phenyl] fluorene; 1, 4: 3, 6-dianhydromanitol; 1.4: 3,6-dianhydroidi ol; and 1, 4 -anhydroerythritol. The terephthaloyl moieties in the polyester can vary from 25-50 mole%, preferably from about 40-50 mole% although larger amounts may be included as necessary to obtain the desired results. If desired, other aromatic diacid portions in the polymer can include, for example, those derived from isophthalic acid, 2,5-furanedicarboxylic acid, 2,5-thiophenedicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 2-acid, 7-naphthalenedicarboxylic acid and 4'-benzoic acid, at combined levels of up to about 10 mole%, preferably between 0.01 and 5 mole% of the total polymer, although larger amounts can be included as necessary to obtain the desired results . It is preferable that equimolar amounts of the diacid monomer units and the diol monomer units are present in the polymer in order to obtain a high molecular weight and a high inherent viscosity, which provides a lower shrinkage rate and a lower temperature. Greater vitreous transition (Tg) than, for example, poly (ethylene terephthalate). The polyester formed has an inherent viscosity, which is an indicator of molecular weight, of at least about 35 dl / g, measured in a 1% (w / v) solution of the polymer in o-chlorophenol at a temperature of 25 ° C. Preferably, the inherent viscosity is at least about 0.40 dl / g and preferably at least about 0.5 dl / g and about 1.0 dl / g, more preferably between about 0.7 and about 1.0 dl / g. However, the inherent viscosity can be as high as 2.0 dl / g or even higher, as needed. The molecular weight is not usually measured directly. Instead, the inherent viscosity of the polymer in solution or the molten viscosity is used as an indicator of molecular weight. For the present polymers, the inherent viscosity is measured by the method previously described, with a molecular weight corresponding to an inherent viscosity of about 0.35 dl / g or greater. Higher molecular weights corresponding to inherent viscosity of at least about 0.45 dl / g are preferred, and molecular weights corresponding to inherent viscosities as high as about 1.0 dl / g at 2.0 dl / g or even higher, can be obtained if desired. Generally, the ratio of inherent viscosity / molecular weight can be adjusted to the linear equation: log (IV) = 0.586 x log (Mw) -2.9672 Inherent viscosities are a better indicator of molecular weight for sample comparisons and are used as the molecular weight indicator here. The polyester sheets of the present invention may be amorphous or partially crystalline, depending on the desired properties of the sheet. The compositions have isosorbide in concentrations of less than about 10% and are semicrystalline if they cool slowly after forming or if they anneal above their vitreous transition temperatures, but are amorphous and if they cool rapidly after their formation. In general, semicrystalline compositions are slower to crystallize compared to poly (ethylene terephthalate) compositions due to the inclusion of isosorbide. Isosorbide increases Tg, which allows items to remain transparent even when exposed to conditions under which they can normally crystallize. In addition, the presence of isosorbide reduces the size of any crystal actually formed, thus allowing optical transparency to be maintained even at higher degrees of crystallization. The polyesters used to make the sheets of the invention can be manufactured in any of several methods. The product compositions vary to some extent depending on the method used, particularly on the amount of diethylene glycol residues that is present in the polymer. These methods include the reaction of the diol monomers with the acid chlorides of terephthalic acid and any other acid that may be present. The reaction of terephthaloyl dichloride with isosorbide and ethylene glycol is easily carried out by combining the monomers in a solvent (for example toluene) in the presence of a base, such as pyridine, which neutralizes the HCl as it is produced. This procedure is described in R. Storbeck et al., J. Appl. Polymer Science, Vol. 59, pp. 1199-1202 (1996). Other well known variations can also be used using terephthaloyl dichloride (for example interfacial polymerization) or simply by stirring the monomers together while heating. When the polymer is made using acid chlorides, the ratio of monomer units in the polymer of the product is approximately the same as the ratio of monomers that react. Therefore, the ratio of monomers charged to the reactor is approximately the same as the desired ratio in the product. A stoichiometric equivalent of the diols and diacids will generally be used to obtain a high molecular weight polymer, for example one with an inherent viscosity of at least about 0.35 dl / g, suitable for making sheets. The polymers can also be manufactured by a melt polymerization process, in which the acid component is terephthalic acid or dimethyl terephthalate, and which can also include the free acid or the dimethyl ester of any other aromatic diacid that may be desired in the composition of the polyester polymer. The diacids or dimethyl esters are heated with the diols (ethylene glycol, isosorbide, optional diols) in the presence of a catalyst at a high enough temperature so that the monomers combine to form esters and diesters, then oligomers and finally polymers. The polymer product at the end of the polymerization process is a molten polymer. The diol monomers (for example ethylene glycol and isosorbide) are volatile and are distilled from the reactor as the polymerization proceeds. Therefore, an excess of these diols is desirably loaded into the reaction to obtain a polymer, and the amounts must be adjusted according to the characteristics of the polymerization vessel, such as the efficiency of the distillation column and the efficiency of the recovery of monomers and recycling. Such modifications in the amounts of monomers and the like according to the characteristics of a reactor can be easily carried out by persons skilled in the art. further, a person skilled in the art can easily determine the amount of each component desirably charged to any particular reactor to form the polymer of the invention. The melt polymerization process described above is the preferred method for making the polymer and is described in detail in commonly assigned, co-pending US application No. 09/064, 844 (Attorney's File Number 032358-001), incorporated herein by reference. The melt polymerization process uses dimethyl terephthalate and terephthalic acid, also summarized in the following.

Process of dimethyl terephthalate In this process, which is carried out in two stages, terephthalic acid and the optional diacid monomers, if present, are used as their dimethyl ester derivatives. The diols (for example ethylene glycol and isosorbide) are mixed with the dimethyl ester of the aromatic diacid (for example dimethyl terephthalate) in the presence of an ester exchange catalyst, which causes an exchange of ethylene glycol of the methyl group of the esters of dimethyl through a transesterification reaction. This results in the formation of methanol, which is removed by distillation from the reaction flask, and hydroxyethyl terephthalate) due to the stoichiometry of the reaction, a little more than two moles of ethylene glycol are desirably added as reagents for the reaction of ester exchange. Catalysts that carry out ester exchange include salts (usually acetates) of the following metals: Li, Ca, Mg, Mn, Zn, Pb and combinations thereof, Ti (0R) 4, wherein R is a group alguilo that has 2-12 carbon atoms, and PbO. The catalyst components are generally included in an amount of about 10 ppm to about 100 ppm. Preferred catalysts for ester exchange include Mn (0Ac) 2, Co (0Ac) 2, and Zn (0AC) 3, where OAc is the abbreviation for acetate and combinations thereof. The polycondensation catalyst which is necessary for the second stage of the reaction, preferably Sb (III) oxide, can now be added or at the beginning of the polycondensation step. A catalyst that has been used particularly successfully for ester exchange is based on salts of Mn (II) and Co (II) at levels of about 50 to about 100 ppm each. These are used in the form of Mn (II) acetate tetrahydrate and Co (II) acetate tetrahydrate, although other salts of the same metals can also be used. The ester exchange is carried out approximately by heating and stirring the reagent mixture under an inert atmosphere (eg nitrogen) at atmospheric pressure from room temperature to a temperature high enough to introduce ester exchange (approximately 150 °). C). The methanol is formed as a by-product and is distilled off from the reactor. The reaction is gradually heated to about 250 ° C until the methanol production is stopped. The completion of methanol production can be recognized by a decrease in the upper temperature of the reaction vessel. A small amount of an additive having a boiling point of 170-240 ° C can be added to the ester exchange to aid in heat transfer within the reaction medium and to help retain volatile components in the container that can Sublimate in the fill column. The additive must be inert and must not react with alcohols or dimethyl terephthalate at temperatures below 300 ° C. Preferably, the additive has a boiling point greater than 170 ° C, more preferably within the range of 170 ° C to 240 ° C, and is used in an amount between about 0.05 and 10% by weight, more preferably between about 0.25 and 1% by weight of the reaction mixture. A preferred additive is tetrahydronaphthalene. Other examples include diphenylether, diphenylsulphan and benzophenone. Other such solvents are described in U.S. Patent 4,248,956, the content of which is incorporated herein by reference. The second stage of the reaction is initiated by adding a polycondensation catalyst (if not present in advance) and a sequestering agent for the transesterification catalyst. Polyphosphoric acid is an example of a sequestering agent and is preferred. It is usually added in an amount of about 10 to about 100 ppm phosphorus per g of dimethyl terephthalate. Examples of preferred polycondensation catalysts are antimony (III) oxide, which can be used at levels of about 100 to about 400 ppm.

The polycondensation reaction is typically carried out at a temperature from about 250 ° C to 285 ° C. During this time, ethylene glycol is distilled off from the reaction due to the condensation of bis (2-hydroxyethyl) terephthalate to form a polymer and a by-product of ethylene glycol, which is collected as a distillate. The polycondensation reaction described above is preferably carried out under vacuum, which can be applied while the reactor is heated to the polycondensation reaction temperature after the polyphosphoric acid and the Sb (III) oxide have been added. Alternatively, vacuum may be applied after the polycondensation reaction temperature reaches 280 ° C-285 ° C. In any case, the reaction is accelerated by the application of vacuum. Heating under vacuum continues until the molten polymer reaches the desired molecular weight, usually recognized by an increase in melt viscosity to a predetermined level. This is observed as an increase in the torque required for the agitation motor to maintain agitation at constant rpm. An inherent viscosity of at least 0.5 dl / g and generally up to about 0.65 dl / g or greater, can be obtained by this melt polymerization process without additional efforts being made to increase the molecular weight. For a certain composition, the molecular weight ranges can be further increased by solid state polymerization, described below.

Process of terephthalic acid The process of terephthalic acid is similar to the process of dimethyl terephthalate, except that the initial esterification reaction leading to bis (2-hydroxyethyl) terephthalate and to the other low molecular weight esters is carried out at a slightly elevated pressure ( autogenous pressure of approximately 172 to 345 kPa (25 to 50 psig)). Instead of a two-fold excess of the diols, a smaller excess (from about 10% to about 60%) of the diols is used (ethylene glycol, isosorbide and other diols, if any). The intermediate esterification product is a mixture of oligomers, since sufficient diol is not present to generate a diester of terephthalic acid. The catalysts are also different. It is not necessary to add catalysts in the esterification reaction. A polycondensation catalyst is still necessary (for example salts of Sb (III), or Ti (IV)) to obtain a high molecular weight polymer. The catalyst that is needed to obtain a high molecular weight can be added after the esterification reaction, or it can be conveniently loaded with the reagents at the start of the reaction. Catalysts that are useful for making a high molecular weight polymer directly from terephthalic acid and the diols include acetate or other salts of Co (II) alkanoate and Sb (III), Sb (III) oxides and Ge (IV), and Ti (OR) 4 (wherein R is an alkyl group having 2 to 12 carbon atoms) as well as metal oxides solubilized in glycol. The use of these and other catalysts in the preparation of the polyesters is well known in the art. The reaction can be carried out in discrete stages, but this is not necessary. In large-scale practice, it can be carried out in stages as the reactants and intermediates are pumped from the reactor to the reactor at increasing temperatures. In a batch process, the reactants and catalyst can be charged to the reactor at room temperature and then gradually heated to about 285 ° C as the polymer is processed. The pressure is vented in the range of about 200 ° C to about 250 ° C, and then vacuum is desirably applied. The esterification to form the esters of hydroxyethyl terephthalate and the oligomers is carried out at elevated temperatures (between room temperature and about 220 ° C to 265 ° C under autogenous pressure), and the polymer is processed at temperatures in the range of approximately 275 ° C to approximately 285 ° C under high vacuum (less than 10 Torr, preferably less than 1 Torr). The vacuum is necessary to remove residual ethylene glycol and water vapor from the reaction to increase molecular weight. A polymer having an inherent viscosity of at least 0.5 dl / g and generally up to about 0.65 dl / g can be obtained by a direct polymerization process, without subsequent polymerization in the solid state. The development of the polymerization can be followed by melt viscosity, which is easily observed by the torque required to maintain the stirring of the molten polymer.

Solid state polymerization The polymers can be made by melt condensation processes described above having an inherent viscosity of at least about 0.5 dl / g, and often as high as about 0.65 dl / g or greater, without further treatment. The compositions of ethylene glycol, isosorbide and terephthalic acid having isosorbide in an amount of about 0.25% to about 10% on a mole basis can have their molecular weight further increased by solid state polymerization. The product made by melt polymerization, after extrusion, cooling and granulation, is essentially non-crystalline. The material can be made of semicrystalline material by heating at a temperature in the range of about 115 ° C to about 140 ° C for an extended period of time (about 2 to about 12 hours). This induces crystallization so that the product can be heated to a much higher temperature to increase the molecular weight. The process works best for low levels of isosorbide, from (approximately 0.25 mol% to approximately 3 mol%), because the polyester crystallizes more easily with low levels of isosorbide. The polymer can also be crystallized prior to polymerization in the solid state by treatment with a relatively poor solvent for polyesters, such as acetone, which induces crystallization. Solvent-induced crystallization is known for polyesters and is described in U.S. Patent Nos. 5,164,478 and 3,684,766, which are incorporated herein by reference. The crystallized polymer is subjected to solid state polymerization by placing the granulated or powdered polymer in a stream of inert gas, usually nitrogen, or under vacuum of a Torr, at an elevated temperature, above about 140 ° C, but below of the melting temperature, for a period of about 2 to about 16 hours. The solid state polymerization is preferably carried out at temperatures from about 190 ° C to about 210 ° C for a period from about 2 to about 16 hours. Good results are obtained by heating the polymer from about 195 ° to about 198 ° C for about 10 hours. This polymerization in the solid state can increase the inherent viscosity to about 0.8 dl / g or greater.

Sheet formation The polyester polymer of the present invention formed by one of the above methods, or by any other method known in the art, can be formed into sheets directly from the polymerization melt. Alternatively, the polyester can be formed into an easily manageable form (eg, granules) from the melt, which can then be used to form a sheet. The sheet of the present invention can be used to form signals, glass placement (for example at bus stops, sky lighting or recreational vehicles), advertisements, automobile lights and in thermoforming articles, for example.

The difference between a film and a sheet is the thickness, but in the industry a standard has not been established to differentiate a film from a sheet. For purposes of this invention, a sheet is defined as having a thickness greater than about 0.25 mm (10 mils). Preferably, the thickness of the sheets of the present invention are from about 0.25 mm to about 25 mm, more preferably from about 2 mm to about 15 mm, and even more preferably from about 3 mm to about 10 mm. In a preferred embodiment, the sheets of the present invention have a thickness sufficient to cause the sheet to be rigid, which generally occurs at about 0.50 mm and greater. However, the thicker sheets of 25 mm and thinner 0.25 mm can also be processed. The sheets can be made by any process known in the art, such as extrusion, solution casting or injection molding. The parameters for each of these processes can be easily determined by a person ordinarily skilled in the art depending on the viscosity characteristics of the polyester and the desired thickness of the sheet. The sheet of the invention is preferably formed by either solution casting or extrusion. Particularly preferred is extrusion for the formation of "endless" products such as films and sheets, which arise as a continuous length. For example, see the applications P.C.T. published WO 96/38282 and WO 97/00284, which describe the formation of thermoplastic sheets crystallizable by melt extrusion. In extrusion, the polymeric material, whether it is provided as a molten polymer or as plastic granules or shots, is fluidized and homogenized. This mixture is then driven through a suitably shaped die to produce the sheet shape in cross section that is desired. The extrusion force can be exerted by a piston or ram (ram extrusion), or by a rotating screw (screw extrusion), which operates inside a cylinder and in which the material is heated and plasticized and from the which is then extruded through the die in a continuous flow. Single screw, double screw or multiple screw extruders can be used, as are known in the art. Different kinds of dies are used to make different products, such as sheets and strips (slot dies) and hollow and solid sections (circular dies). In this way, sheets of different widths and thicknesses can be made. After extrusion, the polymeric sheet is captured by rollers, cooled and extracted by means of suitable devices which are designed to avoid any subsequent deformation of the sheet. By using extruders as is known in the art, a sheet can be made by extruding a polymer layer onto cooled rolls and then further pulling down to a size (<.0.25 mm) by tension rollers. Preferably, the finished sheet is < 0.25 mm thick. To produce large quantities of sheets, a rolling calender is used. The rough sheet is fed into the separation of the calender, a machine consisting of several heatable parallel cylindrical rollers which rotate in opposite directions and disperse the polymer and stretch it to the required thickness. The last rollers smooth the sheet produced in this way. If the sheet is required to have a textured surface, the final roll is provided with an appropriate pattern of embossing. Alternatively, the sheet can be reheated and then passed through a stamping calender. The calender is followed by one or more cooling drums. Finally, the finished sheet is rolled up. The previous extrusion process can be combined with various post-extrusion operations for greater versatility. Such post-shaping operations include altering round or oval shapes, stretching the sheet to different dimensions, perforated machine and the like, as are known to those skilled in the art. The polymeric sheet of the invention can be combined with other polymeric materials during extrusion or finishing to form multilayer sheet laminates with improved characteristics, such as water vapor resistance. In particular, the polymer sheet of the invention can be combined with one or more of the following: polyethylene terephthalate (PET) aramid, polyethylene sulfide (PES), polyphenylene sulfide (PPS), polyimide (Pl), polyethyleneimine (PEI), polyethylene naphthalate (PEN), polysulfone (PS), polyetheretherketone (PEEK), polyolefins, polyethylene, poly (cyclic olefins) and poly (cyclohexylene terephthalate and dimethylene), for example. Other polymers which may be used in combination with the polyester polymer of the invention are those which are included in the co-pending applications serial numbers 09 / 064,826 (Attorney's File Number 032358-005) and 09 / 064,720 (Attorney's File Number 032358-008). A multilayer or laminate sheet may be made by a method known in the art, and may have up to five or more separate layers which are bonded by heat, adhesive or an adherent layer, as is known in the art. A sheet can also be formed by pouring solution, which produces a laminate of consistently more uniform caliper than that produced by melt extrusion. Solution casting comprises dissolving polymeric, powdered granules or the like in a suitable solvent with a desired formulant, such as a plasticizer or refrigerant. The solution is filtered to remove dirt or large particles and emptying from a slot die to a moving band, preferably stainless steel, where the sheet is cooled. The sheet is then removed from the web to a winding roller. The extruded thickness is five to ten times in the finished sheet. The sheet can then be finished in a manner similar to the extruded sheet. In addition, sheets and sheet-like articles such as discs can be made by injection molding by any method known in the art. A person ordinarily skilled in the art will be able to identify the appropriate process parameters based on the polymer composition and the processes used for sheet formation. Regardless of the manner in which the sheet is formed, it is desirable to subject it to biaxial orientation by stretching in both machine and transverse directions after forming. Stretching in the machine direction starts by forming the sheet simply by removing it from the rollers and capturing the sheet. This inherently stretches the sheet in the pickup direction, orienting some of the fibers. Although this makes the sheet more resistant to the direction of the machine, it allows the sheet to easily tear in the direction at right angles, because all the fibers are oriented in one direction. Therefore, biaxially stretched sheets are preferred for certain uses where a uniform laminate is desired. The biaxial stretching directs the fibers parallel to the plane of the sheet, but leaves the fibers oriented randomly within the plane of the sheet. This provides superior tensile strength, flexibility, robustness and shrinkability, for example in comparison with unoriented sheets. It is desirable to stretch the sheet along two axes at right angles to each other. This increases the tensile strength and the elastic modulus in the stretching directions. It is more desirable for the amount of stretching in each direction to be generally equivalent, so properties or similar behavior are provided within the sheet when tested from any direction. The biaxial orientation can be obtained by any process known in the art. However, tensioning is preferred, wherein the material is stretched while heating in the transverse direction simultaneously with, or subsequent to, stretching in the machine direction.

The shrinkage can be controlled by holding the sheet in a stretched position and heating it for a few seconds before cooling. This heat stabilizes the oriented sheet, which can be driven to shrink only at temperatures above the thermal stabilization temperature. The above conditions and process parameters for the manufacture of the laminate by any method known in the art is readily determined by those skilled in the art for any given polymer composition and application as desired. The properties shown by a sheet will depend on several factors indicated above, which include the polymer composition, the method of shaping the polymer, the method of shaping the sheet and whether the sheet is treated for stretching or is biaxially oriented. These factors affect many properties of the sheet, such as shrinkage, tensile strength, elongation at break, impact resistance, dielectric strength and constant, stress modulus, chemical resistance, point of fusion and similar. The sheet of the present invention may contain additives typically used in the art of plastic sheets, such as lubricants, antioxidants, plasticizers, optically active additives, colorants, pigments, fillers, and fibers, as are known in the art. Ultraviolet (UV) stabilizers may also be added as necessary, however, the sheet of the invention has inherent resistance to UV radiation. The characteristics of the isotrepsic polyester polymer of the invention can also be improved by combining the polymer with core / shell elastomers or with thermoplastic polymers having refractive indices equal to or greater than those of the polyester polymer. This will increase the robustness of polyester at ambient and cold temperatures, and at the same time maintain optical transparency. Polymers suitable for combination with the polyester polymer of the invention are known to those skilled in the art, but can preferably include polymers such as the core / shell polymers described in U.S. Patent Nos. 5,321,056 and 5,409,967. , incorporated herein by reference. The characteristics of the isotropic polyester polymers of the invention can also be improved by combining the polymer with one or more additional polymers, forming a polymer which can be formed into a sheet as described herein. For example, a polyester polymer of the invention can be combined with polyethylene to improve its use as a barrier against water vapor. Other polymers can be added to change characteristics such as air permeability, optical clarity or elasticity. The sheet of the invention can also be made with the polyesters described in co-pending application 09 / 064,720 [Attorney's File Number 032358-008] and the combinations described in co-pending application 09 / 064,826 [Attorney's File Number 032358-005], whose contents are incorporated herein by reference. The sheets of the present invention, as described in the foregoing, can be thermoformed by any known method in a desired form, for example in covers, skylights, glass for shaped greenhouses and screens. The thermoforming is carried out by heating the sheet at a sufficient temperature and for a sufficient time to soften the polyester so that the sheet can be easily molded in the desired shape. In this regard, a person ordinarily in the art can easily determine the optimum thermoforming parameters, depending on the viscosity characteristics of the polyester sheet. This invention is further illustrated by the following non-limiting examples.

EXAMPLES Synthesis of polymers used for sheet applications The molecular weights of the polymers are estimated based on the inherent viscosity (IV), which is measured for a 1% (w / v) polymer solution in o-chlorophenol at a temperature of 25 ° C. The levels of catalyst components are expressed as ppm, based on a comparison of the weight of the metal with the weight of either dimethyl terephthalate or terephthalic acid, depending on which monomer is used.

Example 1 The polymerization reactor used for this reactor is a Hastalloy B reactor with a maximum capacity of 189 1 (50 gallons) to which a Hastalloy B water cooled reflux column with a radius of 15 cm (6") with rings is placed. stainless steel, a stainless steel propeller stirrer, a water cooled and bypass condenser The following reagents are added to the polymerization reactor: 78.02 kg of dimethyl terephthalate, 15.42 kg of isosorbide and 49.90 kg of ethylene glycol (which corresponds to a mole ratio of 1: 0.26: 2.00, respectively.) In addition, the catalyst is charged to the reactor and consists of 29.57 g of Mn (II) acetate tetrahydrate, 21.43 g of Co (II) acetate tetrahydrate and 35.02 g of Sb (III) oxide This corresponds to 85 ppm of manganese (weight of the metal as a fraction of the weight of dimethyl terephthalate), 90 ppm of cobalt and 375 ppm of antimony, and the reaction mixture. (50 rpm) is purged with a nitrogen stream while increasing the temperature to 250 ° C for a period of 4 hours. The reactor is coated and temperature controlled. A hot oil cycle system is used as a heating medium. The methanol is continuously collected as the reaction is heated above about 150 ° C. By noting the moment when the temperature in the upper part of the packed reflux column decreases, it is possible to determine the end of methanol production. The end of methanol production indicates the completion of the first stage of the reaction, which is the transesterification of the diols and dimethyl terephthalate. After the temperature drop that indicates the end of methanol production, 77 ppm of phosphorus is added in the form of a solution of polyphosphoric acid in ethylene glycol. In the present example, 153 ml of a solution having a concentration of 10.91 g of phosphorus per 100 g of polyphosphoric acid solution are used. Also at this time, the nitrogen purge is stopped (but stirring is continued). The reaction is heated to 285 ° C for a period of about 2 hours. Then vacuum is gradually applied using a multi-blade vacuum pump with a 20-horsepower fan. Obtaining a complete vacuum (less than 1 Torr) requires approximately 1 hour. During this time, the ethylene glycol is distilled off, and a polymer with a low molecular weight is formed. The molten polymer is heated under vacuum at 285 ° C, for about 2 hours, until the polymer obtains a sufficient melt viscosity, determined by an increase in the torque of the agitator. When sufficient viscosity is obtained, the polymerization is stopped and the reactor is emptied through a heated die in the lower part. The molten polymer emerges as a filament and is then cooled by immersion in a cold water channel and chopped or cut into granules. The polymer granules are dried overnight in a rotating drum which is heated to 120 ° C. The cooled polymer is removed from the flask and crushed. The inherent viscosity of the solution (I.V.) of the material 0.64 dl / g. The composition of the polymer monomer unit, determined by proton NMR, is about 6% isosorbide, 42% ethylene glycol, 2% diethylene glycol and 50% terephthalic acid, all expressed as moles% of the polymer. It is notable that the amount of isosorbide in the polymer is about half the amount that is charged, when compared to the amount of terephthalic acid. The unreacted isosorbide is found in the distillates, especially in ethylene glycol. Therefore, the amount of isosorbide in the polymer by this process is highly dependent on the efficiency of the distillation and / or the separation methods used in the process. A person skilled in the art can easily establish specific process details according to the characteristics of the reactor, distillation columns and the like.

Example 2 The second example is prepared in a manner similar to that of Example 1, however a smaller reactor (with a maximum capacity of 18.9 1) (5 gallons) is used). The equivalent reagent ratios also change in order to prepare a polymer with a higher isosorbide content. Therefore, 10,680 g of dimethyl terephthalate, 5,787 g of isosorbide, 4,881 g of ethylene glycol (corresponding to a molar ratio of 1: 0.72: 1.43, respectively) are charged to the reactor and charged to the reactor as in Example 1, together with the catalyst consisting of 4.76 g of Mn (II) acetate tetrahydrate and 4.66 g of Ge (IV) oxide. This corresponds to 100 ppm manganese (weight of the metal as a fraction of the weight of dimethyl terephthalate) and 300 ppm of germanium. The germanium oxide is added in the form of a solution in ethylene glycol (0.100 normal (N) GeQ2 in ethylene glycol). A solution of the polyphosphoric acid in ethylene glycol is added as in Example 1, however, in this case, 9.6 ml of a phosphoric acid solution (which has a phosphorus concentration of 3.45 g of phosphorus per 100 ml) are used. The above variants are carried out as in example 1. The resulting polymer has an I.V. in solution of 0.42 dl / g. The composition of the monomer unit, the polymer, determined by NMR of the proton, is about 13% isosorbide, 34% ethylene glycol, 3% diethylene glycol and 50% terephthalic acid, all expressed as moles% of the polymer. The degree of incorporation of isosorbide is a bit lower in this case than in the previously observed one, but this reflects the efficiency of the different reactors instead of the polymer that is made.

Example 3 The third example is prepared in a manner similar to that of Example 1, except that a larger reactor of 378 1 (100 gallons) equipped with a stainless steel anchor type stirrer is used. The charged monomers are added to result in an isosorbide content in the finished polymer of 1 mole%, assuming that part of the introduced isosorbide is still removed by distillation during the polymerization. As such, 197 kg of dimethyl terephthalate, 5.12 kg of isosorbide, 135 kg of ethylene glycol, 72.1 g of Mn (II) acetate tetrahydrate, 54.1 g of Co (II) acetate tetrahydrate and 88.5 g of sodium oxide are used. Sb (III). The catalyst additions correspond to 82 ppm of manganese, 65 ppm of Co and 375 ppm of Sb, calculated as in example 1. The transesterification process is carried out in a manner analogous to that of example 1. An acid solution polyphosphoric in ethylene glycol is added so that 80 ppm of phosphorus is used to sequester the transition metals after the transesterification step and before the polycondensation, as indicated in example 1. The polycondensation is also similar to that of example 1 The polymer is extruded and granulated to provide a colorless and transparent resin. Unlike the previous examples, the resin produced with a lower isosorbide content can be polymerized in the solid state. The polymer and granulate is loaded in a drum dryer and heated to a nitrogen stream of 115 ° C for 4 hours and then maintained at that temperature for another 6 hours. This allows the polymer to partially crystallize. After this treatment, vacuum is applied to the drum dryer, which finally generates a vacuum of less than 1 mm Hg. The heating is continued and reaches a maximum temperature of 213 ° C. The polymer is then maintained at this elevated temperature for a total of about 15 hours. This carries out a polymerization in the solid state and increases the molecular weight of the polymer. In this regard, the I.V. of the material solution is increased from about 0.5 dl / g to about 0.7 dl / g during the solid state polymerization.

Example 4 This polymer is prepared in a manner similar to the polymer produced in Example 3, except that the amounts of diols are charged in order to result in a resin with a slightly increased isosorbide content. Therefore, the only alterations are in the amount of isosorbide being loaded, 17.8 kg, and the amount of Mn (II) acetate tetrahydrate catalyst used, 79.2 g (corresponding to 90 pp of Mn (II)). calculated on the same basis as in the previous examples). The transesterification and polycondensation are repeated as in example 3. The finished polymer is granulated, crystallized and polymerized in the solid state as in example 3. The resulting polymer contains approximately 3 moles% isosorbide.

Ejep lo 5 42 The materials described in examples 1-4 are injection molded into discs (3.2 mm thick, (1/8"), diameter 10 cm (4")) to measure the multiple axial mechanical impact resistance . In addition, tension bars are molded to measure their Izod impact resistance with notches and their tension properties. A Boy 30M device (Boy, Gmbh, Fernthalr, Germany) is used for the injection molding of the parts. The conditions used are the following: Barrel temperature: 300 ° C Mold temperature: 50 ° C Screw speed: 210 rpm Injection speed: 100% Injection pressure: 13 bar Retention pressure: 12 bar Back pressure: 3 bar Injection time: 2 seconds Time Cooling time: 25 seconds Table 1 shows the mechanical characteristics of the resulting sheets. In addition, the results for discs (thickness = 3.2 mm (1/8 inch), approximately 3.3 mm, diameter = 10 cm) (4 inches)), manufactured for standard PET material are reported. The PET sheet material is obtained from Hostaglas "(Hoechst AG, Frankfurt, Germany) .The multiaxial impact resistance is measured by a descending plunger instrument (Dynatup 8250 manufactured by Instron, Canton, Mass.) Impact resistance results multiaxial are summarized below in Table 1.

Table 1 Example 6 This example illustrates the thermoforming and biaxial stretching of the polymer made in Example 1. The polymer in Example 1 is used to produce a sheet with a thickness of 356 μm (14 mils) by extrusion using a pilot film line / sheet manufactured by Egan Machinery (Somerville, NJ). The conditions for extrusion are the following: Extruder barrel (zone 1); 245 ° C zone 2: 245 ° C zone 3: 245 ° C zone 4: 245 ° C zone 5: 265 ° C zone 6: 265 ° C Melting line temperature: 60 ° C Die temperature: 260 ° C Roller 1: 25 ° C Roller 2: 25 ° C Roller 3: 19 ° C A. Thermoforming.

The sheet is cut to a width of 15-18 cm (6"-7") wide and approximately 28 cm (11"long) After heating in a rectangular retaining clamp at 165 ° C in a convection oven until softening occurs, the sheet is vacuum thermoformed in molds at room temperature of 38 mm and 51 mm (1.5"and 2") to demonstrate the thermoformability The resulting sheets are optically transparent and mechanically strong.

B. Stretched Film The extruded film is stretched uniaxially and biaxially using a Bruckner drawing frame (Bruckner, Siegsdorf, Germany). The sample is inserted in the direction of the machine (MD) (on the Y axis of the machine) The drawing speed is 38 mm (1.50 in.) / Sec Table 2 describes the drawing ratios, the temperatures of the machine and drawing conditions, as well as the mechanical properties measured in accordance with ASTM 882.

Table 2 - It should be understood that the modalities described in the foregoing are only illustrative and that modifications may occur to a person skilled in the art. Accordingly, this invention should not be considered as limited by the embodiments described herein. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (40)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. A sheet, characterized by porgue, comprises a polyester, wherein the polyester comprises portions of terephthaloyl; optionally, one or more additional aromatic diacid portions; portions of ethylene glycol; portions of isosorbide and, optionally, one or more additional diol portions, wherein the polyester has an inherent viscosity of at least about 0.35 dl / g, when measured as a 1%, weight / volume solution of the polyester in or -chlorophenol, at a temperature of 25 ° C.

2. The sheet according to claim 1, characterized in that the sheet has a thickness greater than about 0.25 mm.

3. The sheet according to claim 1, characterized in that the sheet has a thickness greater than 0.25 mm to approximately 25 mm.

4. The sheet of conmunity with claim 1, characterized in that the sheet is thermoformable.

5. The sheet according to claim 1, characterized in that the sheet is biaxially oriented.

6. The sheet of conmunity with claim 1, characterized in that the polyester has an inherent viscosity of at least about 0.5 dl / g.

7. The sheet according to claim 6, characterized in that the polyester has an inherent viscosity of about 0.7 to about 1.0 dl / g.

8. The sheet according to claim 1, characterized in that the polyester further comprises one or more portions of diethylene glycol.

9. The sheet of conmunity with claim 1, characterized in that the terephthaloyl moieties are present in an amount from about 40 to about 50 mole% of the polyester, one or more aromatic diacid portions are present in an amount of up to about 10.0 mole%. of the polyester, the ethylene glycol portions are present in an amount from about 33 to about 49.9 mole% of the polyester, the isosorbide portions are present in an amount from about 0.25 to about 20.0 mole% of the polyester, one or more additional diol portions they are present in an amount of up to about 2.0 mole% of the polyester.

10. The sheet according to claim 9, characterized by one or more additional diol portions are a portion of diethylene glycol which is present in an amount of up to about 5.0 mole% of the polyester.

11. The sheet according to claim 9, characterized in that the isosorbide portions are present in an amount from about 1.0 to 12.0 mol%.

12. The sheet of conmunity with claim 1, characterized in that the terephthaloyl moieties are derived from terephthalic acid or dimethyl terephthalate.

13. The conformance sheet with claim 1, characterized in that one or more additional diol portions are derived from aliphatic alkylene glycols or branched aliphatic glycols having 3-12 carbon atoms and having the empirical formula HO-CnH2n-OH, wherein n is an integer of 3-12, cis or trans-1,4-cyclohexanedimethanol or mixtures thereof; triethylene glycol; 2, 2-bis [4- (2-hydroxyethoxy) phenyl] propane; 1, l-bis [4- (2-hydroxyethoxy) phenyl] -cciohexane; 9, 9-bis [4- (2-hydroxyethoxy) phenyl] fluorene; 1.4: 3, 6-dianhydromanitol; 1,4: 3,6-dianhydroiditol; and 1,4-anhydroerythritol.

14. The reference sheet according to claim 13, characterized in that one or more additional diol portions are derived from cis-1,4-cyclohexanedimethanol, trans-1, 4-cyclohexanediminol or mixtures thereof.

15. The consistency sheet with claim 1, characterized in that one or more additional aromatic diacid portions are derived from isophthalic acid, 2,5-furanodicarboxylic acid, 2,5-thiodenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid or 4,4'-benzoic acid.

16. The sheet according to claim 15, characterized in that one or more additional aromatic diacid portions are derived from isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-benzoic acid or mixtures thereof.

17. An article, characterized in that it comprises the sheet according to claim 1.

18. The article according to claim 17, characterized in that it is selected from the group consisting of signaling, placement of crystals, a display substrate and a disc.

19. The article according to claim 17, characterized in that the article is thermoformed or molded by injection.

20. A method for making a sheet, wherein the sheet comprises a polyester, the method is characterized in that it comprises: a) forming the polyester; and b) producing a sheet from the polyester; wherein the polyester comprises portions of terephthaloyl; optionally, one or more additional aromatic diacid portions; portions of ethylene glycol; portions of isosorbide; and, optionally, one or more additional diol portions,. wherein the polyester has an inherent viscosity of at least about 0.35 dl / g when measured as a 1%, weight / volume solution of the polyester in o-chlorophenol at a temperature of 25 ° C.

21. The method according to claim 20, characterized in that the production of the sheet comprises extrusion, pouring of solution or injection molding of the polyester.

22. The method according to claim 20, characterized in that the sheet has a thickness greater than about 0.25 mm.

23. The method according to claim 22, characterized in that the sheet has a thickness greater than 0.25 mm to about 25 mm.

24. The method according to claim 20, characterized in that it further comprises thermoforming the sheet into a desired shape.

25. The method according to claim 20, characterized in that the sheet has an inherent viscosity of at least about 0.5 dl / g.

26. The method according to claim 25, characterized in that the sheet has an inherent viscosity from about 0.7 to about 1.0 dl / g.

27. The method according to claim 20, characterized in that the polyester comprises portions of diethylene glycol.

28. The method according to claim 20, characterized in that the terephthaloyl moieties are present in an amount of about 40 to about 50 mole% of the polyester, one or more additional aromatic diacid moieties are present in an amount of up to about 10 mole%. of the polyester, the ethylene glycol portions are present in an amount of about 33 to about 49.9 moles% of the polyester, the isosorbide portions are present in an amount of about 0.25 to about 20.0 moles% of the polyester, and one or more portions of the diol additional are present in an amount of up to about 2.0 mole% of the polyester.

29. The method according to claim 28, characterized in that the terephthaloyl moieties are derived from terephthalic acid or dimethyl terephthalate.

30. The method according to claim 28, characterized in that one or more additional diol portions are derived from aliphatic alkylene glycols or branched aliphatic glycols having 3-12 carbon atoms and having the empirical formula H0-CnH2n-0H, wherein n is an integer of 3-12; cis or trans-1,4-cyclohexanedimethanol or mixtures thereof, triethylene glycol; 2, 2-bis [4- (2-hydroxyethoxy) phenyl] propane; 1, l-bis [4- (2-hydroxyethoxy) phenyl] -cydohexane; 9, 9-bis [4- (2-hydroxyethoxy) phenyl] fluorocarbon; 1.4: 3, 6-dianhydromanitol; 1,4: 3,6-dianhydroiditol; and 1,4-anhydroerythritol.

31. The method according to claim 28, characterized in that one or more of the additional aromatic diacid portions are derived from isophthalic acid, 2,5-furanedicarboxylic acid, 2,5-thiophenedicarboxylic acid, 2,6-naphthanedicarboxylic acid , 2,7-naphthalenedicarboxylic acid or 4,4'-benzoic acid.

32. The method according to claim 28, characterized in that the isosorbide portions are present in an amount from about 1 to about 12 mol%.

33. The method according to claim 28, characterized in that one or more additional diol portions comprises a portion of ethylene glycol in an amount of up to about 5.0 mole% of the polyester.

34. The method according to claim 28, characterized in that the sheet has a thickness greater than 0.25 mm.

35. The method according to claim 28, characterized in that the sheet is biaxially oriented.

36. The method according to claim 20, characterized in that the formation of the polyester comprises: (a) combining in a reactor a monomer comprising a portion of terephthaloyl; optionally one or more additional monomers comprising a portion of aromatic diacid; a monomer comprising a portion of ethylene glycol; a monomer comprising a portion of isosorbide; and optionally one or more additional monomers comprising a portion of diol with a condensation catalyst suitable for condensing aromatic diacids and glycols; and (b) heating the monomers of the catalyst at a temperature sufficient to polymerize the monomers in a polyester polymer having at least the terephthaloyl portion, the ethylene glycol portion and the isosorbide portion, wherein the heating is continued for, a time sufficient to provide a polyester having an inherent viscosity of at least about 0.35 dl / g when measured as a 1%, weight / volume solution of the polyester in o-chlorophenol at a temperature of 25 ° C.

37. The method according to claim 36, characterized in that it further comprises increasing the molecular weight of the polyester by polymerization in the solid state.

38. The method according to claim 37, characterized in that the solid state polymerization comprises: (a) crystallizing the polyester by heating the polyester at a temperature in the range of about 115 ° C to about 140 ° C; and (b) heating the polyester under vacuum or in an inert gas stream at an elevated temperature above 140 ° C but below the melting temperature of the polyester to provide a polyester having an increased inherent viscosity.

39. The method according to claim 38, characterized in that the heating step (b) is carried out at a temperature of about 195 ° to 198 ° C for about 10 hours.

40. The method according to claim 38, characterized in that the increased inherent viscosity is at least about 0.65 dl / g.