MXPA00010107A - Poly(alkylene arylates) having optical properties - Google Patents

Abstract

Poly(alkylene arylates) having excellent optical properties are disclosed and can be prepared using an organic titanate-ligand catalyst solution containing organic silicates and/or zirconates and, preferably, certain phosphorus compounds.

Description

POLY (ALKYLENE ARILATES) THAT HAVE OPTICAL PROPERTIES BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to poly (alkylene arylates), such as poly (ethylene terephthalate), PET; poly (propylene terephthalate), PPT; poly (butylene terephthalate), PBT; poly (ethylene naphthalate), PEN; poly (propylene naphthalate), PPN; poly (butylene naphthalate); poly (ethylene isophthalate), PEI; poly (propylene isophthalate), PPI; poly (butylene isophthalate), PBI; to homopolymers and their copolymers and mixtures, which contain the residue of organic titanate-ligand catalyst systems. The poly (alkylene arylate) has better optical properties than similar polymers that to date are prepared with other organic titanate-ligand catalysts. The resulting PET, for example, is particularly useful in the preparation of transparent articles, such as films, which have excellent clarity, reduced light scattering and absorb less light than conventional PET. Thus, PET resins prepared with the catalyst have particular utility as a substrate for X-ray and photographic films. Ref: 122677 DESCRIPTION OF THE RELATED ART Poly (ethylene terephthalate) PET is a widely used polyester which is typically manufactured by two routes: (1) transesterification of a dialkyl terephthalate ester (eg dimethyl terephthalate) with ethylene glycol to form an intermediate bis-2-hydroxyethyl terephthalate, followed by a polycondensation to form the PET; or (2) by direct esterification of terephthalic acid with ethylene glycol, followed by polycondensation to form PET. A catalyst is commonly used to accelerate the reaction in any case. The same or a different catalyst can be selected for the transesterification step and the polycondensation step. Many commercial processes use manganese or zinc salts as catalysts for the transesterification stage. Antimony, in the form of a glycol solution of antimony oxide, is typically used as the polycondensation catalyst either in the transesterification processes or in the direct esterification processes mentioned above. There is an interest in replacing antimony by another catalyst; however, as insoluble antimony species tend to form, they increase the polymer's darkness, scatter light, and interfere with the formation of yarns. and other forms. In addition, antimony catalysts suffer from increasing regulatory or regulatory pressure. Thus, there is a need for new polycondensation catalysts that reduce or replace antimony, in the manufacture of PET and other poly (alkylene arylates). Organic titanates, such as tetraisopropyl and tetra n-butyl titanates, are known to be effective polycondensation catalysts for preparing poly (alkylene arylates) in general and are often the catalyst of choice in the manufacture of polybutylene terephthalate ( PBT), due to its greater reactivity than conventional antimony catalysts. However, organic titanates are not generally used in the manufacture of PET because the residual titanate catalyst tends to react with trace impurities formed during the polycondensation and processing of the PETs (eg, aldehydes), generating a yellow discoloration that it can not be tolerated in products typically made with PET (eg, X-ray and photographic films, bottles and packaging films). The lack of glycol solubility is also a practical limitation for most organic titanate catalysts. It is preferred to add catalyst to a continuous polycondensation reaction as a solution of Diluted glycol (instead of a dispersion), to obtain a uniform distribution of the small quantities of catalyst used. Organic titanates typically form a precipitate when added to a glycol, which tends to complicate the manufacturing control and introduces quality problems in the products due to the non-uniform distribution of the catalyst in the reaction mixture. Numerous binary compositions containing organic titanates and phosphorus compounds (organic and inorganic) have been proposed in the technical and patent literature to be used as polycondensation catalysts in the manufacture of poly (alkylene arylates). For example, it has been proposed to add phosphoric acid or other phosphorus-based compounds, together with organic titanates, to control the color by complexing with the residual titanate catalyst. However, the use of such strong complexing agents invariably reduces the efficiency of the titanate catalyst and introduces problems for the control of the polymerization. Thus, there is a need for a non-antimony based polycondensation catalyst that is soluble in glycol, efficient and that produces poly (alkylene arylates) in general, and PET and PPT in particular, which possess excellent properties optical BRIEF DESCRIPTION OF THE INVENTION The present invention provides a more useful and attractive form of poly (alkylene arylates), such as PET and PPT, which are polymerized using an organic titanate-ligand catalyst. The polymer has a low visible reflective color and can be compressed, extruded or shaped in some other way to form an article, such as a film, such that the article has a high transmissibility of light between the wavelengths of 320 and 800 nm. The polymer can be prepared using an organic titanate-ligand catalyst system, which (1) can be soluble in the reaction mixture, (2) can be soluble in the alcohol used to prepare the polymer, (3) can provide high polymerization rates in the reaction mixture, (_) may include cocatalysts or supplementary additives for the polymer that help prevent the formation of titanate chromophores or (5) may prevent or greatly reduce the formation of chromophores. The term "organic titanate-ligand catalyst" as used herein, refers to a catalyst that is derived from or that contains an organic ortho titanate with ligands and cocatalysts that can prevent the formation of titanate chromophores, such cocatalysts can understand organic silicates, organic zirconates and organic phosphors. DETAILED DESCRIPTION OF THE INVENTION The poly (alkylene arylate) polymer of the present invention can be a homopolymer or a copolymer. The term "poly (alkylene arylate)" as used in the present invention, refers to a polymer having repeating units derived from at least one methylene monomer or comonomer containing an aromatic carboxylic group. The term "copolymer" as used herein, includes a polymer comprising repeating units derived from two or more comonomers. Any comonomer containing a polymerizable ethylenic structure such as, for example, ethylene, propylene, hexene, decene, can be used to produce the polymer. It is well known that organic titanates promote rapid polycondensation rates in the preparation of poly (alkylene arylates). However, organic titanates are generally not used commercially for this purpose when optical properties are important such as in many commercial products made from PET, PEI, PPT and PBT, because organic titanates tend to cause unacceptable color formation and light absorption. All Once the present invention is generally applied to poly (alkylene arylates), it will now be described in greater detail with respect to PET, which is a preferred embodiment. Without adhering to any theory, degradation by-products are inevitably produced in small quantities during the polymerization and processing of PET. These by-products (e.g., aldehydes, especially acetaldehyde) form chemical complexes with the catalyst residues (i.e., titanates) that generate discoloration and absorb the light that passes through the PET. Thus, PET is not suitable for consumer applications because it is not attractive or for applications such as photographic film or X-ray substrates, because the complexes affect the desired image resolution and image sensitivity. These optical properties include two phenomena: (1) How PET reflects light; and (2) how PET absorbs the light that is being transmitted through it. The organic titanate-ligand catalyst decreases or eliminates the combination of organic titanate with polymerization byproducts (eg, aldehydes), thereby reducing or eliminating the absorbance of light in the polymer at ultraviolet and visible wavelengths of 320 to 800 nm. Without adhering to any theory, the ligand or ligands prevent the formation of titanium complexes which affect the desired optical properties and / or form complexes with by-products that do not affect the desired optical properties. The organic titanate-ligand catalyst system may include a cocatalyst that provides alternative sites for the byproducts and the combined cocatalyst, and the byproducts are not chromophores. In accordance with the present invention, the poly (alkylene arylate) has an average molecular weight of at least 21,000 Daltons and contains between 0.1 and 500 ppm of organotin-ligand titanium catalyst residue. The poly (alkylene arylate) can have an AB? / L value of 0 to less than or equal to 6.1, preferably less than or equal to 6 and more preferably less than or equal to 5 and still more preferably less than or equal to _. The polymer can have a Hunter L value greater than 65, preferably greater than 75, a Hunter value a between -2 and +2, preferably approximately zero, and a Hunter b value between -2 and 6, preferably approximately zero Alternatively, the polymer can have a combination of an average molecular weight of at least about 21,000, containing from about 0.5 to 500 ppm of titanium residue of an organic titanate-ligand catalyst solution, an ABS / L value of less than 7, an L value of Hunter greater than 65, a Hunter value a between -2 and +2 and a Hunter b value between -2 and 8.3. In addition, alternatively, the polymer can have the combination of an average molecular weight of at least about 21,000 and containing between 0.5 and 500 ppm of titanium catalyst residue, an ABS / L value of less than 7, a Hunter L value greater than 65, a Hunter value a between -2 and +2 and a Hunter value b between -2 and 6. The catalyst residue (between 0.1 and 500 ppm) refers to the presence of elemental titanium in parts by weight per million of parts by weight of the polymer and does not include any particulate titanium dioxide compound that may be present for other reasons. The amount of titanium catalyst residue is conveniently determined by elemental analysis or by spectroscopy. REFLECTED LIGHT The color of the polymer is conventionally evaluated by measuring the intensity of the reflected light at various wavelengths when the polymer is exposed to a broad spectrum light source, using an instrument such as a spectrophotometer. The techniques are generally described in The Measurement of Appearance, R.S. Hunter and R. Harold, 2nd ed., Wiley Publishers, New York (1987); and Color Science: Concepts and Methos, Quantitative Data and Formulae, G. Wyszecki and W.?. Useful, 2nd ed., Wiley Publishers, New York (1982). The color can be measured and reported by specifying the three numerical values L, a and b of the Hunter color scale. The value L represents the whiteness or the shadow of gray; the larger the numerical value, the higher the whiteness. The upper limit of the scale L is 100, which denotes white in the absence of dye and the lower limit is zero, which denotes black. The values a and b indicate the dye intensity. When both values a and b are zero, the material is a shadow of gray or is said to have a neutral tint. A positive value of a denotes redness and a negative value of a denotes greenness. A positive value of b denotes amarulence and a negative value of b denotes blueness. The physical form of the poly (ethylene terephthalate) polymer has an influence on the numerical values of the color numbers L, a and b, measured with a spectrophotometer in the reflectance mode. The polymer in the form of a thin fiber or a powder of small particle size or rough surface reflects more light than the respective thicker fiber or powder of larger particle size or smooth surface. Thus, a sample of the first type of shape will have more whiteness and a more neutral tint than a sample of the latter form, if the chemical composition of the samples is identical. The crystalline polymer reflects more light than the less crystalline or amorphous. Thus, a more crystalline sample will have a higher whiteness and more neutral tint than an amorphous sample if the chemical composition of the samples is identical. Then, comparing the reflected color of the polymer samples that differ by the catalyst composition is useful to ensure the physical form and the shapes are very similar to evaluate the advantages of particular catalyst systems. A color measurement method can capture only the light reflected from the polymer or a measurement can capture the light that is reflected and transmitted through the polymer. Examples of the first case include incident light reflected from the surface of the fibers of the polymer or flakes of ground polymer or powder particles. Examples of the latter case include light that is incident on a stack of films, such that part of the light is reflected directly from the outer surface of the first film, while part of the light is transmitted through some layers and it is reflected outside the movies by the internal interfaces within the movie stack. This last method of color measurement is not preferred by the inventors, because part of the wavelengths can be absorbed and / or transmitted by the polymer, so the values of L, a and b do not provide a pure indication of the colorful light only reflected by the surface of the polymer. The Hunter color values mentioned herein are determined in accordance with the following procedure, as illustrated in the Examples. A preparation of a specific sample is used to measure and compare the color that is reflected from several PET samples that differ in their catalyst composition. A PET sample is first crystallized to at least 20% crystallinity, typically 30%, by annealing in an oven at 160 ° C for 16 hours. After the sample is crushed to a uniform fine powder, using a Wiley Mili shredder (model ED-5 obtained in Thomas Scientific, PO Box 99, Swedesboro, New Jersey 08085) that shreds the polymer so that the particles can pass through. of a 2 mm mesh. This ground powder is placed in a spectrophotometer to measure the color in a pure reflectance mode. Typical PET resins used for photographic or X-ray films, packaging applications, bottles and the like, have an L value of at least 65. Typical PET resins prepared using an antimony catalyst will have values of a and b in the range from -2 to +2. It is preferred to have values of L close to 100 and values of a and b close to zero.

ABSORBED LIGHT PET has a strong absorbance by light that has a wavelength (?) Close to 310 nm. For many applications, such as X-ray and photographic films, it is important that the PET absorbs little, preferably no light at wavelengths in the 320-800 nm band, due to the presence of other materials (eg, complexes with the catalyst) in the PET. There is no conventional technique for reporting the light absorbance property of a transparent polymer, although the theory on which the measurement of light absorption is based is well known in the art. Some sample references that describe the absorption of light, which can be consulted to understand the formula that was developed, are Mechanism and Theory in Organic Chemistry by T.H. Lowry and K.S. Richardson, Herper & Row Publishers (1976); Physical Chemistry, by W. J. Moore, Prentice Hall Publishers, 4th ed. (1972 (and Physical Methods in Chemistry, RS Drago, Saunders Publishers (1977).) The absorbed light values (ABS / L) mentioned herein are determined in accordance with the following procedure, as illustrated in the examples. A specific sample preparation method is used to measure and compare the light absorbencies of several PET samples that differ in the composition of catalyst. A PET sample is first melted and compressed into a typically 10 mil thick film between two metal plates. The film and the metal plates are cooled with water before the polymer can substantially crystallize. The measured crystallinity is less than 5% by weight, typically 3% by weight. The resulting films are visibly transparent. The film is removed from the plates and placed in a spectrophotometer to measure the absorption of light. Using a spectrophotometer, the absorption of light within the film is measured by comparing the intensity of light transmitted through the thin dimension of the film, in relation to the intensity of the original incident light in the plane of the film. The absorbance, A, at a wavelength,?, Is defined as A (?) = Ln, ??) where I0 is the intensity of incident light and I is the intensity of light that has been transmitted through the film and ln () is the logarithm with base e, or natural logarithm. In accordance with the Beer-Lambert Law, the absorbance is proportional to the thickness of the polymer film, L, and the concentration of any material present in the film that can absorb light. Thus, the figure A (?) / L indicates the amount of absorbance per unit of film thickness that depends only on the composition within the film and is independent of the thickness of the film. The spectral data provides with a background correction, so that Io (?) Is the unit. Intensity is provided in terms of percentage (%) of light transmitted through the film. Thus, the absorbance per unit of film thickness is determined according to the formula: As the pure PET itself has a strong absorbance band near a wavelength of 310 nm, the films have a practical use when the transmission is in a spectrum of longer wavelengths in the ultraviolet and the visible; i.e., at wavelengths of 320 to 800 nm. A useful means to measure and report the absorbance of light over the useful range is to integrate the absorbance per unit thickness through the spectrum of useful wavelengths. There is no standard way to report the absorption of film over these wavelengths, so the inventors selected a non-weighted integration over wavelengths from 320 to 800 nm. This property of the film, defined herein as ABS / L, is represented by the formula where the thickness is given in milliliters (ml). It is noted that this property is not a measurement of color or darkness. It is a total measurement of how much light does not pass through the material. However, when ABS / L is very close to zero, then the material will be transparent and colorless. It is also observed that this property is applied to regions of light that are invisible, between 320 and 400 nm. The absorbance of confined light between 320 and 400 nm is outside the common definition of visible light and is not characterized by the color scale of Hunter L, a and b or by any other description of visible color or visible transparency. Typical commercial PET films used as a substrate for X-ray or photographic films have an ABS / L value of less than 15. For these films it is preferred that they have an ABS / L value close to zero. The antimony catalyst is the catalyst of choice currently used to prepare these PET films. In the practice of this invention, the advantages of the organic titanate catalysts can be obtained, while achieving a color and an ABS / L yield comparable or superior to that obtained with the antimony catalyst. PET PREPARATION The PET films and articles of the present invention are prepared by the transesterification or direct esterification processes mentioned above, using techniques in the molten or solid state, but using the catalyst system described above instead of, or as a catalyst. partial replacement of the conventional antimony catalyst or other polycondensation catalysts of the prior art. The catalyst system is soluble in ethylene glycol, has a high degree of activity for polycondensation and results in polymers having better optical properties (eg, less unwanted color, less light absorbance and less light scattering) compared to the polymer obtained using an organic titanate catalyst alone, or titanate catalyst systems described in the prior art. The catalyst system is prepared by adding an organic titanate, a compound that will provide the ligands (such as an organic silicate and / or an organic zirconate) and preferably an organic phosphoric acid and / or phosphoric acid, to the selected alcohol. The alcohol that is typically selected will be the glycol used for the preparation of the polyester (i.e., ethylene glycol for the PET), for its convenience to carry out the polymerization process. Polyester is produced at a minimum temperature to help reduce byproducts by thermal degradation, and in an atmosphere with a minimum amount of oxygen, to help reduce byproducts by oxidative degradation, and in contact with building materials that leave minimal impurities in the reaction mixture. The polymer can be of any molecular weight, but it is currently preferred that the average molecular weight be about 21,000 and more preferably above 44,000 Daltons. The polymer can also be prepared with comonomers having at least one alcohol group or at least one acid group, or both groups. The concentration of the titanate catalyst may be from about 0.01 to 500 ppm, preferably from 0.5 to 100 ppm. ORGANIC TITANATE Organic titanates can be selected to prepare the present invention, they have the general formula: Ti (OR) 4 wherein R is a ligand group typically composed of carbon, oxygen, phosphorus, silicon and / or hydrogen. Typically each ligand group R may contain at least one carbon, preferably 3 or more. The presence of a halide or other active substituent in the ligand group is generally avoided since such groups can interfere with the catalytic reactions or form undesired byproducts, which could contaminate the polymer. Since different ligand groups may be present in the same titanium atom, generally these may be identical to facilitate the synthesis of the titanate. In some cases 2 or more R groups may come from a common compound chemically linked to another place than titanium (i.e., a multidentate ligand such as triethanolamine, citric acid, glycolic acid, malic acid, succinic acid, ethanediamine). For the description of dentate ligands, see for example F. Albert Cotton and G. Wilkinson, Advanced Inorganic Chemistry, 4tn ed., Wiley-Interscience, 1980. Organic titanates are commonly prepared by mixing titanium tetrachloride with the selected precursor alcohol in the presence from a base, such as ammonia, to form the tetraalkyl titanate. The alcohol typically is ethanol, n-propanol, isopropanol, n-butanol or isobutanol. Usually methanol is not selected, that the resulting tetramethyl titanate is insoluble in the reaction mixture, which complicates its isolation. The tetraalkyl titanates produced in this manner are recovered by first removing the ammonium chloride that is formed as a by-product (e.g., by filtration) and then distilling the tetraalkyl titanate from the reaction mixture. This process is generally limited to the production of titanates having 4 carbon atoms or shorter alkyl groups, since the high temperatures required to distill longer chain titanates (eg, tetra-2-hexyl titanate) cause titanate degradation. . Titanates having longer alkyl groups are conveniently prepared by the transesterification of those having alkyl groups of up to 4 carbon atoms with longer chain alcohols. As a practical point, the selected tetraalkyl titanate will usually have alkyl chains of less than 12 carbon atoms, since the solubility of the titanate tends to decrease and manufacturing costs tend to increase as the number of carbons increases. Some commercial representatives of organic titanates that can be advantageously selected include Tyzor® TPT (tetraisopropyl titanate), TBT (tetra-n-butyl titanate) and TE (X titanate). isopropoxide triethanolamine) available from E. I. du Pont de Nemours and Company, Wilmington, Delaware, E.U.A. ORGANIC PHOSPHORO COMPOUNDS Organic phosphonic and phosphinic acids can be included in the organic titanate-ligand catalyst solution to block titanium sites that would otherwise fix materials such as phosphorus that are typically present in the polymerization solution. However, if such materials are not present, there is no need to include these acids. Without adhering to any theory, it appears that the conjugate base of the acid binds to the organic titanate during the preparation of the catalyst system. The phosphonic and phosphinic acids have an alkyl or aryl group directly linked to the phosphorus atom. Typically, the alkyl group will be a lower alkyl group, having up to 3 carbon atoms, such as a methyl or ethyl group. If an aryl group is selected, it may be a phenyl or naphthyl ring. The alkyl and aryl groups may be substituted with substituent groups that do not unduly interfere with the preparation of the catalyst system and with the subsequent reactions that use the catalyst. If phosphonic acid is selected, one of the two OH groups linked to the phosphorus atom can be esterified, if desired. The Phosphonic acid esters usually do not bind effectively to the titanate, so they will not be selected. Organic phosphonic acids tend to be stronger chelating agents than phosphinic acids and can be selected for applications in which a strong bond between the phosphorus compound and the organic titanate is desired. Phenylphosphinic acid and diphenylphosphinic acid have been found to provide an excellent balance between the reaction rate and the prevention of color generation, when the catalyst system is used as a polycondensation catalyst for the preparation of PET. ORTO-SILICATES AND ZIRCONATES The organic titanate-ligand catalyst system contains a cocatalyst or ligand radical, typically added as ortho-silicate and / or organic zirconate, to improve the color of the polymer prepared with the catalyst system and to promote the solubility of the system catalyst in the glycol (ie, to make the catalyst system soluble in glycol). The term "glycol soluble" as used herein, means that essentially all of the titanium present in the catalyst system is dissolved in ethylene glycol, at room temperature, at the catalyst concentrations. desired for the particular application. Normally the components are selected to form a catalyst system which is dissolved in concentrations of at least 3 grams, preferably at least 5 grams of the catalyst per 100 grams of the glycol, to minimize the amount of glycol introduced into the reaction where The catalyst system is used. However, sufficient glycol must be present to allow effective control over the rate of catalyst addition for purposes of controlling the process. The ortho-silicates and organic zirconates that can be selected advantageously have the structure Si (OR)? and Zr (OR) 4, respectively, and are generally prepared by introducing silicon tetrachloride or zirconium tetrachloride in an alcohol bath, to replace the chloride groups with alkyl groups in the alcohol, in the same manner as described above for preparing the Ti ( OR> 4. The R group is a ligand typically composed of carbon, oxygen, phosphorus and / or hydrogen.The presence of a halide or other active substituent in the ligand group, is generally avoided since such groups can interfere with catalytic reactions or form undesirable byproducts that could contaminate the polymer, since different ligand groups may be present in the same titanium atom, so In general, these will be identical to facilitate the synthesis of the titanate. In some cases two or more R groups may come from a common chemically linked compound, in a different place from the titanium atom (ie, a ligated ligand such as triethanolamine, citric acid, glycolic acid, malic acid, succinic acid, ethylenediamine). ).

If an organic silicate is selected, R is an alkyl group having 1 to 8 carbon atoms. The tetraethyl and tetra-n-propyl ortho-silicates are examples of compounds available from the Silbond Company under the trademark "Silbond". The tetraethyl ortho-silicate is the preferred ingredient. If an organic ortho-zirconate is selected, R is an alkyl group of 2 to 8 carbon atoms. The tetra-n-propyl ortho-zirconate and tetra-n-butyl are examples of organic zirconates available from E. I. du Pont de Nemours and Company under the trademark "Tyzor". The selection of a particular ortho-silicate or zirconate will vary depending on the particular reaction being promoted. However, an orthosilicate is preferred over an orthozirconate, since it has less effect on the rate of condensation. PREPARATION OF THE CATALYST The catalyst system can be prepared in ethylene glycol. While the components can be add to glycol in any order, it is preferred to first add the organic orthosilicate or zirconate and then add the organic phosphonic or phosphonic acid, since the organic silicate or zirconate helps to dissolve the phosphorus compound. In general, the mixture is stirred and can be slightly heated (e.g., from 40 to 45 ° C) to completely dissolve the organic phosphonic or phosphinic acid. A minimum amount of the glycol (e.g., from 10 to 20 moles per mole of organic titanate which will be added later) is used to facilitate the subsequent reaction between the organic phosphonic or phosphinic acid and the organic titanate. The presence of too much glycol has no useful purpose and unnecessarily increases the amount of glycol that is handled in the process. Then, the organic titanate is added to the glycol solution containing the phosphorus compound and the orthosilicate and / or organic zirconate, conveniently at room temperature and under stirring. This addition is typically carried out under an inert atmosphere, such as nitrogen, since the organic titanate (e.g., tetraisopropyl titanate) reacts with the phosphorus compound, releasing a flammable alcohol (e.g., isopropanol). This reaction is exothermic, causing the temperature of the glycol solution to rise from 10 to 30 ° C (for the particular components mentioned above).

Normally the organic titanate will be added with agitation in a period of 0.5 to 2 hours or more, then it is allowed to cool to room temperature. Then the catalyst system is ready for use. Alternatively, the phosphonic or phosphinic acid can be reacted with the titanate to form a complex that can be isolated from the alcohol obtained as a by-product of the reaction, by filtration. The isolated complex can then be added to a mixture of the orthosilicate or zirconate, in ethylene glycol. The relative amounts of the components will vary according to the selected compounds, but are generally selected in such a way that the molar ratio of P: Ti in the catalyst system is within the range of 1: 1 to 4: 1. Larger amounts of the phosphorus compound tend to cause an unacceptable decrease in catalytic activity, while lower amounts tend to create an unacceptable level of polymer discoloration. The molar ratio of Si or Zr: Ti will usually be selected within a range of 1: 1 to 4: 1, since higher silicate or zirconate loads tend to cause an unacceptable loss in polymerization rate (with some color degradation) and lower charges usually do not provide the desired level of glycol solubility. The molar ratio of P: Si or Zr, will normally be greater than or equal to 0.5: 1, already > that lower ratios typically cause unacceptable levels of PET discoloration. The structure of the catalyst system has not been established. However, based on the observed exotherm, it is believed that the components have reacted or complexed in some way to form binary or tertiary compositions, at least to some degree, which makes the catalyst system especially useful as a polycondensation catalyst in the manufacture of PET. POLYMERIZATION REACTION Antimony compounds are currently the catalysts of choice for the polycondensation reaction that forms PET, either through transesterification, or through the route of direct esterification. In accordance with the present invention, the catalyst system described above is replaced in whole or in part by the antimony catalyst to form PET having the desired optical properties (ie, it does not have or has acceptable levels of discoloration and reduced light absorption). ). The catalyst system efficiently promotes the polycondensation reaction at the commercially required rates comparable to those achieved with the conventional antimony catalysts. Because it can be soluble in glycol, the catalyst can be easily distributed evenly throughout the reaction mass, minimizing production control problems and producing PETs of uniform quality. The catalysts are compatible with conventional esterification and transesterification catalysts (e.g., manganese, cobalt and / or zinc salts) and the production process can be introduced concurrently with or after the introduction of the esterification catalyst. It has also been found that the new catalysts are effective to promote the esterification reaction and "can be used as substitutes for part or all of the esterification catalyst, as well as the polycondensation catalyst." The amounts of catalyst will vary according to the selected process , but will generally be in the range of 0.01 to 2000 ppm of titanium, based on the weight of the prepolymer in the polycondensation reaction mass.The preferred range selected in the PET preparation is from 10 to 200 ppm, typically from 10 to 200 ppm. 50 ppm Other ingredients may also be present to enhance catalyst stability or performance.

The catalyst system is particularly useful for preparing PET having an average molecular weight of 21,000 or greater, typically used in applications such as films, resins for engineering and bottling, and fibers. Comonomers may be present to modify the properties of the resulting PET copolymer. For example, the comonomers may comprise diethylene glycol, dipropylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, glycolic acid, isophthalic acid, 2,6-naphthoic acid, isophthalic acid with lithium sulfonate. While the present invention has been described in detail with respect to PET, it also applies to other poly (alkylene arylates) when it is desired to use an antimony alternative as a polycondensation catalyst, while still obtaining excellent optical properties. Having described the present invention, it will now be illustrated, but not limited, by the following examples. EXAMPLES AND COUNTERMEASURES All the examples and counterexamples were prepared identically, except for the identity of the catalyst systems that are added. A master batch of oligo (ethylene terephthalate) was prepared by esterification of terephthalic acid and ethylene glycol, without catalyst, up to an average polymerization degree of 16. The use of a masterbatch of esterified oligomer helps to avoid loss of material due to sublimation during polycondensation and increases the reproducibility of the experimental results. All examples and counterexamples were made from quantities of this single master batch of this oligo (ethylene terephthalate). For each example and counterexample a 1 liter resin container was provided with a Jiffy Mixer with rotation at 60 rpm, a thermocouple, a condenser and a nitrogen absorber. To this vessel was added 400 grams of oligo (ethylene terephthalate), 115 ml of ethylene glycol and then the catalyst system to be tested. The agitator was turned on and the temperature was increased to 275 ° C in a period of 45 minutes. The contents were polymerized maintaining the stirring at 275 ° C and a pressure of 120 torr for 20 minutes, and at 280 ° C at a pressure of 30 torr for another 20 minutes. Afterwards, the contents were kept under agitation at 280 ° C at a pressure of 0.5 torr for a sufficient time to reach 15 oz-pg (ounce-inch) of torque, measured with an Electro-Craft Motomatic torsion controller. The time in minutes of this stage was recorded as the Final Time and was varied according to the catalyst used. Subsequently, the polymer melted was emptied in a water bath to solidify. A portion of the resulting solid was annealed at 160 ° C for 16 hours and triturated to pass through a 2 mm filter for color measurements, in the manner previously described. A separate portion of the resulting solid was placed between two sheets of metal, melt pressed to a thickness typically 7 mils, and an amorphous film formed for the light absorption measurements, in the manner previously described. The following Table of Examples and the Table of Counterexamples provide the catalyst system briefly, the aforementioned Completion Time in minutes; the average molecular weight M2, determined by size exclusion chromatography in a solvent of hexafluoroisopropanol; the reflected color measurements of Hunter L, a and b of the ground powder, in the manner previously described; and the absorbance of light per unit of film thickness (ABS / L) for the film portion, in the manner described above. The catalyst components added to each resin container were measured in grams relative to the weight of the master batch of oligo (ethylene terephthalate) in grams, expressed in parts per million, ie, mg of aggregate catalyst per kg of oligomer. The Table of Examples and the Table of Counterexamples report the weight of the component catalyst in ppm of the active element within the catalyst compound, such as ppm titanium for a titanium compound, ppm silicon for a silicon compound, ppm zirconium for a zirconate compound or ppm phosphorus for a phosphorus acid. The abbreviations of each compound are identified after the table in which the compound has appeared. Table of Examples Tyzor TE is titanium (IV) isopropoxide (triethanolamine) isopropoxide commercially available from E.l. du Pont de Nemours, Inc. TPZr is tetra-n-propyl zirconate TEOS is tetraethyl orthosilicate H3PO4 is phosphoric acid Ti (PhP) 4 is salt of tetra-phenylphosphinate of titanium (IV) Zr (PhP) is salt of tetra-phenylphosphinate of zirconium (IV) Zr (acac) 4 is tetra (acetylacetonate) of zirconium (IV) Zr (Bu2PHO) is tetra (dibutylphosphinate) of zirconium TLF8954 is a mixture of Ti (OC3H.) 3 [02P (OC4H.) 2] Ti (OC3H7) 3 [0 (HO) P (OC4H9)] Table of Counterexamples Sb2? 3 is antimony trioxide Ti (OBu) is tetra (n-butoxide) titanium (IV) Zr (OPr) is tetra (n-propoxide) zirconium (IV) H3PO4 is phosphoric acid Ti (TEA) 4 is tetrakis -triethanolamine titanium (IV) Ti (OiPr) 4 is tetra (isopropoxide) titanium (IV) Ti (OAc) 4 is tetra (acetate) titanium (IV) ZrOCl2 is zirconyl dichloride ZrO (N? 3) 2 is zirconium dinitrate Zr (acac) 4 is zirconium tetrakis (acetylacetonate) (IV) Zr (EDTA) is zirconium (IV) edetic acid salt (MBT) is zirconium mercaptobenzotriazole (IV) Tyzor TE is (triethanolamine) isopropoxide of titanium (IV) supplied commercially by El du Pont de Nemours, Inc. TEO? is tetraethylorthosilicate Ti (PhP) is tetra-phenylphosphinate salt of titanium (IV) Zr (PhP) a is tetra-phenylphosphinate salt of zirconium (IV) Zr (acac) 4 is tetra (acetylacetonate) of zirconium (IV) TLF8954 is a mixture of Ti (OC3H7) 3 [02P (OC4H9) 2] + Ti (OC3H7) 3.02 (HO) P (OC4H9)] Examples 1 and 2 illustrate the use of titanate, silicate, zirconate and oxyphosphorus compounds. The polymerization times are small to reach a high weight molecular and final materials have little color (low values of Hunter a, b) and absorb very little light (high value of Hunter L and low value ABS / L). This system illustrates excellent results for the preferred polymer quality. Example 3 uses a single catalyst system of organic titanate-phosphinate ligand and a combination of organic titanate-phosphinate and organic zirconate-phosphinate, respectively. The polymerizations reach a high molecular weight quickly and the products transmit light well, although the color of Hunter b is high. Examples 5, 6 and 7 are additional examples using other organic compounds of titanate, zirconate and oxyphosphorus. The polymerization times are low to achieve high molecular weights, while the color of the product is low and the total absorption of light within the films is low. Counterexample 1 illustrates the typical performance of antimony catalysts at the concentrations typically used in commercial manufacturing. Although the value of Hunter b is low, the Finish Time is prolonged and the polymer films absorb too much light (highest value of ABS / L). Counterexamples 2 and 3 are counterexamples of the technology described in the Hoeschele Patent [US 5,120,822] and Schultheis [US 3,326,965]. Compared with the examples of the present invention, these materials are more yellow (higher b-values) and absorb more light (higher ABS / L value). Thus, this use of titanates and zirconates is not as desirable as the examples. However, the Hoeschele patent specifically excludes the consideration of titanates and zirconates for PET, since the repeating unit of ethylene glycol has "neighboring" alcohols. Counterexample 4 illustrates that the addition of phosphoric acid greatly extends the Finish Time without improving the Hunter b value or the light absorbance of the film. The results of the use of titanates and zirconates in the polymerization of PET, are not anticipated by the patents because we have learned (a) when phosphoric acid is added to a polymerization mixture the catalysts of titanium alkoxide are no longer highly active and (b) zirconium alkoxides form gels in ethylene glycol. The catalyst and cocatalyst systems employed to prepare polyethylene terephthalate of the present invention are soluble in ethylene glycol, which allows a convenient injection of the catalyst into the polymerizing mixture. Counterexamples 5, 6 and 7 are counterexamples of the technology described in the Werber Patent [U.S. 3,056,818]. Counterexamples 8 and 9 illustrate this technology when phosphoric acid is added to the mixture of reaction. Compared to the examples, the polymerization times are longer, since the catalyst is more deactivated when H3PO4 is added to the polymerization mixture. The final materials absorb more light (higher ABS / L value). Thus, this use of titanates is not as desirable as the examples. The investigation provides the unanticipated result that erber titanium and / or zirconium catalysts are deactivated even by small amounts of metal scavengers, e.g., phosphoric acid, present during polymerization. In addition, no results are mentioned that include Ti + Zr, nor is there any mention of benefits from the combination. Werber's claims include compounds that produce color and / or have only a minute solubility in ethylene glycol. The examples also quantify the surprisingly high reaction rate with the color and light transmission advantages of the use of oxyphosphorus-containing ligands in the titanate and / or zirconate. Counterexamples 10 and 11 are counter-examples of the technology described in the Hasegawa Patent [JP 46-27,552]. Counterexamples 12 and 13 illustrate the effect of adding phosphoric acid to the reaction mixture. Compared to the examples, the final materials are much more yellow (higher Hunter b values) and absorb more light (higher ABS / L values). Thus, this use of the titanates and zirconates is not as desirable as the examples. The results of Hasegawa do not mention color properties or light absorbance of the final material, only the heat resistance. The titanate is reacted with a titanium fatty acid salt and only titanium acetate is described. In addition, all zirconium compounds are restricted to zirconils. The only compound Zr + P mentioned is zirconyl metaphosphate, which is insoluble in ethylene glycol. The counterexamples show that zirconils have a detrimental effect on the color and light absorbance properties of the final material. Counterexample 14 contains the same organic titanium-ligand catalyst system as in Example 6, except that the titanium concentration is four times higher. Polymerization times, average molecular weights and colors are comparable, however counter-example 14 absorbs much more light. So, it is not useful in some critical applications. The counter-example 15 contains the same catalyst system as Example 4 in the same relative concentrations, with the addition of phosphoric acid. The polymerization times, the molecular weights of the product and the Hunter L values, a are comparable. Although the Counterexample 15 is much less yellow, absorbs more light. In this field it is known that the addition of phosphoric acid reduces color, but this is obtained with the price of increasing the absorbance of global light. So, this counterexample is not useful in some critical applications. Counterexamples 16 and 17 use the same organic titanate-ligand catalyst as in Examples 1, 2, 5 and 7, except that it is with different cocatalyst systems. In both cases, high molecular weights are achieved with lower reaction times, such that they are effective catalysts. The products of the previous runs are substantially less colorful, but both runs produce polymers that absorb substantial amounts of light (higher ABS / L value). Therefore, these products are not useful in some critical applications. ADDITIONAL EXAMPLES Example 8. Preparation of poly (propylene terephthalate) Oligo (propylene terephthalate) was prepared by esterification of terephthalic acid and 1,3-propylene glycol, without a catalyst, up to an average polymerization number of about 16. A 1-liter resin vessel was provided with a Jiffy Mixer stirrer rotating at 60 rpm, a thermocouple, a condenser and a nitrogen eliminator. To this ..--. .-----. container was added 400 grams of oligo (propylene terephthalate), 115 ml of propylene glycol and then an organic titanate-ligand catalyst system. The agitator was turned on and the temperature was increased to 225 ° C in a period of 45 minutes. The contents were polymerized maintaining the agitation at 255 ° C and a pressure of 220 torr for 20 minutes and at 255 ° C at 30 torr pressure for another 20 minutes. Afterwards, the contents were kept under agitation at 255 ° C at 0.5 torr of pressure for a sufficient time to reach 15 oz-pg (ounce-inch) of torque, measured with an Electro-Craft Motomactic torque controller. The time in minutes for this stage is recorded as the Completion Time and this varies according to the catalyst used. Then, the molten polymer is emptied into a water bath to solidify it. A portion of the resulting solid is subjected to an annealing at 160 ° C for 16 hours and crushed to pass through a 2 mm filter for the previously described color measurements. A separate portion of the resulting solid is placed between two metal sheets, pressed by melting to a thickness typically 7 mils, an amorphous film is formed for the light absorption measurements as previously described. The average molecular weight is greater than 21,000 and the ABS / L value is less than 6.1 Example 9. Preparation of poly (butylene terephthalate) Oligo (butylene terephthalate) was prepared by esterification of terephthalic acid and butylene glycol without catalyst, up to an average polymerization number of about 16. A 1 liter resin vessel was provided with a Jiffy Mixer agitator rotating at 60 rpm, a thermocouple, a condenser and a nitrogen eliminator. To this vessel was added 400 grams of oligo (butylene terephthalate), 115 ml of butylene glycol and then an organic titanate-ligand catalyst system. The agitator was turned on and the temperature was increased to 275 ° C in a period of 45 minutes. The content was polymerized maintaining the stirring at 275 ° C and a pressure of 120 torr for 20 minutes and at 275 ° C at 30 torr pressure for another 20 minutes. Afterwards, the contents were kept stirred at 275 ° C 'at 0.5 torr of pressure for a sufficient time to reach 15 oz-pg (ounce-inch) of torque, measured with an Electro-Craft Motomactic torque controller. The time in minutes for this stage is recorded as the Completion Time and this varies according to the catalyst used. Then, the molten polymer is emptied into a water bath to solidify it. A portion of the resulting solid is subjected to an annealing at 160 ° C for 16 hours and crushed to pass through a 2 mm filter for measurements of color previously described. A separate portion of the resulting solid is placed between two metal sheets, pressed by melting to a thickness typically 7 mils, an amorphous film is formed for the light absorption measurements as previously described. The average molecular weight is greater than 21,000 and the ABS / L value is less than 6.1 Example 10. Preparation of poly (propylene naphthalate) Oligo (propylene naphthalate) was prepared by esterification of 2, 6-naphthaoic acid and 1, 3-propylene glycol without catalyst, up to an average polymerization number of about 16. A 1 liter resin vessel was provided with a Jiffy Mixer stirrer at 60 rpm, a thermocouple, a condenser and a nitrogen scavenger. To this vessel was added 400 grams of oligo (propylene naphthalate), 115 ml of propylene glycol and then an organic titanate-ligand catalyst system. The agitator was turned on and the temperature was increased to 255CC in a period of 45 minutes. The contents were polymerized maintaining the agitation at 255 ° C and a pressure of 120 torr for 20 minutes and at 255 ° C at 30 torr pressure for another 20 minutes. Afterwards, the contents are kept under agitation at 255 ° C at 0.5 torr of pressure for a sufficient time to reach 15 oz-pg (ounce-inch) of torque, measured with a controller of Electro-Craft Motomactic twist. The time in minutes for this stage is recorded as the Completion Time and this varies according to the catalyst used. Then, the molten polymer is emptied into a water bath to solidify it. A portion of the resulting solid is subjected to an annealing at 160 ° C for 16 hours and crushed to pass through a 2 mm filter for the previously described color measurements. A separate portion of the resulting solid is placed between two metal sheets, pressed by melting to a thickness typically 7 mils, an amorphous film is formed for the light absorption measurements as previously described. The average molecular weight is greater than 21,000 and the ABS / L value is less than 6.1 Example 11. Preparation of poly (ethylene naphthalate) Oligo (ethylene naphthalate) was prepared by esterification of 2,6-naphthoic acid and ethylene glycol without catalyst, up to an average polymerization number of about 16. A 1 liter resin vessel was provided with a Jiffy Mixer stirrer at 60 rpm, a thermocouple, a condenser and a nitrogen eliminator. To this vessel was added 400 grams of oligo (ethylene naphthalate), 115 ml of ethylene glycol and then an organic titanate-ligand catalyst system. The agitator was turned on and the temperature increased to 275 ° C in a period of 45 minutes. The content was polymerized maintaining the stirring at 275 ° C and a pressure of 120 torr for 20 minutes and at 275 ° C at 30 torr pressure for another 20 minutes. Afterwards, the contents were kept stirred at 275 ° C at 0.5 torr of pressure for a sufficient time to reach 15 oz-pg (ounce-inch) of torque, measured with an Electro-Craft Motomactic torque controller. The time in minutes for this stage is recorded as the Completion Time and this varies according to the catalyst used. Then, the molten polymer is emptied into a water bath to solidify it. A portion of the resulting solid is subjected to an annealing at 160 ° C for 16 hours and crushed to pass through a 2 mm filter for the previously described color measurements. A separate portion of the resulting solid is placed between two metal sheets, pressed by melting to a thickness typically 7 mils, an amorphous film is formed for the light absorption measurements as previously described. The average molecular weight is greater than 21,000 and the ABS / L value is less than 6.1 Example 12. Preparation of poly (ethylene isophthalate) Oligo (ethylene isophthalate) was prepared by esterification of isophthalic acid and ethylene glycol without catalyst, up to average polymerization number of approximately 16. A 1 liter resin vessel was provided with a Jiffy Mixer rotating at 60 rpm, a thermocouple, a condenser and a nitrogen scavenger. To this vessel were added 400 grams of oligo (ethylene isophthalate), 115 ml of ethylene glycol and then an organic titanate-ligand catalyst system. The agitator was turned on and the temperature was increased to 275 ° C in a period of 45 minutes. The content was polymerized maintaining the agitation at 275 ° C and a pressure of 120 torr for 20 minutes, and at 275 ° C at 30 torr pressure for another 20 minutes. The content was maintained under agitation at 275 ° C at 0.5 torr pressure for a sufficient time to reach 15 oz-pg (ounce-inch) of torque, measured with an Electro-Craft Motomactic torque controller. The time in minutes for this stage is recorded as the Completion Time and it varies according to the catalyst used. Then, the molten polymer is emptied into a water bath to solidify it. A portion of the resulting solid is subjected to an annealing at 160 ° C for 16 hours and crushed to pass through a 2 mm filter for the previously described color measurements. A separate portion of the resulting solid is placed between two metal sheets, pressed by melting to a thickness typically 7 mils, an amorphous film is formed for the absorption measurements of light as previously described. The average molecular weight is greater than 21,000 and the ABS / L value is less than 6.1 Example 13. Preparation of poly (propylene isophthalate) Oligo (propylene isophthalate) was prepared by esterification of isophthalic acid and 1,3-propylene glycol without catalyst, to an average polymerization number of about 16. A 1 liter resin vessel was provided with a Jiffy Mixer stirrer at 60 rpm, a thermocouple, a condenser and a nitrogen scavenger. To this vessel was added 400 grams of oligo (propylene isophthalate), 115 ml of propylene glycol and then an organic titanate-ligand catalyst system. The agitator was turned on and the temperature was increased to 275 ° C in a period of 45 minutes. The content was polymerized maintaining the stirring at 275 ° C and a pressure of 120 torr for 20 minutes and at 275 ° C at 30 torr pressure for another 20 minutes. Afterwards, the contents were kept under agitation at 275 ° C at 0.5 torr of pressure for a sufficient time to reach 15 oz-pg (ounce-inch) of torque, measured with an Electro-Craft Motomactic torque controller. The time in minutes for this stage is recorded as the Completion Time and this varies according to the catalyst used. Then, the molten polymer is emptied into a water bath to solidify it.

A portion of the resulting solid is subjected to an annealing at 160 ° C for 16 hours and crushed to pass through a 2 mm filter for the previously described color measurements. A separate portion of the resulting solid is placed between two metal sheets, pressed by melting to a thickness typically 7 mils, an amorphous film is formed for the light absorption measurements as previously described. The average molecular weight is greater than 21,000 and the ABS / L value is less than 6.1 Example 14. Preparation of poly (ethylene-co-propylene terephthalate) Oligo (ethylene terephthalate) was prepared by esterification of terephthalic acid and ethylene glycol without catalyst, to an average polymerization number of about 16. A 1 liter resin vessel was provided with a Jiffy Mixer stirrer at 60 rpm, a thermocouple, a condenser and a nitrogen scavenger. To this vessel was added 400 grams of oligo (ethylene terephthalate), 115 ml of propylene glycol and then an organic titanate-ligand catalyst system. The stirrer was turned on and the temperature was increased to 255 ° C in a period of 45 minutes. The content was polymerized maintaining the stirring at 255 ° C and a pressure of 120 torr for 20 minutes and at 255 ° C at 30 Press for another 20 minutes. Afterwards, the contents were kept under agitation at 255 ° C at 0.5 torr of pressure for a sufficient time to reach 15 oz-pg (ounce-inch) of torque, measured with an Electro-Craft Motomactic torque controller. The time in minutes for this stage is recorded as the Completion Time and this varies according to the catalyst used. Then, the molten polymer is emptied into a water bath to solidify it. A portion of the resulting solid is subjected to an annealing at 160 ° C for 16 hours and crushed to pass through a 2 mm filter for the previously described color measurements. A separate portion of the resulting solid is placed between two metal sheets, pressed by melting to a thickness typically 7 mils, an amorphous film is formed for the light absorption measurements as previously described. The average molecular weight is greater than 21,000 and the ABS / L value is less than 6.1 Example 15. Preparation of poly (ethylene-co-propylene naphthalate) Oligo (ethylene naphthalate) was prepared by esterification of naphthalic acid and ethylene glycol without catalyst, to an average polymerization number of approximately 16. A 1 liter resin vessel was provided with a Jiffy Mixer stirrer rotating at 60 rpm, a thermocouple, a condenser and a nitrogen eliminator. To this vessel was added 400 grams of oligo (ethylene naphthalate), 115 ml of propylene glycol and then an organic titanate-ligand catalyst system. The stirrer was turned on and the temperature was increased to 255 ° C in a period of 45 minutes. The contents were polymerized maintaining the agitation at 255 ° C and a pressure of 120 torr for 20 minutes and at 255 ° C at 30 torr pressure for another 20 minutes. Afterwards, the contents were kept under agitation at 255 ° C at 0.5 torr of pressure for a sufficient time to reach 15 oz-pg (ounce-inch) of torque, measured with an Electro-Craft Motomactic torque controller. The time in minutes for this stage is recorded as the Completion Time and this varies according to the catalyst used. Then, the molten polymer is emptied into a water bath to solidify it. A portion of the resulting solid is subjected to an annealing at 160 ° C for 16 hours and crushed to pass through a 2 mm filter for the previously described color measurements. A separate portion of the resulting solid is placed between two metal sheets, pressed by melting to a thickness typically 7 mils, an amorphous film is formed for the light absorption measurements as previously described. The average molecular weight is greater than 21,000 and the ABS / L value is less than 6.1 It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention is that which is clear from the present description of the invention.

Claims (22)

1. CLAIMS Having described the invention as an antecedent, the content of the following claims is claimed as property: 1. A poly (ethylene terephthalate) characterized in that it has an average molecular weight of at least 21,000 and contains between 0.5 and 500 ppm of catalyst residue. titanium, where the polyethylene terephthalate has an ABS / L value of less than 7, a Hunter L value of greater than 65, a Hunter value of between -1 and +2 and a Hunter value of b between -2 and 6 2. The poly (ethylene terephthalate) according to claim 1, characterized in that the catalyst residue is from a catalyst system prepared by adding an organic titanate having the formula Ti (OR) 4 wherein each R is an alkyl group which has up to 12 carbon atoms, an organic phosphonic or phosphinic acid and an organic ortho-silicate or zirconate, to ethylene glycol. The poly (ethylene terephthalate) according to claim 2, characterized in that the concentration of the mixture of organic titanate, phosphonic acid or organic phosphinic and organic ortho-silicate or zirconate in the glycol is at least 5% in weight. 4. The poly (ethylene terephthalate) of according to claim 3, characterized in that the molar ratios of titanium, phosphorus and zirconium are P / Ti, 1: 1 to 4: 1, Zr / Ti, 1: 1 to 4: 1; P / Zr greater than or equal to 0.5: 1. The poly (ethylene terephthalate) according to any of claims 2, 3, or 4, characterized in that the organic titanate is tetraisopropyl titanate, tetra-n-butyl titanate or mixtures thereof. The poly (ethylene terephthalate) according to any of claims 2, 3 or 4, characterized in that a tetraalkyl ortho-zirconate is added to the ethylene glycol. 7. The poly (ethylene terephthalate) according to any of claims 2, 3 or 4, characterized in that phenylphosphinic acid and a tetraalkyl ortho-zirconate are added to ethylene glycol. 8. A poly (alkylene arylate) polymer characterized in that it has an average molecular weight of at least 21,000, contains from about 0.1 to 500 ppm of titanium residue from the organic titanate-ligand catalyst system and has an ABS / L value less than or equal to 6.0. 9. The poly (alkylene arylate) polymer according to claim 8, characterized in that the poly (alkylene arylate) polymer has an ABS / L value less than or equal to 6.1, a Hunter L value greater than 65, a Hunter value between -2 and +2 and a Hunter value b between -2 and 6.0. The poly (alkylene arylate) polymer according to claim 8, characterized in that the poly (alkylene arylate) polymer has an ABS / L value less than or equal to 5.0. The poly (alkylene arylate) polymer according to claim 8, characterized in that the poly (alkylene arylate) has an ABS / L value of less than or equal to 4.0. 12. A poly (alkylene arylate) polymer, characterized in that it has an average molecular weight of at least about 21,000 which contains about 0.5 to 500 ppm of titanium residue of an organic titanate-ligand catalyst solution, such poly ( Alkylene arylate has a value of ABS / L less than 6.1, a Hunter L value greater than 65, a Hunter value between -2 and +2, and a Hunter value b between -2 and 8.3. 13. The poly (alkylene arylate) polymer according to claims 8 to 12, characterized in that the poly (alkylene arylate) polymer is selected from the group consisting of poly (ethylene terephthalate), poly (propylene terephthalate), poly (butylene terephthalate), poly (ethylene naphthalate), poly (propylene naphthalate), poly (butylene naphthalate), poly (ethylene isophthalate), poly (propylene isophthalate), poly (butylene isophthalate), and combinations of two or more of them. The poly (alkylene arylate) polymer according to any of claims 8 to 13, characterized in that the poly (alkylene arylate) polymer is a copolymer or homopolymer of poly (ethylene terephthalate). 15. The poly (alkylene arylate) polymer according to claims 8 to 13, characterized in that the poly (alkylene arylate) polymer is a copolymer or homopolymer of poly (propylene terephthalate). 16. The poly (alkylene arylate) polymer according to any of claims 8 to 13, characterized in that the poly (alkylene arylate) polymer is a copolymer or homopolymer of poly (butylene terephthalate). The poly (alkylene arylate) polymer according to any of claims 8 to 13, characterized in that the poly (alkylene arylate) polymer is a copolymer or homopolymer of poly (ethylene naphthalate). 18. The poly (alkylene arylate) polymer according to any of claims 8 to 13, characterized in that the poly (alkylene arylate) polymer is a copolymer or homopolymer of poly (propylene naphthalate). The poly (alkylene arylate) polymer according to any of claims 8 to 13, characterized in that the poly (alkylene arylate) polymer is a copolymer or homopolymer of poly (butylene naphthalate). 20. The poly (alkylene alkali) polymer according to any of claims 8 to 13, characterized in that the poly (alkylene arylate) polymer is a copolymer or homopolymer of poly (ethylene isophthalate). The poly (alkylene arylate) polymer according to any of claims 8 to 13, characterized in that the poly (alkylene arylate) polymer is a copolymer or homopolymer of poly (propylene isophthalate). The poly (alkylene arylate) polymer according to any of claims 8 to 13, characterized in that the poly (alkylene arylate) polymer is a copolymer or homopolymer of poly (butylene isophthalate).