MXPA99011497A - Method for producing polyesters and copolyesters - Google Patents

Abstract

The invention relates to a method for producing polyesters and copolyesters. According to said method, coprecipitates are used as polycondensation catalysts alone or as mixtures, which coprecipitates were produced by simultaneous hydrolytic precipitation of a titanium compound and a metal compound of a metal selected from the groups IA, IIA, VIIIA, IB, IIB, IIIB and IVB. The titanium compound and the metal compound independently of each other are an alkylate, alcoholate or carboxylate of the titanium or metal and the molar ratio of titanium compound to metal compound is=50:50 mol/mol. The coprecipitates have a greater catalytic activity than Sb2O3, so that the preferred quantity used is only between 10 and 100 ppm in relation to the esters or oligo-esters to be polycondensated.

Description

PROCEDURE TO PRODUCE POLYESTERS AND COPOLYTHERES DESCRIPTIVE MEMORY Regardless of their constitution, which can cover a number of possible variations from aliphatic to fully aromatic, polyesters and copolyesters are generally produced in a two-stage process. In the first stage the esters that have to pass through polycondensation, or a polyester precondensate consisting of a mixture of oligoesters and having an average relative molecular weight of normally 100-200 depending on the molar ratio of the starting compounds, produced by transesterification of dicarboxylic acid esters or esterification of dicarboxylic acids with an excess of dialcohols. If a branching modification is desired, limited amounts of more functional starting components such as glycerin, pentaerythritol, or trimellitic acid may also be used. The methods of equivalent procedures for the first stage are the conversion of dicarboxylic acid chlorides with diols, the adhesion of ethylene oxide to dicarboxylic acids, the esterification of an anhydride with a dialcohol, the conversion of anhydrides with epoxides, and the conversion of dicarboxylic acids or dicarboxylic acid esters with the diacetate of a diol. The second reaction stage is the current polycondensation, in which the desired high molecular weight of the polyesters and copolyesters must be obtained by dividing the alcohol and / or water. In addition to applying a vacuum, introducing an inert gas, and increasing the reaction temperature, the polycondensation is accelerated in particular by specific polycondensation catalysts. For the production of polyesters that form films and fibers, a legion of polycondensation catchers has been proposed to accelerate the polycondensation reaction. Because the vast majority of the compounds cited in numerous patents have insufficient catalytic activity or other disadvantages, compounds containing Sb have found almost exclusive use as polycondensation catalysts in the art. Unfortunately, this catalyst has recently found criticism based on environmental issues, so a replacement seems generally desirable. Attempts are constantly being made to supply catalysts to replace Sb2O3. In particular, alkoxy titanates, especially tetrabutyl titanate, have been proposed, whereby these compounds are used either only for transesterification (JA-PS 74 11 474), transesterification and polycondensation (JA-OS 77 86 496) or only for polycondensation (JA-OS 80 23 136), because they are catalytically active in both stages. Because the use of titanium compounds causes discoloration of the polycondensate polyesters JA-OS 78 106 792 requires the pretreatment of titanium compounds with various organic substances, for example, amines, or must be combined with other polycondensation catalysts, in particular with Sb2O3 (JA-OS 78 109 597). DE P 947 517 teaches that metal oxides such as zinc oxide, boron trioxide, lead oxide, and titanium dioxide can be used as polycondensation catalysts to produce polyethylene terephthalate. The time of polycondensation with these metal oxides, however, is unusually long, of 7-14 hours in the examples given in that publication. For this reason BE P 619 210 uses Sb2O3 (see example 1) as a polycondensation catalyst to supplement TiO2 to produce the polyesters described therein, which dramatically increases the speed of the polycondensation process. Under these circumstances, it became of course practical to only work with Sb2O3 or titanium tetrabutylate as a polycondensation catalyst (see additional examples of BE P 619 210). DE-AI 44 00 300 and DE-AI 44 43 648 describe coprecipitates of TÍO2 SÍO2 and Ti? 2 / ZrO2 as polycondensation catalysts. The present invention responds to the task of providing new additional polycondensation catalysts for the general synthesis of polyesters and copolyesters as replacements for SD2O3 whereby the catalysts are distinguished in particular by a higher catalytic activity than that demonstrated by Sb2? 3, TiO2 , or titanium tetrabutylate in the same respective concentration.

The object of the invention is a process for producing polyesters and copolyesters by polycondensation of polyester-forming starting compounds, whereby in a first reaction step, esters or oligoesters are produced which in a second reaction stage are polycondensed in the presence of catalysts. of titanium, the process being characterized by the use of coprecipitates, individually or in a mixture, as polycondensation catalysts in the polycondensation step for polycondensing the esters or oligoesters, the coprecipitates being prepared by simultaneous hydrolytic precipitation of a titanium compound and a composed of a metal selected from the groups IA, NA, VIIIA, IB, IIB, IIIB, or IVB, in which the titanium and the metal compounds are, independently of one another, an alkylate, an alcohollate, or a titanium carboxylate or the metal, respectively, and the molar ratio of the titanium compound to metallic compound is > 50:50 mole / mole Preferred metals as metal compounds are sodium, potassium, magnesium, calcium, iron, cobalt, copper, zinc, aluminum, germanium, and tin. The preferred molar ratio of the titanium compound to the metal compound is > 80:20 mole / mole. The group "alkylate, alcohol", or titanium carboxylate or the metal, respectively, is for example a compound with 1 to 6 C atoms, whereby the butyl group is especially preferred as the alkylate; the methylate, ethylate, or i-propylate group such as alcohol; and the acetate or oxalate group such as the carboxylate. A particularly high catalytic activity is exhibited by coprecipitates of the invention derived from titanium (IV) tetraisopropylate and tin (IV) dioxalate in a molar ratio of 90:10 mole / mole. In general, the coprecipitates of the invention have a water content of 0 to 15% by weight, determined by the Karl Fischer titration and referred to the hydrated coprecipitate. In the case of water content exceeding 15% by weight, shelf life decreases because these catalysts exhibit considerably reduced activity after storage. Due to the fact that TIO2 represents a polycondensation catalyst deficient for the synthesis of polyesters (see Comparative Examples 3a and 3b), it is surprising that the coprecipitates used according to claim 1 are all highly effective polycondensation catalysts, in particular for the production of high molecular filament forming polyesters and copolyesters, and even more so in the very small amounts that are preferred. The production of the coprecipitates of the invention from alcoholates is in principle already known (see for example BE Yoldes, J. Non-Cryst, Solids, 38 and 39, 81 (1980), EA Barringer, HK Bowen, J. Am. . Ceram.

Soc, 65 C199 (1982); E.A. Barringer, Ph.D. Thesis, MIT (1982); B. Fegley jr., E.A. Barringer, H.K. Bowen, J.Am. Ceram. Soc, 67 C 113 (1984)). The starting metal alkoxides have the formula M (OR) m, where M is Ti and a metal selected from groups IA, HA, VIIIA, IB, IIB, IIIB, and IVB, depending on the desired coprecipitate, and m is the state of more stable oxidation of the metal. The alkoxides are subjected to hydrolysis, whereby a network is formed as a result of polymerization reactions. Suitable alcohols for preparing metal alkoxides according to methods known per se are, for example, monohydric alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, n-butanol, isobutyl alcohol, n-amyl alcohol, 3-methyl-1-butanol, n-hexanol, 2-hexanol, 2-heptanol, n-octanol, and n-decanol , which can be used individually or as mixtures. However, polyhydric alcohols, possibly as a mixture with monohydric alcohols, can also be used, such as ethylene glycol, 1,2-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, glycerin, trimethylolpropane. and pentaerythritol. In an analogous manner, the coprecipitates can be produced from alkylates such as butylates or from carboxylates such as acetates or oxalates. The hydrolysis of organometallic compounds, such as titanium tetraisopropylate and Sn (IV) dioxylate, can be carried out in a number of ways. For example, titanium and metal compounds dissolved in pure alcohols, such as ethanol, can be hydrolyzed by adding water or an aqueous alcohol within 20 minutes to 2 hours at 0 to 50 ° C. The hydrolysis can, however, also be carried out by adding water or a solution of aqueous alcohol by dripping into the undissolved mixture of the titanium and metal compounds under the conditions mentioned above. The water required for hydrolysis may also be present as moisture in a gas phase, for example, by feeding wet nitrogen to the mixture of titanium and metal compound for 3 to 30 hours at 0 to 50 ° C. The near "in situ formation" of a dispersion, suitable for use in the reactor, of the co-precipitate in glycol can also be advantageous. In this case, undissolved titanium mixtures and metal compounds can be precipitated as a coprecipitate, under the conditions mentioned above, by the addition of glycol containing the amount of water required for hydrolysis. If the glycol contains smaller amounts of water, the hydrolysis can be carried out additionally for example by feeding moist nitrogen to the reaction vessel. Advantageous ways of producing coprecipitates used in accordance with the invention at room temperature are described in the experimental part in Examples 1 to 13. The hydrolytic conditions described in the examples preclude gel formation, which must be avoided, and in a homogeneous precipitation of the respective coprecipitates. The added amounts of the precipitates and coprecipitates of the invention, used as polycondensation catalysts, can be varied within broad scales and comprise a total amount of 5 to 500 ppm with respect to the esters or oligoesters that have to undergo polycondensation. However, these quantities can in principle be extended to the same order of magnitude as when Sb2? 3 is used, which as a rule is used in amounts of 300 to 600 ppm as a polycondensation catalyst. If, however, special attention must be paid in certain applications for the produced polyesters and copolyesters to obtain good color values, it is preferred to use the co-precipitate in a total amount of only 10 to 100 ppm, with respect to the esters and oligoesters which they have to go through polycondensation. The increased catalytic activity of the coprecipitates used in accordance with the invention allows the use of added amounts which are considerably less than when Sb2O3 is used, whereby the same time of polycondensation and - at least using a coprecipitate derived from titanium tetraisopropylate (IV) and tin dioxide (IV) - a completely acceptable b * value of 3.0 to 8.0 is obtained in this case with the polyesters thus produced. This b * value scale corresponds in particular to the values that are also obtained in the production of polyethylene terephthalate when 400 ppm Sb2O3 is used as a polycondensation catalyst. The addition of the coprecipitates of the invention is preferably carried out in the form of a 5 to 20% glycolic suspension >; to the esters or oligoesters synthesized in the first reaction step, for example the bis-glycol ester of the dicarboxylic acid which is to undergo polycondensation and / or the precondensate from one or more of said bis-glycol esters, before its polycondensation . It is also possible in principle, however, to add the coprecipitate as early as some time during the first reaction stage, in the case of transesterification possibly together with one or more transesterification catalysts. In the case of transesterification in the first reaction step, it may sometimes be advantageous to block the transesterification catalyst after transesterification, in a manner known per se, by adding phosphorus compounds. Suitable phosphorus compounds are, for example, carbethoxymethyl diethyl phosphonate, di (polyoxyethylene) hydroxymethylene phosphonate, tetraisopropylmethylene diphosphonate, and H 3 PO 4, wherein in general an added P concentration of 30-50 ppm is sufficient. Under conventional reaction conditions, the coprecipitates of the invention are suitable in principle as polycondensation catalysts for producing a wide variety of polyesters and copolyesters where Sb2? 3 has hitherto been used as a polycondensation catalyst, possibly also in combination with one or more than other polycondensation catalysts. The variety of polyester and copolyester types also corresponds to a wide variety of applications. To the extent that alkyd resins and saturated polyester resins (hydroxypolyesters) with a relative molecular weight of < 10,000 are produced with the coprecipitates of the invention, these can be used as binders in paints and coating materials. The alkyd resins in the current terminology are understood to be modified polyesters of oil or fatty acid derived from polycarboxylic acids and polyalcohols and their conversion products with vinyl compounds, for example epoxy resins, silicones, diisocyanates, and organometallic compounds (aminic resins) "modified"). The main polycarboxylic acids used for alkyd resins are phthalic acid, isophthalic acid, malonic acid, succinic acid, adipic acid, acelaic acid, sebasic acid, dodecanoic diacid, dimerized fatty acids, hexahydrophthalic acid, hexahydroterephthalic acid, maleic acid, fumaric acid, and , to retard flame, dicarboxylic acids containing halogen as tetrachlorophthalic acid anhydride. As polyols, glycerin, pentaerythritol, dipentaerythritol, trimethylolpropane, trimethylolethane, sorbitol, and difunctional polyols such as ethylene glycol, 1,2-propylene glycol, 1,3-, and 1,4-butanediol, diethylene glycol, dipropylene glycol, and neopentyl glycol are generally used. The third component for producing alkyd resins are long-chain fatty acids either synthetic fatty acids such as pelargonic acid, abietic acid, or mixtures of synthetic fatty acid (C-Cg) or natural fatty acids, which are used almost exclusively in the form of their fats and oils, such as flaxseed oil, castor oil, coconut oil, soybean oil, and cottonseed oil. To prepare the saturated polyester resins defined in DIN 55 945, in contrast, relatively long chain fatty acids are not used in the polycondensation, while in some other way the saturated polycarboxylic acids and the polyalcohols used are mainly the same used to produce the alkyd resins. If the (co) polyesters are synthesized with the coprecipitates of the invention as precursors for polyurethanes with a relative molecular weight of < 10,000, this leads, depending on additional processing using known methods, not only to polyurethane paints but also to a variety of plastics of variable valuable utilization characteristics (durums, thermoplasts, casting elastomers, hard and soft expanded plastics, pressed compounds, hard and flexible coatings, adhesives). The low molecular weight polyesters and copolyesters as precursors for polyurethanes are generally produced from saturated aliphatic or aromatic dicarboxylic acids and difunctional or di-and trifunctional alcohols and are linear or slightly or extensively branched. With the coprecipitates used according to the invention, production of the known total broad blade of hydroxypolyesters with hydroxyl numbers of 28-300 mg KOH / g and acid numbers usually under 1 mg KOH / g is possible. The extensively branched polyesters, which for the most part are obtained on the basis of aromatic or hydroaromatic dicarboxylic acids, serve mainly as binders for polyurethane paints. Under conventional reaction conditions, the coprecipitates used in accordance with the invention are particularly suitable as polycondensation catalysts for producing the high melting fiber and the film-forming polyesters known as polyethylene terephthalate, polybutylene terephthalate, poly (ethylene-2,6). -naphthalene dicarboxylate), poly (butylene-2,6-naphthalenedicarboxylate), poly (1,4-dimethylenecyclohexane terephthalate), and their polyester mixtures based on high homopolyester fractions of at least 80 mole percent, which belong to the category of thermoplastic polyesters. Such polyesters and copolyesters have in principle a molecular weight of >; 10 000. The polyalkylene terephthalates preferably polycondensed with the coprecipitates, in particular polyethylene terephthalate and polybutylene terephthalate, can, as polyester blends, consist of up to 20 mole percent of units derived from at least one additional polyester-forming component. Otherwise, it is by nature unimportant, when using the polycondensation catalysts of the invention, if the bisglycolic esters of the dicarboxylic acid (s) are to be polycondensed and / or the precondensates from one or more such Bisglycolic esters are produced using a transesterification or direct esterification process. The polycondensation catalysts of the invention are therefore suitable for producing a film-forming polyethylene terephthalate with an intrinsic viscosity [?] Of 0.65-0.75, which is usually further processed into fiber strands for textile purposes, and polyethylene terephthalates fiber-forming. with an intrinsic viscosity [?] of 0.75-0.80 and 0.95-1.05 from which filament yarns are produced for industrial purposes. The increased molecular weights can be obtained by continuous polycondensation with direct rotation or preferably by postcondensation in the solid phase. For postcondensation in the solid phase, it is advantageous to block any existing transesterification catalyst using phosphorus compounds in a manner known per se. Suitable phosphorus compounds for this are, for example, di (polyoxyethylene) hydroxylmethyl phosphonate, tetraisopropylmethylene diphosphonate, and H3PO4, whereby an added P concentration of 30-50 ppm is sufficient. The fiber and film-forming thermoplastic polyesters produced with the polycondensation catalysts of the invention, in particular polyethylene terephthalate and polybutylene terephthalate, can, of course, also be processed, for example, by injection molding or extrusion to form all types of objects formed and Profiles If, for example, a polyethylene terephthalate produced by the polycondensation catalyst of the invention is processed in PET bottles, the latter exhibits increased transparency. The additional polyester forming components for fiber-forming and film-forming copolyesters can be an aliphatic diol such as ethylene glycol, propylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, polyethylene glycol, polypropylene glycol or poly (tetrahydrofuran) diol; an aromatic diol such as pyrocatechol, resorcinol, or hydroquinone; an alicyclic diol such as 1,4-cyclohexaned methanol or cyclohexane diol; an aliphatic dicarboxylic acid such as adipic acid, sebasic acid, or decanedicarboxylic acid; an aromatic dicarboxylic acid such as soft acid, 5-sodiosulfoisophthalic acid, sodiosulfoterephthalic acid, or 2,6-naphthalenedicarboxylic acid; or an alicyclic dicarboxylic acid such as hexahydroterephthalic acid or 1,3-cyclohexane dicarboxylic acid. Analogous polyester forming components for forming polyester blends can also be considered for the partially mentioned above-mentioned filament-forming homopolyethers which do not belong to the polyalkylene terephthalate category. Of course, the fiber and film-forming polyesters can as conventional modifying agents also contain known branching agents such as pentaerythritol, trimellitic acid, pyromellitic acid, or trimesic acid, or their esters, in conventionally small amounts such as 1 to 15 microequivalents per g of polymer, which ensure not only a rapid spinning of 3000 to 4000 m / min and more but also a stretch texturing at a speed of at least 1000 m / min. These branching agents are advantageously added as a solution in ethylene glycol to the bis-glycol ester of the dicarboxylic acid which is to undergo polycondensation. The term copolyester also includes the broad classes of polyether esters. Thermoplastic polyether esters are known to be block copolymers which are synthesized from mutually incompatible amorphous and rigid crystalline soft segments. The rigid segments, short chain consist mainly of an aromatic polyester as units of ethylene terephthalate or butylene terephthalate, while the soft, long chain segments consist in particular of the reaction product of an aliphatic polyether, such as poly (butylene glycol) or poly (ethylene glycol), with an aliphatic, caliphatic or aromatic dicarboxylic acid. The short and long chain ester units are often copolyesters resulting from the limited co-use of one or more additional dicarboxylic acid and glycol components. The thermoplastic polyether esters, for the production of which the coprecipitates used as polycondensation catalysts according to the invention are also suitable, are described in, for example, US-PS 3,023,192, GB-PS 682 866, DE-PS 23 52 584, EP-A-0 051 220, and EP-A-0 109 123. The coprecipitates used according to the invention are also suitable for producing fully aromatic or liquid-crystalline polyesters, if this production is based on polycondensation catalysts such as Sb2Ü3 or titanium alkoxides. For example, according to US-PS 4,421, 908, the fully aromatic polyesters are known to consist of 10-90 mole percent of a hydroxynaphthalene carboxylic acid, 5-45 mole percent of at least one additional aromatic dicarboxylic acid, as terephthalic acid and 5-45 mole percent of at least one aromatic diol such as hydroquinone. According to EP-A-0 472 366, fully aromatic polyesters are produced from (A) isophthalic acid, (B) hydroquinone, (C) 4,4-dihydroxydiphenyl and / or p-hydroxybenzoic acid and / or acid 2-hydroxy-6-naphthalene carboxylic, and (D) a phenol. And in EP-A-0 496 404, fully aromatic polyesters are disclosed which are obtained by converting at least one dialkyl ester of an aromatic dicarboxylic acid, for example, DMT, with at least one aromatic polycarbonate as poly (4,4'- isopropylidenediphenylene carbonate) and / or an aromatic dialkyl dicarbonate. In these processes for producing fully aromatic polyesters, which are cited as examples, the polycondensation catalysts used therein, such as Sb 2 O 3, titanium alkoxides, and zirconium alkoxides, can be advantageously replaced by the specific coprecipitates according to the invention , without considering whether they are added in the first reaction stage or in the current polycondensation stage that follows it. The invention will be described in more detail based on the following examples. The relative viscosity of the solution given therein was measured at 25 ° C as a solution in meta-cresol at 1% by weight. The number of carboxyl groups was given as equivalents of carboxyl group / 106 g or mmoles / kg of the polymer. This value was determined by titrating the polymer in ortho-cresol with potassium hydroxide. The characterization of the colors of the polyesters was based on the color system L a * b *. This is one of the color systems for uniform color measurement and was recommended in 1976 by the Commission (Commission Internationale de l'Eclairage) for its higher accuracy to represent perceptible colors and color differences. In this system, L is the luminescence factor and a * and b * are quantities of color measurements. In the present case, the value b * is important, which indicates the yellow / blue balance. A b * positive value means a discoloration towards the yellow, while a b * negative value means a discoloration towards the blue. Polyesters conventionally produced using antimony trioxide exhibit a b * value of between 3 and 8 if coloring agents (such as cobalt salts) are not added. For products whose color is not critical, higher values are also acceptable.

EXAMPLES 1-13 Production of catalytically active co-precursors In Table 1, the titanium and metal compounds which are used to produce the catalytically active coprecipitates according to Examples 1-13 are summarized. Titanium (IV) tetraisopropylate (0.18 mole) and the corresponding metal compound (0.02 mole) are dissolved in 100 ml of pure ethanol (solution A). 10.27 g of distilled H2O (0.57 mole) are mixed with 100 ml of pure ethanol (solution B). Solution A is placed in a container and solution B is added dropwise within 30 minutes at 22 ° C. It turns out a white precipitate. After stirring for 1 hour the mixture is centrifuged and the residue is washed three times with distilled H2O. The resulting coprecipitates are dried in a vacuum at 70 ° C.

TABLE 1 Titanium and metal compounds to produce catalytically active coprecipitates according to examples 1-13 with a molar ratio of the titanium compound to the metal compound of 90:10 mole / mole.

EXAMPLES 14-26 And comparative example 1 Polyethylene terephthalate was produced in a two-stage process. In the first stage the transesterification, the conversion of ethylene glycol and dimethylterephthalate (DMT) took place in a molar ratio of 2.5: 1 in the presence of 100 ppm ZnAc2 «2 H2O (Ac = acetate) and 150 ppm MnAC2 • 4 H2O, with with respect to DMT, at temperatures of 175 to 250 ° C, whereby the continuous temperature increase from 175 to 250 ° C was not conducted too quickly in order to avoid sublimation of the DMT. In addition to the transesterification catalyst, 10 ppm M10 defoaming agent was added, with respect to DMT. The methanol released in the transesterification was distilled through a column. When the reaction temperature of 240 ° C was reached, 50 ppm of phosphorus was added with respect to the DMT used, such as phosphonoacetic acid ethyl ester to block the transesterification catalyst. As soon as the reaction temperature of 250 ° C was obtained, 100 ppm, with respect to the bis- (2-hydroxyethyl) terephthalate present, of one of the coprecipitates prepared according to examples 1-12 in examples 14 were added. -25 in the form of a 10% by weight suspension in glycol. In example 26, only 50 ppm was used, with respect to the bis- (2-hydroxyethyl) terephthalate present, of the coprecipitate prepared according to example 13. The polycondensation reaction was conducted at 290 ° C under a vacuum of 1.3 mbar . Table 2 summarizes the amounts of catalyst added, the polycondensation times, the relative viscosities of the solution, and the b * values obtained with the coprecipitates prepared according to examples 1-13, and the results obtained with Sb2? 3 in comparative example 1. The comparison of the polycondensation times of the coprecipitated catalysts of the invention with those of Sb2O3 demonstrates that the co-precipitated catalysts of the invention cause a significantly reduced polycondensation time, although their amounts are 4 or even 8 times more. small (compare examples 14-25 and example 26 with comparative example 1).

TABLE 2 Catalyst amounts, polycondensation times, relative solution viscosities, and b * values of co-precipitated catalysts prepared in Examples 1-13 compared to SD2O3.

COMPARATIVE EXAMPLE 2: Preparation of a malonate resin with dibutyl tin oxide as a catalyst As an apparatus for this example, a 200 ml five-necked flask was used, which was equipped with a metal stirrer, drip funnel, oxygen feed tube, thermosensor for indoor temperature, a vigreux silver-coated column 300 mm long, and a distillation column head. The initial reaction mixture consisted of the following components: 312.45 g (3 mole) 1,5-pentanediol as component A. 560.60 g (3.5 mole) of malonate diethyl ester as component B, 0.87 g (= 0.1% by weight, with respect to A + B) tin dibutyl oxide, as component C. 43.5 g (15% by weight with respect to A + B) metaxylene as component D. 130. 5 g (15% by weight, with respect to A + B) metaxylene as component E. As a catalyst, the common tin dibutyl oxide was used for this reaction. Components A, B, C and D were weighed into the flask and rinsed with nitrogen. The mixture was then heated slowly and the first drops of ethanol were distilled at an interior temperature of 115 ° C. At a declining distillation speed, the interior temperature was increased to 200 ° C. Component E was then added by drip as a vehicle for distillation, and the ethanol / metaxylene distillate removal continued. When the yield reached 99.5%, the polycondensation was completed. This yield had been obtained after 16 hours. The total amount of distillate at that time was 378.03 g. The amount of ethanol distilled was 274.92 g (theoretical total of ethanol = 276.42 g). The Gardner color index was 13.

EXAMPLE 27 Preparation of a malonate resin with a co-precipitated catalyst of the invention according to Example 13 The experiment of comparative example 2 was repeated with the coprecipitated catalyst prepared from Ti (IV) tetraisopropylate and tin dioxide (IV) according to example 13. The initial reaction mixture consisted of the following components: 312.45 g ( 3 mole) 1, 5-pentanediol as component A. 560.60 g (3.5 mole) of malonate diethyl ester as component B. 0.87 g (= 0.1% by weight, relative to A + B) co-precipitated catalyst according to example 13 as a component C. 43.5 g (5% by weight with respect to A + B) metaxylene as component D. 87.0 g (10% > by weight, with respect to A + B) metaxylene as component E. Components A, B, C and D were weighed into the flask and rinsed with nitrogen. The mixture was then heated slowly and the first drops of ethanol mixed with metaxylene were distilled at an interior temperature of 142 ° C. At a declining distillation speed, the interior temperature was increased to 200 ° C. Component E was then added by drip as a vehicle for distillation, and the ethanol / metaxylene distillate removal continued. When the yield reached 99.6%, the polycondensation was discontinued. This performance had been obtained after only 7 hours. The total amount of distillate at that time was 342.28 g. The amount of ethanol distilled was 276.04 g (theoretical total of ethanol = 276.42 g). The Gardner color index was 10.

COMPARATIVE EXAMPLES 3A AND 3B With commercially available titanium dioxides a) Analogous to Examples 14-26, the preparation of polyethylene terephthalate was attempted, in which the commercially available titanium dioxides were to function as polycondensation catalysts. For this purpose, after the transesterification conducted as in examples 14-26, and after blocking the transesterification catalysts when the reaction temperature of 250 ° C was reached, 500 ppm of Hombitec KO 3 TiO2 (a titanium dioxide produced by Sachtleben), with respect to the bis- (2-hydroxyethyl) terephthalate present, were added to the reaction mixture in the form of a 10% by weight suspension in glycol as a polycondensation catalyst. The polycondensation reaction took place at 290 ° C under a vacuum of 1.3 mbar. After 180 minutes of reaction time, the experiment was discontinued, because the melt viscosity, and therefore the relative viscosity, was insufficient, due to the excessively low molecular weight of the polycondensation product. b) A second experiment conducted under the same reaction conditions also failed with the same results in which 500 ppm Tilcon HPT 3 TiO2 (a titanium dioxide produced by Thioxide), with respect to the bis- (2-hydroxyethyl) terephthalate present, were added as a polycondensation catalyst in the form of a suspension of 10% by weight in glycol .

COMPARATIVE EXAMPLE 4 In a polycondensation conducted as in Examples 14-26, 213 ppm of titanium tetrabutylate, with respect to the bis- (2-hydroxyethyl) terephthalate present, were added as a polycondensation catalyst at 250 ° C in the form of a solution to 5% by weight in glycol. The polycondensation reaction took place at 290 ° C under a vacuum of 3.5 mbar. After a reaction time of 134 minutes, a polymer with a relative solution viscosity of 1633 was obtained. The value b * was 15.5, the content of the final group COOH 20.2 equivalents / 106 g of polymer. This comparative example shows in particular that while titanium tetrabutylate, with a significantly lower b * value, had a higher catalytic activity than Sb2? 3, it must nevertheless be used at a higher concentration than the catalysts of the invention for obtain comparably short polycondensation times.

Claims (19)

NOVELTY OF THE INVENTION CLAIMS

1. - A process for producing polyesters and copolyesters by polycondensation of polyester-forming starting components, in which in a first reaction step esters or oligoesters are produced which in a second reaction stage are polycondensed in the presence of titanium catalysts, characterized in that the coprecipitates are used individually or in a mixture, as polycondensation catalysts in the polycondensation step for the polycondensation of the esters or oligoesters, the coprecipitates being prepared by simultaneous hydrolytic precipitation of a titanium compound and a metal compound of a metal selected from groups IA, HA, VINA, IB, IIB, IIIB, and IVB, in which the titanium and the metal compounds are, independently of each other, an alkylate, alcohol, or titanium carboxylate or metal, respectively, and the molar ratio of the titanium compound to the metal compound is > 50:50 mole / mole

2. The process according to claim 1 characterized in that the metal of the metal compound is sodium, potassium, magnesium, calcium, iron, cobalt, copper, zinc, aluminum, germanium, or tin.

3. - The process according to claim 1 or 2 characterized in that the molar ratio of the titanium compound to the metal compound is > 80:20 mole / mole.

4. The process according to claims 1 to 3, characterized in that the alkylate, alcohollate, or titanium carboxylate group or the metal, respectively, is a compound with 1-6 carbon atoms.

5.- The process according to claims 1 to 4, characterized in that the alkyl group is a butyl group, the alcoholyl group is a methylate, ethylate or i-propylate group, and the carboxylate group is an acetate or oxalate group.

6. The method according to claims 1 to 5, characterized in that the coprecipitate is produced from titanium (IV) tetraisopropylate and tin (IV) dioxylate in a molar ratio of 90:10 mole / mole.

7. The process according to one or more of claims 1 to 6, characterized in that the coprecipitate has a water content of 0 to 15% by weight with respect to the hydrated coprecipitate.

8. The process according to one or more of claims 1 to 7, characterized in that the coprecipitate is used in a total amount of 5-500 ppm with respect to the esters or oligoesters that have to undergo polycondensation.

9. The process according to claim 8, characterized in that the coprecipitate is used in a total amount of 10 to 100 ppm with respect to esters or oligoesters that have to undergo polycondensation.

10. The process according to one or more of claims 1 to 9, characterized in that the coprecipitate is added to esters or oligoesters that have to undergo polycondensation before their polycondensation in the form of a glycolic suspension of 5 to 20% in weight

11. The process according to one or more of claims 1 to 10, characterized in that any transesterification catalyst present in the first reaction stage is blocked by adding one or more phosphorus compounds.

12. The process according to claim 11, characterized in that the blocking agent is carbidoxymethyldiethyl phosphonate, di (polyoxyethylene) hydroxymethylphosphonate, tetraisopropylmethylene diphosphonate, and / or H3PO4.

13. The use of the polycondensation catalysts according to claims 1 to 9 to produce alkyd resins with a relative molecular weight of < 10,000.

14. The use of the polycondensation catalysts according to claims 1 to 9 to produce saturated polyester resins with a relative molecular weight of < 10,000.

15. - The use of the polycondensation catalysts according to claims 1 to 9 to produce polyesters and copolyesters as precursors for polyurethanes with a relative molecular weight of <; 10,000.

16. The use of the polycondensation catalysts according to claims 1 to 12 to produce thermoplastic polyesters and copolyesters with a relative molecular weight of > 10,000.

17. The use of the polycondensation catalysts according to claim 16 to produce polyethylene terephthalate, polybutylene terephthalate, poly (ethylene-2,6-naphthalene dicarboxylate), poly (butylene-2,6-naphthalene dicarboxylate), poly (1,4-dimethylenecyclohexane terephthalate), or its polyester blends based on high homopolyester fractions of at least 80 mole percent.

18. The use of the polycondensation catalysts according to claim 16 to produce polyether esters.

19. The use of the polycondensation catalysts according to claims 1 to 9 to produce fully aromatic or liquid-crystalline polyesters.