Process for the preparation of thermostable, neutral colour, antimony-free polyesters and products therefrom

The present invention relates to a process for the production of thermally stable, color-neutral, antimony-free polyester using a titanium polycondensation catalyst which is very reproducible, has a very high polycondensation rate even with very low additions of the titanium polycondensation catalyst, and in which there is a considerable reduction in thermal degradation and the uncontrolled crosslinking of the polyester formed, as well as the products that can be manufactured afterwards, which are characterized by excellent clarity and color neutrality.

Polyesters have become very important in many areas of application. In particular, saturated polyesters are used on a large scale for the production of fiber materials, but also of other types of shaped bodies, such as beverage bottles. For perfect processing of these polyesters by extrusion processes and for the further use of the extrudates, for example in the textile or beverage industry there are very high demands on the quality of the polyester. In particular, it is required that the processing and application properties for certain types of polyester used for certain processing are always the same within very narrow limits. For processing by extrusion processes, e.g. by melt spinning it is of crucial importance that they always have a uniform molecular weight and an always reproducible molecular weight distribution, are free of gel fractions, and if possible do not tend to yellowing or to thermal degradation. For further processing in the dyeing process, no catalyst metals should come out of the fiber material, since these have to be removed and disposed of from the dyeing wastewater by complex cleaning operations. The disposal or recycling (recycling) of the used polyester products should not cause any problems due to disruptive components.

Polyesters are usually prepared by esterification of aromatic dicarboxylic acids or transesterification of lower aliphatic esters of aromatic dicarboxylic acids with aliphatic diols and subsequent polycondensation until the molecular weight required for the intended use is reached.

A possible transesterification is carried out in the presence of transesterification catalysts which have to be deactivated after the transesterification has ended by adding complexing agents. Most of the complexing agents used are phosphoric acid, phosphorous acid and / or phosphonic acids or derivatives thereof. After the esterification or transesterification, the polycondensation to the desired molecular weight takes place, which is also carried out in the presence of a suitable catalyst. Antimony compounds, mostly antimony trioxide, have established themselves as large-scale polycondensation catalysts. Here it can happen that part of the antimony compound is reduced to antimony metal by reducing agents, which leads to graying of the polyester. This results in poor clarity and a non-neutral hue.

In addition, the relatively high content of antimony compounds in the polyester is considered a disadvantage because it makes the production more expensive. There is also the possibility that antimony compounds are released in further processing processes, for example in dyeing. The relatively high content of antimony compounds, in addition to the formation of antimony deposits, influences the spinning behavior.

Proposals have therefore already been made to eliminate the disadvantages of the production method described.

It is known to improve the color of the polyester by adding cobalt compounds and / or optical brighteners. It is also known to use titanium compounds as the polycondensation catalyst instead of antimony compounds.

From various publications, for example US-A-3,962,189, JP-PS-28006 (1979), JP-PS-123311 (1976), JP-PS-43564 (1979), JP-PS-111985 (1980 ) or JP-PS-280048 (1989) discloses a process for the preparation of polyesters in which a cobalt compound is added to improve the color tone of the polyester, which - like the transesterification catalyst - must be complexed before the start of the polycondensation, and in which the polycondensation is carried out in the presence of a titanium compound. According to these publications, the amount of the complexing agent used for complexing the cobalt additive should be in the range from 0.5 to 7.5 mol per mol of cobalt blending. Thus, in JP-PS-28006 a P / Co ratio of 0.5 to 1.5, in JP-PS 111985 from 0.7 to 3, in JP-PS-280048 from 0.5 to 7 , 5 [mol / mol] applied. This known method has the considerable advantage that all the disadvantages associated with the use of antimony compounds are eliminated and that it can actually succeed in producing color-neutral and clear polyesters which are suitable for demanding processing methods and applications. A disadvantage of this known method, however, is that its reproducibility leaves something to be desired. So sometimes the desired products are not obtained, but there are disturbances in the polycondensation reaction, the required molecular weights are not achieved and if the polycondensation time is considered necessary, the polyester yellows, gel fractions form due to uncontrolled crosslinking and thermal sensitivity of the products which significantly impair further processing. This means that the advantages offered by the process are not always realizable.

It has now been found that it is surprisingly possible to produce thermostable, color-neutral, antimony-free polyesters in a reproducible manner by esterifying aromatic dicarboxylic acids or transesterifying lower aliphatic esters of aromatic dicarboxylic acids with aliphatic diols and subsequent polycondensation if    a possible transesterification in the presence of 20 to 120 ppm, based on the catalyst metal, of a transesterification catalyst, preferably of manganese in the form of a manganese compound,    after completion of the esterification or transesterification the esterification or transesterification approach    100% of the amount equivalent to the transesterification catalyst used and up to 99% of the amount equivalent to the cobalt to be used of phosphoric acid, phosphorous acid and / or phosphonic acids or a derivative thereof is added as a complexing agent, then 0 to 80 ppm cobalt, be added in the form of a cobalt compound,    and the polycondensation without the addition of antimony in the presence of 1 to 10 ppm of titanium, which is added in the form of a titanium compound, and optionally in the presence    of organic compounds delivering crosslinking assemblies of up to 1000 ppm    and if necessary up to 50 ppm of an optical brightener is carried out.

Suitable transesterification catalysts are known from the literature. For example, compounds of metals of groups Ia (for example Li, Na, K), IIa (for example Mg, Ca) and VIIa (for example Mn) of the periodic table are suitable for the process according to the invention, in particular those which have a certain solubility in the transesterification batch, such as salts of organic acids. Salts of group VIIa, in particular of manganese, with lower aliphatic carboxylic acids, in particular acetic acid, are preferred.

A preferred embodiment of the process according to the invention is therefore that a possible transesterification is carried out in the presence of 20 to 120 ppm of manganese (calculated as metal) in the form of a manganese compound, in particular manganese acetate.

The cobalt compound added to improve the color tone of the polyester is advantageously also a salt of cobalt with an organic acid, for example with acetic acid or adipic acid. The minimum amount of the cobalt compound depends on the extent of the color shift that is required in individual cases in order to achieve a neutral shade. If additional optical brighteners are used for color correction, the amount of the cobalt compound can of course be reduced. As a rule, the amount of cobalt addition required, as stated above, is a maximum of 50 ppm (calculated as metal), always based on the weight of the polyester. Preferably 20 to 40 ppm cobalt, in the form of a cobalt compound, are added to the batch, ie such an amount of the cobalt compound is added that corresponds to an amount of 20 to 40 ppm free cobalt.

As in conventional processes, the transesterification catalyst in the present invention is inactivated before the start of the polycondensation by adding a complexing agent, because otherwise the polycondensation is hindered, i.e. the required high molecular weights of the polyesters cannot be achieved and, moreover, the polyester obtained has an increased sensitivity to thermal stress . Occasionally, the cobalt compounds added before the polycondensation have been complexed in order to improve the thermal stability of the polyesters produced.

For the process according to the invention, it is now essential that the total amount of cobalt compound added must in no case be inactivated, but that 1 to 10% of the cobalt compound added remain uncomplexed.

The amount of complexing agent is therefore such that the transesterification catalyst is 100% deactivated by complexing, but only 90 to 99% of the cobalt compound is complexed.

If the complexing ability of a complexing agent is precisely known, one can simply use 90 to 99% of the amount of the complexing agent equivalent to the amount of cobalt. As a rule, however, it is more expedient to determine the required amount of the complexing agent by means of preliminary tests. For this purpose, for example, some sample batches of the polycondensation batch, all of which have the same composition as a planned main batch, are mixed with from about 80% to 120% of the theoretically required amount of the complexing agent and then polycondensed under the same conditions. After the polycondensation reaction is complete, the viscosity (ie the molecular weight) achieved is determined from all batches. The results of such a series of preliminary tests are shown in the figure. The viscosities achieved are plotted against the ratio of complexing agent to cobalt compound (for example the P / Co ratio) in a coordinate system. It can be seen that if the P / Co ratio is too high, only low viscosities, ie low molecular weights, can be achieved. The molecular weights reached rise below a certain limit of the P / Co ratio. The crossing point between the flat and the rising curve branch characterizes the equivalent P / Co ratio. Up to 99% of the amount of complexing agent determined in this way is then added to the main batch.

It is particularly advantageous if, after completion of the esterification or transesterification, the esterification or transesterification batch is 100% of the amount equivalent to the transesterification catalyst used and 90 to 99% of the amount of phosphoric acid, phosphorous acid and / or phosphonic acids a derivative equivalent to the cobalt to be used the same is added as a complexing agent.

The measure of only partially deactivating the added cobalt compounds surprisingly leads to a drastic improvement in the reproducibility of the process; the result is a very high polycondensation rate even with very small additions of the titanium polycondensation catalyst, a considerable reduction in the thermal degradation and the uncontrolled crosslinking of the formed polyester with the consequence that no yellowing and no gel formation occurs. When carrying out the reaction according to the invention, therefore, one can get by with smaller fining additives and achieve perfect processability. The polyesters obtained meet the highest quality requirements in terms of clarity and color neutrality.

In principle, all compounds known as complexing agents and inactivators for transesterification catalysts are suitable as complexing agents for the process according to the invention. Compounds containing phosphorus, such as phosphoric acid, polyphosphoric acid, phosphorous acid and phosphonic acids and derivatives thereof, have proven to be particularly suitable. Specific examples of phosphoric acid derivatives are the "PHM esters", which are mixtures of oxalkylated alkyl-hydroxyalkyl-phosphoric acid esters of the formula I or phosphonic acid esters of the formula II.         O = P (OR¹) ₃, (I) wherein the R¹ radicals are the same or different alkyl, hydroxyalkyl or alkoxylated hydroxyalkyl radicals.         (R²O) ₂-PO-R³-COOR⁴, (II) wherein R², R³ and R⁴ are alkyl radicals.

Titanium compounds are used as the polycondensation catalyst in the process according to the invention. In principle, all titanium compounds already described for this purpose are suitable, in particular potassium titanyl oxalate or titanium isopropylate.

It is particularly preferred that the polycondensation without addition of antimony in the presence of 1 to 10 ppm titanium up to an IV, measured in dichloroacetic acid at 25 ° C., from 0.4 to 0.9 dl / g, preferably from 0.5 to 0, 7 dl / g, and up to a carboxyl group concentration of 10 to 50 mmol / kg, preferably from 10 to 40 mmol / kg, in the melt, and then to the desired final viscosity in the solid phase.

The final viscosity of the polyesters according to the invention should be in the range from 0.7 to 2.0 dl / g, preferably from 0.7 to 1.5 dl / g, measured under the conditions specified above. The polycondensation time and the polycondensation temperature are regulated in a known manner so that the desired final viscosity is achieved. As a rule, the polycondensation, as is customary in the art of polyester production, depending on the type of polyester, at a temperature of 260 to 350 ° C., preferably under an inert gas, for example under nitrogen, and / or under reduced pressure in the range of 0.2 to 10 mbar, preferably from 0.4 to 5 mbar.

To set certain polyester properties, such as the melt viscosity, it may be desirable to bring about a defined degree of crosslinking. For this purpose, the polycondensation is carried out without the addition of antimony in the presence of 2-8 ppm of titanium and in the presence of up to 1000 ppm, preferably from 100 to 500 ppm, of organic compounds (crosslinking agents) providing crosslinking structural groups.

Compounds which have at least three functional groups capable of ester formation are used as crosslinkers. Functional groups capable of ester formation are the OH group, the carboxyl group, alkoxycarbonyl, in particular lower alkoxycarbonyl, the carboxylic anhydride group, and reactive groups derived therefrom. Examples of common crosslinkers are pentaerythritol, trimethylolpropane, trimellitic acid, trimesic acid, pyromellitic acid and the like.

In order to further improve the color of the polyester and to save some of the cobalt, it has proven expedient to carry out the polycondensation without the addition of antimony in the presence of up to 50 ppm, preferably from 5 to 25 ppm, of an optical brightener.

Of course, the chemical composition of the polyester is extremely important for its properties. For the production of polyesters, which are suitable for the abovementioned uses are under the conditions mentioned above for the process according to the invention    80 to 100 mol% of aromatic dicarboxylic acids of the formula III         HOOC-X-COOH (III) or their lower aliphatic esters and 0 to 20 mol% of aromatic hydroxycarboxylic acids of the formula IV         HO-X¹-COOH (IV) or their lower aliphatic esters with diols of the formula V         HO-Y-OH (V) esterified or transesterified, whereby    X, based on the total amount of di- and hydroxycarboxylic acids, more than 80 mol% aromatic residues with 5 to 16, preferably 6 to 12 carbon atoms and at most 20 mol% aliphatic residues with 4 to 10 carbon atoms, preferably 6 to 8 carbon atoms,    X¹, the p-phenylene radical,    Y, based on the total amount of the transesterified or esterified diols, to at least 80 mol% alkylene or polymethylene groups with 2 to 4 carbon atoms or cycloalkane or dimethylene-cycloalkane groups with 6 to 10 carbon atoms and    to a maximum of 20 mol% straight-chain or branched alkanediyl having 4 to 16, preferably 4 to 8, carbon atoms or radicals of the formula - (C₂H₄-O)_n-C₂H₄-, in which n is an integer from 1 to 40, where n = 1 or 2 are preferred for proportions up to 20 mol% and groups with n = 10 to 40 preferably only in proportions of less than 5 mol.- % available.

It is particularly preferred to make the selection of the starting materials in such a way that    X, based on the total amount of di- and hydroxycarboxylic acids, 90 to 100 mol% p-phenylene radicals, 0 to 7 mol% m-phenylene radicals and 0 to 5 mol% aliphatic radicals having 4 to 10 carbon atoms, preferably 6 to 8 Carbon atoms    X¹, the p-phenylene radical,    Y, based on the total amount of the transesterified or esterified diols, to at least 90 mol% alkylene or polymethylene groups with 2 to 4 carbon atoms or cycloalkane or dimethylene-cycloalkane groups with 6 to 10 C atoms and    to a maximum of 10 mol% straight-chain or branched alkanediyl having 4 to 16, preferably 4 to 8, carbon atoms or radicals of the formula - (C₂H₄-O)_n-C₂H₄-, wherein n represents the numbers 1 or 2 means.

It is particularly preferred not to use hydroxycarboxylic acid of the formula IV in the process according to the invention and to select the dicarboxylic acid component of the formula III such that X, based on the total amount of the di- and hydroxycarboxylic acids, is 93 to 99 mol%, preferably 95 to 98 mol % p-phenylene radicals, 1 to 7 mol%, preferably 2 to 5 mol%, m-phenylene radicals. The aromatic radicals represented by X and X¹ can be unsubstituted or, if certain properties of the polyester are to be modified, can carry one or two substituents. The radicals are preferably predominantly unsubstituted, ie not more than 10 mol% of the aromatic radicals carry substituents. The exact proportion of substituted residues is determined according to the effect to be achieved.

The methyl group and the sulfonic acid group are preferred as substituents.

In addition to the above-mentioned starting materials, up to 10 mol%, preferably up to 7 mol%, of other co-condensable compounds can be condensed into the polyester if certain special properties are desired. For example, flame-retardant polyesters can be produced by the process according to the invention if the polyester, based on the total of the condensed dicarboxylic acids and, if appropriate, Hydroxycarboxylic acids, 1 to 10 mol% of the compounds known from DE-C-23 46 787 and 24 54 189 are condensed in, the polyester units of the formula VI<chemistry id="chem0001" num="0001"><img file="EP0699700A2_D0001.tif" /></chemistry> deliver what<dl id="dl0001" compact="compact"><dt>R</dt><dd>a saturated open-chain or cyclic alkylene, arylene or aralkylene radical, preferably alkane-diyl having 2 to 6 carbon atoms, cycloalkane-diyl having 6 carbon atoms, methylenephenyl or phenylene, in particular ethylene, and</dd><dt>R¹</dt><dd>an alkyl radical with up to 6 carbon atoms or an aryl or aralkyl radical, preferably alkyl with 1 to 6 carbon atoms, or aryl or aralkyl with 6 to 7 carbon atoms, in particular methyl, ethyl, phenyl or benzyl.</dd></dl>

Up to 10% by weight of modification additives, fillers, pigments, dyes, antioxidants, hydrolysis, light and temperature stabilizers and / or processing aids can be added to the esterification, transesterification or polycondensation batches, provided that these additives do not inhibit the titanium catalyst. In the process according to the invention, preference is given in particular to the addition of up to 10% by weight, preferably up to 5% by weight, of polyester stabilizers which protect the polyester content of the mixture against hydrolysis and thermal degradation. Particularly advantageous stabilizers are those compounds which can react with terminal carboxyl groups of the polyester to form non-acidic end groups, such as, for example, glycidyl ethers, ketenimines, aziridines, isocyanates. Carbodiimides and polycarbodiimides are particularly advantageous as stabilizers, particularly when they are used in combination with one another.

The present invention also relates to the polyesters based on aromatic dicarboxylic acids and aliphatic diols which can be prepared by the process described above and which are distinguished by the fact that their color number components are present in the unmatted state    a * in the range from -3 to +3, preferably from -2 to +2,    b * in the range from -6 to +6, preferably from -3.5 to +3.5 and    L * are in the range from 55 to 75, preferably from 60 to 70.

Furthermore, the polyester according to the invention is characterized in that it    is free of antimony,    1 to 10 ppm titanium (calculated as metal),    20 to 120 ppm of a transesterification catalyst metal in the form of catalytically inactive complexes with phosphoric acid,    phosphorous acid and / or phosphonic acids or a derivative thereof,    and 0 to 80 ppm cobalt (calculated as metal), which is partly in the form of catalytically inactive complexes with phosphoric acid, phosphorous acid and / or phosphonic acids or a derivative thereof is present,    and possibly contains up to 50 ppm of an optical brightener.

The polyester according to the invention is preferably free from and contains antimony    2 to 8 ppm titanium (calculated as metal), 50 to 90 ppm of manganese (calculated as metal) in the form of catalytically inactive complexes with phosphoric acid, phosphorous acid and / or phosphonic acids or a derivative thereof,    and 20 to 40 ppm cobalt, which is partly in the form of catalytically inactive complexes with phosphoric acid, phosphorous acid and / or phosphonic acids or a derivative thereof, and if appropriate up to 25 ppm of an optical brightener.

It is further preferred that 90 to 99% of the cobalt is in the form of catalytically inactive complexes with phosphoric acid, phosphorous acid and / or phosphonic acids or a derivative thereof and / or that it contains 5 to 25 ppm of an optical brightener. The catalytically inactive complexes of the transesterification catalyst, preferably manganese, and cobalt can in principle contain all complexing agents known for the inactivation of these metals. The catalytically inactive complexes of the transesterification catalyst, in particular manganese, and cobalt with phosphoric acid, polyphosphoric acid or in particular phosphorous acid or a derivative, in particular an ester of these acids, are preferred. Of course, the structure of the polyester chain is of particular importance for all of the technical features. From a purely qualitative point of view it can be said that it is built up from the assemblies customary in known fiber-forming polyesters.

Mostly, ie at least 80 mol%, they consist of building blocks which are derived from aromatic dicarboxylic acids and from aliphatic diols. Common aromatic dicarboxylic acid building blocks are the divalent residues of benzenedicarboxylic acids, in particular terephthalic acid and isophthalic acid; Common diols have 2-4 carbon atoms, with the ethylene glycol being particularly suitable. Modified polyesters preferably contain at least 80 mol% of ethylene terephthalate units. The remaining 20 mol% then build up from dicarboxylic acid units and glycol units, which act as so-called modifying agents and which allow the person skilled in the art to specifically target the physical and chemical properties of the products made from the polyesters, such as filaments and packaging materials (eg beverage bottles) influence. Examples of such dicarboxylic acid units are residues of isophthalic acids or of aliphatic dicarboxylic acid such as, for example Glutaric acid, adipic acid, sebacic acid; Examples of diol residues with a modifying action are those of longer-chain diols, for example of propanediol or butanediol, of di- or triethylene glycol or, if present in small amounts, of polyglycol with a molecular weight of approximately 500-2000.

In particular, polyesters according to the invention are preferred whose polymer chains consist of    80 to 100 mol% of assemblies of the formula VI<chemistry id="chem0002" num="0002"><img file="EP0699700A2_D0002.tif" /></chemistry>    and 20 to 0 mol% of assemblies of the formula VII<chemistry id="chem0003" num="0003"><img file="EP0699700A2_D0003.tif" /></chemistry> are built up in what    X more than 80 mol% of aromatic residues with 5 to 16, preferably 6 to 12 carbon atoms and a maximum of 20 mol% of aliphatic residues with 4 to 10 carbon atoms,    preferably 6 to 8 carbon atoms,    X¹ is the p-phenylene radical    Y to at least 80 mol% of alkylene or polymethylene groups with 2 to 4 carbon atoms or cycloalkane or dimethylene-cycloalkane groups with 6 to 10 C atoms and    to a maximum of 20 mol% straight-chain or branched alkanediyl having 4 to 16, preferably 4 to 8, carbon atoms or radicals of the formula - (C₂H₄-O)_n-C₂H₄-, in which n is an integer from 1 to 40, where n = 1 or 2 are preferred for proportions up to 20 mol% and groups with n = 10 to 40 preferably only in proportions of less than 5 mol.- % available.

Polyesters according to the invention which consist of structural groups of the formula IV are particularly preferred    X 90 to 100 mol% of p-phenylene radicals, 0 to 7 mol% of m-phenylene radicals and 0 to 5 mol% of aliphatic radicals having 4 to 10 carbon atoms, preferably 6 to 8 carbon atoms    Y to at least 90 mol% alkylene or polymethylene groups with 2 to 4 carbon atoms or cycloalkane or dimethylene-cycloalkane groups with 6 to 10 carbon atoms and    to a maximum of 10 mol% straight-chain or branched alkanediyl having 4 to 16, preferably 4 to 8, carbon atoms or radicals of the formula - (C₂H₄-O)_n-C₂H₄-, wherein n represents the numbers 1 or 2 means.

Those polyesters according to the invention which consist of structural groups of the formula IV are particularly preferred    X means 93 to 99 mol% of p-phenylene radicals, and 1 to 7 mol% of m-phenylene radicals.

It is often expedient to set a defined degree of crosslinking of the polyester. In these cases it is preferred that the polyester contains up to 1000 ppm of the above-mentioned crosslinking components.

Advantageously, the polyesters according to the invention produced by melt polycondensation have an intrinsic viscosity (IV) of 0.600 to 0.900, measured in dichloroacetic acid at 25 ° C.

Polyesters which have assemblies of the formula VII preferably contain 70 to 100 mol%, in particular 85 to 100 mol%, assemblies of the formula VI and 0 to 30 mol%, in particular 0 to 15 mol%, Assemblies of formula VII.

The aromatic radicals represented by X can all be the same within the scope of the definition given, or they can be different. In particular, the above-mentioned assemblies represented by X, which form at least 80 mol% of the polyester chain, can be present individually or as a mixture in the polyester chain. It is preferred if the at least 80 mol% of the polyester chain is formed by only one or two individuals from the group of the radicals specified for these main components. Any desired further modification of the polyester chain is then preferably carried out by other assemblies within the scope of the definition given for the assemblies represented by X to a maximum of 20 mol%.

For example, the at least 80% by weight of aromatic radicals can all be 1,4-phenylene radicals, or they can be composed of 1,4- and 1,3-phenylene radicals in a molar ratio of 95: 5 to 99: 1 or in a molar ratio of 4 : 6 to 6: 4 from 2,6-naphthylene residues and biphenyl-4,4'-diyl residues. Preferred are polyesters in which X represents at least 95 mol% of aromatic and a maximum of 5 mol% of aliphatic radicals, but in particular those in which X stands exclusively for aromatic radicals.

The radicals for which Y stands can all be the same within the scope of the given definition, or they can be different. In particular, the above-mentioned assemblies represented by Y, which form at least 80 mol% of the polyester chain, can be present individually or as a mixture in the polyester chain. It is preferred if the at least 80 mol% of the polyester chain is formed by only one or two individuals from the group of the radicals specified for these main components.

A possibly desired further modification of the polyester chain is then preferably carried out by other assemblies within the scope of the definition given for the assemblies represented by Y to a maximum of 20 mol%. For example, the at least 80% by weight aliphatic radicals can all be ethylene radicals or they can be composed, for example, in a molar ratio of 10: 1 to 1:10 from ethylene and 1,4-dimethylene-cyclohexane radicals. Polyesters in which Y is at least 95 mol% of ethylene radicals are particularly preferred.

Preferred aromatic radicals for which X is 1,4- and 1,3-phenylene. Suitable radicals are also 1,4-, 1,5-, 1,8-, 2,6- and 2,7-naphthylene, 4,4'-biphenylene, furylene and radicals of the formula VI<chemistry id="chem0004" num="0004"><img file="EP0699700A2_D0004.tif" /></chemistry> wherein Z is polymethylene or alkylene having 1 to 4 carbon atoms, -SO₂-, -COO-, -O- or -S-.

The aromatic radicals for which X stands can in turn carry one or two substituents. In this case, however, it is preferred that only a proportion of up to 15%, in particular up to 7%, of the aromatic radicals present is substituted. The substituted aromatic radicals preferably each carry only one substituent. Particularly suitable substituents are alkyl with 1 to 4 carbon atoms, alkoxy with 1 to 4 carbon atoms, chlorine and the sulfo group.

Residues derived from aliphatic dicarboxylic acids and aromatic residues which give angled chains, for example isophthalic acid residues, or which have bulky aromatic nuclei, such as the naphthalene nucleus, as well as the longer-chain units which represent Y are incorporated into the polyester chain in particular if one Modification of the properties of the polyester is desired. Polyesters are preferred which contain less than 7% of these modifying components.

To achieve special usage properties, for example, the incorporation of building blocks containing sulfo groups (e.g. sulfo-isophthalic acid) into the polyester, which thereby has an affinity for basic dyes, or the incorporation of assemblies of the formula VI given above, which leads to flame-retardant polyesters.

Example 1a

A transesterification reactor is charged with 9.75 kg of dimethyl terephthalate, 0.25 kg of dimethyl isophthalate, 6 kg of ethylene glycol and 3 g of manganese acetate · 4 H₂O (68 ppm manganese, based on polyester) and the mixture is stirred and under nitrogen as a protective gas at 140 ° C. warmed up. The reaction temperature is increased to 230 ° C. in the course of 4 hours and the methanol which is split off and the excess of ethylene glycol are distilled off. The molten reaction product is then transferred to a polycondensation vessel, with 1.65 g (165 ppm) of H₃PO₃ as a complexing agent, and 1.27 g (127 ppm) of cobalt acetate (corresponding to 30 ppm Co) and added for 10 to 15 minutes at 230 ° C touched. Then 0.27 g (27 ppm) of potassium titanyl oxalate (corresponding to 3.6 ppm of Ti) are added and the mixture is stirred under nitrogen at 240 ° C., ethylene glycol being distilled off under a slight vacuum. Then the internal pressure is reduced to 1.13 mbar over the course of an hour and the temperature of the melt is increased from 240 to 270 ° C. In the course of a further half an hour, the temperature is then raised to 280 ° C. and stirring is continued until a sample of the melt has a specific solution viscosity, measured in a solution of 1 g of the melt in 100 ml of dichloroacetic acid at 25 ° C., from 0. 83 has. Alternatively and more conveniently, the polycondensation can also be continued up to a certain melt viscosity if the melt viscosity at 280 ° C., which corresponds to the solution viscosity of 0.83, was determined in preliminary tests.

The melt is cooled and processed in the usual way to pellets with a diameter of 2 to 3 mm. The polyester thus obtained has the following key figures: <tables id="tabl0001" num="0001"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">Carboxyl group content [mmol / kg]:</entry><entry namest="col2" nameend="col2" align="left">12</entry></row><row><entry namest="col1" nameend="col1" align="left">Diethylene glycol content [%]:</entry><entry namest="col2" nameend="col2" align="left">0,5</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">Color numbers: L * = 63.44; a * = -0.62;</entry><entry namest="col2" nameend="col2" align="left">b * = 3.09</entry></row></tbody></tgroup></table></tables>

The polyester thus produced can be further condensed by solid condensation. For this purpose, the pellets produced above are heated in a conventional manner at 220 ° C. for 17 hours with slow mixing in vacuo or under nitrogen. A polyester with a specific viscosity of 1.014 as measured above is thus obtained.

Examples 1b to 1l

The above example was repeated several times in the discontinuous manner described in Example 1a (Examples 1j to 1l) or analogously in continuous operation (Examples 1b to 1i), the amount of cobalt addition, the type and amount of complexing agent, and the type and amount of Titanium catalyst was changed and in some cases a commercial optical brightener (® HOSTALUX KS from Hoechst AG) or a crosslinker (pentaerythritol) was added. The polycondensation in the melt was carried out under different pressures and with different reaction times, and the condensation duration and temperature were varied in the case of solid condensation.

The composition of the batches and the reaction conditions, insofar as they were varied, the color numbers, the specific viscosity achieved and the content of carboxylic acid groups and diglycol in the polyesters are given in Tables 1 and 2 below. The abbreviations used in the tables have the following meanings: KTi = potassium titanyl oxalate; Tiip = isopropyl titanate Co (AcO) ₂ · 4 H₂O = cobalt acetate tetrahydrate PO3 = phosphorous acid; PO4 = phosphoric acid; PPA = polyphosphoric acid; PHM = PHM ester HLX = ® HOSTALUX KS; Penta = pentaerythritol SV = specific viscosity; [COOH] carboxyl end group concentration; DEG = concentration of diethylene glycol All ppm figures relate to the amount of the batch <u>theoretically</u> polyester to be obtained. If the additive is a metal compound (eg catalyst), the name of the compound abbreviation means that the ppm indication denotes the amount of the compound, if the metal symbol is indicated, the ppm indication means the amount of the metal contained in the additive.<tables id="tabl0002" num="0002"><img file="EP0699700A2_D0005.tif" /></tables><tables id="tabl0003" num="0003"><img file="EP0699700A2_D0006.tif" /></tables>

Example 2

The following embodiment illustrates the production of a polyester by direct esterification: An esterification reactor is charged with 8.29 kg of terephthalic acid, 0.124 kg of isophthalic acid and 4.0 kg of ethylene glycol, and the mixture is heated under stirring and under nitrogen as a protective gas under a pressure of 3.2 bar so that the water which is split off distills off. When the elimination of water has ended, the molten reaction product is transferred to a polycondensation vessel with 0.35 g (32 ppm) of H₃PO₃ as a complexing agent, and 1.47 g (135 ppm) of cobalt acetate tetrahydrate (equivalent to 32 ppm Co).

Then 0.49 g (45 ppm) of potassium titanyl oxalate (corresponding to 6.1 ppm of Ti) are added and the mixture is stirred under nitrogen at 240 ° C., ethylene glycol being distilled off under a slight vacuum. Then the internal pressure is reduced to 1.13 mbar over the course of an hour and the temperature of the melt is increased from 240 to 270 ° C. In the course of a further half an hour, the temperature is then raised to 280 ° C. and stirring is continued until a sample of the melt has a specific solution viscosity, measured in a solution of 1 g of the melt in 100 ml of dichloroacetic acid at 25 ° C., from 0. 83 has. The melt is cooled and processed in the usual way to pellets with a diameter of 2 to 3 mm. The polyester thus obtained has the following key figures: <tables id="tabl0004" num="0004"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">Carboxyl group content [mmol / kg]:</entry><entry namest="col2" nameend="col2" align="left">13</entry></row><row><entry namest="col1" nameend="col1" align="left">Diethylene glycol content [%]:</entry><entry namest="col2" nameend="col2" align="left">1,19</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">Color numbers: L * = 63.6; a * = 1.90;</entry><entry namest="col2" nameend="col2" align="left">b * = -1.5</entry></row></tbody></tgroup></table></tables>

The polyester thus produced can be further condensed by solid condensation. For this purpose, the pellets produced above are heated to 220 ° C. for 9.5 hours with slow mixing under nitrogen or in vacuo. A polyester with a specific viscosity of 1.087, as measured above, is thus obtained.

In an analogous manner, with the conditions shown in Tables 3 and 4, further polyesters can be produced. The products have the characteristics shown in Table 4.<tables id="tabl0005" num="0005"><img file="EP0699700A2_D0007.tif" /></tables>