WO2025132369A1

WO2025132369A1 - Process for the preparation of polyesters using terephthalic acid

Info

Publication number: WO2025132369A1
Application number: PCT/EP2024/086809
Authority: WO
Inventors: Clemens LIEDEL; Hiroe Yamada; Michael Mager; Peter Klug
Original assignee: Clariant International Ltd
Current assignee: Clariant International Ltd
Priority date: 2023-12-19
Filing date: 2024-12-17
Publication date: 2025-06-26
Anticipated expiration: 2026-06-19
Also published as: WO2025132402A1; WO2025132368A1

Abstract

A process for preparing polyesters from at least terephthalic acid, propylene glycol and one or more specific substances resulting in terminal groups is described. The process, e.g., possesses the advantage that recycling of side products is facilitated. The polyesters may be used as soil release polymers, in particular in laundry detergent compositions.

Description

PROCESS FOR THE PREPARATION OF POLYESTERS USING TEREPHTHALIC ACID

The invention relates to a process for preparing polyesters, products or polyesters obtainable by the process, the use of the products or polyesters as soil release polymers and laundry detergent compositions comprising the products or polyesters.

Polyesters based on dimethyl terephthalate and their use as soil release polymers especially in laundry detergent compositions are already known. GB 1 ,466,639, US 4,132,680, US 4,702,857, EP 0 199 403, US 4,711 ,730, US 4,713,194, and US 4,759,876 describe polyesters based on dimethyl terephthalate and their use as soil release polymers and disclose aqueous detergent compositions containing soil release polymers.

However, processes of the prior art for preparing soil release polymers often result in the formation of mixed side product streams, e.g., comprising dimethyl terephthalate, methanol, alkylene glycols, and/or other products which are hard and/or expensive to separate and reuse or recycle.

Therefore, it was an object of the present invention to provide a process for the preparation of polyesters which might be used as soil release polymers during which recycling of side products is facilitated.

It has been found that this object can be solved by a process for preparing a polyester by reacting at least

- terephthalic acid (formula (I))

and propylene glycol (formula (II))

HO-(C₃H₆)-OH (II) wherein the propylene glycol (formula (II)) preferably is 1 ,2-propylene glycol and

- one or more substances of the formula (III)

R¹-[OR²]_a-OH (III) or mixtures thereof wherein

R¹ is a linear or branched, preferably a linear, alkyl group comprising from 1 to 6 carbon atoms or a linear or branched, preferably a linear, alkenyl group comprising one or more double bonds and from 2 to 6 carbon atoms or mixtures thereof, preferably is a linear or branched, preferably a linear, alkyl group comprising from 1 to 4 carbon atoms or a linear or branched, preferably a linear, alkenyl group comprising one or more double bonds and from 2 to 4 carbon atoms or mixtures thereof, more preferably is methyl, a is, based on a molar average, a number of from 1 to 200, preferably of from 2 to 200, more preferably of from 3 to 150, and

R² is a linear or branched alkylene group (C_mH2m) with m being an integer of from 2 to 10 or mixtures thereof, preferably with m being an integer of from 2 to 6 or mixtures thereof, more preferably is selected from the group consisting of (C2H4), (CsHe), (C4H8) and mixtures thereof, even more preferably is selected from the group consisting of (C2H4), (CsHe) and mixtures thereof, particularly preferably is (C2H4) or a mixture of (C2H4) and (CsHe), and extraordinarily preferably is (C2H4), characterized in that the preparation of the polyester comprises the steps of: a) heating a mixture comprising terephthalic acid, propylene glycol, and one or more substances of the formula (III) or mixtures thereof and removing water until at least 50%, preferably at least 75%, more preferably at least 90%, even more preferably at least 95%, and particularly preferably at least 97% of the carboxylic acid groups of terephthalic acid are esterified and b) polycondensing the mixture obtained in step a) or a composition comprising the mixture obtained in step a) at ambient pressure or reduced pressure, preferably at reduced pressure, while removing propylene glycol and preferably also side products.

Therefore, a subject matter of the invention is a process for preparing a polyester by reacting at least

- terephthalic acid (formula (I))

and

- propylene glycol (formula (II))

- one or more substances of the formula (III)

R¹-[OR²]_a-OH (III) or mixtures thereof wherein R¹ is a linear or branched, preferably a linear, alkyl group comprising from 1 to 6 carbon atoms or a linear or branched, preferably a linear, alkenyl group comprising one or more double bonds and from 2 to 6 carbon atoms or mixtures thereof, preferably is a linear or branched, preferably a linear, alkyl group comprising from 1 to 4 carbon atoms or a linear or branched, preferably a linear, alkenyl group comprising one or more double bonds and from 2 to 4 carbon atoms or mixtures thereof, more preferably is methyl, a is, based on a molar average, a number of from 1 to 200, preferably of from 2 to 200, more preferably of from 3 to 150, and

R² is a linear or branched alkylene group (C_mH2m) with m being an integer of from 2 to 10 or mixtures thereof, preferably with m being an integer of from 2 to 6 or mixtures thereof, more preferably is selected from the group consisting of (C2H4), (C3H6), (C4H8) and mixtures thereof, even more preferably is selected from the group consisting of (C2H4), (CsHe) and mixtures thereof, particularly preferably is (C2H4) or a mixture of (C2H4) and (CsHe), and extraordinarily preferably is (C2H4), characterized in that the preparation of the polyester comprises the steps of: a) heating a mixture comprising terephthalic acid, propylene glycol, and one or more substances of the formula (III) or mixtures thereof and removing water until at least 50%, preferably at least 75%, more preferably at least 90%, even more preferably at least 95%, and particularly preferably at least 97% of the carboxylic acid groups of terephthalic acid are esterified and b) polycondensing the mixture obtained in step a) or a composition comprising the mixture obtained in step a) at ambient pressure or reduced pressure, preferably at reduced pressure, while removing propylene glycol and preferably also side products. WO 2016/146429 A1 describes polyesters obtainable from the dicarboxylic acid terephthalic acid and, where appropriate, isophthalic acid, and from ethylene glycol and polyethylene glycol, with average molecular weights ranging between 2000 g/mol and 8000 g/mol.

DE 44 17 686 A1 describes a process for preparing polyesters, wherein a dicarboxylic acid HOOC-Ph-COOH or its reactive derivative is reacted with a monomeric diol under esterification conditions, subsequently is reacted with a polymeric diol under transesterification conditions and is reacted with a monocarboxylic acid, hydroxymonocarboxylic acid, and/or dicarboxylic acid monoester under esterification conditions.

JPH0232123A discloses a copolymer which can be produced by compounding (A) a dicarboxylic acid (derivative) composed mainly of terephthalic acid, (B) ethylene glycol, (C) a polyalkylene glycol having an average molecular weight of 500-4,000 and (D) a polyalkylene glycol blocked at one terminal and having an average molecular weight of 500-4,000 and subjecting the mixture to polycondensation reaction. The amount of the component D is 0.5-5wt.% and that of C+D is 1 -10wt.%.

EP 1 734 171 A1 describes a fiber-treating agent, e.g., comprising a polyester compound produced by carrying out a condensation polymerization of a polyoxyalkylene monol, an alkylene glycol, and at least one member selected from the group consisting of aromatic dicarboxylic acids and their ester-forming derivatives.

WO 2021/233987 A1 describes a process for the preparation of a polyester comprising the steps of: heating one or more substances of the formula Q1 -OOC-C6H4-COO-Q2, wherein Q1 and Q2, independently of one another, are selected from the group consisting of H and (Ci-C4)-alkyl and preferably are CH3, and 1 ,2-propyleneglycol, and one or more specific (poly)alkylene glycol mono C7-C30 alkyl or alkenyl ethers or mixtures thereof, with the addition of a catalyst, to temperatures of from 160 to 220 °C, preferably beginning at atmospheric pressure, and then continuing the reaction under reduced pressure at temperatures of from 160 to 240 °C.

The inventive process possesses the advantage that low levels of side products are generated. For example, formation of dimethyl terephthalate and/or methanol is omitted or largely reduced. Recycling of removed propylene glycol is possible. The process is sustainable and the amount of side products is low. The process leads to products which possess good soil release properties. Obtained products have a high purity and are available in good yield. The inventive process also possesses the advantage that it can be interrupted between step a) and step b) and/or during step a) and/or during step b), which facilitates taking of samples, determining the completeness of the reaction, storing of intermediates, combination with further chemicals, and combination of batches.

Different grades of terephthalic acid can be used in the inventive process.

In one preferred embodiment of the inventive process, combinations of purified and non-purified terephthalic acid can be used, more preferably comprising at least 50 wt.-%, even more preferably comprising at least 80 wt.-%, and particularly preferably comprising 100 wt.-% purified terephthalic acid, in each case based on the total weight of terephthalic acid used in the inventive process.

In another preferred embodiment of the inventive process, combinations of recycled and non-recycled terephthalic acid can be used, more preferably comprising at least 50 wt.-%, even more preferably comprising at least 80 wt.-%, and particularly preferably comprising 100 wt.-% recycled terephthalic acid, in each case based on the total weight of terephthalic acid used in the inventive process.

The process of obtaining recycled terephthalic acid by hydrolysis of polyethylene terephthalate is known to the person skilled in the art. For example, it is available via the process described in V. Tournier et al., Nature, Vol. 580, 9. April 2020, p.216-219. In another preferred embodiment of the inventive process, combinations of renewable and non-renewable terephthalic acid can be used, more preferably comprising at least 50 wt.-%, even more preferably comprising at least 80 wt.-%, and particularly preferably comprising 100 wt.-% renewable terephthalic acid, in each case based on the total weight of terephthalic acid used in the inventive process.

The process of obtaining renewable terephthalic acid is known to the person skilled in the art. US 2023/0125062 describes systems and methods for producing aromatic compounds such as para-xylene in high yield from oxygenated hydrocarbons such as carbohydrates, sugars, sugar alcohols, sugar degradation products, and the like. Renewable terephthalic acid can be obtained by oxidation of para-xylene.

Propylene glycol (formula (II)) preferably is 1 ,2-propylene glycol, i.e., preferably is of the formula HO-CH(CH₃)-CH₂-OH or HO-CH₂-CH(CH₃)-OH.

In a preferred embodiment of the inventive process, combinations of recycled and non-recycled propylene glycol can be used, more preferably comprising at least 30 wt.-%, even more preferably comprising at least 50 wt.-%, particularly preferably comprising at least 60 wt.-%, and extraordinarily preferably comprising 100 wt.-% recycled propylene glycol, in each case based on the total weight of propylene glycol used in the inventive process.

In another preferred embodiment of the inventive process, combinations of renewable and non-renewable propylene glycol can be used, more preferably comprising at least 50 wt.-%, even more preferably comprising at least 80 wt.-%, and particularly preferably comprising 100 wt.-% renewable propylene glycol, in each case based on the total weight of propylene glycol used in the inventive process. The process of obtaining renewable propylene glycol is known to the person skilled in the art. For example, it is available via the process described in US 8,378,152.

Examples of the alkyl and alkenyl groups R¹ in the one or more substances of the formula (III) or mixtures thereof are, for example, methyl, ethyl, linear or branched propyl, butyl, pentyl, hexyl, vinyl, linear or branched propenyl, butenyl, pentenyl, hexenyl, or mixtures thereof.

In a preferred embodiment of the inventive process, R¹ in the one or more substances of the formula (III) or mixtures thereof is a linear or branched, preferably a linear, alkyl group comprising from 1 to 4 carbon atoms or a linear or branched, preferably a linear, alkenyl group comprising one or more double bonds and from 2 to 4 carbon atoms or mixtures thereof.

In a more preferred embodiment of the inventive process, R¹ in the one or more substances of the formula (III) or mixtures thereof is a linear or branched, preferably a linear, alkyl group comprising from 1 to 6 and preferably from 1 to 4 carbon atoms, or mixtures thereof.

In an even more preferred embodiment of the inventive process, R¹ in the one or more substances of the formula (III) or mixtures thereof is methyl.

In a preferred embodiment of the inventive process, in the one or more substances of the formula (III) or mixtures thereof, at least a part of the groups R² are (CH2CH2) groups. More preferably, in the one or more substances of the formula (III) or mixtures thereof, at least 50 mol-%, even more preferably at least 60 mol-% and particularly preferably at least 70 mol-% of the groups R², in each case based on the total amount of the groups R², are (CH2CH2) groups.

In the one or more substances of the formula (III) or mixtures thereof, the groups R² extraordinarily preferably are (CH2CH2) groups or a mixture of (CH2CH2) groups and (C3H6) groups, wherein preferably at least 50 mol-%, more preferably at least 60 mol % and even more preferably at least 70 mol-% of the groups R², in each case based on the total amount of the groups R², are (CH2CH2) groups and especially preferably, the groups R² are (CH2CH2) groups.

In another preferred embodiment of the inventive process, in the one or more substances of the formula (III) or mixtures thereof, at least a part of the groups R² are (CH2CH2) groups made from renewable ethylene oxide. More preferably, in the one or more substances of the formula (III) or mixtures thereof, at least 50 mol-%, even more preferably at least 60 mol-% and particularly preferably at least 70 mol-% of the groups R², in each case based on the total amount of the groups R², are (CH2CH2) groups made from renewable ethylene oxide.

In the one or more substances of the formula (III) or mixtures thereof, the groups R² extraordinarily preferably are (CH2CH2) groups made from renewable ethylene oxide or a mixture of (CH2CH2) groups made from renewable ethylene oxide and (C3H6) groups, wherein preferably at least 50 mol-%, more preferably at least 60 mol-% and even more preferably at least 70 mol-% of the groups R², in each case based on the total amount of the groups R², are (CH2CH2) groups made from renewable ethylene oxide and especially preferably, the groups R² are (CH2CH2) groups made from renewable ethylene oxide.

Renewable ethylene oxide can be obtained from bio-ethanol, which can be obtained from natural sources like com, sugarcane, or cellulosic biomass through fermentation. Bio-ethanol can be dehydrated to produce bio-ethylene which can be oxidized with oxygen over a silver catalyst to produce renewable ethylene oxide.

In the case that at least two different types of [0(C_mH2m)] groups, for example [O(C2H4)], [O(C3He)], and [O(C4Hs)] groups, exist in the one or more substances of the formula (III) or mixtures thereof, they may be arranged blockwise, alternating, periodically and/or statistically, preferably blockwise and/or statistically. This means that in a substance of the formula (III), the [0(C_mH2m)] groups, and, e.g., the groups [O(C2H4)], [O(C3He)] and [O(C4Hs)], may be arranged, for example, in a purely statistically or blockwise form but may also be arranged in a form which could be considered as both statistical and blockwise, e.g., small blocks of [(OC2H4)] and [O(C3He)] arranged in a statistical manner, or in a form wherein adjacent instances of statistical and blockwise arrangements of the groups [O(C₂H₄)], [O(C₃H₆)], and [O(C₄H₈)l exist.

Any of the groups [0(C_mH2m)], e.g., any of the groups [O(C2H4)], [O(C3H₈)], and [O(C4HS)], can be linked to R¹- and -OH in a substance of the formula (III). This means, for example, that both, R¹- and -OH in a substance of the formula (III), may be connected to a [O(C2H4)] group, they may both be connected to a [O(C3H₈)] group, they may both be connected to a [O(C4Hs)] group, or they may be connected to different groups [0(C_mH2m)], e.g., selected from [O(C2H4)], [O(C3H₈)] and [O(C₄H₈)].

In a preferred embodiment of the inventive process, the one or more substances of the formula (III) or mixtures thereof are of the formula (111-1 )

R¹-(OC₂H₄)b-(OC3H6)c-OH (111-1 ) or mixtures thereof, wherein

R¹ has the meaning as described above for formula (III), the -(OC2H4) groups and the -(OCsHe) groups are arranged blockwise, alternating, periodically and/or statistically, preferably blockwise, wherein the block consisting of the -(OCsHe) groups is bound to -OH, b is, based on a molar average, a number of from 1 to 199, preferably of from 2 to 199, more preferably of from 3 to 149, even more preferably of from 12 to 120 and particularly preferably of from 40 to 50, c is, based on a molar average, a number of from 1 to 199, preferably of from 1 to 10 and more preferably of from 1 to 7, and the sum b + c is, based on a molar average, a number less than or equal to 200 and preferably a number less than or equal to 150.

In the one or more substances of the formula (111-1 ) or mixtures thereof, preferably at least 50 mol-%, more preferably at least 60 mol-% and even more preferably at least 70 mol-% of the groups (OC2H4) and (OC3H6), in each case based on the total amount of the groups (OC2H4) and (OC3H6), are (OCH2CH2) groups.

In the one or more substances of the formula (111-1 ) or mixtures thereof, particularly preferably at least 50 mol-%, more preferably at least 60 mol-% and even more preferably at least 70 mol-% of the groups (OC2H4) and (OC3H6), in each case based on the total amount of the groups (OC2H4) and (OC3H6), are (OCH2CH2) groups made from renewable ethylene oxide.

In the case that more than one substance of the formula (III) is used in the inventive process, the definition of R¹, R² and “a” may vary between those substances.

In the case that more than one substance of the formula (111-1 ) is used in the inventive process for preparing a polyester, the definition of R¹, “b” and “c” may vary between those substances.

In the inventive process, step b) is performed after step a) has been performed.

Between step a) and step b), further actions such as, e.g., adjusting the temperature and/or adjusting the pressure and/or combination with further chemicals may be performed.

In a preferred embodiment of the inventive process, the mixture obtained in step a) is polycondensed in step b).

In another preferred embodiment of the inventive process, a composition comprising the mixture obtained in step a) is polycondensed in step b).

In a preferred embodiment of the inventive process, step b) is performed immediately after step a) has been performed. In this preferred embodiment of the inventive process, the mixture obtained in step a) is polycondensed in step b). In another preferred embodiment of the inventive process, step b) is performed after (i) step a) has been performed and (ii) the reaction conditions have been adjusted. In this preferred embodiment of the inventive process, the mixture obtained in step a) is polycondensed in step b).

In another preferred embodiment of the inventive process, step b) is performed after (i) step a) has been performed and (ii) the mixture obtained in step a) has been combined with further chemicals, e.g., by addition of further chemicals to the mixture obtained in step a) or by addition of the mixture obtained in step a) to further chemicals, and, optionally, (iii) the reaction conditions have been adjusted. In this preferred embodiment of the inventive process, a composition comprising the mixture obtained in step a) is polycondensed in step b).

In another preferred embodiment of the inventive process, the mixture obtained in step a) is stored and used at a later time to execute step b). Before executing step b), the reaction conditions may be adjusted and/or the mixture obtained in step a) may be combined with further chemicals, e.g., by addition of further chemicals to the mixture obtained in step a) or by addition of the mixture obtained in step a) to further chemicals. In this preferred embodiment of the inventive process, the mixture obtained in step a) is polycondensed in step b) or a composition comprising the mixture obtained in step a) is polycondensed in step b).

In another preferred embodiment of the inventive process, the mixture obtained in step a) is combined with one or more other mixtures which were obtained from step a) of the inventive process, e.g., by running step a) of the inventive process twice or multiple times in the same or different vessels and combining both/all batches, and optionally further chemicals, before executing step b). In this preferred embodiment of the inventive process, a composition consisting of or comprising the mixtures obtained in step a) is polycondensed in step b).

When heating a mixture comprising terephthalic acid, propylene glycol, and one or more substances of the formula (III) or mixtures thereof and removing water until at least 50%, preferably at least 75%, more preferably at least 90%, even more preferably at least 95%, and particularly preferably at least 97% of the carboxylic acid groups of terephthalic acid are esterified in step a), either one or both of the carboxylic acid groups of terephthalic acid may be esterified with propylene glycol so that monopropyleneglycol terephthalate, dipropyleneglycol terephthalate, oligomers, polymers, and mixtures thereof are formed, either one or both of the carboxylic acid groups of terephthalic acid may be esterified with the same or different substances of the formula (III), either one or both of the carboxylic acid groups of terephthalic acid may be esterified with other species which may be present, or all combinations of esterification reactions may be possible. For example, the resulting mixture may comprise

and/or

and/or oligomers and/or polymers and/or mixtures thereof. Preferably, the mixture in step a) is heated to temperatures of more than 90 °C, more preferably to temperatures of from 100 °C to 300 °C, even more preferably to temperatures of from 120 °C to 280 °C, particularly preferably to temperatures of from 140 °C to 260 °C and extraordinarily preferably to temperatures of from 160 °C to 250 °C.

In one preferred embodiment of the inventive process, heating in step a) is executed partly at ambient pressure and partly at reduced pressure or completely at ambient pressure or completely at reduced pressure, more preferably at ambient pressure, to temperatures of more than 90 °C, more preferably to temperatures of from 100 °C to 300 °C, even more preferably to temperatures of from 120 °C to 280 °C, particularly preferably to temperatures of from 140 °C to 260 °C and extraordinarily preferably to temperatures of from 160 °C to 240 °C.

In another preferred embodiment of the inventive process, heating in step a) is executed partly at ambient pressure and partly at elevated pressure or completely at elevated pressure and more preferably partly at ambient pressure and partly at elevated pressure to temperatures of more than 90 °C, more preferably to temperatures of from 100 °C to 300 °C, even more preferably to temperatures of from 120 °C to 280 °C, particularly preferably to temperatures of from 140 °C to 260 °C and extraordinarily preferably to temperatures of from 160 °C to 250 °C.

In another preferred embodiment of the inventive process, heating in step a) is executed partly at elevated pressure, partly at ambient pressure, and partly at reduced pressure to temperatures of more than 90 °C, more preferably to temperatures of from 100 °C to 300 °C, even more preferably to temperatures of from 120 °C to 280 °C, particularly preferably to temperatures of from 140 °C to 260 °C and extraordinarily preferably to temperatures of from 160 °C to 250 °C.

To determine whether at least 50%, preferably at least 75%, more preferably at least 90%, even more preferably at least 95%, and particularly preferably at least 97% of the carboxylic acid groups of terephthalic acid are esterified in step a), suitable analytical methods may be used. Suitable analytical methods may be for example:

- Infrared spectroscopy (IR): This method measures the absorption of infrared light by the molecules of the sample and produces a characteristic spectrum that reflects the functional groups and bonds of terephthalic acid and reaction products, e.g., the relative amount of carboxyl groups and ester groups.

- Nuclear magnetic resonance spectroscopy (NMR): This method uses the magnetic behavior of atomic nuclei to obtain information about the structure and environment of molecules. The number, chemical shift, and shape of the signals in the NMR spectrum depend on the kind, coupling constants and relaxation times of the molecules present in the sample. The integration of the signals provides information about the relative amounts of the different nuclei in the sample. NMR spectroscopy can help to determine unreacted carboxylic acid groups of terephthalic acid in the mixture by comparing the intensity of the signals assigned to the carboxyl groups that are not esterified with the signals assigned to the aromatic rings or other components of the mixture.

- Titration: This method determines the concentration of carboxylic acid groups of terephthalic acid by a neutralization reaction with a known concentration of a base, such as sodium hydroxide (NaOH). The amount of base consumed is measured, e.g., with a pH meter or an indicator that shows a color change. The concentration of carboxylic acid groups of terephthalic acid can be calculated from the equivalence point.

- Measurement of the amount of water formed in step a), e.g., by determining the amount and water content of the distillate, e.g., by Karl Fischer titration.

The choice of the most suitable analytical method may depend on the presence of further constituents of the mixture heated in step a) in addition to terephthalic acid, propylene glycol, and one or more substances of the formula (III) or mixtures thereof.

In a preferred embodiment of the inventive process, ¹³C NMR is employed as analytical measure to determine whether at least 50%, preferably at least 75%, more preferably at least 90%, even more preferably at least 95%, and particularly preferably at least 97% of the carboxylic acid groups of terephthalic acid are esterified in step a). Preferably, 500 mg of the sample are weighed in a 5 ml vial, and 2 ml solvent dimethylsulfoxide-d6 and 10 mg chrome-(lll)-acetoacetate are added. Once the sample is completely dissolved, the solution is filled in an NMR tube. ¹³C NMR is performed using a Bruker ADVANCE III 400 MHz spectrometer operating at 100.59 MHz using the pulse sequence zgig30 in the range -20 to 220 ppm. 1024 scans are measured with an acquisition time of 4.0 seconds and a relaxation delay of 4.0 seconds at 26 °C. By comparing the sum of the integrated intensities of the peak or peaks of the unreacted carbonyl groups of terephthalic acid around 167 ppm to other peaks, the degree of esterification can be calculated.

In a more preferred embodiment of the inventive process, therefore, the sum of the integrated intensities of the terephthalic acid ester carbonyl peaks around 165 ppm is divided by the sum of (i) + (ii), with (i) being the sum of the integrated intensities of the terephthalic acid ester carbonyl peaks and (ii) being the sum of the integrated intensities of the peak or peaks of the unreacted carbonyl groups of terephthalic acid around 167 ppm, and multiplied by 100 to give the percent esterification of terephthalic acid groups. This method is versatile and particularly suited if the chemical shift of all components present in the reaction is known, e.g., by reference measurements, and if terephthalic acid ester carbonyl peaks are clearly distinguishable from other peaks.

In another more preferred embodiment of the inventive process, therefore, the ratio R = (i)/(ii) is calculated, with (i) being the sum of the integrated intensities of the peak or peaks of the unreacted carbonyl groups of terephthalic acid around 167 ppm and (ii) being to the sum of the integrated intensities of those aromatic carbon peaks around 129-134 ppm which belong to terephthalic acid groups or terephthalic acid ester groups, and the change of this ratio during the reaction in step a) is monitored. The degree of esterification is calculated by degree of esterification = [100 - (100 * Rt/Ro)] % with Rt being the ratio as described above at reaction time “t” in step a) and Ro being the ratio as described above before the reaction started. This method is versatile and particularly suited if the chemical shift of all components present in the reaction is known, e.g., by reference measurements, and if aromatic carbon peaks which belong to terephthalic acid groups or terephthalic acid ester groups are clearly distinguishable from other peaks.

In another preferred embodiment of the inventive process, IR is employed as analytical measure to determine whether at least 50%, preferably at least 75%, more preferably at least 90%, even more preferably at least 95%, and particularly preferably at least 97% of the carboxylic acid groups of terephthalic acid are esterified in step a). Preferably, the sum of the integrated areas under the C=O stretch peaks of terephthalic acid (mono- and di-) esters around 1750 cm^-1 is divided by the sum of (i) + (ii), with (i) being the sum of the integrated areas under the C=O stretch peaks of terephthalic acid (mono- and di-) esters around 1750 cm^-1 and (ii) being the sum of the integrated areas under the C=O stretch peaks of acid groups -COOH of terephthalic acid and of terephthalic acid monoesters around 1700 cm^-1 and multiplied by 100 to give the percent esterification of terephthalic acid groups. This method is particularly suited in case the C=O stretch peaks of terephthalic acid (mono- and di-) esters and terephthalic acid are clearly distinguishable from other chemical functionalities present in the reaction.

In another preferred embodiment of the inventive process, the mixture heated in step a) does not comprise components with acidic groups in addition to terephthalic acid. In this preferred embodiment of the inventive process, the percentage of the carboxylic acid groups of terephthalic acid which are esterified in step a) may be determined by measuring the acid value of a sample taken during step a), calculating the amount of acid groups, and comparing with the amount of acid groups which were initially present.

The acid value of a sample taken during step a) may be determined by volumetric titration with phenolphthalein as indicator, preferably as detailed in the following: 0.5 g of a homogeneous sample, which may, e.g., be a homogeneous dispersion, melt or solution, is dissolved in 60 mL isopropanol. Up to 60 mL xylene may be added to obtain a clear solution. In case no clear solution is reached, the acid value is considered not measurable, and heating in step a) is continued. Three drops of a solution of phenolphthalein in isopropanol (1 .0 wt.-%) are added. The obtained solution is slowly titrated with a fresh solution of potassium hydroxide (KOH) in isopropanol (0.01 mol/L) until a color change from colorless to pink is observed. The acid value in mg KOH/g is calculated from the amount of KOH used, and from the mass of the sample according to

wherein AV is the acid value in mg KOH/g, V_K0H [mL] is the added volume of the fresh solution of potassium hydroxide until a color change from colorless to pink is observed in mL, c_KOH [mol/L] is the concentration of the fresh solution of potassium hydroxide (KOH) in isopropanol (0.01 mol/L), M_KOH [g/mol] is 56.11 g/mol, and m_sampie [g] is the mass of the sample in g.

Polycondensing the mixture obtained in step a) or a composition comprising the mixture obtained in step a) means that by condensation reactions, oligomeric and/or polymeric species are formed. Besides those species, the product obtained after step b) may additionally contain, e.g., side products and/or unreacted species (e.g., species which have been present already at the beginning of step b)) and/or auxiliary materials such as, e.g., catalysts and/or their decomposition products. Besides condensation reactions, in particular transesterification reactions, further reactions such as, e.g., esterification reactions may also take place in step b), e.g., esterification reactions of previously unreacted terephthalic acid with propylene glycol and/or with one or more substances of the formula (III) or mixtures thereof and/or with species formed in step a).

Polycondensing in step b) is preferably executed at a pressure of from 0.1 to 900 mbar, more preferably at a pressure of from 0.5 to 500 mbar, even more preferably at a pressure of from 0.5 to 400 mbar, and preferably at temperatures of more than 90 °C, more preferably at temperatures of from 100 °C to 300 °C, even more preferably at temperatures of from 150 °C to 280 °C, particularly preferably at temperatures of from 160 °C to 270 °C and extraordinarily preferably at temperatures of from 180 °C to 260 °C.

In a preferred embodiment of the inventive process, the polycondensation reaction in step b) is, on average or completely, executed at a higher temperature than the esterification reaction in step a).

In another preferred embodiment of the inventive process, the polycondensation reaction in step b) is executed, on average or completely, at a lower pressure than the esterification reaction in step a).

In a more preferred embodiment of the inventive process, heating in step a) is executed at a pressure of more than 400 mbar, and polycondensing in step b) is, on average or completely, executed at a pressure of from 0.5 to 400 mbar.

In a preferred embodiment of the inventive process, removal of water in step a) is executed in a way that the majority of other components is not removed.

In a more preferred embodiment of the inventive process, from 0 to 10 wt.-%, even more preferably from 0 to 5 wt.-%, particularly preferably from 0 to 3 wt.-%, and extraordinarily preferably from 0.1 to 2 wt.-% of the propylene glycol initially present in the mixture which is heated in step a) is removed during step a).

Removing more preferably of from 0 to 10 wt.-%, even more preferably of from 0 to 5 wt.-%, particularly preferably of from 0 to 3 wt.-%, and extraordinarily preferably of from 0.1 to 2 wt.-% of the propylene glycol initially present in the mixture which is heated in step a) of the inventive process may be achieved by choosing appropriate reaction conditions.

Preferably, removal of water in step a) and/or removal of propylene glycol in step b) is achieved in part or completely by distillation. In case removal of water in step a) is achieved partly or completely by distillation, preferably the pressure and/or the temperature of the mixture heated in step a) of the inventive process may be chosen in a way that the majority of water distills off while only a small portion of propylene glycol distills off. Distillation of water in the presence of propylene glycol may more preferably be achieved by using a fractionating column or a reflux condenser.

In step b), removing propylene glycol may include but is not limited to (i) removing propylene glycol which has reacted, e.g., in step a) and/or step b) and is released during polycondensation, and (ii) removing propylene glycol which has been present as a solvent and has not taken part in a reaction.

Preferably, step a) and/or step b), more preferably step a) and step b), are performed under protective atmosphere. Preferably, the protective atmosphere is achieved by replacing parts of the oxygen of the atmosphere by nitrogen, e.g., by alternatingly applying reduced pressure and flooding with nitrogen or by alternatingly increasing the pressure by the addition of nitrogen and releasing the pressure.

In a preferred embodiment of the inventive process, the molar ratio of propylene glycol to terephthalic acid in step a) is at least 1 .0:1.0, more preferably is at least 1 .2:1.0, even more preferably is at least 1 .5:1.0, particularly preferably is at least 1.8: 1.0, and extraordinarily preferably is at least 2.0:1.0. Furthermore, the molar ratio of propylene glycol to terephthalic acid in step a) preferably is lower than 10.0:1.0, more preferably is lower than 7.0:1.0 and even more preferably is lower than 3.0:1 .0.

In another preferred embodiment of the inventive process, the molar ratio of the terephthalic acid to the one or more substances of the formula (III) or mixtures thereof is from 1 :1 to 30: 1 , more preferably is from 1 :1 to 20: 1 , even more preferably is from 1 :1 to 15:1 , particularly preferably is from 1 :1 to 10:1 and extraordinarily preferably is from 1 :1 to 8:1 . In a more preferred embodiment of the inventive process, the molar ratio of the terephthalic acid to the one or more substances of the formula (III) or mixtures thereof is from 1 :1 to 8:1 , R¹ is methyl, and “a” is, based on a molar average, a number of from 1 to 150, preferably of from 10 to 100, and more preferably of from 15 to 60.

In a preferred embodiment of the inventive process, one or more alkylene glycols of the formula (11-1 ) or mixtures thereof are additionally reacted and are preferably contained in the mixture used in step a) and/or are combined with the mixture obtained in step a) before executing step b) and more preferably are contained in the mixture used in step a)

HO-(C_nH_2n)-OH (11-1 ) wherein

(C_nH2n) is (C2H4) or a linear or branched alkylene group with n being an integer of from 4 to 10 or mixtures thereof, preferably is (C2H4) or a linear or branched alkylene group with n being an integer of from 4 to 6 or mixtures thereof, more preferably is selected from the group consisting of (C2H4), (C4H8) and mixtures thereof, even more preferably is (C2H4).

Examples for the one or more alkylene glycols of the formula (11-1 ) or mixtures thereof are ethylene glycol, 2-methyl-1 ,3-propanediol, 1 ,4-butanediol, 1 ,3-butanediol, 2,3-butanediol, 1 ,2-butanediol, 2,2-dimethyl-1 ,3-propanediol, 1 ,2-pentanediol, 1 ,5-pentanediol, 1 ,2-hexanediol, 1 ,6-hexanediol or mixtures thereof.

In the case that more than one alkylene glycol of the formula (11-1 ) is used in the inventive process, the definition of "n" may vary between those alkylene glycols.

Preferably, the one or more alkylene glycols of the formula (11-1 ) or mixtures thereof is ethylene glycol. In a more preferred embodiment of the inventive process, combinations of recycled and non-recycled alkylene glycols of the formula (11-1 ) or mixtures thereof can be used, more preferably comprising at least 50 wt.-%, even more preferably comprising at least 80 wt.-%, and particularly preferably comprising 100 wt.-% recycled alkylene glycols of the formula (11-1 ) or mixtures thereof, in each case based on the total weight of alkylene glycols of the formula (11-1 ) or mixtures thereof used in the inventive process.

In another more preferred embodiment of the inventive process, combinations of renewable and non-renewable alkylene glycols of the formula (11-1 ) or mixtures thereof can be used, more preferably comprising at least 50 wt.-%, even more preferably comprising at least 80 wt.-%, and particularly preferably comprising 100 wt.-% renewable alkylene glycols of the formula (11-1 ) or mixtures thereof, in each case based on the total weight of alkylene glycols of the formula (11-1 ) or mixtures thereof used in the inventive process.

In another more preferred embodiment of the inventive process, the molar ratio of the one or more alkylene glycols of the formula (11-1 ) or mixtures thereof to propylene glycol is 1 :1 or lower, even more preferably is 1 :2 or lower, and particularly preferably is 1 :3 or lower.

In another preferred embodiment of the inventive process, no alkylene glycols of the formula (11-1 ) or mixtures thereof are used in the inventive process.

In another preferred embodiment of the inventive process, one or more substances of the formula (IV) or mixtures thereof are additionally reacted and are preferably contained in the mixture used in step a) and/or are combined with the mixture obtained in step a) before executing step b)

wherein

¹/_p M^p+ is a cation, preferably selected from the group consisting of monovalent cations M⁺ (p = 1 ), divalent cations 7 M²⁺ (p = 2) and trivalent cations % M³⁺ (p = 3) and more preferably selected from the group consisting of H⁺, Li⁺, Na⁺, K⁺, Mg²⁺, 7 Ca²⁺, % Al³⁺, NH₄ ⁺ and R_aR_bR_cRdN⁺, wherein R_a, R_b, Rc and Rd, independently of one another, are H, linear or branched, preferably linear, alkyl groups comprising from 1 to 22 carbon atoms or linear or branched, preferably linear, hydroxyalkyl groups comprising from 2 to 10 carbon atoms, and wherein in the cations R_aR_bR_cRdN⁺ at least one of R_a, R_b, R_c and Rd is not H,

R⁴ is H or an alkyl group comprising from 1 to 4 carbon atoms, preferably is H or methyl, and more preferably is methyl.

Typically, such substances of the formula (IV) or mixtures thereof would be used in a molar ratio of the one or more substances of the formula (IV) or mixtures thereof to the terephthalic acid (formula (I)) of less than 1 :2, and preferably of less than 1 :3.

In another preferred embodiment of the inventive process, one or more polyalkyleneglycols of the formula (V) or mixtures thereof are additionally reacted and are preferably contained in the mixture used in step a) and/or are combined with the mixture obtained in step a) before executing step b)

H-[OR³]_d-OH (V) wherein

R³ is a linear or branched alkylene group (C_PH2_P), with p being an integer of from 2 to 10 or mixtures thereof, preferably with p being an integer of from 2 to 6 or mixtures thereof, more preferably is selected from the group consisting of (C2H4), (CsHe), (C4H8) and mixtures thereof, even more preferably is selected from the group consisting of (C2H4), (CsHe) and mixtures thereof, and particularly preferably is (C2H4), and d is an integer of from 2 to 400, preferably of from 2 to 200, more preferably of from 4 to 150, even more preferably of from 10 to 120 and particularly preferably of from 35 to 120.

In a more preferred embodiment of the inventive process, in the one or more polyalkyleneglycols of the formula (V) or mixtures thereof, at least a part of the groups R³ are (CH2CH2) groups. More preferably, in the one or more polyalkyleneglycols of the formula (V) or mixtures thereof, at least 50 mol-%, even more preferably at least 60 mol-% and particularly preferably at least 70 mol-% of the groups R³, in each case based on the total amount of the groups R³, are (CH2CH2) groups.

In the one or more polyalkyleneglycols of the formula (V) or mixtures thereof, the groups R³ extraordinarily preferably are (CH2CH2) groups or a mixture of (CH2CH2) groups and (CsHe) groups, wherein preferably at least 50 mol-%, more preferably at least 60 mol % and even more preferably at least 70 mol-% of the groups R³, in each case based on the total amount of the groups R³, are (CH2CH2) groups and especially preferably, the groups R³ are (CH2CH2) groups.

In another more preferred embodiment of the inventive process, in the one or more polyalkyleneglycols of the formula (V) or mixtures thereof, at least a part of the groups R³ are (CH2CH2) groups made from renewable ethylene oxide. More preferably, in the one or more polyalkyleneglycols of the formula (V) or mixtures thereof, at least 50 mol-%, even more preferably at least 60 mol-% and particularly preferably at least 70 mol-% of the groups R³, in each case based on the total amount of the groups R³, are (CH2CH2) groups made from renewable ethylene oxide. In the one or more polyalkyleneglycols of the formula (V) or mixtures thereof, the groups R³ extraordinarily preferably are (CH2CH2) groups made from renewable ethylene oxide or a mixture of (CH2CH2) groups made from renewable ethylene oxide and (C3H6) groups, wherein preferably at least 50 mol-%, more preferably at least 60 mol % and even more preferably at least 70 mol-% of the groups R³, in each case based on the total amount of the groups R³, are (CH2CH2) groups made from renewable ethylene oxide and especially preferably, the groups R³ are (CH2CH2) groups made from renewable ethylene oxide.

In the case that at least two different types of [O(C_PH2_P)] groups, for example [O(C2H4)], [O(C3He)], and [O(C4Hs)] groups, exist in the one or more polyalkyleneglycols of the formula (V) or mixtures thereof, they may be arranged blockwise, alternating, periodically and/or statistically, preferably blockwise and/or statistically. This means that in a polyalkyleneglycol of the formula (V), the [O(C_PH2_P)] groups, and, e.g., the groups [O(C2H4)], [O(C3He)], and [O(C4Hs)], may be arranged, for example, in a purely statistically or blockwise form but may also be arranged in a form which could be considered as both statistical and blockwise, e.g., small blocks of [O(C2H4)] and [O(C3He)] groups arranged in a statistical manner, or in a form wherein adjacent instances of statistical and blockwise arrangements of different [O(C_PH2_P)] groups, e.g., the groups [O(C2H4)], [O(C3He)], and [O(C4HS)], exist.

Within the structure element -[OR³]d- in a polyalkyleneglycol of the formula (V), any of the groups [O(C_PH2_P)], e.g., any of the groups [O(C2H4)], [O(C3He)] and [O(C4HS)], can form an end group of the structure element -[OR³]d-. This means, for example, that the two end groups of the structure element -[OR³]d- in a polyalkyleneglycol of the formula (V) may be formed by [O(C2H4)] groups, may be formed by [O(C3He)] groups, may be formed by [O(C4Hs)] groups or may be formed by different [O(C_PH2_P)] groups, e.g., different groups selected from [O(C₂H₄)], [O(C₃H₆)l and [O(C₄H₈)]. In the case that more than one polyalkyleneglycol of the formula (V) is used in the inventive process, the definition of R³ and “d” may vary between those polyalkyleneglycols.

Typically, such polyalkyleneglycols of the formula (V) or mixtures thereof would be used in a molar ratio of the one or more polyalkyleneglycols of the formula (V) or mixtures thereof to propylene glycol (formula (II)) of less than 1 :2, preferably of less than 1 :3 and more preferably of less than 1 :4.

In another preferred embodiment of the inventive process, one or more crosslinking compounds, preferably having 3 to 6 functions capable of polycondensation, or mixtures thereof are additionally reacted and are preferably contained in the mixture used in step a) and/or are combined with the mixture obtained in step a) before executing step b).

For example, compounds with multiple hydroxyl functions such as triols (e.g., glycerol or 1 ,2,3-hexanetriol), tetraols (e.g, pentaerythritol), or hexaols (e.g., sorbitol or mannitol), compounds with multiple carboxylic acid functions or their salts, their alkylesters, or their anhydrides such as trimellitic acid, trimel litic anhydride, or trimesic acid, or compounds with both hydroxyl functions and carboxylic acid functions or their salts, their alkylesters, or their anhydrides such as citric acid, malic acid, tartaric acid, or gallic acid may be additionally reacted and preferably may be contained in the mixture used in step a) and/or combined with the mixture obtained in step a) before executing step b).

More preferably, the one or more crosslinking compounds, preferably having 3 to 6 functions capable of polycondensation, or mixtures thereof are selected from the group consisting of citric acid, malic acid, tartaric acid, gallic acid, pentaerythritol, glycerol, sorbitol, mannitol, 1 ,2,3-hexanetriol, trimellitic acid, trimellitic anhydride, trimesic acid, and mixtures thereof.

Typically, such crosslinking compounds, preferably having 3 to 6 functions capable of polycondensation, or mixtures thereof would be used in a molar ratio of the one or more crosslinking compounds, preferably having 3 to 6 functions capable of polycondensation, or mixtures thereof to propylene glycol (formula (II)) of less than 1 :10, preferably of less than 1 :15 and more preferably of less than 1 :20.

In another preferred embodiment of the inventive process, one or more substances of the formula (VI-1 ) or (VI-2) or mixtures thereof are additionally reacted and are preferably contained in the mixture used in step a) and/or are combined with the mixture obtained in step a) before executing step b)

(M_b ⁱ⁺)x -O3S-(C₂H₄O)y-H (VI-1 )

(VI-2)

wherein

Mb is hydrogen or a monovalent cation or bivalent cation, preferably an ammonium cation, a substituted ammonium cation, or an alkali metal cation, i is 1 or 2, x is 0.5 or 1 , and the product i ■ x = 1 , and y is, based on a molar average, a number from 1 to 15, preferably from 1 to 3 and more preferably is 1 .

Typically, such substances of the formula (VI-1 ) or (VI-2) or mixtures thereof would be used in a molar ratio of the one or more substances of the formula (VI-1 ) or (VI-2) or mixtures thereof to the one or more substances of the formula (III) or mixtures thereof of less than 1 :2, preferably of less than 1 :3 and more preferably of less than 1 :4.

In addition to the terephthalic acid (formula (I)) and the propylene glycol (formula (II)) and the one or more substances of the formula (III) (or (111-1 )) or mixtures thereof and, optionally, the one or more alkylene glycols of the formula (11-1 ) or mixtures thereof and, optionally, the one or more substances of the formula (IV) or mixtures thereof and, optionally, the one or more polyalkyleneglycols of the formula (V) or mixtures thereof and, optionally, the one or more crosslinking compounds, preferably having 3 to 6 functions capable of polycondensation, or mixtures thereof and, optionally, one or more substances of the formula (VI-1 ) or (VI-2) or mixtures thereof, one or more further substances which can take part in polycondensation reactions can additionally be reacted and be added separately or be contained in the mixture used in step a) and/or be combined with the mixture obtained in step a) before executing step b). Examples for such further substances which can take part in polycondensation reactions are phthalic acid, isophthalic acid, 3-sulfophthalic acid, 4-sulfophthalic acid, naphthalene-1 ,4-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, tetrahydrophthalic acid, diphenoxyethane-4,4'-dicarboxylic acid, diphenyl-4,4'- dicarboxylic acid, 2,5-furandicarboxylic acid, adipic acid, sebacic acid, decan-1 , 10- dicarboxylic acid, fumaric acid, succinic acid, 1 ,4-cyclohexanedicarboxylic acid, cyclohexanediacetic acid, glutaric acid, azelaic acid, or their salts or their (di)alkyl esters, preferably their (Ci-C4)-(di)alkyl esters and more preferably their (di)methyl esters, or mixtures thereof. Typically, such further substances would be used to a minor extent, for example in a molar amount smaller than 5 mol%, based on the total amount of terephthalic acid (formula (I)) used in the inventive process.

In addition to reactants, e.g., terephthalic acid (formula (I)) and propylene glycol (formula (II)) and one or more substances of the formula (III) (or (111-1 )) or mixtures thereof and, optionally, the one or more alkylene glycols of the formula (11-1 ) or mixtures thereof and, optionally, one or more substances of the formula (IV) or mixtures thereof and, optionally, one or more polyalkyleneglycols of the formula (V) or mixtures thereof and, optionally, one or more crosslinking compounds, preferably having 3 to 6 functions capable of polycondensation, or mixtures thereof and, optionally, one or more substances of the formula (VI-1 ) or (VI-2) or mixtures thereof, the mixture used in step a) of the inventive process may comprise further substances such as catalyst systems or substances which do not take part in polycondensation reactions, e.g., one or more solvents or one or more additives. Further substances such as catalyst systems or substances which do not take part in polycondensation reactions, e.g., one or more solvents or one or more additives, may also be combined with the mixture obtained in step a) before executing step b) of the inventive process or may be added separately to the reaction vessel at other times, e.g., may be added during heating in step a) and/or may be added during step b) separately.

Preferably, one or more catalyst systems, and more preferably one or more metal catalyst systems, are used in step a) and/or in step b).

More preferably, one or more catalyst systems, and even more preferably one or more metal catalyst systems, are used in step a) and/or in step b) and are contained in the mixture used in step a) and/or are combined with the mixture obtained in step a) before executing step b) and/or are added to the reaction vessel at any other time before or during the reaction, e.g., are added during heating in step a) and/or are added during step b) separately.

In a more preferred embodiment of the inventive process, one or more esterification catalysts or catalyst systems are used in step a) of the inventive process and are contained in the mixture used in step a) and/or are added to the reaction vessel at any other time before or during heating in step a).

Examples for the one or more esterification catalysts or catalyst systems comprise homogeneous or heterogeneous acid catalysts such as, e.g., sulfuric acid, p-toluenesulfonic acid, lewis acids such as aluminum chloride or boron trifluoride, or sulfonated materials, enzyme catalysts or other esterification catalysts or catalyst systems known to the person skilled in the art, for example as described in Z. Khan et al., Journal of Industrial and Engineering Chemistry, Vol. 103 (2021), p. 80-101.

In another more preferred embodiment of the inventive process, one or more condensation catalysts or catalyst systems are used in step b) of the inventive process and are contained in the mixture used in step a) and/or are combined with the mixture obtained in step a) before executing step b) and/or are added to the reaction vessel at any other time before or during the inventive process, e.g., are added during heating in step a) and/or are added during step b) separately.

Examples for the one or more condensation catalysts or catalyst systems comprise antimony, germanium and titanium-based catalysts or other condensation catalysts or catalyst systems known to the person skilled in the art.

In another more preferred embodiment of the inventive process, one or more esterification catalysts or catalyst systems are used in step a) of the inventive process and one or more condensation catalysts or catalyst systems are used in step b) of the inventive process.

In another more preferred embodiment of the inventive process, the same catalyst or catalyst system is used in step a) and in step b) of the inventive process.

In another more preferred embodiment of the inventive process, the catalyst system used in step a) and/or the catalyst system used in step b) further comprises additives, stabilizers, and/or bluing agents.

Even more preferably, one or more metal catalyst systems are used in the inventive process. Particularly preferably, the one or more metal catalyst systems comprise at least one titanium-based catalyst, extraordinarily preferably comprise titanium tetraisopropoxide and/or titanium tetrabutoxide, and especially preferably comprise titanium tertabutoxide.

In the inventive process, the amount of the one or more substances of the formula (III) (or (111-1 )) or mixtures thereof, or, in case one or more polyalkyleneglycols of the formula (V) or mixtures thereof are additionally reacted, the combined amount of the one or more substances of the formula (III) (or (111-1 )) or mixtures thereof and the one or more polyalkyleneglycols of the formula (V) or mixtures thereof, preferably is at least 10 wt.-%, more preferably is at least 20 wt.-%, even more preferably is at least 40 wt.-%, particularly preferably is from 40 to 90 wt.-% and extraordinarily preferably is from 50 to 90 wt.-%, in each case based on the combined weight of the terephthalic acid (formula (I)) and the one or more substances of the formula (III) (or (111-1 )) or mixtures thereof and, if used in the inventive process, the one or more substances of the formula (IV) or mixtures thereof and, if used in the inventive process, the one or more polyalkyleneglycols of the formula (V) or mixtures thereof and, if used in the inventive process, the one or more crosslinking compounds, preferably having 3 to 6 functions capable of polycondensation, or mixtures thereof and, if used in the inventive process, the one or more substances of the formula (VI-1 ) or (VI-2) or mixtures thereof.

In a preferred embodiment of the inventive process, the amount of the one or more substances of the formula (III) (or (111-1 )) or mixtures thereof in the inventive process is at least 40 wt.-%, more preferably is from 40 to 90 wt.-% and even more preferably is from 50 to 90 wt.-%, in each case based on the combined weight of the terephthalic acid (formula (I)) and the one or more substances of the formula (III) (or (111-1 )) or mixtures thereof and, if used in the inventive process, the one or more polyalkyleneglycols of the formula (V) or mixtures thereof and, if used in the inventive process, the one or more crosslinking compounds, preferably having 3 to 6 functions capable of polycondensation, or mixtures thereof and, if used in the inventive process, the one or more substances of the formula (VI-1 ) or (VI-2) or mixtures thereof. In such an inventive process, preferably no substances of the formula (IV) or mixtures thereof are additionally reacted.

In another preferred embodiment of the inventive process, the amount of the one or more substances of the formula (III) (or (111-1 )) or mixtures thereof in the inventive process is at least 10 wt.-%, more preferably is from 12 to 90 wt.-%, even more preferably is from 15 to 85 wt.-% and particularly preferably is from 50 to 80 wt.-%, in each case based on the combined weight of the terephthalic acid (formula (I)) and the one or more substances of the formula (III) (or (111-1 )) or mixtures thereof and, if used in the inventive process, the one or more substances of the formula (IV) or mixtures thereof and, if used in the inventive process, the one or more polyalkyleneglycols of the formula (V) or mixtures thereof and, if used in the inventive process, the one or more crosslinking compounds, preferably having 3 to 6 functions capable of polycondensation, or mixtures thereof and, if used in the inventive process, the one or more substances of the formula (VI-1 ) or (VI-2) or mixtures thereof. In such an inventive process, preferably substances of the formula (IV) or mixtures thereof are additionally reacted.

In an inventive process which comprises the use of one or more polyalkyleneglycols of the formula (V) or mixtures thereof as reactant, the combined amount of the one or more substances of the formula (III) (or (111-1 )) or mixtures thereof and the one or more polyalkyleneglycols of the formula (V) or mixtures thereof preferably is at least 35 wt.-%, more preferably is from 40 to 90 wt.-%, even more preferably is from 50 to 90 wt.-%, particularly preferably is from 60 to 90 wt.-% and extraordinarily preferably is from 70 to 90 wt.-%, in each case based on the combined weight of the terephthalic acid (formula (I)) and the one or more substances of the formula (III) (or (111-1 )) or mixtures thereof and the one or more polyalkyleneglycols of the formula (V) or mixtures thereof and, if used in the inventive process, the one or more substances of the formula (IV) or mixtures thereof and, if used in the inventive process, the one or more crosslinking compounds, preferably having 3 to 6 functions capable of polycondensation, or mixtures thereof and, if used in the inventive process, the one or more substances of the formula (VI-1 ) or (VI-2) or mixtures thereof.

In step a) of the inventive process, the combined amount of the terephthalic acid (formula (I)) and the propylene glycol (formula (II)) which is used as reactant (and not as solvent) and, if present, the one or more alkylene glycols of the formula (11-1 ) or mixtures thereof which are used as reactants (and not as solvent) and, if present, the one or more substances of the formula (IV) or mixtures thereof and, if present, the one or more polyalkyleneglycols of the formula (V) or mixtures thereof and, if present, the one or more crosslinking compounds, preferably having 3 to 6 functions capable of polycondensation, or mixtures thereof and, if present, the one or more substances of the formula (VI-1 ) or (VI-2) or mixtures thereof, preferably is at least 50 wt.-%, more preferably is at least 60 wt.-% and even more preferably is at least 70 wt.-%, in each case based on the total weight of all reactants contained in the mixture used in step a). In a preferred embodiment of the inventive process, in addition to the reactants 1 ),

2), and 3) contained in the mixture used in step a)

1 ) terephthalic acid (formula (I)) and

2) propylene glycol (formula (II)) and

3) one or more substances of the formula (III) (or (111-1 )) or mixtures thereof further reactants contained in the mixture used in step a) and/or combined with the mixture obtained in step a) before executing step b) are selected from the group consisting of 4), 5), 6), 7), and 8)

4) one or more alkylene glycols of the formula (11-1 ) or mixtures thereof,

5) one or more substances of the formula (IV) or mixtures thereof,

6) one or more polyalkyleneglycols of the formula (V) or mixtures thereof,

7) one or more crosslinking compounds, preferably having 3 to 6 functions capable of polycondensation, or mixtures thereof and

8) one or more substances of the formula (VI-1 ) or (VI-2) or mixtures thereof. The mixture may further comprise, e.g., a catalyst system, preferably a metal catalyst system, further additives, and/or one or more solvents.

In a more preferred embodiment of the inventive process, in addition to the reactants 1 ), 2), and 3) contained in the mixture used in step a)

1 ) terephthalic acid (formula (I)) and

2) propylene glycol (formula (II)) and

3) one or more substances of the formula (III) (or (111-1 )) or mixtures thereof further reactants contained in the mixture used in step a) and/or combined with the mixture obtained in step a) before executing step b) are selected from the group consisting of 4), 5), and 6)

4) one or more alkylene glycols of the formula (11-1 ) or mixtures thereof,

5) one or more polyalkyleneglycols of the formula (V) or mixtures thereof and

6) one or more crosslinking compounds, preferably having 3 to 6 functions capable of polycondensation, or mixtures thereof.

The mixture may further comprise, e.g., a catalyst system, preferably a metal catalyst system, further additives, and/or one or more solvents. In another more preferred embodiment of the inventive process, in addition to the reactants 1 ), 2), and 3) contained in the mixture used in step a)

1 ) terephthalic acid (formula (I)) and

2) propylene glycol (formula (II)) and

4) one or more alkylene glycols of the formula (11-1 ) or mixtures thereof,

5) one or more substances of the formula (IV) or mixtures thereof and

6) one or more polyalkyleneglycols of the formula (V) or mixtures thereof. The mixture may further comprise, e.g., a catalyst system, preferably a metal catalyst system, further additives, and/or one or more solvents.

In an even more preferred embodiment of the inventive process, in addition to the reactants 1 ), 2), and 3) contained in the mixture used in step a)

1 ) terephthalic acid (formula (I)) and

2) propylene glycol (formula (II)) and

3) one or more substances of the formula (III) (or (111-1 )) or mixtures thereof further reactants contained in the mixture used in step a) and/or combined with the mixture obtained in step a) before executing step b) are selected from the group consisting of 4) and 5)

4) one or more alkylene glycols of the formula (11-1 ) or mixtures thereof and

5) one or more substances of the formula (IV) or mixtures thereof.

The mixture may further comprise, e.g., a catalyst system, preferably a metal catalyst system, further additives, and/or one or more solvents.

In a particularly preferred embodiment of the inventive process, the reactants contained in the mixture used in step a) are

1 ) terephthalic acid (formula (I)) and

2) propylene glycol (formula (II)) and

3) one or more substances of the formula (III) (or (111-1 )) or mixtures thereof and 4) one or more alkylene glycols of the formula (11-1 ) or mixtures thereof and

5) one or more polyalkyleneglycols of the formula (V) or mixtures thereof

In another particularly preferred embodiment of the inventive process, the reactants contained in the mixture used in step a) are

1 ) terephthalic acid (formula (I)) and

2) propylene glycol (formula (II)) and

3) one or more substances of the formula (III) (or (111-1 )) or mixtures thereof and

4) one or more alkylene glycols of the formula (11-1 ) or mixtures thereof and

5) one or more substances of the formula (IV) or mixtures thereof.

1 ) terephthalic acid (formula (I)) and

2) propylene glycol (formula (II)) and

3) one or more substances of the formula (III) (or (111-1 )) or mixtures thereof. The mixture may further comprise, e.g., a catalyst system, preferably a metal catalyst system, further additives, and/or one or more solvents.

In an extraordinarily preferred embodiment of the inventive process, the mixture used in step a) consists of

1 ) terephthalic acid (formula (I)) and

2) propylene glycol (formula (II)) and

4) a catalyst system, preferably a metal catalyst system. In another extraordinarily preferred embodiment of the inventive process, the mixture used in step a) consists of

1 ) terephthalic acid (formula (I)) and

2) propylene glycol (formula (II)) and

4) one or more alkylene glycols of the formula (11-1 ) or mixtures thereof and

5) a catalyst system, preferably a metal catalyst system.

In another extraordinarily preferred embodiment of the inventive process, the mixture used in step a) consists of

1 ) terephthalic acid (formula (I)) and

2) propylene glycol (formula (II)) and

3) one or more substances of the formula (III) (or (111-1 )) or mixtures thereof.

Preferably, at least 20 wt.-%, more preferably at least 30 wt.-%, even more preferably at least 50 wt.-%, and particularly preferably at least 60 wt.-% of the propylene glycol used in step a), in each case based on the total weight of the propylene glycol used in step a), is propylene glycol which has been obtained from step b) of a previous polycondensation reaction or which has been accumulated from step b) of two or more previous polycondensation reactions.

In an extraordinarily preferred embodiment of the inventive process, 100 wt.-% of the propylene glycol used in step a) is propylene glycol which has been obtained from step b) of a previous polycondensation reaction.

In another extraordinarily preferred embodiment of the inventive process, 100 wt.-% of the propylene glycol used in step a) is propylene glycol which has been accumulated from step b) of two or more previous polycondensation reactions.

In another extraordinarily preferred embodiment of the inventive process, the propylene glycol used in step a) is a mixture of propylene glycol which has been obtained from step b) of a previous polycondensation reaction or which has been accumulated from step b) of two or more previous polycondensation reactions and propylene glycol which was not obtained from step b) of one or more previous polycondensation reactions. In this embodiment of the inventive process, preferably at least 10 wt.-%, more preferably at least 20 wt.-%, and even more preferably at least 30 wt.-% of the propylene glycol used in step a) is propylene glycol which was not obtained from step b) of one or more previous polycondensation reactions.

A further subject matter of the invention is a product or polyester obtainable by the inventive process.

Preferred embodiments for the inventive process apply analogously to the product or polyester obtainable by the inventive process.

Products obtainable by the inventive process comprise the inventive polyesters and additionally may comprise unreacted reactants, side products, catalysts, decomposition products, additives, and/or solvents. Furthermore, the product may, e.g., comprise substances such as intermediates, e.g., that have been formed in step a) but have not further reacted thereafter.

Polyesters obtainable by the inventive process comprise one or more structural units of the formula (la)

and one or more structural units of the formula (Ila)

-O-(C₃H₆)-O- (Ha) and one or more terminal groups of the formula (Illa)

or mixtures thereof wherein R¹, a, and R² have the meaning as described above for formula (III).

Polyesters obtainable by the inventive process in which the one or more substances of the formula (III) or mixtures thereof are of the formula (111-1 ) comprise one or more structural units of the formula (111-1 a)

R¹-(OC₂H₄)b-(OC3H6)c-O- (111-1 a) wherein

R¹ has the meaning as described above for formula (III), the -(OC2H4) groups and the -(OC3H6) groups are arranged blockwise, alternating, periodically and/or statistically, preferably blockwise, wherein the block consisting of the -(OCsHe) groups is bound, in the polyester, to a COO group, and b and c have the meaning as described above for formula (111-1 ).

Polyesters obtainable by the inventive process in which one or more alkylene glycols of the formula (11-1 ) or mixtures thereof are additionally reacted additionally comprise one or more structural units of the formula (11-1 a)

-O-(C_nH_2n)-O- (11-1 a) or mixtures thereof wherein (C_nH_2n) has the meaning as described above for formula (11-1 ).

Polyesters obtainable by the inventive process in which one or more substances of the formula (IV) or mixtures thereof are additionally reacted additionally comprise one or more structural units of the formula (IVa)

or mixtures thereof wherein ¹/_p M^p+ has the meaning as described above for formula (IV).

Polyesters obtainable by the inventive process in which one or more polyalkyleneglycols of the formula (V) or mixtures thereof are additionally reacted additionally comprise one or more structural units of the formula (Va)

-[OR³]_d-O- (Va) or mixtures thereof, wherein R³ and “d” have the meaning as described above for formula (V).

Polyesters obtainable by the inventive process in which one or more crosslinking compounds, preferably having 3 to 6 functions capable of polycondensation, or mixtures thereof are additionally reacted additionally comprise the respective one or more crosslinking structural units or mixtures thereof, preferably derived from crosslinking compounds having 3 to 6 functions capable of polycondensation or mixtures thereof.

Polyesters obtainable by the inventive process in which one or more substances of the formula (VI-1 ) or (VI-2) or mixtures thereof are additionally reacted additionally comprise one or more further terminal groups of the formula (VI-1 a) or (Vl-2a)

(M_b ⁱ⁺)x -O3S-(C₂H₄O)y- (Vl-1a) (Vl-2a)

or mixtures thereof wherein Mb, i, x, and y have the meaning as described above for formulas (VI-1 ) and (VI-2).

Polyesters obtainable by the inventive process in which one or more further substances which can take part in polycondensation reactions are additionally reacted additionally comprise the respective one or more structural units derived from the one or more further substances which can take part in polycondensation reactions.

The weight average molecular weight (Mw) of the polyesters obtainable by the inventive process preferably is from 1500 to 20000 g/mol, more preferably from 4000 to 20000 g/mol and even more preferably from 5000 to 20000 g/mol.

The weight average molecular weight (Mw) of the polyesters obtainable by the inventive process may be determined by GPC analysis, preferably as detailed in the following: 10 pl of sample is injected onto a PSS Suprema column of dimensions 300 x 8 mm with porosity 30 A and particle size 10 pm. The detection is monitored at 235 nm on a multiple wavelength detector. The employed eluent is 1 .25 g/l of disodium hydrogen phosphate in a 45 / 55 % (v/v) water I acetonitrile mixture. Separations are conducted at a flow rate of 0.8 ml/minute. Quantification is performed by externally calibrating standard samples of different molecular weight polyethylene glycols.

Preferably, the number of structural units of the formula (la) in the polyesters obtainable by the inventive process is, based on a molar average, from 2 to 60, more preferably from 2 to 40, even more preferably from 2 to 30, particularly preferably from 2 to 20 and extraordinarily preferably from 5 to 20. The polyesters obtainable by the inventive process comprise one or more terminal groups of the formula (Illa) or mixtures thereof. In addition to these one or more terminal groups or mixtures thereof, the polyesters obtainable by the inventive process may comprise further terminal groups, preferably selected from the group consisting of -OH,

and -O-(C3He)-OH. Polyesters obtainable by the inventive process may also comprise terminal groups of the formula -O-(C_nH2n)-OH, wherein “n” has the meaning given above for formula (11-1 ), and mixtures thereof in case one or more alkylene glycols of the formula (11-1 ) or mixtures thereof are additionally reacted. Polyesters obtainable by the inventive process may also comprise terminal groups of the formula

wherein ¹/_p M^p+ and R⁴ have the meaning as described above for formula (IV), and mixtures thereof in case one or more substances of the formula (IV) or mixtures thereof are additionally reacted. Polyesters obtainable by the inventive process may also comprise terminal groups of the formula -[OR³]d-OH wherein R³ and “d” have the meaning given above for formula (V) in case one or more polyalkyleneglycols of the formula (V) or mixtures thereof are additionally reacted. Polyesters obtainable by the inventive process may also comprise terminal groups derived from crosslinking structural units in case one or more crosslinking compounds, preferably having 3 to 6 functions capable of polycondensation, or mixtures thereof, are additionally reacted. Furthermore, and as already stated above, the polyesters obtainable by the inventive process may also comprise one or more terminal groups of the formula (VI-1 a) or (Vl-2a) or mixtures thereof in case one or more substances of the formula (VI-1 ) or (VI-2) or mixtures thereof are additionally reacted.

Preferably, the polyester molecules of the polyesters obtainable by the inventive process comprise two or more terminal groups of the formula (Illa) or mixtures thereof. Even more preferably, all terminal groups of the polyester molecules of the polyesters obtainable by the inventive process are terminal groups of the formula (Illa) or mixtures thereof.

The polyesters obtainable by the inventive process preferably are anionic or nonionic and more preferably are nonionic.

The groups (CsHe) in the propylene glycol (formula (II)) or in the structural units of the formula (Ila), in the substances of the formula (III) (or (111-1 )) or in the terminal groups of the formula (Illa) (or (111-1 a)), or in the polyalkyleneglycols of the formula (V) or in the structural units of the formula (Va) preferably are of the formula -CH(CH3)-CH2- or -CH2-CH(CH3)-, i.e., of the formula:

The groups (C2H4) in the alkylene glycols of the formula (11-1 ) or in the structural units of the formula (11-1 a), in the substances of the formula (III) (or (111-1 )) or in the terminal groups of the formula (Illa) (or (111-1 a)), in the polyalkyleneglycols of the formula (V) or in the structural units of the formula (Va), or in the substances of the formula (VI-1 ) or in the terminal groups of the formula (VI-1 a) preferably are of the formula -CH2-CH2-.

The groups (C4H8) in the alkylene glycols of the formula (11-1 ) or in the structural units of the formula (11-1 a), in the substances of the formula (III) or in the terminal groups of the formula (Illa), or in the polyalkyleneglycols of the formula (V) or in the structural units of the formula (Va) preferably are of the formula -CH(CH3)-CH(CH3)-, i.e., of the formula:

C H₃ CH₃

- C H — C H -

In the polyesters obtainable by the inventive process, the terminal groups or structural units of the formulae (Ila), (Illa), (111-1 a), (11-1 a), (Va), or (VI-1 a) may, e.g., be linked directly to structural units of the formula (la) or, if present, to structural units of the formula (IVa) resulting in ester groups.

In the polyesters obtainable by the inventive process, the terminal groups of the formula (Vl-2a) may, e.g., be linked directly to structural units of the formulae (Ila), (11-1 a), or (Va) resulting in ester groups.

The inventive process describes a polycondensation process. Such a process leads to statistically determined mixtures of polyesters in which a mixture of molecular species with a distribution around a molar average is obtained.

The following paragraphs will show illustrative, but by no means limiting, structural entities that can be found in the polyesters obtainable by the inventive process.

The structural units of the formula (la) and optional additional di- or polycarboxylic acid-derived structural units are linked indirectly, preferably via the structural units of the formula (Ila) and optionally via alkylene glycol-derived structural units of the formula (11-1 a) or polyalkyleneglycol-derived structural units of the formula (Va), which - in the case of structural units of the formulae (la) and (Ila), wherein the structural units of the formula (Ila) are derived from 1 ,2-propylene glycol - results in the following structural entity:

Preferably, the terminal group of the formula (Illa) is linked to an acyl group derived from a dicarboxylic acid, preferably to the structural unit of the formula (la) derived from terephthalic acid, which - in the case of structural unit of the formula (la) and terminal group of the formula (Illa) - results in the following structural entity:

The products or polyesters obtainable by the inventive process may be used as soil release polymer.

Therefore, a further subject matter of the invention is the use of a product or polyester obtainable by the inventive process as soil release polymer.

"Soil release polymer” as used herein means a product or polymer that enhances soil removal during laundering by modifying the surface of the fabric that is laundered, preferably by increasing surface polarity.

In the use according to the invention as soil release polymer, the product or polyester preferably is present in a laundry detergent composition.

A further subject matter of the present invention is laundry detergent compositions comprising

Z1 ) one or more products or polyesters obtainable by the inventive process. The laundry detergent compositions of the invention comprise the one or more products or polyesters of component Z1) preferably in an amount of at least 0.1 wt.-%, more preferably in an amount from 0.1 to 10 wt.-%, even more preferably in an amount from 0.2 to 5 wt.-% and particularly preferably in an amount from 0.2 to 3 wt.-%, in each case based on the total weight of the laundry detergent composition.

The laundry detergent compositions of the invention preferably comprise Z2) one or more surfactants.

Surfactants assist in removing soil from textile materials and also assist in maintaining removed soil in solution or suspension in the wash liquor.

Preferably, the one or more surfactants of component Z2) of the laundry detergent compositions of the invention are selected from the group consisting of anionic, nonionic, cationic and zwitterionic surfactants, and more preferably from the group consisting of anionic, nonionic and zwitterionic surfactants.

Anionic Surfactants

Suitable anionic surfactants that may be used are any of the conventional anionic surfactant types typically used in laundry detergent compositions. These include alkyl sulfonates, alkyl ether sulfates, alkyl sulfates, alkyl ester sulfonates and soaps. Preferred anionic surfactants are alkylbenzene sulfonates, alkyl ether sulfates, alkyl sulfates and soaps.

Preferred alkyl sulfonates are alkylbenzene sulfonates, particularly linear alkylbenzene sulfonates (LAS) having an alkyl chain length of Cs-Cis. Possible counter ions for concentrated alkaline liquids are ammonium ions, e.g., those generated by the neutralization of alkylbenzene sulfonic acid with one or more ethanolamines, for example monoethanolamine (MEA) and triethanolamine (TEA), or alternatively, alkali metals, e.g., those arising from the neutralization of alkylbenzene sulfonic acid with alkali hydroxides. The linear alkyl benzene sulfonate surfactants may be LAS with an alkyl chain length of preferably from 8 to 15 and more preferably from 12 to 14. The neutralization of the acid may be performed before addition to the laundry detergent compositions of the invention or during the process of formulating the laundry detergent compositions of the invention through excess addition of neutralizing agent.

Preferred alkyl ether sulfates (AES) are alkyl polyethoxylate sulfate anionic surfactants of the formula

R⁵O(C₂H₄O)ZSO3’MC⁺ wherein

R⁵ is a saturated or unsaturated alkyl chain having preferably from 10 to

22 carbon atoms, and more preferably from 12 to 16 carbon atoms, M_c ⁺ is a cation which makes the compound water-soluble, preferably an ammonium cation, a substituted ammonium cation, an alkali metal cation, or other material chosen from the list of buffers, and z averages preferably from 1 to 15, more preferably from 1 to 3 and even more preferably is 3.

Preferred alkyl sulfates (AS) are surfactants of the formula

R⁶OSO₃ M_d ⁺ wherein

R⁶ is a linear or branched alkyl chain having preferably from 8 to 24 carbon atoms, and more preferably from 12 to 18 carbon atoms, and

Md⁺ is a cation which makes the compound water-soluble, preferably an ammonium cation, a substituted ammonium cation, an alkali metal cation, or other material chosen from the list of buffers.

Soaps are preferably fatty acids and more preferably linear saturated or unsaturated fatty acids having from 10 to 18 carbon atoms. Nonionic Surfactants

Nonionic surfactants include primary and secondary alcohol ethoxylates, preferably C8-C20 aliphatic alcohol ethoxylated with an average of from 1 to 35 moles of ethylene oxide per mole of alcohol, and more preferably the C10-C15 primary and secondary aliphatic alcohols ethoxylated with an average of from 1 to 10 moles of ethylene oxide per mole of alcohol. Non-ethoxylated nonionic surfactants include alkyl polyglycosides, glycerol monoethers and polyhydroxy amides (glucamides) such as N-methyl glucamides. Mixtures of nonionic surfactant may be used.

If included therein, the laundry detergent compositions of the invention contain preferably from 0.2 to 40 wt.-% and more preferably from 1 to 20 wt.-% of a nonionic surfactant, such as alcohol ethoxylate, nonylphenol ethoxylate, alkylpolyglycoside, alkyldimethylamineoxide, ethoxylated fatty acid monoethanolamide, fatty acid monoethanolamide, polyhydroxy alkyl fatty acid amide, or N-acyl N-alkyl derivatives of glucosamine ("glucamides"), in each case based on the total weight of the laundry detergent composition.

Zwitterionic Surfactants

The laundry detergent compositions of the invention may comprise up to 10 wt.-% of a zwitterionic surfactant, e.g., amine oxide or betaine, based on the total weight of the laundry detergent composition.

Typical amine oxides used are of the formula

R⁷N(O)(CH₂R⁸)₂ wherein

R⁷ is a long chain moiety, and each CH2R⁸ are short chain moieties, and

R⁸ is preferably selected from the group consisting of H, CH3 and -CH2OH. In general, R⁷ is a primary or branched hydrocarbyl moiety with a chain length of from 8 to 18, which can be saturated or unsaturated. Preferably, R⁷ is a primary alkyl moiety with a chain length of 8 to 18 carbon atoms.

Preferred amine oxides have compositions wherein R⁷ is a Cs-C alkyl and R⁸ is H. These amine oxides are illustrated by C12-14 alkyldimethyl amine oxide, hexadecyl dimethylamine oxide, octadecylamine oxide.

A preferred amine oxide material is lauryl dimethylamine oxide, also known as dodecyldimethylamine oxide or DDAO.

Betaines may be alkyldimethyl betaines or alkylamido betaines, wherein the alkyl groups have C12-18 chains.

In a preferred embodiment of the invention, the one or more surfactants of component Z2) of the laundry detergent compositions of the invention are selected from the group consisting of linear alkyl benzene sulfonates, alkyl ether sulfates, alkyl sulfates, soaps, nonionic surfactants, amine oxides and betaines, and preferably the one or more surfactants of component Z2) of the laundry detergent compositions of the invention are selected from the group consisting of linear alkyl benzene sulfonates, alkyl ether sulfates, alkyl sulfates, soaps and nonionic surfactants.

Additional Surfactants

Other surfactants than the preferred LAS, AES, AS, soaps and nonionic surfactants may be added to the mixture of surfactants.

The laundry detergent compositions of the invention comprise the one or more surfactants of component Z2) preferably in an amount of at least 3 wt.-%, more preferably in an amount from 3 to 65 wt.-%, even more preferably in an amount from 4 to 60 wt.-% and particularly preferably in an amount from 5 to 55 wt.-%, in each case based on the total weight of the laundry detergent composition. Further Optional Ingredients

In addition to the one or more products or polyesters of component Z1 ) and optionally the one or more surfactants of component Z2), the laundry detergent compositions of the invention may comprise one or more further optional ingredients, e.g., they may comprise conventional ingredients commonly used in laundry detergent compositions. Examples of optional ingredients include, but are not limited to builders, bleaching agents, bleach active compounds, bleach activators, bleach catalysts, photobleaches, dye transfer inhibitors, colour protection agents, anti-redeposition agents, dispersing agents, fabric softening and antistatic agents, fluorescent whitening agents, enzymes, enzyme stabilizing agents, foam regulators, defoamers, malodor reducers, preservatives, disinfecting agents, hydrotropes, fibre lubricants, anti-shrinkage agents, buffers, fragrances, processing aids, colorants, dyes, pigments, anti-corrosion agents, fillers, stabilizers and other conventional ingredients for laundry detergent compositions.

Polyalkoxylated polyethyleneim ine

For detergency boosting, it is advantageous to use a second polymer alongside the one or more products or polyesters of component Z1 ) in the laundry detergent compositions of the invention. This second polymer is preferably a polyalkoxylated polyethyleneimine (EPEI). Polyethyleneimines are materials composed of ethyleneimine units -CH2CH2NH- and, where branched, the hydrogen on the nitrogen is replaced by another chain of ethyleneimine units. These polyethyleneimines can be prepared, for example, by polymerizing ethyleneimine in the presence of a catalyst such as carbon dioxide, sodium bisulfite, sulfuric acid, hydrogen peroxide, hydrochloric acid, acetic acid, and the like.

Other Polymers

In addition to the one or more products or polyesters of component Z1 ) and the optional EPEI, the laundry detergent compositions of the invention may comprise other polymeric materials, for example: dye transfer inhibition polymers, antiredeposition polymers, and cotton soil release polymers, especially those based on modified cellulosic materials. Especially, if EPEI is not present, the laundry detergent compositions of the invention may further comprise a polymer of polyethylene glycol and vinyl acetate, for example the lightly grafted copolymers described in WO 2007/138054. Such amphiphilic graft polymers based on water- soluble polyalkylene oxides as graft base and side chains formed by polymerisation of a vinyl ester component have the ability to enable reduction of surfactant levels whilst maintaining high levels of oily soil removal.

Hydrotropes

In the context of this invention a hydrotrope is a solvent that is neither water nor conventional surfactant that aids the solubilisation of the surfactants and other components, especially polymer and sequestrant, in the liquid to render it isotropic. Among suitable hydrotropes there may be mentioned as preferred: monopropylene glycol (MPG), glycerol, sodium cumene sulfonate, ethanol, other glycols, e.g., dipropylene glycol, diethers, and urea. MPG and glycerol are preferred hydrotropes.

Enzymes

It is preferable that one or more enzymes selected from protease, mannanase, pectate lyase, cutinase, lipase, amylase, and cellulase may be present in the laundry detergent compositions of the invention. Less preferred additional enzymes may be selected from esterase, peroxidase and oxidase. The enzymes are preferably present with corresponding enzyme stabilizers. The total enzyme content in the laundry detergent compositions of the invention is preferably from 0 to 5 wt.-%, more preferably from 0.2 to 4 wt.-% and even more preferably from 0.4 to 2 wt.-%, in each case based on the total weight of the laundry detergent composition.

Sequestrants

Sequestrants are preferably included. Preferred sequestrants include organic phosphonates, alkanehydroxy phosphonates, and carboxylates available under the DEQUEST trademark from Thermphos. The preferred sequestrant level is less than 10 wt.-% and preferably less than 5 wt.-%, in each case based on the total weight of the laundry detergent composition of the invention. A particularly preferred sequestrant is HEDP (1 -Hydroxyethyl idene-1 ,1-diphosphonic acid). Also suitable but less preferred as it gives inferior cleaning results is diethylenetriamine penta(methylene phosphonic acid) (DTPMP) or Heptasodium DTPMP.

Buffers

In addition to agents optionally included for the generation of anionic surfactants, e.g., from LAS or fatty acids, the presence of buffer is preferred for pH control. Possible buffers are one or more ethanolamines, e.g., monoethanolamine (MEA) or triethanolamine (TEA). They are preferably used in the laundry detergent compositions of the invention at levels of from 1 to 15 wt.-%, based on the total weight of the laundry detergent composition. Other suitable amino alcohol buffer materials may be selected from the group consisting of compounds having a molecular weight above 61 g/mol, which includes MEA. Suitable materials also include, in addition to the already mentioned materials: monoisopropanolamine, diisopropanolamine, triisopropanolamine, monoamino hexanol, 2-[(2-methoxyethyl) methylamino]-ethanol, propanolamine, N-methylethanolamine, diethanolamine, monobutanolamine, isobutanolamine, monopentanolamine, 1-amino-3-(2-methoxyethoxy)-2-propanol, 2-methyl-4-(methylamino)-2-butanol and mixtures thereof.

Potential alternatives to amino ethanol buffers are alkali hydroxides such as sodium hydroxide or potassium hydroxide.

Builders

Further washing and cleaning ingredients which may be present in the laundry detergent compositions of the invention include inorganic and/or organic builders in order to reduce the degree of hardness of the water. These builders may be present in the laundry detergent compositions of the invention in amounts of from about 5 to about 80 wt.-%, based on the total weight of the laundry detergent compositions. Inorganic builders include, for example, alkali metal, ammonium and alkanolammonium salts of polyphosphates, silicates, carbonates, sulfates and aluminosilicates. Suitable organic builders include polycarboxyl compounds, such as, for example, ether polycarboxylates, ether hydroxypolycarboxylates, copolymers of maleic anhydride with ethylene or vinyl methyl ether, 1 ,3,5-trihydroxybenzene-2,4,6- trisulfonic acid and carboxymethyloxysuccinic acid, the alkali metal, ammonium and substituted ammonium salts of polyacetic acids, such as, for example, ethylenediaminetetraacetic acid and nitrilotriacetic acid, and also polycarboxylic acids, such as mellitic acid, succinic acid, oxydisuccinic acid, polymaleic acid, benzene-1 ,3,5-tricarboxylic acid, carboxymethyloxysuccinic acid, and soluble salts thereof. Builders based on citrates, for example citric acid and its soluble salts, in particular the sodium salt, are preferred polycarboxylic acid builders, which can also be used in granulated compositions, in particular together with zeolites and/or sheet silicates.

It may be advantageous to include fluorescer and/or bleach catalyst in the laundry detergent compositions of the invention as further high efficiency performance additives. Perfume and colorants will also desirably be included. The laundry detergent compositions of the invention may additionally contain viscosity modifiers, foam boosting agents, preservatives (e.g., bactericides), pH buffering agents, polyelectrolytes, anti-shrinking agents, anti-wrinkle agents, anti-oxidants, sunscreens, anti-corrosion agents, drape imparting agents, anti-static agents, and ironing aids. The laundry detergent compositions of the invention may further comprise pearlisers and/or opacifiers or other visual cues and shading dye.

Form, packaging and dosing

The laundry detergent compositions of the invention may be in solid or in liquid form, including a gel form. The laundry detergent compositions of the invention may be packaged as unit doses in a polymeric film soluble in the wash water. Alternatively, the laundry detergent compositions of the invention may be supplied in multidose plastics packs with a top or bottom closure. A dosing measure may be supplied with the pack either as a part of the cap or as an integrated system.

In one embodiment of the invention the laundry detergent composition is solid. In a further embodiment of the invention the laundry detergent composition is liquid.

A further subject matter of the invention is a method of washing a textile comprising the step of contacting the textile with an aqueous solution comprising a laundry detergent composition according to the invention, preferably at a temperature between 10°C and 90°C, furthermore preferably for a time between 5 minutes and 4 hours, and more preferably in a washing machine.

The concentration of the one or more products or polyesters obtainable by the inventive process in the aqueous solution is typically in the range of from 0.001 g/l to 0.5 g/l, from 0.002 g/l to 0.5 g/l, from 0.01 g/l to 0.5 g/l, from 0.02 g/l to 0.5 g/l, from 0.1 g/l to 0.5 g/l, or from 0.2 g/l to 0.4 g/l, or from 0.001 g/l to 0.2 g/l, from 0.002 g/l to 0.2 g/l, from 0.01 g/l to 0.2 g/l, from 0.02 g/l to 0.2 g/l, or from 0.1 g/l to 0.2 g/l.

Further preferred embodiments of the invention may arise from the combination of above-described preferred embodiments.

EXAMPLES

The examples below are intended to illustrate the invention in detail without, however, limiting it thereto. Unless explicitly stated otherwise, all percentages given are percentages by weight (% by wt. or wt.-%).

Key to abbreviations used:

TPA terephthalic acid

PG 1 ,2-propylene glycol

TTB titanium tetrabutoxide mPEG750 mono hydroxyl-functional polyethylene glycol monomethyl ether, average molecular weight 0.75 kDa

The synthesis was carried out in two steps. In step a), terephthalic acid was esterified with 1 ,2-propylene glycol and a terminal capped polyalkylene glycol. In step b), the resulting mixture was polycondensed. A catalyst system was used in the examples.

Example I

23.2 g TPA, 15.9 g PG, and 90.9 g mPEG750 were introduced into a reaction vessel at room temperature under a nitrogen atmosphere and stirred. The reaction mixture was heated up to 100 °C. At this temperature, 0.178 g TTB was added, and the mixture was further slowly heated up to 250 °C. Water was distilled out of the system using a distillation column. Once the conversion of the esterification reaction of >98% was achieved (i.e. , >98% of the carboxylic acid groups of terephthalic acid have been esterified) as determined by measuring the amount and water content of the distillate, which was approximately 6 hours after distillation commenced, the temperature was set to 230 °C, and the pressure was slowly reduced to 1 mbar. PG and impurities were distilled out of the system. The mixture was stirred for 4 hours at 230 °C and a pressure of 1 mbar. After this time, the inner pressure of the reaction vessel was increased to 1 bar using nitrogen, and the molten product was subsequently removed from the reactor and allowed to solidify.

Example II

46.8 g TPA, 42.8 g PG, and 183.5 g mPEG750 were introduced into a reaction vessel at room temperature under a nitrogen atmosphere and stirred. The reaction mixture was heated up to 100 °C. At this temperature, 0.718 g TTB was added, and the mixture was further slowly heated up to 235 °C. Water was distilled out of the system using a distillation column. Once the conversion of the esterification reaction of >99% was achieved (i.e., >99% of the carboxylic acid groups of terephthalic acid have been esterified) as determined by measuring the acid value of the sample, which was approximately 12-13 hours after distillation commenced, the temperature was set to 230 °C, and the pressure was slowly reduced to 1 mbar. PG and impurities were distilled out of the system. The mixture was stirred for 4 hours at 230 °C and a pressure of 1 mbar. After this time, the inner pressure of the reaction vessel was increased to 1 bar using nitrogen, and the molten product was subsequently removed from the reactor and allowed to solidify. 15.2 mg dioxane were formed in this process.

Example III

242.0 g TPA, 332.5 g PG, and 950.0 g mPEG750 were introduced into a reaction vessel at room temperature under a nitrogen atmosphere and stirred. The reaction mixture was heated up to 110 °C. At this temperature, 1 .884 g TTB was added, and the mixture was further slowly heated up to 222 °C. Water was distilled out of the system using a distillation column. Once the conversion of the esterification reaction of >99% was achieved (i.e. , >99% of the carboxylic acid groups of terephthalic acid have been esterified) as determined by measuring the acid value of the sample, which was approximately 5-6 hours after distillation commenced, the temperature was set to 230 °C, and the pressure was slowly reduced to 15 mbar. PG and impurities were distilled out of the system. The mixture was stirred for 1 hour at 230 °C and a pressure of 15 mbar. After this time, the inner pressure of the reaction vessel was increased to 1 bar using nitrogen, and the molten product was subsequently removed from the reactor and allowed to solidify.

Example IV

259.83 g terephthalic acid, 238.02 g propylene glycol, and 1020 g mPEG750 were introduced into a reaction vessel at room temperature under a nitrogen atmosphere and stirred. The reaction mixture was heated up to 110 °C. At this temperature, 2.02 g TTB was added, and the mixture was further slowly heated until distillation started (approximately 194 °C). Water was distilled out of the system using a heated distillation column. The temperature was slowly increased up to 230 °C to keep distillation going on, subsequently held at this temperature and further stirred. Samples were taken during the heating period, and their acid value was determined. Once an acid value of 3.9 mg KOH/g was reached (corresponding to a conversion of the esterification reaction of 96.5%), the mixture was heated to 230 °C, and the pressure was slowly reduced to 15 mbar. Propylene glycol and impurities were distilled out of the system. The mixture was stirred for 1 hour at 230 °C and a pressure of 15 mbar. After the end of this time period, the inner pressure of the reaction vessel was increased to 1 bar using nitrogen, and the molten product was subsequently removed from the reactor and allowed to solidify. 86.1 mg dioxane were formed in this process.

Laundry detergent formulations

Key to ingredients used in the formulations:

LAS is C12-14 linear alkylbenzene sulfonate, sodium salt

SLES 2EO is sodium lauryl ether sulfate with 2 moles EO

Nl 7EO is C12-15 alcohol ethoxylate 7EO nonionic

Fatty Acid is a C12-18 stripped palm kernel fatty acid

A series of exemplary liquid laundry detergent formulations according to the invention (with a polyester obtained by the inventive process) were prepared. Preformulations were prepared according to the compositions listed in Table I. Exemplary liquid laundry detergent formulations were subsequently prepared according to the compositions listed in Table II.

Table I - Pre-formulations for preparing liquid laundry detergent formulations

Table II - Liquid laundry detergent compositions for performance testing

Soil release test The detergent formulations 1 to 4 were tested for their soil release performance according to the “Dirty-Motor Oil” Test (DMO-Test) using a Lini Apparatus. The conditions for the test are listed in Table III.

Table III - Washing conditions - Soil Release Test

As test fabric, white polyester standard swatches (WFK 30A from WFK Testgewebe GmbH) were used. The fabrics were prewashed three times with the laundry detergent formulations. The swatches were then rinsed, dried, and soiled with 25 pL of dirty motor oil. After 1 hour the soiled fabrics were washed again with the same stored laundry detergent compositions used in the pre-washing step. After rinsing and drying the washed swatches, a measurement of the remission of the stained fabric at 457 nm was made using a spectrophotometer (Datacolor 650).

The soil release performance is shown as an improvement in soil removal of the swatches washed with a formulation containing a polyester obtained by the inventive process (Soil Release Polymer, SRP), Formulation 2 to Formulation 4, compared with the same formulation containing no SRP, Formulation 1 :

AR = Rwith SRP - Rwithout SRP

The washing results obtained for the laundry detergent formulations comprising a polyester obtained by the inventive process are shown in Table IV, expressed as AR along with the 95% confidence intervals (95 % Cl).

Table IV - Washing results for liquid laundry detergent formulations

Claims

Claims:

1 . Process for preparing a polyester by reacting at least

- terephthalic acid (formula (I))

and

- propylene glycol (formula (II))

- one or more substances of the formula (III)

R¹-[OR²]_a-OH (III) or mixtures thereof wherein

R¹ is a linear or branched, preferably a linear, alkyl group comprising from 1 to 6 carbon atoms or a linear or branched, preferably a linear, alkenyl group comprising one or more double bonds and from 2 to 6 carbon atoms or mixtures thereof, preferably is a linear or branched, preferably a linear, alkyl group comprising from 1 to 4 carbon atoms or a linear or branched, preferably a linear, alkenyl group comprising one or more double bonds and from 2 to 4 carbon atoms or mixtures thereof, more preferably is methyl, a is, based on a molar average, a number of from 1 to 200, preferably of from 2 to 200, more preferably of from 3 to 150, and R² is a linear or branched alkylene group (C_mH2m) with m being an integer of from 2 to 10 or mixtures thereof, preferably with m being an integer of from 2 to 6 or mixtures thereof, more preferably is selected from the group consisting of (C2H4), (C3H6), (C4H8) and mixtures thereof, even more preferably is selected from the group consisting of (C2H4), (CsHe) and mixtures thereof, particularly preferably is (C2H4) or a mixture of (C2H4) and (CsHe), and extraordinarily preferably is (C2H4), characterized in that the preparation of the polyester comprises the steps of: a) heating a mixture comprising terephthalic acid, propylene glycol, and one or more substances of the formula (III) or mixtures thereof and removing water until at least 50%, preferably at least 75%, more preferably at least 90%, even more preferably at least 95%, and particularly preferably at least 97% of the carboxylic acid groups of terephthalic acid are esterified and b) polycondensing the mixture obtained in step a) or a composition comprising the mixture obtained in step a) at ambient pressure or reduced pressure, preferably at reduced pressure, while removing propylene glycol and preferably also side products.

2. The process according to claim 1 , characterized in that the mixture in step a) is heated to temperatures of more than 90 °C, preferably to temperatures of from 100 °C to 300 °C, more preferably to temperatures of from 120 °C to 280 °C, even more preferably to temperatures of from 140 °C to 260 °C and particularly preferably to temperatures of from 160 °C to 250 °C.

3. The process according to claim 1 or 2, characterized in that polycondensing in step b) is executed at a pressure of from 0.1 to 900 mbar, preferably at a pressure of from 0.5 to 500 mbar, more preferably at a pressure of from 0.5 to 400 mbar, and preferably at temperatures of more than 90 °C, more preferably at temperatures of from 100 °C to 300 °C, even more preferably at temperatures of from 150 °C to 280 °C, particularly preferably at temperatures of from 160 °C to 270 °C and extraordinarily preferably at temperatures of from 180 °C to 260 °C.

4. The process according to one or more of claims 1 to 3, characterized in that removal of water in step a) and/or removal of propylene glycol in step b) is achieved in part or completely by distillation.

5. The process according to one or more of claims 1 to 4, characterized in that the molar ratio of propylene glycol to terephthalic acid in step a) is at least 1 .0:1.0, preferably is at least 1.2: 1.0, more preferably is at least 1.5: 1.0, even more preferably is at least 1.8: 1.0, and particularly preferably is at least 2.0:1.0, and preferably is lower than 10.0:1.0, more preferably is lower than 7.0:1.0 and even more preferably is lower than 3.0:1.0.

6. The process according to one or more of claims 1 or 5, characterized in that the molar ratio of the terephthalic acid to the one or more substances of the formula (III) or mixtures thereof is from 1 :1 to 30:1 , preferably is from 1 :1 to 20:1 , more preferably is from 1 :1 to 15:1 , even more preferably is from 1 :1 to 10:1 and particularly preferably is from 1 :1 to 8:1 .

7. The process according to one or more of claims 1 to 6, characterized in that the molar ratio of the terephthalic acid to the one or more substances of the formula (III) or mixtures thereof is from 1 :1 to 8:1 , R¹ is methyl, and “a” is, based on a molar average, a number of from 1 to 150, preferably of from 10 to 100, and more preferably of from 15 to 60.

8. The process according to one or more of claims 1 to 7, characterized in that one or more alkylene glycols of the formula (11-1 ) or mixtures thereof are additionally reacted and are preferably contained in the mixture used in step a) and/or are combined with the mixture obtained in step a) before executing step b) and more preferably are contained in the mixture used in step a) HO-(C_nH_2n)-OH (H-1 ) wherein

(CnH2n) is (C2H4) or a linear or branched alkylene group with n being an integer of from 4 to 10 or mixtures thereof, preferably is (C2H4) or a linear or branched alkylene group with n being an integer of from 4 to 6 or mixtures thereof, more preferably is selected from the group consisting of (C2H4), (C4H8) and mixtures thereof, even more preferably is (C2H4).

9. The process according to claim 8, characterized in that the molar ratio of the one or more alkylene glycols of the formula (11-1 ) or mixtures thereof to propylene glycol is 1 :1 or lower, preferably is 1 :2 or lower, more preferably is 1 :3 or lower.

10. The process according to one or more of claims 1 to 9, characterized in that one or more substances of the formula (IV) or mixtures thereof are additionally reacted and are preferably contained in the mixture used in step a) and/or are combined with the mixture obtained in step a) before executing step b)

wherein

¹/_p M^p+ is a cation, preferably selected from the group consisting of monovalent cations M⁺ (p = 1 ), divalent cations 7 M²⁺ (p = 2) and trivalent cations % M³⁺ (p = 3) and more preferably selected from the group consisting of H⁺, Li⁺, Na⁺, K⁺, Mg²⁺, 7 Ca²⁺, % Al³⁺, NH₄ ⁺ and R_aR_bR_cRdN⁺, wherein R_a, R_b, Rc and Rd, independently of one another, are H, linear or branched, preferably linear, alkyl groups comprising from 1 to 22 carbon atoms or linear or branched, preferably linear, hydroxyalkyl groups comprising from 2 to 10 carbon atoms, and wherein in the cations R_aRbR_cRdN⁺ at least one of R_a, Rb, R_c and Rd is not H,

11 . The process according to one or more of claims 1 to 10, characterized in that one or more polyalkyleneglycols of the formula (V) or mixtures thereof are additionally reacted and are preferably contained in the mixture used in step a) and/or are combined with the mixture obtained in step a) before executing step b)

H-[OR³]_d-OH (V) wherein

R³ is a linear or branched alkylene group (C_PH2_P), with p being an integer of from 2 to 10 or mixtures thereof, preferably with p being an integer of from 2 to 6 or mixtures thereof, more preferably is selected from the group consisting of (C2H4), (C3H6), (C4H8) and mixtures thereof, even more preferably is selected from the group consisting of (C2H4), (CsHe) and mixtures thereof, and particularly preferably is (C2H4), and d is an integer of from 2 to 400, preferably of from 2 to 200, more preferably of from 4 to 150, even more preferably of from 10 to 120 and particularly preferably of from 35 to 120.

12. The process according to one or more of claims 1 to 11 , characterized in that one or more crosslinking compounds, preferably having 3 to 6 functions capable of polycondensation, or mixtures thereof are additionally reacted and are preferably contained in the mixture used in step a) and/or are combined with the mixture obtained in step a) before executing step b), and more preferably, the one or more crosslinking compounds, preferably having 3 to 6 functions capable of polycondensation, or mixtures thereof are selected from the group consisting of citric acid, malic acid, tartaric acid, gallic acid, pentaerythritol, glycerol, sorbitol, mannitol, 1 ,2,3-hexanetriol, trimellitic acid, trimellitic anhydride, trimesic acid, and mixtures thereof.

13. The process according to one or more of claims 1 to 12, characterized in that one or more catalyst systems, and preferably one or more metal catalyst systems, are used in step a) and/or in step b), which more preferably comprise at least one titanium-based catalyst, even more preferably comprise titanium tetraisopropoxide and/or titanium tetrabutoxide, and particularly preferably comprise titanium tetrabutoxide.

14. The process according to one or more of claims 1 to 13, characterized in that at least 20 wt.-%, preferably at least 30 wt.-%, more preferably at least 50 wt.-%, even more preferably at least 60 wt.-%, and particularly preferably

100 wt.-% of the propylene glycol used in step a), in each case based on the total weight of the propylene glycol used in step a), is propylene glycol which has been obtained from step b) of a previous polycondensation reaction or which has been accumulated from step b) of two or more previous polycondensation reactions.

15. A product or polyester obtainable by the process according to one or more of claims 1 to 14.