Polyester polymers for hair care

Abstract

The present invention provides a polyester polymer which is effective and biodegradable in hair straightening. The invention also provides a method for synthesizing such a polyester polymer.

Description

This application claims priority from Application No. 202221037108 filed in India on June 28, 2022, the entire contents of which are incorporated herein by reference for all purposes. Technical Field

[0001] The present invention provides a polyester polymer for use in hair care formulations, namely hair straightening compositions. Background Art

[0002] Human hair is made of keratin, which in turn is made of polypeptide chains held together by disulfide, hydrogen and salt bonds. Temporary straightening using physicochemical techniques (such as hair dryers, hair straighteners and the electric combs of the past) only lasts until the next wash. More permanent hair straightening can be achieved by chemically altering the disulfide bonds of keratin, but this weakens the hair fiber. Conditioning polymers can also improve the manageability of hair and make it softer and smoother. Cationic polymers are preferred because they are retained by negatively charged proteins in the hair through electrostatic forces, while non-ionic polymers are more easily washed out by surfactants. However, most of the currently available conditioning polymers are not biodegradable, so when they end up in wastewater, they may contribute to the formation of microplastics.

[0003] US 5662893 discloses a hair spray comprising a sulfopolyester containing repeating units of 20 to 26 mole percent of dimethyl-5-sodiosulfoisophthalate and 74 to 80 mole percent of isophthalic acid based on 100 mole percent of dicarboxylic acid; 10 to 30 mole percent of 1,4-cyclohexanedimethanol and 70 to 90 mole percent of diethylene glycol based on 100 mole percent of diol. This document does not address the problem of long-term hair straightening, but only addresses the problem of providing a specific shape or form to human hair by applying a thin film of resin or gum to the hair to bond adjacent hairs together so that they maintain a specific shape or form when applied. This document also does not address the problem of degradability.

[0004] It is an object of the present invention to provide a polyester polymer that is effective in long term hair straightening. It is another object of the present invention to provide a biodegradable polyester polymer.

[0005] In another aspect of the present invention, a method for synthesizing a polyester polymer is provided.

[0006] Finally, the invention also relates to the use of the given polyester polymers in hair care compositions, in particular in hair straightening compositions. DETAILED DESCRIPTION

[0007] The polyester polymers of the present invention are prepared by polycondensation of at least the following monomers: (a) aliphatic / aromatic unsulfonated dicarboxylic acids / esters of dicarboxylic acids; (b) aliphatic diols; (c) aliphatic / aromatic sulfonated dicarboxylic acids / esters of dicarboxylic acids; (d) aliphatic / aromatic secondary or tertiary amines with two carboxylic acid / ester functions, or aliphatic / aromatic quaternized amines with two carboxylic acid / ester functions.

[0008] The aliphatic unsulfonated dicarboxylic acids / esters of dicarboxylic acids according to the invention may be linear or cyclic. Preferred linear aliphatic unsulfonated dicarboxylic acids / esters of dicarboxylic acids according to the invention are esters of alkyl dicarboxylic acids / esters of alkyl dicarboxylic acids having the formula ROOC-(CH2)n-COOR(I), wherein n=2-4 and R is H, C1 to C8 alkyl or phenyl. Preferred cycloaliphatic unsulfonated dicarboxylic acids / esters of dicarboxylic acids according to the invention are based on rings having 5 or 6 C atoms, i.e. alkyl esters of cyclopentanedicarboxylic acid / alkyl esters of cyclohexanedicarboxylic acid / alkyl esters, in particular 1,2-cyclopentanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid or 1,4-cyclohexanedicarboxylic acid and their corresponding alkyl esters, wherein the alkyl group may vary from methyl to octyl, or may be phenyl.

[0009] Preferred aromatic unsulfonated dicarboxylic acids / esters of dicarboxylic acids according to the invention are terephthalic acid / alkyl esters of terephthalic acid and isophthalic acid / alkyl esters of isophthalic acid, wherein the alkyl group may vary from methyl to octyl, or may be phenyl.

[0010] The aliphatic / aromatic unsulfonated dicarboxylic acids / esters of dicarboxylic acids (a) of the present invention are preferably aliphatic unsulfonated dicarboxylic acids / esters of dicarboxylic acids, more preferably cyclohexane derivatives. In particular, 1,4-cyclohexanedicarboxylic acid (CHDA) gives good results within the scope of the present invention.

[0011] The aliphatic diol used in the present invention may be a linear aliphatic diol selected from the group consisting of an alkyl diol like ethylene glycol or propylene glycol, diethylene glycol, triethylene glycol or a polyethylene glycol with an ethylene oxide number ranging from 4 to 75. Alternatively, it may be a cyclic saturated diol preferably containing 5 or 6 C atoms, i.e. cyclopentanediol or cyclohexanediol, in particular 1,2-cyclopentanediol, 1,3-cyclopentanediol, 1,3-cyclohexanediol or 1,4-cyclohexanediol.

[0012] Preferably, linear aliphatic diols are used, more preferably alkyl diols, in particular ethylene glycol (EG).

[0013] The aliphatic / aromatic sulfonated dicarboxylic acids / esters of dicarboxylic acids (c) have at least one sulfonic acid group, preferably in the form of an alkali metal (preferably sodium) sulfonate, and two acid / ester functions attached to one or more aromatic rings (when it comes to aromatic dicarboxylic acids or their alkyl diesters), or two acid / ester functions attached to an aliphatic chain (when it comes to aliphatic dicarboxylic acids / alkyl diesters of aliphatic dicarboxylic acids), wherein the alkyl group can vary from methyl to octyl, or can be phenyl.

[0014] Aromatic sulfonated dicarboxylic acids / esters of dicarboxylic acids monomers that can be used in the framework of the present invention are preferably esters of isophthalic acid / isophthalic acid, esters of terephthalic acid / terephthalic acid and esters of naphthalene dicarboxylic acid / naphthalene dicarboxylic acid. Preferred are esters of 2-sodiosulfoisophthalic acid / 2-sodiosulfoisophthalic acid, esters of 4-sodiosulfoisophthalic acid / 4-sodiosulfoisophthalic acid, esters of 5-sodiosulfoisophthalic acid / 5-sodiosulfoisophthalic acid, esters of 2-sodiosulfoterephthalic acid / 2-sodiosulfoterephthalic acid, esters of 2,6-dicarboxynaphthalene-4-sodiosulfonic acid / 2,6-dicarboxynaphthalene-4-sodiosulfonic acid and esters of 2,6-dicarboxynaphthalene-7-sodiosulfonic acid / 2,6-dicarboxynaphthalene-7-sodiosulfonic acid. An aliphatic sulfonated dicarboxylic acid / ester of a dicarboxylic acid that can be used within the framework of the present invention is sodium dialkyl sulfosuccinate.

[0015] In the context of the present invention, preference is given to using aromatic sulfonated dicarboxylic acids / ester monomers of dicarboxylic acids, more preferably 5-sodiosulfoisophthalic acid / esters of 5-sodiosulfoisophthalic acid, in particular 5-sodiosulfoisophthalic acid (SSIA).

[0016] As examples of aliphatic secondary or tertiary amines according to the invention, mention may be made of N-methyldiethanolamine, ethylenediamine N,N'diacetic acid / alkyl diesters and iminodiacetic acid / alkyl diesters of iminodiacetic acid, wherein the alkyl group may vary from methyl to octyl or may be phenyl.

[0017] As examples of aromatic secondary or tertiary amines according to the invention, mention may be made of pyridine derivatives, such as alkyl diesters of pyridine-2,6-dicarboxylic acid / pyridine-2,6-dicarboxylic acid, alkyl diesters of pyridine-2,4-dicarboxylic acid / pyridine-2,4-dicarboxylic acid, alkyl diesters of pyridine-3,5-dicarboxylic acid / pyridine-3,5-dicarboxylic acid, alkyl diesters of pyridine-2,3-dicarboxylic acid / pyridine-2,3-dicarboxylic acid and alkyl diesters of pyridine-2,5-dicarboxylic acid / pyridine-2,5-dicarboxylic acid; pyrazine derivatives, such as alkyl diesters of pyrazine-2,6-dicarboxylic acid / pyrazine-2,6-dicarboxylic acid, alkyl diesters of pyrazine-2,3-dicarboxylic acid / pyrazine-2,3-dicarboxylic acid and alkyl diesters of pyrazine-2,5-dicarboxylic acid / pyrazine-2,5-dicarboxylic acid; imidazole derivatives, such as 1 Alkyl diesters of 1H-imidazole-2,5-dicarboxylic acid / 1H-imidazole-2,5-dicarboxylic acid and alkyl diesters of 1H-imidazole-4,5-dicarboxylic acid / 1H-imidazole-4,5-dicarboxylic acid; and indole derivatives, like alkyl diesters of 1H-indole-4,6-dicarboxylic acid / 1H-indole-4,6-dicarboxylic acid, alkyl diesters of 1H-indole-2,5-dicarboxylic acid / 1H-indole-2,5-dicarboxylic acid, alkyl diesters of 1H-indole-2,6-dicarboxylic acid / 1H-indole-2,6-dicarboxylic acid, alkyl diesters of 1H-indole-3,5-dicarboxylic acid / 1H-indole-3,5-dicarboxylic acid and alkyl diesters of 1H-indole-2,3-dicarboxylic acid / 1H-indole-2,3-dicarboxylic acid, wherein the alkyl group can vary from methyl to octyl, or can be phenyl.

[0018] As examples of aliphatic quaternized amines according to the invention, mention may be made of the quaternized forms of the abovementioned tertiary aliphatic amines, in particular of N-methyldiethanolamine.

[0019] As examples of aromatic quaternized amines according to the invention, mention may be made of the quaternized forms of the abovementioned aromatic tertiary amines, in particular of pyridine-2,6-dicarboxylic acid / esters of pyridine-2,6-dicarboxylic acid, such as, for example, 2,6-bis(methoxycarbonyl)-1-methylpyridin-1-ium trifluoromethanesulfonate, chloride, bromide, iodide, sulfate.

[0020] The synthesis of 2,6-bis(methoxycarbonyl)-1-methylpyridin-1-ium trifluoromethanesulfonate has been described in the article "Photodetachment of Zwitterions: Probing Intramolecular Coulomb Repulsion and Attraction in the Gas Phase Using Pyridinium Dicarboxylate Anions", J. AM. CHEM. SOC. [Journal of the American Chemical Society] 2003, 125, 296-304.

[0021] Aromatic tertiary or quaternized amines are preferred, especially the abovementioned pyridine derivatives, more particularly pyridine-2,6-dicarboxylic acid (PDA) and 2,6-bis(methoxycarbonyl)-1-methylpyridin-1-ium trifluoromethanesulfonate (quatPDA).

[0022] In a preferred embodiment, the polyester polymer of the present invention is prepared by polycondensation of the following monomers: (a) aliphatic unsulfonated dicarboxylic acids / esters of dicarboxylic acids, preferably cyclohexane derivatives, in particular 1,4-cyclohexanedicarboxylic acid (CHDA); (b) linear aliphatic diols, in particular ethylene glycol (EG); (c) aromatic sulfonated dicarboxylic acids / esters of dicarboxylic acids, preferably 5-sodiosulfoisophthalic acid / esters of 5-sodiosulfoisophthalic acid, in particular 5-sodiosulfoisophthalic acid (SSIA); (d) Aromatic tertiary or quaternized amines carrying two carboxylic acid / ester functions of a carboxylic acid, preferably pyridine derivatives, in particular pyridine-2,6-dicarboxylic acid (PDA) or 2,6-bis(methoxycarbonyl)-1-methylpyridin-1-ium trifluoromethanesulfonate (quarPDA).

[0023] Particularly preferred polyesters of the present invention are prepared by polycondensation of the following monomers: (a) 1,4-cyclohexanedicarboxylic acid (CHDA); (b) ethylene glycol (EG); (c) 5-sodiosulfoisophthalic acid (SSIA); (d) Pyridine-2,6-dicarboxylic acid (PDA) or 2,6-bis(methoxycarbonyl)-1-methylpyridin-1-ium trifluoromethanesulfonate (quatPDA).

[0024] The present invention also relates to a novel and inventive polyester polymer comprising the following repeating units: CHDA-EG, SSIA-EG and (quat)PDA-EG (ie, PDA-EG or quatPDA-EG).

[0025] In a particularly preferred embodiment, the polymer is an aliphatic aromatic polyester derived from (a) a mixture of dicarboxylic acids comprising cyclohexanedicarboxylic acid (varying from 10% to 40% by mole), 5-sodiosulfoisophthalic acid (varying from 5% to 20% by mole) and 2,6-pyridinedicarboxylic acid / quaternized 2,6-pyridinedicarboxylic acid (or ester) (varying from 5% to 20% by mole), and (b) a diol component, preferably ethylene glycol. The weight average molecular weight of the polyester may vary from 5000 to 15000, and the polyester is preferably soluble / dispersible in water.

[0026] Preferred polyesters according to the invention contain up to 20 mol% of aromatic compounds (eg SSIA and (quat)PDA) in order to promote / facilitate biodegradability (for more details on biodegradability, see below).

[0027] The invention also relates to a process for synthesizing the above polyester polymer by polycondensation of monomers (a), (b), (c) and (d), preferably in the presence of a catalyst. The catalyst is preferably a hydrolytically stable catalyst, more preferably selected from chelates of titanium or zirconium salts derived from ethanolamine, alone and / or in mixtures or solutions thereof. In particular, titanium(IV) (triethanolamine) isopropoxide gives good results. This compound is known under the trade name TE is available as an 80 wt % solution in isopropanol.

[0028] The polycondensation according to the invention preferably starts on a mixture of all monomers (a) to (d), i.e. first the monomers (a), (b), (c) and (d) are mixed and then reacted by polycondensation (preferably by increasing the temperature and / or reducing the pressure). Alternatively, the polycondensation can be started only on a mixture of some of the monomers, the other monomers being introduced in a delayed manner. Yet another possibility is to prepare two or more prepolymers by polycondensation and then to carry out the transesterification of the prepolymers.

[0029] In a preferred embodiment, the procedure for preparing the polyester according to the present invention is as follows. First, all monomers are mixed in a reaction vessel and the mixture is heated from about 110°C to 200°C, preferably from 120°C to 180°C under nitrogen protection. The reaction mixture is then preferably kept at the same temperature for 30 to 240 minutes, preferably 60 to 180 minutes, under stirring. Subsequently, the reaction temperature is preferably increased to 200°C and a reduced pressure of 50 to 300 mbar, preferably 100 to 200 mbar, is gradually reached; under this condition, ethylene glycol begins to distill and is preferably collected in a receiver. The reaction temperature is then preferably increased to between about 210°C and 250°C under reduced pressure. When the reaction reaches the desired temperature, the pressure is then preferably further reduced to about 10 mbar to 50 mbar, preferably to about 20 to 40 mbar. The reaction is then preferably kept under this condition for 30 to 240 minutes, preferably 60 to 180 minutes, after which the polymer can be discharged in a hot state.

[0030] In one embodiment of the present invention, the quaternized form of the polymer is obtained due to the quaternization of the tertiary amine groups in the polyester backbone (modification after polymerization). In this embodiment, the polyester is preferably dissolved in a suitable solvent, mixed with a magnetic stirrer and heated to reflux. The quaternizing agent is then preferably added with a syringe through a rubber septum in a molar ratio of tertiary amine (polyester): quaternizing agent, wherein the molar ratio varies from 1:1.1 to 1:2, preferably from 1:1.2 to 1:1.8. After the reaction, the solvent is removed and the resulting polyester is obtained.

[0031] The present invention also relates to the use of the above-described polyester polymers in hair care compositions, in particular in hair straightening compositions.

[0032] Should the disclosure of any patents, patent applications, and publications incorporated herein by reference conflict with the description of the present application to the extent that it might render a term unclear, the present invention shall take precedence. Examples

[0033] Examples 1 to 7: Polyester Polymers Using PDA Monomers: Synthesis and Properties A glass reactor equipped with an overhead stirrer, nitrogen inlet, condenser assembly with receiving vessel, and solid addition port was charged with 228.71 (1.31 mol) of 1,4CHDA, 46.4 g (0.164 mol) of SSIA, 27.45 g (0.164 mmol) of PDA, 2.08 g (6.57 mmol) of (triethanolamine) isopropoxide titanium (IV) solution (80 wt. % in isopropanol) ( TE) and 309.18g (4.93mol) of EG. Excess ethylene glycol (3 equivalents) was used to dissolve SSIA; however, at the end of the reaction, excess ethylene glycol was distilled off (refer to Table 1 for the initial and final charge of EG). Initially, the reaction mixture was heated to 160°C under a nitrogen blanket, and the reaction mixture was kept at the same temperature for 60 minutes under stirring, then the reaction temperature was increased to 200°C, and a reduced pressure of 100 mbar was gradually reached, under which conditions ethylene glycol began to distill and was collected in a receiver. The reaction temperature was then increased to 235°C under reduced pressure. When the reaction reached 235°C, the pressure was further reduced to 20 mbar. The reaction was kept under this condition for 60 minutes, after which the polymer was discharged in a hot state. Characteristics of the polyester polymer obtained (Example 1): Molecular weight (Mw): 4600 Da (measured by gel permeation chromatography using hexafluoroisopropanol as eluent); Glass transition temperature (Tg): -3°C Following the protocol outlined above, Examples 2 to 7 were prepared having different compositions and their characteristics / properties are listed in Table 1 below.

[0034] Examples 8 to 14: Polyester Polymers Using QuatPDA Monomers: Synthesis and Properties A glass reactor equipped with an overhead stirrer, nitrogen inlet, condenser assembly with receiving vessel, and solid addition port was charged with 37.09 g (0.213 mol) of CHDA, 7.52 g (0.026 mol) of SSIA, 9.59 g (0.026 mol) of pyridinium, 2,6-bis(methoxycarbonyl)-1-methylpyridin-1-ium trifluoromethanesulfonate, 0.337 g (1.067 mmol) of titanium(IV) (triethanolamine) isopropoxide solution (80 wt. % in isopropanol) ( TE) and 50.15g (0.808mol) of ethylene glycol. Excess ethylene glycol (3 equivalents) was used to dissolve SSIA; however, at the end of the reaction, excess ethylene glycol was distilled off (refer to Table 2 for the initial and final charge of EG). Initially, the reaction mixture was heated to 160°C under a nitrogen blanket, and the reaction mixture was kept at the same temperature for 60 minutes under stirring, then the reaction temperature was increased to 200°C, and a reduced pressure of 100 mbar was gradually reached, under which conditions ethylene glycol began to distill and was collected in a receiver. The reaction temperature was then increased to 235°C under reduced pressure. When the reaction reached 235°C, the pressure was further reduced to 20 mbar. The reaction was kept under this condition for 60 minutes, after which the polymer was discharged in a hot state. Characteristics of the polyester polymer obtained (Example 8): Molecular weight (Mw): 29100 Da (measured by gel permeation chromatography using hexafluoroisopropanol as eluent); Glass transition temperature (Tg): -10°C Following the protocol outlined above, additional examples with different compositions were prepared and their characteristics / properties are listed in Table 2 below. Table 2

[0035] Biodegradability Test Results

[0036] The biodegradability test was performed according to OECD (1992), Test No. 302B: Intrinsic Biodegradability: Zahn-Wellens / EVPA Test, OECD Guidelines for the Testing of Chemicals, Section 3, OECD Publishing, Paris, the contents of which are incorporated herein by reference.

[0037] In summary, in this test, a mixture containing a test substance, mineral nutrients and a relatively large amount of activated sludge in an aqueous medium is stirred and aerated at 20°C-25°C in the dark or under diffuse light for up to 28 days. A blank control containing activated sludge and mineral nutrients but not containing the test substance is run in parallel. The biodegradation process is monitored by determining the DOC (dissolved organic carbon) or COD (chemical oxygen demand) in the filtered samples collected every day or at other time intervals. After each time interval, the ratio of the DOC (or COD) eliminated for blank correction to the initial DOC value is expressed as the percentage of biodegradation at the time of sampling. The percentage of biodegradation is plotted against time to give a biodegradation curve.

[0038] The degree of biodegradation achieved at the end of the test after 28 days, or earlier if complete degradation is achieved in less than 28 days, is the "inherent biodegradability" of the polymer.

[0039] As shown in Table 3 below, the polyester polymers of Examples 1 to 3, 8, 10 and 15 (containing less than 20 mol % aromatic compounds) are inherently more biodegradable than the polyester polymers of Examples 4 to 7 (containing greater than 20 mol % aromatic compounds).

[0040] Table 3

[0041] Hair straightening properties

[0042] Straightening test solution

[0043] Preprocessing

[0044] 2.7 g of natural mixed race grade 3 curly hair tresses were used in the study. All tresses were pre-treated with 1 ml of a 14% active sodium laureth sulfate solution to remove any impurities. The tresses were dried overnight at 25°C. For each experiment (treatment), 3 tresses were used (i.e. the experiments were performed in triplicate).

[0045] Processing and measurement

[0046] The processing steps are as follows:

[0047] Step 0: When the hair is dry, measure the volume of the hair tresses before treatment but after the pre-treatment step.

[0048] Step 1: Soak the hair strands in 37°C tap water for 10 minutes.

[0049] Step 2: Remove excess water manually and comb through the locks

[0050] Step 3: Soak the hair tresses in a 1% w / w aqueous polymer solution for 3 min.

[0051] Step 4: Remove excess solution manually and comb through hair until hair is detangled

[0052] Step 5: Blow-dry the tresses using a hair dryer for 1 minute 30 seconds on each side. Keep the hair fibers aligned during the blow-drying process.

[0053] Step 6: Apply a hair straightener set at 230°C five times, each time for 5 seconds

[0054] Step 7: Measure the volume of the treated lock using the Bolero device (see below). This constitutes T=0.

[0055] Step 8: Place all tresses in a climate chamber set at 20°C and 50% RH or 25°C and 80% RH

[0056] Step 9: Measure the volume of the hair strands at T=4, T=24, T=48 and T=72 hours

[0057] Measurement and calculation details:

[0058] The measurement of hair bulk and flyaways was achieved using a Bolero device from Bossa Nova Technologies. These parameters are defined as follows:

[0059] • Bulk volume (in cm3) corresponds to the area showing the highest hair density.

[0060] • Flyaways (=FAF in cm3) represent the individual hairs outside the bulk. If there are no flyaways, the hair locks are well straightened.

[0061] As an indicator of the straightening effect, the following values ​​were calculated:

[0062] Bulk volume reduction % = 100-100*(bulk volume / initial bulk volume)

[0063] FAF volume reduction % = 100-100*(FAF volume / initial FAF volume)

[0064] In these equations, the initial value refers to the value measured on the tress before treatment but after the above-mentioned pre-treatment. This is a necessary step because the initial volume of the tresses is different despite having the same mass, which can be attributed to the mechanical thermal and humidity history of the tresses.

[0065] The higher the value, the more efficient the straightening.

[0066] The polyester polymers of Examples 1, 8, and 10 and Frizz Therapy (commercial conditioner) The results obtained are shown in the attached Figure 1 and Figure 2 middle.

Claims

1. A polyester polymer prepared by polycondensation of at least the following monomers: (a) aliphatic / aromatic unsulfonated dicarboxylic acids / esters of dicarboxylic acids; (b) aliphatic diols; (c) aliphatic / aromatic sulfonated dicarboxylic acids / esters of dicarboxylic acids; (d) aliphatic / aromatic secondary or tertiary amines with two carboxylic acid / ester functions, or aliphatic / aromatic quaternized amines with two carboxylic acid / ester functions.

2. The polyester polymer according to claim 1, wherein The aliphatic / aromatic unsulfonated dicarboxylic acid / ester of dicarboxylic acid (a) is selected from: - alkyl dicarboxylic acids / esters of alkyl dicarboxylic acids of the formula ROOC-(CH2)n-COOR (I) wherein n=2-4 and R is H, C1 to C8 alkyl or phenyl; - alkyl esters of cyclopentanedicarboxylic acid / cyclopentanedicarboxylic acid or alkyl esters of cyclohexanedicarboxylic acid / cyclohexanedicarboxylic acid, in particular 1,2-cyclopentanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid or 1,4-cyclohexanedicarboxylic acid and the corresponding alkyl esters, wherein the alkyl group may vary from methyl to octyl or may be phenyl; - terephthalic acid / alkyl esters of terephthalic acid and isophthalic acid / alkyl esters of isophthalic acid, wherein the alkyl group may vary from methyl to octyl, or may be phenyl.

3. The polyester polymer according to claim 2, wherein The aliphatic / aromatic unsulfonated dicarboxylic acids / esters of dicarboxylic acids (a) are aliphatic unsulfonated dicarboxylic acids / esters of dicarboxylic acids, preferably cyclohexane derivatives, in particular 1,4-cyclohexanedicarboxylic acid (CHDA).

4. The polyester polymer according to any one of claims 1 to 3, wherein The aliphatic diol (b) is selected from: - alkyl glycols, such as ethylene glycol or propylene glycol, diethylene glycol, triethylene glycol; polyethylene glycols with an ethylene oxide number ranging from 4 to 75; - a cyclic saturated diol, preferably cyclopentanediol or cyclohexanediol, in particular 1,2-cyclopentanediol, 1,3-cyclopentanediol, 1,3-cyclohexanediol or 1,4-cyclohexanediol.

5. The polyester polymer according to claim 4, wherein The aliphatic diol (b) is an alkyl diol, in particular ethylene glycol (EG).

6. The polyester polymer according to any one of claims 1 to 5, wherein The aliphatic / aromatic sulfonated dicarboxylic acid / ester of dicarboxylic acid (c) is selected from: - esters of isophthalic acid / isophthalic acid, terephthalic acid / terephthalic acid and naphthalene dicarboxylic acid / naphthalene dicarboxylic acid, in particular esters of 2-sodiosulfoisophthalic acid / 2-sodiosulfoisophthalic acid, 4-sodiosulfoisophthalic acid / 4-sodiosulfoisophthalic acid, 5-sodiosulfoisophthalic acid / 5-sodiosulfoisophthalic acid, 2-sodiosulfoterephthalic acid / 2-sodiosulfoterephthalic acid, 2,6-dicarboxynaphthalene-4-sodiosulfo acid / 2,6-dicarboxynaphthalene-4-sodiosulfo acid and 2,6-dicarboxynaphthalene-7-sodiosulfo acid / 2,6-dicarboxynaphthalene-7-sodiosulfo acid; -Sodium dialkyl sulfosuccinate.

7. The polyester polymer according to claim 6, wherein The aliphatic / aromatic sulfonated dicarboxylic acid / ester of a dicarboxylic acid (c) is an aromatic sulfonated dicarboxylic acid / ester of a dicarboxylic acid, preferably 5-sodiosulfoisophthalic acid or an ester thereof, in particular 5-sodiosulfoisophthalic acid (SSIA).

8. The polyester polymer according to any one of claims 1 to 7, wherein Monomer (d) is selected from: - N-methyldiethanolamine, ethylenediamine N,N'diacetic acid / alkyl diesters of ethylenediamine N,N'diacetic acid and iminodiacetic acid / alkyl diesters of iminodiacetic acid, wherein the alkyl group may vary from methyl to octyl, or may be phenyl; - Pyridine derivatives, such as pyridine-2,6-dicarboxylic acid / alkyl diesters of pyridine-2,6-dicarboxylic acid, pyridine-2,4-dicarboxylic acid / alkyl diesters of pyridine-2,4-dicarboxylic acid, pyridine-3,5-dicarboxylic acid / alkyl diesters of pyridine-3,5-dicarboxylic acid -3,5-dicarboxylic acid alkyl diesters, pyridine-2,3-dicarboxylic acid / pyridine-2,3-dicarboxylic acid alkyl diesters and pyridine-2,5-dicarboxylic acid / pyridine-2,5-dicarboxylic acid alkyl diesters; pyrazine derivatives, such as pyrazine -2,6-dicarboxylic acid / alkyl diesters of pyrazine-2,6-dicarboxylic acid, pyrazine-2,3-dicarboxylic acid, and pyrazine-2,5-dicarboxylic acid / alkyl diesters of pyrazine-2,5-dicarboxylic acid; imidazole derivatives, such as alkyl diesters of 1H-imidazole-2,5-dicarboxylic acid / alkyl diesters of 1H-imidazole-2,5-dicarboxylic acid, and alkyl diesters of 1H-imidazole-4,5-dicarboxylic acid / alkyl diesters of 1H-imidazole-4,5-dicarboxylic acid; and indole derivatives, such as alkyl diesters of 1H-indole-4,6-dicarboxylic acid / alkyl diesters of 1H-indole-4,6-dicarboxylic acid, -2,5-dicarboxylic acid / 1H-indole-2,5-dicarboxylic acid alkyl diester, 1H-indole-2,6-dicarboxylic acid / 1H-indole-2,6-dicarboxylic acid alkyl diester, 1H-indole-3,5-dicarboxylic acid / 1H-indole-3,5-dicarboxylic acid alkyl diester and 1H-indole-2,3-dicarboxylic acid / 1H-indole-2,3-dicarboxylic acid alkyl diester, wherein the alkyl group can vary from methyl to octyl, or can be phenyl.

9. The polyester polymer according to any one of claims 1 to 7, wherein Monomer (d) is a quaternized form of an aromatic tertiary amine, preferably a quaternized form of a pyridine derivative, in particular a quaternized form of pyridine-2,6-dicarboxylic acid / ester of pyridine-2,6-dicarboxylic acid, more particularly 2,6-bis(methoxycarbonyl)-1-methylpyridin-1-ium trifluoromethanesulfonate.

10. The polyester polymer according to claim 8 or 9, wherein Monomer (d) is an aromatic tertiary amine or a quaternized amine, preferably pyridine-2,6-dicarboxylic acid (PDA) or 2,6-bis(methoxycarbonyl)-1-methylpyridin-1-ium trifluoromethanesulfonate (quatPDA).

11. The polyester polymer according to any one of claims 1 to 10, which is prepared by polycondensation of the following monomers: (a) 1,4-cyclohexanedicarboxylic acid (CHDA); (b) ethylene glycol (EG); (c) 5-sodiosulfoisophthalic acid (SSIA); (d) Pyridine-2,6-dicarboxylic acid (PDA) or 2,6-bis(methoxycarbonyl)-1-methylpyridin-1-ium trifluoromethanesulfonate (quatPDA).

12. A polyester polymer comprising the following repeating units: CHDA-EG, SSIA-EG and (quat)PDA-EG.

13. A method for synthesizing a polyester polymer according to any one of claims 1 to 11, the method comprising: A polycondensation step of monomers (a), (b), (c) and (d) in the presence of a catalyst, preferably a hydrolytically stable catalyst, more preferably a chelate derived from a titanium or zirconium salt of ethanolamine, in particular titanium(IV)(triethanolaminate)isopropoxide.

14. The method according to claim 13, wherein: The monomers (a), (b), (c) and (d) are first mixed and then subjected to polycondensation by increasing the temperature and / or decreasing the pressure.

15. Use of a polyester polymer according to any one of claims 1 to 12 or obtained by a process according to claim 13 or 14 in a hair care composition, in particular in a hair straightening composition.

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