WO2021004845A1

WO2021004845A1 - Lysine-branched copolymer

Info

Publication number: WO2021004845A1
Application number: PCT/EP2020/068467
Authority: WO
Inventors: Anna Maria Mueller-Cristadoro; Christina Kohlmann; Olivier FLEISCHEL; Catherine Weichold; Christoph Schunicht; Bjoern Klotz
Original assignee: Basf Se
Priority date: 2019-07-08
Filing date: 2020-07-01
Publication date: 2021-01-14

Abstract

The present invention relates to a lysine-branched copolymer comprising repeating units derived from lysine and repeating units derived from one or more further proteinogenic amino acids, wherein lysine-branched copolymer means a copolymer that comprises at least one repeating unit per copolymer-molecule which is a lysine-moiety and which is bound to another repeating unit via its alpha-amino group, and to yet another repeating unit via its epsilon-amino group, and to yet another repeating unit via its carboxylic acid group. Furthermore, the present invention relates to a process for making the lysine-branched copolymer, to a composition suitable for treating hair comprising it and to the use of the copolymer or of the composition for treating hair.

Description

LYSINE-BRANCHED COPOLYMER

The present invention relates to a lysine-branched copolymer comprising repeating units derived from lysine and repeating units derived from one or more further proteinogenic amino acid, wherein lysine-branched copolymer means a copolymer that comprises at least one repeating unit per copolymer-molecule which is a lysine-moiety and which is bound to another repeating unit via its alpha-amino group, and to yet another repeating unit via its epsilon- amino group, and to yet another repeating unit via its carboxylic acid group. Furthermore, the present invention relates to a process for making the lysine-branched copolymer, to a composition suitable for treating hair comprising it and to the use of the copolymer or of the composition for treating hair.

The surface of hair, especially of human hair, can be damaged by hair treatment, e. g. by bleaching. Therefore, there is a need for substances that have a repair effect on damaged hair.

An indication of hair repair is the denaturation temperature of human hair (T_max) . The denaturation temperature of human hair protein can be determined as described by Wortmann et al. (J. Appl. Polym. Sci. volume 48 (1993), page 137) using differential scanning calorimetry with a heating rate of 2K/min. Denaturation temperatures are expressed as T_max, i.e. the temperature of the denaturation peak maximum.

Untreated, virgin hair has a higher T_max than a damaged hair (e.g. bleached hair). Hereinafter, a“hair repair effect” can be determined by and thus can be defined as an increase of the T_max of (damaged) hair.

Lysine is an amino acid. There are two enantiomers of lysine, L-lysine and D-lysine. Lysine has two amino groups, one at the alpha-position, one at the epsilon-position. Linear L- polylysine is produced by natural fermentation and it is referred to as epsilon-Polylysine or e- Polylysine. This fermentation can be carried out with bacteria strains of the genus Streptomyces, e. g. Streptomyces albulus.

Branched polylysine is formed when both amino-groups of lysine (alpha and epsilon) react in a polycondensation reaction with the carboxylic acid group of lysine. Incorporating one or more further proteinogenic amino acids in the polymer leads to a lysine-branched copolymer. US 2013/0309190 describes a cosmetic composition useful for imparting shape to hair or maintaining shape of hair comprising a maleic acid copolymer, a polyamine selected from polyamino acids and aminated polysaccharides, a neutralizer, and water.

JP 2002293719 describes a hair treatment composition containing polypeptides (hydrolyzed proteins) together with a cationic watersoluble polymer.

EP 1 563 826 A1 describes the use of polylysine in spray applications (having a conditioner effect).

WO 2015/128566 describes the treatment of keratin fibers (hair) with polyamines (polylysine is mentioned) and thereafter the application of an activated ester to the creatine fibers. Repair effects are mentioned.

International patent application no. PCT/EP2019/055811 (BASF internal file no. PF 170072 WO01 ) discloses a composition suitable for hair care comprising branched polylysine.

WO 2012/148397 discloses polycondensation products of L-lysin and other amino acids (example 8). Allegedly, water-soluble polycondensates of L-lysine and aspartic acid and of L- lysine and leucine are described. However, as could by shown by experiments described in the experimental section of the present text the polycondensates described in WO 2012/148387 are in fact not water soluble according to the definition of the term water soluble given in the present text.

US 6,407,053 B1 discloses a polycondensation product of L-lysin and aminocaproic acid (examples III, IV and V). In table XI a polycondensate of L-lysine and tryptophan is mentioned, a process for making this polycondensate is not disclosed.

WO 00/71601 discloses polycondensation-products of basic amino acids. A product obtained by the polycondensation of L-lysine is disclosed (examples 1 and 2). A product obtained by the polycondensation of L-lysine and aminocaproic acid is disclosed (example 3).

Parameters to characterize a lysine-branched copolymer (apart from the differentiation between L- and D-lysine) are the average molar mass, either the number average Mn or the weight average Mw, the polydispersity PD = Mw/Mn (measured via gel permeation chromatography), the degree of branching, and the amine number. These parameters can be determined by methods known in the art and/or as disclosed in WO 2016/062578. In general, it is assumed that the backbone of a lysine-branched copolymer as well as the side chains of a lysine-branched copolymer both have amide groups formed by alpha-amino groups and by epsilon amino-groups. The relative amount of alpha- and epsilon amide groups in the backbone and in the side chains is not known.

The problem underlying the present invention is to provide a substance and/or a composition having a hair repair effect, i. e. providing a substance and/or a composition that is capable of increasing the denaturation temperature of human hair (T_max) , especially if this denaturation temperature has been decreased before by damaging the hair.

A first solution to this problem, and therefore a first subject of the present invention is a lysine- branched copolymer comprising repeating units derived from lysine and repeating units derived from one or more further proteinogenic amino acids, wherein lysine-branched copolymer means a copolymer that comprises at least one repeating unit per copolymer- molecule which is a lysine-moiety and which is bound to another repeating unit via its alpha- amino group, and to yet another repeating unit via its epsilon-amino group, and to yet another repeating unit via its carboxylic acid group, and wherein the one or more further proteinogenic amino acids are selected from the group consisting of alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine and valine, and wherein the lysine-branched copolymer is water soluble, wherein water-soluble means that at 20 °C 1 g of the lysine-branched copolymer can be dissolved in 99 g of water, preferably 10 g of copolymer in 90 g of water, without leaving any insoluble residue that is detectable by the naked eye.

A further solution to this problem, and therefore a further subject of the present invention is a composition suitable for treating hair comprising the lysine-branched copolymer according to the present invention, optionally at least one surfactant selected from the group consisting of an anionic surfactant, a cationic surfactant, a nonionic surfactant, a zwitterionic surfactant, and mixtures thereof, and optionally one or more further cosmetically acceptable ingredients (including water) different from the copolymer, and different from the surfactant.

A further subject of the present invention is a process for making the lysine-branched copolymer according to the present invention, the process comprising providing an aqueous solution comprising the lysine and the one or more further proteinogenic amino acids, heating the aqueous solution to a temperature not exceeding 185 °C, preferably not exceeding 180°C, wherein water may be distilled off during the heating, cooling the heated aqueous solution and obtaining the copolymer.

Normally polycondensation of amino acids is difficult as the melting points of several amino acids is higher than their decomposition temperature. Therefore, in the attempt to melt them one would get decomposition. Within the present invention, a strategy for obtaining polymeric materials out of amino acids via condensation chemistry is described. A crucial step for obtaining reaction conditions reducing decomposition is the homogenization of the amino acids starting from their aqueous solution. By dissolving the amino acids in water the melting point of the amino acid mixture is reduced (eutectic formation) and the condensation reaction can take place without significant decomposition.

A further subject of the present invention is the use of the copolymer according to the present invention, or of the composition according to the present invention for treating hair (preferably human hair).

A further subject of the present invention is the use of the copolymer according to the present invention, or of the composition according to the present invention for bringing about a hair repair effect when the copolymer or the composition is applied to hair.

A further subject of the present invention is a process for treating hair, preferably human hair, comprising contacting the hair with the copolymer according to the present invention, or with the composition according to the present invention.

Preferred embodiments of the subjects of the present invention are given in the dependent claims of the present text.

“A composition suitable for treating hair” according to the present invention can be any composition suitable for treating hair. It can be a composition suitable for cleansing hair, especially a shampoo, it can be a composition for conditioning hair (a conditioner), it can be a mask.

The meaning of hair conditioning is known to the person skilled in the art. It is described in US 2017/0333734 (BASF internal reference PF 77681 US02) in paragraph [0007]

In the copolymer according to the present invention the amino acid repeating units can be derived from L- amino acids or from D-amino acids or from a mixture of L- and D-amino acids, especially from a racemic mixture. Preferably these repeating units are derived from L-amino acids.

The copolymer according to the present invention typically has the following properties:

• The number average of the molar mass Mn is 300 to 5000 g/mol.

• The weight average of the molar mass MW is 500 to 100000 g/mol, preferably 1000 to 50000 g/mol, most preferably 1000 to 20000g/mol.

• The polydispersity PD (= Mw/Mn) is 1.2 to 7, preferably 1.2 to 3, more preferably 1.2 to 2.5

• The amine number is 350 to 600 mgKOH/g, preferably 350 to 500 mgKOH/g.

• The degree of branching DB is 0.15 to 0.5, preferably 0.2 to 0.35, more preferably 0.2 to 0.3.

The definition of amine number and of“degree of branching” DB can be found in the examples section of the present text.

The copolymer according to the present invention can be made by heating a mixture comprising lysine and the other amino acids and water, especially analogous to the process as described in WO 2016/062578.

According to the present invention the surfactant in the composition according to the present invention can be selected from the group consisting of an anionic surfactant, a cationic surfactant, a nonionic surfactant, a zwitterionic surfactant, and mixtures thereof. The surfactants according to the present invention can be selected amongst the surfactants described in US 2017/0333734 (BASF internal reference PF 77681 US02) in paragraphs [0029] to [0032]

Further cosmetically acceptable ingredients can be any cosmetically acceptable ingredients known to the person skilled in the art. These further cosmetically acceptable ingredients can be selected amongst the ingredients described in US 2017/0333734 (BASF internal reference PF 77681 US02) in paragraphs [0033] to [0066]

Further cosmetically acceptable ingredients can also be selected amongst the ingredients described in text books known to the person skilled in the art, e. g. in the International Cosmetic Ingredient Dictionary and Handbook (published by the Personal Care Products Council) or in Schrader, Domsch,“Cosmetology - Theory and Practice”. The copolymer according to the present invention may be used in the form of the following compositions which are listed here as non-limiting examples. These formulations are analogous to the formulations of the international patent application with the application number PCT/EP2019/055811 (BASF internal file no. PF 170072 WO01).

Formulation 1 : a sulfate-free soft shampoo

Formulation 2: a mild baby wash

Formulation 3: an Argan oil hair conditioner

Examples

Methods and Definitions

Concentrations

% means % by weight, unless defined differently.

Degree of Branching (DB)

The degree of branching (DB) of branched polylysine is defined according to H. Frey et al., Acta Polymer., 48, pages 30 to 35 (1997) as

DB [%] = 100 x 2D/(2D+L)

wherein D denotes the fraction of dendritic units and L denotes the fraction of linear units in the sample that is concerned.

DB was determined by ¹H NMR.

Amine Number

The amine number (unit: mg KOH/g), also referred to as amino number, was determined by titration. It was determined as described in WO 2016/062578 according to the formula given on page 13 of WO 2016/062578:

Calculation:

with

Amine number = Fraction of total amine, calculated as mg KOH/g

Vp = Consumption of standard solution up to the inflection point [ml]

VB = Consumption of standard solution in blank value titration [ml]

t = titer of the standard solution

c = concentration of the standard solution [= 0.1 mol/I]

56.1 = molar weight of KOH [g/mol]

E = weight of sample taken [g]. Average Molar Mass Mn (number average) and Mw (weight average)

Mn and Mw were determined by gel permeation chromatography as described in WO 2016/062578 (see page 12 of WO 2016/062578, wherein trifluoroacetate means trifluoroacetic acid):

M_w and M_nwere determined by size exclusion chromatography under the following conditions:

Solvent: 0.1% (w/w) trifluoroacetate, 0.1 M NaCI in distilled water

Flow: 0.8 ml/min

Injection volume: 100 mI

Column material: hydroxylated polymethacrylate (TSKgel G3000PWXL)

Calibration: poly(2-vinylpyridine) standards in the molar mass range from 839 to

1.020.000 g/mole (from PSS, Mainz, Germany)

Polydispersity

PD is defined as PD = Mw/Mn

Synthesis of Polymers

Example 1 : Polymer 1 : GM 1322-0189 (Poly-L-lysine/L-alanine)

800 g of a 50% aqueous solution of L-lysine were placed in a 2I four-necked flask equipped with a stirrer, a condensation column, a thermometer and a nitrogen inlet. 138.32 g L-alanine were added to the reaction flask. The reaction mixture was slowly heated up to the boiling point. Then the temperature of the external heat source was increased according to the following profile 1 h at 150 °C, 1h at 160 and 1h at 170 and 1 h at 180 °C while water was distilled off. The pressure was then decreased to 200 mbar while the external heat source was maintained at 180 °C. The reaction for circa 2 hours continued under vacuum (200 mbar). The reaction melt was cooled to 120 °C and collected into an aluminum vessel. The polymer was characterized by gel permeation chromatography and by determining the amino number.

Mn: 1270 g/mol

Mw: 2070 g/mol

PD: 1.6

Amino number: 322 mgKOH/g

Degree of branching: 0.46 Example 2: Polymer 2: GM 1322-0190 (Poly-L-lysine/L-arginine)

800 g of a 50% aqueous solution of L-lysine were placed in a 2I four-necked flask equipped with a stirrer, a condensation column, a thermometer and a nitrogen inlet. 118.4 g L-arginine were added to the reaction flask. The reaction mixture was slowly heated up to the boiling point. Then the temperature of the external heat source was increased according to the following profile 1 h at 150 °C, 1h at 160 and 1 h at 170 and 1 h at 180 °C while water was distilled off. The pressure was then decreased to 200 mbar while the external heat source was maintained at 180 °C. The reaction for circa 2 hours continued under vacuum (200 mbar). The reaction melt was cooled to 120 °C and collected into an aluminum vessel. The polymer was characterized by gel permeation chromatography and by determining the amino number.

Mn: 1650 g/mol

Mw: 6260 g/mol

PD: 3.8

Amino number: 369 mgKOH/g

Degree of branching: 0.30

Example 3: Polymer 3: GM1322:0191 (Poly-L-lysine/L-threonine)

800 g of a 50% aqueous solution of L-lysine were placed in a 2I four-necked flask equipped with a stirrer, a condensation column, a thermometer and a nitrogen inlet. 144 g L-threonine were added to the reaction flask. The reaction mixture was slowly heated up to the boiling point. Then the temperature of the external heat source was increased according to the following profile 1 h at 150 °C, 1h at 160 and 1 h at 170 and 1 h at 180 °C while water was distilled off. The pressure was then decreased to 200 mbar while the external heat source was maintained at 180 °C. The reaction for circa 2 hours continued under vacuum (200 mbar). The reaction melt was cooled to 120 °C and collected into an aluminum vessel. The polymer was characterized by gel permeation chromatography and by determining the amino number.

Mn: 935 g/mol

Mw: 1280 g/mol

PD: 1.4

Amino number: 410 mgKOH/g

Degree of branching: 0.28

Example 4: Polymer 4: GM1322:0194 (Poly-L-lysine/L-methionine)

800 g of a 50% aqueous solution of L-lysine were placed in a 2I four-necked flask equipped with a stirrer, a condensation column, a thermometer and a nitrogen inlet. 40 g L-methionine were added to the reaction flask. The reaction mixture was slowly heated up to the boiling point. Then the temperature of the external heat source was increased according to the following profile 1 h at 150 °C, 1h at 160 and 1 h at 170 and 2 h at 180 °C while water was distilled off. The pressure was then decreased to 200 mbar while the external heat source was maintained at 180 °C. The reaction for circa 2 hours continued under vacuum (200 mbar). The reaction melt was cooled at 120 °C and collected into an aluminum vessel. The polymer was characterized by gel permeation chromatography and by determining the amino number.

Mn: 1810 g/mol

Mw: 3680 g/mol

PD: 2.0

Amino number: 371 mgKOH/g

Degree of branching: 0.25

Example 5: Polymer 5: GM1322:0198 (Poly-L-lysine/L-cysteine)

800 g of a 50% aqueous solution of L-lysine were placed in a 2I four-necked flask equipped with a stirrer, a condensation column, a thermometer and a nitrogen inlet. 80 g L-cysteine were added to the reaction flask. The reaction mixture was slowly heated up to the boiling point. Then the temperature of the external heat source was increased according to the following profile 1 h at 150 °C, 1h at 160 and 1 h at 170 and 2 h at 180 °C while water was distilled off. The pressure was then decreased to 300 mbar while the external heat source was maintained at 180 °C. The reaction for circa 2 hours continued under vacuum (300 mbar). The reaction melt was cooled at 120 °C and collected into an aluminum vessel. The polymer was characterized by gel permeation chromatography and by determining the amino number.

Mn: 1630 g/mol

Mw: 4050 g/mol

PD: 2.5

Amino number: 333 mgKOH/g

Degree of branching: 0.3

Example 6: Polymer 6: GM1322:0200 (Poly-L-lysine/L-cysteine)

800 g of a 50% aqueous solution of L-lysine were placed in a 2I four-necked flask equipped with a stirrer, a condensation column, a thermometer and a nitrogen inlet. 112 g L-cysteine were added to the reaction flask. The reaction mixture was slowly heated up to the boiling point. Then the temperature of the external heat source was increased according to the following profile 1 h at 150 °C, 1h at 160 and 1 h at 170 and 2 h at 180 °C while water was distilled off. The pressure was then decreased to 250 bar while the external heat source was maintained at 180 °C. The reaction for circa 1 + 1/2 hour continued under vacuum (250 mbar). The reaction melt was cooled at 120 °C and collected into an aluminum vessel. The polymer was characterized by gel permeation chromatography and by determining the amino number.

Mn: 1550 g/mol

Mw: 4020 g/mol

PD: 2.6

Amino number: 323 mgKOH/g

Degree of branching: 0.34

Example 7: Polymer 7: GM1322:0232 (Poly-L-lysine/L-arginine)

800 g of a 50% aqueous solution of L-lysine were placed in a 2I four-necked flask equipped with a stirrer, a condensation column, a thermometer and a nitrogen inlet. 88.8g L-arginine were added to the reaction flask. The reaction mixture was slowly heated up to the boiling point. Then the temperature of the external heat source was increased according to the following profile 1 h at 150 °C, 1h at 160 and 1 h at 170 and 2 h at 180 °C while water was distilled off. The pressure was then decreased to 250 mbar while the external heat source was maintained at 180 °C. The reaction for circa 1 hour continued under vacuum (250 mbar). The reaction melt was cooled at 120 °C and collected into an aluminum vessel. The polymer was characterized by gel permeation chromatography and by determining the amino number.

Mn: 1880 g/mol

Mw: 12700 g/mol

PD: 6.7

Amino number: 370 mgKOH/g

Example 8: Polymer 8: GM 1691 :0027 (Poly-L-lysine/L-aspartic acid/L-histidine/L- tyrosine)

800 g of a 50% aqueous solution of L-lysine were placed in a 2I four-necked flask equipped with a stirrer, a condensation column, a thermometer and a nitrogen inlet. 33.28 g aspartic acid, 45.3 g tyrosine and 38.79 g histidine were added to the reaction flask. The reaction mixture was slowly heated up to the boiling point. Then the temperature of the external heat source was increased according to the following profile 1 h at 150 °C, 1 h at 160 and 1 h at 170 and 2 h at 180°C while water was distilled off. The pressure was then decreased to 250 mbar while the external heat source was maintained at 180 °C. The reaction for circa 1 hour continued under vacuum (250 mbar). The reaction melt was cooled at 120C and collected into an aluminum vessel. The polymer was characterized by gel permeation chromatography and by determining the amino number.

Mn: 1000 g/mol

Mw: 1550 g/mol

PD: 1.5

Amino number: 432 mgKOH/g

Comparative example 1 : Linear epsilon-polylysine

Linear epsilon-polylysine from Zhengzhou Bainafo Bioengineering Co. Ltd. was used as comparative example in the application examples.

Comparative example 2: Polymer of lysine hydrate and aspartic acid according to WO 2012/14838 A1, example 8 (lysine hydrate : aspartic acid = 15:1 (weight:weight)) GM 1322-0887)

146 mg of L-lysine hydrate and 8.9 mg of aspartic acid were placed in Pyrex dishes and dissolved in 5 g of distilled water. The pH was reduced to 3 using 85% phosphoric acid. The solution was dried overnight at 90 °C. Then the temperature was increased to 200°C and kept for 5 hours. 5 g of water were then added to the pyrex dish containing the resulting dark colored product. The product was only partially soluble in water and it was not possible to characterize it via GPC, amine number or NMR.

Example 9: Polymer of L-lysine and aspartic acid 15:1 (weight:weight) according to the present invention)

1000 g of a 50% aqueous solution of L-lysine were placed in a 2I four-necked flask equipped with a stirrer, a condensation column, a thermometer and a nitrogen inlet. 30.35 g aspartic acid were added to the reaction flask. The reaction mixture was slowly heated up to the boiling point. Then the temperature of the external heat source was increased according to the following profile 1 h at 150 °C, 1h at 160 °C and 1h at 170 °C while water was distilled off. The pressure was then decreased to 250 mbar while the temperature was increased to 180°C. The reaction for circa 2 hours continued under vacuum (250 mbar).

The reaction melt was cooled to 120°C and collected into an aluminum vessel. A portion of polymer was dissolved in order to obtain a 50% aqueous solution. No rests of insoluble material were detectable. The polymer was characterized by gel permeation chromatography and by determining the amine number. Mn: 1650 g/mol

Mw: 7660 g/mol

PD: 4.6

Amino number: 373 mgKOH/g

Application Examples

The denaturation temperatures of human hair proteins were determined as described by Wortmann et al. (J. Appl. Polym. Sci. 48 (1993) 137) using a heating rate of 2K/min. Denaturation temperatures are expressed as T_max, i.e. the temperature of the denaturation peak maximum. The higher this temperature is the better. In case of damaged hair this denaturation temperature is lower than in case of virgin, not damaged, hair. If the denaturation temperature of damaged hair can be increased by treating it with a hair care composition this indicates a hair repair effect. Table 1 summarizes the DSC-data obtained.

Table 1 : DSC data on virgin hair, 3 times bleached hair, and hair that has been bleached 3 times and after this treated with an aqueous polymer solution having a polymer-concentration of 1 % by weight.

Claims

1. A lysine-branched copolymer comprising repeating units derived from lysine and

repeating units derived from one or more further proteinogenic amino acids, wherein lysine-branched copolymer means a copolymer that comprises at least one repeating unit per copolymer-molecule which is a lysine-moiety and which is bound to another repeating unit via its alpha-amino group, and to yet another repeating unit via its epsilon-amino group, and to yet another repeating unit via its carboxylic acid group, and wherein the one or more further proteinogenic amino acids are selected from the group consisting of alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine and valine,

and wherein the lysine-branched copolymer is water soluble, wherein water-soluble means that at 20 °C 1 g of the lysine-branched copolymer can be dissolved in 99 g of water, preferably 10 g of copolymer in 90 g of water, without leaving any insoluble residue that is detectable by the naked eye.

2. The lysine-branched copolymer according to claim 1 , comprising per 100 g of lysine 9 to 40 g of one or more further proteinogenic amino acids, wherein the amounts in g are the amounts of the free amino acids.

3. The lysine-branched copolymer according to claim 2, comprising per 100 g of lysine 9 to 40 g of an amino acid selected from the group consisting of L-alanine, L-arginine, L- threonine, L-methionine, L-cysteine, L-arginine, L-aspartic acid, L-tyrosine, L-histidine, and mixtures thereof.

4. The lysine-branched copolymer according to claim 2, comprising per 400 g of lysine an amino acid selected from the group consisting of 138 g (± 10%) alanine, 118 g (± 10%) arginine, 144 g (± 10%) threonine, 40 g (± 10%) methionine, 80 g (± 10%) cysteine, 112 g (± 10%) cysteine, 89 g (± 10%) L-arginine and 33 g (± 10%) L-aspartic acid + 45 g (± 10%) tyrosine + 39 g (± 10%) L-histidine.

5. A process for making the lysine-branched copolymer of any of claims 1 to 4, the pro cess comprising

providing an aqueous solution comprising the lysine and the one or more further pro teinogenic amino acids,

heating the aqueous solution to a temperature not exceeding 185 °C, preferably not exceeding 180 °C, wherein water may be distilled of during the heating, cooling the heated aqueous solution and obtaining the copolymer.

6. The process of claim 5, wherein the heating is carried out for 1 to 20, preferably for 1 to 10 hours.

7. A composition suitable for treating hair comprising

the lysine-branched copolymer according to any of claims 1 to 4,

optionally at least one surfactant selected from the group consisting of an anionic sur factant, a cationic surfactant, a nonionic surfactant, a zwitterionic surfactant, and mix tures thereof,

and optionally one or more further cosmetically acceptable ingredients (including water) different from the copolymer, and different from the surfactant.

8. The composition according to claim 7, wherein this composition is a composition suit able for cleansing hair or a composition suitable for conditioning hair.

9. The composition according to claim 7 or 8 comprising

0.1 to 10 % by weight, preferably 0.5 to 5 % by weight of the copolymer,

0.1 to 30 % by weight, preferably 1 to 25 % by weight of the surfactant, and

0 to 99.8 % by weight, preferably 0 to 98.5 % by weight of the one or more further cosmetically acceptable ingredients.

10. The composition according to claim 7 or 8 comprising

0.5 to 1.5 % by weight by weight of the copolymer,

6 to 19 % by weight by weight of the surfactant, and

0 to 93.5 % by weight by weight of the one or more further cosmetically acceptable ingredients,

or comprising

0.5 to 1.5 % by weight by weight of the copolymer,

16 to 24 % by weight by weight of the surfactant, and

0 to 83.5 % by weight by weight of the one or more further cosmetically acceptable ingredients,

or comprising

0.5 to 1.5 % by weight by weight of the copolymer,

0.5 to 1.2 % by weight by weight of the surfactant, and

0 to 99 % by weight by weight of the one or more further cosmetically acceptable ingredients.

11. The composition according to any of claims 7 to 10 comprising not more than 5, pre ferably not more than 2, more preferably not more than 1 % by weight inorganic salt.

12. The composition according to any of claims 7 to 10 comprising not more than 5, prefer ably not more than 2, more preferably not more than 1 % by weight sodium chloride.

13. The use of the copolymer as defined in any of the preceding claims, or of the composi tion according to any of claims 7 to 12 for treating hair (preferably human hair).

14. The use of the copolymer as defined in any of the preceding claims, or of the composi tion according to any of claims 7 to 12 for bringing about a hair repair effect when the copolymer or the composition is applied to hair.

15. A process for treating hair, preferably human hair, comprising contacting the hair with the copolymer as defined in any of the preceding claims, or with the composition according to any of claims 7 to 12.