The present invention relates to a method for caring for keratin fibres, more particularly human keratin fibres such as the hair, using a cosmetic composition comprising at least one particular diaminoalkanoic acid.

The present invention also relates to said cosmetic composition and to the use of at least one particular diaminoalkanoic acid or of said cosmetic composition comprising same for caring for keratin fibres, preferably for repairing and/or preventing the breakage of keratin fibres, more particularly human keratin fibres such as the hair.

The hair may be damaged and made brittle by external atmospheric agents such as pollution and bad weather, and also by mechanical or chemical treatments, or certain routines, such as brushing, combing, dyeing, bleaching, permanent-waving, straightening and/or repeated washing. The hair may then end up damaged and may in the long run become dry, coarse, brittle, dull, split and/or limp.

To overcome these disadvantages, then, it is common practice to employ haircare compositions intended for conditioning the hair by giving it satisfactory cosmetic properties, notably smoothness, sheen, a soft feel, suppleness and lightness, and also good disentangling properties leading to easy combing and good manageability of the hair, which is thus easier to style and holds its shape. However, the conditioning effect obtained via these haircare compositions fades out rapidly over time and does not allow the hair cortex to be strengthened. An effect which is highly durable over time cannot be obtained with such treatments.

As an example, shampoos are typically used to cleanse the hair, imparting to it satisfactory cosmetic properties, but these compositions do not improve the quality of the fibre. In particular they do not allow the bonding density between the proteins present in the cortex of the fibre to be improved, so as to repair the fibre or reduce its breakage, during combing or disentangling, for example.

There is therefore still a genuine need to find a means of treating keratin fibres, more particularly human keratin fibres such as the hair, preferably those which have been damaged and/or sensitized, that is capable of conserving or even improving the quality of said fibres, by increasing in particular the bonding density between the proteins present in the cortex of these fibres, so allowing them to be repaired and/or their breakage reduced and/or them to be strengthened in view of a treatment that may be detrimental to them, as for example during combing or disentangling.

It has now been found that applying a cosmetic composition comprising at least one particular diaminoalkanoic acid to the keratin fibres allows the objectives set out above to be met, and particularly allows said keratin fibres to be cared for, in particular to be repaired and/or their breakage prevented, by increasing in particular the bonding density between the proteins present in the cortex of said fibres.

A particular subject of the present invention is a method for caring for keratin fibres, more particularly human keratin fibres such as the hair, and preferably for repairing and/or preventing the breakage of keratin fibres, comprising at least one step i) of applying to said keratin fibres a cosmetic composition comprising from 0.01% to 50% by weight, relative to the total weight of the composition, of one or more diaminoalkanoic acids of formula (I) below, optical isomers thereof, geometric isomers thereof, tautomers thereof, organic or inorganic base or acid addition salts thereof, solvates thereof and mixtures thereof: in which:

- X represents a hydrogen atom or a negative charge,

- Ri represents a hydrogen atom or a linear or branched, preferably linear, alkyl group comprising from 1 to 4 carbon atoms,

- R2 and R3, which are identical or different, represent a hydrogen atom or a linear or branched alkyl group comprising from 1 to 4 carbon atoms,

- R4 and R5, which are identical or different, represent a hydrogen atom or a linear or branched alkyl group comprising from 1 to 4 carbon atoms,

- R7 and Rs, which are identical or different, represent a hydrogen atom or a linear or branched alkyl group comprising from 1 to 4 carbon atoms,

- Re and R9, which are identical or different, represent a linear or branched alkyl group comprising from 1 to 4 carbon atoms, and

- m and n, independently of one another, are 0 or 1 , it being understood that:

- when n and/or m is 0, the nitrogen bearing the group Re and/or R9 is not quatemized;

- when n = m = 0, X represents a hydrogen atom; and

- when n and/or m is 1, X represents a hydrogen atom or a negative charge and the electroneutrality of the compounds of formula (I) is ensured by the presence of one or more anions An’ and/or by the presence of the negative charge.

The application of the cosmetic composition of the invention, comprising at least one diaminoalkanoic acid of formula (I) as defined above, makes it possible to repair and/or prevent the breakage of keratin fibres, preferably those which have been damaged and/or sensitized. This is because the application of this cosmetic composition increases the bonding density between the proteins present in the cortex of said fibres. These fibres are then more resistant to external stresses, especially to combing and/or disentangling.

These properties are also persistent with respect to several shampooing operations. The keratin fibres treated with the method of the invention are repaired and/or protected durably towards external agents and/or towards treatments that may adversely affect said fibres.

The keratin fibres thus treated also exhibit enhanced cosmetic properties in terms especially of sheen, sleekness and manageability. Their feel is notably softer and more natural.

Another subject of the present invention is therefore said cosmetic composition as defined previously.

Another subject of the present invention is the use of one or more diaminoalkanoic acids of formula (I) as defined above, optical isomers thereof, geometric isomers thereof, tautomers thereof, organic or inorganic base or acid addition salts thereof, solvates thereof and mixtures thereof, for caring for keratin fibres, preferably for repairing and/or preventing the breakage of keratin fibres, more particularly human keratin fibres such as the hair.

Another subject of the present invention relates to the use of a cosmetic composition as defined above for caring for keratin fibres, preferably for repairing and/or preventing the breakage of keratin fibres, more particularly human keratin fibres such as the hair.

Other subjects, features, aspects and advantages of the invention will emerge even more clearly on reading the description and the examples that follow. In the text hereinbelow, unless otherwise indicated, the limits of a range of values are included in that range, notably in the expressions “between” and “ranging from ... to ...”.

Moreover, the expression “at least one” used in the present description is equivalent to the expression “one or more”.

The cosmetic composition

The cosmetic composition according to the present invention comprises one or more diaminoalkanoic acids of formula (I) as defined above, optical isomers thereof, geometric isomers thereof, tautomers thereof, organic or inorganic base or acid addition salts thereof, solvates thereof and mixtures thereof.

The one or more anions An’ are preferably selected from halides such as chloride, sulfate, methosulfate; alkylsulfonates such as methylsulfonate or mesylate or ethylsulfonate; arylsulfonates such as benzenesulfonate or toluenesulfonate or tosylate; sulfate, citrate; succinate; tartrate; lactate; alkylsulfates such as methylsulfate; arylsulfates such as benzenesulfate or toluenesulfate; phosphate; acetate; triflate; perchlorate; borates such as tetrafluoroborate; carbonate; and hydrogencarbonate.

According to one form of the invention, m is 0. According to another form of the invention, n is 0. According to one preferred form, n and m are identical and are 0.

Advantageously, m is 0 and R7 and Rs, which are identical or different, represent a hydrogen atom or a linear or branched alkyl group comprising from 1 to 4 carbon atoms, preferably a methyl group.

Advantageously, m is 1 and R7, Rs and R9, which are identical or different, represent a hydrogen atom or a linear alkyl group comprising from 1 to 4 carbon atoms, preferably a methyl group.

According to one particular embodiment, n is 1 and R4, R5 and Re, which are identical or different, represent a linear alkyl group comprising from 1 to 4 carbon atoms. According to this embodiment, R4, Rs and Re are preferably identical and represent a methyl group.

According to this embodiment, n is 0 and R4 and Rs, which are identical or different, represent a hydrogen atom or a linear alkyl group comprising from 1 to 4 carbon atoms, such as methyl, ethyl, propyl or n-butyl, preferably a methyl group.

The one or more diaminoalkanoic acids are preferably selected from the compounds of formula (I) for which: - m is 0 and R7 and Rs, which are identical or different, represent a hydrogen atom or a linear or branched alkyl group comprising from 1 to 4 carbon atoms, preferably a methyl group, and

- n is 0 or 1 and R4, R5 and optionally Re, which are identical or different, represent a linear alkyl group comprising from 1 to 4 carbon atoms. According to this embodiment, R4, Rs and Re are preferably identical and represent a methyl group.

The addition salts of the diaminoalkanoic acids of formula (I), as defined above, are selected in particular from the addition salts with an acid, such as the hydrochlorides, hydrobromides, sulfates, citrates, succinates, tartrates, lactates, tosylates, benzenesulfonates, phosphates and acetates, and the addition salts with a base such as sodium hydroxide, potassium hydroxide, aqueous ammonia, amines or alkanolamines.

Moreover, the solvates of the diaminoalkanoic acids of formula (I) more particularly represent the hydrates of said compound and/or the combination of said compound with a linear or branched Ci to C4 alcohol such as methanol, ethanol, isopropanol or n-propanol. Preferably, the solvates are hydrates.

The one or more diaminoalkanoic acids of formula (I) are selected notably from the following compounds, and optical isomers thereof, geometric isomers thereof, tautomers thereof, organic or inorganic base or acid addition salts thereof, solvates thereof and mixtures thereof: The total amount of the one or more diaminoalkanoic acids of formula (I), optical isomers thereof, geometric isomers thereof, tautomers thereof, organic or inorganic base or acid addition salts thereof, solvates thereof and mixtures thereof, present in the cosmetic composition according to the invention, ranges from 0.01% to 50% by weight, relative to the total weight of the composition. Preferably, the total amount of the one or more diaminoalkanoic acids of formula (I), optical isomers thereof, geometric isomers thereof, tautomers thereof, organic or inorganic base or acid addition salts thereof, solvates thereof and mixtures thereof is from 0.05% to 25% by weight, and more preferentially from 0.1% to 10% by weight, relative to the total weight of the composition.

The cosmetic composition according to the present invention is preferably aqueous.

An “aqueous composition” according to the present invention means a composition in which the total water content is greater than or equal to 20% by weight, relative to the weight of the composition. The total water content is preferably greater than or equal to 30% by weight, more preferentially greater than or equal to 40% by weight of water, and even better still greater than or equal to 50% by weight, relative to the total weight of the composition. Advantageously, the total water content ranges from 50% to 99.99% by weight, relative to the total weight of the composition.

Besides water, the cosmetic composition according to the present invention may optionally comprise one or more organic solvents.

The one or more organic solvents are preferably selected from linear or branched monoalcohols having from 1 to 8 carbon atoms and more preferentially from 1 to 4 carbon atoms, polyols, polyethylene glycols, aromatic alcohols and mixtures thereof.

Examples of organic solvents that can be used according to the invention notably include ethanol, propanol, butanol, isopropanol, isobutanol, propylene glycol, dipropylene glycol, isoprene glycol, butylene glycol, glycerol, sorbitol, benzyl alcohol and phenoxyethanol, and mixtures thereof.

The one or more organic solvents that may be used according to the invention may be selected from linear or branched monoalcohols containing from 1 to 4 carbon atoms, and mixtures thereof, preferably from ethanol, propanol, butanol, isopropanol, isobutanol, and mixtures thereof.

The one or more organic solvents are preferably selected from polyols and mixtures thereof. The pH of the cosmetic composition according to the invention varies preferably from 3 to 10, more preferably from 2 to 7 and better still from 2 to 5.

The pH of the cosmetic composition may be adjusted to the desired value by means of basifying agents or acidifying agents customarily used. Among the basifying agents, mention may be made, by way of examples, of aqueous ammonia, alkanolamines or inorganic or organic hydroxides. Among the acidifying agents, mention may be made, by way of examples, of mineral or organic acids, such as hydrochloric acid, orthophosphoric acid, sulfuric acid, carboxylic acids, such as for example acetic acid, tartaric acid, citric acid or lactic acid, and sulfonic acids.

The cosmetic composition according to the present invention may optionally further comprise one or more additional compounds, different from the ingredients of the invention and among which mention may be made of fatty substances, cationic, anionic, nonionic, amphoteric or zwitterionic surfactants, cationic, anionic, nonionic or amphoteric polymers or mixtures thereof, anti-dandruff agents, anti-seborrhoea agents, agents for preventing hair loss and/or for promoting hair regrowth, vitamins and provitamins including panthenol, sunscreens, mineral or organic pigments, sequestrants, plasticizers, solubilizers, mineral or organic thickeners, especially polymeric thickeners, opacifiers or nacreous agents, antioxidants, hydroxy acids, fragrances, preservatives, pigments, ceramides and mixtures thereof.

Of course, a person skilled in the art will take care to select this or these optional additional compounds such that the advantageous properties intrinsically attached to the cosmetic composition according to the invention are not, or not substantially, detrimentally affected by the envisaged addition(s).

The additional compounds above may generally be present in an amount, for each of them, of between 0% and 20% by weight, with respect to the total weight of the composition.

The method

The present invention relates to a method for the care of the keratin fibres, preferably for repairing and/or preventing the breakage of keratin fibres, more particularly human keratin fibres such as the hair, comprising i) applying to said keratin fibres a cosmetic composition as defined above.

The cosmetic composition may advantageously be applied before, during and/or after a haircare composition, such as a shampoo or a conditioner. Preferably, the cosmetic composition is applied after a shampoo. Preferably, the method for caring for according to the present invention is a method for repairing and/or preventing the breakage of keratin fibres, more particularly human keratin fibres such as the hair.

The cosmetic composition defined above may be applied to wet or dry keratin fibres, preferably to wet keratin fibres.

The bath ratio of the cosmetic composition applied applied to the keratin fibres may range from 0.1 to 10. The term “bath ratio” means the ratio between the total weight of the cosmetic composition applied and the total weight of keratin fibres to be treated.

The method for caring for keratin fibres according to the present invention may optionally further comprise at least one additional successive step selected from steps ii) to iv) below: ii) a step of placing the cosmetic composition on the keratin fibres, preferably for a time of at least 10 seconds, said placing step being optionally performed under a hermetic film such as a curlpaper or a plastic film; iii) a step of rinsing and/or washing the keratin fibres; iv) a step of drying the keratin fibres in ambient air or using a heating device.

The placing step may have a duration ranging from 10 seconds to 60 minutes, preferably from 30 seconds to 30 minutes.

The washing step may be performed, for example, using a shampoo.

The temperature of the heating device may range from 45°C to 230°C, preferably from 45°C to 100°C, more preferentially from 50°C to 80°C. A hairdryer, a heating hood, a tool or a heating brush may be used, for example, as heating device.

The drying step iv) may also be a combination of drying with air or with a heating device at a temperature ranging from 50°C to 80°C, such as a hairdryer or a heating hood, followed by a step of treating with a tool, preferably a straightener.

Steps i) to iii) or steps i) to iv) may be repeated as many times as necessary and each cycle of steps i) to iii) or i) to iv) may be spaced from the next one by several minutes to several days or weeks. Hair treatments different from the invention may be carried out between different cycles of application, before or after.

The one or more diaminoalkanoic acids of formula (I) or the cosmetic composition, as are defined above, may be integrated into a shampoo, a conditioner, a mask or any other formulation conventional within the haircare field.

The present invention also relates to the use of one or more diaminoalkanoic acids of formula (I) as defined above, optical isomers thereof, geometric isomers thereof, tautomers thereof, organic or inorganic base or acid addition salts thereof, solvates thereof and mixtures thereof, for caring for keratin fibres, preferably for repairing and/or preventing the breakage of keratin fibres, more particularly human keratin fibres such as the hair.

The present invention also relates to the use of a cosmetic composition as defined above for caring for keratin fibres, preferably for repairing and/or preventing the breakage of keratin fibres, more particularly human keratin fibres such as the hair.

The keratin fibre or fibres are preferably damaged and/or sensitized keratin fibres, more particularly damaged and/or sensitized human keratin fibres such as damaged and/or sensitized hair.

“Damaged fibres” in the sense of the present invention are dry, coarse, brittle, split and/or limp fibres.

“Sensitized fibres” in the sense of the present invention are bleached, artificially coloured, straightened and/or permanent-waved fibres.

The following examples serve to illustrate the invention without, however, having a limiting character.

Examples

Example 1: a. Preparation of the formulations

Formulation A according to the invention and comparative formulation B were prepared from the ingredients stated in the table below.

Table 2 b. Protocol

Locks of Caucasian hair, damaged by two successive bleaching operations, weighing 2.7 g and 27 cm in length are washed with Elseve Color Vive shampoo and then squeezed out between the fingers (2 passes). The locks are then placed on a flat surface and formulations A (invention) and B (comparative) are applied to said locks with a bath ratio of 0.4 (i.e. 0.4 g of formulation per 1 g of hair).

The hair is then massaged with the fingers, making circular movements along the entire length of each lock (5 times), and the locks are then left for 5 minutes. The locks are then rinsed with tap water for 30 seconds, squeezed out and subsequently dried at 60°C (10 min/g of hair). These various steps are repeated to give 5 applications in total.

The same protocol was reproduced on locks of damaged Chinese hair, using the same formulations A (invention) and B (comparative) .

Locks of natural hair (Caucasian and Chinese), undamaged, were used as reference. c. Study of hair fibre repair by differential scanning calorimetry

The differential scanning calorimetry technique is known to those skilled in the art as a method for quantifying the strengthening of proteins in the cortex of keratin fibres (Kinetics of the changes imparted to the main structural components of human hair by thermal treatment, https://doi.Org/10.1016/j.tca.2018.01.014 & F.-J. Wortmann and H. Deutz, J. Appl. Polym Sci., 48, 137 (1993). The principle of the test is to measure the protein denaturing temperature. It is widely acknowledged that the higher the protein denaturing temperature, the better the integrity of the proteins of the cortex, which translates to a reduction in the breakage of the fibres.

The denaturing temperature is directly linked to the bonding density of the keratin proteins present in the cortex. Accordingly, the lower the denaturing temperature, the lower the bonding density of the proteins and the more the disulfide bridges break and the cortex is damaged. A difference of 2°C is acknowledged by those skilled in the art as a significant modification.

The instrument used for performing the measurements is a TA Instruments DSC2500 reference instrument (temperature range: 30°C-200°C; heating ramp of 5°C/min). This instrument measures the energy flow during heating of the sample. The temperature of maximum energy flow represents the denaturing temperature.

The results of the denaturing temperature measurements for each of the locks are summarized in the table below and correspond to the mean of the measurements carried out on 6 hair strands. Table 3

The results above show that applying the composition of the invention, comprising diaminoalkanoic acids of formula (I) as defined above, increases the bonding density of the keratin proteins present in the cortex of the treated hair, so enabling repair of the damaged hair.

Indeed, the denaturing temperatures measured on the locks treated with the composition of the present invention (formulation A) are higher, regardless of the type of the hair (Caucasian or Chinese), than the denaturing temperatures measured on the locks treated with comparative formulation B .

Furthermore, the denaturing temperature for the locks treated according to the present invention is equivalent to (Chinese hair) or even better than (Caucasian hair) that measured for the natural and undamaged hair, thus demonstrating that the hair is repaired. d. Study of hair breakage via the flexabrasion test

The principle of the flexabrasion test is to measure the strength of a dry hair subjected to repeated stresses of extension and abrasion (Cosmetics & Toiletries, Flexabrasion: A Method for Evaluating Hair Strength, June 26, 2009). A strand of hair is attached to a 20 g weight at one end and the other end is attached to an immobile bar. The strand of hair moves back and forth over a 300 m stainless steel wire. The movement has an amplitude of 10 mm and a frequency of 0.5 Hz.

Breakage is detected by an optical sensor which records the lifetime of the hair (also called “drop time before breakage”, i.e. the time that the hair takes to break). The longer this time, the more breakage-resistant the hair.

One series of measurements comprises 75 hair strands. A difference in drop time of 100 s is acknowledged by those skilled in the art as a significant modification.

The results of the drop time before breakage measurements for each of the Caucasian hair locks treated according to the protocol described above are summarized in the table below and correspond to the mean of the measurements carried out on 75 hair strands.

Table 4

The results above show that the hair lock treated with the composition of the invention (formulation A) is more resistant to breaking than the lock treated with comparative formulation B . Indeed, the lock treated according to the invention takes longer to break than that treated with comparative formulation B.

Furthermore, the drop time for the lock treated on the basis of the method of the invention is better than the drop time recorded for the natural and undamaged hair, thus demonstrating that the hair is repaired. Example 2:

Formulation A according to the invention (same as in example 1) and comparative formulation C were prepared from the ingredients stated in the table below.

Table 5 b. Protocol

Locks of Caucasian hair, damaged by two successive bleaching operations, weighing 2.7 g and 27 cm in length are washed with Elseve Color Vive shampoo and then squeezed out between the fingers (2 passes). The locks are then placed on a flat surface and formulations A (invention) and C (comparative) are applied to said locks with a bath ratio of 0.4 (i.e. 0.4 g of formulation per 1 g of hair).

The hair is then massaged with the fingers, making circular movements along the entire length of each lock (5 times), and the locks are then left for 5 minutes. The locks are then rinsed with tap water for 30 seconds, squeezed out and subsequently dried at 60°C (10 min/g of hair). These various steps are repeated to give 5 applications in total.

Locks of natural Caucasian hair, undamaged, were used as reference. c. Study of hair fibre repair by differential scanning calorimetry

As for Example 1, the differential scanning calorimetry technique is known to those skilled in the art as a method for quantifying the strengthening of proteins in the cortex of keratin fibres (Kinetics of the changes imparted to the main structural components of human hair by thermal treatment, https://doi.Org/10.1016/j.tca.2018.01.014 & F.-J. Wortmann and H. Deutz, J. Appl. Polym Sci., 48, 137 (1993). The principle of the test is to measure the protein denaturing temperature. It is widely acknowledged that the higher the protein denaturing temperature, the better the integrity of the proteins of the cortex, which translates to a reduction in the breakage of the fibres.

The denaturing temperature is directly linked to the bonding density of the keratin proteins present in the cortex. Accordingly, the lower the denaturing temperature, the lower the bonding density of the proteins and the more the disulfide bridges break and the cortex is damaged. A difference of 2°C is acknowledged by those skilled in the art as a significant modification.

The instrument used for performing the measurements is a TA Instruments DSC2500 reference instrument (temperature range: 30°C-200°C; heating ramp of 5°C/min). This instrument measures the energy flow during heating of the sample. The temperature of maximum energy flow represents the denaturing temperature.

The results of the denaturing temperature measurements for each of the locks are summarized in the table below and correspond to the mean of the measurements carried out on 6 hair strands.

Table 6

The results above show that applying the formulation A of the invention, comprising diaminoalkanoic acids of formula (I) as defined above, increases the bonding density of the keratin proteins present in the cortex of the treated hair, so enabling repair of the damaged hair.

Indeed, the denaturing temperature measured on the locks treated with the composition of the present invention (formulation A) are higher, than the denaturing temperature measured on the locks treated with comparative formulation C.

Furthermore, the denaturing temperature for the locks treated according to the present invention is even better than that measured for the natural and undamaged hair, thus demonstrating that the hair is repaired.