Hair lightening method containing special oxo-carboic acids

Description

[0001] The present invention lies in the field of cosmetics. The present invention relates to a method for lightening keratin fibers, in particular human hair, in which a multi-component packaging unit is used, which separately comprises at least a first agent containing a peroxide compound and at least a second agent containing a specific oxocarboxylic acid.

[0002] When hair is dyed or bleached using oxidative methods, the aggressive agents can cause damage to the keratin fiber. In particular, the natural hydrophobicity of the keratin fiber is reduced, as the dyeing or bleaching agents must first penetrate the hair to take effect. However, the water-repellent effect is, on the one hand, a natural protection for the hair, and, on the other, closely linked to consumer-desired parameters such as shine, softness, hair strength, feel, and hair "fall."

[0003] To overcome these disadvantages, the use of so-called keratin crosslinkers is known from the state of the art. These keratin crosslinkers are unsaturated, monomeric compounds with a molecular weight of less than 500 g / mol. When applied to hair, the keratin crosslinkers can easily diffuse into the hair fiber due to their small molecular weight. Inside the hair fiber, the keratin crosslinkers then form adducts – either directly with the hair fiber or with other crosslinker molecules. This adduct formation occurs at the double bond of each crosslinker molecule.

[0004] Corresponding keratin crosslinkers are described, for example, in EP 2478892 A1. Chemically speaking, this crosslinking involves the addition to a double bond. To activate the double bond of the keratin crosslinker, it is often located in direct proximity to a strongly electron-withdrawing group (such as a carboxyl group). Furthermore, the addition reaction can also be facilitated by the use of initiators. In EP 2478892 A1, persulfates, peracids, or azo compounds, for example, can be used as initiators. In this context, an acidic pH range of 4.0 to 6.9 is described as the optimal pH for this reaction.

[0005] However, in the work underlying this application, it has now been discovered that the keratin crosslinkers described in EP 2478892 A1 are not optimally suited to the bleaching or lightening of keratin fibers.

[0006] Setting an alkaline pH is essential to achieve a sufficiently strong bleaching effect. If the acidic pH is set as suggested in EP 2478892 A1, the bleaching performance is far too weak.

[0007] JP 2014080384 A relates to a hair treatment based on two agents, the first agent containing cystine (A) and an alkalizing agent (B), and the second agent containing an organic acid (C). The pH of the first agent is 8.5-11, and the pH of the second agent is in the range of 3-5.

[0008] EP 3181113 A1 describes a hair dye composition containing at least one acrylic acid derivative of formula (I) and at least one oxidation dye precursor. The pH of the hair dye composition is 8-12.

[0009] EP 3287120 A1 relates to a hair coloring method, wherein a first composition and a second composition are applied to the hair. The second composition contains at least one acid of formula (II) and at least one further acid of formula (III).

[0010] DE 20 2016 008131 U1 describes a hair treatment kit comprising two separate formulations, the first formulation containing a bifunctional Brönsted base and having a pH of 7-12, and the second formulation containing a bifunctional Brönsted acid and having a pH of 1.7 to 7.

[0011] US 2012 / 204357 A1 describes a colorant containing a hydrophobic direct dye with a log P value of more than 2, an organic carbonyl compound and another organic compound with a specific Hansen solubility parameter.

[0012] The object of the present invention was therefore to provide an agent for the oxidative lightening or bleaching of hair that does not damage the hair or damages it as little as possible, but nevertheless has a very strong lightening performance.

[0013] In particular, lightening agents should be available that allow the hair to be bleached to a high degree without causing it to become brittle, dull, or otherwise damaged. Despite the strong lightening effect, the entire hair fiber should be stabilized. Furthermore, the achieved hair protection should be as time-consuming as possible and, if possible, be applied simultaneously with the coloring or lightening step itself.

[0014] It has now been found that the above-mentioned object can be fully achieved if a multi-component packaging unit is used for lightening or bleaching, which comprises at least two agents (A) and (B) packaged separately in two containers.

[0015] The agent (A), located in the first container, is an oxidizing agent preparation and contains at least one peroxide compound, preferably hydrogen peroxide. The second agent (B) contains at least one oxocarboxylic acid of a specific formula (I).

[0016] A first object of the present invention is a method for lightening human hair, comprising the following steps in the order given (1) Mixing an agent (A) with an agent (C) and / or an agent (D), wherein the agent (A) contains (a) hydrogen peroxide, and the agent (C) contains at least one persulfate from the group consisting of ammonium persulfate, potassium persulfate and / or sodium persulfate, and the agent (D) contains at least one alkalizing agent from the group consisting of ammonia, 2-aminoethane-1-ol, 2-amino-2-methylpropane-1-ol, 2-amino-2-methylpropane-1,3-diol, L-arginine, D-arginine, D / L-arginine, L-lysine, D-lysine and D / L-lysine, (2) Applying the mixture prepared in step (1) to the hair, (3) Allowing the mixture applied in step (2) to act on the hair, (4) If necessary, rinsing the hair, (5) Applying an agent (B) to the hair, wherein the agent (B) (b) contains at least one acid of formula (I), where R 1 represents a C 1 -C 6 alkyl group, R 2 , R 3 independently of one another represent a hydrogen atom, a C 1 -C 6 alkyl group or a C 2 -C 6 alkenyl group, M represents a hydrogen atom or an equivalent of a mono- or polyvalent cation, n represents the number 1 or 2 and m represents the number 0 or 1, and where the agent (B) contains water and has a pH of 1.8 to 3.0.

[0017] It was found that using the multi-component packaging unit in the inventive process resulted in less hair breakage during subsequent combing and increased fiber stability. The increase in fiber stability was determined, for example, using DSC (Difference Scanning Calorimetry) measurements. Furthermore, the hair lost less elasticity than after the application of non-inventive bleaching agents. Hair elasticity could be measured, for example, using tensile-elongation measurements.

[0018] The term "lightening of keratin fibers" used in the invention refers in particular to the bleaching or bleaching of the fibers. After application of the lightening agent, the treated keratin fiber has a lighter shade than before application of the lightening or bleaching agent. The intensity of the lightening can be assessed visually, for example, or quantified by colorimetric measurement of the hair strand (measurement of the Lab values). In colorimetric measurement, the L value indicates the brightness of a keratin fiber or hair strand (at L=100, the hair strand is diffusely white; at L=0, the hair strand is black). After application of the lightening agent according to the invention, the strand therefore has a higher L value.

[0019] The term "lightening of keratin fibers" used in the present invention also includes a lightening color (or coloring bleaching). In this case, the product may contain dyes in addition to the peroxide compound, although these dyes are only present in small amounts to nuance the lightening result. Therefore, after applying a dye-containing lightening product, the treated keratin fiber also has a lighter shade than before application of the product.

[0020] The agents (A) and (B) used in the process according to the invention each contain the essential components (a) and (b) in a cosmetic carrier. For the purpose of lightening (or lightening coloring), such carriers are, for example, creams, emulsions, gels, or surfactant-containing foaming solutions, such as shampoos, foam aerosols, foam formulations, or other preparations suitable for application to the hair. The cosmetic carriers of agents (A) and / or (B) are particularly preferably aqueous or aqueous-alcoholic.

[0021] For the purposes of the present invention, aqueous-alcoholic solutions are understood to mean, in particular, aqueous solutions containing 0.1 to 70 wt.% of a C 1 -C 4 alcohol, in particular ethanol or isopropanol. The compositions according to the invention may additionally contain other organic solvents, such as methoxybutanol, benzyl alcohol, ethyl diglycol, or 1,2-propylene glycol. Preference is given to all water-soluble organic solvents. Medium (A)

[0022] As the essential component (a) of the invention, agent (A) contains at least one peroxide compound. Peroxide compound (a) is the oxidizing agent that causes the lightening, bleaching, or bleaching of the keratin fibers. The peroxide compound is hydrogen peroxide.

[0023] Hydrogen peroxide is used either in the form of its aqueous solution and / or in the form of one of its solid adducts with organic or inorganic compounds, such as urea, melamine, and sodium borate. Hydrogen peroxide is particularly preferably used in the form of its aqueous solution.

[0024] The amount of hydrogen peroxide in the agent (A) is preferably 0.1 to 12.5 wt.%, preferably 1.5 to 12.5 wt.%, more preferably 4.5 to 12.5 wt.% and most preferably 6.5 to 12.5 wt.% hydrogen peroxide (calculated as 100% H 2 O 2 ), in each case based on the total weight of the agent (A).

[0025] In a particularly preferred embodiment, a process according to the invention is characterized in that the agent (A) - based on the total weight of the agent (A) - contains 0.1 to 12.5 wt.%, preferably 1.5 to 12.5 wt.%, more preferably 4.5 to 12.5 wt.% and most preferably 6.5 to 12.5 wt.% of hydrogen peroxide (a). Medium (B)

[0026] As component (b) essential to the invention, the agent (B) contains at least one acid of the formula (I), where R 1 represents a C 1 -C 6 alkyl group, R 2 , R 3 independently represent a hydrogen atom, a C 1 -C 6 alkyl group or a C 2 -C 6 alkenyl group, M represents a hydrogen atom or an equivalent of a mono- or polyvalent cation, n represents the number 1 or 2 and m represents the number 0 or 1.

[0027] It has been found that the acids of formula (I) according to the invention effectively reduce damage to the keratin fibers when they are applied to the keratin fibers during or after bleaching.

[0028] Measurements in which the effects of the acids of formula (I) according to the invention were compared with the effect of other acids not according to the invention showed that the acids of formula (I) at the same pH value brought about a greatly improved structuring and increased protection of the keratin fiber and effectively minimized the damage to the keratin fiber caused by bleaching.

[0029] Examples of the substituents R 1 , R 2 and R 3 mentioned in formula (I) are given below: Examples of C 1 -C 6 alkyl groups are -CH 3 , -CH 2 CH 3 , -CH 2 CH 2 CH 3 , - CH(CH 3 ) 2 , -CH 2 CH 2 CH 2 CH 3 , -CH 2 CH(CH 3 ) 2 , -CH(CH 3 )CH 2 CH 3 , -C(CH 3 ) 3 , -(CH 2 ) 4 CH 3 , -(CH 2 ) 5 CH 3 . Particularly preferred alkyl radicals are methyl and ethyl. Examples of C 2 -C 6 alkenyl groups are vinyl, prop-2-enyl (allyl), 2-methyl-prop-2-enyl, but-3-enyl, but-2-enyl, pent-4-enyl or pent-3-enyl.

[0030] In the carboxylic acids of formula (I), the radical R 1 represents a C 1 -C 6 alkyl group.

[0031] In this context, it was found that the best protective effect could be achieved with the acids of formula (I) in which R 1 represents a C 1 -C 6 alkyl group, preferably a methyl group, an ethyl group or a propyl group, and most preferably a methyl group.

[0032] In a particularly preferred embodiment, a process according to the invention is characterized in that the agent (B) contains at least one acid of the formula (I), where R 1 represents a methyl group, an ethyl group or a propyl group and particularly preferably a methyl group.

[0033] In the carboxylic acids of formula (I), the radicals R 2 and R 3 can be chosen independently of one another. The radicals R 2 , R 3 independently of one another represent a hydrogen atom, a C 1 -C 6 alkyl group or a C 2 -C 6 alkenyl group

[0034] It has further been found that the carboxylic acids of formula (I) are particularly suitable for achieving the object of the invention when the radicals R 2 and R 3 independently of one another represent a hydrogen atom, a C 1 -C 6 alkyl group or a C 2 -C 6 alkenyl group.

[0035] In a further particularly preferred embodiment, a process according to the invention is characterized in that the agent (B) contains at least one acid of the formula (I), where R 2 , R 3 both represent a hydrogen atom.

[0036] In the compounds of formula (I), n indicates the number of repeating units for the grouping (CHR 2 ). Analogously, m indicates the number of repeating units for the grouping (CHR 3 ).

[0037] For example, if n stands for the number 1 and m for the number 1, the acid of formula (I) is the compound R 1 C(O)-CHR 2 -CHR 3 -COOM.

[0038] For example, if n stands for the number 2 and m for the number 1, the acid of formula (I) is the compound R 1 C(O)-CHR 2 -CHR 2 -CHR 3 -COOM.

[0039] The process according to the invention is characterized in that the agent (B) contains an acid of formula (I), where n stands for the number 1 or 2 and m stands for the number 0 or 1.

[0040] In the compounds of formula (I), M represents a hydrogen atom or an equivalent of a mono- or polyvalent cation.

[0041] When M represents a hydrogen atom, the compound of formula (I) is present in the form of its acid. The hydrogen atom of the acid function is acidic, and in an aqueous medium, the acid is deprotonated. For this reason, the acid (I) is in equilibrium with its anion in the cosmetic product (B)—particularly when the product comprises an aqueous cosmetic carrier.

[0042] The acid can also be used directly in the form of its salt in the cosmetic product (B). In this case, the carboxylate anion is neutralized by M, where M represents an equivalent of a mono- or polyvalent cation. Suitable inorganic cations include, in particular, Na +< , K +< , (NH 4 ) +< , ½ Mg 2+< , ½ Ca 2+< . Organic cations such as tetra-C 1 -C 22 -alkylammonium are also suitable.

[0043] Agent (B) contains water and is adjusted to an acidic pH. The acidic pH can be adjusted, for example, by using the acid(s) of formula (I) in their free acid form. Accordingly, it has been found to be particularly preferred if M represents a hydrogen atom.

[0044] In a particularly preferred embodiment, a process according to the invention is characterized in that the agent (B) contains at least one acid of the formula (I) (or (Ia)), where M stands for a hydrogen atom.

[0045] Agents (B) for lightening keratin fibers preferred according to the invention are characterized in that they contain at least one carboxylic acid formula (I) selected from 4-Oxopentanoic acid (levulinic acid) 4-oxohexanoic acid 2-methyl-4-oxo-pentanoic acid 3-methyl-4-oxo-pentanoic acid

[0046] Within the aforementioned group of preferred carboxylic acid formula (I), the compound - 4-Oxopentanoic acid (levulinic acid). 4-Oxopentanoic acid (levulinic acid) is commercially available.

[0047] To achieve optimal fiber protection, the agents (B) according to the invention preferably contain the acid(s) of formula (I) in specific quantity ranges. It is very particularly preferred if the agent (B) according to the invention contains (b) one or more acids of formula (I) in a total amount of 0.1 to 10.0 wt. %, preferably 0.3 to 8.5 wt. %, more preferably 0.5 to 7.5 wt. %, and very particularly preferably 0.7 to 6.5 wt. %, based on its total weight.

[0048] In a particularly preferred embodiment, a process according to the invention is characterized in that the agent (B) - based on the total weight of the agent (B) - contains one or more acids of the formula (I) in a total amount of 0.1 to 10.0 wt.%, preferably 0.3 to 8.5 wt.%, more preferably 0.5 to 7.5 wt.% and most preferably 0.7 to 6.5 wt.%. pH value of the agent (B)

[0049] As already described above, the acids of formula (I) in which M represents a hydrogen atom are particularly preferably used in the agent (B) according to the invention; that is, the use of the acids in their free form has proven particularly advantageous. The acidity of the acid group contributes to the pH of the agent (B) remaining in the acidic range. Agent (B) particularly preferably contains water.

[0050] The agent (B) is adjusted to a pH value in the range of 1.8 to 3.0.

[0051] The pH value can be measured, for example, using a glass electrode, which is usually commercially available in the form of a combination electrode. Before measuring the pH value, the glass electrodes are usually calibrated with calibration solutions of known pH values. For the purposes of the present invention, pH values ​​are understood to be pH values ​​measured at a temperature of 22 °C.

[0052] To adjust the preferred pH values, the acids of formula (I) can be used in particular. In addition, further amounts of acidifying agents can also be contained in agent (B). Other acidifying agents suitable according to the invention include, for example, citric acid, lactic acid, acetic acid, tartaric acid, malic acid, etidronic acid, pyridine-2,6-dicarboxylic acid, or diluted mineral acids (such as hydrochloric acid, sulfuric acid, phosphoric acid).

[0053] For fine adjustment of the pH value, various alkalizing agents can also be used in agent (B). Alkalizing agents suitable according to the invention can be selected from the group consisting of ammonia, alkanolamines, alkali metal hydroxides, alkali metal metasilicates, alkali metal phosphates, and alkali metal hydrogen phosphates. Preferred inorganic alkalizing agents are sodium hydroxide, potassium hydroxide, sodium silicate, and sodium metasilicate. Organic alkalizing agents usable according to the invention are preferably selected from monoethanolamine, 2-amino-2-methylpropanol, and triethanolamine. Sodium silicate and sodium metasilicate are particularly preferred. Medium (C)

[0054] The agents (B) containing the acids of formula (I) according to the invention are excellently suited for reducing the damage caused by bleaching and bleaching hair. The bleaching of hair is achieved by the agents (A), which contain at least one peroxide, preferably hydrogen peroxide.

[0055] If the user desires particularly strong lightening performance, hydrogen peroxide alone is usually not sufficient. In this case, bleaching agents containing a combination of the oxidizing agents hydrogen peroxide and persulfates are typically used.

[0056] In the course of the work leading to this invention, it has been found that the agents (B) with the acids of formula (I) also bring about a significant reduction in damage when, or in particular after, the combination of hydrogen peroxide / persulfate is used.

[0057] For this reason, it is particularly preferred to apply agent (B) containing the acids of formula (I) after bleaching the hair using a combination of hydrogen peroxide and persulfates. For this purpose, a third agent (C) is particularly preferably used in the process according to the invention. This third agent (C) contains ammonium persulfate, potassium persulfate, and / or sodium persulfate.

[0058] Persulfates are also alternatively called peroxodisulfates. Suitable persulfates are ammonium persulfate (ammonium peroxodisulfate), potassium persulfate (potassium peroxodisulfate), and sodium persulfate (sodium peroxodisulfate).

[0059] Potassium peroxodisulfate is also known as potassium persulfate and has the molecular formula K 2 S 2 O 8.

[0060] Ammonium peroxodisulfate is also alternatively called ammonium persulfate and has the molecular formula (NH 4 ) 2 S 2 O 8 .

[0061] Sodium peroxodisulfate is also known as sodium persulfate and has the molecular formula Na 2 S 2 O 8 .

[0062] The persulfate(s) are preferably used in a total amount of 1.0 to 40.0 wt.%, preferably 5.0 to 30.0 wt.%, more preferably 10.0 to 25 wt.% and very particularly 15.0 to 20.0 wt.% in the agent (C), wherein the above-mentioned amounts are based on the total amount of persulfates used in the agent (C), which is related to the total weight of the agent (C). pH value of the bleaching agent

[0063] Bleaching or bleaching hair usually takes place under alkaline conditions. The alkalizing agent ensures sufficient swelling of the hair, and the bleaching performance of hydrogen peroxide or hydrogen peroxide / persulfate also increases in an alkaline environment. For this reason, the ready-to-use bleaching agent usually has a pH value of 7.5 to 12.5, preferably 8.5 to 10.5.

[0064] For stability reasons, agent (A), which contains hydrogen peroxide, is acidified. For this reason, an alkalizing agent is not usually packaged together with the hydrogen peroxide.

[0065] To produce an alkaline bleaching agent, the alkalizing agent can therefore be incorporated, for example, into agent (C). Agent (C) contains persulfates and is preferably provided in the form of a powder or paste.

[0066] The use of alkalizing agents in agent (C) is therefore particularly suitable for alkalizing agents that are also present in solid or powder form. Suitable solid alkalizing agents include, for example, alkali metal hydroxides, alkali metal metasilicates, alkali metal phosphates, and alkali metal hydrogen phosphates. Preferred inorganic alkalizing agents are sodium hydroxide, potassium hydroxide, sodium silicate, and sodium metasilicate. Sodium silicate and sodium metasilicate are particularly preferred.

[0067] Sodium silicates are the sodium salts of various silicic acids. A distinction can be made between sodium silicates in which the ratio of silicon dioxide to sodium monoxide is greater than or equal to 2 or less than or equal to 1. Sodium metasilicate belongs to the latter group, meaning that sodium metasilicate refers to polymeric silicates of the formula [Na 2 SiO 3 ] x . Sodium metasilicate can be used anhydrous or in the form of its hydrates.

[0068] Sodium silicate can also be used in the form of sodium water glass. Sodium water glass is amorphous sodium silicate solidified from a melt.

[0069] Preferred inorganic alkalizing agents are sodium hydroxide, potassium hydroxide, sodium silicate and sodium metasilicate.

[0070] On the other hand, the bleaching agent can also be adjusted to the optimal pH value by using liquid or flowable alkalizing agents. Suitable liquid or flowable alkalizing agents include ammonia, 2-aminoethanol, 2-amino-2-methylpropane-1-ol, and 2-amino-2-methylpropane-1,3-diol.

[0071] Amino acids such as L-arginine, D-arginine, D / L-arginine, L-lysine, D-lysine and D / L-lysine are also suitable as alkalizing agents.

[0072] The aforementioned alkalizing agents can be provided in a further container containing another agent (D). In this embodiment, agent (D) contains at least one alkalizing agent from the group consisting of ammonia, 2-aminoethane-1-ol, 2-amino-2-methylpropane-1-ol, 2-amino-2-methylpropane-1,3-diol, L-arginine, D-arginine, D / L-arginine, L-lysine, D-lysine, and D / L-lysine. Other ingredients

[0073] The agents (A) and (B) (and optionally the agents (C) and / or (D)) may additionally contain other active ingredients, auxiliaries and additives, such as, for example, cationic surfactants, non-ionic surfactants, amphoteric or zwitterionic surfactants, anionic surfactants, anionic, non-ionic and / or cationic polymers, structurants such as glucose, perfume oils, fiber structure-improving active ingredients, in particular mono-, di- and oligosaccharides such as, for example, glucose, galactose, fructose, fructose and lactose; dyes for coloring the agent; anti-dandruff active ingredients such as piroctone olamine, zinc omadine and climbazole; amino acids and oligopeptides; protein hydrolysates of animal and / or plant origin, as well as in the form of their fatty acid condensation products or, optionally, anionically or cationically modified derivatives; vegetable oils; light stabilizers and UV blockers;Active ingredients such as panthenol, pantothenic acid, pantolactone, allantoin, pyrrolidinonecarboxylic acids and their color-changing salts as well as bisabolol; polyphenols, in particular hydroxycinnamic acids, 6,7-dihydroxycoumarins, hydroxybenzoic acids, catechins, tannins, leucoanthocyanidins, anthocyanidins, flavanones, flavones and flavonols; vitamins, provitamins and vitamin precursors; plant extracts; swelling and penetrating agents such as glycerin, propylene glycol monoethyl ether, carbonates, hydrogen carbonates, guanidines, ureas as well as primary, secondary and tertiary phosphates; opacifiers such as latex, styrene / PVP and styrene / acrylamide copolymers; pearlescent agents such as ethylene glycol mono- and distearate and PEG-3 distearate; Pigments and propellants such as propane-butane mixtures, N 2 O, dimethyl ether, CO 2 and air.;

[0074] The additional active ingredients and excipients are preferably used in the agents according to the invention in amounts of 0.0001 to 10% by weight, in particular 0.0005 to 5% by weight, based on the total weight of the respective agent. Method for bleaching hair

[0075] The procedure for lightening hair includes the following steps in the order given (1) Mixing an agent (A) with an agent (C) and / or an agent (D), wherein the agent (A) is an agent as already disclosed in detail and the agent (C) is an agent as already disclosed in detail b, and the agent (D) is as already disclosed in detail, (2) Applying the mixture prepared in step (1) to the hair, (3) Allowing the mixture applied in step (2) to act on the hair, (4) If necessary, rinsing the hair, (5) Applying an agent (B) to the hair, wherein the agent (B) is an agent as already disclosed in detail.

[0076] Agent (A) contains hydrogen peroxide and represents the oxidizing agent component. To produce the ready-to-use bleaching agent, agent (A) is mixed - depending on the desired degree of lightening - either with agent (C) and / or with agent (D), wherein agent (C) contains one or more persulfates and agent (D) contains one or more alkalizing agents (step (1)).

[0077] The mixture of agents (A) and (C) represents a ready-to-use bleaching agent.

[0078] The mixture of agents (A) and (D) also represents a ready-to-use bleaching agent. The mixture of agents (A), (C) and (D) also represents a ready-to-use bleaching agent.

[0079] For example, 100 g of agent (A) are mixed with 100 g of agent (C) or 100 g of agent (A) are mixed with 100 g of agent (D) or 100 g of agent (A) are mixed with 100 g of agent (C) and 100 g of agent (D) or 100 g of agent (A) are mixed with 50 g of agent (C) and 50 g of agent (D)

[0080] Other mixing ratios are also possible according to the invention. Thus, agents (A) and (C) can be mixed together in a ratio of 1:5 to 5:1, preferably 1:3 to 1:3.

[0081] The agents (A) and (D) can be mixed together, for example, in a ratio of 1:5 to 5:1, preferably 1:3 to 1:3.

[0082] The mixture prepared in step 1, which is the ready-to-use bleaching agent, is then applied to the hair (step 2). Application can be done with a gloved hand or with an applicator (comb, brush, or applicette). After application, the ready-to-use bleaching agent is left on the hair for a period of 5 to 60 minutes, preferably 15 to 45 minutes (step 3).

[0083] Now the bleaching agent can be rinsed out of the hair (step 4).

[0084] It has been found to be particularly preferable to rinse the hair for a short period of time of 5 to 60 seconds, preferably 5 to 45 seconds.

[0085] Particularly preferred is a method for lightening hair, comprising the following steps in the order given (1) Mixing an agent (A) with an agent (C) and / or an agent (D), wherein the agent (A) is an agent as already disclosed in detail and the agent (C) is an agent as already disclosed in detail and the agent (D) is as already disclosed in detail, (2) Applying the mixture prepared in step (1) to the hair, (3) Allowing the mixture applied in step (2) to act on the hair, (4) Rinsing the hair for a period of 5 to 60, preferably 5 to 45 seconds, (5) Applying an agent (B) to the hair, wherein the agent (B) is an agent as already disclosed in detail.

[0086] In a further embodiment, the agent (B) can also be applied to the hair that still contains bleaching agent without rinsing.

[0087] Also suitable is a method for lightening hair comprising the following steps in the order given (1) Mixing an agent (A) with an agent (C) and / or an agent (D), wherein the agent (A) is an agent as already disclosed in detail and the agent (C) is an agent as already disclosed in detail and the agent (D) is as already disclosed in detail, (2) Applying the mixture prepared in step (1) to the hair, (3) Allowing the mixture applied in step (2) to act on the hair, (4) Applying an agent (B) to the hair, wherein the agent (B) is an agent as already disclosed in detail.

[0088] The agent (B) containing the acid(s) of formula (I) is applied in the process according to the invention as a post-treatment agent, which is applied to the hair after the ready-to-use bleaching agent has been applied.

[0089] Particularly preferably, the agent (B) is in the form of a water-containing cosmetic agent which has an acidic pH value and can be packaged, for example, as a gel, shampoo, conditioner or cream. Examples: 1. Formulations

[0090] The following formulations were prepared (all data in wt%) Formulation with hydrogen peroxide (agent (A))

[0091] Substance (INCI) OX Na-benzoates 0,04 Dipicolinic acid 0,10 Disodium pyrophosphate 0,10 Potassium hydroxide 50% 0,19 Propanediol-1,2 0,50 HEDP 60% 0,25 Paraffinum Liquidum 2,00 Cetearyl Alcohol 3,60 Ceteareth-20 1,20 Hydrogen peroxide 50% 12,20 Water, demineralized to 100 Paste with persulfate (agent (C))

[0092] Substance (INCI) V1 Versagel M1600 5,00 Lanette N 7,00 Eumulgin B 5 4,00 Xanthan NaTrue 1,50 Sodium metasilicate (anhydrous) 6,50 Potassium persulfate 42,00 Perfume 0,60 Paraffinum Liquidum to 100 Versagel M1600: Paraffinum Liquidum (Mineral Oil), Ethylene / Propylene / Styrene Copolymer, Butylene / Ethylene / Styrene Copolymer Lanette N: Cetearyl Alcohol, Sodium Cetearyl Sulfate Eumulgin B 5: Ceteareth-50 Xanthan NaTrue: Xanthan Gum Aftertreatment agent (B)

[0093] (B1) (B2) (B3) (B4) (B5) (B6) E V E V E V Levulinic acid 1,0 --- 5,0 --- 10,0 --- hydrochloric acid --- to pH 2.7 --- to pH 2.3 --- to pH 2.2 PH value 2,7 2,7 2,3 2,3 2,2 2,2 Water to 100 to 100 to 100 to 100 to 100 to 100 Levulinic acid (alternative names: Levulinic acid, 4-oxo-pentanoic acid, CAS No. 123-76-2, Merck)

[0094] (B7) (B8) (B9) (B10) (B11) (B12) E V V V V V Levulinic acid 3,0 --- --- --- --- --- Itaconic acid --- --- 0,14 --- 0,56 --- hydrochloric acid --- to 2.4 --- to pH 2.7 --- to pH 2.3 PH value 2,4 2,4 2,7 2,7 2,3 2,3 Water to 100 to 100 to 100 to 100 to 100 to 100 Itaconic acid (alternative names: methylenesuccinic acid, 1-propene-2,3-dicarboxylic acid, CAS No. 97-65-4, Merck)

[0095] For comparison (V) in each case, an aftertreatment agent was used which did not contain any acid of the formula (I) according to the invention, but in which sufficient hydrochloric acid was added until the comparison formulation had the same pH as the corresponding aftertreatment agent (E) according to the invention. 2. Application

[0096] The hydrogen peroxide formulation (agent A) and the persulfate paste (agent C) were each mixed in a 1:1 ratio and immediately applied to 12 hair strands (45 minutes at room temperature). The pH of the application mixture was 9.5. The strands were rinsed with tap water for 10 seconds after the contact time.

[0097] The strand serving as reference (R) was not treated with a treatment (B), but instead was thoroughly rinsed with tap water. Subsequently, the strands were immersed in each of the treatments (B) for 10 minutes, then thoroughly rinsed with water and dried. 3. Measurement of fiber stabilization

[0098] The following melting points were determined using DSC analysis (Perkin Elmer DSC-7). A detailed description of the method can be found, for example, in DE 196 173 95 A1.

[0099] The higher the measured value (Peak Apex Temp, °C), the more stable the hair’s keratin matrix is. Hair stability (12-fold determination with averaging)

[0100] (R) without (B1) (B2) (B3) (B4) (B5) (B6) Follow-up treatment E V E V E V DSC: Peak Apex Temp. (°C) 143 159 147 163 151 164 157 (R) without (B7) (B8) (B9) (B10) (B11) (B12) Follow-up treatment E V V V V V DSC: Peak Apex Temp. (°C) 143 161 150 159 147 162 151

Claims

1. A method for lightening hair, comprising the following steps in the indicated order (1) mixing an agent (A) with an agent (C) and / or an agent (D), wherein - agent (A) contains hydrogen peroxide, and - agent (C) contains at least one persulfate from the group consisting of ammonium persulfate, potassium persulfate and / or sodium persulfate, and - agent (D) contains at least one alkalizing agent from the group consisting of ammonia, 2-aminoethane-1-ol, 2-amino-2-methylpropane-1-ol, 2-amino-2-methylpropane-1,3-diol, L-arginine, D-arginine, D / L-arginine, L-lysine, D-lysine and D / L-lysine, (2) applying the mixture prepared in step (1) to the hair, (3) allowing the mixture applied in step (2) to act on the hair, (4) optionally rinsing the hair, (5) applying an agent (B) to the hair, wherein agent (B) contains at least one acid of formula (I), where R1 represents a C1-C6 alkyl group, R2, R3 represent, independently of one another, a hydrogen atom, a C1-C6 alkyl group, a C2-C6 alkyl group, M represents a hydrogen atom or an equivalent of a monovalent or polyvalent cation, n represents the number 1 or 2, and m represents the number 0 or 1, and wherein agent (B) contains water and has a pH of 1.8 to 3.0.

2. The method according to claim 1, characterized in that agent (A), based on the total weight of agent (A), contains 0.1 to 12.5 wt.%, preferably 1.5 to 12.5 wt.%, more preferably 4.5 to 12.5 wt.% and very particularly preferably 6.5 to 12.5 wt.%, hydrogen peroxide.

3. The method according to one of claims 1 to 2, characterized in that agent (B) contains at least one acid of formula (I), where R1 represents a methyl group, an ethyl group or a propyl group, and preferably a methyl group.

4. The method according to one of claims 1 to 3, characterized in that agent (B) contains at least one acid of formula (I), where M represents a hydrogen atom.

5. The method according to one of claims 1 to 4, characterized in that agent (B) contains at least one acid of formula (I) which is selected from the group consisting of 4-oxopentanoic acid (levulinic acid), 4-oxohexanoic acid, 2-methyl-4-oxo-pentanoic acid and / or 3-methyl-4-oxo-pentanoic acid.

6. The method according to one of claims 1 to 5, characterized in that agent (B), based on the total weight of the agent (B), contains one or more acids of formula (I) in a total amount of 0.1 to 10.0 wt.%, preferably 0.3 to 8.5 wt.%, more preferably 0.5 to 7.5 wt.%, and very particularly preferably 0.7 to 6.5 wt.%.