Hair treatment composition

Abstract: An aqueous composition for hair treatment containing a low molecular weight non-acidic compound intended to penetrate the hair shaft, together with at least one of certain 2-hydroxyalkanoic acids which have been found to act as penetration enhancers.

Description: FIELD OF INVENTION The present invention relates to a hair treatment composition containing a low molecular weight compound which is intended to be retained in the hair shaft. BACKGROUND OF THE INVENTION Certain 2-hydroxyalkanoic acids have been included in compositions for topical application to the skin, for the purpose of increasing extensibility and improving the appearance of the skin. In EP 0 403 303 there is disclosed the combination of 2-hydroxyoctanoic acid, a conditioning agent and perfumes and colours. The function of the 2-hydroxyoctanoic acid is to increase elasticity of hair. There is no disclosure of the problem of enhancing delivery of perfume or dye to the hair shaft. In GB 2 116 036 (Unilever) compositions are disclosed which comprise substituted octanoic acid (including 2-hydroxyoctanoic acid and 2-ketooctanoic acid) together with C₂₋₄ alkyl lactate. It is stated that these compositions improve the condition of the skin. It is known that certain compounds enhance the penetration of dyes into the hair shaft. For example, EP 161 073 (Repligen) discloses the use of a range of compounds which are alcohols, phenols or esters, to aid the penetration of dopa and its analogues into the hair. Dopa is a dye precursor which is practically insoluble in water and solvents, and would penetrate the hair only slightly if applied on its own. We have now found that certain 2-hydroxyalkanoic acids aid the penetration of some low molecular weight molecules into the hair shaft. The low molecular weight compound is retained in the hair shaft more effectively than if 2-hydroxyalkanoic acids were not present in the composition. BRIEF SUMMARY OF THE INVENTION Accordingly, the invention provides an aqueous hair treatment composition which comprises: (i) from 0.05 to 5% by weight of a non-acidic compound being a hair dye or dye precursor having a molecular weight not over 5000; and (ii) from 0.05 to 30% by weight of an acidic compound chosen from 2-hydroxyhexanoic acid, 2-hydroxyoctanoic acid, 2-hydroxydecanoic acid or mixtures thereof, to serve as hair shaft penetration enhancer for the non-acidic compound. The invention further comprises a method for delivering a non-acidic low molecular weight compound to hair so as to penetrate into the hair shaft, which method comprises the step of contacting hair with an aqueous composition comprising: (i) from 0.05 to 5% by weight of a non-acidic compound being a hair dye or dye precursor having a molecular weight not over 5000; and (ii) from 0.05 to 30% by weight of an acidic compound chosen from 2-hydroxyhexanoic acid, 2-hydroxyoctanoic acid, 2-hydroxydecanoic acid or mixtures thereof, to serve as a hair shaft penetration enhancer for the non-acidic compound. The invention still further comprises the use of an acidic compound chosen from 2-hydroxyhexanoic acid, 2-hydroxyoctanoic acid, 2-hydroxydecanoic acid, or mixtures thereof, as a hair shaft penetration enhancer for a nonacidic compound of molecular weight less than 5000, the non-acidic compound being chosen from hair dyes, dye precursors and perfumes. DETAILED DESCRIPTION OF THE INVENTION The 2-hydroxyalkanoic acid The composition of the invention comprises 2-hydroxyalkanoic acid chosen from 2-hydroxyhexanoic acid, 2-hydroxyoctanoic acid, 2-hydroxydecanoic acid or mixtures thereof in an amount from 0.05 to 30% by weight. The 2-hydroxyalkanoic acid is preferably 2-hydroxyoctanoic acid and is preferably present in an amount of from 0.5 to 5% by weight. It is preferred that the pH of the hair treatment composition of the invention is maintained at below 7, most preferably at a pH of from 2.5 to 5. This may be achieved simply by the acidic nature of the hydroxyalkanoic acid itself or preferably by the addition of a co-acid. The co-acid may be included in an amount sufficient to adjust the pH of the composition to a value of 2.5 to 5. A suitable amount is up to 5% by weight, preferably from 0.5 to 2% by weight. The hair is an effective buffer and may cause the penetration enhancement effect of the 2-hydroxyalkanoic acid to be lost if the pH value of the composition is greater than 7. Preferred examples of co-acids are citric acid and lactic acid. The non acidic low molecular weight compound The composition of the invention also comprises a non-acidic low molecular weight compound in an amount from 0.05 to 5% by weight. The molecular weight is preferably not over 5000, most preferably below 3000. In general, compounds having a molecular weight of greater than 5000 are too large to penetrate the hair shaft in the relatively short contact times used for hair products. The non-acidic low molecular weight compound may be, for example, a dye or dye precursor, which is preferably chosen from oxidative hair dyes, auto-oxidative hair dyes, metal chelatic dyes, direct dyes, melanin precursors or mixtures thereof. Particularly suitable examples of hair dyes include Food red 9 (CI No. 16185) sold under the trade name AMARANTH, Food red 14 (CI No. 45430) sold under the trade name ERYTHROSINE, Food red 3 (CI No. 14720) sold under the trade name CARMOSINE, Food red 7 (CI No. 16255) sold under the trade name PONCEAU 4R, Food yellow 13 (CI NO. 47005) sold under the trade name QUINOLINE YELLOW. Acid Black (CI No. 28440) sold under the trade name BLACK PN. When the non-acidic low molecular weight compound is a dye or a dye precursor, it is preferred that it is present in the composition of the invention in an amount of from 0.1 to 5% by weight. The non-acidic low molecular weight compound for use in the composition of the invention may alternatively be a perfume. Suitable examples of perfumes include eugenol, 2,6-dimethyl-7-octen-2-ol, ortho-tertiarybutyl-cyclohexyl acetate and 9-decen-1-ol, or proprietary perfumes containing mixtures of perfume components. When the non-acidic low molecular weight compound is a perfume, it is preferably present in the composition in an amount of from 0.05 to 1% by weight. The composition of the invention may also comprise certain ingredients known in the art and necessary to the particular formulation required. The composition may be formulated as a shampoo, conditioner, styling mousse or lotion, hair spray or setting composition or as any other composition suitable for application to the hair. Examples of other ingredients are surfactants, viscosity control agents, solubility control agents, foam boosters, opacifiers, perfumes, colouring agents, conditioning agents, preservatives, proteins, polymers, buffering agents and water. PROCESS The hair treatment composition of the invention is formulated by mixing together the required ingredients in the amounts specified. ADVANTAGES OF THE INVENTION In the hair treatment composition of the invention the 2-hydroxyalkanoic acid has been demonstrated to enhance the penetration of non-acidic low molecular weight compounds into the hair shaft. The composition therefore provides an improved delivery system for molecules such as hair dyes or perfumes. If a hair dye molecule, for example, penetrates the hair shaft, the colour is retained during washing and the original colour of the hair is seen only in the new hair growth. Similarly, if perfume molecules are delivered to the interior of the hair shaft in the presence of 2-hydroxyalkanoic acid, the perfume is discernable in the hair for much longer periods than if the perfume molecules were merely retained on the surface of the hair shaft. COMPARATIVE TESTS The effect of 2-hydroxyalkanoic acids on the penetration of non-acidic low molecular weight compounds is illustrated by the following Comparative tests. Comparative test 1 Blonde hair switches were treated with a solution at pH 3.0 containing 2% by weight of 2-hydroxyoctanoic acid and 1% by weight of BLACK PN, a water-soluble acid black food dye. The switches maintained a dark grey colour which remained fast to washing for up to five shampoos. Control switches, treated with a similar solution containing no 2-hydroxyoctanoic acid, showed no darkening. Comparative test 2 Hair switches were treated with a solution at pH 3.0 containing 1% by weight of 2-hydroxyoctanoic acid and 1% by weight of each of the water soluble anionic food dyes known as Ponceau 4R and Amaranth. Control hair switches were treated with a dye solution containing no 2-hydroxyoctanoic acid. It was shown that there is a significant increase in dyeing in the presence of 2-hydroxyoctanoic acid, and also that the anisotropy in dyeing is greatly reduced in the presence of the 2-hydroxyoctanoic acid. Comparative test 3 Hair switches were treated with a solution at pH 3.0 containing 1% by weight of 2-hydroxyoctanoic acid, 1% by weight of lactic acid and 1% by weight of Ponceau 4R. Control hair switches were treated with a similar solution containing no lactic acid. The results indicated that dyeing enhancement by the 2-hydroxyoctanoic acid was markedly improved in the presence of lactic acid. Comparative test 4 8cm/1.5g hair switches were placed for 5 minutes in 90g of a solution containing sodium lauryl ether sulphate with average two ethylene oxide residues (SLES 2EO), Eugenol and 1% by weight 2-hydroxyoctanoic acid (a hair: liquor ratio of 1:20 by weight) at pH 3.0. After removal from the solution, switches were rinsed under running water for 30 seconds and then dried at 55°C for 30 minutes. The switches were assessed by means of a paired-comparison test against control switches treated in a similar way but with a solution containing no 2-hydroxyoctanoic acid. Twelve panellists were asked to assess 6 pairs of switches, comparing strength and intensity of perfume over a period of 48 hours. The results of the assessment are set out in Table 1 below. All percentages are by weight. The invention is further illustrated by the following Examples. Example 1 The following is an example of a shampoo according to the invention. The pH was adjusted to between 3 and 5 with triethanolamine. Example 2 The following is an example of a shampoo according to the invention. The pH was adjusted to between 3 and 5 with triethanolamine. Example 3 The following is an example of a shampoo according to the invention. The pH was adjusted to between 3 and 5 with triethanolamine. Example 4 The following is an example of a conditioner according to the invention. The pH was adjusted to between 3 and 5 with triethanolamine. Example 5 The following is an example of a conditioner according to the invention. The pH was adjusted to between 3 and 5 with triethanolamine.

Claims: An aqueous hair treatment composition which comprises: (i) from 0.05 to 5% by weight of a non-acidic compound being a hair dye or dye precursor having a molecular weight not over 5000; and (ii) from 0.05 to 30% by weight of an acidic compound chosen from 2-hydroxyhexanoic acid, 2-hydroxyoctanoic acid, 2-hydroxydecanoic acid or mixtures thereof, serving as a hair shaft penetration enhancer for the non-acidic compound. An aqueous hair treatment composition as claimed in claim 1 wherein the acidic compound is 2-hydroxyoctanoic acid. An aqueous hair treatment composition as claimed in claim 1 or claim 2 wherein the acidic compound is present in an amount from 0.5 to 5% by weight. An aqueous hair treatment composition as claimed in any one of claims 1 to 3, wherein the composition further comprises a co-acid in an amount from 0.5 to 5% by weight. An aqueous hair treatment composition as claimed in claim 4, wherein the co-acid is lactic acid or citric acid. An aqueous hair treatment composition as claimed in any preceding claim, wherein the hair dye or dye precursor is chosen from oxidative hair dyes, auto-oxidative hair dyes, metal chelatic dyes, direct dyes, melanin precursors or mixtures thereof. An aqueous hair treatment composition as claimed in any preceding claim wherein the composition is formulated as a shampoo. An aqueous hair treatment composition as claimed in any one of claims 1 to 6 wherein the composition is formulated as a hair conditioner. A method for delivering a non-acidic compound, being a hair dye or dye precursor having a molecular weight not over 5000, to hair so as to penetrate into the hair shaft, which method comprises the step of contacting hair with an aqueous composition comprising: (i) from 0.05 to 5% by weight of the non-acidic compound having a molecular weight not over 5000; and (ii) from 0.05 to 30% by weight of an acidic compound, chosen from 2-hydroxyhexanoic acid, 2-hydroxyoctanoic acid, 2-hydroxydecanoic acid or mixtures thereof, as a hair shaft penetration enhancer. Use of an acidic compound chosen from 2-hydroxyhexanoic acid, 2-hydroxyoctanoic acid, 2-hydroxydecanoic acid, or mixtures thereof, as a hair shaft penetration enhancer for a non-acidic compound of molecular weight not over 5000, the non-acidic compound being chosen from hair dyes, dye precursors and perfumes. Use of an acidic compound as claimed in claim 10, wherein the acidic compound is 2-hydroxyoctanoic acid. Use of an acidic compound as claimed in claim 10 or 11 wherein the acidic compound is present in an amount from 0.5 to 5% by weight. Use of an acidic compound as claimed in any one of claims 10 to 12, wherein the penetration is further enhanced by use of a co-acid in an amount from 0.5 to 5% by weight. Use of an acidic compound as claimed in claim 13, wherein the co-acid is lactic acid or citric acid. Use of an acidic compound as claimed in any preceding claim, wherein the said non-acidic compound is a hair dye or dye precursor. Use of an acidic compound as claimed in claim 15, wherein the hair dye or dye precursor is chosen from oxidative hair dyes, auto-oxidative hair dyes, metal chelatic dyes, direct dyes, melanin precursors or mixtures thereof.

Inventors: BOWSER PAUL ANTHONY, GALLAGHER PETER, MARTI VERNON PETER JOHN, BOWSER, PAUL ANTHONY, GALLAGHER, PETER, MARTI, VERNON PETER JOHN
Applicants: UNILEVER NV, UNILEVER PLC, UNILEVER N.V.
Application year: 1990
Main classification: A61K7
IPC codes: A61Q5, A61K8