Process for preserving the dyeing capacity of 5,...

Details Process for preserving the dyeing capacity of 5,... Process for preserving the dyeing capacity of 5,...

1997-10-08

2001-07-10

Liott, Caroline D. (Department: 1751)

Bleaching and dyeing; fluid treatment and chemical modification

Dyeing involving animal-derived natural fiber material ,...

Hair dyeing

C008S406000, C008S604000

Reexamination Certificate

active

06258131

ABSTRACT:

Process for preserving the dyeing capacity of 5,6-dihydroxyindole and of its derivatives in an aqueous medium, composition and dyeing process.
The present invention relates to a process for preserving the dyeing capacity of 5,6-dihydroxyindole and of certain derivatives in an aqueous medium, to aqueous dyeing compositions based on 5,6-dihydroxyindole and on its derivatives exhibiting improved dyeing capacity retention properties and to the dyeing process making use thereof.
The color of hair, of the skin and of body hair, particularly of human origin is due chiefly to melanin related pigments secreted by the melanocytes. These pigments, of natural origin, include in particular pigments which are called eumelanins. Their natural biosynthesis takes place in several steps by polymerization of the oxidation products of an amino acid, tyrosine, and one of these oxidation products is 5,6-dihydroxyindole, which in its turn polymerizes to eumelanin.
It has already been proposed in the past to repigment human hair with 5,6-dihydroxyindole, more particularly by employing aqueous 5,6-dihydroxyindole compositions. Hair can be dyed by virtue of such compositions, it being possible for this dyeing to be performed a number of times or progressively, by repigmenting the hair by virtue of this dye to give light shades using one application of the product and to an increasingly intensified shade by superposing the applications.
These compositions are generally adjusted to a pH of between 5 and 10 and more particularly between 7 and 9. However, the Applicant has found that the hair coloring could be impared following the storage of the dye composition based on 5,6-dihydroxyindole in an aqueous medium. It is found, in fact, that after the dyeing composition has been stored for a few weeks or months, the hair shades obtained are modified or impaired when compared with the initial shade.
The applicant have found that, surprisingly, this problem of preserving the dyeing capacity and characteristics of 5,6-dihydroxyindole and of its derivatives in an aqueous medium could be solved by virtue of the use, in the aqueous medium, of an agent containing two components which do not complex the indole-related dye, as an agent enabling the pH to be adjusted.
A subject-matter of the present invention is therefore a process for preserving the dyeing capacity of 5,6-dihydroxyindole and of its derivatives in an aqueous medium by the use of a pH-regulating agent containing two components which do not inhibit the dyeing capacity of the indole-related dye.
Another subject of the invention consists of the dyeing composition based on 5,6-dihydroxyindole and/or on its derivatives containing such a pH-regulating agent and of the dyeing process making use thereof.
Other subjects of the invention will become apparent on reading the description and the examples which follow.
The process for preserving the dyeing capacity of 5,6-dihydroxyindole and/or of its derivatives corresponding to the formula (I):
in which R
1
, R
2
, R
3
and R
4
, which are identical or different, denote hydrogen or a C
1
-C
4
lower alkyl, R
1
, R
2
and R
3
denoting hydrogen when R
4
denotes alkyl in an aqueous medium, in accordance with the invention, is characterized essentially by the fact that, in order to adjust the pH to a value pH
C
of between 5 and 10 and preferably between 7 and 9, a pH-regulating agent comprising two components (A) and (B) is employed, the component (A) exhibiting a dissociation constant K
CA
in aqueous solution at 25° C., such as pk
CA
, that is:
 0<pk
CA
−pH
C
<2.5
the component (B) having a dissociation constant K
CB
in aqueous solution at 25° C., such as pk
CB
, that is:
2<pk
CB
<pH
C
the components (A) and (B) not inhibiting the dyeing capacity of the indole-related dye.
In the formula (I), an alkyl preferably denotes methyl and R
1
, R
2
and R
3
do not denote an alkyl simultaneously.
The preferred compounds of formula (I) are chosen from 5,6-dihydroxyindole, 2-methyl-5,6-dihydroxyindole, 3-methyl-5,6-dihydroxyindole, 1-methyl-5,6-dihydroxyindole, 2,3-dimethyl-5,6-dihydroxyindole and 5-methoxy6-hydroxyindole.
A preferred embodiment of the invention consists in employing the component (A) in such proportions that the weight ratio of component (A) to component (B) is higher than 1 and that the molar ratio of component (A) to component (B) is higher than or equal to 2 and lower than 15.
The pH-regulating agent containing two components, employed in accordance with the invention, is employed in proportions which are preferably between 5×10
−3
and 50×10
−3
moles per 100 g of dyeing composition.
The components A and B which are more particularly preferred in the process in accordance with the invention are chosen from the following pairs: triethanolamine (pk
CA
: 4.7)/tartaric acid (pk
CB
: 3.2); dipotassium hydrogen phosphate (pk
CA
: 7.2)/potassium dihydrogen phosphate (pk
CB
: 2.1).
The dyeing compositions for keratinous fibers, in particular for human hair, which form another subject of the present invention are more particularly characterized by the fact that they contain, in a suitable aqueous medium for dyeing, at least 5,6-dihydroxyindole and/or one of its derivatives of formula (I) and a pH-regulating agent which makes it possible to obtain a pH
C
having a value of between 5 and 10 and preferably between 7 and 9, this pH-regulating agent comprising two components (A) and (B) which do not complex the indole-related dye and correspond to the definition outlined above.
In the compositions in accordance with the invention, 5,6-dihydroxyindole and/or its derivatives of formula (I) is (are) preferably employed in proportions of between 0.01 and 5% by weight and preferably between 0.03 and 3% by weight relative to the total weight of the composition. The proportions which are particularly preferred are the proportions between 0.2 and 1% by weight and more particularly between 0.3 and 0.9% by weight relative to the total weight of the composition.
These compositions may contain suitable adjuvants for dyeing, which are well known in dyeing compositions and, in the case where these compositions are intended to be applied to hair, these adjuvants are cosmetically acceptable. More particularly, they may contain organic solvents in proportions of 0.5 to 50% by weight and preferably of 2 to 20% by weight relative to the total weight of the composition, these being chosen more particularly from C
1
-C
4
lower alcohols such as ethyl alcohol, propyl alcohol, isopropyl alcohol, tert-butyl alcohol, ethylene glycol, propylene glycol, ethylene glycol monomethyl, monoethyl and monobutyl ethers, ethylene glycol monoethyl ether acetate, propylene glycol and dipropylene glycol monomethyl ethers and methyl lactate. The preferred solvents are chosen more particularly from ethyl alcohol and propylene glycol.
These compositions may be thickened with thickening agents which are preferably employed in proportions by weight of between 0.1 and 5%, in particular between 0.5 and 3% relative to the total weight of the composition. These thickeners are chosen more particularly from sodium alginate, gum arabic, guar gum, heterobiopolysaccharides such as xanthan gum or scleroglucans, cellulose derivatives such as methyl cellulose, hydroxyethyl cellulose and hydroxypropyl methyl cellulose, carboxymethyl cellulose sodium salt and acrylic acid polymers, or else inorganic thickening agents such as bentonite.
These compositions may also contain anionic, cationic, nonionic or amphoteric surface-active agents or mixtures thereof. These surface-active agents are preferably employed in proportions of between 0.1 and 50% by weight relative to the total weight of the composition, and advantageously between 1 and 20% by weight.
Another subject of the invention is a dyeing process making use of a composition of this kind, which is stabilized with time. This process consists in applying the composition such as defined above to keratinous fibers, and in particular to human hair, for an application time of 1

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