The invention relates to a method and a kit for providing brown colour to keratinous fibres. The invention more particularly relates to a method and a kit for providing brown colour to hair and reducing the blueness generally obtained with such types of colouring methods.

Background of the invention

Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field. Presently, the number of people wishing to have their hair coloured has increased. In order to obtain a uniform colour over the hair, permanent hair colours are used more often than temporary and semi-permanent hair colours. These types of temporary and semi-permanent hair colours do not give any control to the consumer over the amount of colour deposited. Hence most people prefer the permanent hair colours.

There are several permanent hair colouring compositions which generally come in two parts: a dye solution and a developer solution. People generally perceive that synthetic chemicals have a damaging effect on their hair. They also believe that use of these dyes can cause allergenic reactions in some people in addition to damage to structure of hair fiber. Therefore, more and more people are opting for colourant systems that use actives obtained from natural sources.

A method of colouring hair comprising contacting hair with an iron or copper salt followed by contacting with gallic acid or an ester thereof, is known. Such a method gives a bluish tinge to the hair which is not liked by some consumers. Consumers generally prefer a more brownish tinge which they believe gives one a natural look. The present inventors have found that a sequential treatment comprising first treating with a complex of a Copper ion and gallic acid / gallate followed by rinsing and then treating with iron salt gives the hair the much needed brownish tinge. This provides better colour than the step of first treating with Cu and/or Fe ion followed by treating with gallic acid / gallate.

Various sequential hair colouring methods involving iron and copper salts and mordants have been reported in US patent 1405458 (Stoll, 1922). However the specific sequence claimed in the present invention has not been disclosed, which the present inventors through extensive experiments have determined is superior to any other sequence.

It is thus an object of the present invention to develop a method of colouring keratinous fibers that enhances the brown tinge.

It is another object of the present invention to develop a method of colouring keratinous fibers that enhances the brown tinge and uses material derivable from natural sources.

Summary of the invention

According to an aspect of the present invention there is provided a method of colouring keratinous fibers comprising the steps of

(a) contacting the keratinous fibers with a complex of an copper salt with gallic acid or an alkyl ester of gallic acid or a mixture thereof; followed by

(b) rinsing the fibers to be substantially free of the complex; followed by

(c) contacting the hair with an iron salt. According to another aspect of the present invention there is provided a kit for colouring keratinous fibers comprising (a) 0.1 to 10% of a solution of an copper salt;

(b) 0.1 to 10% of a solution of gallic acid or an alkyl ester of gallic acid or a mixture thereof;

(c) 0.1 to 10% of a solution of an iron salt; and

(d) instructions for use.

Detailed description of the Invention

These and other aspects, features and advantages will become apparent to those of ordinary skill in the art from a reading of the following detailed description and the appended claims. For the avoidance of doubt, any feature of one aspect of the present invention may be utilized in any other aspect of the invention. The word "comprising" is intended to mean "including" but not necessarily "consisting of or "composed of." In other words, the listed steps or options need not be exhaustive. It is noted that the examples given in the description below are intended to clarify the invention and are not intended to limit the invention to those examples per se. Similarly, all percentages are weight/weight percentages unless otherwise indicated. Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and/or use are to be understood as modified by the word "about". Numerical ranges expressed in the format "from x to y" are understood to include x and y. When for a specific feature multiple preferred ranges are described in the format "from x to y", it is understood that all ranges combining the different endpoints are also contemplated.

"Keratinous fibres" as used herein, is meant to include fibers which contain keratin of mammals including humans e.g. hair on the body and head. By colouring is meant changing the colour generally from grey which is a state where the keratin content is low to a colour which may include black or brown. Preferred colour to be achieved as per the present invention is brown with a minimal blue tint. A composition to achieve this may be generally classified as leave-on or rinse off, preferably rinse off. This may be achieved by including the actives in well known hair care products like shampoo, conditioner and combinations of these.

The first aspect of the invention provides for a method of colouring keratinous fibers comprising the steps of (a) contacting the keratinous fibers with a complex of an copper salt with gallic acid or an alkyl ester of gallic acid or a mixture thereof; followed (b) by rinsing the fibers to be substantially free of the complex; followed by (c) contacting the hair with an iron salt.

Step (a) in the method above may be carried out by contacting the hair using a complex of copper with gallic acid / gallate that has been pre-prepared as a composition. When the complex is pre-prepared, it is preferred that the composition is prepared not more than 60 minutes, preferably not more than 20 minutes, further more preferably not more than 5 minutes before contacting the keratinous fibres. An alternate way of achieving this is to include the copper salt in a first composition and the gallic acid or the alkyl ester thereof in a second composition. The complex may be prepared insitu on the keratinous fibers by contacting the fibers first with the composition comprising the gallic acid or alkyl ester thereof followed by contacting the fibres with the copper salt. In a preferred aspect the fibers are first contacted with the copper containing composition followed by contacting the fibers with the gallic acid or alkyl ester thereof. When either of the sequential sub-steps of step (a) are carried out the sub-steps are preferably carried out not more than 30 minutes, preferably not more than 5 minutes apart.

The step of contacting the fibres with the pre-prepared complex of copper with gallic acid / gallate is preferred over the sequential sub-steps described above. The copper salt is preferably copper chloride, copper formate, copper sulfate, copper tartarate, or copper gulconate, more preferably copper chloride or copper formate. The copper salt is preferably used as an aqueous composition at 0.1 to 10 wt%, preferably 0.5 to 5 wt% by weight of said aqueous

composition.

Gallic acid and its esters have the structure:

Gallic acid Methyl gallate Ethyl gallate Propyl gallate

The alkyl ester of gallic acid preferably has the alkyl chain length of 1 to 4 carbon atoms of which ethyl, methyl or propyl gallate is preferred. Of these methyl or propyl gallate are further more preferred. The gallic acid or the alkyl ester thereof is preferably used as an aqueous composition at 0.1 to 10 wt%, preferably 0.2 to 2 wt% by weight of said aqueous composition.

Alternately and as a preferred aspect, the gallic acid is present as an extract of a plant species of the Terminalia genus, or an extract of Embelica officinalis, or Mucuna pruriens. Of these, the extract of the Terminalia or Embelica species is preferred. The extract is preferably of the leaf, stem, seed, flower or fruit of the above plant. A suitable method of preparing an extract of the plants comprises the steps of

(i) Extracting the plant source with a hydroalcoholic solvent comprising 50 to 90% of a C1 - C3 alcohol at a temperature of 70 to 85° C for 10 to 60 minutes;

(ii) separating the solvent from the mixture; and

(iii) Concentrating and drying the solvent extract to prepare the desired

extract. The complex is formed ex-situ or insitu by reaction of a copper salt with gallic acid or alkyl ester of gallic acid. In this, the more preferred copper salts are copper chloride or copper formate. The copper salt is preferably present in aqueous solution at a pH in the range of 2 to 6 more preferably 3 to 5. The aqueous solution of the copper salt is preferably at a concentration of 0.5 to 5 %. Once the copper - gallate complex is formed, the pH is preferably in the range of 3 to 6. The weight ratio of the copper salt to gallic acid / ester is in the range of 5:1 to 0.5:1 .

Once the fibers have been treated with the copper - gallate complex, they are rinsed with plenty of water to be substantially free of the complex.

The keratinous fibers are then contacted with an iron salt. The iron salt is preferably iron chloride (II), iron chloride (III), iron gluconate, iron sulphate, iron ascorbate, or iron tartrate, more preferably iron chloride (II), or iron (II) gluconate. The iron salt is preferably used as an aqueous composition at 0.1 to 10 wt%, preferably 1 to 6 wt% by weight of said aqueous composition. A suitable way to enable the method of the invention is to carry out step (a) by including the copper salt and the gallic acid / alkyl gallate in a shampoo composition. It is possible that both the copper salt and the gallic acid / gallate are mixed together in the shampoo. A more preferred option is that the copper salt and the gallic acid / gallate are included in two separate compartments of a shampoo composition and are mixed just prior to application on to the keratinous fibres which need to be coloured. The iron salt is preferably included in a conditioner composition. Alternately the copper salt and the gallic acid / gallate are included in a composition in the form of a gel / cream which are of a leave-on nature. After a predetermined period of time of contact of this composition with the desired keratinous fibrers, they may be rinsed off with water and a leave-on composition, say in the form of a cream or gel may then be applied to the fibers to enable the method of the invention.

According to another aspect of the present invention there is provided a kit for colouring keratinous fibers comprising

(a) 0.1 to 10% of a solution of a copper salt;

(b) 0.1 to 10% of a solution of gallic acid or an alkyl ester of gallic acid or a mixture thereof;

(c) 0.1 to 10% of a solution of an iron salt; and

(d) instructions for use.

The invention will now be illustrated with the help of the following non-limiting examples. Examples

Comparative Examples A to J: Methods outside the invention; and

Example - 1 : Method as per the invention

Several experiments were conducted as described below which involved first treating hair with a shampoo composition followed by rinsing with water followed by treating hair with a conditioner composition.

The shampoo composition and the conditioner composition are given below:

Shampoo composition:

All experiments were performed on switches of white yak hair as the starting substrate. The colour of the white yak hair was measured using the following method:

A Minolta CR-10 hand held color reader was used to measure the colour of hair switches. This instrument measures reflected light using 8° illumination/diffuse viewing and gives the colour difference - expressed in L ^* a ^* b ^* and dE ^* or L ^* C ^* H ^* and dE ^* . For the current studies, measurements were made in L ^* a ^* b ^* .

The white yak hair had the following L ^* a ^* b ^* value

L ^* = 74.2, a ^* = 1 .3, b ^* = 7.1

The colouring method involved the following steps. The switches of white yak hair were first dipped in distilled water and then treated with the shampoo (0.2 g/ g hair) for 5 minutes. They were then washed well and then treated with the conditioner composition (0.2 g/ g hair) for 5 minutes. The hair switches were then washed once more under running water. This cycle was repeated 4 times. The hairs were then dried using a hair drier and the colour intensity was measured using a chromameter (CR 10). The desired values for the coloured hair are

L ^* < 50

b ^* between -0.5 and 8.

The above desired values indicate that the hair has become sufficiently black (L ^* < 50) and the blueness is minimised and the browness enhanced (b ^* between -0.5 and 8). The various examples A to J were carried out using different Active A and Active B as shown in Table - 1 . The results in terms of the L ^* a ^* b ^* values of the coloured hair switches of the various experiments are summarised in Table - 1 .

Table -1

The data in Table -1 above indicates that using conventional methods (Examples A to J) one is not able to obtain the desired colour charactertics i.e either the L ^* value is higher than 50 or the b ^* value is not in the desired range (-0.5 to 8). But when one uses the method of the invention (Example - 1 ) the desired colour is obtained.

Examples 2 & 3 and Example K: Experiments carried out in pure aqueous media

Further experiments were carried out in pure aqueous media as follows.

Switches of white yak hair having the colour characteristics

L ^* = 74.2, a ^* = 1 .3, b ^* = 7.1

were used as representative grey hairs. They were dipped in distilled water and then dipped in a solution containing Active A for 30 minutes. They were then washed with water and then dipped in a solution containing Active B for 5 minutes. The hair switches were then washed with shampoo and rinsed with plenty of water. The hairs were then dried using a hair drier and the colour intensity was measured using a chromameter (CR 10).

The examples 2 and 3 and K were carried out using different Actives A and Active B as shown in Table - 2. The results in terms of the L ^* a ^* b ^* values of the coloured hair switches of the various experiments are summarised in Table - 2.

Table -2

The data in Table - 2 indicates that method as per the invention (Examples 2 and 3) are able to colour hair to the desired tones while a conventional method Example K does not provide that benefit.

The invention thus provides for a method of colouring keratinous fibers where the desired level of blackness is obtained while minimising blueness and enhancing browness.