DESC:FIELD OF THE INVENTION
The present invention provides for hair protein bound molybdenum-tannic acid complex comprising Mo bound polygalloyl glucose suitable as hair colouring agent and hair colouring formulations/ kit comprising the same. More particularly, the present invention relates to the method of colouring the hair with said hair colouring formulation/ kit comprising sequential application of the hair colouring ingredients of sodium molybdate followed by tannic acid in selective amounts with optional involvement of pH modifiers/ pH adjusting agents and/ or sonication for attaining said hair protein bound molybdenum-tannin complex based stable, wash proof and non-toxic hair colour in shades selected from brown to burgundy.
BACKGROUND ART
Commonly used hair colouring technique involves oxidative colouring agent, oxidizing agent and swelling agents. This combination is vigorously affecting physical properties of the natural hair i.e. strength, shinning. Also, these chemicals are hazardous to health. Few natural dyes such as henna and indigo are used for hair colouring; however the colour is not stable. Some metal compounds, such as lead sulfide [Walter et al., Early Use of PbS Nanotechnology for an Ancient Hair Dyeing Formula, Nano Lett., 2006, 6 (10), pp 2215–2219], mercury sulfide [G. Patriarche et al., Characteristics of HgS nanoparticles formed in hair by a chemical reaction, Philosophical Magazine,2013, 93:1-3, 137-151] and metal nanoparticles, such as gold nanoparticles [S. D. Haveli et al., Hair Fiber as a Nanoreactor in Controlled Synthesis of Fluorescent Gold Nanoparticles, Nano Lett., 2012, 12, pp 6212–6217] and semiconductor nanoparticles [Use of luminescent semiconductor nanoparticles in cosmetics, EP 1440681 A1, 2004] are also reported for hair colouring application. However it takes long time (3-16 days) and also affects the mechanical behavior of the hair.
Metal complexes are reported to be used in hair colour as catalyst, though this process needs oxidizing agent like hydrogen per oxide [Catalysed dye systems, US 8,535,391 B2. 2013] and works in acidic pH. Another aspect of hair colour by metal complex is the production of desired colour shade. Different metals produce different shades based on the complex formation, concentration, pH and time. In the context of the present invention only water insoluble Mo-salts are reported to be used as catalyst in hair colour [Catalysed dye systems, US 8,535,391 B2. 2013]. WO2011157666 A1 describes hair colouring formulation containing beetroot extract, an oxidizing agent, a basifying agent and optionally a metallic derivative that is based on oxidative hair colour wherein the incorporation of metal compounds are optional.
Usually while the selection of precursors and treatment conditions the solubility of the precursors, toxicity of the precursors, production of desired shade by addition of base by involving cheap and easily available chemicals remains the pre-requisites to be met for the development of suitable hair colour, there is a strong need in the art to provide for hair colour formulations/ compositions that would impart various colour shades by simple change of the pH and/ or treatment time to provide for increased variance of colours by employing minimum possible ingredients and its amount that may favourably be water soluble and also non-toxic to skin and hair.
OBJECTS OF THE INVENTION
It is thus the primary object of the present invention to provide for a hair colour formulation/composition that would impart various colour shades on the hair by simply changing the pH and/ or treatment time.
It is another object of the present invention to provide for said hair colour formulation/composition that would enable creation of various colour shades by employing minimum amount of precursors that would be preferably water soluble precursors and hence be non-toxic for topical application.
It is yet another object of the present invention to provide for said hair colour formulation/composition that would involve precursors that would be water soluble and yet provide for said hair colour that would be stable to several wash cycles.
It is still another object of the present invention to provide for said hair colour formulation/composition that would on one hand impart colour to the hair and on the other would also possess antimicrobial properties (antidandruff) to favour an additional advantage.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided a molybdenum-tannic acid complex comprising Mo bound polygalloyl glucose, a complexation product of water soluble precursors of sodium molybdate and tannic acid adapted to impart stable wash proof colour on hair and bind to hair protein in being generated inside the hair shaft.
According to another aspect of the present invention there is provided a hair colouring agent comprising effective amounts of molybdenum-tannic acid complex comprising Mo bound polygalloyl glucose as a stable wash proof colour stable to upto at least 15 washes that binds to hair protein by coordination and non-covalent interactions.

According to another preferred aspect of the present invention there is provided a hair colouring agent involving the precursors of sodium molybdate in the levels of 0.1-2 M and tannic acid in the levels of 0.01-0.3 M in water base favouring molybdenum-tannic acid complex suitable for colouring the hair in colour shades selected from brown and burgundy.
According to another aspect of the present invention there is provided a hair colouring kit/formulation for hair colour comprising
a. sodium molybdate in the levels of 0.1-2 M as a water based hair colour active combination;
b. a tannin source providing tannic acid in the levels of 0.01-0.3 M as a water based hair colour active combination;
c. instructions for sequential addition of sodium molybdate, tannin, for generating molybdenum-tannin complex dye based stable wash proof colour on the hair.
Preferably in said hair colouring kit/formulation said colour involves shades including brown and burgundy.
More preferably, said hair colouring kit/formulation comprises selectively pH modifiers, adjusting agents, dyes suitable for complex formation.
Advantageously said hair colouring kit/formulation comprises pH modifiers in the levels of 1-10 wt % of the formulation favouring generation of the pH range to facilitate swelling of the hair and cuticle for enhanced tannic acid penetration and complex formation with sodium molybdate and to favour lower R, G, B values of ~125, 95, 56 after 30 min and 6 h of treatment in Na-molybdate and tannic acid, respectively.
Preferably in said hair colouring kit/formulation said pH modifiers/adjusting agents selected from K2CO3, Na2CO3, NaHCO3, triethanol amine, aq.NH3.
Most advantageously, said hair colouring kit/formulation comprises pH modifiers/adjusting agents of aq.NH3 for darkest colour shade with R,G,B value of about 125, 95, 56 after 30 min treatment in N-molybdate followed by 6 hours of treatment in tannic acid
Preferably, said hair colouring kit/formulation possesses antidandruff/ antimicrobial properties effective against dandruff causing organisms.
According to another preferred aspect of the present invention there is provided said hair colouring kit/formulation suitable for application on the hair involving treatment times of 30 min to 24 hrs with or without sonication.
According to another aspect of the present invention there is provided a method of colouring the hair comprising sequentially applying the hair colour ingredients of the hair colouring kit/ formulation selected from
a. sodium molybdate in the levels of 0.1-2 M as a water based hair colour active combination;
b. a tannin source providing tannic acid in the levels of 0.01-0.3 M as a water based hair colour active combination;
c. optionally applying pH modifiers/ pH adjusting agents and/ or sonication for attaining said molybdenum-tannin complex dye based stable wash proof colour on hair in shades selected from brown and burgundy.
Preferably in said method said sequential application of the hair colour ingredients involve water based colouring of hair following the sequence of:
a. providing sodium molybdate on grey and/ or beached hair with or without pH modifiers/ pH adjusting agents on hair for application time of about 30 mins;
b. providing a tannin source involving tannic acid solution with or without pH modifiers/ pH adjusting agents involving total application time of 6 hrs to 24 hrs at room temperature to obtain brown or burgundy coloured hair therefrom.
Preferably in said method said step (a) optionally involves sonication for about 30 mins while applying sodium molybdate on grey and/ or beached hair with or without pH modifiers/ pH adjusting agents.
More preferably in said method said step (b) optionally involves application of suitable dyes having complex forming ability with water soluble sodium molybdate selected from alizarin, 2-hydroxy-1-4-naptha chinon and 2.5-dihydroxy-p-benzochinon complexes to provide variations in colour shades including the colour shades of brown and burgundy.
According to another preferred aspect of the present invention there is provided said method of colouring the hair involving molybdenum-tannin complex/dye imparting stable wash proof colour on the hair free of any p-PDA based ingredients (p-Phenylenediamine: an oxidative dye commonly used) and other toxic ingredients.
The present invention is described hereunder in greater details in relation to the non-limiting exemplary illustrations and figures.
BRIEF DESCRIPTION OF THE FIGURES
Fig. 1: Illustrating reaction schematics between tannic acid and Na2MoO4 towards the formation of the complex;
Fig. 2: SEM image showing the deposition of Mo-complex at the cuticle edges;
Fig. 3: Step 1: illustrating the treatment of gray hair in sodium molybdate (Na2MoO4,) solution for 30 min, Step 2: Transfer hair from step one to tannic acid potassium carbonate solution and allowed for several hours;
Fig. 4: Bleached hair treated with Na-molybdate (2M) 30 min followed by treatment with tannic acid (0.01-0.3 M) for 24 hours, (a) without base, (b) with base;
Fig. 5: Bleached hair treated with Na2MoO4 (2M) 30 min followed by treatment with tannic acid (2 M) and base solution;
Fig. 6: Bleached hair treated with Na2MoO4 (2M) and base mixture for 30 min followed by treatment with tannic acid (2 M) and base solution;
Fig. 7: Bleached hair sonicated with Na2MoO4 (2M) for 30 min followed by treatment with tannic acid (2 M) and base solution;
Fig. 8: Illustrations of colours attained on the hair with dyes other than tannin with Na-molybdate.
DETAILED DESCRIPTION OF THE INVENTION
As discussed hereinbefore the present invention provides for molybdenum-tannic acid complex comprising Mo bound polygalloyl glucose, a complexation product of water soluble sodium molybdate and tannic acid as precursors that binds to hair protein inside the hair shaft to thereby generate a stable wash proof colour on the hair that is stable to upto at least 15 washes. A hair colouring agent comprising said molybdenum-tannic acid complex is also provided together with a hair colouring kit/formulation comprising effective amounts of hair colouring precursors of sodium molybdate and tannin acid with instructions for sequential addition of said precursors for generating molybdenum-tannin complex dye based stable wash proof colour on the hair.
Molybdenum occurs naturally in various oxidation states. It is also present in the form of complex (e.g., enzyme) in plants and animals. MoO42- containing salts have some solubility in water, however, other than Na2MoO4, most of the other molybdenum compounds are less-soluble in water.
Tannic acid is polygalloyl glucose (Fig. 1), it can form complex network of supramolecular structure, which has higher molecular weight and strongly bind to hair protein by co-ordination as well as by non-covalent interaction.
It has been surprisingly found by way of the present invention that the precursors of water soluble Na2MoO4 with natural dye tannic acid could form strong molybdenum-tannic acid complex inside the hair shaft, which can produce stable wash proof colour on hair. Alteration of pH and treatment-time leads to various penetration depths and intensity of colour formation in the hair shaft. While tannic acid or Na-molybdate alone cannot facilitate hair colouration it is thus the significant finding of the present invention that when precursors sodium molybdate and tannic acid are applied sequentially in selective amounts on hair, formation of said molybdenum-tannic acid complex takes place inside the hair shaft thereby generating stable wash proof colour on hair selected from brown and burgundy. The precursor’s when applied on hair only in selective amounts enables generation of said hair colour which otherwise leads to either very dull colour or results in rapid precipitation outside the hair leading to uneven/non-uniform hair colouration.
The sequence of application of the precursors is another important finding of the present invention for colour generation and intensity that could be attained based on diffusion of precursor compounds. If Na-molybdate is applied initially, the same ensures diffusion of both precursors inside the hair whereas an initial tannic acid application on the hair leads to thick precipitate formation outside hair that blocks further sodium molybdate diffusion resulting in less-colour.
Advantageously, it was also found by way of the present invention that hair colouring kit/formulation optionally in combination with a base produces intense colour in the absence of which the colour is light. Moreover, combination of a base with both the precursors produces darker colour as compared to the combination of a base with single precursor
While water insoluble Mo-salt like MoS2 or sparingly soluble MoO3 fail to produce any colour on hair when used with tannic acid, Na-molybdate successfully yields stable colour on hair.
Fig. 2 shows such deposition of the tannin-Mo-complex at the cuticle edges on hair surface based on the SEM image. Molybdenum complex of alizarin, 2-hydroxy-1-4-naptha chinon and 2.5-dihydroxy-p-benzochinon has also been investigated for hair colouring. The above complexes produced dark blue, brown and pinkish maroon colour, respectively. Changing pH using NH3 solution, or K2CO3, in the above complex, makes the colour darker with lower RGB values.
Molybdenum complex of tannic acid is stable to several tap-water wash as well as after shampoo wash upto at least 15 times.
While molybdenum-tannic acid complex is neither known nor is known for use in hair colour, and at higher concentration the molybdenum salt forms gel with tannic acid, it was thus a significant finding of the present invention that sequential application of sodium molybdate in selective concentration followed by tannic acid on hair could effectively colour the hair by forming a complex bound to hair protein by coordination and non-covalent interactions inside the hair shaft to generate a stable, non-toxic and wash proof colour on the hair as per the steps of application illustrated in Fig. 3.
Formation of complex and colouring
Tannic acid is obtained from Sigma Aldrich, China.

While neither tannic acid nor Na-molybdate individually can create any colour on hair, when applied sequentially in selective concentrations on hair the formation of complex takes place inside the hair that binds to the hair protein by coordination and non-covalent interactions. For this purpose the hair is treated with water soluble Na-molybdate followed by tannic acid in desired concentrations to form the hair protein bound complex to thus give stable wash proof colour in various shades of brown to burgundy.
In another aspect of the invention hair colouring kit/formulation is provided comprising
a. sodium molybdate in the levels of 0.1-2 M as a water based hair colour active combination;
b. a tannin source providing tannic acid in the levels of 0.01-0.3 M as a water based hair colour active combination;
c. instructions for sequential addition of sodium molybdate, tannin, for generating molybdenum-tannin complex dye based stable wash proof colour on the hair.
Below the working concentration ranges as mentioned above very dull colour forms and above the mentioned concentration due to rapid formation of the complex the same precipitated outside the hair resulting in uneven/non-uniform colouration.
According to yet another aspect of the present invention the sequence of addition of the components is important as the observed colour intensity is based on diffusion of precursor compounds and if Na-molybdate is applied first followed by tannic acid the same ensures diffusion of both precursors inside the hair where as random treatment with tannic acid followed by Na-molybdate leads to thick precipitate formation outside hair to block further diffusion of sodium molybdate resulting in only feeble colour.
The molybdenum complex based hair colour of the present invention while having hair colouring ability also has antimicrobial property therefore molybdenum complex based hair colour also shows antidandruff properties. This is an additional benefit along with the hair colour.
According to yet another aspect of the present invention it was found that the presence of base could produce intense colour favouring R,G,B value of at least ~ R=125, G=95, B=56, while in the absence of any base the colour is light. When base is present in one precursor then the colour is darker. When base is present in both the precursors then the colour is darkest, with the lowest RGB values. The images in Fig. 4 clearly illustrate the effect of base.
Grey hair was treated with sodium molybdate (Na2MoO4, 0.1-2 M) for 30 min and this metal treated hair was transferred to tannic acid solution (0.01-0.3 M) (Fig. 3). After treatment for 6 h the hair became golden brown colour. Increase of pH can open up the hair cuticles and allow maximum penetration of tannic acid inside the hair shaft. Therefore, sodium molybdate treated hair was further treated with tannic acid solution in presence of NH3 solution or potassium carbonate (K2CO3). The above process produces brown colour on gray hair after 6 h of dipping and the colour became darker after 24h of application. Colour intensity was increased further by increasing the treatment time. With increasing time darker brown colour was observed after 7 days.
Hair colour intensity study (L,a,b) and (R,G,B) of Na2MoO4 /Tannic acid coloured hair.
Five gram each natural grey hair was treated with Na2MoO4 (2 M) with aq.NH3 (25 % ) mixture solution for 30 min followed by treatment with tannic acid (0.2 M) with aq.NH3 (25 %) mixture solution for 6 and 24 hr produced brown colour. The (L, a, b) and (R, G, B) values of pre-treated hair is also included for comparison. To prove the wash-fastness L, a, b and R, G, B values are also recorded from a post colour swatch after 10 shampoo washes.

Table: 1
Treatment Time L, a, b R, G, B
Na2MoO4 (2 M) + Aq NH3 ?–
Tannic acid (0.2M) +
Aq NH3 6 hr 42.5, 6.9, 26.8 124.6, 95.1, 56.1
Na2MoO4 (2 M) + Aq NH3 ?–
Tannic acid (0.2M) +
Aq NH3 24 hr 38.9, 7.6, 26.3 115.9, 86.1, 48.8
Na2MoO4 (2 M) + Aq NH3 ?–
Tannic acid (0.2M) +
Aq NH3 6hr-after 10 shampoo washes 46,6,28 133,104,62
Without treatment, starting grey hair sample - 66,0.2,11 169,159.5,140.7

Table 1 above shows the L,a,b and R,G,B values of hair before any treatment, after 6 h, after 24 h (post metal treatment in tannic acid) and after 10 shampoo washes (post treatment wash). It clearly shows that the longer duration of treatment in tannic acid darken the shades. Also, after 10 shampoo washes there is no significant colour loss. Therefore, the developed hair colour is quite stable against shampoo wash.
Both the pH and colouring time are important in the present invention. In general NH3 produces darker shade than K2CO3 due to the higher pH of NH3 solution (2-5 %) than K2CO3. Also, step 1 and step 2 can be carried out with or without the addition of NH3 (basic condition). When NH3 was used in both the steps, darkest shade was obtained. Depending on the presence of NH3 the colour shade changes as per the following trends:

Colour intensity increasing
Figs. 5-6 show various shades of colour obtained on bleached hair after treatment with Na2MoO4 and tannic acid with or without the presence of base. Fig. 7 shows the effect of sonication on the colour intensity when the hair samples presented in Fig. 7 are sonicated for 30 min. The general observation is that sonication improves the intensity slightly. However, comparing the Fig. 6 and 7, it is clear that the contribution of NH3 (when mixed with Na2MoO4) is more than the contribution of sonication towards the colour intensity.
Fig. 8 illustrates the colours attained on the hair with alizarin, 2-hydroxy-1-4-naptha chinon and 2.5-dihydroxy-p-benzochinon complexes with water soluble Na2MoO4 however, the same showed reduction of colour intensity during subsequent washings.
It is thus possible by way of the present advancement to provide for hair protein bound complex of tannic acid and water soluble Na2MoO4 as hair colouring agent and hair colour formulations/ kit involving the same. The process of colouring the hair can be advantageously performed at room temperature under mild conditions suitable for colouring human hair that is stable to shampoo wash and is non-toxic that does not damage the hair. The colouring method of the present invention can also be advantageously extended to other dyes with higher complex formation ability with metals. Hence in the absence of any harmful chemicals various colour shades of burgundy to brown with very low RGB values could be produced.

,CLAIMS:We Claim:
1. A molybdenum-tannic acid complex comprising Mo bound polygalloyl glucose, a complexation product of water soluble precursors of sodium molybdate and tannic acid adapted to impart stable wash proof colour on hair and bind to hair protein in being generated inside the hair shaft.
2. A hair colouring agent comprising effective amounts of molybdenum-tannic acid complex
comprising Mo bound polygalloyl glucose as a stable wash proof colour stable to upto at least 15 washes that binds to hair protein by coordination and non-covalent interactions.
3. A hair colouring agent as claimed in preceding claim 2 involving the precursors of sodium molybdate in the levels of 0.1-2 M and tannic acid in the levels of 0.01-0.3 M in water base favouring molybdenum-tannic acid complex suitable for colouring the hair in colour shades selected from brown and burgundy.
4. Hair colouring kit/formulation for hair colour comprising
a. sodium molybdate in the levels of 0.1-2 M as a water based hair colour active combination;
b. a tannin source providing tannic acid in the levels of 0.01-0.3 M as a water based hair colour active combination;
c. instructions for sequential addition of sodium molybdate, tannin, for generating molybdenum-tannin complex dye based stable wash proof colour on the hair.
5. Hair colouring kit/formulation as claimed in preceding claim 4 wherein said colour involves shades including brown and burgundy.
6. Hair colouring kit/formulation as claimed in anyone of preceding claims 4 or 5 comprising selectively pH modifiers, adjusting agents, dyes suitable for complex formation.
7. Hair colouring kit/formulation as claimed in anyone of the preceding claims 4-6 comprising pH modifiers in the levels of 1-10 wt % of the formulation favouring generation of the pH range to facilitate swelling of the hair and cuticle for enhanced tannic acid penetration and complex formation with sodium molybdate and to favour lower R, G, B values of ~125, 95, 56 after 30 min and 6 h of treatment in Na-molybdate and tannic acid, respectively.
8. Hair colouring kit/formulation as claimed in anyone of preceding claims 4-7 wherein said pH modifiers/adjusting agents selected from K2CO3, Na2CO3, NaHCO3, triethanol/monoethanol amine, aq.NH3.
9. Hair colouring kit/formulation as claimed in anyone of preceding claims 4-8 comprising pH modifiers/adjusting agents of aq.NH3 for darkest colour shade with R,G,B value of about 125, 95, 56 after 30 min treatment in N-molybdate followed by 6 hours of treatment in tannic acid.
10. Hair colouring kit/formulation as claimed in anyone of preceding claims 4-9 with antidandruff/ antimicrobial properties effective against dandruff causing organisms.
11. Hair colouring kit/formulation as claimed in anyone of preceding claims 4-10 suitable for application on the hair involving treatment times of 30 min to 24 hrs with or without sonication.
12. A method of colouring the hair comprising sequentially applying the hair colour ingredients of the hair colouring kit/ formulation selected from
a. sodium molybdate in the levels of 0.1-2 M as a water based hair colour active combination;
b. a tannin source providing tannic acid in the levels of 0.01-0.3 M as a water based hair colour active combination;
c. optionally applying pH modifiers/ pH adjusting agents and/ or sonication for attaining said molybdenum-tannin complex dye based stable wash proof colour on hair in shades selected from brown and burgundy.
13. A method as claimed in preceding claim 12 wherein said sequential application of the hair colour ingredients involve water based colouring of hair following the sequence of:
a. providing sodium molybdate on grey and/ or beached hair with or without pH modifiers/ pH adjusting agents on hair for application time of about 30 mins;
b. providing a tannin source involving tannic acid solution with or without pH modifiers/ pH adjusting agents involving total application time of 6 hrs to 24 hrs at room temperature to obtain brown or burgundy coloured hair therefrom.
14. A method as claimed in anyone of preceding claims 12 or 13 wherein said step (a) optionally involves sonication for about 30 mins while applying sodium molybdate on grey and/ or beached hair with or without pH modifiers/ pH adjusting agents.
15. A method as claimed in anyone of preceding claims 12-14 wherein said step (b) optionally involves application of suitable dyes having complex forming ability with water soluble sodium molybdate selected from alizarin, 2-hydroxy-1-4-naptha chinon and 2.5-dihydroxy-p-benzochinon complexes to provide variations in colour shades including the colour shades of brown and burgundy.
16. A method of colouring the hair as claimed in anyone of preceding claims 12-15 involving molybdenum-tannin complex/dye imparting stable wash proof colour on the hair free of any p-PDA based ingredients (p-Phenylenediamine: an oxidative dye commonly used) and other toxic ingredients.

Dated this the 18th day of September, 2015

Anjan Sen
Of Anjan Sen and Associates
(Applicants Agent)