DESC:Field of the Invention
The present invention provides for a hair colouring formulation/kit for colouring the hair in variable shades ranging from dark brown to black involving simply a developer and silver salt enabling wash fast black colour on hair in a reduced application time and even as a one stage process. Advantageously, hair colour formulation is directed to being free of harmful chemicals like p-PDA (p-phenylenediamine) and peroxide (H2O2) and would thus find wide end use and application for colouring various types of hair, e.g. bleached hair to natural gray hair.
Background Art
Covering grey hair is one of the important cosmetic needs in todays developing worlds. The most used hair colour which is avaialble for providing natural black or other black/brown shade is para-phenylenediamine (p-PDA) hair colour. However, it is already known fact that p-PDA is toxic, it casues skin irritation and other skin diseases. Prolonged use of p-PDA may casue skin irritation, contact dermatitis, chemosis, lacrimation, exophthalmos, or even permanent blindness due to local contact. [a) Katsumi. I.; Yuichi. I.; Osamu. N.; Keisuke. N.; Nobuyuki. I. Carcinogenicity and toxicity tests on p-phenylenediamine in F344 rats. Toxicology Letters. 1983, 16, 259-269. b) Anuradha. S.; Arora. S.; Mehrotra. S.; Arora. A.; Kar. P. Acute Renal Failure Following para-Phenylenediamine (PPD) Poisoning: A Case Report and Review. Renal Failure, 2004, 26, 329-332. Hooff. G. P.; van Huizen. N. A.; Meesters. R. J. W.; Zijlstra. E. E.; Abdelraheem. M.; Abdelraheem. W.; Hamdouk. B. M.; Lindemans. J.; Luider. T. M. PLoS One, 2011, 6, e22191. Singla. S.; Miglani, S.; Lal. A. K.; Gupta. P.; Agarwal. A. K, JIACM, 2005, 6, 236-8.]
Therefore, there is a need to develop an alternate p-PDA free hair colour, which will deliver the colour shade as dark as p-PDA and at the same time it will not cause any harm to the user. In this backdrop, many scientists are involved to develop a p-PDA free hair colour. Many p-PDA drivatives [US 6,228,130 B1; US 7,905,926 B2] and amino phenol derivative with less sensitization potential are prepared and tried for hair colour [US 5,980,584; US 6,074,438]. Hetrocylic compound such as tetramino pyrimidine (TAP) and its derivative as a developer is one of such method due to their less-toxic nature. TAP and its derivatives along with several other couplers are reported to produce different shades of colour other than black [US 4,003,699; US 4,745,652].
Natural dyes such as catechins, gallic acid and gallates along with silver salts are reported for hair colouring [WO2013078492 A2]. Nanoparticle is another source of hair dye to colour the hair. Nanoparticles formed in and out side of hair shaft have been utilized to produce permanent colour. Nanoparticle formed by metal such as lead, mercury and gold are reported for hair colouring application, however, it takes long time of about 3-16 days [S. D. Haveli et al., Hair Fiber as a Nanoreactor in Controlled Synthesis of Fluorescent Gold Nanoparticles, Nano Lett., 2012, 12, pp 6212–6217; G. Patriarche et al., Characteristics of HgS nanoparticles formed in hair by a chemical reaction, Philosophical Magazine, 93:1-3, 137-151; EP 1440681 A1].
US 2007/0277330A1 describes various formulations employing TAP-sulphate. They have used various couplers and other oxidative dyes including p-PDA to achieve hair colour in various colour shade minus black.

US 2003/0066140 discloses hair colour formation by using transition metal salt followed by treatment of peroxygen oxidizing agent and an oxidative hair colouring agent which cover a range of organic compounds including p-PDA and TAP.

US patent RE30199 (patent No. 4003699) teaches hair dye formulation using tetraminopyrimidine developers along with many different couplers. 123 different combinations of TAP and other couplers in presence of atmospheric oxygen or 1 % H2O2 led to the achievement of various colour shades. However, dark black shade could not be achieved using all their possible combination.

US4745652 describes the use of tetraminopyrimidine derivatives for colouring hair. 8 different TAP derivatives as a developer and 18 different couplers were used for 33 formulations to achieve various colour shades of blue, green, violet, red, burgundy and brown. Black colour could not be achieved.

CA 2856937 A1 (WO2013078492A2, WO2013078492A3) describes the method of colouring keratin fiber specially eye brows and eye lashes using cathechins, gallic acids, gallates and mixture thereof with a silver salt. Various fruit extracts were used as the source materials. Additionally, various organic developers/couplers (including TAP and p-PDA) were used to achieve various shades.

Reference is invited to co-pending (Indian Patent Application No. 1599/CHE/2014) directed to silver nanoparticles based hair colouring formulation involving water soluble silver salts and other reducing agents like ascorbic acid, Na/K tartarate, hydroquinone, maltodextrin. Black and black-brown shade on the hair was achieved using this method. While the RGB values attained were around 50-60, the method of colouring the hair involving the ingredients of this co-pending prior formulation was two step method. Single step method, which is considered convenient for the application purposes could not be applied to this co-pending formulation. Therefore, it is challenging to make hair colour much darker by using a user friendly formulation in a single step method.

It is also a longfelt need in the art to overcome the challenges in developing p-PDA free hair colour formulation that are also free of other harmful chemical such as H2O2 and would yet produce desired brown/ black shade on the hair in one application and in reduced application time.

Objects of the Invention
Thus the primary object of the present invention is to provide for hair colouring formulation/kit free of toxic ingredients like p-PDA, H2O2 that would yet provide for brown/ black colour on the hair in reduced application time preferably in one application.

It is another object of the present invention to provide for said hair colour formulation/kit that would provide for various colour shades involving selectiveratio of ingredients and treatment time.

It is yet another object of the present invention to provide for said hair colour formulation/kit that would use minimum possible amount of ingredients to generate colour on hair.

It is still another object of the present invention to develop a hair colour, which could produce intense black and black-brown shade using a user friendly single step method in reduced application time.

Summary of the Invention

Thus according to a basic aspect of the present invention there is provided a hair colouring formulation/ kit comprising
a. tetraaminopyrimidine (TAP) developer;
b. water soluble silver salt; and
c. pH modifier;
with or without other hair care benefiting agents.

Preferably said hair colouring formulation/ kit is provided wherein concentrations of silver salt and TAP vary in the ratio of 1:4-4:1 favouring variable colour shade ranging from dark brown to black and variable intensity on hair in application time of only about 20 mins that is stable to upto at least 25 shampoo wash cycles.

According to another preferred aspect of the present invention there is provided said hair colouring formulation/ kit wherein
said (a) TAP is in the range of 0.3-1.24 % wt./v;
said (b) water soluble silver salt is in the range of 0.2-2.4 % wt./v;
said pH modifier is in the range of (i) 6-15% v/v, enable desired concentration and time dependent generation of hair colour actives in the hair shaft to favour variable shades and intensity of colour from dark brown to black.

According to yet another preferred aspect of the present invention there is provided said hair colouring formulation/ kit comprising a water based formulation of ingredients suitable for application and wherein water soluble silver salt in the range of 0.62-2.4 % wt./v favours dark black colour on hair in one application.

According to yet another preferred aspect of the present invention there is provided said hair colouring formulation/ kit wherein said water soluble silver salt includes silver nitrate (AgNO3), silver acetate; and wherein said pH modifiers are selected from ammonia, monoethanol amine to favour increase of pH of the formulation and swelling of the hair during application of ingredients for in-situ colour generation.

Preferably said hair colouring formulation/ kit is provided comprising a package having atleast one set of said
a. tetraaminopyrimidine (TAP) developer;
b. water soluble silver salt; and
c. pH modifiers selected from ammonia, monoethanol amine in varied concentrations for generation of variety of shades and intensity of colour from dark brown to black.

According to another preferred aspect of the present invention there is provided a process for the manufacture of said hair colouration formulation/ kit comprising
a. providing said atleast a tetraaminopyrimidine (TAP) developer;
b. providing said atleast a water soluble silver salt; and
c. providing said atleast a pH modifier with or without other hair care benefiting agents,and instructions for mixing to favour swelling of hair and in-situ colouration of hair.

According to another aspect of the present invention a process for colouring the hair in variable shades and intensity ranging from dark brown to black comprising
applying ingredients of hair colouring formulation/kit comprising tetraaminopyrimidine (TAP) developer, water soluble silver salt and a pH modifier for in-situ generation of hair colour actives under ambient conditions to thus attain coloured hair in variable shades and intensity ranging from dark brown to black therefrom.

Preferably said process for colouring the hair is provided which is carried out as a single stage process comprising applying ingredients
said (a) TAP is in the range of 0.3-1.24 % wt./v;
said (b) water soluble silver salt is in the range of 0.62-2.4 % wt./v;
said pH modifier is in the range of (i) 6-15% v/v; and thereby in-situ generation of hair coloured actives in the hair shaft of variable shades and intensity of colour on hair ranging from dark brown to black.

More preferably, said process of colouring the hair involves progressive hair colouration wherein water soluble silver salt concentration of 0.2-0.6 % wt./v favours dark black on hair in plurality of applications and under reduced consumption of ingredients.

According to another preferred aspect a process for colouring the hair is provided which is carried out as two stage process comprising the steps of
a. applying a water solution of silver salt on hair in basic pH range of 9-11 involving an application time of about 10-15 mins;
b. applying a solution of TAP on water soluble silver salt treated hair involving an application time of about 10-15 min; and obtaining brown and/ or black coloured hair therefrom.

Advantageously, a process for colouring the hair in shades of dark black colour comprising providing selective concentrations of TAP:0.55-0.65 % w/v, AgNO3: 1.14-1.35 wt% w/v, and NH3 : 8-9 % v/v on hair under ambient conditions and obtaining dark black coloured hair therefrom.

Detailed Description of the Invention
As discussed hereinbefore the present invention provides for a hair colouring formulation/ kit for colouring the hair in variable shades ranging from dark brown to black comprising
a. tetraaminopyrimidine (TAP) developer;
b. Water soluble silver salt (AgNO3, Ag-acetate etc.); and
c. pH modifier;
with or without other hair care benefiting agents.

Silver salts like silver nitrate and tetraaminopyrimidine (TAP) while both are non toxic and are reported in hair dye formulation separately with separate ingredients, and TAP being used as a developer only, this is for the first time both the chemicals are used in single stage hair colour formulation in combination with a pH modifier to produce dark black colour in much reduced application time.
It is thus surprisingly found by way of the present invention that a hair colour formulation comprising water soluble silver salt, tetraaminopyrimidine (TAP) developer together with a pH modifier favours brown to dark black colour on the hair in one application and in reduced application time of as low as 20 mins. Interestingly, it is for the first time that a developer like TAP produces black colour on hair in combination with silver. Advantageously, said hair colour formulation in one step process under mild conditions of room temperature, colours human hair in black shade that is stable to shampoo wash to upto at least 25 wash cycles without any change in colour shade, and most advantageously, in not using any toxic chemicals is safe for application and does not damage hair, skin and eyes.

The hair colour formulation of the present invention delivers colour on hair by the formation of hair colour actives including silver nanoparticles and/or Tetraaminopyrimidine-Ag-complex nanoparticles that effectively embed within the hair structure extending to the medulla region of the hair to generate a stable wash proof hair colour stable to upto at least 25 wash cycles. Nanoparticle formation is noted on surface as well as inside the hair shaft. Significantly, by mild variation in the formulation based on the wt % of the ingredients, the nanoparticle formation on the surface of the hair can be minimized/ avoided. Fig. 3 shows such topographical image of hair after colour application. Fig. 4 shows the formation nanoparticles inside the hair shaft. The nanoparticles are more in number in the cuticle region and gradually decrease towards the cortex region. The nanoparticles were found even in the medulla region of the hair. It is thus clearly seen from Fig. 4 that the black dots being silver nanoparticles and when one traverses from the left hand side of said Fig. 4, two layers of cuticles are visible and then cortex wherein the nanoparticles are still visible that also extend to the medulla and hence formation of intense colour in one application under reduced application time by using TAP could be due to the formation of nanoparticles deep inside the hair shaft (extending to the medulla region of the hair).
According to a preferred aspect of the present invention there is provided a hair colouring formulation/ kit wherein
said (a) TAP is in the range of 0.3-1.24 % w/v;
said (b) Water soluble silver salt (AgNO3, Ag-acetate etc.) is in the range of 0.62-2.4 % w/v;
said pH modifier is in the range of 6-15% v/v; enabling desired concentration and time dependent generation of silver nanoparticles and/or Tetraaminopyrimidine-Ag complex nanoparticles bound on hair favouring said variable shades and intensity of colour from dark brown to black.

Preferably, said hair colouring formulation/ kit comprises said ingredients for application in anyone or more forms including water solution, powders, creams.

According to another preferred aspect of the present invention there is provided said hair colouring formulation/ kit wherein said pH modifiers are selected from ammonia, monoethanol amine favouring increase of pH of the formulation and swelling of the hair during application.

According to yet another aspect of the present invention there is provided said hair colouring formulation/ kit favouring hair colouration in reduced application time of only about 20 mins, which hair colour is stable for upto at least 25 shampoo wash cycles showing no visual colour change.

Advantageously, said hair colouring formulation/ kit comprises plurality of sets of said
a. tetraaminopyrimidine (TAP) developer;
b. Water soluble silver salt (AgNO3, Ag-acetate etc.); and
c. pH modifier in varied concentrations for generation of variety of said shades and intensity of colour from dark brown to black.

According to another aspect of the present invention there is provided a process for colouring the hair in variable shades and intensity ranging from dark brown to black comprising generating a desired colour shade and intensity on hair involving selective concentrations of tetraaminopyrimidine (TAP), Silver salt and a pH modifier for desired generation of silver nanoparticles and/or Tetraaminopyrimidine-Ag complex nanoparticles inside hair under ambient conditions to thus obtain variable shades and intensity ranging from dark brown to black therefrom.

According to another preferred aspect said process for colouring the hair is carried out in two step process comprising the steps of
a. applying a solution of silver salt on hair in basic pH range of 9-11 involving an application time of about 10-15 mins;
b. applying a solution of TAP on silver salt treated hair involving an application time of about 10-15 min; and obtaining brown and/ or black coloured hair therefrom.

According to yet another preferred aspect a process for colouring the hair is provided in one step process comprising the steps of
a. applying a mix of silver salt, TAP and a pH modifier favouring pH range of the mix in the range of 9-11 for an application time of about 20-30 mins and obtaining brown and/ or black coloured hair therefrom.

According to yet another preferred aspect said process is provided wherein Ag-salt is applied in concentration in the range of 0.62-2.4 %, TAP concentration applied is in the range of 0.3 to 1.24 % and pH modifier applied in the range of 6-15% to favour an increase of pH of said formulation in the range of 9-11 and desired swelling of the hair during application.

According to another preferred aspect a process is provided wherein when the treatment time is varied from 5 min to 30 min involving varying concentrations of silver salt and TAP in a ratio of 1:4-4:1 favours applying different colour shade and intensity on hair.
Thus not only the concentration but also the ratio of water soluble Ag-salt and TAP was found to be important to achieve hair colour. Therefore, in the ratio range of silver salt: TAP = 1: 4 up to 4:1 acceptable shades could be achieved below and beyond which inconsistency, non-uniformity and over deposition of silver was observed.
It was also found by way of the present invention that pH modifier of 6-15% v/v gave acceptable colour shade. Lower than this concentration, inconsistency and non-uniformity of colouration on hair occurs and concentration more than this is unsafe for use wherein saturation is also noted at about 8 wt.% range.
The present invention is discussed hereunder in greater details in relation to the non-limiting exemplary illustrations and the figures wherein the figures involving photographs looks darker than actual.
BRIEF DESCRIPTION OF FIGURES
FIG. 1: illustrates in a flowchart the method of colour application by employing the hair colouring formulation/kit of the present invention;
Fig 2: illustrates dark black colour hair attained in a single step method of colouring natural gray hair;
Fig 3: illustrates SEM image showing the surface topography after colour application wherein no deposition on surface was found;
Fig 4: illustrates TEM cross-section of coloured hair showing formation of nanoparticles from cuticles to cortex region of the hair;

Fig. 5: illustrates brownish black colour on hair attained with low ammonia concentration;

Fig. 6: illustrates varying colour shade and intensity on hair with change in concentration of the ingredients and by changing the base.

The present invention thus provides for hair colour formulation/kit based on non-toxic precursors of silver salt and tetraaminopyrimidine (TAP) developer in combination with a pH modifier for external application, which favourably provides black/ brown shade on hair in one application and in reduced application time of only about 20 mins.
It is surprisingly found by way of the present invention that in presence of a pH modifier, water soluble silver salt and tetraaminopyrimidine (TAP), a developer in hair colour formulations, react by dissolving in water to produce dark colour (lower RGB values) of brown/ black on hair that is stable until upto several shampoo washes i.e. upto at least 25 shampoo cycles showing no visual colour change. The colour shade varies from brown to black depending on the ratio of ingredients, pH and treatment time. Colouring was due to the formation of silver nanoparticles and/or tetraaminopyrimidine-Ag-complex nanoparticles formation. Ammonia/MEA acts as a pH modifier and hair swelling agent.

Silver nitrate is used as an anti-microbial and present in various skin care products [a) Spacciapoli P, Buxton D, Rothstein D, Friden P. J Periodont Res 2001, 36, 108-113. b) Jung. W. K.; Koo. H. C.; Kim. K. W.; Shin. S.; Kim. S. H.; Park. Y. H.; Applied and Environmental Microbiology, Apr. 2008, 2171–2178] whereas Tetraaminopyrimidine (TAP) is also less toxic, a developer, that produces various colour shade with different couplers [Oxidation hair dyes based upon tetraaminopyrimidine developers. US 4,003,699; New tetra aminopyrimidine derivatives and their use in hair-dyeing preparations, US 4,745,652].
The present invention thus provides a hair colouring process based on said ingredients which is preferably a single stage process where hair is treated with 8ml water/g of hair with water soluble silver salt and tetraaminopyrimidine preferably in 2:1 ratio in presence of a pH modifier preferably ammonia for 10 to 30 min to produce varied colour shades on hair ranging from brown to black with different intensities. Colour of the hair varies from dark brown to natural balck depending on the concentration of precursor compounds and pH modifiers which delivers colour on hair by the formation of silver nanoparticles and/or Tetraaminopyrimidine-Ag-complex nanoparticles that effectively embed in the hair structure to generate a stable colour.

Example 1
The application of TAP in water soluble silver salt in a two stage process involves treatment of hair using aqueous silver salt in basic pH followed by the treatment with TAP. The pH of silver salt can be changed using ammonia solution, ethylene amine or any other pH adjusting compounds provided in amounts of 6-15% v/v. The Ag-salt concentration is in the range of 0.62-2.4 % w/v, concentration of TAP is in the range of 0.3 to 1.24 % w/v and pH range of 9-11. The total treatment time is 20-30 minutes (10-15 minutes each step). 30 minute treatment produces acceptable dark black colour on hair. The colour darkness can be changed by varying treatment time from 5 min to 30 min. Fig. 1 shows the colour application method in a diagram.

Example 2
The second method is to mix water soluble silver salt, TAP and a pH modifier solution preferably ammonia solution together and apply directly on hair. Here the single stage treatment time is 20-30 min. Similar to the two step method the colour intensity depends on the time and concentration. The range of Ag-salt concentration is 0.62-2.4 % w/v, concentration of TAP is 0.3 to 1.24 % w/v and the pH range of 9-11 provided by pH modifier taken in the range of 6-15% v/v. Fig. 2 shows a dark black coloured hair on natural gray hair using a single step method.

In said range of the ingredients employed in the process of the present invention as discussed above desired black colour could be obtained. Beyond the range lighter colour was obtained or in some cases deposition of silver took place on the surface of the hair which was not desired. SEM and TEM analysis of hair samples are illustrated under Figures 3 and 4 respectively. Fig. 3 shows such topographical image of hair after colour application. Fig. 4 shows the formation of nanoparticles inside the hair shaft. The nanoparticles are more in number in the cuticle region and gradually decrease towards the cortex region. The nanoparticles were found even in the medulla region of the hair.
It is thus clearly seen from Fig. 4 that the black dots being silver nanoparticles and when one traverses from the left hand side of said Fig. 4, two layers of cuticles are visible and then cortex wherein the nanoparticles are still visible that also extend to the medulla. The size of the nanoparticles is approximately 10-40 nm seen as dark black dots indicating the presence of high atomic weight element of silver producing enough contrast for TEM viewing and the TEM image could be retrieved without staining with heavy metal salt.
In the co-pending Indian patent Application 1599/CHE/2014 the reducing agents like ascorbic acid, Na/K tartarate, hydroquinone, maltrodextrin limits the nanoparticle formation upto a distance in the cortex whereas TAP of the present invention allows nanoparticle formation beyond the cortex and upto the medulla region and hence formation of intense colour using TAP in one application under reduced application time could be due to the formation of nanoparticles deep inside the hair shaft (extending to the medulla region of the hair).

Again beyond and below the stated range of the pH modifier such as ammonia though nanoparticles form, however, the colour imparted on hair was not the desired colour and the colour imparted was found to depend on the size of the particles as well as the concentration of the particles and/or also extent of the hair colour actives formed.

Fig. 5 clearly illustrates that when ammonia concentration is towards lower limit e.g. 6.2 % v/v of 25 % ammonia solution, with TAP: 0.62 % and AgNO3: 1.24 %, the colour shade obtained on hair is brownish black.
Example 3

The colour shade and intensity can be varied from dark brown to black by changing the concentration of Ag-salt and TAP and by appropriately choosing the ratio of TAP and Ag-salt and also by changing the type of base as illustrated below and demonstrated under Fig.6.

Change in base:
1. TAP: 0.62 % w/v, AgNO3 : 1.24 % w/v, Base: MEA (8.5 % v/v), Colour: dark brown
[With same concentration of ingredients different base NH3 (8.5 % of 25 % NH3 v/v) produces dark black colour]

2. TAP: 0.62 % w/v, AgNO3: 1.24 % w/v, different Base: K2CO3 (3.75 % w/v) Colour: Very light gray/brown with patches of uncoloured regions.

Change in TAP and AgNO3 concentration and ratio:
3. TAP: 0.31 % w/v, AgNO3: 1.24% w/v, Base NH3 (8.5 % of 25 % NH3 v/v), Colour: grayish black

4. TAP: 1.24 % w/v, AgNO3: 1.24 % w/v, Base: NH3 (8.5 % of 25 % NH3 v/v), Colour: Black, Hair became stiffer

5. TAP: 0.62 % w/v, AgNO3: 0.62 % w/v, Base NH3 (8.5 % of 25 % NH3 v/v), Colour: Brownish black

6. TAP: 0.62 %, AgNO3: 2.48 % w/v, Base NH3 (8.5 % of 25 % NH3 v/v), Colour: brown

Change in Ammonia concentration:
7. TAP: 0.62 %, AgNO3: 1.24 % w/v, Base NH3 (2.8 % of 25 % NH3 v/v), Colour: Light brown

Table 1 shows the change in RGB values (Row 1 vs. Row 2) when base is changed (NH3 or MEA) and change in RGB values when concentration of ingredients change (Row 1 vs. Row 3). When NH3 is used with certain ingredient concentrations RGB values are almost equal means the colour is black. However, with the same composition when base is changed to MEA, R value is more than G and B which means the shade is towards dark brown. When concentration is reduced keeping NH3 as base, again the R value is more compared to G and B, means dark brown shade. It is also an important finding of the present invention that the intensity of colour developed on the hair involving the formulation/ kit of the present invention further favourably gradually darkens with time beyond the values as presented collected soon after the colouring experiments were done.

It is thus possible for the present invention to provide for non-toxic precursors water soluble Silver salt and tetraaminopyrimidine (TAP) developer based hair colour formulation/kit for permanent dyeing of hair in presence of a pH modifier wherein advantageously the hair can be coloured in reduced application time in stable colour shades ranging from brown to black.

Table 1: Five gram each natural grey hair was coloured using TAP/AgNO3 in different concentration and base condition, keeping the TAP: AgNO3 ratio same. L, a, b value being representative colour space where L is lightness and a, b are colour-opponent dimensions of above hair was measured and the RGB values were calculated from Lab values. From the instrument L, a, b values were obtained that were later converted to RGB values.

Dye composition TAP : AgNO3 AgNO3 conc.% w/v L a b R G B
TAP- 250 mg (0.57 % w/v)
AgNO3- 500 mg (1.14 % w/v)
Water – 40 mL (91.43 % v/v)
Aq. NH3 (25 %) – 3.75 mL (8.57 % v/v) 1:2 1.14 18.34 -0.167 0.776 44.98 44.76 43.60
TAP- 250 mg (0.57 % w/v)
AgNO3- 500 mg (1.14 % w/v)
Water – 40 mL (91.43 % v/v)
MEA – 3.75 mL (8.57 % v/v) 1:2 1.14 18.158 0.680 1.131 46.08 43.96 42.73
TAP- 125 mg (0.29 % w/v)
AgNO3- 250 mg (0.57 % w/v)
Water – 40 mL (91.43 % v/v)
Aq. NH3 – 3.75 mL (8.57 % v/v) 1:2 0.57 16.559 2.552 1.867 45.76 39.64 38.37

Experiments were conducted using lower concentration of AgNO3 as well; like 0.2 %. In case of 0.2 % AgNO3, dark black colour was found after 2-3 repeated applications. To obtain the similar level of dark colour, repeated applications of lower concentration AgNO3 consume less amount of silver compared to the single application. With lower silver concentration as more than one application is required, lower concentration AgNO3 can be used for progressive hair colouring. In general when lower concentration of silver salt is used the colour will be brown. However, progressive application will make it black.
For example, 1.2 % w/v of Ag-salt with TAP (2:1 ratio) produces dark black colour. Lowering the concentration of Ag-salt (0.2 % w/v) and TAP keeping the ratio at same 2:1, single application results in brown colour. But consecutive application of the same formulation upto about three times (total Ag-salt consumption 0.2 % w/v x 3= 0.6 % w/v) enables similar dark black colour that is obtained upon use of higher wt.% 1.2 wt. % Ag-salt. Therefore, the progressive hair colouration could also be attained by the formulation of the present invention in about two-three steps also advantageously facilitating hair colouration by reduced wt % ingredients as compared to the wt% amount of ingredients involved in colouration in one application.

Table 2: Exemplary formulation for water based TAP/AgNO3 hair color formulation for 1 g of natural grey hair.
Example of water based colour formulation:
Ingredients Amount
Tetra amino pyrimidine (TAP) 0.05 g
Silver nitrate 0.1 g
aq NH3 (25%) 0.75 mL
Water 8 mL

More advantageously, the formulation of the present invention can also be provided in various forms including cream, shampoo and the like formulations.

It is thus possible for the present advancement to provide for a hair colour formulation/kit for colouring the hair in variable shades ranging from dark brown to black comprising tetra amino pyrimidine (TAP) developer, water soluble silver salt and base in reduced application time of only about 20 mins as a one stage process or a multi stage process facilitating progressive hair colouration involving reduced consumption of ingredients. Advantageously, the formulation/ kit of the present invention not only enabled hair colouration in a single step but also in much reduced application time and in a darker shade as compared to other known reducing agents as evidenced by lower RGB values as recorded which is also washproof to at least upto 25 wash cycles due to the nanoparticle formation upto the medulla region of the hair.
,CLAIMS:We Claim:

1. A hair colouring formulation/ kit comprising
a. tetraaminopyrimidine (TAP) developer;
b. water soluble silver salt; and
c. pH modifier;
with or without other hair care benefiting agents.

2. A hair colouring formulation/ kit as claimed claim 1 wherein concentrations of silver salt and TAP vary in the ratio of 1:4-4:1 favouring variable colour shade ranging from dark brown to black and variable intensity on hair in application time of only about 20 mins that is stable to upto at least 25 shampoo wash cycles.

3. A hair colouring formulation/ kit as claimed in anyone of preceding claims 1 or 2 wherein
said (a) TAP is in the range of 0.3-1.24 % wt./v;
said (b) water soluble silver salt is in the range of 0.2-2.4 % wt./v;
said pH modifier is in the range of 6-15% v/v, enable desired concentration and time dependent generation of hair colour actives in the hair shaft to favour variable shades and intensity of colour from dark brown to black.

4. A hair colouring formulation/ kit as claimed in anyone of preceding claims 1-3 comprising a water based formulation of ingredients suitable for application and wherein water soluble silver salt in the range of 0.62-2.4 % wt./v favours dark black colour on hair in one application.

5. A hair colouring formulation/ kit as claimed in anyone of preceding claims 1-4 wherein said water soluble silver salt includes silver nitrate (AgNO3), silver acetate; and wherein said pH modifiers are selected from ammonia, monoethanol amine to favour increase of pH of the formulation and swelling of the hair during application of ingredients for in-situ colour generation.

6. A hair colouring formulation/ kit as claimed in anyone of preceding claims 1-5 comprising a package having atleast one set of said
a. tetraaminopyrimidine (TAP) developer;
b. water soluble silver salt; and
c. pH modifiers selected from ammonia, monoethanol amine in varied concentrations for generation of variety of shades and intensity of colour from dark brown to black.

7. A process for the manufacture of said hair colouration formulation/ kit as claimed in anyone of preceding claims 1-6 comprising
a. providing said atleast a tetraaminopyrimidine (TAP) developer;
b. providing said atleast a water soluble silver salt; and
c. providing said atleast a pH modifier with or without other hair care benefiting agents,and instructions for mixing to favour swelling of hair and in-situ colouration of hair.

8. A process for colouring the hair in variable shades and intensity ranging from dark brown to black comprising
applying ingredients of hair colouring formulation/kit comprising tetraaminopyrimidine (TAP) developer, water soluble silver salt and a pH modifier for in-situ generation of hair colour actives under ambient conditions to thus attain coloured hair in variable shades and intensity ranging from dark brown to black therefrom.

9. A process for colouring the hair as claimed in preceding claim 8 carried out as a single stage process comprising applying ingredients
said (a) TAP is in the range of 0.3-1.24 % wt./v;
said (b) water soluble silver salt is in the range of 0.62-2.4 % wt./v;
said pH modifier is in the range of 6-15% v/v; and thereby in-situ generation of hair coloured actives in the hair shaft of variable shades and intensity of colour on hair ranging from dark brown to black.

10. A process for colouring the hair as claimed in preceding claim 8 involving progressive hair colouration wherein water soluble silver salt concentration of 0.2-0.6 % wt./v favours dark black on hair in plurality of applications and under reduced consumption of ingredients.

11. A process for colouring the hair as claimed in preceding claim 8 carried out as two stage process comprising the steps of
a. applying a water solution of silver salt on hair in basic pH range of 9-11 involving an application time of about 10-15 mins;
b. applying a solution of TAP on water soluble silver salt treated hair involving an application time of about 10-15 min; and obtaining brown and/ or black coloured hair therefrom.

12. A process for colouring the hair as claimed in anyone of claims 8-11 in shades of dark black colour comprising providing selective concentrations of TAP:0.55-0.65 % w/v, AgNO3: 1.14-1.35 wt% w/v, and NH3 : 8-9 % v/v on hair under ambient conditions and obtaining dark black coloured hair therefrom.

Dated this the 6th day of February, 2016 Anjan Sen
Of Anjan Sen and Associates
(Applicants Agent)