WO2013072675A2

WO2013072675A2 - Method of manufacture

Info

Publication number: WO2013072675A2
Application number: PCT/GB2012/052815
Authority: WO
Inventors: Jane Evison
Original assignee: Reckitt & Colman (Overseas) Limited
Priority date: 2011-11-14
Filing date: 2012-11-13
Publication date: 2013-05-23
Also published as: GB201119607D0; WO2013072675A3

Abstract

The present invention is directed to a method of manufacture of an aqueous gel depilatory composition which comprises the following steps: mixture of at least one C_10-20 carboxylic acid with a metal hydroxide and water to form a first premix; mixture of a crosslinked co-polymer comprising maleic anhydride with water to form a second premix; admixture of the first premix to the second premix to form a homogeneous composition; and addition of a depilatory compound having a thiol group to the homogeneous composition.

Description

METHOD OF MANUFACTURE

The present invention relates to method of manufacture of a depilatory composition comprising a depilatory compound having a thiol group, comprising the step of forming a premix with a mixture of at least one carboxylic acid with a metal hydroxide, to the composition obtained by such a method, and to a method of depilation using such a composition. In particular, the present invention relates to depilatory gel which has foams when applied to the skin. Compositions for removing superfluous body hair which include a compound that degrades hair keratin are well known. After the composition has been applied it is allowed to remain on the skin to degrade the hairs and is then removed together with the degraded hairs. Depilatory compositions of this type typically comprise depilatory compounds which have a thiol group such as potassium thioglycolate, which typically contain sodium hydroxide to provide a high pH. However, there is a significant disadvantage in using these compounds in that they can irritate and even damage the skin as a result of the high pH (usually above 12).

WO 2006021782 describes depilatory compositions in the form of a cream for use in the shower which comprise a homopolymer of polyethylene to reduce tendency to being washed off, thus ensuring optimum residence time of the composition on the skin to effect depilation.

Surprisingly, it has been found that addition of a premix of one or more carboxylic acids to the mix for manufacture of a gel depilatory composition gives a product with the appearance of a gel but which foams on contact with the skin, thus improving residence time.

Accordingly, there is described in a first embodiment of the present invention a method of manufacture of an aqueous gel depilatory composition which comprises the following steps: • mixture of at least one Cio-2o carboxylic acid with a metal hydroxide and water to form a first premix;

• mixture of a crosslinked co-polymer comprising maleic anhydride with water to form a second premix;

· admixture of the first premix to the second premix to form a homogeneous composition; and,

• addition of a depilatory compound having a thiol group to the homogeneous composition. Preferably the method according to the first embodiment of the invention as hereinbefore described is one wherein the final composition comprises between from 1 .0 to 4.0 wt% of the at least one carboxylic acid, more preferably from 1 .5 to 3.0 wt% of the at least one carboxylic acid. Preferably in the method according to the first embodiment of the invention as hereinbefore described the first premix comprises a mixture of at least two different Cio-2o carboxylic acids, more preferably the two different Cio-2o carboxylic acids are C12-18 carboxylic acids, and especially the two different carboxylic acids are myristic acid (CM) and palmitic acid (C16).

Preferably in the method according to the first embodiment of the invention as hereinbefore described the weight ratio of lower molecular weight carboxylic acid to higher molecular weight carboxylic acid is from 3:1 to 1 .1 :1 Preferably in the method according to the first embodiment of the invention as hereinbefore described the metal hydroxide is a Group I metal hydroxide; more preferably sodium or potassium hydroxide, especially potassium hydroxide.

Preferably in the method according to the first embodiment of the invention as hereinbefore described the cross-linked polymer is present in the composition in an amount of from 1 .5 to 5 wt% based on the total weight of the composition, more preferably in an amount of from 2 to 3 wt% based on the total weight of the composition. Preferably the cross-linked polymer is poly(methylvinyl ether/maleic anhydride) co-polymer crosslinked with 1 ,9 decadiene.

In a further aspect of the first embodiment of the present invention as hereinbefore described, there is provided a method of manufacture which further comprises the addition of a salt selected from di- and tri-valent salts, such as magnesium chloride, calcium chloride, ammonium chloride, magnesium sulphate, calcium sulphate, aluminium sulphate, magnesium carbonate, calcium sulphate, calcium carbonate; preferably the salt is magnesium chloride.

In a particular preference of the method as hereinbefore described, the depilatory compound having a thiol group may be any compound capable of degrading keratin; preferably the depilatory compound is selected from the group consisting of potassium thioglycolate, dithioerythritol, thioglycerol, thioglycol, thioxanthine, thiosalicylic acid, N-acetyl-L-cysteine, lipoic acid, sodium dihydrolipoate 6,8- dithioocatanoate, sodium 6,8-diothioocatanoate, a hydrogen sulphide salt, thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, thiomalic acid, ammonium thioglycolate, glyceryl monothioglycolate, monoethanolamine thioglycolate, monoethanolamine thioglycolic acid, diammoniumdithiodiglycolate, ammonium thiolactate, monoethanolamine thiolactate, thioglycolamide, homocysteine, cysteine, glutathione, dithiothreitol, dihydrolipoic acid, 1 ,3- dithiopropanol, thioglycolamide, glycerylmonothioglycolate, thioglycol-hydrazine, keratinase, guanidine thioglycolate, calcium thioglycolate and/or cysteamine; especially preferred is a method wherein the depilatory compound is potassium thioglycolate.

In a particular preference of the method as hereinbefore described the depilatory compound is present in the composition in an amount of from 5 to 20 wt% based on the total weight of the composition, more preferably in an amount of from 10 to 15 wt%.

In a further aspect of the first embodiment of the present invention as hereinbefore described, there is provided a method of manufacture which further comprises the addition of a component which accelerates the keratin degradation reaction such as urea, thiourea, dithioerythritol, dimethyl isosorbide (DMI), ethoxydiglycol (Transcutol) or methyl propyl diol (MT diol). In a particularly preferable aspect of the method as hereinbefore described the composition comprises up to 15 wt% of the accelerator based on the total weight of the composition.

In a second embodiment of the present invention, there is provided a depilatory composition manufactured by a method according to the first embodiment as hereinbefore described comprising:

(a) 1 - 5% w/w poly(methylvinyl ether/maleic anhydride) co-polymer crosslinked with 1 ,9 decadiene;

(b) 1 .5 - 4 wt% of a mixture of CM and Ci6 carboxylic acids;

(c) 0.01 - 1 % w/w an inorganic salt;

(d) 0 - 10% w/w glycerine;

(e) 5 - 10% w/w urea;

(f) 0.01 - 1 % w/w sodium gluconate;

(g) 0.01 - 1 % w/w lotus milk extract;

(h) 10 - 15% w/w aqueous potassium thioglycolate solution;

(i) 1 - 5% w/w sodium silicate solution;

(j) 1 - 5% w/w potassium hydroxide; and

(k) water up to 100%.

In a further aspect of the second embodiment of the present invention as hereinbefore described, there is described a depilatory composition comprising:

(a) 2.2% w/w poly(methylvinyl ether/maleic anhydride) co-polymer crosslinked with 1 ,9 decadiene;

(b) 2.5 wt% of a mixture of CM and Ci6 carboxylic acids;

(c) 0.02% w/w magnesium chloride;

(d) 3% w/w glycerine;

(e) 0.5% w/w urea; 0.1 % w/w sodium gluconate;

0.1 % w/w lotus milk extract;

12% w/w aqueous potassium thioglycolate solution

2.5% w/w sodium silicate solution;

0.365% w/w potassium hydroxide pellets; and

water up to 100%.

In an especially preferred aspect of the second embodiment of the present invention, the depilatory composition consists essentially of components (a) - (k).

Example embodiments of the present invention will now be described.

Lathering Gel

The composition was prepared as follows:

1 . Melt the Myristic acid and Palmitic acid to 75 °C, add the potassium hydroxide pellets already dissolved in small amount of water and mix for 20-25 minutes. This forms premix A

2. In a separate vessel, Stabileze QM & glycerin is stirred in to 24% purified water.

3. Add magnesium chloride pre-dissolved in a little water, the colours and homogenise for 5 minutes. Then heat to 85 °C and add in premix A and homogenise for 5 minutes. Stir in the Crodasinic LS30 NP and cool to 50 °C.

4. Then add a solution of urea, sodium gluconate ,and sodium silicate. Homogenise for 5 minutes and cool to 40 °C

5. Add the potassium thioglycolate, potassium hydroxide solution 50%, cosmetic extract and colorant and homogenise for further 10 minutes.

6. Dispense the product

Claims

Claims:

1 . A method of manufacture of an aqueous gel depilatory composition which comprises the following steps:

· mixture of at least one Cio-2o carboxylic acid with a metal hydroxide and water to form a first premix;

• admixture of the first premix to the second premix to form a homogeneous composition; and,

• addition of a depilatory compound having a thiol group to the homogeneous composition.

2. A method according to claim 1 wherein the final composition comprises between from 1 .0 to 4.0 wt% of the at least one carboxylic acid.

3. A method according to claim 2 wherein the final composition comprises between from 1 .5 to 3.0 wt% of the at least one carboxylic acid. 4. A method according to any preceding claim wherein the first premix comprises from a mixture of at least two different Cio-2o carboxylic acids.

5. A method according to claim 4 wherein the two different Cio-2o carboxylic acids are C12-18 carboxylic acids.

6. A method according to claim 5 wherein the two different carboxylic acids are myristic acid (CM ) and palmitic (C16 ).

7. A method according to any of claims 4 to 6 wherein the weight ratio of lower molecular weight carboxylic acid to higher molecular weight carboxylic acid is from 3:1 to 1 .1 :1

8. A method according to any preceding claim wherein the cross-linked polymer is present in the composition in an amount of from 1 .5 to 5 wt% based on the total weight of the composition. 9. A method according to claim 8 wherein the cross-linked polymer is present in the composition in an amount of from 2 to 3 wt% based on the total weight of the composition.

10. A method according to any preceding claim wherein the cross-linked polymer is poly(methylvinyl ether/maleic anhydride) co-polymer crosslinked with

1 ,9 decadiene.

1 1 . A method according to any of the preceding claims which further comprises the addition of a salt selected from di- and tri-valent salts, such as magnesium chloride, calcium chloride, ammonium chloride, magnesium sulphate, calcium sulphate, aluminium sulphate, magnesium carbonate, calcium sulphate, calcium carbonate.

12. A method according to claim 9 wherein the salt is magnesium chloride.

13. A method according to any preceding claim wherein the depilatory compound having a thiol group may be any compound capable of degrading keratin. 14. A method according to claim 13 wherein the depilatory compound is selected from the group consisting of potassium thioglycolate, dithioerythritol, thioglycerol, thioglycol, thioxanthine, thiosalicylic acid, N-acetyl-L-cysteine, lipoic acid, sodium dihydrolipoate 6,8-dithioocatanoate, sodium 6,8-diothioocatanoate, a hydrogen sulphide salt, thioglycolic acid, 2-mercaptopropionic acid, 3- mercaptopropionic acid, thiomalic acid, ammonium thioglycolate, glyceryl monothioglycolate, monoethanolamine thioglycolate, monoethanolamine thioglycolic acid, diammoniumdithiodiglycolate, ammonium thiolactate, monoethanolamine thiolactate, thioglycolamide, homocysteine, cysteine, glutathione, dithiothreitol, dihydrolipoic acid, 1 ,3-dithiopropanol, thioglycolannide, glycerylmonothioglycolate, thioglycol-hydrazine keratinase guanidine thioglycolate, calcium thioglycolate and/or cysteamine. 15. A method according to claim 13 wherein the depilatory compound is potassium thioglycolate.

16. A method according to any preceding claim wherein the depilatory compound is present in the composition in an amount of from 5 to 20 wt% based on the total weight of the composition.

17. A method according to any preceding claim wherein the depilatory compound is present in the composition in an amount of from 10 to 15 wt%. 18. A method according to any preceding claim which further comprises the addition of a component which accelerates the keratin degradation reaction such as urea thiourea, dithioerythritol, dimethyl isosorbide (DMI), ethoxydiglycol (Transcutol) or methyl propyl diol (MT diol). 19. A method according to claim 18 wherein the composition comprises up to 15 wt% of the accelerator based on the total weight of the composition.

20. A depilatory composition manufactured by a method according to any preceding claim comprising:

(b) 1 .5 - 4 wt% of a mixture of CM and Ci6 carboxylic acids;

(c) 0.01 - 1 % w/w an inorganic salt;

(d) 0 - 10% w/w glycerine;

(e) 5 - 10% w/w urea;

(f) 0.01 - 1 % w/w sodium gluconate;

(9) 0.01 - 1 % w/w lotus milk extract; (h) 10 - 15% w/w aqueous potassium thioglycolate solution;

(i) 1 - 5% w/w sodium silicate solution;

G) 1 - 5% w/w potassium hydroxide; and

(k) water up to 100%.

A depilatory composition according to claim 20 comprising:

(b) 2.5 wt% of a mixture of CM and Ci6 carboxylic acids;

(c) 0.02% w/w magnesium chloride;

(d) 3% w/w glycerine;

(e) 0.5% w/w urea;

(f) 0.1 % w/w sodium gluconate;

(g) 0.1 % w/w lotus milk extract;

(h) 12% w/w aqueous potassium thioglycolate solution;

(i) 2.5% w/w sodium silicate solution;

G) 0.365% w/w potassium hydroxide pellets; and

(k) water up to 100%.

22. A depilatory composition as claimed in either Claim 20 or Claim 21 which consists essentially of components (a) - (k).