WO2005051343A1 - Stable personal wash soap composition and process to prepare the same - Google Patents

Abstract

A storage stable personal wash soap composition comprising 15-85 % detergent active, 0.1-20 % of skin lightening agent selected from niacin, niacinamide, their precursors and derivatives, and 0.02 % to 2 % of diethylene triamine penta acetic acid (DTPA).

Description

STABLE PERSONAL WASH SOAP COMPOSITION AND PROCESS TO PREPARE THE SAME

The present invention relates to personal wash soap compositions, and in particular to stable personal wash soap compositions incorporating essentially skin lightening benefit agent niacinamide, and also to their process of manuf cture.

The personal wash soap composition of the invention would enable direct incorporation of skin benefit agent niacinamide in soaps at higher levels to impart better skin lightening properties of the bar, and yet will be stable, maintaining desired consumer attributes of the product even upon long storage in hot and humid conditions .

Usually, sunscreens and skin lightening agents like niacinamide and Parsol are skin benefit agents and incorporated in mutually compatible cosmetic formulations . Skin lightening agents such as niacinamide, lactic acid and others are generally unstable in alkaline pH. Personal wash formulations are usually soap based, and have an alkaline pH that can prove detrimental to the formulations containing skin lightening agents. Hence, it is a problem to formulate wash-off product comprising these skin-lightening agents.

Importantly, it is not possible to deliver skin lightening agents such as niacinamide in personal wash bars processed in a conventional way at substantive levels where the total fatty matter is in the range of 30 % to 80 %, as these compounds are unstable in alkaline pH at high temperature. Usually, therefore, to deliver benefit agents to skin through wash-off products, it has been found necessary to utilize a delivery system such as those including a cationic polymer.

WO 01/82884 Al discloses a detergent bar comprising 15 % to

85 % detergent active and 0.1 % to 20 % of skin lightening- agents. Preferably, the skin lightening-agent is incorporated into the detergent bar at a temperature of 20-

60°C. Importantly, this formulation was directed to a synergistic soap/detergent formulations which would provide for improved delivery of skin lightening-agents, i.e. niacinamide, onto substrates on which they are applied, thereby obtaining maximum effective value of the benefit agents used in such formulations.

Whilst the above prior art provides soap/detergent formulations which would enable incorporation of the actives such as niacinamide in such a base formulation, and also while such selective synergistic formulations also provide for enhanced delivery of skin benefit agents such as niacinamide, it is found that problems still exist in incorporation of actives such as niacinamide in such formulations. This is because the same leads to loss of storage stability of product, especially under humid conditions. In particular, it is found that formulations including unsaturated fatty matter containing soap having such sunscreen or skin lightening benefit agents such as e.g. niacinamide show discoloration in long storage, especially under hot and humid conditions.

Thus, such sunscreen care protection soap bars are known to develop discoloration upon long time storage in hot, humid and mushy conditions. Particularly soaps bases containing unsaturated soaps or fatty acids with 0.1 % to 5 % niacinamide show discoloration in hot, humid and mushy conditions typically in about 30-40 days. Importantly, it is also found that in case of formulations involving soaps derived from unsaturated fatty acid (e.g. oleic acid) with niacinamide, problems of discoloration and rancidity appear with even 0.5 or lower weight percent niacinamide at ambient temperature.

It is for the above reasons that soaps derived from unsaturated fatty acids are especially found to be not compatible with the skin benefit agents such as niacinamide, and are usually found to lead to discoloration and loss of consumer attributes of the product. Also, considering that iron (Fe) and copper (Cu) impurities in soap formulation catalyze the air oxidation of unsaturated fatty acids moiety, attempts to control discoloration of such soap formulation in the presence of niacinamide by the use of known ethylenediamine tetraacetic acid (EDTA) /ethylene hydroxy diphosphonate (EHDP) chelating agents of Fe/Cu in soap was found not sufficient to avoid problems of product stability, such as discoloration of niacinamide containing soaps. Higher amounts such as up to 0.2 % of EDTA-4Na(35 % solution), 1 % of EHDP (60 % solution) could not avoid the discoloration in soaps having niacinamide.

It is, therefore, apparent from the above that soap formulations such as personal wash formulations involving niacinamide which involve soaps derived from espcially unsaturated fatty acids are subject to loss of stability by way of discoloration of the product upon storage, especially in hot, humid & mushy conditions. Such discoloration of the product form, apart from affecting the constitutional balance of soap formulations and its related loss of benefit properties, also essentially resulted in loss in consumer appeal for the product. Also, due to such stability problems, in spite of possible formulations involving the active niacinamide in soaps especially for achieving high rate of delivery of the active on skin during use, the wide scale use and application of niacinamide at desired levels in soap formulations is a continuing problem in the art.

It is thus the basic object of the present invention to be able to provide for soap/personal wash compositions having unsaturated fatty matter containing soap and skin lightening/benefit agents such as niacinamide which would avoid the problems of storage stability and discoloration in long storage, even in hot and humid conditions.

Another object of the present invention is to be able to provide for soap formulations, especially personal wash bars with detergent actives in the range of 15-85% and including soaps derived from unsaturated fatty acid, and skin lightening agent niacinamide which would achieve the desired stability in alkaline pH and high temperatures, and deliver benefit agent to skin through wash-off products without problems of discoloration on storage, especially in hot and humid conditions.

Yet another object is to be able to provide for a storage stable discoloration-free soap formulations including niacinamide which would achieve the desired storage stability, which cannot be achieved by use of conventional EDTA/EHDP chelating agents used to chelate trace amounts of Fe/Cu present in such soaps.

Another object of the present invention is to be able to provide for synergistic soaps/detergent formulations which would on the one hand provide for improved delivery of skin lightening-agents onto substrates on which they are applied, thereby obtaining maximum effective value of the benefit agents used in such formulations, and on the other hand avoid problems of storage stability and discoloration on long storage, even under hot and humid conditions.

Yet another object of the present invention is to be able to provide for soaps/skin care formulations involving skin lightening-agents such as niacinamide and Parsol sunscreens maintaining desired effective levels of niacinamide and the sunscreen for the intended skin protection benefit, and at the same time avoiding the problem of soap discoloration in long storage, especially in hot, humid and mushy conditions.

Another object of the present invention is to help enable storage stable incorporation of niacinamide in soaps without the need to avoid unsaturated fatty acid based soaps, and yet achieve the desired storage stability, even in humid and mushy conditions to maintain desired consumer appeal/attributes of the product, and meet the marketing demands of the same.

Thus according to one aspect of the present invention there is provided a storage stable personal wash/detergent composition comprising 15-85 % detergent active, 0.1-20 % of skin lightening agent selected from niacin, niacinamide, it's precursors and derivatives and 0.02 to 2% of diethylene triamine penta acetic acid (DTPA) .

The above formulation of the invention can include the other usual additives and/or skin/benefit agents used in such personal wash formulations.

It is surprisingly found by way of the present invention that selective incorporation of DTPA in the above soap based formulation including niacinamide could avoid the problems of storage stability and discoloration which the usual EDTA and EHDP chelating agents for trace amounts of Fe/Cu cannot achieve or control.

Thus, according to a preferred aspect of the present invention, there is provided a personal wash detergent composition comprising 15-85 % detergent active, 0.1-20 % of niacinamide 0.02 % to 2 % of diethylene triamine penta acetic acid (DTPA) and 0.2-0.8 % of a chelating agent.

In accordance with a more preferred aspect, it is found that a combination of the DTPA and EHDP in niacinamide containing soap formulations provides for surprisingly improved storage stability even in hot and humid conditions, and provides for making of the soap comprising desired levels of the active niacinamide free of any discoloration problems on storage.

Thus, according to such preferred aspect of the present invention, there is provided a personal wash detergent composition comprising 15-85 % detergent active, 0.1-20 % of niacinamide, 0.02 % to 2 % of diethylene triamine penta acetic acid (DTPA) and 0.2-0.8 % of ethylene hydroxy diphosphonate (EHDP) .

In accordance with another aspect of the present invention, there is provided a process for manufacture of personal wash detergent composition comprising selectively providing

i) 15-85 % detergent active; ii) 0.1-20 % skin lightening agent selected from niacin, niacinamide, its precursors and derivatives; iii) providing selectively 0.02-2 % of DTPA with or without other usual additives, preferably a chelating agent, and obtaining the soap therefrom.

It is particularly preferred that the chelating agent used is EHDP.

In accordance with another preferred aspect of the present invention, there is provided a process for manufacture of personal wash detergent composition comprising: providing soap noodles following conventional process and mixing niacinamide with said DTPA and EHDP, the DTPA and EHDP being added before and/or at the time of adding of the niacinamide to thereby obtain the stable soap.

In accordance with yet further aspect of the present invention, there is provided a storage stable system of enhanced delivery of skin lightening-agent niacinamide for use in detergent/soap formulations wherein the system comprises 15-85 % active, 0.1-20 % skin lightening-agent niacinamide 0.02-2 % DTPA and 0.2-0.8 % EHDP, and optionally other benefit agents/additives, wherein the skin lightening- agent niacinamide is incorporated into the soap at temperature in the range of 20-60°C.

It would thus be possible by way of the present invention to effectively and advantageously provide soap with skin benefit agent niacinamide which would be storage stable and free of problems of discoloration, even in humid and mushy conditions. Importantly, the formulation of the invention would take care of stability problems which the usual

EDTA/EHDP used to chelate trace amounts of Fe/Cu present in soap cannot achieve, and favour also storage stable incorporation of niacinamide in soap derived from unsaturated fatty acids.

The selected lightening agents may be selected from niacin, niacinamide, its precursors or derivatives. Optionally, the formulation can include other benefit agents such as extracts of placenta, hydroquinone and its derivatives (eg. Arbutin) , kojic acid, dicarboxylic acids (azelaic acid, sebacic acid}, represented by the formula HOOC- (CxHy) -COOH where x=4 to 20 and y=6 to 40, ascorbic acid and its derivatives, hydroxy acids or their esters (lactic acid, glycolic acid, malic acid, tartaric acid citric acid etc) , ferulic acid retinol and derivatives or any other known skin lightening agents. The above skin lightening agents may also be introduced as macro domains during plodding.

The soap used in the formulation may include unsaturated fatty matter containing soap. The term soap denotes salts of carboxylic fatty acids. The soap may be derived from any of the triglycerides conventionally used in soap manufacture - consequently the carboxylate anions in the soap may contain from 8 to 22 carbon atoms.

The soap may be obtained by saponifying a fat and/or a fattty acid. The fats or oils generally used in soap manufacture may be such as tallow, tallow stearines, palm oil, palm stearines, soya bean oil, fish oil, caster oil, rice bran oil, sunflower oil, coconut oil, babassu oil, palm kernel oil, and others. In the above process the fatty acids are derived from oils/fats selected from coconut, rice bran, ground nut, tallow, palm, palm kernel, cotton seeds, soya bean, castor etc. The fatty acid soaps can also be synthetically prepared (e.g. by the oxidation of petroleum or by the Fischer-Tropsch process) . Resin acids, such as those present in tall oil, may be used. Naphthenic acids are also suitable.

Tallow fatty acids can be derived from various animal sources and generally comprise about 1-8 % myristic acid, about 21-32 % palmitic acid, about 14-31 % stearic acid, about 0-4 % palmitoleic acid, about 36-50 % oleic acid and about 0-5 % linoleic acid. A typical distribution is 2.5 % myristic acid, 29 % palmitic acid, 23 % stearic acid, 2 % palmitoleic acid, 41.5 % oleic acid, and 3 % linoleic acid. Other similar mixtures, such as those from palm oil and those derived from various animal tallow and lard are also included.

Coconut oil refers to fatty acid mixtures having an approximate carbon chain length distribution of 8 % C8, 7 % CIO, 48 % C12, 17 % C14, 8 % C16, 2 % C18, 7 % oleic and 2 % linoleic acids (the first six fatty acids listed being saturated) . Other sources having similar carbon chain length distributions, such as palm kernel oil and babassu kernel oil, are included within the term coconut oil.

Optionally benefit agents such as organic sunscreen, Parsol MCX (a registered trade name of Givaudan Roure and chemically 2-ethyl-hexyl-methoxy cinnamate) , Parsol 1789 (chemically known as butyl methoxy benzoylmethane) may be incorporated. Other benefit agents may be selected from moisturisers, emollients, humectants, non-soap surfactants, antimicrobial agents and anti-ageing compounds may also be incorporated.

The non-soap surfactants may be anionic, nonionic, cationic, amphoteric/zwitterionic or a mixture thereof.

Examples of suitable moistures and humectants include polyols, glycerol, cetyl alcohol, carbopol 934, ethoxylated castor oil, paraffin oils, lanolin and its derivatives. Silicone compounds such as silicone surfactants like DC3225C (Dow Corning) and/or silicone emollients, silicone oil (DC 200 Ex-Dow Corning) may also be included. It is preferred to incorporate 1-5 % of the benefit agents at any step prior to step of milling. Alternatively certain of these benefit agents are introduced as macro domains during plodding.

Other additives such as one or more water insoluble particulate materials such as talc, kaolin, polysaccharides such as starch or modified starches and cellulose may be incorporated. Minor additives such as perfume, color, preservatives, opacifiers and other conventional additives at 1 to 2 % by weight can be incorporated.

Personal wash products may be formulated in several forms. One of the examples of a personal wash product is a soap bar, the process of manufacture of which is described herein.

The soap may be prepared by neutralising a suitable blend of fatty acids or saponifying a suitable blend of oils, or saponifying a blend of fatty acids and oil. The soap is converted into noodles typically having water content in the range of 12-18 %, and to the noodles thus produced the niacinamide as the essential skin benefit agent is added. The selective DTPA with EHDP with or without EDTA is mixed with the noodles prior to and/or at the time of the adding to the noodles of the niacinamide. Minors such as perfume, colour, etc. are admixed.

Preferably the skin lightening agents are added in the sigma mixer and mixed with the temperature during the mixing stage being in the range of 20-60°C. The mixed soap mass is further milled, plodded and stamped to produce bars .

In case of soap made from oil saponification, a similar process is followed after recovery of glycerine from the soap mass. The neat soap is spray-dried to reduce moisture, and the resulting noodles are processed as described above. Suitable equipment used for the soap making is any equipment that is used in soap/detergent manufacture, and is preferably a high shear kneading mixer. The preferred mixers include a ploughshare mixer, mixers with kneading members of Sigma type, multi-wiping overlap, single curve or double arm. The double arm kneading mixers can be of overlapping or tangential design. Alternatively the invention can be carried out in a helical screw agitator vessel or multi-head dosing pump/high shear mixer and spray drier combinations, as in conventional processing.

The details of invention, its objects and advantages are explained hereunder in greater detail in relation to non- limiting exemplary illustrations as hereunder.

EXAMPLES

Under Examples 1 to 7 (comparative examples) a conventional soap wash composition was prepared incorporating the skin lightening-agents niacinamide at varying levels of 0.1 - 5 % with the soap including the conventional Fe/Cu chelating agents EDTA at level of 0.02-0.2 % and EHDP at 0.2-1 % . The procedure followed is as detailed hereunder.

Personal wash soap compositions were prepared by the conventional route to obtain 78 % total fatty matter. The soap was converted into noodles having water content in the range of 12-18 % and to the noodles thus produced was mixed with niacinamide, EHDP in the level of 0.2-1 % and EDTA in the level of 0.02-0.2 %. Thereafter, niacinamide of varying amounts ranging from 0.1 % to 5 % was added, and mixed in a sigma mixer at a temperature of 40°C. The mixed soap was next milled, plodded and stamped to produce bar. EDTA has been used in soap as EDTA-4Na, and the highest allowed limit in soap is 0.02 % (35 % solution) and EHDP limit is 0.8 % (60 % solution) . The DTPA limit is 0.5 %

The various amounts of the active niacinamide used in the soap base is as detailed hereunder in Table I.

Table I

The storage stability of the above soap formulations incorporation niacinamide and the usual iron/copper chelating agents EHDP/EDTA were tested under humid condition at 35-40°C. In all the soap formulations as above discoloration after 40-50 days was noted.

The above clearly go to show that the conventional EDTA/EHDP generally used to chelate trace amounts of Fe/Cu present in soap is not capable of avoiding the discoloration in the formulation involving niacinamide. This therefore confirms the problems of niacinamide based soap to achieve desired storage stability and maintain consumer attributes of the product.

Examples 8 to 21 Under the following Examples 8 to 14, selective formulations of the present invention were obtained involving the selective DTPA in combination with EHDP but without any EDTA, and with the varying amounts of active niacinamide as tried in case of the Examples under Table I.

The amount of niacinamide and the level of DTPA and EHDP tried are reproduced hereunder in Table II, and that along with EDTA is reproduced hereunder in Table III.

Table II

Table III

The exemplary formulations obtained in accordance with the present invention incorporating niacinamide in soap and having the combination the DTPA and EHDP of Examples 8 to 14 and 15 to 21 were next subjected to the same storage stability test as that followed in the formulations under

Table I.

In all the exemplary formulations of Examples 8 to 14 and 15 to 21 in accordance with the present invention there was no discoloration even in humid condition at 35-40°C.

The above clearly and sufficiently go to demonstrate the advantages in the selective incorporation of DTPA and EHDP combination with and without EDTA in soap based personal wash compositions which enable incorporation of the skin benefit agent niacinamide in levels of 0.1-5 %, without problems of any discoloration of the soap.

Demonstration of the benefit of DTPA and EHDP on discoloration

Soap formulation comprising predominantly sodium oleate soap and niacinamide at 5 % along with 0.04 % DTPA and 0.2 % EHDP (Example 22) or 0.04 % EDTA and 0.2 % EHDP (Example 23) were stored at room temperature for 1 to 3 weeks. The discoloration obtained in the absence of DTPA in soap samples and the inventive formulation containing DTPA are presented in Figure 1.

The sample of Example 22 was clear even after storage for 3 weeks (Figure 1A) , but the other control samples of Example 23, showed significant discoloration even after 1 week (Figure IB) which worsened after 2 weeks (Figure IC) . It is thus possible by way of the present invention to avoid problems of discoloration of soaps, especially personal wash formulations involving soaps derived from unsaturated fatty acid in combination with niacinamide as a skin lightening- agent. The composition of the invention would therefore on the one hand enable the conventional process of manufacture of soap based wash formulations, and especially enable obtaining compositions/systems for enhanced delivery of skin lightening-agent niacinamide without the problems of discoloration of the product and/or loss of consumer attribute due to presence of niacinamide in such a base formulation.

The composition of the invention would, therefore, favour wider and effective use/application of the skin lightening- agent niacinamide in soaps/personal wash compositions, and avoid limitations of the advantageous use of niacinamide in such cosmetic/personal wash products.

Claims

1. A storage stable personal wash/detergent composition comprising 15-85 % detergent active, 0.1-20 % of skin lightening agent selected from niacin, niacinamide, their precursors and derivatives, and 0.02 % to 2 % of diethylene triamine penta acetic acid (DTPA) .

2. A storage stable personal wash/detergent composition as claimed in claim 1 comprising up to 0.2-0.8 % chelating agent .

3. A storage stable personal wash/detergent composition as claimed in claims 1 to 2 comprising up to 0.2-0.8 % ethylene hydroxy diphosphonate (EHDP) .

4. A storage stable personal wash/detergent composition as claimed in any one of claims 1 to 3 comprising other conventional additives and/or skin benefit agents.

5. A storage stable composition as claimed in any one of claim 4 wherein the other benefit agents include extracts of placenta, hydroquinone and it's derivatives, preferably Arbutin; kojic acid; dicarboxylic acids preferably azelaic acid, sebacic acid, represented by the formula H00C- (CxHy) -COOH where x = 4 to 20 and y = 6 to 40, ascorbic acid and its derivatives, hydroxy acids or their esters preferably lactic acid, glycolic acid, malic acid, tartaric acid citric acid etc; ferulic acid retinol and derivatives and other conventional known skin lightening agents.

6. A storage stable system as claimed in any one of claims 1 to 5 wherein the skin lightening agents are introduced as macro domains during plodding.

7. A storage stable system as claimed in any one of claims 1 to 6 wherein the soap used in the formulation comprises unsaturated fatty matter-containing soap.

8. A storage stable system as claimed in any one of claims 4 to 7 wherein the benefit agents are selected from organic sunscreen preferably 2-ethyl-hexyl-methoxy cinnamate, butyl methoxy benzoylmethane, moisturisers, emollients, humectants, non-soap surfactants, antimicrobial agents and antiageing compounds.

9. A storage stable system as claimed in any one of claims 1 to 8 wherein the non-soap surfactant is selected from anionic, nonionic, cationic, amphoteric/zwitterionic surfactants, and mixtures thereof.

10. A storage stable system as claimed in any one of claims 4 to 9 comprising incorporating 1-5 % of the benefit agents at any step prior to step of milling.

11. A storage stable system as claimed in any one of claims 1 to 10 comprising selectively provided benefit agents as macro domains during plodding.

12. A storage stable system as claimed in any one of claims 1 to 11 wherein the additives are selected from one or more water insoluble particulate materials, preferably talc, kaolin, polysaccharides including starch or modified starches and cellulose.

13. A storage stable system as claimed in any one of claims 1 to 12 comprising minor additives comprising perfume, color, preservatives, opacifiers and other conventional additives at 1 to 2 % by weight.

14. A storage stable system of enhanced delivery of skin lightening-agent niacinamide for use in detergent/soap formulations wherein the system comprises 15-85 % active, 0.1-20 % skin lightening-agent selected from niacin, niacinamide, it' s precursors and derivatives 0.02-2 % DTPA and 0.2-0.8 % EHDP and optionally other benefit agents/additives, wherein the skin lightening- agent niacinamide is incorporated into the soap at temperature in the range of 20-60°C.

15. A process for manufacture of personal wash detergent composition comprising selectively providing i) 15-85 % detergent active; ii) 0.1-20 % skin lightening agent selected from niacin, niacinamide, it' s precursors and derivatives; iii) 0.02-2 % of DTPA and obtaining the soap therefrom.

16. A process as claimed in claim 15 comprising incorporating other conventional additives, preferably up to 0.2-0.8 % of chelating agent which may be EHDP.

17. A process as claimed in any one of claims 15 or 16 comprising: - providing soap noodles following a conventional process and mixing niacinamide -with said DTPA and EHDP, said DTPA and EHDP being added before and/or at the time of adding of the said niacinamide to thereby obtain the stable soap.

18. A process as claimed in any one of claims 15 to 17 comprising incorporating 1-5 % of benefit agents at any step prior to step of milling.

19. A process as claimed in any one of claims 15 to 18 comprising selectively provided benefit agents as macro domains during plodding.

20. A process as claimed in any one of claims 15 to 19 comprising preparing the soap by neutralising a suitable blend of fatty acids or saponifying a suitable blend of oils or saponifying a blend of fatty acids and oil, converting the soap into noodles having water content in the range of 12-18 % and adding to the noodles thus produced the niacinamide based skin benefit agent, wherein the selective DTPA and EHDP with or without EDTA is mixed to the noodles prior to and/or at the time of adding niacinamide to the noodles .

21. A process as claimed in any one of claims 15 to 20 wherein the skin lightening agents are added in the sigma mixer and mixed with the temperature during the mixing stage maintained in the range of 20-60°C , the mixed soap mass being further milled, plodded and stamped to produce bars.

22. A process as claimed in any one of claims 14 to 18 wherein the soap mass used is made from oil saponification, and the glycerine is recovered from the soap mass prior to it's use in the process.

23. A storage stable personal wash/detergent composition substantially as herein described and illustrated with reference to the accompanying examples.