MXPA99009258A - Depilatory compositions, their preparation and use - Google Patents

Abstract

A depilatory composition in the form of an aqueous gel comprises a substance capable of degrading hair keratin and a water-soluble polymeric binder and is buffered to a pH of from 10.5 to 13.0. The polymeric binder is formed from a first component that is a charged cross-linked polymer and a second component that comprises a linear non-ionic and/or charged polymer. The composition is preferably in the form of a stable gel that can be applied by means of a pump spray.

Description

DEPILATORY COMPOSITIONS, ITS PREPARATION AND USE FIELD OF THE INVENTION This invention relates to depilatory compositions in particular to those in the form of a gel. BACKGROUND OF THE INVENTION Compositions for removing superfluous body hair are well known. There are various types. One type of composition is in the form of a cream containing a depilatory agent, which degrades the keratin of the hair.

In the case of a depilatory cream, the hair is removed when the cream is applied to an area of the skin - to be depilated, leaving the cream on the skin for a sufficient time for the hair to dissolve chemically and then cleaned and / or Rinse the cream and unwanted hair from the skin. Another type of composition is in the form of wax, which is initially heated before being applied to the skin in a generally molten state. It is then allowed to solidify before being removed from the skin along with the unwanted hair. British Patent Specification No. GB 2 223 170 discloses a depilatory composition in two parts, wherein the first part comprises polyvinyl alcohol (PVA) and the second part comprises borax and a polyhydroxyl alcohol, or Congo red; the second part is functioning to effect a controlled rate of degradation of the PVA. Then, from the degradation in si t u, such solidified compositions, require a plasticizer to allow the solid to detach from the skin. Such compositions preferably also include a surfactant. Depilatory compositions in the form of a gel are less common and attempts to market them have had limited success. Gels tend to produce a greater irritation of the skin than depilatory creams and become very sticky when rinsed given the nature of the polymer present in the formulation. Moreover, the depilatory compositions must possess a high pH value and problems have been found in the formulation of a gel that is stable under such high alkalinity conditions. SUMMARY OF THE INVENTION It is an object of the present invention to provide a depilatory composition in the form of a gel, which does not present such disadvantages.

It is further an object of the present invention to provide a depilatory composition in the form of a gel, which can be sprayed onto the skin without propellant. It is another object of the present invention to provide a depilatory gel, whose tendency to irritate the skin is reduced. It has been found that these objectives can be achieved by forming a gel from two water-soluble polymer components, in a pH environment maintained by a preferred buffer system. One of the polymer components provides the gel with appropriate viscosity and the other polymer component contributes to its stability. Accordingly, an aspect of the present invention provides a depilatory composition in the form of an aqueous alkaline gel comprising: (i) a first polymeric binder comprising a charged, water soluble polymer; (ii) a second polymeric binder comprising a linear polymer soluble in water; (iii) a depilatory agent; and (iv) a buffer system capable of maintaining the pH of the composition in a value between 10.5 and 13.0. Preferably, the composition in use is maintained in the form of an aqueous alkaline gel. According to another aspect of the present invention there is provided a process for producing a depilatory composition, which process comprises: (i) forming a first premix by mixing water and a first polymeric binder comprising a water soluble, degraded, charged polymer; forming a second premix by mixing water, a buffer and a second polymeric binder comprising a linear polymer soluble in water; and optionally forming a third premix by mixing a depilatory agent and an accelerator of keratin degradation; (ii) adding a depilatory agent or the third premix to the second premix with agitation; (iii) adding the first premix to the resulting mixture with agitation; and (iv) adjust the pH between 10.5 and 13.0.

The depilatory compositions of the present invention according to the above have unique rheological qualities, which can be defined in t a l by their characteristic viscosity properties. For example, the cutting speed (in seconds "1) necessary to decrease the viscosity of the gel by half is in the range of from about 10" 2 s "1 to about 200 s" 1, preferably from about 1 s " 1 to about 50 sU Such a large drop in the viscosity of depilatory compositions is not observed in the prior art formulations over these ranges of cutting speed.A low cutting speed of about 10"2 s" 1, the viscosity of the compositions of the present invention are in the order of 103 Pas (106 cP), while at a cutting speed greater than about 500 s "1, their viscosity is in the order of about 0.1 Pas (100 cP). At a very high cutting speed of the order of 4 x 104 s * 1, such as that made by a spray pump (see Table 2 below), it is extremely difficult to measure the viscosity, but it can be visualized that that of the compositions of the present invention would be very low. Preferably, a gel according to the present invention has unique elasticity and viscosity supporting high ionic strength and high pH. The degraded polymer of the first component is swollen with high pH (pH 10.5 to 13) and preferably has only carbon-carbon crosslinking. More preferably, the elastic coefficient of the first component is in the range of from 200 Pa to 1000 Pa, conveniently from 400 Pa to 600 Pa, when measured at a frequency of 10 rad / s; at a temperature of 20 ° C and a deformation of 0.1. The elastic (storage) coefficient (G1) corresponds to the energy that can be stored and released by the material. Suitable first components include a degraded acrylic polymer, such as a carbomer, for example, Ultrez 10 and / or Carbopol ETD 2020 from Goodrich and Structure 2000 and 3001 from National Starch. Another suitable polymer is a degraded polyacrylamide such as Seppigel 305. More preferably, the polymer of the first component is a copolymer of methylavinyl ether and maleic anhydride degraded with dodecadiene, available from ISP under the trade designation Antaron Stabilize 06. Preferably, the depilatory composition includes between 0.1% and 3.0% by weight of the first component. The second component is a non-ionic linear polymer and / or a positively charged polymer and / or negatively charged polymer. The second linear component is one that acts as a suspension agent for the gel and moderates the elastic coefficient thereof to allow its propagation. Any suitable linear polymer that allows the gel structure to be maintained at the osmotic pressure in the composition can be selected. Such linear polymers include hydrophilic polymers having a molecular weight of less than about 600 and nonionic gel forming polymers. For example, the second component may comprise a water-soluble nonionic polymer such as polyethyleneimine, polyethylene oxide or polyethylene glycol (PEG), a hydrophobically modified polyol such as Acrysol 44 from Rohm and Haas, or a polyvinylpyrrolidone such as PVP K from ISP or Luviskol from BASF. Alternatively or additionally, the second component may comprise a natural water-soluble polymer such as cellulose, hydroxypropylcellulose, cet i lhydroxyethyl or propylcellulose (for example Natrosol Plus from Aquelon), starch, a polyglucoside, a polysaccharide such as alginate, guar gum, carrageenan (lambda, kappa, iota), sclerotium gum, a polypeptide with or without modification of any alkyl chain. { C1 to C18) and cationic end groups such as quaternary ammonium groups with counterions such as chlorides and bromides or, a copolymer of sodium acrylate and dimethyldiallylammonium chloride (such as that known as Merquat) or a copolymer of hydroxyethylcellulose and dimethyldiallylammonium chloride (such as that known as Celquat). More preferably, the second component comprises polyethyleneimine (such as that which is known under the trade name Lupasol from BASF) and / or polyvinylpyrrolidone (such as that which is known under the trade designation PVP K-30 from ISP). Preferably, the depilatory composition includes from 0.2% to 3.0% by weight of the second component. The first and second components, when combined according to the present invention, form a polymeric binder having unique viscosity and elasticity. The depilatory agent can comprise any substance capable of degrading keratin and can be, for example, a sulfur compound such as potassium thioglycolate, dipotassium thioglycolate or thioglycerol. Preferably, the depilatory composition includes from 0.1% to 6.0% by weight of the depilatory agent, preferably from about 3.0% to 5.0%. Also, the composition may optionally include component (s) which will accelerate the keratin reduction reaction, such as urea, thiourea or di tioeri tri tol, dimethyl isosorbide (DMI), ethoxydiglycol (Transcutol) and met ilpropyldiol (MP diol). DMI is preferred. It is important that the pH of the composition is in the range of between about 10.5 and 13 and preferably between about 11.0 and 12.5, to provide good depilation in about 5 minutes. In order to achieve this, a suitable buffer must be present, such as sodium silicate and / or L-arginine, sodium nicotinate and potassium polyethyleneimine or a phosphate. In general, the buffer system will be present in an amount between approximately 2. 0% and 8.0% by weight, preferably between approximately 2.0% and 4.0% by weight. Advantageously, the buffer system comprises from 2.0% to 3.0% by weight of L-arginine and from 0 to 1. 0% by weight of polyethyleneimine. The buffer system of pH preferably ensures the effectiveness of hair removal in 5 minutes while also minimizing skin irritation. In order to achieve minimal skin irritation, a composition including L-arginine and / or polyethyleneimine, urea and potassium thioglycolate and / or dipotassium is preferred. According to a preferred depilatory composition of the present invention, an aqueous alkaline gel is provided which comprises: (i) 0.1% to 3.0% w / w of a first polymeric binder comprising a water soluble, degraded, charged polymer, preferably a copolymer of meth i vinyl ether and maleic anhydride degraded with dodecadiene; (ii) 0.2% to 3.0% w / w of a second polymeric binder comprising a water-soluble linear polymer, preferably polyethyleneimine and / or polyvinylpyrrolidone; (iii) 0.1% at 6.0% w / w, preferably 3.0% at 5.0% w / w of a depilatory agent, preferably dipotassium and / or potassium thioglycolate; (iv) 2.0% to 6.0% w / w, preferably 2.0% to 4.0% w / w of a buffer system, preferably L-arginine and / or polietiniminimine; and optionally (v) 5.0% to 10.0% weight / weight of an accelerator for the degradation of keratin, preferably urea; whereby the composition in use preferably remains in the form of an aqueous alkaline gel. The gels according to the present invention are preferably transparent, and remain transparent in use, depending on the amount of active ingredients present and in the process of the mixture. In general, they have a thick and rich touch and excellent rinsing capacity with water. Moreover, it is not necessary to include a surfactant in the composition of the present invention and, therefore, it is less likely to cause skin lesions. Due to the special rheology of the polymeric binder, it is possible to include beads, tinctures and oily particles that will remain dispersed in the gel. Optionally, the excipients include skin softening compounds such as azulejo or jojoba and polyethylene glycol to reduce irritation. Suitable pearls include encapsulated seaweed extracts and sweet almond oil (Elespher). It is also possible to include hydration, acceleration and / or reduction agents in the beads. For example, water-soluble materials such as urea, potassium thioglycolate or thioglycerol may be included in the beads, such that these active ingredients are encapsulated. Although it is possible to provide a gel according to the present invention having suitable viscoelastic properties for the spray, the depilatory material can alternatively be applied by means of a roller device or in a conventional shower gel pack.

Other ingredients may be included in the compositions of the invention, such as those known in the art. Unless stated otherwise, all percentages by weight referred to herein are% by weight based on the weight of the total composition. BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the invention and to show how it can be carried out to be carried out, reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 is a graph of the cutting tension (Pa) with respect to the cutting speed (s ~ 1) for a series of polymeric binders (first component) of the composition of the invention; Figure 2 is a graph of the strength limits (Pa) of the binders of Figure 1, against the content of degraded polymer (first component) (% w / w) of the binders; Figure 3 is a graph of the viscosities (Pas) of the binder of Figure 1, against the cutting speed (s_1) of the binders; and Figure 4 is a graph of the coefficient of elasticity (G1) and viscosity (G ") against the tension / strain (Pa) of the first component of the composition. The following examples illustrate the invention: EXAMPLES 1 TO 6 A series of depilatory gels having the compositions shown in the following Table 1 were prepared: TABLE 1 All amounts are expressed in% weight / weight of the total composition. Polymer A was a copolymer of methylene vinyl ether / maleic anhydride degraded with dodecadiene known under the trade designation Antaron ST06 from ISP; and polymer B was polyvinylpyrrolidone known under the trade designation PVP K-30 of ISP. The pH buffer system was a combination of 2% weight / weight of L-arginine and 1% w / w of polyethyleneimine. In each case, an Olsa mixer with planar stirring and a high-cut agitator equipped with a vacuum and heating / cooling system was used. The procedure was as follows: Phase 1: Premix of polymer A and water. Water was placed in the mixer and polymer A was added slowly and with stirring. When the polymer dispersed, it began to heat while maintaining a vacuum system of approximately 0.5 to 0.8 bar to avoid air bubbles. The vacuum pump was running intermittently in order to reduce the loss of water. When the temperature reached approximately 80 ° C an almost clear gel had formed. This was allowed to cool and swell overnight. Phase 2: Premix of Polymer B, water and pH buffer. Water and polymer B were introduced into the mixer and homogenized for 2 minutes. Then the pH buffer system was added and the mixture was homogenized for 2 more minutes. Phase 3: Urea and potassium thioglycolate. Urea was added to the potassium thioglycolate in a beaker and stirred for 1 hour to complete the dissolution. Final mixture: The final mixture was made as follows: Phase 2 was placed in a container and Phase 3 was added with agitation for 15 minutes. A white precipitate appeared. Phase 1 was added while mixing slowly under vacuum (0.5 bar) with planar stirring and the high-cut shaker operated at low speed. The mixture was homogenized for 30 minutes until a lumpy gel formed. Then potassium hydroxide was added. The gel became clear and transparent. The pH was adjusted, as necessary, to between 11.0 and 12.5. Each of the resulting gels was subjected to rheological measurement. The parameters considered were, cutting tension, cutting speed, viscosity and resistance limit. The results are shown in the Figures As. can be observed from Figure 1, the variation of the cutting tension with the cutting speed is non-linear between 0 and 500 s "1 and thus the gel has a non-Newtonian behavior with a limit of resistance. of resistance is the tension required to make the gel flow, Figure 2 shows that the variation of the resistance limit (TauO), that is, the shear stress for the zero shear rate, varies exponentially. the amount of polymer A, the variation of the resistance limit, that is, the variation in the capacity of propagation or consistency, can be significant.The following table, Table 2, gives the typical cutting speeds of the products to be sprayed. with a conventional pump sprayer and the products that must be applied from a shower gel pack.

TABLE 2 The relation between the cutting speed and the viscosity is shown in Figure 3, in which it can be seen that, at the cutting speeds given in Table 2, the viscosity is very low. It has been found that, in order for the gel to be sprayable with a pump sprayer, its resistance limit must be no more than 100-200 Pa. However, if the gel is to be used in a shower gel package, the resistance limit should be as high as 300 Pa. In addition, in order for the product to remain fixed for 5 minutes on the skin, when it remains vertical, the resistance limit should be approximately 60 Pa or more. So the gels where polymer A constitutes between 2.0% and 2.5% weight / weight are preferred for spraying, whereas rather lower percentages of polymer A may be present where the gel should be used in the form of a shower gel pack. In a further series of experiments, Azulene blue powder was dissolved in a coarse paraffin oil to produce a 1% w / w solution. The 2% w / w of this solution was then added slowly to each of the above gels and stirred for 5 minutes. The Azulene remained stably suspended within the gel in the form of blue oily droplets. Depending on the concentration of Azulene in the premix and the concentration of the premix in the gel, the size and color of the droplets and the overall transparency of the gel could be adjusted. In a further series of experiments, 0.5% weight / weight of Elespher was slowly added to each gel and stirred for 5 minutes. The Elespher consists of encapsulated pearls of algae extract and sweet almond oil and is green. The pearls remained stably suspended in the gel. EXAMPLE 7 Gels were added according to the following Table 3: TABLE 3 The amount of water varied according to the amounts present of polymers A and B. Polymers A and B were as used in Examples 1 to 6 and the mixing technique employed was as also described in such Examples. In each case, stable and sprayable depilatory gels were obtained. This showed that for a range of polymer A between 1.0% and 3.0%, a range of polymer B between 0.6% and 3.0% can be used a gel formed sprayable and stable.

Claims (13)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and therefore the property described in the following claims is claimed as property. A depilatory composition in the form of an aqueous alkaline gel comprising: (i) a first polymeric binder comprising a water soluble, degraded, charged polymer; (ii) a second polymeric binder comprising a linear polymer soluble in water; (iii) a depilatory agent; and (iv) a buffer system capable of maintaining the pH of the composition at a value between 10.5 and 13.0. A depilatory composition according to claim 1, characterized in that the degraded polymer of the first component is a degraded acrylic polymer, a degraded polyacrylate or a copolymer of methylavinyl ether and maleic anhydride degraded with dodecadiene. 3. A depilatory composition according to claim 1 or 2, characterized in that it includes from 0.1 to 3.00% weight / weight of the first component. A depilatory composition according to any of claims 1 to 3, characterized in that the second component comprises a non-ionic linear polymer and / or a positively charged polymer and / or a negatively charged polymer. A depilatory composition according to claim 4, characterized in that the second component comprises one or more of polyethyleneimine, polyvinylpyrrolidone, polyethylene oxide, polyethylene glycol, cellulose, hydroxypropylcellulose, cet and lhydroxyethylcellulose, cethexydroxypropylcellulose, starch, a polyglycoside, a polysaccharide, guar, carrageenan, a sclerotium gum, a polypeptide and a copolymer of sodium acrylate or of hydroxyethyl cellulose with dimethyl butyl ammonium chloride. 6. A depilatory composition according to any of the preceding claims characterized in that it includes from 0.2 to 3.0% weight / weight of the second component. 7. A depilatory composition as claimed in any of the preceding claims, characterized in that the depilatory agent is potassium thioglycolate or thioglycerol. 8. A depilatory composition according to any of the preceding claims, characterized in that it includes an accelerator for the degradation of keratin, such as urea, thiourea, di t ioeri t ri tol, ethoxydigl icol or met ilpropi ldiol. 9. A depilatory composition according to any of the preceding claims, characterized in that it includes a buffer system comprising a silicate, an arginine, such as L-arginine, a nicotinate, polyethyleneimine or a phosphate. 10. A depilatory composition according to any of the preceding claims and having a strength limit of not more than 200 Pa. A depilatory composition according to any of the preceding claims, characterized in that the cutting speed necessary to reduce the viscosity of the gel by half lies in the range from 10 ~ 2 s "1, to 200 s" 1, preferably 1 sxa 50 sU 12 A depilatory composition according to any of the preceding claims in the form of a sprayable gel. 13. A process for producing a depilatory composition according to any of the preceding claims, which process comprises: (i) forming a first premix by mixing water and a first component; forming a second premix by mixing water, a buffer and the second component; and optionally forming a third premix by mixing a depilatory agent and an accelerator of keratin degradation; (ii) adding a depilatory agent or the third premix to the second premix with agitation; (iii) adding the first premix to the resulting mixture with agitation; and (iv) adjust the pH between 10.5 and 13.0.