Method for thickening a cosmetic formulation using an alkali swellable emulsion of a polymer with amps and which is rich in acrylic acid

Abstract

Process for thickening a composition, through the use of a direct emulsion in water, which is alkali-swellable, of a polymer of the ASE or HASE type, which is both rich in acrylic acid and which has a certain quantity of AMPS. The use of such emulsions simultaneously allows there to be no obligation to use surfactants and organic solvents other than water, and allows the thickening phenomenon to be activated for pHs of less than 7: this latter characteristic is particularly advantageous for formulations intended to be used in contact with skin.

Claims

1. A method for thickening a formulation, the method comprising: contacting the formulation with a direct aqueous emulsion of a polymer, followed by regulating a pH of the formulation to a value between 5 and 7, thereby forming a thickened formulation, wherein the emulsion is free from surfactants and organic solvents other than water and the polymer consists, expressed as a content by weight of monomers therein, of: a) from 20% to 60% by weight of acrylic acid and, optionally, methacrylic acid, wherein a content by weight of acrylic acid compared to a total weight of acrylic and methacrylic acid is at least 50%, b) from 40% to 80% by weight of ethyl acrylate, butyl acrylate, methyl methacrylate, or any combination thereof, c) from 0.05% to 22% by weight of 2-acrylamido-2-methylpropane sulfonic acid, and d) from 0 to 1% by weight of at least one cross-linked monomer.

2. The method according to claim 1, wherein the cross-linked monomer is present and is ethylene glycol dimethacrylate, trimethylolpropanetriacrylate, diallyl phtalate, allyl acrylate, an allyl maleate, methylene-bis-acrylamide, methylene-bis-methacrylamide, tetraallyloxyethane, a triallylcyanurate, an allylic ether, an acrylic ester obtained from a polyol, a methacrylic ester obtained from a polyol, a methacrylurethane ester obtained from a polyol, or any combination thereof.

3. The method according to claim 1, wherein the aqueous emulsion has a dry extract of between 10% and 50% by dry weight of polymer, compared to its total weight.

4. The method according to claim 1, wherein the emulsion has a particle size of between 50 nm and 500 nm.

5. The method according to claim 1, wherein the polymer has an average molar mass by weight of between 20,000 g/mole and 1,000,000 g/mole.

6. The method according to claim 1, wherein the content by weight of acrylic acid compared to the total weight of the acrylic acid and methacrylic acid is from 80% to 100%.

7. The method according to claim 1, wherein the content by weight of acrylic acid compared to the total weight of the acrylic acid and methacrylic acid is from 98% to 100%.

8. The method according to claim 1, wherein the polymer does not comprise methacrylic acid.

9. The method according to claim 1, wherein the formulation is a cosmetic formulation.

10. The method according to claim 9, wherein the cosmetic formulation comprises a surfactant and is suitable for application to human skin.

11. The method according to claim 1, wherein the formulation has a pH of from 5 to 6.5 after thickening.

12. The method according to claim 8, wherein the formulation has a pH of from 5.5 to 6 after thickening.

13. The method according to claim 1, wherein the 40% to 80% by weight of (b) is a combination of two monomers selected from the group consisting of ethyl acrylate, butyl acrylate, and methyl methacrylate, or else is a combination of ethyl acrylate, butyl acrylate, and methyl methacrylate.

14. The method according to claim 1, wherein, for a 1% dry weight content of the polymer in the thickened formulation, a viscosity of the thickened formulation is at least 1200 mPas at a pH of 7.

15. The method according to claim 1, wherein, for a 1% dry weight content of the polymer in the thickened formulation, a viscosity of the thickened formulation is at least 400 mPas greater at a pH of 6 than at a pH of 5.

16. The method according to claim 1, wherein, for a 1% dry weight content of the polymer in the thickened formulation, a viscosity of the thickened formulation is at least 1200 mPa.Math.s greater at a pH of 7 than at a pH of 5.

17. The method according to claim 15, wherein, for a 1% dry weight content of the polymer in the thickened formulation, a viscosity of the thickened formulation is at least 1200 mPa.Math.s greater at a pH of 7 than at a pH of 5.

18. The method according to claim 1, wherein: the emulsion has a particle size of between 50 nm and 500 nm, and the polymer has an average molar mass by weight of between 20,000 g/mole and 1,000,000 g/mole.

19. The method according to claim 18, wherein the content by weight of acrylic acid compared to the total weight of the acrylic acid and methacrylic acid is from 80% to 100%.

20. The method according to claim 19, wherein the cross-linked monomer is present and is ethylene glycol dimethacrylate, trimethylolpropanetriacrylate, diallyl phtalate, allyl acrylate, an allyl maleate, methylene-bis-acrylamide, methylene-bis-methacrylamide, tetraallyloxyethane, a triallylcyanurate, an allylic ether, an acrylic ester obtained from a polyol, a methacrylic ester obtained from a polyol, a methacrylurethane ester obtained from a polyol, or any combination thereof.

Description

BRIEF DESCRIPTION OF THE FIGURE

(1) FIG. 1 shows the results of tests where the change in the Brookfield™ viscosity in mPa.Math.s of a gel (Y axis) was measured as a function of the pH (X axis).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(2) As used herein the expression “direct emulsion of a polymer in water” designates a stable and uniform dispersion of polymer particles in water (no reference is made here to emulsions of the oil-in-water or water-in-oil type, which imply the existence of two separate phases, one water-based and the other oil-based). Concerning the expression “alkali-swellable polymer”, it signifies that the polymer is capable, when the medium is alkaline, of incorporating a quantity of water such that there is formation of a gel and therefore an increase of viscosity.

(3) The emulsions referred to in the present invention cover two major families of thickening agents: those of the ASE type (Alkali-Swellable Emulsion) and those of the HASE type (Hydrophobically modified Alkali-Swellable Emulsion). The former designate copolymers of (meth)acrylic acid with a non-water-soluble ester of these acids, and the latter designate copolymers with a (meth)acrylic acid base of a non-water-soluble ester of (meth)acrylic acid and of a monomer having hydrophobic groups called “associative” groups. These copolymers can also be cross-linked.

(4) The action mechanisms of these products, and notably the alkali-swellable character of these emulsions and their ability to thicken an aqueous medium with a pH close to neutrality, have been described in documents WO 2007/144721 and “Practical guide to associative thickeners” (Proceedings of the Annual Meeting Technical Program of the FSCT, 2000, 78th, 644-702), Thickening agents of the ASE and HASE type are generally manufactured in the form of direct emulsions of the alkali-swellable polymer in water, the active product content of which varies between 10% and 45% of their total weight.

(5) The corresponding synthesis method is notably described in the following publications: “Synthesis of an alkali-swellable emulsion and its effect on the rate of polymer diffusion in poly(vinyl acetate-butyl acrylate) latex films” (Journal of Polymer Science, Part A: Polymer Chemistry, 2005, 43 (22), pp. 5632-5642), “Structural and rheological properties of hydrophobically modified alkali-soluble emulsion solutions” (Journal of Polymer Science, Part B: Polymer Physics, 2002, 40(18), pp. 1985-1994). It is also the subject of many patent applications (EP 0 089 213 A1, EP 0 646 606 A1, EP 0 979 833 A1 in respect of ASEs and EP 0 013 836 A1, WO 93/2454 A1, U.S. Pat. No. 4,268,641 A1, U.S. Pat. No. 4,421,902 A1 U.S. Pat. No. 3,915,921 A1 in respect of HASEs).

(6) One object of the present invention is a method for thickening a cosmetic formulation, through contact of the formulation with a direct aqueous emulsion of a polymer, followed by regulation of the pH to a value between 5 and 7, preferentially between 5 and 6.5, and very preferentially between 5.5 and 6, wherein the emulsion is free from surfactants and organic solvents other than water, and in that the polymer comprises, consists essentially of, or consists of, expressed as a % by weight of each of the monomers: a) 20% to 60% by weight of methacrylic acid and acrylic acid, b) 40% to 80% by weight of at least one monomer chosen from among ethyl acrylate, butyl acrylate, methyl methacrylate and their blends, c) 0.05% to 22% by weight of 2-acrylamido-2-methylpropane sulfonic acid, d) 0 to 1% by weight of at least one cross-linked monomer, where the total a)+b)+c)+d) equals 100%,

(7) or a) 20% to 60% by weight of methacrylic acid and acrylic acid, b) 40% to 80% by weight of at least one monomer chosen from among ethyl acrylate, butyl acrylate, methyl methacrylate and their blends, c) 0.5% to 25% by weight of a monomer containing a hydrophobic group, d) 0.05% to 22% by weight of 2-acrylamido-2-methylpropane sulfonic acid, e) 0 to 1% by weight of at least one cross-linked monomer, where the total a)+b)+c)+d)+e) equals 100%,

(8) where in both cases the % by weight of acrylic acid compared to the total weight of the acrylic and methacrylic acids is between 50% and 100%, preferentially between 80% and 100%, very preferentially between 98% and 100%, and extremely preferentially where this % equals 100% (there is thus no methacrylic acid).

(9) The first type of composition indicated above is an emulsion of the ASE type which is rich in acrylic acid, and the second is an emulsion of the HASE type which is rich in acrylic acid.

(10) In the polymers of the invention it is understood that the monomers that make up the polymers exist in polymerized form, but they are nevertheless commonly referred to as polymers containing monomers, in accord with convention.

(11) In the invention method a preferred embodiment is wherein the monomer containing a hydrophobic group has the general formula R-(OE).sub.m-(OP).sub.n-R′, where: m and n designate integers of less than or equal to 150, at least one of which is non-zero, OE and OP designate respectively ethylene oxide and propylene oxide, R designates a polymerisable group, and preferentially the methacrylate or methacrylurethane group, R′ designates a hydrophobic group having at least 6 and at most 36 carbon atoms.

(12) In the invention method a preferred embodiment is wherein the cross-linked monomer is chosen from among ethylene glycol dimethacrylate, trimethylolpropanetriacrylate, diallyl phtalate, allyl acrylate, the allyl maleates, methylene-bis-acrylamide, methylene-bis-methacrylamide, tetrallyloxyethane, the triallylcyanurates, the allylic ethers and the acrylic, methacrylic and methacrylurethane esters obtained from polyols.

(13) In the invention method a preferred embodiment is wherein the aqueous emulsion has a dry extract of between 10% and 50% by dry weight of polymer, compared to its total weight.

(14) In the invention method a preferred embodiment is wherein the emulsion has a particle size of between 50 nm and 500 nm.

(15) In the invention method a preferred embodiment is wherein the polymer has an average molar mass by weight of between 20,000 Oriole and 1,000,000 g/mole.

(16) In the invention method a preferred embodiment is wherein the formulation, preferably a cosmetic formulation, is chosen from among the forms containing at least one surfactant, and notably from among those intended to be applied to skin (care creams, make-up products, foaming agents, shampoos, etc.).

(17) The following examples allow the invention to be better understood, without however limiting its scope.

EXAMPLES

Example 1

(18) This example relates to the thickening of water at a pH of 5.5.

(19) 3 emulsions of the HASE type according to the invention, using a polymer the mass composition of which is given in table 1, were tested.

(20) TABLE-US-00001 TABLE 1 Test Methacrylate n° AA AMA AE C.sub.22(OE).sub.25 AMPS 1 35.7 0.6 52.5 10 1.2 2 44.2 0.3 49.35 4.95 1.2 3 38.40 0.3 55.2 4.9 1.2 AA: acrylic acid AMA: methacrylic acid AE: ethyl acrylate Methacrylate C.sub.22(OE).sub.25: a monomer of general formula R—(OE).sub.m—(OP).sub.n—R’, where m = 25, n = 0, OE and OP designate respectively ethylene oxide and propylene oxide, R designates the methacrylate group, and R’ designates the linear alkyl group having 22 carbon atoms AMPS: 2-acrylamido-2-methylpropane sulfonic acid

(21) In the course of test n° 4 a polymer sold by the company Lubrizol™ under the name Aqua SF-1 was also used.

(22) For each test, 1% by dry weight of the polymer for testing, compared to the total weight of water to be thickened, was used. The change in the Brookfield™ viscosity in mPa.Math.s of the gel, measured at 100 revolutions per minute and at 25° C., was measured, as a function of the pH which was increased through the gradual addition of sodium hydroxide.

(23) FIG. 1/1 shows this change in the case of tests n° 1 (lozenges), 2 (squares), 3 crosses) and 4 (circles).

(24) It can be seen clearly that the method according to the invention which uses the emulsions with AMPS enables the thickening phenomenon to be activated for much lower pH values than with the commercial polymer.

(25) In addition, the thickening power in the pH zone between 5.5 and 6 is greater in the case of the polymers of the invention than for the polymer of the prior art.

(26) In view of the above, a preferred embodiment of the invention herein is a method for thickening a formulation, comprising contacting the formulation with a direct aqueous emulsion of a polymer to form a thickened formulation, followed by regulation of the pH of the thickened formulation to a value between 5 and 7, wherein the emulsion is free from surfactants and organic solvents other than water and the polymer consists, expressed as a % by weight of each of the monomers therein, of: a) 20% to 60% by weight of methacrylic acid and, optionally, acrylic acid where the % by weight of acrylic acid compared to the total weight of acrylic and methacrylic acid is at least 50%, b) 40% to 80% by weight of at least one monomer chosen from among ethyl acrylate, butyl acrylate, and methyl methacrylate, c) (105% to 22% by weight of 2-acrylamido-2-methylpropane sulfonic acid, and d) 0 to 1% by weight of at least one cross-linked monomer,

(27) or a) 20% to 60% by weight of methacrylic acid and, optionally acrylic acid, where the % by weight of acrylic acid compared to the total weight of acrylic acid and methacrylic acid is at least 50%, b) 40% to 80% by weight of at least one monomer chosen from among ethyl acrylate, butyl acrylate, and methyl methacrylate, c) 0.5% to 25% by weight of a monomer comprising a hydrophobic group, d) 0.05% to 22% by weight of 2-acrylamido-2-methylpropane sulfonic acid, and e) 0 to 1% by weight of at least one cross-linked monomer.

(28) The above written description of the invention provides a manner and process of making and using it such that any person skilled in this art is enabled to make and use the same, this enablement being provided in particular for the subject matter of the appended claims, which make up a part of the original description.

(29) As used herein, the words “a” and “an” and the like carry the meaning of “one or more.” The phrases “selected from the group consisting of,” “chosen from,” and the like include mixtures of the specified materials. Terms such as “contain(s)” and the like are open terms meaning ‘including at least’ unless otherwise specifically noted.

(30) All references, patents, applications, tests, standards, documents, publications, brochures, texts, articles, etc. mentioned herein are incorporated herein by reference. Where a numerical limit or range is stated, the endpoints are included. Also, all values and subranges within a numerical limit or range are specifically included as if explicitly written out.

(31) The above description is presented to enable a person skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the preferred embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the invention. Thus, this invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein. In this regard, certain embodiments within the invention may not show every benefit of the invention, considered broadly.