CROSSLINKED POLYMER LATEX AND LOW-PH TRANSPARENT AQUEOUS COMPOSITION FOR HAIR OR SKIN CARE

Abstract

The present invention relates to a latex comprising a crosslinked polymer, the polymer comprising 20 to 45 wt % of (meth)acrylic acid monomer units, 35 to 78 wt % of methylacrylate and/or ethylacrylate monomer units, 0 to 30 wt % of monomer units of at least one linear alkyl acrylate, the linear alkyl comprising 3 to 9 carbon atoms, characterized in that the polymer is crosslinked with N-methylenebisacrylamide. The latex according to the invention helps thicken a composition for hair and/or skin care having a pH of between 3.5 and 5.5.

Claims

1. A latex comprising a crosslinked polymer, said polymer comprising: from 20 to 45% by weight of monomer unit of (meth)acrylic acid; from 35 to 78% by weight of monomer unit of methyl acrylate and/or ethyl acrylate; and from 0 to 30% by weight of monomer unit of at least one linear alkyl acrylate, the linear alkyl comprising 3 to 9 carbon atoms; the sum of the monomer units being equal to 100% by weight; wherein: the polymer is crosslinked with N-methylene-bis-acrylamide; and in that the polymer is free of monomer unit having an alkyl chain of at least 10 carbon atoms, and monomer unit of formula —(CHR.sup.1—CHR.sup.2—O)—, R.sup.1 and R.sup.2 being, independently of each other, a hydrogen atom or an alkyl group.

2. The latex according to claim 1, wherein the polymer is crosslinked with an amount of N-methylene-bis-acrylamide of between 500 and 5000 ppm by weight relative to the total weight of monomers.

3. The latex according to claim 1, wherein the polymer is crosslinked with N-methylene-bis-acrylamide as sole crosslinking agent.

4. The latex according to claim 1, wherein the amount of monomer unit of (meth)acrylic acid is between 25 and 40% by weight.

5. The latex according to claim 1, wherein the polymer comprises an amount of monomer unit of acrylic acid of less than 20% by weight.

6. The latex according to claim 1, wherein the polymer is free of monomer unit of acrylic acid.

7. The latex according to claim 1, wherein the crosslinked polymer comprises: from 20 to 45% by weight of monomer unit of methacrylic acid; from 35 to 78% by weight of monomer unit of ethyl acrylate; and from 0 to 30% by weight of monomer unit of at least one linear alkyl acrylate, the alkyl comprising 3 to 9 carbon atoms.

8. The latex according to claim 1, wherein the amount of linear alkyl acrylate monomer unit, the linear alkyl comprising 3 to 9 carbon atoms, is between 1 and 25% by weight.

9. The latex according to claim 1, wherein the linear alkyl acrylate, the linear alkyl comprising 3 to 9 carbon atoms, is chosen from butyl acrylate, ethylhexyl acrylate and mixtures thereof.

10. The latex according to claim 1, wherein the latex comprises between 20 and 40% by weight of crosslinked polymer, between 60 and 80% by weight of water, and between 0.1 and 2% of surfactant compounds and/or post-treatment compounds, relative to the weight of the latex.

11. The latex according to claim 1, wherein the latex is free of monomer unit of 2-acrylamido-2-methylpropanesulfonic acid.

12. The latex according to claim 1, wherein the latex is free of a strong acid monomer unit.

13. A hair and/or skin care composition comprising at least one latex according to claim 1.

14. The composition for hair and/or skin care according to claim 13, wherein the composition also comprises: at least a first surfactant; at least one second surfactant different from the first surfactant; optionally at least one silicone agent; optionally at least one active ingredient; and some water.

15. A method for thickening a hair and/or skin care composition having a pH of between 3.5 and 5.5, said method comprising preparing the hair and/or skin care composition such that it comprises the latex according to claim 1.

16. The latex according to claim 2, wherein the polymer is crosslinked with N-methylene-bis-acrylamide as sole crosslinking agent.

17. The latex according to claim 16, wherein the amount of monomer unit of (meth)acrylic acid is between 25 and 40% by weight.

18. The latex according to claim 16, wherein the polymer comprises an amount of monomer unit of acrylic acid of less than 5% by weight.

19. The latex according to claim 16, wherein the crosslinked polymer comprises: from 20 to 45% by weight of monomer unit of methacrylic acid; from 35 to 78% by weight of monomer unit of ethyl acrylate; and from 0 to 30% by weight of monomer unit of at least one linear alkyl acrylate, the alkyl comprising 3 to 9 carbon atoms.

20. The latex according to claim 19, wherein: the linear alkyl acrylate, the linear alkyl comprising 3 to 9 carbon atoms, is chosen from butyl acrylate, ethylhexyl acrylate and mixtures thereof; the amount of the linear alkyl acrylate monomer unit, the linear alkyl comprising 3 to 9 carbon atoms, is between 1 and 25% by weight; and the latex comprises between 20 and 40% by weight of crosslinked polymer, between 60 and 80% by weight of water, and between 0.1 and 2% of surfactant compounds and/or post-treatment compounds, relative to the weight of the latex.

Description

EXAMPLES

[0085] Glossary

[0086] AMA: MethAcrylic Acid

[0087] AE: Ethyl Acrylate

[0088] ABu: Butyl Acrylate

[0089] AEH: EthylHexyl Acrylate

[0090] ABe: Poly(ethylene oxide) behenyl acrylate (25 ethoxylated units)

[0091] MBA: N-MethyleneBisAcrylamide

[0092] TMPTA: TriMethylol Propane TriAcrylate

[0093] APE: Allyl Penta Erythritole

[0094] TAAC: TretraAllyl Ammonium Chloride

[0095] SLES: Sodium Lauryl Ether Sulfate

[0096] NaOH: Sodium Hydroxide

[0097] CAPB: CocAmidoPropyl Betaine

[0098] 1/ Synthesis of crosslinked polymer latices

[0099] Examples I1 to I15 and comparative examples C1 to C12 are synthesized according to the following protocol. The amounts of monomers are adjusted in order to comply with the ratios specified in Table 1 and while maintaining an amount of crosslinked polymer of 30% by weight relative to the total weight of the latex.

[0100] Latex Synthesis Protocol

[0101] 423.0 g of deionized water and 2.5 g of a 30% by weight solution of sodium dodecyl sulphate are introduced into a jacketed reactor equipped with mechanical stirring and a condenser. The medium is heated to 89° C.

[0102] A pre-emulsion containing 154.0 g of deionized water, 7.5 g of a 30% by weight solution of sodium dodecyl sulfate, 90.0 g (1.05 mol) of methacrylic acid, 135 g (1.35 mol) of ethyl acrylate, 75.0 g (0.59 mol) of butyl acrylate and 0.6 g (3.9 mmol) of N-methylene-bis-acrylamide are added in this order under magnetic stirring for 10 minutes (solution A).

[0103] 70.1 g of a solution of sodium persulfate at 850 ppm in deionized water is prepared (solution B).

[0104] When the reactor is at the set temperature, 28.1 g of a 4250 ppm solution of sodium persulfate in deionized water are injected into the reactor and the 2 solutions A and B are added respectively to 1.2 mL/min and 5.4 L/h for 20 minutes, then the flow rate is increased to 2.4 mL/min and 10.3 L/h respectively until the solutions are consumed.

[0105] When the additions of solutions A and B are completed, the medium is left under stirring at 84° C. for 30 minutes then cooled to 70° C. 7.4 g of a 5.1% solution of terbutyl hydroperoxide in deionized water are then added to the reactor. 10 minutes after this addition, 7.3 g of a 4.1% solution of isoascorbic acid are added in the deionized water.

[0106] After 30 minutes, the latex is filtered at 300 μm.

TABLE-US-00001 TABLE 1 Composition of crosslinked polymers of latices Monomers Crosslinking agents AMA ABe AE ABu AEH AA MBA TMPTA APE TAAC I1 35 65 0.2 I2 35 55 10 0.2 I3 35 55 10 0.2 I4 25 55 20 0.2 I5 24 60 16 0.2 I6 28 62 10 0.2 I7 40 55 5 0.2 I8 30 45 25 0.2 I9 25 70 5 0.2 I10 30 65 5 0.2 I11 30 55 10 5 0.2 I12 30 55 10 5 0.2 I13 25 65 10 0.2 I14 25 55 10 10 0.2 I15 25 55 10 10 0.2 C1 35 65 0.4 C2 35 65 0.66 C3 35 65 0.05 C4 35 65 0.2 C5 51 49 1 0.2 C6 35 55 10 0.3 C7 18 50 32 0.2 C8 35 8 57 0.2 C9 35 65 0.03 C10 35 65 0.6 C11 28 62 10 0.03 C12 28 62 10 0.6

[0107] All polymerizations lead to stable latices with the exception of comparative examples C2 and C4.

[0108] 2/ Formulation of Composition for Hair and/or Skin Care

[0109] The latices of polymers of examples I1-I15 and comparative examples C1-C12 are used to formulate a composition for hair and/or skin care. Table 2 describes the composition of the formulation. The amounts of the ingredients are given as a percentage of active ingredient.

TABLE-US-00002 TABLE 2 Composition for hair and/or skin care (Sa = sufficient amount) Ingredients % by weight Water 84.5 Polymer  2.4 SLES 11.2 NaOH Sa pH 6.6 CAPB  1.9 Citric acid Sa pH 5.5 or 4.5

[0110] The composition contains 2.4% by weight of polymer, i.e., 8% by weight of latex.

[0111] 3/ Formulation Analysis

[0112] The formulations are evaluated according to three criteria: their Brookfield viscosity at 20 rpm, their transmittance at 500 nm and their threshold stress.

[0113] The viscosity measurement is carried out at 25° C. on a Brookfield RVT viscometer equipped with a module 4. A viscosity value of between 3000 and 8000 cP (centipoise) is sought and desired in order to maintain adequate flow properties.

[0114] The transmittance of the formulation is measured on a Hach Lange DR 600 spectrophotometer at 500 nm in 1.5 mL polystyrene (PS) cups (10-mm optical path), at 25° C. The formulation is considered to be transparent when the transmittance value is greater than 85%.

[0115] The threshold stress measurement is carried out at 25° C. on a Malvern Kinexus Pro+ rheometer equipped with a cone-plane geometry (2°/60 mm). A stress rise programming from 0.1 to 100 Pa is applied and ten acquisitions are carried out per logarithmic decade. The formulation samples are centrifuged beforehand for 5 minutes at 5000 rpm in order to remove the air bubbles. This value reflects the suspensivity of the formulations and is considered sufficient and satisfactory beyond 1.5 Pa.

[0116] A result for a composition is considered good and satisfactory when the three criteria are satisfied for at least one of the tests, either at pH=5.5 or at pH=4.5.

[0117] The results are summarized in Table 3 below:

TABLE-US-00003 TABLE 3 Results of the analyzes Brookfield Threshold Transmittance viscosity (cP) stress (Pa) (%) pH 5.5 pH 4.5 pH 5.5 pH 4.5 pH 5.5 pH 4.5 I1 3200 4100 2.12 2.38 88.1 87.5 I2 4100 6850 2.49 2.61 93 92.8 I3 1900 3600 1.68 1.99 93 93.4 I4 5900 12600 1.98 2.38 95.1 92.6 I5 2500 7800 1.57 3.36 97.2 96.9 I6 4200 7500 2.67 3 94.8 94.4 I7 2200 3300 1.54 1.93 87.1 85.9 I8 7300 18600 1.89 2.38 96.2 93.8 I9 4700 8000 2.61 2.93 94 93.2 I10 3400 4200 1.8 2.0 86.2 85.8 I11 4200 7100 2.1 2 3 89.8 89.2 I12 2000 4200 1.6 1.8 90.4 90.1 I13 3600 4400 1.6 1.7 85.7 85.2 I14 4300 7100 1.8 1.9 87.3 86.9 I15 4500 4700 1.5 1.6 87.9 87.6 C1 2500 3100 1.25 1.22 88.7 88.7 C2 N/A N/A N/A N/A N/A N/A C3 2000 2600 1.37 1.47 86.5 85.6 C4 N/A N/A N/A N/A N/A N/A C5 2000 2200 2.03 1.79 61.9 51.9 C6 1600 2500 0.62 0.73 94.2 93.8 C7 5200 4200 2.23 1.65 51.1 42.7 C8 11000 11200 4.9 5.6 79.4 76..8 C9 1100 1200 0.3 0.4 98.9 98.6 C10 8500 13700 3.8 4.6 37.6 33.2 C11 1300 1500 0.2 0.5 99.6 99.4 C12 9200 12800 4.1 5.2 27.5 25.8 N/A: Not Applicable because counter-examples C2 and C4 do not lead to stable latices.

[0118] The results of the examples I1 to I15 demonstrate that the latices according to the invention make it possible to satisfy the three criteria of viscosity, transmittance and threshold stress for at least one of the two pH values, whereas the latices of the comparative examples do not allow it. The latices according to the invention display, for at least one of the pH values, both a viscosity of between 3000 and 8000 cP, a transmittance greater than 85% and a threshold stress greater than 1.5 Pa. On the contrary, none of the counter-examples C1-C8 meets these three criteria for the same pH value. Therefore, the latices according to the invention offer a better compromise in terms of rheological properties and transparency.

[0119] Furthermore, it is observed that the latices according to the invention containing acrylic acid (I10 to I15) offer a satisfactory compromise in terms of rheological properties and transparency. This compromise is improved even more markedly when the respective latices contain more methacrylic acid, and even more so when they do not contain acrylic acid, which results, in particular, in a lower threshold stress and transmittance. This is appreciable by comparing in particular the latices I1, I2, and I3 with the latices I10, I11 and I12 respectively, and I13, I14 and I15 respectively, the latter having been obtained by replacing 5% or 10% of methacrylic acid by acrylic acid in the former. This compromise becomes more advantageous as the amount of methacrylic acid increases, i.e., when the amount of acrylic acid decreases.

[0120] Latices C9 to C12 are similar to latices I1 and I6, but differ in their amount of MBA crosslinking agent and respectively equal to 0.03% by weight (300 ppm) and 0.6% by weight (6000 ppm). It is observed that the best results are obtained when the MBA concentration is between 0.05% by weight (500 ppm) and 0.5% by weight (5000 ppm). In this case (500-5000 ppm of MBA), the latices obtained provide the best compromise in terms of rheological properties and transparency.

[0121] 4/ Evaluation of the Latices of the Invention Compared to the Comparative Examples.

[0122] The latices of examples I1, I2, I6 and I9 are compared with the examples deemed relevant from the patents cited in the prior state of the art (Table 4). Latices are used in the formulation described previously and the same parameters were studied.

TABLE-US-00004 TABLE 4 Comparative examples C13 to C15 of the prior art Comparative example Prior art Example C13 US 2013/0112185 Example 1 C14 WO 2015/158668 Example 7 C15 WO 2016/102790 Example 6

[0123] The results are recorded in Table 5 below.

TABLE-US-00005 TABLE 5 Test results Brookfield Threshold Transmittance viscosity (cP) stress (Pa) (%) pH 5.5 pH 4.5 pH 5.5 pH 4.5 pH 5.5 pH 4.5 I1 3200 4100 2.12 2.38 88.1 87.5 I2 4100 6850 2.49 2.61 93 92.8 I6 4200 7500 2.67 3 94.8 94.4 I9 4700 8000 2.61 2.93 94 93.2 C13 2200 2500 0.97 1.19 82.6 78.6 C14 9100 10300 1.82 2.34 84.2 82.8 C15 8300 8600 1.77 2.44 83.4 83.7

[0124] The results of the tests show that the polymers of comparative examples C13 to C15 do not make it possible to achieve levels of transmittance as high as those of the polymers of the invention. The C13 latex polymer, having the same composition as that of example I1 but crosslinked with TMPTA, does not make it possible to achieve properties as advantageous as when the polymer is crosslinked with MBA. The polymers of comparative examples C14 and C15, which contain monomer units having an alkyl chain of at least 10 carbon atoms, or monomer units of formula —(CHR.sup.1—CHR.sup.2—O)— with R.sup.1 and R.sup.2 being, independently of each other, a hydrogen atom or an alkyl group, offer levels of transmittance lower than those obtained with the latices according to the invention.