Inverse latex for a cosmetic composition comprising a specific sequestering agent and a polyelectrolyte combining a strong acid function and a weak acid function

1 . A self-invertible inverse latex comprising an aqueous phase comprising:

a) a crosslinked anionic polyelectrolyte (P) consisting of:

at least one first monomer unit resulting from 2-methyl-2-[(1-oxo-2-propenyl)amino]-1-propanesulfonic acid in free acid form or partially or totally salified form; and

at least one second monomer unit derived from at least one monomer chosen from the elements of the group consisting of acrylic acid, methacrylic acid, 2-carboxyethylacrylic acid, itaconic acid, maleic acid, 3-methyl-3-[(1-oxo-2-propenyl)amino]butanoic acid, the carboxylic function of said monomers being in free acid form or partially salified or totally salified form; and

at least one third monomer unit derived from a polyethylenic crosslinking monomer (AR), and

b) ethylenediaminedisuccinic acid in trisodium salt form, in an amount of at least 250 molar ppm calculated relative to the molar sum of said first and second monomer units.

2 . The inverse latex as claimed in claim 1 , wherein the polyethylenic crosslinking monomer (AR) is chosen from methylenebis(acrylamide), ethylene glycol dimethacrylate, diethylene glycol diacrylate, ethylene glycol diacrylate, diallylurea, triallylamine, trimethylolpropane triacrylate, diallyloxyacetic acid or a salt thereof, or a mixture of these compounds.

3 . The inverse latex as claimed in claim 1 , wherein the crosslinking monomer (AR) is methylenebis(acrylamide) or triallylamine.

4 . The inverse latex as claimed in claim 1 , wherein the crosslinked anionic polyelectrolyte comprises, per 100 mol %:

a proportion of between 20 mol % and 90 mol % of the monomer unit derived from 2-methyl-2-[(1-oxo-2-propenyl)amino]-1-propanesulfonic acid in free acid form or partially or totally salified form;

a proportion of between 10 mol % and 80 mol % of the monomer unit derived from at least one monomer chosen from the elements of the group consisting of acrylic acid, methacrylic acid, 2-carboxyethylacrylic acid, itaconic acid, maleic acid, 3-methyl-3-[(1-oxo-2-propenyl)amino] butanoic acid, the carboxylic function of said monomers being in free acid form or partially salified or totally salified form; and

a proportion of greater than 0 mol % and less than or equal to 1 mol % of monomer units derived from at least one polyethylenic crosslinking monomer (AR).

5 . A process for preparing an inverse latex as defined in claim 1 , comprising the following steps:

a) preparing the aqueous phase,

b) preparing an organic phase comprising at least one oil (O) and an emulsifying system (S1) of water-in-oil type,

c) mixing the aqueous phase and the organic phase prepared in steps a) and b) and emulsifying so as to form an emulsion,

d) inertizing the emulsion with nitrogen,

e) initiating the polymerization reaction by introduction, into the inertized emulsion, of a free-radical initiator, and

f) introduction, into the reaction medium resulting from step e), of an emulsifying system (S2) of oil-in-water type at a temperature of between 30° C. and 60° C.

6 . The process as claimed in claim 5 , further comprising between steps a) and b) a step of adding, to the aqueous phase prepared in step a), a solution chosen from a sodium hydroxide solution, a potassium hydroxide solution, an ammonium hydroxide solution, a monoethanolamine salt solution and a lysine salt solution.

7 . The process as claimed in claim 5 , wherein, in step e), the radical initiator is a redox pair which generates hydrogen sulfite (HSO 3 − ) ions.

8 . The process as claimed in claim 5 , wherein, in step e), a polymerization coinitiator is introduced into the inertized emulsion.

9 . The process as claimed in claim 5 , wherein, in step a), the pH of the aqueous phase is adjusted to between 3.0 and 7.0.

10 . The process as claimed in claim 5 , wherein the reaction medium derived from step e) is concentrated by distillation before performing step f).

11 . The process as claimed in claim 5 , wherein the reaction medium derived from step e) or f) is spray-dried.

12 . A thickening and/or emulsifying and/or stabilizing agent for a topical cosmetic composition, comprising the inverse latex of claim 1 .

13 . A topical cosmetic composition (F), comprising as thickener, per 100% of its total mass, between 0.1% and 10% by mass of said inverse latex as defined in claim 1 .

14 . A topical pharmaceutical composition (G), comprising, as thickener, per 100% of its total mass, between 0.1% and 10% by mass of said inverse latex as defined in claim 1 .

15 . The process of claim 7 , wherein the redox pair is the cumene hydroperoxide/sodium metabisulfite (Na 2 S 2 O 5 ) pair.

16 . The process of claim 7 , wherein the redox pair is the cumene hydroperoxide/thionyl chloride (SOCl 2 ) pair.

17 . The process of claim 8 , wherein the polymerization coinitiator is azobis(isobutyronitrile).

18 . The inverse latex as claimed in claim 1 , wherein the polyethylenic crosslinking monomer (AR) is chosen from methylenebis(acrylamide), ethylene glycol dimethacrylate, diethylene glycol diacrylate, ethylene glycol diacrylate, diallylurea, triallylamine, trimethylolpropane triacrylate, diallyloxyacetic acid or a salt thereof, or a mixture of these compounds.

19 . The inverse latex as claimed in claim 2 , wherein the polyethylenic crosslinking monomer (AR) is chosen from methylenebis(acrylamide), ethylene glycol dimethacrylate, diethylene glycol diacrylate, ethylene glycol diacrylate, diallylurea, triallylamine, trimethylolpropane triacrylate, diallyloxyacetic acid or a salt thereof, or a mixture of these compounds.