Composition comprising a dicarbonyl derivative and method for straightening the hair using this composition

A cosmetic composition comprising:

• at least one compound chosen from dicarbonyl compounds of formula (I), derivatives thereof, hydrates thereof, or salts thereof:
• wherein in formula (I):
• R represents an atom or group chosen from i) hydrogen, ii) carboxyl —C(O)—OH, iii) linear or branched C1-C6 alkyl which is optionally substituted, iv) optionally substituted phenyl, v) optionally substituted benzyl, vi) an indolyl group, or vii) an imidazolylmethyl group and tautomers thereof, and compounds represented by the formula below:
• and tautomers thereof, wherein * represents the part linked to the rest of the dicarbonyl compound;
• and
• at least one silane of formula (II) and/or oligomers thereof:
• R1Si(OR2)z(R3)x(OH)y (II)
• wherein in formula (II):
• R1 is a linear or branched, saturated or unsaturated, cyclic or acyclic C1-C6 hydrocarbon-based chain substituted with a group chosen from the following groups:
• amine NH2 or NHR wherein R is chosen from C1-C20 alkyl and C1-C6 alkyl, optionally substituted with a group comprising a silicon atom, C3-C40 cycloalkyl or C6-C30 aromatic,
• a hydroxyl group,
• a thiol group, or
• an aryl or aryloxy group which is optionally substituted with an amino group or with a C1-C4 aminoalkyl group;
• R1 being optionally interrupted with a heteroatom, O, S, NH, or a carbonyl group (CO),
• R2 and R3, which may be identical or different, each represent a linear or branched C1-C6 alkyl group,
• y denotes an integer ranging from 0 to 3,
• z denotes an integer ranging from 0 to 3, and
• x denotes an integer ranging from 0 to 2,
• wherein z+x+y=3;
• wherein the cosmetic composition has a pH of less than 4.

A method for straightening hair, the method comprising:

• applying to the hair a composition A comprising:
• at least one compound chosen from dicarbonyl compounds of formula (I), derivatives thereof, hydrates thereof, or salts thereof:
• wherein in formula (I):
• R represents an atom or group chosen from i) hydrogen, ii) carboxyl —C(O)—OH, iii) linear or branched C1-C6 alkyl which is optionally substituted, iv) optionally substituted phenyl, v) optionally substituted benzyl, vi) an indolyl group, or vii) an imidazolylmethyl group and tautomers thereof, or compounds represented by the formula below:
• and tautomers thereof, wherein * represents the part linked to the rest of the dicarbonyl compound;
• and
• at least one silane of formula (II) and/or oligomers thereof:
• R1Si(OR2)z(R3)x(OH)y (II)
• wherein in formula (II):
• R1 is a linear or branched, saturated or unsaturated, cyclic or acyclic C1-C6 hydrocarbon-based chain substituted with a group chosen from the following groups:
• amine NH2 or NHR wherein R is chosen from C1-C20 alkyl and C1-C6 alkyl, optionally substituted with a group comprising a silicon atom, C3-C40 cycloalkyl or C6-C30 aromatic,
• a hydroxyl group,
• a thiol group, or
• an aryl or aryloxy group which is optionally substituted with an amino group or with a C1-C4 aminoalkyl group;
• R1 being optionally interrupted with a heteroatom, O, S, NH, or a carbonyl group (CO),
• R2 and R3, which may be identical or different, each represent a linear or branched C1-C6 alkyl group,
• y denotes an integer ranging from 0 to 3,
• z denotes an integer ranging from 0 to 3, and
• x denotes an integer ranging from 0 to 2,
• wherein z+x+y=3;
• wherein the composition A has a pH of less than 4;
• and
• performing a straightening step using a straightening device at a temperature of at least 150° C.