Process for relaxing or straightening hair, using weak dicarboxylic acids with heat

1. A process for straightening or relaxing hair, comprising the following steps:

(a) providing a hair straightening or relaxing composition having a pH ranging from 8 to 11.5, and containing, in a cosmetically acceptable medium, at least one weak acid chosen from monocarboxylic, dicarboxylic and tricarboxylic acids, their salts, and mixtures thereof, and at least one denaturant capable of disrupting hydrogen bonds in the hair, in an amount of from 0.1% to 25% by weight, based on the total weight of the composition;

(b) contacting the hair with the hair straightening or relaxing composition to form treated hair; and

(c) straightening or relaxing the treated hair by applying heat, wherein hydroxide-containing compounds are not used.

2. The process of claim 1 , wherein the hair straightening or relaxing composition used in step (a) has a pH of at least 9 and up to 11.

3. The process of claim 1 , wherein the at least one weak acid is chosen from dicarboxylic acids.

4. The process of claim 1 , wherein the at least one weak acid is employed in the hair straightening or relaxing composition in an amount of from 0.1% to 50% by weight, based on the total weight of the composition.

5. The process of claim 1 , wherein the hair straightening or relaxing composition used in step (a) further contains at least one viscosity modifying agent.

6. The process of claim 5 , wherein the viscosity modifying agent is chosen from:

(a) cationic polymers;

(b) polysaccharides or polysaccharide derivatives;

(c) homopolymers and copolymers of carboxyvinyl monomers.

7. The process of claim 1 , wherein step (c) is performed with simultaneous use of means for smoothing hair at a temperature of at least 100° C.

8. A process for straightening or relaxing hair, comprising the following steps:

(a) providing a hair straightening or relaxing composition having a pH ranging from 8 to 11.5, and containing, in a cosmetically acceptable medium, at least one weak acid chosen from monocarboxylic, dicarboxylic and tricarboxylic acids, their salts, and mixtures thereof, wherein the at least one weak acid is chosen from malic acid, maleic acid, itaconic acid, oxalic acid, malonic acid, mesoxalic acid, fumaric acid, succinic acid, tartaric acid, alpha-ketoglutaric acid, iminodiacetic acid, galactartic acid, adipic acid, glutaric acid, their salts, and mixtures thereof;

(b) contacting the hair with the hair straightening or relaxing composition to form treated hair; and

(c) straightening or relaxing the treated hair by applying heat, wherein hydroxide-containing compounds are not used.

9. The process of claim 1 , wherein the amount of the at least one weak acid is from 0.5% to 20% by weight, based on the total weight of the composition.

10. The process of claim 1 , wherein the amount of the at least one weak acid is from 0.5% to 10% by weight, based on the total weight of the composition.

11. The process of claim 5 , wherein the amount of the at least one viscosity modifying agent is from 0.1% to 10% by weight, based on the total weight of the composition.

12. The process of claim 1 , wherein the at least one viscosity modifying agent is chosen from the group consisting of celluloses and derivatives thereof; xanthan gum, guar gum; starch and starch derivatives.

13. The process of claim 1 , wherein step (c) is performed with simultaneous use of means for smoothing using a flat iron having a heating temperature ranging from 150 to 200° C.

14. The process of claim 6 wherein said viscosity modifying agent comprises polyquaternium-37.