Application of the anionic-cationic mixed surfactants to shampoos as conditioning agents.

The interaction between stearyltrimethylammonium chloride (STAC) and sodium N-lauroyl-N-metyl-beta-alanine (NaLMA) has been investigated by viscosity, phase diagram, conductivity and phase inversion temperature techniques. The solution properties of the NaLMA-STAC mixture indicate the formation of hydrophobic ion-pairs between NaLMA and STAG. It has been demonstrated that the NaLMA-STAC mixture is water soluble over a wide temperature range because of its low Krafft point and exhibits cloud point behavior similar to that of polyoxyetylenated nonionic surfactants. In addition, the NaLMA-STAC mixture shows a weak interaction with proteins.The hydrophobic nature of these ion-pairs is effective for the sorption by hair and for the lowering of the coefficient of friction of the hair. It has been shown that the use of anionic cationic mixed conditioners makes it possible to formulate a newtype of conditioning shampoo (all-in-one shampoo and conditioner) which sufficiently decreases the friction of the hair and suppresses the electrostatic charge generated by combing.