1. Field of the Invention
The present invention relates to a transparent liquid shampoo composition. More particularly, the invention relates to a transparent liquid shampoo that imparts a good finish to washed hair.
2. Description of the Prior Art
Shampoos have previously been prepared by using as a main component an anionic surface active agent such as a sodium alkyl sulfate, a triethanolamine alkyl sulfate, a sodium or triethanolamine salt of a polyoxyethylene alkyl ether sulfuric acid ester, a potassium salt of a higher fatty acid, a triethanolamine salt of a higher fatty acid or a sodium alkyloyl taurine, and incorporating into such anionic surface active agent a foaming enhancing agent such as a higher fatty acid alkanolamide.
It is considered necessary that shampoos possess a good foaming property, a good detergency and a property of imparting a supple and soft finish to washed hair. In connection with the foaming property and the detergency, these properties can easily be obtained by appropriately selecting the kind and concentration of the anionic surface active agent and the kind and the concentration of the higher fatty acid alkanolamide. However, attempts to impart suppleness and softness to washed hair have not been completely satisfactory.
It has been attempted to incorporate liquid paraffin, a higher alcohol, an ester, other oils or fats, an amphoteric surface active agent, a cationic surface active agent or the like into an anionic surface active agent shampoo base in order to impart a supple and soft finish to washed hair. However, since the primary purpose of a shampoo is to wash away contaminants (mainly composed of oils and fats) on the hair and head skin, it is substantially impossible to cause oil and fat components of the shampoo to remain in the hair after washing, and even if some amount of them is left, the amount is very small and it exerts little, if any, effect of rendering washed hair supple and manageable.
It has also been attempted to incorporate an amphoteric surface active agent or a cationic surface active agent into an aqueous solution of an anionic surface active agent. However, it is difficult to obtain a transparent composition, and even if the additive is dissolved at a high temperature, crystals are precipitated when the composition is cooled to a low temperature. Accordingly, a transparent liquid shampoo having an acceptable commercial value cannot be obtained. In order to increase the water solubility of the amphoteric or cationic surface active agent for overcoming the above disadvantage, it has been attempted to shorten the length of the alkyl chain, or to use an ethylene oxide adduct derivative or to introduce two quaternary ammonium nitrogen atoms into the molecule. However, enhancement of the water solubility of the amphoteric or cationic surface active agent results in a considerable reduction of the hair-softening effect. Accordingly, even if a transparent shampoo is obtained by using such a modified surface active agent, the shampoo does not exert an acceptable effect of softening hair and rendering same supple and manageable.