As taught in U.S. Pat. No. 3,489,687 (Inamorato et al.), U.S. Pat. No. 4,276,205 (Ferry), and U.S. Pat. No. 4,659,565 (Smith et al.), it is known that mixed tert-amine oxides containing alkyl groups of different chain lengths can be used in conjunction with other materials, such as other surfactants, detergent builders, and/or other additives, to prepare liquid or solid detergents.
The mixed tert-amine oxides which have been synthesized by conventional techniques, i.e., the typical aqueous solutions of mixed tert-amine oxides, present no particular problems in the preparation of liquid detergents in which their water content is not a liability. However, they have to be dried in order to be used in the preparation of solid detergents.
The technique used by Inamorato et al. to dry their aqueous tert-amine oxides is to mix them with sufficient amounts of hydratable inorganic salts, such as sodium sulfate or sodium tripolyphosphate, to react with substantially all of the water in the solution. Using this technique, they form a friable amine oxide/hydrated salt mixture which they can granulate to obtain a free-flowing detergent composition.
When Ferry uses tert-amine oxides to prepare solid detergents, he spray-dries the aqueous solutions--a technique that is effective in removing the water but has the unfortunate side-effect of subjecting the amine oxides to temperatures at which they are apt to decompose and form amines that are corrosive to the skin.