1993 年 27 巻 1 号 p. 3-10
(1) Catalytic activity of pigments often causes problems in mixture systems used in cosmetics, such as oxidation of oils and decomposition of perfumes. These pigments generally contain transition elements, such as chromium, iron, and manganese. Linalool, a common component of perfumes, is dehydrated via a carbonium-ion intermediate at acidic sites of the pigments. Linalool molecules experience allyl rearrangement to form a cyclized structure. The cyclized molecules are further dehydrogenated to result in p-cymene, which is a main cause of unpleasant odor in certain pigmented cosmetics.
(2) Surfaces of the pigments used in cosmetics were modified with various chemical substances, which include metal oxides, metallic soap, silicone-and fluorine-contained compounds. In particular, a novel two-step method to produce pigments possessing various functional groups was developed. The method consists of chemical vapor deposition of 1, 3, 5, 7-tetramethylcyclotetrasiloxane and hydrosilylation of various vinyl compounds. The silicone film formed on the pigments at the first step has a thickness of less than 1.0nm and various functional groups could be attached to the film.