Synthesis of Titanium Dioxide-Based Pigments with Co-Precipitated Phosphate

Titanium dioxide is used as a white pigment in cosmetics and other products, but it possesses photocatalytic activity and has become problematic for decomposing sebum when exposed to sunlight. Consequently, titanium phosphate has been investigated as a new white pigment, with expectations for its biocompatibility. However, this pigment had the drawback of having particles that were too large. Therefore, in this study, as a new process for cosmetic pigments, we prepared samples where titanium hydroxide and titanium phosphate were coprecipitated, and we attempted to create a mixed material of titanium oxide and titanium phosphate by heating. This method aimed to suppress photocatalytic activity and produce a novel pigment with particle sizes suitable for cosmetics. With this method, thorough rinsing with water is necessary to remove the sodium sulfate. Even in samples with a low phosphorus ratio of Ti/P = 10/1, photocatalytic activity was sufficiently suppressed. Under this Ti/P = 10/1 condition, the drawback of excessively large particle sizes typically found in phosphate pigments is not particularly noticeable. This study is expected to contribute to the development of new white pigments for use in cosmetics.