Development of Cosmetic Formulations Using Rheological Properties -Generation of New Aqueous Thickeners and Novel Attempt for Quantitative Sensory Evaluation-

Cosmetic formulations are composed by various ingredients. In particular, aqueous thickeners play important role in both functional and sensory aspects in formulations. We mention about our attempts to use microgels as intelligent aqueous thickener and to quantify the texture of the cosmetics, by using the rheological properties. Agar microgel dispersion was prepared from agar bulk-gel which was granulated by high-speed mixer (5000 rpm). The inverse microemulsion polymerization system was also studied to create a fine microgel. The thickening effect of the microgel prepared by using the system was higher than that of the agar microgel. The flow characteristic parameters of the microgels were analized by using Herschel-Bulkley equation which is a scaling law model. It was revealed that both the microgels present refresh feeling through power index n in H-B equation. Flow properties of cosmetic lotions, containing various kinds of aqueous thickeners, were studied by creep measurement, and parameters were calculated from their rheological data based on the Nutting equation, which is an empirical equation. There were some correlations among the time dependency parameter a and some sensory evaluation points, assessed by human panels. Simple linear regression analysis revealed that the evaluation scores of slimy feeling, sticky feeling, refresh feeling, and penetrating feeling of the cosmetic lotions were converted to numerical data by the parameter a. This quantification method for the texture of cosmetic products will be a useful tool for efficient development of cosmetic formulations.