SILICA BASE MATERIAL FOR DENTIFRICE FORMULATION AND METHOD FOR MAKING SAME

摘要

The invention provides a silica base material for dentifrice formulation having a specific surface area by the BET method of 270-500 m2/g-anhydride, and having a specific surface area by the CTAB method of 5-60 m2/ g-anhydride. The material gives virtually amorphous Xray diffraction patterns after firing at 1100.degree.C, and the material has a refractive index of 1.455-1.470. The invention also provides a method for production of the silica base material wherein the reaction between alkali metal silicate solution and hydrochloric or sulfuric acid in the presence of electrolyte is conducted in two stages, namely the crystallization stage where the pH is adjusted to 10.0, and the acidification stage where the pH is adjusted to 3.5 or less. The ratio of the rate of addition of chloride or sulfate ions between the acidification and silica crystallization stages is at least 3:2, and the acidification is carried out within 30 minutes.