Silicon oxide pigments used for toothpaste prodn - made by stepwise acid-ification of alkali metal silicate solns

摘要

Title compsn. with high abrasion props. low water retention, layer structure, low specific surface and low oil absorption are made by (1) acidifying an alkali metal silicate soln. to the onset of ppn., (2) interrupting the addition of acid e.g. for 10 mins.-2 hours and allowing the mixt. to ripen, (3) adding more acid to complete the ppn. and (4) filtering, washing and drying the ppte. In general a Na silicate solution is acidified with aqs. H2SO3, HCl, HNO3, acetic acid or formic acid soln. until just opalescent, the mixt. is then aged for 10-15 mins. and acidification then continued to a pH of 5-7 to complete the pptn. The ppte. filters rapidly and the filter cake has low water retention. Products are useful as molecular sieves, matting agents, carriers, fillers and viscosity control agents, and especially as fillers in toothpastes, e.g. of the clear gel type.