Dentifrice-compatible silica particulates

Abstract

Novel silica particulates especially adapted for formulation to dentifrice compositions exhibit unique physical and chemical properties. In one embodiment, silica particulates have a unique surface chemistry as to be at least 50% compatible with zinc values, and have a number of OH functions, expressed as OH/nm.sup.2, of at most 15 and a zero charge point (PZC) of from 3 to 6.5. In a second embodiment, particulates have a surface chemistry as to be at least 65%, and preferably at least 90% compatible with guanidine values, notably chlorhexidine, and acidity function thereof, Ho, of at least 3.3. In a third embodiment, silica particulates are compatible with organic amines, and have a pH, in aqueous suspension, which varies according to the equations pH.ltoreq.7.5-0.7 log(C) and pH.gtoreq.5.0-0.5 log(C) and which also varies as a function of the electrical conductivity thereof, according to the equations pH.ltoreq.8.5-0.4 log(D) and pH.gtoreq.7.0-0.6 log(D) wherein (C) represents the weight concentration of said silica suspension, expressed % SiO.sub.2 and (D) represents the electrical conductivity of such aqueous silica suspension expressed in microsiemens.multidot.cm.sup.-1. In a fourth embodiment, novel silica particulates are compatible with such metal cations as zinc, tin, strontium, and the like, as well as with the fluorides, and have a unique surface chemistry such that the number of OH.sup.- functions thereof, expressed in OH.sup.- /nm.sup.2, is equal to or less than 10, and also have a zero charge point (ZCP) ranging from 3 to 6.5 and a pH, in aqueous suspension, which varies as a function of the electrical conductivity thereof according to the equation pH=b-a log (D) in which a is a constant equal to or less than 0.6; b is a constant equal to or less than 8.5; and (D) represents the electrical conductivity of such aqueous silica suspension, expressed in microsiemens.multidot.cm.sup.-1.