Heat Treated Precipitated Silica

Abstract

Process for heat treating precipitated silica to improve stability. Oral care compositions comprising such heat treated precipitated silica abrasives and a stannous ion source.

We claim: 
     
         1 . A process for improving the stability of precipitated silica particles with metal ions, said process comprising the steps of:
 a) providing one or more precipitated silica particles;   b) subjecting the precipitated silica particles to a temperature of at least about 800° C. for a period of time to produce one or more treated precipitated silica particles;   
       wherein the period of time is less than 5 minutes. 
     
     
         2 . A process according to  claim 1  wherein the temperature is from about 850° C. to about 1050° C. 
     
     
         3 . A process according to  claim 1  wherein the temperature is from about 900° C. to about 1000° C. 
     
     
         4 . A process according to  claim 1  wherein the period of time is less than or equal to about 3 minutes. 
     
     
         5 . A process according to  claim 2  wherein the period of time is less than or equal to about 2 minutes. 
     
     
         6 . A treated precipitated silica produced by the process of  claim 1 . 
     
     
         7 . An oral care composition comprising one or more treated precipitated silica particles produced by the process of  claim 1  and a metal ion source. 
     
     
         8 . The composition of  claim 7  wherein the metal ion source is a stannous ion source. 
     
     
         9 . The composition of  claim 8  wherein the stannous ion source is a stannous salt selected from the group consisting of stannous chloride, stannous gluconate, stannous acetate, stannous tartrate, stannous oxalate, stannous sulfate, stannous citrate, stannous malonate, stannous lactate, stannous phosphate, stannous pyrophosphate, stannous bromide, stannous iodide, and combinations thereof. 
     
     
         10 . The composition of  claim 8  wherein the amount of stannous ion is from about 50 ppm to about 15,000 ppm. 
     
     
         11 . The composition of  claim 8  wherein the amount of stannous ion is from less than about 10,000 ppm. 
     
     
         12 . The composition of  claim 8  wherein the stannous ions have a compatibility of greater than 80% after two weeks of storage at 25° C. 
     
     
         13 . The composition of  claim 8  wherein the stannous ions have a compatibility of greater than 80% before use. 
     
     
         14 . The composition of  claim 13  wherein the stannous ions have a compatibility of greater than 90% before use. 
     
     
         15 . The composition of  claim 8  wherein the stannous ion loss to heat treated precipitated silica is from about 5 to about 50 ppm/1% load of heat treated precipitated silica. 
     
     
         16 . The composition of  claim 7  further comprising a chelant. 
     
     
         17 . The composition of  claim 16  wherein the chelant is selected from polymeric organophosphate compounds including ethoxylated and non-ethoxylated mono or di alkyl phosphates or phosphonates. 
     
     
         18 . The composition of  claim 7  further comprising one or more essential oils. 
     
     
         19 . The composition of  claim 18  comprising two essential oils wherein the first essential oil is selected from the group consisting of acyclic or non-ring structures and a second essential oil is selected from ring-containing structures. 
     
     
         20 . The composition of  claim 7  further comprising a gel network.