Method for production of abrasive composition for use in toothpaste

Claim 1

A method for the production of an abrasive composition useful for incorporation into a theraupeutic toothpaste composition and for preventing fluoride-caused corrosion and staining of an unlined aluminum tube containing said toothpaste composition, said abrasive composition comprising a silica which has been treated with a water-soluble alkaline earth metal compound so as to have present therein from about 168-7000 ppm of the alkaline earth metal, said silica being an amorphous precipitated silica and functioning as a carrier for the alkaline earth metal; said method comprising the following sequence of steps: (a) forming an aqueous solution of an alkali metal silicate having an SiO 2 to X 2 O mole ratio of about 2.0 to 2.7 and of an alkali metal sulfate at a reaction temperature in the range of about 66° to 83° C., wherein X represents the alkali metal; (b) acidulating said aqueous solution with a mineral acid with continuous agitation until precipitation of silicon dioxide is substantially complete at a pH of about 8.0 to 10.4; (c) continuing the mineral acid addition until the pH is 6.0 or less; (d) digesting at a temperature that is 10°-30° C. higher than the reaction temperature for a period of about 10 to 30 minutes; (e) filtering the resulting slurry and washing the solid product with fresh water; (f) reslurrying the resulting wet cake in water, and under agitation conditions, adding thereto at ambient temperature a water soluble alkaline earth metal compound in an amount sufficient to add to said wet cake from about 168-7000 ppm of the alkaline earth metal based on the dry recoverable product; (g) agitating the resulting mixture to provide adherence of the effective level of said metal on the surface of said silicon dioxide; and (h) drying and recovering said abrasive composition.

Claim 2

A method for the production of an abrasive composition useful for incorporation into a theraupeutic toothpaste composition and for preventing fluoride-caused corrosion and staining of an unlined aluminum tube containing said toothpaste composition, said abrasive composition comprising a silica which has been treated with a water-soluble alkaline earth metal compound so as to have present therein from about 168-7000 ppm of the alkaline earth metal, said silica being an amorphous precipitated silica and functioning as a carrier for the alkaline earth metal; said method comprising the following sequence of steps: (a) forming an aqueous solution of an alkali metal silicate having an SiO 2 to X 2 O mole ratio of about 2.0 to 2.7 and of an alkali metal sulfate at a reaction temperature in the range of about 66° to 83° C., wherein X represents the alkali metal; (b) acidulating said aqueous solution with a mineral acid with continuous agitation until precipitation of silicon dioxide is substantially complete at a pH of about 8.0 to 10.4; (c) continuing the mineral acid addition until the pH is 6.0 or less; (d) digesting at a temperature that is 10°-30° C. higher than the reaction temperature for a period of about 10 to 30 minutes; (e) filtering the resulting slurry and washing the solid product with fresh water; (f) reslurrying the resulting wet cake in water, and under agitation conditions, adding thereto at ambient temperature a water soluble alkaline earth metal compound in an amount sufficient to add to said wet cake from about 168-7000 ppm of the alkaline earth metal based on the dry recoverable product; (g) agitating the resulting mixture to provide adherence of the effective level of said metal on the surface of said silicon dioxide; and (h) drying and recovering said abrasive composition.