Surface treating mineral particles to reduce halide adsorption
AssigneeAluminum Company of America
InventorsLawrence L. Musselman, Larry F. Wieserman
Life of this patent
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Abstract
Mineral particles are surface treated with an alkali metal silicate, hydrogen peroxide, an acid, or an organophosphorus compound. A preferred surface treating method utilizes sodium silicate in aqueous solution at pH greater than 9, followed by neutralization with acid to precipitate a silica coating onto surface portions of the particles. The mineral particles are preferably alumina particles. The surface-treated alumina particles may be incorporated into fluoride dentifrices or compounded with halogenated hydrocarbons and polymeric resins to form flame-retardant polymer compounds.
Claims20
A method for surface treating particles of a mineral to reduce adsorption of halide ions and halide free radicals onto surface portions of the particles, said method comprising:
- (a) surface treating mineral particles with an alkali metal silicate surface treating agent in an aqueous solution having an initial pH of at least 8.5;
- (b) neutralizing the aqueous solution to a pH of about 5-7, thereby to precipitate a silica coating onto surface portions of the particles;
- (c) separating the surface-treated mineral particles from the solution;
- and
- (d) drying the surface-treated particles.
In a polymer composition comprising about 100 parts by weight of a polymeric resin, about 1-400 parts by weight alumina hydrate particles having average particle size of about 0.1-200 microns and about 5-50 parts by weight of a halogenated hydrocarbon, the improvement wherein said alumina hydrate particles are surface-treated by:
- (a) mixing the particles with an aqueous solution of a surface treating agent selected from the group consisting of
- (1) an alkali metal silicate at an initial pH of at least 8.5,
- (2) hydrogen peroxide,
- (3) an acid selected from the group consisting of hydrochloric acid, acetic acid, phosphoric acid, phosphonic acid and phosphinic acid,
- (4) an organophosphorous compound selected from the group consisting of organophosphonates having the formula RPO(OH).sub.2 wherein R is a C.sub.1 C.sub.30 hydrocarbon group, organophosphinates having the formula RR'PO(OH) wherein R is as defined above and R' is hydrogen or a C.sub.1 -C.sub.30 hydrocarbon group, C.sub.1 -C.sub.5 alkyl esters of said organophosphonates and organophosphinates, phosphoric acid monoesters having the formula ROPO(OH).sub.2 and phosphoric acid diesters having the formula R.sub.2 OPO(OH);
- (b) adjusting the pH of the aqueous solution to about 5-7;
- (c) separating the alumina hydrate particles from the solution;
- and
- (d) drying the surface-treated particles.
In a fluoride dentifrice comprising about 30-98 wt. % of a vehicle having a pH of about 5-8, about 2-70 wt. % alumina abrasive particles having average particle size of about 1-20 microns and about 0.01-2 wt. % fluoride ions dissolved in the vehicle, the improvement wherein said alumina particles are surface-treated by:
- (a) mixing the particles with an aqueous solution of a surface treating agent selected from the group consisting of
- (1) an alkali metal silicate at an initial pH of at least 8.5,
- (2) hydrogen peroxide,
- (3) an acid selected from the group consisting of hydrochloric acid, acetic acid, phosphoric acid, phosphonic acid and phosphinic acid,
- (4) an organophosphorous compound selected from the group consisting of organophosphonates having the formula RPO(OH).sub.2 wherein R is a C.sub.1 -C.sub.30 hydrocarbon group, organophosphinates having the formula RR'PO(OH) wherein R is as defined above and R' is hydrogen or a C.sub.1 -C.sub.30 hydrocarbon group, C.sub.1 -C.sub.5 alkyl esters of said organophosphonates and organophosphinates, phosphoric acid monoesters having the formula ROPO(OH).sub.2 and phosphoric acid diesters having the formula R.sub.2 OPO(OH);
- (b) adjusting the pH of the aqueous solution to about 5-7;
- (c) separating the alumina hydrate particles from the solution;
- and
- (d) drying the surface-treated particles.
Dependencies are inferred from the claim text.