Production of high silica glass microspheres
AssigneeSaint-Gobain Vitrage
InventorsPatrick Garnier, Daniel Abriou, Benoit Beghin
Life of this patent
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Abstract
Production of microspheres having a very high silica content produced from a starting glass whose silica content is less than 80% by weight, with the remainder being essentially made up of boron oxide and one or more alkaline oxide(s). This starting glass is reduced into fine particles by grinding, optionally mixed with a fluidizing agent, and then passed through the flame of a burner at a temperature at least equal to 1500.degree. C. to form molten hollow microspheres which are suddenly cooled to form solid hollow microspheres. The microspheres produced thereby are recovered and contacted with a dealkalization agent to increase the silica content thereof to at least 92%.
Claims22
A process for the production of hollow microspheres with a high silica content from a starting glass whose silica content is less than 80% by weight, with the balance being essentially boron oxide and one or more alkaline oxides, which process comprises:
- grinding the starting glass into fine particles;
- passing these fine particles through the flame of a burner at a temperature of at least about 1500.degree. C. but less than about 1750.degree. C. to form molten hollow microspheres;
- suddenly cooling the molten hollow microspheres to solid hollow microspheres;
- recovering the microspheres;
- and
- contacting the recovered microspheres with a gaseous dealkalization agent of a temperature greater than 200.degree. C. but below that which would alter the structure of the microspheres to increase the silica content of the microspheres to at least 92%.
A process for the production of hollow microspheres with a high silica content from a starting glass whose silica content is less than 80% by weight, with the balance being essentially boron oxide in an amount of 15% or less and one or more alkaline oxides in an amount of 15% or less, which process comprises:
- grinding the starting glass into fine particles;
- adding to said particles a fluidizing agent of an organic compound having a first part which exhibits an affinity for the glass and a second part which promotes the independence of the particles, said fluidizing agent added in an amount sufficient to reduce the forces of attraction of the particles but less than that which would reduce the fluidity of the mixture;
- passing these fine particles through the flame of a burner at a temperature of at least about 1500.degree. C. to form molten hollow microspheres;
- suddenly cooling the molten hollow microspheres to solid hollow microspheres;
- recovering the microspheres;
- and
- contacting the recovered microspheres with a gaseous dealkalization agent of a temperature greater than 200.degree. C. but below that which would alter the structure of the microspheres to increase the silica content of the microspheres to at least 92%.
A process for the production of hollow microspheres having a high silica content from a starting glass whose silica content is less than 80% by weight, which process comprises:
- preparing a starting glass having a silica content of at least 60% but less than 80% by weight, with the balance being essentially boron oxide;
- one or more alkaline oxides in an amount sufficient to impart a softening temperature of less than about 1400.degree. C. to the glass and less than 0.5% of alkaline earth oxides;
- grinding the starting glass into fine particles;
- passing the fine particles through the flame of a burner at a temperature of between about 1500.degree. C. and 1750.degree. C. for a time sufficient to form molten hollow microspheres;
- suddenly cooling the molten hollow microspheres to solid hollow microspheres;
- recovering the microspheres;
- and
- dealkalizing the recovered microspheres at a temperature of between about 200.degree. C. and 500.degree. C. to increase the silica content thereof to at least 92%.
Dependencies are inferred from the claim text.