Method of preparing modified hollow, largely spherical particles by spray drying
AssigneePhiladelphia Quartz Company
InventorsDavid I. Netting, Elliot P. Hertzenberg
Life of this patent
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Abstract
Products of a generally spherical nature with particulate matter embedded in the walls are prepared by forming a suspension of said particulate matter in a solution of a film-forming substance in a volatile solvent, spray drying said suspension-solution thereby forming the product which may be further dried if necessary to remove solvent and to "set" the walls. Such products can be used to provide pigmenting, reactive and/or fire retardant properties to organic systems to which they are added as fillers. The density of the product can also be controlled by this method for use as fillers in applications in which segregation of such fillers from the plastic matrix is normally a problem.
Claims23
The process for producing hollow spherical products of 1 to 500 microns with particulate matter imbedded in the walls, comprising the steps of;
- a. forming a solution of 5 to 50% film-forming substance consisting of sodium silicate and a polysalt selected from the group consisting of ammonium pentaborate, sodium pentaborate and sodium hexametaphosphate and 50 to 95% water, wherein the ratio of polysalt to silicate solids is between 0.02:1 and 3:1;
- b. introducing into said solution a particulate matter having a particle size of 0.05 to 10 microns which is substantially unreactive and insoluble in the solution;
- c. agitating said solution and particulate matter to produce a homogeneous suspension-solution, the amount of said particulate solids being sufficient to provide 0.5 to 75% of the solids contained in said suspension-solution;
- d. spray drying the suspension-solution at an inlet temperature of 200.degree. to 500.degree.C and an outlet temperature of 100.degree. to 300.degree.C;
- e. collecting the product having a true particle density of 20 to 200 lbs/ft.sup.3.
A hollow product of largely spherical nature with a particle size of 10 to 500 microns and a true particle density of 20 to 200 lbs/ft.sup.3 consisting essentially of 25 to 99.5% film-forming substance consisting of sodium silicate and a polysalt selected from a group consisting of ammonium pentaborate, sodium pentaborate and sodium hexametaphosphate;
- 0.5 to 75% particulate matter embedded in the walls and 0 to 7% water with the ratio of polysalt solids to sodium silicate solids between 0.02:1 and 3:1.
Dependencies are inferred from the claim text.