Hollow borosilicate microspheres and method of making
AssigneePQ Corporation
InventorsJ. Stanley Miller, Reginald Thompson
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Abstract
The present invention provides hollow borosilicate microspheres having a mean particle size between 15 and 20 microns, and a true density below 0.25 g/cc. The invention also provides a method for making such microspheres comprising spray drying a solution of sodium silicate and sodium borate in a spray tower to form a precursor, milling the precursor, and heating the crushed precursor to a temperature in excess of 600.degree. F. to form hollow borosilicate microspheres.
Claims8
Hollow borosilicate microspheres having a mean diameter below 25 microns and a true density below 0.25 g/cc.
Hollow borosilicate microspheres comprising Na.sub.2 O, SiO.sub.2, and B.sub.2 O.sub.3 wherein the ratio of Na.sub.2 O:SiO.sub.2 :B.sub.2 O.sub.3 is between 1.0:2.5:0.2 and 1.0:3.22:0.5, said microspheres having a mean diameter between 15 and 20 microns, a diameter between 5 and 45 microns, and a true density below 0.25 g/cc.
Hollow borosilicate microspheres made according to a process comprising the steps of:
- spray drying a solution of sodium silicate and sodium borate in a spray tower to form a borosilicate precursor;
- milling said precursor to form a crushed borosilicate precursor;
- heating said crushed precursor to form hollow borosilicate microspheres having a mean diameter below 25 microns and true density below 0.25 g/cc.
Dependencies are inferred from the claim text.