Novolac coated ceramic particulate
AssigneeMinnesota Mining and Manufacturing Company
InventorsJames L. Gibb, James A. Laird, Leslie G. Berntson
Life of this patent
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Abstract
Ceramic particulates useful as a proppant in hydraulic fracturing and in gravel packing operations is provided which comprises a ceramic (sometimes vitreous) core surrounded by an epoxy resin coating. Novolac epoxy resin compounds without any substantial acid soluble filler are used to coat ceramic particulates similar to those discloses in U.S. Pat. Nos. 4,680,230 and 4,632,876. The result is a product which combines the excellent solvent resistance of the ceramics with the acid resistance of the resin. The resin coating gives the added benefits of lower specific gravity and improved crush resistance.
Claims5
A process for making coated ceramic particulates which comprises:
- (A) furnishing raw materials comprising:
- (1) ceramic particles which have been fired and are made from raw materials which comprise:
- (a) mineral particulates comprising a ceramic which melts below about 1300.degree. C., vitrifies upon cooling and has a fired density of less than about 2.9 grams per cubic centimeter;
- and
- (b) sufficient binder to adhere the mineral particulates together after they have been formed but before they have been fired;
- (2) an epoxidized cresol novolac resin compound containing less than one weight percent of fillers which are soluble in aqueous 12:3 molar ratio HCl:HF solutions:
- (B) mixing said raw materials at a temperature sufficient to melt the epoxidized cresol novolac resin compound and allow it to flow around and coat the fired ceramic particles;
- and
- (C) curing the resulting coating on the particles.
Dependencies are inferred from the claim text.