High ratio silicate foundry sand binders
AssigneeE. I. Du Pont de Nemours and Company
InventorHoracio E. Bergna
Life of this patent
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Abstract
Binder solution for preparing sand cores of initial high strength but with essentially no strength after casting metals above 700.degree. C., said binder solution comprising an aqueous solution of sodium, potassium or lithium silicate having an overall molar ratio of SiO.sub.2 /alkali metal oxide from 3.5:1 to 10:1, and containing sufficient amorphous silica so that the fraction of the total silica in the binder solution which is present as amorphous silica is from 2 to 75%, the amorphous silica having a particle size in the range from about 2 nanometers to 500 nanometers.
Claims9
A stable binder component composition consisting essentially of (a) 95 to 991/2% by weight of an aqueous binder comprising an aqueous sodium, potassium or lithium silicate solution or mixtures thereof and amorphous silica, the amorphous silica in the silicate solution determined by the gore test procedure, the binder characterized by (1) a molar ratio of silica to alkali metal oxide of from 3.5:1 to 10:1;
- (2) a weight fraction of the total silica present as amorphous silica is from 2 to 50%;
- (3) a weight fraction of the total silica present as silicate ions is from 98 to 50% and the amorphous silica has a particle size of from 2 nanometers to 500 nanometers and (b) 1/2 to 5% by weight of a suspending agent system comprising (1) carboxymethyl cellulose and (2) carboxyvinyl polymer in a total amount of about 36 to 65% by weight with the relative amount of (1) to (2) ranging from a weight ratio of about 1:4 to 4:1 and (3) magnesium montmorillonite clay in a concentration of about 35 to 64% by weight, said aqueous binder having 15 to 35% by weight silica solids.
Dependencies are inferred from the claim text.