Fatty epoxide hydrophobized silica as antifoams in brownstock washing aids

摘要

An improved aqueous defoamer composition of the type comprising from 70-90% by weight of a water-insoluble organic liquid, from 0.1 to about 20% of a hydrophobic silica suspended in the organic liquid, and from about 1 to about 20% of an oil-soluble spreading agent, the improvement which comprises utilizing as the hydrophobic silica a silica which has at least a portion of its surface esterified with a fatty epoxide. The invention also contemplates an improved method for hydrophobizing silica particles by reacting them in an organic liquid with a fatty epoxide.