Combination of surface modifiers for powdered inorganic fillers

Claim 1

A filler composition containing a combination of surface modifiers, said composition comprising (a) a powdered inorganic filler having a median particle size of less than about 15 microns, said filler being selected from the group consisting of alumina hydrate and bauxite, and (b) surface modifiers for the filler comprising (1) about 0.25 to 2.5 wt % of a mixture of saturated carboxylic acids consisting essentially of about 16 to 20 carbon atoms, said mixture having an iodine value of about 15 or less, and (2) about 0.25 to 2.5 wt % of an organosilane comprising (i) an organosilane of the formula R.sub.n (SiX.sub.4-n).sub.b wherein R is selected from the group consisting of alkyl radicals containing 1 to 8 carbon atoms, alkenyl and alkynyl radicals containing 2 to 8 carbon atoms, and phenyl radicals, X is a hydrolyzable group; n=0 or 1; and b is at least 1 and not greater than 4, or (ii) an organosilane of the formula R.sub.1 R.sub.2 Si(OR.sub.2).sub.2 or R.sub.1 Si(OR.sub.2).sub.3 wherein R 1 is selected from the group consisting of alkyl radicals having 1 to 8 carbon atoms, phenyl radicals, alkenyl radicals having 2 to 8 carbon atoms, and fluoroalkyl radicals having 3 to 8 carbon atoms, and R 2 is selected from the group consisting of alkyl radicals having 1 to 8 carbon atoms, or (iii) an organosilane of the formula R.sub.1 R.sub.2 Si(OOCR.sub.2).sub.2 or R.sub.1 Si(OOCR.sub.2).sub.3 wherein R 1 and R 2 are defined above.