US Patent 7459495 Acrylic rubber composition and crosslinked object

An acrylic rubber composition comprising (A) 100 weight parts of an acrylic rubber comprising 80-99.9 weight % of units of a monomer selected from acrylic acid ester monomers and methacrylic acid ester monomers, and 0.1-20 weight % of units of an α,β-ethylenically unsaturated carboxylic acid monomer, (B) 5-200 weight parts of synthetic silica, and (C) 0.05-20 weight parts of a crosslinking agent. The acrylic rubber composition preferably further comprises 5-200 weight parts of aluminum silicate containing at least 5 weight % of Al2O3 wherein the total amount of Al2O3 and SiO2 is at least 60 weight %. The rubber composition has good storage stability and gives a crosslinked object having good heat aging resistance, reduced compression set and good mechanical properties.