NOVEL WET-PROCESS SILICA PREPARED FROM ALKYL SILICATES .1. SYNTHESIS

Conventional silicone elastomers contain particulate fillers to improve strength and performance. The extent of reinforcement provided by the filler is generally improved by an increase in the filler surface area, an increase in the filler structure, and an increase in adhesion of the polymer to the filler surface. Although fillers such as calcium carbonate, iron oxide, titanium oxide, zinc oxide, diatomaceous earth, and quartz find application in silicone elastomers, amorphous silicas having a surface area of 150 to 400 m**2/g provide the best reinforcement. This paper describes a novel wet process which meets the need wherein alkyl silicates are hydrolyzed and condensed in the presence of a silica surface treatment agent to provide hydrophobic, reinforcing silica fillers in a one-step process generating only easily recycled by-products.