GB980385A - Reinforcing filler for rubber - Google Patents

Abstract

Calcium carbonate having a necklace-like structure in which particles of 0.01 m width and 0.02-0.03 m length are connected together, and which is mixed with a second metal carbonate, is made by introducing gas containing 15-35% by volume of carbon dioxide at a flow rate of above 150 1./min./kg. Ca(OH)2 into a calcium hydroxide suspension of concentration less than 15% and at a temperature less than 30 DEG C. to give a viscous colloidal suspension, and continuing inflow of carbon dioxide until a highest viscosity is reached, at which point the suspension is reacted with 0.02-0.08 mols per mol of calcium hydroxide of a second metal salt convertible to hydroxide on hydrolysis, the second salt being introduced with gas containing 15-35% by volume of carbon dioxide at a flow rate of more than 150 1./min./kg. Ca(OH)2. Inflow of gas is continued until the viscosity of the suspension begins to fall, at which point, gas containing 15-35% by volume of carbon dioxide is introduced at a 40-80 1./min./kg. Ca(OH)2 until the calcium and second metal hydroxides are completely converted to carbonates. In an example, the second metal salt is zinc chloride. The mixed carbonates are used as rubber reinforcing filler.