PRODUCTION OF LIQUID SILICONE RUBBER BASE AND PRODUCTION OF LIQUID SILICONE RUBBER COMPOSITION

摘要

PROBLEM TO BE SOLVED: To produce a liquid silicone rubber base by conducting multistage kneading under varying shear stresses so as to afford its high storage stability with rise in its viscosity suppressed to a minimum after stored. ;SOLUTION: This liquid silicone rubber base is produced by kneading a mixture comprising (A) an organopolysiloxane having two or more alkenyl groups bound to an silicon atom in one molecule and a viscosity of 100-300,000cSt at 25°C, (B) reinforcing silica ≥50m²/g in specific surface area (determined by BET method), and, if needed, (C) a mixing auxiliary. In this case, the 1st stage kneading is conducted under a shear stress of ≥1×10⁶N/m² followed by the 2nd stage kneading under a shear stress not greater than 1/2 times that in the 1st stage kneading. It is preferable that part of the 1st stage kneading is conducted at 150-300°C for 5min or shorter, part or the whole of the 2nd stage kneading at 150-300°C for 2min or longer, and the total kneading time is 2.5min or longer.;COPYRIGHT: (C)1998,JPO