Silicone rubber monocomponent compositions curable at ambient temperature and containing hydrophobic silicic acid

摘要

Introduction of hydrophobic silicic acid of low water content and low moisture uptake into a single component room temperature crosslinked silicone rubber formulation, improves the mechanical properties, the whiteness grade and the rheological properties without affecting the storage stability. A silicone rubber formulation (RTV-1K) contains: (a) 0.5-60 wt.% of hydrophobic silicic acid having the properties: C content less than 3.1%, methanol utilizability greater than 60%, remission value greater than 94%, BET/STAB ratio greater than 1 and less than 3, DBP take up less than 230 g/100 g, BET surface 50-110 m2/g, STAB surface greater than 30 m2/g, water vapor absorption at 30 degrees C and 30 RF less than 1.3 and at 30 degrees C and 70 REF less than 1.7, and (b) 40-99.5 wt.% of an organopolysiloxane of formula (I). ZnSiR3-n-O-(SiR2O)x-SiR3-nZ'n (I) R = alkyl, acetoxy, oxime, alkoxy, amido, aryl, 1-50C alkenyl, optionally substituted with O, S, F, Cl, Br or I, and/or polystyrene, polyvinyl acetate, poly(meth)acrylate- or polyacrylonitrile with 50-10,000 repeating units; Z = OH, Cl, Br, I or up to 20 C acetoxy, amino, amido, aminoxy, oxime, alkoxy, alkenyloxy, acryloxy or phosphate, where the organic residue can have up to 20 C; Z' = oxime, alkoxy, amido or acetoxy; n = 1-3; and x = 100-15,000.