Patent ID: 8287174

Claim:
A process for the production of base compositions with viscosity from 500,000 to 12,000,000 mPaÂ·s, measured at 25Â° C. and at a shear rate of 1 s âˆ’1 , which comprises, in a first stage of the process, homogeneously mixing and kneading the following with one another A) at least one diorganopolysiloxane comprising units of the formula (I) R 1 a R 2 b SiO (4-a-b)/2 (I) where R 1 is a hydroxy moiety or a monovalent, optionally halogen-substituted C 1-20 hydrocarbon moiety which optionally contains O atoms, N atoms, S atoms, or P atoms, and which is free from aliphatically unsaturated groups, R 2 is a monovalent, aliphatically unsaturated, optionally halogen-substituted C 2-10 hydrocarbon moiety which optionally contains O atoms, N atoms, S atoms, or P atoms, b is on average from 0.0001 to 2, with the proviso that 1.5<(a+b)â‰¦3.0 and that there is an average of at least two aliphatically unsaturated moieties R 2 per molecule, and that the viscosity of the diorganopolysiloxanes, determined at 25Â° C., is from 1 to 40,000,000 mPaÂ·s, and B) at least one prehydrophobized oxidic reinforcing filler having at least 0.5% by weight carbon content gained via a hydrophobizing process, in a kneading cascade with at least two kneading chambers arranged alongside one another in series, each of these comprising, parallel to the axis, two kneading units driven so as to corotate or counterrotate, connection to other kneading chamber(s) being by passage apertures running perpendicularly with respect to the axes of the kneading units, where at least the first kneading chamber has a supply aperture and the last kneading chamber has a discharge aperture, and subjecting the resultant composition, in a second downstream stage of the process, to aftertreatment in a mixing apparatus, which has a supply aperture, by way of which the composition produced by way of the first stage of the process is introduced at a defined volume flow rate X to the mixing apparatus, subjected to shear force and devolatilized, wherein the composition is present in the mixing apparatus in an amount which occupies from 20 to 90% of the total volume of the mixing apparatus, thus forming a surface of the composition which is exposed to a gas atmosphere within the mixing apparatus, with constant renewal of the surface of the composition with use of rotating mixing/kneading units, and optionally scrapers, and discharging the composition from the second stage of the process by way of a discharge aperture at a volume flow rate Y.