Continuous Process For The Production Of Base Compositions For Improved-Stability Silicone Compositions
AssigneeWacker Chemie AG
InventorsThomas Frese, Thomas Hierstetter, Johann Schuster, Christof Woerner
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Abstract
Base compositions for addition-crosslinking silicone compositions are continuously produced by, in a first stage, homogeneously mixing and kneading organopolysiloxanes and flowable prehydrophobized oxidic reinforcing fillers in a continuous kneading machine with kneading chambers arranged alongside one another. In a second, downstream, stage of the process, the compositions produced in the first stage are subjected to aftertreatment in a mixing apparatus in which the compositions have been subjected to a mixing procedure with introduction of shear force.
Claims12
A process for the production of base compositions with viscosity from 500,000 to 12,000,000 mPa·s, measured at 25° C. and at a shear rate of 1 s−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)
- R1aR2bSiO(4-a-b)/2 (I)
- where
- R1 is a hydroxy moiety or a monovalent, optionally halogen-substituted C1-20 hydrocarbon moiety which optionally contains O atoms, N atoms, S atoms, or P atoms, and which is free from aliphatically unsaturated groups,
- R2 is a monovalent, aliphatically unsaturated, optionally halogen-substituted C2-10 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)≦3.0 and that there is an average of at least two aliphatically unsaturated moieties R2 per molecule, and that the viscosity of the diorganopolysiloxanes, determined at 25° C., is from 1 to 40,000,000 mPa·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, 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.
Dependencies are inferred from the claim text.