Durch Hitze aktivierte,haertbare Formmassen auf Grundlage von Organosiliciumverbindungen

摘要

1,221,511. Organosilicon compositions having sulphoxide-retarded cure. DOW CORNING CORP. 1 Jan., 1969 [31 Jan., 1968], No. 19/69. Heading C3T. [Also in Division B1] A curable organosilicon composition comprises (1) an organosilicon compound having at least two unsaturated monovalent hydrocarbon radicals per molecule, and (2) an organosilicon compound having at least two Si-bound H atoms per molecule, there also being in (1) one to three and in (2) up to two monovalent unsaturation-free hydrocarbon or halohydrocarbon or cyanoalkyl radicals per Si atom, and any remaining Si valences in each compound being satisfied by oxygen atoms or divalent hydrocarbon, hydrocarbon ether or haloarylene radicals linking Si atoms, with (3) at least 1 p.p.m. of (1) + (2) + (4) of Pt in a platinum catalyst and (4) a sulphoxide in amount sufficient to retard cure of the composition at room temperature, the sulphoxide being of the formula R 2 SO, wherein each R is a monovalent hydrocarbon group or the two may together with the sulphur form a ring, or being an organosilicon compound having attached to at least one Si atom a group RSiR1 wherein R1 is a monovalent aliphatic hydrocarbon group, and optionally (5) a filler. Preferred compositions contain (1) (2) and (5) in amounts of 45-75%, 0À5-10% and 20-50% respectively, by weight of the sum of (1), (2) and (5), and at least one sulphoxide group per atom of Pt. Cure is effected by heating to 70‹ C. or more. The preferred sulphoxides (4) are the silicon compounds, which may be obtained by oxidation of the corresponding thioethers with, e.g. H 2 O 2 , O 2 , O 3 , MnO 4 -, Cr 2 O 7 -- , NO 3 - or N 2 O 4 . In examples compositions are prepared containing a methylphenylvinylsiloxane-terminated polydimethylsiloxane, a benzene-soluble vinylmethylpolysiloxane resin, and a hydrogen methyl polysiloxane, using as catalyst H 2 PtCl 6 and as inhibitor dimethyl or diphenyl sulphoxide, tetramethylene sulphoxide or a disiloxane sulphoxide [RSOR1Si(CH 3 ) 2 ] 2 O in which R is methyl or phenyl and R1 is ethylene or propylene. Filled compositions are prepared containing calcined diatomaceous earth and zirconium silicate and optionally Fe 2 O 3 and a hydroxy-terminated polydimethylsiloxane in addition to the above.