Rhodia Chimie

Bluestar Silicones France

Thomas Deforth

Jean-Marc Frances

Christian Pusineri

Kamel Ramdani

J&eacute;r&ocirc;me Bressieux

A method for hydrolyzing/condensing, by acid catalysis, silanes bearing hydrolyzable groups, preferably halogenosilanes and more preferably still chlorosilanes, in a polyphase reaction medium (preferably biphasic), includes contacting the silanes bearing the hydrolyzable groups with water, buffer solution and neutralizing agent, while stirring, then in separating the aqueous phase from the organic phase, which contains the hydrolysis/condensation products, namely hydroxylated polyorganosiloxanes; such method is characterized by (a) employing intensively stirring means producing, in the reaction medium, an agitation at least equivalent to that induced by a shearing corresponding to that provided by a rotor whereof the peripheral speed is not less than 8 m.s, preferably not less than 10 m.s, and more preferably still ranging between 15 and 20 m.s, enabling thus organic phase droplets to be formed, of dless than 500 &#x3bc;m; and (b) ensuring that the silanes/aqueous phase mass fraction is not less than 0.05, preferably not less than 0.10, and more preferably still ranging from 0.5 to 2.0.

Synthesis of hydroxylated polyorganosiloxanes by hydrolysis/condensation of halosilanes and apparatus therefor

The invention concerns the use for increasing the life span of molds made of silicone elastomer crosslinking by polyaddition or polycondensation reaction, of an additive capable of stabilizing the silicone elastomer whereof the mold is constituted with respect to materials to be mouded, said additive corresponding the following formula (1) wherein R and R are linear or branched alkyl radicals or cycloaliphatic radicals having 1 to 40 carbon atoms. Preferably, said additive is methyl laurylthiopropionate. C H &mdash;S&mdash;CH &mdash;CH &mdash;CO&mdash;O&mdash;CH . The invention also concerns the corresponding silicone compositions and the resulting molds.

Method for stabilising silicone elastomer moulds

The invention relates to a heat-activated initiator for polymerising and/or cross-linking polyorganosiloxane-type monomers, oligomers and/or polymers with organofunctional groups, comprising a boron derivative of formula (I): (A) B(R&prime;) , wherein the symbols R&prime; are the same or different and represent an alkyl or alkenyl radical in C -C , an alkoxy radical in C -C , a phenyl radical substituted by at least one electroattractor element, an aryl radical containing at least two aromatic rings such as biphenyl, naphthyl, optionally substituted by at least one electroattractor element, especially a halogen atom (particularly fluorine), or an electroattractor group, especially a CF , NO , CN group; and a radical &mdash;C H &mdash;Si(Q) with the symbols Q being the same or different and representing an alkyl or alkoxy group in C to C or a siloxane oligomer with less than 10 silicon atoms. The invention also relates to a corresponding cross-linkable composition and to the uses thereof.

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Lyons, France

Thomas Deforth