Rhodia Chimie

Rhodia Services

Fabienne Howe

Alain Pouchelon

Christian Pusineri

Michel M Gay

Georges Barrandon

Olivier Loubet

Marco Del Torto

Bernard Moulin

Jo&euml;lle Viennet

Dominique Canpont

A process for production of an assembly including several silicone elements crosslinked by polyaddition of &#x2261;Si&#x2014;H units onto &#x2261;Si-alkenyl (preferably &#x2261;Si-vinyl) units, the elements adhering to one another without detracting from their mechanical properties. The process includes: (I) forming (1coating) a silicone element (i) with a liquid silicone preparation (i) containing polyorganosiloxanes (POS) A with &#x2261;Si-vinyl units, (POS) B with &#x2261;Si&#x2014;H units, a platinum catalyst C; (II) crosslinking so that (i) has a surface density SD of unreacted, residual vinyl, per nm, of 0.0100&#x2267;SD&#x2267;0.0040; (III) optionally repeating steps (I) and (II) n times to give n elements (i) that adhere to one another; (IV) forming (2coating) a silicone element (ii) with a liquid silicone preparation (ii) of the same type as described above; (v) crosslinking to give crosslinked (ii) that adheres to (i).

Process for the production of an assembly comprising several silicone elements crosslinked by polyaddition and adhering firmly to one another

A non-drip, preferably self-adhesive, silicone elastomer composition crosslinkable by polyaddition, such as those polyorganosilanes (POS) bearing C&#x2550;C&#x2261;Si-alkenyl units and &#x2261;Si&#x2014;H units but excluding fluorinated POS. The composition includes at least a thixotropic additive containing at least a fluorinated resin, preferably based on polyfluoroethylene (PTFE). The composition may be prepared from a Si&#x2014;Vi polydimethylsiloxane (PDMS) and a Si&#x2014;H PDMS crosslinked by platinum catalysis. Polytetrafluorethylene, a filler, particularly one containing silicone, optionally a ternary adherence promoter such as vinyltrimethosilane/glycidoxypropyltrimethoxysilane/butyl orthotitanate, and other typical additives may be added to the composition. The composition (not excluding the fluorinated POS as a possible constituent in the composition) may be used to produce joints in situ and/or as an adhesive, particularly in upholstery.

Non-drip silicone elastomer composition, crosslinkable by polyaddition, and its uses for making joints in situ as adhesive in particular in saddlery

Silicone material crosslinkable into silicone elastomer by polyaddition reactions is described. A material is provided offering a compromise between the following characteristics: fluidity (in non-crosslinked state), hydrophilicity (in non-crosslinked or crossliked state) and high mechanical properties (in crosslinked state). The following materials are added to crosslinkable silicone material: (i) a reinforcing siliceous filler in the form of a suspension obtained by subjecting the filler to a treatment in two stages by an agent providing compatibility and by operating in the presence of a polyorganosiloxane with Si-alkenyl functions; and (ii) one or more non-ionic, ionic or amphoteric surfactants. Said silicone material is particularly useful for impressions, for example dental impressions and for making pads used in pad printing techniques.

Hydrophilic silicone elastomer material used in particular for impressions

The invention concerns a silicone composition cross-linkable by hydrosilylation into adhesive gel and absorber, characterized in that it comprises:(I) at least a polyorganosiloxane POS (I); (II) at least a polyorganosiloxane POS (II); (III) at least an adhesive promoter (III); (IV) hollow organic microspheres ; (V) optionally at least a polyorganosiloxane POS (V) particularly useful as diluent of POS (I); (VI) an effective amount of hydrosilylation catalyst, preferably of the platinous type.

Silicone composition cross-linkable into adhesive gel and absorber with microspheres

The invention concerns a method for preparing a silica suspension in a silicone matrix, said suspension capable of being used for producing organopolysiloxanes crosslinkable by polycondensation. The invention aims at seeking a technical compromise between the rheology of said compositions and the mechanical properties of the resulting crosslinked elastomers. As a solution, the invention discloses a method for preparing a silica suspension treated with organosilazane in a silicone material comprising a linear reactive polyorganosiloxane bearing for example at each chain end a hydroxy group. The invention is characterized in that it consists essentially in introducing the organosilozane in the preparation medium: before and/or substantially simultaneously before bringing together at least part of the silicone material and the particulate filler used, said organosilozane introduction being carried out with a fraction of organosilazane corresponding to a proportion ranging between 8% and 30% by dry weight relatively to the silica filler, and after bringing together the filler and all or part of the silicone material.

Process for preparing a silica suspension in a silicone matrix crosslinkable by polycondensation to form elastomers

The invention concerns the use, for increasing the durability of moulds made of silicone elastomer crosslinkable by a poly addition or polycondensation reaction, of additive capable of stabilizing the silicone elastomer constituting the mold with respect to materials to be molded, of an additive selected among: (a) antioxidant additives comprising, in their structure additives containing at least one R&mdash;S &mdash;R&prime; group in which R and R&prime; are monovalent hydrocarbon groups with at least 3 carbon atoms or a monovalent hydrocarbon group with an ester bond or R and R&prime; together form a cycle, q being a whole number between 1 and 3 inclusively, (b) additives inhibitors of free radicals capable, in moulding conditions of generating radicals &boxH;N&mdash;O; the invention concerns the synergistic combination of (a)&plus;(b), the synergistic combination of (a) and/or (b) with phosphites (c), except for the use of bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate as only additive in a silicone elastomer mould cross-linked by polycondensation.

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Caluire, France

Fabienne Howe