Wacker-chemie Gmbh

Jurgen Burkhardt

Karl-Heinrich Wegehaupt

Bernward Deubzer

Eckhart Louis

Paul Hittmair

Jorg Patzke

Erich Brunner

Konrad Sallersbeck

Herbert Krohberger

Werner Rauchberger

Andreas Bock

Oligomeric siloxanol mixtures containing siloxanols of the formula

Process for chain stabilization of organopolysiloxanes

Diorganopolysiloxanes containing triorganosiloxy groups as terminal units are prepared by mixing the diorganopolysiloxanes which may already contain triorganosiloxy terminal groups, after they have reached the desired average viscosity by condensation and/or equilibration in the presence of catalysts other than chlorophosphazenes, with a hexaorganodisilazane in an amount of from 0.05 to 2 percent by weight, based on the weight of the diorganopolysiloxanes employed and after mixing, a catalytic amount of a chlorophosphazene is added.

Process for preparing diorganopolysiloxanes containing triorganosiloxy

Linear triorganosiloxy-terminated organopolysiloxanes are prepared by the condensation of linear organopolysiloxanes having one Si-bonded hydroxyl group in each teminal unit in the presence of phosphonitrilic chloride, and after the organopolysiloxane has reached the desired average viscosity and while still containing the phosphonitrilic chloride, the organopolysiloxane is reacted with from 0.05 to 1 weight percent of hexaorganodisilazane, based on the weight of the starting organopolysiloxane, with the proviso that a filler having a BET surface area of at least 50 m.sup.2 /g does not exceed 1 weight percent, based on the weight of the starting organopolysiloxane.

Process for preparing linear organopolysiloxanes having terminal

A method for stablizing organopolysiloxanes containing phosphonitrilic chlorides and/or their reaction products against viscosity changes by reacting the phosphorus compounds present in the organopolysiloxanes with at least one oxide, hydroxide or carbonate of a divalent or trivalent metal, and thereafter separating the solid from the organopolysiloxanes.

Method for stabilizing organopolysiloxanes

Hydrophilic, crosslinked organopolysiloxanes are obtained from the polymerization of hydroxyalkylmethacrylate and/or hydroxalkylacrylate in the presence of an organopolysiloxane containing at least 40 mol percent of monoorganosiloxane units. These hydrophilic, crosslinked, modified organopolysiloxanes are prepared by polymerizing hydroxyalkylmethacrylate and/or hydroxyalkylacrylate in the presence of free radical initiators and an organopolysiloxane containing at least 40 mol percent of monoorganosiloxane units which can be crosslinked or has been crosslinked by the condensation reaction in the presence of a condensation catalyst, the amount and type of condensation catalyst and/or catalytic system, including the inhibitor for the polymerization of the hydroxyalkylmethacrylate and/or hydroxyalkylacrylate, is selected so that the crosslinking of the organopolysiloxane which is substantially uniformly distributed in the hydroxyalkylmethacrylate and/or hydroxyalkylacrylate is initiated and preferably completed before the polymerization of the hydroxyalkylmethacrylate and/or hydroxyalkylacrylate is completed.

Hydrophilic, crosslinked, modified organopolysiloxanes and process for

Cyclic dimethylpolysiloxanes are prepared by heating a mixture containing linear or branched organopolysiloxanes consisting of at least 50 mol percent dimethylsiloxane units and aqueous sulfuric acid in which the aqueous sulfuric acid contains from 50 to 85 percent by weight of sulfuric acid, while simultaneously recovering the cyclic dimethylpolysiloxanes thus formed.

Process for preparing cyclic dimethylpolysiloxanes

A method for stabilizing organopolysiloxanes which are obtained from the condensation and/or equilibration of organosilicon compounds in the presence of phosphoronitrile chlorides which comprises treating the organopolysiloxanes with ammonia or an amine of the general formula

Stabilization of organopolysiloxanes

An improved process for preparing N-triorganosilylcarbamide acid esters by reacting in the substantial absence of a solvent a carbamide acid ester having two hydrogen atoms linked to the nitrogen atom with a hexaorganodisilazane and a triorganohalosilane and thereafter separating the resultant N-triorganosilylcarbamide acid ester from ammonium halide.

Process for preparing N-triorganosilylcarbamide acid esters

A process for preparing organopolysiloxanes by the condensation and/or equilibration of an organosilicon compound containing silicon-bonded oxygen atoms in the presence of a phosphoronitrile chloride and an aryl compound having one or two hydroxy groups linked to the aryl radical.

Preparation of organopolysiloxanes

Highly transparent or optically clear elastomers are prepared by mixing (1) a nitrogen containing compound having at least one triorganosilyl group in which at least one nitrogen atom is linked either directly to a silicon atom or via an oxygen atom, but no more than one triorganosilyl group is linked to a nitrogen atom and no more than one condensable group is linked to a silicon atom, (2) a hexaorganodisilazane, (3) silicon dioxide having a surface area of at least 50 m.sup.2 /g with (4) a highly viscous diorganopolysiloxane. The resulting composition may be cured by the addition of a curing agent to form highly transparent or optically clear elastomers.

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Winhoring, Germany

Jurgen Burkhardt