Process for the manufacture of cyclosiloxanes by depolymerization of polysiloxanes
AssigneeRhone-Poulenc Chimie
InventorsChristian Allandrieu, Denis Cardinaud
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Abstract
The present invention relates to a process for the manufacture of cyclic polydiorganosiloxanes, especially octamethylcyclotetrasiloxane (D.sub.4) and decamethylcyclopentasiloxane (D.sub.5) by depolymerization of polydiorganosiloxanes in the presence of an initiator, characterized in that the initiator comprises either: 1) at least one hydroxide chosen especially from the group made up of caesium, rubidium or quaternary phosphonium hydroxides, or: 2) the association of a fluorine-free caesium or rubidium salt, or of a salt of quaternary phosphoniums, with a hydroxyl-containing strong base of an alkali or alkaline-earth metal other than Cs and Rb.
Claims26
A process for the manufacture of cyclic polydiorganosiloxanes comprising depolymerizing a polydiorganosiloxane in the presence of an initiator which comprises a cesium, rubidium or quaternary phosphonium hydroxide, or a combination of a fluorine-free cesium, fluorine-free rubidium or quaternary phosphonium salt and a hydroxyl containing base of an alkali or alkaline-earth metal other than cesium or rubidium, or mixtures thereof.
A process for the manufacture of cyclic polydiorganosiloxanes comprising deploymerizing a polydiorganosiloxane in the presence of an initiator which comprises cesium, rubidium, a quaternary phosphonium hydroxide or mixtures thereof, with the proviso that cesium hydroxide is not the sole initiator.
A process for the manufacture of cyclic polydiorganosiloxanes comprising depolymerizing a polydiorganosiloxanes in the presence of a reaction mass which consists essentially of cyclic polydiorganosiloxane and a cesium hydroxide initiator.
Dependencies are inferred from the claim text.