Polymerisation of siloxane polymers

An acid catalysed process for the preparation of linear or branched siloxane polymers and copolymers, by the ring-opening polymerisation of macrocyclic cyclosiloxane oligomers having from 7 to 10

• units per molecule, wherein each R″ group per unit is the same or different and is an alkyl group having from 1 to 6 carbons;
• which acid catalysed process comprises the steps of
• (a) introducing
• (i) said macrocyclic cyclosiloxane oligomers in an amount of from 20 to 99 wt. % of the starting ingredients with
• (ii) one or more end-blockers in an amount of from 1 to 80 wt. % of the starting ingredients and optionally
• (iii) a co-monomer selected from a linear organosiloxane co-monomer, a branched organosiloxane co-monomer or a cyclosiloxane co-monomer wherein said cyclosiloxane co-monomer has from 3 to 10
• units per molecule, wherein each R8 group per is the same or different and is selected from an alkenyl group, an alkynyl group, an aryl group, a fluoroalkyl such as trifluoropropyl or a perfluoroalkyl group and each R9 group is selected from an alkyl group having from 1 to 6 carbons or R8;
• in an amount of from 1 to 80 wt. % of the starting ingredients into a mixing vessel and mixing;
• (b) optionally introducing an organic solvent in an amount of up to 7.5 wt. % of the starting ingredients into the mixing vessel during or subsequent to step (a);
• (c) heating said mixture of starting ingredients to a predetermined reaction temperature of from 25 to 160° C. in an inert atmosphere;
• (d) once the predetermined reaction temperature has been reached, introducing a final starting ingredient, an acid catalyst (iv) selected from one or more sulphonic acids and/or perfluorinated sulfonic acids, one or more sulfonated polystyrene resins, one or more sulfonated tetrafluoroethylene bases fluoropolymer-copolymer resins or a mixture thereof;
• (e) reacting the complete reaction mixture of step (d) at the predetermined reaction temperature for up to 24 hours until a step (e) product within a desired number average molecular weight range and/or a cyclics equilibration is obtained;
• (f) quenching the reaction after step (e) by either filtering off heterogeneous acid catalysts when used or with a suitable neutralising agent to form a step (f) product;
• (g) Cooling the step (f) product to ambient temperature to form a step (g) product and optionally,
• (h) Stripping out remaining volatile materials from the step (g) product;
• to give a final linear or branched siloxane polymer or copolymer.