Polymerisation of siloxane polymers

A base 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 base catalysed process comprises the steps of
• (a) introducing
• (a) said macrocyclic cyclosiloxane oligomers in an amount of from 50 to 99 wt. % of the starting ingredients with
• (ii) one or more end-blockers in an amount of from 1 to 50 wt. % of the starting ingredients and optionally
• (iii) a co-monomer selected from a linear organosiloxane co-monomer, a branched organosiloxane co-monomer or cyclosiloxane co-monomer wherein said cyclosiloxane co-monomer has from 3 to 10
• units per molecule, wherein each R8 group 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;
• said co-monomer (iii), when present being present in an amount of from 1 to 50 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 starting ingredient (i) to a predetermined reaction temperature of from 25 to 160° C. in an inert atmosphere before introducing component (ii) and optionally component (iii), when present, or
• heating a mixture of starting ingredients (i), (ii) and optionally (iii) to a predetermined reaction temperature of from 25 to 160° C. in an inert atmosphere;
• (d) once the desired temperature has been reached, and starting materials (i),
• (ii) and optionally (iii) are thoroughly mixed together, introducing a final starting ingredient, a base catalyst (iv) in an amount of from 0.001 to 10 wt. % of the starting ingredients;
• thereby forming an initial reaction mixture;
• (e) agitating the initial reaction mixture 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 base catalysts when used or with a suitable neutralising agent to form a step (f);
• (g) Cooling the step (f) product to ambient temperature to form a cooled step (g) product and optionally,
• (h) Stripping volatile cyclosiloxanes the cooled step (f) product to give a final linear or branched siloxane polymer or copolymer.