Room temperature vulcanisable silicone compositions

A method of reducing modulus and/or increasing elasticity of an elastomeric body obtained or obtainable by curing a moisture curable composition, the composition comprising:

• (i) an organopolysiloxane polymer having at least two hydroxyl or hydrolysable groups per molecule and of the general formula
• X3-nRnSi—(Z)—(R1ySiO(4-y)/2)z—(SiR12—Z)—Si—RnX3-n
• in which each X is an alkoxy group, each R is an alkyl, alkenyl or aryl group, each R1 is an X group, alkyl group, alkenyl group or aryl group, and Z is a divalent organic group;
• and n is 0 or 1, y is 0, 1 or 2, and z is an integer such that the organopolysiloxane polymer (i) has a viscosity of from 1,000 to 75,000 mPa·s at 25° C.;
• (ii) a siloxane and/or silane cross-linker having at least three groups per molecule which are reactable with the hydroxyl or hydrolysable groups in the organopolysiloxane polymer (i);
• and
• optionally
• (iv) a suitable condensation cure catalyst;
• the method comprising introducing (iii) a solid organosilicate resin into the composition prior to cure, and subsequently curing the composition;
• wherein the solid organosilicate resin (iii) is a product of a reaction of an organosilicate resin precursor with a treating agent such that the solid organosilicate resin is substantially unreactive with components (i) and (ii), comprises R23SiO1/2 siloxane units and SiO4/2 siloxane units, the molar ratio of the R23SiO1/2 siloxane units to SiO4/2 siloxane units is from 0.5:1 to 1.2:1, and R2 is selected from hydrocarbon groups;
• the solid organosilicate resin (iii) having a weight average molecular weight of from 3,000 to 30,000 g/mol;
• and
• wherein the solid organosilicate resin (iii) comprises vinyl functional groups.

A method of preparing a silicone elastomeric sealant composition which is stable in the absence of moisture and cures upon exposure to moisture, the method comprising:

• (A) mixing in the absence of moisture components (i), (ii), and (iii), and optionally component (iv), to form a mixture;
• (i) an organopolysiloxane polymer having at least two hydroxyl or hydrolysable groups per molecule and of the general formula
• X3-nRnSi—(Z)—(R1ySiO(4-y)/2)z—(SiR12—Z)—Si—RnX3-n
• in which each X is an alkoxy group, each R is an alkyl, alkenyl or aryl group, each R1 is an X group, alkyl group, alkenyl group or aryl group, and Z is a divalent organic group;
• and n is 0 or 1, y is 0, 1 or 2, and z is an integer such that the organopolysiloxane polymer (i) has a viscosity of from 1,000 to 75,000 mPa·s at 25° C.;
• (ii) a siloxane and/or silane cross-linker having at least three groups per molecule which are reactable with the hydroxyl or hydrolysable groups in the organopolysiloxane polymer (i);
• (iii) a solid organosilicate resin which is a product of a reaction of an organosilicate resin precursor with a treating agent such that the solid organosilicate resin is substantially unreactive with components (i) and (ii) and comprising R23SiO1/2 siloxane units and SiO4/2 siloxane units, wherein the molar ratio of the R23SiO1/2 siloxane units to SiO4/2 siloxane units is from 0.5:1 to 1.2:1, and R2 is selected from hydrocarbon groups;
• the solid organosilicate resin (iii) having weight average molecular weight of from 3,000 to 30,000 g/mol;
• (iv) a suitable condensation cure catalyst;
• and
• wherein the solid organosilicate resin (iii) comprises vinyl functional groups;
• and
• (B) storing the mixture in the absence of moisture.