Patent ID: 8039570

Claim:
A method for preparing a solvent-free silicone composition, the method comprising steps of: i) reacting an organopolysiloxane (I) represented by the following average compositional formula (1) and has an OH group content of from 0.02 to 0.1 mol/100 g, wherein R 1 may be the same with or different from each other and is a substituted or unsubstituted saturated monovalent C 1-10 hydrocarbon group, and a, b and c are positive numbers with [a/(b+c)] ranging from 0.5 to 1.0, and an organopolysiloxane (II) represented by the following formula (2), wherein R 2 may be the same with or different from each other and is a substituted or unsubstituted saturated monovalent C 1-10 hydrocarbon group, R 3 is an alkenyl group represented by the formula, —(CH 2 ) e —CH═CH 2 , wherein e is an integer of from 0 to 6, and d is such an number that a viscosity of the organopolysiloxane(II) ranges from 50 to 400 mPa·s, in a weight ratio of organopolysiloxane (I)/organopolysiloxane (II) ranging from 20/80 to 80/20 in an organic solvent in the presence of an alkaline catalyst at a temperature of from 70 to 140° C. for 0.5 to 12 hours, ii) removing the organic solvent to obtain a first component, wherein the first component comprises a reaction product via a reaction between a hydroxyl group on the organopolysiloxane (I) and a cleaved siloxane bond of the organopolysiloxane (II) and has an OH group content of less than 0.02 mol/100 g, and iii) mixing the following (A)-(D) components, (A) 5 to 60 parts by weight of the obtained first component; (B) 95 to 40 parts by weight of an organopolysiloxane represented by the following formula (3); wherein R 4 is a monovalent hydrocarbon group, provided that at least two R 4 s are alkenyl groups represented by the formula, —(CH 2 ) e —CH═CH 2 , wherein e is an integer of from 0 to 6, k is a number ranging from 0 to 6, f, g and h are such numbers that the organopolysiloxane of the formula (3) has a viscosity of from 50 to 1000 mPa·s at 25° C.; (C) a polyorganohydrogensiloxane having at least two SiH bonds per molecule in such an amount that a molar ratio of the SiH bonds to a total of the alkenyl groups of the mixture (A) and the organopolysiloxane(B) ranges from 1.0 to 4.0; and (D) a catalytic amount of a platinum group metal compound.