Method of producing organopolysiloxanes containing hydrolyzable functional groups, and curable resin composition using said organopolysiloxanes

A method of producing a curable resin composition containing as the main component an organopolysiloxane having hydrolyzable functional groups, said method comprising:

• a) producing an organopolysiloxane by hydrolytic condensation of organoalkoxysilanes and/or organoalkoxysiloxanes in the presence of water and a hydrolysis catalyst, wherein at least 50% by weight of said organoalkoxysilanes and/or organoalkoxysiloxanes are represented by an average compositional formula (A):
• R.sup.1.sub.a SiX.sub.b Y.sub.c O.sub.(4-a-b-c)/2 (A)
• wherein
• each R.sup.1 independently represents an unsubstituted alkyl, alkenyl or aryl group or chloro, fluoro, glycidyl, amino, mercaptyl, methacryloxy or acryloxy, substituted alkyl, alkenyl or aryl group;
• X represents an alkoxy group containing 1-10 carbon atoms;
• Y represents an alkoxy group containing 2-10 carbon atoms which is different from the alkoxy group represented by X, has a hydrolysis rate lower than that of X and appears on the same silicon atom as X;
• a is a real number of from 0 to 2;
• b and c are each a real number from 0.1 to 3, provided that a+b+c is.ltoreq.4;
• said organopolysiloxane containing silanol groups and alkoxy groups represented by Y and having a degree of dispersion, Mw/Mn, below 2.5, wherein Mw is weight average molecular weight and Mn is number average molecular weight;
• and
• (b) subjecting said organopolysiloxane produced to
• an ester exchange reaction and a hydrolytic condensation reaction, in the presence or absence of a catalyst, with an organosilane containing at least two hydrolyzable functional groups to introduce hydrolyzable functional groups to said organopolysiloxane,
• wherein the ester exchange takes place between silanol groups in said organopolysiloxane and hydrolyzable functional groups in said organosilane as well as between unhydrolyzed alkoxy groups remaining in the organopolysiloxane and hydrolyzable functional groups in said organosilane.