Solvent-soluble polyimidesiloxane oligomer and process for producing the same

A polymer having an inherent viscosity .eta. of 0.001-0.5 dl/g as measured at a concentration of 0.5 g/dl in N-methyl-2-pyrrolidone at 30.degree. C., which has been obtained by subjecting to polymerization and imidization (a) an acid component containing 50 mole % or more of 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride and/or a derivative thereof and (b) a diamine component containing 50 mole % or more of an alkyl-substituted aromatic diamine represented by the following formula (II):

• ##STR16## wherein R.sub.7 to R.sub.10 are each an alkyl group of 1-4 carbon atoms;
• X, Y and Z are each --O--, ##STR17## m.sub.1 is an integer of 1-4;
• m.sub.2, m.sub.3 and m.sub.4 are each an integer of 0 to 4;
• and n, p and q are each an integer of 0 to 10.

A low molecular weight polymer having an inherent viscosity .eta. of 0.001-0.5 dl/g as measured at a concentration of 0.5 g/dl in N-methyl-2-pyrrolidone at 30.degree. C. and having an imidization degree of 80-100%, which has been obtained by subjecting to polymerization and imidization (a) an acid component consisting of an aromatic tetracarboxylic acid dianhydride and/or a derivative thereof and (b) a diamine component consisting of 5-100 mole % of a diaminosiloxane represented by the undermentioned formula (I) and 95-0 mole % of an organic diamine other than the formula (I):

• ##STR18## wherein R.sub.1 is a divalent aliphatic group of 1-5 carbon atoms or a divalent aromatic group of 6 or more carbon atoms;
• R.sub.2 and R.sub.3 are each a monovalent aliphatic or aromatic group and may be the same or different;
• and m is an integer of 1-100;
• wherein the alkyl-substituted aromatic diamine is 2,4-diaminotoluene, 2,6-diaminotoluene, or 2,2-bis[4-(4-aminophenoxy)phenyl]propane.