Patent ID: 8779085

Claim:
A method of producing a modified polyimide, comprising a first step in which an isocyanate-terminated oligomer represented by Formula (I): (wherein each R independently represents a C 1 -C 18 alkylene group; each X independently represents a C 1 -C 18 alkylene group or arylene group, or C 1 -C 18 alkylene groups bound through an ether bond(s), ester bond(s), urethane bond(s) or amide bond(s); and m and n represent an integer of 1 to 20) and a tetracarboxylic dianhydride represented by Formula (II): (wherein Y represents a tetravalent aromatic group) are allowed to react to synthesize a tetracarboxylic dianhydride oligomer represented by Formula (III): (wherein R has the same meaning as in said Formula (I); X has the same meaning as in said Formula (I); Y has the same meaning as in said Formula (II); m and n have the same meanings as in said Formula (I); and p represents an integer of 1 to 20); and a second step in which the thus synthesized tetracarboxylic dianhydride oligomer is allowed to react with an aromatic diamine represented by Formula (IV): NH 2 -A-NH 2 (IV) (wherein A represents a divalent aromatic group) and a tetracarboxylic dianhydride represented by Formula (II′): (wherein Y′ represents a tetravalent aromatic group) to synthesize a modified polyimide which has a polycarbonate structure and aromatic polyimide structure, said modified polyimide being represented by Formula (V): (wherein R has the same meaning as in said Formula (I); X has the same meaning as in said Formula (I); Y has the same meaning as in said Formula (II); m and n have the same meanings as in said Formula (I); p has the same meaning as in said Formula (III); A has the same meaning as in said Formula (IV); Y′ has the same meaning as in said Formula (II′); and q represents an integer of 1 to 20), wherein the weight ratio of the repeating units whose number is represented by said n in said Formula (V) to said modified polyimide represented by said Formula (V) is 0.3 to 0.7 (with the proviso that the weight of X is excluded when X is aromatic).