Patent ID: 8722758

Claim:
A water soluble polyimide resin, which consists of a repeat unit (I) and a repeat unit (II) in a block or random arrangement: wherein B represents a tetravalent organic group; c represent a mole fraction for the repeating unit and is in the range of from 3 to 50 mole %; and Z represent a group of the following formula: wherein R 4 and R 5 are the same or different, and each represents a alkylene group containing 1 to 6 carbon atoms, arylene group containing 6 to 20 carbon atoms, aralkylene containing 6 to 20 carbon atoms, or arylene-oxy-alkylene group containing 6 to 20 carbon atoms; n, x, and y each represents an integral more than or equal to 1; wherein B represents a tetravalent organic group; R represents a phenylene group; b represents a number of 1 or 2; A represents a group selected from —OH and —COOH, when b is the number of 2, the plural A's are each the same or different; and a represents a mole fraction for the repeating unit and is in the range of from 50 to 97 mole %.