Process for preparation of linear polyamide-imides from aromatic tricarboxylic acid anhydrides and diamines

Abstract

Linear polyamide-imides having recurring units of the formula ##STR1## in which A is an aromatic radical; R and R' are araliphatic, aliphatic, or cycloaliphatic radicals; and R" is H, or an aliphatic, araliphatic, or cycloaliphatic radical; and a process for their preparation are disclosed. The process involves three steps (1) condensation of a diamine and an aromatic tricarboxylic acid anhydride to form an intermediate diimide-diacid; (2) converting the diimide-diacid to the diacid chloride, e.g. by reaction with SOCl.sub.2 ; and (3) reaction of the diacid chloride with further diamine to produce the amide linkages in the desired polyamide-imide. This method avoids a final step of imide formation by cyclodehydration, necessary in the prior art processes, which step causes some crosslinking undesirable in polymers intended for molding applications.

Dependencies are inferred from the claim text.