To obtain a polymer composition having substantially improved physicochemical characteristic and mechanical characteristic compared with a binary mixture by integrating some modified polymers into a non-compatible polymer composition and/or mixture.

This polymer composition is a thermoplastic polymer composition composed of at least two different polymers, which is composed of at least one polymer (P1) containing at least one reactive functional group and at least one modified polyolefin (P2) containing at least one substituted succinimide ring having a reactive group substituted on nitrogen, and in which the substituted succinimide ring is supported by the main chain or a side chain. Further, the thermoplastic polymer composition constitutes a thermoplastic polymer mixture exhibiting improved mechanical characteristics when used as a compatibility-increasing agent for a non-compatible polymer. The polymer composition enables the production of tubes or containers exhibiting especially improved mechanical characteristic in the conventional processing materials.