Urethane prepolymer, process for producing the same and pressure-sensitive adhesive comprising the same

摘要

Novel urethane prepolymers which can be applied onto substrates without using any solvent, processes for producing the same, and pressure-sensitive adhesives using the prepolymers, which are excellent in adhesive strength, holding power and low temperature properties are provided. The urethane prepolymer is represented by the following formula ÄIÜ or ÄIIÜ: d-c-(a-c)k-e or d-c-(a-c)n-(b-c)m-(a-c)l-e wherein k is from 4 to 100; n and l each are from 2 to 50; m is from 1 to 50; a represents a polyester group having a number average molecular weight of 1 x 10<3> to 5 x 10<3>; b represents a divalent group; c represents an organic isocyanate group; d represents a monool having functional groups; and e is a monool, which is the same as or different from d, having a number average molecular weight of 5 x 10<3> to 5 x 10<5>. Such an urethane prepolymer is crosslinked to increase its molecular weight, thereby providing a pressure-sensitive adhesive.