Process for production of urethane resin and adhesive agent

Abstract

An object of the invention is to provide a process for urethane resin production in which the molecular weight of the urethane resin can be easily controlled regardless of the kind of polyisocyanate compound and which can yield a urethane resin for use as a removable pressure-sensitive adhesive usable in extensive applications ranging from a strong-tack region to a slight-tack region. The process for urethane resin production of the invention is a process for producing a urethane resin which comprises reacting a polyol with a first polyisocyanate compound in such a proportion that isocyanate groups are present in excess to thereby obtain an isocyanate-group-terminated prepolymer, subsequently reacting the isocyanate-group-terminated prepolymer with a chain extender, and further reacting the resultant polymer with a chain terminator, wherein the chain extender comprises a polyfunctional compound (X) having three or more functional groups reactive with an isocyanate group, wherein two of the functional groups of the polyfunctional compound (X) are primary hydroxyl groups and the remaining functional group(s) is secondary hydroxyl or tertiary hydroxyl group(s).