PROCESS FOR PRODUCTION OF THERMALLY EXPANDABLE BEADS AND APPLICATION THEREOF

摘要

A production method for heat-expandable microspheres, which have high expanding ratio and are thermally expanded into hollow particulates having excellent repeated-compression durability, and application thereof are provided. The method produces heat-expandable microspheres a shell of thermoplastic resin and a blowing agent being encapsulated therein and having a boiling point not higher than the softening point of the thermoplastic resin. The production method includes a step of polymerizing a polymerizable component in an aqueous dispersing medium in which the polymerizable component and the blowing agent are dispersed, in the presence of at least one water-soluble compound selected from oxygen-containing aluminum salts and/or their hydrates, and polyalkyleneimines which have a molecular weight not lower than 1000 and at least one bond of nitrogen atom and an alkyl group substituted with a hydrophilic functional group selected from the group consisting of carboxylic acid (salt) groups and phosphonic acid (salt) groups.