Abstract: The object of the present invention is to provide a thermoexpandable microcapsule which can be expanded at a lower temperature without decrease of various properties such as chemical resistance and heat resistance; said thermoexpandable microcapsule contains at least two kinds of volatile expanding agents having different boiling points lower than softening temperature of a polymeric material forming a shell, production thereof; and a method of expanding the microcapsule in which it is subjected to first heating below the starting temperature of expanding and then to the second heating.

Abstract: The present invention provides a thermoplastic microcapsule which is softened by heat, has a good thermoexpandability, and can provide a MICROBALLOON which shows a high heat resistance after thermoexpanded; such a thermoexpandable microcapsule is composed of a shell and an expanding agent therein, in which said shell is made from a copolymer essentially consisting of a polymerizable monomer having two or more polymerizable double bonds and a monomer which can produce a homopolymer having a high glass transition temperature, and said expanding agent is vaporizable at a temperature lower than the softening temperature of the copolymer.

Abstract: Microspheres, the blowing agent of which is microencapsulated with a thermoplastics having an acrylonitrile moiety, are prepared. Acrylonitrile monomer remaining therein is eliminated from the microspheres by cyanoethylation. The microspheres have an excellent solvent-resistance and an expansibility hardly changeable with time but no harmfulness attributed to the acrylonitrile monomer.