Method of producing thermally expansive microcapsule

摘要

A method of producing a thermally expansive microcapsule that is excellent in heat resistance and solvent resistance, narrow in breadth of the distribution of particle size, and extremely low in secondary cohesion of the particles when heated, wherein a polymer obtained from the component comprising not less than 80 weight % of monomer of nitrile series, less than weight % of monomer of non-nitrile series, and 0.05-1 weight % of at least tetrafunctional cross-linking agent and/or of long side chain of cross-linking agent is used to micro-encapsulate a volatile expanding agent that comes into its gaseous state at a temperature equal to or less than a softening point of the polymer.