PURPOSE: To form an org. halogen compd. into a microcapsule and to remote the reforming or curing of a resin composition by using a film consisting of a fine-grain org. polymer carrying an inorg. fine grain on the surface.

CONSTITUTION: The core material of the org. halogen compd., halogenated resin having a functional group or organotin compd. is dispersed in an aq. medium, a coagulant for coagulating a fine-grain org. polymer, especially a positively charged alumina sol, is added, and then the emulsion of an org. polymer carrying an inorg. fine grain on the surface is added in small amts. under strong agitation. A deionizing agent such as an amphoteric ion exchanger is added, as required, agitation is continued, hence a composite film of the org. polymer and inorg. fine grain is formed on the core material, and a microcapsule slurry is obtained. The microcapsule is excellent in compatibility with resin and dispersibility, and the toxicity, corrosiveness or chemical reaction acceleration of the org. halogen compd., etc., as the core material are retarded.