Method of forming microcapsule films having low porosity

Claim 1

In a method of forming microcapsules having low porosity microcapsule films using a complex coacervation process which comprises the following steps of: (1) emulsifying a water-immiscible oil as a core material to be encapsulated in an aqueous solution of at least one hydrophilic colloid inonizable in water (the first sol), and admixing an aqueous solution of a hydrophilic colloid (the second sol) having an electric charge opposite to that of the first sol, the time of admixing the second sol being freely varied, or emulsifying a water-immiscible oil in an aqueous solution of hydrophilic colloids which are ionizable in water and at least one of which is positively charged; (2) either adding water thereto or adjusting the pH thereof to cause coacervation, thus obtaining coacervates wherein a complex colloid is adhered to the individual oil droplets; (3) cooling the coacervates to cause gelation thereof; (4) and adjusting the pH to the alkaline side in the presence of a hardening agent, or adding a hardening agent after adjusting the pH to the alkaline side, the improvement which comprises chemically or ionically binding a water soluble or water dispersible heterocyclic amine, said heterocyclic amine being a symmetrical or asymmetrical spiroacetal diamine represented by the following formula ##STR6## wherein R 1 and R 1 ' each represent a hydrogen atom of a lower alkyl group and R 2 and R 2 ' each represents a linear or a branched chain alkylene group having 1 to 7 carbon atoms or a derivative thereof selected from the group consisting of a condensation product of said heterocyclic amine with a compound containing at least one oxirane group, an addition product produced by reacting said heterocyclic amine with acrylonitrile, a reaction product produced by reacting said heterocyclic amine with urea, thiourea or guanidine and a reaction product produced by reacting said heterocyclic amine with an alkylene oxide, to the microcapsule film forming material by adding said amine during said complex coacervation process, or depositing said heterocyclic amine alone or a water insoluble material formed by reaction with said amine onto the microcapsule films after formation of said films, said heterocyclic amine being used in an amount of from 1/1000 to 1/2 by weight based on the weight of said core material.