Quaternization of amines entrained in a microporous matrix

An improved process for quaternizing a normally liquid tertiary amine entrained in a three-dimensional synthetic thermoplastic polymeric microporous matrix having an average pore size from about 0.2 to about 40 microns wherein the improvement comprises subjecting the microporous matrix to methyl chloride vapors for a length of time sufficient to distribute methyl chloride throughout the matrix, at a temperature at which substantially no quaternization of the amine occurs and subsequently heating the matrix to a temperature and for a time sufficient to quaternize at least a portion of the amine.