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Filter media comprised of charge modified, resin coated inorganic microfibers are prepared by mixing inorganic microfibers with an aqueous solution of a water soluble, noncolloidal cationic thermosetting binder resin to form a dispersion, following which a precipitating agent is added to precipitate

Filter media comprised of charge modified, resin coated inorganic microfibers are prepared by mixing inorganic microfibers with an aqueous solution of a water soluble, noncolloidal cationic thermosetting binder resin to form a dispersion, following which a precipitating agent is added to precipitate the binder resin and coat the microfibers. The coated microfibers may be used in the dispersed or suspended form as a filter aid. Preferably they are formed into a filter sheet which is then dried and cured to form a filter sheet of narrowly distributed pore size, pore sizes as small as one-half micron, and having a positive zeta potential in alkaline media. Glass is the preferred microfiber and polyamine-epichlorohydrins the preferred resins. By providing the normally negative zeta potential microfibers with a positive zeta potential the binder resins used to coat the microfibers substantially enhance particulate removal capabilities of the microfiber filter sheet.

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A process for forming a filter sheet exhibiting a positive zeta potential in alkaline media comprising: (1) mixing inorganic microfibers normally having a negative zeta potential with an aqueous solution of a water soluble, non-colloidal cationic thermo-setting binder resin or polymer to form a micr

A process for forming a filter sheet exhibiting a positive zeta potential in alkaline media comprising: (1) mixing inorganic microfibers normally having a negative zeta potential with an aqueous solution of a water soluble, non-colloidal cationic thermo-setting binder resin or polymer to form a microfiber dispersion; (2) adding a precipitating agent comprising a synthetic, water soluble or dispersible polymer containing anionic groups to said dispersion to precipitate said binder resin or polymer and coat said microfibers with said binder resin or polymer; and (3) forming the coated microfibers of step (2) into a filter sheet, said filter sheet exhibiting a positive zeta potential in alkaline media.