FILTER AIDS, THEIR PREPARATION AND USE

摘要

Filter aid materials are treated with anion exchange resin particles having an average particle diameter from 0.05 to 1 micrometer to produce a filter aid composition wherein the anion exchange resin particles are electrostatically bonded to the filter aid material. The bonding may be sufficiently strong that the resin is substantially irremovable from the filter aid material which is preferably completely covered by the resin particles. The treatment may be effected by mixing the filter aid material and the resin particles in aqueous suspension then removing excess particles. An efficacious filter has as a precoat layer, a floc of finely divided anion and cation exchange resins and an overcoat layer of filter aid composition of the invention.