Abstract: A method is provided for filtration of particulates from a fluid medium which includes passing the medium through a surface modified, skinless, hydrophilic, microporous, alcohol-insoluble polyamide membrane derived from an alcohol-insoluble hydrophobic polyamide resin having a ratio of CH.sub.2 :NHCO of methylene CH.sub.2 to amide NHCO groups within the range of from about 5:1 to about 7:1. The membrane is characterized by (1) the surface properties thereof being substantially controlled by functional polar groups of a membrane surface-modifying polymer having a molecular weight of 20,000 or greater, (2) the membrane surface-modifying polymer being homogeneously distributed in the membrane, and (3) having the capability of reacting or interacting in a controlled manner with (a) particulate matter in a fluid, (b) non-particulate matter in a fluid, or (c) both (a) and (b).

Abstract: A polyvinylidene difluoride structure with a critical surface energy of at least about 80 dynes/cm and a method of making such a structure comprising the steps of contacting a polyvinylidene difluoride structure with an alkalized solution, such as potassium hydroxide, to form activated sites on the surface of the structure; rinsing the activated structure to remove residual alkali; contacting the rinsed, activated structure with a solution of a polymerization initiator, such as potassium peroxydisulfate, and a polymerizable vinylic monomer, such as acrylic acid; and polymerizing and grafting the monomer to the activated structure to form a polyvinylidene difluoride structure with a critical surface energy of at least about 80 dynes/cm.

Abstract: A polyvinylidene difluoride structure with a critical surface energy of at least about 80 dynes/cm and a method of making such a structure comprising the steps of contacting a polyvinylidene difluoride structure with an alkalized solution, such as potassium hydroxide, to form activated sites on the surface of the structure; rinsing the activated structure to remove residual alkali; contacting the rinsed, activated structure with a solution of a polymerization initiator, such as potassium peroxydisulfate, and a polymerizable vinylic monomer, such as acrylic acid; and polymerizing and grafting the monomer to the activated structure to form a polyvinylidene difluoride structure with a critical surface energy of at least about 80 dynes/cm.

Abstract: 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.

Abstract: Surface modified, skinless, hydrophilic, microporous, polyamide membranes with controlled surface properties are prepared by the steps of preparing a casting solution comprised of (A) a casting resin system comprised of (a) an alcohol-insoluble polyamide resin, and (b) a water-soluble membrane surface modifying polymer having functional polar groups and a molecular weight of 10,000 or greater, and (B) a solvent system in which the casting resin system is soluble; inducing nucleation of the casting solution by controlled addition of a nonsolvent for the casting resin system under controlled conditions to obtain a visible precipitate of casting resin system particles, thereby forming a casting composition; spreading the casting composition on a substrate to form a thin film; contacting and diluting the film of the casting composition with a liquid nonsolvent system for the casting resin system, thereby precipitating the casting resin system from the casting composition in the form of a thin, skinless, hydrophil

Abstract: Surface modified, skinless, hydrophilic, microporous, polyamide membranes are formed by preparing a casting solution comprised of (A) a casting resin system comprised of (a) an alcohol-insoluble polyamide resin, and (b) a cationic, water-soluble, quaternary ammonium, thermosetting, membrane surface modifying polymer, and (B) a solvent system in which the casting resin system is soluble; inducing nucleation of the casting solution by controlled addition of a nonsolvent for the casting resin system under controlled conditions to obtain a visible precipitate of casting resin system particles, thereby forming a casting composition; spreading the casting composition on a substrate to form a thin film; contacting and diluting the film of the casting composition with a liquid nonsolvent system for the casting resin system, thereby precipitating the casting resin system from the casting composition in the form of a thin, skinless, hydrophilic, surface modified, microporous, polyamide membrane; and washing and drying

Abstract: 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.