Charge modified polyamide membrane
First Claim
1. A process for preparing a surface modified, skinless, hydrophilic, microporous, alcohol-insoluble polyamide membrane that is readily wetted by water which comprises:
- (1) preparing a casting solution comprised of (A) a casting resin system comprised of (a) an alcohol-insoluble polyamide resin having a ratio CH2 ;
NHCO of methylene CH2 to amide NHCO groups within the range of from about 5;
1 to about 7;
1, and (b) a cationic, water-soluble, quaternary ammonium, thermosetting, membrane surface modifying polymer and (B) a solvent system in which said casting resin system is soluble;
(2) inducing nucleation of said casting solution by controlled addition of a nonsolvent for said casting resin system under controlled conditions of concentration, temperature, addition rate and degree of agitation to obtain a visible precipitate of casting resin system particles, thereby forming a casting composition;
(3) spreading said casting composition on a substrate to form a thin film thereof on the substrate;
(4) contacting and diluting the film of said casting composition with a liquid nonsolvent system for said casting resin system comprised of a mixture of solvent and nonsolvent liquids, thereby precipitating said casting resin system from said casting composition in the form of a thin, skinless, hydrophilic, surface modified, microporous, polyamide membrane;
(5) washing said membrane to remove solvent; and
(6) drying said membrane.
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Accused Products
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 the membrane. The membranes of this invention are characterized by having fine pore ratings, the surface properties thereof being substantially controlled by cationic, quaternary ammonium groups of a modifying polymer thereby providing a positive zeta potential in alkaline media, and for those with moderate or low levels of surface modifying polymer present, a time to reach an effluent resistivity of 14 megaohms/cm under the Resistivity Test of 10 minutes or less. They have greatly enhanced filtration efficiency over a broad pH range with a variety of contaminants, including very fine negatively charged particles, bacteria and endotoxins.
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Citations
64 Claims
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1. A process for preparing a surface modified, skinless, hydrophilic, microporous, alcohol-insoluble polyamide membrane that is readily wetted by water which comprises:
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(1) preparing a casting solution comprised of (A) a casting resin system comprised of (a) an alcohol-insoluble polyamide resin having a ratio CH2 ;
NHCO of methylene CH2 to amide NHCO groups within the range of from about 5;
1 to about 7;
1, and (b) a cationic, water-soluble, quaternary ammonium, thermosetting, membrane surface modifying polymer and (B) a solvent system in which said casting resin system is soluble;(2) inducing nucleation of said casting solution by controlled addition of a nonsolvent for said casting resin system under controlled conditions of concentration, temperature, addition rate and degree of agitation to obtain a visible precipitate of casting resin system particles, thereby forming a casting composition; (3) spreading said casting composition on a substrate to form a thin film thereof on the substrate; (4) contacting and diluting the film of said casting composition with a liquid nonsolvent system for said casting resin system comprised of a mixture of solvent and nonsolvent liquids, thereby precipitating said casting resin system from said casting composition in the form of a thin, skinless, hydrophilic, surface modified, microporous, polyamide membrane; (5) washing said membrane to remove solvent; and (6) drying said membrane. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A process for preparing a surface modified, skinless, hydrophilic, microporous, alcohol-insoluble polyhexamethylene adipamide resin membrane that is readily wetted by water and which has pores that are substantially uniform from surface to surface which comprises:
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(1) preparing a casting solution comprised of (A) a casting resin system comprised of (a) an alcohol-insoluble polyhexamethylene adipamide resin in a concentration within the range from about 10% to about 18% by weight and (b) a cationic, water-soluble, quaternary ammonium, thermosetting, membrane surface modifying polyamine-epichlorohydrin resin or polymer in a concentration within the range of from about 0.1% to about 0.9% and (B) a solvent system comprised of (a) formic acid in a concentration of from about 65% to about 75% and (b) from 10 to about 20% water (all percentages based on the weight of all the components in said solution); (2) inducing nucleation of said casting solution by adding water thereto while controlling temperature, rate of addition of water and degree of agitation to obtain a visible precipitate of casting resin system particles, thereby forming a casting composition; (3) spreading said casting composition on a polyester substrate to form a thin film of said casting composition thereon; (4) contacting and diluting said thin film of said casting composition with an aqueous solution containing from about 37% to about 55% formic acid, thereby precipitating said casting resin system from said casting composition as a thin, surface modified, skinless, hydrophilic, microporous, polyamide membrane; (5) washing said membrane to remove formic acid; and (6) drying said membrane. - View Dependent Claims (20, 21, 22)
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23. A charge modified, skinless, hydrophilic, microporous, alcohol-insoluble polyamide membrane derived from an alcohol-insoluble hydrophobic polyamide resin having a ratio CH2 NHCO of methylene CH2 to amide NHCO groups within the range of from about 5:
- 1 to about 7;
1, said membrane having an integral microstructure whose characteristics are substantially controlled by cationic, quaternary ammonium groups of a cationic, quaternary ammonium, thermoset, charge modifying polymer homogeneously distributed in said membrane, thereby providing a positive zeta potential in alkaline media. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46)
- 1 to about 7;
- 47. A method for the filtration of particulates from a fluid medium comprising passing said medium through the microporous, alcohol-insoluble polyamide membrane of claim 65.
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49. A charge modified, skinless, hydrophilic, microporous, alcohol-insoluble polyamide membrane derived from about 80 to about 99.9 percent of an alcohol-insoluble, hydrophobic polyamide resin having a ratio CH2 :
- NHCO of methylene CH2 to amide NHCO groups within the range of from about 5;
1 to about 7;
1 and from about 20 to about 0.1 percent of a cationic, quaternary ammonium, thermoset, charge modifying polymer homogeneously distributed in said membrane, said membrane having an integral microstructure whose characteristics are substantially controlled by cationic, quaternary ammonium groups of said modifying polymer, thereby providing a positive zeta potential in alkaline media. - View Dependent Claims (50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63)
- NHCO of methylene CH2 to amide NHCO groups within the range of from about 5;
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64. A charge modified, skinless, hydrophilic, microporous, alcohol-insoluble polyhexamethylene adipamide membrane derived from about 80 to about 99.9 percent of an alcohol-insoluble, hydrophobic polyhexamethylene adipamide resin and from about 20 to about 0.1 percent of a cationic, quaternary ammonium, thermoset, charge modifying polymer homogeneously distributed in said membrane, said membrane having an integral microstructure whose characteristics are substantially controlled by quaternary ammonium groups of said modifying polymer, thereby providing a positive zeta potential in alkaline media.
Specification