Abstract: A composite polyamide reverse osmosis membrane comprising a polyamide layer; where the polyamide layer has a thickness in the range of 50-250 nm, and large open spaces (i.e., free volumes); where the open spaces are defined by a ratio of water flux, Jw, (gfd) divided by the average surface roughness, Ra, (nm) of the polyamide layer; wherein the composite polyamide reverse osmosis membrane has the ratio of Jw/Ra>0.35 gfd/nm when tested at 65 psi, using an aqueous solution containing 250 ppm of NaCl; and a microporous support with a thickness ranging from 100-150 ?m. The present invention also relates to processes of fabricating the composite polyamide reverse osmosis membrane.

Abstract: In the treatment, a reverse osmosis membrane element having a polyamide skin layer is loaded in a pressure vessel in a membrane separator and contacted with a bromide-containing aqueous solution of free chlorine. The thus treated reverse osmosis membrane element retains for a long time its effect of reducing solute concentration in a solution treated with the reverse osmosis membrane and rejects efficiently non-electrolytic organic materials or substances such as boron that will not be dissociated in a neutral region. A reverse osmosis membrane module having the thus treated reverse osmosis membrane element is provided as well.

Abstract: A spiral wound type separation membrane element includes a spiral wound type membrane component formed by superposing separation membranes of membrane materials supported on nonwoven fabric members on both surfaces of a permeated liquid passage forming member and bonding three sides with an adhesive thereby defining an envelope-like membrane, mounting an opening of the envelope-like membrane on a water collection pipe and bonding the same with an adhesive and spirally winding the envelope-like membrane around the outer peripheral surface of the water collection pipe along with a raw liquid passage forming member. The outer peripheral surface of the envelope-like membrane forming the spiral wound type membrane component is covered with a sheath member, and anti-telescopic members are mounted on both end surfaces of the envelope-like membrane respectively. Each of the aforementioned components forming the spiral wound type separation membrane element is made of heat-resistant alkali-resistant plastic.

Abstract: In the treatment, a reverse osmosis membrane element having a polyamide skin layer is loaded in a pressure vessel in a membrane separator and contacted with a bromide-containing aqueous solution of free chlorine. The thus treated reverse osmosis membrane element retains for a long time its effect of reducing solute concentration in a solution treated with the reverse osmosis membrane and rejects efficiently non-electrolytic organic materials or substances such as boron that will not be dissociated in a neutral region. A reverse osmosis membrane module having the thus treated reverse osmosis membrane element is provided as well.

Abstract: A reverse osmosis composite membrane comprises a sponge layer, and a separation layer formed on a surface of the sponge layer, wherein at least one substance selected from the group consisting of an electrically neutral organic substance and an electrically neutral polymer is present in the separation layer or a surface of the separation layer is coated with at least one substance selected from the group consisting of an electrically neutral organic substance and an electrically neutral polymer, and wherein the specific surface area of the layer in which the at least one substance is present or the separation layer before the surface coating is in the range of 2 to 1,000. The reverse osmosis composite membrane has a high salt rejection, a high water permeability, and a high fouling tolerance, and permits practical desalination at a relatively low pressure.

Abstract: A reverse osmosis composite membrane that has a high salt rejection, a high water permeability, and a high fouling tolerance, and permits practical desalination at a relatively low pressure is provided by coating the surface of a reverse osmosis membrane of aromatic polyamide with polyvinyl alcohol (PVA), for example, and controlling the surface zeta potential of the separation layer within±10 mV at pH 6. This reverse osmosis composite membrane is electrically neutral and controls the electrical adsorption of membrane-fouling substances having a charge group present in water. Therefore, a high separation property can be maintained without fouling the membrane even if water containing a surfactant or a transition metal component is supplied as raw water.

Abstract: A reverse osmosis composite membrane comprising at least a porous support membrane layer and a separation layer, wherein a water-insoluble polymer layer having an anionic hydrophilic group formed on the surface of the separation layer is provided. Therefore, it has high anion property, high salt rejection, high water permeability, and chlorine tolerance, and can perform practical desalination under relatively low pressure.

Abstract: A separation membrane and a method of producing the membrane are provided. The membrane can control its permselectivity and its fouled pores can be easily washed by using the reversible shape change of the membrane. For this purpose, porous shape memory polymers are used for the separation membrane.

Abstract: The semipermeable membrane of polysulfone resin is formed of a continuous structure of a homogeneous skin layer part having an average thickness of 5 to 1000 nm and a porous layer which is made of the same material as that of the homogeneous skin layer and is thicker than the homogeneous skin layer, and the porous layer is formed of a structure having voids having an average pore diameter less than 3 .mu.m. Therefore, a gas separation membrane that has high permeation flux and requires practically satisfactory cost can be provided. Diethylene glycol dimethyl ether was added to polysulfone for dissolution, and the resultant solution was defoamed for preparation. The solution was cast on a support layer of polyester non-woven fabric using an applicator, dipped in water as a solidifying liquid, and dried. As a result, a semipermeable membrane comprising a homogeneous skin layer part and a porous layer is obtained.

Abstract: A polyimide resin semipermeable membrane has a continuous structure of a homogeneous skin layer part having an average thickness of 5-1000 nm and a porous layer that is made of the same materials and has the same thickness as the skin layer. The porous layer is formed by the void structure having the average hole diameter of less than 3 .mu.m so that a gas separation membrane can be provided, having high permeability and satisfying cost efficiency requirements can be provided. The above-mentioned membrane is formed by the following steps: a solution is made by adding diethylene glycol dimethyl ether into polyimide; the obtained solution is left for deaeration and adjusted; the film-forming solution is cast on a polyester nonwoven cloth, which serves as a supporting layer, with an applicator; the solution is soaked in water as a solidifying solution for 5 minutes and in a water. Thus semipermeable membrane comprising the homogeneous skin layer part and the porous layer.

Abstract: A fluorine-containing polyquinazolone polymer having a bisquinazolone unit represented by Formula 1 as the repeating unit is used for a gas separation membrane so that great chemical and heat resistance is provided. The membrane also has great permeability and effective separability, as well as excellent mechanical strength. ##STR1## where R.sub.1 indicates a tetravalent organic group, R.sub.2 respectively indicate an alkyl group or an aromatic group, R.sub.3 indicates a divalent organic group, and R.sub.1 and/or R.sub.3 indicates an organic group having at least one fluorine atom.

Abstract: A fluorine-containing polyimide gas separation membrane which is pinhole-free, uniform over a large area, and has a high permeability and a high separation factor .alpha. is provided. A polyimide resin is dissolved in at least one solvent selected from the group consisting of an organic solvent (A) or (B). The organic solvent (A) has a dielectric constant of 30 or less and a dipole moment of 3.0 D or less. The organic solvent (B) mainly contains an organic solvent having at least one ether bonding in the molecular unit. In the next step, the polyimide resin is dipped in a solvent (C) in order for desolvation. The solvent (C) does not dissolve the fluorine-containing polyimide resin while it is miscible with the organic solvent (A) or (B). As a result, an asymmetric gas separation membrane is formed. The fluorine-containing polyimide resin layer comprises a skin layer the thickness L.sub.1 thereof is about 40 nm and a sponge like layer the thickness L.sub.2 thereof is about 30 .mu.m.

Abstract: A laminated asymmetric membrane comprising first and second asymmetric membranes having different molecular structures, in which the first and second asymmetric membranes are laminated. Consequently, the laminated asymmetric membrane having the excellent property of the separation and permeability can be provided at a low cost. The laminated asymmetric membranes of the present invention is manufactured by the following steps: a film-forming dope (1) was prepared by synthesizing fluorine-containing polyimide having a repeating unit expressed by the following Chemical Formula by using diethylene glycol dimethyl ether as a solvent; a film-forming dope (2) was prepared by dissolving polysulfone in diethylene glycol dimethyl ether; the dope (2) from the resulted two dopes was cast on a polyester nonwoven cloth to a thickness of approximately 50 .mu.m by means of an applicator; the dope (1) was lap coated thereon to a thickness of 30 .mu.

Abstract: A homogeneous membrane or an asymmetric membrane which is made of polyimide resin containing fluorine as a main component and has high separation and permeation properties, is used in a method of separating unsaturated hydrocarbon from a mixture of unsaturated and saturated hydrocarbon. The method includes the steps of contacting the mixture onto the membrane made of the polyimide resin having a repeating unit shown in the following formula as a main component, selectively permeating unsaturated hydrocarbon through the membrane, and separating unsaturated hydrocarbon from the mixture. The membrane satisfies the condition of a solubility coefficient ratio between unsaturated and saturated hydrocarbon.gtoreq.1.2 at 25.degree. C. and more than 50 Torr when the absorption of hydrocarbon to the polyimide resin is in equilibrium.

Abstract: A dope for cast formation comprising a fluorine including polyimide resin and an organic solvent (P) as main components. The fluorine including polyimide resin has at least one --CF.sub.3 group in the repeating molecular unit. The organic solvent (P) is present during the resin polymerization of the fluorine including polyimide resin. The organic solvent (P) is diethylene glycol dimethyl ether.

Abstract: A method of separating a gas, especially carbon dioxide, from a gas mixture of the gas and nitrogen at a low temperature of -20.degree. C. to 50.degree. C. using a gas separation membrane permeable to the gas, including the step of cooling the gas mixture using at least one cooling medium selected from the group consisting of liquefied petroleum gas and liquefied natural gas. The liquefied petroleum gas comprises at least one selected from the group consisting of propane gas and butane gas in an amount of more than 50 vol. %. The gas separation membrane has a CO.sub.2 permeation rate of 1.times.10.sup.-4 to 5.times.10.sup.-2 N cm.sup.3 /(cm.sup.2 cm Hg sec) at 25.degree. C. and a CO.sub.2 /N.sub.2 separation factor of 10 to 200 at 25.degree. C.

Abstract: Polyimide resin dope having at least three fluorine atoms in a repeating molecular unit and an organic solvent (A) are extruded in a tube form or coating the dope on a supporting body. The polyimide resin dope is then immersed in a solvent (B), which the organic solvent (A) is miscible with the solvent (B). Thus, a polyimide-type gas separation membrane including fluorine is virtually defect free in the skin layer, and manufactured cost-effectively by a simple manufacturing method.

Abstract: A gas separating composite membrane comprising two types of polyimide resin layers having different molecular structures and each having solubility in an organic solvent different from each other, the two layers being laminated being substantially independent or via a mixed layer, the first polyimide resin layer comprising a porous polyimide supporting membrane having a nitrogen gas permeation flux density at 25.degree. C. of at least 2 Nm.sup.3 /m.sup.2 /h/atm., and the second polyimide resin layer, which contributes to a gas separating performance comprising a fluorine-containing polyimide thin film containing at least three fluorine atoms in a repeating molecular structure unit which constructs the second polyimide resin layer has a very high gas permeation flux density while maintaining a high gas permeability, excels in heat resistance and chemical resistance, and satisfies a practical use in terms of cost.

Abstract: An acid chloride, bicyclo 2,2,2!oct-7ene-(2.alpha.,3.beta.,5.alpha.,6.beta.)tetracarbonyl chloride (C.sub.12 H.sub.8 O.sub.4 Cl.sub.

Abstract: A composite reverse osmosis membrane comprising a thin membrane and a microporous supporting membrane supporting it, wherein said thin membrane mainly comprises a crosslinked polyamide comprising; (a) an amine component containing at least one member selected from the group consisting of substantially monomeric amine compounds each having at least two primary and/or secondary amino groups, and (b) an acid halide component containing at least one member selected from the group consisting of substantially monomeric cyclic acid halide compounds each having at least two acid halide groups and comprising at least two rings.