Nitto-denko Corporation

Tomomi Ohara

Masahiko Hirose

Hisao Hachisuka

Hiroki Ito

Atsuhito Koumoto

Ichirou Kawada

Masaaki Andou

Hajimu Hisada

Ping Xu

Kenichi Ikeda

Toshiyuki Kawashima

Naoki Kurata

Akira Shimazu

Masaaki Ando

Takashi Kamada

Tetsurou Adachi

The present invention aims at providing a composite semipermeable membrane in which water permeability and salt-blocking rate cannot deteriorate by long-term storage, and at providing a process for producing the same. The present invention relates to a composite semipermeable membrane having a skin layer formed on the surface of a porous support, the skin layer including a polyamide resin obtained by interfacial polymerization of a polyfunctional amine component and a polyfunctional acid halide component, wherein the porous support contains at least one kind of additives selected from the group consisting of antioxidants, antibacterial agents, antifungal agents, and moisturizers, in an amount of 95% by weight or more with respect to the whole composite semipermeable membrane.

Composite semipermeable membrane and process for producing the same

The present invention aims at providing a process for producing a dried composite semipermeable membrane having extremely small content of unreacted components, outstanding water permeability and salt-blocking rate even after drying treatment, and outstanding contamination resistance and durability. The present invention relates to a process for producing a dried composite semipermeable membrane comprising the steps of: preparing a composite semipermeable membrane having a skin layer including a polyamide resin obtained by reaction between a polyfunctional amine component and a polyfunctional acid halide component formed on the surface of a porous support; washing the composite semipermeable membrane; contacting a moisturing solution including a moisturizer and a hydrophilization agent only to the surface of the porous support of the washed composite semipermeable membrane and contacting a protecting solution only to the surface of the skin layer of the washed composite semipermeable membrane; and drying the treated composite semipermeable membrane.

Process for producing a dried composite semipermeable membrane

A composite semipermeable membrance of the present invention comprises a thin film and a porous support membrane supporting the thin film, wherein the thin film includes polyamide based resin having a constituent unit with amide bond between diamine residue and di or tri carboxylic acid residue, in which nitrogen atom of the amide bond has a substituent of aromatic ring. A production method of this invention includes a contacting step of contacting the above composite semipermeable membrane with solution including an oxidizer. In addition, a water treatment method of this invention comprises a step of separating a raw water by a composite semipermeable membrane to obtain permeation water in which salt and/or organic substance is removed sufficiently in practical use, characterized in that the composite semipermeable membrane of this invention is used and a fungicide is added into the raw water. This invention provides a composite semipermeable membrane having practically permeability, and excellent desalting faculty and oxidizer resistance, a production method thereof, and water treatment method using the same.

Composite semipermeable membrane, production method thereof, and water treatment method using the same

A composite reverse osmosis membrane is described, which includes a polyamide skin layer on a porous support, with a contact angle between the polyamide skin layer surface and water of 45&deg; or less. The composite reverse osmosis membrane has a high salt rejection and also a high water permeability. This composite reverse osmosis membrane is produced by forming a polyamide skin layer on a porous support having the steps of: forming a layer on the porous support by coating a solution A including one or more compounds having at least two reactive amino groups; contacting the layer with a solution B comprising one or more polyfunctional acid halide compounds; and subsequently, contacting the layer with a solution C comprising the polyfunctional acid halide compound of a higher concentration than the solution C. The concentration of the polyfunctional acid halide compound in the solution C is preferably at least 1.2 times of the solution B.

Composite reverse osmosis membrane and process for preparing the same

A spiral wound type membrane element is formed by covering a spiral membrane component prepared by winding a plurality of independent or continuous envelope-like membranes around the outer peripheral surface of a water collection pipe through raw water spacers with a separation membrane and further covering the same with an outer peripheral passage forming material. In filtration, raw water introduced from a raw water inlet of a spiral wound type membrane module permeates through the separation membrane from at least the outer peripheral side of the spiral wound type membrane element and infiltrates into the clearances between the envelope-like membranes along the raw water spacers. Part of the supplied raw water axially flows along the outer peripheral portion of the spiral wound type membrane element and is thereafter discharged from a raw water outlet of the spiral wound type membrane module, to be returned to a raw liquid tank again. Back wash reverse filtration is performed in washing of the spiral wound type membrane element. The permeate flow rate in filtration, the filtration time, the wash water flow rate in washing and the washing time are set to prescribed values so that the permeate volume in filtration to the permeate volume in back wash reverse filtration is not more than 600.

Methods of running and washing spiral wound membrane modules

A spiral wound membrane element is formed by covering a spiral membrane component prepared by winding a plurality of independent or continuous envelope-like membranes around the outer peripheral surface of a water collection pipe through raw water spacers with a separation membrane and further covering the same with an outer peripheral passage forming material. In washing, permeate containing a chemical is introduced from an opening end of the water collection pipe while the permeate derived from the outer peripheral surface of the water collection pipe is discharged from at least the outer peripheral side of the spiral wound type membrane element and raw water is axially fed along the outer peripheral portion of the spiral wound type membrane element. In filtration running, the raw water in which bubbles are diffused by an air diffuser may be supplied to the spiral wound membrane element stored in a pressure vessel. Alternatively, filtration running may be temporarily stopped for holding the spiral wound type membrane element for a prescribed time in a state sealing the raw water and the permeate in the pressure vessel.

Methods of running and washing spiral wound membrane module

A module that can be practically used at a pressure of about 3 kgf/cm,is obtained by treating a polyamide based reverse osmosis membrane with an oxidizing agent. A composite reverse osmosis membrane comprises a thin film which is a polyamide based skin layer obtained by polycondensation of a compound having two or more reactive amino groups and a polyfunctional acid halide compound having two or more reactive acid halide groups, and a microporous support for supporting the thin film. The polyamide based skin layer formed on the surface of the membrane has a mean roughness of 50 nm or more. The composite reverse osmosis membrane is treated with an oxidizing agent. A salt rejection of 99% or more and a flux of 1.5 m,/m,&middot;day or more are obtained when evaluated by using a solution having pH 6.5 containing 500 ppm of sodium chloride at an operating pressure of 7.5 kgf/cm,and a temperature of 25&deg; C.

Highly permeable composite reverse osmosis membrane

The present invention provides a composite reverse osmosis membrane and a reverse osmosis membrane module using the same, having a high salt rejection, high water permeability, and a high rejection of organic substances such as isopropyl alcohol, which can be used to remove organic substances as well as ionic substances with suitable efficiency and economy. The highly permeable composite reverse osmosis membrane of the invention can be produced by adding alcohols or ethers or the like having a solubility parameter of 8-14 (cal/cm.sup.3).sup.1/2 to the solution containing at least one compound selected from the group consisting of a compound having two or more reactive amino groups and a polyfunctional acid halide having two or more reactive acid halide groups which is used when conducting the polycondensation of a compound having two or more reactive amino groups and a polyfunctional acid halide having two or more reactive acid halide groups on a microporous support.

Highly permeable composite reverse osmosis membrane and a reverse

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.

Dope for cast formation and method of manufacturing the same

Disclosed is a method for producing a composite reverse osmosis membrane comprising the steps of coating a porous support with (A) a solution containing a compound having at least two reactive amino groups per molecule and bringing (B) a solution containing a polyfunctional acid halide into contact with the solution (A) to induce crosslinking to form a crosslinked polyamide skin layer, in which the crosslinking is carried out in the presence of a substance having a solubility parameter of 8 to 14 (cal/cm.sup.3).sup.1/2. The resulting composite reverse osmosis membrane exhibits high salt rejection and high water permeability.

Method for producing highly permeable composite reverse osmosis membrane

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.

Method of manufacturing a polyimide-type gas permeation membrane

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.

Growing community of inventors

Ibaraki, Japan

Tomomi Ohara