Nitto-Denko Corporation

Hiroki Ito

Masahiko Hirose

Tomomi Ohara

Kazuo Tanaka

Masatoshi Maeda

Takuji Shintani

Masaaki Ando

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 liquid separation membrane module includes a semipermeable membrane receiving a pressure of a feed liquid, and a channel material arranged so as to support the back side of the semipermeable membrane. The channel material is a tricot knitted fabric knitted by a tricot knitting machine with two reeds and has a ground stitch portion and a convex portion. The tricot knitted fabric includes a thermoplastic synthetic filament yarn with a core/sheath type conjugated fiber having a high melting point polymer as a core component and a low melting point polymer as a sheath component. Thermoplastic synthetic filament yarns for forming the ground stitch portion and the convex portion have a substantially same fineness, and the yarns in the tricot knitted fabric are bonded with one another by melt adhesion of the low melting point component to rigidity the entire knitted fabric.

Liquid separation membrane module

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 composite reverse osmosis membrane has a polyamide type skin layer whose specific surface area ranges from 3 to 1000. The composite reverse osmosis membrane of this invention is superior in the salt rejection property and water permeability. The composite reverse osmosis membrane comprises a negatively-charged crosslinked polyamide type skin layer obtained by reacting a compound having polyfunctional amino groups and a polyfunctional acid halide compound having polyfunctional acid halide groups, and a microporous support to support the skin layer. The specific surface area of the skin layer is at least 3. A first stage of reverse osmosis treatment is carried out in a membrane module using this composite reverse osmosis membrane. The skin layer can be coated with a layer of an organic polymer having positively-charged groups e.g. polyethyleneimine in order to be used as another membrane module. The organic polymer of this case is crosslinked, for example, by glutaraldehyde. The layer which is crosslink-coated on its surface area is a composite reverse osmosis membrane excellent in desalination of mineral salt in a low-concentration region and removal of cationic organic materials.

Osmosis membrane

This invention provides a composite reverse osmosis membrane having a polyamide type skin layer whose average surface roughness is at least 55 nm, and the polyamide type skin layer comprises the reaction product of a compound having amino groups and polyfunctional acid halide compound having acid halide groups. The composite reverse osmosis membrane of this invention is superior in salt rejection and water permeability. A polymer film is formed on a supporting film by contacting a solution containing e.g., m-phenylenediamine with a porous polysulfone supporting film so as to form a layer of the solution on the supporting film, then contacting the film with a solution of trimesic acid chloride and holding the film in a hot air dryer so that a polymer film is formed on the supporting film. The surface of the polyamide type skin layer can also be treated with quaternary ammonium salt and coated with a crosslinked layer of an organic polymer having positively-charged groups. Raw liquid is transmitted from a raw liquid tank to a membrane module for the first stage through a first transmission pump, and the first stage of reverse osmosis treatment is carried out. The composite reverse osmosis membrane coated with the crosslinked layer is used when another reverse osmosis treatment is carried out by using another membrane module for the second stage.

Highly permeable composite reverse osmosis membrane, method of producing

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.

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Shiga, Japan

Hiroki Ito