Toyo Boseki Kabushiki Kaisha

Akihiro Ariji

Hideki Yamada

Hideki Sugihara

Koichi Baba

Kenta Kochi

Tsuyoshi Hoshiyama

An object of the present invention is to provide a hollow-fiber ultrafiltration membrane that can be used in treatment in various aqueous fluids such as water purification, beverage treatment, seawater clarification, and that has excellent fractionation characteristics and permeability, while deterioration of its performance due to passage of time is minimized, and that has excellent recovery of the membrane-separation characteristics by cleaning. The main feature of the hollow-fiber ultrafiltration membrane of the present invention is that the specific surface area of the membrane surface to which raw water is supplied falls within the range from not less than 1.10 to not greater than 1.55. The present invention also provides a process for producing a hollow-fiber ultrafiltration membrane, wherein a heat treatment is conducted under the condition that the membrane having a residual organic solvent content of not greater than 300 mg/g.

Hollow-fiber ultrafiltration membrane with excellent fouling resistance

This disclosure relates to an anisotropic polyvinylidene fluoride hollow fiber microporous membrane containing a polyvinylidene fluoride resin. The hollow fiber microporous membrane does not include macrovoids, and has mainly a net-like structure. In addition, the hollow fiber microporous membrane has a dense outer layer on an outer surface, and a homogeneous bulk layer that is internally adjacent to the outer layer and has a coarser structure than the outer layer. The porosity of the bulk layer is at least 1.5 times the membrane surface porosity of the outer layer. The dense structure of the outer layer changes substantially discontinuously into the coarse structure of the bulk layer.

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Ohtsu, Japan

Akihiro Ariji