US 4,399,035 AGranted

Polyvinylidene fluoride type resin hollow filament microfilter and process for producing the same

AssigneeAsahi Kasei Kogyo Kabushiki Kaisha

InventorsTakashi Nohmi, Takao Yamada

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Abstract

A screen type hollow filament microfilter made of a polyvinylidene fluoride type resin and having a layer structure of two kinds of layers with the support layer and the internal and external skin layers having an easily-controllable and wide average effective pore diameter of 0.05 to 1.0 .mu.m, characterized by having a high selectivity in permeation, a high permeability, a high porosity, an excellent mechanical strength and an excellent chemical resistance and an excellent inertness to living bodies. The microfilter, which has a number of excellent performances, can be produced by extruding a spinning solution comprising a polyvinylidene fluoride type resin, a solvent therefor and at least one kind of surfactant from an annular hollow filament spinning orifice and coagulating the extrudate by using coagulating liquids.

Claims4

Dependent claims

A hollow filament microfilter which comprises a polyvinylidene fluoride type resin membrane having a substantially annular shape in cross-section and comprising internal and external surface skin layers and a support layer connected thereto;

said skin layers being uniformly porous layers with a average pore diameter (2r.sub.s) of 0.05 to 1.0 .mu.m, said support layers being a uniformly porous layer with an average pore diameter (2r.sub.a) of 1 to 10 .mu.m, a relationship represented by the formula r.sub.a /r.sub.s .gtoreq.4 being satisfied, said support layer having a plurality of macrovoids extending radially in the substantially annular cross-section of the resin membrane, said macrovoids each having a length of at least 10% and at most 80%, based on the thickness of the resin membrane, in the radially extending axis direction in said cross-section, said resin membrane having an average effective pore diameter (2r) of 0.05 to 1.0 .mu.m and a porosity of 60 to 85%.

Dependencies are inferred from the claim text.