The present invention relates to a composite porous hollow-fiber membrane including a first layer and a second layer which each include a fluororesin-based polymer, in which the first layer has a columnar texture oriented in a longitudinal direction of the composite porous hollow-fiber membrane, the columnar texture has an average value v of a Raman orientation parameter calculated with the specific formula, and the second layer has a three-dimensional network texture and has an average surface-pore diameter of 5.0 nm to 5.0 μm.

Polytetrafluoroethylene (PTFE) composite articles that have a macro textured surface. The composite articles include at least two different PTFE membranes in a layered or stacked configuration. The composite article has a macro textured surface characterized by a plurality of strands raised from the surface of the PTFE membrane. The strands may be formed of either interconnected nodes of PTFE or of at least one nodal mass of PTFE and have a length equal to or greater than about 1.5 mm. The macro textured surface provides a topography to the first PTFE membrane. The composite articles have a bubble point from about 3.0 psi to about 200 psi, a thickness from about 0.01 to about 3.0 mm, and a bulk density from about 0.01 g/cm.sup.3 to about 1.0 g/cm.sup.3.

This application is directed to new and/or improved MD and/or TD stretched and optionally calendered membranes, separators, base films, microporous membranes, battery separators including said separator, base film or membrane, batteries including said separator, and/or methods for making and/or using such membranes, separators, base films, microporous membranes, battery separators and/or batteries. For example, new and/or improved methods for making microporous membranes, and battery separators including the same, that have a better balance of desirable properties than prior microporous membranes and battery separators. The methods disclosed herein comprise the following steps: 1.) obtaining a non-porous membrane precursor; 2.) forming a porous biaxially-stretched membrane precursor from the non-porous membrane precursor; 3.) performing at least one of (a) calendering, (b) an additional machine direction (MD) stretching, (c) an additional transverse direction (TD) stretching, and (d) a pore-filling on the porous biaxially stretched precursor to form the final microporous membrane. The microporous membranes or battery separators described herein may have the following desirable balance of properties, prior to application of any coating: a TD tensile strength greater than 200 or 250 kg/cm2, a puncture strength greater than 200, 250, 300, or 400 gf, and a JIS Gurley greater than 20 or 50 s.

A microporous membrane is made by a dry-stretch process and has substantially round shaped pores and a ratio of machine direction tensile strength to transverse direction tensile strength in the range of 0.5 to 5.0. The method of making the foregoing microporous membrane includes the steps of: extruding a polymer into a nonporous precursor, and biaxially stretching the nonporous precursor, the biaxial stretching including a machine direction stretching and a transverse direction stretching, the transverse direction stretching including a simultaneous controlled machine direction relax.

The present disclosure relates to improved semipermeable membranes based on acrylonitrile copolymers for use in dialyzers for the extracorporeal treatment of blood in conjunction with hemodialysis, hemofiltration or hemodiafiltration. The present disclosure further relates to methods of producing such membranes.

Disclosed herein is an improved membrane, separator and/or method for forming a multilayer microporous membrane for use in an improved battery separator, particularly a battery separator for a lithium ion secondary battery. Also disclosed herein is the multilayer microporous membrane formed by this method, which has properties that compete with or exceed those of wet process, coated or uncoated, membranes that are also useable in battery separators. Also disclosed are battery separators comprising the multilayer microporous membrane and batteries, vehicles, or devices comprising the separators. The method may comprise at least the following steps: (1) forming a stretched first non-porous precursor film that has pores due to the stretching of a first non-porous precursor film; (2) separately forming a second stretched non-porous precursor film that has pores due to the stretching of a second non-porous precursor film; and then (3) laminating the stretched first non-porous precursor and the stretched second non-porous precursor.

The present disclosure provides a fluorine-based resin porous membrane exhibiting high mechanical strength and low heat shrinkage rate while having a fine pore size, and a method for preparing the same.

The present invention relates to a polypropylene resin composition for a microporous film which can reduce the product defect rate due to stabilization of porous formation by stabilizing film formation and also can obtain a film suitably usable for a separator, a filtration membrane, a separation membrane and a filter since the microporous film can be thinned due to high rigidity, and more specifically, relates to a polypropylene resin composition for a microporous film wherein the composition comprises 5 to 30% by weight of polypropylene resin (X) having specific MFR, molecular weight distribution Mw/Mn by GPC, melt tension (MT), branching index g and mm fraction of the propylene unit triads by .sup.13C-NMR, satisfying specific conditions concerning gels and having a long chain branched structure and 95 to 70% by weight of polypropylene resin (Y) having a specific MFR and excluding the polypropylene resin (X).

A polyolefin composite porous membrane includes a first layer and a second layer. The first layer contains a polypropylene (A), a first high-density polyethylene (B) having a melting point of 130 C. or higher, and a second high-density polyethylene (C) having a melting point of 120 C. or higher and lower than 130 C. The second layer contains a polyethylene (D). The first layer and the second layer are integrally laminated with each other.

An object of the present invention is to provide a porous hollow-fiber membrane satisfying both high strength and high pure-water permeation performance and at the same time, having high bending resistance. The present invention relates to a porous hollow-fiber membrane including a fluororesin-based polymer, in which the porous hollow-fiber membrane has a columnar texture oriented in a longitudinal direction of the porous hollow-fiber membrane and when a photograph of a cross-section parallel to the longitudinal direction of the porous hollow-fiber membrane is binarized into a structure portion and a void portion, the following 1) and 2) are satisfied: 1) a proportion of an area of the void portion is from 20 to 50%, and 2) a value obtained by dividing a total of peripheral lengths of the void portions by a total of areas of the void portions is 2.0 m.sup.1 or less.