A composite porous membrane contains at least one porous base layer and at least one uniaxially stretched coating layer located on at least one side surface of the porous base layer. For example, the composite porous membrane comprises at least one porous base layer and at least one nanofiber-like non-polyolefin polymer porous layer oriented along the transverse stretching direction of the composite porous membrane and located on one or two side surfaces of the porous base layer, or the composite porous membrane comprises a biaxially stretched polypropylene porous base layer and a uniaxially stretched coating layer located on at least one side surface of the porous base layer. The composite porous membrane is coated with a coating solution prior to transversely stretching. The nanofiber-like non-polyolefin polymer porous layer may reduce cracking of the composite porous membrane in the machine direction.

Asymmetric composite membranes and methods for their preparation are disclosed. The membranes comprise a cross-linked poly(vinyl alcohol) polymer coated on a film of cross-linked sulfonated poly(ether ether ketone) adhered to a sheet of hydrophilicitized microporous polyolefin. The microporous polyolefin is typically microporous poly(ethylene). The membranes have improved selectivity with the regard to the rejection of solutes in reverse osmosis and ultrafiltration applications.

A semipermeable membrane according to an embodiment of the present invention includes a semipermeable membrane layer containing an amorphous resin as a main component, and a sheet-like supporting body that supports the semipermeable membrane layer. The supporting body has a porous first supporting layer and a porous second supporting layer laminated on one of surfaces of the first supporting layer. The second supporting layer has a smaller mean flow pore diameter than the first supporting layer. The second supporting layer is impregnated with the semipermeable membrane layer. A ratio of the mean flow pore diameter of the second supporting layer to the mean flow pore diameter of the first supporting layer is preferably 1/1,000 or more and or less. The mean flow pore diameter of the first supporting layer is preferably 0.05 m or more and 20 m or less, and the mean flow pore diameter of the second supporting layer is preferably 0.01 m or more and 1 m or less.

A membrane element includes a filtration membrane and a flowpath member joined thereto. The flowpath member is made of yarn arranged into a three-dimensional structure, and includes inner spaces through which a permeated liquid permeated through the filtration membrane flows, and an outer bonding surface joined to the filtration membrane. At least part of the yarn forming the outer bonding surface is a low-melting point yarn having a softening point lower than that of a material forming the filtration membrane, or the yarn forming the outer bonding surface is formed by twisting a plurality of constituent yarns, and at least one of the constituent yarns is a low-melting point yarn having a softening point lower than that of the material forming the filtration membrane.

Provided is an internal pressure adjustment member to be attached to an outer surface of a housing, the member having high air permeability even when a differential pressure that can be generated between the inside and the outside of a housing to which the internal pressure adjustment member is attached is small, and inhibiting damage to the member and a reduction in the air permeability of the member due to coming soil and mud. The internal pressure adjustment member includes: a filter portion including a net-like or mesh-like support layer and first and second porous polytetrafluoroethylene (PTFE) membranes laminated on the support layer such that the support layer is interposed therebetween, the first porous PTFE membrane being exposed on one surface of the filter portion, the second porous PTFE membrane being exposed on another surface of the filter portion; and an adhesive portion, formed on the one surface of the filter portion, for attaching the filter portion to the outer surface of the housing. The first porous PTFE membrane and the second porous PTFE membrane each have an average pore diameter of 2.0 m or more, the filter portion has a thickness of 140 m or less, and the filter portion has a density of 0.60 g/cm.sup.3 or less.

The present invention provides a porous hollow fiber membrane suitable for the removal of minute substances, e.g., viruses, contained in a liquid. The present invention relates to a porous hollow fiber membrane which is provided with a separation-functioning layer containing a fluororesin, has a gas diffusion amount of 0.5 to 5.0 mL/m.sup.2/hr as measured in a diffusion test, and also has foaming points at a density of 0.005 to 0.2 point/cm.sup.2 as measured in a foaming test under the immersion in 2-propanol.

A water exchanger for a fuel cell based power generator includes a plurality of hollow tubular structures. Each respective hollow tubular structure includes a membrane that is selectively permeable to water vapor over oxygen and hydrogen. A manifold is coupled to the tubular structures to provide wet air on one side of the membrane and hydrogen on the other side of the membrane.

The present invention relates to the technical field of filtering materials and provides a reverse osmosis membrane support material. The support material is obtained by hot pressing treatment of a surface layer, a middle layer and a bottom layer which are sequentially disposed from top to bottom. The surface layer and the bottom layer are each a spunbond non-woven fabric layer made of thermoplastic polymer spunbonded fibers, and the middle layer is a polymer nanofiber membrane. In accordance with the invention, the comprehensive mechanical strength of the reverse osmosis membrane support material is improved, and the overall anti-leakage performance is enhanced. A spunbond technology and a nanofiber preparation technology are combined organically, and the method is simple and controllable. The support material can be produced in batches.

A nanofiber for a filter medium is provided that includes fiber-forming ingredients including polyacrylonitrile (PAN) and polyvinylidene fluoride (PVDF) and an emulsifying agent for improving the miscibility of the fiber-forming ingredients. The nanofiber has excellent mechanical strength and chemical resistance and, at the same time, significantly increased hydrophilicity without a separate surface modification/treatment to/on the nanofiber. A filter medium comprising said nanofiber can exhibit improved flux and filtration efficiency and excellent physical properties in a water treatment process in which a pressure equal to or more than a predetermined level is applied and which requires the filter medium to have high mechanical strength and in a water treatment process which requires chemical resistance as the liquid being filtered is strongly acidic or alkaline. Further, since the nanofiber has significantly superior spinnability, the mass productivity of the filter medium is significantly improved, and the unit costs of production can be reduced.

The present invention relates to: an alumina powder wherein a ratio (TBD/LBD) of a tapped bulk density (TBD) to a loose bulk density (LBD) is 1.5 or more; an alumina slurry containing the same; an alumina-containing coating layer; a multilayer separation membrane; and a secondary battery.