A porous membrane comprising a thermoplastic resin, and having a densely structured layer, wherein the ratio of crystal strength to crystal strength of the thermoplastic resin in the densely structured layer is 5.0 or more.

There is provided a hollow fiber membrane for vacuum membrane distillation having a maximum tensile strength of a 3.5 MPa and a liquid entry pressure (LEP) of 3.0 bar, wherein the hollow fiber membrane is a single layer hollow fiber membrane comprising a wall with a thickness of 150 m and a cross-section comprising two open cell layers with an array of interconnected pores and a macrovoid layer between the two open cell layers. The hollow fiber has improved mechanical strength and vacuum membrane distillation flux.

A polyimide separation membrane is comprised of a polyimide, a halogen compound (e.g., halogenated aromatic epoxide) that is soluble in the polyimide and a hydrocarbon having 2 to 5 carbons (e.g., ethane, ethylene, propane or propylene). The gas separation membrane has improved selectivity for small gas molecules such as hydrogen compared to polyimide membrane not containing the halogen compound or hydrocarbon. The polyimide separation membrane may be made by shaping a dope solution comprised of a polyimide, a halogen containing compound that is soluble in the polyimide, removing the solvent and then exposing the untreated polyimide membrane to a treating atmosphere comprising a hydrocarbon having 2 to 5 carbons for a sufficient time to form the polyimide membrane.

To provide a hollow fiber type semipermeable membrane which achieves both water permeability and salt rejection ability at high level, so as to conduct, with small membrane area, a water treatment utilizing concentration difference from liquid mixture of high concentration and high osmotic pressure. A hollow fiber type semipermeable membrane comprising cellulose acetate, characterized in that, between an aqueous solution of 25 C. having sodium chloride concentration of 35,000 mg/L and freshwater of 25 C. having sodium chloride concentration of 0 g/L at 0 MPa, the permeation flow rate flown from inner side to the outer side of the hollow fiber type semipermeable membrane is 60 to 180 L/m.sup.2/day, the outer diameter of the hollow fiber type semipermeable membrane is 100 to 350 m, the inner diameter thereof is 50 to 250 m and the hollow ratio thereof is 24 to 51%.

Systems and methods can be used to produce fibers with external corrugations, internal corrugations, or both. These fibers can be used, for example, in hollow fiber membrane modules

Systems and methods can be used to produce fibers with external corrugations, internal corrugations, or both. These fibers can be used, for example, in hollow fiber membrane modules.

A hollow fibre membrane having a coiled, a hemihelix, a helical or an undulated native form, in which the membrane can be stretched by up to 4-times its original length with no plastic deformation, and wherein the native form of the membrane is produced by the asymmetric flow of liquid polymer through an opening of a die or nozzle.

Disclosed is a thin film composite hollow fiber that includes an outer support layer having a thickness of 10 to 1000 m and a polyamide thin film layer having a thickness of 1 to 10000 nm; and has a transmembrane pressure resistance rate of higher than 15 bar and a pure water permeability rate of higher than 0.8 Lm.sup.2h.sup.1bar.sup.1. Also disclosed are methods of preparing the above-described support and composite hollow fiber.

The present invention relates to a method for the production of a positively charged membrane. Furthermore the present invention relates to a positively charged membrane obtainable by the methods of present invention and the use of these positively charged membranes.

A carbon membrane for fluid separation, i.e., a fiber-form carbon membrane for fluid separation, has protrusions having a height difference of at least 1 m formed on the fiber surface. In the carbon membrane for fluid separation, adhesion between membranes is inhibited and clogging tends not to occur when a gas mixture containing water vapor is separated. A carbon membrane module for fluid separation that includes the fibrous carbon membrane for fluid separation is also disclosed.