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.

The invention relates to an undulated thermostable hollow fiber membrane of reduced wall thickness, wherein the wall thickness amounts to 20 μm or greater and 30 μm or less and the waveform of the hollow fiber membrane exhibits a wavelength in the range of from more than 1 mm and less than 5 mm. In particular, the invention relates to a method for producing an undulated thermostable hollow fiber membrane of lower wall thickness.

Provided is a porous hollow fiber membrane made of a thermoplastic resin, wherein a membrane thickness is 0.050 mm or larger and 0.25 mm or smaller, and when a strength coefficient is defined as K=(compressive strength)/((membrane thickness)/(inside diameter/2)).sup.3, K=1.7 or more.

The present disclosure relates to a device and a process for cutting hollow fiber membranes having a large inner diameter.

The present invention relates to a continuous process for preparing permselective hollow fiber membranes being suitable e.g. for hemodialysis, hemodiafiltration and hemofiltration of blood which comprises a two-stage drying and tempering treatment of the hollow fiber membranes. According to a further aspect, the invention relates to a continuous process for drying permselective hollow fiber membranes on-line. The invention also relates to devices for on-line drying of permselective hollow fiber membranes.

The disclosure provides a method for preparing a hollow fiber membrane by melt spinning-stretching and selective swelling, including: preparing a nascent hollow fiber by melt spinning in an inert gas protective atmosphere by using an amphiphilic block copolymer as a film forming material, and stretching the nascent hollow fiber in the cooling process, a stretch rate being controlled at 200-540 mm/min, and a stretch ratio being controlled at 150-600%; immersing the obtained hollow fiber in a swelling solvent, and treating the hollow fiber in a water bath at 65° C. for 1 h; and then transferring the hollow fiber into a long-chain alkane solvent, treating the hollow fiber at the same temperature for 1-12 h, and after the completion of the treatment, immediately taking out the hollow fiber and drying the hollow fiber to obtain the hollow fiber membrane with a bicontinuous porous structure. By combining the melt spinning-stretching and the selective swelling, the method of the disclosure can synchronously and continuously improve the permeability and selectivity of the hollow fiber membrane. The treatment in the long-chain alkane solvent can make the polar chain excessively enriched on the surface of the membrane migrate inward, thereby improving the performance of the hollow fiber membrane.

An object of the present invention is to provide a porous hollow-fiber membrane having high strength while maintaining high pure-water permeation performance. A porous hollow-fiber membrane of the present invention is 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 a molecular chain of the fluororesin-based polymer is oriented in the longitudinal direction of the porous hollow-fiber membrane.

A method for manufacturing a hollow fiber membrane has a spinning step of applying a first membrane forming stock solution and a second membrane forming stock solution for forming a porous membrane layer to the outer peripheral surface of a hollow porous base material using a nozzle for hollow fiber membrane spinning and solidifying these membrane forming stock solutions, wherein a draft ratio (V.sub.B/V.sub.A), which is the ratio of feed velocity V.sub.B for hollow porous base material fed out from a base material feed opening to linear velocity V.sub.A for the first membrane forming stock solution and the second membrane forming stock solution discharged from a membrane forming stock solution discharge opening of the nozzle for hollow fiber membrane spinning, is set to 1-6.

A method for producing a hollow fiber pre-product for a dialysis membrane is disclosed. The dialysis membrane includes a distribution of the pore sizes which follows an exponential function such as an e-function. The inverse value of the exponential coefficient (K) is at least 30 nm.sup.2. The dialysis membrane includes at least 50 pores per μm.sup.2 and the share of a free flow area at a surface of the dialysis membrane amounts to at least 2.5%.

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.