A polyimide random copolymer has a structure represented by formula (I). A method for preparing the polyimide random copolymer, a membrane made of the polyimide random copolymer, and a method for preparing a polyimide-based hollow fiber membrane are also provided. A system for purifying helium gas and a method for purifying helium gas are related to the membrane made of the polyimide random copolymer.

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Problems that the invention is to solve is to provide a composite hollow fiber membrane being excellent in separation performance and permeation performance, having high membrane strength, and capable of being easily produced, and a method for producing the same. The present invention relates to a composite hollow fiber membrane including at least a layer (A) and a layer (B), in which the composite hollow fiber membrane has an outer diameter of 20 to 350 ?m and an inner diameter of 14 to 250 ?m, the tensile modulus of the composite hollow fiber membrane is from 1,000 to 6,500 MPa, the layer (A) contains a cellulose ester, the thickness of the layer (A) is from 0.01 to 5 ?m, and the open pore ratio H.sub.A of the layer (A) and the open pore ratio H.sub.B of the layer (B) satisfy H.sub.A<H.sub.B.

A preparation method of a metal-organic framework (MOF)-801@chitosan (CS) mixed matrix pervaporation membrane for separating methanol and dimethyl carbonate is provided. Chitosan (CS) is soluble in an acid and the synthesis of metal-organic framework (MOF)-801 requires an acid, an MOF-801@CS mixed matrix pervaporation membrane is creatively prepared in-situ. Because MOF-801 allows preferential adsorption for methanol and provides an additional transmission channel, a pore size-sieving role can be played, which improves the separation performance of the membrane for an organic azeotropic system of methanol/dimethyl carbonate (DMC). Compared with physical doping, the in-situ preparation method improves the dispersion uniformity of particles and the roughness of a surface of a membrane. Moreover, the membrane exhibits excellent swelling resistance and excellent structural stability in an organic methanol/DMC system.

Provided is a novel continuous single-step method of manufacturing a multilayer sorbent polymeric membrane having superior productivity, properties and performance. At least one layer of the polymeric membrane comprises sorbent materials and a plurality of interconnecting pores. The method includes: (a) coextruding layer-forming compositions to form a multilayer coextrudate; (b) casting the coextrudate into a film; (c) extracting the film with an extractant; and (d) removing the extractant from the extracted film to form the multilayer sorbent polymeric membrane. The sorbent membrane of this disclosure can find a wide range of applications for use in filtration, separation and purification of gases and fluids, CO.sub.2 and volatile capture, structural support, vehicle emission control, energy harvesting and storage, electrolyte batteries. device, protection, permeation, packaging, printing, and etc.

Disclosed are a bundle of hollow fiber membranes to improve use efficiency of the hollow fiber membranes and a method of manufacturing the same. The bundle of hollow fiber membranes includes a plurality of yarns to form fluid channels and serve as spacers disposed between the hollow fiber membranes to create a bundle. The method includes spinning including supplying a spinning dope to a nozzle and conducting spinning to form a plurality of hollow fiber membranes, coagulating the hollow fiber membranes formed during spinning, and yarn feeding including inserting a plurality of yarns between the hollow fiber membranes to form a bundle. The method is effective in uniformly distributing a fluid through fluid channels formed between the hollow fiber membranes and maximizes usage efficiency of the hollow fiber membranes.

An embodiment of the invention provides a substrate for a liquid filter, the substrate including at least one A layer which is a microporous membrane-like layer containing a polyolefin, and at least one B layer which is a microporous membrane-like layer containing a polyolefin and a filler, the substrate having a bubble point of from 0.40 Mpa to 0.80 Mpa and a water permeation efficiency of from 1.0 mL/min.Math.cm.sup.2 to 4.0 mL/min.Math.cm.sup.2.

In a method of fabricating high performance CMS membranes, in which a dual-layer hollow fiber precursor fiber membrane that contains a nano-particle-filler containing core layer is extruded, a sheath layer is co-extruded with the core layer so that at least a portion of the core layer is surrounded by the sheath layer. The nano-particle filler is defect sealed. The dual-layer hollow fiber precursor fiber and the sheath layer are pyrolysed. A CMS membrane includes a core layer, a sheath layer surrounding at least a portion of the core layer and a plurality of nanoparticles disposed in the core layer.

Methods of preparing reinforced anion exchange membranes are provided, as well as produced membranes and corresponding devices utilizing the membranes. Methods comprise compounding a halide-functionalized polymer (selected to react with amines to yield anion-conducting quaternary amine groups) with thermoplastic polymer(s) (selected to support and/or reinforce the membrane), and with copolymer(s) (selected to enhance the compounding of the polymers)by heating, mixing and coolingto form blend pellets, extruding the blend pellets to form a blend film, cross-linking polymer(s), and functionalizing the blend film to prepare the anion exchange membrane. Functionalization comprises a quaternization step comprising reacting halogen groups of the first polymer with tertiary amines to produce the quaternary amine groups with ion-exchange functionality. Reinforced anion exchange membranes are provided, which are produced by the disclosed methods, functionalized to yield a membrane for fuel cell(s), electrolyzer(s), reversible electrochemical device(s), desalination unit(s), etc.

The disclosure provides a solvent resistant polyimide/polyethyleneimine@titanium dioxide nanohybrid ultrafiltration membrane with high solvent permeability and a preparation method thereof. The preparation method comprises the following steps: dissolving a titanium dioxide precursor Ti-BALDH and polyimide into N-methylpyrrolidone to prepare a casting solution, then coating on the non-woven fabric, and preparing the solvent resistant nanohybrid polyimide membrane in one step through a non-solvent induced phase separation-interface crosslinking-in-situ biomimetic mineralization coupling method. According to the disclosure, a solvent resistant polyimide/polyethyleneimine@TiO.sub.2 nanohybrid ultrafiltration membrane (PEIPI@TiO.sub.2) with high solvent permeability prepared through a simple non-solvent induced phase separation-interface chemical crosslinking-in-situ bionic mineralization coupling method.

Provided are a lined hollow fiber membrane (HFM) with a sandwich structure, and a preparation method and use thereof. In the lined HFM with a sandwich structure, a membrane structure of the lined HFM includes an inner PVDF layer, a braided liner layer, and an outer PVDF layer in sequence from inside to outside.