Abstract: An asymmetric membrane is formed using a mixture of two or more different polymers including at least one type of polyimide. It is thereby possible to produce a gas separation membrane with low permeation resistance (a high permeation rate) for permeate gases passing through the porous layer of the membrane, which also maintains a practical level of mechanical strength of the membrane and has excellent water resistance and hot water resistance.

Abstract: A partially carbonized asymmetric hollow fiber separation membrane which is a hollow fiber separation membrane having an asymmetric structure obtained by partial carbonization of an aromatic polyimide hollow fiber separation membrane with an asymmetric structure, wherein the thickness of the aromatic polyimide hollow fiber membrane to be partially carbonized is 8-50 &mgr;m, the thickness of the hollow fiber separation membrane obtained by the carbonization is 8-45 &mgr;m, and the carbon content of the hollow fiber membrane obtained by partial carbonization is at least 1.05 times the carbon content of the aromatic polyimide hollow fiber membrane to be partially carbonized, and no greater than 90 wt %; also, a process for its production and a gas separation method employing it.

Abstract: An asymmetric membrane is formed using a mixture of two or more different polymers including at least one type of polyimide. It is thereby possible to produce a gas separation membrane with low permeation resistance (a high permeation rate) for permeate gases passing through the porous layer of the membrane, which also maintains a practical level of mechanical strength of the membrane and has excellent water resistance and hot water resistance.

Abstract: A mixed gas-separating membrane module having a high separating efficiency includes a cylindrical container having a mixed gas-feed section, a non-permeated gas-delivery section, and a middle section; a bundle of a plurality of hollow fibers each extending through the middle section and each having an end portion opening to the mixed gas-feed section and an opposite end portion opening to the non-permeated gas-delivery section; a pair of a first disk supporting the hollow fiber end portion opening to the mixed gas-feed section and partitioning the middle section from the mixed gas-feed section, and a second disk supporting the opposite hollow fiber end portions opening to the non-permeated gas-delivery section and partitioning the middle section from the non-permeated gas-delivery section, the first and second disks supporting the hollow fibers so that the hollow fibers are spaced from each other, to leave a continuous space between the hollow fibers; and a cylindrical film member surrounding the hollow fiber

Abstract: An aromatic polyimide having a recurring unit of the formula (I): ##STR1## wherein Ar is a divalent aromatic group having one or two benzene rings which has a sulfonate group of --SO.sub.3 H, --SO.sub.3 M, and --SO.sub.3 N(L).sub.4 on the ring, wherein M is an alkali metal and L is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, is favorably employed in the form of a semipermeable film for gas separation.

Abstract: A gas separating asymmetric membrane such as a gas separating asymmetric hollow fiber comprises an aromatic polyimide comprising recurring units of the formulae (I) and (II): ##STR1## wherein A.sup.1 is a tetravalent unit having a diphenylhexafluoropropane structure, A.sup.2 is a tetravalent unit having a benzene structure, and A.sup.3 is a divalent aromatic unit which is a unit derived from a sulfur atom-containing diamine such as diaminodibenzothiophene, diaminodiphenylenesulfone, diaminothioxanthene-5,5-dioxide or diaminothioxanthone-5,5-dioxide. The aromatic polyimide contains the recurring unit of the formula (I) in an amount of 40 to 90 molar % and the recurring unit of the formula (II) in an amount of 10 to 40 molar %. Further, a process for the preparation of the gas separating asymmetric hollow fiber membrane is also disclosed.

Abstract: A method of enhancing the gas-separation performance of an aromatic polyimide membrane with high reproducibility, by plasma-treating an asymmetric aromatic polyimide membrane comprising 80 to 100 molar % of at least one type of recurring units selected from those of the formulae (A) and (B) and 0 to 20 molar % of recurring units of the formula (C): ##STR1## in the formulae of which, R.sup.1, R.sup.2, R.sup.3 =an aromatic residue derived from an aromatic diamine compound and R=a tetravalent aromatic residue derived from an aromatic tetracarboxylic acid compound and different from tetravalent the aromatic tetracarboxylic acid residues appearing in the formulae (A) and (B), and has a helium gas-permeation rate [P.sub.He ] of 1.times.10.sup.-4 cm.sup.3 /cm.sup.2.sec.cmHg or more at 80.degree. C. and a ratio [P.sub.He ]/[P.sub.N2 ] of the helium gaspermeation rate [P.sub.He ] to a nitrogen gas-permeation rate [P.sub.N2 ] of 20 or more at 80.degree. C., in an atmosphere comprising ammonia.

Abstract: An aromatic polyimide double layered hollow filamentary membrane having an excellent heat resistance, chemical resistance, pressure-resistance, and gas-permeating and separating properties comprises (A) an aromatic imide polymer hollow filamentary microporous inner layer and (B) an aromatic imide polymer tubular filamentary asymmetric outer layer composed of (a) tubular filamentary microporous intermediate layer covering and united with the outside surface of the inner layer (A) and (b) a thin dense outside surface layer covering and united with the intermediate layer (a).

Abstract: A purified light gas consisting of hydrogen or helium and having a high purity of, for example, 99.99% or more is prepared from a feed gas containing at least 90 molar % or more of H.sub.2 or He and substantially no CO.sub.2 by gas-separating the feed gas through a plurality of gas-separating membrane modules each comprising at least one polymeric gas-separating membrane and having a gas-permeating ratio P.sub.A /P.sub.CH4 of 100 or more, wherein P.sub.A is a permeating rate of the light gas and P.sub.CH4 is a permeating rate of methane gas, in such a manner that each fraction of the feed gas permeated through and delivered from a preceding membrane module is fed to a next membrane module under the pressure, per se, of the delivered fraction of the feed gas without pressurizing the delivered fraction.

Abstract: A pervaporation separation method of water from an organic material aqueous solution at a high separating efficiency is effected by using a specific asymmetric separating membrane comprising a heat-resistant, solvent-soluble aromatic imide polymer prepared by the polymerization and imidization of an aromatic tetracarboxylic acid component comprising, as a principal ingredient, at least one biphenyl tetracarboxylic acid compound with an aromatic diamine component comprising a principal member selected from: ##STR1## and an additional member selected from another aromatic diamine compounds having 2 to 5 benzene ring structures and different from the diamine compounds (I) and (II).

Abstract: A pervaporation method of separating a liquid organic compound mixture at a high speed and efficiency through an aromatic polyimide asymmetric separating membrane produced from an aromatic tetracarboxylic acid component comprising at least 70 molar % of biphenyl or diphenylether tetracarboxylic dianhydride and an aromatic diamine component comprising 85 molar % or more of an aromatic diamine having 2 to 3 benzene ring structure, or 15 molar % or more of 9,10-di(aminophenyl)anthracene, di(aminophenoxy)diphenylsulfone, di(aminophenoxy)biphenyl or di(aminophenoxy)diphenylalkane compounds, or a mixture of 15 to 50 molar % of an aromatic diamine having alone benzene or pyridine ring structure and 50 to 85 molar % of an aromatic diamine having a 2 to 3 benzene ring structure.

Abstract: An aromatic imide polymer hollow filament having an excellent gas separating property is produced by a process comprising the steps of:(1) dissolving an aromatic imide copolymer comprising(A) 20 to 85 molar % of recurring units of the formula (I): ##STR1## (B) 10 to 35 molar % of recurring units of the formula (II): ##STR2## and (C) 5 to 55 molar % of recurring units of the formula (III): ##STR3## wherein R represents a divalent radical of the formula (IV) or (V): ##STR4## wherein R.sup.1 and R.sup.

Abstract: An aromatic imide polymer hollow filament having an excellent gas separating property is produced by a process comprising the steps of:(1) dissolving an aromatic imide copolymer comprising (A) 20 to 85 molar % of recurring units of the formula (I): ##STR1## (B) 10 to 35 molar % of recurring units of the formula (II): ##STR2## and (C) 5 to 55 molar % of recurring units of the formula (III): ##STR3## wherein R represents a divalent radical of the formula (IV) or (V): ##STR4## and ##STR5## wherein R.sup.1 and R.sup.

Abstract: A method for piling and cleaning a spun yarn in a wet spinning in which a yarn is withdrawn at a predetermined velocity and is dropped by its own weight into a rotating cylindrical container with the bottom formed with drain holes while simultaneously traversing the yarn in the radial direction of the cylindrical container so that the yarn is piled at the bottom of the cylindrical container in the form of a ring; and a cleaning liquid is sprayed against the yarn which is being piled, thereby cleaning the yarn.

Abstract: An aromatic polyimide composite membrane having a satisfactory gas-permeating property and an excellent gas-separating property comprises an aromatic polyimide porous membrane substrate and at least one coating layer which has been prepared (A) by coating at least one surface of the substrate with a dilute dope solution containing 0.01 to 5 parts by weight of a soluble aromatic polyimide and/or polyamic acid dissolved in a solvent which consists essentially of 100 parts by weight of a base component incapable of dissolving therein the substrate in an amount of 3% by weight or more and 0 to 15 parts by weight of an additional component capable of dissolving therein the 5% by weight or more of the aromatic polymeric material and compatible with the base component; and (B) by gradually evaporating the solvent from the coated dilute dope solution layer.

Abstract: A porous aromatic imide polymer membrane usable as a gas or liquid separator or concentrator is prepared by a process comprising the steps of:(1) dissolving 3 to 30% by weight of an aromatic imide polymer which comprises at least 80 molar % of a recurring unit selected from those of the formulae (I) and (II): ##STR1## wherein R represents a divalent aromatic or heterocyclic radical in 70 to 97% by weight of a solvent consisting essentially of a homogeneous mixture of:(A) 100 parts by weight of a base solvent which consists essentially of at least one polar organic compound and is capable of dissolving therein said aromatic imide polymer in a concentration of 5% by weight or more therein and of evaporating at a temperature of from 50.degree. to 400.degree. C.

Abstract: A modified polymeric membrane having an excellent separating property is produced by applying, to a porous polymeric membrane, a volatile treating liquid containing a modifying agent which consists of at least one member selected from:(A) volatile dissolving organic liquids each capable of dissolving therein at least 1% by weight of the porous polymeric membrane at a temperature of 25.degree. C.; and(B) volatile shrinking organic liquids each capable of causing the porous polymeric membrane to shrink at a shrinkage of 3% or more.

Abstract: An aromatic polyimide separating membrane is produced by a process comprising the steps of:forming a thin film of a dope solution containing an aromatic polyamic acid dissolved in a polar organic solvent at a temperature of approximately 100.degree. C. or less;coagulating the thin dope solution film in a coagulating liquid containing at least 60% by volume of at least one member selected from water and lower aliphatic alcohols at a temperature of 60.degree. C. or less;drying the resultant coagulated aromatic polyamic acid membrane; andheating the dried aromatic polyamic acid membrane at a temperature of 100.degree. C. to 300.degree. C. to convert it to an aromatic polyimide membrane.

Abstract: An aromatic polyimide membrane having an excellent gas-separating property comprises (A) a substrate consisting of a porous membrane comprising at least one aromatic polyimide having at least 80 molar % of at least one type of recurring unit of the formula (I): ##STR1## wherein R is a tetravalent aromatic radical and R.sup.1 is a divalent aromatic radical, the porous membrane exhibiting a hydrogen gas permeability (PH.sub.2) of 1.times.10.sup.-5 to 5.times.10.sup.-1 cm.sup.3 /cm.sup.2.sec.cmHg and a ratio of hydrogen gas permeability (PH.sub.2) to carbon monoxide gas permeability (PCO) of 2 to 5; and (B) 50% or more, based on the weight of the porous membrane substrate, of a gas-separating liquid contained in the porous membrane substrate, the gas-separating liquid being substantially incapable of dissolving therein the porous membrane substrate and having a boiling point of 180.degree. C. or more.

Abstract: A porous membrane of an aromatic polyimide having an enhanced permeability of a gas or liquid is produced by a process comprising the steps of(1) preparing a dope solution of 3 to 30% by weight of an aromatic polyimide in a mixed solvent of (A) 100 parts by weight of a base solvent capable of dissolving 5% by weight or more of the polymeric acid and of evaporating at 30.degree. C. to 400.degree. C. and (B) 5 to 150 parts by weight of an additional liquid not capable of dissolving 3% by weight or more of the polyamic acid and capable of evaporating at a smaller evaporating rate than that of the base solvent at the above-mentioned evaporating temperature;(2) forming a thin layer of the dope solution at 0.degree. C. to 120.degree. C.; and(3) heating the dope solution layer at 30.degree. C. to 400.degree. C. so as to evaporate off the mixed solvent and to convert the polyamic acid to the corresponding polyimide.