A preparation method of separation membrane is provided. First, a polyimide composition including a dissolvable polyimide, a crosslinking agent, and a solvent is provided. The dissolvable polyimide is represented by formula 1: ##STR00001## wherein B is a tetravalent organic group derived from a tetracarboxylic dianhydride containing aromatic group, A is a divalent organic group derived from a diamine containing aromatic group, A′ is a divalent organic group derived from a diamine containing aromatic group and carboxylic acid group, and 0.1≤X≤0.9. The crosslinking agent is an aziridine crosslinking agent, an isocyanate crosslinking agent, an epoxy crosslinking agent, a diamine crosslinking agent, or a triamine crosslinking agent. A crosslinking process is performed on the polyimide composition. The polyimide composition which has been subjected to the crosslinking process is coated on a substrate to form a polyimide membrane. A dry phase inversion process is performed on the polyimide membrane.

A preparation method of separation membrane is provided. First, a polyimide composition including a dissolvable polyimide, a crosslinking agent, and a solvent is provided. The dissolvable polyimide is represented by formula 1: ##STR00001## wherein B is a tetravalent organic group derived from a tetracarboxylic dianhydride containing aromatic group, A is a divalent organic group derived from a diamine containing aromatic group, A′ is a divalent organic group derived from a diamine containing aromatic group and carboxylic acid group, and 0.1≤X≤0.9. The crosslinking agent is an aziridine crosslinking agent, an isocyanate crosslinking agent, an epoxy crosslinking agent, a diamine crosslinking agent, or a triamine crosslinking agent. A crosslinking process is performed on the polyimide composition. The polyimide composition which has been subjected to the crosslinking process is coated on a substrate to form a polyimide membrane. A dry phase inversion process is performed on the polyimide membrane.

A process for producing nitrogen-rich air by feeding high temperature air at 150° C. or more to an air separation membrane module is described. After being placed at 175° C. for two hours, the air separation module exhibits a shape-retention ratio of 95% or more in one embodiment. The nitrogen-rich air can be fed to a fuel tank for an aircraft, for example.

A process for producing nitrogen-rich air by feeding high temperature air at 150° C. or more to an air separation membrane module is described. After being placed at 175° C. for two hours, the air separation module exhibits a shape-retention ratio of 95% or more in one embodiment. The nitrogen-rich air can be fed to a fuel tank for an aircraft, for example.

Disclosed herein is a composite hollow fiber polymer membrane including a porous core layer and a selective sheath layer. The porous core layer includes a polyamide-imide polymer, or a polyetherimide polymer, and the selective sheath layer includes a polyimide polymer, which is prepared from monomers A, B, and C. The monomer A is a dianhydride of the formula ##STR00001##
wherein X.sub.1 and X.sub.2 are independently halogenated alkyl group, phenyl or halogen and R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, and R.sub.6 are independently H, alkyl, or halogen. The monomer B is a diamino cyclic compound without a carboxylic acid functionality and the monomer C is a diamino cyclic compound with a carboxylic acid functionality. The polyimide polymer further includes covalent ester crosslinks. Also disclosed herein is a method of making the composite polymer membrane and a process for purifying natural gas utilizing the composite polymer membrane.

Disclosed herein is a composite hollow fiber polymer membrane including a porous core layer and a selective sheath layer. The porous core layer includes a polyamide-imide polymer, or a polyetherimide polymer, and the selective sheath layer includes a polyimide polymer, which is prepared from monomers A, B, and C. The monomer A is a dianhydride of the formula ##STR00001##
wherein X.sub.1 and X.sub.2 are independently halogenated alkyl group, phenyl or halogen and R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, and R.sub.6 are independently H, alkyl, or halogen. The monomer B is a diamino cyclic compound without a carboxylic acid functionality and the monomer C is a diamino cyclic compound with a carboxylic acid functionality. The polyimide polymer further includes covalent ester crosslinks. Also disclosed herein is a method of making the composite polymer membrane and a process for purifying natural gas utilizing the composite polymer membrane.

A method for preparing a nanoporous membrane includes alternatively repeating, on the surface of a porous substrate, the laminating of a hydrophilic homopolymer and the laminating of an amphiphilic block or graft copolymer to provide a polymer multilayer film in which the alternative laminate of the hydrophilic homopolymer and the amphiphilic block or graft copolymer is formed. The polymer multilayer film is annealed to form a microphase separated polymeric membrane. The laminating of a hydrophilic homopolymer and the laminating of a supramolecular structure compound are alternatively repeated, on the surface of the polymeric membrane, to form the alternative laminate of the hydrophilic homopolymer and the supramolecular structure compound.

The present invention relates to a method of controlling a gas separation plant, to a plant thus controlled and also to its use for separation of gas mixtures, especially in the processing of biogas or natural gas, or syngas.

An ion-permeable membrane is substantially free of holes and has excellent ion permeability, heat resistance, strength, and flexibility. A battery electrolyte membrane uses the ion-permeable membrane, and can form an electrode composite body. The polymer-ion-permeable membrane has an average radius of free volume of 0.32-0.50 nm.

An ion-permeable membrane is substantially free of holes and has excellent ion permeability, heat resistance, strength, and flexibility. A battery electrolyte membrane uses the ion-permeable membrane, and can form an electrode composite body. The polymer-ion-permeable membrane has an average radius of free volume of 0.32-0.50 nm.