Ube Industries, Inc.

Hiroshi Shimazaki

Yoshihiro Kusuki

Takashi Harada

Hiroshi Makino

Tosio Isida

Makoto Matsuo

Toshimune Yoshinaga

Toshikazu Machida

Shyusei Ohya

Kanji Nakagawa

Yoshiaki Watanabe

Yuuichi Fujii

Makoto Babazono

Dai Yokoyama

Koji Miyauchi

A porous polyimide film having a three-layer structure that comprises two surface layers (a) and (b) and a macrovoid layer sandwiched between the surfaces layers (a) and (b). The macrovoid layer has a partition wall bonding to the surface layers (a) and (b), and multiple macrovoids each surrounded by the partition wall and the surface layers (a) and (b) and having a mean pore size in the film plane direction of from 10 to 500 &#x3bc;m. The partition wall of the macrovoid layer has a thickness of from 0.1 to 50 &#x3bc;m and has multiple pores having a mean pore size of from 0.01 to 50 &#x3bc;m. The surface layers (a) and (b) each have a thickness of from 0.1 to 50 &#x3bc;m, at least one of the surface layers has multiple pores having a mean pore size of from more than 5 &#x3bc;m to 200 &#x3bc;m, and the other surface layer has multiple pores having a mean pore size of from 0.01 to 200 &#x3bc;m. The pores in the partition wall of the macrovoid layer as well as in the surface layers (a) and (b) communicate with each other and further communicate with the macrovoids. The film has a total thickness of from 5 to 500 &#x3bc;m and a porosity of from 60 to 95%.

Porous polyimide membrane and process for production thereof

A catalyst for dimerizing a lower .alpha.-olefin monomer with an enhanced selectivity comprises a carrier comprising at least one anhydrous potassium compound, preferably a mixture of potassium fluoride with potassium carbonate, and a carbon material; and a catalytic component carried on the carrier and comprising an alkali metal, preferably sodium metal, the catalyst preferably being compression molded into grains.

Catalyst for dimerizing .alpha.-olefin monomer

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).

Aromatic polyimide double layered hollow filamentary membrane and

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.

Aromatic polyimide composite separating membrane

A porous aromatic imide polymer membrane usable as a gas or liquid separator or concentrator is prepared by a process comprising the steps of:

Porous aromatic imide polymer membrane and a process for its manufacture

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

Process for modifying porous polymeric membrane

An aromatic polyimide separating membrane is produced by a process comprising the steps of:

Production of aromatic polyimide separating membranes

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.

Aromatic polyimide gas-separating membrane

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

Process for producing porous aromatic polyimide membranes

Aromatic polyimide hollow fibers having an enhanced mechanical strength are produced by a process comprising the steps of: preparing a spinning dope solution of at least one aromatic polyimide having 90 molar % or more of a recurring unit of the formula (I). ##STR1## wherein R is a divalent aromatic radical, in a phenolic solvent; converting the dope solution into at least one filamentary stream thereof; and introducing the filamentary dope solution stream into a coagulating liquid having a coagulating rate coefficient of 1.5 microns/sec for the dope solution, to provide rigid hollow filaments.

Process for producing aromatic polyimide hollow filaments

An aromatic polyimide composite membrane having an excellent gas-separating property is produced by a process comprising the steps of: coating at least one surface of a substrate consisting of an aromatic polyimide porous membrane with a solution of 0.05% to 10% by weight of an aromatic polyamic acid in a polar organic solvent, which is not capable of dissolving the polyimide porous membrane, at a temperature not exceeding 140.degree. C.; after a during drying the resultant thin coating layer of the polyamic acid solution, heating the resultant polyamic acid layer at a temperature of 150.degree. C. or more so as to convert the polyamic acid layer to the corresponding polyimide layer.

Process for producing aromatic polyimide composite separating membrane

A gas separating material having excellent heat and chemical resistance, mechanical strength and gas-separating function, comprises a gas separating layer consisting of at least one dense film having a thickness of from 0.1 to 20 microns and comprising at least one aromatic imide polymer which comprises at least 80 molar % of at least one type of recurring unit of the formula (I): ##STR1## wherein R represents a divalent aromatic radical.

Gas separating material

Aromatic polyimide fibers having an enhanced mechanical strength are produced by a process comprising the steps of: preparing a spinning dope solution of at least one aromatic polyimide having 90 molar % or more of a recurring unit of the formula (I): ##STR1## wherein R is a divalent aromatic radical, in a phenolic solvent; converting the dope solution into at least one filamentary stream thereof; solidifying the filamentary dope solution stream by removing the solvent therefrom to provide at least one undrawn filament, and; drawing the undrawn filament at a temperature of 20.degree. to 600.degree. C. at a draw ratio of 1.5 to 5.0.

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Ichihara, Japan

Hiroshi Shimazaki