Ube Industries, Inc.

Katsuo Imatani

Hiroshi Inoue

Toshikazu Hamamoto

Tetsuji Hirano

Seiichirou Takabayashi

Yuji Matsui

Takashi Kohno

Kazuaki Mii

Genji Koga

Kenji Matsubara

Yoshiyuki Miwa

Akira Ishikawa

Masaki Kashibe

Shinichirou Yamamoto

Shuji Watakabe

A process for the preparation of an aromatic polyimide film includes the steps of casting a polyamide acid solution containing an imidization agent on a support in the form of a film, heating the filmy cast solution on the support at a temperature of 80.degree. to 200.degree. C. to obtain a self-supportable film; peeling the self-supportable film from the support; and further heating the film at a temperature of not lower than 300.degree. C. The polyamide acid solution includes a polyamide acid obtained by polymerization reaction of 3,4,3',4'-biphenyltetracarboxylic dianhydride and p-phenylenediamine in a mixture of a polar organic solvent and a small amount of an imidization agent selected from imidazole, a substituted imidazole, benzimidazole, a substituted benzimidazole, isoquinoline, and a substituted pyridine.

Process for the preparation of aromatic polyimide film

An aromatic polyimide film directly laminated with a metal foil and an aromatic polyimide film directly laminated on both sides with a metal foil wherein the polyimide film (substrate) comprises an aromatic polyimide layer-A of 6-200 .mu.m thick whose polyimide is derived from a biphenyltetracarboxylic acid or its derivative and a phenylenediamine and an aromatic polyimide layer-B of 0.2-15 .mu.m thick whose polyimide is derived from an aromatic tetracarboxylic acid or its derivative and an aromatic diamine having plural benzene rings, and the polyimide layer-A has a thickness of not less than 55% of the total thickness of the aromatic polyimide substrate film, the polyimide layer-B is fixed to the polyimide layer-A under the condition that the layer-B cannot be peeled from the layer-A along the interface between these layers-A and -B and the metal foil is directly fixed on the surface of the polyimide layer-B via no adhesive.

Aromatic polyimide film laminated with metal foil

An abrasive sheet having a high flexibility, mechanical strength and heat resistance, comprises (A) a matrix comprising an aromatic polyimide resin and (B) abrasive grains having an average size of 65-150 .mu.m and evenly dispersed in an amount of 2 to 50% by weight in the matrix, and is produced by forming a thin liquid layer from a dispersion comprising an aromatic polyamic acid solution with a rotation viscosity of 3000 to 6000 poises at 30.degree. C. and the above-mentioned abrasion grains dispersed in the solution, and dry-solidifying the liquid layer of the dispersion while imidizing the aromatic polyamic acid to a corresponding aromatic polyimide, the abrasive sheet having a thickness of 1.1 to 3.0 times the average size of the abrasive grains.

Abrasive sheet and process for producing same

High purity crystals of a biphenyltetracarboxylic dianhydride produced by dehydration of a biphenyltetracarboxylic acid, which contain almost no biphenyltricarboxylic acid or its anhydride, or a small amount such as an amount of not more than 0.2 wt. %, are of value to produce an aromatic polyamic acid or polyimide having an increased high molecular weight. The high purity crystals of a biphenyltetracarboxylic dianhydride can be prepared from a biphenyltetracarboxylic acid by a dehydration process wherein the biphenyltetracarboxylic acid is heated under carefully controlled conditions.

High purity crystals of biphenyltetracarboxylic dianhydride and process

An improved method of recovering a palladium catalyst from a liquid reaction mixture having been produced by oxidative coupling reaction of an aromatic compound in the presence of a catalyst containing palladium(II) salt is disclosed. The improved method comprises heating the liquid reaction mixture under stirring at a temperature of 180.degree. to 280.degree. C. in an atmosphere containing hydrogen gas at a partial pressure of 5 to 60 kg/cm.sup.2 whereby reducing the catalyst in the reaction mixture and precipitating a metallic palladium from the reaction mixture.

Method of recovering palladium catalyst

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Ube, Japan

Katsuo Imatani