Ube Industries, Inc.

Yoshiyuki Miwa

Hidetomo Ashitaka

Kazuya Jinda

Hiroshi Inoue

Toshikazu Hamamoto

Tetsuji Hirano

Katsuo Imatani

Takashi Kohno

Kenji Matsubara

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

A process for the preparation of a diazocyano acid, which comprises reacting a keto-acid or its sodium salt with a cyanogen compound such as sodium cyanide or hydrogen cyanide and a hydrazine in water to form a concentrated aqueous solution of a hydrazo compound, adding acetone or acetone and water to the concentrated aqueous solution to form an acetone-water solution of the hydrazo compound, adding an oxidant such as chlorine gas to the solution to oxidize the hydrazo compound and form a diazocyano acid, forming at least two transparent liquid layers by adding acetone and/or water to the obtained reaction mixture during or after oxidation if necessary, and further adding sodium chloride to the reaction mixture if necessary, and separating and recovering the upper layer of the acetone-water solution containing the diazocyano acid from the mixture.

Preparation of azo compounds having carboxyl and cyano groups

A process for the preparation of a diazocyano acid, which comprises reacting a keto-acid or its sodium salt with a cyanogen compound such as sodium cyanide or hydrogen cyanide and a hydrazine in water to form a concentrated aqueous solution of a hydrazo compound, adding acetone and/water to the concentrated aqueous solution to form a solution of the hydrazo compounds, adding chlorine gas to the solution to oxidize the hydrazo compound and form a diazocyano acid, adding acetone to the obtained reaction mixture during or after the oxidation if necessary, and separating and recovering the supernatant layer of the acetone-water solution containing the diazocyano acid from the mixture.

Process for the preparation of diazocyano acids by reacting keto-acids

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Ichihara, Japan

Yoshiyuki Miwa