Ube Industries, Inc.

Kazuhiko Mitsui

Kazuo Kumamoto

Keiichirou Koyashiki

Toshiyuki Nishino

Kenji Kuniyasu

A new honeycomb core structure of heat-resistant aromatic polyimide is disclosed. The structure comprises plural aromatic polyimide sheets having a second-order transition temperature in the range of 250.degree. C. to 400.degree. C. wherein adjoining aromatic polyimide sheets are adhered to each other by welding the two sheets in regions apart from each other at equal intervals and the welding regions on one side of any aromatic polyimide sheet are located at positions shifted from positions of welding regions arranged on another side of the sheet. The honeycomb structure is formed by extending the combined aromatic polyimide sheets in the direction vertical to the plane of the polyimide sheets while heating the sheets at a temperature higher than their second-order transition temperature.

Honeycomb structure of aromatic polyimide

A new honeycomb core structure of heat-resistant aromatic polyimide is disclosed. The structure comprises plural aromatic polyimide sheets wherein adjoining two aromatic polyimide sheets are combined to each other with a heat resistant adhesive at adhesive regions arranged between the two sheets at equal intervals and the adhesive regions on one side of any aromatic polyimide sheet are located at positions shifting from positions of adhesive regions arranged on another side of the sheet. The honeycomb structure is formed by extending the combined aromatic polyimide sheets in the direction vertical to the plane of the polyimide sheets.

Disclosed is an aromatic polyimide film which is well resistant to sagging and dimensional change in the heat treatment. The aromatic polyimide film is formed from a polymer solution which is produced by a polymerization reaction of a biphenyltetracarboxylic acid component and a phenylenediamine component, and characterized in that any rectangle optionally supposed within the film has a ratio between a length of any side and a length of the central portion between the side and a side opposite thereto is in the range of 100:100 to 100:100.15, and a heat shrinkage ratio of the film is not more than 0.3% (0.003) in any direction after the film is heated at 300.degree. C. for 2 hours. A process for the preparation of the above aromatic polyimide film is also disclosed.

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Yamaguchi, Japan

Kazuhiko Mitsui