The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 07, 1981
Filed:
Apr. 20, 1979
Koichi Okita, Osaka, JP;
Sumitomo Electric Industries, Ltd., Osaka, JP;
Abstract
Porous film materials composed of polytetrafluoroethylene having an asymmetric structure are produced by stretching the film using a pair of revolving rolls which are heated to a temperature lower than the melting point of the film. Stretching is produced by revolving the two rolls at different speeds which also tends to produce a compressive force in the thickness of the film. The rolls are heated to different temperatures to produce a temperature difference of preferably 50.degree. C. or more. The combination of the compressive force and the temperature gradient in the thickness of the film is believed to produce the asymmetric structure in the resulting porous film materials which are characterized by a fiber structure in the surface which is different from that in the back.