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:
Jan. 22, 1980
Filed:
May. 06, 1977
Mitsubishi Rayon Company Limited, Tokyo, JP;
Abstract
A polypropylene film which is useful for electrical devices is produced by biaxially stretching an unstretched polypropylene molded article having, on at least one side, a surface layer having .beta.-form crystals, of mean diameter over 7 .mu.m, under such conditions that the stretching temperature at the stretch initiation point is in the range of 145.degree. to 176.degree. C., and the stretch ratio in one direction is less than a factor of 8. The resulting stretched polypropylene film is characterized by excellent mechanical properties, a very dense inner structure, and high air-tightness. The surface of the film has an efficiently roughened, fine, uneven structure containing crater-like patterns or an isotropic network structure and an anisotropic network structure, which is aligned in the extrusion direction. Therefore, the polypropylene film of the present invention can be readily impregnated with insulating oils, and hence can be used in various electrical devices, such as capacitors, electric cables, transformers and the like.