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:
Sep. 23, 1986
Filed:
Apr. 20, 1983
Asahi Kasei Kogyo Kabushiki Kaisha, Osaka, JP;
Abstract
A porous membrane formed of a thermoplastic resin having a critical surface tension of not higher than 35 dyn/cm and having a three-dimensional network structure is provided. Communicating pores having a porosity of at least 60% and an average pore diameter of 0.1 to 2.0 microns are formed in the porous membrane. The strength factor F defined by the following formula is at least 1 as measured in any direction: F=A/[B(1-.alpha.)], wherein A is the tensile strength at break of the membrane, B is the tensile strength at break of a non-porous film formed of the same resin and .alpha. is the porosity fraction of the membrane. The thickness of the porous membrane is 5 to 500 microns. The porous membrane is prepared by a process wherein a porous membrane formed of a thermoplastic resin having a critical surface tension of not higher than 35 dyn/cm and having a three-dimensional network structure including communicating pores having an average pore diameter of 0.05 to 1 micron with a porosity of 30 to 70%, is subjected to a space drawing operation in at least one direction at a temperature between 50.degree. C. lower than the melting or softening point of the thermoplastic resin and 5.degree. C. lower than the melting or softening point of the thermoplastic resin.