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. 21, 1993
Filed:
Nov. 19, 1992
Yoshihiro Kusuki, Ichihara, JP;
Shunsuke Nakanishi, Ichihara, JP;
Ube Industries, Ltd., Yamaguchi, JP;
Abstract
A method of enhancing the gas-separation performance of an aromatic polyimide membrane with high reproducibility, by plasma-treating an asymmetric aromatic polyimide membrane comprising 80 to 100 molar % of at least one type of recurring units selected from those of the formulae (A) and (B) and 0 to 20 molar % of recurring units of the formula (C): ##STR1## in the formulae of which, R.sup.1, R.sup.2, R.sup.3 =an aromatic residue derived from an aromatic diamine compound and R=a tetravalent aromatic residue derived from an aromatic tetracarboxylic acid compound and different from tetravalent the aromatic tetracarboxylic acid residues appearing in the formulae (A) and (B), and has a helium gas-permeation rate [P.sub.He ] of 1.times.10.sup.-4 cm.sup.3 /cm.sup.2.sec.cmHg or more at 80.degree. C. and a ratio [P.sub.He ]/[P.sub.N2 ] of the helium gaspermeation rate [P.sub.He ] to a nitrogen gas-permeation rate [P.sub.N2 ] of 20 or more at 80.degree. C., in an atmosphere comprising ammonia.