| abstract |
The invention is an improved gas separation membrane comprising a thin, discriminating layer consisting predominantly of a carbonate polymer derived from a bisphenol corresponding to Formula I <IMAGE> wherein R at each occurrence is independently H, Cl, Br, or C1-C4 alkyl and R1 is <IMAGE> -S-, -SO2-, -O-, or a C1-C6 divalent hydrocarbon or a C1-C6 divalent fluorocarbon radical or inertly substituted hydrocarbon radical, with the proviso that at least 25 weight percent of the moieties derived from the bisphenol of Formula I present in the discriminating layer bear R groups which are exclusively Br or Cl, the gas separation membrane exhibiting a separation factor for oxygen and nitrogen at 24 DEG C. of at least 6.1. In another aspect this invention relates to a process for separating oxygen from nitrogen, or a nitrogen-containing gas. |