Abstract: A membrane comprised of a graft copolymer includes a base component and a copolymer component. The base component includes a first polymer with a repeating unit: ##STR1## wherein m=0.1-0.9, n=0.9-0.1, p=0.03-0.04, R.sub.1 can be a linear, branched or cyclic C.sub.1 -C.sub.12 hydrocarbon radical, R.sub.2 can be a linear, branched or cyclic C.sub.1 -C.sub.12 hydrocarbon radical, and at least one of R.sub.1 and R.sub.2 is a linear or branched hydrocarbon radical with a terminal C.dbd.C double bond. The base component can include a second polymer with C.dbd.C double bonds located in the main chain and/or a side chain. The second polymer has a repeating unit: ##STR2## wherein m=n; R.sup.1 and R.sup.2 are identical or different; and 10 to 100% of R.sup.1 and/or R.sup.2 have a C.dbd.C double bond.

Abstract: A method of manufacturing an integral asymmetric membrane for separating gases from each other, wherewith a membrane-former, a solvent, and/or an agent which is not a solvent for the membrane-former are mixed, are spread out or otherwise extended over a greater area, and are contacted with a precipitation agent. The integral asymmetric membrane for gas separation is particularly suitable for CO.sub.2 /CH.sub.4 separation, has improved insensitivity to water and relatively high strength and durability, and has high separation throughput and selectivity (permeability of .gtoreq.=0.1 cu m/sq m/hr/bar for CO.sub.2, and CO.sub.2 /CH.sub.4 selectivity of about 30-40), which high separation throughput and selectivity are necessary for economical separation of materials.