| http://www.w3.org/ns/prov#value | - Preferable nonfibrous porous membranes, in the laminate of a fibrous porous membrane and a nonfibrous porous membrane are blushed polymer membranes composed of a cellulose ester, such as cellulose acetate, cellulose acetate/butyrate or cellulose nitrate, disclosed in U.S. Pat. No. 3,992.158 or U.S. Pat. No. 1,421,341.
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