Permea, Inc.

Clint A Cruse

Raymond F Malon

Milton K Murphy

Alfred K Fritzsche

Robert E Kesting

Alan C Handerman

Alan C Handermann

A dope for forming membranes and the resulting asymmetric gas separation membranes are disclosed, the membranes having graded density skins which exhibit improved permeability characteristics and increased failure pressure strength. The membranes are produced from a process utilizing membrane forming dopes of complexing solvent systems formulated from two non-solvents and one or more solvents. The non-solvents are chosen one each, from non-solvents grouped according to non-solvent strength, i.e., one strong non-solvent and one weak non-solvent which are combined with one or more solvents in an acid:base complex solvent system for dissolving high weight percent total solids of membrane forming polymers. The process for forming the membranes is also disclosed.

Asymmetric gas separation membranes having improved strength

Asymmetric gas separation membranes having graded density skins and macrovoid-free morphology comprised of glassy, hydrophobic polymers are disclosed which are effective for separation gases with significante increases in permeation while maintaining equal or greater separation electivity. The membranes have increased free volume and the graded density skin exhibits a density gradient which becomes more dense with increasing proximity to the surface, the membrane effectively decouples the interdependency between permeability and separation selectivity.

Asymmetric gas separation membranes having graded density skins

A process for forming high free volume, asymmetric gas separation membranes having graded density skins and macrovoid-free morphology from a solvent system comprising a Lewis acid, Lewis base, and a Lewis acid:base complex which dissolve hydrophobic polymers. The dopes have high total solids, high viscosity and low coagulation (g) values which enhance rapid gelation without the formation of macrovoids and which minimize densification. The dope solvent system complexes are readily disassociated by the coagulation medium and the component molecules are miscible in the medium which provides for rapid desolvation of the formed membrane thus providing a membrane having low residual solvent retention.

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St. John, MO, United States of America

Clint A Cruse