Asymmetric polyimide membranes
AssigneeE. I. Du Pont de Nemours and Company
InventorConstance Wright Alegranti
Life of this patent
Estimating the term…
Abstract
Asymmetric polyimide membranes are prepared from tetracarboxylic acid dianhydrides and diamines. They are semipermeable and useful in the separation of different chemical species by osmosis, dialysis, electrodialysis and reverse osmosis.
Claims6
A microporous, opaque, asymmetric polyimide membrane not dissolving more than 10% by weight at 25.degree. C in N,N-dimethylacetamide and consisting essentially of a polyimide having the repeating formula ##STR58## wherein R.sup.5 is selected from the group consisting of ##STR59## and R.sup.6 is selected from the group consisting of phenylene, tolylene, naphthylene, biphenylene, anthrylene, pyridinediyl and ##STR60## in which R.sup.7 is selected from the group consisting of oxygen, sulfur and methylene, said membrane being shiny on one surface and dull on the other surface, and having a corrected small angle X-ray scattering pattern such that the intensity of the scattering radiation from nickel filtered CuK.alpha. radiation multiplied by the fourth power of the scattering angle (21/4) does not vary more than .+-. 10% for at least 0.2.degree. within the angle range (2.theta.) from 0.2-0.8.degree..
Dependencies are inferred from the claim text.