Microporous membrane and method for forming
Assignee3M Innovative Properties Company
InventorsIlyess H. Romdhane, Mikhail S. Mezhirov
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Abstract
The present disclosure describes a method for forming microporous membranes. More specifically, vapor induced phase separation techniques are used for forming multizone microporous membranes having improved material throughput.
Claims20
A method for forming a microporous membrane comprising:
- casting a plurality of dope formulations on a support to provide a multilayer sheet having a first major surface;
- exposing the multilayer sheet to a first relative humidity level such that water vapor diffuses into the first major surface;
- exposing the multilayer sheet to a second relative humidity level such that additional water vapor diffuses into the multilayer sheet effecting a phase separation to provide the microporous membrane, wherein the second relative humidity level is greater than the first relative humidity level;
- washing the microporous membrane;
- and
- drying the microporous membrane.
A multizone microporous membrane comprising a first zone and a second zone independently comprising pores having average pore diameters, such that the average pore diameters of the first zone are greater than the average pore diameters of the second zone, the multizone microporous membrane having a water flux measurement of at least 3,000 lmh/psi and a forward flow bubble point measurement comprising a first zone pressure peak less than 5 psi and an initial bubble point pressure measurement less than 15 psi.
Dependencies are inferred from the claim text.