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US 4,963,304 AGranted
Process for preparing microporous membranes
AssigneeThe Dow Chemical Company
InventorsJang-hi Im, C. C. Chau
Life of this patent
Estimating the term…
Abstract
A process for preparing microporous membranes by coextruding a melt of a plurality of interdigitated layers of at least two polymers, one having preferential solubility over the other, dividing and reorienting the layers of said melt into discrete domains of random orientation, forming a thin membrane or like article and leaching the preferentially soluble polymer out of the resulting article.
Claims28
A process for preparing a microporous membrane having a narrow pore size distribution and sharp size cutoff comprising:
- forming a lamellar polymeric composition by dividing and reorienting a plurality of adjacent layers of polymeric materials, each layer comprising at least two different polymeric materials and having a thickness of from 0.03 to 5 microns to form discrete domains of said polymeric materials of random orientation, at least one of said different polymeric materials having a preferential solubility in a selected solvent with respect to at least one other of said different polymeric materials;
- forming a melt composition of said lamellar polymeric composition into a thin solid structure;
- contacting said solid unitary structure with an extraction medium which has a preferential solubility for at least one of said at least two different polymeric materials, whereby said preferentially soluble polymeric material is removed from said solid unitary structure to form a porous unitary structure;
- and
- separating said extraction medium from said porous unitary structure.
2 more elements
A process for preparing a microporous membrane comprising:
- forming a melt blend comprising an admixture of at least two different polymeric materials, at least one of said different polymeric materials having a differential solubility in a selected solvent with respect to at least one other of said different polymeric materials;
- forming said melt blend into a melt stream comprising a layered stream of a plurality of thin, substantially parallel layers, each layer comprising a blend of said different polymeric material and being from about 0.03 to about 5 microns in thickness;
- passing said melt stream through a mixing means;
- forming said mixed melt stream into a solid unitary structure;
- contacting said solid unitary structure with an extraction medium which has a differential solubility for at least one of said at least two different polymeric materials whereby said preferentially soluble polymeric material is removed from said solid uniform structure to form a solid unitary microporous structure;
- and
- separating said extraction medium from said unitary porous structure.
4 more elements
Dependencies are inferred from the claim text.