Large pore synthetic polymer membranes
AssigneeUSF Filtration and Separations Group, Inc.
InventorsJerome Ditter, Richard A. Morris, Robert Zepf
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Abstract
Highly asymmetric polymeric membranes with large pores which yield bubble points in the range of 0.5 to 25 psid and superior flow characteristics. The membranes can be cast from both metastable dispersions and from homogenous casting formulations. The technique of synthesis involves exposure of the cast membrane to humid air to create large surface pores on the exposed side.
Claims5
A method for preparing a polymer membrane having a first and second surface and having a relatively large pore size in the first surface, a substantially asymmetric structure, and an enhanced flow rate, comprising:
- preparing a homogeneous casting solution comprising a polymer, a solvent for the polymer, and a non-solvent for the polymer at a selected casting temperature;
- casting the dispersion into a thin layer at the casting temperature;
- contacting the cast layer with a pore forming atmosphere for a period of time sufficient to form surface pores greater than 1.2 microns;
- and
- quenching the cast layer with a non-solvent quench liquid in which the solvent is miscible and in which the polymer is substantially insoluble to precipitate the polymer as an integral membrane;
- recovering the membrane from the quench liquid, wherein the membrane has a region of substantial asymmetry through at least fifty percent of the membrane, and wherein the membrane further has a substantially isotropic region extending from the first surface to the region of substantial asymmetry.
In a process to prepare an integral highly asymmetric polymer membrane having a first and second surface, the improvement comprising:
- contacting the cast layer with a gaseous atmosphere with a pore forming atmosphere for a period of time sufficient to form surface pores greater than 1.2 microns in the first surface, a substantially asymmetric structure extending through at least fifty percent of the membrane, and a substantially isotropic structure extending from the first surface to the substantially asymmetric structure.
Dependencies are inferred from the claim text.