Patent DE-19543055-A1 (DE)
Title: Large pore synthetic polymer membranes
Inventor: DITTER JEROME
IPC: B32B7/02
Filed: 1995-11-06
Abstract: The following are claimed: (A) polymer membrane comprising a first surface, a second surface, and a porous supporting structure between the surfaces. The first surface comprises a relatively open pore structure, and the second surface comprises a more open pore structure. The supporting structure comprises a high degree of asymmetry through at least 50%, but no more than 80%, of the supporting structure; (B) Polymer membrane comprising a first porous surface, a second porous surface, and a porous supporting structure having a thickness between the surfaces. The supporting structure has a generally isotropic structure from the first surface to a point at about one quarter of the thickness of the supporting structure, and a generally asymmetric structure from the point to the second surface; (C) Polymer membrane comprising a first porous surface, a second porous surface, and a supporting structure having a thickness between the two surfaces. The supporting structure defines porous flow channels between the surfaces. The flow channels have a constant mean diameter from the first surface to a point at about one-quarter of the thickness of the supporting structure, and an increasing mean diameter from the point to the second surface; (D) Porous polymer membrane, suitable for isolating a liquid fraction from a suspension, comprising: (a) an integral porous skin, lying at one face of the membrane, in which all the pores of the skin have diameters greater than 1.2 microns; and (b) a support region of the membrane, lying below the skin and having an asymmetric structure; (E) Prepn. of polymer membranes having a relatively large skin pore size, an asymmetric structure, and an enhanced flowrate, comprising: (a) preparing a metastable casting dispersion, comprising a polymer-rich phase and a polymer-poor phase, at a selected casting temp.; (b) casting the dispersion into a thin layer at the casting temp.; (c) contacting the cast layer with a pore forming atmosphere to form surface pores greater than 1.2 microns; (d) quenching the cast layer with a non-solvent quench liquid, in which the solvent is miscible and in which the polymer is insoluble, to ppte. the polymer as an integral membrane; and (e) recovering the membrane from the quench liquid; (F) Prepn. of polymer membranes having a relatively large skin pore size, an asymmetric structure and an enhanced flowrate, comprising: (a) preparing an homogeneous casting soln. comprising a polymer, a solvent for the polymer, and a non-solvent for the polymer, at the casting temp.; (b) casting the dispersion into a thin layer at the casting temp.; (c) contacting the cast layer with a pore forming atmosphere for a time sufficient to form surface pores greater than 1.2 microns; (d) quenching the cast layer with a non-solvent quench liquid, in which the solvent is miscible and the polymer is insoluble, to ppte. the polymer as an integral membrane; and (e) recovering the membrane, which has symmetry through at least fifty percent of the membrane, from the quench liquid; (G) Improved diagnostic device comprising a filtering means that delivers a filtrate (which is particle-free) contg. an analyte to an analyte-detecting region of the device. The filtering means contains a polymer membrane as described above, having surface pores of mean diameter above 1.2 microns, and having a flowrate above 4.5 cm/min./psi; and (H) Improved diagnostic device comprising a lateral wicking means which transfers a sample (which is particle-free) contg. an analyte, from a sample receiving region of the device to an analyte-detecting region of the device. The lateral wicking means comprises a polymer membrane as described above, having surface pores of a mean dia. of 1.2 microns or more, and having a lateral transfer rate of above 2 cm. per min.