Highly porous polyvinylidene difluoride membranes
First Claim
1. A microporous polyvinylidene difluoride polymer membrane, the membrane having a microporous surface comprising minimum pores, an opposite surface comprising maximum pores, and a thickness therebetween, the thickness comprising a porous support formed from filamentous webs of polymer material.
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Abstract
The present invention relates to the field synthetic polymeric membrane materials formed from casting polyvinylidene difluoride (PVDF) polymer solutions and/or dispersions. Membranes formed in accordance with the present invention are all highly porous. Both internally isotropic membranes and highly asymmetric PVDF membranes are disclosed. The membranes of the invention are useful in a variety of microfiltration and ultrathin applications.
105 Citations
37 Claims
- 1. A microporous polyvinylidene difluoride polymer membrane, the membrane having a microporous surface comprising minimum pores, an opposite surface comprising maximum pores, and a thickness therebetween, the thickness comprising a porous support formed from filamentous webs of polymer material.
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20. A method of preparing a polyvinylidene difluoride membrane comprising the steps of:
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providing a casting dope comprising between about 12% and 20% by weight of polyvinylidene difluoride and between about 0% and 30% by weight of a hydrophilic polymer, dissolved in a solvent; casting the dope to form a thin film; exposing the thin film to a humid gaseous environment; coagulating the film in a water bath; and recovering a formed microporous polyvinylidene difluoride polymer membrane, the membrane having a microporous surface comprising minimum pores, an opposite surface comprising maximum pores, and a thickness therebetween, the therebetween thickness comprising a porous support formed from filamentous webs of polymer material. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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32. An asymmetric integral microporous polyvinylidene difluoride polymer membrane, formed from a solution or suspension comprising at least 12% by weight of polyvinylidene difluoride, the membrane having a microporous surface comprising minimum pores, an opposite surface comprising maximum pores, and a thickness therebetween, the thickness therebetween comprising a porous support formed from filamentous webs of polymer material, wherein the porous support comprises flow channels having diameters, and wherein the diameters of the flow channels gradually increase along a gradient from the microporous surface to the opposite surface.
- 33. An internally isotropic microporous polyvinylidene difluoride polymer membrane, the membrane having a microporous surface comprising minimum pores, the minimum pores having a first average diameter, an opposite surface comprising maximum pores, the maximum pores having a second average diameter, and a thickness therebetween, the thickness therebetween comprising a porous support formed from filamentous webs of polymer material, wherein the porous support comprises flow channels having diameters, and wherein the diameters of the flow channels substantially correspond to the first average diameter within a first region of the porous support, the first region of the porous support being adjacent the microporous surface, and wherein the diameters of the flow channels substantially correspond to the second average diameter within a second region of the porous support, the second region of the porous support being adjacent the opposite surface, and wherein the diameters of the flow channels between the first region of the porous support and the second region of the porous support have a substantially constant diameter.
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36. In an improved filtering device having a membrane for filtering aqueous solutions, the improvement comprising:
an ozone resistant microporous polyvinylidene difluoride polymer membrane, formed from a solution or suspension comprising at least 12% by weight of polyvinylidene difluoride, the membrane having a microporous surface comprising minimum pores, an opposite surface comprising maximum pores, and a thickness therebetween, the thickness therebetween comprising a porous support formed from filamentous webs of polymer material. - View Dependent Claims (37)
Specification