Integral asymmetric polyether-sulfone membrane, process for its production, and use for ultrafiltration and microfiltration
First Claim
1. An integral polyether-sulfone membrane having properties sufficient for allowing a flow of fluid therethrough which is largely independent of membrane thickness, said membrane having two surfaces and comprising a pore diameter of 0.02μ
- m to 2 μ
m, measured by the blow point method, wherein the pore system is cellular throughout with cells having polyhedrally symmetrical boundaries and the cells being arranged asymmetrically from one surface of the membrane to the other surface, as asymmetry factor AF relative to the maximum pore diameter being 0.01 to 2.0, and a ratio of a maximum mean free path length of a flow path to a diameter of the largest pore being greater than 3, and a cell size changing steadily from one surface to the other surface.
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Accused Products
Abstract
An integral polyether-sulfone membrane with a pore system open at the outer boundaries is in the form of flat films, tubular films or hollow fibers having a maximum pore diameter of 0.02 μm to 2 μm. The pore system is cellular throughout with cells having polyhedrally symmetrical boundaries. The cells are arranged asymmetrically from one surface of the membrane to the other, the asymmetry factor AF relative to the maximum pore diameter being 0.01 to 2.0. The ratio of the maximum mean free path length of the flow path to the diameter of the largest pore is greater than 3. The cell size changes steadily from one surface to the other surface. The membrane is produced by dissolving 12 to 35% by weight, relative to the total solution, of polyethersulfone in a mixture of 15 to 65% by weight of ε-caprolactam, 0 to 85% by weight of latent solvent, 0 to 15% by weight of thickener and 0 to 50% by weight of non-solvent, and if appropriate up to 1% by weight of auxiliaries, forming the solution into flat films, tubular films or hollow fibers (the latter preferably with the aid of an internal fluid), and transformation into the solid phase and removal of the mixture forming the solvent. The membrane may be used for ultrafiltration and microfiltration.
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Citations
20 Claims
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1. An integral polyether-sulfone membrane having properties sufficient for allowing a flow of fluid therethrough which is largely independent of membrane thickness, said membrane having two surfaces and comprising a pore diameter of 0.02μ
- m to 2 μ
m, measured by the blow point method, wherein the pore system is cellular throughout with cells having polyhedrally symmetrical boundaries and the cells being arranged asymmetrically from one surface of the membrane to the other surface, as asymmetry factor AF relative to the maximum pore diameter being 0.01 to 2.0, and a ratio of a maximum mean free path length of a flow path to a diameter of the largest pore being greater than 3, and a cell size changing steadily from one surface to the other surface. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
- m to 2 μ
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9. A process comprising producing a polyethersulfone membrane, having properties sufficient for allowing a flow of fluid therethrough which is largely independent of membrane thickness, by dissolving 12 to 35% by weight, relative to a total solution, of polyethersulfone in a mixture of 15 to 65% by weight of ε
- -caprolactam, 0 to 85% by weight of latent solvent, 0 to 15% by weight of thickener and 0 to 5% by weight of non-solvent, and a 0 to 1% by weight of auxiliaries, each relative to the mixture;
forming a resultant solution into flat films, tubular films or hollow fibers;
transforming said films or fibers into a solid phase; and
removing the mixture forming solvent. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18)
- -caprolactam, 0 to 85% by weight of latent solvent, 0 to 15% by weight of thickener and 0 to 5% by weight of non-solvent, and a 0 to 1% by weight of auxiliaries, each relative to the mixture;
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19. An integral polyether-sulfone membrane having properties sufficient for allowing a flow of fluid therethrough which is largely independent of membrane thickness, said membrane having two surfaces and comprising a pore system open at the outer boundaries, the pore system being cellular throughout with cells having polyhedrally symmetrical boundaries and the cells being arranged asymmetrically from one surface of the membrane to the other surface,
said membrane having been formed from a mixture comprising ε - -caprolactam.
- View Dependent Claims (20)
Specification