US4454085A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for producing asymmetrical hollow filament membranes of polyamide
Assignee: Akzo NV
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Filing: 1982-09-20
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Granted: 1984-06-12
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Expires: 2002-09-20
Abstract
Abstract A process is disclosed for the production of asymmetrical hollow filament membranes suitable for ultrafiltration and/or microfiltration, in which a spinning solution composed of a polyamide or a mixture of polyamides and/or copolyamides, formic acid and a coagulating core liquid, is extruded into a coagulating setting bath liquid, and the hollow filaments are stretched after leaving the setting bath, in the wet state. The pH-value-difference between core liquid and setting bath liquid should be at least 3. The spinning solution contains, in particular, 15 to 25% by weight polyamide, 5 to 20% by weight polyethylene glycol, up to 10% by weight customary additive and formic acid. Preferred embodiments include a stretching ratio amounting to between 1:1.5 and 1:2.5, and having core liquid and setting bath liquid chosen from various combinations of caustic soda, glycol, formic acid or polyethylene glycol. Also disclosed are hollow filament membranes in which the hollow filament is of uniform, eccentric or profiled shape.
Inventors
- 👤 Erich Schindler
- 👤 Franz Maier
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 18:35
CPC Classifications
D; D01; D01D; D01D5/00; D01D5/24; B; B01; B01D; B01D69/00; B01D69/08; B01D71/00; B01D71/06; B01D71/56; Y; Y10; Y10T; Y10T428/00; Y10T428/29; Y10T428/2913; Y10T428/2973; Y10T428/2975
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
114 words
Process for the production of an asymmetrical hollow filament membrane suitable for ultrafiltration and/or microfiltration, comprising extruding a spinning solution composed of a polyamide or a mixture of polyamides and/or copolyamides with formic acid and a coagulating core liquid into a coagulating setting bath liquid different from the core liquid, stretching hollow filaments produced thereby, in the wet state, after leaving the setting bath and then drying the hollow filaments, wherein said spinning solution containing 15 to 25% by weight of polyamide, 5 to 20% by weight polyethylene glycol, up to 10% by weight customary additive and formic acid and the pH-value difference between core liquid and setting bath liquid is at least 3.
Claim 2
Dependent Claim
114 words
Process for the production of an asymmetrical hollow filament membrane suitable for ultrafiltration and/or microfiltration, comprising extruding a spinning solution composed of a polyamide or a mixture of polyamides and/or copolyamides with formic acid and a coagulating core liquid into a coagulating setting bath liquid different from the core liquid, stretching hollow filaments produced thereby, in the wet state, after leaving the setting bath and then drying the hollow filaments, wherein said spinning solution containing 15 to 25% by weight of polyamide, 5 to 20% by weight polyethylene glycol, up to 10% by weight customary additive and formic acid and the pH-value difference between core liquid and setting bath liquid is at least 3.
Claim 3
Dependent Claim
16 words
Process according to claim 1, wherein the hollow filaments are stretched about 1:1.5 up to 1:2.5.
Claim 4
Dependent Claim
19 words
Process according to claim 1, wherein the core liquid contains caustic soda and the setting bath liquid contains glycol.
Claim 5
Dependent Claim
33 words
Process according to claim 3, wherein the core liquid is a 1 to 10% by weight NaOH-containing caustic soda and the setting bath liquid is a 15 to 30% glycol-containing solution in water.
Claim 6
Dependent Claim
26 words
Process according to claim 1, wherein the core liquid is a 5 to 10% by weight NaOH-containing caustic soda and the setting bath liquid is water.
Claim 7
Dependent Claim
20 words
Process according to claim 1, wherein the core liquid contains caustic soda and the setting bath liquid contains formic acid.
Claim 8
Dependent Claim
32 words
Process according to claim 6, wherein the core liquid is a 1 to 10% by weight NaOH-containing caustic soda and the setting bath liquid contains 20 to 40% by weight formic acid.
Claim 9
Dependent Claim
20 words
Process according to claim 1, wherein the core liquid contains polyethylene glycol and the setting bath liquid contains formic acid.
Claim 10
Dependent Claim
32 words
Process according to claim 8, wherein the core liquid contains 15 to 30% by weight polyethylene glycol in water and the setting bath liquid contains 20 to 40% by weight formic acid.
Claim 11
Dependent Claim
19 words
Process according to claim 1, wherein the core liquid contains polyethylene glycol and the setting bath liquid contains NaOH.
Claim 12
Dependent Claim
34 words
Process according to claim 10, wherein the core liquid contains 15 to 30% by weight polyethylene glycol in water and the setting bath liquid is a 1 to 10% by weight NaOH-containing caustic soda.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-06-12 | 1987-12-12 | 1988-06-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-06-12 | 1991-12-12 | 1992-06-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-06-12 | 1995-12-12 | 1996-06-12 | $7700.00 | Window Closed / Lapsed |