US4601827A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Multistage annealing of aramide reverse osmosis membranes
Assignee: EIDP Inc
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Filing: 1984-09-27
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Granted: 1986-07-22
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Expires: 2004-09-27
Abstract
Abstract A process for forming a reverse osmosis membrane is disclosed. The process involves casting a solution of an aromatic polyamide and a modifying salt to form a layer which is dried and quenched with water to gel the aromatic polyamide, and annealed in water at 40°-110° C. and preferably 40° to 90° in a plurality of stages with the final stage being at more than 60° C.
Inventors
- 👤 John J. Buckfelder
- 👤 Henry M. Schleinitz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 04:20
CPC Classifications
B; B01; B01D; B01D67/00; B01D67/0081; B01D67/0083; B01D71/00; B01D71/06; B01D71/56
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
116 words
A process for preparing a reverse osmosis membrane comprising casting a solution comprising 10 to 30 wt. % an aromatic polyamide and 30 to 60 wt. % based on aromatic polyamide of a modifying salt in a polar organic solvent to form a layer from 1 to 10 mils in thickness, evaporating solvent from said layer, quenching said layer with an aqueous medium to gel the aromatic polyamide, and annealing the gelled aromatic polyamide in water in a plurality of stages at from 40° to 110° C. with each successive stage being at a higher temperature than the previous stage, wherein the final stage is above 60° C. and lasts from 5 seconds to twenty minutes.
Claim 2
Dependent Claim
116 words
A process for preparing a reverse osmosis membrane comprising casting a solution comprising 10 to 30 wt. % an aromatic polyamide and 30 to 60 wt. % based on aromatic polyamide of a modifying salt in a polar organic solvent to form a layer from 1 to 10 mils in thickness, evaporating solvent from said layer, quenching said layer with an aqueous medium to gel the aromatic polyamide, and annealing the gelled aromatic polyamide in water in a plurality of stages at from 40° to 110° C. with each successive stage being at a higher temperature than the previous stage, wherein the final stage is above 60° C. and lasts from 5 seconds to twenty minutes.
Claim 3
Dependent Claim
49 words
The process of claim 1 wherein the aromatic polyamide is essentially derived from metaphenylenediamine, metaphenylenediamine-4-sulfonic acid, isophthalyl chloride and terephthalyl chloride wherein the ratio of isophthalyl chloride to terephthalyl chloride is from 50:50 to 80:20 and the sulfur content of the polymer is from 0 to 4.5 weight percent.
Claim 4
Dependent Claim
16 words
The process of claim 2 wherein the solvent is at least 80 weight percent dimethyl acetamide.
Claim 5
Dependent Claim
38 words
The process of claim 3 wherein the modifying salt consists essentially of lithium nitrate, lithium chloride, magnesium chloride or mixtures thereof and is present in an amount of from 20 to 60 weight percent based on aromatic polyamide.
Claim 6
Dependent Claim
13 words
The process of claim 4 wherein there are two or three annealing steps.
Claim 7
Dependent Claim
17 words
The process of claim 5 wherein the annealing steps are carried out at 40° to 90° C.
Claim 8
Dependent Claim
17 words
The process of claim 6 wherein the aromatic polyamide contains from 1.5 to 3.8 weight percent sulfur.
Claim 9
Dependent Claim
18 words
The process of claim 7 wherein the final annealing step is carried out at 68° to 85° C.
Claim 10
Dependent Claim
19 words
The process of claim 8 wherein the casting solution contains from 10 to 30 percent by weight aromatic polyamide.
Claim 11
Dependent Claim
17 words
The process of claim 9 wherein the solution is cast onto a woven polyester or polyamide fabric.
Claim 12
Dependent Claim
11 words
A reverse osmosis membrane made by the process of claim 1.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-07-21 | 1990-01-20 | 1990-07-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-07-21 | 1994-01-20 | 1994-07-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-07-21 | 1998-01-20 | 1998-07-22 | $7700.00 | Window Closed / Lapsed |