US3877978A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Semipermeable membranes
Assignee: United States Department of the Interior
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Filing: 1974-03-27
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Granted: 1975-04-15
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Expires: 1994-03-27
Abstract
Abstract A method of improving the rejection performance of semipermeable membranes by incorporating thereinto an effective amount of a supplemental polymer containing a substantial amount of acetyl groups. A suitable supplemental polymer is a copolymer of vinyl acetate and one or more reactants, such as maleic acid or a halfester thereof, crotonic acid, and lower alkyl esters of acrylic acid. The copolymer may be stabilized by subsequent treatment with a multivalent cation.
Inventors
- 👤 Seymour S Kremen
- 👤 Gerald E Foreman
- 👤 John M Chirrick
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 19:26
CPC Classifications
B; B01; B01D; B01D67/00; B01D67/0081; B01D67/0088; Y; Y10; Y10S; Y10S521/00; Y10S521/905
Claims Analysis
Total Claims: 32
Claim 1
Independent Claim
43 words
A METHOD OF IMPROVING THE REJECTION PERFORMANCE OF SEMIPERMEABLE REVERSE OSMOSIS MEMBRANES COMPRISING INCORPORATING INTO THE MEMBRANE AN EFFECTIVE AMOUNT OF A SUPPLEMENTAL POLYMER CONSISTING OF A COPOLYMER OF VINYL ACETATE AND ONE OR MORE MEMBERS SELECTED FROM THE GROUP HAVING THE FORMULA:
Claim 2
Independent Claim
43 words
A METHOD OF IMPROVING THE REJECTION PERFORMANCE OF SEMIPERMEABLE REVERSE OSMOSIS MEMBRANES COMPRISING INCORPORATING INTO THE MEMBRANE AN EFFECTIVE AMOUNT OF A SUPPLEMENTAL POLYMER CONSISTING OF A COPOLYMER OF VINYL ACETATE AND ONE OR MORE MEMBERS SELECTED FROM THE GROUP HAVING THE FORMULA:
Claim 3
Dependent Claim
20 words
A method in accordance with claim 1 wherein said supplemental polymer is a copolymer of vinyl acetate and maleic acid.
Claim 4
Dependent Claim
25 words
A method in accordance with claim 1 wherein said supplemental polymer is a copolymer of vinyl acetate and a lower alkyl half-ester of maleic acid.
Claim 5
Dependent Claim
16 words
A method in accordance with claim 1 wherein said semipermeable membrane is made of cellulose acetate.
Claim 6
Dependent Claim
23 words
A method in accordance with claim 1 wherein said copolymer contains maleic acid, crotonic acid or a lower alkyl ester of acrylic acid.
Claim 7
Dependent Claim
16 words
A method in accordance with claim 1 wherein said supplemental polymer contains the following repeating group:
Claim 8
Dependent Claim
42 words
The method of claim 1 in which the incorporation of the supplemental polymer is achieved by contacting the membrane with an aqueous solution of about 0.1 to 2 weight percent of the polymer for a period of about 0.5 to 15 minutes.
Claim 9
Dependent Claim
40 words
A method in accordance with claim 1 wherein said incorporating is effected using a dilute slightly alkaline aqueous solution of said supplemental polymer which is insolubilized for attachment to said membrane by lowering the pH of the solution below neutral.
Claim 10
Dependent Claim
25 words
A method in accordance with claim 1 wherein treatment with a multivalent cation is used in said incorporation of said supplemental polymer into said membrane.
Claim 11
Dependent Claim
17 words
A method in accordance with claim 6 wherein said semipermeable membrane is made of a cellulose ester.
Claim 12
Dependent Claim
27 words
A method in accordance with claim 6 wherein said semipermeable membrane is made of cellulose acetate or of a mixture of cellulose acetate and another cellulose ester.
Claim 13
Dependent Claim
21 words
The method of claim 7 in which the aqueous solution of the polymer has a pH of about 7.5 to 10.
Claim 14
Dependent Claim
22 words
The method of claim 7 in which the contacting consists of immersion of the membrane in the aqueous solution of the polymer.
Claim 15
Dependent Claim
21 words
The method of claim 12 in which the polymer is subsequently insolubilized by lowering the pH to about 6.5 to 4.0.
Claim 16
Dependent Claim
25 words
The method of claim 14 in which the aqueous solution of the polymer additionally contains about 0.5 to 2.0 weight percent of a multivalent cation.
Claim 17
Dependent Claim
12 words
The method of claim 15 in which the multivalent cation is zinc.
Claim 18
Dependent Claim
12 words
A method in accordance with claim 9 wherein said cation is zinc.
Claim 19
Dependent Claim
42 words
A semipermeable reverse osmosis membrane having improved rejection performance, which membrane has uniformly attached thereto an effective amount of an insolubilized supplemental polymer consisting of a copolymer of vinyl acetate and one or more members selected from the group having the formula:
Claim 20
Dependent Claim
42 words
A semipermeable reverse osmosis membrane having improved rejection performance, which membrane has uniformly attached thereto an effective amount of an insolubilized supplemental polymer consisting of a copolymer of vinyl acetate and one or more members selected from the group having the formula:
Claim 21
Dependent Claim
20 words
A membrane in accordance with claim 18 wherein said supplemental polymer is a copolymer of vinyl acetate and maleic acid.
Claim 22
Dependent Claim
25 words
A membrane in accordance with claim 18 wherein said supplemental polymer is a copolymer of vinyl acetate and a lower alkyl half-ester of maleic acid.
Claim 23
Dependent Claim
20 words
A membrane in accordance with claim 18 wherein said supplemental polymer is a copolymer of vinyl acetate and crotonic acid.
Claim 24
Dependent Claim
16 words
A membrane in accordance with claim 18 wherein said semipermeable membrane is made of cellulose acetate.
Claim 25
Dependent Claim
15 words
A membrane in accordance with claim 18 wherein said polymer contains the following repeating group:
Claim 26
Dependent Claim
19 words
A membrane in accordance with claim 19 wherein said supplemental polymer includes a lower alkyl ester of acrylic acid.
Claim 27
Dependent Claim
18 words
A membrane in accordance with with claim 23 wherein said semipermeable membrane is made of a cellulose ester.
Claim 28
Dependent Claim
27 words
A membrane in accordance with claim 23 wherein said semipermeable membrane is made of cellulose acetate or of a mixture of cellulose acetate and another cellulose ester.
Claim 29
Dependent Claim
16 words
A membrane in accordance with claim 23 wherein said semipermeable membrane is made of a polyamide.
Claim 30
Dependent Claim
22 words
A membrane in accordance with claim 23 wherein said insolubilized supplemental polymer includes a multivalent cation which assists in rendering it insoluble.
Claim 31
Dependent Claim
12 words
A membrane in accordance with claim 28 wherein said cation is zinc.
Claim 32
Dependent Claim
37 words
In a process for desalination of saline water by reverse osmosis comprising contacting the saline water under pressure with a reverse osmosis membrane, the improvement comprising using the membrane of claim 18 as the reverse osmosis membrane.
References Cited (Backward Citations)
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US3676203A
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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) | 1978-04-14 | 1978-10-14 | 1979-04-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-14 | 1982-10-14 | 1983-04-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-14 | 1986-10-14 | 1987-04-15 | $7700.00 | Window Closed / Lapsed |