Patent US3807571A successfully refreshed from Google Patents.
US3807571A
Expired / Lapsed
US
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Membranes for reverse osmosis
Assignee: United Kingdom Atomic Energy Authority
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Filing: 1973-04-09
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Granted: 1974-04-30
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Expires: 1993-04-09
Abstract
Abstract The invention comprises a cellulose acetate reverse osmosis membrane, a method of making such a membrane by casting and a solution suitable for use in casting such a membrane as a real composition of matter. The particular features of the invention lie in the selection of a narrow range of acetyl values for the cellulose acetate, obtained by blending cellulose acetates having acetyl values falling outside the selected range, and in the composition of the casting solution which included acetone dioxan and formamide. The membranes of the invention are further characterised in having Indices of Performance (I.O.P.) of at least 50 and frequently the I.O.P. is higher than 100.
Inventors
- 👤 D Walmsley
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 16:49
CPC Classifications
B; B01; B01D; B01D71/00; B01D71/06; B01D71/08; B01D71/12; B01D71/14; B01D71/16; B01D67/00; B01D67/0002; B01D67/0009; B01D67/0011; B01D69/00; B01D69/02; B01D61/00; B01D61/02; B01D61/025
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
21 words
A cellulose acetate reverse osmosis membrane as claimed in claim 1 having an acetyl value of from 40.9 to 41.2 percent.
Claim 2
Dependent Claim
27 words
A cellulose acetate reverse osmosis membrane as claimed in claim 1 wherein the casting solution comprises from 21.0 to 26.0 percent by weight of the cellulose acetate.
Claim 3
Dependent Claim
25 words
A cellulose acetate reverse osmosis membrane as claimed in claim 1 wherein the casting solution comprises from 23.2 to 37.6 percent by weight of acetone.
Claim 4
Dependent Claim
25 words
A cellulose acetate reverse osmosis membrane as claimed in claim 1 wherein the casting solution comprises from 20.0 to 34.7 percent by weight of dioxan.
Claim 5
Dependent Claim
25 words
A cellulose acetate reverse osmosis membrane as claimed in claim 5 wherein the casting solution comprises from 28.0 to 32.0 percent by weight of dioxan.
Claim 6
Dependent Claim
25 words
A cellulose acetate reverse osmosis membrane as claimed in claim 1 wherein the casting solution comprises from 10.0 to 21.3 percent by weight of formamide.
Claim 7
Dependent Claim
13 words
A membrane as claimed in claim 1 from 25 to 500 Mu thick.
Claim 8
Dependent Claim
17 words
A membrane as claimed in claim 8 wherein the membrane is from 125 to 375 Mu thick.
Claim 9
Dependent Claim
85 words
In a method of casting cellulose acetate reverse osmosis membranes from cellulose acetate casting solutions the improvement which consists in using cellulose acetate consists essentially of from 25.6-63.9 percent by weight of at least one cellulose acetate having an acetyl value of less than 40.9 percent and from 74.4-36.1 percent by weight of at least one cellulose acetate having an acetyl value greater than 41.4 percent and having an acetyl value of from 40.9 to 41.4 percent, and the casting solution having the following composition:
Claim 10
Dependent Claim
29 words
A method as claimed in claim 10 wherein the acetyl value of the cellulose acetate is from 40.9 to 41.2 percent and the casting solution has the following composition:
Claim 11
Dependent Claim
71 words
As a new composition of matter the solution comprising cellulose acetate consisting essentially of from 25.6-63.9 percent by weight of at leAst one cellulose acetate having an acetyl value of less than 40.9 percent and from 74.4-36.1 percent by weight of at least one cellulose acetate having an acetyl value greater than 41.4 percent and having an acetyl value of from 40.9 percent to 41.4 percent and having the following composition:
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-04-29 | 1977-10-29 | 1978-04-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-04-29 | 1981-10-29 | 1982-04-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-04-29 | 1985-10-29 | 1986-04-30 | $7700.00 | Window Closed / Lapsed |