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US4255309A
Expired / Lapsed
US
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Polyacrylic acids and methyl vinyl ether/maleic anhydride copolymers as soft scale inhibitors
Assignee: Veolia WTS USA Inc
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Filing: 1979-08-16
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Granted: 1981-03-10
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Expires: 1999-08-16
Abstract
Abstract A method is disclosed for inhibiting soft scale precipitation in black liquor systems by adding thereto a treatment comprising in combination polyacrylic acid and methyl vinyl ether/maleic anhydride copolymer.
Inventors
- 👤 Frederick C. Klaessig
- 👤 Donald F. Jacques
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 16:51
CPC Classifications
D; D21; D21C; D21C11/00; D21C11/10; D21C11/106; C; C02; C02F; C02F5/00; C02F5/08; C02F5/10; C08; C08L; C08L33/00; C08L33/02; C08L35/00; C08L35/08
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
64 words
A method for inhibiting the precipitation of soft scale from black liquor, which method comprises adding to said black liquor an effective amount for the purpose of a treatment comprising in combination effective polyacrylic acid and effective methyl vinyl ether/maleic anhydride copolymer, wherein said treatment is added in an amount of from about 1 to about 500 parts per million parts of black liquor.
Claim 2
Independent Claim
64 words
A method for inhibiting the precipitation of soft scale from black liquor, which method comprises adding to said black liquor an effective amount for the purpose of a treatment comprising in combination effective polyacrylic acid and effective methyl vinyl ether/maleic anhydride copolymer, wherein said treatment is added in an amount of from about 1 to about 500 parts per million parts of black liquor.
Claim 3
Dependent Claim
12 words
A method according to claim 1, wherein said soft scale comprises burkeite.
Claim 4
Independent Claim
75 words
A method for inhibiting the precipitation of soft scale from black liquor in a multiple-effect evaporator, which method comprises adding to said black liquor an effective amount for the purpose of a treatment comprising in combination effective polyacrylic acid and effective methyl vinyl ether/maleic anhydride copolymer, wherein said treatment is added in an amount of from about 1 to about 500 parts per million parts of black liquor and wherein said soft scale comprises burkeite.
Claim 5
Independent Claim
75 words
A method for inhibiting the precipitation of soft scale from black liquor in a multiple-effect evaporator, which method comprises adding to said black liquor an effective amount for the purpose of a treatment comprising in combination effective polyacrylic acid and effective methyl vinyl ether/maleic anhydride copolymer, wherein said treatment is added in an amount of from about 1 to about 500 parts per million parts of black liquor and wherein said soft scale comprises burkeite.
Claim 6
Dependent Claim
20 words
A method according to claim 1, wherein said polyacrylic acid has a molecular weight of from about 500 to 1,000,000.
Claim 7
Dependent Claim
22 words
A method according to claim 4, wherein said copolymer has an apparent number-average molecular weight of from about 20,000 to about 67,000.
Claim 8
Dependent Claim
23 words
A method according to claim 5, wherein said copolymer has a mole ratio of methyl vinyl ether to maleic anhydride of about 1:1.
Claim 9
Dependent Claim
24 words
A method according to claim 4, 5 or 6, wherein said polyacrylic acid has a molecular weight of from about 1,500 to about 100,000.
Claim 10
Dependent Claim
18 words
A method according to claim 4, 5 or 6, wherein said soft scale further comprises thermonatrite and thenardite.
Claim 11
Dependent Claim
21 words
A method according to claim 7, wherein said polyacrylic acid has a molecular weight of from about 5,000 to about 100,000.
Claim 12
Dependent Claim
28 words
A method according to claim 3, wherein the relative proportion of said polyacrylic acid to said methyl vinyl ether/maleic anhydride copolymer is from about 5:95 to about 95:5.
Claim 13
Dependent Claim
24 words
A method according to claim 10, wherein said treatment comprises on a weight basis: Polyacrylic acid--10% Methyl vinyl ether/maleic anhydride copolymer--3% 50% NaOH--13.5% Water--73.5%
Claim 14
Dependent Claim
29 words
A method according to claim 11, wherein said polyacrylic acid has a molecular weight of about 5,000 and said copolymer has an apparent number-average molecular weight of about 20,000.
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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) | 1984-03-09 | 1984-09-08 | 1985-03-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-03-09 | 1988-09-08 | 1989-03-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-03-09 | 1992-09-08 | 1993-03-10 | $7700.00 | Window Closed / Lapsed |