US4255259A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Scale inhibition
Assignee: WR Grace and Co Conn
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Filing: 1979-09-18
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Granted: 1981-03-10
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Expires: 1999-09-18
Abstract
Abstract This invention relates to an improved method for inhibiting deposition of scale in aqueous systems. More specifically, it relates to the use of small quantities of an improved composition for preventing formation of scale and sludge deposits in steam generating boilers. The composition is characterized by the fact that by using a plurality of selected ingredients a synergistic effect is obtained. The ingredients comprise a copolymer of styrene sulfonic acid and maleic anhydride or maleic acid, along with a water soluble organophosphonic acid compound.
Inventors
- 👤 Chih M. Hwa
- 👤 Dionisio G. Cuisia
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 15:20
CPC Classifications
C; C02; C02F; C02F5/00; C02F5/08; C02F5/10; C02F5/14
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
105 words
Method of inhibiting scale in a boiler water system comprising maintaining in said system about 0.2-50 ppm of a composition which consists essentially of (a) a member selected of the group consisting of copolymers of styrene sulfonic acid and maleic anhydride or maleic acid, and water soluble salts of said copolymers, the styrene sulfonic acid moiety in said copolymer being about 50-95 wt. % and the molecular weight of the copolymers being about 1500-6000 and (b) a member selected from a group consisting of a water soluble phosphonic acid and its water soluble salts; the weight ratio of copolymer to phosphonic acid being about 0.3-4:1.
Claim 2
Dependent Claim
105 words
Method of inhibiting scale in a boiler water system comprising maintaining in said system about 0.2-50 ppm of a composition which consists essentially of (a) a member selected of the group consisting of copolymers of styrene sulfonic acid and maleic anhydride or maleic acid, and water soluble salts of said copolymers, the styrene sulfonic acid moiety in said copolymer being about 50-95 wt. % and the molecular weight of the copolymers being about 1500-6000 and (b) a member selected from a group consisting of a water soluble phosphonic acid and its water soluble salts; the weight ratio of copolymer to phosphonic acid being about 0.3-4:1.
Claim 3
Dependent Claim
12 words
Method according to claim 1 in which the moiety is about 67-90%.
Claim 4
Dependent Claim
13 words
Method according to claim 1 in which the molecular weight is about 2000-4000.
Claim 5
Dependent Claim
18 words
Method according to claim 1 in which the weight ratio of copolymer to phosphonic acid is about 0.5-5:1.
Claim 6
Dependent Claim
87 words
Method according to any one of claims 1, 2, 3, or 4 in which the phosphonic acid is selected from the group consisting of hydroxyethylidene diphosphonic acid, nitrilo tri(methylene phosphonic acid), N-carboxymethyl imino di(methylene phosphonic acid), N,N-bis(carboxymethyl) amino methylene phosphonic acid, ethylene diamine tetra(methylene phosphonic acid), hydroxypropylidene diphosphonic acid, hexamethylenediamine tetra (methylene phosphonic acid), diethylenetriamine penta(methylene phosphonic acid), aminoethylidene diphosphonic acid, n-butyl amino di(ethyl phosphonic acid), isopropyl phosphonic acid, 2-phosphono butane tricarboxylic acid-1,2,4, 2-aminoethyl phosphonic acid, sodium salt of tetraethylenepentamine hepta(methylene phosphonic acid), and methylene diphosphonic acid.
Claim 7
Dependent Claim
101 words
Method of inhibiting scale in a boiler water system comprising maintaining in said system about 0.2 to 50 ppm of a composition which consists essentially of (a) a member selected of the group consisting of copolymers of styrene sulfonic acid and maleic anhydride, and water soluble salts of said copolymers, the styrene sulfonic acid moiety in said copolymer being about 67-90% and the molecular weight of the copolymers being about 2000-4000; and (b) a member selected from a group consisting of hydroxyethylidene diphosphonic acid and its water soluble salts; the weight ratio of copolymer to hydroxyethylidene phosphonic acid being about 0.3-4:1.
Claim 8
Dependent Claim
101 words
Method of inhibiting scale in a boiler water system comprising maintaining in said system about 0.2 to 50 ppm of a composition which consists essentially of (a) a member selected of the group consisting of copolymers of styrene sulfonic acid and maleic anhydride, and water soluble salts of said copolymers, the styrene sulfonic acid moiety in said copolymer being about 67-90% and the molecular weight of the copolymers being about 2000-4000; and (b) a member selected from a group consisting of hydroxyethylidene diphosphonic acid and its water soluble salts; the weight ratio of copolymer to hydroxyethylidene phosphonic acid being about 0.3-4:1.
Claim 9
Dependent Claim
30 words
Method according to any one of claims 1, 2, 3, 4, or 6 in which the composition is maintained in the aqueous system at a level of about 20 ppm.
Claim 10
Dependent Claim
24 words
Method according to any one of claims 1, 2, 3, 4, or 6 in which the maleic component in the copolymer is maleic anhydride.
Claim 11
Dependent Claim
24 words
Method according to any one of claims 1, 2, 3, 4, or 6 in which the maleic component in the copolymer is maleic acid.
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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 |