Claims
- 1. A composition for dissolving an alkaline earth metal sulfate scale comprising:
- a) an aqueous solution having a pH of from about 10 to about 14;
- b) a chelating agent comprising a polyaminopolycarboxylic acid or a salt of such an acid; and
- c) a synergistic scale-dissolving quantity of anions of at least one monocarboxylic acid selected from a substituted acetic acid or an aromatic carboxylic acid having the carboxyl group attached directly to the aromatic nucleus.
- 2. The composition as recited in claim 1 where the chelating agent is DTPA.
- 3. The composition as recited in claim 1 where the pH is obtained by the addition of hydroxides of potassium.
- 4. The composition as recited in claim 1 where the chelating agent is present in an amount of 0.1M to 1.0M.
- 5. The composition as recited in claim 4 where the chelating agent is present in an amount of from 0.3M to 0.6M.
- 6. The composition as recited in claim 1 where the monocarboxylic acid anions are present in a concentration of from 0.1M to 0.6M.
- 7. The composition as recited in claim 6 where the monocarboxylic anions are present in a concentration of 0.3M to 0.6M.
- 8. The composition as recited in claim 1 where the substituted acetic acid is mercaptoacetic acid, hydroxyacetic acid or aminoacetic acid.
- 9. The composition as recited in claim 1 where the synergist comprises anions of salicylic acid.
- 10. The composition as recited in claim 1 where the pH of the solution is about 12.
- 11. An aqueous composition for dissolving alkaline earth sulfate scale comprising an aqueous alkaline solution having a pH of from about 10 to about 14, from about 0.05M to about 1.0M of a chelating agent comprising a polyaminopolycarboxylic acid or a salt of such an acid, and from about 0.05M to about 1.0M of at least one monocarboxylic acid selected from a substituted acetic acid or an aromatic carboxylic acid having the carboxyl group attached directly to the aromatic nucleus to improve the scale removing characteristics of the composition.
- 12. The composition as recited in claim 11 where the pH is obtained by the presence of a potassium base.
- 13. The composition as recited in claim 11 where the chelating agent comprises DTPA.
- 14. The composition as recited in claim 11 where the pH is adjusted to a value from about 11 to 13 with potassium hydroxide, the chelating agent comprises DTPA and the monocarboxylic acid is present in a concentration of from 0.3M. to 0.6M.
- 15. The composition as recited in claim 11 where the substituted acetic acid is mercaptoacetic acid, hydroxyacetic acid or aminoacetic acid.
- 16. The composition as recited in claim 11 where the substituted aromatic monocarboxylic acid is salicylic acid.
CROSS REFERENCE TO RELATED APPLICATIONS
This is a division of copending U.S. patent application Ser. No. 07/431,114, filed on Nov. 3, 1989, now U.S. Pat. No. 5,084,105, which is a continuation part of prior co-pending U.S. patent application Ser. No. 07/332,147, filed Apr. 3, 1989, now U.S. Pat. No. 5,093,020, of J. M. Paul and R. L. Morris.
This application is also related to prior U.S. patent application Ser. No. 07/369,897, filed Jun. 22, 1989, of the same inventors.
US Referenced Citations (18)
Foreign Referenced Citations (3)
Number |
Date |
Country |
57-107297 |
Jul 1982 |
JPX |
61-174990 |
Jan 1985 |
JPX |
63-178199 |
Jan 1987 |
JPX |
Divisions (1)
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Number |
Date |
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Parent |
431114 |
Nov 1989 |
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Continuation in Parts (1)
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Number |
Date |
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332147 |
Apr 1989 |
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