Boric acid-free composition for removing deposits containing cryolite

Patent metadata

Field	Value
Publication number	US-11434573-B2
Application number	US-201816769966-A
Country	US
Kind code	B2
Filing date	Dec 7, 2018
Priority date	Dec 12, 2017
Publication date	Sep 6, 2022
Grant date	Sep 6, 2022

Abstract

Described herein is an aqueous composition for removing cryolitic deposits from plants or parts of plants which serve for the conversion treatment of metal surfaces, said composition includinga) at least one mineral acid, andb) at least one dicarboxylic acid of the formula HOOC—(CH2)x—COOH,where x is 0 to 3 and no borate-containing compounds have been added to the composition. Also described herein is a corresponding method for removing cryolitic deposits.

First claim

The invention claimed is:

1. An aqueous composition for removing cryolitic deposits from plants or parts of plants serving for the conversion treatment of metal surfaces, which composition comprises
a) at least one mineral acid having a total normal concentration in the range from 3.0 to 10 mol/l; and
b) at least one dicarboxylic acid of the formula HOOC—(CH 2 ) x —COOH;
wherein x is 0 to 3 and no borate-containing compounds have been added to the composition.

2. The aqueous composition according to claim 1 , which comprises
b) at least one dicarboxylic acid of the formula HOOC—(CH 2 ) x —COOH having a total concentration in the range from 0.07 to 1.7 mol/l.

3. The aqueous composition according to claim 1 , which comprises the at least one mineral acid and the at least one dicarboxylic acid in a molar ratio in the range from 2.4:1 to 60:1.

4. The aqueous composition according to claim 1 , wherein the at least one mineral acid comprises sulfuric acid.

5. The aqueous composition according to claim 4 , which further comprises nitrate.

6. The aqueous composition according to claim 1 , wherein the at least one dicarboxylic acid comprises malonic acid and/or oxalic acid.

7. The aqueous composition according to claim 4 , which composition comprises
a) sulfuric acid having a total normal concentration in the range from 3.0 to 6.0 mol/l, and
b) oxalic acid having a total concentration in the range from 0.35 to 1.0 mol/l,
and comprises the sulfuric acid and the oxalic acid in a molar ratio in the range from 4.0:1 to 12:1.

8. The aqueous composition according to claim 1 , which additionally comprises at least one nonionic surfactant.

9. The aqueous composition according to claim 1 , which additionally comprises at least one corrosion inhibitor.

10. The aqueous composition according to claim 9 , wherein the at least one corrosion inhibitor is a mixture of a compound of the formula I
R 1 O—(CH 2 ) x —C≡C—(CH 2 ) y —OR 2   (I),

in which R 1 and R 2 are both H, and a compound of the formula I in which R 1 and R 2 each independently of one another are an HO—(CH 2 ) w group with w≥2, wherein for each of the two compounds of the formula I, x and y in each case independently of one another are 1 to 4.

11. A concentrate from which, by dilution with a suitable solvent and/or dispersion medium, an aqueous composition according to claim 1 is obtainable.

12. A method for removing cryolitic deposits from plants or parts of plants serving for the conversion treatment of metal surfaces, which comprises contacting the plants and/or parts of plants with an aqueous composition according to claim 1 .

13. The method according to claim 12 , wherein the aqueous composition has a temperature in the range from 40 to 80° C.

14. The aqueous composition according to claim 1 , which comprises
a) at least one mineral acid having a total normal concentration in the range from 3.0 to 6 mol/l, and
b) at least one dicarboxylic acid of the formula HOOC—(CH 2 ) x —COOH having a total concentration in the range from 0.35 to 1.5 mol/l.

15. The aqueous composition according to claim 1 , which comprises the at least one mineral acid and the at least one dicarboxylic acid in a molar ratio in the range from 2.6:1 to 12:1.

16. The aqueous composition according to claim 1 , wherein the at least one dicarboxylic acid comprises oxalic acid.

17. The aqueous composition according to claim 4 , which composition comprises
a) sulfuric acid having a total normal concentration in the range from 3.5 to 4.5 mol/l, and
b) oxalic acid having a total concentration in the range from 0.5 to 0.8 mol/l,
and comprises the sulfuric acid and the oxalic acid in a molar ratio in the range from 5.0:1 to 8.0:1.

18. The aqueous composition according to claim 1 , which additionally comprises at least one nonionic surfactant selected from the group consisting of ethoxylated fatty alcohol polyglycol ethers.

19. The aqueous composition according to claim 1 , which additionally comprises at least one compound selected from the group consisting of urea derivatives, diols, and alkoxylated diols.

20. The method according to claim 12 , wherein the aqueous composition has a temperature in the range from 50 to 70° C.

Assignees

• Chemetall Gmbh

Inventors

• Mohr Anna Verena

Classifications

• B08B2203/007

  Heating the liquid · CPC title

• C11D3/323

  urea or derivatives thereof · CPC title

• C11D7/265

  Carboxylic acids or salts thereof · CPC title

• C11D7/08

  Acids · CPC title

• C11D3/048

  Nitrates or nitrites · CPC title