JPH0441687A - Composition for removing scale - Google Patents

Abstract

PURPOSE:To obtain enough descaling performance at normal temp., to eliminate the need for pH treatment for waste liquid and to improve safety by adding nitrate ions to the aq. soln. of phosphate to control the pH in a specified range. CONSTITUTION:The descaling agent is prepared by adding nitrate ions to one or more kinds of aq. soln. of phosphate and controlling the pH of the soln. to 5.5-9.5. The concns. of phosphate and nitrate ions are specified to from about 0.1 to 50%. Or, the descaling agent is prepared by adding nitrate ions to one or more kinds of chelate agent and controlling the pH to 5.5-9.5. Or, one or more kinds of chelate agent and nitrate ions are added to one or more kinds of aq. soln. of phosphate. Though each of phosphate, chelate agent and nitrate ions in the descaling composition has weak or no descaling property by itself, the combination of these gives the function to remove scale incorporating metal oxides from metal surface. This descaling composition is neutral and required no neutralization treatment after descaling.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a composition for removing scale containing metal oxides from metal surfaces.

[Conventional technology]

Conventional general scale removing agents are shown in Table 1, and the type and concentration of the agent are selected depending on the type and situation of the object to be cleaned.

Table 1 [Problems to be Solved by the Invention] Conventional scale removers each have the following problems.

[1] Pickling with inorganic acid (1) High acidity and over-pickling is a concern.

(2) There is a risk of hydrogen embrittlement.

(3) After removing scale, it is necessary to neutralize the object to be cleaned.

(4) There is a danger in handling.

(5) Requires heating operation.

(6) pH treatment of the waste liquid is required.

(7) Generates acid gas and pollutes the environment.

(8) Depending on the type of auxiliary agent, COD treatment of the waste liquid may be necessary.

[2] Pickling with organic acids In addition to the same problems as pickling with inorganic acids, there are the following problems.

(1) The COD load of the effluent is large.

(2) The cost of drugs is high.

In view of the above-mentioned state of the art, the present invention aims to provide a composition for dissolving and removing scale that does not have the disadvantages of conventional pickling with inorganic acids and organic acids.

[Means to solve the problem]

The present invention includes (1) a metal oxide characterized by adding nitrate ions to an aqueous solution of one or more phosphates and adjusting the pH value to 5.5 to 9.5. Scale removal composition (hereinafter referred to as the first invention) (2) A scale removal composition comprising one or more chelating agents added with nitrate ions and the pH value adjusted to 5.5 to 9.5. Scale removal composition containing a characteristic metal oxide (hereinafter referred to as the second invention) (3) One or more chelating agents and nitrate ions are added to an aqueous solution of one or more phosphates. This is a scale removal composition (hereinafter referred to as the third invention) containing a metal oxide, characterized in that it is made by adding a metal oxide and adjusting the pH value to 5.5 to 9.5.

[First invention] The phosphates in this composition include pyrophosphate, tripolyphosphate,
Polymer phosphates such as tetrapolyphosphate, pentapolyphosphate, hexametaphosphate, ultrametaphosphate, etc., orthophosphates such as primary, secondary, and tertiary phosphates, and other orthophosphates and pyrophosphates. Water-soluble phosphites and hypophosphites such as phosphates can be used.

Examples of nitrate ions include alkali metal salts of nitric acid such as sodium and potassium salts, salts of organic cations such as amines and ammonia, and the like, as long as they dissolve in water to produce nitrate ions.

The combined ratio of phosphate and nitrate ions is 95; 5 to 5 by weight.
:95, preferably 9C1:10 to 70:30.

Further, the concentration of phosphate and nitrate ions in the composition of the first invention is preferably 0.1 to 50%, preferably 0.5 to 10%. The pH value of the composition is adjusted to 5.5 to 9.5, and for this adjustment, inorganic acids or inorganic alkalis such as sulfuric acid, hydrochloric acid, sodium hydroxide, potassium hydroxide, or gluconic acid, citric acid, oxalic acid are used. Organic acids such as , acetic acid, alkanolamines, and ammonia, or organic alkaline agents can be used. Note that if the pH value is 5.5 or less, descaling will occur by conventional pickling, and these drawbacks cannot be improved.

Furthermore, if the pH value is 9.5 or higher, the scale removal ability will be significantly reduced, which is not suitable. In addition, in order to promote the descaling effect, anionic, cationic, nonionic, etc. surfactants can also be used in combination.

[Second invention] The chelating agents in this composition include malonic acid, itaconic acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid,
Carboxylic acids such as thioglycolic acid, citric acid, malic acid, and gluconic acid, polymeric acids such as polyacrylic acid and polymaleic acid, phosphonic acids such as 1-hydroxyethylidene-1,1-diphosphonic acid, and phytic acid, ethylenediamine,
Amine-based agents such as triethanolamine, amino acid-based agents such as alanine and glutamic acid, aldehyde-based agents such as salicylaldehyde, ketone-based agents such as acetylacetone, and other water-soluble chelating agents with a pH value in the range of 5.5 to 9.5. It can be used if

As the nitrate ion, the same ones mentioned in connection with the first invention can be used.

The mixing ratio of chelating agent and nitrate ion is 95=5 by weight.
-5;95, preferably 90:10-70:30.

Further, the concentration of the chelating agent and nitrate ion in the composition of the second invention is preferably 0.1 to 50%, preferably 0.5 to 10%. The pH value of the composition is adjusted to 5.5 to 9.5, and for this adjustment, inorganic acids or inorganic alkalis such as sulfuric acid, hydrochloric acid, sodium hydroxide, potassium hydroxide, or gluconic acid, citric acid, oxalic acid are used. , organic acids such as acetic acid, amines, and ammonia, or organic alkaline agents can be used. Note that if the pH value is 5.5 or less, descaling will occur by conventional pickling, and these drawbacks cannot be improved. Furthermore, if the pH value is 9.5 or higher, the scale removal ability will be significantly reduced, which is not suitable. In addition, to promote the descaling effect, anionic,
A cationic surfactant, a nonionic surfactant, or the like can also be used in combination.

[Third invention] The phosphate and nitrate ions in this composition are those of the first invention.
The same substances mentioned in connection with the invention can be used, and the same substances mentioned in connection with the second invention can be used as the chelating agent.

The combined ratio of phosphate and chelating agent is 95:5 to 5 by weight.
:95, preferably 90:10 to 10:90. The mixing ratio of nitrate ions to the mixture of phosphate and chelating agent is 95:5 to 5:95, preferably 90:10 to 7.
0:30 is good. The concentration of phosphate, chelating agent, and nitrate ion in the composition of the third invention is preferably 0.1 to 50%, preferably 0.5 to 10%. The pH value of the composition is 5.5-9.
5, but for this adjustment, inorganic acids or inorganic alkalis such as sulfuric acid, hydrochloric acid, sodium hydroxide, and hydroxide, or organic acids such as gluconic acid, citric acid, oxalic acid, acetic acid, alkanolamines, and ammonia are used. Acids or organic alkaline agents can be used. Note that if the pH value is 5.5 or less, descaling will occur by conventional pickling, and these drawbacks cannot be improved. Furthermore, if the pH value is 9.5 or higher, the scale removal ability will be significantly reduced, which is not suitable. Incidentally, in order to promote the descaling effect, anionic, cationic, nonionic, etc. surfactants may also be used in combination.

[For production]

Although the effect of the composition of the present invention is not clear, the phosphate, chelating agent, and nitrate ion in the composition each have weak or no scale removal effect when used alone, so it is believed that the synergistic effect of these compositions is responsible. Presumed.

[Example of the first invention] A 300-meter composition according to the first invention (solid content concentration is 5%) was placed in a 500-meter beaker, and a test piece with mill scale attached to the surface (hot-rolled steel plate, JIS- G-3
1312 type, 35x50x1.2 (mm)) and a test piece (structural steel material, JIS
-G-3101, 2 types, 40 x 75 x 4 (mm
), exposed to the atmosphere for 3 weeks after blasting), test pieces with mill scale were immersed for 3 days, and test pieces with red rust were immersed for 10 minutes (at room temperature, left standing). The descaling status of the test piece after the test was observed.

The scale remover according to the first invention includes (Example 1) a mixture of sodium nitripolyphosphate, sodium pyrophosphate and sodium nitrate (weight ratio 35:35:30), pH value of the composition 5.8 (implemented) Example-2):)! J Sodium polyphosphate, sodium pyrophosphate, sodium ultrametaphosphate, and sodium nitrate (weight ratio 50:20:20:10), PAL value of composition (Example-3) Sodium nitric polyphosphate, sodium pyrophosphate, and hexamediphosphoric acid Mixture of sodium and sodium nitrate (weight ratio 20:15:15:50), pH value of composition 8.0 (Example-4) Mixture of sodium nitripolyphosphate and sodium nitrate (weight ratio 20:80), composition A p)l value of 9,3 was used.

As comparative examples for this, (Comparative example-1): Sodium nitrate (Comparative example-2) Sodium nitripolyphosphate (Comparative example-
3); Sodium pyrophosphate (Comparative Example-4) Mixture of sodium nitripolyphosphate and sodium pyrophosphate (weight ratio 50:50) (Comparative Example-5) Mixture of sodium nitripolyphosphate, sodium pyrophosphate and sodium ultrametaphosphate (weight A ratio of 50:25:25) was used. Note that the total concentration of each solution was 5%. The pH values of Examples and Comparative Examples were adjusted to predetermined pH values using sulfuric acid or sodium hydroxide.

The descaling effects of Examples and Comparative Examples are shown in Table 2.

Table 2 Immersion test results "Notes" Some scales remain after complete descaling and some have no scale at all [Example of the second invention] 20: △ : × Same conditions as the first invention The descaling status of the composition of the second invention was observed.

On the right, as the scale remover of the second invention, (Example-
1); A mixture of malonic acid and nitric acid (weight ratio 7)
5:25) (Example-2): Ethylenediamine and sodium nitrate (
Weight ratio 50:50) (Example-3): Mixture of ethylenediaminetetraacetic acid and sodium nitrate (weight ratio 25:5) (Example-4): Mixture of alanine and sodium nitrate (
Weight ratio 75:25) (Example-5): Mixture of polyacrylic acid (molecular weight 5000) and sodium nitrate (weight ratio 65:35) (Example-6) Mixture of nigerconic acid and sodium nitrate (weight ratio 95: 5) (Example-7): Mixture of nitroacetic acid and sodium nitrate (weight ratio 10:90) (Example-8) Mixture of dioxalacetic acid and sodium nitrate (weight ratio 40:60) (Example-9) : Mixture of salicylaldehyde and sodium nitrate (weight ratio 50:50) (Example 10): Mixture ratio of 1 hydroxyethylidene 1.1 diphosphonic acid and sodium nitrate (weight ratio 85: (Example 11) A mixture of acetylacetone and sodium nitrate (weight ratio 75°) was used.

As comparative examples for this, (Comparative example-1): Sodium nitrate (Comparative example-2): Malonic acid (Comparative example-3): Ethylenediamine (Comparative example-4): Ethylenediaminetetraacetic acid (Comparative example-5): Alanine (Comparative Example-6): Polyacrylic acid (molecular weight 5000) (
Comparative example = 7) Nigelconic acid (Comparative example-8): Nitroacetic acid (Comparative example-9) Dioxalacetic acid (Comparative example-10): Salicylaldehyde (Comparative example-11)
): 1 hydroxyethylidene 1.1 diphosphonic acid (Comparative Example-12) Niacetylacetone was used.

Note that the total concentration of each solution was 5%. The pH values of Examples and Comparative Examples were adjusted to predetermined pH values using nitric acid or sodium hydroxide.

The descaling effects of Examples and Comparative Examples are shown in Table 3.

Table 3 Immersion test results Completely descaled: ○ Scale remains: △ No descaling at all; × [Example of the third invention] Third invention under the same conditions as the first invention The descaling status of the composition was observed.

(Example-1) Mixture of sodium tripolyphosphate, sodium pyrophosphate, malic acid, and sodium nitrate (weight ratio 30:15:15; (Example-2); Mixture of sodium tripolyphosphate, malonic acid, and sodium nitrate (weight ratio: 30:15:15; Ratio 60:20:20) (Example-3
): Mixture of sodium hexametaphosphate, citric acid, and sodium nitrate (weight ratio 25:25: (Example-4) Mixture of sodium nitripolyphosphate, ethylenediaminetetraacetic acid, and sodium nitrate (weight ratio 10:20 near 0): Pyro Mixture of sodium phosphate, polyacryl (molecular weight 5000) and sodium nitrate (weight ratio 45° 45:10) 6): Mixture of sodium tetrapolyphosphate, sodium pyrophosphate, alanine and sodium nitrate (weight ratio 25:25:25: ( Example-7): Mixture of dibasic sodium phosphate, sodium hypophosphite, nitrotric acid, and sodium nitrate (weight ratio 30:20:15: : Mixture of sodium pyrophosphate, nitroacetic acid, and sodium nitrate (weight ratio 65: 10:25) Sodium nitripolyphosphate (Example-9) (Example-8) (Example-5) (Example sodium lutrametaphosphate, oxalacetic acid, and nitric acid) Mixture of IJium (weight ratio 40:25) : 5:30) (Example-10) : Mixing ratio of sodium hexametaphosphate, salicylaldehyde and sodium nitrate (weight ratio 65:10:25> (Example-11) : Sodium tripolyphosphate, sodium hexametaphosphate and 1 Hydroxyethylidene IS 1 Mixture of diphosphonic acid and sodium nitrate (weight ratio 25:25:25:25) (Example-12): Mixture of ultrasodium metaphosphate, acetylacetone and sodium nitrate (weight ratio 65:10:25) It was used.

As a comparative example for this, (Comparative Example-1): Sodium nitrate (Comparative Example-2) A mixture of sodium nitripolyphosphate, sodium pyrophosphate and malic acid (weight ratio 50:25: (Comparative Example-3):) Ribolyphosphoric acid Mixture of sodium and malonic acid (weight ratio 75:25) (Comparative Example-4): Mixture of sodium hexametaphosphate and citric acid (weight ratio 50:50) (Comparative Example-5) Mixture of sodium nitripolyphosphate and ethylenediamine (weight Ratio 33:67) (Comparative Example-6): Mixture of sodium pyrophosphate and polyacrylic acid (molecular weight 5000) (weight ratio 50:50) (Comparative Example-7): Sodium tetrapolyphosphate, sodium pyrophosphate and alanine mixture ( Weight ratio 33:33: (Comparative example (Comparative example-9)) (Comparative example (Comparative example (Comparative example-12): Mixture of dibasic sodium phosphate, sodium hypophosphite, and nitrotric acid (weight ratio 55: 18: 27>: Mixture of sodium pyrophosphate and nitroacetic acid (weight ratio: 87): Mixture of sodium nitripolyphosphate, sodium ultrametaphosphate, and oxalacetic acid (weight ratio: 57:36:7): Mixture of sodium hexametaphosphate and salicylaldehyde (weight ratio: 87:13) Mixture of sodium nitripolyphosphate, sodium hexametaphosphate, and 1 hydroxyethylidene 1,1 diphosphonic acid (weight ratio 33:33:34) (Comparative Example-13); Mixture of ultrasodium metaphosphate and acetylacetone (weight ratio 87:13) was used.The total concentration of each solution was 5%.The p)I value in Examples and Comparative Examples is sulfuric acid or hydroxylated.
The desired pH value was adjusted using IJum.

The descaling effects of Examples and Comparative Examples are shown in Table 4.

Table 4 Immersion test results "Notes" Completely descaled: ○ Scale remains: △ Not descaled at all: × [Effects of the invention] The scale removal composition of the present invention It has the following advantages:

■ The composition of the present invention is near neutral (p) 15.5 to 9.5
) also exhibits a descaling effect, and there is no need for pH treatment of waste liquid.

■ Highly safe.

■ Cheaper chemical costs compared to conventional organic acid type cleaning agents.

■ It has sufficient descaling performance even at room temperature and does not necessarily require heating operations.

■ Since it does not generate acid gas, it does not pollute the environment.

■ It is neutral and does not require any special neutralization treatment after descaling.

Claims (3)

[Claims] (1) Removal of scale containing metal oxides, characterized by adding nitrate ions to an aqueous solution of one or more phosphates and adjusting the pH value to 5.5 to 9.5. Composition. (2) A composition for removing scales containing metal oxides, characterized by adding nitrate ions to one or more chelating agents and adjusting the pH value to 5.5 to 9.5. thing. (3) One or more chelating agents and nitrate ions are added to one or more phosphate aqueous solutions, and the pH value is adjusted to 5.5 to 9.5. A scale removal composition containing an oxide of a metal.