JP3192562B2 - Aqueous cleaning aqueous solution of aluminum-based metal and cleaning method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous cleaning solution for an aluminum-based metal and a cleaning method thereof, and more particularly to a cleaning aqueous solution capable of satisfactorily removing a lubricating oil and aluminum powder adhered to an aluminum surface by molding and a cleaning method thereof.

[0002]

2. Description of the Related Art Products having an aluminum surface, such as aluminum containers for beverages made of an aluminum-based metal, ie, aluminum or an aluminum alloy, are usually manufactured by a forming operation called drawing and ironing (hereinafter, referred to as DI processing). . During this molding operation, lubricating oil is applied to the metal surface, and the resulting container has aluminum powder (smut) adhered to its inner wall, particularly. Such containers are generally subsequently protected on their surface, for example by chemical conversion or painting. Therefore, it is necessary to remove the lubricating oil or smut from the metal surface and clean it before the chemical conversion treatment or the like.

[0003] For this surface cleaning, an acidic cleaning agent is generally used which cleans the metal surface by etching it appropriately. Conventionally, a chromic acid-based or hydrofluoric acid-based cleaning agent has been often used as such an acidic cleaning agent. In particular,
Hydrofluoric acid type cleaning agent is low temperature acidic cleaning (~ 50 ℃)
It is excellent in that it is possible. However, since the above-mentioned detergent is a harmful substance, wastewater regulations are strict. Therefore, in recent years, it has been desired to establish a chromium-free and fluorine-free low-temperature acidic cleaning technology.

[0004] Such chromium-free and fluorine-free acidic cleaning technology is referred to as "aluminum surface cleaning agent" in Japanese Patent Publication No. 3-50838 and "Aluminum surface cleaning agent management method" in Japanese Patent Publication No. 3-65436. Proposed.

[0005] Japanese Patent Publication No. 3-50838, "Aluminum Surface Cleaner" and Japanese Patent Publication No. 3-65436, "Aluminum Surface Cleaner Management Method" contain no or a small amount of fluorine ion and sulfuric acid. And / or a cleaning agent containing ferric ions instead of fluorine ions as a promoting agent for etching in an acidic cleaning agent adjusted to pH 2 or lower with nitric acid, and controlling the oxidation-reduction potential of the cleaning bath. And a management method for managing the ferric ion concentration in the medium.

[0006] Usually, the etching reaction of aluminum in an acidic cleaning solution is based on an anodic reaction in which aluminum is converted into aluminum ions (Al ³⁺ ) and a cathode reaction in which H ^{+ in} the cleaning solution is reduced to 1 / 2H _2. Become. Therefore, when ferric iron (Fe ³⁺ ) in the acidic cleaning solution is added,
The anode reaction in which Fe ³⁺ is reduced to Fe ²⁺ is caused by the H
^Since it occurs simultaneously with the reduction of ⁺ , the etching reaction of aluminum is accelerated.

Further, by controlling the oxidation-reduction potential of the cleaning bath by using an oxidizing agent to control the ferric ion concentration in the bath, the Fe ²⁺ concentration which increases as the aluminum etching reaction proceeds is suppressed. And this Fe ²⁺ is F
It can be oxidized to e ³⁺ .

[0008]

However, the acidic cleaning agents disclosed in Japanese Patent Publication No. 3-50838 and Japanese Patent Publication No. 3-65436 contain iron ions. In addition, a precipitate (sludge), particularly a hydroxide, derived from iron ions is generated. Further, there is a problem that sludge adheres to the heater portion of the tank in the pre-cleaning step which is a step before the main cleaning.

[0009]

According to the present invention, sulfuric acid and / or nitric acid in an amount of pH 2 or less, oxidized metal ions,
An acidic cleaning aqueous solution of an aluminum-based metal containing a chelate dispersant.

[0010] Further, sulfuric acid and / or an amount of pH 2 or less are used.
Provides an acidic cleaning aqueous solution of an aluminum-based metal containing nitric acid , an oxidized metal ion, a surfactant, and a chelating dispersant.

[0011] Further, in the cleaning method for cleaning the aluminum surface, an amount of at least one selected from sulfuric acid and / or nitric acid at a pH of 2 or less, an oxidized metal ion,
A chelating dispersant, and a surfactant according to a degreasing request, using an acidic cleaning aqueous solution of an aluminum-based metal containing
Acid washing of "oxidized metal ions and oxidizing agent" or "oxidizing agent"
Supplemented water purification solution, by measuring the redox potential of the aqueous solution to provide an aluminum-based acidic cleaning method of metals characterized by maintaining the oxidized metal ion concentration in the aqueous solution.

The acidic cleaning aqueous solution is used as a cleaning bath for cleaning aluminum-based metal materials.
It is obtained by diluting the concentrated aqueous solution of the acidic cleaning aqueous solution with a suitable amount of water to a concentration within the range of use.

[0013]

The oxidized metal ions include ferric ion (Fe ³⁺ ), metavanadate ion (VO ₃ ⁻ ),
Cerium ion (Ce ⁴⁺ ), cobalt ion (C
o ⁵⁺ ), tin (Sn ⁴⁺ ) and the like. Preferably,
Ferric ion (Fe ³⁺ ), metavanadate ion (VO
₃ ^-) it is. In the case of a metal having a plurality of valences, an oxidized metal ion refers to a metal ion having a higher valence.

The source of the ferric ion includes a water-soluble ferric salt such as ferric sulfate, ferric nitrate, and ferric perchlorate. The source of metavanadate ions includes sodium metavanadate, potassium metavanadate, ammonium metavanadate and the like. The source of the second cerium ion includes cerium ammonium sulfate and the like. The source of cobalt ions is cobaltous sulfate,
Cobalt ammonium sulfate and the like can be mentioned. The source of tin ions includes stannic sulfate, stannic nitrate, and the like.

The chelating dispersant used in the present invention is an oxidizing agent.
Type metal ion chelate is formed, the stabilization of oxidized metal ions in aqueous solution under a strong acid is obtained, it may be any compound enhancing the dispersibility in an aqueous solution of a strong acid of oxidizing metal ions. Preferably, a phosphonic acid compound is used. As preferred phosphonic acid compounds, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid) and the like can be used.

As the surfactant, any of nonionic, cationic, anionic and amphoteric surfactants can be used as before. Among them, nonionics such as ethoxylated alkylphenols, hydrocarbon derivatives, abietic acid derivatives, primary ethoxylated alcohols, and modified polyethoxylated alcohols are particularly preferable.

It is preferable to add bromine ions and / or polyhydric alcohol as a surfactant decomposition inhibitor.

The source of bromine ions is 47% HB
r aqueous solution, potassium bromide, sodium bromide, aluminum bromide, iron bromide and the like.

As the polyhydric alcohol, a hydroxyl group directly bonded to an adjacent carbon atom in the main chain has at least two hydroxyl groups in one molecule.
Of the dihydric alcohols, such as 1,2-ethanediol (ethylene glycol), 1,2-propanediol (propylene glycol), 1,2-pentanediol, 1,2-butanediol, and trihydric alcohol 1,2,3-propanetriol (glycerin),
Examples include 1,2,4-butanetriol and 1,2,3,4-butanetetraol of a tetrahydric alcohol.

Normally, when washing is performed, when ferric ion is used as an oxidized metal ion with the passage of time,
The ferric ion is changed to ferrous ion by Fe ³⁺ + e → Fe ²⁺ , the oxidation-reduction potential is lowered (also referred to as aging of the cleaning bath), and the effect of promoting the etching of the aluminum surface is lost. Similarly, the washing bath ages with time for metavanadate ions. Therefore, when ferric ion is used as the oxidized metal ion, the ferrous ion is replenished as needed, or an ORP control oxidizing agent is added as needed to oxidize ferrous ion to ferric ion. Is also good. At this time, as the ORP control oxidizing agent, hydrogen peroxide (H ₂ O ₂ ), persulfate (for example, NaS
₂ O ₈ ^2- ), ozone (O ₃ ), cerium compounds (for example, cerium ammonium sulfate: (NH ₄ ) ₄ Ce (S
O ₄ ) ₄ )), nitrite (eg, NaNO ₂ , KN
O ₂ ) and compounds that generate metavanadate ion (VO ₃ ⁻ ). Incidentally, such an oxidizing agent is disclosed in Japanese Patent Publication No. 3-65436.
ORP is an oxidation-reductio potential.
n potential).

It is preferable that the pH of the aqueous acidic cleaning solution of the present invention is adjusted to 2 or less with sulfuric acid and / or nitric acid . More preferably, the acidic cleaning aqueous solution has a pH of 0.6.
~ 2. When the pH exceeds 2, the etching rate on the aluminum surface is extremely reduced, and it is difficult to exhibit the effectiveness as a cleaning bath. On the other hand, if the pH is less than 0.6, the economic efficiency is poor, and the amount brought into the next chemical conversion step increases,
It causes formation failure.

The oxidized metal ion is preferably contained in the aqueous acidic washing solution in an amount of 0.05 to 4 g / l.
More preferably, the content is 0.2 to 2 g / l.
If the content of the oxidized metal ion is less than 0.05 g / l, the amount of etching tends to be insufficient, and the desmutting property tends to decrease. On the other hand, if the content exceeds 4 g / l, there is no difference in the cleaning properties, and it is uneconomical.

The chelating dispersant is used in an acidic aqueous solution at a concentration of 0.0
The content is preferably 5 to 5 g / l, more preferably 0.1 to 2 g / l. If the amount is less than 0.05 g / l, chelation is not sufficient, hydroxide of an oxidized metal is formed, and precipitate (sludge) is generated in the aqueous solution. Further, in the heater section in the pre-cleaning step, the hydroxide of the oxidized metal ion may be fixed. When the cleaning method of the present invention is performed by spraying, clogging of a spray riser and a spray nozzle occurs. If it exceeds 5 g / l,
There is no difference in chelate dispersibility, which is uneconomical.

The surfactant is contained in the aqueous acidic washing solution at 0.1%.
It is preferably contained in an amount of 0.5 to 10 g / l.
More preferably, the content is 2 g / l. When the content of the surfactant is less than 0.1 g / l, the detergency tends to decrease, especially the degreasing property. On the other hand, the content is 10 g / l
When the value exceeds, there is no difference in cleaning properties, and it is uneconomical.

The bromine ions are contained in the aqueous acidic washing solution at a concentration of 0.0
It is preferably contained in the range of 02 to 0.1 g / l. When the bromine ion content is less than 0.002 g / l, the effect of suppressing the oxidative decomposition reaction of the surfactant tends to decrease. No further effect can be obtained in suppressing the above.

The polyhydric alcohol having at least two hydroxyl groups directly bonded to adjacent carbon atoms in the main chain in one molecule is preferably contained in the acidic washing aqueous solution in an amount of 0.1 to 5 g / l. More preferably, it is contained in an amount of 0.2 to 3 g / l. When the content of the polyhydric alcohol having the above structure is less than 0.1 g / l, the effect of suppressing the decomposition reaction tends to be insufficient. On the other hand, when the content exceeds 5 g / l, no difference is observed in the cleaning properties, which is uneconomical, and the load of wastewater treatment increases because the polyhydric alcohol concentration is high.

The acidic washing bath has a voltage of 0.5 to 0.8 V (vs.
It is preferable to control the oxidation-reduction potential (ARP) of Ag / AgCl). When the acidic cleaning bath is less than 0.5V,
Oxidized metal ions are deficient, and the amount of etching of the aluminum surface tends to decrease. On the other hand, if it exceeds 0.8 V, it is inferior in economic efficiency. More preferably, 0.55-0.
7 (vs. Ag / AgCl).

In the case where ferric ions are used as the oxidized metal ions in the acidic cleaning bath, the ferrous ions (F ³⁺ ) can be replenished only by ^adding new ferric ions (Fe ³⁺ ).
e ²⁺ ) accumulates in the acidic cleaning bath, and as a result, the acidic cleaning bath becomes muddy, and precipitates derived from ferrous ions are formed, thereby deteriorating the processing workability. Furthermore, since an object to be treated, such as an aluminum can, taken out of the acidic cleaning bath brings iron ions into the next step, a precipitate may be generated in the next step or the chemical conversion treatment may be adversely affected. Therefore,
The above problem can be solved by replenishing “oxidized metal ions and oxidizing agent” or “oxidizing agent” and maintaining the oxidation-reduction potential (ORP) in the above range.

The acidic cleaning method for the aluminum surface of the present invention may use either a spray method or a dipping method.
In addition, when performing the acidic cleaning, the processing temperature is 35 to
80 ° C is preferable, and 50 to 70 ° C is more preferable. If the processing temperature exceeds 80 ° C., excessive etching occurs and the aging of the processing bath is accelerated.

The acidic cleaning treatment time is preferably 30 to 300 seconds. If the processing time exceeds 300 seconds, excessive etching will occur and the aging of the processing bath will be accelerated. More preferably, it is 45 to 120 seconds.

The aluminum surface cleaned by the acidic cleaning agent of the present invention may be washed with water and then subjected to, for example, a phosphate chemical treatment according to a conventional method.

[0033]

According to the present invention, a chelate is formed between an oxidized metal ion and a chelate stabilizer in an acidic aqueous solution, particularly by using a chelate dispersant, and the oxidized metal ion is dispersed in an acidic aqueous solution. By improving the property, it is possible to prevent the generation of the precipitation (sludge) of the hydroxide of the oxidized metal ion. Thereby, satisfactory cleaning of the aluminum-based metal surface can be achieved without generating sludge.

[0034]

Next, the present invention will be described in detail with reference to examples and comparative examples.

Examples 1 to 16 and Comparative Examples 1 to 4 (1) Object to be treated: An aluminum plate made of 3004 alloy was
A lidless container with lubricating oil and smut adhered to it.

(2) Detergent: An acidic washing aqueous solution composed of an additive amount described in Examples and Comparative Examples shown in Table 1 below was used.

(3) Treatment conditions: The above container was sprayed with each cleaning agent at 70 to 75 ° C. for 60 seconds, then washed with tap water for 15 seconds, then with deionized water for 5 seconds, and sprayed with 95 ° C. Let dry.

(4) Evaluation of detergency: The following items were tested. Table 1 shows the results.

(A) Appearance: The whiteness in the dried container is visually determined. The case where the degreasing and de-smutting had a complete and sufficiently etched white appearance was judged as good, and the following five grades were evaluated according to the degree of whitening.

◎: White on the whole surface ○: Partially light gray △: Partially light gray ×: Partially gray ××: Fully gray (b) Water wettability: Shake the container immediately after spray washing 3 times to drain Then, the container is allowed to stand upward, and the water-wetted area (%) of the outer surface of the container after 30 seconds is measured.

(C) Desmutability: A transparent adhesive tape is adhered to the inner surface of the dried container, and then peeled off and pasted on a white mount, and the whiteness of the tape-attached surface is compared with that of other mounts. I do. The case where the smut was completely removed and there was no contamination was regarded as good, and the evaluation was made according to the following five levels according to the degree of contamination.

5: No contamination 4: Slight contamination 3: Slight contamination 2: Moderate contamination 1: Severe contamination (5) Sludge prevention The cleaning agent used for the evaluation of cleaning properties was diluted 20 times with water. Then, the mixture was heated with an electric heater (60 ° C., 1 day), and the state of fixation of the sludge in the electric heater was evaluated in three stages.

3: No sludge sticking 2: Slight sludge sticking 1: Sludge sticking over the whole The evaluation results are shown below. The base of the acidic cleaning bath is 75% sulfuric acid, 67.5% nitric acid, and the ferric ion (Fe ³⁺ ) is 41% ferric sulfate (Fe ₂ (SO ₄ ) ₃ ).
Ce ⁴⁺ is supplied from ceric sulfate (Ce (S
O ₄ ) ₂ ).

[0044]

[Table 1] Example 17 The same procedure as in Example 3 was carried out except that 0.04 g / l of bromine ions was added to the detergent of Example 3. The results were the same as in Example 3, and all the evaluation items were good.

From these results, according to the acidic cleaning agent for aluminum-based metal and the cleaning bath of the present invention, good cleaning can be obtained without using fluorine ions.

Embodiment 18 (Performance Change by ORP Value)

1-hydroxyethylidene-1,1-diphosphonic acid 1.0 g / l H ₂ SO ₄ 12.5 g / l Fe ²⁺ 1.0 g / l nonylphenol EO adduct 1.0 g / l hydrocarbon derivative 1 ORP was 0.60, 0.50, 0.45 V (vs. A) by changing the amount of H ₂ O ₂ added to the aqueous solution (water temperature: 70 ° C.).
g / AgCl).

[0047]

Table 3 ORP (vs. Ag / AgCl) Appearance Water wettability (%) Desmutability 0.60 V ◎ 100 5 0.50 V ○ 100 4 0.45 V △ 100 3 Examples 19 to 24 (1) Coating Processed product: DI of 3004 alloy aluminum plate
A lidless container with lubricating oil and smut adhered to it.

(2) Cleaning agent: an acidic cleaning aqueous solution used in "(4) Oxidation efficiency evaluation" described later, after oxidizing ferrous ions in the cleaning aqueous solution to ferric ions with hydrogen peroxide. An acidic aqueous washing solution was used.

(3) Treatment conditions: The above-mentioned containers were spray-treated with each cleaning agent at 70 ° C. for 60 seconds, and then washed with tap water for 15 seconds, followed by deionized water for 5 seconds,
Dried at 95 ° C. (4) Oxidation efficiency evaluation: An acidic washing aqueous solution composed of the addition amounts described in Examples shown in Table 4 below was heated to 70 ° C., and hydrogen peroxide was added dropwise with stirring. All first
When oxidizing iron ions (Fe ²⁺ ) to ferric ions (Fe ³⁺ ), the amount of hydrogen peroxide theoretically required is a and the amount required for the operation is b, and the oxidation efficiency is calculated by the following equation. Was calculated.

Oxidation efficiency = (a / b) × 100 (%) ：: 80 to 100 (%): 60 to 80 (%) (5) Evaluation of detergency: The following items were tested. Table 4 shows the results. The appearance, water wettability, and de-smuttability conform to the evaluation criteria used in the evaluation of Examples 1 to 16 and Comparative Examples 1 to 4 described above.

[0051]

[Table 4] Preferred embodiments of the present invention include the following embodiments.

1. A cleaning aqueous solution or cleaning method in which the oxidized metal ion is a ferric ion, a metavanadate ion, or a ceric ion.

2. A washing aqueous solution or a washing method in which an oxidized metal ion is 0.05 to 4 g / l in an acidic aqueous solution.

[0054]

4. 4. A cleaning aqueous solution or a cleaning method having a pH of 0.6 to 2. A washing aqueous solution or a washing method in which the chelate dispersant is a phosphonic acid compound.

6. A washing aqueous solution or method wherein the chelate dispersant is at least one phosphonic acid compound selected from 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri (methylenephosphonic acid), and ethylenediaminetetra (methylenephosphonic acid).

7. The chelating dispersant is added in an acidic aqueous solution to a concentration of 0.1.
A cleaning aqueous solution or a cleaning method of 0.05 to 5 g / l.

8. A cleaning aqueous solution or a cleaning method, wherein the surfactant is at least one nonionic surfactant selected from ethoxylated alkylphenols, hydrocarbon derivatives, and abietic acid derivatives.

9. Surfactant in acidic aqueous solution 0.1 ~
An aqueous washing solution or washing method of 10 g / l.

10. A cleaning aqueous solution or a cleaning method to which bromine ions and / or a polyhydric alcohol are further added.

11. The amount of bromine ion added is 0.002-
A washing aqueous solution or a washing method of 0.1 g / l.

12. The amount of polyhydric alcohol added is 0.1 to
An aqueous washing solution or washing method of 5 g / l.

13. ORP of acid washing bath is 0.55-
A cleaning method that is 0.7 (vs. Ag / AgCl).

14. A cleaning method wherein the oxidizing agent is H ₂ O ₂ .

[0065]

As described above, according to the acidic cleaning agent for aluminum-based metal, the cleaning bath, and the method for cleaning the same according to the present invention, harmful chromium ions and fluorinated ions which pollute the working environment are not contained. In addition, the lubricating oil and smut adhered to the aluminum surface can be removed, and the aluminum alloy can be cleaned so that the chemical conversion treatment and the painting operation can be smoothly performed.

Claims (3)

(57) [Claims] 1. An acidic cleaning aqueous solution of an aluminum-based metal, comprising: sulfuric acid and / or nitric acid in an amount of not more than pH 2, an oxidized metal ion, and a chelate dispersant. 2. An aqueous acidic cleaning solution for an aluminum-based metal, comprising: sulfuric acid and / or nitric acid in an amount of not more than pH 2, an oxidized metal ion, a chelate dispersant, and a surfactant. 3. A method for cleaning an aluminum surface, comprising: at least one selected from sulfuric acid and / or nitric acid in an amount of pH 2 or less; an oxidized metal ion; a chelating dispersant; Using an acidic cleaning aqueous solution of an aluminum-based metal containing an activator and, replenishing “oxidized metal ions and an oxidizing agent” or “oxidizing agent” into the acidic cleaning aqueous solution, and measuring the oxidation-reduction potential of the aqueous solution the acidic cleaning method of an aluminum-based metal, characterized by maintaining the oxidized metal ion concentration in the aqueous solution.