JP3453448B2 - Aluminum plate cleaning solution for laminating evaporator and cleaning method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum plate cleaning liquid for a laminated evaporator and a cleaning method, and more particularly to an aluminum plate cleaning liquid for a laminated evaporator and a cleaning method suitable for manufacturing a laminated evaporator by good vacuum brazing.

[0002]

2. Description of the Related Art Laminate evaporators are used as heat exchangers for automobiles and other vehicles. This laminated evaporator is formed by laminating and brazing multiple aluminum plates, but if an oxide film is formed on the surface of the aluminum plate, this oxide film is strong and dense, so brazing is not possible. Have difficulty. Therefore, flux was first developed as a means of removing and destroying the oxide film. However, since this flux is expensive and has problems such as cleaning the flux and treatment of its waste liquid, a brazing method that does not use flux has been developed. In recent years, brazing technology has been improved and brazing in vacuum has been improved. The non-flux method is used. This vacuum brazing is called brazing.

Usually, an aluminum plate used in a vacuum evaporator-based laminate evaporator is an aluminum alloy, such as an Al-Mg alloy or an Al-Mg-Si alloy containing a small amount of magnesium (Mg). As will be described later, the magnesium contained in the aluminum alloy in a small amount functions as a getter material, and removes and destroys the oxide film on the surface of the aluminum alloy, so that good brazing can be performed.

When high-strength brazing is performed, an Al-Mg-Si alloy is generally used, which is heated at a brazing temperature of about 600 ° C., air-cooled, and then age-hardened under each condition. .

The action of magnesium as a getter material will be described below. Magnesium is a metal that is more easily oxidized than aluminum and has a high vapor pressure, so
Evaporation occurs just before the brazing temperature to destroy the oxide film covering the base material and remove a trace amount of water or oxygen molecules in the atmosphere as shown in the following reaction formula.

[0006]

[Equation 1] Mg + 1 / 2O ₂ → MgO (1) Mg + H ₂ O → MgO + H ₂ (2) Mg + 1 / 3Al ₂ O ₃ → MgO + 2 / 3Al (3 However, when the aluminum plate is usually formed into a desired shape, the press oil such as paraffin hydrocarbon is used to roll the aluminum plate, so that the press oil inevitably remains on the surface of the aluminum plate. Therefore, as described above, even if pure Al appears on the surface of the aluminum plate due to the getter effect of magnesium, this pure A
If the press oil remains on the l surface, brazing is still difficult.

Therefore, conventionally, in the brazing pretreatment step,
The aluminum plate was washed with a halogenated hydrocarbon solvent such as 1,1,1-trichloroethane, which has high removability of press oil.

[0008]

[Problems to be Solved by the Invention]
Halogenated hydrocarbon solvents such as 1,1-trichloroethane have good detergency, but on the other hand, their use is prohibited due to their impact on the environment. The effects on the human body from the environment, the problem of fire, etc. remain, and the development of a new cleaning alternative to these solvents is desired.

Therefore, it is conceivable to clean with an alkaline cleaning agent, but it is difficult to control the cleaning property because the aluminum plate is heavily etched. For this reason, a method of adding sodium phosphate or caustic soda and sodium silicate or borax (sodium borate) to an alkaline detergent to form a silicate film or the like on the surface of an aluminum plate and control it is also conceivable.

However, since sludge is generated during cleaning, extra dust adheres to the surface of the aluminum plate, and a silicate film remains on the surface of the aluminum plate.
In the brazing in the next step, there was a problem that the adhesion strength between the aluminum plates deteriorates.

The present invention has been made in view of the above conventional problems, and an object thereof is an aluminum for a laminated evaporator for removing press oil or the like which inhibits the wettability of wax in a pretreatment step of vacuum brazing. A plate washing solution and a washing method are provided.

[0012]

To achieve the above object, the aluminum plate cleaning liquid for a laminated evaporator according to the present invention has a pH of 2 to 5 and a builder of 50%.
0 to 10,000 ppm and a surfactant of 100 to 3,
And 000 ppm.

The method of cleaning an aluminum plate for a laminated evaporator according to the present invention has a pH of 2 to 5, an aluminum plate for a laminated evaporator, a builder of 500 to 10,000 ppm, and a surfactant of 1.
It is a method of bringing into contact with an aqueous cleaning liquid containing 0 to 3,000 ppm, followed by washing with water and drying.

In the aluminum plate cleaning solution for a laminated evaporator according to the present invention, a builder is used to adjust the pH to 2-5. As the builder, mineral acid salts are preferable. And, as the acid component of the mineral acid salt, sulfuric acid,
Common ones such as nitric acid, hydrochloric acid, phosphoric acid can be used,
Sulfuric acid is particularly preferable from the viewpoint of the influence on the facility and the wastewater treatment burden. As the base component, alkali metal, alkaline earth metal, ammonium and the like are preferable, and magnesium is particularly preferable from the viewpoint of solubility.

The pH of the cleaning liquid of the present invention is preferably 2-5, more preferably 3.5-4.2. When the pH of the cleaning liquid is less than 2, the aluminum plates are excessively etched, the surface of the aluminum plates is whitened, and the adhesion strength between the aluminum plates after brazing is deteriorated. On the other hand, when the pH of the cleaning liquid exceeds 5, the degreasing power decreases, the press oil on the surface of the aluminum plate remains, and the adhesion strength between the plates after brazing deteriorates.

The builder concentration in the cleaning solution of the present invention is 500 to 10,000 ppm. If the builder concentration is less than 500 ppm, the degreasing power decreases, the press oil on the aluminum plate surface remains, and the adhesion strength between the plates after brazing deteriorates. On the other hand, when the builder concentration exceeds 10,000 ppm, problems occur in economic efficiency and further improvement in degreasing property cannot be expected.
The cleaning solution of the present invention is usually prepared by diluting a stock solution as needed. Therefore, in the case of a builder having a low solubility in water, the builder concentration of the cleaning solution at the time of use is 10,000.
The possibility of exceeding ppm is low.

Further, the surfactant in the cleaning liquid of the present invention is preferably a nonionic surfactant, for example, polyoxyethylene laurate ester, polyoxyethylene myristic ester, polyoxyethylene palmitate ester, polyoxy ester. Ethylene stearic acid ester, polyoxyethylene oleic acid ester, polyoxyethylene hydroxyoutearic acid ester, polyoxyethylene-9,10-dihydroxystearic acid ester, polyoxyethylene phenylstearic acid ester, polyoxyethylene-o-xylyl ester Polyoxyethylene fatty acid ester such as stearic acid ester, polyoxyethylene alkylamine such as polyoxyethylene lauryl amine, polyoxyethylene stearyl amine, etc. Polyoxyethylene alkyl amide or the like polyoxyethylene lauryl amide,
Polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan stearate, polyoxyethylene sorbitan oleate and other polyoxyethylene sorbitan fatty acid monoesters, polyoxyethylene lauryl alcohol, polyoxyethylene oleyl alcohol, polyoxyethylene pine Polyoxyethylene higher alcohols such as fragrance alcohols, polyoxyethylene alkylphenols such as polyoxyethylene octylphenol, polyoxyethylene octyl cresol, polyoxyethylene benzyl cresol, oleyl alcohol, polyoxyethylene octyl cresol ester, poly Oxyethylene nonyl phenyl ether, polyoxyethylene alkylphenol,
Is mentioned. Preferably, considering cost and safety,
Examples include polyoxyethylene nonylphenyl ether and polyoxyethylene higher alcohols.

The concentration of the surfactant in the cleaning liquid of the present invention is 100 to 3,000 ppm, preferably 1,000 to 3,000 ppm. When the concentration of the surfactant is less than 100 ppm, the degreasing power is lowered, the press oil on the surface of the aluminum plate remains, and the adhesion strength between the plates after brazing deteriorates. on the other hand,
If the concentration of the surfactant exceeds 3,000 ppm, problems will occur in economic efficiency and further improvement in degreasing property cannot be expected. In addition, it is not preferable in terms of time for subsequent water washing.

The water-based cleaning liquid used in the method for cleaning the aluminum plate for a laminated evaporator according to the present invention is the same as the above-mentioned cleaning liquid, and therefore its explanation is omitted.

The cleaning method of the present invention uses the cleaning liquid of the present invention 5
~ 60 seconds, 40 ° C-65 ° C, preferably 55 ° C-65
Degreasing is preferably performed by spraying at a spraying temperature of 1.5 to 3.0 kg / cm ² .
In the case of degreasing by immersing in the cleaning liquid of the present invention,
It is preferable to immerse the aluminum plate in the cleaning liquid at 55 ° C to 65 ° C for 2 minutes. And after degreasing, washing with water,
Wash with pure water and dry. The plurality of aluminum plates that have been subjected to the cleaning treatment of the present invention are laminated and brazed.

The cleaning solution and the aqueous cleaning solution of the present invention are
In addition to the above builder and surfactant, a polyethylene ethylene polypropylene derivative foam suppressor can be contained, if desired. Examples of the polyethyleneethylene polypropylene derivative foam suppressor include those containing polyethylene oxide and polypropylene oxide in the structural formula, and polyoxyethylene polyoxypropylene polyoxypropylene oleyl alcohol and other polyoxyethylene poly Examples include oxypropylene higher alcohols, Pluronic type foam suppressors and the like. This foam suppressor is for suppressing foaming during washing and foaming during washing with water, and usually has an HLB of 6 or less, preferably 2.5 to 5.5, and more preferably 3 to 5.5.
When the HLB exceeds 6, the effect of the foam suppressor cannot be sufficiently obtained.

[0022]

According to the aluminum plate cleaning liquid for a laminated evaporator and the cleaning method of the present invention, the press oil or the like on the surface of the aluminum plate is removed by the surfactant,
Further, since the drops of the press oil removed by the surfactant are captured by the builder, it is possible to prevent the removed press oil from reattaching to the surface of the aluminum plate.

Further, according to the aluminum plate cleaning liquid for a laminated evaporator of the present invention, since the surface of the aluminum plate is not etched, the adhesion strength between the aluminum plates in the brazing in the next step does not decrease. Further, since the press oil is gradually removed in an acidic atmosphere without etching the surface of the aluminum plate, no further oxide film is formed on the surface of the aluminum plate.

[0024]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples.

Examples 1 to 8 and Comparative Examples 1 to 6 (1) Object to be processed: 7.5 cm × 20 cm aluminum plate for laminated evaporator.

(2) Cleaning solution: An aqueous cleaning solution was prepared by adding the pH, builder and surfactant shown in Tables 1 and 2 below. Magnesium sulfate (MgSO ₄ ) was used as the builder.

(3) Treatment conditions: The aluminum plate for a laminate evaporator having the surface thereof on which press oil made of paraffin hydrocarbon is attached is immersed (dipped) in the cleaning solution at 60 ° C. for 2 minutes, and then at room temperature for 10 seconds. It was washed with a spray, and then with pure water (ion-exchanged water) for 10 seconds.

(4) Detergency evaluation: The following items were tested. The results are shown in Tables 1 and 2.

(A) Water riding property: After washing with pure water for 5 minutes, the water riding property was visually observed and evaluated.

◯: The entire surface of the aluminum plate was wet with water ×: Water repellency was found on the surface of the aluminum plate (b) Appearance: After evaluation of watering, after drying at 80 ° C. for 3 minutes, the gloss of the surface of the aluminum plate was visually observed. It was evaluated whether it was maintained. In addition, if the surface is etched, whitening occurs.

○: Gloss maintenance ×: With whitening (c) Contact angle (θ): After evaluation on water, after drying at 80 ° C. for 3 minutes, a contact angle of 5 μl of pure water dropped and an aluminum plate Was measured twice with a goniometer.
A desired adhesion strength can be obtained when the contact angle (θ) <40 °.

(D) Etching amount: After the evaluation of water riding, the aluminum plate was further immersed in the above cleaning liquid for 30 minutes at 60 ° C., and the weight loss of the aluminum plate per 1 m ² 1 minute was measured.

[0033]

[Table 1]

[Table 2] (Note) The surfactants in Tables 1 and 2 are nonionic surfactants and are as follows.

"Adecatol PC10": Asahi Denka Co., Ltd. "Adecanol B722": Asahi Denka Co., Ltd. "Adecatol NP675": Asahi Denka Co., Ltd. As a result, the aluminum plate cleaning liquid for laminate evaporator of the present invention is obtained. According to the cleaning method, the press oil, dust, and the like on the surface of the aluminum plate are satisfactorily removed.

Further, another preferred embodiment of the present invention will be described below.

1. The pH of the aluminum plate cleaning liquid for a laminate evaporator is 3.5 to 4.2.

2. The content concentration of the builder in the aluminum plate cleaning liquid for a laminated evaporator is 2,000 to 5,
It is 000 ppm.

3. The acid group of the above builder is SO ₄ ^2- , N
An aluminum plate cleaning liquid for a laminated evaporator, which is at least one selected from O ₃ ⁻ , Cl ⁻ , and PO ₄ ³⁻ .

4. A washing liquid for an aluminum plate for a laminated evaporator, wherein the acid group of the builder is SO ₄ ^2- .

5. An aluminum plate cleaning liquid for a laminated evaporator, wherein the builder's base is at least one selected from alkali metals, alkaline earth metals, and ammonium.

6. A washing liquid for an aluminum plate for a laminated evaporator, in which the builder's base is magnesium.

7. The above builder is an aluminum plate cleaning liquid for a laminated evaporator, in which magnesium sulfate is used.

8. The concentration of the surfactant contained in the aluminum plate cleaning liquid for laminate evaporator is 1,000 to
It is 3,000 ppm.

9. The surfactant is a nonionic surfactant.

[0045]

As described above, according to the aluminum plate cleaning liquid and the cleaning method for a laminated evaporator of the present invention, the surfactant removes the press oil and the like on the surface of the aluminum plate, and further removes the surfactant. Since the press oil droplets are captured by the builder, it is possible to prevent the removed press oil from reattaching to the surface of the aluminum plate.

Further, according to the aluminum plate cleaning liquid for a laminated evaporator of the present invention, since the surface of the aluminum plate is not etched, the adhesion strength between the aluminum plates in the brazing in the next step does not decrease. Furthermore, since the press oil is gradually removed in an acidic atmosphere without etching the surface of the aluminum plate, no further oxide film is formed on the surface of the aluminum plate.

Therefore, according to the aluminum plate cleaning liquid and the cleaning method for a laminated evaporator according to the present invention,
Degreasing properties equivalent to those of halogenated hydrocarbon solvents such as 1,1,1-trichloroethane can be obtained, and as a result, good breathing properties can be obtained.

Claims (2)

(57) [Claims] 1. A pH of 2-5 and 50 builders.
0 to 10,000 ppm and a surfactant of 100 to 3,
An aluminum plate cleaning liquid for a laminated evaporator, which contains 000 ppm. 2. An aluminum plate for a laminated evaporator having a pH of 2 to 5 and a builder of 500 to 1
50,000 ppm and 100-3,000 surfactant
A method for cleaning an aluminum plate for a laminated evaporator, which comprises contacting with an aqueous cleaning solution containing ppm, and then cleaning with water and drying.