JP5143416B2 - Method for producing surface-treated aluminum material - Google Patents

Description

  The present invention relates to a method for producing a surface-treated aluminum material having an anodized film capable of obtaining high adhesion with a resin coating film or a resin film.

  Aluminum materials are light and excellent in formability and thermal conductivity, and are therefore widely used in containers, casings for electrical components, air conditioning fin materials, automobile structural members, building material panels, and the like. Generally, these aluminum materials are subjected to a surface treatment, and a resin coating film and a resin film for imparting corrosion resistance and design properties are formed on the surface-treated aluminum material.

As a typical surface treatment of an aluminum material, an anodizing treatment in which the aluminum material is electrolytically treated in an electrolytic solution can be given. Before the anodizing treatment of the aluminum material, it is desirable to carry out a pretreatment for removing oil adhering to the aluminum material and a non-uniform natural oxide film on the surface (see, for example, Patent Document 1). As such pretreatment, after etching with an alkaline solution, an insoluble component called smut made of Mg, Fe, Si, Cu, or a hydroxide thereof adhering to the surface by the etching treatment is treated with an acidic solution. There is a method of removing (desmut treatment) with an aqueous solution.
JP 2006-22362 A

However, when an anodized film is formed on the surface of an aluminum material using a conventional technique, the adhesiveness between the aluminum material and the resin coating film or resin film may be insufficient. In particular, the use of aluminum materials has been diversified in recent years, and it has become even more adherent to cope with strict molding processing, retort processing when used in food containers, high temperature storage, storage of highly corrosive contents, etc. There is a demand for improvement.
Conventionally, an aqueous nitric acid solution that hardly corrodes aluminum has been widely used for desmutting treatment. However, nitric acid is desired to reduce the amount of use because it may corrode manufacturing equipment and is subject to drainage regulations due to its large environmental load.
This invention is made | formed in view of such a situation, and makes it a subject to provide the manufacturing method of the surface treatment aluminum material which has an anodized film with which high adhesiveness with a resin coating film or a resin film is obtained. Yes.

  In order to solve the above-mentioned problems, the inventor paid attention to a smut adhering to the surface of the aluminum material when the etching process was performed before forming the anodized film on the surface of the aluminum material, and The present invention has been conceived by earnestly examining the relationship between the amount of smut remaining on the surface of the aluminum material to be formed and the adhesion of the aluminum material after forming the anodized film.

The method for producing a surface-treated aluminum material according to the present invention includes an etching step of attaching smut to the surface of the aluminum material by etching an aluminum material containing 1.0% by mass or more of Mg with an alkaline solution, and removing the smut. And an anodizing step of forming an anodized film on the surface of the aluminum material by electrolyzing the aluminum material in a weakly acidic to alkaline electrolyte without performing the neutralizing step. .

The method for producing a surface-treated aluminum material according to the present invention comprises an etching step of attaching a smut to the surface of the aluminum material by etching an aluminum material containing 1.0% by mass or more of Mg with an alkaline solution; An anodizing step of forming an anodized film on the surface of the aluminum material by electrolyzing the aluminum material adhering to the surface of 0.01 g / m ² or more in a weakly acidic to alkaline electrolyte. It is characterized by that.

Also, a method for producing a surface-treated aluminum material of the present invention may be a method porosity of the anodic oxide film is 5% or less.
Moreover, the manufacturing method of the surface treatment aluminum material of this invention can be set as the method provided with the process of apply | coating a silane coupling agent on the said anodized film.

According to the method for producing a surface-treated aluminum material of the present invention, an aluminum material containing 1.0% by mass or more of etched Mg is electrolyzed in a weakly acidic to alkaline electrolyte without performing a desmut treatment, Since the anodized film is formed with the smut remaining on the surface of the aluminum material, it is possible to provide a surface-treated aluminum material having an anodized film that provides high adhesion to a resin coating film or resin film.
Further, since the desmut process can be omitted, the manufacturing facility can be simplified, and the number of processes can be reduced, so that the cost can be reduced. In addition, nitric acid aqueous solution is widely used for desmut treatment, but nitric acid aqueous solution used for desmut treatment is not necessary because omission of desmut treatment, which can reduce the burden on the environment and improve safety and health. Can contribute.

Hereinafter, 1st Embodiment of the manufacturing method of the surface treatment aluminum material which concerns on this invention is described in detail.
As the aluminum material used in the present invention, aluminum or an aluminum alloy can be used and is not particularly limited. Specifically, for example, pure aluminum 1000 series alloy, Al-Cu series, Al-Cu-Mg series 2000 series alloy, Al-Mn series 3000 series alloy, Al-Si series 4000 series alloy, Al -Mg-based 5000 alloy, Al-Mg-Si-based 6000-based alloy, Al-Zn-Mg-Cu-based, Al-Zn-Mg-based 7000-based alloy, Al-Fe-Mn-based 8000-based alloy, etc. And casting alloys such as forming alloys, structural alloys, electrical alloys, AC1A, AC2A, AC3A, AC4B, and the like are used.

  Among the above aluminum materials, it is particularly desirable to use an aluminum material containing 1.0% by mass or more of Mg. Mg is easy to concentrate on the surface layer of aluminum material and does not dissolve in alkaline aqueous solution. For this reason, smut remains after the etching process. A smut mainly composed of Mg is active and greatly contributes to improvement of adhesion. Therefore, higher adhesion can be obtained by using an aluminum material containing Mg in an amount of 1.0% by mass or more.

  In addition, as an aluminum material, for example, an ingot of an aluminum alloy is manufactured, and this ingot is subjected to a hot rolling process and a cold rolling process a plurality of times, and an annealing treatment is performed as necessary during the cold rolling process. The aluminum alloy plate obtained by performing can be used. In addition, the aluminum material may be a processed material that has been previously subjected to press molding or the like, or may be an extruded material or a cast product. In addition, aluminum materials obtained by subjecting the above alloys to various tempering treatments such as solution treatment and aging treatment can also be used. Further, a clad material obtained by cladding these aluminum alloys on the surface can also be used.

(Etching process)
In the present embodiment, such an aluminum material is etched with an alkaline solution. By performing the etching process, the oil adhering to the aluminum material is removed (degreasing), and the heterogeneous natural oxide film formed on the surface of the aluminum material is removed. Further, by performing the etching step, smut, which is a component insoluble in an alkaline solution made of Mg, Fe, Si, Cu, or a hydroxide thereof, is attached to the surface of the aluminum material.
Examples of the alkaline solution used in the etching step include aqueous solutions of sodium hydroxide, potassium hydroxide, sodium carbonate, or a mixed aqueous solution thereof. Further, a surfactant may be added to these alkaline solutions in order to improve the degreasing property.

Etching amount of the aluminum material in the etching step is preferably ^{0.05g / m 2 ~2.0g / m 2} , it can be controlled by such concentration and temperature, etching time of the alkaline solution.
If the etching amount of the aluminum material is less than 0.05 g / m ^2, not the amount of smut is 0.01 g / m ² or more, an effect of sufficiently improving the adhesiveness may not be exhibited. In addition, when the etching amount of the aluminum material exceeds 2.0 g / m ² , there is a problem of a decrease in productivity and an increase in cost due to an increase in the etching processing time or an increase in the temperature or concentration of the alkaline solution. This is not preferable because it occurs. When the etching amount of the aluminum material exceeds 2.0 g / m ² , the surface is roughened and the metallic luster is lowered, and the film uniformity of the anodized film formed in the anodizing process described later is lowered. Therefore, it is not preferable.

(Anodizing process)
Next, the aluminum material after the etching process in which the smut adhered by the etching process is adhered to the surface in an amount of 0.01 g / m ² or more is electrolyzed in a weakly acidic to alkaline electrolytic solution, thereby eliminating the surface of the aluminum material. A porous anodic oxide film is formed.
In the present invention, the “nonporous anodic oxide film” means that the porosity of 10 to 50 nm pores with respect to the surface area of the anodic oxide film is 5% or less.
The weakly acidic to alkaline electrolyte solution is not particularly limited, but an alkaline metal salt, borate, silicate, tartrate, phosphate, etc. is used, and a weakly acidic to alkaline aqueous solution having a pH of 4 to 12 is used. Is desirable.

  The electrolytic solution is preferably weakly acidic to weakly alkaline in order to obtain a nonporous anodic oxide film, but a strongly alkaline one having a pH exceeding 12 may be used. Examples of the strong alkaline electrolyte include sodium phosphate, a mixed solution of sodium hydroxide and hydrogen peroxide. When a strongly alkaline electrolyte is used, the obtained anodized film may not be a nonporous anodized film but may be porous. In this case, a non-porous anodic oxide film can be formed by closing the pores of the porous anodic oxide film formed in the anodizing step by a sealing process such as high-temperature water or pressurized steam.

(Desmut treatment)
In the present invention, the desmut treatment can be omitted in the anodizing step. By omitting the desmut process, the manufacturing facility can be simplified and the number of steps can be reduced, thereby reducing the cost.
Conventionally, an aqueous nitric acid solution that does not corrode aluminum is used for the desmut treatment. However, nitric acid is desired to reduce the amount of use because it may corrode manufacturing equipment and is subject to drainage regulations due to its large environmental load. Omission of the desmut treatment eliminates the need for an acidic solution used in the desmut treatment, thereby reducing the burden on the environment and contributing to improved safety and hygiene.
If the amount of smut is too large, the smut may become an insulating layer in the anodic oxidation step and inhibit electrolysis. In the present invention, when the amount of smut is too large, a desmut treatment with an acidic solution can be performed between the etching step and the anodic oxidation step, but it is not necessary if it is controlled in the etching step. Suitable range of the amount of smut ^{is 0.01g / m 2 ~2.0g / m 2} .

(Application of silane coupling agent)
In this embodiment, it is desirable to apply a silane coupling agent on the anodized film obtained by the anodizing step.
As the silane coupling agent, those having an organic functional group which is an amino group, a vinyl group, an epoxy group or a methacryl group are preferably used. The silane coupling agent is preferably applied after being diluted with a volatile solvent such as water or alcohol. Examples of the application method include, but are not limited to, a dipping method, a spray method, and a roll coating method. The coating amount of the silane coupling agent is not particularly limited, but in order to effectively obtain the crosslinking effect of the silane coupling agent, the solid content after drying is 0.1 to 100 mg / m ^2. It is preferred that

  In the manufacturing method of the surface-treated aluminum material of the present embodiment, the surface of the aluminum material is electrolyzed by electrolyzing the aluminum material in which the smut adhered by the etching process remains on the surface in a weakly acidic to alkaline electrolytic solution. Since the oxide film is formed, the smut present on the surface of the aluminum material at the time of the formation of the anodized film is also anodized at the same time, so that the hydroxyl groups increase and the bond with the coating film or film becomes stronger. Further, it is considered that the adhesion area is increased and the adhesion is improved by increasing the surface area.

  Further, in the method for producing the surface-treated aluminum material of the present embodiment, the aluminum material is electrolyzed in a weakly acidic to alkaline electrolytic solution. For example, when the electrolytic solution is made strongly acidic typified by sulfuric acid, smut is performed. Will be dissolved and removed. In the method for producing a surface-treated aluminum material according to the present embodiment, when the aluminum material is electrolyzed in a weakly acidic to alkaline electrolyte, the smut is not dissolved and removed during the formation of the anodized film. It becomes what has an anodic oxide film from which high adhesiveness is obtained.

  In addition, when an aluminum material is electrolyzed in a weakly acidic to strongly acidic or strongly alkaline electrolyte, the oxide film dissolves simultaneously with the formation of the oxide film, so that the resulting oxide film becomes a porous film having pores. There is a case. The pore diameter of the porous coating is 10 to 50 nm. When a coating film is applied on the porous film, an anchor effect is obtained because the coating material flows into the pores, and adhesion is improved. However, when a resin film is laminated on the porous film, the resin film does not flow into the pores, the adhesion area is reduced, and sufficient adhesion may not be obtained. In addition, when laminating a resin film on the porous film, the electrolyte that has entered the pores during the formation of the porous film is released by the heating during the lamination, thereby improving the adhesion between the porous film and the resin film. It may be reduced.

  In the method for producing a surface-treated aluminum material according to this embodiment, when the aluminum material is electrolyzed in a weakly acidic to alkaline electrolyte, a nonporous anodic oxide film is formed. Further, in the method for producing the surface-treated aluminum material of the present embodiment, an anodized film is formed using a strong alkaline electrolyte, and the hole of the obtained anodized film is closed by a sealing process. A nonporous anodized film is formed. The surface-treated aluminum material having a nonporous anodic oxide film thus obtained is excellent in that even higher adhesion can be obtained with both the resin coating film and the resin film.

Further, a method for producing a surface-treated aluminum material of the present embodiment, since the etching amount of the aluminum material in the etching step is preferably ^{0.05g / m 2 ~2.0g / m 2} , in the etching process, efficiently A sufficient amount of smut can be deposited on the surface of the aluminum material.

Moreover, in the manufacturing method of the surface treatment aluminum material of this embodiment, still higher adhesiveness is obtained by using what contains 1.0 mass% or more of Mg as an aluminum material.
Moreover, since the manufacturing method of the surface treatment aluminum material of this embodiment is equipped with the process of apply | coating a silane coupling agent on an anodic oxide film, the anodic oxide film which is inorganic by the crosslinking effect of a silane coupling agent And organic resin coating film or resin film can be enhanced, and higher adhesion can be obtained.

"Example 1 to Example 7, Example 9 to Example 10, Comparative Example 2 to Comparative Example 4"
As an aluminum material, using an aluminum alloy plate having a thickness of 0.2 mm by rolling the alloy shown in Table 1 which is one of JIS1050 aluminum alloy, JIS5052 aluminum alloy, and aluminum alloy added with 1.0% by weight of Mg, Alkalinity shown in Table 1 which is either 1% sodium hydroxide aqueous solution or 2% aqueous solution of alkali degreasing agent (trade name: Surf Cleaner EC370 (medium etching type, surfactant added)) manufactured by Nippon Paint Co., Ltd. Using the solution, etching treatment (etching process) was performed at a bath temperature of 50 ° C. by the spray method for the time shown in Table 1. The etching amount of the aluminum material at this time was obtained from the weight difference before and after the etching process. The results are shown in Table 1.

After the etching process, the amount of smut adhered by the etching process was measured. The amount of smut was measured from the difference in weight between the weight after the etching treatment and the weight after completely desmutted with a 10% nitric acid solution for measurement. The results are shown in Table 1.
Thereafter, the aluminum material is used as an anode, the carbon plate is used as a cathode, and electrolysis is performed in an electrolytic solution at a pH of 50 ° C. including the electrolyte shown in Table 1 so that the thickness of the anodized film becomes 0.15 μm. As a result, an anodized film was formed on the surface of the aluminum material (anodizing step). In the anodizing step, when the electrolytic solution contains borate or silicate, electrolysis is performed at a constant voltage of 107 V, and when the electrolytic solution contains sodium hydroxide or sulfuric acid, 1 A / dm ² Electrolysis was performed at a constant current of.

"Example 11, Comparative Example 1, Comparative Example 5"
After performing the etching process in the same manner as in Example 1, a 10% aqueous nitric acid solution was used as the acidic solution, and the desmutting treatment shown in Table 1 was performed at 25 ° C. by the spray method. Thereafter, the amount of smut that adhered by the etching process and remained after the desmut treatment was measured. The amount of smut was measured from the difference in weight between the weight after desmut treatment and the weight after complete desmutting with a 10% nitric acid solution for measurement. The results are shown in Table 1.
Thereafter, an anodic oxidation process was performed in the same manner as in Example 1 to form an anodic oxide film on the surface of the aluminum material.

"Example 8"
After performing the steps up to the anodizing step in the same manner as in Example 1, a silane coupling agent was applied on the anodized film. As the silane coupling agent, an organic functional group having an amino group was used and applied by roll coating so that the solid weight after drying was 10 mg / m ² .

The porosity of the aluminum materials having the anodic oxide films of Examples 1 to 11 and Comparative Examples 1 to 5 obtained as described above was examined as follows. That is, the surface of the anodized film was observed with a scanning electron microscope at an arbitrary magnification of 50,000 times (minimum viewing area of 2.0 μm ² ) or more at 10 arbitrary locations, and the average value of the area ratio of holes having a diameter of 10 to 50 nm Was determined as the porosity. The results are shown in Table 1.

Subsequently, the resin layer shown in Table 1 which consists of a polyester-type coating film (coating film) or a PET film layer (film) was formed on the anodized film of Examples 1 to 11 and Comparative Examples 1 to 5. .
The polyester-based coating film was formed by coating by a roll coating method so that the thickness after drying was 2 μm, and baking and drying at 200 ° C. for 10 minutes.
The PET film layer is a biaxially stretched film obtained by copolymerizing ethylene terephthalate and isophthalate, and consists of two layers of an orientation layer having a melting point of 260 ° C. and a thickness of 14 μm and an adhesive layer having a melting point of 230 ° C. and a thickness of 1 μm. A PET film was formed by pressure-bonding on an aluminum material heated to 170 ° C. by a heat roll with a pressure roll at a linear pressure of 18 kg / cm 2.

  In order to evaluate the adhesion of the aluminum materials of Examples 1 to 11 and Comparative Examples 1 to 5 in which the resin layer was formed on the anodized film thus obtained, hot water at 85 ° C. After applying a load to be immersed in (85 ° C.) or after applying a load (retort) to be exposed to pressurized steam at 125 ° C., the following cross cut test and Eriksen test were performed. The results are shown in Table 2.

"Cross-cut test"
According to JIS 5600-5-6, a grid of 25 squares with a 1 mm interval was formed, and cellotape (registered trademark) was peeled off. And it evaluated as shown below with the number of the masses which the resin layer peeled.
○: No peeling Δ: Number of peeling masses 1 to 5 squares ×: Number of peeling masses 6 or more “Erichsen test (extruded tape peeling test)”
Using an Erichsen tester, a steel ball punch having a diameter of 20 mm was used to overhang the workpiece to a height of 5 mm, and the cellotape (registered trademark) was peeled off from the processed portion. And it evaluated as shown below with the area ratio of the part which the resin layer peeled.
○: No peeling Δ: Peeling area ratio less than 20% ×: Peeling area ratio of 20% or more

As shown in Table 2, in Examples 1 to 11, the evaluations of the cross cut test and the Eriksen test were all ◯ or Δ.
On the other hand, in Comparative Examples 1 to 5, as shown in Table 1, the smut amount is less than 0.01 g / m ² , and as shown in Table 2, the cross-cut test and the Eriksen test are evaluated. X was included.
From this, it became clear that according to this invention, adhesiveness with a resin coating film or a resin film can be improved.

Claims (4)

An etching step of attaching smut to the surface of the aluminum material by etching an aluminum material containing 1.0% by mass or more of Mg with an alkaline solution;
An anodizing step of forming an anodic oxide film on the surface of the aluminum material by electrolyzing the aluminum material in a weakly acidic to alkaline electrolyte without performing the neutralization step of removing the smut. A method for producing a surface-treated aluminum material. An etching step of attaching smut to the surface of the aluminum material by etching an aluminum material containing 1.0% by mass or more of Mg with an alkaline solution;
Anodization that forms an anodic oxide film on the surface of the aluminum material by electrolyzing the aluminum material in which the smut adheres to the surface in an amount of 0.01 g / m ² or more in a weakly acidic to alkaline electrolyte. A process for producing a surface-treated aluminum material. The method for producing a surface-treated aluminum material according to claim 1 or 2 , wherein the anodized film has a porosity of 5% or less. The method for producing a surface-treated aluminum material according to any one of claims 1 to 3 , further comprising a step of applying a silane coupling agent on the anodized film.