JP3239137B2 - Aluminum or its alloy and its surface treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to surface-treated aluminum or its alloys. More specifically, the present invention relates to a method for surface-treating aluminum or an alloy thereof in which the surface of aluminum or an alloy thereof surface-treated by anodizing treatment is further coated with a perfluoroalkyl compound.

[0002]

2. Description of the Related Art A surface treatment method for forming a corrosion-resistant oxide film on the surface of aluminum or its alloy by anodizing aluminum or its alloy is known. However, since the oxide film formed by this treatment method is porous, aluminum or its alloy has a high coefficient of friction on its surface and is inferior in wear resistance. For this reason, a surface treatment method of aluminum or an alloy thereof in which the surface of the anodic oxide film is further coated with a perfluoroalkyl compound or an acrylic resin composition has been proposed (Japanese Patent Publication No. 60-15718, Japanese Patent Publication No. 1-1947).
9).

[0003] After forming a porous anodic oxide film on the surface of aluminum or its alloys, Japanese Patent Publication No. 60-15718
The surface treatment method disclosed in Japanese Patent Application Laid-Open Publication No. H11-15064 is a method in which aluminum or an alloy thereof is subjected to secondary electrolysis in an electrolytic solution of an aqueous solution containing a perfluoroalkyl compound.
The surface treatment method disclosed in JP-A-19479 is a method of performing secondary electrolysis in an acidic electrolytic solution containing a low-polymerized acrylic resin composition polymerized at the anode. According to these methods, corrosion resistance and abrasion resistance are improved, and in particular, JP-B-60-15718.
According to the surface treatment method disclosed in Japanese Patent Application Laid-Open No. H10-107, water repellency and oil repellency are further improved.

[0004]

[Problems to be solved by the invention]
Aluminum or an alloy thereof formed on the surface with an anodic oxide film composited with an acrylic resin composition by the method of No. 9479 has a problem that water repellency and oil repellency are lacking. Further, since the coating agent of the perfluoroalkyl compound and the acrylic resin composition used in both of the above methods is dissolved in an electrolytic solution which is an aqueous solution, these coating agents are water-soluble. For this reason, when aluminum or its alloy formed with a water-soluble coating agent on the oxide film surface and in the fine pores is used in a humid or humid atmosphere, the coating agent is easily eluted, and the coating effect is lost. . That is, when aluminum or its alloy is used in a humid atmosphere or in water, when a perfluoroalkyl compound is used as a coating agent, its abrasion resistance, corrosion resistance, water repellency and oil repellency are disadvantageously reduced. Alternatively, when an acrylic resin composition is used as a coating agent, there is a disadvantage that its wear resistance and corrosion resistance are reduced.

It is an object of the present invention to provide a water-resistant aluminum or an alloy thereof having abrasion resistance, corrosion resistance, water repellency and oil repellency, and whose properties are not deteriorated even when used in a humid or humid atmosphere. An object of the present invention is to provide a surface treatment method.

[0006]

Means for Solving the Problems To achieve the above object, the aluminum or its alloy according to the present invention has a porous oxide film 11 formed on the surface of aluminum or its alloy 10 as shown in FIG. Water-insoluble perfluoroalkyl acrylyl having an alkyl group having 1 to 5 carbon atoms in the side chain
Monomer or perfluoroalkyl acrylate poly
Perfluoroalkyl compound 16 consisting of
4, the entire inner surface is adsorbed or filled into the entirety of the micropores 14,
Further, it is characterized by being formed on the surface of the film 11.

The surface treatment method of aluminum or its alloy according to the present invention comprises forming a porous anodic oxide film on the surface of aluminum or its alloy, and then forming a water-insoluble solution having an alkyl group having 1 to 5 carbon atoms on the side chain. This is a method in which aluminum or an alloy thereof is subjected to secondary electrolysis in a polar organic solvent containing an acidic perfluoroalkyl acrylate monomer. Another surface treatment method is a method of polymerizing a perfluoroalkyl acrylate monomer after the secondary electrolysis.

Hereinafter, the present invention will be described in detail. The workpiece of the present invention includes not only a pure aluminum material but also an alloy thereof. As the aluminum alloy, Al-Cu-Mg based, Al-
Si-based, Al-Zn-Mg-Cu-based processing alloy, Al
-Cu-Si system, Al-Si system, Al-Cu-Ni-M
g-based, Al-Mg-based, Al-Si-Cu-Ni-Mg-based casting alloys, and the like. As shown in FIG. 1, a porous oxide film 11 for protecting aluminum is formed on the surface of the base material aluminum or its alloy 10. The oxide film 11 comprises a barrier layer 12 formed on the surface of a base aluminum or its alloy 10 and a bulk layer 13 formed on the barrier layer. Barrier layer 1
2 is a dense and active amorphous alumina (Al ₂ O ₃ ), and the bulk layer 13 is a porous and extremely hard crystalline boehmite (Al ₂ O ₃ .H ₂ O) containing water. .

The fine pores 14 of the bulk layer 13 have 1 carbon atoms.
A water-insoluble perfluoroalkyl compound 16 having an alkyl group of 5 to 5 in its side chain is adsorbed on the entire inner surface thereof as shown in part A of FIG. Is filled throughout. Micropore 1 in each case
4, the perfluoroalkyl compound 16 penetrates and is adsorbed. The perfluoroalkyl compound 16 is also formed on the surface of the bulk layer 13. The perfluoroalkyl compound of the present invention is a water-insoluble compound having an alkyl group having 1 to 5 carbon atoms in a side chain. When the number of carbon atoms in the alkyl group is 6 or more, steric hindrance is caused in the molecular structure, polymerization becomes difficult, and the concentration of fluorine is relatively reduced, so that it is difficult to achieve the object of the present invention. Therefore, the alkyl group preferably has 3 or 4 carbon atoms. The perfluoroalkyl compound is a perfluoroalkyl acrylate monomer and a perfluoroalkyl acrylate polymer that is a polymer thereof. Next, the structural formula of the C4 perfluoroalkyl acrylate monomer is shown.

[0010]

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In order to produce the aluminum or its alloy, first, a known primary electrolysis is performed on the workpiece. This primary electrolysis is performed by using an aqueous solution of oxalic acid, sulfuric acid, or chromic acid as an electrolytic solution, and subjecting the workpiece to anodic treatment with a constant current in the electrolytic solution. As a result, the above-described anodic oxide film composed of the barrier layer and the bulk layer is formed on the surface of the base aluminum or its alloy. Next, aluminum or an alloy thereof on which an oxide film is formed is subjected to secondary electrolysis. The surface treatment method of the present invention is characterized by this secondary electrolysis. After the adhered water is sufficiently removed from the workpiece, the workpiece is placed in a polar organic solvent. Examples of the organic solvent include pyridine, a pyridine derivative, acetonitrile, dimethyl sulfate, N, N-dimethylacetamide,
N, N-dimethylformamide, dimethylsulfoxide, sulfolane, formamide, dimethoxyethane,
Examples thereof include propylene carbonate, dioxane, methanol, ethanol, γ-butyl lactone, nitrobenzene, tetrahydrofuran, and nitromethane. A conductive compound may be added to the organic solvent during the electrolysis. As the conductive compound, an inorganic acid (for example, HCl, H ₂ SO ₄ ,
HClO ₄ , BF ₄ ), organic acids (eg, sulfonic acids such as toluenesulfonic acid, trifluoromethylsulfonic acid, polystyrenesulfonic acid, carboxylic acids such as formic acid, acetic acid, polyacrylic acid), and organic bases (eg, pyridine,
Triethanolamine). In this organic solvent, a water-insoluble perfluoroalkyl acrylate monomer having an alkyl group having 1 to 5 carbon atoms in a side chain is previously dissolved. The side chain of the alkyl group having 1 to 5 carbon atoms increases the polarity of the monomer during electrolysis, and improves the adsorbability of the perfluoroalkyl compound to the inner surface of the coating micropores.

According to the surface treatment method of the present invention, the inside of the micropores and the surface of the coating can be coated in the form of a polymer in addition to the form of a monomer. In this case, it is preferable to dissolve the perfluoroalkyl acrylate monomer polymerization agent in the organic solvent. Examples of the polymerization agent include azobisisobutyronitrile, benzoyl peroxide and the like. The temperature of the electrolytic solution at the time of electrolysis may be room temperature, but in the case of a perfluoroalkyl acrylate monomer having low solubility, it may be heated. The current density during electrolysis is several mA / d in DC electrolysis.
adjusted to the range of m ² to several 100 mA / dm ² ,
A / dm ² or less is preferred.

[0013]

By the secondary electrolysis, the perfluoroalkyl compound is adsorbed on the fine pores of the anodic oxide film of aluminum or its alloy as the workpiece. Since this compound has an alkyl group having 1 to 5 carbon atoms in the side chain, the polarity at the time of electrolysis is increased, and the compound is quickly and firmly adsorbed to the entire fine pore. This adsorbed perfluoroalkyl compound gives the workpiece abrasion resistance,
Provides corrosion resistance, water repellency and oil repellency. Further, since the perfluoroalkyl compound is insoluble in water, the properties imparted do not deteriorate even when the workpiece is used in a humid atmosphere or in water. Further, when the perfluoroalkyl compound is a perfluoroalkyl acrylate monomer, if this monomer is in the form of a polymer, an anchor effect is produced on the adsorption surface of the workpiece, and the wear resistance and corrosion resistance are further improved.

[0014]

Next, examples of the present invention will be described together with comparative examples. <Example 1> A5052 material (5
0 × 20 × 2 mm) was prepared as a workpiece. After the workpiece is degreased, it is placed in a 15 wt% H ₂ SO ₄ electrolytic solution at 10 ° C., and the workpiece is subjected to DC 3 A / dm in this electrolytic solution.
^The primary electrolysis was performed at ² for 30 minutes to form a porous anodic oxide film on the surface of the workpiece. After the workpiece on which the oxide film was formed was washed with water, the attached moisture was sufficiently removed. Then C
8 perfluoroalkyl acrylate monomer (trade name:
EF-125M, manufactured by Tochem Products Co., Ltd.)
A pyridine solution containing wt% is prepared, the solution is used as an electrolytic solution, the work piece is used as an anode, and an aluminum plate is used as a counter electrode, and secondary electrolysis is performed for 10 minutes at a direct current of 50 A / dm ² to obtain an oxide film surface of the work piece. Was coated with a water-insoluble perfluoroalkyl compound.

Example 2 Instead of a pyridine solution containing C8 perfluoroalkyl acrylate monomer, C8
Perfluoroalkyl methacrylate monomer (trade name:
EF-135M, manufactured by Tochem Products Co., Ltd.)
Example 1 except that an acetonitrile solution containing wt% was used.
The surface of the oxide film of the workpiece was coated with a water-insoluble perfluoroalkyl compound in the same manner as in the above.

Example 3 Instead of a pyridine solution containing a C8 perfluoroalkyl acrylate monomer, a C4 perfluoroalkyl acrylate monomer represented by the above formula (1) (trade name: EF-C4-125M, Tochem Products Co., Ltd.) Was coated with a water-insoluble perfluoroalkyl compound in the same manner as in Example 1 except that an N, N-dimethylformamide solution containing 50% by weight of the same was used.

Example 4 Instead of a pyridine solution containing a C8 perfluoroalkyl acrylate monomer, trifluoroethyl acrylate (trade name: TFEA, Inc.)
The surface of the oxide film of the workpiece was coated with a water-insoluble perfluoroalkyl compound in the same manner as in Example 1 except that a dimethyl sulfoxide solution containing 50 wt% of Tochem Products was used.

Example 5 Instead of a pyridine solution containing a C8 perfluoroalkyl acrylate monomer, trifluoroethyl methacrylate (trade name: TFEMA,
The surface of the oxide film of the workpiece was coated with a water-insoluble perfluoroalkyl compound in the same manner as in Example 1 except that a formamide solution containing 50 wt% (manufactured by Tochem Products Co., Ltd.) was used.

Example 6 Instead of the pyridine solution containing C8 perfluoroalkyl acrylate monomer of Example 1, 50 wt% of C8 perfluoroalkyl acrylate monomer (trade name: EF-125M, manufactured by Tochem Products Co., Ltd.) was used. Secondary electrolysis was performed in the same manner as in Example 1 using a methanol solution containing 0.5 wt% of azobisisobutyronitrile as a polymerization agent. Thereafter, the electrolytic solution was heated to 70 ° C. and maintained for 2 hours to polymerize the above monomer.

<Example 7> Instead of the pyridine solution containing the C4 perfluoroalkyl acrylate monomer of Example 3, 50 wt% of C4 perfluoroalkyl acrylate monomer (trade name: EF-C4-125M, manufactured by Tochem Products Co., Ltd.) % And azobisisobutyronitrile as a polymerization agent in an ethanol solution containing 0.5 wt%, and secondary electrolysis was performed in the same manner as in Example 1. Thereafter, the electrolytic solution was heated to 70 ° C. and maintained for 2 hours to polymerize the above monomer.

<Comparative Example 1> The same aluminum alloy as in Example 1 was used as a workpiece, and primary electrolysis was performed in the same manner as in Example 1 to form an oxide film on the surface of the workpiece. Name: Surflon s11
1, an aqueous solution containing 0.5 wt%)
Using this solution as an electrolytic solution, the workpiece on which an oxide film was formed was used as an anode, and an aluminum plate was used as a counter electrode, and secondary electrolysis was performed at 10 ° C. and a direct current of 50 A / dm ² for 10 minutes to obtain an oxide film surface of the workpiece. Coated with a water-soluble perfluoroalkyl compound.

<Comparative Example 2> The same aluminum alloy as in Example 1 was used as a workpiece, and primary electrolysis was performed in the same manner as in Example 1 to form an oxide film on the surface of the workpiece. An aqueous solution was prepared by adding and mixing 5 g of dissolved aluminum, 5 g of nickel sulfate and 10 g of an acrylic resin. Using this solution as an electrolytic solution, the workpiece on which the oxide film was formed was used as an anode, and an aluminum plate was used as a counter electrode to form
Secondary electrolysis was performed at 1.1 ° C. and a direct current of 1.1 A / dm ² for 30 minutes to coat the surface of the oxide film of the workpiece with a water-soluble perfluoroalkyl compound.

<Comparative Test and Evaluation> The surface-treated workpieces of Examples 1 to 7 and Comparative Examples 1 and 2 were washed with water, dried, and immediately after the surface treatment and 50 ° C. water. 1 in
The workpiece was immersed for 0 hours, and the contact angle of water with a goniometer and the static friction coefficient of the workpiece with copper as a mating material were measured by a goniometer. Table 1 shows the results.

[0024]

[Table 1]

As is clear from Table 1, the workpieces of Examples 1 to 7 exhibited good values of the contact angle and the coefficient of friction immediately after the surface treatment and after immersion in water for 10 hours. Excellent lubricity. In addition, each measured value hardly changed, and it was found to have high water resistance. On the other hand, the work piece of Comparative Example 1 was excellent in water repellency immediately after the surface treatment without a difference in contact angle from Examples 1 to 7, but after immersion in water for 10 hours, the contact angle and the coefficient of friction were low. It was found that each of them significantly decreased, the water repellency and the lubricity decreased, and the water resistance was poor. It was also found that the workpiece of Comparative Example 2 was inferior in water repellency both immediately after the surface treatment and after immersion in water for 10 hours, and that each measured value was slightly deteriorated after immersion in water.

The surface-treated workpiece of Example 3 was embedded in an epoxy resin, cut with the cured epoxy resin, and the cut surface was polished. The cross section was analyzed by an electron probe microanalyzer (EPMA). Then, the adsorption state of C4 perfluoroalkyl acrylate monomer in the micropores of the oxide film was examined. The result is shown in FIG. In FIG. 2, the horizontal axis indicates the thickness direction in which the workpiece enters the substrate from the surface, and the vertical axis indicates the strength. The solid line in the figure shows the concentration distribution of aluminum, and the broken line shows the concentration distribution of fluorine. As is apparent from FIG. 2, C4 perfluoroalkyl acrylate monomer was detected over a depth of about 25 μm in the oxide film over a depth of about 25 μm, and the C4 perfluoroalkyl acrylate monomer was adsorbed on the entire inner surface including the deep portion of the micropore. You can see that

[0027]

As described above, the conventional Japanese Patent Publication No. 1-1
While aluminum or an alloy thereof surface-treated by the method of No. 9479 has no oil repellency and water repellency, the aluminum or alloy thereof of the present invention has water repellency and oil repellency in addition to abrasion resistance and corrosion resistance. Is given. Japanese Patent Publication No. 60-15718 and Japanese Patent Publication No. 1-194
When aluminum or an alloy thereof surface-treated by the method of JP-A-79 is used in a humid or humid atmosphere, a perfluoroalkyl compound or an acrylic resin composition is easily eluted, whereas a perfluoroalkyl compound of the present invention is not. Since it is water-soluble, it is water-resistant and has an excellent effect that the imparted abrasion resistance, corrosion resistance, water repellency and oil repellency do not decrease.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of an aluminum film portion on which an anodized film of the present invention is formed.

FIG. 2 is a line analysis diagram of a cross section of the surface-treated aluminum alloy by an electron probe microanalyzer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Aluminum or its alloy 11 Oxide film 14 Micropore 16 Water-insoluble perfluoroalkyl compound

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shinya Takenuki 4-6-23 Takanawa, Minato-ku, Tokyo Inside Tochem Products Co., Ltd. (56) References JP-A-3-100182 (JP, A) (58) ) Surveyed field (Int.Cl. ⁷ , DB name) C25D 11 / 18,11 / 20

Claims (4)

(57) [Claims] A porous oxide film (11) is formed on the surface of aluminum or its alloy (10), and a water-insoluble perfluoroalkyl compound (16) having an alkyl group having 1 to 5 carbon atoms in a side chain is formed. Aluminum or an alloy thereof adsorbed on the entire inner surface of the micropores (14) or filled in the entire micropores (14) and formed on the surface of the coating (11);
Fluoroalkyl compound (16) is a perfluoroalkyl
Aluminum or an alloy thereof, which is an acrylate monomer . 2. On the surface of aluminum or its alloy (10)
A porous oxide film (11) is formed.
-Insoluble perfluoroalkylation with a side group
The compound (16) is adsorbed on the entire inner surface of the micropores (14) or
Filled in the entire pores (14), and on the surface of the coating (11)
Formed aluminum or an alloy thereof,
Fluoroalkyl compound (16) is a perfluoroalkyl
Aluminum or an alloy thereof, which is an acrylate polymer . 3. A polar organic solvent containing a water-insoluble perfluoroalkyl acrylate monomer having an alkyl group having 1 to 5 carbon atoms in a side chain after forming a porous anodic oxide film on the surface of aluminum or an alloy thereof. Wherein the aluminum or its alloy is subjected to secondary electrolysis in a surface treatment method of aluminum or its alloy. 4. After forming a porous anodic oxide film on aluminum or its alloy, in a polar organic solvent containing a water-insoluble perfluoroalkyl acrylate monomer having an alkyl group having 1 to 5 carbon atoms in a side chain. A surface treatment method for aluminum or its alloy, comprising subjecting said aluminum or its alloy to secondary electrolysis and further polymerizing said perfluoroalkyl acrylate monomer.