JPH11222683A - Surface treated aluminum alloy sheet and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface treated aluminum alloy sheet excellent in the adhesion of a resin film in such a manner that the peeling of the resin film does not occur even in hot water and water vapor and preferably excellent in corrosion resistance. SOLUTION: In an aluminum alloy sheet contg., by weight, 0.5 to 5.0% Mg, the surface is subjected to roughening treatment into a rugged shape, and its substantial area is regulated to >=2 cm<2> per cm<2> of the apparent surface area. Moreover, in the case the parts in which the depth from the surface is >=0.05 μm are defined as recessed parts, and the surface parts including indentations in which the depth from the surface is <0.05 μm are defined as projecting parts, the apparent surface area of the projecting parts is regulated to 10 to 90% of the total surface, and the depth of the recessed parts is regulated to <=0.5 μm. For producing such aluminum alloy sheet, a treating soln. contg. phosphoric acid, chromic acid and hydrofluoric acid, and in which the weight ratio of the hydrofluoric acid to the chromic acid is regulated to 0.23 to 0.7 is used, and the surface of the aluminum alloy sheet is subjected to etching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated aluminum alloy sheet suitable for a packaging container or the like used with a resin film or the like coated on the surface thereof, and in particular, has excellent adhesion to a film such as a resin film. The present invention relates to a surface-treated aluminum alloy plate.

[0002]

2. Description of the Related Art Aluminum sheets and aluminum alloy sheets are lightweight and have excellent properties such as moldability and corrosion resistance.
It is widely used as a material for building materials and side plates of electrical products.

[0003] In practical use, many of them have been subjected to surface treatment and resin coating for the purpose of improving coating film adhesion, corrosion resistance and decoration of the material. For example, when used in a packaging container, before or after forming into a container, the surface of an aluminum or aluminum alloy plate is subjected to a chromate phosphate treatment or a zirconium-based surface treatment, and then the surface is made of resin. Coated with a layer.

[0004] Such a resin coating is obtained by subjecting a coating liquid in which an epoxy-based, phenol-based or vinyl chloride-based resin is dissolved or dispersed in an appropriate solvent to a chromate phosphate treatment or a zirconium-based surface treatment. After applying to the surface of the aluminum plate, remove the solvent from the coating solution by heating,
This is performed by a method of curing the resin layer.

However, in such a resin coating method involving the removal of a solvent, it is necessary to take measures against environmental pollution.
Further, since it is necessary to lengthen a heating furnace for removing the solvent and baking the paint to cure the resin layer, a resin coating method that does not use a solvent is desired.

As one of such resin coating methods, there is a method of laminating a resin film on the surface of a metal material, and among them, a heat fusion lamination method has attracted attention as a resin coating method using no solvent. In this heat fusion lamination method, the metal material is heated to a temperature near or above the melting temperature of the resin film, the resin film is supplied on the heated metal material, and the metal film is heated using a press roller or the like. This is a method of fusing a film on a metal material under pressure.

In such a resin film laminating method as well, the adhesion between the metal material and the film is strengthened,
In order to be able to withstand processing such as molding after lamination, it is necessary to perform a surface treatment on the metal material before lamination.

In general, various methods are known for surface treatment of an aluminum material for improving the adhesion to a resin. Among them, boehmite treatment, anodic oxidation treatment, phosphoric acid chromate treatment, and chromic acid treatment are known. Chromate treatment is typical.

These surface treatments are appropriately selected and used in accordance with the characteristics required for various uses. For example, in the case of a lid material of a packaging container, coating film adhesion, corrosion resistance, food hygiene and mass production. Phosphoric acid chromate treatment is applied from the viewpoint of properties.

[0010]

However, usually,
As a result of investigating the film adhesion of an aluminum plate obtained by laminating a polyester film using heat and adhesiveness of the film using an aluminum material subjected to a phosphoric acid chromate treatment, the plate is not processed Even if the adhesion is good, the film peels off when exposed to hot water or steam after drawing and overhanging, packaging containers that are hot-filled and retort sterilized, vending machines It was found that these materials were not suitable as materials for packaging containers stored at high temperatures among vendors.

The present invention has been made in view of the above-mentioned problems, and has excellent adhesiveness of the resin film so that the resin film does not peel off even in hot water or steam, and preferably has high corrosion resistance. An object is to provide an excellent surface-treated aluminum alloy plate.

[0012]

The surface-treated aluminum alloy sheet according to the present invention is an aluminum alloy sheet containing 0.5 to 5.0% by weight of Mg, the surface of which is roughened in an uneven manner. The surface area is ² cm ² or more per 1 cm ^{2 of} apparent surface area, and the portion whose depth from the surface is 0.05 μm or more is a concave portion, and the depth from the surface is less than 0.05 μm. When the surface portion containing is a convex portion, the apparent surface area of the convex portion is 10 to 90% of the entire surface, and the depth of the concave portion is 0.5 μm or less.

As a result of intensive experiments and research conducted by the inventors of the present application to solve the above-mentioned problems, the shape of the irregularities formed on the surface of the aluminum alloy plate whose surface has been roughened has been determined to be appropriate. As a result, it has been found that the adhesiveness of the resin film can be significantly improved. In the present invention, the apparent surface area is a surface area assuming that the surface of the aluminum alloy plate is a smooth surface,
The substantial surface area is a surface area in consideration of the area of irregularities formed on the surface.

In the present invention, the substantial surface area,
By appropriately defining the surface occupancy of the convex portion and the depth of the concave portion, the adhesiveness of the resin film can be improved.

In the present invention, the surface roughening treatment may be etching with a treatment solution containing phosphoric acid, chromic acid and hydrofluoric acid. A film containing chromium, phosphorus and oxygen as main components is formed on the surface of the aluminum alloy plate etched by such a treatment liquid, thereby improving corrosion resistance.

The method for producing a surface-treated aluminum alloy sheet according to the present invention is characterized in that phosphoric acid, chromic acid, and hydrofluoric acid are contained, and the ratio of the weight of the hydrofluoric acid to the weight of the chromic acid is 0.23 to 0. Mg using a processing solution that is 0.7
The method further comprises a step of etching the surface of the aluminum alloy plate containing 0.5 to 5.0% by weight to roughen the surface of the aluminum alloy plate.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The surface-treated aluminum alloy sheet according to the present invention will be further described below. First, the surface shape of the surface-treated aluminum alloy sheet will be described.

The adhesion of the film largely depends mainly on three types of bonding force: mechanical bonding force, chemical bonding force and intermolecular force.

In order to improve the adhesion between the film and the aluminum alloy plate, it is necessary to improve any of the above three types of bonding force.

A concave portion is formed on the surface of the surface-treated aluminum alloy sheet according to the present invention, and the improvement of the film adhesion of the present invention can be achieved by improving the adhesion between the film and the aluminum alloy sheet by improving the mechanical bonding force. This is achieved by: Here, the mechanical coupling force is also called an anchor effect, and is a force generated when a film is caught on a concave portion or the like of an aluminum alloy plate.

When the depth from the surface of the concave portion exceeds 0.50 μm, the laminated resin film does not reach the bottom of the concave portion, and the resin film does not catch on the concave portion. For this reason, the mechanical coupling force decreases. Therefore,
The depth of the concave portion from the plate surface is 0.50 μm or less.

However, when the apparent surface area of the convex portion, which is a surface portion including a dent having a depth of less than 0.05 μm from the surface, exceeds 90% of the entire surface, the concave portion is insufficient, so that the mechanical coupling is insufficient. The force is weakened, and the desired adhesion improving effect cannot be obtained. On the other hand, the apparent surface area of the convex portion is 1% of the entire surface.
If it is less than 0%, the number of convex portions is insufficient, so that the mechanical bonding force is weakened, and the desired effect of improving the adhesion cannot be obtained.
Therefore, the apparent surface area of the convex portion is 10 to 90 of the entire surface.
%. Further, even when substantial surface area of the aluminum alloy plate is less than the surface area 1 cm ² per 2 cm ² apparent,
The mechanical bonding force is weak, and the desired effect of improving the adhesion cannot be obtained. Therefore, the substantial surface area of the aluminum alloy plate is set to ² cm ² or more per 1 cm ² of apparent surface area.

Next, a method of manufacturing the above-mentioned surface-treated aluminum alloy sheet will be described. In order to manufacture the above-mentioned surface-treated aluminum alloy plate, it is necessary to etch the aluminum alloy plate with a treatment solution containing phosphoric acid, chromic acid and hydrofluoric acid. Generally, a treatment solution containing phosphoric acid, chromic acid and hydrofluoric acid is used as a phosphoric acid chromate treatment solution. Hydrofluoric acid has the effect of accelerating the formation of a film in the phosphoric acid chromate treatment and the effect of etching the surface of the aluminum alloy plate prior to the formation of the film, which has the effect of roughening the surface. In order to obtain such an effect, it is necessary to set the weight concentration ratio of hydrofluoric acid to chromic acid to 0.23 to 0.7. Is insufficient, and the desired effect cannot be obtained. On the other hand, if the weight concentration ratio exceeds 0.7, the etching becomes excessive, so that the area occupied by the convex portion is less than 10%, or the concave portion is formed in a region whose distance from the plate surface is 0.05 to 0.50 μm. No part is formed, and the desired effect cannot be obtained. Therefore, the ratio of the weight of hydrofluoric acid to the weight of chromic acid in the treatment liquid is 0.23 to 0.7.

When the aluminum alloy plate is etched by the above-described method, a film containing chromium, phosphorus and oxygen as main components is formed on the surface of the aluminum alloy plate. This coating has the effect of improving the corrosion resistance of the aluminum alloy plate without inhibiting the adhesion of the film. In order to obtain good corrosion resistance, the chromium content in the coating is preferably 5 to 60 (mg / m ² ), and particularly preferably 10 to 40 (mg / m ² ).

The existence form of Mg in the aluminum alloy differs depending on the chemical composition of the alloy, the heat history received, and the like. For example, it exists as a solid solution in an aluminum alloy or forms a compound with Al or Si contained in the alloy. Further, it may be diffused to the surface by heating and exist in an oxidized state. On the other hand, Mg has a property of being easily dissolved in an acid, and is also easily dissolved in the above-mentioned processing solution containing phosphoric acid, chromic acid and hydrofluoric acid, and assists in etching of an aluminum alloy. Mg also has the effect of improving the strength of the aluminum alloy plate. For example, to be used for a member such as a packaging container, the Mg content in the aluminum alloy needs to be 0.5 to 5.0% by weight.

[0026]

EXAMPLES Examples of the present invention will be specifically described below in comparison with comparative examples that fall outside the scope of the claims.

First, JIS A5005 having a thickness of 0.3 mm and a width of 250 mm as an aluminum alloy plate.
P, a rolled coil shown in JIS A5052P or JIS A5182P was prepared and used as a test material. Next, each test material was degreased using an alkaline degreasing solution having a pH of about 10 to 13, and then subjected to a surface treatment using a treatment solution shown in Table 1 below and dried. As a result, a film having a chromium content shown in Table 1 below was formed on the surface of each test material.

[0028]

[Table 1]

Next, Examples 1 to 5 and Comparative Examples 7 to 9
Using the obtained surface-treated aluminum alloy sheet, the sheet was heated so that the ultimate temperature of the sheet was 190 ° C., and immediately thereafter, an adhesive polyester film (crystal melting point: 180 ° C., glass (Transition point: 58 ° C., thickness: 10 μm) was pressed with a press roller to produce a resin film laminate.

In Example 6 and Comparative Example 10, the obtained surface-treated aluminum alloy sheet was used, and the sheet was heated so that the ultimate temperature of the sheet became 200 ° C., and immediately applied to both surfaces of the sheet. Polyester resin (melting point: 230
° C, intrinsic viscosity: 0.70 (deciliter / g)) was melt-pressed using an extrusion laminator. In addition, immediately 50 ℃
It was cooled to the following to produce an extruded resin film laminate.

Next, the resin film laminate and the extruded resin film laminate thus manufactured were drawn at a drawing ratio of 1.6.

Thereafter, the evaluation of the surface state and the evaluation of the film adhesion were performed. In the evaluation of the surface state, the actual surface area per 1 cm ² of the apparent surface area, the ratio of the apparent surface area of the convex portion to the entire surface, and the depth of the concave portion from the surface were measured.

Here, the surface area is a value determined by the BET method (a measuring method using a BET adsorption isotherm). The ratio of the convex portions was calculated from an electron micrograph taken at a magnification of 10,000 times. Specifically, a photograph (actual area 16μ)
m ² ) is divided into 400 grids (0.2 μm square per square)
Then, a square having a concave portion that was not subjected to dissolution due to surface treatment using a treatment solution containing phosphoric acid, chromic acid, and hydrofluoric acid is regarded as a convex portion, and the ratio of the number is referred to as the ratio of the convex portion. And The depth of the concave portion from the plate surface was obtained from an electron micrograph taken at a magnification of 20,000 times with the observation sample inclined at 45 degrees.

The film adhesion was evaluated by exposing the resin film to water vapor at 125 ° C. for 30 minutes using a pressure cooker and peeling off the resin film. The results are shown in Table 2 below. The depth of the concave portion is an average value.

[0035]

[Table 2]

As shown in Table 2 above, in Examples 1 to 6, a treatment liquid having an appropriate composition was used at the time of etching the aluminum alloy plate, and irregularities having an appropriate shape were formed on the plate surface. , Surface condition and film adhesion were good.

On the other hand, in Comparative Examples 7 and 10, the weight concentration ratio of hydrofluoric acid to chromic acid in the treatment liquid was less than the lower limit of the range of the present invention, and the ratio of the convex portions formed on the plate surface was Since the upper limit of the range was exceeded, the film adhesion was poor.

In Comparative Example 8, the weight concentration ratio of hydrofluoric acid to chromic acid in the treatment liquid exceeded the upper limit of the range of the present invention, and the ratio of the convex portions formed on the plate surface was lower than the lower limit of the range of the present invention. , The film adhesion was poor.

In Comparative Example 9, the weight concentration ratio of hydrofluoric acid to chromic acid in the treatment liquid exceeded the upper limit of the range of the present invention, and the ratio of the convex portions formed on the plate surface was lower than the lower limit of the range of the present invention. , The film adhesion was poor.

In Comparative Example 11, the weight concentration ratio of hydrofluoric acid to chromic acid in the treatment liquid was less than the lower limit of the present invention, and the actual surface area per 1 cm ^{2 of} apparent surface area was less than the lower limit of the present invention. Therefore, the film adhesion was poor.

[0041]

As described in detail above, according to the present invention,
Even in hot water or steam, the adhesion of the resin film is so excellent that the resin film does not peel off.
Therefore, by using the surface-treated aluminum alloy plate according to the present invention, in addition to being applicable as various packaging container materials, daily necessities used in film lamination or melt-laminated resin are used ,
The present invention has an excellent effect that it can be applied to building materials and side plates of electric or electronic products. Further, by forming a film containing chromium, phosphorus and oxygen on the surface, corrosion resistance can be improved.

According to the method of the present invention, an aluminum alloy plate is etched with a treatment liquid having an appropriate chemical composition, so that an aluminum alloy plate having excellent adhesion as described above can be manufactured.

Claims (3)

[Claims] 1. An aluminum alloy sheet containing 0.5 to 5.0% by weight of Mg, the surface of which is roughened to have an irregular surface, and the actual surface area of which is apparent surface area 1c.
² cm ² or more per m ² , a portion having a depth from the surface of 0.05 μm or more was a concave portion, and a surface portion including a dent having a depth from the surface of less than 0.05 μm was a convex portion. When the apparent surface area of the convex portion is 10
A surface-treated aluminum alloy plate, wherein the depth of the concave portion is 0.5 μm or less. 2. The surface-treated aluminum alloy plate according to claim 1, wherein the uneven surface roughening treatment is etching with a treatment solution containing phosphoric acid, chromic acid and hydrofluoric acid. 3. Using a treatment solution containing phosphoric acid, chromic acid, and hydrofluoric acid, wherein the ratio of the weight of the hydrofluoric acid to the weight of the chromic acid is from 0.23 to 0.7.
A method for producing a surface-treated aluminum alloy sheet, comprising the step of etching the surface of an aluminum alloy sheet containing 0.5 to 5.0% by weight to roughen the surface of the aluminum alloy sheet. .