JP2000104021A - Aluminum coating material for can top and preparation thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum coating material for a can top having excellent corrosion resistance by combining a titanium-based chemical treatment film having a specific property with a water-based coating material. SOLUTION: In the coating material for aluminum to be used as the can top material by providing a chemical treatment film on the surface of an aluminum or aluminum alloy plate and forming a coated film on this chemical treatment film, the chemical treatment film is composed of a titanium-based chemical treatment film with an amount of the titanium adhered of 3-60 mg/m2, and the coated film contains from 0.1 to less than 1.0 wt.% phenol-formaldehyde resin in terms of the solids content of the coated film. This coating material enables coating by a chromium-free chemical treatment and an organic solvent- free water-based coating material and can contribute to the prevention of environmental pollution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum coating material for a can lid of a beverage can or a food can and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, aluminum coating materials for can lids of beverage cans and food cans are obtained by degreasing and etching an aluminum plate or an aluminum alloy plate, forming a chemical conversion coating by phosphoric acid chromate treatment, and forming a vinyl chloride resin paint. It is manufactured by forming and drying a coating film using a solvent-based paint such as an epoxyphenol resin-based paint, and is supplied as a can lid by forming the obtained aluminum coated plate into a can lid mold.

However, in recent years, from the viewpoints of environmental problems and resource saving, problems have also arisen in the chemical conversion treatment and coating treatment of aluminum materials for can lids. That is,
Phosphate chromate treatment agents that have been used for chemical conversion
Since harmful hexavalent chromium is contained, wastewater treatment for eliminating the harm is necessary, and there is a problem that waste sludge treatment requires a large cost.

[0004] Further, conventionally used solvent-based paints include:
The working environment at the time of painting is deteriorated, and the problems of waste gas contamination and odor during drying and baking occur. The solvent contained in the paint in a large amount evaporates at the time of drying and does not remain in the dried film, which is problematic in terms of resource saving.

In order to solve the problems of the chemical conversion treatment agent, a zirconium phosphate-based chemical conversion treatment agent or a titanium phosphate-based chemical conversion treatment agent (Japanese Patent Application Laid-Open No. 9-20984) is used to form a coating base of an aluminum material. A water-based paint and a high-solid paint have been developed to solve the problems of the solvent-based paint.

[0006] However, when strict quality is required not only for the adhesion of the coating film but also for the corrosion resistance when the contents are stored for a long period of time, as in the case of a can lid material, a zirconium phosphate-based material is used. A coating obtained by applying a water-based paint using a titanium phosphate-based chemical conversion coating as a coating base does not necessarily have sufficient corrosion resistance as compared with a conventional coating obtained by coating a solvent-based coating on a phosphoric acid chromate-treated coating.

Hitherto, as a means for improving the adhesion and corrosion resistance of a coating film, a method of adding a phenol resin to a coating material has been known, and several proposals have been made. For example, an aqueous resin dispersion has been proposed in which 3 to 100 parts by weight of a methylolated phenol compound is blended with respect to 100 parts by weight of an acrylic resin-aromatic epoxy resin partial combination (JP-A-4-363179). A water-based paint in which 5 to 30 parts by weight of a phenol formaldehyde resin obtained by reacting phenolic acid with formaldehyde is dispersed and dissolved in 100 parts by weight of a carboxyl group-containing acrylic-modified epoxy resin has also been proposed. (JP-A-4-363179)

However, when these water-based paints are applied on a chemical conversion treatment film and dried to form a coating film, since the phenol resin is added in a large amount, curing of the coating film proceeds,
Since the processability of the coating film is significantly deteriorated, there is a problem that it is difficult to apply as a paint for a can lid.

[0009]

SUMMARY OF THE INVENTION The present inventors have found that the present invention has been applied to a zirconium phosphate-based or titanium phosphate-based chemical conversion coating formed on the surface of aluminum or an aluminum alloy material, and has been applied to a can lid. In order to find a water-based paint with sufficient corrosion resistance even in the case, based on the water-based paint that has been proposed previously, further experiments and examinations were conducted on the properties of the chemical conversion coating, and the relationship between the composition of the paint and the corrosion resistance. The present invention was achieved as a result of researching a combination of a chemical conversion coating film and a coating film capable of giving excellent corrosion resistance to aluminum materials for use. An object of the present invention is to provide an aluminum coating material for a can lid which has excellent corrosion resistance even when the coating is performed, and a method for producing the same.

[0010]

According to a first aspect of the present invention, there is provided an aluminum coating material for a can lid according to the present invention, wherein a chemical conversion coating is provided on the surface of an aluminum or aluminum alloy plate. In an aluminum coating material formed by forming a coating film on a film and used as a can lid material, the chemical conversion coating film has a titanium adhesion amount of 3 to 60 mg.
/ M ² of a titanium-based chemical conversion coating film, wherein the coating film is a phenol formaldehyde resin in an amount of 0.1 to the solid content of the coating film.
It is characterized in that it is contained at a ratio of not less than 1.0% by weight and not more than 1.0% by weight.

According to a second aspect of the present invention, there is provided an aluminum coating material for a can lid according to the first aspect, wherein the aluminum or aluminum alloy plate has a titanium-based material containing phosphate ions, a titanium compound and a fluoride on the surface thereof. It is characterized in that a chemical conversion coating is formed.

In order to achieve the object of the present invention, a method for producing an aluminum coating material for a can lid according to claim 3 of the present invention comprises:
Forming a titanium-based chemical conversion coating containing phosphate ions, a titanium compound, and fluoride on the surface of an aluminum or aluminum alloy plate and having a titanium adhesion amount of 3 to 60 mg / m ² ; A water-based paint containing a phenol formaldehyde resin in a ratio of 0.1% by weight or more and less than 1.0% by weight based on the solid content of the coating film.

[0013]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a titanium-based chemical conversion coating is formed as a coating base, and a phenolic phenolic resin, for example, a phenol obtained by reacting phenolic acid with formaldehyde, is used as a curing resin to be added to an aqueous paint. By using a formaldehyde resin, a coating film having excellent corrosion resistance can be obtained with a very small addition amount of a phenol resin without lowering workability.

As a method of forming the titanium-based chemical conversion treatment film, a reactive titanium-based chemical conversion treatment is preferable.
Known methods such as spraying can be applied. The titanium adhesion amount in the titanium-based chemical conversion treatment film is 3 to 60 mg / m ^2.
If the amount of titanium is less than 3 mg / m ² , the effect is small, and if it exceeds 60 mg / m ² , corrosion is likely to occur due to cohesive failure in the titanium chemical conversion coating.

A water-based paint is applied on the titanium-based chemical conversion coating film. The water-based paint preferably contains a phenol formaldehyde resin as a curing resin among phenolic phenol resins, and other resins such as a melamine resin. In the case of using, a desired coating film performance cannot be obtained.

In the water-based paint, phenol formaldehyde resin is contained in an amount of 0.1% by weight or more to 1.0% by weight based on the solid content of the paint.
It is preferable to include the phenol formaldehyde resin in a proportion of less than 0.1% by weight to less than 1.0% by weight based on the solid content of the coating. . If it is less than 0.1% by weight, the corrosion resistance of the coating film is not sufficient, and if it is 1.0% by weight or more, the workability of the aluminum coating material tends to be deteriorated.

The molecular weight range of the phenol formaldehyde resin to be applied is preferably from 250 to 1500. If the molecular weight is less than 250, the stability of the resin is lowered, the amount of water extracted from the cured coating film is increased, and a hygienic problem is likely to occur. Become. When the molecular weight exceeds 1500, the adhesion and corrosion resistance of the coating film are liable to be reduced, the affinity for water is also reduced, and it is difficult to uniformly dissolve or disperse in the water-based paint.

[0018]

Hereinafter, examples of the present invention will be described in comparison with comparative examples. Example 1 Si: 0.11% (% by weight, the same applies hereinafter), Fe: 0.2
4%, Cu: 0.05%, Mn: 0.28%, Mg:
4.5%, Cr: 0.03%, Zn: 0.02%, T
i: A JIS 5182 aluminum alloy ingot containing 0.02%, the balance being Al and unavoidable impurities, was homogenized by a conventional method, hot-rolled to a thickness of about 3 mm, and then 1.2 mm thick. Cold-rolled, re-crystallized by rapid heating in a continuous annealing furnace, and further cold-rolled to a thickness of 0.3 mm, and using the obtained aluminum alloy plate as a test material, by the following processing steps Chemical conversion treatment and coating treatment were performed. Degreasing: A commercially available medium alkaline etching type degreasing agent (Nippon Paint Co., Ltd., registered trademark "Surf Cleaner" 3)
(2% aqueous solution of 22N-8) at 70 ° C. for 30 seconds.

Rinsing: Dipping in tap water at room temperature for 30 seconds. Chemical conversion treatment: Titanium phosphate chemical conversion treating agent containing 3.5 parts by weight of phosphate ion, 0.5 to 1.5 parts by weight of titanium ion and 7.7 parts by weight of fluorine ion No. 20984) corresponding to the surface treatment solution described in JP-A-20984, except that the accelerator is removed.
The immersion treatment was performed by changing the immersion time to form a chemical conversion treatment film. Rinsing: Immerse in tap water at room temperature for 30 seconds.

Rinse with deionized water: Spray-wash in deionized water (conductivity: 0.2 μS / cm) at room temperature for 5 seconds. Draining drying: performed at 80 ° C. for 300 seconds. Coating treatment: A coating treatment was performed under the conditions shown in Table 1 using an acrylic-modified epoxy resin (water-based paint) to which a cured resin was added. In addition, the molecular weight of the cured resin was adjusted to a range of 300 to 1200.

[0021]

[Table 1]

The prepared aluminum alloy coated plate (test material) was cut with a sharp cutter to reach the substrate, subjected to DuPont impact processing, and the end face was coated with a silicone resin (available from Shin-Etsu Chemical Co., Ltd., KE- 45-TS) and immersed in a corrosion test solution (containing 5 g / l of citric acid and 5 g / l of sodium chloride) at 40 ° C. for 4 weeks, and visually observed the corrosion state of the cross-cut portion and the impact-processed portion. The punch diameter in DuPont impact processing was 1/2 inch, the weight was 1 kg, and the drop height was 20 cm.

Table 2 shows the results of the corrosion test. As can be seen from Table 2, all the test materials according to the present invention exhibited excellent corrosion resistance and workability.

[0024]

[Table 2] << Table Note >> Corrosion resistance ○: No corrosion Workability ○: No crack

Comparative Example 1 In the same manner as in Example 1, an aluminum alloy plate (JIS A5182, thickness 0.3 m) having the same composition as in Example 1 was used.
m) was prepared, and this was used as a test material.
Commercially available phosphate chromate treatment agent (Nippon Paint Co., Ltd.)
2.5 / of registered trademark "Al Surf" 401/45
(0.5% aqueous solution), and treated in the same manner as in Example 1. The coating treatment was performed under the conditions shown in Tables 1 and 3.

[0026]

[Table 3]

The prepared aluminum alloy coated plate (test material) was subjected to a DuPont impact working and corrosion test in the same manner as in Example 1 to evaluate the corrosion resistance and workability.
Table 4 shows the test results.

[0028]

[Table 4] << Table Note >> Corrosion resistance ○: No corrosion △: Slight corrosion ×: Remarkable corrosion Workability ○: No crack △: Some crack X: Crack

As shown in Table 4, the test material No. No. 6 has a low content of the phenol formaldehyde resin, and thus has poor corrosion resistance. Test material No. 7 has a high content of a phenol formaldehyde resin, and thus has poor processability. Test material No. 8, no. In No. 9, the corrosion resistance was lowered because the titanium adhesion amount in the chemical conversion treatment film was not appropriate. Test material No. In Nos. 10 to 14, the use of a cured resin other than the phenolic phenolic resin resulted in poor corrosion resistance.

Test material No. No. 15 is obtained by applying the water-based paint of the present invention on the existing phosphoric acid chromate-treated film, and is inferior in workability. Test material No. Reference numeral 16 shows a conventional phosphoric acid chromate-treated film coated with a conventional solvent-based paint. The test material No. In 3, a coating material was prepared using a water-based paint in which the molecular weight of the phenol formaldehyde resin was adjusted to 1700, and the dispersion of the cured resin in the water-based paint was slightly uneven. Minor corrosion occurred.

[0031]

According to the present invention, an aluminum coating material for a can lid having excellent corrosion resistance is provided by combining a titanium-based chemical conversion treatment film having a specific property and a water-based paint. ADVANTAGE OF THE INVENTION According to this invention, the chemical conversion treatment which does not contain chromium, and the coating treatment by the aqueous paint which does not have an organic solvent are attained, and can contribute to prevention of environmental pollution.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // (C09D 201/00 161: 06)

Claims (3)

[Claims] An aluminum or aluminum alloy sheet is provided with a chemical conversion coating on the surface thereof, and a coating is formed on the chemical conversion coating. In an aluminum coating material used as a can lid material, the chemical conversion coating is titanium. 3 as adhesion amount
To 60 mg / m consists of ^two titanium-based chemical conversion film, wherein the coating film comprising a proportion of less than 0.1 wt% to 1.0 wt% of phenol formaldehyde resin relative to the solid content of the coating Aluminum coating material for can lids. 2. The aluminum for can lid according to claim 1, wherein a titanium-based chemical conversion coating containing phosphate ions, a titanium compound and fluoride is formed on the surface of the aluminum or aluminum alloy plate. Painting material. 3. A titanium-based chemical conversion treatment film containing phosphate ions, a titanium compound and fluoride and having a titanium adhesion amount of 3 to 60 mg / m ² is formed on the surface of an aluminum or aluminum alloy plate. On the chemical conversion coating,
A method for producing an aluminum coating material for a can lid, characterized by applying an aqueous paint containing a phenol formaldehyde resin in a ratio of 0.1% by weight or more and less than 1.0% by weight based on the solid content of a coating film.