JPS61241138A - Steel plate for can having excellent corrosion resistance - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a steel plate for cans with excellent corrosion resistance used for forming processing, and more specifically, a laminated steel plate consisting of at least a thin steel plate, an organic layer, and an aluminum foil. This relates to steel plates for cans.

[Conventional technology]

As is well known, in recent years the mainstream of carbonated beverage cans containing beer and carbonated beverages have been so-called DI cans (Dratzn & Ironed cans), which are formed by a combination of drawing and ironing processes, and are made of aluminum alloy or tinplate. ing.

Tinplate is made by electrolytically tin-plating a steel plate, but since tin is an expensive resource, the minimum thickness (2.8 to 5.6
g/durability). In the case of DI cans, unlike conventional solder cans, many defects occur in the tin plating layer because they are subjected to strong processing (drawing and ironing reduce the thickness of the can side wall to about 1/3). . Therefore, in order to ensure corrosion resistance for the contents, protection with an organic coating is essential.
Especially for tin cans (painting-baking) (painting-baking)
The coating is applied twice to completely eliminate coating defects. In the case of aluminum cans, aluminum itself has relatively good corrosion resistance, so even if there are some coating defects, a material made by applying a specific paint directly to a steel plate is used as the material for DI cans instead of using tinplate. Examples are JP-A-54-94585 and JP-A-57-1742.
This is proposed in Publication No. 42.

[Problem that the invention seeks to solve]

As mentioned above, in order to cope with the thinner tin plating of steel sheets for cans, it is unavoidable that the cost will increase if the inner surface of the can is painted twice after the can is made, and it is also possible to directly paint the can without tin plating. If it is processed after this process, it cannot be said that the corrosion resistance is sufficient.

The present invention was made to solve these conventional problems, and its purpose is to provide an inexpensive steel plate for cans that has excellent corrosion resistance and can be coated on the inside of a can with just one coat. There is a particular thing.

[Means and effects for solving the problems] The feature of the present invention is that the thickness of 5 to 100 μm on at least one surface of the thin steel plate is
Aluminum prefectural bonds made of pure aluminum or aluminum alloy are laminated with an organic material layer of 1 to 20 μm in thickness interposed therebetween. Aluminum has excellent corrosion resistance for beer and carbonated drinks, but it is usually necessary to add alloying elements such as Mg and Mn to maintain the strength of the can body, and it has better corrosion resistance than pure aluminum. 0 In the case of the present invention, the main core material is steel and there is no problem in terms of strength, so it is desirable to use aluminum foil with as high purity as possible. 1 In the present invention, the thickness of aluminum prefectural bonds can be reduced. The reason for setting the thickness to 5 to 100 μm is that below 5 μm, the effect of improving corrosion resistance is small, and above 100 μm, the economical benefits are reduced.This is an organic layer of 1 to 20 μm in the zeroth order, but this layer has two important functions. It is. The first is its function as an adhesive that firmly joins the base steel and the outermost aluminum prefectural bond. Second, the organic layer itself effectively works to suppress iron elution even when the protective effect of the aluminum bond is no longer present. What is more desirable is to electrically insulate the base steel and aluminum seedlings, and
The purpose is to prevent an increase in the AQ elution rate due to local battery action between 1 and 2 hours.

As described above, in the present invention, by using a thin steel plate as a substrate, utilizing the high corrosion resistance of aluminum, and effectively utilizing the organic layer, it is possible to obtain a steel plate for cans that is economically superior and has extremely high corrosion resistance.

The organic layer must be able to maintain its adhesive strength even after strong ironing (reducing the board thickness by 1/3) and must have continuity as a film. The organic material used for this purpose is preferably a soft plastic material such as acrylic, polyester, polyamide, or polynylefin, or synthetic rubber.
When applying an aluminum film to the outside of the can, it is necessary to have an adhesive strength that prevents the aluminum film from peeling off due to surface friction caused by ironing.
It is desirable to have an adhesive strength of 0 kg/10 mm or more, and in such cases, thermosetting materials such as epoxy, polyester, polyurethane, and phenol are preferable.

When using the steel sheet for cans of the present invention, use the aluminum prefecture bond on the inner side of the can for corrosion resistance.The outer side of the can does not necessarily require an aluminum coating, but has lubricity that can withstand ironing. It is only necessary to ensure appearance printability and rust resistance after molding.Therefore, coatings having such quality characteristics include Sn plating, phosphate coating, and organic coating.

In the case of Sn plating, a deposition amount of 1 g/rd or more is sufficient. In the case of a phosphate film, it is necessary to use lubricating oil at a rate of 0.5 g/m or more. In the case of an organic film, adhesion to the substrate is important with a film thickness of 2μ or more, so depending on the degree of processing, a metallic chromium and/or hydrated chromium oxide film may be applied between the organic film and the steel plate. 200 mg
/ rrr may be used to improve adhesion.

As described in detail above, the present invention exhibits excellent performance as a steel plate for cans formed by drawing and ironing, but it can be said that it will exhibit even more excellent performance if applied to the drawing process alone. (not even).

Examples of the present invention will be described below.

[Example 1] A polyurethane adhesive was applied to one side of a surface-cleaned steel plate with a thickness of 0.28 mm to a dry film thickness of 7 μm.
Aluminum foil (purity 99.9%) having a thickness of 0 μm was adhered. The other side was plated with Sn at 2°8 g/rtf. With the Sn-plated surface as the outer surface of the can, 2 stages of drawing and 3
Step ironing was performed to form a can body (outer diameter 65 mm) with a side wall thickness of 0.100 mm. After degreasing the inner and outer surfaces of the can with a sodium phosphate degreaser, the surface was treated with a chromic acid-phosphoric acid agent, and then the inner surface of the can was spray-painted using an epoxy phenol paint (dry film thickness 5 μm, one coat) Paint baking conditions is 210°C for 10 minutes.

The cans were filled with a cola-based carbonated drink and a transparent carbonated drink (trade name: Sprite), and the number of perforated cans and the amount of iron eluted were measured. The results are shown in Table 1 along with other examples.

[Example 2] Aluminum foil with a thickness of 20 μm was adhered to the front and back surfaces of a clean steel plate (thickness: 0.27 mm) using an epoxy adhesive (dry film thickness: 5 μm). Thereafter, cans were manufactured and filled with contents in the same steps as in Example 1, and the corrosion resistance was examined. The results are shown in Table 1.

[Example 3] 0 having metallic chromium and hydrated chromium oxide films on both sides,
A modified vinyl paint with a film thickness of 5 μm was applied to one side of a 25 mm steel plate, and baked at 180'C for 10 minutes. On the opposite side, a 50 μm thick aluminum foil was adhered via a hot melt type polyester adhesive (15 μm thick). Cans were manufactured and filled with contents in the same steps as in Example 1, with the aluminum film side serving as the inner surface of the can, and the corrosion resistance was examined. The results are shown in Table 1.

[Example 4] After zinc-based phosphate treatment (adhesion amount: 2°Og/n?) was applied to both sides of a steel plate with a thickness of 0.25 mm, an acrylic adhesive (10 μm thick) was applied to one side. Then, a 20 μm aluminum foil was attached. The other phosphate-treated surface was coated with 0.2 g/g of synthetic lubricating oil and used as the outer surface of the can.
Table 1 shows the results of making cans and filling them using the same process as above and examining the corrosion resistance.

[Comparative example]

Tin plating on both sides of a steel plate with a thickness of 0.25 mm (adhesion amount 2.
8g/rrF), the cans were manufactured and filled with contents in the same steps as in the examples, and the corrosion resistance was examined. The results are shown in Table 1.

As shown in Table 1, in all of the examples of the present invention, the amount of iron eluted is smaller than in the comparative examples, no perforation occurs even after 6 months, and the corrosion resistance is excellent.

〔Effect of the invention〕

By molding the steel sheet for cans of the present invention so that the surface on which the aluminum or aluminum alloy film is laminated becomes the inner surface of the can, excellent corrosion resistance can be obtained with just one coat of can inner surface coating, and the cost is reduced. is also advantageous.

Patent applicant: Nippon Steel Corporation Representative Patent Attorney Furushima Nei Procedural Amendment July 1985 ll; Sun

Claims (1)

[Claims] 1) A can with excellent corrosion resistance, characterized by having an organic layer of 1 to 20 μm on at least one side of a thin steel plate and an aluminum foil or aluminum alloy foil of 5 to 100 μm on the organic layer. steel plate. 2) The steel sheet for cans according to claim 1, which uses a thin steel sheet formed with a single film of metallic chromium or hydrated chromium oxide, or a film consisting of both. 3) A thin steel plate with an organic layer on one side and an aluminum or aluminum alloy foil on the upper layer, and a tin plating layer on the other side; a phosphate layer; an organic layer; a single layer of metallic chromium or hydrated chromium oxide; The steel sheet for cans according to claim 1, comprising: a steel coating having an organic substance coating on an upper layer of the coating consisting of both;