JPH0253303B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an easy open end (hereinafter referred to as EOE) used for containers such as food cans and beverage cans whose can bodies are made of surface-treated steel sheets such as tinplate and electrolytic chromic acid treated steel sheets. ) related to composite metal objects. (Prior art) Recently, various food containers, etc., have been widely used as lids with notches (scores) engraved with appropriate shapes and lids with handles (tabs) attached, that is, EOEs, because they can be opened easily. There is. The materials used are aluminum and steel. aluminum EOE, steel
Both EOE and EOE have advantages and disadvantages, and they are put into practical use by taking these advantages and disadvantages into consideration. aluminum
EOE has the advantages of being easy to open, that is, it can be opened with a small amount of force, and the outer surface of the lid has excellent rust resistance, but on the other hand, it is resistant to contents containing chlorine ions. It also has the disadvantage of being susceptible to pitting corrosion, and if the can body is made of steel, the lid and can body are made of dissimilar metals, forming a battery and causing rapid corrosion (bimetallic corrosion). There is. Made of steel on the other hand
In the case of EOE, although it has excellent corrosion resistance against contents containing chlorine ions, and does not form a battery with the steel can body, its opening performance is slightly inferior, meaning that it requires a large amount of force to open the can. Another drawback is that rust is likely to form on the outer surface of the lid, mainly on the seam. In addition, made of steel
The corrosion resistance of EOE to the contents becomes excellent only after EOE processing such as score processing and correction coating is applied to the inner surface of the lid.
Corrosion of EOE to contents containing chloride ions,
The problem of corrosion due to battery formation (bimetallic corrosion) still remains a serious problem, even though it has been improved, since paint film defects cannot be completely eliminated even with correction coating. The correction coating applied to the inner surface of the lid after processing the EOE significantly increases the manufacturing cost of the lid, so from the perspective of manufacturing EOE at a low cost,
It is strongly desired to eliminate correction painting. From the point of omitting correction painting, JP-A-58-
EOE of polyester resin film-coated aluminum plates and steel plates manufactured by the manufacturing method disclosed in No. 220729.
However, the problem of scratches (damage) on the organic film during score processing remains unsolved. (Problems to be solved by the invention) EOE materials currently in practical use include external rust resistance, avoidance of bimetallic corrosion, corrosion resistance in contents containing chlorine ions, can openability, and internal correction. There is no material that simultaneously satisfies all of these characteristics required for EOE, such as eliminating the need for painting, and a material that satisfies them at the same time can be an excellent material for EOE. (Means to solve the problem) External rust resistance necessary for EOE, avoidance of bimetallic corrosion, corrosion resistance in contents containing chlorine ions, can opening ability, and omission of internal correction coating which has great economic benefits. With the aim of obtaining an EOE material that satisfies these five points at the same time, we conducted many other studies such as steel modification, aluminum modification, and surface treatment. , 50 to 250 μm aluminum plate is bonded to the other surface, which is the inner surface of the lid, and the elongation according to JIS C2318 and (elongation (%) / 100 + 1) x breaking strength are 10 to 1000% and 20 to 80 kg, respectively. / ^mm2 and thickness is 5
A composite metal body coated with an organic film of ~100 μm is
I found it fit the purpose. Before explaining the composite metal body of the present invention in detail, in order to make the understanding clearer, FIG. 1 shows one aspect of the composite metal body of the present invention subjected to score processing. The organic film indicated by 1 in Figure 1 is a biaxially stretched polyethylene terephthalate film (30 μm thick), 2 in Figure 1 is a steel plate (75 μm thick), and 3 in Figure 1 is an aluminum plate (thickness 30 μm).
155 μm). Next, the reason for limiting the configuration of the composite metal body as described above will be explained. First, the reason for arranging the steel plate on the inner surface of the lid and the aluminum plate on the outer surface of the lid will be explained. By arranging the steel plate on the inner surface side, two main purposes can be achieved. One point is to avoid bimetal corrosion with the can body, and the other point is to prevent pitting corrosion in the contents containing chlorine ions. In addition, by placing the aluminum plate on the outer surface, 3
One purpose can be achieved. One point is prevention of external rust, one point is prevention of scratches on the organic film on the innermost surface of the lid, which means omitting the inner surface correction coating of the lid, and the other point is improvement of can opening performance (reduction of can opening force). ). First, the reason why the inner surface correction painting can be omitted will be explained with reference to FIG. The score is processed (engraved) from the outer surface of the lid, but at this time, the press pressure of score processing acts on the organic film on the inner surface of the lid, and plastic strain is also generated. That is, a compressive force as shown by the arrow 6 in FIG. 2 acts on the organic film 1 sandwiched between the score blade 4 and the anvil 5. This press pressure is proportional to the deformation strength of the material being scored, and when aluminum, which has low deformation strength, is processed, the press pressure is small, but
When steel, which has a higher deformation strength than aluminum, is processed, the press pressure increases. Furthermore, when aluminum with low deformation strength is processed, the plastic strain of the steel plate 2 with high deformation strength bonded to the inner surface of the aluminum is small, and as a result, the plastic strain of the organic film coated on the steel plate is also small. . As described above, by using the aluminum plate 3 with low deformation strength as the main part of the part to be scored and using the steel plate 2 as the remaining part, the plastic strain on the organic coating 1 on the innermost surface of the lid is small, and Pressure is also reduced. Even if the plastic strain is reduced and the press pressure is reduced in this way, with the conventionally used inner coating (epoxy/phenolic resin), the true value of elongation and breaking strength divided by the cross-sectional area at break is The breaking strength, ie (elongation (%)/100+1) x breaking strength, is insufficient and the coating film is damaged during scoring. Therefore, it is necessary to arrange an organic film each having a weight of 10% or more and 20Kg/mm ² or more. Note that if the elongation is too large, the organic film will break when the can is opened, resulting in an unfavorable appearance, and the upper limit was set at 1000%. Also (elongation (%)/
100+1)×breaking strength increases the opening force, so the upper limit was set to 80 Kg/mm ² . This omission of inner surface correction painting is not only possible due to the effect of arranging aluminum on the outer surface, but is also achieved not only by the effect of the combination with the steel plate, but also by limiting the characteristics of the organic coating. It's watery. In addition, in the case where the organic film is a laminate of two or more types in terms of corrosion resistance, oxygen permeability, moisture permeability, etc., the object of the present application is met if the characteristics of the laminate satisfy the above-mentioned characteristic range. Next, the reason why the can opening performance is improved by arranging the aluminum plate on the outer surface side, that is, the reason why the can can be opened with a smaller force will be explained. 1st
This will be explained according to the diagram. FIG. 1 shows a state in which the score processing has progressed deeper and the score remaining thickness 7 has become less than the thickness of the steel plate 2. In this case, the score remaining thickness 8
The aluminum has a thickness score of 7
Approximately 1/2 of the original remains. It is considered that the can-opening force is significantly improved by the aluminum having low breaking strength remaining in the score remainder 8. Next, the reason for limiting the thickness of the steel plate, aluminum plate, and organic film will be described. The reason why the thickness of the steel plate is set to 30 to 180 μm is based on the following reasons. Normally, the score remaining thickness of EOE is controlled at around 45μm from the viewpoint of press accuracy, but if the thickness of the steel plate is set to 30μm or less, the score processing will not affect the steel plate and the can opening force will be slightly higher. In addition, if the adhesive strength between the aluminum plate and the steel plate is insufficient, peeling may sometimes occur at the adhesive interface, and the manufacturing cost increases significantly when manufacturing steel plates with a thickness of 30 μm or less. For this reason, the lower limit was set at 30 μm. Moreover, if the plate thickness is 180 μm or more, the amount of processing of the steel plate increases during score processing, and the press pressure and plastic strain applied to the inner organic film increase, resulting in damage to the organic film. In addition, the thickness of the aluminum plate is closely related to the strength required for the lid and the thickness of the steel plate to be assembled, but the lower limit is 50 μm from the point of view of leaving a certain amount of aluminum in the remaining part of the score and improving the openability of the can. did.
In addition, the upper limit was set at 250μm, even if the thickness of the steel plate is the lower limit of 30μm, the aluminum plate cannot be used.
This is because if the thickness is 250 μm, sufficient strength as a lid can be ensured. Next, the thickness of the organic film is 5~
The reason for setting it to 100 μm will be explained. Thickness is 5μ
m or less, elongation and (elongation (%)/100
+1) Even if the breaking strength is appropriate, dust,
It is easily affected by scratches and unevenness on the anvil 5, and the organic film is easily damaged. From this point, the lower limit was set to 5 μm. On the other hand, the amount of deformation of the film during scoring increases in proportion to the film thickness, so the thicker the film, the more difficult it becomes to accurately manage the remaining score thickness. The appearance of the fracture also deteriorates. Therefore, the upper limit is 100μm
And so. The reasons for limiting the structure of the composite metal body of the present invention have been described above. Regarding joining aluminum plates and steel plates, and coating steel plates with organic films,
The method is not limited, but the adhesive strength required for bonding aluminum plates and steel plates is adhesives such as polyurethane, epoxy, acrylic, polyester, olefin, polyamide, etc., or diffusion bonding. can be obtained. Regarding the coating of an organic film on a steel plate, the type of organic film may be one that satisfies the above characteristics, such as biaxially oriented polyethylene terephthalate, biaxially oriented polypropylene, unoriented polypropylene, nylon, etc., and laminated layers thereof. The body is compatible and can be covered by film lamination, powder coating, etc. Next, examples of the present invention will be described. Example 1 Composition is C: 0.04%, Mn: 0.25%, P: 0.02%,
After melting steel containing Al: 0.055% and other unavoidable impurities in a converter, it is made into a slab by continuous casting.
A hot-rolled plate with a thickness of 2.0 mm was obtained by hot rolling. After that, by cold rolling, the plate thickness is 0.23mm, 0.15mm, 0.12mm.
mm and 0.075 mm, and box-type annealing was performed. After box-shaped annealing, a skin pass was performed in each case to obtain a soft steel plate (hereinafter referred to as annealed material). In addition, for plates with a thickness of 0.23 mm, DR rolling is also performed after box annealing.
Hard steel plates (hereinafter referred to as rolled materials) with thicknesses of 0.15 mm, 0.12 mm, and 0.075 mm were created. These steel plates were subjected to electrolytic chromic acid treatment, and a biaxially stretched polyethylene terephthalate film with a thickness of 30 μm was laminated on one side of the steel plate with a Uthalene adhesive to form an inner surface coating. And steel plate (thickness 0.15mm, 0.12
An aluminum plate with a thickness such that the sum of the thicknesses of the steel plate and aluminum plate was 0.23 mm was adhered to the other side of the aluminum plate using urethane adhesive. In addition, a commercially available aluminum plate (alloy code and temper: 5052H38, 0.23 mm thick, laminated with biaxially stretched polyethylene terephthalate film on one side) was used as a comparative material.
After processing the lid of the 211 full open end (diameter 58 mm), the same score as 211 full open end is engraved from the opposite side where the film is laminated. Scratch resistance, corrosion resistance in contents containing chloride ions, and bimetallic corrosion were tested. Can openability was evaluated by attaching a tab to a fixed position on the outer surface of the lid with adhesive, and evaluating the magnitude of the force (score tear value: ST value) that was applied to the can after the initial opening (score break). The quality of the scratch resistance of the laminate film was evaluated based on the score residual thickness (metal thickness of the score remainder 8) at which scratches begin to appear on the film.
In addition, external rust was evaluated by performing a salt spray test after tightening the lid onto the can body. Bimetal corrosion and corrosion resistance in contents containing chlorine ions were evaluated by making a certain amount of scratches on the laminate film on the inner surface of the lid, and conducting actual can tests using a citric acid solution and a saline solution as contents. The results are shown in Table 1.

[Table] Scratch resistance of inner surface film: Remaining score thickness at which cracks begin to appear on the inner surface film due to score processing

[Table] Example 2 Plate thickness 0.075mm created using the same process as Example 1
On one side of the electrolytic chromic acid treated steel plate (annealed material),
Example 1: An aluminum plate (thickness: 0.155 mm) was coated with the organic film shown in Table 2 and bonded to the other side of the steel plate with an epoxy adhesive.
The scratch resistance of the organic film during score processing was tested using the same method as above. The results are shown in Table 2. (Effects of the Invention) As shown in the examples, the EOE made of the composite metal body of the present invention is superior to the steel EOE in terms of can openability and external surface rust, and is superior to the steel EOE in terms of scratch resistance of the internal coating, bimetallic corrosion, and chlorine. Its corrosion resistance in contents containing ions is superior to that of aluminum EOE.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a cross-sectional state when a composite metal body of the present invention is subjected to score processing. FIG. 2 is a schematic diagram showing the state of score processing. 1: organic film, 2: steel plate, 3: aluminum plate, 4: score blade, 5: anvil, 6: direction of compressive force acting on the organic film during score processing, 7: score remaining thickness, 8: score remainder.

Claims (1)

[Claims] 1. On one side of a steel plate with a thickness of 30 to 180 μm,
A 250 μm aluminum plate is bonded, and the other surface, which is the inner surface of the lid, has elongation according to JIS C2318 and (elongation (%) / 100 + 1) x breaking strength of 10 ~
1000%, 20~80Kg/ ^mm2 , and thickness 5~100μ
A composite metal body for an easy open end, which is characterized by being coated with an organic film of m and is combined with a steel can body to form a can body.