JP2791842B2 - Easy-to-open lid made of steel plate with no repair on the inside and outside with excellent openability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal container lid, and more particularly to a steel plate easy-to-open lid which can be easily opened manually or partially on the entire surface of a can lid. Used for a wide range of applications.

[0002]

2. Description of the Related Art An easy-open can lid, which can easily open a part or almost the entire surface of a container lid by hand, is a tear-off type in which a handle and an opening piece are torn off and separated from a can body, and both a handle and an opening piece are opened. A stay-on tub method that remains fixed to the can body after the can has been put to practical use. In either system, most easy-open can lids are manufactured from aluminum plates for manufacturing technology reasons, and steel plates are currently used for some limited applications.

[0003] As a typical example of the prior art, a coated aluminum or steel plate is used as a material, and after punching into a basic lid shape, the lid body is placed on a flat lower mold, and has a required contour shape from the upper surface thereof. By pressing the sharp blade and cutting the blade into the lid main body, an opening piece shape surrounded by a cutting guide groove having a V-shaped cross section (FIG. 5) has been formed.

[0004] The steel material itself has a fundamental feature of high strength, and in order to form a cutting guide groove that can be easily opened by hand, a sharpness reaching about half to 2/3 of the sheet thickness before processing. Intense pressing of the blade is required. If the depth of this cutting guide groove is too shallow, poor openability,
If it is too deep, it will cause insufficient impact strength against external shocks, so that considerable accuracy is required.

[0005] Therefore, although a considerable accuracy is required for a working tool, there is a drawback that the tool life cannot be maintained in the case of a steel plate which requires a sharp pressing of a sharp blade. In addition, in order to ensure corrosion resistance to the contents or to prevent the occurrence of rust on the outer surface, it is necessary to repair and coat a portion where the metal surface is exposed by processing the cutting guide groove. As measures for extending the tool life, Japanese Patent Application Laid-Open Nos. Sho 55-70434 and
As disclosed in Japanese Patent Publication No. 175034 and the like, a method of forming a cutting guide groove by composite extrusion has been proposed.
This known method was premised on the use of steel sheets, and was an effective measure for extending tool life,
Since the cross-sectional structure of the cutting guide groove is complicated, the coating does not spread to all parts in the cutting guide groove by the ordinary spray coating method, and there is a defect that sufficient corrosion resistance cannot be obtained even when repair painting is performed.

[0006]

In the prior art using a sharp blade, aluminum is considered to be preferable as a material thereof, and a material using a steel plate is used only for very limited applications. Is as described above. The main reasons are the strong resistance of the steel plate to the intense pressing of the sharp blade, the very short tool life of the processing tool, the coating on the steel plate surface being destroyed by the processing, the entire circumference of the cutting guide groove or the handle caulking part, etc. On the other hand, it was necessary to apply repair painting, and there was concern about corrosion resistance.

On the other hand, in response to the increasing awareness of global environmental issues in recent years, it has been required to focus on products suitable for recycling. Even in metal cans, the can body and can lid are formed of the same material. In addition, the importance of so-called “monometal cans” has been emphasized. At present, most metal cans use steel body cans, which have excellent openability and do not require repair painting of the inner and outer surfaces.
The emergence of measures that can be manufactured with high productivity has been eagerly awaited. Naturally, the steel sheet itself is excellent in economic efficiency, and it is expected that by using steel plates for both the can body and the can lid, the product will be more economical and easy to reuse as resources.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems at once, and the gist thereof is as follows. (1) Hardness ( _HR30T ): 54-68, elongation: 10-4
A glass transition temperature of 5 on both sides of a surface-treated steel sheet having 0%
0 ° C or higher, crystal melting temperature 210 ° C or higher, orientation degree 0.03
Using a steel sheet laminated with a polyester resin of 0 to 0.160, the thickness of the thinnest portion at the peripheral portion of the opening piece is 1 / th of the thickness before processing.
An easily openable can-opening lid made of a non-repairable steel plate with excellent openability, characterized in that a cutting guide groove whose main component is a thin-walled portion of 2 or less is formed by composite extrusion.

(2) Under the resin film to be laminated, 50
2. The easy-open can-open lid made of a non-repairable steel plate having an inner and outer surface excellent in can openability according to the above item 1, wherein the lid has a polyester resin layer having a glass transition temperature of not more than ° C. Hereinafter, the present invention will be described in detail. The steel sheet used in the present invention has a hardness ( _HR30T ) of 54 to 68 and an elongation of 10 to 40.
You need to have%. In the present invention, the cutting guide groove which affects the openability is formed by a composite extrusion process described later. Basically, a thin portion is formed by utilizing the elongation of the material, and the thin portion is opened by tearing the thinnest portion. What can be. Therefore, to obtain a lid that is easier to open,
It is important to make the thinnest part thinner. Therefore, the material needs to have excellent elongation characteristics.

On the other hand, the lid itself constitutes a part of the can body, and a material having high strength is required to maintain the strength of the can. In particular, in the case of an internal pressure can such as a beer can or a carbonated beverage can, a sufficient strength to withstand the internal pressure is required. In general, it is well known that elongation characteristics decrease when trying to increase the material strength, and the most excellent can strength, openability (reduction in thickness at the thinnest part), and economic efficiency (sheet thickness). The range in which the balance can be obtained is hardness ( _HR30T ): 54 to
68, elongation: 10-40%. Among them, the one with high hardness and large elongation gives the best economic efficiency.

A steel sheet having such mechanical properties is used as a base material and surface treatment is performed thereon, but the type of plating is not specified. Sn, Cr, Ni, A
A surface-treated steel sheet plated with one or more metals of l and Zn and having a thickness of 0.15 to 0.30 mm is often used. It is desirable that a chromic acid-treated film be present on the outermost surface of the plated steel sheet in order to ensure adhesion of the polyester resin film. A chromium hydrated oxide film alone or a film having metallic chromium as a base is effective, and it is important that the chromium hydrated oxide film uniformly covers the entire surface.

A glass transition temperature of 50 ° C. or more, a crystal melting temperature of 210 ° C. or more, and a degree of orientation of 0.
The presence of a polyester resin from 030 to 0.160 is required. This polyester resin film completely adheres to the substrate even after processing, because the polyester resin film follows the substrate with good adhesion when processing the cutting guide groove by composite extrusion and the film itself has excellent workability. It is an important entity that makes repair painting unnecessary.

The polyester resin in the present invention is a linear thermoplastic polyester obtained by polycondensation of a dicarboxylic acid and a diol, and is represented by polyethylene terephthalate. As the dicarboxylic acid component, terephthalic acid, isophthalic acid, phthalic acid, adipic acid, sebacic acid, azelaic acid, 2,6-naphthalenedicarboxylic acid,
It is a single or mixture of decanedicarboxylic acid, dodecanedicarboxylic acid, cyclohexanedicarboxylic acid and the like, and the diol component is a single or mixture of ethylene glycol, butanediol, decanediol, hexanediol, cyclohexanediol, neopentyl glycol and the like. It may be a copolymer of two or more dicarboxylic acid components or diol components, or a copolymer with another monomer or polymer such as diethylene glycol or triethylene glycol. If necessary, additives such as plasticizers, antioxidants, heat stabilizers, inorganic particles, pigments, and organic lubricants are blended.

The polyester resin thus obtained has a T
-It is formed into a film in a molten state by a die, and is biaxially stretched from an amorphous state to form a film having an excellent balance of heat resistance, workability, barrier properties, and the like. As a physical property of the resin film required for the present invention, it is first important that the glass transition temperature is 50 ° C. or higher. As is well known, the glass transition temperature is a temperature at which a resin changes from a glassy state to a rubber elastic state, and a lower glass transition temperature means that the workability at room temperature is better, but it is soft and easily scratched. Or, it has drawbacks such as build-up in a mold or the like, and causes a problem when performing industrial mass production. Therefore, it is important that the resin film has a glass transition temperature of 50 ° C. or more, more preferably 60 ° C. or more.

When a very high level of performance is expected, a layer having a glass transition temperature of 50 ° C. or less, which is excellent in adhesion and workability, is provided on the steel sheet surface side, and a flaw is formed on the surface side and the mold is hardened. A layer having a glass transition temperature of 50 ° C. or higher without adhesion.
It is effective to form a layer structure. Glass transition temperature of 50
The second reason for setting the temperature to not less than ° C. is a problem of feathering resistance at the time of opening the can. When the opening piece is torn off and opened, 50
This is because, in a resin having a glass transition temperature of less than 0 ° C., broken pieces of the film are conspicuous at the cut portion, and there is a concern that the resin may give an uncomfortable appearance.

Next, the reason why the crystal melting temperature of the resin is specified is that when the crystal melting temperature is lower than 210 ° C., the heat resistance of the polyester resin is reduced, and the heat treatment conditions required in the can-making process are significantly restricted. Because it becomes. Here, the crystal melting temperature is 5 ° C./min by a differential scanning calorimeter.
The maximum endothermic peak that appears when the temperature is increased at a heating rate of 1.

Further, as another physical property, the degree of orientation is in the range of 0.030 to 0.160, more preferably 0.030 to 0.160.
It is important to be in the range of 50 to 0.140. The degree of orientation (N) here is expressed by the following equation. N = ( _Nx + _Ny ) / 2- _Nz ( _Nx : refractive index in the horizontal direction, _Ny : refractive index in the vertical direction,
(N _z : refractive index in the thickness direction) As the original polyester film, the higher the degree of orientation, the better the properties such as mechanical properties, heat resistance and gas permeability can be obtained. In applications for processing, there is an optimum range in terms of workability, openability, heat resistance after processing, and the like. If the degree of orientation is less than 0.030, there is a problem because the resin itself is inferior in heat resistance and gas permeability, and if the degree of orientation is more than 0.160, problems arise in workability, openability, and heat resistance after processing. In particular, when the can is opened, it is necessary to break the laminated resin film along the cutting guide groove, and if the degree of orientation is too high, a film remaining phenomenon is likely to occur. Degree is desirable.

The thickness of the film to be laminated is 5 to 100 μm
However, in consideration of the stability and economy of performance, the range of 12 to 40 μm is often used. As a laminating method, the film itself is thermally bonded, or a thermosetting adhesive is applied, and the film is laminated on both surfaces of the steel plate as described above. When a surface-treated steel sheet having a polyester resin film described in detail above is formed into an easily-openable lid, the processing method is extremely important. That is, the formation of the cutting guide groove by the pressing method of the sharp blade, which is a typical prior art,
It is not preferable because it also breaks the laminate film and requires repair painting after molding.

In order to form a cutting guide groove which ensures easy opening without breaking the polyester resin film,
It is important that the entire material is stretched by elongation deformation to form a thin portion without locally applying a large shearing force. With such a processing method, a cutting guide groove whose main component is a thin-walled portion whose thinnest portion thickness is not more than の of the thickness before processing is formed on the peripheral edge portion of the opening piece, so that the can opening property is improved. This makes it possible to obtain a steel plate easy-to-open lid that is excellent in terms of repair and does not require repair painting of the inner and outer surfaces. Ultimately, the openability is determined by the thickness of the thinnest part, so that it is processed as thin as possible.

As a specific processing method, a portion corresponding to the shape of the opening piece is formed by pressing a portion corresponding to the shape of the opening piece upward or downward by pressing an important portion of the lid main body using an upper and lower mold substantially corresponding to the shape and size of the opening piece. Extrusion molding is performed. At this time, the peripheral edge portion of the opening is extended between the upper and lower dies so as to reach a desired thickness, thereby forming a thin portion having a gradual change in plate thickness. The thickness of the thinnest portion is required to be 以下 or less, more preferably １ ／ or less, of the thickness before processing from the surface of can opening.

By this processing, the breaking position at the time of opening the can is determined. However, in order to improve the opening property and to make the shape of the opening after the opening of the can desirable, the opening piece portion extruded upward or downward. Is pushed back to the level before processing.
At this time, the thin portion having a gentle plate thickness change formed by the extrusion process is bent into a V-shaped cross section,
This forms a thin cutting guide groove. The depth or the thickness of the thinnest portion of the cutting guide groove can be set to a desired value according to the workability of the material by appropriately setting the processing conditions. Processing conditions are selected according to the processability.

In these series of processing steps, the polyester resin film is uniformly stretched together with the substrate, and no processing defects are generated. Therefore, there is no need for repair coating after processing, and good corrosion resistance can be ensured. In addition, since the processing is based on press working such as extrusion or push-back, there is no problem of tool life seen in the sharp blade pressing method, and excellent productivity is guaranteed.

The present invention is mainly characterized by optimizing a cutting guide groove present at a peripheral portion of an opening piece, and a tear-off method in which a handle and an opening piece are torn off to be separated from a can body, and a handle and a handle are provided. It is possible to apply to both the stay-on tub system, in which both the opening pieces remain fixed to the can body even after the can is opened.

[0024]

Embodiments of the present invention will be described below. Example 1 Plate thickness 0.250 mm, hardness 62 ( _HR30T ), elongation 25
% Of the steel sheet was subjected to electrotin plating with an adhesion amount of 2.8 g / m ² . After tin is heated and melted to obtain a mirror glossy surface, an electrolytic post-treatment is carried out in a treatment bath mainly composed of chromic acid, and metallic chromium 10 mg / m ² and hydrated chromium oxide 13 mg / m ² thereon A chromate film having ² (as Cr) was formed. After washing and drying, the steel sheet was heated to a glass transition temperature of 68 ° C. and a crystal melting temperature of 235.
A 20 μm-thick polyester resin film having a degree of plane orientation of 0.15 ° C. and 0.105 was laminated on both sides of the steel sheet via a thermosetting polyester adhesive.

When a steel plate having a polyester resin film on both sides is formed into an easy-open can lid as shown in FIG. 1, as shown in FIG. 2, upper and lower dies 5, 6 corresponding to the shape and dimensions of the opening piece are used. By pressing key portions of the lid body, a portion corresponding to the opening piece 2 was extruded upward. At this time, the peripheral portion of the opening piece 2, the lid body 1 and the connecting piece 7
A thin portion inclined downward and having a gentle change in plate thickness due to elongation was formed. The thinnest part thickness in this example was 62 μm.

Next, as shown in FIG. 3, the opening piece 2 is placed inside the recessed groove 8 on a lower mold 9 having a recessed groove 8 in a portion corresponding to the peripheral edge of the opening piece 2. , Lid body 1
And pressed by an upper mold 10 having a flat lower surface. By this operation, the continuous piece 7 having a gradual change in plate thickness is bent downward in a V-shape from a substantially middle portion, and protrudes into the concave groove 8. Thus, a thin cutting guide groove 4 having a V-shaped cross section is formed at the periphery of the opening piece 2 on the upper surface of the lid main body 1.

The easy-open can lid thus formed was subjected to an evaluation of the openability by measuring the tearing force of the opening piece and an electric current test for examining the degree of destruction of the resin film on the inner and outer surfaces of the can. . As a result, both the raising force and the tearing force of the handle were about 1.8 kg, indicating excellent openability. In a current test in 1% saline, the inner and outer surfaces of the can were 0.1 mA or less, and the polyester resin film was completely sound and satisfied the target.

Example 2 A plate thickness of 0.190 mm, a hardness of 56 (H _R30T ) and an elongation of 30
% Of the surface of a thin steel sheet having the same percentage as in Example 1, washed with water and dried, and then using a two-layer polyester resin film having different melting points and glass transition temperatures,
A polyester resin film having a thickness of 25 μm was laminated on both surfaces of the steel sheet. At this time, the lower layer resin serving as the adhesive layer has a thickness of 5 μm, a melting point of 215 ° C. and a glass transition temperature of 40 ° C., and the upper layer has a thickness of 20 μm, a melting point of 240 ° C. and a glass transition temperature of 65 ° C.
° C copolyester resin was used. The degree of orientation was about 0.080.

Using this steel plate to form an easy-open can lid as shown in FIG. 1, as shown in FIG. 4 (a), the upper and lower dies 5, 6 corresponding to the shape and size of the opening piece are used to form the lid body. A portion corresponding to the opening piece 2 was extruded downward by pressing a key point. At this time, the peripheral portion of the opening piece 2, the lid main body 1 and the connecting piece 7 formed a thin-walled portion which was inclined upward and widened and had a gentle change in plate thickness due to elongation. At the same time, a biting groove 16 is provided at the peripheral edge of the lower surface, and then the opening piece is pressed upward, so that the thin portion having a gradual change in plate thickness is V-shaped upward (FIG. 4).
(B) was bent to form a cutting guide groove. The presence of the biting groove 16 is intended to improve the can openability by forming a remarkably thin portion between the cutting guide groove 4 and the biting groove 16. The thickness of the thinnest part in this example was 53 μm.

The performance of the molded lid is as follows.
It was 6 kg, which was excellent, and no electric current was observed in the resin film, which was very excellent and satisfied the target. Comparative Example 1 Plate thickness 0.230 mm, hardness 70 ( _HR30T ), elongation 8%
After the same plating as in Example 1 was performed on the surface of the thin steel plate of Example 1 and a resin film similar to that of Example 1 was laminated, the thinnest part was 60
It was processed by the same processing method as in Example 1 so as to have a thickness of μm. A part of the cutting guide groove was broken due to insufficient elongation of the material, and a normal lid could not be formed.

Comparative Example 2 A thickness of 0.250 mm, a hardness of 50 (H _R30T ) and an elongation of 40
% Of the surface of a thin steel plate is plated in the same manner as in Example 1.
Furthermore, after laminating the same resin film as in Example 1, the thinnest part was 6
It was processed by the same processing method as in Example 1 so as to have a thickness of 0 μm. Processing could be performed without any problem, but 2
When the carbonated beverage was filled into an 11-diameter (lid: 209-diameter) can, the can lid buckled (local deformation) due to insufficient lid strength.

Comparative Example 3 The same steel plate as in Example 1 was subjected to the same plating as in Example 1, washed with water and dried, and then heated to a glass transition temperature of 40 ° C., a crystal melting temperature of 220 ° C. and 0.080 ° C. A 20 μm-thick polyester resin film having the degree of plane orientation was laminated on both sides of the steel sheet via a thermosetting polyester adhesive.

When this steel sheet was subjected to lid forming in the same manner as in Example 1, a resin adhesion phenomenon was observed at the convex corners R of the lower die and the upper die shown in FIG. Needed to be done frequently.

[0034]

As described above, the easy-open can lid according to the present invention specifies a material and a processing method, that is, a polyester resin film having excellent workability and a composite extrusion processing method which does not use a sharp blade. It is built by adoption. Therefore, it is possible to completely eliminate the problems of the service life of the working tool, the problem that requires repair painting, and the uneasiness of the corrosion resistance, which are the major problems of the prior art.

If a steel plate easy-open can lid is put into practical use, it can be made into a “monometal can”, and it will be possible to provide products suitable for recycling in response to recent global environmental problems to the market. It is. Naturally, the steel sheet itself is excellent in economic efficiency, and it is expected that by using steel plates for both the can body and the can lid, the product will be more economical and easy to reuse as resources.

[Brief description of the drawings]

FIG. 1 is a perspective view of a can lid having a tear-opening piece formed according to the present invention.

FIG. 2 is a longitudinal sectional view showing the procedure of the present invention in the order of steps.

FIG. 3 is a longitudinal sectional view showing the procedure of the present invention in the order of steps.

FIG. 4 (a) is a longitudinal sectional view showing a state in which a dish-shaped opening piece having a biting groove on the lower peripheral edge is formed on the entire lid;
(B) is a longitudinal sectional view showing a state where a cutting guide groove is formed from the state of (a).

FIG. 5 is a sectional view of a cutting guide groove having a V-shaped cross section formed by a conventional sharp blade pressing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lid main body 2 Opening piece 4 Cutting guide groove 5 Upper die 6 Lower die 7 Connecting piece 8 Depression groove 9 Lower die 10 Upper die 16 Biting groove

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Keiji Yaniuchi 2-6-7 Nishikojiya, Ota-ku, Tokyo Inside the limited company Tanikei Seisakusho (58) Field surveyed (Int.Cl. ⁶ , DB name) B65D 17 / 28

Claims (2)

(57) [Claims] 1. Hardness ( _HR30T ): 54-68, elongation: 1
Using a steel sheet in which a polyester resin having a glass transition temperature of 50 ° C. or more, a crystal melting temperature of 210 ° C. or more, and a degree of orientation of 0.030 to 0.160 is laminated on both surfaces of a surface-treated steel sheet having 0 to 40%, A cutting guide groove having a thin-walled portion whose main part is a thin-walled portion having a thickness of 1/2 or less of the thickness before processing as a main component is formed in a composite extrusion process. Excellent inner and outer surface repair-free steel plate easy-open can lid. 2. The repairable inner and outer steel sheet according to claim 1, further comprising a polyester resin layer having a glass transition temperature of 50 ° C. or lower under the resin film to be laminated. Easy-to-open lid.