JPH09108756A - Manufacture of easily openable can lid having excellent can operanability without necessitating repair coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an easily openable steel can lid without necessitating repair coating by using a stock obtained by laminating a resin film on a steel sheet and forming a cutting guiding groove with a thin wall forming method by pressing without using a sharp blade. SOLUTION: A cutting guiding groove forming position corresponding to the shape dimension of an opening piece 2 of a lid main body 1 is pressed with respective shoulder radius part 8, 9 of an upper die 5 and a lower die 6, whereby the part corresponding to the opening piece 2 is formed. In this case, the die wherein the shoulder radius R of the upper and lower die 5, 6 are respectively 0.1-1.0mm and the clearance (overlap allowance) between the upper and lower die 5, 6 are respectively 0.1-1.0mm, is used. And the steel sheet, both surfaces of which are coated with the resin film having the thickness of 10-100μm and the breaking elongation >=100%, is pressed and formed with the shoulder 8, 9 of the upper and lower die 5, 6, and the cutting guiding groove is formed so that the metal thickness of the thinest wall part becomes 35-65μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lid for a metal container, and more particularly to an easy-open can lid which can easily open a part of the can lid or the whole surface of the can lid by hand. Used in a wide range of container lid applications.

[0002]

2. Description of the Related Art An easily openable can lid that allows a part or almost the entire surface of a container lid to be opened easily by hand is, for example, the handle 3 shown in FIG. The tear-off method and the Stein-tab method in which both the handle 3 and the opening piece 2 remain fixed to the can body after opening the can have been put into 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. As a typical example of the prior art,
Using a painted aluminum plate or steel plate as a material, after punching into a basic lid shape, place the lid body on a flat lower mold, press the sharp edged blade with the required contour shape from the top surface, By digging into the lid body,
As shown in FIG. 4, an opening piece shape surrounded by a cutting guide groove having a V-shaped cross section was formed.

With respect to the formation of the cutting guide groove, it is necessary to violently press the sharp blade up to about half to ⅔ of the plate thickness before processing, and the depth of the cutting guide groove is very important. That is, when the depth of the cutting guide groove is too shallow, the can openability is poor, and when it is too deep, shock from the outside, for example, insufficient impact strength when dropped, is required. Considerable processing accuracy is required.
Therefore, although the machining tool is required to have a considerable accuracy, the tool life is a problem because the sharp blade needs to be pressed strongly. In particular, the steel plate has a drawback that the tool life cannot be maintained. Further, in the case of a steel plate material, in order to secure corrosion resistance to the contents or prevent the occurrence of external rust, it is necessary to carry out repair coating on the portion where the metal surface is exposed due to the processing of the cutting guide groove. Due to the economic efficiency and the can openability, the impact strength against dropping, etc., the easy-open can lid made of aluminum is superior to the easy-can open lid made of steel plate at present.

As a measure for extending the tool life, Japanese Patent Laid-Open No. Sho 55 has been proposed.
As disclosed in JP-A-70434 and JP-A-57-175034, a method of forming a cutting guide groove by composite extrusion molding has been proposed. Such a proposed method was premised on the use of steel sheet, and was an effective measure for extending the tool life, but due to the complicated cross-sectional structure of the cutting guide groove, it was not possible to use ordinary spray coating. The method has the drawback that the paint does not spread to all the parts in the cutting guide groove, and sufficient corrosion resistance cannot be obtained even if repair painting is performed. Further, from the viewpoint of ensuring corrosion resistance, JP-A-5-77358.
As can be seen in the publication, etc., even though the corrosion resistance of the inner surface of the can is ensured, the outer surface of the can is subjected to severe pressing with a sharp blade,
Rust resistance is not ensured and repair coating of the cutting guide groove is required.

[0005]

As described above, the easily openable lid, which is preliminarily painted, is used regardless of whether an aluminum plate or a steel plate is used as a material. Further, after the processing, it is necessary to perform repair painting on a portion where the metal surface is exposed by the processing. Especially in the case of steel plate materials, repair painting is essential. Not only is the painting process complicated in the subsequent baking process, but it also requires a long period of time for baking, and a large amount of the solvent contained in the paint is discharged during the baking process. The discharged solvent must be incinerated in a special incinerator.

Further, there are the following major problems in the recycling process. It is a material for the current easy-open lid,
For both aluminum and steel sheets, vinyl chloride paints, especially vinyl chloride organosols, are widely used as paints because of their excellent workability, corrosion resistance, retention of content flavor, and price. However, in the easy-opening lid using the current vinyl chloride-based paint, when the used metal can is collected and incinerated or re-melted, it is necessary to sufficiently consider environmental hygiene. Current,
It seems that research and development of paints to replace vinyl chloride-based paints are also underway, but there is no promising one that can be used for a wide range of contents.

Regarding metal recycling, a so-called "monometal can", in which a metal case and a metal case lid are made of the same material, is a suitable product for recycling. Most of the open can lids are made of aluminum. On the other hand, most of the can lids except the can body and the easy-open can lid are made of steel plate. Therefore, it has excellent openability,
It is eagerly desired to develop a method that can manufacture not only aluminum easy-opening can lids, which have no need of painting at all, and have excellent corrosion resistance, but also steel plate easy-opening can lids with high productivity. Therefore, an object of the present invention is to provide a method for producing an easy-open can lid excellent in can-openability that does not require repair painting, which has both reciprocal characteristics of can openability and soundness of a resin film in a well-balanced manner. It is in.

[0008]

The present invention has been made to solve the above problems, and the shoulder radii R of the upper and lower dies for forming the cutting guide grooves forming the opening piece shape are 0.1 respectively. ˜1.0 mm, the upper and lower dies have clearances (overlap margins) of 0.1 to 1.0 mm, and the thickness is 10 to 100 μm and the breaking elongation is 10.
A steel sheet having a resin coating of 0% or more on both surfaces is press-formed by the shoulder radius portions of the upper and lower molds to form a cutting guide groove with a metal thickness of the thinnest processed portion of 35 μm to 65 μm. It is a method of manufacturing an easily openable lid that is excellent in openability and does not need to be opened.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The method of the present invention will be described in detail below. The present invention, by combining a material and a processing method, has excellent openability, and since it has high corrosion resistance, it does not require repair coating, and further has excellent film residual property in the open part called a feather, which is easy to use. It is a manufacturing method of an open can lid. (1) First, materials used in the method of the present invention will be described. The steel plate used in the method of the present invention has a plate thickness t ₀ :
It is in the range of 0.15-0.25 mm, and Sn,
Resin that has excellent adhesion, workability, and corrosion resistance because it is plated with one or more metals of Cr, Ni, Al, Zn and does not require repair coating after the lid-making process on the chromate-treated film. The coating is laminated.

As the steel sheet used specifically, the adhesion amount
0.5-3.0 g / m^Two After tin plating of
Tin-plated steel sheet, adhesion amount 0.3-2.0g / m^Two Nicke
Nickel-plated steel sheet that has been subjected to chemical conversion treatment after nickel plating, Sn
And 0.5 to 2.0 g / m as the amount of Ni deposited respectively^Two ,
0.01-0.5 g / m^Two After plating in order of Ni, Sn
Chemically treated Sn / Ni plated steel sheet, metal Cr adhesion
Amount 50-200mg / m ^Two , Cr oxide 5-30 mg / m
^Two Normal TFS (Tin Free Steel)
Chromium-chromate treated steel sheet is suitable.
You.

The resin laminated on both sides of the above-mentioned steel sheet adheres well to the base material when the cutting guide groove is processed by pressure molding, and the coating itself has excellent workability, so that the base material is completely processed even after the processing. It is important because it does not require repair painting, which was required in the past. Therefore, the resin has a breaking elongation of 100% or more and a thickness of 10 to 100 μm.
As the physical properties of the resin film, if the elongation at break is less than 100%, the elongation is insufficient for forming a thin portion at the time of pressing, which will be described later.
This is not preferable because it causes many defects in the resin film. Therefore, the lower limit is 100%. Preferably 200
% Is preferable. In addition, the elongation property of the laminated resin film is measured according to JIS C231 by peeling the resin film from the base material.
The value measured by the method according to 8 is adopted.

If the thickness of the resin film to be laminated is too thin, the film is likely to be broken by processing, and conversely 60 μm.
When the film becomes ultra thick, especially 80 μm or more, the corrosion resistance after working advances in a better direction, but when the cutting guide groove is broken (when the can is opened), the film stretches long before breaking and the film remains It is disadvantageous to use an excessively thick film because it easily causes a phenomenon (feather). Therefore, it is within the range of 10 to 100 μm. Considering performance stability and economic efficiency, 1
Those having a range of 6 to 60 μm are particularly effective. The resin applied in the method of the present invention is a resin composed of one or more thermoplastic resins such as polyethylene, polypropylene, polyester, polyamide, and ionomer in view of performances such as food hygiene, corrosion resistance, and processability. It is preferable to use a film.

Some of the above resins will be supplementarily described below. The polyester resin used in the method of the present invention is a linear thermoplastic polyester obtained by polycondensation of dicarboxylic acid and diol, and is represented by polyethylene terephthalate. The dicarboxylic acid component may be terephthalic acid, isophthalic acid, phthalic acid, adipic acid, sebacic acid, azelaic acid, 2,6-naphthalenedicarboxylic acid, decanedicarboxylic acid, dodecanedicarboxylic acid, cyclohexanedicarboxylic acid, etc., alone or in a mixture. As the diol component, ethylene glycol, butanediol, decanediol, hexanediol, cyclohexanediol, neopentyl glycol or the like may be used alone or in a mixture. It may be a copolymer of two or more kinds of dicarboxylic acid components or diol components, or a copolymer with another monomer or polymer such as diethylene glycol or triethylene glycol.

The polyamide resin is nylon 6, nylon 7, nylon 11, nylon 66, nylon 610, nylon 612, poly-m-phenylene isophthalamide, etc., alone or in a mixture. The ionomer resin is
It is a resin in which a copolymer of α-olefin and an unsaturated carboxylic acid is crosslinked between the molecular chains with a metal ion, and the α-olefin component is ethylene, propylene, butene, pentene or the like alone or as a mixture, and is unsaturated. The carboxylic acid is acrylic acid, methacrylic acid or the like alone or a mixture, and the metal ion component is sodium, zinc or the like alone or a mixture. Furthermore, the resin film used in the method of the present invention may contain a plasticizer /
Additives such as antioxidants, heat stabilizers, inorganic particles, pigments and organic lubricants are added. The resin film is laminated on both sides of the metal plate by heat-bonding the film itself or applying a thermosetting adhesive.

(2) Next, a method of processing the can lid will be described. The formation of the cutting guide groove as shown in FIG. 4 by the conventional sharp edge pressing method is not preferable because the resin film is broken and repair coating after molding is required. As a processing method for forming a cutting guide groove that ensures easy opening without breaking the resin film, the inventors of the present invention, as shown in FIG. Then, it was found that the above-mentioned method of forming the cutting guide groove by thinning the steel plate with resin-coated both sides as shown in FIG. 3 and thinning it is optimal.

That is, when a steel plate having a resin coating on both sides is made into an easy-can lid as shown in FIG. 1, as shown in FIG. The portion corresponding to the opening piece 2 is formed by pressing the cutting guide groove forming position corresponding to the shape and size of the opening piece of the lid body 1 with a press. At this time, the connecting piece 7 that connects the opening piece 2 and the lid body 1 is processed so as to form a thin portion having a smooth plate thickness change by pressing. The metal thickness of the thinnest processed part is 35 μm to 65 μm
Limited to.

The metal thickness of the cutting guide groove is closely related to the openability and the soundness of the laminated resin film. If it is less than 35 μm, the breaking strength of the cutting guide groove is low and the openability is good, but the laminated resin film has When a crack is generated or is severe, the film is broken and the soundness is not secured and the corrosion resistance is poor. On the other hand, 65μ
If it exceeds m, on the contrary, the film integrity of the cutting guide groove is secured, but the breaking strength of the material is high and the can openability is poor. From the can openability and soundness of the laminated resin film, the metal thickness of the thinnest part is 3
The range of 5 μm to 65 μm can be combined, but the range of 40 μm to 55 μm is preferable.

Next, the shoulder radius R of the upper and lower molds for forming the cutting guide groove is determined from the viewpoint of ensuring the openability and the soundness of the laminated resin film.
It is as important as the metal thickness of the thinnest processing part described above,
It is set to 0.1 to 1.0 mm. In the study by the inventors, there is a relationship with the metal thickness of the thinnest machining portion, but at the same level of metal thickness, the smaller the shoulder radius R of the upper and lower dies, the lower the breaking strength of the cutting guide groove portion tends to be. , Openability is good. However, when the shoulder radius R is smaller than 0.1 mm, the breaking strength is low and the can openability is good, but since the shoulder radius part is sharp, cracks and fractures occur in the laminated resin film of the work material during pressing. It is difficult to secure the soundness of the film due to the occurrence of scratches or scratches.

On the other hand, when the pressing process is performed under the condition that the shoulder radius R exceeds 1.0 mm, the soundness of the laminated resin film is good, but
The breaking strength is high and the can openability is poor. Further, since the material is pressed in a wide area, the adhesion between the metal and the resin is reduced in the pressed area due to the processing. Forming an adhesion failure portion more than necessary causes feathers, and the adhesion failure portion of the coating film is not preferable from the viewpoint of corrosion resistance.

In the method of the present invention, the shoulder radii R of the upper and lower molds may be the same for the upper and lower molds, or the shoulder radii R of the upper and lower molds may be different. When the shoulder radii R of the upper and lower molds are different, the shoulder radius R of the lower mold is set to the shoulder radius R of the upper mold in order to keep the metal thickness of the thinnest part to be processed within a desired range and to secure the film integrity. It is advantageous to apply a value smaller than R.

Next, according to the method of the present invention, the product of the average R obtained by averaging the shoulder radii R of the upper and lower molds and the metal thickness of the thinnest portion to be machined,
R (mm) × metal thickness (μm) is the essence of the present invention,
R (mm) × metal thickness (μm) is 3.5 to 55, which is a main index in ensuring the openability and the soundness of the laminated resin film.
And The product of the average R of the shoulder radius R of the upper and lower molds and the metal thickness of the thinnest processed portion, R (mm) x metal thickness (μm), is 3.5.
˜55 means that when the shoulder radius R is small,
It means that the metal thickness of the thinnest processed portion can be increased, and when the shoulder radius R is large, it means that the metal thickness of the thinnest processed portion needs to be reduced. R (mm) x metal thickness (μ
If m) is less than 3.5, the soundness of the laminated resin film cannot be ensured. On the other hand, if it exceeds 55, the can openability is not ensured. Here, the lower limit value 3.5 of R (mm) x metal thickness (μm) is
The average radius R of the shoulder radii R of the upper and lower dies is 0.1 mm, and the metal thickness of the thinnest part to be machined is 35 μm. The upper limit value 55 means that the average radius R of the shoulder radii R of the upper and lower dies is 1.0 mm. The case where the metal thickness of the thinnest processed portion is 55 μm. R (mm)
The metal thickness (μm) is preferably in the range of 4 to 50.

In the method of the present invention, usually, the upper and lower dies of the upper and lower dies for forming the cutting guide groove have a punch relationship and the lower die has a die relationship, and the punch diameter of the upper die is larger than the die diameter of the lower die. Is larger, the steel plate is pressed at the shoulder radius of the upper and lower molds to form a cutting guide groove. The width of this cutting guide groove is determined by the clearance (overlap margin) of the upper and lower molds. Width affects the desired metal thickness of the thinnest processed portion, and as a result, is important for ensuring the openability and the soundness of the laminated resin film. That is, if the width of the cutting guide groove is small, the steel plate in the machined part may break, and if it is large, the desired metal thickness of the thinnest part may not be obtained. As a result, the openability and the soundness of the laminated resin film are greatly affected.

Therefore, in the method of the present invention, the clearance between the upper and lower molds is set to 0.1 to 1.0 mm. If the clearance between the upper and lower molds is less than 0.1 mm, especially if the shoulder radius R of the upper and lower molds is small, it is not preferable because the steel plate is likely to break in the machined portion. On the other hand, if the thickness exceeds 1.0 mm, even if the desired metal thickness of the thinnest portion is obtained, the width of the cutting guide groove is large, so that the can openability and the soundness of the resin film are likely to deteriorate, which is not preferable. It is necessary to select the optimum condition for the clearance of the upper and lower molds in relation to the shoulder radius R of the upper and lower molds. The relationship between the shoulder radius R of the upper and lower molds and the clearance of the upper and lower molds, that is, clearance / shoulder Setting the radius R in the range of 1 to 2 may ensure the openability and the soundness of the resin film.

In the method of the present invention, during processing, the peripheral edge portion of the opening piece is pressed between the upper and lower molds so as to reach the desired thickness, thereby forming a thin-walled portion with a smooth plate thickness change. However, after this processing, it is possible to make the shape of the opening into a desired shape by forming a bead or a step in the vicinity of the thin portion having the gentle plate thickness change formed by the pressing processing. . The depth of the cutting guide groove or the plate thickness of the thinnest part can be set to a desired value according to the workability of the material by setting the processing conditions as required. The processing conditions are selected according to the workability of. In the series of processing steps, the resin film having the above characteristics is stretched together with the base material, and no processing defects occur. Therefore, repair coating after processing is not necessary, and good corrosion resistance can be guaranteed.

Further, according to the method of the present invention, since the processing is basically based on press working such as extrusion or push-back by shoulder radius portions having mutually convex and smooth curved surfaces, it is found in the sharp blade pressing method. There is no problem of tool life, and excellent productivity is guaranteed. The method of the present invention is characterized mainly by optimizing a cutting guide groove present at a peripheral portion of an opening piece, a tear-off method in which a handle and an opening piece are separated from a can body, a handle and an opening piece. Both can be applied to both the stay-on tub system, which remains fixed to the can body even after the can is opened.

[0026]

EXAMPLES The method of the present invention will be specifically described below with reference to examples. Example 1 100 m of metallic chrome was formed on the surface of a thin steel plate having a thickness of 0.20 mm.
g / m ² , hydrated chromium oxide 20 mg / m ^{2 on top}
Electrolytic chromium / chromate treatment (as Cr)
After being washed and dried, this steel sheet is heated to a two-layer polyester resin having different melting points. The upper layer has a thickness of 37μ, the lower layer has a thickness of 3μ, and the lower layer resin has a lower melting point than the upper layer resin and has a total thickness of 40μ. Was laminated on both sides of the chromate-treated steel sheet. The elongation of the film measured after peeling after lamination was 450%. In preparing an easy-open can lid as shown in FIG. 1 using a steel sheet having a polyester resin film on both surfaces, as shown in FIG.
The upper and lower molds 5 and 6 having a shoulder radius R of 0.5 mm and a clearance 1 of 0.5 mm corresponding to the shape and size of the opening piece are pressed by pressing the essential parts of the lid main body to form the opening piece 2. The corresponding part was molded. The steel plate thickness of the thinnest part in this example is 31 μm (Sample-N
o. 1), 38 μm (Sample-No. 2), 51 μm
(Sample-No. 3), 62 μm (Sample-No.
4) and 70 μm (Sample-No. 5). With respect to the easily openable lid thus formed and processed, the openability was evaluated and the soundness of the resin film on the inner and outer surfaces of the can was investigated. The can openability was evaluated by using a tensile tester and pulling the handle 3 in a state where the periphery of the lid body was restrained, and measuring the maximum load until the opening piece 2 was torn off. Also, the film integrity evaluation is
A 1% saline solution was used as an electrolytic solution, a can lid sample was used as an anode, and platinum was used as a cathode, and a current value after 2 minutes at an applied voltage of 6 V was measured. The results are shown in Table 1.

[0027]

[Table 1]

As can be seen from Table 1, the sample of the method of the present invention-No. 2, sample-No. 3 and Sample-No. No. 4 shows low values for both the can-opening power and the soundness of the film, which is at a level with no practical problems. On the other hand, sample-N of Comparative Example which is not the object of the method of the present invention
o. Sample No. 1 had a small can-opening power, but a high current value indicating the film integrity, and thus Sample-No. On the other hand, in No. 5, the current value showing the film soundness is small, but the can-opening power is large, and both are problems in practical use. Further, in the vicinity of the cut end of the cutting guide groove after opening the can, the sample of the comparative example-No. Feather was visually confirmed in Sample No. 1, but the sample of the present invention-No. No visually noticeable feathers were observed in Nos. 2, 3, and 4.

Example 2 The steel plate having polyester resin coatings on both sides used in Example 1 was subjected to the procedure of Example 1 and the shoulder radius R was 0.2 m.
m, a die with a clearance 1 of 0.2 mm, a shoulder radius R of 0.7 mm, a die with a clearance 1 of 0.7 mm, a die with a shoulder radius R of 0.9 mm and a clearance 1 of 0.9 mm. By doing so, a portion corresponding to the opening piece was molded. Then, as in Example 1, a portion corresponding to the opening piece was extruded upward by pressing a key portion of the lid main body with a press. The thickness of the steel plate at the thinnest portion in this example is 48 μm (sample-
No. 6), 52 μm (Sample-No. 7), 55 μm
m (Sample-No. 8). 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 a power-on test for examining the soundness of the resin film on the inner and outer surfaces of the can in the same manner as in Example 1. went. The results are shown in Table 1. As can be seen from Table 1, the sample of the present invention-No. 6, sample-No. 7 and Sample-No. No. 8 shows low values for both the can-opening power and the soundness of the film, which is a level with no practical problems. In addition, sample-No. No visually noticeable feathers were found around the cut guide groove after opening the cans 6, 7, and 8.

Example 3 The surface of a thin steel sheet having a thickness of 0.20 mm was electrotin-plated with a single-sided coating amount of 2.8 g / m ² , and then tin was heated.
It was melted to give a surface having a specular gloss. Immediately, electrolysis post-treatment was carried out in a treatment bath mainly containing chromic acid to obtain 12 mg / m ^{2 of} chromium metal and 1 layer of hydrated chromium oxide as an upper layer.
A chromate film having ² mg / m ² (as Cr) was formed, washed with water and dried, and then this steel plate was heated to give Example 1.
The two-layer structure polyester resin used in, the upper layer is 37
μ, the lower layer had a thickness of 3 μ, and the lower layer resin was a resin film having a lower melting point than the upper layer resin and containing an ionomer and having a total thickness of 40 μ was laminated on both surfaces of the steel sheet. The steel plate having a polyester resin film on both sides thus obtained is molded by extruding upward the portion corresponding to the opening piece according to the mold and the procedure performed in Example 1, and then pressing the key part of the lid main body with a press. After molding the part corresponding to the opening piece,
The openability and the soundness of the resin coating on the inside and outside of the can were evaluated. In addition, the steel plate thickness of the thinnest part in this Example was 45 μm (Sample-No. 9). The results are shown in Table 1. As can be seen from Table 1, the sample of the present invention-No. No. 9 has low values for both the can-opening power and the film soundness, and there is no visually noticeable feather around the cut guide groove after can-opening, which is at a level with no practical problems. .

Example 4 On the same plated steel plate as in Example 1, 20 μm nylon 6 film was laminated on both sides of the steel plate using a 50 μm modified polypropylene-polyethylene copolymer resin film as an adhesive layer. The thickness of the resin film was 70μ. The elongation of the film measured by peeling after lamination was 350%. This steel plate having a resin film on both sides is pressed as shown in FIG. 2 by using upper and lower molds 5 and 6 having a shoulder radius R of 0.2 mm, so that a portion corresponding to the opening piece 2 is formed. Molded.
In this example, the thickness of the steel plate at the thinnest portion was 53 μm (Sample-No. 10). 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 a power-on test for examining the soundness of the resin film on the inner and outer surfaces of the can in the same manner as in Example 1. went. The results are shown in Table 1. As can be seen from Table 1, the sample of the present invention-No. No. 10 shows low values for both the can-opening power and the film soundness, and is at a level that poses no practical problems. Further, no visually noticeable feather was observed around the cut end of the cutting guide groove after opening the can.

Comparative Example 1 On the same plated steel sheet as in Example 1, a two-layer polyester resin having different melting points was used. The upper layer had a thickness of 20 μ, the lower layer had a thickness of 20 μ, and the lower layer resin had a lower melting point than the upper layer resin. A resin film having a total thickness of 40 μm containing was laminated on both sides of the steel plate. The elongation of the film measured by peeling after lamination was 350%. A steel plate having a resin coating on both sides has a shoulder radius R of 0.08 mm and a clearance of 0.
After molding the portion corresponding to the opening piece in accordance with the procedure of Example 1 using the upper and lower molds of 08 mm, the can openability was evaluated and the soundness of the resin film on the inner and outer surfaces of the can was evaluated. In this comparative example, the thickness of the steel plate at the thinnest portion is 53 μm. As a result of the evaluation, the can openability was 1.8 kg or less and the can was opened without any problem, but the energization value of the resin film was 53 mA on the inner surface side and 48 m on the outer surface side.
A very large value was shown as A, many defects were observed in the resin film of the cutting guide portion, and even if the shoulder radius was too small, it could not be practically used.

Comparative Example 2 On the same plated steel sheet as in Example 1, a two-layer structure polyester having different melting points was used. The upper layer had a thickness of 20 μ, the lower layer had a thickness of 20 μ, and the lower layer resin had a lower melting point than the upper layer resin and was an ionomer. A resin film having a total thickness of 40 μ was contained on both sides of the steel plate. The elongation of the film measured by peeling after lamination was 310%. This steel plate with resin coating on both sides, shoulder radius R 1.2mm, clearance 1.2mm
The upper and lower molds were used to mold the portion corresponding to the opening piece according to the procedure of Example 1, and then the can openability was evaluated and the soundness of the resin film on the inner and outer surfaces of the can was evaluated. In this comparative example, the thickness of the steel plate at the thinnest portion is 53 μm. The openability is as high as 3.5 kg, and the energization value of the resin coating is 2.5 m on the inner surface side.
A was 2.2 mA on the outer surface side, which was a practical problem.

Comparative Example 3 On the same plated steel plate as in Example 1, 60 μm nylon 6 film was laminated on both sides of the steel plate with a 60 μm modified polypropylene-polyethylene copolymer resin film as an adhesive layer. The thickness of the resin film was 120μ. The elongation of the film measured by peeling after lamination was 450%. This steel plate having a resin film on both sides was molded into a portion corresponding to an opening piece according to the procedure of Example 1 using upper and lower molds having a shoulder radius R of 0.5 mm and a clearance of 0.5 mm.
The openability and the soundness of the resin coating on the inside and outside of the can were evaluated. In this comparative example, the steel plate thickness of the thinnest part is 55 μm.
It is. The can opening strength was 2.2 kg, the amount of electricity applied to the resin coating was 0.000 mA, and it was judged to be practical in terms of can openability and corrosion resistance, but the area around the cut guide groove that was broken during opening was The film remained violently, giving discomfort in appearance, and there was a problem in practicality.

[0035]

As described above, the method for manufacturing an easy-open can lid according to the present invention uses a material obtained by laminating a resin film on a steel plate and uses a thin portion forming method by pressing without using a sharp blade. By adopting the method of forming the cutting guide groove, there is no need to paint at all in the manufacturing process, and the problems of the tool life for machining, the concern about corrosion resistance, etc. You can do it. In particular, if a steel easy-open can lid is put into practical use, it will be possible to make it into a "monometal can", and it will be possible to provide the market with products that are suitable for recycling in response to recent global environmental problems. is there. 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-off opening piece formed according to the present invention;

FIG. 2 is a cross-sectional view of the present invention before press molding.

FIG. 3 is a longitudinal sectional view of a press molding process,

FIG. 4 is a cutting guide groove having a V-shaped cross section according to a conventional pressing method of a sharp blade.

[Explanation of symbols]

 1 Lid body 2 Opening piece 3 Handle 4 Cutting guide wire 5 Upper mold 6 Lower mold 7 Continuous piece 8 Upper mold R part 9 Lower mold R part l Upper and lower mold clearance

Claims (3)

[Claims] 1. The shoulder radii R of the upper and lower dies for forming the cutting guide groove forming the opening piece shape are 0.1 to 1.0 mm, respectively, and the clearances (overlap allowances) of the upper and lower dies are 0.1. ~ 1.0 mm mold, thickness 10
˜100 μm, a steel sheet having a resin film with a breaking elongation of 100% or more on both sides is press-formed by the shoulder radius parts of the upper and lower molds, and the metal thickness of the thinnest processed part is 35 μm to 6 μm.
A method for manufacturing an easy-open can lid that is excellent in can openability without repair painting, characterized by forming a cutting guide groove at 5 μm. 2. The average R (unit: m) of the shoulder radius R of the upper and lower molds.
2. The opening without repair painting according to claim 1, wherein the cutting guide groove is formed so that the product of m) and the metal thickness (unit: μm) of the thinnest processed portion is in the range of 3.5 to 55. A method for manufacturing an easily opened can lid having excellent can property. 3. The resin film present on both sides of the steel sheet is composed of one or more thermoplastic resins such as polyethylene, polypropylene, polyamide, polyester, ionomer and the like. A method for producing an easy-open can lid that does not require the repair painting described above and has excellent openability.