JPH0899140A - Manufacture of easily opening can cover by warm working - Google Patents

Abstract

PURPOSE: To provide a manufacturing method for easily opening a can cover which is widely used for a food can, etc., and satisfies utilizing performance in a steel sheet coated with resin having thin film thickness. CONSTITUTION: Dies having 0.1-1.0mm shoulder radius of an upper and a lower dies 12, 13 for forming cutting guide groove 4, forming the opening hole piece 2 shape are used. The metallic sheet 1 having the resin film of 5-100μm thickness and >=100% rapture elongation on both surfaces at the shoulder radial part of these dies is press-formed in the temp. range of becoming 10<6> -10<8> dyne/cm<2> shear elastic modulus of the resin and the thinnest part of the metal thickness by press-forming is thinned at <=1/2 of the metal thickness before working to manufacture the easily opening can cover 1 for forming the cutting guide groove 4. By this method, the easily openable can cover with low opening force and excellent electric insulation of the resin and stable performance without developing feather can be manufactured.

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 that can easily open a part or almost the entire surface of a can lid by hand. Used in a wide range of other applications.

[0002]

2. Description of the Related Art An easy-open can lid in which a part or almost the entire surface of a container lid can be opened manually by hand is a tear that is separated from the can body by tearing off a handle 5 and an opening piece 2 as shown in FIG. -The off-type and the Stein-tab type in which both the handle and the opening piece remain fixed to the can body after opening the can have been put into practical use.

In any of the methods, most of the easy-open can lids are manufactured from aluminum plates for the reasons of manufacturing technology, and steel plates are currently used for some limited applications.

As a typical example of the prior art, a coated aluminum plate or steel plate is used as a material, and a sharp blade 6 is pressed to form an opening piece shape surrounded by a cutting guide groove 4 having a V-shaped cross section as shown in FIG. To form.

The cutting guide groove 4 is formed by pressing the sharp edged blade 6 until the machined portion reaches about ⅔ of the plate thickness before machining, in order to achieve both openness and external impact resistance. In addition, it is required to accurately engage the groove so that the groove has a predetermined depth.

Therefore, although the machining tool is required to have a considerable accuracy, the tool life is a problem because the sharp blade 6 needs to be pressed strongly. Particularly in the case of steel plate, there is a drawback that the tool life is short.

Further, in order to secure the corrosion resistance to the contents or prevent the generation of outer surface rust, it is necessary to collect and coat the metal surface exposed by the processing of the cutting guide groove portion 4.

Further, the easy-open can lid uses an aluminum plate or a steel plate which has been pre-painted, and further requires coating and baking twice in order to carry out collecting paint after processing, which not only complicates the process. The use of organic solvents, the generation of carbon dioxide due to the incineration of solvents, etc. are also problems from the perspective of pollution and the global environment.

In order to solve these problems, the present applicant discloses in Japanese Patent Application No. 04-329703 that the upper and lower dies for forming the cutting guide groove forming the opening piece have a shoulder radius of 0.1 to 1.0.
Using a metal mold with a thickness of 10 mm, press-molding a steel plate or aluminum plate having a resin film on both sides with a thickness of 10 to 100 μm and a breaking elongation of 100% or more at the shoulder radius parts of the upper and lower molds, the thinnest processing It proposes a method for manufacturing an easily openable lid characterized in that a cutting guide groove is formed by reducing the metal thickness of a portion to 1/2 or less of the metal thickness before processing. 1 to 3 sequentially show a method of forming the cutting guide groove.

[0010]

In the above method, it is particularly effective that the thickness of the resin film is 16 to 60 μm from the viewpoint of stability of performance.

If the resin film has a thickness of 16 μm or less, a large film defect occurs in the cutting guide groove processed portion 4, the rivet processed portion 3, and the periphery thereof, and the covering property is remarkably deteriorated, and the practical performance is not satisfied. Further, even if the resin film has a thickness of 16 μm or more, a film defect that deteriorates the insulating property is generated, and it is necessary to further reduce the film defect in a content having a severe corrosive environment.

It is an object of the present invention to provide a method for producing an easily openable lid which is a resin-coated steel sheet having a thinner film thickness and which satisfies practical performance, using the above method as a basic technique.

[0013]

The present invention has been made in order to achieve the above-mentioned object, and improves the elongation at break of the resin by lowering the shear elastic modulus of the resin by heating, and reduces the thinned portion at the time of pressing. The resin film thickness required to prevent defects in the resin is reduced.

Specifically, a pair of upper and lower molds are pressed against a metal plate having a resin coating on both sides to provide cutting guide grooves, and the shoulder radii of the upper and lower molds for forming the cutting guide grooves forming the opening piece shape are , 0.1 to 1.0 mm, the upper and lower dies have shoulder thicknesses of 5 to 100 μm and 100% elongation at break.
The metal plate having the above resin coating on both sides is press-formed at a temperature at which the shear modulus of the resin decreases to 10 ⁶ to 10 ⁸ dyne / cm ² , preferably 10 ⁷ to 10 ⁸ dyne / cm ² , and processed. The cutting guide groove is formed by reducing the metal thickness of the thinnest part to 1/2 or less of the metal thickness before processing.

Further, it is preferable that the resin coatings present on both sides of the metal plate are composed of one or more thermoplastic resins such as polyethylene, polypropylene, polyamide, polyester and ionomer.

[0016]

The function of the present invention will be described in detail below.

As shown in FIGS. 1 to 3, a lid main body 1 made of a metal plate having a resin coating is provided with a pair of upper and lower molds 7,
In the manufacturing method of the easy-open can lid in which the cutting guide groove 4 is provided by pressing 8 to form the opening piece 2, when the cutting guide groove 4 forming the opening piece shape is formed by pressing, both the inner and outer surfaces of the can are made of resin. When a film has a defect, in a beverage can or a food can, the base plate is corroded by the contents on the inner surface, and rust is generated on the outer surface, which poses a practical problem.

Defects in the resin film can be caused by pressing the rivet portion 3 for fixing the tab 5 or the counter sink portion, where tensile stress acts during processing, or the cutting guide groove 4 in the can lid 1 shown in FIG. It tends to occur on the rolled part.
This film defect is considered to occur when the deformation resistance of the resin exceeds the deformability in both cases of tension and rolling. In other words, it can be said that if the deformation resistance can be lowered without changing the deformability of the resin film, defects are less likely to occur.

Therefore, the influence of temperature on the deformation resistance and deformability of the resin was examined. Considering the shear modulus as a physical quantity expressing the deformation resistance, when the thermoplastic resin such as polyethylene, polypropylene, polyamide, polyester, and ionomer is amorphous, the shear modulus of the resin is 10 ¹⁰ to 10 ¹¹ dyne at room temperature. / Cm ^2, but 10 ⁶ to 10 ⁸ dyne / c above the glass transition point
It drops sharply to m ² .

At this time, the tensile load is also reduced and the deformation resistance of the resin film is reduced. However, even if the shear modulus becomes 10 ⁶ dyne / cm ² or less by raising the temperature further,
This time, the fluidity of the resin is too high, and the continuous coating of the resin is hindered, especially in the rolled part.

On the other hand, the deformability of the resin film becomes large above the glass transition point, and for example, the tensile load increases, but when the temperature further increases and crystallization progresses, the deformability remarkably decreases.

From the above, there are upper and lower limits to the temperature at which the deformability becomes higher than room temperature and the deformation resistance decreases, which is because the shear modulus of the resin is 10 ⁶ to 10 ⁸ dyne / cm ^2.
The temperature range is By performing processing in this temperature range, the film defects that occur in the part that is subjected to tensile stress during processing, such as the rivet part that fixes the tab or the counter sink part, or the part that is rolled by pressing, such as the cutting guide groove, are suppressed. be able to.

Further, since the resin is softened and the workability is improved as described above, the deterioration of the adhesion between the metal and the resin due to the processing which is seen in the pressing processing is suppressed, and the feathering property (the resin is locally applied to the end surface of the cut end). Film remaining phenomenon) and corrosion resistance are improved.

Further, in an actual resin-coated steel sheet, it is impossible to reduce dust between the steel sheet and the resin coating to zero, but the softening of the resin alleviates the phenomenon that the resin is torn by the dust during the lid-making process. . In other words, there is an effect that the tolerance of dust between the steel plate and the resin is increased.

Next, the pressing process of the present invention will be described.

The shoulder radii of the upper and lower molds 7 and 8 for forming the cutting guide groove 4 are 0.1 to 1.0 mm. Shoulder radius is 0.1mm
When it is smaller, the shoulder radius portion is sharp, so that the laminating resin film of the material to be processed is damaged or broken during processing. On the other hand, when pressing is performed with a shoulder radius of more than 1.0 mm, the material is pressed in a wide area.

In this pressing process, the adhesion between the metal and the resin deteriorates due to the process. Forming a poor adhesion portion more than necessary causes a feathering property. Further, the poor adhesion portion of the coating is not preferable in terms of corrosion resistance.

At the time of processing, the peripheral portion of the opening piece is pressed between the upper and lower molds so as to reach the desired thickness to form a thin-walled portion having a gentle plate thickness deformation. The metal thickness of the thinnest part needs to be ½ or less, more preferably ⅓ or less of the metal thickness before processing from the viewpoint of can openability.

Although the breaking position at the time of opening the can is determined by this processing, in order to improve the can opening property and to make the shape of the opening after opening the opening desirable, the opening piece extruded upward or downward is , Push back to near the previous level. There are various processing methods for push-back processing.

As an example thereof, as shown in FIGS. 2 and 3, a thin-walled portion formed by the pressing process and having a smooth plate thickness change is bent into a V-shaped cross section to form a thin-cutting guide groove. There is a method of forming. Further, there is a method of making the shape of the opening desirable by forming a bead or a step in the vicinity of the thin portion having the gentle plate thickness change formed by the pressing process.

Next, a resin film laminated on a metal plate for a can lid will be described.

As the physical properties of the resin film, the elongation at break is 100%.
If it is less than the above range, a large number of defects will occur in the resin film due to insufficient elongation in thin molding at the time of pressing, which will be described later, which is not preferable. Therefore, the lower limit is 100%, but 200%
The above is preferable. In addition, the elongation property of the laminated resin film is measured according to JIS C2318 by peeling the resin film from the base material.
The value measured by the method according to is adopted.

If the thickness of the resin film to be laminated is too thin, breakage of the film is likely to occur due to processing, and conversely, if it exceeds 60 μm,
In particular, when the film has a thickness of 80 μm or more, the corrosion resistance after working progresses in a better direction, but when the cutting guide groove is broken (at the time of opening the can), the film stretches long before the break and a film remaining phenomenon ( Feathering) is likely to occur, and it is disadvantageous to use an excessively thick film. Therefore, it is within the range of 5 to 100 μm. Considering performance stability and economy, 1
Those having a range of 0 to 60 μm are particularly effective.

The resin used in the present invention is made of one or more thermoplastic resins such as polyethylene, polypropylene, polyamide, polyester and ionomer in view of food hygiene, corrosion resistance, processability and the like. Some of the above resins will be supplementarily described below.

The polyester resin in the present invention is a linear thermoplastic polyester obtained by polycondensation of dicarboxylic acid and 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,
Decanedicarboxylic acid, dodecanedicarboxylic acid, cyclohexanedicarboxylic acid, etc. may be used alone or as a mixture, and as the diol component, ethylene glycol, butanediol, decanediol, hexanediol, cyclohexanediol, neopentyl glycol, etc. may be used alone or as a mixture.

It may be a copolymer with two or more kinds of dicarboxylic acid components or a diol component, or a copolymer with another monomer such as diethylene glycol or triethylene glycol, or a polymer.

The polyamide resin is nylon 6, nylon 7, nylon 11, nylon 66, nylon 610, nylon 612, polym-phenylene isophthalamide, etc., alone or in a mixture.

The ionomer resin is a resin in which a copolymer of an a-olefin and an unsaturated carboxylic acid is crosslinked between the molecular chains with a metal ion, and as the a-olefin component, ethylene, propylene, butene, penten, etc. The unsaturated carboxylic acid is acrylic acid or methacrylic acid alone or a mixture thereof, and the metal ion component is sodium or zinc alone or a mixture thereof.

If necessary, the resin film used in the present invention may contain additives such as plasticity, antioxidant, heat stabilizer, inorganic particles, pigment, organic lubricant and the like.

The resin film is laminated on both sides of the metal plate by thermally adhering the film itself or applying a thermosetting adhesive.

[0042]

EXAMPLES The present invention will be described below with reference to examples.

As shown in Table 1, various metal plates (tin plate,
Resin films having different thicknesses and elongations at break were laminated on the respective surfaces of TFS and aluminum). An adhesive was used for the lamination.

Next, in order to manufacture the tear-off type can open lid shown in FIG. 4 from the obtained metal plate having the resin film, the pressing process shown in FIG. 1 was performed. The shoulder radius (R part) of the upper and lower molds A used was 0.5 mm. In the pressing process, the can lid was heated to the processing temperature shown in Table 2 according to the film resin as an example of the present invention for processing. On the other hand, as a comparative example, processing was performed at room temperature.

Next, an upper extrusion mold B1 having a groove 14 as shown in FIG.
2 and the lower mold B13 having the convex portion 15 are used to form the concave portion 1
4 and the convex part 15 were overlapped and pressed.

As a result, the cutting guide groove 4 as shown in FIG. 3 was formed. The thickness of the cutting guide groove 4 can be set to a desired value by changing the processing conditions in the processing steps of FIGS. 1 and 2. In this embodiment, the thickness was changed as shown in Table 2. .

With respect to the open-can lid molded as described above, an open test and a feather property were evaluated, and an energization test was conducted to investigate the degree of destruction of the resin film on the inner and outer surfaces of the can. In evaluating the can openability, a commercially available electromyographic meter was attached to a human hand, and the force causing the tab (pop value) and the force tearing the cutting guide groove (tear value) were measured.

As for the can-opening power, both values are 2.0 kg.
The following is desirable. Next, in the evaluation of the feather property, the presence of a resin film residue was examined by visually observing the cutting guide groove portion of the opening piece torn in the evaluation of the can opening property.

In the energization test, the processed test piece was dipped in an electrolytic solution, the value of the current flowing when a voltage of 6 V was applied between the test piece and the counter electrode, and the insulation property of the film was examined. The energization value is ideally 0 mA, but practically 0.1
It is preferably mA or less.

Table 2 shows the results of the above evaluation tests. As is clear from Table 1 and Table 2, according to the method of the present invention, the can-opening force is low, the insulating property of the resin is excellent, and the feather does not easily occur even if the thickness of the resin film is much thinner than before. An open can lid is obtained.

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

As described above, according to the method of manufacturing the easily-openable lid of the present invention, the thickness of the resin film of the metal plate of the can lid, the elongation at break, the shoulder radius of the die for providing the cutting guide groove, the metal plate By specifying the temperature range for processing and forming, the metal thickness of the thinnest part of the cutting guide groove, and the thermoplastic resin of the resin film, a resin-coated metal plate with a thinner film than before can be used for processing tools. The cutting guide groove is formed without applying a high load, and the can opening force is low, and the electrical insulation of the resin is excellent.
It is possible to manufacture an easily openable lid with stable performance that does not generate feathers.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a state during pressing in an example.

FIG. 2 is a vertical cross-sectional view showing a state in which a push-back process is performed after the press process in the embodiment.

FIG. 3 is a vertical cross-sectional view showing a state after pushback processing in the example.

FIG. 4 is a perspective view showing a tear-off type can lid.

FIG. 5 is a partially enlarged sectional view showing a cutting guide groove having a V-shaped cross section according to the prior art.

[Explanation of symbols]

 1 Entire lid 2 Opening piece 3 Riveting part 4 Cutting guide groove 5 Handle (tab) 6 Sharp blade 7 Upper mold A 8 Lower mold A 9 Connecting piece 10 Upper mold R part 11 Lower mold R part 12 Upper mold Mold B part 13 Lower mold B part 14 Recessed groove 15 Convex groove

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B65D 17/353 (72) Inventor Oyagi Yachichi 1-1 Hibatacho, Tobata-ku, Kitakyushu City Inside Yawata Works

Claims (2)

[Claims] 1. A method of manufacturing an easy-open can lid in which a pair of upper and lower molds are pressed against a metal plate having a resin film on both sides to form a cutting guide groove, and an opening piece is formed. The thickness is 5 to 100 μm, the elongation at break is 100% or more, and (b) the shoulder radius of the pair of upper and lower molds for providing the cutting guide groove is 0.1 to 1.0 mm. The temperature at which the metal plate having the resin coating is pressed by the shoulder radius portions of the pair of upper and lower molds is a temperature range in which the shear elastic modulus of the resin is 10 ⁶ to 10 ⁸ dyne / cm ² , D) Warm of the easily openable lid, characterized in that the cutting guide groove is formed so that the metal thickness of the thinnest part formed by the press forming is reduced to 1/2 or less of the metal thickness before processing. Manufacturing method by processing. 2. The easily openable lid according to claim 1, wherein the resin film is composed of one or more thermoplastic resins such as polyethylene, polypropylene, polyamide, polyester, and ionomer. Manufacturing method by warm working.