JPH0541507B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an easy-open can lid made of a laminated material in which a plastic resin or film is adhered to a thin metal plate, and a method for manufacturing the same.

(Prior technology) The easy-open can lids that are attached to canned goods currently sold in stores are manufactured by press-forming thin sheets of metal such as aluminum or tin plate with protective coatings on the inside and outside surfaces. . The press molding includes severe molding such as processing of score lines that will become openings and riveting to attach tabs that open the processed parts. The inner surface coating of the can lid is likely to be damaged in the harsh molding area, and if the damage is left untreated and used as a can lid, the area will corrode and eventually become perforated. Therefore, in order to prevent this, after the can lid is formed, the inner surface of the can lid is repaired using a spray coating method or an electrodeposition coating method.

Since these repair coatings require complicated equipment, there is a desire for can lids made of laminated materials that do not require repair coating. For this purpose, Japanese Utility Publication No. 51-13312, Special Publication No. 51-25797, and Japanese Unexamined Patent Publication No. 48
Various laminated structures are disclosed in publications such as No.-49589 and Japanese Unexamined Patent Publication No. 48-49590. However, while these structures can withstand scoring, the rivets completely expose the sheet metal. Therefore, it is still necessary to repaint at least the rivet parts.

(Problems to be Solved by the Invention) The conventional inner surface repair painting after forming can lids always requires a conveying device to convey can lids one by one, and the operation and maintenance of these devices is difficult. requires a lot of effort.

The object of the present invention is to obtain an easy oven can lid made of laminated material that is free from corrosion and perforation by performing a simple treatment instead of the above-mentioned repair painting, and a method for manufacturing the lid.

Further, if the can lid is a so-called full-open can lid that opens the entire surface of the lid, sharp edges may be formed on the side of the can after the lid is opened, which may injure fingers or the like.

The object of the present invention is to obtain an easy oven can lid made of laminated material that does not form such sharp edges after opening the lid, and a method for manufacturing the lid.

(Means for solving the problem) The above-mentioned problem is that the laminated material of the easy-open can lid made of laminated material is a thin metal plate with an inner paint layer and a film layer attached, and the inner paint layer is The film layer is selected from epoxy phenol, epoxy urea, or vinyl chloride sol so that it firmly adheres to the thin metal plate and can be easily deformed along with the deformation of the thin metal plate in the plane direction during can lid forming. , a group consisting of polypropylene, nylon, polycarbonate, polyethylene, linear polyethylene, ionomer, vinyl chloride, or polyester, or modified polypropylene, so as to be flexible in a direction perpendicular to the surface direction of the thin metal plate during can lid formation.
A can lid selected from the group consisting of modified polyethylene, 12 nylon, 11 nylon, or copolymerized nylon, in which the film layer is amorphous and hardened after forming the can lid, and its manufacturing method, i.e., a thin metal sheet. A laminated material in which the inner surface paint layer and the film layer are laminated, and the inner surface paint layer is firmly adhered to a thin metal plate,
The problem is solved by a method of manufacturing an easy-open can lid made of laminated material by subjecting the can lid to a reheating treatment after forming it into the shape of an easy-open can lid, and immediately thereafter quickly cooling the can lid.

More specifically, it is as follows.

FIG. 1 is a cross-sectional view showing a laminated material for an easy-open can lid according to the present invention, and the laminated material 1 includes, in order from the outer side, an outer coating layer 2, a thin metal plate 3,
The inner coating layer 4, the adhesive layer 5, the film layer 6, or the film layer 6 is directly attached to the inner coating layer 4 without using an adhesive, and the outer coating layer 2, the metal layer is attached in order from the outer side. It has a structure consisting of a thin plate 3, an inner paint layer 4, and a film layer 6. External coating layer 2 contains 35 to 60 mg/d of resin such as thermosetting epoxy, thermosetting vinyl epoxy phenol, epoxy urea, acrylic, etc., which have been conventionally used as external coating.
^m2 coated structure. The thin metal plate 3 can be made of aluminum plate, aluminum alloy plate, tinplate plate, stain-free steel plate, black plate, or other can lid material, and its thickness is in the range of 0.20 to 0.35 mm, depending on the diameter of the lid and its purpose. used in The inner surface paint layer 4 is made of 40 to 120 mg/dm2 of epoxy phenol, epoxy wear, or chlorinated beer sol, preferably 50 to 110 mg/ ^dm2 , which strongly adheres to metal and has good corrosion resistance.
mg/dm ² coated. Examples of the adhesive layer 5 include a layer formed by spraying and baking modified polypropylene powder, a urethane adhesive, an acrylic adhesive, an epoxy adhesive, and a polyester adhesive. The film layer 6 has a thickness of 20 to 60μ, preferably 20 to 30μ.
Polypropylene, nylon polycarbonate, or polyester films are used when canned goods are subjected to high-temperature sterilization; polyethylene, linear polyethylene, ionomer, or vinyl chloride films are used when pasteurized or hot-filled. can be used. In addition, when forming the film layer 6 directly on the inner surface paint layer 4 without using the adhesive layer 5,
Adhesive films of modified polypropylene, modified polyethylene, 12 nylon, 11 nylon, and copolymer nylon are used.

The method for producing the laminated material 1 is to simultaneously apply predetermined amounts of the paint for the outer coating layer 2 and the paint for the inner coating layer 4 on both sides of a thin metal plate 3 using a roll method or a spray method, and then apply the paint in an oven or the like. Heat it through and bake it. Next, an adhesive is applied or sprinkled on the inner surface paint layer 4 by a roll method or a spray method, and dried or baked in an oven or the like.

Next, a film is pressed onto the adhesive layer 5 or, if no adhesive is used, onto the inner surface paint layer with a heated roll, and baked in an oven.

The laminated material 1 manufactured through the above steps is formed into an easy-open can lid using conventional methods and equipment. FIG. 2 is a partial sectional view showing the score processing process, and FIGS. 3 and 4 are partial sectional views showing the rivet processing process. Normal easy-open can lids are
After being formed into the shape of a can lid with a countersink wall and flange, it is scored and riveted. As shown in Fig. 2, the scoring process is performed to ensure that the remaining thickness reaches the inside of the thin metal plate 3 of the laminated material 1 on the anvil 11.
It is molded by press-fitting the score punch 12 so that it has a thickness of 80-120μ. Therefore, the thin metal plate 3 bulges toward the inner surface, and the inner surface paint layer 4 and the film layer 6 are also compressed between the anvil 11 and the thin metal plate 3.
At the same time, it bulges inward. Rivet processing is the third
As shown in FIG.
Step 4 consists of the step of crushing the head of the cup-shaped portion 15. In this step, when forming the cup-shaped portion 15, a strong force is applied to the laminated material 1 near the base of the radius at the tip of the pin punch 13, causing slippage. In the easy-open can lid made of laminated material of the present invention, cracks occurred in the inner paint layer 4 at the score portion, and tears occurred in the film layer 6 at the rivet portion. However, in the score section, film layer 6
However, the inner paint layer 4 remains intact at the rivet part,
The thin metal plate 4 was protected from the contents. This is because the inner surface paint layer 4 is made of the above-mentioned material and is therefore weak against impact during score processing, but it adheres well to the thin metal plate 4 and can be deformed together with the thin metal plate.
In addition, the film layer 6 is made of polypropylene and other materials as described above, which are weak against deformation in the shear direction such as riveting, but are flexible and strong against deformation in the compression direction such as score processing. Seem. Furthermore, after being formed into a can lid, the surface of the film layer 6 is deformed in the shearing direction in areas that have been deformed due to processing such as the countersink area, bead area, score area, and rivet area, resulting in thin wrinkles. , whitening occurred.

The flexibility of the film layer 6 having such properties means that when the tap 16 is pulled up and the score is broken,
The film layer 6 does not break below the score, but tends to break at the point where the force acting along the surface of the film layer 6 is greatest. For this reason, a state in which the film unnaturally protruded into the opening after opening the lid occurred (hereinafter, this state is referred to as film remaining).

In order to eliminate the film residue, it would be good if each layer were to break integrally when the lid was opened, but for this purpose, the adhesive strength between the inner surface paint layer 4 and the film layer 6 had to be strengthened. The adhesive strength should be made close to that between the thin metal plate 3 and the inner surface paint layer 4, or the tear strength of the film layer 4 itself should be weakened by making the film layer 4 brittle. Based on this idea, in order to eliminate film residue and further eliminate whitening, after forming into a can lid, the can lid was reheated and allowed to cool. As a result of experiments, the temperature and time of the reheating treatment were set to 195 in Examples 1 to 4 shown below.
The most suitable condition was heating in a hot air oven at 180°C for 3 minutes, ie, the temperature of the film layer reached 180°C. As a result of the reheating treatment, the whitening disappeared, and the remaining film protruded by 0.05 to 0.5 mm from the broken part of the score, becoming a suitable and safe remaining film that covered the broken part.

However, when we conducted real can storage tests for seasoned bonito, simmered tuna, and tomato juice using can lids subjected to the reheating treatment, the score film layer of the can lid used for seasoned bonito and simmered tuna was found. Cracks occurred, and some perforations occurred in the bonito-flavored score portions. The reason for the cracks that occur in this film is that when the thin metal plate 3 bulges toward the inner surface during scoring, the film layer 6 also bulges.
A force in the direction parallel to the film surface was applied inside the film layer, and as a result of reheating and cooling in this state, crystals grew within the film layer and cracks occurred along the grain boundaries. This seems to be because the contents came into contact with the thin metal plate 3 from the inner surface paint layer 4 that had been cracked during the scoring process. Therefore, in order to prevent the film layer 6 from cracking after the reheating treatment, it is sufficient to restrict the growth of crystals, but this method is suitable for mass production, has simple equipment, and has easy quality control. After reheating, we immediately immersed it in a pool of tap water to quickly cool it down. As a result of the rapid cooling, most of the film layer became amorphous and cracks in the film layer 6 disappeared. In addition, whitening disappeared and the remaining film was satisfactory.

(Function) Since the easy-open can lid was manufactured using the laminated material 1 in which the thin metal plate 3 was coated with the inner surface paint layer 4 of the above materials and the film layer, the thin metal plate 3 did not stretch or bend during the manufacturing process. At the receiving site,
The inner surface paint layer 4 deforms together with the thin metal plate 3 without cracking, and the film layer 6 covers the thin metal plate 3 without cracking at a portion where the thin metal plate 3 is compressed.

The film layer 6 made of the above-mentioned material will leave an unnatural film residue after the lid is opened, so it should be used after the lid is made.
The lid was reheated and rapidly cooled. The reheating treatment and quenching make most of the film layer amorphous and integrate the film layer 6, while adding appropriate brittleness to the flexibility of the film layer 6.

Example 1 Aluminum (5052・H・
19, alodine treatment) with a thickness of 0.27 mm,
42± thermosetting epoxy paint as outer coating layer 2
At the same time, an epoxy phenol paint was applied as the inner coating layer ⁴ to the metal sheet 3 using a roll in an amount of 6 mg/dm ² in an amount of 100±10 mg/dm 2 and dried and cured in an oven at 270° C. for 30 seconds.

Next, a dispersion (registered trademark Mol Prime) of modified polypropylene powder was applied on the inner surface paint layer 4 as an adhesive layer 5 using a #85 gravure coater at a rate of 1.4 mm.
g/m ² and dried at 220°C for about 3 minutes. When the thin metal plate 3 is still kept at 104-110°C, a film layer 6 with a thickness of 30μ is applied on top of this adhesive layer 5. An unstretched polypropylene film was temporarily attached using a pressure roll with a surface temperature of 150 to 160°C, heated again in an oven to 180 to 220°C to completely fuse the film, and then left to cool to obtain a laminate 1.

Next, after applying 4.5±1 mg/1400 cm ² of microwax as a lubricant to both sides of the laminated material 1, a full-opening can lid with a diameter of 211 was manufactured using a conventional method. At this time, whitening had occurred in the film layer 6.

Next, the 211-diameter can lid was reheated by passing it through an oven at 180° C. for 3 minutes, and then immediately immersed in a pool of tap water to rapidly cool it. As a result, the whitening of the film layer 6 disappeared.

When the lid of the 211-diameter full-open can mentioned above was opened, a film with a width of 0.1 to 0.8 mm remained on the edges. Because of this residual film, there was no risk of injury to the fingers even if the edges were touched.

Further, the lid of the 211-diameter fully open can was immersed in a saturated copper sulfate solution for 3 days, but no reaction occurred. Therefore, we performed a storage test on actual cans by wrapping the can lid around a tin can body, and found that conventional repaired can lids corrode and cause perforations, such as bonito seasoned, boiled tuna, and sweet corn quail eggs. Even after 6 months of high-temperature storage of pet food, Yamato beef, etc. at 38℃, there was no corrosion, showing good results.

This time, a 200-diameter partially open can lid was manufactured using the laminate material 1 of this example described above, subjected to reheating treatment at 180°C for 3 minutes, rapidly cooled, and wrapped around a can body made of stain-free steel. A storage test was conducted on a tomato youth sports drink (containing salt) that required the use of a partially opened tin can lid.38
No noticeable corrosion was observed during 4 months of high-temperature storage at ℃. The remaining film was also suitable.

Example 2 This example differs from the laminated material shown in Example 1 and the adhesive layer, and after baking the outer surface paint layer 2 and the inner surface paint layer 4 on the thin metal plate 3 in the same manner as in Example 1. As the adhesive layer 5, a urethane two-component adhesive was applied at 5 to 6 g/m ² using a #85 gravure roll, and immediately after heating and drying at 90 to 110°C for about 30 seconds, the film layer 6 was coated as the adhesive layer 5. An unstretched polypropylene film having a thickness of 30 μm was pressed with a pressure roll heated to 70 to 90°C, and this was aged at 40°C for 4 days to obtain a laminate 1.

A 211-diameter full-open can lid and a 200-diameter partially-open can lid were manufactured using the laminated material 1 in the same manner as in Example 1. In the manufactured can lid, the film layer was whitened in Example 1, but in this example, whitening did not occur, but there was a large amount of film remaining, so this can lid was subjected to reheating treatment at 180 to 220°C and rapid cooling. However, film residue and corrosion resistance were as good as in Example 1.

Example 3 The outer coating layer 2, the thin metal plate 3, and the inner coating layer 4 have the same features as in Example 1, and the inner coating layer 4
A modified polypropylene film of 30 μm was heat-pressed as film layer 6 using a roll at 200° C., and this was passed through an oven at 200° C. for 3 minutes to obtain laminate material 1.

Using this laminated material, a 211 diameter full-opening can lid was manufactured in the same manner as in Example 1, subjected to reheating treatment and rapid cooling, and the can lid was wrapped around a tin can body and subjected to a high temperature storage test at 38°C with tuna flavoring. No corrosion was observed even after 9 months. The remaining film was also suitable.

Example 4 Instead of the film layer of Example 3, a 40μ 12/
6/66 nylon copolymer film as inner coating layer 4
Laminated material 1 was obtained by heating and pressing with a roll at 200°C and heating this in an oven at 220°C for 3 minutes.

Using this laminated material, a 211 diameter full-opening can lid was manufactured in the same manner as in Example 1, and when it was subjected to reheating treatment and rapid cooling, the same effect as in Example 3 was obtained.

In addition, in this example, the inner coating layer 4 was 100±10mg/
The effect was comparable even when the dose was 50 mg/dm ² to 50 mg/dm ² .

Example 5 Laminated material 1 was produced in the same manner as in Example 2 except that a 30 μm thick unstretched or 5-20% stretched polyester film was used in place of the film layer of Example 2.

A full-open can lid with a diameter of 211 mm was manufactured using the laminated material 1 in the same manner as in the example. At this time, no whitening was observed in the film layer. No corrosion was observed in the can lid in an actual can test. Since there was a large amount of film remaining,
310-320 above 260℃ which is the melting point of polyester
When the film was reheated at 0.degree. C. and rapidly cooled, the remaining film and corrosion properties were as good as in Example 1.

(Effects of the Invention) The easy oven can lid made of laminated material and the method for manufacturing the same according to the present invention are as described above, and the easy oven can lid is free from corrosion and perforation without the conventional repair painting that requires a great deal of labor. I got a can lid. In addition, the can lid of the present invention leaves a suitable film residue on the edges after opening, eliminating the fear that the edges may injure fingers. Furthermore, if a cooled sterilizing liquid or the like is used in the rapid cooling of can lids during reheating treatment, can lids can be manufactured in a sterile state, and the additional effects are immeasurable.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the laminated material for easy oven can lids of the present invention, FIG. 2 is a partial cross-sectional view showing the scoring process in the can lid manufacturing process. It is a partial sectional view showing a rivet processing process similarly. DESCRIPTION OF SYMBOLS 1... Laminated material, 2... External coating layer, 3... Metal thin plate, 4... Inner coating layer, 5... Adhesive layer, 6...
...Film layer, 11...Anvil, 12...Score punch, 13...Pin punch, 14...Hammer,
15...cup-shaped part, 16...tab.

Claims (1)

[Claims] 1. An easy-open can lid made of a laminated material, wherein the laminated material is a thin metal plate, an inner coating layer selected from epoxyphenol, epoxyurea, or vinyl chloride sol, and polypropylene, nylon, polycarbonate, or polyethylene. , linear polyethylene, ionomer, vinyl chloride, or polyester, or a film layer selected from the group consisting of modified polypropylene, modified polyethylene, 12 nylon, 11 nylon, or copolymerized nylon. , An easy-open can lid made of laminated material, characterized in that the film layer is amorphous and hardened after the can lid is formed. 2. The film layer is selected from the group consisting of polypropylene, nylon, polycarbonate, polyethylene, linear polyethylene, ionomer, vinyl chloride, or polyester, and the film layer is selected from modified polypropylene powder, urethane, acrylic, epoxy, or polyester. The easy-open can lid made of laminated material according to claim 1, which is bonded to the inner surface paint layer with an adhesive. 3. The film layer according to claim 1, wherein the film layer is selected from the group consisting of modified polypropylene, modified polyethylene, 12 nylon, 11 nylon, or copolymerized nylon, and the film layer is thermally bonded to the inner coating layer. Easy-open can lid made of laminated material. 4. In a method for manufacturing an easy-open can lid made of laminated materials, a thin metal plate is coated with an inner coating layer selected from epoxyphenol, epoxyurea, or vinyl chloride sol, and polypropylene, nylon, polycarbonate, polyethylene, linear polyethylene, A film layer selected from the group consisting of ionomer, vinyl chloride, or polyester, or modified polypropylene, modified polyethylene, 12 nylon, 11 nylon, or copolymerized nylon is laminated, and the inner coating layer is covered with a thin metal plate. An easy-open can lid made of laminated material, characterized in that the laminated material firmly adhered to is formed into the shape of an easy-open can lid, the can lid is reheated, and then the can lid is immediately rapidly cooled. manufacturing method. 5 A film layer selected from the group consisting of polypropylene, nylon, polycarbonate, polyethylene, linear polyethylene, ionomer, vinyl chloride, or polyester is modified with polypropylene powder, urethane, acrylic, epoxy,
The method for producing an easy-open can lid made of laminated material according to claim 4, wherein the lid is adhered to the inner surface paint layer with an adhesive selected from polyester or polyester, and reheated so that the film layer reaches 180°C. 6 Modified polypropylene, modified polyethylene, 12
The laminate according to claim 4, wherein a film layer selected from the group consisting of nylon, 11 nylon, or copolymerized nylon is thermally bonded to the inner coating layer, and a reheating treatment is performed so that the film layer reaches 180°C. Method for manufacturing easy-open can lids made of wood. 7. A patent claim in which a film layer made of polyester is adhered to an inner paint layer with an adhesive selected from modified polypropylene powder, urethane, acrylic, epoxy, or polyester, and the film layer is reheated to a temperature of 310°C. A method for producing an easy-open can lid made of laminated material according to item 4.