JP3271819B2 - Can lid and manufacturing method thereof - 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 can lid used for canning food and drink and the like and a method for producing the same.

[0002]

2. Description of the Related Art In a metal can lid used for canning food and drink, when the metal forming the can lid comes into contact with the contents, the metal can lid is corroded or the metal is eluted and eluted. If the flavor of the product changes, or if the can lid is made of a metal different from that of the can body, a partial battery is formed through the contents at the contact portion between the can lid and the can body, resulting in corrosion. There is a risk of progressing. Therefore, in order to prevent the above problem, a protective coating layer has been conventionally formed on the inner surface of the metal can lid.

[0003] The can lid includes a can lid which is not provided with an opening for taking out contents called a separate lid, and a can lid which forms the opening such as an easy-open can lid.

As shown in FIGS. 2 and 3, the separate lid has a chuck wall 12 formed on the outer periphery of a flat panel portion 11, and the outside of the chuck wall 12 is bent to form a can body. Seaming panel 13 for tightening
And the structure in which the winding part 14 is formed. Also,
A sealing compound 15 is applied to a lower surface of the seaming panel 13. The separate lid is for closing one end of a can body obtained by rolling a can body material formed of a strip-shaped surface-treated metal plate and welding or bonding the end of the can body material. This name is given to a canner manufacturer separately from a bottomed cup-shaped can body in which an easy-open can lid is wound around one end of the can body. After filling the contents in the bottomed cup-shaped can body, the canned manufacturer closes the other open end of the cup-shaped can body with the separate lid to produce a can.

There are two types of easy-open can lids: a pull-tab type and a stay-tab type. The former is a type in which an opening tab is separated from the can lid when it is opened as described later, and the latter is an opening type. However, the opening tab is of a type that is connected to the surface of the lid and cannot be separated, and both are generally used. Here, a pull-tab type easy-open can lid having a simple configuration will be described as an example.

[0006] The pull tab type easy open can lid,
As shown in FIGS. 4 and 5, a chuck wall 12 is formed on the outer periphery of a flat panel portion 11, and a seaming panel 13 for curving the outside of the chuck wall 12 and winding it around a can body. And a winding portion 14. Further, a sealing compound 15 is applied to a lower surface of the seaming panel 13. Then, a score 17 defining the opening portion 16 is provided on the panel portion 11, and a pull tab 19 for opening is attached to a rivet 18 provided by processing the panel portion 11 in the opening portion 16,
At the time of opening, by pulling up the opening pull tab 19, the opening portion 16 is broken along the score 17 and separated from the panel portion 11, so that the opening can be easily opened. The easy-open can lid is provided with a bead 20 along the score 17 on the panel portion 11 to facilitate opening. The easy-open can lid is wound around the open end of a cup-shaped can body obtained by ironing and drawing the bottomed cup-shaped can body or metal plate, and an opening for taking out the contents. It can be formed.

Conventionally, in the can lid, a resin coating layer formed by applying a resin-based paint is provided as a protective coating layer for preventing contact between the metal forming the can lid and the contents. However, when the resin coating layer is coated with a resin-based paint, pinholes may be formed, and since the can lid has a configuration shown in FIGS. 2 to 4, the seaming panel 13 and the tightening portion 14 are formed. In this case, cracks may occur in the resin coating layer, and a complete protective effect cannot be obtained. Further, in the easy open can lid, the score 17, the rivet 18 and the bead 20 are provided on the panel portion 11.
Therefore, processing with a large amount of deformation is required to form the resin film, and the resin coating film is easily cracked or peeled. In order to repair pinholes, cracks, peeled portions, etc. of the resin coating layer, it is conceivable to perform coating correction by spray coating after processing, but there is a problem that the operation becomes complicated and the production cost increases. .

Accordingly, it has been proposed to form the protective coating layer by bonding a synthetic resin film to the can lid. For example, Japanese Patent Publication No. 5-7262 discloses an easy-open can lid formed by bonding a thermoplastic polyester film to an inner side of an aluminum plate via an epoxy phenol resin adhesive.

According to the description of the above publication, a film made of a thermoplastic polyester such as polyethylene terephthalate is bonded to the side of the aluminum plate serving as the inner surface of the can by thermocompression bonding via an epoxyphenol resin adhesive. It is said that when forming a seaming panel and a tightened portion, or when processing a score, a rivet, or the like, a protective coating layer excellent in adhesive strength and free from pinholes, cracks, sagging, etc. is obtained.

[0010] However, in order to obtain the above-mentioned sufficient adhesive strength using the epoxyphenol-based resin adhesive, long time heating is required, and there is a disadvantage that the production line becomes long. In consideration of the production of the can lid and the subsequent winding process, it is desired that the protective coating layer has a higher adhesive strength.

[0011]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems, and obtains sufficient adhesive strength between the protective coating layer and the metal plate by heating for a short time. And a method for manufacturing the same.

[0012]

In order to solve the above problems, the can lid of the present invention is obtained by bonding a polyester film to at least the inner surface of a metal plate via a thermosetting resin-based adhesive layer. In a can lid having a protective coating layer made of the polyester film formed thereon, the thermosetting resin-based adhesive is a 70/30 epoxy resin having a number average molecular weight of 5,000 to 20,000 and a trimellitic anhydride-based curing agent.
It is characterized by being mixed at a weight ratio of up to 99/1.

In the thermosetting resin adhesive used for the can lid of the present invention, the epoxy resin has a number average molecular weight of 500.
When it is less than 0, the adhesive strength is insufficient, and when it exceeds 20,000, the viscosity becomes high and the coating workability is inferior. When the number average molecular weight is less than 5,000, the adhesiveness of the adhesive layer is increased and the tack-free property is reduced when the adhesive layer is formed by previously applying and drying the polyester film. The epoxy resin is preferably a bisphenol-type epoxy resin obtained by reacting bisphenol with epichlorohydrin.

The thermosetting resin-based adhesive is a trimellitic anhydride-based curing agent because of its excellent curing properties as a curing agent for the epoxy resin, excellent blocking resistance of the film after application, and tack-free properties. Is used. Examples of the trimellitic anhydride-based curing agent include trimellitic anhydride and derivatives thereof. Examples of the derivative of trimellitic anhydride include glycerol tristrimellitate anhydride, a dimer of trimellitic anhydride, and ethylene glycol bistrimellitate anhydride.

In the thermosetting resin-based adhesive, the weight ratio of the epoxy resin to the trimellitic anhydride-based curing agent is 9%.
If it is less than 9/1, it takes a long time to cure the epoxy resin even when heated at a high temperature, and even if the ratio exceeds 70/30, the effect of accelerating the curing of the epoxy resin is not further improved.

The thermosetting resin-based adhesive may contain another curing agent such as a phenolic resin in addition to the trimellitic anhydride-based curing agent, and may further include a low molecular weight epoxy resin, an acrylic resin, It may contain an aminoplast resin, a polyester resin, a urethane resin, a polysiloxane resin, an organic or inorganic pigment, or the like.

In the can lid of the present invention, a conventionally known surface-treated steel plate or aluminum alloy plate for can lid material is used as the metal plate. The metal plate has a thickness of 0.10 to 0.40.
The range of mm is suitable for use as a can lid.

Examples of the metal plate include the following. First, a tin-plated steel sheet in which the surface of a base steel sheet is plated with tin in an amount of 0.5 to 2.0 g / m ² . Second, tin is plated in an amount of 0.5 to 1.7 g / m ² on a base layer made of metallic nickel formed on the surface of the base steel sheet, and tin amount is 0.05 g / m ² on the base steel sheet. A tin-plated steel sheet in which a tin layer distributed in the range of 10 to 60% of the surface area of the base steel sheet is formed in a mottled or island shape. Third, a thin tin-plated steel sheet in which tin is plated in an amount of 0.1 to 1.0 g / m ² on a base layer made of metallic chromium formed on the surface of the base steel sheet. Fourth, a tin-free steel in which a chromium oxide layer is formed in an amount of 5 to 50 mg / m ² on an underlayer made of disc-like and granular metallic chromium formed on the surface of a base steel plate. Fifth, one surface of the base steel sheet is subjected to the same surface treatment as the second tin-plated steel sheet, and the other surface is subjected to a different surface treatment, for example, 8.4 g / m ² . Tinplate with tin plating. Each of the first to fifth surface-treated steel sheets may be provided with a metal chromium layer or a chromium oxide layer on its surface. Sixth, 50 to 150 m on the surface of the base steel sheet
g / m ² of metallic chromium layer is formed, on which 5 to 3
A surface-treated steel sheet on which a chromium metal layer in an amount of 0 mg / m ² is formed. Seventh, an aluminum alloy plate having an alloy number 5182 specified in JIS-H4000. Eighth, JIS-H40
An aluminum alloy plate having an alloy number of 5052 specified in 00.

In the can lid of the present invention, the polyester film adhered to each of the metal plates is excellent in strength, transparency, suitability for contents such as retention of flavor, and polycondensation of a dicarboxylic acid component and a diol component. Any polyester may be obtained as long as
Terephthalic acid, isophthalic acid, aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, and ethylene glycol, propylene glycol, preferably a polyester obtained by polycondensation with diols such as butylene glycol, terephthalic acid and ethylene glycol Particularly preferred is a polyester (polyethylene terephthalate) obtained by polycondensation. The polyester may contain another dicarboxylic acid component or diol component in the dicarboxylic acid component or diol component as desired.

Other preferred polyesters other than polyethylene terephthalate include JP-A-51-42786.
JP-A-64-70352, JP-A-2-24273
And polyesters described in JP-A No. 8 and other publications.

The polyester film has a thickness of 5 to 5.
It is preferably in the range of 50 μm. When the thickness is 5 μm or less, the effect of preventing corrosion of the can lid and elution of metal cannot be sufficiently obtained, and there is a possibility that pinholes and cracks may occur during processing. When the thickness is 50 μm or more, the residual stress becomes large, and the adhesiveness to the can lid may be reduced when the can is double-wrapped around the can body.

As the polyester film, an unstretched polyester film, a stretched polyester film, a copolymerized polyester film, or the like may be appropriately used from the viewpoint of material properties, but scores, rivets, beads, etc., such as an easy-open can lid, may be used. When it is necessary to perform processing with a large amount of deformation, it is desirable to make the film thickness larger than that in a separate lid, and a copolyester film excellent in processability is suitable as polyester. As the copolymerized polyester film,
Examples thereof include a type in which part of terephthalic acid is substituted with isophthalic acid, and a copolymerized polyester film in which part of ethylene glycol is substituted with butylene glycol.

In the can lid of the present invention, the protective coating layer may also be formed on the outer surface of the metal plate on the outer surface of the can. However, the outer surface of the can does not contact the contents and does not require a high degree of corrosion resistance. Therefore, a resin coating layer may be formed by applying a paint for surface protection. Examples of the paint for forming the resin coating layer include an epoxy phenol resin paint and an epoxy urea resin paint.

In the can lid of the present invention, an epoxy resin having a number average molecular weight of 5,000 to 20,000 and a trimellitic anhydride-based curing agent are coated on one side of a polyester film at a ratio of 70/30 to
A thermosetting resin-based adhesive mixed at a weight ratio of 99/1 is applied, dried by heating to a temperature at which the curing reaction of the thermosetting resin-based adhesive does not substantially proceed, and the polyester film is dried. A thermosetting resin-based adhesive layer forming step of forming a thermosetting resin-based adhesive layer thereon, and heating the metal plate to form the thermosetting resin-based adhesive layer on at least the inner side of the can of the metal plate. Bonding the polyester film on which is formed, through the thermosetting resin-based adhesive layer to form a protective coating layer made of the polyester film; and a metal plate on which the protective coating layer is formed. And a can lid forming step of forming a can lid from the above.

In the manufacturing method, in order to more securely adhere the metal plate and the polyester film in the protective coating layer forming step, first, the polyester film is attached to the heated metal plate by a thermosetting resin. It is preferable to perform temporary bonding via the system adhesive layer, and then further heat the metal plate to which the polyester film has been temporarily bonded to cure and bond the thermosetting resin-based adhesive.

The heating for the temporary bonding of the polyester film may be performed so long as the polyester film can be adhered to the metal plate via the thermosetting resin-based adhesive. Is 120 to 25
It is performed within the range of 0 ° C. When the temperature of the metal plate is 120 ° C. or lower, a sufficient adhesive force may not be obtained, and at 250 ° C. or higher, an active group necessary for curing the thermosetting resin-based adhesive in a post-process may be insufficient. May be lost prematurely. The heating of the metal plate for curing the thermosetting resin-based adhesive is performed at a temperature in the range of 180 to 225C.

[0027]

According to the present invention, when a polyester film is bonded to a metal plate, the number average molecular weight is 5,000 to 20,000.
70% epoxy resin and trimellitic anhydride curing agent
Since the thermosetting resin-based adhesive mixed at a weight ratio of / 30 to 99/1 is used, the protective coating layer made of the polyester film is provided on the metal plate via the thermosetting resin-based adhesive layer. A can lid that is securely bonded is obtained. Therefore, in the can lid of the present invention, generation of pinholes, cracks, slack, and the like in the protective coating layer due to processing at the time of lid manufacturing is prevented.

In the can lid of the present invention, the protective coating layer may be formed on the outer surface of the metal plate on the outer surface of the can. However, the outer surface of the can does not come into contact with the contents and does not require high corrosion resistance. Therefore, the surface can be protected also by forming the resin coating layer by applying a paint.

According to the production method of the present invention, first, the thermosetting resin-based adhesive is applied to one surface of the polyester film, and the curing reaction of the thermosetting resin-based adhesive proceeds substantially. By heating and drying at a temperature that is not high, a polyester film having the thermosetting resin-based adhesive layer formed thereon is obtained. Next, by heating the metal plate and adhering the polyester film to at least the inner surface side of the metal plate via the thermosetting resin-based adhesive layer, the thermosetting resin-based adhesive is short-lived. And a sufficient adhesive strength is obtained between the polyester film and the metal plate to form a protective coating layer made of the polyester film. Next, a can lid having the above-described configuration is obtained by forming a can lid from the metal plate on which the protective coating layer is formed.

In the manufacturing method of the present invention, it is desirable that the heating be sufficiently performed when forming the protective coating layer. However, the polyester film is bonded to the heated metal plate by a thermosetting resin-based adhesive. Temporarily bonding via the agent layer, and then heating the metal plate to which the polyester film is temporarily bonded to cure and bond the thermosetting resin-based adhesive, whereby the heating can be performed in a short time. As much as possible, the metal plate and the polyester film are more securely bonded.

[0031]

Embodiment 1 Next, the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is an explanatory sectional view showing a configuration of a can lid of the present invention, FIG. 2 is a top view showing an example of a can lid of the present invention, FIG. 3 is a sectional view taken along line III-III of FIG.
FIG. 5 is a top view showing another example of the can lid of the present invention, and FIG.
FIG. 6 is a plan view schematically showing a processing apparatus for forming a protective coating layer on a metal plate in the manufacturing method of the present invention,
FIG. 7 is a front view showing the configuration of the transport path of the apparatus shown in FIG.

As shown in FIG. 1 (a), the separate feeding lid of this embodiment has a polyester film 2 on a metal plate 1 inside the can.
An epoxy resin having a number average molecular weight of 5,000 to 20,000,
Glycerol tristrimellitate anhydrous 70/3
The protective coating layer 4 is formed by bonding via a thermosetting resin-based adhesive layer 3 mixed at a weight ratio of 0 to 99/1.

The separate feeding cover of this embodiment has the structure shown in FIG. 1A, and has a chuck wall 12 formed on the outer periphery of a flat panel portion 11 as shown in FIGS. A seaming panel 13 and a tightening portion 14 are formed by curving the outside of the chuck wall 12, and a sealing compound 15 is provided on the lower surface of the seaming panel 13.
Is applied.

In the separate lid, as the metal plate 1, an underlayer made of metallic nickel is formed on one surface of the base steel plate, and tin is applied in an amount of 0.5 to 1.7 g / m ² thereon. As a result, a tin layer having a tin amount of 0.05 g / m ² or more and distributed in the range of 10 to 60% of the surface area of the base steel sheet is formed on the base steel sheet in a mottled or island shape, and the other surface is formed. Has a thickness of 0.2 g coated with tin in an amount of 8.4 g / m ^2.
1 mm tin plate (hereinafter abbreviated as TND tin plate)
Is used. As the polyester film 2, a biaxially stretched polyethylene terephthalate (hereinafter abbreviated as PET) film having a thickness of 12 μm is used, and the thermosetting resin-based adhesive layer 3 has a number average molecular weight of 1
A thermosetting resin-based adhesive in which 0000 epoxy resin and glycerol tristrimellitate anhydride are mixed at a weight ratio of 97/3 is used.

Next, a method for manufacturing the separate lid will be described.

In manufacturing the separate lid, first, a long polyester film (biaxially stretched PET film)
2 is pulled out and subjected to corona discharge treatment on one side,
A resin solution obtained by dissolving the epoxy resin and glycerol tristrimellitate anhydride in an organic solvent in the above-mentioned weight ratio was applied to the surface subjected to the corona discharge treatment by gravure roll.
The coating was performed at a speed of 7 m / min. Then, the adhesive was dried at a temperature of 120 ° C. for 10 seconds to prevent the curing reaction of the adhesive from proceeding, to form an adhesive layer 3 made of the thermosetting resin-based adhesive, and wound up. In the polyester film 2 on which the thermosetting resin-based adhesive layer 3 is formed, the thermosetting resin-based adhesive layer 3 does not cause blocking, and thus has excellent tack-free properties when wound up. Therefore, there is no risk that the wound polyester film 2 will be hindered when it is drawn out and used in the next step.

Next, the metal plate (TND tin plate) 1 for separate feeding is heated by the apparatus shown in FIG. 6 and FIG. Bonded via the resin adhesive layer 3. As shown in FIG. 6, the apparatus for heating and bonding the polyester film 2 is provided with a metal plate supply means on the upstream side of a transport path 21 for temporarily bonding the polyester film 2 to one surface while transporting the metal plate 1. A heating oven 23 is provided to heat and cure the thermosetting resin-based adhesive layer 3 by heating the metal plate 1 to which the polyester film 2 is temporarily bonded on the downstream side. Cooling means 2 for cooling
4 are provided. The metal plate 1 is long and has a predetermined width, and is provided wound around a coil 22a of the metal plate supply means 22, as shown in FIG.

In the transport path 21, as shown in FIG.
In order from the upstream side, a feed roller 25 for guiding the metal plate 1 supplied from the metal plate supply means 22 to the transport path 21, a high-frequency heating device 26 for preheating the metal plate 1, and a preheated metal plate 1
Roller 27 for pressure-bonding and temporarily bonding the polyester film 2 to a metal plate, and knife cylinder 28 for cutting the metal plate 1 to which the long polyester film 2 is temporarily bonded to a predetermined length.
Is provided at the end, and a payout means 29 for paying out the cut metal plate 1 is provided. The pressure roller 27
Is capable of heating itself, and also serves as a heating means.

A film supply means 31 is provided above the transport path 21 so as to draw the polyester film 2 from the coil 30 around which the long polyester film 2 is wound and supply the polyester film 2 to the pressure roller 27.

According to the apparatus shown in FIGS. 6 and 7, first,
The long metal plate 1 is pulled out of the coil 22a by the metal plate supply means 22. The long metal plate 1 is supplied to the transport path 21 via the feed roller 25, and is supplied to the transport path 21.
It is transported at a speed of 60 m / min above. Next, the metal plate 1
Is preheated to 220 ° C. by the high-frequency heating device 26 on the conveying path 21 and guided to the pressure roller 27. Crimping roller 27
Is heated to 170 ° C., and the polyester film 2 supplied from the film supply means 31 is thermocompression-bonded to the metal plate 1 on the surface on which the thermosetting resin-based adhesive layer 3 is formed, and is temporarily bonded. .

Next, the metal plate 1 to which the polyester film 2 has been temporarily adhered is cut into a predetermined length by a knife cylinder 28, discharged from a conveying path 21 by a discharging means 30, and guided to a heating oven 23. The metal plate 1 is heated in a heating oven 23 at 215 ° C. for 1 minute, whereby the thermosetting resin-based adhesive layer 3 is cured, and the polyester film 2 is securely bonded.

Next, the metal plate 1 is cooled by the cooling means 24. After the metal plate 1 is heated in the heating oven 23, the metal plate 1 may be cooled by simply allowing it to cool. However, since the metal plate 1 is cooled in a short time by providing the cooling means 24, the production line can be shortened. .

Next, the metal plate 1 on which the protective coating layer 4 was formed was processed by a conventionally known lid-making apparatus to manufacture a separate lid having the above configuration.

The film-laminated easy-open can lid (hereinafter referred to as easy-open can lid (A)) of the present embodiment has a polyester film 2 on the inner side of a metal plate 1 as shown in FIG. Has a number average molecular weight of 5,000 to
20,000 epoxy resin and glycerol tristrimellitate anhydride are bonded via a thermosetting resin-based adhesive layer 3 in which the weight ratio is 70/30 to 99/1, and the protective coating layer 4 Is formed, and a resin coating layer 5 made of an epoxy urea resin-based paint is formed on the outer surface of the can.
Is provided.

Easy open can lid of this embodiment (A)
Has the configuration shown in FIG. 1B, and has the configuration shown in FIGS.
As shown in FIG. 3, in addition to the configuration of the separate cover shown in FIGS. 3 and 4, a score 17 defining an opening portion 16 is provided on the panel portion 11, and the panel portion 11 in the opening portion 16 is processed. The opening pull tab 19 is attached to the rivet 18 provided as above, and when opening, the opening pull tab 19 is pulled up, so that the opening portion 16 is broken along the score 17 so that the opening can be easily opened. I have. The easy-open can lid (A) has a bead 20 along the score 17 on the panel portion 11 to facilitate opening.
Is provided.

In the easy-open can lid (A), the metal plate 1 is a JIS-H4000 having a thickness of 0.30 mm.
An aluminum alloy plate of alloy number 5182 specified in
5182 aluminum plate). As the polyester film 2, a 20 μm-thick copolymerized polyester film composed of polyethylene terephthalate and ethylene glycol and having a composition obtained by copolymerizing a small amount of isophthalic acid is used. For No. 3, a thermosetting resin-based adhesive in which an epoxy resin having a number average molecular weight of 10,000 and glycerol tristrimellitate anhydride are mixed at a weight ratio of 97/3 is used.

Next, a method for manufacturing the easy-open can lid will be described.

In manufacturing the easy-open can lid, first, a long polyester film (copolymerized polyester film) 2 is drawn out, and the epoxy resin and glycerol tristri are formed in the same manner as the polyester film 2 for separate feeding. Melitate anhydride and a resin solution obtained by dissolving in an organic solvent in the above weight ratio are applied and dried,
An adhesive layer 3 made of the thermosetting resin-based adhesive was formed and wound. In the polyester film 2 on which the thermosetting resin-based adhesive layer 3 is formed, the thermosetting resin-based adhesive layer 3 does not cause blocking, and thus has excellent tack-free properties when wound up. Therefore, there is no risk that the wound polyester film 2 will be hindered when it is drawn out and used in the next step.

Next, the long metal plate (5182 aluminum plate) 1 for the easy-open can lid is heated by the apparatus shown in FIGS. A polyester film 2 was adhered to the side of the plate 1 which is to be the inner surface of the can via a thermosetting resin-based adhesive layer 3.

Next, as described above, an epoxy urea resin-based paint is applied to the outer surface of the can of the metal plate 1 on which the protective coating layer 4 is formed by adhering the polyester film 2, and is baked and dried. A resin coating layer 5 composed of a coating film was formed.

Next, the protective coating layer 4 and the resin coating layer 5
The metal plate 1 on which was formed was processed by a conventionally known easy-open can lid manufacturing apparatus to manufacture the easy-open can lid (A) having the above-described configuration.

Next, the adhesion of the polyester film 2 to the metal plate 1 in the separate lid and the easy-open can lid (A) was observed to evaluate the adhesion, and the exposed metal parts such as pinholes and cracks were evaluated. As a result, the adhesiveness was good and there was no exposed metal part.
The above results are shown in Table 1 for only the separate lid.

Next, a surface-treated steel sheet whose both sides except for both ends are covered with a polyester film is rolled, and the both ends are overlapped and welded together, and neck-in processing is performed on both ends of the can body. The easy open can lid (A) was double-wrapped at one end to produce a welded can body. In addition, the welding can body is provided with a coating correction with an epoxy phenol resin-based correction paint on a welding seam portion on the inner surface side of the can. The welding can body was filled with coffee, the separate feeding lid was double-wrapped around the open end, and then heat sterilization (retort sterilization) was performed at 124 ° C. for 25 minutes to produce a can. After storing the cans at 37 ° C. for 6 months, the cans were opened and the appearance of the protective coating layer on the can lid was observed. Table 1 shows the results.

[0054]

Example 2 A separate lid was manufactured in exactly the same manner as in Example 1, and the adhesion of the polyester film 2 to the metal plate 1 in the separate lid was evaluated by evaluating the adhesion, and pinholes, cracks, etc. Was examined for the presence of exposed metal parts. Table 1 shows the results.

Next, the same 518 as that used in the first embodiment is used.
Using an aluminum plate, an easy-open can lid (hereinafter referred to as an easy-open can lid (B)) coated with an epoxy phenol resin on the inner surface of the lid was manufactured according to a conventional method. The easy open can lid (B) has a resin coating film formed by double-coating an epoxy phenol resin paint on the inner side of the can, and an epoxy urea resin paint on the outer side of the can. The resin coating layer made of the resin coating film is formed by baking and drying. The easy-open can lid (B) is the same as the easy-open can lid (A) of Example 1, except that the polyester film 2 is bonded to the protective coating layer 4 via the thermosetting resin-based adhesive layer 3 in the above-mentioned easy-open can lid (A). Except for forming the resin coating film, it has the same configuration as the easy-open can lid (A), and is conventionally known.

Next, the both ends of the welding can body manufactured in the same manner as in Example 1 were subjected to neck-in processing, and the above-mentioned conventional easy-open can lid (B) was double-tightened to one end of the welding can body. Body manufactured. Filling the welding can body with coffee,
Example 1 After double-tightening the separate cover at the open end,
The same retort sterilization treatment as described above was performed to produce a can. After storing the cans at 37 ° C. for 6 months, the cans were opened and the appearance of the protective coating layer on the can lid was observed. Table 1 shows the results.

[0057]

Embodiment 3 In a separate cover according to this embodiment, a metal plate 1 is provided with a base layer made of disc-like and granular metal chromium on the surface of a base steel plate, and a metal chromium layer having an amount of 10 mg / m ^2.
Tin-free steel material having a thickness of 0.21 mm on which a chromium oxide layer is formed (hereinafter abbreviated as TFS material)
The structure is the same as that of the separate cover of Example 1 except that a resin coating layer 5 is formed on the outer surface of the metal plate 1 as shown in FIG.

The separate lid is heated by the apparatus shown in FIGS. 6 and 7 by heating the metal plate (TFS material) 1 for the separate lid and forming a polyester film (PET film) on the side of the metal plate 1 which becomes the inner surface of the can. ) 2 is bonded by heating through a thermosetting resin-based adhesive layer 3, the strip-shaped metal plate 1 cut to a predetermined width from the original plate is transported by the metal plate supply means 22 to the transport path 2.
1 and the metal plate 1 is
The polyester film 2 was bonded to the metal plate 1 with a pressure roller 27 preheated to 5 ° C. and heated to 160 ° C., and was manufactured in the same manner as the separate feeding lid of Example 1 except that the heating oven 23 was not used.

Next, the adhesiveness of the polyester film 2 to the metal plate 1 in the separate lid was observed to evaluate the adhesiveness, and the presence or absence of a metal exposed portion such as a pinhole or a crack was examined. Table 1 shows the results.

Next, both ends of the welding can body manufactured in the same manner as in Example 1 were subjected to neck-in processing, and the above-mentioned conventional easy-open can lid (B) was double-tightened to one end of the welding can body. Body manufactured. The welding can body was filled with green tea, and the separate feeding lid was double-wrapped around the open end, and then subjected to the same retort sterilization treatment as in Example 1 to produce a can. After storing the cans at 37 ° C. for 6 months, the cans were opened and the appearance of the protective coating layer on the can lid was observed. Table 1 shows the results.

[0061]

Embodiment 4 A separate lid according to the present embodiment is a metal plate 1 having the structure shown in FIG.
The configuration is the same as that of the separate cover of Example 1 except that an aluminum plate is used and a resin coating layer 5 is formed on the outer surface of the metal plate 1 as shown in FIG. 1B.

The separate lid is heated by the apparatus shown in FIGS. 6 and 7 by heating the metal plate (5182 aluminum plate) 1 for the separate lid and forming a polyester film (PET) on the side of the metal plate 1 which will become the inner surface of the can. When the film (film) 2 is bonded via the thermosetting resin-based adhesive layer 3, the strip-shaped metal plate 1 cut to a predetermined width from the original plate is transported by the metal plate supply means 22 to the transport path 21.
To the metal plate 1 by the high-frequency heating device 26.
The polyester film 2 was manufactured in the same manner as the separate lid of Example 1 except that the polyester film 2 was pre-heated to 170 ° C. and the polyester film 2 was temporarily bonded to the metal plate 1 by the pressure roller 27 heated to 170 ° C.

Next, the adhesiveness of the polyester film 2 to the metal plate 1 in the separate lid was observed to evaluate the adhesiveness, and the presence or absence of a metal exposed portion such as a pinhole or a crack was examined. Table 1 shows the results.

Next, the both ends of the welded can body manufactured in the same manner as in Example 1 were subjected to neck-in processing, and the above-mentioned known easy-open can lid (B) was double-wrapped at one end thereof to form a welded can. Body manufactured. The welding can body was filled with lemon tea, and the separate lid was double-wrapped around the open end, and then subjected to the same retort sterilization treatment as in Example 1 to produce a can. After storing the cans at 37 ° C. for 6 months, open the cans,
The appearance of the protective coating layer on the can lid was observed. Table 1 shows the results.

[0065]

[Embodiment 5] A separate lid of this embodiment is different from that of Embodiment 1 in that
The metal plate (5182 aluminum plate) 1 on which the protective coating layer 4 and the resin coating layer 5 formed for the easy open can lid (A) were formed was processed by a conventionally known lid manufacturing apparatus.

Next, the adhesion of the polyester film 2 to the metal plate 1 in the separate lid was observed to evaluate the adhesion, and the presence or absence of a metal exposed portion such as a pinhole or a crack was examined. Table 1 shows the results.

Next, the both ends of the welding can body manufactured in the same manner as in Example 1 were subjected to neck-in processing, and the above-mentioned conventional easy-open can lid (B) was double-wrapped at one end thereof to form a welding can. Body manufactured. After the sports can was filled into the welded can body while being heated to a temperature of 80 to 90 ° C. (hot pack filling), the separate lid was double-wrapped around the opening end to produce a can. After storing the cans at 37 ° C. for 6 months, the cans were opened and the appearance of the protective coating layer on the can lid was observed.
Table 1 shows the results.

[0068]

[Table 1]

In Table 1, EO can lid means easy-open can lid, and PE means polyester. Also, E.
In the section of the type of O can lid, A indicates an easy open can lid (A) according to the present invention, and B indicates a conventionally known easy open can lid (B).

From Table 1, it can be seen that in the can lid of the present invention, the protective coating layer adheres well to the metal plate even after various processes.
It is clear that there is no exposed metal portion such as a pinhole or a crack, and that the adhesion of the protective coating layer to the metal plate is excellent. In addition, it is apparent from the appearance of the protective coating layer after storage that the protective coating layer does not become white even by retort sterilization and adheres well to the metal plate even after long-term storage.

In each of the above embodiments, the separate feeding lid and the easy-open can lid are attached to an end of a can body obtained by rolling a can body material formed of a strip-shaped metal plate and welding or bonding the end thereof. Although a three-piece can to be tightened is described, the can lid of the present invention is a two-piece can in which an easy-open can lid or the like is wound around an open end of a cup-shaped can body obtained by ironing and drawing a metal plate. May be used. Further, the can lid of the present invention can be applied to a bottom lid or a dome-shaped portion of an aerosol can.

In each of the above-described embodiments, the long metal plate 1 is drawn out from the coil 22a as the metal plate 1 to which the polyester film 2 is adhered. However, a strip obtained by cutting the original plate into predetermined widths is used. Metal plate 1 may be used.
When the strip-shaped metal plate 1 is used, heating conditions and the like can be performed in the same manner as in the case of the elongated metal plate 1, but the strip-shaped metal plate 1 is connected by the elongated polyester film 2. Therefore, each of the strip-shaped metal plates 1 is cut by the knife cylinder 28. In addition, when the polyester film 2 is temporarily bonded to the strip-shaped metal plate 1, the contact between the thermosetting resin-based adhesive layer 3 and the lower pressure roller 27 at the portion between the strip-shaped metal plates 1, 1. Care must be taken to avoid contact or to avoid contact as much as possible. Since the thermosetting resin-based adhesive layer 3 of the present invention is excellent in tack-free property, it is also preferable in terms of resistance to adhesion to the pressure roller 27.

[0073]

According to the present invention, the number average molecular weight is 5000
By using a thermosetting resin-based adhesive obtained by mixing an epoxy resin and a trimellitic anhydride-based curing agent at a weight ratio of 70/30 to 99/1, a polyester film is formed on the metal plate. Adhesion can be securely performed via the thermosetting resin-based adhesive layer, and a can lid having a protective coating layer made of the polyester film and having excellent adhesion to the metal plate can be obtained.

The can lid of the present invention can protect the surface by forming a resin coating layer on the outer surface side of the can that does not come into contact with the contents.

According to the production method of the present invention, a metal plate is heated to form a polyester film having the thermosetting resin-based adhesive layer formed on one surface thereof, and the polyester film having the thermosetting resin-based adhesive layer formed thereon. By bonding through, the thermosetting resin-based adhesive is cured in a short time and a sufficient adhesive strength is obtained between the polyester film and the metal plate, and a protective coating layer made of the polyester film is formed. Can be formed.

In the production method of the present invention, when forming the protective coating layer, the polyester film is temporarily bonded to the heated metal plate via a thermosetting resin-based adhesive layer. By heating the metal plate to which the polyester film is temporarily bonded and curing and bonding the thermosetting resin-based adhesive, the metal plate and the polyester film are more securely bonded by heating for a short time. Can be.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view showing a configuration of a can lid of the present invention.

FIG. 2 is a top view showing an example of the can lid of the present invention.

FIG. 3 is a sectional view taken along line III-III of FIG. 2;

FIG. 4 is a top view showing another example of the can lid of the present invention.

FIG. 5 is a sectional view taken along line VV of FIG. 4;

FIG. 6 is a plan view schematically showing a processing apparatus for forming a protective coating layer on a metal plate in the manufacturing method of the present invention.

FIG. 7 is a front view showing a configuration of a transport path of the apparatus shown in FIG. 6;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Metal plate, 2 ... Polyester film, 3 ... Thermosetting type resin adhesive layer, 4 ... Protective coating layer, 5 ... Resin coating layer.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Koji Matsushima, Inventor 839-1 Shimuro, Iwatsuki City, Saitama Prefecture (56) References JP-A-1-124551 (JP, A) JP JP-A-63-125152 (JP, A) JP-A-62-227643 (JP, A) JP-A-56-36262 (JP, A) JP-A-61-287537 (JP, A) JP-A-1-182248 (JP) , A) JP-A-62-250662 (JP, A) JP-A-62-252044 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 15/08

Claims (4)

(57) [Claims] 1. A can lid having a protective coating layer made of a polyester film formed by bonding a polyester film to at least the inner surface of a metal plate via a thermosetting resin-based adhesive layer, The curable resin-based adhesive has a number average molecular weight of 5,000 to 2,
A can lid made by mixing 0000 epoxy resin and trimellitic anhydride-based curing agent in a weight ratio of 70/30 to 99/1. 2. The can lid according to claim 1, wherein a resin coating layer is formed on an outer surface of the metal plate. 3. A thermosetting resin obtained by mixing an epoxy resin having a number average molecular weight of 5,000 to 20,000 and a trimellitic anhydride-based curing agent on one surface of a polyester film in a weight ratio of 70/30 to 99/1. Thermosetting to form a thermosetting resin-based adhesive layer on the polyester film by applying a thermosetting resin-based adhesive and drying by heating to a temperature at which the curing reaction of the thermosetting resin-based adhesive does not substantially proceed. Mold resin-based adhesive layer forming step; heating the metal plate to form a polyester film having the thermosetting resin-based adhesive layer formed on at least the inner surface side of the metal plate with the thermosetting resin-based adhesive A protective cover layer forming step of adhering through a layer to form a protective cover layer made of the polyester film, and a can cover forming step of forming a can cover from the metal plate on which the protective cover layer is formed. Features Method of manufacturing a can lid. 4. The method according to claim 1, wherein the step of forming the protective coating layer temporarily bonds the polyester film to the heated metal plate via a thermosetting resin-based adhesive layer, and then temporarily bonds the polyester film to the heated metal plate. 4. The method for manufacturing a can lid according to claim 3, further comprising heating the thermosetting resin-based adhesive to bond the thermosetting resin-based adhesive.