JPH0272027A - Production of can with film cap - Google Patents

Abstract

PURPOSE:To obtain complete waterproof and airtight status by a method wherein a film cap of a covering cap shape made of a shrinkable film having a heat- sensitive adhered layer on the rear and corresponding to the top shape of a can is press-heated to be adhered and a skirt section is shrinked with hot air or radiant heat applied. CONSTITUTION:A film cap 3 is made into a shape corresponding to a shape of the upper portion of a can, the inside from a top 11 of a peripheral skirt section 10 is descended, and a recessed groove 13 is formed inside. The film cap 3 is provided with a knob piece 14 for tearing. After a can 1 is mounted on a base 2, the film cap 3 is put on the can 1. Then, a press-heating member 4 is lowered to let its heater 18, press and heat the top 11 of the film cap 3 so that an adhered layer 16 of the cap 3 is pressed and adhered to the top of a seamer rim 7 of the can 1 until they are completely sealed. At the same time, the base 2, the can 1 and the press-heating member 4 are rotated with respect to a vertical axis as the center, and hot air is blown out from a hot air outlet 5 to have the skirt section 10 of the film cap heat-shrinked, sealing the skirt section 10 onto the upper end periphery of the can 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing canned beverage cans, such as canned beverage cans and pull-top beverage cans, in which the top surface of the beverage cans is sealed with a film cap.

[Prior Art] In general, canned goods consist of a can body, a can lid, and a can bottom, and the can body and can lid are always rolled by rolling the periphery of the can lid around the upper edge of the can body and rolling it from the side. The upper end seamer is joined by forming the top of the ridge on the upper side of the can.

To open this, use a can opener to cut off the lid just inside the top of the seamer ridge.Also, beverage cans such as beer and juice have a pull-top structure with a metal ring attached to the canopy. Lift this metal ring with your fingers to open it.

When opening a can of canned food, the contents spill onto the can lid, or in the case of beverage cans, after opening the can, people drink directly by touching the rim of the can, but the can lid and the sides around the top of the can are exposed during the distribution process. They are often contaminated and have the disadvantage of being unhygienic.

Furthermore, even if there is no such contamination, consumers do not know what kind of contamination the can lid has been exposed to until after the can is manufactured and the food or drink is removed from the can, so consumers may not eat or eat the can. It has the disadvantage of making people feel anxious when drinking it.

It is sanitary to keep a cover on the can lid and the vicinity of its upper edge until just before drinking the can, and then remove the cover, open the lid, and take out the contents.

As such sanitary covers for cans, thick plastic caps are already used for a small number of cans. This is simply a plastic lid made of a thick sheet that fits over the top of the seamer ridge around the lid of the can.

However, although such a lid can be attached and removed freely, it has the drawback that consumers cannot confirm that there is no contamination.

Further, depending on the type of canned food, for example, canned beer, canned juice, and canned sweet potato, some cans are soaked in cooling water before being opened.

If you simply put a lid on the can, the space between the film on the can lid and the can lid will not be watertight and airtight, and if the can is immersed in water,
The disadvantage is that the cooling water is contaminated.

Furthermore, this lid uses a lot of plastic raw material and is not resource-saving.

Additionally, conventional methods have been to cover the lid or stopper of a bottle with a relatively thick film for sealing, but these methods involve wrapping the side of the mouth of the bottle with a cylindrical film. Not suitable for preventing contamination of the top surface.

[Problems to be Solved by the Invention] As mentioned above, it is known that a lid made of synthetic resin is attached to the top of a can, but in order to make this lid more inexpensive, a film cap is attached using a heat shrink film. It is conceivable to create a film cap, place the film cap on the top of the can, apply hot air from the side to cause the film cap to shrink, and make the skirt portion of the film cap shrink and adhere to the side of the top of the can.

In the case of film caps made from the above-mentioned heat-shrinkable film, wrinkles occur when the film is shrunk by applying hot air, making it impossible to achieve water-resistance and airtightness. Because it is tightly attached to the side, sufficient adhesion pressure cannot be obtained, and in cans where the tip is tapered, such as beer cans,
It has the disadvantage of falling off during handling.

Even if you simply shrink the heat-shrinkable film to cover the top and top sides of the can, when it is placed in ice water and cooled, water will leak from the wrinkles or incompletely bonded areas to the film cap on the top of the can. This poses a problem of being unfavorable from a sanitary standpoint.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, it is an object of the present invention to provide a method for producing a can with a film cap, in which the space between the top surface of the can and the film cap is completely watertight.

[Means for Solving the Problems] To achieve this, in the present invention, a cover-type film cap made of a shrink film having an adhesive layer on the back side is placed over the top of the can, and a suppressing heating member is used to heat the top seamer of the can. We focused on the fact that very strong adhesion can be achieved by pressing and heating the fitting part of the film cap to the top of the rim, and we also applied hot air to the adhesive-covered skirt part of the film cap to shrink the skirt part by heat. The present invention was completed based on the idea of preventing the film cap from falling off by using a combination of adhesive action and shrinkage to bring the skirt portion into close contact with the upper side of the can.

That is, the present invention provides a can with a cover lid made of a shrink film having a heat-sensitive adhesive layer on the back surface, and a can with a top surface shape L: correspondingly, a convex ring is provided on the periphery of the canopy portion, and the center portion is concave. The convex ring of the film cap is fitted onto the top of the upper seamer rim of the can placed on the can mounting table, and the convex ring of the film cap is fitted to cover the top of the upper seamer rim of the can placed on the can mounting table. A can with a film cap, characterized in that the fitting part is bonded by pressing and heating, and the skirt part of the film cap is contracted by applying hot air or radiant heat to bring the skirt part into close contact with the upper side of the can. The present invention provides a method for manufacturing.

In the manufacturing method of the present invention, it is desirable that the can mounting table and the pressing/heating member are rotatable, and hot air is applied to the skirt portion of the film cap from the side while rotating the can. As another method, a hood-shaped blowing section having a shape that wraps around the top of the can can be provided on the outside of the suppressing heating member, and the hot air can be sent out from this blowing section.

Alternatively, after pressing with a heating member, the outside of the pressing part may be made to whiten downwards, and then simply radiated heat from an infrared lamp or the like may be used to heat-shrink it and bring it into close contact with the side surface of the can.

The material of the film cap used in the present invention may be any thermoplastic resin, such as vinyl chloride resin, polyethylene, polypropylene, polystyrene, polyethylene tere-7-thaleate, polybutylene terephthalate, A heat shrinkable film such as polyamide having a heat shrinkage rate of 15% or more, preferably 30% or more can be used.

In the case of the present invention, it is more preferable to use a heat-shrinkable film manufactured by biaxial stretching since there is no anisotropy in the heat-shrinkage rate.

The thickness of the film used in the present invention is not particularly limited, but
Usually about 10 to 200 μm can be used.

If the thickness of the film is less than 10μ, there is no strength and
If it exceeds μ, it becomes difficult to shrink by heat.

As the heat-sensitive adhesive to be attached to the film cap of the present invention, any adhesive that can bond plastic film and metal can be used. For example, in addition to commercially available heat-sensitive adhesives, a polymer film having a softening point lower than that of the film cap may be laminated to form an adhesive.

Compared to pressure-sensitive adhesives, the heat-sensitive adhesive of the present invention has no tackiness at room temperature, making it easier to cover the film cap, which is desirable. This is convenient because it can be carried out at the same time and the heat shrinkability of this part is eliminated, so that wrinkles or deformation will not occur in the subsequent heat shrink treatment of the skirt part.

Examples of heat-sensitive adhesives include ethylene-vinyl acetate copolymer adhesives, copolyester adhesives, polyamide adhesives, atactic polypropylene adhesives, ethylene-ethyl acrylate copolymer adhesives, and polyurethane. Adhesives based on adhesives and tackifiers such as petroleum resins, rosin, and pinene resins can be suitably used.

The cover-type film cap used in the present invention consists of a concave canopy that faces the top of the can and a skirt that faces the side of the can. More desirable is a film cap that is shaped to fit the can superstructure.

If the canopy of the film cap is made concave to match the upper structure of the can, the bottoms of beer cans and other cans will fit into the concave shape, allowing stacking. It is suitable because it does not float and will not break even if it is poked with a pin.

Furthermore, as shown in the plan view of FIG. 3 and the cross-sectional view of FIG. A film cap having a skirt portion on the outermost periphery of the molded convex ring with a film portion that maintains the high heat shrinkage rate of the raw material film unaffected by heating during molding is desirable because it has a strong heat shrinkage force.

The present invention is characterized in that the top of the seamer rim of the can is selected as the adhesive sealing part with the film cap in order to ensure water resistance and airtightness, so that strong pressure and temperature cannot be applied to this part. is very easy, and by selecting the film and adhesive used, it is possible to obtain very strong adhesion, that is, good watertightness. In addition, if the shape and material of the member that presses this is made soft or has a downwardly concave curved surface, the width of this sealing portion can be increased along the curved surface of the top of the seamer ridge, and this method The adhesive seal can also be strengthened by

The method for manufacturing canned goods with film caps of the present invention includes, for example, forming a continuously supplied long strip-shaped film with a heat-sensitive adhesive into the shape of a film cap, and placing the strip film with the adhesive layer facing down. Then, the film is fitted onto a can on a mounting table that is supplied intermittently, and the fitting part is strongly pressed from above with a heating member to firmly fix the film to the top of the seamer ridge on the periphery of the can lid. Glue the film to the plate with adhesive.

The temperature of the heating member is set to a temperature lower than the melting point of the material of the film cap, but higher than the bonding temperature determined by the type of heat-sensitive adhesive, and the pressing time is usually 3 seconds or less. can.

Then, the film is punched and cut, leaving a skirt portion with a diameter of about 5 to 40 mm protruding from the lid of the can, and the skirt portion is heat-shrinked with hot air or radiant heat, and the film of the skirt portion is attached to the top of the can. When the cans are brought into close contact with the sides, the film capped cans of the present invention can be manufactured continuously.

At this time, if a soft or curved heating member is used to bond the seamer ridge top and the film cap,
Seamer - A somewhat wide width at the top of the ridge, for example 2
Since the adhesive is bonded with a width of ~4 mm, a fairly strong bond can be obtained.

A feature of the present invention is that there are no wrinkles in the crimping operation of the film cap to the seamer ridge top ring, and sufficient pressure and heat are applied evenly. The advantage is that the type can be freely selected, and by this selection it is possible to obtain extremely strong adhesion, that is, complete airtightness.

That is, by selecting a film with a high melting point, it is possible to freely select a heat-sensitive adhesive to be used that has high adhesiveness between the metal and the film.

For example, a thermoplastic film with a low melting point can be laminated and used as an adhesive, and the thickness of the adhesive layer can be increased.

As specific examples of this, for example, a combination of a polyamide resin film laminated with an acid-modified polypropylene resin film, a polyester resin film or a vinyl chloride resin, and an ethylene-vinyl acetate copolymer heat-sensitive adhesive can be particularly preferably used. It is something.

The long continuous band film formed into the film cap used in the manufacturing method of the present invention may have, for example, a concave portion corresponding to the concave-convex annular shape of the film cap, which has a concave-convex surface that conforms to the rim and canopy surface of the can. A shrink film with an adhesive layer on one side is placed on the vacuum forming mold with the adhesive layer facing upward, and a clamp frame, preferably a concave mold, that clamps the shrink film on the vacuum forming mold is used. While the shrink film is held between clamps whose inner diameter is approximately equal to the outer diameter of the frame, the sandwiched film is heated with a heater, for example, a heating plate, that does not come into contact with the shrink film, which is integrally provided inside the clamp frame. It is possible to use a film produced by softening the film, evacuating the inside of a vacuum molding mold, and suction molding the film.

[Function] In the film-capped canned food produced by the method of the present invention, the film and the top of the seamer rim of the can are bonded very well by pressure bonding.

This means that the space at the top of the can lid is highly watertight and airtight.

The film on the side of the upper can plays the role of fixing the film cap to the can, and the action of the adhesive applied to it allows the film to be fixed to the can surface and to bond between the once-shrinked films. This has the effect of preventing the tightening force from loosening.

However, the film on the side of the upper can is tightened with only a weak tightening force compared to the pressure applied by the heat-shrinking pressure plate, and this part also has films that are used during shrinkage, so there is a problem with water resistance and airtightness. However, despite the width of this side, it is not possible to completely block out water.

[Example] According to the attached drawings, the present invention uses a film cap formed from a biaxially stretched heat-shrinkable film as a raw material, provided with a skirt portion having a flange portion 20 with a high heat-shrinkage rate, and a concave canopy portion. A preferred embodiment of the method is described.

This flange portion 20 is protected from receiving heat during the molding process of the film cap, and maintains a high heat shrinkage rate of the raw material film.

The drawing shows a method for sealing the top of a beer can. In the figure, 1 is a beer can, and this beer can 1 is rotatable and placed on a stand 2. In the figure, 3 is a film cap molded into a shape corresponding to the upper end of the beer can 1, as will be described in detail later, and 4 is a pressing heating member.

Furthermore, numeral 5 in the figure is a hot air outlet provided facing the side surface of the upper end.

The beer can l has its upper and lower ends smaller in diameter than the can body, and the can bottom 6 fits inside the seamer ridge 7 on the top of the can to allow the cans to be stacked. In order to improve stability, a groove 9 is formed in the can top plate 8 along the inside of the seamer protrusion 7, and the convex peripheral edge of the can bottom fits into this groove 9.

For this purpose, the film cap 3 is shaped to correspond to the shape of the upper part of the can, and the top 11 of the surrounding skirt part 10
A downward slope 12 is formed on the inner side, and a concave groove portion 13 is formed on the inner side. If the cans are straight cans, such as ordinary cans, and the cans are not fitted and stacked, the recessed groove portion 13 is not necessarily required.

This film cap 3 is provided with a knob piece 14 for tearing.

Further, as shown in FIG. 4, this film cap 3 has an adhesive layer 16 provided on the back surface of a heat-shrinkable film 15.

The rotary mounting table 2 is supported by the elasticity of a spring 17, and this springing elasticity allows the pressure of the pressing and heating member 4, which will be described later, to be adjusted.

The pressing/heating member 4 has a ring-shaped heating portion 18 corresponding to the top portion 11 of the film cap 3, is movable up and down, and is configured to rotate in synchronization with the mounting table 2.

Now, when carrying out the method of the present invention according to the above embodiment, first the can 1 is placed on the mounting table 2, and then the film cap 3 is placed on the can 1. In this state, the skirt part 10 of the film cap 3 covers the top of the can, the top part 11 of the skirt part 10 is located on the top seamer ridge top part 7 of the can 1, and the groove part 13 is similarly positioned on the top of the can. It coincides with the groove 9 of the plate 8.

Next, the pressing/heating member 4 is lowered, and its heating portion 18 presses and heats the top 11 of the film cap 3, thereby bonding the adhesive layer 16 of the cap 3 to the seamer flange 7 of the can l.
Crimp and adhere tightly to the top of the.

At the same time, the mounting table 2, the can l, and the pressing heating member 4 are rotated around their vertical axes, and hot air is blown from the hot air outlet.
Heat-shrink the skirt portion lO of the film cap 3,
As shown in FIG. 2, this skirt portion 1O is brought into close contact with the upper circumferential surface of the can 1.

[Effects of the Invention] As described above, in the method of the present invention, a cover-type film cap made of a shrink film having an adhesive layer on the back side is used, and this film cap is placed over the top of the can, and the can is heated by a pressing heating member. Since the corresponding part of the film cap is brought into close contact with the top of the seamer flange at the upper end by pressing and heating, the entire periphery of the can is surely brought into close contact with the film cap by the top of the seamer flange of the can, and a watertight structure can be obtained.

Furthermore, the skirt portion of the film cap adheres to the circumferential side of the upper can due to heat shrinkage, but the adhesive applied to the film adheres the film, the can portion, and each other.
Since the film is securely fixed to the can part, it is easy to handle when transporting, displaying, cooling, etc. cans with film caps.
The structure is such that the film cap does not fall off.

Due to the synergistic effect of both such a good watertight structure and a good drop-off prevention structure, the top surface of the can is free from contamination and has the great advantage of being kept in a hygienic condition.

[Brief explanation of the drawing]

Figure 1 is a partially cutaway front view of the state in which the method of the present invention is carried out, Figure 2 is an enlarged sectional view of the main part in the sealed state, and Figure 3 is a cross-sectional view of the film cap. 4 is an enlarged sectional view of a part of the film cap, and FIG. 5 is a sectional view thereof. The symbols in the figure are l: can, 2: 0 units, 3: film cap, 4: press heating member, 5: hot air outlet, 7;
Seamer projecting edge, 8; Can top surface, 9: Concave groove, lO; Skirt portion, 11: Top, 12: Inside side surface, 13; Concave groove, 1
4; Knob piece; 15; Bi-stretched heat-shrinkable film; Adhesive layer; Shrinkable flange.

Claims (1)

[Scope of Claims] 1. A cover lid made of a shrink film with a heat-sensitive adhesive layer on the back surface, which has a convex ring on the periphery of the canopy portion corresponding to the shape of the top surface of the can, and has a concave central portion. placing a film cap on the top of the upper seamer ridge of a can placed on a can mounting table by fitting the convex ring of the film cap;
The top of the upper seamer ridge and the fitting part of the film cap are pressed and heated by a pressing heating member to bond them together, hot air or radiant heat is applied to the skirt part of the film cap to shrink the skirt part, and the skirt part is attached to the top of the can. A method for producing a canned food with a film cap, characterized in that it is tightly attached to the side. 2. The method for producing a can with a film cap according to claim 1, wherein the skirt film is thermally shrunk by blowing hot air while rotating the can mounting table and the pressing/heating member. 3. As a film cap, a convex ring that fits on the top of the seamer ridge is continuously provided on the periphery of the central circular lid in accordance with the shape of the top of the can, and furthermore, a raw material film is placed on the outside of the convex ring. 3. The method for producing a can with a film cap according to claim 1, wherein a can having a skirt portion having an outer edge made of a film having a heat shrinkage rate as high as that of the can is used.