JPS6158294B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a plastic/metal composite can, and more specifically, a plastic cup-shaped container with a bottom formed by injection molding is covered with a metal foil layer over the entire surface thereof. In particular, the present invention relates to a method for producing a plastic/metal composite can that has excellent gas barrier properties, light shielding properties, light weight, sealing reliability, and shape retention.

Metal cans have been used for many years as packaging containers that have almost perfect sealing properties, gas barrier properties, and excellent shape retention, but in recent years, there has been a problem of so-called can pollution due to the difficulty of disposal. There are problems in that the container is heavy and the packaging cost is high.

On the other hand, containers made of plastic
Although it has the advantage of being lightweight and having a relatively low packaging cost, it has the problem that a non-negligible amount of gas permeates through the container wall and that it cannot be printed as beautifully as metal cans.

Containers made of composites of metal foil and plastic are also widely used in the field of flexible packaging such as so-called retort pouches, but they are still insufficient in the field of shape-retaining containers that can be handled in vending machines. have not been successful in this. for example,
As a shape-retaining plastic/metal foil composite container, a metal foil laminate is wrapped and pasted around the outer circumferential surface of a plastic body with openings at both ends, and a lid is engaged with the openings at both ends and sealed by heat sealing. A method has been proposed (Japanese Unexamined Patent Publication No. 52-39489). This composite container requires heat-sealing at both ends of the body, making the sealing operation cumbersome, and having heat-sealed sections at both ends also poses a problem in sealing reliability. There is.

According to the present invention, the entire surface of the bottomed cup-shaped container formed by plastic injection molding is covered with a metal foil layer, and a seal is formed by heat sealing with the lid only at one open end. As a result, a method for manufacturing a plastic/metal composite can with an excellent combination of gas barrier properties, light shielding properties, lightness, sealing reliability, and shape retention is provided.

That is, the present invention manufactures by injection molding a seamless plastic cup body consisting of a body and a bottom and having a notch with a smaller diameter than the body on the outer periphery of the body near the bottom, and a resin protective layer on the outer surface. A metal foil with A sheet of metal foil that is fitted and glued to the bottom and has a resin protective layer on the outer surface is placed so that its upper edge and the upper edge of the plastic cup body coincide or leave a sealing margin between them with the lid. At the same time, the sheet is wrapped and glued around the outer periphery of the body of the plastic cup body so that its lower edge and the short side wall of the metal foil shallow drawing cup overlap, and the opposing ends of the sheet are overlapped and bonded, and the outer surface side A lid body made of metal foil with a resin protective layer and a heat-sealable resin layer on the inner side,
The present invention relates to a method for manufacturing a plastic/metal foil composite can, which is characterized in that the plastic/metal foil composite can is placed on the open end of the obtained plastic/metal foil composite cup and sealed by heat sealing.

The present invention will be explained in detail below based on specific examples shown in the accompanying drawings.

According to the present invention, first, a seamless plastic cup body 1 shown in FIG. 1 is manufactured by injection molding. This cup body 1 has an integrally formed body 2.
and a bottom part 3, and a notch 4 having a diameter D2 smaller than the outer diameter _D1 of the shell 2 is provided on the outer periphery of the shell near the bottom part ₃ .
is provided. Cup body 1 shown in this specific example
In this case, a bead 5 serving as a sealing margin is provided at the opening edge of the cup body. The outer surface of the shell 2 is almost straight, but the inner surface 6 of the shell 2 is gradually tapered downward in order to improve mold removal during injection molding and to improve internal pressure resistance when compared with the same amount of plastic used. It is desirable that the diameter be tapered so that the diameter becomes smaller, that is, the wall thickness becomes larger downward. This taper angle is generally preferably 0.5 to 3 degrees, particularly 1 to 2 degrees.

The plastic constituting the cup body 1 may be a thermoplastic resin or a thermosetting resin as long as it can be injection molded. Thermoplastic resins are advantageous in terms of productivity and cost, such as low-, medium- or high-density polyethylene, crystalline polypropylene, crystalline ethylene-propylene copolymer, propylene-butene-1 copolymer, ionic Olefin resins such as crosslinked olefin copolymers; polystyrene, styrene-butadiene copolymers, styrene-
Styrene resins such as butadiene-acrylonitrile copolymers; polycarbonates; polyvinyl chloride resins; polyesters; polyamides; acrylic resins; polyacetal resins and the like are used.

The basis weight of the plastic is between 5 and 30 to obtain the desired combination of shape retention and lightness.
g/100ml, preferably in the range of 8 to 20g/100ml.

In FIG. 2, which shows an exploded view of a plastic/metal foil composite can according to the invention, the metal foil is formed into the shape of a shallowly drawn cup 8 with short side walls 7. In FIG.
Next, as shown in FIG. 3, this shallow drawing cup 8
is fitted into the bottom 3 of the plastic cup 1 so that its short side wall 7 is accommodated in the cutout 4 of the plastic cup 1 and glued.

As shown in detail in FIG.
0, and is adhered to the cup body 1 via an adhesive layer 11 provided on the inner surface side of the metal foil 10.

This adhesive layer 11 may be a thermosetting adhesive such as urethane-based or epoxy-based adhesive, or a thermoplastic resin adhesive, but it can be used to smoothly fit the shallowly drawn cup 8 into the bottom part 3 of the cup body 1. From this point of view, it is preferable that the film is made of a heat-adhesive thermoplastic resin film. That is, the metal foil cup 8 having this film layer on its inner surface can be smoothly fitted into the bottom, and by heating the metal foil 10 with high frequency induction, it can be thermally bonded to the plastic cup body 1. It has the advantage of being easy to perform. As the heat-adhesive film, olefin resins, homo- or co-polyesters, homo- or co-polyamides, etc., as exemplified above, can be used, as well as ethylenically unsaturated carboxylic acids such as maleic anhydride, acrylic acid, and methacrylic acid. Olefinic resins graft-modified with their anhydrides are also advantageously used.

Aluminum foil is suitable as the metal foil 10, but iron foil, steel foil, tin foil, etc. may also be used if desired, and the thickness is such that the desired gas barrier properties can be obtained, and the molding into the cup 8 is possible. As is possible,
A range of 7 to 150 microns, particularly 9 to 50 microns is preferred. The resin protective layer 9 is made of epoxy-phenol paint, epoxy-amino paint, epoxy-acrylic paint, vinyl paint,
Excellent mechanical and thermal properties for various coatings such as vinyl-phenol paints, vinyl-epoxy paints, and polyester paints, as well as biaxially oriented polyester films, biaxially oriented polyamide films, and biaxially oriented polypropylene films. It can be a film of any type.

The shallow drawing cup 8 is formed by punching a laminate consisting of a metal foil, an outer resin protective layer, and an inner heat-adhesive resin layer into a predetermined shape, and drawing or press-forming using a combination of a punch and a die. Cup 8
The wall thickness d is set so that d≈D ₁ −D ₂ with respect to the outer diameter D ₁ of the body 2 and the outer diameter D ₂ of the notch 4, so that the side wall 7 is tightly accommodated in the notch 4. so that

According to the present invention, the metal foil sheet 12 is wrapped around the outer periphery of the body of the plastic cup body 1 into which the metal foil shallow drawing cup 8 is fitted and is adhered (the second
figure). At this time, as shown in Figures 2 and 4,
A sealing margin 5 with the lid is left between the upper edge 13 of the metal foil sheet and the upper edge of the plastic cup body 1, and as shown in FIGS. 2, 3, and 4, the metal foil sheet The lower edge 14 of the metal foil cup and the short side wall 7 of the metal foil cup fitted into the plastic cup overlap to form a circumferential overlapping joint 15.
The metal foil sheet 12 is wrapped around the plastic cup body in such a position that a .

Furthermore, in FIGS. 2, 4, and 5, both ends 15a and 15b of the metal foil sheet 12 are overlapped around the cup body 1, and an overlapping joint 16 is formed.
to form.

The metal foil sheet 12 wrapped around the plastic cup body 1 is also made of a metal foil 10 with a protective resin layer 9 on the outer surface, and a protective resin layer 9 on the inner surface of the metal foil 10, as shown in the cross-sectional view of FIG. It is adhered to the cup body body 2 via the adhesive layer 17 provided. As the metal foil 10 and the protective resin layer 9, those already described in detail regarding the metal foil shallow drawing cup 8 are similarly used.

As the adhesive layer 17, any of the adhesives mentioned in detail with respect to the shallow draw cup can be used, but in the present invention, isocyanate adhesives are particularly advantageously used. That is, this isocyanate-based adhesive not only exhibits excellent adhesion properties that are resistant to both metal foils and plastics, but also
Adhesive curing can be completed at a relatively low temperature, and the formation of a metal foil coating is extremely simple, fast, and economical.

More specifically, the metal foil body outer covering is formed as follows. That is, an isocyanate adhesive in the form of a solution is applied to the other surface of the metal foil 10 having the protective resin layer 9, and then the solvent is evaporated.
An isocyanate adhesive layer 17 is formed. The metal foil coating thus formed is applied and
The metal foil is supplied to the nip position between the roller and the plastic cup body into which the metal foil cup is inserted, and the metal foil is pasted and bonded around the cup body. In order to improve the wetting of the isocyanate adhesive around the cup body, it is desirable to heat the abrasion roller.

In the specific example shown in the attached drawing, metal foil sheet 1
2 is wrapped around the upper edge of the cup body 1 so as to leave a sealing margin 5, but if the upper edge of the cup body 1 is not provided with a bead or the like and therefore has a straight outer surface, Alternatively, the metal foil sheet may be attached so that the upper edge of the cup body 1 and the upper edge 13 of the metal foil sheet 12 are aligned.

According to the present invention, a plastic/metal foil composite cup whose outer surface is completely covered with metal foil is obtained, and after filling the cup with the contents, a lid is attached to the open end of the cup. Place and seal with heat seal.

A suitable example of this heat seal lid is shown in Section 7-A, 7.
-B and 7-C, the lid body 18 is composed of a metal foil 19 having a resin protective layer 9 on the outer surface and a heat-sealable resin layer 20 on the inner surface, and is formed by, for example, press molding. The center panel 21 is made up of a flat center panel 21 and a groove 22 having a U-shaped cross section around the center panel 21. This center panel 21
A score 23 is provided to define a portion to be opened, and an opening tab 24 is bonded to the portion defined by the score.

As the resin protective layer 9 and the heat-sealable resin layer 20, those exemplified above are similarly used, and as the metal foil 19, the same as exemplified above is used, except that the thickness is 7 to 100 microns. is used similarly.

The bead-shaped opening end 5 of the plastic/metal foil composite cup is inserted into the U-shaped groove 22 of the lid 18, and the inner and outer walls of the U-shaped groove 22 are heated while being pressed against the bead 5. Sealing with a seal is ensured. Heating of this heat-sealed portion is easily performed by high-frequency induction heating, while pressurization is easily performed by passing the U-shaped groove 22 between a pair of pressure rollers (pinch rollers).

According to the method of the present invention described above, the container body is manufactured as an integral bottomed cup by plastic injection molding, and a metal foil covering is formed on the entire surface in the above-mentioned order, and finally the metal foil is By heat-sealing the lid to the open end, it has gas barrier properties, light shielding properties, light weight,
A plastic/metal foil composite can with excellent sealing reliability and shape retention can be easily obtained with a small number of steps.

The present invention is equally applicable not only to cans with a circular cross section, but also to cans with a rectangular cross section as shown in FIG. 8 and FIGS. 9-A and 9-B.

The invention is illustrated by the following example.

Example 1 Melting point is 160℃, density is 0.90g/cc, MI is 8g/cc
The inner diameter of the opening is 52.5 mm by injection molding using 10 mm ethylene-propylene block copolymer.
mm, the wall thickness at the top of the side wall is 0.8 mm, the wall thickness at the bottom of the side wall is
A bottomed cylindrical body as shown in FIG. 1 was molded, having a bottom portion measuring 1.5 mm, a height of 130 mm, and a radius of 3 mm at the end.

Next, a 12μ biaxially stretched polyethylene terephthalate film with a melting point of 159℃ and a density of 0.90g/
cm ³ , MI of 7.0 g/10 mm, and ethylene content of 4 mol% ethylene-propylene-block copolymer film with a thickness of 50 μ produced by the T-die method and a soft aluminum foil with a thickness of 20 μ. Both sides were adhered using urethane adhesive. A circular blank is cut out from this laminate, and a cup-shaped piece with a height of 6 mm as shown in Figure 2, which matches the shape of the bottom part in Figure 1, is cut out so that the ethylene-propylene-block copolymer layer is on the inner surface. It was then molded.

This molded product was fitted into the bottom of the bottomed cylinder of the ethylene-propylene-block copolymer and fused by high-frequency induction heating.

Next, a 12μ biaxially stretched polyethylene terephthalate film and a 15μ soft aluminum foil were bonded together using a urethane adhesive, and the resulting laminate was
A blank with a size of 126 mm x 96 mm was cut out.
This blank is attached to the side wall of the flame-treated ethylene-propylene-block copolymer of the bottomed cylinder to which the bottom of the aluminum foil laminate is fused, and a polyethylene terephthalate film layer is attached to the outer surface using a urethane adhesive. I glued them in such a positional relationship.

Pour coffee into the resulting plastic can.
Filled with 250c.c., epoxy phenol paint/100μ
Cover the lid with a liquid pot type score and tab as shown in Figure 7-A, which is made of a laminate of aluminum foil/50μ polypropylene, and simultaneously clinch the skirt part to the can mouth part with a roll. By high-frequency induction heating, the polypropylene inner surface of the lid was thermally fused to the ethylene-propylene-block copolymer of the can opening. This sealed can at 120℃
Heat sterilization was performed in a hot water differential pressure retort for 30 minutes.
In this case, no defects such as deformation of the plastic can or delamination of the aluminum foil laminate were observed. Moreover, the sealability was perfect, and no coffee was observed to get wet. Next, I opened it from the tab and sampled the coffee inside, which was delicious.

Example 2 A 12 μ biaxially stretched polyethylene film and a 50 μ
Plastics were made in the same manner as in Example 1, except that a laminate consisting of a soft aluminum foil and a urethane adhesive was used, and it was adhered to the bottom of the bottomed cylinder with a urethane adhesive instead of heat fusion. I got a can.

Pour coffee into the resulting plastic can.
When the container was filled with 250 c.c., sealed with the same lid as in Example 1, and subjected to the same retort treatment as in Example 1, no defects such as deformation of the plastic can or delamination of the aluminum foil laminate were observed. I couldn't help it. Moreover, the sealability was perfect, and no coffee was observed to get wet. Next, open from the tab part,
When I sampled the coffee inside, it was delicious.

Example 3 Melting point is 160℃, density is 0.90g/cc, MI is 8g/cc
By injection molding using 10mm ethylene-propylene block copolymer, the opening has an inner diameter of 71mm x
It is a square type with 60 mm and 12.5 mm radius at the corner, the upper side wall thickness is 0.8 mm, the lower side wall thickness is 1.5 mm, and the height
A rectangular bottomed cylindrical body as shown in FIG. 8 was molded, having a bottom portion measuring 139 mm and having a radius of 3 mm at the end.

Next, from the laminate of the 12μ biaxially stretched polyethylene terephthalate film/20μ aluminum foil/50μ ethylene propylene block copolymer used in Example 1, a square shape with a height of 6 mm that matched the shape of the bottom of the square bottomed cylinder was formed. Cup with ethylene-propylene
It was molded so that the block copolymer layer was on the inner surface.

This molded product was fitted into the bottom of the square bottomed cylinder of the ethylene-propylene-block copolymer and fused by high-frequency induction heating.

Next, the laminate of 12μ biaxially stretched polyethylene terephthalate film/15μ aluminum foil used in Example 1 was adhered to the side wall of the square bottomed cylinder in the same manner as in Example 1.

The plastic can thus obtained was filled with 500 c.c. of potage soup, and a fully open type score and tab made of a laminate of epoxy phenol paint/100μ aluminum foil/50μ polypropylene as shown in Figure 9-A was attached. The skirt portion is clinched to the can opening using rolls, and at the same time, high-frequency induction heating is applied to thermally fuse the inner polypropylene of the lid to the ethylene-propylene-block copolymer of the can opening. Ta. This sealed can was heat sterilized at 120°C for 30 minutes in a hot water differential pressure retort. In this case, no defects such as deformation of the plastic can or delamination of the aluminum foil laminate were observed. Moreover, the sealability was perfect, and no soup was observed to get wet at all. Next, when I opened it from the tab and sampled the soup inside, it was delicious.

[Brief explanation of the drawing]

Fig. 1 is a partial cross-sectional side view showing a seamless plastic cup, Fig. 2 is an exploded perspective view showing the composite can disassembled into a plastic cup, a metal foil shallow drawing cup, and a metal foil sheet, and Fig. 3. 4 is an enlarged sectional view showing the fitted state of the bottom of the cup body of the metal foil shallow drawing cup and the overlapping portion of the metal foil sheets, FIG. 4 is a perspective view of the plastic/metal foil composite cup according to the present invention, and FIG. 5 is the metal foil cup. Fig. 6 is an enlarged cross-sectional view showing the overlapping joints of both ends of the foil sheet, Fig. 6 is an enlarged cross-sectional view showing the state of adhesion of the metal foil sheet to the outer periphery of the plastic cup body, and Fig. 7-A is a perspective view of the lid body. Figure 7-B is a sectional view of the lid body in Figure 7-A, Figure 7-C
The figure is an enlarged cross-sectional view of this lid, Figure 8 is a perspective view of a square plastic/metal foil cup, Figure 9-A is a perspective view of a lid applicable to the cup in Figure 8,
-B figure is a sectional view of the lid body of figure 9-A. 1 is a plastic cup body, 2 is a body part, 3 is a bottom part, 4 is a notch part, 5 is a sealing area, 7 is a short side wall part, 8 is a metal foil shallow drawing cup, 9 is a resin protective layer, 10 and 19 11 and 17 are metal foils, 11 and 17 are adhesive layers, 12 are metal foil sheets, 15 and 16 are overlapping joints, 18 is a lid body, 20 is a heat-sealable resin layer, and 22 is a U-shaped groove.

Claims (1)

[Scope of Claims] 1. A seamless plastic cup body consisting of a body and a bottom and having a notch with a diameter smaller than the diameter of the body on the outer periphery of the body near the bottom is manufactured by injection molding, and the outer surface is protected by resin. The layered metal foil is pressed into the shape of a shallowly drawn cup with short sidewalls, and the shallowly drawn cup is inserted into a plastic cup body such that the short sidewalls are received in the notches of the plastic cup body. A sheet of metal foil with a resin protective layer on the outer surface is fitted and glued to the bottom of the
Place the plastic cup so that its upper edge and the upper edge of the plastic cup body coincide or leave a sealing margin between them with the lid, and so that its lower edge overlaps the short side wall of the shallow-drawn metal foil cup. Wrap it around the outer circumference of the body of the cup and glue it,
The opposing ends of the sheet are overlapped and bonded, and a lid made of metal foil with a resin protective layer on the outer surface and a heat-sealable resin layer on the inner surface is inserted into the opening of the resulting plastic/metal foil composite cup. A method for manufacturing a plastic/metal foil composite can, which is characterized by placing it on the edge and sealing it by heat sealing.