JPH0144583B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a plastic/metal foil composite container, and more specifically, it has excellent gas barrier properties, flavor retention, hygienic properties, and retort sterilization properties. The present invention also relates to a plastic/metal foil composite container that has excellent sealing properties due to heat sealing with the lid.
Furthermore, the present invention relates to a plastic/metal foil composite container that can be filled, has low loss of carbon dioxide gas, and can be manufactured at low cost.

Prior Art and Technical Problems of the Invention 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, they have become difficult to dispose of. This has led to the problem of so-called can pollution.

In recent years, plastic/metal foil composite containers have been attracting attention as an alternative to metal cans. As an example of this composite container,
No. 35458 and No. 59-18263 disclose a method in which a metal foil laminate is wrapped around the outer circumferential surface of a plastic body with openings at both ends and adhered thereto, and a lid body is engaged with the openings at both ends and sealed by heat sealing. something is proposed. Although this composite container has shape retention properties due to the plastic shell and gas barrier properties due to the metal foil laminate, it is recognized that direct contact between the contents and the plastic shell causes various inconveniences.

The first problem is the so-called hygienic characteristics and flavor retention, where plastic is extracted from the food contents, or the odor of plastic is transferred to the contents. This is a problem of carbon dioxide loss, which occurs when carbon dioxide gas is adsorbed or dissolved into plastic when filled with plastic.

Furthermore, another serious problem with such composite containers is that even though the container body has excellent gas barrier properties, there is a problem with the sealing structure by heat sealing between the open end of the body and the lid. There is a problem in that leakage is likely to occur during retort sterilization or over time thereafter.

OBJECTS OF THE INVENTION Accordingly, it is an object of the present invention to provide a plastic/metal foil composite container that eliminates the various drawbacks of the conventional composite containers described above.

Other objects of the present invention are excellent gas barrier properties,
To provide a plastic/metal foil composite container which has flavor retention, hygienic properties, retort sterilization, and has excellent sealability by heat sealing with a lid.

Still another object of the present invention is to produce a plastic/metal foil composite in which a metal foil laminate is bonded to the inner circumferential surface of a plastic body, and this metal foil laminate is also interposed in the heat-sealed portion with the lid. There are containers to provide.

Structure of the Invention According to the present invention, there is provided a body member comprising a seamless plastic cylinder and a metal foil-containing laminate wrapped around the inner peripheral surface thereof, and a flange heat-sealed to the open end of the body member. a lid member having a portion;
The metal foil-containing laminate has a metal foil intermediate layer and an inner and outer surface layer of heat-sealable resin, and the metal foil-containing laminate covers the cut edge and the outer end of the plastic cylinder and is in close contact therewith. There is provided a plastic/metal foil composite container characterized in that it has an extension, and the lid member is heat-sealed to the body member via the extension of the metal foil-containing laminate.

Preferred embodiments of the invention The present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings.

Composite Container In FIG.
The metal foil composite container 1 is composed of a thick seamless cylinder 2 made of thermoplastic resin and a metal foil-containing laminate 3 applied to the inner surface of the cylinder.

The thick cylindrical body 2 is formed by thermoforming a thermoplastic resin, for example, by injection molding, extrusion molding, blow molding, vacuum molding, pressure molding, or the like. In the specific example of the container shown in FIG. 1, the cylindrical body 2 is formed by extruding thermoplastic resin into a cylindrical or pipe shape, and cutting this cylinder or pipe into a certain size. There are open ends 4 and 5 at both ends.

Laminate layer 3 applied to the inner surface of this cylindrical body 2
As is clear from the cross-sectional view of FIG. 2, it consists of a laminate of a metal foil 6, a heat-sealable resin layer 7 inside the metal foil, and a heat-sealable resin layer 8 outside the metal foil.

The laminate layer 3 is applied to the inner surface of the cylindrical body 2 in the form of a sheet having a dimension slightly larger in the lateral direction than the unfolded dimension of the cylindrical body 2, and the seam 9 is formed by overlapping both ends of the sheet. is formed. Further, the laminate layer 3 has a dimension longer in the axial direction than the length (axial dimension) of the cylinder 2, and has a portion that protrudes outward beyond both open ends 4 and 5 of the cylinder 2. This becomes the extension section 10 described below. That is, this extension part 10 is bent outward, and the cut edges 11a, 11b of the cylinder 2 and the outer ends 12a, 12
It covers and is in close contact with b.

The laminate layer 3 and the cylindrical body 2 are bonded not only on the inner surface 13 of the cylindrical body but also on the cut edges 11a and 11b.
Also at the outer end portions 12a and 12b, the outer peripheral surface heat-sealable resin layer 8 of the laminate layer 3 and the cylinder body 2
This is done by thermal bonding with the resin that makes up the material.

The seam 9 may be formed by any method such as lap joint or lock seam joint, but
In the specific example shown in FIG. 3, a bond is formed between one end edge 14 located on the outer surface side of the laminate 3, that is, on the side of the cylindrical body 2, and the outer folded part 16 of the other end edge 15. is done to form the seam. According to this aspect, the cut edges 17a, 1 of the metal foil laminate 3
7b will be located outwardly with respect to the seam and will be effectively protected from contact with the contents.

A lid 18 shown in FIG. 4 is applied to both open ends 4, 5 of this plastic/metal foil composite container body. The lid body 18 includes a flat center panel 19 formed by press molding, for example, and a groove portion 20 around the center panel 19 having a U-shaped cross section. This lid body 18 is also made of a laminate of a metal foil 21 and a heat-sealable resin 22 on the inner surface, and a protective resin layer 23 is further provided on the outer surface of the metal foil 21.

As shown in FIG. 5, the open ends 4 and 5 of the plastic/metal foil composite container body, that is, the open end covered with the extension part 10 of the metal foil-containing laminate 3, are inserted into the U-shaped groove 20 of the lid body 18. The extension part (folded part) of the metal foil-containing laminate 3 is formed by heating the inner and outer walls and the upper wall of the U-shaped groove while pressing it against the open end 4.
The heat-sealing resin layer 7 in 10 and the heat-sealing resin layer 22 of the lid 18 are thermally bonded to perform sealing by heat sealing. As one of the lids, it is of course possible to use a heat-sealed lid equipped with a known easy-to-open mechanism.

In the plastic/metal foil composite container of the present invention, since the metal foil-containing laminate is provided on the side in contact with the contents, it has excellent gas barrier properties and prevents contact between the contents and the plastic body. Therefore, it has excellent flavor retention and hygienic properties, and also effectively eliminates the problem of carbonation loss caused by adsorption or dissolution of carbon dioxide gas into the plastic body.

Moreover, in the composite container of the present invention, the open end portion to be sealed with the lid by heat sealing is completely covered with the metal foil-containing laminate 3 and its extended portion (folded portion) 10, and It has the characteristic that the laminate is tightly adhered to this.
Because of this feature, in the composite container according to the present invention, the sealing by heat sealing between the lid and the open end of the container body is performed reliably and firmly, and a leak-free seal is formed even during retort sterilization and subsequent aging. It has the advantage of being possible. The reason for this is that the metal foil 6 is always present directly under the heat-sealing resin layer 7 at the container opening ends 4 and 5.
This is thought to be because the temperature of the heat-sealing resin layer 7 is maintained at a uniform and uniform heat-sealing temperature when the lid body 18 is heat-sealed.
In fact, compared to a composite container in which a metal foil-containing laminate is not provided at the open end to be heat-sealed to the lid, the composite container of the present invention can form a sealed structure with significantly superior leakage resistance. was confirmed.

In the present invention, the resin constituting the cylinder 2 is meltable and thermoformable, such as low-, medium-, or high-density polyethylene, crystalline polypropylene, crystalline ethylene-propylene copolymer, Olefin resins such as propylene-butene copolymers and ionic crosslinked olefin copolymers; styrene resins such as polystyrene, styrene-butadiene copolymers, and styrene-butadiene-acrylonitrile copolymers; polycarbonates; polyesters; pomiamides; acrylics System resin; polyacetal resin etc. are used. Among these, olefin resins are preferred in terms of economy and ease of production, and polypropylene is most desirable in terms of retort sterilization. The thickness of the cylinder 2 is preferably in the range of 0.2 to 3 mm, particularly 0.5 to 1.0 mm.
It is advantageous in terms of shape retention and thermal bonding operation.

Aluminum foil is suitable as the metal foil 6, but
If desired, iron foil, steel foil, tin foil, etc. may be used, and the thickness thereof is preferably in the range of 7 to 150 microns, particularly 9 to 50 microns, so as to obtain the desired gas barrier properties.

As the heat-sealing resin layer 8, a thermoplastic resin is used which exhibits thermal adhesiveness not only to the constituent resin of the cylinder 2 described above but also to the metal foil 6. For example, for olefinic resins, olefinic resins graft-modified with ethylenically unsaturated carboxylic acids such as maleic anhydride, acrylic acid, methacrylic acid, or their anhydrides are advantageously used. Further, for polyamide, a polyamide resin modified by copolymerization or polymer blending, etc. is used, and for polyester, a polyester resin modified by copolymerization, polymer blending, etc. is used. These thermoadhesive modified resin layers 8 generally have a thickness of 1 to 30 microns, particularly 2 to 30 microns.
It can have a thickness of 10 microns and is applied to metal foils, for example in the form of suspensions, emulsions, solutions, powders, films, etc. These heat-sealable resin layers 8 may have a single-layer or multi-layer structure; for example, the metal side may be a modified resin layer and the surface may be made of the same resin layer as the resin forming the cylinder.
Advantageously used for the purposes of the present invention.

In the metal foil-containing laminate, the inner surface layer and the outer surface layer may be made of the same resin or may be made of different types of resin. For example, as the inner resin layer, a film excellent in hygienic properties and flavor retention, such as polyester film, polyamide film, or polypropylene film, can be used. These films may be bonded to metal foil via an adhesive such as polyurethane.

Manufacturing method of composite container In FIG. 5 for explaining the manufacturing method of the composite container of the present invention, first in step A, a metal foil-containing laminate 3 is placed on the inner surface of the seamless plastic cylinder 2 at its upper and lower ends. 10'a and 10'b are bonded so that they protrude above and below both open ends 4 and 5 of the cylinder. It is desirable that the adhesion be carried out over the entire inner surface, but since a sealing bond is to be performed between the metal foil-containing laminate and the lid, partial adhesion is not necessarily required. .

Next, in step B, the open end 4 of the cylinder 2,
The laminate that protrudes from 5 is folded back and glued. The protruding parts 10a, 10b of the laminate 3 can be folded back using a brush, hot air, a roller, etc., and the protruding parts 10a, 10b of the laminate 3 can be bonded to the cylinder by high-frequency induction heating, a burner, etc. Direct flame heating, heating with hot air, etc. can be used.

Finally, in step C, the lids 18 are attached to both open ends 4 and 5 of the cylindrical body 8 and adhered under pressure. Roll pressure or the like can be used to pressurize the lid 18, and high frequency induction heating means such as the above-mentioned heating means can be used for heating.

Example The invention is illustrated in the following example.

Example 1 A pipe having an inner diameter of 52.3 mm and a wall thickness of 0.6 mm was extruded using polypropylene having a melting point of 163° C., a density of 0.89 g/cm ² , and an MI of 1.0, and cut into a length of 135 mm.

Next, graft-polymerized modified polypropylene resin powder (melting point 162°C) was coated on aluminum foil with a thickness of 20 μm so that maleic anhydride became a polymer with a carbonyl group concentration of 140 mg/100 g, and melt-rolled (average The film thickness was 5 μm) to form a laminate.

Further, polyethylene terephthalate with a thickness of 12 μm was laminated on the aluminum foil surface of the laminate using a urethane adhesive.

Next, the laminate was slit to a length of 145 mm x width of 175 mm, and heated and bonded to the inner surface of the thick-walled polypropylene pipe while applying pressure with a small-diameter roll so that the laminate protruded 5 mm from both ends of the pipe. At this time, the cut edge at the seam overlap part of the laminate was also protected.

A lid material made of a laminate of 5 μm epoxy phenol resin/100 μm aluminum foil/12 μm polyethylene terephthalate/20 μm copolyester resin was placed on one open end of the plastic/metal foil composite can obtained in this manner by high-frequency induction heating. The copolyester resin on the inner surface of the lid and the polyethylene terephthalate layer bonded to the outer surface of the can body were thermally bonded.

A plastic can provided with this lid was filled with 250 ml of coffee, and a lid made of the same laminate as the lid was heat-bonded to the opening in the same manner.

The sealed can thus obtained was heat sterilized in a hot water retort at 122°C for 30 minutes. At this time, no defects such as deterioration of the plastic can body due to temperature differences or delamination between adhesive layers were observed. Furthermore, the sealing properties between the can body and the lid were good, preventing air, moisture, etc. from entering the can.

Also, when I opened the top lid and sampled the contents,
There was no can odor, and no off-taste or odor was observed.

Therefore, it has been revealed that the container of the present invention has excellent flavor retention and sealing properties.

Effects of the Invention According to the present invention, by adhering a laminate containing metal foil to the inner surface of a seamless plastic cylinder, it has excellent gas barrier properties and is resistant to harsh treatments such as retort sterilization. I can do it.

It is possible to use a film with excellent hygienic properties and extraction resistance, such as polyethylene terephthalate, for the innermost layer, and by using this film, a container with excellent flavor retention can be obtained.

Since the cylindrical body is placed on the outside surface, an inexpensive material can be used for the cylindrical body without considering flavor retention, so the container is highly economical. It is also possible to use scrap material.

The following advantages are achieved.

In addition, since the metal foil laminate on the inner surface covers the cut edge and the outer end of the cylindrical body in close contact with each other, the sealing performance of the joint surface between the lid material and the body is excellent. That is, since the outer cover material and the laminate are firmly and reliably joined, there is no fear of fluid, steam, etc. entering.

The container of the present invention cannot be made using the spiral cans described in JP-A-58-209561 and others.

Compared to spiral cans, it is easier to make the container (especially the body), so productivity is high.

The following advantages are also achieved.

[Brief explanation of drawings]

FIG. 1 is a perspective view of the plastic/metal foil composite container body of the present invention, FIG. 2 is an enlarged vertical sectional view of the open end of the body in FIG. 1, and FIG. FIG. 4 is an enlarged horizontal sectional view of the joint of the main body shown in FIG. 4, FIG. 4 is a perspective view of the lid applied to the opening end, and FIG. FIG. 1 is a plastic/metal foil composite container body, 2 is a seamless cylindrical body, 3 is a metal foil-containing laminate, 4 and 5
1 is an open end, 6 is a metal foil, 7 and 8 are heat-sealable resin layers, 9 is a seam, 10 is an extension, 11 is a cut edge, 12 is an outer end, and 18 is a lid.

Claims (1)

[Claims] 1. A body member consisting of a seamless cylinder made of plastic and a metal foil-containing laminate applied to the inner peripheral surface of the body, and a lid member having a flange portion heat-sealed to the open end of the body member. The foil-containing laminate has a metal foil intermediate layer and an inner and outer surface layer of heat-sealable resin, and the metal foil-containing laminate has an extension portion that covers and is in close contact with the cut edge and outer end of the plastic cylinder. 1. A plastic/metal foil composite container comprising: a lid member heat-sealed to a body member via an extension of the metal foil-containing laminate.