JPH0360736B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to can-like container lids, and in particular, can containers such as various beverage cans and canned containers, and the like, which can be opened without the need for an auxiliary tool such as a can opener. The present invention relates to a lid for a can-like container that can be opened, and in particular to a lid for a can-like container that has improved breakage strength characteristics such as pinhole resistance when dropped and also has good opening characteristics.

[Prior Art] Concerning the above can-like containers, can-like containers mainly made of synthetic resin have been proposed (Japanese Patent Laid-Open Publication No. 52-39489).

The present inventors previously proposed the following lid for a can-like container mainly made of such synthetic resin.

For example, Al foil having polypropylene resin layers that can be heat-melted and bonded on both sides is preformed into a dish shape in a flat state or without substantially stretching, and then injection molded. A can-like container lid is constructed by setting the lid in advance in a machine mold, injecting resin into the mold, and performing simultaneous (integral) injection molding.

According to this, since the molten resin by injection is laminated on the heat-melt bondable polypropylene resin layer on the Al foil, the mutual adhesion strength is high, and the two resins of the molded product may peel off due to heat history such as retort treatment. It has the advantages of not causing any damage, and the molded product has high drop strength.
It has the advantage that the number of steps can be reduced and the cost can be reduced by molding or the like.

FIG. 16 shows a plan view of the conventional upper cover 1.
FIG. 7 shows a - sectional view of FIG. 16.

In the above-mentioned injection-molded top lid 1, the flap part 2 around the flap part 2 is attached to the body of a can-like container having a resin surface that can be similarly heat-melted and bonded, and the side on which the injection resin layer of the Al foil surface is laminated is on the opposite side. With the polypropylene resin layer on the side that can be heat-melted and bonded, it can be attached by heat-sealing, for example. or,
Furthermore, the lid panel part 3 inside the flap 2 part of the lid
In this case, an Al foil (multilayer base material 4A) with no injection resin layer laminated thereon, that is, a polypropylene resin layer that can be heat-melted and bonded on both sides, is exposed in the form of a band, with the apex near the opening point of the can. One end portion of a hard handle portion 12 that is substantially unbendable is fixed to the base portion 8 inside the score portion 6 having an acute angle portion, for example, via a boss 11;
By lifting the other end of the handle part 12 upward, the injection resin part formed at an acute angle on the side to which the grip part is fixed bends downward to pierce the multilayer base material 4A, and then pull the grip part, By further pulling along the score part 6, the score part 6
The multilayer base material 4A is cut, and the injection-molded upper lid 1 is then opened.

Note that an injection-molded lower lid having the same structure as the upper lid 1 without the opening part is attached to the bottom of the container at the same time, but if the container is not cylindrical but bowl-shaped, the lower lid may not be necessary. Of course.

However, the present inventors have found that such can-like containers have the following problems.

In other words, food products such as soup and soft drinks are stored in the can-like container after being sterilized by retort.
It is filled and stored, and then transported to the product distribution process. In addition, the hot pack allows the contents to be filled and stored while they are still hot. Furthermore, in the winter, coffee and other products are heated at relatively high temperatures at stands and the like.

As mentioned above, the upper lid of the can-like container is made by laminating the injection resin layer 5A on the multilayer base material 4A, which is made of a thin Al foil having polypropylene resin layers on both sides. An exposed notch (score part 6) of the base material 4A is provided, and the stress applied to the multilayer base material A when a can is dropped, for example, is concentrated at the acute-angled part of the score part 6 that is the starting point for opening the can. Pinhole breakage is likely to occur at the secondary acute angle part, which is easy to bend and has little flexibility, and the score part 6 of the top lid is deformed at high temperatures as described above, and damage due to stress concentration (particularly when the opening is configured at an acute angle). The cut edge of the score part 6 at the time of opening is likely to be damaged due to the deformation and elongation of the score part 6, which has an important effect on the opening mode. If the Al foil layer is very weak compared to the polypropylene resin layer on both sides, the metal layer (for example, the Al layer) is cut first, and the polypropylene resin on both sides is stretched and cut, resulting in a spread film (plastic). In the worst case, the resin may remain in a state where the resin is torn into fine fibers, or in the worst case, the can may not open, greatly reducing the ease with which the can can be opened and reducing the product value.

[Problem that the invention seeks to solve]

As mentioned above, the present invention is a can-like container lid which is mainly made of synthetic resin and can be opened without the need for auxiliary tools such as a can opener, and which has high can-drop strength and excellent opening properties. In addition to meeting the requirements for product drop strength as stipulated by legal standards (Ministry of Health and Welfare Notification No. 20), which has traditionally been a major hindrance to commercializing containers with synthetic resin lids. The purpose of the present invention is to provide a lid for a can-like container.

[Means for Solving the Problems] and [Operations] The object of the present invention is to provide a multilayer base material in which a polypropylene resin layer that can be thermally melted and bonded is formed on both sides of a metal foil that is impermeable to gases and liquids. A handle that is substantially unbendable on the top surface of the opening part, which is made by injection laminating another resin layer consisting of an opening part inside the notch separated through a notch and a part other than the opening part outside the opening part. In the can-like container lid formed by welding the parts, the overall shape of the notch part is made into a non-sharp shape, and the breaking strength of the metal foil is made higher than the breaking strength of the polypropylene resin layer constituting the multilayer base material. This can be achieved by means of a can-like container lid that is characterized by its enlarged size.

In other words, as a result of detailed research on the mechanism of can opening, we found that a notch (score part) is formed with an acute angle and a pointed protrusion with the apex near the can opening starting point, which was generally thought to have good opening performance. Rather than an opening with a sharp angle, for example, the entire notch has a continuous curved shape (non-sharp shape) such as a circle or an ellipse to increase the breaking strength of the metal foil with multiple layers. It has been found that when the temperature is higher than that of the polypropylene resin used to form the base material, the can can be opened extremely easily, and there is little left behind in the form of an opened film due to elongation of the resin for the multilayer base material at the cutting site of the can. .

This means that when a multilayer base material such as the one described above containing an easily stretchable polypropylene resin layer is pierced with a conventional acute-angled opening protrusion (point protrusion), a destructive force (stress) is generated at a single point of the protrusion. However, even if the metal foil is cut under this low stress, if the grip is pulled and the scores are cut one after another, the stress of the polypropylene resin layer will be higher than that of the metal layer. If the strength is higher, the polypropylene resin layer tends to elongate, and the resin layer is more likely to remain in the form of a spread film. If the shape of the opening is not large and the strength of the metal layer is greater than that of the polypropylene resin layer, when the handle is lifted and a force is applied to generate shear stress at the opening start part by lever action, the opening start of the present invention According to the section, stress is generated that is widely distributed in a line rather than a point as in the conventional case, and a much larger stress can be accumulated in a wide opening starting part than the small conventional stress that forms a pinhole, and the stress is considerable. When the degree of cutting becomes large, the resin layer can be cut almost at the same time as the metal foil is cut, and a large (long) cut can be made at the beginning of opening. That is, the large accumulation of stress increases the destructive force at the start of cutting, so that the multilayer base material can be cut in a large amount at once without giving the polypropylene resin layer any room to stretch.

Additionally, since the breaking strength of the metal foil is greater than the breaking strength of the resin layer constituting the multilayer base material as in the present invention, a large stress (energy) is released so that the can can be opened smoothly. Since it can be stored in a stable state until just before the opening of the can, it is resistant to external forces such as pinholes that cause the can to break on the side, and when the can is opened, the opening is substantially based on the cutting performance of metal foil. In other words, in the cutting process of the multilayer base material at the time of opening, the cutting performance that appears on the surface can be very similar to that of metal foil, and the resin laminated on the metal foil can be cut smoothly with as little elongation as possible. It is possible to obtain excellent aperture performance. The large stress mentioned above is not large enough to cause problems when a person opens a can with their fingers, and when viewed from the overall characteristics of opening a can, there is almost no problem in practical use due to the lever action of the handle. It's so big that it won't be.

Therefore, a container using the lid of the present invention does not suffer from pinhole breakage due to the impact caused by the impact when the can is dropped, as is the case with conventional cans, and has significantly improved strength against cans being dropped. It has two contradictory properties: it also has excellent can properties.

〔Example〕

Next, one embodiment of the present invention illustrated in the drawings will be described in detail.

FIG. 1 shows an example of a cross section of the multilayer base material of the upper lid used in the present invention, and the multilayer base material 4A of the upper lid is made of polypropylene that can be heat-melted and bonded to one surface of the metal foil 19A, as shown in FIG. It has a polypropylene resin layer 20A, and a polypropylene resin layer 21A that can be heat-melted and bonded on the other side.

FIG. 2 shows a plan view of an example of the upper lid main body before the handle is attached, and FIG. 3 shows a sectional view taken along the line of FIG. 2.

The upper lid body 1 has a flap portion 2 at its peripheral end.
and a lid panel part 3 inside thereof.

The upper lid main body 1 is formed by laminating an injection resin layer 5A on a multilayer base material 4A, but the injection resin layer 5A is not laminated on the panel portion 3, and therefore the multilayer base material 4A is exposed. Score part (notch part) 6
is provided. As shown in FIG. 2, the score section 6 is entirely formed in a curved shape.
FIG. 2 shows an example of an elliptical shape.

As will be described later, the lid is opened along the outer peripheral edge 7 of the band-shaped score portion 6.

Inside this score part 6, on the left side in FIG. establish.

The D-shaped interior surrounded by the extension part 9 and the pedestal part 8 is an exposed part 10 of the multilayer base material 4, similar to the score part 6.

Although this shaped portion 10 is an exposed portion of the multilayer base material 4A in the above embodiment, the injection resin layer 5A may be laminated thereon.

A boss 11 is erected on the base portion 8. This second
Although the illustrated embodiment shows an example in which two bosses 11 are provided upright, the number of bosses 11 may be one.

FIG. 4 shows a handle part 12 attached to the upper lid main body 1 shown in FIG. 2.
A plan view of an example of the upper lid 13 welded thereto is shown. Moreover, FIG. 5 shows a sectional view taken along the line of FIG. 4.

The attachment of the handle portion 12 to the boss 11 is performed, for example, by
A number of circular holes, for example, corresponding to the number of bosses 11 are made in the tip of the handle part 12, the head part of the boss 11 is made to protrude from the hole, and the protruding head part is melted by ultrasonic welding. This can be done by filling the hole with resin.

The handle part 12 is made of resin and is attached to the upper lid main body 1 by post-fitting as described above, but if one end is lifted, the handle part 12 is bent between the fixed part and no stress is applied to the opening start point of the score. So,
It cannot be used if it is bendable.

FIG. 6 shows a plan view of a lid formed by attaching a handle 14 different from that shown in FIG. 4 to the upper lid main body 1 similar to that shown in FIG. A straw is inserted into the multilayer base material 4 through this hole 140 so that the contents of the can can be ingested. FIG. 7 shows a sectional view taken along the line in FIG. 6, and FIG. 8 shows the upper lid 15 shown in FIG. The bottom cover 1
7 is attached to form a can-like container.

In addition, Fig. 9 is a plan view of the upper cover after opening, and Fig. 10 is a plan view of the upper cover after opening.
The figure shows a sectional view taken along the line of FIG. That is, an example of the opening of the upper lid will be explained with reference to FIG. 5. As shown in FIG. The pedestal part 8 is inserted into the multilayer base material 4A together with the tip of the multilayer base material 4A, and when the handle part 12 is subsequently pulled, the multilayer base material 4A is cut along the outer peripheral edge 7 of the score part 6, and the top lid is opened. It's summery.

In the can-like container top lid of the present invention, the score portion 6 separates the top lid panel portion 3 into an open portion (inside the score portion) and the other portion (outside the score portion). The portion 6 may be formed into a curved shape such as an elliptical shape with an appropriate width, or
The score part 6 is attached to the upper lid flap part 2 as much as possible.
The handle portions 12 and 14 may be firmly attached to the boss 11 by ultrasonic welding, and the breaking strength of the metal foil 19A may be increased by increasing the breaking strength of the metal foil 19A as described above.
Since the breaking strength is stronger than that of A and 21A, it is possible to provide a can-like container top lid with excellent opening properties.

In the above, when the metal foil 19A of the upper lid is made of aluminum, for example, the thickness is preferably 9 μm, particularly preferably 9 to 60 μm. Also, in order to make the breaking strength of the resin layers 20A, 21A smaller than the breaking strength of this aluminum, the resin layers 20A, 2
When 1A is composed mainly of polypropylene, for example, it is preferable that the thickness of one side is 100 μm or less.

The metal foil 19A is used for the purpose of providing so-called gas barrier properties that prevent permeation of oxygen, water, and the like. In particular, Al foil is preferable.

Although an example of the thickness of Al foil and polypropylene is shown above, the present invention is not limited to this, and in the case of the multilayer base material 4A made of other metal foils and other polypropylene resins, , the thickness relationship can be appropriately set based on the mechanical strength of each material.

In the present invention, the thickness of the multilayer base material 4A, especially,
By selecting the thickness of the metal foil 19A, for example, aluminum foil, complete incineration can be achieved. In recent years, the problem of empty can disposal has been raised, but by considering the thickness of the aluminum foil, the resin materials 20A and 21A of the multilayer base material, etc., complete incineration becomes possible and the problem of can disposal can be addressed. Also, the calories burned are 5000 ~
It is also possible to reduce the amount to 6000Kcal/Kg and solve the problem of empty can disposal.

The multilayer base material 4A used in the present invention has polypropylene resin layers (hereinafter referred to as first resin layers) on both sides of the gas barrier base material (metal foil) 19A, that is, heat-melt bondable resin layers 20A and 21A. was formed.

In the first resin layers 20A and 21A, the outer layer 20
A is heat-sealed to the injection resin layer 5A to form a highly adhesive lid, and the other first resin layer (inner layer) 21A is heat-sealed to the body of the container and crowned to the body.

When forming (laminating) the resin constituting the first resin layers 20A and 21A on the surface of the metal foil 19A, the resin may be laminated with or without an adhesive resin layer such as an adhesive or a film-like hot melt adhesive. I can do it.

The can-like container top lid according to the present invention can be obtained, for example, as follows.

This will be explained with reference to FIGS. 11 to 13. As shown in FIG. 11, the multilayer base material 4A is inserted into the guide member (stripper plate) 22. This may be done while adsorbing the multilayer base material 4A to the moving cylinder 23 of the robot. As shown in FIG. 12, while fixing the multilayer base material 4A within the stripper plate 22 to prevent positional shift,
Clamp the mold as shown in the figure. By this mold clamping, the flat plate-shaped (two-dimensional shape) multilayer base material 4A is
As shown in FIG. 3, the end thereof is bent within the mold (core mold, receiving mold) 24, and the mold (cavity mold, injection mold) 27 has a resin inflow passage 25 and a gate 26. A molten resin is injected into a cavity (mold space) 28 formed by a core mold 24 and a cavity mold 27, and a second resin layer 5A made of the molten resin is laminated on the surface (one side) of the multilayer base material 4A. Further, a boss 11 is erected on the base portion 8 made of the resin layer 5A, and an upper lid main body 1 having an extension portion 9 is obtained.

In this way, by injecting the resin 5A onto the multilayer base material 4A, the flap part 2 and the panel part 3 are formed, and the pedestal part 8 and the pedestal part 8 are made of the injected resin layer 5A and integrally molded. Boss 1 installed above
1 and an extension part 9 extending from the pedestal part 8, and further has a notch part 6 which can be formed at the same time during injection molding.

The handle portion 12 is preferably manufactured from the same resin in a separate process from the injection molding described above, and attached to the boss 11 by ultrasonic welding.

The can-like container lid upper lid body 1 of the present invention can be obtained as described above, but in the present invention, subsequent research on such injection molded lids has revealed that the following method is even better. This will be explained with reference to FIGS. 14 and 15.

Disc-shaped multilayer base material 4A as shown in Fig. 14
are set between a female mold 32 (a male mold 31 with longitudinal grooves 29 and 30 respectively (there is a flanged flat plate on the upper surface, but not shown in the figure)), and By inserting the male mold 31 into the interior and vertically absorbing the excess portion of the multilayer base material as wrinkles 33, the flange portion 34, body wall portion 35, and bottom portion 36 are formed without substantially stretching the multilayer base material 4A. A container-like preformed multilayer base material 37 having

This preformed multilayer base material 37 is set in an injection mold 38, and the injection resin 5 (resin forming the injection resin layer 5A) is injected. At the time of injection,
The multilayer base material 37 is pressed against the mold 38 by injection molding resin pressure, and the wrinkles 33 are smoothed.

As a result, the multilayer base material 4A produced in the flat insert molding method shown in FIGS. 11 to 13
As shown in FIG. 8, the flap part 2 made of the second resin layer of the lid 15 of the can-like container is welded to the body 16 of the can-like container by high-frequency induction heating. In this case, it is possible to prevent seaming defects from occurring, and also to prevent the gas barrier base material 19 of the multilayer base material 4A from being cut due to local heating, and furthermore, without substantially stretching. Since it is preformed, a thin Al foil can be used, and the resulting molded product has the advantage that the Al foil has a uniform thickness.

Various types of resins can be used for the injection resin 5A used in the present invention, including synthetic resins such as polyolefin-based synthetic resins such as polypropylene and ethylene polypropylene copolymer, which have excellent heat resistance against high temperatures during retort sterilization. An example is resin. An inorganic filler may be mixed with the injection resin. Mixing an inorganic filler has the following advantages.

The dimensional stability of the can-like container is improved and the shrinkage rate is reduced, which is advantageous.

The heat resistance is improved and the heat distortion temperature is increased, which is advantageous for retorting.

Burning calories are reduced, and combustion furnaces are not damaged, which is advantageous in terms of pollution prevention.

It can provide rigidity, which is advantageous in terms of product distribution.

Heat conduction becomes good, which is advantageous for retorting.

Cost can be reduced.

As the inorganic filler, any filler that is widely used in the fields of synthetic resins and rubbers may be used. These inorganic fillers are preferably inorganic compounds that have good food hygiene properties, do not react with oxygen and water, and do not decompose during mixing and molding. Examples of the inorganic filler include compounds such as metal oxides, hydrates (hydroxides), sulfates, carbonates, and silicates;
It is broadly classified into these double salts and mixtures thereof. Typical examples of such inorganic fillers include aluminum oxide (alumina), its hydrates, calcium hydroxide, magnesium oxide (magnesia), magnesium hydroxide, zinc oxide (zinc white), red lead, and lead such as white lead. oxide, magnesium carbonate,
Calcium carbonate, basic magnesium carbonate, white carbon, asbestos, mica, talum, glass fiber, glass powder, glass beads, clay,
diatomaceous earth, silica, wollastonite, iron oxide,
Antimony oxide, titanium oxide (titania), litobone, pumice powder, aluminum sulfate (Shigo etc.),
These include silica zirconium, zirconium oxide, barium carbonate, dolomite, molybdenum disulfide and iron sand. Among these inorganic fillers, those in powder form preferably have a diameter of 20 microns or less (preferably 10 microns or less). In addition, fibrous materials have a diameter of 1 to 500 microns (preferably 1 to 300 microns) and a length of 0.1 to 6 mm.
(preferably 0.1 to 5 mm). Furthermore, it is preferable that the diameter of the flat plate is 30 microns or less (preferably 10 microns or less). Among these inorganic fillers, those in the form of flat plates (flake) and those in the form of powder are particularly suitable.

In addition, various additives such as pigments may be added to the injection resin.

〔Effect of the invention〕

(1) According to the present invention, in addition to being high in drop strength and easy to open, it also has excellent properties such as excellent retortability and food hygiene, good formability, complete incineration, and low cost. We succeeded in obtaining a can-like container lid with the following properties.

(2) According to the present invention, the entire notch has a continuous non-sharp shape (shape without sharp edges), and the breaking strength of the metal foil is greater than the breaking strength of the resin layer constituting the multilayer base material. This not only further improved the can drop strength, but also made it possible to effectively match the cutting performance of the multilayer base material to the performance of metal foil during opening, resulting in extremely high opening characteristics (opening characteristics). A good synthetic resin can-like container lid could be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the structure of the multilayer base material of the top cover showing an embodiment of the present invention, FIG. 2 is a plan view of the top cover body showing an embodiment of the present invention, and FIG. 3 is a cross-sectional view taken along the line shown in FIG. FIG. 4 is a plan view of the top cover showing an embodiment of the present invention, FIG. 5 is a sectional view taken along the line of FIG. 4, FIG. FIG. 6 is a line sectional view, FIG. 8 is a perspective view of a can-like container showing an embodiment of the present invention, FIG. 9 is a plan view after opening the top lid showing an embodiment of the present invention, and FIG. 11 to 13 are sectional views explaining the lid forming process, FIG. 14 is an explanatory sectional view of the lid forming process, and FIG. 15 is an explanatory sectional view of the lid forming process,
FIG. 16 is a plan view of a conventional can-like container lid, and FIG. 17 is a sectional view taken along the line -- in FIG. 16. Symbols in the figure: 1...Top lid main body, 2...Flap part, 3...Panel part, 4A...Multilayer base material, 5A...
...Injection resin layer, 6...Score part (notch part), 7
...Outer peripheral edge, 8...Pedestal portion, 9...Extension portion, 1
0...Exposed part, 11...Boss, 12,14
... Handle part, 13, 15 ... Top lid, 16 ... Body part, 17 ... Bottom lid, 19 ... Metal foil, 20A, 2
1A: Heat-meltable resin layer.

Claims (1)

[Claims] 1. On the surface of a multilayer base material in which a polypropylene resin layer that can be heat-melted and bonded is formed on both sides of a gas- and liquid-impermeable metal foil, an opening part inside the notch and an outside part are separated through a notch. In a can-like container lid formed by injecting and laminating another resin layer consisting of a part other than the opening part and welding a substantially unbendable handle part to the upper surface of the opening part, the overall shape of the notch part is A can-like container lid characterized in that it has a non-sharp shape and the breaking strength of the metal foil is greater than the breaking strength of the polypropylene resin layer that constitutes the multilayer base material.