JPH0446820B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for preforming can-like containers, ie, can containers such as various beverage cans and canned containers, and lid components of similar items.

[Prior Art] As for the can-like containers mentioned above, metal cans have been on the market for some time, but metal cans have problems such as coldness peculiar to metal, lack of durability, and disposal of empty cans.

In response, can-like containers mainly made of plastic have been proposed. The present inventor has developed a can-like container made mainly of plastic by replacing the conventional adhesive method of attaching a pre-injection-molded plastic sheet to a metal foil with plastic layers on both sides. , we have earnestly studied methods for integrally molding within the mold of an injection molding machine using the injection molding method, and have made numerous proposals (patent application filed in 1983).
−90749, No. 58-124756, No. 59-146946,
No. 59-146943, No. 59-146944, No. 59-248082
number, etc.).

An example of the injection molding method will be explained with reference to FIGS. 25 to 27. As shown in FIG. The insert material 40 is inserted into the guide member (stripper plate) 43 by moving the moving cylinder 42, and the insert material 40 is inserted into the stripper plate 43 as shown in FIG.
While temporarily fixing the molds to prevent displacement, the molds are clamped as shown in FIG. 27. Due to this mold clamping,
As shown in FIG. 27, the flat plate-shaped (two-dimensional shape) insert material 40 is bent at its end in a mold (cavity mold, receiving mold) 44, and a resin inflow channel 45 is formed.
and a mold with a gate 46 (core mold, injection mold)
The molten resin is injected from the gate 46 of 47 into a cavity (intra-mold space) 48 formed by a cavity mold 44 and a core mold 47 to obtain a lid for a can-like container. This type of simultaneous molding (integral molding) reduces the number of steps, and the molded product has high adhesion strength, so it does not peel off even under harsh conditions such as retort processing, and the product has high drop strength. In addition, a can-like container lid with excellent food hygiene properties could be obtained.

By the way, in such injection molding, when a flat insert material 40 is clamped and bent into a three-dimensional shape as shown in FIG. 27, distortion occurs in the insert material 40. This distortion is mainly caused by wrinkles, and when the insert material 40 is mounted in a mold while being flat, irregular and large wrinkles usually occur, and the depth of the lid is difficult to maintain. In this case, this problem can be alleviated to some extent by making the insert material relatively large; however, in such a case, troubles such as the insert material being caught in the parting line may occur.

If injection molding is performed on such a distorted insert material, the presence of this uneven distortion will result in defects in the molded product.

As will be described later, FIG. 11 shows a bottom view of an example of a can-like container lid obtained by injection molding in this way. A phenomenon occurs in which the injection resin 170 flows and adheres to the outside of the side wall. This resin surrounding phenomenon is particularly often seen in wrinkled areas.

In the lid, the body of the can-like container is fitted between the flap portion and the outside of the side wall, and the lid is attached to the body. The flap portion is made of the above-mentioned injection resin, and the body portion of the can-like container also has a heat-meltable resin layer on its surface.

Attachment of the lid to the body is generally performed by melting the resin using high-frequency induction heating, which generates heat in the Al foil of the insert material, melts the resin layer of the insert material by the heat transfer, and welds it to the body. This is done by letting

As mentioned above, if more resin is attached to the back side of the lid around the resin, a large amount of heat will be required to generate heat in the Al foil and melt the resin layer on the side wall. This may cause irregular heat generation during high-frequency heating, causing uneven sealing when the lid and body are attached as described above, or causing cuts in the Al foil due to local heating. It can also cause defects such as leakage of the contents filled in the container.

[Problems to be Solved by the Invention] An object of the present invention is to provide a method for preforming a can-like container lid component that eliminates the drawbacks of the prior art. Prevents seaming troubles during heating,
It is an object of the present invention to provide a preforming method for a can-like container lid component that ensures good seaming conditions, has high food hygiene, and has good injection moldability.

Other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means for Solving the Problems] The present invention involves injecting a gas-impermeable (barrier) base material (multilayer base material) having heat-bondable synthetic resin layers on both sides as a can-like container lid component. Before obtaining a synthetic resin can-like container lid with barrier properties by injection molding, a thermoplastic resin is placed in a molding die and a thermoplastic resin is injected onto the surface of the multilayer base material. and on the upper surface of the recess of the female mold of the cylindrical part, the inner surface of the recess is provided with a groove having a cross-sectional shape having a large number of parallel edges inward from the entrance of the recess,
The flat multilayer base material having a diameter larger than the diameter of the recess of the female mold is placed, the multilayer base material is lightly pressed onto the upper surface of the female mold, and then the multilayer base material is By pushing a cylindrical male mold having a narrow outer radius corresponding to the thickness of the base material and a flange into the recess, the female mold and male mold are inserted while sliding the multilayer base material. It has a flange part, a body wall part, and a bottom part, characterized in that the multilayer base material is formed in a crease state in the gap with the mold,
The invention consists in a preforming method for a can-like container lid component in which a crease is formed over at least the entire circumference of the body wall.

[Example] Next, the present invention will be described based on an example shown in the drawings.

A multilayer base material 1 having a cross section as shown in FIG. 2 is punched out into a circular shape of an appropriate size as shown in FIG. 1A. This multilayer base material 1 is set between a male mold 4 (having a flange not shown on the upper surface) and a female mold 5, each having longitudinal grooves 2 and 3, as shown in FIG. 1B. Then, the male mold 4 is pushed into the circular hollow part (recess 50) of the female mold 5, and the remaining part of the multilayer base material is absorbed in the longitudinal direction as wrinkles (folds) 6, thereby substantially forming the multilayer base material. The base material 1 has a flange portion 7 (formed by the front foam flange portion), a body wall portion 8 and a bottom portion 9 without stretching, and a crease 6 is formed over the entire circumference of the flange portion 9 and the body wall portion 8. A container-like preformed multilayer base material 10 is prepared. The multilayer base material 1 is made to have a diameter larger than the diameter of the recess 50 of the female mold 5, as shown in FIG. 1B. The female mold 5 has a cylindrical shape and has a circular recess 50 on the end face. The male mold 4 also has a cylindrical shape, and the female mold 5
The outer radius of the recess 50 is smaller than the inner radius by an amount corresponding to the thickness of the multilayer base material 1. The details of the above procedure are as follows: A flat multilayer base material 1 having a diameter larger than the diameter of the recess 50 of the female mold 5 is placed on the female mold 5, and the female mold of the multilayer base material 1 is Recess 50 of mold 5
Lightly press the outside against the female mold 5 using a holding jig, then push the male mold 4 into the recess 50 of the female mold 5, and while sliding the multilayer base material 1, press the male mold 4 against the female mold 5. The multilayer base material 1 is molded with creases 6 in the gap between the mold 5 and the male mold 4. Examples of the base material 11 that is impermeable to oxygen, water, etc. (hereinafter referred to as gas barrier base material) (hereinafter referred to as gas barrier base material) constituting the multilayer base material 1 used in the present invention include metal foil, sheet, Examples include film.

A typical example of metal foil is aluminum foil (hereinafter simply referred to as aluminum foil), and the present invention particularly relates to a can-like container lid made of this aluminum foil as a gas barrier base material. Examples of other gas barrier substrates include sheets and films of saponified ethylene-vinyl acetate copolymers, polyvinylidene chloride, polyamide, polyacrylonitrile, and the like.

When manufacturing the container-like multilayer base material 10 as described above, the peripheral end of the multilayer base material 1 is clamped to a support stand, and pressure is applied to the multilayer base material 1 from above to make the base material 1. By stretching (stretching) downward, it is possible to form a container-like multilayer base material 10 as shown in FIG. 1C.

However, since this method involves stretching a multilayer film, not only the thickness of the aluminum foil in the base material becomes uneven, but also pinholes and cracking are likely to occur.

When forming a can-like container lid, the present inventors
In order to prevent the occurrence of irregular large wrinkles in flat inserts as shown in Figures to Figure 27, and to improve seaming performance,
We considered preforming a multilayer base material, but
In the above-mentioned drawing method, when a thin metal foil of about 7 to 60 μm is used as a gas barrier base material, cracking will already occur at a stretching ratio of about 1.8 times or more, and this will result in insufficient barrier properties for can-like containers. It has been found that this causes a decrease in heat generation by high-frequency induction heating, making the state of heat generated by high-frequency induction heating uneven, and causing seaming troubles. On the other hand, the thickness of the metal foil is 70μ
In the above case, although the stretching ratio is improved, the cost is considerable and problems arise in opening the lid as the object of the present invention.

According to the above-mentioned preform molding as in the present invention, it is possible to use a gas barrier substrate (aluminum foil) with a thickness of about 7 to 60 μm, and unlike drawing processing, the preform can be formed without substantially stretching. can be obtained, and the thickness can be made uniform.

The stretching ratio may be as low as 1.0 to 1.8 times.

By making the gas barrier base material thin in this way, it is easy to open and can be completely incinerated, and the incineration calories are 5,000 to 5,000.
It can be reduced to 6000KCal/Kg and solve the problem of empty can disposal.

The multilayer base material 1 has a heat-meltable resin layer (hereinafter referred to as a first layer) on both sides or one side of the gas barrier base material 11.
(referred to as resin layers) 12 and 13. In the embodiment shown in FIG. 2, this first resin layer is formed on both surfaces.

As described above, the can-like container lid of the present invention is attached to the body of a can-like container. This body also has a similar resin layer surface.

The first resin layer on the attachment side to the body of the lid is referred to as the inner layer 12, while the resin layer (hereinafter referred to as the second resin layer) is laminated on the preformed multilayer base material 10 by injection molding or the like, as described later. Assuming that the first resin layer on the side to be heat-sealed is the outer layer 13, the multilayer base material 1 according to the present invention has the inner and outer layers 12 and 13 formed as shown in the above embodiment. It is preferable. Due to the presence of this outer layer 13, a lid with high adhesiveness can be formed by thermal fusion with the second resin layer. However,
The outer layer 13 can also be omitted.

As the resin constituting the first resin layers 12 and 13, a resin that melts by heat, typically a thermoplastic resin, is used.

The inner and outer layers 12 and 13 may be made of the same resin, or may be made of different resins.

When the first resin layers 12 and 13 are formed on the gas barrier substrate 11, they can be formed with or without an adhesive resin layer such as an adhesive or a film-like hot melt adhesive.

The thickness of the first resin layer is preferably 100 μm or less on one side.

Preformed multilayer substrate 10 according to the invention
The wrinkle 6 is preformed from a two-dimensional (flat) shape as shown in FIG. 1A to a three-dimensional (three-dimensional) shape as shown in FIG. They are formed uniformly over the entire circumference of the wall portion 8 at appropriate intervals.

In other words, the wrinkles 6 that are uniform around the entire circumference absorb the distortion that occurs when the shape is transformed from a flat shape to a three-dimensional shape under a low stretching ratio.

The wrinkle shape may be any shape, but if there is time before setting (inserting) into the mold in the next process, the spring back may make it difficult to insert.
As a preventive measure, it is preferable to use a cross-sectional shape with clearly defined edges, such as the shapes shown in FIGS. 3A and 3B, rather than the waveform shape shown in FIG. 3C. Furthermore, such a wrinkle shape allows a uniform heating state in the circumferential direction to be obtained during high-frequency induction heating, leading to a significant improvement in seaming performance. Note that the preformed multilayer base material 10 can be formed using a machine or a hydraulic press device if the method is to slide the disc-shaped punched multilayer base material 1 into a mold as illustrated in FIGS. 1A to 1C. You can also do this by

Next, the injection molding process will be explained.

As shown in FIG. 4A, the preformed multilayer base material 10 is attached to the female mold 14 portion of the injection mold, and the mold 16 having the gate 15 is clamped as shown in FIG. 4B. When the injection molding material 17 is injected from the gate 15 of the mold 16, the opposing surfaces of the molding material 17 and the multilayer base material 10 are welded to form a can-like container having a cross section as shown in FIG. 4C. A lid 18 is formed.

In the above, during injection, the wrinkle 6 surfaces of the preformed multilayer base material 10 are pressed against the female mold 14, and the wrinkles 6 are smoothed.

FIG. 5 shows how the wrinkles 6 of the multilayer base material 10 having a wrinkle shape as shown in FIG. 3A are smoothed by injection, and in this way, the multilayer base material 1 is preformed. However, when the flap part 7 is tilted, it collides with the wall surface of the mold 16 [see FIG. 4A], and most of the injection molding material 17 is
As shown in the figure, the resin flows in parallel to the direction of the trunk wall 8 of the multilayer base material 10 to form a sealed lid around the resin.

FIG. 7 is a perspective view of the bottom side of the lid, showing that there is no resin around the lid, there is no resin adhesion on the bottom side surface 19, and smoothed wrinkles 60 are uniformly formed at appropriate intervals on the entire circumferential surface. Ru.

Figure 8 shows the second model which has not been preformed in advance.
5 to 27 are cross-sectional views of the can-like container lid 20 formed by the flat insert molding method;
As shown in the figure, since the multilayer base material 21 does not have a flap part, the injection molding material 17 wraps around the side wall 23 as shown by the arrow 22 in the figure, and the injection molding material 17 is attached to the side wall 23. Make it adhere.

In the flat insert molding, irregular and large wrinkles as shown in FIG. 10 occur in the multilayer base material 21 when the mold is clamped, and in particular, the resin surroundings as shown in FIG. 9 are likely to occur in the wrinkled portions 24. .

FIG. 11 is a bottom view of a can-like container lid 20 formed by such flat insert molding, in which injection molding material 170 tends to adhere to the side wall 23 around the resin.

In addition, in this flat insert molding, the insert material is fixed to the stripper plate and insert molded, so the spring back of the insert material is likely to occur, but by preforming it in advance, such spring back
It prevents backing and improves shape retention, making it easier to fit into injection molds.

In the present invention, in order to further improve the ease of attachment to the mold, it is preferable to perform vacuum suction 25 from one of the molds, as shown in FIG. It becomes easier.

Next, FIG. 12 shows a top view of the lid of the can-like container according to the invention as shown in FIG. 7, which shows the bottom lid 26 of the can-like container and, like the top lid, Attached to the body.

FIG. 13 is a plan view showing an example of a similar upper lid, FIG. 14 is a sectional view taken along the line of FIG. 13, FIG. 15 is a plan view with the tab for opening the lid removed, and FIG. It is a figure-line sectional view.

The upper lid 18 is made of a preformed multilayer base material 1.
0, an injection resin 17 is laminated thereon. A notch 29, which is an exposed portion of the multilayer base material, is provided in the lid main body portion 28 on the center side of the flange portion 27 of the lid 18.

An example is shown in which the notch 29 is formed in an elliptical band shape. It is preferable to have a curved shape such as a circle.

The lid is opened along this notch 29 as will be described later.

The inside of the notch 29 has a tab attachment part 31 to which a tab 30 is attached. The tab 30 can be attached, for example, by erecting a boss 32 at the end of the tab attaching portion 31, as shown in FIG.

FIG. 17 is an example of a plan view of the tab 30, and the end of the tab 30 is provided with a hole 33 as shown in the figure.

Figures 18 and 19 show tab 3 to boss 32.
0, the tab 30 is attached to the boss 32 using its hole 33. Figure 19 shows hole 3 of tab 30.
An example is shown in which the head portion 34 of the boss 32 protruding from the boss 3 is melted by high-frequency heating and the tab 30 is attached to the tab attachment portion 31. But in this case,
Attach the head portion 3 of the boss 32 to the hole 33 of the tab 30.
4 will swell and worsen the appearance, so
As shown in FIG. 8, by adjusting the diameter of the boss 32 and the hole diameter of the tab 30, the head portion 34 of the boss 32 is filled in the hole 33 of the tab 30, and the top surface of the tab 30 and the top surface of the boss 32 are on the same plane. It is best to position it at the top.

The lid 18 has a notch 29 and an exposed portion 35 of the multilayer base material inside the attachment portion 31 of the tab 30.
will be established.

Next, another example of the lid on the can-like container of the present invention will be explained.

FIG. 20 is a plan view showing another example of the upper lid, and FIG. 21 is a sectional view taken along the line taken along the line shown in FIG. 20.

The present invention can also be applied to such an upper lid 18'.

In this lid 18', unlike the previous embodiment,
A tab 36 made of injection resin is laminated on the multilayer base material 10 with a printing ink layer 37 interposed therebetween. That is, this upper lid 18' is made by laminating the injection resin 17 on a multilayer base material by injection molding in the same manner as described above.

This lid 18' is designed to insert a fingertip into the groove 38, lift the tab 36, and open the lid along the notch 29'.

In this case, since the injection molding is used, the multilayer base material 10 and the tab 36 made of the injection resin may come into close contact with each other, making it difficult to separate them.

Therefore, a treated layer 37 such as the above-mentioned printing ink layer is provided for the purpose of easily separating the multilayer base material 10 and the tab 36.

However, applying such printing ink can be complicated.

In this respect, as shown in FIGS. 13 to 16, the exposed portion 3 of the multilayer substrate is not provided with the treatment layer 37.
5, it is possible to omit the easy peeling treatment using printing ink, etc., and by providing the exposed portion 35 of the multilayer base material, the strength against dropping cans when forming a can-like container can be improved. I can do it.

Next, the lid 18 shown in FIGS.
To explain an example of the opening, when one end of the tab 30 opposite to the mounting side is lifted with a finger, the notch 29
The can-like container lid 18 is opened along this line.

FIG. 22 is a plan view of the lid 18 after opening, and FIG. 23 is a sectional view taken along the line of FIG. 31, it can be seen that the lower multilayer base material part and the exposed part (multilayer base material) 35 of the multilayer base material inside the attachment part 31 are also removed by the opening.

In addition to attaching the tab 30, the attachment part 31 also lifts the lower multilayer base material part that is in close contact with the attachment part 31 as the attached tab 30 is lifted when opening the lid. Can cut multilayer substrates.

Various types of injection resins can be used for the injection resin used in the present invention, including synthetic resins such as polyolefin-based synthetic resins such as polypropylene, ethylene, and propylene copolymers, 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 inorganic fillers 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.

Burned calories are reduced and incinerators are not damaged, which is advantageous for empty can disposal.

It can provide rigidity, which is advantageous for product distribution.It has good heat conduction, which is advantageous for retorting.

Cost can be reduced.

As the inorganic filler, any material widely used in the field 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 kneading and molding. Examples of the inorganic filler include compounds such as metal oxides, their 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, talc, glass fiber, glass powder, glass beads, clay,
diatomaceous earth, silica, wollastonite, iron oxide,
Antimony oxide, titanium oxide (titania), lithopone, pumice powder, aluminum sulfate (stone bone, etc.),
Examples 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 microns.
-6 mm (preferably 0.1-5 mm) is desirable.
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.

FIG. 24 shows the top cover 18 and bottom cover 26 attached to the body 3.
9 is a perspective view of an example of a can-like container that is attached to a body 39. After the contents of the can are filled into the body 39, retort processing is performed if necessary, and the product is placed in the distribution process.

The main uses of can-like containers include soup cans and various beverage cans.

[Effects of the Invention] (1) According to the present invention, gas barriers such as metal foil around the resin or in the multilayer base material, which cause seaming troubles when attached to the body of the lid by high-frequency induction heating, etc. This prevents the base material from being cut and maintains a uniform heating state in the circumferential direction, making it possible to perform stable seaming work.

(2) According to the present invention, there is no cutting of the gas barrier base material and stable seaming can be performed, making it possible to obtain a can-like container with high food hygiene properties.
Furthermore, since there is no resin surrounding the food, the food contents do not come into contact with it, and from this point of view as well, the food can be highly hygienic. especially,
This is advantageous when mixing pigments, fillers, etc. into the injection resin.

(3) According to the present invention, by preforming the multilayer base material in advance, attachment to the injection molding die is stabilized, and the yield in the injection molding process is improved.

(4) According to the present invention, since wrinkles are absorbed by folding, it is possible to preform at a low stretching ratio, and as a result, thin metal foil can be used, which is advantageous in terms of economic cost. In addition to being dry, the lid is also advantageous in terms of easy opening.

(5) Since the present invention is preformed in advance and has a shape with a flap part, the top surface of the flange part is also welded to the body part, and the can can withstand long-term storage with improved sealing performance. It could be made into a similar container.

[Brief explanation of the drawing]

1A to 1C are explanatory diagrams of the manufacturing process of a preformed article according to the present invention, in which Figure A is a plan view of the multilayer base material before preforming, B is a preforming process, and C is a perspective view of the preformed article after the preforming process. , FIG. 2 is a cross-sectional view of an example of the multilayer base material used in the present invention, FIGS. 3 A to C are illustrations of examples of wrinkle shapes, and FIGS. 4 A to C are explanations of the manufacturing process of the lid of the present invention. In the figure, A is a pre-mold clamping process, B is a mold clamping process, C is a sectional view of the molded product, FIG. 5 is a sectional view of a main part showing an embodiment of the present invention, and FIG. FIG. 7 is a bottom view of the lid according to the present invention; FIG. 8 is a sectional view of the lid showing a conventional example; FIG. 9 is a sectional view of the same essential part; FIG. 11 is a bottom view of the multilayer base material, FIG. 12 is a perspective view of an example of the bottom cover, FIG. 13 is a plan view showing an embodiment of the present invention, and FIG. line cross section,
Fig. 15 is a plan view of the lid showing an embodiment of the present invention with the tab removed, Fig. 16 is a sectional view taken along the line of Fig. 15, Fig. 17 is a plan view of the tab, and Figs. 18 and 19 are FIG. 17 is a sectional view explaining the installation of the tab along the line, FIG. 20 is a plan view of the lid showing another embodiment of the present invention, FIG. 21 is a sectional view taken along the line in FIG. 20, and FIG. 22 is the lid. Fig. 23 is a cross-sectional view taken along the line shown in Fig. 22, Fig. 24 is a perspective view of an example of a can-like container, Figs. 25 to 27 are illustrations of conventional processes, and Fig. 25 is an insert. The process, FIG. 26 shows the mold clamping pre-process, and FIG. 27 shows the mold clamping process. 10...Multilayer base material formed by preforming.

Claims (1)

[Claims] 1. A gas-impermeable (hereinafter referred to as barrier property) base material (hereinafter referred to as multilayer base material) having heat-bondable synthetic resin layers on both sides is set in an injection mold as a can-like container lid component. Prior to injecting a thermoplastic resin onto the surface of a multilayer base material to obtain a synthetic resin can-like container lid with barrier properties by injection molding,
On the upper surface of the recess of a female mold having a cylindrical portion, the end face has a circular recess, and the inner surface of the recess is provided with a groove having a cross-sectional shape having a large number of parallel edges extending inward from the entrance of the recess. The flat multilayer base material having a diameter larger than the diameter of the recess of the female mold is placed, the multilayer base material is lightly pressed onto the upper surface of the female mold, and then the multilayer base material is By pushing a cylindrical male mold having a narrow outer radius corresponding to the thickness of the base material and a flange into the recess, the female mold and male mold are inserted while sliding the multilayer base material. A can-like can having a flange portion, a body wall portion, and a bottom portion, the multilayer base material being formed with creases in the gap between the mold and the mold, and having creases formed over at least the entire circumference of the body wall portion. Preform method for container lid components.