JPS6410170B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an injection molding method for can-like container lids, and particularly to an injection molding method suitable for obtaining easy-open can-like container lids. Specifically, the present invention relates to an injection molding method for making the lid of a can-like container, which is composed of a body, a bottom, and a lid and can be used as various beverage cans, easy to open. Conventionally, this lid was made by using an adhesive to bond together an aluminum foil having heat-fusible resin layers on both sides and a resin sheet previously made by injection molding. This method increases the number of steps and costs, the molded product may peel off due to heat history such as retort treatment, the resulting product has poor drop strength, and because it uses adhesive, there are food hygiene concerns. There were various difficulties. The present invention does not involve post-adhesion as in conventional methods, but instead involves inserting and fixing an insert material such as the above-mentioned aluminum foil into the mold of an injection molding machine, injecting resin into this, and simultaneously molding. This involves an injection molding method for obtaining can-like container lids by (integral molding), which shortens the number of steps, the molded product has high adhesion strength, so it does not peel off during retort processing, etc., and the product has high drop strength. We also succeeded in obtaining a lid for a can-like container that has excellent food hygiene properties. By the way, the lid of such a can-like container can be simultaneously molded (integrated molding) by injection molding (insert molding).
In this case, the accuracy of inserting the insert material and the resin layer formed from the injection resin becomes a problem, and it is not preferable that the insert material inserted into the mold moves and misaligns during the molding process. The present applicant first proposed a method for fixing the insert material in the mold without causing any displacement and obtaining a molded product with high insert precision by using a stripper plate or the like in the mold device of an injection molding machine. They discovered a method for inserting and fixing an insert material into a guide member, and filed a separate patent application (Japanese Patent Laid-Open No. 59-215842). By the way, in the lid of such a can-like container,
An important issue is how to provide an opening that allows easy opening. Conventionally, in order to improve the unsealability of such an opening, a cut that can be opened is generally provided in the lid. However, on the other hand, it cannot be avoided that formability is insufficient due to the provision of this notch. Therefore, conventionally, when using the post-bonding method described above, the above-mentioned notches are interrupted at one or more places in the resin sheet to be injection molded in advance to facilitate the flow of the injection molding material. The method used was to connect the cut points to improve formability (Japanese Patent Application Laid-open No. 1973-
Publication No. 39489). However, although this method certainly improves moldability, it is clear that the connecting portions hinder easy opening. The purpose of the present invention is to obtain a container lid that has good moldability and is easy to open in the above-mentioned integral injection molding, and is made of a metal foil, sheet, film, etc. that is impermeable to oxygen, water, etc. Consisting of an opening part with a handle part completely separated via a notch on the surface of a multilayer base material in which a heat-meltable first resin layer is formed on both sides or one side of the material, and an outer peripheral part other than the opening part. By forming the second resin layer by injection molding with one or more gates in each of the opening part and the outer periphery, a container lid with various advantages such as good moldability and easy opening can be obtained. succeeded in obtaining it.
The present invention will be explained in detail below. Examples of base materials used in the present invention include metal foils, sheets, films, and the like. These base materials need to be impermeable to oxygen, water, etc. (hereinafter referred to as gas barrier properties). A typical example of metal foil is aluminum foil (hereinafter simply referred to as aluminum foil). Examples of other gas barrier substrates include sheets and films of saponified ethylene-vinyl acetate copolymers, polyvinylidene chloride, polyamide, polyacrylonitrile, and the like. The multilayer base material used in the present invention is one in which a first resin layer, that is, a heat-meltable resin layer is formed on both or one side of the gas barrier base material. The first resin layer may be formed on both sides of the gas barrier base material, but the first resin layer (outer layer) on the side to be welded to the second resin layer may be omitted.
When the first resin layer is formed on both sides of the gas barrier substrate, the outer layer of the first resin layer is thermally fused to the second resin layer to form a lid with high adhesion, and The first resin layer (inner layer) is heat-sealed to the body of the container to attach the lid to the body. On the other hand, in the case of a gas barrier base material in which the first resin layer is formed only on one side (inner side), the second resin layer is laminated directly on the base material (outer side), and the second resin layer is laminated directly on the lower side (inner side). The first resin layer is heat welded, and the lid is attached to the body. As the resin constituting the first resin layer, a resin that melts by heat, typically a thermoplastic synthetic resin, is used. When forming (laminating) the first resin layer on the gas barrier substrate, it can be laminated with or without an adhesive resin layer such as an adhesive or a film-like hot melt adhesive. The can-like container lid of the present invention is obtained by using the multilayer base material described above and laminating a resin by injection molding on the surface of the multilayer base material on the side opposite to the side where the body of the can-like container is attached. As a preferable example of injection molding, the base material (insert material) may be fixed in advance in a mold using a base material insert robot, and injection molding may be performed. Kaisho
It is even more preferable to use the method described in Japanese Patent No. 59-215842. Next, a few examples of can-like containers and easy-open container lids according to the present invention will be explained with reference to drawings showing examples, and examples of the molding method of the present invention will also be described in detail. FIG. 1 shows a perspective view of the entire can-like container formed by attaching the easy-to-open square can container lid of the present invention to the body. Also second
The figure shows a perspective view of the entire can-like container formed by attaching the easy-to-open round can container lid of the present invention to the body. In FIG. 1, 1 is a body, 2 is a bottom, and 3 is a lid, and in FIG. 2, 4 is a body, 5 is a bottom, and 6 is a lid. FIG. 3 shows an enlarged plan view of the square can lid shown in FIG. 1, and FIG. 4 shows an enlarged sectional view taken along the line XX' in FIG. In FIGS. 3 and 4, 7 is a lid, 8 is an opening part formed by the second resin layer, 9 is an outer peripheral part also formed by the second resin layer, and 10 is a notch part, This notch 10 is completely continuous and uninterrupted, as shown in FIG. Therefore, the unsealing portion 8 and the outer peripheral portion 9 are completely separated by the cutout portion 10. Also, in Figures 3 and 4, 11 is the opening part 8.
A handle portion (bullet top portion) 12 is a cutting and opening portion, and the handle portion 11 and the cutting and opening portion 12 are separated by a groove 13. In FIG. 4, 14 is a multilayer base material, and in the embodiment shown in FIG. Here is an example. The can-like container lid 7 of the present invention is shown in FIG.
It is attached to the body 18 of the can-like container. To explain how to open this square can lid, when the fingertip is inserted into the groove 13 and the handle part 11 is lifted, the handle part 11 is peeled off from the multilayer base material 14, and the reference numeral 19 shown in FIGS. 3 and 4 At the position where the tip of the handle part 11 touches the multilayer base material 1
4, the multilayer base material 14 is cut, and the handle part 11 is pulled as it is, the multilayer base material 14 is cut along the cutout part 10, and the opening part 8 of the container lid is opened. The container lid of the present invention has an opening section 8 having a handle section 11.
Since the outer peripheral part 9 and the outer peripheral part 9 are completely separated through the notch part 10 and there is no bridge part that connects the opening part 8 and the outer peripheral part 9, the above-mentioned opening is extremely easy. Such an easily openable container lid can be obtained by the molding method of the present invention. This will be explained based on FIGS. 3 and 4 showing examples.
and the outer peripheral portion 9 are each formed with one or more gates. That is, the unsealing portion 8 is molded independently using its own gate, and the outer peripheral portion 9 is also molded independently using its own gate. The notch 10 is a cutout on the top of the mold. At least one gate is required for each of the above gates. FIG. 3 shows an example of such gate positions with reference numerals 20, G1, 2.
1, indicated as G2. That is, to illustrate the above method with reference to FIG. 3, the unsealing part 8 is formed by the gates 20 and G1, and the outer peripheral part 9 is formed by the gates 21 and G2, respectively. According to the injection molding method using such multi-point gates of the present invention, moldability is good and injection molding is easy. Therefore, even materials with relatively poor moldability, such as materials with a small melting index (MFR) or resins containing fillers, can be molded well. In this regard, in the conventional method mentioned above, it was necessary to select a material with particularly good fluidity in consideration of moldability, and it was difficult to use a resin containing fillers, but the present invention solves these problems. I was able to resolve the issue. Further, according to the molding method of the present invention, molding temperature and injection pressure can be significantly lowered, and productivity (molding cycle) is also high. Furthermore, in the present invention, since a push-cut notch is formed in the mold part, the mold clamping pressure is preferably low.
This is because, in addition to the problem of mold durability, the lower the mold clamping pressure, the better in order to prevent the base material such as aluminum foil from being cut and to prevent the notch from being cut. According to the present invention, mold clamping pressure can be made relatively low.
Furthermore, depending on the molding conditions, the product corner base material, such as aluminum foil, may be cut in the mold during injection molding, but this can be prevented by lowering the injection pressure. Furthermore, according to the molding method of the present invention, a can-like container lid with high adhesion strength can be obtained as described above. Particularly when using a multilayer base material having a heat-meltable first resin layer on both sides, the first resin layer and the second resin layer are molded and fused in a molten state, so the adhesion strength increases. Therefore, a molded article with high product drop strength can be obtained. However, on the other hand, there is a problem in that the handle part (pull top part) of the lid is tightly attached and the handle part does not separate from the lid body. In such a case, it is preferable to subject the portion where the bottom surface of the handle portion and the surface of the multilayer substrate are in contact with each other to a treatment for easy peelability. Examples of such treatments include the use of printing inks to form treatment layers. In FIG. 4, reference numeral 22 is a treated layer applied for the purpose of easily peeling the handle part 11 from the multilayer base material 14.
1 from the multilayer base material 14, and the opening part 8 and the outer peripheral part 9 are completely separated via the notch part 10, the lid can be opened even more easily. The above-mentioned treatment for the purpose of easy peelability is described in detail in Japanese Patent Application Laid-Open No. 59-221256, which was filed separately by the present applicant. Next, FIG. 5 is an enlarged plan view of the round can lid shown in FIG. 2, and FIG. 6 is an enlarged sectional view taken along the line Y-Y' in FIG. In Figs. 5 and 6, parts with the same reference numerals as in Figs. 3 and 4 have the same functions, and explanations will be omitted. It is manufactured in a way that makes it easy to open. In FIG. 5, numerals 23 and G3 indicate the gate positions of the unsealing part 8, and numerals 24 and G4 indicate the gate positions of the outer peripheral part 9, and the opening part and the outer periphery are formed independently by each gate G3 and G4. be done. Next, the present invention will be explained based on Examples and Comparative Examples. Example 1 Using a Toshiba IS-50A (30Z) injection molding machine, the third
The square can container lid shown in the figure was molded. The multilayer base material is aluminum foil and ethylene propylene block copolymer [MFR1.1, ethylene content
9 wt%] was laminated on both sides. This multilayer base material was fixed in advance in a mold by a robot, and injection molding was performed. The gates were molded from two points, gate G1 and gate G2 shown in FIG. 3, and the notches were cut out on the top of the mold. Showa Allomer MK411C (Showa Denko K.K.) was used as the second resin at a cylinder temperature of 240℃ and an injection pressure of 60Kg/ ^cm2 .
Injection was carried out using a propylene-ethylene block copolymer manufactured by MFR 10.0g/10min) manufactured by Mfg. Co., Ltd.). In the above, the thickness of the aluminum foil and the first resin layer on both sides is resin (outer layer)/aluminum foil/resin (inner layer) = 30μ/15μ/70μ, and the thickness of the second resin layer laminated on this outer layer is The thickness was 0.7mm. Table 1 shows the evaluation results of the ease of opening of the obtained square can lids, and Table 2 shows the evaluation results of the injection moldability. Further, Table 3 shows detailed comparison results of molding conditions with Comparative Example 1, which will be described later. Example 2 Same as Example 1 except that instead of Showaromer MK411C, a resin made by adding 40% carbon to the resin was used, and the cylinder temperature was 260°C and the injection pressure was 80Kg/cm ² Injection molding was performed in the same manner as in Example 1, and the ease of opening and injection moldability of the square can lids were evaluated. The results are shown in Tables 1 and 2 respectively.
Shown in the table. Comparative Example 1 Injection molding was performed using a single gate, gate G1, in FIG. In this case, there are four bridges (connections) at intervals in the notch 10 [each bridge is 0.5 mm
Injection molding was performed in the same manner as in Example 1 through this bridge. The results are shown in Tables 1 and 2. Although the bridge part was difficult to open and the cylinder temperature was 280°C and the injection pressure was 110Kg/cm ² , the moldability was the same as in Examples 1 and 2.
It wasn't as good as the previous one. Further, Table 3 shows detailed comparison results of the molding conditions of Comparative Example 1 and Example 1. Comparative Example 2 Molding was carried out in the same manner as in Comparative Example 1 except that injection molding was performed using a single gate, gate G2 instead of gate G1 in FIG. The results are shown in Tables 1 and 2, and as with Comparative Example 1, it was difficult to open and the moldability was not good. Example 3 A round can lid shown in FIG. 5 was molded. In the same manner as in Example 1, except that gates 23 and G3 in FIG.
A round can lid was molded at two points, gate 24 and G4, at a cylinder temperature of 240°C and an injection pressure of 55 kg/cm ² . The results are shown in Tables 1 and 2. Comparative Example 3 In Figure 5, at one point gate (gate 23),
Install 4 bridges each with a width of 0.6 mm in the notch 10.
Molding was carried out in the same manner as in Comparative Example 1, except that the injection pressure was 100 kg/cm ² . The results are shown in Tables 1 and 2.

【table】

【table】

[Table] As shown in Examples 1 to 3, the present invention was easy to open and had a smooth opening. or,
In terms of moldability, molding temperature and injection pressure are extremely low, and productivity (molding cycle) is high.
In addition, it was possible to mold even materials with poor moldability, such as those containing fillers, resulting in a clear difference from Comparative Examples 1 to 3. Furthermore, in the present invention, the notch part is formed by press-cutting the mold part, so it is better to have a lower mold clamping pressure (mold durability, prevention of cutting of the notch part of the multilayer base material), but it is not possible to make it significantly lower than in the comparative example. did it. Furthermore, depending on the molding conditions, the aluminum foil at the corners of the product may break during injection molding in the mold.
Cutting could be prevented by lowering the injection pressure. As described above, according to the molding method of the present invention, not only can-like container lids can be manufactured at relatively low cost, but also
It has excellent properties as shown below. Injection molding is easy because the opening part (handle part) and the outer peripheral part are molded with one or more gates separated by the notch part, and wrinkles and damage of the insert multilayer base material in the mold can be prevented. Due to its good moldability, even materials with poor moldability could be molded successfully. The unsealing part (handle part) and the outer periphery part are separated by a completely continuous notch, and only the multilayer base material is cut when unsealing, so it has excellent unsealing properties. By providing a treated layer for the purpose of peeling, the handle part could be easily peeled off and the bag could be opened more easily. A lid with excellent retort properties and food hygiene properties can be obtained, and by using the lid according to the present invention, a container that can be stored for a long period of time can be obtained. Since the present invention has the above-mentioned favorable characteristics, it is expected that it will be used in a wide variety of fields, and typical applications are shown below. Beverage coffee cans, soup cans Edible oil and seasoning cans Various canned containers Motor oil cans

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of a can-like container according to the present invention, FIG. 2 is a perspective view showing an example of another can-like container according to the present invention, and FIG. 3 is an enlarged view of the lid shown in FIG. 1. 4 is an enlarged sectional view taken along the line X-X' in FIG. 3, FIG. 5 is an enlarged plan view showing another embodiment of the present invention, and FIG. 6 is an enlarged sectional view taken along the line Y-Y' in FIG. FIG. 7...Lid, 8...Opening part (second resin layer), 9
...Outer peripheral part (second resin layer), 10... Notch part,
11... Handle portion, 14... Base material (multilayer base material), 1
5... Gas barrier base material, 16, 17... 1st
resin layer, 20, 21...gate (position), 22
...Easily peelable treated layer, 23, 24...Gate (position).

Claims (1)

[Claims] 1 A base material (hereinafter referred to as a multilayer base material) in which a heat-meltable resin layer (hereinafter referred to as the first resin layer) is formed on both or one side of a base material such as a metal foil, sheet, or film that is impermeable to oxygen, water, etc. (hereinafter referred to as the "opening part") that is completely separated via a notch and has a handle on the surface opposite to the side where the body of the can-like container is attached (hereinafter referred to as the "opening part")
A resin layer (hereinafter referred to as a second resin layer) consisting of a part other than the opening part (hereinafter referred to as the outer peripheral part) is formed by injection molding, and the opening part and the outer peripheral part are each formed with one or more gates. An injection molding method for an easy-to-open can-like container lid, characterized by: