JPS6355046A - Plastic vessel and manufacture thereof - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to plastic containers and Mg methods thereof, and in particular to filling conventional metal cans.

The present invention relates to a container for obtaining a plastic can that has strength to withstand double @ giving up due to a seal (1), and has excellent performance in terms of weight reduction, resilience upon impact, storage stability, etc., and a method for manufacturing the same.

(Prior art) Metal cans have various shapes, but they can be classified into 3-piece cans and 2-piece cans based on the structure of the can body. 3-piece cans are tin solder cans. Also known as a cylindrical can body, the lid and bottom are double-sealed and sealed. Two-piece cans are also known as stamped tin cans, and the can body and bottom are integrally molded, and the lid is double-sealed. These metal cans are used as food packaging containers for various canned foods and juices.

It is a rigid container that is used for containers such as soft drinks, jams, and dried foods, and has particularly excellent sealing and preservation functions.

However, metal cans have the following points to be improved. That is, (1) Since it is a metal can, there is a limit to its weight reduction.

■If it is crushed by an impact, it will not recover and will be deformed.

■The energy cost for manufacturing is higher than plastic containers.

■If the display effect of the container exterior is made of metal, it cannot be changed freely and the only means of exterior packaging is printing.

■It is impossible to create a transparent container that allows 1iVH without opening the contents.

(Problems to be Solved by the Invention) The above-mentioned drawbacks of conventional metal cans can be solved by using plastic cans instead of metal cans. It can be manufactured by integrally forming the can body and bottom by thermoforming, and then sealing the lid by double seaming.

However, even if a plastic container with a flange that can be double-sealed is made using the conventional thermoforming method, that is, sheet forming using a sheet of thermoplastic resin, the thickness of the flange is large and the circumference of the flange is has poor dimensional stability.

Problems such as a weak buckling strength of the container to withstand the force applied to the joint between the container body and bottom during seaming have occurred, making it difficult to manufacture plastic cans that can withstand practical use.

SUMMARY OF THE INVENTION An object of the present invention is to provide a container for plastic cans that can be double-wrapped and a method for manufacturing the same.

[Means for Solving the Problems] The plastic container according to the present invention that can be double-sealed with a lid has a flange thickness of 0.2 to L O#I and a flange length of 1-00 to 2 The container has a can body and a bottom integrally formed with a flange of .5 mm, and the container includes:
It can be manufactured by a two-stage molding method in which a step portion is provided in the cavity to form a flange having the dimensions described above.

For plastic containers that can be double-sealed, the flange must be as thin as 0.4 mm for seaming.
Further, in order to perform seaming, a sufficient buckling strength is required to resist the force applied to the joint between the top and bottom of the container.

FIG. 5 shows a general vacuum molding method using thermoplastic resin.

In the drawings, 1 is a cavity, 2 is a core, 3 is a plug, and 4 is a plastic sheet. The molded container is
It has a joint X between the container body and the bottom, a bottom Y, and a flange Z. In the molded product obtained by such a molding method, the flange part Z becomes thick, and on the other hand, the joint part X between the container body and the bottom part and the bottom part Ytfi become weak, and the buckling strength is insufficient, making it impossible to seam. becomes. That is, if the buckling strength is increased, the thickness of the flange will be increased, and if the thickness of the flange is decreased, X and Y will become insignificant and the buckling strength will also decrease, making it impossible to obtain a container that can be rolled up.

In order to solve these problems, the present invention performs molding by a two-stage molding method as shown in FIG.

In the present invention, a step 5 is installed in the cavity 1, and the flange portion Z of the container is formed by the step 5. In the two-stage molding method according to the present invention, first, the plug 3 places the sheet 4 in the cavity 1, and then the plug 3 places the sheet 4 in the cavity 1 and the core 2.
This is done by holding the sheet 4 in place by using compressed air, and then applying compressed air to bring the sheet 4 into close contact with the inside of the cavity 1. The obtained molded product is punched out so that the flange length has a value suitable for double-sealing the lid to obtain the desired plastic container.

In this case, it is important that the plug 3 enters the cavity 1 before the cavity 1 and the core 2 stop to hold the sheet 4. By doing this,
The surrounding sheet is drawn into the cavity,
The thickness of the Y portion can be increased. According to such a molding method, even if the thickness of the edge W formed between the upper end surface of the cavity and the core is large, the thickness of Z, which is the flange portion of the container, is 0.4. , it becomes possible to form the container so that it has a sufficient thickness so that the X and Y portions of the container have high buckling strength.

Further, when the conditions for a container that can be wrapped by the above-described multi-stage molding method to be a container that can be rolled and tightened once were investigated as described in the Examples below, the following findings were found. That is, as shown in Figure 2-2, the flange d is between the length a of the flange forming step 5, the flange thickness d, and the distance from the upper end surface of the mold to the flange forming step. In order to make a book, it is necessary to choose the ratio of a and b. In other words, the larger b/a is, the thinner d becomes, but this is also related to the thickness of the original plastic sheet, and b/a
The larger the size, the more difficult it is to mold. As a result of graphing this relationship and examining it, a plastic container that can be rolled up and given up was created by molding it under the conditions that satisfy the relationship expressed by the following equation. In b/a=-1
0d+c(2<c<7. 0.2<d<
1.0, where a is the length of the flange forming step, b is the distance from the upper end surface of the mold to the flange forming step, d is the thickness constant of the flange, and C is a constant. ) The container according to the invention uses a special plastic sheet of multi-layer M4 construction to enhance storage stability. Since this multilayer structure is intended for the plastic can of the present invention to be used in place of a metal can, it can be selected as appropriate depending on the situation and purpose in which the metal can is used.

For example, it has long-term shelf life by adding common retort treatments such as boiling tuna in water and soaking tuna in oil, and also
In cases where it is necessary to withstand heat sterilization for about minutes, polypropylene/ethylene-vinyl alcohol copolymer/polypropylene (A>) or polypropylene/nylidene chloride copolymer/polypropylene... ...(B) It is possible to use sheets of thermoplastic resin laminated with an adhesive so as to have the structure shown in FIG.

The above-mentioned ethylene-vinyl alcohol copolymer is a saponified ethylene-vinyl acetate copolymer with an ethylene content of 20 to 50 mol% and a degree of saponification of 90% or more, and the vinylidene chloride copolymer is a saponified product of ethylene-vinyl acetate copolymer with an ethylene content of 20 to 50 mol% and a saponification degree of 90% or more. Vinyl chloride is made mainly from nylidene.

Those copolymerized with comonomers such as acrylonitrile, acrylic esters, and acrylic acid can be used.

Furthermore, in the above-mentioned sheet, a plastic sheet having a structure using nylon, polyethylene terephthalate, high-density polyethine, polycarbonate, etc., can also be used instead of polypropylene.

In addition to stacked plastic sheets with the above-mentioned structure, polycarbonate can also be used for products that have a strong scent component, such as fragrances and waxes, and that do not undergo any particular heat treatment after being filled with the contents.

A sheet of polyethylene terephthalate alone, or a combination of polycarbonate/polypropylene, polyethylene terephthalate/polypropylene, polycarbonate, polyethylene terephthalate and olefin resin, etc. are also possible. Furthermore, it is also effective to use an acrylonitrile-methyl acrylate copolymer (for example, manufactured by Vistron, commercially available under the registered trademark Barex) as the barrier resin.

In addition, for things such as juice that are generally heated and filled at about 85 to 100°C and then not heat-treated, in addition to the above specifications (A>(B)), low-density polyethylene, medium-density polyethylene, which has a low heat resistance temperature as a resin, It is also possible to use copolymers mainly composed of ethylene, such as linear low-density polyethylene, ethylene-vinyl acetate copolymers, and ionomers.

Furthermore, in the case of dry goods such as candies and potato chips, no heat treatment is applied, and in cases where the aroma component is not particularly strong, polystyrene, polyvinyl chloride, etc. may also be used in addition to the above.

〔Example〕

A plastic can was manufactured as follows. The original fabric sheet used was: Polypropylene/G/Ethylene-vinyl alcohol copolymer/G/Voribropylene: manufactured by Mitsui Petrochemical Co., Ltd.

Product name: Noblen B-200 G = swallowing agent, manufactured by Mitsui Petrochemical ■, product name: Atmer QF
500 Ethylene-vinyl alcohol copolymer: manufactured by Kuraray Co., Ltd., trade name: Barth 1, and the thickness of each constituent resin layer is 540 μm from the left.

A co-pressed sheet of five layers of three types having a total thickness of 1200μ, 40μ, 40μ, 40μ, and 540μ, was sheeted.

The mold used is shown in Fig. 3-1, and Fig. 3-2 is a partially enlarged view of section A in Fig. 1.

The diameter of the mold is φ85.5 m to match the size of metal can No. 307. However, what is shown is a product drawing, and the actual mold is 1.
It is necessary to increase the size by about 5/1000.

What is important is that in order to keep the thickness d of the flange at point A, which is the flange forming part, the ratio of the flange length a to the distance from the upper end surface of the cavity to the step part for flange formation @b should be selected. There is a need to. The larger b/a is, the thinner the thickness d becomes, but there is also a relationship with the thickness of the original fabric, and the larger b/a is, the more difficult the molding becomes. The thickness of the original fabric is 1.4. ．． 1.6 When the relationship between the dimensions a and b and the thickness d of the flange is investigated, the results shown in Table 1 are obtained, and this relationship is shown in a graph as shown in FIG. 4.

If b/a is a semi-logarithm, In b/a=-10d+c (2<c<7
) is represented by a straight line. Among these, d is 0.3
The best results were obtained with a value of ~0.5.

Table 1 The thickness of the molded product obtained by molding the original fabric with a thickness of 1.2M using the mold shown in Figure 2-1 is as shown in Figure 3.
The molded product was cut out so that the flange length was 2.0rlI+. When this was tightened with metal wire for cans No. 307, good tightening was achieved.

For comparison, a metal can of tuna No. 2 (307@can) was similarly wrapped with a metal lid. Table 2 shows a comparison of the obtained plastic cans and metal cans.

Table 2 [Effects of the Invention] According to the present invention, a plastic container in which a flange of a specific dimension is formed by punching after molding by two-stage molding using a cavity in which a stepped portion for forming a flange is provided can be manufactured in a way that is different from conventional plastic containers. It can be sealed with a metal lid in the same way as metal cans. Therefore, conventional equipment can be used as is, and plastic cans can be used instead of metal cans.

By using plastic cans, it is possible to achieve weight reduction and energy cost reduction, and by making containers from plastic, it is possible to use transparent containers, and the packaging method can be freely selected. So the display effect can be enhanced.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a molding device for carrying out the plastic container molding method of the present invention, FIG. 2-1 is a vertical cross-sectional view showing an embodiment of a molding die of the same device, and FIG. Fig. 3 is an explanatory diagram showing the thickness of each part of the container molded by the entire mold shown in Fig. 2-1, and Fig. 4 is a partial enlarged view of part A in Fig. 2-1. Fig. 5 is a graph showing the relationship between a and the distance from the end face of the cavity to the stepped part of the flange formation, and the thickness d of the flange. Fig. 5 is a partial vertical cross-sectional view of a molding apparatus for carrying out a conventional plastic container molding method. . 1... Cavity, 2... Core, 3... Plug, 4... Plastic sheet, 5... Step part, Z... Flange part.

Claims (4)

[Claims] (1) The thickness is 0.2 to 1.0 mm, and the length is 1.0 mm.
A plastic container having a 0-2.5 mm flange at the upper end of the can body, the flange, the can body, and the bottom part being integrally molded, and the lid can be double-sealed. (2) After molding by two-stage molding using a cavity provided with a step for forming a flange in the cavity, the upper end of the can body is punched to a thickness of 0.2 to 1.0 mm, To have a flange with a length of 1.0 to 2.5 mm,
A method for manufacturing a plastic container whose lid can be double-sealed, characterized by integrally molding the flange, can body, and bottom. (3) The multistage ratio of two-stage molding is Inb/a=-10d+c (where a is the length of the step for forming the flange, b is the distance from the upper end surface of the cavity to the step, and d is the thickness constant of the flange. , c is a constant, 2<c<7, 0.2<d<1.
It is 0. ) The manufacturing method according to claim 2, which satisfies the following conditions. (4) Molding within the cavity by two-stage molding is performed by compressed air or vacuum molding, in which the plug first pushes a sheet made of thermoplastic resin into the cavity, and then the sheet is held by the cavity and core. The manufacturing method according to claim 2, characterized in that: