JPH02219768A - Manufacture of easy-to-open sealed container - Google Patents

Abstract

PURPOSE:To provide the combined features of a secure sealing and easy unpacking by forming the end of a projecting heating part into contact with at least the surface of an adjoining layer of container flange when the flange and a lid are heat sealed together. CONSTITUTION:A container 1 and a lid 2 placed on a flange 3 thereof are heat sealed together using a sealing plate having a projecting heating part 4. When the end T of the projecting heating part 4 is forced into contact with at least the surface S of an adjoining layer, the resin constituting the sealed layer 6 and the adjoining layer 8 of the container 1 and those constituting the sealed layer 7 of the lid 2 are squeezed out to form resinous swellings of 9-12 and 13 and 14, respectively, on both boundaries between the sealed and unsealed parts. In this way, the sealing strength becomes equal to at least the laminating strength of the sealed layer and the adjoining layer of the container. When the lid 2 is being peeled from the peripheral edge of the container, a separation of the sealed layer 7 from the sealed layer 6 progresses to point A where cutting of the sealed layer 6 starts and then a separation of the sealed layer 6 from the adjoining layer 8 starts and progresses to point B where the sealed layer 6 is cut off.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to the production of a sealed container that is composed of a plastic cup body having a flange portion and a lid material, and whose lid can be easily opened. Regarding the method.

[Conventional technology]

BACKGROUND ART Easy-open sealed plastic containers with lids that can be easily opened are widely used as food packaging containers.

The most common easy-open method conventionally used is to appropriately control the seal strength with the container by changing the composition of the resin that makes up the sealing layer of the lid. The container is opened by applying beer to the interface between the material and the container. However, the seal strength is easily affected by sealing conditions, environmental temperature, adhesion of contents, etc., and variations in strength often occur.

If this variation is biased toward the weak side, there is a risk of seal leakage, and conversely, when the variation is biased toward the strong side, beer quality deteriorates and opening becomes difficult. However, seal leakage is a fatal defect, so in order to avoid this phenomenon and ensure safety, it was necessary to set the seal temperature and pressure higher, even at the expense of easy opening.

In order to improve these problems, we developed a method for opening the seal by delaminating the seal layer and the adjacent layer (
For example, Japanese Patent Publication No. 50-37598) has been attempted, but the conventional sealing method has the disadvantage that the sealing layer does not break properly and it is difficult to remove the contents.

In addition, a structure in which a cut is provided in the flange part to facilitate separation of the release layer and the adjacent layer has been proposed (Japanese Patent Application Laid-open Nos. 62-251363 and 63-78,
Publication No. 63-25037, etc.). However, in the case of containers with these structures, the periphery of the container at the notch must be sealed from the outside during the manufacturing stage, which poses a manufacturing problem in that strict control is required for positioning during sealing. . Furthermore, in the method of peeling off the main container seal layer and the seal layer, since the seal is performed up to the peripheral edge of the flange, it is necessary to start peeling from the peripheral edge, which also limits the shape of the container. There are drawbacks to receiving it.

As a measure to solve this problem, Japanese Patent Publication No. 63-96060
As described in the publication, there is an example in which a notch for starting peeling and a notch for stopping peeling are installed on the flange.
In this case as well, there is an inconvenience in the manufacturing process that the seal position accuracy of the seal disk must be set strictly.

[Problem to be solved by the invention]

The inventor of the present invention has conducted intensive research on means for solving the above-mentioned conventional problems, and has created a simple sealed container that is free from the risk of seal leakage and that provides stable and easy opening regardless of sealing conditions. The method involves sealing a flange part with specific properties and a lid material using a convex sealing plate so as to form a resin pool of the seal layer constituent resin and the adjacent layer constituent resin on both sides of the interface between the sealed part and the non-sealed part. (Japanese Patent Application No. 63-216227).

The method of heat-sealing the container body and lid using a convex sealing disc has been known for some time, and it has been recognized that it has the advantage of being able to provide a stable seal even when the contents overflow to the flange. In the case of opening that involves interfacial peeling between the seal layer of the main body and the seal layer of the lid, both seal layers undergo complex plastic deformation during the sealing process, which improves pressure resistance but reduces ease of opening. there were.

Although the above-mentioned prior application greatly improved this problem regarding ease of opening, there were still points to be improved in manufacturing conditions and the like.

As a result of pursuing this point, the present invention was developed after confirming that when the convex seal plate is press-fitted to a certain level or more during sealing, the resin pool that is formed becomes larger and the ease of opening is further improved. This is what we have come to.

[Means for Solving the Problems] That is, the method for manufacturing an easily openable sealed container provided by the present invention is such that the lamination strength of the seal layer and the adjacent layer facing it is 300 to 2000 g/IIIm, and the lamination strength of the seal layer is 300 to 2000 g/IIIm. The flange part of the container and the lid material having a thickness of 10 to 70 μm are sealed using a convex seal plate so that the sealing strength is equal to or higher than the laminate strength, and a sealing layer and an adjacent layer are formed at both ends of the boundary between the sealed part and the non-sealed part. In the sealing method for forming a box-shaped resin reservoir using a constituent resin, the structure is characterized in that the tip of the convex heating part is press-fitted until it is connected to at least the adjacent layer surface of the container flange part.

The material of the container body used in the present invention is a multilayer sheet having at least a sealing layer and an adjacent layer facing it. For example, it may be a simple two-layer sheet with a sealing layer made of polyethylene resin and an adjacent layer made of polypropylene resin. It may also be a six-layer sheet in which a barrier layer of a saponified ethylene-vinyl acetate copolymer or a polyvinylidene chloride resin, an adhesive layer, and an outermost layer of polypropylene are arranged adjacent to the adjoining layer via an adhesive layer. Depending on the case, a multilayer plastic sheet with other materials such as metal or paper laminated on the outside may also be used.

However, the multilayer sheet has a lamination strength between the seal layer and the adjacent layer of 300 to 2000 g/25 mm (when measured at a peel angle of 180° and a peel speed of 200 m/win),
It is important to set the thickness of the sealing layer in the range of 10 to 70 microns. The reason for this is that the laminate strength is 300
If the laminate strength exceeds 2000 g / 25 mm and the seal layer thickness is 70 μ, it will not be possible to secure sufficient sealing performance. This is because the peel strength increases and the smooth beer properties are impaired.

It is desirable that the film forming the lid material forms a sealing layer made of a material that easily and firmly bonds with the sealing layer of the container body, and the most preferred embodiment is to form a sealing layer of the lidding material with the sealing layer of the container body. They should be made of the same material. Also,
The film of the lid material may be a single layer, but it may also be a multilayer film containing aluminum foil, polypropylene, etc. with good barrier properties.

Hereinafter, the present invention will be explained based on the drawings.

FIG. 1 is a schematic cross-sectional view showing a sealing process using a convex seal disc. A lid material 2 is stacked on a flange portion 3 of a container 1, and a seal disc 5 having a convex heating portion 4 is used to heat-seal. The seal plate 5 is particularly suitable if it can be sealed so as to extrude the seal layer of the container body and the adjacent layer resin on both sides of the interface between the sealed part and the non-sealed part to form a box-shaped resin pool during hot pressurization. There are no restrictions on the shape (for example, you can choose an appropriate shape such as a 7-shape or a U-shape.The width of the seal plate is 1
A range of ~3 m is preferable, and considering the pressure of commercially available sealing equipment, if it is less than 1 m, the sealing pressure will be high and the main body sealing layer will be cut, and if it is wider than 4 m, the pressure will be low and the resin pool of the present invention will be formed. This becomes difficult. Also,
The height of the convex heating part 4 of the sealing plate is 0.1 to 3.0 m.
It is desirable to set it at a certain level.

FIG. 2 is a sectional view showing the state at the time of sealing. Due to the press-fitting of the convex heating part 4, the constituent resins of the sealing layer 7 of the lid material 2, the sealing layer 6 of the container 1, and the adjacent layer 8 located near the bottom of the pressure surface undergo plastic deformation, and the boundary between the sealed part and the non-sealed part is formed. Extruded at both ends.

The convex heat section 4 is further press-fitted until the tip T of the convex heat section 4 is connected to at least the adjacent layer surface S, as shown in FIG. Due to this strong press-fitting, the swelling of the resin becomes even larger, resulting in box-shaped resin pools 9.10 and 1.
1.12.

At this time, the sealing layer 7 of the lid material 2 also accompanies the resin pool 13.
．． Form 14.

At the sealing part, the lid material 2 and the container 1 are in complete contact with each other.
The interface between the sealing layer 7 of the lid material and the sealing layer 6 of the container exhibits a mixed state of resin. In this state, the sealing strength is greater than or equal to the laminate strength of the sealing layer of the container and the adjacent layer.

[For production]

At the time of opening, when the lid 2 is turned over from the peripheral edge, a force X as shown in FIG. 4 is applied, and the sealing layer 7 of the lid 2 is peeled off from the sealing layer 6 of the container l. When this peeling reaches point A in FIG. 3, the seal N6 of the container 1 is cut, and the peeling changes to peeling of the seal layer 6 and the adjacent layer 8.

At this time, the presence of the large resin pool 9.10 at point A exerts a resistance force in the opposite direction to the pressing force X on the sealing layer 6, thereby aiding in cutting.

The peeling between the seal layer 6 and the adjacent layer 8 continues up to the resin pool on the container side, but in the process up to this stage, the force X functions only for peeling. Next, when the peeling reaches point 8 in FIG. 3, the force part is used as a force for tearing off the sealing layer 6.

Due to the combination of the cutting and beer action caused by such distribution of force X, the package is finally opened easily in the state shown in FIG.

If a positive size condition is applied in which the tip T of the convex heating part does not reach the adjacent layer surface S during the sealing stage, the resin pool will not become large, and the peeling force will always be more dominant than the cutting force, causing the sealing layer 6 to be cut. It becomes difficult to do.

〔Example〕

The total thickness is 850μ, and the material of the sealing layer has a density of 0°95.
5. Melt index (Ml) 5 g /10s+
in high density polyethylene (IOPR), the adjacent layer (also serves as the outer layer) has a melt index (old) of 0.5/s
A two-layer seal made of polypropylene (PP) in was made by coextrusion. Next, this sheet was vacuum formed to obtain a container body with an inner diameter of 7°, a flange outer diameter of 82 am, and a height of 30 mm.The flange thickness of this container body was 800 mm.
μ, the thickness of the sealing layer was 20μ, and the lamination strength between the sealing layer and the adjacent layer was 800 g/25μ.

Two-wheel stretching 6-6, Ny (ON
Y) Layer the lid material made of 25μ/HDPH60μ and use a sealing plate 5 with a U-shaped convex heating part 4 to adjust the temperature and 18μ.
Under the conditions of 0° C. and a pressure of 10 kg/d, the convex heating portion was press-fitted until the tip T was connected to the adjacent layer S, and heat-sealed.

Due to this sealing, box-shaped resin pools 9 to 12 as shown in FIG. 3 were formed at both ends of the boundary between the sealed portion and the non-sealed portion.

When the lid of the above-mentioned sealed container was opened, the cutting of the seal layer 6 at points A and B and the glabellar beer were performed extremely smoothly, and the peel strength (JIS K6854) was 8.
00g/15m, and the cutting strength was 1000g/15m, showing good easy-opening properties.

For comparison, when we opened the lid of a sealed container with a resin reservoir that was sealed under press-fit conditions in which the tip T of the convex heating part did not reach the adjacent layer surface S, we found that points A and B, especially B
The seal layer was not cut smoothly at the points. That is, in this case, the peel strength is 800 g/
15■, which was excellent in ease of opening, but a phenomenon occurred in which the sealing layer 6 continued to peel even after point B, and even when the sealing layer 6 was cut and opened, the sealing layer 6 remained separated from the adjacent layer 8. It was unsightly in appearance.

〔Effect of the invention〕

The safety and easy openability of a seal in a sealed container are mutually contradictory performances, so it has been difficult to achieve both with conventional sealing methods. However, with the sealing structure of the present invention, the sealing interface and beer Because the interface at which the A combination of perfect sealing and easy opening is ensured.

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional view showing the sealing process for manufacturing the easy-to-open sealed container of the present invention, Fig. 2 is a cross-sectional view showing the sealing stage, and Fig. 3 shows the sealing mode and the state of the resin pool. It is an enlarged sectional view. FIG. 4 is a sectional view showing the direction of the force required to open the seal, and FIG. 5 is a sectional view showing the state when the seal is opened. 1... Container 2... Lid material 3... Flange portion 4... Convex heat portion 5... Seal plate 6... Seal layer 7... Seal layer of lid material 8... Adjacent layer 9.10.11.12.13.14...Resin pool A
, B...Seal layer cutting point S...adjacent layer surface T...tip X of convex heating part
···Power. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. The sealing strength is determined using a convex sealing plate between the flange part and lid material of a container in which the lamination strength of the sealing layer and the adjacent layer facing it is 300 to 2000g/25mm, and the thickness of the sealing layer is 10 to 70μ. In a sealing method in which the laminate strength is higher than the above-mentioned laminate strength, and a lump-shaped resin pool is formed by the constituent resins of the seal layer and the adjacent layer at both ends of the border between the sealed part and the non-sealed part, the tip of the convex heated part is at least close to the container flange. 1. A method for manufacturing an easily openable sealed container, which comprises press-fitting the container until it connects to the surface of an adjacent layer.