JPH02233378A - Manufacture of sealed container - Google Patents

Abstract

PURPOSE:To provide the combined features of sealing integrity and opening easiness by applying heat sealing to a lid from above using a sealing plate having a sloping surface set at a specific angle to the surface of the flange under a specific condition. CONSTITUTION:A lid 2 is sealed to the flange 3 of a container 1 having a laminating strength of 300-2000g/mm between the sealed layer 6 and its adjoining layer 8 and a thickness of the sealed layer 6 of 10-70mum. At this time, the lid 2 is placed on the flange 3 with an angle theta set at 3-15 deg. between the sloping surface 4 of a sealing plate 5 and the flange surface from the inner to outer peripheral edge of the container. With respect to the sealing operation, the sealing plate 5 is set on the flange 3 with its inner peripheral edge E positioned thereon and the heat sealing is applied to the lid 2 from above under such heat pressing conditions as to make the resulting sealing strength larger than the laminating strength and cause the resinous swellings 9, 10 and 11 to be extended from the resins formed by the sealing layer 6 and the adjoining layer 8 on a boundary between the sealed part and the unsealed part on the container side. This ensures the combined features of sealing integrity and opening easiness.

Description

Detailed Description of the Invention (Industrial Field of 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, the lid of which can be easily opened. Regarding the method.

[Prior 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 strength of the seal with the container (for example, 600 to 1000 g/mm) 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 the harakki is too weak, there is a risk of seal leakage, and on the other hand, if it is too strong, the beer quality will deteriorate and it will be difficult to open. 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, a method of 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.

Furthermore, a structure in which a cut is provided in the flange to facilitate separation of the release layer and the adjacent layer has been proposed (Japanese Unexamined Patent Publications No. 62-251363, No. 63-78, No. 63-25037). Public notices, 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 sealing layer and the sealing 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 imposes restrictions on 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.

Japanese Unexamined Patent Publication No. 63-307073 discloses a method for making the multilayer peel strength smaller than the heat seal strength and forming a concave seal layer on the inner edge of the human seal part of the multilayer material by pressing through another resin material layer. An openable package and a method for manufacturing the same have been proposed. If this structure is adopted, there is no need to strictly set the position of the seal plate, but since the heat seal part and the concave seal layer are formed at the same time, if the heat and pressure conditions are increased, the resin forming the seal layer will wrap around the innermost layer. This causes the initial beer quality to deteriorate.

In addition, the applicant has developed a sealing method that forms a resin pool of the seal layer-constituting resin and the adjacent layer-constituting resin on both sides of the interface between the flange portion with specific properties and the non-sealed portion (patent application No. No. 63216227).

[Problem to be solved by the invention] A method of heat-sealing the container body and the lid using a convex sealing plate has been known for a long time, and it is possible to perform a stable seal even when the contents overflow to the flange part. However, in the case of opening accompanied by interfacial peeling between the container body seal layer and lid seal layer, both seal layers undergo complex plastic deformation during the sealing process, resulting in improved pressure resistance. There was a drawback in terms of easy openness.

Although the above-mentioned prior invention greatly improved this problem regarding easy openness, there was still room for improvement.

As a result of repeated multifaceted research on improvements, the present inventor found that forming a resin pool made of the constituent resins of the seal layer and the adjacent layer at the boundary between the sealed part and the non-sealed part on the container side will improve the ease of opening. It was demonstrated that it is effective to increase the resin pool, and it was confirmed that it is effective to apply a seal disc having a sloped surface as a means to form this resin pool.

A method of sealing using a seal disc having an inclined surface is also disclosed in Japanese Patent Publication No. 7975/1983, but usually,
If such pressure fluctuations are applied, the seal strength at the innermost end of the seal becomes extremely high, which may actually reduce the easy opening property.

The present invention eliminates this drawback by using a container flange with specific properties and adding other elements, thereby providing a method for manufacturing a sealed container with excellent easy-open performance.

[Means for Solving the Problems] That is, the method for manufacturing a 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/mm, and the thickness of the seal layer is 1
When sealing the flange part of the container and the lid material, which have a diameter of 0 to 70μ, a seal plate having an inclined surface of 3 to 15 degrees from the inner peripheral edge to the outer peripheral edge with respect to the flange surface is used. Set so that the inner peripheral edge portion is located at the flange portion, the seal strength formed is greater than the laminate strength, and the seal layer and adjacent layer of the container are arranged at the boundary between the seal portion and the non-seal portion on the container side. The structural feature is that the lid material is heat-sealed from the top to form a voluminous resin pool.

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 halia 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 this layer with an adhesive layer interposed therebetween. In some cases, a multilayer plastic sheet with other materials such as metal or paper laminated on the outside may also be used.

However, the multilayer sheet 1 has a lamination 1 strength between the sheet layer and the adjacent layer of 300 to 2000 g/25 mm (peel angle 1
80° when measured at a peeling rate of 200 mm/min),
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 lamination strength is less than 2000g/25mm and the sheet layer thickness is less than 10μ, sufficient sealing performance cannot be ensured.On the other hand, if the lamination strength exceeds 2000g/25mm and the sheet layer thickness exceeds 70μ, the sealing strength will be insufficient. This is because the beer becomes extremely high, which increases the strength of the beer when opening, impairing the ease of opening.

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. It is to be composed of the same paddy 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 manufacturing process of the present invention will be explained based on the drawings.

FIG. 1 is a schematic cross-sectional view showing the sealing process, in which the M-shape 2 is stacked on the flange portion 3 of the container 1, and a seal plate 5 having an inclined surface 4 is shown.
Heat seal using.

As shown in FIG.
) is set. If the angle of this slope is less than 3 degrees, it will be difficult to form the resin reservoir, making it difficult to cut and open the seal layer smoothly during beer brewing.On the other hand, if the angle exceeds 15 degrees, the edges will become acute and the lid There would be a risk of cutting the material 2, which would make it impossible to achieve the object of the invention. Also, the width of the seal plate 5 is determined by the width of the flange portion 3.
It is desirable to design the width to be 1/2 or more of the width.

For sealing, set the inner circumferential edge portion E of the seal disc 5 so that it is located on the flange portion 3 (see Part 2), and set the formed seal so that the strength of the seal is equal to or higher than the laminated uneven strength.
The lid material 2 is heat-sealed from the top under hot-pressure conditions to form a lump-shaped resin pool made of the constituent resins of the seal layer and the adjacent layer of the container at the boundary between the sealed portion and the non-sealed portion on the container side.

FIG. 3 is a sectional view showing the state of the flange portion 3 that has been heat-sealed as described above. The flange surface is fused on the entire surface where the seal disc 5 contacts, but due to the action of the inclined surface 4, the degree of pressure increases as it approaches the inner peripheral edge and reaches its maximum at the lower part of the edge portion E. For this reason, the resin components constituting the sealing layer 6 and the adjacent layer 8 of the container l are pushed out from the lower part of the edge E where the pressure is strongest toward the container, resulting in a bump-like shape that rises at the boundary between the sealed and non-sealed parts. Resin reservoirs 9 and 10 are formed. At this time, the sealing layer 7 of the lid material 2 is also attached to form a resin reservoir 11.

At the sealing part, the lid material 2 and the container 1 are completely fused together.
The boundary surface between the seal layer 7 of the lid shrine and the seal layer 6 of the container exhibits a state in which both resins are mixed. 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]

In the sealed container manufactured by the method of the present invention as described above, there is no risk of seal leakage because the container body and the lid are completely fused together by the action of heat and pressure.

When opening, a force X as shown in Fig. 4 is applied to the lid material 2.
First, peeling starts smoothly between the seal layer 6 and the adjacent layer 90 of the container 1. This peeling continues to the resin accumulation area, but
Up to this stage, the force X functions to cause separation between the sealing layer 6 and the adjacent layer 8 of the container. Next, when reaching point A, force
The distribution is dominant in the direction of tearing off the seal N6.

Through the above-mentioned peeling and cutting action, the package can be easily opened in the final state as shown in FIG. 5.

[Example] The total thickness is 850μ, and the material of the sealing layer has a density of 0955.
, high-density polyethylene (HDPE) with a melt index (Ml) of 5 g/lomin, and the adjacent layer (which also serves as an outer layer) is a melt index (Ml) of 0.5 g/lomin.
A two-layer seal consisting of 10 min polypropylene (PP) was made by coextrusion. Next, this sheet was vacuum formed to have an inner diameter of 70 mm, a flange outer diameter of 82+n+n,
A container body with a height of 30 mm was obtained. The flange thickness of this container body is 800μ, the thickness of the sealing layer is 20μ, and the lamination strength between the sealing layer and the adjacent layer is 800g/25mm.
Met.

Biaxial stretching 6-6. 6Ny
(ONY) Layer lid materials made of 25μ/HDPH60μ and heat at 180'C and pressure 10kg/cffl using seal discs with different slopes from the inner edge to the outer edge with a seal width of 8IIllll. I sealed it.

The angle of inclination of the seal disc (
The table below shows a comparison with θ).

[Effect of the invention] Since the safety and easy openability of a seal in a sealed container are mutually contradictory performances, it has been difficult to achieve both with conventional sealing methods. However, according to the present invention, the sealing Since the interface for brewing and the interface for brewing are different, it is possible to brew beer without being influenced by seal strength. Therefore, even if the seal is sufficiently secured, the ease of brewing is not impaired, and a combination of perfect sealing performance and easy-opening performance is guaranteed.

Furthermore, if the sealing method of the present invention is adopted, the pressure on the outer periphery of the flange will be relatively small, so the initial beer will be good, and the seal layer will be cut smoothly at point A. This makes it possible to manufacture sealed containers that always have excellent opening performance.

is a partially enlarged sectional view showing the state of the flange portion after heat sealing. FIG. 4 is a schematic sectional view showing the direction of the force required to open the package, and FIG. 5 is a partially enlarged sectional view showing the state when the package is opened.

1... Container 2... Lid shrine 3... Flange part 4
... Inclined surface 5 ... Seal plate 6 ... Seal layer 7 ... Seal layer of lid material 8 ... Adjacent layers 9, 10
, 11... Resin pool A... Cutting point E...
Edge portion χ...force Applicant Sumitomo Bakelite 11 Co., Ltd. Agent Patent attorney Masaya Takahata

[Brief explanation of the drawing]

Fig. 1 is a schematic sectional view showing the heat sealing process of the present invention, Fig. 2 is a partially enlarged sectional view showing the state of the seal disk and flange surface during sealing, Fig. 3 Fig. 2 Fig. 4 /// / , ///7/7r' θ //E2 Figure Figure

Claims (1)

[Claims] 1. The lamination strength between the sealing layer and the adjacent layer facing it is 300-2000g/25mm, and the thickness of the sealing layer is 1.
When sealing the flange part of the container and the lid material, which have a diameter of 0 to 70μ, a seal disc having an inclined surface of 3 to 15 degrees from the inner peripheral edge to the outer peripheral edge with respect to the flange surface is used. Set so that the inner peripheral edge portion is located at the flange portion, the seal strength formed is greater than the laminate strength, and the seal layer and adjacent layer of the container are arranged at the boundary between the seal portion and the non-seal portion on the container side. A method for producing a sealed container, characterized by heat sealing from the top of the lid material to form a knob-shaped resin pool.