JP2578229B2 - Manufacturing method of easily openable sealed container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an easily openable seal in which a lid can be easily opened in a container composed of a plastic cup body having a flange portion and a lid member. The present invention relates to a method for manufacturing a container.

[Conventional technology]

2. Description of the Related Art As a container for packaging various foods, a plastic sealed container having an easy-open structure that can be easily opened with a lid is widely used.

The most common easy-open type structure that has been practically used in the past is to change the composition of the resin that constitutes the sealing layer of the lid material so that the sealing strength with the container flange can be adjusted within a suitable range (usually 500 to 1500 g / 15mm), and the seal interface is peeled off and opened (interface peeling type).

However, this interfacial peeling type has a disadvantage in that the target range is difficult to control because the sealing strength to be applied is easily affected by conditions at the time of sealing, environmental temperature, adherence of contents, etc. There is. This variation results in seal leakage when biased toward the weak side, and conversely, when biased toward the strong side, impairs the peelability and impairs the ease of opening. In particular, since leakage of a seal becomes a fatal defect as a sealed container, a measure is usually taken to set the heat and pressure conditions of the seal to be higher even at the expense of peelability.

In order to improve such problems, for example,
As described in Japanese Patent No. 37597, there is known a method of delamination between a sealing layer on a container side and a layer adjacent to the sealing layer to open (delamination type).
However, if this structure is to be adopted by a normal sealing method, there is a problem that the sealing layer portion does not break smoothly, and it is difficult to take out the contents. In this case, in order to facilitate separation of the peeling layer and the adjacent layer, a structure in which a cut is formed in the flange portion (JP-A-62-251363, JP-A-63-78, and JP-A-63-78).
63-25037), a structure in which a notch for starting peeling and a notch for stopping peeling are provided in a flange portion (Japanese Patent Laid-Open No. 63-25037).
A number of improvements have been proposed,
In these structures, there remains a problem in the pressure resistance.

In addition to the above-mentioned interfacial peeling type and interlayer peeling type, there is also known an agglomeration peeling type easy-open system in which a resin structure between a container and a lid is broken and peeled off at the time of opening.

[Problems to be solved by the invention]

However, in the case of the cohesive peeling type, there is a problem that a smooth easy-opening property cannot be obtained unless the cohesive force and the adhesive force between the container flange portion and the cover material are adjusted in a well-balanced manner.

The inventors have conducted intensive studies on the easy-open structure by the cohesive peeling type, and as a result, a lid member including a flange portion of a container having a minute concave portion formed on an upper surface and a sealant layer in which adhesive and non-adhesive components are mixed. It has been confirmed that heat sealing can form a seal structure which has sufficient pressure resistance and can be easily coagulated and peeled off, thereby leading to the present invention.

Accordingly, an object of the present invention is to provide a method for manufacturing a sealed container that can be easily opened through a smooth cohesion and peeling action while maintaining stable high pressure tightness.

[Means for solving the problem]

In order to achieve the above object, a method for producing an easily-openable sealed container according to the present invention comprises the steps of:
Heat-sealing the container body formed with the minute concave portion of ² , and a lid material provided with a sealant tank of a mixed composition comprising a component having adhesiveness and a component having non-adhesiveness with the flange portion. Features.

 Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view showing a sealed container to be manufactured according to the present invention. Reference numeral 1 denotes a container main body having a flange portion 2 formed into a predetermined shape by, for example, vacuum forming, and reference numeral 3 denotes a lid. The container body 1 is composed of a simple resin such as polypropylene or polystyrene, or a multilayer sheet in which a saponified ethylene vinyl acetate copolymer or a polyvinylidene chloride-based resin is combined with these resin layers. Further, in some cases, it is possible to laminate a material such as metal, paper, or ceramic on the outer layer or the intermediate layer of the multilayer sheet, but in the present invention, a container material in which the flange adhesive surface is polypropylene is preferably used. You.

On the upper surface of the flange portion 2, a predetermined number of minute concave portions 4 are formed in advance as shown in FIG. The formation of the minute concave portion 4
Appropriate means such as ultrasonic treatment, press by heating or cold, method of forming countless irregularities on the flange part of the mold for pressure injection molding using high frequency, and simultaneously forming it on the flange part of the container body during injection molding Can do it.
Among them, the method of performing ultrasonic treatment using a convex ultrasonic horn is most effective in that a uniform and fine concave pattern can be formed on the entire surface of the flange. It is desirable that the number of the minute concave portions 4 to be formed is in the range of 50 to 500 per 1 cm ² . If the number is less than 50 pieces / cm ² , the opening property is reduced, and the processing exceeding 500 pieces / cm ² becomes difficult.

The lid member 3 is made of a material having a sealant layer 5 of a mixed composition containing both components that are adhesive and non-adhesive to the flange portion 2 of the container body 1 described above. Therefore, as long as the sealant layer 5 is provided, the sealant layer may be a single layer or a multilayer structure combining materials such as aluminum foil and plastic having good barrier properties.

A specific constituent material of the sealant layer 5 of the lid member is, for example, a material obtained by blending adhesive homogeneous polypropylene and non-adhesive polyethylene when the flange 2 of the container body is made of a polypropylene material. The most preferable material combination of the flange portion and the cover material sealant layer in the present invention is that the flange material is made of polypropylene and the material of the cover material sealant layer is polyethylene.
40-78% by weight, ethylene-propylene random copolymer
20-40% by weight, ethylene-α-olefin copolymer 2-40
This is an embodiment in which the composition is composed of a weight percent, and it is possible to achieve both good sealing properties and easy-opening properties under good conditions.

The container main body 1 having the minute concave portion formed on the upper surface in this manner.
A sealed container is manufactured by superposing the sealant layer 5 of the lid member 3 having the specified adhesive ability and the sealant layer 5 on the state shown in FIG. 3 and heat sealing.

(Operation)

In the seal structure manufactured by the above-described process of the present invention, as shown in FIG. 4, the sealant layer 5 of the lid member 3 completely fills the minute concave portion formed on the upper surface of the flange portion 2. Therefore, it is structurally strong and the pressure resistance against external pressure and internal pressure is extremely stable. The adhesion in this case is
While being appropriately adjusted by the material action of the adhesive / non-adhesive component mixture composition constituting the lid material sealant layer 5,
The adhesive force at point B, which strikes the bottom of the recess, is relatively weaker than the adhesive force at position A where the sealing pressure is high.

Peeling at the time of opening, when the lid material 3 is pulled upward, as shown in FIG. 5, the sealant layer at the position A is destroyed in a portion having a strong adhesive force, and in a concave portion having a relatively weak adhesive force, the shape is changed to the form. The two types of separation patterns that peel off along a continuous progress. In this process, the unique strong and weak adhesive mechanism according to the present invention works well, and it becomes possible to open the package by cohesive peeling without a sense of resistance.

〔Example〕

Vacuum forming a multilayer sheet composed of polypropylene (PP) with a melt index (MI) of 0.5 g / min. To be the adhesive surface of the flange, 65 mm inside diameter and 75 outside diameter flange
A container body having a height of 25 mm and a height of 25 mm was prepared. Then, ultrasonic treatment was performed by applying a concave ultrasonic horn having a projection number of 256 / cm ² to the upper surface of the flange portion to form a fine concave portion over the entire area. The conditions of the ultrasonic treatment in this case were as follows: output 2 KW (use energy 225 J), pressure 338 KPa, time 0.3 seconds.

55% by weight of high density polyethylene (HDPE) as lid material
A sealant layer (thickness: 50 μm) composed of 40% by weight of an ethylene-propylene random copolymer and 10% by weight of an ethylene-α-olefin copolymer was dry-laminated with 6-6 nylon (25 μm). .

A sealant layer of a lid material was superimposed on the upper surface of the flange portion of the container, and heat-sealed twice under the conditions of a surface pressure of 2 kg / cm ² , a temperature of 170 ° C. and a time of 1.5 seconds.

When the lids were opened for the 20 sealed containers produced in this manner, all the containers were opened smoothly to the end with a light peeling feeling, and the state of the opened surface was good.

A sticky rubber plate (1.5 mm thick) was attached to the center of the lid, and the puncture pressure when air was injected at a rate of 2 cc / sec by inserting a syringe needle was measured. is 0.
8 kg / cm ^2, showed stable breakdown voltage sealability in variation width 0.2 kg / cm ^2.

For comparison, when the lid was opened for 20 sealed containers produced under the same conditions as above except that no micro concave portion was formed in the flange portion by ultrasonic treatment, six unopenable containers were generated. In the measurement of the puncture pressure, the average puncture pressure was 7 kg / cm ² , but it was confirmed that the variation width was as large as 0.5 kg / cm ² .

〔The invention's effect〕

As described above, according to the present invention, by sealing the sealant layer of the lid material whose adhesiveness is adjusted with the flange portion having the minute concave portion formed on the upper surface, a smooth peel feeling can be maintained while always maintaining a stable high pressure tightness. Thus, it is possible to form a seal structure by a cohesive peeling mechanism that can easily open the lid.

Therefore, a high-quality easily-openable sealed container effective for packaging all kinds of foods can be efficiently manufactured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a sealed container to be manufactured according to the present invention, FIG. 2 is a plan view of the container showing a state in which a lid is half-opened, and FIGS. FIG. 5 is an enlarged cross-sectional view of the flange portion showing a state in which the lid is opened. DESCRIPTION OF SYMBOLS 1 ... Container main body, 2 ... Flange part 3 ... Lid material, 4 ... Micro concave part 5 ... Sealant layer

Claims (1)

(57) [Claims] 1. A sealant having a mixed composition comprising a container body having a fine concave portion of 50 to 500 pieces / cm ² formed on an upper surface of a flange portion, and a component having an adhesive property to the flange portion and a component having a non-adhesive property. A method for producing an easily-openable sealed container, comprising heat-sealing a lid provided with a bath.