JPH05338099A - Cover material made of plastic - Google Patents

Abstract

PURPOSE:To provide a cover material causing no cutting when the cover material is heat-sealed with a flange part of a packaging container and having no curl as a whole. CONSTITUTION:A cover material 13 has the following layer structure: an unoriented polypropylene film 1 as the uppermost layer; a heat-resistant polyester film 2 and an ethylene-vinyl alcohol copolymer film 3 as intermediate layers; and an polyethylene-polypropylene blended polymer film 4 as the lowermost layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic lid member which is heat-sealed to a flange portion of a packaging container.

[0002]

2. Description of the Related Art Conventionally, there has been known a sealing container in which a plastic packaging container is filled with fruits, jelly liquid, etc. and the packaging container is sealed with a plastic lid member.

Of these, the packaging container has a container body and a flange portion provided at the upper end opening of the container body, and the packaging container is obtained by thermoforming a plastic laminate. On the other hand, the lid member is composed of a heat-sealing portion that overlaps the flange portion of the packaging container and a drop lid portion that covers the opening of the packaging container, and is obtained by thermoforming a plastic laminate in the same manner.

The heat-sealing portion of the lid member is heat-sealed to the flange portion of the packaging container.

[0005]

By the way, as described above, the lid member is obtained by thermoforming a plastic laminate, and such a lid member is required to have gas barrier properties and to be formed between the lid member and the flange portion. It is required to maintain high sealing strength. Further, the lid material is required to have an easy opening property. However, the fact is that a lid material excellent in these requirements, especially in gas barrier properties, has not been developed yet.

The present invention has been made in consideration of the above points, and provides a plastic lid material which is excellent in gas barrier property, maintains a high sealing strength between itself and a flange portion, and is also easily opened. The purpose is to do.

[0007]

The present invention provides an unstretched polypropylene film as the uppermost layer, a heat-resistant polyester film and an ethylene vinyl alcohol copolymer film as the intermediate layer, and a polyethylene-polypropylene blend polymer as the lowermost layer. A plastic lid material characterized by being made of a film.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. First, a sealed container including a packaging container and a lid member will be described with reference to FIGS. 3 to 5.

As shown in FIG. 3, the packaging container 12 is filled with the fruit 14 and the jelly liquid 15, and the packaging container 12 is sealed with a lid member 13 to form a sealed container 11.

The packaging container 12 includes a container body 12a and a flange portion 12b provided on the periphery of the upper end opening of the container body 12a.
It consists of On the other hand, the lid member 13 includes a heat seal portion 13b overlapping the flange portion 12b of the packaging container 12,
The heat seal portion 13b is composed of a drop lid portion 13a which is continuously provided inside the heat seal portion 13b. The dropping lid 13a is the container body 1
The heat seal portion 13 covers the upper opening of 2a.
It is provided by dropping downward from b.

The packaging container 12 is made of polypropylene (PP).
/ Ethylene / vinyl alcohol copolymer (EVOH) /
It is prepared by thermoforming a laminate made of polypropylene (PP).

On the other hand, the lid member 13 is obtained by thermoforming a laminated body having a gas barrier property as described later. The laminated body that constitutes the lid member 13 is thinner than that of the packaging container 12 because it is less necessary to have strength. Therefore, the lid material 13
The moldability is excellent, and the heat-sealed portion 13b can be molded with the same thickness distribution and high accuracy.

Next, the heat sealing work between the flange portion 12b of the packaging container 12 and the heat sealing portion 13b of the lid member 13 will be described with reference to FIG. As shown in FIG. 5, first, the fruit 14 and the jelly liquid 15 are placed in the lower sealing mold 21.
The packaging container 12 filled with is stored. Next, packaging container 1
The heat-sealing portion 1 of the lid member 13 on the flange portion 12b of 2
Stack 3b. After that, the heating upper mold 22 is lowered with respect to the lower mold 21, and the pressing portion 24 of the heating upper mold 22 is depressed.
Is pressed against the heat-sealing portion 13b of the lid member 13 to perform heat-sealing between the heat-sealing portion 13b of the lid member 13 and the flange portion 12b of the packaging container 12.

Next, an embodiment of the plastic lid member according to the present invention will be described. FIG. 1 is a diagram showing an embodiment of a plastic lid member according to the present invention.

In FIG. 1, the lid material of the present invention is an unstretched polypropylene (CPP) 1 as the uppermost layer, a polycarbonate film (PC) 2 and an ethylene vinyl alcohol copolymer film (EVOH) 3 as an intermediate layer.
And a polyethylene-polypropylene blend polymer film (PP-P as a sealant layer as the bottom layer).
E) 4, each film 1, 2, 3, 4 is dry laminated using an isocyanate adhesive.

In the present invention, however, the unstretched polypropylene film 1 is for imparting rigidity to the lid material and cushioning properties, and its thickness is 150 μm.
The following is preferable, and when it is 150 μm or more, heat is less likely to be transferred during heat sealing, and heat sealing tends to be poor, which is not preferable.

The polycarbonate film 2 is laminated in order to impart properties such as heat resistance and shape retention property to the lid material, and the thickness thereof is preferably 15 to 150 μm, and when it is 15 μm or less, a pin is formed at a corner portion of the molded product. Holes and perforations occur, shape retention deteriorates, and the shape of the lid cannot be maintained, which is not desirable. When it is 150μ or more, it becomes extremely difficult to transfer heat during heat sealing, which easily causes heat seal failure and is costly. It is not preferable because it will be up.

Next, the ethylene-vinyl alcohol copolymer film 3 is laminated on the lid material in order to impart an oxygen barrier property, and is preferably 10 to 50 .mu.m, and when it is 10 .mu.m or less, pin holes or holes are formed at the corners during molding. A perforation occurs,
The barrier effect is lost, which is not preferable, and when it is 50 μm or more, moldability is deteriorated.

The polyethylene-polypropylene blend polymer film 4 functions as a heat-sealing layer, and its thickness is preferably 10-100 .mu.m, and when it is 10 .mu.m or less, the peel strength after heat fusion is less than the practical strength. When it is 100 μm or more, not only the cost increases but also the film-forming property deteriorates extremely, which is not preferable. or,
If it is 100 μm or more, stringing and fluffing will be observed on the flange portion of the packaging container after opening, which is not preferable.

The blending ratio of polyethylene and polypropylene is preferably 7: 3 to 3: 7. When the amount of polyethylene becomes large and the blending ratio becomes 7: 3 or more, cohesive failure does not occur, interfacial peeling occurs, and heat sealing is performed. The strength is not preferable because it changes depending on temperature and is unstable. On the other hand, when the amount of polypropylene is large and the blend ratio is 3 to 7 or less, complete fusion occurs and easy opening property is lost, which is not preferable. In addition, since the polyethylene-polypropylene blend polymer film does not contain a low molecular weight one, it has little odor and is suitable for fruit packaging. Further, the sealant layer is a coextruded two-layer film, but it may be two layers of a cohesive failure sealant layer made of PE-PP blend polymer and a PE support layer (not shown).

In the above examples, the polycarbonate film 2 was used as the intermediate layer. However, if the polyester is thermoplastic and has a melting point of 200 ° C. or higher (hereinafter referred to as heat resistant polyester), the polycarbonate film 2 Can be used instead.

As such heat-resistant polyester,
Examples of the crystalline polyester include polyethylene terephthalate (PET) and polybutylene terephthalate (P
BT), polyethylene naphthalate (PEN), etc. are considered. As the amorphous polyester, in addition to the above-mentioned polycarbonate (PC), polyarylate (PAR)
Etc. are possible.

According to this embodiment, since the heat-resistant polyester film having good wettability such as the polycarbonate film 2 is used as the intermediate layer, it is necessary to perform corona treatment on both surfaces of the unstretched polypropylene 1 during dry lamination. Disappear. For example, when the polycarbonate film 2 is provided on the uppermost layer, corona treatment is required on both surfaces of the unstretched polypropylene to be the intermediate layer. Therefore, according to the present invention, the manufacturing process is simplified as compared with this case. be able to.

Since the unstretched polypropylene film 1 as the uppermost layer and the polyethylene-polypropylene blend polymer film 4 as the heat seal layer are arranged with the polycardnate film 2 having excellent heat resistance,
The uppermost unstretched polypropylene film 1 and the polyethylene-polypropylene blend polymer film 4 do not melt at the time of heat sealing. Therefore, it is possible to prevent defective root cutting of the lid member 13 (fusion of the lid member lid member to the packaging container side).

Further, the unstretched polypropylene film 1 having a large heat shrinkage rate is arranged in the uppermost layer, and the polyethylene-polypropylene blend polymer film 4 having a large heat shrinkage rate is also arranged in the lowermost layer.
3 It is possible to balance heat shrinkage as a whole.
That is, even in the case where the polycarbonate film 2 having a small heat shrinkage rate is arranged in the middle and the lid 13 is formed by thermoforming such a laminated body as in the present embodiment, the unstretched polypropylene film 1 of the uppermost layer is formed. Since the heat shrinkages of the polyethylene-polypropylene blend polymer film 4 as the lowermost layer are substantially the same and have relatively large values, it is possible to balance the heat shrinkage between the uppermost layer and the lowermost layer. For this reason, the curling of the lid member 13 after thermoforming is reduced as a whole, and the heat sealing property between the lid member 13 and the flange portion 12b of the packaging container 12 can be improved.

Next, another embodiment of the lid member will be described with reference to FIG. That is, the lid member shown in FIG. 2 is the same as the lid member shown in FIG. 1 except that the polycarbonate film 2 and the ethylene vinyl alcohol copolymer film 3 are arranged at different positions.

(Specific Example) Next, a specific example of the present invention will be described. First, films having the following layer structures were dry-laminated with each other using an isocyanate adhesive, and the laminate was thermoformed to form a lid material.

Unstretched polypropylene film (CPP)
(100μ) / Polycarbonate film (PC) (3
0 μ) / ethylene vinyl alcohol copolymer film (EVOH) (20 μ) / polyethylene-polypropylene blend polymer film (PP-PE) (50 μ)
In this case, the polyethylene-polypropylene blend polymer film has a density of 0.97, M as polyethylene.
50 wt% as polypropylene using I = 8
A random copolymer having a density of 0.90 = 60 was used.

Next, the curling property of the lid material was judged, and the lid material was heat-sealed at the flange portion of the packaging container.

As a comparative example, a polycarbonate film (PC) (30 μ) / unstretched polypropylene film (PCC) (100 μ) / ethylene vinyl alcohol copolymer film (20 μ) / polyethylene-polypropylene blend polymer film (PP-PE). ) (5
A lid member was formed by thermoforming from a laminated body having a layer structure of 0 μ). Then, the curling property of the lid material of this comparative example was judged, and this lid material was heat-sealed to the flange portion of the packaging container. The results are shown in Table 1.

[0031]

[Table 1] As is clear from Table 1, in the case of the lid material of the present invention, there was no curl and good sealing property with the flange portion of the packaging container was obtained.

[0032]

As described above, according to the present invention,
Since the heat-resistant polyester film having good wettability is used as the intermediate layer, the unstretched polypropylene corona treatment at the time of lamination can be improved by the one-side treatment. Therefore, the manufacturing process can be simplified. In addition, a polycarbonate film with excellent heat resistance was placed between the unstretched polypropylene film as the uppermost layer and the polyethylene-polypropylene blend polymer film as the heat-sealing layer (lowermost layer), so that it was not stretched when heat-sealed. It does not fuse with the polyethylene-polypropylene blend polymer film. further,
The unstretched polypropylene film of the uppermost layer and the polyethylene-polypropylene blend polymer film of the lowermost layer have almost the same and have a relatively large heat shrinkage ratio, so that the heat shrinkage can be balanced between the uppermost layer and the lowermost layer. .. For this reason, the lid material obtained by thermoforming has less curl as a whole.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a lid member according to the present invention.

FIG. 2 is a sectional view showing another embodiment of the lid member according to the present invention.

FIG. 3 is a cross-sectional view of a sealed container including a packaging container and a lid member.

FIG. 4 is an enlarged view of part A of FIG.

FIG. 5 is a diagram showing heat sealing work.

[Explanation of symbols]

1 unstretched polypropylene film 2 heat resistant polyester film 3 ethylene vinyl alcohol copolymer film 4 polyethylene-polypropylene blend polymer film

Claims (1)

[Claims] 1. An unstretched polypropylene film as the uppermost layer, a heat-resistant polyester film and an ethylene vinyl alcohol copolymer film as the intermediate layer, and a polyethylene-polypropylene blend polymer film as the lowermost layer. Plastic lid material.