JPH061368A - Lid member made of plastic - Google Patents

Abstract

PURPOSE:To provide a lid member which does not generate root cutting at the heat-sealed part with a packaging container, and can improve the oxygen barrier property. CONSTITUTION:A lid member 13 has the following layer constitution. It has a polycarbonate film 1 as the uppermost layer, an ethylene-vinyl alcohol copolymer film 2 and undrawn polypropylene film 3 as medial layers and a coextruded two-layer film 4 of polyethylene-polypropylene as the lowermost layer. The coextruded two-layer film 4 consists of a supporting layer 5 on the medial layer side and a sealant layer 6.

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 and the like, and the packaging container is sealed with a plastic lid material.

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 similarly obtained by thermoforming a plastic laminate.

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. Therefore, it is required to maintain high seal strength. Further, the lid material is required to have easy opening property. Examples of materials that can be easily opened include Japanese Patent Publication No. 63-45304 and Japanese Patent Publication No. 63-4530.
Those described in Japanese Patent Publication No. 5 and Japanese Patent Publication No. 63-45306 and Japanese Patent Publication No. 63-45307 are known. However, in reality, the lid materials described in these publications do not take much into consideration especially the gas barrier property.

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 easy in opening. Intended for the purpose.

[0007]

The present invention provides a heat-resistant polyester film as the uppermost layer, an ethylene vinyl alcohol copolymer film and an unstretched polypropylene film as the intermediate layer, and a coextruded two-layer film as the lowermost layer. The coextruded two-layer film comprises two layers of a cohesive failure sealant layer made of a polyethylene-polypropylene blend polymer and a support layer made of a resin having a good heat fusion property with the polyethylene-polypropylene blend polymer. And a plastic lid material, wherein the side surface of the support layer is laminated so as to face the intermediate layer side, a heat-resistant polyester film as the uppermost layer, and an ethylene vinyl alcohol copolymer film as the intermediate layer And a coextrusion two-layer film as the bottom layer, The extruded two-layer film comprises two layers of a cohesive failure sealant layer made of a polyethylene-polypropylene blend polymer and a support layer made of a resin having a good heat fusion property with the polyethylene-polypropylene blend polymer, and the side surface of the support layer. Are laminated so as to face the intermediate layer side, which is a plastic lid member.

[0008]

According to the present invention, since the heat-resistant polyester film is arranged as the uppermost layer, it is possible to prevent the root material of the lid material from being cut off, and the ethylene vinyl alcohol copolymer film is arranged as the intermediate layer. The gas barrier property of the material can be improved.

[0009]

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 around 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-sealing portion 13b includes a dropping lid portion 13a that is continuously provided inside the heat-sealing 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).
/ Adhesive layer (AD) / Ethylene / vinyl alcohol copolymer (EVOH) / Adhesive (AD) / Polypropylene (P
It is prepared by thermoforming a laminate of P).

On the other hand, the lid member 13 is made of a gas barrier laminate as described later. Since the laminated body forming the lid member 13 is less required to have strength, the packaging container 12
It is thinner than the one. Therefore, the moldability of the lid member 13 is good.

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 packaging container 12 filled with the fruit 14 and the jelly liquid 15 is housed in the retainer 21. Next, the heat seal portion 13b of the lid member 13 is superposed on the flange portion 12b of the packaging container 12. After that, the seal head 22 is lowered with respect to the retainer 21, the pressing portion 24 of the seal head 22 is pressed against the heat seal portion 13b of the lid member 13, and the lid member 1
The heat sealing work is performed between the heat sealing portion 13b of No. 3 and the flange portion 12b of the packaging container 12.

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

In FIG. 1, a lid member 13 according to the present invention comprises a polycarbonate film (PC) 1 as an uppermost layer,
An ethylene vinyl alcohol copolymer film (EVOH) 2 and an unstretched polypropylene film (PP) 3 as an intermediate layer and a coextruded two-layer film (PP-PE) 4 as a lowermost layer are laminated. Of these, the coextruded two-layer film (PP-PE) 4 is a cohesive failure sealant layer 6 made of a polyethylene-polypropylene blend polymer and a support layer 5 made of a resin having a good heat fusion property with the polyethylene-polypropylene blend polymer. And the side surface of the support layer 5 is the intermediate layer 2,
It is laminated so as to face the 3 side.

In the present invention, the polycarbonate film 1 is laminated in order to impart properties such as heat resistance and shape retention property to the lid material, and the thickness thereof is 15 to 150.
When μ is less than 15μ, pinholes and holes are likely to occur in the corners of the molded product, shape retention is poor, and the shape of the lid cannot be maintained. At times, it becomes extremely difficult for heat to be transferred, and it is easy to cause a defective seal, and there is a problem in terms of cost.

Next, the ethylene vinyl alcohol copolymer film 2 is laminated to give an oxygen barrier property to the lid material, and preferably has a thickness of 10 to 50 .mu.m. A perforation occurs,
It is not preferable because the barrier effect is lost, and when it is 50 μm or more, the moldability of the lid material deteriorates.

Next, the unstretched polypropylene film 3 is laminated in order to give the lid material rigidity and cushioning property, and its thickness is preferably 150 μm or less,
When it is 150 μm or more, heat is not easily transferred during heat sealing, and heat sealing tends to be poor, which is not preferable. The unstretched polypropylene film does not necessarily have to be provided as described later.

Next, as the coextruded two-layer film 4, a polyethylene-polypropylene blend polymer is extruded together with a resin which is easy to form a film for a supporting layer and has a good heat fusion property with the polyethylene-polypropylene blend polymer. Alternatively, a film formed by the inflation method may be applied.

The cohesive failure sealant layer 6 made of a polyethylene-polypropylene blend polymer has a thickness of 3 to
When it is 50 or less, it is not preferable because the peel strength after heat fusion is less than the practical strength, and when it is 50 or more, not only the cost is increased but also the film-forming property is extremely deteriorated, which is not preferable.

The polyethylene-polypropylene blend polymer preferably has a blending ratio of polyethylene and polypropylene of 7: 3 to 3: 7. When the amount of polyethylene is large and the blend ratio is 7: 3 or more, cohesive failure does not occur, interfacial peeling occurs, and the heat seal strength varies depending on temperature and is unstable, which is not preferable. On the other hand, the amount of polypropylene is large and the blend ratio is 3
When the ratio is 7 or less, it is not preferable because complete fusion occurs and easy opening cannot be achieved.

Next, as a resin for the support layer 5, ethylene-
α-olefin copolymer, high density polyethylene, medium density polyethylene, low density polyethylene, polypropylene, etc. can be applied, and the thickness thereof is 20 to 100 μm.
Is preferred. When the thickness of the support layer 5 is 20 μm or less, cracks occur in the support layer and normal opening cannot be performed, and delamination occurs between the unstretched polypropylene film and the support layer,
It is not preferable because it easily becomes a film beam. On the other hand, if the thickness of the indicator layer 5 is 100 μm or more, it is not preferable because heat is difficult to be transferred during heat-sealing and heat-sealing is likely to occur.

Next, in the present invention, the polyethylene-polypropylene blend polymer and the above-mentioned resin for supporting layer are adjoined to the resin layer for supporting layer, and polypropylene, polyethylene, ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer are adjoined. A resin such as a polymer, a saponified product of an ethylene-vinyl acetate copolymer, an ionomer resin, polyamide, or polyvinylidene chloride may be extruded to form the support layer with two resin layers.

Although the polycarbonate film 1 is used as the uppermost layer in the above-mentioned examples, any film may be used as long as it is a thermoplastic polyester having a melting point of 200 ° C. or higher (hereinafter referred to as heat resistant polyester). May be.

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

Thus, the uppermost layer has a melting point of 200 ° C.
By using the above heat-resistant polyester film, the uppermost layer can be left without melting even at the time of heat sealing with heating from the seal head 22. Therefore, defective root cutting of the lid member 13 (the entire lid member is fused to the packaging container side) can be reliably prevented.

According to this embodiment, it is possible to provide a lid member which can be easily opened with an appropriate peel strength without causing stringing or fluffing on the flange surface of the packaging container. Moreover, since the thickness of the lid member is such that the heat of the upper mold 22 for heating can be sufficiently transmitted to the sealing surface through the lid member, it is possible to provide a lid member that does not cause a sealing failure. Further, since the lid material contains the ethylene vinyl alcohol copolymer film having excellent gas barrier properties, the gas barrier property of the entire lid material can be improved.

Next, another embodiment of the lid member will be described with reference to FIG. That is, the lid material shown in FIG. 2 is the same as the lid material shown in FIG. 1 except that the arrangement positions of the ethylene vinyl alcohol copolymer film 2 and the unstretched polypropylene film 3 are exchanged.

(Specific Example 1) 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-based adhesive, and this laminated body was vacuum-pressure formed to form a lid material.

Polycarbonate film (PC) (30
μ) / unstretched polypropylene film (CPP) (10
0 μ) / ethylene vinyl alcohol copolymer film (EVOH) (20 μ) / polyethylene-polypropylene coextruded two-layer film (PP-PE) (50 μ) In this case, the coextruded two-layer film has a density of 0.9.
4, polyethylene (30μ) having MI = 2.0 was used as a support layer, and polyethylene-polypropylene blond polymer (20μ) was used for cohesive failure. The polyethylene-polypropylene blend polymer of the sealant layer is 50 wt% random copolymer, density 0.90, MI
= 6.0 polypropylene, density 0.97, MI =
It was composed of 8.0 polyethylene.

Next, the oxygen transmission rate was measured for this lid member. The measurement conditions in this case are OXTRAN100.
(ASTM D3985), 20 ° C.

As a comparative example, a polycarbonate film (PC) (30 μ) / unstretched polypropylene film (PCC) (100 μ) / polyvinylidene chloride film (PVDC) (25 μ) / polyethylene-polypropylene coextruded two-layer film (PP-PE) (50
A lid member was formed by vacuum pressure forming from the laminated body having the layer structure of (μ). Then, the oxygen permeability was measured for the lid member of this comparative example. The results are shown in Table 1. The co-extruded two-layer film of Comparative Example has the same structure as the co-extruded two-layer film shown in Example 1 of the present invention.

[0034]

[Table 1] As is clear from Table 1, the lid material of the present invention has excellent oxygen barrier properties. (Specific Example 2) Next, as the lid material of the present invention, films having different layer constitutions as described below are dry-laminated with each other using an isocyanate adhesive, and the laminated body is vacuum-pressure molded to obtain three types of lids. The material was molded.

Polyethylene terephthalate (PE
T) (20μ) / unstretched polypropylene film (CP
P) (150μ) / ethylene vinyl alcohol copolymer film (EVOH) (20μ) / polyethylene-polypropylene coextruded two-layer film (PP-PE) (5
0 μ) Polycardnate (PC) (20 μ) / Unstretched polypropylene film (CPP) (150 μ) / Ethylene vinyl alcohol copolymer film (EVOH) (20
μ) / polyethylene-polypropylene coextrusion double-layer film (PP-PE) (50 μ) Polycarbonate (PC) (120 μ) / ethylene vinyl alcohol copolymer film (EVOH) (20
μ) / polyethylene-polypropylene coextruded two-layer film (PP-PE) (50 μ) Similarly, as a comparative example, a lid member having the following layer structure was formed.

Unstretched polypropylene film (CPP)
(180μ) / ethylene vinyl alcohol copolymer film (EVOH) (20μ) / polyethylene-polypropylene co-extruded two-layer film (PP-PE) (50
μ) Here, as the polyethylene-polypropylene co-extruded two-layer film of the present invention and the comparative example, one having the same constitution as the co-extruded two-layer film described in the specific example 1 of the present invention was used. Also, of the present invention does not include unstretched polypropylene film (CPP).

Next, these lids were heat-sealed in a plastic packaging container at 190 ° C. to 210 ° C. for 2 seconds and twice (sealing total pressure 80 kg). Next, the heat-sealed surface was sufficiently cooled, the lid member was opened, and the appearance of the peeled surface after opening was confirmed.

The results are shown in Table 2.

[0039]

[Table 2] As is clear from Table 2, in the case of the lid materials of the present invention,
It is possible to reliably prevent the root material of the lid from breaking,
A good release surface can be obtained.

[0040]

As described above, according to the present invention,
It is possible to reliably prevent the lid material from being broken. Therefore, the peeled surface after peeling the lid material from the packaging container can be kept clean. Moreover, since the oxygen barrier property of the lid member can be improved, the storability of the contents in the packaging container can be improved.

[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 sectional view of a hermetically sealed container including a packaging container and a lid member.

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

FIG. 5 is a diagram showing heat sealing work.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Polycarbonate film 2 Ethylene vinyl alcohol copolymer film 3 Unstretched polypropylene film 4 Polyethylene-polypropylene coextrusion two-layer film 5 Support layer 6 Cohesive failure sealant layer

Claims (7)

[Claims] 1. A heat-resistant polyester film as the uppermost layer, an ethylene vinyl alcohol copolymer film and an unstretched polypropylene film as the intermediate layer, and a coextruded two-layer film as the lowermost layer. The layer film comprises two layers of a cohesive failure sealant layer composed of a polyethylene-polypropylene blend polymer and a support layer composed of a resin having a good heat fusion property with the polyethylene-polypropylene blend polymer, and the side surface of the support layer is an intermediate layer. A plastic lid material that is laminated so as to face the layers. 2. The plastic lid member according to claim 1, wherein the support layer is made of an ethylene-α-olefin copolymer. 3. The plastic lid member according to claim 1, wherein the support layer is made of high-density polyethylene. 4. The plastic lid member according to claim 1, wherein the support layer is made of medium density polyethylene. 5. The plastic lid member according to claim 1, wherein the support layer is made of low density polyethylene. 6. The heat-resistant polyester film has a thickness of 10
To 150 μ, the thickness of the ethylene vinyl alcohol copolymer film is 10 to 50 μ, the thickness of the unstretched polypropylene film is 150 μ or less, the thickness of the support layer is 20 to 100 μ, and the cohesive failure sealant layer is The plastic lid member according to any one of claims 1 to 5, which has a thickness of 3 to 50 µm. 7. A heat-resistant polyester film as the uppermost layer, an ethylene vinyl alcohol copolymer film as the intermediate layer, and a coextruded two-layer film as the lowermost layer, wherein the coextruded two-layer film is polyethylene- It consists of two layers, a cohesive failure sealant layer made of polypropylene blend polymer and a support layer made of a resin having good heat fusion property with the polyethylene-polypropylene blend polymer, and the side surface of the support layer faces the intermediate layer side. A plastic lid material that is laminated on the.