JPH0585570A - Sealed container - Google Patents

Abstract

PURPOSE:To obtain a transparent sealed container good in formability and high in sealability and rigidity. CONSTITUTION:The sealed container is provided with a polypropylene made container body having a flange part 2b and a plastic made lid 3 having a heat sealing part 3b adapted to be heat sealed to the flange part 2b. The container body is formed of a laminate sheet 20 whose outer layer is constituted of the blended polypropylene layers 21 and 25 formed by adding a polypropylene random copolymer to a polypropylene homopolymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed container which is filled with food such as fruit and jelly liquid and has excellent transparency.

[0002]

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

Of these, the plastic container body has a container body and a flange portion provided at the upper end opening of the container body. The container body is formed by thermoforming a plastic laminated sheet. It On the other hand, the lid member is heat-sealed to the flange portion of the container body.

That is, the lid member has a heat-sealing portion that is heat-sealed to the flange portion of the container body and covers the opening of the container body.

[0005]

As described above, the container body is formed by thermoforming a polypropylene sheet at a temperature below the melting point of polypropylene. The container body thus prepared is filled with fruit, jelly liquid, etc., and the flange portion of the container body is heat-sealed with the heat-sealing portion of the lid member.

In such a case, if a container body having a good moldability and a good heat-sealing property can be obtained, a sealed container having a good sealing property and transparency can be obtained, which is convenient.

The present invention has been made in view of the above points, and an object thereof is to provide a hermetically sealed container having excellent hermeticity and transparency.

[0008]

The present invention relates to a hermetically sealed container provided with a polypropylene container body having a flange portion at the upper end opening, and a plastic lid member having a heat seal portion heat-sealed to the flange portion. The container body is formed by preheating a plastic sheet containing polypropylene resin as a main component to a temperature not higher than the melting point of polypropylene and pressure molding the sheet, and at least the outer layer on the lid side of the sheet has a single polypropylene weight. It is a mixed polypropylene layer formed by adding a random copolymer of polypropylene to the coalescence, of which the weight ratio of the homopolymer of polypropylene to the random copolymer is 90-
The sealed container is characterized in that it is 70:10 to 30.

[0009]

According to the present invention, at least the outer layer of the polypropylene sheet on the side of the lid material is a mixed polypropylene layer having high heat sealability and moldability and high strength. It is possible to obtain a container body which is good, has molding stability, has high strength, and is transparent.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

1 to 4 are views showing an embodiment of a sealed container according to the present invention. As shown in FIGS. 1 and 2,
The sealed container 1 is configured by filling a solid fruit 4 and a jelly liquid 5 in a plastic container main body 2 and sealing the container main body 2 with a plastic lid member 3.

Of these, the container body 2 includes a container body portion 2a and a flange portion 2b provided on the periphery of the upper end opening of the container body portion 2a.
It consists of

On the other hand, the lid member 3 is the flange portion 2 of the container body 2.
The heat-sealing portion 3b is heat-sealed (fused) to b, and the dropping lid portion 3a is provided inside the heat-sealing portion 3b. The drop lid portion 3a covers the opening of the container body 2 and is connected to the heat seal portion 3b via the first step portion 7 and the second step portion 8.

The shape of the lid member 3 is as shown in FIG.
Corresponding to the shape of the opening of the
A tab 10 is attached for peeling off. The shape of the lid material can be various shapes such as a square shape, a round shape, and a hexagonal shape according to the container body 2.

Next, the properties of each of the above constituent members will be described. The container body 2 is formed by thermoforming a plastic laminated sheet 20 as shown in FIG. 3, and the laminated sheet 20 has a layer structure in which the mixed polypropylene layer 21 /
A single polypropylene layer 22 / ethylene / vinyl alcohol copolymer layer 23 / a single polypropylene layer 24 / a mixed polypropylene layer 25. A mixed polypropylene layer may be used instead of the single polypropylene layers 22 and 24.

Of these, the mixed polypropylene layers 21, 2
5 is constituted by adding a polypropylene random copolymer to a polypropylene homopolymer, and the ratio of the polypropylene homopolymer to the random copolymer is 90%.
It is about 70:10 to 30. A homopolymer of polypropylene is homopolypropylene consisting of polypropylene alone. On the other hand, the random copolymer of polypropylene is obtained by simultaneously polymerizing a mixed gas of propylene and a comonomer such as ethylene, and the comonomer is randomly distributed in the propylene chain, and the comonomer prevents propylene from crystallizing. Comonomers are other α-olefins (ethylene, butene-1, hexene-1, etc.). In the polypropylene random polymer, the comonomer content is 1 to 10 wt%, preferably 3 to 5 wt%.

As described above, the random polymer of polypropylene is characterized in that the comonomer interferes with the crystallization of propylene, so that the degree of crystallinity is lowered and the polypropylene is softened, the impact strength is increased and the melting point is lowered.

Next, the characteristics of the mixed polypropylene layer will be described in comparison with the single polypropylene layer. In this example, as the mixed polypropylene, a mixture of a homopolymer of polypropylene and a random copolymer of polypropylene in a weight ratio of 80%: 20% was used.
The properties of the mixed polypropylene layer thus mixed are shown in Tables 1 to 5.

The heating behavior is summarized in Table 1 and described in detail with reference to FIG.

[0020]

[Table 1] Of these, FIG. 4A shows the heating behavior of the mixed polypropylene, and FIG. 4B shows the heating behavior of the single polypropylene.

As shown in FIGS. 4 (a) and 4 (b), the mixed polypropylene has a retention time of 14.5 seconds, and the single polypropylene has a retention time of 8.5 seconds. ing. In this way, since the mixed polypropylene has a long holding time, sagging due to heating is reduced and moldability is improved. Next, Table 2 shows the tensile yield strength and the like.

[0022]

[Table 2] Further, according to Table 2, it is understood that in the case of the mixed polypropylene, the tensile yield strength, the tensile breaking strength and the punching impact strength are all improved as compared with the single polypropylene. [Experiment 1] After filling a 120-g container having a single polypropylene cup and a mixed polypropylene cup with water,
The drop test was performed at room temperature of 23 ° C. In the drop test, 30 specimens each were dropped twice under the iron surface, and it was confirmed that there were no cracks. It was confirmed that the height was 50, 80, 120, 150 cm in order. The test was terminated when the cracks occurred. The results are shown in Table 3.

[0023]

[Table 3] From Table 3, it was found that the mixed polypropylene cup had a drop strength higher than that of the single polypropylene cup.

Next, the haze value of the container will be described with reference to Table 4.

[0025]

[Table 4] As shown in Table 4, the transparency of the molded product of the mixed polypropylene is equal to or higher than that of the single polypropylene. It can be said that the haze value is 30% or less on the side wall of the container and the container has transparency.

On the other hand, the lid member 3 shown in FIG. 2 is composed of a gas barrier laminate sheet of, for example, a single polypropylene layer / ethylene / vinyl alcohol copolymer layer / sealant layer,
The lid member 3 is heat-sealed with the sealant layer facing the flange portion 2b side of the container body 2.

[Experimental Example 2] After filling a single polypropylene container body and a mixed polypropylene container body with water,
Sealant lid materials made of PP and PE blends prepared by the co-press dry lamination method were heat-sealed and sealed in these container bodies, and the seal strength was investigated. The results are shown in Table 5.

[0028]

[Table 5] As shown in Table 5, at the same sealing temperature, the mixed polypropylene container body has a seal strength improved by about 0.2 to 0.5 kg / 15 mm as compared with the single polypropylene container body. Therefore, it can be said that the container body made of mixed polypropylene has a lower temperature sealing property.

Next, a method of manufacturing the hermetically-sealed container having such a structure will be described. First, the laminated sheet having the two types of layered structure as described above is vacuum-pressurized at a temperature not higher than the melting point of polypropylene to form the container body 2 and the lid member 3 having good transparency.

Next, the solid fruit 4 and the jelly liquid 5 are filled in the container body 2, and the flange portion 2b of the container body 2 is heat-sealed with the heat-sealing portion 3b of the lid member 3 to seal the container body 2. In this way, the sealed container 1 is manufactured.

According to this embodiment, in the laminated sheet 20 constituting the container body 2, the layer on the side of the lid material 3 is the mixed polypropylene layer 21 having a high heat-sealing property. 2b and the lid member 3 heat seal portion 3
It is possible to improve the heat-sealing property with b and perform a lower temperature sealing. Therefore, it is possible to obtain a hermetically sealed container having excellent hermeticity. Further, since the laminated sheet 20 constituting the container body 2 has the mixed polypropylene layers 21 and 25 having high moldability on the lid member 3 side and the opposite side, respectively,
The container body 2 can be provided with molding stability. Further, as described above, the mixed polypropylene layers 21 and 25 are
Since it has excellent properties with respect to tensile yield strength, tensile breaking strength, and punching impact strength, the strength of the container body 2 can be improved.

Further, the contents can be made to look fresh in a container having good transparency and a haze value equivalent to that of single polypropylene. In addition, in the above-mentioned embodiment, an example in which both outer layers of the laminated sheet 21 are the mixed polypropylene layers is shown, but only the outer layer on the lid material side may be the mixed polypropylene layer.

[0033]

As described above, according to the present invention,
It is possible to obtain a container body having good heat-sealing properties with a lid material, good moldability, and high strength. Therefore, it is possible to obtain a hermetically sealed container having excellent hermeticity and high strength and transparency.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an embodiment of a sealed container according to the present invention.

FIG. 2 is a view taken along the line II in FIG.

FIG. 3 is a cross-sectional view showing a plastic laminated sheet constituting a container body.

FIG. 4 is a view showing heating behavior of mixed polypropylene and single polypropylene.

[Explanation of symbols]

 1 Sealed Container 2 Container Body 2a Container Body 2b Flange Part 3 Lid Material 3b Heat Seal Part 20 Laminated Sheet 21 Mixed Polypropylene Layer 22 Single Polypropylene Layer 23 Ethylene / Vinyl Alcohol Copolymer Layer 24 Single Polypropylene Layer 25 Mixed Polypropylene Layer

Claims (1)

[Claims] 1. A hermetically sealed container comprising a polypropylene container body having a flange portion at an upper end opening thereof and a plastic lid member having a heat seal portion heat-sealed to the flange portion, wherein the container body is made of polypropylene resin. Plastic sheet as the main component is preheated to a temperature below the melting point of polypropylene and molded,
In this sheet, at least the outer layer on the lid material side is a mixed polypropylene layer formed by adding a random copolymer of polypropylene to a homopolymer of polypropylene,
Among these, the sealed container characterized in that the weight ratio of the polypropylene homopolymer and the random copolymer is 90 to 70:10 to 30.