JPH05254568A - Packaging material - Google Patents

Abstract

PURPOSE:To prevent oxygen gas, etc., from entering by a method wherein a packaging material consists of an outer sheet with a gas barrier layer, an inner sheet and a tight-closed space between the outer and inner sheets, and air in the tight-closed space is replaced with inert gas. CONSTITUTION:A packaging material 10 consists of an outer sheet 20, a tight- closed space 21 and an inner sheet 22. The outer and inner sheets 20 and 22 each are made of a three-layer laminate consisting of polypropylene 11, ethylene- vinyl alcohol copolymer 12 and polypropylene 11. The hems of the sheets 20 and 22 are bonded together to form the tight-closed space 21 between them and air in the tight-closed space 21 is replaced with inert gas such as N2 gas. And, a number of oxygen absorbents 15 and desiccants 16 are arranged in the tight-closed space 21. In addition, ethylene-vinyl alcohol copolymer 12 used for the outer and inner sheets 20 and 22 has an oxygen permeability of 5cc.25mum/m<2>.24hr or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packaging material used for a packaging container for containing food therein.

[0002]

2. Description of the Related Art Conventionally, a packaging container for containing food is formed by thermoforming a plastic laminated material. Further, injection molding may be performed by inserting a plastic laminated material into an injection mold and injecting a synthetic resin on the surface of the laminated material.

[0003]

By the way, both the laminated material used for thermoforming and the laminated material inserted into the injection mold have a gas barrier layer, which improves the gas barrier resistance of the packaging container. I am letting you.

However, the packaging container containing the food inside is retort (heat-treated) and put on the market, and when the gas barrier property of the laminated material is insufficient, the packaging container from the outside is exposed during this treatment. Oxygen may invade the inside and cause food inside to deteriorate. Further, during storage of the packaging container, oxygen may enter from the outside into the packaging container to deteriorate the food inside.

The present invention has been made in view of the above points, and an object of the present invention is to provide a packaging material capable of reliably preventing the intrusion of oxygen gas and the like.

[0006]

The present invention comprises an outer sheet having a gas barrier layer and an inner sheet forming a closed space layer between the outer sheet and the closed space device replaced with an inert gas. It is a packaging material characterized by the following.

[0007]

According to the present invention, gas such as oxygen in the outside air is prevented from permeating by each layer of the outer sheet, the closed space layer replaced with the inert gas and the inner sheet.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 are views showing an embodiment of a packaging material according to the present invention.

As shown in FIG. 1, the packaging material 10 comprises an outer sheet 20 and an enclosed space layer 2 between the outer sheet 20.
1 and an inner sheet 22 forming a unit 1. Of these, the outer sheet 20 and the inner sheet 22 are both made of a laminated material of polypropylene 11 / ethylene / vinyl alcohol copolymer (EVOH) 12 / polypropylene (PP) 11, and the outer sheet 20 and the inner sheet 22 have their peripheral edges adhered to each other. Thus, the closed space layer 21 is formed inside.

The inside of the closed space layer 21 is replaced with an inert gas such as N ₂ gas. Further, in the closed space layer 21, a large number of oxygen absorbents 15 and a large number of hygroscopic agents 16 are arranged. As the oxygen absorbent 15, an iron-based or ascorbic acid-based material is used.

Also, the outer sheet 20 and the inner sheet 2
The EVOH used in No. 2 has an oxygen permeability of 5 cc.
Those having a thickness of 25 μm / m ² · 24 hr or less are used.

According to this embodiment, between the outer sheet 20 and the inner sheet 22, the closed space layer 2 substituted with N ₂ gas is used.
1 is formed and the oxygen absorbent 15 and the moisture absorbent 16 are arranged in the closed space layer 21, the gas barrier property of the packaging material 10 can be greatly improved.

In the above embodiment, the packaging material 10 is used.
In the closed space layer 21 of the oxygen absorbent 15 and the moisture absorbent 1
Although the example in which 6 is arranged is shown, the oxygen absorbent 15 and the hygroscopic agent 16 do not necessarily have to be arranged, and only one of them may be arranged. Further, an example in which the outer sheet 20 and the inner sheet 22 are both made of a laminated material having EVOH is shown, but the inner sheet 22 is not necessarily made of E.
It is not necessary to have VOH and may be composed of a PP single layer.

Next, an application example of the present invention will be described with reference to FIG. The container body 32 having the flange portion 32a is molded using the packaging material 10 having the above-described configuration, and the lid member 33 made of the packaging material 10 is heat-sealed to the flange portion 32a to form the packaging container 30. . In this case, the packaging container 30 having an excellent gas barrier property can be obtained.

Next, referring to FIGS. 3 and 4, a first experiment of the oxygen permeation amount of the packaging material according to the present invention will be described.

First, as shown in FIG. 3, two packaging materials 10 according to the present invention were prepared. Then 2 sheets of packaging material 1
The peripheral edges 10a and 10a of 0 and 10 were adhered to each other to form the packaging container 40, and the inside 41 of the packaging container 40 was replaced with N ₂ gas.

Next, the packaging container 40 was stored under the storage conditions of a temperature of 37 ° C. and a humidity of 65%, and the oxygen partial pressure (%) of the inside 41 of the packaging container 40 was measured with time.

In the first experiment of the amount of oxygen permeation, the outer sheet 20 and the inner sheet 21 of the packaging material 10 were both laminated materials having a layer structure of PP / EVOH / PP. The following materials were used as the packaging material 10.

The inside of the closed space layer was replaced with N ₂ , and no oxygen absorbent or hygroscopic agent was used.

The inside of the closed space layer is replaced with N ₂ , and only the oxygen absorbent is arranged.

The inside of the closed space layer is replaced with N ₂ , and only the hygroscopic agent is arranged.

The inside of the closed space layer is replaced with N ₂ , and an oxygen absorbent and a hygroscopic agent are arranged.

At the same time, as a comparative example, the packaging material 10
Instead of the outer sheet 20 (PP / EVOH /
A packaging container similar to that shown in FIG. 3 was prepared using only the PP laminating agent), and the same oxygen permeation amount experiment was conducted.

Oxygen Permeation Rate The results of the first experiment are shown in FIG.
As shown in FIG. 4, in the case of the present invention, it is found that the oxygen permeation amount is extremely small as compared with the comparative example in which the outer container is used instead of the packaging material to form the packaging container. Therefore, it has been found that the packaging material according to the present invention has an extremely good oxygen transmission rate. In particular, when an oxygen absorbent and a moisture absorbent were arranged, almost no oxygen permeation was observed.

The reason why the oxygen content in the packaging container varies in FIG. 4 immediately after the start of the experiment is as follows. That is, even if the inside of the packaging container is replaced with N ₂ , it cannot be completely replaced, and a small amount of water vapor, oxygen and the like remain. Then, the water vapor and oxygen remaining inside these packaging containers are immediately absorbed by the oxygen absorbent, the moisture absorbent, and the like contained in the packaging material 10 forming the inner sheet 22, so immediately after the start of the packaging container. The internal oxygen partial pressure varies.

Next, another oxygen permeation amount experiment (second experiment) was conducted. In the second experiment of the oxygen permeation amount, instead of measuring the oxygen partial pressure (%) in the inside 41 of the packaging container 40, when the inside 41 of the packaging container 40 was replaced with N ₂ gas, methylene blue and a reducing agent were added together. After encapsulating and retort-treating, the oxygen permeation amount is determined from the change in the color of methylene blue. That is, the amount of oxidative permeation into the inside 41 of the packaging container 40 was determined by utilizing the characteristic of methylene blue that changes from transparent to blue (blue) as oxygen is absorbed.

Table 1 shows the results of the second experiment of oxygen transmission rate.

Table 1 Test subject Immediately after retort 1 week 2 weeks 3 weeks 4 weeks N ₂ substitution △ △ △ △ △ N ₂ substitution, oxygen absorbent ○ ○ ○ ○ ○ N ₂ substitution, hygroscopic agent ○ ○ ○ ○ ○ N ₂ substitution, oxygen absorbent ○ ○ ○ ○ ○ and moisture absorbent outer sheet substitute × × × × × × Methylene blue change △ Methylene blue slight ○ Methylene blue change As is clear from Table 1, in the case of the present invention, the amount of oxygen permeation is smaller than that of the comparative example. I understand.

[0029]

As described above, according to the present invention,
Gases such as oxygen in the outside air are less likely to permeate through the outer sheet, the closed space layer and the inner sheet. Therefore, it is possible to improve the storability of the contents such as foods stored in the packaging container made by using this packaging material.

[Brief description of drawings]

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

FIG. 2 is a side sectional view showing a packaging container made of the packaging material according to the present invention.

FIG. 3 is a side sectional view showing a packaging container prepared for conducting an oxygen permeation amount experiment of the packaging material according to the present invention.

FIG. 4 is a diagram showing the results of a first experiment of the oxygen permeation amount of a packaging material.

[Explanation of symbols]

 10 Packaging Material 11 Polypropylene 12 Ethylene / Vinyl Alcohol Copolymer 15 Oxygen Absorber 16 Moisture Absorber 20 Outer Sheet 21 Sealed Space Layer 22 Inner Sheet 30 Packaging Container 40 Packaging Container

Claims (3)

[Claims] 1. A package comprising an outer sheet having a gas barrier layer and an inner sheet forming a closed space layer between the outer sheet and the closed space layer, wherein the inside of the closed space layer is replaced with an inert gas. Materials. 2. The packaging material according to claim 1, wherein at least one of an oxygen absorbent and a moisture absorbent is arranged in the closed space layer. 3. The oxygen permeability of the gas barrier layer is 5 cc.25.
The packaging material according to claim 1, wherein the packaging material has a thickness of μm / m ² · 24 hr or less.