JP2596588Y2 - Food containers - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a container for retort foods, and more particularly to a food container comprising a composite sheet suitable for heating the contents of a food together with the container by a microwave oven.

[0002]

2. Description of the Related Art Conventionally, non-foamed polyester resins and non-foamed polyester resins have been used as food containers used for heating and cooking stored foods by using a microwave oven.
Many are formed from a sheet made of a polypropylene resin or a resin mixed with a filler. In addition, many of the multi-layer sheets have the resin sheet as a base layer and another resin film layer laminated thereon.

However, non-foamed polyester resins and polypropylene resins are inferior in heat insulation properties, and when cooked at a high temperature using a microwave oven, the containers cannot be handled with bare hands, which is inconvenient. . Particularly, in the case of oil-based foods, heat resistance of a polypropylene-based resin or the like is insufficient because the heating temperature of a microwave oven may be 150 ° C. or more.

[0004] For this reason, a foamed sheet made of a heat-resistant polyester resin such as polyethylene terephthalate or a polyamide resin such as nylon has excellent heat insulation properties, and is therefore an optimal material for heating cooking in a microwave oven. However, as containers for retort foods, which are increasingly used for cooking in microwave ovens, there is a problem in the preservability of the stored foods. This is because there is a problem in the gas barrier properties of the container.

[0005] That is, although a foamed sheet of a polyester resin or a polyamide resin is excellent in heat resistance and heat insulation, it does not have sufficient gas barrier properties by itself, and can be stored for a long time even after retort sterilization. There is a problem in the properties, and it cannot be said that it is preferable. This problem is not limited to the polyester-based resin described above, but also applies to foamed sheets made of other resin materials such as the polypropylene-based resin described above.

[0006] In order to solve the above problems, there are many methods of laminating a resin film such as an ethylene-vinyl alcohol copolymer or a polyvinylidene chloride resin on the inner surface of a container by using the foamed sheet as a base layer. Has been proposed,
The ethylene-vinyl alcohol copolymer has a significantly reduced gas barrier property against oxygen and the like under moisture or a humid atmosphere. In particular, the gas barrier property after retort treatment is greatly reduced, and as it is, the long-term preservability of the content of the retort food is inferior.

[0007] Therefore, it is generally necessary to laminate a resin film having further excellent water resistance, such as a polypropylene film, on the resin film layer of the ethylene-vinyl alcohol copolymer or the like having excellent gas barrier properties. A complicated multi-layered structure, and the laminated foam sheet waste and used containers generated during molding become industrial wastes that cannot be collected and reused, and have recently become a particular social problem. In addition, limited resources cannot be used effectively.

Accordingly, in the present invention, a thermoplastic polyamide resin is used as a material having excellent heat resistance, particularly a foamed sheet having heat insulating properties, as a container for this kind of retort food which is cooked and eaten in a microwave oven. The above-mentioned problem is solved by using as a base material and combining this with a nylon resin film having excellent gas barrier properties.

The present invention combines a foamed sheet of a thermoplastic polyamide resin with a nylon resin film having excellent gas barrier properties, and uses a composite sheet made of this combination as a material to provide heat resistance, heat insulation properties, gas barrier properties, and the like. It can be used as a container for retort foods that are eaten by heating in a microwave oven, and waste of laminated foam sheet and used containers generated during molding can be collected and reused. A container is provided.

[0010]

The food container of the present invention which solves the above-mentioned problems is a container having a foamed sheet of a thermoplastic polyamide resin as a base layer, wherein meta-xylene diamine and adipic acid are used as inner layers of the container. And a film layer made of a copolymer resin of the above is laminated on the base material layer and integrally molded.

The thermoplastic polyamide resin constituting the base layer is obtained, for example, by ring-opening polymerization of lactam, self-condensation of aminocarboxylic acid, or condensation of diamine and organic dibasic acid. As a linear polymer having
Nylon 6, Nylon 66, Nylon 10, Nylon 1
1, nylon 12, MXD6 nylon, nylon 61
2. Nylon 1212, Nylon 46, etc., or a polycondensate of terephthalic acid and trimethylhexamethylenediamine, which has some aromatic rings in its molecular structure. It is possible to include those which give amorphous to crystalline nylon, and among them, when amorphous nylon such as polycondensate of terephthalic acid and trimethylhexamethylenediamine is used, the film layer is used. This is particularly preferable because it can be more easily laminated by heat fusion.

A foamed sheet is formed by extruding and foaming the thermoplastic polyamide resin using a volatile agent such as butane, pentane, dimethyl ether, fluorocarbon or chlorofluorocarbon as a foaming agent. This foam sheet has a density of 0.05 to
By setting it to 0.8 g / cc, heat insulation and rigidity required for the intended food container can be obtained.

The above-mentioned nylon resin having excellent gas barrier properties is a polyamide obtained by polycondensation of metaxylenediamine and adipic acid, that is, a kind of nylon similar to the above-mentioned base material layer. Under normal conditions, a film using this resin has excellent gas barrier properties comparable to resin films of polyvinylidene chloride and ethylene-vinyl alcohol copolymer. In particular, by biaxially stretching this film, the gas barrier properties are significantly improved. Moreover, the gas barrier properties under an atmosphere containing a large amount of moisture and humidity are far superior to resin films such as the above-mentioned ethylene-vinyl alcohol copolymer, and are several times superior especially after retort treatment. It has oxygen barrier properties and has a fast recovery after retort treatment.

[0014]

As described above, the food container of the present invention has a foamed sheet of a thermoplastic polyamide resin as a base layer, and a film made of a copolymer resin of metaxylene diamine and adipic acid having excellent gas barrier properties on its inner surface layer. Since the layer is provided, the gas barrier properties as a container are very excellent, and the gas barrier properties are not significantly reduced especially in an atmosphere containing a lot of moisture or moisture, and the good gas barrier properties can be maintained even after retort treatment. , To ensure good long-term preservation of food.

In addition, the thermoplastic polyamide resin foam sheet as the base layer not only has a heat insulating property that can be handled by hand even after being heated in a microwave oven, but also has a heat-resistant thermoplastic polyamide foam. The resin container is a material, and since the film made of the copolymer resin of meta-xylene diamine and adipic acid laminated thereon is also excellent in heat resistance, the food container of the present invention in which these are integrally molded is a food container of this kind. It has sufficient heat resistance as a container, enables food to be retorted, and has no risk of deformation even when heated in a microwave oven.

Further, since the film composed of the thermoplastic polyamide resin as the base material layer and the copolymer resin of meta-xylenediamine and adipic acid laminated on the base material layer is a nylon resin of the same type, When stacking
It is possible to integrally mold by heat bonding without using an adhesive, and of course, use the same type of nylon resin as the adhesive layer, particularly preferably use amorphous nylon such as polycondensate of terephthalic acid and trimethylhexamethylenediamine It can be collected and reused even if it is a laminated foam sheet waste or a used container generated during molding. The resin recovered for reuse can be used in the range of 5 to 50 parts by weight based on 100 parts by weight of the thermoplastic polyamide resin as the base material layer to form a foamed sheet.
In other words, it is a resource that can effectively utilize limited resources and can also solve the problem of industrial waste, which has become a social problem.

[0017]

In the drawings, (A) shows a food container according to the present invention, and (B) shows a lid which is sealed to the food container (A) by means of heat sealing or heat bonding.

The food container (A) has a foamed sheet (1) of a thermoplastic polyamide resin as a base layer, and the inner layer of the container is made of a copolymer resin of metaxylenediamine and adipic acid having excellent gas barrier properties. Film layer (2)
From a composite sheet (3) obtained by extrusion lamination on the foamed sheet (1) as the base material layer by means of dry lamination or hot melt lamination or by co-extrusion to simultaneously extrude the base material layer and the film layer from the composite sheet (3). It is molded into a tray shape by molding means such as. (4) indicates an adhesive layer or a fusion layer.

In the embodiment shown in FIGS. 1 to 3, only the film layer (2) made of the copolymer resin of metaxylenediamine and adipic acid is laminated with the foamed sheet (1) as the base material layer. In order to improve the gas barrier property, the resin film can be used after being biaxially stretched. In this case, since it is difficult to laminate the stretched resin film layer (2) to the foamed sheet (1) as the base material layer, the gas barrier resin film is stretched as in the embodiment of FIG. Before, as an adhesive layer, a similar nylon resin, particularly preferably an amorphous nylon such as a polycondensate of terephthalic acid and trimethylhexamethylenediamine is used and laminated, and then stretched to form a stretched film. It can be easily laminated by laminating on the foamed sheet (1) as the base material layer. .

The thermoplastic polyamide-based resin foam sheet (1) serving as the base material layer has a density of 0.05 to 0.8 g.
/ Cc and a thickness of 0.3 to 5 mm are used. That is, the heat insulating property expected to have a density of the foamed sheet (1) larger than 0.8 g / cc cannot be obtained, and the density is 0.05 g / cc.
If it is smaller than cc, sufficient rigidity cannot be obtained. Further, when the thickness of the foamed sheet (1) is O.D. When the thickness is less than 3 mm, the heat insulating property and the shape retention are reduced, which is not preferable. When the thickness is more than 5 mm, the moldability is deteriorated, which is not preferable.

The resin film layer (2) made of a copolymer resin of meta-xylene and adipic acid has a thickness of 0.3
It is preferable that the thickness is 0.05 mm or less. If this resin is increased in crystallinity by biaxial stretching or the like, the gas barrier property is improved, so that even if the thickness is 0.05 mm or less, sufficient gas barrier performance can be obtained.

This resin film layer (2) is excellent in heat-resistant gas barrier properties, and particularly excellent in maintaining gas barrier properties in an atmosphere containing moisture and humidity.

Therefore, in the composite sheet (3) including the resin film layer (2), the decrease in the gas barrier property by the retort treatment is much smaller than that in the multilayer sheet including the ethylene-vinyl alcohol copolymer. Also, the recovery after processing is fast, and good gas barrier property can be maintained,
Good storage of the stored food can be achieved.

Moreover, the foamed sheet (1) as a base material is made of a thermoplastic polyamide resin having excellent heat resistance, and the resin film layer (2) laminated thereon is also excellent in heat resistance. In addition to having sufficient heat resistance as a container, it is possible to perform high retort treatment, and is not deformed by heating in a microwave oven, so that sufficient shape retention can be maintained.

Further, the foamed sheet (1) of the thermoplastic polyamide resin as a base material has excellent heat insulating properties, and can have excellent heat insulating properties which can be held by hand immediately after heating in a microwave oven. Is easy to handle.

Furthermore, a foamed sheet of a thermoplastic polyamide resin (1) is combined with a nylon resin film (2), which is a resin of the same type, and a composite sheet made of this combination is used as a material. Waste and used containers can be collected and reused.

[0027]

[Effect of the Invention] The food container of the present invention has a retort treatment by laminating a resin film layer made of a copolymer resin of meta-xylene and adipic acid on a foamed thermoplastic polyamide resin sheet as a base layer. Foods that can retain excellent gas barrier properties even afterwards, have heat resistance for long-term storage of food, and have properties such as heat insulation and shape retention that can be held by hand after heating, and are cooked and eaten with a microwave oven In particular, it can be suitably used as a container for retort foods. Furthermore, it is industrially effective that can be recycled and reused.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing an embodiment of the present invention.

FIG. 2 is a sectional view of the same.

FIG. 3 is an enlarged sectional view of a part of the above.

FIG. 4 is a partially enlarged cross-sectional view showing another embodiment.

[Explanation of symbols]

(A): Food container of the present invention (1): Foamed sheet of thermoplastic polyamide resin (2): Resin film layer made of copolymer resin of meta-xylene and adipic acid (3) ..Composite sheet (5) ・ ・ ・ Nylon resin layer

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B65D 1/00-1/48 B65D 67/00-79/02 B65D 81/18-81/30 B65D 81 / 38 B65D 85/00-85/84 B32B 1/00-35/00

Claims (2)

(57) [Scope of request for utility model registration] 1. A container comprising a foamed sheet of a thermoplastic polyamide resin as a substrate layer, wherein at least an inner layer of the container comprises a film layer comprising a copolymer resin of meta-xylene diamine and adipic acid as the substrate layer. A food container characterized by being laminated and integrally molded. 2. The food container according to claim 1, wherein the density of the foamed sheet of the thermoplastic polyamide resin is 0.05 to 0.8 g / cc.