JPH1111468A - Hermetically sealing container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discharge steam as it is, generated when a container with a cover is heated in a microwave oven or the like and easily heat and cook food, by providing a seal layer having a specified melting point at the inside face of the cover and hermetically heat-sealing it on the flange of the container body. SOLUTION: A polypropylene film or a laminate material with the polypropylene film is laminated on the inside face of a paper tray-shaped container body 10 by vacuum forming or both vacuum forming and pressure forming. After food has been charged in the container body 10, a cover 20 provided with a seal layer with melting point of 85-110 deg.C and composed of either polyethylene synthesized with a singlesite catalyst or ethyleneα olefin copolymer is hermetically heat-sealed on the flanges 4, 5, 8 of the container body 10 at a temperature higher than the melting poit of the resin of the seal layer and lower than the melting point of the polypropylene layer. In this way, the container can be heated without unsealing a part of the cover.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a container in which the contents of uncooked and cooked foods are filled and stored, and the lid is sealed with a fixed sealing strength. And a sealed container which does not burst.

[0002]

2. Description of the Related Art As a container for storing frozen foods and the like, for example, as shown in Japanese Patent Publication No. 52-4315, a tray-shaped container in which a blank made of paperboard coated with a synthetic resin is assembled has been proposed and put into practical use. Have been. This tray-shaped container is coated with a synthetic resin on the inner surface,
In addition, since the blank is folded back and formed so that the end face of the blank is not exposed at the corner, the blank can be used for contents containing a liquid material or permeable contents.

On the other hand, recently, such a paper tray-shaped container is filled with cooked food or semi-cooked food, and then sealed with a lid material. When used, the tray-shaped sealed container is directly used in a microwave oven. There is a demand that the food be cooked or cooked in an oven or used as it is as it is. Therefore, as the synthetic resin provided on the inner surface, polypropylene having both heat resistance and heat sealing properties is preferable, and in order to withstand the heating step, it is preferable to use a film of 100 μm or more.

[0004] However, when the sealed container is heated in a microwave oven, the sealed lid must be partially or entirely peeled off from the container body. As described above, there is a demand for a so-called contradictory function that the sealing property must be excellent before use under heating and the opening property must be excellent during use.

[0005] Further, as a container body, for example,
As shown in 1-31-1202 and Japanese Utility Model Publication No. 54-42830, a tray-shaped container is proposed in which a synthetic resin film is heated and softened on the inner surface of an outer container made of paper and laminated and bonded by means such as vacuum forming. Have been. This tray-shaped container could be configured so as to have no step in the flange portion, and could be used as a container having good sealing performance.

Further, a plastic having a certain adhesive strength with the polypropylene layer has been used for an inner surface sealing layer of a lid member for sealing an opening of a container body having a polypropylene layer as an inner surface. It is common to use a polyethylene resin in view of a certain adhesive strength and releasability.

[0007]

As described above, when the polypropylene layer of the container main body and the polyethylene resin of the sealing layer of the lid member are sealed and sealed, heating or cooking as it is does not exhaust the gas. Due to the risk of rupture, a portion of the lid had to be opened and heated before heating.

[0008]

SUMMARY OF THE INVENTION The present invention is directed to a sealed container in which a tray-shaped container body is filled with contents and then sealed and sealed with a lid material.
Polyethylene or ethylene-α-olefin made of a polypropylene film alone consisting of a paper base material having a flange on the opening periphery or a laminated structure material having a polypropylene film on the inner surface and synthesized using a single-site catalyst on the inner surface of the lid material A sealing layer having a melting point of 85 ° C. to 110 ° C. made of any one of the copolymers is provided, and a lid material is provided on the flange portion of the container body at a temperature not lower than the melting point of the lid material and not higher than the melting point of the polypropylene film of the container body. A sealed container characterized by being heat-sealed and sealed.

Further, the present invention provides a method wherein the container body is formed by vacuum forming, or a vacuum forming and air pressure forming, a polypropylene film on the inner surface of a paper-based outer container or a laminated material having a polypropylene film on the inner surface. It is a hermetically sealed container that is integrated by using it together. Further, the present invention is a sealed container in which the polypropylene film is any one of polypropylene alone and a resin obtained by mixing polypropylene with an ethylene resin. Further, the present invention is a sealed container wherein the sealing layer of the lid member is a co-extruded film.

[0010]

Embodiments of the present invention will be described below. As shown in FIG. 1, the present invention is a sealed container in which an opening of a tray-shaped container main body 10 is sealed with a lid member 20. The tray-shaped container body 10 includes a pair of side plates 2, 2, and a pair of side plates 3, 3, which are opposed to the four sides of the rectangular bottom plate 1 inclining upward and outward. Then, an inverted isosceles triangular-shaped triangular corner plate 6 and an overlapping piece 7 are provided on the side edges of the side plates 2 and 2, respectively, and the overlapping piece 7 is provided. It has a corner formed by a triangular corner plate. Also,
A flange 4 extending horizontally outward is provided at the upper end of the side plates 2 and 2, and a flange 5 extending horizontally outward is provided at an upper end of the side plate 3. A flange 8 is provided which extends horizontally outward from above the corner plate 6.

Then, a synthetic resin film 40 is laminated and adhered to the inner surface of the paper tray-shaped container body 10 by vacuum forming or a combination of vacuum forming and pressure forming to be integrated. Further, the bottom plate 1,
The printed layer 30 is provided on the entire outer surface of the side plates 2 and 2, the side plates 3 and 3, the triangular corner plate 6, the flanges 4, 5 and 8, or partially.

Further, as shown in FIG. 4, the tray-shaped container body does not need to be provided with the triangular corner plate 6. In order to obtain the rigidity of the tray-shaped container body, it is necessary to overhang the overlapping piece on the adjacent side plate. Further, the superposed pieces need to be superposed on the inner surfaces of the adjacent side plates. This is because, in this state, the synthetic resin films are laminated and adhered, and when they are integrated, the polymer pieces are also adhered by the synthetic resin film. Further, the tray-shaped container body may be a polygonal tray such as an octagonal tray container as shown in FIG.

On the other hand, the lid member 20 for sealing the opening of the tray-shaped container body is provided with the flange 4 of the tray-shaped container 10,
A cover material having a shape and dimensions conforming to 5 and 8, wherein a seal layer is laminated and adhered to the inner surface, and a printed layer 30 is provided on the entire outer surface or an appropriate portion. The shape of the lid member 20 can be various shapes according to the tray-shaped container body.

After filling the tray-shaped container body 10 with food, the flange 4 of the tray-shaped container body 10
The lid member 20 is superimposed on 5 and 8, and the inner surfaces of both members are sealed and sealed by heat fusion before use.

In the present invention, as shown in FIG. 3, the synthetic resin film 40 is provided only on the inner surfaces of the tray-shaped container body 10 and the lid member 20.
It is necessary to provide. This causes a phenomenon that when the container is heated by a microwave oven, an oven, or the like, the moisture of the paper 50 as the base material boils and evaporates, and appears on the surface of the paper. As a result, when the synthetic resin film is provided on both sides of the paper, there is a problem that the vapor peels off the adhesive between the paper and the synthetic resin film. At this time, if a synthetic resin film having a low melting point is arranged, there is a problem that the synthetic resin film foams due to the melting of the synthetic resin film itself and the ejection of the steam.

Therefore, according to the present invention, when a paper substrate is used, the synthetic resin film is provided only on the inner surface, and is not provided on the outer surface, so that the release of vapor is not hindered. Also,
When a synthetic resin film is disposed on the outside, another means that does not hinder the release of such a vapor can be achieved by laminating and bonding a highly permeable synthetic resin film having fine through holes.

The paper base 50 used for the tray-shaped container body 10 and the lid member 20 has appropriate rigidity (for example, a basis weight of 200 to 500 g / m ² ).
In order to impart resistance to heating by a microwave oven, an oven, or the like, it is necessary to use a material that does not generate odor due to heating or has low odor. As a material satisfying this requirement, a paper made of virgin pulp is suitable. Further, since it is necessary to prevent adhesion of moisture generated by heating and cooking, it is necessary to use a material that is resistant to water and does not absorb moisture from the end face, or has a low material. As a material satisfying this requirement, a material generally called cup base paper is suitable.

These required qualities are determined when the sealed paper container is frozen or refrigerated in a refrigerator or the like, or when the container is degraded due to dew condensation on the surface of the container from the storage state to the purchase and return by the consumer. It is also effective for the purpose of prevention. Further, oil resistance can be imparted as required. Further, it is necessary that the material be a material that does not peel off the paper in peeling strength with the lid when opened.

The synthetic resin film 40 used in the tray-shaped container body 10 is excellent in water resistance, maintains sufficient hermeticity during storage such as refrigerated freezing after filling and sealing the contents, and has excellent heat-fusing properties. Needless to say, resistance to heating of a microwave oven, an oven or the like is required. That is, high water resistance and heat resistance are required.

For example, the layer in contact with the contents is made of polypropylene (PP), specifically, a homopolypropylene, a random polypropylene copolymer, or a block polypropylene copolymer. Is preferred. The layer in contact with the outer container is
It is a synthetic resin film comprising at least two layers using an ethylene-based copolymer layer having a carbonyl group. The thickness of this synthetic resin film is required to be 100 μm or more for moldability, heat resistance and content protection, and is preferably 1 μm.
The range is from 00 to 200 μm.

Specific examples of the ethylene-based copolymer containing a carbonyl group include ethylene-methyl methacrylate copolymer, ethylene-vinyl acetate copolymer, and ethylene-acrylic ester-maleic anhydride terpolymer. The polymer is raised. The synthetic resin film 40 may have a multi-layer structure in which a PP layer other than the PP alone, a PP other than the PP used on the side in contact with the content, a polyethylene, or an amorphous polyester is used in addition to the above-described structure. Good. Each of the synthetic resin films may be laminated by a dry lamination method, but a film formed by a co-extrusion method, which is simultaneously melt-extruded, is preferable.

On the other hand, the lid for sealing the opening of the tray-shaped container body must have both sealing properties and opening properties. Are preferably laminated. This peelable resin has a melting point of 85 ° C to 110 ° C.
Polyethylene polymerized by single-site catalyst at ℃
Alternatively, it is preferable to use a resin obtained by mixing an ethylene-α-olefin copolymer and an ethylene-α-olefin copolymer polymerized by a multisite catalyst. Then, heat sealing is performed at a temperature not lower than the melting point of the resin used for the sealing layer of the lid material and not higher than the melting point of the polypropylene layer.

When the printing layer 30 is provided on the tray-shaped container body 10, it is necessary that the ink has resistance to heating by a microwave oven or an oven. That is, high heat resistance is required. Further, it is necessary that no odor is generated or low due to heating. Further, air permeability is required so as not to hinder the release of steam from the paper due to the heating.

The printing layer 30 used for the tray-shaped container body 10 can be provided with an overcoat varnish (OP varnish) 31 on the outermost surface of the printing layer in addition to the ink 31 for forming a picture. By providing this OP varnish, when manufacturing a tray-shaped container, the synthetic resin film is laminated and adhered to the paper substrate by vacuum forming or vacuum pressure forming together, and is integrated in a mold. By providing the OP varnish, it is easy to take out the tray-like container from the mold, and the deformation of the tray-like container main body in the take-out process,
Destruction can be prevented. This OP varnish also needs to have heat resistance, air permeability, and generation of odor due to heating, like other inks.

[0025]

As described above, the present invention has the following effects. That is, a polypropylene layer is vacuum-molded on the inner surface, or at least a layer in contact with the contents is formed by a combination of vacuum molding and air-pressure molding, and polyethylene or ethylene-α polymerized by a single-site catalyst is used as a seal layer for the one-side cover material. Since an olefin copolymer, or a resin obtained by mixing an ethylene-α olefin copolymer polymerized by a multi-site catalyst with the resin, was used,
Before heating, it has complete sealing properties, and when heated in a microwave oven or the like, the generated steam can be exhausted as it is, so that a container in a microwave oven, an oven or the like can be easily used as a cooking container.

[Brief description of the drawings]

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

FIG. 2 is a plan view showing an embodiment of the container body of the present invention.

FIG. 3 is a sectional view showing the same embodiment of the container body of the present invention.

FIG. 4 is a plan view showing a second embodiment of the container body of the present invention.

FIG. 5 is a plan view showing a third embodiment of the container body of the present invention.

[Explanation of symbols]

 10 容器 Container body 20 ‥‥‥‥‥ Lid material 30 ‥‥‥‥‥ Printing layer 31 ‥‥‥‥‥ OP varnish 40 合成 Synthetic resin film 50 ‥‥‥‥‥ Paper substrate 1 ‥‥‥‥‥ Bottom plate 2, 3 側 Side plate 4, 5, 8 フ ラ ン ジ Flange 7 重合 Polymerized piece

Claims (4)

[Claims] 1. A sealed container, in which contents are filled into a tray-shaped container body and then sealed and sealed with a lid material, wherein the container body is formed of a paper base material having an open upper surface and having a flange on the periphery of the opening. The melting point consisting of either polyethylene or ethylene-α-olefin copolymer, consisting of a polypropylene film alone consisting of a laminated material having a polypropylene film on the inner surface, or a single-site catalyst on the inner surface of the lid material 85 ° C to 110 ° C
Wherein the lid is provided on the flange portion of the container body, and the lid is heat-sealed at a temperature not lower than the melting point of the lid material and not higher than the melting point of the polypropylene film of the container body. 2. A container body in which an outer container made of paper is made of a polypropylene film on the inner surface or a laminated material having a polypropylene film on the inner surface by vacuum forming or a combination of vacuum forming and pressure forming. The sealed container according to claim 1. 3. The sealed container according to claim 1, wherein the polypropylene film is made of one of polypropylene alone and a resin obtained by mixing ethylene resin with polypropylene. 4. The sealed container according to claim 1, wherein the sealing layer of the lid member is a co-extruded film.