JPH11139465A - Package for microwave oven - Google Patents

Abstract

(57) [Problem] To provide a peeling layer in a package that can be heated by a microwave oven without opening a hole before heating in a microwave or cutting a part of the package and opening the package. Improve product image by preventing direct food contact. An outer package obtained by heat-sealing a tray containing foods with a multilayer laminate composed of at least two layers including a heat-sealable sealant layer has at least a heat-sealing portion of a sealant. When the internal pressure of the package becomes equal to or higher than a predetermined value, the heat-sealed portion is peeled and opened by the release layer 4 on the back seal portion 5 side (at the bottom of the tray) ).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a package for a microwave oven used for packaging frozen foods, chilled foods and the like which can be heat-treated in a microwave oven or the like.

[0002]

2. Description of the Related Art It is accepted that frozen foods, such as dim sums such as shumai and meatballs, and baked rice balls, which can be cooked simply by heating, can be cooked easily and in a short time. Various products have been commercialized and sold according to the diversifying needs of family. Packaging materials used for these food packages are required to have good airtightness, gas barrier properties against oxygen, and the like. For this reason, packaging materials in which a heat-resistant plastic film and a metal foil are stacked and laminated are often used. As an example of the laminated packaging material, a material obtained by laminating an aluminum foil on an outer layer polyester film and laminating a polypropylene on the aluminum foil as an inner layer is often used. A bag-shaped package using this packaging material, filled with foodstuffs, and sealed by heat sealing has been commercialized.

[0003] A package made of a metal foil or a packaging material containing a metal deposited with a metal has no problem when heated using steam (hot steam), but when heated using a microwave oven, it is sparked by microwaves. Is generated, and there is a problem that heating cannot be performed in a microwave oven.

In order to be able to heat in a microwave oven,
It is necessary to use packaging materials that do not contain metals,
Plastic materials such as polyethylene, polypropylene, ethylene / vinyl alcohol copolymer, ethylene / vinyl acetate copolymer, ethylene / methacrylic acid copolymer, and polyvinylidene chloride are used. If the frozen food produced in this plastic package is heated as it is, the moisture contained in the content evaporates, increasing the pressure inside the container, and the package ruptures, and there is a risk of soiling the microwave oven and sometimes burning.

In order to prevent the rupture of the package, it is necessary to make a hole before heating with a microwave oven or to cut a part of the package to open the package, which is troublesome. There is a strong demand that the package be heated in a microwave oven without any modification. Silicone, ethylene-vinyl acetate copolymer, polyamide / nitrocellulose are used to release the vapor from the seal by the vapor pressure during heating. Is coated on the seal portion as a release agent.

[0006] Although the release agent is generally said to be harmless, direct contact with the contents is not very desirable as a product image.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a plastic package which can be heated in a microwave oven and has a structure in which an opening is formed from a release layer by vapor pressure and the release layer does not directly touch the contents. A microwave oven package is provided.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. The present invention relates to a method for heat-sealing a tray containing foods by heat-sealing a multilayer laminate comprising at least two heat-sealable sealant layers. In the obtained outer packaging, the heat seal surface of the sealant is preliminarily applied to at least a portion to be heat-sealed, and when the internal pressure of the packaging becomes equal to or higher than a predetermined value, the heat seal portion is pressed by the pressure. A package for a microwave oven, wherein a peelable layer capable of being peeled and opened is provided on the back seal portion side (the bottom side of the tray).

3. The microwave oven package according to claim 1, wherein the base film of the multilayer laminate is a barrier film on which an inorganic oxide is deposited.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 shows a state in which a product including a tray is packaged with a packaging material, and a release layer is provided on the bottom side of the tray container. 2 is a cross-sectional view taken along line XX in FIG. 1. FIG. 3 (a) is an end view taken along line YY of the heat seal portion at the end in FIG. 1, and FIG. 3 (b).
FIG. 4 is a diagram showing a state in which the packaging material is peeled off from the release layer when the microwave package is heated and is opened.

In FIG. 1, the release layer (4) is partially applied to the heat seal portion (3) of the sealant of the package (1). The heat seal part (3) peels off from a peeling layer by pressure, and shows the package which can be opened. Release layer (4)
By forming the package, it is not necessary to open the package in advance when heating in a microwave oven, so that the package can be heated while maintaining the sealing property, and the package is reliably opened, so that the package due to a rise in the pressure inside the package is formed. Can be prevented from exploding.

The release layer (4) is provided on the back seal side (the bottom side of the tray) to prevent the contents placed on the tray from directly touching. That is, a release agent is applied to the packaging material (10a) located on the bottom side of the tray in FIG. 3 and heat-sealed at the end with the packaging material (10b) located on the top side of the tray.

As the release agent, silicone, ethylene / vinyl acetate copolymer, polyamide / nitrocellulose, cyclized rubber and the like are used.

A heat-resistant plastic film such as polyester (PET), polypropylene (PP) or nylon (Ny) is used as the base film (11) of the packaging material, and unstretched polypropylene (CPP) is used as the sealant layer (13). ), Low density polyethylene (LDPE), and linear low density polyethylene (L-LDPE). When the above-mentioned thermoplastic film is laminated on the base film (11) as a sealant layer (13) to produce a packaging material, an adhesive layer (12) is provided as necessary.

Further, a barrier film on which an inorganic oxide such as silicon oxide or aluminum oxide having a high barrier property against oxygen or water vapor is deposited as a base film for protecting foods of the contents, or as a base film, When a composite film obtained by laminating a film is used, a package having excellent gas barrier properties can be obtained.

As shown in FIG. 3 (b), when the pressure inside the package rises to a certain level or more due to the steam generated from the food as the content by heating, the release layer (4) and the sealant layer ( An opening (7) is formed by peeling and opening from the interface with (13), and the opening (7) is evacuated to reduce the pressure and prevent the rupture of the package.

Regarding where and how many and in what width the release layer (4) is to be provided on the heat seal portion (3), the weight and type of the food as the contents, the shape of the package, etc. May be appropriately selected and determined according to the conditions. In FIG.
Although the striped layer is shown in the figure, the shape of the release layer may be arbitrarily set.

[0018]

EXAMPLES <Example> A base film (11) having a thickness of 3 μm as a sealant layer (3) was formed on a 12 μm-thick polyethylene terephthalate (PET) via an adhesive layer (12).
A cyclized rubber dissolved in xylene as a release layer is gravure coated on the back seal side with a width of 4 mm on a laminate packaging material laminated with 0 μm unstretched polypropylene (CPP).
Was provided. Left and right ends at 180 ° C and pressure 3
A heat-sealed portion (3) was formed by melting and pressing at kg / cm ² .

A comparative example was prepared under exactly the same conditions except that a release layer was not provided on the packaging material of the above-mentioned laminated body of the example. At this time, 15 "shumai" (225 g) were put in the tray as contents.

The microwave oven packages of these Examples and Comparative Examples were heated in a microwave oven at 500 W for 3 minutes, and the state after heating was visually evaluated.

In the case of the comparative example, there is a case where the internal pressure is increased by heating and the resin bursts.
The microwave oven was opened with the release layer, and did not rupture by heating and did not stain the microwave oven.

[0022]

According to the package of the present invention, since the opening is surely opened when heating, it is necessary to make a hole or cut a part before opening the package before heating in a microwave oven. Eliminate the hassle of becoming unnecessary. Moreover, there is no danger of burning the microwave oven and no risk of burns due to the rupture. Further, since the release layer does not directly touch the food of the contents, the image of the product is not spoiled.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a package according to claim 1 of the present invention.

FIG. 2 is a sectional view taken along line XX in FIG. 1;

FIG. 3A is an end view of a heat-sealed portion taken along a line YY in FIG. 1; FIG. 3B is an end view showing a state where the portion (a) is opened by heating.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Packaging container 2 ... Tray 3 ... Sealant layer part 4 ... Release layer 5 ... Back seal part 10 ... Opening 10a ... Packaging material located at the bottom of the tray 10b ... Packaging material located at the top of the tray 11 ... Group Material film 12: adhesive layer 13: sealant layer

Claims (2)

[Claims] 1. An outer package obtained by heat-sealing a tray containing foodstuffs with a multilayer laminate comprising at least two layers including a heat-sealable sealant layer, wherein at least heat is applied to the heat-sealing surface of the sealant in advance. When the internal pressure of the package becomes higher than a certain level, the seal layer is opened at the back seal part side (tray bottom side) when the internal pressure of the package exceeds a certain level. A package for a microwave oven, wherein the package is provided. 2. The microwave oven package according to claim 1, wherein the base film of the multilayer laminate is a barrier film on which an inorganic oxide is deposited.