JPH10218118A - Seal packaging material for foodstuffs heat cooked by microwave oven - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly heat-cook foodstuffs sealed with a packaging material as it is by means of a microwave oven. SOLUTION: A tray 2 and a cover material 3 are heat-sealed to package foodstuffs 6 airtightly. Projecting ends 4a, 4b are provided at a corner of the tray 2 and cover material 3 to interpose a heating unit 5 therebetween. If the foodstuffs are cooked with its packaging material tightly sealed by a microwave oven, the heating unit 5 absorbs microwaves to generate heat. Until the sealing strength of a sealant layer 7 falls sufficiently by the generated heat, a proper heat cooking is performed in water vapor generated within the packaging material. If the temperature of the unit 5 reaches a predetermined temperature and hence the sealing strength of a heat-sealed part falls, the pressure in the packaging material is exerted on the heat-sealed part so that the heat-sealed part around the unit 5 is unsealed to allow the water vapor within the packaging material to escape to the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packaging material for hermetically packaging foods to be cooked in a microwave oven.
The present invention relates to a hermetically sealed packaging material capable of performing good heating cooking.

[0002]

2. Description of the Related Art With the spread of microwave ovens, various foods that can be provided to a dining table only by heating and cooking in a microwave oven have been commercialized. Such microwave cooking foods include polypropylene (PP), polyethylene (P
E), polyethylene terephthalate (PET), polyvinyl alcohol (EVOH), vinylidene chloride (PV
DC), vinyl chloride (PVC), and other thermoplastic plastic sheets and films, or a combination of these and laminated and packaged.

[0003] When heating and cooking in a microwave oven, a hole is made in the packaging material or a part of the packaging material is opened in advance, or after the packaging is unpacked and transferred to another container,
Furthermore, they are wrapped roughly in a wrapping film for cooking and then placed in a microwave oven. This prevents the moisture from evaporating during the heating of the food and causing the vapor pressure to rise abnormally inside the packaging material to prevent the packaging material from exploding. This is for a plump finish.

[0004]

However, in the above-mentioned conventional methods, if the degree of opening is insufficient or if the wrapping film is almost sealed, the boiling of water will be particularly severe. After the start of the process, the vapor pressure inside the packaging material rapidly increases, so that the packaging material may burst and a part of the food may be blown into the microwave oven. Conversely, if heating is performed after the packaging material has been sufficiently opened, the steam generated during heating cannot be used for cooking, and the finished product will have a crisp finish and the original taste of food. Will not be able to taste.

The present invention has been made in consideration of the above circumstances, and has as its object the purpose of heating and cooking in a microwave oven without any modification to a packaging material in which food is hermetically sealed.
A sealed package for microwave-heated food that can be cooked simply by putting it in a microwave oven as it is and then heating it, while preventing the food from spilling over due to the high vapor pressure inside the packaging material. To provide materials.

[0006]

In order to achieve the above-mentioned object, the present invention provides a heat-sealed portion in which the outer peripheral portions of a thermoplastic plastic packaging material are overlapped with each other and heated and welded in order to hermetically package food. A thin strip-shaped heating element that generates heat by being irradiated with waves is sandwiched therebetween. When heating and cooking is performed in a microwave oven, the heating element generates heat by being irradiated with microwaves, and partially softens or melts the heat seal portion to partially lower the seal strength. Thus, pressurized steam generated inside the packaging material is blown out from the portion where the sealing strength is reduced, and the hermetically sealed packaging of the packaging material is released.

As described above, by sandwiching the thin strip-shaped heating element between the heat sealing portions, the sealing is released from the portion where the packaging materials are overlapped with each other. For example, the lid is covered so as to cover the upper surface of the tray. In the case of a packaging material which is covered with a material and sealed, the lid material can be smoothly peeled off along the heat-sealed portion in the opening operation after being taken out of the microwave oven.

[0008] Until the heating element reaches a temperature at which the heat sealing portion is softened and melted, the inside of the packaging material gradually fills with steam, which is effectively used for cooking food. Then, after the heating element reaches a predetermined temperature and the sealing is partially released, the steam escapes to the outside of the packaging material, so that there is no possibility that the packaging material is ruptured.

[0009] When the food sealed in the packaging material is a liquid or a beverage, in order to prevent them from spilling out of the unsealed part, the packaging material must be self-supporting and must be free-standing. The heating element may be provided above the contents of (1).

As heating elements that generate heat by absorbing microwaves, there are known several heating elements such as microwave heating elements or microsusceptors. Japanese Patent Publication No. 4-68758 discloses a conductive substance in which aluminum and aluminum oxide are mixed as an example of such a heating element.

Other known heating elements include a titanium nitride (TiN) deposited layer and a stainless steel deposited layer. These heat generation characteristics are schematically shown in FIG. 1. In the figure, the TiN deposited layer, the aluminum deposited layer, and the stainless steel deposited layer represent the heat generation characteristics of the stainless steel deposited layer. In addition, these heat generation characteristics are as follows.
It is when it was made.

When the above is used as the heating element of the present invention, when the heating element reaches a temperature of about 180 ° C., a part of the surrounding packaging material or the heat seal is partially softened or melted to form a packaging material. If you make the configuration that the seal of the
Since the sealing of the packaging material is maintained in the substantially initial state for about 30 seconds after the heating and cooking is started in the microwave oven, the steam generated in the packaging material during that time can be used for heating and cooking as it is. Then, since the heat generated by the heating element lowers the sealing strength of the heat sealing portion, and furthermore, the internal pressure inside the packaging material is sufficiently increased, and the sealing of the packaging material is automatically released from the portion where the sealing strength is reduced. In addition, the pressurized steam in the packaging material can escape to the outside of the packaging material.

[0013]

FIG. 2 shows an example of an embodiment of the present invention. In this example, the packaging material for hermetic packaging is composed of two types of packaging materials, a tray 2 formed into a dish shape and a film-like lid material 3. After the food is served on the tray 2, the tray 2 and the lid 3 are heat-sealed at the outer periphery, and the inside is kept in a sealed state. As shown, the tray 2 and the lid member 3 have tongue-shaped protruding ends 4a and 4b at one corner. The protruding end 4b is placed on the tray 2 after heating and cooking.
Used as an open end when peeling off from

A heating element 5 that absorbs microwaves and generates heat is provided at a heat sealing portion with the protruding ends 2a and 3a. The heating element 5 is formed by depositing a thin film of aluminum on one side of a sheet-like support and laminating a polypropylene film on both sides thereof, as is known as a microsusceptor. It is shown.

As shown in FIG. 3A, the tray 2 is made of a thermoplastic resin having a three-layer structure using a polyurethane-based adhesive. A PP (polypropylene) layer 2a and a polyvinyl alcohol (EVOH) are sequentially arranged from the outside. : Eval) layer 2b and PP (polypropylene) layer 2c. The eval layer 2b has a function of blocking the flow of oxygen gas and preventing the food 6 inside from being spoiled. Similarly, the lid member 3 is also made of a thermoplastic resin having a three-layer structure using a polyurethane-based adhesive, and includes a PET (polyethylene terephthalate) layer 3a, a PET layer 3b on which ceramic is deposited, and a PP layer 3c in order from the outside. Film is used,
The PET layer 3b formed by ceramic vapor deposition has a function of blocking oxygen gas, similarly to the EVAL layer 2b.

As shown in FIG. 4, the heating element 5 has an aluminum vapor-deposited layer 5b formed on one surface of a PET film 5a, and furthermore, as shown in FIG.
PP on the front and back so that it can be heat-sealed
The film layers 5c, 5c are laminated with a polyurethane adhesive. Note that a heat-resistant paper 5d is sandwiched between the aluminum vapor-deposited layers 5b.

The heating element 5 is sandwiched between the protruding ends 4a and 4b of the tray 2 and the plastic film 3, and the outer peripheral portion of the cover 3 is overlapped with the outer peripheral portion of the tray 2 at a sealing temperature of 180 ° C. When heated, the tray 2 and the lid member 3 are brought into close contact with each other of the PP layers 2c and 3c, so that good heat sealing can be performed. Also, since the heating element 5 has the PP film layers 5c on both sides thereof, it is similarly melted in the above-mentioned heat sealing step to form the sealant layers 7, 7 shown in FIG. 3 and is fixed closely. As a result, the food 6 is sealed inside the packaging material.

The length of the heating element 5 is determined according to the length of the protruding ends 4a and 4b, one end of which faces the inside of the packaging material containing the food 6, and the other end of which extends to the outside of the packaging material. . By sandwiching such a heating element 5 in the heat sealing portion between the tray 2 and the lid member 3, a slight gap is formed around the heating element 5;
Since the P film layer is melted to form the sealant layer in a form that fills the gap, the inside of the packaging material is securely sealed.

In cooking the food 6 by heating, the packaging material is put into a microwave oven with the food material 6 kept in a sealed state without any modification. The heating of the food 6 is advanced by the irradiation of the microwave, and the inside of the packaging material is filled with water vapor. The heating element 5 also generates heat by starting the heating cooking,
Until about 30 seconds elapse after receiving the microwave irradiation, the heat generation temperature does not reach about 180 ° C. at which the sealant layer 7 softens or remelts, so that the sealing strength of the heat seal portion is sufficient. And the packaging material is still hermetically sealed. Therefore, the food 6 has a plump finish due to the steam generated during this time.

As shown in FIG. 5, the heat seal strength after heat-sealing and welding the polypropylene co-material gradually decreases as the temperature increases. When the microwave irradiation time becomes about 30 seconds, the temperature of the heating element 5 becomes 18
When the temperature reaches about 0 ° C., the sealant layer 7 around the heating element 5 starts to soften and melt, and the seal strength is 200 g / 15.
mm. At this time, since the inside of the packaging material is filled with water vapor and is in a pressurized state, the sealant layer 7 around the heating element 5 can be pushed out, and the pressurized steam inside reduces the sealing strength. The seal is released by blowing out to the outside through the portion that has been made.

When a small amount of pressurized steam blow-off port is formed in the heat sealing portion, the pressurized steam inside acts intensively on this portion thereafter, and as shown by a broken line in FIG. To be leaked to As a result, the heating element 5
The heat sealing part peels off so that the gap widens from near the
The sealing of the packaging material is released. After the sealing of the packaging material has been released in this way, the food 6
Is heated above the boiling point of water, and even if water vapor is generated suddenly, the water vapor can easily escape to the outside because the seal has already been released, and the packaging material bursts due to internal pressure. There is no.

FIG. 3B shows the protruding end 4b of the lid member 3.
Is completely peeled off from the heating element 5, but even if the protruding end 4 b partially adheres to the heating element 5,
It is sufficient if there is a gap around the heating element 5 through which water vapor can pass. Of course, the heating element 5 and the protruding end 4a of the tray 2
Exactly the same effect can be obtained also when the and are partially separated. Further, as shown in FIG.
Is peeled off from the tray 2 after heating, which is a key to peeling off the lid 3, and the sealing strength of other heat-sealed parts is also reduced due to the heating, so that the lid 3 is easily peeled off. There is also the advantage of becoming.

In the above embodiment, the tray 2 and the lid 3
Although a thermoplastic resin having a multilayer structure is used for each of the layers, other layers may be used as long as the layers that are heat-sealed to each other are the same material, and a single-layer structure may be used. It is also possible. As for the heating element 5, a thermoplastic resin serving as a common material with the heat sealing layer of the tray 2 and the lid 3 may be laminated on both sides.

The packaging material shown in FIG.
And a lid material 12 heat-sealed on its upper surface. The container 11 and the lid member 12 are each made of a thermoplastic resin,
The container 11 and the lid 12 are heat-sealed at the peripheral edge.
Then, the heating element 13 is sandwiched between the heat sealing portions,
As in the above-described embodiment, one end reaches the inside of the packaging material, and the other end faces the outside of the packaging material. In addition, a heating element 15 elongated in a belt shape is used, and both ends thereof are respectively connected to the container 1.
It may be arranged so as to reach the outside of the packaging material by sandwiching it between the heat-sealed portion of the cover material 1 and the lid material 12.

With this packaging material, exactly the same action as in the packaging material of FIG. 2 can be obtained. In the case of using the heating element 15 elongated in a belt shape, the heating element 15 is preferably provided in a straight line in advance on the web-shaped lid member 12 before being attached to the container 11. Then, when the lid 12 is successively heat-sealed on the upper surface of the container 11 by the automatic packaging machine, the web-shaped lid 12 is guided so that the heating element 15 does not come off the upper surface of the container 11. Often, the positioning of the container 11 and the heating element 15 is simplified.

FIG. 7 shows an embodiment in which the present invention is used for pouch packaging. As shown in FIG. 8, for example, the packaging material 16 includes a PET layer 16a, an Eval layer 16b, and a PP layer 16c.
Each of the layers is bonded with a polyurethane-based adhesive. Then, the three sides are heat-sealed so that the PP layer 16c is on the inner side, and the food 6 inside is kept in a sealed state. By broadly shaping the bottom, the packaging packaging material 16 is provided with self-sustainability and has a so-called stand pouch shape. The food 6 enters the position indicated by the two-dot chain line in the figure, and the heating element 18 is sandwiched between heat seal portions above the food 6. Reference numeral 19 denotes a notch for opening.

When the pouch package is heated and cooked in a microwave oven, a gap is formed around the heating element 18 and the sealing is released. However, since this gap can be formed above the food 6, the food 6 is made of liquid. Even if it is, it does not blow out from the packaging material 16. The heating element 18 may be sandwiched between heat sealing portions on the upper side of the packaging material 16.

FIG. 9 shows still another embodiment of the present invention. A laminate film made of a thermoplastic resin is used for the packaging material 22, and the tray 23 made of PP and the foods placed therein are hermetically packaged. For hermetic packaging, the end pieces 22a and 22b and the central bent piece 22c are closely adhered to each other by heat sealing. In such a packaging form, a similar heating element 25 may be heat-sealed so as to be sandwiched between the heat-sealing portions of the end pieces 22a, and the heating element 26 is heat-sealed to the heat-sealing portion of the central bent piece 22c. You may keep it.

These heating elements 25 and 26 also have one end reaching the inside of the sealed packaging material 22 and the other end reaching the outside of the packaging material 22. The heating elements 25 and 26
As a position for sandwiching the heating element, one end of the heating element is
If the other end of the package 22 reaches the outside of the packaging material 22, the packaging material 22 may be not only a double-layered heat-sealed portion but also a four-layered heat-sealed portion, for example, both side edge portions of the end 22 a. .

If the packaging material 22 is put into a microwave oven as it is and cooked by heating, the temperature of the heating element 25 or the heating element 26 rises to the melting temperature of the sealant layer in the heat sealing portion due to the absorption of microwaves. The sealant layer around the heating element softens and the sealing strength is weakened. The pressurized steam inside the packaging material 22 acts intensively on this portion, and the sealing of the packaging material 22 is released.

As shown in FIG. 10, when the package 23 in which a liquid seasoning such as soy sauce is sealed in addition to the rice 30 and the prepared food 31 is placed in the tray 23, the package is placed in the tray 23 as shown in the figure. It is preferable to provide a depression 35 for keeping the material 32 in an upright state, and to provide a heating element 36 also in the small package material 32 as shown in FIG. Note that a suitable support piece may be connected to the parcel material 32, thereby supporting the parcel material 32 in an upright state.

The parcel material 32 is made by laminating a laminate film made of a single thermoplastic resin and heat-sealing the three sides thereof, and a heating element 36 is sandwiched at the upper end thereof. When the entire packaging material 22 is placed in a microwave oven and cooked, the internal pressure of the small packaging material 32 also increases. However, the heating element 36 also softens the heat sealing portion to weaken the sealing strength. Since the seal of the package 32 is released, the package material 3 does not burst. In addition, since the heating element 36 is provided at the upper end of the parcel material 32 and the parcel material 32 is kept in an upright state, when the parcel material 32 is unsealed, a liquid seasoning is used. Never spill out. Furthermore, since the portion of the parcel material 32 that has been unsealed by the heating element 36 also serves as a spout, it is not necessary to partially cut the parcel 32 after cooking.

FIG. 12 shows a main part of an embodiment using a sound generator together. The packaging sheets 38, 39 made of PP resin are heat-sealed so as to sandwich the heating element 41 via the sealant layers 40, 40, and the left side in the figure is the inside of the sealed packaging material. One end of the heating element 41 faces the inside of the sealed packaging material, and the other end thereof is a PP resin sound generator 44 fixed between the packaging material sheets 38 and 39 by sealant layers 40 and 40. Is facing.

The sound generator 44 is of a whistle type and emits a sound when an air current passes through the sound generator. When the entire package is heated in a microwave oven, and the heating element 41 absorbs microwaves and reaches a predetermined temperature, the heat sealing strength between the sealant layers 40 and 40 decreases as in the previous embodiments. Then, the seal between the sealant layers 40, 40 and the heating element 41 is released by receiving pressure from the inside of the packaging material.

When a gap is formed around the heating element 41, the water vapor inside the packaging material is released to the outside of the packaging material through the sounding body 44. At this time, the sound generator 44 emits a sound. Therefore, if the cooking is stopped when the sounding device 44 emits a sound, it is possible to prevent the food from drying due to excessive microwave heating. In addition, if the sound emitted by the sound generator 44 and the increase in pressure due to the release of the sealing of the packaging material, and furthermore, the water vapor released from the inside of the packaging material is detected by the microwave oven and the operation of the microwave oven is turned off, it is easy to eat. The heating can be automatically finished at the timing of.

Although the present invention has been described with reference to the illustrated embodiments, the present invention can be applied to various shapes of packaging materials such as a bag shape, a cup shape, and a bottle shape. Also, the heating element is not limited to the exemplified materials as long as the heating temperature rises with the absorption of microwaves, and may be set to the softening temperature of the heat sealing portion of the thermoplastic resin used for the packaging material. What has a suitable heat generation characteristic may be used.

The heating element as described above is generally formed by applying a thin film of TiN, aluminum, stainless steel or the like to a sheet-like support. It is also possible to form a thin film directly by applying a heat-sealing resin layer on the surface of the thin film and heat-sealing it with the other packaging material.

[0038]

As described above, in the hermetically sealed packaging material of the present invention, a heating element that absorbs microwaves and generates heat is sandwiched between the heat-sealed portions of the packaging material. Since the sealing of the packaging material is automatically released from the heat sealing part of the packaging material by the heat of the heating element,
Even if a consumer cooks the packaging material in a microwave oven without any modification, the packaging material does not burst due to abnormal pressure inside the packaging material. Moreover, until the sealing of the packaging material is released, the cooking can be performed while effectively utilizing the steam generated inside the packaging material. Then, after the heating and cooking, the packaging material can be peeled off from the heat-sealed portion, and the opening after the heating and cooking can be easily performed. Further, in the present invention, since the heating element may be sandwiched between the heat-sealed portions between the packaging materials, it is possible to easily implement the present invention without substantially changing the form of the packaging material.

[Brief description of the drawings]

FIG. 1 is a graph showing characteristics of a heating element that absorbs microwaves and generates heat.

FIG. 2 is an external view of an embodiment of the present invention.

FIG. 3 is a sectional view of a main part of the packaging material shown in FIG. 2;

FIG. 4 is a schematic diagram showing a layer configuration of a heating element.

FIG. 5 is a graph showing a change in seal strength when a heat seal portion is reheated.

FIG. 6 is an external view showing another embodiment of the present invention.

FIG. 7 is an external view showing an example in which the present invention is applied to a stand pouch packaging.

8 is a schematic diagram showing a layer configuration of the packaging material shown in FIG.

FIG. 9 is an external view showing still another embodiment of the present invention.

FIG. 10 is a sectional view of a main part of the packaging material and the tray shown in FIG. 9;

FIG. 11 is an external view of the parcel material shown in FIG.

FIG. 12 is a sectional view of a main part showing an embodiment in which a sounding device is combined.

[Explanation of symbols]

 2 tray 3 lid 5 heating element 7 sealant layer 13, 15, 18, 25, 26 heating element 16, 22 packaging material 23 tray 32 small packaging material 36 heating element 44 sounding device

Claims (2)

[Claims] 1. A packaging material for sealing and packaging foods cooked in a microwave oven, wherein the outer peripheral portions of thermoplastic packaging materials constituting said packaging material are overlapped with each other and heated and welded. A thin strip-shaped heating element that generates heat by being irradiated with microwaves is sandwiched in the section, and the heating element is heated by microwaves when heating and cooking in a microwave oven to partially reduce the sealing strength of the heat sealing section. ,
A sealed packaging material for a microwave cooked product, wherein pressurized steam generated inside the packaging material is blown out from a portion having a reduced seal strength to release the sealed packaging of the packaging material. 2. The microwave oven according to claim 1, wherein the heating element is provided above the contents contained in the self-supporting packaging material, while providing the packaging material with autonomy. Sealed packaging for cooked items.