JPH09142542A - Microwave-shielding packaging container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the speed of temperature rise at every food on heating it by a microwave oven and have subdivided food at an appropriate temperature, by providing a conductive cover having a specified surface specific resistance at the outer periphery of a plastic container body. SOLUTION: This packing container preferably used for subdividing packaging containers of food required to control the microwave heat in a microwave oven or the like, is provided with a conductive lining with the surface specific resistance of 10<2> (Ω/square), of which outer peripheral shape is formed by curves with 3m/m or larger radius of curvature or the combination thereof, at a part of the plastic container body face or the whole face thereof. The outer peripheral shape of the conductive lining is circular or elliptic and the diameter or the larger or shorer diameter are set to range 6-50cm. Materials chiefly made of metal like aluminum, inorganic materials like carbon black, or various conductive polymers, etc., can be used as the constituent of the conductive lining material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packed lunch box or a packaging container for subdivision of instant foods to be served before meals by microwave heating with a microwave oven, etc. Relates to a packaging container for subdivision of foods in which suppression of microwave heating is desired, for example, in the case of assorted foods.

[0002]

2. Description of the Related Art Container-packed foods prepared by assembling cooked foods occupy a position indispensable for modern dietary habits. In many cases, this assorted food product is frozen and distributed, and a microwave heating device typified by a microwave oven is often used as the reheating means. However, not all foods require heating. For example, soy sauce, sauces, seasonings such as dressings, pickles, salads,
Fruit and sashimi are served before meals without warming. Of these, seasonings and the like are usually put in mini-bottles or sachets and sealed, so that they are ruptured in a microwave oven and are dangerous. As a countermeasure, it is possible to take out only foods that do not require heating in advance, but then the convenience as an instant food is considerably diminished. Also, for the same reason, handling in a vending machine becomes difficult.

Therefore, an invention has been disclosed in which a food that does not require heating is contained in a packaging container made of a microwave shielding material such as aluminum as a packaging container for assorted foods (JP-A-63-216459, Japanese Patent Publication No. 2-500970, etc.). ).

[0004]

However, such a technique presented in the related art merely devises the shape and size of the container, and the article substantially composed entirely of a conductive material is irradiated under microwave irradiation. It is impossible to completely prevent the electric charge concentration and the spark generation, which are the most difficult problems when exposed to the odor. In addition, the conventionally presented food container has a form
Lack of flexibility in assortment was also a problem.

A first object of the present invention is to provide a structure of a packaging container for ensuring the safety of microwave heating treatment of assorted foods in a family, a store, or a vending machine, and a second object. In addition to this, the present invention is to present a packaging container which is easier to process and has more flexibility in assembling. The present inventor has, as a result of intensive studies on such problems, solved the above-mentioned difficult problems by providing a conductive coating formed in a specific curve on the surface of a plastic container, and in particular, pouch packaging. The present invention has been completed by discovering that the form is more preferable in terms of workability and handling.

[0006]

According to the present invention, the outer peripheral shape has a radius of curvature of 3 m on part or all of the surface of a plastic container.
A microwave shielding packaging container provided with a conductive coating having a surface resistivity of 10 ² (Ω / □) or less, which is composed of a curve of / m or more or a combination thereof, and the body is a sachet. The packaging container according to claim 1, wherein the outer peripheral shape of the conductive coating is circular or elliptical, and the diameter or major axis / minor axis is 6 mm to 50 cm, respectively. Present the packaging container of.

[0007] The plastic container (hereinafter simply referred to as a container) in the present invention means all kinds of sealable packaging containers having plastic as a main material. As the constituent material thereof, those mainly composed of materials having a small microwave loss coefficient such as polyethylene, polypropylene, polystyrene, and styrofoam are preferable, but nylon, polyvinyl chloride, polyvinylidene chloride, ethylene-vinyl acetate copolymers are preferable. A resin, a saponified product thereof, a polyester resin such as PET / PBT, or the like having an appropriately thin wall thickness can be used. Further, as the packaging container form, various packaging forms such as bags / pouches, boxes, barrels, and bottles can be adopted. Above all, because of the ease of processing and the flexibility of assortment, pillow type packaging,
Small package packaging forms such as three-way seal packaging and four-way seal packaging are suitable for the present invention.

Next, the constituent material of the conductive coating in the present invention
As a metal such as aluminum, iron, silver, gold, carbon
Inorganic materials such as racks and graphite and various conductive materials
Mainly made of molecules etc. 10^Two (Ω / □) or less
Any conductive material with surface resistivity can be used.
Can be used. Single or multiple combinations of these
Can be used. Surface resistivity of conductive material is 1
0^Two If it exceeds (Ω / □), 10^Three -10⁶ 
(Ω / □), the conductive material itself generates heat, 10 ⁶ 
If it exceeds (Ω / □), microwaves penetrate and the contents are warmed.
It is not preferable because it will end up.

When the body has a multi-layer structure, a conductive coating may be provided on at least one of the layers. In addition to the usual lamination, any method such as transfer printing, coating, or vapor deposition may be used as the method for providing the conductive coating, as long as the thickness is 3 μm to 0.5 mm. It is also possible to attach it directly to. In the case of sticking, it is preferable that the conductive coating is preliminarily laminated with another film because it is easy to handle. Further, it is preferable to further increase the adhesion strength with the container body after the application, or to cover it with another film so as not to touch other foods when the coated surface is exposed.
It goes without saying that the conductive coating is not exposed and used especially when contact with food is not preferable.

The thickness of the conductive coating in the present invention is 3 μm.
A suitable range is m to 0.5 mm, preferably 9 μm.
５０50 μm. If the thickness is less than 3 μm, the material may have pinholes, the effect of shielding microwaves may be inferior, and the material may be destroyed by the energy of microwaves and may evaporate in extreme cases, which is preferable. Absent. On the other hand, if it exceeds 0.5 mm, it is disadvantageous in terms of workability, cost and disposal.

When a conductive coating is laminated on the surface of the body,
It is preferable to stack so as to cover the entire portion containing the contents so as not to be irradiated with microwaves, but there may be a portion that is not laminated to a part of the container.
This is because the allowable ultimate temperature is different for each content, and the area to be stacked may be determined according to the reached temperature.
Among the contents of the assorted foods, the ones that do not need to interfere with heating are side dishes such as rice and hamburger, and those that do not require heating or those that want to gradually heat and lower the reached temperature are the soy sauce mentioned above. , Seasonings such as sauces and dressings, pickles, salads, fruits, and sashimi. Here, for example, when the content is a seasoning such as a sauce and is in a frozen state at -18 ° C, it is preferably heated to 2 to 10 ° C,
If it is not heated and remains frozen, there is a problem that it cannot be eaten. Needless to say, the time required to reach the required temperature depends on the output of the microwave oven and the weight of the contents.
In most cases, one meal is heated for 5 to 10 minutes with the output of 1. However, for commercial use, it is often heated at a high output of 1.4 KW for 2 to 3 minutes, and a plurality of meals may be simultaneously heated.

In order to moderate the heating of food, a conductive coating is usually provided on 10% or more, preferably 60% or more, of the surface area of the container filled with the contents. Just do it. This value is arbitrarily determined according to the relationship with the food to be heated, which is placed in the assorted food. For example, when microwaves are applied to the hamburger and the sauce, it is preferable to fill the packaging container of the present invention with the sauce at about 10 ° C. when the hamburger is about 50 to 60 ° C. Further, when the conductive coating is provided on 100% of the surface area, the portion filled with the content may be smaller than the conductive coating. At that time,
The shape of the portion containing the contents may be a combination of curves in accordance with the outer peripheral shape of the conductive coating.

The size of the conductive coating of the present invention is not particularly limited, but when the outer peripheral shape is formed by a combination of curved lines,
In consideration of putting it in the assorted food, it is preferable that the maximum distance between any two points on the end portion does not exceed 50 cm. Also, avoid curves with a radius of curvature of less than 3 mm so as not to concentrate electric charges, preferably with a radius of curvature of 5 mm or more,
Particularly preferably, the curve is 7 mm or more. Further, when the outer peripheral shape is circular, the diameter thereof is preferably 6 mm to 50 cm, and when the outer peripheral shape is elliptical, the minor axis and the major axis thereof are preferably 6 mm to 50 cm. Here, in the case of an ellipse, if the ratio of the major axis to the minor axis is extremely increased, a portion having a radius of curvature of less than 3 mm is formed, and electric charges are concentrated on the portion, which is not preferable because it easily sparks. The usual ratio of major axis / minor axis is 15 times or less, preferably 5 times or less, and a shape with a longer diameter than this is not preferable because charges are concentrated on the tip portion.

Examples of combinations of curves include a sine curve and the like, but the invention is not limited to this, and it is possible to combine any curves having a radius of curvature of 3 mm or more. When the conductive coating of the present invention is manufactured by machining, the presence of minute protrusions or edges on the cut surface may cause sparks, so the edge portion should be rounded. Is preferred. Furthermore, the conductive coating of the present invention can be used by arranging a plurality of sheets on the surface of the container.

The microwave shielding effect according to the present invention will be specifically described below with reference to a pouch packaging form suitable for the present invention, but the present invention is not limited to these claims. .

[0016]

【Example】

Example 1 12 cm × 9 cm plastic bag (structure PP + L
-LDPE, inside dimensions Y11 cm x T8 cm) were filled with 30 g of water at 20 ° C. As shown in FIG. 1, an aluminum foil having a thickness of 20 μm and having an outer peripheral curve 1 formed with a radius of curvature of 5 mm was attached to each of the both surfaces of this bag with a rubber-based adhesive (on the inside dimension). The shielding area is about 85%).
In a microwave oven with an output of 500 W, irradiate microwaves,
The temperature rising rate of water was measured. As a result, the temperature was raised at a rate of 0.7 ° C./sec and reached 41 ° C. after 30 seconds. Also,
No sparks were generated during microwave irradiation.

Example 2 The temperature rising rate of water was measured under the same conditions as in Example 1 except that the aluminum foil was circular and the size was 9 cmφ (the shielding area with respect to the inner size was about 70%). As a result, 1.0
The temperature was raised at a rate of ° C / sec and reached 50 ° C after 30 seconds. Further, no spark was generated during microwave irradiation.

Example 3 The temperature rising rate of water was measured under the same conditions as in Example 1 except that the aluminum foil was circular and the dimension was 6 cmφ (the shielding area against the inner dimension was 32%). As a result, 2.0 ℃
The temperature was raised at a rate of / sec and reached 80 ° C after 30 seconds. Further, no spark was generated during microwave irradiation.

Example 4 A circular aluminum foil was used, the size of which was 5 cmφ, and two aluminum foils were attached to each surface (shielding area for inner size was 45).
%. The two sheets were arranged side by side with an interval of 1 cm. Other than the above), the temperature rising rate of water was measured under the same conditions as in Example 1. As a result, the temperature was raised at a rate of 1.6 ° C / sec and 70 ° C after 30 seconds.
Reached Further, no spark was generated during microwave irradiation.

Example 5 The temperature rising rate of water was measured under the same conditions as in Example 1 except that the aluminum foil was elliptical with a major axis of 15 cm and a minor axis of 11 cm (shielding area relative to the inner dimension was 100%). as a result,
The temperature was raised at a rate of 0.4 ° C./second and reached 60 ° C. up to 45 ° C. Further, no spark was generated during microwave irradiation.

Comparative Example 1 The temperature rising rate of water was measured under the same conditions as in Example 1 without attaching the aluminum foil. As a result, the temperature was raised at a rate of 2.7 ° C./sec, the boiling point was reached after 30 seconds, and the bag burst after 35 seconds.

COMPARATIVE EXAMPLE 2 Microwave irradiation was performed under the same conditions as in Example 1 except that the aluminum foil was formed into a rectangle of 11.5 cm × 8.5 cm and the entire surface of the contents was shielded. I could not continue the irradiation because sparks were generated from some areas.

Comparative Example 3 When microwaves were irradiated under the same conditions as in Comparative Example 2 except that the four corners of the rectangular aluminum foil were rounded with a radius of curvature of 1 mm, sparks were generated from some of the four corners of the aluminum foil. The irradiation could not be continued because it occurred.

[0024]

Since the microwave shielding packaging container of the present invention has the above constitution and performance, the heating rate of each food can be controlled even if the packed food is heated in the microwave oven. , It is possible to eat the subdivided foods in their proper temperature conditions.

[Brief description of the drawings]

1 is a plan view of an aluminum foil conductive coating used in Example 1. FIG.

[Explanation of symbols]

 Y horizontal dimension T vertical dimension l Perimeter curve

Claims (3)

[Claims] 1. A conductive coating having a surface specific resistance of 10 ² (Ω / □) or less, which is formed by a curve having a radius of curvature of 3 m / m or more or a combination thereof on a part or all of the plastic container surface. A microwave shielding packaging container provided with. 2. The packaging container according to claim 1, wherein the container is a pouch. 3. The packaging container according to claim 1, wherein the outer peripheral shape of the conductive coating is circular or elliptical, and the diameter or major axis / minor axis is 6 mm to 50 cm, respectively.