JPH0440005B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a food container for microwave ovens that automatically opens when the vapor pressure inside the container reaches a certain level.

(Conventional technology) Many foods that are intended to be heated in a microwave oven have been released in recent years, but among them, foods with high water content must be placed in sealed packaging containers, heat sterilized, sterile packaging, etc. Many products are sold with a longer shelf life.

However, if these sealed packaging containers are heated as they are in a microwave oven, the packaging will expand due to the steam generated as the contents warm up, and in the worst case scenario, the packaging will burst due to the steam and the contents will be destroyed. There was a risk of objects flying off or burns.

In order to safely and quietly exhaust the steam generated when microwaved foods are heated in the microwave, conventionally, microwave foods are prepared by using a sharp tool to make holes in the body or lid of the container before placing them in the microwave. Some instructions tell you to open the package or peel off the heat seal a little before placing it in the microwave.

An example of the former is FIG. 22 of US Pat. No. 4,425,368.

In addition, it is made of thermoplastic packaging material that is made of a non-metallic material that absorbs microwave energy and generates heat, and is attached to the container. Japanese Patent Application Laid-Open No. 61-69576 discloses a packaging material in which the portion of the packaging material that is in contact with the container softens and a hole is formed in that portion due to steam pressure.

(Problem to be solved by the invention) Instructing consumers to perform special treatment on containers before placing them in a microwave oven is time-consuming, and if consumers fail to read the instructions, there is a risk of the container bursting. Also, methods such as attaching a microwave heating element to a thermoplastic film require a specific structure, and the films used are limited.

Therefore, it is an object of the present invention to provide a microwaveable food container that is safe, does not pose the risk of container rupture even if a consumer fails to read the instructions, and has a simple structure in which the film used is not limited. It is something.

(Means for Solving the Problems) In order to achieve the above objects, the present invention provides the following microwave food container.

In other words, a part of the seal line that seals the container,
A food container for a microwave oven, which has a bent portion that protrudes toward the inside of the container with a width that is almost the same as the other seal width, and has an apex portion where tensile force is concentrated due to internal pressure at the bent portion, The material of the bag and lid, which has a seal that receives tensile force due to internal pressure, is relatively soft and consists of a single-layer plastic film, a laminate of plastic, or a laminate of plastic and other materials. The shape of the seal part that protrudes toward the side is approximately V-shaped,
The angle used is from 5° to 140°.

(Function) In the present invention, when cooking using a microwave oven, the food in the container receives microwaves and generates heat, generates steam, and expands the container.
Increase the internal pressure of the container.

At this time, the internal pressure expands the container film,
The tensile force is concentrated, for example, at the apex of the V-shaped seal surface, and the seal is separated from the apex of the V-shaped portion to open an opening, from which steam is safely and quietly exhausted.

(Example) The following will explain based on the drawings.

According to the present invention, the contents do not scatter or cause burns due to the bursting that occurs when a food container is placed in a microwave oven, and the food container is sufficiently sealed until it is heated and automatically opens when heated. Steam is discharged quietly through the opening.

In other words, when the food in the container absorbs microwave energy and generates heat, the temperature of the food rises, the movement of water molecules in the food increases, the water molecules evaporate, and the container is filled with steam. The container gradually expands.

When the container expands, the film or lid that makes up the container tends to lift perpendicularly to the sealing surface, applying a force that tends to tear the sealing surface vertically.

At this time, if the sealing surface is just a straight line,
The force that tries to tear the seal surface vertically is dispersed over the entire length of the seal, and the force applied per unit length becomes small, so the seal surface will not peel off unless a very large force is applied.

When it finally separates, it opens explosively with a popping sound because of the large force applied to it.

In the case of the present invention, when a force is applied to tear the seal surface vertically, the force is first concentrated at the apex of, for example, a V-shaped seal portion that protrudes inward of the container, so the force applied to the apex is extremely large. becomes larger.

Therefore, even if the container is tightly sealed, the apex of the V-shaped seal portion easily peels off and opens, and the steam inside the container is smoothly exhausted from the opening.

In the present invention, the apex of the V-shaped seal portion described above must always face inward of the container.

If an inverted V shape is used with the apex facing outward from the container, even if a force is applied that tears the sealing surface vertically,
Since the force is first distributed and applied to the normal straight seal part connected to the inverted V-shaped seal part, the force sufficient to cause it to peel and open is not concentrated at the apex of the inverted V-shaped seal part, and eventually , it will rupture in the same way as if it were a simple straight line seal.

The apex of the V-shaped seal in the present invention must always face inward of the container, but the apex may be slightly rounded, and if it is a V-like type, the steam inside the container will automatically flow and is exhausted smoothly.

That is, in the present invention, a part of the seal line that seals the container is provided with a bent part that protrudes toward the inside of the container with a width that is almost the same as the other seal width, and the bent part is pulled by internal pressure. It is characterized by having an apex portion where force is concentrated, and the shape of the bent portion that protrudes inward of the container is such that it is weakly peeled off by the tensile force where the tensile force is concentrated due to internal pressure, and the opening is opened. As long as the apex shape is similar, other similar shapes other than V-shape may be used.

Next, the present invention will be explained based on the embodiments shown in FIGS. 1, 2, 3, and 4.

<Example 1> In Figures 1 and 2, 1 is a microwaveable food container containing frankfurter sausage, the bag body is made of plastic film, and the seal width is 3.
The container is heat-sealed and sealed by a seal part 2 having a V-shaped seal part of mm in diameter and a seal part 3 at the other end of the container.

When the container 1 is placed in a microwave oven and microwave heating is started, the moisture in the contents (here, 90 g of frankfurter sausage with an initial temperature of 10°C) evaporates, and steam is generated 25 to 30 seconds after heating starts. However, the internal pressure of the container increases, and the temperature of the frankfurter sausage reaches 75 to 80 degrees Celsius 35 to 45 seconds after the start of heating, and container 1 expands, causing the film that makes up the container to touch the sealing surface. The force that tries to open up and down and tear the seal up and down is first concentrated at the apex of the V-shaped part of the seal, so the force is concentrated at the apex, causing the seal to peel and open. The steam was then exhausted from the opening.

In this case, two sides AB of the V-shaped part of the seal part 2
The angle between BC and BC is preferably between 5° and 110°,
Even at angles between 110° and 140°, there is a slight plosive sound, but an opening is automatically created and the air is exhausted.

The seal width of the V-shaped portion of the seal portion 2 is preferably 1 mm to 5 mm, but it needs to be changed slightly depending on the angle formed by the two sides AB and BC.

In Example 1, the angle between the two angles is 5°.
When the angle is 15°, the seal width is preferably 1 mm to 2 mm, and 3 mm makes it somewhat difficult to open.

If the above angle is 15° to 140°, the seal width is 2
A diameter of 3 mm to 3 mm is desirable, and a diameter of 4 to 5 mm is somewhat difficult to open.

In addition, the apex B of the V-shaped portion of the seal portion 2 must always face inward of the container, and the apex B
If the container faces outward from the container and forms an inverted V shape, it will not open even if the internal pressure increases and will burst with a popping sound.

Furthermore, even if the vertex B of the V-shaped part of the sealing part 2 faces inward of the container, if the triangular part surrounded by line segments AB, BC, and CA is sealed,
Even if the internal pressure increases and the seal peels off slightly from the vertex B, it will burst without opening.

Therefore, it is necessary that the width of the seal line protruding inward of the container is almost the same as the width of the other seals.

Even if the seal width exceeds 5 mm, the seal will peel off from the apex B of the V-shaped portion of the seal portion 2, but it will take time to open and may be accompanied by a slight plosive sound.

Although the sealing method and the material of the sealed container are not specified, the seal strength ranges from 0.5Kg/15mm to 3.0Kg/15mm in tensile strength when pulled perpendicular to the sealing surface.
Kg/15mm is preferable.

Although the container will open automatically if the container weighs less than 0.5 kg, the V-shaped portion of the seal portion 2 will easily peel off as soon as the container starts expanding, so there is a possibility that the container will open before the cooking is complete. If it exceeds 3.0Kg/15mm, opening will be slow and the contents may be overheated.

Note that the apex B of the V-shaped portion of the seal portion 2 may be somewhat rounded.

<Embodiment 2> Next, another embodiment of the present invention will be described with reference to FIGS. 3 and 4.

Figure 3 shows a microwave food container containing soup, which has a diameter of 10 cm, a height of 3 cm, and a volume of 200 ml.
A polypropylene molded container 4 is filled with 160 ml of soup, and a polypropylene film that becomes the lid 6 is attached to the flange 7 of the ring-shaped container including the V-shaped seal part 2.
It is heat-sealed and hermetically sealed with a seal part formed in the .

When the container 5 is placed in a microwave oven and microwave heating is started, the temperature of the contents (in this case, soup with an initial temperature of 20°C) rises and moisture begins to evaporate, and within 20 to 30 seconds after heating starts. After steam is generated and heating starts
After 35 to 45 seconds, the temperature of the soup will be 80°.
As the temperature reaches 85°C, the lid 6 expands and the lid 6
tries to lift up perpendicularly to the sealing surface of the V-shaped seal part, and the force that tries to peel the seal part up and down is first concentrated at the apex of the V-shaped part, so the V-shaped part The seal peeled off and opened, and steam was exhausted from the opening.

As in Example 1, the angle between the two sides AB and BC of the V-shaped portion of the seal portion 2 is preferably from 5° to 110°, but even from 110° to 140°, a slight plosive sound may be produced. It automatically creates an opening and exhausts the air.

The seal width of the V-shaped portion of the seal portion 2 is preferably 1 mm to 3 mm, but it needs to be changed slightly depending on the angle formed by the two sides AB and BC.

In Example 2, the angle between the two sides is 5°.
120°, 1mm to 2mm is preferable, 3mm
It became a little difficult to open.

If the above angle is 120° to 140°, 2mm to 2.5mm
is desirable, and 3 mm makes it somewhat difficult to open.

In addition, the apex B of the V-shaped portion of the seal part 2 must always face inward of the container, as in Example 1, and if the apex B faces outward of the container, it will form an inverted V-shape. In this case, even if a force is applied to the sealing surface of the sealing part 2 to peel it up and down, it will not open, and the sealing part will burst and the soup will spill out.

Even if the apex B of the V-shaped part of the seal part 2 faces inward of the container, if the triangular part surrounded by line segments AB, BC, and CA is sealed, the seal surface of the seal part 2 will be Even if the seal is slightly peeled off from the apex B due to the force of trying to peel it up and down, it will not open and will burst.

Therefore, in this case as well, as in Example 1, the width of the seal line protruding inward of the container needs to be almost the same width as the other seal widths.

Further, although the sealing method and the material of the container to be sealed are not specified, it is desirable that the film serving as the lid 6 be relatively soft.

Further, the seal strength is preferably 0.5 Kg/15 mm to 3.0 Kg/15 mm in terms of tensile strength pulled perpendicular to the seal surface. It will open automatically if it is less than 0.5Kg/15mm, but as soon as the container starts to expand, the seal part 2 will easily open.
Since the V-shaped part of the container will peel off, there is a possibility that the container will open before cooking is complete.

Note that the apex B of the V-shaped portion of the seal portion 2 may be somewhat rounded.

Based on Example 1, we made 20 prototype microwave food containers containing frankfurter sausage and tried heating them in a microwave oven (high frequency output 500W).
All 20 pieces reached 70℃ - 80℃ in 35 seconds after heating started, and at the same time the container expanded and reached 75℃ after 40 seconds.
When the temperature reached -85°C, the V-shaped seal was opened and the steam was gently exhausted.

Hot frankfurt sausage was produced without cracking due to excessive heating of the frankfurt sausage.

Also, based on Example 2, soup at 20℃
When I put a microwave container filled with 160ml (approximately 7 minutes) in the microwave (high frequency output 500W),
The temperature reaches 90℃ 50 seconds after the start of heating, and after 60 seconds it reaches a boiling state (95℃), the center of the lid expands and bulges, the top of the V-shaped seal gently peels off, and the soup spills out. The steam inside the container was smoothly exhausted.

As described above, when a solid food (frankfurter sausage) and a liquid food (soup) were heated in the microwave using the microwaveable food container according to the present invention, the contents were sufficiently warmed and at the same time the V-shaped seal opened and the steam was gently released. Therefore, the effects of the present invention were fully demonstrated.

(Effects of the Invention) According to the present invention, during cooking using a microwave oven, the food in the container receives microwaves and generates heat and generates steam, causing the container to expand and the inside of the container to be heated. The pressure increases, and at that time, the internal pressure expands the container film, and the tensile force is concentrated at the apex of the seal part that protrudes inward of the container.
The seal portion is peeled off from the apex and opened, and the steam is safely and quietly exhausted from this opening. Therefore, the contents will not burst due to steam and the contents will not scatter, and there will be no risk of burns.

Therefore, there is no need to request or instruct the consumer to perform any special treatment on the container before placing it in the microwave.

Therefore, the material of the bag body and lid body, which has a sealing part that receives tensile force due to internal pressure, is relatively soft, such as a single-layer plastic film, a laminate of plastic, or a laminate of plastic and other materials. This, combined with the fact that the seal part is formed to protrude inward from the container, eliminates the need for a special film with a complicated structure, and when the vapor pressure reaches a certain level, it automatically peels off from the top part and opens. do.

Moreover, its protruding shape is V-shaped, and its angle is
When the temperature is between 5° and 140°, the container opens after cooking is completed, a simple sealing structure is required, and the food container can have both sealing and opening functions.

[Brief explanation of drawings]

Figures 1 and 2 are a perspective view and a plan view of a microwaveable food container containing frankfurter sausage used in Example 1 of the present invention, and Figures 3 and 4 are views of a microwave food container used in Example 2 of the present invention. FIG. 2 is a perspective view and a plan view of a microwave food container containing soup. 1... Food container containing frankfurt sausage, 2... V-shaped seal part, 3... Seal part, 4
... Frankfurt sausage, 5 ... Food container containing soup, 6 ... Lid, 7 ... Tsuba, 8 ... Soup.

Claims (1)

[Claims] 1. A part of the seal line that seals the container is provided with a bent portion that protrudes inward of the container with a width that is almost the same as the width of the other seals, and the bent portion is provided with an internal pressure. A microwaveable food container characterized by forming an apex portion where tensile force is concentrated. 2. Claims where the material of the bag or lid, which has a seal that receives tensile force due to internal pressure, is relatively soft, such as a single-layer plastic film, a laminate of plastic, or a laminate of plastic and other materials. The food container for microwave oven according to item 1. 3 The shape of the seal part that protrudes inward of the container is approximately V.
3. A food container for microwave oven according to claim 1, which is shaped like a letter. 4. The food container for microwave oven according to claim 3, wherein the angle of the V-shape of the V-shaped seal portion protruding inward of the container is 5° to 140°.