JP2001322683A - Packaging material compatible with microwave oven and packaging bag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packaging material and a packaging bag which has no risk of explosive rupture due to the increase of the internal pressure by steam even in the case where foodstuffs in the packaging bag are heated by a microwave oven while the bag is being kept in a sealed state. SOLUTION: The packaging material 8 applicable to cooking by a microwave oven is made by laminating a heat-resistant base layer 1 and a sealant layer 2 on each other. The sealant layer is formed out of three layers made of a thermoplastic resin, that is, a first layer 3 positioned on the base layer side, a second layer 4 positioned at an intermediate portion and a third layer 5 positioned on the contents side when the sealant layer and the base layer are laminated on each other. The packaging bag is formed by heat-sealing a predetermined portion of the packaging material under the condition that a thickness ratio of the second layer of the sealant layer to the third layer thereof is the second layer: the third layer = 1:2 to 1:1 and that the sealant layers of the packaging materials compatible with the microwave oven are arranged so as to be opposed to each other in the interior of the packaging bag.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave oven capable of heating contents while being stored in a sealed packaging bag and automatically releasing the internal pressure of the packaging bag which rises due to heating. The present invention relates to a packaging material and a packaging bag using the same.

[0002]

2. Description of the Related Art When a microwave oven is used to heat a package with its contents stored in a sealed packaging bag, the pressure inside the bag rises rapidly due to the evaporation of moisture in the contents, causing the packaging bag to explode. It is well known that a rupture occurs. Then, in order to avoid the explosive rupture, a special process is performed on the sealing portion of the packaging bag. For example, Japanese Patent Application Laid-Open No. Hei 9-42541
By providing a weak seal, the heat seal of the weak seal comes off due to an increase in the internal pressure inside the bag, the water vapor inside is slowly discharged out of the bag, and the bag makes a loud popping sound. Without any adhesion, it is opened. Also,
Japanese Patent Application Laid-Open No. H10-95471 discloses that when the internal pressure of a bag is increased by performing heat sealing (low heat sealing portion) so as to have a lower heat sealing portion strength than other portions and providing a cutout in the low heat sealing portion. In addition, since the notched portion of the low heat seal portion is peeled off, the inside of the bag is filled, and the high-pressure steam is diffused outside the bag, so that the explosive burst of the bag can be prevented. Further, Japanese Patent Application Laid-Open No. 2-84908 discloses that a seal portion having a shape protruding inside the bag is provided. When the pressure in the bag increases due to microwave heating, the force for peeling off the seal portion of the bag concentrates on the tip of the seal portion having a shape protruding inside the bag, and the seal at the tip portion first comes off. As a result, water vapor in the bag is released, so that explosive rupture can be prevented. An object of the present invention is to provide a packaging material that does not cause explosive rupture of a home even when heated in a microwave oven while being housed in a bag and hermetically sealed, and a packaging bag using the same.

[0003]

The method of cutting the packaging bag with scissors or applying a special processing to the seal portion to prevent the package from being ruptured before heating in a microwave oven requires a lot of time and costs. . Further, the method of forming the seal into a protruding shape has a problem that the pillow wrapping machine widely used in the food industry cannot be used because the pillow can be supplied only in the form of a bag, resulting in low productivity. Therefore, an object of the present invention is to provide a packaging material and a packaging bag which do not explode due to an increase in internal pressure due to water vapor even when heated by a microwave oven while being sealed.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a packaging material for a microwave oven comprising at least a heat-resistant base material layer and a sealant layer, wherein the sealant layer is laminated with the base material layer. Substrate layer side first
Layer, a middle layer is a second layer, and the contents side is a third layer. The first layer and the third layer are low-density polyethylene, linear low-density polyethylene, and ultra-low-density. Polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ionomer,
The resin is any one of ethylene-methyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-ethyl acrylate copolymer or ethylene-acrylic acid copolymer, and the second layer is made of polypropylene. Wherein the thickness ratio of the second layer and the third layer of the sealant layer is as follows: the second layer: the third layer =
1: 2 to 1: 1, and is a packaging bag formed by disposing the sealant layers of the microwave-compatible packaging material so as to face each other and heat-sealing a predetermined seal portion. .

[0005]

FIG. 1 shows a microwave oven pair according to the present invention.
It is sectional drawing which shows the material composition of the Example of a response material. FIG.
Is used for heating the bag using the microwave-compatible packaging material of the present invention.
(A) a bag before heating,
(B) X₁-X₁(B) Microwave heating
The seal is peeled off and the steam is released outside the bag.
State, (d) X _Two-X_TwoFIG. Figure 3 shows heating
FIGS. 3A and 3B are schematic diagrams for explaining a state of peeling due to the process shown in FIG.
Sectional view of the seal before heating, (b) generated by high frequency heating
Sectional view of the seal portion opened by the internal pressure of the steam,
(C) Y₁It is an enlarged view of a part. FIG. 4 shows the electronic laser of the present invention.
The figure which shows the example of the tray type which can apply the packaging material
is there. FIG. 5 shows the use of the packaging material for a microwave oven of the present invention.
(A) sectional view explaining the packaging state of the tray type
(B) Y_TwoIt is a part enlarged view. Figure 6 shows a tray-type package.
The internal pressure of the steam generated by high-frequency heating of the package
(A) Sectional view of the opened package, (d) Y_ThreeExpansion of department
FIG. FIG. 7 shows the packaging material for a microwave oven according to the present invention.
It is a figure which shows the example of the packaging form of various bags which can be used.

[0006] When heating a beverage, food, or the like containing the contents and sealing and selling the contents for the purpose of hygiene or preventing deterioration of the contents using a microwave oven, if the contents are heated in a sealed state, It is well known that packaging bags explode as described above. The present inventor has conducted intensive studies on a microwave-compatible packaging material and a packaging bag that can be sufficiently heated without explosive rupture even when high-frequency heating is performed by a microwave oven while the packaged food and the like are sealed. As a result, as shown in FIG. 1 (a), the structure of the laminate forming the bag is, as shown in FIG. 1 (a), in a microwave-compatible packaging material obtained by laminating at least a heat-resistant base material layer 1 and a sealant layer 2. When the layer 2 is laminated with the base material layer, the base material layer has a three-layer structure made of a thermoplastic resin having the first layer 3 on the side, the second layer 4 on the middle, and the third layer 5 on the content side,
The first layer 3 and the third layer 5 are made of low-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ionomer, ethylene-methyl acrylate. A resin of any of a polymer, an ethylene-methacrylic acid copolymer, an ethylene-ethyl acrylate copolymer, or an ethylene-acrylic acid copolymer;
Is polypropylene, and the thickness ratio of the second layer and the third layer of the sealant layer is a second layer: the third layer = 1: 2 to 1: 1 to form a packaging material, and The above problem can be solved by using a packaging material, using the packaging material, disposing the sealant layers so as to face each other, and forming a packaging bag formed by heat-sealing a predetermined seal portion. Heading, the present invention has been completed. In addition, as the packaging material, FIG.
As shown in (b), an intermediate layer 7 may be laminated between the base material layer 1 and the sealant layer 2.

The heat-resistant base material layer 1 in the present invention is not particularly limited as long as it is generally used for packaging foods to be heated or cooked by a microwave oven. For example, stretched polyethylene terephthalate film, silica-deposited polyethylene terephthalate film, alumina-deposited polyethylene terephthalate film, stretched nylon film, silica-deposited stretched nylon film, alumina-deposited stretched nylon film, stretched polypropylene film, polyvinyl alcohol coated stretched polypropylene, nylon 6 / meta-xylene Films such as a diamine nylon 6 coextrusion stretched film and a polypropylene / ethylene-vinyl alcohol copolymer extrusion stretched film can be used. The melting point of these heat-resistant base material layers 1 is 15
The temperature is 0 ° C. or higher, and the thickness is in the range of about 10 to 50 μm.

[0008] A printing layer may be provided on the surface of the heat-resistant base material layer or on the surface to be laminated with the sealant, if necessary, by a conventionally known method.

The resin used for the first layer 3 and the third layer 5 is low-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer. , An ionomer, an ethylene-methyl acrylate copolymer, an ethylene-methacrylic acid copolymer, an ethylene-ethyl acrylate copolymer, or an ethylene-acrylic acid copolymer. The second layer of the sealant of the packaging material of the present invention is polypropylene. The second
The polypropylene used for the layer 4 may be either a homotie type or a copolymer type.

[0010] As a packaging material for a microwave oven, in the initial stage, the internal pressure in the bag generated by heating is peeled off at the seal portion, and the steam is diffused as a gradual peeling instead of an explosive burst. (Hereinafter, in the naturally opened state) As a result of various studies on each layer of the sealant layer, the second layer was formed in the three layers constituting the sealant.
The ratio of the thickness of the layer to the thickness of the third layer was preferably in the range of the second layer / third layer = 1/2 to 1/1. When the ratio of the layer thickness is less than 1/2, it is difficult to form a stable layer of the second layer in the laminating step, and when the ratio of the layer thickness is more than 1/1, when the layer is heat-sealed, In addition, the seal portion does not have a sea-island structure as described later due to the resin forming the second layer and the resin forming the third layer, and a natural unsealing state due to pressure cannot be expected.

The heat seal layer 2 is previously formed into a film by a coextrusion film forming method such as an inflation method or a T-die method, and is laminated with a substrate film by a method such as a dry laminating method or a sandwich laminating method. You may.

The heat-sealing layer to be laminated on the packaging material for a microwave oven according to the present invention is formed by forming a first layer 3 on one side of a substrate.
The second layer 4 and the third layer 5 may be sequentially extruded and laminated in this order, or the three layers of the heat seal layer 2 may be simultaneously extruded and coated on the base material layer 1 by a co-extrusion lamination method to form a film. May be. In either case of the sequential extrusion or the simultaneous extrusion,
It is preferable to provide an anchor coat layer on the laminate surface (heat seal layer extrusion surface) of the base material for promoting adhesion. As an anchor coating agent to be used, organic titanium-based,
It can be appropriately selected from those composed of components such as polyethyleneimine and isocyanate.

By using the packaging material of the present invention, even if the content is sealed and packaged and heated in a microwave oven, the packaging bag is not explosively ruptured due to an increase in internal pressure. It is avoided that it scatters in the storage.
That is, since the seal portion peels off at an initial stage in the increase of the internal pressure due to the heating, the vapor Vp generated in the bag is
As shown in FIGS. 2 (c) and 2 (d), the vapor Vp is diffused out of the bag from the part where it was firstly peeled off, and when the internal pressure rises, the peeled portion becomes wide and the vapor Vp is easily diffused out of the bag. As a result, the bursting of the packaging bag was not explosive, so that the contents were not scattered, and the heating in the microwave oven became stable.

As shown in FIG. 3 (c), when a bag is formed using the packaging material for a microwave oven according to the present invention, the second layer 4 and the third layer 5 of the heat seal layer 2 are mixed. It is believed that a fused portion is formed.
When the package containing the contents in the bag is heated in a microwave while keeping the package in a sealed state, the resin in the fused portion softens and melts, and as the pressure of the vapor Vp generated in the bag increases,
A force acts in the direction of peeling the seal portion. In the heat seal portion 8 of the bag, as shown in FIG. 3A, the second layer of the polypropylene resin and the third layer of the resin such as polyethylene are combined with the polyethylene by heat transfer from water vapor by microwave heating. It melts and becomes a state like a sea-island structure where polypropylene is softened but not melted, and
It seems that as the heating is performed, the molten polyethylene resin layer of the heat-sealed portion peels off. The peeling occurs partially and at an initial stage of the increase of the internal pressure. With the rise of the internal pressure, the peeling portion expands and the generated steam can be easily discharged out of the bag.

There is no particular limitation on the form of the bag using the packaging material of the present invention. That is, any bag that is sealed by heat sealing may be used, and can be applied to various bags as shown in FIG. For example, three-side seal type (a), four-side seal type (b), standing tie (e), side gusset pouch type (f),
(G), pillow type (h) or any other pouch type. Further, the present invention can be applied to a tray-type hermetically sealed package as shown in FIG. 4 or a sealed container such as various cups (not shown).

When the microwave-compatible packaging material of the present invention is applied to a tray type, as shown in FIG.
By using the sealant of the present invention, as in the case of the above-described bag, it was confirmed that even if high-frequency heating was performed by a microwave oven, cooking was possible without automatic opening and explosive bursting as shown in FIG. .

The microwave packaging material of the present invention makes it possible to heat a microwave oven while the contents such as food are sealed and packaged. Compared with the conventional method, there is no need to provide a special weak seal part in the seal part, and without changing the seal shape, bag making, sealing etc. can be performed under the same conditions as when manufacturing a normal package. it can.

[0018]

EXAMPLES Example 1 A biaxially oriented polypropylene of 20 μm was used as a heat-resistant base material layer, an anchor coating agent was applied thereto, and a first layer of polyethylene, a second layer of polypropylene, and a layer of polyethylene were used. The third layer was laminated by a coextrusion coating method. An adhesive resin layer is provided between each layer. The thickness of the first layer of the sealant layer was 10 μm, the thickness of the second layer was 10 μm, and the thickness of the third layer was 15 μm. As the adhesive resin layer, an adhesive polyolefin resin was provided in a thickness of 5 μm. The rolls were stored in a polypropylene tray, and the obtained packaging material for a microwave oven was used to obtain a horizontal pillow type package using a high-speed fully automatic horizontal pillow packaging machine according to Example 1 (bag size:
130 mm x 240 mm). The package was frozen, and the obtained package of frozen sweet potato was directly cooked in a microwave oven. Heated to about 100 ° C by microwave heating, the bag whose internal pressure is increased by steam breaks the sealant, presents an automatic opening state, and the contents of sweet potato can be heated to a good state to eat. Was. Example 2 As a molded sheet, a sealant material was laminated on a 200 μm-thick polypropylene sheet by a dry lamination method. The layer structure of the sealant material is low-density polyethylene (10 μm), polypropylene (12 μm), linear low-density polyethylene (20 μm)
And the surface of the low-density polyethylene (10 μm) layer was used as a laminate surface. A molded sheet 2 of a packaging material example for a microwave oven was obtained. The obtained molded sheet 2 was formed by using a vacuum pressure forming method. The tray shape was formed into a tray shape of 70 mm × 150 mm and a depth of 30 mm, and the flange was set to a width of 7 mm. A biaxially stretched polyethylene terephthalate film is used as a lid material film, and a sealant layer is a co-extruded film made of low-density polyethylene (10 μm), polypropylene (12 μm), and linear low-density polyethylene (15 μm). Coextruded film of low density polyethylene (10 μm)
μm) layer was used as a lamination surface and laminated by a dry lamination method to obtain a packaging material example lid material 2 for a microwave oven. As contents, 200 g of mabo tofu was stored, and the lid material 2 was covered, heat-sealed and sealed to obtain a packaged product example 2 of a tray. After storing the package 2 of the example in a refrigerator for 24 hours, the package 2 was taken out of the refrigerator.
Was cooked in a microwave oven as it was. The bag heated to about 100 ° C by microwave heating and the internal pressure increased by steam breaks the sealant, presents a naturally opened state, and the contents of Marbo Tofu can be heated to a good state to eat. did it. [Comparative Example 1] A biaxially oriented polypropylene of 20 µm was used as a heat-resistant base material layer, and an anchor coat agent was applied thereto.
35 μm of linear low density polyethylene as sealant layer
Was extruded to a thickness of 5 mm and laminated by a coating method. The thickness of the first layer of the sealant layer was 10 μm, the thickness of the second layer was 10 μm, and the thickness of the third layer was 15 μm. The umami was stored in a polypropylene tray, and a horizontal pillow type package was obtained using a high-speed fully automatic horizontal pillow wrapping machine according to the obtained microwave-compatible packaging material Comparative Example 1 (bag size: 130 mm ×). 240 mm). The package was frozen, and the obtained package of frozen sweet potato was directly cooked in a microwave oven. The microwave heating caused an explosive rupture after 4 minutes, and Shumai was scattered in the microwave oven. And the heating of the contents was not enough. Comparative Example 2 As a molded sheet, a 200-μm-thick polypropylene sheet was laminated by dry lamination with a medium-density polyethylene (55 μm) as a sealant layer to obtain a molded sheet 2 for a microwave-compatible packaging material. Was. The obtained comparative example sheet 2 was formed into a 70 mm × 150 mm, depth 30
mm tray shape, the flange is 7mm wide,
A molding tray 2 for a comparative example of a microwave-compatible packaging material was obtained. A biaxially stretched polyethylene terephthalate film was used as a lid material film, and a medium density polyethylene (15 μm) was laminated as a sealant layer by a dry lamination method to obtain a lid material 2 for a microwave-compatible packaging material. As contents, 200 g of mabo tofu was used as a comparative molding tray 2
And covered with the lid material 2 of the comparative example, heat-sealed and sealed to obtain a comparative example 2 of a package of a tray. The package for the comparative example was stored in a refrigerator for 24 hours, then removed from the refrigerator, and the package was directly cooked in a microwave oven. Three minutes after the start of microwave heating, the package exploded and the marbo tofu scattered in the microwave oven.

Even if the contents are sealed and packaged and heated in a microwave oven, the packaging bag does not explode due to an increase in the internal pressure, and the contents are prevented from being scattered in the refrigerator. In the initial stage of the increase in internal pressure due to heating, the seal part peels off, and the vapor generated in the bag is released from the part where it first peeled off, and the vapor diffuses out of the bag. Is easily dissipated out of the bag, so that the rupture of the packaging bag is not explosive, so that the contents are not scattered, and the heating in the microwave oven is stable.

[0020]

According to the present invention, the contents are sealed and packaged. The microwave oven, even when heated, does not cause explosive rupture of the packaging bag due to an increase in the internal pressure. The vapor generated in the bag is released from the part where it was peeled off first, and when the internal pressure rises, the peeled part widens and the vapor is easily diffused out of the bag. No rupture occurred, and thus the contents were not scattered, and heating in the microwave oven became stable.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a material configuration of an embodiment of a packaging material for a microwave oven according to the present invention.

FIGS. 2A and 2B are diagrams showing a bag using the packaging material for a microwave oven of the present invention and peeling of a seal portion by heating, wherein (a) a bag before heating;
(B) X ₁ -X ₁ part cross-sectional view of, (b) by microwave heating, the state in which the sealing portion is steam peeling is dissipated to the outside of the bag, cross-sectional view of (d) X ₂ -X ₂ parts Is shown.

3A and 3B are schematic diagrams illustrating a state of peeling by heating, in which FIG. 3A is a cross-sectional view of a seal portion before heating, and FIG. 3B is a cross-sectional view of a seal portion opened by an internal pressure of steam generated by high-frequency heating. is an enlarged view of (d) Y ₁ parts.

FIG. 4 is a diagram showing an example of a tray type to which the packaging material for a microwave oven according to the present invention can be applied.

5 (a) is a cross-sectional view illustrating a tray type packaging state using the packaging material for a microwave oven according to the present invention, and FIG. 5 (b).
Y ₂ parts an enlarged view.

[6] The inner pressure of the steam and the packaging of the tray type generated by high-frequency heating, (a) cross-sectional view of the apertured package is an enlarged view of (d) Y ₃ parts.

FIG. 7 is a view showing an example of a packaging form of various bags to which the microwave oven-compatible packaging material of the present invention can be applied.

[Explanation of symbols]

 S Packaging material for microwave oven C Contents P Bag using packaging material for microwave oven F Tray packaging using packaging material for microwave oven K Peeling opening Vp Steam 1 Base layer 2 Heat seal layer 3 First layer 4 First 2 layer 5 3rd layer 6 Adhesive layer 7 Intermediate layer 8 Heat seal part 9 Peeling surface 11 Molding tray 12 Lid 13 Depressed part 14 Flange 20 Lamination of molding tray 21 Plastic sheet 30 Lamination of lid

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 3E064 AA04 AA05 AA09 AA13 AB23 BA17 BA25 BA27 BA28 BA29 BA30 BA36 BA40 BA46 BA55 BA60 BB03 BC18 EA30 GA01 HD10 HE10 HN05 3E086 AA23 AB01 AD01 BA04 BA15 BB90 CA03 AK04 AK04 AK04 AK04 AK04 AK04 AK04 AK04 AK04 AK04B AK06B AK06D AK07A AK07C AK63B AK63D AK68B AK68D AK70B AK70D AK71B AK71D AR00A AR00B AR00C AR00D BA04 BA07 BA10A BA10D BA13 BA25 CB00 EJ38A GB15 GB23 JJ03 JL12J12B12L

Claims (3)

[Claims] 1. A packaging material for a microwave oven, wherein at least a heat-resistant base material layer and a sealant layer are laminated, when the sealant layer is laminated with the base material layer, the base material layer side is a first layer. , Middle layer 2 and contents side 3
A three-layer structure made of a thermoplastic resin,
Layer and third layer are low-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ionomer, ethylene-methyl acrylate copolymer, ethylene A packaging material for a microwave oven, characterized in that the resin is any one of methacrylic acid copolymer, ethylene-ethyl acrylate copolymer and ethylene-acrylic acid copolymer, and the second layer is polypropylene. 2. The method according to claim 1, wherein the thickness ratio of the second layer and the third layer of the sealant layer is 2: 1: 3 = 1: 1 to 1: 1. Microwave packaging material. 3. A packaging bag wherein the sealant layers of the packaging material for a microwave oven are arranged so as to face each other, and are formed by heat sealing a predetermined sealing portion.