JP2013006607A - Container used in microwave oven - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a container for microwave oven with improved openability after heating by a microwave oven.
SOLUTION: A container body 30 and a lid body 20 that seals an opening of the container body, the lid body 20 being base material layers 22 and 24, and a heating element layer that generates heat by microwave irradiation. 26 and a sealing layer 28 that adheres to the opening of the container body, and the sealing layer is in contact with one surface of the heating element layer by a coating film mainly composed of a thermoplastic resin. A microwave oven container, wherein the sealing layer has a thickness of 1 to 15 μm.
[Selection] Figure 2

Description

  The present invention relates to a container for a microwave oven having improved openability after heating by a microwave oven.

  Conventionally, various synthetic resin containers capable of heating contents in a microwave oven have been proposed as food containers for solid foods and liquid foods. As such a microwave oven container, Japanese Patent Application Laid-Open No. 2-152679 discloses a flaky or powdery microwave interaction in a heat-sealable resin layer for bonding a tray and a closure in a food package. It is described that, by blending, dispersing, or embedding a conductive substance, the microwave interactive substance generates heat during microwave heating by a microwave oven, and the peel strength of the heat-sealable resin layer is reduced. ing.

JP-A-2-152679

  However, as a result of various investigations by the present inventors, in the microwave oven container described in JP-A-2-152679, the microwave interactive substance is blended, dispersed or embedded in the heat-sealable resin layer. Therefore, the heat-seal resin layer becomes thicker by that amount, and the heat-seal resin layer melts more than necessary when the microwave-interactive substance generates heat during microwave heating. There was a possibility that it would be difficult to open the seal surface due to melting.

  This invention is made | formed in view of the said subject, Comprising: It aims at providing the container for microwave ovens which the openability after the heating by a microwave oven was improved.

  In order to achieve the above object, a microwave oven container according to the invention of claim 1 includes a container main body and a lid that seals an opening of the container main body, and the lid includes a base material layer and a base layer. And a heating element layer that generates heat when irradiated with microwaves and a seal layer that adheres to the opening of the container body, and the seal layer is formed by a coating mainly composed of a thermoplastic resin. It is formed so as to be in contact with one surface of the body layer, and the thickness of the seal layer is 1 to 15 μm.

  Further, in the microwave oven container according to the invention of claim 2, the heating element layer is formed of a vapor deposition film made of aluminum or a mixture of aluminum and aluminum oxide, and the thickness of the heating element layer is 30 to 100 nm. It is characterized by being.

  The microwave oven container according to the invention of claim 3 is characterized in that the thermoplastic resin contained in the seal layer has a melting point in the range of 130 to 250 ° C.

According to the first aspect of the present invention, the seal layer is formed so as to be in contact with one surface of the heating element layer by a coating film mainly composed of a thermoplastic resin, and the thickness of the seal layer is 1 to By setting the thickness to 15 μm, the heat generated by the heating element layer can be directly applied to the sealing layer, so that the sealing layer can be efficiently melted and the sealing layer made of a coating film is formed on the surface of the heating element layer. When forming the thermoplastic resin can be spread over the fine irregularities on the surface of the heating element layer without gaps, the adhesion between the heating element layer and the seal layer can be improved, As a result, the sealing property of the container and the peel strength of the lid body with respect to the container body can be sufficiently ensured. Further, since the thickness of the seal layer is thinner than that of a general sealant film, even if the thermoplastic resin in the seal layer melts when the heating element layer generates heat by microwave heating, the amount of the thermoplastic resin is reduced. Since there is little, the resin on the seal layer side and the resin layer on the container body side hardly melt, and the resin of the seal layer can be effectively melted to reduce the adhesive strength, and as a result, the container is easily opened. be able to.
According to the invention of claim 2, the heating element layer is formed of a vapor deposition film made of aluminum or a mixture of aluminum and aluminum oxide, and the heating element layer has a thickness of 30 to 100 nm. Thus, heat generation by the heating element layer can be sufficiently generated, and damage to the deposited film can be prevented when forming a coating film serving as a seal layer on one surface of the heating element layer.
Moreover, according to invention of Claim 3, even if it is a case where a container is retort-treated by making melting | fusing point of the thermoplastic resin in a sealing layer into the range of 130-250 degreeC, thermoplastic resin is Since it does not melt, the adhesive strength of the seal layer is not impaired, and when heated in a microwave oven, the thermoplastic resin in the seal layer is surely melted to lower the adhesive strength and improve the openability.

It is a front view of the container for microwave ovens concerning one Embodiment of this invention. It is sectional drawing of the cover body of the container for microwave ovens concerning one Embodiment of this invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
The front view of the container for microwave ovens concerning one Embodiment of this invention is shown in FIG. 1, and sectional drawing of a cover body is shown in FIG. 2, respectively.
The microwave oven container 10 of the present invention is a food packaging container that can be heated in a microwave oven, and has an opening of the container body 30 sealed with a lid 20 having heat sealability. It is.

  The lid 20 used in the microwave oven container of the present invention includes base material layers 22 and 24, a heating element layer 26 that generates heat by absorbing microwaves, and a sealing layer 28 that has adhesiveness to the container body. It is formed from a laminated multilayer sheet material. The lid 20 includes a disc-shaped top plate 20a that seals the opening of the container body, and a knob 20b that is formed so as to protrude outward from the peripheral edge of the top plate in the radial direction of the container. have.

  The base material layers 22 and 24 are formed of a known thermoplastic resin film. The thermoplastic resin film is not particularly limited, but a single layer film such as a polyester resin such as polyethylene terephthalate, a polyamide resin such as nylon 6, an olefin resin such as polyethylene or polypropylene, or these films may be used. A multilayer film appropriately laminated can be preferably used. In addition, the kind of thermoplastic resin and film thickness of the base material layers 22 and 24 are appropriately set so that the base material layers 22 and 24 themselves are not damaged by the heat generation of the heating element layer 26 by microwave heating. In general, the base layers 22 and 24 have a total thickness of 20 to 50 μm.

  The heating element layer 26 is formed in a thin film shape with a deposited film of a conductive material that generates heat by absorbing microwaves, a conductive ink metal foil, or the like. As the conductive material, a metal such as aluminum, tin, zinc, iron, copper, or one or a mixture of two or more of these metal oxides can be used. In particular, in view of material cost and productivity, it is preferable to use a vapor deposition film made of aluminum alone or a mixture of aluminum and aluminum oxide. When a mixture is used, the mass ratio of aluminum to aluminum oxide is 4: 1. More preferably, it is ˜1: 9. Moreover, when using these, when forming a coating film on the surface of a vapor deposition film, it becomes difficult to damage a vapor deposition film. In addition, the heat generation temperature of the vapor deposition film when heated by a microwave oven can be suitably about 160 to 300 ° C. The thickness of the deposited film is preferably 30 to 100 nm, and by setting within this range, when heated for a longer time than necessary in a microwave oven, the deposited film is cracked to stop or suppress heating. As a result, the container can be prevented from being overheated. In addition, if the thickness of the deposited film is less than 30 nm, it is liable to be damaged when forming a coating film serving as a seal layer on the surface of the deposited film, and a sufficient heat generation effect may not be obtained. Then, the vapor deposition film is liable to be cracked by heating, and there is a risk that the vapor deposition film may crack when the coating applied to form a coating film on the surface of the vapor deposition film is baked.

  The sealing layer 28 is directly formed so as to be in contact with one surface of the heating element layer 26 by a coating film mainly composed of a thermoplastic resin. In addition, such a coating film is formed by, for example, applying a paint in which fine particles of thermoplastic resin are dispersed in a solvent on the surface of the heating element layer 26 using a known means, and heating and baking the paint. The resin in the paint is melted to form a thin film. Examples of the thermoplastic resin include olefin resins such as polypropylene and polyethylene, aromatic polyester resins such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate, aliphatic polyester resins such as polylactic acid and polyglycolic acid, Polyamide resins such as nylon 6, nylon 6,6, nylon 12, and MXD6 nylon, polycarbonate resins, and the like can be suitably used. Examples of the solvent for dispersing the thermoplastic resin fine particles include ester solvents such as ethyl acetate, dibasic acid ester solvents such as dimethyl adipate, ketone solvents such as cyclohexanone, hydrocarbon solvents such as cyclohexane, and benzyl alcohol. Known solvents such as alcohol solvents such as water, water, or a mixture of these solvents can be used. As for the compounding quantity to the solvent of a thermoplastic resin, 1-30 mass parts is preferable with respect to 100 mass parts of solvents, and the productivity at the time of forming a coating film is bad that a compounding quantity is less than 1 mass part. On the other hand, if the amount exceeds 30 parts by mass, the fine particles of the thermoplastic resin may aggregate to deteriorate the paintability. The melting point of the thermoplastic resin is preferably in the range of 130 to 250 ° C. A part of the thermoplastic resin in the seal layer 28 is melted by a process such as heat sealing and is welded to the opening of the container body 30.

  The average particle diameter of the thermoplastic resin fine particles used for forming the seal layer 28 is preferably 10 nm to 100 μm. If the average particle diameter of the thermoplastic resin fine particles is less than 10 nm, the viscosity of the paint may be too high and the paintability may be deteriorated. On the other hand, if it exceeds 100 μm, uniform coating may be inhibited. As a result, there is a possibility that the sealing performance is impaired, or the bursting strength when the internal pressure of the container is increased is lowered. Furthermore, the thickness of the seal layer 28 is set in the range of 1 to 15 μm. If the thickness of the sealing layer 28 is less than 1 μm, there is a possibility that sufficient adhesive strength with the container cannot be obtained. On the other hand, if the thickness exceeds 15 μm, the sealing surface of the thermoplastic resin in the seal layer 28 and the container body melts, so that the peel strength after heating cannot be lowered sufficiently. That is, when the thickness of the seal layer 28 exceeds 15 μm, the amount of the thermoplastic resin on the seal layer 28 side increases, so that the polymers of the thermoplastic resin constituting the seal layer 28 and the container body 30 are easily connected to each other. As a result, the interface between the seal layer 28 and the container main body 30 may be melted together, and it may be difficult to reduce the peel strength.

  The container body 30 of the present invention is a container in which a thermoplastic resin material such as an olefin resin such as polyethylene or polypropylene, a polyester resin such as polyethylene terephthalate, a nylon resin, or a styrene resin is molded by injection molding or pressure molding. Can be preferably used. In the present embodiment, the container body 30 is a cup-shaped container, and includes a disk-shaped bottom portion, a cylindrical body portion that extends upward so as to expand in a tapered shape from a peripheral portion of the bottom portion, and a body portion An annular flange portion 30a is formed around the opening defined by the upper end and extends outward in the radial direction of the container. And the sealing layer 28 of the cover body 20 is welded to the upper surface of the flange portion 30a of the container 30 by heat sealing or the like, so that the inside of the container 30 is sealed.

  When the microwave oven container 10 of the present invention as described above is heated in a microwave oven, the heating element layer 26 absorbs microwaves and generates heat, and the heat causes the thermoplastic resin in the coating film constituting the seal layer 28 to be heated. Melt. As a result, the adhesiveness between the lid body and the container main body due to the seal layer is lowered, and the openability of the lid body 20 is improved.

Hereinafter, the Example of the container for microwave ovens of this invention is described.
[Example 1]
An aluminum vapor deposition film (VM-PET 1015HT: laminated with a vapor deposition film made of a mixture of aluminum and aluminum oxide with a thickness of 50 nm serving as a heating element layer on one surface of a 12 μm thick polyethylene terephthalate resin film serving as a base material layer. Toray Film Processing Co., Ltd.) was laminated. Further, a polyethylene terephthalate resin film (Embret: manufactured by Unitika Co., Ltd.) having a thickness of 25 μm serving as a base material layer was laminated on the surface of the base material layer opposite to the heating element layer. Subsequently, a coating material (Eipoc-1805: manufactured by Kakinomiya Chemical Co., Ltd.) containing fine particles of a thermoplastic resin (olefin resin) serving as a seal layer on the outer surface of the heating element layer 26 is used with a bar coater # 14. By applying once and baking at 180 ° C., a lid having a sealing layer (coating film) having a film thickness of 1 to 2 μm was prepared. The sealing layer of the lid is heat sealed (180 ° C.-1) to a flange portion (outer diameter 70.2 mm, inner diameter 61 mm) of a polypropylene resin pressure cup container (manufactured by Yamato Chiba Steel Co., Ltd.) filled with 180 g of water. 2 seconds × 2 times) to obtain a microwave oven container of Example 1.

[Example 2]
In the same manner as in Example 1, a laminate of a base material layer and a heating element layer was prepared, and a coating material containing thermoplastic resin fine particles similar to that in Example 1 was applied to the outer surface of the heating element layer using a bar coater # 30. The lid body in which a seal layer (coating film) having a film thickness of 5 to 8 μm was formed by applying the film once and baking at 180 ° C. was prepared. The container for microwave oven of Example 2 was obtained by heat-sealing the sealing layer of this lid body to a cup container similarly to Example 1.

[Example 3]
In the same manner as in Example 1, a laminate of a base material layer and a heating element layer was prepared, and a coating material containing thermoplastic resin fine particles similar to that in Example 1 was applied to the outer surface of the heating element layer with a bar coater # 65. It was applied once and baked at 180 ° C. to prepare a lid on which a seal layer (coating film) having a film thickness of 10 to 15 μm was formed. The container for microwave oven of Example 3 was obtained by heat-sealing the sealing layer of this lid body to a cup container similarly to Example 1.

[Comparative Example 1]
In the same manner as in Example 1, a laminate of a base material layer and a heating element layer was prepared, and a coating material containing thermoplastic resin fine particles similar to that in Example 1 was applied to the outer surface of the heating element layer with a bar coater # 65. The coating layer was applied three times and baked at 180 ° C. to form a sealing layer (coating film) having a film thickness of 30 μm, thereby producing a lid. The lid sealing layer was heat-sealed to a cup container in the same manner as in Example 1 to obtain a microwave oven container of Comparative Example 1.

[Comparative Example 2]
In the same manner as in Example 1, a laminate of a base material layer and a heating element layer was prepared, and a sealant film having a thickness of 30 μm serving as a seal layer (Allomer U: manufactured by Okamoto Co., Ltd.) was formed on the outer surface of the heating element layer. ) Was laminated. The lid sealing layer was heat sealed to a cup container in the same manner as in Example 1 to obtain a microwave oven container of Comparative Example 2.

  Table 1 below shows the results of heating the microwave oven containers of Examples 1 to 3 and Comparative Examples 1 and 2 in a microwave oven with a rated high-frequency output of 500 W for 30 seconds and measuring the peel strength before and after the heating. . The peel strength was measured using a tensile tester (V10-C: manufactured by Toyo Seiki Seisakusho Co., Ltd.), at a speed of 300 mm / min, an angle of 90 ° (a microwave oven container was placed upright, and the knob part of the lid) And is pulled up directly above, that is, pulled upward at an angle of 90 ° with respect to the extending direction of the lid.

  From the result of the said Table 1, as for the container for microwave ovens of Examples 1-3, all peel strength fell to about 1/10 before a heating by the heating in a microwave oven. On the other hand, as in Comparative Example 1, when the film thickness is thick even if a thermoplastic resin coating is used as the seal layer, the peel strength before heating is increased, and the thermoplastic resin in the coating is Since the sealing surface with the container body melts, the peel strength after heating was not sufficiently reduced. Further, as in Comparative Example 2, when a film was used as the sealing layer, the film was melted and melted with the flange portion of the container body, so that it could not be opened at all.

  As mentioned above, although one Embodiment of the microwave oven container of this invention was described, this invention is not limited to said embodiment. For example, in this embodiment, a laminate of two polyethylene terephthalate resin films is used as a base material layer, a heating element layer is laminated on one side, and a seal layer is directly applied to the surface of the heating element layer. However, the configuration of the lid is not limited to this. For example, a heating element layer is laminated between two polyethylene terephthalate resin films, and a sealing layer is applied to the outer surface of the polyethylene terephthalate resin film. In addition, a resin film serving as a base material layer may be interposed between the heating element layer and the sealing layer. Moreover, you may use a single layer resin film as a base material layer, without using what laminated | stacked two polyethylene terephthalate resin films. Further, the form of the container body is not limited to the cup-type container, and the form is not particularly limited as long as the lid is sealed by heat sealing at the opening.

  As described above, according to the microwave oven container of the present invention, the coating film mainly composed of thermoplastic resin is formed so as to be in contact with one surface of the heating element layer, and the thickness of the sealing layer. By setting the thickness to 1 to 15 μm, heat generated by the heating element layer can be directly applied to the sealing layer, so that the sealing layer can be efficiently melted and coated on the surface of the heating element layer. When forming a sealing layer with a film, the thermoplastic resin can be distributed without any gaps to fine irregularities on the surface of the heating element layer, so that the adhesion between the heating element layer and the sealing layer is improved. As a result, the sealing property of the container and the peel strength of the lid body with respect to the container body can be sufficiently secured. Moreover, since the thickness of the sealing layer is 1 to 15 μm, the thickness of the sealing layer is thinner than a general sealant film. Therefore, when the heating element layer generates heat by microwave heating, the heat in the sealing layer Even if the plastic resin melts, the amount of the thermoplastic resin is small, so the resin on the seal layer side and the resin layer on the container body side hardly melt, effectively melting the resin on the seal layer and reducing the adhesive strength. As a result, the container can be easily opened. Furthermore, when the sealing layer is formed on the surface of the heating element layer, since the sealing layer is relatively thin, less heat is required for baking the applied paint. When a thermoplastic resin film is used, the thermal contraction of the resin film can be suppressed, and as a result, damage to the heating element layer laminated on the base material layer can be prevented.

  Furthermore, the container for microwave oven of the present invention can easily reduce the adhesive strength by heating in a microwave oven. Therefore, by setting a relatively high adhesive strength in the state of the product before heating, Sufficient product quality can be ensured during transportation and storage. Further, the heating element layer is formed of a vapor deposition film made of aluminum or a mixture of aluminum and aluminum oxide, and the thickness of the vapor deposition film is set to 30 to 100 nm, whereby heat generation by the heating element layer can be sufficiently generated. At the same time, when the coating film is formed on the surface of the deposited film, damage to the deposited film can be prevented. Furthermore, by setting the thickness of the deposited film within this range, when heated for longer than necessary in a microwave oven, it is possible to stop or suppress heating by causing cracks in the deposited film. The container can be prevented from being heated excessively. If the thickness of the vapor deposition film is less than 30 nm, the film tends to be damaged when forming a coating film serving as a seal layer on the surface of the vapor deposition film, and a sufficient heat generation effect may not be obtained. Then, the vapor deposition film is liable to be cracked by heating, and there is a risk that the vapor deposition film may crack when the coating applied to form a coating film on the surface of the vapor deposition film is baked. In addition, by setting the melting point of the thermoplastic resin in the seal layer in the range of 130 to 250 ° C., for example, even when the container is retorted, the adhesive strength of the seal layer is impaired because the thermoplastic resin does not melt. In addition, when heated in a microwave oven, the thermoplastic resin in the sealing layer is surely melted to lower the adhesive strength and improve the openability. That is, when the melting point of the thermoplastic resin is lower than 130 ° C., when the container after filling the contents is retort-treated, the thermoplastic resin may be melted by heating during the retort treatment and the sealing performance may be impaired. On the other hand, when the temperature exceeds 250 ° C., the thermoplastic resin is not sufficiently melted when the heat generating layer generates heat, and the adhesive strength by the seal layer may not be sufficiently reduced.

10 Microwave Oven 20 Lid 22 Base Material Layer 1 (PET Film)
24 Base material layer 2 (PET film)
26 Heating element layer (deposition film)
28 Seal layer (thermoplastic coating)
30 Container body

Claims (3)

A container body, and a lid for sealing the opening of the container body,
The lid comprises a laminate having a base material layer, a heating element layer that generates heat by microwave irradiation, and a seal layer that adheres to the opening of the container body,
The seal layer is formed of a coating mainly composed of a thermoplastic resin so as to be in contact with one surface of the heating element layer, and the thickness of the seal layer is 1 to 15 μm. A container for a microwave oven.   2. The electron according to claim 1, wherein the heating element layer is formed of an evaporated film made of aluminum or a mixture of aluminum and aluminum oxide, and the heating element layer has a thickness of 30 to 100 nm. Range container. The container for a microwave oven according to claim 1 or 2, wherein a melting point of the thermoplastic resin contained in the seal layer is in a range of 130 to 250 ° C.

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