Package body for microwave-heating processing

Abstract

To provide a package body allowed to be heated with an electronic oven, prevent a content from oxidizing and keep taste and flavor over a long time.SOLUTION: A package body 1 for heating processing in the present invention comprises a bag body 8 that multi-layer films are superposed to form a front side 2 and a back side 3 and sealed at doubly-superposed outer peripheral edges 6 with an opening 5 for accommodating an object left so as to provide at least in part a gas-discharge portion 7 through which vapor or gas can be discharged. The multi-layer film 4 has a heat seal layer, a gas barrier layer and, between these layers, an oxygen-absorbing layer containing a thermoplastic resin dispersed with an iron-based oxygen-absorbing agent. The iron-based oxygen-absorbing agent has a content of 5-50 mass% with respect to a total mass of the oxygen-absorbing layer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a package for microwave heating treatment that enables cooking in a microwave oven. [Background technology]

[0002] A known heat treatment package for cooking in a microwave oven has plastic films that are abutted on the same sides and joined together in a gabled shape by a heat seal of a specified width, with the contents to be heated sealed inside. The first joint is offset to one side of the package, providing an easy-open seal that allows pressure to escape when the internal pressure of the package increases due to heating (see Patent Document 1).

[0003] Also, as a packaging container which improves the gas barrier properties of the container and imparts an oxygen absorbing function to the container itself by constructing the container from a multilayer material having an oxygen absorbing layer made of an oxygen absorbing resin composition in which an iron-based oxygen absorber is blended with a thermoplastic resin, a container is known in which the multilayer material is used as an oxygen absorbing multilayer film in which an oxygen absorbing layer made of a thermoplastic resin having an iron-based oxygen absorber dispersed therein is provided between layers of a gas barrier multilayer film of a conventional configuration in which a heat seal layer and a gas barrier layer are laminated, and the same sides of the films are abutted against each other and heat sealed to a predetermined width to form a bag (see Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 09-150864 [Patent Document 2] Japanese Patent Application Publication No. 09-234832 [Patent Document 3] International Publication No. 2014 / 057991 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional containers made of multilayer materials, such as those disclosed in Patent Document 2, are provided with an oxygen absorbing layer made of an oxygen absorbing resin composition in which an iron-based oxygen absorber is blended with the thermoplastic resin. It was thought, however, that these containers could not be heated in a microwave oven because the iron-based oxygen absorber absorbs microwaves and generates heat, which indirectly heats and softens the surrounding resin (see Patent Document 3).

[0006] An object of the present invention is to provide a package for microwave oven heating treatment that can be heated in a microwave oven, can prevent oxidation of the contents, and can retain the taste and flavor for a long period of time. [Means for solving the problem]

[0007] As a result of intensive research into solving the above problems, the inventors have found that the above problems can be solved by using a multilayer material including an oxygen absorbing layer containing a specific amount of an iron-based oxygen scavenger, and have thus completed the present invention.

[0008] That is, the present invention relates to a package for microwave oven heating treatment, which comprises a bag body in which multilayer films are overlapped to form a front portion and a rear portion, the outer peripheral edge of the double overlap is sealed except for an opening for accommodating an object, and an exhaust portion is provided in at least a part thereof to allow the exhaust of steam or gas, the multilayer film having a heat seal layer, a gas barrier layer, and an oxygen absorbing layer between these layers which contains a thermoplastic resin having an iron-based oxygen absorbent dispersed therein, and the content of the iron-based oxygen absorbent is 5 to 50 mass% relative to the total mass of the oxygen absorbing layer. In addition, the exhaust portion is sealed by overlapping the cut ends of the multilayer film with the surfaces of the heat seal layers facing each other and sandwiching an easy-to-open film between the heat seal layers, with a heat seal strength that makes it easier to open than the outer peripheral end, and it is preferable that the heat seal strength (N / 15 mm) of the exhaust portion is 2 / 3 or less of the heat seal strength (N / 15 mm) of the outer peripheral end in an atmosphere of 100°C. Furthermore, it is preferable that the resin constituting the heat seal layer contains polypropylene. The present invention also relates to a heat treatment package in which an article is placed inside any one of the packages for microwave heating treatment described above and the opening is sealed. Effect of the Invention

[0009] By using the microwave heating processing packaging of the present invention to make a heat processing package, the oxygen within the heat processing package can be efficiently absorbed, the freshness of the packaged items can be maintained for a long period of time, and the heat processing package can be heated in a microwave oven without bursting. [Brief description of the drawings]

[0010] [Figure 1] 1 is a front view showing a schematic diagram of a package for microwave heating treatment according to one embodiment of the present invention. FIG. [Diagram 2] FIG. 1 is a diagram showing a schematic structure of a multilayer film of a package for microwave heating treatment according to one embodiment of the present invention. [Diagram 3] FIG. 2 is a diagram showing a schematic diagram of another example of the structure of the multilayer film of the package for microwave heating treatment according to one embodiment of the present invention. [Figure 4] 1 is a front view showing a schematic diagram of a heat treatment package according to one embodiment of the present invention; [Diagram 5] 4 is a graph showing the change over time in oxygen concentration in the package for heat treatment of the present invention shown in Example 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] As shown in FIG. 1, a package for microwave heating treatment (hereinafter referred to as "package for heating treatment") 1 according to one embodiment of the present invention comprises a bag body 8 in which multilayer films 4 are laminated to form a front portion 2 and a rear portion 3, an outer peripheral edge 6 is sealed except for an opening 5 for inserting an item to be packaged (not shown), and at least a portion of which is provided with an exhaust section 7 capable of releasing steam, etc.

[0012] 2, the multilayer film 4 has a heat seal layer 11 and a gas barrier layer 13, and further has an oxygen absorbing layer 12 containing a thermoplastic resin having an iron-based oxygen absorbent dispersed therein between these layers 11 and 13. The content of the iron-based oxygen absorbent is 5 to 50 mass % based on the total mass of the oxygen absorbing layer 12. A packaged product for heat treatment 50 according to the present invention shown in FIG. 4 is produced by accommodating an article to be packaged inside the package for heat treatment 1 and sealing the opening 5. The packaged product for heat treatment 50 shown in FIG.

[0013] Specifically, as shown in Fig. 1, the bag body 8 is formed by overlapping two sheets of multilayer film 4 so that the heat seal layers 11 shown in Fig. 2 and Fig. 3 face each other, or by folding one sheet of multilayer film 4 to form a double layer at the front part 2 and the rear part 3, and sealing the outer peripheral edge 6 except for the opening 5. In this embodiment, the latter configuration is adopted, and one edge 2a opposite to the opening 5 is closed by folding the multilayer film 4.

[0014] The package for heat treatment 1 has the heat seal layer 11 facing the inner surface side and the gas barrier layer 13 facing the outer surface side. The shape of the bag body 8 is not particularly limited, but in this embodiment, it is formed into a substantially rectangular shape overall.

[0015] The front portion 2 has a joint 9 near one edge 2a in one direction (the direction of arrow L1 in Figure 1) at a position within 40%, more preferably within 30%, of the total dimension of the bag body 8 in one direction L1 from a position a short distance from the one edge 2a toward the other edge 2b. Here, the term "slight distance" refers to a dimension greater than 0, and means that the joint 9 does not include one end edge 2a of the package for heat treatment 1.

[0016] The joint 9 is a portion in which the ends of the multilayer film 4 that has been cut are heat-sealed together in a state in which the heat-seal layers 11 (i.e., inner surfaces) are overlapped and faced to each other along the entire direction of the front portion 2 that is approximately perpendicular to the aforementioned one direction. The joint portion 9 has a fold at its base end so as to lie substantially along the surface 2f on one end edge 2a side of the front surface 2 of the front portion 2.

[0017] An easy-to-open film 20 is inserted into at least a part of the joint 9. In this embodiment, it is formed over the entire longitudinal direction of the joint 9. The part of the joint 9 where the easy-to-open film 20 is inserted is formed with a heat seal strength described later, and serves as an exhaust part 7 that can be easily opened by steam pressure. A non-sealed portion 21 surrounded by an arch shape is formed in the center in the extension direction of the joint 9. When the heat treatment package 1 is made into the heat treatment package 50 shown in Fig. 4 and heated in a microwave oven, the non-sealed portion 21 allows the center of the joint 9 where the non-sealed portion 21 is provided to pass outside the bag first when the sealed portion of the easy-open film 20 is peeled off due to internal steam pressure, thereby allowing steam to be discharged.

[0018] At the outer peripheral edge 6 where both widthwise ends of the front portion 2 and the rear portion 3 are overlapped and heat-sealed, a notch 22 is formed for opening the heat-processed package 50 after it has been made into the heat-processed package 50 and heated. From the viewpoint of ease in opening the bag body 8 in as straight a line as possible, the notch 22 is preferably formed in the vicinity of the joint 9.

[0019] As shown in FIG. 2, the multilayer film 4 has a configuration in which a heat seal layer 11 containing a thermoplastic resin, an oxygen absorbing layer 12 formed by dispersing an iron-based oxygen absorber in a thermoplastic resin, and a gas barrier layer 13 are laminated in this order.

[0020] The layers constituting the multilayer film 4 may be in direct contact with each other and heat-sealed, or may be laminated via a layer of adhesive or the like (not shown).

[0021] The heat seal layer 11 is located on the side in contact with the packaged goods as the innermost layer of the bag body 8, and serves as an isolation layer that prevents chemical components and odorous components in the oxygen absorbing layer 12 from contacting or moving to the packaged goods such as food. Furthermore, the heat seal layer 11 allows oxygen and moisture from the packaged goods to pass through to the oxygen absorbing layer 12 so that the adjacent oxygen absorbing layer can exhibit its oxygen absorbing ability.

[0022] The structure of the heat seal layer 11 is preferably a non-porous resin film, but it must have appropriate oxygen permeability and moisture permeability, and it is more preferable that it further has heat sealability in order to perform the function of sealing the outer peripheral edge 6 shown in FIG.

[0023] The heat seal layer 11 is made of a thermoplastic resin having oxygen permeability, specifically, polyolefin resins such as polyethylene, polypropylene, various ethylene-α-olefin copolymers, ethylene-acrylic acid (or methacrylic acid) copolymers, ethylene-maleic anhydride copolymers, ethylene-vinyl acetate copolymers, ionomers, polybutene, polymethylpentene, etc. are used, and it is preferable to select the resin in consideration of the thermal adhesion with the adjacent oxygen absorbing layer 12. Among them, polypropylene is preferably used as the heat seal layer 11, and non-oriented polypropylene is more preferable. These resins used in the heat seal layer 11 may be used alone or in a blend, and may be used in multiple layers.

[0024] The heat seal layer 11 may be a molten film obtained by melt-extruding pellets, or may be a preformed film. Various polyolefin-based resin films are preferably used as the film for the heat seal layer 11. Note that the heat seal layer 11 may contain coloring pigments and fillers to the extent that the function is not impaired.

[0025] The oxygen permeability of the heat seal layer 11 is 1000 cc / m 2The thickness of the heat seal layer 11 is preferably 5 to 100 μm, more preferably 10 to 50 μm, and from the viewpoint of ensuring oxygen permeability, the thinner the better. However, a suitable thickness is also necessary to obtain a suitable seal strength and to prevent pinholes from being formed during manufacture or use, which would impair the insulating properties. From the viewpoint of the insulating properties, the thickness of the heat seal layer 11 is preferably 5 to 100 μm, and more preferably 10 to 50 μm.

[0026] The oxygen absorbing layer 12 is made of an oxygen absorbing resin composition in which an iron-based oxygen scavenger is dispersed in a thermoplastic resin. As the iron-based oxygen scavenger, it is preferable to use metallic iron as a main agent for the oxygen absorption reaction, from the standpoints of oxygen absorption capacity, safety, cost, etc. Specific examples of the metallic iron include reduced iron powder, atomized iron powder, and iron powder of crushed or ground steel, cast iron, etc. The average particle size of the iron powder is not particularly limited, but is preferably in the range of 1 to 50 μm.

[0027] Specific examples of other components of the iron-based oxygen absorber containing metallic iron as a main component include metal halides, and more specific examples of other components include chlorides, bromides, iodides, and the like of alkali metals or alkaline earth metals. The amount of the metal halide to be added is specifically within a range of 0.1 to 20 parts by mass per 100 parts by mass of the metallic iron.

[0028] The metal halide is preferably attached to the surface of the metallic iron to be integrated as an iron-based oxygen scavenger, and then blended into the thermoplastic resin. The metal halide can be attached to and integrated with the surface of the metallic iron to effectively utilize the catalytic action of the metal halide, and the amount of the metal halide can be reduced to 0.1 to 10 parts by mass per 100 parts by mass of the metallic iron. Even when the iron-based oxygen scavenger is integrated and processed into particles in this manner, the average particle size of the particles is the same as that of the iron powder.

[0029] The thermoplastic resin in which the iron-based oxygen scavenger is dispersed is not particularly limited as long as it is an oxygen-permeable thermoplastic resin. 2 Preferred examples of thermoplastic resins include those having a thermal expansion coefficient of 1 atm·day (23° C., 100% RH) or higher.

[0030] Specific examples of the thermoplastic resin in which the iron-based oxygen scavenger is dispersed include polyolefin-based resins such as polyethylene, polypropylene, various ethylene copolymers, modified polyolefins, elastomers, etc. The thermoplastic resin in which the iron-based oxygen scavenger is dispersed may be used alone or in the form of a blend of two or more kinds.

[0031] The amount of the iron-based oxygen scavenger in the oxygen absorbing layer 12 is in the range of 5 to 50 parts by mass, preferably 10 to 45 parts by mass, and more preferably 20 to 40 parts by mass, relative to the total mass of the oxygen absorbing layer 12, taking into consideration the oxygen scavenging performance, film processability, durability when heated in a microwave oven, and flexibility of the film.

[0032] If the amount of the iron-based oxygen scavenger is more than 50 parts by mass, when the heat treatment package 50 containing the packaged item is heated in a microwave oven and the pressure inside the package for heat treatment 1 rises, the flexibility of the multilayer film 4 is insufficient and expansion is suppressed. As a result, the steam pressure inside the package for heat treatment 1 cannot be lowered sufficiently just by releasing the steam or gas from the exhaust section 7, and the package for heat treatment 1 may burst. In addition, if the amount of the iron-based oxygen scavenger is more than 50 parts by mass, there is a risk that the microwaves and the iron-based oxygen scavenger will react to generate sparks, causing the package for heat treatment 1 to melt and burn.

[0033] On the other hand, if the amount of the iron-based oxygen scavenger is less than 5 parts by mass, sufficient oxygen absorbing ability cannot be obtained. The thickness of the oxygen absorbing layer 12 is preferably in the range of 10 to 100 μm, more preferably in the range of 20 to 90 μm, and even more preferably in the range of 30 to 80 μm, taking into consideration the properties of the iron-based oxygen scavenger, oxygen scavenging performance, film processability, etc.

[0034] Furthermore, by blending alkaline earth metal oxides such as calcium oxide in the oxygen absorbing layer 12, foaming during film processing can be prevented, and the oxygen absorbing ability of the multilayer film 4 can be maintained.

[0035] The amount of the alkaline earth metal oxide is preferably in the range of 0.1 to 5 parts by mass per 100 parts by mass of the iron-based oxygen scavenger. The oxygen absorbing layer 12 may further contain additives such as a deodorizing component, a coloring component, and a water-retaining component. The average particle size of these compounds is the same as that of the iron powder.

[0036] When forming the oxygen absorbing layer 12, a layer A for absorbing the protruding portions of particles of an iron-based oxygen scavenger or the like can be provided on the opposite side of the oxygen absorbing layer 12 to the heat seal layer 11 (i.e., the side facing the gas barrier layer). The resin forming the layer A is preferably a polyolefin resin that is compatible with the resin of the oxygen absorbing layer 12, capable of being heat-sealed, and softened at the extrusion temperature of the oxygen absorbing layer 12. More specifically, polyethylene, polypropylene, etc. may be used depending on the extrusion temperature of the oxygen absorbing layer 12.

[0037] The layer A may be formed from pellets or may be a film. The thickness of the layer A, when combined with the thickness of the oxygen absorbing layer 12, is preferably greater than the maximum particle size of the granular material to be blended in the oxygen absorbing layer 12, and specifically, may be in the range of 10 to 50 μm.

[0038] In addition, it is preferable to provide layer B on the opposite side of the oxygen absorbing layer 12 to the heat seal layer 11 (i.e., the side facing the gas barrier layer 13), taking into consideration heat resistance when heated in a microwave oven, pinhole resistance to prevent the packaged contents from leaking to the outside, and impact resistance. When both Layer A and Layer B are disposed on the oxygen absorbing layer 12, the heat seal layer 11, the oxygen absorbing layer 12, Layer A, Layer B, and the gas barrier layer 13 are laminated in this order, as shown in FIG.

[0039] Specific examples of materials constituting the layer B include polyolefins such as polyethylene and polypropylene, halogenated polyolefins such as polyvinylidene chloride and polyvinylidene fluoride, polyvinyl alcohol, polyamides such as nylon 6, nylon 6,6 and polymetaxylylene adipamide, polyesters such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate and polybutylene naphthalate, polyacrylic acid esters such as polymethyl(meth)acrylate, polyethyl(meth)acrylate and polybutyl(meth)acrylate, and copolymers of monomers forming these. Note that "(meth)acrylic" means methacrylic or acrylic.

[0040] Specific examples of the polyethylene include linear low-density polyethylene, high-pressure low-density polyethylene, high-density polyethylene, metallocene polyethylene, etc. Specific examples of the polypropylene include propylene homopolymers, random or block copolymers of propylene and ethylene or 1-butene, etc.

[0041] The layer B may be formed of a single layer or multiple layers. When the layer B is composed of multiple layers, at least one of the multiple layers is preferably composed of polyester, and more preferably composed of polybutylene terephthalate. This can improve the heat resistance of the layer B and make the hardness of the multilayer film 4 appropriate. The plastic film constituting the layer B is preferably stretched, and more preferably biaxially stretched.

[0042] Suitable materials for forming Layer B include biaxially oriented films made of polypropylene, polyamide, polyester, ethylene-vinyl alcohol copolymer, etc., vinylidene chloride-acrylate copolymer films, aluminum oxide vapor-deposited biaxially oriented polyester films, polymetaxylylene adipamide polyamide oriented films (including coextrusion laminated films with nylon 6), biaxially oriented nylon 6, etc.

[0043] The gas barrier layer 13 is a layer that is positioned on the outer surface side of the bag body 8 . Preferred examples of materials constituting the gas barrier layer 13 include foil or film materials that can be laminated as one of the layers constituting the multilayer film 4 and that can minimize the intrusion of oxygen from outside the bag body 8.

[0044] The gas barrier layer 13 may be a single layer or a composite layer, and for the purpose of printing, concealment, or the like, separate layers may be provided inside and outside the layer having gas barrier properties. When the multilayer film 4 is heat-sealed, the melting point of the gas barrier layer 13 is preferably higher than the melting point of the resin that constitutes the heat seal layer 11, and more preferably is 20° C. or more higher.

[0045] Specific examples of materials constituting the gas barrier layer 13 include nylon films such as nylon 6 and nylon MXD6, polyester films such as polyethylene terephthalate and polybutylene terephthalate, and films in which aluminum, aluminum oxide, silicon oxide, etc. are vapor-deposited on the surface of a nylon film or polyester film. The gas barrier layer 13 can be formed by using one layer of these materials alone or by combining two or more layers of these materials. Among them, suitable materials for forming the gas barrier layer 13 include composite films such as vinylidene chloride coated nylon films, nylon 6 / nylon MXD6 laminates, and metal oxide vapor deposited polyester films.

[0046] The easy-open film 20 may be of an interface peeling type that peels off at the bonding interface of the heat seal layer 11, a cohesive peeling type that peels off with cohesive failure (breakage of the material itself) near the bonding interface, or an interlayer peeling type that peels off between layers of the sealant resin layer composed of a multilayer film, but it is preferable to use the interface peeling type or cohesive peeling type. Of these, it is more preferable to use the cohesive peeling type as the easy-open film 20 from the viewpoint of cost.

[0047] Specific examples of materials constituting the easy-open film 20 include mixed resins of ethylene-based resins and other olefin-based resins. Specific examples of the ethylene-based resins include linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methacrylic acid copolymer (EMAA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-methyl acrylate copolymer (EMA), and ionomers thereof. These can be used alone or in combination.

[0048] Specific examples of other olefin resins include polypropylene resins, polybutene resins, ethylene-butene copolymers, and propylene-butene copolymers. Of these, polypropylene resins and polybutene resins are preferred. Specific examples of polypropylene resins include random copolymers, homopolymers, and block copolymers, of which random copolymers are preferred, and copolymer components of copolymers include α-olefins such as ethylene. Examples of polybutene resins include homopolybutene and copolymers of butene and ethylene.

[0049] The thickness of the easy-open film 20 is preferably 3 μm or more, more preferably 4 μm or more, and even more preferably 5 μm or more, from the viewpoints of film-forming property and appearance when peeled off. The thickness of the easy-open film 20 is preferably 100 μm or less, more preferably 80 μm or less, and even more preferably 50 μm or less, from the viewpoints of film-forming property and appearance when peeled off. By making the thickness of the easy-open film 20 3 μm or more, stable film-forming property can be obtained. On the other hand, by making the thickness of the easy-open film 20 100 μm or less, it is possible to suppress the occurrence of fluffing and film residue when the heat treatment package 1 is opened, and a good appearance when peeled off can be obtained.

[0050] The heat seal strength (N / 15 mm) of the easy-to-open film 20 is preferably 2 / 3 of the heat seal strength (N / 15 mm) of the outer peripheral edge 6 in an atmosphere of 100°C.

[0051] Heat seal strength refers to a method of evaluating how strongly materials bonded by heat are bonded and whether they can withstand external forces, and is measured at a specified temperature under T-peel conditions (measurement width: 15 mm, peel speed: 300 mm / min) in accordance with the method described in JIS Z 0238 (1998). More specifically, the heat-sealed part of a sealed container package is cut open, and both open ends are pulled at a speed of 300±20 mm per minute, and the maximum load (N / 15 mm) until the sealed part peels off is measured.

[0052] Specifically, the multilayer film 4 can be produced by any one of the following methods I to VII.

[0053] Method I 1) a step of extruding and laminating an oxygen absorbing resin composition for the oxygen absorbing layer 12 on the layer B; and 2) a step of further laminating a thermoplastic resin for the heat seal layer 11 on the oxygen absorbing layer 12 side of the film having a layer configuration of the layer B and the oxygen absorbing layer 12 obtained in the previous step. 3) forming the gas barrier layer 13 by laminating a gas barrier material for the gas barrier layer 13 on the Layer B side of the film obtained in the previous step, in which the heat seal layer 11, the oxygen absorbing layer 12, and the Layer B are laminated in this order; The method according to claim 1,

[0054] Method II 1) laminating the layer B and a gas barrier material relating to the gas barrier layer 13; 2) a step of extruding an oxygen absorbing resin composition for the oxygen absorbing layer 12 onto the layer B side of the film having a layer configuration of the layer B and the gas barrier layer 13 obtained in the previous step, thereby laminating the oxygen absorbing layer 12; 3) a step of laminating a thermoplastic resin for the heat seal layer 11 on the oxygen absorbing layer 12 side of the film obtained in the previous step, in which the oxygen absorbing layer 12, the layer B, and the gas barrier layer 13 are laminated in this order, to form a heat seal layer; The method according to claim 1,

[0055] Method III 1) a step of co-extruding and laminating an oxygen absorbing resin composition for an oxygen absorbing layer and a thermoplastic resin for a heat seal layer on the front layer B; 2) a step of laminating a gas barrier material constituting a gas barrier layer 13 on the layer B side of the film having a layer structure of the heat seal layer 11, the oxygen absorbing layer 12 and the layer B obtained in the previous step; The method according to claim 1,

[0056] Method IV 1) a step of extruding and laminating an oxygen absorbing resin composition for the oxygen absorbing layer 12 between the layer B and the heat seal layer 11; 2) a step of laminating a gas barrier material constituting a gas barrier layer 13 on the layer B side of the film having a layer structure of the heat seal layer 11, the oxygen absorbing layer 12 and the layer B obtained in the previous step; The method according to claim 1,

[0057] Method V 1) laminating the layer B and a gas barrier material relating to the gas barrier layer 13; 2) a step of extruding an oxygen absorbing resin composition between the film layer B having the layer configuration of the gas barrier layer 13 and the layer B obtained in the previous step and the film or film-like melt of the thermoplastic resin for the heat seal layer 11, and laminating the composition; The method according to claim 1,

[0058] Method VI 1) forming an oxygen absorbing layer 12 and a heat seal layer 11 in a laminated state by a co-extrusion film forming method; 2) laminating the layer B and a gas barrier material relating to the gas barrier layer 13; 3) a step of laminating a film having a layered structure consisting of an oxygen absorbing layer 12 and a heat seal layer 11 onto the film having a layered structure consisting of the gas barrier layer 13 and the layer B obtained in the previous step, so that the layer B and the oxygen absorbing layer 12 are in contact with each other; The method according to claim 1,

[0059] Method VII 1) a step of extruding and laminating an oxygen absorbing resin composition for the oxygen absorbing layer 12 onto a heat seal layer 11; 2) laminating the layer B and a gas barrier material relating to the gas barrier layer 13; 3) a step of laminating a film having a layered structure consisting of an oxygen absorbing layer 12 and a heat seal layer 11 onto the film having a layered structure consisting of the gas barrier layer 13 and the layer B obtained in the previous step, so that the layer B and the oxygen absorbing layer 12 are in contact with each other; The method according to claim 1,

[0060] Next, a method of using the package for heat treatment 1 will be described. In the heat treatment package 1 shown in FIG. 1, an object to be heated (packaged item) such as food is placed through the opening 5, and the opening 5 is sealed in the same manner as the already sealed outer edge portion 6 to produce the heat treatment package 50 shown in FIG. 4.

[0061] Then, the heat-processing package 50 is placed in a microwave oven and heated at a predetermined temperature for a predetermined time. Then, due to the rise in temperature and expansion of the air and water vapor inside the completely sealed package for heat treatment 1, the packaged item is heated and the package for heat treatment 1 expands.

[0062] At this time, since the multilayer film 4 contains an iron-based oxygen scavenger mainly made of metallic iron in the oxygen absorbing layer 3, the temperature rise is more gradual than when the film does not contain the iron-based oxygen scavenger mainly made of metallic iron. Therefore, when the packaged item is thick and the center is difficult to heat, the temperature difference with the outer surface side of the packaged item can be reduced, allowing heating. This has the effect of avoiding excessive heating of the surface layer of the packaged item in order to properly heat the center, thereby enabling heating with a reduced temperature difference between the center and the surface layer.

[0063] When the heat treatment package 1 shown in Fig. 1 is inflated to a degree that prevents it from expanding any further and further internal pressure is applied by steam, cohesive peeling of the easy-open film 20 occurs, or peeling occurs between the easy-open film 20 and the heat seal layer 11 of the multilayer film 4 of the front portion 2. This causes the outlet 9 to open from the non-sealed portion 21. Then, steam is discharged to reduce the internal pressure while maintaining the heat treatment package 50 in an expanded state.

[0064] In this case, the joint 9 is formed at a position from a position with a small gap from one edge 2a of the bag body 8 to 40% of the dimension in one direction L1. Therefore, when the package for heat treatment 1 expands, the angle between the joint 9 and the surface 2f of the front part 2 is prevented from approaching 0, which would cause a significant decrease in the exhaust action. In addition, by adopting a similar configuration, the package for heat treatment 1 and the packaged product for heat treatment 50 can prevent the packaged item from leaking from the exhaust part 7.

[0065] In this way, the package for heat treatment 1 of the present invention can store and preserve the packaged item, such as food, while maintaining its freshness, flavor, etc., by the oxygen absorbing layer 12, by housing and sealing the packaged item inside. Furthermore, the package for heat treatment 1 and the packaged product for heat treatment 50 can suitably heat food, etc., in a microwave oven, and have the effect of appropriately expanding the multilayer film 4, and then releasing steam as appropriate, thereby maintaining a predetermined internal pressure and temperature during heating.

[0066] There is no particular limit to the wattage of the microwave oven used for heating; either a 1500W commercial microwave or a 600W household microwave can be used. Furthermore, the configuration of the exhaust section 7 and the joint section 9 of the present invention may be formed with a number or length different from the number or length exemplified in the above embodiment, as long as the internal pressure can be appropriately maintained.

[0067] Furthermore, the package for heat treatment 1 may be one that reduces the internal pressure by a configuration other than the exhaust section 9 that is joined using the easy-open film 20 of this embodiment. Specifically, for example, an exhaust valve or the like that can start exhausting air just before the package for heat treatment 1 exceeds its expansion limit may be used. EXAMPLES

[0068] The present invention will be described in detail below using examples, but the present invention is not limited to these examples. EXAMPLES

[0069] A heat treatment package (length 150 mm × width 160 mm) having the configuration shown in FIG. 1 was produced. The multilayer film 4 was constructed using aluminum oxide vapor-deposited polyethylene terephthalate (film thickness 12) as the gas barrier layer 13, biaxially oriented nylon (film thickness 15 μm) as layer B, a film (film thickness 30 μm) made by kneading and extruding reduced iron powder with calcium chloride attached and low-density polyethylene in a mass ratio of 30:70 as the oxygen absorbing layer 12, and unstretched polypropylene (film thickness 50 μm) as the heat seal layer 11. The joint 9 was formed by inserting a polypropylene-based cohesive peelable easy-open film and heat sealing it. The joint 9 was formed at a position 40 mm from one edge 1a. EXAMPLES

[0070] A heat treatment package 1 (length 130 mm x width 140 mm) was prepared in the same manner as in Example 1, except that linear low-density polyethylene was used as the heat seal layer 11 instead of unstretched polypropylene, and a polyethylene-based condensation peelable type easy-open film was used at the joint 9.

[0071] <Heat seal strength> Measurements were performed at four locations (P1, P2 on the left and right sides of the exhaust section 7, and P3, P4 on the left and right outer peripheral end portions 6) shown in Fig. 1 at a prescribed temperature under the conditions of T-type peeling (measurement width: 15 mm, peeling speed: 300 mm / min) according to the method described in JIS Z 0238 (1998). The samples were heated in a microwave oven until they reached the prescribed temperature. The results are shown in Table 1.

[0072] [Comparative Example 1] The heat seal strength was measured at the same location using a Microwave Do! T-type standard retort bag (small) (manufactured by San-A Chemical Co., Ltd.) (similar to that of Example 1 except that it does not have the oxygen absorbing layer 12 and the heat seal layer 11 is made of unstretched polypropylene with a thickness of 60 μm). The results are shown in Table 1.

[0073] [Table 1]

[0074] From the above, it was found that the heat treatment package 1 of the present invention exhibits the same performance as the retort pack for microwave heating that is already on the market. This shows that the heat treatment package 1 of the present invention can be suitably used in a microwave oven. EXAMPLES

[0075] The heat treatment package 1 produced in Examples 1 and 2 was filled with 100 ml of tap water to produce a heat treatment package 50. When this heat treatment package 50 was heated in a 600 W microwave oven, the exhaust section 7 was opened in 1 minute and 30 seconds, and the internal pressure air was gradually degassed. Furthermore, no water leaked from the heat treatment package 1. EXAMPLES

[0076] A package for heat treatment 1 was produced by sealing 100 ml of air in the package for heat treatment 1 produced in Example 1 and Example 2. The change in oxygen concentration inside the bag was measured. The results are shown in FIG. In both cases, it was found that the oxygen concentration was lower than when air was enclosed. EXAMPLES

[0077] The heat treatment packaging body 1 was produced in the same manner as in Example 1, except that the outer dimensions of the bag body 8 were 150 mm in length x 115 mm in width, the inner dimensions were 130 mm in length x 100 mm in width, and a joint 9 was constructed 25 mm from one edge 1a with a width of 10 mm (the longitudinal dimension of the bag body 8).

[0078] [Comparative Example 2] A packaging body for heat treatment 1 was produced in the same configuration as in Comparative Example 1, except that the heat seal layer 11 was made of unstretched polypropylene with a thickness of 80 μm. 80 g of tap water was enclosed inside each of the heat treatment packages of Example 5 and Comparative Example 2 to prepare heat treatment packages 50.

[0079] This heat-treated packaged product 50 was heated in a microwave oven at 600 W for 1 minute and 30 seconds. The temperature and pressure inside the bag while it was being heated in the microwave were measured starting from the point when the temperature of the water inside reached 30°C. The heat treatment packages 50 using the heat treatment packages of Example 5 and Comparative Example 2 were subjected to the heat treatment three times as described above. The evaluation results are shown in Table 2 below.

[0080] The definitions of each item name in Table 2 are as follows: "Steaming time" is the time (seconds) it takes for the bag to expand when heated in the microwave and for the steam vent to open. "Time to reach 100°C" is the time (seconds) required for the temperature of the content (water) to reach 100°C. "Temperature rise rate" is calculated by dividing 70°C (the difference between 30°C and 100°C) by the time it takes to reach 100°C, and is expressed in "°C / sec." "Maximum temperature" is the maximum temperature when heated at 600 W for 1 minute 30 seconds.

[0081] [Table 2]

[0082] [Table 3]

[0083] From the evaluation results in Tables 2 and 3, contrary to expectations considering that the oxygen absorbing layer of the embodiment contains an iron-based oxygen scavenger, the "steam passage time" of the oxygen absorbing range bag was about 1 second slower. In addition, the time to reach 100°C was about 3 seconds slower on average for the oxygen absorbing microwave bag. The "heating rate" of the oxygen absorbing microwave bag was about 0.6°C / second slower on average. The "maximum temperature" was about 0.5°C lower on average for the oxygen absorbing microwave bag. From the above, it was confirmed that in Example 5, the speed at which the contents warmed up tended to be slower than in Comparative Example 2. [Industrial Applicability]

[0084] The heat treatment package of the present invention can be used in the food industry where microwave heating and long-term storage are required.

Claims

1. The bag body is made of multi-layer films overlapped to form a front part and a rear part, and the outer peripheral edge part where the films are overlapped is sealed except for an opening part for accommodating an object, and an exhaust part capable of discharging steam or gas is provided in at least a part of the bag body. The multi-layer film has a heat seal layer, a gas barrier layer, and an oxygen absorbing layer between these layers, the oxygen absorbing layer containing a thermoplastic resin having an iron-based oxygen absorbent dispersed therein; The content of the iron-based oxygen absorbent in the oxygen absorbing layer is 5 to 50% by mass based on the total mass of the oxygen absorbing layer.

2. The exhaust section is formed by overlapping the cut ends of the multilayer film with the surfaces of the heat seal layers facing each other and sandwiching an easy-to-open film between the heat seal layers, and is sealed with a heat seal strength that allows the cut ends to be opened more easily than the outer peripheral end, 2. The package for microwave oven heating treatment according to claim 1, wherein the heat seal strength (N / 15 mm) of the exhaust part is 2 / 3 or less of the heat seal strength (N / 15 mm) of the outer peripheral edge in an atmosphere of 100° C.

3. 2. A package for microwave oven heating treatment according to claim 1, wherein the resin constituting the heat seal layer contains polypropylene.

4. A heat treatment package comprising the package for microwave heating treatment according to any one of claims 1 to 3, containing an article to be packaged therein, and the opening of the package being sealed.

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