JP2018172151A - Packaging bag for microwave oven and laminate body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packaging bag for a microwave oven which includes at least a base material layer and a sealant layer in this order and can reduce an internal pressure of the packaging bag in heating by a microwave oven while improving a biomass degree.SOLUTION: A packaging bag for a microwave oven according to the invention uses a laminate body including at least a base material layer and a sealant layer in this order. The packaging bag has a steam ventilation mechanism. The sealant layer is made of low density polyethylene derived from biomass and low density polyethylene derived from a fossil fuel. The packaging bag for a microwave oven can reduce an internal pressure since a part of the packaging bag is broken in heating by a microwave oven while improving a biomass degree.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a microwave packaging bag using a laminate including at least a base material layer and a sealant layer in this order. Furthermore, it is related with the laminated body used for the packaging bag for microwave ovens.

  In recent years, with the growing demand for the establishment of a recycling-oriented society, the use of biomass has been attracting attention in the materials field, as it is desired to move away from fossil fuels as well as energy. Biomass is an organic compound photo-synthesized from carbon dioxide and water, and by using it, it is so-called carbon neutral renewable energy that becomes carbon dioxide and water again. In recent years, biomass plastics using these biomasses as raw materials have been rapidly put into practical use, and attempts have been made to produce various resins from biomass raw materials.

  As a biomass-derived resin, commercial production of polylactic acid (PLA) produced via lactic acid fermentation has begun, but it is biodegradable, and its performance as a plastic is now a general-purpose plastic. Therefore, it has not been widely used due to its limitations in product applications and product manufacturing methods. Moreover, life cycle assessment (LCA) evaluation is performed for PLA, and discussion is made on energy consumption at the time of PLA production, equivalence at the time of replacement of general-purpose plastics, and the like.

  Here, various types such as polyethylene, polypropylene, polyvinyl chloride, polystyrene, and polyester are used as the general-purpose plastic. In particular, polyethylene is molded into films, sheets, bottles, etc., and is used for various applications such as packaging materials, and is used in large amounts all over the world. Therefore, using a conventional fossil fuel-derived polyethylene has a large environmental impact. Therefore, it is desired to reduce the amount of fossil fuel used by using raw materials derived from biomass for the production of polyethylene. For example, a resin film for packaging products using biomass-derived polyethylene has been proposed so far (see Patent Document 1).

JP 2012-251006 A

  The present inventors, together with polyolefins produced using ethylene obtained from conventional fossil fuels (hereinafter sometimes simply referred to as “polyolefins derived from fossil fuels”), biomass polyolefins using biomass-derived ethylene as a raw material (Hereinafter, it may be simply referred to as “biomass polyolefin”), a laminate having a high degree of biomass and particularly a packaging bag for a microwave oven was developed while suppressing cost. Here, when the packaging bag sealed with the contents is heated in a microwave oven, the internal pressure of the sealed packaging bag rises due to the expansion of air and the generation of water vapor from the food, and finally the content of the packaging bag is ruptured. I was faced with the technical problem that unfavorable situations such as the scattering of things could occur. Thus, as a result of further studies, the present inventors have found a packaging bag and a laminate for a microwave oven that can reduce the internal pressure of the packaging bag when heated in a microwave oven while improving the biomass degree. The present invention has been completed.

  Therefore, the objective of this invention is providing the packaging bag for microwave ovens and a laminated body which can reduce the internal pressure of a packaging bag in the case of microwave oven heating, improving a biomass degree.

According to a first aspect of the invention,
At least a packaging bag for a microwave oven using a laminate comprising a base material layer and a sealant layer in this order,
The packaging bag includes a steam escape mechanism;
There is provided a packaging bag for a microwave oven, wherein the sealant layer is composed of low density polyethylene derived from biomass and low density polyethylene derived from fossil fuel.

  In the 1st aspect of this invention, it is preferable that the thickness of the said sealant layer is 20 micrometers or more and 50 micrometers or less.

  In the 1st aspect of this invention, it is preferable that the biomass degree of the said sealant layer is 5% or more and less than 50%.

  In the first aspect of the present invention, the laminate is a laminate in which at least a base material layer, an adhesive layer, and a sealant layer are sequentially laminated, and the base material layer and the adhesive layer or the adhesive layer and the It is preferable to partially include a heat-softening resin layer between the sealant layers.

According to a second aspect of the invention,
At least a laminate comprising a base material layer, an adhesive layer, and a sealant layer in this order,
A partially heat-softening resin layer is provided between the base material layer and the adhesive layer or between the adhesive layer and the sealant layer,
There is provided a laminate in which the sealant layer is made of biomass-derived low density polyethylene and fossil fuel-derived low density polyethylene.

  A packaging bag for a microwave oven according to the present invention uses a laminate including at least a base material layer and a sealant layer in this order, and the packaging bag includes a vapor escape mechanism, and the sealant layer includes: By comprising the low density polyethylene derived from biomass and the low density polyethylene derived from fossil fuel, the internal pressure of the packaging bag can be lowered when heated in a microwave oven while improving the degree of biomass.

It is a schematic cross section which shows an example of the laminated body used for the packaging bag for microwave ovens by this invention. It is a schematic cross section which shows an example of the laminated body used for the packaging bag for microwave ovens by this invention. It is an expanded sectional view showing an example of the packaging bag for microwave ovens by the present invention. It is a top view which shows an example of the packaging bag for microwave ovens (form of a pillow bag) by this invention. It is a perspective view which shows an example of the packaging bag for microwave ovens by this invention. It is a top view which shows an example of the packaging bag for microwave ovens by this invention. It is a top view which shows an example of the packaging bag for microwave ovens by this invention. It is a top view which shows an example of the packaging bag for microwave ovens by this invention.

<Laminate>
The laminated body by this invention is equipped with a base material layer and a sealant layer in this order at least, and can be used suitably in order to manufacture the packaging bag for microwave ovens. When used as a packaging bag for a microwave oven, the packaging bag needs to have a vapor escape mechanism. For example, the laminate has a partially heat-softening resin layer between the base material layer and the sealant layer. It may be. The laminate may further include a printed layer, an adhesive layer, other layers, and the like. When the laminate includes two or more other layers, each may have the same composition or a different composition.

The laminate according to the present invention will be described with reference to the drawings. Examples of schematic cross-sectional views of the laminate according to the present invention are shown in FIGS.
The laminated body 10 shown in FIG. 1 is provided with the base material layer 11, the thermosoftening resin layer 12, and the sealant layer 13 in this order. In the microwave oven packaging bag using the laminate 10, the sealant layer 13 is located on the content side.
The laminated body 20 shown in FIG. 2 includes a base material layer 21, a printing layer 24, a thermosoftening resin layer 22, an adhesive layer 25, and a sealant layer 23 in this order. In the microwave oven packaging bag using the laminate 10, the sealant layer 23 is located on the content side.
Hereinafter, each layer which comprises a laminated body is demonstrated.

[Base material layer]
As the base material layer, for example, a polyethylene terephthalate film or a nylon film is preferably used. The polyethylene terephthalate used for the base material layer may be derived from biomass or fossil fuel. The base material layer may include both biomass-derived polyethylene terephthalate and fossil fuel-derived polyethylene terephthalate. The biomass degree of the whole laminate can be improved by using biomass-derived polyethylene terephthalate as at least a part of the base material layer. Biomass-derived polyethylene terephthalate is polyethylene terephthalate having biomass-derived ethylene glycol as a diol unit and fossil fuel-derived terephthalic acid as a dicarboxylic acid unit. Note that the laminate may include a plurality of base material layers.

  The substrate layer is preferably a stretched film, and is preferably biaxially stretched. Stretching can be performed by a conventionally known method. For example, the film of the base material layer extruded on the cooling drum is subsequently heated by roll heating, infrared heating, or the like, and stretched in the longitudinal direction to obtain a longitudinally stretched film. This stretching is preferably performed by utilizing the difference in peripheral speed between two or more rolls. The longitudinally stretched film is successively subjected to the transverse stretching, heat setting, and thermal relaxation treatment steps to form a biaxially stretched film.

When the base material layer is a stretched polyethylene terephthalate film, the stretched polyethylene terephthalate film used for the base material layer has a tensile strength in the MD direction, preferably from 150 MPa to 300 MPa, more preferably from 200 MPa to 300 MPa, in the TD direction. Preferably, it is 150 MPa or more and 300 MPa or less, more preferably 150 MPa or more and 300 MPa or less, and the tensile elongation is preferably 50% or more and 250% or less, more preferably 70% or more and 200% or less in the MD direction. It is preferably 50% or more and 250% or less, more preferably 60% or more and 200% or less in the direction.
When the base material layer is a stretched nylon film, the stretched nylon film used for the base material layer has a tensile strength in the MD direction, preferably 150 MPa or more and 350 MPa or less, more preferably 200 MPa or more and 300 MPa or less, preferably TD direction. 150 MPa to 400 MPa, more preferably 200 MPa to 350 MPa, and the tensile elongation is MD direction, preferably 50% to 200%, more preferably 70% to 150%, and TD direction. Preferably they are 30% or more and 200% or less, More preferably, they are 50% or more and 150% or less.
The tensile strength and tensile elongation can be measured in accordance with JIS K 7127.

  The base material layer preferably has a thickness of 5 μm to 40 μm, more preferably 8 μm to 25 μm. The thicknesses of the base material layers may be different or the same. If the thickness of the base material layer is in the above range, the molding process is easy and it can be suitably used as a packaging material.

[Thermosoftening resin layer]
The laminate according to the present invention may partially include a heat-softening resin layer between the base material layer and the adhesive layer or between the adhesive layer and the sealant layer. As a specific layer configuration of a laminate including a thermosoftening resin layer, for example, a base material layer, a thermosoftening resin layer, an adhesive layer, and a sealant layer are laminated in this order, a base material layer, an adhesive An agent layer, a thermosoftening resin layer, and a sealant layer are laminated in this order, and a base material layer, a thermosoftening resin layer, an anchor coat layer, an adhesive resin layer, and a sealant layer are laminated in this order. .

  The thermosoftening resin layer has a predetermined strength in a temperature environment below room temperature, but has a property that the strength decreases at a high environmental temperature. The environmental temperature below room temperature that maintains a predetermined strength is usually the environmental temperature at the time of packaging the contents such as food using a packaging bag for microwave oven, the packaging bag after the contents are sealed and packaged, It is the environmental temperature at the time of a container freezing process, and the environmental temperature at the time of transporting and storing frozen food. At such an environmental temperature, the thermosoftening resin layer has a predetermined strength. On the other hand, the high environmental temperature at which the predetermined strength is reduced is a temperature applied when a packaging bag in which contents such as food are hermetically packaged is heated in a microwave oven. At such a high temperature, the heat softening resin is used. When the strength of the layer is reduced, the layer is destroyed and the vapor is easily removed.

  The heat-softening resin layer contains a resin material having a melting point of 60 to 110 ° C., preferably 60 to 90 ° C., such as an ethylene-vinyl acetate copolymer resin, or polyamide, nitrified cotton, and polyethylene wax. It can be formed using a resin. As the resin containing polyamide, nitrified cotton, and polyethylene wax, MWOP varnish (softening point: 105 ° C.) manufactured by DIC Graphics Co., Ltd. can be used. By using a resin material having a melting point of 60 to 110 ° C., the heat softening resin layer is easily broken when heated in a microwave oven, and it is possible to promote the escape of vapor.

  The heat-softening resin layer can be formed by a conventionally known resin coating method, and the thickness is preferably 1 μm or more and 5 μm or less. When the thickness of the thermosoftening resin layer is in the above range, the thermosoftening resin layer is easily broken when heated in a microwave oven.

  In the laminate, the adhesive strength of the portion provided with the thermosoftening resin layer is 700 (g / 15 mm) or more in a temperature region of 25 ° C. or less, and 300 (g / 15 mm) in a high temperature region of 80 ° C. or more. The following is preferable. This suppresses peeling between the thermosoftening resin layer and the sealant layer or between the adhesive layer and the thermosoftening resin layer due to handling, transportation, storage, etc. at room temperature or during freezing. In addition, when heated in a microwave oven, a void can be easily formed between the base material layer and the sealant layer. The seal strength is an average value when measured at a tensile speed of 300 mm / min using a Tensilon tensile testing machine (RTC-1310A manufactured by Orientec Co., Ltd.).

[Sealant layer]
The laminate according to the present invention is provided with a sealant layer on the contents side when a microwave packaging bag is manufactured. The sealant layer is composed of low-density polyethylene derived from biomass and low-density polyethylene derived from fossil fuel. In the sealant layer, only low-density polyethylene is used instead of linear low-density polyethylene as a resin material, so that when the sealant layer is heated in a microwave oven, the sealant layer is partially broken, and from the heat-softening resin layer Vapor can easily escape. The low density polyethylene is obtained by polymerizing ethylene by a high pressure polymerization method.

  In the sealant layer, the content of the low-density polyethylene derived from biomass is preferably 5% by mass or more and less than 50% by mass, more preferably 10% by mass or more and 40% by mass or less. The content is preferably more than 50% by mass and 595% by mass or less, and more preferably 60% by mass or more and 90% by mass or less. If the content of the low-density polyethylene derived from biomass is within the above range in the sealant layer, the biomass degree of the entire laminate can be increased while suppressing costs.

  The biomass degree of the sealant layer is preferably 5% or more and less than 50%, more preferably 10% by mass or more and 40% by mass or less. If the degree of biomass is in the above range, the amount of fossil fuel used can be reduced while reducing costs, and the environmental load can be reduced. In addition, in this invention, "biomass degree" shows the weight ratio of a biomass origin component.

The “biomass degree” (carbon concentration derived from biomass) is a value of C14 content obtained by a radioactive carbon (C14) measurement method based on ASTM-D6866. Since carbon dioxide in the atmosphere contains C14 at a constant ratio (105.5 pMC), the C14 content in plants that grow by incorporating carbon dioxide in the atmosphere, for example, corn, is also about 105.5 pMC. It is known. It is also known that fossil fuel contains almost no C14. Therefore, the proportion of carbon derived from biomass can be calculated by measuring the proportion of C14 contained in all carbon atoms in the sealant layer. In the present invention, the biomass-derived carbon content Pbio when the content of C14 in the sealant layer is PC14 can be obtained as follows.
Pbio (%) = PC14 / 105.5 × 100

  Biomass polyethylene is a monomer polymer containing biomass-derived ethylene. Since ethylene derived from biomass is used as a monomer as a raw material, the polymerized polyolefin is derived from biomass. The content of ethylene derived from biomass in the raw material monomer is not necessarily 100% by mass, and is preferably 50% or more, more preferably 80% or more, for example. The raw material monomer may contain fossil fuel-derived ethylene.

  For example, biomass-derived ethylene can be produced using biomass-derived ethanol as a raw material. In particular, it is preferable to use biomass-derived fermented ethanol obtained from plant raw materials. A plant raw material is not specifically limited, A conventionally well-known plant can be used. For example, corn, sugar cane, beet, and manioc can be mentioned.

  In the present invention, biomass-derived fermented ethanol refers to ethanol that has been purified after contacting a microorganism-producing product or a crushed product thereof with a culture solution containing a carbon source obtained from plant raw materials. For the purification of ethanol from the culture solution, conventionally known methods such as distillation, membrane separation, and extraction can be applied. For example, a method of adding benzene, cyclohexane or the like and azeotropically or removing water by membrane separation or the like can be mentioned.

Low density polyethylene is less than 0.93 g / cm ^3, preferably 0.91 g / cm ³ or more 0.93 g / cm less than ^3, more preferably 0.912 g / cm ³ or more 0.928 g / cm ³ or less, more preferably Has a density of 0.915 g / cm ³ or more and 0.925 g / cm ³ or less. The density of the low density polyethylene is a value measured according to the method defined in Method A of JIS K7112-1980 after annealing described in JIS K6760-1995.

  The low density polyethylene has a melt of 0.1 g / 10 min to 10 g / 10 min, preferably 0.2 g / 10 min to 9 g / 10 min, more preferably 1 g / 10 min to 8.5 g / 10 min. It has a flow rate (MFR). The melt flow rate is a value measured by the method A under the conditions of a temperature of 190 ° C. and a load of 21.18 N in the method defined in JIS K7210-1995. If the MFR of the low density polyethylene is 0.1 g / 10 min or more, the extrusion load during the molding process can be reduced. Moreover, if the MFR of the low density polyethylene is 10 g / 10 min or less, the mechanical strength of the sealant layer can be increased.

In the present invention, the biomass polyethylene preferably used is a low-density polyethylene derived from biomass (trade name: SBC818, density: 0.918 g / cm ³ , MFR: 8.1 g / 10 min, biomass degree) manufactured by Braschem 95%), low-density polyethylene derived from biomass manufactured by Braschem (trade name: SPB681, density: 0.922 g / cm ³ , MFR: 3.8 g / 10 min, biomass degree 95%), derived from biomass manufactured by Braschem Low density polyethylene (trade name: STN7006, density: 0.923 g / cm ³ , MFR: 0.6 g / 10 min, biomass degree 95%), and the like.

  The total thickness of the sealant layer is preferably 20 μm or more and 50 μm or less, more preferably 25 μm or more and 40 μm or less. When the thickness of the sealant layer is within the above range, the sealant layer is easily destroyed while exhibiting the sealing performance and when heated in a microwave oven, and the vapor can sufficiently escape from the packaging bag.

[Print layer]
The printed layer can be used to display decorations, contents, display of the best-before period, display of manufacturers, sellers, etc., and display of other characters and letters, numbers, pictures, figures, symbols, patterns, etc. It is a layer for forming a desired arbitrary printed pattern. A printing layer can be provided as needed, for example, can be provided between a base material layer and a sealant layer. The printing layer may be provided on the entire surface of the base material layer, or may be provided on a part thereof. A printing layer can be formed using a conventionally well-known pigment and dye, The formation method is not specifically limited.

  The printed layer preferably has a thickness of 0.1 μm to 10 μm, more preferably 1 μm to 5 μm, and still more preferably 1 μm to 3 μm.

[Adhesive layer]
The adhesive layer is a layer provided when two arbitrary layers are bonded, and can be provided, for example, between the printed layer and the sealant layer.

  When two layers are bonded by a dry laminating method, the adhesive layer can be an adhesive layer formed by applying an adhesive to the surface of the layer to be laminated and drying it. Examples of the adhesive include one-part or two-part cured or non-cured vinyl, (meth) acrylic, polyamide, polyester, polyether, polyurethane, epoxy, rubber, etc. An adhesive such as a solvent type, an aqueous type, or an emulsion type can be used. As a two-component curable adhesive, a cured product of a polyol and an isocyanate compound can be used. Examples of the coating method for the laminating adhesive include a direct gravure roll coating method, a gravure roll coating method, a kiss coating method, a reverse roll coating method, a fountain method, a transfer roll coating method, and other methods to form a laminate. It can apply | coat to the application surface of a layer.

  The adhesive layer may be an adhesive resin layer used when two layers are bonded by a sand lamination method. Examples of the thermoplastic resin that can be used for the adhesive resin layer include a polyethylene resin, a polypropylene resin, or a cyclic polyolefin resin, or a copolymer resin, a modified resin, or a mixture (including alloy) containing these resins as a main component. ) Can be used. Examples of polyolefin resins include low density polyethylene (LDPE), high density polyethylene (HDPE), linear (linear) low density polyethylene (LLDPE), polypropylene (PP), and polymerized ethylene using a metallocene catalyst. -Α-olefin copolymer, ethylene-polypropylene random or block copolymer, ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer ( EEA), ethylene-methacrylic acid copolymer (EMAA), ethylene-methyl methacrylate copolymer (EMMA), ethylene / maleic acid copolymer, ionomer resin, and the above in order to improve adhesion between layers Polyolefin resin made from acrylic acid, methacrylic acid, It can be used in acid, maleic acid anhydride, fumaric acid, and an acid-modified polyolefin resin modified with an unsaturated carboxylic acid such as itaconic acid. Further, a resin obtained by graft polymerization or copolymerization of an unsaturated carboxylic acid, an unsaturated carboxylic acid anhydride, or an ester monomer can be used as the polyolefin resin. These materials can be used alone or in combination of two or more. As the cyclic polyolefin-based resin, for example, cyclic polyolefins such as ethylene-propylene copolymer, polymethylpentene, polybutene, and polynorbornene can be used. These resins can be used alone or in combination. In addition, as said polyethylene-type resin, what used the above ethylene derived from biomass as a monomer unit can be used, and a biomass degree can further be improved.

  When the adhesive resin layer is laminated by the melt extrusion laminating method, an anchor coat layer formed by applying an anchor coat agent and drying it may be provided on the surface of the layer to be laminated. Examples of the anchor coating agent include an anchor coating agent made of any resin having a heat resistant temperature of 135 ° C. or higher, such as a vinyl-modified resin, an epoxy resin, a urethane resin, a polyester resin, or a polyethyleneimine. An anchor coating agent that is a cured product of a polyacrylic or polymethacrylic resin (polyol) having two or more hydroxyl groups and an isocyanate compound as a curing agent can be preferably used. Moreover, a silane coupling agent may be used in combination as an additive, and nitrified cotton may be used in combination in order to improve heat resistance.

  There may be one adhesive layer in the laminate, or two or more may be included. For example, when two adhesive layers are included in the laminate, one adhesive layer may be referred to as an adhesive layer, and the other adhesive layer may be referred to as a second adhesive layer.

  The anchor coat layer after drying has a thickness of 0.1 μm or more and 1 μm or less, preferably 0.3 μm or more and 0.5 μm or less. The adhesive layer after drying preferably has a thickness of 1 to 10 μm, preferably 2 to 5 μm. The adhesive resin layer preferably has a thickness of 5 μm to 50 μm, preferably 10 μm to 30 μm.

[Other layers]
The laminate according to the present invention may include a barrier layer as another layer. The barrier layer is provided to extend the storage period of the contents, and is a vapor-deposited layer of metal oxide such as aluminum oxide or inorganic oxide such as silicon oxide, ethylene-vinyl alcohol copolymer (EVOH), poly A resin layer having gas barrier properties such as vinylidene chloride resin (PVDC) or aromatic polyamide such as nylon MXD6 can be used. Further, on the deposited layer, the general formula ^{_{R 1 n M (OR 2)}} m ( where in the ^formula, R 1, ^{R 2} represents an organic group having 1 to 8 carbon atoms, M represents a metal atom , N represents an integer of 0 or more, m represents an integer of 1 or more, and n + m represents a valence of M), and a polyvinyl alcohol as described above A transparent gas barrier composition containing a benzene-based resin and / or an ethylene / vinyl alcohol copolymer, and further polycondensed by a sol-gel method in the presence of a sol-gel method catalyst, acid, water, and an organic solvent. The obtained gas barrier coating film may be provided.

<Method for producing laminate>
The manufacturing method of the laminated body by this invention is not specifically limited, It can manufacture using conventionally well-known methods, such as a dry lamination method and a sand lamination method.

  The laminate according to the present invention is provided with chemical functions, electrical functions, magnetic functions, mechanical functions, friction / abrasion / lubrication functions, optical functions, thermal functions, surface functions such as biocompatibility, etc. For the purpose, it is also possible to perform secondary processing. Examples of secondary processing include embossing, painting, adhesion, printing, metalizing (plating, etc.), machining, surface treatment (antistatic treatment, corona discharge treatment, plasma treatment, photochromism treatment, physical vapor deposition, chemical vapor deposition, Coating, etc.). Further, the laminate according to the present invention can be subjected to laminating processing (dry laminating or extrusion laminating), bag making processing, and other post-processing processing to produce a molded product.

<Packaging bag for microwave oven>
The packaging bag for microwave ovens by this invention can be used conveniently for the packaging for frozen foods which needs to be heated by a microwave oven. When heating in a microwave oven, the sealant layer and part of the heat-softening resin layer of the packaging bag are destroyed, and steam is sufficiently removed from the broken part, so that the packaging bag is not adversely affected. The internal pressure can be reduced.

  The packaging bag for a microwave oven according to the present invention can be manufactured in various forms such as a pillow bag by stacking the sealant layers of the laminate facing each other and further heat-sealing the peripheral edge thereof. . As a heat sealing method, for example, a known method such as a bar seal, a rotary roll seal, a belt seal, an impulse seal, a high frequency seal, or an ultrasonic seal can be used.

A microwave oven packaging bag according to the present invention will be described with reference to the drawings. An example of an enlarged sectional view of a packaging bag for a microwave oven according to the present invention is shown in FIG. The sealing portion 34 of the microwave packaging bag 30 in FIG. 3 is laminated with the base material layer 31, the thermosoftening resin layer 32, and the sealant layer 33 of the laminate in which the sealant layer 33 is sequentially laminated facing each other. The peripheral edge is sealed. When the microwave packaging bag 30 is heated in the microwave oven, the internal pressure rises (arrow 35) due to the expansion of air in the microwave packaging bag 30 and the water vapor contained in the contents. In the high temperature range of microwave heating, the strength of the thermosoftening resin layer 32 decreases, so that the internal pressure increased in the sealed microwave packaging bag 30 must be maintained by the strength of the sealant layer 33 itself. Disappear. Therefore, the sealant layer 33 in the vicinity of the boundary surface of the seal portion 34 inside the microwave packaging bag 30 is liable to crack due to a decrease in strength of the thermosoftening resin layer 32 and cannot withstand the increase in internal pressure (arrow 35). In addition, the thermosoftening resin layer 32 with reduced strength is destroyed starting from an arbitrary portion 36 of the sealant layer 33 in the vicinity of the seal portion 34 (37 indicates a virtual line to break). As a result, between the sealant layer 33 and the base material layer 31 of the seal portion 34, a relatively small sized steam escape mechanism due to the breakage of the thermosoftening resin layer 32 from the inside to the outside of the microwave packaging bag 30. Therefore, water vapor or the like in the microwave packaging bag 30 escapes, and the internal pressure can be reduced. In the present invention, since the breakage is partially caused, a relatively small size of steam escapes, the internal pressure of the microwave packaging bag 30 does not drop at a stretch, and the contents are not scattered and the contents are adversely affected. Not give.
In FIG. 4, the top view (form of a pillow bag) of the packaging bag 30 for microwave ovens is shown. The heat-softening resin layer 32 in the packaging bag 30 is formed so as to extend at least from the outer edge to the inner edge of the seal portion 34. The laminate constituting the microwave packaging bag 30 includes a base layer, an adhesive layer, and a sealant layer in this order, and is partially heat softened between the base layer and the adhesive layer or between the adhesive layer and the sealant layer. By providing the resin layer and forming the heat-softening resin layer so as to extend at least from the outer edge to the inner edge of the seal portion 34, the microwave packaging bag 30 can be provided with a vapor escape mechanism. In FIG. 4, a portion indicated by reference numeral 41 is a portion where the thermosoftening resin layer 32 is formed. As shown in FIG. 4, the thermosoftening resin layer 32 may be formed from the outer edge of the seal portion 34 beyond the inner edge of the seal portion 32. Heating in the microwave oven causes partial breakage of the thermosoftening resin layer 32 and the sealant layer 33 in the formation region 41 of the thermosoftening resin layer 32 in the seal portion 34, resulting in steam loss, and packaging. The internal pressure of the bag 30 can be reduced.

The following example demonstrates the example which forms the packaging bag provided with a vapor | steam escape mechanism using the laminated body which is not provided with the thermosoftening resin layer 32. FIG.
An example of the perspective view of the packaging bag for microwave ovens by this invention is shown in FIG. A microwave packaging bag 50 shown in FIG. 5 is formed using a laminate that includes at least a base material layer and a sealant layer, and does not include a heat-softening resin layer, and is a seal for sealing the packaging bag. The standing pouch includes a portion 52, a point seal portion 53 isolated from the seal portion 52, and a through portion 54 formed in the point seal portion 53. The through portion 54 is a hole or a notch. The point seal part 53 and the penetrating part 54 constitute a steam escape mechanism. When the microwave packaging bag 50 is heated by the microwave oven, when the point seal portion 53 is peeled back and reaches the penetration portion 54, the steam is released from the penetration portion 54, and the internal pressure of the packaging bag 50 can be reduced. The shape of the point seal portion 53 is not particularly limited, and may be other shapes such as a square, a rectangle, a circle, an ellipse, and a triangle.

  An example of the top view of the packaging bag for microwave ovens by this invention is shown in FIG. Although FIG. 5 demonstrated the example in which the point seal part 53 was provided isolated from the seal part which seals a packaging bag, as shown in FIG. 6, the seal part which comprises a vapor | steam escape mechanism seals a packaging bag It may be connected to the part. The packaging bag 60 for microwave ovens shown in FIG. 6 is formed using a laminate that includes at least a base material layer and a sealant layer, and does not include a heat-softening resin layer, and a seal for sealing the packaging bag. Parts 64, 65, 66, a projecting seal part 61 connected to the seal part 64 and projecting toward the accommodation space, an unsealed part 62 formed between the projecting seal part 61 and the seal part 64, and an unsealed It is a standing pouch provided with a penetration part 63 formed in the part. The penetration part 63 is a hole or a notch. The protruding seal part 61, the non-seal part 62, and the through part 63 constitute a steam escape mechanism. When the projecting seal portion 61 peels and retreats and reaches the unsealed portion during heating by the microwave oven, steam escapes from the through portion 63 provided in the unsealed portion, and the microwave packaging bag 60 reduces the internal pressure of the packaging bag 60. Can be reduced.

  An example of the top view of the packaging bag for microwave ovens by this invention is shown in FIG. The packaging bag 70 shown in FIG. 7 is a standing pouch formed using a laminate that includes at least a base material layer and a sealant layer, and does not include a thermosoftening resin layer. Although FIG. 6 illustrates an example in which the unsealed portion 62 does not reach the outer edge of the pouch, the unsealed portion constituting the steam release mechanism may reach the outer edge of the pouch. The packaging bag 70 includes a pair of side seal portions 71, a bottom seal portion 72, and an upper seal planned portion 73, and one side seal portion 71 is separated into an upper portion and a lower portion via an unsealed portion 74. . The unsealed portion 74 is formed from the outer edge of the packaging bag toward the housing space, separates the unsealed portion 74 and the housing space, and protrudes so as to be connected to the upper portion and the lower portion of the side seal portion 71. A seal portion 75 is formed. The unsealed portion 74 is formed so as to protrude from the inner edge of one side seal portion 71 toward the accommodation space. The protruding seal part 75 and the non-seal part 74 constitute a steam escape mechanism. When the protruding seal portion 75 peels and retreats and reaches the unsealed portion 74 during heating by the microwave oven, the microwave packaging bag 70 may cause vapor to escape from the unsealed portion 74 and reduce the internal pressure of the packaging bag 70. it can. Note that a through portion such as a hole or a cut may be formed in the unsealed portion 74.

  An example of the top view of the packaging bag for microwave ovens by this invention is shown in FIG. A packaging bag 90 shown in FIG. 8 is a pouch that includes at least a base material layer and a sealant layer, and is formed using a laminated body that does not include a thermosoftening resin layer and includes a palm joint portion 92. The packaging bag 90 includes a seal portion 94 for sealing and sealing the packaging bag, a protruding seal portion 95 formed on the wing portion 92, and an unsealed portion 96 formed between the protruding seal portion 95 and the seal portion 94. The through-hole 97 is formed in the unsealed portion 96. The through portion 97 is a hole or a notch. The protruding seal part 95, the non-seal part 96, and the penetration part 97 constitute a steam escape mechanism. In the microwave packaging bag 90, when the projecting seal portion 95 is peeled and retracted and reaches the unsealed portion 96 during heating by the microwave oven, the vapor is released from the through portion 97 provided in the unsealed portion 96, and the packaging bag 90. The internal pressure can be reduced.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

[Example 1]
<Preparation of laminated body 1>
A biaxially stretched polyethylene terephthalate film (thickness 12 μm, manufactured by Toyobo Co., Ltd., T4102) was prepared as a base material layer, a printing layer was formed on one surface of the polyethylene terephthalate film by gravure printing, and then MWOP varnish (Dic Graphics Co., Ltd.) was coated on a part of the printing layer to form a heat-softening resin layer. In addition, 80 parts by mass of low-density polyethylene derived from fossil fuel (density: 0.923 g / cm ³ , MFR: 3.5 g / 10 min, biomass degree: 0%), and low-density polyethylene derived from biomass manufactured by Braschem ( (Trade name: SPB681, density: 0.922 g / cm ³ , MFR: 3.8 g / 10 min, biomass degree 95%) 20 parts by mass were melt-kneaded to obtain a tree composition. Subsequently, the obtained resin composition was formed into a film by a top-blown air-cooled inflation coextrusion film forming machine to obtain a polyethylene film 1 (thickness 30 μm, biomass degree: 19%) for a sealant layer. Next, the heat-softening resin layer surface of the polyethylene terephthalate film and the polyethylene film 1 for the sealant layer are pasted using a two-component curable adhesive (Rock Paint Co., Ltd., RU-40 / H-5). In addition, a laminate 1 was obtained in which a base material layer, a printing layer, a thermosoftening resin layer, an adhesive layer, and a sealant layer were sequentially laminated.

[Example 2]
<Preparation of laminated body 2>
A laminate 2 was obtained in the same manner as in Example 1 except that the thickness of the polyethylene film 1 for the sealant layer was changed to 50 μm.

[Comparative Example 1]
<Preparation of laminate 3>
The same as Example 1 except that the low-density polyethylene derived from fossil fuel of the polyethylene film 1 for the sealant layer was changed to C6-LLDPE (density: 0.929 g / cm ³ , MFR: 2.6 g / 10 min). A laminate 3 was obtained. C6-LLDPE uses hexene-1 as a comonomer.

<Manufacture of pillow bags>
The sealant layers of the laminates obtained in the examples and comparative examples were heat-sealed to produce a pillow bag shown in FIG.

<Microwave test>
After putting 100 g of water into the pillow bag obtained above, it was sealed and sealed. The sealed pillow bag was heated at 500 W for 3 minutes using a microwave oven, and the effect on steam escape and contents was evaluated. The evaluation results are shown in Table 1.
(Evaluation criteria)
○: Vapor escaped through the thermosoftening resin layer.
X: Vapor escaped without going through the thermosoftening resin layer.

The results of the performance evaluation test are shown in Table 1.

10, 20, 51 Laminate 11, 21, 31 Base material layer 12, 22, 32 Thermosoftening resin layer 13, 23, 33 Sealant layer 24 Print layer 25 Adhesive layer 30, 50, 60, 70, 90 For microwave oven Packaging bag 34, 52 Seal part 35 Increase in internal pressure 36 Arbitrary point of failure 37 Virtual line to break 41 Thermosoftening resin layer formation region 53, 61, 95 Point seal part 54, 63, 96 Notch 62 Not sealed Part 64 Side seal part 65 Upper seal part 66 Lower seal part 71 Side seal part 72 Bottom seal part 73 Upper seal part 74 Unsealed part 75 Projected seal part 91 Lower sheet 92 Wing part 93 Upper sheet 94 Peripheral part 95 Projected seal Part 96 unsealed part 97 penetration part

Claims (5)

At least a packaging bag for a microwave oven using a laminate comprising a base material layer and a sealant layer in this order,
The packaging bag includes a steam escape mechanism;
A packaging bag for a microwave oven, wherein the sealant layer is composed of low-density polyethylene derived from biomass and low-density polyethylene derived from fossil fuel.   The packaging bag according to claim 1 whose thickness of said sealant layer is 20 micrometers or more and 50 micrometers or less.   The packaging bag according to claim 1 or 2, wherein the biomass degree of the sealant layer is 5% or more and less than 50%.   The laminate is a laminate in which at least a base material layer, an adhesive layer, and a sealant layer are sequentially laminated, and heat is partially applied between the base material layer and the adhesive layer or between the adhesive layer and the sealant layer. The packaging bag as described in any one of Claims 1-3 provided with a softening resin layer. At least a laminate comprising a base material layer, an adhesive layer, and a sealant layer in this order,
A partially heat-softening resin layer is provided between the base material layer and the adhesive layer or between the adhesive layer and the sealant layer,
The laminate in which the sealant layer is composed of biomass-derived low density polyethylene and fossil fuel-derived low density polyethylene.

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