JP2018162073A - No-extending and co-extruded multi-layered film for lid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a no-extending and co-extruded multi-layered film for lids with high gas barrier property, good sealing performance with a food tray and anti-fogging, leaving no traces of upper food trays when stacked.SOLUTION: A multi-layered film at least includes outer layers, middle layers and inner layers. The outer layers are made of each one or more of a layer containing polypropylene resin and polystyrene-polyolefin copolymer resin, a layer containing polypropylene resin and a layer containing polystyrene-polyolefin copolymer resin. The middle layers have a gas barrier layer containing either ethylene-vinyl acetate copolymer saponification product or polymethaxylyleneadipamide resin. The inner layers have a heat seal layer containing anti-fogging agent and polyolefin resin. Total thickness of the film ranges from 20 μm to 60 μm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a non-stretched coextruded laminated film for a lid material using a plastic film having gas barrier properties, heat sealing properties, and antifogging properties.

In recent years, the food industry has become active in reducing food waste loss as a means of reducing environmental impact, reducing costs, and effectively using resources.
In packaging materials, we have contributed to the above efforts by providing packaging materials and packaging methods that extend the shelf life of foods.For example, measures to suppress oxygen inflow and germ growth that cause food degradation are used. Has been.
Heat sterilization in sealed packaging and sealed packaging in an aseptic room are performed as methods for suppressing oxygen inflow and miscellaneous bacteria growth, and vacuum packaging and gas replacement packaging with gas barrier packaging materials can be used to further enhance the effect. Is used.
In particular, foods with a short shelf life, such as meat, fresh fish, and sugar beets, have traditionally been made by wrapping a plastic tray with a foamed polystyrene or polypropylene sheet wrapped with a wrap film, or just having a lid fitted to the resin tray. These packaged foods have a short shelf life and are sold in large quantities, so reducing waste loss is an urgent issue.

Therefore, there is a need for a gas replacement package that improves the gas barrier of food resin trays and that is filled with an inert gas or the like and sealed with a gas barrier lid. As for the form, the thing which melt-adheres the lid | cover material film to the edge of the resin tray shown in FIG. 1 by heat seal, for example is mentioned.
However, conventional lids for gas replacement packaging bodies (gas packs) include, for example, a polyamide resin layer and an ethylene-vinyl acetate copolymer saponified resin layer as disclosed in Patent Document 1 and Patent Document 2. Co-extruded multilayer film having a heat-sealable polyolefin resin layer and a base material such as a biaxially stretched polyester film, an unstretched polyester sheet (APET), a polyvinyl chloride sheet, or a polystyrene sheet, and a total thickness of about 100 to It is a 300 μm thick laminate, and cannot be used for a tray cover material that requires flexibility and tension like an existing wrap film. Moreover, the anti-fogging property for preventing the inner surface of the lid from being fogged by moisture from fresh foods and side dishes and maintaining the contents visibility of the package is insufficient.
Examples of the lid material provided with gas barrier property and anti-fogging property include Patent Document 3 and Patent Document 4. However, these are laminates of a polyvinyl alcohol resin film and a polyolefin resin film coated with an antifogging agent, and the antifogging property is not good because the antifogging agent coating layer is partially lost due to contact with the contents. There was a problem that the film was sufficient or the appearance was impaired, and the film was fixed by the antifogging agent layer. Furthermore, there is a problem that the gas barrier property is greatly reduced by moisture absorption of the film.
In addition, since any technique disclosed in the above-mentioned patent document includes a step of laminating films by secondary processing, there is another problem that manufacturing cost and manufacturing time are required.

  On the other hand, there are heat-shrinkable films as similar packaging materials, but these are inexpensive and have good transparency, but the dimensional change of the film itself is large depending on packaging and storage conditions, and the product after packaging is caused by film shrinkage. There was a problem of deformation and loss of value.

  On the other hand, the conventional non-stretched coextruded film has a problem that the lid material is recessed when the trays are stacked, and the recessed marks remain after the trays are lowered, so that the appearance is poor.

JP-A-10-095075 Japanese Patent Laid-Open No. 11-227125 Japanese Unexamined Patent Publication No. 7-060919 JP-A-7-060922

  The present invention has been made in view of the above-mentioned problems, has a high gas barrier property, has both a hermetic seal property and anti-fogging property with a food tray, and is used for a lid material that does not leave a mark even when the trays are stacked. It is an object to provide a stretched coextruded laminated film.

  As a result of intensive studies on the layer structure of the film and the composition of each layer in order to solve the above-mentioned problems, the present inventor has completed the following present invention. That is, the gist of the present invention is as follows.

  [1] A laminated film having at least an outer layer, an intermediate layer, and an inner layer, wherein the outer layer includes a polypropylene resin and a polystyrene-polyolefin copolymer resin, or a layer including a polypropylene resin and a polystyrene-polyolefin copolymer. One or more layers each containing a polymer resin, the intermediate layer has a gas barrier layer containing a saponified ethylene-vinyl acetate copolymer or a polymetaxylylene adipamide resin, and the inner layer is an antifogging agent A non-stretched coextruded laminated film for a lid material having a heat seal layer containing a polyolefin resin and a total film thickness of 20 μm to 60 μm.

  [2] The unstretched coextruded laminated film for a lid material according to [1], having a layer containing a polyamide-based resin between the intermediate layer and the inner layer of the laminated film.

  [3] The unstretched coextruded laminated film for a lid according to any one of [1] or [2], which has an easy peel layer adjacent to the heat seal layer on the intermediate layer side of the heat seal layer of the laminate film.

  [4] A lid for a deep-drawn package using the unstretched coextruded laminated film for a lid according to any one of [1] to [3].

  [5] A deep drawn package comprising the lid material according to [4] and a bottom material for the deep drawn package.

  [6] The deep drawn package according to [5], which is a gas replacement deep drawn package.

  Although the film of the present invention is a thin film having a total film thickness of 60 μm or less, it has tensile strength, stretchability, and antifogging properties, and has aesthetics like a wrap film wound around a conventional tray. Furthermore, it can be melt-sealed and sealed at the edge of a molded tray made of expanded polystyrene or propylene, and has a gas barrier property, so it can be suitably used as a top seal lid material for gas replacement packaging bodies such as fresh foods and side dishes. .

The gas replacement packaging body which concerns on embodiment of this invention is illustrated. As shown in FIG. 1, an unstretched coextrusion film for a lid material of the present invention is used for 1 lid material, and polyethylene terephthalate / ethylene-vinyl acetate copolymer soap is mainly used for 2 bottom material (tray). Constituents such as fluoride / polyethylene or polypropylene / ethylene-vinyl acetate copolymer saponification / polypropylene are used. The heat seal adhesion part (top seal part) 3 of the lid material and the bottom material is a portion where the lid material and the bottom material (tray) are fused and adhered by heat sealing. Reference numeral 4 denotes a container such as fresh food, and reference numeral 5 denotes a filling portion filled with an inert gas or the like. Ten gas replacement packaging bodies are produced by combining 1 to 5.

The film of the present invention is an unstretched coextruded laminated film having a composition and thickness of each layer described later and a total film thickness of 20 μm or more and 60 μm or less. As a result, it is possible to provide a film having high gas barrier properties, having both a hermetic sealing property with a food tray and anti-fogging property, and a film in which no trace remains even when the trays are stacked.
The film production method of the present invention can be carried out using a known method, for example, a coextrusion inflation method and a coextrusion T-die method.

<Outer layer>
The film of the present invention includes a layer containing a polypropylene resin (hereinafter sometimes abbreviated as PP) and a polystyrene-polyolefin copolymer resin (hereinafter sometimes abbreviated as PS-PO) in an outer layer, Alternatively, one or more layers each containing a polypropylene resin and one layer containing a polystyrene-polyolefin copolymer resin are disposed.

Heat resistance is provided by including polypropylene resin in the outer layer, and it is possible to prevent the outer layer of the film from fusing to the hot plate during heat sealing, and the film expands and contracts by including polystyrene-polyolefin copolymer resin in the outer layer. Therefore, even when the film is depressed due to stacking of trays, the depression disappears when the tray is lowered.
Even if the outer layer is provided as a layer containing both a polypropylene resin and a polystyrene-polyolefin copolymer resin, the outer layer is provided with at least one layer containing a polypropylene resin and one layer containing a polystyrene-polyolefin copolymer resin. It doesn't matter.
In the case where a layer containing a polypropylene resin and a layer containing a polystyrene-polyolefin copolymer resin are provided on the outer layer, the layer containing the polypropylene resin is made of a polystyrene-polyolefin from the viewpoint of preventing fusion with a hot plate during heat sealing. It is preferable to provide the outer layer side of the layer containing the copolymer resin.

  Examples of the polypropylene resin include homopolypropylene, a random copolymer or a block copolymer of propylene and an α-olefin having 1 to 20 carbon atoms. Among them, in order to prevent fusion at the time of heat sealing, the melting point of the polypropylene resin is preferably 140 ° C. or higher, more preferably 145 ° C. or higher, and further preferably 155 ° C. or higher. The melting point can be measured according to JIS K 7121 method.

  The polystyrene-polyolefin copolymer resin is a hydrogenated derivative of a vinyl aromatic hydrocarbon-conjugated diene block copolymer, represented by the general formula: a (ba) n, (ab) n, or a- One or more hydrogenated derivatives of the block copolymer represented by bc. However, in the formula, (a) is a polymer block of a monovinyl-substituted aromatic hydrocarbon, (b) is a random copolymer block of a monovinyl-substituted aromatic hydrocarbon and a conjugated diene or an elastomeric polymer block of a conjugated diene, (C) is a block of a monovinyl-substituted aromatic hydrocarbon and a conjugated diene, and is a tapered block in which the monovinyl-substituted aromatic hydrocarbon gradually increases, and n is an integer of 1 to 5.

Examples of the vinyl aromatic hydrocarbon monomer constituting the polymer block (a), (b) or (c) include styrene, α-methylstyrene, (o-, m-, p-) methylstyrene. 1,3-dimethylstyrene, vinylnaphthalene, vinylanthracene and the like. Among these, styrene or α-methylstyrene is preferable. The conjugated diene monomer in the polymer block (b) or (c) is preferably butadiene and / or isoprene. When butadiene is used as the single conjugated diene monomer to form the polymer block (b) or (c), after the block copolymer is hydrogenated and the double bond is saturated For the purpose of increasing the compatibility with the propylene-based polymer, it is preferable to employ polymerization conditions in which the 1,2-microstructure in the microstructure of polybutadiene is 50% by mass or more. A desirable ratio of the 1,2-microstructure is 50% by mass to 90% by mass.
The ratio of the polymer block (a) in the hydrogenated block copolymer or the sum of the vinyl aromatic compounds in the polymer block (a) and the polymer block (c) is usually 3 to 30% by mass, preferably Is 5 to 20% by mass. When the ratio of the polymer block (a) or the sum of the vinyl aromatic compound content in the polymer block (a) and the polymer block (c) is less than 3% by mass, the mechanical strength of the resulting composition foreign matter is It tends to be inferior. When the ratio of the polymer block (a) or the sum of the vinyl aromatic compounds in the polymer block (a) and the polymer block (c) exceeds 30% by mass, the flexibility and transparency of the composition Tend to be inferior.

  The weight average molecular weight of the polystyrene-polyolefin copolymer resin is usually 10 to 550,000, preferably 150,000 to 500,000, and more preferably 200 to 450,000 as a value in terms of polystyrene measured by gel permeation chromatography. When the weight average molecular weight is less than 100,000, rubber elasticity and mechanical strength tend to be inferior, and when it exceeds 550,000, viscosity tends to be high and molding processability tends to be inferior.

  Examples of the polystyrene-polyolefin copolymer as described above include “Kraton G” (registered trademark) manufactured by Kraton Polymers, “Septon” (registered trademark), “Hibler” (registered trademark) manufactured by Kuraray Co., Ltd., “ “Tuftec” (registered trademark), “Dynalon” (registered trademark) manufactured by JSR, “SIBSTAR” (registered trademark) composed of styrene block and isobutylene block obtained by cationic polymerization manufactured by Kaneka Corporation, and the like. It is done. Examples of the resin composition of the propylene resin and the styrene elastomer include “Zeras” (registered trademark) manufactured by Mitsubishi Chemical.

  The mixing ratio of the polystyrene-polyolefin copolymer in the outer layer is preferably 25% by mass or more and 50% by mass or less. By setting the polystyrene-polyolefin copolymer to 25% by mass or more, it becomes easy to develop the property of removing the dents when stacking trays, and by setting it to 50% by mass or less, it is fused to the hot plate during heat sealing. Can be prevented.

  For the polypropylene resin and the polystyrene-polyolefin copolymer resin, the same raw materials as those described above can be used.

<Intermediate layer>
In the film of the present invention, an oxygen gas barrier layer is disposed in the intermediate layer for the purpose of preventing the food contained in the contents from being spoiled.
As the gas barrier layer, a saponified ethylene-vinyl acetate copolymer (hereinafter sometimes abbreviated as EVOH) layer or a polymetaxylylene adipamide resin (hereinafter abbreviated as MXD) composed of polymetaxylene and adipic acid. Oxygen barrier properties necessary for extending the shelf life can be easily provided. From the viewpoint of higher gas barrier properties, it is more preferable to dispose an EVOH layer, and from the viewpoint of combining heat resistance and water resistance, it is preferable to dispose an MXD layer.

  The ethylene content of the saponified ethylene-vinyl acetate copolymer is not particularly limited, but from the viewpoint of film formation stability, the lower limit is preferably 27 mol% or more, more preferably 32 mol% or more, and the upper limit. Is preferably 47 mol% or less, and more preferably 44 mol% or less.

The lower limit of the thickness of the gas barrier layer is preferably 1 μm or more, and more preferably 2 μm or more. The upper limit is preferably 8 μm or less, more preferably 6 μm or less, and even more preferably 5 μm or less.
By setting the thickness of the gas barrier layer to 1 μm or more, oxygen barrier properties sufficient for the purpose of the present invention can be imparted and stable film formation can be achieved. In addition, by making the thickness 8 μm or less, not only is it economical, it is possible to avoid a decrease in pinhole resistance.

<Inner layer>
The film of the present invention has at least one heat seal layer made of a polyolefin resin containing an antifogging agent in the inner layer, thereby suppressing fogging of the inner surface of the lid due to moisture from food contained in the contained material, and so on. A heat sealing function with the adherend can be provided.

The polyolefin resin is not particularly limited as long as it can provide heat sealability. For example, high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl methacrylate copolymer (EMMA) It is preferably composed of at least one selected from the group consisting of ethylene-methacrylic acid copolymer (EMAA) and polypropylene (PP).
Among these, EVA is preferable from the viewpoint of imparting transparency and flexibility. LLDPE is preferable from the viewpoint that the heat-sealable temperature range is wide and the surface strength and slipperiness are good.

  The composite film of the present invention preferably has a layer containing a polyamide-based resin (hereinafter sometimes abbreviated as PA) in order to improve pinhole resistance and adhesive strength between the inner layer and the intermediate layer. As the polyamide resin to be used, homopolymers or copolymers of various polyamide resins can be used alone or as a mixture. For example, nylon 4, nylon 6, nylon 7, nylon 11, nylon 12, nylon 46, nylon 66, nylon 69, nylon 610, nylon 611, nylon 6T, nylon 6I, nylon 6-66, nylon 6-610, nylon 6 -611, nylon 6-12, nylon 6-612, nylon 6-6T, nylon 6-6I, nylon 6-66-610, nylon 6-66-12, nylon 6-66-612, nylon 66-6T, nylon 66-6I, nylon 6T-6I, nylon 66-6T-6I, and the like. Among these, as the polyamide, 6 nylon or 6-66 nylon is preferably used from the viewpoint of pinhole resistance. Moreover, the layer which consists of PA can also provide two or more layers, and each layer may be formed with a different kind of polyamide.

  The thickness of the PA layer is desirably 1 μm or more and 8 μm or less. If the thickness is less than 1 μm, thickness fluctuation is likely to occur, and the strength of the film becomes insufficient. When the thickness exceeds 8 μm, other layers such as an outer layer and an inner layer become thin and the function tends to be impaired.

<Inner layer (heat seal layer)>
A heat seal layer containing an antifogging agent and a polyolefin resin is disposed on the inner layer (heat seal layer) of the film of the present invention. The antifogging agent is mixed with the polyolefin resin and contained. The mixing of the antifogging agent and the resin is a method of preparing a kneaded pellet with a master batch, and the resin and the antifogging agent are supplied to a film-forming extruder and extruded. The method of mixing in a machine etc. are mentioned. The antifogging agent concentration of the master batch is not particularly limited, and may be adjusted so that the antifogging agent-containing concentration in the film inner layer falls within the concentration range described later.
Compared to the case where an antifogging agent layer is formed by a coating method, an antifogging agent is mixed with a polyolefin resin to form an inner layer of the film. The antifogging effect can be stably maintained without reducing the amount of the clouding agent. In addition, the presence of the gas barrier layer suppresses migration and diffusion of the antifogging agent to the outer layer side of the film and the outer side of the package, and the antifogging agent effectively deposits on the surface of the inner layer of the film, effectively expressing antifogging properties. obtain. Furthermore, the anti-fogging agent adhesion stain | pollution | contamination does not generate | occur | produce on the packaging machine hotplate which the outer-layer side of a lid | cover material film contacts by the transfer suppression to an outer-layer side.

Known components can be used as the antifogging agent, and examples thereof include glycerin fatty acid ester monoglyceride, glycerin fatty acid ester organic acid monoglyceride, polyglycerin fatty acid ester, and sorbitan fatty acid ester. Especially, when using the film of this invention for a food contact use, a polyglycerol fatty acid ester is preferable from the point of kneading | mixing suitability with the polyolefin resin which comprises an inner layer, and an antifogging effect.
The lower limit of the antifogging agent-containing concentration is preferably 0.020% by mass or more, more preferably 0.025% by mass or more, and further preferably 0.030% by mass or more with respect to the film inner layer. The upper limit is preferably 0.100% by mass or less, more preferably 0.090% by mass or less, and further preferably 0.080% by mass or less.
When 0.020% by mass or more, a good antifogging effect can be exhibited, and when 0.100% by mass or less, excessive precipitation of the antifogging agent on the inner layer surface is suppressed, and stickiness of the film surface and generation of powder are suppressed. be able to.

  The lower limit of the thickness of the inner layer (heat seal layer) is preferably 10 μm or more, and more preferably 15 μm or more. The upper limit is preferably 30 μm or less. By setting the thickness to 10 μm or more, good heat sealability, sufficient antifogging property and antifogging performance can be maintained over time, and by setting the thickness to 30 μm or less, the rigidity of the film becomes preferable.

<Easy peel layer>
In the film of the present invention, an easy peel layer adjacent to the heat seal layer can be further provided on the intermediate layer side of the inner layer (heat seal layer). After heat-sealing with the bottom material (tray) and sealing, the lid can be easily opened and opened by hand without pulling the cover material with a large force.
The easy peel layer is formed by mixing two or more kinds of mutually incompatible polyolefin resins and has cohesive failure. When opening, the easy peel layer causes cohesive failure inside the layer and can be easily opened. At the time of opening, the heat seal layer around the opening of the lid film remains on the tray side.

  In the case of disposing an easy peel layer, it is preferable to add a liquid antifogging agent to the liquid antifogging agent in the same manner as the heat seal layer described above. By including a liquid antifogging agent in the easy peel layer adjacent to the heat seal layer of the film inner layer, the liquid antifogging agent mixed in the heat seal layer is effective on the heat seal surface without shifting to the easy peel layer side. And the antifogging property of the film is maintained over time. On the other hand, when the easy peel layer does not contain a liquid antifogging agent, the liquid antifogging agent in the heat seal layer migrates and diffuses not only to the surface on the film inner layer side but also to the easy peel layer, thus maintaining antifogging properties. Is not preferable because it becomes insufficient.

  In this case, it is preferable that the amount of the liquid antifogging agent in the easy peel layer contains the liquid antifogging agent in the heat seal layer of the adjacent film inner layer in a proportion greater than the content ratio. The liquid antifogging agent for the easy peel layer can be used in the same manner and in the same manner as the kind contained in the polyolefin resin layer of the heat seal layer.

From the viewpoint of cohesive failure, it is preferable to use a polyethylene-based resin as the main component of the resin used in the easy peel layer in order to ensure co-extrusion adhesion with the adjacent polyolefin resin and heat seal layer. Examples thereof include low density polyethylene (LDPE), ethylene-vinyl acetate copolymer (EVA), ionomer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid methyl copolymer, and the like.
For the subcomponent, it is preferable to select one or more resins that are low in compatibility with the main component of the resin used in the easy peel layer and that can be uniformly dispersed, because good cohesiveness can be obtained. For example, propylene homopolymer, propylene-ethylene copolymer, polybutene (PB), polystyrene (PS) and the like are preferable.
Among these, as a combination of the main component and the subcomponent, a combination of LDPE and PB, or LLDPE and PB is more preferable in terms of achieving both stable openability and interlayer adhesion strength.

  The film of the present invention is heat-sealed with a bottom material (tray) using the film of the present invention as a lid, and after sealing, the easy peel strength when the lid is opened is 23 ° C., and the lower limit is 4.0 N / 15 mm width or more, preferably 6.0 N / The width is 15 mm width or more, more preferably 8.0 N / 15 mm width or more, and the upper limit is 15.0 N / 15 mm width or less, preferably 13.0 N / 15 mm width or less, more preferably 12.0 N / 15 mm width or less. When the width is less than the lower limit of 4.0 N / 15 mm, the strength becomes too small, which is not preferable from the viewpoint of the sealing property of the package, and when the upper limit of 15.0 N / 15 mm is exceeded, opening is difficult.

The main component of the resin used in the easy peel layer is 50% by mass or more, preferably 55% by mass or more, and the upper limit is 80% by mass or less, preferably 75% by mass or less, with respect to the entire easy peel layer. More preferably, it is 70 mass% or less. If the amount is less than the lower limit of 50% by mass, the easy peel strength becomes too small, which is not preferable, and if the upper limit of 70% by mass is exceeded, the easy peel strength increases and it is difficult to open.
The subcomponent used in the easy peel layer is 20% by mass or more, preferably 25% by mass or more, more preferably 30% by mass or more, and the upper limit is 50% by mass or less, preferably with respect to the entire easy peel layer. Is 45 mass% or less. If the amount is less than the lower limit of 20% by mass, the cohesive fracture property of the easy peel layer at the time of opening becomes small and is difficult to open, and if the upper limit of 50% by mass is exceeded, the cohesive fracture property of the easy peel layer increases, which is not preferable. .

The thickness of the heat seal layer inside the film adjacent to the easy peel layer is preferably thinly formed from the viewpoint that it needs to be broken at the time of opening, and the upper limit is preferably 10 μm or less, and more preferably 5 μm or less. The lower limit is preferably 1 μm or more and more preferably 2 μm or less from the viewpoint of film formation stability.
The thickness of the easy peel layer is desirably thin from the viewpoint of transparency and openability, and the upper limit is preferably 10 μm or less, and more preferably 5 μm or less. The upper limit of 10 μm is not preferable because the transparency is lowered and the openability is lowered. In particular, the lower limit is preferably 1 μm or more, and more preferably 2 μm or less. If it is less than the lower limit of 1 μm, it may not be preferable from the viewpoint of film forming stability and thickness accuracy.

  In the case of disposing an easy peel layer, it is preferable to dispose a layer composed of a polyolefin resin and a liquid antifogging agent on the intermediate layer side from the easy peel layer. (Hereinafter, it may also be referred to as a polyolefin-based resin layer.) The polyolefin-based resin layer is not particularly limited, but the same heat-seal layer as that described above can be used. I do not care.

  When the polyolefin resin layer is further arranged on the intermediate layer side from the easy peel layer, the combined thickness of the heat seal layer, the easy peel layer and the polyolefin resin layer is preferably at least 10 μm, more preferably at least 15 μm. preferable. The upper limit is preferably 30 μm or less. By setting the thickness to 10 μm or more, good antifogging performance can be obtained, and by setting the thickness to 30 μm or less, the rigidity of the film is preferable and preferable.

<Adhesive layer>
The film of the present invention can be provided with an adhesive layer as necessary for the purpose of increasing the delamination strength of each layer. The adhesive layer may be a single layer or a plurality of layers.
Adhesive resins that can be used as the adhesive layer include polyethylene (PE) such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), and high density polyethylene (HDPE), polypropylene (PP ), Ethylene-vinyl acetate copolymer (EVA) and the like, and other modified polyolefin resins such as ethylene-vinyl acetate copolymer or ethylene elastomer, monobasic such as acrylic acid or methacrylic acid. Examples include unsaturated fatty acids or chemically bonded dibasic fatty acid anhydrides such as maleic acid, fumaric acid or itaconic acid. Among them, it is preferable to use an adhesive resin based on polyethylene or polypropylene.

  When the adhesive layer is provided, the thickness of the adhesive layer is not particularly limited, but the lower limit is preferably 2 μm or more and the upper limit is preferably 8 μm or less from the viewpoints of adhesiveness, workability, economy, and handleability. When the thickness of the adhesive layer is 2 μm or more, the delamination strength can be improved. If the adhesive layer is too thick, the transparency is deteriorated and the total thickness of the film is increased, and the manufacturing cost is increased, so that the upper limit is preferably 8 μm or less.

<Whole film>
The layer structure of the film of the present invention is such that the outer layer is a mixed layer of a polypropylene resin and a polystyrene-polyolefin resin, or a laminate of a polypropylene resin layer and a polystyrene-polyolefin copolymer resin layer, and the intermediate layer is an ethylene-vinyl acetate copolymer. There is no particular limitation as long as the gas barrier layer is composed of a saponified product or polymetaxylylene adipamide resin, and the inner layer has an anti-fogging agent-containing heat seal layer, and other layers such as an adhesive resin layer are arranged between the layers. You may do it.
The total thickness of the film of the present invention is the film total thickness, from the viewpoint of satisfactorily combining film-forming properties, film rigidity and strength, heat sealability and hot plate non-fusibility, gas barrier properties, resilience, economy, etc. Is preferably 20 μm or more. The upper limit of the total film thickness is preferably 60 μm or less, more preferably 50 μm or less, and still more preferably 45 μm or less. If the total film thickness is less than 20 μm, it is not preferable from the viewpoint of film forming properties, film rigidity and strength, and if the total film thickness exceeds 60 μm, it is not preferable from the viewpoint of production cost.

The oxygen gas permeability of the film of the present invention is preferably low from the viewpoint of suppressing deterioration of food, preferably 20 cc / (m ² · day · atm) or less, more preferably 15 cc / (m ² · day · atm) or less. preferable.

<Packaging body>
The film of the present invention is suitable for use in various packaging bodies. The film of the present invention has a good gas barrier property, and has a hermetically sealing property with a tray (tray) etc., sufficient anti-fogging property, and continuous anti-fogging performance, and is particularly tightly packed without deforming the package during packaging. Because it is possible, traces (transfer) during stacking, transportation, storage, and display are unlikely to occur. Deep drawn packaging such as gas replacement packaging (gas pack), blister pack, tray (tray) packaging, etc. It is useful for use as a lid material.

  The bottom material of the deep drawn package and the bottom material (tray) of the tray package are not particularly limited in terms of material, size, shape, etc., and known packaging materials can be used. As the bottom material of the deep-drawn package, for example, a polyamide resin layer / heat seal layer, a polyolefin resin layer / polyamide resin layer / heat seal layer, and the like, and a gas barrier layer is arranged between these layers. Examples include a bottom material formed using an unstretched coextruded film having a layer structure. As the tray bottom material, for example, a tray bottom material formed using a foamed polystyrene sheet, a polypropylene sheet, a polyethylene terephthalate sheet, or the like, or a film having a sealing layer made of an olefin resin is laminated on the sheet, and the film is accommodated. Examples thereof include a tray bottom material formed so as to be located on the object side.

    Examples of the present invention will be described below, but the present invention is not limited thereto.

In the films having the layer structures shown in Examples 1 to 5 and Comparative Examples 1 to 3, the resin constituting each layer was put into a single-screw extruder and coextruded at a resin temperature of 250 ° C. by the T-die method. An unstretched coextruded laminated film was produced by rapid cooling with a cast roll at 0 ° C.
The content of the antifogging agent in the inner layer (heat seal layer) is determined by using a master batch prepared by mixing and kneading the antifogging agent at a ratio of 15% by mass with respect to the linear low density polyethylene resin (LLDPE). It mixed with LLDPE, and the antifogging agent containing density | concentration in an inner layer was 0.075 mass%. In Examples 4 and 5, a polyolefin resin layer was further provided inside the easy peel layer and the easy peel layer. The easy peel layer is composed of a linear low-density polyethylene resin (LLDPE) and a polybutene resin (PB) in a mass ratio of 70/30, and the same anti-fogging agent master batch added to the inner layer. The antifogging agent content concentration was 0.075% by mass. Like the inner layer (heat seal layer), the polyolefin resin layer inside the easy peel layer uses the same antifogging agent master batch for the linear low density polyethylene resin (LLDPE), The amount was 0.075% by mass.
In Comparative Example 3, a non-stretched coextruded laminated film was prepared, and then put into a stretching machine, and stretched at a stretch ratio of 1.5 and 1.5 times without heat fixing to obtain a heat-shrinkable film.

Next, using a deep-drawing packaging machine (R535 manufactured by MULTIVAC), the film obtained in each example was provided as a lid material film, and the bottom material film had a layer configuration of APET (270 μm) / EVOH (10 μm) / PE (20 μm). An unstretched coextruded film was provided.
The bottom material film is vacuum-molded into a substantially rectangular parallelepiped deep drawing shape with a 10 cm square bottom and a depth of 5 cm, containing 50 ml of water, and the flange portion of the bottom material and the lid material film are stacked, and the peripheral portion is 140 ° C., 2 ° C. In addition to heat-sealing at a setting condition of 0.5 MPa for 2 seconds, nitrogen gas was sealed under the conditions of a pressure of 300 kPa and a flow rate of 8 L to produce a gas replacement package (gas pack). The heat seal hot plate is located on the outer layer side of the lid member.

In the layer configuration shown in each example, the following abbreviations were used for the notation of the resin composition constituting each layer described in order from the outer layer side to the inner layer side. Moreover, the inside of () shows the thickness of each layer, and the description of "+" means inclusion.
PP; polypropylene homopolymer, melting point 160 ° C.
PS-PO; polystyrene-polyolefin copolymer Ny; nylon 6 homopolymer EVOH; saponified ethylene-vinyl acetate copolymer 32 mol%
MXD; polymetaxylylene adipamide resin PE; linear low-density polyethylene resin PB; polybutene resin anti-fogging; anti-fogging agent, polyglycerin fatty acid ester AD; unsaturated carboxylic acid-modified polyethylene adhesive resin

<Example 1>
[PP 60 wt% + PS-PO 40 wt%] (10 μm) / AD (2 μm) / EVOH (2 μm) / AD (4 μm) / PE + anti-fogging (22 μm), total thickness 40 μm

<Example 2>
PP (2 μm) / PS-PO (8 μm) / AD (2 μm) / EVOH (2 μm) / AD (4 μm) / [PE + antifogging] (22 μm), total thickness 40 μm

<Example 3>
PP (2 μm) / PS-PO (8 μm) / AD (2 μm) / PA (2 μm) / EVOH (2 μm) / AD (4 μm) / [PE + antifogging] (20 μm), total thickness 40 μm

<Example 4>
PP (2 μm) / PS-PO (8 μm) / AD (2 μm) / PA (2 μm) / EVOH (2 μm) / AD (4 μm) / [PE + antifogging] (16 μm) / [(PE / PB = 70/30 ) + Anti-fogging] (2 μm) / [PE + Anti-fogging] (2 μm), total thickness 40 μm

<Example 5>
PP (2 μm) / PS-PO (8 μm) / AD (2 μm) / PA (2 μm) / MXD (2 μm) / AD (4 μm) / [PE + antifogging] (16 μm) / [(PE / PB = 70/30 ) + Anti-fogging] (2 μm) / [PE + Anti-fogging] (2 μm), total thickness 40 μm

<Comparative Example 1>
PP (10 μm) / AD (2 μm) / EVOH (2 μm) / AD (4 μm) / [PE + antifogging] (22 μm), total thickness 40 μm

<Comparative example 2>
PS-PO (10 μm) / AD (2 μm) / EVOH (2 μm) / AD (4 μm) / [PE + antifogging] (22 μm), total thickness 40 μm

<Comparative Example 3> Heat-shrinkable film Ny (16 μm) / EVOH (2 μm) / AD (2 μm) / [PE + antifogging] (20 μm), total thickness 40 μm

The following evaluation was performed about the gas replacement packaging body produced using the film obtained in each example, and the result was described in Table 1.
<Hot plate fusion>
In the case of heat sealing, the case where the lid material film was not fused to the hot plate was evaluated as “◯”, and the case where it was evaluated as “×”.

<Restorability (lid material remains)>
An 8 cm square, 300 g metal plate was placed at the center of the lid of the gas replacement package on the horizontal table, and the plate was stored at 5 ° C. for 24 hours. After that, the metal plate is lowered and the lid of the package is observed, and “○” indicates that the dent mark disappears within 5 minutes on the place where the metal plate is placed, “△” indicates that the mark disappears within 10 minutes, Those which did not disappear within 10 minutes were designated as “x”.

<Bottom material deformation>
Immediately after making the gas replacement package, place it on a horizontal table, and with respect to the horizontal plane, the heat seal part (flange part) warpage was less than 2 mm, “○”, and those with more than 2 mm as “×” did.

<Adhesive strength (interlaminar peel strength)>
After producing the gas replacement package, the laminated film (cover material film) of the present invention was peeled off to evaluate whether delamination occurred in the laminated film. The case where 10 packs were peeled and the delamination was 0 pack was designated as “◯”, the case where the delamination was 1 to 3 packs was designated as “Δ”, and the case where four or more packs were delaminated as “x”.

<Easy opening (easy peel)>
When the laminated film (cover material film) of the present invention is peeled after the gas replacement package is produced, the peel strength of less than 15 N / 15 mm width is indicated as “◯”, and the peel strength of 15 N / 15 mm width or greater is indicated as “X”. did.

As can be seen from Table 1, the non-stretched coextruded laminated film for lids according to the above examples is a layer containing a polypropylene resin and a polystyrene-polyolefin copolymer resin in the outer layer, or a polypropylene resin layer and a polystyrene-polyolefin. Since each layer containing a copolymer resin was disposed, it was not fused to the hot plate during heat sealing, and the restorability was good.
On the other hand, Comparative Example 1 is not good in restorability because only the polypropylene-based resin layer is arranged on the outer layer, and Comparative Example 2 has only a polystyrene-polyolefin copolymer resin layer on the outer layer. Fusion to the hot plate occurred during sealing. The heat-shrinkable film of Comparative Example 3 had problems with bottom material deformation and adhesive strength.
Furthermore, in Example 4 and Example 5, since an easy peel layer was provided, an easy opening property (easy peel property) was satisfactory.

  When the film of the present invention is used as a lid for a package, the package has good tension without being deformed, has good gas barrier properties, sealing properties, antifogging properties, and traces when the packages are stacked. Because of its disappearance, it is particularly useful as a gas-replacement deep-drawn package (gas pack), which helps to extend the shelf life of fresh foods, etc., and in turn contributes greatly to reducing the amount of food and packaging materials discarded. It is done.

DESCRIPTION OF SYMBOLS 1; Cover material 2; Bottom material, tray 3; Heat seal contact | adherence part (top seal part) of a cover material and a bottom material
4; Containment such as fresh food 5; Inert gas filling part 10; Deep drawn package

Claims (6)

  A laminated film having at least an outer layer, an intermediate layer, and an inner layer, wherein the outer layer is a layer containing a polypropylene resin and a polystyrene-polyolefin copolymer resin, or a layer containing a polypropylene resin and a polystyrene-polyolefin copolymer. Each having at least one layer containing a resin, the intermediate layer has a gas barrier layer containing a saponified ethylene-vinyl acetate copolymer or a polymetaxylylene adipamide resin, and the inner layer is an antifogging agent. An unstretched coextruded laminated film for a lid material having a heat seal layer containing a polyolefin-based resin and having a total film thickness of 20 μm to 60 μm.   The non-stretched co-extrusion laminated film for lid | cover materials of Claim 1 which has a layer containing a polyamide-type resin between the intermediate | middle layer and inner layer of the said laminated | multilayer film.   The unstretched coextrusion laminated film for lid | cover materials of Claim 1 or 2 which has an easy peel layer adjacent to this heat seal layer in the intermediate | middle layer side of the heat seal layer of the said laminated film.   The lid | cover material for deep-drawing packaging bodies using the unstretched coextrusion laminated | multilayer film for lid | cover materials in any one of Claims 1-3.   A deep drawn package comprising the lid according to claim 4 and a bottom material for a deep drawn package.   6. The deep drawn package according to claim 5, which is a gas replacement deep drawn package.

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