Laminated material for food packaging

Abstract

To provide a film laminated material more excellent in vapor barrier property and oxygen barrier property, as a food packaging material.SOLUTION: Provided is a laminated material for food packaging comprising a substrate including a stretched polyolefin resin film, a heat-sealable layer including an unstretched polyolefin resin film, and a gas barrier laminate layer provided between the substrate and the heat-sealable layer, and provided with a gas barrier resin layer and a polyolefin resin layer, wherein the substrate and the gas barrier resin layer each have surfaces treated to impart gas barrier properties, and the treated surfaces face each other and are bonded with an adhesive.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a film laminate material that can be used as a packaging material for food products. [Background technology]

[0002] Film laminate materials in which polyolefin films or the like are laminated are often used as packaging materials for foods such as seasonings. In order to prevent deterioration of the packaged food, such film laminate materials are generally made by laminating a gas barrier film onto a polyolefin film.

[0003] For example, Patent Document 1 discloses a laminate for packaging materials, which comprises at least a substrate, a gas barrier laminate, and a heat seal layer, wherein the substrate and the gas barrier laminate are stretched resin films, the gas barrier laminate comprises a gas barrier resin layer and a polyolefin resin layer, the substrate, the polyolefin resin layer, and the heat seal layer are made of the same polyolefin, and the thickness of the gas barrier resin layer is smaller than the thickness of the polyolefin resin layer. However, there is still room for improvement in the water vapor barrier property and oxygen barrier property as a food packaging material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-37189 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a film laminated material having excellent water vapor barrier properties and oxygen barrier properties as a packaging material for foods such as seasonings and dried soups. [Means for solving the problem]

[0006] The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result, have found that in a laminate for food packaging materials comprising a substrate containing a stretched polyolefin resin film, a heat seal layer containing an unstretched polyolefin resin film, and a gas barrier laminate layer provided between the substrate and the heat seal layer and comprising a gas barrier resin layer and a polyolefin resin layer, the water vapor barrier property and oxygen barrier property of the laminate for food packaging materials can be significantly improved by configuring the substrate and the gas barrier resin layer so that their surfaces are treated to impart gas barrier property and the surfaces are bonded together with an adhesive so that the gas barrier property-treated surfaces face each other, thereby completing the present invention. The present invention provides the following:

[0007] [1] A substrate including a stretched polyolefin resin film; a heat seal layer containing an unstretched polyolefin resin film; a gas barrier laminate layer provided between the substrate and the heat seal layer, the gas barrier laminate layer including a gas barrier resin layer and a polyolefin resin layer; A laminate for food packaging materials comprising: The food packaging laminate is characterized in that the surfaces of the substrate and the gas barrier resin layer are each treated to impart gas barrier properties, and the substrate and the gas barrier resin layer are bonded together with an adhesive so that the gas barrier treated surfaces face each other. [2] The gas barrier property imparting treatment is a coating treatment of a gas barrier film according to [1]. The food packaging laminate described above. [3] The gas barrier film according to [2], wherein the gas barrier film is one or more selected from the group consisting of polyvinyl alcohol films, ethylene-vinyl alcohol copolymer films, and vapor-deposited films of one or more inorganic materials selected from aluminum, aluminum oxide, and silicon oxide (silica). Laminate for food packaging. [4] The food packaging laminate according to any one of [1] to [3], wherein the adhesive is a barrier adhesive. [5] The food packaging laminate according to [4], wherein the barrier adhesive is a cured product of a composition containing a polyester polyol and an isocyanate compound. [6] The laminate for packaging food according to any one of [1] to [5], wherein the proportion of polyolefin relative to the total mass is 80 mass % or more. [7] The food packaging laminate according to any one of [1] to [6], wherein the gas barrier laminate and the heat seal layer are bonded with an adhesive. [8] The laminate for food packaging according to any one of [1] to [7], wherein the heat seal layer is unstretched polyethylene or unstretched polypropylene. [9] A food packaged with the food packaging laminate according to any one of [1] to [8].

[10] The food product according to [9], which is a seasoning or a dried soup. [Effects of the Invention]

[0008] According to the present invention, a laminate for food packaging material comprising a substrate containing a stretched polyolefin resin film, a heat-seal layer containing an unstretched polyolefin resin film, and a gas-barrier laminate layer disposed between the substrate and the heat-seal layer and comprising a gas-barrier resin layer and a polyolefin resin layer, wherein the surfaces of the substrate and the gas-barrier resin layer are each treated to impart gas-barrier properties and are bonded together with an adhesive so that the gas-barrier-treated surfaces face each other, provides a laminate for food packaging material with excellent water vapor barrier properties and oxygen barrier properties, and is suitable for use as a packaging material for foods such as seasonings and dried soups. Because the substrate of the laminate for food packaging material of the present invention has been treated to impart gas barrier properties, there is no need to use a material treated with gas-barrier properties for the heat-seal layer, making it possible to select a sealant that exhibits excellent impurity sealing properties when packaging food and excellent heat-sealing properties in packaging machines. Here, "excellent impurity sealing properties" means that high sealing strength can be obtained even when heat-sealing is performed with powder or liquid attached to the sealing portion, and "excellent heat-sealing properties" means that the sealing strength is high. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing one embodiment of a laminate for food packaging materials of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Laminate for food packaging materials> The laminate for food packaging materials of the present invention comprises a substrate containing a stretched polyolefin resin film; a heat seal layer containing an unstretched polyolefin resin film; a gas barrier laminate layer provided between the substrate and the heat seal layer, the gas barrier laminate layer including a gas barrier resin layer and a polyolefin resin layer; A laminate for food packaging materials comprising: The substrate and the gas barrier resin layer each have a surface treated to impart gas barrier properties, and are bonded together with an adhesive so that the surfaces treated to impart gas barrier properties face each other. In the laminate for food packaging materials of the present invention, the proportion of polyolefin to the total mass is preferably 80 mass % or more.

[0011] <Base material> The substrate in the laminate for food packaging materials of the present invention comprises a stretched polyolefin resin film, the surface of which is treated to impart gas barrier properties, thereby maintaining high gas barrier properties while maintaining the strength and heat resistance required for packaging materials. Examples of polyolefin resins include polyethylene, polypropylene, ethylene-propylene copolymers, etc. Among these, polyethylene and polypropylene are preferred. The polyethylene may be low density polyethylene, medium density polyethylene, or high density polyethylene. The stretched polyolefin resin film may be a uniaxially stretched polyolefin resin film or a biaxially stretched polyolefin resin film. The thickness of the substrate is preferably 5 μm or more and 100 μm or less, and more preferably 15 μm or more and 35 μm or less.

[0012] The substrate can be produced by forming a polyolefin into a film by a T-die method, an inflation method, or the like, and then stretching the film.

[0013] The surface of the substrate is treated to impart gas barrier properties. The gas barrier property imparting treatment is carried out on the surface of the stretched polyolefin resin film serving as the substrate that faces the gas barrier laminate. The gas barrier treatment may be carried out by coating the surface of the stretched polyolefin resin film facing the gas barrier laminate with a gas barrier film. Examples of gas barrier films include coated films of polyvinyl alcohol (PVA) or ethylene-vinyl alcohol (EVOH) copolymers, or vapor-deposited films of inorganic materials such as metals such as aluminum, aluminum oxide, and silicon oxide (silica) or metal oxides (the definition of metal oxides also includes silica). These may be used alone or in combination of two or more, and may be a combination of either or both of the coated and vapor-deposited films. The substrate has a surface that has been treated to provide gas barrier properties and a water vapor permeability of 0.2 to 5.0 g / m 2 ·day, and the oxygen permeability is 0.1 to 3.0 cc / m 2 ·day·atm is preferred.

[0014] The coating film can be formed using a known method. For example, a gas barrier substance such as PVA or EVOH is first dissolved in water or an organic solvent, and the solution is then applied to a substrate and dried to form a gas barrier coating film on the substrate.

[0015] The vapor deposition film can be formed by a known method, for example, a physical vapor deposition method (PVD method) such as a vacuum deposition method, a sputtering method, and an ion plating method, and a plasma chemical deposition method. Chemical vapor deposition (CVD) methods such as vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition etc. can be used.

[0016] <Gas barrier laminate> The gas barrier laminate in the laminate for food packaging materials of the present invention comprises a gas barrier resin layer and a polyolefin resin layer. It preferably has a three-layer structure consisting of a first polyolefin resin layer, a second polyolefin resin layer, and a gas barrier resin layer therebetween. Note that adhesive layers made of adhesive may be included between the first polyolefin resin layer and the gas barrier resin layer, and between the second polyolefin resin layer and the gas barrier resin layer. Examples of polyolefin resins that constitute the polyolefin resin layer contained in the gas barrier laminate include polyethylene, polypropylene, and ethylene-propylene copolymers. Of these, polyethylene and polypropylene are preferred. Examples of the gas barrier resin contained in the gas barrier laminate include ethylene-vinyl alcohol copolymer (EVOH).

[0017] The gas barrier laminate can be produced by co-extrusion of the material constituting the gas barrier resin layer, the material constituting the polyolefin resin layer, and, if necessary, a material for forming an adhesive layer therebetween, by a known method such as the T-die method or the inflation method, and stretching the resulting film. A commercially available gas barrier laminate may be used, or one produced by oneself may be used.

[0018] The thickness of the gas barrier laminate is preferably 5 μm or more and 100 μm or less, and more preferably 5 μm or more and 35 μm or less.

[0019] The surface of the gas barrier laminate facing the substrate is treated to provide gas barrier properties. The gas barrier treatment can be performed in the same manner as the treatment for providing gas barrier properties to the substrate surface. That is, the surface of the gas barrier laminate facing the substrate is preferably coated with a coating film such as polyvinyl alcohol (PVA) or ethylene-vinyl alcohol (EVOH) copolymer, or a vapor-deposited film of an inorganic material such as aluminum, aluminum oxide, silicon oxide (silica), or a metal oxide (metal oxide includes silica) (the definition of metal oxide also includes silica). These may be used alone or in combination of two or more, or a combination of either or both of the coating film and the vapor-deposited film. Coating with a coating film or a vapor-deposited film can be performed in the same manner as described above. The gas barrier laminate has a water vapor permeability of 0.01 to 1.0 g / m when the surface is treated to provide gas barrier properties. 2 ·day, and the oxygen permeability is 0.01 to 3.0 cc / m 2 ·day·atm is preferred.

[0020] <Adhesive layer> In the laminate for food packaging materials of the present invention, an adhesive layer, i.e., an adhesive layer, is provided between the substrate and the gas barrier laminate, and the substrate and the gas barrier resin layer are bonded together with the gas barrier treatment surface facing inward. Here, the adhesive may be a barrier adhesive that imparts or complements gas barrier properties, or may be a general adhesive that does not impart or complement gas barrier properties, but is more preferably a barrier adhesive.

[0021] Examples of adhesives with gas barrier properties or barrier adhesives that complement gas barrier properties include two-component curing adhesives, which are cured products of resin compositions containing polyester polyols and isocyanate compounds. Examples of polyester polyols include polyester polyols obtained by polycondensation of ortho-oriented polycarboxylic acids or their anhydrides with polyhydric alcohols, polyester polyols with glycerol skeletons, and polyester polyols with isocyanuric rings. Examples of isocyanate compounds include tetramethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, metaxylylene diisocyanate, hydrogenated xylylene diisocyanate, and isophorone diisocyanate.

[0022] The barrier adhesive may be a two-component curing adhesive, which is a cured product of a resin composition containing a polyester polyol, an isocyanate compound, and a phosphoric acid-modified compound. Here, examples of the phosphoric acid-modified compound include phosphoric acid, pyrophosphoric acid, triphosphoric acid, methyl acid phosphate, ethyl acid phosphate, butyl acid phosphate, and dibutyl phosphate. Acid phosphate, 2-ethylhexyl acid phosphate, bis(2-ethylhexyl) phosphate, isododecyl acid phosphate, butoxyethyl acid phosphate, oleyl acid phosphate, tetracosyl acid phosphate, 2-hydroxyethyl methacrylate acid phosphate, and polyoxyethylene alkyl ether phosphate. Specific examples of such adhesives include Paslim (DIC) and Maxy. Examples include Mitsubishi Gas Chemical.

[0023] By providing a layer of a barrier adhesive, i.e., a barrier adhesive layer, between the gas barrier property-imparting treated surface of the substrate and the gas barrier laminate, the oxygen barrier property and water vapor barrier property of the packaging material laminate of the present invention can be further improved. In particular, by arranging the gas barrier treated surface of the substrate and the gas barrier treated surface of a gas barrier laminate, the surface of which has also been treated with a gas barrier coating film or vapor deposition film, adjacent to each other with a barrier adhesive layer in between, it is possible to effectively prevent cracks from occurring in the gas barrier coating film or vapor deposition film, and the gas barrier properties are improved.

[0024] The general adhesive may be a one-component curing type, a two-component curing type, or a non-curing type, and any adhesive that is generally used for bonding films can be used.

[0025] <Heat seal layer> The heat seal layer in the laminate for food packaging materials of the present invention contains an unstretched polyolefin resin film. The unstretched polyolefin resin film may be, for example, an unstretched polyethylene resin film or an unstretched polypropylene resin film, or may be an unstretched polyethylene-polypropylene copolymer resin film. The unstretched polyethylene resin film is preferably an unstretched linear low-density polyethylene.

[0026] The heat seal layer may be formed by forming a film from polyolefin by a T-die method, an inflation method, or the like. The thickness of the heat seal layer is preferably 10 μm or more and 300 μm or less, and more preferably 10 μm or more and 100 μm or less.

[0027] It is also preferable that an adhesive layer be present between the gas barrier laminate and the heat seal layer. The adhesive layer between the gas barrier laminate and the heat seal layer may be formed by curing a general adhesive, or may be formed by curing an adhesive having gas barrier properties or a barrier adhesive that complements the gas barrier properties as described above. The general adhesive may be a one-component curing type, a two-component curing type, or a non-curing type, and any adhesive that is generally used for bonding films can be used.

[0028] The laminate of the present invention can be obtained by bonding together, with an adhesive, a substrate comprising a stretched polyolefin resin film that has been treated to impart gas barrier properties, and a gas barrier laminate that has also been treated to impart gas barrier properties, with the gas barrier properties-treated surfaces facing inwards, and further bonding the resulting bonded substrate and gas barrier laminate to a heat seal layer with an adhesive. However, the order of lamination is not particularly limited, and the gas barrier laminate and the heat seal layer may be laminated together first with an adhesive, and then the substrate may be laminated together with the adhesive therebetween.

[0029] More preferred embodiments of the laminate for food packaging materials of the present invention are exemplified below, but the laminate for food packaging materials of the present invention is not limited to the following embodiments. (outside) 1) Base material: oriented polypropylene resin or oriented polyethylene resin 2) Gas barrier film on the substrate surface: PVA coating film, aluminum vapor deposition film, or alumina vapor deposition film 3) Adhesive layer: General adhesive or cured resin composition containing polyester polyol and isocyanate compound 4) Gas barrier film on the surface of the gas barrier laminate: one or more of aluminum vapor deposition film, alumina vapor deposition film, PVA coating film, and EVOH coating film 5) Gas barrier laminate: gas barrier resin 6) Adhesive layer: General adhesive or cured resin composition containing polyester polyol and isocyanate compound 7) Heat seal layer: Unstretched polypropylene resin or unstretched polyethylene resin (Inside: Food side)

[0030] <Food packaging materials> The food packaging material of the present invention is characterized in that it is composed of the above-mentioned food packaging laminate. The shape of the packaging material is not particularly limited, but it can be, for example, in the shape of a bag.

[0031] A bag-shaped food packaging material can be produced, for example, by folding the laminate of the present invention in half, overlapping them so that the heat-sealable layer is on the inside, and heat-sealing the edges. Alternatively, a bag-shaped packaging material can be produced by preparing two laminates of the present invention, overlapping them so that the heat-sealable layers face each other, and heat-sealing the edges. The heat-sealing method is not particularly limited, and can be any known method such as bar sealing, rotary roll sealing, belt sealing, impulse sealing, high-frequency sealing, or ultrasonic sealing.

[0032] The food packaging material of the present invention can also have a stand-up pouch shape with a body and a bottom. A stand-up pouch food packaging material can be produced by forming the laminate into a cylindrical shape with the heat-sealable layer facing inward, heat-sealing to form the body, folding another laminate into a V shape with the heat-sealable layer facing inward, and then sandwiching one end of the body and heat-sealing to form the bottom.

[0033] The food to be enclosed in the packaging material is not particularly limited and may be liquid, powder, or gel. Examples include seasonings and dried soup. Here, dried soup includes powdered soup, granular soup, solid soup, etc. After the food is enclosed, the opening is heat-sealed to form a food package. [Example]

[0034] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

[0035] Materials and manufacturing methods for polyolefin laminates <Material> Example 1 ·Base material The substrate is a 18μm thick sheet with alumina vapor deposition to provide gas barrier properties. Air permeability <1.5 (g / m 2·day), oxygen permeability <0.5(cc / m 2 Biaxially oriented polypropylene (days atm) A pyrene film (manufactured by SAES Coated Films) was prepared. First adhesive As the general adhesive, a two-component curing adhesive, which is a cured product of a resin composition containing polyurethane polyol and an isocyanate compound, was used. Gas barrier laminate As a gas barrier laminate, Toppan Specialty Films has a thickness of 18 μm and a water vapor permeability of ≦0.08 (g / m 2 ·day), oxygen permeability ≦0.08 (cc / m 2 ·day·atm) with aluminum vapor deposition on the surface A biaxially oriented polypropylene film was prepared. Second adhesive As with the first adhesive, a two-component curing adhesive, which is a cured product of a resin composition containing polyurethane polyol and an isocyanate compound, was used as the general adhesive. Sealants As a sealant layer, a 50 μm thick unstretched linear low-density polyethylene film (Mitsui Chemicals Tokyo) was used. A centrifuge (FCD-TUX, manufactured by Cero) was used.

[0036] Example 2 A laminate was produced in the same manner as in Example 1, except that a two-component curing adhesive, which was a cured product of a resin composition containing a polyester polyol and an isocyanate compound, was used as the first adhesive.

[0037] Example 3 A laminate was produced in the same manner as in Example 1, except that a two-component curing adhesive, which was a cured product of a resin composition containing a polyester polyol and an isocyanate compound, was used as the first adhesive and the second adhesive.

[0038] Example 4 As a gas barrier laminate, JINDAL's 16 μm thick film with a water vapor permeability of 0.1 (g / m 2 ·day) oxygen Transparency 0.1(cc / m 2 A laminate was prepared in the same manner as in Example 3, except that a biaxially oriented polypropylene film having a surface subjected to aluminum vapor deposition treatment was used.

[0039] Example 5 The substrate is a 20 μm thick PVA coated sheet with a water vapor permeability of <6 (g / m 2 ·day), oxygen permeability <1.5(cc / m 2 ·day·atm) uniaxially oriented polyethylene A laminate was produced in the same manner as in Example 3, except that a film (manufactured by SAES Coated Films) was used.

[0040] Example 6 The base material is a 20 μm thick sheet that has been aluminum vapor-deposited to provide gas barrier properties. Air permeability <1 (g / m 2 ·day), oxygen permeability <1(cc / m 2 ·day·atm) uniaxially stretched polyethylene A laminate was produced in the same manner as in Example 3, except that a polyimide film (manufactured by SAES Coated Films) was used.

[0041] Comparative Example 1 A laminate was produced in the same manner as in Example 3, except that no substrate was used.

[0042] Comparative Example 2 A laminate was produced in the same manner as in Example 4, except that no substrate was used.

[0043] Comparative Example 3 A laminate was produced in the same manner as in Example 2, except that the substrate surface was not subjected to alumina vapor deposition treatment.

[0044] Table 1 summarizes the structure of the laminate. [Table 1]

[0045] <Production method> For general adhesives The surface of the gas barrier laminate that was not aluminum-deposited was laminated with an unstretched linear low-density polyethylene film via an adhesive, and then the alumina-deposited surface of the biaxially oriented polypropylene film substrate was attached with 3.0 g / m adhesive using a wire bar. 2 The coating was applied in an amount of 1000 ppm, and the coating was dried and cured at 50° C. Then, the aluminum vapor deposition surface of the gas barrier laminate and the substrate were The laminate was dry laminated at a pressure of 0.5 MPa and left to stand at 40°C for 72 hours to obtain a laminate for packaging material.

[0046] <Measurement method> Using an oxygen transmission rate measuring device (OX-TRAN2 / 22 L manufactured by MOCON), the test piece was set so that the first substrate side was the oxygen supply side, and the oxygen transmission rate (OTR) was measured in an environment of 23°C and a relative humidity of 50% RH in accordance with JIS K 7126.

[0047] Using a water vapor permeability measuring device (MOCON, PERMATRAN-W 3 / 34) The test piece was set so that the first substrate side was the water vapor supply side, and the water vapor transmission rate (WVTR) was measured in accordance with JIS K 7129 under an environment of 40°C and 90% relative humidity and an environment of 24°C and 78% relative humidity.

[0048] The results are shown in Table 2. It was found that the laminates of Examples 2 to 4 had improved water vapor barrier properties and oxygen barrier properties.

[0049] [Table 2] [Explanation of symbols]

[0050] 10...Laminate for food packaging material, 1...Base material, 2...Gas barrier resin layer, 3...Heat seal layer, 4a, 4b...Gas barrier property imparting treated surface, 5a, 5b...Adhesive layer

Claims

1. a substrate including a stretched polyolefin resin film; a heat seal layer containing an unstretched polyolefin resin film; a gas barrier laminate layer provided between the substrate and the heat seal layer, the gas barrier laminate layer including a gas barrier resin layer and a polyolefin resin layer; A laminate for food packaging materials comprising: The food packaging laminate is characterized in that the surfaces of the substrate and the gas barrier resin layer are each treated to impart gas barrier properties, and the substrate and the gas barrier resin layer are bonded together with an adhesive so that the gas barrier treated surfaces face each other.

2. The food packaging laminate according to claim 1 , wherein the gas barrier property-imparting treatment is a coating treatment with a gas barrier film.

3. 3. The food packaging laminate according to claim 2, wherein the gas barrier film is one or more selected from the group consisting of a polyvinyl alcohol film, an ethylene-vinyl alcohol copolymer film, and a vapor-deposited film of one or more inorganic materials selected from aluminum, aluminum oxide, and silicon oxide (silica).

4. The food packaging laminate according to claim 1 , wherein the adhesive is a barrier adhesive.

5. The food packaging laminate according to claim 4 , wherein the barrier adhesive is a cured product of a composition containing a polyester polyol and an isocyanate compound.

6. 2. The food packaging laminate according to claim 1, wherein the proportion of the polyolefin relative to the total mass is 80 mass % or more.

7. 2. The food packaging laminate according to claim 1, wherein the gas barrier laminate and the heat seal layer are bonded together with an adhesive.

8. 2. The food packaging laminate according to claim 1, wherein the heat seal layer is made of unstretched polyethylene or unstretched polypropylene.

9. A food packaged with the food packaging laminate according to any one of claims 1 to 8.

10. 10. The food product of claim 9, which is a seasoning or a dried soup.

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