Multilayer film using solvent-free adhesive, its manufacturing method, and packaging container

Abstract

To provide a multilayer film capable of suppressing the generation of bubbles in an adhesive layer and suppressing the generation of winding dislocation upon winding directly after lamination, a method for producing the same, and a packaging container using the multilayer film.SOLUTION: A multilayer film comprises: plural resin films; and one or more adhesive layers. At least one of the adhesive layers is formed by a solventless type adhesive, the solventless type adhesive comprises: a main agent made of a polyester resin; and a hardening agent made of aliphatic isocyanate, and the viscosity of the solventless type adhesive is 650 to 1,600 m Pa s at 80°C.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a multilayer film using a solvent-free adhesive, a method for producing the same, and a packaging container formed from the multilayer film. [Background technology]

[0002] Pouch packaging containers used for food packaging, medical product packaging, cosmetic packaging, etc., and flexible packaging containers used as cup lids have conventionally been made of multilayer films laminated with resin films, metal foils, etc. For example, Patent Documents 1 to 3 disclose packaging containers such as pouch packaging bags and laminated tubes made of multilayer films. In such packaging containers, when resin films with different properties are laminated together, such as a combination of nylon film and polyethylene film, the adhesion between the two is poor, so an adhesive is generally used.

[0003] From the viewpoint of reducing the burden on the global environment, it is desirable to use a solvent-free adhesive as such an adhesive. Conventionally, a multilayer film using a solvent-free adhesive has been known, which has an adhesive layer made of a solvent-free adhesive that is composed of a base agent made of polyester polyol and a curing agent made of an aliphatic diisocyanate compound and an alicyclic diisocyanate, and has a viscosity of 300 to 900 mPa·s at 70°C (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5397584 Summary of the Invention [Problem to be solved by the invention]

[0005] However, multilayer films using solvent-free adhesives have the problem of easily generating large bubbles in the adhesive layer, which can cause poor appearance. Furthermore, during the multilayer film manufacturing process, there is a problem of easily causing misalignment when the multilayer film is wound up immediately after lamination. These phenomena are particularly pronounced in multilayer films with a large number of layers or multilayer films containing vapor-deposited layers. The reason for this phenomenon is thought to be that a slight misalignment occurs between each resin film between the time when each resin film is laminated via the adhesive layer and the time when the solventless adhesive that makes up the adhesive layer is completely hardened.

[0006] The present invention has been made in light of the above circumstances, and its object is to provide a multilayer film that can suppress the formation of bubbles in the adhesive layer and the occurrence of winding slippage when the film is wound immediately after lamination, a method for producing the same, and a packaging container using the multilayer film. [Means for solving the problem]

[0007] The multilayer film of the present invention is a multilayer film having a plurality of resin films and one or more adhesive layers, At least one of the adhesive layers is formed from a solventless adhesive, The solventless adhesive contains a base agent made of a polyester resin and a curing agent made of an aliphatic isocyanate, The viscosity of the solvent-free adhesive is 600 to 1400 mPa·s at 80°C. the law of nature, The viscosity of the base agent is 2000 to 4500 mPa s at 80°C, and The viscosity of the curing agent is 50 to 250 mPa·s at 80°C. It is characterized by:

[0008] Also, The curing agent preferably comprises 1,6-hexamethylene diisocyanate (HDI). The solvent-free adhesive preferably contains 50 to 200 parts by mass of the curing agent per 100 parts by mass of the base agent.

[0009] In the multilayer film of the present invention, at least one resin film has a vapor-deposited layer, The adhesive layer formed from the solvent-free adhesive is preferably formed between the vapor deposition layer and the adjacent resin film.

[0010] The method for producing a multilayer film of the present invention includes a step of laminating one resin film and another resin film while superimposing them with an adhesive coating layer made of a solventless adhesive interposed therebetween, The solventless adhesive contains a base agent made of a polyester resin and a curing agent made of an aliphatic isocyanate, The viscosity of the solvent-free adhesive is 600 to 1400 mPa·s at 80°C. the law of nature, The viscosity of the base agent is 2000 to 4500 mPa s at 80°C, and The viscosity of the curing agent is 50 to 250 mPa·s at 80°C. It is characterized by:

[0011] In the method for producing a multilayer film of the present invention, the amount of the solvent-free adhesive applied to the adhesive coating layer is 0.5 to 3.0 g / m 2 It is preferable that: Preferably, the one resin film has a vapor-deposited layer on the surface that contacts the adhesive coating layer.

[0012] The packaging container of the present invention is characterized by being formed from the above multilayer film. [Effects of the Invention]

[0013] According to the present invention, the viscosity of the solvent-free adhesive forming the adhesive layer is 600 to 1400 mPa·s at 80°C, which makes it possible to prevent bubbles from forming in the adhesive layer and to prevent misalignment when the film is wound immediately after lamination. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is an explanatory cross-sectional view showing the configuration of an example of a multilayer film of the present invention. [Figure 2] FIG. 1 is an explanatory diagram showing the configuration of an example of a laminator for producing the multilayer film of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 is an explanatory cross-sectional view showing the structure of one example of the multilayer film of the present invention. This multilayer film 10 has an outer layer resin film 11, an inner layer resin film 12, and an intermediate layer resin film 13 provided between the inner layer resin film 12 and the outer layer resin film 11. An ink layer 14 is formed on the inner surface of the outer layer resin film 11 (the surface on the intermediate layer resin film 13 side). A vapor deposition layer 15 is formed on the surface of the intermediate layer resin film 13 on the outer layer resin film 11 side. An adhesive layer 16 formed of a solventless adhesive is formed between the ink layer 14 and the vapor deposition layer 15, and an adhesive layer 17 formed of a solventless adhesive is formed between the inner layer resin film 12 and the intermediate layer resin film 13.

[0016] The outer layer resin film 11 is preferably a film with excellent thermal dimensional stability. By using such an outer layer resin film 11, it is possible to perform a baking process at a temperature of about 80°C after, for example, gravure printing on the outer layer resin film 11, making it easy to form an ink layer. In addition, it is preferable to use a biaxially stretched film as the outer layer resin film 11, as this provides high tensile strength.

[0017] The material for the outer resin film 11 is preferably a polyamide resin or a polyester resin. Examples of polyamide resins that can be used include nylon 6, nylon 8, nylon 6,6, nylon 6 / 6,6 copolymer, nylon 6,10, metaxylylene adipamide (MXD6), nylon 11, and nylon 12. Examples of polyester resins that can be used include polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). Copolyesters containing other polyester units can also be used, provided that the properties of these resins are not impaired. Among the copolymerization components for forming such copolyesters, dicarboxylic acid components include isophthalic acid, p-β-oxyethoxybenzoic acid, naphthalene 2,6-dicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid, 5-sodium sulfoisophthalic acid, adipic acid, sebacic acid, and alkyl ester derivatives thereof. Examples of glycol components that can be used include propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexylene glycol, cyclohexanedimethanol, ethylene oxide adducts of bisphenol A, diethylene glycol, and triethylene glycol. These compounds can be used alone or in combination as copolymerization components.

[0018] The thickness of the outer layer resin film 11 is selected appropriately depending on the type of resin that constitutes the outer layer resin film 11 and the use of the multilayer film, but for example, if the outer layer resin film 11 is made of nylon, it is preferably 10 to 30 μm, and if the outer layer resin film 11 is made of polyethylene terephthalate (PET), it is preferably 6 to 28 μm.

[0019] Furthermore, it is preferable that the surface of the outer resin film 11 that comes into contact with the adjacent layer be subjected to a surface modification treatment such as a corona treatment in order to improve adhesion to the adjacent layer.

[0020] A resin with excellent heat-sealing properties is preferably used as the material for the inner layer resin film 12 in order to form a pouch packaging bag or a heat-sealed lid. Examples of such resins include polyolefin resins such as polyethylene (PE) and polypropylene (PP).

[0021] There are no particular restrictions on the thickness of the inner layer resin film 12, but for example, if the inner layer resin film 12 is made of polyethylene, it is preferably 50 to 200 μm, and if the inner layer resin film 12 is made of polypropylene, it is preferably 30 to 150 μm. It is preferable to use a non-stretched film as the inner resin film 12.

[0022] The material constituting the intermediate layer resin film 13 can be a resin having gas barrier properties, and specific examples thereof include nylon resins such as aliphatic nylons such as nylon 6, nylon 8, nylon 11, nylon 12, nylon 6,6, nylon 6,10, nylon 10,6, and nylon 6 / 6,6 copolymer, partially aromatic nylons such as polymetaxylylene adipamide, and polyglycolic acid resins. In addition, the material constituting the intermediate layer resin film 13 may be an olefin resin, for example, polyethylene (PE) such as low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), linear very low-density polyethylene (LVLDPE), etc., polypropylene (PP), ethylene-propylene copolymer, polybutene-1, ethylene-butene-1 copolymer, propylene-butene-1 copolymer, ethylene-propylene-butene-1 copolymer, ethylene-vinyl acetate copolymer (EVA), ionically cross-linked olefin copolymer (ionomer), or a mixture thereof. The thickness of the intermediate layer resin film 13 is not particularly limited, but is preferably 5 to 100 μm.

[0023] The ink layer 14 is formed on the inner surface of the outer resin film 11 by, for example, gravure printing. The thickness of such ink layer 14 is preferably 1 to 8 μm.

[0024] The material that can be used to form the vapor deposition layer 15 includes a metal material such as aluminum, a non-metallic inorganic material such as silica, and the like.

[0025] The adhesive layers 16 and 17 are formed of a solvent-free adhesive, which is a two-component reactive curing adhesive consisting of a base agent and a curing agent. The thickness of the adhesive layers 16 and 17 is preferably 0.5 to 3 μm.

[0026] As the main component of the solvent-free adhesive, it is preferable to use a polyester-based resin, which has good adhesion to the inner layer resin film 12, the intermediate layer film 13, the ink layer 14, and the vapor deposition layer 15, and which also has excellent lamination strength and impact resistance, and polyester polyol resin is particularly preferable.

[0027] The polyester polyol resin may be one produced by an esterification reaction between a polybasic acid such as succinic acid, adipic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, or terephthalic acid and a polyhydric alcohol such as ethylene glycol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, 3,3-bis(hydroxymethyl)heptane, diethylene glycol, dipropylene glycol, glycerin, or trimethylolpropane.

[0028] Specific examples of polyester polyol resins include: (1) adipate-based polyester glycols such as poly(ethylene adipate), poly(diethylene adipate), poly(propylene adipate), poly(tetramethylene adipate), poly(hexamethylene adipate), and poly(neopentylene adipate); (2) polycaprolactone-based polyester glycols such as poly-ε-caprolactone; and (3) other polyester polyol resins such as poly(hexamethylene sebacate) and poly(hexamethylene carbonate).

[0029] The base resin may contain, for example, a polyurethane compound in addition to the polyester resin. By using such a base resin, adhesion to the ink layer 14 provided on the inner surface of the outer resin film 11 can be ensured because the ink layer 14 usually contains a urethane component.

[0030] The number-average molecular weight of the resin constituting the base resin is preferably 700 to 1700, more preferably 800 to 1600. If the number-average molecular weight of the resin constituting the base resin is less than 700, the viscosity of the solvent-free adhesive decreases, which can lead to poor suitability for continuous lamination during the production of a multilayer film. Furthermore, the number of terminal reactive groups increases, necessitating the use of a larger amount of curing agent. As a result, the resulting adhesive layers 16, 17 have a high degree of crosslinking, increasing their hardness and potentially reducing their impact resistance. On the other hand, if the number-average molecular weight of the resin constituting the base resin exceeds 1700, the impact resistance of the resulting adhesive layers 16, 17 improves, but the viscosity of the solvent-free adhesive increases, resulting in poor wetting during application of the solvent-free adhesive, which can lead to poor appearance and reduced lamination strength in the resulting multilayer film 10.

[0031] The viscosity of the base resin at 80°C is preferably 2000 to 4500 mPa·s, and more preferably 2500 to 4000 mPa·s. If this viscosity is less than 2000 mPa·s, uneven roll transfer may occur, making film formation of adhesive layers 16, 17 unstable, resulting in poor appearance and a significant decrease in laminate strength of the resulting multilayer film 10. On the other hand, if this viscosity exceeds 4000 mPa·s, poor wetting may occur during application of the solventless adhesive, resulting in poor appearance and a decrease in laminate strength of the resulting multilayer film 10.

[0032] As the curing agent constituting the solventless adhesive, it is preferable to use only an isocyanate compound, particularly an aliphatic isocyanate. The aliphatic isocyanate constituting the curing agent may be butane-1,4-diisocyanate, 1,6-hexamethylene diisocyanate (HDI), isopropylene diisocyanate, methylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, m-tetramethylxylylene diisocyanate, lysine diisocyanate, dimer diisocyanate in which the carboxyl group of dimer acid is converted to an isocyanate group, etc., which may be used alone or in combination of two or more. Of these, 1,6-hexamethylene diisocyanate (HDI) is preferred.

[0033] The viscosity of the curing agent constituting the solventless adhesive is preferably 50 to 250 mPa·s at 80°C, and more preferably 50 to 150 mPa·s. If this viscosity is less than 50 mPa·s, the viscosity of the curing agent will be low, and the resulting adhesive layers 16, 17 will be soft, which may result in reduced laminate strength. On the other hand, if this viscosity exceeds 250 mPa·s, the viscosity of the curing agent will be high, and the resulting adhesive layers 16, 17 will be hard, which may result in reduced impact resistance.

[0034] In solventless adhesives, the curing agent is preferably contained in an amount of 50 to 200 parts by mass, particularly 50 to 100 parts by mass, per 100 parts by mass of the base agent. If the proportion of curing agent is too small, the resulting adhesive layers 16, 17 will be insufficiently crosslinked, which may reduce the laminate strength of the resulting multilayer film 10. On the other hand, if the proportion of curing agent is too large, the base agent and curing agent will not be sufficiently mixed, and the resulting adhesive layers 16, 17 will contain a mixture of insufficiently crosslinked and over-crosslinked portions, which may reduce the laminate strength and impact resistance of the resulting multilayer film 10.

[0035] In the present invention, the viscosity of the solvent-free adhesive at 80°C is 600 to 1400 mPa·s, and more preferably 800 to 1200 mPa·s. If the viscosity of the solvent-free adhesive is less than 600 mPa·s, poor transfer between rolls during application of the solvent-free adhesive may occur, resulting in "uneven transfer." Furthermore, the solvent-free adhesive may not be applied uniformly and may be partially thin, resulting in reduced laminate strength and impact resistance. On the other hand, if the viscosity of the solvent-free adhesive exceeds 1400 mPa·s, poor wetting may occur during application of the solvent-free adhesive, resulting in partially thin adhesive layers 16 and 17. Thinner portions of the adhesive layers 16 and 17 may result in reduced laminate strength and impact resistance.

[0036] The solventless adhesive may contain a polyurethane compound in addition to the above-mentioned base agent and curing agent. By containing a polyurethane compound, adhesion to the ink layer 14 provided on the inner surface of the outer resin film 11 can be ensured, since the ink layer 14 usually contains a urethane component. The solvent-free adhesive may also contain various additives, such as fillers, softeners, antioxidants, stabilizers, adhesion promoters, leveling agents, antifoaming agents, plasticizers, inorganic fillers, tackifying resins, fibers, colorants such as pigments, and pot life extenders.

[0037] Furthermore, the solventless adhesive may contain an adhesion promoter, such as a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, or an epoxy resin.

[0038] Specific examples of silane coupling agents include aminosilanes such as γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethyldimethoxysilane, and N-phenyl-γ-aminopropyltrimethoxysilane; epoxysilanes such as β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-glycidoxypropyltriethoxysilane; vinylsilanes such as vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane; hexamethyldisilazane, γ-mercaptopropyltrimethoxysilane, and the like.

[0039] Specific examples of titanate coupling agents include tetraisopropoxytitanium, tetra-n-butoxytitanium, butyl titanate dimer, tetrastearyl titanate, titanium acetylacetonate, titanium lactate, tetraoctylene glycol titanate, titanium lactate, and tetrastearoxytitanium.

[0040] Specific examples of aluminum-based coupling agents include acetoalkoxyaluminum diisopropylate.

[0041] Specific examples of epoxy resins include various epoxy resins that are generally commercially available, such as epibis type, novolak type, β-methylepicro type, cyclic oxirane type, glycidyl ether type, glycidyl ester type, polyglycol ether type, glycol ether type, epoxidized fatty acid ester type, polycarboxylic acid ester type, aminoglycidyl type, and resorcinol type.

[0042] The multilayer film 10 is produced, for example, as follows. First, an ink layer 14 is formed on one surface of the outer resin film 11 by, for example, gravure printing. Also, a vapor deposition layer 15 is formed on one surface of the intermediate resin film 13 by vapor deposition. Then, the outer resin film 11 on which the ink layer 14 has been formed and the intermediate resin film 13 on which the vapor deposition layer 15 has been formed are laminated together using a laminator as shown in FIG.

[0043] Specifically, in FIG. 2, 30 denotes a laminator, 31 denotes a base agent tank containing a base agent, 32 denotes a curing agent tank containing a curing agent, 33 denotes an adhesive supply unit that supplies the base agent and curing agent, and 34 denotes a winding roll that supplies the outer layer resin film 11. 35 denotes an adhesive application unit that mixes the base agent and curing agent to prepare a solventless adhesive and applies the prepared solventless adhesive. This adhesive application unit 35 is provided with multiple rolls 35a, 35b, 35c, 35d, and 35e (five in the illustrated example). 36 denotes a laminating unit that laminates the outer layer resin film 11 and the intermediate layer resin film 13 and has a pair of pressure rolls 36a and 36b. 37 denotes a winding roll that supplies the intermediate layer resin film 13, and 38 denotes a winding roll that winds up the intermediate laminate film, which will be described later.

[0044] In this laminator 30, the outer layer resin film 11 on which the ink layer 14 has been formed is supplied from a winding roll 34 at a predetermined speed to an adhesive coating section 35. Meanwhile, in a base agent tank 31 and a curing agent tank 32, the base agent and curing agent are heated to predetermined temperatures and melted. The heated and melted base agent and curing agent are supplied in predetermined amounts from an adhesive supply section 33 to the adhesive coating section 35, where the base agent and curing agent are mixed to prepare a solventless adhesive. Then, in the adhesive coating section 35, the solventless adhesive is applied to the surface of the ink layer 14 formed on the outer layer resin film 11, thereby forming an adhesive coating layer.

[0045] Next, the outer layer resin film 11 is sent to the laminating section 36. Meanwhile, the intermediate layer resin film 13 on which the vapor-deposited layer 15 has been formed is supplied to the laminating section 36 from a winding roll 37. In this laminating section 36, the outer layer resin film 11 and the intermediate layer resin film 13 are laminated under pressure while being superimposed so that the vapor-deposited layer 15 is in contact with the adhesive coating layer formed on the ink layer 14, thereby obtaining an intermediate laminate film in which the outer layer resin film 11, ink layer 14, adhesive layer 16, vapor-deposited layer 15, and intermediate layer resin film 13 are laminated. This intermediate laminate film is taken up by a take-up roll 38.

[0046] Then, in the above process, the outer layer resin film 11 on which the ink layer 14 is formed is replaced with an intermediate laminate film, and the intermediate layer resin film 13 on which the vapor deposition layer 15 is formed is replaced with the inner layer resin film 12, and the same operation is performed, whereby the inner layer resin film 12 is laminated to the other surface of the intermediate layer resin film 13 via the adhesive layer 17, thereby obtaining the multilayer film 10. The obtained multilayer film 10 is subjected to an aging treatment to promote the effects of the adhesive layers 16, 17.

[0047] In the above, the heating temperature of the base agent and the curing agent is, for example, 40 to 80°C. The supply speed of each resin film, that is, the application speed of the solventless adhesive, is preferably 100 to 200 m / min. The temperature of the solvent-free adhesive when applied is preferably 40 to 80°C. The amount of solvent-free adhesive applied is 0.5 to 3.0 g / m 2 is preferably 1.2 to 2.1 g / m 2 is. The temperature of the pressure rolls 36a and 36b in the laminating section 36 is, for example, 30 to 80°C. The temperature for the aging treatment of the multilayer film 10 is, for example, 30 to 70° C., and the treatment time is, for example, 48 to 96 hours.

[0048] In such a multilayer film 10, the viscosity of the solvent-free adhesive that forms the adhesive layers 16, 17 is 650 to 1600 mPa·s at 80°C, which prevents air bubbles from forming in the adhesive layers 16, 17 and prevents the film from slipping when wound up immediately after lamination.

[0049] The packaging container of the present invention is made of the above-mentioned multilayer film and is suitable as a packaging container such as a refill pouch or a retort pouch containing liquids such as detergents, fabric softeners, bleaches, shampoos, conditioners, or beverages.

[0050] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications can be made. For example, the layer structure of the multilayer film is not limited to the structure shown in Figure 1, and may consist of two resin films, an outer layer resin film and an inner layer resin film, or may have multiple intermediate layer resin films. The ink layer and the vapor deposition layer are provided as needed, but are not essential to the present invention. [Example]

[0051] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0052] Example 1 and Comparative Example 1 [Solvent-free adhesive] Table 1 shows the compositions of the solventless adhesives used in Example 1 and Comparative Example 1. In Table 1, the viscosities of the base agent, curing agent, and solventless adhesive were measured using a B8L viscometer manufactured by Tokimec Corporation according to a method in accordance with JIS K7117-2.

[0053] [Resin film] The outer resin film used was a biaxially oriented nylon film with a thickness of 15 μm. As the intermediate layer resin film, a biaxially stretched polyethylene terephthalate (PET) film having a thickness of 12 μm and having an aluminum vapor deposition layer formed on one surface was used. The inner layer film used was a non-stretched linear low-density polyethylene (LLDPE) film with a thickness of 130 μm.

[0054] [Manufacturing of multilayer films] A multilayer film was produced using a laminator having the configuration shown in FIG. 2 as follows. The base agent and curing agent shown in Table 1 below were placed in a base agent tank and a curing agent tank, respectively, and heated to 80°C. The base agent and curing agent were then supplied to the adhesive coating section by the adhesive supply section and mixed in the mass blending ratio shown in Table 1 below. A solvent-free adhesive was then prepared. In the adhesive coating section, the solvent-free adhesive was applied at 70°C to one side of the outer layer resin film supplied from the unwinding roll, thereby forming an adhesive coating layer. The amount of solvent-free adhesive applied was 2.5 g / m 2 The coating speed was 150 m / min. The outer layer resin film on which the adhesive coating layer was formed was then transported to a laminating section, where the outer layer resin film and an intermediate layer resin film on which a vapor deposition layer was formed, which was supplied from a winding roll, were laminated under pressure at 60°C to produce an intermediate laminate film. The laminating speed was 150 m / min. The resulting intermediate laminate film was wound on a roll, and an adhesive coating layer was formed on the other side of the intermediate layer resin film in the intermediate laminate film under the same conditions as above, and this intermediate layer resin film was laminated with the inner layer resin film to produce a multilayer film. The resulting multilayer film was subjected to an aging treatment by keeping it at 40°C for 4 days.

[0055] [Production of packaging containers (pouches)] A bottom member having a width of 130 mm and a folded width of 36 mm was cut out from the obtained multilayer film, and was sandwiched between two multilayer films with the inner layers facing each other, and the bottom was heat-sealed at 200°C to seal the bottom.The inner layer sides of the two multilayer films were then joined together and heat-sealed at 200°C to seal the two side edges, producing a refill pouch having a width of 130 mm, a height of 260 mm, and a capacity of 540 ml.

[0056] [evaluation] Poor appearance: Immediately after lamination, the multilayer film was visually inspected over an area of ​​1 m width and 1 m length to check for repellency. The film was evaluated as ◯ if no repellency was observed and x if repellency was observed. Lamination suitability: Immediately after lamination, the multilayer film was visually observed over an area of ​​1 m wide and 1 m long to check for the presence or absence of tunneling (lifting of the bonded area). If no tunneling was observed, it was evaluated as ◯, and if tunneling was observed, it was evaluated as ×. Winding deviation: The film (raw roll) was wound immediately after lamination, and the degree of deviation with respect to the end of the paper tube set on the winding shaft was measured using a scale. Shock resistance: The prepared pouches were filled with 400 g of tap water cooled to 5°C, and then heat-sealed to produce 20 sample pouches. The sample pouches were dropped 10 times from a height of 1.2 m with the bottom facing downwards, and then dropped 10 times in a horizontal position. This drop test was performed on 20 pouches, and the number of pouches that broke out of the 20 pouches was counted. The results are shown in Table 1 below.

[0057] [Table 1]

[0058] As is clear from the results in Table 1, it was confirmed that, according to Example 1, the viscosity of the solvent-free adhesive was within a specific range at 80°C, so that a multilayer film was obtained that had no bubbles in the adhesive layer, had a good appearance, was suitable for lamination, and could suppress the occurrence of slippage when wound up immediately after lamination. In contrast, in Comparative Example 1, the viscosity of the solvent-free adhesive was too low at 80°C, so the resulting multilayer film had a poor appearance and was insufficiently suitable for lamination, and significant winding misalignment occurred when the film was wound up immediately after lamination. [Explanation of symbols]

[0059] 10 Multilayer Film 11 Outer layer resin film 12 Inner layer resin film 13 Intermediate layer resin film 14 Ink layer 15 Deposited layer 16,17 Adhesive layer 30 Laminator 31 Main agent tank 32 Hardener tank 33 Adhesive supply section 34 Unwinding roll 35 Adhesive application section 35a, 35b, 35c, 35d, 35e Roll 36 Laminating Department 36a, 36b Pressure roll 37 Unwinding roll 38 Winding Roll

Claims

1. A multilayer film having a plurality of resin films and one or more adhesive layers, At least one of the adhesive layers is formed from a solventless adhesive, The solventless adhesive contains a base agent made of a polyester resin and a curing agent made of an aliphatic isocyanate, The viscosity of the solventless adhesive is 600 to 1400 mPa s at 80°C, The viscosity of the base agent is 2000 to 4500 mPa s at 80°C, and A multilayer film characterized in that the viscosity of the curing agent is 50 to 250 mPa·s at 80°C.

2. The multilayer film described in Claim 1, characterized in that the curing agent is 1,6-hexamethylene diisocyanate (HDI).

3. A multilayer film as described in claim 1 or claim 2, characterized in that the solvent-free adhesive contains the curing agent in a range of 50 to 200 parts by mass per 100 parts by mass of the main agent.

4. At least one resin film has a vapor deposition layer, 4. The multilayer film according to claim 1, wherein an adhesive layer formed from the solvent-free adhesive is formed between the vapor deposition layer and the adjacent resin film.

5. A method for producing a multilayer film, comprising a step of laminating one resin film and another resin film while superimposing them with an adhesive coating layer made of a solventless adhesive interposed therebetween, The solventless adhesive contains a base agent made of a polyester resin and a curing agent made of an aliphatic isocyanate, The viscosity of the solventless adhesive is 600 to 1400 mPa s at 80°C, The viscosity of the base agent is 2000 to 4500 mPa s at 80°C, and A method for producing a multilayer film, wherein the viscosity of the curing agent is 50 to 250 mPa·s at 80°C.

6. The method for manufacturing a multilayer film according to claim 5, wherein the amount of the solvent-free adhesive applied to the adhesive coating layer is 0.5 to 3.0 g / m 2 .

7. A method for manufacturing a multilayer film as described in claim 5 or claim 6, characterized in that one of the resin films has a vapor deposition layer on the surface that contacts the adhesive coating layer.

8. A packaging container characterized by being formed from a multilayer film described in any one of claims 1 to 4.

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