Multilayer film using solvent-free adhesive, method for producing same, and packaging container

Abstract

The invention provides a multilayer film, a method for manufacturing the same, and a packaging container using the multilayer film. The multilayer film is capable of suppressing generation of air bubbles in an adhesive layer and suppressing winding deviation during winding immediately after lamination. The multilayer film according to the present invention has a plurality of resin films and one or more adhesive layers, and is characterized in that at least one of the adhesive layers is formed from a solvent-free adhesive that contains a main agent that is formed from a polyester resin and a curing agent that is formed from an aliphatic isocyanate. And the viscosity of the solvent-free adhesive agent at 80 DEG C is from 650 mPa * s to 1600 mPa * s.

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 Art

[0002] Bag packaging containers used for food packaging, medical product packaging, cosmetic packaging, etc., and flexible packaging containers for cup lids have conventionally been made of multilayer films laminated with resin films, metal foils, etc. For example, packaging containers such as sachets and laminated tubes made of multilayer films have conventionally been used.

[0003] In such packaging containers, when different types of resin films having different properties are laminated, such as a combination of a nylon film and a polyethylene film, adhesion between the two is insufficient, and therefore an adhesive is generally used.

[0004] From the perspective of reducing the environmental impact of the global environment, it is ideal to use a solvent-free adhesive as this adhesive. Conventionally, multilayer films using solvent-free adhesives include those having an adhesive layer formed of a solvent-free adhesive. These solvent-free adhesives are composed of a base agent consisting of a polyester polyol and a curing agent consisting of an aliphatic diisocyanate compound and an alicyclic diisocyanate, with a viscosity of 300 to 900 mPa·s at 70°C (see Patent Document 1).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent No. 5397584 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] However, multilayer films using solvent-free adhesives are prone to large bubbles forming in the adhesive layer, resulting in poor appearance. Furthermore, during the multilayer film manufacturing process, winding deviation is prone to occur when the multilayer film is wound up immediately after lamination. These phenomena are particularly prominent in multilayer films with many layers or those having vapor-deposited layers.

[0010] The reason for this phenomenon is presumably that slight positional deviation occurs between the resin films during the period from when the resin films are laminated with the adhesive layer interposed therebetween until the solvent-free adhesive constituting the adhesive layer is cured.

[0011] The present invention has been made based on the above circumstances, and its object is to provide a multilayer film capable of suppressing the generation of bubbles in the adhesive layer and suppressing winding deviation when winding immediately after lamination, a method for producing the same, and a packaging container using the multilayer film.

[0012] Solutions for solving problems

[0013] The multilayer film of the present invention is characterized by comprising a plurality of resin films and one or more adhesive layers.

[0014] At least one of the adhesive layers is formed of a solvent-free adhesive,

[0015] The solvent-free adhesive contains a main agent formed of a polyester resin and a curing agent formed of an aliphatic isocyanate, and the viscosity of the solvent-free adhesive at 80° C. is 600 mPa·s to 1400 mPa·s.

[0016] Furthermore, in the multi-layer film of the present invention, it is preferred that the viscosity of the main agent is 2000 mPa·s to 4500 mPa·s at 80°C.

[0017] Furthermore, it is preferred that the curing agent be formed of 1,6-hexamethylene diisocyanate (HDI).

[0018] Furthermore, it is preferable that the solvent-free adhesive contain the curing agent in an amount ranging from 50 parts by mass to 200 parts by mass relative to 100 parts by mass of the main agent.

[0019] In the multilayer film of the present invention, it is preferred that at least one resin film has a vapor-deposited layer.

[0020] An adhesive layer formed of the solvent-free adhesive is formed between the vapor-deposited layer and the adjacent resin film.

[0021] The method for producing a multilayer film of the present invention is characterized by comprising the step of laminating one resin film and the other resin film while overlapping each other with an adhesive coating layer formed of a solvent-free adhesive interposed therebetween.

[0022] The solvent-free adhesive contains a main agent formed of a polyester resin and a curing agent formed of an aliphatic isocyanate, and the viscosity of the solvent-free adhesive at 80° C. is 600 mPa·s to 1400 mPa·s.

[0023] In the method for producing a multilayer film of the present invention, it is preferred that the coating amount of the solvent-free adhesive in the adhesive coating layer is 0.5 g / m 2 ~3.0g / m 2 .

[0024] Furthermore, it is preferable that the one resin film has a vapor-deposited layer on a surface in contact with the adhesive coating layer.

[0025] The packaging container of the present invention is characterized by being formed of the above-mentioned multilayer film.

[0026] Effects of the Invention

[0027] 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., thereby suppressing the generation of bubbles in the adhesive layer and suppressing the occurrence of winding deviation during winding immediately after lamination. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is an explanatory cross-sectional view showing the structure of an example of the multilayer film of the present invention.

[0029] Figure 2 This is an explanatory diagram showing the configuration of an example of a laminator for producing the multilayer film of the present invention. DETAILED DESCRIPTION

[0030] Hereinafter, embodiments of the present invention will be described in detail.

[0031] Figure 1 This is an explanatory cross-sectional view showing the structure of an example of the multilayer film of the present invention.

[0032] The multilayer film 10 includes an outer resin film 11, an inner resin film 12, and an intermediate resin film 13 disposed between the inner resin film 12 and the outer resin film 11. An ink layer 14 is formed on the inner surface of the outer resin film 11 (the surface on the intermediate resin film 13 side). A vapor-deposited layer 15 is formed on the outer resin film 11 side surface of the intermediate resin film 13. An adhesive layer 16 formed of a solvent-free adhesive is formed between the ink layer 14 and the vapor-deposited layer 15, and an adhesive layer 17 formed of a solvent-free adhesive is formed between the inner resin film 12 and the intermediate resin film 13.

[0033] The outer resin film 11 preferably has excellent thermal dimensional stability. Using such an outer resin film 11 allows, for example, baking at approximately 80°C after gravure printing, thereby facilitating ink layer formation. Furthermore, a biaxially oriented film is preferably used as the outer resin film 11 to achieve high tensile strength.

[0034] As a material constituting the outer layer resin film 11 , polyamide-based resins and polyester-based resins are preferably used.

[0035] As the polyamide resin, for example, nylon 6, nylon 8, nylon 6,6, nylon 6 / 6,6 copolymer, nylon 6,10, meta-xylylenediamine adipamide (MXD6), nylon 11, nylon 12, etc. can be used.

[0036] As polyester resins, for example, polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) can be used. In addition, within the range of not damaging the properties of these resins, copolyesters containing other polyester units can also be used. Among the copolymer components used to form such copolyesters, as dicarboxylic acid components, isophthalic acid, p-β-oxyethoxybenzoic acid, 2,6-naphthalene dicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid, 5-sodium sulfoisophthalate, adipic acid, sebacic acid or their alkyl ester derivatives can be used. In addition, as diol components, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, cyclohexanedimethanol, ethylene oxide adducts of bisphenol A, diethylene glycol, triethylene glycol, etc. can be used. These compounds can be used alone or in combination of two or more and used as copolymer components.

[0037] The thickness of the outer layer resin film 11 can be appropriately selected according to the type of resin constituting the outer layer resin film 11, the purpose of the multilayer film, etc., but for example, when the outer layer resin film 11 is composed of nylon, it is preferably 10μm to 30μm, and when the outer layer resin film 11 is composed of polyethylene terephthalate (PET), it is preferably 6μm to 28μm.

[0038] Furthermore, it is preferable that the surface of the outer layer resin film 11 that contacts the adjacent layer be subjected to a surface modification treatment such as a corona treatment in order to improve the adhesion with the adjacent layer.

[0039] In order to form a sachet packaging bag or a heat-sealable lid, a resin having excellent heat-sealability is preferably used as the material constituting the inner layer resin film 12. Examples of such resins include polyolefin resins such as polyethylene (PE) and polypropylene (PP).

[0040] The thickness of the inner resin film 12 is not particularly limited. For example, when the inner resin film 12 is made of polyethylene, it is preferably 50 μm to 200 μm, and when the inner resin film 12 is made of polypropylene, it is preferably 30 μm to 150 μm.

[0041] Furthermore, as the inner layer resin film 12 , it is preferable to use a non-stretched film.

[0042] As the material constituting the intermediate layer resin film 13, a resin having gas barrier properties can be used. Specific examples thereof include 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 copolymers, partially aromatic nylons such as poly(m-xylylene adipamide), and nylon resins such as polyglycolic acid resins.

[0043] In addition, as the material constituting the intermediate layer resin film 13, olefin resins can also be used, for example: polyethylene (PE) such as low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), linear ultra-low-density polyethylene (LVLDPE), 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 mixtures thereof, etc.

[0044] The thickness of the intermediate layer resin film 13 is not particularly limited, but is preferably 5 μm to 100 μm.

[0045] The ink layer 14 is formed by, for example, performing gravure printing on the inner surface of the outer resin film 11 .

[0046] The thickness of the ink layer 14 is preferably 1 μm to 8 μm.

[0047] As a material constituting the vapor deposition layer 15 , a metal material such as aluminum, a non-metallic inorganic material such as silicon dioxide, or the like can be used.

[0048] The adhesive layers 16 and 17 are formed of a solvent-free adhesive, which is a two-component reaction-curing adhesive composed of a base agent and a curing agent.

[0049] The thickness of the adhesive layers 16 and 17 is preferably 0.5 μm to 3 μm.

[0050] As the main component of the solvent-free adhesive, a polyester resin having good adhesion to the inner layer resin film 12, the intermediate layer film 13, the ink layer 14 and the vapor deposited layer 15 and excellent lamination strength and impact resistance is preferably used, and a polyester polyol resin is particularly preferred.

[0051] The polyester polyol resin may be any one produced by an esterification reaction of a polybasic acid such as succinic acid, adipic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, or terephthalic acid with a polyhydric alcohol such as ethylene glycol, 1,2-propylene glycol, 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, glycerol, or trimethylolpropane.

[0052] Specific examples of polyester polyol resins include: (1) adipate-based polyester diols such as poly(ethylene adipate), poly(diethylene adipate), poly(propylene adipate), poly(tetramethylene adipate), poly(hexamethylene adipate), and poly(neopentyl adipate); (2) polycaprolactone-based polyester diols such as poly-ε-caprolactone; and (3) other polyester polyol resins such as poly(hexamethylene sebacate) and poly(hexamethylene carbonate).

[0053] In addition, as a main agent, in addition to polyester resin, a polyurethane compound may also be contained. By using such a main agent, the ink layer 14 provided on the inner surface of the outer resin film 11 usually contains a urethane component, thereby ensuring the adhesion to the ink layer 14.

[0054] The number average molecular weight of the resin constituting the main agent is preferably 700 to 1700, more preferably 800 to 1600. When the number average molecular weight of the resin constituting the main agent is less than 700, the viscosity of the solvent-free adhesive is reduced, so the continuous lamination adaptability is sometimes poor when manufacturing a multilayer film. In addition, since the number of terminal reactive groups increases, it is necessary to increase the amount of curing agent. As a result, in the adhesive layers 16 and 17 obtained, there is a problem that the crosslinking amount is large and the hardness increases, and the impact resistance of the adhesive layers 16 and 17 is sometimes reduced. On the other hand, when the number average molecular weight of the resin constituting the main agent exceeds 1700, the impact resistance of the adhesive layers 16 and 17 obtained is improved, but the viscosity of the solvent-free adhesive increases, so poor wetting occurs when the solvent-free adhesive is applied, sometimes causing the appearance of the obtained multilayer film 10 to be poor and the reduction of lamination strength.

[0055] The viscosity of the main agent at 80°C is preferably 2000 mPa·s to 4500 mPa·s, more preferably 2500 mPa·s to 4000 mPa·s. If the viscosity is less than 2000 mPa·s, uneven transfer of the rollers occurs, and the film formation of the adhesive layers 16 and 17 becomes unstable, which may cause the appearance of the resulting multilayer film 10 to be poor or the lamination strength to be extremely reduced. On the other hand, if the viscosity exceeds 4000 mPa·s, poor wetting is likely to occur during application of the solvent-free adhesive, which may cause the appearance of the resulting multilayer film 10 to be poor or the lamination strength to be reduced.

[0056] As the curing agent constituting the solvent-free adhesive, it is preferred to use only isocyanate compounds, and it is particularly preferred to use only aliphatic isocyanates.

[0057] As the aliphatic isocyanate constituting the curing agent, 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 obtained by converting the carboxyl groups of dimer acid into isocyanate groups, etc. can be used alone or in combination of two or more. Among them, 1,6-hexamethylene diisocyanate (HDI) is preferred.

[0058] The viscosity of the curing agent constituting the solvent-free adhesive is preferably 50 mPa·s to 250 mPa·s at 80°C, more preferably 50 mPa·s to 150 mPa·s. If the viscosity is less than 50 mPa·s, the viscosity of the curing agent is low, resulting in a soft adhesive layer 16, 17, which may result in reduced lamination strength. On the other hand, if the viscosity exceeds 250 mPa·s, the viscosity of the curing agent is high, resulting in a hard adhesive layer 16, 17, which may result in reduced impact resistance.

[0059] In a solvent-free adhesive, the curing agent is preferably contained in an amount of 50 to 200 parts by mass, particularly 50 to 100 parts by mass, relative to 100 parts by mass of the main agent. If the proportion of the curing agent is too low, the resulting adhesive layers 16 and 17 may be insufficiently cross-linked, and the lamination strength of the resulting multilayer film 10 may be reduced. On the other hand, if the proportion of the curing agent is too high, the main agent and the curing agent are not fully mixed, and the resulting adhesive layers 16 and 17 may contain a mixture of insufficiently cross-linked portions and excessively cross-linked portions. This may reduce the lamination strength and impact resistance of the resulting multilayer film 10.

[0060] In the present invention, the viscosity of the solvent-free adhesive is 600 mPa·s to 1400 mPa·s at 80°C, more preferably 800 mPa·s to 1200 mPa·s. When the viscosity of the solvent-free adhesive is less than 600 mPa·s, transfer between rollers becomes poor when the solvent-free adhesive is applied, and "uneven transfer" may occur. In addition, the solvent-free adhesive is not applied uniformly and becomes less in some areas, which may cause a decrease in lamination strength and impact resistance. On the other hand, when the viscosity of the solvent-free adhesive exceeds 1400 mPa·s, "poor wetting" may occur when the solvent-free adhesive is applied, and the resulting adhesive layers 16 and 17 may become partially thin. If there are thin portions in the adhesive layers 16 and 17, the lamination strength and impact resistance may be reduced.

[0061] In addition to the above-mentioned main agent and curing agent, the solvent-free adhesive may also contain a polyurethane compound. By containing the polyurethane compound, the ink layer 14 provided on the inner surface of the outer resin film 11 generally contains a urethane component, thereby ensuring adhesion to the ink layer 14.

[0062] In addition, solvent-free adhesives may also contain various additives, such as fillers, softeners, antioxidants, stabilizers, adhesion promoters, leveling agents, defoamers, plasticizers, inorganic fillers, tackifying resins, fibers, colorants such as pigments, pot life extenders, etc.

[0063] Furthermore, the solvent-free adhesive may contain an adhesion promoter. Examples of the adhesion promoter include silane coupling agents, titanate coupling agents, aluminum coupling agents, and epoxy resins.

[0064] Specific examples of the silane coupling agent 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 vinyltri(β-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane; hexamethyldisilazane, γ-mercaptopropyltrimethoxysilane, and the like.

[0065] Specific examples of the titanate coupling agent include tetraisopropoxytitanium, tetra-n-butoxytitanium, butyl titanate dimer, tetrastearyl titanate, titanium acetylacetonate, titanium lactate, tetraoctanediol titanate, and tetrastearyl titanium.

[0066] Specific examples of the aluminum coupling agent include acetylalkoxyaluminum diisopropylate and the like.

[0067] Specific examples of epoxy resins include various epoxy resins that are generally commercially available, such as epi-bis (Epi-Bis) type, novolac type, β-methyl epichlorohydrin 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.

[0068] The multilayer film 10 is produced, for example, as follows.

[0069] First, the ink layer 14 is formed by performing, for example, gravure printing on one side of the outer layer resin film 11. Furthermore, the vapor deposition layer 15 is formed by performing vapor deposition on one side of the intermediate layer resin film 13.

[0070] Then, by Figure 2 The laminator shown laminates the outer layer resin film 11 on which the ink layer 14 is formed and the intermediate layer resin film 13 on which the vapor deposited layer 15 is formed.

[0071] If you explain it in detail, Figure 2 In the figure, 30 is a laminator, 31 is a main agent tank containing a main agent, 32 is a curing agent tank containing a curing agent, 33 is an adhesive supply section for supplying the main agent and the curing agent, and 34 is a pay-off roller for supplying the outer layer resin film 11. 35 is an adhesive coating section for preparing a solvent-free adhesive by mixing the main agent and the curing agent, and coating the prepared solvent-free adhesive. The adhesive coating section 35 is provided with a plurality of rollers 35a, 35b, 35c, 35d, and 35e (five in the example shown in the figure). 36 is a laminating section for laminating the outer layer resin film 11 and the intermediate layer resin film 13, and has a pair of pressure rollers 36a and 36b. 37 is a pay-off roller for supplying the intermediate layer resin film 13, and 38 is a winding roller for winding up the intermediate laminate film described later.

[0072] In this laminator 30, the outer resin film 11, on which the ink layer 14 is formed, is supplied from a take-up roller 34 to an adhesive coating section 35 at a predetermined speed. 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 from an adhesive supply section 33 to an adhesive coating section 35 in predetermined amounts. In the adhesive coating section 35, the base agent and curing agent are mixed to prepare a solventless adhesive. Furthermore, in the adhesive coating section 35, a solventless adhesive is applied to the surface of the ink layer 14 formed on the outer resin film 11, thereby forming an adhesive coating layer.

[0073] Next, the outer layer resin film 11 is fed to the laminating section 36. Meanwhile, the intermediate layer resin film 13, on which the vapor-deposited layer 15 is formed, is fed from the unwinding roll 37 to the laminating section 36. In the 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. This results in an intermediate laminated film formed by laminating the outer layer resin film 11, the ink layer 14, the adhesive layer 16, the vapor-deposited layer 15, and the intermediate layer resin film 13. This intermediate laminated film is then taken up by the take-up roll 38.

[0074] Then, in the above process, the outer layer resin film 11 having the ink layer 14 formed thereon is replaced with the intermediate laminate film, and the intermediate layer resin film 13 having the vapor-deposited layer 15 formed thereon is replaced with the inner layer resin film 12. The same operation is then repeated, and the inner layer resin film 12 is laminated to the other side of the intermediate layer resin film 13 via the adhesive layer 17, thereby obtaining the multilayer film 10. In order to promote the effects of the adhesive layers 16 and 17, the obtained multilayer film 10 is subjected to an aging treatment.

[0075] As described above, the heating temperature of the main agent and the curing agent is, for example, 40°C to 80°C.

[0076] The feeding speed of each resin film, that is, the coating speed of the solvent-free adhesive, is preferably 100 m / min to 200 m / min.

[0077] The temperature of the solvent-free adhesive during coating is preferably 40°C to 80°C.

[0078] The coating amount of the solvent-free adhesive is preferably 0.5 g / m 2 ~3.0g / m 2 , more preferably 1.2 g / m 2 ~2.1g / m 2 .

[0079] The temperature of the press rollers 36a and 36b in the laminating unit 36 ​​is, for example, 30°C to 80°C.

[0080] The temperature of the aging treatment of the multilayer film 10 is, for example, 30° C. to 70° C., and the treatment time is, for example, 48 hours to 96 hours.

[0081] According to such a multilayer film 10, the viscosity of the solvent-free adhesive forming the adhesive layers 16 and 17 is 650 mPa·s to 1600 mPa·s at 80°C, thereby suppressing the generation of bubbles in the adhesive layers 16 and 17 and suppressing the occurrence of winding deviation when winding immediately after lamination.

[0082] The packaging container of the present invention is composed of the above-mentioned multilayer film and is suitable as a packaging container such as a refill bag or a retort bag containing liquids such as detergents, softeners, bleach, shampoo, conditioner or beverages.

[0083] As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, Various changes are possible.

[0084] For example, the layer structure of the multilayer film is not limited to Figure 1 The structure shown may be composed of two resin films, an outer layer resin film and an inner layer resin film, or may have a plurality of intermediate layer resin films.

[0085] In addition, the ink layer and the vapor deposition layer are provided as needed and are not essential in the present invention.

[0086] Example

[0087] Hereinafter, examples of the present invention will be described, but the present invention is not limited to these examples.

[0088] <Example 1 and Comparative Example 1>

[0089] [Solvent-free adhesive]

[0090] Table 1 shows the compositions of the solvent-free adhesives used in Example 1 and Comparative Example 1. In Table 1, the viscosities of the base, curing agent, and solvent-free adhesive were measured using a B8L viscometer manufactured by TOKIMEC Corporation according to a method in accordance with JIS K7117-2.

[0091] [Resin film]

[0092] As the outer layer resin film, a biaxially stretched nylon film having a thickness of 15 μm was used.

[0093] As the intermediate layer resin film, a biaxially stretched polyethylene terephthalate (PET) film having a thickness of 12 μm and an aluminum vapor-deposited layer formed on one surface was used.

[0094] As the inner layer film, a non-stretched linear low-density polyethylene (LLDPE) film having a thickness of 130 μm was used.

[0095] [Manufacturing of multilayer films]

[0096] use Figure 2 The laminator having the structure shown above produces a multilayer film as follows.

[0097] The base agent shown in Table 1 below was placed in a base agent tank, and the curing agent was placed in a curing agent tank. These were heated to 80°C. The base agent and curing agent were then supplied to the adhesive coating section at the mass ratio shown in Table 1 below via the adhesive supply section and mixed to prepare a solvent-free adhesive. Next, in the adhesive coating section, the solvent-free adhesive was applied to one side of the outer layer resin film supplied from a take-off roll at 70°C to form an adhesive coating layer. The amount of solvent-free adhesive applied was 2.5 g / m². 2 The coating speed was 150 m / min. The outer resin film with the adhesive coating layer was then transported to the lamination section, where it was laminated under pressure at 60°C with an intermediate resin film with a vapor-deposited layer, fed from a feed roll. This produced an intermediate laminate film. The lamination speed was 150 m / min.

[0098] The resulting interlayer laminate film was wound onto a roll, and an adhesive coating layer was formed on the other side of the interlayer resin film in the interlayer laminate film under the same conditions as above. This interlayer resin film was then laminated with the inner layer resin film to produce a multilayer film. The resulting multilayer film was aged by maintaining it at 40°C for 4 days.

[0099] [Production of packaging containers (pouches)]

[0100] From the obtained multilayer film, a bottom material with a width of 130 mm and a folded edge width of 36 mm was cut out, and the bottom material was sandwiched between the two multilayer films with the inner surface layers aligned with the inner surface layers. After the bottom was sealed by heat sealing at 200°C, the inner layer sides of the two multilayer films were aligned and heat sealed at 200°C to seal the sides, thereby producing a small replacement bag with a width of 130 mm, a height of 260 mm, and a capacity of 540 ml.

[0101] [evaluate]

[0102] Poor appearance:

[0103] The multilayer film immediately after lamination was visually observed within a range of 1 m in width and 1 m in length to check for the presence of dents. A case where no dents were observed was evaluated as 0, and a case where dents were observed was evaluated as ×.

[0104] Lamination adaptability:

[0105] The multilayer film immediately after lamination was visually observed within a range of 1 m in width and 1 m in length to investigate the presence or absence of tunneling effect (lifting of the bonded portion). A case where no tunneling effect was observed was evaluated as 0, and a case where the tunneling effect was observed was evaluated as ×.

[0106] Winding offset:

[0107] The film (original roll) wound up immediately after lamination was measured by a ruler to determine how much the film was offset relative to the end of the paper tube set on the winding shaft, and then wound up.

[0108] Impact resistance:

[0109] The prepared pouches were filled with 400g of tap water cooled to 5°C and heat-sealed to produce 20 sample pouches. The sample pouches were then dropped from a height of 1.2m 10 times with their bottoms facing downward, and then dropped 10 times horizontally. All 20 pouches were subjected to this drop test, and the number of broken pouches was determined.

[0110] The above results are shown in Table 1 below.

[0111] [Table 1]

[0112]

[0113]

[0114] HDI: 1,6-hexamethylene diisocyanate

[0115] IPDI: 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate

[0116] The results in Table 1 indicate that, according to Example 1, the viscosity of the solvent-free adhesive is within a specific range at 80°C, so that the adhesive layer does not generate bubbles and has a good appearance. Furthermore, a multilayer film can be obtained that has good lamination adaptability and can suppress winding deviation when winding immediately after lamination.

[0117] In contrast, in Comparative Example 1, the viscosity of the solvent-free adhesive at 80° C. was too low, resulting in a poor appearance and insufficient lamination suitability of the obtained multilayer film. In addition, large winding deviation occurred during winding immediately after lamination.

[0118] Description of Reference Numerals

[0119] 10: Multilayer film;

[0120] 11: outer resin film;

[0121] 12: inner resin film;

[0122] 13: middle layer resin film;

[0123] 14: ink layer;

[0124] 15: Evaporation layer;

[0125] 16, 17: adhesive layer;

[0126] 30: Laminator;

[0127] 31: Main agent tank;

[0128] 32: Curing agent tank;

[0129] 33: adhesive supply unit;

[0130] 34: unwinding roller;

[0131] 35: adhesive coating portion;

[0132] 35a, 35b, 35c, 35d, 35e: rollers;

[0133] 36: lamination unit;

[0134] 36a, 36b: pressure rollers;

[0135] 37: unwinding roller;

[0136] 38: Winding roller.

Claims

1. A multilayer film, characterized in that It has multiple resin films and one or more adhesive layers, At least one of the adhesive layers is formed of a solvent-free adhesive, The solvent-free adhesive contains a main agent formed of a polyester resin and a curing agent formed of an aliphatic isocyanate, and the viscosity of the solvent-free adhesive at 80° C. is 600 mPa·s to 1400 mPa·s.

2. The multilayer film according to claim 1, wherein The viscosity of the main agent is 2000mPa·s to 4500mPa·s at 80°C.

3. The multilayer film according to claim 1 or 2, characterized in that The curing agent is formed from 1,6-hexamethylene diisocyanate, namely HDI.

4. The multilayer film according to any one of claims 1 to 3, characterized in that The solvent-free adhesive contains the curing agent in an amount ranging from 50 parts by mass to 200 parts by mass based on 100 parts by mass of the main agent.

5. The multilayer film according to any one of claims 1 to 4, characterized in that At least one resin film has a vapor-deposited layer, An adhesive layer formed of the solvent-free adhesive is formed between the vapor-deposited layer and the adjacent resin film.

6. A method for producing a multilayer film, characterized in that: The method comprises the steps of laminating one resin film and the other resin film while overlapping each other with an adhesive coating layer formed of a solvent-free adhesive interposed therebetween. The solvent-free adhesive contains a main agent formed of a polyester resin and a curing agent formed of an aliphatic isocyanate, and the viscosity of the solvent-free adhesive at 80° C. is 600 mPa·s to 1400 mPa·s.

7. The method for producing a multilayer film according to claim 6, wherein: In the adhesive coating layer, the coating amount of the solvent-free adhesive is 0.5 g / m 2 ~3.0g / m 2 .

8. The method for producing a multilayer film according to claim 6 or 7, wherein: The one resin film has a vapor-deposited layer on a surface in contact with the adhesive coating layer.

9. A packaging container, characterized in that: The multilayer film is formed from the multilayer film according to any one of claims 1 to 5.

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