Method for producing laminate for packaging material, and laminate for packaging material

Abstract

The present invention relates to a method for producing a laminate for a packaging material, the method comprising: a lamination step for obtaining a laminate by bonding a first resin film and a second resin film with an isocyanate-curable solvent-free adhesive interposed therebetween; and a curing step for curing the laminate at 25-80 DEG C, the carbon dioxide permeability of the first resin film and / or the second resin film is 200 cc / m2 day atm or more.

Description

Technical Field

[0001] The present invention relates to a method for producing a laminate for packaging materials and the laminate for packaging materials. Background Art

[0002] There is known a laminating ink containing at least a polyurethane resin, a colorant, and a solvent for laminating resin films used in packaging materials (Patent Document 1). This ink is a so-called solvent-based adhesive.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2010-126562 Summary of the invention

[0006] Problems to be solved by the invention

[0007] In recent years, from the perspective of environmental protection, attempts have been made to use solvent-free adhesives to replace the solvent-based adhesives described above. As such adhesives, isocyanate-curing adhesives with excellent high-speed productivity have attracted much attention. However, isocyanate-curing solvent-free adhesives not only generate carbon dioxide during curing, but also may involve air when applied to the resin film. These carbon dioxide and involved air may cause poor appearance of the manufactured laminate.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a laminate for packaging materials having a good appearance, using an isocyanate-curing solvent-free adhesive.

[0009] Another object of the present invention is to provide a laminate for packaging materials having a good appearance obtained by the production method.

[0010] Means for solving problems

[0011] One aspect of the present invention provides a method for producing a laminate for packaging materials, comprising the following steps: a lamination step of laminating a first resin film and a second resin film via an isocyanate-curing solvent-free adhesive to obtain a laminate; and a curing step of curing the laminate at 25 to 80° C.; the carbon dioxide permeability of at least one of the first resin film and the second resin film is 200 cc / m 2 ·day·atm or more.

[0012] In one embodiment, the curing step may be performed at 50° C. or less for 1 hour or more.

[0013] In one embodiment, the viscosity of the solvent-free adhesive may be 100 mPa·s or more at 40° C.

[0014] One aspect of the present invention provides a laminate for packaging materials, wherein a first resin film and a second resin film are laminated via a cured product of an isocyanate-curing solvent-free adhesive, wherein at least one of the first resin film and the second resin film has a carbon dioxide permeability of 200 cc / m 2 ·day·atm or more.

[0015] Effects of the Invention

[0016] According to the present invention, there is provided a method for producing a laminate for packaging materials having a good appearance, using an isocyanate-curing solvent-free adhesive.

[0017] Furthermore, according to the present invention, there is provided a laminate for packaging materials having a good appearance obtained by the production method. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic cross-sectional view of a laminate for packaging materials according to one embodiment of the present invention. DETAILED DESCRIPTION

[0019] Hereinafter, preferred embodiments of the present disclosure will be described in detail. However, the present disclosure is not limited to the following embodiments.

[0020] <Method for producing a laminate for packaging materials>

[0021] The method for producing a laminate for packaging materials comprises the steps of: a lamination step of laminating a first resin film and a second resin film via an isocyanate-curing solvent-free adhesive to obtain a laminate; and a curing step of curing the laminate at 25 to 80°C.

[0022] (Lamination process)

[0023] In the lamination process, a solvent-free adhesive is first applied to one surface of the first resin film or the second resin film, and then the resin films are bonded together so that the surface of the resin film coated with the solvent-free adhesive faces the other resin film not coated with the adhesive.

[0024] The lamination process can be implemented using a processing device equipped with a delivery roller and a winding roller, and can be implemented specifically by a forward transfer coating device or a reverse transfer coating device (reverse coating machine). For example, taking the coating of a solvent-free adhesive on a first resin film as an example, the first resin film is fed out from a delivery roller, and the adhesive is coated on one surface of the first resin film using a roller coater or the like. Then, the adhesive-coated surface of the first resin film is bonded to one surface of a second resin film fed out from another delivery roller. In this way, the laminate formed by bonding the resin films to each other is wound up using a winding roller.

[0025] From the viewpoint of productivity, the processing speed of the processing device can be set to more than 50m / min, or more than 100m / min. When using a solvent-free adhesive, if the processing speed is accelerated, air is more likely to be involved, but in this manufacturing method in which the carbon dioxide permeability of the resin film is adjusted, the involved air can be appropriately released. Therefore, even if the processing speed is accelerated to a certain extent, it is easy to obtain a laminate with good appearance. The upper limit of the processing speed is not particularly limited, but from the viewpoint of processing stability, it can be set to less than 500m / min.

[0026] From the viewpoint of reducing viscosity, the temperature of the adhesive during coating can be set to 35° C. or higher, or 40° C. or higher. The upper limit of the temperature is not particularly limited, but from the viewpoint of pot life, it can be set to 100° C. or lower, 90° C. or lower, or 85° C. or lower.

[0027] The viscosity of a solvent-free adhesive that does not use a solvent becomes higher to a certain extent. The viscosity of the adhesive during coating may be 100 mPa·s or more, 200 mPa·s or more, 300 mPa·s or more, or 500 mPa·s or more at 40°C. The upper limit of the viscosity is not particularly limited, but from the viewpoint of coating adaptability, it is preferably 1200 mPa·s or less, and more preferably 1000 mPa·s or less.

[0028] From the viewpoint of adhesive strength, the amount of adhesive applied can be set to 0.5 to 5 g / m 2 , can also be 1 to 5 g / m 2 , can also be 1.5 ~ 4.5g / m 2 .

[0029] (Maintenance process)

[0030] In the curing step, the laminate obtained by the lamination step is cured (placed) in an environment of 25 to 80°C. The curing step may also be called an aging step. The curing temperature may be appropriately adjusted according to the composition of the adhesive. In this step, the curing of the solvent-free adhesive progresses, and a laminated body can be obtained in which the first resin film and the second resin film are laminated via a cured product of an isocyanate-curing solvent-free adhesive.

[0031] In this manufacturing method, since an isocyanate-curing adhesive is used, carbon dioxide is generated when the adhesive is cured, and since the adhesive is a solvent-free type, the viscosity is high, and air is easily drawn in when the adhesive is applied. However, since at least one of the laminated resin films uses a resin film with excellent carbon dioxide permeability, the silicon dioxide and the drawn air can be appropriately released outside the laminate.

[0032] From the viewpoint of better releasing these carbon dioxide and entrained air outside the laminate, the upper limit of the curing temperature is 80°C or less, but it can also be 50°C or less, or it can be 40°C or less. In addition, the curing time can be set to 1 hour or more, but it can also be 12 hours or more, or it can be 24 hours or more. The upper limit of the curing time is not particularly limited, but from the viewpoint of the manufacturing efficiency of the laminate, it can be set to about 72 to 192 hours, for example.

[0033] When the stacked body for packaging materials also has a third resin film, the third resin film can be laminated by an adhesive on the surface of the first resin film side or the surface of the second resin film side of the stacked body of the first resin film and the second resin film. The third resin film can be laminated before the curing of the stacked body of the first resin film and the second resin film, or after the curing. When the third resin film is laminated, the same solvent-free adhesive as described above can be used according to its carbon dioxide permeability, or other adhesives used in the field of the stacked body for packaging materials can be used. For example, if the third resin film has sufficient carbon dioxide permeability, even if the same solvent-free adhesive as described above is used, carbon dioxide and entrained air can be well released from the third resin film side to the outside of the stacked body.

[0034] (Solvent-free adhesive)

[0035] As isocyanate-curing solvent-free adhesives, adhesives containing polyisocyanate components and polyol components and not containing organic solvents and water can be cited. Since the polyisocyanate component and the polyol component are prepared in appropriate amounts in advance and then mixed before use, the solvent-free adhesive can be said to be a two-component curing solvent-free adhesive. The isocyanate-curing solvent-free adhesive can be a solvent-free polyurethane adhesive.

[0036] The polyisocyanate component may contain diphenylmethane diisocyanate. The polyisocyanate component may further contain an isocyanate group-terminated prepolymer which is a reaction product of the isocyanate and a polyol.

[0037] Examples of diphenylmethane diisocyanate include 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, and 2,2′-diphenylmethane diisocyanate. These isocyanates may be used alone or in combination of two or more.

[0038] The polyol component may include, for example, a low molecular weight polyol or a high molecular weight polyol.

[0039] Examples of the low molecular weight polyol include polyols having two or more hydroxyl groups in the molecule and having a number average molecular weight of 50 to 300.

[0040] Examples of the low molecular weight polyol include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 1,2-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2,2,2-trimethylpentanediol, 3,3-dihydroxymethylheptane, alkane (C7-20) diols, 1,3- or 1,4-cyclohexanedimethanol and mixtures thereof, 1,3- or 1,4-cyclohexanediol and mixtures thereof, Diols such as hydrogenated bisphenol A, 1,4-dihydroxy-2-butene, 2,6-dimethyl-1-octene-3,8-diol, bisphenol A, diethylene glycol, triethylene glycol, and dipropylene glycol, triols such as glycerol, trimethylolpropane, and triisopropanolamine, tetrahydroxymethylmethane (pentaerythritol), diglycerol, and other tetraols, pentaols such as xylitol, hexaols such as sorbitol, mannitol, allitol, iditol, dulcitol, altritol, inositol, and dipentaerythritol, heptaols such as mannoheptitol, and octaols such as sucrose. These polyols may be used alone or in combination of two or more.

[0041] Examples of the high molecular weight polyol include polyols having two or more hydroxyl groups in the molecule and having a number average molecular weight exceeding 300.

[0042] Examples of the high molecular weight polyol include polyether polyol, polyester polyol, polycarbonate polyol, polyurethane polyol, epoxy polyol, vegetable oil polyol, polyolefin polyol, acrylic polyol, vinyl monomer-modified polyol, etc. These polyols may be used alone or in combination of two or more.

[0043] The solvent-free adhesive may also contain other components besides the polyisocyanate component and the polyol component. Examples of other components include phosphoric acid, silane coupling agents, defoamers, epoxy resins, catalysts, coating improvers, leveling agents, stabilizers, plasticizers, surfactants, pigments, fillers, organic or inorganic microparticles, and mildew inhibitors.

[0044] From the viewpoint of improving adhesion, the mixing ratio of the polyisocyanate component and the polyol component can be set to, for example, 0.5 to 5 in terms of the equivalent ratio of isocyanate groups of the polyisocyanate component to hydroxyl groups of the polyol component (NCO group / OH group molar ratio).

[0045] The mixing ratio of the polyisocyanate component and the polyol component can be set to, for example, 30 to 100 parts by mass of the polyol component relative to 100 parts by mass of the polyisocyanate component.

[0046] (resin film)

[0047] The resin film used for the first resin film and the second resin film is not particularly limited as long as it has a desired carbon dioxide permeability. Examples of the resin film include cellophane, polyamide resin film, polyester resin film, olefin resin film, acid-modified polyolefin resin film, polystyrene resin film, polyurethane resin film, acetal resin film, and the like. Specifically, resin films include polyethylene (low-density, medium-density, high-density or linear low-density polyethylene), polypropylene, polybutene, polyvinyl alcohol, ethylene-ethyl acetate copolymer, ionomer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylate copolymer, ethylene-propylene copolymer, methylpentene, polyacrylonitrile, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, polycarbonate, polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyvinylidene fluoride (PVDF), ethylene-tetrafluoroethylene copolymer (ETFE), polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, etc., K-coated films, composite films formed by laminating two or more of them, etc.

[0048] The resin film may be obtained by extrusion, casting, T-die, cutting, blow molding, etc. using one or more resins, or by multilayer co-extrusion using two or more resins.

[0049] The resin film may be a film stretched by a single screw or a twin screw.

[0050] The thickness of the resin film is not particularly limited, but can be set to 1 to 300 μm from the viewpoints of moldability, transparency, carbon dioxide permeability, and the like.

[0051] The carbon dioxide (carbonic acid gas) permeability of at least one of the first resin film and the second resin film is 200 cc / m 2 ·day·atm or more. Thus, the carbon dioxide generated when the adhesive is cured and the air drawn in when the adhesive is applied can be appropriately released outside the laminate. Thus, a laminate with good appearance can be obtained. In addition, according to the inventors' insights, it can be seen that by making the carbon dioxide permeability of the resin film as described above, the drawn in air can also be appropriately released.

[0052] From the viewpoint of better releasing the carbon dioxide and the entrained air outside the laminate, the carbon dioxide permeability may be 250 cc / m 2 ·day·atm or more, 300cc / m 2The upper limit of carbon dioxide permeability is not particularly limited, but can be set to 20000cc / m from the viewpoint of film forming properties. 2 ·day·atm. The carbon dioxide permeability can be measured at 23°C and 0%RH using a differential pressure gas permeability measuring apparatus according to JIS K 7126A by a differential pressure method.

[0053] The resin film may be provided with a transparent deposited layer such as a silica deposited layer or an alumina deposited layer, an aluminum deposited layer, etc. In addition, a primer coating layer, a base coat layer, an anchor coat layer, a barrier coat layer, etc. may be formed on the resin film.

[0054] In order to improve adhesion with other layers such as adhesives and vapor-deposited layers, the resin film may be subjected to physical treatments such as corona discharge treatment, ozone treatment, low-temperature plasma treatment using oxygen or nitrogen, glow discharge treatment, or chemical treatments such as oxidation treatment using chemicals.

[0055] <Laminate for packaging material>

[0056] Figure 1 Schematic cross-sectional view of a laminate for packaging material according to one embodiment of the present invention. The laminate for packaging material can be manufactured by the above-mentioned method for manufacturing a laminate for packaging material. That is, the laminate for packaging material 10 is formed by laminating a first resin film 1 and a second resin film 2 via an adhesive layer (a cured product of a solvent-free adhesive of an isocyanate curing system) 3. The carbon dioxide permeability of at least one of the first resin film and the second resin film of the laminate for packaging material is 200 cc / m 2 ·day·atm or more.

[0057] In the method for producing the packaging laminate, carbon dioxide generated during curing of the solventless adhesive and air entrained during adhesive coating can be suitably released outside the laminate, so that the obtained packaging laminate can have an extremely good appearance.

[0058] Example

[0059] The present invention is explained in more detail by the following examples, but the present invention is not limited to these examples.

[0060] <Preparation of various membranes>

[0061] Resin films were prepared as shown in Table 1. In the table, printed GL indicates a GL film coated with white ink (ink in which titanium oxide is dispersed in a polyurethane binder: thickness 2 μm), VMCPP indicates aluminum-deposited CPP, LL indicates low-density polyethylene (LLDPE), and VMPET indicates aluminum-deposited PET.

[0062] The carbon dioxide permeability of each resin film was measured at 23° C. and 0% RH using a differential pressure gas permeability measuring apparatus in accordance with JIS K 7126A.

[0063] Table 1

[0064]

[0065] <Preparation of solvent-free adhesive>

[0066] Isocyanate-curing solvent-free adhesive A: "LA6172 / LA7772" (manufactured by Henkel, viscosity 800 mPa·s at a liquid temperature of 40°C)

[0067] Isocyanate-curing solvent-free adhesive B: "A248B / A246A (Mitsui Chemicals, Inc., viscosity 1150 mPa·s at a liquid temperature of 40°C)

[0068] <Production of Laminated Body for Packaging Materials>

[0069] (Example 1)

[0070] The ONy film "ONMB-RT" was used as the first film, and the transparent vapor-deposited barrier film "GL-ARH" was used as the second film. They were laminated (bonded) at a processing speed of 100 m / min using a laminating device. The barrier layer side of the second film was made to face the first film. During the lamination process, an isocyanate-curing solvent-free adhesive A heated to 40°C was used. The solvent-free adhesive was applied using a roll coater equipped with a laminating device at a coating amount of 2 g / m 2 After the first film and the second film were bonded together, they were cured at 40° C. for 3 days in a roll state. Thus, a laminate for packaging material was obtained.

[0071] (Example 4)

[0072] The transparent vapor-deposited barrier film "GL-ARH" was used as the first film, the ONy film "ONMB-RT" was used as the second film, and the CPP sealant film "ZK207" was used as the third film. They were laminated (bonded) in the above order at a processing speed of 100 m / min using a laminating device. The barrier layer side of the first film was made to face the second film. During the lamination process, an isocyanate-curing solvent-free adhesive A heated to 40°C was used. The solvent-free adhesive was applied using a roll coater equipped in the laminating device at a coating amount of 2 g / m 2 After the first to third films were laminated together, the roll was cured at 40° C. for 3 days. Thus, a laminate for packaging material was obtained.

[0073] (Other Examples and Comparative Examples)

[0074] A laminate for packaging material was obtained in the same manner as in Example 1 or 4 except that the layer structure, adhesive type, and processing speed were changed as shown in Table 2. For the printed GL, the white ink-coated surface was laminated as the adhesive-coated surface. In the layer structure column of Table 2, the underlined film is a film with a carbon dioxide permeability of 200 cc / m 2 ·day·atm or more membrane.

[0075] <Appearance inspection>

[0076] The appearance of the laminate for packaging materials obtained in each example was observed under a microscope or visually.

[0077] A: Good appearance under microscope and visual observation.

[0078] B: The appearance is good in visual observation.

[0079] C: A large number of bubbles were found in the laminate by visual observation, and the appearance was poor.

[0080] Table 2

[0081] Layer composition Adhesive Processing speed Appearance Example 1 <![CDATA[ ON / GL]]> A 100m / min B Example 2 <![CDATA[ PET / GL]]> B 150m / min A Example 3 <![CDATA[GL / CPP ]]> A 150m / min A Example 4 <![CDATA[GL / ON / CPP ]]> A 100m / min B Example 5 <![CDATA[ OPP / GL / CPP ]]> A 100m / min B Example 6 <![CDATA[GL / LL(1) ]]> B 150m / min A Example 7 <![CDATA[Printing GL / CPP > A 100m / min B Example 8 <![CDATA[ ON / VMPET / LL(2) ]]> B 100m / min B Comparative Example 1 GL / VMCPP B 150m / min C Comparative Example 2 GL / GL A 50m / min C

[0082] Explanation of symbols

[0083] 1 first resin film, 2 second resin film, 3 adhesive layer, 10 laminate for packaging material.

Claims

1. A method for producing a laminate for packaging materials, comprising the following steps: a lamination step of laminating the first resin film and the second resin film via an isocyanate-curing solvent-free adhesive to obtain a laminate; and A curing step of curing the laminate at 25 to 80° C.; The carbon dioxide permeability of at least one of the first resin film and the second resin film is 200 cc / m 2 ·day·atm or more.

2. The manufacturing method according to claim 1, wherein: The curing step is performed at 50° C. or lower for 1 hour or longer.

3. The manufacturing method according to claim 1 or 2, wherein: The solvent-free adhesive has a viscosity of 100 mPa·s or more at 40° C.

4. A laminate for packaging material, wherein a first resin film and a second resin film are laminated via a cured product of an isocyanate-curing solvent-free adhesive, The carbon dioxide permeability of at least one of the first resin film and the second resin film is 200 cc / m 2 ·day·atm or more.

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