Film for bag-in-box inner-container, bag-in-box inner-container, and bag-in-box

Abstract

To provide a film for an inner-container of a bag-in-box that has a gas barrier property, is suitable for recycling, and has excellent pinhole resistance.SOLUTION: There are provided: a film for bag-in-box inner-container, comprising a first layer containing an ethylene-based polymer, a gas barrier adhesive layer and a second layer containing an ethylene-based polymer, in which a thickness of the gas barrier adhesive layer is 3.3 to 4.2 μm; an inner container for a bag-in-box; and a bag-in-box comprising the inner container.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a film for an inner container of a bag-in-box, an inner container for a bag-in-box, and a bag-in-box. [Background technology]

[0002] In recent years, growing environmental awareness regarding global warming, marine plastic waste, and other issues has led to calls for further improvements in the efficiency of the sorted collection and recycling of plastic materials. Conventional packaging laminates, which have achieved high performance by combining different materials, are now being made into monomaterials in order to improve their recyclability. For example, Patent Document 1 discloses a monomaterial gas barrier laminate that is primarily composed of a polyolefin film and has excellent recyclability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 176948 Summary of the Invention [Problem to be solved by the invention]

[0004] One application of plastic materials is the inner container of a bag-in-box. The bag-in-box comprises a flexible inner container made of plastic film and an outer container (outer container) that houses the inner container. The outer container is, for example, a box made of cardboard. When this bag-in-box is transported and used, the internal plastic film may be subjected to strong impacts. This may damage the plastic film, resulting in leakage of the contents. The problem of damage to the inner container becomes more pronounced when the plastic film is made into a mono-material, as in Patent Document 1.

[0005] Additionally, the inner container of a bag-in-box is also required to have gas barrier properties to preserve the contents for a long period of time.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a film for a bag-in-box inner container that has gas barrier properties, is highly recyclable, and has excellent resistance to breakage even when subjected to strong impacts (drop resistance). Another aim of the present invention is to provide an inner container for a bag-in-box that has gas barrier properties, is highly recyclable, and has excellent drop resistance, and a bag-in-box equipped with such an inner container. [Means for solving the problem]

[0007] One aspect of the present invention provides a film for use in a bag-in-box inner container, the film comprising a first layer containing an ethylene-based polymer, a gas barrier adhesive layer, and a second layer containing an ethylene-based polymer, wherein the gas barrier adhesive layer has a thickness of 3.2 to 4.3 μm.

[0008] By using this film, it is possible to produce inner containers for bag-in-boxes that have excellent drop resistance. This film also has excellent processability. Furthermore, since the film is not made of oriented nylon film or the like to impart bending and impact resistance to the film, but is essentially made from a mono-material, the inner container (film) is also highly recyclable after use.

[0009] In one embodiment, the oxygen permeability at 30°C / 70RH% is 50cc / m 2 ·day·atm or less may be acceptable.

[0010] In one embodiment, the thickness of the first layer and the second layer may be 30 to 120 μm.

[0011] In one embodiment, the ratio of the thickness of the first layer to the thickness of the second layer may be 1:1 to 1:3.

[0012] In one embodiment, the first layer and the second layer may contain linear low density polyethylene as a primary component.

[0013] In one embodiment, the first layer and the second layer may be unstretched films.

[0014] One aspect of the present invention provides an inner container for a bag-in-box, which is produced by forming the above-mentioned film into a bag. Such an inner container for a bag-in-box has excellent recyclability and drop resistance.

[0015] One aspect of the present invention provides a bag-in-box inner container comprising an inner bag made from the above-mentioned film and an outer bag made from another film. Such an inner bag has excellent drop resistance.

[0016] One aspect of the present invention provides a bag-in-box comprising an inner container having a spout and an outer container for housing the inner container, the inner container being the above-described inner container for a bag-in-box. Because such a bag-in-box comprises the above-described inner container, it has excellent drop suitability and drop resistance, thereby preventing leakage of the contents due to external impact during transportation and use. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a film for a bag-in-box inner container that has gas barrier properties and is excellent in recyclability and drop resistance. Also, according to the present invention, it is possible to provide an inner container for a bag-in-box that has gas barrier properties and is excellent in recyclability and drop resistance, and a bag-in-box including the inner container. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a cross-sectional view showing one embodiment of a film for an inner container of a bag-in-box. [Figure 2] FIG. 2 is an external view showing one embodiment of the bag-in-box. DETAILED DESCRIPTION OF THE INVENTION

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

[0020] <Bag-in-box inner container film> Fig. 1 is a cross-sectional view showing one embodiment of a film for a bag-in-box inner container. The film for a bag-in-box inner container (hereinafter sometimes referred to as "inner container film") 10 comprises, in this order, a first layer 1 containing an ethylene-based polymer, a gas-barrier adhesive layer 2, and a second layer 3 containing an ethylene-based polymer. An inner container can be made with either the first layer 1 or the second layer 3 facing inward. The first layer 1 and the second layer 3 can be referred to as base films.

[0021] The film for the inner container may have gas barrier properties from the viewpoint of storage stability of the contents. Specifically, the oxygen permeability of the film for the inner container at 30°C / 70% RH is 50 cc / m 2 m 2 ·day·atm or less is preferable, and 20cc / m 2 It is more preferable that the oxygen permeability is 1000 kJ / day atm or less. The oxygen permeability can be measured in accordance with JIS K-7126-2.

[0022] (First and second layers) The ethylene-based polymer (polyethylene-based polymer) contained in the first layer and the second layer refers to a polymer containing more than 70% by mass of units derived from ethylene monomers. Units derived from other monomers that the ethylene-based polymer may contain include units derived from monomers such as propylene, methyl methacrylate, styrene, and cyclic olefins. From the perspective of recyclability and pinhole resistance, the ethylene-based polymer may contain 30% by mass of a polymer derived from an olefin-based monomer, such as methylpropylene. Pinholes are breaks caused by strong stress applied to the bending portion of the internal plastic film during transportation and use of the bag-in-box. This causes pinholes in the plastic film, resulting in leakage of the contents. The property of preventing pinholes from opening even when strong stress is applied is called pinhole resistance.

[0023] Specific examples of ethylene-based polymers include low-density polyethylene ("LDPE"), linear low-density polyethylene ("LLDPE"), very low-density polyethylene ("ULDPE"), very low-density polyethylene ("VVLDPE"), single-site catalyst linear low-density polyethylene ("m-LLDPE") containing both linear and substantially linear low-density resins, medium-density polyethylene ("MDPE"), and high-density polyethylene ("HDPE"). From the viewpoints of low-temperature sealability and pinhole resistance, the ethylene-based polymer is preferably linear low-density polyethylene. Linear low-density polyethylene is more flexible than other polyethylenes, resulting in excellent flexibility as a film (its excellent flex resistance contributes to improved pinhole resistance). In other words, it is preferable that the first layer and the second layer contain linear low-density polyethylene as a major component. Here, "major component" refers to a component that accounts for 50 to 100% by mass, preferably 70 to 100% by mass, and more preferably 90 to 100% by mass of the total amount of the layer.

[0024] The first layer and the second layer may contain additives such as antistatic agents, ultraviolet absorbers, and plasticizers as minor components. The first layer and the second layer may contain 90% by mass or more, preferably 95% by mass or more, of an ethylene-based polymer, i.e., may be layers essentially composed of an ethylene-based polymer. The second layer and the second layer may also be layers composed of an ethylene-based polymer. The ethylene-based polymers contained in the first layer and the second layer may be the same or different. The first layer and the second layer may each independently be a single layer, or may be a laminate formed by laminating layers containing an ethylene-based polymer. When the first layer and the second layer are a laminate, the constituent materials of the individual layers may be the same or different.

[0025] The first layer and the second layer may be subjected to a surface treatment such as a plasma treatment in order to improve adhesion to the adjacent layer.

[0026] The first layer and the second layer may be a stretched film or an unstretched film, but from the viewpoint of pinhole resistance, an unstretched film is preferable. Furthermore, from the viewpoint of gas barrier property and heat resistance, a stretched film is preferable. Examples of the stretched film include a uniaxially stretched film and a biaxially stretched film, but from the viewpoint of heat resistance and cold resistance, a biaxially stretched film is preferable.

[0027] The thickness of the first layer and the second layer can be 30 to 120 μm. A thickness of 30 μm or more makes it easier to improve the strength of the layer. A thickness of 120 μm or less makes it easier to improve the flexibility of the layer and to obtain pinhole resistance. From these viewpoints, the thickness of the first layer and the second layer is more preferably 40 to 100 μm, and even more preferably 50 to 80 μm.

[0028] The thicknesses of the first layer and the second layer may be the same or different. The ratio of the thickness of the first layer to the thickness of the second layer may be 1:1 to 1:3, or may be 1:1 to 1:2. However, if the thickness ratio between the two is large, cracks may occur in the thinner layer, making pinholes more likely to occur. Therefore, if the thickness ratio is large, the total thickness must be increased to achieve the desired pinhole resistance, which can easily result in poor economic efficiency and environmental friendliness.

[0029] The tensile modulus of the first layer and the second layer at 23°C is 400 MPa or less in both the MD and TD directions. Pinholes that occur during transport of bag-in-boxes are caused by bending regardless of the direction of the film, so the tensile modulus is set within the above range in both the MD and TD directions. A tensile modulus of 400 MPa or less can suppress the occurrence of pinholes during bending compared to a tensile modulus of more than 400 MPa. Furthermore, a tensile modulus of 400 MPa or less makes it easier to obtain an inner container film with excellent processability. From this perspective, a tensile modulus of 250 MPa or less is more preferable.

[0030] Although the lower limit of the tensile modulus is not particularly limited, if the tensile modulus is too low, processing problems such as stretching and flapping are likely to occur during film processing and inner container bag making. Furthermore, if the tensile modulus is too low, the films may adhere to each other, impairing content discharge or causing problems in use such as a large amount of content remaining. Therefore, the tensile modulus of the first layer and the second layer at 23°C is preferably 100 MPa or more, and more preferably 150 MPa or more, in both the MD and TD directions. At least one of the first layer and the second layer may satisfy these lower limits of the modulus.

[0031] The tensile modulus in each direction of the first layer and the tensile modulus in each direction of the second layer may be the same or different.

[0032] The tensile modulus of the ethylene-based polymer can be increased by increasing the crystallinity of the ethylene-based polymer, increasing the units derived from methyl methacrylate monomers in the ethylene-based polymer, increasing the stretch ratio of the first layer and the second layer, etc. On the other hand, the tensile modulus can be decreased by decreasing the crystallinity of the ethylene-based polymer, increasing the units derived from ethylene monomers in the ethylene-based polymer, decreasing the stretch ratio of the first layer and the second layer, etc.

[0033] The tensile modulus (MPa) can be measured as follows. The films used as the first and second layers are cut into strips with a total length of 200 mm and a width of 15 mm to form test pieces, which are then attached to the fixed and movable grips of a tensile testing machine (a testing device conforming to JIS7127:1999) with a distance between the grips of 150 mm. The test temperature is set to 23°C, and the movable clamp is moved at a tensile speed of 50 mm / min to determine the ratio of the tensile stress to the corresponding strain within the tensile proportional limit. The average value of three test pieces is taken as the tensile modulus. The measurement result of a test piece cut out with the machine direction of the film as the full length direction of the strip is taken as the tensile modulus in the MD direction, and the measurement result of a test piece cut out with the width direction of the film as the full length direction of the strip is taken as the tensile modulus in the TD direction.

[0034] (Gas barrier adhesive layer) The gas barrier adhesive layer is not particularly limited as long as it has gas barrier properties (oxygen permeation suppression properties) and contains a component capable of adhering the first layer and the second layer. The gas barrier properties are exhibited by curing the gas barrier adhesive. Examples of gas barrier adhesives for forming the gas barrier adhesive layer include epoxy adhesives and polyester polyurethane adhesives. The gas barrier adhesive layer is formed by curing the gas barrier adhesive, and the gas barrier properties are exhibited. Examples of gas barrier adhesives include Maxive manufactured by Mitsubishi Gas Chemical Company, Inc. and PASLIM manufactured by DIC Corporation.

[0035] By using a gas barrier adhesive, excellent gas barrier properties can be achieved while keeping the adhesive layer thickness low (while maintaining recyclability). The thickness of the gas barrier adhesive layer can be set to 3.2 to 4.3 μm. A thickness of 3.3 μm or more facilitates sufficient gas barrier properties. A thickness of 4.3 μm or less prevents deterioration of gas barrier properties even when the inner container is subjected to a strong impact. In other words, a thickness of 4.2 μm or less improves the drop resistance of the inner container. In particular, if the thickness of the gas barrier adhesive layer is greater than 4.2 μm, the gas barrier adhesive layer, which tends to be harder and less flexible than the first and second layers, may be more likely to cause pinholes. From these perspectives, the thickness of the gas barrier adhesive layer is more preferably 3.6 to 4.2 μm, and even more preferably 3.6 to 4.0 μm.

[0036] Specific examples of gas barrier adhesives include epoxy resin compositions containing an epoxy resin, an epoxy resin curing agent including an amine-based curing agent, and an unsaturated fatty acid amide having a carbon number of 14 to 24. Examples of such gas barrier adhesives include Maxive manufactured by Mitsubishi Gas Chemical Company, Inc.

[0037] The epoxy resin may be any of a saturated or unsaturated aliphatic compound, alicyclic compound, aromatic compound, or heterocyclic compound, but in consideration of the development of high gas barrier properties, an epoxy resin containing an aromatic ring or alicyclic structure in the molecule is preferred.

[0038] The epoxy resin may be at least one resin selected from the group consisting of epoxy resins having a glycidylamino group derived from meta-xylylenediamine, epoxy resins having a glycidylamino group derived from para-xylylenediamine, epoxy resins having a glycidylamino group derived from 1,3-bis(aminomethyl)cyclohexane, epoxy resins having a glycidylamino group derived from 1,4-bis(aminomethyl)cyclohexane, epoxy resins having a glycidylamino group derived from diaminodiphenylmethane, epoxy resins having a glycidylamino group and / or a glycidyloxy group derived from para-aminophenol, epoxy resins having a glycidyloxy group derived from bisphenol A, epoxy resins having a glycidyloxy group derived from bisphenol F, epoxy resins having a glycidyloxy group derived from phenol novolak, and epoxy resins having a glycidyloxy group derived from resorcinol. These epoxy resins may be used alone, but from the viewpoint of improving flexibility, impact resistance, moist heat resistance, etc., two or more types may be used in combination.

[0039] Among the above, from the viewpoint of gas barrier properties, the epoxy resin is preferably one whose main component is at least one selected from the group consisting of epoxy resins having a glycidylamino group derived from meta-xylylenediamine, epoxy resins having a glycidylamino group derived from para-xylylenediamine, and epoxy resins having a glycidyloxy group derived from bisphenol F, and more preferably one whose main component is an epoxy resin having a glycidylamino group derived from meta-xylylenediamine. The meaning of the main component is as described above.

[0040] The epoxy resin curing agent contains an amine-based curing agent from the viewpoint of exhibiting high gas barrier properties. The amine-based curing agent can be a polyamine or a modified product thereof that has been conventionally used as an epoxy resin curing agent. From the viewpoint of obtaining high gas barrier properties, the amine-based curing agent is preferably a modified product of polyamine. The epoxy resin curing agent may contain a curing agent component other than the amine-based curing agent, but from the viewpoint of obtaining high gas barrier properties, a high content of the amine-based curing agent is preferred. From the viewpoint of obtaining high gas barrier properties, the content of the amine-based curing agent in the epoxy resin curing agent is preferably 50% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more. The upper limit is 100% by mass.

[0041] The blending ratio of the epoxy resin and the epoxy resin curing agent in the epoxy resin composition is not particularly limited. For example, the ratio of the number of active amine hydrogens in the epoxy resin curing agent to the number of epoxy groups in the epoxy resin (number of active amine hydrogens in the epoxy resin curing agent / number of epoxy groups in the epoxy resin) may be in the range of 0.2 to 12.0, 0.4 to 10.0, 0.6 to 8.0, more than 1.0 but not more than 5.0, or 1.1 to 3.5.

[0042] By using an unsaturated fatty acid amide having 14 to 24 carbon atoms (unsaturated fatty acid amide), an adhesive layer with good transparency can be formed.

[0043] The unsaturated fatty acid constituting the unsaturated fatty acid amide may be a fatty acid having at least one unsaturated bond and having 14 to 24 carbon atoms. The number of unsaturated bonds in the unsaturated fatty acid is preferably 1 to 6, more preferably 1 to 4, and even more preferably 1 to 2.

[0044] Examples of unsaturated fatty acids constituting the unsaturated fatty acid amide include monounsaturated fatty acids such as myristoleic acid, sapienic acid, palmitoleic acid, oleic acid, elaidic acid, vaccenic acid, gadoleic acid, eicosenoic acid, erucic acid, and nervonic acid; diunsaturated fatty acids such as linoleic acid, eicosadiene acid, and docosagenic acid; triunsaturated fatty acids such as linolenic acid, pinolenic acid, eleostearic acid, mead acid, and eicosatrienoic acid; and tetra-unsaturated fatty acids such as stearidonic acid, arachidonic acid, eicosatetraenoic acid, and adrenic acid. These may be used alone or in combination. Among these, from the viewpoint of transparency, at least one selected from the group consisting of monounsaturated and diunsaturated fatty acids having 14 to 24 carbon atoms is preferred, with monounsaturated fatty acids having 14 to 24 carbon atoms being more preferred, monounsaturated fatty acids having 16 to 24 carbon atoms being more preferred, and monounsaturated fatty acids having 18 to 22 carbon atoms being more preferred.

[0045] From the viewpoints of reducing blocking and improving conformability to the base layer and transparency, the unsaturated fatty acid amide is preferably at least one selected from the group consisting of palmitoleic acid amide, oleic acid amide, eicosenoic acid amide, and erucic acid amide, and more preferably at least one selected from the group consisting of oleic acid amide and erucic acid amide.

[0046] The content of the unsaturated fatty acid amide in the epoxy resin composition is 0.1 to 20 parts by mass, 0.2 to 15 parts by mass, 0.5 to 15 parts by mass, 1 to 15 parts by mass, 3 to 15 parts by mass, or 5 to 12 parts by mass, per 100 parts by mass of the total amount of the epoxy resin and the non-volatile content in the epoxy resin curing agent. When the content of the unsaturated fatty acid amide is 0.1 parts by mass or more per 100 parts by mass of the total amount of the epoxy resin in the epoxy resin composition and the non-volatile content in the epoxy resin curing agent, conformability to the substrate layer and anti-blocking effects are easily achieved. When the content is 20 parts by mass or less, high gas barrier properties and transparency are easily maintained, and leaching of the unsaturated fatty acid amide is easily suppressed.

[0047] The epoxy resin composition may further contain non-spherical inorganic particles. By containing non-spherical inorganic particles in the epoxy resin composition, a blocking suppression effect can be obtained when the composition is used to form a gas barrier adhesive layer, and the gas barrier properties and flex resistance can be further improved.

[0048] The shape of the non-spherical inorganic particles may be any three-dimensional shape other than a spherical shape (approximately perfect spherical shape), such as a plate-like, scale-like, columnar, chain-like, or fibrous shape. A plurality of plate-like or scale-like inorganic particles may be stacked to form a layer. Among these, from the viewpoint of improving gas barrier properties and flex resistance, plate-like, scale-like, columnar, or chain-like inorganic particles are preferred, plate-like, scale-like, or columnar inorganic particles are more preferred, and plate-like or scale-like inorganic particles are even more preferred.

[0049] Examples of inorganic substances constituting the non-spherical inorganic particles include silica, alumina, mica, talc, aluminum, bentonite, smectite, etc. Among these, from the viewpoint of improving gas barrier properties and flex resistance, at least one selected from the group consisting of silica, alumina, and mica is preferred, at least one selected from the group consisting of silica and alumina is more preferred, and silica is even more preferred.

[0050] The average particle size of the non-spherical inorganic particles is preferably in the range of 1 to 2000 nm, 1 to 1500 nm, 1 to 1000 nm, 1 to 800 nm, 1 to 500 nm, 5 to 300 nm, 5 to 200 nm, 5 to 100 nm, or 8 to 70 nm. If the average particle size is 1 nm or more, the inorganic particles can be easily prepared, and if it is 2000 nm or less, the gas barrier properties, flex resistance, and transparency will all be good when the epoxy resin composition is used to form a gas barrier adhesive layer.

[0051] When non-spherical inorganic particles are used, the content of the non-spherical inorganic particles in the epoxy resin composition is preferably 0.5 to 10.0 parts by mass, 1.0 to 8.0 parts by mass, 1.5 to 7.5 parts by mass, or 3.0 to 7.0 parts by mass per 100 parts by mass of the combined epoxy resin and epoxy resin curing agent. When the content of the non-spherical inorganic particles in the epoxy resin composition is 0.5 parts by mass or more per 100 parts by mass of the combined epoxy resin and epoxy resin curing agent, the epoxy resin composition exhibits excellent effects of improving gas barrier properties and flex resistance when used to form a gas barrier adhesive layer. Furthermore, when the content is 10.0 parts by mass or less, transparency is also excellent.

[0052] The epoxy resin composition may contain additives such as a thermosetting resin, a wetting agent, a tackifier, an antifoaming agent, a curing accelerator, a rust-preventive additive, a pigment, and an oxygen scavenger, as needed. The total content of the epoxy resin, the epoxy resin curing agent, and the unsaturated fatty acid amide having 14 to 24 carbon atoms in the solid content of the epoxy resin composition is preferably 60% by mass or more, 70% by mass or more, 80% by mass or more, or 85% by mass or more, with the upper limit being 100% by mass. The "solid content of the epoxy resin composition" refers to the components in the epoxy resin composition excluding water and organic solvents.

[0053] A specific example of such an adhesive resin composition consisting of an epoxy resin and an amine-based curing agent and containing a phosphoric acid-modified compound is PASLIM manufactured by DIC Corporation.

[0054] The glass transition temperature of the cured coating film of the adhesive resin composition is preferably in the range of -30°C to 80°C, more preferably 0°C to 70°C, and even more preferably 25°C to 70°C. If the glass transition temperature is higher than 80°C, the flexibility of the cured coating film at around room temperature may decrease, resulting in poor adhesion to the substrate film and therefore reduced adhesive strength. On the other hand, if the glass transition temperature is lower than -30°C, the molecular motion of the cured coating film at around room temperature may be so intense that sufficient gas barrier properties may not be achieved, or the adhesive strength may be reduced due to insufficient cohesive strength.

[0055] The polyester structure in the polyol is obtained by polycondensation of a polycarboxylic acid and a polyhydric alcohol by a known, conventional method. Examples of the polycarboxylic acid include aliphatic polycarboxylic acids and aromatic polycarboxylic acids. Specific examples of the aliphatic polycarboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid.

[0056] Specific examples of aromatic polycarboxylic acids include polybasic acids such as orthophthalic acid, terephthalic acid, isophthalic acid, pyromellitic acid, trimellitic acid, 1,2-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, 1,2-bis(phenoxy)ethane-p,p'-dicarboxylic acid, and anhydrides or ester-forming derivatives of these dicarboxylic acids; p-hydroxybenzoic acid, p-(2-hydroxyethoxy)benzoic acid, and ester-forming derivatives of these dihydroxycarboxylic acids.

[0057] Specific examples of ortho-oriented aromatic dicarboxylic acids include orthophthalic acid, 1,2-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, and anhydrides or ester-forming derivatives of these dicarboxylic acids. Polycarboxylic acids can be used alone or in combination of two or more. Examples of polyhydric alcohols include aliphatic polyhydric alcohols and aromatic polyhydric phenols.

[0058] Specific examples of aliphatic polyhydric alcohols include ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, cyclohexanedimethanol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, methylpentanediol, dimethylbutanediol, butylethylpropanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol.

[0059] Specific examples of aromatic polyhydric phenols include hydroquinone, resorcinol, catechol, naphthalenediol, biphenol, bisphenol A, bisphenol F, tetramethylbiphenol, and ethylene oxide-extended products and hydrogenated alicyclic phenols thereof.

[0060] The isocyanate compound has two or more isocyanate groups in the molecule, and may be either aromatic or aliphatic, and may be either a low-molecular-weight compound or a high-molecular-weight compound, and known compounds such as diisocyanate compounds with two isocyanate groups or polyisocyanate compounds with three or more isocyanate groups can be used. The isocyanate compound may also be a blocked isocyanate compound obtained by addition reaction using a known isocyanate blocking agent by an appropriate known and commonly used method.

[0061] Among these, polyisocyanate compounds are preferred from the viewpoint of adhesiveness and retort resistance, and those having aromatic rings are preferred in terms of imparting gas barrier properties. Isocyanate compounds containing a meta-xylene skeleton are particularly preferred because they can improve gas barrier properties not only through hydrogen bonding of urethane groups but also through π-π stacking between aromatic rings.

[0062] Specific examples of the isocyanate compound include tetramethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, metaxylylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, or trimers of these isocyanate compounds, and mixtures of excess amounts of these isocyanate compounds with, for example, ethylene glycol, propylene glycol, metaxylylene alcohol, 1,3-bis(2-methyl-2-propanol), and the like. Examples of the active hydrogen compounds include low molecular weight active hydrogen compounds such as bishydroxyethylbenzene, 1,4-bishydroxyethylbenzene, trimethylolpropane, glycerol, pentaerythritol, erythritol, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine, and metaxylylenediamine, and alkylene oxide adducts thereof; and adducts, biuret compounds, and allophanate compounds obtained by reacting various polyester resins, polyether polyols, and polyamides with high molecular weight active hydrogen compounds.

[0063] The phosphate-modified compound has the effect of improving adhesive strength, and known and commonly used compounds can be used.Specific examples include phosphoric acid, pyrophosphoric acid, triphosphoric acid, methyl acid phosphate, ethyl acid phosphate, butyl acid phosphate, dibutyl 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, polyoxyethylene alkyl ether phosphate, and the like, and one or more of these can be used.

[0064] There are no particular limitations on the solvent, as long as it can dissolve the polyol and isocyanate compound, can uniformly disperse the phosphoric acid-modified compound and plate-like inorganic compound, and has a boiling point and volatility appropriate for the manufacturing process.

[0065] The plate-like inorganic compound has the effect of improving the laminate strength and gas barrier properties of the gas barrier adhesive layer obtained by curing the adhesive resin composition. Specific examples of the plate-like inorganic compound include kaolinite-serpentine group clay minerals (halloysite, kaolinite, endelite, dickite, nacrite, etc., antigorite, chrysotile, etc.) and pyrophyllite talc group minerals (pyrophyllite, talc, kerola, etc.), and one or more of these can be used.

[0066] <Manufacturing method for film used in bag-in-box containers> The film for the inner container of the bag-in-box is produced by bonding the first layer and the second layer together with a gas barrier adhesive.

[0067] The gas barrier adhesive is applied to, for example, the first layer by, for example, bar coating, dipping, roll coating, gravure coating, reverse coating, air knife coating, comma coating, die coating, screen printing, gravure offset, or the like. The coating film formed by applying the gas barrier adhesive is dried, and then the second layer is laminated. The drying temperature can be, for example, 30 to 200°C, and preferably 50 to 180°C. Furthermore, after the second layer is laminated, the coating film is cured. The curing temperature can be, for example, room temperature to 70°C, and preferably 30 to 60°C. By keeping the drying and curing temperatures within the above ranges, the occurrence of cracks in the gas barrier adhesive layer can be suppressed.

[0068] <Bag-in-box inner container> The inner container for a bag-in-box is made by forming the above-mentioned inner container film into a bag. Specific methods for making the bag include blow molding of the film and vacuum or pressure molding of two films and then fusing or sealing the periphery with heat or ultrasonic waves.

[0069] In order to more easily prevent leakage of contents due to external impacts or scratches during transportation and use of the bag-in-box, the bag-in-box inner container may include an inner bag made from the above-mentioned inner container film and an outer bag made from another film. That is, the bag-in-box inner container may be a double-layered bag. The other film used in the outer bag may be the same film as that of the inner bag, or may be a different film. Examples of different films include polyethylene film and polypropylene film. Using an olefin-based resin film as the film constituting the outer bag improves recyclability. An inner container comprising an inner bag and an outer bag can be obtained by sealing the film constituting the outer bag around the periphery of the inner bag.

[0070] <Bag in box> Fig. 2 is an external view showing one embodiment of a bag-in-box. As shown in Fig. 2, the bag-in-box 100 includes an inner container 11 having a spout 11a and an outer container 12 that houses the inner container 11. The inner container 11 is an inner container for a bag-in-box, made from the inner container film for the bag-in-box. The spout 11a is provided so as to be continuous with the inner container 11 and protrude to the outside of the outer container 12, and the contents are poured through this spout 11a. The spout 11a can include, for example, a pouring outlet fused to the inner container 11 and a cap that fits over the pouring outlet to enable opening and closing.

[0071] The contents housed in the inner container include food and non-food liquids. Examples of the contents include food liquids such as beverages such as fruit juice drinks, juice, carbonated drinks, tea, coffee, dairy drinks, and soup, and alcoholic beverages such as sake and shochu, as well as non-food liquids such as developer, ink, paint, oil, disinfectant, liquid fertilizer, fungicide, and insecticide. The outer container 12 (outer box) can be a box made primarily of cardboard or a box made primarily of cardboard, so as to be able to withstand the weight of these contents. [Example]

[0072] The present invention will be described in more detail by the following examples, but the present invention is not limited to these examples.

[0073] (Base film) First layer: LLDPE (manufactured by Tamapoly Co., Ltd.), thickness 40 μm, unstretched film Second layer: LLDPE (manufactured by Tamapoly Co., Ltd.), thickness 120 μm, unstretched film

[0074] The tensile modulus (MPa) was measured as follows. Each substrate film was cut into a strip measuring 200 mm in length and 150 mm in width to form a test specimen. The test specimen was attached to the fixed and movable jaws of a tensile testing machine (a test device conforming to JIS K7127:1999) with a distance of 150 mm between the jaws. The test temperature was set to 23°C, and the movable jaw was moved at a pulling speed of 50 mm / min. The ratio of the tensile stress to the corresponding strain within the tensile proportional limit was determined. The average value for three test specimens was taken as the tensile modulus. The measurement result for the test specimen cut so that the machine direction of the substrate film was the length direction of the strip was taken as the MD tensile modulus, and the measurement result for the test specimen cut so that the width direction of the substrate film was the length direction of the strip was taken as the TD tensile modulus.

[0075] (glue) Adhesive: Maxieve (gas barrier adhesive, manufactured by Mitsubishi Gas Chemical Company, Inc.) An epoxy-based adhesive was prepared by mixing 23 parts by mass of a solvent made by mixing ethyl acetate and methanol in a mass ratio of 1:1 with 16 parts by mass of Maxieve c93T, 5 parts by mass of ethyl acetate, and Maxieve M-100.

[0076] (Production of film for bag-in-box container) An adhesive was applied to one of the substrate films using a wire bar and dried at 60°C to form an adhesive layer, after which the other substrate film was laminated. This was then aged at 50°C for 4 days. This resulted in a laminated film having a substrate film / adhesive layer / substrate film structure. The layer details for each example are shown in Table 1.

[0077] (Bending pinhole test) The laminated films obtained in each example were subjected to a flex pinhole test. The detailed procedure was as follows. The results are shown in Table 1. [procedure] The laminated film obtained in each example was cut to A4 size (297 mm in the MD direction of the film, 210 mm in the TD direction). The film on the liquid-contacting side (first layer) was placed on the inside and fixed cylindrically to a 3.5-inch diameter fixed head and a 3.5-inch diameter movable head of a Gelboflex Tester (BE-1006 Gelboflex Tester with Thermostatic Bath, manufactured by Tester Sangyo Co., Ltd.). At the start of the stroke, the surfaces were spaced 7 inches apart. The ambient temperature was set to 5°C, and the flex test began 1 minute after the thermometer reached 5°C. The movable head of the tester was rotated 440° while moving 89.0 mm toward the fixed head, then moved another 63.5 mm toward the fixed head without rotating, and then reversed and returned to the original position. This cycle was repeated at a speed of 40 cycles / min for 1,000 cycles. This procedure was repeated three times for each bag. After the flex test, the samples were visually inspected and the number of pinholes was counted (in accordance with ASTM-F392). A water-washable penetrant (R-3B(NT)W-1 Plus, manufactured by Eishin Kagaku Co., Ltd.) was used to count pinholes.

[0078] (Oxygen permeability measurement) The oxygen permeability (unit: cc / m2·day·atm) of the laminated film obtained in each example was measured using an oxygen permeability measuring device (product name "OX-TRAN2 / 20", manufactured by MOCON) at a temperature of 30°C and a relative humidity of 70%. The measurement was carried out in accordance with JIS K-7126-2. The results are shown in Table 1.

[0079] (Drop test) Three sides of the laminated film obtained in each example, measuring 500 mm x 425 mm, were heat-sealed to form a bag, after which 9.5 L of water was poured into the bag and the remaining side was heat-sealed to seal the bag. The resulting bag was dropped five times horizontally and five times vertically from a height of 1 m to evaluate whether it broke. The drop test results are shown in Table 1.

[0080] [Table 1]

[0081] As shown in Table 1, it was confirmed that the laminate films of the Examples had superior oxygen barrier properties compared to the laminate film of Comparative Example 1. Furthermore, they had superior drop resistance compared to the laminate film of Comparative Example 2, and pinhole formation after a flex test was suppressed. It can be said that the laminate films of the Examples, which have excellent drop resistance and pinhole resistance, are suitable as films for inner containers of bag-in-boxes. From these findings, it was confirmed that the laminate films of the Examples have both oxygen barrier properties and drop resistance and pinhole resistance. Since the laminate films of the Examples are formed from mono-material materials, it can be said that they also have excellent recyclability for the inner container (film) after use. [Explanation of symbols]

[0082] 1. First Layer 2 Gas barrier adhesive layer 3 Second Layer 10 Bag-in-box container film 11 Inner container 11a Spout 12 Outer container 100 Bag in Box

Claims

1. A film comprising a first layer, a barrier adhesive layer, and a second layer, wherein the barrier adhesive layer has a thickness of 3.2 to 4.3 μm.

2. Oxygen permeability at 30°C / 70%RH is 50cc / m ２ 2. The film of claim 1, wherein the film has a viscosity of 0.5 sq. day atm or less.

3. 2. The film of claim 1, wherein the first layer and the second layer have a thickness of 30 to 120 μm.

4. 10. The film of claim 1, wherein the ratio of the thickness of the first layer to the thickness of the second layer is from 1:1 to 1:

3.

5. 10. The film of claim 1, wherein the first layer and the second layer comprise linear low density polyethylene as a primary component.

6. The film of claim 1 , wherein the first layer and the second layer are unstretched films.

7. An inner container for a bag-in-box, produced by making a bag from the film according to any one of claims 1 to 6.

8. 7. An inner container for a bag-in-box, comprising an inner bag made from the film according to claim 1, and an outer bag made from another film.

9. A bag-in-box comprising an inner container having a spout and an outer container that houses the inner container, the inner container comprising the film according to any one of claims 1 to 6.

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