Method for recovering plastic film

Abstract

The present invention provides a method for recovering a plastic film from a multilayer body, wherein: the multilayer body comprises a plastic film (I), an inorganic layer (II) which is composed of at least one substance that is selected from the group consisting of silicon oxides, aluminum and aluminum oxides, and a resin cured layer (III); and the resin cured layer (III) is composed of a cured product of an epoxy resin composition that contains an epoxy resin and an epoxy resin curing agent including an amine-based curing agent. This method comprises a step in which the multilayer body is brought into contact with an acid aqueous solution or an alkaline aqueous solution.

Description

How to recycle plastic film

[0001] The present invention relates to a method for recovering plastic films from laminates.

[0002] Inorganic vapor-deposited films, in which inorganic substances such as alumina and silica are vapor-deposited onto thermoplastic plastic films, have high gas barrier properties and are therefore used as gas barrier packaging materials. In addition to inorganic vapor-deposited films, gas barrier packaging materials also include those with printed layers. Packaging materials in the form of laminated films in which inorganic vapor-deposited films and plastic films are laminated via an adhesive layer are also known. However, in recent years, in consideration of the effective use of resources and energy and environmental pollution issues, laws promoting the recycling of plastic materials have been established in countries around the world. Accordingly, methods for recovering plastic films from packaging materials containing plastic films have been investigated.

[0003] For example, Patent Document 1 discloses a method for producing a recycled substrate, which includes a step of immersing a laminate in a basic aqueous solution, wherein the laminate comprises a plastic substrate, a release layer containing at least one selected from the group consisting of aluminum, aluminum oxide, and silica, and a printed layer, in this order, and the basic aqueous solution has a basic compound concentration and a water temperature within a predetermined range. This production method discloses that the plastic substrate constituting the laminate can be efficiently and simply obtained as a recycled substrate from a printed matter, a laminated laminate, or the like.

[0004] Patent Document 2 discloses a packaging material comprising a first substrate and a first release layer for removing the first substrate to recycle the first substrate, and a second substrate and a second release layer for removing the second substrate to recycle the second substrate, wherein the first release layer-forming composition contains a predetermined amount of at least one inorganic substance selected from the group consisting of aluminum, aluminum oxide, and silica, and the second release layer-forming composition is an adhesive composition containing a predetermined polyol component and a polyisocyanate component. The publication also discloses that the packaging material has excellent substrate adhesion, which is necessary for packaging, and allows the removal of not only the outer printed layer of the package but also the inner printed layer, and has excellent release properties for both substrates constituting the packaging material, making it suitable for plastic recycling.

[0005] JP 2020-175620 A JP 2021-107159 A

[0006] The technology disclosed in Patent Document 1 exemplifies a resin selected from polyurethane resin, acrylic resin, polyester resin, and polyvinyl alcohol as the binder resin to be contained in the release layer, and exemplifies an anchor layer, a resin layer formed from a molten polyolefin resin, a urethane adhesive layer, an acrylic adhesive, etc. as the adhesive layer. Furthermore, Patent Document 2 discloses a second release layer-forming composition as an adhesive composition containing a polyol component and a polyisocyanate component. However, laminates containing layers made of these resins have insufficient gas barrier properties and, further, have problems such as limited flexibility in the recovery conditions for the plastic film. In particular, a technology for easily recovering plastic films from laminated laminates having two or more plastic films has been desired.

[0007] An object of the present invention is to provide a method for efficiently recovering plastic films from laminates containing the plastic films.

[0008] The present inventors have found that the above-mentioned problems can be solved by a method comprising the step of contacting a laminate having a plastic film and a predetermined layer with an acidic aqueous solution or an alkaline aqueous solution. That is, the present invention relates to a method for recovering a plastic film from a laminate, the laminate comprising: a plastic film (I), at least one inorganic layer (II) selected from the group consisting of silicon oxide, aluminum, and aluminum oxide, and a cured resin layer (III), the cured resin layer (III) being a cured product of an epoxy resin composition containing an epoxy resin and an epoxy resin curing agent including an amine-based curing agent, the method comprising the step of contacting the laminate with an acidic aqueous solution or an alkaline aqueous solution.

[0009] According to the method of the present invention, it is possible to efficiently recover plastic films from laminates containing plastic films. The method of the present invention has a high degree of freedom in the conditions for recovering plastic films, and in particular, it is possible to easily recover plastic films from laminated laminates having two or more plastic films.

[0010] 10 is a photograph of a laminate pulverized by a dry pulverizer in Example 32.

[0011] [Method for recovering plastic film] The present invention is a method for recovering plastic film from a laminate (hereinafter also referred to as "the method of the present invention"), the laminate comprising a plastic film (I), at least one inorganic layer (II) selected from the group consisting of silicon oxide, aluminum, and aluminum oxide, and a cured resin layer (III), the cured resin layer (III) being a cured product of an epoxy resin composition containing an epoxy resin and an epoxy resin curing agent including an amine-based curing agent, and the method comprising the step of contacting the laminate with an acid aqueous solution or an alkaline aqueous solution.

[0012] The method of the present invention, having the above-described configuration, can efficiently recover plastic films from laminates containing plastic films. The reason for this is not clear, but is thought to be as follows.

[0013] At least one inorganic layer (II) selected from the group consisting of silicon oxide, aluminum, and aluminum oxide (hereinafter simply referred to as "inorganic layer (II)") dissolves upon contact with an acidic or alkaline aqueous solution. Therefore, plastic films are easily recovered from laminates having the inorganic layer (II). However, laminates having two or more plastic films have the problem that acidic or alkaline aqueous solutions do not easily penetrate between the layers, making the plastic films difficult to recover. In laminates having two or more plastic films, the films are generally laminated via a resin-cured layer such as an adhesive layer. Furthermore, when the laminate is used as a packaging material, it contains multiple layers, such as a primer layer, an anchor coat layer, a colored layer formed with a colored ink, a medium layer formed with an ink that does not contain a colorant, and an overcoat layer for surface protection. The inventors' studies have found that when recovering plastic films from laminates containing such multiple layers, not only the presence or absence of the inorganic layer (II) but also the type of other layers, particularly the resin-cured layer, affect the ease of recovery of the plastic film. In other words, it was found that even in laminates containing the same inorganic layer (II) and having the same layer structure, the ease of recovery of the plastic film varies depending on the type of cured resin layer.

[0014] The laminate defined in the present invention has a resin-cured layer (III) that is a cured product of an epoxy resin composition containing an epoxy resin and an epoxy resin curing agent including an amine-based curing agent. Because the resin-cured layer (III) is a cured product of an epoxy resin composition, it differs from a resin layer that is soluble in an acid or alkaline aqueous solution, a solvent, or the like. However, when an epoxy resin curing agent including an amine-based curing agent is used in an epoxy resin composition, it is believed that an acidic aqueous solution and an alkaline aqueous solution easily penetrate between the layers of the formed resin-cured layer (III), promoting dissolution of the inorganic layer (II) and facilitating delamination of the resin-cured layer (III). Unlike the techniques disclosed in Patent Documents 1 and 2, the present invention has the advantage that a plastic film can be recovered even when the laminate is contacted with an acidic aqueous solution as well as an alkaline aqueous solution. It is presumed that when the inorganic layer (II) and the resin-cured layer (III) are adjacent or close to each other, the presence of the resin-cured layer (III) facilitates penetration of an acidic or alkaline aqueous solution between the layers of the laminate, thereby facilitating recovery of the plastic film. Here, "the inorganic layer (II) and the cured resin layer (III) are adjacent to each other" means that the inorganic layer (II) and the cured resin layer (III) are separated by one or two layers.

[0015] The method of the present invention will be described below. <Laminate> The laminate defined in the present invention comprises a plastic film (I), at least one inorganic layer (II) selected from the group consisting of silicon oxide, aluminum, and aluminum oxide, and a resin-cured layer (III), wherein the resin-cured layer (III) is a cured product of an epoxy resin composition containing an epoxy resin and an epoxy resin curing agent including an amine-based curing agent.

[0016] (Plastic Film (I)) The plastic film (I) may be any plastic film commonly used for packaging materials and the like, and examples thereof include polyolefin films such as low-density polyethylene, high-density polyethylene, linear low-density polyethylene, and polypropylene; polyester films such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; polyamide films such as nylon 6, nylon 6,6, and polymetaxylylene adipamide (N-MXD6); polyimide films; biodegradable films such as polylactic acid; polyacrylonitrile films; poly(meth)acrylic films; polystyrene films; polycarbonate films; saponified ethylene-vinyl acetate copolymer (EVOH) films; and polyvinyl alcohol films. Among these, from the viewpoints of the transparency, strength, heat resistance, and resistance to acid or alkaline aqueous solutions of the laminate, the plastic film is preferably at least one selected from the group consisting of polyolefin films, polyester films, polyamide films, and polyimide films, more preferably at least one selected from the group consisting of polyolefin films and polyester films, and even more preferably at least one selected from the group consisting of polypropylene films and polyethylene terephthalate (PET) films. The above film may be unstretched or may be stretched uniaxially or biaxially.

[0017] The thickness of the plastic film (I) is not particularly limited, but is preferably 5 to 300 μm, more preferably 5 to 100 μm, and even more preferably 5 to 50 μm, from the viewpoints of transparency, strength, heat resistance, and resistance to an acid or alkaline aqueous solution used for recovering the plastic film (I). The above thickness is the thickness per sheet of the plastic film (I).

[0018] (Inorganic Layer (II)) The inorganic layer (II) is a layer made of at least one selected from the group consisting of silicon oxide, aluminum, and aluminum oxide. When the laminate has the inorganic layer (II), the plastic film (I) can be easily recovered by contacting it with an acid aqueous solution or an alkaline aqueous solution. Examples of silicon oxide include silica (SiO ｘ ), and aluminum oxide is alumina (Al ２ O ｘ ) can be exemplified. From the viewpoint of ease of recovery of the plastic film (I) using an acidic aqueous solution, the inorganic layer (II) is preferably a layer made of at least one selected from the group consisting of aluminum and aluminum oxide (alumina), more preferably a layer made of aluminum. Furthermore, from the viewpoint of ease of recovery of the plastic film (I) using an alkaline aqueous solution, the inorganic layer (II) is preferably a layer containing silica. Examples of the layer containing silica include a layer made of silica and a layer made of silica-alumina.

[0019] Examples of the inorganic layer (II) include those made of metal foil and those formed by a vapor deposition method. However, from the viewpoint of imparting gas barrier properties and the like to the laminate, it is preferably an inorganic vapor deposition layer formed by a vapor deposition method. That is, the inorganic layer (II) is more preferably at least one selected from the group consisting of a silica vapor deposition layer, an aluminum vapor deposition layer, and an alumina vapor deposition layer. From the viewpoint of ease of recovery of the plastic film (I) using an acidic aqueous solution, it is even more preferably at least one selected from the group consisting of an aluminum vapor deposition layer and an alumina vapor deposition layer, and even more preferably an aluminum vapor deposition layer. From the viewpoint of ease of recovery of the plastic film (I) using an alkaline aqueous solution, the inorganic layer (II) is preferably a vapor deposition layer containing silica, more preferably at least one selected from the group consisting of a silica vapor deposition layer and a silica-alumina binary vapor deposition layer. The thickness of the inorganic layer (II) is not particularly limited, but from the viewpoint of ease of recovery of the plastic film (I) and from the viewpoint of imparting gas barrier properties and the like, it is preferably 5 nm or more. When the inorganic layer (II) is an inorganic vapor-deposited layer, the thickness thereof is preferably 100 nm or less, more preferably 50 nm or less, from the viewpoint of improving the transparency and flex resistance of the laminate and from the viewpoint of economy. The thickness is the thickness per layer of the inorganic layer (II).

[0020] The method for forming the inorganic layer (II) is not particularly limited, and examples of vapor deposition methods include known vapor deposition methods such as physical vapor deposition methods such as vacuum deposition, sputtering, and ion plating, and chemical vapor deposition methods such as plasma chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition. The inorganic layer (II) can also be formed by laminating a metal foil such as an aluminum foil with another layer.

[0021] (Cured Resin Layer (III)) The cured resin layer (III) is a cured product of an epoxy resin composition containing an epoxy resin and an epoxy resin curing agent including an amine-based curing agent. Components contained in the epoxy resin composition will be described below.

[0022] [Epoxy Resin] The epoxy resin used in the epoxy resin composition may be any of a saturated or unsaturated aliphatic compound, alicyclic compound, aromatic compound, or heterocyclic compound. In consideration of imparting gas barrier properties, an epoxy resin containing an aromatic ring or alicyclic structure in the molecule is preferred. Specific examples of the epoxy resin include 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 novolac, and epoxy resins having a glycidyloxy group derived from resorcinol. Two or more of the above epoxy resins can also be mixed in appropriate proportions to improve various properties such as flexibility, impact resistance, and moist heat resistance. Among the above, from the viewpoint of imparting gas barrier properties, preferred epoxy resins are those containing as a main component 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 preferred are those containing as a main component an epoxy resin having a glycidylamino group derived from meta-xylylenediamine. Note that the term "main component" as used herein means that other components may be contained within the scope of the present invention, and preferably means 50 to 100% by mass, more preferably 70 to 100% by mass, and even more preferably 90 to 100% by mass of the total.

[0023] [Epoxy resin curing agent containing an amine-based curing agent] The epoxy resin curing agent used in the epoxy resin composition contains an amine-based curing agent from the viewpoint of easily recovering the plastic film (I) from the laminate and from the viewpoint of imparting gas barrier properties. As the amine-based curing agent, polyamines conventionally used as epoxy resin curing agents or modified products thereof can be used. From the viewpoint of easily recovering the plastic film (I) from the laminate, improving adhesion, and imparting gas barrier properties, the amine-based curing agent is preferably a modified product of polyamine, more preferably at least one selected from the group consisting of the following amine-based curing agents (i) and (ii), and even more preferably contains the following amine-based curing agent (i). (i) A reaction product of the following components (A) and (B): (A) At least one selected from the group consisting of metaxylylenediamine and paraxylylenediamine; (B) At least one selected from the group consisting of unsaturated carboxylic acids represented by the following general formula (1) and derivatives thereof: (In formula (1), R １ , R ２ each independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 13 carbon atoms. (ii) A reaction product of epichlorohydrin with at least one member selected from the group consisting of metaxylylenediamine and paraxylylenediamine.

[0024] <<Amine-based curing agent (i)>> The amine-based curing agent (i) is a reaction product of the following components (A) and (B). In this specification, the "reaction product of X and Y" includes not only the reaction product (adduct) of X and Y, but also by-products other than the reaction product, and unreacted raw materials such as X and Y. (A) At least one selected from the group consisting of metaxylylenediamine and paraxylylenediamine (B) At least one selected from the group consisting of unsaturated carboxylic acids represented by the following general formula (1) and derivatives thereof (In formula (1), R １ , R ２each independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 13 carbon atoms.) The component (A) is used from the viewpoints of easily recovering the plastic film (I) from the laminate, improving adhesion to other layers, and improving gas barrier properties, and metaxylylenediamine is preferred from the viewpoint of gas barrier properties. The component (A) may be used alone or in combination of two types.

[0025] The component (B) is at least one selected from the group consisting of unsaturated carboxylic acids represented by the general formula (1) and derivatives thereof, and from the viewpoints of easily recovering the plastic film (I) from the laminate, improving adhesion to other layers, and improving gas barrier properties, R in the general formula (1) １ is preferably a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, even more preferably a hydrogen atom or a methyl group, and even more preferably a hydrogen atom. ２ is preferably a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, even more preferably a hydrogen atom or a methyl group, and even more preferably a hydrogen atom.

[0026] Examples of the derivative of the unsaturated carboxylic acid represented by the general formula (1) include esters, amides, acid anhydrides, and acid chlorides of the unsaturated carboxylic acid. As the ester of the unsaturated carboxylic acid, alkyl esters are preferred, and from the viewpoint of obtaining good reactivity, the number of alkyl carbon atoms is preferably 1 to 6, more preferably 1 to 3, and even more preferably 1 to 2.

[0027] Examples of the unsaturated carboxylic acid represented by the general formula (1) and its derivatives include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, α-ethylacrylic acid, α-propylacrylic acid, α-isopropylacrylic acid, α-n-butylacrylic acid, α-t-butylacrylic acid, α-pentylacrylic acid, α-phenylacrylic acid, α-benzylacrylic acid, crotonic acid, 2-pentenoic acid, 2-hexenoic acid, 4-methyl-2-pentenoic acid, 2-heptenoic acid, 4-methyl-2-hexenoic acid, 5-methyl-2-hexenoic acid, 4,4-dimethyl-2-pentenoic acid, 4-phenyl-2-butenoic acid, cinnamic acid, o-methylcinnamic acid, m-methylcinnamic acid, p-methylcinnamic acid, and 2-octenoic acid, as well as esters, amides, acid anhydrides, and acid chlorides thereof. Among the above, from the viewpoints of easily recovering the plastic film (I) from the laminate, improving adhesion to other layers, and improving gas barrier properties, the component (B) is preferably at least one selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, and derivatives thereof, more preferably at least one selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, and alkyl esters thereof, still more preferably at least one selected from the group consisting of acrylic acid, methacrylic acid, and alkyl esters thereof, even more preferably alkyl esters of acrylic acid, and even more preferably methyl acrylate. The component (B) may be used singly or in combination of two or more.

[0028] When an unsaturated carboxylic acid, ester, or amide is used as component (B), the reaction between component (A) and component (B) is carried out by mixing component (A) and component (B) at a temperature of 0 to 100°C, more preferably 0 to 70°C, and then carrying out a Michael addition reaction and an amide group-forming reaction by dehydration, dealcoholization, and deamination at a temperature of 100 to 300°C, preferably 130 to 250°C. In this case, during the amide group-forming reaction, the reactor may be depressurized at the final stage of the reaction, if necessary, to complete the reaction. Furthermore, the reaction mixture may be diluted with a nonreactive solvent, if necessary. Furthermore, a catalyst such as a phosphite ester may be added as a dehydrating agent or a dealcoholizing agent.

[0029] On the other hand, when an acid anhydride or acid chloride of an unsaturated carboxylic acid is used as component (B), the components are mixed at a temperature of 0 to 150°C, preferably 0 to 100°C, followed by the Michael addition reaction and the amide group formation reaction. In this case, during the amide group formation reaction, the reactor may be decompressed as needed in the final stage of the reaction to complete the reaction. Furthermore, the reaction may be diluted with a non-reactive solvent as needed. Furthermore, a tertiary amine such as pyridine, picoline, lutidine, or trialkylamine may also be added.

[0030] The amide group moiety formed by the reaction between the component (A) and the component (B) has high cohesive strength, and therefore the resin-cured layer (III) formed using the epoxy resin composition containing the epoxy resin curing agent that is the reaction product between the component (A) and the component (B) has high gas barrier properties and good adhesiveness.

[0031] The reaction molar ratio of the component (B) to the component (A) [(B) / (A)] is preferably in the range of 0.3 to 1.0. When the reaction molar ratio is 0.3 or more, a sufficient amount of amide groups is generated in the epoxy resin curing agent, resulting in a high level of gas barrier properties. On the other hand, when the reaction molar ratio is in the range of 1.0 or less, the amount of amino groups necessary for reaction with the epoxy groups in the epoxy resin is sufficient, resulting in excellent heat resistance and excellent solubility in organic solvents and water. When particular consideration is given to improving gas barrier properties, the reaction molar ratio of the component (B) to the component (A) [(B) / (A)] is more preferably in the range of 0.6 to 1.0.

[0032] The amine-based curing agent may be a reaction product of the components (A) and (B) and at least one compound selected from the group consisting of the following components (C), (D), and (E): ３ At least one (R ３represents a hydrogen atom, an alkyl group having 1 to 7 carbon atoms which may have a hydroxyl group, or an aryl group having 6 to 12 carbon atoms.) (D) a cyclic carbonate (E) a monoepoxy compound having 2 to 20 carbon atoms

[0033] The component (C), R ３ The monocarboxylic acid represented by —COOH and its derivatives are used as needed to reduce the reactivity between the epoxy resin curing agent and the epoxy resin, thereby improving workability. ３ represents a hydrogen atom, an alkyl group having 1 to 7 carbon atoms which may have a hydroxyl group, or an aryl group having 6 to 12 carbon atoms; R ３ is preferably an alkyl group having 1 to 3 carbon atoms or a phenyl group. ３ Derivatives of monocarboxylic acids represented by -COOH include, for example, esters, amides, acid anhydrides, and acid chlorides of the carboxylic acids. The esters of the carboxylic acids are preferably alkyl esters, and the number of alkyl carbon atoms is preferably 1 to 6, more preferably 1 to 3, and even more preferably 1 to 2. Examples of the component (C) include monocarboxylic acids and derivatives thereof, such as formic acid, acetic acid, propionic acid, butyric acid, lactic acid, glycolic acid, and benzoic acid. The component (C) may be used singly or in combination of two or more.

[0034] The cyclic carbonate of component (D) is used as needed to reduce the reactivity between the epoxy resin curing agent and the epoxy resin and improve workability. From the viewpoint of reactivity with component (A), it is preferably a cyclic carbonate having a six-membered ring or less. Examples include ethylene carbonate, propylene carbonate, glycerin carbonate, 1,2-butylene carbonate, vinylene carbonate, 4-vinyl-1,3-dioxolan-2-one, 4-methoxymethyl-1,3-dioxolan-2-one, and 1,3-dioxan-2-one. Among these, from the viewpoint of improving gas barrier properties, at least one selected from the group consisting of ethylene carbonate, propylene carbonate, and glycerin carbonate is preferred. One type of component (D) may be used alone, or two or more types may be used in combination.

[0035] The monoepoxy compound of component (E) is a monoepoxy compound having 2 to 20 carbon atoms, and is used as needed from the viewpoint of reducing the reactivity between the epoxy resin curing agent and the epoxy resin and improving workability. From the viewpoint of gas barrier properties, a monoepoxy compound having 2 to 10 carbon atoms is preferred, and a compound represented by the following formula (2) is more preferred.

[0036] (In formula (2), R ４ is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group, or R ５ -O-CH ２ represents -, and R ５ represents a phenyl group or a benzyl group.) Examples of the monoepoxy compound represented by formula (2) include ethylene oxide, propylene oxide, 1,2-butylene oxide, styrene oxide, phenyl glycidyl ether, and benzyl glycidyl ether. The component (E) may be used alone or in combination of two or more.

[0037] When the component (C), component (D), or component (E) is used as the amine-based curing agent, any one compound selected from the group consisting of the component (C), component (D), and component (E) may be used alone, or two or more types may be used in combination.

[0038] The amine-based curing agent may be a reaction product obtained by reacting other components in addition to the components (A) to (E) as long as the effects of the present invention are not impaired. Examples of other components include aromatic dicarboxylic acids and derivatives thereof. However, the amount of the "other components" used is preferably 30% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less of the total amount of the reaction components constituting the amine-based curing agent.

[0039] The reaction product of the components (A) and (B) and at least one compound selected from the group consisting of the components (C), (D), and (E) can be obtained by reacting the component (A), which is a polyamine compound, with at least one compound selected from the group consisting of the components (C), (D), and (E) in combination with the component (B). The reaction can be carried out by adding the components (B) to (E) in any order and reacting them with the component (A), or by mixing the components (B) to (E) and reacting them with the component (A). The reaction between the component (A) and the component (C) can be carried out under the same conditions as the reaction between the component (A) and the component (B). When the component (C) is used, the components (B) and (C) can be mixed and reacted with the component (A), or the components (A) and (B) can be reacted first and then the component (C) can be reacted. On the other hand, when using the component (D) and / or component (E), it is preferable to first react the component (A) with the component (B), and then react the component (D) and / or component (E). The reaction between the component (A) and the component (D) and / or component (E) is carried out by mixing the component (A) with the component (D) and / or component (E) at 25 to 200°C, and then carrying out an addition reaction at 30 to 180°C, preferably 40 to 170°C. If necessary, a catalyst such as sodium methoxide, sodium ethoxide, or potassium t-butoxide can be used. During the above reaction, the component (D) and / or component (E) can be melted or diluted with a non-reactive solvent as needed to promote the reaction.

[0040] Even when the amine curing agent is a reaction product of the components (A) and (B) with at least one compound selected from the group consisting of the components (C), (D), and (E), the reaction molar ratio of the component (B) to the component (A) [(B) / (A)] is preferably in the range of 0.3 to 1.0, and more preferably in the range of 0.6 to 1.0, for the same reasons as above. On the other hand, the reaction molar ratio of the components (C), (D), and (E) to the component (A) [{(C)+(D)+(E)} / (A)] is preferably in the range of 0.05 to 3.1, more preferably in the range of 0.07 to 2.5, and even more preferably in the range of 0.1 to 2.0. However, from the viewpoint of improving the gas barrier property, the reaction molar ratio of the components (B) to (E) to the component (A), [{(B)+(C)+(D)+(E)} / (A)], is preferably in the range of 0.35 to 2.5, and more preferably in the range of 0.35 to 2.0.

[0041] From the viewpoint of easily recovering the plastic film (I) from the laminate and from the viewpoint of imparting gas barrier properties, the amine-based curing agent (i) is more preferably a reaction product obtained by reacting only the component (A) and the component (B).

[0042] (Amine-based curing agent (ii)) The amine-based curing agent (ii) is a reaction product of epichlorohydrin and at least one selected from the group consisting of metaxylylenediamine and paraxylylenediamine. The amine-based curing agent (ii) preferably contains a compound represented by the following general formula (3) as a main component. The "main component" here refers to a component whose content is 50% by mass or more when the total amount of all components in the amine-based curing agent (ii) is taken as 100% by mass. (In formula (3), A is a 1,3-phenylene group or a 1,4-phenylene group. n is a number from 1 to 12.) It is more preferable that A is a 1,3-phenylene group. The content of the compound represented by the general formula (3) in the amine curing agent (ii) is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 75% by mass or more, and even more preferably 85% by mass or more. The upper limit is 100% by mass. From the viewpoint of obtaining good curing performance as a curing agent, it is preferable that the proportion of the compound represented by the general formula (3) where n = 1 is high. The content of the compound represented by the general formula (3) where n = 1 in the amine curing agent (ii) is preferably 15% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more. The upper limit is 100% by mass. The content of the compound represented by the general formula (3) in the amine curing agent (ii) and the composition of the compound represented by the general formula (3) can be determined by GC analysis and gel permeation chromatography (GPC) analysis.

[0043] The amine curing agent (ii) can be obtained by subjecting epichlorohydrin to an addition reaction with at least one member selected from the group consisting of metaxylylenediamine and paraxylylenediamine in a conventional manner.

[0044] The total content of the amine curing agent (i) and the amine curing agent (ii) in the amine curing agent is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and still more preferably 90% by mass or more, but 100% by mass or less, from the viewpoint of easily recovering the plastic film (I) from the laminate and from the viewpoint of imparting gas barrier properties.

[0045] The epoxy resin curing agent may contain a curing agent component other than the amine-based curing agent, but from the viewpoints of easily recovering the plastic film (I) from the laminate, improving adhesion to other layers, and improving gas barrier properties, a high content of the amine-based curing agent is preferred. From the above viewpoints, the content of the amine-based curing agent in the epoxy resin curing agent is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and still more preferably 90% by mass or more, and is 100% by mass or less.

[0046] In the epoxy resin composition, the content ratio of the epoxy resin to the epoxy resin curing agent is such that the ratio of the number of active hydrogens in the epoxy resin curing agent to the number of epoxy groups in the epoxy resin (number of active hydrogens in the epoxy resin curing agent / number of epoxy groups in the epoxy resin) is preferably in the range of 0.2 to 12.0, more preferably 0.2 to 10.0, from the viewpoints of easily recovering the plastic film (I) from the laminate, improving adhesion to other layers, and improving gas barrier properties; and from the viewpoints of easily peeling the resin-cured layer (III) from the laminate when it comes into contact with an acid or alkaline aqueous solution and more easily recovering the plastic film (I), the ratio is still more preferably in the range of 0.2 to 8.0, even more preferably 0.2 to 5.0, still more preferably 0.5 to 5.0, and still more preferably 0.8 to 5.0.

[0047] The epoxy resin composition may further contain a coupling agent from the viewpoint of improving adhesion between the resulting cured resin layer (III) and other layers. Examples of such coupling agents include silane coupling agents, titanate-based coupling agents, and aluminate-based coupling agents. Silane coupling agents are preferred from the viewpoint of improving adhesion between other layers. Examples of silane coupling agents include silane coupling agents having a vinyl group, silane coupling agents having an amino group, silane coupling agents having an epoxy group, silane coupling agents having a (meth)acrylic group, and silane coupling agents having a mercapto group. Among these, from the viewpoint of improving adhesion between the resulting cured resin layer (III) and other layers, at least one selected from the group consisting of silane coupling agents having an amino group and silane coupling agents having an epoxy group is preferred. When a coupling agent is used, the content of the coupling agent in the epoxy resin composition is preferably 0.1 to 10 parts by mass, more preferably 1 to 8 parts by mass, per 100 parts by mass of the epoxy resin curing agent.

[0048] The epoxy resin composition may contain an organic solvent, and the organic solvent is preferably a non-reactive solvent. Specific examples of such organic solvents include protic polar solvents such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol, 2-butoxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, and 1-propoxy-2-propanol, as well as ethyl acetate, butyl acetate, methyl isobutyl ketone, and toluene. Among these, at least one solvent selected from the group consisting of methanol, ethanol, and ethyl acetate is preferred from the viewpoint of improving the drying rate.

[0049] When the epoxy resin composition contains an organic solvent, the solids concentration of the epoxy resin composition is not particularly limited, but from the viewpoint of coatability, it is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more. From the viewpoint of coatability and adjusting the thickness of the resulting cured resin layer (III) to a desired value, it is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less.

[0050] The epoxy resin composition may contain additives such as thermosetting resins, wetting agents, tackifiers, antifoaming agents, curing accelerators, rust-preventive additives, pigments, oxygen scavengers, etc., as needed, within the scope of not impairing the effects of the present invention. From the viewpoint of achieving higher adhesiveness, the total content of the above additives in the epoxy resin composition is preferably 20.0 parts by mass or less, more preferably 0.001 to 15.0 parts by mass, per 100 parts by mass of the total amount of the epoxy resin and epoxy resin curing agent.

[0051] However, from the viewpoint of obtaining the effects of the present invention, the total content of the epoxy resin and the epoxy resin curing agent in the solid content of the epoxy resin composition is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and still more preferably 85% by mass or more, with the upper limit being 100% by mass. The "solid content of the epoxy resin composition" means the components in the epoxy resin composition excluding water and organic solvents.

[0052] From the viewpoint of exhibiting higher adhesiveness in the resulting cured resin layer (III), the epoxy resin composition preferably has a low lubricant content. Specifically, the content of the lubricant in the epoxy resin composition is preferably less than 10 parts by mass, more preferably less than 5 parts by mass, even more preferably less than 2 parts by mass, still more preferably less than 1 part by mass, even more preferably less than 0.1 parts by mass, still more preferably less than 0.01 parts by mass, and even more preferably 0 part by mass, relative to 100 parts by mass of the total amount of the epoxy resin and epoxy resin curing agent in the epoxy resin composition. The lubricant includes not only components conventionally known as lubricants, but also unsaturated fatty acid amides having 14 to 24 carbon atoms, such as erucic acid amide and oleic acid amide.

[0053] From the viewpoint of exhibiting higher adhesiveness in the obtained cured resin layer (III), the epoxy resin composition preferably contains a small amount of filler, such as organic or inorganic powder, organic or inorganic fiber, etc. Specifically, the content of the filler in the epoxy resin composition is preferably less than 10 parts by mass, more preferably less than 5 parts by mass, even more preferably less than 2 parts by mass, still more preferably less than 1 part by mass, still more preferably less than 0.1 parts by mass, still more preferably less than 0.01 parts by mass, and still more preferably 0 part by mass, relative to 100 parts by mass of the total amount of the epoxy resin and the epoxy resin curing agent in the epoxy resin composition.

[0054] (Preparation of Epoxy Resin Composition) The epoxy resin composition can be prepared, for example, by blending predetermined amounts of an epoxy resin, an epoxy resin curing agent including an amine-based curing agent, and optionally additives and an organic solvent, and then stirring and mixing the mixture using a known method and apparatus. The epoxy resin and the epoxy resin curing agent may be mixed immediately before use.

[0055] (Formation of cured resin layer (III)) The cured resin layer (III) is formed using the epoxy resin composition. The epoxy resin composition is a thermosetting resin composition containing the epoxy resin and the epoxy resin curing agent. For example, in the production of a laminate, the epoxy resin composition is applied to a plastic film (I) or another layer, and after removing the organic solvent as necessary, another plastic film or layer is laminated, followed by curing to form the cured resin layer (III). The method for curing the epoxy resin composition is not particularly limited, and is carried out by a known method at a concentration and temperature of the epoxy resin composition sufficient to obtain the cured product. Details of the method for forming the cured resin layer (III) will be described later in the section "Method for producing a laminate."

[0056] From the viewpoint of improving adhesiveness and facilitating recovery of the plastic film (I) from the laminate, the thickness of the cured resin layer (III) is preferably 0.05 to 20 μm, more preferably 0.1 to 15 μm, even more preferably 0.2 to 10 μm, still more preferably 0.5 to 7 μm, still more preferably 1 to 5 μm, and still more preferably 2 to 5 μm. The above thickness is the thickness per layer of the cured resin layer (III).

[0057] (Layer structure of laminate) The laminate used in the present invention may have one or more of the plastic film (I), inorganic layer (II), and resin cured layer (III), and may have two or more. When the laminate has two or more plastic films (I), inorganic layers (II), and resin cured layers (III), the types and thicknesses of the multiple plastic films (I) may be the same or different. The same applies to the types and thicknesses of the inorganic layer (II) and the resin cured layer (III). Note that when two or more plastic films (I) are included, from the viewpoint of ease of recovery of the plastic films (I), it is preferable that the resins constituting all of the plastic films (I) are the same type of resin.

[0058] The stacking order of the plastic film (I), the inorganic layer (II), and the cured resin layer (III) is not particularly limited, but the laminate preferably includes two or more plastic films (I). From the viewpoint of easily recovering the plastic film (I) from the laminate, it is preferable that the inorganic layer (II) and the cured resin layer (III) are stacked between any two plastic films (I).

[0059] The laminate may have layers other than the plastic film (I), the inorganic layer (II), and the resin-cured layer (III). Examples of such layers include a primer layer, an anchor coat layer, an overcoat layer, an ink layer, a thermoplastic resin layer other than the plastic film (I), a resin-cured layer that is a cured product of a photocurable or thermosetting resin composition, and an adhesive layer other than the resin-cured layer (III). One or more of these may be included. Among the above, for example, when a laminate derived from a packaging material is used, the laminate may further include an ink layer. Examples of the ink layer include a colored layer formed with an ink containing a colorant and a medium layer formed with an ink not containing a colorant.

[0060] The colored layer of the ink layer can be formed using a printing ink containing a colorant such as a pigment and a binder resin. The medium layer can be formed using a printing ink (medium) that does not contain a colorant. The ink layer may be formed over the entire surface of the laminate, or may be formed partially. In addition, the ink layer may be provided with letters, logos, patterns, etc.

[0061] The thickness of the ink layer is usually 0.05 to 20 μm, preferably 0.1 to 15 μm, more preferably 0.2 to 5 μm, and even more preferably 0.4 to 2 μm. The above thickness is the thickness per ink layer.

[0062] The ink layer is preferably formed by a known printing method using a printing ink. Examples of such a printing method include gravure printing, flexographic printing, and screen printing, with gravure printing being preferred from the viewpoint of productivity.

[0063] Examples of laminates containing two or more plastic films (I) include laminates having a plastic film (I), an inorganic layer (II), a cured resin layer (III), and a plastic film (I) in this order. Preferred layer structures of laminates containing two or more plastic films (I) are as follows: In the following description, when it is written as I / II / III, it means that the layers are laminated in the order of I, II, and III from the top. (1): Plastic film (I) / inorganic layer (II) / resin cured layer (III) / plastic film (I) (2): Plastic film (I) / inorganic layer (II) / colored layer / medium layer / resin cured layer (III) / plastic film (I) (3): Plastic film (I) / colored layer / medium layer / resin cured layer (III) / inorganic layer (II) / plastic film (I) (4): Plastic film (I) / adhesive layer / resin cured layer (III) / inorganic layer (II) / plastic film (I) (5): Plastic film (I) / resin cured layer (III) / adhesive layer / inorganic layer (II) / plastic film (I) (6): Plastic film (I) / inorganic layer (II) / colored layer / medium layer / resin cured layer (III) / adhesive layer / plastic film (I) (7): Plastic film (I) / colored layer / medium layer / adhesive layer / resin cured layer (III) / inorganic layer (II) / plastic film (I) (8): Plastic film (I) / inorganic layer (II) / resin cured layer (III) / inorganic layer (II) / plastic film (I) (9): Plastic film (I) / inorganic layer (II) / colored layer / medium layer / resin cured layer (III) / inorganic layer (II) / plastic film (I) (10) Plastic film (I) / inorganic layer (II) / adhesive layer / resin cured layer (III) / inorganic layer (II) / plastic film (I)

[0064] However, the layer structure of the laminate is not limited to the above, and may have a primer layer, an anchor coat layer, an overcoat layer, etc. between any of the above layers. Furthermore, the laminate is not limited to the structures (8) to (10), and may include two or more inorganic layers (II), and may also include two or more resin-cured layers (III).

[0065] From the viewpoint of easily recovering the plastic film (I) from the laminate, the laminate preferably has a configuration in which the inorganic layer (II) and the cured resin layer (III) are adjacent to each other or separated by one or two layers, more preferably has a configuration in which the inorganic layer (II) and the cured resin layer (III) are adjacent to each other or separated by only one layer, and further preferably has the inorganic layer (II) and the cured resin layer (III) be adjacent to each other.

[0066] The laminate may be in the form of a film, or may be in the form of a bag, a bottle, a lid material thereof, a sealing material, a cylindrical plastic label, or the like, as long as it has a laminate structure including the plastic film (I), the inorganic layer (II), and the cured resin layer (III).

[0067] <Method for manufacturing laminate> The method for manufacturing the laminate is not particularly limited, and known methods can be used. For example, a method for manufacturing a laminate having the structure (1): plastic film (I) / inorganic layer (II) / cured resin layer (III) / plastic film (I) can be exemplified by forming an inorganic layer (II) on one side of one of the plastic films (I) by the method described above, applying the epoxy resin composition to the surface of the inorganic layer (II) to a desired thickness, immediately laminating another plastic film (I) to the coated surface using a nip roll or the like, and then curing the epoxy resin composition by the method described above to form a cured resin layer (III). It is also possible to form a cured resin layer (III) on the surface of the inorganic layer (II) using a film in which an inorganic layer (II) has already been formed on the plastic film (I). Examples of the coating method for applying the epoxy resin composition include bar coating, Mayer bar coating, air knife coating, gravure coating, reverse gravure coating, microgravure coating, microreverse gravure coating, die coating, slot die coating, vacuum die coating, dip coating, spin coating, roll coating, spray coating, brush coating, etc. Among these, bar coating, roll coating, and spray coating are preferred, and industrially, gravure coating, reverse gravure coating, microgravure coating, and microreverse gravure coating are preferred.

[0068] After applying the epoxy resin composition, a step of volatilizing the solvent (drying step) is carried out as needed. The conditions for the drying step can be selected appropriately, but for example, the drying step can be carried out under conditions of a drying temperature of 40 to 180°C and a drying time of 5 to 180 seconds. After the drying step, the epoxy resin composition is cured to form a cured resin layer (III). The curing temperature can be selected, for example, from 10 to 140°C, and preferably from 10 to 80°C. The curing time can be selected, for example, from 1 minute to 7 days, and preferably from 2 to 100 hours.

[0069] <Aqueous Acid or Alkaline Solution> The method of the present invention includes a step of contacting the laminate with an aqueous acid or an aqueous alkali solution. The acid used in the aqueous acid solution may be either an inorganic acid or an organic acid. Examples of inorganic acids include hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid. Examples of organic acids include carboxylic acid compounds, sulfonic acid compounds, and organic phosphoric acid compounds. From the viewpoint of easily recovering the plastic film (I) from the laminate, at least one selected from the group consisting of carboxylic acid compounds and sulfonic acid compounds is preferred. Examples of carboxylic acid compounds include formic acid, acetic acid, citric acid, malic acid, lactic acid, adipic acid, sebacic acid, stearic acid, maleic acid, succinic acid, tartaric acid, fumaric acid, and gluconic acid. Examples of sulfonic acid compounds include methanesulfonic acid, ethanesulfonic acid, and p-toluenesulfonic acid.

[0070] Among the above, from the viewpoint of easily recovering the plastic film (I) from the laminate and from the viewpoint of economy, the acid used in the acid aqueous solution is preferably at least one selected from the group consisting of hydrochloric acid and carboxylic acid compounds, more preferably at least one selected from the group consisting of hydrochloric acid, acetic acid, citric acid, and lactic acid, still more preferably at least one selected from the group consisting of hydrochloric acid, acetic acid, and lactic acid, and even more preferably at least one selected from the group consisting of acetic acid and lactic acid.

[0071] The concentration of the acid in the acid aqueous solution is preferably 0.1 to 4 N, more preferably 0.2 to 3 N, and even more preferably 0.5 to 2 N, from the viewpoint of easily recovering the plastic film (I) from the laminate and from the viewpoint of suppressing deterioration of the plastic film (I).

[0072] The pH of the aqueous acid solution at 25°C is preferably 6.0 or less, more preferably 5.0 or less, even more preferably 4.0 or less, and even more preferably 3.0 or less, from the viewpoint of easily recovering the plastic film (I) from the laminate, and is preferably 0.2 or more, more preferably 0.5 or more, even more preferably 1.0 or more, and even more preferably 1.8 or more, from the viewpoint of easily recovering the plastic film (I) from the laminate and from the viewpoint of suppressing deterioration of the plastic film (I).

[0073] The alkaline compound used in the alkaline aqueous solution may be either an inorganic alkaline compound or an organic alkaline compound. Examples of inorganic alkaline compounds include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; alkali metal carbonates or bicarbonates such as lithium carbonate, lithium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate, sodium carbonate, and sodium hydrogen carbonate; and ammonia. Examples of organic alkaline compounds include amine compounds and tetraalkylammonium hydroxides. Examples of amine compounds include alkanolamines, alkylamines, and aralkylamines. From the viewpoint of water solubility, the carbon number of these compounds is preferably 10 or less, more preferably 8 or less. Examples of alkanolamines include mono-, di-, or trimethanolamine, and mono-, di-, or triethanolamine. Examples of alkylamines include methylamine, dimethylamine, ethylamine, diethylamine, N-methylethylamine, propylamine, and butylamine. Examples of aralkylamines include benzylamine. Examples of tetraalkylammonium hydroxides include tetramethylammonium hydroxide and tetraethylammonium hydroxide.

[0074] The alkali compounds may be used alone or in combination of two or more thereof. Among them, from the viewpoint of easy recovery of the plastic film (I) from the laminate and from the viewpoint of economy, the alkali compound used in the alkaline aqueous solution is preferably an inorganic alkali compound, more preferably an alkali metal hydroxide, and still more preferably at least one selected from the group consisting of sodium hydroxide and potassium hydroxide.

[0075] The concentration of the alkaline compound in the alkaline aqueous solution varies depending on the type of alkaline compound, but from the viewpoint of easily recovering the plastic film (I) from the laminate and suppressing deterioration of the plastic film (I), it is preferably 0.1 to 20 mass%, more preferably 1 to 15 mass%, and even more preferably 2 to 10 mass%.

[0076] The pH of the alkaline aqueous solution at 25°C is preferably 8.0 or more, more preferably 9.0 or more, and even more preferably 10.0 or more from the viewpoint of easily recovering the plastic film (I) from the laminate, and is preferably 15.0 or less from the viewpoint of suppressing deterioration of the plastic film (I).

[0077] From the viewpoint of easier recovery of the plastic film (I) from the laminate, particularly when the inorganic layer (II) is a layer made of at least one selected from the group consisting of aluminum and aluminum oxide (alumina), the method of the present invention preferably includes a step of contacting the laminate with an acid aqueous solution, and more preferably includes a step of immersing the laminate in an acid aqueous solution.

[0078] Methods for contacting the laminate with an acidic or alkaline aqueous solution include immersion, spraying, casting, etc., but immersion is preferred from the viewpoint of easily recovering the plastic film (I) from the laminate. The temperature of the aqueous solution when the laminate is contacted with the acidic or alkaline aqueous solution is not particularly limited, but from the viewpoint of easily recovering the plastic film (I) from the laminate and suppressing deterioration of the plastic film (I), it is preferably 5 to 90°C, more preferably 5 to 70°C, even more preferably 10 to 60°C, and still more preferably 15 to 45°C. The time for which the laminate is contacted with the acidic or alkaline aqueous solution is also not particularly limited, but from the viewpoint of recovery efficiency of the plastic film (I), it is preferably 30 minutes to 7 days, more preferably 1 hour to 5 days.

[0079] When the laminate is brought into contact with the aqueous acid solution or the aqueous alkali solution, the amount of the aqueous acid solution or the aqueous alkali solution used is preferably 2 to 2,000 times, more preferably 2 to 500 times, and even more preferably 2 to 100 times the mass of the laminate, from the viewpoint of easy recovery of the plastic film (I) from the laminate and from the viewpoint of economy.

[0080] The laminate after contact with the aqueous acid solution or the aqueous alkali solution, and the plastic film (I) peeled from the laminate, can be washed with water, dried, and recovered.

[0081] In the method of the present invention, it is determined that recovery of a plastic film is easy when, in a laminate containing only one plastic film (I), the film is separable from one or more other layers (preferably the inorganic layer (II)), and when, in a laminate containing two or more plastic films (I), the films are separable from each other. Other layers may remain on the separated plastic film (I), and in this case, the method of the present invention may further include a step of removing the other layers. For example, if the ink layer remains on the plastic film (I), the ink layer can be easily removed by a known deinking process.

[0082] The present invention will now be described in detail with reference to examples, although the present invention is not limited to these examples in any way.

[0083] Production Example 1 (Preparation of Epoxy Resin Curing Agent Solution A Containing an Amine-Based Curing Agent) 1 mol of metaxylylenediamine (MXDA) was charged into a reaction vessel. The temperature was raised to 60°C under a nitrogen stream, and 0.93 mol of methyl acrylate was added dropwise over 1 hour. The temperature was raised to 165°C while distilling off the resulting methanol, and the temperature was maintained at 165°C for 2.5 hours to obtain an amine-based curing agent. Methanol was added dropwise thereto over 1.5 hours, and then 3-aminopropyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., "KBE-903"), a silane coupling agent, was added to obtain an epoxy resin curing agent solution A containing 62.2% by mass of the amine-based curing agent, 2.8% by mass of 3-aminopropyltriethoxysilane, and 35% by mass of methanol.

[0084] Production Example 2 (Preparation of Epoxy Resin Curing Agent Solution B Containing Amine-Based Curing Agent) 1 mol of metaxylylenediamine (MXDA) was charged into a reaction vessel. The temperature was raised to 60°C under a nitrogen stream, and 0.93 mol of methyl acrylate was added dropwise over 1 hour. The temperature was raised to 165°C while distilling off the resulting methanol, and the temperature was maintained at 165°C for 2.5 hours to obtain an amine-based curing agent. Industrial ethanol ("Econol H" manufactured by Imazu Pharmaceutical Co., Ltd.) was added dropwise over 1.5 hours, and then 3-aminopropyltriethoxysilane ("KBE-903" manufactured by Shin-Etsu Chemical Co., Ltd.), a silane coupling agent, was added to prepare a solution containing 62.2% by mass of the amine-based curing agent, 2.8% by mass of 3-aminopropyltriethoxysilane, and 35% by mass of ethanol. 35.2 g of ethanol and 42.6 g of ethyl acetate as dilution solvents and 21.2 g of the above solution were added and stirred, and 1 g of erucic acid amide was added thereto and stirred to obtain an epoxy resin curing agent solution B with a solid content concentration of 14.7 mass %.

[0085] Production Example 3 (Preparation of Epoxy Resin Composition A) 1.98 g of methanol and 3.25 g of ethyl acetate, which were used as dilution solvents, and 3.64 g of the epoxy resin curing agent solution A obtained in Production Example 1 were added and stirred. To this solution, 1.13 g of an epoxy resin having a glycidylamino group derived from metaxylylenediamine ("TETRAD-X" manufactured by Mitsubishi Gas Chemical Company, Inc.) (number of active hydrogens in the epoxy resin curing agent / number of epoxy groups in the epoxy resin=1.2) was added and stirred to prepare an epoxy resin composition A for forming a resin-cured layer (III)-1 with a solids concentration of 35 mass %.

[0086] Production Example 4 (Preparation of Epoxy Resin Composition B) 1.56 g of methanol and 3.25 g of ethyl acetate, which were used as dilution solvents, and 4.83 g of the epoxy resin curing agent solution A obtained in Production Example 1 were added and stirred. To this solution, 0.36 g of an epoxy resin having a glycidylamino group derived from metaxylylenediamine ("TETRAD-X" manufactured by Mitsubishi Gas Chemical Company, Inc.) (number of active hydrogens in the epoxy resin curing agent / number of epoxy groups in the epoxy resin=5.0) was added and stirred to prepare an epoxy resin composition B for forming the resin-cured layer (III)-2 with a solids concentration of 35% by mass.

[0087] Production Example 5 (Preparation of Epoxy Resin Composition C) 2.15 g of methanol and 3.25 g of ethyl acetate as dilution solvents, and 3.13 g of the epoxy resin curing agent solution A obtained in Production Example 1 were added and stirred to this solution, and 1.46 g of an epoxy resin having a glycidylamino group derived from metaxylylenediamine ("TETRAD-X" manufactured by Mitsubishi Gas Chemical Company, Inc.) (number of active hydrogens in the epoxy resin curing agent / number of epoxy groups in the epoxy resin=0.8) was added as the epoxy resin and stirred to prepare an epoxy resin composition C for forming a resin-cured layer (III)-3 with a solids concentration of 35 mass %.

[0088] Production Example 6 (Preparation of Epoxy Resin Composition D) 8.83 g of ethanol as a dilution solvent and 1.14 g of the epoxy resin curing agent solution B obtained in Production Example 2 were added and stirred. To this solution, 0.03 g of an epoxy resin having a glycidylamino group derived from metaxylylenediamine ("TETRAD-X" manufactured by Mitsubishi Gas Chemical Company, Inc.) (number of active hydrogens in the epoxy resin curing agent / number of epoxy groups in the epoxy resin=3.0) was added and stirred to prepare an epoxy resin composition D for forming a resin-cured layer (III)-4 with a solids concentration of 2% by mass.

[0089] Example 1 (Preparation of Laminate and Recovery of Plastic Film) (Preparation of Laminate) A laminate having the layer structure shown in Table 1 was prepared by the following procedure. A white ink (Sakata Inx Corporation's "Bellcolor R115" diluted two-fold with a diluting solvent (Sakata Inx Corporation's "L Solvent")) was applied to one side of a biaxially oriented polypropylene film (OPP) (Futamura Chemical Co., Ltd., thickness: 25 μm) using a bar coater No. 8, and dried by heating at 80°C for 10 seconds (thickness after drying: approximately 0.5 μm) to form a colored layer. A reverse printing gravure ink (Sakata Inx Corporation's "Bellflora R Medium" diluted two-fold with a diluting solvent (Sakata Inx Corporation's "K Solvent")) was applied to the colored layer using a bar coater No. The epoxy resin composition was applied onto the medium layer using a bar coater No. 8, heated at 80°C for 10 seconds, and dried (thickness after drying: approximately 0.5 μm), forming a medium layer. In the tables below, the colored layer and medium layer are collectively referred to as the "ink layer." Next, the epoxy resin composition A obtained in Production Example 3 was applied onto the medium layer using a bar coater No. 8, and heated at 80°C for 10 seconds and dried (thickness after drying: approximately 3 μm). The coated surface of the epoxy resin composition and the aluminum-vapor-deposited surface of an aluminum-vapor-deposited CPP ("S-F-1" manufactured by Nakai Industrial Co., Ltd., thickness: 25 μm), in which aluminum was vapor-deposited on one side of the non-oriented polypropylene film (CPP), were placed opposite each other and bonded together using a nip roll. The resulting mixture was heated at 40°C for 2 days to form a cured resin layer (III)-1, thereby obtaining a laminate having the layer structure shown in Table 1.

[0090] (Recovery and Evaluation of Plastic Film) The prepared laminate was cut into strips of 1.5 cm x 5 cm, and one strip of the laminate was immersed in a 1N acetic acid aqueous solution (approximately 10 g) at 40°C for 16 hours. After immersion, the laminate was recovered and evaluated as follows. <Peeled Interface> The laminate recovered after immersion in the 1N acetic acid aqueous solution was visually observed to determine at which layer interface peeling had occurred, and the results are shown in Table 1. The "Peeled Interface" listed in Table 1 indicates that peeling occurred at the interface indicated by " / / ".

[0091] <State of Vapor-Deposited Layer> The presence or absence of dissolution of the aluminum vapor-deposited layer in the laminate was visually observed, and the results are shown in Table 1. In the table, when it was found that at least a part of the vapor-deposited layer had dissolved, it was recorded as "dissolved."

[0092] <Separation of CPP> The state of separation of the CPP film from the laminate was evaluated according to the following criteria, and the results are shown in Table 1. [Evaluation criteria] A: The CPP film peeled off from the laminate, and elemental analysis of the surface of the recovered CPP film by SEM-EDX (scanning electron microscope-energy dispersive X-ray spectroscopy) measurement showed that no aluminum remained on the film surface. B: The CPP film peeled off from the laminate, but aluminum remained on the surface of the recovered CPP film. C: The CPP film did not peel off from the laminate and could not be recovered. [SEM-EDX measurement conditions] Equipment used: Scanning electron microscope "SU-8020" manufactured by Hitachi High-Tech Corporation Measurement conditions: Acceleration voltage 10 kV Probe current 10 μA, High Condenser lens 1.1 Working distance 15 mm Conductive treatment Au-Pd vapor deposition

[0093] <Separation of OPP + ink layer> The state of separation of the OPP film + ink layer of the laminate recovered after immersion in a 1N-acetic acid aqueous solution was visually observed and evaluated according to the following criteria, and the results are shown in Table 1. [Evaluation criteria] A: The OPP film + ink layer peeled off from the laminate, and the cured resin layer did not remain on the ink layer B: The OPP film + ink layer peeled off from the laminate, but the cured resin layer remained on the ink layer C: The OPP film + ink layer peeled off from the laminate, but the cured resin layer and a part of the vapor-deposited layer remained on the ink layer D: The OPP film + ink layer did not peel off from the laminate, and recovery was not possible

[0094] Examples 2 to 4 Evaluations were carried out in the same manner as in Example 1, except that the aqueous solution in which the laminate was immersed was changed to one shown in Table 1. The results are shown in Table 1.

[0095] Example 5 A laminate having the layer structure shown in Table 1 was prepared and evaluated in the same manner as in Example 1, except that the epoxy resin composition B obtained in Production Example 4 was used instead of the epoxy resin composition A obtained in Production Example 3. The results are shown in Table 1.

[0096] Examples 6 to 8 Evaluations were carried out in the same manner as in Example 5, except that the aqueous solution in which the laminate was immersed was changed to one shown in Table 1. The results are shown in Table 1.

[0097] Comparative Example 1 A laminate having the layer structure shown in Table 1 was prepared and evaluated in the same manner as in Example 2, except that a urethane adhesive ("TM-569 / CAT-RT37" manufactured by Toyo-Morton Co., Ltd.) was used instead of the epoxy resin composition A obtained in Production Example 3. The results are shown in Table 1.

[0098] Comparative Examples 2 and 3 Evaluations were carried out in the same manner as in Comparative Example 1, except that the aqueous solution in which the laminate was immersed was changed to one shown in Table 1. The results are shown in Table 1.

[0099]

[0100] Table 1 shows that by immersing a laminate having an OPP film, a CPP film, an aluminum vapor-deposited layer, and a predetermined cured resin layer (III) in an aqueous acid solution, the CPP film and the OPP film + ink layer could be separated (Examples 1 to 8). In particular, in Examples 1, 2, 4 to 6, and 8, in which the laminate was immersed in a 1N aqueous acetic acid solution, a 1N aqueous lactic acid solution, or a 1N aqueous hydrochloric acid solution, no vapor-deposited layer remained on the CPP film, which was advantageous for recovering the CPP film. In contrast, in Comparative Examples 1 to 3, separation of the plastic film was not possible.

[0101] Example 9 (Preparation of Laminate and Recovery of Plastic Film) (Preparation of Laminate) A laminate having the layer structure shown in Table 2 was prepared by the following procedure. A white ink (Sakata Inx Corporation's Bellcolor R115 diluted two-fold with a diluent (Sakata Inx Corporation's L Solvent)) was applied to the alumina-deposited surface of a biaxially oriented polyethylene terephthalate (PET) film ("Barrierox 1011HG" manufactured by Toray Advanced Film Co., Ltd., thickness: 12 μm), in which alumina was vapor-deposited on one side of the film. The ink was then heated at 80°C for 10 seconds and dried (thickness after drying: approximately 0.5 μm) to form a colored layer. A reverse printing gravure ink (Sakata Inx Corporation's Bellflora R Medium diluted two-fold with a diluent (Sakata Inx Corporation's K Solvent)) was then applied to the colored layer using a bar coater No. The epoxy resin composition was applied onto the medium layer using a bar coater No. 8, and then heated at 80°C for 10 seconds to dry (thickness after drying: approximately 0.5 μm), forming a medium layer. Next, the epoxy resin composition C obtained in Production Example 5 was applied onto the medium layer using a bar coater No. 8, and then heated at 80°C for 10 seconds to dry (thickness after drying: approximately 3 μm). The epoxy resin composition-coated surface and a non-oriented polypropylene film (CPP) ("Pylen Film-CT P1146" manufactured by Toyobo Co., Ltd., thickness: 50 μm) were placed opposite each other and bonded together using a nip roll, and then heated at 40°C for 2 days to form a cured resin layer (III)-3, thereby obtaining a laminate having the layer structure shown in Table 2.

[0102] (Recovery and Evaluation of Plastic Film) The prepared laminate was cut into strips of 1.5 cm × 5 cm, and one strip of the laminate was immersed for 16 hours in a 1N aqueous acetic acid solution (about 10 g) at 40° C. After immersion, the laminate was recovered and evaluated as follows.

[0103] <State of peeled interface and vapor deposition layer> Evaluation was carried out in the same manner as in Example 1.

[0104] <PET Separation> The state of separation of the PET film from the laminate was evaluated according to the following criteria, and the results are shown in Table 2. The SEM-EDX measurement conditions were the same as above. [Evaluation criteria] A: The PET film was peeled from the laminate, and elemental analysis of the surface of the recovered PET film by SEM-EDX measurement revealed that no alumina remained on the film surface. B: The PET film was peeled from the laminate, but alumina remained on the surface of the recovered PET film. C: The PET film was not peeled from the laminate and could not be recovered.

[0105] <Separation of CPP + cured resin layer> The state of separation of the CPP + cured resin layer in the laminate recovered after immersion in a 1N aqueous acetic acid solution was visually observed and evaluated according to the following criteria, and the results are shown in Table 2. [Evaluation criteria] A: The CPP film + cured resin layer peeled off from the laminate, and the ink layer did not remain on the cured resin layer B: The CPP film + cured resin layer peeled off from the laminate, but the ink layer remained on the cured resin layer C: The CPP film + cured resin layer did not peel off from the laminate, and the laminate could not be recovered

[0106] Examples 10 and 11 Evaluations were carried out in the same manner as in Example 9, except that the aqueous solution in which the laminate was immersed was changed to one shown in Table 2. The results are shown in Table 2.

[0107] Comparative Example 4 A laminate having the layer structure shown in Table 2 was prepared and evaluated in the same manner as in Example 9, except that a urethane adhesive ("TM-569 / CAT-RT37" manufactured by Toyo-Morton Co., Ltd.) was used instead of the epoxy resin composition C obtained in Production Example 5. The results are shown in Table 2.

[0108] Comparative Examples 5 and 6 Evaluations were made in the same manner as in Comparative Example 4, except that the aqueous solution in which the laminate was immersed was changed to one shown in Table 2. The results are shown in Table 2.

[0109]

[0110] Example 12 (Preparation of Laminate and Recovery of Plastic Film) (Preparation of Laminate) A laminate having the layer structure shown in Table 3 was prepared by the following procedure. The epoxy resin composition A obtained in Preparation Example 3 was applied to the silica-deposited surface of a biaxially oriented polyethylene terephthalate (PET) film ("Techbarrier L" manufactured by Mitsubishi Chemical Corporation, thickness: 12 μm), in which silica was vapor-deposited on one side of the film, using a bar coater No. 8, and the film was dried by heating at 80°C for 10 seconds (thickness after drying: approximately 3 μm). The surface coated with the epoxy resin composition and a non-oriented polypropylene (CPP) film ("Pylen Film-CT P1146" manufactured by Toyobo Co., Ltd., thickness: 25 μm) were placed opposite each other and bonded together using nip rolls. The film was then heated at 40°C for 2 days to form a cured resin layer (III)-1, thereby obtaining a laminate having the layer structure shown in Table 3.

[0111] (Recovery and Evaluation of Plastic Film) The prepared laminate was cut into strips of 1.5 cm × 5 cm, and one strip of the laminate was immersed for 16 hours in a 1N aqueous acetic acid solution (about 10 g) at 40° C. After immersion, the laminate was recovered and evaluated as follows.

[0112] <State of peeled interface and vapor deposition layer> Evaluation was carried out in the same manner as in Example 1.

[0113] <PET Separation> The state of separation of the PET film from the laminate was evaluated according to the following criteria, and the results are shown in Table 3. The SEM-EDX measurement conditions were the same as above. [Evaluation criteria] A: The PET film was peeled from the laminate, and elemental analysis of the surface of the recovered PET film by SEM-EDX measurement revealed that no silica remained on the film surface. B: The PET film was peeled from the laminate, but silica remained on the surface of the recovered PET film. C: The PET film was not peeled from the laminate and could not be recovered.

[0114] <Separation of CPP + cured resin layer> The state of separation of the CPP + cured resin layer of the laminate recovered after immersion in a 1N aqueous acetic acid solution was visually observed and evaluated according to the following criteria, and the results are shown in Table 2. [Evaluation criteria] A: The CPP film + cured resin layer peeled off from the laminate. C: The CPP film + cured resin layer did not peel off from the laminate and could not be recovered.

[0115] Examples 13 and 14 Evaluations were carried out in the same manner as in Example 12, except that the aqueous solution in which the laminate was immersed was changed to one shown in Table 3. The results are shown in Table 3.

[0116] Comparative Example 7 A laminate having the layer structure shown in Table 3 was prepared and evaluated in the same manner as in Example 12, except that a urethane adhesive ("TM-569 / CAT-RT37" manufactured by Toyo-Morton Co., Ltd.) was used instead of the epoxy resin composition A obtained in Production Example 3. The results are shown in Table 3.

[0117] Comparative Examples 8 and 9 Evaluations were made in the same manner as in Comparative Example 7, except that the aqueous solution in which the laminate was immersed was changed to one shown in Table 3. The results are shown in Table 3.

[0118]

[0119] Example 15 (Preparation of Laminate and Recovery of Plastic Film) (Preparation of Laminate) A laminate having the layer structure shown in Table 4 was prepared by the following procedure. The epoxy resin composition A obtained in Production Example 3 was applied to one side of a biaxially oriented polypropylene film (OPP) (Futamura Chemical Co., Ltd., "FOR," thickness: 25 μm) using a bar coater No. 8, and the film was dried by heating at 80°C for 10 seconds (thickness after drying: approximately 3 μm). The surface coated with the epoxy resin composition and the aluminum-vapor-deposited surface of an aluminum-vapor-deposited CPP (Nakai Industrial Co., Ltd., "S-F-1," thickness: 25 μm), in which aluminum was vapor-deposited on one side of a non-oriented polypropylene film (CPP), were bonded together using nip rolls, and the film was heated at 40°C for 2 days to form a cured resin layer (III)-1, thereby obtaining a laminate having the layer structure shown in Table 4.

[0120] (Recovery and Evaluation of Plastic Film) The prepared laminate was cut into strips of 1.5 cm × 5 cm, and one strip of the laminate was immersed for 96 hours in 1N-hydrochloric acid (about 10 g) at 23° C. After immersion, the laminate was recovered and evaluated as follows.

[0121] <State of peeled interface and vapor deposition layer> Evaluation was carried out in the same manner as in Example 1.

[0122] <Separation of CPP> Evaluation was carried out in the same manner as in Example 1.

[0123] <Separation of OPP + cured resin layer> The state of separation of the OPP film + cured resin layer of the laminate recovered after immersion in 1N hydrochloric acid was visually observed and evaluated according to the following criteria, and the results are shown in Table 4. [Evaluation criteria] A: The OPP film + cured resin layer peeled off from the laminate. C: The OPP film + cured resin layer did not peel off from the laminate and could not be recovered.

[0124] Example 16 Evaluation was carried out in the same manner as in Example 15, except that the aqueous solution in which the laminate was immersed was changed to a 5% KOH aqueous solution (pH at 25° C.: 14.7). The results are shown in Table 4.

[0125] Example 17 (Preparation of Laminate and Recovery of Plastic Film) (Preparation of Laminate) A laminate having the layer structure shown in Table 4 was prepared by the following procedure. The epoxy resin composition D obtained in Preparation Example 6 was applied to the aluminum-vapor-deposited surface of aluminum-vapor-deposited CPP ("S-F-1" manufactured by Nakai Industrial Co., Ltd., thickness: 25 μm), which had aluminum vapor-deposited on one side of a non-oriented polypropylene film (CPP), using a bar coater No. 3, and the film was dried by heating at 80°C for 30 seconds (thickness after drying: approximately 0.1 μm). Next, a urethane adhesive ("TM-569 / CAT-RT37" manufactured by Toyo-Morton Co., Ltd.) was applied to one side of a biaxially oriented polypropylene film (OPP) ("FOR" manufactured by Futamura Chemical Co., Ltd., thickness: 25 μm) using a bar coater No. 8, and the film was dried by heating at 80°C for 10 seconds (thickness after drying: approximately 3 μm). The surface coated with the epoxy resin composition and the urethane adhesive layer were placed opposite each other and bonded together using a nip roll, and heated at 40°C for 2 days to form a cured resin layer (III)-4, thereby obtaining a laminate having the layer structure shown in Table 4.

[0126] (Recovery and Evaluation of Plastic Film) The prepared laminate was cut into strips of 1.5 cm x 5 cm, and one strip of the laminate was immersed in 1N-hydrochloric acid (approximately 10 g) at 23°C for 96 hours. After immersion, the laminate was recovered and evaluated in the same manner as in Example 12. The results are shown in Table 4.

[0127] Example 18 Evaluation was carried out in the same manner as in Example 17, except that the aqueous solution in which the laminate was immersed was changed to a 5% KOH aqueous solution (pH at 25°C: 14.7). The results are shown in Table 4.

[0128]

[0129] As can be seen from Tables 2 to 4, according to the method of the present invention, even when laminates having different layer structures are used, the plastic film can be separated using an acidic or alkaline aqueous solution.

[0130] Example 19 (Preparation of Laminate and Recovery of Plastic Film) (Preparation of Laminate) A laminate having the layer structure shown in Table 5 was prepared by the following procedure. The epoxy resin composition A obtained in Preparation Example 3 was applied to the silica-deposited surface of a silica-deposited polyethylene terephthalate (PET) film ("Techbarrier L" manufactured by Mitsubishi Chemical Corporation, thickness: 12 μm), which had silica deposited on one side thereof, using a bar coater No. 8, and the film was dried by heating at 80°C for 10 seconds (thickness after drying: approximately 3 μm). The surface coated with the epoxy resin composition and the deposited layer surface of a binary-deposited PET sealant film ("VE034" manufactured by Toyobo Co., Ltd., thickness: 30 μm), in which a binary-deposited layer of silica-alumina was formed on one side of the PET sealant, were then bonded together using nip rolls, with the coated surface facing the deposited layer, and the resulting film was heated at 40°C for 2 days to form a cured resin layer (III)-1, to obtain a laminate having the layer structure shown in Table 5.

[0131] (Recovery and Evaluation of Plastic Film) The prepared laminate was cut into strips of 1.5 cm × 5 cm, and one strip of the laminate was immersed for 16 hours in a 5% KOH aqueous solution (about 10 g) at 40° C. After immersion, the laminate was recovered and evaluated as follows.

[0132] <State of peeled interface and vapor deposition layer> Evaluation was carried out in the same manner as in Example 1.

[0133] <PET Separation> The state of separation of the PET film from the laminate was evaluated according to the following criteria, and the results are shown in Table 5. The SEM-EDX measurement conditions were the same as above. [Evaluation criteria] A: The PET film was peeled from the laminate, and elemental analysis of the surface of the recovered PET film by SEM-EDX measurement revealed that no silica remained on the film surface. B: The PET film was peeled from the laminate, but silica remained on the surface of the recovered PET film. C: The PET film was not peeled from the laminate and could not be recovered.

[0134] <Separation of PET sealant> The state of separation of the PET sealant from the laminate was evaluated according to the following criteria, and the results are shown in Table 5. [Evaluation criteria] A: The PET sealant peeled off from the laminate, and elemental analysis of the surface of the recovered PET sealant by SEM-EDX measurement revealed that no binary vapor deposition layer remained on the sealant surface. B: The PET sealant peeled off from the laminate, but a binary vapor deposition layer remained on the surface of the recovered PET sealant. C: The PET sealant did not peel off from the laminate and could not be recovered.

[0135] Examples 20 to 22 Evaluations were carried out in the same manner as in Example 19, except that the aqueous solution in which the laminate was immersed was changed to one shown in Table 5. The results are shown in Table 5.

[0136] Comparative Example 10 A laminate having the layer structure shown in Table 5 was prepared and evaluated in the same manner as in Example 19, except that a urethane adhesive ("TM-569 / CAT-RT37" manufactured by Toyo-Morton Co., Ltd.) was used instead of the epoxy resin composition A obtained in Production Example 3. The results are shown in Table 5.

[0137] Comparative Examples 11 to 13 Evaluations were made in the same manner as in Comparative Example 10, except that the aqueous solution in which the laminate was immersed was changed to one shown in Table 5. The results are shown in Table 5.

[0138]

[0139] Example 23 (Preparation of laminate and recovery of plastic film) (Preparation of laminate) A laminate having the layer structure shown in Table 6 was prepared in the same manner as in Example 19, except that a PET sealant film ("HS-PET (C)" manufactured by Nissei Chemical Industries, Ltd.) was used instead of the binary vapor-deposited PET sealant film in Example 19.

[0140] (Recovery and Evaluation of Plastic Film) The prepared laminate was cut into strips of 1.5 cm × 5 cm, and one strip of the laminate was immersed for 96 hours in a 5% KOH aqueous solution (about 10 g) at 40° C. After immersion, the laminate was recovered and evaluated as follows.

[0141] <State of peeled interface and vapor deposition layer> Evaluation was carried out in the same manner as in Example 1.

[0142] <PET Separation> The state of separation of the PET film from the laminate was evaluated according to the following criteria, and the results are shown in Table 6. The SEM-EDX measurement conditions were the same as above. [Evaluation criteria] A: The PET film was peeled from the laminate, and elemental analysis of the surface of the recovered PET film by SEM-EDX measurement revealed that no silica remained on the film surface. B: The PET film was peeled from the laminate, but silica remained on the surface of the recovered PET film. C: The PET film was not peeled from the laminate and could not be recovered.

[0143] <Separation of PET sealant + cured resin layer> The state of separation of the PET sealant + cured resin layer of the laminate recovered after immersion in a 5% KOH aqueous solution was visually observed and evaluated according to the following criteria, and the results are shown in Table 6. [Evaluation criteria] A: The PET sealant + cured resin layer peeled off from the laminate. C: The PET sealant + cured resin layer did not peel off from the laminate and could not be recovered.

[0144] Examples 24 to 26 Evaluations were carried out in the same manner as in Example 19, except that in Example 23, the aqueous solution in which the laminate was immersed was changed to one shown in Table 6. The results are shown in Table 6.

[0145] Comparative Example 14 A laminate having the layer structure shown in Table 6 was prepared and evaluated in the same manner as in Example 24, except that a urethane adhesive ("TM-569 / CAT-RT37" manufactured by Toyo-Morton Co., Ltd.) was used instead of the epoxy resin composition A obtained in Production Example 3. The results are shown in Table 6.

[0146] Comparative Examples 15 and 16 Evaluations were made in the same manner as in Comparative Example 14, except that the aqueous solution in which the laminate was immersed was changed to one shown in Table 6. The results are shown in Table 6.

[0147]

[0148] Example 27 (Preparation of Laminate and Recovery of Plastic Film) (Preparation of Laminate) A laminate having the layer structure shown in Table 7 was prepared by the following procedure. A white ink (Sakata Inx Corporation's "Bellcolor R115" diluted two-fold with a diluent (Sakata Inx Corporation's "L Solvent")) was applied to one side of a biaxially stretched polyethylene terephthalate film (PET) (Toyobo Co., Ltd.'s "E5100", thickness: 12 μm) using a bar coater No. 8, and dried by heating at 80°C for 10 seconds (thickness after drying: approximately 0.5 μm) to form a colored layer. A reverse printing gravure ink (Sakata Inx Corporation's "Bellflora R Medium" diluted two-fold with a diluent (Sakata Inx Corporation's "K Solvent")) was applied to the colored layer using a bar coater No. The epoxy resin composition was applied onto the medium layer using a bar coater No. 8, and then heated at 80°C for 10 seconds to dry (thickness after drying: approximately 0.5 μm), forming a medium layer. Next, the epoxy resin composition A obtained in Production Example 3 was applied onto the medium layer using a bar coater No. 8, and then heated at 80°C for 10 seconds to dry (thickness after drying: approximately 3 μm). The epoxy resin composition-coated surface and the vapor-deposited layer surface of a two-component vapor-deposited PET sealant film ("VE034" manufactured by Toyobo Co., Ltd., thickness: 30 μm), in which a silica-alumina two-component vapor-deposited layer was formed on one side of the PET sealant, were placed facing each other and bonded together using a nip roll, and then heated at 40°C for 2 days to form a cured resin layer (III)-1, thereby obtaining a laminate having the layer structure shown in Table 7.

[0149] (Recovery and Evaluation of Plastic Film) The prepared laminate was cut into strips of 1.5 cm × 5 cm, and one strip of the laminate was immersed for 16 hours in a 5% KOH aqueous solution (about 10 g) at 40° C. After immersion, the laminate was recovered and evaluated as follows.

[0150] <State of peeled interface and vapor deposition layer> Evaluation was carried out in the same manner as in Example 1.

[0151] <PET Separation> The state of separation of the PET film from the laminate was evaluated according to the following criteria, and the results are shown in Table 7. The SEM-EDX measurement conditions were the same as above. [Evaluation criteria] A: The PET film peeled from the laminate, and no ink layer remained on the surface of the recovered PET film. B: The PET film peeled from the laminate, but an ink layer remained on the surface of the recovered PET film. C: The PET film did not peel from the laminate, and could not be recovered.

[0152] <Separation of PET sealant> The state of separation of the PET sealant from the laminate was evaluated according to the following criteria, and the results are shown in Table 7. [Evaluation criteria] A: The PET sealant peeled off from the laminate, and elemental analysis of the surface of the recovered PET sealant by SEM-EDX measurement revealed that no binary vapor deposition layer remained on the sealant surface. B: The PET sealant peeled off from the laminate, but a binary vapor deposition layer remained on the surface of the recovered PET sealant. C: The PET sealant did not peel off from the laminate and could not be recovered.

[0153] Examples 28 to 31 Evaluations were carried out in the same manner as in Example 27, except that the aqueous solution in which the laminate was immersed was changed to one shown in Table 7. The results are shown in Table 7.

[0154] Comparative Example 17 A laminate having the layer structure shown in Table 7 was prepared and evaluated in the same manner as in Example 27, except that a urethane adhesive ("TM-569 / CAT-RT37" manufactured by Toyo-Morton Co., Ltd.) was used instead of the epoxy resin composition A obtained in Production Example 3. The results are shown in Table 7.

[0155] Comparative Examples 18 to 21 Evaluations were made in the same manner as in Comparative Example 17, except that the aqueous solution in which the laminate was immersed was changed to one shown in Table 7. The results are shown in Table 7.

[0156]

[0157] Tables 5 to 7 show that the method of the present invention allows the separation of plastic films (PET or PET sealant) with an acidic or alkaline aqueous solution, even when laminates with different layer structures are used. Furthermore, when the vapor-deposited layer in the laminate contains silica, it is preferable to bring the laminate into contact with an alkaline aqueous solution.

[0158] Example 32 (Recovery of Plastic Film Using Actual Machine) A plastic film was recovered using the laminate having the layer structure of Example 1 (OPP / ink layer / cured resin layer (III) / Al vapor-deposited layer / CPP) by the following method. A laminate having the layer structure of Example 1 (a 300 mm wide roll film) was placed in a dry grinder having fixed and rotary blades and fitted with a 12 mm mesh screen, and the laminate was pulverized. The shape of the laminate after pulverization is as shown in FIG. 1. 300 mL of a 1N lactic acid aqueous solution was placed in a 500 mL separable flask and heated to 75°C using an oil bath. After heating to 75°C, 10 g of the pulverized laminate was placed in the flask and stirred for 1 hour at 240 rpm using a stirring blade. It was confirmed that the aluminum vapor-deposited layer had completely dissolved after 30 minutes of stirring. After stirring for 1 hour, the flask was removed from the oil bath and allowed to cool while stirring for an additional 1 hour. After stirring was completed, the separated cured resin layer settled at the bottom of the flask, while the OPP / ink layer and CPP film floated on the surface of the aqueous solution, allowing for easy recovery of the OPP / ink layer and CPP film. The recovered film was placed in 500 mL of water and washed by stirring at room temperature for 1 hour at a stirring speed of 300 rpm. SEM-EDX analysis of the washed OPP / ink layer and CPP film confirmed no trace of the aluminum vapor deposition layer. Furthermore, a plastic film recovery test was conducted again using the lactic acid aqueous solution after recovering the cured resin layer and film, using the same method as above, and the same results were obtained. From this, it can be said that the lactic acid aqueous solution can be reused.

[0159] According to the method of the present invention, it is possible to efficiently recover plastic films from laminates containing plastic films. The method of the present invention has a high degree of freedom in the conditions for recovering plastic films, and in particular, it is possible to easily recover plastic films from laminated laminates having two or more plastic films.

Claims

1. A method for recovering a plastic film from a laminate, comprising the steps of: The laminate comprises: Plastic film (I), At least one inorganic layer (II) selected from the group consisting of silicon oxide, aluminum, and aluminum oxide; and resin hardening layer (III), Including, the resin-cured layer (III) is a cured product of an epoxy resin composition containing an epoxy resin and an epoxy resin curing agent including an amine-based curing agent, The method includes contacting the laminate with an aqueous acid or alkaline solution.

2. 2. The method of claim 1, wherein the amine-based curing agent comprises an amine-based curing agent (i) below: (i) A reaction product of the following components (A) and (B): (A) at least one selected from the group consisting of metaxylylenediamine and paraxylylenediamine (B) At least one member selected from the group consisting of unsaturated carboxylic acids and derivatives thereof represented by the following general formula (1): 【Chemistry 1】 (In formula (1), R １ , R ２ each independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 13 carbon atoms.

3. The method according to claim 1 or 2, wherein the inorganic layer (II) is an inorganic vapor deposition layer.

4. The method according to claim 1 or 2, wherein the inorganic layer (II) is an aluminum vapor deposition layer.

5. The method according to claim 1 or 2, wherein the laminate comprises two or more plastic films (I).

6. 3. The method according to claim 1, wherein in the epoxy resin composition, a ratio of the number of active hydrogens in the epoxy resin curing agent to the number of epoxy groups in the epoxy resin (number of active hydrogens in epoxy resin curing agent / number of epoxy groups in epoxy resin) is in the range of 0.2 to 8.

0.

7. The method according to claim 1 or 2, wherein the resin-cured layer (III) has a thickness of 0.05 to 20 μm.

8. The method of claim 1 or 2, wherein the laminate further comprises an ink layer.

9. The method according to claim 1 or 2, further comprising the step of immersing the laminate in an aqueous acid solution.

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