Laminate

Abstract

The present invention is a laminate having a paper substrate layer, a temperature-responsive water-soluble resin layer, and a water-insoluble layer in the order listed. According to the present invention, it is possible to provide a laminate with which a highly water-resistant packaging material can be realized while it is also possible to recover pulp, which is the raw material of the paper substrate layer, and the raw material of the water-insoluble layer with high quality and a high recovery rate.

Description

Laminate

[0001] The present invention relates to a laminate.

[0002] Laminates in which a water-insoluble layer such as a thermoplastic resin layer is laminated on a base layer such as a paper base layer are used as packaging materials for food, etc. After use, such packaging materials are sometimes subjected to a recycling process in which the base material and the water-insoluble layer are separated.

[0003] The present invention is a laminate having a paper substrate layer, a temperature-responsive water-soluble resin layer, and a water-insoluble layer in this order. Detailed Description of the Invention

[0004] Since it is generally not easy to separate the substrate and the water-insoluble layer of a laminate, the raw material of the substrate after the recycling process may contain a large amount of the thermoplastic resin that is the raw material of the water-insoluble layer, or conversely, the raw material of the substrate may contain a large amount of the thermoplastic resin that is the raw material of the water-insoluble layer after the recycling process. Therefore, the recovery rate of the raw material of the substrate and the raw material of the water-insoluble layer was not high, and the quality of the recovered materials was also not satisfactory.

[0005] To address the above-mentioned problems, it has been considered to use a laminate having a water-soluble adhesive layer containing a water-soluble resin between a substrate and a water-insoluble layer as a packaging container, and to bring the packaging container into contact with water after use to dissolve the adhesive layer and separate the substrate and the water-insoluble layer (for example, JP-T No. 2000-501755).

[0006] However, conventional water-soluble resins have poor water resistance, and therefore, when a packaging material having a laminate with a water-soluble adhesive layer containing a conventional water-soluble resin is used in a relatively humid environment, the water-soluble resin layer may swell, etc., and the packaging material may be damaged.

[0007] The present invention provides a laminate that can realize a packaging material that is excellent in water resistance while allowing the pulp that is the raw material for the paper base layer and the raw material for the water-insoluble layer to be recovered with high quality and at a high recovery rate.

[0008] The present invention is a laminate having a paper substrate layer, a temperature-responsive water-soluble resin layer, and a water-insoluble layer in this order.

[0009] According to the present invention, it is possible to provide a laminate that can realize packaging materials with excellent water resistance while allowing the pulp, which is the raw material for the paper base layer, and the raw material for the water-insoluble layer to be recovered with high quality and at a high recovery rate.

[0010] An embodiment of the present invention will be described below.

[0011] <Laminate> The laminate of this embodiment has a paper base layer, a temperature-responsive water-soluble resin layer, and a water-insoluble layer in this order, and is preferably a laminate in which a sheet constituting the paper base layer and a sheet constituting the water-insoluble layer are bonded together by the temperature-responsive water-soluble resin layer. The laminate of this embodiment makes it possible to realize a packaging material that is excellent in water resistance while allowing the pulp that is the raw material for the paper base layer and the raw material for the water-insoluble layer to be recovered with high quality and at a high recovery rate.

[0012] [Paper Base Layer] The paper base layer is not particularly limited as long as it has a paper base material that can be used as a packaging material.

[0013] [Temperature-responsive water-soluble resin layer] In this specification, "temperature-responsive water-soluble" refers to the property of being poorly soluble in water at room temperature, which is the temperature at which the packaging material is used, and readily soluble in water heated above room temperature, preferably being poorly soluble in water at 25°C and readily soluble in water at 70°C. That is, the temperature-responsive water-soluble resin layer is poorly soluble in water at room temperature and readily soluble in water heated above room temperature, preferably being poorly soluble in water at 25°C and readily soluble in water at 70°C. "Poorly soluble in water" refers to the property of being unable to dissolve 10 g or more in 100 g of water, and "easily soluble in water" refers to the property of being able to dissolve 90 g or more in 100 g of water. The temperature-responsive water-soluble resin layer is not particularly limited as long as it is a layer having temperature-responsive water solubility, and an example of the temperature-responsive water-soluble resin layer is a layer containing a temperature-responsive water-soluble resin.

[0014] [Temperature-responsive water-soluble resin] The temperature-responsive water-soluble resin is not particularly limited as long as it is a resin that has temperature-responsive water solubility and dispersibility in neutral water. Examples of the temperature-responsive water-soluble resin include a temperature-responsive water-soluble resin having a hydrophilic group (hereinafter also simply referred to as a hydrophilic group) other than the hydrophilic group constituting the polymerization involved in producing the temperature-responsive water-soluble resin, preferably a temperature-responsive water-soluble resin having a monomer unit A having the hydrophilic group and a monomer unit B not having the hydrophilic group.

[0015] The neutral water may be water or an aqueous solution having a pH of 6 to 8 at 25°C, preferably 6.5 to 7.5. Specific examples of the neutral water include deionized water, pure water, tap water, and industrial water. Deionized water or tap water is preferred due to its availability. The neutral water may also contain other components such as a water-soluble organic solvent and a surfactant. Examples of the water-soluble organic solvent include lower alcohols such as methanol, ethanol, and 2-propanol; glycol ethers such as propylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monotertiary butyl ether, and diethylene glycol monobutyl ether; and ketones such as acetone and methyl ethyl ketone. Examples of the surfactant include anionic surfactants such as alkyl sulfates, alkyl ether sulfates, olefin sulfonates, and alkyl ether carboxylates; cationic surfactants such as alkyltrimethylammonium salts; and nonionic surfactants such as polyoxyethylene alkyl ethers and alkyl glycosides.

[0016] Examples of the temperature-responsive water-soluble resin include water-soluble polyester resins, water-soluble polyamide resins, water-soluble polyimide resins, water-soluble acrylic resins, water-soluble polyurethane resins, water-soluble polyallylamine resins, water-soluble phenolic resins, water-soluble epoxy resins, water-soluble phenoxy resins, water-soluble urea resins, water-soluble melamine resins, and polyvinyl alcohol resins, as well as modified versions of these resins. These resins can be used alone or in combination of two or more. Among these, from the viewpoint of achieving the effects of the present invention, one or more selected from the group consisting of water-soluble polyester resins, water-soluble polyamide resins, and water-soluble acrylic resins are preferred, and water-soluble polyester resins are more preferred.

[0017] [Monomer Unit A] The monomer unit A has a hydrophilic group. The monomer from which the monomer unit A is derived is referred to as "monomer A."

[0018] The hydrophilic group imparts dispersibility in neutral water, and therefore may be one or more selected from the group consisting of a primary amino group, a secondary amino group, a tertiary amino group, a quaternary ammonium base, an oxyalkylene group, a hydroxyl group, a carboxyl group, a carboxyl group, a phosphate group, a sulfonic acid group, and a sulfonate group. Among these, from the same viewpoint, one or more selected from the group consisting of a quaternary ammonium base, an oxyalkylene group, a carboxyl group, a phosphate group, and a sulfonate group are preferred, one or more selected from the group consisting of a quaternary ammonium base, an oxyalkylene group, and a sulfonate group are more preferred, and a sulfonate group is even more preferred.

[0019] The sulfonate group is -SO 3 from the viewpoint of dispersing the temperature-responsive water-soluble resin layer in neutral water to separate the paper base layer from the water-insoluble layer, and from the viewpoint of facilitating a polymerization reaction during production of the temperature-responsive water-soluble resin. ３ M ３ (However, M ３represents a counter ion of the sulfonic acid group that constitutes the sulfonate group, and from the viewpoint of dispersing the temperature-responsive water-soluble resin layer in neutral water to separate the paper base layer and the water-insoluble layer, is preferably one or more types selected from the group consisting of metal ions and ammonium ions, more preferably one or more types selected from the group consisting of metal ions, even more preferably one or more types selected from the group consisting of alkali metal ions and alkaline earth metal ions, even more preferably one or more types selected from the group consisting of alkali metal ions, even more preferably one or two or more types selected from the group consisting of sodium ions and potassium ions, and even more preferably sodium ions.

[0020] The content of the hydrophilic group in the temperature-responsive water-soluble resin is preferably 0.5 mmol / g or more, more preferably 0.6 mmol / g or more, even more preferably 0.7 mmol / g or more, and even more preferably 0.8 mmol / g or more, from the viewpoint of dispersing the temperature-responsive water-soluble resin layer in neutral water to separate the paper base layer and the water-insoluble layer, and is preferably 1.8 mmol / g or less, more preferably 1.4 mmol / g or less, even more preferably 1.0 mmol / g or less, and even more preferably 0.9 mmol / g or less, from the viewpoint of improving the moisture resistance of the composite material. Note that the content of the hydrophilic group in this specification can be determined by the method described in the Examples.

[0021] The monomer unit A is not particularly limited as long as it is a monomer unit having the hydrophilic group. However, from the viewpoint of dispersing the temperature-responsive water-soluble resin layer in neutral water to separate the paper base layer from the water-insoluble layer, and from the viewpoint of improving moisture resistance, a dicarboxylic acid monomer unit having the hydrophilic group is preferred.

[0022] From the viewpoints of dispersing the temperature-responsive water-soluble resin layer in neutral water to separate the paper substrate layer and the water-insoluble layer, improving moisture resistance, and facilitating the polymerization reaction during production of the temperature-responsive water-soluble resin, the monomer A is preferably one or more selected from the group consisting of carboxylic acids, amines, amino acids, and salts thereof having a hydrophilic group, and more preferably a carboxylic acid or a salt thereof having a hydrophilic group. Among the carboxylic acids or salts thereof, from the same viewpoints, aromatic carboxylic acids or salts thereof having a hydrophilic group are preferred, and one or more selected from the group consisting of sulfonate group-containing aromatic dicarboxylic acids and salts thereof are more preferred. Among these, from the same viewpoints, one or more selected from the group consisting of sulfophthalic acid, sulfonaphthalenedicarboxylic acid, and salts thereof are preferred, and one or more selected from the group consisting of sulfophthalic acid and salts thereof are even more preferred, and one or more selected from the group consisting of sulfoisophthalic acid, sulfoterephthalic acid, and salts thereof are even more preferred, and 5-sulfoisophthalic acid or a salt thereof is even more preferred.

[0023] The ratio of the amount of substance of the monomer unit A to the total amount of substance of all monomer units of the temperature-responsive water-soluble resin is preferably 8 mol% or more, more preferably 9 mol% or more, and even more preferably 10 mol% or more, from the viewpoint of dispersing the temperature-responsive water-soluble resin layer in neutral water to separate the paper base layer and the water-insoluble layer, and from the viewpoint of improving the moisture resistance of the temperature-responsive water-soluble resin layer, it is preferably 24 mol% or less, more preferably 20 mol% or less, and even more preferably 16 mol% or less. In this specification, the ratio of each monomer unit in the resin is measured by the method described in the Examples.

[0024] When the temperature-responsive water-soluble resin is a water-soluble polyester resin, the ratio of the dicarboxylic acid monomer unit having a hydrophilic group to the sum of all dicarboxylic acid monomer units in the temperature-responsive water-soluble resin is preferably 16 mol% or more, more preferably 18 mol% or more, and even more preferably 20 mol% or more, from the viewpoint of dispersing the temperature-responsive water-soluble resin layer in neutral water to separate the paper base layer and the water-insoluble layer; and from the viewpoint of improving the moisture resistance of the temperature-responsive water-soluble resin layer, it is preferably 48 mol% or less, more preferably 40 mol% or less, and even more preferably 32 mol% or less.

[0025] [Monomer Unit B] The monomer unit B does not have a hydrophilic group. A monomer for deriving the monomer unit B is referred to as monomer B. From the viewpoint of improving moisture resistance, the monomer unit B is preferably a dicarboxylic acid monomer unit (hereinafter also referred to as dicarboxylic acid monomer unit B) that does not have a hydrophilic group.

[0026] From the viewpoint of improving moisture resistance and facilitating the polymerization reaction during production of the temperature-responsive water-soluble resin, the dicarboxylic acid for deriving the dicarboxylic acid monomer unit B is preferably one or more selected from the group consisting of aromatic dicarboxylic acids having no hydrophilic group and aliphatic dicarboxylic acids having no hydrophilic group, and more preferably one or more selected from the group consisting of aromatic dicarboxylic acids having no hydrophilic group.

[0027] Examples of the aromatic dicarboxylic acid having no hydrophilic group include one or more selected from the group consisting of benzenedicarboxylic acid, furandicarboxylic acid, and naphthalenedicarboxylic acid. Among these, from the viewpoint of improving moisture resistance, one or more selected from the group consisting of terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid are preferred.

[0028] Examples of the aliphatic dicarboxylic acid having no hydrophilic group include one or more selected from the group consisting of malonic acid, succinic acid, glutaric acid, adipic acid, 1,4-cyclohexanedicarboxylic acid, and 1,3-adamantanedicarboxylic acid. Among these, adipic acid is preferred from the viewpoint of improving moisture resistance.

[0029] The ratio of the amount of substance of the monomer unit B to the total amount of substance of all monomer units in the temperature-responsive water-soluble resin is preferably 26 mol% or more, more preferably 28 mol% or more, and even more preferably 30 mol% or more, from the viewpoint of improving moisture resistance, and is preferably 42 mol% or less, more preferably 41 mol% or less, and even more preferably 40 mol% or less, from the viewpoint of dispersing the temperature-responsive water-soluble resin layer in neutral water to separate the paper base layer and the water-insoluble layer.

[0030] When the temperature-responsive water-soluble resin is a water-soluble polyester resin, the ratio of the amount of substance of the dicarboxylic acid monomer unit B to the total amount of all dicarboxylic acid monomer units in the temperature-responsive water-soluble resin is preferably 52 mol% or more, more preferably 56 mol% or more, and even more preferably 60 mol% or more, from the viewpoint of improving moisture resistance; and is preferably 84 mol% or less, more preferably 82 mol% or less, and even more preferably 80 mol% or less, from the viewpoint of improving moisture resistance of the temperature-responsive water-soluble resin layer.

[0031] The molar ratio of the monomer unit A to the monomer unit B in the temperature-responsive water-soluble resin (the monomer unit A / the monomer unit B) is preferably 16 / 84 or more, more preferably 18 / 82 or more, and even more preferably 20 / 80 or more, from the viewpoint of dispersing the temperature-responsive water-soluble resin layer in neutral water to separate the paper base layer and the water-insoluble layer, and is preferably 48 / 52 or less, more preferably 40 / 60 or less, and even more preferably 32 / 68 or less, from the viewpoint of improving moisture resistance.

[0032] (Diol Monomer Unit C) When the temperature-responsive water-soluble resin is a water-soluble polyester resin, it has a diol monomer unit C other than the monomer unit A and the monomer unit B. The diol for deriving the diol monomer unit C is also referred to as diol C.

[0033] As the diol C, an aliphatic diol, an aromatic diol, or the like can be used, but an aliphatic diol is preferred from the viewpoint of easy availability of raw materials for the water-soluble polyester resin.

[0034] The number of carbon atoms in the diol C is preferably 2 or more from the viewpoint of dispersing the temperature-responsive water-soluble resin layer in neutral water to separate the paper base layer from the water-insoluble layer, and is preferably 31 or less, more preferably 25 or less, even more preferably 20 or less, and still more preferably 15 or less from the viewpoint of improving moisture resistance.

[0035] The aliphatic diol may be one or more selected from the group consisting of chain diols and cyclic diols. From the viewpoint of easy availability of raw materials, chain diols are preferred, and from the viewpoint of improving water resistance, cyclic diols are preferred.

[0036] The ratio of the monomer units derived from cyclic diol to the total of the diol monomer units C is preferably 40 mol% or more, more preferably 50 mol% or more, and even more preferably 60 mol% or more, from the viewpoint of dispersing the temperature-responsive water-soluble resin layer in neutral water to separate the paper base layer and the water-insoluble layer, and is preferably 90 mol% or less, more preferably 85 mol% or less, and even more preferably 80 mol% or less, from the viewpoint of easy availability of raw materials.

[0037] The number of carbon atoms in the chain diol is preferably 2 or more from the viewpoint of improving moisture resistance, and is preferably 20 or less, more preferably 15 or less, and even more preferably 6 or less, from the viewpoint of dispersing the temperature-responsive water-soluble resin layer in neutral water to separate the paper base layer and the water-insoluble layer.

[0038] From the viewpoint of improving moisture resistance and dispersing the temperature-responsive water-soluble resin layer in neutral water to separate the paper base layer and the water-insoluble layer, the chain diol is preferably one or more selected from the group consisting of ethylene glycol, propanediol, butanediol, neopentyl glycol, pentanediol, hexanediol, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, and polypropylene glycol, and more preferably one or more selected from the group consisting of ethylene glycol, 1,3-propanediol, and 1,6-hexanediol.

[0039] The number of carbon atoms in the cyclic diol is preferably 3 or more, more preferably 4 or more, and even more preferably 6 or more, from the viewpoint of improving moisture resistance, and is preferably 31 or less, more preferably 20 or less, and even more preferably 15 or less, from the viewpoint of dispersing the temperature-responsive water-soluble resin layer in neutral water to separate the paper base layer and the water-insoluble layer.

[0040] From the viewpoint of improving moisture resistance and dispersing the temperature-responsive water-soluble resin layer in neutral water to separate the paper base layer and the water-insoluble layer, the cyclic diol is preferably one or more selected from the group consisting of cyclohexanedimethanol, hydrogenated bisphenol A, isosorbide, bisphenoxyethanolfluorene, bisphenolfluorene, biscresoxyethanolfluorene, and biscresolfluorene, and 1,4-cyclohexanedimethanol is more preferred.

[0041] The water-soluble polyester resin may contain a monomer unit other than the dicarboxylic acid monomer unit A, the dicarboxylic acid monomer unit B, and the diol monomer unit C, as long as the effect of this embodiment is not impaired.

[0042] The method for producing the water-soluble polyester resin is not particularly limited, and any conventionally known method for producing a polyester resin can be used.

[0043] From the viewpoint of improving moisture resistance, the weight average molecular weight of the temperature-responsive water-soluble resin is preferably 1,000 or more, more preferably 3,000 or more, and even more preferably 4,000 or more, and from the viewpoint of dispersing the temperature-responsive water-soluble resin layer in neutral water to separate the paper base layer and the water-insoluble layer, it is preferably 80,000 or less, more preferably 50,000 or less, and even more preferably 30,000 or less. In this specification, the weight average molecular weight is measured by the method described in the examples.

[0044] The glass transition temperature of the temperature-responsive water-soluble resin is preferably 0° C. or higher, more preferably 5° C. or higher, and even more preferably 10° C. or higher, from the viewpoint of improving moisture resistance, and is preferably 200° C. or lower, more preferably 160° C. or lower, and even more preferably 120° C. or lower, from the viewpoint of dispersing the temperature-responsive water-soluble resin layer in neutral water to separate the paper base layer and the water-insoluble layer. In this specification, the glass transition temperature is measured by the method described in the examples.

[0045] The crystalline melting point of the temperature-responsive water-soluble resin is preferably 30° C. or higher, more preferably 40° C. or higher, and even more preferably 50° C. or higher from the viewpoint of improving moisture resistance, and is preferably 150° C. or lower, more preferably 130° C. or lower, and even more preferably 110° C. or lower from the viewpoint of dispersing the temperature-responsive water-soluble resin layer in neutral water to separate the paper base layer and the water-insoluble layer. In this specification, the crystalline melting point is measured by the method described in the Examples.

[0046] From the viewpoint of dispersing the temperature-responsive water-soluble resin layer in neutral water to separate the paper base layer from the water-insoluble layer, the content of the temperature-responsive water-soluble resin in the temperature-responsive water-soluble resin layer is preferably 30% by mass or more, more preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably substantially 100% by mass, and even more preferably 100% by mass. In this specification, substantially 100% by mass means a state in which a trace amount of impurities and the like is inevitably contained.

[0047] The thickness of the temperature-responsive water-soluble resin layer is appropriately changed depending on the application of the packaging material to be used, and is not particularly limited, but is generally 0.01 to 100 μm.

[0048] [Water-insoluble layer] Examples of the water-insoluble layer include a resin layer, a metal layer, a glass layer, etc., and function as a sealing layer, a barrier layer, a laminate layer, a heat-seal layer, a release agent layer, a pressure-sensitive adhesive layer, a receiving layer, a flame retardant layer, etc. Examples of resins that constitute the resin layer include thermoplastic resins such as polyolefins, acrylic resins, and polyvinyl chloride resins, and thermosetting resins such as urethane resins and silicone resins. Among these, polyethylene resins (PE), preferably low-density polyethylene resins (LDPE), more preferably linear low-density polyethylene resins (LLDPE), etc. can be used.

[0049] <Method for manufacturing laminate> The method for manufacturing the laminate of this embodiment is a method for manufacturing the laminate, and includes: Step A of providing the temperature-responsive water-soluble resin layer on the paper base layer; and Step B of, after Step A, forming the water-insoluble layer on the surface of the temperature-responsive water-soluble resin layer opposite to the paper base layer.

[0050] [Step A] In step A, the method for providing the temperature-responsive water-soluble resin layer on the paper base layer is not particularly limited, and examples thereof include a method in which a coating liquid containing the temperature-responsive water-soluble resin is prepared, the coating liquid is applied by a conventional coating method such as a gravure method, a letterpress (flexographic) method, an offset method, a roll coater method (transfer method), a spray method, a brush coating method, a bar coater method, an inkjet method, a screen method, a die coating method, a spin coating method, a dip method, a Mayer bar method, or an air knife method, and then the coating liquid is dried.

[0051] The concentration of the temperature-responsive water-soluble resin in the coating solution is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, from the viewpoint of improving coating efficiency and uniformity of the temperature-responsive water-soluble resin layer, and is preferably 60% by mass or less, more preferably 40% by mass or less, and even more preferably 20% by mass or less.

[0052] The solvent used in preparing the coating liquid is not particularly limited as long as it can be used as a solvent.

[0053] The method for drying the coating liquid applied onto the paper substrate layer is not particularly limited, and any conventional drying method can be applied.

[0054] [Step B] In step B, the method for forming the water-insoluble layer on the surface of the temperature-responsive water-soluble resin layer opposite the paper substrate layer is not particularly limited, and a known method can be used depending on the content of the water-insoluble layer. When the surface of the temperature-responsive water-soluble resin layer opposite the paper substrate layer and the water-insoluble layer are bonded with an adhesive, the laminate has an adhesive layer. The type of adhesive and the thickness of the adhesive layer can be appropriately changed depending on the type of the temperature-responsive water-soluble resin layer and the water-insoluble layer, the purpose of the packaging material in which the laminate is used, and other factors.

[0055] <Laminate Treatment Method> The laminate treatment method of this embodiment includes a step C of treating the laminate with the neutral water at 50° C. or higher to separate the paper substrate layer from the temperature-responsive water-soluble resin layer.

[0056] In step C, the temperature of the neutral water used to treat the laminate is preferably 60°C or higher, more preferably 70°C or higher, from the viewpoint of efficiently separating the paper base layer and the temperature-responsive water-soluble resin layer, and from the viewpoint of the upper limit of the water temperature and ease of temperature control, it is preferably 100°C or lower, more preferably 90°C or lower, and even more preferably 80°C or lower.

[0057] The method for treating the laminate with neutral water at 50° C. or higher is not particularly limited, and examples thereof include a method of immersing the laminate in the neutral water. Alternatively, the laminate may be treated with the neutral water after being subjected to a process such as cutting.

[0058] <Pulp Recovery Method> The pulp recovery method of the present embodiment includes a step D1 of recovering pulp derived from the paper base layer after the step C of the laminate treatment method.

[0059] A known method can be applied to the method for recovering the pulp in step D1. For example, after the pulp is disintegrated after step C, the pulp can be recovered by a known method. The recovered pulp can be used as a raw material for recycled paper. In other words, the method for producing recycled paper includes the pulp recovery method.

[0060] <Method for recovering water-insoluble layer> The method for recovering a water-insoluble layer of this embodiment includes a step D2 of recovering raw materials for the water-insoluble layer after the step C of the laminate processing method.

[0061] As a method for recovering the water-insoluble layer in the step D2, a known method can be applied depending on the raw material of the water-insoluble layer.

[0062] <Method for recovering temperature-responsive water-soluble resin> The method for recovering a temperature-responsive water-soluble resin according to this embodiment includes a step D3 of recovering the temperature-responsive water-soluble resin after the step C of the laminate treatment method.

[0063] As a method for recovering the temperature-responsive resin in the step D3, a known method can be applied depending on the temperature-responsive resin.

[0064] <Packaging Material> The packaging material of this embodiment has the laminate. The packaging material of this embodiment can be used in a humid environment, and after use, the paper base layer and the water-insoluble layer can be separated by the laminate processing method. Specific examples of the packaging material include packaging containers, display labels, and release papers.

[0065] This specification further discloses the following embodiments. <1> A laminate having a paper substrate layer, a temperature-responsive water-soluble resin layer, and a water-insoluble layer, in this order. <2> The laminate according to <1>, wherein the temperature-responsive water-soluble resin layer is poorly soluble in water at 25°C and readily soluble in water at 70°C. <3> The laminate according to <1> or <2>, wherein the water-insoluble layer is a resin layer. <4> The laminate according to <3>, wherein the resin constituting the resin layer is preferably polyolefin, more preferably polyethylene resin (PE), even more preferably low-density polyethylene resin (LDPE), and even more preferably linear low-density polyethylene resin (LLDPE). <5> The laminate according to any one of <1> to <4>, wherein the temperature-responsive water-soluble resin layer contains a temperature-responsive water-soluble resin. <6> The laminate according to <5>, wherein the temperature-responsive water-soluble resin has a hydrophilic group. <7> The laminate according to <5> or <6>, wherein the temperature-responsive water-soluble resin comprises a monomer unit A having a hydrophilic group and a monomer unit B not having a hydrophilic group. <8> The laminate according to <6> or <7>, wherein the content of hydrophilic groups in the temperature-responsive water-soluble resin is preferably 0.5 mmol / g or more, more preferably 0.6 mmol / g or more, even more preferably 0.7 mmol / g or more, and even more preferably 0.8 mmol / g or more. <9> The laminate according to any of <6> to <8>, wherein the content of hydrophilic groups in the temperature-responsive water-soluble resin is preferably 1.8 mmol / g or less, more preferably 1.4 mmol / g or less, even more preferably 1.0 mmol / g or less, and even more preferably 0.9 mmol / g or less. <10> The laminate according to any of <6> to <9>, wherein the hydrophilic group is a sulfonate group. <11> The laminate according to any of <5> to <10>, wherein the temperature-responsive water-soluble resin is a water-soluble polyester resin having a hydrophilic group. <12> The laminate according to <11>, wherein the ratio of the dicarboxylic acid units having a hydrophilic group to all dicarboxylic acid units constituting the water-soluble polyester resin is preferably 16 mol % or more, more preferably 18 mol % or more, and even more preferably 20 mol % or more.<13> The laminate according to <11> or <12>, wherein the ratio of the dicarboxylic acid unit having a hydrophilic group to all dicarboxylic acid units constituting the water-soluble polyester resin is preferably 48 mol% or less, more preferably 40 mol% or less, and even more preferably 32 mol% or less. <14> The laminate according to any one of <5> to <13>, wherein the ratio of the amount of substance of the monomer unit B to the total amount of substance of all monomer units in the temperature-responsive water-soluble resin is preferably 26 mol% or more, more preferably 28 mol% or more, and even more preferably 30 mol% or more. <15> The laminate according to any one of <5> to <14>, wherein the ratio of the amount of substance of the monomer unit B to the total amount of substance of all monomer units in the temperature-responsive water-soluble resin is preferably 42 mol% or less, more preferably 41 mol% or less, and even more preferably 40 mol% or less. <16> A laminate having, in this order, a paper base layer, a temperature-responsive water-soluble resin layer, and a water-insoluble layer, wherein the temperature-responsive water-soluble resin layer is poorly soluble in water at 25°C and readily soluble in water at 70°C, and the water-insoluble layer is a resin layer, and the resin constituting the resin layer is a polyolefin. <17> A method for producing the laminate according to any of <1> to <16>, comprising: Step A of providing a temperature-responsive water-soluble resin layer on the paper base layer; and Step B of forming a water-insoluble layer on the surface of the temperature-responsive water-soluble resin layer opposite the paper base layer, after Step A. <18> A laminate treatment method comprising Step C of treating the laminate according to any of <1> to <16> with neutral water at 50°C or higher to separate the paper base layer from the temperature-responsive water-soluble resin layer. <19> A pulp recovery method comprising Step D1 of recovering pulp derived from the paper base layer after Step C of the laminate treatment method according to <18>. <20> A method for producing recycled paper, comprising the pulp recovery method according to <19>. <21> A method for recovering a water-insoluble layer, comprising step D2 of recovering raw materials for the water-insoluble layer after step C, which is included in the laminate treatment method according to <20>. <22> A method for recovering a temperature-responsive water-soluble resin, comprising step D3 of recovering the temperature-responsive water-soluble resin after step C, which is included in the laminate treatment method according to <21>.<23> A packaging material comprising the laminate according to any one of <1> to <16>.

[0066] Pressure is expressed as absolute pressure. "Normal pressure" refers to 101.3 kPa.

[0067] <Synthesis of Temperature-Responsive Water-Soluble Resins> [Temperature-Responsive Water-Soluble Resin 1] The raw materials listed in Table 1 were charged into a 2L stainless steel separable flask (equipped with a K-shaped tube, a stirrer, and a nitrogen inlet tube), and the surface temperature of the mantle heater was raised from 160°C to 260°C while stirring under a nitrogen atmosphere. The mixture was then stirred at that temperature for 6.5 hours to carry out a transesterification reaction. The surface temperature of the mantle heater was then raised from 260°C to 290°C, and the reaction was carried out for 1.5 hours while simultaneously reducing the pressure from normal pressure to 1.5 kPa. The reaction was then carried out for 1.5 hours while reducing the pressure from 1.5 kPa to 1.0 kPa, and the reaction was carried out for 6 hours. Finally, nitrogen was introduced into the stainless steel separable flask, and the pressure was returned to normal pressure, yielding the temperature-responsive water-soluble resin 1 listed in Table 1.

[0068] [Temperature-responsive water-soluble resin 2] The raw materials listed in Table 1 were charged into a 2L stainless steel separable flask (equipped with a K-shaped tube, stirrer, and nitrogen inlet tube), and the surface temperature of the mantle heater was raised from 160 ° C to 220 ° C while stirring under a nitrogen atmosphere. The mixture was then stirred at that temperature for 6.5 hours to carry out a transesterification reaction. The surface temperature of the mantle heater was then raised from 220 ° C to 240 ° C, and the reaction was carried out for 1.5 hours while simultaneously reducing the pressure from normal pressure to 8.5 kPa. The pressure was then reduced from 8.5 kPa to 1.3 kPa, and the reaction was carried out for 3 hours. Finally, nitrogen was introduced into the stainless steel separable flask, and the mixture was returned to normal pressure to obtain the temperature-responsive water-soluble resin 2 listed in Table 1.

[0069] [Temperature-responsive water-soluble resin 3] The raw materials listed in Table 1 were charged into a 2L stainless steel separable flask (equipped with a K-shaped tube, a stirrer, and a nitrogen inlet tube), and the surface temperature of the mantle heater was raised from 160°C to 220°C while stirring under a nitrogen atmosphere. The mixture was then stirred at that temperature for 6.5 hours to carry out a transesterification reaction. The surface temperature of the mantle heater was then raised from 220°C to 250°C, and the reaction was carried out for 5 hours while simultaneously reducing the pressure from normal pressure to 0.4 kPa. Finally, nitrogen was introduced into the stainless steel separable flask, and the pressure was returned to normal, yielding the temperature-responsive water-soluble resin 3 listed in Table 1.

[0070] [Temperature-responsive water-soluble resin 4] The raw materials listed in Table 1 were charged into a 2L stainless steel separable flask (equipped with a K-shaped tube, a stirrer, and a nitrogen inlet tube), and the surface temperature of the mantle heater was raised from 160°C to 220°C while stirring under a nitrogen atmosphere. The mixture was then stirred at that temperature for 6.5 hours to carry out a transesterification reaction. The surface temperature of the mantle heater was then raised from 220°C to 240°C, and the reaction was carried out for 15 hours while simultaneously reducing the pressure from normal pressure to 1.3 kPa. Finally, nitrogen was introduced into the stainless steel separable flask, and the pressure was returned to normal pressure to obtain the temperature-responsive water-soluble resin 4 listed in Table 1.

[0071] [Temperature-responsive water-soluble resin 5] The raw materials listed in Table 1 were charged into a 2L stainless steel separable flask (equipped with a K-shaped tube, a stirrer, and a nitrogen inlet tube), and the surface temperature of the mantle heater was raised from 160°C to 220°C while stirring under a nitrogen atmosphere. The mixture was then stirred at that temperature for 6 hours to carry out a transesterification reaction. The surface temperature of the mantle heater was then raised from 220°C to 260°C, and the reaction was carried out for 8 hours while simultaneously reducing the pressure from normal pressure to 1.3 kPa. Finally, nitrogen was introduced into the stainless steel separable flask, and the pressure was returned to normal pressure, yielding the temperature-responsive water-soluble resin 5 listed in Table 1.

[0072] <Synthesis of Non-Temperature-Responsive Water-Soluble Resins> [Non-Temperature-Responsive Water-Soluble Resin 1] The raw materials listed in Table 1 were charged into a 2L stainless steel separable flask (equipped with a K-shaped tube, a stirrer, and a nitrogen inlet tube), and the mantle heater surface temperature was raised from 160°C to 260°C while stirring under a nitrogen atmosphere. The mixture was then stirred at that temperature for 6 hours to carry out a transesterification reaction. The pressure was then reduced from normal pressure to 4.7 kPa, and the reaction was carried out for 1 hour. After the reaction for 1 hour, the mantle heater surface temperature was raised from 260°C to 270°C, and the reaction was carried out for 3.5 hours. Finally, nitrogen was introduced into the stainless steel separable flask, and the pressure was returned to normal, yielding Non-Temperature-Responsive Water-Soluble Resin 1 listed in Table 1.

[0073] [Non-thermoresponsive water-soluble resin 2] The raw materials listed in Table 1 were charged into a 2L stainless steel separable flask (equipped with a K-shaped tube, a stirrer, and a nitrogen inlet tube), and the surface temperature of the mantle heater was raised from 160°C to 260°C while stirring under a nitrogen atmosphere. The mixture was then stirred at that temperature for 6.5 hours to carry out a transesterification reaction. The pressure was then reduced from atmospheric pressure to 5.5 kPa and the reaction was carried out for 3 hours. After the 3-hour reaction, the surface temperature of the mantle heater was raised from 260°C to 290°C and the reaction was carried out for 5.5 hours. Finally, nitrogen was introduced into the stainless steel separable flask, and the pressure was returned to atmospheric pressure to obtain the non-thermoresponsive water-soluble resin 2 listed in Table 1.

[0074]

[0075] The symbols in Table 1 mean the following: NDCM: dimethyl naphthalenedicarboxylate (manufactured by Tokyo Chemical Industry Co., Ltd., first grade) DMT: dimethyl terephthalate (manufactured by Tokyo Chemical Industry Co., Ltd.) DMI: dimethyl isophthalate (manufactured by Tokyo Chemical Industry Co., Ltd.) DMA: dimethyl adipate (manufactured by Tokyo Chemical Industry Co., Ltd.) SID: 5-sodium dimethyl isophthalate (manufactured by Fujifilm Wako Pure Chemical Industries Co., Ltd.) EG: ethylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries Co., Ltd., special grade) 1,4-CHDM: 1,4-cyclohexanedimethanol (manufactured by Fujifilm Wako Pure Chemical Industries Co., Ltd., cis-trans mixture) 1,3-PD: 1,3-propanediol (manufactured by Tokyo Chemical Industry Co., Ltd.) 1,6-HD: 1,6-hexanediol (manufactured by Tokyo Chemical Industry Co., Ltd.) Ti(OBu) ４: Titanium tetrabutoxide (Tokyo Chemical Industry Co., Ltd., first grade) AcONa: Sodium acetate (Fujifilm Wako Pure Chemical Industries, Ltd., special grade)

[0076] <Evaluation Method> [Ratio of the Amount of Substance of Monomer Units Derived from 5-Dimethyl Sodium Sulfoisophthalate (Sulfonate Group-Containing Monomer Units) to the Total Amount of Substance of All Dicarboxylic Acid Monomer Units Constituting the Water-Soluble Resin] 10 mg of each water-soluble resin was dissolved in a mixed solvent of deuterated chloroform and deuterated trifluoroacetic acid (mass ratio 3:2), and proton NMR was measured using an NMR MR400 manufactured by Agilent. For the monomer units derived from 5-dimethyl sodium sulfoisophthalate, the peak integral value derived from the aromatic ring was divided by the number of protons directly bonded to the aromatic ring to calculate the amount of substance L of the sulfonate group-containing monomer units. For the dicarboxylic acid monomer units derived from dimethyl naphthalenedicarboxylate, dimethyl terephthalate, or dimethyl isophthalate, the peak integral value derived from the aromatic ring was divided by the number of protons directly bonded to the aromatic ring, and the results were summed to calculate the total amount of substance M of dicarboxylic acid monomer units not containing a sulfonate group. The value obtained by dividing the amount of substance L by the sum of the amount of substance L and the amount of substance M (total amount of substance of all dicarboxylic acid monomer units) using the following formula (1) was defined as the ratio (mol %) of the amount of substance of the sulfonate group-containing monomer unit to the total amount of substance of all dicarboxylic acid monomer units constituting the water-soluble resin: 100 × amount of substance L / (amount of substance L + amount of substance M) (1)

[0077] [Weight-average molecular weight (Mw)] For each water-soluble resin, a calibration curve was created from standard polystyrene using gel permeation chromatography (GPC) under the following conditions to determine the weight-average molecular weight (Mw): Apparatus: HLC-8320GPC (Tosoh Corporation, detector integrated) Column: α-M x 2 (Tosoh Corporation, 7.8 mm I.D. x 30 cm) Eluent: 60 mmol / L phosphoric acid + 50 mmol / L lithium bromide dimethylformamide solution Flow rate: 1.0 mL / min Column temperature: 40°C Detector: RI detector Standard sample: polystyrene

[0078] [Glass transition temperature (Tg)] 5 mg of each water-soluble resin was sealed in an aluminum pan, and using a DSC device (DSC8500, manufactured by Hitachi High-Tech Science Corporation), the temperature was raised from 30°C to 250°C, cooled to -20°C, and then raised again to 250°C. At this time, the heating and cooling rates were 10°C / min. The glass transition temperature Tg (°C) was determined from the baseline shift of the DSC curve obtained by raising the temperature again.

[0079] [Crystalline Melting Point (Tm)] For the temperature-responsive water-soluble resins 3 and 5, an aqueous dispersion adjusted to a solids concentration of 10% by mass was poured into a Teflon (registered trademark) Petri dish and dried by heating on a hot plate at 50°C for 8 hours. 5 mg of the resulting dried film was sealed in an aluminum pan, and the temperature was raised from 30°C to 250°C at a rate of 10°C / min using a DSC device (DSC8500, manufactured by Hitachi High-Tech Science Corporation). The crystalline melting point Tm (°C) was determined from the endothermic peak top of the resulting DSC curve.

[0080] [Water Solubility Test] 1.0 g of each powdered water-soluble resin listed in Table 2 was added to a 20 mL screw cap bottle containing 10 g of deionized water at 25°C and 70°C, and the mixture was stirred at 300 rpm. After 10 minutes, the test solution was suction filtered through dried filter paper (Advantec Co., Ltd., No. 5C), and the water solubility (%) was calculated using the difference in weight including the filter paper using the following formula (2). Drying was performed under reduced pressure at 60°C for 2 hours. 100 × (resin weight - (filter paper dry weight after test - filter paper dry weight before test)) / (resin weight) (2) Note that polyvinylpyrrolidone K30 (Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the water-soluble resin in Comparative Example 3.

[0081] [Evaluation of Laminates] [Examples 1 to 6 and Comparative Examples 1 to 3] (Preparation of Water-Soluble Resin-Coated Paper) The water-soluble resin according to each Example was stirred in water at 80°C for 1 hour to give a solid content of 10% by mass or 20% by mass, thereby obtaining an aqueous dispersion of the water-soluble resin according to each Example. 1.0 mL of each aqueous dispersion was applied to a sheet of fine paper (basis weight: 64 g / m²) that had been previously dried for 1 minute on a hot plate maintained at 90°C. ２) using a bar coater (Matsuo Sangyo Co., Ltd., #6, #8, #18) so that the coating area was 100 mm x 150 mm. Excess aqueous dispersion was wiped off, and the paper was dried for 1 minute on a hot plate maintained at 90°C to obtain water-soluble resin-coated paper having a water-soluble resin layer containing the water-soluble resin according to each example, and a paper base layer made of fine paper. The resin coating amount (g / m) was calculated by dividing the weight (g) of the coated resin, calculated from the difference in dry weight of the paper before and after coating, by the coating area. ２ )

[0082] (Preparation of Laminate by Dry Lamination) A polyester polyurethane polyol (DIC Corporation, LX-500) was used as the base agent, and an aromatic polyisocyanate (DIC Corporation, KW-75) was used as the curing agent. The base agent, curing agent, and dilution solvent, ethyl acetate, were mixed in a weight ratio of 10:1:16 to obtain an adhesive composition. 1.0 mL of this adhesive composition was applied to the corona-treated surface of a linear low-density polyethylene (LLDPE) (Wako Corporation, WZ-1N) film (thickness: 50 μm) whose surface had been corona-treated using a bar coater (Matsuo Sangyo Co., Ltd., #8) to a coating area of ​​100 mm x 150 mm. Excess adhesive was wiped off, and the solvent was evaporated by drying at room temperature for 1 minute. Next, the adhesive-coated surface of each film was bonded to the water-soluble resin layer of the water-soluble resin-coated paper, and a curing reaction was carried out at 40°C for 2 days while applying a load of 10 kg, thereby obtaining laminates according to Examples 1 to 6 and Comparative Examples 1 to 4, respectively.

[0083] Example 7 A laminate according to Example 7 was obtained in the same manner as in Example 2, except that the film (thickness: 50 μm) of linear low-density polyethylene (LLDPE) (WZ-1N, manufactured by Wako Co., Ltd.) whose surface had been subjected to a corona treatment was changed to a film (thickness: 30 μm) of biaxially oriented polypropylene (OPP) (Futamura Chemical Co., Ltd., FOR-AQ) whose surface had been subjected to a corona treatment.

[0084] [Example 8] The fine paper was replaced with kraft paper (basis weight: 70 g / m ２ ) and the resin coating amount was changed to 4.7 g / m ２ A laminate according to Example 8 was obtained in the same manner as in Example 1, except that the above-mentioned changes were made.

[0085] [Example 9] (Preparation of laminate by melt lamination) Resin coating amount: 6.2 g / m ２ A laminate according to Example 9 was obtained in the same manner as in Example 8, except that the temperature was changed to 100°C, and the lamination method was changed from dry lamination to melt lamination as described below. A film (thickness: 50 μm) of linear low-density polyethylene (LLDPE) (WZ-N, manufactured by Wako Co., Ltd.) placed on a release-treated SUS plate was placed on a hydraulic molding machine (TM-26, manufactured by Toho Machinery Co., Ltd.) heated to 280°C, and the film was melted. The water-soluble resin-coated paper using the temperature-responsive water-soluble resin 1 as the water-soluble resin was overlaid on the molten film, and the resulting mixture was cold-pressed at 15°C and 20 MPa for 60 seconds using a press molding machine (Lab Press P2-30T, manufactured by Toyo Seiki Seisakusho Co., Ltd.) to obtain a laminate according to Example 9.

[0086] Example 10 (Preparation of Release Paper Laminate) A solvent-based silicone release agent (KS-847, manufactured by Shin-Etsu Chemical Co., Ltd.), a catalyst (CAT-PL-10T, manufactured by Shin-Etsu Chemical Co., Ltd.), and toluene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a solvent were mixed in a mass ratio of 100:1:899 to obtain a release agent composition. 1.0 mL of the release agent composition was applied to the water-soluble resin layer surface of water-soluble resin-coated paper obtained in the same manner as the preparation method for the water-soluble resin-coated paper of Example 1 using a bar coater (#8, manufactured by Matsuo Sangyo Co., Ltd.) to a coating area of ​​100 mm x 150 mm. Excess release agent composition was wiped off, and the laminate was subjected to a curing treatment for 1 minute on a hot plate maintained at 120°C to obtain a laminate of Example 10.

[0087] Comparative Example 4 A laminate according to Comparative Example 4 was obtained in the same manner as in Example 1, except that the wood-free paper and the film were bonded together without being coated with a water-soluble resin.

[0088] [Comparative Example 5] The paper was kraft paper (basis weight: 70 g / m ２ ) and the resin coating amount was changed to 5.5 g / m ２ A laminate according to Comparative Example 5 was obtained in the same manner as in Comparative Example 1, except that the above-mentioned change was made.

[0089] [Comparative Example 6] Resin coating amount: 6.3 g / m ２A laminate according to Comparative Example 6 was obtained in the same manner as in Comparative Example 5, except that the lamination method was changed to melt lamination.

[0090] Comparative Example 7: The water-soluble resin was changed to non-temperature-responsive water-soluble resin 2, and the resin coating amount was 7.1 g / m ２ A laminate according to Comparative Example 7 was obtained in the same manner as in Comparative Example 6, except that the above-mentioned change was made.

[0091] [Laminate Detachment Test] The laminate was cut into 20 mm squares and temporarily attached to a 30 mm x 100 mm glass slide with double-sided tape (Nichiban Co., Ltd., Nicetack Super Strong Type, 15 mm wide) with the paper side facing outward to prepare a test specimen. The prepared test specimen was added to a 300 mL beaker containing 300 g of tap water at 25 ° C. and 70 ° C., fixed to the beaker so that the test specimen did not come into contact with the stirrer, and stirred at 400 rpm. The time it took for the paper to completely peel off from the test specimen was recorded as the detachment time (seconds). Those that did not peel after 60 minutes were deemed to have failed to detach. The test specimen from which the paper had completely peeled was removed from the beaker, and the LLDPE film (water-insoluble layer) was recovered.

[0092] [Paper recovery rate] A test piece was prepared in the same manner as in the laminate detachment test, and added to a 300 mL beaker containing 300 g of tap water at 70°C. The test piece was fixed to the beaker so that it would not come into contact with the stirrer, and stirred at 400 rpm. For pieces that peeled off within 60 minutes, the paper was recovered, washed with tap water, and dried under reduced pressure at 60°C for 2 hours. For pieces that did not peel off after 60 minutes, they were deemed unrecoverable. The paper recovery rate (%) was calculated using the difference in paper weight before and after the test using the following formula (3): 100 x paper mass after test / paper mass before test (3)

[0093] The evaluation results are shown in Table 2.

[0094]

Claims

1. A laminate having a paper substrate layer, a temperature-responsive water-soluble resin layer, and a water-insoluble layer in this order.

2. The laminate according to claim 1 , wherein the temperature-responsive water-soluble resin layer is poorly soluble in water at 25° C. and readily soluble in water at 70° C.

3. The laminate according to claim 1 , wherein the water-insoluble layer is a resin layer.

4. The laminate according to claim 3 , wherein the resin constituting the resin layer is a polyolefin.

5. The laminate according to claim 1 , wherein the temperature-responsive water-soluble resin layer contains a temperature-responsive water-soluble resin.

6. The laminate according to claim 5 , wherein the temperature-responsive water-soluble resin has a hydrophilic group.

7. The laminate according to claim 5 , wherein the temperature-responsive water-soluble resin comprises a monomer unit A having a hydrophilic group and a monomer unit B having no hydrophilic group.

8. The laminate according to claim 6 , wherein the content of the hydrophilic group in the temperature-responsive water-soluble resin is 0.5 mmol / g or more and 1.8 mmol / g or less.

9. The laminate according to claim 6 , wherein the hydrophilic group is a sulfonate group.

10. The laminate according to claim 6 , wherein the temperature-responsive water-soluble resin is a water-soluble polyester resin having a hydrophilic group.

11. 11. The laminate according to claim 10, wherein the ratio of the dicarboxylic acid units having a hydrophilic group to all dicarboxylic acid units constituting the water-soluble polyester resin is 16 mol % or more and 48 mol % or less.

12. A method for producing the laminate according to any one of claims 1 to 11, Step A: providing a temperature-responsive water-soluble resin layer on the paper substrate layer; A method for producing a laminate, comprising, after step A, step B of forming a water-insoluble layer on the surface of the temperature-responsive water-soluble resin layer opposite to the paper substrate layer.

13. A laminate treatment method comprising a step C of treating the laminate according to any one of claims 1 to 11 with neutral water at 50°C or higher to separate the paper base layer from the temperature-responsive water-soluble resin layer.

14. A pulp recovery method comprising a step D1 of recovering pulp derived from the paper base layer after the step C of the laminate treatment method according to claim 13.

15. A method for producing recycled paper, comprising the pulp recovery method according to claim 14.

16. A method for recovering a water-insoluble layer, comprising a step (D2) of recovering raw materials for the water-insoluble layer after the step (C) of the laminate processing method according to claim 13.

17. A method for recovering a temperature-responsive water-soluble resin, comprising the step D3 of recovering the temperature-responsive water-soluble resin after the step C of the laminate treatment method according to claim 13.

18. A packaging material comprising the laminate according to any one of claims 1 to 11.