Laminate, packaging material, and food packaging material

Abstract

Provided is a laminate for which the time required for delamination is shortened and which has excellent recoverability.　The laminate has an outer layer 1, an intermediate layer, and an outer layer 2, wherein: the outer layer 1, the intermediate layer, and the second outer layer 2 are arranged in this order; the intermediate layer contains a polyvinyl alcohol-based resin; the difference between the water vapor permeability of the outer layer 1 and the water vapor permeability of the outer layer 2 is at least 100 cc·30 μm / m2·day; and the water vapor permeability of the outer layer 1 and the water vapor permeability of the outer layer 2 satisfy the following expression (1).　Water vapor permeability of outer layer 1 < Water vapor permeability of outer layer 2…(1)

Description

[Technical field]

[0001] The present invention relates to a laminate, and more particularly to a laminate that is used for packaging materials and the like and has excellent recyclability. [Background technology]

[0002] In recent years, the problem of microplastics has come up, and regulations on waste plastics are becoming stricter. Until now, waste plastics have been exported to China and other countries, but from now on, they will be collected and recycled domestically. Previously, waste was collected without being separated, and only simple sorting was carried out before export. However, from now on, in order to promote domestic resource circulation, waste will be collected separately, subjected to advanced sorting, and turned into raw materials.

[0003] When carrying out separate collection or advanced sorting, it is easy to separate products made of a single resin, such as monolayer films, but it is extremely difficult to separate laminates made of multiple types of resins.

[0004] Under these circumstances, a laminate having a water-soluble resin laminated in an intermediate layer has been proposed as a laminate having excellent recyclability, mainly recoverability. For example, it has been described that in a laminate in which a water-soluble ethylene-modified polyvinyl alcohol resin is used as an intermediate layer and a thermoplastic resin is laminated thereon, the thermoplastic resin layer and the intermediate layer can be separated and recovered after use (e.g., Patent Documents 1 and 2). In addition, it has been proposed to provide an intermediate layer containing wax between a polyvinyl alcohol-based resin film and a substrate film to improve the peelability (for example, Patent Document 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-348200 [Patent Document 2] Japanese Patent Application Publication No. 11-348201 [Patent Document 3] JP 2003-112393 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the laminates described in Patent Documents 1 and 2, the peeling of the layers depends on the water solubility of the ethylene-modified polyvinyl alcohol resin, so there is room for improvement in terms of the peeling speed. The wax-mediated adhesion of Patent Document 3 makes it easy to peel off the polyolefin layer, but there is a risk that the polyolefin layer will peel off during distribution or use due to insufficient bonding strength. In particular, since the viscosity of the wax decreases in a high-temperature atmosphere, there is a risk that the polyolefin layer will not be able to maintain a stable desired bonding strength during distribution in midsummer or as a beverage container for hot water such as hot coffee.

[0007] The present invention has been made in view of the above circumstances, and provides a laminate which takes a short time until delamination occurs and has excellent recoverability. [Means for solving the problem]

[0008] The laminate of the present invention is a laminate having an outer layer 1, an intermediate layer, and an outer layer 2, which are arranged in this order: the outer layer 1, the intermediate layer, and the outer layer 2, the intermediate layer being a layer containing a polyvinyl alcohol-based resin, and the difference in water vapor permeability between the outer layer 1 and the outer layer 2 being 50cc·30μm / m 2 ·days or more, and the water vapor permeability of the outer layer 1 and the water vapor permeability of the outer layer 2 satisfy the following formula (1). Water vapor permeability of outer layer 1 < Water vapor permeability of outer layer 2 (1) Effect of the Invention

[0009] In the laminate of the present invention, outer layers 1 and 2 have different properties and behave differently in water, and therefore the time required for peeling of outer layers 1 and 2 when immersed in water is short. Furthermore, this exposes the intermediate layer containing a polyvinyl alcohol-based resin, which quickly dissolves in water and provides excellent recoverability. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments for carrying out the present invention will be described in detail, however, these are merely examples (representative examples) of the embodiment of the present invention and the present invention is not limited to the contents thereof. In the embodiment of the present invention, the term "main component" means that the content of each component is preferably 50% by weight or more, more preferably 80% by weight or more, even more preferably 95% by weight or more, and particularly preferably 100% by weight, based on the total components constituting each layer (100% by weight).

[0011] The laminate according to an embodiment of the present invention is a laminate in which an intermediate layer contains a polyvinyl alcohol (hereinafter referred to as "PVA")-based resin, and layers are laminated together such that the difference in water vapor transmission rate (hereinafter referred to as "WVTR") between outer layer 1 and outer layer 2 is equal to or greater than a specific range. The difference between the WVTR of outer layer 1 and the WVTR of outer layer 2 is 100cc·30μm / m 2 ·day or more, and is characterized by satisfying the above formula (1). The difference in WVTR is 150 to 1000cc·30μm / m 2 ·day is preferable, and 200 to 1000cc·30μm / m 2 ·day, and especially 300 to 900cc·30μm / m 2 If the difference in WVTR is too large, the WVTR of the outer layer 2 increases, and the barrier properties as a packaging material may decrease, whereas if the difference is too small, the peeling time of the layers tends to be longer.

[0012] In the present invention, when both outer layer 1 and outer layer 2 are single-layered, the difference between the WVTRs of the outer layers 1 and 2 means the difference between the WVTRs of the outer layers each consisting of a single layer. In addition, the difference between the WVTR of outer layer 1 and the WVTR of outer layer 2 means, when one of outer layer 1 and outer layer 2 is a single layer and the other is a multi-layer consisting of two or more single layers, the difference between the WVTR of the single layer outer layer and at least one of (1) the WVTR of the entire multi-layer outer layer, (2) the WVTR of some of the multi-layer outer layer, or (3) the WVTR of any one of the single layers that make up the multi-layer outer layer. In addition, the difference between the WVTR of outer layer 1 and the WVTR of outer layer 2 means, in the case where both outer layer 1 and outer layer 2 are multi-layered, the difference between at least one of (1) the WVTR of the entire multi-layered outer layer, (2) the WVTR of some of the multi-layered outer layer, or (3) the WVTR of any one of the single layers that make up the multi-layered outer layer, in one outer layer, and (4) the WVTR of the entire multi-layered outer layer, (5) the WVTR of some of the multi-layered outer layer, or (6) the WVTR of any one of the single layers that make up the multi-layered outer layer, in the other outer layer. Next, each layer will be described.

[0013] <Outer layer 1> The outer layer 1 used in the laminate according to the embodiment of the present invention has a WVTR of 100 cc·30 μm / m 2 ·day or less, and more preferably 0.1 to 50cc·30μm / m 2 ·day, especially 2~30cc·30μm / m 2 ·day is preferable. If this value is too large, the difference in WVTR with the outer layer 2 is small, that is, the difference in behavior with respect to water is small, and it tends to take time for the outer layer 1 and the outer layer 2 to peel off. If it is too small, there is no particular problem, but in practice the lower limit is 0.1cc 30μm / m 2 About one day.

[0014] The WVTR measurement method in the present invention conforms to JIS Z 0208 (1976), and involves sealing the mouth of a cup containing a moisture absorbent with the layer to be measured (single layer or multiple layers) in the outer layer 1, placing the cup in a thermo-hygrostat at 40°C and 90% RH, and calculating the water vapor transmission rate per unit area from the change in weight of the moisture absorbent.

[0015] The outer layer 1 may be a single layer or a multi-layer structure made up of a plurality of layers made of different materials and having different functions. Such a plurality of layers may include an outermost layer, an adhesive resin layer, a waterproof layer, an ultraviolet protection layer, a regrind layer, and the like, and these may be appropriately combined and laminated to form the outer layer 1. Furthermore, the outermost layer can be printed, colored, or otherwise applied with a design.

[0016] The outermost layer of the outer layer 1 is preferably a layer containing a thermoplastic resin as a main component, for example, polyolefins such as polyethylene, polypropylene, EVOH, aromatic polyesters such as polyethylene terephthalate, polyvinylidene chloride, polycarbonate, polyacrylonitrile, etc. These may be used alone or in combination of two or more kinds. Among these, polyolefins are preferred, and polyethylene is particularly preferred, because of their excellent heat sealability.

[0017] In addition to the thermoplastic resin as the main component, the outermost layer of the outer layer 1 may appropriately contain known additives such as plasticizers, fillers, antiblocking agents, antioxidants, colorants, antistatic agents, UV absorbers, lubricants, adhesive resins, etc., within a range that does not impair the effects of the present invention, preferably within a range that does not impair the effects of the present invention and does not impair food safety. These may be used alone or in combination of two or more kinds.

[0018] The thickness of the outermost layer of the outer layer 1 is usually 1 to 1000 μm, preferably 10 to 500 μm, more preferably 15 to 200 μm, and even more preferably 15 to 100 μm.

[0019] The resin constituting the main component of the adhesive resin layer in the outer layer 1 is not particularly limited, but for example, a modified olefin-based polymer containing a carboxy group that can be obtained by chemically bonding an unsaturated carboxylic acid or its anhydride to an olefin-based polymer by addition reaction, graft reaction, or the like is preferably used.

[0020] The thickness of the adhesive resin layer is usually 0.5 to 50 μm, more preferably 1 to 30 μm, particularly preferably 2 to 20 μm, and especially preferably 3 to 10 μm. If the thickness is less than 0.5 μm, there is a risk of insufficient adhesive strength. On the other hand, if the thickness exceeds 50 μm, the mechanical strength becomes insufficient and it is also economically disadvantageous, which is undesirable.

[0021] In addition, examples of the layer configuration in the case where layers other than the outermost layer in the outer layer 1 are laminated include the following. (a) Outer layer 1 (outermost layer / adhesive resin layer) / PVA resin layer / outer layer 2 (b) Outer layer 1 (outermost layer / waterproof layer / adhesive resin layer) / PVA resin layer / outer layer 2 (c) Outer layer 1 (outermost layer / regrind layer / adhesive resin layer) / PVA resin layer / outer layer 2 (d) Outer layer 1 (printing / outermost layer / adhesive layer) / PVA resin layer / outer layer 2 (e) Outer layer 1 (outermost layer / heat seal layer) / PVA-based resin layer / outer layer 2

[0022] The thickness of the outer layer 1 must be within a range in which there are no pinholes, etc., so that the water vapor barrier properties can be ensured. Specifically, it is usually 1 to 1000 μm, preferably 10 to 500 μm, and more preferably 15 to 200 μm. If it is too thin, there is a risk that the moisture resistance and waterproof properties will be insufficient, and the mechanical strength will be insufficient and the layer will be prone to tearing. If it is too thick, secondary molding will tend to be difficult.

[0023] <Outer layer 2> The outer layer 2 used in the laminate according to the embodiment of the present invention has a WVTR of 200 to 1000 cc·30 μm / m 2 ·day, and more preferably 300 to 900cc·30μm / m2 ·day, especially 400~800cc·30μm / m 2 ·day is preferable. If this value is too small, the difference in WVTR with the outer layer 1 is small, the difference in behavior with respect to water is small, and it tends to take a long time for the outer layer 1 to peel off from the outer layer 2. If this value is too large, water vapor permeates, and the gas barrier property of the PVA-based resin layer, which is the intermediate layer, tends to decrease.

[0024] The method for measuring the WVTR of the outer layer 2 is the same as that for the outer layer 1. That is, according to JIS Z 0208 (1976), the mouth of a cup containing a moisture absorbent is sealed so as to be covered with the layer to be measured (single layer or multiple layers) of the outer layer 2, the cup is placed in a thermohygrostat at 40°C and 90% RH, and the water vapor transmission rate per unit area is calculated from the change in weight of the moisture absorbent.

[0025] The outer layer 2 may be a single layer or a multi-layer structure made up of a plurality of layers made of different materials and having different functions. Such a plurality of layers may include an outermost layer, an adhesive resin layer, a waterproof layer, an ultraviolet protection layer, a regrind layer, and the like, and these may be appropriately combined and laminated to form the outer layer 2. Furthermore, the outermost layer can be printed, colored, or otherwise applied with a design.

[0026] The outermost layer of the outer layer 2 is preferably a layer containing a thermoplastic resin as a main component, for example, aliphatic polyesters such as polybutylene succinate, polybutylene adipate terephthalate, polylactic acid, polyamides such as nylon 6, polystyrene, etc. These may be used alone or in combination of two or more kinds. Among these, polyamide is preferred for reasons of adhesiveness and mechanical properties.

[0027] In addition to the thermoplastic resin as the main component, the outermost layer of the outer layers 2 may appropriately contain known additives such as plasticizers, fillers, antiblocking agents, antioxidants, colorants, antistatic agents, UV absorbers, lubricants, adhesives, etc., within a range that does not impair the effects of the present invention, preferably within a range that does not impair the effects of the present invention and does not impair food safety. These may be used alone or in combination of two or more kinds.

[0028] The thickness of the outermost layer of the outer layer 2 is usually 1 to 50 μm, preferably 2 to 20 μm, more preferably 3 to 10 μm, and further preferably 4 to 10 μm.

[0029] The resin constituting the main component of the adhesive resin layer in the outer layer 2 is, for example, not particularly limited, preferably a modified olefin-based polymer containing a carboxy group that can be obtained by chemically bonding an unsaturated carboxylic acid or its anhydride to an olefin-based polymer by addition reaction, graft reaction, or the like.

[0030] The thickness of the adhesive resin layer is usually 0.5 to 50 μm, preferably 1 to 30 μm, more preferably 2 to 20 μm, and particularly preferably 3 to 10 μm. If the thickness is less than 0.5 μm, there is a risk of insufficient adhesive strength. On the other hand, if the thickness exceeds 50 μm, the mechanical strength becomes insufficient and it is also economically disadvantageous, which is undesirable.

[0031] In addition, examples of the layer configuration in the case where layers other than the outermost layer in the outer layer 2 are laminated include the following. (a) Outer layer 1 / PVA resin layer / (adhesive resin layer / outermost layer) Outer layer 2 (b) Outer layer 1 / PVA resin layer / (Adhesive resin layer / Waterproof layer / Outermost layer) Outer layer 2 (c) Outer layer 1 / PVA resin layer / (Adhesive resin layer / Regrind layer / Outermost layer) Outer layer 2 (d) Outer layer 1 / PVA resin layer / (adhesive resin layer / outermost layer / printing) Outer layer 2 (e) Outer layer 1 / PVA resin layer / (heat seal layer / outermost layer) Outer layer 2

[0032] The thickness of the outer layer 2 must be within a range in which there are no pinholes and the like so as to ensure liquid impermeability. Specifically, it is usually 1 to 50 μm, preferably 2 to 20 μm, and more preferably 3 to 10 μm. If it is too thin, there is a risk that the moisture resistance and waterproofness will be insufficient, and the mechanical strength will be insufficient and the layer will be prone to tearing. If it is too thick, secondary molding will tend to be difficult.

[0033] <Middle Class> The intermediate layer according to the embodiment of the present invention is a PVA-based resin layer containing a PVA-based resin as a main component. Such a PVA-based resin has vinyl alcohol structural units corresponding to the degree of saponification and vinyl acetate structural units in the unsaponified portion.

[0034] The thickness of the PVA-based resin layer must be within a range without pinholes, etc., so as to ensure gas barrier properties. Specifically, it is usually 0.1 to 30 μm, preferably 1 to 10 μm, and more preferably 2 to 5 μm. If it is too thin, the gas barrier properties may be insufficient, and the mechanical strength may be insufficient, making it prone to tearing. If it is too thick, secondary molding tends to be difficult.

[0035] Examples of the PVA-based resin used in the PVA-based resin layer of the present invention include unmodified PVA, modified PVA obtained by copolymerizing various monomers during the production of vinyl ester-based resin and saponifying the copolymer, and various post-modified PVAs obtained by introducing various functional groups into unmodified PVA by post-modification. These can be used alone or in combination of two or more kinds. The modification can be performed within a range in which the water solubility of the PVA-based resin is not lost. In some cases, the modified PVA may be further post-modified.

[0036] Examples of monomers that can be used for copolymerization with vinyl ester monomers in the production of vinyl ester resins include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-octadecene; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, and itaconic acid, or their salts, or their mono- or dialkyl esters; nitriles such as acrylonitrile and methacrylonitrile; amides such as acrylamide and methacrylamide; olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid, or their salts; alkyl vinyl ethers; N-acrylamidomethyltrimethylammonium chloride; allyl trimethylammonium chloride; dimethylallyl vinyl ketone; N-vinylpyrrolidone; vinyl chloride; vinylidene chloride; polyoxyethylene (meth)allyl ether, polyoxypropylene (meth)allyl ether, and other polyoxyalkyl ethers. polyoxyalkylene (meth)acrylates such as polyoxyethylene (meth)acrylate and polyoxypropylene (meth)acrylate; polyoxyalkylene (meth)acrylamides such as polyoxyethylene (meth)acrylamide and polyoxypropylene (meth)acrylamide; polyoxyethylene (1-(meth)acrylamide-1,1-dimethylpropyl) ester; polyoxyalkylene vinyl ethers such as polyoxyethylene vinyl ether and polyoxypropylene vinyl ether; polyoxyalkylene allylamines such as polyoxyethylene allylamine and polyoxypropylene allylamine; polyoxyalkylene vinylamines such as polyoxyethylene vinylamine and polyoxypropylene vinylamine; hydroxyl group-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, etc., or derivatives thereof, such as acylated products thereof. Also, 3,4-dihydroxy-1-butene, 3,4-diacyloxy-1-butene, 3-acyloxy-4-hydroxy-1-butene, 4-acyloxy-3-hydroxy-1-butene, 3,4-diacyloxy-2-methyl-1-butene, 4,5-dihydroxy-1-pentene, 4,5-diacyloxy-1-pentene, 4,5-dihydroxy-3-methyl-1-pentene, 4,5-diacyloxy-3-methyl-1-pentene, 5,6-dihydroxy-1-hexene, 5 Examples of compounds having diols include glycerin monovinyl ether, glycerin monoisopropenyl ether, vinyl ethylene carbonate, and 2,2-dimethyl-4-vinyl-1,3-dioxolane. These can be used alone or in combination of two or more.

[0037] Examples of post-modified PVAs in which functional groups have been introduced by post-reaction include those having acetoacetyl groups by reaction with diketene, those having polyalkylene oxide groups by reaction with ethylene oxide, those having hydroxyalkyl groups by reaction with epoxy compounds, and those obtained by reacting aldehyde compounds having various functional groups with PVA resins, etc. These can be used alone or in combination of two or more.

[0038] The PVA resin used in the present invention is preferably a PVA resin suitable for melt molding. As the PVA resin suitable for melt molding, a PVA resin containing a structural unit having a primary hydroxyl group in a side chain or an ethylene-modified PVA resin is preferable, and in particular, a PVA resin containing a structural unit having a primary hydroxyl group in a side chain is preferable because of its excellent melt moldability and water solubility. The number of primary hydroxyl groups in such a structural unit is usually 1 to 5, preferably 1 to 2, and particularly preferably 1. In addition to the primary hydroxyl group, it is preferable to have a secondary hydroxyl group.

[0039] Examples of such PVA resins containing a structural unit having a primary hydroxyl group in the side chain include modified PVA resins having a 1,2-diol structural unit in the side chain, modified PVA resins having a hydroxyalkyl group structural unit in the side chain, etc. Among them, it is particularly preferable to use a modified PVA resin containing a 1,2-diol structural unit in the side chain (hereinafter, sometimes referred to as a "modified PVA resin containing a 1,2-diol structural unit in the side chain") represented by the following general formula (2). The portions other than the 1,2-diol structural units are vinyl alcohol structural units and unsaponified vinyl ester structural units, like ordinary PVA resins.

[0040] [ka] (In the above general formula (2), R 1 ~R 6 each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and X represents a single bond or a bonding chain.

[0041] In the above general formula (2), R 1 ~R 6 each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 1 ~R 6 are preferably all hydrogen atoms since the terminals of the side chains become primary hydroxyl groups, but may be alkyl groups having 1 to 4 carbon atoms in an amount that does not significantly impair the resin properties. The organic group is not particularly limited, but examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and tert-butyl groups, and the alkyl group may have a substituent such as a halogen group, a hydroxyl group, an ester group, a carboxylic acid group, or a sulfonic acid group, as necessary.

[0042] In the above general formula (2), X is a single bond or a bond chain, and is preferably a single bond in terms of thermal stability and stability under high temperature and acidic conditions. The bond chain is not particularly limited, and examples thereof include hydrocarbons such as alkylene, alkenylene, alkynylene, phenylene, and naphthylene (these hydrocarbons may be substituted with halogens such as fluorine, chlorine, and bromine), as well as -O-, -(CHO)-, -(OCH-, -(CHO)CH-, -CO-, -COCO-, -CO(CH)CO-, -CO(CHH)C Examples of the compound include O-, -S-, -CS-, -SO-, -SO2-, -NR-, -CONR-, -NRCO-, -CSNR-, -NRCS-, -NRNR-, -HPO4-, -Si(OR)2-, -OSi(OR)2-, -OSi(OR)2O-, -Ti(OR)2-, -OTi(OR)2-, -OTi(OR)2O-, -Al(OR)-, -OAl(OR)-, and -OAl(OR)O-. Each R is independently a hydrogen atom or any substituent, and preferably a hydrogen atom or an alkyl group (particularly a C1-C4 alkyl group). Furthermore, m is a natural number, preferably 1 to 10, and particularly preferably 1 to 5. Among these, from the standpoint of viscosity stability during production, heat resistance, and the like, alkylene groups having 6 or less carbon atoms, particularly methylene groups, or CH2OCH2- are preferred.

[0043] A particularly preferred structure in the 1,2-diol structural unit represented by the above general formula (2) is R 1 ~R 6 are all hydrogen atoms and X is a single bond.

[0044] The saponification degree (measured in accordance with JIS K 6726) of the PVA resin used in the present invention is usually 60 to 100 mol %. The preferred range of the saponification degree varies depending on the type of modification, and for example, in the case of an unmodified PVA resin, it is usually 60 to 99.9 mol%, preferably 65 to 95 mol%, and particularly preferably 70 to 90 mol%. If the saponification degree is too high, the melting point and the decomposition temperature become close to each other, which tends to make melt molding difficult, and if the saponification degree is too low, water solubility tends to decrease. The degree of saponification of the modified PVA resin containing a 1,2-diol structural unit in a side chain is usually 60 to 99.9 mol%, preferably 65 to 99.8 mol%, and particularly preferably 70 to 99.5 mol%. If the degree of saponification is too low, the water solubility tends to decrease. Furthermore, the saponification degree of the ethylene-modified PVA-based resin modified with a small amount of ethylene is usually 60 mol% or more, preferably 70 to 95 mol%, and particularly preferably 75 to 90 mol%. If the saponification degree is too high, the melting point and the decomposition temperature become close to each other, and melt molding tends to become difficult, whereas if the saponification degree is too low, water solubility tends to decrease.

[0045] The average degree of polymerization (measured in accordance with JIS K 6726) of the PVA resin used in the present invention is usually 100 to 3000, preferably 150 to 2000, particularly preferably 180 to 1000, and further preferably 200 to 800. If the average degree of polymerization is too high, the melt viscosity during melt molding tends to increase, making melt molding difficult.

[0046] When the PVA resin is a modified PVA resin, the modification rate in the modified PVA resin, i.e., the content of structural units derived from various monomers in the copolymer or functional groups introduced by a post-reaction, cannot be generally determined because the characteristics vary greatly depending on the type of functional group, but is usually 0.1 to 20 mol %. Furthermore, when the PVA resin is a modified PVA resin containing a 1,2-diol structural unit in a side chain, the modification rate is usually 0.1 to 20 mol%, preferably 0.5 to 10 mol%, and particularly preferably 1 to 8 mol%. If the modification rate is too high or too low, melt molding tends to become difficult. The content of 1,2-diol structural units in the PVA resin is the same as that of a PVA resin with a saponification degree of 100 mol%. 1 It can be determined from H-NMR spectrum (solvent: DMSO-d6, internal standard: tetramethylsilane). Specifically, it can be calculated from the peak areas derived from the hydroxyl group protons, methine protons, and methylene protons in the 1,2-diol structural unit, the methylene protons of the main chain, and the protons of the hydroxyl group linked to the main chain.

[0047] When the PVA resin is an ethylene-modified PVA resin modified with a small amount of ethylene, the modification rate is usually 0.1 to 15, preferably 0.5 to 10 mol%, more preferably 1 to 10 mol%, and particularly preferably 5 to 9 mol%. If the modification rate is too high, the water solubility tends to decrease, and if it is too low, melt molding tends to become difficult.

[0048] The melting point of the PVA resin is usually 140 to 230°C, preferably 145 to 220°C, more preferably 180 to 200°C, particularly preferably 150 to 200°C, and further preferably 155 to 190°C. The melting point is a value measured by a differential scanning calorimeter (DSC) at a temperature increase and decrease rate of 10° C. / min.

[0049] The PVA resin used in the present invention may be one type or a mixture of two or more types. When two or more types of PVA resins are used, for example, a combination of two or more unmodified PVA resins having different saponification degrees, average polymerization degrees, melting points, etc., a combination of an unmodified PVA resin and a modified PVA resin, a combination of two or more modified PVA resins having different saponification degrees, average polymerization degrees, melting points, types of functional groups, modification rates, etc., are included, and the average values ​​of the saponification degrees, average polymerization degrees, modification rates, etc. are preferably within the preferred ranges of the present invention.

[0050] The main chain of the PVA resin used in the present invention is mainly formed of 1,3-diol bonds, and the content of 1,2-diol bonds is about 1.5 to 1.7 mol %. However, by increasing the polymerization temperature during polymerization of the vinyl ester monomer, the content of 1,2-diol bonds can be increased to 1.8 mol % or more, and further increased to 2.0 to 3.5 mol %.

[0051] The PVA resin used in the present invention can be produced, for example, by polymerizing a vinyl ester monomer such as vinyl acetate and saponifying the polymer.

[0052] As the vinyl ester monomer, for example, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexane carboxylate, vinyl piperate, vinyl octylate, vinyl monochloroacetate, vinyl adipate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl benzoate, vinyl cinnamate, vinyl trifluoroacetate, etc. can be used, but from the viewpoint of price and availability, vinyl acetate is preferably used. Next, such vinyl ester monomer is polymerized and saponified to produce a PVA resin.

[0053] The modified PVA resin containing 1,2-diol structural units in the side chains can be produced by known production methods, for example, the methods described in JP-A-2002-284818, JP-A-2004-285143, and JP-A-2006-95825.

[0054] The PVA resin used in the present invention may be one type or a mixture of multiple types of PVA resins. When a mixture is used, it is preferable that the average saponification degree and average polymerization degree are within the above ranges. In addition to the PVA resin, other water-soluble or water-dispersible resins may be contained as long as they are soluble in water and do not impair the melt extrudability. Examples of water-soluble or water-dispersible resins that can be used in combination include starch derivatives such as starch, oxidized starch, and cation-modified starch; natural proteins such as gelatin and casein; cellulose derivatives such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, and carboxymethyl cellulose; natural polymeric polysaccharides such as sodium alginate and pectic acid; water-soluble resins such as polyvinylpyrrolidone and poly(meth)acrylate salts; SBR latex, NBR latex, vinyl acetate resin emulsion, ethylene-vinyl acetate copolymer emulsion, (meth)acrylic ester resin emulsion, vinyl chloride resin emulsion, and urethane resin emulsion. These can be used alone or in combination of two or more. In order to improve the adhesion between the outer layer 1 and the outer layer 2, an adhesive resin may be mixed into the PVA resin layer.

[0055] <Laminate> As described above, the laminate according to the embodiment of the present invention is a laminate in which the outer layer 1, the intermediate layer, and the outer layer 2 are arranged in this order. The outer layer 1 is the portion of the laminate excluding the intermediate layer and the outer layer 2. The outer layer 2 is the portion of the laminate excluding the intermediate layer and the outer layer 1. As described above, the laminate according to the embodiment of the present invention has a layer containing a PVA-based resin as an intermediate layer, and the difference between the WVTR of the outer layer 1 and the WVTR of the outer layer 2 is 100 cc·30 μm / m 2 It is notable that the period is set at 10 days or more. In particular, the difference between the WVTR of the outermost layer of the outer layer 1 and the WVTR of the outermost layer of the outer layer 2 is 100cc·30μm / m 2 ·day or more is preferable, and 150 to 1000cc·30μm / m 2 ·day is more preferable, especially 200~1000cc·30μm / m 2 ·day, and especially 300 to 900cc·30μm / m 2 ·day is preferable. The outermost layer is the layer located outermost among the layers constituting the laminate. When each outer layer is composed of a single layer, the single layer is the outermost layer. When each outer layer is composed of multiple layers, the single layer that is located farthest from the intermediate layer among the single layers constituting the multiple layers is the outermost layer. In addition, the difference between the WVTR of the composite layer consisting of the outermost layer and another layer adjacent to the outermost layer among the layers constituting outer layer 1 and the WVTR of the outermost layer among the layers constituting outer layer 2, or the WVTR of the composite layer consisting of the outermost layer and another layer adjacent to the outermost layer among the layers constituting outer layer 2, is 100cc·30μm / m 2 ·day or more is preferable, and 150 to 1000cc·30μm / m 2 ·day is more preferable, especially 200~1000cc·30μm / m 2 ·day, and especially 300 to 900cc·30μm / m 2 It is preferable that the difference between the WVTR of the multi-layer structure consisting of the outermost layer and another layer adjacent to the outermost layer among the layers constituting outer layer 2 and the WVTR of the outermost layer among the layers constituting outer layer 1 or the WVTR of the multi-layer structure consisting of the outermost layer and another layer adjacent to the outermost layer among the layers constituting outer layer 1 is also within the above-mentioned numerical ranges. In addition, the difference between the WVTR of the composite layer consisting of the outermost layer and the adhesive resin layer adjacent to the outermost layer among the layers constituting outer layer 1 and the WVTR of the outermost layer among the layers constituting outer layer 2, or the WVTR of the composite layer consisting of the outermost layer and the adhesive resin layer adjacent to the outermost layer among the layers constituting outer layer 2, is 100cc·30μm / m 2 ·day or more is preferable, and 150 to 1000cc·30μm / m 2 ·day is more preferable, especially 200~1000cc·30μm / m 2 ·day, and especially 300 to 900cc·30μm / m 2It is preferable that the difference between the WVTR of the composite layer consisting of the outermost layer and the adhesive resin layer adjacent to the outermost layer among the layers constituting the outer layer 2 and the WVTR of the outermost layer among the layers constituting the outer layer 1, or the WVTR of the composite layer consisting of the outermost layer and the adhesive resin layer adjacent to the outermost layer among the layers constituting the outer layer 1, is also within the above-mentioned numerical ranges. Furthermore, the difference between the WVTR of all layers constituting outer layer 1 and the WVTR of all layers constituting outer layer 2 is 100cc·30μm / m 2 ·day or more is preferable, and 150 to 1000cc·30μm / m 2 ·day is more preferable, especially 200~1000cc·30μm / m 2 ·day, and especially 300 to 900cc·30μm / m 2 ·day is preferable.

[0056] The thickness of the laminate according to the embodiment of the present invention is not particularly limited, but from the viewpoint of significantly exhibiting the effects of the present invention, it is, for example, 3 to 1000 μm, preferably 10 to 500 μm, and more preferably 20 to 200 μm.

[0057] <Method of manufacturing laminate> The laminate of the present invention can be manufactured by a conventionally known molding method, specifically, a melt molding method or a molding method from a solution state can be used. For example, the melt molding method includes a method of melt extrusion laminating an adhesive resin constituting the outer layer 1, a PVA-based resin constituting the intermediate layer, and a resin (e.g., polyamide resin) constituting the outer layer 2, sequentially or simultaneously, on a film or sheet made of a resin constituting the outer layer 1; a method of melt extrusion laminating a PVA-based resin constituting the intermediate layer, an adhesive resin constituting the outer layer 1, and a resin (e.g., aliphatic polyester resin) constituting the outer layer 1, sequentially or simultaneously, on a film or sheet made of a resin constituting the outer layer 2; or a method of co-extrusion or co-injection of the resin and adhesive resin constituting the outer layer 1, the PVA-based resin constituting the intermediate layer, and the resin constituting the outer layer 2. As a molding method from a solution state, there can be mentioned a method in which a solution of an adhesive resin dissolved in a good solvent is solution-coated onto a film or sheet of outer layer 1 or outer layer 2, and after drying, an aqueous solution of a PVA-based resin is solution-coated thereon, and a film or sheet of outer layer 1 or outer layer 2 is laminated thereon. Among them, the melt molding method is preferred, and the co-extrusion method is particularly preferred, since it can be produced in one step and can give a laminate with excellent interlayer adhesion. When using such a melt molding method, it is preferable to use a PVA resin having a 1,2-diol structure in the side chain.

[0058] Specific examples of the coextrusion method include the inflation method, the T-die method, the multi-manifold die method, the feed block method, and the multi-slot die method. As the shape of the die for the outer die bonding method, a T-die, a round die, etc. can be used. The melt molding temperature during melt extrusion is usually 190 to 250°C, and preferably in the range of 200 to 230°C.

[0059] <Packaging material> A packaging material according to an embodiment of the present invention includes the laminate. Specifically, the laminate is preferably used as a packaging material for containers and lids such as bags, cups, trays, tubes, and bottles, and is particularly suitable as a packaging material for food packaging. The packaging material for food packaging is useful as a packaging material for various types of general foods, seasonings such as mayonnaise and dressings, fermented foods such as miso, oily foods such as salad oil, and beverages. Furthermore, the packaging material according to the embodiment of the present invention, since the PVA-based resin having a 1,2-diol structure in the side chain has gas barrier properties, can be suitably used as a packaging material requiring barrier properties. The packaging material according to the embodiment of the present invention may be, for example, a packaging material in which the layer in contact with the packaged item, such as food, is outer layer 2, and the layer in contact with the outside air is outer layer 1. Conversely, the packaging material may be such that the layer in contact with the packaged item, such as food, is outer layer 1, and the layer in contact with the outside air is outer layer 2.

[0060] The laminate and packaging material according to the embodiment of the present invention are excellent in terms of recyclability. For example, the end of a sheet-formed laminate or a used laminate can be immersed in water and stirred to separate the outer layer 1 and the outer layer 2, which can then be recovered.

[0061] <Recycling methods for laminates, etc.> The present invention is also suitably provided as a recycling method for separating and recovering the constituent materials of the laminate or the like. More specifically, one embodiment of the present invention is a laminate having an outer layer 1, an intermediate layer, and an outer layer 2, in which the outer layer 1, the intermediate layer, and the outer layer 2 are arranged in this order, the intermediate layer is a layer containing a polyvinyl alcohol-based resin, and the difference between the WVTR of the outer layer 1 and the WVTR of the outer layer 2 is 100 cc·30 μm / m 2 The present invention is also preferably provided as a recycling method including a step of washing a laminate having a shelf life of 1.0 s or more days, a packaging material including the laminate, or a food packaging material including the laminate with a solvent containing water, and a step of separating outer layer 1 and outer layer 2.

[0062] Furthermore, as one embodiment of the present invention, the present invention is preferably provided as a laminate having an outer layer 1, an intermediate layer, and an outer layer 2, the outer layer 1 being arranged in this order, the intermediate layer being a layer containing a polyvinyl alcohol-based resin, the WVTR of outer layer 1 and the WVTR of outer layer 2 satisfying the following formula (1), a packaging material containing the laminate, or a food packaging material containing the laminate, a recycling method including a step of washing the laminate with a solvent containing water, and a step of separating outer layer 1 and outer layer 2. WVTR of outer layer 1 < WVTR of outer layer 2 (1)

[0063] In addition, a preferred embodiment of the present invention is a laminate having an outer layer 1, an intermediate layer, and an outer layer 2, the outer layer 1, the intermediate layer, and the outer layer 2 being arranged in this order, the intermediate layer being a layer containing a polyvinyl alcohol-based resin, and the difference between the WVTR of the outer layer 1 and the WVTR of the outer layer 2 being 100 cc·30 μm / m 2The present invention is particularly suitable as a recycling method including a step of washing a laminate having a WVTR of 1.0 s or more and in which the WVTR of outer layer 1 and the WVTR of outer layer 2 satisfy the following formula (1), a packaging material including the laminate, or a food packaging material including the laminate, with a solvent containing water, and a step of separating outer layer 1 and outer layer 2. WVTR of outer layer 1 < WVTR of outer layer 2 (1)

[0064] According to this recycling method, the outer layer 1 and the outer layer 2 used as constituent materials of the laminate or packaging material can be quickly separated, and further, the PVA-based resin layer is exposed, so that it dissolves quickly in water, and this is extremely useful in that waste plastic can be easily recovered. EXAMPLES

[0065] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the description of the examples as long as it does not deviate from the gist of the present invention. In the examples, "parts" and "%" are by weight unless otherwise specified.

[0066] Example 1 (1) Preparation of PVA-based resin 1 A reaction vessel equipped with a reflux condenser, a dropping funnel, and a stirrer was charged with 68.0 parts of vinyl acetate, 23.8 parts of methanol, and 8.2 parts of 3,4-diacetoxy-1-butene, and 0.3 mol % (relative to the charged vinyl acetate) of azobisisobutyronitrile was added, and the temperature was raised under a nitrogen stream while stirring to start polymerization. When the polymerization rate of vinyl acetate reached 90%, m-dinitrobenzene was added to terminate the polymerization, and then methanol vapor was blown in to remove unreacted vinyl acetate monomer from the system, yielding a methanol solution of the copolymer.

[0067] Next, the above methanol solution was further diluted with methanol, adjusted to a concentration of 45%, and charged into a kneader. While maintaining the solution temperature at 35°C, a 2% methanol solution of sodium hydroxide was added in a ratio of 10.5 mmol per mol of the total amount of vinyl acetate structural units and 3,4-diacetoxy-1-butene structural units in the copolymer, to carry out saponification. As the saponification proceeded, the saponified product precipitated, and at the point where it became particulate, it was filtered off, thoroughly washed with methanol, and dried in a hot air dryer to produce PVA-based resin 1 having a 1,2-diol structural unit represented by general formula (2) in the side chain. The 1,2-diol structural unit of the obtained PVA-based resin 1 is represented by the general formula (2), which is represented by R 1 ~R 6 is a hydrogen atom and X is a single bond.

[0068] The degree of saponification of the obtained PVA resin 1 was 99.2 mol % as analyzed based on the amount of alkali consumed for hydrolysis of the remaining vinyl acetate and 3,4-diacetoxy-1-butene.

[0069] The average degree of polymerization of PVA resin 1 was analyzed in accordance with JIS K 6726 and was found to be 450. The content of the 1,2-diol structural unit represented by the general formula (2) is 1 %. The concentration was calculated from the integral value measured by 1 H-NMR (300 MHz proton NMR, d6-DMSO solution, internal standard: tetramethylsilane, 50° C.), and was found to be 6 mol %.

[0070] (2) Water vapor transmission rate (WVTR) measurement In accordance with JIS Z 0208 (1976), the mouth of the cup containing the moisture absorbent was sealed by covering it with a measurement sample of the outer layer 1 or outer layer 2, and the cup was placed in a thermo-hygrostat at 40°C and 90% RH. The water vapor transmission rate per unit area was calculated from the change in weight of the moisture absorbent and converted into a thickness of 30 μm. Specifically, in accordance with JIS Z 0208 (1976), a measurement sample of the outer layer 1 or the outer layer 2 cut to a diameter of 70 mm was set in a moisture permeability cup containing approximately 10 g of calcium chloride, and then placed in a thermohygrostat (LH21-11M, manufactured by Nagano Science Co., Ltd.) at a temperature of 40°C and a humidity of 90% RH. The weight increase before and after leaving the sample undisturbed for 24 hours was measured to calculate the water vapor transmission rate, which was then converted to a thickness of 30 μm (multiplied by [thickness of measurement sample (μm) / 30 μm]) to determine the WVTR. In the examples and comparative examples, the WVTR was determined using a single-layer film made of the resin constituting the outermost layer as a measurement sample for the outer layer 1 and the outer layer 2. The results are shown in Table 1.

[0071] (3) Preparation of the laminate A laminate having a four-type, four-layer structure of polyethylene layer / adhesive resin layer / one PVA-based resin layer / polyamide layer was produced using a four-type, five-layer multilayer film-forming device equipped with four extruders. The resin constituting the outermost layer of outer layer 1 was polyethylene (Novatec UF960 manufactured by Japan Polypropylene), the resin constituting the adhesive resin layer of outer layer 1 was modified polyolefin (Modic M533 manufactured by Mitsubishi Chemical), the resin constituting outer layer 2 was polyamide (Novamid 2030J manufactured by DSM), and the PVA-based resin 1 obtained above was used as the resin constituting the PVA-based resin layer, which is the intermediate layer. The set temperatures of each extruder and roll were as follows.

[0072] [Set temperature] (C1~C4: cylinders, H: head, J: joint, FD1,2: front dies, D1~3: dies.) Polyamide: C1 / C2 / C3 / C4 / H / J=200℃ / 225℃ / 230℃ / 235℃ / 230℃ / 220℃ PVA resin 1: C1 / C2 / C3 / C4 / H / J=180℃ / 200℃ / 210℃ / 210℃ / 210℃ / 210℃ Polyethylene: C1 / C2 / C3 / C4 / H / J=190℃ / 210℃ / 210℃ / 220℃ / 220℃ / 220℃ Adhesive resin: C1 / C2 / C3 / C4 / H / J=190℃ / 210℃ / 210℃ / 220℃ / 220℃ / 220℃ Dies: FD1 / FD2 / D1 / D2 / D3=220℃ Roll: 60℃

[0073] (4) Evaluation (peeling time) The laminate obtained above was cut into 2 cm squares to prepare test pieces. 600 mL of water was placed in a 750 mL container and heated to 40° C., and the test pieces were immersed in the water and stirred at 400 rpm. The time until the outer layer 1 and the outer layer 2 were completely peeled off was measured with a stopwatch. The results are shown in Table 1.

[0074] Example 2 A laminate was prepared in the same manner as in Example 1, except that the intermediate layer was replaced with a composition of 80 parts of the PVA resin 1 obtained above and 20 parts of polybutylene adipate terephthalate (hereinafter referred to as "PBAT"; "Ecoflex" manufactured by BASF) instead of the PVA resin 1 in Example 1 (polyethylene layer / adhesive resin layer / composition layer containing PVA resin 1 and PBAT / polyamide layer). Evaluation was performed in the same manner as in Example 1, and the results are shown in Table 1.

[0075] Comparative Example 1 A laminate was prepared in the same manner as in Example 1, except that outer layer 1 and outer layer 2 were made of polyamide ("Novamid 2030J" manufactured by DSM). (Polyamide layer / 1 PVA-based resin layer / polyamide layer) Evaluation was performed in the same manner as in Example 1, and the results are shown in Table 1.

[0076] Comparative Example 2 A laminate was prepared in the same manner as in Example 2, except that the outer layer 1 and the outer layer 2 were made of polyamide ("Novamid 2030J" manufactured by DSM). (Polyamide layer / composition layer containing PVA-based resin 1 and PBAT / polyamide layer). Evaluation was performed in the same manner as in Example 1, and the results are shown in Table 1.

[0077] Comparative Example 3 A laminate was prepared in the same manner as in Example 1 (polyethylene layer / adhesive resin layer / 1 layer of PVA-based resin / adhesive resin layer / polyethylene layer) except that the outer layer 2 was a multilayer consisting of an outermost layer and an adhesive resin layer, the resin constituting the outermost layer of the outer layer 2 was polyethylene ("Novatec UF960" manufactured by Japan Polypropylene Corporation), and the resin constituting the adhesive resin layer of the outer layer 2 was modified polyolefin ("Modic M533" manufactured by Mitsubishi Chemical Corporation). Evaluation was performed in the same manner as in Example 1, and the results are shown in Table 1.

[0078] Comparative Example 4 In Example 1, the resin constituting the outermost layer of the outer layer 1 was polypropylene ("Novatec EA7AD" manufactured by Japan Polypropylene Corporation), the outer layer 2 was a multilayer consisting of the outermost layer and an adhesive resin layer, the resin constituting the outermost layer of the outer layer 2 was polypropylene ("Novatec EA7AD" manufactured by Japan Polypropylene Corporation), and the resin constituting the adhesive resin layer of the outer layer 2 was modified polyolefin ("ModicM533" manufactured by Mitsubishi Chemical Corporation). Except for this, a laminate was produced in the same manner as in Example 1 (polypropylene layer / adhesive resin layer / 1 layer of PVA-based resin / adhesive resin layer / polypropylene layer). Evaluation was performed in the same manner as in Example 1, and the results are shown in Table 1.

[0079] [Table 1]

[0080] In Examples 1 and 2, which used the laminate of the present invention, the laminate peeled off within 10 minutes and was highly recoverable, whereas in Comparative Examples 1 to 4, which used the same resin for outer layer 1 and outer layer 2, the laminate took 20 minutes or more to peel off and was poor in recoverability.

[0081] In the above embodiment, specific embodiments of the present invention are shown, but the above embodiment is merely illustrative and should not be interpreted as being limiting. Various modifications that are obvious to those skilled in the art are intended to be within the scope of the present invention. [Industrial Applicability]

[0082] The laminate of the present invention can be quickly separated into the outer layer 1 and the outer layer 2 used as constituent materials by simply immersing it in water, and waste plastic can be recovered. Therefore, the laminate of the present invention is suitably used as a packaging material, particularly a food packaging material.

Claims

1. A laminate having an outer layer 1, an intermediate layer and an outer layer 2, The outer layer 1, the intermediate layer, and the outer layer 2 are arranged in this order, the intermediate layer is a layer containing a polyvinyl alcohol-based resin, The intermediate layer has a thickness of 0.1 to 5 μm, The polyvinyl alcohol resin is a modified polyvinyl alcohol resin having a modification rate of 0.1 to 20 mol % (excluding ethylene-modified polyvinyl alcohol resins having an ethylene modification rate of 10 mol % or more), and has a primary hydroxyl group in a side chain, The difference between the water vapor permeability of the outer layer 1 and the water vapor permeability of the outer layer 2 is 100 cc·30 μm / m 2 ・day or more, A laminate, wherein the water vapor permeability of the outer layer 1 and the water vapor permeability of the outer layer 2 satisfy the following formula (1): Water vapor permeability of outer layer 1 < water vapor permeability of outer layer 2 ... (1)

2. The water vapor permeability of the outer layer 1 is 100cc・30μm / m 2 day or less, and the water vapor permeability of the outer layer 2 is 200 to 1000cc 30μm / m 2 2. The laminate according to claim 1, wherein the average molecular weight is 1000.

3. 3. The laminate according to claim 1 or 2, wherein the outer layer 1 comprises a layer containing a polyolefin.

4. The laminate according to any one of claims 1 to 3, wherein the outer layer 2 comprises a layer containing polyamide.

5. A packaging material comprising the laminate according to any one of claims 1 to 4.

6. A food packaging material comprising the laminate according to any one of claims 1 to 4.

7. A laminate having an outer layer 1, an intermediate layer and an outer layer 2, The outer layer 1, the intermediate layer, and the outer layer 2 are arranged in this order, the intermediate layer is a layer containing a polyvinyl alcohol-based resin, The difference between the water vapor permeability of the outer layer 1 and the water vapor permeability of the outer layer 2 is 100 cc·30 μm / m 2 - washing the laminate that has been used for 1 day or more with a solvent containing water; A step of separating the outer layer 1 and the outer layer 2; Recycling methods including:

8. A laminate having an outer layer 1, an intermediate layer and an outer layer 2, The outer layer 1, the intermediate layer, and the outer layer 2 are arranged in this order, the intermediate layer is a layer containing a polyvinyl alcohol-based resin, A laminate in which the water vapor permeability of the outer layer 1 and the water vapor permeability of the outer layer 2 satisfy the following formula (1) washing with a solvent containing water; A step of separating the outer layer 1 and the outer layer 2; Recycling methods including: Water vapor permeability of outer layer 1 < water vapor permeability of outer layer 2 ... (1)

Images