JP2023018713A - Film for heat seal and separation and recovery method for the same - Google Patents

Abstract

To provide a film for heat seal which has a heat fusion layer soluble in an aqueous solution, and is excellent in separation recovery property and heat seal strength under high humidity, and a separation and recovery method for the film for heat seal.SOLUTION: A film for heat seal is provided in which a heat fusion layer (X) composed of a water-soluble resin composition (S) is provided on one outermost layer, and a water-insoluble base material layer (Z) including at least one selected from the group consisting of a thermoplastic resin, paper and a metallic foil is provided on the other outermost layer, wherein an equilibrium moisture content at a temperature of 23°C and relative humidity of 50% of the water-soluble resin composition (S) is 3 mass% or more and 10 mass% or less, the water-soluble resin composition (S) includes a hydroxyl group-containing resin (A) having a melting point of 220°C or lower as a main component, and the water-soluble resin composition (S) includes 100 ppm or more and 2,000 ppm or less of alkali metal ions (B).SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a heat-sealing film in which a heat-sealable layer can be easily dissolved and removed, and layers other than the heat-sealable layer can be separated and recovered with high purity, and a method for separating and recovering the same.

Various materials having various functions such as heat resistance, mechanical properties, gas barrier properties, and heat sealing properties are laminated and used for packaging materials such as food packaging. For example, polyester is used to improve heat resistance, polyamide to improve mechanical properties, ethylene-vinyl alcohol copolymer and polyvinylidene chloride to improve gas barrier properties, and polyethylene and polypropylene to improve heat sealability. Various polyolefins such as

On the other hand, in recent years, environmental problems and waste problems have triggered a demand for so-called post-consumer recycling (hereinafter sometimes simply referred to as recycling), which collects and recycles packaging materials that have been consumed in the market. rising worldwide. In this regard, packaging materials are required to be composed of a single material as much as possible (mono-materialization), so that high-purity and high-quality recycled raw materials can be obtained. On the other hand, when it is difficult to make a monomaterial, a method has been proposed in which the layers that hinder recyclability are separated from each other, and each layer is separated and collected individually. The concept of facilitating recycling is described by providing an intervening layer in the layer and separating by immersion in a solvent.

WO2020/166685

In recent years, while various recycling technologies have been studied, in the technology for separating substrate layers made of different materials adjacent to each other in a solution as described in Patent Document 1, the separated layers are separated. It is necessary to collect them individually and without mixing them together. However, in the recycling technology that requires separation in a short time or under mild conditions, the intervening layer does not dissolve sufficiently and the process There were problems with passageability and separation and recovery accuracy.

On the other hand, the present inventors have discovered the possibility of widening the range of film production methods and the range of layer structures of packaging materials by using a solvent-soluble layer as a heat-sealable layer, and have started investigations. However, it was found that, as a result of increasing the solubility in a solvent in order to improve the process passability and the separation and recovery properties as described above, the heat seal strength may decrease especially under high humidity.

The present invention has been made to solve the above problems, and provides a heat-sealing film having a heat-sealable layer soluble in an aqueous solution and having excellent separation-recoverability and high-humidity heat-sealing strength, and a method for separating and recovering the same. for the purpose.

The above issues are
[1] A heat-sealable layer (X) made of a water-soluble resin composition (S) is provided on one outermost layer and contains at least one selected from the group consisting of a thermoplastic resin, paper, and metal foil. The substrate layer (Z) is provided as the other outermost layer, and the equilibrium moisture content at a temperature of 23 ° C. and a relative humidity of 50% of the water-soluble resin composition (S) is 3% by mass or more and 10% by mass or less, and water-soluble A film for heat sealing, wherein the resin composition (S) contains a hydroxyl group-containing resin (A) having a melting point of 220° C. or less as a main component, and the water-soluble resin composition (S) contains an alkali metal ion (B) of 100 ppm or more and 2000 ppm or less. ;
[2] The heat-sealing film of [1], wherein the heat-sealable layer (X) is directly laminated on the substrate layer (Z);
[3] The heat-sealing film of [1], further comprising an adhesive layer (Y), wherein the heat-sealable layer (X) is laminated on the substrate layer (Z) via the adhesive layer (Y);
[4] The heat sealing film of [3], wherein the heat-sealable layer (X), the adhesive layer (Y) and the substrate layer (Z) are coextruded films or a part thereof;
[5] The heat-sealing film of any one of [1] to [4], wherein the substrate layer (Z) consists of a plurality of layers;
[6] The heat-sealing film of any one of [1] to [5], wherein the hydroxyl-containing resin (A) is a vinyl alcohol polymer (A1);
[7] The heat-sealing film of [6], wherein the vinyl alcohol polymer (A1) has a viscosity average degree of polymerization of 400 or more and 2000 or less;
[8] The heat-sealing film of [6] or [7], wherein the degree of saponification of the vinyl alcohol polymer (A1) is 70 mol% or more and 95 mol% or less;
[9] The water-soluble resin composition (S) contains 5% by mass or more and 40% by mass or less of the plasticizer (C), and the plasticizer (C) is glycerin, polyethylene glycol, polypropylene glycol, polyglycerin, mannitol, sorbitol, and pentaerythritol, the heat-sealing film of any one of [1] to [8];
[10] The heat seal of any one of [1] to [9], wherein the total thickness is 20 μm or more and 350 μm or less, and the thickness ratio of the heat sealing layer (X) to the total thickness is 1% or more and 20% or less. film for;
[11] Oxygen permeability at a temperature of 20° C. and a relative humidity of 65%, measured according to JIS K 7126-2 (isobaric method; 2006), is 10 cc/(m ² ·day · atm) or less. 1] The heat-sealing film according to any one of [10];
[12] Of [1] to [11], having a moisture permeability of 50 g/(m ² day) or less at a temperature of 40°C and a relative humidity of 90%, measured according to JIS Z 0208 (1976). Any heat sealing film;
[13] The heat sealing strength obtained by placing the heat sealing layers (X) facing each other and pressing them for 1 second at a temperature of 185 ° C. and a pressure of 0.1 MPa using a hot plate heat sealer is 1 N / 15 mm or more. The heat-sealing film of any one of [1] to [12];
[14] According to any one of [1] to [13], the thermal adhesive layer (X) is dissolved and removed within 5 minutes when the sheet is cut into a 2 cm square and stirred in an aqueous solution (W) at 50°C. of the heat sealing film;
[15] A packaging material comprising the heat-sealable film of any one of [1] to [14];
[16] The heat-sealing film according to any one of [1] to [14] is brought into contact with an aqueous solution (W) at 20° C. or higher and 98° C. or lower to dissolve the heat-sealable layer (X), and heat-seal the film. Separation and recovery method for recovering the film from which the deposited layer (X) has been removed;
is resolved by providing

According to the present invention, it is possible to provide a heat-sealing film having a heat-sealable layer soluble in an aqueous solution and having excellent separation-recoverability and high-humidity heat-seal strength, and a method for separating and recovering the same.

As used herein, the term "heat-sealable layer" means a layer that can be heat-sealed. "Aqueous solution soluble" means being soluble in an aqueous solution (W) described later. The “separation and recovery property” refers to the property that the heat sealing layer (X) does not remain when the film from which the heat sealing layer (X) is removed is recovered by the separation and recovery method of the present invention (heat sealing layer (X ) means the property of being sufficiently dissolved), and can be specifically evaluated by the method described in Examples. The term "heat seal strength under high humidity" means the T-peel strength after heat-sealing the heat-sealable layer of the heat-sealable film of the present invention and storing it under high humidity. It can be evaluated by the method described in Examples.

The heat-sealing film of the present invention includes a heat-sealable layer (X) made of a water-soluble resin composition (S) on one outermost layer, and at least one selected from the group consisting of thermoplastic resins, paper and metal foil. The water-insoluble base layer (Z) containing seeds is provided as the other outermost layer, and the equilibrium moisture content of the water-soluble resin composition (S) at a temperature of 23 ° C. and a relative humidity of 50% is 3% by mass or more and 10% by mass. The water-soluble resin composition (S) contains a hydroxyl-containing resin (A) having a melting point of 220° C. or less (hereinafter, sometimes simply referred to as “hydroxyl-containing resin (A)”) as a main component, The resin composition (S) contains 100 ppm or more and 2000 ppm or less of alkali metal ions (B). The heat-sealing film of the present invention is provided with the heat-sealing layer (X) made of the water-soluble resin composition (S) as one of the outermost layers, so that the heat-sealing property under high humidity and the separating and recovering property are excellent. can demonstrate In addition, depending on the type of the substrate layer (Z) provided as the other outermost layer, necessary functions such as heat resistance, mechanical properties and gas barrier properties can be imparted. Further, when the equilibrium moisture content of the water-soluble resin composition is within a specific range, there is a tendency to achieve both solubility in an aqueous solution and high-humidity heat seal strength. In addition, when the water-soluble resin composition (S) contains the hydroxyl group-containing resin (A) having a melting point of 220° C. or less as a main component, it tends to be enhanced in thermal fusion bondability. Furthermore, when the water-soluble resin composition (S) contains a specific amount of the alkali metal ion (B), it tends to achieve both solubility in an aqueous solution and high-humidity heat seal strength. Therefore, the heat-sealing film of the present invention exhibits sufficient heat-sealing properties under normal conditions of use as a packaging material, while the heat-sealable layer can be easily dissolved and removed after use as a packaging material. Layers other than the heat-sealable layer can be separated and recovered with high purity. In addition, by selecting the base material layer, it is possible to improve recyclability without deteriorating the performance and quality as a packaging material, thereby contributing to the realization of a recycling-oriented society.

(Thermal fusion layer (X))
The heat-sealable film of the present invention has a heat-sealable layer (X) made of a water-soluble resin composition (S) as one outermost layer. The heat-sealable layer (X) has excellent heat-sealing properties and water solubility, and imparts heat-sealing properties and recyclability (separability and recovery properties) to the heat-sealable film of the present invention. The heat-sealable layer (X) used in the present invention is a layer in which the main component thereof dissolves in an aqueous solution (W), and the main component thereof is brought into contact with the aqueous solution (W) at 20°C to 98°C. It may be a layer that dissolves at

The thickness of the thermal adhesive layer (X) is preferably 5 μm or more and 50 μm or less, more preferably 15 μm or more and 30 μm or less, from the viewpoint of heat sealing property and dissolution removal property.

(Water-soluble resin composition (S))
The water-soluble resin composition (S) has an equilibrium moisture content of 3% by mass or more and 10% by mass or less at a temperature of 23° C. and a relative humidity of 50%. The lower limit of the equilibrium moisture content at a temperature of 23° C. and a relative humidity of 50% is preferably 5% by mass, and the upper limit is preferably 8% by mass. If the equilibrium moisture content is less than the lower limit, the water solubility of the heat-sealable layer (X) made of the water-soluble resin composition (S) will be insufficient, and separation and recovery properties will tend to deteriorate. On the other hand, if the equilibrium moisture content exceeds the upper limit, the appearance of the heat-sealed portion of the heat-sealable layer (X) made of the water-soluble resin composition (S) and the heat-seal strength under high humidity tend to deteriorate. Become.

(Hydroxyl group-containing resin (A))
The water-soluble resin composition (S) contains a hydroxyl group-containing resin (A) having a melting point of 220°C or less as a main component. Since the water-soluble resin composition (S) contains the hydroxyl-containing resin (A) as a main component, the heat-sealable layer (X) tends to exhibit heat sealability and water solubility. Here, "containing as a main component" means containing more than 50% by mass. Further, the hydroxyl group-containing resin (A) means a resin containing a hydroxyl group, and from the viewpoint of increasing the solubility in an aqueous solution (W) described later, hydroxyl groups is preferably 80 mol% or more, more preferably 85 mol% or more, and may be 90 mol% or more or 95 mol% or more. On the other hand, the proportion of monomer units having a hydroxyl group in the total monomer units of the hydroxyl-containing resin (A) may be 99 mol % or less. The melting point of the hydroxyl group-containing resin (A) is preferably 200° C. or lower, more preferably 180° C. or lower, in order to improve melt moldability and heat-sealability. The lower limit of the melting point of the hydroxyl group-containing resin (A) is not particularly limited, but from the viewpoint of maintaining heat resistance as a packaging material, it is generally 100°C or higher, and may be 150°C or higher.

Examples of the hydroxyl group-containing resin (A) include starch-based polymer components such as cornstarch, cellulose-based polymers such as carboxymethyl cellulose and carboxyethyl cellulose, acrylic acid-based polymers such as sodium polyacrylate, and vinyl alcohol-based polymers such as polyvinyl alcohol. A coalescence etc. are mentioned. Among them, the vinyl alcohol polymer (A1) is preferred from the viewpoint of melt moldability, solution stability, heat-sealability, biodegradability, and adhesion to the adhesive layer (Y) described later.

The vinyl alcohol polymer (A1) is a polymer containing vinyl alcohol units. Examples of the vinyl alcohol polymer (A1) include polyvinyl alcohol (hereinafter sometimes referred to as "PVA") obtained by homopolymerizing and saponifying a vinyl ester, and modified PVA having other modifying groups. mentioned. Modified PVA may be copolymer-modified or post-modified.

The viscosity average degree of polymerization of the vinyl alcohol polymer (A1) is preferably 400 or more and 2000 or less. The lower limit of the viscosity-average degree of polymerization is more preferably 500, and even more preferably 700. When the viscosity-average degree of polymerization is at least the above lower limit, the vinyl alcohol polymer (A1) tends to have good thermal stability and heat-sealability. On the other hand, the upper limit of the viscosity-average degree of polymerization is more preferably 1,500, more preferably 1,000. When the viscosity-average degree of polymerization is equal to or less than the above upper limit, the melt moldability and water solubility of the vinyl alcohol polymer (A1) tend to be good.

The viscosity average degree of polymerization of the vinyl alcohol polymer (A1) is measured according to JIS K 6726:1994. Specifically, the intrinsic viscosity [η] (liter / g) of the vinyl alcohol polymer (A1) is measured in water at 30 ° C., and the value of the intrinsic viscosity [η] is used to calculate the viscosity average according to the following formula. The degree of polymerization P is calculated. When the degree of saponification of the vinyl alcohol polymer (A1) is less than 99.5 mol%, the intrinsic viscosity [η] is measured after saponification until the degree of saponification reaches 99.5 mol% or more.
P = ([η] x 104/8.29) ^(1/0.62)

The degree of saponification of the vinyl alcohol polymer (A1) is preferably 70 mol% or more, more preferably 75 mol% or more, and even more preferably 85 mol% or more. When the degree of saponification is 70 mol % or more, the vinyl alcohol polymer (A1) has excellent water solubility, and the separation and recovery of the heat-sealing film is improved. The degree of saponification of the vinyl alcohol polymer (A1) is preferably 95 mol% or less, more preferably 93 mol% or less, even more preferably 90 mol% or less. When the degree of saponification is 95 mol% or less, the melt moldability of the vinyl alcohol polymer (A1) is excellent. The degree of saponification of the vinyl alcohol polymer (A1) is measured according to JIS K6726:1994.

The vinyl alcohol-based polymer (A1) may contain monomer units other than vinyl alcohol units and vinyl ester units as long as the effects of the present invention are not impaired. Examples of such monomers include α-olefins such as ethylene, propylene, n-butene and isobutylene; acrylic acid and its salts; acrylic acid esters; methacrylic acid and its salts; methacrylic acid esters; , N-ethylacrylamide, N,N-dimethylacrylamide, diacetoneacrylamide, acrylamidopropanesulfonic acid and its salts, acrylamidopropyldimethylamine and its salts or quaternary salts thereof, N-methylolacrylamide and its derivatives and other acrylamide derivatives; Methacrylamide; N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamide propanesulfonic acid and its salts, methacrylamidopropyldimethylamine and its salts or quaternary salts thereof, N-methylolmethacrylamide and its derivatives, and other methacrylamides Derivatives; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile vinyl halides such as vinyl chloride and vinyl fluoride; vinylidene halides such as vinylidene chloride and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; unsaturated dicarboxylic acids such as maleic acid, itaconic acid and fumaric acid; salts thereof or esters thereof; vinylsilyl compounds such as vinyltrimethoxysilane; isopropenyl acetate; The content of these monomers varies depending on the purpose and application, but is preferably 10 mol% or less, more preferably less than 5 mol%, even more preferably less than 3 mol%, and particularly less than 1 mol%. Preferably, it may be 0 mol %. The vinyl alcohol polymer (A1) may contain one type alone or may contain two or more types.

(Alkali metal ion (B))
The water-soluble resin composition (S) contains 100 ppm or more and 2000 ppm or less of alkali metal ions (B). The lower limit of the content of alkali metal ions (B) is more preferably 300 ppm, more preferably 500 ppm. When the content of the alkali metal ion (B) is less than the above lower limit, the thermal stability of the water-soluble resin composition (S) is lowered, the adhesiveness to the adhesive layer (Y) described later is lowered, and high humidity Insufficient heat seal strength underneath. Moreover, the water solubility of the water-soluble resin composition (S) is lowered. On the other hand, the upper limit of the content of alkali metal ions (B) is more preferably 1500 ppm, more preferably 1000 ppm. If the content of the alkali metal ion (B) exceeds the above upper limit, the water-soluble resin composition (S) tends to be colored and the heat seal strength under high humidity becomes insufficient.

Alkali metal ions (B) include lithium ions, sodium ions and potassium ions. From the viewpoint of economy and balance of physical properties, sodium ion or potassium ion is preferred, and sodium ion is more preferred.

The alkali metal ion (B) may exist in a state of being dissociated from the anion that constitutes the alkali metal salt, or may exist in a state of a salt bound to the anion. In addition, it may exist in a coordinated state with a group (for example, a carboxy group, a hydroxyl group, etc.) possessed by the vinyl alcohol-based polymer (A1) or other optional components.

The alkali metal ion (B) is usually derived from a salt, but the components constituting the alkali metal ion (B) are not particularly limited, and fatty acid metal salts and metal salts other than fatty acid metal salts (nitrates, sulfate, etc.) can also be used.

The fatty acid metal salt may be a higher fatty acid metal salt having 12 or more carbon atoms or a fatty acid metal salt having 11 or less carbon atoms. A higher fatty acid metal salt is preferred, and a fatty acid metal salt having 11 or less carbon atoms is preferred from the viewpoint of improving the water solubility of the water-soluble resin composition (S). Higher fatty acid metal salts having 12 or more carbon atoms include lauric acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, hydroxystearic acid, nonadecanic acid, oleic acid, behenic acid, montan Metal salts of acids and fatty acids such as linoleic acid are included. Examples of fatty acid metal salts having 11 or less carbon atoms include acetates and propionates. These may be contained singly or in combination of two or more.

It is preferable that the water-soluble resin composition (S) of the present invention further contains a plasticizer (C) in an amount of 5% by mass or more and 40% by mass or less. Inclusion of the plasticizer (C) improves the melt moldability, heat-sealability, and solubility in an aqueous solution (W) described below of the vinyl alcohol polymer (A1). Although the molecular weight of the plasticizer (C) is not particularly limited, it is preferably 10,000 or less, more preferably 2,000 or less, even more preferably 200 or less, and particularly preferably 100 or less from the viewpoint of improving water solubility. As a lower limit of content of a plasticizer (C), 10 mass % is more preferable. The upper limit of the content of the plasticizer (C) is more preferably 30% by mass. The plasticizer (C) is preferably at least one selected from the group consisting of glycerin, polyethylene glycol, polypropylene glycol, polyglycerin, mannitol, sorbitol, and pentaerythritol, consisting of glycerin, polyethylene glycol, mannitol, and sorbitol. It is more preferably at least one selected from the group, more preferably at least one selected from the group consisting of glycerin, mannitol and sorbitol, and particularly preferably glycerin.

The water-soluble resin composition (S) contains other components other than the hydroxyl group-containing resin (A), the alkali metal ion (B), and the plasticizer (C) as long as the effects of the present invention are not impaired. good too. Other components include, for example, polyvalent metal ions, carboxylic acids, phosphoric acid compounds, antioxidants, antioxidants, heat stabilizers (melt stabilizers), photoinitiators, deodorants, ultraviolet absorbers, and antistatic agents. , lubricants, colorants, fillers, desiccants, fillers, pigments, dyes, processing aids, flame retardants, antifog agents, and the like. The content of other components in the water-soluble resin composition (S) is usually 5% by mass or less, preferably 3% by mass or less, more preferably 1% by mass or less.

The proportion of the hydroxyl group-containing resin (A) in the water-soluble resin composition (S) is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and particularly preferably 90% by mass or more. It may be 95% by mass or more, 97% by mass or more, 98% by mass or more, or 99% by mass or more. Further, the proportion of the hydroxyl group-containing resin (A) in the total resins constituting the water-soluble resin composition (S) is preferably 70% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more. 99% by mass or more is particularly preferable, and all resins constituting the water-soluble resin composition (S) may substantially consist only of the hydroxyl group-containing resin (A). The ratio of the hydroxyl group-containing resin (A) and the alkali metal ion (B) in the water-soluble resin composition (S) is preferably 70% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more. 99% by mass or more is particularly preferable, and the water-soluble resin composition (S) may consist essentially of the hydroxyl group-containing resin (A) and the alkali metal ion (B). Further, when the water-soluble resin composition (S) contains a plasticizer (C), the hydroxyl group-containing resin (A), the alkali metal ion (B) and the plasticizer (C) in the water-soluble resin composition (S) The proportion occupied is preferably 70% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, particularly preferably 99% by mass or more, and the water-soluble resin composition (S) is substantially a hydroxyl-containing resin ( A), alkali metal ion (B) and plasticizer (C) may be used alone.

The method for preparing the water-soluble resin composition (S) of the present invention is not particularly limited. Any method may be used as long as it can be mixed. For example, a method of blending a hydroxyl group-containing resin (A), an alkali metal ion (B), and optionally a plasticizer (C) and other components, followed by melt kneading and pelletizing, a method of pelletizing a hydroxyl group-containing resin ( A), a method in which alkali metal ions (B) and, if necessary, a plasticizer (C) and other components are separately charged at a constant rate while kneading and pelletizing; B) is introduced in advance, and then the plasticizer (C) and other components are blended as necessary, followed by melt-kneading and pelletizing; After introduction, these components and, if necessary, the plasticizer (C) and other components are separately charged into a melt-kneader at a constant rate while kneading and pelletizing.

(Base layer (Z))
The heat-sealable film of the present invention comprises a non-water-soluble substrate layer (Z) containing at least one selected from the group consisting of thermoplastic resins, paper and metal foil, which is the othermost layer than the heat-sealable layer (X). Prepare for the outer layer. Thermoplastic resins constituting the substrate layer (Z) include, for example, various polyolefins (polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene-propylene copolymer, ethylene and 4 or more carbon atoms α-olefin copolymer, polyolefin and maleic anhydride copolymer, ethylene-vinyl ester copolymer, ethylene-vinyl alcohol copolymer, ethylene-acrylic acid ester copolymer, or modified polyolefin graft-modified with saturated carboxylic acid or its derivative), various polyamides (nylon 6, nylon 6.6, nylon 6/66 copolymer, nylon 11, nylon 12, poly-meta-xylylene adipamide, etc.), various Examples include polyester (polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), polyvinyl chloride, polyvinylidene chloride, polystyrene, polyacrylonitrile, polyurethane, polycarbonate, polyacetal, polyacrylate and the like. Among them, polyethylene terephthalate is preferable as the thermoplastic resin constituting the substrate layer (Z) from the viewpoint of excellent balance between heat resistance and mechanical properties.

The thermoplastic resin constituting the substrate layer (Z) may contain various additives as long as the effects of the present invention are not impaired. Such additives include heat stabilizers, antioxidants, UV absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, stabilizers, surfactants, desiccants, cross-linking agents, fiber reinforcement agents and the like. The content of the additive in the thermoplastic resin is usually 5% by mass or less, preferably 3% by mass or less, more preferably 1% by mass or less.

Various types of natural paper, synthetic paper, and the like can be used as the paper that constitutes the base material layer (Z). Examples of the metal foil constituting the base layer (Z) include at least one metal foil selected from the group consisting of gold, silver, copper, nickel, stainless steel, magnesium alloys and aluminum. Aluminum foil is preferable from the viewpoint of gas barrier properties.

The substrate layer (Z) may be a single layer or may have a multi-layer structure consisting of a plurality of layers. When the substrate layer (Z) is a multi-layer structure, the number of layers is preferably 2 or more and 9 or less from the viewpoint of economically imparting functions such as gas barrier properties. The thickness of the base layer (Z) is preferably 10 μm to 300 μm, more preferably 25 μm to 150 μm, and may be 75 μm to 150 μm, from the viewpoint of handling property as a packaging material and resource saving. When the substrate layer (Z) has a multi-layer structure, it preferably has an inorganic deposition layer (I), which will be described later, from the viewpoint of efficiently imparting gas barrier properties.

The method for forming the multilayer structure of the base material layer (Z) is not particularly limited, and examples thereof include lamination methods such as known dry lamination methods, co-injection molding methods, and co-extrusion methods, but are not particularly limited. . The coextrusion molding method includes a coextrusion lamination method, a coextrusion film/sheet molding method, a coextrusion blow molding method, and the like. Moreover, you may use these methods together.

The substrate layer (Z) may comprise an inorganic deposition layer (I). The inorganic deposition layer (I) is a layer made of inorganic substances such as metals and inorganic oxides and having gas barrier properties against oxygen and water vapor. The thickness of the inorganic vapor deposition layer (I) is generally less than 500 nm. When the thickness is less than 500 nm, the pulverized product of the multilayer structure containing the inorganic deposition layer (I) is melt-molded with excellent viscosity stability, and the generation of gels and lumps can be suppressed, resulting in excellent recyclability. become a trend.

The inorganic vapor deposition layer (I) is preferably either a metal vapor deposition layer or an inorganic oxide vapor deposition layer. A metal vapor deposition layer is preferable when imparting a light-shielding property, but from the viewpoint of the visibility of the contents as a packaging material, the range suitability, and the ability to suppress the generation of gels and lumps when melting and molding the pulverized material, inorganic oxidation A vapor deposited layer is preferred.

A metal deposition layer is generally a layer containing aluminum as a main component. The content of aluminum atoms in the metal deposition layer is preferably 50 mol% or more, more preferably 70 mol% or more, still more preferably 90 mol% or more, and particularly preferably 95 mol% or more. The average thickness of the vapor-deposited metal layer is preferably 120 nm or less, more preferably 100 nm or less, and even more preferably 90 nm or less. Moreover, the average thickness of the metal deposition layer is preferably 25 nm or more, more preferably 35 nm or more, and even more preferably 45 nm or more. The average thickness of the vapor deposited metal layer is the average value of the thickness at arbitrary 10 points on the cross section of the vapor deposited metal layer measured with an electron microscope. When the substrate layer (Z) has a vapor-deposited metal layer, the light transmittance at a wavelength of 600 nm can be 10% or less, and the light shielding property is excellent.

The inorganic oxide deposition layer is an inorganic oxide such as oxides of silicon, aluminum, magnesium, calcium, potassium, tin, sodium, boron, titanium, lead, zirconium, yttrium, preferably alumina (aluminum oxide). Alternatively, a deposited film of silica (oxide of silicon) may be used. The average thickness of the inorganic oxide deposition layer is preferably 60 nm or less, more preferably 50 nm or less, and even more preferably 40 nm or less. Moreover, the average thickness of the inorganic oxide deposition layer is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more. The average thickness of the deposited inorganic oxide layer is the average value of the thickness at arbitrary 10 points on the cross section of the deposited inorganic oxide layer measured with an electron microscope. When the substrate layer (Z) has an inorganic oxide deposition layer, the light transmittance at a wavelength of 600 nm can be 80% or more, and the visibility of the contents when used as a packaging material is excellent.

The inorganic vapor deposition layer (I) can be formed by a known physical vapor deposition method or chemical vapor deposition method. Specific examples include vacuum vapor deposition, sputtering, ion plating, ion beam mixing, plasma CVD, laser CVD, MO-CVD, and thermal CVD, but physical vapor deposition is used. Among them, it is particularly preferable to use a vacuum deposition method. If necessary, a protective layer (topcoat layer) may be provided on the inorganic deposition layer (I) as long as the effects of the present invention are not hindered. The upper limit of the surface temperature during film formation of the inorganic deposition layer (I) is preferably 60°C, more preferably 55°C, and even more preferably 50°C. The lower limit of the surface temperature during the formation of the inorganic deposition layer (I) is not particularly limited, but is preferably 0°C, more preferably 10°C, and even more preferably 20°C. The surface to be processed for film formation may be plasma-treated before film formation. A known method can be used for the plasma treatment, and atmospheric pressure plasma treatment is preferred. In atmospheric pressure plasma treatment, nitrogen, helium, neon, argon, krypton, xenon, radon, etc. are used as discharge gas. Among them, nitrogen, helium, and argon are preferably used, and nitrogen is particularly preferable because it can reduce costs.

(Adhesion layer (Y))
Preferably, the heat-sealable film of the present invention further has an adhesive layer (Y), and the heat-sealable layer (X) is laminated on the substrate layer (Z) via the adhesive layer (Y). By laminating the heat-sealable layer (X) on the substrate layer (Z) via the adhesive layer (Y), the adhesion between the layers is improved, the quality as a packaging material is improved, and the heat under high humidity The seal strength is also improved. In the heat-sealable film of the present invention, it is preferable that the heat-sealable layer (X), the adhesive layer (Y) and the substrate layer (Z) are directly laminated in this order. The thickness of the adhesive layer (Y) is preferably 0.5-25 μm, more preferably 1-15 μm.

As a component constituting the adhesive layer (Y), it is preferable to have an adhesive resin such as carboxylic acid-modified polyolefin or carboxylic acid-modified polyester as a main component. It is more preferable to have Examples of carboxylic acid-modified polyolefins include modified olefinic polymers containing carboxyl groups obtained by chemically bonding unsaturated carboxylic acids or their anhydrides to olefinic polymers by addition reaction, grafting reaction, or the like. can be done. Examples of unsaturated carboxylic acids or anhydrides thereof include maleic acid, maleic anhydride, fumaric acid, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, citraconic acid, hexahydrophthalic anhydride and the like. is preferably used. Specifically, maleic anhydride graft-modified polyethylene, maleic anhydride graft-modified polypropylene, maleic anhydride graft-modified ethylene-propylene copolymer, maleic anhydride graft-modified ethylene-ethyl acrylate copolymer, maleic anhydride graft-modified ethylene - One or a mixture of two or more selected from the group consisting of vinyl acetate copolymers and the like is preferable. Adhesiveness may be improved by mixing a rubber/elastomer component such as polyisobutylene or ethylene-propylene rubber with the adhesive resin, or a polyolefin resin different from the base polyolefin resin of the adhesive resin.

In addition, the adhesive layer (Y) is formed by treating the surface of one layer (thermal adhesive layer (X) or base layer (Z)) with a known anchor coating agent, or by treating the surface of one layer with a known adhesive agent. It can also be formed by applying an agent. As the anchor coating agent and the adhesive, a two-liquid reaction type polyurethane adhesive in which a polyisocyanate component and a polyol component are mixed and reacted is preferable. Moreover, by adding a small amount of additive such as a known silane coupling agent to the anchor coating agent or adhesive, the adhesiveness can be further enhanced in some cases. Silane coupling agents include, but are not limited to, silane coupling agents having reactive groups such as isocyanate groups, epoxy groups, amino groups, ureido groups, and mercapto groups.

(Heat sealing film)
The heat-sealing film of the present invention may have a structure in which the heat-sealing layer (X) is directly laminated on the base layer (Z), or the heat-sealing layer (X) is laminated with the adhesive layer (Y). It may be a structure laminated on the base material layer (Z) via. The heat-sealable layer (X), the adhesive layer (Y), and the substrate layer (Z) may be manufactured in different steps and then laminated in a post-step such as a dry lamination method, or a solution coating method or the like. Alternatively, some or all of them may be produced simultaneously by a coextrusion method or the like. That is, in the heat-sealable film of the present invention, the heat-sealable layer (X), the adhesive layer (Y) and the substrate layer (Z) may be coextruded films or parts thereof.

In producing the heat-sealable film of the present invention, it is sufficient to obtain a heat-sealable layer in which the heat-sealable layer (X) is one of the outermost layers and the substrate layer (Z) is the other outermost layer. For example, a heat-sealing film having a layer structure of (X)/(Z) or (X)/(Y)/(Z) is exemplified. In addition, the layer (Z) itself may consist of a plurality of layers, and in the present invention, all layers other than the layer (X) and the layer (Y) are partly or wholly of the layer (Z). regarded as The total thickness of the heat-sealing film of the present invention is preferably 20 μm or more and 350 μm or less, more preferably 60 μm or more and 200 μm or less, from the viewpoint of achieving both handleability and functionality as a packaging material. For the same reason, the thickness ratio of the heat sealing layer (X) to the total thickness is preferably 1% or more and 20% or less.

The oxygen permeability of the heat-sealing film of the present invention may be adjusted according to the application, but is not particularly limited ^. It is preferably 1 cc/(m ² ·day·atm) or less, more preferably 0.1 cc/(m ² ·day·atm) or less. A heat-sealing film having an oxygen permeability within this range can suppress putrefaction and deterioration of the content and maintain the quality of the content for a long period of time. Oxygen permeability is measured according to JIS K 7126-2 (isobaric method; 2006), and specifically, the method described in Examples is employed.

The moisture permeability ^of the heat-sealing film of the present invention may be adjusted according to the application, but is not particularly limited. It is preferably 10 g/(m ² ·day) or less, more preferably 1 g/(m ² ·day) or less. A heat-sealing film having a moisture permeability within this range can suppress putrefaction and deterioration of the content and maintain the quality of the content for a long period of time. Moisture permeability is measured according to JIS Z 0208 (1976), and specifically, the method described in Examples is employed.

In the heat-sealing film of the present invention, the heat-sealing layers (X) of two heat-sealing films are faced to each other, and a hot plate heat sealer is used to press them under the conditions of a temperature of 185 ° C. and a pressure of 0.1 MPa for 1 second. The strength of the heat seal obtained by this is preferably 1 N/15 mm or more, more preferably 1.5 N/15 mm or more, and even more preferably 2 N/15 mm or more. When the strength of the heat seal is within the above range, the quality retention of the contents is improved. Specifically, the heat seal strength can be measured by the method described in Examples.

When the heat-sealing film of the present invention is cut into a 2 cm square and stirred in an aqueous solution (W) at 50° C. described below, the heat-sealable layer (X) is preferably dissolved and removed within 5 minutes. More preferably, it is dissolved and removed within 3 minutes. Dissolution and removal of the heat-fusible layer (X) under the above conditions is preferable because separation and recovery properties are improved and recycling can be carried out economically. Here, removal by dissolution means removal of more than 75% by mass of the heat sealing layer (X), preferably more than 90% by mass, more preferably complete dissolution. preferable.

The heat-sealing film of the present invention is formed into a container or package (bag, cup, tube, tray, bottle, etc.) with the heat-sealing layer on the inside by stacking the heat-sealing layers and heat-sealing them. be able to. The heat-sealable film of the present invention exhibits sufficient heat-sealing properties under normal conditions of use as a packaging material, while the heat-sealable layer can be easily dissolved and removed after being used as a packaging material. Since the layer other than the deposited layer can be separated and recovered with high purity, it is preferably used as a packaging material for foods and the like.

(Separation and recovery method)
In the separation and recovery method of the present invention, the heat sealing film of the present invention is brought into contact with an aqueous solution (W) at 20° C. to 95° C. to dissolve the heat-sealable layer (X) made of the water-soluble resin composition (S). , is achieved by recovering the film from which the heat-sealable layer (X) has been removed. At this time, by raising the temperature of the water or stirring it, the effect of increasing the dissolution rate of the heat-sealing layer (X) and the effect of removing adhering contaminants and the like are expected. Also, the size of the heat-sealing film to be dropped into the aqueous solution (W) is not particularly limited, but as an example, it is preferably smaller than 10 cm square, and may be about 2 cm square. After the dissolution and removal of the thermal adhesive layer (X) is completed, the film remaining as an insoluble component is collected, washed with pure water or the like as necessary, dried, and then melt-molded using an extruder to produce a recycled resin. can be re-pelletized as Using the pellets thus obtained, various shaped bodies are produced. Here, the aqueous solution (W) may be an aqueous solution containing a chloride salt such as sodium chloride, potassium chloride or calcium chloride as a solute, or may be water containing no solute. The pH range of the aqueous solution (W) is not particularly limited, but the equipment and processes required for dissolution and removal are greatly simplified, so the pH of the aqueous solution (W) is preferably in the range of 5 to 9, and 6 to 9. It may be in the range of 8 or in the range of 6.5 to 7.5. The heat-sealable layer (X) of the present invention has excellent solubility even in a pH range close to neutrality, eg pH 5 to 9, and can be easily removed by dissolution.

Whether the film from which the heat sealing layer (X) has been removed floats or sinks in the aqueous solution (W) depends on the relative specific gravities of the film and the aqueous solution (W). In the case of substances with a specific gravity greater than 1, such as polyesters and ethylene-vinyl alcohol copolymers, they tend to sink in normal aqueous solutions. By adding a chloride salt such as sodium, potassium chloride, or calcium chloride to increase the specific gravity of the aqueous solution, it becomes possible to float and recover the solution. In this case, from the viewpoint of economy and handling, the concentration of the chloride salt or the like required to develop the required specific gravity w of the aqueous solution (W) is preferably 40% by mass or less. If the concentration exceeds 40% by mass, the cost of procuring chloride salts and the like becomes excessive, and there is a risk that the washing process after separation will be hindered.

In addition, from the viewpoint of the stability of the separation process, the concentration of the chloride salt or the like required to express the specific gravity w of the required aqueous solution (W) is 10% by mass or more than the saturated concentration of the chloride salt or the like. Small is preferred. If the difference between the concentration of the chloride salt or the like required to express the specific gravity w of the required aqueous solution (W) and the saturated concentration of the chloride salt or the like is less than 10% by mass, it takes time to dissolve the chloride salt or the like. Otherwise, chloride salts or the like may be precipitated in the separation tank or the substance after separation, which may lead to destabilization of the process.

EXAMPLES The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

Example 1
(1) Synthesis of PVA A vinyl acetate polymer obtained by polymerizing vinyl acetate by a conventional method was saponified by a conventional method to obtain PVA1 having a viscosity average degree of polymerization of 800 and a degree of saponification of 88 mol%. However, the viscosity average degree of polymerization and the degree of saponification of PVA1 were obtained by the method described in JIS K6726 (1994). The obtained PVA1 was heated from 20° C. to 250° C. at a rate of 10° C./min using a differential scanning calorimeter DSC (“Q2000” manufactured by TA Instruments), and the temperature of the maximum value of the endothermic peak was measured. was obtained and used as the melting point. As a result, the melting point of the obtained PVA1 was 175°C.

(2) Production of PVA resin composition Next, 87 parts by mass of the obtained PVA1 and 13 parts by mass of glycerin as a plasticizer were mixed using a planetary mixer, and then an aqueous sodium acetate solution was added so that the sodium ion content was 800 ppm. and melt-kneaded to obtain PVA1 resin composition pellets. For melt kneading, a 25 mm extruder (D (mm) = 25, L / D = 25, compression ratio = 2.0, screw: same direction full mesh type) manufactured by Toyo Seiki Seisakusho Co., Ltd. is used, and the resin temperature is 220. °C.

(3) Measurement of Equilibrium Moisture Content of PVA Resin Composition The obtained PVA1 resin composition pellets were allowed to stand at a temperature of 23° C. and a relative humidity of 50% for 30 days or longer, then dried at 120° C. for 3 hours. Equilibrium moisture content was calculated based on and judged according to the following criteria. Table 1 shows the results.
Judgment: Criteria A: 5% by mass or more and less than 8% by mass BL: 3% by mass or more and less than 5% by mass BH: 8% by mass or more and less than 10% by mass CL: less than 3% by mass CH: 10% by mass or more

(4) Production of heat-sealing film Using a coextrusion multi-layer cast film forming apparatus, the heat-sealable layer (X) is made of the PVA1 resin composition, and the adhesive layer (Y) is maleic anhydride graft-modified ethylene-acetic acid. It consists of a vinyl copolymer ("Bynel 3810" manufactured by Dow Chemical Japan Co., Ltd., adhesive layer (Y1)), and the base layer (Z) is made of polyethylene terephthalate ("Belpet EFG70" manufactured by Bell Polyester Products Co., Ltd.). A heat-sealing film (a three-kind three-layer coextruded multilayer cast film having a layer thickness and layer structure of (X)/(Y)/(Z)=20 μm/10 μm/100 μm) was obtained. The film forming conditions at this time are shown below.
Co-extrusion conditions Extrusion temperature of heat-fusible layer (X): supply section/compression section/measuring section/die = 180/220/220/270°C
Extrusion temperature of adhesive layer (Y): feed section/compression section/measuring section/die = 150/200/200/270°C
Extrusion temperature of substrate layer (Z): Feeding section/compressing section/measuring section/die = 240/260/270/270°C
Extruder heat-sealing layer (X): 32φ extruder UT-32-H type (manufactured by Plastics Engineering Laboratory Co., Ltd.)
Adhesive layer (Y): 40φ extruder GT-40-A type (manufactured by Plastic Engineering Laboratory Co., Ltd.)
Base layer (Z): 65φ extruder SZW65GT-22MG-STD type (manufactured by Technobell Co., Ltd.)
T die: 600 mm width (manufactured by Cloeren Incorporated)
Cooling roll temperature: 60°C

(5) Evaluation of Appearance Characteristics The heat-sealing film obtained in (4) above was visually evaluated and evaluated according to the following criteria. Table 1 shows the results.
Judgment: Criteria A: Appearance is uniform and good without coloring B1: Defects such as spots are observed B2: Coloring (yellowing) is observed B3: Unevenness due to thickness variation is observed

(6) Measurement of heat seal strength The heat-sealing layers (X) of the heat-sealing film obtained in (4) above are faced to each other, and a hot plate heat sealer is used at a temperature of 185 ° C. and a pressure of 0.1 MPa. Heat sealing was performed by pressure bonding for 1 second. After the film was conditioned in an atmosphere of 40° C. and 90% RH for 7 days, a strip-shaped test piece with a width of 15 mm was cut out. The T-peel strength (N/15 mm) of the obtained test piece was measured using an "Autograph AGS-H type" manufactured by Shimadzu Corporation under the conditions of a chuck interval of 50 mm and a tensile speed of 300 mm/min. Five test pieces were measured, and based on the average value, judgment was made according to the following criteria. Table 1 shows the results.
Judgment: Criteria A: 2.0 N/15 mm or more B: 1.5 N/15 mm or more and less than 2.0 N/15 mm C: 1.0 N/15 mm or more and less than 1.5 N/15 mm D: 0.5 N/15 mm or more and 1.0 N / less than 15 mm E: less than 0.5 N/15 mm

(7) Oxygen permeability measurement For the heat-sealing film obtained in (4) above, the oxygen permeability was measured with the base layer (Z) side as the oxygen supply side and the heat sealing layer (X) side as the carrier gas side. It was measured. Specifically, using an oxygen permeation measurement device ("MOCON OX-TRAN2/21" manufactured by Modern Control Co., Ltd.), the temperature was 20 ° C., the humidity on the oxygen supply side was 65% RH, the humidity on the carrier gas side was 65% RH, oxygen The oxygen permeation rate (unit: cc/(m ² ·day·atm)) was measured under the conditions of 1 atm pressure and 1 atm carrier gas pressure, and judged according to the following criteria. Nitrogen gas containing 2% by volume of hydrogen gas was used as the carrier gas. Table 1 shows the results.
Criteria A: Less than 0.1 cc/(m ² · day · atm) B: 0.1 cc / (m ² · day · atm) or more, less than 1 cc / (m ² · day · atm) C: 1 cc / (m ²・day・atm) or more and less than 10 cc/(m ²・day・atm) D: 10 cc/(m ²・day・atm) or more and less than 50 cc/(m ²・day・atm) E: 50 cc/(m ²・day・atm) or more

(8) Moisture permeability measurement A metal cup with a volume of 50 cc is filled with granular calcium chloride dried at 120 ° C., and the heat-sealing film obtained in (4) above is placed on the lid surface of the cup. , paraffin-encapsulated. After measuring the mass of this cup, the mass was measured after storage for 24 hours in a constant temperature and humidity chamber at a temperature of 40 ° C. and a relative humidity of 90%, and the water vapor permeability was calculated from the surface area of the lid surface and the mass increase of the cup. , was determined according to the following criteria. Table 1 shows the results.
Criteria A: Less than 1 g/(m ² ·day) B: 1 g/(m ² ·day) or more, less than 10 g/(m ² ·day) C: 10 g/(m ² ·day) or more, 50 g/(m ^2.day ) D: 50g/( ^m2.day ) or more, less than 100g/( ^m2.day ) E: 100g/( ^m2.day ) or more

(9) Evaluation of Separation and Collection Performance The heat-sealing film obtained in (4) above was cut into 10 2 cm squares to obtain test pieces for evaluation of separation and collection performance. After the obtained test piece was stirred in hot water at 50°C for 5 minutes, undissolved film pieces were collected, rinsed lightly with cold water at 20°C, and dried in hot air at 120°C for 2 hours. The film piece after drying was measured using a differential scanning calorimeter DSC under the same conditions as in (1), and the thermal adhesive layer (X) with respect to the endothermic amount of the base layer (Z) before and after the separation and recovery treatment. Based on the change in the endothermic amount, judgment was made according to the following criteria. Table 1 shows the results.
Judgment Criteria A: No endotherm was observed in the heat-fusible layer (X) after the separation and recovery treatment B: The amount of endotherm in the heat-fusible layer (X) was less than 10% after the separation and recovery treatment C: Separation After the recovery treatment, the heat absorption amount of the heat sealing layer (X) was 10% or more and less than 25%. D: After the separation and recovery treatment, the heat absorption amount of the heat sealing layer (X) was 25% or more and less than 50%. E: After the separation and recovery process, the heat absorption amount of the heat sealing layer (X) became 50% or more

Examples 2 to 5, Comparative Examples 1 and 2
A PVA resin composition and a heat-sealing film were prepared and evaluated in the same manner as in Example 1, except that the amount of sodium acetate aqueous solution added was changed so that the sodium ion content was as shown in Table 1. Table 1 shows the results.

Example 6
A PVA resin composition and a heat-sealing film were produced and evaluated in the same manner as in Example 1, except that an aqueous potassium acetate solution was used instead of the aqueous sodium acetate solution and added so that the content of potassium ions was 800 ppm. bottom. Table 1 shows the results.

Examples 7-9, Comparative Example 3
A PVA resin composition and a heat-sealing film were prepared and evaluated in the same manner as in Example 1, except that the content of glycerin was changed as shown in Table 1. Table 1 shows the results.

Examples 10-12
A PVA resin composition and a heat-sealing film were prepared and evaluated in the same manner as in Example 1, except that mannitol, sorbitol and polyethylene glycol were used instead of glycerin. Table 1 shows the results.

Example 13
A PVA resin composition and a heat-sealing film were produced and evaluated in the same manner as in Example 1, except that PVA2 having a viscosity average polymerization degree of 350 and a saponification degree of 88 mol% was used instead of PVA1. Table 1 shows the results.

Example 14
Instead of PVA1, PVA3 with a viscosity average polymerization degree of 600 and a saponification degree of 80 mol% and PVA4 with a viscosity average polymerization degree of 800 and a saponification degree of 74 mol% are mixed at a ratio of (PVA3/PVA4) 70/30 and used for plasticization. A PVA resin composition and a heat-sealing film were prepared and evaluated in the same manner as in Example 1, except that no agent was added. Table 1 shows the results.

Example 15
Same as Example 1 except that PVA5 (modified PVA) with an ethylene modification degree of 8.5 mol%, a viscosity average polymerization degree of 350, and a saponification degree of 98 mol% was used instead of PVA1, and no plasticizer was added. Then, a PVA resin composition and a heat-sealing film were produced and evaluated. Table 1 shows the results.

Examples 16-20
A heat-sealing film was produced and evaluated in the same manner as in Example 1, except that the thicknesses of the heat-sealing layer (X), the adhesive layer (Y), and the base layer (Z) were changed as shown in Table 1. . Table 1 shows the results.

Example 21
10 parts by mass of the PVA resin composition used in Example 1 was dissolved in 90 parts by mass of pure water to prepare a PVA resin composition solution. A PVA resin composition solution was coated on a 100 μm thick polyethylene terephthalate film (substrate layer (Z)) with a bar coater so that the thickness after drying was 10 μm, and dried at 100° C. for 5 minutes to heat. A sealing film ((X)/(Z)=PVA resin composition layer/PET=10 μm/100 μm) was obtained. Evaluations were made in the same manner as in Example 1 using the obtained heat-sealing film. Table 1 shows the results.

Example 22
A two-liquid reactive polyurethane adhesive (manufactured by Mitsui Chemicals, Inc.: 24 parts by mass of “Takelac A-520” and 4 parts by mass of “Takenate A-50”) is mixed with 37 parts by mass of ethyl acetate to prepare an adhesive solution. (solution for adhesive layer (Y2)). A polyethylene terephthalate film (substrate layer (Z)) having a thickness of 100 μm was coated with the adhesive solution by a bar coater so that the thickness after drying was 2 μm, and dried at 100° C. for 5 minutes. Next, the PVA resin composition solution prepared in Example 21 was applied with a bar coater so that the thickness after drying was 10 μm, and dried at 100° C. for 5 minutes to form a heat-sealing film ((X)/( Y)/(Z)=PVA resin composition layer/adhesive layer/PET=10 μm/2 μm/100 μm). Evaluations were made in the same manner as in Example 1 using the obtained heat-sealing film. Table 1 shows the results.

Example 23
Example 22 except that VM-PET having an aluminum metal vapor deposition layer having a thickness of 50 nm provided on a polyethylene terephthalate film by a known vacuum vapor deposition method was used as a base layer, and an adhesive solution was applied onto the metal vapor deposition layer. A heat-sealing film was prepared and evaluated in the same manner as above. Table 1 shows the results.

Example 24
Except that VM-EVOH using a 50 μm thick ethylene-vinyl alcohol copolymer film (ethylene modification degree 32 mol%, saponification degree 99.9 mol%) instead of the polyethylene terephthalate film was used as the base layer. , and a heat-sealing film was produced and evaluated in the same manner as in Example 23. Table 1 shows the results.

Example 25
A heat-sealing film was prepared and evaluated in the same manner as in Example 22, except that an aluminum foil having a thickness of 15 μm was used instead of the polyethylene terephthalate film. Table 1 shows the results.

Example 26
A heat-sealing film was prepared and evaluated in the same manner as in Example 22, except that unbleached kraft paper having a thickness of 50 µm was used instead of the polyethylene terephthalate film. Table 1 shows the results.

Comparative example 4
A PVA resin composition and a heat-sealing film were produced in the same manner as in Example 1, except that PVA6 with a viscosity average polymerization degree of 1700 and a saponification degree of 98 mol% was used instead of PVA1, and no plasticizer was added. and evaluated. Table 1 shows the results.

Comparative example 5
PVA resin was prepared in the same manner as in Example 1 except that EVOH having a degree of ethylene modification of 44 mol%, a viscosity average polymerization degree of 930, and a degree of saponification of 99.9 mol% was used instead of PVA1, and no plasticizer was added. Compositions and heat-sealing films were prepared and evaluated. Table 1 shows the results.

The heat-sealable film of the present invention exhibits sufficient heat-sealing properties under normal conditions of use as a packaging material, while the heat-sealable layer can be easily dissolved and removed after being used as a packaging material. Layers other than deposited layers can be separated and recovered with high purity. Moreover, various functions such as necessary heat resistance, mechanical properties and gas barrier properties can be imparted by selecting the base material layer. As a result, recyclability can be improved without degrading the performance and quality as a packaging material, and it is possible to contribute to the realization of a recycling-oriented society.

Claims (16)

A water-insoluble base material comprising a heat-sealable layer (X) made of a water-soluble resin composition (S) on one outermost layer and containing at least one selected from the group consisting of a thermoplastic resin, paper and metal foil. The layer (Z) is provided as the other outermost layer, and the equilibrium moisture content of the water-soluble resin composition (S) at a temperature of 23 ° C. and a relative humidity of 50% is 3% by mass or more and 10% by mass or less, and the water-soluble resin composition A heat-sealing film in which (S) contains a hydroxyl group-containing resin (A) having a melting point of 220° C. or less as a main component, and the water-soluble resin composition (S) contains 100 ppm or more and 2000 ppm or less of alkali metal ions (B). 2. The heat-sealing film according to claim 1, wherein the heat-sealable layer (X) is directly laminated on the substrate layer (Z). 2. The heat-sealing film according to claim 1, further comprising an adhesive layer (Y), wherein the heat-sealable layer (X) is laminated on the substrate layer (Z) via the adhesive layer (Y). 4. The heat-sealing film according to claim 3, wherein the heat-sealable layer (X), the adhesive layer (Y) and the substrate layer (Z) are coextruded films or parts thereof. The heat-sealable film according to any one of claims 1 to 4, wherein the substrate layer (Z) consists of a plurality of layers. The heat-sealing film according to any one of claims 1 to 5, wherein the hydroxyl-containing resin (A) is a vinyl alcohol polymer (A1). The heat-sealing film according to claim 6, wherein the vinyl alcohol polymer (A1) has a viscosity average degree of polymerization of 400 or more and 2000 or less. The heat-sealing film according to claim 6 or 7, wherein the vinyl alcohol polymer (A1) has a degree of saponification of 70 mol% or more and 95 mol% or less. The water-soluble resin composition (S) contains 5% by mass or more and 40% by mass or less of the plasticizer (C), and the plasticizer (C) is glycerin, polyethylene glycol, polypropylene glycol, polyglycerin, mannitol, sorbitol, and pentaerythritol. The heat-sealing film according to any one of claims 1 to 8, which is at least one selected from the group consisting of: The heat-sealing film according to any one of claims 1 to 9, wherein the total thickness is 20 µm or more and 350 µm or less, and the thickness ratio of the heat sealing layer (X) to the total thickness is 1% or more and 20% or less. According to JIS K 7126-2 (isobaric method; 2006), the oxygen permeability at a temperature of 20 ° C. and a relative humidity of 65% is 10 cc / (m ² · day · atm) or less, claims 1 to 11. The heat-sealable film according to any one of 10. The moisture permeability at a temperature of 40° C. and a relative humidity of 90% measured according to JIS Z 0208 (1976) is 50 g/(m ² ·day) or less, according to any one of claims 1 to 11. Film for heat sealing. The heat-sealing strength is 1 N/15 mm or more obtained by pressing the heat-sealing layers (X) against each other for 1 second at a temperature of 185° C. and a pressure of 0.1 MPa using a hot plate heat sealer. Item 13. The heat-sealable film according to any one of items 1 to 12. 14. The heat-sealing film according to any one of claims 1 to 13, wherein when the film is cut into 2 cm squares and stirred in an aqueous solution (W) at 50°C, the thermal adhesive layer (X) is dissolved and removed within 5 minutes. . A packaging material comprising the heat-sealable film according to any one of claims 1 to 14. The heat-sealable film according to any one of claims 1 to 14 is brought into contact with an aqueous solution (W) at 20° C. or higher and 98° C. or lower to dissolve the heat-sealable layer (X). A method for separating and collecting the film from which the is removed.