JP7105472B2 - Gas barrier laminate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a gas barrier laminate exhibiting excellent gas barrier properties.

Plastic films such as polyamide films are used in a wide range of applications as packaging materials because of their excellent strength, transparency and moldability. However, these plastic films have a relatively high permeability to gases such as oxygen. Oxygen and other gases entering the container may cause deterioration of the contents. For this reason, plastic films used for these packaging applications are required to have gas barrier properties, and packaging of foods containing moisture also requires gas barrier properties under high humidity conditions.

As a method of imparting gas barrier properties to a plastic film, there is a method of laminating a gas barrier layer on the film, and a method of using a material composed of a polycarboxylic acid-based polymer and a metal compound as such a gas barrier layer is known. there is For example, a gas barrier laminate in which a gas barrier layer (II) is laminated on a plastic substrate (I), the plastic substrate (I) is a single-layer film, and a metal compound is contained in the film layer. 0.1 to 70% by mass, the gas barrier layer (II) contains a polycarboxylic acid, and the polycarboxylic acid is an olefin-maleic acid copolymer (Patent Document 1). Various gas barrier laminates have been proposed, including the above.

Patent No. 5843988

However, conventional gas barrier laminates develop desired gas barrier properties only after being subjected to hot water treatment under relatively severe conditions of, for example, 95° C.×30 minutes. If hot water treatment can be performed under milder conditions, it will lead to expanded applications. That is, there is a strong demand for materials that exhibit desired gas barrier properties under conditions of lower hot water treatment temperatures and shorter hot water treatment times, but such materials have yet to be developed.

Accordingly, the main object of the present invention is to provide a gas barrier laminate that exhibits excellent gas barrier properties even when subjected to hydrothermal treatment at a lower temperature or for a shorter period of time.

As a result of intensive research in view of the problems of the prior art, the inventors of the present invention have found that a laminate formed using a specific material can achieve the above objects, and have completed the present invention.

That is, the present invention relates to the following gas barrier laminate.
1. A laminate comprising, in order, at least a protective layer (III), a plastic substrate (I) and a gas barrier layer (II),
(1) The plastic base material (I) contains a resin component and a metal compound, and the content of the metal compound is 0.1 to 20% by mass,
(2) The gas barrier layer (II) contains polycarboxylic acid or its anhydride and is laminated on one side of the plastic substrate (I),
(3) The protective layer (III) contains a resin component having a glass transition temperature of 60° C. or higher, and is laminated on the other surface of the plastic substrate (I).
A gas barrier laminate characterized by:
2. 2. The gas barrier laminate according to item 1, wherein the plastic substrate (I) is a polyamide film.
3. 3. The gas barrier laminate according to item 1 or 2, wherein the gas barrier layer (II) further contains polyalcohol.
4. 4. The gas barrier laminate according to any one of items 1 to 3, wherein the protective layer (III) contains polyalcohol.
5. 5. The gas barrier laminate according to any one of Items 1 to 4, wherein the protective layer (III) has a thickness of 1 μm or less.
6. In the oxygen permeability at a temperature of 20 ° C. and a relative humidity of 90%, the oxygen permeability after the hot water treatment at 80 ° C. for 30 minutes is 100 ml / (m ² day MPa) or less, and the temperature is 120 ° C. 6. The gas barrier laminate according to any one of Items 1 to 5, wherein the oxygen permeability after 30 minutes of hot water treatment is 100 ml/(m ² ·day·MPa) or less.
7. 6. The gas barrier laminate according to any one of Items 1 to 5, which is used for a hot water treatment with hot water at a temperature of 30 to 130°C.
8. A packaging material comprising the gas barrier laminate according to any one of 1 to 7 above.
9. 9. The packaging material according to Item 8, which is used for sealing contents.

According to the present invention, it is possible to provide a gas barrier laminate that exhibits excellent gas barrier properties even when subjected to hot water treatment at a lower temperature or for a shorter period of time.

In particular, in the present invention, a gas barrier layer (II) containing a polycarboxylic acid is laminated on one side of a plastic substrate (I) containing 0.1 to 20% by mass of a metal compound, and the specific gas barrier layer (II) is laminated on the other side. By laminating the protective layer (III) containing a resin with a glass transition temperature of , it is possible to reduce the amount of metal compounds eluted from the plastic substrate (I) into water during hydrothermal treatment, and the gas barrier layer (II ) and the metal compound can be improved in reactivity (reaction efficiency). As a result, sufficient ionic cross-linking reaction between the gas barrier layer (II) and the metal compound can proceed even under relatively mild hydrothermal conditions, so that even relatively low-temperature or short-time hydrothermal treatment is stable and excellent. It becomes possible to develop gas barrier properties. In other words, a sufficient amount of the metal compound can be reacted with the gas barrier layer (II) without the need for hot water treatment at a high temperature and for a long time as in the prior art, so excellent gas barrier properties can be obtained. .

Since such a gas barrier laminate of the present invention exhibits excellent gas barrier properties when treated with hot water at a low temperature or for a short period of time, it can be used in a wide range of applications as a packaging material for foods, pharmaceuticals, etc. that require hot water treatment. can be used for In particular, it is suitable for packaging products that are susceptible to alteration or deterioration due to high-temperature or long-term hot water treatment. Moreover, since the gas barrier property exhibited by the gas barrier laminate of the present invention is excellent even under high humidity, it is suitable for long-term storage under relatively severe environments.

1 is a schematic diagram showing a basic layer structure of a gas barrier laminate of the present invention; FIG.

1. Gas Barrier Laminate The gas barrier laminate of the present invention (the laminate of the present invention) is a laminate comprising, in order, at least a protective layer (III), a plastic substrate (I) and a gas barrier layer (II),
(1) The plastic base material (I) contains a resin component and a metal compound, and the content of the metal compound is 0.1 to 20% by mass,
(2) The gas barrier layer (II) contains polycarboxylic acid or its anhydride and is laminated on one side of the plastic substrate (I),
(3) The protective layer (III) contains a resin component having a glass transition temperature of 60° C. or higher, and is laminated on the other surface of the plastic substrate (I).
It is characterized by

FIG. 1 shows the basic structure of the laminate of the present invention. In the laminate 10 of the present invention, a gas barrier layer 12 is laminated on one surface of a plastic substrate 11, and a protective layer 13 is laminated on the other surface. Thus, the laminate 10 of the present invention has a basic structure of "protective layer 13/plastic substrate 11/gas barrier layer 12". These layers may be laminated so as to be in direct contact with each other, or may be laminated via other layers (for example, adhesive layers, etc.) as necessary. In particular, in the present invention, it is preferable that the gas barrier layer 12 is laminated so as to be in direct contact with the plastic substrate 11 .

The laminate of the present invention has a basic structure of a layer structure including "protective layer 13/plastic substrate 11/gas barrier layer 12", and other layers are laminated on the surface of the protective layer 13 and/or the gas barrier layer 12 as necessary. It's okay to be. Other layers include, for example, a printed layer, an adhesive layer, a heat seal layer, a metal foil layer, and the like. Each layer constituting the laminate of the present invention will be described below.

(1) Plastic substrate (I)
The plastic substrate (I) contains a resin component (hereinafter also referred to as “resin component A”) and a metal compound, and contains 0.1 to 20% by mass of the metal compound. In particular, in the present invention, a molded article (such as a sheet) obtained by molding a mixture (particularly a melt-kneaded material) containing the resin component A and a metal compound can be suitably used as the plastic substrate (I).

As the resin component A, either a thermoplastic resin or a thermosetting resin can be used, but the thermoplastic resin can be particularly preferably used in the present invention. The thermoplastic resin is not particularly limited, and for example a) polyolefin resins such as polyethylene and polypropylene, b) polyamide resins such as nylon 6, nylon 66, nylon 46, nylon MXD6 and nylon 9T, c) polyethylene terephthalate, polyethylene iso Polyester resins such as phthalate, polyethylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, and polylactic acid; arylate resins, ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, etc.), e) mixtures of the above a) to d), and the like.

In the present invention, among thermoplastic resins, polyamide resins are preferred, and nylon 6 is particularly preferred. When a polyamide resin is used, when the laminate of the present invention is subjected to wet heat treatment or hot water treatment, the reaction between the metal compound in the plastic substrate (I) and the gas barrier layer (II) can further enhance the gas barrier properties. When a packaging material (especially packaging bag) is constructed from the laminate of the present invention, it is possible to obtain superior piercing strength, impact resistance, and the like. Polyamide resins can be used singly or as a mixture of two or more.

The content of the resin component A in the plastic base material (I) can be appropriately set according to the type of the resin component used, etc., but it is usually about 70 to 100% by mass, particularly 80 to 99% by mass. preferable. When a polyamide resin is used as the resin component A, the content of the polyamide resin in the resin component A is generally 80-100% by mass, preferably 90-99% by mass.

Metals constituting the metal compound are not particularly limited, and examples include monovalent metals such as lithium, sodium, potassium, rubidium and cesium, magnesium, calcium, zirconium, zinc, copper, cobalt, iron, nickel and aluminum. Divalent or higher metals are mentioned. The kind of metal is not limited to one kind, and may be two or more kinds.

Among these, metals having a high ionization tendency are preferable because they are likely to react with polycarboxylic acids. From the viewpoint of gas barrier properties, monovalent or divalent metals are preferred. Therefore, at least one of lithium, sodium, potassium, magnesium, calcium and zinc is preferred, and at least one of magnesium, calcium and zinc is more preferred.

In the present invention, the metal compound is not particularly limited as long as it is a compound containing any of the above metals. For example, oxides, hydroxides, halides, inorganic acid salts (carbonates, hydrogen carbonates, phosphates, sulfates, etc.), organic acid salts (carboxylates (acetates, formates, stearates, citrate, malate, maleate), sulfonate, etc.). In the present invention, oxides or carbonates are particularly preferred from the viewpoint of exhibiting excellent gas barrier properties.

Preferred examples of the above metal compounds include lithium carbonate, sodium hydrogen carbonate, magnesium oxide, magnesium carbonate, magnesium hydroxide, magnesium acetate, calcium oxide, calcium carbonate, calcium hydroxide, calcium chloride, calcium phosphate, calcium sulfate, and acetic acid. At least one of calcium, zinc acetate, zinc oxide, zinc carbonate and the like can be mentioned.

From the viewpoint of gas barrier properties, a divalent metal compound is preferable, and it is particularly preferable to use at least one of a magnesium compound, a calcium compound and a zinc compound. Therefore, at least one of magnesium oxide, magnesium carbonate, magnesium hydroxide, magnesium acetate, calcium oxide, calcium carbonate, calcium acetate, zinc oxide and zinc acetate can be preferably used. From the viewpoint of transparency of the plastic substrate (I), at least one of monovalent metal compounds and divalent metal compounds is preferred, and at least one of alkali metal compounds and alkaline earth metal compounds is more preferred. Therefore, for example, at least one of lithium carbonate, sodium hydrogen carbonate, magnesium oxide, magnesium carbonate and magnesium hydroxide can be preferably used.

Although the form (property) of the metal compound is not limited, it is usually preferably in the form of powder. That is, it is preferable to adopt a structure in which particles of the metal compound are dispersed in the plastic substrate (I). More specifically, a structure in which particles (powder) of the metal compound are dispersed in a matrix containing the resin component A is preferable.

The average particle size in this case is not particularly limited, but it is usually about 0.001 to 10 μm, preferably 0.005 to 5 μm, more preferably 0.01 to 2 μm, Among them, 0.05 to 1 μm is most preferable. From the standpoint that the haze of the plastic substrate (I) can be reduced, the smaller the average particle size, the better. However, when the average particle size is less than 0.001 μm, the surface area is large and aggregation tends to occur. A plastic substrate (I) containing a metal compound having an average particle size of more than 10.0 μm is likely to break during film formation, resulting in a decrease in productivity.

The metal compound can be subjected to surface treatment (surface film formation treatment) as necessary. Thereby, dispersibility, weather resistance, wettability with thermoplastic resin, heat resistance, transparency, etc. can be improved. Surface treatment can employ known inorganic or organic treatments. The inorganic treatment includes, for example, a treatment of forming alumina, silica, titania, zirconia, tin oxide, antimony oxide, zinc oxide, etc. on the surface of particles of a metal compound. As the organic treatment, for example, fatty acid compounds, polyol compounds such as pentaerythritol and trimethylolpropane, amine compounds such as triethanolamine and trimethylolamine, silicone compounds such as silicone resins and alkylchlorosilanes are applied to the particle surfaces of the metal compounds. Forming processing can be mentioned.

The content of the metal compound in the plastic substrate (I) is usually 0.1 to 20% by mass, preferably 0.1 to 15% by mass, and further 0.2 to 10% by mass. is more preferable, and among them, 0.2 to 5% by mass is most preferable. From the viewpoint of haze, it is preferably 5% by mass or less. When the content of the metal compound in the plastic substrate (I) is 0.1 to 20% by mass, excellent gas barrier properties can be obtained. On the other hand, when the content of the metal compound in the plastic substrate (I) is less than 0.1% by mass, the ion crosslinked structure formed by reaction with the polycarboxylic acids in the gas barrier layer (II) is reduced. , the desired gas barrier properties cannot be obtained. On the other hand, the plastic substrate (I) having a content of more than 20% by mass tends to break more frequently during stretching during film formation, resulting in lower productivity and lower mechanical properties.

The plastic substrate (I) (especially thermoplastic resin) contains, within a range that does not adversely affect the performance of the plastic substrate (I), for example, heat stabilizers, antioxidants, reinforcing agents, pigments, antidegradants, One or more of various additives such as weathering agents, flame retardants, plasticizers, preservatives, ultraviolet absorbers, antistatic agents, antiblocking agents, etc. may be added as necessary. In addition, an inorganic or organic lubricant other than the metal compound may be added for the purpose of improving the slip property of the plastic substrate (I). For example, silica can be suitably added as a lubricant. These additives may also be blended into the mixture (particularly the melt-kneaded product) in the same manner as the metal compounds.

The thickness of the plastic substrate (I) is not particularly limited, and can be appropriately selected according to, for example, the mechanical strength required by the resulting gas barrier laminate. In particular, the thickness of the plastic substrate (I) is usually preferably 5 to 100 μm, more preferably 10 to 30 μm, for the reasons of securing mechanical strength, ease of handling, and the like. If the thickness of the plastic substrate (I) is less than 5 μm, sufficient mechanical strength may not be obtained, and the piercing strength may be reduced.

(2) Gas barrier layer (II)
The gas barrier layer (II) contains polycarboxylic acid or its anhydride (in the present invention, both are collectively referred to as "polycarboxylic acids"), and is formed on one surface of the plastic substrate (I). is laminated to

The polycarboxylic acids contained in the gas barrier layer (II) play a role of developing gas barrier properties by reacting with the metal compound in the plastic substrate (I).

Polycarboxylic acids are compounds having two or more carboxyl groups in the molecule or anhydrides thereof. In the case of an anhydride, all the carboxyl groups may have the anhydride structure [--CO--O--CO--], or some of the carboxyl groups may have the anhydride structure. Moreover, polycarboxylic acids may be in either the form of a monomer or a polymer.

Specific examples of polycarboxylic acids include a) monomer compounds such as 1,2,3,4-butanetetracarboxylic acid, b) polyacrylic acid, polymethacrylic acid, acrylic acid-methacrylic acid copolymers, acrylic Homopolymer or copolymer of (meth)acrylic acid such as acid-maleic acid copolymer, acrylic acid-maleic anhydride copolymer, d) polymaleic acid, ethylene-maleic acid copolymer, ethylene-maleic anhydride Examples include olefin-maleic acid copolymers such as copolymers, e) polysaccharides having carboxyl groups in side chains such as alginic acid, and f) polyamides or polyesters having carboxyl groups. These polycarboxylic acids can be used alone or in combination of two or more. The above-mentioned "(meth)acrylic acid" is a general term for acrylic acid or methacrylic acid (the same shall apply hereinafter).

When the polycarboxylic acid is a polymer, its weight average molecular weight is not particularly limited, but is generally preferably from 1,000 to 1,000,000, particularly from 10,000 to 150,000. is more preferable, and among them, 15,000 to 110,000 is most preferable. If the weight average molecular weight of the polycarboxylic acid is too low, the obtained gas barrier layer (II) will be brittle, while if the molecular weight is too high, the handling property will be impaired, and in some cases the gas barrier layer (II) described later will be formed. There is a risk that the gas barrier properties of the resulting gas barrier layer (II) will be impaired due to aggregation in the coating solution for the purpose.

In the present invention, an olefin-maleic acid copolymer is preferably used as the polycarboxylic acid, and an ethylene-maleic acid copolymer (hereinafter also referred to as "EMA") is particularly preferably used. By using EMA, better gas barrier properties can be obtained. A known or commercially available EMA can be used. Moreover, what was obtained by the well-known manufacturing method can also be used. Therefore, a copolymer obtained by polymerizing maleic anhydride and ethylene by a method such as solution radical polymerization can also be used.

The maleic acid unit in EMA is preferably 5 mol% or more, more preferably 20 mol% or more, still more preferably 30 mol% or more, and most preferably 35 mol% or more. . In addition, the maleic acid unit in the olefin-maleic acid copolymer tends to have a maleic anhydride structure in which the adjacent carboxyl group is cyclodehydrated in a dry state, and when wet or in an aqueous solution, the ring is opened to form a maleic acid structure. . Therefore, in the present invention, maleic acid units and maleic anhydride units are collectively referred to as "maleic acid units" unless otherwise specified.

In addition, the weight average molecular weight of EMA is usually about 1,000 to 1,000,000, preferably 3,000 to 500,000, more preferably 7,000 to 300,000, Most preferably 10,000 to 200,000.

The content of the polycarboxylic acid in the gas barrier layer (II) is not particularly limited, and can be appropriately set according to the type of polycarboxylic acid used. It is preferably about mass %, and more preferably 50 to 80 mass %.

The gas barrier layer (II) in the laminate of the present invention may contain, in addition to polycarboxylic acids, other components (especially components that react with polycarboxylic acids to crosslink polycarboxylic acids). For example, the laminate of the present invention preferably contains polyalcohol or the like.

Higher gas barrier properties can be obtained by including polyalcohol in the gas barrier layer (II). That is, the polycarboxylic acid in the gas barrier layer (II) can undergo an ionic cross-linking reaction with the metal compound (metal ions) in the plastic substrate (I), and can also undergo an ester cross-linking reaction with the polyalcohol. can be further improved.

Polyalcohol is a compound having two or more hydroxyl groups in the molecule, and may be either a low-molecular-weight compound or a high-molecular-weight compound (polymer). Examples thereof include sugar alcohols such as glycerin and pentaerythritol, monosaccharides such as glucose, disaccharides such as maltose, and oligosaccharides such as galacto-oligosaccharides. Polymer compounds include, for example, polyvinyl alcohol, ethylene-vinyl alcohol copolymers, and polysaccharides such as starch. The above polyalcohols may be used alone or in combination of two or more.

When the polyalcohol is polyvinyl alcohol, ethylene-vinyl alcohol copolymer, etc., the degree of saponification is not limited, but is usually preferably 95 mol% or more, more preferably 98 mol% or more. preferred. Also, the average degree of polymerization is preferably 50 to 2,000, more preferably 200 to 1,000. This makes it possible to obtain better gas barrier properties.

The content of the polyalcohol is not limited, but in particular, the OH groups contained in the polyalcohol and the COOH groups contained in the polycarboxylic acids ([-CO-O-CO-] in the case of anhydrides are two The molar ratio (OH group/COOH group) may be set to 0.01 to 20, preferably 0.01 to 10. , more preferably 0.02 to 5, most preferably 0.04 to 2. This can further enhance gas barrier properties.

The gas barrier layer (II) may contain, for example, a heat stabilizer, an antioxidant, a reinforcing material, a pigment, an anti-deterioration agent, a weathering agent, a Additives such as flame retardants, plasticizers, release agents, lubricants, preservatives, antifoaming agents, wetting agents and viscosity modifiers may be added.

Examples of heat stabilizers, antioxidants, and deterioration inhibitors include hindered phenols, phosphorus compounds, hindered amines, sulfur compounds, copper compounds, and alkali metal halides. Also good.

Examples of reinforcing materials include clay, talc, wollastonite, silica, alumina, calcium silicate, sodium aluminate, sodium aluminosilicate, magnesium silicate, glass balloons, carbon black, zeolite, montmorillonite, hydrotalcite, fluoromica, and metals. Fibers, metal whiskers, ceramic whiskers, potassium titanate whiskers, boron nitride, graphite, glass fibers, carbon fibers, fullerenes (C60, C70, etc.), carbon nanotubes, and the like.

The thickness of the gas barrier layer (II) is preferably 0.05 μm or more in order to more reliably obtain the gas barrier properties of the gas barrier laminate. Although the upper limit of the thickness is not particularly limited, it is preferably about 5 μm from the standpoint of economy and the like.

(3) Protective layer (III)
Protective layer (III) contains a resin component having a glass transition temperature (Tg) of 60° C. or higher, and is laminated on the other surface of plastic substrate (I). As shown in FIG. 1, the protective layer (III) is preferably laminated on the entire surface of the plastic substrate (I) opposite to that on which the gas barrier layer (II) is laminated. The formation of the protective layer (III) can effectively suppress the elution of the metal compound in the plastic substrate (I) to the outside of the gas barrier laminate during the hot water treatment. As a result, the reactivity between the metal compound and the gas barrier layer (II) is enhanced, and excellent gas barrier properties can be stably obtained even in hydrothermal treatment at lower temperatures and for shorter periods of time.

The protective layer (III) contains a resin component having a glass transition temperature of 60° C. or higher (hereinafter also referred to as “resin component B”), and the glass transition temperature of resin component B is preferably 80° C. or higher. , particularly preferably 100° C. or higher. When the glass transition temperature of the resin component B is lower than 60°C, the effect of suppressing the elution of the metal compound in the plastic substrate (I) is small, and the desired gas barrier property is obtained in the hydrothermal treatment at a relatively low temperature for a short period of time. may become difficult. The upper limit of the glass transition temperature is, for example, about 150° C., and can be about 130° C., but is not limited to this.

The content of the resin component B in the protective layer (III) is not limited, but is usually preferably 20% by mass or more, and more preferably 30% by mass or more. If the content of the resin component B is less than 20% by mass, the above effects may not be obtained. Although the upper limit of the content of the resin component B is not limited, it is usually about 100% by mass, preferably 95% by mass. Therefore, it can be, for example, 25 to 100% by mass, or, for example, 90 to 100% by mass.

Examples of the resin component B include various resins such as polyvinyl alcohol, ethylene-vinyl alcohol copolymer, urethane resin, polyester resin, acrylic resin, epoxy resin, alkyd resin, melamine resin, amino resin and olefin resin. Among these, polyvinyl alcohol and ethylene-vinyl alcohol copolymer are preferable from the viewpoint of barrier properties. Urethane resins are preferred from the viewpoint of water resistance, solvent resistance, heat resistance, and curing temperature, and among these, urethane resins having self-crosslinking properties are preferred. The above resin components may be used alone or in combination of two or more.

The protective layer (III) preferably contains polyvinyl alcohol. By containing polyvinyl alcohol, gas barrier properties are imparted to the protective layer (III), so that the gas barrier properties of the gas barrier laminate are further improved.

Although any type of polyvinyl alcohol can be used, those having the following physical properties can be preferably used. That is, the degree of saponification of polyvinyl alcohol is preferably 95 mol % or more, more preferably 98 mol % or more. Also, the average degree of polymerization is preferably from 50 to 2,000, and more preferably from 200 to 1,000. As such polyvinyl alcohol itself, a known or commercially available one can be used.

In addition to the resin component B, the protective layer (III) may contain other additives as necessary. Examples of additives include the same additives as in the case of the gas barrier layer (II).

In addition, as an additive, a compound that acts as a cross-linking agent may be included. Thereby, the water resistance, solvent resistance, heat resistance, etc. of the protective layer (III) can be further enhanced. Examples of such compounds include isocyanate compounds, melamine compounds, urea compounds, epoxy compounds, carbodiimide compounds, zirconium salt compounds such as ammonium zirconium carbonate, and metal alkoxides. These compounds can be used singly or in combination of two or more. In particular, when polyvinyl alcohol is contained as the resin component B, a compound having a plurality of (preferably about 500 to 10,000) carboxyl groups that undergo an ester cross-linking reaction with hydroxyl groups in the molecule is preferably blended as a cross-linking agent. When a cross-linking agent is used, its content is not limited, but generally it may be appropriately set within a range of about 1 to 500 parts by mass per 100 parts by mass of the resin component B.

In the present invention, the thickness of the protective layer (III) is preferably 0.05 to 5 μm, more preferably 0.1 to 3 μm, from the standpoint of enhancing the effect of suppressing elution of the metal compound, and more preferably 0.1 to 3 μm. .2 to 2 μm is most preferred.

(4) Other Layers The laminate of the present invention has a basic structure including a protective layer, a plastic base material and a gas barrier layer. One layer or two or more layers may be laminated. Other layers include, for example, a printed layer, an adhesive layer, a heat seal layer, a metal foil layer, a primer layer, an anchor coat layer, and a metal deposition layer.

2. Physical Properties of Gas Barrier Laminate The laminate of the present invention is basically provided in the form of a sheet. The total thickness can be appropriately set depending on the application and the like, and can be set appropriately within the range of 5 to 50 μm, preferably 10 to 35 μm.

In addition, since the laminate of the present invention has a protective layer formed on the surface of the plastic substrate, metal compounds that can be eluted from the plastic substrate (I) particularly when the laminate of the present invention is subjected to hot water treatment. amount can be suppressed. More specifically, the amount of metal compound eluted when the laminate of the present invention (preferably not yet immersed in water) is subjected to hot water treatment at 120 ° C. for 30 minutes (before hot water treatment reduction rate) is usually preferably 20% by mass or less, more preferably 15% by mass or less, and most preferably 10% by mass or less. If the amount of the eluted metal compound exceeds 20% by mass, the reactivity between the metal compound and the gas barrier layer (II) is reduced, and the desired gas barrier property cannot be exhibited by hydrothermal treatment at a lower temperature for a shorter time. The lower limit of this reduction rate is most preferably 0% by mass, but may be, for example, about 1% by mass or about 5% by mass.

The laminate of the present invention (preferably one that has not yet been immersed in water) has an oxygen permeability at 20 ° C. in an atmosphere of 90% relative humidity, and an oxygen permeability after hot water treatment at 80 ° C. for 30 minutes. Oxygen permeability after hot water treatment at 120°C for 30 minutes is 100 ml/(m ² ·day MPa) or less, especially both oxygen permeability is 50 ml/(m ² ·day · MPa) or less more preferably 20 ml/(m ² ·day·MPa) or less, and most preferably 10 ml/(m ² ·day·MPa) or less. Both oxygen permeabilities may be the same as each other, or may be different from each other. Although the lower limit of both oxygen permeabilities is not limited, it is usually about 0.01 ml/(m ² ·day·MPa).

The laminate of the present invention preferably has a tensile strength of 150 MPa or more, more preferably 180 MPa or more. If the tensile strength is less than 150 MPa, the mechanical strength tends to be insufficient and the puncture strength tends to decrease. Also, from the same viewpoint as the tensile strength, the tensile elongation is preferably 60% or more, and more preferably 80% or more.

Regarding the pinhole resistance of the laminate of the present invention, the number of pinholes generated in a 500-times repeated bending fatigue test in an atmosphere of 5° C. is preferably 100 or less, and more preferably 20 or less. Specifically, the pinhole resistance described above is Fed. Test Method Std. According to Method 2017 of 101C, a 12-inch × 8-inch sample was gripped in a cylindrical shape with a diameter of 3.5 inches, with an initial grip interval of 7 inches and a grip interval at maximum bending of 1 inch. The number of pinholes generated after bending 500 times under the condition of 5° C. and 5° C. is measured and evaluated.

Regarding the transparency of the laminate of the present invention, the haze is preferably 70% or less, particularly preferably 50% or less, further preferably 30% or less, and particularly preferably 15% or less. , 10% or less. However, this is not the case because transparency may not be required depending on the application.

3. Production of Gas Barrier Laminate The production method of the laminate of the present invention is not particularly limited. It can be suitably carried out by any of a method of laminating a coating film from a coating liquid containing constituent components, c) a method of combining the above a) and b), and the like.

In particular, in the present invention, an unstretched film containing a resin component A and a metal compound (powder) is used as a precursor of the plastic substrate (I), and a coating solution for forming the gas barrier layer (II) is applied to one side of the unstretched film. Forming a coating film, forming a coating film on the other surface with the coating solution for forming the protective layer (III), and stretching the unstretched film after the coating film is formed. can be adopted.

In this case, as a method for stretching the unstretched film, either uniaxial stretching or biaxial stretching can be employed. In the case of biaxial stretching, either simultaneous biaxial stretching or sequential biaxial stretching can be employed.

The draw ratio for drawing is not particularly limited, but can be set as follows. In the case of uniaxial stretching, it is preferably 1.5 times or more, more preferably 2 to 6 times. In the case of biaxial stretching, it is preferably 1.5 times or more in each direction, more preferably 2 to 4 times. The area magnification is usually preferably 3 times or more, more preferably 6 to 20 times, and most preferably 6.5 to 13 times. By setting the draw ratio within the above range, it is possible to obtain a gas barrier laminate capable of exhibiting better mechanical properties.

In the present invention, when biaxial stretching is employed, the following methods can be suitably used by either simultaneous biaxial stretching or sequential biaxial stretching.

The first method (in the case of simultaneous biaxial stretching) is a method for producing a gas barrier laminate, comprising (1) forming a gas barrier layer (II) on one side of an unstretched film containing resin component A and a metal compound; A step of applying a coating solution (gas barrier layer (II) forming step), (2) a step of applying a protective layer (III) forming coating solution to the other surface of the unstretched film (protective layer (III) forming step) step), and (3) the step of simultaneously biaxially stretching the unstretched film coated with at least one of the two coating liquids (stretching step), the laminate of the present invention can be suitably produced. .

The second method (in the case of sequential biaxial stretching) is a method for producing a gas barrier laminate, comprising (1) a step of stretching an unstretched film containing resin component A and a metal compound in the machine direction (MD). (First stretching step), (2) Coating liquid for forming gas barrier layer (II) is applied to one side of the film stretched in the longitudinal direction, and coating liquid for forming protective layer (III) is applied to the other side. (coating film forming step), and (4) laterally stretching the film coated with both coating liquids (second stretching step). can.

In particular, it is preferable to employ the first method (simultaneous biaxial stretching) in the present invention. The simultaneous biaxial stretching method can generally combine practical properties such as mechanical properties, optical properties, thermal dimensional stability, and pinhole resistance. On the other hand, in the sequential biaxial stretching method in which the longitudinal stretching is followed by the lateral stretching, orientational crystallization of the film proceeds during the longitudinal stretching, and the stretchability of the thermoplastic resin during the lateral stretching is reduced, resulting in the formation of metal compounds. When the compounding amount is large, the frequency of film breakage tends to increase. Therefore, in the present invention, it is preferable to adopt the simultaneous biaxial stretching method. Therefore, in the following, the first method will be described more specifically as a representative example of the method for producing the laminate of the present invention.

(1) Gas Barrier Layer (II) Forming Step In the gas barrier layer (II) forming step, a gas barrier layer (II) forming coating liquid is applied to one side of the unstretched film containing the resin component A and the metal compound.

The unstretched film used in this step is not particularly limited, and can be produced, for example, by molding a mixture containing a resin component (thermoplastic resin) and a metal compound into a sheet or film.

The method of preparing the above mixture is not particularly limited. For example, a) a method of adding a metal compound when synthesizing (polymerizing) a resin component (particularly a thermoplastic resin), b) a method of kneading a resin component and a metal compound with an extruder, For example, a masterbatch is prepared by kneading to a certain concentration, and the masterbatch is added to a thermoplastic resin for dilution (masterbatch method). In the present invention, the masterbatch method is preferably employed because it is easy to adjust the content of the metal compound and is excellent in workability.

The molding method is not particularly limited, and known molding methods such as press molding, extrusion molding, and injection molding can be employed. For example, a mixture containing a resin component (thermoplastic resin) and a metal compound is heated and melted in an extruder, extruded into a film form from a T-die, and rotated by a known casting method such as an air knife casting method or an electrostatic application casting method. An unstretched film can be obtained by cooling and solidifying on a cooling drum. If the unstretched film is oriented, the stretchability may be lowered in the post-process, so the unstretched film is preferably in a substantially amorphous and non-oriented state.

The types and contents of the thermoplastic resin, the metal compound, and other additives may be the same as those described in "1. Gas barrier laminate."

Here, when a polyamide resin is used as the thermoplastic resin, the obtained unstretched film is transferred to a water tank whose temperature is controlled so as not to exceed 80 ° C., subjected to water immersion treatment within 5 minutes, and 0.5 to 15 % moisture absorption treatment is preferred.

In this step, the gas barrier layer (II)-forming coating liquid is applied to the unstretched film as described above so as to be in contact with the surface of the unstretched film.

The coating liquid for forming the gas barrier layer (II) can be prepared by dissolving or dispersing the components constituting the gas barrier layer (II) in a solvent.

As the solvent, water and various organic solvents can be used. Examples of organic solvents include hydrocarbon solvents such as cyclohexane, normal hexane and benzene; alcohol solvents such as methanol, ethanol, propanol, isopropyl alcohol and isobutyl alcohol; ketone solvents such as acetone, ketones and methyl ethyl ketone; Examples include ester solvents such as ethyl acetate, isopropyl acetate, isobutyl acetate and isopentyl acetate, and ether solvents such as ethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate and ethylene glycol monomethyl ether. Among these, water and at least one of water-soluble organic solvents are preferred, and water is particularly preferred. When water is used, the coating liquid is preferably in the form of an aqueous solution or aqueous dispersion (i.e., aqueous coating liquid), and in particular at least polycarboxylic acids (or at least one polyalcohol and polycarboxylic acids) More preferably, it is in the form of an aqueous solution dissolved in water.

Further, when preparing the gas barrier layer (II) forming coating liquid, it is preferable to add 0.1 to 20 equivalent % of an alkali compound to the carboxyl groups of the polycarboxylic acids. Polycarboxylic acids with a high carboxyl group content have high hydrophilicity, so they can be made into an aqueous solution without adding an alkaline compound. The gas barrier properties of the laminate can be significantly improved. In this case, the alkaline compound may be any compound capable of neutralizing the carboxyl groups of the polycarboxylic acids, and examples thereof include sodium hydroxide. Also, the amount of the alkali compound to be added is preferably set to 0.1 to 20 mol % with respect to the carboxyl groups of the polycarboxylic acids.

The gas barrier layer (II)-forming coating solution can be prepared by a known method using, for example, a dissolution vessel equipped with a stirrer. For example, it is preferable to prepare polycarboxylic acids and polyalcohol separately as aqueous solutions and mix them before coating. At this time, if the alkali compound is added to the aqueous solution of polycarboxylic acids, the stability of the aqueous solution can be improved.

The method of applying the gas barrier layer (II)-forming coating liquid is not particularly limited. For example, an air knife coater, a kiss roll coater, a metering bar coater, a gravure roll coater, a reverse roll coater, a dip coater, a die coater, or a combination of any of these can be used.

After applying the gas barrier layer (II)-forming coating liquid, it may be naturally dried or dried by heating, if necessary. The drying method by heating is not particularly limited, and examples thereof include a method in which moisture is evaporated by blowing hot air from a dryer or the like, infrared irradiation, or the like to form the gas barrier layer (II) as a dry film.

The drying temperature in the case of heat drying can be appropriately set depending on the presence or absence of additive components and their content, etc., but it is usually about 50 to 200 ° C., particularly preferably 80 to 150 ° C., further preferably 100 to 120 ° C. °C is more preferred. If the drying temperature is too low, it takes a long time to form a dry film, resulting in a decrease in productivity. On the other hand, if the drying temperature is too high, the plastic substrate (I), the gas barrier layer (II), etc. may become brittle. Heat drying can be performed, for example, in a temperature range lower than the temperature of the heat treatment (heat setting) in the stretching step.

When the gas barrier layer (II)-forming coating solution is applied, it may be irradiated with high-energy rays such as ultraviolet rays, X-rays, electron beams, etc. before and after drying, if necessary. In such a case, a component that crosslinks or polymerizes upon exposure to high-energy rays may be blended.

(2) Protective Layer (III) Forming Step In the protective layer (III) forming step, a protective layer (III) forming coating solution is applied to the other surface of the unstretched film.

The protective layer (III)-forming coating liquid can be prepared by dissolving or dispersing the components constituting the protective layer (III) in a solvent.

As the solvent, water and various organic solvents can be used. Examples of organic solvents include hydrocarbon solvents such as cyclohexane, normal hexane and benzene; alcohol solvents such as methanol, ethanol, propanol, isopropyl alcohol and isobutyl alcohol; ketone solvents such as acetone, ketones and methyl ethyl ketone; Examples include ester solvents such as ethyl acetate, isopropyl acetate, isobutyl acetate and isopentyl acetate, and ether solvents such as ethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate and ethylene glycol monomethyl ether. Among these, at least one of water and a water-soluble organic solvent is preferred, and water is particularly preferred. When water is used, the coating liquid is preferably in the form of an aqueous solution or aqueous dispersion (that is, an aqueous coating liquid), and more preferably in the form of an aqueous solution in which at least the resin component B is dissolved in water. .

The protective layer (III)-forming coating solution can be prepared by a known method using, for example, a dissolving pot equipped with a stirrer. In this case, the concentration of the resin component B in the coating liquid is not particularly limited, but can be appropriately set within a range of, for example, 5 to 30% by mass.

The method of applying the protective layer (III)-forming coating liquid is not particularly limited. For example, an air knife coater, a kiss roll coater, a metering bar coater, a gravure roll coater, a reverse roll coater, a dip coater, a die coater, or a combination of any of these can be used.

After applying the protective layer (III)-forming coating liquid, it may be dried naturally, but may also be dried by heating, if necessary. The drying method by heating is not particularly limited, and examples thereof include a method in which moisture is evaporated by blowing hot air from a dryer or the like, infrared irradiation, or the like to form the gas barrier layer (II) as a dry film.

The drying temperature in the case of heat drying can be appropriately set depending on the presence or absence of additive components and their content, etc., but it is usually about 50 to 200 ° C., particularly preferably 80 to 150 ° C., further preferably 100 to 120 ° C. °C is more preferred. If the drying temperature is too low, it takes a long time to form a dry film, resulting in a decrease in productivity. On the other hand, if the drying temperature is too high, the plastic substrate (I), the gas barrier layer (II), etc. may become brittle. Heat drying can be performed, for example, in a temperature range lower than the temperature of the heat treatment (heat setting) in the stretching step.

In addition, when the protective layer (III)-forming coating solution is applied, it may be irradiated with high-energy rays such as ultraviolet rays, X-rays, electron beams, etc., as required, before and after drying. In such a case, a component that crosslinks or polymerizes upon exposure to high-energy rays may be blended.

(3) Stretching Step In the stretching step, the unstretched film coated with both coating liquids is stretched. That is, the laminate of the present invention can be more preferably obtained by a so-called in-line coating method. By using the in-line coating method, it is possible to carry out the heat treatment necessary for film stretching and heat setting, and the heat treatment of the gas barrier layer (II) and protective layer (III) at a relatively high temperature at the same time. Efficiency can be increased. On the other hand, when the stretched film is coated with the gas barrier layer (II) and the protective layer (III) and then subjected to heat treatment (using the so-called off-line coating method), the stretched film that has undergone heat treatment in the stretching process is further coated with Since the heat treatment is performed, the plastic substrate (I) may become brittle due to excessive heat, and the strength and elongation may decrease.

In the present invention, the stretching may be either uniaxial stretching or biaxial stretching, but biaxial stretching is particularly preferred. In the case of biaxial stretching, either sequential biaxial stretching or simultaneous biaxial stretching may be used. For example, the unstretched film coated with both coating liquids is subjected to simultaneous biaxial stretching in the machine direction (MD) and transverse direction (TD) with a tenter type simultaneous biaxial stretching machine. A gas barrier laminate can be obtained. Alternatively, for example, after stretching the unstretched film coated with both coating liquids in the machine direction (MD), the gas barrier layer (II) and the protective layer (III) are formed by the method described above, and then the film is stretched in the transverse direction (TD). A sequentially biaxially stretched gas barrier laminate can be obtained by stretching. In particular, in the first method, simultaneous biaxial stretching can be suitably employed as described above.

Moreover, the draw ratio of the unstretched film is preferably 1.5 times or more in each of the machine direction (MD) and the transverse direction (TD), and more preferably 2 to 4 times. The area magnification is usually preferably 3 times or more, more preferably 6 to 20 times, and most preferably 6.5 to 13 times. By setting the draw ratio within the above range, it is possible to obtain a gas barrier laminate having better mechanical properties.

As for the temperature conditions in the stretching step, for example, it is preferable to stretch in a temperature range of 100 to 250° C. (preferably 150 to 200° C.) when performing the simultaneous biaxial stretching. By controlling the temperature within such a range, it is possible to more reliably produce the film of the present invention. These temperatures and the like can be set and controlled while preheating, for example, in a preheating roll, a preheating zone, or the like of a stretching apparatus.

The film that has undergone the stretching process is generally heat set at a temperature of 100 to 300 ° C. (especially 150 to 300 ° C.) in the tenter where the stretching process was performed, and optionally 0 to 10%, preferably 2 to 6%. The relaxation treatment is performed in the longitudinal direction and/or the lateral direction within the range of . In order to reduce the heat shrinkage, it is desirable not only to optimize the temperature and time of the heat setting time, but also to perform the heat relaxation treatment at a temperature lower than the maximum temperature of the heat setting treatment.

Incidentally, in the in-line coating method which is suitable in the present invention, the heat treatment in the heat setting of the film is mainly the heat treatment of the gas barrier layer (II). Therefore, by adopting the heat treatment conditions shown below as the heat treatment conditions for heat setting, the heat treatment of the gas barrier layer (II) can be performed simultaneously with the stretching treatment. As a result, the total amount of heat received by the laminate during the manufacturing process can be reduced, so thermal deterioration is suppressed and the physical properties (mechanical properties, etc.) inherent in the laminate (especially the plastic base material) are effectively expressed. can be made

Here, the heat treatment temperature for the gas barrier layer (II) can be appropriately set depending on the presence or absence of additive components and their content, etc., but it is usually about 100 to 300°C, particularly 120 to 250°C. It is preferably 140 to 240°C, and most preferably 160 to 220°C. If the heat treatment temperature is too low, for example, the ester cross-linking reaction between polycarboxylic acids and polyalcohol cannot proceed sufficiently. The cross-linking reaction cannot proceed sufficiently, and it may be difficult to obtain a laminate having sufficient gas barrier properties. On the other hand, if the heat treatment temperature is too high, the laminate may become brittle.

The heat treatment time is usually 5 minutes or less, preferably 1 second to 5 minutes, more preferably 3 seconds to 2 minutes, most preferably 5 seconds to 1 minute. If the heat treatment time is too short, the cross-linking reaction cannot proceed sufficiently, making it difficult to obtain a laminate having gas barrier properties.

The gas-barrier laminate of the present invention may be subjected to surface treatment such as corona discharge treatment, if necessary, as long as the effects of the present invention are not impaired.

The gas barrier laminate of the present invention can be made into various laminated films by laminating a sealant or the like as necessary, as long as the effects of the present invention are not impaired.

Examples of resins used as sealants include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, polypropylene, polyethylene/polypropylene copolymer, ethylene-vinyl acetate copolymer, ionomer resin, ethylene-acryl. Acid/methacrylic acid copolymer, ethylene-acrylic acid/methacrylic acid ester copolymer, polyvinyl acetate resin, etc. Polyethylene, polypropylene, polyethylene/polypropylene copolymer with high heat seal strength and strength of the material itself Polyolefin resin such as polyolefin resin is preferable. These resins may be used alone, or may be used after being melt-mixed with other resins. Further, these resins may be subjected to modification treatment such as acid modification.

Methods for forming a sealant layer on a gas barrier laminate include a method of laminating a film or sheet made of a sealant resin onto the gas barrier laminate via an adhesive, and a method of extrusion laminating a sealant resin onto the gas barrier laminate. mentioned. In the former method, the film or sheet made of the sealant resin may be in an unstretched state or may be in a low-ratio stretched state, but practically it is preferably in an unstretched state.

Although the thickness of the sealant layer is not particularly limited, it is usually preferably 20 to 100 μm, more preferably 40 to 70 μm.

4. Use of Gas Barrier Laminate The laminate of the present invention can be used for various purposes, and particularly, it can be suitably used as a packaging material by taking advantage of its gas barrier properties. In particular, it can be used as a material (packaging bag) for forming a bag. More specifically, it can be preferably used as a material for constructing a packaging bag for sealing contents. Furthermore, like a retort pouch, it can be suitably used as a sealed packaging bag that is subjected to hot water treatment (for example, a sealed packaging bag that is immersed in hot water while the contents are sealed). . Here, the conditions for the hot water treatment are not particularly limited, and can be set within a range where the desired oxygen permeability (gas barrier property) can be exhibited. For example, the temperature (water temperature) of the hot water treatment is about 30 to 130°C (under pressure when the temperature is 100°C or higher), preferably 60 to 125°C, and most preferably 70 to 121°C. preferable. Therefore, for example, hot water treatment at less than 100° C. (60 to 90° C. as an example) in air can also be performed. Also, the time of the hot water treatment can be appropriately set generally within the range of 10 seconds to 100 hours, depending on the treatment temperature and the like.

The form of the bag is not particularly limited, and examples include a two-sided bag, a three-sided bag, a three-sided bag with a zipper, a folded bag, a gusseted bag, a bottom gusseted bag, a stand bag, a stand zippered bag, a two-sided bag, and a four-sided prism flat-bottomed gusseted bag. , side-seal bags, bottom-seal bags, and the like.

Such packaging bags are suitable for food and beverages, fruits, juices, drinking water, sake, cooked foods, fish paste products, frozen foods, meat products, boiled foods, rice cakes, liquid soups, seasonings, etc. Various contents such as food and drink, liquid detergents, cosmetics, and chemical products can be filled and packaged.

EXAMPLES Examples and comparative examples are shown below to describe the features of the present invention more specifically. However, the scope of the present invention is not limited to the examples.

A. Raw Materials Used Raw materials used in Examples and Comparative Examples are as follows.

(1) Thermoplastic resin for constituting plastic substrate (I) a) PA6: Nylon 6 resin ("A1030BRF" manufactured by Unitika Ltd., relative viscosity 3.0 (25°C))
(2) Metal compound for constituting plastic substrate (I) a) MgO: magnesium oxide (“PUREMAG FNM-G” manufactured by Tateho Chemical Industry Co., Ltd., average particle size 0.4 μm)
b) CaCO ₃ : calcium carbonate (“VIgot15” manufactured by Shiraishi Kogyo Co., Ltd., average particle size 0.5 μm)
c) ZnO: Zinc oxide (“FINEX-50” manufactured by Sakai Chemical Industry Co., Ltd., average particle size 0.02 μm)
(3) Polycarboxylic acid component of coating liquid for forming gas barrier layer (II) a) EMA aqueous solution:
EMA (weight average molecular weight 60,000) and sodium hydroxide are added to water, dissolved by heating, and then cooled to room temperature to prepare a solid in which 10 mol% of the carboxyl groups of EMA are neutralized with sodium hydroxide. 15% by weight EMA aqueous solution. (Denoted as "EMA" in Table 1)
b) PAA aqueous solution:
Polyacrylic acid ("A10H" manufactured by Toagosei Co., Ltd., weight average molecular weight 200,000, 25% by weight aqueous solution) and sodium hydroxide, 10 mol% of the carboxyl groups of polyacrylic acid are sodium hydroxide 15 wt% solids polyacrylic acid (PAA) aqueous solution neutralized with (Denoted as "PAA" in Table 1)
(4) Other resin components of gas barrier layer (II) forming coating solution a) PVA aqueous solution:
Polyvinyl alcohol ("Poval 105" manufactured by Kuraray Co., Ltd., degree of saponification 98-99%, average degree of polymerization about 500) is added to water, dissolved by heating, and then cooled to room temperature. Alcohol (PVA) aqueous solution. (Denoted as "PVA" in Table 1)
b) EVOH aqueous solution:
An ethylene-vinyl alcohol copolymer (EVOH) aqueous solution with a solid content of 10% by mass, in which an ethylene-vinyl alcohol copolymer (“Exceval AQ-4105” manufactured by Kuraray Co., Ltd.) is dissolved. (Denoted as "EVOH" in Table 1)
(5) Coating liquid for forming protective layer (III) a) Polyurethane resin 1
A water-based polyurethane resin (“Takelac WS-4022” manufactured by Mitsui Chemicals, solid content 30% by mass, Tg: 115° C.) was prepared to prepare a coating liquid having a solid content of 10% by mass. (Denoted as "WS-4022" in Table 1)
b) polyurethane resin 2
A water-based polyurethane resin (“Takelac WS-5984” manufactured by Mitsui Chemicals, solid content 40% by mass, Tg: 70° C.) was prepared to prepare a coating liquid having a solid content of 10% by mass. (Denoted as "WS-5984" in Table 1)
c) polyurethane resin 3
A water-based polyurethane resin (“Hydran AP-40F” manufactured by DIC, solid content 22.5% by mass, Tg: 55° C.) was prepared to prepare a coating liquid having a solid content of 10% by mass. (Denoted as "AP-40F" in Table 1)
d) polyurethane resin 4
A water-based polyurethane resin (“Hydran AP-201” manufactured by DIC, solid content 23% by mass, Tg: 10° C.) was prepared to prepare a coating liquid having a solid content of 10% by mass. (Denoted as "AP-201" in Table 1)
e) polyester resin 1
A water-based polyester resin (“Elitel KZA-1734” manufactured by Unitika Ltd., solid content 30% by mass, Tg: 66° C.) was prepared to prepare a coating liquid having a solid content of 10% by mass. (Denoted as "KZA-1734" in Table 1)
f) PVA aqueous solution:
Polyvinyl alcohol ("Poval 105" manufactured by Kuraray Co., Ltd., saponification degree 98-99%, average polymerization degree about 500, Tg: 85 ° C.) is added to water, dissolved by heating, and then cooled to room temperature. 10 mass % polyvinyl alcohol (PVA) aqueous solution. (Denoted as "PVA" in Table 1)
(6) Other resin components of coating solution for forming protective layer (III) a) Melamine resin Methylolmelamine resin ("Amidia APM" manufactured by DIC, solid content 80% by mass) (indicated as "APM" in Table 1) )
b) Isocyanate resin polyisocyanate resin (manufactured by BASF "HW-100", solid content 100% by mass) (denoted as "HW-100" in Table 1)
c) Polycarboxylic acid aqueous solution EMA (weight average molecular weight 60,000) and sodium hydroxide were added to water, dissolved by heating, and then cooled to room temperature. A neutralized aqueous solution of EMA with a solids content of 15% by weight. (Denoted as "EMA" in Table 1)

B. Examples and Comparative Examples
Example 1
A nylon 6 resin and a master chip were mixed so that the content of magnesium oxide was 0.1% by mass. This mixture was put into an extruder and melted in a cylinder at 270°C. The melt was extruded into a sheet through a T-die orifice, brought into close contact with a rotating drum cooled to 10° C., and quenched to obtain an unstretched film having a thickness of 150 μm. The obtained unstretched film was sent to a hot water bath at 50° C. and subjected to water immersion treatment for 2 minutes.
Next, an aqueous EMA solution and an aqueous PVA solution were mixed so that the mass ratio (solid content) of EMA and PVA was 70/30, to obtain a gas barrier layer (II) forming coating solution having a solid content of 10% by mass. Obtained. This coating liquid was applied to one side of the unstretched film that had been subjected to water immersion treatment by an air knife coating method, and dried for 30 seconds using an infrared ray irradiator at a temperature of 110°C.
In the unstretched film coated with the coating liquid for forming the gas barrier layer (II), the coating liquid for forming the protective layer (III) is applied to the opposite side of the film coated with the coating liquid for forming the gas barrier layer (II). A coating liquid composed of polyurethane resin 1 was applied by an air knife coating method, and dried for 30 seconds using an infrared ray irradiator at a temperature of 110°C.
The ends of the unstretched film, in which the gas barrier layer (II)-forming coating solution and the protective layer (III)-forming coating solution are laminated on both sides, are held by clips of a tenter-type simultaneous biaxial stretching machine, It was stretched 3.3 times each in MD and TD at 180°C. After that, the relaxation rate of the TD was set to 5%, and heat treatment was performed at 210° C. for 4 seconds, followed by slow cooling to room temperature. Thus, a laminate was obtained in which the gas barrier layer (II) with a thickness of 0.3 μm and the protective layer (III) with a thickness of 0.5 μm were formed on the plastic substrate (I) with a thickness of 15 μm.

Examples 2-16 and Comparative Examples 1-6
As shown in Table 1, except that the type and content of the metal compound in the thermoplastic composition resin film (I), the composition and coating thickness of the gas barrier layer (II) and the protective layer (III) were changed, A laminate was obtained in the same manner as in 1.

Test example 1
The following physical properties of the samples (laminates) obtained in Examples and Comparative Examples were measured according to the respective measuring methods. Table 1 shows the results.

(1) Thickness of Each Layer After leaving the obtained gas barrier laminate in an environment of a temperature of 23° C. and a relative humidity of 50% RH for 2 hours or longer, the cross section of the film was observed with a scanning electron microscope (SEM). thickness was measured.

(2) Oxygen Permeability The obtained gas barrier laminate was subjected to a hydrothermal treatment under the conditions of 80° C.×30 minutes or 120° C.×30 minutes, and after wiping off adhering water droplets, the temperature was 23° C. and the relative humidity was 90% RH. After leaving it for 2 hours or more under the environment of , the oxygen permeability was measured in an atmosphere of a temperature of 20° C. and a relative humidity of 90% using an oxygen barrier measuring device (OX-TRAN 2/20) manufactured by Mocon. The unit is ml/(m ² ·day · MPa).

(3) Measurement of metal content and reduction in film After heating the gas barrier laminate before and after the hot water treatment at 120°C for 30 minutes in a mixed acid of nitric acid and sulfuric acid, the insoluble portion was treated with perchloric acid and hydrofluoric acid. It was completely dissolved by heating in mixed acid. The metal concentration in this solution was measured by a plasma atomic emission spectrometer (iCAP6500Duo) manufactured by Thermo Fisher Scientific, the metal content in the film was calculated, and the metal content reduction rate was calculated based on the following formula. did.
Metal content reduction rate (%) = (MA-MB) / MA x 100
MA: metal content in film before hot water treatment MB: metal content in film after hot water treatment at 120°C for 30 minutes

As is clear from the results in Table 1, in Examples 1 to 16, a gas barrier layer ( II) is laminated, and the protective layer (III) containing a resin component with a glass transition temperature of 60 ° C. or higher is laminated on the other side, so even if it is a relatively low-temperature and short-time hot water treatment It can be seen that good gas barrier properties are obtained. In particular, in Examples 3 and 4, etc., it can be seen that a high gas barrier property of 2 to 10 ml/(m ² ·day · MPa) can be exhibited even after the hot water treatment at 80°C for 30 minutes.

On the other hand, in Comparative Example 1, since the protective layer (III) was not laminated, the amount of metal outflow during the hot water treatment was large, and the oxygen permeability was high in the hot water treatment at a relatively low temperature and in a short time. It can be seen that high gas barrier properties cannot be obtained. In Comparative Examples 2 and 3, since the glass transition temperature of the protective layer (III) is lower than the range specified in the present invention, the metal outflow amount due to the hot water treatment is large, and after the hot water treatment at a relatively low temperature and in a short time Oxygen permeability is high. In Comparative Example 4, the amount of the metal compound contained in the plastic substrate (I) is smaller than the range specified in the present invention, so the oxygen permeability after the hot water treatment is high. In Comparative Example 5, since the gas barrier layer (II) does not contain polycarboxylic acid, it can be confirmed that the oxygen permeability after the hydrothermal treatment is high. In Comparative Example 6, since the gas barrier layer (II) was not formed, the obtained laminate had a high oxygen permeability after the hot water treatment.

Claims (9)

A laminate comprising, in order, at least a protective layer (III), a plastic substrate (I) and a gas barrier layer (II),
(1) The plastic base material (I) contains a resin component and a metal compound, and the content of the metal compound is 0.1 to 20% by mass,
(2) The gas barrier layer (II) contains polycarboxylic acid or its anhydride and is laminated on one surface of the plastic substrate (I),
(3) The protective layer (III) contains a polyalcohol and/or polyurethane resin as a resin component having a glass transition temperature of 60° C. or higher, and is laminated on the other surface of the plastic substrate (I). there is
A gas barrier laminate characterized by: 2. The gas barrier laminate according to claim 1, wherein the plastic substrate (I) is a polyamide film. 3. The gas barrier laminate according to claim 1, wherein the gas barrier layer (II) further contains polyalcohol. 4. The gas barrier laminate according to any one of claims 1 to 3, wherein the content of the resin component in the protective layer (III) is 25-100% by mass. The gas barrier laminate according to any one of claims 1 to 4, wherein the protective layer (III) has a thickness of 1 µm or less. In the oxygen permeability at a temperature of 20 ° C. and a relative humidity of 90%, the oxygen permeability after the hot water treatment at 80 ° C. for 30 minutes is 100 ml / (m ² day MPa) or less, and the temperature is 120 ° C. x The gas barrier laminate according to any one of claims 1 to 5, which has an oxygen permeability of 100 ml/(m ² ·day · MPa) or less after 30 minutes of hot water treatment. The gas barrier laminate according to any one of claims 1 to 5, which is used for hot water treatment with hot water at a temperature of 30 to 130°C. A packaging material comprising the gas barrier laminate according to any one of claims 1 to 7. 9. The packaging material according to claim 8, used for sealing contents.

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