JP2015168163A - gas barrier laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas barrier laminate which has excellent productivity and economic efficiency and has excellent gas barrier properties even in high humidity, and which suppresses occurrence of poor appearance during heat sterilization process when used as a package for loading a volatile acid substance as a content.SOLUTION: A gas barrier laminate is obtainable by laminating a gas barrier layer (II) containing polycarboxylic acid onto a plastic substrate (I) containing 0.3-20 mass% of a calcium compound. After being subjected to a hot water treatment of 120°C for 30 minutes, an oxygen permeability in atmosphere having a relative humidity of 65% at 20°C is not more than 200 ml/(mday MPa).

Description

  The present invention relates to a gas barrier laminate having excellent gas barrier properties that does not cause poor appearance even when subjected to a heat sterilization treatment when used as a package filled with contents containing a volatile acidic substance.

  Plastic films such as polyamide films are excellent in strength, transparency and moldability, and are therefore used in a wide range of applications as packaging materials. However, since these plastic films have a large gas permeability such as oxygen, when used for packaging general foods, retort processed foods, cosmetics, medical supplies, agricultural chemicals, etc., the oxygen that permeated the film during long-term storage. The contents may be altered by such gases. Therefore, the plastic film used for these packaging applications is required to have a gas barrier property, and in the packaging of foods containing moisture, the gas barrier property under high humidity is also required.

  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 as the gas barrier layer, it is possible to use a material composed of a polycarboxylic acid polymer, a polyalcohol polymer, and a metal compound. Are known.

  For example, in Patent Document 1, as a method for producing a gas barrier laminate having a gas barrier property even under high humidity, a gas barrier formed by laminating a plastic substrate, a gas barrier layer, and a polymer layer containing a divalent or higher metal compound. Describes a method for producing a gas barrier laminate by heat-treating the porous laminate in the presence of water.

JP 2004-322626 A

However, in the method of Patent Document 1, after forming a gas barrier layer, pressure treatment using an autoclave is performed in water containing a metal compound, and it is difficult to carry out continuously, resulting in poor productivity. It was a thing.
In Patent Document 1, an undercoat layer is formed by applying and drying a solvent-based paint, and a gas barrier layer is formed thereon by applying and drying a water-based paint. Therefore, the method of Patent Document 1 has problems in terms of economy and productivity, such as requiring an explosion-proof facility for using a solvent-based paint, and requiring application several times.

  The inventors of the present invention studied the simultaneous application of a solvent-based undercoat layer-forming paint and a water-based gas barrier layer-forming paint using a curtain coater, etc. Occasionally, the coating film became uneven, and the obtained laminate did not exhibit gas barrier properties.

  In addition, instead of using a water-based paint for forming the undercoat layer, it may be applied simultaneously using a curtain coater or the like, or after applying and drying the water-based paint for forming the undercoat layer, the water-based paint for forming the gas barrier layer However, none of the obtained laminates exhibited gas barrier properties.

Furthermore, when the gas barrier laminate obtained by the method of Patent Document 1 is used for a package that is filled with contents such as food containing volatile acidic substances, the package containing the contents is packaged when heat-sterilized. Appearance defects may occur on the body. Examples of poor appearance of the package include, for example, whitening of a part of the transparent laminated film constituting the package, and formation of water bubble-like protrusions on the surface or inside of the laminated film. Examples of the heat sterilization method include a hot pack method, a boil sterilization method, and a retort sterilization method. Among these, when using the retort sterilization method with the highest heat treatment temperature, the appearance of the package is particularly likely to deteriorate.

  The problem of the present invention is to solve the above problems, excellent in productivity and economy, excellent gas barrier properties even under high humidity, and used as a package filled with volatile acidic substances as contents, An object of the present invention is to provide a gas barrier laminate in which the occurrence of poor appearance during heat sterilization treatment is suppressed.

As a result of intensive studies on the above problems, the present inventors have used a plastic substrate (I) containing a specific amount of a calcium compound and a laminate obtained by laminating a gas barrier layer (II) containing a polycarboxylic acid thereon. However, it has an excellent gas barrier property even under high humidity, and when used as a package filled with contents containing a volatile acidic substance, it has been found that the occurrence of poor appearance during heat sterilization treatment is suppressed, The present invention has been reached.
That is, the gist of the present invention is as follows. (1) A gas barrier laminate in which a gas barrier layer (II) containing polycarboxylic acid is laminated on a plastic substrate (I) containing 0.3 to 20% by mass of a calcium compound, which is 120 ° C., 30 A gas barrier laminate having an oxygen permeability of 200 ml / (m ² · day · MPa) or less in an atmosphere of 20 ° C. and a relative humidity of 65% after hydrothermal treatment for 1 minute.
(2) The gas barrier laminate according to (1), wherein the plastic substrate (I) is a multilayer film, and at least one layer thereof contains 0.3 to 20% by mass of a calcium compound.
(3) The gas barrier laminate according to (1) or (2), wherein the thermoplastic resin constituting the plastic substrate (I) is a polyamide resin or a polyester resin.
(4) The gas barrier laminate according to any one of (1) to (3), wherein the gas barrier layer (II) contains a polyalcohol.
(5) A packaging bag comprising the gas barrier laminate according to any one of (1) to (4).
(6) The packaging bag according to (5), which is for heat sterilization treatment.
(7) The packaging bag according to (6), for filling a content containing a volatile acidic substance.

According to the present invention, it is excellent in productivity and economy, has an excellent gas barrier property even under high humidity, and is used as a package filled with a content containing a volatile acidic substance. It is possible to provide a gas barrier laminate in which occurrence of poor appearance is suppressed.
That is, the plastic base material in the present invention can be produced simply by adding a calcium compound to the raw material of the plastic base material, and the conventional step of laminating a layer containing a metal compound on the base material is omitted. be able to. Therefore, a gas barrier laminate can be obtained with a smaller number of processes than before, and therefore, industrial merit is extremely large from the viewpoint of productivity and cost. Further, the obtained gas barrier laminate has an excellent gas barrier property even under high humidity, and when used as a package filled with contents containing a volatile acidic substance, it has a poor appearance at the time of heat sterilization treatment. Occurrence is suppressed.

Hereinafter, the present invention will be described in detail.
The gas barrier laminate of the present invention contains 0.3 to 20% by mass of a calcium compound in a plastic substrate (I), and a gas barrier layer (II) containing a polycarboxylic acid is laminated on the plastic substrate (I). It is necessary.

The form of the calcium compound contained in the plastic substrate (I) is not particularly limited, and includes simple metals, inorganic salts such as oxides, hydroxides, halides, carbonates, sulfates, acetates, formic acid. Examples thereof include carboxylates such as salts, stearates, citrates, malates and maleates, and organic acid salts such as sulfonates, and oxides and carbonates are preferred.

The average particle size of the calcium compound used is preferably in the range of 0.001 to 10.0 μm, more preferably in the range of 0.005 to 2.0 μm. Since the haze of the plastic substrate (I) can be reduced, a smaller average particle size is preferable. However, if the average particle size is less than 0.001 μm, the surface area is large, and thus aggregation tends to occur, and coarse aggregates are scattered in the film, which may deteriorate the mechanical properties of the substrate. On the other hand, when the average particle diameter exceeds 10.0 μm, the plastic substrate (I) tends to be less productive because the frequency of the film breaking when the film is formed increases.

  A calcium compound can improve dispersibility, weather resistance, wettability with a thermoplastic resin, heat resistance, transparency, and the like by performing surface treatment such as inorganic treatment or organic treatment. Examples of the inorganic treatment include alumina treatment, silica treatment, titania treatment, zirconia treatment, tin oxide treatment, antimony oxide treatment, and zinc oxide treatment. Examples of the organic treatment include treatment using a fatty acid compound, a polyol compound such as pentaerythritol and trimethylolpropane, an amine compound such as triethanolamine and trimethylolamine, a silicone compound such as a silicone resin and alkylchlorosilane. .

  The content of the calcium compound in the plastic substrate (I) needs to be in the range of 0.3 to 20% by mass, preferably 0.5 to 10% by mass, and more preferably 1 to 5% by mass. When the content is in the range of 1 to 5% by mass, excellent mechanical properties and oxygen permeability can be obtained, and furthermore, a gas barrier laminate having a low haze can be obtained. However, when the content is less than 0.3% by mass, the cross-linked structure formed by reacting with the polycarboxylic acid of the gas barrier layer (II) is reduced, and the gas barrier laminate obtained has a reduced gas barrier property. On the other hand, the plastic base material (I) having a content exceeding 20% by mass has a high frequency of breakage when stretched in addition to a decrease in mechanical properties, and the productivity tends to decrease. Furthermore, when it uses as a package which fills a volatile acidic substance as a content, the external appearance defect at the time of a heat sterilization process will generate | occur | produce easily.

  The method for incorporating the calcium compound into the plastic substrate (I) is not particularly limited, and the plastic compound (I) can be blended at any point in the production process. For example, a method of adding a calcium compound when polymerizing a thermoplastic resin constituting the plastic substrate (I), a method of kneading a thermoplastic resin and a calcium compound with an extruder, a high concentration of the calcium compound Examples include a method (masterbatch method) in which a masterbatch kneaded and blended is manufactured and added to a thermoplastic resin for dilution. In the present invention, the master batch method is preferably employed.

In the present invention, the thermoplastic resin constituting the plastic substrate (I) includes polyolefin resins such as polyethylene, polypropylene and ionomer, polyamide resins such as nylon 6, nylon 66, nylon 46, nylon MXD6 and nylon 9T, and polyethylene terephthalate. Polyester resins such as polyethylene isophthalate, polyethylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, polylactic acid, vinyl chloride, polystyrene resin, polycarbonate resin, polyarylate resin, ethylene -Vinyl acetate copolymers, ethylene-vinyl alcohol copolymers or mixtures thereof. Among these thermoplastic resins, when a packaging bag is configured, polyamide resin is preferable because of excellent puncture strength and impact resistance, and polyester resin is preferable because of excellent heat resistance and economy. preferable.

  The thermoplastic resin, if necessary, within a range that does not adversely affect the performance of the plastic substrate (I), a thermal stabilizer, an antioxidant, a reinforcing material, a pigment, a deterioration inhibitor, a weathering agent, a flame retardant, You may add 1 type, or 2 or more types of various additives, such as a plasticizer, antiseptic | preservative, a ultraviolet absorber, an antistatic agent, and an antiblocking agent. In addition, inorganic particles other than metal compounds and organic lubricants may be added to the thermoplastic resin for the purpose of improving the slip property of the plastic substrate (I), and among them, silica may be added. preferable.

  The thickness of the plastic substrate (I) can be appropriately selected according to the mechanical strength required for the obtained gas barrier laminate. For reasons of mechanical strength and ease of handling, the thickness of the plastic substrate (I) is preferably 5 to 100 μm, and more preferably 10 to 30 μm. When the thickness of the plastic substrate (I) is less than 5 μm, sufficient mechanical strength cannot be obtained, and the piercing strength tends to deteriorate.

The plastic substrate (I) may be a single-layer film or a multi-layer film. When the plastic substrate (I) is a multilayer film, it is necessary that at least one layer thereof contains 0.3 to 20% by mass of a calcium compound.
Hereinafter, a layer containing a metal compound including a calcium compound (a single layer or a single layer film in a multilayer film) is referred to as a “metal-containing layer (M)”, and a “metal-containing layer (M)” in the multilayer film is referred to as a “metal-containing layer (M)”. Other layers may be referred to as “resin layer (R)”.

When the plastic substrate (I) is a multilayer film, the gas barrier laminate is obtained by contacting the gas barrier layer (II) with the metal-containing layer (M) of the plastic substrate (I). , (R) / (M) / (II), (M) / (R) / (M) / (II), (II) / (M) / (R) / (M) / (II) Etc. Since these structures are such that the gas barrier layer (II) and the metal-containing layer (M) are in contact with each other, the polycarboxylic acid in the gas barrier layer (II) and the calcium compound in the metal-containing layer (M) are likely to react. Gas barrier properties can be obtained efficiently. Among these, the structure of (R) / (M) / (II) is preferable in consideration of equipment for manufacturing and operability.
Further, the gas barrier layer (II) and the resin layer (R) of the plastic substrate (I) are in contact with each other, (M) / (R) / (II) and (R) / (M) / (R) / (II) and (II) / (R) / (M) / (R) / (II). Among these, considering the equipment for manufacturing and operability, the configuration of (M) / (R) / (II) is preferable.

  The thickness constitution ratio of the metal-containing layer (M) and the resin layer (R) constituting the multilayer film is not particularly limited, and the total thickness (Mt) of the metal-containing layer (M) and the total of the resin layer (R). The ratio of thickness (Rt) ((Rt) / (Mt)) is preferably 1/1000 to 1000/1, and the thickness control of each layer is easy, so 1/100 to 100/1. More preferably, it is more preferably 1/10 to 10/1.

  The above-mentioned additives may be added to the thermoplastic resin constituting the resin layer (R), and the resin layer (R) which is the outermost layer of the gas barrier laminate is made of silica for the purpose of improving the slip property. Etc. are preferably added.

  The gas barrier layer (II) constituting the gas barrier laminate of the present invention needs to contain a polycarboxylic acid. The polycarboxylic acid in the gas barrier layer (II) can exhibit gas barrier properties by reacting with the metal compound in the plastic substrate (I).

The polycarboxylic acid in the present invention is a compound or polymer having two or more carboxyl groups in the molecule, and these carboxyl groups may form an anhydride structure.
Specific examples of the polycarboxylic acid include 1,2,3,4-butanetetracarboxylic acid, polyacrylic acid, polymethacrylic acid, acrylic acid-methacrylic acid copolymer, acrylic acid-maleic acid copolymer, polymaleic acid Examples thereof include olefin-maleic acid copolymers such as ethylene-maleic acid copolymers, polysaccharides having a carboxyl group in the side chain such as alginic acid, polyamides containing carboxyl groups, and polyesters. The above polycarboxylic acids can be used alone or in combination of two or more.

  When the polycarboxylic acid is a polymer, the weight average molecular weight is preferably 1,000 to 1,000,000, more preferably 10,000 to 150,000, and more preferably 15,000 to 1,000,000. More preferably, it is 110,000. If the weight average molecular weight of the polycarboxylic acid is too low, the resulting gas barrier layer (II) becomes fragile. On the other hand, if the molecular weight is too high, the handling property is impaired, and in some cases, the gas barrier layer (II) described later may be used. The gas barrier layer (II) obtained by agglomeration in the coating liquid for forming may have a gas barrier property impaired.

In the present invention, among the above polycarboxylic acids, polyacrylic acid and olefin-maleic acid copolymer, particularly ethylene-maleic acid copolymer (hereinafter, sometimes abbreviated as EMA) are from the point of gas barrier property. Preferably used. EMA is obtained by polymerizing maleic anhydride and ethylene by a known method such as solution radical polymerization.
The maleic acid unit in the olefin-maleic acid copolymer tends to have a maleic anhydride structure in which the adjacent carboxyl group is dehydration-cyclized in a dry state, and opens to form a maleic acid structure when wet or in an aqueous solution. Therefore, in the present invention, unless otherwise specified, maleic acid units and maleic anhydride units are collectively referred to as maleic acid units.
The maleic acid unit in EMA is preferably 5 mol% or more, more preferably 20 mol% or more, further preferably 30 mol% or more, and most preferably 35 mol% or more. .
Further, the weight average molecular weight of EMA is preferably 1,000 to 1,000,000, more preferably 3,000 to 500,000, and further preferably 7,000 to 300,000. It is preferably 10,000 to 200,000.

In the present invention, the gas barrier layer (II) preferably contains a polyalcohol. By containing a polyalcohol, the polycarboxylic acid in the gas barrier layer (II) reacts with the polyalcohol in addition to reacting with the metal compound in the plastic substrate (I), thereby improving the gas barrier property. be able to.
Polyalcohol is a compound having two or more hydroxyl groups in the molecule, and low molecular weight compounds include sugar alcohols such as glycerin and pentaerythritol, monosaccharides such as glucose, disaccharides such as maltose, and oligosaccharides such as galactooligosaccharides. Examples of the polymer compound include polysaccharides such as polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and starch. The above polyalcohols can be used alone or in combination of two or more.
The saponification degree of polyvinyl alcohol or ethylene-vinyl alcohol copolymer is preferably 95 mol% or more, and more preferably 98 mol% or more. The average degree of polymerization is preferably 50 to 2,000, and more preferably 200 to 1,000.

  The polycarboxylic acid and the polyalcohol in the gas barrier layer (II) are preferably contained so that the molar ratio of OH group to COOH group (OH group / COOH group) is 0.01 to 20. It is more preferable to contain so that it may become 01-10, It is more preferable to contain so that it may become 0.02-5, It is most preferable to contain so that it may become 0.04-2.

  In the present invention, the gas barrier layer (II) preferably contains polyacrylamide, polymethacrylamide or polyamine. By containing these compounds, the polycarboxylic acid in the gas barrier layer (II) reacts with these compounds in addition to reacting with the calcium compound in the plastic substrate (I), so that the gas barrier property is improved. Can be improved.

The polyamine has two or more amino groups selected from primary and secondary as amino groups in the molecule. Specific examples thereof include polyallylamine, polyvinylamine, branched polyethyleneimine. And polysaccharides having an amino group in the side chain such as linear polyethyleneimine, polylysine and chitosan, and polyamides having an amino group in the side chain such as polyarginine.
The weight average molecular weight of the polyamine is preferably 5,000 to 150,000. If the weight average molecular weight of the polyamine is too low, the resulting gas barrier layer (II) becomes fragile. On the other hand, if the molecular weight is too high, handling properties are impaired, and in some cases, a gas barrier layer (II) described later is formed. Therefore, the gas barrier layer (II) obtained by agglomeration in the coating solution may have a gas barrier property impaired.

  In the gas barrier layer (II), the mass ratio of polyamine to polycarboxylic acid (polyamine / polycarboxylic acid) is preferably 12.5 / 87.5 to 27.5 / 72.5. If the mass ratio of the polyamine is lower than this, the crosslinking of the carboxyl group of the polycarboxylic acid becomes insufficient. Conversely, if the mass ratio of the polyamine is higher than this, the crosslinking of the amino group of the polyamine becomes insufficient. However, the gas barrier laminate obtained may be inferior in gas barrier properties.

The gas barrier layer (II) in the present invention may contain a crosslinking agent. By containing a cross-linking agent, gas barrier properties can be enhanced.
The content of the crosslinking agent in the gas barrier layer (II) is preferably 0.1 to 30 parts by mass and more preferably 1 to 20 parts by mass with respect to 100 parts by mass of the polycarboxylic acid.
Examples of the crosslinking agent include a compound having a self-crosslinking property and a compound having a plurality of functional groups that react with a carboxyl group in the molecule. When the gas barrier layer (II) contains a polyalcohol, it reacts with a hydroxyl group. A compound having a plurality of functional groups in the molecule may also be used. Preferable examples of the crosslinking agent include isocyanate compounds, melamine compounds, urea compounds, epoxy compounds, carbodiimide compounds, zirconium salt compounds such as zirconium ammonium carbonate, metal alkoxides, and the like. These crosslinking agents may be used in combination.

  A metal alkoxide is a compound containing a metal to which an alkoxy group is bonded, and an alkyl group substituted with a functional group having reactivity with a halogen or a carboxyl group may be bonded instead of a part of the alkoxy group. . Here, the metal includes atoms such as Si, Al, Ti and Zr, the halogen includes chlorine, iodine, bromine and the like, and the functional group having reactivity with a carboxyl group is an epoxy group. , Amino groups, isocyanate groups, ureido groups and the like, and alkyl groups include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group and the like. Examples of such compounds include tetramethoxysilane, tetraethoxysilane, chlorotriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-aminopropyltrimethoxysilane, Alkoxysilane compounds such as 3-aminopropyltriethoxysilane, 3-ureidopropyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, alkoxytitanium compounds such as tetraisopropoxytitanium and tetraethoxytitanium, alkoxy such as triisopropoxyaluminum Examples thereof include aluminum compounds and alkoxyzirconium compounds such as tetraisopropoxyzirconium.

  These metal alkoxides must be partially or wholly hydrolyzed, partially hydrolyzed or condensed, fully hydrolyzed and partially condensed, or a combination of these. You can also.

  When the above metal alkoxide and polycarboxylic acid are mixed, it may be difficult for both to react and to be applied. Therefore, it is preferable to form a hydrolysis condensate in advance before mixing. As a method for forming the hydrolysis-condensation product, a method used in a known sol-gel method can be applied.

In the gas barrier layer (II) in the present invention, a heat stabilizer, an antioxidant, a reinforcing material, a pigment, a deterioration preventing agent, a weather resistance, as long as the gas barrier property and the adhesion to the plastic substrate (I) are not significantly impaired. An agent, a flame retardant, a plasticizer, a release agent, a lubricant, an antiseptic, an antifoaming agent, a wetting agent, a viscosity modifier, and the like may be added.
Examples of heat stabilizers, antioxidants, and deterioration inhibitors include hindered phenols, phosphorus compounds, hindered amines, sulfur compounds, copper compounds, alkali metal halides, and the like. May be.
Examples of the reinforcing material include clay, talc, wollastonite, silica, alumina, calcium silicate, sodium aluminate, sodium aluminosilicate, magnesium silicate, glass balloon, carbon black, zeolite, montmorillonite, hydrotalcite, fluorine mica, Examples thereof include metal fibers, metal whiskers, ceramic whiskers, potassium titanate whiskers, boron nitride, graphite, glass fibers, carbon fibers, fullerenes (C60, C70, etc.), carbon nanotubes, and the like.

  In the present invention, the thickness of the gas barrier layer (II) laminated on the plastic substrate (I) is preferably thicker than 0.05 μm in order to sufficiently enhance the gas barrier property of the gas barrier laminate, which is economical. Therefore, it is preferable that the thickness is less than 5.0 μm.

The gas barrier layer (II) in the present invention can be formed by applying and drying a gas barrier layer (II) forming coating solution on the plastic substrate (I).
Since the coating liquid is preferably aqueous from the viewpoint of workability, the polycarboxylic acid, polyalcohol and polyamine constituting the coating liquid are preferably water-soluble or water-dispersible, and water-soluble. It is more preferable that

  In the present invention, when an aqueous coating solution is prepared by mixing a polycarboxylic acid and a polyalcohol, it is preferable to add 0.1 to 20 equivalent% of an alkali compound with respect to the carboxyl group of the polycarboxylic acid. . Since polycarboxylic acid has high hydrophilicity when the content of carboxyl group is large, it can be made into an aqueous solution without adding an alkali compound. However, the gas barrier property of the obtained gas barrier laminate can be remarkably improved by adding an appropriate amount of an alkali compound. The alkali compound only needs to be capable of neutralizing the carboxyl group of the polycarboxylic acid, and the addition amount thereof is preferably 0.1 to 20 mol% with respect to the carboxyl group of the polycarboxylic acid.

  The coating liquid can be prepared by a known method using a melting pot equipped with a stirrer. For example, a polycarboxylic acid and a polyalcohol are separately made into aqueous solutions and mixed before coating. The method is preferred. At this time, if the alkali compound is added to the aqueous solution of the polycarboxylic acid, the stability of the aqueous solution can be improved.

  Moreover, in this invention, when mixing polycarboxylic acid and polyamine and preparing an aqueous coating liquid, in order to suppress gelatinization, it is preferable to add a base to polycarboxylic acid. The base may be any as long as it does not inhibit the gas barrier properties of the resulting gas barrier laminate, and examples include inorganic substances such as sodium hydroxide and calcium hydroxide, and organic substances such as ammonia, methylamine, and diethanolamine, Ammonia is preferable because it is easily volatilized by heat treatment. The addition amount of the base is preferably 0.6 equivalents or more, more preferably 0.7 equivalents or more, and more preferably 0.8 equivalents or more based on the carboxyl group of the polycarboxylic acid. preferable. If the amount of the base added is small, the coating solution may gel during coating, and it may be difficult to form the gas barrier layer (II) on the plastic substrate (I).

  The method for applying the coating liquid for forming the gas barrier layer (II) to the plastic substrate (I) is not particularly limited, and is an air knife coater, kiss roll coater, metering bar coater, gravure roll coater, reverse roll coater, dip coater. , Die coater, etc., or a combination of these can be used.

After applying the coating liquid for forming the gas barrier layer (II) to the plastic substrate (I), heat treatment may be performed immediately to form a dry film and heat treatment at the same time. Heat treatment may be performed after moisture or the like is evaporated by spraying or infrared irradiation to form a dry film. It is preferable to perform the heat treatment immediately after coating unless there is a particular problem with the physical properties such as the gas barrier layer (II) and gas barrier properties.
It does not specifically limit as a heat processing method, The method of heat-processing in dry atmosphere, such as oven, is mentioned. Considering shortening of the process, it is preferable to stretch the plastic substrate (I) after applying the gas barrier layer (II) forming coating solution.
In any of the above cases, the plastic substrate (I) on which the gas barrier layer (II) is formed is preferably subjected to a heat treatment for 5 minutes or less in a heated atmosphere of 100 ° C. or higher.

When the gas barrier layer (II) contains a polycarboxylic acid and a polyalcohol, it can be affected by the ratio, presence / absence of an additive component, the content thereof, and the like. The heat treatment temperature cannot be generally specified, but is preferably 100 to 300 ° C, more preferably 120 to 250 ° C, further preferably 140 to 240 ° C, and 160 to 220 ° C. It is particularly preferred. If the heat treatment temperature is too low, the cross-linking reaction between the polycarboxylic acid and the polyalcohol cannot sufficiently proceed, and it may be difficult to obtain a laminate having sufficient gas barrier properties, while it is too high. In addition, the gas barrier layer (II) and the like may become brittle.
The heat treatment time is preferably 5 minutes or less, more preferably from 1 second to 5 minutes, further preferably from 3 seconds to 2 minutes, and particularly preferably from 5 seconds to 1 minute. . If the heat treatment time is too short, the crosslinking reaction cannot proceed sufficiently, and it becomes difficult to obtain a laminate having gas barrier properties. On the other hand, if it is too long, productivity decreases.

  The coating liquid for forming the gas barrier layer (II) applied to the plastic substrate (I) is irradiated with high energy rays such as ultraviolet rays, X-rays, and electron beams as necessary before and after the drying. May be. In such a case, a component that is crosslinked or polymerized by irradiation with high energy rays may be blended.

Since the gas barrier laminate of the present invention has the above-described configuration, it has excellent gas barrier properties. A gas barrier laminate subjected to hydrothermal treatment at 120 ° C. for 30 minutes is 20 ° C. in an atmosphere with a relative humidity of 65%. in the measured oxygen ^{permeability, 200ml / (m 2 · day} · MPa) can be less, is preferably ^{0.01~200ml / (m 2 · day ·} MPa), 0.01~100ml / (M ² · day · MPa) is more preferable.

The gas barrier laminate of the present invention preferably has a tensile strength of 150 MPa or more, and more preferably 180 MPa or more. If the tensile strength is less than 150 MPa, the mechanical strength is not sufficient, and the piercing strength tends to decrease. In addition, the tensile elongation is preferably 60% or more, and more preferably 80% or more, from the same viewpoint as the tensile strength.

The pinhole resistance of the gas barrier laminate of the present invention is preferably 100 or less, more preferably 20 or less, in the 500 times repeated bending fatigue test at 5 ° C. preferable.
Specifically, the pinhole resistance is Fed. Shown in MIL-B-131F. Test Method Std. In accordance with Method 2017 of 101C, a sample of 12 inches × 8 inches is gripped in a cylindrical shape with a diameter of 3.5 inches, with an initial gripping distance of 7 inches and a gripping distance of 1 inch at maximum bending, a so-called gel bot tester (manufactured by Rigaku Corporation) The number of pinholes generated after being bent 500 times at 5 ° C. was measured and evaluated.

The gas barrier laminate of the present invention can be produced by the following method.
Plastic base material (I) consisting of a single layer film, for example, a thermoplastic resin mixed with a calcium compound is heated and melted with an extruder and extruded into a film from a T-die, air knife casting method, electrostatic application It cools and solidifies on the cooling drum rotated by well-known casting methods, such as a casting method, and the film of the unstretched plastic base material (I) is obtained.
In addition, the plastic substrate (I) composed of a multilayer film, for example, heat-melts a thermoplastic resin mixed with a calcium compound in the extruder A, and heat-melts the thermoplastic resin in the extruder B, respectively. By superposing two types of melted resins in a die, for example, extruding a film having a two-layer structure of metal-containing layer (M) / resin layer (R) from a T-die, and cooling and solidifying in the same manner as above, It can be obtained in a stretched state.
By including a calcium compound in the plastic substrate (I) by such a method, the step of laminating a layer containing a metal compound, which has been conventionally performed, on the substrate can be omitted.
The gas barrier layer (II) forming coating solution is applied to the obtained single-layer or multi-layer unstretched film by the method described above to form the gas barrier layer (II). By performing simultaneous biaxial stretching in the machine direction (MD) and the transverse direction (TD), a gas barrier laminate that has been biaxially stretched can be obtained.
Further, after stretching the obtained unstretched film in the machine direction (MD), the gas barrier layer (II) forming coating liquid is applied by the above-described method to form the gas barrier layer (II), and then the transverse direction (TD) ) To obtain a gas barrier laminate that is successively biaxially stretched.
If the unstretched film is oriented, the stretchability may be lowered in a later step. Therefore, it is preferable that the unstretched film is substantially amorphous and non-oriented.

When using a polyamide resin as the thermoplastic resin, transfer the unstretched film to a water tank whose temperature is adjusted so as not to exceed 80 ° C., and subject it to a water immersion treatment within 5 minutes and a moisture absorption treatment of 0.5 to 15%. Is preferred.
In addition, the stretching ratio of the film is preferably 1.5 times or more in the case of uniaxial stretching, and also in the case of longitudinal and lateral biaxial stretching, it is preferably 1.5 times or more in the vertical and horizontal directions. Usually, it is preferably 3 times or more, more preferably 6 to 20 times, and even more preferably 6.5 to 13 times. When the draw ratio is in this range, a gas barrier laminate having excellent mechanical properties can be obtained.
The film that has undergone the stretching process is heat-set at a temperature of 150 to 300 ° C. in the tenter where the stretching process has been performed, and in the range of 0 to 10%, preferably 2 to 6% as necessary, in the machine direction and A lateral relaxation treatment is performed. In order to reduce the heat shrinkage rate, it is desirable not only to optimize the temperature and time of the heat setting time, but also to perform the heat relaxation process at a temperature lower than the maximum temperature of the heat setting process.

  The stretching method is not particularly limited, but it is preferable to use a simultaneous biaxial stretching method. The simultaneous biaxial stretching method can generally have practical characteristics such as mechanical characteristics, optical characteristics, thermal dimensional stability, and pinhole resistance. In addition, in the sequential biaxial stretching method in which the transverse stretching is performed after the longitudinal stretching, the orientation crystallization of the film proceeds during the longitudinal stretching, and the stretchability of the thermoplastic resin during the transverse stretching is reduced, whereby the compounding of the calcium compound is performed. When the amount is large, the breaking frequency of the film tends to increase. For this reason, in this invention, it is preferable to perform a water absorption process and to take the simultaneous biaxial stretching method.

  The gas barrier laminate of the present invention can be treated in a humidified atmosphere after producing the laminate for the purpose of enhancing gas barrier properties. By the humidification treatment, the action of the calcium compound of the plastic substrate (I) and the polycarboxylic acid of the gas barrier layer (II) can be further promoted. In such humidification treatment, the laminate may be left in an atmosphere of high temperature and high humidity, or the laminate may be directly contacted with high temperature water. Humidification conditions vary depending on various purposes, but when left in an atmosphere of high temperature and high humidity, a temperature of 30 to 130 ° C. and a relative humidity of 50 to 100% are preferable. Also when making it contact with high temperature water, the temperature of about 30-130 degreeC (100 degreeC or more is under pressure) is preferable. The humidifying treatment time varies depending on the treatment conditions, but generally a range of several seconds to several hundred hours is selected.

  The gas barrier laminate of the present invention may be subjected to surface treatment such as corona discharge treatment, if necessary.

The gas barrier laminate of the present invention can be made into various laminated films by laminating resin layers such as a printing ink layer, an adhesive layer, and a sealant.
The resin used as the sealant is low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, polypropylene, polyethylene / polypropylene copolymer, ethylene-vinyl acetate copolymer, ionomer resin, ethylene-acrylic acid. / Methacrylic acid copolymer, ethylene-acrylic acid / methacrylic acid ester copolymer, polyvinyl acetate resin, etc., polyethylene, polypropylene, polyethylene / polypropylene copolymer, etc. with high heat seal strength and material strength The polyolefin resin is preferred. These resins may be used alone, or may be copolymerized or melt-mixed with other resins, or may be further acid-modified.
Methods for forming the sealant layer on the gas barrier laminate include a method of laminating a film or sheet made of a sealant resin to the gas barrier laminate via an adhesive, a method of extrusion laminating the sealant resin to the gas barrier laminate, etc. Is mentioned. In the former method, the film or sheet made of the sealant resin may be in an unstretched state or in a stretched state at a low magnification, but practically preferably in an unstretched state.
Although the thickness of a sealant layer is not specifically limited, It is preferable that it is 20-100 micrometers, and it is more preferable that it is 40-70 micrometers.
As a material used for forming the laminating adhesive, known materials are used. Examples include isocyanate, polyurethane, polyester, polyethyleneimine, polybutadiene, polyolefin, and alkyl titanate. Among these, in view of effects such as adhesion, heat resistance, and water resistance, isocyanate, polyurethane, and polyester are preferable. Furthermore, it may be a mixture and reaction product of one or more of isocyanate compounds, polyurethanes and urethane prepolymers; and a mixture and reaction product of one or more of polyester, polyol and polyether with isocyanate. preferable.
The thickness of the laminating adhesive is preferably thicker than 0.1 μm, and preferably about 10 μm or less from the viewpoint of productivity.
A printing ink layer is a character, a pattern, etc. formed with ink. As inks, various pigments, extenders, and additives such as plasticizers, desiccants, stabilizers, etc. are added to urethane, acrylic, nitrocellulose, rubber and vinyl chloride ink binder resins. Any ink can be used.
As a method for forming the printing ink layer, for example, a known printing method such as an offset printing method, a gravure printing method, or a screen printing method can be used.

  A packaging bag can be produced using the gas barrier laminate of the present invention. Examples of the packaging bag include foods and drinks, fruits, juices, drinking water, liquor, cooked foods, fish paste products, frozen foods, Various foods and beverages such as meat products, boiled foods, rice cakes, liquid soups, seasonings, etc., liquid detergents, cosmetics, and chemicals can be filled and packaged.

The gas barrier laminate of the present invention is most effective as a packaging bag for performing a heat sterilization treatment after filling a content containing a volatile acidic substance.
Examples of the volatile acidic substance include acids such as acetic acid, propionic acid, butyric acid, and isovaleric acid.

  EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.

1. Measuring method

(1) Thickness of each layer The obtained gas barrier laminate was allowed to stand for 2 hours or more in an environment of 23 ° C. and 50% RH, and then the film cross-section was observed with a scanning electron microscope (SEM) to measure the thickness of each layer. .

(2) Oxygen permeability After the obtained gas barrier laminate was hydrothermally treated at 120 ° C. for 30 minutes, it was left in an environment of 20 ° C. and 65% RH for 2 hours or more, and then an oxygen barrier manufactured by Mocon Co., Ltd. Using a measuring instrument (OX-TRAN 2/20), the oxygen permeability was measured in an atmosphere at a temperature of 20 ° C. and a relative humidity of 65%. The unit is ml / (m ² · day · MPa).

(3) Appearance evaluation of packaging body In a three-sided bag (outside dimension: length direction 200 mm × width direction 150 mm, seal width: 10 mm) produced by laminating a sealant film using an adhesive to the obtained gas barrier laminate, After filling and sealing 150 g of the contents having the following configuration, a retort treatment (hot water shower type, 120 ° C., 30 minutes, 1.8 kg / cm ² ) was performed, and the appearance of the package after the treatment was evaluated. Appearance was judged visually, and a case where there was no appearance defect was marked with ◯, and a case where a whitening or water bubble-like projection was generated and there was an appearance defect was marked as x.
As the contents to be filled, an acetic acid aqueous solution having an acetic acid concentration of 0.5% by mass, 1.0% by mass, 1.5% by mass, 2.0% by mass, 2.5% by mass and 3.0% by mass, respectively. Was used.

2. Raw materials The raw materials used in the following examples and comparative examples are as follows.
(1) Thermoplastic resin for construction of plastic substrate (I) PA6: Nylon 6 resin (A1030BRF manufactured by Unitika Ltd., relative viscosity 3.0)
PET: Polyethylene terephthalate resin (UT-CBR intrinsic viscosity 0.62 manufactured by Unitika)

(2) Plastic base material (I) Metallic compound / calcium carbonate for construction (Brilliant-1500, average particle size 0.4 μm, manufactured by Shiroishi Kogyo Co., Ltd.)
Magnesium oxide (Puremag FNM-G average particle size 0.4 μm, manufactured by Tateho Chemical Co., Ltd.)
・ Lithium carbonate (Shiraishi Kogyo Co., Ltd. Industrial average particle size 2.9μm)

(3) Plastic compound (I) Metal compound master chip / master chip 1 for construction
A master chip was prepared by kneading 85 parts by mass of PA6 and 15 parts by mass of calcium carbonate, and used to prepare a metal-containing layer (M) having a metal compound content of less than 15% by mass.
・ Master chip 2
A master chip was prepared by kneading 55 parts by mass of PA6 and 45 parts by mass of calcium carbonate, and used to prepare a metal-containing layer (M) having a metal compound content of 15 to 30% by mass. .
・ Master chip 3
It was prepared by kneading 85 parts by mass of PET and 15 parts by mass of calcium carbonate.
・ Master chip 4
It was prepared by kneading 85 masses of PA6 and 15 mass parts of magnesium oxide.
・ Master chip 5
It was prepared by kneading 85 masses of PA6 and 15 mass parts of lithium carbonate.

4). The aqueous solutions used in the following examples and comparative examples are as follows.
(1) PVA (manufactured by Kuraray Co., Ltd., Poval 105 (degree of saponification 98-99%, average degree of polymerization: about 500)) is dissolved in hot water and then cooled to room temperature, whereby a PVA aqueous solution having a solid content of 15% by mass is obtained. Obtained.
(2) EVOH (ethylene-vinyl alcohol copolymer (Kuraray Co., Ltd., Exval AQ-4105)) was dissolved to obtain an EVOH aqueous solution having a solid content of 10% by mass.
(3) Using EMA (weight average molecular weight 60000) and sodium hydroxide, dissolved in hot water and then cooled to room temperature to neutralize 10 mol% of the carboxyl group with sodium hydroxide, solid content 15 mass% EMA aqueous solution was prepared.
(4) A solid obtained by neutralizing 10 mol% of a carboxyl group with sodium hydroxide using PAA (polyacrylic acid (number average molecular weight 200000, 25 wt% aqueous solution, manufactured by Toagosei Co., Ltd., A10H)) and sodium hydroxide. A 15% by weight aqueous PAA solution was obtained.
(5) PAM (polyacrylamide (manufactured by Kishida Chemical Co., Ltd., reagent, weight average molecular weight 9 million to 10 million, degree of polymerization 12.7 to 141,000)).

・ Sealant film:
CPP: Mitsui Chemicals Tosero RXC-22, 50 μm thick polypropylene film

·adhesive:
Polyurethane adhesive: Dick Dry LX-500 / KR-90S manufactured by DIC Graphics.

Example 1
Nylon 6 resin and master chip were mixed so that the content of calcium carbonate was 0.3% by mass. This mixture was charged into an extruder and melted in a 270 ° C. cylinder. The melt was extruded into a sheet form from a T-die orifice, brought into close contact with a rotating drum cooled to 10 ° C., and rapidly cooled to obtain an unstretched plastic substrate (I) film having a thickness of 150 μm. The obtained unstretched film was sent to a 50 ° C. hot water tank and subjected to a water immersion treatment for 2 minutes.
Next, an EMA aqueous solution and a PVA aqueous solution are mixed so that the mass ratio (solid content) of PVA and EMA is 30/70, and a coating solution for forming a gas barrier layer (II) having a solid content of 10% by mass. Got. This coating solution was applied to one side of an unstretched film that had been subjected to water immersion treatment, and then dried.
The end of the film was held by a clip of a tenter simultaneous biaxial stretching machine, and stretched at 180 ° C. to MD and TD by 3.3 times. Thereafter, a relaxation rate of TD was set to 5%, heat treatment was performed at 210 ° C. for 4 seconds, and the mixture was gradually cooled to room temperature. A plastic substrate (I) having a thickness of 15 μm was formed on a gas barrier layer (II ) Was obtained.

Examples 2 to 7, 9 and Comparative Examples 1 to 6
Example 1 except that the nylon 6 resin and the master chip were mixed so that the metal compound content shown in Table 1 was obtained, and the thickness after stretching was adjusted to the thickness shown in Table 1. Similarly, an unstretched plastic substrate (I) film was obtained and subjected to a water immersion treatment.
Next, for other resins such as PVA and polycarboxylic acids, the gas barrier layer (II) was the same as in Example 1 except that the types and mass ratios (solid content) were as shown in Table 1. ) A forming coating solution was prepared.
Using the obtained coating solution, it was applied to an unstretched film, dried and then simultaneously biaxially stretched in the same manner as in Example 1, except that the thickness after stretching was as shown in Table 1. Thus, a gas barrier laminate was obtained.
In Example 9, a polyethylene terephthalate resin (PET) was used as the thermoplastic resin, and the conditions were further changed as follows. That is, an unstretched film was produced at a cylinder temperature of 280 ° C., and the obtained unstretched film was not subjected to water immersion treatment. Moreover, the temperature in simultaneous biaxial stretching was 90 degreeC, and the temperature of heat processing was 230 degreeC.

Example 8
A coating solution for forming the gas barrier layer (II) was prepared as follows.
That is, polyacrylic acid (PAA) having a number average molecular weight of 200,000 was dissolved in distilled water to obtain a PAA aqueous solution having a solid content concentration of 13% by mass in the aqueous solution. Subsequently, a 13% by mass aqueous ammonia solution was added to the aqueous PAA solution to neutralize 1 mol% of the carboxyl groups of the PAA, thereby obtaining a partially neutralized aqueous solution of PAA.
Further, 100 parts by mass of polyacrylic acid (PAA) having a number average molecular weight of 40,000 was dissolved in 1064 parts by mass of methanol, and then 166 parts by mass of γ-aminopropyltrimethoxysilane (APTMOS) was added with stirring. In this way, an APTMOS methanol solution (8-1) was obtained. In the APTMOS methanol solution (8-1), at least a part of the amino group of APTMOS is neutralized by the carboxyl group of PAA.
Next, a TMOS methanol solution was prepared by dissolving 34.5 parts by mass of tetramethoxysilane (TMOS) in 34.5 parts by mass of methanol. While maintaining the temperature of this TMOS methanol solution at 10 ° C. or lower, 2.3 parts by weight of distilled water and 5.7 parts by weight of 0.1M hydrochloric acid were added, and hydrolysis and condensation were carried out at 10 ° C. for 60 minutes with stirring. By performing the reaction, a solution (8-2) was obtained.
Subsequently, after the solution (8-2) was diluted with 214.7 parts by mass of methanol and 436.1 parts by mass of distilled water, 235.9 parts by mass of the partially neutralized aqueous solution of PAA was added with stirring. A solution (8-3) was obtained.
Subsequently, 36.2 parts by mass of APTMOS methanol solution (8-1) was added while stirring the solution (8-3), and the mixture was further stirred for 30 minutes to obtain a solution (8-4).
A gas barrier laminate was obtained in the same manner as in Example 1 except that the solution (8-4) prepared by the above method was used as the gas barrier layer (II) forming coating solution.

Example 10 and Comparative Example 7
The nylon 6 resin and the master chip were mixed so that the content of calcium carbonate was 2% by mass (Example 10) and the content of magnesium oxide was 0.5% by mass (Comparative Example 7). This mixture was put into an extruder A and melt-extruded at 260 ° C. On the other hand, nylon 6 resin was charged into Extruder B and melt extruded at 260 ° C.
Two types of resins melted in the extruder A and the extruder B are overlapped in a die, and a sheet having a two-layer structure of a metal-containing layer (M) / resin layer (R) is extruded from a T die, and a surface temperature of 20 An unstretched multi-layer film having a thickness of 150 μm, which is (M) / (R) = 20/130 μm, was obtained by closely adhering to a cooling roll at 0 ° C. The obtained unstretched multilayer film was sent to a 50 ° C. hot water tank and subjected to water immersion treatment for 2 minutes.
Next, the coating liquid prepared in the same manner as in Example 1 was applied to the metal-containing layer (M) surface of the unstretched multilayer film and then dried.
In the same manner as in Example 1, a plastic substrate having a thickness of 15 μm comprising a metal-containing layer (M) having a thickness of 2 μm and a resin layer (R) having a thickness of 13 μm by simultaneous biaxial stretching and heat treatment ( A gas barrier laminate in which a gas barrier layer (II) having a thickness of 0.3 μm was laminated on the metal-containing layer (M) of I) was obtained.

An adhesive (LX-500 / KR-90S: mass ratio 13/1) manufactured by DIC Graphics was applied to the gas barrier layers of the obtained gas barrier laminates of Examples 1 to 10 and Comparative Examples 1 to 7 using a dry laminator. This was applied to form an adhesive layer having a thickness of 2.5 μm.
After affixed with a polypropylene film (CPP, RXC-22, thickness 50 μm) made by Mitsui Chemicals, Inc. as a heat seal layer on the adhesive layer, it was left at 40 ° C. for 2 days to cure the adhesive layer, A packaging bag was obtained.

  Table 1 shows the results of evaluating the configuration of the gas barrier laminates obtained in Examples and Comparative Examples, the oxygen permeability, and the appearance of the package after retorting.

In each of Examples 1 to 10, gas barrier laminates excellent in content suitability for gas barrier properties and volatile acidic substances were obtained.
On the other hand, in Comparative Example 1, since the calcium compound contained in the plastic substrate (I) was less than 0.3% by mass, a gas barrier laminate having sufficient gas barrier properties could not be obtained.
In Comparative Example 2, since the calcium compound contained in the plastic substrate (I) was contained in an amount of more than 20% by mass, poor appearance occurred after the retort treatment in which the acetic acid aqueous solution was filled as the contents.
In Comparative Examples 3 and 6, since the gas barrier layer (II) did not contain polycarboxylic acid, a gas barrier laminate having sufficient gas barrier properties could not be obtained.
In Comparative Examples 4, 5, and 7, since a metal compound other than the calcium compound was used, poor appearance occurred after retorting with an acetic acid aqueous solution as a content.

Claims (7)

A gas barrier laminate obtained by laminating a gas barrier layer (II) containing a polycarboxylic acid on a plastic substrate (I) containing 0.3 to 20% by mass of a calcium compound, and heat at 120 ° C. for 30 minutes A gas barrier laminate having an oxygen permeability of 200 ml / (m ² · day · MPa) or less in an atmosphere of 20 ° C. and a relative humidity of 65% after water treatment.   The gas barrier laminate according to claim 1, wherein the plastic substrate (I) is a multilayer film, and at least one layer thereof contains 0.3 to 20% by mass of a calcium compound.   The gas barrier laminate according to claim 1 or 2, wherein the thermoplastic resin constituting the plastic substrate (I) is a polyamide resin or a polyester resin.   The gas barrier layered product according to any one of claims 1 to 3, wherein the gas barrier layer (II) contains a polyalcohol.   A packaging bag comprising the gas barrier laminate according to any one of claims 1 to 4.   The packaging bag according to claim 5, which is used for heat sterilization treatment. The packaging bag according to claim 6 for filling a content containing a volatile acidic substance.