Retort packaging bag

Abstract

To provide a retort packaging bag excellent in gas barrier immediately after retort treatment.SOLUTION: This retort packaging bag comprises: a barrier layer (AS) on an outermost layer; and a heat fusion layer (B) on an innermost surface. The barrier layer (AS) is composed of a resin composition (a) containing EVOH (a1) and PA (a2) having ethylene unit contents of 20-50 mol% and saponification degrees of 90 mol% or more, a mass ratio (a1 / a2) of the EVOH (a1) to the PA(a2) being 55 / 45-98 / 2. The heat fusion layer (B) contains a polyolefin resin (b) having a melting point of 130-170°C as a main component. The resin composition (a) does not include a layer containing, as a main component, a resin containing alkali metal ions (k) of 40-2000 ppm and having a melting point of lower than 130°C, a layer containing, as a main component, polyester having a melting point of 200°C or higher, a layer containing, as a main component, polyamide having a melting point of 200°C or higher, and a metal layer having an average thickness of 1 μm or thicker.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a retort packaging bag.

[0002] For packaging materials for long-term preservation of foods, gas barrier properties such as oxygen barrier properties are often required. By using a packaging material with high gas barrier properties, oxidation of foods by oxygen and growth of microorganisms can be suppressed. As foods with an extended edible period, the number of retort foods is increasing, in which after filling the packaging material with the food, heat sterilization treatment under pressure (hereinafter sometimes simply abbreviated as "retort treatment") is performed. For the gas barrier layer for retort packaging materials, a property that the gas barrier property does not decrease after the hot water treatment (hereinafter sometimes simply abbreviated as "retort resistance") is required, and generally used is a gas barrier film in which a transparent vapor deposition layer of silica (silicon oxide) or alumina (aluminum oxide) is laminated on an aluminum foil or a polyester film with high heat resistance. When using an aluminum foil, light-shielding properties can be imparted in addition to the gas barrier property, and when using a gas barrier film in which a vapor deposition layer of silica or alumina is laminated, visibility of the contents can be imparted (Patent Documents 1 and 2).

[0003] Ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as "EVOH"), which is widely used as a gas barrier resin for packaging materials, exhibits gas barrier properties by crystallization and densification due to hydrogen bonding between hydroxyl groups in the molecule, but there are problems such as a decrease in the gas barrier property due to EVOH absorbing water during the retort treatment. As a means for suppressing the decrease in the gas barrier property due to the retort treatment, Patent Document 3 describes a resin composition produced by mixing EVOH and polyamide (hereinafter sometimes abbreviated as PA), and it has been reported that such a resin composition has improved retort resistance compared to EVOH alone and can be preferably used as a retort packaging material. Further, Patent Document 4 reports that a resin composition produced by mixing a specific modified EVOH and polyamide has excellent retort resistance and bending resistance.

Prior Art Documents

Patent Document

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, due to environmental problems and waste problems, the demand for so-called post-consumer recycling (hereinafter sometimes simply abbreviated as recycling), which recovers and re-resources packaging materials consumed in the market, has been increasing globally. In recycling, the general process is to cut the recovered packaging materials, separate and wash them if necessary, and then melt and mix them using an extruder. In this regard, it is required that the packaging materials be composed of a single material as much as possible (monomaterialization), so that high-purity and high-quality recycled raw materials can be obtained. In particular, aluminum foil, polyesters and polyamides with high melting points are inferior in compatibility and dispersibility with polyolefin-based resins widely used as packaging materials, and may inhibit recyclability.

[0006] Therefore, there is a demand for a retort pouch that can suppress a decrease in gas barrier properties immediately after retort treatment, even for a monomaterialization-conscious packaging bag that does not have a layer containing a polyester with a melting point of 200 °C or higher as a main component, a layer containing a polyamide with a melting point of 200 °C or higher as a main component, and a metal layer with an average thickness of 1 μm or more, and has a high thickness ratio (for example, 75% or more) of a layer containing a polyolefin-based resin as a main component.

[0007] However, although the retort packaging bags described in the above-mentioned Documents 3 and 4 tend to have their gas barrier properties recover over time after retort processing, in order to accelerate the recovery rate of the gas barrier properties, it is necessary to use a layer mainly composed of a resin with high moisture permeability such as polyester or polyamide adjacent to the resin composition layer, and it was difficult to have a layer structure that does not include a layer mainly composed of polyester with a melting point of 200 °C or higher and a layer mainly composed of polyamide with a melting point of 200 °C or higher. In addition, since the edible period of retort foods greatly depends on the cumulative amount of oxygen that penetrates through the packaging bag, even when the gas barrier properties recover over time after retort processing, if the gas barrier properties immediately after retort processing are greatly reduced or if it takes a long time for the gas barrier properties to recover, there may be a limitation in extending the edible period of retort foods.

[0008] The present invention has been made to solve the above problems, and even for a packaging bag that does not have a layer containing polyester with a melting point of 200 °C or higher as a main component, a layer containing polyamide with a melting point of 200 °C or higher as a main component, and a metal layer with an average thickness of 1 μm or more, and has a high thickness ratio (for example, 75% or more) of a layer containing a polyolefin-based resin as a main component, it is an object to provide a retort packaging bag that can suppress a decrease in gas barrier properties immediately after retort processing.

Means for Solving the Problems

[0009] The inventors of the present invention have found that a retort packaging bag having a barrier layer made of a resin composition containing specific EVOH and polyamide as the outermost layer has excellent appearance immediately after retort processing and can suppress a decrease in gas barrier properties immediately after retort processing even when it does not have an adjacent layer mainly composed of polyester or polyamide. That is, the above object is achieved by [1] having a barrier layer (AS) as the outermost layer and a heat-sealing layer (B) as the innermost layer respectively, The barrier layer (AS) consists only of a resin composition (a) containing an ethylene-vinyl alcohol copolymer (a1) (hereinafter sometimes abbreviated as "EVOH (a1)") with an ethylene unit content of 20 to 50 mol% and a saponification degree of 90 mol% or more and a polyamide (a2) (hereinafter sometimes abbreviated as "PA (a2)"), and the mass ratio (a1 / a2) of EVOH (a1) to PA (a2) is 55 / 45 to 98 / 2. The heat-sealing layer (B) mainly contains a polyolefin resin (b) with a melting point of 130 to 170°C. The resin composition (a) contains 40 to 2000 ppm of an alkali metal ion (K) and does not have a layer mainly composed of a resin with a melting point of less than 130°C, a layer mainly composed of a polyester with a melting point of 200°C or higher, a layer mainly composed of a polyamide with a melting point of 200°C or higher, and a metal layer with an average thickness of 1 μm or more; a retort pouch for packaging; [2] A retort pouch for packaging according to [1], further having a barrier layer (AM) consisting only of the resin composition (a), and the barrier layer (AM) is located between the barrier layer (AS) and the heat-sealing layer (B); [3] A retort pouch for packaging according to [1] or [2], wherein the polyolefin resin (b) mainly contains polypropylene; [4] A packaging bag according to any one of [1] to [3], further having an adhesive layer (C) mainly containing an adhesive resin (c) with a melting point of 130 to 170°C, and at least one adhesive layer (C) is located adjacent to the barrier layer (AS) or the barrier layer (AM); [5] A retort pouch for packaging according to [4], wherein the adhesive resin (c) mainly contains acid-modified polypropylene; [6] A packaging bag according to any one of [1] to [5], further having a moisture-proof layer (D) mainly containing a polyolefin resin (d) with a melting point of 130 to 170°C, and the moisture-proof layer (D) is located between the barrier layer (AS) and the heat-sealing layer (B); [7] A retort pouch for packaging according to [6], wherein the polyolefin resin (d) mainly contains polypropylene; [8] A retort pouch for packaging according to any one of [1] to [7], wherein the resin composition (a) contains 10 to 500 ppm of at least one polyvalent metal ion (L) selected from the group consisting of magnesium ions, calcium ions, and zinc ions; [9] The retort pouch according to any one of [1] to [8], wherein the heat-sealing layer (B) contains polypropylene as a main component, and the total average thickness ratio of the layers mainly composed of polypropylene-based resin to the average thickness of the retort pouch is 0.75 or more;

[10] After 10 hours of retort treatment at 120 °C for 30 minutes, the oxygen transmission rate (under the conditions of 20 °C and 65 / 100% RH) measured by the method described in JIS K 7126-2:2006 is 20 cc / (m 2 ·day·atm) or less, the retort pouch according to any one of [1] to [9]; It is achieved by providing.

Effect of the Invention

[0010] According to the present invention, a retort pouch can be provided which has excellent gas barrier properties immediately after retort treatment, even if it has a layer containing polyester having a melting point of 200 °C or higher as a main component, a layer containing polyamide having a melting point of 200 °C or higher as a main component, and no metal layer having an average thickness of 1 μm or more, and a high thickness ratio (for example, 75% or more) of the layer containing polyolefin-based resin as a main component.

Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described. In the following description, specific materials (compounds, etc.) may be exemplified as those that exhibit specific functions, but the present invention is not limited to embodiments using such materials. Also, the exemplified materials may be used alone or in combination, unless otherwise specified.

[0012] The retort packaging bag of the present invention is provided with a barrier layer (AS) as the outermost layer and a heat-sealing layer (B) as the innermost layer, respectively. The barrier layer (AS) contains EVOH (a1) and PA (a2) with an ethylene unit content of 20 to 50 mol% and a saponification degree of 90 mol% or more, and consists only of a resin composition (a) in which the mass ratio (a1 / a2) of EVOH (a1) to PA (a2) is 55 / 45 to 98 / 2. The heat-sealing layer (B) contains a polyolefin resin (b) with a melting point of 130 to 170°C as the main component. The resin composition (a) contains 40 to 2000 ppm of alkali metal ions (K) and does not have a layer mainly composed of a resin with a melting point of less than 130°C, a layer mainly composed of a polyester with a melting point of 200°C or more, a layer mainly composed of a polyamide with a melting point of 200°C or more, and a metal layer with an average thickness of 1 μm or more.

[0013] When the resin composition (a) constituting the barrier layer (AS) contains EVOH (a1) and polyamide (a2) in a specific ratio, the retort resistance tends to be good. Further, when the barrier layer (AS) is located on the outermost layer, the decrease in gas barrier properties immediately after retort treatment can be significantly suppressed. Furthermore, since the heat-sealing layer (B) contains a polyolefin resin (b) with a melting point of 130 to 170°C as the main component, the heat-sealing property and retort resistance of the obtained retort packaging bag can be further improved, and the thickness ratio of the layer mainly composed of the polyolefin-based resin in the retort packaging bag can be increased. In addition, the resin composition (a) constituting the barrier layer (AS) and the polyolefin resin (b) constituting the heat-sealing layer (B) are easily compatible and dispersed with each other, and the recyclability can be further enhanced by the resin composition (a) containing 40 to 2000 ppm of alkali metal ions (K). Moreover, the recyclability can be further enhanced by not having a layer mainly composed of a resin with a melting point of less than 130°C, a layer mainly composed of a polyester with a melting point of 200°C or more, a layer mainly composed of a polyamide with a melting point of 200°C or more, and a metal layer with an average thickness of 1 μm or more.

[0014] In the present specification, "main component" means a component contained in an amount exceeding 50% by mass. The "average thickness" refers to the average value of the thickness measured at any five locations. "ppm" means the content based on mass (ppm by mass). "Polypropylene" refers to a homopolymer of propylene and a copolymer having 70 mol% or more of propylene units. "Acid-modified polypropylene" refers to a polymer obtained by modifying polypropylene with an acid. The acid-modified polypropylene may be a polymer in which at least one of an acidic group and an acid anhydride group is introduced into the polypropylene. "Polypropylene-based resin" refers to polypropylene and modified polypropylene (such as acid-modified polypropylene). Modified polypropylene refers to a polymer obtained by modifying polypropylene. "Acid-modified polyolefin" refers to a polyolefin obtained by modifying a polyolefin with an acid. "Polyolefin-based resin" refers to polyolefin and modified polyolefin (such as acid-modified polyolefin). Modified polyolefin refers to a polymer obtained by modifying a polyolefin. In addition, in this specification, "substantially consisting only of" allows the inclusion of optional components within a range that does not affect the effects of the present invention, and "consisting only of" means excluding optional components other than unavoidably contained impurities. In this specification, the numerical range described using "~" means including the numerical values described before and after "~" as the lower limit value and the upper limit value. That is, "α~β" means "α or more and β or less". Also, in this specification, the upper limit value and the lower limit value of the numerical range (content, physical properties, etc.) can be combined as appropriate. The "recyclability" in this specification means that when the recovered product of the retort packaging bag of the present invention is melt-kneaded to produce a recovered composition, the coloring of the resin, the generation of lumps due to gelation, and the viscosity change of the resin are suppressed, and a recovered composition with excellent appearance can be efficiently produced, and it can be evaluated by the recovery test described in the examples. As used herein, "immediately after retort treatment" means about 10 hours later. For example, in the examples, measurement samples are prepared immediately after the retort treatment, and the measurement results "10 hours later" are used as the evaluation results of the barrier properties immediately after the retort treatment.

[0015] <Barrier layer (AS) and resin composition (a)> The retort packaging bag of the present invention has a barrier layer (AS) composed only of a resin composition (a) containing EVOH (a1) having an ethylene unit content of 20 to 50 mol% and a saponification degree of 90 mol% or more and polyamide (a2), and the mass ratio (a1 / a2) of EVOH (a1) to polyamide (a2) is 55 / 45 to 98 / 2 on the outermost layer. The resin composition (a) contains 40 to 2000 ppm of an alkali metal ion (K) as an essential component. Further, the resin composition (a) may contain at least one polyvalent metal ion (L) selected from the group consisting of magnesium ions, calcium ions, and zinc ions, and other components described later as optional components. This will be described in detail below.

[0016] <EVOH (a1)> The resin composition (a) contains a specific amount of EVOH (a1). By containing a specific amount of EVOH (a1) in the resin composition (a), the gas barrier property becomes good. EVOH (a1) is usually obtained by saponifying an ethylene-vinyl ester copolymer obtained by polymerizing ethylene and a vinyl ester. The ethylene unit content of EVOH (a1) is 20 to 50 mol%. When the ethylene unit content is 20 mol% or more, the melt moldability of EVOH (a1) and the pulverized product of the retort packaging bag containing EVOH (a1) is improved. The ethylene unit content is preferably 24 mol% or more, and more preferably 26 mol% or more. On the other hand, when the ethylene unit content is 50 mol% or less, the gas barrier property of the retort packaging bag of the present invention is improved, and the appearance after retort treatment also tends to be good. The ethylene unit content is preferably 40 mol% or less, and more preferably 35 mol% or less. Further, the saponification degree of EVOH (a1) is 90 mol% or more. The saponification degree means the ratio of the number of vinyl alcohol units to the total number of vinyl alcohol units and vinyl ester units in EVOH (a1). When the saponification degree is 90 mol% or more, the gas barrier property of the retort packaging bag of the present invention is improved. The saponification degree is preferably 95 mol% or more, more preferably 99 mol% or more, and even more preferably 99.9 mol% or more. The ethylene unit content and the saponification degree of EVOH (a1) are 1 determined by 1H-NMR measurement.

[0017] EVOH (a1) may be a mixture of two or more types of EVOH having different ethylene unit contents. In this case, the difference in ethylene unit content between the EVOHs with the most different ethylene unit contents is preferably 30 mol% or less, more preferably 20 mol% or less, still more preferably 15 mol% or less, and may be 3 mol% or more. Similarly, EVOH (a1) may be a mixture of two or more types of EVOH having different degrees of saponification. In this case, the difference in degree of saponification between the EVOHs with the most different degrees of saponification is preferably 7 mol% or less, more preferably 5 mol% or less, and may be 0.5 mol% or more. When it is desired to achieve both high thermoformability and gas barrier properties at a higher level, EVOH (a1-1) having an ethylene unit content of 24 mol% or more and less than 34 mol% and a degree of saponification of 99 mol% or more, and EVOH (a1-2) having an ethylene unit content of 34 mol% or more and less than 50 mol% and a degree of saponification of 99 mol% or more are mixed so that the blending mass ratio (a1-1 / a1-2) is 60 / 40 to 90 / 10, and it is preferably used as EVOH (a1).

[0018] EVOH (a1) may contain monomer units other than ethylene units, vinyl ester units, and vinyl alcohol units, as long as the effects of the present disclosure are not inhibited. The content of other monomer units is preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 1% by mass or less, and particularly preferably not substantially contained.Examples of such other monomers include α-olefins such as propylene, n-butene, isobutylene, 1-hexene; acrylic acid and its salts; unsaturated monomers having an acrylate group; methacrylic acid and its salts; unsaturated monomers having a methacrylate group; acrylamide, N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetoneacrylamide, acrylamidopropanesulfonic acid and its salts, acrylamidopropyldimethylamine and its salts (e.g., quaternary salts); methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidopropanesulfonic acid and its salts, methacrylamidopropyldimethylamine and its salts (e.g., quaternary salts); vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, 2,3-diacetoxy-1-vinyloxypropane; vinyl cyanides such as acrylonitrile, methacrylonitrile; vinyl halides such as vinyl chloride, vinyl fluoride; vinylidene halides such as vinylidene chloride, vinylidene fluoride; allyl compounds such as allyl acetate, 2,3-diacetoxy-1-allyloxypropane, allyl chloride; unsaturated dicarboxylic acids such as maleic acid, itaconic acid, fumaric acid and their salts or esters; vinyl silane compounds such as vinyltrimethoxysilane; alkenes having an ester group such as isopropenyl acetate, 3-acyloxy-1-propene, 3-acyloxy-1-butene, 4-acyloxy-1-butene, 3,4-diacyloxy-1-butene, 3-acyloxy-4-methyl-1-butene, 4-acyloxy-2-methyl-1-butene, 4-acyloxy-3-methyl-1-butene, 3,4-diacyloxy-2-methyl-1-butene, 4-acyloxy-1-pentene, 5-acyloxy-1-pentene, 4,5-diacyloxy-1-pentene, 4-acyloxy-1-hexene, 5-acyloxy-1-hexene, 6-acyloxy-1-hexene, 5,6-diacyloxy-1-hexene, 1,3-diacetoxy-2-methylenepropane or their enolates, etc.

[0019] The MFR (at 190 °C under a load of 2.16 kg) measured in accordance with JIS K7210 (2014) for EVOH(a1) is preferably 0.2 to 20 g / 10 min. The MFR of EVOH(a1) is more preferably 0.5 g / 10 min or more, and even more preferably 0.8 g / 10 min or more. On the other hand, the MFR of EVOH(a1) is more preferably 15 g / 10 min or less, even more preferably 10 g / 10 min or less, particularly preferably 5 g / 10 min or less, and may even be 3 g / 10 min or less. When the MFR of EVOH(a1) is within the above range, the melt formability of EVOH(a1) and the pulverized product of the retort packaging bag containing EVOH(a1) is also improved.

[0020] <PA(a2)> The resin composition (a) contains a specific amount of PA (a2). When the resin composition (a) contains a specific amount of PA (a2), the retort resistance and the appearance after retort treatment tend to be good. Specific examples of PA (a2) used in the present invention include polycaproamide (nylon 6), poly-ω-aminoheptanoic acid (nylon 7), poly-ω-aminononanoic acid (nylon 9), polyundecanamide (nylon 11), polylauryl lactam (nylon 12), polyethylene diamine adipamide (nylon 26), polytetramethylene adipamide (nylon 46), polyhexamethylene adipamide (nylon 66), polyhexamethylene sebacamide (nylon 610), polyhexamethylene dodecamide (nylon 612), polyoctamethylene adipamide (nylon 86), polydecamethylene adipamide (nylon 106), caprolactam / lauryl lactam copolymer (nylon 6 / 12), caprolactam / ω-aminononanoic acid copolymer (nylon 6 / 9), caprolactam / hexamethylene diammonium adipate copolymer (nylon 6 / 66), lauryl lactam / hexamethylene diammonium adipate copolymer (nylon 12 / 66), ethylenediammonium adipate / hexamethylene diammonium adipate copolymer (nylon 26 / 66), caprolactam / hexamethylene diammonium adipate / hexamethylene diammonium sebacate copolymer (nylon 6 / 66 / 610), ethylenediammonium adipate / hexamethylene diammonium adipate / hexamethylene diammonium sebacate copolymer (nylon 26 / 66 / 610), polyhexamethylene isophthalamide (nylon 6I), polyhexamethylene terephthalamide (nylon 6T), hexamethylene isophthalamide / hexamethylene terephthalamide copolymer (nylon 6I / 6T), 11-aminoundecanamide / hexamethylene terephthalamide copolymer, polynonamethylene terephthalamide (nylon 9T), polydecamethylene terephthalamide (nylon 10T), polyhexamethylene cyclohexylamide, polynonamethylene cyclohexylamide, or those obtained by modifying these polyamides with aromatic amines such as methylene benzylamine and metaxylylenediamine.In addition, metaxylylenediammonium adipate and the like can also be mentioned. Among these, from the viewpoint of particularly improving the gas barrier property and appearance immediately after retort treatment, it is preferably a polyamide resin mainly composed of caproamide. Specifically, it is preferable that 75 mol% or more of the structural units of PA(a2) are caproamide units. Among them, from the viewpoint of compatibility with EVOH(a1), PA(a2) is preferably nylon 6.

[0021] The degree of polymerization of PA(a2) is preferably 1.7 to 5.0, more preferably 2.0 to 5.0, in terms of relative viscosity measured according to JIS K 6920-1(2018). <##

[0022] As the polymerization method of PA(a2), melt polymerization, interfacial polymerization, solution polymerization, bulk polymerization, solid-phase polymerization, or a combination of these methods can be adopted.

[0023] The mass ratio (a1 / a2) of EVOH(a1) to PA(a2) is 55 / 45 to 98 / 2, preferably 65 / 35 to 96 / 4, more preferably 75 / 25 to 94 / 6, and even more preferably 80 / 20 to 92 / 8. When the mass ratio (a1 / a2) is less than 55 / 45, the gas barrier property tends to be insufficient. When the mass ratio (a1 / a2) exceeds 98 / 2, the gas barrier property immediately after retort treatment tends to be insufficient.

[0024] <Alkali metal ion (K)> The resin composition (a) contains 40 to 2000 ppm of alkali metal ions (K). When the resin composition (a) contains alkali metal ions (K) within the above range, the interlayer adhesiveness with the adhesive layer (C) described later tends to be significantly improved, and the decrease in gas barrier properties immediately after retort treatment can be suppressed, and the recyclability also tends to be good. When the alkali metal ions (K) are 40 ppm or more, the resin composition (a) tends to suppress thickening during melt molding, can suppress appearance defects due to lumps, and also tends to suppress a decrease in interlayer adhesiveness with the adhesive layer (C) described later. On the other hand, when the alkali metal ions (K) are 2000 ppm or less, the resin composition (a) tends to promote appropriate decomposition during melt molding and suppress thickening, and also tends to suppress coloring. Further, in the retort packaging bag of the present invention, when the content of alkali metal ions (K) is 40 ppm or more, generation of lumps can be suppressed and the recyclability tends to be improved when the recovered product of the retort packaging bag is melt-kneaded to produce a recovered composition. On the other hand, when the content of alkali metal ions (K) is 2000 ppm or less, an excessive decomposition reaction can be suppressed and the recyclability tends to be improved when the recovered product of the retort packaging bag is melt-kneaded to produce a recovered composition. From the viewpoint of recyclability, the lower limit of the content of alkali metal ions (K) is preferably 80 ppm, more preferably 120 ppm. The upper limit of the content of alkali metal ions (K) is preferably 1000 ppm, more preferably 500 ppm, still more preferably 400 ppm, and particularly preferably 300 ppm. Further, by controlling the content ratio of alkali metal ions (K) and the carboxylic acid described later, the melt moldability and coloring resistance of the obtained resin composition (a) can be further improved.

[0025] Examples of the alkali metal ions (K) include ions of lithium, sodium, potassium, rubidium, and cesium. From the viewpoint of industrial availability, sodium or potassium ions are preferred. In particular, when potassium ions are used, it may be possible to achieve both a high level of the hue of the resin composition (a) and the interlayer adhesiveness with the adhesive layer (C) described later. These may be used alone or in combination of two or more.

[0026] Examples of alkali metal compounds that provide alkali metal ions (K) include aliphatic carboxylates, aromatic carboxylates, carbonates, hydrochlorides, nitrates, sulfates, phosphates, hydroxides, and metal complexes of alkali metals such as lithium, sodium, and potassium. Among these, aliphatic carboxylates and phosphates are more preferred because of their ease of availability and handling. Preferred aliphatic carboxylates are acetates, caprylates, and stearates.

[0027] <Polyvalent metal ions (L)> The resin composition (a) preferably contains 10 to 500 ppm of at least one polyvalent metal ion (L) selected from the group consisting of magnesium ions, calcium ions, and zinc ions. When the polyvalent metal ion (L) is contained in an amount of 10 ppm or more, poor appearance such as thickening and the generation of particles during melt molding of the resin composition (a) tends to be suppressed. On the other hand, when the content of the polyvalent metal ion (L) is 500 ppm or less, excessive decomposition and coloration during melt molding of the resin composition (a) tends to be suppressed. Furthermore, in the retort pouch packaging bag of the present invention, crosslinking of the resin may progress during recycling, causing thickening and gelation. However, when the polyvalent metal ion (L) is contained in an amount of 10 ppm or more, thickening, gelation, and adhesion of the resin to the screw are suppressed. On the other hand, when the content of the polyvalent metal ion (L) is 500 ppm or less, the generation of particles during recycling is suppressed, while deterioration of the color during recycling tends to be suppressed. From this viewpoint, the content of the polyvalent metal ion (L) is preferably 40 to 400 ppm, more preferably 70 to 300 ppm, and even more preferably 100 to 200 ppm. The resin composition (a) preferably contains magnesium ions or calcium ions as the polyvalent metal ions (L), and more preferably magnesium ions. Furthermore, by controlling the content ratio of the polyvalent metal ions (L) to the carboxylic acid described below, the melt moldability and coloration resistance of the resulting resin composition (a) can be further improved.

[0028] Examples of the polyvalent metal compound that provides the polyvalent metal ion (L) include aliphatic carboxylates, aromatic carboxylates, carbonates, hydrochlorides, nitrates, sulfates, phosphates, hydroxides, and metal complexes of magnesium, calcium, and zinc. Among them, aliphatic carboxylates and hydroxides are more preferable because they are easy to obtain and handle. As the aliphatic carboxylate, acetates, caprylate, and stearates are preferable. From the viewpoint of further suppressing the deterioration of the appearance after retort treatment, the polyvalent metal compound that provides the polyvalent metal ion (L) is preferably a hydroxide.

[0029] The resin composition (a) may contain components other than EVOH (a1), PA (a2), alkali metal ion (K), and polyvalent metal ion (L) as long as the effects of the present invention are not inhibited. Examples of other components include alkaline earth metal ions and transition metal ions other than the polyvalent metal ion (L), higher aliphatic carboxylic acids, carboxylic acids other than higher aliphatic carboxylic acids (monocarboxylic acids, polyvalent carboxylic acids), thermoplastic resins other than EVOH (a1) and PA (a2), phosphate compounds, boron compounds, oxidation accelerators, antioxidants (hindered phenol-based compounds, etc.), plasticizers, heat stabilizers (melt stabilizers), photoinitiators, deodorants, ultraviolet absorbers, antistatic agents, lubricants, colorants, fillers, desiccants, fillers, pigments, dyes, processing aids, flame retardants, antifogging agents, etc. From the viewpoint of suppressing coloring when melt-molding the pulverized product of the retort packaging bag containing the resin composition (a), it is preferable to contain a higher aliphatic carboxylic acid, a carboxylic acid other than a higher aliphatic carboxylic acid, and / or a phosphate compound. Further, by containing a boron compound, the melt viscosity of the resin composition (a) and the pulverized product of the retort packaging bag containing the resin composition (a) can be controlled.

[0030] <Higher aliphatic carboxylic acid> The resin composition (a) may further contain a higher fatty acid having 8 to 30 carbon atoms. The higher fatty acid may be partially or entirely contained in the form of a salt, and may also be contained as a salt of an alkali metal ion (K) or a polyvalent metal ion (L). As the higher fatty acid, caprylic acid or stearic acid is preferably used. The retort packaging bag of the present invention has a barrier layer (AS) composed only of the resin composition (a) as the outermost layer. During the production, in the die, the higher fatty acid acts as a lubricant between the die metal surface, thus it is considered that the appearance defects caused by uneven film thickness and the occurrence of bumps due to the retained resin can be suppressed. Therefore, the resin composition (a) preferably contains 100 ppm or more of the higher fatty acid. On the other hand, when the content of the higher fatty acid is 4000 ppm or less, it tends to suppress the thickening during the melt molding of the resin composition (a) and maintain the interlayer adhesiveness with the adhesive layer (C) described later. From these viewpoints, the content of the higher fatty acid is more preferably 200 to 3000 ppm, and even more preferably 300 to 2500 ppm.

[0031] <Carboxylic acid> The resin composition (a) may further contain a carboxylic acid other than the higher fatty acid. The lower limit of the content of the carboxylic acid is preferably 50 ppm, and more preferably 100 ppm. On the other hand, the upper limit of the content of the carboxylic acid is preferably 500 ppm, and more preferably 450 ppm. When the content of the carboxylic acid is 50 ppm or more, the coloring resistance tends to be good. On the other hand, when the content of the carboxylic acid is 500 ppm or less, it tends to maintain the interlayer adhesiveness and suppress the generation of odor.

[0032] The pKa of the carboxylic acid is preferably 3.5 to 5.5. When the pKa of the carboxylic acid is within the above range, the pH buffering capacity of the obtained resin composition (a) is enhanced, the melt moldability is further improved, and the coloring caused by acidic substances or basic substances is further improved.

[0033] The carboxylic acid may be a monocarboxylic acid. These may be used alone or in combination of two or more. A monocarboxylic acid is a compound having one carboxyl group in the molecule. The monocarboxylic acid having a pKa in the range of 3.5 to 5.5 is not particularly limited, and examples thereof include formic acid (pKa = 3.77), acetic acid (pKa = 4.76), propionic acid (pKa = 4.85), acrylic acid (pKa = 4.25), and the like. These carboxylic acids may further have substituents such as a hydroxyl group, an amino group, and a halogen atom. Among them, acetic acid is preferable because of its high safety and easy availability and handling.

[0034] The carboxylic acid may be a polycarboxylic acid. When the carboxylic acid is a polycarboxylic acid, the coloring resistance of the resin composition (a) at high temperatures and the coloring resistance of the melt-molded product of the crushed material of the resulting retort packaging bag may be further improved. Further, it is also preferable that the polycarboxylic acid compound has three or more carboxyl groups. In this case, the coloring resistance may be more effectively improved. A polycarboxylic acid is a compound having two or more carboxyl groups in the molecule. In this case, it is preferable that the pKa of at least one carboxyl group is in the range of 3.5 to 5.5. For example, oxalic acid (pKa2 = 4.27), succinic acid (pKa1 = 4.20), fumaric acid (pKa2 = 4.44), malic acid (pKa2 = 5.13), glutaric acid (pKa1 = 4.30, pKa2 = 5.40), adipic acid (pKa1 = 4.43, pKa2 = 5.41), pimelic acid (pKa1 = 4.71), phthalic acid (pKa2 = 5.41), isophthalic acid (pKa2 = 4.46), terephthalic acid (pKa1 = 3.51, pKa2 = 4.82), citric acid (pKa2 = 4.75), tartaric acid (pKa2 = 4.40), glutamic acid (pKa2 = 4.07), aspartic acid (pKa = 3.90), and the like can be mentioned.

[0035] <Phosphoric acid compound> The resin composition (a) may further contain a phosphate compound. The lower limit of the content of the phosphate compound is preferably 5 ppm in terms of phosphate radical. On the other hand, the upper limit of the content of the phosphate compound is preferably 100 ppm in terms of phosphate radical. By containing the phosphate compound within this range, the coloring of the melt-molded product of the obtained resin composition (a) and the pulverized product of the obtained retort packaging bag may be suppressed, and the thermal stability may be improved.

[0036] As the phosphate compound, for example, various acids such as phosphoric acid and phosphorous acid and their salts are used. The phosphate may be any of primary phosphate, secondary phosphate, and tertiary phosphate. The cation species of the phosphate is not particularly limited, but alkali metals and alkaline earth metals are preferred as the cation species. Among them, sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, and dipotassium hydrogen phosphate are preferred as the phosphate compound.

[0037] <Boron compound> The resin composition (a) may further contain a boron compound. When containing a boron compound, the lower limit of the content in the resin composition (a) is preferably 50 ppm in terms of boron element, and more preferably 100 ppm. On the other hand, the upper limit of the content of the boron compound in the resin composition (a) is preferably 400 ppm in terms of boron element, and more preferably 200 ppm. By containing the boron compound within this range, the thermal stability during the melt molding of the resin composition (a) and the pulverized product of the obtained retort packaging bag may be improved, and the generation of gels and lumps may be suppressed. Also, the drawdown resistance and the neck-in resistance during film formation may be improved, or the mechanical properties of the obtained retort packaging bag may be improved. These effects are presumably due to the occurrence of a chelate interaction between EVOH (a1) and the boron compound.

[0038] Examples of the boron compound include boric acid, borate ester, borate, and boron hydride. Specifically, boric acids such as orthoboric acid (H3BO3), metaboric acid, and tetraboric acid; borate esters such as trimethyl borate and triethyl borate; alkali metal salts or alkaline earth metal salts of the boric acid, borates such as borax, etc. are included. Among them, orthoboric acid is preferred.

[0039] <Hindered phenol-based compound> The resin composition (a) may further contain a hindered phenol-based compound as an antioxidant. When the hindered phenol-based compound is contained, the content of the hindered phenol-based compound in the resin composition (a) is preferably 1000 to 10000 ppm. When the content is 1000 ppm or more, coloring, thickening, and gelation of the resin can be suppressed when melt-molding the pulverized product of the retort packaging bag. The content of the hindered phenol-based compound is more preferably 2000 ppm or more. On the other hand, when the content of the hindered phenol-based compound is 10000 ppm or less, coloring and bleed-out derived from the hindered phenol-based compound can be suppressed. The content of the hindered phenol-based compound is more preferably 8000 ppm or less.

[0040] The hindered phenol-based compound has at least one hindered phenol group. The hindered phenol group refers to a group in which a bulky substituent is bonded to at least one of the carbons adjacent to the carbon to which the hydroxyl group of phenol is bonded. As the bulky substituent, an alkyl group having 1 to 10 carbon atoms is preferred, and a t-butyl group is more preferred.

[0041] The hindered phenol compound is preferably in a solid state near room temperature. From the viewpoint of suppressing the bleed-out of the compound, the melting point or softening temperature of the hindered phenol compound is preferably 50°C or higher, more preferably 60°C or higher, and still more preferably 70°C or higher. From the viewpoint of suppressing the bleed-out, the molecular weight of the hindered phenol compound is preferably 200 or higher, more preferably 400 or higher, and still more preferably 600 or higher. On the other hand, the molecular weight is usually 2000 or lower. Further, from the viewpoint of facilitating the mixing with EVOH(a1) or PA(a2), the melting point or softening temperature of the hindered phenol compound is preferably 200°C or lower, more preferably 190°C or lower, and still more preferably 180°C or lower. [[ID=P1]] [[ID=P2]]

[0042] [[ID=P3]] From the viewpoint of more easily facilitating the mixing with EVOH(a1) or PA(a2), the hindered phenol compound preferably has an ester bond or an amide bond. Examples of the hindered phenol compound having an ester bond include esters of aliphatic carboxylic acids having a hindered phenol group and aliphatic alcohols, and examples of the hindered phenol compound having an amide bond include amides of aliphatic carboxylic acids having a hindered phenol group and aliphatic amines. Among them, it is preferable that the hindered phenol compound has an amide bond. [[ID=P5]] [[ID=P6]]

[0043] [[ID=P7]] Specific structures of hindered phenolic compounds having an ester bond or an amide bond include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], which is commercially available from BASF as Irganox 1010; stearyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, which is commercially available as Irganox 1076; 2,2'-thiodiethyl bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], which is commercially available as Irganox 1035; octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, which is commercially available as Irganox 1135; ethylene bis(oxyethylene) bis(3-tert-butyl-4-hydroxy-5-methylbenzenepropanoate), which is commercially available as Irganox 245; 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], which is commercially available as Irganox 259; and N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide], which is commercially available as Irganox 1098. Among them, N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide], which is commercially available as Irganox 1098, and pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], which is commercially available as Irganox 1010, are preferred, and the former is more preferred.

[0044] The resin composition (a) may further contain a thermoplastic resin other than EVOH (a1) and PA (a2). Examples of the thermoplastic resin other than EVOH (a1) and PA (a2) include various polyolefins (such as polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene-propylene copolymer, copolymer of ethylene and an α-olefin having 4 or more carbon atoms, copolymer of polyolefin and maleic anhydride, ethylene-vinyl ester copolymer, ethylene-acrylic ester copolymer, or modified polyolefin obtained by graft-modifying these with an unsaturated carboxylic acid or its derivative, etc.), various polyesters (such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), polyvinyl chloride, polyvinylidene chloride, polystyrene, polyacrylonitrile, polyurethane, polycarbonate, polyacetal, polyacrylate, and modified polyvinyl alcohol resin, etc. The content of the thermoplastic resin in the resin composition (a) is usually less than 40% by mass, preferably less than 30% by mass, more preferably less than 20% by mass, still more preferably less than 10% by mass, and may even be less than 5% by mass or less than 1% by mass, and it is particularly preferred that it is substantially absent.

[0045] From the viewpoint that the effects of the present invention can be more significantly exhibited, the total proportion of EVOH (a1) and PA (a2) in the resin constituting the resin composition (a) is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may be 97% by mass or more, or even 99% by mass or more. The resin constituting the resin composition (a) may consist essentially of only EVOH (a1) and PA (a2), or may consist of only EVOH (a1) and PA (a2). Further, from the viewpoint that the effects of the present invention can be more significantly exhibited, the total proportion of EVOH (a1) and PA (a2) in the resin composition (a) is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may be 98% by mass or more, or even 99% by mass or more. The resin composition (a) may consist essentially of only EVOH (a1), PA (a2) and alkali metal ions (K).

[0046] The manufacturing method of the resin composition (a) is not particularly limited, but it can be manufactured by melt-kneading EVOH (a1), PA (a2), and other components and additives such as alkali metal ions (K) and, if necessary, polyvalent metal ions (L). The alkali metal ions (K) and polyvalent metal ions (L) may be blended in a solid state such as powder or as a melt, or may be blended as a solute contained in a solution or a dispersed substance contained in a dispersion. As the solution and the dispersion, an aqueous solution and an aqueous dispersion are preferably used, respectively. For melt-kneading, known mixing devices or kneading devices such as a kneader extruder, an extruder, a mixing roll, and a Banbury mixer can be used. The temperature range during melt-kneading can be appropriately adjusted according to the melting points of the EVOH (a1) and PA (a2) used, and usually, 190 to 250 °C is adopted. Also, it may be manufactured by adding some components to EVOH (a1) or PA (a2) in advance and then melt-kneading the other necessary components as described above. As a method of adding some components to EVOH (a1) or PA (a2) in advance, a method of immersing EVOH (a1) or PA (a2) as pellets or powder in a solution in which the added component is dissolved can be exemplified. As the solution, an aqueous solution is preferably used.

[0047] <Barrier layer (AM) and resin composition (a)> The retort packaging bag of the present invention further has a barrier layer (AM) composed only of the resin composition (a), and it is preferable that the barrier layer (AM) is located between the barrier layer (AS) and the heat-sealing layer (B). Regarding the resin composition (a) used for the barrier layer (AM), the content described as the resin composition (a) used for the above-mentioned barrier layer (AS) can be applied as it is.

[0048] <Heat-sealing layer (B) and polyolefin resin (b)> The retort packaging bag of the present invention has a heat-sealing layer (B) containing a polyolefin resin (b) with a melting point of 130 to 170°C as the innermost layer. The polyolefin resin (b) is not particularly limited as long as it is a polyolefin with a melting point of 130 to 170°C. However, from the perspective of improving the recyclability of the retort packaging bag containing the polyolefin resin (b), the polyolefin resin (b) preferably contains polypropylene as the main component. Polypropylene is widely used as a packaging material regardless of the presence or absence of gas barrier properties, and its recycling infrastructure is relatively well-established in various countries. Examples of polypropylene include polypropylene; propylene-based copolymers obtained by copolymerizing propylene with α-olefins such as ethylene, 1-butene, 1-hexene, and 4-methyl-1-pentene. The content of propylene units in the propylene-based copolymer is 70 mol% or more, preferably 80 mol% or more, and may be 90 mol% or more.

[0049] From the perspective of making the effects of the present invention more remarkable, the melt flow rate (MFR) (at 230°C under a load of 2160 g) measured according to the method described in JIS K7210 (2014) of the polyolefin resin (b) is preferably 0.1 to 30 g / 10 min, more preferably 0.3 to 25 g / 10 min, and even more preferably 0.5 to 20 g / 10 min.

[0050] The melting point of the polyolefin resin (b) is 130 to 170°C, preferably 140 to 167°C, and more preferably 150 to 164°C. When the melting point of the polyolefin resin (b) is within the above range, it tends to have excellent gas barrier properties immediately after retort treatment.

[0051] The proportion of polyolefin in the polyolefin resin (b) is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 95% by mass or more, and may be substantially composed of only polyolefin. When the polyolefin resin (b) contains polypropylene, the proportion of polypropylene in the polyolefin resin (b) is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 95% by mass or more, and may be substantially composed of only polypropylene. Further, the proportion of the polyolefin resin (b) in the heat-sealing layer (B) is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 95% by mass or more, and may be substantially composed of only the polyolefin resin (b).

[0052] <Adhesive layer (C) and adhesive resin (c)> The retort packaging bag of the present invention further has an adhesive layer (C) containing an adhesive resin (c) having a melting point of 130 to 170°C as a main component, and at least one adhesive layer (C) is preferably located adjacent to the barrier layer (AS) or the barrier layer (AM). By including the adhesive layer (C) in the retort packaging bag of the present invention, a retort packaging bag excellent in appearance and interlayer adhesiveness tends to be obtained. Further, by including the adhesive layer (C), the compatibility between the barrier layer (AS) or the barrier layer (AM) and the heat-sealing layer (B) is improved when recycling, so that the recyclability tends to be improved. Examples of the adhesive resin (c) include acid-modified polyolefins obtained by graft-polymerizing an unsaturated carboxylic acid such as maleic anhydride or a derivative thereof to a polyolefin, and preferably contains an acid-modified polypropylene obtained by graft-polymerizing an unsaturated carboxylic acid such as maleic anhydride or a derivative thereof to polypropylene as a main component. The melting point of the adhesive resin (c) mainly depends on the polyolefin before acid modification. For the polyolefin, the content described for the polyolefin resin (b) above can be applied as it is.

[0053] The melting point of the adhesive resin (c) is 130 to 170°C, preferably 140 to 167°C, more preferably 150 to 164°C. When the melting point of the adhesive resin (c) is within the above range, the gas barrier property immediately after retort treatment tends to be excellent.

[0054] The proportion of the acid-modified polyolefin in the adhesive resin (c) is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 95% by mass or more, and may be substantially composed of only the acid-modified polyolefin. When the adhesive resin (c) contains an acid-modified polypropylene, the proportion of the acid-modified polypropylene in the adhesive resin (c) is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 95% by mass or more, and may be substantially composed of only the acid-modified polyolefin. Further, the proportion of the adhesive resin (c) in the adhesive layer (C) is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 95% by mass or more, and may be substantially composed of only the adhesive resin (c).

[0055] <Moisture-proof layer (D) and polyolefin resin (d)> The retort packaging bag of the present invention further has a moisture-proof layer (D) containing a polyolefin resin (d) having a melting point of 130 to 170°C as a main component, and the moisture-proof layer (D) is preferably located between the barrier layer (AS) and the heat-sealing layer (B). Regarding the polyolefin resin (d), the content described as the above-mentioned polyolefin resin (b) can be applied as it is.

[0056] The proportion of polyolefin in the polyolefin resin (d) is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 95% by mass or more, and may be substantially composed of only polyolefin. When the polyolefin resin (d) contains polypropylene, the proportion of polypropylene in the polyolefin resin (d) is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 95% by mass or more, and may be substantially composed of only polypropylene. Further, the proportion of the polyolefin resin (d) in the moisture-proof layer (D) is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 95% by mass or more, and may be substantially composed of only the polyolefin resin (d).

[0057] The heat-sealing layer (B), the adhesive layer (C), and the moisture-proof layer (D) each contain a polyolefin resin (b), an adhesive resin (c), and a polyolefin resin (d) as main components. However, these layers may contain other components such as antioxidants, plasticizers, heat stabilizers (melt stabilizers), photoinitiators, deodorants, ultraviolet absorbers, antistatic agents, lubricants, colorants, fillers, desiccants, fillers, pigments, dyes, processing aids, flame retardants, antifogging agents, etc., as long as the effects of the present invention are not inhibited. However, the total amount is less than 50% by mass for each layer, preferably less than 40% by mass, more preferably less than 30% by mass, still more preferably less than 20% by mass, particularly preferably less than 10% by mass, and may be less than 5% by mass, less than 3% by mass, or less than 1% by mass.

[0058] <Retort packaging bag> The retort packaging bag of the present invention has a structure in which a barrier layer (AS) is an essential layer on the outermost layer and a heat-sealing layer (B) is an essential layer on the innermost surface. Further, it preferably has a structure in which at least one layer of a barrier layer (AM), an adhesive layer (C), and / or a moisture-proof layer (D) is laminated as an optional layer between the barrier layer (AS) and the heat-sealing layer (B). The barrier layer (AM), the adhesive layer (C), and / or the moisture-proof layer (D) may each have a plurality of layers. As the layer structure of the multilayer film of the present invention, the barrier layer (AS) is represented by S, the heat-sealing layer (B) is represented by B, the barrier layer (AM) is represented by M, the adhesive layer (C) is represented by C, and the moisture-proof layer (D) is represented by D. When " / " represents direct lamination, examples include S / B, S / C / B, S / C / D / B, S / C / M / C / B, S / C / M / C / D / B, S / C / D / C / M / C / B, S / C / D / C / M / C / D / B, and the like.

[0059] From the viewpoints of gas barrier property, recyclability, and economy, the average thickness of each layer of the barrier layer (AS) and / or the barrier layer (AM) of the retort packaging bag of the present invention is preferably 1 μm or more and less than 20 μm. The average thickness is more preferably 2 μm or more and less than 15 μm, still more preferably 3 μm or more and less than 12 μm, and may be 4 μm or more and less than 9 μm. From the viewpoint of further emphasizing recyclability, the average thickness is particularly preferably less than 9 μm, and may be less than 7 μm or less than 4 μm. Further, from the viewpoints of gas barrier property, recyclability, and economy, it is also preferable that the ratio of the total average thickness of the barrier layer (AS) and / or the barrier layer (AM) to the total average thickness of the retort packaging bag of the present invention is 3% or more and less than 25%. From the viewpoint of further emphasizing recyclability, the ratio is more preferably less than 20%, and may be less than 15% or less than 10%.

[0060] From the viewpoints of heat sealability, recyclability, and resource efficiency, the average thickness of the heat-sealing layer (B) of the retort packaging bag of the present invention is preferably 5 μm or more and less than 200 μm. The average thickness of the heat-sealing layer (B) is more preferably 15 μm or more, still more preferably 25 μm or more, and may be 35 μm or more or 45 μm or more. Further, the average thickness of the heat-sealing layer (B) is more preferably less than 150 μm, still more preferably less than 100 μm, particularly preferably less than 80 μm, and may be less than 70 μm or less than 60 μm. Further, from the viewpoints of heat sealability, recyclability, and resource efficiency, it is also preferable that the ratio of the average thickness of the heat-sealing layer (B) to the total average thickness of the retort packaging bag of the present invention exceeds 30%. The ratio is more preferably more than 40%, and may be more than 50% or more than 60%.

[0061] From the viewpoints of interlayer adhesiveness, recyclability, and economy, the average thickness per layer of the adhesive layer (C) of the multilayer film is preferably 1 μm or more and less than 20 μm. The average thickness is more preferably 2 μm or more and less than 15 μm, still more preferably 3 μm or more and less than 12 μm, and may be 4 μm or more and less than 9 μm. From the viewpoint of further emphasizing recyclability, the average thickness is particularly preferably less than 9 μm, and may be less than 7 μm or less than 4 μm. Further, from the viewpoints of interlayer adhesiveness, recyclability, and economy, it is also preferable that the ratio of the total average thickness of the adhesive layer (C) to the total average thickness of the retort packaging bag of the present invention is 3% or more and less than 25%. From the viewpoint of further emphasizing recyclability, the ratio is more preferably less than 20%, and may be less than 15% or less than 10%.

[0062] From the viewpoints of moisture resistance, recyclability, and resource efficiency, the average thickness of the heat moisture-resistant layer (D) of the retort packaging bag of the present invention is preferably 5 μm or more and less than 200 μm. The average thickness of the moisture-resistant layer (D) is more preferably 15 μm or more, still more preferably 25 μm or more, and may be 35 μm or more or 45 μm or more. Further, the average thickness of the moisture-resistant layer (D) is more preferably less than 150 μm, still more preferably less than 100 μm, particularly preferably less than 80 μm, and may be less than 70 μm or less than 60 μm. Further, from the viewpoints of moisture resistance, recyclability, and resource efficiency, it is also preferable that the ratio of the total average thickness of the moisture-resistant layer (D) to the total average thickness of the retort packaging bag of the present invention exceeds 20%. The ratio is more preferably more than 30%, and may be more than 40% or more than 50%.

[0063] The average thickness of the retort packaging bag of the present invention is preferably 30 μm or more and less than 300 μm, and more preferably 135 μm or more and less than 250 μm.

[0064] The retort packaging bag of the present invention may be composed of an unstretched multilayer film that is not substantially stretched, or may be composed of a stretched multilayer film stretched in a uniaxial direction or a biaxial direction, or may be a combination thereof. In the case of an unstretched multilayer film, it has excellent impact resistance and particularly good heat sealability. On the other hand, by stretching in a uniaxial direction or a biaxial direction, the mechanical properties and gas barrier properties may be improved in some cases. When composed of a stretched multilayer film, from the viewpoints of economy and openability (easy to open by hand), a uniaxially stretched multilayer film is preferable, and from the viewpoint of less anisotropy in mechanical properties and excellent toughness, a biaxially stretched multilayer film is preferable. When composed of a stretched multilayer film, from the viewpoints of thickness uniformity and mechanical strength, it is preferably stretched at least 3 times and less than 12 times in at least the uniaxial direction. In the case of a uniaxially stretched multilayer film, it is preferably stretched substantially only in the uniaxial direction 3 times or more and less than 12 times, and more preferably 4 times or more and less than 10 times. In the case of a biaxially stretched multilayer film, it is preferably stretched 3 times or more and less than 12 times in each of the biaxial directions, and more preferably 4 times or more and less than 10 times. In the case of a tenter-type sequential biaxially stretched film, it is common to stretch 4 to 6 times in the film flow direction (MD direction) and then 8 to 10 times in the width direction (TD direction).

[0065] The method for forming the multilayer film constituting the retort packaging bag of the present invention is not particularly limited. Generally, a conventional coextrusion method in which each resin is extruded from a separate die or a common die and laminated can be used. As the die, either an annular die or a T-die can be used. The method of stretching in the uniaxial direction or the biaxial direction is also not particularly limited, and by a conventionally known stretching method such as roll-type uniaxial stretching, tubular simultaneous biaxial stretching, tenter-type sequential biaxial stretching, tenter-type simultaneous biaxial stretching, etc., the film can be produced by performing a stretching process in the flow direction of the film and / or in a direction perpendicular to the flow direction, that is, the width direction. The temperature during stretching is usually 70 to 180°C, more preferably 80 to 170°C, and may be 90 to 160°C from the viewpoint of processability. If necessary, after the stretching process, it is preferable to perform a so-called heat setting operation by heat-treating at a temperature above the glass transition point and below the melting point to increase the crystallinity and fix the orientation of the molecular chains.

[0066] As the lower limit of the total average thickness ratio of the layer mainly composed of polyolefin resin in the retort packaging bag of the present invention, 0.75 is preferable, 0.85 is more preferable, 0.88 is further preferable, and 0.90 may also be acceptable. By increasing the total average thickness ratio of the layer mainly composed of polyolefin resin in the retort packaging bag, the recyclability can be improved. As the upper limit of the total average thickness ratio of the layer mainly composed of polyolefin resin in the retort packaging bag, 0.995 is preferable, 0.99 is more preferable, and 0.98 may also be acceptable. When the polyolefin resin in the retort packaging bag of the present invention contains a polypropylene resin, as the lower limit of the total average thickness ratio of the layer mainly composed of polypropylene resin, 0.75 is preferable, 0.80 is more preferable, 0.83 is further preferable, and 0.86 may also be acceptable. By increasing the total average thickness ratio of the layer mainly composed of polypropylene resin in the retort packaging bag, the recyclability can be improved. As the upper limit of the total average thickness ratio of the layer mainly composed of polypropylene resin in the retort packaging bag, 0.97 is preferable, 0.95 is more preferable, and 0.93 may also be acceptable. Examples of the layer mainly composed of polypropylene resin include the heat-sealing layer (B) when the polyolefin resin (b) is polypropylene, the adhesive layer (C) when the adhesive resin (c) is, for example, acid-modified polypropylene, and the moisture-proof layer (D) when the polyolefin resin (d) is polypropylene.

[0067] The retort packaging bag of the present invention does not have a layer containing a resin with a melting point of less than 130°C as a main component, a layer containing a polyester with a melting point of 200°C or higher as a main component, a layer containing a polyamide with a melting point of 200°C or higher as a main component, and a metal layer with an average thickness of 1 μm or more. That is, it does not have a layer containing a resin with a melting point of less than 130°C as a main component, does not have a layer containing a polyester with a melting point of 200°C or higher as a main component, does not have a layer containing a polyamide with a melting point of 200°C or higher as a main component, and does not have a metal layer with an average thickness of 1 μm or more. By not having these layers, the heat resistance and recyclability of the retort packaging bag tend to be improved. Here, the metal layer is a layer having continuous and discontinuous surfaces made of a metal such as an aluminum foil. Also, the barrier layer (AS), the barrier layer (AM), the heat-sealing layer (B), the adhesive layer (C), and the moisture-proof layer (D) do not correspond to a layer containing a resin with a melting point of less than 130°C as a main component.

[0068] The retort packaging bag of the present invention preferably has an oxygen transmission rate (under the conditions of 20°C and 65 / 100%RH) measured according to the method described in JIS K 7126-2 (isobaric method; 2006) of less than 10 cc / (m 2 ·day·atm), more preferably less than 8 cc / (m 2 ·day·atm), even more preferably less than 6 cc / (m 2 ·day·atm), still more preferably less than 4 cc / (m 2 ·day·atm), even still more preferably less than 3 cc / (m 2 ·day·atm) or less than 2 cc / (m 2 ·day·atm), particularly preferably less than 0.7 cc / (m 2 ·day·atm) in some cases. A retort packaging bag with an oxygen transmission rate within the above range has excellent gas barrier properties, so the preservability of the contents is good.

[0069] The retort packaging bag of the present invention has an oxygen transmission rate (under the conditions of 20°C and 65 / 100%RH) measured according to the method described in JIS K 7126-2 (isobaric method; 2006) after 10 hours of retort treatment of 20 cc / (m 2·day·atm) is preferably less than, more preferably less than 16 cc / (m 2 ·day·atm), even more preferably less than 12 cc / (m 2 ·day·atm), still more preferably less than 8 cc / (m 2 ·day·atm), even still more preferably less than 6 cc / (m 2 ·day·atm), less than 4 cc / (m 2 ·day·atm), less than or less than 2 cc / (m 2 ·day·atm) in some preferred cases. The retort packaging bag with an oxygen transmission rate within the above range has excellent gas barrier properties even immediately after retort treatment, so that the storage stability of the contents is good. The retort treatment is to be carried out according to the method described in the examples.

[0070] The retort packaging bag of the present invention has an oxygen transmission rate (under the conditions of 20 °C and 65 / 100% RH) measured according to the method described in JIS K 7126-2 (isobaric method; 2006) after the drop test of less than 10 cc / (m 2 ·day·atm), preferably less than 8 cc / (m 2 ·day·atm), more preferably less than 6 cc / (m 2 ·day·atm), even more preferably less than 4 cc / (m<s 2 ·day·atm), even still more preferably less than 3 cc / (m 2 ·day·atm), less than or less than 2 cc / (m 2 ·day·atm), particularly preferably less than 1.2 cc / (m 2 ·day·atm) in some preferred cases.

[0071] The retort packaging bag of the present invention may have other layers other than those described above, as long as the effects of the present invention are not inhibited. Examples of other layers include a recovery layer. In particular, it is preferable to reuse, as part or all of the recovery layer, a recovery composition containing the recovered material of the retort packaging bag of the present invention described later. Another example of another layer is, for example, a printing layer. The printing layer may be included at any position of the retort packaging bag of the present invention. Examples of the printing layer include a film obtained by coating and drying a solution containing, for example, a pigment or a dye and, if necessary, a binder resin. Examples of the coating method for the printing layer include various coating methods using a gravure printing method, a wire bar, a spin coater, a die coater, etc., in addition to the gravure printing method. The average thickness of the ink layer is not particularly limited, but is preferably 0.5 to 10 μm, more preferably 1 to 4 μm.

[0072] When manufacturing the retort packaging bag of the present invention, it is preferable to reuse the recovered materials (scraps) obtained by collecting the ends and defective products generated. A method for recovering the retort packaging bag by pulverizing it and then melt-molding it, and a recovery composition containing the recovered material of the retort packaging bag of the present invention are also preferred embodiments of the present invention.

[0073] When recovering the retort packaging bag of the present invention, first, the recovered material of the retort packaging bag of the present invention is pulverized. The pulverized recovered material may be directly melt-molded to obtain a recovery composition, or may be melt-molded together with other components as necessary to obtain a recovery composition. A preferable component to be added to the recovered material is a polyolefin resin, and a polypropylene-based resin is more preferable. As the polyolefin resin, the same type as the polyolefin resin (b) described above used in the retort packaging bag of the present invention can be used. The pulverized recovered material may be directly used for manufacturing molded articles such as retort packaging bags, or after the pulverized recovered material is melt-molded to obtain pellets made of a recovery composition, the pellets may be used for manufacturing molded articles.

[0074] The retort packaging bag of the present invention is excellent in appearance and gas barrier properties immediately after retort treatment, so it can be suitably used as a material for various packagings such as food packaging, pharmaceutical packaging, industrial chemical packaging, and agricultural chemical packaging. In particular, the packaging material provided with the retort packaging bag of the present invention can be suitably used as a packaging material with excellent recyclability.

Example

[0075] Hereinafter, the present invention will be described more specifically using examples, but the present invention is not limited by these examples at all.

[0076] Example 1 (1) Preparation of an EVOH (a1) and PA (a2) - containing resin composition (a) for the barrier layer (AS) and the barrier layer (AM) 85 parts by mass of EVOH - 27 (ethylene unit content 27 mol%, saponification degree 99.9 mol% or more, melting point 191 °C, MFR (210 °C, 2.16 kg load) 4.0 g / 10 min, containing 220 ppm of sodium acetate in terms of sodium ions, 30 ppm of phosphate ions in terms of phosphate radicals, 150 ppm of boric acid in terms of boron element, and no polyvalent metal ions), 15 parts by mass of nylon 6 "SF1018A" pellets manufactured by Ube Industries, Ltd. (hereinafter abbreviated as "PA6": relative viscosity [ηr] 3.0, melting point 221 °C), and magnesium hydroxide powder (150 ppm in terms of magnesium ions) were mixed and then supplied to a twin - screw extruder "TEX30α" (screw diameter 30 mm) manufactured by Japan Steel Works, Ltd. Using a screw having a sequential displacement kneading disk with L (screw length) / D (screw diameter) = 3, melt extrusion was carried out under the conditions of a melting temperature of 230 - 240 °C and an extrusion speed of 20 kg / hr to obtain strands. After cooling and solidifying the obtained strands in a cooling tank, they were cut to obtain pellets of the resin composition (EVOH (a1) and PA (a2) - containing resin composition (a) for the barrier layer (AS) and the barrier layer (AM)).

[0077] (2) Polyolefin resin (b) - containing resin composition for the heat - sealing layer (B) Polypropylene manufactured by Nippon Polyprop Co., Ltd. ("Novatech (trademark) PP EA7AD" (MFR (at 230°C, under a load of 2.16 kg) 1.4 g / 10 min, melting point 161°C)) was used as it was as resin composition pellets for the heat-sealing layer (B) as the polyolefin resin (b).

[0078] (3) Resin composition containing the adhesive resin (c) for the adhesive layer (C) Maleic anhydride-modified polypropylene manufactured by Mitsui Chemicals, Inc. ("Admer (trademark) QF500" (MFR (at 230°C, under a load of 2.16 kg) 3.0 g / 10 min, melting point 161°C) was used as it was as resin composition pellets for the adhesive layer (C) as the adhesive resin (c).

[0079] (4) Resin composition containing the polyolefin resin (d) for the moisture-proof layer (D) Polypropylene manufactured by Nippon Polyprop Co., Ltd. ("Novatech (trademark) PP EA7AD" (MFR (at 230°C, under a load of 2.16 kg) 1.4 g / 10 min, melting point 161°C)) was used as it was as resin composition pellets for the moisture-proof layer (D) as the polyolefin resin (d).

[0080] (5) Preparation of the multilayer film Using each of the resin composition pellets of (1) to (4) above, a multilayer film having an average thickness and layer structure of (AS) / (C) / (D) / (C) / (AM) / (C) / (B) = 5 μm / 5 μm / 25 μm / 5 μm / 5 μm / 5 μm / 50 μm = EVOH5 / Tie5 / PP25 / Tie5 / EVOH5 / Tie5 / PP50 was produced using a co-extrusion film-forming facility. The notation "EVOH5" for the above layer structure means a layer consisting only of the resin composition (a) with an average thickness of 5 μm. Although the resin composition (a) contains PA(a2), it was denoted as "EVOH" for simplicity. "Tie5" means an adhesive layer (C) with an average thickness of 5 μm. "PP25" and "PP50" respectively mean a polypropylene layer (moisture-proof layer (D)) with an average thickness of 25 μm and a polypropylene layer (heat-sealing layer (B)) with an average thickness of 50 μm. All the extruders were single-screw extruders with D(mm) = 30, and a full-flight screw with L / D = 28 and a compression ratio of 3.0 was used. As the die, a T-die of the feed block lamination type with a width of 350 mm was used. The temperature conditions at this time are shown below. Extrusion temperature of the resin composition (a): Feeding section / Compression section / Metering section / Adapter = 190 / 230 / 230 / 230 °C Extrusion temperature of the resin composition containing the polyolefin resin (b): Feeding section / Compression section / Metering section / Adapter = 175 / 220 / 230 / 230 °C Extrusion temperature of the resin composition containing the adhesive resin (c): Feeding section / Compression section / Metering section / Adapter = 175 / 220 / 230 / 230 °C Extrusion temperature of the resin composition containing the polyolefin resin (d): Feeding section / Compression section / Metering section / Adapter = 175 / 220 / 230 / 230 °C Die temperature: 230 °C Cooling roll temperature: 80 °C

[0081] (5) Production of a retort packaging bag After cutting out two pieces of the multilayer film obtained in (4) to A4 size, they were overlapped so that the heat-sealing layer (B) sides faced each other, and a three-side bag (retort packaging bag) was produced by heat-sealing three sides.

[0082] (6) Oxygen transmission rate before retort treatment of the retort packaging bag (OTR before retort) (5) A film was cut out from the retort packaging bag obtained in (5), with the barrier layer (AS) side as the oxygen supply side and the heat-sealing layer (B) side as the carrier gas side, and the oxygen transmission rate was measured in accordance with JIS K 7126-2 (isobaric method; 2006). Specifically, using an oxygen transmission rate measuring device ("MOCON OX-TRAN2 / 21" manufactured by Modern Controls), the oxygen transmission rate (unit: cc / (m 2 ·day·atm)) was measured under the conditions of a temperature of 20°C, a humidity of 65% RH on the oxygen supply side, a humidity of 100% RH on the carrier gas side, an oxygen pressure of 1 atm, and a carrier gas pressure of 1 atm. Nitrogen gas containing 2% by volume of hydrogen gas was used as the carrier gas. The results are shown in Table 1.

[0083] (7) Oxygen transmission rate immediately after retort treatment of the retort packaging bag (OTR after retort) (5) 900 g of water was filled into the opening of the retort packaging bag obtained in (5), and the opening was heat-sealed to produce a pouch filled with water. The obtained pouch was subjected to a retort treatment at 120°C for 30 minutes using a retort apparatus ("RCS-40RTGN", a high-temperature and high-pressure cooking sterilization tester manufactured by Nisshapan Co., Ltd.). After the retort treatment, the water on the surface of the pouch was wiped off, the pouch was immediately opened to remove the water, a 9 cm square measurement sample was cut out from the center part (non-heat-sealed part) of the pouch, with the barrier layer (AS) side as the oxygen supply side and the heat-sealing layer (B) side as the carrier gas side, and the oxygen transmission rate was measured in accordance with JIS K 7126-2 (isobaric method; 2006). Specifically, using an oxygen transmission rate measuring device ("MOCON OX-TRAN2 / 21" manufactured by Modern Controls), the oxygen transmission rate (unit: cc / (m 2 ·day·atm)) was measured under the conditions of a temperature of 20°C, a humidity of 65% RH on the oxygen supply side, a humidity of 100% RH on the carrier gas side, an oxygen pressure of 1 atm, and a carrier gas pressure of 1 atm. Nitrogen gas containing 2% by volume of hydrogen gas was used as the carrier gas. The measurement value 10 hours after the start of measurement was taken as the oxygen transmission rate immediately after the retort treatment. The results are shown in Table 1. The OTR immediately after the retort treatment was 20 cc / (m 2·day·atm) that exceeded this value were judged to be unable to suppress the deterioration of gas barrier properties immediately after retort treatment.

[0084] (8) Oxygen transmission rate after the drop test of the retort packaging bag (5) 900 g of water was filled into the retort packaging bag obtained in (5) through the opening, and the opening was heat-sealed to produce a water-filled pouch. This was dropped 20 times from a height of 1 m onto a concrete floor surface in an environment at 20°C. After the drop test, the pouch was opened to remove the water, and a 9 cm square measurement sample was cut out from the center part (non-heat-sealed part) of the pouch. With the barrier layer (AS) side as the oxygen supply side and the heat-sealed layer (B) side as the carrier gas side, the oxygen transmission rate was measured in accordance with JIS K 7126-2 (isobaric method; 2006). Specifically, using an oxygen transmission rate measuring device ("MOCON OX-TRAN2 / 21" manufactured by Modern Control), the oxygen transmission rate (unit: cc / (m 2 ·day·atm)) was measured under the conditions of a temperature of 20°C, a humidity of 65% RH on the oxygen supply side, a humidity of 100% RH on the carrier gas side, an oxygen pressure of 1 atm, and a carrier gas pressure of 1 atm. Nitrogen gas containing 2% by volume of hydrogen gas was used as the carrier gas. The measured value 10 hours after the start of the measurement was taken as the oxygen transmission rate after the drop test. The results are shown in Table 1.

[0085] (9) Appearance after retort treatment (5) The retort packaging bag obtained in (5) was subjected to retort treatment in the same manner as in (7) above. After the retort treatment, the water on the surface of the pouch was wiped off, and visual observation was immediately carried out. The appearance characteristics of the pouch were evaluated in 5 grades from A to E as follows. The results are shown in Table 1. Judgment criteria A: Almost no change in appearance was observed compared to before retort treatment B: Slight whitening was observed C: Slight whitening or / and deformation was observed D: Moderate whitening or / and deformation was observed, or partial delamination was observed E: Severe whitening or / and deformation was observed, or extensive delamination was observed

[0086] (10) Lumps and coloring of the melt-molded product of the crushed material of the retort packaging bag The retort packaging bag obtained in (5) was crushed into a size of 4 mm square or less. This crushed material and polypropylene manufactured by Nippon Polypropylene Co., Ltd. ("Novatec (trademark) PP EA7AD" (MFR (under 230 °C, 2.16 kg load) 1.4 g / 10 min, melting point 161 °C)) were blended at a mass ratio (crushed material / polypropylene resin) of 10 / 90, and a single-layer film with a thickness of 100 μm was obtained by performing single-layer film formation under the extrusion conditions shown below. The thickness of the single-layer film was adjusted by appropriately changing the screw rotation speed and the take-up roll speed. Also, as a control, a single-layer film with a thickness of 100 μm was obtained in the same manner using only polypropylene ("Novatec (trademark) PP EA7AD" (MFR (under 230 °C, 2.16 kg load) 1.4 g / 10 min, melting point 161 °C)). Extruder: Single-screw extruder manufactured by Toyo Seiki Seisakusho Screw diameter: 20 mm φ (L / D = 20, compression ratio = 3.5, full flight type) Extrusion temperature: Feeding section / Compression section / Measuring section / Die C1 / C2 / C3 / D = 235 / 235 / 235 / 235 °C Take-up roll temperature: 80 °C The lumps and coloring status of the obtained single-layer film were evaluated in the following five grades A to E. The results are shown in Table 1. Criteria for judging lumps A: Compared with the control, the amount of lumps hardly changed B: Compared with the control, the amount of small lumps was slightly more C: Compared with the control, the amount of small lumps was more D: Compared with the control, the amount of large lumps was more E: Compared with the control, the amount of large lumps was much more Criteria for judging coloring A: Compared with the control, the degree of hue change was small B: Compared with the control, slight coloring was observed C: Compared with the object, medium coloring was observed D: There was significant coloring compared to the target, but it was uniform overall. E: There was significant coloring compared to the target, and unevenness by location was also observed.

[0087] (11) Melting viscosity stability of the crushed product of the retort packaging bag (5) The retort packaging bag obtained in (5) was crushed into a size of 4 mm square or less. This crushed product and polypropylene manufactured by Nippon Polypro Co., Ltd. ("Novatech (trademark) PP EA7AD" (MFR (under 230 °C, 2.16 kg load) 1.4 g / 10 min, melting point 161 °C)) were blended at a mass ratio (crushed product / polypropylene resin) of 10 / 90, and 75 g was weighed. Using a lab plastomill (twin-screw non-oriented), it was kneaded for 30 minutes under a nitrogen atmosphere at 235 °C and 100 rpm. Also, as a control, only polypropylene ("Novatech (trademark) PP EA7AD" (MFR (under 230 °C, 2.16 kg load) 1.4 g / 10 min, melting point 161 °C)) was used for kneading in the same manner. It was evaluated in 5 grades of A to E below according to the ratio (TR / TP) of the torque value (TR) of the blended resin after 30 minutes of kneading and the torque value (TP) of polypropylene (control). The results are shown in Table 1. Judgment criteria A: 90 / 100 or more and less than 110 / 100 B: 80 / 100 or more and less than 90 / 100, or 110 / 100 or more and less than 120 / 100 C: 70 / 100 or more and less than 80 / 100, or 120 / 100 or more and less than 130 / 100 D: 60 / 100 or more and less than 70 / 100, or 130 / 100 or more and less than 140 / 100 E: Less than 60 / 100, or 140 / 100 or more

[0088] Example 2 Instead of EVOH-27, resin composition pellets, multilayer films, and retort pouches were produced and various measurements and evaluations were conducted in the same manner as in Example 1, except that EVOH-44 (ethylene unit content: 44 mol%, saponification degree: 99.9 mol% or more, melting point: 165°C, MFR (210°C, 2.16 kg load): 4.5 g / 10 min, containing 280 ppm of sodium acetate in terms of sodium ions, 30 ppm of phosphate ions in terms of phosphate radicals, 250 ppm of boric acid in terms of boron element, and no polyvalent metal ions) was used. The results are shown in Table 1.

[0089] Examples 3 to 13, Comparative Examples 1 to 3 Resin composition pellets, multilayer films, and retort pouches were produced and various measurements and evaluations were conducted in the same manner as in Example 1, except that the composition of the resin composition and the layer structure of the retort pouch were changed as shown in Table 1. In Examples 8 to 10, magnesium stearate, calcium stearate, and zinc stearate were used instead of magnesium hydroxide.

[0090] Comparative Example 4 Instead of EVOH-27, resin composition pellets, multilayer films, and retort pouches were produced and various measurements and evaluations were conducted in the same manner as in Example 1, except that EVOH-27A (ethylene unit content: 27 mol%, saponification degree: 99.9 mol% or more, melting point: 191°C, MFR (210°C, 2.16 kg load): 4.0 g / 10 min, containing 30 ppm of sodium acetate in terms of sodium ions, 30 ppm of phosphate ions in terms of phosphate radicals, 150 ppm of boric acid in terms of boron element, and no polyvalent metal ions) was used. The results are shown in Table 1.

[0091] Comparative Example 5 Except that EVOH-27B (ethylene unit content: 27 mol%, saponification degree: 99.9 mol% or more, melting point: 191 °C, MFR (210 °C, 2.16 kg load): 4.0 g / 10 min, sodium acetate: 2500 ppm in terms of sodium ions, phosphate ions: 30 ppm in terms of phosphate radicals, boric acid: 150 ppm in terms of boron element, containing no polyvalent metal ions) was used instead of EVOH-27, resin composition pellets, multilayer films, and retort packaging bags were produced in the same manner as in Example 1, and various measurements and evaluations were performed. The results are shown in Table 1.

[0092]

Table 1

Claims

1. A barrier layer (AS) is provided as the outermost layer, and a heat-sealing layer (B) is provided as the innermost layer, the barrier layer (AS) contains an ethylene-vinyl alcohol copolymer (a1) having an ethylene unit content of 20 to 50 mol% and a saponification degree of 90 mol% or more and a polyamide (a2), and the mass ratio (a1 / a2) of the ethylene-vinyl alcohol copolymer (a1) to the polyamide (a2) is 55 / 45 to 98 / 2, and consists only of a resin composition (a), the heat-sealing layer (B) contains a polyolefin resin (b) having a melting point of 130 to 170°C as a main component, the resin composition (a) contains 40 to 2000 ppm of an alkali metal ion (K), a retort packaging bag having no layer mainly composed of a resin having a melting point of less than 130°C, no layer mainly composed of a polyester having a melting point of 200°C or higher, no layer mainly composed of a polyamide having a melting point of 200°C or higher, and no metal layer having an average thickness of 1 μm or more.

2. Further having a barrier layer (AM) consisting only of the resin composition (a), and the barrier layer (AM) is located between the barrier layer (AS) and the heat-sealing layer (B), the retort packaging bag according to Claim 1.

3. The polyolefin resin (b) contains polypropylene as a main component, the retort packaging bag according to Claim 1 or 2.

4. Further having an adhesive layer (C) mainly composed of an adhesive resin (c) having a melting point of 130 to 170°C, and at least one layer of the adhesive layer (C) is located adjacent to the barrier layer (AS) or the barrier layer (AM), the packaging bag according to Claim 1 or 2.

5. The adhesive resin (c) contains acid-modified polypropylene as a main component, the retort packaging bag according to Claim 4.

6. Further having a moisture-proof layer (D) mainly composed of a polyolefin resin (d) having a melting point of 130 to 170°C, and the moisture-proof layer (D) is located between the barrier layer (AS) and the heat-sealing layer (B), the packaging bag according to Claim 1 or 2.

7. The polyolefin resin (d) contains polypropylene as a main component, the retort packaging bag according to Claim 6.

8. The resin composition (a) contains 10 to 500 ppm of at least one polyvalent metal ion (L) selected from the group consisting of magnesium ions, calcium ions, and zinc ions, the retort packaging bag according to Claim 1 or 2.

9. The heat-sealing layer (B) contains polypropylene as a main component, The retort packaging bag according to claim 1 or 2, wherein the total average thickness ratio of the layer mainly composed of a polypropylene-based resin to the average thickness of the retort packaging bag is 0.75 or more.

10. After 10 hours of retort treatment at 120°C for 30 minutes, the oxygen transmission rate (under the conditions of 20°C and 65 / 100% RH) measured by the method described in JIS K 7126-2:2006 is less than 20 cc / (m ２ ·day·atm), the retort packaging bag according to claim 1 or 2.

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