Air-permeable packaging material for oxygen scavenger and method for manufacturing same

Abstract

This air-permeable packaging material for an oxygen scavenger includes, in the order given, the following: an outer layer containing a thermoplastic resin; an intermediate layer containing at least one selected from paper and nonwoven fabric; and an inner layer containing linear low-density polyethylene. The inner layer has a through hole H1, and the diameter φ1 of the through hole H1 is 150-3000 μm. When differential scanning calorimetry is performed in a nitrogen atmosphere with the inner layer as a measurement sample, and under a condition in which the temperature is raised from 50°C to 200°C at 10°C per minute (temperature increase 1), then lowered from 200°C to 50°C at 10°C per minute (temperature decrease 1), and subsequently, raised again from 50°C to 200°C at 10°C per minute (temperature increase 2), during the process (temperature increase 2), the maximum heat absorption peak is at least 120°C.

Description

Breathable packaging material for oxygen absorbers and its manufacturing method

[0001] The present invention relates to a breathable packaging material for an oxygen absorber and a method for producing the same.

[0002] Oxygen absorbers are used to remove oxygen from sealed containers containing various items that are susceptible to deterioration or spoilage due to oxygen, such as food, beverages, pharmaceuticals, medical supplies, cosmetics, metal products, and electronic products, in order to prevent oxidative deterioration and enable long-term storage. Oxygen absorbers are used in a variety of ways depending on the purpose and manner of use, including, for example, packaging powder or tablet oxygen absorbers in a packaging material to form small pouches into oxygen absorber packages. When this oxygen absorber package is placed inside a sealed container in which food or the like is stored, the oxygen absorber inside the oxygen absorber package removes oxygen from the sealed container, thereby preventing oxidative deterioration of the food or the like.

[0003] Packaging materials for such oxygen absorbers include sheets of resin, paper, or nonwoven fabric, as well as laminates of these. Packaging materials with a resin layer, paper, or nonwoven fabric layer laminated together include a resin layer with pre-formed air vents laminated on a paper or nonwoven fabric layer. The use of a resin layer with pre-formed air vents ensures ventilation with the outside, allowing the oxygen absorber to effectively exhibit its oxygen scavenging performance. However, conventional breathable packaging materials for oxygen absorbers have a problem of inconsistent oxygen scavenging time. This is thought to be due in part to the inconsistent air permeability of the breathable packaging material. To address this problem, Patent Document 1 proposes a technology that uses a specially processed breathable packaging material to easily control the target air permeability of the breathable packaging material.

[0004] Japanese Patent Application Laid-Open No. 2004-082460

[0005] The special processing proposed in Patent Document 1 requires equipment and conditions suitable for the processing, which means that existing manufacturing equipment and manufacturing conditions cannot be used as is, making the process complicated and placing a heavy burden on producers. Therefore, there has been a need for the development of a breathable packaging material for oxygen absorbers that can exhibit stable oxygen absorption performance with little individual variation using existing manufacturing equipment and manufacturing conditions without using special manufacturing equipment. The present invention has been made in light of these circumstances, and an object of the present invention is to provide a breathable packaging material for oxygen absorbers and a manufacturing method thereof that can produce oxygen absorber packages that have a short oxygen absorption time, excellent oxygen absorption performance, and stable oxygen absorption performance with little individual variation using existing manufacturing equipment and manufacturing conditions without using special manufacturing equipment.

[0006] The inventors discovered that the above problems can be solved by including an outer layer, an intermediate layer, and an inner layer, with the inner layer being made of a specific material and having specific through holes, and thus completed the invention.

[0007] That is, the gist of the present invention is as follows: [1] A breathable packaging material for an oxygen absorber, comprising, in this order, an outer layer containing a thermoplastic resin, an intermediate layer containing at least one material selected from paper and nonwoven fabric, and an inner layer containing linear low-density polyethylene, the inner layer having through holes H1 with an opening diameter φ1 of 150 μm or more and 3000 μm or less, and when differential scanning calorimetry is performed on the inner layer as a measurement sample under conditions of heating from 50° C. to 200° C. at a rate of 10° C. per minute (heating 1) and then cooling from 200° C. to 50° C. at a rate of 10° C. per minute (heating 2) in a nitrogen atmosphere, the maximum endothermic peak during the heating process (heating 2) is 120° C. or more. [2] The breathable packaging material for an oxygen absorber according to [1] above, wherein the intermediate layer contains fluorine-free oil-resistant paper. [3] The breathable packaging material for an oxygen absorber according to [1] above or [2] above, wherein the air permeability resistance measured by the Oken testing machine method in accordance with JIS P8117:2009 is 10,000 seconds or more. [4] The density of the through holes H1 is 1 hole / cm ２ More than 60 holes / cm ２[5] The breathable packaging material for an oxygen absorber according to any one of [1] to [3], wherein the intermediate layer has an air permeability resistance of 2000 seconds or less as measured by an Oken testing machine method in accordance with JIS P8117:2009. [6] The breathable packaging material for an oxygen absorber according to any one of [1] to [5], wherein the intermediate layer is fluorine-free greaseproof paper. [7] The breathable packaging material for an oxygen absorber according to any one of [1] to [6], wherein the outer layer comprises, in this order toward the intermediate layer, a base layer containing one or more selected from polyethylene terephthalate and biaxially oriented polypropylene, and a welding layer containing one or more selected from polyethylene and ethylene copolymers. [8] An oxygen absorber package comprising the breathable packaging material for an oxygen absorber according to any one of [1] to [7], and an oxygen absorber packaged in the breathable packaging material for an oxygen absorber. [9] A method for producing a breathable packaging material for an oxygen absorber, comprising: a step of pressing a heated metal needle against a film containing linear low-density polyethylene to form a through hole H1 to obtain an inner layer; and a step of laminating an outer layer containing a thermoplastic resin, an intermediate layer containing one or more selected from paper and nonwoven fabric, and the inner layer in this order to obtain a breathable packaging material for an oxygen absorber, wherein the diameter of the metal needle is 0.3 mm or more and 2.0 mm or less, the surface temperature of the metal needle is 150°C or more and 450°C or less, and when differential scanning calorimetry is performed on the inner layer as a measurement sample under conditions of heating from 50°C to 200°C at 10°C per minute in a nitrogen atmosphere (heating 1), cooling from 200°C to 50°C at 10°C per minute (heating 2), and then heating again from 50°C to 200°C at 10°C per minute (heating 2), the maximum endothermic peak observed during the heating 2 step is 120°C or more.

[0008] According to the present invention, it is possible to provide a breathable packaging material for oxygen absorbers and a method for producing the same, which can produce oxygen absorber packages that have a short oxygen absorbing time, excellent oxygen absorbing performance, and exhibit stable oxygen absorbing performance with little individual variation, using existing manufacturing equipment and manufacturing conditions without using special manufacturing equipment.

[0009] Embodiments of the breathable packaging material for oxygen absorbers and the method for producing the same according to the present invention are described in detail below. In this specification, the term "A to B" used to describe numerical values ​​means "A or more and B or less" (when A<B) or "A or less and B or more" (when A>B). In the present invention, a combination of preferred embodiments is a more preferred embodiment. Furthermore, in this specification, unless otherwise specified, "(meth)acrylate," "(meth)acrylic," "(meth)acrylic acid," etc. mean acrylate and / or methacrylate, acrylic and / or methacrylic, acrylic acid and / or methacrylic acid, etc., respectively.

[0010] [Breathable Packaging Material for Oxygen Absorbers] The breathable packaging material for oxygen absorbers of the present invention comprises, in this order, an outer layer containing a thermoplastic resin, an intermediate layer containing at least one material selected from paper and nonwoven fabric, and an inner layer containing linear low-density polyethylene, the inner layer having through holes H1 with an opening diameter φ1 of 150 μm or more and 3000 μm or less, and when differential scanning calorimetry is performed on the inner layer as a measurement sample under the following conditions in a nitrogen atmosphere: heating from 50° C. to 200° C. at a rate of 10° C. per minute (temperature rise 1), cooling from 200° C. to 50° C. at a rate of 10° C. per minute (temperature fall 1), and then heating again from 50° C. to 200° C. at a rate of 10° C. per minute (temperature rise 2), the maximum endothermic peak during the temperature rise 2 is 120° C. or more.

[0011] The packaging material of the present invention, with its above-described configuration, can provide an oxygen absorber package that exhibits a short deoxidation time, excellent oxygen absorption performance, and stable oxygen absorption performance with minimal individual variation, without the need for special manufacturing equipment, using existing manufacturing equipment and manufacturing conditions. The reasons why the packaging material of the present invention exhibits the above effects are unclear, but the following reasons are thought to be the case. The inner layer of the packaging material of the present invention contains linear low-density polyethylene. Linear low-density polyethylene is characterized by a narrow molecular weight distribution, few branched chains, and a large molecular weight. It is believed that, perhaps due to its good crystallinity, through-holes with nearly circular openings can be obtained, particularly when perforated with a hot needle. Furthermore, because of its good crystallinity and the maximum endothermic peak in the DSC curve obtained by differential scanning calorimetry being 120°C or higher, the portion away from the needle (the heat source) can quickly return to its original rigid state, preventing unnecessary stretching of the polyethylene film and resulting in through-holes that conform to the shape of the needle. From the above, it is believed that the resulting oxygen absorber package, which has stable breathability with minimal individual variation, exhibits a short deoxidation time, excellent oxygen absorption performance, and stable oxygen absorption performance with minimal individual variation.

[0012] The air resistance of the breathable packaging material for oxygen absorbers of the present invention, measured by the Oken Tester Method in accordance with JIS P8117:2009, is preferably 10,000 seconds or more, more preferably 11,000 seconds or more, and even more preferably 13,000 seconds or more. Furthermore, the air resistance of the breathable packaging material for oxygen absorbers of the present invention, measured by the Oken Tester Method in accordance with JIS P8117:2009, is preferably 100,000 seconds or less, more preferably 90,000 seconds or less, even more preferably 50,000 seconds or less, and even more preferably 20,000 seconds or less. The air resistance is the average value of 30 measurements performed in accordance with JIS P8117:2009. A more specific method for measuring the air resistance is, as shown in the examples, a method in which measurements are made 30 times in accordance with JIS P8117:2009 using a digital Oken air resistance tester (EG02, manufactured by Asahi Seiko Co., Ltd.) in a mode in which the median value of the measurable range is 2000. The air resistance is the average value (ave.) of the 30 measurements.

[0013] Hereinafter, each layer of the packaging material according to this embodiment and its components will be described in detail.

[0014] <Outer Layer> The outer layer is a layer containing a thermoplastic resin. The outer layer is preferably a layer in which external ventilation holes H2 are formed. The outer layer can be a single-layer film or a multilayer film of two or more layers made of different materials. Since thermal lamination is preferably used to bond the outer layer and the intermediate layer, the outer layer is preferably a multilayer film made of two or more thermoplastic resins with a large difference in melting point. It is preferable that the outer layer includes, in this order, a base layer made of a thermoplastic resin with a high melting point and a welding layer made of a thermoplastic resin with a low melting point toward the intermediate layer.

[0015] Examples of thermoplastic resins preferably used for the base layer include polyethylene terephthalate, biaxially oriented polypropylene, and nylon, and more preferably at least one selected from polyethylene terephthalate and biaxially oriented polypropylene. The thermoplastic resin preferably used for the welding layer preferably contains a material having heat-sealability. Examples of thermoplastic resins preferably used for the welding layer include polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene; ethylene copolymers such as ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-α-olefin copolymer polymerized using a metallocene catalyst, ethylene-methyl methacrylate copolymer, and ethylene-propylene copolymer; polypropylene; ionomer resins; methylpentene polymers; polybutene polymers; acid-modified polyolefin resins obtained by modifying polyolefin resins such as polyethylene or polypropylene with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, and itaconic acid; polyvinyl acetate resins, poly(meth)acrylic resins, and polyvinyl chloride resins, and more preferably at least one selected from polyethylene and ethylene copolymers. That is, the outer layer preferably comprises, in this order toward the intermediate layer, a base layer containing one or more selected from polyethylene terephthalate and biaxially oriented polypropylene, and a welding layer containing one or more selected from polyethylene and ethylene copolymers. Note that a larger difference in melting point between the thermoplastic resin of the inner layer and the thermoplastic resin of the outer layer is preferred, as this increases the degree of freedom in heat-sealing conditions (temperature, pressure, time).

[0016] The outer layer may further contain components other than the thermoplastic resin, as long as the effects of the present invention are not impaired. Examples of other components that can be used in the outer layer include additives such as stabilizers, lubricants, antistatic agents, antifogging agents, fillers, colorants, plasticizers, and nucleating agents.

[0017] The thickness of the outer layer is not particularly limited, but is preferably 1 to 50 μm, more preferably 2 to 40 μm, even more preferably 4 to 35 μm, and even more preferably 8 to 30 μm. By setting the thickness of the outer layer within the above range, a packaging material having sufficient strength can be obtained, and also a packaging material having appropriate flexibility necessary for processing such as folding in the production of an oxygen absorber package described below can be obtained.

[0018] The outer layer can have its surface printed or drawn by gravure printing or the like.

[0019] The outer layer is preferably a layer in which an external air vent H2 is formed. The external air vent H2 is a hole that penetrates the outer layer. The arrangement of the through-hole H1 and the external air vent H2 in the inner layer is not particularly limited, but it is preferable that the through-hole H1 and the external air vent H2 are not located in the same place. "Located in the same place" refers to a state in which a portion of the through-hole H1 in the inner layer is visible when the external air vent H2 is viewed from the surface of the outer layer. Not being located in the same place effectively prevents external components from adhering to the internal oxygen absorber when the oxygen absorber package is made, and also effectively prevents the internal oxygen absorber from leaking to the outside.

[0020] The diameter or hole density of the external air vents H2 can be adjusted as appropriate so that the desired breathability (air permeability) can be obtained for the breathable packaging material as a whole. Specifically, the method of forming the external air vents H2, the shape, hole diameter, etc. can be adjusted as appropriate under the conditions described below for the through holes H1 in the inner layer.

[0021] <Intermediate layer> The intermediate layer is a layer containing one or more materials selected from paper and nonwoven fabric. It provides the packaging material with a certain level of durability, breathability, etc., while preventing leakage of the oxygen absorber contained in the oxygen absorber package. The intermediate layer is preferably a layer containing greaseproof paper. By including greaseproof paper, it is possible to impart oil resistance in addition to the above-mentioned properties.

[0022] The material of the paper used in the intermediate layer is not particularly limited, and examples thereof include water-repellent paper, kraft paper, fine paper (western paper), and Japanese paper. The material of the nonwoven fabric used in the intermediate layer is not particularly limited, and examples thereof include thermoplastic resins such as polyethylene, polypropylene, polyamide, and polyester. More specifically, examples of the nonwoven fabric used in the intermediate layer include linear low-density polyethylene (LLDPE) nonwoven fabric, polyethylene terephthalate nonwoven fabric, composite nonwoven fabric (e.g., polyethylene terephthalate-polyethylene sheath-core structure), and TYVEK (registered trademark, manufactured by DuPont-Asahi Flashspun Products Co., Ltd.).

[0023] As described above, the intermediate layer preferably contains greaseproof paper. Oxygen absorber packages are used for a wide range of products, such as food, beverages, pharmaceuticals, medical supplies, cosmetics, metal products, and electronic products, and therefore may contain a lot of moisture, oil, and the like depending on the product to be stored and the storage environment. In such cases, moisture and oil may penetrate from the packaging material into the oxygen absorber, causing deterioration of the oxygen absorber and a decrease in its oxygen-absorbing performance, or contaminating the oxygen absorber. However, by providing an intermediate layer containing greaseproof paper, it is possible to suppress the penetration of moisture, oil, and the like, and prevent deterioration and contamination of the oxygen absorber.

[0024] In this specification, greaseproof paper refers to paper or nonwoven fabric that has been given oil resistance. The method for imparting oil resistance is not particularly limited, but examples include (1) a method of making the paper or nonwoven fabric oil-resistant by tightening the mesh, (2) a method of forming an oil-resistant coating by applying an oil-resistant agent or an agent that solidifies oil to the surface of the paper or nonwoven fabric, and (3) a method of impregnating (impregnating or adding) an oil-resistant agent to the paper or nonwoven fabric.

[0025] Furthermore, the intermediate layer preferably contains fluorine-free greaseproof paper. More preferably, the greaseproof paper of the intermediate layer does not contain fluorine. Even more preferably, the intermediate layer is fluorine-free greaseproof paper. Specific examples of fluorine-free greaseproof paper include greaseproof paper (non-fluorine-based greaseproof paper) in which oil resistance is imparted to paper or nonwoven fabric without using a fluorine-containing greaseproofing agent. Such non-fluorine-based greaseproof paper is not particularly limited as long as it does not contain fluorine and has a certain level of oil resistance, and known products can be used. Examples of such non-fluorine-based greaseproof paper include (1) paper or nonwoven fabric that is imparted with oil resistance by narrowing the mesh, (2) paper or nonwoven fabric in which an oil-resistant non-fluorine-based greaseproofing agent or a non-fluorine-based agent that solidifies oil is applied to the surface of the paper or nonwoven fabric to form an oil-resistant coating, and (3) paper or nonwoven fabric in which a non-fluorine-based greaseproofing agent having oil resistance has been impregnated (impregnated or added). Among these, the greaseproof paper (3) is preferred from the viewpoint of preventing oil stains (oil penetration) into the oxygen absorber package caused by oil penetrating through the intermediate layer from the outer edge of the oxygen absorber package or the inside (inner side surface of the hole) of the external vent hole H2 provided as needed into the internal through-hole H1. Examples of non-fluorine-based oil-proofing agents include starch-based oil-proofing agents, acrylic-based oil-proofing agents, and polyester-based oil-proofing agents.

[0026] The basis weight of the greaseproof paper is not particularly limited, but is preferably 5 to 200 g / m ２ , more preferably 15 to 150 g / m ２ , more preferably 25 to 90 g / m ２ By setting the basis weight of the greaseproof paper within the above range, sufficient oil resistance and durability can be obtained.

[0027] Furthermore, the intermediate layer preferably has an air resistance of 2000 seconds or less, more preferably 1000 seconds or less, as measured by the Oken air resistance tester method in accordance with JIS P8117:2009. There is no lower limit for the air resistance, but the air resistance is typically 100 seconds or more. The air resistance is the average value of 30 measurements performed in accordance with JIS P8117:2009. A more specific method for measuring air resistance, as shown in the examples, is to measure 30 times in accordance with JIS P8117:2009 using a digital Oken air resistance tester (EG02, manufactured by Asahi Seiko Co., Ltd.) in a mode with a median value of 2000 in the measurable range. The air resistance is the average value (ave.) of the 30 measurements.

[0028] The intermediate layer may contain components other than those constituting paper, nonwoven fabric, and greaseproof paper. Examples of other components that can be used in the intermediate layer include sizing agents (anti-bleeding agents), water-resistant agents, water-repellent agents, paper strength agents, dyes, etc. It is preferable that the intermediate layer be composed only of greaseproof paper.

[0029] The thickness of the intermediate layer is not particularly limited, but is preferably 5 to 300 μm, more preferably 15 to 200 μm, and even more preferably 30 to 150 μm. By setting the thickness of the intermediate layer within the above range, sufficient oil resistance and durability can be obtained.

[0030] <Inner Layer> The inner layer is a layer containing linear low-density polyethylene. The inner layer has through holes H1, and the opening diameter φ1 of the through holes H1 is 150 μm or more and 3000 μm or less. Furthermore, when differential scanning calorimetry was performed on the inner layer as a measurement sample under the following conditions: temperature increase from 50°C to 200°C at 10°C per minute (temperature increase 1), temperature decrease from 200°C to 50°C at 10°C per minute (temperature decrease 1), and then temperature increase again from 50°C to 200°C at 10°C per minute (temperature increase 2), the maximum endothermic peak during the temperature increase 2 was 120°C or more.

[0031] The inner layer may further contain other components in addition to the linear low-density polyethylene, such as stabilizers, lubricants, antistatic agents, anti-fogging agents, fillers, colorants, plasticizers, and nucleating agents.

[0032] The inner layer may contain a thermoplastic resin other than linear low-density polyethylene. However, from the viewpoint of heat-sealability, it is preferable that the inner layer contains substantially no thermoplastic resin other than linear low-density polyethylene. The content of linear low-density polyethylene in the inner layer is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and still more preferably 95% by mass or more, but 100% by mass or less, based on the total amount of resin in the inner layer. Examples of thermoplastic resins other than linear low-density polyethylene that are preferably used for the inner layer include polyethylenes such as low-density polyethylene other than linear low-density polyethylene, medium-density polyethylene, and high-density polyethylene; ethylene copolymers such as ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-α-olefin copolymer polymerized using a metallocene catalyst, ethylene-methyl methacrylate copolymer, and ethylene-propylene copolymer; polypropylene; ionomer resins; methylpentene polymers; polybutene polymers; acid-modified polyolefin resins obtained by modifying polyolefin resins such as polyethylene or polypropylene with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, and itaconic acid; polyvinyl acetate resins, poly(meth)acrylic resins, and polyvinyl chloride resins.

[0033] The thickness of the inner layer is not particularly limited, but is preferably 0.5 to 80 μm, more preferably 1 to 60 μm, even more preferably 2 to 50 μm, and particularly preferably 4 to 40 μm. By setting the thickness of the inner layer within the above range, sufficient adhesive strength can be obtained with short-term heat sealing.

[0034] When differential scanning calorimetry (DSC) is performed on the inner layer under the following conditions: the inner layer is used as a measurement sample, and the temperature is increased from 50°C to 200°C at a rate of 10°C per minute (temperature increase 1), then decreased from 200°C to 50°C at a rate of 10°C per minute (temperature decrease 1), and then increased again from 50°C to 200°C at a rate of 10°C per minute (temperature increase 2), the maximum endothermic peak during temperature increase 2 is 120°C or higher. The phrase "using the inner layer as a measurement sample" means that all components (linear low-density polyethylene or a resin composition) comprising the inner layer, including a thermoplastic resin containing linear low-density polyethylene and other components (additives), are used as the sample for differential scanning calorimetry (DSC). Note that "all components" refers to linear low-density polyethylene when the inner layer is composed only of linear low-density polyethylene, and refers to the resin composition containing linear low-density polyethylene when the inner layer is composed of linear low-density polyethylene and other components (additives). Furthermore, the "maximum endothermic peak" refers to the largest endothermic peak present on the DSC curve obtained during the temperature rise process, and the temperature of the maximum endothermic peak refers to the temperature at the apex of the peak. Therefore, "the maximum endothermic peak is 120°C or higher" means "the temperature at the apex of the maximum endothermic peak is 120°C or higher."

[0035] The maximum endothermic peak when differential scanning calorimetry is performed under the above conditions is 120° C. or higher, preferably 121° C. or higher, more preferably 122° C. or higher, and even more preferably 123° C. or higher. There is no upper limit, but it is usually 140° C. or lower, and from the viewpoints of heat sealing properties and easy formation of through holes, it is preferably 130° C. or lower.

[0036] (Through Hole H1) The inner layer has a through hole H1, and the opening diameter φ1 of the through hole H1 is 150 μm or more and 3000 μm or less. The through hole H1 is a hole that penetrates the inner layer.

[0037] The diameter or opening density of the internal through-holes H1 can be appropriately adjusted so that the desired breathability (air permeability) is obtained for the entire packaging material. Specifically, when a blade or needle is used, the adjustment can be made by the shape, penetration direction, arrangement, number, etc. of the blade or needle, and when a laser or electron beam is used, the adjustment can be made by the perforation conditions, such as the irradiation voltage, current, irradiation time, irradiation direction, etc.

[0038] The shape of the through hole H1 is not particularly limited and may be a circle, a polygon such as a triangle or a square, an ellipse, or the like in cross section (a surface along the inner layer surface), but the longitudinal section (a cut surface perpendicular to the inner layer surface) preferably has a shape that tapers from the outer surface of the inner layer (a surface not in contact with the intermediate layer) toward the intermediate layer side, or from the intermediate layer side toward the outer surface of the inner layer. That is, the shape of the through hole H1 preferably has a tapered shape such as a substantially conical shape (conical, truncated conical shape) or a substantially pyramidal shape (pyramidal, truncated pyramidal shape) from the outer surface of the inner layer toward the intermediate layer side, or from the intermediate layer side toward the outer surface of the inner layer.

[0039] The opening diameter φ1 of the through hole H1 (also simply referred to as diameter φ1) is 150 μm or more and 3000 μm or less. The diameter φ1 of the through hole H1 can be measured by the method described in the Examples, and is taken as the dimension (major axis) of the longest part of the opening diameter. From the viewpoints of breathability and productivity, the diameter φ1 of the through hole H1 is 150 μm or more and 3000 μm or less, preferably 200 μm or more and 2000 μm or less, more preferably 300 μm or more and 1000 μm or less, and even more preferably 300 μm or more and 800 μm or less. By setting the diameter within the above range, excellent productivity and stable breathability can be achieved, thereby stabilizing the oxygen absorption performance of the resulting oxygen absorber package. It also prevents the oxygen absorber inside from leaking to the outside. Furthermore, when the through hole has a tapered shape, from the viewpoints of breathability and productivity, it is more preferable that the opening diameter of the surface of the inner layer in contact with the intermediate layer and the opening diameter of the surface not in contact with the intermediate layer are both within the above range.

[0040] The density of the through holes H1 is preferably 1 hole / cm ２ More than 60 holes / cm ２ More preferably, 2 holes / cm or less. ２ More than 60 holes / cm ２More preferably, 5 holes / cm or less. ２ More than 60 holes / cm ２ By setting the content within the above range, excellent productivity and stable breathability can be achieved, and the oxygen absorbing performance of the obtained oxygen absorber package can also be stabilized.

[0041] [Manufacturing Method of Breathable Packaging Material for Oxygen Absorber] The manufacturing method of the breathable packaging material for oxygen absorber of the present invention is not particularly limited, but is preferably the following method: The manufacturing method of the breathable packaging material for oxygen absorber of the present invention comprises the steps of pressing a heated metal needle against a film containing linear low-density polyethylene to form through holes H1 to obtain an inner layer, and laminating an outer layer containing a thermoplastic resin, an intermediate layer containing one or more selected from paper and nonwoven fabric, and the inner layer in this order to obtain a breathable packaging material for oxygen absorber, wherein the diameter of the metal needle is 0.3 mm or more and 2.0 mm or less, and the surface temperature of the metal needle is 150° C. or more and 4.0 mm or less. and when differential scanning calorimetry is performed on the inner layer as a measurement sample under the conditions of heating from 50°C to 200°C at a rate of 10°C per minute (heating 1), then cooling from 200°C to 50°C at a rate of 10°C per minute (heating 1), and then heating again from 50°C to 200°C at a rate of 10°C per minute (heating 2), the maximum endothermic peak observed during the heating 2 step is 120°C or higher.

[0042] <Step of Obtaining Inner Layer> The inner layer is obtained by pressing a heated metal needle against a film containing linear low-density polyethylene to form through holes H1.

[0043] The perforation process for forming the through holes H1 is preferably a method of pressing a heated metal needle against a film containing linear low-density polyethylene to form holes, from the viewpoint of easy control of the size and position of the holes. The diameter of the metal needle may be any diameter that can form holes satisfying the hole diameter φ1, but is preferably 0.3 mm to 2.0 mm, more preferably 0.3 mm to 1.0 mm, and even more preferably 0.5 mm to 0.7 mm. By setting the needle diameter within the preferred range, the shape of the holes is stabilized and the air permeability can be easily adjusted. Furthermore, the surface temperature of the metal needle is preferably 150°C to 450°C, preferably 200°C to 400°C, and preferably 300°C to 380°C. Heating the metal needle allows the perforation process to be performed more stably. From the viewpoint of continuously producing a breathable packaging material for an oxygen absorber with a stable perforation density and shape, a more preferred method is to perforate the material through a cylindrical jig with needles attached to the side (hereinafter also referred to as a "needle roll"). The needle pattern can be appropriately adjusted taking into account the air permeability, etc.

[0044] The diameter of the through hole H1 can be controlled by the jig used for the hole opening process, the forming direction, etc. When a tapered conical needle is used, the longitudinal cross section (a cut surface perpendicular to the inner layer surface) tapers from the outer surface of the inner layer (the surface not in contact with the intermediate layer) toward the intermediate layer side, or from the intermediate layer side toward the outer surface of the inner layer, i.e., the through hole H1 has a tapered, approximately conical shape (a conical shape, a truncated conical shape, etc.).

[0045] When differential scanning calorimetry is performed on the obtained inner layer as a measurement sample under the conditions of heating from 50°C to 200°C at 10°C per minute (temperature rise 1), cooling from 200°C to 50°C at 10°C per minute (temperature fall 1), and then heating again at 10°C per minute from 50°C to 200°C (temperature rise 2) in a nitrogen atmosphere, the maximum endothermic peak observed during (temperature rise 2) is 120°C or higher. When differential scanning calorimetry is performed under the above conditions, the maximum endothermic peak is 120°C or higher, preferably 121°C or higher, more preferably 122°C or higher, and even more preferably 123°C or higher. There is no upper limit, but it is usually 140°C or lower, and from the viewpoints of heat sealability and ease of formation of through holes, it is preferably 130°C or lower.

[0046] <Step of Laminating to Obtain a Breathable Packaging Material for an Oxygen Absorber> Next, an outer layer containing a thermoplastic resin, an intermediate layer containing one or more selected from paper and nonwoven fabric, and the inner layer are laminated in this order to obtain a breathable packaging material for an oxygen absorber. "Laminating in this order" refers to the layer structure of the resulting packaging material and does not indicate the order of the lamination steps. In other words, the outer layer and the intermediate layer may be laminated in advance, the intermediate layer and the inner layer may be laminated in advance, or all three layers may be laminated simultaneously. For the sake of convenience, the following describes as an example a method of laminating the intermediate layer and the inner layer in advance, but as mentioned above, the order is not limited to this.

[0047] The method for laminating the inner layer and intermediate layer is not particularly limited, and any known method can be used. For example, thermal lamination or dry lamination may be used. In the case of dry lamination, the layers may be laminated in the order of inner layer / adhesive layer / intermediate layer using an adhesive. From the viewpoint of preventing leakage of the adhesive, it is preferable not to use an adhesive, and specifically, thermal lamination is preferable to dry lamination.

[0048] The method for laminating the outer layer onto the laminate including the inner layer and the intermediate layer is not particularly limited, and any known method can be used. For example, thermal lamination or dry lamination may be used. In the case of dry lamination, the layers may be laminated in the order of intermediate layer / adhesive layer / outer layer using an adhesive. From the viewpoint of preventing leakage of the adhesive, it is preferable not to use an adhesive, and specifically, thermal lamination is preferable to dry lamination.

[0049] In particular, in the case of thermal lamination, partial welding is preferred from the viewpoint of improving breathability. In a packaging material in which an intermediate layer and an outer layer are partially welded, gas can move from the through-holes H1 in the inner layer through the gap between the intermediate layer and the outer layer to the external ventilation holes H2 penetrating the outer layer, which is thought to further improve the breathability of the packaging material. The method of partial welding is not particularly limited, and known methods can be used, but examples include welding methods using a heat roll having a pattern such as a lattice pattern or a dot pattern. Among these, a lattice pattern is preferred from the viewpoint of improving adhesiveness. Furthermore, the welding rate of partial welding (the area ratio (%) of the welded portion to the entire area of ​​the partially welded region) is, from the viewpoint of improving breathability, for example, 50% or less, preferably 30% or less, more preferably 20% or less, and from the viewpoint of improving adhesiveness, preferably 8% or more, more preferably 12% or more.

[0050] Furthermore, when laminating a laminate including an inner layer and an intermediate layer with an outer layer having an external air vent H2, it is preferable to arrange the through-hole H1 of the inner layer and the external air vent H2 so that they are not in the same location. "In the same location" means that when the external air vent H2 is viewed from the surface of the outer layer, part of the through-hole H1 of the inner layer is visible. By arranging the through-hole H1 of the inner layer and the external air vent H2 not in the same location, when an oxygen absorber package is made, it is possible to effectively prevent external components from adhering to the oxygen absorber inside and also to effectively prevent the oxygen absorber inside from leaking to the outside.

[0051] [Oxygen Absorber Package] The packaging material of the present invention is suitable for use in producing an oxygen absorber package. Specifically, an oxygen absorber package can be obtained by packaging an oxygen absorber using the packaging material of the present invention. That is, the oxygen absorber package of the present invention includes the above-mentioned breathable packaging material for an oxygen absorber and an oxygen absorber wrapped in the breathable packaging material for an oxygen absorber. The packaging material of the present invention can be produced using existing production equipment and production conditions without using special production equipment, and exhibits stable breathability with little individual variation. Therefore, the oxygen absorber package obtained using this packaging material has a short oxygen scavenging time, excellent oxygen absorption performance, and exhibits stable oxygen absorption performance with little individual variation.

[0052] The method for packaging an oxygen absorber using the packaging material of the present invention is not particularly limited, and any suitable method can be adopted taking into consideration the intended use, environment, etc. For example, it is preferable to wrap the oxygen absorber so that it is in contact with the inner layer of the packaging material.

[0053] The type of oxygen scavenger is not particularly limited, and known oxygen scavenger agents can be used. Examples include metal powders such as iron powder, organic compounds such as ascorbic acid and glycerin, and polymer compounds having carbon-carbon double bonds. The oxygen scavenger does not necessarily have to be a single component, and may be, for example, a combination of metal powder such as iron powder with a metal catalyst, water, a metal salt, a carrier, and the like.

[0054] The form of the oxygen scavenger is not particularly limited, and a suitable form can be adopted as appropriate taking into consideration the intended use, environment, etc. For example, it may be in powder form, or may be formed into tablets, etc. In the case of powder form, it is preferable to adjust the size and shape of the holes, as well as the layer structure, etc., so that the powder does not leak out from the through-holes H1 and the external vent holes H2 of the inner layer to the outside.

[0055] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, but includes all aspects encompassed by the concept of the present invention and the scope of the claims, and can be modified in various ways within the scope of the present invention.

[0056] The present embodiment will be described in detail below using examples and comparative examples, but the present embodiment can be modified as appropriate as long as the effects of the present invention are achieved. In the examples and comparative examples, "parts" refers to parts by mass unless otherwise specified. Furthermore, various measurements and evaluations in the examples and comparative examples were performed as follows.

[0057] (Maximum Endothermic Peak of Inner Layer) The inner layer used in the Examples and Comparative Examples was punched into a circle with a diameter of 4 mm to serve as a measurement sample. Approximately 10 mg of the inner layer measurement sample was packed into an aluminum pan, and differential scanning calorimetry was performed using a DSC-60 differential scanning calorimeter (manufactured by Shimadzu Corporation) under the following conditions. (Measurement Conditions) Differential scanning calorimetry was performed under the following conditions in a nitrogen atmosphere: temperature increase from 50°C to 200°C at 10°C per minute (temperature increase 1), temperature decrease from 200°C to 50°C at 10°C per minute (temperature decrease 1), and then temperature increase again from 50°C to 200°C at 10°C per minute (temperature increase 2). The maximum endothermic peak during the (temperature increase 2) process was defined as the maximum endothermic peak of the inner layer. The temperature of the maximum endothermic peak was defined as the temperature at the peak's apex. A maximum endothermic peak of 120°C or higher can provide a packaging material that has stable breathability and can exhibit stable oxygen absorption performance.

[0058] (Aperture diameter) The aperture diameter was measured by observing the through holes H1 on the surface of the inner layer of the packaging multi-layer film (the surface not in contact with the intermediate layer) and measuring the dimension (major axis) of the longest part of the aperture diameter. The measurement was performed using a digital microscope (VHX-5000, manufactured by Keyence Corporation) and the attached software to measure the distance between two points. The measurement was also performed on any four through holes H1 on the surface of the inner layer, and the average of the measured values ​​(N=4) was taken as the aperture diameter (diameter φ1).

[0059] (Air Resistance) The air resistance of the breathable packaging material for oxygen absorbers and the intermediate layer was measured in accordance with JIS P8117:2009 using a digital Oken air permeability tester (EG02, manufactured by Asahi Seiko Co., Ltd.). The measurement was performed in a mode in which the median of the measurable range was 2000. The air resistance of the breathable packaging material for oxygen absorbers was measured 30 times for each of the same packaging material obtained by the method described in each Example and Comparative Example (i.e., for each Example and Comparative Example, 30 breathable packaging materials for oxygen absorbers corresponding to each Example and Comparative Example were prepared, and the air resistance of each was measured). Table 2 shows the air resistance of the breathable packaging material for oxygen absorbers. Specifically, Table 2 shows the average (ave.), maximum (max.), minimum (min.), and standard deviation (σ) of the air resistance obtained from the 30 measurements. The breathable packaging material for oxygen absorbers used for the measurement was a sheet formed by laminating an outer layer and a two-layer composite film before being folded in half to form a small pouch. The measurement of the air resistance of the intermediate layer was performed 30 times for the same intermediate layer. That is, 30 test pieces for measuring the air resistance were taken from the same greaseproof paper used as the intermediate layer in the Examples and Comparative Examples, and the air resistance of each test piece was measured. The average value of the air resistances of the 30 test pieces obtained was taken as the air resistance of the intermediate layer.

[0060] (Melting Point) Using the following apparatus, a DSC curve was obtained upon heating, cooling, and reheating under the following conditions. The melting point was determined as the apex temperature of the melting peak in accordance with "9.1 Determination of Melting Temperature" of JIS K7121:2012. Apparatus: DSC-60, manufactured by Shimadzu Corporation. Conditions: The temperature was increased from 60°C to 200°C at 10°C / min, then decreased from 200°C to 70°C at 10°C / min, and then increased from 70°C to 160°C at 5°C / min.

[0061] (Oxygen Absorption Performance) The oxygen absorption performance was evaluated by the following method (2) using an oxygen absorber package prepared by the following method (1). The preparation method and evaluation method of the oxygen absorber package will be described in detail below.

[0062] (1) Preparation of Oxygen Absorber Packages 1.4 g of oxygen absorber (an iron-based self-reacting oxygen absorber containing iron powder, calcium chloride, sodium chloride, water-impregnated diatomaceous earth, and activated carbon) was filled into the breathable packaging material for oxygen absorbers (small pouches with outer dimensions of 40 mm x 40 mm) obtained in the Examples and Comparative Examples, and one open side was heat-sealed to close the pouch, thereby obtaining oxygen absorber packages. Thirty oxygen absorber packages were prepared in this manner for each Example and Comparative Example. The prepared oxygen absorber packages were stored in a gas-barrier bag with low oxygen permeability (made by Fukusuke Kogyo Co., Ltd., laminated with barrier nylon and LLDPE) with the opening heat-sealed to prevent reaction with atmospheric oxygen until they were used to measure the oxygen absorption capacity.

[0063] (2) Evaluation The obtained oxygen absorber package was placed in an oxygen barrier bag (size: 180 mm x 250 mm, oxygen permeability: 0.53 mL / m) together with 250 mL of air. ２ The oxygen barrier bag was sealed in a 24-hour pressure of MPa or less (Mocon method, 20°C, 65% RH). The sealed oxygen barrier bag was then promptly placed in a constant temperature bath at 25°C. Thereafter, the oxygen concentration in the oxygen barrier bag was measured sequentially every 8 hours, and the change in oxygen concentration was plotted. The estimated time at which the oxygen concentration in the oxygen barrier bag reached 0.1% by volume or less was evaluated as the oxygen scavenging time. The oxygen concentration was measured automatically using a gas analyzer ("Check Mate 3" manufactured by Mocon Dansensor) by inserting a measuring needle into the oxygen barrier bag through a sampling rubber sheet (25mm x 25mm, 2mm thick) previously attached to the surface of the oxygen barrier bag. The above measurement was performed on 30 oxygen absorber packages, and the average (ave.), maximum (max), minimum (min), and standard deviation (σ) of the oxygen scavenging time were evaluated for each oxygen absorber package of each Example or Comparative Example. A shorter oxygen scavenging time means better oxygen absorption performance. Also, a smaller standard deviation (σ) of the oxygen scavenging time means less individual variation and more stable oxygen absorption performance. In this example, an average oxygen scavenging time (ave.) of less than 40 hours was evaluated as good, and a standard deviation (σ) of the oxygen scavenging time of 4.0 or less was evaluated as good.

[0064] [Production of Breathable Packaging Material for Oxygen Absorbers] Example 1 <Outer Layer> The outer layer was a two-layer film that had been perforated as follows. First, polyethylene terephthalate (thickness 12 μm, melting point 265°C; hereinafter referred to as "PET") and low-density polyethylene (thickness 15 μm, melting point 110°C; hereinafter referred to as "PE") were laminated and extrusion-laminated to obtain a two-layer film. Next, the obtained two-layer film was perforated using a needle roll (needle pattern 2.0 mm × 4.0 mm) so as to penetrate from the surface of the PET to the PE, forming external ventilation holes.

[0065] <Intermediate layer> The intermediate layer is an oil-resistant paper impregnated with a starch-based oil-resistant agent (air resistance 911 seconds, basis weight 35 g / m) as an oil-resistant paper that does not use a fluorine-containing oil-resistant agent. ２ (hereinafter referred to as "greaseproof paper 35").

[0066] <Inner layer> The inner layer was a film made of linear low-density polyethylene (HR543, manufactured by Sky Films Co., Ltd., thickness 30 μm). The film made of linear low-density polyethylene was coated with a needle roll (needle pattern 2.0 mm × 2.0 mm, 44 holes / cm) having metal needles (metal needle diameter 0.6 mm) heated to 350°C. 2 ) was pressed against the inner layer to form through holes H1, thereby obtaining an inner layer.

[0067] <Breathable Packaging Material> First, the inner layer and the intermediate layer were laminated so that the surface of the inner layer facing the tip of the needle roll when the through-holes H1 were formed faced the intermediate layer, and the surface of the inner layer facing the base of the needle roll when the through-holes H1 were formed faced the interior (opposite the intermediate layer). Then, they were heat-laminated at 200°C to achieve full-surface welding, resulting in a two-layer composite film. The outer layer and the two-layer composite film were then cut to the product dimensions, and the PE side of the outer layer and the intermediate layer side of the two-layer composite film were laminated facing each other. Then, they were heat-laminated at 200°C to achieve full-surface welding. The outer layer and the two-layer composite film were folded in half with the inner layer facing inward, and two sides were welded at 200°C to a width of 6 mm to obtain a breathable packaging material for oxygen absorbers. The resulting breathable packaging material for oxygen absorbers was in the form of a small pouch with outer dimensions of 40 mm x 40 mm, one side of which was an opening. The obtained breathable packaging material for oxygen absorbers had a layer structure of outer layer (PET / PE) / middle layer (greaseproof paper 35) / inner layer (LLDPE 30). The through-holes H1 formed in the inner layer of the obtained breathable packaging material for oxygen absorbers had an opening diameter φ1 of 351 μm. The oxygen absorption performance of the obtained breathable packaging material for oxygen absorbers was evaluated. The results are shown in Table 2.

[0068] Examples 2 to 3 and Comparative Examples 1 to 4 Breathable packaging materials for oxygen absorbers were obtained in the same manner as in Example 1, except that the inner layer was changed from HR543 to a film made of a linear low-density polyethylene shown in Table 1. The oxygen absorption performance of the obtained breathable packaging materials for oxygen absorbers was evaluated. The results are shown in Table 2.

[0069]

[0070]

[0071] As shown in Table 2, the oxygen absorber packages obtained using the breathable packaging materials for oxygen absorbers of the Examples have a small standard deviation of the oxygen absorbing time, which indicates that there is no variation in the packaging material, there is little individual variation, and they can exhibit stable oxygen absorbing performance. Furthermore, the oxygen absorber packages obtained using the breathable packaging materials for oxygen absorbers of the Examples have a short average oxygen absorbing time, which indicates that they have excellent oxygen absorbing performance. Thus, it can be seen that the breathable packaging material for oxygen absorbers of the present invention is a breathable packaging material for oxygen absorbers that can produce oxygen absorber packages with a short oxygen absorbing time, excellent oxygen absorbing performance, little individual variation, and stable oxygen absorbing performance, using existing manufacturing equipment and manufacturing conditions, without using special manufacturing equipment.

Claims

1. A breathable packaging material for an oxygen absorber comprising, in this order, an outer layer containing a thermoplastic resin, an intermediate layer containing one or more selected from paper and nonwoven fabric, and an inner layer containing linear low-density polyethylene, the inner layer having through holes H1 and an opening diameter φ1 of the through holes H1 being 150 μm or more and 3000 μm or less, and when differential scanning calorimetry is performed on the inner layer as a measurement sample under the conditions of heating from 50°C to 200°C at 10°C per minute (heating 1) in a nitrogen atmosphere, cooling from 200°C to 50°C at 10°C per minute (heating 1), and then heating again from 50°C to 200°C at 10°C per minute (heating 2), the maximum endothermic peak during the process (heating 2) is 120°C or more.

2. The breathable packaging material for an oxygen absorber according to claim 1, wherein the intermediate layer comprises a fluorine-free greaseproof paper.

3. The breathable packaging material for oxygen absorbers according to claim 1 or 2, which has an air resistance of 10,000 seconds or more as measured by an Oken testing machine method in accordance with JIS P8117:2009.

4. The density of the through holes H1 is 1 hole / cm ２ More than 60 holes / cm ２ The breathable packaging material for an oxygen absorber according to any one of claims 1 to 3, which is as follows:

5. The breathable packaging material for oxygen absorbers according to any one of claims 1 to 4, wherein the intermediate layer has an air resistance of 2000 seconds or less as measured by an Oken type testing machine method conforming to JIS P8117:2009.

6. The breathable packaging material for an oxygen absorber according to any one of claims 1 to 5, wherein the intermediate layer is a fluorine-free greaseproof paper.

7. The breathable packaging material for an oxygen absorber according to any one of claims 1 to 6, wherein the outer layer comprises, facing the intermediate layer, a base layer containing one or more selected from polyethylene terephthalate and biaxially oriented polypropylene, and a welding layer containing one or more selected from polyethylene and ethylene copolymers, in this order.

8. An oxygen absorber package comprising the breathable packaging material for an oxygen absorber according to any one of claims 1 to 7, and an oxygen absorber wrapped in the breathable packaging material for an oxygen absorber.

9. A method for producing a breathable packaging material for an oxygen absorber, comprising the steps of: pressing a heated metal needle against a film containing linear low-density polyethylene to form a through hole H1 to obtain an inner layer; and laminating an outer layer containing a thermoplastic resin, an intermediate layer containing one or more types selected from paper and nonwoven fabric, and the inner layer in this order to obtain a breathable packaging material for an oxygen absorber, wherein the diameter of the metal needle is 0.3 mm or more and 2.0 mm or less, the surface temperature of the metal needle is 150°C or more and 450°C or less, and when differential scanning calorimetry is performed on the inner layer as a measurement sample under conditions of heating from 50°C to 200°C at 10°C per minute in a nitrogen atmosphere (heating 1), cooling from 200°C to 50°C at 10°C per minute (heating 1), and then heating again from 50°C to 200°C at 10°C per minute (heating 2), the maximum endothermic peak observed during the process (heating 2) is 120°C or more.

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