Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D65/00—Wrappers or flexible covers; Packaging materials of special type or form
  • B65D65/38—Packaging materials of special type or form
  • B65D65/40—Applications of laminates for particular packaging purposes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D81/00—Containers, packaging elements, or packages, for contents presenting particular transport or storage problems, or adapted to be used for non-packaging purposes after removal of contents
  • B65D81/24—Adaptations for preventing deterioration or decay of contents; Applications to the container or packaging material of food preservatives, fungicides, pesticides or animal repellants
  • B65D81/26—Adaptations for preventing deterioration or decay of contents; Applications to the container or packaging material of food preservatives, fungicides, pesticides or animal repellants with provision for draining away, or absorbing, or removing by ventilation, fluids, e.g. exuded by contents; Applications of corrosion inhibitors or desiccators

Definitions

• the present invention relates to a breathable packaging material for oxygen absorbers and a method for producing the same.
• Oxygen absorbers are used to remove oxygen from sealed containers that store various items such as food, beverages, medicines, medical supplies, cosmetics, metal products, and electronic products, which are susceptible to deterioration or alteration due to the effects of oxygen, in order to prevent these items from deteriorating due to oxidation and enable them to be stored for long periods of time.
• Oxygen absorbers are used in various ways depending on the purpose and manner of use, for example, by packaging a powder or tablet oxygen absorber in a packaging material to make a small bag-shaped oxygen absorber package. If this oxygen absorber package is placed in 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, preventing oxidative deterioration of the food or the like.
• Packaging materials for such oxygen absorbers include sheets of resin, paper, nonwoven fabric, etc., and laminates of these.
• Packaging materials with laminated resin layers, paper, or nonwoven fabric layers include packaging materials in which a resin layer with pre-formed ventilation holes is laminated with a paper or nonwoven fabric layer. By using a resin layer with pre-formed ventilation holes, ventilation with the outside is ensured, and the oxygen absorbing performance of the oxygen absorber is effectively exhibited.
• conventional breathable packaging materials for oxygen absorbers have a problem in that the oxygen absorbing time is not stable. One of the reasons for this is thought to be that the air permeability of the breathable packaging material is not stable.
• Patent Document 1 proposes a technique for easily controlling the target value of the air permeability of a breathable packaging material by using a breathable packaging material that has been specially processed.
• Patent Document 1 The special processing proposed in Patent Document 1 requires equipment and conditions suitable for the processing, so existing manufacturing equipment and manufacturing conditions cannot be used as is, which makes the process complicated and places a heavy burden on producers. Therefore, there has been a demand 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 view of the above circumstances, and an object of the present invention is to provide a breathable packaging material for an oxygen absorber, and a manufacturing method thereof, which can provide an oxygen absorber package having a short oxygen absorbing time, excellent oxygen absorbing performance, and stable oxygen absorbing performance with little individual difference, using existing manufacturing equipment and manufacturing conditions, without using any special manufacturing equipment.
• the inventors discovered that the above problems could 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.
• 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 ⁇ 1 of the through holes H1 being 150 ⁇ m or more and 3000 ⁇ m or less, and when the inner layer is used as a measurement sample and differential scanning calorimetry is performed under conditions of heating from 50° C. to 200° C. at 10° C. per minute (heating 1) and then cooling from 200° C. to 50° C. at 10° C.
• 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 a diameter of the metal needle is 0.3 mm or more and 2.0 mm or less, a surface temperature of the metal needle is 150° C. or more and 450° C. or less, and when the inner layer is used as a measurement sample and differential scanning calorimetry is performed under conditions of heating from 50° C.
• heating 1 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 in the process of (heating 2) is 120° C. or more.
• the present invention provides 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.
• the breathable packaging material for an oxygen absorber of the present invention comprises, 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 ⁇ 1 of the through holes H1 being 150 ⁇ m or more and 3000 ⁇ m 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 (heating 1) and then 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.
• the packaging material of the present invention by virtue of the above-mentioned configuration, it is possible to obtain an oxygen absorber package that has a short oxygen absorbing time, excellent oxygen absorption performance, and exhibits stable oxygen absorption performance with little individual variation, using existing manufacturing equipment and manufacturing conditions, without using special manufacturing equipment.
• the reason why the packaging material of the present invention exhibits the above-mentioned effects is not clear, but the following reasons are thought to be the cause.
• the inner layer of the packaging material of the present invention contains linear low-density polyethylene.
• Linear low-density polyethylene has the characteristics of a narrow molecular weight distribution, few branched chains, and a large molecular weight, and is considered to have good crystallinity, and therefore, when a hole-opening process is performed using a hot needle, through-holes having nearly circular openings can be obtained. Furthermore, since the polyethylene film has good crystallinity and the maximum endothermic peak in the DSC curve obtained by differential scanning calorimetry is 120°C or higher, the part away from the needle, which is the heat source, can immediately return to its rigid state, so that the polyethylene film does not unnecessarily stretch and through-holes can be obtained that follow the shape of the needle. From the above, it is considered that the obtained oxygen absorber package has stable breathability with little individual difference, has short oxygen absorption time, is excellent in oxygen absorption performance, and exhibits stable oxygen absorption performance with little individual difference.
• the air permeability resistance of the breathable packaging material for oxygen absorbers of the present invention is preferably 10,000 seconds or more, more preferably 11,000 seconds or more, and even more preferably 13,000 seconds or more, as measured by the Oken type testing machine method in accordance with JIS P8117: 2009.
• the air permeability resistance of the breathable packaging material for oxygen absorbers of the present invention 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, as measured by the Oken type testing machine method in accordance with JIS P8117: 2009.
• the air resistance is an average value of 30 measurements 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.
• the outer layer is a layer containing a thermoplastic resin.
• the outer layer is preferably a layer in which the outer air hole H2 is formed.
• the outer layer may be a single layer film or a multilayer film having two or more layers made of different materials. Since the outer layer and the intermediate layer are preferably bonded to each other by thermal lamination, the outer layer is preferably a multi-layer film made of two or more thermoplastic resins having a large difference in melting point.
• the insulating film includes, in order toward the intermediate layer, a base layer made of a thermoplastic resin having a high melting point and a welding layer made of a thermoplastic resin having a low melting point.
• thermoplastic resin preferably used for the base layer examples include polyethylene terephthalate, biaxially oriented polypropylene, and nylon, and more preferably, one or more selected from polyethylene terephthalate and biaxially oriented polypropylene.
• the thermoplastic resin preferably used in the welding layer preferably contains a material having heat sealability.
• the thermoplastic resin preferably used in the welding layer includes polyethylene such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear (linear) low-density polyethylene; ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene- ⁇ -olefin copolymer polymerized using a metallocene catalyst, ethylene-methyl methacrylate copolymer, and ethylene-propylene copolymer; polypropylene; ionomer resin; methylpentene polymer; polybutene polymer; acid-modified polyolefin resin obtained by modifying a polyolefin resin such as polyethylene or polypropylene with an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, and itac
• the outer layer preferably includes, 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.
• a base layer containing one or more selected from polyethylene terephthalate and biaxially oriented polypropylene
• a welding layer containing one or more selected from polyethylene and ethylene copolymers.
• the difference in melting point between the thermoplastic resin of the inner layer and the thermoplastic resin of the outer layer is large, since this increases the degree of freedom in the heat sealing conditions (temperature, pressure, time).
• the outer layer may further contain other components besides the thermoplastic resin, as long as the effects of the present invention are not impaired.
• 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.
• the thickness of the outer layer is not particularly limited, but is preferably 1 to 50 ⁇ m, more preferably 2 to 40 ⁇ m, even more preferably 4 to 35 ⁇ m, and even more preferably 8 to 30 ⁇ m.
• a packaging material with sufficient strength can be obtained, and at the same time, a packaging material with the appropriate flexibility required for processing such as folding in the production of the oxygen absorber package described below can be obtained.
• the outer layer can be printed or drawn on by gravure printing, etc.
• the outer layer is preferably a layer in which the outer air hole H2 is formed.
• the external ventilation hole H2 is a hole penetrating 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 in the same place. "In the same place” refers to a state in which a part 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.
• the diameter or hole density of the external ventilation holes H2 can be adjusted as appropriate so that the desired breathability (air permeability) is obtained for the breathable packaging material as a whole.
• the method of forming the external ventilation holes H2, their shape, hole diameter, etc. can be adjusted as appropriate under the conditions described below for the through holes H1 in the inner layer.
• the intermediate layer is a layer containing at least one material selected from paper and nonwoven fabric, and serves to impart a certain degree of durability, breathability, etc. to the packaging material, while preventing leakage of the oxygen absorber contained in the oxygen absorber package.
• the intermediate layer is preferably a layer containing greaseproof paper. By containing greaseproof paper, it is possible to impart oil resistance in addition to the above-mentioned properties.
• the material of the paper used in the intermediate layer is not particularly limited, but examples thereof include water-repellent paper, craft paper, wood-free 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, polyester, etc. More specifically, examples of the nonwoven fabric used in the intermediate layer include linear low-density polyethylene (LLDPE)-based nonwoven fabric, polyethylene terephthalate-based nonwoven fabric, composite nonwoven fabric (polyethylene terephthalate-polyethylene sheath-core structure, etc.), TYVEK (registered trademark, manufactured by Asahi DuPont Flashspan Products Co., Ltd.), etc.
• LLCPE linear low-density polyethylene
• polyethylene terephthalate-based nonwoven fabric polyethylene terephthalate-based nonwoven fabric
• composite nonwoven fabric polyethylene terephthalate-polyethylene sheath-core structure, etc
• the middle layer preferably comprises greaseproof paper. Since oxygen absorber packages are used for a wide range of items such as food, beverages, medicines, medical products, cosmetics, metal products, and electronic products, they may contain a lot of moisture, oil, etc., depending on the object to be stored and the storage environment. In such cases, moisture or oil may penetrate from the packaging material into the oxygen absorber, degrading the oxygen absorber and reducing its oxygen scavenging performance, or contaminating the oxygen absorber, but by providing an intermediate layer containing greaseproof paper, it is possible to suppress the penetration of moisture, oil, etc., and prevent the oxygen absorber from degrading or contaminating.
• grease-resistant paper refers to paper or nonwoven fabric that has been given oil resistance.
• the method for imparting oil resistance includes (1) a method of making the paper or nonwoven fabric oil-resistant by tightening the mesh, (2) a method of forming an oil-resistant film 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 that has oil resistance into the paper or nonwoven fabric.
• the intermediate layer preferably contains grease-resistant paper that does not contain fluorine. More preferably, the grease-resistant paper of the intermediate layer does not contain fluorine. Even more preferably, the intermediate layer is a grease-resistant paper that does not contain fluorine.
• the grease-resistant paper that does not contain fluorine is a grease-resistant paper (non-fluorine-based grease-resistant paper) in which oil resistance is imparted to paper or nonwoven fabric without using a fluorine-containing grease-resistant agent.
• non-fluorine-based grease-resistant paper is not particularly limited as long as it does not contain fluorine and has a certain degree of oil resistance, and any known grease-resistant paper can be used.
• the paper or nonwoven fabric is made oil-resistant by tightening the mesh
• the paper or nonwoven fabric is coated with a non-fluorine-based grease-resistant agent having oil resistance or a non-fluorine-based agent that solidifies oil to form an oil-resistant film
• the paper or nonwoven fabric is impregnated with a non-fluorine-based grease-resistant agent having oil resistance (impregnated or added).
• the grease-resistant paper (3) above is preferred from the viewpoint of preventing oil stains (oil penetration) into the oxygen absorber package caused by oil penetrating from the outer edge of the oxygen absorber package or the inside (inner side surface) of the external vent hole H2 provided as required through the intermediate layer into the inside of the internal through hole H1.
• non-fluorine-based oil-resistant agents include starch-based oil-resistant agents, acrylic-based oil-resistant agents, and polyester-based oil-resistant agents.
• 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 , and even 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.
• the intermediate layer preferably has an air resistance of 2000 seconds or less, more preferably 1000 seconds or less, as measured by an Oken tester method in accordance with JIS P8117: 2009. There is no lower limit to the air resistance, but the air resistance is usually 100 seconds or more.
• the air resistance is an average value of 30 measurements 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.
• the intermediate layer may contain components other than those constituting the paper, nonwoven fabric, and grease-resistant paper.
• 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 is composed only of grease-resistant paper.
• the thickness of the intermediate layer is not particularly limited, but is preferably 5 to 300 ⁇ m, more preferably 15 to 200 ⁇ m, and even more preferably 30 to 150 ⁇ m. By keeping the thickness of the intermediate layer within the above range, sufficient oil resistance and durability can be obtained.
• the inner layer is a layer containing linear low density polyethylene.
• the inner layer has through holes H1, and the opening diameter ⁇ 1 of the through holes H1 is 150 ⁇ m or more and 3000 ⁇ m or less.
• 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), 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) in a nitrogen atmosphere, the maximum endothermic peak during the process (heating 2) is 120° C. or more.
• the inner layer may further contain other components in addition to the linear low-density polyethylene.
• Other components that can be used in the inner layer include additives such as stabilizers, lubricants, antistatic agents, anti-fogging agents, fillers, colorants, plasticizers, and nucleating agents.
• the inner layer may contain a thermoplastic resin other than the linear low density polyethylene. However, from the viewpoint of heat sealability, it is preferable that the inner layer does not substantially contain any other thermoplastic resin than the linear low density polyethylene.
• the content of the linear low density polyethylene contained 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 even more preferably 95% by mass or more, and may be 100% by mass or less, based on the total amount of the resin in the inner layer.
• 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- ⁇ -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,
• the thickness of the inner layer is not particularly limited, but is preferably 0.5 to 80 ⁇ m, more preferably 1 to 60 ⁇ m, even more preferably 2 to 50 ⁇ m, and particularly preferably 4 to 40 ⁇ m. By keeping the thickness of the inner layer within the above range, sufficient adhesive strength can be obtained with short heat sealing times.
• Using the inner layer as a measurement sample means that all components (linear low-density polyethylene or resin composition) including the thermoplastic resin containing linear low-density polyethylene and other components (additives) constituting the inner layer are used as a sample for differential scanning calorimetry (DSC).
• 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).
• 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.”
• 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.
• the inner layer has through holes H1, and the opening diameter ⁇ 1 of the through holes H1 is 150 ⁇ m or more and 3000 ⁇ m or less.
• the through hole H1 is a hole that penetrates the inner layer.
• the diameter or opening density of the internal through holes H1 can be adjusted as appropriate so that the desired breathability (air permeability) is obtained for the entire packaging material. Specifically, when a blade or needle is used, it can be adjusted by its shape, penetration direction, arrangement, number, etc., and when a laser or electron beam is used, it can be adjusted by the perforation conditions such as the irradiation voltage, current, irradiation time, irradiation direction, etc.
• 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, etc. in the cross section (surface along the inner layer surface), but it is preferable that the longitudinal section (cut surface perpendicular to the inner layer surface) has a shape that tapers from the inner layer outer surface (surface not in contact with the intermediate layer) toward the intermediate layer side, or from the intermediate layer side toward the inner layer outer surface.
• the shape of the through hole H1 has a tapered shape such as an approximately conical shape (conical, truncated conical shape) or an approximately pyramidal shape (pyramidal, truncated pyramidal shape) from the inner layer outer surface toward the intermediate layer side, or from the intermediate layer side toward the inner layer outer surface.
• a tapered shape such as an approximately conical shape (conical, truncated conical shape) or an approximately pyramidal shape (pyramidal, truncated pyramidal shape) from the inner layer outer surface toward the intermediate layer side, or from the intermediate layer side toward the inner layer outer surface.
• the through hole H1 has an opening diameter ⁇ 1 (also simply referred to as diameter ⁇ 1) of 150 ⁇ m to 3000 ⁇ m.
• the diameter ⁇ 1 of the through hole H1 can be measured by the method described in the Examples, and is the dimension (major axis) of the longest part of the opening diameter. From the viewpoint of breathability and productivity, the diameter ⁇ 1 of the through hole H1 is 150 ⁇ m or more and 3000 ⁇ m or less, preferably 200 ⁇ m or more and 2000 ⁇ m or less, more preferably 300 ⁇ m or more and 1000 ⁇ m or less, and even more preferably 300 ⁇ m or more and 800 ⁇ m or less.
• the through holes have a tapered shape, from the viewpoints of breathability and productivity, it is more preferable that the opening diameters of the surface of the inner layer that is in contact with the intermediate layer and the surface that is not in contact with the intermediate layer are both within the above ranges.
• the density of the through holes H1 is preferably 1 hole/cm2 or more and 60 holes/cm2 or less, more preferably 2 holes/cm2 or more and 60 holes/cm2 or less, and even more preferably 5 holes/ cm2 or more and 60 holes/cm2 or less.
• the method for producing the breathable packaging material for an oxygen absorber is not particularly limited, but the following method is preferable.
• the method for producing the breathable packaging material for an oxygen absorber of the present invention includes 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 at least one 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, and the surface temperature of the metal needle is 150° C.
• the inner layer is obtained by pressing a heated metal needle against a film containing linear low density polyethylene to form through holes H1.
• the opening process for forming the through hole H1 is preferably a method of pressing a heated metal needle against a film containing linear low-density polyethylene to open the opening.
• the diameter of the metal needle may be any diameter that can open the opening so as to satisfy the opening diameter ⁇ 1, but is preferably 0.3 mm or more and 2.0 mm or less, more preferably 0.3 mm or more and 1.0 mm or less, and even more preferably 0.5 mm or more and 0.7 mm or less.
• the surface temperature of the metal needle is preferably 150 ° C. or more and 450 ° C.
• the opening process can be performed more stably.
• a method of perforating the material through a cylindrical jig having needles attached to the side (hereinafter also referred to as a "needle roll") is more preferable.
• the needle pattern can be appropriately adjusted taking into consideration the air permeability, etc.
• the diameter of the through hole H1 can be controlled by the jig used for the hole opening process, the formation direction, etc.
• the longitudinal 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 is tapered to an approximately conical shape (cone-shaped, truncated cone-shaped, etc.).
• the maximum endothermic peak observed during the process (heating increase 2) was 120° C. or higher.
• 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.
• an outer layer containing a thermoplastic resin, an intermediate layer containing at least one material 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.
• laminate in this order refers to the layer structure of the resulting packaging material, and does not indicate the order of the lamination process.
• 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 the three layers may be laminated simultaneously.
• the following describes, as an example, a method in which the intermediate layer and the inner layer are laminated in advance, but as described above, the order is not limited to this.
• the method for laminating the inner layer and intermediate layer is not particularly limited, and any known method can be used.
• it may be thermal lamination or 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.
• the method for laminating the outer layer onto the laminate including the inner layer and intermediate layer is not particularly limited, and any known method can be used.
• it may be thermal lamination or 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.
• partial welding is preferable from the viewpoint of improving breathability.
• a packaging material in which the intermediate layer and the outer layer are partially welded it is considered that gas can move from the through hole H1 of the inner layer through the gap between the intermediate layer and the outer layer to the external ventilation hole H2 penetrating the outer layer, thereby further improving the breathability of the packaging material.
• the method of partial welding is not particularly limited, and known methods can be adopted, such as a method of welding using a heat roll having a pattern such as a lattice pattern or a dot pattern. Among them, a lattice pattern is preferable from the viewpoint of improving adhesiveness.
• the welding rate of partial welding (area rate (%) of the area of the welded part in the area of the entire partially welded region) is, for example, 50% or less, preferably 30% or less, more preferably 20% or less from the viewpoint of improving breathability, and is preferably 8% or more, more preferably 12% or more from the viewpoint of improving adhesiveness.
• the through hole H1 of the inner layer and the external air vent H2 are not in the same place.
• “In the same place” refers to a state in which a part of the through hole H1 of the inner layer is visible when the external air vent H2 is viewed from the surface of the outer layer.
• the packaging material of the present invention is suitably used for producing an oxygen absorber package.
• the 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 manufactured using existing manufacturing equipment and conditions without using special manufacturing equipment, and exhibits stable breathability with little individual variation, so that the oxygen absorber package obtained using this has a short oxygen absorbing time, excellent oxygen absorption performance, and exhibits stable oxygen absorption performance with little individual variation.
• the method of packaging the 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 and environment of use. For example, it is preferable to wrap the oxygen absorber so that it is in contact with the inner layer of the packaging material.
• 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 polymeric compounds with 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 powders such as iron powder with a metal catalyst, water, a metal salt, and a carrier.
• the form of the oxygen absorber is not particularly limited, and a suitable form can be adopted in consideration of the application and environment of use.
• it may be in powder form, or may be molded into tablets or the like. If it is in powder form, it is preferable to adjust the size and shape of the holes, as well as the layer structure, so that the powder does not leak out from the through holes H1 and external ventilation holes H2 in the inner layer.
• the inner layer used in the examples and comparative examples was punched out into a circular shape having a diameter of 4 mm to prepare a measurement sample.
• Air permeability resistance The air permeability 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 value of the measurable range was 2000.
• the measurement of the air permeability resistance of the breathable packaging material for oxygen absorbers was carried out 30 times for each of the same packaging materials obtained by the method described in each Example and Comparative Example (i.e., for each Example and Comparative Example, 30 pieces of breathable packaging materials for oxygen absorbers corresponding to each Example and Comparative Example were prepared, and the air permeability resistance of each of them was measured).
• Table 2 shows the air permeability resistance of the breathable packaging material for oxygen absorbers.
• the breathable packaging material for oxygen absorbers used for the measurement was a sheet-like material in which the outer layer and the two-layer composite film were laminated before being folded in half to form a small bag shape.
• 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 resistance of the obtained 30 test pieces was taken as the air resistance of the intermediate layer.
• the oxygen absorbing performance was evaluated by the following method (2) using the 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.
• oxygen absorber package The breathable packaging material for oxygen absorbers (small pouches with outer dimensions of 40 mm ⁇ 40 mm) obtained in the Examples and Comparative Examples was filled with 1.4 g of oxygen absorber (iron-based self-reacting oxygen absorber containing iron powder, calcium chloride, sodium chloride, diatomaceous earth impregnated with water, and activated carbon), and one open side was closed by heat sealing to obtain an oxygen absorber package. As described above, 30 oxygen absorber packages were prepared for each of the Examples and Comparative Examples.
• oxygen absorber iron-based self-reacting oxygen absorber containing iron powder, calcium chloride, sodium chloride, diatomaceous earth impregnated with water, and activated carbon
• the prepared oxygen absorber package was stored in a gas barrier bag with low oxygen permeability (manufactured by Fukusuke Kogyo Co., Ltd., laminated with barrier nylon and LLDPE) with the opening heat sealed to prevent reaction with oxygen in the air until it was used to measure the amount of oxygen absorbed.
• a gas barrier bag with low oxygen permeability manufactured by Fukusuke Kogyo Co., Ltd., laminated with barrier nylon and LLDPE
• the obtained oxygen absorber package was placed in an oxygen barrier bag (size 180 mm x 250 mm, oxygen permeability 0.53 mL/ m2 ⁇ 24 h ⁇ MPa or less (Mocon method, 20°C, 65% RH)) together with 250 mL of air and sealed.
• the sealed oxygen barrier bag was then immediately placed in a thermostatic chamber 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 became 0.1% by volume or less was evaluated as the deoxidation 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 (25 mm x 25 mm, thickness 2 mm) that had been previously attached to the surface of the oxygen barrier bag.
• the above measurements were carried out on 30 oxygen absorber packages, and the average value (ave.), maximum value (max), minimum value (min), and standard deviation ( ⁇ ) of the oxygen absorbing time were evaluated for each oxygen absorber package of each Example or Comparative Example.
• the shorter the deoxidation time the better the oxygen absorption performance.
• the standard deviation ( ⁇ ) of the deoxidation time the smaller the individual difference and the more stable the oxygen absorption performance.
• an average deoxidation time (ave.) of less than 40 hours was evaluated as good, and a standard deviation ( ⁇ ) of the deoxidation time of 4.0 or less was evaluated as good.
• Example 1 ⁇ Outer layer> The outer layer used was a two-layer film that had been subjected to the following perforation treatment.
• PET polyethylene terephthalate
• PE low-density polyethylene
• PE needle roll
• the inner layer was a film made of linear low-density polyethylene (HR543, manufactured by Sky Films, Inc., thickness 30 ⁇ m).
• a needle roll (needle pattern 2.0 mm ⁇ 2.0 mm, 44 holes/cm 2 ) having metal needles (metal needle diameter 0.6 mm) heated to 350° C. was pressed against the linear low density polyethylene film to form through holes H1, obtaining an inner layer.
• ⁇ 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 hole H1 was formed faced the intermediate layer, and the surface of the inner layer facing the base of the needle roll when the through hole H1 was formed faced the inside (the opposite side to the intermediate layer), and then thermally laminated at 200°C to weld the entire surface, thereby obtaining a two-layer composite film. Thereafter, the outer layer and the two-layer composite film were cut to the product dimensions, and then the PE side of the outer layer and the intermediate layer side of the two-layer composite film were laminated facing each other and thermally laminated at 200°C to weld the entire surface.
• 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 a width of 6 mm at 200° C. to obtain a breathable packaging material for an oxygen absorber.
• the obtained breathable packaging material for an oxygen absorber was in the form of a small pouch with outer dimensions of 40 mm ⁇ 40 mm and one side being an opening.
• the obtained breathable packaging material for an oxygen absorber had a layer structure of outer layer (PET/PE)/middle layer (greaseproof paper 35)/inner layer (LLDPE 30).
• the through hole H1 formed in the inner layer of the obtained breathable packaging material for an oxygen absorber had an opening diameter ⁇ 1 of 351 ⁇ m.
• the oxygen absorbing performance of the obtained breathable packaging material for oxygen absorbers was evaluated. The results are shown in Table 2.
• Examples 2 to 3 and Comparative Examples 1 to 4 A breathable packaging material for an oxygen absorber was obtained in the same manner as in Example 1, except that the inner layer was changed from HR543 to a film made of linear low-density polyethylene as shown in Table 1. The oxygen absorption performance of the obtained breathable packaging material for an oxygen absorber was evaluated. The results are shown in Table 2.
• the oxygen absorber package obtained using the breathable packaging material for oxygen absorbers of the embodiment has a small standard deviation of the oxygen absorption time, which shows that there is no variation in the packaging material, there is little individual difference, and it can exhibit stable oxygen absorption performance. Furthermore, the oxygen absorber package obtained using the breathable packaging material for oxygen absorbers of the embodiment has a short average oxygen absorption time, which shows that it has excellent oxygen absorption performance.
• the breathable packaging material for oxygen absorbers of the present invention is a breathable packaging material for oxygen absorbers that can obtain an oxygen absorber package that has a short oxygen absorption time, excellent oxygen absorption performance, little individual difference, and can exhibit stable oxygen absorption performance, without using special manufacturing equipment, using existing manufacturing equipment and manufacturing conditions.

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