oxygen absorbent

Abstract

The present invention relates to an oxygen absorbent. An oxygen absorbent comprising: a liquid oligomer having an unsaturated group, an oxygen absorption promoting substance, a carrier for supporting the liquid oligomer having an unsaturated group and the oxygen absorption promoting substance, an inorganic gas adsorbing particle, and activated carbon, the amount of the liquid oligomer having an unsaturated group adsorbed to the inorganic gas adsorbing particle being 6.5 parts by mass or less relative to 100 parts by mass of the inorganic gas adsorbing particle.

Description

[0001] This application is a divisional application of Chinese patent application No. 202280028383.6, filed on April 11, 2022, entitled "Oxygen Absorber". Technical Field

[0002] This invention relates to oxygen absorbers. Background Technology

[0003] As a preservation technique for food, pharmaceuticals, etc., methods using oxygen absorbers are known. In this method, the item to be preserved and the oxygen absorber are sealed inside an airtight container, allowing the oxygen absorber to absorb oxygen from the sealed container, effectively maintaining an oxygen-free atmosphere within the container. For the oxygen absorber to function, it needs to be small in size and absorb a large amount of oxygen. In other words, an oxygen absorber composition with a high oxygen absorption capacity per unit volume is required.

[0004] Representative deoxidizers include iron-based deoxidizers with iron (iron powder) as the main component and non-iron-based deoxidizers with ascorbic acid, glycerol, etc. as the main components. Among non-iron-based deoxidizers, those that do not require water during oxygen absorption include unsaturated hydrocarbons, unsaturated hydrocarbon compounds, unsaturated fatty acids, and unsaturated fatty acid compounds such as oils and fats.

[0005] This moisture-free oxygen absorber can be used not only for food preservation, but also for the preservation of metal parts, electronic parts, electrical parts, precision parts, magnetic / optical parts, jewelry, weapons, aircraft, automobiles, glass products, rubber products, photographic films, medicines, compressed dried flowers, paintings, ancient documents, cultural relics, etc.

[0006] For example, in Patent Document 1, in order to obtain an oxygen-absorbing composition with high oxygen absorption capacity, easy manufacturing, and low gas generation or odor, an oxygen-absorbing composition is disclosed, which is formed by an oxygen absorber and a gas absorbent. The oxygen absorber is a liquid hydrocarbon oligomer with unsaturated groups of a specific molecular weight and viscosity as the main agent, and is obtained by loading a carrier containing the main agent and an oxygen-absorbing promoting substance.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 10-113555 Summary of the Invention

[0010] The problem the invention aims to solve

[0011] Patent Document 1 discloses an oxygen-absorbing composition that requires no moisture and has minimal odor. However, pharmaceuticals, medical supplies, and hygiene products are used directly and for extended periods on the human body, or come into contact with the face. Therefore, the oxygen-absorbing agents used in their storage require extremely high odorlessness, exceeding that of the oxygen-absorbing composition disclosed in Patent Document 1. Furthermore, pharmaceuticals, medical supplies, and hygiene products require strict management of their storage environment, thus necessitating even higher oxygen absorption capacity.

[0012] Therefore, the problem that this invention aims to solve is to provide an oxygen absorber that has excellent oxygen absorption performance without the need for water and can suppress the generation of odors.

[0013] Solution for solving the problem

[0014] The inventors have discovered that the following oxygen absorber can solve the aforementioned problems. The oxygen absorber contains: a liquid oligomer having unsaturated groups, an oxygen-absorbing substance, a carrier, gas-absorbing inorganic particles, and activated carbon, and the liquid oligomer having unsaturated groups and the gas-absorbing inorganic particles adsorbed onto the aforementioned gas-absorbing inorganic particles are in a specific ratio.

[0015] This invention relates to oxygen absorbers, their manufacturing methods, and oxygen absorber packaging.

[0016] <1> An oxygen absorber comprising: a liquid oligomer having unsaturated groups, an oxygen-absorbing promoting substance, a carrier for loading the aforementioned liquid oligomer having unsaturated groups and the oxygen-absorbing promoting substance, gas-absorbing inorganic particles, and activated carbon.

[0017] The amount of the liquid oligomer with unsaturated groups adsorbed onto the aforementioned gas-absorbing inorganic particles is 6.5 parts by mass or less relative to 100 parts by mass of the gas-absorbing inorganic particles.

[0018] <2> According to the above <1> The oxygen absorber, wherein the aforementioned gas-absorbing inorganic particles are selected from at least one of the group consisting of silicates, oxides of alkaline earth metals, and hydroxides of alkaline earth metals with an average pore size of 1 to 150 Å.

[0019] <3> According to the above <1> or <2> The oxygen absorber, wherein the aforementioned gas-absorbing inorganic particles are silica gel.

[0020] <4> According to the above <1> ~ <3> The oxygen absorber according to any one of the following methods, wherein the aforementioned oxygen-absorbing promoting substance is at least one selected from the group consisting of transition metal salts and free radical initiators.

[0021] <5> According to the above <1> ~ <4> The oxygen absorber according to any one of the following methods, wherein the aforementioned carrier is a silicate with an average pore size of 200 to 5000 Å.

[0022] <6>The oxygen absorber according to any one of <1> to <5> above, wherein the liquid oligomer having an unsaturated group is at least one selected from the group consisting of liquid butadiene-based oligomers, liquid isoprene-based oligomers, liquid acetylene-based oligomers, liquid chloroprene-based oligomers, liquid unsaturated polyester resins, and natural rubber.

[0023] <7>The oxygen absorber according to any one of <1> to <6> above, which further contains polyethylene powder.

[0024] <8>The oxygen absorber according to any one of <1> to <7> above, wherein the mass ratio [liquid oligomer having an unsaturated group / gas-absorbing inorganic particles] of the liquid oligomer having an unsaturated group in the oxygen absorber to the gas-absorbing inorganic particles in the oxygen absorber is 10 / 90 to 30 / 70.

[0025] <9>A method for manufacturing an oxygen absorber, which is a method for manufacturing the oxygen absorber according to any one of <1> to <8> above. In this manufacturing method, a mixture of a liquid oligomer having an unsaturated group and an oxygen-promoting substance is loaded on a carrier, and then the carrier, gas-absorbing inorganic particles, and activated carbon are mixed to obtain an oxygen absorber.

[0026] <10>An oxygen absorber package, which includes: the oxygen absorber according to any one of <1> to <8> above; and a breathable packaging material that houses the oxygen absorber.

[0027] Effects of the Invention

[0028] The oxygen absorber of the present invention has excellent oxygen absorption performance without the need for moisture and can suppress the generation of odors. Therefore, it is particularly suitable for the preservation of pharmaceuticals, medical supplies, hygiene products, etc. Specific Embodiments

[0029] Hereinafter, an embodiment of the present invention will be described. The content of the present invention is not limited to the embodiments described below.

[0030] It should be noted that in this specification, terms such as "A to B" related to numerical records mean "not less than A and not more than B" (when A < B) or "not more than A and not less than B" (when A > B). In addition, in the present invention, combinations of preferred embodiments are more preferred embodiments.

[0031] [Oxygen Absorber]

[0032] The oxygen absorber of the present invention comprises: a liquid oligomer having unsaturated groups, an oxygen-absorbing promoting substance, a carrier for loading the aforementioned liquid oligomer having unsaturated groups and the oxygen-absorbing promoting substance, gas-absorbing inorganic particles, and activated carbon, wherein the amount of the aforementioned liquid oligomer having unsaturated groups adsorbed on the aforementioned gas-absorbing inorganic particles is 6.5 parts by mass or less relative to 100 parts by mass of the gas-absorbing inorganic particles.

[0033] (Liquid oligomers with unsaturated groups)

[0034] The oxygen absorber of the present invention comprises a liquid oligomer having unsaturated groups. Furthermore, the liquid oligomer having unsaturated groups is loaded onto a carrier described later, and the amount of the aforementioned liquid oligomer having unsaturated groups adsorbed onto the gas-absorbing inorganic particles described later is 6.5 parts by mass or less relative to 100 parts by mass of the gas-absorbing inorganic particles.

[0035] The liquid oligomer with unsaturated groups used in the oxygen absorber of the present invention is preferably at least one selected from the group consisting of liquid butadiene-based oligomers, liquid isoprene-based oligomers, liquid acetylene-based oligomers, liquid chloroprene-based oligomers, liquid unsaturated polyester resins, and natural rubber. Liquid butadiene-based oligomers are more preferred in terms of cost and odor control. These liquid oligomers with unsaturated groups are not necessarily a single substance, but may be a mixture of two or more, or may be copolymerized. Furthermore, small amounts of impurities such as solvents introduced during manufacturing are permissible within the scope of common sense.

[0036] Furthermore, the liquid oligomers with unsaturated groups used in this invention can have substituents other than unsaturated groups, such as halogen groups, hydroxyl groups, carbonyl groups, ether groups, carboxyl groups, and ester groups. For example, they can be replaced by functional groups such as alicyclic hydrocarbon groups, aromatic hydrocarbon groups, hydroperoxy groups, epoxy groups, oxo groups, hydroxymethyl groups, acyl groups, amino groups, imino groups, hypoazolyl groups, nitro groups, nitroso groups, amide groups, imide groups, cyano groups, isocyano groups, cyanoxy groups, isocyanoxy groups, diazo groups, azide groups, hydrazyl groups, azo groups, and heterocyclic groups.

[0037] As for the aforementioned liquid butadiene oligomers, since they do not have side chains, it is preferable to have low viscosity liquid butadiene oligomers with 65% or more of the bonds in their molecular structure being 1,4 bonds (the bonds in the molecular structure can be determined by NMR analysis). Furthermore, it is more preferable to have liquid butadiene oligomers with 65% or more of the 1,4-cis bonds, which are of the same molecular weight and have even lower viscosity.

[0038] Liquid oligomers with unsaturated groups can also be used after being diluted with non-oxygen-absorbing diluents.

[0039] As such a diluent, an organic compound is preferred that does not have easily oxidized functional groups such as unsaturated groups, hydroxyl groups, or aldehyde groups, and that can be mixed with a liquid oligomer containing unsaturated groups to reduce the viscosity of the liquid oligomer containing unsaturated groups. There are no particular limitations on the non-oxygen-absorbing diluent as long as the above conditions are met; examples include straight-chain saturated hydrocarbons such as decane, tridecane, tetradecane, and n-alkanes, alkylcycloalkanes such as liquid paraffin, and naphthenic acids. These non-oxygen-absorbing diluents need not be a single substance and can be a mixture of two or more. The ratio of the non-oxygen-absorbing diluent to the liquid oligomer containing unsaturated groups is preferably in the range of 1000 parts by mass or less of the non-oxygen-absorbing diluent compared to 100 parts by mass of the liquid oligomer containing unsaturated groups.

[0040] The number average molecular weight of liquid oligomers having unsaturated groups is preferably 150 to 4000, more preferably 300 to 3000, and even more preferably 500 to 2500.

[0041] The viscosity of the liquid oligomer with unsaturated groups at 25°C is preferably 100~4000 mPa·s, more preferably 150~2000 mPa·s, and even more preferably 200~1000 mPa·s.

[0042] If the number-average molecular weight and viscosity are within the above range, the oxygen absorption performance is excellent, the manufacturing is easy, and it can also suppress odors.

[0043] The content of liquid oligomers with unsaturated groups in the oxygen absorber is preferably 2 to 40% by mass, more preferably 5 to 30% by mass, and even more preferably 7 to 20% by mass.

[0044] (Oxygen-enhancing substances)

[0045] The oxygen absorber of the present invention contains an oxygen-enhancing substance. Furthermore, the oxygen-enhancing substance is loaded onto a carrier described later.

[0046] Examples of oxygen-promoting substances used in the oxygen absorber of this invention include metal compounds and free radical initiators that promote the oxidation of the aforementioned liquid oligomers having unsaturated groups.

[0047] The oxygen-absorbing substance is preferably at least one of the following groups: free transition metal salt and free radical initiator.

[0048] The transition metal salt is preferably at least one transition metal salt selected from the group consisting of Cu, Fe, Co, Ni, Cr and Mn. If oxygen absorption performance and safety are taken into consideration, it is more preferably at least one transition metal salt selected from the group consisting of Mn and Fe.

[0049] Furthermore, as transition metal salts, inorganic salts such as sulfates, chlorides, and nitrates, as well as organic salts such as fatty acid salts and acetylacetone metal salts, can be used. From the viewpoint of compatibility with the aforementioned liquid oligomers having unsaturated groups, organic salts are preferred, and fatty acid salts are more preferred.

[0050] Examples of free radical initiators include catechols, azo compounds such as 2,2-azobisisobutyronitrile, and peroxides such as benzoyl peroxide.

[0051] Furthermore, the oxygen-absorbing agent is more preferably contained in the oxygen absorber in a state of uniform mixing with the aforementioned liquid oligomer having unsaturated groups.

[0052] Oxygen-absorbing substances can be dissolved or dispersed in a diluent to mix uniformly with liquid oligomers having unsaturated groups.

[0053] As a diluent for diluting this oxygen-absorbing substance, it can be the aforementioned non-oxygen-absorbing diluent or an oil with unsaturated groups. However, in order to improve the affinity with liquid oligomers with unsaturated groups and further improve the oxygen absorption, it is preferable to use an oil with unsaturated groups as a diluent.

[0054] As for oils containing unsaturated groups, unsaturated fatty acids or oils containing unsaturated fatty acids are preferred. Specifically, unsaturated fatty acids such as oleic acid, linoleic acid, linolenic acid, arachidonic acid, octadecanoic acid, dimer acid, or ricinoleic acid, and oils, esters, and metal salts containing these esters, such as linseed oil, soybean oil, tung oil, rice bran oil, sesame oil, cottonseed oil, rapeseed oil, and tall oil, can be used. Additionally, as unsaturated fatty acids, fatty acids obtained from vegetable oils and animal oils can also be used, such as linseed oil fatty acids, soybean oil fatty acids, tung oil fatty acids, rice bran oil fatty acids, sesame oil fatty acids, cottonseed oil fatty acids, rapeseed oil fatty acids, and tall oil fatty acids. Among these, those with low viscosity are easier to mix and are therefore preferred.

[0055] The content of the oxygen-enhancing substance in the oxygen absorber is preferably 0.001 to 0.2% by mass, more preferably 0.005 to 0.1% by mass, and even more preferably 0.01 to 0.06% by mass.

[0056] The amount of oxygen-promoting substance is preferably 0.01 to 2.0 parts by mass, more preferably 0.05 to 1.0 parts by mass, and even more preferably 0.1 to 0.5 parts by mass, relative to 100 parts by mass of liquid oligomers with unsaturated groups in the oxygen absorber.

[0057] In addition, when using a diluent, the concentration of the oxygen-enhancing substance in the solution containing the diluent is preferably 1 to 50% by mass, more preferably 2 to 20% by mass, and even more preferably 3 to 10% by mass.

[0058] (Carrier)

[0059] The oxygen absorber of the present invention contains a carrier. The carrier is used to load the aforementioned liquid oligomer having unsaturated groups and the oxygen-absorbing agent.

[0060] As a carrier, a carrier with a large surface area is preferred, which increases the contact area between the liquid oligomer with unsaturated groups and oxygen. In addition, for the purpose of being able to support a large amount of liquid oligomer with unsaturated groups, a carrier with a large pore size or pore volume and a low packing density is preferred.

[0061] Examples of such carriers include silicates and wood flour with an average pore size of 200 to 5000 Å, with silicates having an average pore size of 200 to 5000 Å being preferred.

[0062] The average pore size of silicates is more preferably 500 to 4000 Å. It should be noted that the average pore size can be determined, for example, by using a commercially available surface area / pore distribution measuring device (such as "BELSORP-max" manufactured by MicrotracBEL Corp.) and according to the BET multi-point method.

[0063] Examples of silicates with an average pore size of 200 to 5000 Å include diatomaceous earth, zeolite, molecular sieve, sepiolite, quartz, porous glass, silica, activated clay, acid clay, and vermiculite, with diatomaceous earth being the preferred material.

[0064] From the perspective of operability and filling properties, the average particle size of the carrier is preferably 0.1 to 5 mm, more preferably 0.5 to 3 mm. It should be noted that the average particle size can be measured, for example, by a commercially available laser diffraction / scattering particle size distribution measuring device ("LA-960" manufactured by Horiba Corporation).

[0065] Furthermore, the bulk density of the carrier is preferably 0.2~1.0 g / mL, more preferably 0.3~0.7 g / mL, and even more preferably 0.4~0.6 g / mL. It should be noted that the bulk density can be determined, for example, according to JIS K6721:1977 (repeated).

[0066] The carrier content in the oxygen absorber is preferably 4-50% by mass, more preferably 10-40% by mass, and even more preferably 14-35% by mass.

[0067] The amount of carrier is preferably 100 to 1000 parts by mass relative to 100 parts by mass of liquid oligomer with unsaturated groups in the oxygen absorber, more preferably 120 to 500 parts by mass, and even more preferably 150 to 250 parts by mass.

[0068] (Gas-absorbing inorganic particles)

[0069] The oxygen absorber of the present invention contains gas-absorbing inorganic particles. These gas-absorbing inorganic particles primarily absorb gases other than oxygen. Specifically, they absorb, before reacting with a liquid oligomer containing unsaturated groups (which is the main agent), highly volatile, low-number-average molecular weight gases contained in the liquid oligomer itself, or gases generated during the oxygen absorption reaction such as hydrogen, carbon monoxide, carbon dioxide, hydrocarbons, aldehydes, ketones, and carboxylic acids, as well as corrosive gases such as hydrogen sulfide and ammonia in a confined atmosphere. In the oxygen absorber of the present invention, the amount of the aforementioned liquid oligomer containing unsaturated groups adsorbed onto the gas-absorbing inorganic particles is 6.5 parts by mass or less per 100 parts by mass of the gas-absorbing inorganic particles.

[0070] Examples of gas-absorbing inorganic particles include silicates, oxides of alkaline earth metals, hydroxides, alumina, polymer adsorbents, sodium sulfate, sodium carbonate, potassium carbonate, soda lime, organic acid salts, and organic amines, all with an average pore size of 1–150 Å.

[0071] Examples of silicates with an average pore size of 1–150 Å include synthetic zeolites such as molecular sieves; natural zeolites such as mordenite and calomel; clay minerals such as pearlite, acid clay, and activated clay; porous glasses such as silica gel; magnesium silicate; aluminum silicate; and caustic soda asbestos. Porous glasses are preferred, and silica gel is more preferred, when considering silicates with an average pore size of 1–150 Å. It should be noted that the average pore size can be determined, for example, using a commercially available surface area / pore distribution measuring device (such as the "BELSORP-max" manufactured by Microtrac BELCO Corp.) and according to the BET multi-point method.

[0072] Examples of oxides of alkaline earth metals include calcium oxide, barium oxide, and magnesium oxide.

[0073] Examples of hydroxides include hydroxides of alkaline earth metals, sodium hydroxide, potassium hydroxide, and slaked lime.

[0074] The gas-absorbing inorganic particles are preferably selected from at least one of the group consisting of silicates, oxides of alkaline earth metals, and hydroxides of alkaline earth metals with an average pore size of 1 to 150 Å, more preferably silicates with an average pore size of 1 to 150 Å, even more preferably silicates with an average pore size of 1 to 100 Å, and even more preferably silica gel.

[0075] By using silicates with an average pore size of 1–150 Å, oxygen absorbers suitable for preserving hydrophobic products can be obtained, not only absorbing the aforementioned gases or odors but also absorbing moisture. Furthermore, silica gel is suitable for use due to its robustness, high safety, ease of handling, and good filling properties.

[0076] From the perspective of operability and filling properties, the average particle size of the gas-absorbing inorganic particles is preferably 0.1 to 3 mm, more preferably 0.2 to 1 mm, and even more preferably 0.3 to 0.6 mm. It should be noted that commercially available products can be selected for gas-absorbing inorganic particles with an average particle size within the above range, or they can be graded using sieves according to the desired average particle size. Furthermore, the average particle size can be measured, for example, using a commercially available laser diffraction / scattering particle size distribution measuring device (e.g., "LA-960" manufactured by Horiba Corporation).

[0077] Furthermore, the bulk density of the gas-absorbing inorganic particles is preferably 0.3~1.5 g / mL, more preferably 0.4~1.0 g / mL, and even more preferably 0.5~0.8 g / mL. It should be noted that the bulk density can be determined, for example, according to JIS K6721:1977 (repeated).

[0078] Gas-absorbing inorganic particles do not need to be a single substance; they can also be a mixture of two or more substances.

[0079] The content of gas-absorbing inorganic particles in the oxygen absorber is preferably 5-60% by mass, more preferably 10-50% by mass, and even more preferably 20-40% by mass.

[0080] Some organic components, such as liquid oligomers with unsaturated groups loaded on a carrier, are sometimes adsorbed onto gas-absorbing inorganic particles before the use of a deoxidizing agent. This hinders the odor-suppressing effect of the gas-absorbing inorganic particles; therefore, the amount of the aforementioned liquid oligomers with unsaturated groups adsorbed onto the gas-absorbing inorganic particles is preferably less. The amount of the aforementioned liquid oligomers with unsaturated groups adsorbed onto the gas-absorbing inorganic particles is 6.5 parts by mass or less, preferably 5.9 parts by mass or less, more preferably 4.0 parts by mass or less, further preferably 3.0 parts by mass or less, even more preferably 2.0 parts by mass or less, and even more preferably 1.0 parts by mass or less, relative to 100 parts by mass of the gas-absorbing inorganic particles.

[0081] It should be noted that the amount of the aforementioned liquid oligomer with unsaturated groups adsorbed onto the gas-absorbing inorganic particles can be determined according to the method described in the examples.

[0082] By ensuring the amount of the aforementioned liquid oligomers with unsaturated groups adsorbed onto the gas-absorbing inorganic particles is within the range described above, excellent oxygen absorption performance and suppression of odor generation can be achieved. The reasoning is uncertain, but it is considered as follows: Liquid oligomers with unsaturated groups readily adsorb onto gas-absorbing inorganic particles, but the amount of liquid oligomers with unsaturated groups adsorbed on the odor-adsorbing portion of the gas-absorbing inorganic particles is small, thus sufficiently obtaining the adsorption performance of odor components from the gas-absorbing inorganic particles. Furthermore, it is believed that the amount of components simultaneously adsorbed onto activated carbon is also reduced, which can also sufficiently ensure the adsorption performance of the odor components, and oxygen absorption performance based on the residual liquid oligomers with unsaturated groups is also obtained. Therefore, the aforementioned effects of the present invention are achieved.

[0083] The mass ratio of the aforementioned liquid oligomer with unsaturated groups in the oxygen absorber to the aforementioned gas-absorbing inorganic particles in the oxygen absorber [liquid oligomer with unsaturated groups / gas-absorbing inorganic particles] is preferably 10 / 90 to 30 / 70, more preferably 15 / 85 to 25 / 75.

[0084] (Activated carbon)

[0085] The oxygen absorber of this invention contains activated carbon.

[0086] It is believed that the activated carbon in the oxygen absorber of the present invention has the following functions: suppressing the generation of odors as an effect of the present invention, and promoting the oxidation reaction of the aforementioned liquid oligomers having unsaturated groups.

[0087] Activated carbon can be made from wood, coconut shells, coal, etc., but coconut shell activated carbon is preferred.

[0088] The properties of activated carbon are not particularly limited. From the viewpoint of operability in the manufacture of oxygen absorbers, granular or powdery forms with high flowability are suitable, and those with a near-spherical shape are more preferred. Furthermore, regarding the average particle size of activated carbon, from the viewpoint of operability in the manufacture of oxygen absorbers, granular carbon is preferably 0.01 mm or more and 2 mm or less, more preferably 0.1 mm or more and 1 mm or less. Powdered carbon is preferably 10 μm or more and 1000 μm or less, more preferably 100 μm or more and 500 μm or less. Activated carbon particles with the above-mentioned particle size range can be used, whether primary particles, aggregated particles, or granules. Activated carbon with the above-mentioned particle size range can be used alone, or multiple types with different particle sizes can be mixed in any proportion. It should be noted that the average particle size can be measured using, for example, a commercially available laser diffraction / scattering particle size distribution measuring device (Horiba Manufacturing Co., Ltd. "LA-960").

[0089] The content of activated carbon in the oxygen absorber is preferably 1-40% by mass, more preferably 5-30% by mass, and even more preferably 10-20% by mass.

[0090] (Polyethylene powder)

[0091] In addition to the liquid oligomers with unsaturated groups, oxygen-absorbing substances, carriers, gas-absorbing inorganic particles and activated carbon described above, the oxygen absorber of the present invention may also contain other substances within the scope that does not impair the effects of the present invention.

[0092] The oxygen absorber of the present invention preferably contains polyethylene powder.

[0093] Oxygen absorbers release heat as they absorb oxygen, causing their temperature to rise. Therefore, localized heating, depending on the product being preserved, can lead to spoilage, or even swelling and deformation of the oxygen absorber packaging or container. Polyethylene, having crystalline components and a melting point, is locally deprived of its heat of fusion during melting when added to an oxygen absorber, thus suppressing its exothermic reaction.

[0094] The polyethylene constituting the polyethylene powder is preferably polyethylene with a crystallinity of 50% or more, more preferably polyethylene with a crystallinity of 60% or more, and even more preferably polyethylene with a crystallinity of 65% or more.

[0095] The crystallinity of polyethylene refers to the value calculated by the density method [JIS K6760:1995 (repealed), and Lecture on Polyethylene Resin Plastics Materials, Nikkan Kogyo Shimbun, 22 (1969)].

[0096] Polyethylene is a crystalline polymer. Compared with the amorphous portion, the crystalline portion is structurally more stable. Therefore, higher crystallinity results in higher density, which is preferred. Furthermore, the polyethylene used in this invention can also be copolymerized with other monomers, such as propylene and 1-butene.

[0097] The heat of fusion of polyethylene per unit mass is preferably above 190 mJ / mg, and the melting point is preferably 80℃~150℃.

[0098] It should be noted that the crystallinity, heat of fusion, and melting point of polyethylene can be measured, for example, by a commercially available differential scanning calorimeter (DSC-60A manufactured by Shimadzu Corporation).

[0099] The content of polyethylene powder in the oxygen absorber is preferably 3-50% by mass, more preferably 5-40% by mass, and even more preferably 10-30% by mass.

[0100] [Manufacturing method of oxygen absorber]

[0101] The method for manufacturing the oxygen absorber of the present invention is not particularly limited, but is preferably based on the following method: loading a mixture of a liquid oligomer having unsaturated groups and an oxygen-absorbing substance onto a carrier, and then mixing the carrier, gas-absorbing inorganic particles and activated carbon to obtain the oxygen absorber.

[0102] The initial preparation involves a mixture of a liquid oligomer with unsaturated groups and an oxygen-absorbing agent, which is then loaded onto a carrier. This effectively prevents the migration of the liquid oligomer with unsaturated groups to the gas-absorbing inorganic particles, thus effectively obtaining the oxygen absorber of the present invention.

[0103] Preferably, a mixture of a liquid oligomer with unsaturated groups and an oxygen-absorbing substance is loaded onto a carrier, and then the carrier, gas-absorbing inorganic particles, and activated carbon are mixed.

[0104] When the oxygen absorber contains polyethylene powder, it is preferable to mix the carrier, gas-absorbing inorganic particles, and activated carbon simultaneously. That is, when the oxygen absorber contains polyethylene powder, the preferred method for manufacturing the oxygen absorber of the present invention is as follows: after loading a mixture of a liquid oligomer having unsaturated groups and an oxygen-absorbing promoting substance onto a carrier, the carrier, gas-absorbing inorganic particles, activated carbon, and polyethylene powder are mixed to obtain the oxygen absorber.

[0105] There are no particular limitations on the equipment used in the mixing process. For specific examples, a Nota mixer (manufactured by Hosokawamicron Co., Ltd.), a cone mixer (manufactured by Ohno Chemical Machinery Co., Ltd.), a vertical granulator (manufactured by Powrex Corp.), or a high-speed mixer (manufactured by Earth Technica Co., Ltd.) can be used.

[0106] As a method for storing the oxygen absorber of the present invention, it is preferable to store it in a gas-barrier container as an oxygen absorber packaging body, as described later. The gas-barrier container is preferably filled with an inactive gas. The storage temperature is preferably 50°C or lower, more preferably 40°C or lower, and even more preferably 30°C or lower. The lower limit of the storage temperature is not particularly limited, for example, it is -20°C or higher. By storing it in an inactive gas at a low temperature, the amount of the aforementioned liquid oligomers with unsaturated groups adsorbed onto the gas-absorbing inorganic particles can be reduced. Therefore, the oxygen absorber can maintain excellent oxygen absorption performance and suppress odor generation even after storage.

[0107] [Oxygen absorber packaging]

[0108] The oxygen absorber packaging of the present invention comprises: the above-mentioned oxygen absorber, and a breathable packaging material containing the oxygen absorber.

[0109] (Packaging materials)

[0110] Examples of packaging materials include: two breathable packaging materials bonded together to form a bag; one breathable packaging material bonded together with one non-breathable packaging material to form a bag; and one breathable packaging material bent and its edges sealed together except for the bent portion to form a bag.

[0111] Here, when the breathable and non-breathable packaging materials are quadrilateral, examples of packaging materials include: overlapping two sheets of breathable packaging material and heat-sealing all four sides to form a bag; overlapping one sheet of breathable packaging material and one sheet of non-breathable packaging material and heat-sealing all four sides to form a bag; and bending one sheet of breathable packaging material and heat-sealing the three sides excluding the bent portion to form a bag. Alternatively, the packaging material can also be formed by shaping the breathable packaging material into a cylindrical shape and heat-sealing both ends and the main body of the cylindrical shape to form a bag.

[0112] The shape of the aforementioned packaging material is preferably selected from at least one of the group consisting of bag shape, three-sided sealing shape, four-sided sealing shape, rod shape, cylindrical shape, and box shape, and more preferably selected from at least one of the group consisting of rod shape, cylindrical shape, and box shape.

[0113] (Breathable packaging materials)

[0114] As a breathable packaging material, it is selected that allows for the permeability of oxygen and carbon dioxide. Among these, materials with a permeability resistance of 600 seconds or less, more preferably 90 seconds or less, based on the Göttingen density meter method, are suitable. Here, permeability resistance refers to the value measured by the method of JISP8117 (1998). More specifically, it refers to the time required for 100 mL of air to permeate through the breathable packaging material using a Göttingen density meter (manufactured by Toyo Seiki Co., Ltd.).

[0115] In addition to paper and nonwoven fabrics, breathable plastic films can also be used as the aforementioned breathable packaging materials. Examples of plastic films include laminated films that consist of polyethylene terephthalate, polyamide, polypropylene, polycarbonate, etc., laminated with polyethylene, ionomer, polybutadiene, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, or ethylene-vinyl acetate copolymer films as sealing layers. Furthermore, these laminates can also be used as breathable packaging materials.

[0116] In addition to cold-needle and hot-needle perforation, various other methods can be used to impart breathability. When perforation is used to impart breathability, the breathability can be freely adjusted according to the diameter, number, and material of the holes to be perforated.

[0117] Furthermore, the thickness of the laminated film is preferably 50-1000 μm, more preferably 50-500 μm, and particularly preferably 60-250 μm. In this case, compared with the case where the thickness exceeds the above range, the strength is maintained, and a packaging material with excellent heat-sealing properties and packaging suitability can be formed.

[0118] Example

[0119] The present embodiment will be described in detail below using examples and comparative examples. However, the present embodiment can be modified appropriately as long as the effects of the present invention are achieved. It should be noted that, unless otherwise specified, "parts" in the examples and comparative examples refer to parts by mass.

[0120] [Analysis and Evaluation]

[0121] <Amount of liquid butadiene oligomers adsorbed onto silica gel (Amount of liquid oligomers with unsaturated groups adsorbed onto gas-absorbing inorganic particles)>

[0122] Silica gel particles were separated from the oxygen absorbers in the examples and comparative examples. CHN analysis was performed using an MTC-6 CHN elemental analyzer (manufactured by Yanaco Technical Science Co., Ltd.) to determine the carbon ratio in the silica gel, which was then used as the amount of liquid polybutadiene adsorbed on the silica gel (the amount of liquid oligomers with unsaturated groups adsorbed on gas-absorbing inorganic particles).

[0123] In Table 1, "below 0.2 (mass%)" indicates the detection limit value based on this method.

[0124] It should be noted that the CHN analysis was performed under the following conditions.

[0125] Device: Yanaco CHN coder MT-6

[0126] Standard reagent: Aspirin (standard for organic elemental analysis manufactured by Kishida Chemical Co., Ltd.)

[0127] Sample furnace temperature: 950℃

[0128] Furnace temperature: 850℃

[0129] Absorption furnace temperature: 500℃

[0130] Reduction furnace temperature: 550℃

[0131] Pump thermostatic bath temperature: 55℃

[0132] Detector temperature bath: 100℃

[0133] Helium flow rate: 200 mL / min

[0134] Oxygen gas injection rate: 25 mL / min

[0135] <Oxygen absorption performance test>

[0136] One oxygen absorber package from the examples and comparative examples was sealed together with 500 mL of air at 25°C into an aluminum foil-laminated plastic film bag (Sun A. Kaken Co Ltd: 220 mm × 300 mm, hereinafter referred to as the "aluminum barrier bag"). The oxygen concentration inside the aluminum barrier bag at this time (initial oxygen concentration) was measured. The bag was stored at 25°C for 28 days, and the oxygen concentration inside the aluminum barrier bag (post-storage oxygen concentration) was measured. The oxygen reduction was calculated as (initial oxygen concentration - post-storage oxygen concentration). The greater the oxygen reduction, the better the oxygen absorption performance.

[0137] It should be noted that the oxygen concentration was measured using a gas analyzer (MOCON, "Check Mate 3"). The measurement was performed as follows: the hollow needle at the end of the silicone tube of the sampling loop attached to the gas analyzer was inserted into the inside of the bag through the rubber sheet of the sampling loop, which was pre-attached to the aluminum barrier bag, and the oxygen concentration was measured.

[0138] <Odor Test>

[0139] Three members of the odor assessment team smelled the odor inside the aluminum barrier bag after the oxygen absorption performance test, and determined the intensity of the odor produced by the oxygen absorber using a 6-level odor method (the following criteria). Table 1 shows the average of the assessment scores based on the three assessment team members (rounded to one decimal place).

[0140] 0: Odorless

[0141] 1: A barely perceptible odor (detection threshold)

[0142] 2: Identifying a weak odor as a certain scent (cognitive threshold)

[0143] 3: Scents that can be easily detected (scents that can be tolerated)

[0144] 4: Strong odor (unbearable odor)

[0145] 5: Strong odor (an extremely unbearable odor)

[0146] It should be noted that in this embodiment, a value below 3 is considered acceptable; the smaller the value, the better the odor suppression effect.

[0147] [Manufacturing of oxygen absorbers and oxygen absorber packaging]

[0148] Example 1

[0149] 19.0 g of liquid butadiene oligomer (Polyvest 110: manufactured by Evonik Japan Corporation) was mixed with 1.7 g of 4% tall oil fatty acid manganese / tall oil fatty acid (manufactured by Toei Chemical Co., Ltd.) to obtain a homogeneous solution. 0.25 g of this solution was then impregnated with 0.51 g of diatomaceous earth (catalog values: particle size 1 mm, bulk density 0.5~0.6 g / ml).

[0150] Next, the aforementioned diatomaceous earth impregnated with solution, 0.38g of granular activated carbon (coconut shell activated carbon, catalog value: particle size 0.25~0.85mm), 0.86g of silica gel particles (catalog value: particle size 20~40mesh, bulk density 0.74g / mL, average pore size 24Å), and 0.5g of powdered polyethylene (catalog value: crystallinity 65%, melting point 107℃) were placed into a 100ml flask purged with nitrogen and mixed by hand shaking to obtain an oxygen absorber.

[0151] The obtained oxygen absorber is filled into a small bag of breathable packaging material (a laminated film of paper / open-cell polyethylene, thickness: 0.4 mm, size: 26 mm × 62 mm, air resistance 27 seconds), and the bag is heat-sealed to create an oxygen absorber package.

[0152] The aforementioned analysis and evaluation were performed immediately after the oxygen absorber packaging was manufactured. The results are shown in Table 1.

[0153] Example 2

[0154] The oxygen absorber packaging was manufactured using the same method as in Example 1. The resulting oxygen absorber packaging was placed in a nitrogen-purged aluminum barrier bag and sealed. After being stored at atmospheric pressure (0.10 MPa) and 25°C for 30 days, the aluminum barrier bag was opened, and the aforementioned analysis and evaluation were performed. The results are shown in Table 1.

[0155] Example 3

[0156] The oxygen absorber packaging was manufactured using the same method as in Example 1. The resulting oxygen absorber packaging was placed in a nitrogen-purged aluminum barrier bag and sealed. After storage at atmospheric pressure (0.10 MPa) and 25°C for 90 days, the aluminum barrier bag was opened, and the aforementioned analysis and evaluation were performed. The results are shown in Table 1.

[0157] Example 4

[0158] The oxygen absorber packaging was manufactured using the same method as in Example 1. The resulting oxygen absorber packaging was placed in a nitrogen-purged aluminum barrier bag and sealed. After being stored at atmospheric pressure (0.10 MPa) and 25°C for 750 days, the aluminum barrier bag was opened, and the aforementioned analysis and evaluation were performed. The results are shown in Table 1.

[0159] Comparative Example 1

[0160] The oxygen absorber packaging was manufactured using the same method as in Example 1. The resulting oxygen absorber packaging was placed in a nylon bag and vacuum-degassed before sealing. The nylon bag was then placed in a nitrogen-purged aluminum barrier bag and sealed. After storage at 60°C for 21 days, the aluminum barrier bag and nylon bag were opened, and the aforementioned analyses and evaluations were performed. The results are shown in Table 1.

[0161] Comparative Example 2

[0162] The oxygen absorber packaging was manufactured using the same method as in Example 1. The resulting oxygen absorber packaging was placed in a nitrogen-purged aluminum barrier bag and sealed. After being stored at atmospheric pressure (0.10 MPa) and 60°C for 60 days, the aluminum barrier bag was opened, and the aforementioned analysis and evaluation were performed. The results are shown in Table 1.

[0163] [Table 1]

[0164]

[0165] As shown in Table 1, the oxygen absorber of the embodiments exhibits excellent oxygen absorption performance without the need for moisture and can suppress odor generation. Therefore, it is particularly suitable for the preservation of pharmaceuticals, medical supplies, hygiene products, etc.

Claims

1. A method for storing an oxygen absorber, the method comprising storing the oxygen absorber in a gas-barrier container filled with an inactive gas, the oxygen absorber comprising: a liquid oligomer having unsaturated groups, an oxygen-absorbing promoting substance, a carrier for loading the liquid oligomer having unsaturated groups and the oxygen-absorbing promoting substance, gas-absorbing inorganic particles, and activated carbon. The method results in the amount of the liquid oligomer with unsaturated groups adsorbed on the gas-absorbing inorganic particles being 6.5 parts by mass or less relative to 100 parts by mass of the gas-absorbing inorganic particles.

2. The method for storing oxygen absorbers according to claim 1, wherein, The gas-absorbing inorganic particles are selected from at least one group consisting of silicates, oxides of alkaline earth metals, and hydroxides of alkaline earth metals with an average pore size of 1 to 150 Å.

3. The method for storing oxygen absorbers according to claim 1 or 2, wherein, The gas-absorbing inorganic particles are silica gel.

4. The method for storing oxygen absorbers according to any one of claims 1 to 3, wherein, The oxygen-enhancing substance is selected from at least one of the groups consisting of transition metal salts and free radical initiators.

5. The method for storing oxygen absorbers according to any one of claims 1 to 4, wherein, The carrier is a silicate with an average pore size of 200~5000 Å.

6. The method for storing oxygen absorbers according to any one of claims 1 to 5, wherein, The liquid oligomer having unsaturated groups is selected from at least one of the following groups: liquid butadiene oligomers, liquid isoprene oligomers, liquid acetylene oligomers, liquid chloroprene oligomers, liquid unsaturated polyester resins, and natural rubber.

7. The method for storing oxygen absorbers according to any one of claims 1 to 6, further comprising polyethylene powder.

8. The method for storing oxygen absorbers according to any one of claims 1 to 7, wherein, The mass ratio of the liquid oligomer with unsaturated groups in the oxygen absorber to the gas-absorbing inorganic particles in the oxygen absorber [liquid oligomer with unsaturated groups / gas-absorbing inorganic particles] is 10 / 90 to 30 / 70.

9. The method for storing oxygen absorbers according to claim 1, wherein, The storage temperature should be above -20℃ and below 50℃.

10. The method for storing oxygen absorbers according to claim 1, wherein, The carrier is diatomaceous earth.

11. The method for storing oxygen absorbers according to claim 1, wherein, The amount of the carrier is 150 to 250 parts by mass relative to 100 parts by mass of the liquid oligomer with unsaturated groups in the oxygen absorber.

12. A method for storing an oxygen absorber, the method comprising storing the oxygen absorber in a gas-barrier container filled with an inactive gas as an oxygen absorber package, the oxygen absorber package comprising: the oxygen absorber; and a breathable packaging material containing the oxygen absorber. The oxygen absorber comprises: a liquid oligomer with unsaturated groups, an oxygen-absorbing promoting substance, a carrier for loading the liquid oligomer with unsaturated groups and the oxygen-absorbing promoting substance, gas-absorbing inorganic particles, and activated carbon. The method results in the amount of the liquid oligomer with unsaturated groups adsorbed on the gas-absorbing inorganic particles being 6.5 parts by mass or less relative to 100 parts by mass of the gas-absorbing inorganic particles.

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