Oxygen scavenger composition and method for producing the same

Abstract

An oxygen scavenger composition contains mixed granules of a composition containing a water retention agent, a swelling agent, a metal halide, water, iron, and an alkaline substance, the alkaline substance containing at least one substance selected from the group consisting of hydroxides of alkali metals, hydroxides of alkali earth metals, and salts comprising a weak acid and a strong base.

Description

[Technical Field]

[0001] The present invention relates to an oxygen scavenger composition and a method for producing the same, and more particularly to an iron-based oxygen scavenger composition and a method for producing the same. [Background technology]

[0002] A method using an oxygen absorber is known as a preservation technique for foods, pharmaceuticals, etc. In this method, the preserved item and the oxygen absorber are enclosed in a gas-barrier sealed container and then sealed, so that the oxygen in the sealed container is absorbed by the oxygen absorber, thereby maintaining the atmosphere in the sealed container substantially oxygen-free. The function of the oxygen absorber is required to be small and to absorb a large amount of oxygen. In other words, an oxygen absorber composition that has a high oxygen absorption amount per unit volume is required.

[0003] Typical oxygen absorbers include iron-based oxygen absorbers, which are mainly made of iron (iron powder), and non-iron-based oxygen absorbers, which are mainly made of ascorbic acid, glycerin, etc. The oxygen absorber is selected appropriately depending on the application, but iron-based oxygen absorbers are widely used from the viewpoint of oxygen absorption performance.

[0004] Iron powder requires moisture to absorb oxygen. In conventional oxygen absorbers containing iron powder and water, the iron powder and the water retention agent, which retains water to provide moisture, are contained as separate, separate powder particles. As a result, gaps form between the iron powder and the water retention agent, and these gaps contribute to a decrease in the oxygen absorption amount per unit volume of the oxygen absorber composition. In addition, the iron powder and the water retention agent tend to aggregate and bond with each other, or with each other, to form agglomerates. When the iron powder agglomerates, the surface area of ​​the iron powder that can be oxidized decreases, resulting in a problem of a decrease in the oxygen absorption amount compared to when the iron powder and the water retention agent are uniformly dispersed and mixed.

[0005] For example, Patent Document 1 discloses an oxygen absorbing composition that contains an oxygen absorbing substance, water, and a swelling agent, and that is solidified by pressure molding to eliminate gaps between powder particles, thereby reducing the volume and making it compact. However, compared to oxygen absorbing compositions that can be produced simply by mixing, the oxygen absorbing composition described in Patent Document 1 requires an additional pressure molding step, which increases the production cost. In addition, because the iron powder located inside the powder particles is less likely to oxidize, there is room for improvement in the amount of oxygen absorbed per unit volume.

[0006] Patent Document 2 discloses an oxygen absorber composition that aims to solve the problems with the oxygen absorber composition of Patent Document 1 and provide an oxygen absorber composition that has an excellent oxygen absorption amount per unit volume, and that includes a powder or granular material having an α-layer that contains a water retention agent, a swelling agent, a metal salt, and water, a β-layer that contains iron, and a γ-layer that contains a porous carrier, and the powder or granular material forms a layer structure in the order of the α-layer, the β-layer, and the γ-layer from the inside to the outside of the powder or granular material. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2007 / 046449 [Patent Document 2] International Publication No. 2017 / 169015 Summary of the Invention [Problem to be solved by the invention]

[0008] To prevent oxidation of stored items in sealed containers, it is preferable for oxygen absorbers to absorb as much oxygen as possible. However, if large amounts of iron powder and water are used to increase the amount of oxygen absorbed, the amount of hydrogen generated by these reactions during oxygen absorption increases, causing the container to deform or burst. Therefore, there is a need for oxygen absorbers that can absorb large amounts of oxygen while suppressing the amount of hydrogen generated. Furthermore, the oxygen absorber of Patent Document 2 requires a manufacturing process in which an aqueous solution of a metal halide salt is added to a mixture of a water-retaining agent and a swelling agent to prepare a powder that is the raw material for the α layer, and then iron powder is added to the powder to adhere the iron powder to the outside of the α layer (α layer / β layer), thereby preparing a powder. Therefore, a more efficient method for manufacturing oxygen absorbers is desired. Therefore, an object of the present invention is to provide an oxygen absorbing composition that has excellent oxygen absorbing performance and generates little hydrogen upon absorbing oxygen. Another object of the present invention is to provide a method for efficiently producing an oxygen absorbing composition that has excellent oxygen absorbing performance and generates little hydrogen upon absorbing oxygen. [Means for solving the problem]

[0009] The present invention relates to the following oxygen scavenger composition and method for producing the same. <1> An oxygen scavenger composition comprising a mixed granule of a composition containing a water retention agent, a swelling agent, a metal halide, water, iron, and an alkaline substance, wherein the alkaline substance contains at least one selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, and salts of weak acids and strong bases. <2> The content of the alkaline substance is 0.2 to 10 parts by mass per 100 parts by mass of iron. <1> The oxygen scavenger composition according to claim 1. <3> The solubility of the alkaline substance in water at 25°C is 0.1 to 60 mass%. <1> or <2> The oxygen scavenger composition according to claim 1. <4> The alkaline substance contains at least one selected from the group consisting of hydroxides of alkali metals and hydroxides of alkaline earth metals. <1> ~ <3> 10. The oxygen scavenger composition according to claim 9, wherein the oxygen scavenger composition is a scavenger composition having a molecular weight of 100 or more. <5> The alkaline substance contains calcium hydroxide. <1> ~ <4> 10. The oxygen scavenger composition according to claim 9, wherein the oxygen scavenger composition is a scavenger composition having a molecular weight of 100 or more. <6> The above-mentioned mixture granules have a layer containing porous particles on the outside thereof. <1> ~ <5> 10. The oxygen scavenger composition according to claim 9, wherein the oxygen scavenger composition is a scavenger composition having a molecular weight of 100 or more. <7> The water retention agent contains at least one selected from the group consisting of diatomaceous earth, silica, and activated carbon. <1> ~ <6> 10. The oxygen scavenger composition according to claim 9, wherein the oxygen scavenger composition is a scavenger composition having a molecular weight of 100 or more. <8> The swelling agent contains at least one selected from the group consisting of carboxymethylcellulose calcium, carboxymethylcellulose sodium, calcium bentonite, and sodium bentonite. <1> ~ <7> 10. The oxygen scavenger composition according to claim 9, wherein the oxygen scavenger composition is a scavenger composition having a molecular weight of 100 or more. <9> The mixed granules are not pressure-molded products. <1> ~ <8> 10. The oxygen scavenger composition according to claim 9, wherein the oxygen scavenger composition is a scavenger composition having a molecular weight of 100 or more. <10> The iron is dispersed throughout the mixed granules. <1> ~ <9> 10. The oxygen scavenger composition according to claim 9, wherein the oxygen scavenger composition is a scavenger composition having a molecular weight of 100 or more. <11> the above <1> ~ <10> 1. A method for producing the oxygen absorber composition according to any one of claims 1 to 9, comprising the step of collectively mixing a water retention agent, a swelling agent, a metal halide, water, iron, and an alkaline substance, followed by granulation. <12> the above <1> ~ <10> and a breathable packaging material containing the oxygen absorber composition according to any one of the above. [Effects of the Invention]

[0010] The oxygen absorbing composition of the present invention has excellent oxygen absorbing performance, generates little hydrogen upon oxygen absorption, and can absorb oxygen in a sealed container without causing deformation or rupture of the container. Furthermore, according to the production method of the present invention, it is possible to efficiently produce an oxygen absorbing composition that has excellent oxygen absorbing performance, generates little hydrogen upon oxygen absorption, and can absorb oxygen in a sealed container without causing deformation or rupture of the container. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional photograph of the (α layer / β layer) powder particles produced by the method described in Example 1 of Patent Document 2. [Figure 2] FIG. 2 is a photograph of a cross section of the mixed granulated product prepared in Example 1 described below.

Mode for Carrying Out the Invention

[0012] Hereinafter, an embodiment of the present invention will be described. The content of the present invention is not limited to the embodiments described below. In this specification, the term "A to B" regarding the description of numerical values means "A or more and B or less" (when A < B) or "A or less and B or more" (when A > B). Also, in the present invention, a combination of preferred embodiments is a more preferred embodiment.

[0013] 〔Oxygen Absorbent Composition〕 The oxygen absorbent composition of the present invention includes a mixed granulated product of a composition containing a water retention agent, a swelling agent, a metal halide, water, iron, and an alkaline substance, and the alkaline substance contains at least one selected from the group consisting of hydroxides of alkali metals, hydroxides of alkaline earth metals, and salts composed of weak acids and strong bases. In the mixed granulated product of the present invention, it is preferable that iron is dispersed throughout the mixed granulated product. The oxygen absorbent composition of the present invention may consist only of the mixed granulated product, or may have a layer containing porous particles outside the mixed granulated product.

[0014] The inventors have found that an oxygen absorbent composition containing a mixed granulated product of a composition containing a water retention agent, a swelling agent, a metal halide, water, iron, and an alkaline substance, obtained by granulating them together, has excellent oxygen absorption performance, little hydrogen generation during oxygen absorption, no deformation or rupture of the container, and can absorb oxygen in a sealed container. Although the detailed mechanism by which the effects of the present invention are achieved is unclear, it is believed that by mixing and granulating a water-retaining agent, swelling agent, metal halide, water, iron, and alkaline substance together, the iron powder is kept dispersed, preventing aggregation and allowing for effective oxidation, thereby improving oxygen absorption performance. Conventional oxygen absorbers are made by mixing two components: an oxygen absorber made of iron powder, salt, activated carbon, etc., and a moisture donor made of diatomaceous earth, saline solution, etc. When an alkaline substance is mixed with the oxygen absorber to suppress hydrogen generation, the surface of the oxygen absorber is so water-poor that a thick alkaline water film forms during the oxidation reaction, preventing iron corrosion and making the oxidation reaction less likely to occur. On the other hand, even if an alkaline substance is mixed with the moisture donor, the moisture is supplied from the moisture donor to the oxygen absorber by evaporation, so the alkaline substance in the moisture donor does not effectively suppress hydrogen generation. However, by mixing the water retention agent, swelling agent, metal halide, water, iron, and alkaline substance together and granulating them as in the present invention, the alkaline substance can be present on the surface of the iron as an aqueous solution at an appropriate concentration, and it is thought that this makes it possible to suppress hydrogen generation during oxygen absorption without significantly reducing oxygen absorption performance.

[0015] (water retention agent) The water retention agent contained in the oxygen absorbing composition of the present invention is a substance that can be impregnated with water and retain the water without letting it seep out. The water retention agent is not particularly limited as long as it can retain water, and commonly available porous materials and superabsorbent resins can be used. Examples of porous materials include diatomaceous earth, zeolite, sepiolite, cristobalite, porous glass, silica, activated clay, acid clay, activated carbon, vermiculite, and wood flour. Examples of superabsorbent resins include polyacrylate resins, polysulfonate resins, polyacrylamide resins, polyvinyl alcohol resins, starch resins, cellulose resins, and polyalginic acid resins. The water retention agent preferably contains at least one selected from the group consisting of diatomaceous earth, silica, and activated carbon. The above-mentioned water retention agents can be used alone, or two or more can be used in combination as needed. These water retention agents are also readily available commercially.

[0016] Among the above water retention agents, activated carbon is particularly preferred because it has the function of promoting the oxidation reaction of iron in addition to the water retention function. The type of activated carbon is not particularly limited, and may be any of wood, coconut shell, coal, etc. The water retention agent preferably contains at least one selected from the group consisting of diatomaceous earth and silica in addition to activated carbon. By combining these, the water retention function can be further enhanced.

[0017] The properties of the water retention agent are not particularly limited, but from the viewpoint of ease of handling during the production of the oxygen absorber, a powder with high fluidity is preferably used, and the particle shape of the water retention agent is more preferably spherical. Furthermore, from the viewpoint of ease of handling during the production of the oxygen absorber, the average particle diameter of the water retention agent is preferably 10 μm or more and 1000 μm or less, more preferably 100 μm or more and 500 μm or less. As long as the water retention agent particles have a particle size within the above range, they can be used regardless of whether they are primary particles, aggregated particles, or granulated particles. Water retention agents having particle sizes within the above range can be used alone, or multiple types having different particle sizes can be mixed in any ratio.

[0018] The content of the water retention agent in the oxygen absorber composition is not particularly limited, but is preferably 10 to 40% by mass, more preferably 15 to 30% by mass, relative to the oxygen absorber composition. Furthermore, the content is preferably 20 to 300 parts by mass, more preferably 50 to 200 parts by mass, relative to 100 parts by mass of water. When the content of the water retention agent is within this range, the oxygen absorber composition can sufficiently retain water, and the oxygen absorption amount per unit volume of the oxygen absorber composition can be increased.

[0019] (swelling agent) The swelling agent contained in the oxygen absorbing composition of the present invention is a substance that swells with water and has a caking function to maintain the shape of the granules. The swelling agent is preferably used in a substantially dry state or in a semi-swollen or swollen state after absorbing a small amount or a necessary amount of water.

[0020] The swelling agent is not particularly limited as long as it is a commonly known swelling agent, and known swelling agents, binding agents, adhesives, and binders used in foods and the like can be used. Examples of inorganic swelling agents include clay minerals such as sodium bentonite, calcium bentonite, and sodium montmorillonite. Examples of organic swelling agents include organic bentonite; natural products such as defatted frozen tofu, agar, starch, dextrin, gum arabic, gelatin, and casein; semi-synthetic products such as crystalline cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, calcium carboxymethyl cellulose, hydroxyethyl cellulose, lignosulfonic acid, and hydroxyethylated starch; and synthetic products such as water-insolubilized polyvinyl alcohol and polyvinyl methyl ether. The swelling agents described above can be used alone or in combination with two or more types as needed. Commercially available products can also be used as these swelling agents.

[0021] Among the swelling agents, at least one selected from the group consisting of clay minerals and cellulose-based semi-synthetic products is preferred. Clay minerals are preferred because they are inexpensive and have excellent performance. Clay minerals are also known as inorganic soaps and function as lubricants. Clay minerals swollen with water are known to exhibit high thixotropy and caking properties, making them preferred. Cellulose-based semi-synthetic products are also preferred because they exhibit excellent swelling properties. Among these, bentonites such as calcium bentonite and sodium bentonite, as well as carboxymethylcellulose, sodium carboxymethylcellulose, and calcium carboxymethylcellulose are preferred because they are inexpensive and have strong caking properties. Thus, it is more preferred that the swelling agent contained in the oxygen scavenger composition of the present invention contains at least one selected from the group consisting of calcium carboxymethylcellulose, sodium carboxymethylcellulose, calcium bentonite, and sodium bentonite.

[0022] The average particle size of the swelling agent is preferably 0.001 μm or more and 10 μm or less, more preferably 0.01 μm or more and 1.0 μm or less, from the viewpoint of suppressing dust generation and of the binding function.

[0023] The content of the swelling agent in the oxygen absorber composition is not particularly limited, but is preferably 0.1 to 20% by mass, more preferably 1 to 15% by mass, relative to 100 parts by mass of iron. Furthermore, the content is preferably 1 to 15 parts by mass, more preferably 3 to 10 parts by mass, relative to 100 parts by mass of iron. If the content of the swelling agent is within this range, the shape of the oxygen absorber composition is easily maintained, the proportion of the water retention agent is not too small, the amount of moisture supplied to the iron is not reduced, and the amount of oxygen absorbed tends to be higher.

[0024] (metal halide) The metal halide contained in the oxygen absorbing composition of the present invention acts as a catalyst in the oxidation reaction of iron, improving the activity of iron, and also serves to prevent water contained in the oxygen absorbing composition from evaporating and being lost from the oxygen absorbing composition.

[0025] Any commonly known metal halide can be used without any particular limitation. The metal in the metal halide is not particularly limited, but examples thereof include at least one selected from the group consisting of alkali metals, alkaline earth metals, copper, zinc, aluminum, tin, iron, cobalt, and nickel. Among these, at least one selected from the group consisting of lithium, potassium, sodium, magnesium, calcium, barium, and iron is more preferred. Furthermore, the halide in the metal halide is not particularly limited, but examples thereof include chloride, bromide, and iodide.

[0026] As the metal halide, calcium chloride, sodium chloride, calcium bromide, sodium bromide, calcium iodide and sodium iodide are preferred from the viewpoints of handling ease, safety and the like, and calcium chloride and sodium chloride are more preferred. The metal halides may be used singly or in combination of two or more as required. Commercially available metal halides may also be used.

[0027] When a metal halide is used as a raw material in the form of an aqueous solution, the salt concentration is preferably 5% by mass or more and 30% by mass or less, more preferably 10% by mass or more and 20% by mass or less. A salt concentration of 5% by mass or more prevents the catalytic effect on iron oxidation from being reduced, and a salt concentration of 30% by mass or less prevents a decrease in the vapor pressure of water. This prevents a decrease in the amount of oxygen absorbed due to an insufficient supply of water to the iron. Furthermore, when the alkaline substance described below is water-soluble, it is preferable to use an aqueous solution containing the metal halide and the alkaline substance as a raw material. The concentration of the metal halide in the aqueous solution containing the metal halide and the alkaline substance is also preferably within the above-mentioned range.

[0028] The content of the metal halide in the oxygen absorbing composition is not particularly limited, but is preferably 0.5 to 15% by mass, more preferably 1 to 10% by mass, and more preferably 0.5 to 20 parts by mass, more preferably 2 to 10 parts by mass, per 100 parts by mass of iron.

[0029] (water) The oxygen absorbing agent composition of the present invention contains water so that the iron-based oxygen absorbing agent can exhibit oxygen absorbing performance. The content of water in the oxygen absorbing agent composition is not particularly limited, but is preferably 10 to 40% by mass, more preferably 15 to 30% by mass, in the oxygen absorbing agent composition. Furthermore, from the viewpoint of oxygen absorbing performance, the content of water is preferably 20 to 50 parts by mass, more preferably 25 to 40 parts by mass, per 100 parts by mass of iron.

[0030] (iron) The form of the iron contained in the oxygen absorbing composition of the present invention is not particularly limited, but is preferably iron powder from the viewpoints of oxygen absorption performance, availability, and ease of handling. The iron powder is not particularly limited as long as the iron surface is exposed, and reduced iron powder, electrolytic iron powder, atomized iron powder, etc. can be suitably used. Furthermore, crushed or cut pieces of cast iron, etc. can also be used. The iron powder may be used alone or in combination of two or more types as required. These iron powders are also readily available commercially. Iron powder coated with a metal halide can also be used. The iron powder coated with a metal halide can be prepared by mixing iron powder with an aqueous solution of the metal halide, followed by drying to remove moisture. The metal halide coated on the iron powder is preferably one of the metal halides described above. Furthermore, iron powder whose surface is coated with an alkaline substance, which will be described later, can also be used. Iron powder coated with an alkaline substance can be prepared by mixing iron powder with an aqueous solution of the alkaline substance, followed by drying to remove moisture. The alkaline substance coated on the iron powder is preferably an alkaline substance, which will be described later. By using an aqueous solution containing a metal halide and an alkaline substance, as will be described later, iron powder whose surface is coated with both a metal halide and an alkaline substance can also be used, which is preferable.

[0031] The average particle size of the iron powder is preferably 1000 μm or less, more preferably 500 μm or less, and even more preferably 200 μm or less from the viewpoint of improving contact with oxygen, and is preferably 1 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more from the viewpoint of suppressing dust generation. The particle size referred to here refers to the particle size measured from the weight fraction based on the sieve opening size after vibrating for 5 minutes using a standard sieve conforming to ISO 3310-1:2000 (equivalent to JIS Z8801-1:2006).

[0032] In addition, the specific surface area of ​​the iron powder is preferably 0.05 m from the viewpoint of oxygen absorption capacity. 2 / g or more, more preferably 0.1m 2 / g or more. The specific surface area of ​​the iron powder can be measured by the BET multipoint method.

[0033] The oxygen absorbing composition of the present invention contains iron as a main component. The iron content in the oxygen absorbing composition is preferably 40% by mass or more and 90% by mass or less, more preferably 45% by mass or more and 80% by mass or less, and particularly preferably 50% by mass or more and 70% by mass or less.

[0034] (alkaline substances) The oxygen scavenger composition of the present invention contains an alkaline substance containing at least one selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, and salts of weak acids and strong bases. The alkaline substance contained in the oxygen absorbing composition of the present invention is believed to contribute to the suppression of hydrogen generation during oxygen absorption. The alkaline substance contains at least one selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, and salts of weak acids and strong bases, preferably at least one selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides, more preferably at least one selected from the group consisting of alkaline earth metal hydroxides and salts of weak acids and strong bases, and even more preferably at least one selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides. Among these, hydroxides of alkali metals are more preferred because they have a relatively high solubility in water and the concentration of the alkaline aqueous solution can be adjusted as desired, and hydroxides of alkaline earth metals are even more preferred because they have a relatively low solubility in water and do not excessively increase the concentration of the alkaline aqueous solution even when added in a large amount. Examples of alkali metal hydroxides include sodium hydroxide, potassium hydroxide, and lithium hydroxide, with sodium hydroxide and potassium hydroxide being preferred. Examples of the hydroxide of alkaline earth metals include calcium hydroxide, strontium hydroxide, magnesium hydroxide, and barium hydroxide. Calcium hydroxide, strontium hydroxide, and magnesium hydroxide are preferred, and calcium hydroxide is more preferred. The alkaline substance more preferably contains calcium hydroxide, and further preferably is calcium hydroxide. Examples of salts formed from weak acids and strong bases include phosphates, citrates, carbonates, and bicarbonates, with phosphates and citrates being preferred.Specific examples of salts formed from weak acids and strong bases include trisodium phosphate, trisodium citrate, sodium bicarbonate, and sodium carbonate, with trisodium phosphate and trisodium citrate being preferred.

[0035] The solubility of the alkaline substance in water at 25°C is preferably 0.1 to 60% by mass, more preferably 0.1 to 10% by mass, even more preferably 0.1 to 1% by mass, and even more preferably 0.1 to 0.5% by mass. The solubility of the alkaline substance in 100 g of water at 25°C is preferably 0.1 to 150 g, more preferably 0.1 to 11 g, even more preferably 0.1 to 1 g, and even more preferably 0.1 to 0.5 g. Having the solubility of the alkaline substance within this range is preferable because oxygen absorption is not inhibited by iron oxidation, the high oxygen absorption performance derived from the iron-based oxygen scavenger can be maintained, and hydrogen generation can be suppressed. The solubility of alkaline substances can be determined by referring to the values ​​listed in the MSDS of each substance. If an MSDS is not available, the solubility can be measured by the temperature change method (part 2) or evaporation method. The alkaline substance may be used alone or in combination of two or more kinds as required. Commercially available alkaline substances may be used.

[0036] When the alkaline substance is used as a raw material in the form of an aqueous solution, its concentration is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 5% by mass or less. By having the alkaline substance concentration in the above range, it is possible to suppress hydrogen generation while maintaining oxygen absorption performance. Furthermore, an aqueous solution containing both the above-mentioned metal halide and alkaline substance may be used as a raw material. It is preferable that the concentration of the alkaline substance in the aqueous solution containing the metal halide and alkaline substance is also in the above range.

[0037] The content of the alkaline substance in the oxygen absorbing composition is not particularly limited, but is preferably 0.1 to 5% by mass, more preferably 0.2 to 3% by mass, and even more preferably 0.3 to 1.5% by mass in the oxygen absorbing composition. The content is also preferably 0.2 to 10 parts by mass, more preferably 0.3 to 5 parts by mass, and even more preferably 0.5 to 3 parts by mass relative to 100 parts by mass of iron.

[0038] <Mixed granules> The oxygen scavenger composition of the present invention comprises a granulated mixture of a composition containing a water retention agent, a swelling agent, a metal halide, water, iron, and an alkaline substance. Here, in the present invention, "granulation" refers to the operation of mixing raw material powders consisting of single or multiple components with a binder or the like to reduce the proportion of fine powder compared to the raw material powder state and process them into larger granules than the raw material powder. "Granulated product" refers to powder obtained by the granulation operation, which has a reduced proportion of fine powder compared to the raw material powder state and has been processed into larger granules than the raw material powder. The mixed granules in the present invention are not pressure-molded products. That is, the granules contained in the oxygen absorbing agent composition of the present invention can be produced simply and at low cost by simply mixing the raw material powders without performing pressure molding. Furthermore, since the mixed granules are not pressure-molded products, spaces exist in the mixed granules, which facilitates contact between oxygen and iron, and is thought to contribute to improving the oxygen absorption performance.

[0039] Furthermore, "a mixed granule of a composition containing a water retention agent, a swelling agent, a metal halide, water, iron and an alkaline substance" refers to a granule in which the composition that makes up the granule contains a water retention agent, a swelling agent, a metal halide, water, iron and an alkaline substance, and these components are mixed together to form a granule; it does not include powder or granules in which some components are localized in layers to form a layered structure.

[0040] In particular, it is preferable that the mixed granules of the present invention have iron dispersed throughout the mixed granules. In Patent Document 2, a powder as the raw material for the α layer is prepared by adding an aqueous solution of a metal halide while mixing a water retention agent and a swelling agent, and then iron powder is added to the powder to adhere to the outside of the α layer (α layer / β layer), thereby preparing the powder, and therefore the iron powder is localized near the outside of the powder (Fig. 1). In contrast, as will be described later, the method for producing an oxygen absorbing composition of the present invention is a method including a step of collectively mixing and granulating a water retention agent, a swelling agent, a metal halide, water, iron, and an alkaline substance, and the granules obtained by this method have iron dispersed throughout the granules (Fig. 2). Here, Fig. 1 is a cross-sectional photograph of (α layer / β layer) granules prepared by the method described in Example 1 of Patent Document 2, and Fig. 2 is a cross-sectional photograph of the mixed granules prepared in Example 1 described below. Observation samples were prepared by embedding each particle in resin, cutting the particle near its center using a Micro Support "Quick Trimming Tool T-111," and cutting out the particle cross-section for observation. The cross-section observation was also performed using an optical microscope (Keyence "VHX-2000," 50x magnification). In the particle shown in Figure 1, the iron (gray area) is localized on the outside, whereas in the particle shown in Figure 2, the iron (gray area) is sparsely distributed throughout.

[0041] The content of the mixed granules in the oxygen scavenger composition of the present invention is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably substantially 100% by mass.

[0042] (porous particles) The oxygen absorbing composition of the present invention may consist of only the granulated mixture, but it is preferable that the granulated mixture has a layer containing porous particles on the outside thereof. The porous particles that can be used in the present invention are not particularly limited as long as they have a porous shape. Here, "porous" refers to a state in which a large number of pores are present on the surface and inside the particles, which can be seen with an electron microscope. The porous particles can be any of the porous substances used in the water retention agents described above, but silicas are preferred. Silicas refer to those containing silicon dioxide (SiO2) as the main component. The use of silicas increases the bulk density of the resulting powder and granules, thereby increasing the oxygen absorption capacity.

[0043] The silica is not particularly limited, but examples thereof include surface-treated silica, hydrophobic silica, wet silica, dry silica, silica gel, diatomaceous earth, acid clay, activated clay, perlite, kaolin, talc, and bentonite. The porous particles described above can be used alone or in combination of two or more types as needed. These porous particles are also readily available as commercial products.

[0044] When the oxygen absorbing composition of the present invention has a layer containing porous particles, the content of the porous particles in the layer containing porous particles is preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 80% by mass or more.

[0045] When the oxygen absorber composition of the present invention has a layer containing porous particles, the content of the porous particles in the oxygen absorber composition is preferably 0.1% by mass to 5% by mass, more preferably 0.5% by mass to 3% by mass. When the content of the porous particles is in this range, the bulk density of the oxygen absorber composition increases, and the oxygen absorption amount tends to be higher, and the flowability of the oxygen absorber composition is improved, thereby improving the handleability during production of the oxygen absorber package.

[0046] <Shape of oxygen absorbing composition> The shape of the oxygen absorbing agent composition of the present invention is not particularly limited, but examples thereof include a spherical shape, an approximately spherical shape, an elliptical shape, and a cylindrical shape. Since the shape has better packing properties and tends to have a higher bulk density, a spherical shape and an approximately spherical shape are preferred, and a spherical shape is more preferred.

[0047] The average particle size of the oxygen absorber composition of the present invention is preferably 0.3 mm or more and 5.0 mm or less, more preferably 0.5 mm or more and 2.0 mm or less. An average particle size of 0.3 mm or more inhibits adhesion of the powder to the contact area of ​​the packaging machine during filling and packaging due to static electricity or the like. An average particle size of 5.0 mm or less tends to inhibit excessively large gaps between powder particles, which would otherwise reduce the amount of oxygen absorbed per unit volume. To obtain an oxygen absorber composition having an average particle size within the above range, for example, sieving may be performed using sieves with openings of 0.3 mm and 5 mm. The average particle size can be measured, for example, using a commercially available laser diffraction / scattering particle size distribution analyzer ("LA-960" manufactured by Horiba, Ltd.).

[0048] The bulk density of the oxygen absorbing composition of the present invention is not particularly limited, but is preferably 1.0 g / mL or more, more preferably 1.3 g / mL or more, and even more preferably 1.5 g / mL or more. A bulk density of 1.0 g / mL or more tends to result in a better oxygen absorption amount per unit volume. Furthermore, for practical purposes, the bulk density is 2.5 g / mL or less. To obtain an oxygen absorbing composition having a bulk density within the above range, for example, a composition having the desired bulk density can be selected using a gravity classification device (such as the "High Speed ​​Aspirator" manufactured by Tokyo Flour Milling Machinery Co., Ltd.). The bulk density can be measured in accordance with JIS Z8901:2006.

[0049] [Method for producing oxygen scavenger composition] The method for producing the oxygen absorber composition of the present invention preferably includes a step of collectively mixing and granulating a water retention agent, a swelling agent, a metal halide, water, iron, and an alkaline substance (the production method of the present invention). According to the production method of the present invention, a mixed granule is prepared by mixing the water retention agent, the swelling agent, the metal halide, water, iron, and the alkaline substance until they are uniformly dispersed, thereby enabling efficient preparation of the oxygen absorber composition. In Patent Document 2, a powdery material serving as the raw material for the α-layer is prepared by adding an aqueous solution of a metal halide while mixing the water retention agent and the swelling agent. Iron powder is then added to the powdery material to adhere the iron powder to the outside of the α-layer, thereby preparing an (α-layer / β-layer) powdery material. Hydrophobic silica is then added to the (α-layer / β-layer) powdery material to adhere the hydrophobic silica to the outside of the β-layer, thereby preparing an (α-layer / β-layer / γ-layer) powdery material. In other words, a two-step process is required: preparing the powdery material serving as the raw material for the α-layer, and then adhering the iron powder to the outside of the α-layer. In contrast, the production method of the present invention can produce the oxygen absorbing agent composition in a single step of mixing the water retention agent, swelling agent, metal halide, water, iron, and alkaline substance all at once and granulating the mixture, and therefore can produce the oxygen absorbing agent composition more efficiently than the method of Patent Document 2. Furthermore, according to the production method of the present invention, the mixed granules contained in the oxygen absorbing agent composition of the present invention can be produced simply and at low cost by simply mixing the raw material powders without performing pressure molding. The mixing device is not particularly limited, but specific examples that can be used include a Nauta mixer (manufactured by Hosokawa Micron Corporation), a conical mixer (manufactured by Ohno Chemical Machinery Co., Ltd.), a vertical granulator (manufactured by Powrex Corporation), a high-speed mixer (manufactured by Earth Technica Corporation), and a granulator (manufactured by Akira Kiko Co., Ltd.).

[0050] In addition, as a method for producing an oxygen absorbing composition having a layer containing porous particles, porous particles such as hydrophobic silica may be added to and mixed with the mixed granules, and a layer containing porous particles may be formed on the outside of the mixed granules to prepare the oxygen absorbing composition.

[0051] Iron, which is the main component of the oxygen scavenger, reacts with oxygen, and the reaction with oxygen proceeds gradually even in the absence of water, metal halide, etc. Therefore, it is preferable to carry out the mixing in an inert atmosphere (in the case of a substantially closed system, the system is usually kept in an oxygen-free reducing atmosphere) and to take appropriate measures to remove heat.

[0052] [Oxygen absorber packaging] The oxygen absorber package of the present invention comprises the oxygen absorber composition described above and a breathable packaging material containing the oxygen absorber composition.

[0053] (packaging material) Examples of packaging materials include those formed by bonding two sheets of breathable packaging material together to form a bag, those formed by bonding one sheet of breathable packaging material and one sheet of non-breathable packaging material together to form a bag, and those formed by folding one sheet of breathable packaging material and sealing the edges together except for the folded part to form a bag.

[0054] Here, when the breathable packaging material and the non-breathable packaging material are rectangular, the packaging material may be formed by overlapping two sheets of breathable packaging material and heat-sealing the four sides to form a bag, by overlapping one sheet of breathable packaging material with one sheet of non-breathable packaging material and heat-sealing the four sides to form a bag, or by folding one sheet of breathable packaging material and heat-sealing three sides excluding the folded part to form a bag. The packaging material may also be formed by shaping the breathable packaging material into a cylindrical shape and heat-sealing both ends and the body of the cylindrical body to form a bag.

[0055] (breathable packaging material) As the breathable packaging material, a packaging material that allows oxygen and carbon dioxide to pass through is selected. Among these, those with an air resistance of 600 seconds or less, more preferably 90 seconds or less, measured by a Gurley tester are preferred. Here, air resistance refers to a value measured according to the method of JIS P8117 (1998). More specifically, it refers to the time required for 100 mL of air to pass through the breathable packaging material using a Gurley densometer (manufactured by Toyo Seiki Seisakusho, Ltd.).

[0056] The breathable packaging material may be paper, nonwoven fabric, or a plastic film that has been given breathability. Examples of the plastic film include laminated films formed by laminating and bonding a film of polyethylene terephthalate, polyamide, polypropylene, polycarbonate, or the like with a film of polyethylene, ionomer, polybutadiene, ethylene acrylic acid copolymer, ethylene methacrylic acid copolymer, ethylene vinyl acetate copolymer, or the like as a sealing layer. These laminates may also be used as breathable packaging materials.

[0057] As a method for imparting breathability, various methods can be adopted, including perforation processing using a cold needle or a hot needle. When perforation processing is used to impart breathability, the breathability can be freely adjusted by the diameter, number, material, etc. of the holes to be perforated.

[0058] The thickness of the laminated film is preferably 50 to 300 μm, particularly preferably 60 to 250 μm, in which case the packaging material can maintain its strength and have excellent heat-sealing properties and packaging suitability, compared to thicknesses outside the above range. [Example]

[0059] The present embodiment will be described in detail below using examples and comparative examples, but the present embodiment can be modified as appropriate as long as the effects of the present invention are achieved. Note that "parts" in the examples and comparative examples refer to parts by mass unless otherwise specified.

[0060] (Production of oxygen absorber composition and oxygen absorber package) Example 1 Diatomaceous earth (Isolite Industrial Co., Ltd. "CG-2U", average particle size: 0.44 mm) 1240 parts, activated carbon (Futamura Chemical Co., Ltd. "S-W50", average particle size: 10 μm) 1120 parts, calcium bentonite (Kunimine Industrial Co., Ltd. "Neokunibond") 225 parts, sodium carboxymethyl cellulose (Nippon Paper Chemicals Co., Ltd. "F350HC-4") 20 parts, sodium chloride and sodium hydroxide aqueous solution prepared by dissolving 410 parts of sodium chloride and 63 parts of sodium hydroxide in 2000 parts of water, iron powder (average particle size 100 μm, specific surface area: 0.104 m 2 6,000 parts of cellulose acetate (1.2 μm / g) were added to a high-speed mixer ("FS25" manufactured by EarthTechnica Corporation) and mixed for 3 minutes at 240 rpm under a nitrogen gas atmosphere to obtain a mixed granule (average particle size: 0.78 mm). 110 parts of surface-treated silica ("SS-30P" manufactured by Tosoh Silica Corporation, average particle size: 1.2 μm) were then added and mixed for 30 seconds at 240 rpm to obtain an oxygen scavenger composition (average particle size: 0.87 mm, bulk density: 1.47 g / mL) in which a porous particle layer was formed on the outside of the mixed granule. Next, 0.8 g of the oxygen absorber composition was filled into a small pouch of breathable packaging material (composition: PET / nonwoven fabric / perforated polyethylene, dimensions: 50 mm x 60 mm, thickness: 140 μm) to obtain a small pouch-shaped oxygen absorber package 1-1. Also, 30 g of the oxygen absorber composition was filled into a small pouch of breathable packaging material (composition: nonwoven fabric / perforated polyethylene, dimensions: 75 mm×100 mm) to obtain a small pouch-shaped oxygen absorber package 1-2. The oxygen absorber compositions, oxygen absorber packages 1-1 and 1-2 obtained in this example were stored in barrier bags with low oxygen permeability, with the openings of the bags heat-sealed to prevent reaction with atmospheric oxygen, until they were used in the tests. The oxygen absorber compositions and oxygen absorber packages obtained in Examples 2 to 4 and Comparative Examples 1 to 4 were also stored in the same manner until they were used in the tests.

[0061] Examples 2 to 4 In Example 1, the same procedure as in Example 1 was carried out except that 63 parts of each of the alkaline substances shown in Table 1 were used instead of 63 parts of sodium hydroxide (NaOH), to obtain the mixed granulated oxygen absorber composition, oxygen absorber packages 2-1, 3-1 and 4-1 containing 0.8 g of the oxygen absorber composition, and oxygen absorber packages 2-2, 3-2 and 4-2 containing 30 g of the oxygen absorber composition. In Table 1, potassium hydroxide (KOH), calcium hydroxide (Ca(OH)2), and strontium hydroxide (Sr(OH)2) were all reagents manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. In Table 1, the solubility of each alkaline substance in water at 25°C is the value (g / 100g of water) listed in the MSDS of each reagent and the value (mass%) calculated from that.

[0062] Comparative Example 1 An aqueous solution was prepared by dissolving 1.0 g of sodium chloride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 1.0 g of sodium hydroxide in 10 g of water. 0.4 g of activated carbon (Futamura Chemical Co., Ltd.) and the aqueous solution prepared above were added to 100 g of iron powder (average particle size 100 μm) while mixing to form a homogeneous mixture. The mixture was then dried to obtain surface-coated iron powder (A). Next, an aqueous solution prepared by dissolving 14.2 g of sodium chloride (Fujifilm Wako Pure Chemical Industries Co., Ltd.) in 80.2 g of water was added dropwise to 100 g of diatomaceous earth (Isolite Industrial Co., Ltd. "CG-1C") while mixing to uniformly impregnate the powder, yielding 200 g of moisture donor (B). 61.5 parts by mass of the iron powder (A) and 38.5 parts by mass of the moisture donor (B) were mixed to obtain an oxygen absorber composition as a powder mixture. Using the obtained oxygen absorber composition, oxygen absorber package 5-1 containing 0.8 g of the oxygen absorber composition and oxygen absorber package 5-2 containing 30 g of the oxygen absorber composition were obtained in the same manner as in Example 1.

[0063] Comparative Example 2 An oxygen absorber composition which is a powder mixture, an oxygen absorber package 6-1 containing 0.8 g of the oxygen absorber composition, and an oxygen absorber package 6-2 containing 30 g of the oxygen absorber composition were obtained in the same manner as in Comparative Example 1, except that 1.0 g of calcium hydroxide was used instead of 1.0 g of sodium hydroxide.

[0064] Comparative Example 3 An oxygen absorber composition which is a powder mixture, an oxygen absorber package 7-1 containing 0.8 g of the oxygen absorber composition, and an oxygen absorber package 7-2 containing 30 g of the oxygen absorber composition were obtained in the same manner as in Comparative Example 1, except that 1.0 g of sodium hydroxide was not used and only 1.0 g of sodium chloride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in 10 g of water to prepare an aqueous solution.

[0065] Comparative Example 4 An oxygen absorber composition which is a powder mixture, an oxygen absorber package 8-1 containing 0.8 g of the oxygen absorber composition, and an oxygen absorber package 8-2 containing 30 g of the oxygen absorber composition were obtained in the same manner as in Example 1, except that an aqueous sodium chloride solution was prepared by dissolving only 410 parts of sodium chloride in 2000 parts of water without using 63 parts of sodium hydroxide.

[0066] (Average particle size of raw material, mixed granules and oxygen scavenger composition) The average particle sizes of the raw materials, the mixed granules, and the oxygen scavenger composition were measured using a laser diffraction / scattering particle size distribution measuring device (LA-960, manufactured by Horiba, Ltd.).

[0067] (specific surface area of ​​iron powder) The specific surface area of ​​iron powder (unit: m 2 / g) was measured based on the BET multipoint method in accordance with JIS Z8830:2013.

[0068] (Bulk density of oxygen absorbing composition) The bulk density (unit: g / mL) of the oxygen absorbing composition was measured in accordance with JIS Z8901:2006.

[0069] (Oxygen Absorption Amount of Oxygen Absorber Composition) Each of the oxygen absorber packages 1-1 to 8-1 obtained in the Examples and Comparative Examples, each containing 0.8 g of the oxygen absorber composition, was placed in a gas barrier bag (250 mm × 400 mm) made of polyvinylidene chloride-coated stretched nylon / polyethylene together with 3000 mL of air and sealed. After leaving the gas barrier bag at 25°C for one day, the oxygen concentration inside the gas barrier bag was measured using a galvanic oxygen concentration meter (Model RO-102, manufactured by Iijima Electronics Co., Ltd.). The amount of oxygen absorbed by the oxygen absorber composition per 1 g of iron powder was calculated from the difference between the measured oxygen concentration and the oxygen concentration before leaving the bag at 25°C for one day. The calculated oxygen absorption amount per 1 g of iron powder is shown in Table 1. The larger the oxygen absorption amount, the better, since a small amount of oxygen absorber composition can absorb a large amount of oxygen.

[0070] (Amount of hydrogen generated by oxygen absorbing composition) Each of the oxygen absorber packages 1-2 to 8-2 obtained in the Examples and Comparative Examples, each containing 30 g of the oxygen absorber composition, was placed in a gas barrier bag (structure: nylon / aluminum foil / polyethylene, dimensions: 175 mm x 250 mm) together with 25 mL of air and sealed. The gas barrier bag was left standing at 35°C for three days, after which the hydrogen concentration in the gas barrier bag was measured by gas chromatography. The amount of hydrogen generated per 1 g of iron powder was calculated from the measured hydrogen concentration. The calculated amount of hydrogen generated per gram of iron powder is shown in Table 1.

[0071] (Amount of hydrogen generated per 100 mL of oxygen absorbed by the oxygen scavenger composition) From the oxygen absorption amount per 1 g of iron powder calculated by the above-mentioned method and the hydrogen generation amount per 1 g of iron powder, the amount of hydrogen generated per 100 mL of oxygen absorption, which is the amount of hydrogen generated when the oxygen absorber compositions obtained in the Examples and Comparative Examples absorb 100 mL of oxygen, was calculated. The lower the amount of hydrogen generated per 100 mL of oxygen absorption, the better, since less hydrogen is generated relative to the amount of oxygen absorption required in actual use.

[0072] [Table 1]

[0073] As can be seen from the results in Table 1, in the case of an oxygen scavenger composition containing a mixture of a conventional oxygen absorber (iron powder (A)) and a moisture donor (moisture donor (B)) as raw powder, the addition of an alkaline substance (Comparative Examples 1 and 2) suppresses hydrogen generation, but the oxygen absorption performance is significantly reduced compared to the case where no alkaline substance is added (Comparative Example 3). In contrast, in the case of the oxygen absorber compositions of the examples, by making the raw powder into a mixed granule and adding an alkaline substance to it (Examples 1 to 4), it is possible to exhibit the extremely excellent oxygen absorption capacity unique to the mixed granule, and it is also possible to significantly reduce the generation of hydrogen without significantly reducing the oxygen absorption capacity compared to the composition without adding an alkaline substance (Comparative Example 4). Furthermore, it can be seen that, according to the manufacturing method of the Examples, the excellent oxygen absorbing composition as described above can be efficiently obtained by mixing and granulating all at once.

Claims

1. The present invention comprises a granulated mixture of a composition including a water-retaining agent, a swelling agent, a metal halide, water, iron, and an alkaline substance, the solubility of the alkaline substance in water at 25°C is 0.1 to 60 mass%; the alkaline substance contains at least one selected from the group consisting of calcium hydroxide and strontium hydroxide, The oxygen scavenger composition, wherein iron is dispersed throughout the mixed granules.

2. 2. The oxygen absorbing composition according to claim 1, wherein the content of the alkaline substance is 0.2 to 10 parts by mass per 100 parts by mass of iron.

3. 3. The oxygen absorbing composition according to claim 1, wherein the alkaline substance comprises calcium hydroxide.

4. 4. The oxygen absorbing composition according to claim 1, wherein the mixed granules have a layer containing porous particles on the outside thereof.

5. 5. The oxygen absorbing composition according to claim 1, wherein the water retention agent comprises at least one selected from the group consisting of diatomaceous earth, silica, and activated carbon.

6. The oxygen absorbing composition according to any one of claims 1 to 5, wherein the swelling agent comprises at least one selected from the group consisting of carboxymethylcellulose calcium, carboxymethylcellulose sodium, calcium bentonite, and sodium bentonite.

7. The oxygen absorbing composition according to any one of claims 1 to 6, wherein the mixed granules are not a pressure-molded product.

8. A method for producing the oxygen absorbing agent composition according to any one of claims 1 to 7, comprising a step of collectively mixing a water retention agent, a swelling agent, a metal halide, water, iron, and an alkaline substance, followed by granulation.

9. An oxygen absorber package comprising the oxygen absorber composition according to any one of claims 1 to 7 and a breathable packaging material containing the oxygen absorber composition.

Images