Oxygen absorber, oxygen absorber package, and food package

Abstract

To provide a granular deoxidizer having improved oxygen absorbency.SOLUTION: A deoxidizer 20 has a core part 21 that has a porous carrier and an oxygen-absorbing composition supported on the carrier, and a laminar shell part 22 that has hydrophilic inorganic fine particles and covers the surface of the core part. The oxygen-absorbing composition has a liquid having an oxygen-absorbing substance, an alkaline compound, and a transition metal compound. The shell part has the same alkaline compound as that of the core part.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an oxygen absorber and an oxygen absorber package, as well as a food package including the oxygen absorber package and a method for producing the oxygen absorber. [Background technology]

[0002] One method for long-term food preservation is to enclose an oxygen absorber in the food packaging container. In this method, the food and the oxygen absorber are enclosed in a gas-barrier sealed bag or container, and the oxygen in the sealed container is absorbed by the oxygen absorber, thereby maintaining the atmosphere in the sealed container substantially oxygen-free, thereby suppressing quality deterioration due to oxidation and the proliferation of bacteria and microorganisms.

[0003] There are two main types of oxygen absorbers that are commonly used today: inorganic oxygen absorbers that use iron as the main ingredient, and organic oxygen absorbers that use ascorbic acid-based oxygen absorbing substances as the main ingredient. These are used according to the purpose and the food to be treated, but in recent years, there has been an increasing need to put products through metal detectors, so there is a growing demand for organic oxygen absorbers that can be used through metal detectors.

[0004] Organic oxygen absorbers have the disadvantage of absorbing oxygen more slowly than iron-based oxygen absorbers. When using oxygen absorbers to improve the shelf life of food, it is desirable to reduce the oxygen concentration to less than 0.1% within 24 hours in order to prevent the growth of mold, which grows in as little as 24 to 48 hours, but it is not easy to meet this condition with organic oxygen absorbers. Therefore, in order to increase the oxygen absorption rate in organic oxygen scavengers, it has been proposed to add a reaction catalyst or a reaction promoter that accelerates the oxidation reaction of the oxygen absorbing substance, or to add an alkaline compound to adjust the pH to an optimum level (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3541859 Summary of the Invention [Problem to be solved by the invention]

[0006] Based on the above prior art, the inventors have succeeded in increasing the oxygen absorption capacity by a different approach.

[0007] An object of the present invention is to further improve the oxygen absorbing capacity of a granular oxygen scavenger. [Means for solving the problem]

[0008] A first aspect of the present invention is a porous support and a core portion including an oxygen absorbing composition supported on the support; Hydrophilic Silica Particles and a layered shell portion covering the surface of the core portion. The oxygen absorbing composition comprises Glycerin A liquid formulation comprising Calcium hydroxide , and transition metal compounds. The shell part is the same as the core part. Calcium hydroxide Contains: The average particle size of the oxygen scavenger is 0.1 mm or more and 1.0 mm or less, and the ratio of the average thickness of the shell portion to the maximum diameter of the core portion is 0.03 or more and 0.3 or less.

[0009] A second aspect of the present invention is an oxygen absorber package in which the oxygen absorber according to the first aspect is housed in an air-permeable packaging material. A third aspect of the present invention is a food package comprising the oxygen absorber package according to the second aspect and a packaging container in which the oxygen absorber package and a food are sealed. Effect of the Invention

[0011] According to the present invention, the oxygen absorbing capacity of the granular oxygen scavenger can be further improved. [Brief description of the drawings]

[0012] [Figure 1]FIG. 1 is a diagram showing an oxygen absorber package according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view of the oxygen scavenger according to the embodiment. [Diagram 3] 3 is a cross-sectional image of the oxygen scavenger according to the embodiment taken by an electron microscope. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 is a diagram showing an oxygen absorber package 1 according to the present embodiment. The oxygen absorber package 1 includes a breathable packaging material 10 and an oxygen absorber 20 housed in the packaging material 10.

[0014] FIG. 2 shows a schematic cross-sectional view of an oxygen absorber 20. The oxygen absorber 20 is a powder of a core-shell structure having a core 21 and a shell 22 that covers the core 21. In this specification, the term "powder" refers to an aggregate that is composed of many fine particles and maintains fluidity as a whole. Therefore, a single solid tablet formed by fine particles adhering to each other as a whole is not included in the powder.

[0015] The core portion 21 contains a porous support and an oxygen absorbing composition supported on the support. The support may be any porous particle capable of supporting the oxygen absorbing composition. Usually, the oxygen absorbing composition is impregnated into the support, so that the oxygen absorbing substance is supported on the support. As the support, for example, one or more selected from activated carbon, zeolite particles, bentonite particles, activated alumina particles, activated clay, calcium silicate particles, and diatomaceous earth can be used.

[0016] The oxygen absorbing composition contains a liquid agent containing an oxygen absorbing substance, an alkaline compound, and a transition metal compound. By preparing such an oxygen absorbing composition, a sufficient oxygen absorption rate can be obtained.

[0017] The liquid agent containing the oxygen absorbing substance may be an oxygen absorbing substance that is liquid at room temperature (5 to 35°C), or may be a solution containing a liquid or solid oxygen absorbing substance. The oxygen absorbing substance is a main component of the oxygen absorbing composition and is a substance that absorbs oxygen. The oxygen absorbing substance may be, for example, a compound that consumes oxygen by oxidizing itself and absorbs oxygen. In this embodiment, an oxygen absorbing substance that is liquid at room temperature or dissolved in a solvent can be used. Such an oxygen absorbing substance is, for example, one or more compounds selected from the group consisting of glycerin, 1,2-glycol, and sugar alcohol. Specific examples of 1,2-glycol include ethylene glycol and propylene glycol. Specific examples of sugar alcohol include erythritol, arabitol, xylitol, adonitol, mannitol, and sorbitol.

[0018] When the liquid preparation is a solution of an oxygen absorbing substance, examples of the solvent in which the oxygen absorbing substance dissolves include water; lower aliphatic alcohols such as methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, secondary butanol, tertiary butanol, and tertiary amyl alcohol; glycols such as ethylene glycol, propylene glycol, and trimethylene glycol; phenyl, etc.

[0019] The oxygen absorbing material may be any of the above-mentioned compounds, either singly or in combination. By incorporating the oxygen absorbing material into the liquid, the dispersibility with the carrier and the alkaline compound is improved, so that oxygen absorbing performance can be easily obtained.

[0020] The amount of the oxygen absorbing substance is usually 80 to 200 parts by mass, and may be 100 to 180 parts by mass, based on 100 parts by mass of the support. When the amount of the oxygen absorbing substance is within this range, it tends to be easy to obtain an oxygen scavenger having an appropriate oxygen absorbing ability.

[0021] The oxygen absorbing substance may require water for the reaction of absorbing oxygen. Therefore, even if the oxygen absorbing substance itself is liquid at room temperature, water can be added to the liquid agent as needed. The amount of water added as needed is usually 0 to 80 parts by mass, and may be 20 to 60 parts by mass, relative to 100 parts by mass of the oxygen absorbing substance. The amount of water is usually 0 to 90 parts by mass, and may be 20 to 70 parts by mass, relative to 100 parts by mass of the support.

[0022] An alkaline compound is a compound that forms an alkaline aqueous solution when dissolved in water. When the oxygen absorbing substance has a hydroxyl group, the alkaline compound ionizes the hydroxyl group, activating the oxygen absorbing reaction. In the state of the oxygen absorbing composition, a part of the alkaline compound is often dissolved in the liquid agent containing the oxygen absorbing substance. The alkaline compound can be a hydroxide, carbonate, hydrogen carbonate, triphosphate, diphosphate, etc. of an alkali metal or an alkaline earth metal. Specific examples of the alkaline compound include one or more compounds selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, beryllium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide, radium hydroxide, lithium carbonate, sodium carbonate, calcium carbonate, magnesium carbonate, potassium carbonate, potassium hydrogen carbonate, sodium hydrogen carbonate, lithium hydrogen carbonate, trisodium phosphate, trisodium potassium phosphate, disodium phosphate, and dipotassium phosphate. Among these, calcium hydroxide is particularly preferred. This is because calcium hydroxide forms a soluble complex with glycerin, which facilitates the promotion of the oxidation reaction.

[0023] The amount of the alkaline compound is usually 90 to 300 parts by mass, and may be 150 to 250 parts by mass, based on 100 parts by mass of the support. When the amount of the alkaline compound is within this range, it tends to be easy to obtain an oxygen scavenger having an appropriate oxygen absorption capacity. In addition, alkaline compounds such as calcium hydroxide have the property of solidifying when mixed with liquids such as water. By mixing a porous support, an alkaline compound, and water in an appropriate ratio, the mixture is formed into a self-sufficient sphere to produce the core.

[0024] The transition metal compound is a compound containing a transition metal element, and is added to promote the oxygen absorption reaction of the oxygen absorbing material. In the state of the oxygen absorbing composition, the transition metal compound is often dissolved in a liquid agent containing the oxygen absorbing material. Specific examples of the transition metal element include iron, cobalt, nickel, copper, zinc, and manganese. The transition metal compound may be, for example, a halide, sulfate, nitrate, phosphate, carbonate, organic acid salt, oxide, hydroxide, or chelate compound of a transition metal. The transition metal compound may be a double salt containing a transition metal element. The transition metal compound may be one or more compounds selected from the group consisting of copper chloride (I), copper chloride (II), copper sulfate (II), copper hydroxide (II), copper oxide (I), copper oxide (II), manganese chloride (II), manganese nitrate (II), manganese carbonate (II), manganese sulfate (II), and nickel chloride (II).

[0025] The amount of the transition metal compound is usually 10 to 70 parts by mass, and may be 30 to 50 parts by mass, relative to 100 parts by mass of the support. When the amount of the transition metal compound is within this range, it tends to be easy to obtain an oxygen scavenger having an appropriate oxygen absorption capacity.

[0026] The oxygen absorbing composition may further contain a binder so as to easily form the core portion 21. The binder may be gum arabic, polyvinyl alcohol, sodium alginate, gelatin, cellulose, etc. The amount of the binder is usually 0 to 30 parts by mass, and may be 10 to 20 parts by mass, based on 100 parts by mass of the support.

[0027] The oxygen absorbing composition may further contain other substances as necessary. Examples of the other substances include catechol-based compounds that improve the oxygen absorbing performance. The amount of the other substances is usually about 30 parts by mass or less per 100 parts by mass of the support.

[0028] The core portion 21 can be obtained by granulating a mixture containing the support and the components constituting the oxygen absorbing composition. The components constituting the oxygen absorbing composition may be mixed together or separately. The alkaline compound contained in the oxygen absorbing composition contained in the core portion solidifies in the presence of water, and therefore forms an alkaline reaction field for improving the oxygen absorbing performance while also acting as a solidifying agent for forming the core portion. The mixer for mixing is not particularly limited, and may be, for example, a container rotation type mixer such as a cylindrical type or a V type, or a container fixed type mixer such as a ribbon type, a horizontal screw type, a paddle type, or a planetary motion type, or two or more types may be used in combination. In particular, it is preferable to use a container fixed type agitation mixer in order to perform agitation granulation by high speed agitation. Granulation can be carried out by the above-mentioned stirring granulation using a stirring mixer or an extrusion granulation method using a screen having a predetermined opening. Among them, stirring granulation using a stirring mixer that can obtain spherical granules is preferred.

[0029] The shell portion 22 is mainly composed of hydrophilic inorganic fine particles, and covers the periphery of the core portion 21 in the form of a layer. The hydrophilic inorganic fine particles are water-insoluble particles containing a hydrophilic inorganic substance as a main component. The hydrophilic inorganic fine particles usually contain 50 mass% or more of the hydrophilic inorganic substance based on the total mass of the hydrophilic inorganic fine particles. The hydrophilic inorganic substance preferably contains silicon (Si) as an element, and examples of the hydrophilic inorganic substance include hydrophilic silicon dioxide, calcium silicate hydrate, and aluminum silicate.

[0030] The hydrophilic inorganic fine particles may have an average particle size of 150 μm or less. When the hydrophilic inorganic fine particles have an average particle size of 150 μm or less, the oxygen absorbing ability of the oxygen scavenger can be improved. The surface of the core 21 is usually formed with minute projections and recesses, and the hydrophilic inorganic fine particles having a small particle size easily enter the recesses on the surface of the core 21. This is thought to significantly increase the surface area of ​​the oxygen absorber 20 and improve the oxygen absorption capacity. From the same viewpoint, the average particle size of the hydrophilic inorganic fine particles can be 100 μm or less, or 50 μm or less. There is no particular lower limit to the average particle size, but from the viewpoint that nano-sized fine particles are expensive and are difficult to handle because they are taken into the human body through the skin surface, for example, 0.1 μm or more is preferable. In the present invention, the average particle size of the hydrophilic inorganic fine particles is defined as the value of the secondary particle size measured by a laser diffraction method.

[0031] The pore volume of the hydrophilic inorganic fine particles can be 0.5 mL / g or more. When the pore volume of the hydrophilic inorganic fine particles is 0.5 mL / g, the oxygen absorbing ability of the oxygen scavenger can be increased. It is considered that hydrophilic inorganic fine particles having a large pore volume are more likely to absorb the oxygen absorbing composition located near the surface of the core portion 21. In this case, the shell portion 22 contains the same alkaline compound as the alkaline compound contained in the core portion. When an oxygen absorbing composition (particularly an oxygen absorbing substance) is absorbed into hydrophilic inorganic fine particles, the contact area between the oxygen absorbing substance and oxygen in the environment increases, which is thought to result in improved oxygen absorption capacity. Hydrophilic inorganic fine particles that satisfy an average particle size of 150 μm or less and a pore volume of 0.5 mL / g or more are particularly effective in improving oxygen absorption capacity. From the same viewpoint, the pore volume of the hydrophilic inorganic fine particles can be 0.8 mL / g or more, or 1.2 mL / g or more. The upper limit of the pore volume is not particularly limited, but can be, for example, 10 mL / g or less. In the present invention, the pore volume is defined as a value measured by a nitrogen adsorption method or a mercury intrusion method. Therefore, it is sufficient that the pore volume measured by at least one of the nitrogen adsorption method and the mercury intrusion method is within the above-mentioned numerical range.

[0032] The inorganic fine particles exemplified above can be produced by a conventional method, or can be appropriately selected from commercially available products.

[0033] When the oxygen absorber 20 is produced by stirring granulation, a known stirring mixer equipped with a stirring blade, a scraper, etc. can be used. The device configuration of the stirring mixer is preferably a vertical uniaxial mixer. Specific examples of the device include Super Mixer SMP-2 (manufactured by Kawata Co., Ltd.), Intensive Mixer EL1 (manufactured by Nippon Airich Co., Ltd.), and Triple Master TMG-1 (manufactured by Shinagawa Kogyosho Co., Ltd.). First, the materials constituting the core part, excluding the liquid agent, are put into an agitation granulator and agitated and mixed for a predetermined time (Step A). ​​The agitation time in Step A can be 5 to 15 minutes, and the agitation speed can be 3 to 8 m / sec. Next, the liquid agent is added and mixed by stirring for a predetermined time (Step B). The stirring time in Step B is 0.5 to 3 minutes, and the stirring speed is gradually increased from 1 to 5 m / sec to 15 to 30 m / sec. Furthermore, when the mixture is stirred for a predetermined time, the liquid agent wets the material and causes it to aggregate, forming a roughly spherical core (Step C). The stirring time for Step C can be 0.5 to 5 minutes, and the stirring speed can be 3 to 8 m / sec. Finally, the hydrophilic inorganic fine particles are put into a stirring granulator and stirred for a predetermined time, and the core part is covered with the hydrophilic inorganic fine particles, thereby completing the oxygen scavenger 20 having the core part 21 and the shell part 22 (Step D). The stirring time in Step D can be 0.5 to 2 minutes, and the stirring speed can be 3 to 8 m / sec. The above steps may be performed in the same agitation granulator, or some steps may be performed in different agitation granulators. Steps B to D are preferably performed in a uniaxial mixer, but since step A is a mixing process of dry powder, it may be performed using a container rotary mixer.

[0034] In the above-mentioned manufacturing method, in steps B and C, the liquid agent is placed in the form of minute droplets in the core portion 21. Furthermore, in step D, centrifugal force acts on the core portion 21, and some of the minute droplets resulting from the dissolution of the core portion move to the shell portion 22. Therefore, the components of the core portion 21 become an oxygen scavenger present in a larger amount in the shell portion 22 than in the case of manufacturing by extrusion granulation or the like.

[0035] In the oxygen absorber 20 of the present embodiment, when the oxygen absorbing composition transferred to the inorganic fine particles reacts with the air, the oxygen absorbing composition located inside the core portion 21 gradually transfers to the surface layer of the core portion and is absorbed by the shell portion 22. As a result, high oxygen absorbing performance is maintained for a long time.

[0036] The dimensional ratio of the core portion 21 to the shell portion 22 in the oxygen absorber 20 can be set as appropriate, but it is preferable that the ratio of the average thickness of the shell portion 22 to the maximum diameter of the core portion 21 is 0.03 or more and 0.3 or less. If the shell portion is too thin compared to the core portion, it may not be able to absorb all of the oxygen absorbing composition that has migrated from the core portion, and the fluidity of the oxygen absorber may decrease. If the shell portion is too thick compared to the core portion, the distance between the oxygen absorbing composition that has migrated from the core portion and the surface of the oxygen absorber may become large, and the effect of improving the oxygen absorption performance by the components that have migrated from the core portion may decrease. The maximum diameter of the core part may be the diameter when the core part is spherical, or the major axis when the core part is ellipsoidal, or the Feret diameter when the core part is irregular. The average thickness of the shell portion can be, for example, the arithmetic mean value of thickness values ​​at multiple randomly selected points (for example, 10 points) in the cross-sectional image.

[0037] The oxygen absorber package 1 of this embodiment is completed when the oxygen absorber 20 is stored in the breathable packaging material 10 and sealed.

[0038] The food package according to this embodiment is obtained by enclosing the oxygen absorber package 1 in a packaging container containing food and sealing it. The oxygen absorber package 1 can also be suitably used for foods that undergo quality inspection using a metal detector. In the food packaging body according to the present embodiment, the form of the packaging container is not particularly limited as long as it can be sealed, and can be appropriately selected from those commonly used in the field of food packaging. Examples of the packaging container include a bag, a deep-draw packaging body, a tray packaging body, a stretch packaging body, and the like.

[0039] The oxygen scavenger according to the present embodiment will be further described using examples, although the technical scope of the present invention is not limited to the specific contents of these examples.

[0040] Example 1 7.2 parts of activated carbon, 15.6 parts of calcium hydroxide, and 1.2 parts of cellulose were added to a stirring mixer, and step A was carried out at 3.0 m / sec to obtain 24 parts of powder. It was confirmed that the powder was free of lumps and had a uniform gray color. Next, a liquid mixture of 10.5 parts of glycerin, 3.1 parts of copper (II) sulfate, and 4.2 parts of water was added, and step B was carried out at 18.0 m / sec. After confirming that there were no lumps or chunks in the wet powder, step B was completed. Further, step C was carried out at 5.0 m / sec. Step C was terminated when it was visually confirmed that the surfaces of the particles were wetted, black gloss was observed, and the particles were aggregated into spherical shapes. As a result, 41.8 parts of the core portion were obtained.

[0041] Next, 2.1 parts of Silopage 720 (manufactured by Fuji Silysia Chemical Co., Ltd.), which is hydrophilic silica particles, were added to the stirring mixer, and step D was carried out at 5.0 m / sec. After confirming that there were no more silica particles scattered in the mixer, step D was terminated. Through step D, the hydrophilic silica particles uniformly coated the periphery of the wet core part on the surface, forming a shell part. In this manner, an oxygen scavenger having a core-shell structure of Example 1 was obtained.

[0042] Example 2 The oxygen scavenger of Example 2 was obtained in the same manner as in Example 1, except that the amount of Silopage 720 was changed to 1.3 parts. Example 3 The oxygen scavenger of Example 3 was obtained in the same manner as in Example 1, except that the amount of Silopage 720 was changed to 4.2 parts.

[0043] Example 4 The oxygen scavenger of Example 4 was obtained in the same manner as in Example 1, except that 2.1 parts of NIPSIL LP (manufactured by Tosoh Silica Corporation), which is hydrophilic silica particles, was used as the material for the shell portion.

[0044] Example 5 The oxygen scavenger of Example 5 was obtained in the same manner as in Example 1, except that the time for step C was 1.5 minutes and the amount of Silopage 720 was 0.5 parts. Example 6 The oxygen scavenger of Example 6 was obtained in the same manner as in Example 1, except that the time for step C was 7 minutes and the amount of Silopage 720 was 5.0 parts.

[0045] Example 7 7.2 parts of activated carbon, 15.6 parts of calcium hydroxide, 1.2 parts of cellulose, 10.5 parts of glycerin, 3.1 parts of copper sulfate (II), and 4.2 parts of water were mixed uniformly in a sealed state to obtain a mixture of oxygen absorbing compositions with activated carbon as a carrier. This mixture was granulated by an extrusion granulator equipped with a screen with a screen hole diameter of 1.0 mmφ and an aperture ratio of 22.6%, to obtain 41.8 parts of a roughly cylindrical core portion. 41.8 parts of the core portion and 2.1 parts of Silopage 720 were placed in a bag with oxygen barrier properties and heat sealed, and the bag was shaken for about 1 minute to obtain an oxygen absorber of Example 7 in which the granules were softly covered with inorganic fine particles.

[0046] Comparative Example 1 The oxygen scavenger of Comparative Example 1 was obtained in the same manner as in Example 1, except that step D was not performed. That is, the oxygen scavenger of Comparative Example 1 is formed only of a core portion and does not have a shell portion. Comparative Example 2 An oxygen scavenger of Comparative Example 3 was obtained in the same manner as in Example 1, except that 2.1 parts of Aerosil R812S (manufactured by Nippon Aerosil Co., Ltd.), which is hydrophobic silica particles, was used as the material for the shell portion.

[0047] Comparative Example 3 The oxygen absorber of Comparative Example 3 was obtained in the same manner as in Example 7, except that the oxygen absorber was not covered with Silopage 720. That is, the oxygen absorber of Comparative Example 3 is formed only of a core portion and does not have a shell portion.

[0048] The oxygen absorbers of the Examples and Comparative Examples were evaluated as follows. (Oxygen absorption capacity) 2.0 g of the oxygen absorber according to each example was placed in a bag (60 mm long, 60 mm wide) made of a breathable packaging material to prepare an oxygen absorber package according to each example. A laminated material having a layer structure of polyethylene terephthalate / polyethylene / paper / polyethylene was used as the breathable packaging material. Absorbent cotton soaked in 10 mL of 44% sucrose aqueous solution was placed in a bag-shaped packaging container with oxygen barrier properties. The oxygen absorber package according to each example was then placed in the packaging container and sealed in a roughly vacuum state. After that, 500 mL of air was injected into the packaging container with a syringe, and the container was resealed to obtain a food package according to each example. As a result, the water activity in the packaging container became 0.95. Water activity indicates the proportion of free water in the water in a system, and a water activity of 0.95 simulates the state in which high-moisture foods such as cheese, ham, and sausage are stored. The food packages of each example were left to stand in an atmosphere at 25° C. After 24 hours had passed, the oxygen concentration inside was measured using a needle-type oxygen concentration meter. A low oxygen concentration means a high oxygen absorption capacity. Generally, an oxygen concentration of 0.1% or less within 24 hours in a room temperature environment is required.

[0049] (Average particle size) Based on the general rules for sieving test methods (JIS Z 8815-1994), the sieve particle size of each example of the oxygen absorber was measured using JIS test sieves of 2.8 mm, 2.0 mm, 1.0 mm, and 0.5 mm (manufactured by Okutani Wire Mesh Works, JIS Z 8801-1:2019). The sieve particle size was plotted logarithmically, and the median diameter (D50) of each example was calculated.

[0050] (Liquidity) Based on the Japan Powder Process Industry and Technology Association standard "Guidelines for powder specification display methods (SAP 05-98:2013)," measurements were taken using a fluidity tester (manufactured by AS ONE Corporation) consisting of a stand approximately 140 mm high and a chute with a diameter of 3.3 mm. Approximately 171 mL of oxygen absorbers from each example were placed in the chute. The chute mouth was then opened to allow the oxygen absorbers to fall freely, and the angle of repose (the angle the slope of the mountain makes with the horizontal plane) and spread distance (the maximum dimension passing through the center when viewed from above) of the oxygen absorbers that spread radially into a mountain shape were measured. The smaller the angle of repose and the larger the spread distance, the better the fluidity of the oxygen absorber.

[0051] (Loose bulk density) Measurements were made based on the Japan Powder Process Industry and Engineering Association standard "Method for measuring bulk density of granulated materials (SAP 01-79)". Approximately 200 mL of each oxygen absorber was placed in a 10 mm diameter funnel. The oxygen absorber was then dropped 45 mm into a 100 cc pycnometer 290 / I (Erichsen). After the oxygen absorber at the top of the pycnometer was worn out, the weight of the oxygen absorber in the pycnometer was measured to measure the loose bulk density of each oxygen absorber.

[0052] (Cross-section observation of oxygen scavenger particles) Common methods for preparing cross-sectional samples include, for example, ion milling at room temperature and block cutting with a microtome, but these methods are highly likely to cause liquid components such as glycerin and water to volatilize. For this reason, it is difficult to say that a sample reflecting the actual form of the oxygen absorber according to the present invention can be obtained, which is not preferable. Therefore, observation samples of the oxygen absorbers of each example were prepared using a cross-section polisher under cryo-conditions. The cross-sectional images were obtained using a field emission electron microscope at an acceleration voltage of 10 kV, a sample stage temperature of about -80°C, and a magnification of about 80x to about 1000x. The maximum Feret diameter of the core portion 21 and the average thickness (average value of 10-point measurements) of the shell portion 22 were measured. The ratio of the maximum Feret diameter of the core portion to the average thickness of the shell portion was taken as the core / shell length ratio. 3 is a cross-sectional photograph of the oxygen absorbing agent according to Example 1. It can be seen that the shell portion 22 is formed relatively uniformly around the substantially spherical core portion 21.

[0053] (Energy dispersive X-ray analysis EDX analysis) EDX analysis was performed on the cross section of each example of oxygen absorber at an accelerating voltage of 10 kV and a sample stage temperature of approximately -80°C. Elemental quantitative analysis was performed using the ZAF method, and the ratio of the atomic percentage concentration of silicon element to the atomic percentage concentration of calcium element at a certain observation point was calculated as Ca / Si. Table 1 shows an outline of the configuration of each example, and Table 2 shows the evaluation results of each example.

[0054] [Table 1]

[0055] [Table 2]

[0056] As shown in Table 2, the oxygen absorbers of each Example exhibited superior oxygen absorption performance compared to the Comparative Examples, and met the requirement of "oxygen concentration of less than 0.1% 24 hours after sealing," which is a guideline for effectively preventing the growth of mold, bacteria, and the like in food packages. Moreover, the oxygen absorbers of the Examples had higher fluidity than the Comparative Examples, and were excellent in terms of packing ability into packaging materials.

[0057] Comparative Examples 1 and 3, which did not have a shell portion, had significantly inferior oxygen absorption performance, even though they had core portions of the same composition as Examples 1 and 7. In addition, the liquid agent present on the surface caused stickiness and poor flowability. In Comparative Example 2 using hydrophobic silica particles, the hydrophobic silica particles did not sufficiently adhere to the periphery of the core portion, and a shell layer was not formed, even though step D was performed. As a result, the oxygen absorption performance was significantly inferior as in Comparative Example 1, and the flowability was also poor.

[0058] In all the examples, calcium was detected in the shell. Since calcium is not contained in the shell material, it is assumed that calcium hydroxide, an alkaline compound contained in the core, migrated to the shell together with the liquid during the manufacturing process of the oxygen absorber. Although not shown in Table 2, carbon thought to be derived from glycerin and copper thought to be derived from copper (II) sulfate were also detected in the elemental quantitative analysis of the shell, supporting the above assumption.

[0059] In each example, it is considered that the liquid agent containing the oxygen absorbent is absorbed into the shell portion, and the contact efficiency between the oxygen absorbing substance and oxygen in the environment is increased, thereby improving the oxygen absorption capacity. In other words, it is considered that the inclusion of the alkaline compound contained in the core portion in the shell portion is an indicator of high oxygen absorption performance in an oxygen scavenger having a core-shell structure.

[0060] The shell portion 22 absorbs and holds the liquid agent that has migrated from the core portion 21, but the surface of the oxygen absorber in each example was relatively dry. This was thought to be because the amount of the migrated liquid agent was sufficiently small compared to the absorption capacity of the shell portion, and only a small amount of the liquid agent reached the surface layer of the shell portion. As a result, the oxygen absorbers in each example did not become sticky and remained in an easy-to-handle state. Furthermore, because they were in a particulate form, they also had good flowability and bulk density. These characteristics are effective in efficiently filling the oxygen absorber into the breathable packaging material and in forming the breathable packaging material into small bags.

[0061] Although one embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and configuration changes and combinations within the scope that do not deviate from the gist of the present invention are also included.

[0062] For example, in the above embodiment, an example was described in which the alkaline compound contained in the core portion is moved to the shell portion by stirring granulation or the like, thereby causing the core portion and the shell portion to contain the same alkaline compound. Alternatively, the deoxidizer may be formed by previously incorporating the same alkaline compound as the core portion into the material for forming the shell portion. [Industrial Applicability]

[0063] INDUSTRIAL APPLICABILITY The present invention can be used for an oxygen absorber package and a food package that improve the preservation quality of food and the like. [Explanation of symbols]

[0064] 1. Oxygen absorber packaging 10 Packaging material 20. Oxygen absorber 21 Core 22 Shell part

Claims

1. A core portion including a porous support and an oxygen absorbing composition supported on the support; a layered shell portion containing hydrophilic silica particles and covering a surface of the core portion; Equipped with The oxygen absorbing composition comprises a liquid agent containing glycerin, calcium hydroxide, and a transition metal compound; The shell portion contains the calcium hydroxide, The average particle size is 0.1 mm or more and 1.0 mm or less, The ratio of the average thickness of the shell portion to the maximum diameter of the core portion is 0.03 or more and 0.3 or less. Oxygen absorber.

2. The ratio of the average thickness of the shell portion to the maximum diameter of the core portion is 0.05 or more and 0.22 or less. The oxygen scavenger according to claim 1.

3. The core portion is spherical or elliptical. The oxygen scavenger according to claim 1.

4. The oxygen absorber according to any one of claims 1 to 3 is contained in a breathable packaging material. Oxygen absorber packaging.

5. The oxygen absorber package according to claim 4, A packaging container in which the oxygen absorber package and food are enclosed; Equipped with Food packaging.

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