Iron-based powder for oxygen reactants and oxygen reactants

Abstract

Provided is an iron-based powder for an oxygen reaction agent that does not need the use of a metal halide and has excellent oxygen reactivity. The iron-based powder for an oxygen reaction agent includes: an iron powder having an atomic number ratio O / Fe of oxygen to iron of at most 0.3; at least one additive powder selected from the group consisting of a copper powder, a nickel powder, a molybdenum powder, a copper oxide powder, a nickel oxide powder, and a molybdenum oxide powder, wherein the content of the additive powder is 1.0 mass% to 40.0 mass%.

Description

[Technical field]

[0001] The present disclosure relates to iron-based powders for oxygen reactants and oxygen reactants. [Background technology]

[0002] Known applications of oxygen reaction agents that utilize the reaction between iron-based powder and oxygen include, for example, oxygen scavengers and heat generating agents. As oxygen scavengers, they are used to create a low-oxygen state by sealing them in a container together with preserved items such as food and medicines, thereby suppressing quality deterioration due to oxidation of the preserved items and the proliferation of mold and the like. As heat generating agents, they are widely used as disposable hand warmers to warm the human body and the like. In general, in these oxygen reaction agents, activated carbon, sodium chloride, silica powder, wood powder, moisture, sulfur powder, and the like are added to the iron-based powder in order to further promote the oxygen reaction.

[0003] In either application, the rate of reaction between iron and oxygen is important, and mixing of iron oxide powder with iron powder has been studied as a means for controlling the reaction rate.

[0004] For example, Japanese Patent Application Laid-Open No. 05-237373 (Patent Document 1) discloses an oxygen scavenger that has excellent reactivity at low temperatures.

[0005] Furthermore, Japanese Patent Laid-Open Publication No. 53-60885 (Patent Document 2) discloses a metal heating composition in which activated carbon containing iron powder, chloride, and water is mixed with one or more of manganese dioxide, cupric oxide, and iron oxide black to promote oxidation. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 05-237373 [Patent Document 2] Japanese Patent Application Publication No. 53-60885 Summary of the Invention [Problem to be solved by the invention]

[0007] The oxygen absorber disclosed in Patent Document 1 requires the use of a metal halide, which easily absorbs moisture from the air and causes the oxygen reaction of the iron powder to proceed rapidly. Therefore, this oxygen absorber has problems in terms of handling and storage, such as the need to put the iron powder into an oxygen absorber bag immediately after adding the metal halide and store it in an oxygen-free state.

[0008] The heating metal composition disclosed in Patent Document 2 mainly contains iron oxide, lead oxide, manganese oxide, cupric oxide, and manganese dioxide, all of which are already oxidized to some degree. Therefore, this heating metal composition has a problem of poor reactivity with oxygen in the early stages of the reaction.

[0009] The present disclosure has been made in view of the above circumstances, and aims to provide an iron-based powder for an oxygen reactant and an oxygen reactant that do not require the use of metal halides and have excellent oxygen reactivity. [Means for solving the problem]

[0010] Copper, nickel, and molybdenum have a smaller tendency to ionize than iron, so they react less easily with oxygen than iron. Also, copper oxide, nickel oxide, and molybdenum oxide are already oxidized, so they react less easily with oxygen. Therefore, all of the above substances are inferior to iron powder as oxygen reactants.

[0011] In contrast, copper, nickel, and molybdenum have higher standard electrode potentials than iron, and the potential-pH diagram (Pourbaix diagram) for each metal shows that the potential increases further when the metal is oxidized.

[0012] When iron powder comes into contact with metal powder or the like having a higher potential than the iron powder in a corrosive environment such as an electrolyte, a local battery mechanism occurs in which a corrosion current flows from the metal powder or the like having a higher potential to the iron powder or the like having a lower potential, and the corrosion current then returns to the metal powder or the like having a higher potential than the iron powder or the like via the electrolyte, and then flows back to the iron powder or the like having a lower potential. It is believed that the occurrence of such a mechanism promotes the reaction between the low-potential iron powder and oxygen.

[0013] Therefore, the inventors came up with the idea of ​​adding copper powder, nickel powder, molybdenum powder, and oxide powders of these powders, which have not been used conventionally and are less reactive with oxygen than iron, to iron powder in order to promote the reaction between the iron-based powder and oxygen, and conducted extensive research. As a result, they found that there is an appropriate mixing ratio of iron-based powders that exhibit excellent oxygen reactivity.

[0014] The present disclosure is based on the above findings, and has the following gist and configuration. 1. Iron powder having an oxygen to iron atomic ratio O / Fe of 0.30 or less; At least one additive powder selected from the group consisting of copper powder, nickel powder, molybdenum powder, copper oxide powder, nickel oxide powder, and molybdenum oxide powder; The iron-based powder for an oxygen reactant has a content of the additive powder of 1.0% by mass or more and 40.0% by mass or less.

[0015] 2. An oxygen reactant using the iron-based powder for oxygen reactants described in 1 above. Effect of the Invention

[0016] According to the present disclosure, it is not necessary to use a metal halide, and an iron-based powder for an oxygen reactant and an oxygen reactant having excellent oxygen reactivity can be obtained. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, embodiments of the present disclosure will be described. Note that the following embodiments are merely examples for explaining the present disclosure, and the present disclosure is not limited to the embodiments.

[0018] The reason why the iron-based powder for an oxygen reactant of the present disclosure exhibits excellent oxygen reactivity is presumed to be as follows. That is, copper powder, nickel powder, molybdenum powder, and oxide powders of these (also referred to as "additive powder" in the present disclosure) have a higher potential than iron powder. Therefore, when the additive powder and iron powder come into contact with each other in an electrolyte, a corrosion current is generated, promoting the oxidation reaction of the iron powder. And, since the iron-based powder for an oxygen reactant of the present disclosure has excellent reactivity with oxygen, it is suitable for use in the oxygen reactant of the present disclosure. Therefore, the oxygen reactant of the present disclosure can exhibit the same characteristics and effects as the iron-based powder for an oxygen reactant of the present disclosure.

[0019] Here, when iron is oxidized, the potential increases. Therefore, the iron powder before use as an oxygen reactant is preferably not oxidized, which makes it easier to increase the potential difference with the additive powder. As a result, the corrosion current increases. Specifically, the atomic ratio of oxygen to iron (hereinafter also referred to as "O / Fe") must be 0.30 or less. This is because, if the O / Fe is in this range, the potential difference with the additive powder is sufficiently large, and an effective amount of corrosion current (sufficient to promote the oxidation reaction of the iron powder) is generated in the electrolyte. Therefore, in the present disclosure, the O / Fe in the iron powder of the iron-based powder for the oxygen reactant is set to 0.30 or less. The lower limit of O / Fe is not particularly set, and it may be 0, but it is preferably about 0.15 industrially. The value of O / Fe can be measured according to the method described below.

[0020] The iron powder used in the present disclosure can be produced by water atomization, gas atomization, a pulverization method, or an oxide reduction method.

[0021] In addition, the present disclosure adds to the iron powder one or more powders selected from the group consisting of copper powder, nickel powder, molybdenum powder, copper oxide powder, nickel oxide powder, and molybdenum oxide powder (group of additive powders).

[0022] The copper powder, nickel powder, and molybdenum powder can be produced by water atomization, gas atomization, pulverization, oxide reduction, and electrolysis, or may be commercially available products. The copper oxide powder, nickel oxide powder, and molybdenum oxide powder may be obtained by oxidizing the copper powder, nickel powder, and molybdenum powder produced by the above-mentioned methods by spraying water or salt water on them, or may be commercially available products.

[0023] Here, the term "iron-based powder" refers to a metal powder containing 50.0 mass% or more of metallic iron. In addition to the metallic iron (Fe), the iron-based powder may further contain any element such as C, S, O, N, Si, Na, Mg, and Ca. The metallic iron content of the iron-based powder can be measured according to JIS A 5011-2 "Method for determining metallic iron".

[0024] The iron-based powder for oxygen reactant is a mixed powder of iron powder and additive powder, and the content of the additive powder in the mixed powder is 1.0 mass% or more and 40.0 mass% or less. When the content of the additive powder in the iron-based powder for oxygen reactant is less than 1.0 mass%, the corrosion current is small and the effect of promoting the reaction of the iron powder with oxygen is poor. On the other hand, since the additive powder itself is difficult to oxidize and reacts with oxygen less than the iron powder, when the content of the additive powder in the iron-based powder for oxygen reactant is more than 40.0 mass%, the oxygen reaction amount of the mixture of the iron powder and the additive powder becomes too low compared to the oxygen reaction amount of the iron powder alone. From the viewpoint of oxygen reactivity, the content of the additive powder in the iron-based powder for oxygen reactant is preferably 2.0 mass% or more and preferably 25.0 mass% or less.

[0025] From the above, the present disclosure makes it possible to achieve excellent oxygen reactivity by providing an iron-based powder for an oxygen reactant that satisfies the above requirements.

[0026] The particle size of the iron powder and the additive powder is not particularly limited as long as it does not cause any problems in handling. However, the median diameter (median value of particle size from cumulative volume frequency) D 50 The particle size of the iron powder and additive powder is preferably 1 mm or less, more preferably 400 μm or less, and even more preferably 200 μm or less. On the other hand, the lower limit of the particle size of the iron powder and additive powder is preferably about 5 μm from the viewpoint of handling.

[0027] The median diameter D of the iron powder and additive powder in this disclosure 50 The measurement method is as follows: The iron powder and additive powder to be measured are placed in ethanol as a solvent and dispersed by ultrasonic vibration for 30 seconds or more, and the particle size is measured using a laser diffraction particle size distribution analyzer that uses the laser diffraction and scattering method, that is, the volume-based particle size distribution of the iron powder and additive powder particles is measured. The cumulative particle size distribution is calculated from the obtained particle size distribution, and the particle size of the particles that is equivalent to 50% of the total volume of all particles is determined as the median diameter D 50 In this disclosure, this median diameter D 50 are used as representative values ​​of the particle size of the iron powder and the additive powder, respectively.

[0028] [Calculation method for O / Fe in powder] The method of calculating O / Fe in a powder in the present disclosure is preferably as follows: The powder is subjected to X-ray diffraction measurement, and the obtained diffraction data is subjected to Rietveld analysis to determine the content of elemental Fe, compounds of Fe and O, and other compounds in the powder. The number of Fe and O atoms can be obtained from the numerical content, and the value of O / Fe can be calculated.

[0029] [Iron powder manufacturing] The iron powder used in the present disclosure is preferably produced by a water atomization method or a gas atomization method in which water or gas is sprayed onto a molten metal, pulverized, and cooled to solidify, or by reducing iron oxide (mill scale) generated on the surface of a steel sheet during hot rolling of the steel material, or iron ore powder. Furthermore, the produced powder may be classified or mixed by various methods to prepare the iron powder according to the present disclosure. In order to remove oxygen to achieve the above-mentioned O / Fe range, deoxidation may be performed at 750°C or higher using carbon such as coke or graphite, or hydrogen gas.

[0030] [Production of additive powders (copper powder, nickel powder, molybdenum powder, and their metal oxide powders)] The copper powder, nickel powder and molybdenum powder used in the present disclosure can be produced by a water atomization method or a gas atomization method in which water or gas is sprayed onto a molten metal, which is then pulverized and cooled to solidify, a pulverization method or an oxide reduction method. In particular, electrolytic powder, which is electrolytically precipitated on a cathode, is preferred. Each metal powder and its oxide powder can be produced by adjusting the amount of oxygen in the atmosphere during drying. Furthermore, the produced powders may be classified or mixed by various methods to prepare the additive powder according to the present disclosure.

[0031] [Manufacturing of iron-based powder] In producing the iron-based powder for oxygen reactant, it is necessary to mix the above-mentioned iron powder and additive powder until they become uniform. Therefore, it is preferable to use a mixing device such as a V-type mixer, a double cone mixer, or a conical blender. The above-mentioned device and mixing conditions may be conventional.

[0032] [Oxygen reactant] In the present disclosure, the above-mentioned iron-based powder for oxygen reactant can be used to make an oxygen reactant. For example, the oxygen reactant of the present disclosure can be made by sealing the iron-based powder for oxygen reactant in a bag described below. Note that, as for the components in the oxygen reactant other than the iron-based powder for oxygen reactant, any components that are used in conventionally known oxygen reactants can be used without any particular restrictions. Examples of such components include a bag of a breathable packaging material in which a nonwoven fabric and perforated polyethylene are layered together, and a bag of a breathable packaging material in which paper and perforated polyethylene are layered together. EXAMPLES

[0033] The iron-based powder for oxygen reactant used in this example was prepared by the following procedure. Thirty-six types of iron powder with different O / Fe ratios were prepared by hydrogen reduction of iron ore powder. Separately, additive powders were prepared under various drying conditions using a water atomization method. Then, the iron powder and additive powder were each put into a V-type mixer and mixed to prepare each iron-based powder for oxygen reactant. The O / Fe ratio of the iron powder was calculated by measuring the content of Fe alone, the compound of Fe and O, and the compound content using an X-ray diffraction device (SmartLab manufactured by Rigaku Corporation) for Fe and O, respectively.

[0034] In this example, the oxygen reaction rate of the iron-based powder for oxygen reactants was evaluated as follows. 0.6 g of an aqueous solution with a sodium chloride concentration of 12% by mass was added to a mixed powder of 1.5 g of zeolite (Zeophyl 1424#, particle size 1.0-2.0 mm, manufactured by Shin Tohoku Chemical Industry Co., Ltd.) and 0.1 g of activated carbon powder (particle size 3.0-300 μm, manufactured by Fujifilm Wako Pure Chemical Industries Co., Ltd.), and then mixed with 1.5 g of the iron-based powder for oxygen reactants. The mixture was filled into a bag of breathable packaging material (50 mm long x 60 mm wide) to obtain each oxygen reactant. A laminated material composed of nonwoven fabric and perforated polyethylene was used as the breathable packaging material. One of each oxygen reactant was sealed together with 3 L of air in a gas barrier bag, which was a laminated material composed of nylon / aluminum foil / polyethylene. After leaving the bag at 25°C for 8 hours, the oxygen concentration in the bag was measured using a gas chromatograph (GD3210D manufactured by GL Sciences Inc.) The amount of oxygen reaction was calculated from the difference between the measured oxygen concentration and the oxygen concentration in the air, and the amount of oxygen reaction per gram of iron-based powder for oxygen reactant was calculated.

[0035] Table 1 shows the results of the oxygen reaction amounts of the iron-based powders for oxygen reactants of the comparative examples and the examples according to the present disclosure.

[0036] [Table 1]

[0037] As shown in Table 1, the iron-based powders for oxygen reactant of Examples 1 to 7, in which the atomic ratio O / Fe of oxygen to iron in the iron powder is 0.30 or more and the content of the additive powder in the mixed powder of the iron powder and the additive powder is 1.0 mass % or more and 40.0 mass % or less, have a higher oxygen reaction amount than the iron-based powders for oxygen reactant of Comparative Examples 1 to 29. Furthermore, the oxygen reaction amount per 1 g of the iron-based powder for oxygen reactant is 60 mL / g or more, which shows that the iron-based powders have an excellent oxygen reaction amount and excellent oxygen reactivity.

[0038] Among them, Examples 4 and 7, in which the content of the additive powder is 2.0 mass% or more, and Examples 5 and 6, in which the content is 25.0 mass% or less, are superior in that the oxygen reaction amount per 1 g of the iron-based powder for the oxygen reactant is 70 mL / g or more.

Claims

1. an iron powder having an oxygen to iron atomic ratio O / Fe of 0.30 or less; Additive powder, The additive powder contains at least one selected from the group consisting of copper powder, nickel powder, molybdenum powder, copper oxide powder, nickel oxide powder, and molybdenum oxide powder, The content of the additive powder is 1.0 mass% or more and 40.0 mass% or less, The iron-based powder for an oxygen reactant contains at least one of the molybdenum powder and the molybdenum oxide powder as the additive powder.

2. 2. The iron-based powder for an oxygen reactant according to claim 1, wherein the additive powders include the molybdenum powder and the molybdenum oxide powder.

3. 2. The iron-based powder for an oxygen reactant according to claim 1, wherein the additive powder contains 0.3 mass % or more and 25.8 mass % or less of the molybdenum powder.

4. 2. The iron-based powder for an oxygen reactant according to claim 1, wherein the additive powder contains 0.3 mass % or more and 5.8 mass % or less of the molybdenum oxide powder.

5. As the additive powder, The copper powder and the nickel powder, 2. The iron-based powder for an oxygen reactant according to claim 1, which contains said molybdenum powder or said molybdenum oxide powder.

6. An oxygen reactant using the iron-based powder for oxygen reactants according to any one of claims 1 to 5.

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