Iron-based powder for oxygen reactant and oxygen reactant

Abstract

Provided is an iron-based powder for oxygen reactants, which does not require the use of a metal halide and has excellent oxygen reactivity. The iron-based powder for an oxygen reactant contains an iron powder in which the atomic ratio (O / Fe) of oxygen to iron is 0.30 or less and an additive powder that is at least one 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, and the content of the additive powder is 1.0-40.0 mass%.

Description

Technical Field

[0001] The present invention relates to an iron-based powder for an oxygen reactant and an oxygen reactant. Background Art

[0002] As oxygen reactants that utilize the reaction between iron-based powder and oxygen, the uses of deoxidizers and exothermic agents are known. As deoxidizers, they are sealed in a container together with stored items such as food and medicines to form a low oxygen state, and are used to suppress quality degradation caused by oxidation of stored items and the growth of molds, etc. As exothermic agents, they are widely used as disposable heating pads for heating the human body, etc. In general, among these oxygen reactants, activated carbon, sodium chloride, silica powder, wood powder, water, sulfur powder, etc. are added to the iron-based powder in order to further promote the oxygen reaction.

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

[0004] For example, Japanese Patent Application Laid-Open No. 05-237373 (Patent Document 1) discloses a deoxidizing agent having excellent reactivity at low temperatures.

[0005] Japanese Patent Application Laid-Open No. 53-60885 (Patent Document 2) discloses a metal heat-generating composition in which one or more of manganese dioxide, copper oxide and ferrosoferric oxide is mixed with activated carbon containing iron powder, chloride and water to promote oxidation.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 05-237373

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 53-60885 Summary of the invention

[0010] The deoxidizer disclosed in Patent Document 1 requires the use of metal halide, so it easily absorbs moisture in the atmosphere, and the oxygen reaction of the iron powder proceeds rapidly. Therefore, the deoxidizer has problems in operation and storage, such as having to put the metal halide into a bag for the deoxidizer immediately after adding it to the iron powder and having to store it in an oxygen-free state.

[0011] In the metal heat generating composition disclosed in Patent Document 2, ferroferric oxide, lead oxide, manganese oxide, copper oxide, and manganese dioxide account for the majority of the composition, and all of them are oxidized to a certain extent. Therefore, the metal heat generating composition has a problem of poor reactivity with oxygen at the beginning of the reaction.

[0012] In view of such actual conditions, an object of the present disclosure is to provide an iron-based powder for an oxygen reactant and an oxygen reactant which do not require the use of a metal halide and have excellent oxygen reactivity.

[0013] Since copper, nickel, and molybdenum have a lower ionization tendency than iron, they are less likely to react with oxygen than iron. In addition, since copper oxide, nickel oxide, and molybdenum oxide have already been oxidized, they are even less likely to react with oxygen. Therefore, the above substances are worse than iron powder as oxygen reactants.

[0014] In contrast, the standard electrode potential of copper, nickel, and molybdenum is higher than that of iron. In addition, from the potential-pH diagram (Pourbait diagram) of each metal, it can be seen that the potential increases when the metal is oxidized.

[0015] Here, if the iron powder contacts the metal powder with a higher potential than the iron powder in a corrosive environment such as an electrolyte, the following local battery mechanism occurs: the corrosion current flows from the metal powder with a higher potential to the iron powder with a lower potential, and then the corrosion current returns to the metal powder with a higher potential than the iron powder through the electrolyte and then flows to the iron powder with a lower potential again. It is also believed that if such a mechanism occurs, the reaction between the iron powder with a lower potential and oxygen is promoted.

[0016] Therefore, in order to promote the reaction between iron-based powder and oxygen, the inventors thought of adding copper powder, nickel powder, molybdenum powder and their oxide powders, which are not used before and are more difficult to react with oxygen than iron, to iron powder, and conducted intensive research. As a result, they found that there is an appropriate mixing ratio of iron-based powder that exhibits excellent oxygen reactivity.

[0017] The present disclosure is based on the above findings, and its gist is as follows

[0018] 1. An iron-based powder for an oxygen reactant, comprising iron powder and additive powder,

[0019] The oxygen to iron atomic ratio O / Fe of the iron powder is less than 0.30, and

[0020] The additive powder is at least one selected from copper powder, nickel powder, molybdenum powder, copper oxide powder, nickel oxide powder and molybdenum oxide powder.

[0021] The content of the above-mentioned added powder is 1.0 mass % to 40.0 mass %.

[0022] 2. An oxygen reactant using the iron-based powder for oxygen reactant described in 1 above.

[0023] According to the present disclosure, an iron-based powder for an oxygen reactant and an oxygen reactant having excellent oxygen reactivity without using a metal halide can be obtained. DETAILED DESCRIPTION

[0024] Hereinafter, embodiments of the present disclosure will be described. It should be noted that the following embodiments are examples for describing the present disclosure, and the present disclosure is not limited to the embodiments.

[0025] The reason why the iron-based powder for oxygen reactant of the present disclosure exhibits excellent oxygen reactivity is presumed as follows. That is, copper powder, nickel powder, molybdenum powder and their oxide powders (also referred to as "additive powder" in the present disclosure) have a higher potential than iron powder. Therefore, if the additive powder is in contact with the iron powder in the electrolyte, a corrosion current is generated to promote the oxidation reaction of the iron powder. In addition, the iron-based powder for oxygen reactant of the present disclosure has excellent reactivity with oxygen and is therefore suitable for the oxygen reactant of the present disclosure. Therefore, the oxygen reactant of the present disclosure can have the same characteristics and effects as the iron-based powder for oxygen reactant of the present disclosure.

[0026] Here, if the iron is oxidized, the potential increases. Therefore, the iron powder before use as an oxygen reactant is not oxidized as much as possible, so that the potential difference with the added powder is easily increased. As a result, the corrosion current becomes larger. Specifically, it is necessary to make the atomic ratio of oxygen to iron (hereinafter also referred to as O / Fe) less than 0.30. As long as it is within such a range of O / Fe, the potential difference with the added powder becomes large enough to generate an effective corrosion current (sufficient to promote the oxidation reaction of the iron powder) in the electrolyte. Therefore, in the present disclosure, the O / Fe in the iron powder of the iron-based powder for oxygen reactant is less than 0.30. It should be noted that the lower limit of O / Fe is not particularly limited, and it can also be 0, and it is preferably about 0.15 in industry. In addition, the value of O / Fe can be measured according to the method described later.

[0027] The iron powder used in the present disclosure can be produced by water atomization, gas atomization, pulverization, or oxide reduction.

[0028] In the present disclosure, at least one powder selected from the group consisting of copper powder, nickel powder, molybdenum powder, copper oxide powder, nickel oxide powder and molybdenum oxide powder (a group of added powders) is added to the iron powder.

[0029] It should be noted that copper powder, nickel powder, and molybdenum powder can be manufactured by water atomization, gas atomization, pulverization, oxide reduction, and electrolysis, or they can be commercially available products. In addition, copper oxide powder, nickel oxide powder, and molybdenum oxide powder can be materials obtained by oxidizing the copper powder, nickel powder, and molybdenum powder manufactured by the above methods by spraying water, salt water, etc., or they can be commercially available products.

[0030] Here, "iron-based powder" refers to a metal powder containing 50.0% by mass or more of metallic iron. In addition to the above-mentioned metallic iron (Fe), the iron-based powder may further contain any element such as C, S, O, N, Si, Na, Mg, Ca, etc. It should be noted that the metallic iron content of the iron-based powder can be measured according to JIS A5011-2 "Metallic Iron Quantitative Method".

[0031] 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 % to 40.0 mass %. 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 between iron powder and oxygen is lacking. On the other hand, since the additive powder itself is not easily oxidized and the amount of reaction with oxygen is less than that of iron powder, if 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 iron powder and additive powder becomes too low compared to the oxygen reaction amount of iron powder alone. It should be noted that 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, preferably 25.0 mass % or less.

[0032] In summary, the present disclosure can achieve excellent oxygen reactivity by providing an iron-based powder for an oxygen reactant that satisfies the above requirements.

[0033] It should be noted that the particle sizes of the iron powder and the additive powder are not particularly limited as long as there is no problem in operation. The median particle size (the median value of the particle size based on the cumulative volume frequency) is D 50 The particle size is preferably 1 mm or less, preferably 400 μm or less, and more preferably 200 μm or less. On the other hand, the lower limit of the particle size of the iron powder and the additive powder is preferably about 5 μm in terms of handling.

[0034] The median particle size D of the iron powder and the added powder in the present disclosure 50 The measurement method is as follows. The iron powder and additive powder to be measured are put into ethanol as a solvent, dispersed by ultrasonic vibration for more than 30 seconds, and the particle size is measured using a laser diffraction particle size distribution measuring machine using a laser diffraction / scattering method, that is, the volume-based particle size distribution of the particles of the iron powder and additive powder is measured respectively. The cumulative particle size distribution is calculated based on the obtained particle size distribution, and the particle size of the particles corresponding to 50% of the total volume of all particles is taken as the median particle size D. 50 In the present disclosure, the median particle size D is used. 50 As a representative value of the particle size of the above-mentioned iron powder and additive powder.

[0035] [Calculation method of O / Fe in powder]

[0036] The calculation method of O / Fe in the powder disclosed in the present invention is preferably as follows. The powder as the object is subjected to X-ray diffraction measurement, and the obtained diffraction data is subjected to Rietveld analysis, thereby knowing the content of Fe single substance, Fe and O compound, and other compounds in the powder. The number of Fe and O atoms is obtained from the numerical value of the content, and the value of O / Fe can be calculated.

[0037] [Manufacturing of iron powder]

[0038] When manufacturing the iron powder used in the present disclosure, it is preferred to use a water atomization method or a gas atomization method in which water or gas is sprayed on the molten metal to pulverize it and cool it to solidify, and to reduce the iron oxide (scale) and iron ore powder generated on the surface of the steel plate during hot rolling of the steel. Furthermore, the produced powder can also be classified or mixed by various methods to adjust it to the iron powder of the present disclosure. It should be noted that in order to remove oxygen to achieve the above-mentioned O / Fe range, deoxidation can be performed using carbon such as coke and graphite or hydrogen at a temperature above 750°C.

[0039] [Manufacture of additive powder (copper powder, nickel powder and molybdenum powder, and their oxide metal powders)]

[0040] When manufacturing the copper powder, nickel powder and molybdenum powder used in the present disclosure, there are water atomization method, gas atomization method, pulverization method and oxide reduction method in which water and gas are sprayed on the molten metal to pulverize and cool and solidify it, and electrolytic powder precipitated at the cathode by electrolysis is particularly preferred. Each metal powder and its oxidized powder can be manufactured by adjusting the oxygen content in the atmosphere during drying. In addition, the produced powder can also be classified or mixed by various methods to adjust it to the added powder of the present disclosure.

[0041] [Manufacturing of iron-based powder]

[0042] When producing the iron-based powder for oxygen reactant, the iron powder and the additive powder need to be mixed until uniform. Therefore, it is preferred to use a V-type mixer, a double cone mixer, a cone blender, etc. for mixing. It should be noted that the above-mentioned device and its mixing conditions can be conventional methods.

[0043] [Oxygen reactant]

[0044] In the present disclosure, the oxygen reactant can be made using the above-mentioned iron-based powder for oxygen reactant. For example, if the iron-based powder for oxygen reactant is sealed in the bag described below, the oxygen reactant disclosed in the present disclosure can be made. It should be noted that for the components other than the iron-based powder for oxygen reactant in the oxygen reactant, as long as they are substances used in the conventionally known oxygen reactants, they can be used without particular restrictions. As such components, for example, there can be cited bags of breathable packaging materials formed by overlapping non-woven fabrics and open-pore polyethylene, bags of breathable packaging materials formed by overlapping paper and open-pore polyethylene, etc.

[0045] Example

[0046] The iron-based powder for oxygen reactant used in this embodiment is prepared according to the following steps. Iron ore powder is hydrogen reduced to prepare 36 kinds of iron powders with different O / Fe. In addition, an additive powder prepared under various drying conditions is prepared using a water atomization method. Next, the iron powder and the additive powder are respectively added into a V-type mixer and mixed to prepare each iron-based powder for oxygen reactant. It should be noted that the O / Fe of the iron powder is calculated by measuring the content of Fe single substance, the compound of Fe and O, and the content of the compound using an X-ray diffraction device (SmartLab manufactured by Rigaku Co., Ltd.) for Fe and O, respectively.

[0047] In this embodiment, the oxygen reactivity of the iron-based powder for oxygen reactants is evaluated as follows. After adding 0.6 g of an aqueous solution with a concentration of 12% by mass of sodium chloride to a mixed powder of 1.5 g of zeolite (Zeolite 1424# with a particle size of 1.0 to 2.0 mm manufactured by Shintohoku Chemical Industry) and 0.1 g of activated carbon powder (with a particle size of 3.0 to 300 μm manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), the substance obtained by mixing with 1.5 g of the above iron-based powder for oxygen reactants is filled into a bag (length 50 mm × width 60 mm) of a breathable packaging material to obtain each oxygen reactant. The breathable packaging material uses a laminate composed of non-woven fabric and open-pore polyethylene. Each oxygen reactant is sealed together with 3 L of air in a laminate composed of nylon / aluminum foil / polyethylene, i.e., a gas barrier bag. After the bag is left to stand at 25°C for 8 hours, the oxygen concentration in the bag is measured using a gas chromatograph (GD3210D manufactured by GL Sciences Co., Ltd.). The oxygen reaction amount was calculated based on the difference between the measured oxygen concentration and the oxygen concentration in the air, and the oxygen reaction amount per 1 g of the iron-based powder for the oxygen reactant was calculated.

[0048] Table 1 shows the results of the oxygen reaction amount of each iron-based powder for oxygen reactant in the comparative example and the example of the present disclosure.

[0049] [Table 1]

[0050]

[0051] ※ Underlined characters indicate outside the scope of the present invention.

[0052] As shown in Table 1, the iron-based powders for oxygen reactants 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 added powder in the mixed powder of the iron powder and the added powder is 1.0 mass % to 40.0 mass %, have a higher oxygen reaction amount than the iron-based powders for oxygen reactants of Comparative Examples 1 to 29. In addition, the oxygen reaction amount per 1 g of the iron-based powder is 60 mL / g or more, and the oxygen reaction amount is excellent, and the oxygen reactivity is excellent.

[0053] It can be seen that in Examples 4 and 7 where the content of the added powder is 2.0 mass % or more and Examples 5 and 6 where the content is 25.0 mass % or less, the oxygen reaction amount per 1 g of the iron-based powder for oxygen reactant is 70 mL / g or more, which is more excellent.

Claims

1. An iron-based powder for an oxygen reactant, comprising iron powder and additive powder, The oxygen to iron atomic ratio O / Fe of the iron powder is less than 0.30, and The additive powder is at least one selected from copper powder, nickel powder, molybdenum powder, copper oxide powder, nickel oxide powder and molybdenum oxide powder. The content of the added powder is 1.0 mass % to 40.0 mass %.

2. An oxygen reactant using the iron-based powder for oxygen reactant according to claim 1.

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