Iron-based powder for oxygen reactant and oxygen reactant using same

Abstract

Provided is an iron-based powder for oxygen reactants, the iron-based powder being produced at low cost and having appropriately controlled reactivity with oxygen. The interplanar spacing determined from the diffraction intensity curve corresponding to the (110) diffraction plane of the alpha-Fe crystal among the diffraction peaks of X-ray diffraction is in the range of # imgabs 0 # or more and # imgabs 1 # or less.

Description

Technical Field

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

[0002] Oxygen reactants that utilize the reaction between iron-based powder and oxygen are known to have uses such as deoxidizers or exothermic agents. For example, as a deoxidizer, the oxygen reactant can be sealed in a container together with stored items such as food and medicines to create a low-oxygen state inside the container. Therefore, oxygen reactants are used to suppress the quality deterioration of stored items caused by oxidation and the growth of mold, etc. In addition, oxygen reactants can be used as exothermic agents and are widely used as disposable heating pads for warming the human body. Typically, for these oxygen reactants, in order to further promote the reaction between the iron-based powder and oxygen, activated carbon, sodium chloride, silica powder, wood powder, water, sulfur powder, etc. are added to the iron-based powder.

[0003] Furthermore, since the reaction rate between iron and oxygen is important in any application, various methods have been studied as means for controlling the reaction rate.

[0004] For example, Patent Document 1 discloses an iron powder in which, in order to obtain good heat generation characteristics, attention is paid to pore size distribution, specific surface area, particle size, metallic iron content, etc., and these values ​​are kept within predetermined ranges.

[0005] Furthermore, Patent Document 2 discloses activated iron powder obtained by partially coating iron powder with a carbonaceous material.

[0006] Furthermore, Patent Document 3 discloses an oxygen absorbent in which iron powder and the like are mixed to form a mixed powder in order to obtain excellent oxygen absorption performance, and further the half-width of the diffraction peak, specific surface area, average particle size, etc. are controlled.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: International Publication No. 2017 / 082183

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2003-117385

[0011] Patent Document 3: Japanese Patent Application Laid-Open No. 2007-284632 Summary of the Invention

[0012] Problems to be solved by the invention

[0013] However, the invention described in Patent Document 1 focuses on the particle shape such as the pore diameter, and therefore, iron powders whose pore diameters do not meet the prescribed conditions are not used, resulting in an increase in production costs.

[0014] Furthermore, the invention described in Patent Document 2 requires not only the separate preparation of a carbon material but also the partial coating of the iron powder surface with a carbon material at a specified ratio. Furthermore, if the carbon material's coating is poor, dust generation from the carbon material may occur. Furthermore, if the carbon material's coating is poor, the target properties cannot be achieved.

[0015] Furthermore, in the invention described in Patent Document 3, it is necessary to mix a metal halide and an alkaline substance with iron powder, and thus the production cost is high.

[0016] An object of the present invention is to solve the above-mentioned problems and to provide an iron-based powder for an oxygen reactant having a low production cost and appropriately controlled reactivity with oxygen, and an oxygen reactant using the same.

[0017] Means for solving problems

[0018] In the field of mechanochemistry, it is known that when a solid substance is subjected to stress such as crushing, impact, or friction, its crystal properties change. Furthermore, when strain is induced in the solid's crystal structure, the substance becomes chemically activated, making it more susceptible to chemical reactions.

[0019] Therefore, with the purpose of solving the above-mentioned problems, the inventors of the present application conducted in-depth research focusing on the interplanar spacing calculated from the X-ray diffraction intensity curve of the (110) plane of α-Fe crystal, which represents the degree of strain in the crystal structure of the iron-based powder particles, in order to promote the reaction between the iron-based powder and oxygen.

[0020] As a result, they found that by setting the interplanar spacing within a certain range, it is possible to produce an iron-based powder whose reactivity with oxygen is appropriately controlled.

[0021] The present invention is based on the above findings, and its gist is as follows.

[0022] 1. Iron-based powder for oxygen reactant, wherein the interplanar spacing obtained from the diffraction intensity curve corresponding to the (110) diffraction plane of α-Fe crystal among the diffraction peaks of X-ray diffraction is above The following range.

[0023] 2. An oxygen reactant using the iron-based powder for oxygen reactant described in 1 above.

[0024] Effects of the Invention

[0025] According to the present invention, by appropriately setting the range of interplanar spacing in the X-ray diffraction intensity curve corresponding to the (110) plane of an α-Fe crystal, which indicates the degree of strain in the crystal structure of the iron-based powder particles, it is possible to produce an iron-based powder having appropriately controlled reactivity with oxygen at low cost. Furthermore, it is possible to produce an oxygen reactant using the iron-based powder. DETAILED DESCRIPTION

[0026] Hereinafter, the "iron-based powder" refers to a metal powder containing 50% by mass or more of Fe.

[0027] The reason why the iron-based powder for an oxygen reactant of the present invention has excellent oxygen reactivity is presumed to be as follows.

[0028] As mentioned above, it is known that when solid substances are subjected to stresses such as crushing, impact, and friction, their crystal properties change, particularly increasing the number of lattice defects in the crystal structure. Furthermore, these lattice defects can lead to mechanochemical effects and chemical activity.

[0029] In the case of iron-based powder, applying mechanical energy, such as by pulverizing with a pulverizer or mixing with a mixer, causes strain in the crystal structure of the iron-based powder particles, thereby increasing their reactivity with oxygen. Furthermore, the strain in the crystal structure generated within the iron-based powder particles can be evaluated based on the interplanar spacing value obtained from the diffraction intensity curve corresponding to the (110) diffraction plane of α-Fe crystals among the diffraction peaks of X-ray diffraction.

[0030] When compressive stress caused by mechanical energy is applied to the lattice of atoms in a three-dimensional arrangement constituting the α-Fe crystal, the interplanar spacing increases due to uniform strain. As the strain increases, the effect of improving the reactivity with oxygen becomes greater. Therefore, the interplanar spacing of the iron-based powder is set to Above, preferably More preferably On the other hand, if the strain is too large, the effect of improving the reactivity with oxygen becomes significantly larger, making it difficult to use as an oxygen reactant. For example, when used as a deoxidizer, excessive heat generation causes food and medicine to deteriorate due to heating. In addition, when used as a heating agent, there is a risk of burns due to excessive heat generation. Therefore, the above-mentioned interplanar spacing of the above-mentioned iron-based powder is set to the following.

[0031] According to the present invention, by preparing the iron-based powder for oxygen reactant that satisfies the above requirements, appropriately controlled reactivity can be achieved.

[0032] The iron-based powder can be used regardless of the particle shape, so the specific surface area and average pore size of the iron-based powder are not particularly limited. However, the smaller the specific surface area, the less likely it is to react with oxygen and moisture in the atmosphere, and the less likely the particle surface of the iron-based powder is to rust immediately after production. Since the metallic iron concentration of the iron-based powder with less rust is higher, the reactivity when used as an oxygen reactant is further improved. Therefore, it is preferred to have a specific surface area of, for example, 0.4 m 2 / g or less. The lower limit of the specific surface area is not particularly limited and can be 0m 2 For the same reason as the specific surface area, the average pore diameter is preferably set to 5 μm or more, for example.

[0033] The iron-based powder is not particularly limited, and any iron-based powder can be used. Examples of the iron-based powder include iron powder and iron-based alloy powder. It should be noted that the so-called "iron-based alloy powder" refers to an alloy powder containing 50% by mass or more of Fe. In addition, the so-called "iron powder" refers to a powder composed of Fe and inevitable impurities, and is generally referred to as "pure iron powder" in the technical field. In the case where the iron-based powder is an iron-based alloy powder, in addition to Fe, the iron-based alloy powder may also contain any elements such as C, S, O, N, Si, Mn, P, S, Cr, Cu, etc. In the case where the iron-based powder is iron powder, the iron powder may also contain any elements such as C, S, O, N, Si, Mn, P, S, Cr, Cu, etc. as inevitable impurities.

[0034] As described later, the iron-based powder used in the present invention can be produced by water atomization, gas atomization, pulverization, and oxide reduction methods.

[0035] It should be noted that the particle size of the iron-based powder used in the present invention is not particularly limited as long as there is no problem in operation. 50 On the other hand, the median particle size D is preferably 1 mm or less, more preferably 400 μm or less, and further preferably 200 μm or less. 50 There is no lower limit. However, the larger the particle size, the better the operability. For example, when manufacturing deoxidizer products, iron powder is allowed to fall freely from a thin tube and loaded into a packaging container. If the particle size of the iron-based powder is too fine, powder clogging and powder scattering in the tube will occur during loading. By increasing the particle size, the above problems can be avoided. From this point of view, the median particle size D 50 It is preferably 5 μm or more, and more preferably 50 μm or more.

[0036] The median particle size of the iron-based powder used in the present invention (the median value of the particle size calculated from the volume-based particle size distribution) D 50The laser diffraction and scattering method is used for measurement. The specific measurement method is as follows.

[0037] The iron-based powder to be measured is put into a solvent (e.g., ethanol), dispersed by ultrasonic vibration for more than 30 seconds, and the particle size is measured using a laser diffraction particle size distribution analyzer using a laser diffraction / scattering method, that is, the volume-based particle size distribution of the iron-based powder particles is measured.

[0038] The cumulative particle size distribution was calculated from the obtained particle size distribution, and the particle size corresponding to 50% of the total volume of all particles was taken as the median D. 50 , is used as a representative value of the particle size of the above-mentioned iron-based powder.

[0039] [Method for measuring interplanar spacing of α-Fe crystals]

[0040] The method for measuring the interplanar spacing of α-Fe crystals according to the present invention is as follows.

[0041] The powder under investigation is subjected to X-ray diffraction measurement to obtain a diffraction intensity curve corresponding to the (110) diffraction plane of α-Fe. The interplanar spacing can be calculated from the diffraction angle in this diffraction intensity curve and the wavelength of the characteristic X-ray according to Bragg's law shown in the following formula (1).

[0042] Specifically, the characteristic X-rays (wavelength ), measuring the iron-based powder under the conditions of a scanning speed of 4° / minute and a measurement angle range of 35° to 55°, yielding a diffraction intensity curve corresponding to the (110) diffraction plane of α-Fe crystals in the iron-based powder. Interplanar spacing was calculated from the diffraction angle and the wavelength of the characteristic X-ray.

[0043] 2d·sinθ=n·λ · · · (1)

[0044] d: interplanar spacing

[0045] θ: diffraction angle (°)

[0046] n: natural number

[0047] λ: wavelength of X-rays

[0048] [Manufacturing of iron-based powder]

[0049] Next, the method for producing the iron-based powder according to the present invention will be described. The iron-based powder according to the present invention can be produced by any method. For example, the iron-based powder can be produced by further subjecting the iron-based powder produced by a method such as an atomization method, an oxide reduction method or a pulverization method to a treatment for increasing the strain of the α-Fe crystal. Here, the atomization method is a method of obtaining metal powder by spraying water, gas, etc. onto the molten metal to cool and solidify it in a spray form. As the atomization method, either a water atomization method or a gas atomization method can be used. The oxide reduction method is, for example, a method of reducing iron oxide (rolling scale) or iron ore powder generated from the surface of a steel plate during hot rolling of a steel material. The pulverization method is a method of obtaining metal powder by pulverizing a metal sheet. In addition, the produced powder can also be classified or mixed. The classification and mixing can be performed by any method.

[0050] Next, since the strain of the α-Fe crystals is almost non-existent in the iron-based powder obtained by the above method, it is necessary to subject the iron-based powder to a treatment that increases the strain of the α-Fe crystals in the iron-based powder. The above treatment is preferably a treatment that imparts mechanical energy using a mixer or a pulverizer. The above mixer is not particularly limited, and a V-type mixer, a double cone mixer, a conical mixer, a stirring granulator, etc. can be suitably used. In addition, the above pulverizer is not particularly limited, and a ball mill, a vibration mill, a roller mill, a jet mill, a hammer mill, a disc mill, etc. can be suitably used.

[0051] It should be noted that the mixing and pulverizing conditions when using the above-mentioned mixer or pulverizer can be conventional methods, except that the strain of the α-Fe crystal is adjusted to the range of the present invention. For example, the interplanar spacing of the α-Fe crystal can be controlled by adjusting the mixing time or pulverizing time.

[0052] When mechanical energy is applied using the mixer or pulverizer for the purpose of improving reactivity with oxygen, carbon powder such as activated carbon and coke powder may be further added, or metal powder such as Cu, Ni, or Mo may be added.

[0053] [Oxygen reactant]

[0054] In one embodiment of the present invention, the aforementioned iron-based powder for an oxygen reactant can be used to produce an oxygen reactant. In other words, the oxygen reactant according to one embodiment of the present invention utilizes the aforementioned iron-based powder for an oxygen reactant. The iron-based powder for an oxygen reactant of the present invention exhibits excellent reactivity with oxygen and is therefore suitable for use in the aforementioned oxygen reactant. Therefore, the aforementioned oxygen reactant exhibits the same effects as the iron-based powder for an oxygen reactant of the present invention.

[0055] Components of the oxygen reactant other than the iron-based powder for the oxygen reactant are not particularly limited, and conventionally known components can be used as components of the oxygen reactant. For example, additives may be added to the iron-based powder. Examples of such additives include activated carbon and salt water. Furthermore, the oxygen reactant may be enclosed in a bag of breathable packaging material. Examples of such bags include bags formed by overlapping non-woven fabric and open-pore polyethylene, bags formed by overlapping paper and open-pore polyethylene, and the like. It should be noted that the oxygen reactant may also be composed of the iron-based powder for the oxygen reactant.

[0056] Example

[0057] The iron-based powder for the oxygen reactant used in this embodiment was prepared by the following steps.

[0058] First, iron powder is produced from molten steel by water atomization.

[0059] Next, 1 kg of the iron powder was stirred in a high-speed mixer (Fukae Powtech Co., Ltd., stirring granulator model: LFS-GS-2J) to obtain the iron-based powder for the oxygen reactant used in this example. All of the iron-based powders for the oxygen reactant were iron powders. The stirring conditions were: a stirring blade speed of 500 rpm within the sample container, and a stirring time of 0 to 180 minutes.

[0060] The method for calculating the interplanar spacing obtained from the diffraction intensity curve corresponding to the (110) diffraction plane of α-Fe crystal among the diffraction peaks of X-ray diffraction of the iron-based powder is as follows.

[0061] First, X-ray diffraction measurement was performed using an X-ray diffractometer (SmartLab manufactured by Rigaku Holdings Corporation). The characteristic X-rays of Cu-Kα (wavelength ), the iron-based powder to be measured was measured at a scanning speed of 4° / minute and a measurement angle range of 35° to 55° to obtain a diffraction intensity curve corresponding to the (110) diffraction plane of α-Fe crystal. The interplanar spacing was then calculated from the diffraction intensity curve.

[0062] In this example, the oxygen reactivity of the iron-based powder for an oxygen reactant was evaluated as follows.

[0063] To each iron-based powder: 20g, add 8% by mass sodium chloride aqueous solution: 2g and mix to obtain a sample. Then, the obtained sample is sealed in a gas barrier ziplock bag (HSC160-ST made by As One Corporation) with oxygen barrier properties, and allowed to stand at 25°C for 1 hour to make the sample at room temperature. Then, the samples are respectively put into paper cups (SD-729 made by Strix Design, Inc.), and a temperature sensor connected to a data logger (TR-71wf made by T&D Corporation) is inserted into the center of the sample. After inserting the temperature sensor, the temperature is measured at intervals of 1 minute, and the time elapsed until the temperature of the sample reaches 40°C and the highest temperature reached are respectively calculated.

[0064] Table 1 shows the measurement results of the iron-based powders for oxygen reactants according to the comparative examples and the inventive examples of the present invention.

[0065] [Table 1]

[0066] Table 1

[0067]

[0068] It is known that the above-mentioned interplanar spacing obtained by stirring with a high-speed mixer for an appropriate time becomes The iron-based powders of the above invention examples 1 to 6 have a lattice spacing smaller than Compared with the iron-based powders of Comparative Examples 1 to 3, the maximum temperature reached 40° C. or higher, and the oxygen reactivity was good.

[0069] Among them, in the case of invention examples 2 to 6, since the above-mentioned interplanar spacing is As a result, the maximum temperature reached 45° C., and the time until the temperature reached 40° C. was shortened, indicating that the oxygen reactivity was further improved.

[0070] In addition, in Invention Examples 4 to 6, since the above-mentioned interplanar spacing is As a result, the maximum temperature reached 50° C., and the time until the temperature reached 40° C. was shortened, indicating that the oxygen reactivity was particularly good.

[0071] On the other hand, in Comparative Examples 4 and 5, since the above-mentioned interplanar spacing is larger than Therefore, the maximum temperature reached is 70°C or higher, and the time until it reaches 40°C is less than 150 minutes, which makes it difficult to use as an oxygen reactant. It should be noted that under the conditions of this example, the range in which it is difficult to use as an oxygen reactant is the maximum temperature reached is 70°C or higher, and the time until it reaches 40°C is less than 150 minutes.

Claims

1. Iron-based powder for oxygen reactant, wherein: The interplanar spacing obtained from the diffraction intensity curve corresponding to the (110) diffraction plane of α-Fe crystal among the diffraction peaks of X-ray diffraction is above The following range.

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

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