Iron-based powder for oxygen reactants and oxygen reactants

Abstract

Provided is an iron-based powder for an oxygen reactant that has exceptional oxygen reactivity. This iron-based powder for an oxygen reactant contains an iron powder having an atomic number ratio O / Fe of oxygen and iron of 0.30 or less and a carbonaceous powder having a C content of 50 mass% or greater, the content value for the carbonaceous powder being 0.20-30.00 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 reactants that utilize the reaction between iron-based powder and oxygen include 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, these oxygen reactants have activated carbon, sodium chloride, silica powder, wood powder, moisture, sulfur powder, and the like 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 powders of conductive materials other than iron with iron powder has been studied as a means of controlling the reaction rate.

[0004] For example, Japanese Patent Laid-Open Publication No. 2003-117385 (Patent Document 1) discloses an oxygen scavenger using activated iron powder in which the surface of the iron powder is partially coated with 0.3 to 3.0% by weight of a conductive carbonaceous material such as conductive graphite, carbon black, graphite, and activated carbon.

[0005] Patent Document 1 discloses that the so-called free carbon state liberated from the iron powder has no effect on the oxygen absorption properties of the oxygen scavenger, and therefore an operation to partially coat the iron powder surface is necessary. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2003-117385 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, the disclosure of Patent Document 1 does not specify the components of the iron powder itself. In particular, if the surface of iron powder is oxidized, it becomes difficult to become iron ions and emit electrons. Therefore, if the surface of iron powder is oxidized as is commonly seen, there is a problem that the phenomenon described in Patent Document 1, in which the iron powder becomes the anode and the carbon material becomes the cathode to promote the oxidation reaction, does not occur easily.

[0008] The present disclosure has been made in view of the above circumstances, and has an object to provide an iron-based powder for an oxygen reactant having excellent oxygen reactivity, and an oxygen reactant. [Means for solving the problem]

[0009] As described above, the above-mentioned graphite powder and carbonaceous powders such as coal powder and activated carbon powder are considered to have no effect on the oxygen absorption properties of the oxygen scavenger in the free carbon state, and therefore do not function as oxygen reactants.

[0010] Carbonaceous powders such as those described above have a higher standard electrode potential than iron, and the iron potential-pH diagram (Pourbaix diagram) shows that the potential increases when iron is oxidized.

[0011] When iron powder and carbonaceous powder, which is a conductive powder with a higher potential than the iron powder, come into contact in a corrosive environment such as an electrolyte, a local battery mechanism occurs in which a corrosion current flows from the carbonaceous powder with a higher potential to the iron powder with a lower potential, and then the corrosion current returns to the carbonaceous powder with a higher potential than the iron powder via the electrolyte and then flows back to the iron powder. It is believed that the occurrence of such a mechanism promotes the reaction between the low-potential iron powder and oxygen.

[0012] Therefore, the inventors came up with the idea of ​​adding a carbonaceous powder in a free carbon state that is difficult to react with oxygen to the 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 the iron-based powder that exhibits excellent oxygen reactivity.

[0013] The present disclosure is based on the above findings, and has the following gist and configuration.

[0014] 1. Iron powder having an oxygen to iron atomic ratio O / Fe of 0.30 or less; and a carbonaceous powder having a C content of 50% by mass or more; The iron-based powder for an oxygen reactant has a carbonaceous powder content of 0.20% by mass or more and 30.00% by mass or less.

[0015] 2. The iron-based powder for an oxygen reactant according to the above item 1, wherein the carbonaceous powder comprises at least one of coal powder and coke powder.

[0016] 3. The iron-based powder for an oxygen reactant according to the above item 1, wherein the carbonaceous powder comprises coal powder and coke powder.

[0017] 4. The iron-based powder for an oxygen reactant according to any one of 1 to 3 above, wherein the carbonaceous powder comprises at least one of activated carbon powder and carbon black powder.

[0018] 5. The iron-based powder for an oxygen reactant according to any one of 1 to 4 above, wherein the carbonaceous powder contains 0.12 mass % or more of coke powder.

[0019] 6. The iron-based powder for an oxygen reactant according to any one of 1 to 5 above, wherein the carbonaceous powder comprises coke powder and carbon black powder.

[0020] 7. The coke powder is 3.50% by mass or more, and 7. The iron-based powder for an oxygen reactant according to 6 above, containing 6.20 mass % or more of the carbon black powder.

[0021] 8. An oxygen reactant using the iron-based powder for oxygen reactants according to any one of 1 to 7 above. Effect of the Invention

[0022] According to the present disclosure, 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

[0023] 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.

[0024] 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, since the carbonaceous powder has a higher potential than the iron powder, when the carbonaceous powder and the iron powder come into contact in an electrolyte, a corrosion current is generated, promoting the oxidation reaction of the iron powder. In addition, the iron-based powder for an oxygen reactant of the present disclosure has excellent reactivity with oxygen, and is therefore 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.

[0025] Here, since the potential of iron increases when it is oxidized, it is easier to increase the potential difference with the carbonaceous powder if the iron powder is not oxidized as much as possible before use as an oxygen reactant. As a result, the corrosion current increases. Therefore, in the present disclosure, the atomic ratio of oxygen to iron (hereinafter also referred to as "O / Fe") in the iron powder of the iron-based powder for the oxygen reactant must be 0.30 or less. This is because, if the O / Fe range is within this range, the potential difference between the carbonaceous powder and the iron powder in the electrolyte becomes sufficiently large, and an effective amount of corrosion current (sufficient to promote the oxidation reaction of the iron powder) is generated. 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.

[0026] The iron powder used in the present disclosure can be produced by water atomization, gas atomization, pulverization, and oxide reduction. In addition, the present disclosure adds carbonaceous powder to the iron powder. The carbonaceous powder may be a commercially available product such as activated carbon powder, coke powder, or carbon black powder.

[0027] Here, the term "iron-based powder" in the present disclosure refers to a metal powder containing 50.0 mass% or more of Fe. 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 in accordance with JIS A 5011-2 "Method for determining metallic iron."

[0028] The iron-based powder for oxygen reactant is a mixed powder of iron powder and carbonaceous powder, and the content of the carbonaceous powder in the mixed powder is in the range of 0.20% by mass or more and 30.00% by mass or less. If the content of the carbonaceous powder in the iron-based powder for oxygen reactant is less than 0.20% by mass, the corrosion current is small and there is no effect on promoting the oxygen reaction of the iron powder. On the other hand, since the carbonaceous powder itself is difficult to oxidize and reacts with oxygen in a smaller amount than the iron powder, if the content of the carbonaceous powder in the iron-based powder for oxygen reactant is more than 30.00% by mass, the oxygen reaction amount of the mixture of the iron powder and the carbonaceous powder becomes too low compared to the oxygen reaction amount of the iron powder alone (for example, 60 mL / g). From the viewpoint of oxygen reactivity, the content of the carbonaceous powder in the iron-based powder for oxygen reactant is preferably 0.50% by mass or more, and the content of the carbonaceous powder is preferably 15.00% by mass or less.

[0029] The present disclosure provides an iron-based powder for an oxygen reactant that satisfies the above requirements, thereby achieving excellent oxygen reactivity.

[0030] The particle size of the iron powder is not particularly limited as long as it is easy to handle, but the median diameter (median value of particle size from cumulative volume frequency) D 50 The particle size 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 is preferably about 5 μm from the viewpoint of handling. 50can be measured according to the procedures described below.

[0031] The carbonaceous powder of the present disclosure is a carbonaceous powder having a C content (carbon content) of 50% by mass or more. If the C content in the carbonaceous powder is less than 50% by mass, the corrosion current amount is small and there is no effect in promoting the oxygen reaction of the iron powder. The C content in the carbonaceous powder is preferably 60% by mass or more, more preferably 70% by mass or more. On the other hand, there is no particular upper limit, and the C content in the carbonaceous powder may be 100% by mass, but from an economical point of view, it is preferably about 95% by mass.

[0032] The particle size of the carbonaceous powder is not particularly limited as long as it is easy to handle, but the median diameter D 50 The particle size of the carbonaceous powder is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less. On the other hand, the lower limit of the particle size of the carbonaceous powder is preferably about 5 μm from the viewpoint of handling.

[0033] Median diameter D of iron powder and carbonaceous powder 50 The measurement method is as follows: The iron powder and carbonaceous 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 carbonaceous powder particles is measured. The cumulative particle size distribution is calculated from the obtained particle size distribution, and the particle size of the particle 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 carbonaceous powder, respectively.

[0034] [Calculation method for O / Fe in powder] The method for measuring the O / Fe ratio in a powder according to 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 found from the numerical content, and the value of O / Fe can be calculated.

[0035] [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. 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.

[0036] [Carbonaceous powder] The carbonaceous powder of the present disclosure may be a commercially available product such as coal powder, activated carbon powder, coke powder, or carbon black powder, but for example, coke powder can be produced as follows. That is, in producing such coke powder, coal is dry-distilled at 1000°C or higher for 10 hours or more to remove volatile matter and tar contained in the coal, and then crushed and classified. Furthermore, powder generated during crushing and classification can also be preferably used.

[0037] [Manufacturing of iron-based powder] In producing the iron-based powder for oxygen reactants, it is necessary to mix the iron powder and the carbonaceous powder described above. In the iron-based powder for oxygen reactants, it is preferable that the iron powder and the carbonaceous powder are mixed uniformly. For this reason, 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 the mixing conditions may be publicly known.

[0038] [Oxygen reactant] In the present disclosure, the above-mentioned iron-based powder for oxygen reactants can be used to produce an oxygen reactant. For example, the oxygen reactant of the present disclosure can be produced by sealing the iron-based powder for oxygen reactants in a bag described below. Note that, as for the components in the oxygen reactant other than the iron-based powder for oxygen reactants, 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 ventilated packaging material in which a nonwoven fabric and perforated polyethylene are layered together, and a bag of a ventilated packaging material in which paper and perforated polyethylene are layered together. EXAMPLES

[0039] The iron-based powder for oxygen reactant used in this example was prepared by the following procedure. Thirty-nine types of iron powder with different O / Fe ratios were prepared by hydrogen reduction of iron ore powder. The iron powder, as well as two types of powdered lignite (A, B), subbituminous coal, activated carbon powder (Shirasagi PHC-14, manufactured by Osaka Gas Chemicals Co., Ltd.), coke powder produced by pulverizing coke produced by carbonizing coal at 1200°C for 15 hours, and carbon black powder (REGAL330R, manufactured by Cabot Corporation) were each charged into a V-type mixer and mixed to prepare each iron-based powder for oxygen reactant. Here, the C content of the lignite A was 58.7% by mass. The C content of the lignite B was 68.2% by mass. The C content of the subbituminous coal was 75.7% by mass. The C content of the activated carbon powder was 89.8% by mass. The C content of the coke powder was 81.7% by mass. The C content of the carbon black powder was 98.1% by mass. The O / Fe ratio of the iron powder was calculated by measuring the content of Fe alone, Fe and O compounds, and other compounds using an X-ray diffractometer (SmartLab manufactured by Rigaku Corporation).

[0040] In this embodiment, 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 1.5 g of zeolite (Zeophyl 1424# with a particle size of 1.0 to 2.0 mm, manufactured by Shin Tohoku Chemical Industry 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 a breathable packaging material (50 mm long x 60 mm wide) to obtain each oxygen reactant. A laminated material composed of a 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. The bag was left to stand at 25°C for 8 hours, and the oxygen concentration in the bag was measured with a gas chromatograph (GC3210D, manufactured by GL Sciences Inc.). The amount of oxygen reaction was calculated from the difference between the oxygen concentration thus measured and the oxygen concentration in the air, and the amount of oxygen reaction per gram of the iron-based powder for the oxygen reactant was calculated.

[0041] Table 1 shows the results of the oxygen reaction amount of each iron-based powder for oxygen reactants of the comparative example and the examples according to the present disclosure. Table 2 also shows the median diameter (D 50 Table 3 shows the median diameter (D 50 In the following description, the iron-based powder for an oxygen reactant may be simply referred to as an iron-based powder.

[0042] [Table 1]

[0043] [Table 2]

[0044] [Table 3]

[0045] As shown in Table 1, the oxygen to iron atomic ratio O / Fe in the iron powder is 0.30 or more, the carbonaceous powder content in the mixed powder with the iron powder is 0.20 mass% or more and 30.0 mass% or less, and the iron powder contains at least one of coal powder and coke powder. The iron-based powders of Examples 1 to 20 have a higher oxygen reaction amount than the iron-based powders of Comparative Examples 1 to 17, and further have an oxygen reaction amount of 60 mL / g or more per 1 g of the iron-based powder, which is superior in terms of the oxygen reaction amount.

[0046] In particular, the iron-based powders of Examples 10 to 20, which contain coke powder as the carbonaceous powder, all have an oxygen reaction amount of 65 mL / g or more per 1 g of the iron-based powder, and are found to have superior oxygen reactivity in terms of the oxygen reaction amount.

[0047] All of the iron-based powders of Examples 10 to 20 contain 0.12 mass % or more of coke powder. It is understood that when the iron-based powder contains 0.12 mass % or more of coke powder, it has better oxygen reactivity in terms of the oxygen reaction amount.

[0048] The iron-based powders of Examples 16 to 20, which contain coke powder and carbon black powder, all have an oxygen reaction amount of 77 mL / g or more per 1 g of the iron-based powder, and it is clear that the oxygen reaction amount shows very excellent oxygen reactivity.

[0049] Among the iron-based powders of Examples 16 to 20 containing coke powder and carbon black powder, the iron-based powder of Example 19 further containing activated carbon powder has an extremely excellent oxygen reactivity of 81 mL / g of oxygen reaction amount per 1 g of the iron-based powder, despite the fact that the carbonaceous powder content is very small at 1.20 mass %.

[0050] It can be seen that the iron-based powders of Examples 16 to 18 and 20, which contain only coke powder and carbon black powder as the carbonaceous powder, have very good oxygen reactivity when they contain 3.50 mass% or more of coke powder and 6.20 mass% or more of carbon black powder.

[0051] From the results of Comparative Examples 5, 9, 13, and 17, it can be seen that the iron-based powder does not have excellent oxygen reactivity when the total amount of carbonaceous powder exceeds 30.00 mass%. In particular, even when the iron-based powder contains coke powder and carbon black powder as carbonaceous powder, the iron-based powder does not have excellent oxygen reactivity when the total amount of carbonaceous powder exceeds 30.00 mass% as in Comparative Examples 13 and 17. Therefore, the total amount of carbonaceous powder needs to be 30.00 mass% or less.

[0052] In comparison between the iron-based powder of Example 19, which contains coke powder, activated carbon powder, and carbon black powder as the carbonaceous powders, the iron-based powders of Examples 16-18 and 20, which contain only coke powder and carbon black powder as the carbonaceous powders, the iron-based powders of Examples 13-15, which contain only coke powder and activated carbon powder as the carbonaceous powders, and the iron-based powders of Examples 10-12 and Comparative Examples 4 and 5, which contain only coke powder as the carbonaceous powder, the following further points can be seen when the iron-based powder contains coke powder.

[0053] When the iron-based powder contains only coke powder, the iron-based powder has excellent reactivity if the content of coke powder as carbonaceous powder is 0.20 mass% or more and the content of coke powder is 30.00 mass% or less (Examples 10 to 12). However, when the content of coke powder as carbonaceous powder is less than 0.20 mass% (Comparative Example 4) or the content of coke powder exceeds 30.00 mass% (Comparative Example 5), the iron-based powder does not have excellent reactivity.

[0054] As described above, even when the iron-based powder contains only a certain amount of coke powder, the iron-based powder has excellent reactivity, but when other carbonaceous powders such as activated carbon powder and carbon black powder are coexisted in addition to the coke powder (Examples 13 to 20), the iron-based powder has a better oxygen reactivity than when only the coke powder in the iron-based powder is increased or decreased. In particular, when the iron-based powder contains at least the coke powder and the carbon black powder (Examples 16 to 20), the iron-based powder has a very good oxygen reactivity.

[0055] In addition, the iron-based powders of Examples 1 to 9, in which the content of coal powder as the carbonaceous powder is 0.20 mass% or more and 30.00 mass% or less, have a stable and uniform oxygen reaction amount of 60 mL / g or more and 63 mL / g or less per 1 g of the iron-based powder. It can be seen that when the content of coal powder as the carbonaceous powder is 0.20 mass% or more and 30.00 mass% or less, the iron-based powder has excellent oxygen reactivity in the oxygen reaction amount and has stable oxygen reactivity with no uniformity.

[0056] In this manner, it is possible to provide an iron-based powder for an oxygen reactant and an oxygen reactant having excellent oxygen reactivity. [Industrial Applicability]

[0057] The present disclosure is applicable to iron-based powders for oxygen reactants and oxygen reactants.

Claims

1. an iron powder having an oxygen to iron atomic ratio O / Fe of 0.30 or less; and a carbonaceous powder having a C content of 50% by mass or more; The content of the carbonaceous powder is 0.20% by mass or more and 30.00% by mass or less, The iron-based powder for an oxygen reactant contains 0.12 mass % or more of coke powder as the carbonaceous powder.

2. 2. The iron-based powder for an oxygen reactant according to claim 1, further comprising coal powder as said carbonaceous powder.

3. 2. The iron-based powder for an oxygen reactant according to claim 1, further comprising at least one of activated carbon powder and carbon black powder as said carbonaceous powder.

4. 3. The iron-based powder for an oxygen reactant according to claim 2, further comprising at least one of activated carbon powder and carbon black powder as said carbonaceous powder.

5. 3. The iron-based powder for an oxygen reactant according to claim 1, further comprising carbon black powder as said carbonaceous powder.

6. The coke powder is 3.50% by mass or more, and 6. The iron-based powder for an oxygen reactant according to claim 5, comprising 6.20% by mass or more of the carbon black powder.

7. An oxygen reactant using the iron-based powder for oxygen reactants according to any one of claims 1 to 4.

8. An oxygen reactant using the iron-based powder for oxygen reactants according to claim 5.

9. An oxygen reactant using the iron-based powder for oxygen reactants according to claim 6.

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