Iron-based powder for oxygen reactant and oxygen reactant prepared therewith

Abstract

To provide an iron-based powder for oxygen reactants that effectively controls the scattering of added powder and provides high reactivity with oxygen during the initial phase of the reaction.SOLUTION: The content of carbonaceous powder is adjusted at 0.20 mass% or more and 30.00 mass% or less relative to the total amount of iron powder and carbonaceous powder. A hydrocarbon solvent with a kinematic viscosity of 2.00 to 100.00 mm2 / s at 40°C is added at 0.010 pt.mass or more and 10.000 pts.mass or less, relative to the total of iron powder and carbonaceous powder.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] Oxygen reactants that utilize the reaction between iron-based powder and oxygen are known to be used as oxygen scavengers or heat generating agents. As an oxygen absorber, it is used by sealing it in a container together with preserved items such as food and medicines to create a low-oxygen environment, thereby preventing deterioration of the quality of the preserved items due to oxidation and the growth of mold, etc. On the other hand, as a heat generating agent, it is widely used in disposable hand warmers to warm the human body. Generally, in order to promote the oxygen reaction, these oxygen reactants contain activated carbon, sodium chloride, silica powder, wood powder, water, sulfur powder, and the like added to the iron-based powder.

[0003] That is, since the oxygen reactant is made up of a mixture of a plurality of powders, there may be a problem in that the mixed powder may scatter when placed in a package.

[0004] For example, Patent Document 1 proposes an apparatus that can prevent a powdered oxygen absorber composition from scattering outside a package during filling and significantly reduce the amount of oxygen absorber composition adhering to the surface of the manufactured oxygen absorber package.

[0005] Furthermore, Patent Document 2 proposes an oxygen scavenger that uses 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. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2002-2602 A [Patent Document 2] JP 2003-117385 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, the technology described in Patent Document 1 improves the device used for sealing the oxygen reactant, rather than the performance of the oxygen reactant, and does not take into account the case where the amount of fine powder increases in the added powder.

[0008] Furthermore, Patent Document 2 describes that the so-called free carbon state liberated from the iron powder does not have any effect on the oxygen absorption properties of the oxygen scavenger, and therefore an operation to partially coat the iron powder surface is necessary.

[0009] In view of the above problems, the present invention aims to provide an iron-based powder for an oxygen reactant that can effectively suppress scattering of additive powder and can bring about high reactivity with oxygen in the early stage of reaction, together with an oxygen reactant using the same. [Means for solving the problem]

[0010] The inventors considered the following. That is, the iron-based powder, which is the main component, contains multiple powders including activated carbon. Therefore, the scattering matter that is blown up from the iron-based powder during handling is mainly these added powders. Therefore, if the added powders can be efficiently attached to the iron-based powder, the scattering of the added powders can be effectively suppressed, and further the reaction with oxygen can be promoted.

[0011] Here, carbonaceous powder such as graphite has a higher standard electrode potential than iron, and the iron potential-pH diagram (Pourbaix diagram) shows that the potential increases when iron is oxidized.

[0012] 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 corrosion current flows from the carbonaceous powder with the higher potential to the iron powder with the lower potential. Furthermore, this corrosion current passes through the electrolyte, returns to the carbonaceous powder with a higher potential than the iron powder, and then flows back to the iron powder, creating a local cell mechanism. This mechanism promotes the reaction between the low-potential iron powder and oxygen.

[0013] However, carbonaceous powder is less reactive with oxygen than iron, and therefore, if it is mixed in excess, the amount of oxygen reacted with it will be lower than with iron powder alone, so the upper limit of the carbonaceous powder content is set.

[0014] In addition, in the present invention, in order to prevent the carbonaceous powder from scattering, a hydrocarbon solvent is added as an adhesion agent between the iron powder and the carbonaceous powder when the iron powder and the carbonaceous powder are mixed, and extensive research has been conducted.

[0015] As a result, it was found that it is possible to prepare an iron-based powder with excellent oxygen reactivity by setting the range of conditions, such as the amount of carbonaceous powder and hydrocarbon solvent added.

[0016] In addition, in order to promote the reaction between iron-based powder and oxygen, the researchers focused on mixing iron powder with carbonaceous powders such as activated carbon, coke powder, graphite, and carbon black, and adding hydrocarbon solvents such as liquid paraffin and industrial lubricating oil, and found that by setting the respective condition ranges, it is possible to produce iron-based powder with excellent oxygen reactivity.

[0017] The present invention is based on the above findings, and has the following gist and configuration. 1. (A) iron powder, (B) carbonaceous powder, and (C) a mixture having a kinetic viscosity of 2.00 to 100.00 mm at 40°C. 2and a hydrocarbon-based solvent in the range of (A) to (B) / s, wherein the content of the carbonaceous powder (B) relative to the total of the iron powder (A) and the carbonaceous powder (B) is 0.20 mass% or more and 30.00 mass% or less, and the content of the hydrocarbon-based solvent (C) relative to the total of the iron powder (A) and the carbonaceous powder (B) is 0.010 mass parts or more and 10,000 mass parts or less.

[0018] 2. An oxygen reactant comprising the iron-based powder for oxygen reactants as described in 1 above. Effect of the Invention

[0019] According to the present invention, it is possible to obtain an iron-based powder for an oxygen reactant having excellent oxygen reactivity, and an oxygen reactant using the same. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, embodiments of the present invention will be described. Note that the following embodiments are merely examples for explaining the present invention, and the present invention is not limited to these embodiments.

[0021] The iron-based powder for an oxygen reactant of the present invention is an iron-based powder for an oxygen reactant comprising (A) iron powder, (B) carbonaceous powder, and (C) a hydrocarbon solvent. Here, the reason why the iron-based powder for an oxygen reactant of the present invention exhibits excellent oxygen reactivity is presumed to be as follows. That is, since carbonaceous powder has a higher potential than iron powder, a mixed powder of iron powder and carbonaceous powder generates a corrosion current and promotes the oxidation reaction of the iron powder when the carbonaceous powder and iron powder come into contact in an electrolyte, compared to iron powder alone. However, simply mixing the iron powder with the carbonaceous powder limits the improvement of the oxygen reaction due to the presence of free carbonaceous powder that is not in contact with the iron powder. Therefore, in the present invention, in order to improve the contact between the iron powder and the carbonaceous powder, it is necessary to add a hydrocarbon solvent that causes the iron powder and the carbonaceous powder to adhere to each other. Therefore, in the present invention, by providing an iron-based powder that satisfies the above-mentioned characteristics, it is possible to achieve excellent oxygen reactivity.

[0022] The iron powder (A) used in the present invention can be produced by water atomization, gas atomization, a pulverization method, or an oxide reduction method. The carbonaceous powder (B) may be commercially available activated carbon, graphite, carbon black, etc. It may also be powder obtained by crushing and classifying coke produced by carbonizing coal, or collected powder generated during coke production.

[0023] Here, the term "iron-based powder" in the present invention refers to a powder containing 50.0 mass % or more of metallic iron [Fe]. In addition to the metallic iron, the iron-based powder may further contain any element such as carbon [C], sulfur [S], oxygen [O], nitrogen [N], silicon [Si], sodium [Na], magnesium [Mg], calcium [Ca], etc. The metallic iron content of the iron-based powder can be measured in accordance with JIS A 5011-2 "Method for determining metallic iron content."

[0024] The iron-based powder for an oxygen reactant of the present invention is a mixed powder of the iron powder (A) and the carbonaceous powder (B), and the content of the carbonaceous powder (B) is in the range of 0.20 mass % or more and 30.00 mass % or less with respect to the total of the iron powder (A) and the carbonaceous powder (B). If the content of (B) carbonaceous powder is less than 0.20% by mass, the amount of corrosion current is small and there is no effect on promoting the oxygen reaction of iron powder. On the other hand, since the carbonaceous powder itself is difficult to oxidize, the amount of oxygen that reacts with oxygen is smaller than that of iron powder, so if the content of (B) carbonaceous powder is more than 30.00% by mass, the oxygen reaction amount of the mixture of iron powder and carbonaceous powder will be lower than the oxygen reaction amount of iron powder alone. From the viewpoint of oxygen reactivity, the content of the (B) carbonaceous powder is preferably 0.50% by mass or more, and the content of the (B) carbonaceous powder is preferably 15.00% by mass or less.

[0025] The particle size of the iron powder (A) used in the present invention is a median diameter D 50 On the other hand, the lower limit is preferably about 5 μm in terms of ease of handling. In addition, such D50 can be measured according to the procedures described below.

[0026] The carbonaceous powder (B) used in the present invention has a carbon (free carbon) content of 50% by mass or more. If the carbon content is less than 50% by mass, the corrosion current is small and the powder is not effective in promoting the oxygen reaction of the iron powder. On the other hand, the upper limit is not particularly limited and may be 100% by mass, but from an economical point of view, it is preferably about 95% by mass. The carbon content can be measured according to the method described below.

[0027] (B) The particle size of the carbonaceous powder is not particularly limited as long as it is easy to handle. 50 The particle size 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 is preferably about 0.1 μm from the viewpoint of handling. In addition, such D 50 can be measured according to the procedures described below.

[0028] The (C) hydrocarbon solvent has a kinetic viscosity at 40°C of 2.00 to 100.00 mm 2 The solvent should preferably have a kinetic viscosity of 3.00 mm / s at 40°C. 2 A solvent with a kinematic viscosity of 70.00 mm / s or more at 40°C is preferable. 2 Solvents with a viscosity of 1 / s or less are recommended. If the kinetic viscosity of the hydrocarbon solvent is too low, the adhesion between the iron powder and the carbonaceous powder is low, and it is difficult to improve the oxygen reactivity of the iron powder. On the other hand, if the kinetic viscosity of the hydrocarbon solvent is too high, the adhesion between the iron powder and the carbonaceous powder becomes excessively high, and a large number of agglomerates of the iron powder and the carbonaceous powder are formed. Here, if such agglomerates are formed, it becomes difficult for the added moisture to penetrate into the agglomerates and for oxygen to pass through, and the oxygen reactivity decreases instead. As a result, the oxygen reactivity of the entire iron-based powder also decreases.

[0029] Furthermore, the amount of the (C) hydrocarbon solvent added is 0.010 parts by mass or more and 10,000 parts by mass or less based on the total of the (A) iron powder and the (B) carbonaceous powder. If the amount added is less than 0.010 parts by mass, segregation of the hydrocarbon solvent occurs in the iron powder and the carbonaceous powder, resulting in uneven adhesion and making it difficult to improve the oxygen reactivity of the iron powder. On the other hand, if the amount added is more than 10,000 parts by mass, the hydrocarbon solvent adheres excessively to the iron powder surface, inhibiting contact between the iron powder and oxygen, thereby reducing the improvement in the oxygen reactivity of the iron powder. The amount of the hydrocarbon solvent added is preferably 0.020 parts by mass or more, and 8,000 parts by mass or less.

[0030] The median diameter D of the iron powder (A) and the carbonaceous powder (B) 50 The measurement method is as follows. The powder to be measured (iron powder (A) or carbonaceous powder (B)) is placed in a solvent (e.g., ethanol) and dispersed by ultrasonic vibration for 30 seconds or more. The particle size is measured using a laser diffraction particle size distribution analyzer that employs the laser diffraction / scattering method, that is, the volumetric particle size distribution of the 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 set as the median D 50 is used as a representative value of the particle size of the powder.

[0031] The carbon content of the carbonaceous powder (B) is measured as follows. The carbon content of the powder to be measured (carbonaceous powder (B)) is measured according to the carbon determination method described in JIS M 8813 "Coals and cokes - Elemental analysis method", and the value is reported on an anhydrous basis (dry state).

[0032] [Iron powder manufacturing] The iron powder (A) used in the present invention is preferably produced by a water atomization method or a gas atomization method in which water or gas is sprayed onto a molten metal, powdered, 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 invention. In order to further remove oxygen from the iron powder used in the present invention, it is sufficient to heat the iron powder at 750° C. or higher using carbon such as coke or graphite, or hydrogen gas.

[0033] [Carbonaceous powder] The carbonaceous powder (B) of the present invention may be a commercially available product such as graphite powder, coke powder, or carbon black powder. For example, coke powder can be produced as follows. That is, in producing such coke powder, coal is carbonized 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.

[0034] [Hydrocarbon solvents] The hydrocarbon solvent (C) of the present invention may be one obtained during a petroleum refining process, and may contain, as inevitable impurities, petroleum-derived impurities such as sulfur (S), nitrogen (N), chlorine (Cl), and oxygen (O), as well as metals such as vanadium (V), nickel (Ni), and iron (Fe). Examples of the hydrocarbon solvent include liquid paraffin, machine oil, paraffinic, naphthenic, and aromatic mineral oils. The kinetic viscosity of the hydrocarbon solvent of the present invention is measured at 40° C. in accordance with JIS K 2283 "Crude oil and petroleum products -- Test method for kinetic viscosity and calculation method for viscosity index."

[0035] [Manufacturing of iron-based powder] In producing the iron-based powder of the present invention, it is necessary to mix the above-mentioned (A) iron powder, (B) carbonaceous powder, and (C) hydrocarbon solvent until they become homogeneous. For this purpose, 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 apparatus and mixing conditions may be those known in the art.

[0036] [Oxygen reactant] In the present invention, 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 invention can be produced by sealing the iron-based powder for oxygen reactants in a bag as described below. In addition, the components other than the iron-based powder for the oxygen reactant in the oxygen reactant can be any components used in conventionally known oxygen reactants without any particular restrictions. For example, a bag of a breathable packaging material made by overlapping a nonwoven fabric and a perforated polyethylene, a bag of a breathable packaging material made by overlapping a paper and a perforated polyethylene, etc. can be mentioned. EXAMPLES

[0037] The iron-based powder for an oxygen reactant used in this example was prepared by the following procedure. Iron ore powder was reduced with coke to produce iron powder. Activated carbon with a carbon content of 89.78 mass% (Shirasagi PHC, manufactured by Osaka Gas Chemicals Co., Ltd.) was used as the carbonaceous powder. The iron powder, carbonaceous powder, and various hydrocarbon solvents with different kinetic viscosities were mixed using a V-type mixer to produce iron-based powders for each oxygen reactant. The particle size of the activated carbon was the median diameter D 50 The thickness was set at 18 μm.

[0038] 0.6g of an aqueous solution containing 12% sodium chloride by mass was added to 1.5g of zeolite (Zeophyl 1424#, manufactured by Shin Tohoku Chemical Industry Co., Ltd., particle size: 1.0-2.0mm), and then mixed with 1.5g of the iron-based powder for oxygen reactants. The sample was filled into a bag of breathable packaging material (length: 50mm x width: 60mm) to obtain each oxygen reactant. A laminated material consisting of nonwoven fabric and perforated polyethylene was used as the breathable packaging material. Each oxygen reactant was sealed together with 3 L of air in a gas barrier bag made of a laminated material consisting of nylon / aluminum foil / polyethylene. After leaving the bag at rest for 8 hours at 25°C, the oxygen concentration in the bag was measured with a gas chromatograph (GC3210D, manufactured by GL Sciences Inc.). The oxygen reaction amount was calculated from the difference between the oxygen concentration thus measured and the oxygen concentration in the air, and the oxygen reaction amount per 1 g of iron-based powder for oxygen reactants was calculated.

[0039] Table 1 shows the results of the oxygen reaction amounts of the iron-based powders of the comparative examples and the inventive examples according to the present invention. Table 2 shows the hydrocarbon solvents used in the comparative examples and inventive examples.

[0040] [Table 1]

[0041] [Table 2]

[0042] As shown in Table 1, the content of carbonaceous powder is set to 0.20 mass% or more and 30.00 mass% or less with respect to the total of iron powder and carbonaceous powder, and the kinetic viscosity at 40°C is set to 2.00 to 100.00 mm 2 In the iron-based powders of Examples 1 to 8 for use as oxygen reactants, in which 0.010 parts by mass or more and 10,000 parts by mass or less of the hydrocarbon-based solvent in the range of 0.010 parts by mass to 10,000 parts by mass of the hydrocarbon-based solvent is added relative to the total amount of the iron powder and the carbonaceous powder, the oxygen reaction amount is 27.00 mL / g or more, which is greater than that of the iron-based powders of Comparative Examples 1 to 9, and therefore it is clear that the oxygen reaction amount at the initial stage of the oxygen reaction is superior.

[0043] Among them, Examples 6 to 8, in which the carbonaceous powder content is 0.50 mass% or more and 15.00 mass% or less and the amount of hydrocarbon-based solvent added is 0.020 to 8,000 mass parts or less, have an oxygen reaction amount of 30.00 mL / g or more, and are found to be superior in terms of the oxygen reaction amount at the initial stage of the oxygen reaction.

[0044] In addition, a sheet of A4 paper divided into four was placed on a table with a goniometer and made parallel to the ground. Next, using the iron-based powders of the above-mentioned invention examples 1 to 8 and comparative examples 1 to 9, 1.5 g of each mixed powder was placed in the center of the paper, and the angle of the table was tilted to 60 degrees over 30 seconds. Then, the trace of the mixed powder sliding on the paper was observed with a microscope (MS-200 manufactured by Asahi Optical Machinery Works, Ltd.), and the area ratio of the particles was calculated using free image processing software ImageJ. In this example, it was determined that the lower the area ratio, that is, the smaller the brightness difference with the paper, the less free activated carbon there was, and the less scattering of the carbonaceous powder (additive powder) was suppressed.

[0045] As shown in Table 3, in Examples 1 to 8, the area ratio is 5.00% or less, which is greater than that of the iron-based powders (mixed powders) in Comparative Examples 1 to 9. In particular, in Examples 6 to 8, the area ratio is 3.00% or less, which is greater than that of the iron-based powders (mixed powders).

[0046] [Table 3]

Claims

1. (A) iron powder, (B) carbonaceous powder, and (C) a kinetic viscosity at 40°C of 2.00 to 100.00 mm ２ and a hydrocarbon solvent in the range of 0.1 to 1.0 wt. / s, The content of the carbonaceous powder (B) relative to the total of the iron powder (A) and the carbonaceous powder (B) is 0.20 mass% or more and 30.00 mass% or less, The amount of the hydrocarbon solvent (C) relative to the total amount of the iron powder (A) and the carbonaceous powder (B) is 0.010 parts by mass or more and 10,000 parts by mass or less. Iron-based powder for oxygen reactants.

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

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