Antibacterial iron powder

Abstract

To provide an antibacterial iron powder that is inexpensive and exhibits an excellent antibacterial effect.SOLUTION: An antibacterial iron powder according to one aspect of the present invention contains metallic iron as a main component.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to antibacterial iron powder. [Background technology]

[0002] Recently, due to increasing awareness of hygiene and other factors, there is an increasing demand for antibacterial substances. Metals known to have antibacterial properties include silver and copper. For example, Patent Document 1 proposes antibacterial composite particles containing antibacterial inorganic particles A containing silver or silver ions and antibacterial inorganic particles B containing zinc, titanium, copper, or nickel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-179607 Summary of the Invention [Problem to be solved by the invention]

[0004] However, although currently widely used antibacterial metals such as silver and copper have excellent antibacterial activity, they are expensive. In contrast, the antibacterial properties required for products vary. For example, the level of antibacterial activity required in medical settings differs from that required for everyday products. Therefore, there is a growing demand today for antibacterial substances that can reduce production costs while still providing the necessary antibacterial activity.

[0005] The present invention has been made in view of the above circumstances, and has as its object to provide an antibacterial iron powder that is inexpensive and has excellent antibacterial activity. [Means for solving the problem]

[0006] The antibacterial iron powder according to one embodiment of the present invention contains metallic iron as a main component. [Effects of the Invention]

[0007] The antibacterial iron powder according to one aspect of the present invention is inexpensive and has excellent antibacterial activity. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a graph showing the relationship between the elapsed time and the viable cell count of Staphylococcus aureus for No. 1 to No. 4. [Figure 2] FIG. 2 is a graph showing the relationship between the elapsed time and the viable count of E. coli for No. 1 to No. 4. [Figure 3] FIG. 3 is a graph showing the relationship between the elapsed time and the viable cell count of Staphylococcus aureus for Nos. 16 to 21. [Figure 4] FIG. 4 is a graph showing the relationship between the elapsed time and the viable count of E. coli for No. 16 to No. 21. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Description of the embodiment of the present invention] First, embodiments of the present invention will be listed and described.

[0010] The antibacterial iron powder according to one embodiment of the present invention contains metallic iron as a main component.

[0011] The antibacterial iron powder is primarily composed of metallic iron, making it inexpensive and providing excellent antibacterial properties. Furthermore, because the antibacterial iron powder is in the form of a powder, it has a large surface area, and even if rust forms on the surface of the metallic iron, it naturally peels off, leaving a new metallic iron surface continuously exposed. This ensures excellent durability of the antibacterial properties, and makes it easy to incorporate into various products and materials that require antibacterial properties.

[0012] The antibacterial iron powder may further contain an antibacterial element, and the antibacterial element may be contained in the metallic iron. In this way, the antibacterial element contained in the metallic iron can improve the antibacterial effect.

[0013] The antibacterial element is preferably sulfur or phosphorus. When the antibacterial element is sulfur or phosphorus, the antibacterial effect can be significantly improved.

[0014] The sulfur content is preferably 0.02% by mass or more and 5% by mass or less. When the sulfur content is within the above range, the antibacterial effect can be easily and reliably improved.

[0015] The phosphorus content is preferably 1% by mass or more and 5% by mass or less. When the phosphorus content is within the above range, the antibacterial effect can be easily and reliably improved.

[0016] The antibacterial element may be copper. When the antibacterial element is copper, the antibacterial effect can be easily and reliably improved.

[0017] The antibacterial iron powder is preferably a water-atomized powder, which makes it easier to increase the specific surface area compared to bulk materials such as iron plates, and as a result, makes it easier to effectively exert antibacterial effects.

[0018] In the present invention, the term "main component" refers to the component with the highest content in terms of mass, for example, a component with a content of 50 mass% or more. The term "antibacterial element" includes elements that themselves have antibacterial properties and elements that cause other elements to exhibit antibacterial properties through a chemical reaction.

[0019] [Details of the embodiment of the present invention] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the numerical values described in this specification can be arbitrarily combined with the upper and lower limit values. In this specification, all numerical ranges from the upper limit value to the lower limit value that can be combined are described as suitable ranges.

[0020] [Antibacterial iron powder] The antibacterial iron powder is an iron powder whose main component is metallic iron. Examples of the metallic iron include pure iron and iron compounds. Of these, pure iron is preferred as the metallic iron. The antibacterial iron powder contains divalent iron ions (Fe 2+ It is believed that the antibacterial effect is exerted by the elution of ferrous iron. More specifically, it is believed that divalent iron ions are attracted to prokaryotes (bacteria) by electrostatic induction, reduce the cell walls of the prokaryotes, and penetrate into the cell walls, reducing the DNA within the cell walls, thereby exerting the antibacterial effect. In this case, if the metallic iron contains impurities, these impurities may hinder the elution of divalent iron ions. In contrast, when the metallic iron is pure iron, the divalent iron ions are appropriately eluted, making it easier to exert the desired antibacterial effect. The lower limit of the pure iron content in the metallic iron is preferably 50% by mass. When the pure iron content is equal to or greater than the lower limit, the amount of eluted divalent iron ions can be sufficiently increased, thereby enhancing the antibacterial effect and the durability of this antibacterial effect. Note that "pure iron" means iron that is easily available for industrial use and has a purity of 90.0% by mass or more.

[0021] The lower limit of the average particle size of the antibacterial iron powder is preferably 50 μm, more preferably 60 μm. On the other hand, the upper limit of the average particle size is preferably 150 μm, more preferably 100 μm. If the average particle size is less than the lower limit, the production cost of the antibacterial iron powder may be high. Conversely, if the average particle size exceeds the upper limit, it may be difficult to sufficiently increase the specific surface area of the antibacterial iron powder, and the antibacterial effect may not be sufficiently exhibited. Note that the "average particle size" refers to the particle size at which the cumulative mass in the particle size distribution is 50% when the particle size distribution is determined by a dry sieving test using a sieve specified in JIS-Z8801-1:2019.

[0022] The antibacterial iron powder preferably contains an antibacterial element. The antibacterial element is preferably contained in the metallic iron. The antibacterial iron powder can improve its antibacterial action by containing the antibacterial element in the metallic iron. In the present invention, the "antibacterial element" is distinguished from the "metallic iron" as a separate component.

[0023] Examples of the antibacterial element include sulfur (S) and phosphorus (P). The antibacterial iron powder contains sulfur or phosphorus in the metallic iron, which can promote the elution of divalent iron ions.

[0024] When the antibacterial element is sulfur, the sulfur itself also contributes to the antibacterial action, further enhancing the antibacterial effect. More specifically, the inclusion of sulfur in the metallic iron can promote the elution of divalent iron ions by the transfer of electrons from iron to sulfur. Furthermore, for example, when the antibacterial iron powder is placed in a liquid, sulfide ions (S 2- ) is hydroxide ion (OH - It is believed that the antibacterial effect can be enhanced by generating chemical species with antibacterial activity, such as sulfuric acid (H2SO4).

[0025] When the antibacterial element is sulfur, the lower limit of the sulfur content in the antibacterial iron powder is preferably 0.02% by mass, more preferably 0.3% by mass, and even more preferably 0.5% by mass. On the other hand, the upper limit of the sulfur content is preferably 5% by mass, more preferably 3% by mass, and even more preferably 2% by mass. If the content is less than the lower limit, it may be difficult to achieve the desired antibacterial improvement effect. Conversely, if the content exceeds the upper limit, it may be difficult to incorporate sulfur into the antibacterial iron powder, and the production cost may be too high compared to the improved antibacterial effect.

[0026] When the antibacterial element is phosphorus, the lower limit of the phosphorus content in the antibacterial iron powder is preferably 1% by mass, more preferably 1.5% by mass, and even more preferably 2% by mass. On the other hand, the upper limit of the content is preferably 5% by mass, more preferably 4% by mass, and even more preferably 3% by mass. If the content is less than the lower limit, it may be difficult to achieve the desired antibacterial improvement effect. Conversely, if the content exceeds the upper limit, it may be difficult to incorporate phosphorus into the antibacterial iron powder, and the production cost may be too high compared to the improved antibacterial effect.

[0027] The antibacterial element may be copper. Copper is known to have antibacterial properties and has traditionally been used alone (copper alone) or in a mixed powder as described in Patent Document 1. In contrast, in the antibacterial iron powder, copper is alloyed with iron. In the antibacterial iron powder, copper, which has a lower ionization tendency than iron, is less likely to dissolve ions. However, the alloying of copper with iron is thought to cause interactions such as local cell reactions, leading to behavior different from that of copper alone or iron alone. In other words, the antibacterial iron powder does not focus on the antibacterial properties of copper itself, but is based on the new finding that alloying copper and iron can activate the antibacterial properties of iron. Furthermore, although an oxide film may form on the surface of the antibacterial iron powder, this oxide film is primarily composed of iron and is therefore likely to peel off, unlike the copper oxide film that forms on the surface of pure copper. As a result, new iron surfaces are continuously exposed, which is thought to facilitate sustained antibacterial properties. Furthermore, since the antibacterial iron powder contains copper alloyed with iron, the production costs can be kept lower than those of antibacterial materials made of copper alone.

[0028] When the antibacterial element is copper, the lower limit of the copper content in the antibacterial iron powder is preferably 2% by mass, more preferably 3% by mass, and even more preferably 4% by mass. On the other hand, the upper limit of the copper content is preferably 10% by mass, more preferably 8% by mass, and even more preferably 6% by mass. If the content is less than the lower limit, it may be difficult to achieve the desired antibacterial improvement effect. Conversely, if the content exceeds the upper limit, it may be difficult to incorporate copper into the antibacterial iron powder, and the production cost may be too high compared to the improved antibacterial effect.

[0029] The manufacturing method of the antibacterial iron powder is not particularly limited. The antibacterial iron powder may be manufactured by, for example, a reduction method or a gas atomization method. However, the water atomization method is preferred as the manufacturing method of the antibacterial iron powder. That is, the antibacterial iron powder is preferably a water-atomized powder. The water-atomized powder is produced by atomizing and solidifying molten metallic iron by injecting high-pressure water into the metallic iron. The water-atomized powder has an uneven surface, resulting in a large specific surface area. Therefore, the water-atomized powder has excellent leaching properties for divalent iron ions. Furthermore, the water-atomized powder is produced by adding the antibacterial element to the metallic iron during melting. Therefore, the water-atomized powder prevents the incorporation of impurities (i.e., selectively contains the antibacterial element) and facilitates control of the content of the antibacterial element. That is, the water-atomized powder allows for easy and reliable control of the overall composition of the antibacterial iron powder. Therefore, the antibacterial iron powder is a water-atomized powder, which can promote the elution of divalent iron ions and easily exert the antibacterial effect.Furthermore, the antibacterial iron powder is a water-atomized powder, which can reduce the production cost.

[0030] The antibacterial iron powder can be used by being blended into products and materials thereof, such as miscellaneous goods, building materials, furniture, etc. In other words, the antibacterial iron powder can be used by being blended into products and materials thereof that come into contact with daily life and in which bacterial growth is undesirable for hygienic reasons.

[0031] <Advantages> The antibacterial iron powder is primarily composed of metallic iron, making it inexpensive and providing excellent antibacterial properties. Furthermore, because the antibacterial iron powder is in the form of a powder, it has a large surface area, and even if rust forms on the surface of the metallic iron, it naturally peels off, leaving a new metallic iron surface continuously exposed. This ensures excellent durability of the antibacterial properties, and makes it easy to incorporate into various products and materials that require antibacterial properties.

[0032] [Other embodiments] The above-described embodiments do not limit the configuration of the present invention. Therefore, the above-described embodiments may include omissions, substitutions, or additions of components based on the description in this specification and common general technical knowledge, and all of these should be construed as falling within the scope of the present invention.

[0033] For example, if the antibacterial iron powder can exert its antibacterial effect by eluting divalent iron ions, it does not need to contain the above-mentioned antibacterial activity-producing elements. [Example]

[0034] The present invention will be described in detail below based on examples, but the present invention should not be construed as being limited by the descriptions in these examples.

[0035] [Test Example 1] <Preparation of test bacterial solution> Staphylococcus aureus and Escherichia coli were used as test bacteria. Each test bacteria was inoculated onto a nutrient agar medium and cultured at a temperature between 30°C and 35°C for 24 hours. After that, physiological saline was used to grow each test bacteria to a cell count of 10 8 The test bacterial solution was prepared so that the concentration was adjusted to [CFU (Colony Forming Unit) / mL].

[0036] <Preparation of test samples> (No.1 to No.3) A water-atomized powder containing 1% sulfur by mass in pure iron was used as a specimen. This specimen was suspended in sterile water at a concentration of 1 g / L, and 10 mL of the suspension was dispensed into a test tube to form Test Sample No. 1. The specimen was also suspended in the same sterile water at a concentration of 10 g / L, and 10 mL of the suspension was dispensed into a test tube to form Test Sample No. 2. The specimen was also suspended in the same sterile water at a concentration of 100 g / L, and 10 mL of the suspension was dispensed into a test tube to form Test Sample No. 3.

[0037] (No.4) Sterile water without any specimen suspended was used as test sample No. 4.

[0038] <Calculating the number of viable bacteria> Test samples No. 1 to No. 4 were each inoculated with 0.1 mL of the above-mentioned test bacterial solution and allowed to stand at 25°C. Immediately after inoculation, 1 hour, and 4 hours after inoculation, 10-fold serial dilutions of the test samples were prepared in SCDLP liquid medium (soybean-casein-digest liquid medium supplemented with lecithin and polysorbate 80) to obtain test solutions. These test solutions were inoculated onto SCDLP agar medium and cultured for 72 hours at a temperature between 30°C and 35°C. After this culture, the formed colonies were counted and the viable bacterial count was calculated. Tests No. 1 to No. 3 were each performed three times, and the average of the three tests was calculated as the viable bacterial count. The results are shown in Table 1. Note that a viable bacterial count value of "0" in Table 1 means that no bacteria were detected by culture.

[0039] [Table 1]

[0040] <Evaluation results> As shown in Table 1 and Figures 1 and 2, in samples No. 1 to No. 3, in which sulfur was added to pure iron, the viable cell counts of both Staphylococcus aureus and Escherichia coli were significantly reduced. This is thought to be because sulfur effectively promotes the elution of divalent iron ions. Furthermore, as shown in No. 4, when comparing Staphylococcus aureus and Escherichia coli, the viable cell count of Staphylococcus aureus was higher 4 hours after inoculation than 1 hour after inoculation. This is thought to be due to the individual differences resulting from the test bacterial species when compared with E. coli.

[0041] [Test Example 2] The viable cell counts of Staphylococcus aureus and Escherichia coli were calculated using the same procedure as in Test Example 1 using the above-mentioned samples No. 1 to No. 3 and the samples No. 8 to No. 15 described below. Tests No. 1 to No. 3 and No. 8 to No. 15 were each conducted three times, and the average of the three tests was calculated as the viable cell count. Note that the calculated viable cell counts of samples No. 1 to No. 3 in Test Example 1 and Test Example 2 differed from each other. This is thought to be due to errors caused by the test bacteria, etc. The calculated viable cell counts are shown in Table 2.

[0042] (No.8 to No.10) A water-atomized powder containing 0.3% sulfur by mass in pure iron was used as a specimen. This specimen was suspended in sterilized water to a concentration of 1 g / L, and 10 mL of the suspension was dispensed into a test tube to form test specimen No. 8. The same specimen was also suspended in the same sterilized water to a concentration of 10 g / L, and 10 mL of the suspension was dispensed into a test tube to form test specimen No. 9. The same specimen was also suspended in the same sterilized water to a concentration of 100 g / L, and 10 mL of the suspension was dispensed into a test tube to form test specimen No. 10.

[0043] (No.11) The test sample was a water-atomized powder of pure iron containing 0.02% sulfur by mass. This sample was suspended in sterilized water to a concentration of 100 g / L, and 10 mL of the suspension was dispensed into a test tube to prepare test sample No. 11.

[0044] (No.12) The test sample was a water-atomized powder of pure iron containing 0.005% sulfur by mass. This sample was suspended in sterilized water to a concentration of 100 g / L, and 10 mL of the suspension was dispensed into a test tube to prepare test sample No. 12.

[0045] (No.13 to No.15) Glass beads were used as the specimen. This specimen was suspended in sterilized water to a concentration of 1 g / L, and 10 mL of the suspension was dispensed into a test tube to prepare test sample No. 13. The same specimen was also suspended in the same sterilized water to a concentration of 10 g / L, and 10 mL of the suspension was dispensed into a test tube to prepare test sample No. 14. The same specimen was also suspended in the same sterilized water to a concentration of 100 g / L, and 10 mL of the suspension was dispensed into a test tube to prepare test sample No. 15.

[0046] [Table 2]

[0047] <Evaluation results> As shown in Table 2, Nos. 1 to 3, which contain 1% sulfur by mass, significantly reduced the viable cell counts of both Staphylococcus aureus and Escherichia coli. Furthermore, Nos. 8 to 11, which contain 0.02% or more sulfur by mass, also showed a reduction in viable cell counts 4 hours after inoculation compared to 1 hour after inoculation. No. 12, which contains 0.005% sulfur by mass, also showed a tendency to reduce viable cell counts more than the comparative glass beads (Nos. 13 to 15). This indicates that the antibacterial iron powder's antibacterial activity can be enhanced by the inclusion of sulfur in metallic iron, and that a sulfur content of 0.02% or more by mass significantly enhances the viable cell count reduction effect. This indicates that sulfur is an important element for exhibiting antibacterial properties.

[0048] [Test Example 3] A test bacterial solution was prepared using the same procedure as in Test Example 1, and the viable cell counts of Staphylococcus aureus and Escherichia coli were calculated using the above-mentioned samples No. 1 to No. 3 and the samples No. 16 to No. 21 described below using the same procedure as in Test Example 1. The results of the calculation of the viable cell counts are shown in Table 3. Note that the calculation results for the viable cell counts of samples No. 1 to No. 3 differ between Test Example 1 and Test Example 3. This is thought to be due to errors caused by the test bacteria, etc. Also, a viable cell count value of "0" in Table 3 means that no bacteria were detected by culture. Also, the antibacterial element in Table 3 refers to an element that, when contained in metallic iron, provides an antibacterial effect, and the viable cell count in Table 3 does not indicate the antibacterial effect of the antibacterial element alone.

[0049] (No.16 to No.18) A water-atomized powder containing 2% by mass of phosphorus in pure iron was used as a specimen. This specimen was suspended in sterilized water to a concentration of 1 g / L, and 10 mL of the suspension was dispensed into a test tube to obtain test specimen No. 16. The same specimen was also suspended in the same sterilized water to a concentration of 10 g / L, and 10 mL of the suspension was dispensed into a test tube to obtain test specimen No. 17. The same specimen was also suspended in the same sterilized water to a concentration of 100 g / L, and 10 mL of the suspension was dispensed into a test tube to obtain test specimen No. 18.

[0050] (No.19 to No.21) A water-atomized powder containing 5% copper by mass in pure iron was used as a specimen. This specimen was suspended in sterilized water to a concentration of 1 g / L, and 10 mL of the suspension was dispensed into a test tube to form test specimen No. 19. The specimen was also suspended in the same sterilized water to a concentration of 10 g / L, and 10 mL of the suspension was dispensed into a test tube to form test specimen No. 20. The specimen was also suspended in the same sterilized water to a concentration of 100 g / L, and 10 mL of the suspension was dispensed into a test tube to form test specimen No. 21.

[0051] [Table 3]

[0052] <Evaluation results> As shown in Table 3, samples No. 1 to No. 3, which contain 1% sulfur by mass, significantly reduced the viable cell counts of both Staphylococcus aureus and Escherichia coli. Furthermore, as shown in Table 3 and Figures 3 and 4, samples No. 19 to No. 21, which use copper as the antibacterial element, tend to significantly reduce the viable cell counts of both Staphylococcus aureus and Escherichia coli. Furthermore, as shown in Table 3 and Figures 3 and 4, samples No. 16 to No. 18, which use phosphorus as the antibacterial element, tend to slightly reduce the viable cell counts of both Staphylococcus aureus and Escherichia coli, particularly sample No. 18, which was suspended in sterilized water at 100 g / L. This indicates that phosphorus and copper, in addition to sulfur, are also preferred antibacterial elements for the antibacterial iron powder.

[0053] As shown in Table 3 and Figures 3 and 4, the number of viable bacteria was significantly reduced in Nos. 19 to 21, which used copper as the antibacterial element, which is thought to indicate that the antibacterial effect of copper is not weakened by being combined with metallic iron. This shows that the antibacterial iron powder can exert its antibacterial effect by being composed, for example, of an alloy powder containing copper. [Industrial Applicability]

[0054] As described above, the antibacterial iron powder according to one aspect of the present invention is inexpensive and has excellent antibacterial activity, and therefore can be suitably incorporated into various products and their materials.

Claims

1. The main component is metallic iron, It further contains antibacterial elements, The antibacterial element is sulfur or phosphorus, The antibacterial iron powder comprises the antibacterial element contained in the metallic iron.

2. 2. The antibacterial iron powder according to claim 1, wherein the antibacterial element is sulfur, and the sulfur content is 0.02% by mass or more and 5% by mass or less.

3. 2. The antibacterial iron powder according to claim 1, wherein the antibacterial element is phosphorus, and the phosphorus content is 1% by mass or more and 5% by mass or less.

4. The antibacterial iron powder according to any one of claims 1 to 3, which is a water-atomized powder.

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