Iron powder for antibacterial use

Abstract

The present application has an object to provide an antibacterial iron powder which is inexpensive and has excellent antibacterial action. The antibacterial iron powder of one embodiment of the present application contains metallic iron as a main component.

Description

Technical Field

[0001] This invention relates to iron powder for antibacterial purposes. Background Technology

[0002] Today, due to increased awareness of hygiene, the need for antibacterial substances is rising. Metals with antibacterial properties include silver and copper. For example, Patent Document 1 proposes an antibacterial composite particle comprising: antibacterial inorganic particles A containing silver or silver ions; and antibacterial inorganic particles B containing zinc, titanium, copper, or nickel.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2005-179607 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, while widely used antibacterial metals such as silver and copper possess excellent antibacterial properties, they are expensive. Furthermore, the required antibacterial properties for different products vary. For example, the required level of antibacterial properties differs between medical settings and everyday consumer goods. Therefore, the demands for antibacterial substances are constantly increasing, aiming to provide the necessary antibacterial effects while controlling manufacturing costs.

[0008] The present invention is made in view of the following circumstances, and its object is to provide an inexpensive iron powder with excellent antibacterial properties.

[0009] Problem-solving methods

[0010] One aspect of the present invention is an antibacterial iron powder, with metallic iron as the main component.

[0011] The effects of the invention

[0012] One aspect of the present invention provides an antibacterial iron powder that is inexpensive and has excellent antibacterial properties. Attached Figure Description

[0013] Figure 1 This is a graph showing the relationship between the elapsed time and the number of viable Staphylococcus aureus bacteria in No.1 to No.4.

[0014] Figure 2 This is a graph showing the relationship between the elapsed time and the number of viable E. coli in numbers No.1 to No.4.

[0015] Figure 3 This is a graph showing the relationship between the elapsed time and the number of viable Staphylococcus aureus bacteria in No. 16 to No. 21.

[0016] Figure 4 This is a graph showing the relationship between the elapsed time and the number of viable E. coli in numbers No.16 to No.21. Detailed Implementation

[0017] [Description of Embodiments of the Invention]

[0018] First, embodiments of the present invention will be described.

[0019] One aspect of the present invention is an antibacterial iron powder, with metallic iron as the main component.

[0020] This antibacterial iron powder is inexpensive because its main component is metallic iron, and it exhibits excellent antibacterial properties. Furthermore, because it is a powder, it has a large surface area, and even if the surface of the metallic iron rusts, the rust will naturally peel off, exposing new metallic iron surfaces. Therefore, its antibacterial effect is highly sustained, and it is easily blended with various products and materials requiring antibacterial properties.

[0021] This antibacterial iron powder also contains antibacterial active ingredients, which are already present in the aforementioned metallic iron. Thus, by including the antibacterial active ingredients found in the aforementioned metallic iron, the antibacterial effect can be enhanced.

[0022] The antibacterial properties can be achieved by using sulfur or phosphorus as the primary antibacterial element. This significantly enhances the antibacterial effect.

[0023] The sulfur content is preferably 0.02% by mass or more and 5% by mass or less. A sulfur content within this range readily and reliably enhances the antibacterial effect.

[0024] The preferred phosphorus content is 1% by mass or more and 5% by mass or less. A phosphorus content within this range readily and reliably enhances the antibacterial effect.

[0025] The aforementioned antibacterial element can also be copper. Copper, being the antibacterial element mentioned above, can easily and reliably enhance antibacterial activity.

[0026] This antibacterial iron powder can be a water-atomized powder. Because it is a water-atomized powder, compared to large materials like iron plates, it easily increases the specific surface area. As a result, it can more easily and effectively exert its antibacterial effect.

[0027] Furthermore, in this invention, the term "main component" refers to the component with the highest content by mass, for example, meaning a component with a content of 50% or more by mass. The term "antibacterial efficacious element" includes elements that inherently possess antibacterial properties, as well as elements that enable other elements to exhibit antibacterial properties through chemical reactions.

[0028] [Details of embodiments of the present invention]

[0029] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, the upper and lower limits described in this specification can be arbitrarily combined. In this specification, all possible ranges of values ​​from the upper to the lower limits are described as suitable ranges.

[0030] [Antibacterial Iron Powder]

[0031] This antibacterial iron powder is an iron powder with metallic iron as its main component. Examples of metallic iron include pure iron and iron compounds. Among these, pure iron is preferred. This antibacterial iron powder is believed to be able to pass through the ferrous ions (Fe²⁺)... 2+ The antibacterial effect is achieved through the dissolution of ferrous ions. More specifically, it is believed that ferrous ions are attracted to prokaryotes (bacteria) through electrostatic induction, reducing the cell wall of the prokaryote, and then penetrating into the cell wall. By reducing the DNA within the cell wall, the ferrous ions exert their antibacterial effect. However, if the metallic iron contains impurities, these impurities may hinder the dissolution of ferrous ions. In contrast, the aforementioned metallic iron is pure iron, allowing for proper dissolution of ferrous ions and facilitating the desired antibacterial effect. The lower limit for the pure iron content in the aforementioned metallic iron is preferably 50% by mass. A pure iron content of 90.0% or higher sufficiently increases the amount of ferrous ions dissolved, thereby improving the antibacterial effect and its duration. Furthermore, "pure iron" means readily available for industrial use with a purity of 90.0% by mass or higher.

[0032] 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 lower than the lower limit, the manufacturing cost of the antibacterial iron powder may increase. Conversely, if the average particle size is higher than the upper limit, it will be difficult to sufficiently increase the specific surface area of ​​the antibacterial iron powder, and the antibacterial effect may not be fully exerted. Furthermore, the term "average particle size" refers to the particle size distribution obtained by dry sieving test using a sieve specified in JIS-Z8801-1:2019, in which the cumulative mass of the particle size distribution is 50%.

[0033] This antibacterial iron powder preferably contains an antibacterial element. Furthermore, this antibacterial element is preferably contained within the aforementioned metallic iron. By including the aforementioned antibacterial element within the metallic iron, the antibacterial effect of this antibacterial iron powder can be enhanced. Also, in this invention, the "antibacterial element" is distinguished as a separate component from "metallic iron."

[0034] Examples of elements contributing to the aforementioned antibacterial properties include, for instance, sulfur (S) and phosphorus (P). This antibacterial iron powder, containing sulfur or phosphorus in metallic iron, promotes the dissolution of ferrous ions.

[0035] When the aforementioned antibacterial element is sulfur, sulfur itself also participates in the antibacterial effect, thus further enhancing the antibacterial efficacy. In detail, since the aforementioned metallic iron contains sulfur, the transfer of electrons from iron to sulfur promotes the dissolution of ferrous ions. Furthermore, it is believed that, for example, if the antibacterial iron powder is prepared in a liquid, then sulfide ions (S... 2－ ) makes hydroxide ions (OH) － It reacts with chemicals that have antibacterial activity, such as sulfuric acid (H2SO4), and enhances the antibacterial effect.

[0036] When the aforementioned 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 aforementioned content is preferably 5% by mass, more preferably 3% by mass, and even more preferably 2% by mass. If the aforementioned content is lower than the aforementioned lower limit, it may be difficult to achieve the desired antibacterial effect. Conversely, if the aforementioned content is higher than the aforementioned upper limit, it will be difficult to incorporate sulfur into the antibacterial iron powder, and the manufacturing cost may be excessively increased relative to the improvement in antibacterial effect.

[0037] When the aforementioned 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 aforementioned content is preferably 5% by mass, more preferably 4% by mass, and even more preferably 3% by mass. If the aforementioned content is lower than the aforementioned lower limit, it may be difficult to achieve the desired antibacterial effect. Conversely, if the aforementioned content is higher than the aforementioned upper limit, it will be difficult to incorporate phosphorus into the antibacterial iron powder, and the manufacturing cost may be excessively increased relative to the improved antibacterial effect.

[0038] The aforementioned antibacterial element can also be copper. Copper is known to have antibacterial properties and has traditionally been used as a single element (copper alone) or as a mixed powder as described in Patent Document 1. In contrast, in this antibacterial iron powder, copper is alloyed with iron. In this antibacterial iron powder, copper, which has a lower ionization tendency than iron, is considered difficult to dissolve as ions. On the other hand, through the alloying of copper and iron, under the interaction of localized battery reactions, it exhibits properties different from those of copper or iron alone. In other words, this antibacterial iron powder is not based on the antibacterial properties of copper itself, but rather on the novel discovery that the antibacterial properties of iron are activated through alloying copper and iron. Furthermore, this antibacterial iron powder can form an oxide film on its surface, but this oxide film differs from the copper oxide film formed on the surface of copper alone because it is predominantly iron and is therefore considered easy to peel off. As a result, some newly formed iron surfaces continue to be exposed, thus it can be inferred that the antibacterial properties are likely to persist. Furthermore, in this antibacterial iron powder, copper and iron are alloyed, which makes it easier to reduce manufacturing costs compared to antibacterial materials made from copper monomers.

[0039] When the aforementioned antibacterial element is copper, the lower limit for 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 for the aforementioned content is preferably 10% by mass, more preferably 8% by mass, and even more preferably 6% by mass. If the aforementioned content is lower than the aforementioned lower limit, it may be difficult to achieve the desired antibacterial effect. Conversely, if the aforementioned content is higher than the aforementioned upper limit, it will be difficult to incorporate copper into the antibacterial iron powder, and the manufacturing cost may be excessively increased relative to the improved antibacterial effect.

[0040] The manufacturing method of this antibacterial iron powder is not particularly limited. This antibacterial iron powder can be manufactured, for example, by reduction and gas atomization methods. However, water atomization is preferred as the manufacturing method for this antibacterial iron powder. That is, the antibacterial iron powder is preferably water-atomized powder. Water-atomized powder is formed by spraying high-pressure water onto molten iron to a finer particle and solidify it. Because the surface of the aforementioned water-atomized powder is uneven, its specific surface area is larger. Therefore, the aforementioned water-atomized powder exhibits excellent solubility of ferrous ions. Furthermore, the aforementioned water-atomized powder is formed by adding the aforementioned antibacterial embodying element to the molten iron. Therefore, the aforementioned water-atomized powder easily prevents impurities from contaminating (in other words, selectively contains the aforementioned antibacterial embodying element), and the content of the aforementioned antibacterial embodying element is easily controlled. That is, the overall composition of the antibacterial iron powder can be easily and reliably controlled according to the aforementioned water-atomized powder. Therefore, this antibacterial iron powder is a water-atomized powder, which can promote the dissolution of ferrous ions and easily and effectively exert its antibacterial effect. Furthermore, the fact that this antibacterial iron powder is a water-atomized powder reduces manufacturing costs.

[0041] This antibacterial iron powder can be used, for example, in products and materials such as sundries, building materials, and furniture. In other words, this antibacterial iron powder can be used in everyday contact and can be mixed with products and materials where bacterial growth is undesirable for hygiene purposes.

[0042] <Advantages>

[0043] This antibacterial iron powder, with metallic iron as its main component, is inexpensive and possesses excellent antibacterial properties. Furthermore, because it is a powder, it has a large surface area, and even if the surface of the metallic iron rusts, it will naturally peel off, exposing new metallic iron surfaces. Therefore, its antibacterial effect is highly sustained, and it is easily blended with various products and materials requiring antibacterial properties.

[0044] [Other implementation methods]

[0045] The above embodiments are not limited to the structure of the present invention. Therefore, based on the description in this specification and common technical knowledge, the constituent elements of the above embodiments may be omitted, substituted, or added, and these should all be interpreted as falling within the scope of the present invention.

[0046] For example, if the antibacterial iron powder can exert its antibacterial effect through the dissolution of ferrous ions, it may not contain the aforementioned antibacterial elements.

[0047] Example

[0048] The present invention will now be described in detail based on embodiments, but the invention is not to be interpreted in a limiting manner based on the description of these embodiments.

[0049] [Experimental Example 1]

[0050] <Preparation of Test Bacterial Solution>

[0051] Staphylococcus aureus and Escherichia coli were used as test bacteria. Each test bacterium was inoculated onto ordinary agar medium and incubated at a temperature above 30°C and below 35°C for 24 hours. Subsequently, for each test bacterium, physiological saline was used to achieve a bacterial count of 10⁻⁶. 8 The test bacterial suspension was prepared using the method of [CFU (Colony Forming Unit) / mL].

[0052] <Preparation of Test Samples>

[0053] (No.1 to No.3)

[0054] As samples, water atomized powder containing sulfur at a ratio of 1% by mass in pure iron was used. This sample was suspended in sterile water at a concentration of 1 g / L and dispensed into test tubes at 10 mL per tube, serving as test sample No. 1. The same sample was then suspended in the same sterile water at a concentration of 10 g / L and dispensed into test tubes at 10 mL per tube, serving as test sample No. 2. Finally, the same sample was suspended in the same sterile water at a concentration of 100 g / L and dispensed into test tubes at 10 mL per tube, serving as test sample No. 3.

[0055] (No.4)

[0056] Sterile water from the non-suspended sample was used as the test sample for No. 4.

[0057] <Calculation of viable bacteria count>

[0058] For test samples No. 1 to No. 4, 0.1 mL of the above-mentioned test bacterial suspension was inoculated and incubated at 25°C. One hour and four hours after inoculation, a series of 10-fold dilutions of the test samples were prepared using SCDLP liquid medium (lecithin-polysorbate 80 with added soybean-casein-digestion liquid medium). These test solutions were inoculated onto SCDLP agar medium and incubated for 72 hours at a temperature between 30°C and 35°C. After this incubation, the colonies formed were counted, and the viable count was calculated. For No. 1 to No. 3, three tests were performed respectively, and the average of the three tests was taken as the viable count. The results are shown in Table 1. Furthermore, a viable count of "0" in Table 1 means that no bacteria were detected after incubation.

[0059] Table 1

[0060]

[0061] <Evaluation Results>

[0062] As shown in Table 1 and Figure 1 and Figure 2 As shown, in samples No. 1 to No. 3 containing sulfur in pure iron, the viable counts of Staphylococcus aureus and Escherichia coli were significantly reduced. This is believed to be because sulfur effectively promotes the dissolution of ferrous ions. Furthermore, as shown in No. 4, when comparing Staphylococcus aureus and Escherichia coli, the viable count of Staphylococcus aureus 4 hours after inoculation was higher than that 1 hour after inoculation. This is believed to be due to individual differences caused by the test bacterial species when comparing with Escherichia coli, which constitutes an error.

[0063] [Experimental Example 2]

[0064] Using samples No. 1 to No. 3 described above, and samples No. 8 to No. 15 described later, the viable counts of Staphylococcus aureus and Escherichia coli were calculated following the same procedure as in Test Example 1. For samples No. 1 to No. 3 and No. 8 to No. 15, three tests were performed respectively, and the average of the three tests was taken as the viable count. Furthermore, the calculated viable counts for samples No. 1 to No. 3 differed between Test Example 1 and Test Example 2. This is considered to be due to errors caused by the test bacteria, etc. The calculated viable counts are shown in Table 2.

[0065] (No.8 to No.10)

[0066] A water-atomized powder containing sulfur at a concentration of 0.3% by mass in pure iron was used as the sample. This sample was suspended in sterile water at a concentration of 1 g / L and dispensed into test tubes at 10 mL intervals, serving as test sample No. 8. Similarly, the same sample was suspended in the same sterile water at a concentration of 10 g / L and dispensed into test tubes at 10 mL intervals, serving as test sample No. 9. Finally, the same sample was suspended in the same sterile water at a concentration of 100 g / L and dispensed into test tubes at 10 mL intervals, serving as test sample No. 10.

[0067] (No. 11)

[0068] A water-atomized powder containing sulfur at a concentration of 0.02% by mass in pure iron was used as the sample. This sample was suspended in sterile water at a concentration of 100 g / L and dispensed into test tubes at 10 mL intervals as the test sample No. 11.

[0069] (No. 12)

[0070] A water-atomized powder containing sulfur at a concentration of 0.005% by mass in pure iron was used as the sample. This sample was suspended in sterile water at a concentration of 100 g / L and dispensed into test tubes at 10 mL intervals as test sample No. 12.

[0071] (No.13 to No.15)

[0072] Glass beads were used as the sample. This sample was suspended in sterile water at a concentration of 1 g / L and dispensed in 10 mL aliquots into test tubes as test sample No. 13. The same sample was then suspended in the same sterile water at a concentration of 10 g / L and dispensed in 10 mL aliquots into test tubes as test sample No. 14. Finally, the same sample was suspended in the same sterile water at a concentration of 100 g / L and dispensed in 10 mL aliquots into test tubes as test sample No. 15.

[0073] Table 2

[0074]

[0075] <Evaluation Results>

[0076] As shown in Table 2, in samples No. 1 to No. 3 with a sulfur content of 1% by mass, the viable counts of Staphylococcus aureus and Escherichia coli were significantly reduced. Furthermore, in samples No. 8 to No. 11 with a sulfur content of 0.02% by mass or higher, the viable counts 4 hours after inoculation were also lower than those 1 hour after inoculation. Additionally, in sample No. 12 with a sulfur content of 0.005% by mass, the viable counts tended to be lower than those of the glass beads (No. 13 to No. 15) shown as comparative examples. Therefore, this antibacterial iron powder, by containing sulfur in metallic iron, can enhance its antibacterial effect, and in particular, by making the sulfur content 0.02% by mass or higher, the effect of reducing viable counts can be improved. This indicates that sulfur is an important element contributing to antibacterial activity.

[0077] [Experimental Example 3]

[0078] The test bacterial suspension was prepared using the same procedure as in Test Example 1. Using samples No. 1 to No. 3 (described above) and samples No. 16 to No. 21 (described later), the viable counts of Staphylococcus aureus and Escherichia coli were calculated using the same procedure as in Test Example 1. The results of the viable count calculations are shown in Table 3. Furthermore, the viable count calculations for samples No. 1 to No. 3 differed between Test Example 1 and Test Example 3. This is considered to be due to errors caused by the test bacteria, etc. Additionally, the so-called viable count value of "0" in Table 3 means that no bacteria were detected after incubation. Furthermore, the so-called antibacterial element in Table 3 refers to the element whose antibacterial effect is enhanced by its presence in metallic iron. The viable counts in Table 3 do not represent the antibacterial effect solely due to the antibacterial element.

[0079] (No.16 to No.18)

[0080] A water-atomized powder containing phosphorus at a concentration of 2% by mass in pure iron was used as the sample. This sample was suspended in sterile water at a concentration of 1 g / L and dispensed in 10 mL aliquots into test tubes as test sample No. 16. The same sample was also suspended in the same sterile water at a concentration of 10 g / L and dispensed in 10 mL aliquots into test tubes as test sample No. 17. Finally, the same sample was suspended in the same sterile water at a concentration of 100 g / L and dispensed in 10 mL aliquots into test tubes as test sample No. 18.

[0081] (No.19 to No.21)

[0082] A water-atomized powder containing 5% copper by mass in pure iron was used as the sample. This sample was suspended in sterile water at a concentration of 1 g / L and dispensed in 10 mL aliquots into test tubes as test sample No. 19. The same sample was also suspended in the same sterile water at a concentration of 10 g / L and dispensed in 10 mL aliquots into test tubes as test sample No. 20. Finally, the same sample was suspended in the same sterile water at a concentration of 100 g / L and dispensed in 10 mL aliquots into test tubes as test sample No. 21.

[0083] Table 3

[0084]

[0085] <Evaluation Results>

[0086] As shown in Table 3, in samples No. 1 to No. 3 with a sulfur content of 1% by mass, the viable counts of Staphylococcus aureus and Escherichia coli were significantly reduced. Additionally, as shown in Table 3 and... Figure 3 and Figure 4 As shown, in No. 19 to No. 21, where copper is used as an element representing antibacterial properties, a significant reduction in viable bacterial counts was observed in both Staphylococcus aureus and Escherichia coli. Furthermore, as shown in Table 3 and... Figure 3 and Figure 4 As shown, in samples No. 16 to No. 18, where phosphorus is used as the antibacterial element, especially in No. 18 where the sample is suspended in sterile water at 100 g / L, a slight decrease in viable counts of both Staphylococcus aureus and Escherichia coli was observed. Therefore, it can be concluded that, in addition to sulfur, phosphorus and copper are also preferred as the antibacterial elements in this antibacterial iron powder.

[0087] As shown in Table 3 and Figure 3 and Figure 4 As shown, the number of viable bacteria in No. 19 to No. 21, where copper is used as the antibacterial element, is significantly reduced. This can be interpreted as indicating that the antibacterial effect of copper is not weakened by its combination with metallic iron. Therefore, this antibacterial iron powder, for example, configured as an alloy powder containing copper, can exert this antibacterial effect.

[0088] Industrial availability

[0089] As explained above, the antibacterial iron powder of one aspect of the present invention is inexpensive and has excellent antibacterial properties, so it is suitable for blending in various products and materials.

Claims

1. An antibacterial iron powder, wherein pure metallic iron is the main component. It also contains elements that demonstrate antibacterial properties. The antibacterial properties are attributed to sulfur or phosphorus. The antibacterial element is contained in the metallic iron. The content of pure iron is 50% by mass or more. The sulfur content is 0.02% by mass or more and 5% by mass or less. The phosphorus content is 1% by mass or more and 5% by mass or less. The average particle size is 50 μm to 150 μm.

2. The antibacterial iron powder according to claim 1, wherein, The antibacterial iron powder is a water-atomized powder.

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