JP2022158900A - Antibacterial iron powder - Google Patents

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

The present invention relates to an antibacterial iron powder.

Demand for antibacterial substances is increasing today due to heightened awareness of hygiene and the like. Silver, copper and the like are known as metals having an antibacterial effect. For example, Patent Document 1 proposes antibacterial composite particles containing antibacterial inorganic particles A having silver or silver ions and antibacterial inorganic particles B containing zinc, titanium, copper or nickel.

Japanese Patent Application Laid-Open No. 2005-179607

Antibacterial metals such as silver and copper, which are widely used at present, have excellent antibacterial action, but are expensive. On the other hand, the antibacterial properties required for products are not uniform. For example, the degree of antibacterial properties required in the medical field differs from that required for everyday items. Therefore, today, there is an increasing demand for an antibacterial substance that can reduce manufacturing costs while exhibiting the necessary antibacterial action.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an antibacterial iron powder that is inexpensive and has excellent antibacterial action.

An antibacterial iron powder according to one aspect of the present invention contains metallic iron as a main component.

The antibacterial iron powder according to one aspect of the present invention is inexpensive and has excellent antibacterial activity.

FIG. 1 to No. 4 is a graph showing the relationship between the elapsed time in 4 and the viable count of Staphylococcus aureus. FIG. 1 to No. 4 is a graph showing the relationship between the elapsed time in 4 and the number of viable E. coli bacteria. FIG. 16 to No. 21 is a graph showing the relationship between the elapsed time in No. 21 and the viable count of Staphylococcus aureus. FIG. 16 to No. 21 is a graph showing the relationship between the elapsed time in No. 21 and the number of viable E. coli bacteria.

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

An antibacterial iron powder according to one aspect of the present invention contains metallic iron as a main component.

Since the iron powder for antibacterial use is mainly composed of metallic iron, it is inexpensive and has excellent antibacterial action. In addition, since the antibacterial iron powder is a powder, it has a large surface area, and even if rust occurs on the surface of the metallic iron, it will naturally peel off, and the new surface of the metallic iron will continue to be exposed. In addition to being excellent in the persistence of antibacterial properties, it is easy to incorporate into various products and their materials that require antibacterial properties.

It is preferable that the antibacterial iron powder further contains an element exhibiting antibacterial properties, and the element exhibiting antibacterial properties is contained in the metallic iron. Thus, the antibacterial action can be improved by including the antibacterial expression element contained in the metallic iron.

Preferably, the antibacterial element is sulfur or phosphorus. Thus, by using sulfur or phosphorus as the antibacterial element, the antibacterial effect can be remarkably improved.

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.

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.

The antibacterial element may be copper. By using copper as the antibacterial element, the antibacterial effect can be easily and reliably improved.

The antibacterial iron powder is preferably water atomized powder. Since the antibacterial iron powder is water-atomized powder, it is easy to increase the specific surface area compared to a bulk material such as an iron plate. As a result, it is easy to effectively exhibit an antibacterial action.

In the present invention, the term "main component" refers to a component having the highest content in terms of mass, for example, a component having a content of 50% by mass or more. The term "antibacterial-exhibiting element" includes an element that itself has antibacterial properties and an element that causes another element to exhibit antibacterial properties through a chemical reaction.

[Details of the embodiment of the present invention]
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. It should be noted that for the numerical values described in this specification, it is possible to arbitrarily combine the described upper limit values and lower limit values. In this specification, all numerical ranges from the upper limit to the lower limit that can be combined are described as suitable ranges.

[Antibacterial iron powder]
The antibacterial iron powder is iron powder containing metallic iron as a main component. The metallic iron includes pure iron and iron compounds. Among them, pure iron is preferable as the metallic iron. The antibacterial iron powder is considered to exhibit an antibacterial effect by elution of divalent iron ions (Fe ²⁺ ). More specifically, ferrous ions are attracted to prokaryotes (bacteria) by electrostatic induction, reduce the cell wall of the prokaryote, and after penetrating into the cell wall, reduce the DNA within the cell wall, resulting in an antibacterial effect. It is thought that it plays an effect. At this time, if metallic iron contains impurities, the impurities may hinder the elution of divalent iron ions. On the other hand, since the metallic iron is pure iron, the divalent iron ions are appropriately eluted, and the desired antibacterial effect is likely to be exhibited. The lower limit of the content of pure iron in the metallic iron is preferably 50% by mass. When the content of pure iron is equal to or higher than the lower limit, the elution amount of divalent iron ions can be sufficiently increased, and the antibacterial action and the durability of the antibacterial action can be enhanced. The term “pure iron” means one that is readily available for industrial use and has a purity of 90.0% by mass or more.

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 manufacturing cost of the antibacterial iron powder may increase. 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 thus it may be difficult to achieve a sufficient antibacterial action. In addition, "average particle size" refers to the particle size distribution obtained by a dry sieving test using a sieve specified in JIS-Z8801-1: 2019, and the particle size at which the cumulative mass is 50% in this particle size distribution. .

The antibacterial iron powder preferably contains an antibacterial element. Moreover, it is preferable that the antibacterial element is contained in the metallic iron. The antibacterial iron powder can improve the antibacterial action by containing the antibacterial element in the metallic iron. In the present invention, the "antibacterial expression element" is distinguished from the "metallic iron" as a separate component.

Examples of the antibacterial elements include sulfur (S) and phosphorus (P). The iron powder for antibacterial use contains sulfur or phosphorus in the metallic iron, so that the elution of divalent iron ions can be promoted.

When the antibacterial element is sulfur, the antibacterial effect is further enhanced because sulfur itself is involved in the expression of the antibacterial action. More specifically, since the metallic iron contains sulfur, the elution of divalent iron ions can be promoted 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⁻ ) are hydroxide ions (OH ⁻ ), sulfuric acid (H ₂ SO ₄ ), etc. Generating certain chemical species is thought to enhance the antibacterial activity.

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 further 0.5% by mass. preferable. On the other hand, the upper limit of the 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 above lower limit, it may become difficult to exhibit the desired antibacterial improvement effect. Conversely, if the content exceeds the upper limit, it becomes difficult to add sulfur to the antibacterial iron powder, and there is a risk that the production cost will be too high for the effect of improving the antibacterial action.

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 above lower limit, it may become difficult to exhibit the desired antibacterial improvement effect. Conversely, when the content exceeds the upper limit, it becomes difficult to incorporate phosphorus into the antibacterial iron powder, and there is a risk that the production cost will become too high for the effect of improving the antibacterial action.

The antibacterial element may be copper. Copper is known to have an antibacterial effect, and has conventionally been used alone (copper alone) or as 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. It is considered that the behavior is different from that of copper alone or iron alone. In other words, the antibacterial iron powder is not based on the antibacterial action of copper itself, but is based on new findings that the antibacterial properties of iron can be activated by alloying copper and iron. In addition, although an oxide film may be formed on the surface of the antibacterial iron powder, it is believed that this oxide film is likely to peel off because it is mainly composed of iron, unlike the copper oxide film formed on the surface of copper alone. As a result, it is presumed that the nascent surface of the iron part continues to be exposed, so that the antibacterial properties are likely to be sustained. Furthermore, since the antibacterial iron powder is alloyed with iron, the production cost can be kept lower than that of an antibacterial material made of copper alone.

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 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 above lower limit, it may become difficult to exhibit the desired antibacterial improvement effect. Conversely, if the content exceeds the upper limit, it becomes difficult to add copper to the antibacterial iron powder, and there is a risk that the production cost will become too high for the effect of improving the antibacterial action.

The method for producing the antibacterial iron powder is not particularly limited. The antibacterial iron powder may be produced by, for example, a reduction method, a gas atomization method, or the like. However, the water atomization method is preferable as the method for producing the antibacterial iron powder. That is, the antibacterial iron powder is preferably water-atomized powder. Water-atomized powder is obtained by spraying high-pressure water onto molten metallic iron to make the metallic iron finer and solidified. Since the water-atomized powder has irregularities on its surface, it has a large specific surface area. Therefore, the water-atomized powder has excellent dissolution properties of divalent iron ions. The water-atomized powder is obtained by adding the antibacterial element to the metallic iron when the metallic iron is melted. Therefore, the water-atomized powder prevents contamination with impurities (that is, selectively contains the antibacterial element) and facilitates control of the content of the antibacterial element. That is, according to the water-atomized powder, the composition of the entire antibacterial iron powder can be easily and reliably controlled. Therefore, since the antibacterial iron powder is a water-atomized powder, it can promote the elution of divalent iron ions, and can easily exhibit an effective antibacterial action. Furthermore, since the antibacterial iron powder is water-atomized powder, the manufacturing cost can be reduced.

The antibacterial iron powder can be used, for example, by blending with products such as miscellaneous goods, building materials, and furniture and their materials. That is, the antibacterial iron powder can be used by blending it with products and materials thereof that are in daily contact and for which propagation of bacteria is not desired from a sanitary point of view.

<Advantages>
Since the iron powder for antibacterial use is mainly composed of metallic iron, it is inexpensive and has excellent antibacterial action. In addition, since the antibacterial iron powder is a powder, it has a large surface area, and even if rust occurs on the surface of the metallic iron, it will naturally peel off, and the new surface of the metallic iron will continue to be exposed. In addition to being excellent in the persistence of antibacterial properties, it is easy to incorporate into various products and their materials that require antibacterial properties.

[Other embodiments]
The above embodiments do not limit the configuration of the present invention. Therefore, in the above embodiment, the components of each part of the above embodiment can be omitted, replaced, or added based on the description of the present specification and common general technical knowledge, and all of them are interpreted as belonging to the scope of the present invention. should.

For example, the antibacterial iron powder does not need to contain the above-mentioned antibacterial-developing element if it can exhibit an antibacterial action by elution of divalent iron ions.

EXAMPLES The present invention will be described in detail below based on examples, but the present invention is not limitedly interpreted based on the description of these examples.

[Test Example 1]
<Preparation of test bacterial solution>
Using Staphylococcus aureus and Escherichia coli as test bacteria, each test bacteria was inoculated into a nutrient agar medium and cultured at a temperature of 30° C. or higher and 35° C. or lower for 24 hours. Thereafter, each test bacterium was prepared with physiological saline so that the number of bacteria was 10 ⁸ [CFU (Colony Forming Unit)/mL] to prepare a test bacterium solution.

<Preparation of test sample>
(No. 1 to No. 3)
A water-atomized powder containing 1% by mass of sulfur in pure iron was used as a sample. This sample was suspended in sterilized water to a concentration of 1 g/L, and 10 mL was dispensed into a test tube. 1 test sample. In addition, the specimen was suspended in the sterilized water to a concentration of 10 g/L, and 10 mL was dispensed into a test tube. No. 2 test sample was prepared by suspending the above specimen in the above sterilized water to a concentration of 100 g/L and dispensing 10 mL into a test tube. 3 test samples.

(No. 4)
Sterilized water in which no specimen is suspended is added to No. 4 test samples.

<Calculation of the number of viable bacteria>
No. 1 to No. 0.1 mL of the above-described test bacterial solution was inoculated into each of the 4 test samples and allowed to stand at 25°C. Immediately after inoculation, 1 hour and 4 hours after inoculation, a 10-fold dilution series of the test sample was prepared in SCDLP liquid medium (lecithin-polysorbate 80-added soybean-casein digest liquid medium) to obtain test solutions. These test solutions were inoculated on SCDLP agar medium and cultured at a temperature of 30° C. or higher and 35° C. or lower for 72 hours. After this culture, the formed colonies were counted and the number of viable bacteria was calculated. No. 1 to No. For 3, each test was performed three times, and the average value of the three tests was obtained as the viable cell count. Table 1 shows the calculation results. In addition, the viable cell count value “0” in Table 1 means that no bacteria were detected by culturing.

<Evaluation results>
As shown in Table 1 and FIGS. 1 and 2, no. 1 to No. In the specimen No. 3, the viable counts of both Staphylococcus aureus and Escherichia coli are greatly reduced. This is probably because sulfur effectively promotes the elution of ferric ions. In addition, No. As shown in Figure 4, when comparing Staphylococcus aureus and Escherichia coli, the viable count of Staphylococcus aureus is higher 4 hours after inoculation than the number of viable bacteria 1 hour after inoculation. It has increased. It is considered that this is due to the intervening error caused by individual differences caused by the test strain when compared with Escherichia coli.

[Test Example 2]
The above No. 1 to No. 3 sample and No. 3, which will be described later. 8 to No. Viable counts of Staphylococcus aureus and Escherichia coli were calculated in the same manner as in Test Example 1 using 15 specimens. No. 1 to No. 3 and No. 8 to No. For No. 15, each test was performed three times, and the average value in the three tests was obtained as the viable cell count. In addition, in Test Example 1 and Test Example 2, No. 1 to No. The calculation results of the viable count of the samples of 3 are different. This is considered to be an error caused by test bacteria or the like. Table 2 shows the calculation results of the viable cell count.

(No.8 to No.10)
A water-atomized powder containing 0.3% by mass of sulfur in pure iron was used as a sample. This sample was suspended in sterilized water to a concentration of 1 g/L, and 10 mL was dispensed into a test tube. 8 test samples. In addition, the specimen was suspended in the sterilized water to a concentration of 10 g/L, and 10 mL was dispensed into a test tube. No. 9 test sample was suspended in the sterilized water to a concentration of 100 g/L, and 10 mL was dispensed into a test tube. There were 10 test samples.

(No. 11)
A water-atomized powder containing 0.02% by mass of sulfur in pure iron was used as a sample. This sample was suspended in sterilized water to a concentration of 100 g/L, and 10 mL was dispensed into a test tube. There were 11 test samples.

(No. 12)
A water-atomized powder containing 0.005% by mass of sulfur in pure iron was used as a specimen. This sample was suspended in sterilized water to a concentration of 100 g/L, and 10 mL was dispensed into a test tube. There were 12 test samples.

(No. 13 to No. 15)
Glass beads were used as specimens. This sample was suspended in sterilized water to a concentration of 1 g/L, and 10 mL was dispensed into a test tube. There were 13 test samples. In addition, the specimen was suspended in the sterilized water to a concentration of 10 g/L, and 10 mL was dispensed into a test tube. No. 14 test samples were prepared by suspending the above specimens in the above sterilized water at a concentration of 100 g/L and dispensing 10 mL into test tubes. There were 15 test samples.

<Evaluation results>
As shown in Table 2, no. 1 to No. 3 can greatly reduce the number of viable bacteria for both Staphylococcus aureus and Escherichia coli. Further, No. 2 having a sulfur content of 0.02% by mass or more. 8 to No. Regarding No. 11, the number of viable bacteria decreased 4 hours after inoculation as compared to 1 hour after inoculation. Further, No. 1 having a sulfur content of 0.005% by mass. No. 12 also tends to have a lower viable cell count than the glass beads (No. 13 to No. 15) shown as comparative examples. From this, the antibacterial iron powder can enhance the antibacterial action by containing sulfur in the metallic iron, and in particular, by setting the sulfur content to 0.02% by mass or more, viable bacteria It can be seen that the effect of reducing the number can be enhanced. This indicates that sulfur is an important antibacterial expression element.

[Test Example 3]
A test bacterial solution was prepared in the same procedure as in Test Example 1, and the above-mentioned No. 1 to No. 3 sample and No. 3, which will be described later. 16 to No. Using the 21 specimens, the viable counts of Staphylococcus aureus and Escherichia coli were calculated in the same manner as in Test Example 1. Table 3 shows the results of calculating the number of viable bacteria. In addition, in Test Example 1 and Test Example 3, No. 1 to No. The calculation results of the viable count of the samples of 3 are different. This is considered to be an error caused by the test bacteria or the like. In addition, the viable cell count value "0" in Table 3 means that no bacteria were detected by culturing. In addition, the antibacterial expression element in Table 3 means an element that can obtain an antibacterial improvement effect by being contained in metallic iron, and the number of viable bacteria in Table 3 is the antibacterial effect of the antibacterial expression element alone. does not indicate

(No.16 to No.18)
A water-atomized powder containing 2% by mass of phosphorus in pure iron was used as a sample. This sample was suspended in sterilized water to a concentration of 1 g/L, and 10 mL was dispensed into a test tube. There were 16 test samples. In addition, the specimen was suspended in the sterilized water to a concentration of 10 g/L, and 10 mL was dispensed into a test tube. No. 17 test samples were prepared by suspending the above specimens in the above sterilized water at a concentration of 100 g/L and dispensing 10 mL into test tubes. There were 18 test samples.

(No. 19 to No. 21)
A water-atomized powder containing 5% by mass of copper in pure iron was used as a sample. This sample was suspended in sterilized water to a concentration of 1 g/L, and 10 mL was dispensed into a test tube. There were 19 test samples. In addition, the specimen was suspended in the sterilized water to a concentration of 10 g/L, and 10 mL was dispensed into a test tube. 20 test samples, the above specimens were suspended in the above sterilized water to a concentration of 100 g/L, and 10 mL was dispensed into test tubes. There were 21 test samples.

<Evaluation results>
As shown in Table 3, no. 1 to No. 3 can greatly reduce the number of viable bacteria for both Staphylococcus aureus and Escherichia coli. Moreover, as shown in Table 3 and FIGS. 19 to No. Regarding No. 21, it can be confirmed that the viable cell count tends to decrease greatly in both Staphylococcus aureus and Escherichia coli. Furthermore, as shown in Table 3 and FIGS. 3 and 4, no. 16 to No. Regarding No. 18, the specimen was suspended in sterilized water at a concentration of 100 g/L. 18, it can be confirmed that the number of viable bacteria tends to slightly decrease in both Staphylococcus aureus and Escherichia coli. From this, it can be seen that, in addition to sulfur, phosphorus and copper are preferable as the antibacterial expression elements in the antibacterial iron powder.

As shown in Table 3 and FIGS. 3 and 4, no. 19 to No. The fact that the number of viable bacteria can be significantly reduced in No. 21 is considered to indicate that the antibacterial effect of copper is not attenuated by the combination with metallic iron. From this, it can be seen that the antibacterial iron powder can exert its antibacterial effect by being configured as, for example, an alloy powder containing copper.

As described above, the antibacterial iron powder according to one aspect of the present invention is inexpensive and has an excellent antibacterial action, so it can be suitably blended into various products and their materials.

Claims (7)

Antibacterial iron powder with metallic iron as the main component. It further contains an antibacterial expression element,
2. The antibacterial iron powder according to claim 1, wherein the antibacterial element is contained in the metallic iron. 3. The antibacterial iron powder according to claim 2, wherein the antibacterial element is sulfur or phosphorus. 4. The antibacterial iron powder according to claim 3, wherein the antibacterial element is sulfur and the sulfur content is 0.02% by mass or more and 5% by mass or less. 4. The antibacterial iron powder according to claim 3, wherein the antibacterial element is phosphorus and the phosphorus content is 1% by mass or more and 5% by mass or less. 3. The antibacterial iron powder according to claim 2, wherein the antibacterial element is copper. The antibacterial iron powder according to any one of claims 1 to 6, which is water atomized powder.

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