Method for producing rare earth ferrite, and rare earth ferrite

Abstract

To provide a rare earth ferrite: particularly, one that can be used as a fungicide, an antibiotic, or an algicide, and a method for producing the same.SOLUTION: A mixture including a rare earth source having a specific composition and an iron source is fired at a specific firing temperature, to obtain a rare earth ferrite represented by the formula (1): Ln2xFe2(1-x) O3 (where Ln is a rare earth element selected from the group consisting of lanthanum, praseodymium, neodymium, and yttrium, and x is a number that is at least 0.45 and less than 1.00).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing rare earth ferrite and rare earth ferrite. More specifically, the present invention relates to a method for producing rare earth ferrite useful as an antifungal agent, antibacterial agent, and antialgal agent, and to a rare earth ferrite having specific physical properties obtained by the method. [Background technology]

[0002] Exterior walls, interior walls, building materials, air filters, packing, and tanks or pipes for storing or passing water are in an environment where they are exposed to water due to condensation or running water, etc., and therefore become contaminated by mold. In response to this, there is a demand for products with anti-mold properties to prevent the growth of mold and the progression of contamination.

[0003] Known agents that exhibit antifungal effects include phenol-based, organotin-based, triazine-based, halogenated sulfonylpyridine-based, captan-based, organocupropane-based, chloronaphthalene-based, and chlorophenylpyritazine-based compounds (see Patent Document 1).

[0004] Silver ions, copper ions, zinc ions, etc. are known as ions that exhibit an antifungal effect. For example, metal powders such as silver, copper, zinc, etc., or alloys or compounds thereof are held on a carrier, and a trace amount of these metal ions are eluted to utilize their toxicity. Patent Document 2 discloses a dispersion having deodorizing, antibacterial, and antifungal properties, in which a metal carboxylate formed from a carboxyl group-containing polymer and a metal compound is dispersed.

[0005] Furthermore, anti-algae agents are used to prevent the growth of algae on ships, revetments, building materials, fishing nets, etc. As anti-algae agents that have been known to exert an excellent anti-algae effect, organic tin compounds, cuprous oxides, quaternary amine compounds, etc. have been known to exert an excellent anti-algae effect. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 17249 / 1983 [Patent Document 2] Japanese Patent Application Publication No. 2-288804 [Patent Document 3] JP 2005-272320 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, recently, antifungal agents in the form of pharmaceutical agents or antifungal agents utilizing the toxicity of metal ions have been viewed as problematic in terms of environmental pollution and safety.

[0008] In recent years, therefore, ferrite compounds have been proposed as anti-algae agents that are less harmful to the environment and have excellent safety. For example, Patent Document 3 discloses an anti-algae additive mainly composed of orthoferrite containing a rare earth element selected from lanthanum (La), praseodymium (Pr), neodymium (Nd), and yttrium (Y), iron, and oxygen, an anti-algae paint using the same, and an anti-algae product in which the paint is applied to the surface of a substrate.

[0009] In Patent Document 3, the anti-algae effect is considered to be related to the magnetism of the material, and it is explained that orthoferrite with rare earth oxide:Fe2O3=1:1 (molar ratio), which has a small coercive force and exhibits a magnetic force close to the intrinsic magnetic field of plants, is the most preferable as an anti-algae additive. However, Patent Document 3 does not recognize at all that orthoferrite with rare earth oxide:Fe2O3=1:1 (molar ratio) has an anti-mold effect.

[0010] The present invention has been made in view of the above background, and an object of the present invention is to provide a rare earth ferrite, in particular a rare earth ferrite that can be used as an antifungal agent, an antibacterial agent, and an antialgae agent, and a method for producing the same. [Means for solving the problem]

[0011] The present inventors conducted extensive research to solve the above problems. As a result, they found that a rare earth ferrite having a specific composition sintered at a specific sintering temperature can solve the above problems, and thus completed the present invention. That is, the present invention is as follows.

[0012] Aspect 1 A method for producing rare earth ferrite, comprising firing a mixture containing a rare earth source and an iron source at a firing temperature of 700 to 1100° C. to obtain rare earth ferrite represented by the following formula (1): Ln 2x Fe 2(1-x) O3(1) (In formula (1), Ln is a rare earth element selected from the group consisting of lanthanum, praseodymium, neodymium, and yttrium, and x is a number equal to or greater than 0.45 and less than 1.00). Aspect 2 2. The method for producing rare earth ferrite according to aspect 1, wherein x in formula (1) is a number of 0.50 or more and 0.90 or less. Aspect 3 2. The method for producing rare earth ferrite according to aspect 1, wherein x in formula (1) is a number of 0.65 or more and 0.85 or less. Aspect 4 The method for producing a rare earth ferrite according to any one of Aspects 1 to 3, wherein the rare earth source is at least one selected from the group consisting of oxides of rare earth elements, bastnasite, monazite, and xenotime. Aspect 5 5. The method for producing a rare earth ferrite according to any one of aspects 1 to 4, wherein the iron source is at least one selected from the group consisting of an oxide, an oxyoxide, and a hydroxide. Aspect 6 6. The method for producing rare earth ferrite according to any one of aspects 1 to 5, wherein the rare earth element is lanthanum. Aspect 7 7. The method for producing rare earth ferrite according to any one of aspects 1 to 6, wherein the rare earth source is La2O3. Aspect 8 The method for producing rare earth ferrite according to any one of aspects 1 to 7, wherein the iron source is FeOOH. Aspect 9: The method for producing a rare earth ferrite according to any one of aspects 1 to 8, wherein the sintering temperature is 800 to 1000°C. Aspect 10 10. The method for producing a rare earth ferrite according to any one of Aspects 1 to 9, wherein the rare earth ferrite is at least one selected from the group consisting of an antifungal agent, an antibacterial agent, and an anti-algae agent. Aspect 11 A rare earth ferrite having an XRD diffraction pattern in which the ratio (I / I0) of a diffraction peak intensity I at about 2θ=30.1° to a diffraction peak intensity I0 at about 2θ=32.3° is 0.01 or more. Aspect 12 12. The rare earth ferrite according to claim 11, wherein the rare earth ferrite is at least one selected from the group consisting of an antifungal agent, an antibacterial agent, and an antialgal agent. Effect of the Invention

[0013] According to the present invention, there is provided a rare earth ferrite which can be used as an antifungal agent, an antibacterial agent, and an antialgal agent.

[0014] In addition, when the rare earth ferrite obtained by the manufacturing method of the present invention is used as an antifungal agent, the antifungal effect is also exerted on the surroundings. That is, the antifungal effect can be extended to the parts that are not in direct contact with the rare earth ferrite obtained by the manufacturing method of the present invention. Therefore, when producing an antifungal product, the antifungal effect can be exerted even if the rare earth ferrite is not present in the entire article to be the product.

[0015] Furthermore, when the rare earth ferrite obtained by the manufacturing method of the present invention is used as an anti-algae agent, it is possible to inhibit the deterioration of the anti-algae effect over time, and the anti-algae effect can be maintained for a long period of time.

[0016] Furthermore, the rare earth ferrite obtained by the manufacturing method of the present invention has excellent dispersibility in water, organic solvents, etc. Therefore, it is possible to prepare dispersions, paints, etc. in which the rare earth ferrite is dispersed in various media. Therefore, by applying a paint, etc. containing the rare earth ferrite obtained by the manufacturing method of the present invention to a base article, etc. to form a layer, it is possible to impart an antifungal effect, an antibacterial effect, and an antialgal effect to materials to which antifungal agents, antibacterial agents, or antialgal agents have not been applicable until now, or to places with complex shapes. [Brief description of the drawings]

[0017] [Figure 1] 1 is an XRD diffraction pattern of the lanthanum ferrite obtained in Example 1. [Diagram 2] 1 is an XRD diffraction pattern of the lanthanum ferrite obtained in Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] <Production method of rare earth ferrite> The method for producing rare earth ferrite of the present invention comprises the steps of: The method for producing rare earth ferrite comprises firing a mixture containing a rare earth source and an iron source at a firing temperature of 700 to 1100° C. to obtain rare earth ferrite represented by the following formula (1): Ln 2x Fe 2(1-x) O3(1) (In formula (1), Ln is a rare earth element selected from the group consisting of lanthanum, praseodymium, neodymium, and yttrium, and x is a number equal to or greater than 0.45 and less than 1.00).

[0019] The method for providing the mixture containing the rare earth source and the iron source is not particularly limited, and may be, for example, a method in which a mixed raw material containing the rare earth source and the iron source is pulverized and mixed by applying an appropriate stress. Examples of the stress to be applied include frictional force, shear force, shear stress, and impact force. For example, a method in which the mixture of the rare earth source and the iron source is wet-pulverized in a ball mill may be used.

[0020] As the rare earth source, for example, oxides of the desired rare earth elements may be used, as well as bastnaesite, monazite, xenotime, and the like.

[0021] As the rare earth element, lanthanum is preferably used from the viewpoint of the excellent antifungal, antibacterial, and antialgal properties of the obtained rare earth ferrite, and from the viewpoint of cost. Among them, by using La2O3, it is possible to produce lanthanum ferrite that is highly effective and relatively inexpensive.

[0022] As the iron source, oxides such as FeO, Fe3O4, Fe2O3, etc.; oxyoxides such as FeOOH, ferrihydrite, schwermannite, etc.; hydroxides such as Fe(OH)2, Fe(OH)3, etc.; and the like may be used.

[0023] Among these, if FeOOH is used as the iron source, it is possible to sinter at a lower temperature because of its higher reactivity compared to Fe2O3, etc. Also, it is possible to produce rare earth ferrite with a smaller particle size compared to Fe2O3, etc.

[0024] When the mixture of the rare earth source and the iron source is pulverized and mixed by wet pulverization, the liquid medium may be, for example, water, alcohol, etc. After the mixture of the rare earth source and the iron source is pulverized and mixed, the liquid medium may be removed by an appropriate method such as heating and drying, as necessary, and then calcination may be performed.

[0025] In the method for producing rare earth ferrite of the present invention, the mixture of the rare earth source and the iron source is fired at a temperature in the range of 700 to 1100° C. That is, in the method for producing rare earth ferrite of the present invention, firing is performed at a relatively low temperature range. This makes it possible to obtain rare earth ferrite having a specific XRD diffraction peak intensity ratio, and the rare earth ferrite exhibits excellent antifungal, antibacterial, and antialgal effects.

[0026] The calcination temperature of the mixture of the rare earth source and the iron source may be, for example, 700°C or more, 800°C or more, 900°C or more, or 1,000°C or more, and may be, for example, a temperature of 1,050°C or less, 1,000°C or less, 950°C or less, 900°C or less, 850°C or less, 800°C or less, or 750°C or less.

[0027] For example, within the range of 800° C. or more and 1000° C. or less, rare earth ferrite having even better antifungal, antibacterial and antialgal effects can be obtained.

[0028] The calcination time of the mixture of the rare earth source and the iron source is not particularly limited and can be appropriately set. For example, the calcination may be performed for a time of 1 hour or more, 2 hours or more, 3 hours or more, 4 hours or more, 6 hours or more, 8 hours or more, 12 hours or more, or 15 hours or more, and 72 hours or less, 48 ​​hours or less, 36 hours or less, 24 hours or less, 18 hours or less, or 15 hours or less.

[0029] The surrounding atmosphere during firing may be an oxidizing atmosphere, for example, firing may be performed in air.

[0030] After firing, the product may be crushed, classified, or the like, by an appropriate method, if necessary.

[0031] Rare earth ferrite The rare earth ferrite produced by the method for producing rare earth ferrite of the present invention is a rare earth ferrite compound having a specific composition and is represented by the following formula (1): Ln 2x Fe 2(1-x) O3(1) (In formula (1), Ln is a rare earth element selected from the group consisting of lanthanum, praseodymium, neodymium, and yttrium, and x is a number equal to or greater than 0.45 and less than 1.00).

[0032] The present inventors have also conducted detailed studies on the composition of rare earth ferrite and its antifungal effect, and have found that a high antifungal effect can be obtained by setting the rare earth (Ln):Fe ratio in the rare earth ferrite within the above range.

[0033] The rare earth ferrite produced by the method for producing rare earth ferrite of the present invention may be in any form as long as x in the above formula (1) is a number of 0.45 or more and less than 1.00. For example, it may form a solid solution having a uniform composition as a whole, may be a mixture of LnFeO3 phase and Ln2O3 phase, or may be a mixture of a solid solution having a uniform composition and LnFeO3 phase and Ln2O3 phase. It may also contain phases other than these.

[0034] In formula (1), x may be 0.50 or more, 0.55 or more, 0.60 or more, 0.65 or more, 0.70 or more, or 0.75 or more, or may be 0.90 or less, 0.85 or less, 0.80 or less, 0.75 or less, 0.70 or less, 0.65 or less, or 0.60 or less.

[0035] Typically, x in the above formula (1) may be, for example, a number of 0.50 or more and 0.90 or less, and may further be a number of 0.65 or more and 0.85 or less.

[0036] As described above, the rare earth (Ln) in formula (1) may be lanthanum, in particular, from the viewpoint of the excellent antifungal and antialgal properties of the obtained rare earth ferrite and the cost. Therefore, the rare earth ferrite produced by the method for producing rare earth ferrite of the present invention may be lanthanum ferrite.

[0037] Furthermore, the rare earth ferrite obtained by the method for producing rare earth ferrite of the present invention has an XRD diffraction pattern in which the ratio (I / I0) of the diffraction peak intensity I at about 2θ=30.1° to the diffraction peak intensity I0 at about 2θ=32.3° is 0.01 or more.

[0038] The rare earth ferrite having the above-mentioned characteristics has low environmental pollution and is excellent in safety, and also exhibits excellent antifungal, antibacterial and antialgal properties.

[0039] The ratio (I / I0) of the diffraction peak intensity I at about 2θ=30.1° to the diffraction peak intensity I0 at about 2θ=32.3° may be 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, or 0.5 or more, and may be 1.0 or less, 0.9 or less, 0.8 or less, 0.7 or less, or 0.6 or less.

[0040] <Uses of rare earth ferrite> The rare earth ferrite obtained by the method for producing rare earth ferrite of the present invention has a low degree of environmental pollution and is excellent in safety, and therefore can be used in various applications.

[0041] The rare earth ferrite obtained by the method for producing rare earth ferrite of the present invention exhibits excellent performance as an antifungal agent, antibacterial agent, and anti-algae agent, particularly as an antifungal agent or anti-algae agent. For example, when used as an antifungal agent, it exerts an antifungal effect on the surroundings, and when used as an anti-algae agent, it can suppress the decrease in the anti-algae effect over time.

[0042] <Antifungal agents, antibacterial agents, anti-algae agents> (Amount used) When the rare earth ferrite produced by the method for producing rare earth ferrite of the present invention is used as an antifungal agent, antibacterial agent, or anti-algae agent, the form of use is not particularly limited. For example, it can be used in a powder state, an impregnated state, or a coating state.

[0043] When the rare earth ferrite is used in the form of a powder as an antifungal agent, antibacterial agent, or anti-algae agent, it is preferable to use 1 g or more of the rare earth ferrite in order to fully exert the effect.

[0044] When the rare earth ferrite is used in an impregnated state as an antifungal agent, antibacterial agent, or anti-algae agent, it is preferable to impregnate, for example, 0.01 to 0.5 g of rare earth ferrite into 0.06 g of paper.

[0045] When the rare earth ferrite is used as an anti-fungal agent, antibacterial agent, or anti-algae agent in the form of a coating film, and is used as a paint containing rare earth ferrite, it is preferable that the rare earth ferrite is contained in an amount of, for example, 30 mass% or more of the total solid content of the paint.

[0046] (Anti-mold products, anti-bacterial products, anti-algae products) When the rare earth ferrite obtained by the method for producing rare earth ferrite of the present invention is used as an antifungal agent, antibacterial agent, or antialgal agent to form an antifungal product, an antibacterial product, or antialgal product, the product may be, for example, an antifungal product, an antibacterial product, or antialgal product that includes an antifungal layer, an antibacterial layer, or an antialgal layer that contains rare earth ferrite. Specifically, the antifungal product, an antibacterial product, or antialgal product includes a base and an antifungal layer, an antibacterial layer, or an antialgal layer, and the antifungal layer, an antibacterial layer, or an antialgal layer is a layer that includes the rare earth ferrite obtained by the method for producing rare earth ferrite of the present invention.

[0047] The substrate in the antifungal, antibacterial, or antialgal product may be any article to which antifungal, antibacterial, or antialgal properties are to be imparted, including any article made of any material and having any shape for which antifungal, antibacterial, or antialgal properties are required.

[0048] The antifungal layer in the antifungal product, the antibacterial layer in the antibacterial product, and the antialgal layer in the antialgal product are not particularly limited as long as they are layers containing rare earth ferrite obtained by the method for producing rare earth ferrite of the present invention. For example, they may be layers produced by blending rare earth ferrite powder with a resin or the like and extrusion coating, or may be cured products such as antifungal paints described below.

[0049] The antifungal layer, antibacterial layer, and antialgal layer may contain any component other than the rare earth ferrite. The optional component is not particularly limited, but examples thereof include resins, binders, and additives for realizing various functions.

[0050] The thickness of the antifungal layer, antibacterial layer, and antialgal layer is not particularly limited, and may be, for example, about 1 μm or more and 1 mm or less.

[0051] When the antifungal layer, antibacterial layer, or antialgal layer is formed by coating, the coating amount is, for example, 5 g / m2 as the dry mass after removing the solvent per unit area. 2 More than 10g / m 2 More than 15g / m 2 More than 20g / m 2 or more than 25g / m 2 or more, for example, 200 g / m 2 Below 150g / m 2 Below 120g / m 2 Below 100g / m 2 Below 80g / m 2 or less than 70g / m 2 It may be the following:

[0052] The antifungal, antibacterial, and antialgal products need only include a substrate and an antifungal, antibacterial, or antialgal layer as essential components, and may also include other components. Examples of other components include other layers, and the other layers may be on the outside of the substrate, between the substrate and the antifungal, antibacterial, or antialgal layer, or on the outside of the antifungal, antibacterial, or antialgal layer.

[0053] The other layers include, for example, a primer layer formed on the substrate. By forming an antifungal layer, an antibacterial layer, or an antialgal layer on the primer layer, the adhesion can be improved.

[0054] In addition, the outside of the antifungal layer may be covered with a resin or the like to prevent the antifungal effect from decreasing due to the fall-off or leakage of the antifungal agent over long-term use.

[0055] Furthermore, by laminating a hue pigment layer or the like on the outside of the anti-mold layer, the freedom of color design of the anti-mold product can be increased, and other functional layers can be laminated or combined to provide properties other than anti-mold properties.

[0056] The application locations of antifungal products, antibacterial products, and antialgae products are not particularly limited, but examples of antifungal products include exterior walls, interior walls, building materials, air filters, packing, and tanks or pipes for storing or passing water. Examples of antialgae products include ships, revetments, building materials, fishing nets, aquaculture nets, aquariums, pool walls, pool bottoms, pool course ropes, buoys, tiles, etc. Examples of antibacterial products include interior walls, building materials, furniture, air filters, insoles, clothing, sanitary products, bath mats, towels, bedding, etc.

[0057] (Anti-mold paint, anti-bacterial paint, anti-algae paint) The rare earth ferrite obtained by the method for producing rare earth ferrite of the present invention may be used as an antifungal agent, an antibacterial agent, or an anti-algae agent to form an antifungal paint, an antibacterial paint, or an anti-algae paint. The antifungal paint, the antibacterial paint, or the anti-algae paint may contain other components such as a resin and a solvent in addition to the rare earth ferrite.

[0058] The resin optionally contained in the antifungal paint, antibacterial paint, or antialgae paint is not particularly limited, and may be, for example, an acrylic resin, an acrylic silicone resin, a silicone resin, an amino alkyd resin, an epoxy resin, a phenolic resin, a polyurethane resin, an unsaturated polyester resin, a fluororesin, etc.

[0059] The solvent contained in the antifungal paint, antibacterial paint, or antialgae paint is not particularly limited and may be selected from, for example, water, alcohol, ketone, aliphatic hydrocarbon, aromatic hydrocarbon, ester, etc.

[0060] The content of rare earth ferrite in the antifungal paint, antibacterial paint, or antialgal paint of the present invention may be, from the viewpoint of exhibiting high antifungal, antibacterial, or antialgal performance, for example, 1 mass% or more, preferably 2 mass% or more, more preferably 5 mass% or more, even more preferably 10 mass% or more, particularly preferably 20 mass% or more, and especially preferably 30 mass% or more, as a ratio of rare earth ferrite to the total of the resin and rare earth ferrite in the paint; from the viewpoint of obtaining good coatability, the content may be, for example, 80 mass% or less, preferably 70 mass% or less, more preferably 60 mass% or less, even more preferably 50 mass% or less, particularly preferably 40 mass% or less, and especially preferably 30 mass% or less or 20 mass% or less.

[0061] The method for producing the antifungal paint, antibacterial paint, or antialgae paint is not particularly limited. For example, the paint may be prepared by mixing a commercially available synthetic resin paint and the rare earth ferrite obtained by the method for producing rare earth ferrite of the present invention in a predetermined ratio.

[0062] The antifungal paint, antibacterial paint, or antialgae paint of the present invention can be used to form an antifungal layer, antibacterial layer, or antialgae layer in the above-mentioned antifungal product, antibacterial product, or antialgae product. It may also be used, for example, as a joint material (a gap filler for tiles, concrete, bricks, etc.), a sealing material, a caulking material, an adhesive, etc. EXAMPLES

[0063] Example 1 <Synthesis of lanthanum ferrite> In a ball mill using 10 mm diameter alumina balls as the grinding media, 0.25 mol parts of La2O3, 0.5 mol parts of FeOOH, and water were charged and ground and mixed for 5 hours. The obtained ground material was dried at 300°C for 15 hours and then crushed with a rotary grinder. The obtained crushed material was fired at 800°C for 15 hours and then crushed with a hammer mill to obtain lanthanum ferrite (formula LaFeO3) with La:Fe=50:50 (molar ratio).

[0064] Comparative Example 1 Lanthanum ferrite was synthesized in the same manner as in Example 1, except that the firing temperature shown in Table 1 was used.

[0065] <XRD Measurement> For the lanthanum ferrite obtained in Example 1 and Comparative Example 1, XRD analysis was performed using an X-ray diffractometer (model: MiniFlex600, manufactured by Rigaku Corporation). The obtained diffraction peaks are shown in FIGS. 1 and 2.

[0066] FIG. 1 is the diffraction pattern of the lanthanum ferrite obtained in Example 1, and FIG. 2 is the diffraction pattern of the lanthanum ferrite obtained in Comparative Example 1. For the lanthanum ferrite synthesized in Example 1, the ratio (I / I0) of the diffraction peak intensity I near 2θ = 30.1° to the diffraction peak intensity I0 near 2θ = 32.3° in the XRD diffraction pattern was 0.25. On the other hand, for the lanthanum ferrite synthesized in Comparative Example 1, there was no diffraction peak near 2θ = 30.1°.

[0067] <Evaluation> (Evaluation of the anti-mold effect in the powder state) A test simulating the mold resistance test of JIS Z2911:2018 was carried out to evaluate the anti-mold effect in the powder state. Specifically, 1 g of the lanthanum ferrite powder obtained above was placed on the agar medium in a sterilized petri dish, and 200 μL of a 0.01 wt% mold suspension was dropped onto the powder and spread evenly around the powder. After covering the lid of the petri dish and storing it at room temperature, the growth state of the mold after a predetermined time elapsed was visually evaluated.

[0068] The agar medium was prepared by dissolving 10 g of high-quality agar for culture (BA-70, manufactured by Ina Food Industry Co., Ltd.) and 30 g of granulated sugar in 1000 mL of purified water by heating and dissolving, pouring it into a sterilized petri dish, and solidifying it at room temperature.

[0069] The 0.01 wt% mold suspension used to evaluate the anti-mold effect in powder form was prepared by storing commercially available wood in a humid environment to allow mold to grow naturally, then taking 0.001 g of the grown mold and stirring it into 10 mL of purified water.

[0070] The antifungal effect in the powder state was evaluated by visually observing the state of mold growth after 10 days and 45 days according to the following evaluation criteria. The evaluation results are shown in Table 1. ◎: Almost no mold growth on the medium ○: Mold has grown on the medium, but the inhibition zone is 1 cm or more wide. △: Mold has grown on the medium, and the inhibition zone is less than 1 cm. ×: Mold has grown on the medium and there is no inhibition zone.

[0071] Examples 2 to 4 Lanthanum ferrite was synthesized in the same manner as in Example 1, except that the firing temperature was set as shown in Table 1. The obtained lanthanum ferrite was evaluated for its antifungal effect in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0072] Comparative Example 2 Except for the fact that lanthanum ferrite was not placed and 0.01 wt % mold suspension was spread on the agar medium, the antifungal effect was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0073] [Table 1]

[0074] From Examples 1 to 4 and Comparative Example 1, it is found that the expression state of the antifungal effect of lanthanum ferrite with a composition ratio (molar ratio) of La:Fe=50:50 varies depending on the firing temperature. From Examples 1 to 4, it is found that if the firing temperature is 1100°C or less, the obtained lanthanum ferrite exhibits a long-term antifungal effect. Among them, lanthanum ferrite fired at a temperature of 800°C exhibited a particularly excellent antifungal effect.

[0075] Examples 5 to 7, Comparative Example 4 Lanthanum ferrite was synthesized in the same manner as in Example 1, except that the composition ratio and firing temperature were set as shown in Table 2. The obtained lanthanum ferrite was evaluated for its antifungal effect in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0076] [Table 2]

[0077] It is evident from Examples 5 to 7, Example 3, and Comparative Example 3 that lanthanum ferrite with a high La molar ratio tends to have a high antifungal effect.

[0078] However, since no antifungal effect was observed in the lanthanum ferrite of Comparative Example 3, which had a high molar ratio of Fe, it is understood that the antifungal effect will not be achieved unless the composition ratio of La and Fe is appropriate.

[0079] Furthermore, from Example 3 and Examples 5 to 7, in which the firing temperature was 1000° C., it was confirmed that lanthanum ferrite with a La molar ratio of 50% or more formed an inhibition zone. In other words, it was confirmed that lanthanum ferrite with a La molar ratio of 50% or more had an antifungal effect even in areas where the lanthanum ferrite was not in direct contact.

[0080] Examples 8 to 11 and Comparative Example 6 In the same manner as in Example 1, lanthanum ferrite having the composition ratio shown in Table 3 was synthesized.

[0081] <Evaluation> (Evaluation of antifungal effect in impregnated state) A test simulating the mold resistance test of JIS Z2911:2018 was conducted to evaluate the mold-preventing effect in an impregnated state. Specifically, a filter paper soaked in pure water was placed in a sterilized petri dish, and an evaluation sample with a 0.01 wt% mold suspension sugar solution sprayed onto the lower half was placed on the filter paper. The petri dish was covered with a lid and stored at room temperature, and the mold growth state after a specified time had passed was visually evaluated.

[0082] The evaluation samples were prepared by impregnating 0.06 g of paper with the obtained lanthanum ferrite so as to obtain the amounts shown in Table 3.

[0083] The 0.01 wt% mold suspension sugar solution used to evaluate the anti-mold effect in an impregnated state was prepared by leaving commercially available bread in a humid environment to allow mold to grow naturally, then taking 0.001 g of the grown mold and stirring it into 10 mL of a 3% granulated sugar solution.

[0084] The antifungal effect in the impregnated state was evaluated by visually observing the state of mold growth after 10 days and 45 days, using the same evaluation criteria as for the antifungal effect in the powder state. The evaluation results are shown in Table 3.

[0085] Comparative Example 4 The antifungal effect was evaluated in the same manner as in Example 8, except that the 0.01 wt% mold suspension was spread only on the filter paper, without placing the evaluation sample impregnated with lanthanum ferrite. The evaluation results are shown in Table 3.

[0086] Comparative Example 5 Except for using calcined lanthanum oxide (La2O3), which is a raw material for lanthanum ferrite, the antifungal effect was evaluated in the same manner as in Example 8. The evaluation results are shown in Table 3.

[0087] [Table 3]

[0088] It is evident from Examples 8 to 11 and Comparative Example 6 that lanthanum ferrite with a high La molar ratio tends to have a high antifungal effect.

[0089] Moreover, the lanthanum ferrite of Examples 8 to 11 tended to have a higher antifungal effect than that of Comparative Example 5, which used lanthanum ferrite obtained by firing lanthanum oxide (La2O3), which is a raw material for lanthanum ferrite.

[0090] In Comparative Example 5, which used sintered lanthanum ferrite raw material, the anti-mold effect disappeared over time, so when the anti-mold agent (lanthanum ferrite) is used in an impregnated state, the anti-mold effect is highly sustained even when a small amount is used.

[0091] Examples 12 to 23 In the same manner as in Example 1, lanthanum ferrite having the composition ratio shown in Table 4 was synthesized.

[0092] <Evaluation> (Evaluation of anti-mold effect in coating film state) The obtained lanthanum ferrite was mixed with a commercially available water-based acrylic paint at the concentration shown in Table 4 to prepare a paint for evaluation. The prepared paint for evaluation was applied to wood (MDF) by roller coating, and dried at room temperature for one day to form a coating film. For the formed coating film, filter paper soaked in pure water was laid in a sterile petri dish, and an evaluation sample prepared by spraying 0.01 wt% mold suspension sugar solution prepared in the same manner as above was placed on the filter paper. The petri dish was covered with a lid and stored at room temperature, and the mold growth state after a specified time had passed was visually evaluated.

[0093] The antifungal effect of the coating film was evaluated visually by observing the state of mold growth after 7 days and 21 days according to the following evaluation criteria. The evaluation results are shown in Table 4. ◎: No mold growth on the evaluation sample ○: Mold growth on the evaluation sample is less than 10% △: Mold growth on the evaluation sample is between 10% and 40% ×: Mold growth on 40% or more of the evaluation sample

[0094] Comparative Example 7 A coating film was formed using a commercially available water-based acrylic paint without mixing lanthanum ferrite in the same manner as in Example 12. The obtained coating film was evaluated for its antifungal effect in the same manner as in Example 12. The evaluation results are shown in Table 4.

[0095] [Table 4]

[0096] From Examples 12 to 23, it was confirmed that the antifungal effect was observed even in a coating state in which lanthanum ferrite was mixed with a resin. Moreover, from Examples 12 to 23, it was found that lanthanum ferrite with a high La molar ratio tends to have a high antifungal effect.

[0097] It is also apparent that the concentration of the lanthanum ferrite material mixed into the paint is preferably 30% or more, and more preferably 50% or more.

[0098] Examples 24 to 26 In the same manner as in Example 1, lanthanum ferrite having the composition ratio shown in Table 5 was synthesized.

[0099] <Evaluation> (Measurement of antibacterial activity value) The obtained lanthanum ferrite was mixed with a two-component solvent-based acrylic urethane resin (main agent: Acrydic (registered trademark) A-801-P, manufactured by DIC Corporation; hardener: Burnock (registered trademark) DN-980, manufactured by DIC Corporation) so that the concentration relative to the total solid content was the concentration shown in Table 5, to prepare a coating material for evaluation.

[0100] The paint for evaluation prepared was applied to a PET film to a thickness of about 70 μm, and the film was dried at room temperature for one day to prepare a coating film. The antibacterial activity of the obtained coating film against Escherichia coli and Staphylococcus aureus was measured according to JIS Z 2801. The results are shown in Table 5.

[0101] (Assessment of antibacterial effect) Based on the antibacterial activity values ​​obtained above, the antibacterial effect was evaluated according to the following evaluation criteria. The evaluation results are shown in Table 5. ◎: Both Escherichia coli and Staphylococcus aureus antibacterial activity values ​​are 2.0 or higher ○: Antibacterial activity values ​​for both Escherichia coli and Staphylococcus aureus are 1.0 or more and less than 2.0 △: Either the antibacterial activity value for Escherichia coli or Staphylococcus aureus is 1.0 or more and less than 2.0 ×: Antibacterial activity values ​​for both Escherichia coli and Staphylococcus aureus are less than 1.0

[0102] Comparative Example 8 A coating film was formed using only a two-liquid solvent-based acrylic urethane resin without mixing lanthanum ferrite in the same manner as in Example 24. The antibacterial activity value of the obtained coating film was measured in the same manner as in Example 24, and the antibacterial effect was evaluated. The measurement results and evaluation results are shown in Table 5.

[0103] [Table 5]

[0104] Examples 27 to 30, Comparative Example 9 In the same manner as in Example 1, lanthanum ferrite having the composition ratio shown in Table 6 was synthesized.

[0105] <Evaluation> (Evaluation of anti-algae properties) 2 g of the lanthanum ferrite powder obtained above was added to 100 g of chlorella liquid in a 140 mL glass bottle at 2 mass % and stored in a place exposed to sunlight for 3 months, and the growth state of the algae was visually evaluated.

[0106] The chlorella solution was prepared by adding distilled water to 0.1 g of concentrated raw chlorella solution (manufactured by Plankton Company) until the total volume reached 100 g.

[0107] The algae-preventing property was evaluated by visually observing the state of algae growth after 3 months according to the following evaluation criteria. The evaluation results are shown in Table 6. 〇: No algae growth observed △: A small amount of algae was observed growing at the bottom of the glass bottle. ×: Algae growth was observed on the bottom and walls of the glass bottle.

[0108] [Table 6] From Examples 27 to 30 and Comparative Example 9, it can be seen that the expression of the anti-algae effect of lanthanum ferrite with a composition ratio (molar ratio) of La:Fe=50:50 varies depending on the firing temperature. From Examples 27 to 30, it can be seen that if the firing temperature is 1100°C or lower, the obtained lanthanum ferrite exhibits the effect of preventing the proliferation and attachment of algae.

Claims

1. A method for producing rare earth ferrite, comprising firing a mixture containing a rare earth source and an iron source at a firing temperature of 700 to 1100° C. to obtain rare earth ferrite represented by the following formula (1): Ln ２ｘ Fe ２（１－ｘ） O ３ (1) (In formula (1), Ln is a rare earth element selected from the group consisting of lanthanum, praseodymium, neodymium, and yttrium, and x is a number of 0.65 or more and 0.85 or less).

2. 2. The method for producing rare earth ferrite according to claim 1, wherein the rare earth source is at least one selected from the group consisting of oxides of rare earth elements, bastnaesite, monazite, and xenotime.

3. 3. The method for producing rare earth ferrite according to claim 1, wherein the iron source is at least one selected from the group consisting of oxides, oxyoxides, and hydroxides.

4. The method for producing rare earth ferrite according to any one of claims 1 to 3, wherein the rare earth element is lanthanum.

5. The rare earth source is La ２ O ３ The method for producing rare earth ferrite according to any one of claims 1 to 4,

6. The method for producing rare earth ferrite according to any one of claims 1 to 5, wherein the iron source is FeOOH.

7. The method for producing rare earth ferrite according to any one of claims 1 to 6, wherein the firing temperature is 800 to 1000°C.

8. The method for producing rare earth ferrite according to any one of claims 1 to 7, wherein the rare earth ferrite is at least one selected from the group consisting of antifungal agents, antibacterial agents, and anti-algae agents.

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