pH INCREASING AGENT

Abstract

To provide a pH increasing agent which exhibits reduced elution of a metal ion into water and causes increase in the pH of the water to slowly proceed.SOLUTION: A pH increasing agent has a composition represented by Ln2xFe2(1-x)O3 (in which Ln is a rare-earth element selected from the group consisting of lanthanum, praseodymium, neodymium, and yttrium and x is a number of 0.55 or more and less than 1.00).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a pH enhancer. [Background technology]

[0002] In recent years, it has become known that acidic substances such as sulfur oxides and nitrogen oxides emitted from automobiles, factories, etc. dissolve into rain and fall to the earth's surface as acid rain.

[0003] When acid rain is deposited in the sea, rivers, or lakes, and seawater becomes acidic, aquatic plankton, aquatic insects, shellfish, and underwater plants decrease, and the fish, birds, and animals that prey on them also decrease. In addition, as seawater seeps into the soil on the surface of the earth, it can also affect terrestrial organisms.

[0004] In particular, because the ocean has a strong cycle of ecosystems, acidification of one part of the ocean can damage entire nearby ecosystems.

[0005] On the other hand, in aquariums for tropical fish, the pH of the water can become acidic when the water becomes polluted. This is thought to be due to nitrates produced when bacteria in the water decompose ammonia produced by the tropical fish's droppings and leftover food.

[0006] It is known to use a pH enhancer to improve the pH of acidified water and adjust it to a desired pH. For example, Patent Document 1 proposes using an aggregate of fibrous particles containing calcium carbonate and magnesium hydroxide as a neutralizer for acidic water.

[0007] On the other hand, it is necessary to prevent the growth of algae in the fields of ships, revetments, fishing nets, etc. For such a purpose, Patent Document 2 reports that rare earth ferrites having a specific composition have an anti-algae effect. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2018-153712 A [Patent Document 2] International Publication No. 2021 / 193644 Summary of the Invention [Problem to be solved by the invention]

[0009] A neutralizing agent containing calcium carbonate, as described in Patent Document 1, increases the pH of water by hydroxide ions generated when calcium carbonate reacts with water. According to this technology, a component with low solubility in water is used, so the neutralization reaction proceeds slowly over several tens of minutes. Therefore, the pH of water can be increased while avoiding the application of sudden stress to the surrounding environment.

[0010] However, when calcium carbonate reacts with water, hydroxide ions and carbon dioxide are produced, which dissolve in water to produce hydrogen ions. Therefore, the neutralizing effect of neutralizing agents containing calcium carbonate is limited. CaCO 3 +H 2 O → Ca 2+ +CO 2 +2OH - CO 2 +H 2 O→HCO 3 - +H +

[0011] In addition, when calcium carbonate reacts with water, calcium ions are dissolved into the water as shown in the above formula, which raises concerns about the impact on the surrounding environment.

[0012] The present invention has been made in consideration of the above circumstances, and has an object to provide a pH improver that reduces the elution of metal ions into water and slowly improves the pH of the water. [Means for solving the problem]

[0013] The present invention is as follows.

[0014] Aspect 1: 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 equal to or greater than 0.55 and less than 1.00.) A pH improver having a composition represented by the formula: Aspect 2: The pH enhancer according to aspect 1, wherein Ln in formula (1) is lanthanum. Aspect 3: The pH enhancer according to aspect 1, wherein x in formula (1) is a number between 0.65 and 0.85. Aspect 4: The pH improver according to aspect 2, wherein x in formula (1) is a number between 0.65 and 0.85. Aspect 5: An article for improving pH, comprising the pH improver described in any one of aspects 1 to 4. Aspect 6 includes a substrate and a coating film on the substrate, The coating film contains the pH enhancer. 6. The pH-improving article of claim 5. Aspect 7: The pH-improved article of aspect 6, wherein the coating comprises the pH enhancer and a resin. Aspect 8: The pH-improving article of aspect 7, wherein the resin is one or more selected from acrylic resin, acrylic silicone resin, silicone resin, amino alkyd resin, epoxy resin, phenolic resin, polyurethane resin, unsaturated polyester resin, and fluororesin. Aspect 9: A pH improving paint comprising the pH improver according to any one of aspects 1 to 4, a resin, and a solvent. Aspect 10: The pH-improving paint of Aspect 9, wherein the resin is one or more selected from acrylic resin, acrylic silicone resin, silicone resin, amino alkyd resin, epoxy resin, phenolic resin, polyurethane resin, unsaturated polyester resin, and fluororesin. Effect of the Invention

[0015] According to the present invention, there is provided a pH improver which reduces the elution of metal ions into water and slowly improves the pH of the water. The pH improver of the present invention may be applied to wave-dissipating blocks, seaweed beds, fish cages, nets, bottom stones, filters, etc., which are installed in seaweed beds, aquaculture farms, ornamental fish tanks, water purification facilities, etc. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] 《pH improver》 The pH enhancer of the present invention is 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 equal to or greater than 0.55 and less than 1.00.) It is a pH improver having a composition represented by the formula:

[0017] The above-mentioned Patent Document 2 explains that the rare earth ferrite having the composition represented by the above formula (1) functions as an anti-algae agent that exhibits excellent anti-algae effects. However, the present inventors have found that this rare earth ferrite reduces the elution of metal ions into water when it comes into contact with water, and functions as a pH improver that slowly improves the pH of water.

[0018] Therefore, the pH improver of the present invention is capable of neutralizing acidic water while minimizing the burden on the surrounding environment.

[0019] The rare earth (Ln) in formula (1) may be lanthanum, in particular, from the viewpoints of the effect of suppressing the elution of metal ions, the effect of improving the pH of water, and the cost. Therefore, the pH improver of the present invention may be lanthanum ferrite.

[0020] The pH improver of the present invention may be in any form as long as x in formula (1) is a number of 0.55 or more and less than 1.00. For example, it may form a solid solution having a uniform composition as a whole, or may be LnFeO 3 and Ln(OH) 3 or a mixture of a uniform composition solid solution and LnFeO 3 and Ln(OH) 3 The liquid crystal layer may be a mixture of these phases or may contain phases other than these phases.

[0021] The pH improver of the present invention is LnFeO 3 and Ln(OH) 3 and LnFeO 3 and Ln(OH) 3 In addition, lanthanum hydroxycarbonates may be included. Here, "lanthanum hydroxycarbonates" refers to LaCO 3 It is a concept that includes OH and its derivatives. 3 The derivative of OH is La 2 O 2 (CO 3 ), La 2 O(CO 3 ) 2 etc.

[0022] The pH improver of the present invention is Ln 2 O 3 The content of Ln is small, especially 2 O 3 does not have to include

[0023] When the pH improver of the present invention was measured by XRD, LnFeO 3 , Ln(OH) 3 , lanthanum hydroxide carbonates, and Ln 2 O 3 The ratios of the peak intensities of the peaks assigned to each of the above, when the sum of these peak intensities is taken as 100, are as follows: LnFeO 3 : 10 or more, 20 or more, 30 or more, 35 or more, 40 or more, or 45 or more, and 90 or less, 85 or less, 80 or less, 70 or less, or 60 or less Ln(OH) 3 : 5 or more, 10 or more, 15 or more, or 20 or more, and 80 or less, 75 or less, 70 or less, 65 or less, or 60 or less Lanthanum hydroxycarbonate: 15 or less, 10 or less, 8 or less, 5 or less, 3 or less, or 1 or less Ln 2 O 3 : 5.0 or less, 3.0 or less, 1.0 or less, 0.5 or less, or 0.1 or less, or 0

[0024] In the XRD measurement of the pH improver of the present invention, the peak positions (2θ) of each crystal phase are as follows, for example, when the rare earth (Ln) in formula (1) is lanthanum (La). LaFeO 3 :2θ=32.1° La(OH) 3 :2θ=27.9° Lanthanum hydroxycarbonate: 2θ=30.3° La 2 O 3 :2θ=29.9°

[0025] The ratio of the XRD peak intensities of the respective crystal phases is considered to reflect the abundance ratio of each crystal phase in the pH improver.

[0026] In formula (1), x is 0.55 or more, and may be 0.60 or more, 0.65 or more, 0.70 or more, or 0.75 or more. Also, x may be less than 1.00, and 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.

[0027] In the above formula (1), x may typically be, for example, a number of 0.65 or more and 0.85 or less, and may further be a number of 0.70 or more and 0.80 or less.

[0028] The specific surface area of ​​the pH improver of the present invention is preferably large from the viewpoint of increasing the pH improving ability. On the other hand, from the viewpoints of maintaining the pH improving ability for a long period of time and preventing the particles from falling off when the pH improver of the present invention is used by applying it to an article as a paint, it is preferable that the specific surface area of ​​the pH improver is small. From the above viewpoints, the specific surface area of ​​the pH improver is, for example, 3 m 2 / g or more, 5m 2 / g or more, 10m 2 / g or more, 12m 2 / g or more, or 15m 2 / g or more, for example, 50m 2 / g or less, 30m 2 / g or less, 25m 2 / g or less, 20m 2 / g or less, or 15m 2 / g or less.

[0029] From the viewpoint of handling, the particle size of the pH improver of the present invention is preferably large. On the other hand, from the viewpoints of increasing the surface area per mass, preventing the particles from falling off when the pH improver of the present invention is applied to an article as a coating material, etc., the particle size of the pH improver is preferably small. From the above viewpoints, the particle size of the pH improver may be, for example, 0.1 μm or more, 0.3 μm or more, 0.5 μm or more, 1.0 μm or more, 3.0 μm or more, 5.0 μm or more, or 10 μm or more, and may be, for example, 15 μm or less, 12 μm or less, 10 μm or less, or 8.0 μm or less.

[0030] <Production method of pH improver> The method for producing the pH improver of the present invention is not particularly limited.

[0031] The pH improver of the present invention may be produced, for example, by applying an appropriate stress to a mixture containing a rare earth source and an iron source in a predetermined ratio, pulverizing and mixing the mixture, and then calcining the mixture.

[0032] As the rare earth source, for example, oxides of the desired rare earth elements may be used, as well as bastnaesite, monazite, xenotime, etc. As the rare earth element, lanthanum is preferably used from the viewpoint of improving the pH of the obtained rare earth ferrite particles and from the viewpoint of cost. Among them, La 2 O 3 can be used to produce a highly effective, relatively inexpensive pH enhancer.

[0033] The iron source is FeO, Fe 3 O 4 , Fe 2 O 3 Oxides such as FeOOH, ferrihydrite, and schwermannite; oxyoxides such as Fe(OH) 2 Among these, when FeOOH is used as the iron source, Fe 2 O 3 It has a higher reactivity than Fe, making it possible to sinter at a lower temperature. 2 O 3 It is possible to produce a pH improver with a smaller particle size compared to the above.

[0034] The ratio of the rare earth source and the iron source used may be appropriately determined so as to match the value of x in formula (1) for the desired pH improver.

[0035] The grinding and mixing may be a dry grinding or a wet grinding. In this grinding, the stress applied to the mixture of the rare earth source and the iron source may be, for example, a frictional force, a shear force, a shear stress, an impact force, or the like.

[0036] Examples of the method of applying the above-mentioned stress include wet pulverization using a ball mill, a bead mill, a paint shaker, etc. When pulverization is performed by wet pulverization, for example, water, alcohol, etc. may be used as the liquid medium. After the mixture of the rare earth source and the iron source is pulverized and mixed by wet pulverization, the liquid medium may be removed by an appropriate method such as heating and drying, as necessary.

[0037] The firing temperature and firing time are not particularly limited and can be set appropriately.

[0038] The firing temperature may be, for example, 600°C or more, 650°C or more, 700°C or more, or 750°C or more, and may be, for example, 1,200°C or less, 1,100°C or less, 1,050°C or less, or 1,000°C or less.

[0039] The firing time may be, for example, 1 hour or more, 2 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 may be, for example, 72 hours or less, 48 ​​hours or less, 36 hours or less, 24 hours or less, 18 hours or less, or 16 hours or less.

[0040] The surrounding atmosphere during firing may be an oxidizing atmosphere, for example, firing may be performed in air.

[0041] The rare earth ferrite is obtained as described above. This rare earth ferrite may be used as the pH improver of the present invention as it is, or may be used after being pulverized to adjust the particle size, if necessary.

[0042] 《pH improving article》 According to another aspect of the present invention, there is provided a pH improving article comprising the pH improving agent of the present invention. The pH improving article of the present invention has the function of improving the pH of water when it comes into contact with the water.

[0043] The pH-improving article of the present invention is, for example, A substrate and a coating on the substrate, The coating comprises a pH enhancer of the present invention. It may be a pH enhancing article.

[0044] The material and shape of the substrate may be appropriately set depending on the application of the pH-improving article of the present invention. For example, when the pH-improving article is used as a wave-dissipating block, the substrate may be a concrete tetrapod, and when the pH-improving article is used as a net, the substrate may be a synthetic resin net.

[0045] The coating of the pH enhancing article may be formed on at least a portion of a surface of a substrate.

[0046] The coating of the pH-improved article contains the pH improver of the present invention. The coating may contain optional components other than the pH improver. The optional components include, for example, resins, dispersants, preservatives, antioxidants, colorants, viscosity modifiers, antifoaming agents, wettability improvers, etc.

[0047] The resin contained in the coating film may have a function of maintaining the shape of the coating film and holding the pH improver on the substrate. The resin may be one or more selected from, for example, acrylic resin, acrylic silicone resin, silicone resin, amino alkyd resin, epoxy resin, phenol resin, polyurethane resin, unsaturated polyester resin, fluororesin, etc.

[0048] The dispersant contained in the coating film may have the function of stably dispersing the pH improver of the present invention in the coating film, and may be appropriately selected from known dispersants such as, for example, acrylic acid-based dispersants, carboxylic acid-based dispersants, sulfonic acid-based dispersants, and ammonium salt-based dispersants.

[0049] The amount of the pH improver in the coating film is preferably large from the viewpoint of increasing the pH improving ability, and is preferably small from the viewpoint of maintaining the stability of the coating film. From these viewpoints, the amount of the pH improver in the coating film is, for example, 5 g / m as the mass of the pH improver per unit area of ​​the coating film formation region. 2 More than 10g / m 2 More than 15g / m 2 More than 20g / m 2 More than 25g / m 2 or more than 30g / m 2 or more, for example, 125 g / m 2 Below 100g / m 2 Below 80g / m 2 Below 60g / m 2 Below 50g / m 2 Below 45g / m 2 or less than 40 g / m 2 It may be the following:

[0050] The amount of resin in the coating film is preferably large from the viewpoint of maintaining the stability of the coating film, and is preferably small from the viewpoint of effectively expressing the function of the pH improver. From these viewpoints, the amount of resin in the coating film may be, for example, 30 parts by mass or more, 50 parts by mass or more, 60 parts by mass or more, 70 parts by mass or more, or 80 parts by mass or more, and may be, for example, 900 parts by mass or less, 700 parts by mass or less, 500 parts by mass or less, 200 parts by mass or less, 180 parts by mass or less, 150 parts by mass or less, 120 parts by mass or less, or 100 parts by mass or less, relative to 100 parts by mass of the pH improver.

[0051] The amount of coating of the coating film in the pH-improved article of the present invention may be appropriately determined by a person skilled in the art from the viewpoint of maintaining the functionality of the article and exhibiting the pH-improving property. The amount of coating film is, for example, 80 g / m as the mass of the coating film per unit area of ​​the coating film-forming region. 2 More than 100g / m 2 More than 120g / m 2 More than 130g / m 2 or more, or 140 g / m 2 or more, for example, 250 g / m 2 Below 220g / m 2 Below 200g / m 2 Below 180g / m 2 or less than 160g / m 2 It may be the following:

[0052] 《pH improving paint》 According to yet another aspect of the present invention, there is provided a pH-improving paint comprising the pH-improving agent of the present invention, a resin, and a solvent. The pH-improved article of the present invention described above may be produced, for example, by applying the pH-improving paint to a desired substrate.

[0053] The pH-improving paint may contain optional components other than the pH improver, resin, and solvent, such as dispersants, preservatives, antioxidants, colorants, viscosity modifiers, defoamers, and wettability improvers.

[0054] The resin contained in the pH improving paint of the present invention may be selected according to the type of resin contained in the coating film of the desired pH improving article. Thus, the resin may be one or more selected from, for example, acrylic resin, acrylic silicone resin, silicone resin, amino alkyd resin, epoxy resin, phenolic resin, polyurethane resin, unsaturated polyester resin, fluororesin, etc.

[0055] The dispersant contained in the pH-improving paint may be selected according to the type of dispersant contained in the coating film of the pH-improving article. Therefore, the dispersant may be selected from known dispersants such as acrylic acid-based dispersants, carboxylic acid-based dispersants, sulfonic acid-based dispersants, and ammonium salt-based dispersants. When a wetting dispersant is used as the dispersant, a paint in which the pH improver is stably dispersed can be obtained. The coating film formed using this paint has the pH improver highly and stably dispersed in the film, and can stably exhibit suitable pH improvement properties.

[0056] The solvent contained in the pH improving paint may be selected from the viewpoints of dispersibility of the pH improving agent and solubility of the resin. The solvent may be, for example, one or more selected from water, alcohol, ester, ketone, ether, aromatic hydrocarbon, etc.

[0057] The ratio of the pH improver and the resin contained in the pH improving paint may be appropriately set according to the ratio of the pH improver and the resin contained in the coating film of the desired pH-improving article. Therefore, the amount of the resin contained in the pH improving paint may be, for example, 30 parts by mass or more, 50 parts by mass or more, 60 parts by mass or more, 70 parts by mass or more, or 80 parts by mass or more, and may be, for example, 200 parts by mass or less, 180 parts by mass or less, 150 parts by mass or less, 120 parts by mass or less, or 100 parts by mass or less, relative to 100 parts by mass of the pH improver.

[0058] The amount of the solvent contained in the pH improving paint may be appropriately set depending on the application method. For example, the amount of the solvent may be set so that the solid content concentration of the pH improving paint is 30% by mass or more, 35% by mass or more, 40% by mass or more, or 45% by mass or more, and 80% by mass or less, 70% by mass or less, 60% by mass or less, or 50% by mass or less.

[0059] The pH-improved article of the present invention can be produced by applying the pH-improving paint of the present invention to the surface of a desired substrate, and then removing the solvent as necessary to form a coating film. Before applying the pH-improving paint, a suitable primer may be applied to the substrate.

[0060] The pH improving paint may be applied to the surface of the substrate by a known method. For example, known application devices such as a bar coater, doctor blade, spray coater, roll coater, slit coater, gravure coater, dip coater, etc. may be used. Also, known application tools such as a spray, roller, brush, and trivet may be used.

[0061] The removal of the solvent after application may be carried out, for example, by leaving the composition to stand at a temperature of 10° C. or more, 20° C. or more, 30° C. or more, 40° C. or more, 50° C. or more, 60° C. or more, 70° C. or more, 80° C. or more, 90° C. or more, or 100° C. or more and 400° C. or less, 300° C. or less, or 200° C. or less, for a period of 10 seconds or more, 1 minute or more, 30 minutes or more, 1 hour or more, 4 hours or more, 6 hours or more, 8 hours or more, or 12 hours or more, and 48 hours or less or 24 hours or less. EXAMPLES

[0062] Synthesis of pH improver In a ball mill using 10 mm diameter alumina balls as grinding media, La 2 O 3and FeOOH were weighed and charged so that the molar ratio of La to Fe was a predetermined value (La:Fe=90:10, 70:30, 50:50, or 100:0), water was added, and the mixture was pulverized and mixed for 5 hours. The pulverized material obtained was dried at 300°C for 15 hours and then crushed with a rotary crusher. The pulverized material obtained was fired at a predetermined temperature (700°C or 900°C) for 15 hours and then crushed with a hammer mill to obtain lanthanum ferrite (LaFe, pH improver).

[0063] <XRD analysis of lanthanum ferrite> The obtained lanthanum ferrite was subjected to XRD analysis under the following conditions. Measurement equipment: Rigaku Corporation, desktop X-ray diffraction equipment, model "MiniFlex600" Tube:CuK α (Wavelength 1.541862Å) Output: 40kV-15mA Measurement angle range (2θ): 10 to 80° Sampling interval: 0.01°

[0064] In the obtained XRD spectrum, the peak intensity ratios of the peaks at 2θ = 32.1°, 27.9°, 29.9°, and 30.3° (I 32.1 , I 27.9 , I 29.9 , and I 30.3 ) were investigated. These peaks correspond to LaFeO 3 , La(OH) 3 , La 2 O 3 , and lanthanum hydroxycarbonate (LaHC).

[0065] <Specific surface area (SSA) of lanthanum ferrite> The specific surface area of ​​the lanthanum ferrite was measured by the BET one-point method in accordance with JIS Z8830.

[0066] Examples 1 to 4 and Comparative Examples 1 to 3 In Examples 1 to 4 and Comparative Examples 1 to 3, the effect of adding powdered lanthanum ferrite (pH improving agent) to pure water was investigated.

[0067] Example 1 (1) Measurement of change in suspension pH over time 60 g of lanthanum ferrite with a La:Fe=90:10 (molar ratio) and a firing temperature of 700°C was added to 200 g of pure water and stirred with a magnetic stirrer to form a suspension. Stirring with the magnetic stirrer was continued, and the pH of the suspension was measured with a portable pH meter manufactured by Horiba, Ltd., one hour, one day (24 hours), and one month (720 hours) after adding the lanthanum ferrite.

[0068] The initial pH of the pure water used here was 7.3.

[0069] (2) Measurement of ion elution amount The same lanthanum ferrite as above was added to 98 g of pure water and left to stand for 7 days (168 hours). After standing, the supernatant was sampled and subjected to inductively coupled plasma atomic emission spectrometry (ICP-AES) under the following conditions to quantify the amount of La ions in the supernatant. Measurement equipment: Shimadzu Corporation, inductively coupled plasma emission spectrometer, model "ICPS-8100" Transmission method: Free running Transmission frequency: 27MHz±1MHz Rated output: 0.8~1.6kW First spectrometer: 1m Czerny-Turner mounting Diffraction grating: 4,960 lines / mm Wavelength range: 160~372nm Second spectrometer: 1m Czerny-Turner mounting Diffraction grating: 4,320 lines / mm Wavelength range: 250~426nm

[0070] Examples 2 to 4 and Comparative Examples 1 to 3 The change in pH of the suspension over time and the amount of ion elution were investigated in the same manner as in Example 1, except that lanthanum ferrite produced under the conditions described in Table 1 (lanthanum hydroxide was used in Comparative Examples 2 and 3) was used instead of the lanthanum ferrite in Example 1.

[0071] <Reference example 1> The change in pH of the suspension over time and the amount of ion elution were examined in the same manner as in Example 1, except that commercially available calcium hydroxide was used instead of the lanthanum ferrite in Example 1.

[0072] The above results are shown in Table 1.

[0073] [Table 1]

[0074] Referring to Table 1, even when lanthanum ferrite having a La:Fe molar ratio of 50:50 or lanthanum hydroxide was added to water, the function of increasing the pH of the water was not exhibited.

[0075] In addition, when commercially available calcium hydroxide was added to water, a large amount of Ca ions were dissolved into the water, and the pH of the water rose rapidly.

[0076] In contrast, it was confirmed that when lanthanum-rich ferrite with a molar ratio of La:Fe greater than 50:50 was added to water, the amount of La ions dissolved in the water was small, and the pH of the water was gradually increased. Furthermore, the results of XRD analysis showed that lanthanum ferrite with this pH-improving ability contains LaFeO 3 With La(OH) 3 was confirmed to contain.

[0077] Examples 5 to 7 and Comparative Examples 4 to 6 In Examples 5 to 7 and Comparative Examples 4 to 6, a coating liquid containing lanthanum ferrite (pH improver) and a resin was applied onto an FRP plate to examine the effect of forming a coating film.

[0078] Example 5 In Example 5, a coating liquid containing an acrylic resin as the resin was prepared and evaluated.

[0079] In a 450mL mayonnaise bottle, 11.6g of lanthanum ferrite (LaFe, pH improver) produced under conditions of La:Fe=70:30 and baking temperature of 700°C, 58.1g of acrylic resin solution (solvent: butyl acetate, solid content concentration: 60% by mass), 1.11g of solventless wetting and dispersing agent "BYK-180" (manufactured by BYK-Chemie GmbH), 29.2g of butyl acetate as an additional solvent, and 120g of zirconia beads with a diameter of 3mm were added, and the mixture was shaken for 2 hours with a paint shaker to prepare a pH-improved paint. The lanthanum ferrite content in the resulting paint was 25.0% by mass based on the total mass of the acrylic resin (solid content) and lanthanum ferrite.

[0080] The pH-improving paint obtained above was applied to one side of a rectangular FRP plate (made by Miecast Co., Ltd.) measuring 40 mm x 60 mm, with the total coating amount of the acrylic resin (solid content) and lanthanum ferrite in the paint being 150 g / m 2 (LaFe coating amount 37.5g / m 2 ) was applied with a brush to prepare an evaluation sample.

[0081] With the evaluation sample placed in the dish, 100 μL of pure water was dropped onto the paint-coated surface of the sample. The dish was then covered and sealed, and stored in a closed, cool, dark place at a temperature of 20 to 25° C. After dropping the pure water, the dish was opened 1 hour and 1 month (720 hours), and the pH of the water droplets on the sample was measured using litmus paper.

[0082] Examples 6 and 7 In Example 6, instead of the acrylic resin, a coating liquid containing a methacrylic acid ester copolymer resin was prepared, and in Example 7, a two-component urethane resin was prepared, and evaluated.

[0083] Specifically, paints were prepared and evaluated in the same manner as in Example 5, except that the resin and additional solvent were used in the types and amounts shown in Table 2. In Example 7, a mixture of a solution containing a hydroxyl-containing acrylic resin as the base agent and a solution containing a polyisocyanate as the curing agent was used as the resin.

[0084] Comparative Examples 4 to 6 Coating materials were prepared and evaluated in the same manner as in Examples 5 to 7, except that lanthanum ferrite and the solvent-free wetting and dispersing agent were not used.

[0085] The above results are shown in Table 3.

[0086] [Table 2]

[0087] [Table 3]

[0088] Referring to Tables 2 and 3, it was confirmed that the coating film containing lanthanum-rich lanthanum ferrite also has the function of increasing the pH of water that comes into contact with it.

Claims

1. 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 equal to or greater than 0.55 and less than 1.00.) A pH improver having a composition represented by the formula:

2. The pH improver according to claim 1 , wherein Ln in formula (1) is lanthanum.

3. The pH improver according to claim 1 , wherein x in the formula (1) is a number of 0.65 or more and 0.85 or less.

4. The pH improver according to claim 2, wherein x in the formula (1) is a number of 0.65 or more and 0.85 or less.

5. A pH improving article comprising the pH improving agent according to any one of claims 1 to 4.

6. A substrate and a coating on the substrate, The coating film includes the pH enhancer. The pH-improved article of claim 5.

7. The pH-enhanced article of claim 6 , wherein said coating comprises said pH enhancing agent and a resin.

8. The pH-improving article according to claim 7, wherein the resin is one or more selected from the group consisting of acrylic resins, acrylic silicone resins, silicone resins, aminoalkyd resins, epoxy resins, phenolic resins, polyurethane resins, unsaturated polyester resins, and fluororesins.

9. A pH improving paint comprising the pH improving agent according to any one of claims 1 to 4, a resin, and a solvent.

10. The pH improving paint according to claim 9, wherein the resin is one or more selected from acrylic resins, acrylic silicone resins, silicone resins, amino alkyd resins, epoxy resins, phenolic resins, polyurethane resins, unsaturated polyester resins, and fluororesins.

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