Lightweight plate with excellent radiation resistance

Abstract

To provide a building material which is a wall material, a flooring material, or a ceiling material usable for a long period under a very high radiation environment, is lightweight, has high bending strength, and is excellent in impact resistance and radiation resistance.SOLUTION: A flat wall, floor, or ceiling material using lightweight ALC panels or a gypsum board as a core material is provided with a mesh fabric made of a high-strength fiber for reinforcing at least one surface of the core material, and the whole including both surfaces of the core material and a resin layer made of a polyurea resin for covering the mesh fabric made of a high-strength fiber.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a lightweight board that can be used as a building material such as a wall material, floor material, or ceiling material in a radiation environment such as a nuclear power plant, a spent nuclear fuel reprocessing facility, a proton accelerator or other nuclear-related facility, a medical facility where radiation therapy is performed, or other locations where industrial or medical radiation inspection equipment is installed. [Background technology]

[0002] Immediately after the massive tsunami that occurred in March 2011, Tokyo Electric Power Company's Fukushima Daiichi Nuclear Power Plant experienced a meltdown, in which nuclear fuel melted down, and countermeasures are currently being implemented. Decommissioning the plant requires the removal of the melted nuclear fuel from the reactor containment vessel, and extensive research is underway into removal methods. Because the work of removing nuclear fuel and fuel debris from the reactor building is carried out in a highly radioactive environment, and the fuel debris is located at the bottom of the reactor containment vessel and covered with cooling water, the materials and equipment used for the removal must be constructed from materials that are highly radiation-resistant and water-resistant (see, for example, Non-Patent Documents 1 and 2).

[0003] Debris removal operations under high radiation levels are primarily performed using robots. However, rather than the usual robots with electrical wiring, robots powered by hydraulics or air pressure are used. This is because electrical equipment is vulnerable to radiation. Therefore, the load that the robots can handle is limited. The robots excavate the hard debris, breaking it into small pieces, and then place them in radiation-shielded containers and transport them outside the containment vessel. To prevent the spread of radioactive materials, the shielded containers must be washed with water. The process involves a series of remotely controlled tasks: excavation, transportation, cleaning, and transportation. Each step must be carried out in an isolated environment to prevent the spread of radioactive materials. Therefore, isolated rooms will be built inside the containment vessel, requiring wall, floor, and ceiling materials. These materials must also be transported and assembled by robots. Therefore, the materials must be lightweight, strong, and radiation-resistant.

[0004] Commonly used building materials include wood, steel plates, gypsum board, ALC panels, plastic, concrete, and blocks. However, organic materials, with the exception of special cases, are not radiation-resistant and therefore cannot withstand use inside a nuclear reactor containment vessel. Furthermore, most inorganic materials, such as concrete and blocks, are dense and heavy, making them difficult to handle with robots. This is why we focused on ALC panels and gypsum board. ALC stands for Autoclaved Lightweight Aerated Concrete. ALC panels are lightweight aerated concrete building materials made primarily from silica, cement, quicklime, and aluminum powder as a foaming agent, using a unique manufacturing process called high-temperature, high-pressure steam curing. Combining lightness, strength, and insulating properties, these building materials are positioned as lightweight boards made from inorganic materials, making them ideal for use inside a nuclear reactor containment vessel. However, because ALC panels are water-absorbent, they require a highly waterproof finish when used in humid environments, but there are currently very few waterproof finishing materials that are radiation-resistant. Furthermore, ALC panels have low bending strength and problems with impact resistance, so they cannot be used as is inside nuclear reactor containment vessels. Also, gypsum board is made primarily from calcium sulfate, an inorganic substance, so it has good radiation resistance and is lightweight with a specific gravity between 0.6 and 1.0, but like ALC panels, it also has problems with bending strength and impact resistance.

[0005] Patent Document 1 discloses a method for reinforcing the outer surface of a polystyrene foam core with impact-resistant fibers, forming a polyurethane resin layer covering substantially the entire outer surface, and uniformly forming exposed ceramic particle sections exposed through the polyurethane resin layer on the outer surface of the polyurethane resin layer. This method allows for the easy formation of an outer shell structural material for a floating water-based shelter, integrating an unsinkable material, mesh-sized impact-resistant fibers, and a polyurethane resin layer. This prevents the shell from melting and the interior of the shelter from becoming too hot, even in high-temperature environments such as water-based fires, resulting in a floating water-based shelter that is less susceptible to damage to personnel inside. Furthermore, when not in use, the shelter can be repurposed for other purposes, such as a soundproof room (karaoke room, musical instrument practice room, etc.) or a heat storage tank. However, because the proposed core materials include synthetic resin foams such as polystyrene foam and hollow boxes (wooden or steel boxes with air sealed inside), there are concerns that synthetic resins and wood may deteriorate and lose strength due to strong radiation. Furthermore, the steel box requires a considerable weight to be strong, which creates problems in handling it inside the reactor containment vessel.

[0006] Patent Document 2 proposes a method for reinforcing structural surfaces by sequentially performing the following steps: preparing a base, spraying an adhesive onto the prepared structural surface to form an adhesive layer, attaching a reinforcing net made of reinforcing wires arranged in a mesh pattern to the surface of the adhesive layer, and spraying an adhesive onto the reinforcing net to form an adhesive protective layer. Examples of structural surfaces mentioned include concrete structural surfaces, mortar surfaces, and rock surfaces, but these materials are not lightweight and are heavy, making them difficult to handle with robots. Furthermore, no consideration is given to the radiation resistance of the adhesive resin. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-51732 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-27764 [Non-patent literature]

[0008] [Non-Patent Document 1] Kanako Kaji et al. "Effects of Radiation on Fully Aromatic Polyamides" SEN-I GAKKAISHI Vol.34, No.12(1978), pp.57-62 [Non-patent document 2] Isao Funakawa et al., "Radiation Resistance Evaluation of Synthetic Polymer Resin Materials," 68th Annual Academic Conference of the Japan Society of Civil Engineers (September 2013), pp. 773-774 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0009] In view of the background of the prior art, the present invention aims to provide a building material (wall material, floor material, or ceiling material) that is lightweight, has high bending strength, is excellent in impact resistance and radiation resistance, and can be used for a long period of time even under high radiation conditions, which is necessary for the removal of debris from the reactor containment vessel of the Tokyo Electric Power Company's Fukushima Daiichi Nuclear Power Plant. [Means for solving the problem]

[0010] In order to solve the above problems, the inventors of the present invention have conducted extensive research into building materials that are lightweight, have high bending strength, and are excellent in impact resistance and radiation resistance. As a result, they have unexpectedly found that a flat wall, floor, or ceiling material having an ALC panel or gypsum board as a core material, which is equipped with a high-strength fiber mesh fabric reinforcing at least one side of the core material, and a resin layer made of polyurethane resin that covers the entire core material, including both sides, and the high-strength fiber mesh fabric, can solve all of the above problems at once, which led to the completion of the present invention. That is, the present invention is as follows.

[0011] (1) A flat wall, floor or ceiling material having an ALC panel or gypsum board as a core material, comprising a high-strength fiber mesh fabric that reinforces at least one side of the core material, and a resin layer made of a polyurea resin that covers the entire core material, including both sides, and the high-strength fiber mesh fabric. The maximum bending load measured in accordance with JIS A 1106:2018 after exposure to a cumulative radiation dose of 500 kGy is at least 1.00 kN. A wall material, floor material or ceiling material characterized by the above. ( 2 ) The bending load retention rate after irradiation with a cumulative radiation dose of 500 kGy, calculated by the following formula (1), is 75% or more. (1) The wall material, floor material or ceiling material described in 1. Bending load retention rate after radiation exposure (%) = (maximum bending load after radiation exposure / maximum bending load before radiation exposure) × 100 (1) ( 3 ) The thickness of the core material made of ALC panel is 5 mm or more and 100 mm or less, (1) to ( 2 ) Wall materials, floor materials or ceiling materials described in any one of the above. ( 4 ) The thickness of the core material made of gypsum board is 5 mm or more and 30 mm or less, 2 ) Wall materials, floor materials or ceiling materials described in any one of the above. ( 5 ) The high-strength fiber mesh fabric is at least one selected from the group consisting of woven fabrics, knitted fabrics, knitted articles, grid-like sheets, and honeycomb-like articles. 4 ) Wall materials, floor materials or ceiling materials described in any one of the above. ( 6 ) The high-strength fiber is at least one selected from the group consisting of glass fiber, boron fiber, carbon fiber, ceramic fiber, basalt fiber, aramid fiber, polyparaphenylene benzbisoxazole fiber, high-strength polyethylene fiber, and wholly aromatic polyester fiber. 5 ) Wall materials, floor materials or ceiling materials described in any one of the above. ( 7 ) The high-strength fiber is an aramid fiber, 6 ) Wall materials, floor materials or ceiling materials described in any one of the above. ( 8) The high-strength fiber mesh fabric has a void ratio of 70% or more and the number of warp and weft threads per inch is 0.5 to 10. 7 ) Wall materials, floor materials or ceiling materials described in any one of the above. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide lightweight, highly flexurally strong, and impact-resistant building materials, such as wall, floor, and ceiling materials, which are necessary for establishing isolated rooms within a nuclear reactor containment vessel. Because these materials are lightweight, they can be transported and assembled by robots. Furthermore, because they have a large maximum bending load and a high bending load retention rate before and after radiation exposure, they can be used even under radiation. Furthermore, because they have excellent radiation resistance, there is no need to frequently replace the materials. Therefore, they are suitable as building materials for debris removal during decommissioning work. This makes it possible to provide lightweight building materials that can be used for long periods of time, even under high radiation levels. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is an explanatory diagram (front view (a) and back view (b)) illustrating a wall material, floor material, or ceiling material according to one embodiment of the present invention, in which polyurethane resin is sprayed onto the entire surface, including both sides of the core material, and a high-strength fiber mesh fabric is adhered to only one side of the core material. [Figure 2] FIG. 1 is an explanatory diagram (front view (a) and back view (b)) illustrating a wall material, floor material, or ceiling material according to one embodiment of the present invention, in which polyurethane resin is sprayed onto the entire surface, including both sides of the core material, and high-strength fiber mesh fabric is adhered to both sides of the core material. [Figure 3] FIG. 2 is an explanatory diagram illustrating the void ratio, mesh opening, and thread width of the high-strength fiber mesh fabric of the present invention. [Figure 4] FIG. 1 is an explanatory diagram of a bending strength test. [Figure 5] FIG. 2 is a load-displacement curve showing the results of a bending strength test after irradiation of a wall material, floor material, or ceiling material having the ALC panel of the present invention as a core material. [Figure 6]FIG. 2 is a load-displacement curve showing the results of a bending strength test after irradiation of a wall material, floor material, or ceiling material having the gypsum board of the present invention as a core material. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be specifically described below with reference to the drawings. 1 and 2 show one embodiment of the wall, floor, or ceiling material (hereinafter, these may be collectively referred to as "wall material, etc.") of the present invention, and are diagrams illustrating a wall material, etc., in which a polyurethane resin and a high-strength fiber mesh fabric are bonded to a flat core material made of an ALC panel or gypsum board. In Fig. 1 and Fig. 2, 1 denotes the core material made of an ALC panel or gypsum board, 2 and 2a denote resin layers made of polyurethane resin, 3 denotes the high-strength fiber mesh fabric, and 10 denotes the wall, floor, or ceiling material (wall material, etc.).

[0015] The wall material or the like 10 according to the present invention can be formed by the following method. First, a polyurethane resin 2 is sprayed onto the entire surface of one side (front side) of a core material 1 made of an ALC panel or gypsum board (FIG. 1(a)). On the other hand, an appropriate amount of polyurethane resin 2a is first sprayed onto the entire surface of the opposite side (back side) of core material 1, and immediately thereafter, high-strength fiber mesh fabric 3 is attached to the entire surface. After pressing fabric 3 with a roller to firmly adhere it to the core material, polyurethane resin 2 is sprayed onto high-strength fiber mesh fabric 3 to completely adhere high-strength fiber mesh fabric 3 to the core material (Fig. 1(b)). Polyurea resin is sprayed onto the entire top, bottom and both side surfaces of the core material 1 (not shown). When installing wall materials, etc., it is up to the user to choose whether the surface reinforced with the high-strength fiber mesh fabric is on the inside or outside of a building such as a room.

[0016] Moreover, a mesh fabric made of high-strength fibers may be attached to both sides of the core material 1 to form a reinforcing structure. As in the case of reinforcing one side of the core material 1, polyurethane resin is sprayed onto one side of the core material 1, and immediately thereafter, a high-strength fiber mesh fabric 3 is attached to the entire surface, and after the fabric 3 is firmly adhered to the core material 1, more polyurethane resin is sprayed onto the high-strength fiber mesh fabric 3 (Figure 2(a)). Similarly, on the opposite side, polyurethane resin is sprayed over the entire surface, and immediately thereafter, high-strength fiber mesh fabric 3 is attached to the entire surface, firmly adhering fabric 3 to core material 1. After that, polyurethane resin is sprayed onto high-strength fiber mesh fabric 3, completely adhering high-strength fiber mesh fabric 3 to core material 1 (Figure 2(b)). Polyurea resin is sprayed onto the entire top, bottom and both side surfaces of the core material 1 (not shown).

[0017] The wall materials of the present invention are made by reinforcing a core material of low-density ALC panels or gypsum boards, and the high toughness of the polyurethane resin and the high tensile strength and high tensile elasticity of the high-strength fiber mesh fabric improve the bending strength, shear strength, and impact resistance of the core material.

[0018] The core material, gypsum board, is a board-shaped structure with paper pasted on both sides of a core material mainly composed of gypsum. Paper is usually placed on both sides, but it deteriorates due to radiation, so it is preferable not to have paper on both sides. Gypsum board may also contain glass fiber, carbon fiber, or glass fiber nonwoven fabric. The thickness of the gypsum board (thickness excluding paper) may be any thickness that allows it to be used as a wall material, etc., as specified in JIS A6901:2014 Gypsum Board Products, and is preferably 5 mm to 30 mm, more preferably 5 mm to 15 mm, and even more preferably 5 mm to 13 mm. A thickness of 5 mm or more can provide sufficient strength for use as a building material, while a thickness of 30 mm or less can be used as a lightweight building material.

[0019] The specific gravity of the gypsum board should be within a range that allows it to be lightweight and easily transportable, and is preferably 0.60 to 1.00, more preferably 0.65 to 0.90, and even more preferably 0.75 to 0.90. If the specific gravity is 0.60 or higher, it can be lightweight and have sufficient strength as a building material, and if it is 1.00 or lower, it can be used as a lightweight building material.

[0020] The size of the gypsum board is not particularly limited as long as it can be carried into the reactor containment vessel. For example, a board with a width x height of 500 mm to 1,000 mm x 1,500 mm to 3,000 mm can be used. A board with a width of 500 mm or more and a height of 1,500 mm or more can be suitably used as a wall material, while a board with a width of 1,000 mm or less and a height of 3,000 mm or less can be easily carried into the reactor containment vessel. Specifically, a board with a width of 606 mm to 910 mm x a height of 1,820 mm to 2,730 mm or a commercially available board with a width of 910 mm x a height of 1,820 mm to 2,730 mm, which is the size of a tatami mat and easy to install, can be used.

[0021] Furthermore, the ALC panel that serves as the core material, like gypsum board, only needs to have a thickness that allows it to be used as a wall material, etc., and is preferably 5 mm to 100 mm, more preferably 10 mm to 70 mm, and even more preferably 10 mm to 50 mm. A thickness of 5 mm or more can provide sufficient strength for use as a building material, and a thickness of 100 mm or less can be used as a lightweight building material.

[0022] There are no particular restrictions on the ALC panel, as long as it has the density and compressive strength specified in the JIS A5416;2016 Lightweight Aerated Concrete Panel (ALC Panel) test. The density specified in the JIS standard is 450 kg / m 3 Exceeds 550kg / m 3 less than 3.0N / mm 2 That's all.

[0023] The size of the ALC panel is not particularly limited as long as it can be carried into the reactor containment vessel. For example, panels with a width x height of 300 mm to 1,000 mm x 1,500 mm to 2,000 mm can be preferably used. Panels with a width of 300 mm or more and a height of 1,500 mm or more can be suitably used as wall materials, while panels with a width of 1,000 mm or less and a height of 2,000 mm or less can be easily carried into the reactor containment vessel. Specifically, commercially available ALC panels with a width of 300 mm to 606 mm x height of 1,820 mm to 2,000 mm can be used.

[0024] Polyurea resin not only has strong adhesive strength to both sides (front and back) and sides (top, bottom, and both sides) of the core material, but, like high-strength fiber mesh fabric, it can improve the bending strength, shear strength, and impact resistance of wall materials, etc., and also has excellent radiation resistance. By covering the sides of the core material with polyurethane resin, even if a strong impact is applied to the wall material, the core material can be broken and fragments can be effectively prevented from falling off the sides, thereby reducing strength. In addition, the core material can be made waterproof, making it suitable for use in high-humidity locations. In addition, because it has high affinity (wettability) with high-strength fibers, there is no need to pretreat the high-strength fiber mesh fabric to enhance its adhesion to the polyurea resin, making it economically advantageous. Furthermore, by using polyurea resin, it is possible to achieve a film thickness that is 10 times (1 mm) or more thicker than that of general paint, making it possible to efficiently protect the entire high-strength fiber mesh fabric.

[0025] In the wall material of the present invention, the thickness of the polyurethane resin layer 2 formed on the surface (or back surface) and sides (top, bottom, and both sides) of the core material 1 that is not reinforced with the high-strength fiber mesh fabric 3 is preferably 1 mm or more, more preferably 1.5 mm or more, and particularly preferably 2 mm or more. If the thickness is insufficient, the toughness of the resin film will be insufficient, making it difficult to maintain the wall structure against large bending loads and impact forces.

[0026] On the other hand, when reinforcing with a high-strength fiber mesh fabric 3, the thickness of the polyurethane resin layer 2 formed on the high-strength fiber mesh fabric 3 bonded to the core material 1 via the polyurethane resin 2a is preferably 1 mm or more, more preferably 1.5 mm or more, and particularly preferably 2 mm or more. In this case, the thickness of the polyurethane resin 2a sprayed onto the core material 1 in advance is not particularly limited, but is preferably a thickness that can sufficiently cover the irregularities on the surface of the core material 1, for example, 0.5 mm to 1 mm.

[0027] Polyurea resin is a compound formed by a chemical reaction between an isocyanate compound (base) and an amine compound (curing agent) having active hydrogen. Examples of polyurea resins include Extreme 11-50 (manufactured by Rhino Linings). It is believed that the polyurea resin bonds the core material and the high-strength fiber mesh fabric, and also forms a highly tough and highly elongated coating on the surface of the core material.

[0028] Methods for applying the polyurea resin include coating or spraying the polyurea resin onto the core material at a predetermined thickness, but spraying is preferred due to its superior workability. A known spraying device can be used to spray the polyurea resin onto the core material. The polyurea resin is produced by mixing a polyisocyanate compound (base compound) and an amine compound (curing agent) having active hydrogen through collision with a spray gun, causing a chemical reaction. The spraying device is a device that mixes the polyisocyanate compound and the amine compound through collision with each other, turning them into a mist and spraying it onto the core material.

[0029] The spraying device may include a tank containing a polyisocyanate compound, a tank containing an amine compound, pumps for discharging the compounds from each tank, a high-pressure metering pump for applying sufficient pressure to the compounds to dispense a predetermined amount, a heater for heating the compounds being transported, a heated hose for maintaining the temperature of the compounds, a spray gun for mixing the two compounds by collision and injecting them in a mist, and a controller for varying the mixing ratio of the two compounds and a controller for varying the heating temperature. The two compounds are heated to a predetermined temperature by the heater and sent to the spray gun while maintained at the predetermined temperature by the heated hose. The spray gun mixes the two compounds by collision and injects them in a mist. The two compounds react to produce a polyurea resin, which solidifies on the surface of the object to be sprayed, forming a coating film. This has the advantage of extremely short working times.

[0030] The high-strength fiber mesh fabric is preferably at least one selected from the group consisting of woven fabrics, knitted fabrics, lattice sheets, and honeycomb fabrics. Depending on the shape of the wall material and the reinforcing effect required of the wall material, one type may be used, or two or more types of fabrics may be used in combination. In view of the high tensile strength of the high-strength fiber mesh fabric, woven fabrics, lattice sheets, or honeycomb fabrics are preferred. The fabric weave is preferably a plain weave, twill weave, satin weave, or the like, and may be a general biaxial fabric or a multiaxial fabric such as a triaxial fabric or a quadriaxial fabric. Furthermore, the high-strength fiber mesh fabrics used on the front and back surfaces of the core material may be the same or different in terms of the type and fineness of the high-strength fiber and the type and shape of the fabric.

[0031] The high-strength fiber is preferably at least one selected from the group consisting of glass fiber, boron fiber, carbon fiber, ceramic fiber, basalt fiber, aramid fiber, polyparaphenylene benzbisoxazole fiber, high-strength polyethylene fiber, and wholly aromatic polyester fiber. Aramid fiber is particularly preferred due to its high strength, high elastic modulus, and excellent radiation resistance. Examples of aramid fiber include meta-aramid fiber, para-aramid fiber, and copolymers thereof. Specific examples include fibers made of polyparaphenylene terephthalamide, polymetaphenylene isophthalamide, and poly-3,4'-oxydiphenylene terephthalamide copolymer. The fineness of the high-strength fiber is preferably 100 to 8,000 dtex, more preferably 100 to 6,300 dtex.

[0032] If the high-strength fibers constituting the high-strength fiber mesh fabric are untwisted, they are more likely to become disordered or spread when the polyurea resin is sprayed, resulting in a decrease in fabric strength or a change in void ratio. To prevent this, it is preferable that the high-strength fibers are twisted. The preferred twist coefficient (first twist coefficient) is 0.1 to 5.0, more preferably 0.1 to 2.2, and even more preferably 0.1 to 1.6. If the twist coefficient exceeds 5.0, the strength decreases and the twisted yarn becomes thicker, which may be undesirable from the perspective of ensuring void ratio and lightweight properties. The twist coefficient can be calculated using the following formula (1): TIFF0007746123000001.tif16159

[0033] The high-strength fiber mesh fabric preferably has 0.5 to 10 warp and weft threads per inch, more preferably 7 or less. If the number of threads is less than 0.5, it will be difficult to fulfill the role of a ripstop, although this depends on the fineness, so the number is more preferably 1 to 7 threads per inch.

[0034] In the case of a grid-like sheet, the void ratio of the mesh fabric is preferably 70% or more, more preferably 75% or more. A void ratio of 70% or more, combined with the effect of improving the adhesion of the polyurethane resin to the core material, makes it possible to further improve the impact resistance of the wall material. On the other hand, if the void ratio is too high, the strength of the high-strength fiber mesh fabric itself will decrease and the reinforcing effect will be insufficient. Therefore, the void ratio is preferably 93% or less, more preferably 90% or less.

[0035] In the case of a general biaxial woven fabric, the void ratio can be calculated using the following formula (2). TIFF0007746123000002.tif39159

[0036] In addition, for multiaxial fabrics such as triaxial and quadraxial fabrics, the void ratio can be determined using an image analyzer. Simply, a black and white copy is made using an electrophotographic (Xerox) copier, and the void ratio can be calculated using the copied image by multiplying the area of ​​the black area by the area of ​​the entire effective area by 100.

[0037] 3 is a diagram illustrating the void ratio, mesh size, and thread width when the high-strength fiber mesh fabric of the present invention is a grid-like sheet. The warp and weft mesh sizes (Me, Mf) are the distance between adjacent fibers. The warp and weft widths (We, Wf) are the widths of the fibers (threads) that make up the mesh fabric. The fiber width is related to the degree of fiber opening, widening, and flattening, as well as the number of twists; the width increases as the fibers are widened and flattened, and decreases as the number of twists increases.

[0038] In the case of mesh fabrics made of high-strength fibers, the mesh size can be increased by reducing the number of fibers per inch and the width of the fibers used, resulting in a higher void ratio. In order to reduce the fiber width while maintaining the strength of the mesh fabric, it is effective to use high-strength fibers that are thin but difficult to break.

[0039] The wall material 10 of this embodiment comprises a core material 1 made of gypsum board, a high-strength fiber mesh fabric 3 that reinforces at least one side of the core material 1, and a resin layer 2 made of polyurethane resin that covers both sides of the core material 1 and the high-strength fiber mesh fabric 3.The core material 1 may be an ALC panel, and the wall material 10 may be a flooring material or a ceiling material.

[0040] That is, the presence of the core material 1 and the resin layer 2, which has extremely high toughness, significantly improves the bending strength and shear resistance of wall materials, etc. Furthermore, even when an external impact is applied, the high-strength fiber mesh fabric 3, which has high strength and elastic modulus, remains intact and absorbs the external impact, weakening the impact on the core material 1. At the same time, the high-strength fiber mesh fabric 3 freely expands and contracts in response to the deformation of the resin layer 2, thereby appropriately absorbing the movement of the resin layer 2. As a result, even when a large impact is applied to a wall material, etc., the resin layer 2 expands and contracts in response to the deformation of the core material 1 and the high-strength fiber mesh fabric 3, preventing the wall material, etc. from being destroyed. Even if the high-strength fiber mesh fabric 3 is not present, the resin layer 2 made of a polyurethane resin with extremely high toughness flexes in response to the deformation of the core material 1, thereby preventing the wall material, etc. from being destroyed. When high-strength fiber mesh fabric 3 receives a strong impact, the resin peels off from the fiber surface, so if only one side is reinforced with high-strength fiber mesh fabric, a greater effect can be expected by placing it on the opposite side that will receive the impact.

[0041] The wall materials of the present invention preferably have a maximum bending load of at least 1.00 kN, as measured in accordance with the bending strength test method using the central point loading method in Appendix JA (reference) of JIS A 1106:2018 (Testing Methods for Bending Strength of Concrete). If the maximum bending load is at least 1.00 kN, the wall materials will not easily break even when a large load is applied. It is more preferably 1.20 kN or more, and even more preferably 1.35 kN or more. Furthermore, the wall material of the present invention must be radiation-resistant so that it can be used under high radiation levels. It is desirable that the maximum bending load measured by the above-mentioned test method after exposure to a cumulative radiation dose of 500 kGy is at least 1.00 kN. If the maximum bending load is at least 1.00 kN, there is no need to worry about a decrease in strength under high radiation levels, and long-term use is possible. It is more preferably 1.05 kN or more, and even more preferably 1.10 kN or more.

[0042] Furthermore, the wall material of the present invention preferably has a bending load retention of 75% or more before and after irradiation with a cumulative radiation dose of 500 kGy, as calculated by the following formula (1). If the bending load retention is 75% or more, the material has sufficient radiation resistance to withstand long-term use under high radiation. It is more preferably 80% or more, and even more preferably 85% or more. Bending load retention rate after radiation exposure (%) = (maximum bending load after radiation exposure / maximum bending load before radiation exposure) × 100 (1)

[0043] Furthermore, in the present invention, as long as the effect of the wall material is not hindered, the surface of the core material 1 may be subjected to a primer treatment. The primer treatment can improve the adhesion between the core material 1 and the polyurea resin 2a.

[0044] Furthermore, in the present invention, a finishing material (paint) may be sprayed or applied to the surface of the polyurea resin 2. The finishing material may be selected appropriately from polyurethane-based, acrylic silicone-based, fluorine-based, epoxy-based, vinyl-based, polyester-based, melamine-based, aminoalkyd-based, urea-based, and other resin materials in terms of weather resistance, scratch resistance, abrasion resistance, workability, appearance, and the like. The form of the resin material is not particularly limited, and may be aqueous, emulsion, solvent-based, or the like. The curing method may also be selected appropriately from one-component types, two-component types, ultraviolet curing, and the like. Known additives (gloss adjusters, ultraviolet absorbers, light stabilizers, antibacterial agents, and antifungal agents) may be added to the paint.

[0045] In order to improve the design, alumina, silica, silicon nitride, silicon carbide, glass beads, etc. may be added to the paint. Alternatively, tiling is also possible.

[0046] The wall material 10 described in the above embodiment is an example given to embody the technical concept of the present invention, and the shapes and dimensions of each material are not limited to those in this embodiment, and various modifications may be made within the scope of the present invention. [Example]

[0047] The present invention will be explained in more detail below using examples, but the present invention is not limited to the following examples.

[0048] Example 1 The surface of a flat core material (cut to a width of 15 cm, a length of 60 cm, a thickness of 12.5 mm, no paper on both sides) made of gypsum board (product name: Tiger Glass Rock, gypsum board containing glass fiber nonwoven fabric) manufactured by Yoshino Gypsum Co., Ltd. was coated with a polyurea resin (Extreme 11-50 manufactured by Rhino Linings) at a rate of approximately 2.2 kg / m. 2 The spray was applied so that the surface was as shown in Figure 1(a). On the other hand, the backside of the core material is first coated with the same polyurethane resin as above at a coating amount of about 0.5 kg / m 2 Immediately afterwards, an aramid fiber mesh fabric (aramid fiber: Kevlar® manufactured by Toray DuPont Co., Ltd., fabric basis weight: 180 g / m 2 After the fabric was firmly attached to the core material, a polyurea resin was applied in an amount of approximately 2.2 kg / m 2 The solution was sprayed onto a mesh fabric so that the surface was covered with the solution (Figure 1(b)). The top, bottom and both sides of the core are coated with polyurethane resin at a rate of approximately 2.2 kg / m 2 The coating was sprayed to create a radiation-resistant lightweight plate. The lightweight board was coated with an acrylic resin as a finishing material on its front, back, upper, lower and both side surfaces.

[0049] Example 2 A polyurea resin (Extreme 11-50 manufactured by Rhino Linings) was applied to the surface of a flat core material made of the same gypsum board as used in Example 1 at a coating amount of approximately 0.5 kg / m. 2 Immediately afterwards, an aramid fiber mesh fabric (aramid fiber: Kevlar® manufactured by Toray DuPont Co., Ltd., fabric basis weight: 180 g / m 2 After the fabric was firmly attached to the core material, a polyurea resin was applied in an amount of approximately 2.2 kg / m 2 The solution was sprayed onto the mesh fabric so that the solution was uniformly dispersed (Figure 2(a)). On the other hand, the back side of the core material was also coated with the same polyurethane resin as above, at a coating amount of approximately 0.5 kg / m. 2 Immediately afterwards, the same aramid fiber mesh fabric as above was attached, and after the fabric was firmly attached to the core material, polyurethane resin was applied in an amount of approximately 2.2 kg / m 2 The solution was sprayed onto the mesh fabric so that the solution was uniformly dispersed (Figure 2(b)). The top, bottom and both sides of the core are coated with polyurethane resin at a rate of approximately 2.2 kg / m 2 The coating was sprayed to create a radiation-resistant lightweight plate. The lightweight board was coated with an acrylic resin as a finishing material on its front, back, upper, lower and both side surfaces.

[0050] Example 3 Polyurea resin (Rhino Linings Extreme 11-50) was applied to the surface of a flat core material (cut to a width of 15 cm, length of 60 cm, thickness of 35 mm) made of ALC panel (product name: Clion Ace Board) manufactured by Clion Co., Ltd., at a coating rate of approximately 2.2 kg / m. 2 The spray was applied so that the surface was as shown in Figure 1(a). On the other hand, the backside of the core material is first coated with the same polyurethane resin as above at a coating amount of about 0.5 kg / m 2 Immediately afterwards, an aramid fiber mesh fabric (aramid fiber: Kevlar® manufactured by Toray DuPont Co., Ltd., fabric basis weight: 180 g / m 2After the fabric was firmly attached to the core material, a polyurea resin was applied in an amount of approximately 2.2 kg / m 2 The solution was sprayed onto a mesh fabric so that the surface was covered with the solution (Figure 1(b)). The top, bottom and both sides of the core are coated with polyurethane resin at a rate of approximately 2.2 kg / m 2 The coating was sprayed to create a radiation-resistant lightweight plate. The lightweight board was coated with an acrylic resin as a finishing material on its front, back, upper, lower and both side surfaces.

[0051] Example 4 A polyurea resin (Extreme 11-50 manufactured by Rhino Linings) was applied to the surface of a flat core material made of the same ALC panel as used in Example 3 in an amount of approximately 0.5 kg / m. 2 Immediately afterwards, an aramid fiber mesh fabric (aramid fiber: Kevlar® manufactured by Toray DuPont Co., Ltd., fabric basis weight: 180 g / m 2 After the fabric was firmly attached to the core material, a polyurea resin was applied in an amount of approximately 2.2 kg / m 2 The solution was sprayed onto the mesh fabric so that the solution was uniformly dispersed (Figure 2(a)). On the other hand, the back side of the core material was also coated with the same polyurethane resin as above, at a coating amount of approximately 0.5 kg / m. 2 Immediately afterwards, the same aramid fiber mesh fabric as above was attached, and after the fabric was firmly attached to the core material, polyurethane resin was applied in an amount of approximately 2.2 kg / m 2 The solution was sprayed onto the mesh fabric so that the solution was uniformly dispersed (Figure 2(b)). The top, bottom and both sides of the core are coated with polyurethane resin at a rate of approximately 2.2 kg / m 2 The coating was sprayed to create a radiation-resistant lightweight plate. The lightweight board was coated with an acrylic resin as a finishing material on its front, back, upper, lower and both side surfaces.

[0052] (Comparative Example 1) Polyurea resin (Extreme 11-50 manufactured by Rhino Linings) was applied at a rate of approximately 2.2 kg / m to the front, back, top, bottom and both sides of a flat core material (cut to a width of 15 cm, length of 60 cm, thickness of 12.5 mm) made of gypsum board (trade name: Tiger Glass Rock) manufactured by Yoshino Gypsum Co., Ltd. 2 A lightweight board was produced by spraying the coating to achieve this. The lightweight board was coated with an acrylic resin as a finishing material on its front, back, upper, lower and both side surfaces.

[0053] (Comparative Example 2) Polyurea resin (Rhino Linings Extreme 11-50) was applied at a rate of approximately 2.2 kg / m to the front, back, top, bottom, and both sides of a flat core material (cut to a width of 15 cm, length of 60 cm, and thickness of 35 mm) made of ALC panel (product name: Clion Ace Board) manufactured by Clion Co., Ltd. 2 A lightweight board was produced by spraying the coating to achieve this. The lightweight board was coated with an acrylic resin as a finishing material on its front, back, upper, lower and both side surfaces.

[0054] (Comparative Example 3) An acrylic resin was applied as a finishing material to the front, back, top, bottom, and both sides of a flat core material (cut to a width of 15 cm, length of 60 cm, and thickness of 12.5 mm) made of gypsum board (product name: Tiger Glass Rock) manufactured by Yoshino Gypsum Co., Ltd.

[0055] Comparative Example 4 An acrylic resin was applied as a finishing material to the front, back, top, bottom, and both sides of a flat core material (cut to a width of 15 cm, length of 60 cm, and thickness of 35 mm) made of an ALC panel (product name: Clion Ace Board) manufactured by Clion Co., Ltd.

[0056] The maximum bending loads before and after irradiation were measured for the lightweight plates obtained in Examples 1 to 4 and Comparative Examples 1 to 4, and the radiation resistance was evaluated. In addition, the displacement before and after irradiation was measured, the bending load retention rate was calculated, and the damage state of the lightweight plates after the bending strength test was observed. The test method is shown below.

[0057] (1) Maximum bending load measurement method The maximum bending load before and after irradiation was measured in accordance with the bending strength test method using the central point loading method in Appendix JA (reference) of JIS A 1106:2018 (Testing method for bending strength of concrete). However, the span was set to 560 mm. An outline of the test method is shown in Figure 4.

[0058] (2) Evaluation of radiation resistance The irradiation was carried out by irradiating with gamma rays (Co60) at room temperature (in air), and was completed when the cumulative irradiation dose reached 500 kGy. The evaluation of radiation resistance was made in consideration of the maximum bending load of each test specimen after irradiation, and was judged as follows: <Judgment criteria> ◯: Maximum bending load after radiation exposure is 1.00kN or more, △: Less than 1.00kN, 0.50kN or more, ×: Less than 0.50kN

[0059] (3) Displacement measurement method The displacement before irradiation was measured by the crosshead movement, which was monitored by a monitor (not shown) attached to the bending strength tester. The displacement before irradiation was measured up to 168 mm (maximum crosshead movement). The displacement after radiation exposure was measured using a digital strain gauge and an electric displacement meter attached via a mounting jig under the loading point of the specimen (lightweight plate) placed in the bending strength test device (Fig. 4). Displacement after radiation exposure was measured up to 45 mm, and the measurement results were rounded to two decimal places. Displacements exceeding 45 mm were deemed unmeasurable.

[0060] (4) Bending load retention rate The bending load retention rate after radiation irradiation was calculated from the maximum bending load after radiation irradiation relative to the maximum bending load before radiation irradiation according to the following formula (1). Bending load retention rate after radiation exposure (%) = (maximum bending load after radiation exposure / maximum bending load before radiation exposure) × 100 (1)

[0061] (5) Damage to the lightweight board After the above-mentioned bending strength test after irradiation, the back surface (the surface opposite to the loaded surface) of each lightweight plate was visually inspected for damage.

[0062] Table 1 shows the test results of the lightweight plates produced in the examples and comparative examples. 5 and 6 show the results of bending strength tests after irradiation on wall materials and the like that have ALC panels and gypsum boards as core materials. Note that in Fig. 5 (and Fig. 6 as well), the displacement is measured up to a maximum of 45 mm with the origin as the reference point. The origin was set at 0 mm for Comparative Example 4 (Comparative Example 3), 5 mm for Comparative Example 2 (Comparative Example 1), and 10 mm for Example 4 (Example 2).

[0063] [Table 1]

[0064] The results in Table 1 and Figures 5 and 6 show that the ALC panels and gypsum boards reinforced with the polyurea resin and aramid fiber mesh fabric of the present invention are lightweight and have a high maximum bending load, making them suitable for wall, floor, and ceiling materials. Furthermore, the lightweight boards of the present invention, including gypsum board, ALC panel, aramid fiber, and polyurea resin, all have excellent radiation resistance, and therefore exhibit excellent maximum bending load and bending load retention after radiation exposure. Therefore, it can be seen that they can be used for a long period of time even under high load and high radiation environments. Furthermore, the lightweight board of the present invention showed higher displacement both before and after radiation exposure compared to unreinforced boards, and no cracks were observed in the fracture state after bending tests. This is presumably because, while the ACL panel and gypsum board themselves have no elongation, the polyurethane resin has high elongation (400% or more), and the aramid fiber mesh fabric and polyurethane resin are combined into FRP, imparting elongation and strength. When a room is constructed using the lightweight board of the present invention, even if the strength of the core material is impaired by bending loads caused by falling building materials, collapse of the building, or strong impacts such as an explosion or typhoon, the walls, ceiling, etc. will not be destroyed and collapse, ensuring safety inside the room. [Industrial Applicability]

[0065] The construction materials of the present invention can provide flooring, walling, and ceiling materials that are light and durable and have excellent radiation resistance, and can be useful in decommissioning work at the Fukushima Daiichi Nuclear Power Plant. In particular, they are expected to be used in work inside the reactor containment vessel, where extremely high radiation doses are expected. In addition, by using it as a wall material, floor material, or ceiling material for houses, schools, hospitals, shops, factories, shelters, sheds, etc., or as a fence around a site, etc., it is possible to protect the internal facilities from external impacts and provide a safe environment that is not likely to collapse or break down even in an earthquake or typhoon. [Explanation of symbols]

[0066] 1 Core material 2. Resin layer (coating layer) made of polyurea resin 2a Resin layer (adhesive layer) made of polyurea resin 3 High-strength fiber mesh fabric 10 Wall, floor or ceiling materials

Claims

1. A flat wall, floor or ceiling material having an ALC panel or gypsum board as a core material, the wall, floor or ceiling material comprising: a high-strength fiber mesh fabric reinforcing at least one side of the core material; and a resin layer made of a polyurethane resin covering the entire core material, including both sides, and the high-strength fiber mesh fabric, the wall, floor or ceiling material being characterized in that the maximum bending load measured in accordance with JIS A 1106:2018 after exposure to a cumulative radiation dose of 500 kGy is at least 1.00 kN.

2. 2. The wall, floor or ceiling material according to claim 1, wherein the bending load retention rate after irradiation with a cumulative radiation dose of 500 kGy, as calculated by the following formula (1), is 75% or more. Bending load retention rate after radiation exposure (%)=(maximum bending load after radiation exposure / maximum bending load before radiation exposure)×100 (1)

3. 3. The wall, floor or ceiling material according to claim 1, wherein the thickness of the core material made of an ALC panel is 5 mm or more and 100 mm or less.

4. 3. The wall, floor or ceiling material according to claim 1, wherein the thickness of the core material made of gypsum board is 5 mm or more and 30 mm or less.

5. The wall, floor or ceiling material according to any one of claims 1 to 4, wherein the high-strength fiber mesh fabric is at least one selected from the group consisting of woven fabrics, knitted fabrics, knitted materials, lattice sheets and honeycomb materials.

6. The wall, floor or ceiling material according to any one of claims 1 to 5, wherein the high-strength fiber is at least one selected from the group consisting of glass fiber, boron fiber, carbon fiber, ceramic fiber, basalt fiber, aramid fiber, polyparaphenylene benzbisoxazole fiber, high-strength polyethylene fiber and wholly aromatic polyester fiber.

7. 7. The wall, floor or ceiling material according to claim 1, wherein the high strength fiber is an aramid fiber.

8. 8. The wall, floor or ceiling material according to claim 1, wherein the high-strength fiber mesh fabric has a void ratio of 70% or more and the number of warp and weft threads per inch is 0.5 to 10.

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