Porous molded board

Abstract

The present invention pertains to a porous molded plate that contains 35-70 mass% of a substance not involved in a pozzolanic reaction, 20-61.5 mass% of a cement, 1-3 mass% of a synthetic fiber and 2.5-7 mass% of a pulp, wherein the ratio (B) / (A) is 1.70-6.0 [wherein (A) stands for the pore volume within the range of 660-9100 nm in the pore size distribution of the molded plate determined by the mercury injection method, and (B) stands for the pore volume within the range of 6-560 nm therein].

Description

[Technical Field]

[0001] This patent application claims priority under the Paris Convention with respect to Japanese Patent Application No. 2021-179694 (filing date: November 2, 2021), which is incorporated herein by reference in its entirety. This invention relates to a porous molded board. [Background technology]

[0002] Cement-based slabs are obtained by forming sheets using a slab-forming method in which cement and fibers are suspended in an aqueous medium and then formed through a mesh, followed by curing and hardening. Due to its versatility in manufacturing, this slab-forming method is used in a wide range of fields, and is particularly frequently used in the construction industry for the production of ceiling materials, interior materials, exterior materials, and flooring materials. However, the production of cement requires a great deal of energy, and the resulting large emissions of carbon dioxide are a cause for concern. Furthermore, when autoclave curing is required in the manufacturing process, steam boilers are usually used for curing, which also releases carbon dioxide. Therefore, in order to reduce carbon dioxide emissions, cement-based slabs that do not require autoclave curing and have a reduced cement content have been proposed. For example, Patent Document 1 discloses a panel comprising a hydraulic binder such as cement, a filler such as calcium carbonate, and synthetic fibers; Patent Document 2 discloses an inorganic paperboard comprising a hydrateable raw material for matrix formation, an inorganic filler, reinforcing fibers, and calcium silicate hydrate; and Patent Document 3 discloses an energy-saving and environmentally friendly lightweight partition wall manufactured from raw materials containing Portland cement, calcium carbonate, calcium oxide, paraffin-diatomaceous earth composite phase transition material, modified carbon fiber, activated bentonite, rubber powder, modified yellow earth powder, solid industrial waste, fibers, initial strength imparterant, water-reducing agent, foaming agent, rare earth catalyst, and water in specific proportions. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] U.S. Patent Application Publication No. 2005 / 72056 [Patent Document 2] Japanese Patent Publication No. 2005-205879 [Patent Document 3] Chinese Patent Application Publication No. 108276023 Specification [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, there is a constant need to develop molded sheets that have superior performance, such as high bending strength and low dimensional change rate, while also reducing carbon dioxide emissions. Therefore, the problem that this invention aims to solve is to provide a molded sheet with high bending strength and low dimensional change rate. [Means for solving the problem]

[0005] In order to solve the aforementioned problems, the inventors conducted detailed studies on molded plates and have now completed the present invention. In other words, the present invention encompasses the following preferred embodiments. [1] A porous molded board comprising 35-70% by mass of a substance not involved in the pozzolanic reaction, 20-61.5% by mass of cement, 1-3% by mass of synthetic fiber, and 2.5-7% by mass of pulp, A molded plate in which the pore size distribution, determined by mercury intrusion, shows that the ratio (B) / (A) of the pore volume in the range of 6 to 560 nm to the pore volume in the range of 6 to 9100 nm (A) is 1.70 to 6.0. [2] The molded plate according to [1] above, wherein the substance not involved in the pozzolanic reaction is one or more substances selected from the group consisting of calcium carbonate, silica powder, and talc. [3] The molded plate described in [2] above, wherein the calcium carbonate is heavy calcium carbonate. [4] The molded plate according to any one of the above [1] to [3], further comprising one or more substances selected from the group consisting of mica, fly ash and silica fume. [5] The molded plate according to any one of the above [1] to [4], wherein the total content of synthetic fibers and pulp is 7% by mass or less based on the total mass of the molded plate. [6] The molded plate according to any one of the above [1] to [5], wherein the average fiber diameter of the synthetic fibers is 50 µm or less. [7] The molded plate according to the above [6], wherein the average fiber diameter of the synthetic fibers is 5 µm or more and 40 µm or less. [8] The molded plate according to any one of the above [1] to [7], wherein the aspect ratio of the synthetic fibers is 150 or more and 1000 or less. [9] The molded plate according to any one of the above [1] to [8], wherein the synthetic fibers are at least one selected from the group consisting of polyvinyl alcohol fibers, polyethylene fibers, polypropylene fibers, acrylic fibers, aramid fibers and nylon fibers.

[10] The molded plate according to any one of the above [1] to [9], wherein the water absorption measured in accordance with JIS A 5430:2018 is 15% or more and 28% or less.

[11] The total heat generation amount measured in accordance with the exothermic test of JIS A 5430:2018 is 8.0 MJ / m 2 or less, the molded plate according to any one of the above [1] to

[10] .

[12] The bulk density measured in accordance with JIS A 5430:2018 is 1.50 g / cm 3 or more, the molded plate according to any one of the above [1] to

[11] .

[13] The bending strength when absorbing water measured in accordance with JIS A 1408:2017 is 15 N / mm 2 or more, the molded plate according to any one of the above [1] to

[12] .

[14] The molded plate according to any one of the above [1] to

[13] , wherein the water absorption measured in accordance with JIS A 5430:2018 is 26% or less.

[15] The molded plate according to any one of the above [1] to

[14] , wherein the pore volume (B) is 2.50 mL / g or less. Effects of the Invention

[0006] According to the present invention, it is possible to provide a molded sheet having high bending strength and a low rate of dimensional change. [Modes for carrying out the invention]

[0007] The embodiments of the present invention will be described in detail below. However, the scope of the present invention is not limited to the embodiments described herein, and various modifications can be made without impairing the spirit of the invention.

[0008] The molded board of the present invention comprises 35-70% by mass of a substance that does not participate in the pozzolanic reaction, 20-61.5% by mass of cement, 1-3% by mass of synthetic fiber, and 2.5-7% by mass of pulp, based on the total mass of the molded board. If the proportions of each component deviate from the specific ranges described above, it is difficult to obtain a molded board that possesses both high bending strength and a low dimensional change rate. The molded board preferably comprises, with respect to the total mass of the molded board, 40 to 67.5% by mass of a substance that does not participate in the pozzolanic reaction, 25 to 60.5% by mass of cement, 1 to 2% by mass of synthetic fibers, and 2.5 to 6% by mass of pulp, and more preferably 45 to 65% by mass of a substance that does not participate in the pozzolanic reaction, 30 to 59.5% by mass of cement, 1 to 1.5% by mass of synthetic fibers, and 3 to 5% by mass of pulp.

[0009] In one preferred embodiment, the total content of synthetic fibers and pulp is 7% by mass or less, preferably 6% by mass or less, relative to the total mass of the molded board. When the total content of synthetic fibers and pulp is below the above upper limit, the total heat generation of the molded board tends to be lower, which means that the molded board has excellent flame retardancy.

[0010] The molded sheet of the present invention is porous. The ratio (B) / (A) of the pore volume in the range of 6 to 560 nm to the pore volume in the range of 6 to 9100 nm (A) in the pore diameter distribution of the molded sheet determined by the mercury intrusion method is 1.70 to 6.0, preferably 1.75 to 5.8, more preferably 1.80 to 5.6, and particularly preferably 1.85 to 5.4. When the ratio (B) / (A) is preferably 5.3 or less, more preferably 5.1 or less, and even more preferably less than 5.0, it is easier to obtain a higher yield rate in the manufacture of the molded sheet, in addition to higher bending strength and a lower dimensional change rate. The ratio (B) / (A) may also be 4.9 or less, 4.8 or less, 4.5 or less, or 4.0 or less. Furthermore, the ratio (B) / (A) may be preferably 2.00 or more, more preferably 2.10 or more, even more preferably 2.20 or more, and even more preferably 2.50 or more. The ratio (B) / (A) can be adjusted to a desired value, for example, by using a material having a specific Blaine specific surface area as a substance that does not participate in the pozzolanic reaction, and / or by adjusting the molding conditions (especially the press pressure). The pore volume ratio (B) / (A) can be measured by the method described in the examples.

[0011] The inventors of the present invention have surprisingly discovered that a molded board can achieve both high bending strength and low dimensional change rate by containing the four components (a substance not involved in the pozzolanic reaction, cement, synthetic fibers, and pulp) in specific proportions and having a specific ratio (B) / (A). The reason for this is not clear, but the following mechanism of action is presumed. The molded board of the present invention can be manufactured by curing a curable composition containing the four components. By applying appropriate pressure during the curing process, the substance not involved in the pozzolanic reaction adequately fills the voids in the molded board during the curing process, resulting in increased adhesion between the synthetic fibers and the cement matrix. Furthermore, the substance not involved in the pozzolanic reaction does not cause defects such as cracks or warping that may occur as the pozzolanic reaction progresses. Therefore, it is presumed that high bending strength and low dimensional change rate are exhibited in the molded article. However, the above is a presumption, and the present invention is not limited to this mechanism of action.

[0012] The pore volume (B) in the range of 6 to 560 nm is preferably 2.50 mL / g or less, more preferably 2.40 mL / g or less, particularly preferably 2.30 mL / g or less, and even more preferably 2.20 mL / g or less. When the pore volume (B) is below the above upper limit, the resulting molded plate tends to have excellent bending strength when dry and when water is absorbed. It is presumed that the pore volume (B) being below the above upper limit is related to the high adhesion between the synthetic fibers and the cement matrix, as described above, and as a result, the molded plate tends to have excellent bending strength when dry and when water is absorbed. Furthermore, since pores in the range of 6 to 560 nm greatly affect water absorption, it is presumed that the effect of water is reduced when the pore volume (B) is below the above upper limit, and the bending strength, especially when water is absorbed, tends to be higher. Furthermore, if the pore volume (B) is preferably 2.10 mL / g or less, and more preferably 2.00 mL / g or less, it is easier to obtain a higher yield rate in the manufacture of the molded plate. The pore volume (B) can be adjusted to a desired value, for example, by using a material having a specific Blaine specific surface area as a substance that does not participate in the pozzolanic reaction, and / or by adjusting the molding conditions (particularly the press pressure). The pore volume (B) can be measured by the method described in the examples.

[0013] <Substances not involved in the pozzolanic reaction> The substance not involved in the pozzolanic reaction is preferably one or more substances selected from the group consisting of calcium carbonate, silica powder, and talc. From the viewpoint of availability and cost, the substance not involved in the pozzolanic reaction is preferably heavy calcium carbonate.

[0014] Substances not involved in the pozzolanic reaction are preferably present at 2200-12000 cm⁻¹. 2 / g, more comfortably 3000~11000cm 2 / g, particularly preferably 4000-11000 cm 2has a Blaine specific surface area of / g. When the Blaine specific surface area is within the above range, it is easy to obtain a specific ratio (B) / (A) in the molded plate. When using two or more substances that do not participate in the pozzolanic reaction with different Blaine specific surface areas, it is preferable that the Blaine specific surface area corresponding to their proportions is within the above range. For example, the Blaine specific surface area is 2500 cm 2 / g of Substance 1 that does not participate in the pozzolanic reaction and has a Blaine specific surface area of 6500 cm 2 / g of Substance 2 that does not participate in the pozzolanic reaction is used at a mass ratio of 50:50, the Blaine specific surface area corresponding to the proportion for the combination of Substances 1 and 2 is 4500 cm 2 / g (= 2500 × 0.5 + 6500 × 0.5) calculated. In addition, the Blaine specific surface area of the substance that does not participate in the pozzolanic reaction is preferably 10000 cm 2 / g or less, more preferably 9000 cm 2 / g or less, it is easier to obtain a higher yield in the production of the molded plate. The Blaine specific surface area can be measured by the air permeation method in accordance with JIS R5201:2015.

[0015] Such substances that do not participate in the pozzolanic reaction are commercially available, and an example of a commercially available product includes calcium carbonate (first grade) manufactured by Sankyo Seifun Co., Ltd.

[0016] <Cement> Examples of the cement in the present invention include Portland cements such as ordinary Portland cement, early-strength Portland cement, ultra-early-strength Portland cement and moderate-heat Portland cement; alumina cement; blast furnace cement; silica cement; fly ash cement; and white Portland cement. These cements may be used alone or in combination of two or more. From the viewpoint of versatility and / or cost, it is preferable to use ordinary Portland cement. From the viewpoint of easily obtaining strength development early, it is preferable to use high-early-strength Portland cement or ultra-high-early-strength Portland cement. From the viewpoint of easily obtaining the effect of improving long-term strength, it is preferable to use blast furnace cement.

[0017] The cements described above are commercially available, and an example of a commercially available product is ordinary Portland cement manufactured by Taiheiyo Cement Corporation.

[0018] <Synthetic Fibers> The average fiber diameter of the synthetic fibers is preferably 5 μm or more, more preferably 6 μm or more, particularly preferably 7 μm or more, preferably 50 μm or less, more preferably 40 μm or less, and particularly preferably 30 μm or less. When the average fiber diameter of the synthetic fibers is above the lower limit and below the upper limit, it is easier to achieve both good dispersibility of the synthetic fibers in the curable composition and good fiber reinforcement in the molded article. The average fiber diameter is determined by randomly selecting 100 fibers, measuring the fiber diameter at the center of the length direction of each fiber using an optical microscope, and calculating the average value.

[0019] The average fiber length of the synthetic fibers is preferably 2 to 30 mm, more preferably 2 to 20 mm, from the viewpoint of achieving both good fiber dispersion in the curable composition and good fiber reinforcement in the molded article. The average fiber length can be determined in accordance with JIS L 1015:2010.

[0020] The aspect ratio (fiber length / fiber diameter) of the synthetic fiber is preferably 150 or more, more preferably 175 or more, particularly preferably 200 or more, preferably 1000 or less, more preferably 900 or less, and particularly preferably 800 or less. When the aspect ratio of the synthetic fiber is above the lower limit and below the upper limit, it is easier to achieve both good dispersibility of the synthetic fiber in the curable composition and good fiber reinforcement in the molded article. The aspect ratio can be calculated from the average fiber length and the average fiber diameter.

[0021] The tensile strength of the synthetic fiber is preferably 3 cN / dtex or higher, more preferably 5 cN / dtex or higher, and particularly preferably 7 cN / dtex or higher. When the tensile strength of the synthetic fiber is above the lower limit, it is easier to improve the fiber reinforcement in the molded plate. The upper limit of the tensile strength of the synthetic fiber in this invention is set appropriately depending on the type of fiber, but for example, it is 30 cN / dtex or lower. The tensile strength of the fiber can be determined in accordance with JIS L 1015:2010.

[0022] The synthetic fiber may be either an inorganic synthetic fiber or an organic synthetic fiber. Preferably, the synthetic fiber is an organic synthetic fiber, and more preferably, at least one selected from the group consisting of polyvinyl alcohol (hereinafter sometimes referred to as "PVA")-based fibers, polyethylene fibers, polypropylene fibers, acrylic fibers, aramid fibers, and nylon fibers. From the viewpoint of easily providing excellent reinforcement through molded plates and being inexpensive, it is preferable to use PVA-based fibers and / or polypropylene fibers.

[0023] When using PVA-based fibers, such as vinylon fibers, as synthetic fibers, PVA-based fibers having the following characteristics may be used. The degree of polymerization of the PVA-based polymer constituting the PVA-based fiber can be appropriately selected depending on the purpose and is not particularly limited. Considering the mechanical properties of the resulting fiber, the average degree of polymerization of the PVA-based polymer, determined from the viscosity of an aqueous solution at 30°C, is preferably around 500 to 20000, more preferably around 800 to 15000, and particularly preferably around 1000 to 10000. Of these, from the viewpoint of the strength of the resulting fiber, the average degree of polymerization of the PVA-based polymer is preferably 1000 or more, more preferably 1200 or more, more preferably 1500 or more, and particularly preferably 1750 or more. The PVA-based polymer may be a medium-degree of polymerization product with an average degree of polymerization of 1000 to less than 3000, or a high-degree of polymerization product with an average degree of polymerization of 3000 or more.

[0024] The degree of saponification of the PVA-based polymer can be appropriately selected depending on the purpose and is not particularly limited. From the viewpoint of the mechanical properties of the resulting fibers, the degree of saponification of the PVA-based polymer may be, for example, 95 mol% or more, preferably 98 mol% or more. The degree of saponification of the PVA-based polymer may be 99 mol% or more, or 99.8 mol% or more. When the degree of saponification of the PVA-based polymer is above the lower limit, it is easier to obtain good mechanical properties, process passability, and manufacturing costs for the resulting fibers.

[0025] The PVA-based fibers used in this invention are produced by dissolving such a PVA-based polymer in a solvent, spinning it by one of the following methods: wet spinning, wet dry spinning, or dry spinning, and then dry heat stretching. Wet spinning is a method in which the spinning solution is discharged directly from the spinning nozzle into the solidification bath. Wet dry spinning is a method in which the spinning solution is discharged from the spinning nozzle into air or an inert gas at a distance of any choice, and then introduced into the solidification bath. Dry spinning is a method in which the spinning solution is discharged into air or an inert gas. After spinning, the PVA-based fibers may be stretched as needed. In addition, acetalization treatment, which is commonly performed on PVA-based fibers, may be performed.

[0026] The solvent used in the spinning solution for PVA-based fibers is not particularly limited as long as it is capable of dissolving PVA. For example, one or more of the following may be used in combination: water, dimethyl sulfoxide (DMSO), dimethylformamide, dimethylacetamide, and polyhydric alcohols (e.g., glycerin, ethylene glycol, and triethylene glycol). In the present invention, when wet spinning is performed, it is preferable to use water or an organic solvent as the solvent. Among these, water and DMSO are particularly preferred from the viewpoint of ease of supply and impact on the environment. The polymer concentration in the spinning solution varies depending on the composition and degree of polymerization of the PVA-based polymer and the type of solvent, but is generally 6 to 60% by mass.

[0027] Even in dry spinning, the aforementioned solvents may be used. In that case, either water or an organic solvent may be used.

[0028] Within limits that do not impair the effects of the present invention, the spinning solution may contain additives other than the PVA-based polymer, depending on the purpose. Examples of additives include boric acid, surfactants, antioxidants, decomposition inhibitors, antifreeze agents, pH adjusters, opacifiers, colorants, and oils.

[0029] The solvent used in the solidification bath may be appropriately selected depending on the type of solvent used in the spinning solution. If the spinning solution is an aqueous solution, the solidification bath may be an aqueous solution of inorganic salts (e.g., sodium sulfate, ammonium sulfate, sodium carbonate, or sodium hydroxide) that have the ability to solidify PVA polymers, or an alkaline aqueous solution. If the spinning solution is an organic solvent solution, the solidification bath may be an organic solvent that has the ability to solidify PVA polymers, such as alcohols (e.g., methanol, ethanol, propanol, or butanol) or ketones (e.g., acetone, methyl ethyl ketone, or methyl isobutyl ketone).

[0030] In the present invention, PVA-based fibers obtained by dry spinning, or PVA-based fibers obtained by wet spinning from a spinning solution using water or an organic solvent, are preferred from the viewpoint of fiber tensile strength.

[0031] To extract and remove the solvent from the spinning solution from the solidified yarn, it may be passed through an extraction bath, or the yarn may be wet-stretched at the same time as the extraction. Alternatively, after wet stretching, the fibers may be dried, and if necessary, further dry-heat stretching may be performed. When stretching is performed, the total stretch ratio (product of wet stretching and drying stretch ratio) may be, for example, 5 to 25 times, preferably 8 to 20 times.

[0032] Commercially available synthetic fibers may be used, and examples include organic fibers such as polyvinyl alcohol-based fibers manufactured by Kuraray Co., Ltd., polypropylene fibers manufactured by Daiwa Spinning Co., Ltd., and nylon fibers manufactured by Toray Industries, Inc., as well as inorganic fibers such as glass fibers manufactured by Nippon Electric Glass Co., Ltd. and Taiheiyo Material Co., Ltd.

[0033] <Pulp> The pulp may be beaten or unbeaten. From the viewpoint of easily obtaining the desired flexural strength and impact strength, it is preferable to use beaten pulp, and it is even more preferable to use pulp whose degree of beatenness, measured in accordance with the Canadian standard of water permeability testing method JIS P 8121-2:2012, has a CSF value of 50 to 400 mL, more preferably 100 to 150 mL. In the manufacture of molded boards, from the viewpoint of easily obtaining the desired yield rate, when using the cylinder wire papermaking method described later, it is preferable to use pulp with a CSF value of 100 to 150 mL, and when using the flow-on papermaking method, it is preferable to use pulp with a CSF value of 150 to 400 mL.

[0034] A wide variety of pulp can be used as pulp. Examples of pulp include coniferous trees, broad-leaved trees, Manila hemp, Mitsumata, Kozo, Gampi, Sarago, Mulberry, Straw, Bamboo, Reed, Sabai, Lalan grass, Esparto, Bagasse, Sisal, Kenaf, Linter, Banana, and recycled paper. Examples of coniferous trees include those of the Cupressaceae, Pinaceae, Cypressaceae, and Araucariaceae families, and examples of broad-leaved trees include those of the Ulmaceae, Fagaceae, Myrtaceae, Cerciaceae, Oleaceae, Rutaceae, Betulaceae, Aceraceae, Juglandaceae, Tiliaceae, Araliaceae, Sapotaceae, Celastraceae, Apocynaceae, Verbenaceae, Magnoliaceae, and Malvaceae families. These pulps may be bleached or unbleached. The pulp may be used alone or in combination of two or more types.

[0035] Such pulps are commercially available, and an example of a commercially available product is cellofiber manufactured by Paltec Co., Ltd.

[0036] <Other ingredients> The molded plate may optionally further contain one or more substances selected from the group consisting of mica, fly ash, and silica fume. When the molded sheet contains mica and / or silica fume, the content or total content is preferably 2 to 14% by mass, more preferably 2 to 10% by mass, more preferably 3 to 10% by mass, and even more preferably 4 to 8% by mass, relative to the total mass of the molded sheet. In this embodiment, it is preferable that the formulation replaces a portion of the cement with mica and / or silica fume. When the molded sheet contains mica, it is easier to achieve a smaller dimensional change rate and improved flame retardancy (i.e., a reduction in total calorific value). When the molded sheet contains silica fume, it is easier to achieve higher bending strength in the molded sheet. This is thought to be because silica fume also participates in the pozzolanic reaction, and because the fine particle size of silica fume makes it easier to obtain a dense filling effect in the cement matrix. On the other hand, as the silica fume content increases, the viscosity of the curable composition increases, and the papermaking properties in the circular mesh process tend to decrease. By setting the silica fume content to preferably 10% by mass or less relative to the total mass of the molded sheet, it is easier to ensure good papermaking properties in the circular mesh process. If the molded sheet contains fly ash, its content is preferably 10 to 30% by mass, more preferably 15 to 25% by mass, relative to the total mass of the molded sheet. In this embodiment, from the viewpoint of effective utilization of recycled raw materials and / or cost reduction, it is preferable that the formulation replaces some of the substances that do not participate in the pozzolanic reaction with fly ash. Furthermore, when the molded sheet contains fly ash, the fly ash also participates in the pozzolanic reaction, which makes it easier for the molded sheet to exhibit better long-term age strength and higher bending strength.

[0037] From the viewpoint of easily obtaining the desired dimensional change rate and bending strength, mica is preferably of a quality that passes the JIS test sieve test with a mesh size of 30 to 200, more preferably with a mesh size of 40 to 120, and particularly preferably with a mesh size of 60 to 80. As fly ash, you may use Type I (Blaine specific surface area of ​​5000 or more), Type II (Blaine specific surface area of ​​2500 or more), Type III (Blaine specific surface area of ​​2500 or more), or Type IV (Blaine specific surface area of ​​1500 or more) as specified in JIS A6201:2015. As silica fume, silica fume specified in JIS A 6207:2016 may be used. Generally, the average particle size of silica fume is 0.1 to 0.5 μm.

[0038] Mica, fly ash, and silica fume are commercially available. Examples of commercially available mica include mica manufactured by Tomoe Engineering Co., Ltd., examples of commercially available fly ash include Finash, Shikoku Electric Power Business Co., Ltd., and Ecoash, and an example of commercially available silica fume is EFACO, manufactured by Tomoe Engineering Co., Ltd.

[0039] <Optional additives and auxiliaries> The molded plate may further contain one or more optional additives and auxiliary agents. In the manufacturing method of the molded plate by the papermaking method described later, it is preferable to add an aqueous solution of an anionic polymer flocculant with a concentration of 0.5 to 2 g / L to the curable composition in order to increase the yield. In this case, it is preferable to add the anionic polymer flocculant so that the concentration of the anionic polymer flocculant in the curable composition is preferably 50 to 250 ppm / solids, more preferably 75 to 175 ppm / solids, and even more preferably 100 to 150 ppm / solids. An example of anionic polymer flocculant is IK Floc T210 manufactured by Nippon Giken Co., Ltd.

[0040] <Method for manufacturing molded sheets> The molded plates of the present invention are preferably manufactured by a papermaking method. A papermaking method is a method of forming a sheet-like material obtained by filtering a slurry (a hardening composition) obtained by turbiding a solid such as cement in an aqueous medium through a wire mesh. Papermaking methods include the cylinder mesh papermaking method (Hatchek method) or the long mesh papermaking method, in which the filtered thin sheet-like material is sequentially stacked on a making roll until a molded plate is obtained, and the flow-on papermaking method, in which a concentrated slurry is supplied onto felt and sequentially stacked on a making roll in one or several passes until a molded plate is obtained until a molded plate is obtained. From the viewpoint of easily obtaining a uniform molded plate and easily adjusting the thickness, the cylinder mesh papermaking method or the long mesh papermaking method is preferred, and from the viewpoint of mass production, the cylinder mesh papermaking method is more preferred.

[0041] The manufacturing method using the circular mesh papermaking method is usually, A step of preparing a curable composition by mixing substances not involved in the pozzolanic reaction, cement, synthetic fibers, pulp, and water, and optionally other components, optional additives and auxiliaries as described above. The process involves forming the resulting curable composition using a circular mesh to obtain a paper sheet, and then laminating the paper sheets until a desired thickness is achieved. A process of applying pressure to laminated papermaking sheets to extract liquid, and The process of curing the sheet after the liquid has been extracted. Includes.

[0042] The method for preparing the curable composition is not particularly limited. The curable composition can be prepared by mixing the components using known or conventional mixing means such as a mixer. Examples of mixing means include mixers with high stirring performance, such as vertical mixers, blade mixers, screw mixers, cone mixers, and agitator mixers used in papermaking.

[0043] The mixing order of each component is not particularly limited, but from the viewpoint of easily obtaining a curable composition in which the solid components are uniformly dispersed, it is preferable to add pulp to water and stir, then add substances that do not participate in the pozzolanic reaction, cement, and optionally other components, additives, and auxiliary agents in any order and stir, and finally add synthetic fibers.

[0044] The solid content concentration of the curable composition is typically 55-6% by mass, preferably 40-8% by mass, and more preferably 25-10% by mass.

[0045] With respect to the total mass of solids in the curable composition, that is, with respect to the total mass of components other than water in the curable composition, the amount of substances not involved in the pozzolanic reaction is 35-70% by mass (preferably 40-67.5% by mass, more preferably 45-65% by mass), the amount of cement is 20-61.5% by mass (preferably 25-60.5% by mass, more preferably 30-59.5% by mass), the amount of synthetic fibers is 1-3% by mass (preferably 1-2% by mass, more preferably 1-1.5% by mass), and the amount of pulp is 2.5-7% by mass (preferably 2.5-6% by mass, more preferably Preferably, the amount of saturates is 3-5% by mass, the amount of mica is 0-10% by mass (e.g., 2-10% by mass, 4-8% by mass), the amount of fly ash is 0-30% by mass (e.g., 10-30% by mass, 15-25% by mass), the amount of silica fume is 0-14% by mass (e.g., 2-14% by mass, 0-10% by mass, 2-10% by mass, 3-10% by mass, 4-8% by mass), and the amount of any additives and auxiliary agents is 0-3% by mass (for aqueous solutions of anionic polymer flocculants, for example, 50-250 ppm, 75-175 ppm, 100-150 ppm).

[0046] Next, the curable composition is introduced into the feed tank of the wet papermaking machine, and the solid content concentration of the curable composition is usually adjusted to about 10 to 1% by mass (preferably 8 to 3% by mass) using process circulating water. The curable composition supplied from the feed tank to the vat is formed onto the surface of the circular mesh by the rotation of the circular mesh under internal negative pressure inside the vat, becoming a papermaking sheet, which is then transported to the making roll. At the making roll, the papermaking sheets are stacked to the desired thickness, and the stacked papermaking sheets are cut to a predetermined length.

[0047] In one preferred embodiment, the yield rate in the papermaking process is preferably 85% or higher, more preferably 90% or higher. When the yield rate is above the lower limit, it is easier to obtain higher bending strength, higher interlaminar adhesion strength, and / or lower dimensional change. The yield rate can be adjusted to above the lower limit by adjusting the Blaine specific surface area of ​​substances not involved in the pozzolanic reaction, adjusting the degree of beating of the beaten pulp, and / or selecting the mesh size of the orb mesh. From the viewpoint of easily balancing yield rate and productivity, the mesh size of the orb mesh is preferably 45 to 55 meshes per inch. The yield rate in the papermaking process can be determined by the method described in the examples below.

[0048] As described above, the molded board of the present invention comprises 35-70% by mass of a substance not involved in the pozzolanic reaction, 20-61.5% by mass of cement, 1-3% by mass of synthetic fiber, and 2.5-7% by mass of pulp. If the molded board can be manufactured by a papermaking method so that the proportions of the components contained in the curable composition do not change, the proportions of each component in the curable composition may be used as the proportions of each component in the molded board. Such a case is, for example, when the yield rate in the papermaking process is preferably 85% or more (more preferably 90% or more). In this case, the molded board of the present invention is a porous molded board based on a curable composition comprising 35-70% by mass of a substance not involved in the pozzolanic reaction, 20-61.5% by mass of cement, 1-3% by mass of synthetic fiber, and 2.5-7% by mass of pulp, wherein the ratio (B) / (A) of the pore volume in the range of 6-560 nm to the pore volume in the range of 6-9100 nm (A) in the pore size distribution of the molded board determined by the mercury intrusion method is 1.70-6.0. The curable composition may optionally further contain other components (one or more substances selected from the group consisting of mica, fly ash, and silica fume) in the same proportions as the other components in the molded board described above, and may further contain any additives and auxiliary agents in the proportions described above.

[0049] The number of laminated paper sheets depends on the solid content concentration of the curable composition and the thickness of the molded plate produced, but is typically 12 to 18 sheets when the thickness of the molded plate is about 6 mm.

[0050] Next, the liquid is extracted by applying it to the cut sheet with a press. The pressure applied by the press is preferably 2 to 30 MPa, more preferably 7 to 27 MPa, and particularly preferably 15 to 25 MPa. The time for which the pressure is applied is usually 10 to 60 minutes, preferably 15 to 50 minutes, and more preferably 20 to 40 minutes. When the pressure and the time for which the pressure is applied are within the above ranges, it is easy to obtain the desired pore volume ratio (B) / (A) in the molded sheet, and as a result, it is easy to obtain high bending strength and low dimensional stability.

[0051] Next, the sheets from which the liquid has been extracted are covered for protection. Hardening progresses through curing. Hardening is due to the hydration reaction (setting reaction) of the cement components, but if the moisture in the sheet evaporates, the hydration reaction of the cement components is inhibited, and hardening may not progress. Therefore, as primary curing, it is preferable to perform curing in a high-humidity atmosphere in which the moisture in the sheet does not evaporate, that is, in an atmosphere where the relative humidity is preferably 30-100%, more preferably 50-100%, even more preferably 65-100%, even more preferably 80-100%, and particularly preferably 90-100% (for example 100%). As secondary curing, it is preferable to perform curing in a high-humidity atmosphere (preferably 30-100%, more preferably 40-90%, even more preferably 50-80%) by placing the sheet in a container or bag that does not allow moisture to pass through, or by sandwiching the sheet between plastic plates, plastic films (polyethylene sheets, etc.) or metal plates, thereby making it more difficult for the moisture in the sheet to evaporate.

[0052] The curing temperature is not particularly limited. The primary curing temperature is, for example, 10 to 90°C, preferably 30 to 80°C, and more preferably 40 to 80°C. The curing temperature may be changed midway through the process within the aforementioned temperature range. The secondary curing temperature is, for example, 10 to 70°C, preferably 20 to 50°C. The primary curing time depends on the composition of the curable composition and the curing temperature, but is usually 6 to 48 hours, preferably 8 to 36 hours, and more preferably 12 to 24 hours. The secondary curing time is usually 1 to 14 days.

[0053] Additionally, underwater curing may be performed as a secondary curing method. In this case, the water temperature is typically 10-30°C, and the curing time is 8 hours to 13 days. After underwater curing at a water temperature of 10-30°C for 4 to 24 hours, the secondary curing described in the previous paragraph may be performed for 2 to 13 days.

[0054] After secondary curing and drying, a molded board is obtained. The drying method is not particularly limited as long as a uniformly dried molded plate is obtained. Typically, the equilibrium moisture content of a molded plate (for example, the moisture content reached when the molded plate is stored in a well-ventilated room for 7 days or more) is approximately 6% to 10% by mass, so it is dried to a moisture content similar to the equilibrium moisture content. The moisture content and equilibrium moisture content of the molded plate can be measured simply using a Kett moisture meter. Alternatively, after weighing the dried molded plate (W1), the molded plate is dried in an air dryer with a stirrer at 105°C until a constant weight is reached, and then weighed again (W2), and the following formula is used: {(W1-W2) / W2}×100 It can also be calculated using this method.

[0055] The molded plate obtained after drying has the above ratio (B) / (A) of 1.70 to 6.0. Furthermore, all embodiments and preferred embodiments described with respect to the molded plate of the present invention can be considered as embodiments and preferred embodiments relating to the molded plate obtained after drying.

[0056] The thickness of the molded board of the present invention depends on its application, but is, for example, 3 to 30 mm. When the molded board is used as a wall material, for example, the thickness of the molded board is preferably 4 mm or more and 20 mm or less, and when it is used as a floor material, the thickness of the molded board is preferably 8 mm or more and 30 mm or less. Furthermore, there is no particular upper limit to the thickness of the molded board, but up to about 15 mm is suitable for the cylinder mesh papermaking method, and up to about 50 mm is suitable for the long mesh papermaking method. The thickness of the molded board can be appropriately determined by adjusting the number of laminated papermaking sheets and / or the thickness of the squeezed sheets. The thickness of the molded board can be measured by a general method, for example, by measuring the thickness at multiple points using a digital caliper and calculating the average value.

[0057] The length and width dimensions of the molded sheet of the present invention depend on the dimensions of the papermaking machine and press machine, and may be, for example, 3 x 6 feet (910 mm x 1820 mm), 4 x 8 feet (1210 mm x 2440 mm), or 4 x 10 feet (1210 mm x 3030 mm). Of course, smaller molded sheets of desired dimensions can also be cut from these larger molded sheets.

[0058] The bulk density of the molded board of the present invention, measured in accordance with JIS A 5430:2018, is, for example, 1.45 to 1.8 g / cm³. 3 Preferably 1.50 to 1.75 g / cm³ 3 More preferably 1.55 to 1.75 g / cm³ 3 Therefore, when the bulk density is within the above range, it is easier to obtain the desired dimensional change rate, bending strength, interlaminar adhesion strength, and / or flame retardancy. The bulk density can be adjusted within the above range by the type of the four components, the mixing ratio of the four components, the press pressure, and / or the press time.

[0059] The dry bending strength of the molded sheet of the present invention, measured in accordance with JIS A 1408:2017, is preferably 10 N / mm². 2 More preferably 15 N / mm 2 More preferably 20 N / mm 2That concludes the explanation. The bending strength in dry state can be adjusted to be above the lower limit by, for example, adjusting the Blaine specific surface area of ​​the material not involved in the pozzolanic reaction, the mixing ratio of the four components, and the press pressure and / or press time. There is no particular upper limit to the bending strength in dry state, but it is usually 50 N / mm². 2 The following applies: The bending strength of the molded sheet of the present invention when water is absorbed, as measured in accordance with JIS A 1408:2017, is preferably 5 N / mm². 2 More preferably 10 N / mm 2 More preferably 15 N / mm 2 That concludes the explanation. The bending strength during water absorption can be adjusted to be above the lower limit by, for example, adjusting the Blaine specific surface area of ​​the substance not involved in the pozzolanic reaction, the mixing ratio of the four components, and the press pressure and / or press time. There is no particular upper limit to the bending strength during water absorption, but it is usually 35 N / mm². 2 The following applies:

[0060] The dimensional change rate (length change rate) of the molded sheet of the present invention, measured in accordance with JIS A 5430:2018, is preferably 0.150% or less, more preferably 0.130% or less, and particularly preferably 0.100% or less. The dimensional change rate can be adjusted to below the upper limit by, for example, adjusting the Blaine specific surface area of ​​the substance not involved in the pozzolanic reaction, the mixing ratio of the four components, and the press pressure and / or press time.

[0061] The inventors of the present invention have found that the molded sheet of the present invention has a low water absorption rate. A low water absorption rate is preferable because it makes it less likely for the dimensions of the molded sheet to fluctuate depending on the atmosphere in which it is used (e.g., season, region, and / or usage environment). It is also preferable because it improves the bending strength of the molded sheet when it absorbs water. The water absorption rate of the molded plate in this invention, as measured in accordance with JIS A 5430:2018, is preferably 28% or less, more preferably 26% or less, even more preferably 24% or less, even more preferably 22% or less, and particularly preferably 20% or less. The lower limit of the water absorption rate is not limited, but is preferably 15% or more. The water absorption rate can be adjusted to be above the lower limit and below the upper limit by, for example, adjusting the proportion of pulp, adjusting the Blaine specific surface area of ​​substances not involved in the pozzolanic reaction, and by the press pressure and / or press time.

[0062] The total heat generated by the molded board, as measured in accordance with the heat generation test of JIS A 5430:2018, is preferably 8.0 MJ / m². 2 More preferably, 7.0 MJ / m 2 More preferably, 6.0 MJ / m 2 The following applies: If the total heat generation is below the upper limit, the flame retardancy of the molded plate is higher. The lower limit of the total heat generation is not limited to 4.0 MJ / m³. 2 That's all. The total heat generation can be adjusted to be below the upper limit by, for example, reducing the proportion of organic matter (pulp and synthetic organic fibers) in the molded board and / or adjusting the ratio (B) / (A).

[0063] The dry impact strength (Type 1 test piece, no notches) of the molded sheet, measured in accordance with JIS K 7111-1:2012 "Method for determining the Charpy impact properties of plastics," is preferably 1.5 kJ / m². 2 More preferably 1.8 kJ / m 2 More preferably 2.1 kJ / m 2 That concludes the explanation. The impact strength during drying can be adjusted to be above the lower limit by, for example, the press pressure and / or press time. There is no particular upper limit to the impact strength during drying, but it is usually 7 kJ / m 2 The following applies: The impact strength (Type 1 test piece, no notches) of molded sheets under water absorption, measured in accordance with JIS K 7111-1:2012 "Method for determining the Charpy impact properties of plastics," is preferably 2 kJ / m². 2 More preferably 2.5 kJ / m³ 2 More preferably, 3.0 kJ / m 2 That concludes the explanation. The impact strength during water absorption can be adjusted to be above the lower limit by, for example, the press pressure and / or press time. There is no particular upper limit to the impact strength during water absorption, but it is usually 10 kJ / m2 The following applies:

[0064] The interlayer adhesion strength of the molded plate during drying is preferably 1.5 N / mm². 2 More preferably 2.0 N / mm 2 More preferably 2.5 N / mm 2 The above is a description. It is preferable that the interlayer adhesion strength during drying is equal to or greater than the lower limit, as this prevents delamination during use. The interlayer adhesion strength during drying can be adjusted to be equal to or greater than the lower limit by, for example, adjusting the Blaine specific surface area of ​​the material not involved in the pozzolanic reaction, the press pressure and / or the press time. There is no particular upper limit to the interlayer adhesion strength during drying, but it is usually 6 N / mm². 2 The following applies: The interlayer adhesion strength of the molded plate when water is absorbed is preferably 0.2 N / mm². 2 More preferably 0.3 N / mm 2 More preferably 0.5 N / mm 2 That concludes the explanation. It is preferable that the interlayer adhesion strength during water absorption is equal to or greater than the lower limit, as this prevents delamination during use. The interlayer adhesion strength during water absorption can be adjusted to be equal to or greater than the lower limit by, for example, the press pressure and / or press time. There is no particular upper limit to the interlayer adhesion strength during water absorption, but it is usually 3 N / mm². 2 The following applies: The interlayer adhesion strength of the molded plate during drying or water absorption can be measured by the method described in the examples below. [Examples]

[0065] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by such examples. The physical properties in the examples and comparative examples were measured or evaluated according to the following procedure.

[0066] [Pore volume] Two approximately 1 cm square test pieces were cut from the molded plate to be measured, dried at 105°C ± 5°C for more than 12 hours, and then placed in a desiccator humidified with silica gel and left until the temperature reached 20°C ± 1.5°C. The pore size distribution of these test pieces was measured using the mercury intrusion method with a mercury intrusion pore volume analyzer (MicroActive AutoPore V 9600, Micromertics). From the log differential pore volume obtained from the obtained pore size distribution, the pore volume (A) in the range of 660 to 9100 nm and the pore volume (B) in the range of 6 to 560 nm were determined for each test piece. The ratio of pore volume (B) to pore volume (A) was calculated for each test piece using the following formula, and the average value of these ratios was adopted as the pore volume ratio (B) / (A) of the molded plate. Pore ​​volume ratio (B) / (A) = {Pore volume in the range of 6 to 560 nm (B)} / {Pore volume in the range of 660 to 9100 nm (A)}

[0067] [thickness] Using a digital caliper, the thickness of the molded plate was measured at six points, and the average value of these measurements was used as the thickness of the molded plate.

[0068] [bulk density] The bulk density was measured in accordance with JIS A 5430:2018. Specifically, four strip-shaped test pieces, approximately 180 mm in length and 50 mm in width, were cut from the molded board to be measured. These test pieces were then placed in an air dryer with a stirrer and dried at 105°C ± 5°C for 24 hours. After that, the removed test pieces were placed in a desiccator humidified with silica gel and left until the temperature reached 20 ± 1.5°C. The mass and volume of each test piece were then measured to determine the bulk density. The average value of these values ​​was taken as the bulk density of the molded board.

[0069] [Bending strength] Eight strip-shaped test pieces, approximately 180 mm long and 50 mm wide, were cut from the molded plate to be measured. To measure the flexural strength during drying, four test specimens were first dried for 72 hours in an air dryer with a stirrer set to 40°C. Next, the removed specimens were placed in a desiccator humidified with silica gel and left until the temperature reached 20±1.5°C. The flexural strength of each specimen was measured in accordance with JIS A 1408:2017, and the average value was adopted as the flexural strength of the molded sheet during drying. To measure the flexural strength when water is absorbed, four test specimens were first immersed in 20°C water for 72 hours. Then, the test specimens were removed, the water adhering to the surface was wiped off, and the flexural strength of each specimen was immediately measured in accordance with JIS A 1408:2017. The average value of these measurements was adopted as the flexural strength of the molded plate when water is absorbed. The bending strength in both dry and wet conditions was measured using a Shimadzu Autograph "AG50kNX" with a central loading method, under conditions of a bending span of 14.6 cm and a test speed (loading head speed) of 20 mm / min.

[0070] [Impact strength] Six Type 1 test specimens, conforming to JIS K 7111-1:2012, were cut from the molded plate to be measured. To measure the impact strength during drying, three test specimens were first dried for 72 hours in an air dryer with a stirrer set to 40°C. Next, the removed specimens were placed in a desiccator humidified with silica gel and left until the temperature reached 20±1.5°C. The impact strength (without notches) of each specimen was measured in accordance with JIS K 7111-1:2012, and the average value was adopted as the impact strength of the molded board during drying. To measure the impact strength during water absorption, three test specimens were first immersed in 20°C water for 72 hours. Then, the test specimens were removed, the water adhering to the surface was wiped off, and immediately the impact strength (without notches) of each test specimen was measured in accordance with JIS K 7111-1:2012. The average value of these measurements was adopted as the impact strength of the molded plate during water absorption. The impact strength in both dry and wet conditions was measured using a Charpy (digital) impact tester, model DG-CB, manufactured by Toyo Seiki Seisakusho Co., Ltd.

[0071] [Rate of dimensional change] The dimensional change rate (length change rate) of the molded plate was measured in accordance with JIS A 5430:2018. Specifically, three strip-shaped test pieces, approximately 160 mm in length and 50 mm in width, were cut from the molded plate to be measured. These test pieces were then placed in a dryer and the temperature inside the dryer was maintained at 60°C ± 3°C for 24 hours. After that, the test pieces were removed and placed in a desiccator humidified with silica gel and left until the temperature reached 20°C ± 1.5°C. Next, milky glass was attached to each test piece, and markings were engraved so that the distance between the markings was approximately 140 mm. The length between the markings was measured using a comparator with an accuracy of 1 / 500 mm, and this length was defined as L1 (mm). Subsequently, the test pieces were raised so that the longitudinal direction was horizontal, and the upper end of the test piece was immersed in water at 20°C ± 1.5°C so that it was approximately 30 mm below the water surface. After 24 hours, the test specimens were removed from the water, the water adhering to the surface was wiped off, and the length between the gauge marks was measured again, which was defined as L2 (mm). The dimensional change rate (%) due to water absorption was calculated for each test specimen using the following formula, and the average value of these values ​​was adopted as the dimensional change rate of the molded plate. Dimensional change rate due to water absorption = {(L2-L1) / L1} × 100

[0072] [Water absorption rate] The water absorption rate of the molded board was measured in accordance with JIS A 5430:2018. Specifically, four strip-shaped test pieces, approximately 180 mm in length and 50 mm in width, were cut from the molded board to be measured. The test pieces were then immersed in water at 20°C ± 1.5°C. After 24 hours, the test pieces were removed, the water adhering to the surface was wiped off, and the mass of each test piece (mass W3 of the test piece when water was absorbed) was immediately measured. Next, these test pieces were placed in a dryer with a stirrer adjusted to 105°C ± 5°C and dried for 24 hours. After drying, they were removed and placed in a desiccator humidified with silica gel, and left until the room temperature reached 20°C ± 1.5°C. After that, the mass of each test piece (mass W0 of the test piece when dry) was measured. The water absorption rate (%) of each test piece was calculated using the following formula, and the average value was adopted as the water absorption rate of the molded board. Water absorption rate={(W3-W0) / W0}×100

[0073] [Interlayer adhesion strength] Eight test pieces, each approximately 40mm x 40mm in size, were cut from the molded plate to be measured. To measure the interlayer adhesion strength during drying, four air-dried test specimens were first bonded to the front and back surfaces of each specimen using an epoxy resin adhesive. The epoxy resin adhesive was allowed to cure at room temperature for at least 24 hours to achieve sufficient adhesion strength. After that, the specimens were dried for 72 hours in an air dryer with a stirrer set to 40°C. For each specimen, a Shimadzu Autograph AG5000-B was used to pull the bonded surface perpendicular to it at a speed of 0.5 mm / min, and the maximum tensile load was recorded. The interlayer adhesion strength of each specimen was calculated by dividing the maximum tensile load by the area of ​​the specimen, and the average value of these values ​​was adopted as the interlayer adhesion strength of the molded plate during drying. To measure the interlayer adhesion strength when water is absorbed, first, a steel jig measuring approximately 40 mm x 40 mm was bonded to the front and back surfaces of four air-dried test specimens using an epoxy resin adhesive, and the epoxy resin adhesive was allowed to cure by leaving it at room temperature for more than 24 hours. Next, the test specimens were immersed in water at 20°C for 72 hours. After removing the test specimens and wiping off the water adhering to the surface, the specimens were immediately pulled perpendicular to the bonded surface at a speed of 0.5 mm / min using a Shimadzu Autograph AG5000-B, and the maximum tensile load at that time was read. The interlayer adhesion strength of each test specimen was calculated by dividing the maximum tensile load by the area of ​​the test specimen, and the average value of these values ​​was adopted as the interlayer adhesion strength of the molded plate when water is absorbed.

[0074] [Yield rate in the papermaking process] The yield rate in the papermaking process (the process of forming the slurry using a circular mesh) was determined for each example and comparative example. Specifically, the slurry placed in the circular mesh was scooped out and its mass (A1) was measured. The solid content was filtered out using a filtration device (Nutche and suction bottle), dried in a 105°C dryer for 12 hours or more until the dry mass became constant, and the mass of the solid content (B1) was measured. The concentration C1 of the slurry placed in the circular mesh was determined using the following formula. Concentration C1=(B1 / A1)×100 Similarly, the slurry after passing through the circular mesh was collected, and its concentration C2 was determined using the following formula. Concentration C2=(B2 / A2)×100 Here, A2 is the mass of the slurry after it has passed through the circular mesh, and B2 is the mass of its solid content. The yield rate in the papermaking process was calculated using the following formula. Yield rate in the papermaking process (%) = {(C1-C2) / C1} × 100

[0075] [Total heat generation] The total heat generation was determined using the heat generation test specified in JIS A 5430:2018. Specifically, two 99±1mm square test pieces were cut from the molded board to be measured, and after being held at a temperature of 23℃±2℃ and a relative humidity of 50±5% until a constant mass was reached, the heat generation test was performed. The heating time was 20 minutes. The average of the total heat generation of each test piece was adopted as the total heat generation of the molded board.

[0076] The examples and comparative examples used the fibers shown in Table 1 below. [Table 1]

[0077] [Example 1] Pulp (NBKP, Cellofiber manufactured by Paltex Co., Ltd., CSF value: 115 mL) was dispersed in water. Heavy calcium carbonate (Blaine specific surface area: 4000 cm²) was added to the resulting dispersion. 2 ( / g) and ordinary Portland cement (manufactured by Taiheiyo Cement Corporation: ordinary Portland cement) were added and mixed. Polyvinyl alcohol fiber 1 (labeled "PVA1" in Table 2) was added to the resulting mixture and mixed further. The proportions of each component are as shown in Table 2, and a curable composition with a solid content of 16% by mass was obtained. The obtained curable composition was transferred to the feed tank of a quantitative supply device and supplied from the feed tank to the circular mesh. The solid content concentration of the curable composition was adjusted to 4% by mass using process circulating water, and papermaking was performed using a mini-Hatchech machine. Next, 15 sheets of the papermaking material obtained in the cylinder mesh process were stacked on a making roll, and the stacked papermaking material was pressed for 20 minutes while applying a pressure of 21.6 MPa to extract the liquid. The extracted sheets were cured for 24 hours in a constant temperature and humidity curing apparatus under conditions of 50°C and saturated humidity (RH98%), and then wrapped in a wrap sheet and cured for 13 days in an environment of 20°C and 60% humidity (a total curing period of 14 days). The sheets, with the wrap sheet removed, were dried for 2 hours in a roll dryer type dryer set to 120°C to obtain a molded board. Various measurements and evaluations were performed on the obtained molded plates. The results are shown in Table 2. In Table 2, two values ​​for bending strength, impact strength, and interlaminar adhesion strength are listed for each example; the upper row shows the value when dry, and the lower row shows the value when water is absorbed.

[0078] [Examples 2-17 and Comparative Examples 1-3] A molded plate was obtained in the same manner as in Example 1, except that each component was used in the proportions shown in Table 2. Various measurements and evaluations were then performed on the obtained molded plate. The results are shown in Tables 2 and 3. In Example 10, calcium carbonate was used, with a Blaine specific surface area of ​​2500 cm². 2 Heavy calcium carbonate and Blaine specific surface area of ​​6200 cm² / g 2 Heavy calcium carbonate was used in a mass ratio of 50:50 per g. Therefore, the Blaine specific surface area of ​​calcium carbonate in Example 10 was 4500 cm². 2 The calculation is as follows: / g (=2500 × 0.5 + 6500 × 0.5). In the examples where fly ash or silica fume was added, the fly ash or silica fume was added at the same time as the ordinary Portland cement.

[0079] [Example 18] Except for using PVA2 instead of PVA1 and changing the pressing pressure from 21.6 MPa to 7.85 MPa, a molded plate was obtained in the same manner as in Example 1, and various measurements and evaluations were performed on the obtained molded plate. The results are shown in Table 2.

[0080] [Table 2]

[0081] [Table 3]

[0082] As shown in Table 2, molded boards comprising a specific proportion of non-participating material in the pozzolanic reaction, cement, synthetic fibers, and pulp, and having a specific pore volume ratio (B) / (A), exhibited high flexural strength and low dimensional change rate. On the other hand, Table 3 shows that Comparative Example 1, in which the molded sheet does not have a specific pore volume ratio (B) / (A), exhibits lower bending strength and a higher dimensional change rate than the corresponding examples (Examples 1-4). Furthermore, Comparative Example 1 also shows lower interlayer adhesion strength and a lower yield rate in the papermaking process. Comparative Example 2, in which the molded sheet does not contain each component in a specific proportion, exhibits lower bending strength than the corresponding examples (Examples 1 and 5). Furthermore, Comparative Example 2 also shows lower interlayer adhesion strength. Comparative Example 3, in which the molded sheet does not contain each component in a specific proportion and does not have a specific pore volume ratio (B) / (A), exhibits lower bending strength and a higher dimensional change rate than the corresponding examples (Examples 1 and 5). Furthermore, Comparative Example 3 also shows lower interlayer adhesion strength and a higher total heat generation.

[0083] Furthermore, the effect of the proportion of silica fume, an optional component, on the papermaking properties in the cylinder mesh process during the manufacturing of molded sheets was visually evaluated using the following evaluation criteria. A: No dripping of the curable composition from the circular mesh during the papermaking process. B: When forming the curable composition, dripping of the curable composition from the circular mesh occurs at one point per 30 cm of circular mesh width. C: When forming the curable composition, dripping of the curable composition from the circular mesh occurs at two or more points per 30 cm of circular mesh width. [Table 4] [Industrial applicability]

[0084] The molded board of the present invention has high bending strength and a low dimensional change rate. Such a molded board of the present invention can be suitably used as a building material (e.g., ceiling material, interior material, exterior material, floor material) or civil engineering material.

Claims

1. A porous molded board comprising 35 to 70% by mass of a substance not involved in the pozzolanic reaction, 20 to 61.5% by mass of cement, 1 to 3% by mass of synthetic fiber, and 2.5 to 7% by mass of pulp, The substance not involved in the pozzolanic reaction is one or more substances selected from the group consisting of calcium carbonate, silica powder, and talc, having a Blaine specific surface area of ​​3000 to 12000 cm² / g. The aforementioned synthetic fiber has an average fiber diameter of 5 μm or more and 50 μm or less, and an aspect ratio of 150 or more and 1000 or less. A molded plate in which the pore size distribution, determined by the mercury intrusion method, shows that the ratio (B) / (A) of the pore volume in the range of 6 to 560 nm to the pore volume in the range of 6 to 9100 nm (A) is 1.70 to 6.

0.

2. The molded plate according to claim 1, wherein the substance not involved in the pozzolanic reaction is calcium carbonate.

3. The molded plate according to claim 2, wherein the calcium carbonate is heavy calcium carbonate.

4. The molded plate according to claim 1, further comprising one or more substances selected from the group consisting of mica, fly ash, and silica fume.

5. The molded board according to claim 1, wherein the total content of synthetic fibers and pulp is 7% by mass or less of the total mass of the molded board.

6. The molded plate according to claim 1, wherein the average fiber diameter of the synthetic fibers is 40 μm or less.

7. The molded plate according to claim 6, wherein the average fiber diameter of the synthetic fibers is 6 μm or more and 30 μm or less.

8. The molded plate according to claim 1, wherein the aspect ratio of the synthetic fiber is 175 or more and 900 or less.

9. The molded plate according to claim 1, wherein the synthetic fiber is at least one selected from the group consisting of polyvinyl alcohol-based fibers, polyethylene fibers, polypropylene fibers, acrylic fibers, aramid fibers, and nylon fibers.

10. The molded plate according to claim 1, wherein the water absorption rate measured in accordance with JIS A 5430:2018 is 15% or more and 28% or less.

11. The total heat generation measured in accordance with the heat generation test of JIS A 5430:2018 was 8.0 MJ / m³. ２ The molded plate according to claim 1, which is as follows:

12. The bulk density measured in accordance with JIS A 5430:2018 was 1.50 g / cm³. ３ The molded plate according to claim 1.

13. The bending strength when water is absorbed, measured in accordance with JIS A 1408:2017, is 15 N / mm². ２ The molded plate according to claim 1.

14. The molded plate according to claim 1, wherein the water absorption rate measured in accordance with JIS A 5430:2018 is 26% or less.

15. The molded plate according to claim 1, wherein the pore volume (B) is 2.50 mL / g or less.

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