Gypsum board, interior material, and method for manufacturing gypsum board

Abstract

This gypsum board includes: a gypsum core; board base paper disposed on a first main surface and a second main surface of the gypsum core, the second main surface being located opposite the first main surface; and a coating layer disposed on a surface of the board base paper located on the first main surface of the gypsum core, the surface being opposite a surface facing the gypsum core. The gypsum core contains an antifungal agent having water solubility of 100 ppm or more, and the gypsum core has a waterproof agent content of less than 0.1 pts.mass with respect to 100 pts.mass of gypsum.

Description

Gypsum board, interior materials, and manufacturing method of gypsum board

[0001] The present invention relates to a gypsum board, an interior material, and a method for manufacturing a gypsum board.

[0002] Patent Document 1 discloses a gypsum material having antibacterial and antifungal properties, characterized in that soluble glass that elutes silver or copper ions is mixed into gypsum in the form of powder, beads, or fibers.

[0003] Japanese Patent Application Publication No. 2-302354

[0004] Gypsum boards have traditionally been used as interior wall and ceiling materials.

[0005] In gypsum boards used as wall or ceiling materials, there is a case where a temperature difference occurs between the surface facing the room and the back surface facing the opposite side. As a result, depending on the humidity of the environment in which the gypsum board is installed, condensation may occur on the surface or back surface of the gypsum board, and mold may grow on the gypsum board.

[0006] When mold grows on a gypsum board, depending on the extent of the mold, the gypsum board may need to be replaced from the viewpoint of appearance and hygiene. For this reason, in order to suppress the growth of mold on gypsum boards, gypsum boards in which a material capable of imparting mold resistance to the gypsum board is added to the gypsum core or the like have been studied, as disclosed in, for example, Patent Document 1.

[0007] There was also a demand for gypsum boards with excellent mold resistance.

[0008] Therefore, one object of the present invention is to provide a gypsum board having excellent anti-fungal properties.

[0009] In order to solve the above problems, one aspect of the present invention provides a gypsum board comprising: a gypsum core; board base paper arranged on a first main surface of the gypsum core and a second main surface located opposite the first main surface; and a coating layer arranged on a surface of the board base paper located on the first main surface of the gypsum core opposite to the surface facing the gypsum core, wherein the gypsum core contains a mildew inhibitor having a solubility in water of 100 ppm or more, and the gypsum core contains a waterproofing agent in an amount of less than 0.1 part by mass per 100 parts by mass of gypsum.

[0010] According to one aspect of the present invention, a gypsum board having excellent anti-fungal properties can be provided.

[0011] Fig. 1 is a perspective view of a gypsum board according to one embodiment of the present disclosure. Fig. 2 is a cross-sectional view of a gypsum board according to one embodiment of the present disclosure. Fig. 3 is a cross-sectional view of a gypsum board in which a gypsum core has a recess. Fig. 4 is an explanatory view of an interior material according to one embodiment of the present disclosure.

[0012] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments, and various modifications and substitutions can be made to the following embodiments without departing from the scope of the present invention. [Gypsum Board] Hereinafter, a gypsum board according to one embodiment of the present disclosure (hereinafter referred to as "embodiment") will be described with reference to the drawings.

[0013] It should be noted that all of the drawings are schematic diagrams for explaining the configuration of the gypsum board etc. of this embodiment, and do not accurately depict the sizes etc.

[0014] FIG. 1 shows a perspective view of a gypsum board according to this embodiment, and FIGS. 2 and 3 show cross-sectional views of the gypsum board according to this embodiment. FIG. 3 is an explanatory diagram illustrating a case where the gypsum core of the gypsum board according to this embodiment has a recess on the first main surface. Therefore, the gypsum board according to this embodiment will be described primarily using FIGS. 1 and 2 , with FIG. 3 being used as needed. In FIGS. 1 , 2 , and 3 , the Z axis is the axis along the thickness of the gypsum board and the axis along the stacking direction of the gypsum core, board base paper, and coating layer. The XY plane is a plane perpendicular to the Z axis. (1) Regarding the Structure of the Gypsum Board: As shown in FIGS. 1 and 2 , the gypsum board 10 according to this embodiment has a gypsum core 11, board base paper 12, and coating layer 13. (Gypsum Core) The gypsum core 11 is a hardened gypsum slurry, as will be described later in the gypsum board manufacturing method. The gypsum core 11 can contain gypsum, specifically gypsum dihydrate, various additives, and even a mildew inhibitor. Various additives that can be contained in the gypsum core 11 will be described in the method for manufacturing gypsum board. Also, antifungal agents will be described later.

[0015] As shown in FIG. 3 , the first main surface 11A of the gypsum core 11 of the gypsum board 10 of this embodiment may have a recess 31. When the gypsum board 10 of this embodiment is used as an interior material such as a wall material or ceiling material, the first main surface 11A is the surface facing the interior and is the surface into which screws or the like are driven to secure the gypsum board to the substrate. Therefore, by having the recess 31 on the first main surface 11A of the gypsum core 11, a travertine pattern or a marble-like pattern can be formed on the first main surface 11A of the gypsum board 10. As a result, screws or the like driven on the first main surface 11A of the gypsum board 10 are less noticeable, improving the design. (Board Base Paper) The board base paper 12 can be arranged on the first main surface 11A of the gypsum core 11 and the second main surface 11B located opposite the first main surface 11A. The board base paper 12 arranged on the first main surface 11A may be referred to as the first board base paper 121, and the board base paper 12 arranged on the second main surface 11B may be referred to as the second board base paper 122, etc. In FIG. 1, the first board base paper 121 and the second board base paper 122 are depicted as separate, unconnected components, but this is not limited to this form. The first board base paper 121 and the second board base paper 122 may be a single, continuous piece of board base paper arranged to cover the side surface 11C (see FIG. 2) of the gypsum core 11, or two or more pieces of board base paper may be bonded together with glue or the like. Furthermore, as shown in FIGS. 1 and 2, the first board base paper 121 and the second board base paper 122 may be separate components that are not connected anywhere.

[0016] The first main surface 11A and the second main surface 11B are surfaces that intersect with the thickness direction of the gypsum board 10. When the gypsum board 10 is used as an interior material such as a wall material or a ceiling material, the first main surface 11A and the second main surface 11B are surfaces that become a wall surface or a ceiling surface.

[0017] As described above, the gypsum core 11 can also have a recess 31 on the first main surface 11A. When the gypsum core 11 has the recess 31 on the first main surface 11A, it is preferable that the board base paper 12 is also arranged on the bottom surface 31A and side surfaces 31B of the recess 31 of the gypsum core 11, as shown in Fig. 3. In other words, when the gypsum core 11 has the recess 31, it is preferable that the board base paper 12 also has a recess at a position corresponding to the recess 31 of the gypsum core 11.

[0018] The board base paper 12 is not particularly limited, and various board base papers used in gypsum boards can be used, for example. (Coating Layer) The coating layer 13 can be arranged on the board base paper 12 located on the first main surface 11A of the gypsum core 11, i.e., on the first surface 121A of the first board base paper 121, which is the surface opposite to the second surface 121B, which is the surface facing the gypsum core 11.

[0019] The coating layer 13 may cover the entire first surface 121A of the first board base paper 121, or may cover only a portion of the first surface 121A.

[0020] In addition, the second board base paper 122 located on the second main surface 11B of the gypsum core 11 does not have a coating layer, and the second board base paper 122 can be configured to include the back surface 10B, which is the outer surface of the gypsum board 10.

[0021] It is believed that the gypsum board 10 of this embodiment having the coating layer 13 can prevent the antifungal agent contained in the gypsum core 11 from leaking out to the outside and can increase the concentration of the antifungal agent near the surface 10A of the gypsum board 10. Therefore, it is believed that the gypsum board 10 having the coating layer 13 can improve the antifungal performance of the gypsum board 10.

[0022] The coating layer 13 may contain an antifungal agent. That is, in the gypsum board 10 of the present embodiment, the gypsum core 11 and the coating layer 13 may each contain an antifungal agent.

[0023] The coating layer 13 can be formed, for example, by applying paint to the first surface 121A of the first board base paper 121, and if the coating layer 13 contains an anti-fungal agent, the paint may also contain the anti-fungal agent.

[0024] The paint used to form the coating layer 13 may also contain a resin. When the paint contains an anti-fungal agent, the resin can also fix the anti-fungal agent to the first surface 121A of the first board base paper 121.

[0025] That is, the coating layer 13 may contain a resin. The resin contained in the coating layer 13 may be, for example, one or more types selected from an acrylic resin, an acrylamide resin, a urethane resin, a silicone resin, an epoxy resin, and the like.

[0026] As described above, the gypsum core 11 can also have a recess 31 on the first main surface 11A. When the gypsum core 11 has a recess 31 on the first main surface 11A, the coating layer 13 may or may not be disposed on the bottom surface 31A or the side surface 31B of the recess 31. For example, as shown in Fig. 3, the coating layer 13 can be provided only on the surface of the protrusion 32 disposed between the recesses 31 of the gypsum core 11. In this case, the board base paper 12 is disposed on the surface of the bottom surface 31A or the side surface 31B of the recess 31.

[0027] The thickness T13 of the coating layer 13 is not particularly limited, but the average value of the thickness T13 of the coating layer 13 can be, for example, 0.01 mm or more and 0.3 mm or less.

[0028] By making the average thickness of the coating layer 13 0.01 mm or more, it is possible to sufficiently increase the strength of the coating layer 13. Furthermore, when the coating layer 13 contains an antifungal agent, by making the average thickness of the coating layer 13 0.01 mm or more, the coating layer 13 can contain a sufficient amount of the antifungal agent, and the antifungal performance of the gypsum board 10 can be particularly improved.

[0029] By making the average thickness of the coating layer 13 0.3 mm or less, the coating layer 13 can be easily formed, and the productivity of the gypsum board can be increased.

[0030] The average thickness of the coating layer 13 can be determined by the following procedure.

[0031] The thickness of the gypsum board before and after the coating layer 13 is formed can be measured for each gypsum board according to the thickness measurement method specified in JIS A 6901 (2014) "Gypsum Board Products." Specifically, measurements are taken at six equally spaced locations within 25 mm from the end of the sample and at least 80 mm inside from both sides, and the average of the measurements is calculated to determine the thickness of each gypsum board. Note that if the width of the evaluation area is 606 mm or less, the thickness may be measured at three locations.

[0032] Then, the thickness of the coating layer, i.e., the average thickness of the coating layer, can be calculated using the following formula using the thicknesses of the gypsum boards before and after the formation of the coating layer 13.

[0033] (Thickness of coating layer) = (Thickness of gypsum board after coating layer formation) - (Thickness of gypsum board before coating layer formation) If a coating layer has already been formed, the gypsum board after removing the coating layer may be used for evaluation as the gypsum board before coating layer formation. Also, gypsum boards before and after coating layer formation may be manufactured using other materials and used for evaluation. (2) Regarding antifungal agents The inventors of the present invention have studied gypsum boards with excellent antifungal performance.

[0034] From the viewpoint of improving the antifungal performance of the gypsum board 10, an antifungal agent can be added to the gypsum board 10. When adding an antifungal agent to the gypsum board 10, it is considered to add the antifungal agent to the gypsum core 11. However, among the antifungal agents added to the gypsum core 11, the antifungal agent that mainly contributes to the effect of improving the antifungal performance of the gypsum board is the antifungal agent located on the surface 10A of the gypsum board 10 or in the vicinity thereof. For this reason, when an antifungal agent is added to the gypsum core 11, a large amount of the antifungal agent is also contained inside the gypsum core 11, which has been a problem in that the proportion of the antifungal agent that does not contribute to improving the antifungal performance increases.

[0035] Therefore, the inventors of the present invention conducted further studies. As a result, the gypsum core 11 of the gypsum board 10 of this embodiment can contain a mildewproofing agent. The gypsum core 11 can contain a mildewproofing agent with a solubility in water of 100 ppm or more. According to the studies of the inventors of the present invention, the above-mentioned configuration can improve the mildewproofing performance of the gypsum board 10.

[0036] When the gypsum core 11 contains an antifungal agent having a solubility in water of 100 ppm or more, i.e., a water-soluble antifungal agent, the antifungal agent can be dissolved in the water content of the gypsum slurry used in manufacturing the gypsum core 11. When manufacturing the gypsum core 11, the gypsum slurry is placed between base papers for board and during the molding process, the antifungal agent in the gypsum slurry is absorbed into the base paper for board 12, thereby increasing the concentration of the antifungal agent in the base paper for board 12. Therefore, when the gypsum core 11 contains an antifungal agent having a solubility in water of 100 ppm or more, the antifungal performance on the surface 10A, etc. of the gypsum board 10 can be sufficiently improved without adding the antifungal agent directly to the base paper for board 12.

[0037] The amount of the antifungal agent contained in the gypsum core 11 is not particularly limited and can be selected depending on the required antifungal performance, etc. For example, assuming that all of the gypsum contained in the gypsum core is gypsum dihydrate, the antifungal agent is preferably contained in a mass ratio of 50 ppm to 1000 ppm, more preferably 100 ppm to 500 ppm, relative to the gypsum dihydrate.

[0038] The gypsum core 11 contains an antifungal agent at a mass ratio of 50 ppm or more relative to the gypsum dihydrate, thereby making it possible to produce a gypsum board with particularly excellent antifungal performance.

[0039] The antifungal performance tends to increase as the amount of antifungal agent contained in the gypsum core 11 increases. However, since a content of more than 1000 ppm by mass relative to the gypsum dihydrate results in excessive antifungal performance and high costs, it is preferable that the gypsum core 11 contain the antifungal agent at a mass ratio of 1000 ppm or less relative to the gypsum dihydrate.

[0040] 3 is embossed to form a gypsum board having recesses 31 on the surface 10A, the surface of the first board base paper 121 may not have the coating layer 13 on the bottom surface 31A or side surface 31B of the recesses 31. In a gypsum board having recesses 31, if the coating layer 13 is not provided on the surface of the first board base paper 121 on the bottom surface 31A or side surface 31B of the recesses 31, the first board base paper 121 will be exposed on the bottom surface 31A or side surface 31B of the recesses 31. Therefore, by improving the antifungal performance of the surface 10A of the gypsum board 10, particularly on the surface of the first board base paper 121, it is possible to prevent mold from growing in places where the coating layer 13 is not provided, such as the bottom surface 31A or side surface 31B of the recesses 31.

[0041] Furthermore, for example, when gypsum board 10 is used as a ceiling board, if condensation water forms on the back surface 10B of gypsum board 10, the condensation water will penetrate from the back surface 10B to the front surface 10A of gypsum board 10. As the condensation water penetrates into gypsum board 10, the antifungal agent in the gypsum core dissolves in the condensation water and moves toward the front surface 10A, further increasing the concentration of the antifungal agent on and near the front surface 10A. This improves the antifungal performance on the front surface 10A of gypsum board 10. Even if a gypsum board has a recess 31 on the front surface 10A and no coating layer 13 is provided on the bottom surface 31A or side surface 31B of the recess 31, the antifungal performance of the bottom surface 31A, side surface 31B, etc. of the recess 31 can be further improved by the penetration of condensation water into gypsum board 10.

[0042] As described above, the coating layer 13 may also contain an antifungal agent. By disposing the antifungal agent in the coating layer 13 as well, the occurrence of mold on the surface 10A of the gypsum board 10 can be particularly suppressed.

[0043] The amount of the antifungal agent contained in the coating layer 13 is not particularly limited and can be selected depending on the required antifungal performance, etc. For example, when it is assumed that all of the gypsum contained in the gypsum core 11 is gypsum dihydrate, the antifungal agent contained in the coating layer 13 is preferably contained in a mass ratio of 10 ppm to 1000 ppm, more preferably 20 ppm to 500 ppm, relative to the gypsum dihydrate contained in the gypsum core.

[0044] The coating layer 13 contains an antifungal agent at a mass ratio of 10 ppm or more relative to the gypsum dihydrate contained in the gypsum core 11, thereby making it possible to produce a gypsum board with particularly excellent antifungal performance.

[0045] The greater the amount of antifungal agent contained in the coating layer 13, the higher the antifungal performance tends to be. However, if the amount of the antifungal agent contained in the coating layer 13 is more than 1000 ppm by mass relative to the gypsum dihydrate contained in the gypsum core 11, the antifungal performance will be excessive and the cost will be high. For this reason, the coating layer 13 preferably contains the antifungal agent at a mass ratio of 1000 ppm or less relative to the gypsum dihydrate contained in the gypsum core 11.

[0046] The gypsum core 11 can also contain multiple types of anti-mold agents, so that the gypsum core 11 can contain, for example, an anti-mold agent having a solubility in water of 100 ppm or more, as well as an anti-mold agent having a solubility in water of less than 100 ppm.

[0047] When the coating layer 13 contains an antifungal agent, the antifungal agent contained in the coating layer 13 is not particularly limited, and may contain an antifungal agent having a solubility in water of 100 ppm or more, or may contain an antifungal agent having a solubility in water of less than 100 ppm, as in the gypsum core 11. Furthermore, the coating layer 13 may also contain multiple types of antifungal agents.

[0048] Therefore, the anti-mold agent contained in the coating layer 13 may be, for example, one or more types selected from anti-mold agents having a solubility in water of 100 ppm or more and anti-mold agents having a solubility in water of less than 100 ppm.

[0049] The antifungal agent contained in the gypsum core 11 may be different from or the same as that contained in the coating layer 13. Furthermore, the gypsum core 11 and the coating layer 13 may each contain only one type of antifungal agent, or either or both of the gypsum core 11 and the coating layer 13 may contain two or more types of antifungal agents.

[0050] Therefore, for example, the gypsum core 11 may contain at least one type of antifungal agent different from the antifungal agent contained in the coating layer 13 .

[0051] The antifungal agent added to the gypsum core 11 and the coating layer 13 is mainly disposed near the surface 10A of the gypsum board 10, and contributes to improving the antifungal performance on the surface 10A of the gypsum board 10. However, since the materials disposed around the antifungal agent in the coating layer 13 and the gypsum core 11 are different, the suitable antifungal agent may differ.

[0052] Therefore, by having the gypsum core 11 contain at least one type of antifungal agent different from the antifungal agent contained in the coating layer 13, it is possible to particularly optimize the antifungal agents contained in the gypsum core 11 and the coating layer 13 located on the surface 10A of the gypsum board 10. As a result, the antifungal performance of the gypsum board 10 can be improved.

[0053] By containing a mildewproofing agent having a solubility in water of 100 ppm or more in the gypsum core 11, the amount of mildewproofing agent dissolved in the gypsum slurry during the production of the gypsum core 11 can be increased, making it easier to incorporate the mildewproofing agent particularly into the board base paper 12.

[0054] The coating layer 13 may also contain, for example, an antifungal agent having a solubility in water of less than 100 ppm, as described above. By containing an antifungal agent having a solubility in water of less than 100 ppm, the elution of the antifungal agent from the coating layer 13 into the board base paper 12 is suppressed, and the amount of antifungal agent contained in the coating layer 13 can be particularly increased. This allows a particularly large amount of antifungal agent to be located on the surface 10A of the gypsum board 10, thereby particularly improving the antifungal performance of the gypsum board 10.

[0055] The solubility of the antifungal agent in water can be evaluated, for example, by the following procedure.

[0056] For example, an antifungal agent is added to water at 25°C, stirred for 10 to 20 minutes, and then subjected to solid-liquid separation to remove undissolved antifungal agent and extract only the liquid portion. The concentration of the antifungal agent in the liquid portion is then evaluated by mass ratio, which can be used as the solubility of the antifungal agent in water. The water can be water from which impurities have been sufficiently removed, such as distilled water. The concentration of the antifungal agent in the liquid portion can also be evaluated by liquid chromatography or the like.

[0057] Examples of antifungal agents that can be used in the gypsum board of this embodiment include IPBC (3-ido-2-propyl butyl carbamate, solubility: 156 ppm), IMZ (imazalil, solubility: 180 ppm), OIT (2-N-octyl-4-isothiazolin-3-one, solubility: 480 ppm), BCM (2-benzimidazole carbamic acid methyl ester, solubility: 5.6 ppm), OPP (orthophenylphenol, solubility: 700 ppm), TBZ (2-(4-thiazolyl)-benzimidazole, solubility: 30 ppm), (solubility: 15 ppm), ZPT (Zinc Examples of suitable waterproofing agents include one or more selected from the group consisting of methyl methacrylate (MMA), ...

[0058] As described above, for example, when the gypsum board 10 is used as a ceiling board, condensation water may form on the back surface 10B of the gypsum board 10 and penetrate from the back surface 10B to the front surface 10A of the gypsum board 10. When the condensation water penetrates into the gypsum board 10, the anti-fungal agent in the gypsum core 11 dissolves in the condensation water and moves from the back surface 10B to the front surface 10A with the water. Therefore, penetration of the condensation water into the gypsum board 10 further increases the concentration of the anti-fungal agent near the front surface 10A of the gypsum board 10, making it possible to particularly prevent mold from growing on the front surface 10A of the gypsum board 10.

[0059] Furthermore, even when the gypsum board 10 is used as a wall material other than a ceiling board, the same effect can be obtained by condensation water generated on the back surface 10B of the gypsum board 10.

[0060] However, if the gypsum core 11 contains 0.1 parts by mass or more of waterproofing agent per 100 parts by mass of gypsum, condensation water may be less likely to pass through the gypsum core 11, and the anti-fungal agent may be less likely to collect on the surface side of the gypsum board 10. For this reason, as described above, it is preferable that the content of waterproofing agent in the gypsum core 11 is sufficiently reduced, preferably less than 0.1 parts by mass per 100 parts by mass of gypsum, and it is particularly preferable that the gypsum core 11 does not contain any waterproofing agent, i.e., 0. (4) Chamfering The gypsum board 10 of this embodiment may be chamfered around the periphery of the surface 10A, i.e., the edges 131, 132, 133, and 134.

[0061] Since the outer periphery of the surface 10A is chamfered, when the gypsum boards 10 of this embodiment are arranged side by side to form a wall, ceiling, etc., shadows caused by gaps where the gypsum boards 10 butt together or differences in thickness between the boards can be made less noticeable, thereby improving the design. (5) Uses The gypsum board 10 of this embodiment can be used for various uses where gypsum board 10 is required, but since it contains a fungicide, it is preferably used for uses where anti-fungal performance is required.

[0062] In particular, ceiling panels that make up a ceiling can have a temperature difference between the surface facing the room and the back surface facing away from the room, such as the attic. As a result, depending on the humidity of the environment in which the gypsum board is installed, condensation can form on the front and back surfaces of the gypsum board, leading to the growth of mold. Furthermore, condensation is likely to occur near the ventilation holes of ceiling-mounted air conditioners and in the ducts of such air conditioners due to the temperature difference.

[0063] For this reason, gypsum boards used for ceiling panels and the like are particularly prone to mold growth, and there has been a demand for gypsum boards that can suppress mold growth. Therefore, the gypsum board of this embodiment is preferably a gypsum board for ceilings in particular.

[0064] As described above, conventional gypsum boards for ceilings have been prone to mold growth, but by using the gypsum board of this embodiment for ceilings, mold growth can be particularly suppressed, and a high level of effectiveness can be achieved. [Interior Material] The interior material of this embodiment is a structural material for dividing an indoor space. The interior material of this embodiment can be used for, for example, a ceiling or a wall. Below, an example of a ceiling structure (ceiling structural material) using the interior material of this embodiment for the ceiling will be described.

[0065] The interior material 40 of this embodiment can include the gypsum board 10 according to one aspect of the present disclosure. In the interior material 40 of this embodiment, the coating layer 13 can be disposed on the indoor side.

[0066] As shown in Figure 4, in the interior material 40 of this embodiment, the gypsum board 10 can be fixed to a base such as a joist 41, and the joist 41 can be fixed to the ceiling, for example, via a hanging beam or joist support (not shown).

[0067] Although FIG. 4 shows an example in which the gypsum board 10 is directly fixed to the joist 41, the gypsum board 10 can also be fixed to the joist 41 via metal fittings or the like (not shown).

[0068] As shown in FIG. 4, the surface 10A of the gypsum board 10 on which the coating layer 13 is disposed can be placed on the indoor side, that is, on the lower side in FIG.

[0069] Here, the example shows the case where the interior material of this embodiment is used on a ceiling, but when used on a wall, studs or the like can be used as the base instead of the rough framing.

[0070] The interior material 40 of this embodiment includes the gypsum board 10 according to one aspect of the present disclosure, and therefore can particularly suppress the occurrence of mold on the surface 10A, etc. of the gypsum board 10. This can prevent deterioration of the appearance due to mold, etc. [Method for manufacturing gypsum board] The method for manufacturing gypsum board of this embodiment can have a gypsum slurry preparation step, a molding step, a curing step, and a coating layer formation step.

[0071] The gypsum board according to one aspect of the present disclosure can be manufactured by the gypsum board manufacturing method of this embodiment. Therefore, some of the matters already explained in the gypsum board will not be explained again. (1) Gypsum Slurry Preparation Step In the gypsum slurry preparation step, a mildew inhibitor having a solubility in water of 100 ppm or more, calcined gypsum, and water are mixed to prepare a gypsum slurry.

[0072] For example, these raw material components can be kneaded using a mixer or the like to prepare a gypsum slurry. Various additives can also be added to the gypsum slurry as needed. Since the mildew inhibitor has already been described, we will now describe calcined gypsum and additives other than the mildew inhibitor. (Cast gypsum) Calcined gypsum is also known as calcium sulfate hemihydrate and is an inorganic composition having hydraulic properties. As the calcined gypsum, β-type calcined gypsum or α-type calcined gypsum alone, or a mixture of both, can be used. β-type calcined gypsum is obtained by calcining in the atmosphere gypsum alone or a mixture of any of natural gypsum, by-product gypsum, flue gas desulfurization gypsum, and recycled gypsum such as waste gypsum boards, in water (including steam).

[0073] When producing a gypsum board, the calcined gypsum used as a raw material preferably contains β-type calcined gypsum, and it is more preferable that the main component of the calcined gypsum used as a raw material for the gypsum board is β-type calcined gypsum. Note that, when the main component of the calcined gypsum used as a raw material for the gypsum board is β-type calcined gypsum, this means that the β-type calcined gypsum accounts for more than 50% by mass of the calcined gypsum used as a raw material for the gypsum board. When producing a gypsum board, the calcined gypsum used as a raw material may be composed only of β-type calcined gypsum.

[0074] To produce α-type calcined gypsum, it is necessary to pressurize and calcinate dihydrate gypsum such as natural gypsum in water or steam using an autoclave. In contrast, β-type calcined gypsum can be produced by calcining dihydrate gypsum such as natural gypsum in the atmosphere at atmospheric pressure, and β-type calcined gypsum can be produced more productively than α-type calcined gypsum. (Additives) Examples of additives include one or more selected from adhesion improvers, inorganic fibers, lightweight aggregates, fireproofing materials, setting retarders, setting accelerators, water-reducing agents, foaming agents, bubble size adjusters, organic carboxylic acids, organic carboxylates, and organic phosphate compounds.

[0075] Examples of the adhesion improver include starch, polyvinyl alcohol, etc. The adhesion improver can improve the adhesion between the gypsum slurry hardened body and the board base paper.

[0076] Examples of inorganic fibers include glass fibers.

[0077] The fireproof material may be vermiculite or the like.

[0078] Examples of the foaming agent include sodium alkyl sulfate, alkyl ether sulfate, sodium alkylbenzene sulfonate, and polyoxyethylene alkyl sulfate.

[0079] Examples of the bubble size adjuster include sulfosuccinate surfactants.

[0080] The organic phosphate compounds include sodium trimetaphosphate.

[0081] The raw materials for the gypsum slurry may be kneaded all at once or in multiple stages. For example, after only the solid components are mixed to form a gypsum composition, the gypsum composition and the remaining liquid components may be kneaded to form a gypsum slurry.

[0082] Foam can be added to and mixed with the gypsum slurry for the purpose of adjusting the specific gravity of the gypsum core, etc. When foam is added to the gypsum slurry, the timing of adding the foam is not particularly limited. For example, the raw materials of the gypsum slurry, including the foam, may be mixed together. Alternatively, the foam may be added to the gypsum slurry after preparing a gypsum slurry containing components other than the foam.

[0083] The gypsum core obtained by hardening the gypsum slurry can have a waterproofing agent content of less than 0.1 parts by mass per 100 parts by mass of gypsum. The gypsum core 11 does not need to contain a waterproofing agent. Therefore, when preparing the gypsum slurry, it is preferable not to add a waterproofing agent to the gypsum slurry, or, if added, to adjust the content ratio to be within the above range. (2) Molding Process In the molding process, the gypsum slurry is placed between the board base papers 12, and then the gypsum slurry can be molded into a plate shape.

[0084] Specifically, for example, a gypsum slurry formed body can be manufactured by placing a gypsum slurry between gypsum board base papers and passing the gypsum slurry through a molding machine. (3) Hardening Process In the hardening process, the gypsum slurry can be hardened. In the hardening process, a gypsum slurry hardened body can be obtained, which has a gypsum core 11 in which the gypsum slurry is hardened and board base papers 12 arranged on a first main surface of the gypsum core and a second main surface opposite the first main surface.

[0085] The hardening process can be carried out by the hydration reaction of calcined gypsum (hemihydrate gypsum) contained in the gypsum raw material in the gypsum slurry, which generates needle-shaped crystals of gypsum dihydrate, which then coagulate and solidify. Therefore, within the gypsum slurry formed body formed in the molding process, a reaction occurs between the calcined gypsum in the gypsum raw material added to the gypsum slurry and water, and the hydration reaction of the calcined gypsum progresses, thereby carrying out the hardening process. (4) Coating Layer Forming Process In the coating layer forming process, a coating material is applied to the surface of the board base paper 12 located on the first main surface 11A of the gypsum core 11 opposite to the surface facing the gypsum core 11, to form a coating layer 13.

[0086] The resins that can be used in the paint (coating liquid) have already been described as the resins contained in the coating layer 13, and therefore further description will be omitted. Note that when the coating layer 13 is formed after application of the paint, it is sufficient that the coating layer 13 contains a desired resin, and therefore a resin precursor or the like can also be used in the paint.

[0087] When the coating layer 13 contains an antifungal agent, the paint used in the coating layer forming step may contain the antifungal agent. The antifungal agent used in the paint is not particularly limited, but for example, the antifungal agents already described can be suitably used.

[0088] Various solvents may be added to the coating material to adjust the viscosity of the coating material, so that a coating layer of a desired thickness can be formed while preventing dripping.

[0089] The specific means for applying the paint to the board base paper is not particularly limited, and any method such as a roll coater, a flow coater, or spraying can be used. (5) Optional Steps The method for manufacturing a gypsum board of this embodiment can further include any optional steps. Specifically, for example, it can include one or more steps selected from the following recess forming step, chamfering step, cutting step, and drying step. (5-1) Recess Forming Step In the recess forming step, recesses can be formed on the first main surface 11A of the gypsum core 11.

[0090] The specific method for forming the recess in the recess formation process is not particularly limited; for example, after the molding process or the second cutting process, the recess can be formed by pressing a mold or the like against the surface of the gypsum slurry molded body that will become the first main surface 11A of the gypsum core 11.

[0091] In the recess forming step, it is preferable to form the recesses with a force and depth that is not enough to damage the board base paper 12. The recess forming step can be performed, for example, before the coating layer forming step. (5-2) Chamfering Step In the chamfering step, the outer periphery of the surface 10A of the gypsum board 10, i.e., the sides 131, 132, 133, and 134, can be chamfered.

[0092] The chamfering method is not particularly limited, but the chamfering can be performed by grinding the outer periphery of the surface 10A of the gypsum board 10 with a grinder or the like. The chamfering step can be performed, for example, after the coating layer forming step. (5-3) Cutting Step In the cutting step, the gypsum slurry molded body can be cut with a cutting device.

[0093] After the gypsum slurry molded body is formed in the molding step, the gypsum slurry gradually hardens in the hardening step. Therefore, the cutting step can be performed, for example, during the hardening step or after the hardening step is completed. However, it is preferable to perform the cutting step after the hardening step has progressed to an extent that the gypsum slurry molded body can be cut.

[0094] The cutting step can be performed multiple times. Therefore, the method for manufacturing a gypsum board according to the present embodiment can include, for example, a first cutting step, which can also be called a rough cutting step. Furthermore, the method can also include a second cutting step.

[0095] In the first cutting step, the gypsum slurry molded body can be cut to a desired size depending on, for example, the size of a dryer used in the drying step described below.

[0096] Furthermore, the second cutting step can be carried out, for example, after the drying step, and the gypsum slurry molded body can be cut to a desired product size. (5-4) Drying Step In the drying step, the gypsum slurry molded body can be dried. In the drying step, excess moisture contained in the gypsum slurry molded body can be dried. It is preferable to supply a gypsum slurry molded body that has completed the hardening step to the drying step. The drying step can be carried out by force-drying the gypsum slurry molded body using a dryer.

[0097] The method for forcibly drying the gypsum slurry molded bodies with a dryer is not particularly limited, but for example, a dryer can be provided on a transport path of the gypsum slurry molded bodies, and the gypsum slurry molded bodies can be continuously dried by passing through the dryer. Alternatively, the gypsum slurry molded bodies can be transported into the dryer and dried in batches.

[0098] Specific examples are provided below for explanation, but the present invention is not limited to these examples. (1) Method for evaluating antifungal performance of gypsum board The antifungal performance was evaluated by the following method, which further includes a bacterial species in addition to the test method B (measurement of mold growth inhibitory effect) for plastic products described in Appendix A of JIS Z 2911 (2019) "Test method for mold resistance."

[0099] Specifically, a 4 cm square gypsum board test piece was placed on a glucose-added inorganic salt medium with a thickness of about 5 mm. ６ 1 mL of the mixed spore suspension adjusted to spores / mL was sprayed onto the gypsum board test piece.

[0100] The molds used to prepare the mixed spore suspension were prepared by adding Cladosporium (NBRC6348), Aureobasidium (NBRC6353), and Alternaria (NBRC106339) to the five specified species of fungi: Aspergillus (NBRC105649), Penicillium (NBRC100533), Paecilomyces (NBRC107725), Trichoderma (NBRC6355), and Chaetomium (NBRC6347).

[0101] The gypsum board test pieces sprayed with the mixed spore suspension were left in an environment of 29±1°C and 95% RH or higher for four weeks to allow mold to grow. After four weeks, the gypsum board test pieces were evaluated on a six-point scale from 0 to 5 according to the following criteria. 0 indicates the highest antifungal performance, and as the number increases, the antifungal performance decreases. A rating of 0 or 1 indicates sufficient antifungal performance. (Evaluation Criteria) 0: No mold growth was observed with the naked eye or a microscope. 1: Mold growth was not visible with the naked eye but was visible under a microscope. 2: The proportion of the area covered by mold on the surface of the gypsum board test piece was 25% or less. 3: The proportion of the area covered by mold on the surface of the gypsum board test piece was more than 25% but less than 50%. 4: The proportion of the area covered by mold on the surface of the gypsum board test piece was 50% or more but less than 100%. 5: The surface of the gypsum board test piece is completely covered with mold. (2) Regarding the manufacturing conditions of the gypsum board in the experimental examples The manufacturing conditions of the gypsum board in each experimental example are explained below. Experimental examples 1 to 19 are working examples, and Experimental examples 20 to 39 are comparative examples. [Experimental example 1] Calcined gypsum, water, a mildew inhibitor, and starch were mixed to prepare a gypsum slurry (gypsum slurry preparation step). When the calcined gypsum was gypsum dihydrate, the mildew inhibitor was added so that the mass ratio of the gypsum dihydrate to the calcined gypsum was 100 ppm.

[0102] The obtained gypsum slurry was placed between base papers for boards and molded into a board shape to produce a gypsum slurry molded body (molding step).

[0103] Next, the obtained gypsum slurry molded body was hardened (hardening step).

[0104] After the hardening step, the gypsum slurry molded body was cut and dried to produce a gypsum board (cutting step, drying step).

[0105] After the drying step, a coating material containing a mixture of a mildewproofing agent and an acrylic resin was applied to the surface of the board base paper 12 (first board base paper 121) located on the first main surface 11A of the gypsum core 11 opposite to the surface facing the gypsum core 11, to form a coating layer (coating layer forming step). The coating material was applied to a thickness of 0.1 mm (approximately 100 g / m ２ The antifungal agent was added so that the mass ratio of the antifungal agent to the gypsum dihydrate was 20 ppm, assuming that the calcined gypsum contained in the gypsum core was gypsum dihydrate.

[0106] The antifungal agent used in the gypsum core and coating layer was IMZ, and its solubility in water was 100 ppm or more, as shown in the "Type, solubility, and amount of antifungal agent" column in Table 1. In Table 1, when the solubility in water of the antifungal agent used in the gypsum core was 100 ppm or more, a "○" was marked in the "Solubility in water" column.

[0107] In addition, when the average thickness of the coating layer of the obtained gypsum board was measured and calculated, it was confirmed that it was 0.1 mm, the same as the coating thickness of the coating layer. In other experimental examples, the average thickness of the coating layer was also the same as the coating thickness of the coating layer.

[0108] Furthermore, since no waterproofing agent was added to the gypsum slurry, the content of the waterproofing agent in the gypsum core 11 was 0. The same applies to the following Experimental Examples 2 to 32. [Experimental Examples 2 to 8] Gypsum boards were manufactured and evaluated under the same conditions as Experimental Example 1, except that the type of antifungal agent added to the gypsum core and the coating layer was changed to the material shown in Table 1. The evaluation results are shown in Table 1. [Experimental Examples 9 to 12] Gypsum boards were manufactured and evaluated under the same conditions as Experimental Example 2, except that the resin used in the paint was changed from acrylic resin to the resin shown in the "Coating Layer Resin" column in Table 1, and the coating layer was formed using the changed paint. The evaluation results are shown in Table 1. [Experimental Examples 13 and 14] When preparing the paint, the antifungal agent was added in an amount by mass relative to the gypsum dihydrate, as shown in the "Amount to be added to paint" column in Table 1, assuming that the calcined gypsum contained in the gypsum core was gypsum dihydrate. Then, gypsum boards were manufactured and evaluated under the same conditions as in Experimental Example 2, except that a coating layer was formed using the paint. The evaluation results are shown in Table 1. [Experimental Examples 15 and 16] When forming the coating layer, the coating thickness of the paint was set to the value shown in the "Coating Layer Thickness" column in Table 1. Except for the above, gypsum boards were manufactured and evaluated under the same conditions as in Experimental Example 2. The evaluation results are shown in Table 1. [Experimental Examples 17 to 19] Gypsum boards were manufactured and evaluated under the same conditions as in Experimental Example 1, except that the antifungal agent added to the gypsum core was the material shown in Table 1, and no antifungal agent was added to the coating layer. The evaluation results are shown in Table 1. [Experimental Example 20] Gypsum boards were manufactured and evaluated under the same conditions as in Experimental Example 1, except that no antifungal agent was added to the gypsum core or the coating layer. The evaluation results are shown in Table 1. [Experimental Examples 21 and 22] Gypsum boards were manufactured and evaluated under the same conditions as in Experimental Example 1, except that the antifungal agent added to the gypsum core was the material shown in Table 1 and no coating layer was formed. The evaluation results are shown in Table 1. [Experimental Example 23] Gypsum boards were manufactured and evaluated under the same conditions as in Experimental Example 1, except that the antifungal agent added to the gypsum core was the material shown in Table 1 and no antifungal agent was added to the coating layer. The evaluation results are shown in Table 1. [Experimental Example 24] Gypsum boards were manufactured and evaluated under the same conditions as in Experimental Example 1, except that the antifungal agent added to the gypsum core and the coating layer was the material shown in Table 1. The evaluation results are shown in Table 1.[Experimental Examples 25 and 26] When preparing the paint, an antifungal agent was added to the gypsum dihydrate in a mass ratio relative to the gypsum dihydrate shown in the "Amount in Paint" column in Table 1, assuming that the calcined gypsum contained in the gypsum core was gypsum dihydrate. Then, gypsum boards were manufactured and evaluated under the same conditions as in Experimental Example 24, except that a coating layer was formed using the paint. The evaluation results are shown in Table 1. [Experimental Examples 27 and 28] When forming the coating layer, the coating thickness of the paint was adjusted to the value shown in the "Coating Thickness of Coating Layer" column in Table 1. Except for the above, gypsum boards were manufactured and evaluated under the same conditions as in Experimental Example 24. The evaluation results are shown in Table 1. [Experimental Examples 29 to 32] Gypsum boards were manufactured and evaluated under the same conditions as in Experimental Example 1, except that no antifungal agent was added to the gypsum core, and the antifungal agent added to the coating layer was the material shown in Table 1. The evaluation results are shown in Table 1. [Experimental Examples 33 to 39] Gypsum boards were manufactured and evaluated under the same conditions as in Experimental Example 1, except that the antifungal agents added to the gypsum core and coating layer were the materials shown in Table 1 and a waterproofing agent was added to the gypsum core. The evaluation results are shown in Table 1.

[0109] An organopolysiloxane was used as the waterproofing agent, and was added so that the ratio of the waterproofing agent to 100 parts by mass of gypsum dihydrate, assuming that the gypsum contained in the gypsum core is gypsum dihydrate, would be the value shown in the waterproofing agent column in Table 1.

[0110] From the above results, it was confirmed that the gypsum boards of Experimental Examples 1 to 19 have excellent antifungal performance. In other words, it was confirmed that the antifungal performance can be improved by having a coating layer, a gypsum core 11 containing an antifungal agent with a water solubility of 100 ppm or more, and setting the waterproofing agent content in the gypsum core within a predetermined range. (Notes) (1) A gypsum board according to one embodiment of the present disclosure includes a gypsum core; board base paper disposed on a first main surface of the gypsum core and a second main surface opposite the first main surface; and a coating layer disposed on the surface of the board base paper located on the first main surface of the gypsum core opposite the surface facing the gypsum core; the gypsum core containing an antifungal agent with a water solubility of 100 ppm or more; and the gypsum core containing less than 0.1 parts by mass of waterproofing agent per 100 parts by mass of gypsum. (2) In (1), the coating layer may contain an antifungal agent. (3) In (2), the gypsum core may contain at least one type of antifungal agent different from the antifungal agent contained in the coating layer. (4) In any of (1) to (3), the average thickness of the coating layer may be 0.01 mm or more and 0.3 mm or less. (5) In any of (1) to (4), the coating layer may contain a resin. (6) In any of (1) to (5), the first main surface of the gypsum core may include a recess. (7) In any of (1) to (6), the gypsum board may be for a ceiling. (8) An interior material according to one aspect of the present disclosure is an interior material used for a ceiling or wall to divide an indoor space, and includes the gypsum board of any of (1) to (7), wherein the coating layer is located on the indoor side.(9) A method for manufacturing a gypsum board according to one aspect of the present disclosure includes: a gypsum slurry preparation step of mixing a mildew-preventing agent having a solubility in water of 100 ppm or more, calcined gypsum, and water to prepare a gypsum slurry; a shaping step of arranging the gypsum slurry between pieces of base paper for board and then shaping the gypsum slurry into a plate; a hardening step of obtaining a gypsum slurry hardened body having a gypsum core obtained by hardening the gypsum slurry and the base paper for board arranged on a first main surface of the gypsum core and a second main surface located opposite to the first main surface; and a coating layer formation step of applying paint to a surface of the base paper located on the first main surface of the gypsum core opposite to a surface facing the gypsum core to form a coating layer, wherein the gypsum core contains less than 0.1 parts by mass of a waterproofing agent per 100 parts by mass of gypsum.

[0111] Although the gypsum board, interior material, and method for manufacturing the gypsum board have been described above in terms of the embodiments, the present invention is not limited to the above embodiments, etc. Various modifications and changes are possible within the scope of the gist of the present invention as set forth in the claims.

[0112] This application claims priority based on Japanese Patent Application No. 2024-046736, filed with the Japan Patent Office on March 22, 2024, the entire contents of which are incorporated herein by reference.

[0113] 10 Gypsum board 10A Surface 10B Back surface 11 Gypsum core 11A First main surface 11B Second main surface 12 Board base paper 121 First board base paper 122 Second board base paper 121A First surface 121B Second surface 13 Coating layer 131 Side 132 Side 133 Side 134 Side T13 Thickness 31 Concave portion 31A Bottom surface 31B Side surface 32 Convex portion 40 Interior material 41 Rough edging

Claims

1. A gypsum board comprising: a gypsum core; board base paper disposed on a first main surface of the gypsum core and a second main surface opposite the first main surface; and a coating layer disposed on the surface of the board base paper located on the first main surface of the gypsum core opposite to the surface facing the gypsum core, wherein the gypsum core contains a mildew inhibitor having a solubility in water of 100 ppm or more, and the gypsum core contains less than 0.1 parts by mass of waterproofing agent per 100 parts by mass of gypsum.

2. The gypsum board according to claim 1, wherein the coating layer contains a mildew inhibitor.

3. The gypsum board according to claim 2, wherein the gypsum core contains at least one type of anti-mold agent different from the anti-mold agent contained in the coating layer.

4. A gypsum board according to any one of claims 1 to 3, wherein the average thickness of the coating layer is 0.01 mm or more and 0.3 mm or less.

5. The gypsum board according to any one of claims 1 to 3, wherein the coating layer contains a resin.

6. The gypsum board of any one of claims 1 to 3, wherein the first major surface of the gypsum core includes a recess.

7. The gypsum board according to any one of claims 1 to 3, which is a gypsum board for ceilings.

8. An interior material used on a ceiling or wall to divide an indoor space, comprising the gypsum board according to any one of claims 1 to 3, with the coating layer located on the indoor side.

9. A method for manufacturing a gypsum board, comprising: a gypsum slurry preparation step of mixing a mildew inhibitor having a solubility in water of 100 ppm or more, calcined gypsum, and water to prepare a gypsum slurry; a forming step of arranging the gypsum slurry between board base papers and then forming the gypsum slurry into a plate; a hardening step of obtaining a hardened gypsum slurry body having a gypsum core formed by hardening the gypsum slurry, and the board base paper arranged on a first main surface of the gypsum core and a second main surface located opposite the first main surface; and a coating layer formation step of applying paint to a surface of the board base paper located on the first main surface of the gypsum core opposite to the surface facing the gypsum core, to form a coating layer, wherein the gypsum core contains less than 0.1 parts by mass of waterproofing agent per 100 parts by mass of gypsum.

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