Wood-based refractory cladding materials and wood-based refractory structures

Abstract

It is possible to reduce the thickness of the burnt-out layer covering the wooden load-bearing member. [Solution] The wood-based fire-resistant covering material 1 covers the wood-based load-bearing member 5 and carbonizes when exposed to flames to form a carbonized layer. The entire thickness is compressed and plastically processed by heating and compression perpendicular to the length direction of the wood grain, resulting in a compression ratio within the range of 45-70% relative to the air-dry specific gravity of the original wood.

Description

Technical Field

[0001] The present invention relates to a wood fireproof coating material for coating a wood load-bearing support member and forming a char layer, and a wood fireproof structure using the same. In particular, the present invention relates to a wood fireproof coating material capable of reducing the thickness of the char layer covering the wood load-bearing support member, and a wood fireproof structure using the same.

Background Art

[0002] In recent years in Japan, although the artificial forests planted after the war are at a time suitable for use as wood, due to the depression and decline of forestry, these artificial forests have not been properly maintained. In addition, due to the implementation of laws promoting the use of wood in buildings for realizing a decarbonized society, etc., the active promotion of wood use has been carried out. And due to the recent revision of the rationalization of the fire resistance performance standards of wooden buildings, it is expected that wood will be used in all buildings, including medium- and large-scale buildings that were conventionally built with steel frames or concrete structures.

[0003] By the way, according to the Building Standards Law, depending on the use, scale, and location (site) of the building, the main structural parts of the building must be made of a fireproof or semi-fireproof structure. For example, in urban areas where buildings are concentrated, in order to prevent great damage caused by fires, fire prevention areas and semi-fire prevention areas are designated. In these areas, depending on the classification of the number of floors and scale (total floor area), it is necessary to make the main structural parts (walls, columns, floors, beams, roofs, stairs) into fireproof buildings or semi-fireproof buildings that meet the specified fire resistance standards. Also, in areas where there is a demand for medium- and large-scale buildings, it is often required to be a fireproof building or semi-fireproof building. And when it comes to fireproof buildings or semi-fireproof buildings, conventionally, reinforced concrete structures, steel frame structures, steel frame reinforced concrete structures, etc. have been the mainstream. However, due to recent law revisions and the trend of promoting wood use, the number of wooden fireproof buildings and semi-fireproof buildings is also increasing.

[0004] In conventional wooden structural frames, load-bearing members made of wood are covered with fireproofing materials such as mortar or gypsum board. However, covering them with gypsum board or similar materials has the drawback of obscuring the aesthetic appeal and texture of the wood used in the load-bearing members. Therefore, when exposing timber in a semi-fire-resistant wooden structure, there is a method called burn-through design. By providing a burn-through, that is, a surface thickness that can withstand long-term loads even if the surface is exposed to flames and carbonized, and creating a large cross-section that does not impair structural strength, it becomes possible to create a semi-fire-resistant wooden structure while exposing the timber without using covering materials such as gypsum board. However, burn-through design involves performing allowable stress calculations using the effective cross-section that excludes the burn-through, and since the design ensures that there is no impairment in structural strength even if the surface burns, the timber cross-section becomes large, which significantly increases timber costs and reduces interior space.

[0005] Furthermore, fire-resistant wooden structures are also known in which a wood covering material is attached to the outer surface of a wooden structural core. For example, Patent Document 1 discloses a fire-resistant wooden structure used for columns or beams of a building, comprising a wooden structural core that supports a load, and a wood covering material that covers the outer surface of the wooden structural core, wherein a portion of the wooden structural core has its outer surface exposed. In this method, where a wood-based cladding material is attached to the outer surface of a wood-based structural core, it is not necessary to use a large cross-section wood-based structural core, thus reducing wood costs. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-138662 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, even with these fire-resistant wooden structures, the overall structure has a large cross-section, which reduces the interior space compared to cases where it is covered with gypsum board or similar materials.

[0008] Therefore, the present invention aims to provide a wood-based fire-resistant covering material and a wood-based fire-resistant structure that can reduce the thickness of the burnable layer covering a wood-based load-bearing member. [Means for solving the problem]

[0009] The wood fire-resistant covering material of the invention of claim 1 is a wood fire-resistant covering material that covers a wood load-bearing member that supports a long-term load and carbonizes when exposed to flames to form a carbonized layer, wherein the entire thickness is compressed and plastically processed by heating and compression perpendicular to the length direction of the wood grain, and the compression ratio relative to the air-dry specific gravity of the original wood is in the range of 45 to 70%, preferably 48 to 70%, and more preferably 50 to 68%.

[0010] The above-mentioned wooden load-bearing members are parts of a building that bear the load, such as beams and columns, and may be a single piece of lumber (sawn wood), or laminated wood materials such as CLT (Cross Laminated Timber) or LVL (Laminated Veneer Lumber).

[0011] The plastic deformation process described above involves compressing the entire thickness of the wood by heating and compressing it perpendicular to the length direction (fiber direction) of the wood grain. This process involves applying external force using a press or similar tool to wood that has been cut in a flat-sawn or quarter-sawn manner, perpendicular to the fiber direction (tree direction, standing tree direction) of the annual rings, i.e., in the thickness direction of the wood, thereby compressing it. This compresses the entire thickness, reducing the area and thickness of the end grain compared to the original wood, and fixing the shape in this compressed state. It is not required that the entire thickness be compressed at a uniform rate; typically, the front and back sides are compressed at a high density, while the interior is compressed at a low density.

[0012] The compressibility ratio relative to the air-dry specific gravity of the original wood mentioned above was calculated from the average air-dry specific gravity of the original wood species and the air-dry specific gravity of the wood-based fire-resistant coating material. Compression ratio (%) =[1-[(Average air-dry specific gravity of the original wood species) / (Air-dry specific gravity of the wood fire-resistant coating)]] ×100 It is defined as follows. Note that air-dry specific gravity = density of wood (kg / m³) 3 ) / Density of water (kg / m³) 3 ) The air-dry specific gravity mentioned above refers to the specific gravity of wood when it is left to dry in the atmosphere and reaches its air-dry moisture content. This is usually expressed as the specific gravity at a moisture content of 15%, and is a value obtained by comparing the weight of the dried wood to the weight of the same volume of water. A higher number indicates heavier wood, and a lower number indicates lighter wood.

[0013] For example, the average air-dry specific gravity of domestically produced or commonly used timbers is 0.38 for Japanese cedar, 0.44 for cypress, 0.50 for Japanese larch, 0.44 for Dodomatsu, 0.43 for Yezo spruce, 0.52 for Japanese red pine, 0.30 for paulownia, 0.60 for chestnut, 0.47 for Japanese cypress, 0.69 for zelkova, 0.47 for walnut, and 0 for beech. The average air-dry specific gravity of oak is 0.63, chestnut is 0.60, birch is 0.60, Japanese chinquapin is 0.61, quince is 0.61, falcata is 0.27, marapaya is 0.50, gomelina is 0.45, rubber is 0.64, yellow poplar is 0.45, Italian poplar is 0.35, and acacia mangium is 0.63.

[0014] The wood-based fire-resistant covering material of the invention of claim 2 has a total dry specific gravity preferably in the range of 0.55 to 1.30, more preferably 0.70 to 1.20, and even more preferably 0.90 to 1.10. The above-mentioned total dry specific gravity (absolute dry specific gravity) does not mean that the wood fire-resistant coating material is in a completely dry state, but rather refers to the specific gravity of the wood when the moisture content of the wood fire-resistant coating material is reduced to 0%. This is calculated by measuring the weight before drying, drying it in a constant temperature oven at 103±2 °C, and then taking the weight after all moisture has been removed.

[0015] The wood-based fire-resistant coating material of the invention of claim 3 has a moisture content that is preferably in the range of 5.0 to 20.0%, more preferably 10.0 to 15.0%, and even more preferably 11.0 to 13.0%. The above moisture content is measured using a high-frequency moisture meter.

[0016] The wood fire-resistant covering material of the invention of claim 4 is a wood fire-resistant structure comprising a wood load-supporting member that supports a long-term load, and a wood fire-resistant covering material that covers the wood load-supporting member and carbonizes in the event of a flame to form a carbonized layer, wherein the wood fire-resistant covering material is plastically processed by heating and compressing the entire thickness perpendicular to the length direction of the wood grain, resulting in a compression ratio of 45 to 70%, preferably 48 to 70%, and more preferably 50 to 68% relative to the air-dry specific gravity of the original wood.

[0017] Furthermore, the above-mentioned wood fire-resistant covering material may be placed immediately outside the wood load-bearing member, or outside the fire-stopping layer or the like provided between the wood load-bearing member and the member. Whether directly or indirectly, it is sufficient that the entire circumference or a portion of the circumference of the wood load-bearing member is covered when viewed from the axial direction. [Effects of the Invention]

[0018] The wood-based fire-resistant covering material according to claim 1 covers a wood-based load-bearing member and carbonizes when exposed to flames to form a carbonized layer. The entire thickness is compressed and plastically deformed by heating and compression perpendicular to the length direction of the wood grain, resulting in a compression ratio of 45-70%, preferably 48-70%, and more preferably 50-68% relative to the air-dry specific gravity of the original wood.

[0019] In order to make it possible to reduce the thickness of the char layer covering the wooden load-bearing member, the inventors conducted intensive experimental research. As a result, the entire thickness of the wood was heated and compressed in a direction perpendicular to the length direction of its grain, and the compression was fixed. When the compression ratio with respect to the air-dry specific gravity of the original wood is in the range of 45 to 70%, preferably 48 to 70%, more preferably 50 to 68%, although it carbonizes during a fire to form a carbonized layer, it was found that the carbonization rate becomes slower, and the present invention was thus completed.

[0020] Regarding the reason why the carbonization rate of the wood-based fire-resistant coating material, in which the entire thickness is compressed and plastically processed by heating and compression in a direction perpendicular to the length direction of the wood grain, and the compression ratio with respect to the air-dry specific gravity of the original wood is in the range of 45 to 70%, preferably 48 to 70%, more preferably 50 to 68%, becomes slower, it is not necessarily clear. However, due to the increase in density by compression with a predetermined compression ratio, ignition is delayed. In addition, in the compression with a predetermined compression ratio, a large amount of moisture is trapped inside and it is difficult for the internal moisture to be discharged outside the material, which slows down the progress of combustion. Furthermore, it is speculated that in the compression with a predetermined compression ratio, the wood softens during a fire, the volume and thickness expand to form a thick carbonized layer, which can increase the heat insulation effect, thus also slowing down the progress of combustion. Therefore, according to the wood-based fire-resistant coating material according to the invention of claim 1, since the carbonization rate can be slowed down, it becomes possible to reduce the thickness of the char layer as the layer covering the wooden load-bearing member.

[0021] According to the wood-based fire-resistant coating material according to the invention of claim 2, since its total dry specific gravity is preferably in the range of 0.55 to 1.30, more preferably 0.70 to 1.20, still more preferably 0.90 to 1.10, in addition to the effect described in claim 1, even if the thickness of the char layer is reduced, it is possible to ensure the strength capable of bearing the stress of short-term loads.

[0022] According to the wood fire-resistant coating material of claim 3, its moisture content is preferably in the range of 5.0 to 20.0%, more preferably 10.0 to 15.0%, and even more preferably 11.0 to 13.0%. Therefore, in addition to the effects described in claim 1, it can provide good dimensional stability and slow down the carbonization rate without causing cracks during flames.

[0023] The wood fire-resistant structure of the invention of claim 4 comprises a wood load-bearing member that supports a long-term load, and a wood fire-resistant covering material that covers the wood load-bearing member and carbonizes in the event of a flame to form a carbonized layer, wherein the wood fire-resistant covering material is plastically processed by heating and compressing the entire thickness perpendicular to the length direction of the wood grain, resulting in a compression ratio of 45 to 70%, preferably 48 to 70%, and more preferably 50 to 68% relative to the air-dry specific gravity of the original wood.

[0024] The inventors of the present invention conducted diligent experimental research to reduce the thickness of the burnt layer covering the wood load-bearing member. As a result, they discovered that when the entire thickness of the wood is heated and compressed perpendicular to the length of the grain, and this compression is fixed, the compression ratio relative to the original air-dry specific gravity of the wood is in the range of 45-70%, preferably 48-70%, and more preferably 50-68%, although carbonization occurs and a carbonized layer is formed when heated, the rate of carbonization is slowed down, thus completing the present invention.

[0025] The reason why the carbonization rate of wood-based fire-resistant coatings slows down when the entire thickness is compressed and plastically processed by heating and compressing perpendicular to the length direction of the wood grain, resulting in a compression ratio of 45-70%, preferably 48-70%, and more preferably 50-68% relative to the original air-dry specific gravity of the wood, is not entirely clear. However, it is presumed that the increased density due to compression to the predetermined compression ratio slows down ignition, and that the increased compression to the predetermined compression ratio traps a lot of moisture inside, making it difficult for the internal moisture to escape from the material, thus slowing down the progress of combustion. Furthermore, it is speculated that the increased compression to the predetermined compression ratio softens the wood during flames, causing it to expand in volume and thickness, forming a thick carbonized layer that enhances the heat insulation effect, thus slowing down the progress of combustion. Therefore, according to the fire-resistant wood structure of claim 4, the carbonization rate of the fire-resistant wood covering material, which is the burn-out layer, can be slowed down, making it possible to reduce the thickness of the burn-out layer covering the wood load-bearing member. [Brief explanation of the drawing]

[0026] [Figure 1] Figure 1(a) is an explanatory cross-sectional view illustrating how a fire-resistant wood covering material according to an embodiment of the present invention covers a wooden load-bearing member constituting a beam to constitute a fire-resistant wood structure, and Figure 1(b) is an explanatory cross-sectional view illustrating how a fire-resistant wood covering material according to an embodiment of the present invention covers a wooden load-bearing member constituting a column to constitute a fire-resistant wood structure. [Figure 2] Figure 2 is a schematic cross-sectional view showing an example of a plastically formed wood manufacturing apparatus for producing a wood-based fire-resistant coating material according to an embodiment of the present invention. [Figure 3] Figure 3 is an explanatory diagram illustrating an example of the manufacturing process of a wood-based fire-resistant coating material according to an embodiment of the present invention, where (a) is an explanatory diagram of the supply of wood before processing, (b) is an explanatory diagram of the start of heating and compression, (c) is an explanatory diagram of the heating and compression state in a sealed state, (d) is an explanatory diagram of the vapor pressure control process in a sealed state, (e) is an explanatory diagram of the cooling state in a sealed state, and (f) is an explanatory diagram of the removal of the wood-based fire-resistant coating material. [Figure 4]Figure 4 is a graph showing the temperature changes on the back surface of the test specimens in the examples and comparative examples in the cone calorimeter test. [Figure 5] Figure 5 shows photographs of the carbonization state of the test specimens of the examples and comparative examples after predetermined heating in the corn calorimeter test. (a) is a photograph of the test specimen of Example 1-1, (b) is a photograph of test specimen 3-1 of the example, and (c) is a photograph of test specimen 6 of the comparative example. [Figure 6] Figure 6 is an explanatory diagram, viewed from the heated surface side of the test specimen, illustrating the heating test method for the test specimen in an example of a small combustion furnace heating test. [Figure 7] Figure 7(a) is an explanatory diagram showing the side view of the test specimen to illustrate the heating test method for the test specimen in the example of the small combustion furnace heating test, and Figure 7(b) is an explanatory diagram showing the top view of the test specimen to illustrate the heating test method for the test specimen in the example of the small combustion furnace heating test. [Figure 8] Figure 8(a) is an explanatory diagram showing the test specimen viewed from above to illustrate the heating test method for the test specimen of the embodiment installed inside a small combustion furnace during a small combustion furnace heating test, and Figure 8(b) is an explanatory diagram showing the test specimen viewed from the non-heated side (opposite side of the heated side) to illustrate the heating test method for the test specimen of the embodiment installed inside a small combustion furnace during a small combustion furnace heating test. [Figure 9] Figure 9 is a graph showing the temperature changes at predetermined measurement points on the test specimen in the example of the small combustion furnace heating test. [Modes for carrying out the invention]

[0027] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, the same symbols and reference numerals in the illustration represent the same or corresponding functional parts; therefore, a redundant detailed explanation is omitted here.

[0028] [Embodiment] First, the wood-based fire-resistant covering material 1 of the present invention will be described with reference to Figure 1. As shown in Figure 1, the wood fire-resistant covering material 1 of this embodiment is used in wood fire-resistant structures 100 used in columns and beams of buildings, etc. It covers the periphery of wood load-bearing members 5 such as columns and beams, and carbonizes when exposed to flames to form a carbonized layer (carbonized insulating layer, burnable layer). The entire thickness of the wood is compressed and plastically processed by heating and compression perpendicular to the length direction of the wood grain, resulting in a compression ratio of 45 to 70%, preferably 48 to 70%, and more preferably 50 to 68% relative to the air-dry specific gravity of the original wood.

[0029] The wooden load-bearing members 5, such as columns and beams, are the parts that support the load, that is, the parts that bear the load of the building as beams and columns, etc. They constitute a core sufficient to support long-term loads (loads that occur over a long period of time, such as dead loads and live loads), and for example, lumber sawn into rectangular timber (single piece of wood, solid wood) or laminated timber with a rectangular cross-section (laminated veneer lumber (LVL, LVB), plywood, glued laminated timber, CLT, ungraded timber, etc.) made by laminating many veneers or sawn boards (laminas) via adhesive is used. Laminated veneer timber is generally made by laminating and bonding multiple veneers by applying adhesive, and of these, LVL (Laminated Veneer Lumber) is made by laminating and bonding veneers with the fiber direction of the veneers aligned, and LVB (Laminated Veneer Board) is made by laminating and bonding veneers with the fiber direction of the veneers partially perpendicular. CLT is made by laminating and bonding sawn boards (laminas) with the fiber direction perpendicular. The wooden load-bearing member 5 is usually made from commonly available or custom-made timber, but it may also be joined in the width and length directions using appropriate jointing means to achieve a predetermined width and length. Examples of wood species used to make up the wooden load-bearing member 5 include Japanese cedar, cypress, Japanese red pine, Japanese larch, Japanese black pine, Japanese cypress, Western red cypress, Western red pine, Japanese hemlock, Japanese zelkova, chestnut, oak, Japanese oak, and beech. The wooden load-bearing member 5 may also have rounded (R-shaped) or chamfered (C-shaped) edges.

[0030] In this embodiment, if the wood fire-resistant covering material 1 is used in a wood fire-resistant structure 100 used as a column, it is arranged to surround the four surrounding surfaces of the wood load-bearing member 5 column, excluding the end grain surface (to surround the entire circumference). For example, four panel-shaped (rectangular cross-section) wood fire-resistant covering materials 1 are arranged in a rectangular frame shape to surround the four surrounding surfaces of the wood load-bearing member 5 column when viewed from the axial direction of the column. In this case, by covering the four outer surfaces with wood fire-resistant covering materials 1 of the same cross-sectional shape and using the same joints, equivalent fire resistance can be provided to each surface. Furthermore, if used in a fire-resistant wooden structure 100 used as a beam, the wood load-bearing member 5 is arranged to cover at least three outer surfaces of the beam, excluding the end grain surface, for example, by surrounding the three surrounding surfaces (bottom and sides) of the beam, excluding the top surface. For example, at least three panel-shaped (rectangular cross-section) fire-resistant wooden covering materials 1 are arranged in a U-shape to cover the three surrounding surfaces of the beam, excluding the top surface, when viewed from the axial direction of the beam of the load-bearing member 5. Furthermore, the wood-based fire-resistant covering material 1 may have rounded edges (R-shaped) or chamfered edges (C-shaped).

[0031] In this embodiment, the wood fire-resistant covering material 1 is attached (bonded) to the wood load-bearing member 5 by joining it with an adhesive (for example, a resorcinol resin-based adhesive) or fasteners such as nails or screws, so as to cover its outer surface. It is also possible to form the wood fire-resistant structure 100 by joining and covering the wood load-bearing member 5 with the wood fire-resistant covering material 1 at a factory and then transporting it to the construction site, or the wood fire-resistant structure 100 can be formed by assembling the wood load-bearing member 5 at the construction site and then joining and covering it with the wood fire-resistant covering material 1, making it easy to install at the construction site.

[0032] The wood-based fire-resistant covering material 1 of this embodiment is a compacted material in which the entire thickness of the wood is compressed by heating and compression perpendicular to the length direction of the wood grain, and plastically processed (compacted), and compressed to a compression ratio of 45 to 70%, preferably 48 to 65%, and more preferably 50 to 60% relative to the air-dry specific gravity of the original wood.

[0033] According to the inventors' experimental research, materials with a compressibility of less than 45% cannot slow down the carbonization rate, and therefore cannot reduce the thickness of the burnt layer. Furthermore, materials with a compressibility exceeding 70% do not show a reduction in the carbonization rate commensurate with the compressibility. If the compressibility is set to a range of 45-70%, preferably 48-65%, and more preferably 50-60%, the carbonization rate slows down significantly, allowing for a thinner burnt layer. In particular, the carbonized layer, which expands significantly in volume due to the heat of the flame during combustion, exhibits a great insulating effect, making it possible to reduce its thickness during normal operation.

[0034] Furthermore, the wood fire-resistant coating material 1 of this embodiment has a dry specific gravity preferably in the range of 0.55 to 1.30, more preferably 0.70 to 1.20, and even more preferably 0.90 to 1.10. If the dry specific gravity is too low, the required strength cannot be obtained when the thickness is reduced. On the other hand, if the dry specific gravity is too high, the compressibility will be high, and the reduction in carbonization rate commensurate with the compressibility will not be observed. When the total dry specific gravity is preferably in the range of 0.55 to 1.30, more preferably 0.70 to 1.20, and even more preferably 0.90 to 1.10, sufficient strength to withstand short-term load stress can be secured even if the thickness of the burnable layer is reduced.

[0035] The wood fire-resistant coating material 1 of this embodiment has a moisture content preferably in the range of 5.0 to 20.0%, more preferably 10.0 to 15.0%, and even more preferably 11.0 to 13.0%. If the moisture content is too low, cracking may occur during flames, causing loss of the carbonized layer or reducing the expansion of the carbonized layer, which may decrease the heat insulation effect. On the other hand, if the moisture content is too high, dimensional stability will decrease. If the moisture content is preferably in the range of 5.0 to 20.0%, more preferably 10.0 to 15.0%, and even more preferably 11.0 to 13.0%, dimensional stability can be achieved, and the carbonization rate can be effectively slowed without causing cracking during flame.

[0036] In this embodiment, the wood fire-resistant covering material 1 burns during a fire to form a carbonized layer, which functions as a burnable layer (insulating layer, heat-shielding layer) that suppresses the penetration of fire heat into the covered wood load-bearing member 5. That is, by covering the wood fire-resistant covering material 1 with the wood load-bearing member 5, even if the surface of the wood fire-resistant covering material 1 burns during a fire, a carbonized layer is formed, which blocks the penetration of flames and heat, heat transfer, and oxygen supply. As a result, the burning does not rapidly spread to the wood load-bearing member 5, suppressing the temperature rise of the wood load-bearing member 5 and inhibiting mechanical deterioration.

[0037] In particular, in the wood-based fire-resistant coating material 1, the entire thickness of the wood is compressed and plastically processed by heating and compression perpendicular to the length direction of the wood grain, resulting in a predetermined compression ratio, the fire resistance is high and the rate of burning (carbonization rate) can be slowed down because the entire thickness of the wood is compressed and plastically processed at a predetermined compression ratio.

[0038] This is presumed to be because the increased density due to compression delays ignition, and the higher moisture content per unit volume due to compression traps more moisture, making it difficult for it to escape, thus suppressing temperature rise and slowing combustion. Furthermore, the heat from the flame softens the wood, causing it to expand in volume and regain its thickness, forming a thick carbonized layer. This carbonized layer contains many cavities (air pockets), which provides high insulation and suppresses the progress of combustion. Furthermore, it is presumed that the volume expands due to the heat of the flame because, in the wood-based fire-resistant coating material 1, which is compressed and plastically processed by heating and compression perpendicular to the length direction of the wood grain to a predetermined compression ratio, the cell walls undergo significant bending and deformation during the compression process, causing cells to close or the internal volume to decrease, and this state becomes fixed, trapping moisture inside the material. When exposed to flame, the wood softens due to the heat, and the water vapor pressure from the evaporation of moisture increases internally. Additionally, pyrolysis gases are generated during the carbonization process, but they are difficult to release to the outside of the material, causing the pyrolysis gases generated during the carbonization process to accumulate and become high pressure. In other words, it is presumed that this is due to the softening of the wood by heat and the turgor pressure of water vapor and pyrolysis gases.

[0039] Thus, with the wood carbonized coating material 1 of this embodiment, the increased density due to compression delays ignition, and because a large amount of moisture is trapped due to compression, the thick carbonized layer expands and recovers to approximately the same thickness as the original wood when a flame hits, exhibiting a high heat insulating effect. As a result, the rate of burning (carbonization rate) can be slowed, and fire resistance is high even with a thin thickness. Therefore, when the wooden load-bearing member 5 is covered to form the wooden fire-resistant structure 100, the overall cross-sectional area can be reduced, expanding the effective space of the building and improving the openness of the space.

[0040] Furthermore, in the wood-based fire-resistant coating material 1, the entire thickness of the wood is compressed and plastically processed by heating and compression perpendicular to the length direction of the wood grain, resulting in a predetermined compression ratio. This reduces the variation in shrinkage anisotropy based on the original wood (solid wood)'s shrinkage structure and annual ring structure, resulting in homogenization of the material and improved dimensional stability. Consequently, there is no instability in shape when carbonized, and cracks are less likely to occur in the cross-section remaining after being exposed to flames. In addition, in laminated wood, the use of water-based polymer-isocyanate adhesives can easily lead to increased heat generation and reduced adhesive strength, causing the fire to spread more easily, or cracks to form along the laminated surface, which can cause parts of the carbonized layer to detach prematurely. However, in the wood-based fire-resistant coating material 1 of this embodiment, the problem of the carbonized layer peeling off is less likely to occur.

[0041] The thickness (board thickness) of the wood fire-resistant covering material 1 in this embodiment is set appropriately according to the required fire resistance performance. However, even if the thickness is thin, a charred layer expands during flames, providing a high heat insulation effect. Furthermore, compared to sawn lumber, cracks are less likely to occur in the cross-section remaining after flames. Therefore, for a 45-minute semi-fire-resistant structure, the thickness can be set within the range of 20 mm or more and less than 35 mm, preferably 20 mm or more and 33 mm or less.

[0042] In the fire-resistant wooden structure 100, which is formed by covering the wooden load-bearing member 5 with the fire-resistant wooden covering material 1, the cross-sectional design is such that the entire structure is structurally safe against short-term forces (short-term loads) such as fixed loads, live loads, snow loads, wind pressure, and seismic forces, and that the wooden load-bearing member 5 alone is structurally safe against long-term forces (long-term loads) such as fixed loads, live loads, and snow loads. In this embodiment, the fire-resistant wooden covering material 1 has increased strength compared to the original wood, and in particular, if the total dry specific gravity is preferably in the range of 0.55 to 1.30, more preferably 0.70 to 1.20, and even more preferably 0.90 to 1.10, high strength can be obtained, allowing it to bear a predetermined stress even with a thin thickness.

[0043] In addition, the entire thickness of the wood is compressed and plastically processed by heating and compressing it perpendicular to the length direction of the wood grain, resulting in a wood-based fire-resistant coating material 1 with a predetermined compression ratio. Compared to the original wood (solid wood), the surface is easier to process, the smoothness when cut is improved, and the adhesion to the wood-based load-bearing member 5 is improved. Therefore, even when it becomes a carbonized layer during a fire, it is more likely to remain on the wood-based load-bearing member 5.

[0044] Furthermore, if the entire thickness of the wood is compressed and plastically processed by heating and compressing it perpendicular to the length direction of the wood grain, and the wood-based fire-resistant coating material 1 is compressed to a predetermined compression ratio, it can be given a design aesthetic such as a sense of luxury and solidity by becoming darker in color compared to the original wood.

[0045] Thus, according to this embodiment, the wood-based fire-resistant covering material 1 is attached (glued) to the wood-based load-bearing member 5 by joining it with adhesive or screws, etc., so as to cover its outer surface, and can function as a burnable layer while also allowing the texture of the wood to be exposed. In other words, when exposed to flames, the wood-based fire-resistant coating material 1 gradually carbonizes, but the carbonized layer of the carbonized wood-based fire-resistant coating material 1 acts as an insulating layer, suppressing the progression of carbonization caused by the flames.

[0046] Furthermore, if the wooden load-bearing member 5 remains intact after the fire, the charred wooden fire-resistant covering material 1 can be removed, and a new wooden fire-resistant covering material 1 can be attached to the wooden load-bearing member 5, allowing for easy repair and restoration of the wooden fire-resistant structure 100. Additionally, during the demolition of the building, the wooden load-bearing member 5 and the wooden fire-resistant covering material 1 can be dismantled and separated, promoting the recycling of wood resources.

[0047] Here, the method for manufacturing the wood-based fire-resistant coating material 1 of this embodiment will be described with reference to Figures 2 and 3. The raw material for the wood fire-resistant covering material 1 of this embodiment, unprocessed wood NW, is wood that has been sawn to predetermined dimensions (thickness, width, length) beforehand. That is, felled logs or raw timber are cut into square timber or planks and adjusted to predetermined dimensions. It is square timber (a rectangular prism of wood with a rectangular cross-section or a cubic wood with a square cross-section) cut from a log with a saw or the like. Thinned wood, damaged wood that has fallen or cracked due to natural disasters such as wind damage, flood damage, snow damage, forest fires, frost damage, or insect damage and can no longer be used in its log form, and scraps may also be used. This makes it possible to reduce costs and also contribute to environmental beautification.

[0048] The type of wood used in the wood-based fire-resistant covering material 1 is not particularly limited and can be either coniferous or broad-leaved. For example, Japanese cedar, cypress, larch, fir, spruce, Japanese red pine, Japanese cypress, walnut, yellow poplar, Italian poplar, fir, hemlock, spruce, yew, Japanese cypress, paulownia, hinoki cypress, birch, Japanese chinquapin, Chinese quince, falcata, gourd, chinaberry, tulip tree, etc. are used. In particular, Japanese cedar and cypress are widely distributed in Japan and thinned timber can be easily obtained in large quantities, thus contributing to environmental conservation. Furthermore, while laminated timber made from Japanese cedar or cypress has traditionally been considered unsuitable for fire-stopping materials compared to larch or Douglas fir, if a wood-based fire-resistant covering material 1 is made by compressing and fixing the entire thickness of the wood by heating and compressing Japanese cedar or cypress wood perpendicular to the length of its grain, resulting in a compression ratio of 45-70%, preferably 48-65%, and more preferably 50-60% relative to the original air-dry specific gravity of the wood, then fire penetration can be suppressed and a fire-stopping effect can be expected. Generally, coniferous trees such as cedar have a large amount of resin, and since the amount of resin exposed by heat compression is less in the sapwood compared to the heartwood, heartwood-free lumber is preferable. Furthermore, from the viewpoint of being less prone to cracking due to heat compression, flat-sawn or quarter-sawn lumber is preferable. In addition, from the viewpoint of reducing costs, it is preferable to use lumber that has been sawn as flat-sawn or quarter-sawn lumber as the raw material before processing, but quarter-sawn lumber may also be used. Flat-sawn lumber is lumber that has been sawn in the direction tangential to the annual rings of the log, i.e., flat-sawn lumber, while quarter-sawn lumber is lumber that is cut in an intermediate way between quarter-sawn lumber, which is sawn perpendicular to the annual rings of the log, and flat-sawn lumber, which is sawn in the direction tangential to the annual rings of the log.

[0049] Before performing a predetermined plastic deformation (compression) using the plastic deformation wood manufacturing apparatus 20 shown in Figures 2 and 3, the unprocessed lumber NW, which has been sawn to a predetermined size, is dried to a moisture content below the fiber saturation point. Drying to a moisture content below the fiber saturation point, preferably below the air-dry state, provides strength and allows for sufficient chemical changes to occur through subsequent heating and compression. The moisture content of wood is the ratio of the weight of water to the weight of wood without water (total dry weight, dry base), and can be measured using, for example, a high-frequency moisture meter or the total dry method. Generally, since water evaporates from the surface of the wood, the moisture content of the wood decreases closer to the surface, but the moisture content shown here represents the value measured as the moisture content of the entire wood.

[0050] Drying unprocessed wood NW to a predetermined moisture content can be done using known drying equipment, such as an artificial dryer (steam drying, weak vacuum drying, etc.) that uses known high-temperature steam as a heat source and incorporates a refrigerator. It is not limited to artificial drying and may be used in combination with natural drying. In this case, the overall moisture content of the unprocessed wood NW is measured beforehand, and the drying conditions in the drying equipment, such as the artificial dryer, are set using this moisture content, the wood species, and its thickness as parameters, so that the wood reaches a predetermined moisture content after drying. These conditions include a predetermined temperature, humidity, and drying time (for example, in the case of cedar or cypress, a drying temperature of approximately 40-100°C, a wet-bulb temperature difference of approximately 1-30°C, and a drying period of approximately 3-10 days). Typically, the drying temperature is gradually increased and the humidity is gradually decreased during the drying period. While it is possible to increase the strength of wood NW by reducing its moisture content before processing, if the moisture content of the wood NW is reduced too much, the shrinkage of the wood NW will impair its strength and cause cracking during the drying process. Therefore, for example, in the case of cedar or cypress wood, it is preferable to dry the wood NW before processing so that the overall moisture content is in the range of 5% to 15%. More preferably, the moisture content is in the range of 8% to 10%. In this explanation, the wood is cut from logs or raw timber, sawn to a predetermined size, and then dried. However, when implementing the present invention, the wood cut from logs or raw timber may be dried to a predetermined moisture content before being sawn to a predetermined size.

[0051] Then, plastic deformation is performed by applying a heat compression treatment and a compression fixing treatment to the unprocessed wood NW, which has been dried to a predetermined moisture content. In Figures 2 and 3, the plastic deformation wood manufacturing apparatus 20 for manufacturing the wood fire-resistant coating material 1, that is, the plastic deformation apparatus 20 for compressing and compressively fixing the wood NW before processing, mainly consists of a press plate 10 which forms an internal space IS by a two-part structure consisting of an upper press plate 10A and a lower press plate 10B, and a device which is disposed on the peripheral edge 10a of the upper press plate 10A facing the peripheral edge 10b of the lower press plate 10B, and seals the internal space IS within a predetermined range of vertical movement of the upper press plate 10A. The system consists of a sealing member 11, a pipe 12 that communicates with the internal space IS from the upper side of the upper press platen 10A and has a pipe opening 12a for supplying steam to the internal space IS, a valve V4 upstream of the pipe 12, a pipe 13 that communicates with the internal space IS from the side of the lower press platen 10B and has a pipe opening 13a for discharging steam from the internal space IS, a pressure gauge P2 for detecting the steam pressure in the pipe 13, a valve V5 downstream of the pipe 13, and a drain pipe 14 connected to the valve V5.

[0052] As the press plate 10, a flat die with a flat size capable of pressing the entire front and back surfaces of the wood NW before processing is used, and the material of the die is not particularly specified, but in order to prevent the wood from turning black due to iron ion contamination, for example, stainless steel or aluminum may be used for the die, or it may be plated with a non-ferrous metal such as aluminum. Furthermore, the sealing member 11 used to seal the internal space IS is not particularly limited in terms of material, but typically silicone rubber, silicone resin, or the like, which have excellent heat resistance and water resistance, are used.

[0053] In the upper press plate 10A and lower press plate 10B of the press plate 10, piping passages 15 and 16 are formed to raise them to a desired temperature by passing high-temperature steam through them. Pipes ST2 and ST3, which are branched from the steam supply pipe ST1, and pipes ET1 and ET2, which are steam discharge pipes, are connected to these piping passages 15 and 16, respectively. Valves V1, V2, and V3 and a pressure gauge P1 for detecting the steam pressure in pipe ST1 are installed in the middle of the steam supply pipes ST1, ST2, and ST3. Pipes ET1 and ET2, which are steam discharge pipes, are connected to a drain pipe 14 via valve V6. In addition, although not shown, a steam introduction passage is formed in the formwork section provided on the periphery of the upper press plate 10A, which communicates with the internal space IS from its side and supplies steam into the internal space IS. A pipe branched from the steam supply pipe ST1 is connected to this passage.

[0054] Furthermore, pipes ST12 and ST13, which branch off from the cooling water supply pipe ST11, are connected to the pipes ST2 and ST3, respectively. These pipes supply pipes ST11 cools the material to a desired temperature by passing low-temperature cooling water through the piping passages ST5 and ST16 formed within the upper press plate 10A and lower press plate 10B, replacing high-temperature steam. Valves V11, V12, and V13 are also installed along the cooling water supply pipes ST11, ST12, and ST13. Note that in Figures 2 and 3, the boiler device that supplies high-temperature steam to piping ST1, the cooling water supply device that supplies cooling water to piping ST11, and the press lifting device, which includes a hydraulic mechanism for raising / lowering the movable upper press plate 10A relative to the fixed lower press plate 10B of the press plate 10 and applying pressure, are omitted. The upper press plate 10A and the lower press plate 10B, which are arranged at a predetermined interval in the vertical direction, are attached to a press device (not shown) and can move closer to and further apart from each other by raising and lowering the press device.

[0055] When using the plastic deformation wood manufacturing apparatus 20 with this configuration to plastically deform (compact) the wood NW before processing, first, as shown in Figure 3(a), the movable upper press plate 10A is raised relative to the fixed lower press plate 10B that constitutes the press plate 10, and the wood NW before processing is placed on the fixed lower press plate 10B. The unprocessed lumber NW is positioned so that one side of its front and back surfaces, perpendicular to the grain length direction, faces the upper press plate 10A, and the other side faces the lower press plate 10B. In other words, all sides of the unprocessed lumber NW except the end grain and edge faces face the press plates 10A and 10B. If the unprocessed lumber NW is flat-sawn or quarter-sawn, the front-side flat-sawn surface, the front-side quarter-sawn surface, and the back-side flat-sawn surface are all facing the press plates 10A and 10B. If the unprocessed lumber NW is quarter-sawn, the quarter-sawn surface faces the press plates 10A and 10B.

[0056] In this way, the unprocessed wood NW is positioned between the upper press plate 10A and the lower press plate 10 such that the pressing surfaces of the upper press plate 10A and the lower press plate 10 are perpendicular to the thickness direction of the unprocessed wood NW. As a result, the unprocessed wood NW is pressed by the two-part press plate 10, the upper press plate 10A and the lower press plate 10B, in the thickness direction of the unprocessed wood NW, that is, perpendicular to the length direction of the wood grain of the unprocessed wood NW.

[0057] Specifically, the front and back surfaces of the unprocessed wood NW are faced towards the upper press plate 10A and lower press plate 10B of the press plate 10, and the unprocessed wood NW is placed on the fixed lower press plate 10B. As shown in Figure 3(b), first, the upper press plate 10A is lowered at a predetermined pressure (e.g., 0.05 to 0.3 MPa) and brought into contact with the upper surface of the unprocessed wood NW, preferably the flat-sawn or quarter-sawn surface on the wood face side of the unprocessed wood NW, for a predetermined time (e.g., 10 to 120 seconds). At this time, the upper press plate 10A and the lower press plate 10B are heated to a predetermined temperature (e.g., 110 to 210°C) by passing high-temperature steam at a predetermined temperature (e.g., 110 to 210°C, heating time 10 to 25 minutes) through the piping 15 of the upper press plate 10A and the piping 16 of the lower press plate 10B.

[0058] Then, the compression pressure of the upper press plate 10A relative to the fixed lower press plate 10B is set to a predetermined pressure (for example, 2-5 MPa, 20-50 kg / cm²). 2The upper press plate 10A and lower press plate 10B are set to heat and compress the unprocessed wood NW (for example, processing time 0.5 to 3 minutes, compression speed 15 to 100 mm / min). The upper press plate 10A is lowered, and the unprocessed wood NW is heated and compressed by the upper press plate 10A and lower press plate 10B. When the peripheral edge 10a of the upper press plate 10A comes into contact with the peripheral edge 10b of the lower press plate 10B, as shown in Figure 3(c), the sealing member 11 disposed on the peripheral edge 10a of the upper press plate 10A seals the internal space IS formed by the upper press plate 10A and lower press plate 10B.

[0059] Furthermore, when the internal space IS formed by the upper press plate 10A and lower press plate 10B of the press plate 10 is sealed via the sealing member 11, the vertical dimensional spacing of the internal space IS is set to the finished dimension in the thickness direction when the press plate 10 compresses the pre-processed wood NW to a predetermined compression ratio relative to its original thickness. Therefore, the overall compression ratio of the pre-processed wood NW, that is, the change in plate thickness (amount of compression) due to the compression of the pre-processed wood NW, is determined by the contact between the peripheral edge 10a of the upper press plate 10A and the peripheral edge 10b of the lower press plate 10B. At this time, the pressure, heating temperature, heating time, compression speed, etc. of the press plate 10 are set to optimal values ​​in advance through experiments, etc., using parameters such as the type of wood and the moisture content of the dried wood.

[0060] Thus, when the lower press plate 10B is fixed and the upper press plate 10A is moved in a press plate 10 heated to a predetermined temperature, and brought into contact with the upper surface of the unprocessed wood NW at a predetermined pressure and lowered at a predetermined compression speed, the unprocessed wood NW softens due to a decrease in strength caused by changes in the chemical properties of the wood components (hydrolysis of amorphous components such as hemicellulose and lignin, and a decrease in the softening point) from the surface and back layers to the interior, the cells are compressed and deformed, and the voids inside the cells decrease.

[0061] Next, with the internal space IS sealed as shown in Figure 3(d), the compression pressure of the upper press plate 10A and the lower press plate 10B is maintained, and the upper press plate 10A and the lower press plate 10B remain at a predetermined temperature (for example, 110-210°C), while the heat compression treatment of the wood is fixed, or in other words, the wood is immobilized. For example, a predetermined steam pressure is supplied to the sealed internal space IS via the piping 12 connected to valve V4, the piping opening 12a, and the steam introduction passage (not shown) in the formwork section of the upper press platen 10A. The compression pressure and heating temperature of the upper press platen 10A and the lower press platen 10B are maintained at the same predetermined pressure and temperature as during heating and compression, and the sealed internal space IS is maintained at a predetermined temperature and steam pressure for a predetermined time (e.g., 20 to 90 minutes). High-temperature steam at a predetermined temperature (e.g., 110 to 210°C) is introduced into the internal space IS, and the sealed internal space IS is brought to a predetermined temperature and steam pressure. This causes sufficient chemical changes to occur in the heated and compressed wood placed inside the sealed internal space IS due to the action of high-temperature, high-pressure steam, thereby uniformizing its properties. As a result, a wood-based fire-resistant coating material 1 that does not revert to its original state can be formed when the subsequent cooling and compression is released.

[0062] At this time, high-temperature, high-pressure vapor pressure can freely enter and exit the surrounding surface and the interior of the heated and compressed wood. Depending on the moisture content of the heated and compressed wood, the internal space IS, which is sealed by the upper press plate 10A and the lower press plate 10B, may be adjusted to a predetermined vapor pressure. For example, excess moisture in the internal space IS based on the moisture content of the front and back sides of the wood is removed, and the internal space IS is adjusted to a predetermined vapor pressure. That is, when the heat-compressed wood is being fixed in the sealed internal space IS, the vapor pressure in the internal space IS is detected by the pressure gauge P2 as a vapor pressure control process, and the valve V5 is opened and closed as appropriate so that high-temperature, high-pressure water vapor can be discharged from the internal space IS to the drain pipe 14 side through the pipe opening 13a and pipe 13. Also, if necessary, a predetermined vapor pressure may be supplied to the sealed internal space IS as appropriate.

[0063] Then, as shown in Figure 3(d), just before the transition from heating compression by the upper press plate 10A and lower press plate 10B to cooling compression, the valve V5 is opened as a steam pressure control process, causing high-temperature, high-pressure steam to be discharged from the compression space IS to the drain pipe 14 side through the pipe opening 13a and pipe 13. This further promotes the fixing of the wood. At this time, the supply of steam to maintain the upper press plate 10A and lower press plate 10B at a specific temperature is also temporarily stopped.

[0064] Then, as shown in Figure 3(e), by passing room-temperature cooling water through the piping 15 of the upper press platen 10A and the piping 16 of the lower press platen 10B, the upper press platen 10A and the lower press platen 10B are cooled to around room temperature and held for a predetermined time (for example, 20 to 90 minutes). At this time, the compression pressure of the upper press platen 10A relative to the fixed lower press platen 10B is maintained at the same predetermined pressure as during heating and compression (for example, 2 to 5 MPa), while the upper press platen 10A and the lower press platen 10B are cooled. Subsequently, as shown in Figure 3(f), the upper press plate 10A is raised relative to the fixed lower press plate 10B, and the wood fire-resistant coating material 1, which has undergone plastic deformation (consolidation) by heating, compression, and fixation, is removed from the internal space IS, thus completing the series of processing steps. The wood fire-resistant coating material 1 removed from the internal space IS has been compacted by the heating, compression, steam pressure treatment, and cooling treatment in the series of processing steps. That is, it has been compressed, and further, that compression has been fixed and plastically deformed. After this, the surface of the wood fire-resistant coating material 1 is usually cut to ensure flatness. In particular, the surface of the wood fire-resistant coating material 1 is easier to process compared to the original wood (solid wood), improving the smoothness through cutting and improving adhesion with the wood load-bearing member 5. Also, if necessary, a surface coating with resin or the like may be applied to protect against moisture and dirt.

[0065] Next, we will describe the results of a cone calorimeter test and a heating test using a small combustion furnace for the wood-based fire-resistant coating material 1 of this embodiment, which is compressed and plastically deformed by heating and compression perpendicular to the length direction of the wood grain, resulting in a compression ratio of 40-60%, preferably 48-65%, and more preferably 50-60% relative to the air-dry specific gravity of the original wood.

[0066] In the corn calorimeter test, specimens 1-1, 1-2, 2, 3-1, and 3-2 were used as examples, and specimens 4-1, 4-2, 5, and 6 were used as comparative examples. Test specimens 1-1 and 1-2 of the example are wood-based fire-resistant coating material 1, which is obtained by heating and compressing cedar wood perpendicular to the length direction of its grain to compress the entire thickness and perform plastic deformation, resulting in a compression ratio of 51% relative to the air-dry specific gravity of the original wood species (cedar) (compression ratio relative to the original thickness is 55%, and the total dry specific gravity is 0.63). Test specimen 2 of the example is a wood-based fire-resistant coating material 1, which is made by heating and compressing cedar wood perpendicular to the length direction of its grain to compress the entire thickness and perform plastic deformation, resulting in a compression ratio of 65% relative to the air-dry specific gravity of the original wood species (cedar) (compression ratio relative to the original thickness is 67%, and the total dry specific gravity is 0.75). Test specimens 3-1 and 3-2 of the example are wood-based fire-resistant coating material 1, which is obtained by heating and compressing cypress wood perpendicular to the length direction of its grain to compress the entire thickness and perform plastic deformation, resulting in a compression ratio of 55% relative to the air-dry specific gravity of the original wood species (cypress) (compression ratio relative to the original thickness is 55%, and the total dry specific gravity is 0.69).

[0067] Furthermore, comparative specimens 4-1 and 4-2 are uncompressed, solid cedar wood (sawn cedar). Comparative example specimen 5 is uncompressed, solid cypress wood (cypress lumber). Comparative example test specimen 6 is a compressed wood produced by heating and compressing cedar wood perpendicular to the length of its grain, compressing the entire thickness and performing plastic deformation, resulting in a compression ratio of 30% relative to the air-dry specific gravity of the original wood species (cedar) (compression ratio relative to the original thickness is 33%, and total dry specific gravity is 0.45). Each test specimen in the examples and comparative examples had dimensions of 100±1mm in width, 100±1mm in length, and 20±1mm in thickness.

[0068] In the cone calorimeter test, for test specimens 1-1, 1-2, 2, 3-1, 3-2 of these examples and test specimens 4-1, 4-2, 5, 6 of the comparative examples, an electric heater was used to heat the surface of the test specimens at 50 kW / m² in accordance with the ISO 5660-1 cone calorimeter method. 2 The material was heated by radiating heat for 20 minutes (i.e., heated under heating conditions of 50 kW heating intensity and 20 minutes heating time), and the amount of heat generated, the temperature of the back surface, and the state of carbonization were measured. The results are shown in Table 1.

[0069] [Table 1]

[0070] For test specimens 1-1 and 3-1 of the examples, and test specimens 4-1, 5, and 6 of the comparative examples, the amount of heat generated was measured during heating, and observation was conducted after 20 minutes from the start of heating, without extinguishing the flame with water. For test specimens 1-2, 2, and 3-2 of the examples, and test specimen 4-2 of the comparative example, the amount of heat generated and the temperature of the back surface were measured during heating. After heating was completed 20 minutes from the start of heating, the flame was extinguished with water and the carbonization state was observed. The changes in the temperature of the back surface of test specimens 1-2, 2, and 3-2 of the examples, and test specimen 4-2 of the comparative example are shown in the graph in Figure 4.

[0071] In comparative example specimens 4-6, flammable gas ignited from the sides and back of the specimens 14 minutes after the start of heating, causing the entire specimen to burn. As shown in Table 1, comparative example specimens 4-1, 5, and 6, which were not extinguished with water after the heating ended 20 minutes after the start of heating, carbonized and disintegrated completely. Furthermore, in comparative example test specimen 4-2, the temperature on the back surface rose to 200°C after 13 minutes and 30 seconds from the start of heating, reaching a temperature at which thermal decomposition occurred all the way to the back surface of the test specimen.

[0072] In contrast, in the examples, when water was not used to extinguish the fire with test specimens 1-1 and 3-1 after 20 minutes from the start of heating, the specimens extinguished themselves, did not carbonize and collapse, and no cracks or holes penetrating to the back surface were observed. Furthermore, as shown in Table 1 and the graph in Figure 4, the back surface temperatures of test specimens 1-2, 2, and 3-2 remained below 200°C (the temperature at which thermal decomposition of wood begins) even after 20 minutes from the start of heating. In other words, in the test specimens 1 to 3 of the examples, even after being exposed to a flame for 20 minutes, no burning occurred from the heated side (flame generation side) to the opposite side (back side).

[0073] In particular, for test specimens 1-1 and 3-1 of the examples, and test specimen 6 of the comparative example, after heating was completed 20 minutes after the start of heating, the fire was extinguished with water and the carbonization state was observed. As shown in Figure 5, test specimens 1-1 and 3-1 of the examples did not have cracks or holes penetrating to the back surface compared to test specimen 6 of the comparative example. Furthermore, looking at the surface side, the carbonized layer had expanded significantly and recovered to approximately the same thickness as the original wood.

[0074] Therefore, in the examples, although a carbonized layer is formed upon heating, it is presumed that the expansion of that portion due to heating increased the heat insulation effect, suppressing the temperature rise and thus slowing down the rate at which the burning progresses from the surface to the interior, i.e., the carbonization rate. Furthermore, in the examples, the dense surface slows down ignition, and it is also possible that the high specific gravity (density) and the large amount of trapped moisture suppress the temperature rise and slow down the carbonization rate.

[0075] Thus, the wood-based fire-resistant coating material 1 of this embodiment makes it possible to delay the burning time. In particular, when the heated surface is limited, the overall temperature does not rise easily with a 20-minute flame, and thermal decomposition does not continue easily. It is considered possible to suppress the heat input to the unburned portion on the back side even when exposed to a flame for 20 minutes. Furthermore, the volume expands due to the heat of the flame, exhibiting a high heat insulation effect, which allows the thickness to be reduced under normal conditions.

[0076] Furthermore, in heating tests using a small combustion furnace, test specimens A, B, and C were prepared as examples. Test specimen A of the example is a wood-based fire-resistant covering material 1, which is made by heating and compressing cedar wood perpendicular to the length of its grain to compress the entire thickness and plasticize it, resulting in a compression ratio of 51% relative to the air-dry specific gravity of the original wood species (cedar) (compression ratio relative to the original thickness is 55%, total dry specific gravity is 0.63), and a cypress laminated timber (corresponding to the wood-based load-bearing member 5) is joined to its back surface with long screws. Test specimen B of the example is a wood-based fire-resistant covering material 1, which is made by heating and compressing cedar wood perpendicular to the length direction of its grain to compress the entire thickness and plasticize it, resulting in a compression ratio of 65% relative to the air-dry specific gravity of the original wood species (cedar) (compression ratio relative to the original thickness is 67%, total dry specific gravity is 0.75), and a cypress laminated timber (corresponding to the wood-based load-bearing member 5) is joined to its back surface with long screws. Test specimen C of the example is a wood-based fire-resistant covering material 1, which is made by heating and compressing cypress wood perpendicular to the length direction of its grain to compress the entire thickness and plasticize it, resulting in a compression ratio of 55% relative to the air-dry specific gravity of the original wood species (cypress) (compression ratio relative to the original thickness is 55%, total dry specific gravity is 0.69), and a cypress laminated timber (corresponding to the wood-based load-bearing member 5) is joined to its back surface with long screws.

[0077] Each test specimen A to C was constructed by joining two pieces of wood fire-resistant coating material 1 (width 105±1mm × length 900±1mm × thickness 20±1mm) together with a water-based polymer isocyanate adhesive to create a specimen with dimensions of 210±1mm × length 900±1mm × thickness 20±1mm. A piece of cypress laminated timber (E105-F300, width 210±1mm × length 900±1mm × thickness 85±1mm), cut lengthwise, was joined to the back side with long screws, resulting in an overall dimension of 210±1mm × length 900±1mm × thickness 105±1mm. The heating surface of each test specimen A to C was set to 210mm × length 800mm.

[0078] As shown in Figures 6 to 8, test specimens A to C were arranged side by side, and the sides of each specimen were covered with reinforced gypsum board (25 mm thick). They were then placed vertically in a small refractory furnace and heated for 1 hour from the side with the wood refractory covering 1, according to the ISO 834 standard heating curve. After 1 hour of heating, they were left in the refractory furnace for 3 hours without extinguishing the fire with water. The parts of the heating surface other than wood were covered with AES wool on calcium silicate board. In the heating test using the small combustion furnace, a thermocouple was attached to each specimen by drilling a hole (φ3.5 mm) from the back to the front and inserting a sheath-type thermocouple (outer diameter φ3.2 mm). The internal temperature of a predetermined location on the specimen was measured using the attached thermocouple (temperature measurement at the measurement points indicated by [1] to [5] in Figures 6 to 8), and the time until the inside reached 260°C was measured. After 3 hours had elapsed since the end of heating, the specimens were removed from the furnace and the carbonization state of each specimen was observed. The measurement results for the internal temperature (temperature changes at the measurement points indicated by [1] to [5] in Figures 6 to 8) are shown in the graph in Figure 9, and the measurement results for the time it took for the internal temperature to reach 260°C are shown in Table 2. In Table 2, the temperature at the measurement point where the temperature was below 260°C at the end of 1 hour of heating is recorded.

[0079] [Table 2]

[0080] Furthermore, as comparative examples, the test results for specimen D, a solid cedar wood (sawn cedar) (width 210±1mm × length 900±1mm × thickness 105±1mm), and specimen E, a solid cypress wood (sawn cypress) (width 210±1mm × length 900±1mm × thickness 105±1mm), are also shown in Table 2.

[0081] As shown in Table 2, in comparative specimens D and E, the temperature reached over 200°C at 30 mm from the heated surface (10 mm from the surface of the cypress laminated wood) after 1 hour of heating. In contrast, as shown in Table 2 and Figure 9, the carbonization rate for specimens A and C in the example was approximately 0.36 mm / minute, and for specimen B in the example, the carbonization rate was approximately 0.23 mm / minute. In all of specimens A to C, the temperature was kept below 200°C at 30 mm from the heated surface (10 mm from the surface of the cypress laminated wood) after 1 hour of heating. Furthermore, when the cross-sections of specimens A to C were examined after the experiment, the carbonization depth was 30 mm or less in all cases. From this, it was confirmed that test specimens A to C of the examples showed higher fire resistance compared to test specimens D and E of the comparative examples, and that the rise in internal temperature at the end of 1 hour of heating was slower. Furthermore, during the standing time, the wood fire-resistant coating material 1 of test specimens A to C stopped burning and extinguished on its own.

[0082] Furthermore, in the examples A to C, the temperature on the back surface did not reach 200°C even after 1 hour of heating, and no damage such as charring or discoloration was observed in the laminated wood. Therefore, it can be seen that the heat shielding performance of the wood fire-resistant coating material 1 in the examples A to C is effective in preventing combustion of the laminated wood (frame, axial members) (corresponding to the wood load-bearing member 5) and provides high fire resistance.

[0083] In particular, although the wood fire-resistant coating material 1 of test specimens A to C in the examples is 20 mm thick, the time to reach 260°C at the measurement point ([2]) 10 mm from the heated surface was 39 minutes or more, and the time to reach 260°C at the measurement point ([3]) 20 mm from the heated surface was 55 minutes or more, indicating that it is effective for 45-minute semi-fire-resistant structures and 1-hour semi-fire-resistant structures. Given that the burn allowance dimension for sawn timber in columns and beams of current 45-minute semi-fire-resistant structures is 45 mm, and the burn allowance dimension for laminated timber and LVL is 35 mm, it is possible to slim down the thickness of the current burn allowance dimension in 45-minute semi-fire-resistant structures. That is, the thickness of the wood fire-resistant coating material 1 is preferably 20 mm or more and less than 35 mm, more preferably 20 mm or more and 33 mm or less, making it applicable to 45-minute semi-fire-resistant structures. Furthermore, compared to sawn lumber, laminated lumber uses adhesive, which can lead to a decrease in adhesive strength due to heat generated by the adhesive, potentially causing the fire to spread more easily. However, with wood-based fire-resistant coating material 1, the fire is less likely to spread, and a self-extinguishing effect can also be expected.

[0084] As described above, the wood fire-resistant covering material 1 of the above embodiment covers the wood load-bearing member 5 and carbonizes when exposed to flames to form a carbonized layer. The entire thickness is compressed and plastically processed by heating and compression perpendicular to the length direction of the wood grain, resulting in a compression ratio of 40-70%, preferably 45-65%, and more preferably 55-60% relative to the air-dry specific gravity of the original wood. According to the wood fire-resistant coating material 1 of the above embodiment, the density is increased by compression to a predetermined compression ratio, which delays ignition. Furthermore, moisture is trapped inside, making it difficult for the internal moisture to escape to the outside of the material, thus slowing the progress of combustion. In addition, even if the material is thin, it expands during flames to form a thick carbonized layer, which increases heat insulation and slows the progress of combustion and reduces the carbonization rate. Therefore, it becomes possible to reduce the thickness of the burnt layer covering the wood load-bearing member 5. This makes it possible to reduce the overall cross-sectional area of ​​the wooden fire-resistant structure 100. Moreover, according to the wood fire-resistant coating material 1 of this embodiment, when applied to the wooden fire-resistant structure 100 and covering the wood load-bearing member 5, the texture of the wood can be revealed.

[0085] In the wood fire-resistant coating material 1 of the above embodiment, if its total dry specific gravity is preferably in the range of 0.55 to 1.30, more preferably 0.70 to 1.20, and even more preferably 0.90 to 1.10, then even if the thickness of the burnable layer is reduced, sufficient strength to withstand short-term load stress can be secured.

[0086] In the wood-based fire-resistant coating material 1 of the above embodiment, if its moisture content is preferably in the range of 5.0 to 20.0%, more preferably 10.0 to 15.0%, and even more preferably 11.0 to 13.0%, then dimensional stability can be achieved, and the carbonization rate can be slowed without causing cracks during flames.

[0087] Furthermore, the above description of the embodiment can also be interpreted as an invention of a wood fire-resistant structure 100 comprising a wood load-bearing member 5 that supports long-term loads, and a wood fire-resistant covering material 1 that covers the wood load-bearing member 5 and serves as a burnable layer that carbonizes during flames to form a carbonized layer, wherein the wood fire-resistant covering material 1 is plastically processed by heating and compressing the entire thickness perpendicular to the length direction of the wood grain, resulting in a compression ratio of 45-70%, preferably 48-70%, and more preferably 50-68% relative to the air-dry specific gravity of the original wood.

[0088] According to the above embodiment of the fire-resistant wooden structure 100, the fire-resistant wooden covering material 1, which serves as a burnable layer covering the wooden load-bearing member 5, carbonizes during flames to form a carbonized layer. The entire thickness is compressed and plastically processed by heating and compression perpendicular to the length direction of the wood grain, resulting in a compression ratio of 40-70%, preferably 45-65%, and more preferably 55-60% of the original air-dry specific gravity of the wood. As a result of this predetermined compression ratio, the density is increased, which delays ignition. Furthermore, moisture is trapped inside, making it difficult for the internal moisture to escape to the outside of the material, thus slowing the progress of combustion. In addition, even with a thin material thickness, it expands during flames to form a thick carbonized layer, increasing heat insulation and thus slowing the progress of combustion and the rate of carbonization. Therefore, it becomes possible to reduce the thickness of the burnable layer covering the wooden load-bearing member 5. This makes it possible to reduce the overall cross-sectional area of ​​the fire-resistant wooden structure 100. Furthermore, according to the fire-resistant wooden structure 100 of this embodiment, the wooden load-bearing member 5 is covered with the fire-resistant wooden covering material 1, which allows the texture of the wood to be revealed.

[0089] By the way, in the above embodiment, the wood fire-resistant covering material 1 was described as being placed immediately outside the wood load-bearing member 5 to form a burn-through layer. However, when implementing the present invention, a fire-stopping layer (for example, a flame-retardant layer having flame retardancy or a heat-absorbing layer capable of absorbing heat) may be placed immediately outside the load-bearing member 5, and the burn-through layer may be placed outside that fire-stopping layer. That is, the wood fire-resistant covering material 1 may be joined to the fire-stopping layer placed around the wood load-bearing member 5 with an adhesive or the like. In this case, when a fire occurs, the flames ignite the wood fire-resistant covering material 1, which acts as a combustible layer, and the wood fire-resistant covering material 1 burns, forming a carbonized layer. As a result, heat transfer and oxygen supply from the outside of the burning wood fire-resistant covering material 1 to the wood load-bearing member 5 are blocked by the carbonized layer, and the combustion-stopping layer absorbs heat, etc., slowing down the burning rate (carbonization rate) of the wood fire-resistant covering material 1, which is the combustible layer, and stopping the burning of the wood fire-resistant covering material 1 (natural extinguishing). This suppresses the temperature rise of the wood load-bearing member 5 during and after a fire, suppresses the combustion of the wood load-bearing member 5, and makes it possible to create a fire-resistant wooden structure that can support long-term loads on the wood load-bearing member 5 during a fire. In other words, the wood-based fire-resistant coating material 1 of the present invention can be applied as a burnable layer to wood-based columns and beams in semi-fire-resistant or fire-resistant structures.

[0090] Furthermore, when implementing the present invention, the materials, size, and composition of the wood fire-resistant covering material 1 and other parts of the wood fire-resistant structure 100 are not limited to this embodiment. Also, the numerical values ​​given in the embodiments of the present invention do not represent critical values, but rather suitable values ​​for implementation, so slightly changing the above numerical values ​​does not negate implementation. [Explanation of Symbols]

[0091] 1 Wooden fireproof cladding 5. Wooden load-bearing member 100 Wooden fireproof structure

Claims

1. A wood-based fire-resistant covering material that covers a wooden load-bearing member and carbonizes during flames to form a carbonized layer, A wood-based fire-resistant coating material characterized by being compressed and plastically processed across its entire thickness by heating and compression perpendicular to the length direction of the wood grain, resulting in a compression ratio within the range of 45 to 70% relative to the air-dry specific gravity of the original wood.

2. The wood-based fire-resistant coating material is characterized in that its total dry specific gravity is in the range of 0.55 to 1.30, as described in claim 1.

3. The wood-based fire-resistant coating material according to claim 1, characterized in that the moisture content of the wood-based fire-resistant coating material is in the range of 5.0% to 20.0%.

4. A wood fire-resistant structure comprising a wood load-bearing member that supports long-term loads, and a wood fire-resistant covering material that covers the wood load-bearing member and serves as a burnable layer that carbonizes during flames to form a carbonized layer, The aforementioned wood-based fire-resistant covering material is characterized in that its entire thickness is compressed and plastically processed by heating and compression perpendicular to the length direction of the wood grain, resulting in a compression ratio within the range of 45 to 70% relative to the air-dry specific gravity of the original wood.

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