Highly weather-resistant heat-treated wood and its manufacturing method

Abstract

To provide a high weather resistance heat-treated lumber having antiseptic, dimensional stability, and antiseptic / termite repellency performance due to chemicals, which is less susceptible to fading and excellent in weather resistance, and a production method thereof.SOLUTION: A preservation treatment agent is penetrated inside from a surface of a lumber in a state an inside hydroxyl group is hydrophobized as hemicellulose in the lumber is decomposed and modified through heat treatment. The preservation treatment agent includes a copper compound. The preservation treatment agent is penetrated through processes of: receiving an untreated solid lumber body 12 in a sealed tank, carrying out pressure reduction in the sealed tank, carrying out heat treatment to introduce steam in the sealed tank and to increase a temperature; and penetrating the preservation treatment agent through injection.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to highly weather-resistant heat-treated wood obtained by subjecting wood to heat treatment, and to a method for producing the same. [Background technology]

[0002] There is heat-treated wood, which is made by subjecting solid wood sawn from logs to heat treatment with steam or other methods to improve its rot resistance and dimensional stability. Such heat-treated wood has a low moisture content, and the hemicellulose in the wood is decomposed and denatured by the heat treatment, changing the properties of the wood. In addition, the decomposition products of hemicellulose react with other components such as lignin to produce dark colored substances, which give the wood a calm dark brown color. When cedar is heat-treated, the unique contrast between the heartwood and sapwood is toned down, and the overall color can be toned to a dark brown. However, in cases where heat-treated wood is installed outdoors, the above-mentioned colored substances are decomposed by ultraviolet rays such as sunlight, and the color changes due to the decomposition, and the wood fades to a grayish white color in a relatively short period of time outdoors.

[0003] Conventionally, methods have been considered for suppressing discoloration of such heat-treated wood due to ultraviolet rays when used outdoors. For example, a method for producing heat-treated wood disclosed in Patent Document 1 includes a decompression treatment step in which solid wood to be treated is accommodated in an enclosed space and the internal pressure of the enclosed space is maintained at 50 kPa or less, a heated steam treatment step in which superheated steam is introduced into the enclosed space accommodating the treated wood whose oxygen content has been reduced by the decompression treatment step to heat the treated wood to a temperature of 170°C or more, and a discoloration promotion step in which a discoloration promotion treatment is performed on the treated wood after the heated steam treatment step. In the discoloration promotion step, a liquid containing a chlorine-based or oxygen-based oxidizing agent is applied to the treated wood, and then heating or ultraviolet irradiation is performed. According to this method for producing heat-treated wood, discoloration of the treated wood due to decomposition of coloring substances is promoted, thereby forcibly causing aging of the treated wood, and discoloration due to light during use can be suppressed.

[0004] On the other hand, there is treated wood, which is solid wood that has been treated with a wood preservative. A common treatment method is pressure injection treatment, which involves immersing the wood in a liquid in which the preservative is dissolved in water or an organic solvent, and applying pressure in a sealed container to allow the preservative components to penetrate into the wood. This method is specified as a pressurized preservation treatment method for wood materials in JISA9002. Preservatives used include ACQ (Alkaline Copper Quaternary), which is a combination of copper compounds and benzalkonium chloride or didecyldimethylammonium chloride, and CUAZ, which is a combination of copper compounds and cyproconazole. This treated wood has antiseptic properties and anti-termite properties that prevent damage by termites. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-30404 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the case of the background art, the heat-treated wood of Patent Document 1 forcibly discolors the heat-treated wood to a grayish white color, and the dark brown color of the heat-treated wood cannot be utilized. In addition, this heat-treated wood has insufficient termite resistance, and there is a demand for improved termite resistance. On the other hand, general preservative-treated wood can obtain antiseptic and termite resistance, but cannot obtain the improved dimensional stability of heat-treated wood. In addition, when ACQ or CUAZ containing a copper compound is used as a preservative, the wood turns green, giving an artificial and unnatural appearance.

[0007] The present invention has been made in consideration of the problems in the background art described above, and aims to provide highly weather-resistant heat-treated wood that combines anti-corrosion properties and dimensional stability due to heat treatment, and anti-corrosion and anti-termite properties due to chemicals, is resistant to fading, and has excellent weather resistance, as well as a method for producing the same. [Means for solving the problem]

[0008] The present invention relates to a wood material in which hemicellulose in wood is decomposed and modified by heat treatment, and the internal hydroxyl groups are hydrophobized, and A preservative containing a copper compound penetrates into the wood from the surface, giving the surface a dark brown color that does not fade even when exposed to ultraviolet light, and highly weather-resistant heat-treated wood is produced. Solid, untreated wood bodies are placed in a sealed tank, and a decompression treatment is performed by reducing the pressure inside the sealed tank from atmospheric pressure to reduce the amount of air contained in the untreated wood. The temperature is then raised to the heat treatment temperature of the wood, and the heat treatment is performed by maintaining the heated heat treatment temperature of the wood, thereby decomposing and denaturing the hemicellulose in the untreated wood body and reducing the internal hydroxyl groups. the temperature in the sealed tank is lowered from the heat treatment temperature and the untreated wood body is removed from the sealed tank, the untreated wood body becomes a heat-treated wood body that has been subjected to heat treatment, the heat-treated wood body is placed in an injection can and immersed in an aqueous solution of the preservative under reduced pressure and held, then pressurized and held, and then reduced and held again, the pressure is returned to normal pressure, the wood is left in the injection can for preservation, and the heat-treated wood body is removed from the injection can to become the highly weather-resistant heat-treated wood in which preservation has been applied.

[0009] The present invention also provides The method for producing highly weather-resistant heat-treated lumber according to claim 1, characterized in that the heat-treated wood body is placed in the infusion can and immersed in the aqueous solution of the preservative, the pressure is reduced from atmospheric pressure to -0.085 MPa and held for 30 minutes, then pressurized to 1.3 MPa and held for 180 minutes, the pressure is reduced from atmospheric pressure to -0.085 MPa and held for 30 minutes, the pressure is returned to normal pressure and the wood is left in the infusion can for 60 hours for preservation, and the wood body is taken out of the infusion can to obtain the highly weather-resistant heat-treated lumber having been subjected to preservation. The temperature for the heat treatment of the wood is 190 to 220°C. The heat treatment of the wood is performed under a pressurized condition of 0.01 MPa. The type of wood is cedar. Effect of the Invention

[0010] The highly weather-resistant heat-treated wood and its manufacturing method of the present invention have both the antiseptic and dimensional stability that are the characteristics of heat-treated wood, and the termite resistance that is the characteristic of wood treated with a preservative, and furthermore, the dark brown color characteristic of heat-treated wood is maintained for a long period of time and does not fade due to the effects of ultraviolet rays. In the case of cedar, the dark brown color characteristic of heat-treated wood tone down the contrast between the heartwood and sapwood that is characteristic of cedar, and the overall color can be toned to a dark brown, and the toned state can be maintained for a long period of time. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing a method for producing highly weather-resistant heat-treated lumber according to one embodiment of the present invention. [Diagram 2] 1 is a graph showing the results of a preservative test using Ophiopogon palustris on the highly weather-resistant heat-treated wood of this embodiment, where (a) shows highly weather-resistant heat-treated wood using ACQ, and (b) shows highly weather-resistant heat-treated wood using CUAZ. [Diagram 3] 3 is a graph showing the results of a Coriolus versicolor preservative test of the highly weather-resistant heat-treated wood of this embodiment, where (a) shows the highly weather-resistant heat-treated wood using ACQ, and (b) shows the highly weather-resistant heat-treated wood using CUAZ. [Figure 4] 1 is a graph showing the results of an anti-termite test using Formosan subterranean termites on the highly weather-resistant heat-treated wood of this embodiment, in which (a) shows highly weather-resistant heat-treated wood using ACQ, and (b) shows highly weather-resistant heat-treated wood using CUAZ. [Diagram 5] 1 is a graph showing the results of a dimensional stability test of the highly weather-resistant heat-treated wood of this embodiment. [Figure 6]This is an image of an outdoor deck made from the highly weather-resistant heat-treated wood of this embodiment after 18 months. [Figure 7] Graph (a) shows the initial color index of highly weather-resistant heat-treated wood of this embodiment, graph (b) shows the color index after 18 months (1.5 years) of exposure outdoors, and graph (c) shows the color difference between the initial color index and the color index after 18 months (1.5 years) of exposure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] An embodiment of the present invention will now be described. In the highly weather-resistant heat-treated wood 10 of this embodiment, the hemicellulose in the wood is decomposed and denatured by heat treatment, the internal hydroxyl groups are rendered hydrophobic, and a preservative that exerts anti-rot and anti-termite effects has permeated the surface of the wood.

[0013] Furthermore, the moisture content of the highly weather-resistant heat-treated wood 10 is kept low by heat treatment. By keeping the moisture content low, dimensional changes are less likely to occur and the wood is less likely to decay, improving its antiseptic properties. The internal hydroxyl groups are made hydrophobic and are less likely to combine with moisture, so there is no moisture available for wood-rotting bacteria, which also contributes to its high antiseptic properties. In addition, hemicellulose, a component that causes significant changes in dimensions due to moisture absorption, is decomposed and denatured by heat treatment, which also provides high dimensional stability. The preservative is permeated and attached to the surface of the wood, providing antiseptic and anti-termite properties. The low moisture content also improves insulation properties.

[0014] In addition, the decomposition products of hemicellulose produced by the heat treatment react with other components such as lignin to produce dark colored substances, resulting in a dark brown color in the highly weather-resistant heat-treated wood 10. The components of the preservative treatment agent improve the weather resistance, and the color does not fade over time. The dark brown color is maintained and the color does not change to grayish white or other colors over time.

[0015] There is no particular restriction on the type of wood for the highly weather-resistant heat-treated lumber 10. There is also no particular restriction on the size or shape, and the wood may be in the shape of a finished deck material or the like. It is sufficient that the wood is large enough to fit into a sealed tank, which will be described later, for producing the highly weather-resistant heat-treated lumber 10. The preservative used is ACQ, a copper-alkylammonium compound in JIS K1570, or CUAZ, a copper-azole in JIS K1570.

[0016] Next, a manufacturing method of the highly weather-resistant heat-treated wood 10 of this embodiment will be described with reference to FIG. 1. First, the raw material, a solid untreated wood body 12, is cut to a predetermined shape and size. The shape and size of the untreated wood body 12 are not particularly limited, and may be the shape of a product such as a deck material. A treatment device having a sealed tank is used to manufacture the highly weather-resistant heat-treated wood 10. The cut untreated wood body 12 is placed in the sealed tank of the treatment device. A plurality of untreated wood bodies 12 are arranged on a support such as a shelf or stand made of a heat-resistant material such as metal installed in the sealed tank. After the untreated wood bodies 12 are arranged, the door of the sealed tank is closed to seal the inside.

[0017] Next, a vacuum pump or the like is operated to exhaust the air from the sealed tank, reducing the pressure inside, and a decompression treatment is carried out for a predetermined time. The conditions for the decompression treatment are, for example, a pressure reduced by 80 kPa from atmospheric pressure, at 90°C, and maintained for 22.5 hours. The decompression treatment significantly reduces the air content in the untreated wood body 12, and accordingly reduces the oxygen content.

[0018] Next, the sealed tank that has been subjected to the decompression treatment is filled with steam and heated, and after the target temperature is reached, the untreated wood body 12 is heat-treated after a predetermined time. The heat treatment conditions are, for example, under a pressurized condition of 0.01 MPa, heating to 220°C at 10°C / hour, and holding for 3 hours after reaching 220°C. The temperature and time of the heat treatment are appropriately set, and the heat treatment temperature is preferably 190 to 220°C, and the heat treatment time is preferably at least 60 minutes or more, and is appropriately set depending on the heat treatment temperature, and the temperature and time may be such that the hemicellulose of the untreated wood body 12 is decomposed and denatured by the heat treatment, but is not carbonized. The temperature-raising process may be divided into a drying process in which the temperature is raised slowly, and then a heat treatment process in which the temperature is raised rapidly to a high temperature. In this drying process, the temperature is raised slowly to a predetermined temperature of about 100°C in steam, and the untreated wood body 12 is gradually dried until the moisture content becomes almost 0%. The pressure in the sealed tank during the heat treatment may be normal pressure.

[0019] After the heat treatment, the introduction of steam is stopped and the inside of the sealed tank is cooled. The cooling is performed by spraying water on the untreated wood body 12 while adjusting the moisture content of the untreated wood body 12 to lower the temperature. When the heat treatment is completed, the untreated wood body 12 becomes the heat-treated wood body 14, which is then removed from the sealed tank.

[0020] The heat-treated wood body 14 has a low moisture content due to heat treatment. By keeping the moisture content low, dimensional changes are less likely to occur and the wood is less likely to decay, improving its antiseptic properties. The internal hydroxyl groups are made hydrophobic and are less likely to combine with moisture, so there is no moisture available for wood-rotting bacteria, which also improves the wood's antiseptic properties. In addition, hemicellulose, a component that causes significant changes in dimensions due to moisture absorption, is decomposed and denatured by heat treatment, which also gives the wood high dimensional stability. The low moisture content also improves insulation properties. The decomposition products of hemicellulose generated by heat treatment react with other components such as lignin to produce dark colored substances, resulting in a dark brown color.

[0021] Next, a preservation treatment is performed by permeating the heat-treated wood body 14 with a preservative. The preservative used is ACQ, CUAZ, or the like, as described above. In this embodiment, the preservation treatment is performed by injecting a 6% ACQ aqueous solution into the heat-treated wood body 14 under reduced pressure. The injection conditions are as follows: with the heat-treated wood body 14 immersed in the 6% ACQ aqueous solution in an injection can, the pressure is reduced from atmospheric pressure to, for example, -0.085 MPa and held for 30 minutes, the pressure inside the can is then increased to 1.3 MPa and held for 180 minutes, and the pressure is again reduced to -0.085 MPa and held for 30 minutes. After the pressure is returned to normal pressure, the wood is left to stand in the injection can for approximately 60 hours. This completes the preservation treatment, and the heat-treated wood body 14 becomes a highly weather-resistant heat-treated wood 10 that has been preserved, Injection can Take it out.

[0022] The highly weather-resistant heat-treated wood 10 has a preservative applied to it, penetrating up to several centimeters from the surface, and has high anti-rot and anti-termite properties. The color of the heat-treated wood body 14 is the same as that of the heat-treated wood body 14, and is dark brown.

[0023] The highly weather-resistant heat-treated wood 10 of this embodiment has both the antiseptic and dimensional stability that are the characteristics of heat-treated wood and the termite resistance that is the characteristics of preservative-treated wood, and also maintains the dark brown color characteristic of heat-treated wood for a long period of time, making it highly weather-resistant. Taking advantage of these properties, it can be preferably used as a component for wooden buildings, outdoor facilities, etc. By increasing the heat treatment temperature, the dimensional stability, antiseptic properties, and insulation properties increase, so that highly weather-resistant heat-treated wood 10 with performance suited to the application, such as indoors, outdoors, and places exposed to rain, can be manufactured.

[0024] Highly weather-resistant heat-treated lumber 10 has a dark brown color and a calm atmosphere. This dark brown color does not fade even when exposed to ultraviolet rays such as sunlight, is durable, and can maintain the original appearance of the original construction. In the case of cedar wood, the dark brown color tone tones down the contrast between the heartwood and sapwood that is unique to cedar, and has the effect of toning the entire wood to a dark brown color. In addition, the higher the heat treatment temperature, the deeper the dark brown color becomes, and the desired color can be achieved by adjusting the temperature.

[0025] The highly weather-resistant heat-treated wood of the present invention can be used for various purposes such as wooden buildings and outdoor facilities. By appropriately setting the treatment temperature and treatment time according to the purpose, such as indoors, outdoors, or in places exposed to rain, highly weather-resistant heat-treated wood with performance suited to the purpose can be manufactured. The type of preservative that is the wood preservative can also be freely selected, and the preservation method can be changed as appropriate. The treatment conditions are appropriately determined according to the thickness and purpose of the untreated wood body 12. The type of wood can be freely selected. EXAMPLES

[0026] Examples of the present invention will be described below. A durability test, a dimensional stability test, and a weather resistance test were carried out on the highly weather-resistant heat-treated wood 10 of the above embodiment.

[0027] The specimens used in each test are described below. The type of wood is Bokasugi, which is a variety of cedar planted in Toyama Prefecture and elsewhere. The untreated wood body 12 made of Bokasugi has a corrugated surface and is a Bokasugi sapwood deck material with a length of 2 m, a thickness of 30 mm, and a width of 150 mm. First, the untreated wood body 12 is subjected to a decompression treatment. The conditions for the decompression treatment are as in the above-mentioned embodiment, a pressure of 80 kPa is reduced from atmospheric pressure, and the temperature is kept at 90°C for 22.5 hours. Next, heat treatment is performed. The conditions for the heat treatment are also as in the above-mentioned embodiment, a pressure of 0.01 MPa, a temperature increase of 10°C / hour to 220°C, and after reaching 220°C, the temperature is kept for 3 hours. After the heat treatment, the untreated wood body 12 becomes a heat-treated wood body 14.

[0028] Next, a test piece measuring 20 mm x 20 mm x 10 mm is taken from the heat-treated wood body 14 and subjected to a preservation treatment. The preservative used is ACQ. For the preservation treatment, as in the above-mentioned embodiment, the test piece is injected with a 6% aqueous solution of ACQ under reduced pressure. The injection conditions were that the test piece was immersed in the 6% aqueous solution of ACQ and pressure was reduced from atmospheric pressure to 0.09 MPa. to The pressure is reduced, the reduced pressure is maintained for 30 minutes after reaching the pressure, and then the pressure is returned to normal pressure and left to stand for 30 minutes to produce a test specimen of highly weather-resistant heat-treated wood 10. The name of the prototype test specimen is HACQ.

[0029] In addition, a 0.6% aqueous solution of CUAZ (a low concentration about 1 / 5 of that normally used) was applied to another test piece taken from the heat-treated wood body 14, and a test specimen of highly weather-resistant heat-treated wood 10 was prepared using the same preservation treatment as HACQ. The test specimen was named HCUAZ. For comparison, test specimens were also prepared that had only been subjected to the heat treatment process (test specimen H), only been subjected to ACQ treatment (test specimen ACQ), and only been subjected to CUAZ treatment (test specimen CUAZ).

[0030] First, durability tests, i.e., JISK1571 indoor preservative performance test and anti-termite test, were conducted on each specimen of H, ACQ, HACQ, CUAZ, and HCUAZ. In the preservative performance test, the specimen was placed in a container with wood-decaying fungi (two species, P. palustris and P. versicolor) overgrowth and cultivated for 12 weeks to be forcibly decayed. In the anti-termite test, the specimen was placed in a container with 150 workers of Formosan subterranean termites and raised for 3 weeks to be forcibly fed. In both tests, the mass loss of the specimen due to forced decay or forced feeding is used as an index of preservative or anti-termite performance, and a mass loss rate of 3% or less is used as the standard for preservative and anti-termite performance. In order to examine long-term preservative and anti-termite performance, the specimen was subjected to weather resistance by repeatedly stirring in water for 8 hours and stirring at 60°C for 16 hours 10 times, and then the above-mentioned forced decay or forced feeding test was conducted. For comparison, the same test was conducted on untreated cedar sapwood (Ctrl). The mass loss rate was calculated using the following formula (1). Mass reduction rate =((Dry mass before decay - Dry mass after decay) / Dry mass before decay)×100(%) (1)

[0031] The results of the preservative test using P. ostreatus are shown in Figure 2. Untreated cedar sapwood (Ctrl) showed a mass loss rate of over 40%, while the H and ACQ specimens suppressed the mass loss to around 3%, and the HACQ specimen showed an even higher suppression effect. The mass loss in the CUAZ specimen reached 28% due to the low concentration, but in the HCUAZ specimen, which was also heat-treated, this was suppressed to 5%, and as with the ACQ specimen, the preservative effect was complemented by the combination.

[0032] The results of the preservative test using Coriolus versicolor are shown in Figure 3. All of the H, ACQ, and CUAZ test specimens showed high preservative effects, and all of the HACQ and HCUAZ test specimens also showed high preservative effects.

[0033] The results of the anti-termite test are shown in Figure 4. The mass loss rate due to termite damage of the H test specimen was 23%, significantly higher than the 14% of Ctrl, making it clear that heat treatment promotes termite damage. However, the mass loss rate of the HACQ test specimen combined with ACQ treatment dropped to 0%. The mass loss rate of the HCUAZ test specimen combined with low-concentration CUAZ treatment also dropped to 8%, confirming that the anti-termite properties of the H test specimen were greatly improved by the combined use of ACQ and CUAZ treatments.

[0034] From the above durability test results, it was confirmed that the highly weather-resistant heat-treated wood 10 has high anti-corrosion and anti-termite properties.

[0035] Next, a dimensional stability test was conducted on each of the H, ACQ, HACQ, CUAZ, and HCUAZ specimens. The dimensions were measured when completely dry and when saturated with water after decompression injection of ion-exchanged water to determine the volumetric swelling ratio, and the ASE (anti-swelling ability) of each specimen was calculated using the following formula (2). ASE = (Swelling rate of untreated wood - Swelling rate of treated wood) / (Swelling rate of untreated wood) × 100 (%) (2)

[0036] The results of the dimensional stability test are shown in Figure 5. The ASE of H was 67%, confirming high dimensional stability. The ASE of the ACQ and CUAZ specimens was less than 10%, showing no improvement in dimensional stability. However, the ASE of the HACQ and HCUAZ specimens, which were combined with heat treatment, was 62% and 65%, respectively, confirming high dimensional stability almost equivalent to that of heat treatment. It was confirmed that the combination of heat treatment significantly improved dimensional stability.

[0037] In addition, the improvement of ASE, i.e., the improvement of dimensional stability, is expected to have an effect of suppressing the occurrence of cracks and splinters when used as a deck material. Therefore, a heat-treated wood body 14 of deck size, i.e., 2 m long, 30 mm thick, and 150 mm wide, was immersed in an ACQ 6% aqueous solution, depressurized to -0.085 MPa, held for 30 minutes, then pressurized to 1.3 MPa for 180 minutes, and again depressurized to 0.085 MPa and held for 30 minutes to produce a highly weather-resistant heat-treated wood 10 of deck size. In addition, ACQ was injected into untreated wood 12 under the same conditions as above to produce ACQ-treated wood. An outdoor deck consisting of four sections was experimentally constructed using four types of deck materials, untreated wood 12, ACQ-treated wood, heat-treated wood body 14, and highly weather-resistant heat-treated wood 10, and the occurrence of drying cracks after 18 months was compared for each of the Ctrl, ACQ, H, and HACQ sections. The material used for the deck was Bokasugi (top-grade cedar) with corrugated surface, and 10 top-grade cedars from each section were visually inspected for cracks on the surface. The results are shown in Table 1 below. Figure 6 shows examples of images of the deck material from each section. [Table 1]

[0038] As a result, it was confirmed that the occurrence of desiccation cracks was significantly suppressed in the H and HACQ areas. From the above dimensional stability tests, it was confirmed that highly weather-resistant heat-treated wood 10 has high dimensional stability, which contributes to the suppression of desiccation cracks.

[0039] Next, weather resistance tests were conducted on the H, ACQ, HACQ, and Ctrl test pieces. The four types of deck material test pieces, H, HACQ, ACQ, and Ctrl, were exposed outdoors for 18 months (1.5 years) and the color index L * ,a * ,b * The color index L of each type of test piece was measured. * ,a * ,b * is the initial value and the color difference ΔL * ,Δa * ,Δb *, ΔE was calculated and shown in FIG.

[0040] Figure 7(a) shows the initial values. H and L of HACQ * ,a * ,b * Although all of the indices are lower than Ctrl, the relationship between the indices is almost the same. * The value has dropped drastically, * ,a * ,b * The balance of H and HACQ before exposure is significantly different from that of Ctrl. The numerical results show that the material color of H and HACQ before exposure is a calm color similar to that of Ctrl, while ACQ is a completely different green color. * ,a * ,b * The color difference in Fig. 7(c) shows that Ctrl and H have large color differences, suggesting that they have faded significantly, but the color difference in the HACQ specimen is extremely small, and it was numerically confirmed that it is less likely to fade.

[0041] In order to verify the weather resistance of this highly weather-resistant heat-treated wood 10 on an actual deck scale, the appearance of each section of the outdoor deck constructed as above was observed immediately after construction and after 18 months. There were two grades of wood: upper small section and first-class wood. Comparing the appearance immediately after construction, the Ctrl section was pale yellow in color for all grades, giving a natural and favorable impression. The H and HACQ sections were calm dark brown, giving a more favorable impression than the Ctrl section. The ACQ section turned an artificial green color due to the copper, giving an unnatural appearance. On the other hand, when comparing the appearance after 18 months, the Ctrl and H sections faded significantly and turned gray. However, the HACQ section maintained a dark brown color close to that immediately after construction, giving a more favorable impression than the Ctrl section. The ACQ section's artificial green color immediately after construction changed to brown, giving a better impression. As described above, the section that had a favorable wood color immediately after construction and maintained the same wood color even after 18 months, i.e., the section that showed high weather resistance, was the HACQ section. [Explanation of symbols]

[0042] 10 Highly weather-resistant heat-treated wood 12 Untreated wood body 14 Heat-treated wood body

Claims

1. The present invention produces highly weather-resistant heat-treated lumber in which the hemicellulose in the lumber is decomposed and modified by heat treatment, the internal hydroxyl groups are rendered hydrophobic, and a preservative containing a copper compound penetrates from the surface of the lumber to the interior, resulting in a dark brown surface color. A solid untreated wood body is placed in a sealed tank, and a decompression treatment is performed to reduce the pressure inside the sealed tank from atmospheric pressure to reduce the air content in the untreated wood, and then the temperature is raised to a temperature for heat treatment of the wood, and the heat treatment is performed by maintaining the raised temperature for heat treatment of the wood, thereby decomposing and denaturing the hemicellulose in the untreated wood body and making the internal hydroxyl groups hydrophobic, and the temperature inside the sealed tank is lowered from the heat treatment temperature and the untreated wood body is removed from the sealed tank, and the untreated wood body becomes a heat-treated wood body that has been subjected to heat treatment, A manufacturing method for highly weather-resistant heat-treated lumber, characterized in that the heat-treated wood body is placed in an injection can and immersed in an aqueous solution of the preservative while being reduced in pressure and held therein, then pressurized and held therein, then reduced in pressure and held therein again, and then returned to normal pressure, the wood is left stationary in the injection can to carry out preservation treatment, and the wood is removed from the injection can to produce the highly weather-resistant heat-treated lumber in which preservation treatment has been applied to the heat-treated wood body.

2. A method for manufacturing highly weather-resistant heat-treated lumber as described in claim 1, wherein the heat-treated wood body is placed in an injection can and immersed in an aqueous solution of the preservative, while the pressure is reduced from atmospheric pressure to -0.085 MPa and held for 30 minutes, then pressurized to 1.3 MPa and held for 180 minutes, then reduced again from atmospheric pressure to -0.085 MPa and held for 30 minutes, then returned to normal pressure and left in the injection can for 60 hours to carry out preservation treatment, and the heat-treated wood body is removed from the injection can to form the highly weather-resistant heat-treated lumber which has been subjected to preservation treatment.

3. 2. The method for producing highly weather-resistant heat-treated lumber according to claim 1, wherein the temperature for heat-treating the lumber is 190 to 220°C.

4. A method for producing highly weather-resistant heat-treated wood as described in claim 3, wherein the heat treatment of the wood is carried out under a pressurized condition of 0.01 MPa.

5. A method for producing highly weather-resistant heat-treated wood as described in claim 2 or 4, wherein the type of wood is cedar.

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