Method and apparatus for combined heat treatment of wood

Abstract

The present application relates to the technical field of wood heat treatment modification, and discloses a combined heat treatment method and device for wood, which sequentially comprises the following procedures: a pretreatment procedure, wherein wood is soaked in an aluminum sulfate solution until the weight gain reaches 10-35%, and pretreated wood is obtained; a heat treatment procedure, wherein the pretreated wood is placed in a temperature condition of 120-160 DEG C for heat treatment for 1-3h, and heat treated wood is obtained; and a post-treatment procedure, wherein the heat treated wood is soaked in a siloxane modified solution for a period of time, dried, and the siloxane modified solution is a mixed solution comprising methyl triethoxysilane and tetraethyl silicate. The method can ensure that the wood treated by the aluminum sulfate catalysis-heat treatment combination has good dimensional stability and thermal stability, and still has relatively high mechanical strength.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wood heat treatment modification, and discloses a combined heat treatment method for wood, which comprises aluminum sulfate pretreatment, heat treatment and siloxane-based deposition modification aftertreatment. BACKGROUND

[0002] High-temperature heat treatment of wood can improve the dimensional stability, durability and corrosion resistance of wood. Heat-treated wood can be used for indoor and outdoor construction, decoration structure, such as exterior wall panels, deck floors, furniture and window frames. However, the energy consumption of high-temperature heat treatment is high. For example, in the current industrial heat treatment process, the energy consumption of heat treatment accounts for 40%-70% of the total energy consumption of wood production process, which greatly increases the manufacturing cost of wood products.

[0003] In order to reduce the energy consumption of heat treatment, the prior art uses strong acid and weak base salt solution to pretreat wood. The pretreated wood can obtain high-temperature heat treatment effect under relatively low heat treatment temperature and short heat treatment time. For example, the technical solution disclosed in the patent application CN108789718A entitled "Wood heat treatment method" uses a strong base and weak acid salt solution with weak acidity as a wood modification treatment liquid (such as aluminum sulfate solution). The wood modification treatment liquid penetrates into the wood, promotes the decomposition and reduction of water absorption groups inside the wood, and reduces the wood heat treatment temperature, so that heat treatment can be carried out at a lower temperature to obtain heat-treated wood with a higher degree of carbonization, i.e. to obtain similar modification effect as heat treatment at a higher temperature.

[0004] The strong base and weak acid salt solution can catalyze the thermal degradation of hemicellulose in wood at a relatively low temperature by generating an acidic medium, so that acetic acid is produced to further promote the degradation of hemicellulose, cellulose and lignin, so that heat treatment can be carried out at a lower temperature but obtain heat-treated wood with a higher degree of carbonization. The strong base and weak acid salt solution generates hydrated ions that can complex with polar groups such as hydroxyl groups in wood through hydrolysis reaction. The hydrated ions form attachment on the surface of wood and deposition inside, thereby improving the dimensional stability of wood. At the same time, some strong base and weak acid salt solutions, such as aluminum sulfate solution, have good heat resistance, so the attachment of aluminum sulfate solution on the surface of wood and the deposition inside can improve the thermal stability of wood and further improve the anti-aging performance of wood.

[0005] However, this method has not been widely used in actual production, because:

[0006] (1) Although the actual heat treatment temperature is low, the wood pretreated by the strong alkali and weak acid salt solution is affected by temperature and humidity, and the hemicellulose, cellulose and lignin are largely degraded, thus affecting the mechanical properties of the wood to some extent.

[0007] (2) Even the same batch of wood has differences in moisture absorption performance, thus it is difficult to determine the appropriate concentration and immersion time of the strong alkali and weak acid salt solution by statistical methods. If the pretreatment by the strong alkali and weak acid salt solution is insufficient, the heat treatment effect is affected, and it is difficult to obtain the set charring degree at low temperature. If the inorganic salt attached to the surface of the wood or deposited in the interior is excessive, the incompletely hydrolyzed-complexed inorganic salt modifier and the hydroxyl group will instead increase the moisture absorption of the wood, which actually affects the effect of reducing the moisture absorption of the wood by heat treatment.

[0008] In summary, there is a lack of a process method capable of reducing the heat treatment temperature of wood, ensuring the hydrophilicity improvement effect of heat treatment, and avoiding excessive loss of mechanical strength of wood in the prior art. SUMMARY

[0009] The technical purpose of the present application is to overcome at least one of the above technical problems, and to provide a combined heat treatment method for wood. The method directly pretreats the wood with aluminum sulfate to reduce the temperature required for heat treatment of the wood, and then chemically combines the siloxane group with the un-degraded hydroxyl group on the surface of the wood and the incompletely hydrolyzed-complexed inorganic salt modifier through post-deposition treatment, thereby reducing the temperature required for heat treatment while ensuring the hydrophilicity improvement effect of heat treatment. The deposition of the siloxane group on the surface of the wood can also compensate for the loss of mechanical properties caused by the large degradation of hemicellulose, cellulose and lignin, and at least improve the surface hardness of the wood after heat treatment.

[0010] To achieve the above technical purpose, one aspect of the present application provides a combined heat treatment method for wood, which sequentially comprises the following steps:

[0011] A pretreatment step, wherein the wood is soaked in an aluminum sulfate solution until the weight gain reaches 10-35%, to obtain pretreated wood;

[0012] A heat treatment step, wherein the pretreated wood is placed in a temperature condition of 120-160°C for heat treatment for 1-3h, to obtain heat-treated wood;

[0013] A post-treatment step, wherein the heat-treated wood is soaked in a siloxane modified solution for a period of time, and then dried. The siloxane modified solution is a mixed solution comprising methyltriethoxysilane and tetraethyl orthosilicate.

[0014] After the wood is pretreated by the aluminum sulfate solution, in the process of heat treatment, the hemicellulose, cellulose and lignin are largely degraded under the influence of temperature and humidity, thereby affecting the mechanical properties of the wood. In the present case, by limiting the wood soaking degree in the aluminum sulfate solution to "until the weight gain reaches 10-35%", and the heat treatment temperature and time to 120-160℃ and 1-3h respectively, the wood treated by the aluminum sulfate catalysis-heat treatment combination process can have good dimensional stability and thermal stability while still having relatively high mechanical strength.

[0015] Meanwhile, in the present case, the post-treatment process is implemented, and the post-treatment process is achieved by impregnating a siloxane modified solution, thereby:

[0016] In the first aspect, a siloxane-based impregnated layer is formed on the surface of the wood to improve the hydrophobicity of the wood surface.

[0017] In the second aspect, the inventors found that the decrease in the mechanical properties of the wood treated by the aluminum sulfate catalysis-heat treatment combination process is not only due to the large degradation of hemicellulose, cellulose and lignin, but also the wood treated by the combination process has a more severe photodegradation in the aging process, and the siloxane-based deposition post-treatment can more quickly and effectively slow down the photodegradation of the wood treated by the combination process in the aging process, thereby improving its aging resistance and maintaining the mechanical strength of the wood during use.

[0018] In the third aspect, after the wood is treated by the aluminum sulfate catalysis-heat modification combination process, some inorganic salt modifiers and hydroxyl groups that are not completely hydrolyzed and complexed are often left on the surface of the wood, which increases the hydrophilicity of the wood surface. The "-OH" in the siloxane-based sol system can chemically bond with the groups on the surface of the wood, which can not only consume the inorganic salt modifiers and hydroxyl groups left on the surface of the wood, but also reduce the hydroxyl groups in the wood and the siloxane-based layer, and strengthen the deposition modification effect of the siloxane-based layer on the surface of the wood.

[0019] In the fourth aspect, using tetraethyl silicate as a precursor and adding methyl triethoxysilane containing "-CH3" can substitute the "-OH" groups in the sol system, thereby making the siloxane-based layer have higher hydrophobicity.

[0020] As a preferred embodiment, in the implementation of the pretreatment process, the concentration of the aluminum sulfate solution is 0.2-0.6mol / L.

[0021] As a preferred embodiment, in the implementation of the pretreatment process, the wood is first subjected to a circulation treatment and then subjected to an atmospheric pressure impregnation in the aluminum sulfate solution. The circulation treatment is under negative pressure for 3-4min, and the vacuum is released for 25-35s. The circulation treatment lasts for 1-1.5h.

[0022] As a preferred embodiment, the duration of the atmospheric pressure impregnation is 20-26h.

[0023] As a preferred embodiment, in the process of implementing the pretreatment, the wood is soaked in the aluminum sulfate solution until the weight gain reaches 20-35%.

[0024] As a preferred embodiment, the wood is soaked in the siloxane modification solution for 2.5-3.5h, and then aged at a temperature of 20-30℃ for 5-6h.

[0025] In the above technical solution, by implementing the aging treatment at a relatively low temperature after soaking in the siloxane modification solution, the siloxane-based layer deposited on the surface of the combined treatment wood can be cured and dried, further improving the modification effects such as hydrophobicity and durability of the siloxane-based layer.

[0026] As a preferred embodiment, the preparation method of the siloxane modification solution sequentially comprises the following steps:

[0027] Methyl triethoxysilane and tetraethyl silicate are mixed according to a molar ratio of (0.5-1.5):1, followed by adding ethanol and hydrochloric acid, and stirring at a temperature of 20-30℃ and a rotation speed of 300-320rpm / min for 30-35min to obtain a mixed solution;

[0028] After adding deionized water dropwise to the mixed solution, continue to stir for 3.5-4.5h to obtain a preliminary solution;

[0029] The preliminary solution is aged for 2.5-3.5h to obtain the siloxane modification solution.

[0030] The present application also provides a device suitable for implementing the combined heat treatment method of the wood, which comprises:

[0031] At least two groups of impregnation tanks, the impregnation tank comprising a tank body, a material opening arranged at one end of the axial direction of the tank body, a front end cover matched with the material opening, an air supply slot arranged at the top of the tank body, an air door matched with the air supply slot, and a heating assembly arranged at the bottom of the tank body;

[0032] A first medicament mechanism, the first medicament mechanism being suitable for providing the aluminum sulfate solution to the impregnation tank;

[0033] A second medicament mechanism, the second medicament mechanism being suitable for providing the siloxane modification solution to the impregnation tank;

[0034] A vacuum mechanism, the vacuum mechanism being suitable for forming a negative pressure in the impregnation tank;

[0035] The heat treatment system arranged at the top of the impregnation tank comprises a wind box, an air outlet groove arranged at the bottom of the wind box, a plurality of groups of side air fans arranged at one side of the wind box, a wind baffle located below the side air fan, an exhaust skylight, a humidifying assembly, and a heat treatment heating assembly arranged at the front of the air outlet direction of the side air fan.

[0036] The control system.

[0037] As a preferred embodiment, the plurality of groups of side air fans are located at one side of the impregnation tank.

[0038] As a preferred embodiment, the tank body is a cylindrical tank body; the air door comprises a circular arc door plate capable of sliding and rotating along the inner wall of the tank body and taking the axis of the tank body as the axis, a sliding and rotating guide structure, and a sliding and rotating driving structure; the sliding and rotating guide structure comprises a guide strip mounted on the front end cover and a limiting step mounted on the inner wall of the circular arc door plate and matched with the guide strip; and the sliding and rotating driving structure comprises a driving motor arranged on the rear end cover, a driving gear mounted on the output shaft of the driving motor, and an arc-shaped gear rack mounted on the inner wall of the circular arc door plate and matched with the driving gear.

[0039] In summary, the wood combined heat treatment method and device disclosed in the present application have at least the following advantages:

[0040] 1. In the present case, by limiting the wood soaking degree in the aluminum sulfate solution to "up to 10-35% of weight gain", and the heat treatment temperature and time to 120-160 DEG C and 1-3 hours respectively, the wood treated by the aluminum sulfate catalysis-heat treatment combination process can have good dimensional stability and thermal stability while still having relatively high mechanical strength.

[0041] 2. In the present case, by implementing the post-treatment process, a siloxane-based impregnated layer is formed on the surface of the wood, which can improve the hydrophobicity of the wood surface, slow down the photo-degradation of the wood in the aging process to improve its aging resistance, consume residual inorganic salt modifiers and hydroxyl groups on the surface of the wood, reduce the hydroxyl groups in the wood and the siloxane-based layer, and strengthen the deposition modification effect of the siloxane-based layer on the surface of the wood.

[0042] 3. In the present case, using tetraethyl silicate as a precursor and adding methyl triethoxysilane containing "-CH3" can substitute the "-OH" groups in the sol system, so that the siloxane-based layer has higher hydrophobicity.

[0043] 4、In the case, by implementing the pretreatment process and the post-treatment process in the impregnation tank with relatively small volume, the impregnation efficiency can be effectively improved, the vacuum degree can be more accurately controlled, the circulation process can be performed, the waste of reagent can be reduced, and the multiple impregnation tanks can be communicated with the air tank through the air supply groove and the air outlet groove, so that the gas circulation space (including the multiple impregnation tanks and the air tank) can be expanded to avoid the wood cracking caused by the small gas circulation space and effectively control the heat treatment effect.

[0044] 5、In the case, the pretreatment process, the heat treatment process and the post-treatment process do not need to move the wood, so that the time consumption, the labor consumption and other cost consumption of the wood transfer process are saved, and the production efficiency is improved. BRIEF DESCRIPTION OF DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0046] Figure 1 The structure diagram of the combined heat treatment device for wood of the embodiment of the present application.

[0047] Figure 2 The front view schematic diagram of the combined heat treatment device for wood of the embodiment of the present application.

[0048] Figure 3 The structure diagram of the rear end cover of the embodiment of the present application. Figure 2 The sectional structure schematic diagram of A-A in the embodiment.

[0049] Figure 4 The structure schematic diagram of the air door of the embodiment of the present application.

[0050] Figure 5 The structure schematic diagram of the air door of the embodiment of the present application.

[0051] Figure 6 The weight gain rate of the wood after the pretreatment process of the embodiments 1-3.

[0052] Figure 7 The weight loss rate of the wood after the heat treatment process of the embodiments 4-6.

[0053] In the figure: 100, impregnation tank, 200, heat treatment system, 110, tank body, 120, material port, 130, front end cover, 140, air supply groove, 150, air door, 160, rear end cover, 151, circular arc door plate, 152, guide strip, 153, limiting step, 154, drive motor, 155, drive gear, 156, arc-shaped rack, 210, air bellow, 220, air outlet groove, 230, side fan, 240, wind shield, 250, exhaust skylight, 260, heat treatment heating assembly, 270, humidifying assembly. DETAILED DESCRIPTION

[0054] In order to enable persons skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by persons skilled in the art without creative labor should fall within the scope of protection of the present application.

[0055] Reference Figure 1 The figure shows a combined wood heat treatment device, which comprises an impregnation tank 100, a first medicament mechanism, a second medicament mechanism, a vacuum mechanism, a heat treatment system 200, and a control system.

[0056] The impregnation tank 100 comprises at least two groups, and two groups are taken as an example in the embodiment. The two groups of impregnation tanks 100 have the same but mirror image structure and have independent impregnation treatment spaces. The impregnation tank 100 comprises a tank body 110, a material port 120 arranged at one end of the tank body in the axial direction, a front end cover 130 matched with the material port 120, an air supply groove 140 arranged at the top of the tank body 110, an air door 150 matched with the air supply groove 140, and a heating assembly arranged at the bottom of the tank body 110. Please refer to Figure 2 The tank body 110 is a horizontally placed cylindrical impregnation tank, which belongs to the prior art. A material port 120 is arranged at one end of the tank body 110 for feeding and discharging materials. The wood can be stacked on the material rack vehicle suitable for impregnation in the prior art and fed into the tank body 110 through the material port 120. The front end cover 130 is installed at the material port 120. After the front end cover 130 is closed, it forms a sealed fit with the material port 120. The end of the tank body 110 opposite to the material port 120 is closed by a rear end cover 160. The bottom of the tank body 110 is provided with an electric heating heating assembly, which is not shown in the figure. The heating assembly can be any one of the prior art, such as an electric heating rod electrically connected with the control system.

[0057] Different from the impregnation tank in the prior art, the top of the tank body 110 of the impregnation tank 100 in the embodiment is provided with an air supply groove 140 and an air door 150 matched with the air supply groove 140.Figure 2 In one embodiment, one of the air doors 150 is in an open state and the other is in a closed state.

[0058] In combination Figure 3 , Figure 4 , Figure 5 The air supply groove 140 extends through or almost through the entire length of the top of the tank 110. The air door 150 includes a circular arc door plate 151 that can slide and rotate along the inner wall of the tank 110 and about the axis of the tank 110, a slide and rotate guide structure, and a slide and rotate driving structure. The slide and rotate guide structure includes a guide strip 152 that is screwed or welded to the front end cover 130 and a limiting step 153 that is installed on the inner wall of the circular arc door plate 151 and cooperates with the guide strip 152. Preferably, the guide strip 152 is a rubber strip and the limiting step 153 is a circular arc retreat step that is formed in the end of the circular arc door plate 151. The slide and rotate driving structure includes a driving motor 154 that is screwed to the seat body of the rear end cover 160, the driving motor 154 is electrically connected to the control system, the body of the driving motor 154 is located outside the rear end cover 160 and its output shaft enters the tank 110 through the rear end cover 160, and a driving gear 155 that is driven by the driving motor 154 is installed on the output shaft of the driving motor 154 through a bearing. The inner wall of the circular arc door plate 151 is screwed, welded or integrally formed with an arc-shaped rack 156 that cooperates (meshes) with the driving gear 155. The rotation of the driving motor 154 can drive the opening and closing of the circular arc door plate 151 through the driving gear 155, so that the air door 150 is in an open or closed state.

[0059] The first medicament mechanism is adapted to provide aluminum sulfate solution to the immersion tank 100, the second medicament mechanism is adapted to provide siloxane modification solution to the immersion tank 100, the vacuum mechanism is adapted to form negative pressure in the immersion tank 100, and the control system is used to instruct the actions of each mechanism, component and structure connected thereto. The first medicament mechanism, the second medicament mechanism and the vacuum mechanism are not shown in the drawings, and they can all be structures of the prior art. For example, the first medicament mechanism includes a first medicament pool capable of containing aluminum sulfate solution and a first medicament recovery pool, the first medicament pool is connected with a plurality of first liquid inlet pipes corresponding to a plurality of groups of immersion tanks 100, the plurality of first liquid inlet pipes are independently controlled by respective pump bodies and electromagnetic valves, the first medicament recovery pool is connected with a plurality of first liquid outlet pipes corresponding to a plurality of groups of immersion tanks 100, and the first liquid inlet pipes and the first liquid outlet pipes are respectively communicated with the corresponding tank bodies 110. The second medicament mechanism includes a second medicament pool capable of containing siloxane modification solution and a second medicament recovery pool, the second medicament pool is connected with a plurality of second liquid inlet pipes corresponding to a plurality of groups of immersion tanks 100, the plurality of second liquid inlet pipes are independently controlled by respective pump bodies and electromagnetic valves, the second medicament recovery pool is connected with a plurality of second liquid outlet pipes corresponding to a plurality of groups of immersion tanks 100, and the second liquid inlet pipes and the second liquid outlet pipes are respectively communicated with the corresponding tank bodies 110. The vacuum mechanism is provided corresponding to a plurality of groups of immersion tanks 100 and is connected to the control system for control. The control system is a PLC control cabinet.

[0060] The immersion tank 100 is provided with a heat treatment system 200 at the top. The heat treatment system 200 includes a wind box 210, an air outlet groove 220 provided at the bottom of the wind box 210, a plurality of side air blowers 230 provided at one side of the wind box 210, a wind baffle 240 located below the side air blower, an exhaust skylight 250, a heat treatment heating assembly 260 provided at the front of the air outlet direction of the side air blower 230, and a humidifying assembly 270.

[0061] Specifically, the wind box 210 is a rectangular aluminum alloy box body, which is installed at the top of a plurality of immersion tanks 100 and includes a circulation space located directly above the plurality of immersion tanks 100 and a blower mounting space located at one side of the plurality of immersion tanks 100. In fact, the circulation space and the blower mounting space have no physical boundary and are only functionally defined, and they together constitute the internal space of the wind box 210. The blower heads of the plurality of side air blowers 230 are installed in the blower mounting space, so that the plurality of side air blowers 230 are installed in the form of side air blowers, but they are different from the installation mode of the side air blowers of the prior art, and they are installed at a position independent of the circulation space.

[0062] The bottom of the wind box 210 is provided with an air outlet groove 220, and the air outlet groove 220 penetrates or almost penetrates the length direction of the wind box 210. The wind box 210 is communicated with the tank body 110 through the butt joint of the air outlet groove 220 and the air supply groove 140, and the air door 150 controls the communication or isolation state of the two.

[0063] The wind deflector 240 is located directly above the plurality of immersion tanks 100 and is located at one side of the side fan 230, and is fixedly installed on the ceiling of the air box 210 by a support. As a preferred embodiment, the distance between the wind deflector 240 and the ceiling of the air box 210 is the same as the distance between the wind deflector 240 and the air outlet groove 220, that is, the wind deflector 240 is arranged between the ceiling of the air box 210 and the air outlet groove 220.

[0064] The exhaust air window 250 is opened in the ceiling of the air box 210, and as a preferred embodiment, the exhaust air window 250 is located at the middle of the length direction of the air box 210, and includes two exhaust air windows 250 arranged on both sides. The exhaust air window 250 is electrically connected to the control system, and it can exhaust the hot and humid air in the air box 210 and the tank body 110 to reduce the temperature and humidity in the air box 210 when the process requires, and to speed up the efficiency of heat treatment or drying.

[0065] The heat treatment heating assembly 260 is an electric heating rod group of the prior art, which is arranged at the front of the air outlet direction of the side fan 230, and it can increase the temperature of the medium in the air box 210 and the tank body 110 when the process requires.

[0066] The humidifying assembly 270 is any one of the prior art, such as an atomizing water spray head, a steam pipeline connected to the atomizing water spray head, a steam source (such as a steam boiler) connected to the steam pipeline, and some pumps and solenoid valves connected to the control system. The humidifying assembly 270 is suitable for spraying steam into the air box 210 to increase the humidity of the medium in the air box 210 and the tank body 110 when the process requires, or spraying atomizing water into the air box 210 to quickly reduce the temperature in the air box 210 and the tank body 110 while maintaining the humidity of the medium when cooling. As a preferred embodiment, the atomizing water spray head of the humidifying assembly 270 is installed on the rear end tank body wall surface of the air box 210 (that is, the same side as the rear end cover 160), and is located between the adjacent two immersion tanks 100 and below the wind deflector 240.

[0067] The combined heat treatment device for wood is operated in sequence with the pretreatment process, the heat treatment process and the post-treatment process. When the pretreatment process is performed, first, the damper 150 and the exhaust window 250 are opened to make the space of the impregnation tank 100 and the heat treatment system 200 communicate, the front end cover 130 is opened to send the wood stacks into the tank body 110 and closed, the length direction of the wood is substantially parallel to the axial direction of the tank body 110. Then, the first agent mechanism is started to send the aluminum sulfate solution into the tank body 110 to a solution level of about 5-10 cm above the surface of the wood stacks, the damper 150 is closed to make the space of the impregnation tank 100 and the heat treatment system 200 independent of each other and the tank body 110 is in a sealed state, the vacuum mechanism is started to perform the vacuum impregnation step of the aluminum sulfate solution in the pretreatment process, if necessary, the heating component in the impregnation tank 100 can be started to adjust the temperature of the aluminum sulfate solution. According to the need, the above-mentioned vacuum impregnation step can also be repeated multiple times. After the vacuum impregnation step of the aluminum sulfate solution is completed, the vacuum mechanism is closed to restore the tank body 110 to normal pressure, and the normal pressure impregnation step of the aluminum sulfate solution in the pretreatment process is maintained. Finally, the aluminum sulfate solution in the tank body 110 is discharged, the damper 150 is opened to communicate the space of the impregnation tank 100 and the heat treatment system 200 again, and the heat treatment system 200 is started to perform the drying step in the pretreatment process.

[0068] After the drying step is completed, the temperature of the heat treatment heating assembly 260 is directly increased to increase the medium temperature in the wind box 210 and the tank body 110, the exhaust window 250 is opened at an appropriate time to adjust the medium humidity in the wind box 210 and the tank body 110 to always maintain at a level required by the process, so as to enter the implementation process of the heat treatment process. After a set time, the temperature in the tank body 110 is reduced to below 50°C by natural cooling or assisted spraying of atomized water, and the heat treatment process is ended.

[0069] When the temperature in the tank body 110 is reduced to below 50°C but still higher than 40°C, the damper 150 and the exhaust window 250 are kept in an open state, the second agent mechanism is started to send the siloxane modified solution into the tank body 110 to a solution level of about 5-10 cm above the surface of the wood stacks; then, the heating structure is started to maintain the temperature of the siloxane modified solution, and the wood stacks are normal pressure impregnated in the siloxane modified solution for a period of time under the condition that the damper 150 is closed or not closed; finally, the siloxane modified solution in the tank body 110 is discharged, and the wood impregnated with the siloxane modified solution is aged for a period of time under room temperature conditions, so as to finally obtain the wood modified by the combined aluminum sulfate pretreatment-heat treatment-siloxane post-treatment.

[0070] Specifically, the combined aluminum sulfate pretreatment-heat treatment-siloxane post-treatment modification, i.e. a combined heat treatment method for wood, sequentially includes the following processes:

[0071] (1) A pretreatment process, wherein wood with an initial moisture content of 60-70% is soaked in an aluminum sulfate solution with a concentration of 0.2-0.6 mol / L until the weight gain reaches 10-35%, preferably 20-35%, to obtain pretreated wood;

[0072] (2) A heat treatment process, wherein the pretreated wood is subjected to heat treatment at a temperature of 120-160°C for 1-3h to obtain heat-treated wood;

[0073] (3) A post-treatment process, wherein the heat-treated wood is soaked in a siloxane modification solution for 2.5-3.5h.

[0074] In some preferred embodiments, after the heat-treated wood is immersed in the siloxane modification solution under atmospheric pressure, it is removed from the siloxane modification solution and continues to age at a temperature of 20-30°C for 5-6h, and finally dried to obtain wood modified by the combination of aluminum sulfate pretreatment, heat treatment, and siloxane post-treatment.

[0075] The pretreatment process is implemented by first circulating treatment and then atmospheric pressure immersion. The circulating treatment is under negative pressure for 3-4min, vacuum release for 25-35s, and the circulating treatment time is 1-1.5h. The atmospheric pressure immersion time is 20-26h.

[0076] The siloxane modification solution is a mixed solution containing methyltriethoxysilane (MTES) and tetraethyl orthosilicate (TEOS). The preparation method of the siloxane modification solution includes the following steps in sequence:

[0077] (1) Methyltriethoxysilane and tetraethyl orthosilicate are mixed in a molar ratio of (0.5-1.5):1, followed by the addition of ethanol and hydrochloric acid as solvents and catalysts, and stirring at a temperature of 20-30°C and a rotation speed of 300-320rpm / min for 30-35min to obtain a mixed solution;

[0078] (2) Deionized water is added dropwise to the mixed solution and continues to stir for 3.5-4.5h to obtain a preliminary solution;

[0079] (3) The preliminary solution is aged for 2.5-3.5h to obtain a siloxane modification solution.

[0080] The process of the siloxane-based layer prepared by hydrolysis and condensation reaction under the catalysis of HCl adhering and depositing on the wood is as follows:

[0081] (1) Hydrolysis

[0082]

[0083] (2) condensation

[0084]

[0085] (3) deposition

[0086]

[0087] Example 1: A combined heat treatment method of wood, which sequentially comprises the following procedures:

[0088] (1) A procedure for implementing pretreatment, wherein the Chinese fir wood with an initial moisture content of 60-70% is soaked in an aluminum sulfate solution with a concentration of 0.2 mol / L until the weight gain reaches 12±2%, specifically, the steps of vacuuming at -0.09 MPa for 3.5 min, then vacuum releasing for 30 s, and circulating the vacuuming-vacuum releasing steps for 1 h are repeated, and after the completion of the circulation, the soaking is maintained at normal pressure for 24 h to obtain pretreated wood;

[0089] (2) A procedure for implementing heat treatment, wherein the pretreated wood is subjected to heat treatment at a temperature of 120°C for 2 h to obtain heat-treated wood;

[0090] (3) A procedure for implementing post-treatment, wherein the heat-treated wood is soaked in a siloxane modification solution for 2.5 h, then aged at a temperature of 25±2°C for 5.5 h, and finally dried to obtain wood modified by the combined aluminum sulfate pretreatment-heat treatment-siloxane post-treatment.

[0091] The preparation method of the siloxane modification solution sequentially comprises the following steps:

[0092] (1) Methyl triethoxysilane and tetraethyl orthosilicate are mixed at a molar ratio of 0.5:1, then ethanol and hydrochloric acid are added, and stirring is performed at a temperature of 25°C and a rotation speed of 300-320 rpm / min for 30 min to obtain a mixed solution;

[0093] (2) Deionized water is added dropwise to the mixed solution, and stirring is continued for 4 h to obtain a preliminary solution;

[0094] (3) The preliminary solution is aged for 3 h to obtain a siloxane modification solution.

[0095] Example 2: The difference from Example 1 is that the concentration of the aluminum sulfate solution is 0.4 mol / L.

[0096] Example 3: The difference from Example 1 is that the concentration of the aluminum sulfate solution is 0.6 mol / L.

[0097] Example 4: The difference from Example 1 is that the heat treatment temperature in the procedure for implementing heat treatment is 140°C.

[0098] Example 5: The difference from Example 2 is that the heat treatment temperature in the heat treatment process is 140°C.

[0099] Example 6: The difference from Example 3 is that the heat treatment temperature in the heat treatment process is 140°C.

[0100] Example 7: The difference from Example 1 is that the heat treatment temperature in the heat treatment process is 160°C.

[0101] Example 8: The difference from Example 2 is that the heat treatment temperature in the heat treatment process is 160°C.

[0102] Example 9: The difference from Example 3 is that the heat treatment temperature in the heat treatment process is 160°C.

[0103] Example 10: The difference from Example 5 is that the molar ratio of methyl triethoxysilane to tetraethyl orthosilicate is 1:1.

[0104] Example 11: The difference from Example 5 is that the molar ratio of methyl triethoxysilane to tetraethyl orthosilicate is 1.5:1.

[0105] Example 12: The difference from Example 10 is that, in the post-treatment process, only the heat-treated wood is immersed in the siloxane modification solution for atmospheric pressure impregnation, without subsequent aging treatment.

[0106] Example 13: The difference from Example 10 is that the object of treatment is poplar wood.

[0107] Control Group 1: Only the heat treatment process is performed on the treatment object, with a heat treatment temperature of 140°C and a treatment time of 2h.

[0108] Control Group 2: The difference from Example 10 is that only the pre-treatment process and the heat treatment process are performed on the treatment object.

[0109] The weight gain rate of the wood in Examples 1-3 is measured after completing the pre-treatment process, and the weight gain rate is calculated by Formula (1):

[0110]

[0111] In the formula, W1 is the weight of the wood test piece before impregnation treatment, and W2 is the weight of the wood test piece after drying in the pre-treatment process.

[0112] The weight loss rate of the wood in Examples 4-6 is measured after completing the heat treatment process, and the weight loss rate is calculated by Formula (2):

[0113]

[0114] In the formula, W2 is the weight of the wood test piece after drying in the pretreatment process, and W3 is the weight of the test piece after heat treatment.

[0115] The wood of each of the examples after the combined modification of the aluminum sulfate pretreatment-heat treatment-siloxane post-treatment and the wood of the control example were tested for (1) static bending strength to determine the improvement in the mechanical properties of the wood by the post-treatment process, (2) surface color change to determine the improvement in the aging resistance, and (3) moisture absorption to determine the improvement in the moisture absorption properties of the wood by the post-treatment process.

[0116] Figure 6 The weight gain rates of the wood of Examples 1-3 after the pretreatment process are shown in Table 1. Figure 7 The weight loss rates of the wood of Example 1-9 after the heat treatment process are shown in Table 1. Figure 7 Control 0-120, Control 0-140, and Control 0-160 in Table 1 indicate control cases in which the wood was directly subjected to heat treatment at a maximum temperature of 120°C, 140°C, and 160°C, respectively, without being subjected to the pretreatment process.

[0117] The performance improvement effects of the wood of Examples 1-13 and Control Example 1-2 are shown in Table 1.

[0118] Table 1. Performance improvement effects of the wood of Examples 1-13 and Control Example 1-2

[0119]

[0120] The above description is intended to be illustrative and not restrictive. Many embodiments and many applications besides the examples provided herein will be apparent upon reading the above description and will be readily implemented. The scope of the teachings should, therefore, be determined not with reference to the above description, but should instead be determined with reference to the appended claims, along with their full scope of equivalents. For a comprehensive understanding of the present teachings, all articles and references including patents and patent documents are incorporated herein by reference to the extent that they provide procedural or other technical support for the present teachings. Nothing herein is to be construed as an admission that the subject matter disclosed herein is not entitled to antedate any prior publication by virtue of prior disclosure. The disclosure of the foregoing application is also intended to cover all alternatives, modifications and equivalents of the application as can be practiced or implemented by a person in the art.

Claims

1. A method for combined heat treatment of wood, characterized in that, It sequentially comprises the following steps: The step of implementing pretreatment, soaking the wood in an aluminum sulfate solution until the weight gain reaches 10-35%, to obtain pretreated wood; The step of implementing heat treatment, placing the pretreated wood in a temperature condition of 120-160°C for heat treatment for 1-3h, to obtain heat-treated wood; The step of implementing post-treatment, soaking the heat-treated wood in a siloxane modification solution for a period of time, drying, and the siloxane modification solution is a mixed solution comprising methyl triethoxysilane and tetraethyl orthosilicate; The preparation method of the siloxane modification solution sequentially comprises the following steps: Mixing methyl triethoxysilane and tetraethyl orthosilicate according to a molar ratio of (0.5-1.5):1, then adding ethanol and hydrochloric acid, and stirring at a temperature of 20-30°C and a rotation speed of 300-320rpm for 30-35min, to obtain a mixed solution; After adding deionized water dropwise to the mixed solution, continue stirring for 3.5-4.5h, to obtain a preliminary solution; Aging the preliminary solution for 2.5-3.5h, to obtain the siloxane modification solution; The combined heat treatment method of the wood is implemented using a device, and the device comprises: At least two groups of immersion tanks, the immersion tank comprising a tank body, a material opening formed at one end of the axial direction of the tank body, a front end cover matched with the material opening, an air supply slot formed at the top of the tank body, an air door matched with the air supply slot, a heating assembly arranged at the bottom of the tank body; A first medicament mechanism, the first medicament mechanism being adapted to provide an aluminum sulfate solution to the immersion tank; A second medicament mechanism, the second medicament mechanism being adapted to provide a siloxane modification solution to the immersion tank; A vacuum mechanism, the vacuum mechanism being adapted to form a negative pressure in the immersion tank; A heat treatment system arranged at the top of the immersion tank, the heat treatment system comprising an air bellow, an air outlet slot arranged at the bottom of the air bellow, a plurality of groups of side air blowers arranged at one side of the air bellow, a wind baffle located below the side air blowers, an exhaust skylight, a humidifying assembly, and a heat treatment heating assembly arranged at the front of the side air blowers in the air outlet direction, when the air door is in an open state, the air bellow is in communication with the tank body through the butt joint of the air outlet slot and the air supply slot; and A control system.

2. The method for combined heat treatment of wood according to claim 1, characterized in that, In the step of implementing pretreatment, the concentration of the aluminum sulfate solution is 0.2-0.6mol / L.

3. The method for combined heat treatment of wood according to claim 2, characterized in that, In the step of implementing pretreatment, the wood is soaked in the aluminum sulfate solution by first implementing a circulation treatment and then implementing atmospheric pressure immersion, the circulation treatment being under a negative pressure condition for 3-4min, vacuum release for 25-35s, and the time length of the circulation treatment being 1-1.5h.

4. The method for combined heat treatment of wood according to claim 3, characterized in that, The time length of the atmospheric pressure immersion is 20-26h.

5. The method for combined heat treatment of wood according to claim 1, characterized in that, In the step of implementing pretreatment, the wood is soaked in the aluminum sulfate solution until the weight gain reaches 20-35%.

6. The method for combined heat treatment of wood according to claim 1, characterized in that, After the heat-treated wood is soaked in the siloxane modification solution for 2.5-3.5h, it is aged at a temperature of 20-30°C for 5-6h.

7. The method for combined heat treatment of wood according to claim 1, characterized in that, The plurality of groups of side air blowers are located at one side of the immersion tank.

8. The method for combined heat treatment of wood according to claim 1, characterized in that, The tank body is a cylindrical tank body; the air door comprises a circular arc door plate capable of sliding and rotating along the inner wall of the tank body and taking the axis of the tank body as the axis, a sliding and rotating guide structure, and a sliding and rotating driving structure; the sliding and rotating guide structure comprises a guide strip mounted on the front end cover and a limiting step mounted on the inner wall of the circular arc door plate and matched with the guide strip; and the sliding and rotating driving structure comprises a driving motor arranged on the rear end cover, a driving gear mounted on the output shaft of the driving motor, and an arc-shaped gear rack mounted on the inner wall of the circular arc door plate and matched with the driving gear.

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