Dimensional stability treatment method for thin plate

Abstract

The invention relates to the technical field of wood modification, in particular to a size stability treatment method for a thin plate, the thin plate is formed by cutting a log, the thin plate with the initial water content being 1-5% is placed between a pair of closed pressing plates with the temperature not lower than 220 DEG C, and after a set time length, the thin plate is placed between the pressing plates; the closing state of the pressing plate is kept, the thin plate is cooled, and after the thin plate is cooled to the set temperature, the pressing plate is opened; according to the thickness of the thin plate, the set duration is 20-30 s / mm. According to the treatment method provided by the invention, the dimensional stability of the thin plate can be improved, the treated thin plate only has extremely low mass loss and has better hydrophobicity, the influence degree of environmental temperature and humidity on the mechanical strength is remarkably reduced, and the original wood color and appearance of wood can be reserved to a certain extent.

Description

[0001] This application claims priority to patent application number 202411474547.5, filing date October 22, 2024, and titled “A thin sheet material and a method for treating its dimensional stability”. Technical Field

[0002] The present application relates to the technical field of wood modification, and in particular to a method for processing the dimensional stability of a thin plate. Background Art

[0003] Wood, especially fast-growing wood, has the characteristics of swelling and shrinking when wet, that is, the size of wood changes with the change of environmental humidity. This characteristic affects the shape, dimensional stability and mechanical strength of wood products in use. Therefore, the existing technology uses some modification methods to treat wood to reduce the influence of environmental humidity on wood size.

[0004] Heat treatment is a common treatment method suitable for improving the dimensional stability of plates. Traditional drying kiln heat treatment has problems such as large mass loss of plates, large loss of material strength, long treatment time, high treatment energy consumption and production safety. To this end, the prior art has proposed some new heat treatment methods.

[0005] For example, the method described in a Chinese invention patent application with publication number CN118578481A and titled “A Method for Heat Treatment of Wood” specifically involves placing absolutely dry wood (moisture content 0%) in a constant temperature environment of 185~215°C and oxygen content <3% for heat treatment for 27~53 minutes, then cooling the heat-treated wood in a dry environment of -20~0°C for 21~23 minutes, and repeating this several times to obtain surface heat-treated wood.

[0006] In the above technical solution, the heat treatment only occurs on the surface of the wood, so the overall mass loss rate of the surface heat-treated wood is less than that of the traditional overall heat-treated wood, the mass loss rate of the surface is greater than or equal to the overall average mass loss rate of the wood, and because the core layer is not modified by heat treatment, the overall mechanical strength of the material can be retained to a certain extent. At the same time, the above invention patent application also believes that when the thickness of the heat-treated surface layer accounts for 10~37.5% of the total thickness, it can weaken the degree of moisture in the external environment entering the core layer through the surface layer, reduce the penetration of moisture through the wood surface to the core layer, thereby avoiding significant shrinkage and swelling of the core layer, and improving the overall dimensional stability of the surface heat-treated wood.

[0007] The invention patent application with publication number CN102990752A and name “A method for carbonizing thin plates” records a stability treatment method for thin plates with a thickness of 1 to 6 mm, which specifically includes: a thin plate drying process, drying the thin plate to a moisture content of 20 to 30%; the first rapid heating stage, placing the dried thin plate in a carbonization kiln, heating it to 120 to 130°C at a rate of 40 to 60°C / hour; the first insulation stage, heating at 120 to 130°C for 0.5 to 1 hour; the humidification insulation stage, heating the wet-bulb temperature to 100°C for 1 to 1.5 hours; the second rapid heating stage, heating to 180 to 230°C at a rate of 40 to 60°C / hour; the second insulation stage, heating at 180 to 230°C for 1 to 1.5 hours; the rapid cooling stage, cooling the temperature in the carbonization kiln to 130 to 140°C, and then naturally cooling to ≤40°C before exiting the kiln. The above method can stabilize single boards with smaller thickness, but there are problems such as large mass loss, large material strength loss, long processing time, high processing energy consumption and production safety.

[0008] There is no stability treatment method for extremely thin boards (commonly known as veneer or veneer) with a thickness of 0.1-0.6 mm in the prior art. Summary of the invention

[0009] Generally speaking, heat-treated wood needs to go through a moisture balance process (commonly known as rehydration treatment) before use. In the invention patent application with publication number CN118578481A, there is also a record of "taking out the wood after the circulation treatment and placing it in a room temperature environment to balance the moisture content." According to the records in the above application documents, after a relatively short period of balancing treatment, due to the barrier of the surface layer to the moisture absorption of the core layer, although the core layer has a relatively high hygroscopicity, the surface layer and the core layer can still reach the same moisture content, for example, the surface layer and the core layer both have a moisture content of 5-7%.

[0010] However, according to the long-term practical experience of the inventor of this case, the surface layer of the board has reached a balanced moisture content, while the core layer has not reached a balanced moisture content state, so the above-mentioned board only seems to have reached a consistent moisture content balance state for the surface layer and the core layer, but in fact, the core layer still has space for moisture absorption. During the long use process, moisture will gradually penetrate into the core layer from both ends and sides of the board until the core layer reaches a balanced moisture content state.

[0011] Therefore, the inventor of this case believes that the above technical solution only obtains a plate with both dimensional stability and mechanical strength in form, but in long-term use, there will inevitably be a difference in dimensional change between the surface layer and the core layer with a balanced moisture content difference, thereby generating internal stress, and finally causing deformation of the plate during processing and use. At the same time, on one hand, the surface hardness of the plate affects the use of the plate, so the above product has a reduced surface hardness due to the heat treatment of the surface layer, which is not conducive to the application of the plate; on the second hand, the mechanical strength (such as bending strength) of the core layer that has not been heat-treated is largely affected by the moisture content at the time, which limits the application scenarios of the plate.

[0012] Different from the prior art, this case provides a method for treating the dimensional stability of thin boards, which implements overall heat treatment on thin boards cut from logs, that is, sawn timber of solid wood that has not been compounded or reorganized (boards of various specifications obtained by sawing logs longitudinally and transversely as specified in Section 2.4.1.1 of GB / T28202-2011), sliced ​​wood, and peeled wood. The treatment objects of this method include extremely thin boards with a thickness of 0.1 to 0.6 mm, thinner boards with a thickness of 1 to 5 mm, and general thin boards with a thickness of 6 to 20 mm. The thin boards after stability treatment have better dimensional stability, lower mass loss rate and loss of mechanical strength. At the same time, the method has a shorter processing time, simpler processing steps, higher production safety, and no odor during the processing process. This application specifically adopts the following technical solutions: A method for processing the dimensional stability of a thin board, wherein the thin board is cut from a log, and the thin board having an initial moisture content of 1-5% is placed between a pair of closed pressing plates with a temperature not lower than 220°C, and after a set time, the pressing plates are kept closed and the thin board is cooled, and the pressing plates are opened after the thin board is cooled to a set temperature; the set time is 20-30s / mm according to the thickness of the thin board.

[0013] This case provides a technical solution that can improve the dimensional stability of thin plates as a whole, specifically: (1) keeping the thin plates in a state of low moisture content, (2) using heat conduction to heat the thin plates from the upper and lower surfaces, (3) limiting the heat treatment temperature to no less than 220°C, and (4) cooling the press plate while keeping the press plate closed, so that the hydroxyl groups of hemicellulose in the thin plates are fully degraded into lignin during the continuous process of the hot plate closed state of the press plate; the lignin formed by resolidification during the continuous process of the hot plate closed state of the press plate and the continuous process of the cooling closed state of the press plate is not affected by moisture at room temperature, which makes the hydrophilicity of the treated thin plates extremely low and rigid; at the same time, the undegraded lignin can maintain the original quality and color of the wood. This is different from the degradation mechanism of hemicellulose in the high-temperature wet heat treatment of the prior art. In the treatment process of the prior art, hemicellulose is hydrolyzed into acetic acid and water that can catalyze the degradation of cellulose, as well as products such as furfural that cause odor.

[0014] Therefore, the dimensional stability treatment method of this case can complete the overall heat treatment of the thin plate in a relatively short time through relatively simple process steps, and the treated thin plate has improved physical and chemical properties. The degree of heat treatment of the treated thin plate is roughly the same at all places, the hydrophilicity is extremely low, and it has good dimensional stability. At the same time, the re-solidified lignin in this thin plate makes the material rigid, and the undegraded lignin can maintain the quality of the material. Therefore, when the treatment object is a general thin plate, the stability treatment method of this case can basically maintain the original quality and mechanical strength (including surface hardness and bending strength) of the general thin plate.

[0015] In particular, the dimensional stability treatment in this case improves the dimensional stability of the thin plate by: (1) reducing its hydrophilicity, (2) reducing its swelling rate, and (3) reducing its transverse and longitudinal differences.

[0016] Preferably, the thickness of the thin plate is 0.1-20 mm.

[0017] Preferably, during the continuation of the closed state, the pressing plate always applies a pressure not exceeding 1.5 MPa to the thin plate.

[0018] Preferably, during the continuation of the closed state, the pressing plate applies a pressure of 1-1.2 MPa to the thin plate.

[0019] In the above preferred technical solution, the pressing plate applies pressure to the thin plate in the process of the hot plate being closed and the cold plate being closed. The pressing plate applies pressure in the process of the hot plate being closed and the thin plate being closed to correct the possible deformation and thickness dimensional deviation of the thin plate. The principle is to use high temperature and pressure to correct the deformation so that the thin plate at this time becomes straight, and the thicker part is compressed to be equal in thickness to other parts. The improvement of the flatness of the thin plate will be conducive to uniform heating, so that the thin plate can obtain the same or similar degree of heat treatment effect everywhere. The pressing plate applies pressure in the process of the cold plate being closed and the recovery of the corrected bend and the rebound of the compressed thickness part can be prevented, so as to obtain a straight and uniform or similar thickness thin plate. The pressing plate is closed and maintained in the cold plate, which can realize the rapid cooling of the thin plate, avoid excessive degradation of hemicellulose and lignin, and ensure that the mechanical strength of the thin plate does not decrease significantly, so that the stability and strength of the treated thin plate can be more effectively taken into account.

[0020] Preferably, the temperature of the pressing plate is 220-250°C.

[0021] As a further preference, the temperature of the pressing plate is 230-240°C.

[0022] Preferably, the cooling of the thin plate is completed within 120 seconds.

[0023] As a further preference, the set temperature is less than or equal to 90°C.

[0024] In the above preferred technical solution, the temperature of the thin plate is forced to be lowered in a short time to avoid the thin plate from being over-processed, thereby being able to more effectively take into account the stability and strength of the processed thin plate.

[0025] Preferably, the mass loss of the thin plate after the dimensional stability treatment is no more than 2.5%.

[0026] Preferably, when the thickness of the thin plate is 6-20 mm, the transverse heat-resistant dimensional stability of the thin plate after the dimensional stability treatment is not greater than 0.5%, and the transverse moisture-resistant dimensional stability is not greater than 0.3%.

[0027] As a further preference, the ratio of the transverse heat-resistant dimensional stability to the grain heat-resistant dimensional stability of the thin plate is (4-10):1, and the ratio of the transverse moisture-resistant dimensional stability to the grain moisture-resistant dimensional stability is (2-10):1.

[0028] As a further preference, when the ambient temperature and humidity changes from 20°C / 45%RH to 30°C / 92%RH, the decrease in the bending strength of the thin plate is no more than 15%.

[0029] In summary, the dimensional stability processing method of a thin plate provided in this case has the following advantages: (1) It can process thin plates with a thickness of 0.1~20mm, with short processing time, simple processing technology and high processing safety; (2) The dimensional stability of the thin plate after stability treatment is good, which is manifested in lower hydrophilicity, lower shrinkage and swelling rate, and smaller difference in dimensional stability between the transverse direction and the longitudinal direction of the grain; (3) When the thickness of the thin plate is 6-20 mm, the thin plate treated with stability has a small mass loss and high mechanical strength, and the degree to which the mechanical strength is affected by the ambient temperature and humidity is significantly reduced; (4) Under the same treatment temperature, compared with the dimensional stability treatment method based on heat treatment in the prior art, its impact on material color and mechanical strength is lower. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative labor.

[0031] Figure 1 A schematic flow chart of the dimensional stability processing method provided in an embodiment of the present application.

[0032] Figure 2 (a) is a photo of the solid wood sawn timber of the control example 1 provided in the present application; (b) is a photo of the thin board of the embodiment 1 provided in the present application; (c) is a photo of the thin board of the embodiment 2 provided in the present application; (d) is a photo of the thin board of the embodiment 3 provided in the present application.

[0033] Figure 3 These are photos of the water contact angles of the solid wood sawn timber of Comparative Example 1 and the thin boards of Examples 1 to 3 provided in this application. DETAILED DESCRIPTION

[0034] In order to enable those 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 conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this application. Example

[0035] Reference Figure 1 The dimensional stability treatment method of a thin plate is shown in the figure. The treated thin plate is a mangosteen sawn plate with a moisture content of 1±0.5%, a specification of 500×150×12.5mm, and a density of 0.7g / cm 3 .

[0036] First, use a flat-plate hot press to raise the temperature of the upper and lower press plates to 250 ± 0.5 °C; Then, the thin plate is placed on the lower pressing plate, and the upper pressing plate is quickly closed. After closing, the upper pressing plate applies a pressure of 1.2 MPa to the thin plate. After the pressure is applied in place, the hot plate enters the closed state, which is maintained for 300 seconds. Then, the pressure of 1.2 MPa is maintained, and the upper pressing plate and the lower pressing plate are cooled by the forced cooling method of the prior art to cool the temperature of the thin plate to 80° C. The cooling process takes about 110 seconds. Finally, after cooling down to the desired temperature, the pressure is released and the press is opened to take out the thin sheet that has been treated for dimensional stability. Example

[0037] The difference between this embodiment and embodiment 1 is that, during the continuation of the closed state of the hot plate, the temperature of the upper pressing plate and the lower pressing plate is 240±0.5° C., and the cooling process takes about 105 s. Example

[0038] The difference between this embodiment and embodiment 1 is that, during the continuation of the closed state of the hot plate, the temperature of the upper pressing plate and the lower pressing plate is 230±0.5° C., and the cooling process takes about 100 seconds. Example

[0039] The difference between this embodiment and embodiment 1 is that the duration of the closed state of the hot plate is 250 seconds. Example

[0040] The difference between this embodiment and embodiment 1 is that the duration of the closed state of the hot plate is 360 seconds. Example

[0041] The difference between this embodiment and embodiment 1 is that during the continuation of the closed state of the hot plate and the cooling process of the pressing plate, the upper pressing plate contacts the thin plate without pressure, or the pressure applied is no more than 0.3 MPa. Example

[0042] The difference between this embodiment and embodiment 1 is that, while the hot plate is in the closed state, the upper pressing plate contacts the thin plate without pressure, or the pressure applied is no more than 0.3 MPa; subsequently, when the pair of pressing plates begin to cool, the upper pressing plate applies a pressure of 1.2 MPa to the thin plate, and continues to apply the pressure during the cooling process until the thin plate is cooled to 80°C. The cooling process takes about 100 seconds. Example

[0043] The difference between this embodiment and embodiment 1 is that the moisture content of the thin plate is 3±0.5%. Example

[0044] The difference between this embodiment and embodiment 1 is that the specification of the thin plate is 500×150×16 mm, and the duration of the closed state of the hot plate is 400 s. Example

[0045] The difference between this embodiment and embodiment 1 is that the thin plate treated is fir sawn plate (density 0.38g / cm 3 )、Poplar sawn board (density 0.5g / cm 3 )、Lychee sawn board (density 0.85g / cm 3 ) and red oak sawn wood (density 0.75g / cm 3 ).

[0046] The thin plates treated by the stability treatment methods of Examples 1 to 10 were cured in an environment of 50°C / 85% to equilibrium, and then processed into floors using the process methods of the prior art, and were marked as specimens 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and 13, respectively. Example

[0047] A method for processing the dimensional stability of a thin plate material. The processed thin plate material is a mangosteen sliced ​​plate material with a moisture content of 1±0.5% and a specification of 95×65×0.1 mm.

[0048] First, use a flat-plate hot press to raise the temperature of the upper and lower pressing plates to 240 ± 0.5 °C; Then, the thin plate is placed on the lower pressing plate, and the upper pressing plate is quickly closed. After closing, the upper pressing plate applies a pressure of 1.2 MPa to the thin plate. After the pressure is applied in place, the hot plate enters the closed state, and this state is maintained for 2 seconds; Then, the pressure of 1.2 MPa is maintained, and the upper pressing plate and the lower pressing plate are cooled by the forced cooling method of the prior art to cool the temperature of the thin plate to 80° C. The cooling process takes about 5 seconds. Finally, after cooling down to the desired temperature, the pressure is released and the press is opened to take out the thin sheet that has been treated for dimensional stability.

[0049] The thin plate treated by the stability treatment method of this embodiment is cured in an environment of 50°C / 85% to equilibrium, and then attached to the front and back sides of a plywood with a specification of 95×65×0.8mm through a cold pressing process to prepare an IC card substrate with a total thickness of 1mm, which is marked as specimen 14. Example

[0050] The difference between this embodiment and embodiment 11 is that the specifications of the processed thin plate are 500×150×0.5 mm, the duration of the hot plate closed state is 10 s, and the subsequent cooling process takes about 15 s.

[0051] The thin plate treated by the stability treatment method of this embodiment is cured in an environment of 50°C / 85% to equilibrium, and then attached to the surface of a multilayer plate with a specification of 500×150×1.5mm through a cold pressing process to prepare a decorative panel with a total thickness of 2mm, which is marked as specimen 15. Example

[0052] The difference between this embodiment and embodiment 11 is that the thickness of the processed thin plate is 3 mm, the duration of the hot plate closed state is 60 seconds, and the subsequent cooling process takes about 20 seconds.

[0053] The thin plate treated by the stability treatment method of this embodiment is cured in an environment of 50℃ / 85% to equilibrium, and then attached to the surface of a multilayer plate with a width of 2.7m×1.5m and a thickness of 12mm through a cold pressing process to prepare a large-format sliding door panel with a total thickness of 18mm, which is marked as specimen 16.

[0054] Comparative Example 1 Take the mangosteen sawn board (density 0.7g / cm 3 )、Chinese fir sawn board (density 0.38g / cm 3 )、Poplar sawn board (density 0.5g / cm 3 )、Lychee sawn board (density 0.85g / cm 3 ) and red oak sawn wood (density 0.75g / cm 3 ), the moisture content is 1±0.5%, and the specifications are 500×150×12.5mm.

[0055] The solid wood sawn timber of this comparative example was cured to equilibrium in an environment of 50°C / 85%, and then processed into flooring using the process method of the prior art, and were marked as C1, C2, C3, C4 and C5 respectively.

[0056] Comparative Example 2 The processed thin board is a mango sawn board with a moisture content of 1±0.5%, a specification of 500×150×12.5mm, and a density of 0.7g / cm 3 .

[0057] First, use a flat-plate hot press to raise the temperature of the upper and lower press plates to 250 ± 0.5 °C; Then, the thin plate is placed on the lower pressing plate, and the upper pressing plate is quickly closed. After closing, the upper pressing plate applies a pressure of 1.2 MPa to the thin plate. After the pressure is applied in place, the hot plate enters the closed state, which is maintained for 300 seconds. Then, release the pressure and allow the sheet to cool naturally to 80°C; Finally, the press plate is opened and the thin sheet treated for dimension stability is removed.

[0058] Comparative Example 3 The processed thin board is a mango sawn board with a moisture content of 1±0.5%, a specification of 500×150×12.5mm, and a density of 0.7g / cm 3 .

[0059] The heat treatment is carried out in a drying kiln. The heat treatment conditions are a wet bulb temperature of 100°C, a dry bulb temperature of 250±2°C, and a maximum temperature holding time of 2h.

[0060] Comparative Example 4 The processed thin board is a mango sawn board with a moisture content of 8±0.5%, a specification of 500×150×12.5mm, and a density of 0.7g / cm 3 .

[0061] Use a flat plate heat press to raise the temperature of the upper and lower plates to 180±0.5℃; Then, place the solid wood sawn timber on the lower pressing plate, quickly close the upper pressing plate, make the upper pressing plate contact the solid wood sawn timber without pressure, or apply a pressure of no more than 0.3 MPa, and keep the pressing plate closed for 20 minutes; Then, release the pressure and allow the sheet to cool naturally to 80°C; Finally, the press plate is opened and the thin sheet treated for dimension stability is removed.

[0062] The thin boards obtained by the methods of control examples 2 to 4 were cured in an environment of 50°C / 85% to equilibrium, and then processed into floors using the process methods of the prior art, and were marked as C6, C7 and C8, respectively.

[0063] Comparative Example 5 Take the sliced ​​board of mangosteen with a moisture content of 10±0.5% and a specification of 500×150×0.1mm. After curing to equilibrium in an environment of 30℃ / 65%, it is attached to the front and back sides of a plywood with a thickness of 0.8mm by cold pressing to prepare an IC card substrate with a total thickness of 1mm, marked as C9.

[0064] Comparative Example 6 Take the sliced ​​board of mangosteen with a moisture content of 10±0.5% and a specification of 500×150×0.5mm. After curing to equilibrium in an environment of 30℃ / 65%, it is attached to the surface of a multilayer board with a thickness of 1.5mm by cold pressing to prepare a veneer with a total thickness of 2mm, marked as C10.

[0065] Comparative Example 7 The sawn board of mangosteen with a moisture content of 10±0.5% and a specification of 500×150×3mm was taken. After curing to equilibrium in an environment of 30℃ / 65%, it was attached to the surface of a multilayer board with a width of 2.7m×1.5m and a thickness of 12mm through a cold pressing process to prepare a large-format sliding door panel with a total thickness of 18mm, marked as C11.

[0066] The following items were tested on specimens 1 to 13 and C1 to C8: (1) Moisture content, refer to GB1931-2009; (2) Heat resistance dimensional stability (shrinkage rate) and moisture resistance dimensional stability (wet expansion rate), refer to 6.2.1 and 6.2.2 of standard LY / T1700-2018 respectively; (3) Flexural strength, refer to standard GB / T 1927-2021.

[0067] Table 1 shows the dimensional stability test results of specimens 1 to 13 and C1 to C7. C8 was not tested because it had obvious cracks and could not be used.

[0068] Table 1

[0069] Generally speaking, the moisture content of thin sheets without any dimensional stability treatment under 85% relative humidity is 12~16%, the transverse heat-resistant dimensional stability is 1.3~2.2%, the along-grain heat-resistant dimensional stability is 0.07~0.14%, the transverse moisture-resistant dimensional stability is 0.45~0.8%, the along-grain moisture-resistant dimensional stability is 0.03~0.06%, the ratio of transverse heat-resistant dimensional stability to along-grain heat-resistant dimensional stability is (10~20):1, and the ratio of transverse moisture-resistant dimensional stability to along-grain moisture-resistant dimensional stability is (10~20):1. It can be seen that the difference in shrinkage and swelling between the transverse and along-grain of untreated thin sheets is 10~20 times, which makes the material prone to side bending, warping, tiles, and other quality problems during use.

[0070] The thin board is subjected to the dimensional stability treatment of the prior art, such as the kiln heat treatment process or the flat plate heat treatment process. The air-dried moisture content of the treated solid wood sawn timber is 5-7%, the transverse heat-resistant dimensional stability is 0.22, the along-grain heat-resistant dimensional stability is 0.02, the transverse moisture-resistant dimensional stability is 0.16, the along-grain moisture-resistant dimensional stability is 0.02, the transverse heat-resistant dimensional stability is (10-20):1 to the along-grain heat-resistant dimensional stability, and the transverse moisture-resistant dimensional stability is (10-20):1 to the along-grain moisture-resistant dimensional stability. It can be seen that although the means of the prior art have improved the hydrophilicity, shrinkage rate, and swelling rate of the thin board, they have not improved the difference in material properties between the transverse and along-grain, so that the thin board still has quality problems such as lateral bending, warping, tiles, and large and small heads during use.

[0071] It can be seen from Table 1 that the dimensional stability of the specimens 1 to 13 treated and processed by the method provided in the embodiments of the present application is not only reflected in lower hydrophilicity (air-dry moisture content) and lower shrinkage and swelling ratio (wet and heat dimensional stability), but also in smaller lateral and longitudinal differences.

[0072] Figure 3 This proves that the thin plate treated by the method provided in the examples of the present application has lower hydrophilicity.

[0073] For readers' reference and comparison, the air-dried moisture content of the multi-layer solid wood composite board with a specification of 500×150×12.5mm is 10%, the transverse heat-resistant dimensional stability is 0.45, the heat-resistant dimensional stability along the grain is 0.35, the transverse moisture-resistant dimensional stability is 0.28, and the moisture-resistant dimensional stability along the grain is 0.18. The ratio of the transverse heat-resistant dimensional stability to the heat-resistant dimensional stability along the grain is 1:1, and the ratio of the transverse moisture-resistant dimensional stability to the moisture-resistant dimensional stability along the grain is 2:1.

[0074] Table 2 shows the bending strength test results of specimens 1 to 13 and C1 to C8.

[0075] Table 2

[0076] As can be seen from Table 2, heat treatment will cause the loss of mass and mechanical strength of wood. By comparing specimens 1 to 13 with specimens C6 to C8, it can be seen that the technical solution of this case has a lower mass loss rate of the material and a lower loss of mechanical strength under the premise of obtaining better dimensional stability. At the same time, the mechanical strength of specimens 1 to 13 is less affected by the ambient temperature and humidity, which makes the thin plate prepared by the embodiment of this case more suitable for applications requiring certain strength. Among them, specimen C8 has relatively serious surface cracks and internal cracks, so it is not tested for mechanical strength.

[0077] Figure 2 The comparison of the color of the solid wood sawn timber of the comparative example 1 and the thin boards of the embodiments 1 to 3 is shown in FIG. Figure 2 It can be seen that the thin board of Example 3 only darkens the color of the wood to a certain extent, and basically maintains the natural wood color of the thin board.

[0078] Test the flatness of specimens 14-16 and C9-C11, balance the specimens in an environment of 20℃ / 45%RH; then, place the specimens in an environment of 30℃90%RH until the quality is basically stable, test the flatness and record the value of the first test flatness; finally, place the specimens in an environment of 20℃ / 45%RH until the quality is basically stable, test the flatness and record the value of the second test flatness. The flatness measurement method is carried out in accordance with 6.2.2 Flatness Determination in GB / T 3324-2017.

[0079] Table 3 shows the flatness test results of specimens 14-16 and C9-C11.

[0080] Table 3 It can be seen from Table 3 that the thin plate material after the stability treatment of the technical solution of this case can be used to make IC card substrates, thin decorative panels and large-format sliding door panels.

[0081] In order to reduce the use of plastic, it is recommended to use wooden boards as substrates to make IC cards, but due to the poor stability of the surface board, it is difficult to keep the IC card flat during use. By comparing test piece 14 with C9, it can be seen that the IC card substrate prepared from the 0.1mm thick board after stability treatment of the technical solution of this case has almost no warping shape change and can remain flat during use.

[0082] In order to reduce the space occupied by wall decoration in small-sized houses, the market has formed a demand for thin decorative panels, but due to the poor stability of the surface panels, it is difficult for existing thin decorative panels to remain flat during storage, which affects its assembly. By comparing specimens 15 and C10, it can be seen that the decorative panels prepared from the 0.5mm thick sheet material after stability treatment of the technical solution of this case have almost no warping shape changes, and can remain flat during storage, so as to smoothly construct and assemble.

[0083] In order to meet the design requirements of large-format sliding door panels, such as a panel of 2.7m×1.5m, the existing technology increases the thickness of sliding door panels from 18mm to 30mm or even more to cope with the larger warping deformation caused by the large panel. However, this solution also increases the weight of the door panel, increases the load on the hanging track or hinge, and easily causes the door panel to sag. By comparing specimens 16 and C11, it can be seen that the stability of the technical solution of this case can be used to process the large-format sliding door panels made of 3mm thick sheet materials without warping changes that affect the opening and closing of the sliding door, while maintaining the original thickness, thereby being able to take into account both self-weight and stability.

[0084] The above description is intended to be illustrative and not limiting. Upon reading the above description, many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art. Therefore, the scope of the present teachings should not be determined with reference to the above description, but should be determined with reference to the appended claims and the full scope of equivalents to which such claims are entitled. For the purpose of comprehensiveness, all articles and references, including disclosures of patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the preceding claims is not intended to be a waiver of the subject matter, nor should it be considered that the applicant has not considered the subject matter to be part of the disclosed application subject matter.

Claims

1. A method for treating the dimensional stability of a thin plate, wherein the thin plate is cut from a log, characterized in that: The thin plate with an initial moisture content of 1-5% is placed between a pair of closed pressing plates with a temperature not lower than 220°C. After a set time, the pressing plates are kept closed and the thin plate is cooled. After the thin plate is cooled to the set temperature, the pressing plates are opened. Depending on the thickness of the thin plate, the set time is 20-30s / mm.

2. The method for treating the dimensional stability of a thin plate according to claim 1, characterized in that: The thickness of the thin plate is 0.1-20 mm.

3. The method for treating the dimensional stability of a thin plate material according to claim 1, characterized in that: During the continuation of the closed state, the pressing plate always applies a pressure not exceeding 1.5 MPa to the thin plate.

4. The method for treating the dimensional stability of a thin plate according to claim 3, characterized in that: During the continuation of the closed state, the pressing plate always applies a pressure of 1-1.2 MPa to the thin plate.

5. The method for treating the dimensional stability of a thin plate material according to claim 1, characterized in that: The temperature of the pressing plate is 220-250°C.

6. The method for treating the dimensional stability of a thin plate according to claim 1, characterized in that: The cooling of the thin plate is completed within 120 seconds.

7. The method for treating the dimensional stability of a thin plate according to claim 6, characterized in that: The set temperature is less than or equal to 90°C.

8. The method for treating the dimensional stability of a thin plate according to claim 2, characterized in that: When the thickness of the thin plate is 6-20 mm, the transverse heat-resistant dimensional stability of the thin plate after the dimensional stability treatment is not greater than 0.5%, and the transverse moisture-resistant dimensional stability is not greater than 0.3%.

9. The method for treating the dimensional stability of a thin plate material according to claim 8, characterized in that: The ratio of the transverse heat-resistant dimensional stability to the grain heat-resistant dimensional stability of the thin plate is (4-10):1, and the ratio of the transverse moisture-resistant dimensional stability to the grain moisture-resistant dimensional stability is (2-10):1.

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