A bamboo board and a method for manufacturing the same

Abstract

The present application relates to the technical field of bamboo products, and discloses a bamboo board and a preparation method thereof, which comprises at least a plurality of single board strips transversely spliced along the width direction, the density of the bamboo board is 0.7-1.2 g / cm 3 , the density deviation of each part of the single bamboo board is less than 9%, the average density deviation between the bamboo boards in the same batch is less than 5%, the equilibrium moisture content of the bamboo board is less than 9% under the condition of 20 DEG C / 65% RH, the single board strip comprises two bamboo wall sections and bamboo joints connecting the two bamboo wall sections, and the bamboo wall section comprises bamboo green, bamboo pulp and bamboo yellow. The bamboo board prepared by the present application has the advantages of good dimensional stability, excellent mechanical properties and the like, and can be widely applied to furniture, floor, door and bamboo structure building.

Description

Technical Field

[0001] This invention relates to the technical field of bamboo products, specifically a type of bamboo board; the invention also relates to a method for preparing the bamboo board. Background Technology

[0002] Bamboo is an important component of my country's forest resources, with a massive amount of bamboo being harvested annually. Bamboo possesses excellent mechanical properties and grows extremely quickly; therefore, the rational and high-value utilization of bamboo can effectively alleviate the shortage of timber resources in my country. Using bamboo to produce bamboo boards is a method with a relatively high comprehensive utilization rate of bamboo resources.

[0003] Bamboo is a cylindrical material, and the density and strength of the bamboo wall vary greatly from the outside to the inside. To utilize bamboo in its original form, the bamboo must first be flattened. Ideally, the density and properties of the bamboo wall should be made uniform throughout.

[0004] Chinese invention patent application CN101528431A, entitled "Flattened Bamboo Sheets," describes a technical solution for flattening bamboo strips, comprising the following steps: a) longitudinally cutting the bamboo tube along its entire length to form one or more bamboo stalk walls (equivalent to bamboo strips), wherein the bamboo stalk wall includes an outer region (equivalent to bamboo green), a middle region (equivalent to bamboo flesh), and an inner region (equivalent to bamboo yellow); b) soaking and heating the bamboo stalk wall, thereby forming a softened stalk wall (softening process); and c) flattening the softened stalk wall using a gradual or multi-step process. This method retains the bamboo green and bamboo yellow of the bamboo stalk wall. Compared to the traditional method of removing the green and yellow before flattening, it retains the denser bamboo green and bamboo yellow, resulting in bamboo sheets with higher density. This technical solution can only achieve the flattening of bamboo strips, and the resulting bamboo sheets retain the differences in density, mechanical strength, and hygroscopicity among the bamboo green, bamboo flesh, and bamboo yellow. Specifically, the resulting bamboo boards exhibit an asymmetrical and uneven distribution in density and mechanical strength along the thickness direction, with the highest density in the green bamboo portion, the lowest in the flesh, and the second highest in the yellow bamboo portion. Similarly, the moisture absorption is also asymmetrical and uneven, with the lowest moisture absorption in the green bamboo portion, the highest in the flesh, and the second highest in the yellow bamboo portion. This reduces the mechanical properties of the bamboo boards, making them prone to twisting and deformation upon moisture absorption, and also causes the bamboo boards to tend to curl back into a cylindrical shape. To address this, the patent application also describes a preferred technical solution, namely, forming multiple parallel grooves in the internal region, wherein the grooves and the grain direction are formed at an angle between approximately 10° and 60°. However, this preferred technical solution is not only complex to operate and less feasible, but also affects the processability and usability of the marked surface of the bamboo boards, and fails to solve the problems of low mechanical properties and easy deformation due to moisture absorption.

[0005] Bamboo boards are made by horizontally widening flat bamboo sheets or strips along their width or simultaneously vertically thickening them. For example, Chinese utility model patent CN202147305U, entitled "Combined Bamboo Boards," describes a structure for a bamboo board comprising five layers of bamboo strips. The top and bottom layers are side-pressed, with the strips vertically joined. The second, third, and fourth layers are flat-pressed, with the strips horizontally joined. The second and fourth layers are joined in the same way, while the third layer is staggered at 90° with the second and fourth layers. Because of this combined side-pressing and flat-pressing structure, the flexural strength is significantly enhanced, and the structural stability is noticeably better than existing bamboo boards. However, this technology obviously results in relatively thick bamboo boards, making it difficult to produce single-layer or thinner products. Furthermore, the assembly process is complex, and the assembly precision is difficult to control, reducing the stability of product quality.

[0006] To address the aforementioned issues, Chinese utility model patent CN206011329U, entitled "Bamboo Board," describes a structure for a bamboo board. This board is composed of multiple bamboo strips sequentially spliced ​​along their width. Each strip has a first main surface and a second main surface that are parallel to each other and opposite each other along its thickness. The cross-section of each strip is trapezoidal, and the area of ​​the first main surface is smaller than the area of ​​the second main surface. In adjacent strips, the first main surface of one strip is adjacent to the second main surface of the other. However, this technical solution results in bamboo boards with varying densities and strengths across different areas of the surface, making them unsuitable for direct use.

[0007] In summary, there is a lack of bamboo boards with relatively high density and uniform density throughout the existing technology. Summary of the Invention

[0008] The technical objective of this invention is to overcome at least one of the above-mentioned technical problems and provide a bamboo board that has the advantages of being rot-resistant and mildew-resistant, having high mechanical strength, uniform density, and good stability by giving the bamboo board higher density, lower density deviation, lower moisture absorption, and lower moisture absorption deviation.

[0009] The present invention also provides a method for preparing veneer strips for making such bamboo boards. The method involves selecting bamboo strips with some bamboo nodes and applying temperature and pressure to the bamboo strips to compress them into a denser state, thereby obtaining veneer strips with higher density, lower density deviation, lower moisture absorption and lower moisture absorption deviation.

[0010] In one aspect of this application, a bamboo board is provided, comprising at least a plurality of veneer strips joined laterally along the width direction, wherein the density of the bamboo board is 0.7–1.2 g / cm³. 3The density deviation of a single bamboo board is less than 10%, and the average density deviation between bamboo boards in the same batch is less than 5%; under the conditions of 20℃ / 65%RH, the equilibrium moisture content of the bamboo board is less than 9%; the single board strip includes two bamboo wall sections and a bamboo node connecting the two bamboo wall sections, and the bamboo wall section includes bamboo green, bamboo flesh and bamboo yellow.

[0011] Based on the aforementioned product characteristics, compared to existing bamboo boards, the bamboo board in this case has a relatively high density and a relatively small density deviation throughout the board, making it a homogeneous material with relatively high mechanical strength. The bamboo board in this case also has a relatively low equilibrium moisture content, resulting in better dimensional and morphological stability and making it less prone to mold and decay.

[0012] Furthermore, by using veneer strips including bamboo green, bamboo flesh, and bamboo yellow as raw materials, the presence of bamboo green enables the bamboo board in this case to have high mechanical strength and good waterproof performance.

[0013] As a preferred embodiment, the veneer strip selected for use has the following limiting requirement: the density of the near-surface portion of the veneer strip deviates from the density of the middle layer in its thickness direction by 5 to 15%.

[0014] In order to make the veneer strips meet the above-mentioned requirements, the veneer strips are subjected to a special treatment to remove bamboo sap. After the treatment, the relative content of lignin in the veneer strips is increased by 50-60% compared with that before the treatment, and the veneer strips undergo densification compression with a compression rate of 0-30% in the thickness direction.

[0015] Existing techniques for unfolding bamboo strips to obtain veneer typically involve removing the nodes from both ends of a bamboo tube to create an open tube, which is then split to obtain node-free bamboo strips. In some cases, the outer green layer of the bamboo or the inner yellow layer is also removed beforehand. Current techniques recognize that bamboo contains a large amount of moisture, and the thermal resistance created by this moisture prevents the internal temperature of the bamboo from exceeding 100°C under normal pressure. The nodes, where moisture accumulates, represent the areas with the greatest thermal resistance. Therefore, nodes are generally removed, and only the bamboo wall sections are unfolded. Furthermore, existing techniques suggest that while the outer green layer protects the inner and outer layers of the bamboo, its much higher density causes a significant density difference between the outer and core layers of the unfolded veneer, leading to a decrease in mechanical strength. Therefore, at least the outer green layer is removed before unfolding.

[0016] In contrast, this invention differs from existing technologies in its bamboo sap removal process. It uses a bamboo tube containing a single bamboo node, splits it to obtain bamboo strips with nodes, and finally removes the bamboo sap to obtain veneer strips with nodes, compressed thickness, and an increased relative lignin content. In other words, this technical solution retains the bamboo node to create a high temperature and high vapor pressure area at the node, and a low temperature and low vapor pressure area on the bamboo wall section away from the node. This creates a temperature and vapor pressure gradient along the axial direction of the bamboo strip from the node to both ends. This temperature and vapor pressure gradient promotes the removal of moisture and bamboo sap from the bamboo strip. As the moisture content of the bamboo strip decreases, the temperature of the bamboo strip rises relatively quickly, exceeding 120°C, and frees up space within the bamboo strip that was previously occupied by moisture, allowing for compression.

[0017] Therefore, by retaining bamboo nodes in the structure of bamboo strips, veneer strips with increased lignin content and compressed thickness can be obtained. When the veneer strip is compressed in the thickness direction, the bamboo flesh, located in the middle layer with the lowest density, is compressed and compacted first, increasing its density. Therefore, the density deviation between the near-surface portion (the green bamboo portion) and the middle layer (the compressed bamboo flesh portion) of the resulting veneer strip is smaller, resulting in a relatively homogeneous veneer strip that retains the properties of the green bamboo. The utilization of the green bamboo also improves the utilization rate of the bamboo material. With the discharge of bamboo sap, the relative lignin content of the veneer strip increases, meaning that hemicellulose undergoes a chemical reaction under temperature to generate the active components of bamboo sap. This results in veneer strips with lower equilibrium moisture content, lower hygroscopicity, better dimensional stability, finer texture, and higher mechanical strength. The increase in the relative lignin content also means a decrease in the relative content of sugars and starches in the veneer strip, giving it insect-repellent and rot-resistant properties. Of course, the higher the processing temperature of the bamboo sap applied to the bamboo strips, the lower the equilibrium moisture content of the veneer strips.

[0018] In a preferred embodiment, the width of the single-layer strip is 3-8 mm, and the thickness of the single-layer strip is 3-6 mm.

[0019] In a preferred embodiment, the bamboo board comprises a plurality of bamboo veneers stacked and thickened along the thickness direction, and the bamboo veneers comprise a plurality of veneer strips that are laterally widened along the width direction; the fiber directions of the plurality of veneer strips are the same.

[0020] Another aspect of this invention provides a method for preparing bamboo boards, which includes at least the preparation of single-layer strips. First, a bamboo tube is obtained, the bamboo tube comprising two sections of bamboo wall and a bamboo node connecting the two sections of bamboo wall. The bamboo tube is split to obtain bamboo strips. Subsequently, the bamboo strips are placed between a pair of pressure surfaces, both of which have a temperature of 120-200°C. The pair of pressure surfaces simultaneously apply a pressure of 2-4 MPa to the bamboo strips from both the green bamboo side and the yellow bamboo side. The pressure is maintained until the moisture content of the bamboo strips drops to 7-15%, thereby obtaining the single-layer strips.

[0021] In the above-described method, bamboo strips are treated with relatively low temperature and pressure, reducing their moisture content, removing sugars and other nutrients, and flattening their shape. This results in two advantages: firstly, the obtained veneer strips have smaller density deviations, higher density, and greater strength; secondly, the veneer strips can be directly used to prepare bamboo boards without requiring a further drying process or additional pretreatment for mold and corrosion prevention. This method does not use chemical agents, leading to lower production costs and easier process control.

[0022] Specifically, because bamboo often contains a large amount of moisture, it creates thermal resistance, making it difficult for the internal temperature of bamboo to exceed 100℃ under normal pressure. Therefore, existing technologies commonly use steam treatment to soften the bamboo and increase the internal temperature of the bamboo, rather than using heat contact. Please refer to existing technical documents, such as Chinese invention patent application CN106881755A entitled "Method for Densifying Wood / Bamboo by Hot Pressing Combined with Steam Spraying and Densifying Wood / Bamboo" and Chinese invention patent application CN116619503A entitled "A Bamboo Flattening Process," etc. However, once the bamboo strips have been steam-treated, they contain a large amount of moisture and are difficult to compress, only able to flatten. Furthermore, the moisture content, steam pressure, and temperature are basically the same throughout the bamboo strip, making it difficult for nutrients such as sugars and starches to be expelled. In contrast, the technical approach used in this case involves using bamboo strips that retain the bamboo nodes. When heated, this creates a region with higher moisture content, vapor pressure, and temperature at the nodes, and lower temperature and vapor pressure regions at the ends of the strip. This creates a temperature and vapor pressure gradient along the axial direction of the bamboo strip, moving from the nodes towards both ends. Driven by these gradients, the moisture containing bamboo sap migrates and dissipates from the nodes towards both ends, reducing the moisture content of the bamboo strip, weakening its thermal resistance, and creating water-free spaces between the cells. This allows the strip to reach temperatures above 120°C, the softening temperature of bamboo. As the pressure and temperature are maintained, the bamboo strip can be compressed and flattened.

[0023] The bamboo sap removal process involves using temperature and pressure to expel nutrients such as sugars and starches from the bamboo along with moisture to both ends of the bamboo. During this process, sugars, starches, and hemicellulose undergo a chemical reaction under temperature to generate the active ingredients of bamboo sap. Therefore, after the bamboo sap removal process, the nutrients in the bamboo strips are completely removed along with the extraction of the sap, resulting in veneer strips with certain anti-corrosion and anti-mildew properties. The bamboo boards produced thus also possess certain anti-corrosion and anti-mildew properties. The generation and removal of bamboo sap distinguishes this technical solution from existing bamboo strip hot-pressing or heat-treatment techniques. A significant characteristic of existing bamboo strip hot-pressing or heat-treatment techniques is the reduction of lignin content. In this solution, however, the relative lignin content increases due to the large amount of hemicellulose participating in the reaction to form bamboo sap.

[0024] Preferably, both ends of the bamboo strip extend beyond the pressure surface, forming cold ends to amplify the temperature gradient and water vapor pressure gradient. The extended length is further preferably 4.5–5.5 cm.

[0025] Preferably, the bamboo strips are selected with a thickness deviation of less than ±1.5 mm, and a thickness gauge is used to limit the downward pressure stroke of the pressure surface located above, that is, to limit the thickness of the veneer strip, so that the compression rate of the veneer strips made using a thickness gauge of the same thickness is within a certain range.

[0026] In a preferred embodiment, the natural moisture content of the bamboo strips is 60-120%.

[0027] The presence of bamboo nodes overcomes the thermal resistance to moisture formation within the bamboo strips, allowing the use of bamboo strips with a relatively high natural moisture content. When the bamboo strips have a relatively high natural moisture content in their initial state, the technical solution of this invention can simultaneously form bamboo sap during the pressing and flattening process, and allow the bamboo sap to be discharged along with the moisture under the drive of moisture content gradient, water vapor gradient, and temperature gradient. Compared to existing bamboo flattening technology, hot pressing technology, or other homogenization treatments of bamboo materials, this invention, by treating bamboo strips through the discharge of bamboo sap, achieves beneficial effects such as moisture content control, removal of nutrients such as sugars, densification and compression, and reduction of hygroscopicity.

[0028] Regarding moisture content control, by draining bamboo sap, the moisture content of the veneer strips can be reduced to a range of 7-15%, naturally controlling the moisture content deviation within ±0.5%. For example, by setting the treatment to end when the moisture content drops to 10%, the resulting veneer strips have a moisture content of 9.5-10.5%. Therefore, the veneer strips obtained in this way do not require secondary drying before being used to make bamboo boards.

[0029] Regarding the excretion of nutrients such as sugars, the effective components in bamboo sap are formed by the degradation of hemicellulose, starch, etc. When no more bamboo sap drips out, it can be considered that the nutrients such as sugars and starches inside the bamboo have been basically excreted. Therefore, the resulting veneer strips (and subsequent bamboo boards) have a certain ability to prevent decay and mold.

[0030] In terms of densification and compression, as moisture is expelled, space is created inside the bamboo strips that can be compressed, thus achieving a compression rate of up to 30%, thereby increasing the average density of the veneer strips and reducing density deviation.

[0031] Regarding the reduction in hygroscopicity, under the influence of temperature and pressure, especially with the formation of bamboo sap, the effective components in the bamboo sap are degraded from hemicellulose, starch, etc., with a larger amount of hemicellulose being degraded. This process effectively reduces the hydroxyl content inside the bamboo strips, resulting in a lower equilibrium moisture content in the veneer strips (and subsequent bamboo boards) compared to existing processing methods that do not produce bamboo sap. At the same time, the degradation of hemicellulose increases the relative content of lignin in the veneer strips, making the material of the veneer strips finer and more uniform, and improving the mechanical strength and corrosion resistance of the veneer strips.

[0032] As mentioned earlier, another beneficial effect of this application is that while hot-pressing the bamboo strips to flatten them, a processing byproduct—bamboo sap—can also be obtained. Those skilled in the art generally believe that bamboo sap extraction requires relatively high temperatures, such as firing and direct-fire extraction methods. Excessively high extraction temperatures not only easily cause safety hazards in production and increase energy consumption, but also result in a large number of impurities being mixed into the extracted bamboo sap due to overheating of the bamboo. Through long-term experimentation and research, the inventors of this application have discovered that when bamboo is heated to a certain temperature, combined with a certain pressure—even a relatively small pressure value—a similar amount of bamboo sap can be obtained as with firing and direct-fire extraction methods. Specifically, this temperature should exceed 120°C but be below 200°C. Under these conditions, bamboo sap containing guaiacol, an effective functional component, can be extracted, while containing almost no other impurities generated by overheating. Therefore, the processing method in this application is safer, more environmentally friendly, and more efficient, and can ensure the content and purity of the effective components in the bamboo sap.

[0033] Furthermore, the inventors creatively discovered that determining the completion of the bamboo strip plasticity (to achieve uniform density), bamboo sap extraction (to remove sugars and other nutrients), and drying processes by whether the final moisture content of the bamboo strips reaches a set range allows for a more accurate assessment of the appropriate and effective processing time. In other words, when the moisture content of the bamboo strips drops to 7-15%, the processing is essentially complete. Moreover, this 7-15% moisture content range coincides with the usable moisture content range for bamboo boards. In other words, the moisture content required for the intended use of bamboo boards can be directly used as the basis for determining whether the bamboo strip processing is complete.

[0034] While judging the progress of hot-pressing by the moisture content of bamboo strips and determining the end of the process by whether the bamboo strips have reached the target final moisture content is more accurate, the processing time can still serve as a reference for whether sampling and moisture content testing should begin, or as a convenient method for determining the process in less demanding situations. When the pressure on a pair of pressure surfaces is maintained for 10–30 minutes, the hot-pressing process of the bamboo strips is essentially complete. Under relatively high temperature and pressure extraction conditions, maintaining pressure on a pair of pressure surfaces for 10–15 minutes is sufficient to complete the processing and bring the bamboo strips to the aforementioned density range and uniformity requirements.

[0035] Finally, the veneer strips prepared by the above method can be processed into bamboo boards in the above product technical solution through processes such as finger jointing and lamination pressing.

[0036] In summary, the method for preparing bamboo boards and veneer strips disclosed in this invention application has at least the following advantages:

[0037] 1. The bamboo boards in this case have small density deviations and relatively low moisture absorption in various places, resulting in a uniform material with relatively high mechanical strength. They also have good stability, are not prone to mold and rot, and are not prone to warping, twisting, or other deformations caused by uneven moisture absorption.

[0038] 2. The present invention provides a method for preparing veneer strips by treating bamboo strips with some nodes at relatively low temperatures and pressures to obtain veneer strips with good stability, high strength, corrosion and mildew resistance, and uniform density, thereby producing bamboo boards with corresponding advantages. This method does not use chemical agents, resulting in lower production costs and easier process control. Furthermore, this method can obtain high-purity, impurity-free bamboo sap in a safer, more reliable, and higher-yield manner. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of the structure of a bamboo strip according to an embodiment of this application.

[0041] Figure 2 This is a schematic diagram of the end face of the bamboo strip hot pressing device according to an embodiment of this application.

[0042] Figure 3 This is a side view of the bamboo strip hot pressing device according to an embodiment of this application.

[0043] Figure 4 This describes the form of a single-plate strip in an embodiment of this application.

[0044] In the diagram: 100, bamboo strip; 110, bamboo wall; 120, bamboo joint; 200, bamboo board; 200', bamboo veneer; 210, veneer strip; 300, pressure surface; 400, collection tank. Detailed Implementation

[0045] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0046] Example: A method for preparing bamboo board, which includes two steps: (i) preparation of veneer strips and (ii) pressing of bamboo board.

[0047] (I) The preparation process of the single-layer strip includes the following steps: First, bamboo tubes are cut to obtain bamboo tubes, which include two sections of bamboo wall and bamboo nodes connecting the two sections of bamboo wall. The bamboo tubes are split to obtain bamboo strips 100. Then, the bamboo strips 100 are stably placed between a pair of pressure surfaces 300. Both pressure surfaces 300 have a temperature of 120-200°C. The pair of pressure surfaces 300 simultaneously apply a pressure of 2-4 MPa to the bamboo strips 100 from both the green bamboo side and the yellow bamboo side. The pressure is maintained until the moisture content of the bamboo strips 100 drops to 7-15%, so as to complete the treatment of draining bamboo sap and obtain single-layer strips 210. The specific process is as follows.

[0048] Freshly harvested bamboo aged 3-4 years is cut into bamboo tubes. Bamboo with a high natural moisture content (e.g., 60-120%) can be used, or bamboo with a lower moisture content (e.g., 40-60%) can be used after a period of storage. The natural moisture content refers to the moisture content of the bamboo immediately after harvesting, while bamboo with a lower moisture content can be stored for a period or dried from round bamboo. During cutting, one bamboo node is retained in the middle section of the bamboo tube. The middle section of the bamboo tube, divided into three equal parts along its length, can be considered the middle section in this embodiment. The bamboo tube is then split into multiple bamboo strips 100 of a specified width, referring to… Figure 1 As shown, the middle section of the split bamboo strip 100 has two bamboo walls 110 and a bamboo node 120.

[0049] In order to ensure that the veneer strips 210 obtained by the same processing technology have similar compression rates, the thickness deviation of bamboo strips 100 in the same batch is preferably less than ±1.5mm.

[0050] Reference Figure 2 , Figure 3 , Figure 4 As shown, a flatbed press completes the process of removing bamboo sap. The flatbed press has a pair of horizontally arranged pressure plates, providing a pair of pressure surfaces 300 with a width of 50cm × 50cm. The length of the equipment should be adapted to the length of the bamboo strips 100; however, to ensure sufficient water vapor pressure gradient (the ratio of the water vapor pressure difference from the center to the end to the distance) and temperature gradient (the ratio of the temperature difference from the center to the end to the distance) are formed inside the bamboo strips 100, this embodiment uses a pressure plate width of 50cm. Furthermore, to expand the temperature gradient and promote the removal of moisture from the bamboo, the length of the bamboo strips 100 should be slightly greater than the width of the pressure plates, for example, 59–60cm, to ensure that both ends of the bamboo strips 100 can extend beyond the pressure surfaces 300.

[0051] A set of thickness gauges is placed on the surface of the lower pressing plate near both edges to indicate the end of the lower pressing stroke of the upper pressing plate. The thickness of the thickness gauges is the thickness of the single veneer strip 210. Collection tanks 400 are placed below the ends of the bamboo strips 100 at both ends along the length of the flatbed press to collect the discharged bamboo sap. When the bamboo strips 100 used have a relatively high natural moisture content (60-120%), the bamboo sap is called bamboo sap.

[0052] A pair of pressure plates are heated to the temperature set by the process. Then, bamboo strips 100 are placed on the lower pressure plate, ensuring that the lengths of both ends of the bamboo strips 100 extending beyond the lower pressure plate are as uniform as possible. At this point, the yellow bamboo surface of the bamboo strips 100 faces the lower pressure plate, which serves as the lower pressure surface 300. Next, the upper pressure plate is pressed down and contacts the green bamboo surface of the bamboo strips 100, serving as the upper pressure surface 300. Finally, the pair of pressure surfaces 300 continue to move closer together, applying the process-set pressure to the bamboo strips 100 from the green bamboo surface and the yellow bamboo surface respectively until the upper pressure plate contacts the thickness gauge. The pressure is maintained until the moisture content of the bamboo strips 100 decreases to 7-15%. The pressure is then released and the strips are cooled, resulting in bamboo strips 100 that have had their bamboo sap removed, flattened, and compressed.

[0053] In some embodiments, for bamboo strips 100 with the same thickness as the thickness gauge, a pair of pressure surfaces 300 only make thermal contact with it and flatten it without compressing it, resulting in a veneer strip 210 with a compression rate of 0; for bamboo strips 100 with a thickness greater than the thickness gauge, a pair of pressure surfaces 300 flatten it and also compress it with a certain compression rate, resulting in a veneer strip 210 with a certain compression rate.

[0054] After the pressure holding period ended, the density of veneer strip 210 was tested, and the cross-sectional density was analyzed to statistically determine the density deviation at various points on veneer strip 210. The increase rate of lignin content in veneer strip and the equilibrium moisture content of 210 under the conditions of 20℃ / 65%RH were also tested.

[0055] (II) The pressing process of bamboo boards can be carried out using existing technologies. In this embodiment, the following method is used as an example: First, the two surfaces and two sides along the length of the veneer strip 210 are smoothed and sanded, and the two ends along the length of the veneer strip 210 are milled to obtain finger joints; then, adhesive is applied to the finger joints and the two sides along the length of the veneer strip 210. The adhesive used is isocyanate adhesive (MDI); then, the veneer is lengthened by a finger jointing machine and widened by a splicing machine to obtain bamboo veneer 200'; finally, adhesive is applied to one surface of the bamboo veneer 200', and multiple bamboo veneers 200' are stacked and pressed to obtain bamboo board 200.

[0056] The density of bamboo board 200 was tested, the cross-sectional density was analyzed to statistically determine the density deviation at various points on bamboo board 200, and the static bending strength and equilibrium moisture content under the conditions of 20℃ / 65%RH were tested.

[0057] The density deviation between veneer strip 210 and bamboo board 200 is calculated using the following formula:

[0058]

[0059] Specifically, the batch density deviation is the difference between the highest and lowest density values ​​of the detected bamboo boards and the deviation from the batch average density.

[0060] Table 1 shows the specific process parameters of Examples 1 to 9. To facilitate comparison of the static bending strength of each example, the moisture content of the veneer strips in each example is uniformly set to 12±0.5%, and the moisture content of the prepared bamboo boards is uniformly set to 12.5±0.5%.

[0061] Table 2 shows the performance parameters of the single-plate strips of Examples 1-9 and Control Example 1.

[0062] Table 3 shows a comparison of the product performance parameters of bamboo boards from Examples 1-9 with those from Control Examples 2 and 3.

[0063] Among them, Comparative Example 1 is a veneer strip prepared according to the preferred embodiment described in CN101528431A of the prior art; Comparative Example 2 is a bamboo board obtained by pressing the veneer strip in Comparative Example 1 according to the process of the preferred embodiment described in CN202147305U of the prior art, and the board thickness is 25mm during preparation for easy comparison; Comparative Example 3 is a bamboo board prepared according to the preferred embodiment described in CN206011329U of the prior art, and the board thickness is 12mm during preparation for easy comparison.

[0064] Table 1. Process parameters for Examples 1-9

[0065]

[0066] Table 2. Performance parameters of the veneer strips in Examples 1-9 and Comparative Example 1

[0067]

[0068] In Comparative Example 1, bamboo strips with the green and yellow parts removed were used, and the bamboo strips were preheated to 140-200°C by soaking before being subjected to an external high temperature of 160-190°C. Compared with Comparative Example 1, Examples 1-9 of this case, by retaining the bamboo nodes, allow the bamboo strips to be directly heated to a relatively high temperature (above 120°C) through thermal contact, thereby giving the veneer strips a relatively low equilibrium moisture content. Therefore, their effect on improving the hygroscopicity of the veneer strips is better than the technical solution of Comparative Example 1, and the process is significantly simplified and the processing time is greatly shortened.

[0069] Although the veneer strips of Comparative Example 1 were pressed, their average density was still relatively low because only the bamboo flesh was retained. The veneer strips of Examples 1 to 9 in this case have significantly higher average densities.

[0070] The above-mentioned veneer strips were spliced ​​and widened to obtain bamboo veneers with thicknesses of 3mm, 4mm, 5mm and 6mm respectively. Three layers of bamboo veneers from Examples 1 to 3 were stacked to obtain a bamboo board with a thickness of 9mm. Three layers of bamboo veneers from Examples 4 and 5 were stacked to obtain a bamboo board with a thickness of 12mm. Five layers of bamboo veneers from Examples 6 to 8 were stacked to obtain a bamboo board with a thickness of 25mm. Three layers of bamboo veneers from Example 9 were stacked to obtain a bamboo board with a thickness of 18mm.

[0071] Table 3. Comparison of product performance parameters of bamboo boards from Examples 1-9 and Comparative Examples 2 and 3

[0072]

[0073] The veneer strip used in Comparative Example 3 at least retains the bamboo green layer. The density difference between the bamboo green layer and the bamboo flesh makes its internal density deviation much greater than that of Examples 2-9 and Comparative Example 2 in this case. At the same time, the structure of Comparative Example 3 is a single-layer structure, so its static bending strength is less than that of Examples 2-9 and Comparative Example 2 in this case.

[0074] The above description is for illustrative purposes and not for limitation. Many embodiments and applications beyond the provided examples will become apparent to those skilled in the art upon reading the above description. Therefore, the scope of this teaching should not be determined by reference to the above description, but rather by reference to the appended claims and the full scope of their equivalents. For purposes of completeness, all articles and references, including patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject disclosed herein in the preceding claims is not an abandonment of that subject matter, nor should it be construed as an indication that the applicant has not considered that subject matter as part of the disclosed application subject matter.

Claims

1. A bamboo board, comprising at least a plurality of veneer strips joined laterally along its width, characterized in that, The density of the bamboo board is 0.7~1.2 g / cm³. 3 The density deviation of a single bamboo board is less than 10%, and the average density deviation between bamboo boards in the same batch is less than 5%; under the conditions of 20℃ and 65%RH, the equilibrium moisture content of the bamboo board is less than 9%; the single board strip includes two bamboo wall sections and a bamboo node connecting the two bamboo wall sections, and the bamboo wall section includes bamboo green, bamboo flesh and bamboo yellow. The bamboo board is obtained by the following preparation method: First, a bamboo tube is obtained, comprising two sections of bamboo wall and a bamboo node connecting the two sections. The bamboo tube is split to obtain bamboo strips, the natural moisture content of which is 60-120%. Then, the bamboo strip is placed between a pair of pressure surfaces, with both ends of the bamboo strip extending beyond the pressure surfaces by 4.5-5.5 cm. Both pressure surfaces have a temperature of 120-200°C. The pair of pressure surfaces simultaneously apply a pressure of 2-4 MPa to the bamboo strip from both the green and yellow sides of the bamboo strip. The pressure is maintained until the moisture content of the bamboo strip drops to 7-15%, thus obtaining the single-layer strip. The density of the near-surface portion of the veneer deviates from the density of the middle layer in its thickness direction by 5-15%.

2. The bamboo board according to claim 1, characterized in that, The veneer strips undergo a process to remove bamboo sap.

3. The bamboo board according to claim 1, characterized in that, The relative lignin content in the veneer strip is 50-60% higher than that in the raw material, and the compression rate in the thickness direction of the veneer strip is 0-30%.

4. The bamboo board according to claim 1, characterized in that, The bamboo board comprises multiple bamboo veneers stacked and thickened along the thickness direction, and the bamboo veneer comprises multiple strips of veneer that are laterally widened along the width direction; the fiber directions of the multiple strips of veneer are the same.

5. The bamboo board according to claim 1, characterized in that, The thickness deviation of the bamboo strips obtained by splitting is less than ±1.5 mm.

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