Bamboo veneer with outer skin and its manufacturing process

Abstract

This invention discloses a bamboo veneer with skin and its manufacturing process, which belongs to the field of bamboo processing technology, and includes the steps of cutting the bamboo into pieces with a circular cross section, pressing and heating the bamboo pieces to soften them, and then spreading them out with a constant thickness and arc length, and then gradually spreading and flattening the bamboo pieces under heat preservation conditions until they are completely flat, to obtain a bamboo board, and then continuously cooling and cooling the bamboo board, and then weighting it to set it into a shape, drying it, and trimming it to a fixed width to obtain a bamboo veneer with skin. The spreading process of the bamboo pieces with skin provided by this invention can spread the bamboo board with skin under the premise of not destroying the green surface of the bamboo, and does not cause cracking or springback problems during the spreading process, and the obtained bamboo veneer with skin is smooth and flat, has a natural and aesthetic texture, and has good mechanical properties, filling the gap in the bamboo market for natural green bamboo texture materials.

Description

[Technical Field]

[0001] The present invention relates to the field of bamboo processing technology, and more particularly to bamboo pieces with outer skin and the manufacturing process thereof. [Background technology]

[0002] Bamboo's fast growth and strong regenerative capacity make it an important alternative to wood in many industries. Some industries have implemented the "bamboo to wood" initiative, which can effectively alleviate the discrepancy between China's wood supply and demand. It is estimated that using one ton of bamboo reduces deforestation by 3.9 mu and carbon dioxide emissions by 1.62 tons. Therefore, when bamboo is used instead of wood, it can effectively mitigate carbon emissions and improve the greenhouse effect.

[0003] Bamboo naturally grows in a cylindrical shape with nodes, but many bamboo products, such as furniture, building materials, and everyday items, need to be made using flat boards or sheets. Therefore, a flattening process is required after harvesting. To avoid cracking during the flattening process, the bamboo must first be processed by removing the nodes, inner bark, and outer bark, drilling holes, scribing, and other steps before being flattened. Chinese invention patent application number 202110652490.3 discloses a round bamboo flattening process in which the outer and inner bark of the bamboo are removed, and then the round bamboo is flattened to obtain flat bamboo boards. In addition, Chinese invention patent application number 201510695352.8 discloses a method for flattening whole bamboo. The bamboo tube is loaded into a bamboo processing device, and the outer and inner segments are removed. A 2-3 mm thick outer bark is then removed. The bamboo tube is then grooved, softened, flattened, and cold-pressed to obtain a bamboo board. The inner bark on the inside of the board is then removed by 3-5 mm, and the board is then ground and baked to obtain the whole bamboo. The removed bamboo bark has relatively high fiber density, hardness, and strength. If it could be applied without cutting the bamboo bark, it would effectively reduce bamboo waste and produce bamboo products with a blue surface, which is currently lacking on the market. Currently, there are processes for flattening bamboo while retaining the blue surface. For example, Chinese invention patent application number 202110324858.3 discloses an apparatus and method for flattening bamboo while retaining the bark, which involves scribing the bamboo bark and cutting the inner bark to obtain bamboo pieces with the bark retained. However, such a process still requires scribing on the blue surface, which affects the integrity and aesthetics of the product, and the blue surface after scribing is also not suitable for use as an exterior surface. Summary of the Invention [Problem to be solved by the invention]

[0004] In order to overcome the drawbacks of the prior art, the problem that the present invention aims to solve is how to provide a bamboo veneer with an outer skin that has no damage such as scribing on the outer skin surface, and a manufacturing process for the same. [Means for solving the problem]

[0005] In order to solve the above problems, the technical solution adopted by the present invention is a manufacturing process of bamboo veneer with outer skin, which includes: Step 1: After dividing the bamboo, a bamboo tube is obtained, and the bamboo tube is cut lengthwise into bamboo pieces with a cross section of a circular arc; Step 2: softening the bamboo pieces by heating under pressure, unfolding the softened bamboo pieces to a constant arc length and thickness, and then removing the inner bark of the bamboo; Step 3: The bamboo pieces treated in step 2 are gradually unfolded and flattened under heat-retaining conditions, protecting both sides until the bamboo pieces are completely flat, to obtain bamboo boards; The manufacturing process for barked bamboo veneer includes step 4, in which the bamboo board is subjected to continuous temperature and cooling treatment, followed by weighting and drying the board until the moisture content is 6 to 10%, and then trimming to a fixed width to obtain a barked bamboo veneer.

[0006] Another technical solution adopted by the present invention is the barked bamboo veneer produced by the above-mentioned barked bamboo veneer production process. [Effects of the Invention]

[0007] The beneficial effects of the present invention are as follows: The manufacturing process for barked bamboo veneer provided by the present invention allows for the unfolding of barked bamboo veneers without the need for operations that destroy the green surface, such as scribing, drilling nail holes, or scraping the bark, and the problems of cracking and springback do not occur during the unfolding process. The obtained barked bamboo veneer has stable performance and high strength, an undamaged blue surface, a smooth and flat texture, and a natural and aesthetic appearance. The barked bamboo veneer is applicable to some downstream fields with high hardness requirements and fills the gap in the bamboo market for natural green bamboo-textured materials. It can be used alone as a board material, or combined with other board materials to produce composite boards, or used as a material for other bamboo products.

[0008] During the unfolding process, pressure heat softening is used, which increases the steam pressure and temperature compared to traditional heat softening, significantly shortening the softening time and improving the efficiency and softening effect, thereby avoiding the problem of cracks occurring in the subsequent unfolding process. Unfolding with a constant arc length and constant thickness ensures uniform thickness of the bamboo pieces, providing a basis for subsequent gradual unfolding and flattening with double-sided protection, thereby avoiding the problem of uneven force bearing due to uneven thickness. Unfolding and flattening with double-sided protection under warm conditions effectively avoids the problems of springback and cracks. Because the stress on the barked bamboo board is relatively large, continuous cooling and temperature reduction can prevent cracks caused by rapid cooling. Drying the cooled barked bamboo board under weight conditions ensures uniform moisture content at different positions of the barked bamboo board, so that the flattened board will not bend, deform, or spring back after drying. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to preferred embodiments thereof.

[0010] The most important concept of this invention is to use the outer skin of bamboo to produce bamboo veneer with outer skin by optimizing the flattening process, while not destroying the blue surface.

[0011] The present invention provides a process for producing bamboo veneer with skin, comprising the steps of: Step 1: After dividing the bamboo, a bamboo tube is obtained, and the bamboo tube is cut lengthwise into bamboo pieces with a cross section of a circular arc; Step 2: softening the bamboo pieces by heating under pressure, unfolding the softened bamboo pieces to a constant arc length and thickness, and then removing the inner bark of the bamboo; Step 3: The bamboo pieces are spread at a constant arc length and thickness in step 2, and the inner bark of the bamboo is removed. The bamboo pieces are gradually spread and flattened under heat-retaining conditions, protecting both sides until the bamboo pieces are completely flat, to obtain bamboo boards. The present invention provides a manufacturing process for a bamboo veneer with an outer skin, which includes step 4 of subjecting the bamboo board to continuous temperature and cooling treatment, followed by drying under a weight until the moisture content is reduced to 6 to 10%, and then trimming to a fixed width to obtain a bamboo veneer with an outer skin.

[0012] The present invention also provides a bamboo veneer with an outer bark produced by the above manufacturing process. The resulting bamboo veneer with an outer bark may be used alone as a board material, or may be combined with other board materials to produce a composite board material, or may be used as a raw material for other bamboo products.

[0013] As can be seen from the above description, the beneficial effects of the present invention are as follows: The proposed manufacturing process for bamboo veneer with outer skin of the present invention further expands the range and fields of application of bamboo material. This manufacturing process can complete the flattening of bamboo pieces (bamboo boards) without damaging the bamboo's outer skin, and the flattened bamboo pieces will not crack or spring back. This process does not require drilling diagonal grooves or nail holes during the unfolding process, and does not require processing of bamboo nodes, reducing processing steps and effectively saving input costs. During the unfolding process, softening and uniform arc length and constant thickness unfolding can effectively reduce the problem of cracking during processing, but they also pull the inner layer of the barked bamboo pieces and press the outer layer of the barked bamboo pieces, especially the barked parts, which generates extremely large internal stresses and causes springback (rebound) in subsequent processing. This invention subsequently protects the pieces under warm conditions, gradually unfolds and flattens them, and then applies weights and dries them, effectively balancing the problem of internal stresses occurring in the above steps, avoiding the problem of springback during processing and after the finished product is made. The steps are closely connected and interlocked, ensuring smooth unfolding of the barked bamboo board and avoiding the waste of raw materials and increased processing costs caused by cracking and springback. The resulting barked bamboo veneer has no surface damage and can be used directly. Because it retains the bamboo bark, it has good mechanical properties and is suitable for some downstream applications with high hardness requirements.

[0014] In addition, the terms "grooving," "straight groove digging," "oblique groove digging," "scribing," etc. referred to in this field all refer to cutting operations of a certain depth into the surface of bamboo material.

[0015] Furthermore, in step 1, the diameter of the bamboo tube is 60 to 150 mm, and the bamboo tube is cut lengthwise into 3 to 6 bamboo pieces.

[0016] As can be seen from the above explanation, the bamboo tube cannot be directly unfolded as a whole, but must first be cut into sheets before the subsequent flattening process can be carried out.

[0017] Furthermore, the conditions for the heat softening in step 2 are a pressure of 0.8 to 1.3 MPa, a temperature of 160 to 200° C., and a time of 3 to 10 minutes.

[0018] As can be seen from the above explanation, compared with conventional heat softening, both the vapor pressure and temperature are increased, and the increase in vapor pressure and temperature can significantly shorten the softening time, be more efficient, and improve the softening effect, thereby avoiding the problem of cracks occurring in the subsequent expansion process. However, higher pressure and temperature do not bring about better effects and increase energy consumption.

[0019] Furthermore, the expansion to a constant arc length and constant thickness in step 2 involves pressing the softened bamboo pieces into a shape of constant arc length using an arc roller, and then processing them into a constant thickness using an arc blade.

[0020] As can be seen from the above explanation, processing to an equal thickness ensures that the two sides of the bamboo board can be in full contact with the device during the subsequent process of protecting both sides and gradually expanding and flattening, thereby avoiding the problem of cracks caused by uneven force bearing.

[0021] Furthermore, the development of equal arc length and constant thickness involves pressing the softened bamboo pieces into a shape of equal arc length using an arc roller, and then processing them into equal thickness using an arc blade. Equal thickness means that the thickness at each point is equal.

[0022] Furthermore, the temperature retention conditions in step 3 are 80 to 100°C, and the gradual unfolding and flattening with double-sided protection is achieved by gradually flattening using multiple press devices, the press devices including upper and lower press plates, a gap between the upper and lower press plates, and the arc of the gap between the multiple press devices gradually decreases.

[0023] Furthermore, gradually expanding and flattening the surface after double-sided protection means gradually flattening the surface using a plurality of press devices, the press devices including an upper press plate and a lower press plate, a gap being provided between the upper press plate and the lower press plate, and the arc of the gap between the plurality of press devices being successively smaller.

[0024] As can be seen from the above explanation, the key point is the heat retention treatment during the process of gradual unfolding and flattening after double-sided protection. If the treatment is performed at room temperature or at a higher temperature, cracks will occur during the process of gradual unfolding and flattening after double-sided protection.

[0025] Furthermore, the continuous cooling in step 4 is performed by lowering the temperature from 100° C. to 25° C. The temperature lowering rate is 10 to 30° C. / h. Preferably, the temperature lowering rate is 25° C. / h.

[0026] As can be seen from the above explanation, unlike bamboo boards that have had the outer bark or inner bark removed, or that have diagonal grooves or nail holes drilled, bamboo boards with outer bark can crack if they are cooled directly, i.e., placed directly in a room temperature environment. To effectively avoid this, it is necessary to cool the board in stages within a certain temperature range. If the cooling rate is within the above range, cracks will not occur, and the impact on the mechanical properties of the finished product can be negligible.

[0027] Furthermore, the conditions for applying a weight to the product to set it into shape and dry in step 4 are a weight of 1000 to 1200 kg and a drying temperature of 30 to 60°C.

[0028] As can be seen from the above explanation, the shaping and drying process using weights involves placing a weight on one side of the bamboo board, and the pressure can ensure uniform moisture content in each part of the bamboo board. This can effectively relieve the internal stress generated during the softening and expansion process with variable arc length and constant thickness, achieving the effect of no rebound after drying. In order to shorten the drying time and improve efficiency during the drying process, the drying temperature should not be increased too much. If the drying temperature is too high, some bamboo boards with outer skin will experience springback problems after being dried and left for a certain period of time.

[0029] Additionally, bamboo veneer with outer skin is available, with a density of 0.9-1.1g / cm 3 The tensile strength is 296.72 to 311.56 MPa, the deflection strength is 143.14 to 149.65 MPa, the tensile strength in the fiber direction is 177.76 to 185.84 MPa, the crushing strength in the fiber direction is 77.70 to 81.22 MPa, the deflection modulus is 10.12 to 11.67 GPa, the fiber content is 56.10 to 60.65%, and the moisture content is 8 to 10%.

[0030] The manufacturing process of the above-mentioned bamboo veneer with outer skin is specifically as follows: Step 1: After dividing bamboo (5-year-old bamboo or moso bamboo), a bamboo tube is obtained, and the bamboo tube is cut lengthwise into bamboo pieces having a cross section of a circular arc; Step 1: The diameter of the bamboo tube is 60 to 150 mm, and the bamboo tube is cut lengthwise into 3 to 6 bamboo pieces; Step 2: softening the bamboo pieces by heating under pressure, unfolding the softened bamboo pieces to a constant arc length and thickness, and then removing the inner bark of the bamboo; The conditions for the pressure and heat softening are a pressure of 0.8 to 1.3 MPa, a temperature of 160 to 200°C, and a time of 3 to 10 minutes. Step 2: Developing the bamboo into a uniform thickness using an arc roller to press the softened bamboo pieces into a uniform thickness, and then using an arc blade to process it into a uniform thickness. Step 3: The bamboo pieces treated in step 2 are gradually unfolded and flattened under a heat-retaining condition of 100 ° C until the bamboo pieces are completely flattened, to obtain bamboo boards. Step 3: gradually expanding and flattening the double-sided protection means gradually flattening the surface by using a plurality of presses, the presses including an upper press platen and a lower press platen, a gap is provided between the upper press platen and the lower press platen, and the arc of the gap between the plurality of presses is successively reduced; The bamboo board is then subjected to a continuous cooling process (from 100°C to 25°C), followed by drying under a weight (weight 1200 kg, drying temperature 40°C) until the moisture content is 8-10%, after which the board is trimmed to a fixed width and shaved to obtain a bamboo veneer with an outer skin 1-3 mm thick.

[0031] As can be seen from the above explanation, if the age of the outer skin of the bamboo is too small or too large as the bamboo grows, it is not possible to produce a bamboo veneer with the outer skin that has the above mechanical properties.

[0032] The bamboo veneer with outer skin is manufactured from the outer surface of the bamboo wall and extends radially along the bamboo tube.

[0033] As can be seen from the above explanation, the fiber content affects mechanical performance, and the fiber content of the bark-attached bamboo veneer with the above mechanical performance provided by this invention is 56.10-60.65%. The moisture content of the finished product also affects mechanical performance, and all parameters of the bark-attached bamboo veneer are in the moisture content range of 8-10%. Bamboo consists of the inner bark, fleshy layer, and outer bark, from the inside to the outside. The inner bark and fleshy layer are sometimes collectively referred to as the inner bark. If the outermost outer bark and innermost inner bark are not removed during the bamboo processing process, cracks are likely to occur during the flattening process, resulting in a large amount of wasted bark and inner bark. The bark-attached bamboo veneer is produced from the portion extending from the outer surface of the bamboo wall along the diameter of the bamboo tube, thereby utilizing the outer bark, which is usually discarded.

[0034] For testing of moisture content, density, tensile strength in the direction of fiber, crushing strength in the direction of fiber, flexural modulus, and flexural strength, refer to GB / T 17657-2013 "Test methods for physical and chemical properties of artificial boards and decorative artificial boards."

[0035] The bamboo veneer with its outer skin of the present invention can be sold as a finished product or can be used after being combined with other board materials, for example, to produce bamboo flooring boards, bamboo decorative panels, etc., and can also be used as a material to produce other products such as bamboo hangers.

[0036] Furthermore, a bamboo board including the above-mentioned bamboo veneer with outer bark is provided, and the thickness of the bamboo board is 5 to 10 mm. The bamboo board can be thicker depending on the usage needs, and can be a combination of one or more layers of conventional bamboo veneer (bamboo veneer obtained by a processing process that removes the outer bark and inner bark of bamboo) and the bamboo veneer with outer bark.

[0037] Example 1 The process of unfolding the bamboo pieces with the outer skin is as follows: Step 1: After dividing the bamboo, a bamboo tube is obtained, and the bamboo tube is cut lengthwise into bamboo pieces having a cross section of a circular arc surface; Step 1: The diameter of the bamboo tube is 60 to 90 mm, and the bamboo tube is cut lengthwise into three bamboo pieces; Step 2: softening the bamboo pieces by heating under pressure, unfolding the softened bamboo pieces to a constant arc length and thickness, and then removing the inner bark of the bamboo; The conditions for pressure and heat softening were 1.2 MPa, 200°C, and 3 minutes. Step 2: Developing the bamboo into a uniform thickness using an arc roller to press the softened bamboo pieces into a uniform thickness, and then using an arc blade to process it into a uniform thickness. Step 3: The bamboo pieces treated in step 2 are gradually unfolded and flattened under a heat-retaining condition of 100 ° C until the bamboo pieces are completely flattened, to obtain bamboo boards. Step 3: gradually expanding and flattening the double-sided protection means gradually flattening the surface by using a plurality of presses, the presses including an upper press platen and a lower press platen, a gap is provided between the upper press platen and the lower press platen, and the arc of the gap between the plurality of presses is successively reduced; Step 4: The bamboo board is subjected to continuous temperature and cooling treatment, and then weighted and shaped and dried until the moisture content is 6-10%, and then trimmed to a specified width to obtain a finished bamboo veneer with an outer skin; The continuous cooling is performed by lowering the temperature from 100°C to 25°C at a rate of 25°C / h. The conditions for weighting, shaping and drying include step 4, in which the weight is 1200 kg and the drying temperature is 40°C.

[0038] Example 2 The process of unfolding the bamboo pieces with the outer skin is as follows: Step 1: After dividing the bamboo, a bamboo tube is obtained, and the bamboo tube is cut lengthwise into bamboo pieces having a cross section of a circular arc surface; Step 1: The diameter of the bamboo tube is 90 to 120 mm, and the bamboo tube is cut lengthwise into four bamboo pieces; Step 2: softening the bamboo pieces by heating under pressure, unfolding the softened bamboo pieces to a constant arc length and thickness, and then removing the inner bark of the bamboo; The conditions for pressure and heat softening were 0.8 MPa, 180°C, and 10 min. Step 2: Developing the bamboo into a uniform thickness using an arc roller to press the softened bamboo pieces into a uniform thickness, and then using an arc blade to process it into a uniform thickness. Step 3: The bamboo pieces treated in step 2 are gradually unfolded and flattened under a heat-retaining condition of 90 ° C until the bamboo pieces are completely flattened, to obtain bamboo boards. Step 3: gradually expanding and flattening the double-sided protection means gradually flattening the surface by using a plurality of presses, the presses including an upper press platen and a lower press platen, a gap is provided between the upper press platen and the lower press platen, and the arc of the gap between the plurality of presses is successively reduced; Step 4: The bamboo board is subjected to continuous temperature and cooling treatment, and then weighted and shaped and dried until the moisture content is 6-10%, and then trimmed to a specified width to obtain a finished bamboo veneer with an outer skin; The continuous cooling is performed by lowering the temperature from 100°C to 25°C at a rate of 25°C / h. The conditions for weighting, shaping and drying include step 4, in which the weight is 1000 kg and the drying temperature is 60°C.

[0039] Example 3 The process of unfolding the bamboo pieces with the outer skin is as follows: Step 1: After dividing the bamboo, a bamboo tube is obtained, and the bamboo tube is cut lengthwise into bamboo pieces having a cross section of a circular arc surface; Step 1: The diameter of the bamboo tube is 120 to 150 mm, and the bamboo tube is cut lengthwise into five bamboo pieces; Step 2: softening the bamboo pieces by heating under pressure, unfolding the softened bamboo pieces to a constant arc length and thickness, and then removing the inner bark of the bamboo; The conditions for pressure and heat softening were 1.3 MPa, 160°C, and 7 minutes. Step 2: Developing the bamboo into a uniform thickness using an arc roller to press the softened bamboo pieces into a uniform thickness, and then using an arc blade to process it into a uniform thickness. Step 3: The bamboo pieces treated in step 2 are gradually unfolded and flattened under a heat-retaining condition of 80 ° C until the bamboo pieces are completely flattened, to obtain bamboo boards. Step 3: gradually expanding and flattening the double-sided protection means gradually flattening the surface by using a plurality of presses, the presses including an upper press platen and a lower press platen, a gap is provided between the upper press platen and the lower press platen, and the arc of the gap between the plurality of presses is successively reduced; Step 4: The bamboo board is subjected to continuous temperature and cooling treatment, and then weighted and shaped and dried until the moisture content is 6-10%, and then trimmed to a specified width to obtain a finished bamboo veneer with an outer skin; The continuous cooling is performed by lowering the temperature from 100°C to 25°C at a rate of 25°C / h. The conditions for weighting, shaping and drying include step 4, in which the weight is 1100 kg and the drying temperature is 30°C.

[0040] Example 4 Example 4 differs from Example 1 only in that the temperature drop rate in step 4 is 30° C. / h.

[0041] Example 5 Example 5 differs from Example 1 only in that the temperature drop rate in step 4 is 10°C / h.

[0042] (Comparative Example 1) Comparative Example 1 differs from Example 1 only in the softening operation in Step 2 of Comparative Example 1. The bamboo pieces in Comparative Example 1 were softened by heating, with the heating temperature being 180°C and the time being 30 minutes.

[0043] (Comparative Example 2) Comparative Example 2 differs from Example 1 only in that in step 3 of Comparative Example 2, no heat retention is performed, i.e., the bamboo pieces are protected on both sides and gradually unfolded and flattened at room temperature (approximately 25°C) and normal pressure conditions until they are completely flattened, and in step 4, they are not cooled but are directly weighted and shaped to dry.

[0044] (Comparative Example 3) Comparative Example 3 differs from Example 1 only in that it does not unfold at a constant arc length and thickness or scrape off the inner skin, but instead is pressurized and heated to soften it, and then directly protected on both sides at a temperature of 100°C, and gradually unfolds and flattens it.

[0045] Comparative Example 4 Comparative Example 4 differs from Example 1 only in that in step 4 of Comparative Example 4, the cooling temperature in the environment is maintained at 25°C (i.e., cooled by placing directly in a 25°C environment) rather than gradually decreasing the temperature from 100°C to 25°C.

[0046] The number of bamboo boards that experienced springback and cracks during the processing process and the number of finished products that passed (referred to as finished products) were statistically calculated, and the pass rate was calculated. The results are shown in Table 1.

[0047] [Table 1]

[0048] The bamboo boards of Examples 1 to 3 were randomly selected and subjected to performance tests with bamboo boards of the same thickness that had no outer skin. The results are shown in Table 2.

[0049] [Table 2]

[0050] Example 6 Bamboo veneer with outer bark, in which the outer bark is taken from the outer surface of the bamboo wall to the inside with a thickness of 1 to 3 mm as a raw material, and the bamboo veneer with outer bark has a density of 0.9 to 1.1 g / cm 3 The tensile strength is 296.72 to 311.56 MPa, the deflection strength is 143.14 to 149.65 MPa, the tensile strength in the fiber direction is 177.76 to 185.84 MPa, the crushing strength in the fiber direction is 77.70 to 81.22 MPa, the deflection modulus is 10.12 to 11.67 GPa, the fiber content is 56.10 to 60.65%, and the moisture content is 8 to 10%.

[0051] The manufacturing process of the above-mentioned bamboo veneer with outer skin is as follows: Step 1: After dividing bamboo (5-year-old Madake bamboo, Moso bamboo), a bamboo tube is obtained, and the bamboo tube is cut lengthwise into bamboo pieces with a cross section of a circular arc surface; Step 1: The diameter of the bamboo tube is 60 to 150 mm, and the bamboo tube is cut lengthwise into 3 to 6 bamboo pieces; Step 2: softening the bamboo pieces by heating under pressure, unfolding the softened bamboo pieces to a constant arc length and thickness, and then removing the inner bark of the bamboo; The conditions for pressure and heat softening were 1.2 MPa, 200°C, and 3 minutes. Step 2: Developing the bamboo into a uniform thickness using an arc roller to press the softened bamboo pieces into a uniform thickness, and then using an arc blade to process it into a uniform thickness. Step 3: The bamboo pieces treated in step 2 are gradually unfolded and flattened under a heat-retaining condition of 100 ° C until the bamboo pieces are completely flattened, to obtain bamboo boards. Step 3: gradually expanding and flattening the double-sided protection means gradually flattening the surface by using a plurality of presses, the presses including an upper press platen and a lower press platen, a gap is provided between the upper press platen and the lower press platen, and the arc of the gap between the plurality of presses is successively reduced; The bamboo board is then subjected to a continuous cooling process (from 100°C to 25°C), followed by drying under a weight (weight 1200 kg, drying temperature 40°C) until the moisture content is 8-10%, after which the board is trimmed to a fixed width and shaved to obtain a bamboo veneer with an outer skin 1-3 mm thick.

[0052] By using the above method, it is possible to produce bamboo veneers with a smooth surface and no cracks. Although the mechanical properties of bamboo veneers with a smooth surface produced using different parts of the same bamboo are different, they are all within the range of Example 1.

[0053] Three pieces of the bamboo veneer with outer skin of different thicknesses obtained in Example 6 were randomly selected and subjected to a performance test. The results are shown in Table 3.

[0054] [Table 3]

[0055] Example 7 The bamboo board is 10 mm thick and is made up of, from top to bottom, a bamboo veneer with an outer bark, a first bamboo board, and a second bamboo board glued together, the first bamboo board and the second bamboo board being commercially available bamboo veneers obtained by a processing process that removes the outer bark and the inner bark.

[0056] As described above, the unfolding process for barked bamboo veneer provided by the present invention can unfold barked bamboo pieces without drilling diagonal grooves or nail holes, removing the bark, or processing the bamboo nodes, and no cracking or springback problems occur during the unfolding process. The obtained barked bamboo veneer is smooth and flat and has high strength properties, making it applicable to areas where conventional bamboo boards cannot be used due to their insufficient strength and hardness. The proposed manufacturing process further expands the range and fields of application of bamboo material.

[0057] The unfolding process for barked bamboo veneer provided by this invention uses pressure heat softening during the unfolding process, which increases the steam pressure and temperature compared to traditional heat softening, significantly shortening the softening time and improving the efficiency and softening effect, thereby avoiding the problem of cracks occurring during the subsequent unfolding process. Unfolding with a constant arc length and constant thickness ensures uniform thickness of the bamboo pieces, providing a basis for subsequent gradual unfolding and flattening with double-sided protection, thereby avoiding the problem of uneven force bearing due to uneven thickness. Unfolding and flattening with double-sided protection under a temperature retention condition of 80-100°C effectively avoids the problems of springback and cracks. Since barked bamboo boards are subject to relatively high stress, continuous cooling and temperature reduction can prevent cracks caused by rapid cooling. After cooling, the barked bamboo boards can be dried under a weight of 1000-1200 kg, ensuring uniform moisture content at different positions on the barked bamboo board, so that the flattened board will not bend, deform, or spring back after drying.

[0058] The manufacturing process of the bamboo veneer with outer skin provided by the present invention has low requirements for equipment, does not require the addition of new equipment for the process, and is suitable for widespread application in enterprises of different scales.

[0059] The bark-attached bamboo veneer provided by the present invention is produced using the outer bark portion of the bamboo, making effective use of the bamboo's outer bark and avoiding the large amount of raw material waste that would otherwise occur due to bark removal. The produced bark-attached bamboo veneer has high hardness and good tensile and crushing properties. Because the bark-attached bamboo veneer retains the outer bark portion, the finished product has a deep green color, providing products with the natural green bamboo texture that is currently lacking in the market. The bark-attached bamboo veneer can be used alone or joined with other bamboo boards to be used as flooring boards, wall boards, decorative boards, etc., and can also be used to directly or indirectly produce other bamboo products such as bamboo hangers, bamboo chairs, bamboo tables, and bamboo chests.

[0060] The above is merely an example of the present invention, and does not limit the patent scope of the present invention. Equivalent transformations made by utilizing the contents of the specification of the present invention can be directly or indirectly utilized in the relevant technical fields, and all of them are equally included in the patent protection scope of the present invention.

Claims

1. Step 1: obtaining a bamboo tube after dividing the bamboo, and cutting the bamboo tube vertically into bamboo pieces with a cross section of a circular arc; Step 2: softening the bamboo pieces by heating under pressure, spreading the softened bamboo pieces to a constant arc length and thickness, and then removing the inner bark of the bamboo; Step 3: The bamboo pieces treated in step 2 are gradually unfolded and flattened under heat-retaining conditions until they are completely flat, thereby obtaining bamboo boards; The manufacturing process for the bamboo veneer with outer skin is characterized by including step 4, which comprises subjecting the bamboo board to continuous temperature and cooling treatment, followed by drying under a weight until the moisture content is 6 to 10%, and then trimming to a fixed width to obtain the bamboo veneer with outer skin.

2. The manufacturing process of bamboo veneer with outer skin described in claim 1, characterized in that in step 1, the diameter of the bamboo tube is 60 to 150 mm, and the bamboo tube is cut lengthwise into 3 to 6 bamboo pieces.

3. The manufacturing process of bamboo veneer with outer skin as described in claim 1, characterized in that the conditions for heat softening in step 2 are a pressure of 0.8 to 1.3 MPa, a temperature of 160 to 200 ° C, and a time of 3 to 10 minutes.

4. The manufacturing process of bamboo veneer with outer skin described in claim 1, characterized in that the expansion to a constant arc length and constant thickness in step 2 is performed by using an arc roller to press the softened bamboo pieces into a shape of constant arc length, and then using an arc blade to process them into a constant thickness.

5. The manufacturing process of bamboo veneer with outer skin as described in claim 1, characterized in that the temperature retention condition in step 3 is 80 to 100°C, and the gradual unfolding and flattening with double-sided protection is gradual flattening by multiple press devices, the press devices include upper and lower press plates, a gap is provided between the upper and lower press plates, and the arc degree of the gap between the multiple press devices gradually decreases.

6. The manufacturing process of bamboo veneer with bark as claimed in claim 1, characterized in that the continuous cooling in step 4 is from 100°C to 25°C.

7. The manufacturing process of bamboo veneer with outer skin as described in claim 1, characterized in that the conditions for weighting and shaping and drying in step 4 are a weight of 1000 to 1200 kg and a drying temperature of 30 to 60°C.

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