Recombined bamboo preparation method based on glue dipping bamboo bundle moisture content gradient difference directional assembly

Abstract

The invention discloses a recombined bamboo preparation method based on glue dipping bamboo bundle moisture content gradient difference directional assembly, which comprises the following steps that dried glue dipping bamboo bundles are graded according to moisture content values, and the difference between the upper limit value and the lower limit value of the moisture content range of each grade is 3%-8%; the graded impregnated bamboo bundles are laid in a mirror symmetry mode layer by layer, the water content grades of the impregnated bamboo bundle layers on the same layer are the same, the water content of the impregnated bamboo bundle layers is gradually increased from the core layer to the surface layer, the difference between the water content of the core layer and the water content of the surface layer is 10%-25%, and a plate blank is obtained; and carrying out hot press molding on the plate blank, and cooling to obtain the recombined bamboo without balance treatment. According to the recombined bamboo preparation method based on the glue dipping bamboo bundle water content gradient difference directional assembly, the glue dipping bamboo bundles are subjected to water content grading, paving is carried out according to the grading result, the balancing link is omitted, a matched humidifying workshop is not needed, the secondary problems of glue dipping bamboo bundle mildewing and the like possibly caused by long-time stacking are also avoided, and the quality of the recombined bamboo is improved. The production period is shortened and the process stability is improved.

Description

Technical Field

[0001] This invention relates to the field of reconstituted bamboo technology, and in particular to a method for preparing reconstituted bamboo based on the gradient difference in moisture content of resin-impregnated bamboo bundles. Background Technology

[0002] Reconstituted bamboo is produced by mechanically loosening bamboo, high-temperature heat treatment, resin impregnation, and drying to obtain resin-impregnated bamboo bundles, which are then assembled and hot-pressed. Hot pressing is a crucial process affecting the physical and mechanical properties of reconstituted bamboo, and the quality of hot pressing is closely related to the moisture content and distribution of the resin-impregnated bamboo bundles after drying. Therefore, a scientifically sound drying process is necessary after resin impregnation. Considering drying energy consumption, drying quality, and drying efficiency, more and more companies are adopting conventional drying techniques for resin-impregnated bamboo bundles. However, during conventional drying, multiple resin-impregnated bamboo bundles are bundled together (each bundle has a cross-sectional diameter of approximately 15 cm), causing the bundles within each bundle to easily intertwine. This affects the heat and moisture exchange with the drying medium, resulting in a significant moisture content gradient from the inside out after drying. Specifically, the moisture content of the core layer of the bundle is significantly higher, while the moisture content of the surface layer is significantly lower, with the difference sometimes exceeding 20%. If these resin-impregnated bamboo bundles with very large differences in moisture content are laid and hot-pressed directly without sorting, structural design and optimization, the resin-impregnated bamboo bundles with high moisture content may appear on the surface or in the core layer because the reconstituted bamboo bundles are laid randomly. When resin-impregnated bamboo bundles with high moisture content are placed in the core layer, it may cause local high moisture content during the hot-pressing process. In particular, when resin-impregnated bamboo bundles with high moisture content are placed in the core layer, it may cause the steam pressure in the core layer to accumulate, which can easily lead to hot-pressing defects such as blistering or even board bursting.

[0003] Wood-based engineered wood products such as fiberboard and particleboard undergo softening and hot pressing during the hot-pressing process to achieve plastic deformation. To avoid problems such as board bursting and strength reduction caused by high moisture content, the unit moisture content is usually controlled at a low level, and a two-layer moisture content control method is commonly used, with a moisture content difference of about 2%-4% between the surface and core layers. Existing bamboo-based engineered wood products technology largely borrows from wood-based engineered wood products, but the volume of reconstituted bamboo units and impregnated bamboo bundles is larger, making them more susceptible to the influence of moisture content. Current technical solutions use traditional surface and core layer separation, with a moisture content difference of only 2%-6% between the surface and core layers. This means that impregnated bamboo bundles with moisture contents ranging from 1%-7% and 15%-30% after drying require additional balancing and surface humidification treatments before they can be laid and assembled, increasing production energy consumption and costs. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing reconstituted bamboo based on the gradient difference of moisture content of resin-impregnated bamboo bundles with low production cost and good performance.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for preparing reconstituted bamboo based on the gradient difference in moisture content of resin-impregnated bamboo bundles for directional assembly includes the following steps: S1. The dried, resin-impregnated bamboo bundles are graded according to their moisture content. The difference between the upper and lower limits of the moisture content range for each grade is 3%-8%. S2. The graded resin-impregnated bamboo bundles are laid out symmetrically in mirror images, with each layer having the same moisture content. The moisture content of the resin-impregnated bamboo bundles gradually increases from the core layer to the surface layer, and the difference between the moisture content of the core layer and the surface layer is... 10-25% To obtain a slab; S3. The slab is hot-pressed into shape and cooled to obtain reconstituted bamboo.

[0006] As a further improvement to the above technical solution: The process of grading the dried, resin-impregnated bamboo bundles according to their moisture content includes the following steps: A1. The bamboo strips are broken into bamboo bundles, dried to a moisture content of 8%~10%, and kept at 170~190℃ to obtain heat-treated bamboo bundles. A2. Impregnate the heat-treated bamboo bundles in an adhesive and dry them until the moisture content is 1%~30% to obtain the glue-impregnated bamboo bundles. A3. The moisture content of the resin-impregnated bamboo bundles is tested, and the resin-impregnated bamboo bundles are divided into multiple grades according to the moisture content value.

[0007] In step A3, the difference between the upper and lower limits of the moisture content range for each level is 3%-5%.

[0008] In step S2, the following steps are included before the mirror symmetric paving: B1. Based on the target total moisture content of the slab W、 Total number of layers of resin-impregnated bamboo bundle n The nominal moisture content of the i-th impregnated bamboo bundle layer The mass distribution coefficient of the i-th impregnated bamboo bundle layer The paving quality of the i-th impregnated bamboo bundle layer is calculated according to the following formula. m i The moisture content of the resin-impregnated bamboo bundles in the i-th resin-impregnated bamboo bundle layer is the same.

[0009] In the above formula, ; B2. Based on the paving quality of the i-th layer m i The dry mass of the i-th layer is obtained according to the following formula. and the actual oven-dry mass m of the slab dry , ; ; B3. Based on the actual oven-dry weight m of the slab dry The nominal moisture content of the i-th impregnated bamboo bundle layer The actual total moisture content of the slab is obtained according to the following formulas. and the actual average moisture content of the slab ; ; ; B4. Determine the actual oven-dry weight m of the slab. dry and target dry mass M Error values ​​between, actual average moisture content of slab and target average moisture content Check whether the error values ​​are within the preset range. If so, proceed according to the paving quality in step B1. m i Surface each layer symmetrically; otherwise, adjust the mass distribution coefficient. Repeat step B1.

[0010] The following steps are included before step B1: C1. Based on the target density ρ and target volume of the board. V Determine the target oven-dry quality of the board. M ; C2. Based on the target oven-dry quality of the board material M and target average moisture content Determine the oven-dry weight of the slab. ; C3. Based on the oven-dry weight of the slab With the target average moisture content Determine the target total moisture content of the slab. W .

[0011] In step C1, ; In step C2, ; In step C3, .

[0012] In step B1, The value is the nominal moisture content of the resin-impregnated bamboo bundles at the j-th moisture content level. , j represents the moisture content grade. MC s This represents the upper limit of the moisture content of the j-th grade resin-impregnated bamboo bundles. MCx This represents the lower limit of the moisture content of the j-th grade resin-impregnated bamboo bundles. j Moisture content grade; In step B1, , These are weight parameters; In step B4, the actual oven-dry mass m of the slab dry and target dry mass M The preset range for the error value is 0.1g; In step B4, the actual average moisture content of the slab and target average moisture content The preset range for the error value is 1%.

[0013] In step S3, the temperature during hot pressing is 140 ~ 160 ℃, the pressure is 4 ~ 6 MPa, and the time is 35 ~ 50 min.

[0014] A reconstituted bamboo preparation system based on the gradient difference in moisture content of resin-impregnated bamboo bundles for directional assembly includes a microprocessor and a memory interconnected, wherein the microprocessor is programmed or configured to execute the aforementioned reconstituted bamboo preparation method based on the gradient difference in moisture content of resin-impregnated bamboo bundles for directional assembly.

[0015] A computer-readable storage medium storing a computer program for being programmed or configured by a microprocessor to perform the aforementioned method for preparing reconstituted bamboo based on the gradient difference in moisture content of resin-impregnated bamboo bundles.

[0016] In this embodiment, the core layer refers to the resin-impregnated bamboo bundle layer located in the middle of the slab, and the surface layer refers to the resin-impregnated bamboo bundle layer located on the surface of the slab.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention discloses a method for preparing reconstituted bamboo based on the gradient difference in moisture content of resin-impregnated bamboo bundles. By classifying the moisture content of the resin-impregnated bamboo bundles and laying them according to the classification results, the balancing process is omitted, eliminating the need for a humidification workshop and avoiding secondary problems such as mold growth that may occur from prolonged storage. This significantly reduces equipment investment and operating costs while shortening the production cycle, improving process stability, and improving efficiency. Furthermore, compared to the additional and often unsustainable slab wetting process added to improve surface moisture content, the moisture content of the resin-impregnated bamboo bundle layer in this invention gradually increases from the core to the surface. By laying high-moisture-content resin-impregnated bamboo bundles on the slab surface, a "steam impact" is formed internally during hot pressing, replacing additional humidification equipment, simplifying production line configuration, and further saving on equipment investment and maintenance costs. This invention constructs a gradient moisture distribution of "externally moist and internally dry," optimizing the hot-pressing heat transfer and resin curing process. It eliminates the need for balancing treatment of the dried, resin-impregnated bamboo bundles, simplifying the process and reducing production costs while effectively reducing the risk of defects such as blistering and board bursting. Simultaneously, it improves the mechanical properties, dimensional stability, and appearance quality of the finished product, achieving an organic combination of process simplification and product performance enhancement. This provides a practical and feasible technical path for the simple, fast, and efficient production of reconstituted bamboo. By classifying the moisture content of the bamboo bundles, different moisture contents are distributed to different layers of the board. While ensuring product quality, the moisture content difference between the surface and core layers can be increased to 10-25%. Bamboo bundles with a moisture content of 1%-30% after drying can be directly used without additional moisture content adjustment, eliminating the need for subsequent balancing and surface spraying treatments, reducing production costs, and achieving a gradient moisture distribution along a preset direction. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the calibration area for moisture content detection of the sample in Example 1.

[0019] Figure 2 This is a flowchart for slab structure optimization and paving.

[0020] Figure 3 The diagram shows the sample slab paving structure in each embodiment.

[0021] Figure 4 A flowchart for iterative optimization of the weight allocation method.

[0022] Figure 5 This is a comparison chart of TS and WS data for each sample in Example 1, Example 2, Example 3 and Comparative Example 1.

[0023] Figure 6 This is a comparison chart of MOR and MOE data for each sample in Example 1, Example 2, Example 3, and Comparative Example 1.

[0024] Figure 7This is a comparison chart of the vertical and horizontal shear performance data of each sample in Example 1, Example 2, Example 3 and Comparative Example 1.

[0025] Figure 8 This is a comparison chart of TS and WS data for each sample in Examples 4, 5, 6 and Comparative Example 2.

[0026] Figure 9 This is a comparison chart of MOR and MOE data for each sample in Examples 4, 5, 6 and Comparative Example 2.

[0027] Figure 10 This is a comparison chart of the vertical and horizontal shear performance data of each sample in Examples 4, 5, 6 and Comparative Example 2. Detailed Implementation

[0028] The present invention will be further described in detail below. Unless otherwise specified, the instruments or materials used in the present invention are commercially available.

[0029] Example 1: This embodiment of a method for preparing reconstituted bamboo based on the gradient difference in moisture content of resin-impregnated bamboo bundles includes the following steps: (1) Preparation of resin-impregnated bamboo bundles This invention uses moso bamboo ( Phyllostachys edulis The bamboo is 4-6 years old. The bamboo is split into strips and then bundled, processed into bundles measuring 400 mm × 35 mm × 8 mm (length × width × thickness, l × b × h). These bundles are then laid in a superheated steam drying oven and dried at 103 ℃ to a moisture content of 9%, followed by heating to 180 ℃ and holding for 3 hours to obtain heat-treated bamboo bundles.

[0030] Heat-treated bamboo bundles were immersed in a resin adhesive solution under normal pressure for 40 minutes, then removed and air-dried for 32 hours to obtain wet-impregnated bamboo bundles. The resin adhesive solution was a 25% (w / w) phenolic resin adhesive. It was prepared by using distilled water with a 50% solid content, pH 9.0, and molecular weight of 750 phenolic (PF) resin.

[0031] (2) Drying and grading of resin-impregnated bamboo bundles This invention utilizes the naturally occurring moisture content gradation during the drying process, eliminating the need for post-drying equilibration or humidification treatment. Thirty-five bundles of moistened bamboo are bundled together and dried in a superheated steam drying oven at 60°C for 60 hours. The resulting bamboo bundles are then coated with resin. The moisture content of the core and surface samples within the same bundle ranges from 1% to 30%.

[0032] Using a single resin-impregnated bamboo bundle as the testing unit, according to Figure 1Three sites were selected as calibration areas for moisture content testing, each with an area of ​​no less than 20 mm × 20 mm. An inductive electrical resistivity meter was used for non-destructive testing of the moisture content of the resin-impregnated bamboo bundles. The instrument's accuracy was ±0.5%. During testing, full and stable contact between the inductive electrical resistivity meter and the sample surface was ensured. Measurements were taken at each calibration area, and the moisture content readings were recorded. The average moisture content was calculated based on the measurement data from the three sites. The resin-impregnated bamboo bundles were then classified into five grades based on the average moisture content and stored accordingly.

[0033] The moisture content is classified as follows: Grade A: 26% ~ 30%; Grade B: 19% ~ 25%; Grade C: 13% ~ 18%; Grade D: 7% ~ 12%; Grade E: 1% ~ 6%.

[0034] (3) Slab structure optimization and paving like Figure 2 The flowchart shown is for the slab structure optimization and paving.

[0035] Laying out the slabs according to the principle of parallel grain arrangement, the target average moisture content of the slabs is... The target density is set at 12%, and the board design specifications are set at 400 mm (axial direction of the impregnated bamboo bundles) × 450 mm (width direction) × 20 mm (thickness direction of the impregnated bamboo bundles). Set to 1.1 g / cm 3 .

[0036] The nominal moisture content of the resin-impregnated bamboo bundles is defined as follows for each moisture content grade (Grade A, Grade B, Grade C, Grade D, Grade E): MC j , is the average of the upper and lower limits of the moisture content for this grade, as shown in formula (1):

[0037] In the above formula, MC s This represents the upper limit of the moisture content in the resin-impregnated bamboo bundles of moisture content grade j. MC x The lower limit of the moisture content in the resin-impregnated bamboo bundles of moisture content grade j. j represents the moisture content grade. In this embodiment, j = A, E .

[0038] The nominal moisture content of the i-th layer of resin-impregnated bamboo bundle The choice depends on the moisture content grade of the layer. For example, if the i-th layer is selected as grade A resin-impregnated bamboo bundles, then... The nominal moisture content of Grade A resin-impregnated bamboo bundles MC A Based on the target density ρ and target volume of the reconstituted bamboo board. V The target oven-dry mass M of the slab is calculated to be 3960.0g using formula (2).

[0039]

[0040] In the above formula, ρ To determine the target density of reconstituted bamboo boards, V The target volume (product of length, width, and height) of the reconstituted bamboo board.

[0041] Based on the target oven-dry weight of the slab M and target average moisture content The oven-dry mass of the slab is calculated using formula (3). It is 3535.7143g.

[0042]

[0043] In the above formula, This represents the target average moisture content of the slab.

[0044] Based on the oven-dry weight of the slab With the target average moisture content The target total moisture content of the slab is calculated using formula (4). W It weighs 424.2857g.

[0045]

[0046] The method of laying resin-impregnated bamboo bundles is as follows Figure 3 As shown, in the thickness direction of the slab, with the core layer at 1 / 2 of the thickness, bamboo bundles with different moisture content grades are selected and laid in a mirror-symmetrical manner. That is, in the part above the core of the slab, the moisture content grade decreases from the surface layer to the core layer, and in the part below the core layer of the slab, the moisture content grade increases from the core layer to the surface layer.

[0047] In this embodiment, resin-impregnated bamboo bundles with moisture content grades A and E are selected for mirror-symmetrical paving, with a total of 4 paving layers, 2 layers in the upper part.

[0048] Iterative optimization using weight allocation method (e.g.) Figure 4 (As shown) Calculate the mass distribution coefficient of the i-th impregnated bamboo bundle layer. And it satisfies formula (5).

[0049]

[0050] The paving quality of the i-th impregnated bamboo bundle layer is calculated using formula (6). m i . , This is a weighting parameter, with a value range of 0 to 10.

[0051]

[0052] The data obtained are m1=1194.8909g and m2=785.1177g.

[0053] Based on the installation quality of the i-th impregnated bamboo bundle layer m i The oven-dry mass of the i-th layer of resin-impregnated bamboo bundle is calculated using formula (7). The absolute dry mass of all layers The actual oven-dry mass m of the slab is obtained by summing the results. dry =3535.714286g.

[0054]

[0055] .

[0056] The actual total moisture content of the slab is calculated using formula (8). The actual average moisture content of the slab can be calculated using formula (9). =12.520528%

[0057]

[0058] Determine the actual oven-dry mass m of the slab dry and target dry mass M Error values ​​between, actual average moisture content of slab and target average moisture content Whether the error values ​​between them are within the preset range, if so, then according to the paving quality m i Surface each layer symmetrically; otherwise, adjust the mass distribution coefficient. Recalculate paving quality m i .

[0059] In this invention, the mass distribution coefficient is adjusted. The steps include: determining the weight parameters. Check if the traversal is complete. If not, retrieve another parameter from the weight parameter database. Value, regain quality allocation coefficient If the process has already been completed, change one or more of the following: target moisture content, slab size, density, and paving scheme, and start again.

[0060] The comparison showed that the difference between the actual value and the target value met the requirements (dry weight difference less than 0.1g, moisture content difference less than 1%).

[0061] Weigh out the resin-impregnated bamboo bundles according to the calculated quality of each grade, and lay out the four sets of resin-impregnated bamboo bundles according to the paving design. The final thickness of the board blank laid out with resin-impregnated bamboo bundles is about 5 times the thickness of the hot-pressed reconstituted bamboo board. The joints of each layer of resin-impregnated bamboo bundles are staggered to avoid through seams, ensuring that the moisture content in the thickness direction is distributed in a continuous gradient. The upper and lower halves are mirror-symmetrical to form a complete symmetrical structure.

[0062] (4) Hot pressing The prepared slabs are placed into a hot press, and the hot pressing process parameters are set as follows: hot pressing temperature 150℃, hot pressing pressure 5MPa, and hot pressing time 45 min. During the hot pressing process, the closing speed of the pressing plate is controlled at 8 mm / min to ensure uniform compression in the thickness direction of the slabs. The final product is a 20 mm thick reconstituted bamboo board. After hot pressing, the board is allowed to cool naturally to room temperature before being removed from the press.

[0063] Example 2 The method for preparing reconstituted bamboo based on the gradient difference in moisture content of resin-impregnated bamboo bundles is largely the same as that in Example 1, except that: When using mirror-symmetric paving, the number of layers of refractory bamboo bundles with different moisture content grades differs from the total number of paving layers. In this embodiment, refractory bamboo bundles with moisture content grades A, C, and E are selected for mirror-symmetric paving, with a total of 6 paving layers, 3 layers in the upper half; m1=913.1985g, m2=601.3679g, m3=467.0399g, m dry =3535.714286g, =12.090860%.

[0064] Example 3 The method for preparing reconstituted bamboo based on the gradient difference in moisture content of resin-impregnated bamboo bundles is largely the same as that in Example 1, except that: The total number of paving layers differs when using mirror-symmetric paving. In this embodiment, bamboo bundles with moisture content grades A, B, C, D, and E are selected for mirror-symmetric paving, with a total of 10 paving layers, 5 layers in the upper half. The weights are: m1 = 614.9644g, m2 = 447.8908g, m3 = 360.1990g, m4 = 299.1241g, and m5 = 267.0239g. =3535.714286g =12.000485%.

[0065] Comparative Example 1 The method for preparing recombinant bamboo in this comparative example is largely the same as that in Example 1, except that: (1) The resin-impregnated bamboo bundles were not graded according to their moisture content after drying. After drying, the resin-impregnated bamboo bundles were subjected to temperature and humidity control balancing treatment at 25 ℃ and 65% relative humidity, so that the moisture content of the resin-impregnated bamboo bundles basically reached 12%.

[0066] (2) No slab structure optimization and paving were carried out. During paving, the soaked bamboo bundles were weighed and randomly paved according to the principle of assembling the slabs along the grain.

[0067] Performance testing The swelling rate of the reconstituted bamboo specimens from Examples 1, 2, 3, and Comparative Example 1 after 28 hours of cyclic treatment was determined according to the national standard "Reconstituted Bamboo" (GB / T 40247-2021). The results are as follows: Figure 5 As shown.

[0068] According to the national standard "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels" (GB / T 17657-2022), the static bending strength (MOR) and modulus of elasticity (MOE) of the reconstituted bamboo specimens of Examples 1, 2, 3 and Comparative Example 1 were determined, and the results are as follows: Figure 6 As shown.

[0069] The shear properties of reconstituted bamboo specimens from Examples 1, 2, 3, and Comparative Example 1 were determined according to the national standard "Reconstituted Bamboo" (GB / T 40247-2021). The results are as follows: Figure 7 As shown.

[0070] from Figure 5 , Figure 6 , Figure 7 As can be seen from the above, the paving method adopted in this invention (i.e., the embodiment) results in a finished board with a water absorption thickness (TS) / width (WS) expansion rate that is smaller than that of conventional paving (i.e., the comparative example); the static bending strength (MOR) and elastic modulus (MOE) are both greater than those of conventional paving (i.e., the comparative example), indicating that the finished board obtained by the paving method adopted in this invention has better performance than the finished board obtained by conventional paving.

[0071] Under standard lighting conditions, the finished products of Examples 1, 2, 3 and Comparative Example 1 showed no obvious defects such as cracks, bubbles and missing corners on their surfaces.

[0072] Example 4: This embodiment of a method for preparing reconstituted bamboo based on the gradient difference in moisture content of resin-impregnated bamboo bundles includes the following steps: (1) Preparation of resin-impregnated bamboo bundles This invention uses moso bamboo ( Phyllostachys edulisThe bamboo is 4-6 years old. The bamboo is split into strips and then bundled, processed into bundles measuring 400 mm × 35 mm × 8 mm (length × width × thickness, l × b × h). These bundles are then laid in a superheated steam drying oven and dried at 103 ℃ to a moisture content of 9%, followed by heating to 180 ℃ and holding for 3 hours to obtain heat-treated bamboo bundles.

[0073] Heat-treated bamboo bundles were immersed in a resin adhesive solution under normal pressure for 40 minutes, then removed and air-dried for 32 hours to obtain wet-impregnated bamboo bundles. The resin adhesive solution was a 25% phenolic resin adhesive. It was prepared by using phenolic (PF) resin with a solid content of 50%, pH 9.0, and molecular weight of 750, with distilled water.

[0074] (2) Drying and grading of resin-impregnated bamboo bundles Thirty-five wet-impregnated bamboo bundles were bundled together and dried in a superheated steam drying oven at 60 ℃ for 60 h. After drying, the resulting bamboo bundles had a moisture content ranging from 1% to 30% between the core and surface regions of the same bundle.

[0075] Using a single resin-impregnated bamboo bundle as the testing unit, according to Figure 1 Three sites were selected as calibration areas for moisture content testing, each with an area of ​​no less than 20 mm × 20 mm. An inductive electrical resistivity meter was used for non-destructive testing of the moisture content of the resin-impregnated bamboo bundles. The instrument accuracy was ±0.5%. During testing, full and stable contact between the inductive electrical resistivity meter and the sample surface was ensured. Measurements were taken at each calibration area, and the moisture content readings were recorded. The average moisture content was calculated based on the measurement data from the three sites. The resin-impregnated bamboo bundles were then classified into five grades based on the average moisture content and stored accordingly.

[0076] The moisture content is graded as follows: Grade A: 26% ~ 30%; Grade B: 19% ~ 25%; Grade C: 13% ~ 18%; Grade D: 7% ~ 12%; Grade E: 1% ~ 6%. (3) Slab structure optimization and paving Laying out the slabs according to the principle of parallel grain arrangement, the target average moisture content of the slabs is... The target density is set at 14%, and the board design specifications are set at 400 mm (axial direction of the impregnated bamboo bundles) × 450 mm (width direction) × 20 mm (thickness direction of the impregnated bamboo bundles). Set to 1.1 g / cm 3 .

[0077] The nominal moisture content of the resin-impregnated bamboo bundles is defined as follows for each moisture content grade (Grade A, Grade B, Grade C, Grade D, Grade E): MCj , is the average of the upper and lower limits of the moisture content for this grade, as shown in formula (1):

[0078] In the above formula, MC s This represents the upper limit of the moisture content in the resin-impregnated bamboo bundles of moisture content grade j. MC x The lower limit of the moisture content in the resin-impregnated bamboo bundles of moisture content grade j. ，j In this embodiment, the moisture content is classified as follows: j = A, E .

[0079] The nominal moisture content of the i-th layer of resin-impregnated bamboo bundle The choice depends on the moisture content grade of the layer. For example, if the i-th layer is selected as grade A resin-impregnated bamboo bundles, then... The nominal moisture content of Grade A resin-impregnated bamboo bundles MC A .

[0080] Based on the target density of reconstituted bamboo boards and target volume of the board V The mass of the slab is calculated to be 3960g using formula (2).

[0081]

[0082] In the above formula, ρ To determine the target density of reconstituted bamboo boards, V The target volume (product of length, width, and height) of the reconstituted bamboo board.

[0083] Based on the target oven-dry weight of the slab M and target average moisture content The oven-dry mass of the slab is calculated using formula (3). It is 3473.6842g.

[0084]

[0085] In the above formula, This represents the target average moisture content of the slab.

[0086] Based on the oven-dry weight of the slab With the target average moisture content The target total moisture content of the slab was calculated to be 486.3158g using formula (4).

[0087]

[0088] The method of laying resin-impregnated bamboo bundles is as follows Figure 3As shown, in the thickness direction of the slab, with the core layer at 1 / 2 of the thickness, bamboo bundles with different moisture content grades are selected and laid in a mirror-symmetrical manner. That is, in the part above the core of the slab, the moisture content grade decreases from the surface layer to the core layer, and in the part below the core layer of the slab, the moisture content grade increases from the core layer to the surface layer.

[0089] In this embodiment, resin-impregnated bamboo bundles with moisture content grades A and E are selected for mirror-symmetrical paving, with a total of 4 paving layers, 2 layers in the upper part.

[0090] Iterative optimization using weight allocation method (e.g.) Figure 4 (As shown) Calculate the mass distribution coefficient of the i-th impregnated bamboo bundle layer. And it satisfies formula (5).

[0091]

[0092] The paving quality of the i-th impregnated bamboo bundle layer is calculated using formula (6). m i . , This is the weighting parameter; its value ranges from 0 to 10.

[0093] The data obtained are m1=1027.3228g and m2=952.6523g.

[0094] Based on the installation quality of the i-th impregnated bamboo bundle layer m i The oven-dry mass of the i-th layer of resin-impregnated bamboo bundle is calculated using formula (7). The absolute dry mass of all layers The actual oven-dry mass m of the slab is obtained by summing the results. dry =3473.684211g.

[0095]

[0096] .

[0097] The actual total moisture content of the slab is calculated using formula (8). The actual average moisture content of the slab can be calculated using formula (9). =14.033559%

[0098]

[0099] Determine the actual oven-dry mass m of the slab dry and target dry mass MError values ​​between, actual average moisture content of slab and target average moisture content Whether the error values ​​between them are within the preset range, if so, then according to the paving quality m i Surface each layer symmetrically; otherwise, adjust the mass distribution coefficient. Recalculate paving quality m i .

[0100] In this invention, the mass distribution coefficient is adjusted. The steps include: determining the weight parameters. Check if the traversal is complete. If not, retrieve another parameter from the weight parameter database. Value, regain quality allocation coefficient If the process has already been completed, change one or more of the following: target moisture content, slab size, density, and paving scheme, and start again.

[0101] The comparison showed that the difference between the actual value and the target value met the requirements (dry weight difference less than 0.1g, moisture content difference less than 1%).

[0102] Weigh out the resin-impregnated bamboo bundles according to the calculated quality of each grade, and lay out the four sets of resin-impregnated bamboo bundles according to the paving design. The final thickness of the board blank laid out with resin-impregnated bamboo bundles is about 5 times the thickness of the hot-pressed reconstituted bamboo board. The joints of each layer of resin-impregnated bamboo bundles are staggered to avoid through seams, ensuring that the moisture content in the thickness direction is distributed in a continuous gradient. The upper and lower halves are mirror-symmetrical to form a complete symmetrical structure.

[0103] (4) Hot pressing The prepared slabs are placed into a hot press, and the hot pressing process parameters are set as follows: hot pressing temperature 150℃, hot pressing pressure 5MPa, and hot pressing time 45 min. During the hot pressing process, the closing speed of the pressing plate is controlled at 8 mm / min to ensure uniform compression in the thickness direction of the slabs. The final product is a 20 mm thick reconstituted bamboo board. After hot pressing, the board is allowed to cool naturally to room temperature before being removed from the press.

[0104] Example 5 The method for preparing reconstituted bamboo based on the gradient difference in moisture content of resin-impregnated bamboo bundles is largely the same as that in Example 2, except that: When using mirror-symmetric paving, the number of layers of sizing bamboo bundles with different moisture content grades differs from the total number of paving layers. In this embodiment, sizing bamboo bundles with moisture content grades A, C, and E are selected for mirror-symmetric paving, with a total of 6 paving layers, 3 layers in the upper half. m1=728.8510g, m2=652.1488g, m3=599.0493g. =3473.684211g, =14.002825%.

[0105] Example 6 The method for preparing reconstituted bamboo based on the gradient difference in moisture content of resin-impregnated bamboo bundles is largely the same as that in Example 1, except that: The total number of paving layers differs when using mirror-symmetric paving. In this embodiment, bamboo bundles with moisture content grades A, B, C, D, and E are selected for mirror-symmetric paving, with a total of 10 paving layers, 5 layers in the upper half. m1=470.3079g, m2=423.2803g, m3=388.4716g, m4=359.7090g, m5=338.8141g. =3473.684211g, =13.998572%.

[0106] Comparative Example 2 The method for preparing recombinant bamboo in this comparative example is largely the same as that in Example 1, except that: (1) The resin-impregnated bamboo bundles were not graded according to their moisture content after drying. After drying, the resin-impregnated bamboo bundles were subjected to temperature and humidity control balancing treatment at 25 ℃ and 65% relative humidity, so that the moisture content of the resin-impregnated bamboo bundles basically reached 12%.

[0107] (2) No slab structure optimization and paving were carried out. During paving, the soaked bamboo bundles were weighed and randomly paved according to the principle of assembling the slabs along the grain.

[0108] Performance testing The swelling rates of the reconstituted bamboo specimens from Examples 4, 5, 6, and Comparative Example 2 after 28 hours of cyclic treatment were determined according to the national standard "Reconstituted Bamboo" (GB / T 40247-2021). The results are as follows: Figure 8 As shown.

[0109] According to the national standard "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels" (GB / T 17657-2022), the static bending strength (MOR) and modulus of elasticity (MOE) of the reconstituted bamboo specimens in Examples 4, 5, 6 and Comparative Example 2 were determined, and the results are as follows: Figure 9 As shown.

[0110] The shear properties of reconstituted bamboo specimens from Examples 1, 2, 3, and Comparative Example 1 were determined according to the national standard "Reconstituted Bamboo" (GB / T 40247-2021). The results are as follows: Figure 10 As shown.

[0111] from Figure 8 , Figure 9 , Figure 10 As can be seen from the above, the paving method adopted in this invention (i.e., the embodiment) results in a finished board with a water absorption thickness (TS) / width (WS) expansion rate that is smaller than that of conventional paving (i.e., the comparative example); the static bending strength (MOR) and elastic modulus (MOE) are both greater than those of conventional paving (i.e., the comparative example), indicating that the finished board obtained by the paving method adopted in this invention has better performance than the finished board obtained by conventional paving.

[0112] Under standard lighting conditions, the finished products of Examples 4, 5, 6 and Comparative Example 2 showed no obvious defects such as cracks, bubbles and missing corners.

[0113] Example 7 A reconstituted bamboo preparation system based on the directional assembly of bamboo bundles with varying moisture content gradients after sizing, includes a microprocessor and a memory interconnected, wherein the microprocessor is programmed or configured to execute the reconstituted bamboo preparation method based on the directional assembly of bamboo bundles with varying moisture content gradients according to various embodiments.

[0114] Example 8 A computer-readable storage medium storing a computer program for being programmed or configured by a microprocessor to execute the reconstituted bamboo preparation method based on the gradient difference in moisture content of resin-impregnated bamboo bundles as described in the embodiments.

[0115] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-readable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The present invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, produce implementations of the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1The computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to operate in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The functions specified in one or more boxes. These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable apparatus for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0116] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, should fall within the protection scope of the present invention.

Claims

1. A method for preparing reconstituted bamboo based on the gradient difference in moisture content of resin-impregnated bamboo bundles, characterized in that: Includes the following steps: S1. The dried, resin-impregnated bamboo bundles are graded according to their moisture content. The difference between the upper and lower limits of the moisture content range for each grade is 3%-8%. S2. The graded resin-impregnated bamboo bundles are laid out in a mirror-symmetrical manner, with the same moisture content level for each layer of resin-impregnated bamboo bundles. The moisture content of the resin-impregnated bamboo bundles gradually increases from the core layer to the surface layer, and the difference between the moisture content of the core layer and the surface layer is 10-25%, thus obtaining the board blank. S3. The slab is hot-pressed into shape and cooled to obtain reconstituted bamboo.

2. The method for preparing reconstituted bamboo based on the gradient difference in moisture content of resin-impregnated bamboo bundles for directional assembly according to claim 1, characterized in that: The process of grading the dried, resin-impregnated bamboo bundles according to their moisture content includes the following steps: A1. The bamboo strips are broken into bamboo bundles, dried to a moisture content of 8%~10%, and kept at 170~190℃ to obtain heat-treated bamboo bundles. A2. Impregnate the heat-treated bamboo bundles in an adhesive and dry them until the moisture content is 1%~30% to obtain the glue-impregnated bamboo bundles. A3. The moisture content of the resin-impregnated bamboo bundles is tested, and the resin-impregnated bamboo bundles are divided into multiple grades according to the moisture content value.

3. The method for preparing reconstituted bamboo based on the gradient difference in moisture content of resin-impregnated bamboo bundles for directional assembly according to claim 2, characterized in that: In step A3, the difference between the upper and lower limits of the moisture content range for each level is 3%-5%.

4. The method for preparing reconstituted bamboo based on the gradient difference in moisture content of resin-impregnated bamboo bundles for directional assembly according to claim 1, characterized in that: In step S2, the following steps are included before the mirror symmetric paving: B1. Based on the target total moisture content of the slab W、 Total number of layers of resin-impregnated bamboo bundle n The nominal moisture content of the i-th impregnated bamboo bundle layer The mass distribution coefficient of the i-th impregnated bamboo bundle layer The paving quality of the i-th impregnated bamboo bundle layer is calculated according to the following formula. m i The moisture content of the resin-impregnated bamboo bundles in the i-th resin-impregnated bamboo bundle layer is the same. In the above formula, ; B2. Based on the paving quality of the i-th layer m i The dry mass of the i-th layer is obtained according to the following formula. and the actual oven-dry mass m of the slab dry , ； ； B3. Based on the actual oven-dry weight m of the slab dry The nominal moisture content of the i-th impregnated bamboo bundle layer The actual total moisture content of the slab is obtained according to the following formulas. and the actual average moisture content of the slab ; ； ； B4. Determine the actual oven-dry weight m of the slab. dry and target dry mass M Error values ​​between, actual average moisture content of slab and target average moisture content Check whether the error values ​​are within the preset range. If so, proceed according to the paving quality in step B1. m i Surface each layer symmetrically; otherwise, adjust the mass distribution coefficient. Repeat step B1.

5. The method for preparing reconstituted bamboo based on the gradient difference in moisture content of resin-impregnated bamboo bundles for directional assembly according to claim 4, characterized in that: The following steps are included before step B1: C1. Based on the target density ρ and target volume of the board. V Determine the target oven-dry quality of the board. M ; C2. Based on the target oven-dry quality of the board material M and target average moisture content Determine the oven-dry weight of the slab. ; C3. Based on the oven-dry weight of the slab With the target average moisture content Determine the target total moisture content of the slab. W .

6. The method for preparing reconstituted bamboo based on the gradient difference in moisture content of resin-impregnated bamboo bundles for directional assembly according to claim 5, characterized in that: In step C1, ; In step C2, ; In step C3, .

7. The method for preparing reconstituted bamboo based on the gradient difference in moisture content of resin-impregnated bamboo bundles for directional assembly according to claim 4, characterized in that: In step B1, The value is the nominal moisture content of the resin-impregnated bamboo bundles at the j-th moisture content level. , j represents the moisture content grade. MC s This represents the upper limit of the moisture content of the j-th grade resin-impregnated bamboo bundles. MC x This represents the lower limit of the moisture content of the j-th grade resin-impregnated bamboo bundles. j Moisture content grade; In step B1, , These are weight parameters; In step B4, the actual oven-dry mass m of the slab dry and target dry mass M The preset range for the error value is 0.1g; In step B4, the actual average moisture content of the slab and target average moisture content The preset range for the error value is 1%.

8. The method for preparing reconstituted bamboo based on the gradient difference in moisture content of resin-impregnated bamboo bundles for directional assembly according to claim 4, characterized in that: In step S3, the temperature during hot pressing is 140 ~ 160 ℃, the pressure is 4 ~ 6 MPa, and the time is 35 ~ 50 min.

9. A system for preparing reconstituted bamboo based on the gradient difference in moisture content of resin-impregnated bamboo bundles for directional assembly, comprising a microprocessor and a memory interconnected, characterized in that, The microprocessor is programmed or configured to execute the method for preparing reconstituted bamboo based on the gradient difference in moisture content of resin-impregnated bamboo bundles according to any one of claims 1 to 8.

10. A computer-readable storage medium storing a computer program, characterized in that, The computer program is used to be programmed or configured by a microprocessor to execute the method for preparing reconstituted bamboo based on the gradient difference in moisture content of resin-impregnated bamboo bundles according to any one of claims 1 to 8.

Images