Solid wood multilayer composite board and manufacturing process thereof

Abstract

The invention belongs to the technical field of artificial board processing, and particularly discloses a solid wood multilayer composite board which is high in strength, compact, high in wood utilization rate and capable of being automatically produced. The solid wood multi-layer composite board is formed by arranging fine material layers and aggregate layers alternately and forming a paving structure with the fine material layers on the outermost side through hot pressing. According to the solid wood multi-layer composite board, through the alternate paving mode of aggregate and fine aggregate, on one hand, wood is fully utilized, and the high utilization rate of the wood is guaranteed; and on the other hand, the fine material with the small size can partially permeate and fill gaps of the aggregate with the large size in the hot pressing process to compact the aggregate layer, so that the aggregate layer forms a high-strength structural layer similar to a veneer in plywood in the whole plate, the mechanical strength of the whole plate is guaranteed, and the flatness of the plate surface and the compactness of the plate edge are improved. The solid wood multi-layer composite board has the advantages of plywood and a shaving board, and overcomes the defects of the plywood and the shaving board. The invention further discloses a manufacturing process of the solid wood multilayer composite board.

Description

Technical Field

[0001] This invention belongs to the field of engineered wood processing technology. Specifically, it relates to a multi-layer solid wood composite board that combines high strength, density, high wood utilization rate, and automated production characteristics, as well as its manufacturing process. Background Technology

[0002] Plywood is the highest-volume engineered wood product, favored by consumers for its dense edges and excellent mechanical properties. However, its low level of automation, high labor demand, and stringent requirements for raw wood materials (such as the unsuitability of small branches, straw, bamboo, and other wood fiber-containing particles) result in low wood utilization and high production costs. As an alternative, particleboard uses different sizes of wood as raw materials for the surface and core layers, achieving high wood utilization and automated installation. However, its method of laying two layers of fine surface material sandwiching a coarser core layer leads to poor edge density and significantly lower mechanical properties compared to plywood, resulting in a lower market share.

[0003] Therefore, adopting highly automated production processes to manufacture high-strength engineered wood products and improving wood utilization to ultimately reduce costs and increase efficiency is the development trend of the engineered wood products industry.

[0004] In this process, if the problems of flammability, corrosion and mold in wood-based panels can be solved simultaneously, it will also be of great significance to the upgrading of wood-based panel products.

[0005] While there are many solutions for flame retardancy, corrosion prevention, mildew prevention, and antibacterial properties, they are generally achieved by adding flame retardants to the glue, impregnating the wood with flame retardants, or applying anti-mildew and antibacterial treatments to the surface of the board. These processes may affect the bonding performance, or have problems such as moisture absorption and efflorescence, flame retardant leaching, high cost, or poor antibacterial effect.

[0006] In summary, engineered wood products that combine flame retardancy, high strength, and antibacterial properties will provide consumers with better choices. Summary of the Invention

[0007] To address the problems of low automation and low wood utilization in existing plywood technologies, and poor edge density and mechanical properties in particleboard, this invention provides a multi-layer solid wood composite board with a novel structure. This board combines the advantages of both plywood and particleboard while overcoming their drawbacks. It not only fully utilizes wood of different sizes as raw materials, ensuring extremely high wood utilization, but also possesses excellent mechanical properties. Furthermore, this multi-layer solid wood composite board allows for automated installation, reducing labor costs.

[0008] The present invention specifically provides the following technical solutions:

[0009] A type of solid wood multilayer composite board is formed by hot pressing, which consists of alternating layers of fine material and aggregate, with the outermost layer being all fine material.

[0010] The fine layer consists of wood powder with a length of less than 5 mm mixed with adhesive, such as granules made from wood or its branches, straw, bamboo and other wood fiber materials; the aggregate layer consists of wood shavings with a length of more than 10 cm and an aspect ratio of not less than 5 mixed with adhesive, which can be obtained by planing or rotary cutting the wood.

[0011] The fine aggregate layer consists of at least three layers, and the aggregate layer consists of at least two layers. This results in an odd number of paving layers (at least five), with both the top and bottom surfaces being fine aggregate layers. Using fine aggregate layers on both sides helps achieve a smooth surface and improves flame retardant properties.

[0012] The thickness of each fine material layer is 0.5cm to 1cm, and the thickness of each aggregate layer is 0.5cm to 2cm, with the fine material layer being thinner than the aggregate layer.

[0013] This solid wood multi-layer composite board utilizes an alternating "aggregate-fine material" laying method. On the one hand, it fully utilizes the wood and ensures a high utilization rate. On the other hand, the smaller fine materials partially penetrate and fill the gaps between the larger aggregate materials during the hot pressing process, compacting the aggregate layer. This makes the aggregate layer form a high-strength structural layer in the whole board, similar to each veneer layer in plywood, thereby ensuring the mechanical strength of the whole board and improving the flatness of the board surface and the density of the board edges.

[0014] Furthermore, the thickness of the wood shavings should not exceed 2mm. This is because the wood shavings are laid out in a free-fall manner, and controlling the thickness of the shavings appropriately can reduce the probability of "bridging" between shavings and lower the porosity of the board.

[0015] Preferably, each pair of adjacent aggregate layers is laid in an orthogonal orientation. Orthogonal laying can reorganize the wood grain structure, thereby eliminating the influence of internal stress in the wood on processing, making the solid wood multilayer composite board more easy to process and more moisture-resistant.

[0016] Furthermore, the adhesive used in the fine aggregate layer is an inorganic adhesive, which can be selected from any one or a mixture of at least two of magnesium sulfate-magnesium oxide adhesive, magnesium chloride-magnesium oxide adhesive, aluminum phosphate adhesive, and sodium silicate-sodium fluorosilicate adhesive. The use of an inorganic adhesive in the fine aggregate layer serves two purposes: firstly, it provides flame retardancy; secondly, its high water content allows it to penetrate and fill the aggregate layer during hot pressing, generating water vapor that promotes uniform heating within the slab and facilitates thorough curing of the adhesive.

[0017] Preferably, the inorganic adhesive is formulated with magnesium hydroxide. Magnesium hydroxide, when formulated with inorganic adhesive, can, on the one hand, act as an antibacterial agent to enhance the antibacterial and antifungal effects of the board, and on the other hand, exhibit good compatibility with inorganic adhesives, thus avoiding the problems of precipitation and aggregation that easily occur with existing methods of adding anti-corrosion and antibacterial components (adding magnesium hydroxide to organic adhesives).

[0018] Furthermore, the adhesive used for mixing the aggregate layer is an organic adhesive, which can be selected from any one or a combination of at least two of urea glue, phenolic glue, isocyanate glue, and acrylic resin. Using an organic adhesive for mixing the aggregate layer can fully utilize the easy dispersibility of organic adhesives, bonding large-sized aggregates, ensuring uniform application, and thus achieving higher mechanical strength.

[0019] Furthermore, the aggregate layer is dried after adhesive application until the moisture content is no higher than 10% to prevent the organic adhesives such as isocyanate from curing prematurely with water when organic adhesives are used.

[0020] The present invention also provides a method for manufacturing the above-mentioned solid wood multilayer composite board, which includes the following steps:

[0021] S1. Screening: The wood raw materials are processed to select large-sized wood shavings as aggregates and small-sized wood powder as fines; the wood shavings are longer than 10cm and have an aspect ratio of not less than 5, and the wood powder is shorter than 5mm.

[0022] S2. Applying adhesive: Apply adhesive to the aggregate and fine aggregate separately, and control the moisture content of the aggregate after adhesive application to be no higher than 10% and the moisture content of the fine aggregate after adhesive application to be 15% to 25%.

[0023] S3. Laying: Lay at least five layers of the sizing aggregate and the sizing fine aggregate in an alternating pattern of one layer of aggregate and one layer of fine aggregate, with the outermost layer being fine aggregate, to obtain a slab.

[0024] S4. Forming: After pre-pressing, hot pressing, cutting, curing and sanding, the board blank is used to obtain solid wood multilayer composite board.

[0025] Further, in step S2, an organic adhesive is applied to the aggregate; an inorganic adhesive, preferably an inorganic adhesive compounded with magnesium hydroxide, is applied to the fine aggregate.

[0026] Furthermore, in step S2, the amount of adhesive applied to the aggregate is 2% to 15% of the aggregate mass, and the moisture content of the aggregate before adhesive application is not higher than 5%, preferably not higher than 2%; the amount of adhesive applied to the fine material is 20% to 50% of the fine material mass, and the moisture content of the fine material before adhesive application is not higher than 10%.

[0027] Furthermore, when applying an inorganic adhesive formulated with magnesium hydroxide to fine materials, the amount of magnesium hydroxide should be controlled to be 5% to 10% of the inorganic adhesive.

[0028] Furthermore, in step S3, the sizing aggregate is laid in an oriented manner, preferably with each two adjacent aggregate layers arranged orthogonally; while the sizing fine material can be laid by mechanical roller pressing or air-jet laying.

[0029] Furthermore, in step S4, the hot pressing conditions for the slab are 120℃~160℃, the unit pressure is 2MPa~6MPa, the pressing time is 5min~15min, and the venting time is 2min~10min.

[0030] The present invention has the following beneficial effects:

[0031] 1) The solid wood multi-layer composite board provided by this invention improves the mechanical properties of the board through the orthogonal arrangement of similar aggregate layers and the alternating multi-layer arrangement of fine material and aggregate. The aggregate layers provide strength, while the fine material layers serve to fill and compact the surface. Compared to conventional plywood or particleboard, the staggered arrangement of multiple aggregate and fine material layers ensures both high wood utilization and high mechanical strength of the board, while also achieving a smooth surface (compared to plywood) and dense edges (compared to ordinary particleboard).

[0032] 2) The solid wood multilayer composite board provided by the present invention, through the alternating laying method of "aggregate-fine material", has a lower single-layer laying thickness than ordinary particleboard, which reduces the void ratio between the particleboard chips. This is conducive to the dense filling of the fine material layer and the aggregate layer, thus enabling the laying of more layers and further improving the mechanical properties. In addition, the high strength of the aggregate layer can also meet the requirements for producing thicker whole boards (if ordinary particleboard is laid too thickly, the uneven distribution of moisture will easily cause insufficient curing of the middle adhesive layer, resulting in delamination or even board bursting), thereby meeting the application scenarios with large thickness requirements such as walls and containers.

[0033] 3) The solid wood multilayer composite board provided by this invention has a thin fine particle layer that serves as a dense filler and uses a high-moisture inorganic adhesive. The thick aggregate layer provides strength and uses a low-moisture organic adhesive. This alternating "aggregate-fine particle" layer arrangement allows a small amount of moisture from the fine particle layer to evaporate into the aggregate layer, resulting in a more uniform heat distribution and thorough curing of the organic adhesive. This also avoids issues like board bursting or prolonged pressing time caused by excessive moisture in the aggregate layer. Furthermore, while the inorganic adhesive imparts good flame-retardant properties to the fine particle layer and provides water vapor during the hot pressing process of the aggregate layer, its bonding performance to wood is not as strong as that of organic adhesives. Therefore, the smaller amount of fine particle layer dispersed in the aggregate layer also avoids adverse effects on the internal bond strength of the finished board.

[0034] 4) The structure and material selection of the above-mentioned solid wood multilayer composite board provided by the present invention determine that it can draw on the existing particleboard production process, improve the automation level of board production, and thus improve production efficiency. That is, the large-size aggregate layer adopts directional laying, and the small-size fine material layer adopts mechanical roller laying or air-flow laying, which ensures that the internal structure of the board blank is uniform and the density deviation is small. Attached Figure Description

[0035] Figure 1 This is a structural schematic diagram of a multi-layer solid wood composite board according to Embodiment 1 of the present invention;

[0036] Figure 2 This is a physical image showing the side density of a multi-layer solid wood composite board according to Embodiment 1 of the present invention;

[0037] Figure 3 This is a picture of the side density of commercially available oriented strand board;

[0038] Figure 4 This is a schematic diagram of the structure of a multi-layer solid wood composite board according to Embodiment 2 of the present invention;

[0039] Figure 5 This is a structural schematic diagram of a multi-layer solid wood composite board according to Embodiment 5 of the present invention. Detailed Implementation

[0040] Addressing the numerous drawbacks of the two conventional types of engineered wood products—plywood and particleboard—the inventors of this invention have made special adjustments to the board's lining structure. By using large-sized wood chips as aggregate and small-sized wood powder as fines, and alternating between the aggregate and fines layers, with both sides of the surface covered entirely with fines, the invention achieves two advantages: First, it utilizes wood raw materials of different sizes, improving wood utilization and realizing one of the advantages of particleboard. Second, the fines can fill the dense aggregate during hot pressing, resulting in a more compact aggregate layer structure. The structure is similar to the strength structure of each veneer in plywood, which not only achieves high mechanical strength in the board blank, but also ensures the flatness of the board surface. It also overcomes the problems of poor mechanical properties and poor edge compactness of general particleboard (which is also made of coarse and fine materials) with an outermost layer of fine materials and a core layer of coarse materials. Thirdly, the laying of aggregates and fine materials can refer to and adopt the existing processes and machines of general particleboard, realize automated operation, reduce manual input, reduce labor demand, increase the production cost of the board and improve production efficiency.

[0041] Furthermore, the specific restrictions on the selection and arrangement of the above-mentioned raw materials, coupled with the application of organic adhesives to the aggregate layer and inorganic adhesives to the fine material layer, not only achieve the basic properties of the adhesive, but also achieve the homogenization of the adhesive, and minimize the risk of board breakage caused by high water content inorganic adhesives.

[0042] To better understand the present invention, the following examples are further illustrations of the solid wood multilayer composite board of the present invention. They are only used to explain the content of the present invention and do not limit the present invention. All similar embodiments based on the present invention should be within the scope of protection.

[0043] Example 1

[0044] This embodiment provides a method having, as follows Figure 1 The solid wood multilayer composite board with the paving structure shown and its manufacturing process.

[0045] Specifically, the paving structure is a five-layer structure consisting of alternating fine material layers and aggregate layers, with the outermost layer on both sides being a fine material layer.

[0046] The aggregate layer is laid using a free-fall method, without any directional paving requirements.

[0047] The manufacturing process of this solid wood multilayer composite board will be described in detail below.

[0048] First, the preparation of aggregates and fine materials.

[0049] Weigh 16 kg of long wood chips with a length greater than 10 cm, an aspect ratio greater than 5, and a thickness less than 2 mm as aggregate; weigh 11.5 kg of wood powder particles with a size less than 5 mm as fines.

[0050] The moisture content of the aggregate is 5%, and the moisture content of the fine aggregate is 7%.

[0051] Secondly, the application of adhesives to aggregates and fine materials.

[0052] Add 4% isocyanate adhesive by weight of aggregate to aggregate and control the moisture content of aggregate after sizing to 6%; add 15% urea adhesive by weight of fines to fines and control the moisture content of fines after sizing to 15%.

[0053] The third step is the laying out of the slabs.

[0054] With a paving height of 0.8cm for each layer of fine aggregate and 1cm for each layer of aggregate, the sizing aggregate and sizing fine aggregate are laid in a 1.3m*2.5m area according to the structure of "fine aggregate-aggregate-fine aggregate-aggregate-fine aggregate" and both layers of aggregate are laid by free fall. The total number of paving layers is 5.

[0055] Finally, the slab is hot-pressed into shape.

[0056] After the paved boards are pre-pressed, they are pressed for 8 minutes at 160℃ and 3.5MPa pressure, then degassed for 3 minutes and cooled to room temperature. The boards are then cut, cured for 3 days, and sanded to obtain solid wood multilayer composite boards.

[0057] The side density diagram of the solid wood multilayer composite board provided in this embodiment is shown below. Figure 2 As shown. For easy comparison, Figure 3 The image shows a photograph of the side density of commercially available oriented strand board (OSB), a three-layer structure with adjacent layers arranged orthogonally. (Comparison) Figure 2 and Figure 3 As can be clearly seen, the sides of the solid wood multilayer composite board provided in this embodiment are dense and compact.

[0058] Example 2

[0059] The similarities between this embodiment and Embodiment 1 will not be repeated here; only the differences from Embodiment 1 will be described. The solid wood multilayer composite board provided in this embodiment differs from that in Embodiment 1 in that the aggregate layer is oriented, and adjacent aggregate layers are orthogonally arranged. Correspondingly, in its manufacturing process, during the board blank laying step, adjacent aggregate layers are orthogonally laid. Other aspects are the same as described in Embodiment 1, thus obtaining a solid wood multilayer composite board.

[0060] The structural schematic diagram of the solid wood multilayer composite board provided in this embodiment is as follows: Figure 4 As shown.

[0061] Example 3

[0062] This embodiment provides a method having, as follows Figure 4 The solid wood multilayer composite board with the paving structure shown, and its manufacturing process.

[0063] Specifically, the paving structure is a five-layer structure consisting of alternating fine material layers and aggregate layers, with the outermost layer on both sides being a fine material layer.

[0064] Among them, two adjacent aggregate layers are laid in an orthogonal directional arrangement.

[0065] The manufacturing process of this solid wood multilayer composite board will be described in detail below.

[0066] First, the preparation of aggregates and fine materials.

[0067] Weigh 17 kg of long planks with a length greater than 10 cm, an aspect ratio greater than 5, and a thickness less than 2 mm as aggregate; weigh 12 kg of wood powder particles with a size less than 5 mm as fines.

[0068] The moisture content of the aggregate is 5%, and the moisture content of the fine aggregate is 7%.

[0069] Secondly, the application of adhesives to aggregates and fine materials.

[0070] Add 4% isocyanate binder by weight of aggregate to aggregate and control the moisture content of aggregate after sizing to 6%; add 30% magnesium sulfate-magnesium oxide binder by weight of fines to fines and control the moisture content of fines after sizing to 18%.

[0071] Magnesium sulfate-magnesium oxide adhesive was synthesized in the laboratory using the following method: lightly calcined magnesium oxide with an activity of 65% was selected and weighed according to the mass ratio of lightly calcined magnesium oxide, magnesium sulfate heptahydrate, and water of 8:1:16; malic acid was used as a modifier at a mass of 0.5% of the active magnesium oxide; the above four reactants were mixed and prepared.

[0072] The third step is the laying out of the slabs.

[0073] With a paving height of 0.8cm for each layer of fine aggregate and 1cm for each layer of aggregate, the sizing aggregate and sizing fine aggregate are laid in a 1.3m*2.5m area according to the structure of "fine aggregate-aggregate-fine aggregate-aggregate-fine aggregate" and adjacent aggregate layers are laid orthogonally, for a total of 5 paving layers.

[0074] Finally, the slab is hot-pressed into shape.

[0075] After the paved boards are pre-pressed, they are pressed for 8 minutes at 160℃ and 3.5MPa pressure, then degassed for 3 minutes and cooled to room temperature. The boards are then cut, cured for 3 days, and sanded to obtain solid wood multilayer composite boards.

[0076] Example 4

[0077] The similarities between this embodiment and Embodiment 3 will not be repeated here; only the differences from Embodiment 3 will be described. The solid wood multilayer composite board provided in this embodiment differs from that in Embodiment 3 in that the inorganic adhesive used for mixing the fine materials is specifically a magnesium hydroxide-magnesium sulfate-magnesium oxide adhesive comprising 30% of the fine materials by weight, wherein the amount of magnesium hydroxide added is 8% of the mass of the magnesium sulfate-magnesium oxide adhesive; the rest is as shown in Embodiment 3, providing a solid wood multilayer composite board.

[0078] Specifically, in this embodiment, magnesium hydroxide is synthesized in the laboratory using the following method: 20 kg of water is added to 1 kg of deactivated lightly calcined magnesium oxide with an activity of 20% to 30%, and the mixture is stirred and reacted at 140°C for 2.5 h. After filtration, washing, drying, and ball milling, it is ready for use.

[0079] Example 5

[0080] This embodiment provides a method having, as follows Figure 5 The solid wood multilayer composite board with the paving structure shown, and its manufacturing process.

[0081] Specifically, the paving structure is a seven-layer structure consisting of alternating fine material layers and aggregate layers, with the outermost layer on both sides being a fine material layer.

[0082] Among them, two adjacent aggregate layers are laid in an orthogonal directional arrangement.

[0083] The solid wood multilayer composite board provided in this embodiment is formed using the following manufacturing process.

[0084] First, the preparation of aggregates and fine materials.

[0085] Weigh 17 kg of long planks with a length greater than 10 cm, an aspect ratio greater than 7, and a thickness less than 2 mm as aggregate; weigh 11.5 kg of wood powder particles with a size less than 5 mm as fines.

[0086] The moisture content of the aggregate is 3%, and the moisture content of the fine aggregate is 4%.

[0087] Secondly, the application of adhesives to aggregates and fine materials.

[0088] Add 15% urea glue by weight of aggregate to aggregate and control the moisture content of aggregate after sizing to 6%; add 40% magnesium hydroxide compound magnesium chloride-magnesium oxide adhesive by weight of fine aggregate (the amount of magnesium hydroxide added is 5% of the mass of magnesium chloride-magnesium oxide adhesive) to fine aggregate and control the moisture content of fine aggregate after sizing to 15%.

[0089] Specifically, in this embodiment, magnesium hydroxide is synthesized in the laboratory using the following method: 15 kg of water is added to 1 kg of deactivated lightly calcined magnesium oxide with an activity of 20% to 30%, and the mixture is stirred and reacted at 130°C for 4 hours. After stirring, the mixture is filtered, washed, dried, and ball-milled for later use.

[0090] Magnesium chloride-magnesium oxide adhesive was synthesized in the laboratory using the following method: lightly calcined magnesium oxide with an activity of 65% was selected and weighed according to the mass ratio of lightly calcined magnesium oxide, magnesium chloride hexahydrate, and water of 8:1:16; malic acid was used as a modifier at a mass of 0.5% of the active magnesium oxide; the above four reactants were mixed and prepared.

[0091] The third step is the laying out of the slabs.

[0092] With a paving height of 1cm for each layer of fine aggregate and 2cm for each layer of aggregate, the sizing aggregate and sizing fine aggregate are laid in a 1.3m*2.5m area according to the structure of "fine aggregate-aggregate-fine aggregate-aggregate-fine aggregate-fine aggregate-fine aggregate" and adjacent aggregate layers are laid orthogonally, for a total of 7 paving layers.

[0093] Finally, the slab is hot-pressed into shape.

[0094] After the paved boards are pre-pressed, they are pressed for 15 minutes at 120℃ and 5MPa pressure, then degassed for 6 minutes and cooled to room temperature. The boards are then cut, cured for 3 days, and sanded to obtain solid wood multilayer composite boards.

[0095] Example 6

[0096] This embodiment provides a solid wood multilayer composite board and its manufacturing process.

[0097] Specifically, the paving structure is a thirteen-layer structure consisting of alternating fine aggregate layers and aggregate layers, with the outermost layer on both sides being a fine aggregate layer.

[0098] Among them, two adjacent aggregate layers are laid in an orthogonal directional arrangement.

[0099] The solid wood multilayer composite board provided in this embodiment is formed using the following manufacturing process.

[0100] First, the preparation of aggregates and fine materials.

[0101] Weigh 28 kg of long planks with a length greater than 10 cm, an aspect ratio greater than 10, and a thickness less than 1 mm as aggregate; weigh 20 kg of wood powder particles with a size less than 5 mm as fines.

[0102] The moisture content of the aggregate is 3%, and the moisture content of the fine aggregate is 4%.

[0103] Secondly, the application of adhesives to aggregates and fine materials.

[0104] Add 12% phenolic gum by weight of the aggregate to the aggregate and control the moisture content of the aggregate after sizing to 6%; add 40% magnesium hydroxide compound magnesium chloride-magnesium oxide adhesive by weight of the fine aggregate (the amount of magnesium hydroxide added is 5% of the mass of magnesium chloride-magnesium oxide adhesive) to the fine aggregate and control the moisture content of the fine aggregate after sizing to 15%.

[0105] Specifically, in this embodiment, magnesium hydroxide is synthesized in the laboratory using the following method: 15 kg of water is added to 1 kg of deactivated lightly calcined magnesium oxide with an activity of 20% to 30%, and the mixture is stirred and reacted at 130°C for 4 hours. After stirring, the mixture is filtered, washed, dried, and ball-milled for later use.

[0106] Magnesium chloride-magnesium oxide adhesive was synthesized in the laboratory using the following method: lightly calcined magnesium oxide with an activity of 65% was selected and weighed according to the mass ratio of lightly calcined magnesium oxide, magnesium chloride hexahydrate, and water of 8:1:16; malic acid was used as a modifier at a mass of 0.5% of the active magnesium oxide; the above four reactants were mixed and prepared.

[0107] The third step is the laying out of the slabs.

[0108] With a paving height of 1cm for each layer of fine aggregate and 2cm for each layer of aggregate, the sizing aggregate and sizing fine aggregate are laid in a 1.3m*2.5m area according to the structure of "fine aggregate-aggregate-fine aggregate-aggregate-fine aggregate-fine aggregate-fine aggregate-fine aggregate-fine aggregate-fine aggregate-fine aggregate-fine aggregate" and adjacent aggregate layers are laid orthogonally, for a total of 13 paving layers.

[0109] Finally, the slab is hot-pressed into shape.

[0110] After the paved boards are pre-pressed, they are pressed for 15 minutes at 150℃ and 6MPa pressure, then degas for 10 minutes and cooled to room temperature. After cutting, curing for 3 days, and sanding, solid wood multilayer composite boards are obtained.

[0111] It should be noted that, in the manufacturing of the above-mentioned solid wood multilayer composite board provided by the present invention, the amount of aggregate and fine materials does not need to be specifically limited. This is because, firstly, there is no direct relationship between the amount of the two; secondly, the laying density of aggregate and fine materials is relatively certain, and once the laying thickness and size are determined, their respective masses can be calculated based on the initial moisture content of each material and the corresponding amount of adhesive applied.

[0112] To demonstrate the impact of the above-mentioned solid wood multilayer composite board laying method provided by the present invention on the performance of the board, several comparative experiments were conducted.

[0113] Comparative Example 1

[0114] The similarities between this comparative example and Example 2 will not be repeated here; only the differences between them will be described. The difference between this comparative example and Example 2 is that the engineered wood panel provided in this comparative example adopts a conventional five-layer laying method of "fine material layer - aggregate layer - aggregate layer - aggregate layer - fine material layer", wherein the middle three aggregate layers are laid orthogonally, which is the laying method of OSB board.

[0115] Comparative Example 2

[0116] The similarities between this comparative example and Example 3 will not be repeated here; only the differences from Example 2 will be described. The difference between this comparative example and Example 3 is that the artificial board provided in this comparative example adopts a five-layer laying method of "aggregate layer-fine aggregate layer-aggregate layer-fine aggregate layer-aggregate layer".

[0117] Comparative Example 3

[0118] The similarities between this comparative example and Example 5 will not be repeated here; only the differences from Example 5 will be described. The difference between this comparative example and Example 5 is that, under the premise of controlling the total thickness of the engineered wood panels provided in this comparative example to be consistent, when using the conventional "fine material layers on both sides and aggregate layer in the middle" laying method, only a five-layer laying method of "fine material layer-aggregate layer-aggregate layer-aggregate layer-fine material layer" can be achieved. Among them, the three middle aggregate layers are orthogonally laid, which is the laying method of OSB board.

[0119] Comparative Example 4

[0120] The similarities between this comparative example and Example 5 will not be repeated here; only the differences from Example 5 will be described. The difference between this comparative example and Example 5 is that the engineered wood panel provided in this comparative example is made by adding laboratory-prepared magnesium hydroxide (in the same amount as in Example 5) to the isocyanate adhesive and spraying it onto the aggregate, instead of mixing it with magnesium sulfate-magnesium oxide adhesive.

[0121] Comparative Example 5

[0122] The similarities between this comparative example and Example 1 will not be repeated here; only the differences from Example 1 will be described. The difference between this comparative example and Example 1 is that 23 kg of wood powder particles with a size of less than 5 mm were used as the fine material in this comparative example; and, during the laying of the board blank, the laying height was operated according to the following: each layer of fine material was 1.5 cm thick, and each layer of aggregate was 0.8 cm thick.

[0123] The density, static bending strength, flammability rating, and antibacterial rating of the engineered wood panels provided in the above embodiments and comparative examples were tested, and the performance test results are shown in Table 1.

[0124] Density and static bending strength were determined according to the requirements of GB / T 17657-2013 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels"; combustion performance classification was determined according to the requirements of GB 8624-2012 "Classification of Combustion Performance of Building Materials and Products"; and antibacterial grade was determined according to the requirements of LY / T 1926-2020 "Detection and Classification of Antibacterial Properties of Wood-based Panels and Wood (Bamboo) Products".

[0125] Table 1. Performance test results of the engineered wood panels provided in the examples and comparative examples.

[0126]

[0127] The static bending strength and modulus of elasticity of the solid wood plywood provided in Examples 1-5 of this invention meet the requirements of GB / T9846-2015 "Ordinary Plywood": for thicknesses between 12mm and 15mm, the static bending strength parallel to the grain is ≥24MPa, and the static bending strength transverse to the grain is ≥20MPa; for thicknesses greater than 21mm, the static bending strength parallel to the grain is ≥24MPa, and the static bending strength transverse to the grain is ≥18MPa. The static bending strength and modulus of elasticity of the solid wood plywood provided in Example 6 meet the requirements of LY / T 3226-2020 "Oriented Strand Board for Container Floors": longitudinal static bending strength ≥75MPa, and transverse static bending strength ≥28MPa.

[0128] As can be seen from the performance data of Examples 1-5, the solid wood multilayer board provided by the present invention has excellent mechanical properties, reaching the high strength level of general plywood. Meanwhile, in Examples 3-5, where the fine layer uses inorganic adhesive and the aggregate layer uses organic adhesive, the combustion performance and antibacterial rating of the solid wood multilayer board are improved; especially in Examples 4 and 5, which introduce magnesium hydroxide antibacterial agent, the combustion rating reaches B1B and the antibacterial rating reaches Class I.

[0129] As can be seen from the test data of Example 6, the static bending strength of the thirteen-layer solid wood multi-layer composite board meets the requirements of LY / T 3226-2020 "Oriented Strand Board for Container Floors", and the finished board also has good flame retardant properties. Therefore, the solid wood multi-layer composite board provided by this invention, when forming a thick board with a large number of layers, can be applied to scenarios requiring significant thickness, such as containers.

[0130] By comparing Example 2 and Comparative Example 1, it can be seen that the main difference lies in the arrangement of the aggregate layer and the fine particle layer. Obviously, the alternating arrangement of aggregate and fine particle in this invention is superior to the arrangement of surface fine particle and core aggregate in general particleboard. This is because the fine particle in the fine particle layer fills the aggregate layer, greatly improving the density of the board edges and the board interior, thus significantly improving the mechanical properties.

[0131] By comparing Example 3 and Comparative Example 2, it can be seen that the mechanical properties of the "fine aggregate layer-aggregate layer-fine aggregate layer-aggregate layer-fine aggregate layer" structure in Example 3 are similar to those in Comparative Example 2. This is because the mechanical strength of the board is mainly provided by the aggregate layer, while Comparative Example 2 has a larger number of aggregate layers. However, because the fine aggregate layer containing inorganic adhesive is on the surface in the structure of Example 3, the burn-through time of the board is delayed, thus its flame retardant performance reaches B1C, and its surface antibacterial grade reaches Class II, which is better than Comparative Example 2. Furthermore, because the aggregate layer is on the surface in Comparative Example 2, its shavings are larger, the surface is uneven, and it is not conducive to subsequent pressing of the finishing surface.

[0132] By comparing Example 5 and Comparative Example 3, it can be seen that after adjusting the paving method, under the premise that the total thickness of the board remains the same, the number of paving layers will decrease and the thickness of the single layer of the internal aggregate layer will increase. Under the same hot pressing conditions, the thickness of the middle layer will be higher, which is not conducive to moisture transfer, thus making it difficult to transfer heat evenly and affecting the curing of the adhesive in the core layer. Consequently, this paving method leads to a decrease in the mechanical properties, antibacterial properties and flame retardant properties of the entire board.

[0133] By comparing Example 4 and Comparative Example 4, it can be seen that when magnesium hydroxide is added to the organic adhesive as an antibacterial agent, it is not evenly dispersed in the adhesive, which affects the bonding performance of the board and thus affects the mechanical properties of the board. At the same time, the antibacterial agent added to the organic adhesive does not play a role in improving the antibacterial performance of the finished board.

[0134] As can be seen from Comparative Example 5 and Example 1, when the thickness of the fine material layer increases and exceeds the thickness of the aggregate layer, that is, when the amount of fine material increases, the moisture content inside the slab will increase significantly. In order to avoid slab bursting, the venting time during the hot pressing process of the slab is greatly extended, which affects the production efficiency. At the same time, since the fine material layer mainly plays a compacting role, it does not have much effect on the strength of the slab after it is formed. Moreover, because the venting time is extended, the inorganic adhesive is partially dehydrated and decomposed, which has an adverse effect on the strength of the fine material layer.

[0135] The embodiments described above are for illustrative purposes only and do not constitute a specific limitation on the present invention. Any modifications made without departing from the basic concept of the present invention, as well as any obvious modifications derived therefrom, are within the scope of protection of the present invention.

Claims

1. A multi-layer solid wood composite board, characterized in that, It consists of a paving structure with alternating layers of fine aggregate and aggregate, with the outermost layer being a layer of fine aggregate, and is formed by hot pressing; The fine material layer is wood powder mixed with adhesive and less than 5 mm in length; the aggregate layer is wood shavings mixed with adhesive and greater than 10 cm in length and with an aspect ratio of not less than 5.

2. The solid wood multilayer composite board according to claim 1, characterized in that, In the solid wood multilayer composite board, the number of fine material layers is at least 3, and the number of aggregate layers is at least 2.

3. The solid wood multilayer composite board according to claim 2, characterized in that, The thickness of the fine material layer is 0.5cm to 1cm, the thickness of the aggregate layer is 0.5cm to 2cm, and the thickness of the fine material layer is less than the thickness of the aggregate layer.

4. The solid wood multilayer composite board according to any one of claims 1 to 3, characterized in that, In the aggregate layer, the thickness of the wood shavings is no more than 2 mm.

5. The solid wood multilayer composite board according to any one of claims 1 to 3, characterized in that, Each pair of adjacent aggregate layers is laid in an orthogonal directional pattern.

6. The solid wood multilayer composite board according to any one of claims 1 to 3, characterized in that, In the fine material layer, the adhesive used for mixing is an inorganic adhesive; in the aggregate layer, the adhesive used for mixing is an organic adhesive.

7. The solid wood multilayer composite board according to claim 6, characterized in that, The inorganic adhesive contains magnesium hydroxide, and the amount of magnesium hydroxide added is 5% to 10% of the mass of the inorganic adhesive.

8. The method for manufacturing solid wood multilayer composite board as described in any one of claims 1 to 7, characterized in that, Including the following steps: S1. Screening: The wood raw material is processed to select large-sized wood shavings as aggregate and small-sized wood powder as fine material; wherein, the wood shavings are longer than 10cm and have an aspect ratio of not less than 5, and the wood powder is shorter than 5mm. S2. Applying adhesive: Apply adhesive to the aggregate and the fine material respectively, and control the moisture content of the aggregate after adhesive application to be no higher than 10% and the moisture content of the fine material after adhesive application to be 15% to 25%. S3. Laying: Lay at least five layers of the sizing aggregate and the sizing fine aggregate in an alternating pattern of one layer of aggregate and one layer of fine aggregate, with the outermost layer being fine aggregate, to obtain a slab. S4. Molding: After pre-pressing, hot pressing, cutting, curing and sanding, the board blank is obtained as the solid wood multilayer composite board.

9. The manufacturing method according to claim 8, characterized in that, In step S2, the amount of adhesive applied to the aggregate is 2% to 15% of the aggregate mass, and the moisture content of the aggregate before adhesive application is not higher than 5%; the amount of adhesive applied to the fine material is 20% to 50% of the fine material mass, and the moisture content of the fine material before adhesive application is not higher than 10%.

10. The manufacturing method according to claim 9, characterized in that, In step S3, the aggregate after adhesive application is laid in a directional manner.

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