High-strength low-elongation multilayer wood-plastic composite board, preparation method and application thereof

Abstract

The application discloses a kind of high-strength low-elasticity multilayer wood-plastic composite board and its preparation method and application, wood-plastic composite board includes wood-plastic base plate and resin balance layer, resin balance layer is located between two adjacent wood-plastic base plates, resin balance layer is used for bidirectional stress balance to offset the temperature and humidity expansion difference of wood-plastic base plate, preparation method includes the following steps: step S1, preparation wood-plastic base plate;Step S2, compound bonding glue is deployed;Step S3, gluing treatment;Step S4, symmetric blank stacking;Step S5, cold pressing composite;Step S6, post-processing;High-strength low-elasticity multilayer wood-plastic composite board prepared using the above preparation method, transverse temperature and humidity expansion rate ≤0.15%, longitudinal temperature and humidity expansion rate ≤0.15%, static bending strength ≥32MPa, vertical board surface nail holding force ≥2200N, the application of high-strength low-elasticity multilayer wood-plastic composite board includes that high-strength low-elasticity multilayer wood-plastic composite board is processed and made into any one of indoor wallboard, indoor floor, furniture cabinet plate, indoor door plate.

Description

Technical Field

[0001] This invention relates to the field of wood-plastic composite board technology, specifically to a high-strength, low-shrinkage multilayer wood-plastic composite board, its preparation method, and its application. Background Technology

[0002] Most of the conventional multi-layer wood-plastic composite boards on the market are simply made of multiple layers of wood-plastic substrates, and ordinary acrylic adhesives are generally used to complete the interlayer bonding. The structure does not have a resin balancing layer to offset internal stress. Traditional wood-plastic composite boards are susceptible to large dimensional deformation due to changes in temperature and humidity. Long-term use can easily lead to warping and unevenness of the board surface. At the same time, the interlayer bonding strength is insufficient, the board has poor nail-holding performance, and the overall mechanical properties and dimensional stability are weak, making it difficult to meet the long-term use requirements of interior wall panels, interior flooring, furniture cabinet panels, interior door panels, and other application scenarios. Summary of the Invention

[0003] In order to overcome the shortcomings of existing technical solutions, the present invention provides a high-strength, low-shrinkage multilayer wood-plastic composite board, its preparation method and application, which can effectively solve the technical problems raised in the background art.

[0004] The technical solution adopted by the present invention to solve its technical problem is: a high-strength, low-expansion multilayer wood-plastic composite board, comprising at least two wood-plastic substrates and at least one resin balancing layer, wherein the resin balancing layer is disposed between two adjacent wood-plastic substrates, and the resin balancing layer is used for bidirectional stress balancing to offset the temperature and humidity expansion and contraction difference of the wood-plastic substrate. An adhesive layer is applied to the bonding interface between the wood-plastic substrate and the resin balance layer. The adhesive layer is bonded to the wood-plastic substrate and the resin balance layer. After cold pressing and curing, the adhesive layer tightly bonds the wood-plastic substrate and the resin balance layer to form an integrated structure.

[0005] Furthermore, the wood-plastic substrate is a PVC wood-plastic foam board, which, by weight, comprises the following components: 62-72 parts of PVC resin, 32-38 parts of plant fiber powder, 1.2-1.8 parts of composite stabilizer, 1.2-1.8 parts of lubricant, and 0.3-1.6 parts of composite foaming agent. The density of the wood-plastic substrate after molding is 0.85-0.95 g / cm³.

[0006] Furthermore, the composite foaming agent includes a yellow foaming agent and a white foaming agent, with the mass ratio of the yellow foaming agent to the white foaming agent ranging from 1:1.5 to 1:3. The yellow foaming agent is selected from at least one of azodicarbonamide and azobisisobutyronitrile, and the white foaming agent is selected from at least one of sodium bicarbonate and ammonium bicarbonate. The lubricant is a compound of stearic acid, polyethylene wax, and oxidized polyethylene.

[0007] Furthermore, the resin balancing layer is selected from either phenolic resin board or urea-formaldehyde resin board, and the resin balancing layer is a continuous, dense, non-foamed thin board with a thickness of 0.5 to 0.8 mm.

[0008] Furthermore, the adhesive layer comprises, by weight, the following components: 45-55 parts modified acrylic emulsion, 18-25 parts polyurethane prepolymer, 1.2-2.5 parts silane coupling agent, 6-12 parts lignin tackifier, 2-5 parts alumina micro powder, and 10-29 parts deionized water.

[0009] A method for preparing a high-strength, low-shrinkage multilayer wood-plastic composite board includes the following steps: Step S1: The PVC resin, plant fiber powder, composite stabilizer, lubricant and composite foaming agent of the formula are put into a high-speed mixer and fully mixed. After the mixture is evenly mixed, the material is extruded by twin screws, foamed, cooled and shaped, and cut to obtain PVC wood-plastic foamed board with a density of 0.85~0.95g / cm³. Step S2: Weigh the modified acrylic emulsion, polyurethane prepolymer, silane coupling agent, lignin tackifier, alumina powder and deionized water according to the weight parts, and stir at low speed at room temperature until the materials are completely uniform to obtain the composite adhesive. Step S3: Select phenolic resin board or urea-formaldehyde resin board as resin balancing layer. First, remove surface impurities from the PVC wood-plastic foam board bonding surface. Wipe the release agent and oil stains on the surface of the resin balancing layer with isopropanol. After drying, evenly apply the composite adhesive prepared in step S2 to the bonding surface of the resin balancing layer. The thickness of the adhesive coating on one side is controlled between 0.08 and 0.2 mm. Step S4: The resin balancing layer after gluing is applied is placed on top of the wood-plastic substrate and stacked in a symmetrical stacking structure to form a board blank. Step S5: The board blank is fed into a cold press to cold press and cure the adhesive layer, so that the wood-plastic substrate and the resin balance layer are tightly bonded to form an integrated structure. Step S6 involves sanding, trimming, and quality inspection of the board to obtain a high-strength, low-shrinkage multilayer wood-plastic composite board.

[0010] Furthermore, in step S5, the pressure is controlled at 2.8 to 3.5 MPa, and the pressure is maintained at room temperature for 90 to 120 minutes. After cold pressing, the plates are unloaded and neatly stacked, and kept at a constant temperature for 48 hours to release the residual internal stress inside the plates.

[0011] The high-strength, low-shrinkage multilayer wood-plastic composite board prepared by the above method has a transverse temperature and humidity shrinkage rate ≤0.15%, a longitudinal temperature and humidity shrinkage rate ≤0.15%, a static bending strength ≥32MPa, and a vertical nail-holding force ≥2200N.

[0012] Applications of high-strength, low-shrinkage multilayer wood-plastic composite boards include processing them into any one of the following: interior wall panels, interior flooring, furniture cabinet panels, and interior door panels.

[0013] Compared with the prior art, the beneficial effects of the present invention are: 1. The resin balancing layer is set between two adjacent wood-plastic composite substrates. The resin balancing layer is used for bidirectional stress balancing to offset the temperature and humidity expansion and contraction difference of the wood-plastic composite substrate, and to improve the overall bending strength and flatness of the high-strength low-expansion multilayer wood-plastic composite board, while inhibiting the warping deformation of the high-strength low-expansion multilayer wood-plastic composite board. 2. An adhesive layer is applied to the bonding interface between the wood-plastic substrate and the resin balance layer. The adhesive layer is bonded to the wood-plastic substrate and the resin balance layer. After cold pressing and curing, the adhesive layer tightly bonds the wood-plastic substrate and the resin balance layer to form an integrated structure. 3. The adhesive layer, calculated by weight, includes the following components: 45-55 parts modified acrylic emulsion, 18-25 parts polyurethane prepolymer, 1.2-2.5 parts silane coupling agent, 6-12 parts lignin tackifier, 2-5 parts alumina micro powder, and 10-29 parts deionized water. The adhesive layer is configured to have the bonding activity of PVC wood-plastic foam board interface, phenolic resin board interface, or urea-formaldehyde resin board interface. After curing, the adhesive layer has elastic buffering capacity, which can further improve the nail holding power and interlayer peel strength of the wood-plastic composite board. 4. The wood-plastic composite substrate is a PVC wood-plastic foam board. The wood-plastic composite substrate, calculated by weight, includes the following components: 62-72 parts of PVC resin, 32-38 parts of plant fiber powder, 1.2-1.8 parts of composite stabilizer, 1.2-1.8 parts of lubricant, and 0.3-1.6 parts of composite foaming agent. The density of the wood-plastic composite substrate after molding is 0.85-0.95 g / cm³. 5. It can adopt a symmetrical stacking structure with three, five, seven or more layers alternating. The total thickness of the board can be flexibly adjusted according to actual needs. For different use scenarios such as interior wall panels, interior flooring, furniture cabinet panels, and interior door panels, the mechanical properties, dimensional stability, and on-site installation differences can be met by adjusting the number of composite layers of the wood-plastic substrate, selecting the corresponding type of resin balance layer, and changing the overall thickness of the board. The structure has strong versatility. Attached Figure Description

[0014] Figure 1 A schematic diagram of the overall structure of a high-strength, low-shrinkage multilayer wood-plastic composite board; Figure 2 This is a cross-sectional view of a high-strength, low-shrinkage multilayer wood-plastic composite board.

[0015] Numbering on the map: 1. Adhesive layer; 2. Wood-plastic substrate; 3. Resin balancing layer. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] like Figure 1-2 As shown, the present invention provides a high-strength, low-shrinkage multilayer wood-plastic composite board, comprising at least two wood-plastic substrates 2 and at least one resin balancing layer 3. The resin balancing layer 3 is disposed between two adjacent wood-plastic substrates 2. The resin balancing layer 3 is used for bidirectional stress balancing to offset the temperature and humidity shrinkage difference of the wood-plastic substrates 2, and to improve the overall bending strength and surface flatness of the high-strength, low-shrinkage multilayer wood-plastic composite board, while inhibiting the warping deformation of the high-strength, low-shrinkage multilayer wood-plastic composite board. An adhesive layer 1 is applied to the bonding interface between the wood-plastic substrate 2 and the resin balance layer 3. The adhesive layer 1 is bonded to the wood-plastic substrate 2 and the resin balance layer 3. After cold pressing and curing, the adhesive layer 1 tightly bonds the wood-plastic substrate 2 and the resin balance layer 3 to form an integral structure.

[0018] In this embodiment, the wood-plastic substrate 2 is a PVC wood-plastic foam board. The wood-plastic substrate 2, calculated by weight, includes the following components: 62-72 parts of PVC resin, 32-38 parts of plant fiber powder, 1.2-1.8 parts of composite stabilizer, 1.2-1.8 parts of lubricant, and 0.3-1.6 parts of composite foaming agent. The density of the wood-plastic substrate 2 after molding is 0.85-0.95 g / cm³. The composite foaming agent includes a yellow foaming agent and a white foaming agent. The mass ratio of the yellow foaming agent to the white foaming agent is in the range of 1:1.5 to 1:3. The yellow foaming agent is selected from at least one of azodicarbonamide and azobisisobutyronitrile, and the white foaming agent is selected from at least one of sodium bicarbonate and ammonium bicarbonate. The lubricant is composed of stearic acid, polyethylene wax, and oxidized polyethylene. The resin balancing layer 3 is selected from either phenolic resin board or urea-formaldehyde resin board, and the resin balancing layer 3 is a continuous, dense, non-foamed thin board with a thickness of 0.5 to 0.8 mm. The adhesive layer 1, by weight, comprises the following components: 45-55 parts modified acrylic emulsion, 18-25 parts polyurethane prepolymer, 1.2-2.5 parts silane coupling agent, 6-12 parts lignin tackifier, 2-5 parts alumina micro powder, and 10-29 parts deionized water. The adhesive layer 1 is configured to have the bonding activity of PVC wood-plastic composite foam board interface, phenolic resin board interface, or urea-formaldehyde resin board interface. After curing, the adhesive layer 1 has elastic buffering capacity, which can further improve the nail holding power and interlayer peel strength of the wood-plastic composite board.

[0019] A method for preparing a high-strength, low-shrinkage multilayer wood-plastic composite board includes the following steps: Step S1: The PVC resin, plant fiber powder, composite stabilizer, lubricant and composite foaming agent of the formula are put into a high-speed mixer and fully mixed. After the mixture is evenly mixed, the material is extruded by twin screws, foamed, cooled and shaped, and cut to obtain PVC wood-plastic foamed board with a density of 0.85~0.95g / cm³. Step S2: Weigh the modified acrylic emulsion, polyurethane prepolymer, silane coupling agent, lignin tackifier, alumina powder and deionized water according to the weight parts, and stir at low speed at room temperature until the materials are completely uniform to obtain the composite adhesive. Step S3: Select phenolic resin board or urea-formaldehyde resin board as the resin balancing layer. First, remove surface impurities from the PVC wood-plastic foam board bonding surface. If phenolic resin board is selected as the resin balancing layer, wipe the release agent and oil stains on the surface of the resin balancing layer with isopropanol. After drying, evenly apply the composite adhesive prepared in step S2 to the bonding surface of the resin balancing layer. The thickness of the adhesive on one side is controlled at 0.08-0.2mm. Alternatively, if water-based polyurethane adhesive is selected as the adhesive, the coating amount on one side is controlled at 120-180g / ㎡, and the coating amount on both sides is optimized at 120-150g / ㎡. If toughened modified epoxy resin microfoam adhesive is selected as the adhesive, the coating amount is controlled at 160-220g / ㎡. Step S4: The resin balancing layer after gluing is applied is placed on top of the wood-plastic substrate and stacked in a symmetrical stacking structure to form a board blank. Step S5: The board is fed into a cold press to cold press and cure the adhesive layer. The wood-plastic composite substrate and the resin balance layer are tightly bonded to form an integrated structure. More specifically, if water-based polyurethane adhesive is used as the adhesive, the pressure is controlled at 2.8-3.5 MPa, and the pressure is maintained at room temperature for 90-120 minutes. In winter, when the temperature is <18℃, the pressure is extended to 150-180 minutes. During the pressure holding period, pressure release should be avoided. If toughened modified epoxy resin microfoam is used as the adhesive, the pressure is adjusted to 2.2-2.8 MPa, and the pressure is maintained at room temperature for 180-240 minutes. In winter, when the temperature is <18℃, the pressure is extended to 240-300 minutes. After cold pressing, the boards are unloaded and neatly stacked, and left to stand at a constant temperature for 48 hours to release the residual internal stress inside the boards. Step S6 involves sanding, trimming, and quality inspection of the board to obtain a high-strength, low-shrinkage multilayer wood-plastic composite board.

[0020] The high-strength, low-shrinkage multilayer wood-plastic composite board prepared by the above method has a transverse temperature and humidity shrinkage rate ≤0.15%, a longitudinal temperature and humidity shrinkage rate ≤0.15%, a static bending strength ≥32MPa, and a vertical nail-holding force ≥2200N.

[0021] Applications of high-strength, low-shrinkage multilayer wood-plastic composite boards include processing them into any one of the following: interior wall panels, interior flooring, furniture cabinet panels, and interior door panels.

[0022] Example 1

[0023] This embodiment is a high-strength, low-shrinkage multilayer wood-plastic composite board for processing and manufacturing indoor flooring. In this embodiment, three wood-plastic substrates 2 with a thickness of 4.0 mm and a density of 0.90 g / cm³ are used, along with four phenolic resin boards with a thickness of 0.6 mm as resin balancing layers 3. At the same time, a composite adhesive prepared according to the aforementioned weight proportions is uniformly applied to one side of the resin balancing layer 3 to be bonded, with an adhesive application amount of 120 g / m². The multi-layer wood-plastic composite board 2 and the resin balance layer 3 are stacked in a symmetrical stacking structure to form a blank. The blank is sent into a cold press for cold pressing and composite, with the pressure controlled at 2.8MPa and the holding time controlled at 90min. After cold pressing, the board is kept at a constant temperature for 48h to set the shape and eliminate residual internal stress. According to the test, the high-strength low-shrinkage multi-layer wood-plastic composite board prepared in this embodiment has a transverse temperature and humidity shrinkage rate of 0.12% and a longitudinal temperature and humidity shrinkage rate of 0.12%. The static bending strength can reach 32MPa, and the nail holding force vertical to the board surface is 2350N. The board surface is flat without warping, ripples, dents and other defects, and is suitable for long-term indoor flooring installation.

[0024] Example 2

[0025] This embodiment is a high-strength, low-shrinkage multilayer wood-plastic composite board used for processing and manufacturing furniture cabinet panels. In this embodiment, two wood-plastic substrates 2 with a thickness of 8.0 mm and a density of 0.85 g / cm³ are used, along with three urea-formaldehyde resin boards with a thickness of 0.7 mm as resin balancing layers 3. At the same time, a composite adhesive prepared according to the aforementioned weight proportions is uniformly applied to one side of the resin balancing layer 3 to be bonded, with an adhesive application amount of 115 g / m². The multi-layer wood-plastic composite board 2 and the resin balance layer 3 are stacked in a symmetrical stacking structure to form a blank. The blank is sent into a cold press for cold pressing and composite, with the pressure controlled at 2.9 MPa and the holding time controlled at 100 min. After cold pressing, the board is kept at a constant temperature for 48 h to fix the shape and eliminate residual internal stress. According to the test, the high-strength low-shrinkage multi-layer wood-plastic composite board prepared in this embodiment has a transverse temperature and humidity shrinkage rate of 0.13% and a longitudinal temperature and humidity shrinkage rate of 0.13%. The static bending strength can reach 36 MPa, the vertical board surface nail holding force is 2280 N, the bending strength is 36 MPa, the board surface is flat without warping, ripples, dents and other defects, and there is no chipping when cutting. It is suitable for the processing and long-term use of various indoor furniture cabinet boards such as wardrobes and cabinets.

[0026] Example 3

[0027] This embodiment is a high-strength, low-shrinkage multilayer wood-plastic composite board used for processing and manufacturing interior door panels. In this embodiment, four wood-plastic substrates 2 with a thickness of 4.5mm and a density of 0.93g / cm³ are used, along with five phenolic resin boards with a thickness of 0.8mm as resin balancing layers 3. At the same time, a composite adhesive prepared according to the aforementioned weight proportions is uniformly applied to one side of the resin balancing layer 3 to be bonded, with an adhesive application amount of 125g / ㎡. The multi-layer wood-plastic composite board 2 and the resin balance layer 3 are stacked in a symmetrical stacking structure to form a blank. The blank is sent into a cold press for cold pressing and composite, with the pressure controlled at 3.1 MPa and the holding time controlled at 110 min. After cold pressing, the board is kept at a constant temperature for 48 hours to fix the shape and eliminate the residual internal stress inside the board. According to the test, the high-strength low-shrinkage multi-layer wood-plastic composite board prepared in this embodiment has a transverse temperature and humidity shrinkage rate of 0.12% and a longitudinal temperature and humidity shrinkage rate of 0.12%. The static bending strength can reach 38 MPa, and the nail holding force vertical to the board surface is 2420 N. The board surface is flat without warping, ripples, dents and other defects, and is not easily deformed. It can be widely used in the processing and preparation of interior doors and various cabinet doors and for long-term use.

[0028] Example 4

[0029] This embodiment is a high-strength, low-shrinkage multilayer wood-plastic composite board for processing and manufacturing interior wall panels. In this embodiment, a wood-plastic substrate 2 with a thickness of 5.0 mm and a density of 0.88 g / cm³ is used, along with two urea-formaldehyde resin boards with a thickness of 0.5 mm as resin balancing layers 3. At the same time, a composite adhesive prepared according to the aforementioned weight proportions is uniformly applied to one side of the resin balancing layer 3 to be bonded, with an adhesive application amount of 120 g / m². The multi-layer wood-plastic composite board 2 and the resin balance layer 3 are stacked in a symmetrical stacking structure to form a board blank. The board blank is sent into a cold press for cold pressing and composite, with the pressure controlled at 2.8MPa and the holding time controlled at 90min. After cold pressing, the board is kept at a constant temperature for 48h to fix the shape and eliminate the residual internal stress inside the board. According to the test, the high-strength low-shrinkage multi-layer wood-plastic composite board prepared in this embodiment has a transverse temperature and humidity shrinkage rate of 0.14% and a longitudinal temperature and humidity shrinkage rate of 0.14%. The static bending strength can reach 34MPa, the vertical board surface nail holding force is 2300N, and the board surface is flat without warping, ripples, dents and other defects. It can be used for interior wall decoration.

[0030] Comparative Examples

[0031] This comparative example uses only a conventional multi-layer wood-plastic composite substrate 2 structure, and only uses ordinary acrylic adhesive to bond the multi-layer wood-plastic composite substrate 2 together without setting a resin balancing layer 3. Under the same temperature and humidity environment as the above embodiment, the temperature and humidity shrinkage rate of this conventional multi-layer wood-plastic composite substrate 2 structure is as high as 0.42%. After being placed at room temperature for 30 days, the board shows obvious warping. The nail holding force of the board perpendicular to the board surface is only 1460N. The mechanical properties and dimensional stability are extremely poor, and it cannot meet the long-term use requirements of indoor wall panels, indoor flooring, furniture cabinet panels, indoor door panels and other application scenarios.

[0032] Compared to traditional technologies: 1. The resin balancing layer 3 is disposed between two adjacent wood-plastic substrates 2. The resin balancing layer 3 is used for bidirectional stress balancing to offset the temperature and humidity expansion and contraction difference of the wood-plastic substrate 2, and to improve the overall bending strength and flatness of the high-strength low-expansion multilayer wood-plastic composite board, while inhibiting the warping deformation of the high-strength low-expansion multilayer wood-plastic composite board. 2. An adhesive layer 1 is coated on the bonding interface between the wood-plastic substrate 2 and the resin balance layer 3. The adhesive layer 1 is bonded to the wood-plastic substrate 2 and the resin balance layer 3. After cold pressing and curing, the adhesive layer 1 tightly bonds the wood-plastic substrate 2 and the resin balance layer 3 to form an integral structure. 3. The adhesive layer 1, by weight, comprises the following components: 45-55 parts modified acrylic emulsion, 18-25 parts polyurethane prepolymer, 1.2-2.5 parts silane coupling agent, 6-12 parts lignin tackifier, 2-5 parts alumina micro powder, and 10-29 parts deionized water. The adhesive layer 1 is configured to have the bonding activity of PVC wood-plastic composite foam board interface, phenolic resin board interface, or urea-formaldehyde resin board interface. After curing, the adhesive layer 1 has elastic buffering capacity, which can further improve the nail holding power and interlayer peel strength of the wood-plastic composite board. 4. The wood-plastic substrate 2 is a PVC wood-plastic foam board. The wood-plastic substrate 2 includes the following components by weight: 62-72 parts of PVC resin, 32-38 parts of plant fiber powder, 1.2-1.8 parts of composite stabilizer, 1.2-1.8 parts of lubricant, and 0.3-1.6 parts of composite foaming agent. The density of the wood-plastic substrate 2 after molding is 0.85-0.95 g / cm³. 5. It can adopt a symmetrical stacking structure with three, five, seven or more layers alternating. The total thickness of the board can be flexibly adjusted according to actual needs. For different use scenarios such as interior wall panels, interior flooring, furniture cabinet panels, and interior door panels, the mechanical properties, dimensional stability, and on-site installation differences can be met by adjusting the number of composite layers of the wood-plastic substrate 2, selecting the corresponding type of resin balance layer 3, and changing the overall thickness of the board. The structure has strong versatility.

[0033] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A high-strength, low-shrinkage multilayer wood-plastic composite board, characterized in that, It includes at least two wood-plastic composite substrates and at least one resin balancing layer. The resin balancing layer is disposed between two adjacent wood-plastic composite substrates and is used for bidirectional stress balancing to offset the temperature and humidity expansion and contraction differences of the wood-plastic composite substrates. An adhesive layer is applied to the bonding interface between the wood-plastic substrate and the resin balance layer. The adhesive layer is bonded to the wood-plastic substrate and the resin balance layer. After cold pressing and curing, the adhesive layer tightly bonds the wood-plastic substrate and the resin balance layer to form an integrated structure.

2. The high-strength, low-shrinkage multilayer wood-plastic composite board according to claim 1, characterized in that, The wood-plastic substrate is a PVC wood-plastic foam board. The wood-plastic substrate comprises the following components by weight: 62-72 parts of PVC resin, 32-38 parts of plant fiber powder, 1.2-1.8 parts of composite stabilizer, 1.2-1.8 parts of lubricant, and 0.3-1.6 parts of composite foaming agent. The density of the wood-plastic substrate after molding is 0.85-0.95 g / cm³.

3. The high-strength, low-shrinkage multilayer wood-plastic composite board according to claim 2, characterized in that, The composite foaming agent includes a yellow foaming agent and a white foaming agent, and the mass ratio of the yellow foaming agent to the white foaming agent is in the range of 1:1.5 to 1:

3. The yellow foaming agent is selected from at least one of azodicarbonamide and azobisisobutyronitrile, and the white foaming agent is selected from at least one of sodium bicarbonate and ammonium bicarbonate. The lubricant is a compound of stearic acid, polyethylene wax, and oxidized polyethylene.

4. A high-strength, low-shrinkage multilayer wood-plastic composite board according to claim 2, characterized in that, The resin balancing layer is selected from either phenolic resin board or urea-formaldehyde resin board, and the resin balancing layer is a continuous, dense, non-foamed thin board with a thickness of 0.5 to 0.8 mm.

5. A high-strength, low-shrinkage multilayer wood-plastic composite board according to claim 4, characterized in that, The adhesive layer comprises the following components by weight: 45-55 parts modified acrylic emulsion, 18-25 parts polyurethane prepolymer, 1.2-2.5 parts silane coupling agent, 6-12 parts lignin tackifier, 2-5 parts alumina micro powder, and 10-29 parts deionized water.

6. A method for preparing a high-strength, low-shrinkage multilayer wood-plastic composite board as described in any one of claims 1-5, characterized in that, Includes the following steps: Step S1: The PVC resin, plant fiber powder, composite stabilizer, lubricant and composite foaming agent of the formula are put into a high-speed mixer and fully mixed. After the mixture is evenly mixed, the material is extruded by twin screws, foamed, cooled and shaped, and cut to obtain PVC wood-plastic foamed board with a density of 0.85~0.95g / cm³. Step S2: Weigh the modified acrylic emulsion, polyurethane prepolymer, silane coupling agent, lignin tackifier, alumina powder and deionized water according to the weight parts, and stir at low speed at room temperature until the materials are completely uniform to obtain the composite adhesive. Step S3: Select phenolic resin board or urea-formaldehyde resin board as resin balancing layer. First, remove surface impurities from the PVC wood-plastic foam board bonding surface. Wipe the release agent and oil stains on the surface of the resin balancing layer with isopropanol. After drying, evenly apply the composite adhesive prepared in step S2 to the bonding surface of the resin balancing layer. The thickness of the adhesive coating on one side is controlled between 0.08 and 0.2 mm. Step S4: The resin balancing layer after gluing is applied is placed on top of the wood-plastic substrate and stacked in a symmetrical stacking structure to form a board blank. Step S5: The board blank is fed into a cold press to cold press and cure the adhesive layer, so that the wood-plastic substrate and the resin balance layer are tightly bonded to form an integrated structure. Step S6 involves sanding, trimming, and quality inspection of the board to obtain a high-strength, low-shrinkage multilayer wood-plastic composite board.

7. The preparation method according to claim 6, characterized in that, In step S5, the pressure is controlled at 2.8 to 3.5 MPa, and the pressure is maintained at room temperature for 90 to 120 minutes. After cold pressing, the plates are unloaded and neatly stacked. They are then kept at a constant temperature for 48 hours to release the residual internal stress inside the plates.

8. A high-strength, low-shrinkage multilayer wood-plastic composite board prepared by the method of claim 7, characterized in that, The high-strength, low-shrinkage multilayer wood-plastic composite board has a transverse temperature and humidity shrinkage rate of ≤0.15%, a longitudinal temperature and humidity shrinkage rate of ≤0.15%, a static bending strength of ≥32MPa, and a nail-holding force perpendicular to the board surface of ≥2200N.

9. The application of the high-strength, low-shrinkage multilayer wood-plastic composite board according to any one of claims 1-5, characterized in that, Applications include processing high-strength, low-shrinkage multilayer wood-plastic composite boards into any one of the following: interior wall panels, interior flooring, furniture cabinet panels, and interior door panels.

Images