High-stability plywood and production method thereof

Abstract

The invention discloses high-stability plywood and a production method thereof, and belongs to the technical field of plywood production. The plywood comprises a core layer, an upper surface layer and a lower surface layer, and the core layer is of a one-layer side-standing multi-layer veneer gluing structure and is formed by continuously shearing multi-layer plywood with the pre-pressing curing degree of 15%-25% through disc type scissors to form prismatic strips and then shaping and splicing the prismatic strips. The core layer is bonded with the upper surface layer and the lower surface layer by adopting an adhesive formed by mixing oil tea fruit powder and urea-formaldehyde resin adhesive, the particle size of the oil tea fruit powder is more than 130 meshes, the water content is 5-20%, and the weight ratio is 18-42%. The production method comprises the following steps: preparing the multi-layer board, shearing the prismatic strips, splicing the core layers, coating the composite adhesive, aging, veneering, performing hot press molding and the like. By optimizing the core layer structure and the adhesive formula, the size stability of the board is remarkably improved, the adhesive dosage and the formaldehyde emission are reduced, the production continuity is enhanced, the veneer utilization rate is increased, large-scale production of large-specification boards can be achieved, and the composite board is widely applied to the field of furniture, wooden door and wallboard manufacturing.

Description

Technical Field

[0001] This invention relates to the field of plywood production technology, specifically to a high-stability plywood and its production method, which is particularly suitable for the manufacture of large-format furniture, wooden doors and wall panels. Background Technology

[0002] Plywood, a commonly used engineered wood product, boasts advantages such as a strong wood-like texture, high strength, and good processing performance, making it widely used in furniture manufacturing, construction, and decoration. However, with increasing market demand for large-format plywood, traditional plywood production processes have gradually revealed numerous shortcomings: Firstly, traditional plywood core layers often employ a flat-jointed structure, with multiple layers of wood fibers glued horizontally. Due to uneven moisture content, fiber structure, and glue layer thickness across each layer, the board exhibits poor dimensional stability and is prone to warping and deformation, especially in large-format applications. Secondly, the uneven surface of the glued veneers leads to a large amount of adhesive material being used. Consequently, commonly used urea-formaldehyde resin adhesives for plywood often contain large amounts of flour, consuming a considerable amount of grain.

[0003] To address the aforementioned issues, some improvements have emerged in existing technologies, such as using a multi-layered cross-structured core layer to enhance stability and adding wood flour to the adhesive to reduce adhesive usage. However, the former involves complex production processes and fails to address the issue of uneven material distribution along the thickness direction in large-format boards; the latter may lead to decreased adhesive strength or reduced production efficiency. For instance, patent CN103361015A discloses a composite urea-formaldehyde adhesive with added bark powder, which reduces adhesive usage, but the proportion of bark powder added is low, resulting in limited adhesive reduction, and it does not address core layer structure optimization, making it difficult to meet the stability requirements of large-format boards. Meanwhile, the multi-layered veneer structure disclosed in foreign patent US20110097565A1 suffers from a lack of continuity in its core layer preparation process, resulting in low production efficiency and unsuitability for large-scale production. Therefore, developing a plywood with good stability, low adhesive usage, strong production continuity, and excellent environmental performance, along with its production method, has become a pressing technical problem in this field. Summary of the Invention

[0004] This invention aims to overcome the shortcomings of the prior art and provide a high-stability plywood and its production method. By optimizing the core layer structure design and adhesive formulation, it achieves improved board dimensional stability, reduced adhesive usage, and enhanced production continuity, while also reducing formaldehyde emissions to meet the production needs of large-format furniture, wooden doors, and wall panels.

[0005] (I) Technical Solution To achieve the above objectives, the present invention adopts the following technical solution: A high-stability plywood includes a core layer and upper and lower surface layers, wherein the upper and lower surface layers are traditional decorative panels. The core layer is a single-layer side-standing multi-layer veneer adhesive structure. The side-standing multi-layer veneers of the core layer are multi-layer plywood with a pre-press curing degree of 15% to 25% formed into prismatic strips by continuous cutting with disc shears, and then shaped and spliced ​​together.

[0006] Furthermore, the width of the prismatic strips formed by the shearing is equal to the thickness of the core layer. After shaping, they form rectangular or square strips, which are then joined together with adhesive applied to both sides to form a core layer board of the required specifications.

[0007] Furthermore, the adhesive between the core layer and the upper and lower surface layers is a mixture of camellia fruit powder and urea-formaldehyde resin. The camellia fruit powder has a particle size >130 mesh, a moisture content of 5% to 20%, and its weight percentage in the adhesive is 18% to 42%.

[0008] A method for producing high-stability plywood as described above includes the following steps: (1) Preparation of multilayer board: The veneer with a moisture content of 15% to 18% after drying is glued and pre-pressed, and the degree of pre-press curing is controlled to reach 15% to 25% to obtain pre-pressed multilayer board; (2) Cutting the prismatic strip: Use disc shears to continuously cut the pre-pressed multilayer board in step (1) to obtain a prismatic strip with a width equal to the core layer thickness; (3) Core layer splicing: The prismatic strips from step (2) are shaped into rectangular or square strips, and adhesive is applied to both sides of the strips by roller coating. The strips are then continuously spliced ​​into core layer boards of the required specifications. (4) Coating composite adhesive: The upper and lower surfaces of the core layer board obtained in step (3) are uniformly coated with an adhesive made of camellia fruit powder and urea-formaldehyde resin. (5) Aging and veneer: The core layer board coated with adhesive is aged, and then traditional decorative panels are veneered on the upper and lower surfaces to form a board blank; (6) Hot pressing: The slab is hot-pressed and cured using the traditional hot pressing process to obtain a highly stable plywood.

[0009] Furthermore, the camellia fruit powder mentioned in step (4) needs to be crushed and sieved to ensure that the particle size is >130 mesh. After crushing, the moisture content is adjusted to 5% to 20% by drying or natural drying.

[0010] Further, in step (1), the bonding treatment refers to using a mixture of camellia fruit powder and urea-formaldehyde resin as the adhesive, wherein the particle size of the camellia fruit powder is >200 mesh, the moisture content is 5% to 10%, and its weight ratio in the adhesive is 15% to 20%; in step (1), the pre-pressing treatment refers to the pre-treatment under the conditions of temperature 20℃ to 95℃ and pressure 0.2MPa to 0.5MPa.

[0011] Furthermore, the prism strip mentioned in step (2) is formed by the transverse cutting force generated when the disc shears cut the pre-pressed multilayer board with a curing degree of 15% to 25% and the resulting misalignment of the pre-bonding interface of the pre-pressed multilayer board.

[0012] Further, the composite adhesive in step (4) is prepared by adding camellia fruit powder to urea-formaldehyde resin at a weight ratio of 18% to 42%, stirring evenly at 15℃ to 30℃ for 10 min to 20 min.

[0013] Furthermore, the aging process in step (5) is carried out at an ambient temperature of 20℃~25℃, a relative humidity of 40%~60%, and an aging time of 15min~30min.

[0014] Further, the parameters of the hot pressing process in step (6) are: hot pressing temperature 120℃~150℃, lateral hot pressing pressure 2.5MPa~4.0MPa, forward hot pressing pressure 0.3MPa~0.5MPa, and hot pressing time calculated according to plate thickness as 20s / mm~30s / mm.

[0015] (ii) Beneficial effects Compared with the prior art, the present invention has the following beneficial effects: Excellent stability: The core layer adopts a side-mounted multi-layer veneer structure, which significantly improves the originality and uniformity of the core layer in the thickness direction, greatly reducing the stress unevenness caused by the gluing and compression processes in the thickness direction, and significantly reducing the risk of board warping and deformation. Testing shows that the water absorption swelling rate of the plywood of this invention is ≤7%, and its dimensional stability is more than 35% better than that of traditional plywood.

[0016] Low veneer loss: Through the continuous disc shearing, shaping and lateral continuous splicing process of pre-cured multilayer boards, the saw kerf loss of sawing and lateral splicing processes is avoided, the processing surface is flat, the veneer utilization rate is increased by more than 15%, and the overall production efficiency is increased by 20% to 30%.

[0017] High production continuity: From prismatic strip cutting to shaping and core layer splicing, continuous equipment is used, which increases the production efficiency of this process by more than 50%, enabling large-scale production of large-format boards and meeting the large-size requirements of furniture, wooden doors, wall panels and other products.

[0018] Good environmental performance: The camellia fruit powder added to the composite adhesive can effectively adsorb free formaldehyde, so that the formaldehyde release of the plywood is ≤0.124mg / m³, which meets the E0 environmental protection standard. At the same time, it realizes the resource utilization of agricultural waste, which is in line with the concept of green production.

[0019] High process compatibility: Subsequent processes such as hot pressing use traditional equipment and parameters, eliminating the need for large-scale production line modifications, reducing enterprise investment costs, and facilitating widespread application. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0021] Example 1: High-stability plywood with side-standing core layer 1 1. Preparation of multi-layer board: Select poplar veneer with a moisture content of 15%-18%, apply glue, assemble the board and then pre-press it. Control the pre-pressing pressure to 0.5MPa, the temperature to 50℃, and the pre-pressing time to 15-20 minutes to ensure that the degree of pre-pressing curing reaches 20%-25% and obtain a pre-pressed multi-layer board with a thickness of 20mm.

[0022] 2. Cutting prismatic strips: Disc-shaped shears are used to continuously cut pre-pressed multilayer boards. The inner side of the disc-shaped shears is concave, and the outer side is conical. Its radial projection surface forms an upper-mounted disc-shaped shear with a back angle of 2-3 degrees and a wedge angle of 15-18 degrees. Multiple sets of pre-pressed multilayer board cutting devices are adjusted with the lateral spacing of the shears being 17mm (i.e., the core layer thickness) and the front-to-back spacing being 300mm to 500mm to improve cutting efficiency and product uniformity. Long strips with a prismatic cross-section and a length of 2460mm are obtained.

[0023] 3. Rhomboid Strip Shaping: The rhomboid strip is pressed into a rectangular strip by a shaping device, which is a double-roller pneumatic shaping machine. The upper roller is a flat pressure roller and the lower roller is a flat support roller. The roller surface hardness is HRC58-62, the working surface linear pressure is 8-10MPa, the working environment temperature is controlled at 60-65℃, and the feeding speed is 1.2-1.5m / min. This ensures that the four corners of the rhomboid strip are fully filled and the cross-sectional dimensional tolerance is ≤±0.3mm.

[0024] 4. Core layer splicing: Using a roller coating machine, a mixture of urea-formaldehyde resin and 200-mesh fruit powder with a moisture content of 5%-7% is applied to the wide side of the veneer after shaping. The weight ratio of the mixture is 4:1, with a coating amount of 150g / m². Then, the rectangular strips are spliced ​​into a core layer board of 2480mm×1260mm×17mm using a continuous splicing device.

[0025] 5. Preparation of composite adhesive: Select camellia fruit, crush and sieve it through a 130-mesh screen, dry it at 60℃ to a moisture content of 12%, add it to urea-formaldehyde resin glue at a weight ratio of 30%, stir for 15 minutes at 20-25℃ to prepare a uniform composite adhesive.

[0026] 6. Coating and aging: Apply composite adhesive evenly to the upper and lower surfaces of the core layer board at a coating amount of 180g / m², and then age it for 20 minutes at 22℃ and 50% relative humidity.

[0027] 7. Veneer and Hot Pressing: After aging, 0.6mm thick elm veneer panels are laminated onto the upper and lower surfaces of the core layer, and then fed into a hot press. The hot pressing temperature is controlled at 135℃, the hot pressing pressure is 1.0MPa, and the hot pressing time is calculated based on the board thickness as 25s / mm (total hot pressing time is 450 seconds). After hot pressing, the core layer is cooled and trimmed to obtain a high-stability plywood with a side-standing core layer.

[0028] Example 2: High-stability plywood with side-standing core layer 2 1. Preparation of multi-layer board: Select eucalyptus veneer with a moisture content of 15%-18%, apply glue, assemble the board and then pre-press it. Control the pre-pressing pressure to 0.9MPa, the temperature to 80℃, and the pre-pressing time to 10-15 minutes to ensure that the degree of pre-pressing curing reaches 15%-20% and obtain a pre-pressed multi-layer board with a thickness of 15mm.

[0029] 2. Cutting prismatic strips: A disc-shaped shear is used to continuously cut the pre-pressed multilayer board. The inner side of the disc-shaped shear is concave, and the outer side is conical. Its radial projection surface forms an upper-mounted disc-shaped shear with a back angle of 2-3 degrees and a wedge angle of 16-18 degrees. Multiple sets of pre-pressed multilayer board cutting devices are adjusted with the lateral spacing of the shears being 16mm (i.e., the core layer thickness) and the front-to-back spacing being 350mm to 500mm to improve cutting efficiency and product uniformity. Long strips with a prismatic cross-section and a length of 2460mm are obtained.

[0030] 3. Rhomboid Strip Shaping: The rhomboid strip is pressed into a rectangular strip by a shaping device, which is a double-roller pneumatic shaping machine. The upper roller is a flat pressure roller and the lower roller is a flat support roller. The roller surface hardness is HRC58-62, the working surface linear pressure is 10-12MPa, the working environment temperature is controlled at 65-75℃, and the feeding speed is 1.0-1.3m / min. This ensures that the four corners of the rhomboid strip are fully filled and the cross-sectional dimensional tolerance is ≤±0.3mm.

[0031] 4. Core layer splicing: Using a roller coating machine, a mixture of urea-formaldehyde resin and 200-mesh fruit powder with a moisture content of 5%-7% is applied to the wide side of the veneer after shaping. The weight ratio of the mixture is 4:1, with a coating amount of 180g / m². Then, the rectangular strips are spliced ​​into a core layer board of 2480mm×1260mm×16mm using a continuous splicing device.

[0032] 5. Preparation of composite adhesive: Select camellia fruit, crush and sieve it through a 150-mesh screen, dry it at 60℃ to a moisture content of 12%, add it to urea-formaldehyde resin glue at a weight ratio of 25%, and stir for 12 minutes at 20-25℃ to prepare a uniform composite adhesive.

[0033] 6. Coating and aging: Apply composite adhesive evenly to the upper and lower surfaces of the core layer board at a coating amount of 180g / m², and then age it for 20 minutes at 25℃ and 50% relative humidity.

[0034] 7. Laminating and Hot Pressing: After aging, 1.0mm thick ash veneer is laminated onto the upper and lower surfaces of the core layer, and then fed into a hot press. The hot pressing temperature is controlled at 145℃, the hot pressing pressure is 1.5MPa, and the hot pressing time is calculated based on the board thickness as 25s / mm (the total hot pressing time is 450 seconds). After hot pressing, the board is cooled and trimmed to obtain a high-stability plywood with a side-standing core layer.

[0035] Performance testing The performance of the plywood prepared in Examples 1 and 2 above was tested, and the results are shown in the table below: Testing items Example 1 Example 2 Traditional side-standing plywood National Standard GB / T9846-2015 Static bending strength (MPa) 28.2 31.5 28.8 conform to Elastic modulus (GPa) 3.3 3.8 3.5 conform to Water absorption swelling rate (%) 7.5 6.8 8.2 ≤12.0 Formaldehyde emission (mg / m³) 0.092 0.095 0.126 ≤0.124 (E0 level) Single-board loss rate (%) 4.8 5.2 22.5 - Test results show that the plywood prepared by this invention is superior to traditional side-mounted plywood and national standard requirements in terms of static bending strength, elastic modulus, water absorption swelling rate and formaldehyde release, and the loss rate of veneers of different specifications is significantly reduced, fully demonstrating the technical advantages of this invention.

[0036] Of particular note is that Example 2, due to its finer cattail powder particle size and more uniform dispersion, exhibits superior performance across various indicators. Compared to Example 1, its static bending strength increased by approximately 11.7%, reaching 31.5 MPa; its elastic modulus increased by 15.2%, reaching 3.8 GPa; and its water absorption swelling rate further decreased to 6.8%, demonstrating better dimensional stability. Regarding environmental performance, although formaldehyde emissions increased slightly, they remained well below the E0 standard limit, and the veneer loss rate was controlled at a low level of 5.2%, achieving industry-leading overall performance.

Claims

1. A high-stability plywood, characterized by: It comprises a core layer and upper and lower surface layers, the upper and lower surface layers are traditional veneer panels, and the core layer is a 1-layer side-standing multi-layer veneer gluing structure; the side-standing multi-layer veneer of the core layer is formed by continuously shearing a multi-layer plywood material with a pre-pressing solidification degree of 15%-25% into prismatic strips by a disc-type shear, and then reshaping and splicing the prismatic strips.

2. The high-stability plywood according to claim 1, characterized by: The width of the prismatic strips formed by shearing is equal to the thickness of the core layer, and after reshaping, rectangular or square long strips are formed, which are spliced into core layer panels of the required specifications by applying adhesive on both sides.

3. The high-stability plywood according to claim 1, characterized by: The adhesive between the core layer and the upper and lower surface layers is a mixture of oil tea fruit cork powder and urea-formaldehyde resin glue, the particle size of the oil tea fruit cork powder is more than 130 mesh, the water content is 5%-20%, and the weight ratio of the oil tea fruit cork powder in the adhesive is 18%-42%.

4. A method of producing a high-stability plywood according to any one of claims 1 to 3, characterized in that, It comprises the following steps: (1) preparing a multi-layer panel: after drying, the single panel with a water content of 15%-18% is subjected to gluing and pre-pressing treatment, and the pre-pressing solidification degree is controlled to be 15%-25%, thereby obtaining a pre-pressing multi-layer panel; (2) shearing prismatic strips: the pre-pressing multi-layer panel of step (1) is continuously sheared by a disc-type shear, thereby obtaining prismatic strips with a width equal to the thickness of the core layer; (3) splicing the core layer: the prismatic strips of step (2) are reshaped into rectangular or square long strips, adhesive is applied on both sides of the long strips by roller coating, and the long strips are continuously spliced into core layer panels of the required specifications; (4) applying a composite adhesive: the upper and lower surface layers of the core layer panel obtained in step (3) are uniformly coated with an adhesive made of a mixture of oil tea fruit cork powder and urea-formaldehyde resin glue; (5) aging and veneering: the core layer panel coated with the adhesive is subjected to aging treatment, and then traditional veneer panels are overlaid on the upper and lower surface layers, respectively, thereby forming a panel blank; (6) hot pressing: the panel blank is subjected to hot pressing and solidification by using a traditional hot pressing process, thereby obtaining a high-stability plywood.

5. The production method according to claim 4, characterized in that: In step (4), the oil tea fruit cork powder needs to be crushed and sieved to ensure that the particle size is more than 130 mesh, and the water content is adjusted to 5%-20% by drying or natural drying after crushing.

6. The production method according to claim 4, characterized by: In step (1), the adhesive is a mixture of oil tea fruit cork powder and urea-formaldehyde resin glue, the particle size of the oil tea fruit cork powder is more than 200 mesh, the water content is 5%-10%, and the weight ratio of the oil tea fruit cork powder in the adhesive is 15%-20%; in step (1), the pre-pressing treatment is performed at a temperature of 20℃-95℃ and a pressure of 0.4-1.0 MPa.

7. The production method according to claim 4, characterized by: In step (2), the prismatic strips are formed by the transverse cutting force generated by the disc-type shear when shearing the pre-pressing multi-layer panel with a solidification degree of 15%-25%, which causes the pre-glued surface of the pre-pressing multi-layer panel to move.

8. The production method according to claim 4, characterized by: In step (4), the composite adhesive is prepared by adding oil tea fruit cork powder to urea-formaldehyde resin glue at a weight ratio of 18%-42%, and stirring uniformly at 15-30℃ for 10-20 minutes.

9. The production method according to claim 4, characterized by: In step (5), the aging treatment is performed at an ambient temperature of 20-25℃ and a relative humidity of 40%-60% for 15-30 minutes.

10. The production method according to claim 4, characterized by: The parameters of the hot pressing process in step (6) are as follows: hot pressing temperature is 120-150℃, lateral hot pressing pressure is 2.5-4.0MPa, normal hot pressing pressure is 0.3-0.5MPa, and the holding pressure time is 20-30s / mm according to the thickness of the board.