Wood particle veneer plywood and manufacturing method thereof

Abstract

The application discloses a wood particle veneer plywood and a manufacturing method thereof, and belongs to the technical field of plywood preparation. The wood particle veneer plywood is prepared by taking poplar or eucalyptus plywood as a base material and wood particles as a veneer material, and through optimization of unit form, proportion and water content, combination of different glue application modes and interval gradient hot-pressing pressure regulation, compression of the surface wood particle layer and non-compression of the core layer of the plywood are realized, the surface roughness of the plywood is improved, and the problem that the surface of the plywood is difficult to directly veneer is solved; meanwhile, the interface bonding strength between the wood particle layer and the core layer is enhanced, and the technical problem that the wood particle layer and the veneer layer are prone to peeling is solved.

Description

Technical Field

[0001] The invention relates to the technical field of plywood preparation, in particular to a wood particle veneer plywood and a manufacturing method thereof. Background Art

[0002] Plywood is a traditional wood-based panel constructed from rotary-cut veneer sheets. Its solid feel, excellent physical and mechanical properties, and favorable processing properties have made it widely accepted by consumers and the mainstream type of wood-based panel in my country. Currently, the vast majority of plywood requires surface finishing before it can be used in the manufacture and application of household products. However, impregnated paper-veneered plywood (commonly known as eco-board) boasts an attractive, elegant surface, harmonious tones, and heat, wear, and water resistance. It is widely used in furniture, flooring, cabinets, doors, windows, and other home furnishings, as well as decorative and upholstery materials. Currently, the production of veneered wood-based panels exceeds 9 billion square meters, accounting for over 90% of total wood-based panel production.

[0003] More than 70% of my country's plywood is made of fast-growing forest wood, which has problems such as soft base material, many defects, and rough surface. It is impossible to directly carry out melamine impregnated paper or precious tree species veneer veneer. The current process is to first putty-treat the surface and then use sliced ​​veneer or thin fiberboard to press its surface to improve its surface quality to meet the needs of veneer. This process requires that the veneer is free of defects such as knots and decay. However, with the reduction of high-quality wood resources, high-quality rotary cut (sliced) veneer is difficult to meet production needs. Therefore, people have tried to compound a layer of 1.0-3.0mm fiberboard on the upper and lower surfaces of plywood. However, this process has poor impregnation and peeling performance due to the small bonding interface between the fiberboard and the plywood, and usually degumming occurs during use.

[0004] Furthermore, existing processes are complex, difficult to implement continuously, and result in low production efficiency. They also consume significant amounts of energy and materials, resulting in high costs. Product quality is also unstable, with a low pass rate. Achieving continuous production of high-performance, veneer-compatible plywood is crucial for upgrading the wood industry. Summary of the Invention

[0005] In order to solve the problems of low production efficiency and delamination in the plywood finishing process in the prior art, the present invention provides a wood particle veneer plywood and a manufacturing method thereof. The present invention uses poplar or eucalyptus plywood as a base material and wood particles as a covering material. Through a specific pressure application method, the pressure is gradually reduced from the surface layer to the core layer of the plywood, thereby achieving compression of the surface wood particle layer while leaving the core layer of the plywood uncompressed, which is convenient for subsequent finishing and decoration. The present invention also solves the quality defects that have long plagued plywood products, such as delamination, cracking, and surface carbonization, by enhancing the interface bonding strength between the wood particle layer and the core layer.

[0006] To solve the above technical problems, the present application provides technical solutions as follows:

[0007] In one aspect, the present application provides a wood particle veneer plywood, the upper and lower surface layers of which are wood particle layers, and the core layer is composed of wood veneers; the density of the wood particle layer is 0.85-1.15 g / cm 3 , and the thickness is 1.0-5.0 mm; the particle size of the wood particles used in the wood particle layer is shown in the following table:

[0008]

[0009] The thickness of the wood veneer is 1.0-2.0 mm, the number of layers is 5, 7, 9, 11, 13 or 15, and the density is 0.45-0.65 g / cm 3 .

[0010] In another aspect, the present application also provides a preparation method of a wood particle veneer plywood, which consists of the following steps:

[0011] (I) Veneer preparation

[0012] The logs are sawed into wood segments with a length of 1240-1350 mm or 2440-270 mm, and after debarking, the wood segments are rounded, and are then spun into veneers with a thickness of 1-2 mm using a rotary cutting machine, which are then cut into veneers with a length of 600-750 mm or 1200-1300 mm, and then the veneers are dried naturally or by a mesh belt, so that the water content is controlled to be between 6-12%;

[0013] (II) Veneer gluing

[0014] The veneers are uniformly coated with phenolic, urea-formaldehyde melamine or urea-formaldehyde resin on the surface by roller coating, and the glue application amount is 200-250 g / m 2 , the solid content is 62%, and the flour addition amount of the adhesive is 30-40% of flour;

[0015] (III) Veneer assembly

[0016] The 5, 7, 9, 11, 13 or 15 layers of the veneers are assembled in parallel and / or cross structure to obtain a board blank; then, the board blank is pre-pressed by cold pressing, the pre-pressing pressure is 0.8-1.3 MPa, the pre-pressing time is 2-8 h, and the pre-pressing temperature is 5-35℃;

[0017] (IV) Core plate hot pressing

[0018] The board blank of the above step (III) is sent into a hot press for hot pressing, the hot pressing temperature is 110-135℃, the hot pressing time is 0.8-1.5 min / mm, and the hot pressing pressure is 0.8-1.5 MPa.

[0019] (5) Core board thickness determination

[0020] After the slab in step (iv) above is cooled, the hot-pressed slab is sanded using a sanding machine, and the thickness deviation of the sanded slab is controlled within ±0.3mm;

[0021] (6) Core board gluing

[0022] Use roller coating to evenly coat the adhesive phenolic resin, urea-formaldehyde or melamine urea-formaldehyde resin on the upper and lower surfaces of the core board in step (5) with a glue application amount of 150-200g / m 2 The adhesive used is a resin solid content of 58-65%, the amount of flour added to the resin is 30-40% by weight of the glue;

[0023] (7) Wood pellet preparation

[0024] The waste veneers from rounding and the waste veneers left over from cutting are crushed and screened to obtain wood particles with the particle size distribution shown in the table below, and then dried in a drum dryer to a moisture content of 1-3%;

[0025]

[0026] (8) Wood pellet sizing

[0027] The isocyanate is evenly sprayed onto the surface of the wood particles at a spray pressure of 2.5-3.2 MPa. The amount of glue applied is 3-6% of the weight of the wood particles. The amount of tackifier added is 0.7%-1% of the weight of the wood particles. The tackifier is polyethylene glycol. The speed of the glue mixer is 450-550 r / min.

[0028] (9) Wood pellet humidity regulation

[0029] Evenly spray a certain amount of water onto the surface of the wood particles, wherein the amount of water added is 8-15% of the weight of the wood particles;

[0030] (10) Wood particle paving

[0031] The glued wood particles are evenly divided into two parts and enter the paving machine respectively. The bottom layer of wood particles is first paved on the bottom plate conveyor belt using the air paving method with a paving thickness of 1.5-2.0cm. Then the plywood core board is placed on top of the bottom layer of wood particles using a robotic arm. Finally, the other half of the wood particles are also paved on the upper surface of the multilayer board using the air paving method with a paving thickness of 1.5-2.0cm. The belt feed speed is 17-18m / min, which will be adjusted according to production and weather. The slab is pre-pressed using online pre-pressing with a pressure of 3-5MPa; the total thickness of the pre-pressed board is 2.7-2.8cm;

[0032] (11) Hot pressing

[0033] The hot pressing process is the most critical step in new product development and the foundation for a continuous production line. The hot pressing temperature, pressure, and heat transfer oil flow rate directly impact product performance. The pre-pressed sheets are hot pressed for 75 seconds at a temperature of 180-230°C. The pressure is gradually reduced from 480-520 bar to 80-100 bar. After cooling naturally for 8 hours, the sheets are stacked. Both sides are sanded approximately 0.5 mm, with a grit range of 80-100-120-180.

[0034] The wood particles are preferably spindle-shaped with pointed ends; the wood particles are prepared by sawing or cutting.

[0035] Preferably, in the step (eleven), the hot pressing process is specifically: 220-230°C, 480-520 bar, 10-40s; 210°C, 330-240 bar, 15-40s; 190°C, 200-100 bar, 15-40s; 180°C, 100-80 bar, 15-60s.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The present invention employs a layer of wood particles pressed onto the upper and lower surfaces of the core board. The wood particles, like nails, can be embedded into the veneer under pressure, forming a staggered bond and improving the bonding strength between the two. Furthermore, by evenly applying glue to the upper and lower surfaces of the prepared core board and then laying the wood particles on the upper and lower surfaces of the core board, the wood particles in contact with the core board are immersed in the adhesive, coating the surface of the wood particles with a layer of glue. Once embedded in the core layer, the wood particles are more secure and improve the bonding strength. Furthermore, the spindle-shaped structure of the wood particles facilitates their embedding into the core layer under pressure, thereby increasing the bonding strength.

[0038] The surface layer of the present invention is a wood particle layer. The wood particles are small, and their cell walls are significantly damaged during compression, making them easily compressed. The surface layer has a higher moisture content than the core layer, making it more easily compressed. Furthermore, during the compression process, the high temperature increases the plasticizing effect of the adhesive, further making the surface layer more easily compressed. Thus, during the reagent compression process, the initial pressure is high but the duration is short, so the pressure decays in the surface layer and fails to reach the core layer. This achieves an asynchronous compression process in which the surface layer is instantly compressed while the core layer remains uncompressed, resulting in a difference in density between the core and surface layers.

[0039] The plywood prepared by the invention has a relatively high surface density and a relatively low core layer density, has relatively high surface hardness, and has a smooth surface, which is convenient for subsequent finishing and decoration. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the structure of the wood particle plywood prepared in the present invention; wherein 1 is the surface wood particle layer, and 2 is the wood veneer layer;

[0041] Figure 2 This is a picture of the eucalyptus plywood substrate prepared in Example 1;

[0042] Figure 3 This is a picture of the wood reconstructed material prepared in Example 1 after milling, where 1 is the surface of the plywood and 2 is the surface of the wood particle layer. DETAILED DESCRIPTION

[0043] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description will be given below with reference to specific drawings and embodiments.

[0044] In the present invention, the materials and reagents used, unless otherwise specified, can be obtained from commercial sources.

[0045] On the one hand, the present invention provides a wood particle veneer plywood, wherein the upper and lower surface layers of the wood particle veneer plywood are wood particle layers, and the core layer is composed of wood veneer; the density of the wood particle layer is 0.85-1.15g / cm 3 , thickness 1.0-5.0mm; the particle size of the wood particles used in the wood particle layer is shown in the following table:

[0046]

[0047] The wood veneer has a thickness of 1.0-2.0 mm, a number of layers of 5, 7, 9, 11, 13 or 15, and a density of 0.45-0.65 g / cm 3 .

[0048] On the other hand, the present invention also provides a method for preparing a wood particle veneer plywood, comprising the following steps:

[0049] (1) Veneer preparation

[0050] The logs are sawn into wood segments of 1240-1350 mm or 2440-270 mm in length, the wood segments are peeled and rounded, and the wood segments are peeled into veneers with a thickness of 1-2 mm using a peeling machine, which are then cut into veneers of 600-750 mm or 1200-1300 mm. The veneers are then dried naturally or by mesh belt drying to control the moisture content between 6-12%;

[0051] (2) Gluing of veneer

[0052] The veneer is coated evenly on the surface of the veneer by roller coating method, with phenolic, urea-formaldehyde melamine or urea-formaldehyde resin, and the amount of glue applied is 200-250g / m2 , solid content 62%, the flour addition amount of the adhesive is 30-40% flour;

[0053] (3) Single plate assembly

[0054] Assembling 5, 7, 9, 11, 13 or 15 layers of the veneer in a parallel and / or cross structure; then pre-pressing the slab by cold pressing at a pre-pressing pressure of 0.8-1.3 MPa, a pre-pressing time of 2-8 hours and a pre-pressing temperature of 5-35° C.

[0055] (4) Core board hot pressing

[0056] The slab is sent to a hot press for hot pressing at a temperature of 110-135°C, a time of 0.8-1.5 min / mm, and a pressure of 0.8-1.5 MPa.

[0057] (5) Core board thickness determination

[0058] After the slab is cooled, the hot-pressed slab is sanded using a sanding machine, and the thickness deviation of the sanded slab is controlled within ±0.3mm;

[0059] (6) Core board gluing

[0060] Use roller coating to evenly coat the adhesive phenolic resin, urea-formaldehyde or melamine urea-formaldehyde resin on the upper and lower surfaces of the core board in step (5) with a glue application amount of 150-200g / m 2 The adhesive used is a resin solid content of 58-65%, the amount of flour added to the resin is 30-40% by weight of the glue

[0061] (7) Wood pellet preparation

[0062] The waste veneers from rounding and the waste veneers left over from cutting are crushed and screened to obtain wood particles with the particle size distribution shown in the table below, and then dried in a drum dryer to a moisture content of 1-3%;

[0063]

[0064] (8) Wood pellet sizing

[0065] Spray isocyanate evenly onto the surface of the wood particles at a spray pressure of 2.5-3.2 MPa, with a glue application amount of 3-6% of the weight of the wood particles and a tackifier addition amount of 0.7%-1% of the weight of the wood particles; the speed of the glue mixer is 450-550 r / min;

[0066] (9) Wood pellet humidity regulation

[0067] Spray a certain amount of water evenly on the surface of the wood particles, and the amount of water added is 8-15% of the weight of the wood particles;

[0068] (X) Wood particle paving

[0069] The glued wood particles are evenly divided into two parts and respectively enter the paving machine. The bottom layer of wood particles is paved in the bottom plate conveying belt by using air flow paving method, and the paving thickness is 1.5-2.0 cm. Then, the plywood core plate is placed above the bottom layer of wood particles by using a mechanical arm. Finally, the other half of the wood particles is also paved on the upper surface of the multi-layer board by using air flow paving method, and the paving thickness is 1.5-2.0 cm. The belt feeding speed is 17-18 m / min, which will be adjusted according to the yield and weather. The board blank is pre-pressed by using online pre-pressing, and the pressure is 3-5 MPa. The total thickness of the pre-pressed board is 2.7-2.8 cm.

[0070] (XI) Hot pressing

[0071] Hot pressing is the most important link in the development process of new products, and is the basis for the continuous production line. Hot pressing temperature, pressure and heat conduction oil speed will directly affect the performance of the product. The above pre-pressed board is hot pressed, the hot pressing time is 75 s, the hot pressing temperature is 180-230℃, the pressure is gradually reduced from 480-520 bar to 80-100 bar, and then naturally cooled for 8 h, and then stacked. The amount of double-sided sanding is about 0.5 mm, and the sanding mesh is 80-100-120-180 mesh.

[0072] Preferably, in step (XI), the hot pressing process is specifically: 220-230℃, 480-520 bar, 10-40 s; 210℃, 330-240 bar, 15-40 s; 190℃, 200-100 bar, 15-40 s; 180℃, 100-80 bar, 15-60 s.

[0073] The specific implementation is as follows.

[0074] Example 1

[0075] A preparation method of a wood particle veneer plywood, comprising:

[0076] Plywood preparation

[0077] Eucalyptus is prepared into veneer, and then glued, assembled, hot pressed and thicknessed to obtain a plywood with a water content of 6%; Specifically:

[0078] (1) Veneer preparation: Eucalyptus wood was sawn into 1240 mm long segments, the segments were peeled and rounded, and the segments were peeled into 1.5 mm thick veneers using a peeling machine, which were then cut into 600 mm veneers. The veneers were then dried naturally or by mesh belt drying to control the moisture content to 8%;

[0079] (2) Gluing of veneer: The veneer is coated with phenolic resin evenly on the surface of the veneer by roller coating method, and the amount of glue applied is 220g / m 2 , the solid content of phenolic resin is 62%, and the flour addition amount of the adhesive is 30% of flour;

[0080] (3) Single plate assembly

[0081] Assembling 7 layers of the single sheets in a parallel and / or cross structure to obtain a slab; then pre-pressing the slab by cold pressing at a pre-pressing pressure of 1 MPa, a pre-pressing time of 4 hours, and a pre-pressing temperature of 35° C.

[0082] (4) Plywood hot pressing

[0083] The slab from step (3) was sent to a hot press for hot pressing at a temperature of 120°C, a time of 0.8 min / mm, and a pressure of 1 MPa.

[0084] (5) Plywood thickness determination

[0085] After the slab from step (IV) above is cooled, a sanding machine is used to sand the hot pressed slab. The thickness deviation of the sanded slab is controlled within ±0.3mm. See the plywood picture for details. Figure 2 ;

[0086] (6) Plywood Gluing

[0087] Use roller coating to evenly apply the adhesive phenolic resin on the upper and lower surfaces of the plywood. The amount of glue applied is 150g / m 2 ; The adhesive used is a resin solid content of 62%, the resin flour added in an amount of 35% by weight of the glue;

[0088] (7) Wood pellet preparation

[0089] The waste veneers from rounding and the waste veneers left over from cutting were crushed and screened to obtain wood pellets with the particle size distribution shown in the table below. The wood pellets were sawn to form spindle-shaped knots with pointed ends and then dried in a drum dryer to obtain wood pellets with a moisture content of 1%.

[0090]

[0091] (8) Wood Particle Gluing

[0092] Isocyanate was evenly sprayed onto the surface of the wood particles at a spray pressure of 2.5 MPa. The amount of glue applied was 3% of the weight of the wood particles, and the amount of polyethylene glycol added as a tackifier was 0.7% of the weight of the wood particles. The speed of the glue mixer was 450 r / min.

[0093] (9) Wood pellet humidity regulation

[0094] Evenly spraying a certain amount of water onto the surface of the wood particles, the amount of water added being 8% of the weight of the wood particles;

[0095] (10) Wood particle paving

[0096] The glued wood particles are divided into two equal parts and fed into the paving machine respectively. The bottom layer of wood particles is first laid on the bottom conveyor belt using the air paving method with a paving thickness of 1.5 cm. Then the plywood is placed on top of the bottom layer of wood particles using a robotic arm. Finally, the other half of the wood particles are also laid on the upper surface of the multi-layer board using the air paving method with a paving thickness of 1.5 cm. The belt feed speed is 17 m / min. The slab is pre-pressed using online pre-pressing with a pressure of 5 MPa. The total thickness of the pre-pressed board is 2.7 cm.

[0097] (11) Hot pressing

[0098] The pre-pressed plate was hot pressed for 100 seconds. The hot pressing process was as follows: 230°C, 480 bar, 20 seconds; 210°C, 300 bar, 20 seconds; 190°C, 150 bar, 30 seconds; 180°C, 80 bar, 30 seconds, and then naturally cooled.

[0099] The prepared wood particle veneer plywood is milled on its surface. Figure 3 In this embodiment, wood particle layers are successfully laid on the upper and lower surfaces of the substrate, as shown in the schematic diagram. Figure 1 shown.

[0100] Example 2

[0101] A method for preparing a wood particle veneer plywood, comprising:

[0102] (1) The plywood preparation method is the same as in Example 1;

[0103] The poplar wood is prepared into veneers, which are then glued, assembled, hot-pressed, and thickness-set to obtain plywood with a moisture content of 8%. Specifically:

[0104] Steps (1) to (5) The other plywood manufacturing methods are the same as those in Example 1;

[0105] (6) Plywood Gluing

[0106] Use roller coating to evenly apply the adhesive phenolic resin on the upper and lower surfaces of the plywood. The amount of glue applied is 150g / m 2 ; The adhesive used is a resin solid content of 62%, the resin flour added in an amount of 35% by weight of the glue;

[0107] (7) Wood pellet preparation

[0108] The waste veneers from rounding and the waste veneers left over from cutting are crushed and screened to obtain wood pellets with the particle size distribution shown in the table below. The wood pellets are sawn to form spindle-shaped knots with pointed ends and are dried in a drum dryer to obtain wood pellets with a moisture content of 3%.

[0109]

[0110]

[0111] (8) Wood Particle Gluing

[0112] Isocyanate was evenly sprayed onto the surface of the wood particles at a spray pressure of 3.2 MPa. The amount of glue applied was 6% of the weight of the wood particles, and the amount of polyethylene glycol added as a tackifier was 1% of the weight of the wood particles. The speed of the glue mixer was 550 r / min.

[0113] (9) Wood pellet humidity regulation

[0114] Evenly spraying a certain amount of water onto the surface of the wood particles, the amount of water added being 15% of the weight of the wood particles;

[0115] (10) Wood particle paving

[0116] The glued wood particles are divided into two equal parts and fed into the paving machine respectively. The bottom layer of wood particles is first laid on the bottom conveyor belt using the air paving method with a paving thickness of 2.0 cm. Then the plywood is placed on top of the bottom layer of wood particles using a robotic arm. Finally, the other half of the wood particles are also laid on the upper surface of the multi-layer board using the air paving method with a paving thickness of 2.0 cm. The belt feed speed is 18 m / min. The slab is pre-pressed using online pre-pressing with a pressure of 5 MPa. The total thickness of the pre-pressed board is 2.8 cm.

[0117] (11) Hot pressing

[0118] The pre-pressed plate was hot pressed for 75 seconds. The hot pressing process was as follows: 220°C, 520 bar, 10 seconds; 210°C, 330 bar, 15 seconds; 190°C, 200 bar, 20 seconds; and 180°C, 100 bar, 30 seconds.

[0119] Example 3

[0120] A method for preparing a wood particle veneer plywood, comprising:

[0121] (1)-(5) The plywood preparation method is the same as that in Example 2;

[0122] (6) The plywood gluing method is the same as in Example 1;

[0123] (7) Wood pellet preparation

[0124] The waste veneers from rounding and the waste veneers left over from cutting were crushed and screened to obtain wood pellets with the particle size distribution shown in the table below. The wood pellets were sawn to form spindle-shaped knots with pointed ends and then dried in a drum dryer to obtain wood pellets with a moisture content of 2%.

[0125]

[0126] (8) The method of applying glue to wood particles is the same as in Example 1;

[0127] (9) The method for adjusting the humidity of wood particles is the same as in Example 1;

[0128] (10) The wood particle paving method is the same as in Example 1;

[0129] (11) Hot pressing

[0130] The pre-pressed plate was hot pressed for 75 seconds. The hot pressing process was as follows: 230°C, 480 bar, 25 seconds; 210°C, 240 bar, 15 seconds; 190°C, 100 bar, 15 seconds; and 180°C, 80 bar, 20 seconds.

[0131] In order to further illustrate the beneficial effects of the present invention, a comparative example is constructed as follows.

[0132] Comparative Example 1

[0133] In step (9) of this comparative example, the amount of water added is 2% of the weight of the wood particles; the other conditions are the same as those in Example 2.

[0134] Comparative Example 2

[0135] Step (XI) of this comparative example is specifically as follows: hot pressing the pre-pressed plate for 75 seconds at a temperature of 180° C. and a pressure of 520 bar, followed by natural cooling; the remaining conditions are the same as those of Example 2.

[0136] Comparative Example 3

[0137] Step (XI) of this comparative example is specifically as follows: hot pressing the pre-pressed plate for 75 seconds at a temperature of 180° C. and a pressure of 100 bar, followed by natural cooling; the remaining conditions are the same as those of Example 2.

[0138] The wood particle veneer plywood prepared in the above Examples 1-3 and Comparative Examples 1-3 was then subjected to performance testing, and the relevant tests and results are as follows.

[0139] 1. Density

[0140] The wood particle veneer plywood prepared in the above Examples 1-3 was subjected to cross-sectional density testing, and the results are shown in Table 1. The plywood substrates prepared in the corresponding examples were used as controls.

[0141] Table 1

[0142]

[0143] As can be seen from Table 1, the core veneers of Examples 1, 2 and 3 are basically the same as the plywood substrates, while the surface layers are significantly compressed and densified, achieving asynchronous compression of the surface layer and the core layer. The surface layer of Comparative Example 1 has a low moisture content, and the compression rate is significantly lower than that of Example 1, while the core layer also shows significant compression; in Comparative Example 2, the core layer and the surface layer are synchronously compressed under high pressure; and in Comparative Example 3, the surface layer does not meet the requirements for densification due to insufficient pressure.

[0144] 2. Static bending strength and modulus

[0145] The static bending strength and modulus were tested in accordance with the static bending strength and modulus (three-point bending method) in GB / T 17657-2013 "Test methods for physical and mechanical properties of wood-based panels and veneer-based panels", and the results are shown in Table 2.

[0146] Table 2

[0147]

[0148] As can be seen from Table 2, the static bending strength and modulus of the wood particle veneer plywood prepared in the present application are lower than those of the plywood substrates.

[0149] 3. Water absorption thickness swelling rate

[0150] The water absorption thickness swelling rate was tested in accordance with the water absorption thickness swelling rate - Method 1 in GB / T 17657-2013 "Test methods for physical and mechanical properties of wood-based panels and veneer-based panels", and the results are shown in Table 3.

[0151] Table 3

[0152] Material Category Thickness expansion rate after water absorption (%) Example 1 Eucalyptus plywood substrate 5.35 Example 1 8.95 Example 2 Poplar plywood substrate 6.35 Example 2 7.75 Example 3 Poplar plywood substrate 6.35 Example 3 8.10 Comparative Example 1 18.89 Comparative Example 2 12.56 Comparative Example 3 7.37

[0153] As can be seen from Table 3, the water absorption thickness swelling rate of the boards of Examples 1, 2 and 3 of the present application is less than 10%.

[0154] 4. Immersion peel performance

[0155] The immersion and peeling performance test method was carried out with reference to the Class II immersion and peeling test in GB / T17657-2013 “Test methods for physical and chemical properties of wood-based panels and veneered wood-based panels”. The results are shown in Table 4.

[0156] Table 4

[0157] Material Category Wood particle layer and veneer layer Example 1 Eucalyptus plywood substrate -- Example 1 Not stripped Example 2 Poplar plywood substrate -- Example 2 Not stripped Example 3 Poplar plywood substrate -- Example 3 Not stripped Comparative Example 1 peeling Comparative Example 2 peeling Comparative Example 3 Surface shedding

[0158] As can be seen from Table 4, the wooden particle layer laid on the surface of the plywood using the method of the present invention has good bonding performance with the plywood. After the immersion peeling test, it was found that no peeling occurred. However, the boards prepared in Comparative Examples 1-3 all showed surface shedding or peeling.

[0159] The present invention uses plywood as a base material and wood particles as a covering material. Wood particle layers are pressed on the upper and lower surfaces of the plywood, which can be embedded in the veneer under pressure to form a staggered bond, thereby improving the bonding strength of the two. Glue is evenly applied on the upper and lower surfaces of the prepared plywood, and then wood particles are laid on the upper and lower surfaces of the plywood, which is equivalent to applying a layer of glue on the surface of the wood particles. After being embedded in the plywood, the firmness is better, the bonding strength is improved, and the immersion peeling strength between the wood particle layer and the veneer layer reaches the immersion peeling performance of Class II boards.

[0160] In summary, the present invention uses poplar or eucalyptus plywood as the base material and wood particles as the covering material. Through a specific pressure application method, the pressure decreases from the surface layer to the core layer of the plywood, thereby achieving compression of the surface wood particle layer while the core layer of the plywood is not compressed, thereby solving the quality defects that have long plagued plywood products, such as rough surface, debonding, cracking, and surface carbonization.

[0161] The above is a preferred embodiment of the present invention. For ordinary technicians in this technical field, making several improvements and modifications without departing from the principles of the present invention should also be considered as the scope of protection of the present invention.

Claims

1. A method for preparing wood particle veneer plywood, characterized in that: It consists of the following steps: (1) Veneer preparation Saw the logs into wood segments, peel the wood segments into veneers with a thickness of 1-2 mm, and then dry the veneers to a moisture content of 6-12%; (2) Gluing of veneer Apply the adhesive evenly on the surface of the veneer prepared in step (1) with an application amount of 200-250g / m 2 ; (3) Single plate assembly The slabs are assembled in a parallel and / or cross structure to obtain slabs; then, the slabs are pre-pressed by cold pressing at a pre-pressing pressure of 0.8-1.3 MPa, a pre-pressing time of 2-8 hours, and a pre-pressing temperature of 5-35° C. (4) Core board hot pressing The slab from step (3) is fed into a hot press for hot pressing at a temperature of 110-135°C, a time of 0.8-1.5 min / mm, and a pressure of 0.8-1.5 MPa. (5) Core board thickness determination After the slab in step (4) is cooled, the hot-pressed slab is sanded using a sanding machine; (6) Wood pellet preparation The waste veneers from rounding and the waste veneers left over from cutting are crushed and screened to obtain wood particles with the particle size distribution shown in the table below, and then dried in a drum dryer to a moisture content of 1-3%; (7) Wood Particle Gluing Spray isocyanate evenly onto the surface of the wood particles at a spray pressure of 2.5-3.2 MPa, with a glue application amount of 3-6% of the weight of the wood particles and a tackifier addition amount of 0.7%-1% of the weight of the wood particles; the speed of the glue mixer is 450-550 r / min; (8) Wood pellet humidity regulation Evenly spray a certain amount of water onto the surface of the wood particles, wherein the amount of water added is 8-15% of the weight of the wood particles; (9) Wood particle paving The wood pellets from step (eight) are divided into two parts, each of which enters a paving machine. The bottom layer of wood pellets is first paved on the bottom plate conveyor belt using the air paving method to a thickness of 1.5-2.0 cm, and then the core plate is placed on top of the bottom layer of wood pellets. Finally, the other half of the wood pellets are also paved on the upper surface of the core plate using the air paving method to a thickness of 1.5-2.0 cm. The slab is pre-pressed using online pre-pressing at a pressure of 3-5 MPa. (10) Hot pressing The pre-pressed board is hot-pressed for 60-150 seconds at a temperature of 180-230° C. The pressure is gradually reduced from 480-520 bar to 80-100 bar, and then naturally cooled for 8 hours to obtain a wood particle veneer plywood.

2. The method for preparing wood particle veneer plywood according to claim 1, characterized in that: In the step (10), the hot pressing process is specifically as follows: 220-230°C, 480-520 bar, 10-40 seconds; 210°C, 330-240 bar, 15-40 seconds; 190°C, 200-100 bar, 15-40 seconds; 180°C, 100-80 bar, 15-60 seconds.

3. The method for preparing wood particle veneer plywood according to claim 1, characterized in that: The step (1) specifically comprises: sawing the logs into wood segments of 1240-1350 mm or 2440-270 mm in length, peeling the wood segments, rounding them, using a peeling machine to peel the wood segments into veneers with a thickness of 1-2 mm, cutting them into veneers of 600-750 mm or 1200-1300 mm, and then drying the veneers naturally or using a mesh belt drying method to control the moisture content between 6-12%.

4. The method for preparing wood particle veneer plywood according to claim 1, characterized in that: In the step (2), the adhesive is phenolic resin, melamine urea-formaldehyde resin or urea-formaldehyde resin, the solid content of the adhesive is 62%, and the amount of flour added is 30-40% of the weight of the adhesive.

5. The method for preparing wood particle veneer plywood according to claim 1, characterized in that: The step (5) further includes a core board gluing step, specifically: applying adhesive phenolic resin, urea-formaldehyde resin or melamine urea-formaldehyde resin evenly on the upper and lower surfaces of the core board in step (5), with a gluing amount of 150-200g / m 2 The resin solid content in the adhesive is 58-65%, and the flour addition amount is 30-40% of the adhesive liquid weight.

6. The method for preparing wood particle veneer plywood according to claim 1, characterized in that: The wood particle facing plywood is double-sided sanded when in use, the sanding amount is 0.5 mm, and the sanding mesh numbers are 80 mesh, 100 mesh, 120 mesh, and 180 mesh in sequence.

7. A wood particle veneer plywood, characterized in that: Prepared by the method according to any one of claims 1 to 6; the upper and lower surface layers of the wood particle veneer plywood are wood particle layers, and the core layer is composed of wood veneer; the density of the wood particle layer is 0.85-1.15g / cm 3 , thickness 1.0-5.0mm; the wood veneer thickness is 1.0-2.0mm, the number of layers is 5, 7, 9, 11, 13 or 15 layers, and the density is 0.45-0.65g / cm 3 .

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