An asynchronous compression molding method for a wood reconstituted material core layer

Abstract

The application discloses a kind of wood recombination material surface core layer asynchronous compression forming method, belong to wood recombination material preparation technical field.The above-mentioned method is with plywood as base material, with wood particle as covering material, to wood particle gluing, and then adjust its humidity, then wood particle is laid on the upper and lower surfaces of base material and pre-presses, then the pre-pressed board is hot-pressed, hot-pressing time 60-150s, hot-pressing temperature 180-230 DEG C, pressure is segmented from 480-520bar and reduced to 80-100bar, finally, after natural cooling, obtain wood recombination material.The pressure is gradually reduced from surface layer to core layer plywood by specific pressure mode, the compression of surface wood particle layer is realized, and the core layer plywood is not compressed, the surface density of the obtained wood recombination material is larger, and the surface is smooth, can be routed, and is convenient for subsequent finishing decoration.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wood recombination material preparation, in particular to a wood recombination material surface-core layer asynchronous compression forming method. BACKGROUND

[0002] Wood recombination material is a new type of high-performance wood material made of abundant man-made forest wood in China as the main raw material through directional recombination processing technology, which has good solid wood feeling, excellent physical and mechanical properties and good processing performance, and is widely used in furniture, floor, cabinet, door and window manufacturing and decoration materials. With the rapid development of customized furniture, whole house customization, wall integration and other industries, wood recombination material has wide application prospect. At present, the output of veneered wood-based panels exceeds 9 billion square meters, accounting for more than 90% of the output of wood-based panels.

[0003] More than 70% of the plywood in China is made of fast-growing wood such as poplar and eucalyptus, which is rotary cut into 4-8mm single-width and 1mm-2mm thin veneer, glued and pressed into board blanks. Due to the softness, defects and roughness of eucalyptus and poplar, etc. Figure 1 As shown in FIG. 1, when the compression ratio is small, such as the production of plywood or laminated veneer lumber, the surface quality is difficult to directly paint, impregnate with melamine paper or veneer with thin wood of precious tree species; and when the compression ratio is large, such as the production of recombination wood, the density is generally greater than 0.85g / cm 3 , and some even reach 1.30g / cm 3 . This product structure usually causes problems such as high cost, large material waste and excessive product performance. SUMMARY

[0004] In order to solve the surface veneering problem of the existing technology, the present application provides a wood recombination material surface-core layer asynchronous compression forming method. In the present application, poplar or eucalyptus plywood is used as the base material, and wood particles are used as the covering material. By setting different units of the surface and core layers, the compression performance of the surface wood particles is better than that of the core veneer. Furthermore, by controlling the moisture content and pressing method of the surface and core layers, the surface wood particle layer is compressed and the core plywood is not compressed, obtaining a wood recombination material with a larger surface density and a smooth surface, which is convenient for subsequent veneering and decoration, as shown in FIGS. 2 and 3. Figure 2 and Figure 3

[0005] To solve the above technical problems, the technical scheme of the present application is as follows:

[0006] The present application provides a wood recombination material surface-core layer asynchronous compression forming method, which comprises the following steps:

[0007] (I) Core plate preparation ​

[0008] The raw wood is prepared into veneer, then glued, assembled, hot-pressed and fixed thickness to obtain a core board with water content of 6-12%;

[0009] (II) Preparation of wood particles

[0010] The waste veneer is crushed by a pulverizer, and then processed into wood particles with a size of 40-200 mesh after screening, and dried by a roller dryer to a water content of 1-3%;

[0011] (III) Gluing of wood particles

[0012] The isocyanate is uniformly sprayed onto the surface of the wood particles, and the amount of glue is 3-6% of the weight of the wood particles;

[0013] (IV) Humidity adjustment of wood particles

[0014] A certain amount of water is uniformly sprayed onto the surface of the wood particles, and the amount of water added is 8-15% of the weight of the wood particles;

[0015] (V) Wood particle laying

[0016] The wood particles of step (IV) are divided into two parts and respectively enter the laying machine. The bottom layer of wood particles is laid in the bottom plate conveying belt by air laying method, and the laying thickness is 1.5-2.0 cm. Then the core board is placed above the bottom layer of wood particles. Finally, the other half of the wood particles is also laid on the upper surface of the core board by air laying method, and the laying thickness is 1.5-2.0 cm. The board blank is pre-pressed by online pre-pressing, and the pressure is 3-5 MPa;

[0017] (VI) Hot pressing

[0018] The 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 in stages, and then naturally cooled to obtain a wood reconstituted material.

[0019] Preferably, in step (VI), 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.

[0020] Preferably, in step (III), the spraying pressure is 2.5-3.2 MPa, and the amount of tackifier added is 0.7%-1% of the weight of the wood particles.

[0021] Further, the upper and lower surfaces of the core board are evenly glued by using the adhesive, the solid content of the adhesive is 58-65%, and the gluing amount is 150-200g / m 2 The flour addition amount of the adhesive is 30-40% of the weight of the adhesive solution.

[0022] Further, the wood recombination material can be double-sanded when used, the sanding amount is 0.5mm, and the sanding mesh number is 80, 100, 120 and 180 in sequence.

[0023] Further, the core board can be prepared by the following method:

[0024] Preparation of the veneer: the logs are sawed into wood segments with a length of 1240-1350mm or 2440-270mm, after peeling, the wood segments are rounded, and the wood segments are rotary cut into veneers with a thickness of 1-2mm by using a rotary cutting machine, and the veneers are cut into 600-750mm or 1200-1300mm, and then the veneers are naturally dried and web belt dried, and the water content is controlled to be between 6-12%;

[0025] Gluing of the veneer: the veneer is evenly coated with phenolic, urea-formaldehyde, melamine or urea-formaldehyde resin by using a roller coating method, the gluing amount is 200-250g / m 2 , the solid content is 62%, and the flour addition amount of the adhesive is 30-40% of the flour;

[0026] Assembling of the veneer: 5, 7, 9, 11, 13 or 15 layers of the veneer are assembled in parallel and / or cross structure; then, the board blank is pre-pressed by using cold pressing, the pre-pressing pressure is 0.8-1.3MPa, the pre-pressing time is 2-8h, and the pre-pressing temperature is 5-35℃;

[0027] Hot pressing of the core board: the above board blank is sent into a hot press for hot pressing, the hot pressing temperature is 110-135℃, the hot pressing time is 0.8-1.5min / mm, and the hot pressing pressure is 0.8-1.5MPa;

[0028] Thickness determination of the core board: after cooling of the above board blank, the hot-pressed board blank is sanded by using a sander, and the thickness deviation of the sanded board blank is controlled to be ±0.3mm.

[0029] Compared with the prior art, the present application has the following beneficial effects:

[0030] The surface layer of the present application is a wood particle layer, the wood particles are small, the cell wall is largely destroyed, and it is easy to be compressed; the moisture content of the surface layer is higher than that of the core layer, and it is also easier to be compressed. In this way, during the reagent compression process, the initial pressure is larger, but the duration is shorter, and the pressure decays in the surface layer and cannot reach the core layer, realizing the asynchronous compression forming of the surface layer being compressed instantaneously and the core layer not being compressed, so that the density of the core layer and the surface layer is different, the surface layer is denser, and it is convenient for the subsequent attachment of the decorative panel. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 Picture of eucalyptus plywood substrate prepared in Example 1;

[0032] Figure 2 Picture of wood reconstituted material after milling prepared in Example 1, wherein 1 is the surface of the plywood, and 2 is the surface of the wood particle layer;

[0033] Figure 3 Picture of wood reconstituted material prepared in Example 1;

[0034] Figure 4 Surface layer wood particle electron microscope picture of wood reconstituted material prepared in Example 1, wherein D is a transverse section, and D1 is a radial section;

[0035] Figure 5 Core layer wood veneer electron microscope picture of wood reconstituted material prepared in Example 1, wherein A is a transverse section, and A1 is a radial section. DETAILED DESCRIPTION

[0036] To make the technical problems, technical solutions and advantages to be solved by the present application more clear, specific embodiments and examples will be described in detail below.

[0037] In the present application, the materials and reagents used are commercially available if not otherwise specified.

[0038] The present application provides a wood reconstituted material surface-core layer asynchronous compression forming method, which consists of the following steps:

[0039] (I) Core plate preparation

[0040] The raw wood is prepared into veneer, and then glued, assembled, hot-pressed and thicknessed to obtain a core plate with a moisture content of 6-12%;

[0041] (II) Wood particle preparation

[0042] The waste veneer is crushed by a pulverizer, and then processed into wood particles with a size of 40-200 after screening, and dried by a roller dryer to a moisture content of 1-3%;

[0043] (III) Wood particle gluing

[0044] The isocyanate is sprayed evenly on the surface of the wood particles, and the glue application amount is 3-6% of the weight of the wood particles;

[0045] (iv) Wood particle humidity adjustment

[0046] A certain amount of water is sprayed evenly on the surface of the wood particles, and the water addition amount is 8-15% of the weight of the wood particles;

[0047] (v) Wood particle paving

[0048] The wood particles of step (iv) are 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 core plate is placed above the bottom layer of wood particles. Finally, the other half of the wood particles is also paved on the upper surface of the core plate by using air flow paving method, and the paving thickness is 1.5-2.0 cm. The board blank is pre-pressed by using online pre-pressing, and the pressure is 5 MPa.

[0049] (vi) Hot pressing

[0050] The pre-pressed board is hot pressed, the hot pressing time is 75 s, the hot pressing temperature is 180-230℃, the pressure is segmentedly reduced from 480-520 bar to 80-100 bar, and then naturally cooled to obtain the wood reconstituted material.

[0051] Preferably, in step (vi), 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.

[0052] Preferably, in step (iii), the spraying pressure is 2.5-3.2 MPa, and the tackifier addition amount is 0.7%-1% of the weight of the wood particles.

[0053] Further, the upper and lower surfaces of the core plate are evenly glued with adhesive, the adhesive is resin with solid content of 58-65%, the glue application amount is 150-200 g / m 2 , and the flour addition amount of the resin is 30-40% of the weight of the glue solution.

[0054] Further, the wood reconstituted material can be double sanded when used, the sanding amount is 0.5 mm, and the sanding mesh number is 80 mesh, 100 mesh, 120 mesh and 180 mesh in turn.

[0055] The specific implementation is as follows.

[0056] Example 1

[0057] A wood recombination material core layer asynchronous compression forming method, comprising:

[0058] (I) plywood preparation

[0059] The eucalyptus wood is prepared into veneers, and then glued, assembled, hot-pressed, and thicknessed to obtain a plywood with a water content of 6%; specifically:

[0060] Veneer preparation: the eucalyptus wood is sawed into wood segments with a length of 1240 mm, and after debarking, the wood segments are rounded, and the wood segments are rotary cut into veneers with a thickness of 1.5 mm using a rotary cutting machine, which are cut into 600 veneers, and then the veneers are naturally dried and belt dried to control the water content to 8%;

[0061] Veneer gluing: the veneers are uniformly coated with phenolic resin on the surface by roller coating, and the glue application amount is 220 g / m 2 ; the solid content of the phenolic resin is 62%, and the flour addition amount of the adhesive is 30% of the flour;

[0062] Veneer assembly: 7 layers of the veneers are assembled in parallel and / or cross structure; then, the veneer assembly is pre-pressed by cold pressing, the pre-pressing pressure is 1 MPa, the pre-pressing time is 4 h, and the pre-pressing temperature is 35℃;

[0063] Plywood hot pressing: the above veneer assembly is sent into a hot press for hot pressing, the hot pressing temperature is 120℃, the hot pressing time is 0.8 min / mm, and the hot pressing pressure is 1 MPa;

[0064] Plywood thicknessing: after cooling, the hot-pressed veneer assembly is sanded by a sander, and the thickness deviation of the sanded veneer assembly is controlled within ±0.3 mm, see Figure 1 ;

[0065] Plywood gluing: the adhesive phenolic resin is uniformly coated on the upper and lower surfaces of the plywood by roller coating, and the glue application amount is 150 g / m 2 ; the solid content of the adhesive is 62%, and the flour addition amount of the resin is 35% of the weight of the glue solution;

[0066] (II) wood particle preparation

[0067] The waste veneers during rounding and the waste veneers remaining during cutting are processed into wood particles with the particle size distribution in the following table after crushing and screening, the wood particles are obtained by sawing into a shuttle-shaped knot with two pointed ends, and are dried by a roller dryer to obtain wood particles with a water content of 1%;

[0068]

[0069]

[0070] (Three) wood particle sizing

[0071] The isocyanate is evenly sprayed onto the surface of the wood particles, the spraying pressure is 2.5 MPa, the sizing amount is 3% of the weight of the wood particles, the tackifier addition amount is 0.7% of the weight of the wood particles; the rotation speed of the sizing machine is 450 r / min; the tackifier is polyethylene glycol;

[0072] (Four) wood particle humidity adjustment

[0073] A certain amount of water is evenly sprayed onto the surface of the wood particles, and the water addition amount is 8% of the weight of the wood particles;

[0074] (Five) wood particle paving

[0075] The sized wood particles are evenly divided into two parts and respectively enter the paving machine, the airflow paving method is used to pave the bottom layer of wood particles in the bottom plate conveying belt, and the paving thickness is 1.5 cm, then the mechanical arm is used to place the plywood above the bottom layer of wood particles. Finally, the other half of the wood particles is also paved on the upper surface of the multi-layer board by using the airflow paving method, and the paving thickness is 1.5 cm. The belt feeding speed is 17 m / min. The board blank is pre-pressed by using online pre-pressing, and the pressure is 5 MPa; the total thickness of the pre-pressed board is 2.7 cm;

[0076] (Six) hot pressing

[0077] The above pre-pressed board is hot pressed, the hot pressing time is 100 s, and the hot pressing process is as follows: 230℃, 480bar, 20s; 210℃, 300bar, 20s; 190℃, 150bar, 30s; 180℃, 80bar, 30s, and then natural cooling.

[0078] The prepared wood recombination material is shown in Figures 2-3 , and Figures 2-3 It can be seen that the surface of the prepared wood recombination material is relatively smooth and can be milled. From Figures 4-5 It can be seen that the surface layer of the wood recombination material prepared by the present application has fewer pores and is compressed to a large extent; the core board has more pores and is not compressed.

[0079] Example 2

[0080] A wood recombination material surface core layer asynchronous compression forming method, comprising:

[0081] (One) poplar is prepared into a veneer, and then sizing, assembling, hot pressing, sizing, and a plywood with a water content of 8% are obtained; specifically:

[0082] Other plywood manufacturing methods are the same as those in Example 1;

[0083] (II) Wood particle preparation

[0084] The waste single board during the rounding and the waste single board remaining during the cutting are crushed and sieved to obtain the wood particles with the particle size distribution in the following table. The wood particles are obtained by sawing, are in the shape of a shuttle with two pointed ends, and are dried by a roller dryer to obtain wood particles with a water content of 3%;

[0085]

[0086] (III) Wood particle sizing

[0087] The isocyanate is uniformly sprayed onto the surface of the wood particles, the spraying pressure is 3.2 MPa, the sizing amount is 6% of the weight of the wood particles, and the tackifier addition amount is 1% of the weight of the wood particles; the rotation speed of the glue mixer is 550 r / min;

[0088] (IV) Wood particle humidity adjustment

[0089] A certain amount of water is uniformly sprayed onto the surface of the wood particles, and the water addition amount is 15% of the weight of the wood particles;

[0090] (V) Wood particle laying

[0091] The sized wood particles are evenly divided into two parts and respectively enter the laying machine. The airflow laying method is used to lay the bottom layer of wood particles in the bottom plate conveying belt, and the laying thickness is 2.0 cm. Then, the plywood is placed above the bottom layer of wood particles by using a mechanical arm. Finally, the other half of the wood particles is also laid on the upper surface of the multi-layer board by using the airflow laying method, and the laying thickness is 2.0 cm. The belt feeding speed is 18 m / min. The board blank is pre-pressed by using online pre-pressing, and the pressure is 5 MPa. The total thickness of the pre-pressed board is 2.8 cm;

[0092] (VI) Hot pressing

[0093] The pre-pressed board is hot pressed, and the hot pressing time is 75 s. The hot pressing process is as follows: 220℃, 520 bar, 10 s; 210℃, 330 bar, 15 s; 190℃, 200 bar, 20 s; 180℃, 100 bar, 30 s.

[0094] Example 3

[0095] A wood recombination material surface core layer asynchronous compression forming method, comprising:

[0096] (I) The plywood preparation method is the same as that in Example 2;

[0097] (II) Wood particle preparation

[0098] The waste single board in the process of finding circle and the waste single board remained in the process of cutting are crushed and sieved to obtain the wood particles with the particle size distribution in the following table, and the wood particles are dried by using a roller dryer to obtain the wood particles with a water content of 2%;

[0099]

[0100] (III) Wood particle sizing method same as example 1;

[0101] (IV) Wood particle humidity adjustment method same as example 1;

[0102] (V) Wood particle paving method same as example 1;

[0103] (VI) Hot pressing

[0104] The pre-pressed board is hot-pressed for 75 s, and the hot-pressing process is as follows: 230 ℃, 480 bar, 25 s; 210 ℃, 240 bar, 15 s; 190 ℃, 100 bar, 15 s; 180 ℃, 80 bar, 20 s.

[0105] To further illustrate the beneficial effects of the present application, the following comparative examples are constructed.

[0106] Comparative Example 1

[0107] In the step (V) of the present comparative example, the amount of water added is 2% of the weight of the wood particles; and the other conditions are the same as those in example 2.

[0108] Comparative Example 2

[0109] In the step (VII) of the present comparative example, the pre-pressed board is hot-pressed for 75 s, the hot-pressing temperature is 180 ℃, and the pressure is 520 bar, and then the board is naturally cooled; and the other conditions are the same as those in example 2.

[0110] Comparative Example 3

[0111] In the step (VII) of the present comparative example, the pre-pressed board is hot-pressed for 75 s, the hot-pressing temperature is 180 ℃, and the pressure is 100 bar, and then the board is naturally cooled; and the other conditions are the same as those in example 2.

[0112] Then the wood reconstituted materials prepared in examples 1-3 and comparative examples 1-3 are tested for performance, and the relevant tests and results are as follows.

[0113] 1. Density

[0114] The wood reconstituted materials prepared in examples 1-3 are tested for cross-sectional density, and the results are shown in Table 1. The plywood substrates prepared in the corresponding examples are used as controls.

[0115] As can be seen from Table 1, the pressed boards in the examples and the control examples have substantially equivalent densities.

[0116] Table 1

[0117]

[0118]

[0119] As can be seen from Table 1, the core layer single boards in Examples 1, 2 and 3 are substantially the same as the plywood substrates, while the surface layer is obviously compressed and densified, realizing asynchronous compression of the surface layer and the core layer. The surface layer in the control example 1 has a low moisture content, and the compression rate is obviously lower than that of Example 1, while the core layer also presents obvious compression; the core layer and the surface layer are synchronously compressed under the action of high pressure in the control example 2; and the densification degree of the surface layer in the control example 3 does not meet the requirements due to insufficient pressure.

[0120] 2, Surface roughness

[0121] The surface roughness of the above samples was tested by a surface roughness tester (TIME 3202, Beijing). The stylus diameter was 80 μm, the sampling length was L = 7.50 mm each time, and the size of the test sample was 100 mm x 100 mm x 20 mm (length x width x height). Ten different parts of each sample were tested, and the average value was taken as the result, as shown in Table 2.

[0122] Table 2

[0123] Material Class Profile Arithmetic Mean Deviation (Ra) Micro-irregularity Ten-point Height (Rz) Example 1 Eucalyptus Plywood Substrate 6.37 40.63 Example 1 1.21 11.54 Example 2 Poplar Plywood Substrate 5.96 43.75 Example 2 1.24 11.65 Example 3 Poplar Plywood Substrate 5.96 43.75 Example 3 1.19 11.78 Comparative Example 1 3.01 25.68 Comparative Example 2 1.07 10.56 Comparative Example 3 3.56 30.78

[0124] As can be seen from Table 2, the surface roughness of the wood reconstituted material manufactured by the present application is obviously improved compared with the eucalyptus and poplar plywood substrates. As can be seen from Table 2, different processes have a significant influence on the surface roughness of the wood reconstituted material. The wood reconstituted material produced by the optimized process of the present application has good and stable surface roughness.

[0125] In summary, in the present application, the poplar or eucalyptus plywood is used as the substrate, and the wood particles are used as the covering material. By using a specific pressure application method, the pressure decreases from the surface layer to the core layer of the plywood, realizing compression of the surface layer of wood particles and non-compression of the core layer of the plywood, so that a board with a larger surface layer density is obtained, and the surface layer is denser, facilitating the subsequent attachment of the decorative panel.

[0126] The above describes the preferred embodiments of the present application. Those skilled in the art can make some improvements and refinements without departing from the principles of the present application, which should be considered as falling within the scope of protection of the present application.

Claims

1. A method for asynchronous compression molding of the surface and core layers of a wood-based reconstituted material, characterized in that, include: (I) Core board preparation The logs are processed into veneers, and then glued, assembled, hot-pressed, and thickness-fixed to obtain core boards with a moisture content of 6-12%. (II) Preparation of Wood Particles Waste veneer is crushed, screened, and then processed into 40-200 mesh wood particles, which are then dried using a roller dryer to a moisture content of 1-3%. (III) Wood Particle Glue Application The isocyanate is sprayed evenly onto the surface of the wood particles, with an application rate of 3-6% of the weight of the wood particles; (iv) Humidity regulation of wood particles A certain amount of water is evenly sprayed onto the surface of the wood particles, and the amount of water added is 8-15% of the weight of the wood particles. (V) Wood Particle Paving The wood particles from step (four) are divided into two portions and fed into the laying machine. The bottom layer of wood particles is laid on the bottom plate conveyor belt using the air-jet laying method, with a laying thickness of 1.5-2.0cm. Then, the core board is placed on top of the bottom layer of wood particles. Finally, the other half of the wood particles is also laid on the upper surface of the core board using the air-jet laying method, with a laying thickness of 1.5-2.0cm. The board blank is pre-pressed online at a pressure of 3-5MPa. (vi) Hot pressing The pre-pressed boards are then hot-pressed. The hot-pressing process is as follows: 220-230℃, 480-520 bar, 10-40s; 210℃, 330-240 bar, 15-40s; 190℃, 200-100 bar, 15-40s; 180℃, 100-80 bar, 15-60s. After natural cooling, the wood-based reconstituted material is obtained.

2. The asynchronous compression molding method for the surface and core layers of wood-based reconstituted materials according to claim 1, characterized in that, In step (iii), the spraying pressure is 2.5-3.2 MPa, and the amount of tackifier added is 0.7%-1% of the weight of the wood particles.

3. The asynchronous compression molding method for the surface and core layers of wood-based reconstituted materials according to claim 1, characterized in that, The core board is uniformly coated with an adhesive on its upper and lower surfaces. The adhesive has a solid content of 58-65% and an application rate of 150-200 g / m². 2 The amount of flour added to the adhesive is 30-40% of the weight of the adhesive solution.

4. The asynchronous compression molding method for the surface and core layers of wood-based reconstituted materials according to claim 1, characterized in that, The wood-based reconstituted material can be sanded on both sides with a sanding amount of 0.5 mm and sanding mesh counts of 80, 100, 120, and 180 mesh respectively.

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