A fixed-length compacted board based on high frequency

Abstract

The present invention relates to a high-frequency, fixed-length compressed board, comprising a plurality of longitudinally joined compressed wood panels connected in the width direction, each of which comprises a plurality of compressed wood strips connected in the length direction, each of which comprises a single layer of cork strips or multiple layers of joined cork strips treated in the thickness direction by high-frequency hot pressing. The present invention has the beneficial effects of exhibiting excellent processing properties such as screw holding force, bending strength, and bending elasticity, as well as excellent resistance to accelerated aging. The preparation method thereof is easy to mass-produce and relatively low in cost.

Description

Technical Field

[0001] The invention belongs to the technical field of wood board processing, and in particular relates to a fixed-length compacted board based on high frequency. Background Art

[0002] The density boards, particle boards, multi-layer boards and log boards used in panel furniture are basically fixed-length boards, such as the commonly used 48-foot (length and width dimensions are 1220mm×2440mm) and 49-foot (length and width dimensions are 1220mm×2745mm). However, the relevant technology has not yet disclosed a method for preparing fixed-length compacted wood used in the custom furniture industry. CN111347511 A (2020.06.30) is based on a preparation method for high-frequency mixed-material glue-free composite materials, which is to combine at least two pieces with a density not exceeding 0.7kg / m 3 The wooden boards are heated and pressed by high frequency to form a degraded connecting layer between the two adjacent wooden boards. The preparation method specifically includes the following steps: pretreatment, lamination treatment, heating and pressurizing treatment, curing treatment, cooling treatment and curing treatment. However, the patent produces a multi-layer compacted board instead of a horizontal compacted board. It is not easy to mass-produce when it is made into a fixed-length board and the cost is high. CN112847694A (2021.05.28) discloses a glue-free horizontal compacting device (reference Figure 1 , wherein 1-lower pressing plate, 2-upper pressing plate, 4-lower pad, 5-upper pad, 6-hydraulic rod, 30-transverse splicing plate) and a glue-free transverse splicing and compacting method, the method comprising the following steps: (1) taking a number of transverse splicing plates and arranging them in order on a plane, clamping a resin film between two adjacent transverse splicing plates, and the contact surfaces of the two adjacent transverse splicing plates are at an angle of 45-135° to the plane to obtain an arrangement plate; (2) applying a first force F1 in the horizontal direction of the arrangement plate, F1 is 1.5-2MPa; (3) heating the arrangement plate to 60-170℃, applying a second force F2 in the vertical direction of the arrangement plate, F2 is not less than 0.7MPa, and maintaining the pressure for 8-10min; (4) keeping F2 unchanged, increasing F1 to F3, F3 is 2.5-4MPa, and maintaining the pressure until the temperature of the arrangement plate reaches 40-70℃. Although this patent discloses that the cross-joined compacted board is produced by heating during the molding process, it is still difficult to mass-produce the board into a fixed-length board and the cost is relatively high. Summary of the Invention

[0003] At least to address the above-mentioned technical problems, multiple embodiments of the present invention provide fixed-length compressed boards based on high frequency, wherein the fixed-length compressed boards include several longitudinally spliced compressed wood boards connected in the width direction, each longitudinally spliced compressed wood board includes several compressed wood strips connected in the length direction, and each compressed wood strip includes a layer of cork strips or multiple layers of connected cork strips that have been treated with a high-frequency hot pressing step in the thickness direction.

[0004] Further, in the fixed-length compacted board, the longitudinal contact surface of the adjacent compacted wood strips in the length direction of each fixed-length compacted board (or each longitudinally assembled compacted wood board) is a curved surface or an inclined surface, wherein the inclined surface includes an inclined plane or an inclined curved surface; preferably, the curved surface or inclined curved surface is a serrated surface;

[0005] The cross-jointed contact surfaces of the adjacent compressed wood strips in the width direction of each fixed-length compressed wood board (or each cross-jointed compressed wood board) are planes or inclined surfaces, wherein the inclined surfaces include inclined planes or inclined curved surfaces; preferably, the inclined curved surfaces are serrated surfaces;

[0006] Adjacent longitudinal contact surfaces or adjacent transverse contact surfaces are connected by a resin layer, and the resin layer includes, but is not limited to, one or more of a PVA resin layer, a PVB resin layer, and a PVC resin layer. The resin used in the resin layer includes any one or more mixtures of ethylene-vinyl acetate copolymers or polyolefin materials, and the polyolefin material is any one or a mixture of at least two of polyethylene, polypropylene, modified polyethylene, modified polypropylene, or an ethylene-based elastomer containing ethylene units.

[0007] Further, the fixed-length compressed board, the preparation process of the fixed-length compressed board includes the following steps:

[0008] In a first preheating step, a plurality of cork strips having a moisture content of 10% to 20% are heated to an average temperature of 80-90° C. by infrared irradiation to obtain a plurality of preheated cork strips;

[0009] A water layer attachment step is to attach a water layer to the surface of the preheated cork strips irradiated by infrared rays to obtain a plurality of cork strips with attached water layers;

[0010] The high-frequency hot pressing step heats, compresses and solidifies the water-layered cork strips under high-frequency conditions to obtain a plurality of compacted wood strips;

[0011] Cooling treatment step: Cooling several compacted wood strips to an average wood temperature of 70-90°C or room temperature;

[0012] The longitudinal splicing step is to splice the cooled compressed wood strips adjacent in the length direction to obtain a plurality of longitudinally spliced compressed wood boards;

[0013] The horizontal splicing step is to splice the longitudinally spliced compacted wood boards adjacent in the width direction to obtain a plurality of horizontally spliced compacted wood boards;

[0014] The sizing step cuts a plurality of transversely joined compacted wood boards into a plurality of compacted boards of a fixed length.

[0015] Further, in the fixed-length compacted board, the water-attached cork strips are subjected to the second preheating step and then to the high-frequency hot pressing step, wherein:

[0016] In the second preheating step, several water-coated cork strips are irradiated with infrared rays to maintain the temperature to an average of 80-90°C.

[0017] Further, for the fixed-length compressed board, in the first preheating step and / or the second preheating step, the infrared irradiation is performed in an infrared irradiation space, and the temperature of the infrared irradiation space is 130-150°C.

[0018] Further, for the fixed-length compacted board, in the step of attaching the water layer, the surface of the preheated cork strip is coated or sprayed with water 1-4 times.

[0019] Further, the steps of forming the resin layer of the fixed-length compacted board are as follows:

[0020] S1: Processing the joint end surface of the compacted wood strips into a curved surface or an inclined surface, wherein the inclined surface includes an inclined plane or an inclined curved surface; preferably, the curved surface or the inclined curved surface is a serrated surface;

[0021] S2 heat-melting the resin to obtain a hot-melt resin, and coating the hot-melt resin on the joint end surfaces of the compacted wood strips;

[0022] S3 squeezes the joint end faces of adjacent compressed wood strips with a first force.

[0023] For a further fixed-length compacted board, in step S2, the resin is hot-melted and then 20-40 mesh resin particles are added and mixed to obtain a paste-like hot-melt resin, and the paste-like hot-melt resin is coated on the end surface of the fixed-length compacted wood. The weight ratio of the resin to the resin particles is 8:1 to 12:1, and the resin particles include but are not limited to one or more of PVA particles, PVB particles, and PVC particles.

[0024] In the cooling process of the further fixed-length compressed board, liquid nitrogen refrigeration technology is used to place several compressed wood strips in an environment of -150℃ to -130℃ and cool them to room temperature for 9min to 15min before longitudinal splicing.

[0025] The beneficial effects of the present invention are that the high-frequency fixed-length compression plate of the present invention has good processing properties such as screw holding force, bending strength, bending elasticity and excellent resistance to accelerated aging, and its preparation method is easy to mass produce and has low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Prior art horizontal splicing and compacting equipment;

[0027] Figure 2 The fixed-length compression plate according to the embodiment of the present invention;

[0028] Figure 3 The longitudinally spliced and compacted wood board according to the embodiment of the present invention;

[0029] Figure 4 Horizontal puzzle diagram;

[0030] Figure 5 The fixed-length compression plate according to the embodiment of the present invention;

[0031] Figure 6 A side view of a fixed-length compressed plate according to an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The following examples further illustrate the present invention, but should not be construed as limiting the present invention. Without departing from the spirit and substance of the present invention, modifications or substitutions made to the methods, steps or conditions of the present invention are within the scope of the present invention.

[0033] Explanation of terms

[0034] Cut to length refers to the production of boards, for example, to the length and width specified by product standards. Understandably, cut to length boards are more suitable for robotic and assembly line operations, allowing for mass production and lowering costs.

[0035] Single pressing means that the hot press machine hot presses one layer of wood board.

[0036] Combined pressing refers to the hot pressing of multiple layers of wood boards by a hot press. For example, the hot pressing of three layers of wood boards by a hot press is called "three-combined pressing".

[0037] Longitudinal splicing, also known as longitudinal splicing or fixed-length straight pressing, refers to the splicing of adjacent wooden boards in the length direction.

[0038] Cross-joining, also known as horizontal joining or fixed-length side pressing, refers to joining adjacent boards in the width direction. Figure 4 shown.

[0039] Spliced end faces, see Figure 4 As shown, the end face of the wooden board includes 6 faces, and the splicing end face 9 is an end face of the wooden board used for splicing. After splicing, the splicing end face can also be called the longitudinal splicing contact face or the transverse splicing contact face.

[0040] Resin layer, see Figure 4 As shown, the resin layer 8 is located between the spliced end faces 9.

[0041] The first acting force refers to a first acting force F1 applied in the horizontal direction, see Chinese patent application CN112847694A, which can be achieved by a pneumatic compaction device, for example.

[0042] The second force is a second force F2 applied in a vertical direction, as described in Chinese patent application CN112847694A; this can be achieved, for example, by a high-frequency hot press. The uses of the fixed-length compressed board of the present invention are not specifically limited. For example, in addition to being a base material for panel furniture, it can also be used as a base material for flooring, i.e., as a base material for veneer wood-based panels.

[0043] The optional equipment used in the embodiments of the present invention include, but are not limited to: a slicer; an infrared preheating device; a water layer attachment device (which can be a coating device or a spraying device); a high-frequency hot press; a liquid nitrogen refrigeration device; a four-sided planer; a sorting system; a toothing device; a roller coater; a pneumatic compacting device (including various types of board assembly line compacting devices based on a hydraulic press); a woodworking cutter; and a wood board printer. Optional references include Chinese patent application CN201811592197 - High-frequency glueless compacting equipment, Chinese patent application CN201910181348 - High-frequency compacted wood combination production line, Chinese patent application CN201922120903 - A glueless horizontal splicing compacting device, and Chinese patent application CN202010100409 - Equipment for uniformly discharging compressed water vapor on the surface of compacted wood and equipment for compacted wood equipment assembly lines. In addition, equipment or production lines reconstructed according to the concept of the present invention are also within the scope of protection of the present invention.

[0044] The optional infrared preheating equipment in the embodiment of the present invention is a plurality of infrared preheating boxes that can be arranged on the conveying device of the production line (which can be a conveying chain or roller), that is, the conveying device can carry the plate through the bottom of the box body of the plurality of infrared preheating boxes, and each infrared preheating box includes an infrared heating preheating tube arranged above the inside of the box body. The wattage of the infrared heating preheating tube is adjustable so that the space temperature in the infrared preheating box is usually maintained at around 150°C. The length of the infrared preheating box on the production line can be set according to process requirements. When the length of the infrared preheating box on the production line is fixed, the speed of the conveying device (such as the conveying chain) can be adjusted to achieve a preheating temperature of the plate between 60°C and 100°C. For example, if the preheating temperature is 100°C, the speed is slowed down, and if the preheating temperature is 60°C, the speed is increased.

[0045] The optional water layer attachment device of the embodiment of the present invention is a plurality of water layer coating machines that can be set on the conveying device (which can be a conveying chain or roller) of the production line, that is, the conveying device can carry the board through the bottom of the box body of the plurality of coating machines, and each water layer coating machine includes a coating roller group (including a driving roller and a driven roller) and a water supply device arranged inside the box body, wherein the water supply device can spray water on the coating roller group, and the coating roller group can apply water to the wooden board, thereby causing the wooden board to adhere to the water layer. The number of water layer coating machines or the number of roller groups can be set according to the process requirements. For example, each water layer coating machine can be provided with one set of coating roller groups, or each water layer coating machine can be provided with two sets of coating roller groups. Obviously, if coating is performed twice, the former requires two units and the latter requires one unit. The coating speed (the rotation speed of the roller group) is usually consistent with the travel speed of the conveying device.

[0046] Optional liquid nitrogen refrigeration equipment in this embodiment of the present invention is a series of liquid nitrogen refrigeration cabinets installed on a conveyor (which can be a conveyor chain or roller) on a production line. Specifically, the conveyor can carry the plates through the bottom of the liquid nitrogen refrigeration cabinets. The temperature inside the liquid nitrogen refrigeration cabinets is approximately -150°C to -130°C.

[0047] The corresponding designs of the mechanical structure, electrical structure, etc. of the above infrared preheating box, liquid nitrogen refrigeration equipment and water layer coating machine can be achieved by using known technologies, and this application will not go into details one by one.

[0048] The present invention is described below in conjunction with the embodiments, wherein the methods of the cited Chinese patent applications are cited in full. Those skilled in the art may directly cite them or indirectly cite them with slight modifications based on the concept of the present invention. The present invention does not specifically limit the citation method.

[0049] Embodiment 1 Preparation of Cork Strips

[0050] The cork strips used in the embodiments of the present invention can be prepared using any known technique, such as sawing, slicing with a moisture content controlled at 60-80% (using slices instead of saw blades, poplar wood with a higher moisture content is more suitable for slicing, eliminating the need for pre-treatment and drying, and reducing substrate loss), or steaming and slicing (including the steps of material selection, steaming, slicing, and air-drying). The size of the cork strips used in the embodiments of the present invention is determined by the size of the fixed-length compressed board. For example, when preparing a 48-foot (4-foot by 8-foot) fixed-length compressed board, the cork strips can have a thickness of 1-4 cm and a width of 22 cm or 44 cm. The cork is typically poplar wood. The moisture content of the cork strips is typically 10%-20%.

[0051] Embodiment 2 Preparation of Cork Strips with Water Layer

[0052] In some embodiments of the present invention, the aforementioned water layer coater is used to coat 2-4 times, so that a water layer is attached to the surface of the preheated cork strips irradiated by infrared rays, thereby obtaining a number of cork strips with attached water layers. Although it is more convenient to set up the water layer coater on the assembly line, in an optional embodiment, a spray device can also be used to make the surface of the preheated cork strips adhere to a water layer. Of course, during small-scale preparation, a thin layer of water can also be applied manually on the surface of the preheated cork strips. The cork strips with attached water layers generate hot steam at the moment of high-frequency hot pressing, thereby changing the wood properties of the subsequently obtained compacted wood strips (reducing the cow hair pattern). Other implementations based on the concept of the present invention are also within the scope of protection of the present invention.

[0053] Embodiment 3 Preparation of Compacted Wood Strips (Single Pressing)

[0054] The method for preparing the compacted wood slats (single pressing) used in the embodiments of the present invention includes at least the steps of heating and compressing and curing, and optionally includes cooling and curing. The following is a method cited from Chinese patent application CN109465932A as an optional method for preparing the compacted wood slats (single pressing) used in the embodiments of the present invention:

[0055] Heating and compression treatment: The wood is heated by high frequency to an average temperature of 100-110°C, kept warm for 5-7 minutes, and compressed according to the first compression rate.

[0056] Curing treatment: The wood that has been heated and compressed is heated using high frequency to an average temperature of 180-220°C, and kept warm for 5-8 minutes for curing.

[0057] Cooling treatment: Use water cooling technology to cool the surface of the cured wood at a rate of 5-15℃ / min until the average temperature of the wood is 70-90℃; the water flow rate of the water cooling technology is 0.9-1.3m / s; during the cooling process, when the surface temperature of the wood cools to 85-90℃, air cooling is carried out with a wind speed of 9.2-9.7m / s and a wind temperature of 55-60℃.

[0058] Curing treatment: Place the cooled wood at room temperature for 13-15 days to obtain glue-free compressed hardwood; the specific method of curing treatment is: place the cooled wood on a horizontal dry surface, apply a pressure of 5.5-7.2Mpa to the upper surface of the wood, and after curing for 3 days, reduce the pressure by 1.2-1.5Mpa every day until the pressure is 0, and continue curing for 10-12 days.

[0059] Embodiment 4 Preparation of Compacted Wood Strips (Triple Pressing)

[0060] The method for preparing the compacted wood slats (three-in-one pressing) used in embodiments of the present invention includes at least a heating and compression treatment (also known as a heating and pressing treatment) and a curing treatment step, and optionally includes a cooling treatment (also known as a temperature reduction treatment) and a curing treatment. The following is a method cited from Chinese patent application CN111347511A as an optional method for preparing the compacted wood slats (three-in-one pressing) used in embodiments of the present invention:

[0061] Lamination process: taking two or more wood boards and placing them on top of each other in at least one stress direction to produce a laminated wood board, wherein the stress direction includes a direct pressure direction and an indirect pressure direction;

[0062] Heating and pressurizing treatment: heating the degraded connecting layer of the laminated wood board to a wood board temperature of 80-100° C., keeping the temperature for 4-6 minutes, and then performing pressurizing treatment according to the preset compression rate in the direction of the force;

[0063] Curing treatment: The wood board that has been heated and pressurized is heated with high frequency to a temperature of 180-220°C, kept warm for 5-8 minutes, and then cured to obtain a cured wood board;

[0064] Cooling treatment: Use water cooling technology to cool the surface of the cured wood board at a rate of 5-15℃ / min until the temperature of the wood board is 70-90℃. The water flow rate of the water cooling technology is 0.9-1.5m / s. When the surface temperature of the wood board is cooled to 85-90℃, air cooling is carried out at a wind speed of 9.2

[0065] -9.7m / s, wind temperature is 55-60℃;

[0066] Health treatment: Place the wood board after cooling treatment at room temperature for 15-20 days to obtain a high-frequency mixed material without glue composite material.

[0067] The fixed-length compressed board made from compressed wood strips (three-combination compression) has a three-layer design in the thickness direction and two seams in the width direction. The adjacent laminated wood boards can interact and offset the transverse and longitudinal stresses, reflecting the anti-rebound performance of the structure. In addition, since the wood properties of different slices are necessarily different, reference Figure 6 As shown, after hot pressing, unique lines of fixed-length compacted board (equivalent to anti-counterfeiting lines) are formed on the side, which is equivalent to natural wood and is a feature that other products such as particleboard do not have.

[0068] Implementation Method 5: Preparation of Longitudinally Spliced Compressed Wood Board

[0069] The method for preparing the longitudinally spliced and compacted wood board used in the embodiments of the present invention includes, but is not limited to, the method of Chinese patent application CN201911193101, which requires sandwiching a resin film between the wood boards and then hot pressing. In addition, some embodiments of the present invention use the following method for sandwiching the resin mixture:

[0070] Splicing adjacent cooled compressed wood strips in the length direction to obtain a plurality of longitudinally spliced compressed wood boards specifically comprises the following steps:

[0071] a) Mixing a resin: heating and melting the resin to obtain a resin hot melt; then adding 20-40 mesh resin particles and stirring to obtain a resin mixture (also known as a paste-like hot melt resin); the resin includes but is not limited to one or more of PVA, PVB, and PVC, and the resin particles include but are not limited to one or more of PVA particles, PVB particles, and PVC particles.

[0072] b) Comb teeth (finger jointing) (compacting line): After the fixed length three-ply press plate, the first and last end faces are serrated to obtain the combed three-ply plate;

[0073] c) Use a roller machine to apply resin to the comb teeth of the plywood. On the assembly line, the comb teeth plywood dipped in resin are in contact head to tail. The comb teeth of the front and rear comb teeth plywood will be pressed by the pneumatic compaction device on the assembly line while moving, and the plywood with the comb teeth connected will be moved to the fixed-length direct-pressure pneumatic compaction device.

[0074] d) Fixed-length direct pressing: The plywood after the comb teeth are connected is placed on a fixed-length direct pressing pneumatic compacting device for pressing to obtain a fixed-length direct pressing compacted board.

[0075] Implementation Method 6: Preparation of Horizontally Spliced Compacted Wood Board

[0076] The method for preparing the longitudinally spliced and compacted wood board used in the embodiments of the present invention includes, but is not limited to, the method of Chinese patent application CN201911193101, which requires sandwiching a resin film between the wood boards and then hot pressing. In addition, some embodiments of the present invention use the following method for sandwiching the resin hot melt:

[0077] a) heating and melting the resin to obtain a resin hot melt material;

[0078] b) Apply hot-melt resin between adjacent longitudinally spliced compacted wood boards in the width direction, apply force with a pneumatic compacting device, and complete the splicing with a fixed-length side-pressure pneumatic compacting device to obtain a number of horizontally spliced compacted wood boards (also called fixed-length side-pressure compacted boards).

[0079] Implementation Method 7: Preparation of Fixed-Length Compressed Board

[0080] like Figure 2 、 3 As shown in Figures 5 and 6, the fixed-length compressed board 1 of the present invention includes a number of longitudinally assembled compressed wood boards 2 of the same size pressed in the width direction, each longitudinally assembled compressed wood board 2 includes a number of compressed wood strips 3 pressed in the length direction, and each compressed wood strip 3 includes a number of softwood strips 4 pressed in the thickness direction through a high-frequency hot pressing step.

[0081] The joints of adjacent compacted wood planks 3 form vertical stitching lines 5, the joints of adjacent longitudinally spliced compacted wood planks form horizontal stitching lines 6, and the joints of adjacent softwood planks form multiple high-frequency heat-embossed lines 7.

[0082] The vertical stitching lines 5 of adjacent longitudinally spliced compacted wood boards 2 are not on the same straight line.

[0083] The directions of the high-frequency heat embossed lines 7 of the adjacent cork slats 4 are the same but do not intersect. Specifically, since the high-frequency heat embossed lines 7 are formed by high-frequency pressing, and since the wood properties of different cork slats 4 are necessarily different, Figure 2 、 Figure 6 As shown, after hot pressing, unique lines (equivalent to anti-counterfeiting lines) of the fixed-length compacted board are formed on the side.

[0084] Among the plurality of longitudinally assembled compacting wood boards 2 of each fixed-length compacting board 1, the one in the middle is a longitudinally assembled compacting wood board 2 of the same size;

[0085] The widths of the plurality of compressed wood strips 3 of each longitudinally assembled compressed wood board 2 are equal.

[0086] The fixed-length compressed board of the present invention has the following properties: a density of 0.58 to 0.6, strength equivalent to that of pine wood, and can be used as a cabinet board to replace particleboard, multilayer board and density board; the board surface has a screw holding force of 1400N to 1600N; a bending strength of 50MPa to 65MPa; and a bending elasticity of 6500MPa to 7500MPa.

[0087] The preparation process of the fixed-length compressed board comprises the following steps:

[0088] In a first preheating step, a plurality of cork strips having a moisture content of 10% to 20% are heated to an average temperature of 80-90° C. by infrared irradiation to obtain a plurality of preheated cork strips;

[0089] a water layer attaching step of attaching a water layer to the surface of the preheated cork strips irradiated by infrared rays, thereby obtaining a plurality of cork strips with attached water layers;

[0090] In the high-frequency hot pressing step, the water-coated cork wood strips are subjected to a heating, compression, and curing treatment under high-frequency conditions according to the method of Example 2 or Example 3 to obtain a plurality of compacted wood strips;

[0091] Cooling treatment step: cooling a plurality of compressed wood strips according to the method of Example 2 or Example 3 until the average temperature of the wood is 70-90°C;

[0092] The longitudinal splicing step is to splice the cooled compressed wood strips adjacent in the length direction to obtain a plurality of longitudinally spliced compressed wood boards;

[0093] The horizontal splicing step is to splice the adjacent longitudinal compacted wood boards in the width direction, refer to Figure 2 As shown, a number of horizontally spliced and compacted wooden boards are obtained;

[0094] In the sizing step, a plurality of horizontally joined compacted wood boards are cut into a plurality of fixed-length compacted boards by a woodworking cutting machine.

[0095] The screw holding force of the fixed-length compressed board in some embodiments of the present invention can be increased by at least 30%. Taking poplar wood as an example, the density reaches 0.58-0.6, and the strength is equivalent to that of pine wood. It can be used as cabinet board to replace particle board, multi-layer board and density board.

[0096] Implementation Method 8: Preparation of veneer artificial board

[0097] In some optional embodiments, the fixed-length compressed board is used as the base material of the veneer artificial board, and the following steps are also included:

[0098] In the pattern printing step, a plurality of fixed-length compacted boards are sanded and then printed with patterns (printing layers) using a wood panel printer to obtain a plurality of veneered artificial boards.

[0099] The present invention will be further described below with reference to specific embodiments and comparative examples.

[0100] Example 1 Preparation of fixed-length compressed board

[0101] 1. Cork Strip Preparation Step Referring to the method of embodiment 1, prepared are poplar strips (also referred to as cork strips) with a length of 50 cm to 120 cm and a width of 22 cm, with a moisture content of 15±3%.

[0102] 2. First preheating step: several cork strips with a moisture content of 15±3% are passed through the aforementioned infrared preheating box to be heated to an average temperature of 80-90°C by infrared irradiation. The temperature of the infrared irradiation space is 130°C, thereby obtaining several preheated cork strips.

[0103] 3. Water layer attachment step Referring to the third embodiment, two water layer coating machines with one coating roller assembly are used to coat the surface of the preheated cork strips irradiated by infrared rays with a water layer attached thereto, thereby obtaining a plurality of cork strips with attached water layers.

[0104] 4. High-frequency hot pressing step: heating, compressing, and curing the water-coated cork strips under high-frequency conditions according to the method of embodiment 3 to obtain a plurality of compacted wood strips;

[0105] 5. Cooling step: Cooling the plurality of compressed wood strips to an average wood temperature of 70-90°C according to the method of embodiment 3;

[0106] 6. The longitudinal splicing step refers to the method of Chinese patent application CN201911193101, and the cooled compressed wood strips adjacent in the longitudinal direction are spliced to obtain a plurality of longitudinally spliced compressed wood boards;

[0107] 7. The horizontal splicing step refers to the method of Chinese patent application CN201911193101, and the adjacent longitudinally spliced compacted wood boards in the width direction are spliced to obtain a plurality of horizontally spliced compacted wood boards;

[0108] 8. Sizing step: Use a woodworking cutting machine to cut several horizontally spliced compacted wood boards into several fixed-length compacted boards to produce 48-foot (4 feet by 8 feet) fixed-length compacted boards (length, width and thickness are 2440mm*1220mm*20mm).

[0109] Example 2 Preparation of fixed-length compressed board

[0110] It is basically the same as Example 1, except that:

[0111] In the first preheating step, the temperature of the infrared irradiation space was 140°C.

[0112] In the step of attaching the water layer, the coating is performed three times in total by the three aforementioned water layer coating machines with one coating roller assembly;

[0113] Example 3 Preparation of fixed-length compressed board

[0114] It is basically the same as Example 1, except that:

[0115] In the first preheating step, the temperature of the infrared irradiation space is 150°C.

[0116] In the step of attaching the water layer, coating is performed three times by three water layer coating machines provided with one coating roller group as described above;

[0117] The water-layered cork strips are subjected to the second preheating step and then to the high-frequency hot pressing step, wherein:

[0118] In the second preheating step, several water-coated cork strips are irradiated with infrared rays to maintain the temperature to an average of 80-90°C.

[0119] Example 4 Preparation of fixed-length compressed board

[0120] It is basically the same as Example 1, except that:

[0121] The longitudinal splicing step refers to the resin mixture clamping method of embodiment 5, and the cooled compressed wood strips adjacent in the length direction are spliced to obtain a number of longitudinally spliced compressed wood boards; wherein the longitudinal splicing contact surface of the compressed wood strips adjacent in the length direction of each longitudinally spliced compressed wood board is a serrated surface.

[0122] The transverse splicing step refers to the method of clamping resin hot melt material in embodiment 6, and the adjacent longitudinally spliced compressed wood boards in the width direction are spliced to obtain several transversely spliced compressed wood boards; wherein, the transverse splicing contact surface of the adjacent compressed wood board strips in the width direction of each transversely spliced compressed wood board is a plane.

[0123] Two adjacent longitudinal contact surfaces or adjacent transverse contact surfaces are connected through the PVB resin layer.

[0124] The steps for forming the longitudinally spliced PVB resin layer are:

[0125] S1 processes the joint end surface of the compacted wood strips into a serrated surface;

[0126] S2: After hot-melting the PVB resin, add 20-40 mesh PVB resin particles and stir to obtain a PVB resin mixture, and apply the PVB resin mixture on the splicing end surface (longitudinal splicing contact surface) of the fixed-length compacted wood. The weight ratio of the PVB resin to the PVB resin particles is 8:1.

[0127] S3 uses a pneumatic compacting device to squeeze the joint end faces of adjacent compacted wood strips.

[0128] The steps for forming the horizontally spliced PVB resin layer are:

[0129] S1: Processing the joint end surface of the compacted wood strips into a flat surface (this step is omitted if the surface is already flat);

[0130] S2 heat-melts the PVB resin to obtain a PVB resin hot melt material, and applies the PVB resin mixture to the splicing end surface (horizontal splicing contact surface) with the fixed-length compacted wood.

[0131] S3 uses a pneumatic compacting device to squeeze the joint end faces of adjacent compacted wood strips.

[0132] Example 5 Preparation of fixed-length compressed board

[0133] It is basically the same as Example 4, except that:

[0134] In the steps of forming the longitudinal contact surface:

[0135] S1 processes the joint end surface of the compacted wood strips into a serrated surface;

[0136] The weight ratio of S2 PVB resin to PVB resin particles is 10:1.

[0137] In the steps of forming the horizontal contact surface:

[0138] S1 processes the joint end faces of the compacted wood strips into inclined planes.

[0139] Example 6 Preparation of fixed-length compressed board

[0140] It is basically the same as Example 4, except that:

[0141] In the steps of forming the longitudinal contact surface:

[0142] S1 processes the joint end surface of the compacted wood strips into a serrated surface;

[0143] The weight ratio of S2 PVB resin to PVB resin particles is 12:1.

[0144] In the steps of forming the horizontal contact surface:

[0145] S1 processes the joint end faces of the compacted wood strips into flat surfaces.

[0146] Example 7 Preparation of fixed-length compressed board

[0147] It is basically the same as Example 4, except that:

[0148] In the high-frequency hot pressing step (three-combination pressing), the water-coated softwood strips are subjected to a heating, compression, and curing treatment under high-frequency conditions in accordance with the method of the fourth embodiment to obtain a three-combination pressed board with rough edges; the front, back, left, and right edges of the three-combination pressed board with rough edges are trimmed using a four-sided planer to obtain a plurality of compacted wood strips (also called three-combination pressed boards).

[0149] Stacking treatment: Take 3 pieces of cork strips with attached water layer and stack them in one force direction to make a stacked wood board; then arrange 6-8 stacked wood boards in a matrix on the compacting plate / support plate of the hot press, and the force direction is the direct pressure direction.

[0150] The high frequency conditions are: compression speed of 25 seconds / time and compression ratio of 25%.

[0151] Example 8 Preparation of fixed-length compressed board

[0152] It is basically the same as Example 7, except that:

[0153] The high frequency conditions are: compression speed of 27 seconds / time and compression ratio of 30%.

[0154] Example 9 Preparation of fixed-length compressed board

[0155] It is basically the same as Example 7, except that:

[0156] The high-frequency conditions are: compression speed of 30 seconds / time and compression ratio of 28%.

[0157] Example 10 Preparation of fixed-length compressed board

[0158] It is basically the same as Example 7, except that:

[0159] Cooling step: Use liquid nitrogen refrigeration to cool the compressed wood strips to room temperature at -130°C for 15 minutes before longitudinal splicing. Typically, the compressed wood strips are cooled to room temperature using liquid nitrogen refrigeration before leaving the liquid nitrogen refrigeration cabinet. In other embodiments, "room temperature" refers to the temperature before longitudinal splicing. For assembly line operations, the compressed wood strips are cooled to 3-5°C in a -130°C environment before being transported from the assembly line to the longitudinal splicing equipment.

[0160] Example 11 Preparation of fixed-length compressed board

[0161] It is basically the same as Example 10, except that:

[0162] Cooling treatment steps: Use liquid nitrogen refrigeration technology to place several compressed wooden strips in an environment of -140℃ and cool them to room temperature for 12 minutes before longitudinal splicing.

[0163] Example 12 Preparation of fixed-length compressed board

[0164] It is basically the same as Example 10, except that:

[0165] Cooling treatment steps: Use liquid nitrogen refrigeration technology to place several compressed wooden strips in an environment of -150℃ and cool them to room temperature for 9 minutes, and then splice them longitudinally.

[0166] Comparative Example 1 Preparation of fixed-length compacted board

[0167] The method is basically the same as Example 1, except that the step of attaching the water layer is omitted.

[0168] Comparative Example 2 Preparation of fixed-length compacted board

[0169] The method is basically the same as Example 1, except that the step of attaching a water layer is omitted, and the first preheating step is replaced by preheating using a high-frequency hot press.

[0170] Comparative Example 3 Preparation of fixed-length compacted board

[0171] It is basically the same as Example 1, except that:

[0172] In the first preheating step, the temperature of the infrared irradiation space is 160° C., and a number of preheated cork strips are obtained.

[0173] In the step of attaching the water layer, the coating is performed once in total by one water layer coating machine provided with one set of coating rollers.

[0174] Comparative Example 4 Preparation of fixed-length compacted board

[0175] It is basically the same as Example 4, except that:

[0176] In the steps of forming the longitudinal contact surface:

[0177] S1 processes the joint end surface of the compacted wood strips into a flat surface;

[0178] In the steps of forming the horizontal contact surface:

[0179] S1 processes the joint end faces of the compacted wood strips into inclined planes.

[0180] Comparative Example 5 Preparation of fixed-length compacted board

[0181] It is basically the same as Example 4, except that:

[0182] In the steps of forming the longitudinal contact surface:

[0183] S1 processes the joint end surface of the compacted wood strips into an inclined plane;

[0184] In the steps of forming the horizontal contact surface:

[0185] S1 processes the joint end faces of the compacted wood strips into serrated surfaces.

[0186] Comparative Example 6 Preparation of fixed-length compacted board

[0187] It is basically the same as Example 4, except that:

[0188] In the steps of forming the longitudinal contact surface:

[0189] The weight ratio of S2 PVB resin to PVB resin particles is 14:1.

[0190] In the steps of forming the horizontal contact surface:

[0191] S1 processes the joint end faces of the compacted wood strips into inclined planes.

[0192] Comparative Example 7 Preparation of Fixed-Length Compressed Board

[0193] It is basically the same as Example 7, except that:

[0194] The high frequency condition is: compression speed is 40 seconds / time.

[0195] Comparative Example 8 Preparation of Fixed-Length Compressed Board

[0196] It is basically the same as Example 7, except that:

[0197] The high frequency condition is: compression speed is 10 seconds / time.

[0198] Comparative Example 9 Preparation of fixed-length compacted board

[0199] It is basically the same as Example 7, except that:

[0200] High frequency conditions are: compression ratio is 20%.

[0201] The following tests are carried out below in conjunction with the embodiments and comparative examples.

[0202] Test Example 1: Determination of cow hair pattern

[0203] The wood board was sawed along the thickness direction to remove the 3mm thick surface layer (the surface exposed to infrared irradiation) to expose the inner layer, and the density and moisture content were measured. Then, 4 pieces were cut from the four corners and 2 pieces were cut from the center, totaling 6 specimens.

[0204] Specimen size: length 150±1mm; width 50±0.5mm;

[0205] Test method: Inspect the surface of the specimen for cow-hair patterns using normal vision (or corrected to normal vision) and a 6x magnifying glass at an illumination of 800lx to 1000lx.

[0206] The cow-hair grain grade is as follows: Grade 5: no cow-hair grain; Grade 4: cow-hair grain is only observed under a 6x magnifying glass; Grade 3: cow-hair grain can be observed with the naked eye. The cow-hair grain of a wooden board is expressed as the arithmetic mean of the cow-hair grain grades of all test pieces, approximated to an integer. The results are shown in Table 1.

[0207] Table 1 Results of determination of cow hair grain grade

[0208]

[0209] The test results show that the cow-hair pattern of Examples 1 to 3 is significantly less than that of Comparative Examples 1-3. The possible reason is that the softwood strips with attached water layer generate hot steam at the moment of high-frequency hot pressing, which changes the wood properties. Comparison of Examples 1 to 3 with Comparative Example 2 shows that the combination of infrared preheating and high-frequency hot pressing of softwood strips with attached water layer has basically the same cow-hair pattern level as high-frequency preheating and curing, but the former is more suitable for the assembly line and has lower cost, which is better than the latter that preheating is completed by a high-frequency hot press. Comparison of Examples 1 to 3 with Comparative Examples 1 and 3 shows that infrared preheating or an inappropriate attached water layer will cause cow-hair pattern to appear near the 2mm-4mm surface layer of the fixed-length compressed board of poplar wood that is exposed to infrared irradiation. Test Example 1 shows that the methods of Examples 1-3 can basically solve this problem.

[0210] Test Example 2: Bending Strength and Bending Elastic Modulus Test

[0211] The flexural strength test method is GB / T 1936.1-2009 "Test method for flexural strength of wood", and the flexural modulus test method is GB / T 1936.2-2009 "Determination method for flexural modulus of wood". The test results are shown in Tables 2 and 3.

[0212] Table 2 Bending strength test results

[0213]

[0214] Table 3 Flexural elastic modulus test results

[0215]

[0216] It can be seen from the test results that the bending strength and bending modulus of Examples 1 to 6 are better than those of Comparative Examples 4 to 6. The bending strength and bending modulus of Examples 4 to 6 are better. It can be seen that triple pressing has more advantages. Comparison of Examples 4 to 6 with Comparative Example 4 shows that in the step of forming the longitudinal contact surface, the spliced end faces of the compressed wood strips are processed into serrated surfaces, which increases the resin load and has a greater impact on the improvement of the bending strength and bending modulus. Comparison of Examples 4 to 6 with Comparative Example 5 shows that in the step of forming the transverse contact surface, the spliced end faces of the compressed wood strips are processed into serrated surfaces, but the effect on the improvement of the bending strength and bending modulus is not significant. Comparison of Examples 4 to 6 with Comparative Example 6 shows that in the step of forming the longitudinal contact surface, the weight ratio of PVB resin to PVB resin particles has a greater impact on the improvement of the bending strength and bending modulus.

[0217] Test Example 3: Screw Gripping Force Test

[0218] The screw holding force test method is GB / T 17657-2013 "Test methods for physical and chemical properties of wood-based panels and veneered wood-based panels". The test results are shown in Table 4.

[0219] Table 4 Screw holding force test results

[0220]

[0221] The test results show that the screw holding strength of the panels of Examples 4-9 is superior to that of medium-density fiberboard, blockboard, and ordinary particleboard. The screw holding strength of the panels of Examples 7-9 is close to that of veneerable oriented structural lumber. The screw holding strength of the panels of Examples 4-9 is essentially the same, but the screw holding strength at the panel joints of Examples 7-9 is superior to that of Examples 4-6. A comparison of Examples 4-6 with Examples 7-9 shows no significant difference in compression speed or compression ratio.

[0222] Test Example 4 Formaldehyde Content Determination

[0223] The determination basis for formaldehyde (mg / L) is: GB 18584-2001 "Limits of Hazardous Substances in Wooden Furniture for Indoor Decoration and Renovation". See Table 5 for test results.

[0224] Table 5 Formaldehyde test results

[0225] Test items Testing basis Index requirements Test results Example 1 Formaldehyde, mg / L GB 18584-2001 ≤1.5 0.3 Example 4 Formaldehyde, mg / L GB 18584-2001 ≤1.5 0.3 Example 7 Formaldehyde, mg / L GB 18584-2001 ≤1.5 0.3 Example 10 Formaldehyde, mg / L GB 18584-2001 ≤1.5 0.3

[0226] Test results: Example 1, Example 4, Example 7 and Example 10 all meet the formaldehyde index requirements in GB18584-2001 "Limits of Hazardous Substances in Wooden Furniture for Indoor Decoration and Renovation".

[0227] Test Example 5 Accelerated Aging Performance Measurement

[0228] 1. After the specimens are subjected to 6 cycles of hot water soaking, steam spraying, freezing, drying, steam spraying, and drying, the screw holding force and water absorption thickness expansion rate of the specimens are measured.

[0229] 2. The equipment and instruments used are steam accelerated aging test chambers for artificial boards, which comply with the requirements for equipment and instruments for "accelerated aging performance determination" in GB / T17657-2013 "Test methods for physical and chemical properties of artificial boards and veneered artificial boards".

[0230] 3. Specimen size:

[0231] Dimensions of static bending strength specimens (length 450±1mm, width 50±1mm, thickness 20±1mm);

[0232] Screw grip test piece dimensions (length 75±1mm, width 50±1mm, thickness 20±1mm);

[0233] Water absorption thickness expansion test piece dimensions (length 50±1mm, width 50±1mm);

[0234] 4. Specimen balance treatment

[0235] The specimen is placed in an environment of 20±2°C and relative humidity of 65±5% until the mass is constant (weigh twice 24 hours apart, and the mass difference between the two weighings is less than 1% of the mass of the compacted material, which is considered to be constant mass).

[0236] 5. Test methods

[0237] Accelerated aging cycle. The specimen is subjected to 6 cycles of testing. Each cycle includes the following steps:

[0238] a) Soak the specimen in hot water at (49±2)℃ for 1h.

[0239] b) The specimen is sprayed in steam at (93±3)℃ for 3h.

[0240] c) The specimen is frozen in a freezer at (-12±3)℃ for 20h.

[0241] d) Dry the specimen in a forced air drying oven at (99±2)℃ for 3h.

[0242] e) The specimen is steamed in steam at (93±3)℃ for 3h.

[0243] f) Dry the specimen in a forced air drying oven at (99±2)℃ for 18h.

[0244] After the 6-cycle accelerated aging test is completed, the specimen is placed at (20±2)℃ and relative humidity (65±5)% for at least 48 hours, and then the performance test is carried out. The test results are shown in Table 6.

[0245] Table 6 Accelerated aging performance determination

[0246]

[0247] The test results show that after accelerated aging, the screw-holding force of Examples 4, 7, and 10 decreased, but remained superior to or comparable to that of medium-density fiberboard, blockboard, and ordinary particleboard. The water absorption thickness expansion rates of Examples 7 and 10 were lower than that of Example 4, indicating that the triple-pressing technology demonstrates structural anti-rebound performance. Example 10 exhibited the lowest water absorption thickness expansion rate, demonstrating the synergistic effect of quenching and structural anti-rebound performance.

[0248] Although the present invention has been described in detail above using general explanations, specific embodiments, and experiments, it will be apparent to those skilled in the art that modifications and improvements may be made based on the present invention. Therefore, such modifications and improvements, which do not depart from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A high-frequency fixed-length compression board, characterized in that: The fixed-length compressed board comprises a plurality of longitudinally joined compressed wood boards connected in the width direction, each longitudinally joined compressed wood board comprises a plurality of laminated compressed wood strips connected in the length direction, each laminated compressed wood strip comprises three layers of cork strips connected in the thickness direction and subjected to a high-frequency hot pressing step; the vertical grains of adjacent longitudinally joined compressed wood boards are not in the same straight line; the cork strips have a width of 22 cm or 44 cm and a length of 50 cm to 120 cm; the preparation process of the fixed-length compressed board comprises the following steps: Cork wood strip preparation step: preparing fixed-length poplar wood strips with a length of 50 cm to 120 cm and a width of 22 cm or 44 cm to obtain the cork wood strips; In a first preheating step, a plurality of cork strips having a moisture content of 10% to 20% are heated to an average temperature of 80-90°C by infrared irradiation in an infrared preheating box, thereby obtaining a plurality of preheated cork strips. In the first preheating step, the infrared irradiation is performed in an infrared irradiation space having a temperature of 130-150°C. The water layer attaching step comprises applying a water layer to the surface of the preheated cork strips irradiated by infrared rays by a water layer coating machine, thereby obtaining a plurality of cork strips with attached water layers; The high-frequency hot pressing step is to stack the water-attached softwood strips and immediately heat, compress and solidify them under high-frequency conditions to obtain a plurality of stacked and compacted wood strips; the compression ratio under the high-frequency conditions is 25%, 28% or 30%; Cooling treatment step: Cooling several layers of laminated wood strips to an average wood temperature of 70-90°C or room temperature; The longitudinal splicing step comprises splicing adjacent, cooled, laminated, and compacted wood strips in the longitudinal direction to obtain a plurality of longitudinally spliced compacted wood strips. The longitudinal splicing contact surfaces of adjacent compacted wood strips in the longitudinal direction of each longitudinally spliced compacted wood strip are serrated surfaces. Two adjacent longitudinal splicing contact surfaces are connected by a PVB resin layer to form the longitudinally spliced PVB resin layer. The steps of: S1: forming the spliced end surfaces of the compacted wood strips into serrated surfaces; S2: hot-melting the PVB resin, adding 20-40 mesh PVB resin particles, and stirring to obtain a PVB resin mixture. The PVB resin mixture is then applied to the longitudinal splicing contact surfaces of the compacted wood strips of a predetermined length, wherein the weight ratio of the PVB resin to the PVB resin particles is 8:1; and S3: compacting the spliced end surfaces of the adjacent compacted wood strips using a pneumatic compacting device. The transverse splicing step splices adjacent longitudinally joined compacted wood boards in the width direction to obtain a plurality of transversely joined compacted wood boards; wherein the transversely joined contact surfaces of adjacent compacted wood boards in the width direction of each transversely joined compacted wood board are flat, and two adjacent transversely joined contact surfaces are connected by a PVB resin layer. The steps for forming the transversely joined PVB resin layer are as follows: SS1: forming the joined end surfaces of the compacted wood boards into a flat surface; SS2: hot-melting the PVB resin to obtain a PVB resin hot melt, and applying the PVB resin mixture to the transversely joined contact surfaces with the fixed-length compacted wood boards; SS3: using a pneumatic compacting device to compress the joined end surfaces of the adjacent compacted wood boards; The sizing step cuts a plurality of transversely spliced compacted wood boards into a plurality of fixed-length compacted boards.

2. The fixed-length compressed board according to claim 1, characterized in that: The water-attached cork strips are subjected to the second preheating step and then to the high-frequency hot pressing step, wherein: In the second preheating step, several water-coated cork strips are irradiated with infrared rays to maintain an average temperature of 80-90°C.

3. The fixed-length compressed board according to any one of claims 1 to 2, characterized in that: In the step of attaching a water layer, the surface of the preheated cork strips is coated with water 1-4 times.

4. The fixed-length compressed board according to any one of claims 1 to 2, characterized in that: In the cooling treatment step, a plurality of compressed wood strips are placed in an environment of -150°C to -130°C and cooled for 9 minutes to 15 minutes to room temperature using liquid nitrogen refrigeration technology, and then the longitudinal splicing step is carried out.

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