Plywood production process

Abstract

The invention discloses a plywood production process, and particularly relates to the technical field of plywood, and the plywood production process comprises the following seven steps: step 1, selecting a plate, step 2, splicing the plate surfaces and manufacturing a rubber plate, step 3, drilling, step 4, gluing and assembling, step 5, cold pressing and hot pressing, step 6, sanding and edge cutting, and step 7, inspecting. The through holes are formed in the rubber plates and filled with the sponge blocks, during gluing, the sponge blocks can be infiltrated by the resin adhesive, the through holes are filled with the resin adhesive, the upper plates and the lower plates of the rubber plates can be bonded together through the resin adhesive at the through holes, and even non-adjacent plates can also be directly bonded together, so that the service life of the rubber plates is prolonged, and the service life of the rubber plates is prolonged. The connection strength between the layers of the plywood is improved, and the layering condition is effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of plywood, and specifically relates to a plywood production process. Background Art

[0002] Plywood is a kind of artificial board, which is made by slicing wood segments into veneers or planing wooden squares into thin woods, and then gluing them with adhesives to form a three-layer or multi-layer board-like material, mainly used in furniture manufacturing, construction, packaging, shipbuilding, aviation and other fields.

[0003] The production and processing of plywood require multiple processes. For example, a plywood production process and its equipment with the publication number CN112405734B in the prior art, the most core part of which is glue coating and hot pressing adhesion. Using resin glue as an adhesive, the adjacent upper and lower layers of boards are connected together.

[0004] Therefore, for each layer of boards in the middle of the plywood, each layer of board is only adhered to the adjacent boards above and below it, and there is no direct connection relationship with other non-adjacent boards. This leads to the need to improve the connection strength between the boards, and the plywood made is more likely to delaminate. Summary of the Invention

[0005] The purpose of the present invention is to provide a plywood production process. By opening through holes on each layer of glue boards and filling them with sponge blocks, the upper and lower layers of boards of the glue boards can be adhered together through the resin glue at the through holes. This enables even non-adjacent boards to be directly adhered together, improving the connection strength between each layer of boards of the plywood and effectively avoiding the delamination situation.

[0006] In order to achieve the above purpose, the present invention provides the following technical solution: A plywood production process, the specific steps are as follows: Step 1: The plywood is composed of multiple layers of boards. Each layer of board is stacked from bottom to top. The top layer of the plywood is called the face plate, and the bottom layer is called the bottom plate. Before production, it is first necessary to select each layer of board, and select the materials of each layer of board that make up the plywood according to the selection criteria of each layer of board; Step 2: Since the wood grain of the plywood should be horizontally and vertically staggered, the veneer is cut by a panel saw, and then the board surface is spliced by a panel splicer to change its grain direction. The spliced board is used as the glue board; Step 3: Drill a plurality of through holes on the glue board, with a hole diameter of 0.5 - 1 cm. The through holes on the glue board are arranged in a matrix. The distance between any two adjacent through holes in the same row or the same column is 7 - 10 cm. Then fill cylindrical sponge blocks into the holes. The cylindrical sponge blocks are pre-cut. The outer diameter of the sponge block is slightly larger than the hole diameter, but the sponge block has elasticity, so it can be stuck in the through hole, and the height of the sponge block is slightly larger than the thickness of the glue board; Step 4: Evenly apply the resin glue on the surfaces of each layer of boards including the glue board. Before applying the glue, clean the surfaces of the boards to avoid any debris attachment. Only apply the glue on the lower side of the panel and the upper side of the bottom board. Apply the glue on both sides of the remaining layers of boards. When applying the glue, leave a 1 - 3 cm wide area along the edges of the boards without applying glue. The thickness of the applied resin glue is 1.8 - 2.2 mm, and the glue application amount is 280 - 360 g / M². After the glue application is completed, neatly arrange the glue board and the layers of boards in Step 1 from top to bottom in sequence to form a blank assembly; Since there are multiple through - holes on the glue board and sponge blocks are fixed in the holes, when applying the glue, the resin glue will soak the sponge blocks and pass through the glue board through the through - holes. In this way, the through - holes are filled with resin glue, and the boards on both the upper and lower sides of the glue board are not only adhered to the glue board but also directly adhered to each other under the action of the resin glue inside the through - holes. This enables even non - adjacent boards to be directly adhered together, improving the connection strength between the layers of the plywood and effectively avoiding delamination. The height of the sponge block is greater than the thickness of the glue board, aiming to ensure that when adhering, the sponge blocks soaked with resin glue can be in close contact with the board pieces at their top and bottom.

[0007] Step 5: Cold - press the layers of boards after the blank assembly is completed. Use a cold - press to preliminarily shape the boards. Cold - pressing means applying pressure to the assembled boards at normal temperature with a pressure of 10 - 14 MPA for 10 - 40 minutes. After preliminary shaping, continue to perform hot - pressing. The entire hot - pressing process is divided into three periods: pressure - rising, pressure - maintaining, and pressure - dropping. Under the condition of ensuring product quality and bonding strength, reasonably control the bonding process conditions according to different tree species, board blank thickness, adhesive variety, and product strength. After reaching the hot - pressing time, the plywood is preliminarily made. Take out the hot - pressed plywood from the hot - press and then stack it parallel for 24 hours to allow it to naturally dissipate heat and continue to cure completely; Whether it is cold - pressing or hot - pressing, the boards need to bear a large extrusion force. Since resin glue is applied between the layers of boards, before curing, the resin glue is a viscous fluid. After being pressed, the resin glue will inevitably flow around. When applying the glue to each layer of boards, a 1 - 3 cm blank area is left along the edges without applying glue. Therefore, when the pressed resin glue flows around, it will automatically fill the blank area, preventing the resin glue from being directly extruded from the side of the plywood. In this way, the blank area can also be adhered together with resin glue. If the blank area is not reserved, the resin glue will be extruded from the side of the plywood when flowing around after being pressed, causing unnecessary waste. Therefore, this method improves the utilization rate of the resin glue and reduces the waste of resin glue.

[0008] Step 6: The cooled plywood is first sanded to make its surface flat and smooth. When sanding, pay attention to the cleanliness of the sanding belt and the feeding speed should not be too fast to avoid defects such as material jamming and uneven sanded surface. Subsequently, the plywood is trimmed according to the specified dimensions. After trimming, the dimensions should be measured to ensure that the dimensions of the trimmed plywood meet the requirements. Since sanding is carried out after trimming during the processing, the problem of "gnawing the head" during sanding is avoided. Step 7: The trimmed board is inspected by workers. After ensuring that there are no damages such as cracking and delamination, it is then packaged, thus completing the processing and production of plywood.

[0009] Furthermore, in Step 1, if the moisture content of the board exceeds the standard, the board can be dried until the moisture content reaches the standard. If the moisture content of the wood board is too high, it is prone to moisture absorption, deformation, and may also show phenomena such as swelling and cracking during use. In addition, too high humidity is also likely to cause mold growth and shorten the service life of the wood board. Therefore, it is very important to dry the board to reduce its moisture content. If the surface flatness of the board does not meet the requirements, its surface can be polished. The premise of the polishing process is that its flatness is within the repairable range. If the flatness is too poor and cannot be repaired only by polishing, then there is no need to polish.

[0010] Furthermore, the resin glue in Step 4 is prepared by pre-mixing and the specific steps are as follows: S1: Add 3.2 tons of water into the reaction kettle, then add 950 kg of caustic soda, stir evenly, add 4 tons of phenol, continue stirring and cool down to 40 °C, add 5.2 tons of formaldehyde, heat up to 100 - 101 °C, maintain this temperature for 30 - 45 minutes, and monitor the viscosity during the heat preservation period. The target viscosity is 14 - 15 seconds. S2: Cool the reaction solution to 96 - 98 °C, add 600 kg of urea, continue to cool down to 88 °C, then add 1.6 tons of formaldehyde, and react for 50 - 60 minutes. Monitor the viscosity during the reaction process. The target viscosity is 50 - 70 seconds. S3: Add 650 kg of water, cool down to below 80 °C, then add 1200 kg of urea, cool down to 45 °C, add 1250 kg of 32% concentration caustic soda solution, then cool down to 41 °C, and finally add 300 kg of 6% concentration polyvinyl alcohol solution, and continue to react for 15 minutes. S4: After 15 minutes, the processing is completed, the viscosity is detected. After the viscosity is qualified, the glue can be released. At this time, the viscosity is about 60 seconds.

[0011] Furthermore, during the process of preparing the resin glue, ensure that the operating environment is well-ventilated to reduce the accumulation of harmful gases.

[0012] In the above technical solution, the technical effects and advantages provided by the present invention: 1. By opening through holes in each layer of rubber sheet and filling them with sponge blocks, when applying glue, the resin glue can infiltrate the sponge blocks and fill the through holes. The two layers of boards above and below the rubber sheet can be adhered together through the resin glue at the through holes, enabling direct adhesion even between non-adjacent boards, improving the connection strength between the layers of the plywood, and effectively avoiding delamination. 2. When applying glue, leave a blank area 1 - 3 cm wide at the edge of the board. During cold pressing and hot pressing, the resin glue flowing around will automatically fill the blank area, preventing the resin glue from being directly extruded from the side of the plywood, thereby improving the utilization rate of the resin glue and reducing waste. Specific implementation method

[0013] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further introduced in detail below.

[0014] The present invention provides a plywood production process, and the specific steps are as follows: Step 1: The plywood is composed of multiple layers of boards stacked from bottom to top. The top layer of the plywood is called the face plate, and the bottom layer is called the bottom plate. Before production, it is first necessary to select each layer of boards. Select the boards for each layer of the plywood according to the selection criteria, and the selection criteria include tree species grade, moisture content of the board, etc. The surface of the board is flat and smooth, without wormholes and cracks, and has good integrity. Commonly used board materials include pine, poplar, etc. Taking a 7 - layer plywood with a thickness of 12 mm as an example, the sorted boards are arranged from top to bottom in the order of face plate, long middle board, long middle board, bottom plate. During the subsequent process of applying glue and assembling the blanks, workers assemble the blanks in sequence to avoid mistakes and improve work efficiency; If the moisture content of the board exceeds the standard, the board can be dried until the moisture content reaches the standard. If the moisture content of the wood board is too high, it is prone to moisture absorption, deformation, and may also show phenomena such as swelling and cracking during use. In addition, too high humidity is also likely to cause mold growth, shortening the service life of the wood board. Therefore, it is very important to dry the board to reduce its moisture content. If the flatness of the board surface does not meet the requirements, its surface can be polished on the premise that its flatness is within the repairable range. If the flatness is too poor and cannot be repaired only by polishing, there is no need to polish.

[0015] Step 2: Since the wood grain of the plywood should be horizontally and vertically staggered, the veneer is cut by a panel saw and then the board surface is spliced by a panel splicer to change its grain direction. The spliced board is used as the rubber sheet. Step 3: Drill a plurality of through-holes in the rubber plate with a hole diameter of 0.5 - 1 cm. The through-holes on the rubber plate are arranged in a matrix. Any two adjacent through-holes in the same row or the same column are spaced 7 - 10 cm apart. Subsequently, fill the holes with cylindrical sponge blocks. The cylindrical sponge blocks are pre-cut. The outer diameter of the sponge block is slightly larger than the hole diameter, but the sponge block is elastic, so it can be stuck in the through-hole, and the height of the sponge block is slightly larger than the thickness of the rubber plate; Step 4: Evenly apply the resin glue on the surfaces of each layer of plates including the rubber plate. Before applying the glue, the surfaces of the plates need to be cleaned to avoid the attachment of sundries. Only the lower side of the panel needs to be coated, and only the upper side of the bottom plate needs to be coated. Both sides of the remaining layers of plates need to be coated. When applying the glue, a part with a width of 1 - 3 cm is left uncoated at the edge of the plate. The coating thickness of the resin glue is 1.8 - 2.2 mm, and the glue application amount is 280 - 360 g / M². After the glue application is completed, neatly arrange the rubber plate and each layer of plates in Step 1 from top to bottom in sequence to form a blank. Taking a 7-layer plywood as an example, arrange and form a blank in the order of bottom plate, rubber plate, long middle plate, rubber plate, long middle plate, rubber plate, and panel from bottom to top; Since a plurality of through-holes are provided in the rubber plate and sponge blocks are fixed in the holes, when applying the glue, the resin glue will infiltrate the sponge blocks and pass through the rubber plate through the through-holes. In this way, the through-holes are filled with resin glue, and the plates on the upper and lower sides of the rubber plate are not only adhered to the rubber plate, but also directly adhered under the action of the resin glue inside the through-holes. This enables even non-adjacent plates to be directly adhered together, improving the connection strength between each layer of plates of the plywood and effectively avoiding the delamination situation. The purpose of the height of the sponge block being greater than the thickness of the rubber plate is that when adhering, the sponge block infiltrated with resin glue can be in close contact with the plate members at its top and bottom; The above resin glue is prepared and blended in advance, and the specific steps are as follows: S1: Add 3.2 tons of water to the reaction kettle, then add 950 kg of caustic soda, stir evenly, add 4 tons of phenol, continue to stir and cool down to 40 °C, add 5.2 tons of formaldehyde, heat up to 100 - 101 °C, and maintain this temperature for 30 - 45 minutes. Monitor the viscosity during the heat preservation period, and the target viscosity is 14 - 15 seconds; S2: Cool the reaction solution to 96 - 98 °C, add 600 kg of urea, continue to cool down to 88 °C, then add 1.6 tons of formaldehyde, and react for 50 - 60 minutes. Monitor the viscosity during the reaction process, and the target viscosity is 50 - 70 seconds; S3: Add 650 kg of water, cool down to below 80 °C, then add 1200 kg of urea, cool down to 45 °C, add 1250 kg of 32% concentration caustic soda solution, then cool down to 41 °C, and finally add 300 kg of 6% concentration polyvinyl alcohol solution, and continue to react for 15 minutes; S4: The processing is completed after 15 minutes. Then the viscosity is detected. After the viscosity is qualified, the glue can be released. At this time, the viscosity is about 60 seconds. Strictly control the temperature and time of each step to prevent the reaction from being too fast or incomplete.

[0016] During the above process of preparing the resin glue, it should be ensured that the operating environment is well-ventilated to reduce the accumulation of harmful gases.

[0017] Step Five: Cold press each layer of the board after the lamination is completed. The board is preliminarily shaped by a cold press. Cold pressing means applying pressure to the laminated board at normal temperature with a pressure of 10 - 14 MPA for 10 - 40 minutes. After it is preliminarily shaped, continue to perform hot pressing on it. The pre-pressed board blanks should be hot-pressed in sequence. To prevent the glue layer closest to the hot press plate from curing prematurely, try to shorten the loading time of the board. The entire hot pressing process is divided into three periods: pressure increasing, pressure maintaining, and pressure decreasing. Under the condition of ensuring product quality and bonding strength, according to different tree species, board blank thickness, variety of adhesives, and product strength, reasonably master the bonding process conditions. Taking larch as an example for the tree species and phenolic resin glue as an example for the adhesive, during the hot pressing process, the unit pressure should be 8 - 10 kg / cm 2 , the gauge pressure is 10 - 12 mpa, the temperature is controlled at 110 - 125 °C, and the time depends on the thickness of the plywood, which is 55 - 60 s / mm. After reaching the hot pressing time, the plywood is preliminarily made. Take the hot-pressed plywood out of the hot press, and then stack it parallel for 24 hours to allow it to dissipate heat naturally and continue to cure completely; Whether it is cold pressing or hot pressing, the board needs to bear a large extrusion force. Since resin glue is applied between each layer of the board, before curing, the resin glue is a viscous fluid. The pressed resin glue will inevitably flow to the surrounding areas. When applying glue to each layer of the board, a blank space of 1 - 3 cm is left uncoated at the edge position. Therefore, when the pressed resin glue flows to the surrounding areas, it will automatically fill the blank space. In this way, the blank space can also be adhered together by the resin glue. If the blank space is not reserved, the pressed resin glue will be squeezed out from the side of the plywood when flowing to the surrounding areas, resulting in unnecessary waste. Therefore, this method improves the utilization rate of the resin glue and reduces the waste of the resin glue.

[0018] Step Six: The cooled plywood is first sanded to make the surface of the plywood flat and smooth. When sanding, pay attention to the cleanliness of the sanding belt and the feeding speed should not be too fast to avoid defects such as material jamming and uneven sanding surface. Subsequently, trim the plywood according to the specified size. After trimming, measure the size to ensure that the size of the trimmed plywood meets the requirements. Since sanding is performed first and then trimming during the processing, the phenomenon of "gnawing the head" during sanding is avoided; Step 7: The sawn-edge boards are inspected by workers. After ensuring that there are no damages such as cracking and delamination, they are then packaged, thus completing the processing and production of plywood.

[0019] Only some exemplary embodiments of the present invention have been described by way of illustration above. Undoubtedly, for those of ordinary skill in the art, the described embodiments can be modified in various different ways without departing from the spirit and scope of the present invention. Therefore, the above description is illustrative in nature and should not be construed as a limitation on the scope of protection of the claims of the present invention.

Claims

1. A plywood production process, characterized in that: The specific steps are as follows: Step 1: Select the materials for each layer of plywood according to the selection criteria of each layer of board; Step 2: Cut the veneer with a panel saw, then splice the board surface with a splicing machine to change its grain direction. The spliced ​​board is used as a plastic board; Step 3: Drill multiple through holes on the plastic board with a hole diameter of 0.5-1 cm, and then fill the holes with cylindrical sponge blocks; Step 4: Apply the resin glue evenly on the surface of each layer of the board including the glue plate. When applying the glue, leave a 1-3cm width area on the edge of the board without applying the glue. After the glue is applied, arrange the glue plate and each layer of the board in step 1 in order from top to bottom to assemble the board; Step 5: cold press each layer of the assembled board to preliminarily shape the board. After the preliminarily shaping, continue to hot press it. After the hot pressing time is reached, the plywood is preliminarily made. The hot pressed plywood is taken out of the hot press and then stacked in parallel for 24 hours. Step 6: After the plywood has cooled, it is first sanded to make the surface of the plywood flat and smooth, and then the plywood is trimmed according to the specified size. After the trimming is completed, the size is measured to ensure that the size of the plywood after trimming meets the requirements; Step 7: After trimming, the workers will check the boards to ensure that there is no damage before packaging, thus completing the processing and production of plywood.

2. A plywood production process according to claim 1, characterized in that: In step one, if the moisture content of the board exceeds the standard, the board is dried until the moisture content of the board meets the standard. If the flatness of the board does not meet the requirement, the surface is polished.

3. A plywood production process according to claim 1, characterized in that: The resin glue in step 4 is prepared and blended in advance, and the specific steps are as follows: S1: Add 3.2 tons of water to the reactor, then add 950 kg of caustic soda flakes, stir evenly, add 4 tons of phenol, continue stirring and cool to 40°C, add 5.2 tons of formaldehyde, heat to 100-101°C, and maintain the temperature for 30-45 minutes; S2: Cool the reaction solution to 96-98°C, add 600 kg of urea, continue to cool to 88°C, add 1.6 tons of formaldehyde, and react for 50-60 minutes; S3: add 650 kg of water, cool to below 80°C, add 1200 kg of urea, cool to 45°C, add 1250 kg of 32% alkaline water, cool to 41°C, and finally add 300 kg of 6% polyvinyl alcohol solution, and continue to react for 15 minutes; S4: After 15 minutes, the processing is completed and the viscosity is tested. After the viscosity is qualified, the glue can be released.

4. A plywood production process according to claim 3, characterized in that: During the preparation of resin glue, ensure that the operating environment is well ventilated to reduce the accumulation of harmful gases.