Polyvinyl chloride high foam board drying system

Abstract

A polyvinyl chloride high foam board drying system comprises a drying oven, a drying room, a conveying device and an automatic control system, the drying oven and the drying room are sequentially connected, the drying oven comprises a microwave heating device, a hot air circulation heating device and a vacuumizing device, three temperature control intervals are arranged in the drying room, each temperature control interval independently controls the temperature, and the conveying device is connected with the automatic control system. A microwave heating device, a hot air circulation heating device and a moisture removal device are arranged in the drying room, the conveying device comprises a conveying mechanism and a foaming plate carrier, and the automatic control system comprises a PLC, a conveying device controller, an isolation door control device and a valve control device. The continuous drying device can meet the continuous drying requirement of large-scale production of polyvinyl chloride high-foaming boards, improves drying efficiency and product size stability, reduces contact between production personnel and solvent steam, enhances safe operability, and reduces labor intensity of the personnel.

Description

Technical Field

[0001] The utility model relates to the technical field of foam material drying, in particular to a drying system for polyvinyl chloride high-foaming board. Background Technique

[0002] At present, organic solvents are generally added in the production process of polyvinyl chloride high-foaming board materials. The purpose of drying is to remove the residual organic solvents. The residual organic solvents in the polyvinyl chloride high-foaming board will seriously affect various properties such as heat preservation, strength, dimensional stability, bulk density, and flame retardancy of the materials. Prolonged contact with organic solvents will also have an adverse impact on human health.

[0003] At present, the common drying technology for foaming materials mainly adopts a single hot air circulation drying technology. In related technologies, Chinese invention with the application publication number CN102408645A discloses a formula of PVC foaming board and its preparation method. The drying process of its polyvinyl chloride foaming board is mainly divided into two steps: Step 3, put the taken-out foaming board under normal pressure into an oven and heat it to 100-120°C until the target foaming ratio is obtained; Step 4, take out the foaming board with the obtained target foaming ratio, cool it to room temperature, and then send it into a drying room to slowly heat it at 60-80°C until the organic solvents are removed. The problems existing in the above drying technology are as follows: With conventional hot air drying, the heat slowly transfers from the surface of the foaming board to the inside, and the drying efficiency is low. Continuing to dry at a certain higher temperature will cause uneven heating and stress on the surface and inside of the foaming board, resulting in deformation of the board. During the drying process of polyvinyl chloride foaming board, the temperature and the volatilization rate of the solvent are linearly related. The higher the temperature, the faster the volatilization rate of the organic solvent. However, when the polyvinyl chloride foaming board is at a temperature above the micro-Vicat softening point for a long time, the polyvinyl chloride gradually loses its original rigidity and becomes soft. Under a small external force, a large deformation will occur. The high temperature makes the volatilization rate of the organic solvent faster. In the closed cells, the expanded organic solvent vapor makes the volume of the foaming board further increase. When the expanded volume of the cells exceeds the stress of the high-elastic polyvinyl chloride molecular chain, the cells rupture, and the inside of the polyvinyl chloride foaming board tears and delaminates; The solvent residue amounts in different drying stages of the polyvinyl chloride high-foaming board are different. Continuing to dry at a higher temperature will cause uneven heating and stress on the surface and inside of the foaming board, resulting in deformation of the board; When the foaming board cools from a high temperature to room temperature, when the polyvinyl chloride foaming board immediately transfers from a high-temperature state to room temperature, the molecular chain quickly returns to its original state from the high-elastic state under the action of stress, causing a large amount of shrinkage of the foaming board size in a short time. At the same time, the internal and external cooling rates are not synchronized, and the stress actions are inconsistent, resulting in curling deformation of the polyvinyl chloride foaming board. When reheated, it will cause large deformation of the polyvinyl chloride foaming board and increase energy consumption. Content of the Utility Model

[0004] A drying system for polyvinyl chloride high-foam board provided by the utility model has high drying efficiency for polyvinyl chloride high-foam board, uniform heating, not easy to deform, small shrinkage, short curing time and high automation degree.

[0005] To achieve the above object, the utility model provides a drying system for polyvinyl chloride high-foam board, which includes an oven, a drying room with at least 2 temperature control intervals behind the oven, and an isolation door is provided in each temperature control interval; a hot air circulation device, a polyvinyl chloride high-foam board transportation device and a drying automatic control system are provided in the oven, and the hot air circulation device includes a fan, a radiator, a deflector, a control valve and a temperature sensor.

[0006] The freshly molded polyvinyl chloride foam board is placed on the carrier in layers, and is sent into the oven by the conveying mechanism. In the oven, the hot air circulation device circulates and heats the hot air in the oven to maintain a certain temperature, so that the foam board is heated simultaneously inside and outside. Every certain time, the push plate valve of the oven opens to supplement hot air, and the waste gas enters the environmental protection device. After a certain time, the secondary foaming is completed; the conveying mechanism sends the carrier to the drying room connected to the oven in sequence for stage cooling and drying. Intermittent microwave heating and hot air circulation drying are carried out in each temperature control interval, which is beneficial to the volatilization of organic solvents inside the polyvinyl chloride foam board. The exhaust fan sends the waste gas into the pipeline of the environmental protection device. The dried polyvinyl chloride high-foam board is sent into the isolation room at the outlet of the drying room. After the strong exhaust ventilation device in the isolation room completes the ventilation, the conveying mechanism sends the foam board carrier outdoors; the polyvinyl chloride high-foam board is placed on the carrier in layers, and the blowing device cures the polyvinyl chloride high-foam with air flowing at a certain speed. The movement of the carrier, the opening and closing of the isolation door, and the intermittent microwave heating during the drying process are completed by the drying automatic control system. The start and stop of the fan, the opening and closing of the valve are interlocked with the feedback of the temperature sensor and the pressure sensor.

[0007] Preferably, there are 3 temperature control intervals in the drying room, which are divided by isolation doors in the front and rear temperature control intervals. The temperatures of the three temperature control intervals are 65-80°C in the first interval, 50-65°C in the second interval, and 40-50°C in the third interval from front to back.

[0008] Preferably, a microwave heating and control device is provided in the drying room. The hot air circulation device in the drying room is located at the top of the drying room, and the microwave heating device is located on both sides of the drying room.

[0009] Preferably, a microwave heating and control device is provided in the drying room. The microwave heating device in the drying room is located at the top and bottom of the drying room, and the hot air circulation device is located on one side of the drying room.

[0010] Preferably, a negative pressure device is provided in the oven, which includes an exhaust fan, a cut-off valve, a pressure sensor and a push plate valve.

[0011] Preferably, the drying automatic control system includes a PLC, a transportation device controller, an isolation door control device and a valve control device.

[0012] Preferably, a strong exhaust ventilation device is provided inside the oven.

[0013] The beneficial effects of the present utility model are as follows: Microwave heating can directly act on the internal pores of the foaming board, solving the difficulty that organic solvents in the internal pores of the foaming board are not easily volatilized, reducing the drying time, and improving the drying efficiency; The polyvinyl chloride high foaming board is placed in layers on the carrier, and hot air flows upward from the bottom of the foaming board. Combined with the air extraction of the moisture exhaust fan, it ensures that the polyvinyl chloride high foaming board is evenly heated, can effectively reduce the accumulation of organic solvent vapor, and is recycled to the waste gas treatment device in a timely manner; Gradient cooling drying is set in the drying room, solving the deformation problem caused by different solvent residue amounts and different internal and surface tensions of the polyvinyl chloride foaming board at different drying stages, reducing the curing time. The foaming board is arranged in layers for curing with flowing air, quickly releasing the stress caused by the temperature difference between the inside and outside of the polyvinyl chloride high foaming board, effectively reducing the dimensional shrinkage of the polyvinyl chloride high foaming board during the curing stage of being directly placed outdoors from high temperature, reducing the curing time, and improving the product quality; The carriers of unified specifications are universal in different stages, and the carrier conveying mechanism operates automatically according to the set program, effectively reducing the labor intensity of personnel and reducing the contact of personnel with organic solvent vapor.

[0014] In summary, the present utility model reasonably and effectively connects the drying process and equipment device of the polyvinyl chloride high foaming board, can meet the continuous drying requirements of large-scale production of polyvinyl chloride high foaming boards, improve the drying efficiency and product dimensional stability, reduce the contact time of production personnel with solvent vapor, enhance the safety operation, and reduce the labor intensity of personnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 and Figure 2 is a schematic structural diagram of a polyvinyl chloride high foaming drying system of the present utility model;

[0016] In the figure: 1. Carrier, 2. Oven, 3. First temperature control zone, 4. Second temperature control zone, 5. Third temperature control zone, 6. Isolation room, 7. Track, 8. Isolation door, 9. Isolation door, 10. Isolation door, 11. Isolation door, 12. Isolation door, 13. Isolation door, 14. Microwave heating device, 15. Exhaust fan, 16. Cut-off valve, 17. Hot air circulation heating device, 18. Moisture exhaust fan, 19. Strong exhaust fan, 20. Push plate valve DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] In order to enable those skilled in the art to more clearly and accurately understand the design principle, technical solution and implementation effect of the present utility model, the following combines the embodiments and the drawings to detail the specific implementation manner of the present utility model.

[0018] Example 1, referring to Figure 1 and Figure 2, a polyvinyl chloride high-foaming drying system includes an oven 2, and a drying room that is sequentially connected to the oven and is provided with a first temperature control zone 3, a second temperature control zone 4, a third temperature control zone 5, and an isolation room 6. It also includes a carrier 1 of the polyvinyl chloride high-foaming board transportation device and a conveying mechanism track 7, and an automatic drying control system. An isolation door 13 is provided at the inlet of the oven 2, an isolation door 12 is provided between the oven 2 and the first temperature control zone 3 of the drying room, an isolation door 11 is provided between the first temperature control zone 3 and the second temperature control zone 4, an isolation door 10 is provided between the second temperature control zone 4 and the third temperature control zone 5, an isolation door 9 is provided between the third temperature control zone 5 and the isolation room 6, and an isolation door 8 is provided at the outlet of the isolation room.

[0019] The first temperature control zone 3, the second temperature control zone 4, and the third temperature control zone 5 of the oven and the drying room are respectively provided with a microwave heating device 14 and a hot air circulation device 17. Among them, the hot air circulation device 17 is located at the top of the oven 2 and each temperature control zone of the drying room, and the microwave heating device 14 is located on both sides of each temperature control zone of the oven and the drying room. An exhaust fan 15 is provided at the top of the oven, a cut-off valve 16 is installed at the outlet of the exhaust fan, and a push plate valve 20 is provided on one side of the oven; a moisture exhaust fan 18 is provided at the top of each temperature control zone of the drying room, and a strong exhaust fan 19 is provided at the top of the isolation room 6.

[0020] The polyvinyl chloride high-foaming boards are placed layer by layer on the carrier 1, and the carrier 1 is pushed into the oven 2 by the conveying mechanism track 7. The hot air circulation device 17 in the oven 2 circulates and heats the hot air to 75 - 80 °C. The fan of the hot air circulation device 17 blows the hot air around the radiator and guides it through the guide plate to flow upward from the bottom of the oven 2, making the temperature distribution more uniform. The radiator control valve is interlocked with the temperature sensor in the oven 2 to control the steam flow; the exhaust fan 15 of the vacuum device pumps the pressure in the oven 2 to a slightly negative pressure. The exhaust fan 15 and the cut-off valve 16 are interlocked with the pressure sensor in the oven. The microwave generated by the microwave heating device 14 directly acts on the inside of the foaming board, and the surface and inside of the polyvinyl chloride high-foaming board are heated simultaneously, reducing the secondary foaming time when the pores open. In a slightly negative pressure environment, the solvent inside the foaming board is more likely to precipitate. The microwave is heated intermittently for 10 - 15 minutes and then heated for 2 - 5 minutes to prevent the pores inside the foaming board from aging continuously at high temperature, resulting in a decrease in the strength of the foaming board and tearing and delamination. The upward flow of hot air blows the organic solvent vapor precipitated from the foaming board to the top of the oven 2, and is pumped to a slightly negative pressure by the exhaust fan 15 and then discharged to the recovery pipeline for waste gas treatment. The slightly negative pressure is maintained for 10 - 15 minutes, the push plate valve 20 is opened to supplement hot air, and then the exhaust fan 15 pumps the pressure in the oven 2 to a slightly negative pressure. The time from vacuum pumping to hot air supplementation is 10 - 15 minutes. The polyvinyl chloride high-foaming board is continuously heated with hot air at 75 - 80 °C for 45 minutes - 1 hour to prevent the pores from shrinking and continuously precipitate the internal solvent.

[0021] The drying automatic control program opens the isolation door 12 between the drying oven 2 and the first temperature control zone 3 of the drying chamber, and the conveying mechanism track 7 transports the carrier 1 into the first temperature control zone 3. Then the isolation door 12 closes. The fan of the hot air circulation device blows preheated fresh air towards the radiator, and the hot air flows upward from the bottom of the carrier 1 after being guided by the deflector, making the temperature distribution more uniform. The radiator control valve is interlocked with the temperature sensor to control the steam flow. The microwave heating device heats intermittently for 2 - 5 minutes every 10 - 15 minutes. The top moisture exhaust fan 18 discharges the separated organic solvent gas to the recovery pipeline, and the carrier 1 is dried with circulating hot air at 70 - 75°C for 10 - 12 hours. The conveying mechanism track 7 transports the carrier 1 into the second temperature control zone 4. The fan of the hot air circulation device blows the hot air around the radiator and guides it through the deflector to flow upward from the bottom of the carrier 1. The radiator control valve is interlocked with the temperature sensor to control the steam flow. The microwave heating device heats intermittently for 1 - 3 minutes every 10 - 15 minutes. The top moisture exhaust fan 18 discharges the separated organic solvent gas to the recovery pipeline, and the carrier 1 is dried with circulating hot air at 60 - 70°C for 10 - 12 hours. The conveying mechanism track 7 transports the carrier 1 into the third temperature control zone 5. The fan of the hot air circulation device blows the hot air around the radiator and guides it through the deflector to flow upward from the bottom of the carrier 1. The radiator control valve is interlocked with the temperature sensor to control the steam flow. The microwave heating device heats intermittently for 1 - 3 minutes every 10 - 15 minutes. The top moisture exhaust fan 18 discharges the separated organic solvent gas to the environmental protection device, and the carrier 1 is dried with circulating hot air at 40 - 55°C for 10 - 12 hours.

[0022] The drying automatic control program opens the isolation door 9, and the conveying mechanism track 7 transports the carrier 1 into the isolation chamber 6. Then the isolation door 9 closes, and the program starts the forced exhaust fan to ventilate the isolation chamber 6 for 2 - 4 minutes. The program opens the isolation door 8, and the conveying mechanism track 7 or the conveyor belt 21 transports the carrier 1 outdoors. The outlet of the forced exhaust fan is connected to the recovery pipeline, effectively sending the organic solvent gas overflowing from the drying chamber to the environmental protection equipment.

[0023] The dried polyvinyl chloride high - foaming board is placed on the carrier 1 in layers, and the blowing device cures it at normal temperature with flowing air at 3 - 5 m / s to stabilize the size of the polyvinyl chloride high - foaming board.

[0024] The carrier 1 used in the drying process has a unified specification, with a layer height of 20 - 40 cm. There are casters at the four bottom corners for easy movement on the ground. There are 4 track wheels on the bottom crossbeam of the casters, which can simultaneously meet the use of the conveying mechanism track 7 and the conveyor belt 21. At the same time, the casters can move on the ground, effectively reducing the handling process of the polyvinyl chloride foaming board and lowering the labor intensity of workers.

[0025] Example 2. The difference between Example 2 and Example 1 is that the microwave heating devices in each temperature control zone of the drying oven 2 and the drying chamber are located at the top and bottom of each temperature control zone in the drying oven and the drying chamber, and the hot air circulation devices are located on one side of each temperature control zone in the drying oven and the drying chamber.

[0026] The above are only embodiments of the present utility model, and thus do not limit the patent scope of the present utility model. Any equivalent structural or equivalent process transformations made by using the content of the specification and drawings of the present utility model, directly or indirectly applied to other related technical fields, shall similarly be included within the patent protection scope of the present utility model.

Claims

1. A drying system for a high-foamed polyvinyl chloride board, comprising an oven, characterized in that There is a drying room with at least 2 temperature control zones behind the oven, and each temperature control zone is equipped with an isolation door; inside the oven, there is a hot air circulation device, a polyvinyl chloride high-foam board transportation device, and a drying automatic control system. The hot air circulation device includes a fan, a radiator, a deflector, a control valve, and a temperature sensor.

2. The drying system for a high-foamed polyvinyl chloride board according to claim 1, characterized in that, There are 3 temperature control zones in the drying room, which are divided by isolation doors at the front and back. The temperatures of the three temperature control zones are 65 - 80 °C in the first zone, 50 - 65 °C in the second zone, and 40 - 50 °C in the third zone from front to back.

3. A drying system for a polyvinyl chloride high-foam board according to claim 2, characterized in that, There is a microwave heating and control device in the drying room. The hot air circulation device in the drying room is located at the top of the drying room, and the microwave heating device is located on both sides of the drying room.

4. The drying system for a high-foaming polyvinyl chloride board according to claim 2, characterized in that, There is a microwave heating and control device in the drying room. The microwave heating device in the drying room is located at the top and bottom of the drying room, and the hot air circulation device is located on one side of the drying room.

5. A drying system for a high-foamed polyvinyl chloride board according to claim 1, characterized in that The drying automatic control system includes a PLC, a transportation device controller, an isolation door control device, and a valve control device.

6. The drying system for high-foamed polyvinyl chloride boards according to any one of claims 1-5, characterized in that, There is a negative pressure device in the oven, which includes an exhaust fan, a cut-off valve, a pressure sensor, and a push plate valve.

7. The drying system for polyvinyl chloride high-foaming board according to any one of claims 1-5, characterized in that, There is a strong exhaust and ventilation device in the oven.

8. A polyvinyl chloride high-foam board drying system according to claim 6, characterized in that, There is a strong exhaust and ventilation device in the oven.

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