Curing device for improving crystallization uniformity of PUR hot melt adhesive

Abstract

The invention discloses a curing device for improving crystallization uniformity of a PUR hot melt adhesive, comprising: a curing cavity, in which a preheating zone, a melting zone and a crystallization zone which are isolated from each other are sequentially arranged along a product transportation direction; the conveying device is arranged in the center of the interior of the curing cavity and used for continuously conveying products to sequentially pass through the preheating area, the melting area and the crystallization area; the plurality of top plates are fixedly mounted at the tops of the preheating zone, the melting zone and the crystallization zone respectively; the air curtain isolation device is arranged at the feeding end of the preheating area and the discharging end of the crystallization area and used for isolating the external environment from air flow exchange in the curing cavity; the electromagnetic induction heating module is arranged at the bottom of the melting area, through multi-mode collaborative heating and intelligent closed-loop control, the crystallization uniformity of the PUR hot melt adhesive is remarkably improved, the mechanical property of a product is improved, the production efficiency is doubled, the energy consumption is reduced, and excellent process adaptability and environment friendliness are achieved.

Description

Technical Field

[0001] This invention relates to the field of polymer material processing equipment technology, specifically to a curing device for improving the uniformity of crystallization of PUR hot melt adhesive. Background Technology

[0002] Polyurethane reactive hot melt adhesives (PUR) are widely used in packaging, automotive, and electronic packaging due to their excellent bonding strength, weather resistance, and environmental friendliness. However, during the curing process, the uniformity of crystallization directly affects the final bonding performance and product yield of PUR adhesives. Traditional curing devices often use constant temperature ovens or static hot air curing, which have problems such as uneven temperature distribution and disordered airflow organization. This leads to large differences in the crystallization rate of PUR adhesives and concentration of internal stress, which in turn causes defects such as cracking, warping, or bonding failure of the adhesive layer.

[0003] Currently, uneven crystallization is a common problem in the curing process of PUR hot melt adhesives, mainly due to the following defects in traditional curing equipment: Inaccurate temperature control – Constant temperature heating or a single heat source leads to an unreasonable temperature gradient between the melting and crystallization zones, affecting the orderly arrangement of PUR molecular chains; Inefficient airflow organization—static hot air circulation or unidirectional airflow cannot eliminate local temperature differences, resulting in inconsistent crystallization rates; Lack of dynamic control – The lack of real-time monitoring and feedback on the curing process (such as melting state and crystallization phase transformation) makes it difficult to adapt to the process requirements of different PUR formulations.

[0004] Therefore, a curing device for improving the uniformity of crystallization of PUR hot melt adhesive is proposed to solve the problems mentioned above. Summary of the Invention

[0005] The purpose of this invention is to provide a curing device that improves the uniformity of crystallization of PUR hot melt adhesive, thereby solving the problem mentioned in the background art that the existing curing devices have poor uniformity of crystallization of PUR hot melt adhesive due to uneven temperature field, uncontrolled airflow distribution and lack of closed-loop regulation, which in turn affects its final bonding performance and product yield.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a curing apparatus for improving the uniformity of crystallization of PUR hot melt adhesive, comprising: The solidification chamber has a preheating zone, a melting zone, and a crystallization zone arranged sequentially along the product transport direction. A conveying device is located at the center of the solidification chamber and is used to continuously convey the product through the preheating zone, melting zone and crystallization zone in sequence. Multiple top plates are respectively fixedly installed on the top of the preheating zone, melting zone and crystallization zone; An air curtain isolation device is installed at the feeding end of the preheating zone and the discharging end of the crystallization zone to isolate the external environment from the airflow exchange inside the curing chamber. An electromagnetic induction heating module is located at the bottom of the melting zone and arranged along the transport direction of the conveying device, for non-contact induction heating of the product; Infrared radiation heating modules are symmetrically distributed on both sides of the molten zone to provide uniform radiation heating; Hot air circulation modules are installed below the top plate of each functional area for forced convection heat transfer; The detection module, including a temperature sensor and an NIR crystallinity sensor, is set in the melting zone and crystallization zone, respectively, to monitor process parameters in real time and feed them back to the PLC controller.

[0007] Preferably, the electromagnetic induction heating module includes: three induction coils evenly distributed along the transport direction of the conveying device, with the vertical distance between the surface of each coil and the bottom of the conveying device being 10 to 15 mm.

[0008] Preferably, the infrared radiation heating module includes: two rows of parallel carbon fiber heating tubes, each row containing ten carbon fiber heating tubes equidistantly arranged along the conveying direction, symmetrically distributed on both sides of the melting zone; and a mounting bracket, which fixes both ends of each carbon fiber heating tube by quick-release buckles, and the mounting bracket is rigidly connected to the side wall of the curing chamber.

[0009] Preferably, the hot air circulation module includes a centrifugal fan, which is fixed to the surface of the top plate. The air outlet of the centrifugal fan is fixedly connected to a guide air duct. An air outlet frame is provided at the air outlet of the guide air duct. Through holes are evenly opened around the air outlet frame, and guide vanes and flow equalizers are arranged sequentially inside the frame along the airflow direction. A button is provided inside the through holes.

[0010] Preferably, one side of the button is provided with an outer sleeve, one end of which is connected to the base by a thread, and the outer side of the base is fixed to the top plate; the other end of the outer sleeve has two symmetrically opened guide grooves, each guide groove is provided with a connecting rod, and the two ends of the connecting rod are rigidly connected to the button and the inner sleeve provided inside the outer sleeve, respectively; one end of the inner sleeve is provided with three limiting grooves evenly distributed along the central axis, and each limiting groove is provided with a steel ball, one side of the steel ball is in contact with the inner wall of the outer sleeve, and the other side is used to contact the pin block, and the top of the steel ball is elastically connected to the base by a spring; one end of the pin block is kept in close contact with the air outlet frame.

[0011] Preferably, the detection module includes two support columns and four support frames. The two support columns are respectively located on both sides of the conveying device in the melting zone, and each support column is equipped with two sets of temperature sensors for monitoring the temperature difference between the upper and lower surfaces of the product. The four support frames are respectively located at the inlet and outlet of the crystallization zone. Each support frame has an NIR crystallinity sensor engaged in its center and is covered with a detachable heat-insulating protective cover on its outer side.

[0012] Preferably, the PLC controller is configured to execute the following control logic: dynamically adjust the power of the electromagnetic induction heating module based on the data fed back by the temperature sensor, wherein the operating frequency of the electromagnetic induction heating module is 20–50kHz; adjust the hot air temperature of the crystallization zone based on the detection data of the NIR crystallinity sensor, with a control accuracy of ±1℃; and link the wind speed of the air curtain isolation device and the conveyor belt speed of the conveyor device.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: This curing device for improving the uniformity of PUR hot melt adhesive crystallization significantly improves the uniformity of PUR hot melt adhesive crystallization (temperature difference ≤ ±1℃) through multi-mode synergistic heating and intelligent closed-loop control, thereby improving the mechanical properties of the product, doubling production efficiency, reducing energy consumption, and possessing excellent process adaptability and environmental friendliness. The specific details are as follows: 1. Significantly improves crystallization uniformity Multi-level temperature control synergy: Through the precise penetrating heating of the electromagnetic induction heating module (1.2-1.5mm depth), the uniform radiation of the infrared radiation heating module (wavelength 2.5-5μm), and the forced convection of the hot air circulation module, the temperature uniformity of PUR hot melt adhesive throughout the entire process from melting to crystallization is achieved (temperature difference ≤ ±1℃). Three-dimensional monitoring and control: The detection module provides real-time data feedback through upper and lower surface temperature sensors and NIR crystallinity sensor, and the PLC controller dynamically adjusts the heating parameters to avoid crystallization defects caused by local overcooling or overheating; 2. Enhance product performance Improved crystallization uniformity significantly reduces internal stress in the adhesive layer, resulting in superior peel strength and heat resistance compared to traditional processes; optimized microstructure leads to more concentrated grain size distribution and improved crystallinity stability. 3. Improve production efficiency and energy efficiency Continuous production: The coordinated design of the conveying device and the air curtain isolation device enables uninterrupted curing, with a production speed of 1.0-1.5m / min (traditional process ≤0.5m / min). Reduced energy consumption: Electromagnetic induction heating (energy utilization rate > 90%) and hot air circulation (80% airflow reuse) reduce overall energy consumption by 35%, with unit energy consumption ≤ 1.0 kWh / kg; 4. Intelligence and Reliability Closed-loop control: The PLC controller automatically adjusts process parameters based on the crystallinity data (1200-2400nm band) from the NIR crystallinity sensor, reducing human intervention errors; Modular maintenance: The quick-release clip-on carbon fiber heating tube, detachable air outlet frame, and heat insulation protective cover design reduce maintenance time by 50%.

[0014] 5. Compatibility and environmental friendliness Wide process compatibility: It can be used with polyester / polyether type PUR adhesives, and can meet different formulation requirements by adjusting the electromagnetic frequency (20-50kHz) and hot air temperature (±1℃). VOC control: The air curtain isolation device effectively blocks the mixing of external air and reduces the volatilization of isocyanate monomers (TDI residue <0.05%). Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall appearance and structure of the present invention; Figure 2 This is a schematic diagram of the internal structure of the curing cavity of the present invention; Figure 3 This is a top view of the internal structure of the curing cavity of the present invention; Figure 4 This is a schematic diagram of the overall exploded structure of the present invention; Figure 5 This is a schematic diagram of the hot air circulation module structure in this invention; Figure 6 For the present invention Figure 5 A front view structural diagram; Figure 7 For the present invention Figure 6 Schematic diagram of the cross-sectional structure at point A in the middle; Figure 8 For the present invention Figure 6 Enlarged structural diagram at point C; Figure 9 For the present invention Figure 3 Enlarged structural diagram of the mid-infrared radiation heating module; Figure 10 For the present invention Figure 4 Enlarged structural diagram of the detection module; Figure 11 This is a schematic diagram of the fixed state structure of the pin block in this invention; Figure 12 For the present invention Figure 11 A schematic diagram of the exploded structure; Figure 13 This is a schematic diagram of the structure of the NIR crystallinity sensor in this invention; Figure 14 For the present invention Figure 13Schematic diagram of the cross-sectional structure at point B.

[0016] In the diagram: 1. Solidification chamber; 101. Conveying device; 102. Preheating zone; 103. Melting zone; 104. Crystallization zone; 105. Top plate; 106. Air curtain isolation; 2. Electromagnetic induction heating module; 3. Infrared radiation heating module; 301. Carbon fiber heating tube; 302. Mounting bracket; 4. Hot air circulation module; 401. Centrifugal fan; 402. Air duct; 403. Air outlet frame; 404. Guide vane; 405. Uniform Flow plate; 406, Through hole; 407, Button; 408, Outer sleeve; 409, Base; 410, Guide groove; 411, Connecting rod; 412, Inner sleeve; 413, Limiting groove; 414, Steel ball; 415, Spring; 416, Pin block; 5, Detection module; 501, Support column; 502, Temperature sensor; 503, Support frame; 504, NIR crystallinity sensor; 505, Heat insulation protective cover; 6, PLC controller. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Please see Figure 1-14 The present invention provides a technical solution: a curing device for improving the uniformity of crystallization of PUR hot melt adhesive, comprising: a curing chamber 1, wherein a preheating zone 102, a melting zone 103 and a crystallization zone 104 are arranged sequentially along the product transport direction and are isolated from each other. The three-zone independent temperature control design (preheating zone 102 / melting zone 103 / crystallization zone 104) realizes the gradual processing of PUR adhesive from softening to melting to crystallization; the temperature gradient of each zone can be adjusted independently (preheating zone 60-80℃ / melting zone 150-180℃ / crystallization zone 80-100℃), avoiding crystallization defects caused by sudden temperature changes in traditional equipment; Actual test data (test conditions: test material: polyester PUR hot melt adhesive (thickness 1.2mm), ambient temperature: 25±2℃; production capacity: 1.2m / min continuous production; comparison equipment: traditional tunnel curing oven (single temperature zone design)) shows that the partitioned isolation structure reduces heat conduction loss in each temperature zone by 72% (from 15.6kW / m² of traditional equipment to 4.3kW / m²); comprehensive energy consumption comparison tests show that, under the same production capacity, the energy consumption of this device is 0.92kWh / kg, which is 35.2% lower than that of traditional equipment (1.42kWh / kg); moreover, the preheating zone increases the initial temperature of the melting zone. At 75±2℃, thermal imaging measurements showed that the time required for the molten zone to reach the operating temperature (160℃) was reduced by 58% (from 210s to 88s); the steady-state maintenance power of the molten zone decreased by 40.5% (from 18.3kW to 10.9kW); the independent temperature control system reduced the temperature fluctuation range of the crystallization zone from ±5℃ to ±1℃; the overheating time was reduced by 83% (from 32s per minute to 5.4s); the hot air circulation system's operating cycle was extended by 25% (from 8 minutes / cycle to 10 minutes / cycle); and power monitoring data showed that the energy saving rate of the crystallization zone reached 25.7% (power decreased from 12.4kW to 9.2kW). The conveying device 101 is located at the center of the solidification chamber 1 and is used to continuously convey the product through the preheating zone 102, the melting zone 103 and the crystallization zone 104 in sequence. The conveyor device 101 uses a SUS316L stainless steel woven mesh belt with a mesh size of 2mm×2mm and a belt width of 1000mm. It is driven by a 7.5kW servo motor, and the speed can be steplessly adjusted within the range of 0.1-1.5m / min. The SUS316L stainless steel material (containing 2-3% molybdenum) maintains excellent creep resistance even at 250℃, with a service life exceeding 8000 hours, 2.7 times longer than ordinary carbon steel mesh belts (3000 hours). It also effectively resists corrosion from PUR resin volatiles. (2mm×2m) The precision mesh allows for uniform hot air penetration, with a wind speed distribution CV (coefficient of variation) of <5%. Compared to traditional densely textured conveyor belts (CV >12%), this improves heat exchange efficiency by 60%, ensuring a temperature difference of ≤±0.5℃ between the upper and lower surfaces of the PUR adhesive. A 7.5kW servo motor with encoder feedback enables stepless speed regulation from 0.1 to 1.5 m / min, with a speed control accuracy of ±0.5%. The start and stop are smooth and shock-free, adapting to the curing requirements of different PUR adhesive formulations (e.g., low speed of 0.3 m / min for thick adhesive layers, and high speed of 1.2 m / min for thin film coating). Multiple top plates 105 are fixedly installed on the top of the preheating zone 102, the melting zone 103 and the crystallization zone 104 respectively; an air curtain isolation device 106 is set at the feeding end of the preheating zone 102 and the discharging end of the crystallization zone 104 to isolate the external environment from the airflow exchange inside the solidification chamber 1. The air curtain isolation device 106 includes: an outlet slit with a width of 0.5–1 mm and an air velocity of 15–20 m / s; a heating element: a PTC heater that heats the airflow to 80–100℃; angle adjustment: the outlet direction is adjustable ±10°; high-efficiency airflow isolation: the 0.5–1 mm ultra-narrow outlet slit combined with the 15–20 m / s high-speed airflow forms a stable air curtain, effectively blocking the infiltration of external air. Actual measurements show that the amount of external air mixed in is <0.3% (compared to 2–5% for traditional air curtains); the temperature and humidity fluctuations inside the curing chamber are controlled within ±0.5℃ / ±2%. RH; Precise temperature control and anti-condensation: The PTC heater heats the airflow to 80–100℃ (temperature control accuracy ±1℃): avoiding condensation on the PUR adhesive surface caused by low-temperature airflow (condensation risk >30% with traditional unheated air curtains); preheating the product edges reduces the temperature gradient during material feeding (edge ​​temperature difference reduced from ±8℃ to ±1.5℃); Adaptive angle adjustment: ±10° adjustable airflow direction to match different working conditions: when tilted downwards by 5°, dust blocking efficiency is increased by 40%; when airflow is horizontal, airflow interference is reduced by 60%; and the angle is automatically adjusted in conjunction with the PLC. An electromagnetic induction heating module 2, disposed at the bottom of the melting zone 103 and arranged along the transport direction of the conveying device 101, is used for non-contact induction heating of the product. The electromagnetic induction heating module 2 includes three induction coils evenly distributed along the transport direction of the conveying device 101, with a vertical distance of 10 to 15 mm between the surface of each coil and the bottom of the conveying device 101. The magnetic field strength of the induction coils is configured as follows: a. Penetrates the heated product to a depth of 1.2-1.5 mm; The eddy current loss generated by b is less than the tolerance threshold of the metal component of the conveying device 101; The three-coil collaborative working mode: the leading coil (80% power) preheats; the main heating coil (100% power) completes the melting; and the equalizing coil (60% power) eliminates the temperature gradient. This electromagnetic induction heating module achieves precise 1.2-1.5mm penetration heating through a three-coil array (10 to 15mm non-contact spacing), ensuring eddy current loss <50W while maintaining temperature uniformity of ±0.8℃, perfectly adapting to the melting requirements of PUR adhesives of different thicknesses. This 1.2-1.5mm adjustable penetration depth design, through precise electromagnetic field control, achieves a temperature difference of <11℃ (gradient 8.7℃ / mm) across the entire thickness of the PUR adhesive layer, saving 41.5% energy and increasing production efficiency by 63.6% compared to traditional heating methods. Infrared radiation heating module 3, symmetrically distributed on both sides of the melting zone 103, is used to provide uniform radiation heating; the infrared radiation heating module 3 includes: two rows of parallel carbon fiber heating tubes 301, each row containing ten carbon fiber heating tubes 301 equidistantly arranged along the conveying direction, symmetrically distributed on both sides of the melting zone 103; mounting bracket 302, which fixes the two ends of each carbon fiber heating tube 301 by quick-release buckles, and the mounting bracket 302 is rigidly connected to the side wall of the curing chamber 1; the radiation wavelength range of each carbon fiber heating tube 301 is 2.5-5μm; The dual-row symmetrical layout (10 heating tubes per row) achieves three-dimensional thermal field coverage: lateral temperature uniformity reaches ±1.5℃ (traditional single-sided heating ±8℃); axial temperature difference <±2℃ (10 tubes are arranged equidistantly, with a spacing of 100mm); 2.5-5μm wavelength precisely matches the absorption peak of PUR adhesive (absorption rate at 3.5μm >90%); quick-release buckle design makes the replacement time of a single heating tube <3 minutes (traditional welding type requires 30 minutes); carbon fiber tube life >20,000 hours (traditional metal heating tube 8,000 hours); rigid connection bracket (302) ensures that the offset is <0.1mm under vibration environment; Hot air circulation module 4 is installed below the top plate 105 of each functional area for forced convection heat exchange. Hot air circulation module 4 includes a centrifugal fan 401, which is fixed to the surface of the top plate 105. The outlet of the centrifugal fan 401 is fixedly connected to a guide air duct 402. An air outlet frame 403 is provided at the outlet of the guide air duct 402. Through holes 406 are evenly opened around the air outlet frame 403. Inside the frame 403, guide vanes 404 and flow equalization plates 405 are arranged in sequence along the airflow direction. A button 407 is provided inside the through hole 406. The centrifugal fan 401 uses a backward-curved impeller, and the noise level is <65dB when the air volume reaches 1200m³ / h. The 30° spiral angle design of the guide vane 404 can make the airflow more uniform. The honeycomb structure of the flow equalization plate 405 (3mm aperture, 70% opening rate) can make the air velocity distribution uniform. A sleeve 408 is provided on one side of the button 407. One end of the sleeve 408 is connected to the base 409 by a thread, and the outer side of the base 409 is fixed to the top plate 105. Two guide grooves 410 are symmetrically opened on the other end of the sleeve 408. A connecting rod 411 is provided in each guide groove 410. The two ends of the connecting rod 411 are rigidly connected to the button 407 and the inner sleeve 412 located inside the sleeve 408, respectively. Three limiting grooves 413 are evenly distributed along the central axis inside one end of the inner sleeve 412. A steel ball 414 is provided in each limiting groove 413. One side of the steel ball 414 contacts the inner wall of the sleeve 408, and the other side is used to contact the pin block 416. The top of the steel ball 414 is elastically connected to the base 409 by a spring 415. One end of the pin block 416 is in close contact with the air outlet frame 403.

[0019] This button-linked quick-release mechanism achieves 8-second ultra-fast disassembly (37 times faster than the traditional method) through the precise cooperation of the steel ball 414 for limiting and the spring 415 for resetting, with a positioning accuracy of ±0.05mm. It has also passed 100,000 tests with zero failures, improving the maintenance efficiency of the hot air system by more than 90% (data based on GB / T 16823.3-2010 Mechanical Fastener Testing Standard). The detection module 5 includes a temperature sensor 502 and an NIR crystallinity sensor 504, which are respectively located in the melting zone 103 and the crystallization zone 104, for real-time monitoring of process parameters and feedback to the PLC controller 6. The detection module 5 includes two support columns 501 and four support frames 503. The two support columns 501 are respectively located on both sides of the conveying device 101 in the melting zone 103, and each support column 501 is equipped with two sets of temperature sensors 502 for monitoring the temperature difference between the upper and lower surfaces of the product. The four support frames 503 are respectively located at the inlet and outlet ends of the crystallization zone 104. The NIR crystallinity sensor 504 is engaged in the center of each support frame 503, and its outer side is covered with a detachable heat insulation protective cover 505. The detection wavelength of the NIR crystallinity sensor 504 is 1200-2400nm. Dual-zone collaborative detection: Melting zone 103: Simultaneous monitoring of upper and lower surface temperatures (±0.3℃ accuracy) to avoid uneven heating of the adhesive layer; Crystallization zone 104: NIR crystallinity sensor 504 (1200-2400nm band) at the feed / discharge end tracks crystallinity changes in real time (resolution ±1%); Data linkage: PLC controller 6 dynamically adjusts the electromagnetic induction power according to the temperature difference and adjusts the hot air temperature according to the crystallinity; NIR crystallinity sensor 504: The detection wavelength covers the characteristic absorption peaks of PUR adhesive (such as -OH bond at 1450nm and -NCO group at 1900nm); this detection module achieves crystallinity prediction accuracy of ±1% and response speed of 0.5s by monitoring the temperature on both sides of the melting zone and performing online NIR analysis (1200-2400nm) in the crystallization zone, combined with PLC closed-loop control, thereby improving the stability of PUR adhesive curing quality. The PLC controller 6 is configured to execute the following control logic: dynamically adjust the power of the electromagnetic induction heating module 2 based on the data fed back by the temperature sensor 502, the operating frequency of the electromagnetic induction heating module 2 is 20–50kHz; adjust the hot air temperature of the crystallization zone 104 based on the detection data of the NIR crystallinity sensor 504, with a control accuracy of ±1℃; and link the wind speed of the air curtain isolation device 106 and the conveyor belt speed of the conveyor device 101. The air curtain isolation device effectively blocks the ingress of external air and reduces the volatilization of isocyanate monomers (TDI residue <0.05%). Based on real-time data from temperature sensor 502, the power of electromagnetic induction module 2 is adjusted with a period of 100ms (20-50kHz frequency conversion). NIR crystallinity sensor 504 uploads crystallinity data every 5 seconds, and PLC controller 6 automatically corrects the hot air temperature.

[0020] Working principle: Before using this curing device to improve the uniformity of PUR hot melt adhesive crystallization, it is necessary to check the overall condition of the device to ensure it can operate normally. Figure 1 - Figure 14 As shown, Partition curing process The uniform curing of PUR hot melt adhesive is achieved through zoned gradient heating and intelligent closed-loop control. The specific process is as follows: Feeding stage: The substrate coated with PUR adhesive enters the preheating zone 102 through the conveying device 101. The PUR adhesive is initially softened by the uniform convection heating (60-80℃) of the hot air circulation module 4, which eliminates internal stress and prepares for subsequent melting. Melting stage (using a triple heating synergy mechanism): Electromagnetic induction heating 2: The bottom induction coil (20 to 50 kHz) generates an alternating magnetic field, causing eddy currents to heat up inside the PUR adhesive, achieving rapid melting to a depth of 1.2 to 1.5 mm (110 to 130 °C), avoiding surface overheating and carbonization; Infrared radiation heating 3: The carbon fiber tubes on both sides (2.5 to 5 μm wavelength) emit infrared rays, penetrating the adhesive layer to supplement heat and eliminate the "edge effect" of electromagnetic heating; Hot air assistance: Top hot air (100 to 120 °C) maintains the uniformity of ambient temperature; Crystallization zone (104): The crystallization state of the adhesive layer is monitored in real time by an NIR crystallinity sensor 504 (1200 to 2400 nm band). The PLC dynamically adjusts the hot air temperature (±1℃ accuracy) and wind speed to make the PUR molecular chains arrange in an orderly manner and form a uniform crystal structure. Optimization design of hot air circulation system Airflow organization: The centrifugal fan 401 forces hot air into the guide duct 402, and after being divided by the guide vane 404 (arc blade), the air velocity is homogenized by the flow equalization plate 405 (honeycomb porous structure), and blows vertically downward to eliminate temperature stratification. Quick maintenance mechanism: During the installation of the air outlet frame 403: When the pin block 416 is inserted into the corresponding through hole 406, the head of the pin block 416 first contacts the three steel balls 414. Due to the pre-pressure of the spring 415 at the initial position of the steel balls 414, the three steel balls 414 form a natural closed state under the constraint of the inner wall of the conical outer sleeve 408. The diameter of the central gap is smaller than the outer diameter of the end of the pin block 416. Therefore, when the pin block 416 is inserted, it will push the steel balls 414 upward. After being pushed, the steel balls 414 roll outward along the limiting groove 413 and drive the inner sleeve 412 to move towards the base 409, while compressing the spring 415. At this time, the inclined structure of the conical outer sleeve 408 forces the steel balls 414 to expand radially, the central gap increases, and the pin block 416 smoothly enters the locking position. When the pin block 416 is pulled out: When it is pulled out directly: the external force pulls the pin block 416, which will drive the steel ball 414 and the inner sleeve 412 to move towards the air outlet frame 403. The inclined surface of the conical outer sleeve 408 will further press the steel ball 414 against the terminal, producing a self-locking effect (the more it is pulled, the tighter it becomes), preventing accidental fall-off. When unlocking and pulling out: Push button 407 inward gently so that inner sleeve 412 moves steel ball 414 towards base 409. Steel ball 414 is freed from the constraint of conical outer sleeve 408, and the central gap widens, so the pin block 416 can be easily pulled out, thereby disassembling the air outlet frame 403. Closed-loop intelligent control system Temperature feedback loop: Dual temperature sensors 502 monitor the temperature difference on the product surface → PLC controller 6 adjusts the power of the induction coil to ensure consistent melting depth; Crystallinity feedback loop: The NIR crystallinity sensor 504 detects the degree of crystallization phase transition → the PLC controller 6 dynamically adjusts the hot air parameters in the crystallization zone to match the kinetic requirements of different PUR formulations.

[0021] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A curing apparatus for improving the uniformity of crystallization of PUR hot melt adhesive, characterized in that, include: The solidification chamber (1) has a preheating zone (102), a melting zone (103) and a crystallization zone (104) arranged sequentially along the product transport direction. The conveying device (101) is located at the center of the solidification chamber (1) and is used to continuously convey the product through the preheating zone (102), the melting zone (103) and the crystallization zone (104) in sequence. Multiple top plates (105) are respectively fixedly installed on the top of the preheating zone (102), the melting zone (103) and the crystallization zone (104); An air curtain isolation device (106) is installed at the feeding end of the preheating zone (102) and the discharge end of the crystallization zone (104) to isolate the external environment from the airflow exchange inside the curing chamber (1); An electromagnetic induction heating module (2) is disposed at the bottom of the melting zone (103) and arranged along the transport direction of the conveying device (101) for non-contact induction heating of the product; Infrared radiation heating modules (3) are symmetrically distributed on both sides of the molten zone (103) to provide uniform radiation heating; Hot air circulation module (4) is installed below the top plate (105) of each functional area for forced convection heat exchange; The detection module (5) includes a temperature sensor (502) and an NIR crystallinity sensor (504), which are respectively located in the melting zone (103) and the crystallization zone (104) to monitor process parameters in real time and feed them back to the PLC controller (6).

2. The curing apparatus for improving the uniformity of crystallization of PUR hot melt adhesive according to claim 1, characterized in that: The electromagnetic induction heating module (2) includes three induction coils evenly distributed along the transport direction of the conveying device (101), with a vertical distance of 10 to 15 mm between the surface of each coil and the bottom of the conveying device (101).

3. The curing apparatus for improving the uniformity of crystallization of PUR hot melt adhesive according to claim 1, characterized in that: The infrared radiation heating module (3) includes: two rows of parallel carbon fiber heating tubes (301), each row containing ten carbon fiber heating tubes (301) equidistantly arranged along the conveying direction, symmetrically distributed on both sides of the melting zone (103); and a mounting bracket (302) that fixes both ends of each carbon fiber heating tube (301) with quick-release buckles, and the mounting bracket (302) is rigidly connected to the side wall of the curing chamber (1).

4. The curing apparatus for improving the uniformity of crystallization of PUR hot melt adhesive according to claim 1, characterized in that: The hot air circulation module (4) includes a centrifugal fan (401), which is fixed to the surface of the top plate (105). The outlet of the centrifugal fan (401) is fixedly connected to a guide air duct (402). An air outlet frame (403) is provided at the outlet of the guide air duct (402). Through holes (406) are evenly opened around the air outlet frame (403). Inside the frame, guide vanes (404) and flow equalization plates (405) are arranged in sequence along the airflow direction. A button (407) is provided inside the through hole (406).

5. A curing apparatus for improving the uniformity of crystallization of PUR hot melt adhesive according to claim 4, characterized in that: The button (407) has a cover (408) on one side. One end of the cover (408) is connected to the base (409) by a thread, and the outer side of the base (409) is fixed to the top plate (105). The other end of the cover (408) has two symmetrical guide grooves (410), and each guide groove (410) is provided with a connecting rod (411). The two ends of the connecting rod (411) are rigidly connected to the button (407) and the cover (408) respectively. Inner sleeve (412); the inner sleeve (412) has three limiting grooves (413) evenly distributed along the central axis at one end, and each limiting groove (413) has a steel ball (414). One side of the steel ball (414) contacts the inner wall of the outer sleeve (408), and the other side is used to contact the pin block (416). The top of the steel ball (414) is elastically connected to the base (409) through a spring (415). One end of the pin block (416) is in close contact with the air outlet frame (403).

6. The curing apparatus for improving the uniformity of crystallization of PUR hot melt adhesive according to claim 1, characterized in that: The detection module (5) includes two support columns (501) and four support frames (503). The two support columns (501) are respectively located on both sides of the conveying device (101) in the melting zone (103), and each support column (501) is equipped with two sets of temperature sensors (502) for monitoring the temperature difference between the upper and lower surfaces of the product. The four support frames (503) are respectively located at the inlet and outlet of the crystallization zone (104). Each support frame (503) has an NIR crystallinity sensor (504) in its center and is covered with a detachable heat insulation protective cover (505).

7. The curing apparatus for improving the uniformity of crystallization of PUR hot melt adhesive according to claim 1, characterized in that: The PLC controller (6) is configured to execute the following control logic: dynamically adjust the power of the electromagnetic induction heating module (2) based on the data fed back by the temperature sensor (502), the electromagnetic induction heating module (2) having an operating frequency of 20–50 kHz; adjust the hot air temperature of the crystallization zone (104) based on the detection data of the NIR crystallinity sensor (504), with a control accuracy of ±1℃; and link the wind speed of the air curtain isolation device (106) and the conveyor belt speed of the conveying device (101) to control the wind speed.

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