A method for fine granulation of impurity-screened rubber vulcanization accelerator

Abstract

The application discloses a fine granulation method for impurity-screened rubber vulcanization accelerant, relates to the technical field of rubber additive preparation, and integrates melt-state impurity electrophoresis screening and sub-millimeter micro-pore rotary granulation on a micro-fluid scale, realizes full-process continuous production, avoids energy waste and thermal degradation problems caused by multiple melt cooling of materials in traditional processes, and realizes directional migration of organic impurities and oligomers with different electricities to the side wall of the channel and automatic discharge through multi-stage branch micro-channels under the driving of a pulse electric field in the impurity removal link. A high-speed rotary micro-pore nozzle is integrated with the outlet of the micro-channel in the granulation link, precise micro-pores processed by femtosecond laser are matched with rotation speed control, sub-millimeter micro-particles can be stably prepared in the range of 50-500 microns, and micro-fluid inertial focusing screening realizes accurate grading by using the force difference of particles in the curved channel, and unqualified particles are automatically returned to the melting area for recycling.

Description

Technical Field

[0001] This invention relates to the field of rubber additive preparation technology, specifically a method for refining and granulating impurity screening rubber vulcanization accelerators. Background Technology

[0002] Rubber vulcanization accelerators are indispensable core additives in the rubber industry, significantly shortening vulcanization time, lowering vulcanization temperature, reducing vulcanizing agent dosage, and improving the physical and mechanical properties of rubber products. With the increasing demands for vulcanization uniformity and batch stability in high-end rubber products such as aerospace seals, precision medical rubber products, and high-performance tire treads, the market demand for high-purity accelerator microparticles with sub-millimeter size and highly concentrated particle size distribution is becoming increasingly urgent.

[0003] Currently, the main granulation methods for rubber vulcanization accelerators in industry include extrusion granulation, spray granulation, and fluidized bed granulation. Extrusion granulation typically produces particles with a diameter in the range of 1-5 mm, making it difficult to obtain sub-millimeter particles, and the particle size distribution is wide. Although spray granulation can produce smaller particles, it suffers from high energy consumption, large equipment investment, and easy particle agglomeration, and it cannot effectively remove molten impurities during the granulation process. Fluidized bed granulation also suffers from low particle size control precision and difficulty in impurity separation. In terms of impurity removal, existing technologies mostly use melt filtration, which intercepts solid impurities in the molten accelerator through a filter screen. However, for organic impurities and oligomers with similar melting temperatures to the accelerator and significantly different electrical properties, traditional filtration methods are difficult to separate effectively, and the filter screen is prone to clogging, requiring frequent replacement, resulting in low production efficiency and increased costs. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for fine granulation of rubber vulcanization accelerators by screening impurities. This method integrates efficient screening of molten impurities with precise granulation of sub-millimeter-sized particles at the microfluidic scale, avoiding multiple melting and cooling of materials. At the same time, it utilizes the pulsed electric field electrophoretic migration effect and the microfluidic inertial focusing effect to achieve online separation of organic impurities and particle classification, thereby solving the technical problems of difficulty in economically preparing high-purity sub-millimeter-sized accelerator microparticles and low screening efficiency of molten impurities in existing technologies.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for refining and granulating impurity screening rubber vulcanization accelerators, the method comprising: S1. Melt pretreatment: The rubber vulcanization accelerator raw material is converted into a homogeneous molten melt. At the same time, nitrogen gas is introduced into the melting kettle for inert gas protection. After preliminary filtration, the melt is put into an insulated storage tank for later use. S2. Microchannel Laminar Flow Distribution: The molten melt is uniformly distributed into multiple parallel main microchannels, controlling the melt to flow in a stable laminar flow state with a Reynolds number of 100-800. The main microchannels and the pulsed electric field treatment zone are connected in series along the melt flow direction, and the cross-sectional dimensions of the main microchannels are consistent with those of the main microchannels in the pulsed electric field treatment zone to ensure that the melt remains in a stable laminar flow state within the electric field treatment zone. S3. Pulsed electric field online impurity screening: The laminar flow melt enters the pulsed electric field treatment zone. The pulsed electric field causes impurities with different electrical properties to migrate in a direction and accumulate on the side wall of the main microchannel. The impurity-containing melt is automatically discharged through multi-level branched microchannels, and the purified central area melt is collected. S4. Integrated Microporous Rotary Granulation: The purified melt enters a microporous granulation nozzle integrated with the main microchannel outlet. The feed inlet of the microporous granulation nozzle is directly connected to the outlet of the main microchannel without any buffer container or insulation pipe. This allows the purified melt to enter the granulation nozzle for cutting after flowing out of the electric field treatment zone. The melt is cut into droplets by high-speed rotation, and the droplets are cooled and solidified to form fine particles with an adjustable particle size in the range of 50-500μm. S5. Microfluidic inertial focusing sieving: After solidification, the particles enter the microfluidic sieving device with the airflow. The inertial focusing effect is used to automatically divert the particles to different collection channels according to their size. Qualified particles enter the finished product collector, while unqualified particles are automatically returned to the melting zone for recycling.

[0006] Furthermore, the specific steps of S1 are as follows: The rubber vulcanization accelerator raw material is continuously added to a jacketed heated stainless steel melting kettle at a constant rate through a weightless screw feeder. The feeding rate is set to 5-20 kg / h according to the production line capacity. The material in the melting vessel is heated to 5-15°C above the melting temperature of the corresponding accelerator at a heating rate of 2-5°C / min. The mixture is then continuously stirred in an anchor stirrer at a speed of 30-60 r / min and kept at this temperature for 10-30 min to form a homogeneous molten accelerator melt. Throughout the melting process, high-purity nitrogen gas (purity ≥99.99%) with a flow rate of 0.5-2 L / min is continuously introduced into the melting vessel to form a positive pressure protective atmosphere and prevent the accelerator from undergoing thermal oxidative degradation. The molten melt undergoes preliminary filtration through a stainless steel filter screen installed at the bottom of the melting vessel to remove large solid impurities carried in the raw materials. The filter screen has a pore size of 100-200μm. The filtered melt is transported through an insulated pipeline to a jacketed insulated storage tank for later use. The insulation temperature of the storage tank is consistent with the melting temperature, and the temperature control accuracy is ±1℃.

[0007] Furthermore, the specific steps of S2 are as follows: The molten accelerator melt in the insulated storage tank is delivered to the microchannel array distribution system at a constant flow rate by a high-precision plunger metering pump. The flow control accuracy of the metering pump is ±0.5%, and the outlet pressure is 0.2-1.0MPa. The melt first enters the inlet distributor of the microchannel array distribution system, and is evenly distributed into 10-20 parallel main microchannels through a multi-stage flow distribution structure. The main microchannels have a rectangular cross-section, a width of 200-1000μm, a depth of 100-500μm, and are made of high-temperature and corrosion-resistant silicon carbide or borosilicate glass with an inner wall roughness Ra≤0.1μm. By adjusting the output flow rate of the metering pump, the Reynolds number of the melt in each main microchannel is controlled between 100 and 800, ensuring that the melt is in a stable laminar flow state with uniform flow field distribution and no turbulence or eddies.

[0008] Furthermore, the specific steps of S3 are as follows: An integrated pulsed electric field processing area is located in the middle of each main microchannel, with a processing area length of 50-200mm; a pair of parallel plate electrodes are embedded on the two opposite sidewalls of the main microchannel. The electrode material is platinum-iridium alloy (90% platinum content, 10% iridium content), with a thickness of 10-20μm. The electrode spacing is equal to the width of the main microchannel, and the electrode surface roughness Ra≤0.05μm. Connect the electrodes to a high-frequency pulse power supply, and apply the following pulse electric field parameters: electric field strength 500-5000V / cm, pulse frequency 10-1000Hz, pulse width 1-100μs, and duty cycle 10%-50%. Under the action of a pulsed electric field, positively or negatively charged organic impurities and oligomers in the accelerator melt undergo electrophoretic migration, move towards the electrode of opposite polarity, and accumulate in the sidewall region of the main microchannel, forming an impurity-containing melt layer with a thickness of 20-100 μm. Three to five levels of branch microchannels are evenly spaced along the flow direction on both sides of the main microchannel, with a spacing of 5-20 mm between each level. The width of the branch microchannels is 1 / 10 to 1 / 5 of the width of the main microchannel, and the depth is the same as that of the main microchannel. The impurity-containing melt at the sidewall is automatically discharged through the multi-level branch microchannels, and the discharge amount is controlled by a miniature needle valve located at the outlet of the branch microchannel, which is 5%-15% of the total melt flow rate. After impurities are removed, the melt in the central region continues to flow forward along the main microchannel and enters the outlet collector of the microchannel array distribution system, where it is collected and transported to the next process.

[0009] Furthermore, the specific steps of S4 are as follows: The purified melt in the outlet collector enters the microporous granulation nozzle, which is integrated with the main microchannel outlet, through an insulated pipe. The nozzle is connected to the main microchannel array by a flange, and a high-temperature resistant polytetrafluoroethylene sealing gasket is installed at the connection to ensure no leakage. The microporous granulation nozzle is directly driven by a high-speed servo motor through a coupling. The motor speed control range is 3000-15000 r / min, the speed control accuracy is ±10 r / min, and the operation is stable and vibration-free. The microporous granulation nozzle consists of a feed chamber, a rotating shaft, and an end-face microporous plate. The feed chamber is connected to the outlet collector. Under pressure, the melt is extruded from the micropores on the end-face microporous plate to form a continuous liquid filament. The centrifugal force and shear force generated by the high-speed rotating end-face microporous plate cut the liquid filament into uniformly sized droplets. The centrifugal force causes the liquid filament to be thrown outward, while the shear force cuts the liquid filament into uniform droplets. The synergistic effect of the two forces ensures the uniformity of droplet size. The end face microporous plate has 100-1000 cylindrical micropores evenly distributed, with a diameter of 30-300μm. It is processed by femtosecond laser drilling technology, with a diameter tolerance of ±2μm and a micropore inner wall roughness Ra≤0.1μm. After being ejected from the nozzle, the droplets come into full contact with the counter-current cooling air in a closed cooling tower with a flight distance of 0.5-2m. The temperature of the cooling air is 10-25℃ and the wind speed is 1-3m / s. During the flight, the droplets rapidly cool and solidify, forming fine particles with an adjustable particle size in the range of 50-500μm. The particle size is precisely controlled by adjusting the rotation speed and micropore diameter of the micropore granulation nozzle. Specifically, for every 1000 r / min increase in rotation speed, the average particle size decreases by 20-30 μm; for every 10 μm increase in micropore diameter, the average particle size increases by 30-40 μm.

[0010] Furthermore, the specific steps of S5 are as follows: After cooling and solidification, the particles enter the microfluidic sieving device along with the cooling airflow. By adjusting the power of the induced draft fan at the outlet of the cooling tower, the airflow velocity entering the microfluidic sieving device is controlled to be 5-20 m / s. The microfluidic sieving device adopts a 2-4 stage series curved microchannel structure. The radius of curvature of each channel is 5-20mm. The channel cross-section is rectangular, with a width of 500-2000μm and a depth of 200-1000μm. The material is polymethyl methacrylate (PMMA) or borosilicate glass. In a curved microchannel, particles are simultaneously subjected to inertial lift and centrifugal force. Particles of different sizes will reach force balance at different positions on the channel cross-section, forming a stable focused flow. Among them, particles of the appropriate size focus in the central region of the microchannel, larger particles are subjected to greater centrifugal force and focus in the outer region of the microchannel, while smaller particles are subjected to less centrifugal force and focus in the inner region of the microchannel. Three independent collection channels are set at the outlet of each curved microchannel: a qualified product collection channel in the center, a large particle collection channel on the outside, and a small particle collection channel on the inside. Qualified particles flow out from the qualified product collection channel and enter the finished product collector; large and small particles flow out from their respective collection channels. Large and small particles are automatically returned to the melting kettle via a closed screw conveyor to participate in the granulation process again, thus realizing the recycling of raw materials; The intensity of the inertial focusing effect is adjusted by regulating the airflow velocity entering the microfluidic sieving device, thereby changing the splitting position of particles of different sizes and achieving precise adjustment of the sieving particle size threshold with an adjustment accuracy of ±10μm.

[0011] Compared with existing technologies, this method for refining and granulating rubber vulcanization accelerators by screening for impurities has the following advantages: This invention integrates molten impurity electrophoretic sieving with sub-millimeter microporous rotary granulation at the microfluidic scale, achieving continuous production throughout the entire process. This avoids the energy waste and thermal degradation problems caused by repeated melting and cooling of materials in traditional processes. In the impurity removal stage, a pulsed electric field drives organic impurities and oligomers with different electrical properties to migrate directionally to the channel sidewall and are automatically discharged through multi-level branched microchannels. In the granulation stage, a high-speed rotating microporous nozzle integrated with the microchannel outlet is used. The precision micropores processed by femtosecond laser, combined with rotation speed control, can stably prepare sub-millimeter-sized microparticles in the range of 50-500μm. Microfluidic inertial focusing sieving utilizes the force difference of particles in the curved channel to achieve precise classification, and unqualified particles are automatically returned to the melting zone for recycling.

[0012] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0014] Figure 1 A flowchart of a method for refining granulation of rubber vulcanization accelerators by screening for impurities; Figure 2 This is a flowchart of step S3 in a method for refining and granulating rubber vulcanization accelerators by screening for impurities. Detailed Implementation

[0015] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0016] Example 1 This embodiment provides a method for refining and granulating rubber vulcanization accelerator M by screening for impurities. The specific steps are as follows: Melting pretreatment: 100 kg of accelerator M raw material is continuously added to a jacketed and heated stainless steel melting vessel at a rate of 10 kg / h using a loss-in-weight screw feeder. The temperature is increased to 190°C at a rate of 3°C / min, and then held at this temperature for 20 min under stirring at 40 r / min with an anchor stirrer to form a homogeneous molten state. At the same time, high-purity nitrogen gas at a flow rate of 1 L / min is introduced into the melting vessel for protection. After preliminary filtration through a stainless steel filter with a pore size of 150 μm at the bottom of the melting vessel, the melt is placed into an insulated storage tank for later use, with the holding temperature at 190°C.

[0017] Microchannel laminar flow distribution: The molten accelerator M in the insulated storage tank is delivered to the microchannel array distribution system at a constant flow rate of 5 L / h by a high-precision plunger metering pump. The metering pump outlet pressure is 0.5 MPa. The microchannel array distribution system consists of an inlet distributor, 10 parallel main microchannels, and an outlet collector. The main microchannels have a rectangular cross-section, a width of 500 μm, a depth of 200 μm, and are made of silicon carbide. At this time, the Reynolds number of the melt in each main microchannel is about 350, and it is in a stable laminar flow state.

[0018] Online impurity screening using pulsed electric field: The laminar flow melt enters a 100mm long pulsed electric field treatment zone; platinum-iridium alloy electrodes embedded in the side walls of the main microchannel are connected to a high-frequency pulsed power supply, with the electric field strength set at 2000V / cm, pulse frequency at 200Hz, pulse width at 20μs, and duty cycle at 30%; under the action of the pulsed electric field, aniline impurities and oligomers in the accelerator M migrate towards the negative electrode and accumulate on the side walls of the main microchannel; four levels of branched microchannels are equally spaced along the flow direction on both sides of the main microchannel, with a spacing of 10mm between each level, a width of 100μm, and a depth of 200μm; the discharge rate of the impurity-containing melt is controlled to be 8% of the total flow rate by a micro needle-type regulating valve, and the purified melt in the central region continues to flow forward along the main microchannel and enters the outlet collector.

[0019] Integrated microporous rotary granulation: The purified melt in the outlet collector enters directly into the microporous granulation nozzle integrated with the main microchannel outlet through an insulated pipe; 500 cylindrical micropores with a diameter of 100μm are evenly distributed on the microporous plate on the nozzle end face, which is processed by femtosecond laser drilling technology; a high-speed servo motor drives the nozzle to rotate at a speed of 8000r / min; the melt is extruded from the micropores under pressure to form a continuous liquid filament, and the high-speed rotating microporous plate on the end face cuts the liquid filament into uniform droplets; the droplets come into contact with counter-current 20℃ cooling air in a closed cooling tower with a flight distance of 1m and a cooling air wind speed of 2m / s, and the droplets are rapidly cooled and solidified to form fine particles.

[0020] Microfluidic inertial focusing sieving: After cooling and solidification, the particles enter the microfluidic sieving device at a speed of 10 m / s along with the cooling airflow. The microfluidic sieving device adopts a three-stage series curved microchannel structure, with each stage having a radius of curvature of 10 mm, a channel width of 1000 μm, and a depth of 500 μm, and is made of borosilicate glass. Utilizing the inertial focusing effect, qualified particles with a diameter in the range of 100-300 μm flow out from the qualified product collection channel in the center of the microchannel and enter the finished product collector. Large particles with a diameter >300 μm flow out from the outer large particle collection channel, and small particles with a diameter <100 μm flow out from the inner small particle collection channel. Large and small particles are automatically returned to the melting kettle via a closed spiral conveyor to participate in the granulation process again.

[0021] The accelerator M microparticle product prepared in this embodiment has an average particle size of 200 μm, a particle size distribution index (SPAN) of 0.65, an aniline impurity content of less than 0.1%, and a product yield of 91%.

[0022] Example 2 This embodiment provides a method for refining and granulating CZ rubber vulcanization accelerator by screening for impurities. The specific steps are as follows: Melting pretreatment: 100 kg of accelerator CZ raw material is continuously added to a jacketed and heated stainless steel melting vessel at a rate of 12 kg / h using a loss-in-weight screw feeder. The temperature is increased to 100°C at a rate of 2°C / min, and then held at this temperature for 15 min under stirring at 50 r / min with an anchor stirrer to form a homogeneous molten state. At the same time, high-purity nitrogen gas at a flow rate of 0.8 L / min is introduced into the melting vessel for protection. After preliminary filtration through a stainless steel filter with a pore size of 120 μm at the bottom of the melting vessel, the melt is placed into an insulated storage tank for later use, with the holding temperature at 100°C.

[0023] Microchannel laminar flow distribution: The molten accelerator CZ melt in the insulated storage tank is delivered to the microchannel array distribution system at a constant flow rate of 8 L / h via a high-precision plunger metering pump. The metering pump outlet pressure is 0.4 MPa. The microchannel array distribution system consists of an inlet distributor, 12 parallel main microchannels, and an outlet collector. The main microchannels have a rectangular cross-section, a width of 600 μm, a depth of 250 μm, and are made of borosilicate glass. At this time, the Reynolds number of the melt in each main microchannel is approximately 420, indicating a stable laminar flow state.

[0024] Online impurity screening using pulsed electric field: The laminar flow melt enters a 120mm long pulsed electric field treatment zone; platinum-iridium alloy electrodes embedded in the side walls of the main microchannel are connected to a high-frequency pulsed power supply, with the electric field strength set at 1500V / cm, pulse frequency at 300Hz, pulse width at 15μs, and duty cycle at 25%; under the action of the pulsed electric field, cyclohexylamine impurities and oligomers in the accelerator CZ migrate towards the electric field direction and accumulate on the side walls of the main microchannel; three levels of branched microchannels are equally spaced along the flow direction on both sides of the main microchannel, with a spacing of 12mm between each level, a width of 120μm, and a depth of 250μm; the discharge rate of the impurity-containing melt is controlled to be 10% of the total flow rate by a micro needle-type regulating valve, and the purified melt in the central region continues to flow forward along the main microchannel and enters the outlet collector.

[0025] Integrated microporous rotary granulation: The purified melt in the outlet collector enters directly into the microporous granulation nozzle integrated with the main microchannel outlet through an insulated pipe; 600 cylindrical micropores with a diameter of 150μm are evenly distributed on the microporous plate on the nozzle end face, which is processed by femtosecond laser drilling technology; a high-speed servo motor drives the nozzle to rotate at a speed of 6000r / min; the melt is extruded from the micropores under pressure to form a continuous liquid filament, and the high-speed rotating microporous plate on the end face cuts the liquid filament into uniform droplets; the droplets come into contact with counter-current 18℃ cooling air in a closed cooling tower with a flight distance of 1.2m and a cooling air velocity of 1.5m / s, and the droplets are rapidly cooled and solidified to form fine particles.

[0026] Microfluidic inertial focusing sieving: After cooling and solidification, the particles enter the microfluidic sieving device at a speed of 12 m / s along with the cooling airflow. The microfluidic sieving device adopts a 4-stage series curved microchannel structure, with each stage having a radius of curvature of 12 mm, a channel width of 1200 μm, a depth of 600 μm, and made of PMMA. Utilizing the inertial focusing effect, qualified particles with a particle size range of 150-400 μm flow out from the qualified product collection channel in the center of the microchannel and enter the finished product collector. Large particles with a particle size >400 μm flow out from the outer large particle collection channel, and small particles with a particle size <150 μm flow out from the inner small particle collection channel. Large and small particles are automatically returned to the melting kettle via a closed screw conveyor to participate in the granulation process again.

[0027] The accelerator CZ microparticle product prepared in this embodiment has an average particle size of 280 μm, a particle size distribution index (SPAN) of 0.72, a cyclohexylamine impurity content of less than 0.12%, and a product yield of 89%.

[0028] Example 3 This embodiment provides a method for refining and granulating TMTD rubber vulcanization accelerator for impurity screening. The specific steps are as follows: Melting pretreatment: 100 kg of accelerator TMTD raw material is continuously added to a jacketed and heated stainless steel melting vessel at a rate of 8 kg / h using a loss-in-weight screw feeder. The temperature is increased to 160°C at a rate of 4°C / min, and then held at this temperature for 25 min under stirring at 35 r / min with an anchor stirrer to form a homogeneous molten state. At the same time, high-purity nitrogen gas at a flow rate of 1.2 L / min is introduced into the melting vessel for protection. After preliminary filtration through a stainless steel filter with a pore size of 100 μm at the bottom of the melting vessel, the melt is placed into an insulated storage tank for later use, with the holding temperature at 160°C.

[0029] Microchannel laminar flow distribution: The molten accelerator TMTD melt in the insulated storage tank is delivered to the microchannel array distribution system at a constant flow rate of 6L / h through a high-precision plunger metering pump. The metering pump outlet pressure is 0.6MPa. The microchannel array distribution system consists of an inlet distributor, 8 parallel main microchannels, and an outlet collector. The main microchannels have a rectangular cross-section, a width of 400μm, a depth of 180μm, and are made of silicon carbide. At this time, the Reynolds number of the melt in each main microchannel is about 280, and it is in a stable laminar flow state.

[0030] Online impurity screening using pulsed electric field: The laminar flow melt enters an 80mm long pulsed electric field treatment zone; platinum-iridium alloy electrodes embedded in the side walls of the main microchannel are connected to a high-frequency pulsed power supply, with the electric field strength set at 3000V / cm, pulse frequency at 150Hz, pulse width at 30μs, and duty cycle at 40%; under the action of the pulsed electric field, carbon disulfide residue and oligomers in the accelerator TMTD migrate towards the electric field direction and accumulate on the side walls of the main microchannel; five levels of branched microchannels are equally spaced along the flow direction on both sides of the main microchannel, with each level spaced 8mm apart, and the branched microchannels are 80μm wide and 180μm deep; the discharge rate of the melt containing impurities is controlled to be 12% of the total flow rate by a micro needle-type regulating valve, and the purified melt in the central region continues to flow forward along the main microchannel and enters the outlet collector.

[0031] Integrated microporous rotary granulation: The purified melt in the outlet collector enters directly into the microporous granulation nozzle integrated with the main microchannel outlet through an insulated pipe; 400 cylindrical micropores with a diameter of 80μm are evenly distributed on the microporous plate on the nozzle end face, which are processed by femtosecond laser drilling technology; a high-speed servo motor drives the nozzle to rotate at a speed of 12000r / min; the melt is extruded from the micropores under pressure to form a continuous liquid filament, and the high-speed rotating end face microporous plate cuts the liquid filament into uniform droplets; the droplets come into contact with countercurrent 15℃ cooling air in a closed cooling tower with a flight distance of 0.8m and a cooling air velocity of 2.5m / s, and the droplets are rapidly cooled and solidified to form fine particles.

[0032] Microfluidic inertial focusing sieving: After cooling and solidification, the particles enter the microfluidic sieving device at a speed of 8 m / s along with the cooling airflow. The microfluidic sieving device adopts a two-stage series curved microchannel structure, with each stage having a radius of curvature of 8 mm, a channel width of 800 μm, and a depth of 400 μm, and is made of borosilicate glass. Utilizing the inertial focusing effect, qualified particles with a particle size range of 80-250 μm flow out from the qualified product collection channel in the center of the microchannel and enter the finished product collector. Large particles with a particle size >250 μm flow out from the outer large particle collection channel, and small particles with a particle size <80 μm flow out from the inner small particle collection channel. Large and small particles are automatically returned to the melting kettle via a closed spiral conveyor to re-participate in the granulation process.

[0033] The TMTD accelerator microparticle product prepared in this embodiment has an average particle size of 160 μm, a particle size distribution index (SPAN) of 0.68, a carbon disulfide residue of less than 0.08%, and a product yield of 87%.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for refining and granulating rubber vulcanization accelerators by screening for impurities, characterized in that, The method includes: S1. Melt pretreatment: The rubber vulcanization accelerator raw material is converted into a homogeneous molten melt. At the same time, nitrogen gas is introduced into the melting kettle for inert gas protection. After preliminary filtration, the melt is put into an insulated storage tank for later use. S2, Microchannel laminar flow distribution: The molten melt is evenly distributed to multiple parallel main microchannels to control the melt to flow in a stable laminar flow state with a Reynolds number of 100-800; S3. Pulsed electric field online impurity screening: The laminar flow melt enters the pulsed electric field treatment zone. The pulsed electric field causes impurities with different electrical properties to migrate in a direction and accumulate on the side wall of the main microchannel. The impurity-containing melt is automatically discharged through multi-level branched microchannels, and the purified central area melt is collected. S4. Integrated microporous rotary granulation: The purified melt enters the microporous granulation nozzle integrated with the main microchannel outlet, and is cut into droplets by high-speed rotation. The droplets are cooled and solidified to form fine particles with an adjustable particle size in the range of 50-500μm. S5. Microfluidic inertial focusing sieving: After solidification, the particles enter the microfluidic sieving device with the airflow. The inertial focusing effect is used to automatically divert the particles to different collection channels according to their size. Qualified particles enter the finished product collector, while unqualified particles are automatically returned to the melting zone for recycling.

2. The method for refining and granulating impurity screening rubber vulcanization accelerators according to claim 1, characterized in that, In S1, the rubber vulcanization accelerator includes any one or a mixture of accelerator M, accelerator DM, accelerator CZ, accelerator NS, accelerator D, accelerator TMTD, and accelerator TMTM.

3. The method for refining and granulating a rubber vulcanization accelerator by screening impurities according to claim 1, characterized in that, In step S1, the rubber vulcanization accelerator raw material is continuously added to a jacketed heating melting vessel via a screw feeder. The heating rate is 2-5℃ / min, the stirring speed is 30-60r / min, the nitrogen flow rate is 0.5-2L / min, and the initial filtration uses a filter screen with a pore size of 100-200μm.

4. The method for refining and granulating a rubber vulcanization accelerator by screening impurities according to claim 2, characterized in that, In S2, a plunger-type metering pump with a flow control accuracy of ±0.5% is used to transport the melt, and the pump outlet pressure is 0.2-1.0MPa; the number of main microchannels is 10-20, and the cross-section is rectangular.

5. The method for refining and granulating a rubber vulcanization accelerator by screening impurities according to claim 1, characterized in that, In S3, the length of the pulsed electric field processing area is 50-200 mm, and platinum-iridium alloy parallel plate electrodes with a thickness of 10-20 μm are embedded in the side walls of the main microchannel.

6. The method for refining and granulating a rubber vulcanization accelerator by screening impurities according to claim 1, characterized in that, In S3, the applied pulsed electric field intensity is 500-5000V / cm, the pulse frequency is 10-1000Hz, the pulse width is 1-100μs, and the duty cycle is 10%-50%.

7. The method for refining and granulating a rubber vulcanization accelerator by screening impurities according to claim 1, characterized in that, In S3, the multi-level branched microchannel is set with 3-5 levels, the spacing between each level is 5-20mm, the width of the branched microchannel is 1 / 10-1 / 5 of the width of the main microchannel, and the amount of melt containing impurities discharged is 5%-15% of the total melt flow rate.

8. The method for refining and granulating a rubber vulcanization accelerator by screening impurities according to claim 1, characterized in that, In step S4, the droplets are cooled and solidified in a cooling tower with a flight distance of 0.5-2m, and the cooling air temperature is 10-25℃.

9. The method for refining and granulating a rubber vulcanization accelerator by screening impurities according to claim 1, characterized in that, In step S4, the particle size is controlled by adjusting the nozzle rotation speed and the micropore diameter. For every 1000 r / min increase in rotation speed, the average particle size decreases by 20-30 μm; for every 10 μm increase in micropore diameter, the average particle size increases by 30-40 μm.

10. The method for refining and granulating a rubber vulcanization accelerator by screening impurities according to claim 1, characterized in that, In S5, the airflow velocity entering the microfluidic sieving device is 5-20 m / s; the microfluidic sieving device adopts a 2-4 stage series curved microchannel structure, with each stage having a channel curvature radius of 5-20 mm, a rectangular channel cross-section, a width of 500-2000 μm, and a depth of 200-1000 μm.

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