Process and system for synthesizing bismaleimide compound

Abstract

The invention provides a process and system for synthesizing a bismaleimide compound, and relates to the technical field of chemical synthesis, and the process comprises the following steps: (1) amidation reaction; (2) ring-closure dehydration reaction; (3) recovering the organic solvent; (4) a toluene thermal washing process; (5) a cooling crystallization process; (6) alkali washing process; (7) washing with hot water; and (8) drying. The process provided by the invention is high in production efficiency, the synthesized bismaleimide product is high in yield and purity, and compared with the prior art, the process is a clean production process in which the solvent can be recycled, no waste liquid is generated, the environment-friendly requirement is met, and the process has great environmental benefits, social benefits and economic benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical synthesis, in particular to a process and system for synthesizing bismaleimide compounds. Background Art

[0002] Bismaleimide (Bismaleimide, referred to as BMI) has the appearance of light yellow crystals. It is a type of resin derived from the polyimide resin system - addition-polymerized polyimide. It is a bifunctional compound with maleimide (MI) as the active end group. It is cured through the unsaturated end group during the molding process. No volatile substances are released during the curing process, which is beneficial to the molding and processing of composite materials.

[0003] BMI is the main monomer for synthesizing bismaleimide polymers. Its polymers have good high temperature resistance, radiation resistance, moisture resistance, and have the characteristics of high insulation, flame retardancy, friction resistance and low water absorption. In the fields of polymer chemistry and materials science, it is widely used in aerospace, electronics, insulation materials and other fields. It is a relatively promising thermosetting polymer.

[0004] A Chinese patent application CN118164891A discloses a method for preparing bismaleimide compounds, the technical scheme of which is as follows: maleic acid and isocyanate are used as the main raw materials, strong protonic acid is used as the catalyst, toluene and high-boiling-point polar aprotic solvent are used as the solvent, and phenols or quinones are used as the inhibitor, and maleimide compounds are prepared in one step through amidation reaction and dehydration ring-closure reaction. This technology forms amic acid intermediates at a fast speed and has a short heat preservation time, which can shorten the reaction time and improve production efficiency.

[0005] However, the above-mentioned technologies often have the following defects: in the actual production process, organic wastewater will be generated, and the wastewater contains a large amount of components that cause strong pollution to the environment, which will increase the difficulty of wastewater treatment, and the post-processing effect of the process is not ideal, resulting in low yield and purity of the finished product.

[0006] To this end, the present invention provides a process and system for synthesizing bismaleimide compounds. Summary of the invention

[0007] In order to make up for the deficiencies of the prior art, at least one technical problem raised in the background technology is solved.

[0008] The technical solution adopted by the present invention to solve the technical problem is: a process for synthesizing a bismaleimide compound according to the present invention comprises the following steps:

[0009] S1. Amidation reaction: maleic acid, isocyanate and an organic solvent are mixed, and the temperature is controlled at 60-90° C. to react for at least 0.5 h to obtain a yellow paste intermediate bismaleamic acid (BMA);

[0010] S2, closed-loop dehydration reaction: adding an inhibitor and a catalyst to the BMA solution obtained in step S1, heating to 110-140° C. for boiling, refluxing to remove the water generated by the reaction, and the reflux reaction time is 3-6 hours;

[0011] S3, recovering the organic solvent: spray drying the kettle liquid obtained in step S2 to remove the organic solvent in the solution to obtain a powdered crude product BMI, and recovering the solvent therein;

[0012] S4, hot washing with toluene: adding toluene to the crude BMI obtained in step S3, heating to boiling temperature until most of the powder in the system is dissolved, filtering while hot to remove the residue generated by the reaction, and collecting the filtrate;

[0013] S5, cooling crystallization: cooling the filtrate obtained in step S4, filtering the precipitated crystals to obtain yellow coarse crystals;

[0014] S6, alkali washing: washing and heating the crystals obtained in step S5 with a sodium bicarbonate solution to remove the organic acid produced in the side reaction, cooling, crystallizing, and filtering to obtain light yellow crystals;

[0015] S7, hot water washing: wash the crystals obtained in step S6 with hot water until neutral, and filter to obtain light yellow crystals;

[0016] S8, drying: drying the crystals obtained in step S7 to obtain light yellow powdery crystals, which are the product BMI.

[0017] The detailed steps of step S8 are as follows:

[0018] S8a, dry hot air enters the cyclone dryer through the air inlet, forming a downward spiral airflow inside the cylinder, and the crystal material enters the cylinder through the screw conveyor;

[0019] S8b, when the high-speed airflow enters the cylinder, it drives the air-carrying blade and the driven ring to rotate, and uses the paddle to hit the crystal material entering the cylinder from the screw conveyor, breaking up the wet crystals in agglomerates and making the crystals obtain an initial lateral velocity;

[0020] S8c, after the spiral airflow reaches the bottom of the cylinder, it flows upward along the exhaust pipe and is discharged. A part of the exhaust gas enters the heat exchange jacket through the diversion pipe and exchanges heat with the crystals inside the screw conveyor to facilitate preheating and drying in advance;

[0021] S8d. During the rotation of the driven ring, the roller intermittently rolls the air storage block, squeezing the air inside the air storage block into the air ring through the duct. The air pressure pushes the top block to move upward and hit the material blocking pad, lifting the crystal on the surface of the material blocking pad upward.

[0022] A system for synthesizing bismaleimide compounds, which is applicable to the above-mentioned process for synthesizing bismaleimide compounds, comprises an amidation reaction unit, a closed-loop dehydration reaction unit, an organic solvent recovery unit, a toluene hot washing unit, a cooling crystallization unit, an alkali washing unit, a hot water washing unit and a drying unit;

[0023] The amidation reaction unit comprises a metering tank and an amidation reaction kettle; the outlet of the metering tank is connected to the inlet of the amidation reaction kettle;

[0024] The closed-loop dehydration reaction unit comprises a closed-loop reaction tank, a condenser 1 and an oil-water separation device 1; the outlet of the amidation reactor is connected to the inlet of the closed-loop reaction tank; the gas outlet of the closed-loop reaction tank is connected to the inlet of the condenser 1; the outlet of the condenser 1 is connected to the inlet of the oil-water separation device 1; the outlet of the oil-water separation device 1 is connected to the reflux port of the closed-loop reaction tank;

[0025] The organic solvent recovery unit comprises a transfer pump 1, a spray drying device and an intermediate tank 1; the closed-loop reaction tank is connected to the inlet of the spray drying device through a pipeline via the transfer pump 1; the solid outlet of the spray drying device is connected to the inlet of the intermediate tank 1;

[0026] The toluene hot washing unit comprises a hot washing tank, a second condenser, a second oil-water separator, a second material transfer pump and a hot filter; the outlet of the first intermediate tank is connected to the inlet of the hot washing tank; the gas outlet of the hot washing tank is connected to the inlet of the second condenser; the outlet of the second condenser is connected to the inlet of the second oil-water separator; the outlet of the second oil-water separator is connected to the reflux port of the hot washing tank; the outlet of the hot washing tank is connected to the inlet of the hot filter through a pipeline via the second material transfer pump;

[0027] The cooling crystallization unit comprises a crystallization tank and a separator 1; the outlet of the heat filter is connected to the inlet of the crystallization tank; the outlet of the crystallization tank is connected to the inlet of the separator 1;

[0028] The alkali washing unit comprises an alkali washing tank, a separator 2, a silo 1, a condenser 3 and an intermediate tank 2; the separator 1 is connected to the inlet of the alkali washing tank; the gas outlet of the alkali washing tank is connected to the inlet of the condenser 3; the outlet of the condenser 3 is connected to the inlet of the intermediate tank 2; the outlet of the intermediate tank 2 is connected to the reflux port of the alkali washing tank; the outlet of the alkali washing tank is connected to the inlet of the separator 2; the outlet of the separator 2 is connected to the inlet of the silo 1;

[0029] The hot water washing unit comprises a washing tank, a separator three and a silo two; the outlet of the silo one is connected to the inlet of the washing tank; the outlet of the washing tank is connected to the inlet of the separator three; the outlet of the separator three is connected to the inlet of the silo two;

[0030] The drying unit comprises a screw conveyor, a cyclone dryer and a storage tank; the outlet of the second silo is connected to the inlet of the cyclone dryer through the screw conveyor; the outlet of the cyclone dryer is connected to the inlet of the storage tank.

[0031] Preferably, the vertical height of the metering tank outlet is higher than the vertical height of the amidation reactor inlet, so that the isocyanate solution in the metering tank enters the amidation reactor through the potential difference.

[0032] Preferably, the cyclone dryer comprises a cylinder; the screw conveyor is connected to the top of the cylinder; an air inlet is provided at the top of the cylinder; an exhaust pipe is fixedly connected to the inside of the cylinder, and the top of the exhaust pipe extends to the outside of the cylinder;

[0033] A mounting ring is fixedly connected to the outside of the exhaust pipe at a position corresponding to the air inlet; a driven ring is rotatably connected to the outside of the mounting ring, and a ball is arranged between the mounting ring and the driven ring; a group of arc-shaped air-carrying pieces are evenly distributed on the surface of the driven ring; a paddle is fixedly connected to the end of the air-carrying piece.

[0034] Preferably, a heat exchange jacket is provided on the outside of the screw conveyor, and the heat exchange jacket is spirally wrapped around the surface of the screw conveyor; a shunt pipe is connected to the top of the exhaust pipe, and the other end of the shunt pipe is connected to the heat exchange jacket.

[0035] Preferably, a group of support rods are evenly distributed on the surface of the auger inside the screw conveyor; magnetic balls are fixedly connected to the ends of the support rods; a group of movable sheets are evenly distributed inside the heat exchange sleeve; elastic strips are fixedly connected between the movable sheets and the heat exchange sleeve; the magnetic balls and movable sheets attract each other when they are close to each other.

[0036] Preferably, a group of material blocking pads are evenly distributed between the inner wall of the bottom of the cylinder and the exhaust pipe, and the material blocking pads are bent downward in a concave shape; a group of through grooves are evenly distributed on the surface of the material blocking pads; and the through grooves of adjacent material blocking pads are staggered with each other.

[0037] Preferably, an annular groove is provided on the inner side of the driven ring; a roller is rotatably connected inside the annular groove; an air storage block is fixedly connected to the surface of the mounting ring at a position corresponding to the annular groove; the air storage block is designed as an elastic hollow structure, and an elastic member is fixedly connected inside the air storage block;

[0038] The material-blocking pad is made of elastic material; an air ring is fixedly connected to the inside of the cylinder below the material-blocking pad, and the air ring is connected to the air storage block through a conduit; a group of pressure sleeves are distributed on the upper side of the air ring, and the pressure sleeves are connected to the air rings; a top block is slidingly and sealingly connected to the inside of the pressure sleeve; a spring is fixedly connected between the top block and the pressure sleeve.

[0039] Preferably, a connecting rod is fixedly connected to the lower end of the top block; a damping head is fixedly connected to the end of the connecting rod; and a pair of elastic hook blocks are fixedly connected to the inside of the pressure sleeve at both sides of the damping head.

[0040] The beneficial effects of the present invention are as follows:

[0041] 1. The process and system for synthesizing bismaleimide compounds described in the present invention are a complete production process that can achieve scale-up production. Compared with the existing method for synthesizing bismaleimide compounds, the solvent usage of the present invention is greatly reduced, the amount of wastewater generated is small and the process does not contain solvent. It is a clean production process that meets environmental protection requirements and has great environmental, social and economic benefits. In addition, the present invention has the significant advantages of low operating cost and good environmental protection effect. The complete process for synthesizing bismaleimide compounds is of great significance to environmental protection and resource recycling. It is an efficient, energy-saving and environmentally friendly process and system that can reduce solvent usage and solve the problem of waste liquid pollution.

[0042] 2. A process and system for synthesizing bismaleimide compounds described in the present invention, dry hot air enters the cyclone dryer through the air inlet, forming a downward spiral airflow inside the cylinder, and the crystal material enters the cylinder through the screw conveyor. When the high-speed airflow enters the cylinder, it will push the air-carrying plate, thereby driving the air-carrying plate and the driven ring to rotate outside the mounting ring. When the air-carrying plate rotates to one side of the screw conveyor, the paddle can be used to hit the crystal material entering the cylinder from the screw conveyor, thereby breaking up the lumpy wet crystals, improving the drying efficiency of the hot air on the crystals, and the crystals are lighter after being broken up, which is convenient for the spiral airflow inside the cylinder to drive them to move and rub on the inner wall. In addition, after the paddle hits the crystal, it can make it obtain a certain lateral initial velocity, and then the spiral airflow drives the crystal to accelerate, thereby increasing the circumferential linear velocity of the crystal, extending its path along the inner wall of the cylinder during the falling process, and enhancing the drying effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The present invention will be further described below in conjunction with the accompanying drawings.

[0044] Figure 1 It is a process flow chart of the present invention;

[0045] Figure 2 is a detailed flow chart of step S8 in the present invention;

[0046] Figure 3 It is a system structure diagram of the present invention;

[0047] Figure 4 It is a structural schematic diagram of the cyclone dryer in the present invention;

[0048] Figure 5 It is a schematic diagram of the structure of the exhaust pipe in the present invention;

[0049] Figure 6 is a cross-sectional view of the cylinder in the present invention;

[0050] Figure 7 yes Figure 6 A partial enlarged view of the middle part;

[0051] Figure 8 yes Figure 6 A partial enlarged view of point B in the middle.

[0052] In the figure: metering tank 1, amidation reactor 2, closed-loop reaction tank 3, condenser 1 4, oil-water separator 1 5, transfer pump 1 6, spray drying device 7, intermediate tank 1 8, hot washing tank 9, condenser 2 10, oil-water separator 2 11, transfer pump 2 12, hot filter 13, crystallization tank 14, separator 1 15, alkali washing tank 16, separator 2 17, silo 1 18, condenser 3 19, intermediate tank 2 20, washing tank 21, separator 3 22, silo 2 23, screw conveyor 24, cyclone dryer 25, storage tank 26, cylinder 201 , air inlet 202, exhaust pipe 203, mounting ring 204, driven ring 205, ball 206, air-carrying piece 207, paddle 208, heat exchange sleeve 209, shunt pipe 210, support rod 211, magnetic ball 212, movable sheet 213, elastic strip 214, material blocking pad 215, through groove 216, annular groove 217, roller 218, air storage block 219, auger 220, elastic part 221, air ring 222, conduit 223, pressure sleeve 224, top block 225, spring 226, connecting rod 227, damping head 228, elastic hook block 229. DETAILED DESCRIPTION

[0053] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0054] like Figure 1 to Figure 2 As shown, a process for synthesizing a bismaleimide compound according to the present invention comprises the following steps:

[0055] S1, amidation reaction: maleic acid is dissolved in an organic solvent to obtain a maleic acid solution, and the solution is added to an amidation reaction kettle 2. After the isocyanate is melted, the solution is added dropwise to the amidation reaction kettle 2 through a metering tank 1, and the mixture is stirred until the addition is complete. The temperature is controlled at 60-90°C and the reaction is kept warm for at least 0.5h.

[0056] The organic solvents are toluene and polar aprotic solvents, and the volume ratio of toluene to polar aprotic solvents is 1:(0.1-0.5).

[0057] S2, closed-loop dehydration reaction: the liquid after the reaction is sent to the closed-loop reaction tank 3, a strong protonic acid catalyst and an inhibitor are added, and the temperature is raised to 110-140°C, preferably 115°C. After boiling, the gas passes through the condenser-4 and becomes liquid and enters the oil-water separation device-5. The solvent and water are azeotropically evaporated to separate the by-product water, and the solvent is refluxed into the closed-loop reaction tank 3. The reaction time is 3-6 hours, preferably 3.5 hours.

[0058] The reaction formula for preparing bismaleimide compounds is as follows:

[0059]

[0060] S3, recovery of organic solvent: the liquid after the reaction is completed comes out of the closed-loop reaction tank 3, and is pumped into the spray drying device 7 by the transfer pump 6, and is atomized by compressed air, and then dried at a temperature of about 110-160°C, and the solvent is evaporated and recovered for reuse, and the dried powder enters the intermediate tank 8 for standby use;

[0061] Since maleic acid and DMF are easily soluble in water, but the product is insoluble in water, the conventional process adopts a water precipitation treatment method, in which water is added to the reaction solution to precipitate the product, and then the product is filtered and dried to obtain a crude product BMI. However, this process generates a certain amount of wastewater, and the water contains a large amount of DMF solvent and maleic acid, which makes wastewater treatment difficult. The step of the present invention can directly separate the solvent from the crude BMI, and the solvent is recovered after condensation, which effectively avoids the problem of wastewater treatment.

[0062] S4, toluene hot washing: the powder after the solvent is removed enters the hot washing tank 9, toluene is added, and the temperature is raised to boiling temperature until most of the powder in the system is dissolved, and then the solution is pumped into the hot filter 13 through the transfer pump 12, and filtered while hot to filter out the residue generated by the reaction to obtain the desired filtrate.

[0063] S5, cooling crystallization: the filtrate is transferred to the crystallization tank 14, and cooling circulating water is introduced to cool the temperature to about 45°C, and the solid is precipitated by stirring, and filtered in a separator 15 to obtain yellow coarse crystals.

[0064] S6, alkali washing: transfer the obtained crystals into the alkali washing tank 16, add sodium bicarbonate solution, heat and stir to fully wash the crystals, filter in the separator 17 to obtain light yellow crystals, and store in the silo 18.

[0065] S7, hot water washing: transfer the crystals in silo 18 into washing tank 21, add hot water, stir and wash, and after sufficient washing, transfer to separator three 22 for filtration to obtain light yellow crystals, which are stored in silo two 23.

[0066] S8, drying: the crystals in the second silo 23 are transferred to the cyclone dryer 25 through the screw conveyor 24 for drying to obtain light yellow powdery crystals, which are then stored in the storage tank 26 for metering and packaging.

[0067] The detailed steps of step S8 are as follows:

[0068] S8a, the dry hot air enters the cyclone dryer 25 through the air inlet 202, forming a downward spiral airflow inside the cylinder 201, and the crystal material enters the cylinder 201 through the screw conveyor 24;

[0069] S8b, when the high-speed airflow enters the cylinder 201, it drives the air-carrying blade 207 and the driven ring 205 to rotate, and uses the paddle 208 to hit the crystal material entering the cylinder 201 from the screw conveyor 24, breaking up the wet crystals in agglomerates and making the crystals obtain an initial lateral velocity;

[0070] S8c, after the spiral airflow reaches the bottom of the cylinder 201, it flows upward along the exhaust pipe 203 and is discharged. A part of the exhaust gas enters the heat exchange jacket 209 through the diverter pipe 210 and exchanges heat with the crystals in the screw conveyor 24 to facilitate preheating and drying in advance;

[0071] S8d. During the rotation of the driven ring 205, the roller 218 intermittently rolls the air storage block 219, and squeezes the air inside the air storage block 219 into the air ring 222 through the conduit 223. The air pressure pushes the top block 225 to move upward and hit the blocking pad 215, lifting the crystal on the surface of the blocking pad 215 upward.

[0072] The invention discloses a process for synthesizing bismaleimide compounds, which has strong selectivity and solves the problems of many side reactions, large amount of by-products and low product yield in the system; at the same time, the organic solvent can be recycled and the amount of organic wastewater is reduced, and the process is an environmentally friendly process; the process has strong applicability and can also meet the reaction system with 4,4'-diaminodiphenylmethane and maleic anhydride as raw materials, can shorten the reaction time, improve the production efficiency, and realize continuous production.

[0073] like Figures 3 to 8As shown, a system for synthesizing bismaleimide compounds according to the present invention is applicable to the above-mentioned process for synthesizing bismaleimide compounds, comprising an amidation reaction unit, a closed-loop dehydration reaction unit, an organic solvent recovery unit, a toluene hot washing unit, a cooling crystallization unit, an alkali washing unit, a hot water washing unit and a drying unit;

[0074] The amidation reaction unit comprises a metering tank 1 and an amidation reaction kettle 2; the outlet of the metering tank 1 is connected to the inlet of the amidation reaction kettle 2;

[0075] The closed-loop dehydration reaction unit includes a closed-loop reaction tank 3, a condenser 4 and an oil-water separation device 5; the outlet of the amidation reaction kettle 2 is connected to the inlet of the closed-loop reaction tank 3; the gas outlet of the closed-loop reaction tank 3 is connected to the inlet of the condenser 4; the outlet of the condenser 4 is connected to the inlet of the oil-water separation device 5; the outlet of the oil-water separation device 5 is connected to the reflux port of the closed-loop reaction tank 3;

[0076] The organic solvent recovery unit includes a transfer pump 6, a spray drying device 7 and an intermediate tank 8; the closed-loop reaction tank 3 is connected to the inlet of the spray drying device 7 through a pipeline via the transfer pump 6; the solid outlet of the spray drying device 7 is connected to the inlet of the intermediate tank 8;

[0077] The toluene hot washing unit comprises a hot washing tank 9, a condenser 10, an oil-water separator 11, a transfer pump 12 and a hot filter 13; the outlet of the intermediate tank 8 is connected to the inlet of the hot washing tank 9; the gas outlet of the hot washing tank 9 is connected to the inlet of the condenser 10; the outlet of the condenser 10 is connected to the inlet of the oil-water separator 11; the outlet of the oil-water separator 11 is connected to the reflux port of the hot washing tank 9; the outlet of the hot washing tank 9 is connected to the inlet of the hot filter 13 through a pipeline via the transfer pump 12;

[0078] The cooling crystallization unit includes a crystallization tank 14 and a separator 15; the outlet of the heat filter 13 is connected to the inlet of the crystallization tank 14; the outlet of the crystallization tank 14 is connected to the inlet of the separator 15;

[0079] The alkali washing unit includes an alkali washing tank 16, a separator 17, a silo 18, a condenser 19 and an intermediate tank 20; the separator 15 is connected to the inlet of the alkali washing tank 16; the gas outlet of the alkali washing tank 16 is connected to the inlet of the condenser 19; the outlet of the condenser 19 is connected to the inlet of the intermediate tank 20; the outlet of the intermediate tank 20 is connected to the reflux port of the alkali washing tank 16; the outlet of the alkali washing tank 16 is connected to the inlet of the separator 17; the outlet of the separator 17 is connected to the inlet of the silo 18;

[0080] The hot water washing unit includes a washing tank 21, a separator three 22 and a silo two 23; the outlet of the silo one 18 is connected to the inlet of the washing tank 21; the outlet of the washing tank 21 is connected to the inlet of the separator three 22; the outlet of the separator three 22 is connected to the inlet of the silo two 23;

[0081] The drying unit includes a screw conveyor 24, a cyclone dryer 25 and a storage tank 26; the outlet of the second silo 23 is connected to the inlet of the cyclone dryer 25 through the screw conveyor 24; the outlet of the cyclone dryer 25 is connected to the inlet of the storage tank 26.

[0082] The vertical height of the outlet of the metering tank 1 is higher than the vertical height of the inlet of the amidation reactor 2, so that there is a certain level difference between the outlet of the metering tank 1 and the inlet of the amidation reactor 2, so that the isocyanate solution in the metering tank 1 can enter the amidation reactor 2 through the level difference.

[0083] Baffles are provided inside the oil-water separation device 1 5 and the oil-water separation device 2 11. One side of the baffle is an oil-water mixture. By controlling the oil-water interface height, the oil phase overflows through the baffle to the other side of the container and flows back into the reaction tank through the bottom pipeline; the water phase is connected to the waste liquid storage tank.

[0084] In the spray drying device 7, the liquid feed passes through the high-speed centrifugal atomizer at the top of the tower body and contacts with the hot air in parallel flow, and can be dried into a finished product in a very short time. The exhaust gas can be preheated with the air to save energy.

[0085] In the cyclone dryer 25, the air is filtered and heated and enters the top of the cylinder 201. The hot air moves downward in a spiral shape and the finished product is continuously output from the bottom of the cylinder 201 into the storage tank 26. The exhaust gas is discharged to the exhaust gas treatment by the induced draft fan.

[0086] Both the transfer pump 1 6 and the transfer pump 2 12 are conventional pumps used in the art, but they must have corrosion resistance and anti-blocking properties.

[0087] As a preferred embodiment of the present invention, the cyclone dryer 25 includes a cylinder 201; the screw conveyor 24 is connected to the top of the cylinder 201; the top of the cylinder 201 is provided with an air inlet 202; the inside of the cylinder 201 is fixedly connected with an exhaust pipe 203, and the top of the exhaust pipe 203 extends to the outside of the cylinder 201;

[0088] The outside of the exhaust pipe 203 is fixedly connected with a mounting ring 204 at a position corresponding to the air inlet 202; the outside of the mounting ring 204 is rotatably connected with a driven ring 205, and a ball 206 is provided between the mounting ring 204 and the driven ring 205; a group of arc-shaped air-carrying pieces 207 are evenly distributed on the surface of the driven ring 205; the end of the air-carrying piece 207 is fixedly connected with a paddle 208, and the paddle 208 is close to the inner wall of the cylinder 201.

[0089] The dry hot air enters the cyclone dryer 25 through the air inlet 202, and forms a spiral airflow moving downward inside the cylinder 201. The crystal material enters the cylinder 201 through the screw conveyor 24. When the high-speed airflow enters the cylinder 201, it will push the air-carrying piece 207, thereby driving the air-carrying piece 207 and the driven ring 205 to rotate outside the mounting ring 204. When the air-carrying piece 207 rotates to one side of the screw conveyor 24, the paddle 208 can be used to hit the crystal material entering the cylinder 201 from the screw conveyor 24, thereby breaking up the lumpy wet crystals, thereby improving the drying efficiency of the hot air on the crystals. After the crystals are broken up, they are lighter in weight, which is convenient for the spiral airflow inside the cylinder 201 to drive them to move and rub on the inner wall. In addition, after the paddle 208 hits the crystal, it can make it obtain a certain lateral initial velocity, and then the spiral airflow drives the crystal to accelerate, thereby increasing the circumferential linear velocity of the crystal, extending the path of its movement along the inner wall of the cylinder 201 during the falling process, and enhancing the drying effect.

[0090] As a preferred embodiment of the present invention, a heat exchange jacket 209 is provided on the outside of the screw conveyor 24, and the heat exchange jacket 209 is spirally wrapped on the surface of the screw conveyor 24; the top of the exhaust pipe 203 is connected to a shunt pipe 210, and the other end of the shunt pipe 210 is connected to the heat exchange jacket 209. After the spiral airflow reaches the bottom of the cylinder 201, it will flow upward along the exhaust pipe 203 and be discharged, and a part of the exhaust gas will enter the heat exchange jacket 209 through the shunt pipe 210, and flow along its spiral structure on the outside of the screw conveyor 24, thereby exchanging heat with the crystal material inside the screw conveyor 24, so as to facilitate preheating and drying in advance, and further accelerate the drying process of the crystal.

[0091] A group of support rods 211 are evenly distributed on the surface of the auger 220 inside the screw conveyor 24; a magnetic ball 212 is fixedly connected to the end of the support rod 211; a group of movable sheets 213 are evenly distributed inside the heat exchange sleeve 209; an elastic strip 214 is fixedly connected between the movable sheet 213 and the heat exchange sleeve 209; the magnetic ball 212 and the movable sheet 213 attract each other when they are close to each other. The auger 220 inside the screw conveyor 24 will drive the support rod 211 and the magnetic ball 212 to rotate synchronously during the rotation process. When the magnetic ball 212 approaches the movable sheet 213, it can attract it, thereby stretching the elastic strip 214. Subsequently, under the elastic force of the elastic strip 214, the movable sheet 213 is prompted to swing back and forth inside the heat exchange sleeve 209 and push the airflow inside it, thereby disturbing the airflow, enhancing its turbulent effect, and improving the heat exchange efficiency between the airflow and the crystal, so that the crystal can fully absorb the waste heat from the exhaust gas.

[0092] As a preferred embodiment of the present invention, a group of material blocking pads 215 are evenly distributed between the inner wall of the bottom of the cylinder 201 and the exhaust pipe 203, and the material blocking pads 215 are bent downward in a concave shape; a group of through grooves 216 are evenly distributed on the surface of the material blocking pads 215; and the through grooves 216 of adjacent material blocking pads 215 are offset from each other. By providing multiple material blocking pads 215 and the through grooves 216 are offset up and down, the crystal moves downward through the through grooves 216 after falling on the surface of the material blocking pads 215, which can slow down its falling process, prolong the drying time of the hot air flow on the crystal, and further improve the degree of drying of the crystal.

[0093] As a preferred embodiment of the present invention, an annular groove 217 is provided inside the driven ring 205; a roller 218 is rotatably connected inside the annular groove 217; an air storage block 219 is fixedly connected to the surface of the mounting ring 204 at a position corresponding to the annular groove 217; the air storage block 219 is designed as an elastic hollow structure, and an elastic member 221 is fixedly connected inside the air storage block 219;

[0094] The material-blocking pad 215 is made of elastic material; an air ring 222 is fixedly connected to the inside of the cylinder 201 below the material-blocking pad 215, and the air ring 222 is connected to the air storage block 219 through a conduit 223; a group of pressure sleeves 224 are evenly distributed on the upper side of the air ring 222, and the pressure sleeves 224 are connected to the air ring 222; a top block 225 is slidingly and sealingly connected to the inside of the pressure sleeve 224; a spring 226 is fixedly connected between the top block 225 and the pressure sleeve 224.

[0095] During the rotation of the driven ring 205, the roller 218 inside the annular groove 217 will intermittently roll the air storage block 219, and squeeze the air inside the air storage block 219 into the multiple air rings 222 through the duct 223. Then the air pressure pushes the top block 225 inside the pressure sleeve 224 to move upward and hit the material blocking pad 215, thereby lifting the crystals on the surface of the material blocking pad 215 upward. On the one hand, the clumps of crystals are further broken up. On the other hand, when the crystals rise, the movement direction of the hot air flow is exactly opposite to that of the upward movement, forming a counter-attack effect, so that the air flow can fully entrain and carry away the moisture and dust between the crystals, thereby improving the drying effect and reducing the impurity content of the finished product.

[0096] The lower end of the top block 225 is fixedly connected to a connecting rod 227 ; the end of the connecting rod 227 is fixedly connected to a damping head 228 ; and a pair of elastic hook blocks 229 are fixedly connected to the inside of the pressure sleeve 224 at both sides of the damping head 228 . When the air inside the gas storage block 219 begins to fill into the gas ring 222, due to the obstruction of the elastic hook block 229 to the damping head 228, the top block 225 will not move upward immediately at this time. As the internal pressure of the gas ring 222 gradually increases and accumulates energy, the damping head 228 squeezes and deforms the elastic hook block 229. At the moment when the damping head 228 and the elastic hook block 229 are separated, the top block 225 quickly hits the resistance pad 215 upward, which can increase its impact force and increase the amplitude of the resistance pad 215 lifting the crystal upward. When the elastic member 221 drives the gas storage block 219 to expand and recover, the internal air pressure of the gas ring 222 decreases, and the spring 226 drives the top block 225 to return to its original position downward. At this time, due to the inclined end of the elastic hook block 229, it is easier for the damping head 228 to return to its original position, which will allow the damping head 228 to return to its original position smoothly between a pair of elastic hook blocks 229.

[0097] The above-mentioned front, back, left, right, top and bottom are all based on the figures in the specification. Figure 1 As a benchmark, according to the person's observation perspective, the side of the device facing the observer is defined as the front, the left side of the observer is defined as the left, and so on.

[0098] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the scope of protection of the present invention.

[0099] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A process for synthesizing bismaleimide compounds, characterized in that: The following steps are involved: S1. Amidation reaction: maleic acid, isocyanate and an organic solvent are mixed, and the temperature is controlled at 60-90°C to keep the reaction for at least 0.5h to obtain a yellow paste intermediate bismaleamic acid BMA; S2, closed-loop dehydration reaction: adding an inhibitor and a catalyst to the BMA solution obtained in step S1, heating to 110-140° C. for boiling, refluxing to remove the water generated by the reaction, and the reflux reaction time is 3-6 hours; S3, recovering the organic solvent: spray drying the kettle liquid obtained in step S2 to remove the organic solvent in the solution to obtain a powdered crude product BMI, and recovering the solvent therein; S4, hot washing with toluene: adding toluene to the crude BMI obtained in step S3, heating to boiling temperature until most of the powder in the system is dissolved, filtering while hot to remove the residue generated by the reaction, and collecting the filtrate; S5, cooling crystallization: cooling the filtrate obtained in step S4, filtering the precipitated crystals to obtain yellow coarse crystals; S6, alkali washing: washing and heating the crystals obtained in step S5 with a sodium bicarbonate solution to remove the organic acid produced in the side reaction, cooling, crystallizing, and filtering to obtain light yellow crystals; S7, hot water washing: wash the crystals obtained in step S6 with hot water until neutral, and filter to obtain light yellow crystals; S8, drying: drying the crystals obtained in step S7 to obtain light yellow powdery crystals, which are the product BMI.

2. A process for synthesizing bismaleimide compounds according to claim 1, characterized in that: The detailed steps of step S8 are: S8a, the dry hot air enters the cyclone dryer (25) through the air inlet (202), forming a downwardly moving spiral airflow inside the cylinder (201), and the crystal material enters the cylinder (201) through the screw conveyor (24); S8b, when the high-speed airflow enters the cylinder (201), it drives the air-carrying plate (207) and the driven ring (205) to rotate, and uses the paddle (208) to hit the crystal material entering the cylinder (201) from the screw conveyor (24), thereby breaking up the wet crystals in agglomerates and causing the crystals to obtain an initial lateral velocity; S8c, after the spiral airflow reaches the bottom of the cylinder (201), it flows upward along the exhaust pipe (203) and is discharged, wherein a part of the exhaust gas enters the heat exchange jacket (209) through the diversion pipe (210) and exchanges heat with the crystals in the screw conveyor (24) to facilitate preheating and drying; S8d. During the rotation of the driven ring (205), the roller (218) intermittently rolls the air storage block (219), and squeezes the air inside the air storage block (219) into the air ring (222) through the conduit (223). The air pressure pushes the top block (225) to move upward and hit the blocking pad (215), and the crystals on the surface of the blocking pad (215) are lifted upward.

3. A system for synthesizing bismaleimide compounds, which is applicable to the process for synthesizing bismaleimide compounds according to claim 1, characterized in that: It includes an amidation reaction unit, a closed-loop dehydration reaction unit, an organic solvent recovery unit, a toluene hot washing unit, a cooling crystallization unit, an alkali washing unit, a hot water washing unit and a drying unit; The amidation reaction unit comprises a metering tank (1) and an amidation reaction kettle (2); the outlet of the metering tank (1) is connected to the inlet of the amidation reaction kettle (2); The closed-loop dehydration reaction unit comprises a closed-loop reaction tank (3), a condenser (4) and an oil-water separation device (5); the outlet of the amidation reaction kettle (2) is connected to the inlet of the closed-loop reaction tank (3); the gas outlet of the closed-loop reaction tank (3) is connected to the inlet of the condenser (4); the outlet of the condenser (4) is connected to the inlet of the oil-water separation device (5); the outlet of the oil-water separation device (5) is connected to the reflux port of the closed-loop reaction tank (3); The organic solvent recovery unit comprises a transfer pump (6), a spray drying device (7) and an intermediate tank (8); the closed-loop reaction tank (3) is connected to the inlet of the spray drying device (7) via a pipeline via the transfer pump (6); the solid outlet of the spray drying device (7) is connected to the inlet of the intermediate tank (8); The toluene hot washing unit comprises a hot washing tank (9), a second condenser (10), a second oil-water separator (11), a second material transfer pump (12) and a hot filter (13); the outlet of the first intermediate tank (8) is connected to the inlet of the hot washing tank (9); the gas outlet of the hot washing tank (9) is connected to the inlet of the second condenser (10); the outlet of the second condenser (10) is connected to the inlet of the second oil-water separator (11); the outlet of the second oil-water separator (11) is connected to the reflux port of the hot washing tank (9); the outlet of the hot washing tank (9) is connected to the inlet of the hot filter (13) through a pipeline via the second material transfer pump (12); The cooling crystallization unit comprises a crystallization tank (14) and a separator (15); the outlet of the heat filter (13) is connected to the inlet of the crystallization tank (14); the outlet of the crystallization tank (14) is connected to the inlet of the separator (15); The alkali washing unit comprises an alkali washing tank (16), a separator 2 (17), a silo 1 (18), a condenser 3 (19) and an intermediate tank 2 (20); the separator 1 (15) is connected to the inlet of the alkali washing tank (16); the gas outlet of the alkali washing tank (16) is connected to the inlet of the condenser 3 (19); the outlet of the condenser 3 (19) is connected to the inlet of the intermediate tank 2 (20); the outlet of the intermediate tank 2 (20) is connected to the reflux port of the alkali washing tank (16); the outlet of the alkali washing tank (16) is connected to the inlet of the separator 2 (17); the outlet of the separator 2 (17) is connected to the inlet of the silo 1 (18); The hot water washing unit comprises a washing tank (21), a separator three (22) and a silo two (23); the outlet of the silo one (18) is connected to the inlet of the washing tank (21); the outlet of the washing tank (21) is connected to the inlet of the separator three (22); the outlet of the separator three (22) is connected to the inlet of the silo two (23); The drying unit comprises a screw conveyor (24), a cyclone dryer (25) and a storage tank (26); the outlet of the second silo (23) is connected to the inlet of the cyclone dryer (25) through the screw conveyor (24); the outlet of the cyclone dryer (25) is connected to the inlet of the storage tank (26).

4. A system for synthesizing bismaleimide compounds according to claim 3, characterized in that: The vertical height of the outlet of the metering tank (1) is higher than the vertical height of the inlet of the amidation reaction kettle (2), so that the isocyanate solution in the metering tank (1) enters the amidation reaction kettle (2) through the potential difference.

5. A system for synthesizing bismaleimide compounds according to claim 3, characterized in that: The cyclone dryer (25) comprises a cylinder (201); the screw conveyor (24) is connected to the top of the cylinder (201); an air inlet (202) is provided at the top of the cylinder (201); an exhaust pipe (203) is fixedly connected to the inside of the cylinder (201), and the top of the exhaust pipe (203) extends to the outside of the cylinder (201); The outer side of the exhaust pipe (203) is fixedly connected with a mounting ring (204) at a position corresponding to the air inlet (202); the outer side of the mounting ring (204) is rotatably connected with a driven ring (205), and a ball (206) is provided between the mounting ring (204) and the driven ring (205); a group of arc-shaped air-carrying pieces (207) are evenly distributed on the surface of the driven ring (205); and a paddle (208) is fixedly connected to the end of the air-carrying piece (207).

6. A system for synthesizing bismaleimide compounds according to claim 5, characterized in that: A heat exchange jacket (209) is arranged on the outside of the screw conveyor (24), and the heat exchange jacket (209) is spirally wrapped around the surface of the screw conveyor (24); the top of the exhaust pipe (203) is connected to a diverter pipe (210), and the other end of the diverter pipe (210) is connected to the heat exchange jacket (209).

7. A system for synthesizing bismaleimide compounds according to claim 6, characterized in that: A group of support rods (211) are evenly distributed on the surface of the auger (220) inside the screw conveyor (24); magnetic balls (212) are fixedly connected to the ends of the support rods (211); a group of movable sheets (213) are evenly distributed inside the heat exchange sleeve (209); elastic strips (214) are fixedly connected between the movable sheets (213) and the heat exchange sleeve (209); and the magnetic balls (212) and the movable sheets (213) attract each other when they are close to each other.

8. A system for synthesizing bismaleimide compounds according to claim 5, characterized in that: A group of material blocking pads (215) are evenly distributed between the inner wall of the bottom of the cylinder (201) and the exhaust pipe (203), and the material blocking pads (215) are bent downward in a concave shape; a group of through grooves (216) are evenly distributed on the surface of the material blocking pads (215); and the through grooves (216) of adjacent material blocking pads (215) are staggered with each other.

9. A system for synthesizing bismaleimide compounds according to claim 8, characterized in that: An annular groove (217) is provided on the inner side of the driven ring (205); a roller (218) is rotatably connected inside the annular groove (217); an air storage block (219) is fixedly connected to the surface of the mounting ring (204) at a position corresponding to the annular groove (217); the air storage block (219) is designed as an elastic hollow structure, and an elastic member (221) is fixedly connected inside the air storage block; The material blocking pad (215) is made of elastic material; an air ring (222) is fixedly connected to the cylinder (201) at a position below the material blocking pad (215), and the air ring (222) is connected to the air storage block (219) through a conduit (223); a group of pressure sleeves (224) are evenly distributed on the upper side of the air ring (222), and the pressure sleeves (224) are connected to the air ring (222); a top block (225) is slidably sealed inside the pressure sleeve (224); and a spring (226) is fixedly connected between the top block (225) and the pressure sleeve (224).

10. A system for synthesizing bismaleimide compounds according to claim 9, characterized in that: The lower end of the top block (225) is fixedly connected to a connecting rod (227); the end of the connecting rod (227) is fixedly connected to a damping head (228); and a pair of elastic hook blocks (229) are fixedly connected inside the pressure sleeve (224) at both sides of the damping head (228).

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