Synthesis method of benzotripolycyanamide

Abstract

The synthesis method comprises the following steps: a heating addition stage, a washing stage, a suction filtration stage and a drying and screening stage, and in the heating addition stage, the problem of violent reaction caused by reaction heat accumulation is solved by controlling the pressure of circulating water and the heating speed and time of the heating period; therefore, material rushing accidents are avoided; and in the washing stage, the washing degree of the crude product is improved by adopting a repeated washing mode, so that the synthesis purity of the benzoguanamine is improved.

Description

Technical Field

[0001] The invention relates to the technical field of chemical synthesis, in particular to a method for synthesizing benzoguanamine. Background Art

[0002] Benzoguanamine is a white crystalline powder used to make thermosetting resins, modified resins, amino coatings and plastics, medicines, pesticides and dyes. Currently, dicyandiamide and benzonitrile are used as raw materials, and benzoguanamine is produced by heating and reflux reaction under the conditions of inorganic base as catalyst and alkyl alcohol as solvent.

[0003] At present, when producing benzoguanamine, the circulating water pressure is usually controlled at 0.2-0.3MPa. If the circulating water pressure is too low or there is no water pressure, the temperature will rise too fast during the synthesis reaction, and the reaction heat cannot be taken away in time. In addition, the synthesis heating period is controlled for a short time, which will also cause the reaction heat to accumulate, the reaction is violent, the temperature is uncontrollable, and the consequences such as the material impact accident are caused. Therefore, controlling the key process parameters in the synthesis and addition stages determines the production efficiency and production safety of benzoguanamine. At the same time, when washing benzoguanamine, the washing degree also determines the production purity of benzoguanamine. Summary of the invention

[0004] The present invention aims to solve the shortcomings existing in the background technology and provide a method for synthesizing benzoguanamine, which at least solves some technical problems in the prior art.

[0005] To achieve the above object, the present invention provides the following technical solutions: A method for synthesizing benzoguanamine comprises the following steps: Step 1: Heating and Addition Stage High-purity water is added to the reactor through a circulating water pump, and the pressure of the circulating water pump is controlled at 0.4-0.5 MPa. Then, n-butanol is added as a solvent, and then benzonitrile and dicyandiamide are added to the reactor. The temperature is raised to 114-120°C under the condition of potassium hydroxide as a catalyst, and stirred under the condition of a steam pressure of 0.1 MPa. The reflux addition reaction is maintained for 4 hours to generate a crude product, and the crude reaction product is discharged into a washing kettle; Step 2: Washing stage Turn on the oil-free vacuum pump and cooling water pump to filter the washing kettle, extract the synthetic high-concentration wastewater into the high-concentration wastewater transfer tank, then add high-purity water into the washing kettle for stirring and washing. After the washing is completed, the wastewater in the washing kettle is pumped into the wastewater transfer tank under the action of the oil-free vacuum pump; In order to improve the degree of washing of the crude product in the washing kettle, the crude product needs to be washed several times in the washing kettle; Step 3: Filtration stage Open the oil-free vacuum pump and the cooling circulating water inlet and return valves, open the transfer kettle discharge valve, and pump the material to the suction filter tank through the slurry pump for filtration. When the material in the suction filter tank is held by hand and no water drips out, it is drained. The wastewater is pumped to the stainless steel dilute water sedimentation tank through the slurry pump; Step 4: Drying and Screening Turn on the disc dryer and add the material to the dryer distribution disc continuously and evenly for drying. During the drying process, observe the drying condition of the material and adjust the steam volume. After drying, weigh and package the material.

[0006] Furthermore, the dicyandiamide is required to have a particle size greater than 40 meshes, accounting for more than 85% in total, that is, the residue passing through the 40 mesh sieve is less than 15%.

[0007] Furthermore, the heating synthesis process in step 1 is specifically operated as follows: a. Open the steam valve and heat slowly. The steam pressure is 0.05MPa. When the temperature in the reactor rises to 80℃, close the steam valve, let the temperature rise to 85℃ by itself, and exhaust the steam. When the temperature rises to 88-90℃, open the jacket return water. According to the temperature increase, open the jacket cooling water and the inner coil cooling water in time to extend the heat exchange time until the exothermic reaction ends and the reflux is normal, and then close the cooling water valve. It is worth noting that if the reflux temperature cannot be raised to 112~115℃ and the appropriate reflux volume is not seen, steam heating can be turned on until the reflux is normal; b. After the reaction is finished, the n-butanol is removed and stored in the n-butanol storage tank; When the n-butanol removal starts, the fore fraction valve is opened to recover the n-butanol with a small amount of water in the system into the fore fraction tank; when the temperature in the kettle rises to 119-125°C, the solvent in the kettle is significantly reduced (about 2-3 layers of coils are leaked), and samples are taken to test the water content of n-butanol (less than 0.8%). If qualified, switch to the pure phase tank until the pure phase distillation is completed (7-8 layers of coils are leaked); Close the steam valve and pure phase inlet valve, pass nitrogen, open the jacket water inlet and return valve, cool down to below 90°C, add water or high-purity water in the dilute n-butanol storage tank into the reactor, the amount of water should be enough to immerse the coil in the reactor, and heat until the water and n-butanol azeotropic reflux occurs, and a separation layer of water layer and dense n-butanol phase appears in the glass separator, separate the upper dense n-butanol phase into the dense phase storage tank, and the lower water layer into the dilute phase storage tank; c. As the recovery and reflux proceed, the temperature gradually rises. When the temperature reaches above 99°C, the liquid separated from the glass separator is all water without stratification. At this time, the recovery is completed and high-purity water is added to the coil; d. Open the jacket circulating water, cool it down to 75℃, close the cooling water valve, and discharge the material into the washing kettle in equal portions.

[0008] Furthermore, during the temperature rise synthesis stage, the temperature rise rate in the period of 85-117°C is controlled to be 2°C / 5min.

[0009] Furthermore, the specific process of washing the crude product multiple times in the washing kettle is as follows: a. Add 65~70℃ high-purity water to 10cm above the stirring blade in the washing kettle, stir for 10~15 minutes, stop stirring, start the oil-free vacuum pump to pump out the water while it is hot, pump out the wastewater into the high-concentration wastewater transfer tank, and discharge it into the stainless steel concentrated water sedimentation tank; b. Wash for the second time according to the above method; c. Add high-purity water to the washing kettle for the third time and stir for 10-15 minutes. After stopping stirring, start the oil-free vacuum pump to pump out the water while it is hot, pump out the waste water into the dilute waste water transfer tank, and pump the waste water into the stainless steel dilute water sedimentation tank through the slurry pump; d. Add high-purity water to the washing kettle for the fourth time and stir for 10-15 minutes. After stopping stirring, start the oil-free vacuum pump to pump out the water while it is hot, pump out the waste water into the dilute waste water transfer tank, and pump the waste water into the stainless steel dilute water sedimentation tank through the slurry pump; e. In the washing kettle, add high-purity water for the fifth washing, start stirring for 10 to 15 minutes, stop stirring, and use a slurry pump to pump the material into a stainless steel suction filtration tank or transfer kettle. The filtrated water enters the dilute wastewater transfer tank and is pumped into a stainless steel dilute water sedimentation tank through a slurry pump.

[0010] Furthermore, after washing, the pH value is measured with a 1-14 wide range test paper, the pH value is controlled at 7-9 during the first washing, the pH value is controlled at 5-6 during the second washing, and the pH value is controlled at 7.0-8.5 during the third and fourth washings, and the pH value is neutralized and adjusted with glacial acetic acid.

[0011] Furthermore, the drying temperature in the drying and screening stages is maintained at 85-95° C., and the moisture content of the benzoguanamine product after drying is controlled to be less than 0.1%.

[0012] Furthermore, the dense phase n-butanol is recycled after being subjected to rough distillation and rectification.

[0013] Furthermore, the operation of the dense phase n-butanol crude distillation treatment is specifically as follows: a. Start the concentrated n-butanol pump to pump the concentrated n-butanol into the crude distillation kettle; b. Check all valves to make the system in full reflux state, stir, open the steam valve of the crude steam kettle to slowly increase the temperature, and open the condenser water inlet and return valves for cooling and recovery. When the temperature in the kettle reaches 85~95℃, start azeotropic reflux, separate the lower layer of water in the water separator into the dilute phase tank, and reflux the upper layer into the reactor; c. When the temperature at the top of the crude steam kettle reaches 110-115℃, and the water separator is clear and has no stratification, turn off the steam, pass nitrogen, open the jacket and pass cooling water to cool it down to room temperature; d. Open the bottom valve of the crude distillation kettle and discharge the material into the front fraction receiving kettle.

[0014] Furthermore, the dense phase n-butanol distillation treatment operation is specifically as follows: a. Start the concentrated n-butanol pump or the fore fraction pump to pump the concentrated n-butanol or the fore fraction into the distillation kettle; b. Check all valves to make the system in full reflux state, stir, open the steam valve of the distillation kettle to slowly increase the temperature, and open the condenser water inlet and return valves for cooling and recovery. When the temperature at the top of the distillation kettle reaches 90℃, reflux begins, and the water from the water separator enters the dilute phase tank, and the upper layer refluxes to the distillation tower. Control the venting temperature to be less than 40℃; c. When the temperature at the top of the distillation kettle reaches 110-115℃, the water separator is clear and has no stratification, and the front fraction is cut and enters the front fraction receiving kettle; d. When the temperature at the top of the distillation kettle reaches 117°C, take samples to detect that the water content is less than 0.8%, start to recover n-butanol into the n-butanol pure phase tank, and when the liquid level in the distillation kettle reaches the bottom of the stirring tank, the distillation is considered to be over.

[0015] Beneficial effects of the present invention: (1) The present invention solves the problem of violent reaction caused by reaction heat accumulation by controlling the circulating water pressure in the heating addition stage and the heating speed and time in the heating period, thereby avoiding the accident of material impact; (2) The present invention improves the crude product washing effect by multiple high-purity water washings, thereby increasing the crude product conversion rate and the purity of the obtained benzoguanamine; (3) The present invention realizes the recycling of n-butanol through the crude distillation and rectification of the concentrated phase n-butanol, thereby reducing the production cost of benzoguanamine. DETAILED DESCRIPTION

[0016] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0017] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples. This repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides various specific examples of processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0018] A method for synthesizing benzoguanamine comprises the following steps: Step 1: Heating and Addition Stage High-purity water is added to the reactor through a circulating water pump, and the pressure of the circulating water pump is controlled at 0.4-0.5 MPa. Then, n-butanol is added as a solvent, and then benzonitrile and dicyandiamide are added to the reactor. The temperature is raised to 114-120°C under the condition of potassium hydroxide as a catalyst, and stirred under the condition of a steam pressure of 0.1 MPa. The reflux addition reaction is maintained for 4 hours to generate a crude product, and the crude reaction product is discharged into a washing kettle; The chemical reaction formula is: C7H5N+C2H4N4=C9H9N5; During the addition reaction, if the water pressure is lower than the range of 0.4-0.5MPa, the synthesis reaction must be stopped immediately and the cause must be found; Step 2: Washing stage Turn on the oil-free vacuum pump and cooling water pump to filter the washing kettle, extract the synthetic high-concentration wastewater into the high-concentration wastewater transfer tank, then add high-purity water into the washing kettle for stirring and washing. After the washing is completed, the wastewater in the washing kettle is pumped into the wastewater transfer tank under the action of the oil-free vacuum pump; In order to improve the degree of washing of the crude product in the washing kettle, the crude product needs to be washed several times in the washing kettle; Step 3: Filtration stage Open the oil-free vacuum pump and the cooling circulating water inlet and return valves, open the transfer kettle discharge valve, and pump the material to the suction filter tank through the slurry pump for filtration. When the material in the suction filter tank is held by hand and no water drips out, it is drained. The wastewater is pumped to the stainless steel dilute water sedimentation tank through the slurry pump; Step 4: Drying and Screening Turn on the disc dryer and add the material to the dryer distribution disc continuously and evenly for drying. During the drying process, observe the drying condition of the material and adjust the steam volume. After drying, weigh and package the material.

[0019] In this embodiment, the temperature rise synthesis process in step 1 is specifically operated as follows: a. Open the steam valve and heat slowly. The steam pressure is 0.05MPa. When the temperature in the reactor rises to 80℃, close the steam valve, let the temperature rise to 85℃ by itself, and exhaust the steam. When the temperature rises to 88-90℃, open the jacket return water. According to the temperature increase, open the jacket cooling water and the inner coil cooling water in time to extend the heat exchange time until the exothermic reaction ends and the reflux is normal. Close the cooling water valve and use cooling water to extend the 85~117℃ heating period to avoid violent reaction and material rushing accidents. It is worth noting that if the reflux temperature cannot be raised to 112~115℃ and the appropriate reflux volume is not seen, steam heating can be turned on until the reflux is normal; b. After the reaction is finished, the n-butanol is removed and stored in the n-butanol storage tank; When the n-butanol removal starts, the fore fraction valve is opened to recover the n-butanol with a small amount of water in the system into the fore fraction tank; when the temperature in the kettle rises to 119-125°C, the solvent in the kettle is significantly reduced (about 2-3 layers of coils are leaked), and samples are taken to test the water content of n-butanol (less than 0.8%). If qualified, switch to the pure phase tank until the pure phase distillation is completed (7-8 layers of coils are leaked); Close the steam valve and pure phase inlet valve, pass nitrogen, open the jacket water inlet and return valve, cool down to below 90°C, add water or high-purity water in the dilute n-butanol storage tank into the reactor, the amount of water should be enough to immerse the coil in the reactor, and heat until the water and n-butanol azeotropic reflux occurs, and a separation layer of water layer and dense n-butanol phase appears in the glass separator, separate the upper dense n-butanol phase into the dense phase storage tank, and the lower water layer into the dilute phase storage tank; c. As the recovery and reflux proceed, the temperature gradually rises. When the temperature reaches above 99°C, the liquid separated from the glass separator is all water without stratification. At this time, the recovery is completed and high-purity water is added to the coil; d. Open the jacket circulating water, cool it down to 75℃, close the cooling water valve, and discharge the material into the washing kettle in equal portions.

[0020] In this embodiment, the heating rate in the 85-117°C period is controlled at 2°C / 5min during the heating synthesis stage. By controlling the heating time, the problems of reaction heat accumulation and violent reaction can be effectively solved, and material impact accidents can be avoided.

[0021] In this embodiment, the specific process of washing the crude product multiple times in the washing kettle is as follows: a. Add 65~70℃ high-purity water to 10cm above the stirring blade in the washing kettle, stir for 10~15 minutes, stop stirring, start the oil-free vacuum pump to pump out the water while it is hot, pump out the wastewater into the high-concentration wastewater transfer tank, and discharge it into the stainless steel concentrated water sedimentation tank; b. Wash for the second time according to the above method; c. Add high-purity water to the washing kettle for the third time and stir for 10-15 minutes. After stopping stirring, start the oil-free vacuum pump to pump out the water while it is hot, pump out the waste water into the dilute waste water transfer tank, and pump the waste water into the stainless steel dilute water sedimentation tank through the slurry pump; d. Add high-purity water to the washing kettle for the fourth time and stir for 10-15 minutes. After stopping stirring, start the oil-free vacuum pump to pump out the water while it is hot, pump out the waste water into the dilute waste water transfer tank, and pump the waste water into the stainless steel dilute water sedimentation tank through the slurry pump; e. In the washing kettle, add high-purity water for the fifth washing, start stirring for 10 to 15 minutes, stop stirring, and use a slurry pump to pump the material into a stainless steel suction filtration tank or transfer kettle. The filtrated water enters the dilute wastewater transfer tank and is pumped into a stainless steel dilute water sedimentation tank through a slurry pump.

[0022] In this embodiment, the pH value is measured with a 1-14 wide range test paper after washing. The pH value is controlled at 7-9 during the first washing, 5-6 during the second washing, and 7.0-8.5 during the third and fourth washings. The pH value is neutralized and adjusted with glacial acetic acid.

[0023] In this embodiment, the dense phase n-butanol is recycled after being subjected to rough distillation and rectification.

[0024] In this embodiment, the operation of crude distillation of n-butanol in dense phase is as follows: a. Start the concentrated n-butanol pump to pump the concentrated n-butanol into the crude distillation kettle; b. Check all valves to make the system in full reflux state, stir, open the steam valve of the crude steam kettle to slowly increase the temperature, and open the condenser water inlet and return valves for cooling and recovery. When the temperature in the kettle reaches 85~95℃, start azeotropic reflux, separate the lower layer of water in the water separator into the dilute phase tank, and reflux the upper layer into the reactor; c. When the temperature at the top of the crude steam kettle reaches 110-115℃, and the water separator is clear and has no stratification, turn off the steam, pass nitrogen, open the jacket and pass cooling water to cool it down to room temperature; d. Open the bottom valve of the crude distillation kettle and discharge the material into the front fraction receiving kettle.

[0025] In this embodiment, the concentrated phase n-butanol distillation treatment operation is specifically as follows: a. Start the concentrated n-butanol pump or the fore fraction pump to pump the concentrated n-butanol or the fore fraction into the distillation kettle; b. Check all valves to make the system in full reflux state, stir, open the steam valve of the distillation kettle to slowly increase the temperature, and open the condenser water inlet and return valves for cooling and recovery. When the temperature at the top of the distillation kettle reaches 90℃, reflux begins, and the water from the water separator enters the dilute phase tank, and the upper layer refluxes to the distillation tower. Control the venting temperature to be less than 40℃; c. When the temperature at the top of the distillation kettle reaches 110-115℃, the water separator is clear and has no stratification, and the front fraction is cut and enters the front fraction receiving kettle; d. When the temperature at the top of the distillation kettle reaches 117°C, take samples to detect that the water content is less than 0.8%, start to recover n-butanol into the n-butanol pure phase tank, and when the liquid level in the distillation kettle reaches the bottom of the stirring tank, the distillation is considered to be over.

[0026] Embodiment 1 In this embodiment, the particle size of dicyandiamide is required to be greater than 40 mesh and the cumulative amount is more than 85%, that is, the residue passing through the 40 mesh sieve is less than 15%.

[0027] In this embodiment, the drying temperature in the drying and screening stages is maintained at 85-90° C., and the moisture content of the benzoguanamine product after drying is controlled to be less than 0.08%.

[0028] Embodiment 2 In this embodiment, the particle size of dicyandiamide is required to be greater than 40 mesh, which is more than 90%, that is, the residue passing through the 40 mesh sieve is less than 10%.

[0029] In this embodiment, the drying temperature in the drying and screening stages is maintained at 87-92° C., and the moisture content of the benzoguanamine product after drying is controlled to be less than 0.1%.

[0030] Embodiment 3 In this embodiment, the particle size of dicyandiamide is required to be greater than 40 mesh and the cumulative amount is more than 95%, that is, the residue passing through the 40 mesh sieve is less than 5%.

[0031] In this embodiment, the drying temperature in the drying and screening stages is maintained at 90-95° C., and the moisture content of the benzoguanamine product after drying is controlled to be less than 0.1%.

[0032] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of the above disclosed technical contents without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for synthesizing benzoguanamine, characterized in that: The following steps are involved: Step 1: Heating and Addition Stage High-purity water is added to the reactor through a circulating water pump, and the pressure of the circulating water pump is controlled at 0.4-0.5 MPa. Then, n-butanol is added as a solvent, and then benzonitrile and dicyandiamide are added to the reactor. The temperature is raised to 114-120°C under the condition of potassium hydroxide as a catalyst, and stirred under the condition of a steam pressure of 0.1 MPa. The reflux addition reaction is maintained for 4 hours to generate a crude product, and the crude reaction product is discharged into a washing kettle; Step 2: Washing stage Turn on the oil-free vacuum pump and cooling water pump to filter the washing kettle, extract the synthetic high-concentration wastewater into the high-concentration wastewater transfer tank, then add high-purity water into the washing kettle for stirring and washing. After the washing is completed, the wastewater in the washing kettle is pumped into the wastewater transfer tank under the action of the oil-free vacuum pump. The crude product needs to be washed multiple times in the washing kettle; Step 3: Filtration stage Open the oil-free vacuum pump and the cooling circulating water inlet and return valves, open the transfer kettle discharge valve, and pump the material to the suction filter tank through the slurry pump for filtration. When the material in the suction filter tank is held by hand and no water drips out, it is drained. The wastewater is pumped to the stainless steel dilute water sedimentation tank through the slurry pump; Step 4: Drying and Screening Turn on the disc dryer and add the material to the dryer distribution disc continuously and evenly for drying. During the drying process, observe the drying condition of the material and adjust the steam volume. After drying, weigh and package the material.

2. The method for synthesizing benzoguanamine according to claim 1, characterized in that: The dicyandiamide is required to have a particle size greater than 40 meshes, with a cumulative content of more than 85%, that is, the residue passing through a 40-mesh sieve is less than 15%.

3. The method for synthesizing benzoguanamine according to claim 1, characterized in that: The specific operation of the heating synthesis stage in step 1 is as follows: a. Open the steam valve and heat slowly. The steam pressure is 0.05MPa. When the temperature in the reactor rises to 80℃, close the steam valve, let the temperature rise to 85℃ by itself, and exhaust the steam. When the temperature rises to 88-90℃, open the jacket return water. According to the temperature increase, open the jacket cooling water and the inner coil cooling water in time to extend the heat exchange time until the exothermic reaction ends and the reflux is normal, and then close the cooling water valve. If the reflux temperature cannot be raised to 112~115℃ and the appropriate reflux volume is not seen, steam heating can be used until the reflux is normal; b. After the reaction is finished, the n-butanol is removed and stored in the n-butanol storage tank; When the n-butanol removal starts, the fore fraction valve is opened to recover the n-butanol containing a small amount of water in the system into the fore fraction tank; when the temperature in the kettle rises to 119-125°C, the solvent in the kettle is significantly reduced, and samples are taken to test the water content of n-butanol. If it is qualified, switch to the pure phase tank until the pure phase distillation is completed; Close the steam valve and pure phase inlet valve, pass nitrogen, open the jacket water inlet and return valve, cool down to below 90°C, add water or high-purity water in the dilute n-butanol storage tank into the reactor, the amount of water should be enough to immerse the coil in the reactor, and heat until the water and n-butanol azeotropic reflux occurs, and a separation layer of water layer and dense n-butanol phase appears in the glass separator, separate the upper dense n-butanol phase into the dense phase storage tank, and the lower water layer into the dilute phase storage tank; c. As the recovery and reflux proceed, the temperature gradually rises. When the temperature reaches above 99°C, the liquid separated from the glass separator is all water without stratification. At this time, the recovery is completed and high-purity water is added to the coil; d. Open the jacket circulating water, cool it down to 75℃, close the cooling water valve, and discharge the material into the washing kettle in equal portions.

4. The method for synthesizing benzoguanamine according to claim 3, characterized in that: During the temperature rise synthesis stage, the heating rate in the period of 85-117°C was controlled at 2°C / 5min.

5. The method for synthesizing benzoguanamine according to claim 1, characterized in that: The specific process of multiple washing of the crude product in the washing kettle is as follows: a. Add 65~70℃ high-purity water to 10cm above the stirring blade in the washing kettle, stir for 10~15 minutes, stop stirring, start the oil-free vacuum pump to pump out the water while it is hot, pump out the wastewater into the high-concentration wastewater transfer tank, and discharge it into the stainless steel concentrated water sedimentation tank; b. Wash for the second time according to the above method; c. Add high-purity water to the washing kettle for the third time and stir for 10-15 minutes. After stopping stirring, start the oil-free vacuum pump to pump out the water while it is hot, pump out the waste water into the dilute waste water transfer tank, and pump the waste water into the stainless steel dilute water sedimentation tank through the slurry pump; d. Add high-purity water to the washing kettle for the fourth time and stir for 10-15 minutes. After stopping stirring, start the oil-free vacuum pump to pump out the water while it is hot, pump out the waste water into the dilute waste water transfer tank, and pump the waste water into the stainless steel dilute water sedimentation tank through the slurry pump; e. In the washing kettle, add high-purity water for the fifth washing, start stirring for 10 to 15 minutes, stop stirring, and use a slurry pump to pump the material into a stainless steel suction filtration tank or transfer kettle. The filtrated water enters the dilute wastewater transfer tank and is pumped into a stainless steel dilute water sedimentation tank through a slurry pump.

6. The method for synthesizing benzoguanamine according to claim 5, characterized in that: After washing, the pH value is measured with a 1-14 wide range test paper. The pH value is controlled at 7-9 during the first washing, 5-6 during the second washing, and 7.0-8.5 during the third and fourth washings. The pH value is adjusted by neutralization with glacial acetic acid.

7. The method for synthesizing benzoguanamine according to claim 1, characterized in that: The drying temperature in the drying and screening stages is maintained at 85-95° C., and the moisture content of the benzoguanamine product after drying is controlled to be less than 0.1%.

8. The method for synthesizing benzoguanamine according to claim 3, characterized in that: The concentrated n-butanol is recycled after being subjected to rough distillation and rectification.

9. The method for synthesizing benzoguanamine according to claim 8, characterized in that: The operation of the crude distillation of n-butanol in the dense phase is as follows: a. Start the concentrated n-butanol pump to pump the concentrated n-butanol into the crude distillation kettle; b. Check all valves to make the system in full reflux state, stir, open the steam valve of the crude steam kettle to slowly increase the temperature, and open the condenser water inlet and return valves for cooling and recovery. When the temperature in the kettle reaches 85~95℃, start azeotropic reflux, separate the lower layer of water in the water separator into the dilute phase tank, and reflux the upper layer into the reactor; c. When the temperature at the top of the crude steam kettle reaches 110-115℃, and the water separator is clear and has no stratification, turn off the steam, pass nitrogen, open the jacket and pass cooling water to cool it down to room temperature; d. Open the bottom valve of the crude distillation kettle and discharge the material into the front fraction receiving kettle.

10. The method for synthesizing benzoguanamine according to claim 8, characterized in that: The dense phase n-butanol distillation treatment operation is specifically as follows: a. Start the concentrated n-butanol pump or the fore fraction pump to pump the concentrated n-butanol or the fore fraction into the distillation kettle; b. Check all valves to make the system in full reflux state, stir, open the steam valve of the distillation kettle to slowly increase the temperature, and open the condenser water inlet and return valves for cooling and recovery. When the temperature at the top of the distillation kettle reaches 90℃, reflux begins, and the water from the water separator enters the dilute phase tank, and the upper layer refluxes to the distillation tower. Control the venting temperature to be less than 40℃; c. When the temperature at the top of the distillation kettle reaches 110-115℃, the water separator is clear and has no stratification, and the front fraction is cut and enters the front fraction receiving kettle; d. When the temperature at the top of the distillation kettle reaches 117°C, take samples to detect that the water content is less than 0.8%, start to recover n-butanol into the n-butanol pure phase tank, and when the liquid level in the distillation kettle reaches the bottom of the stirring tank, the distillation is considered to be over.