Method for reducing content of residual impurities in solution polymerized styrene-butadiene rubber

Abstract

The invention provides a method for reducing the content of residual impurities in solution polymerized styrene-butadiene rubber, which comprises the following steps: adding halide into a glue solution after polymerization is terminated, and stirring for reaction to generate volatile substances and halide salt; removing and recovering the volatile substances by using a steam flash evaporation technology; and recovering the halide salt by adopting a solid-liquid separation and evaporation technology, and carrying out drying treatment to obtain the rubber particles. According to the method, the residue of lithium byproducts is remarkably reduced, lithium resources can be effectively recycled, the wastewater treatment cost is reduced, the overall production efficiency is improved, and green, economical and efficient production of the solvent styrene butadiene rubber is realized.

Description

Technical Field

[0001] This invention relates to the field of synthetic rubber production technology, and more specifically, to a method for reducing the content of residual impurities in solution-polymerized styrene-butadiene rubber. Background Technology

[0002] Solution styrene-butadiene rubber (SSBR), as an important synthetic rubber material, has wide applications in tire manufacturing, rubber products, and other high-performance materials. In recent years, with increasing demands for environmental performance and overall tire performance, SSBR functionalization technology has been widely adopted due to its ability to significantly enhance the compatibility and interaction between SSBR and silica, thereby improving tires' low rolling resistance, high wet grip, and good wear resistance. However, the residual byproducts in the production process of functionalized SSBR, especially lithium ethoxylate, have become a major challenge restricting its performance and environmental protection.

[0003] In the functionalization production of SSBR (Self-Contained Rubber Rubber), lithium ethoxylate acts as a dissociative agent or terminator, helping to control the microstructure of rubber and the precise introduction of functional groups. However, in subsequent operations, if not effectively treated, residual lithium ethoxylate will convert into strongly alkaline lithium hydroxide, affecting not only the stability of SSBR products but also potentially causing equipment corrosion, increasing the difficulty of wastewater treatment, and wasting lithium resources. Furthermore, while traditional water washing and neutralization techniques can remove lithium hydroxide to some extent, they also bring a series of problems such as high consumption, low efficiency, high cost, and environmental pollution. The requirement of several tons of washing water per ton of rubber contradicts the concept of green chemistry, and the cost of wastewater, waste salt, and waste residue treatment accounts for more than 15% of the overall cost, while facing increasing pressure from tightening environmental regulations.

[0004] Therefore, the traditional water washing-neutralization process, due to its high corrosion, high pollution, low efficiency, and resource waste, has become a bottleneck in the production of functionalized solvent-based styrene-butadiene rubber (SSBR). A new process technology is urgently needed that can effectively remove residual ethoxylithium byproducts from SSBR while also achieving economic benefits and environmental protection, thus paving a more sustainable path for the production of functionalized SSBR. Summary of the Invention

[0005] This invention aims to provide a solution that not only significantly reduces the residue of lithium by-products, but also effectively recovers lithium resources, reduces wastewater treatment costs, improves overall production efficiency, and achieves green, economical, and efficient solvent-based styrene-butadiene rubber production.

[0006] To address the above problems, this invention provides a method for reducing the content of residual impurities in solution-polymerized styrene-butadiene rubber, comprising the following steps: S10. After polymerization is terminated, halides are added to the glue solution and stirred to produce volatile substances and halide salts. S20. Remove and recover the volatile substances using a steam flash evaporation technique; S30. The halide salt is recovered by solid-liquid separation and evaporation technology and dried to obtain rubber particles; The adhesive solution includes unreacted lithium ethoxylate, hexane solvent, and solution-polymerized styrene-butadiene rubber particles; the halide is selected from one or more of silicon tetrachloride, aluminum trichloride, ferric chloride, antimony trichloride, and ferric tribromide, and is used to react with unreacted lithium ethoxylate to convert it into volatile organic compounds and halide salts, wherein the volatile organic compounds can be recycled as by-products.

[0007] Furthermore, in S10, the reaction temperature is 35℃~45℃, and the stirring time is 50 minutes~70 minutes; the halide is added dropwise by a metering pump, and the reaction is terminated when the pH of the liquid phase sample is greater than 7 and the chloride ion concentration is stable.

[0008] Precise temperature control avoids rubber degradation due to high temperatures or incomplete reaction due to low temperatures, and optimized reaction time ensures a conversion rate of >99%; using a metering pump for drip addition can prevent excessively high local concentrations from causing side reactions and improve process stability.

[0009] Furthermore, S10 specifically includes: S11. Add hot water to the reacted solution and stir to dissolve the halide salt and reduce the viscosity of the solution, which facilitates the separation of by-products in the subsequent flash evaporation process.

[0010] Furthermore, in S11, the mass ratio of the adhesive solution to hot water is 1:0.7 to 1:1; the temperature of the hot water is 70℃ to 90℃.

[0011] Hot water dissolves the halide salts, preventing salt particles from being trapped in the rubber; hot water mixing significantly reduces the viscosity of the rubber solution, solving the solid-liquid separation problem caused by high viscosity; high-temperature water promotes the release of volatile substances, enhancing the efficiency of subsequent flash evaporation.

[0012] Furthermore, in S20, the pressure of steam flash evaporation is 0.3MPa to 0.5MPa. Steam is directly injected into the bottom of the condenser to instantly vaporize the hexane solvent in the liquid. The organic matter is recovered by the condenser at the top of the column, and then the residual organic matter is further removed by vacuum, thus achieving efficient solvent removal.

[0013] Furthermore, in S30, solid-liquid separation is performed by centrifugation at a speed of 2000 rpm to 4000 rpm for 10 minutes, resulting in a solid phase containing solution-polymerized styrene-butadiene rubber particles and an aqueous phase containing halide salts.

[0014] High-speed centrifugation achieves efficient separation of rubber and aqueous phase, with rubber moisture content <15%; Furthermore, the aqueous phase after solid-liquid separation is concentrated to saturation concentration by a multi-effect evaporator, cooled and crystallized to obtain solid halide salts with a purity of ≥99%, thus realizing the recycling of halide salt resources.

[0015] Multi-effect evaporators have significant energy-saving characteristics and can achieve the recovery and utilization of high-purity halide salts. In addition, the equipment can effectively reduce the salt content in wastewater during operation, thereby meeting environmental emission standards and playing a positive role in environmental protection.

[0016] Furthermore, in S30, the drying process employs an expansion dryer, with a drying temperature of 110℃~130℃ and a drying pressure of 0.7Mpa~0.9Mpa, effectively removing residual moisture from the synthetic rubber particles to obtain the finished solution-polymerized styrene-butadiene rubber.

[0017] High-temperature and high-pressure instantaneous drying avoids thermal oxidation of rubber, preserves the molecular chain structure, and results in a low final moisture content of the rubber, which can meet the requirements of high-end tire applications. In addition, the expansion dryer also has efficient heat transfer performance, which can uniformly heat rubber particles in a short time and avoid quality degradation caused by local overheating.

[0018] Furthermore, in S10, the reaction takes place in an inert gas, which is one or more of nitrogen, argon, helium, and neon, to protect the reaction system from oxygen interference, provide a stable reaction environment, and ensure the smooth progress of the halogen-alkylation exchange reaction.

[0019] An inert atmosphere can prevent halides from decomposing and becoming ineffective when exposed to water, ensuring reaction efficiency. At the same time, it isolates oxygen to prevent rubber from oxidizing and cross-linking, thus maintaining Mooney viscosity stability.

[0020] The above-described technical solutions of this application can have one or more of the following advantages or beneficial effects: (1) Resource recycling, lithium recovery rate ≥95%, 8-10 kg of lithium chloride can be recovered per ton of solution-polymerized styrene-butadiene rubber, which can be recycled as a by-product; (2) Significant environmental benefits: the COD of wastewater is reduced to below 500 mg / L, and there is no strongly alkaline waste residue. The pH of the wastewater is 6-8, which can be directly treated by biochemical methods. (3) Saves costs, eliminates the need for multi-stage water washing, reduces water consumption by 60%, uses zero neutralizing agent, and reduces waste residue treatment costs by 80%. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 A schematic flowchart of the method for reducing the content of residual impurities in solution-polymerized styrene-butadiene rubber provided by the present invention; Figure 2 This describes the reaction mechanism of the alkylation reaction between unreacted lithium ethoxylate and silicon tetrachloride in the adhesive solution. Detailed Implementation

[0022] To make the above-mentioned objectives, features, and advantages of the present invention more apparent and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] In the production of functionalized solution-polymerized styrene-butadiene rubber (SBR), lithium ethoxylate is often used as a dissociative agent to reduce the viscosity of the polymerization system and promote subsequent functionalization reactions. Traditional water washing-neutralization processes are used to remove this byproduct, but they have at least the following drawbacks: (1) Residual lithium ethoxylates can react with silane coupling agents and vulcanization accelerators in the formulation, and at the same time catalyze the degradation or cross-linking of polymer chains, affecting the performance of vulcanized rubber products and changing the mechanical and processing properties of SSBR. In addition, lithium salts generated by the hydrolysis of lithium ethoxylates and subsequent reactions form impurities, reducing the heat resistance and aging resistance of rubber, catalyzing the oxidative degradation of molecular chains, and accelerating performance degradation. Strong alkaline environment accelerates the vulcanization reaction, resulting in a shortened scorch time. Lithium salt impurities reduce the dispersibility of fillers, affecting the key performance of products and causing abnormal Mooney viscosity of SSBR products. (2) Lithium ethoxylate corrodes production equipment at high temperatures, and the strong alkaline solution generated by hydrolysis exacerbates the corrosion of the equipment, increases the maintenance cost of the production equipment, and poses a safety hazard. (3) Neutralization produces lithium salt wastewater with high COD and salt content, which has high treatment costs. Precipitated lithium salt requires additional solid waste treatment, which puts great pressure on the environment. The high-value lithium element in lithium ethoxy cannot be recovered and is lost in the form of inorganic salt. Moreover, the washing and neutralization process is complicated, which prolongs the production cycle. Incomplete washing affects the purity and stability of the product. The use of a large amount of washing water is contrary to the concept of green chemical industry. The overall treatment cost accounts for more than 15%.

[0024] See Figure 1To address the above problems, embodiments of the present invention provide a method for reducing the content of residual impurities in solution-polymerized styrene-butadiene rubber, comprising the following steps: S10. After polymerization is terminated, halides are added to the glue solution and stirred to produce volatile substances and halide salts. S20. Remove and recover the volatile substances using a steam flash evaporation technique; S30. The halide salt is recovered by solid-liquid separation and evaporation technology and dried to obtain rubber particles; The adhesive solution includes unreacted lithium ethoxylate, hexane solvent, and solution-polymerized styrene-butadiene rubber particles; the halide is selected from one or more of silicon tetrachloride, aluminum trichloride, ferric chloride, antimony trichloride, and ferric tribromide; preferably, the halide is silicon tetrachloride.

[0025] This invention introduces silicon tetrachloride to chemically react with residual impurities, transforming difficult-to-remove byproducts into easily separable volatile organic compounds and halide salts, effectively reducing the impurity content in synthetic rubber materials. The reaction between halides and lithium ethoxylate byproducts is based on a halogen-alkylation exchange reaction. The resulting tetraethoxysilane residue in the rubber product has no impact on product quality or downstream compounding and vulcanization processes, while lithium chloride is water-soluble, facilitating subsequent recovery and treatment. In other embodiments, different halogenating agents, such as aluminum trichloride and ferric chloride, can be used to address the removal of specific impurities, adapting to the production needs of different synthetic rubber materials.

[0026] like Figure 2 As shown, in one embodiment of the present invention, the halide is silicon tetrachloride, and the adhesive solution includes unreacted lithium ethoxylate that undergoes an alkylation reaction with silicon tetrachloride to generate tetraethoxysilane remaining in the rubber material and lithium chloride dissolved in water.

[0027] In the technical solution of this application, firstly, after the chemical reaction is completed, the residual ethoxylithium byproduct in the adhesive solution undergoes a chemical conversion with halogenating agents such as silicon tetrachloride under inert gas protection to generate tetraethoxysilane and lithium chloride. Subsequently, the solvent in the adhesive solution is separated by steam flash evaporation technology, and the halide salts are recovered by centrifugation and evaporation technology. Finally, the synthetic rubber particles are dried by an expansion dryer to obtain the finished SSBR product. The entire process, through precise control of reaction conditions and separation technology, achieves effective removal of impurities and recycling of resources, improves production efficiency, reduces energy consumption, and reduces the generation of wastewater and waste residue, thus achieving environmentally friendly production.

[0028] In some embodiments of the present invention, the halide is selected from one or more of silicon tetrachloride, aluminum trichloride, ferric chloride, antimony trichloride, and ferric tribromide, preferably silicon tetrachloride, and is used to react with residual lithium ethoxylate byproducts to convert them into volatile organic compounds and halide salts. The volatile organic compounds can be recycled as byproducts. This embodiment ensures the high efficiency of byproduct conversion and the economic value of the byproducts by selecting specific halides. The reaction of silicon tetrachloride with lithium ethoxylate produces tetraethoxysilane and lithium chloride. The generated tetraethoxysilane remains in the rubber product and has no impact on product quality or downstream compounding and vulcanization processes, while lithium chloride can be recovered as a valuable halide salt.

[0029] The technical solution in this embodiment achieves effective conversion of by-products and recycling of resources, reducing production costs and improving economic efficiency. In other embodiments, other halides, such as ferric chloride, can be used to treat different types of by-products and solve specific impurity removal problems.

[0030] In some embodiments of the present invention, the temperature during the halogen-alkylation exchange reaction is 35°C to 45°C, and the reaction time is 50 to 70 minutes, preferably 60 minutes. The halide silicon tetrachloride is added dropwise using a metering pump until the pH of the liquid sample is greater than 7 and the chloride ion concentration is stable, at which point the reaction is terminated. The reaction is carried out under an inert gas atmosphere to ensure the completeness of the reaction and the purity of the product.

[0031] Controlling the reaction temperature and time can promote the complete occurrence of the halogen-alkylation exchange reaction. The technical solution in this embodiment significantly improves the efficiency of byproduct conversion and product purity by precisely controlling the reaction conditions, while reducing the complexity of subsequent processing.

[0032] In some embodiments of the present invention, the gel solution after the halogen-alkylation exchange reaction is mixed with hot water at a mass ratio of 1:0.7 to 1:1, preferably 1:0.8, and the hot water temperature is 70℃ to 90℃, preferably 80℃. This mixture is used to dissolve the halide salts and reduce the viscosity of the gel solution, facilitating the separation of by-products in the subsequent flash evaporation process. This embodiment reduces the viscosity of the gel solution by mixing it with hot water, facilitating the subsequent flash evaporation process and achieving efficient separation of by-products. The addition of hot water dissolves the halide salts, reducing the viscosity of the gel solution and facilitating the subsequent flash evaporation process. Controlling the temperature and mass ratio of the hot water ensures complete dissolution of the halide salts and reduces the viscosity of the gel solution, improving the efficiency of by-product separation. The technical solution in this embodiment significantly improves the efficiency of by-product separation, reduces energy consumption, reduces wastewater generation, and achieves environmentally friendly production.

[0033] In some embodiments of the present invention, in the steam flash evaporation technique, the pressure of saturated steam is 0.3 MPa to 0.5 MPa, preferably 0.4 MPa. The steam is directly injected into the bottom of the condenser, instantly vaporizing the hexane solvent in the liquid. The organic matter is recovered by the condenser at the top of the column, and then the residual organic matter is further removed by vacuum treatment, achieving efficient removal of volatile impurities. This embodiment achieves efficient solvent separation by employing steam flash evaporation technology, utilizing the high pressure and instantaneous vaporization effect of saturated steam. The introduction of high-pressure steam can rapidly increase the temperature of the liquid, causing the solvent to vaporize, while the condenser is used to recover these organic matter, and vacuum treatment further removes the residual organic matter.

[0034] The technical solution in this embodiment significantly improves the separation efficiency of by-products and solvents, reduces energy consumption, and decreases wastewater generation, achieving environmentally friendly production. In other embodiments, the separation efficiency can be further improved by adjusting the steam pressure and temperature, as well as optimizing the parameters of the condenser and vacuum treatment, thus solving the problems of high energy consumption and environmental pollution.

[0035] In some embodiments of the present invention, the latex after steam flash evaporation is centrifuged at a speed of 2000 rpm to 4000 rpm, preferably 3000 rpm, for 10 minutes. After centrifugation, the upper layer is solution-polymerized styrene-butadiene rubber particles with a moisture content of ≤15%, and the lower layer is an aqueous phase containing 10-15 wt% lithium chloride.

[0036] In this technical solution, the centrifugal separation step significantly improves the purity of solution-polymerized styrene-butadiene rubber (SBR) particles while reducing the moisture and impurity content in the product. This step not only optimizes the quality of the SBR particles but also achieves resource recycling by recovering and reusing the lithium chloride-containing aqueous phase, effectively reducing production costs and environmental impact. Furthermore, the optimization of this separation process is of great significance for improving the overall quality of the product and promoting environmentally friendly production.

[0037] In some embodiments of the present invention, the step of recovering halide salts includes feeding the aqueous phase after centrifugation into a multi-effect evaporator, concentrating it to halide salt saturation, and obtaining halide salt solids with a purity of ≥99% by cooling and crystallization, so as to realize the recycling of halide salt resources.

[0038] By employing a multi-effect evaporator and cooling crystallization technology, efficient recovery and purification of lithium chloride were achieved. The multi-effect evaporator improves the recovery rate of lithium chloride through multi-stage evaporation and concentration, while cooling crystallization is used to purify lithium chloride and obtain high-purity lithium chloride solid.

[0039] The technical solution in this embodiment significantly improves the recovery rate and purity of lithium chloride, reduces production costs, and realizes the recycling of resources.

[0040] In some embodiments of the present invention, the drying process employs an expansion dryer, the drying temperature is 110℃~130℃, preferably 120℃, and the drying pressure is set to 0.7MPa~0.9MPa, preferably 0.8MPa, in order to effectively remove residual moisture from the synthetic rubber particles and obtain the finished solution-polymerized styrene-butadiene rubber.

[0041] This embodiment achieves efficient drying and complete moisture removal of synthetic rubber granules by employing an expansion dryer and precisely controlling the drying conditions. The expansion dryer accelerates moisture evaporation through a high-temperature and high-pressure environment, while precise control of the drying temperature and pressure ensures the drying effect and product quality of the synthetic rubber granules.

[0042] The technical solution in this embodiment significantly improves drying efficiency, reduces energy consumption, lowers production costs, and improves the quality of synthetic rubber products. In other embodiments, drying efficiency and product quality can be further improved, and the problems of high energy consumption and production costs can be solved, by optimizing drying temperature and pressure, and by changing the type of dryer.

[0043] In some embodiments of the present invention, the inert gas is one or more of nitrogen, argon, helium, and neon, used to protect the reaction system from oxygen interference, provide a stable reaction environment, and ensure the smooth progress of the halogen-alkylation exchange reaction.

[0044] This embodiment uses an inert gas to protect the reaction system, ensuring the smooth progress of the halogen-alkylation exchange reaction and the high quality of the product. The use of an inert gas prevents oxygen from entering the reaction system, avoiding side reactions and protecting the stability of the reaction system and the purity of the product. The technical solution in this embodiment significantly improves reaction efficiency and product purity, reduces production costs, and improves the quality of synthetic rubber products.

[0045]

Example 1

[0046] 20 ml of a cyclohexane solution of silicon tetrachloride (2.124 g / L) was added dropwise to flask #1 at 40 °C using a metering pump while stirring at 200 rpm. The dropwise reaction continued for 60 min. A spherical condenser was then installed on the left side of flask #1, with a receiving bottle attached to its end (to collect the condensed cyclohexane solvent). Under stirring, 1614 ml of 80 °C hot water (water-to-gel ratio 0.8 / 1) was slowly poured into flask #1, while simultaneously heating the flask to 80 °C using a water bath at the bottom. This stirring and heating process continued for 60 min. Finally, the stirring and heating were turned off, and the No. 1 experimental bottle was allowed to stand and separate into layers. The upper layer of concentrated gel solution was taken and vacuum dried in a 70℃ vacuum drying oven for 4 hours. The sample was colorless and transparent. Then, the sample was sent to an external testing institution for analysis of lithium metal content (inductively coupled plasma atomic emission spectrometry (ICP-OES) was used to detect lithium content, according to JY / T015-1996 General Rules for Inductively Coupled Plasma Atomic Emission Spectroscopy). The sample showed lithium metal residue <5ppm. The lower layer water sample was taken for pH analysis, which showed pH=7-8 and chloride ion concentration in the aqueous phase of 21.97mg / L (according to GB / T 15453-2018 "Determination of Chloride Ions in Industrial Circulating Cooling Water and Boiler Water").

[0047] Comparative Example 1 Prepare a 5L three-necked glass bottle beforehand, purge it with 99.999% high-purity nitrogen, and then stopper it. Next, pour the SSBR glue solution from the mixing vessel into the 5L three-necked glass bottle until it reaches approximately 4.5L (weigh 3510g of glue solution upon return). Then, in a glove box, distribute the glue solution from the 5L three-necked glass bottle into two 5L three-necked glass bottles (2018g of glue solution in bottle #1, 1492g of glue solution in bottle #2), attach mechanical stirrers to both, and label them – Experiment #1 and Blank Experiment.

[0048] Then, a spherical condenser was installed on the left side of the blank experimental bottle, and a receiving bottle (to receive the condensed cyclohexane solvent) was installed at the end of the condenser. Under stirring, 1194 ml of 80°C hot water was slowly poured into the blank experimental bottle (water-gel ratio 0.8 / 1), while simultaneously turning on the water bath at the bottom of the blank experimental bottle to control the heating temperature to 80°C. This stirring and heating process lasted for 60 min. Finally, the stirring and heating were turned off, and the blank experimental bottle was allowed to stand and separate into layers. The upper layer of concentrated gel solution was taken and vacuum dried in a 70°C vacuum drying oven for 4 h. The sample was colorless and transparent. Then, the sample was sent to an external testing institution for lithium content analysis (lithium content was detected using inductively coupled plasma atomic emission spectrometry (ICP-OES), according to JY / T015-1996 General Rules for Inductively Coupled Plasma Atomic Emission Spectrometry). The sample showed a lithium residue of 23 ppm. pH analysis of the lower water sample showed a pH of 8-9 and a chloride ion concentration of <5 mg / L (the test was conducted according to GB / T 15453-2018 "Determination of Chloride Ions in Industrial Circulating Cooling Water and Boiler Water").

[0049] Analysis of lithium ion content and chloride ion concentration in the aqueous phase revealed that the silica-treated solution contained virtually no residual metallic lithium. This demonstrates that the alkylation reaction of silica-tetrachloride with the ethoxylithium byproduct effectively converts ethoxylithium into lithium chloride, which is then extracted into the hot water. The relatively high chloride ion concentration in the silica-treated solution further confirms that the reaction of ethoxylithium with silica-tetrachloride converts it into lithium chloride, which is then extracted by hot water, thus increasing the chloride ion concentration in the aqueous phase. This indicates that direct water washing cannot effectively remove residual ethoxylithium from the solution.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for reducing the content of residual impurities in solution-polymerized styrene-butadiene rubber, characterized in that, Includes the following steps: S10. After polymerization is terminated, halides are added to the glue solution and stirred to produce volatile substances and halide salts. S20. Remove and recover the volatile substances using a steam flash evaporation technique; S30. The halide salt is recovered by solid-liquid separation and evaporation technology and dried to obtain rubber particles; The adhesive solution includes unreacted lithium ethoxylate, hexane solvent, and solution-polymerized styrene-butadiene rubber particles; the halide is selected from one or more of silicon tetrachloride, aluminum trichloride, ferric chloride, antimony trichloride, and ferric tribromide.

2. The method according to claim 1, characterized in that, In S10, the reaction temperature is 35℃~45℃, and the stirring time is 50 minutes~70 minutes; the halide is added dropwise by a metering pump.

3. The method according to claim 1, characterized in that, S10 specifically includes: S11. Add hot water to the reacted adhesive solution and stir to dissolve the halide salt and reduce the viscosity of the adhesive solution.

4. The method according to claim 3, characterized in that, In S11, the mass ratio of the adhesive to the hot water is 1:0.7 to 1:1; the temperature of the hot water is 70℃ to 90℃.

5. The method according to claim 1, characterized in that, In S20, the pressure of the steam flash evaporation is 0.3MPa to 0.5MPa, and the steam is directly injected into the bottom of the condensation vessel to instantly vaporize the hexane solvent in the adhesive solution.

6. The method according to claim 1, characterized in that, In S30, the solid-liquid separation is performed by centrifugation, the centrifugation speed is 2000 rpm to 4000 rpm, and the centrifugation time is 10 minutes.

7. The method according to claim 1, characterized in that, The aqueous phase after solid-liquid separation is concentrated to saturation concentration by a multi-effect evaporator and then cooled and crystallized to obtain the solid halide salt.

8. The method according to claim 1, characterized in that, In S30, the drying process is carried out using an expansion dryer, the drying temperature is 110℃~130℃, and the drying pressure is 0.7Mpa~0.9Mpa.

9. The method according to any one of claims 1 to 8, characterized in that, In S10, the reaction occurs in an inert gas, which is one or more of nitrogen, argon, helium, and neon.

Images