Ziram synthesis method

Abstract

The invention discloses a method for synthesizing ziram. The method comprises the following steps: S1, stirring a compound surfactant and zinc oxide to obtain a dispersion liquid; s2, sealing and pressurizing, and adding dimethylamine for reaction to obtain a dimethylamine salt mixture; and S3, dropwise adding carbon disulfide, performing condensation reaction, and removing impurities to obtain the ziram, wherein the compound surfactant contains at least one of a nonionic surfactant, an anionic surfactant or a macromolecular surfactant. According to the method, the efficient and green synthesis of the ziram is realized through the synergistic effect of a compound surfactant system, a sealed pressurized reaction and a progressive charging sequence.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis technology, and more specifically, to a method for synthesizing zinc thiram. Background Technology

[0002] Ziram, chemically known as zinc dimethyl dithiocarbamate, is widely used as an agricultural protective fungicide and an industrial production accelerator for natural rubber, synthetic rubber, and latex due to its excellent bactericidal activity and rubber vulcanization promoting properties. The synthesis method of ziram has evolved from a two-step process to a one-step process. Early industrial synthesis used a two-step method: first, sodium hydroxide, carbon disulfide, and dimethylamine reacted to produce sodium ziram, which then underwent a metathesis reaction with zinc chloride or zinc sulfate to produce zinc ziram. While this process produced a product with a low melting point and wide applicability, it had significant drawbacks: low product yield, dark appearance, and the generation of large amounts of saline wastewater containing sodium sulfate or sodium chloride, which is difficult to treat biochemically. This wastewater did not meet the requirements of green and clean production and has been largely phased out. To overcome the environmental defects of the two-step method, a one-step synthesis process was developed. This method directly reacts dimethylamine, carbon disulfide, and zinc oxide to produce zinc thiram, eliminating the need for sodium hydroxide and avoiding sodium salt formation, thus significantly reducing wastewater discharge and production costs. However, the process still suffers from zinc oxide residue, with approximately 5% unreacted zinc oxide and zinc hydroxide impurities in the product, limiting its application in high-end fields. Furthermore, while wastewater treatment has been simplified, it remains a challenge. To address these issues, researchers have continuously improved the one-step method, using ethanol as a solvent and introducing nonionic surfactants as dispersants. While this process achieves zero wastewater discharge, the ethanol solvent may undergo side reactions such as esterification and etherification with reaction intermediates or products, affecting product purity. Additionally, the ethanol requires distillation for recovery, resulting in high equipment costs and limiting industrial-scale adoption.

[0003] In summary, although the existing one-step synthesis process of zinc thiram represents a significant improvement over the two-step process, it still faces the following technical bottlenecks: First, zinc oxide exhibits poor dispersibility in aqueous systems and readily aggregates with carbon disulfide, resulting in low raw material utilization and low product purity. Second, the reaction process easily generates high-COD wastewater or requires costly solvent recovery, making it difficult to balance environmental protection and economic efficiency. Third, existing surfactant systems have limited dispersibility for zinc oxide, and single surfactants are insufficient to meet the process requirements of zinc oxide with different particle sizes and pH conditions. Summary of the Invention

[0004] The purpose of this invention is to provide a method for synthesizing zinc thiram, which aims to achieve a simple process, high product purity, and environmentally friendly preparation effect.

[0005] To achieve the above objectives, the present invention provides a method for synthesizing zinc thiram, the method comprising: S1: Mix the compound surfactant and zinc oxide by stirring to obtain a zinc oxide dispersion; S2: Seal the zinc oxide dispersion system, pressurize it, add dimethylamine and stir to react, to obtain a reaction mixture containing dimethylamine salt; S3: Add carbon disulfide dropwise to the reaction mixture containing dimethylamine salt, control the reaction temperature, carry out the condensation reaction, and remove impurities to obtain the zinc thiram product; The compound surfactant comprises at least a nonionic surfactant, and further comprises at least one of anionic surfactant and polymeric surfactant.

[0006] The method for synthesizing zinc oxide provided by this invention solves the technical problems existing in the current one-step synthesis process, such as poor zinc oxide dispersibility, low raw material utilization, low reaction efficiency, and difficulty in wastewater treatment, and achieves significant beneficial effects: First, this invention solves the technical problem of poor dispersibility and easy agglomeration of zinc oxide in aqueous systems. By employing a compound system containing at least a nonionic surfactant and a blend of anionic surfactants and / or polymeric surfactants, the surfactants are brought into full contact with zinc oxide in step S1, forming a stable zinc oxide dispersion. The compound surfactants significantly improve the wettability and dispersion of zinc oxide particles in the aqueous phase through multiple synergistic effects of electrostatic repulsion, steric hindrance, and wetting penetration, effectively preventing particle agglomeration and laying the foundation for homogeneous reactions in subsequent reactions. Experiments show that this compound system is applicable to zinc oxide raw materials with a wide particle size range of 0.5 μm to 50 μm, broadening the source of raw materials and reducing the requirements for raw material pretreatment.

[0007] Secondly, this invention solves the technical problems of severe volatile raw material leakage, limited reaction temperature, and low reaction rate. In step S2, the reaction system is sealed and pressurized, which raises the boiling point of low-boiling-point volatile raw materials such as dimethylamine and carbon disulfide, significantly inhibiting their vaporization and leakage, thereby improving raw material utilization and reducing raw material loss and environmental pollution. At the same time, under pressurized conditions, the reaction system can operate stably within the optimal temperature range of 30~45℃, breaking through the limitation of atmospheric pressure operation on reaction temperature, significantly accelerating the reaction rate, shortening the reaction time to about 1 hour, and improving production efficiency.

[0008] Third, this invention solves the technical problems of easy agglomeration and numerous side reactions during the reaction process. By using a progressive feeding sequence, the surfactant preferentially contacts zinc oxide to form a stable coating layer, and then reacts sequentially with dimethylamine and carbon disulfide. This avoids the problem of excessively rapid local reactions and material agglomeration caused by direct contact between carbon disulfide and undispersed zinc oxide, allowing the condensation reaction to proceed fully in a homogeneous system, reducing the formation of by-products, and improving the yield and purity of zinc thiram.

[0009] Fourth, this invention solves the technical problems of high difficulty in wastewater treatment and high environmental pressure. Using water as the reaction medium avoids the use of organic solvents, eliminating the cost of solvent recovery and the risk of side reactions at the source. Simultaneously, by improving raw material utilization and reaction selectivity, it reduces the amount of unreacted raw materials and byproducts entering the wastewater, lowering the COD content and creating conditions for subsequent mother liquor recycling.

[0010] In summary, this invention achieves efficient and green synthesis of zinc thiram through the synergistic effect of a compound surfactant system, a sealed pressurized reaction, and a progressive feeding sequence. Experimental results demonstrate the effectiveness of this invention's technical solution.

[0011] According to an embodiment of the present invention, in step S1, the order of adding the compound surfactant and zinc oxide is as follows: first disperse the compound surfactant, and then add zinc oxide and stir to mix.

[0012] Under the above conditions, a progressive feeding sequence of water, compound surfactant, zinc oxide, dimethylamine, and carbon disulfide was established. First, the compound surfactant was added to water and fully dissolved to ensure uniform distribution of surfactant molecules in the aqueous phase. Then, zinc oxide was added and stirred. At this point, the hydrophilic groups of the surfactant were directionally adsorbed onto the surface of the zinc oxide particles, while the hydrophobic groups extended into the aqueous phase, forming a stable adsorption coating layer on the zinc oxide surface. This significantly improved the wettability and dispersibility of the zinc oxide, effectively preventing particle agglomeration and forming a highly stable zinc oxide dispersion. Next, dimethylamine was added to react with the fully dispersed zinc oxide to generate a dimethylamine salt intermediate. Finally, carbon disulfide was slowly added dropwise to the reaction system, allowing it to undergo a condensation reaction with the dimethylamine salt in a homogeneous system. By optimizing the feeding sequence described above, this invention solves the following technical problems: First, the pre-contact between the surfactant and zinc oxide solves the problem of poor dispersibility and easy agglomeration of zinc oxide in the aqueous phase, thus improving the utilization rate of zinc oxide. Second, the delayed addition of carbon disulfide avoids the problem of excessively rapid local reactions and material agglomeration caused by direct contact between carbon disulfide and undispersed zinc oxide, allowing the reaction to proceed fully under controllable conditions. Third, the progressive feeding ensures the orderly progress of the three-step reaction, reducing the formation of by-products and improving the yield and purity of zinc thiram. Experimental results show that after adopting this optimized feeding sequence, the synthesis yield of zinc thiram can reach over 98%, and the product purity can reach over 99.5%, which is significantly better than the existing process.

[0013] According to an embodiment of the present invention, in step S1, the dispersion step includes: adding water to the reaction vessel, starting stirring, and adding a surfactant.

[0014] According to an embodiment of the present invention, in step S1, the time for adding zinc oxide and stirring is 30-40 minutes.

[0015] According to embodiments of the present invention, the nonionic surfactant includes at least one of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, polyether, sorbitan fatty acid ester, and polyoxyethylene ether derivatives. The anionic surfactant includes at least one of alkylbenzene sulfonate, alkyl sulfonate, fatty alcohol polyoxyethylene ether sulfate and phosphate ester; The polymeric surfactant includes at least one of polyacrylate, polymethacrylate, maleic anhydride-olefin copolymer, and modified polycarboxylate.

[0016] According to an embodiment of the present invention, when the compound surfactant is a nonionic surfactant and anionic surfactant, the mass ratio of the nonionic surfactant to the anionic surfactant is 1.5 to 4:1.

[0017] According to an embodiment of the present invention, when the compound surfactant is a nonionic surfactant and a polymeric surfactant, the mass ratio of the nonionic surfactant to the polymeric surfactant is 2.3 to 9:1.

[0018] According to an embodiment of the present invention, when the compound surfactant is a nonionic surfactant, anionic surfactant and a polymeric surfactant, the mass ratio of the nonionic surfactant, anionic surfactant and polymeric surfactant is 5~8:1~4:1~2, preferably 6:3:1.

[0019] This invention addresses the technical problems of limited dispersion, poor adaptability to zinc oxide particle size, high foaming volume, and high cost caused by the use of a single surfactant in the existing one-step synthesis process of zinc thiram. It optimizes the surfactant system through compound formulation. Specifically, this invention uses a compound of nonionic surfactants with anionic surfactants and / or polymeric surfactants, forming three compound systems: nonionic + anionic, nonionic + polymeric, or nonionic + anionic + polymeric. The optimal compounding ratio for each system has been determined: nonionic surfactants exhibit good electrolyte resistance and low foaming characteristics, enabling them to adapt to reaction systems under different pH conditions; anionic surfactants enhance the adsorption capacity of zinc ions through electrostatic repulsion, resulting in significant dispersion but also producing more foam; polymeric surfactants, through their long-chain structure, form a strong steric hindrance stabilizing layer on the zinc oxide surface, exhibiting high dispersion efficiency and good stability. Combining different types of surfactants can produce synergistic effects: when nonionic and anionic surfactants are combined, the strong dispersing ability of the anionic surfactant is retained, while the amount of foam in the system is reduced by the nonionic surfactant, thus reducing the use of defoamers in subsequent processes; when nonionic and polymeric surfactants are combined, the long-chain steric hindrance of the polymeric surfactant and the wetting and penetrating effect of the nonionic surfactant are combined, which significantly improves the dispersion stability of zinc oxide with a wide particle size range; when all three are combined, the triple effects of electrostatic repulsion, steric hindrance and wetting and penetrating work together to achieve the best dispersion effect. Through the above-mentioned compound optimization, this invention solves the following technical problems: First, it solves the problem of narrow adaptability of single surfactants to zinc oxide particle size, enabling the compound system to effectively disperse zinc oxide particles with a wide particle size range of 0.5μm~50μm, thus broadening the source of raw materials; Second, it solves the problem of unstable dispersion effect of single surfactants under different pH conditions, making the compound system more adaptable to pH; Third, it solves the problem of large foaming volume of anionic surfactants requiring the addition of additional defoamers, effectively controlling foam generation through the low-foaming characteristics of nonionic surfactants, thus simplifying the process flow; Fourth, it reduces the cost of surfactant use, as the compound system can achieve a better dispersion effect than high-addition single surfactants at lower addition levels through synergistic effects.

[0020] According to an embodiment of the present invention, in step S2, the pressure applied is 0.2~0.4 MPa.

[0021] This invention addresses the technical problems in the existing one-step synthesis of zinc thiram, such as severe volatile raw material leakage, limited reaction temperature, and low reaction rate caused by open reaction systems or atmospheric pressure operation. It optimizes the reaction system through sealing and pressurization. Specifically, in step S2, after sealing the reactor containing zinc oxide dispersion, nitrogen is used to replace the air inside the reactor and pressurize it to 0.2~0.4 MPa. Under this pressurized condition, dimethylamine is added and the subsequent reaction proceeds. On the one hand, this raises the boiling points of low-boiling-point volatile raw materials such as dimethylamine and carbon disulfide, significantly inhibiting their vaporization and leakage during the reaction process, thereby improving raw material utilization and reducing raw material loss and environmental pollution. On the other hand, under pressurized conditions, the reaction system can operate stably at higher temperatures, overcoming the temperature limitations imposed by atmospheric pressure operation. This allows the condensation reaction to proceed within an optimal temperature range of 30~45℃, significantly accelerating the reaction rate and shortening the reaction time. Through the above-mentioned sealed pressurization optimization, firstly, the problem of low raw material utilization and high production cost caused by the easy volatilization of dimethylamine and carbon disulfide in atmospheric pressure reaction is solved, increasing the raw material utilization rate to over 98%; secondly, the problem of slow reaction rate and difficulty in increasing reaction temperature due to limited volatilization is solved, shortening the reaction time and improving production efficiency.

[0022] According to an embodiment of the present invention, in step S2, the stirring reaction time is 30-40 min.

[0023] According to an embodiment of the present invention, in step S3, the temperature of the condensation reaction is 30~45°C, and the condensation reaction time is 0.5~2h.

[0024] According to an embodiment of the present invention, in step S3, the condensation reaction includes: adding carbon disulfide dropwise to the reaction mixture containing dimethylamine salt, controlling the temperature at 30~45°C, and after the addition is complete, maintaining the temperature at 40~45°C for 1 hour to carry out the condensation reaction. After the reaction is completed, the temperature is lowered to 30~35°C, the pressure is released, the mixture is filtered, washed with water, and the filter residue is dried to obtain the zinc thiram product. The filtrate is used as the mother liquor for the next synthesis.

[0025] According to an embodiment of the present invention, the molar ratio of the dimethylamine, the carbon disulfide and the zinc oxide is (1~1.05):(1~1.08):0.5.

[0026] According to an embodiment of the present invention, in step S1, when synthesizing zinc thiram for the first time, the amount of the compound surfactant added is 1wt% to 2wt% of the mass of dimethylamine.

[0027] According to an embodiment of the present invention, in step S1, when synthesizing zinc thiram for the first time, the amount of the compound surfactant added is 1.3wt% to 1.6wt% of the mass of dimethylamine.

[0028] According to an embodiment of the present invention, when the mother liquor is recycled, the amount of compound surfactant added in step S1 is 0.3wt% to 0.8wt% of the mass of dimethylamine.

[0029] According to an embodiment of the present invention, when the mother liquor is recycled, the amount of compound surfactant added in step S1 is 0.4wt% to 0.6wt% of the mass of dimethylamine.

[0030] In step S3, the impurity removal step includes: cooling to 30~35℃, depressurizing, obtaining filter residue through solid-liquid separation, and obtaining the zinc fumarate product after washing and drying the filter residue.

[0031] According to an embodiment of the present invention, the method further includes step S4: the filtrate obtained after solid-liquid separation in step S3 is used as mother liquor and returned to step S1 for recycling and use in the synthesis of zinc thiram.

[0032] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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 the structures shown in these drawings without creative effort.

[0034] Figure 1 This is a process flow diagram of an embodiment of the present invention; Figure 2 This is the particle size distribution of the zinc fumarate product in Example 3 of the present invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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.

[0036] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0037] Example 1 This embodiment provides a method for synthesizing zinc thiram, specifically as follows: S1: Add 2 kg of water to a clean reaction vessel, start stirring, add 2.7 g of AEO-9 and AES compound surfactant in a mass ratio of 7:3, add 163 g of zinc oxide with a particle size of 0.5 μm to 10 μm to the above solution, stir for 30 to 40 min to obtain a reaction mixture containing dimethylamine salt; S2: The reaction vessel was sealed, purged with nitrogen three times, and pressurized to 0.3 MPa. 183 g of dimethylamine was introduced into the reaction vessel and stirred for 5 min to obtain a reaction mixture containing dimethylamine salt. S3: Add 310g of carbon disulfide dropwise to the reaction mixture containing dimethylamine salt, controlling the addition rate and the temperature at 35~45℃. After the addition is complete, keep the reaction at 40~45℃ for 1 hour. After the reaction is complete, cool down to 30~35℃, depressurize, and filter. Wash the filter residue with a small amount of water and dry it to obtain zinc thiram. Weigh the product and measure its initial melting point. Mix the filtrate and the washing water as the mother liquor for the next synthesis.

[0038] S4: Pour the obtained mother liquor into a clean reactor, add 0.9g of AEO and AES compound surfactant in a mass ratio of 7:3, repeat the above steps 5 times, and weigh and measure the initial melting point of the zinc thiram obtained each time.

[0039] In this embodiment, the yield of the first synthesis of zinc thiram was 98.9%, the product purity was 99.6%, and the initial melting point was 242.3℃. The results of the first to fifth cycles of mother liquor synthesis of zinc thiram are shown in Table 1. The process flow diagram of this invention is shown below. Figure 1 As shown.

[0040] Table 1. Effect of mother liquor circulation number on the synthesis of zinc thiram. As shown in Table 1, it can be seen that when the mother liquor generated by pressure filtration is recycled for the synthesis of zinc thiram, the yield, product purity and initial melting point of zinc thiram synthesis remain basically unchanged when the number of cycles is 1 to 5, indicating that the filtrate can be recycled.

[0041] Example 2: The surfactant is a mixture of block polyether (F68) and modified polycarboxylate (PC-100) in a mass ratio of 8:2.

[0042] S1: Add 2 kg of water to a clean reactor, start stirring, and add 2.7 g of a compound surfactant consisting of F68 and PC-100 in a mass ratio of 8:2. Add 163 g of zinc oxide with a particle size of 0.5 μm to 10 μm to the above solution, stir for 30 to 40 min, and obtain a reaction mixture containing dimethylamine salt; S2: The reaction vessel was sealed, purged with nitrogen three times, and pressurized to 0.3 MPa. 183 g of dimethylamine was introduced into the reaction vessel and stirred for 5 min to obtain a reaction mixture containing dimethylamine salt. S3: Add 310g of carbon disulfide dropwise to the reaction mixture containing dimethylamine salt, controlling the addition rate and the temperature at 35-45℃. After the addition is complete, maintain the reaction at 40-45℃ for 1 hour. After the reaction is complete, cool to 30-35℃, depressurize, and filter. Wash the filter residue with a small amount of water and dry to obtain zinc thiram. Weigh the product and determine its initial melting point. Mix the filtrate and the washing water as the mother liquor for the next synthesis.

[0043] In this embodiment, the yield of zinc thiram synthesis was 99.3%, the purity of the product was 99.7%, and the initial melting point was 241.9℃.

[0044] Example 3: The surfactants are AEO-9, AES and modified polycarboxylate (PC-100) in a mass ratio of 6:3:1.

[0045] S1: Add 2 kg of water to a clean reaction vessel, start stirring, then add 2.7 g of a surfactant compounded with AEO-9, AES and modified polycarboxylate (PC-100) in a mass ratio of 6:3:1. Add 163 g of zinc oxide with a particle size of 0.5 μm to 10 μm to the above solution, stir for 30 to 40 min, and obtain a reaction mixture containing dimethylamine salt. S2: The reaction vessel was sealed, purged with nitrogen three times, and pressurized to 0.3 MPa. 183 g of dimethylamine was introduced into the reaction vessel and stirred for 5 min to obtain a reaction mixture containing dimethylamine salt; S3: Add 310g of carbon disulfide dropwise, controlling the addition rate and temperature at 35-45℃. After the addition is complete, maintain the reaction at 40-45℃ for 1 hour. After the reaction is complete, cool to 30-35℃, depressurize, and filter. Wash the filter residue with a small amount of water and dry to obtain zinc thiram. Weigh the product and determine its initial melting point. Mix the filtrate and the washing water as the mother liquor for the next synthesis.

[0046] In this embodiment, the yield of zinc thiram synthesis was 99.6%, the purity of the product was 99.9%, and the initial melting point was 241.1℃.

[0047] Comparative Example 1: Compared to Example 1, only AEO-9 surfactant was used, while other conditions remained unchanged.

[0048] In this comparative example, the yield of zinc thiram was 95.6%, the purity of the product was 98.3%, and the initial melting point was >280℃.

[0049] This comparison shows that single-type surfactants, compared to compound surfactants, are more effective at attracting metal ions (Zn). 2+ The directional adsorption capacity of the product is weak, resulting in a lower yield and lower product purity.

[0050] Comparative Example 2: Compared to Example 3, only one surfactant, AEO-9, was used, and the particle size of zinc oxide ranged from 0.5 μm to 50 μm, while other conditions remained unchanged.

[0051] In this comparative example, the yield of zinc thiram was 93.4%, the purity of the product was 97.4%, and the initial melting point was >280℃.

[0052] This comparison shows that, compared with compound surfactants, when the particle size of zinc oxide increases, the yield and purity of single surfactants decrease significantly, and the applicable range for zinc oxide becomes narrower.

[0053] Comparative Example 3 The difference between this comparative example and Example 1 is that the order of adding ingredients is changed to water, zinc oxide, dimethylamine, compound surfactant, and carbon disulfide.

[0054] First, zinc oxide is added to water and stirred to disperse it. Then, dimethylamine is added and stirred. Next, a compound surfactant is added, and finally, carbon disulfide is added dropwise to carry out the reaction. Other process conditions (raw material ratio, temperature, pressure, reaction time, etc.) are exactly the same as in Example 1.

[0055] Under the above conditions, zinc oxide without surfactant dispersion stage is prone to sedimentation and agglomeration. The zinc oxide agglomerated at the bottom of the reactor cannot fully contact dimethylamine and is encapsulated by the subsequently generated zinc trifloxystrobin, making it difficult to participate in the reaction. This results in a decrease in raw material utilization and product purity. In addition, the initial melting point of the product in Comparative Example 3 is significantly higher.

[0056] Table 2 Effects of different conditions on the synthesis of zinc thiram The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for synthesizing zinc thiram, characterized in that, The synthesis method includes: S1: Mix the compound surfactant and zinc oxide by stirring to obtain a zinc oxide dispersion; S2: Seal the zinc oxide dispersion system, pressurize it, add dimethylamine and stir to react, to obtain a reaction mixture containing dimethylamine salt; S3: Add carbon disulfide dropwise to the reaction mixture containing dimethylamine salt, control the reaction temperature, carry out the condensation reaction, and remove impurities to obtain the zinc thiram product; The compound surfactant comprises at least a nonionic surfactant, and further comprises at least one of anionic surfactant and polymeric surfactant.

2. The method for synthesizing zinc thiram according to claim 1, characterized in that, In step S1, the order of adding the compound surfactant and zinc oxide is as follows: first disperse the compound surfactant, then add zinc oxide and stir to mix.

3. The method for synthesizing zinc thiram according to claim 1, characterized in that, The nonionic surfactant includes at least one of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, polyether, sorbitan fatty acid ester and polyoxyethylene ether derivative; The anionic surfactant includes at least one of alkylbenzene sulfonate, alkyl sulfonate, fatty alcohol polyoxyethylene ether sulfate and phosphate ester; The polymeric surfactant includes at least one of polyacrylate, polymethacrylate, maleic anhydride-olefin copolymer, and modified polycarboxylate.

4. The method for synthesizing zinc thiram according to claim 1, characterized in that, When the compound surfactant is a combination of a nonionic surfactant and anionic surfactant, the mass ratio of the nonionic surfactant to the anionic surfactant is 1.5 to 4:

1.

5. The method for synthesizing zinc thiram according to claim 1, characterized in that, When the compound surfactant is a combination of a nonionic surfactant and a polymeric surfactant, the mass ratio of the nonionic surfactant to the polymeric surfactant is 2.3 to 9:

1.

6. The method for synthesizing zinc thiram according to claim 1, characterized in that, In step S2, the pressure applied is 0.2~0.4 MPa.

7. The method for synthesizing zinc thiram according to claim 1, characterized in that, In step S3, the temperature of the condensation reaction is 30~45℃, and the condensation reaction time is 0.5~2h.

8. The method for synthesizing zinc thiram according to claim 1, characterized in that, The molar ratio of the dimethylamine, the carbon disulfide, and the zinc oxide is (1~1.05):(1~1.08):0.

5.

9. The method for synthesizing zinc thiram according to claim 1, characterized in that, In step S3, the impurity removal step includes: cooling to 30~35℃, depressurizing, obtaining filter residue through solid-liquid separation, and obtaining the zinc fumarate product after washing and drying the filter residue.

10. The method for synthesizing zinc thiram according to claim 9, characterized in that, The method further includes step S4: the filtrate obtained after solid-liquid separation in step S3 is used as mother liquor and returned to step S1 for recycling, for the synthesis of zinc thiram.

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