A method for preparing mancozeb

Abstract

The application discloses a preparation method of mancozeb, and belongs to the technical field of pesticides. In the application, 1 mole equivalent of mannan, 1-1.1 mole equivalent of zinc sulfate heptahydrate are added into a hot melt extruder, the screw rotation speed is 50-250 r / min, the temperature of a mixing zone is controlled to be 30-40 DEG C, the temperature of a melting zone is controlled to be 100-110 DEG C, the temperature of a homogenizing zone is controlled to be 110-120 DEG C, and mancozeb is obtained after cooling. The mixing zone, the melting zone and the homogenizing zone of the hot melt extruder can independently set the temperature, and sequentially execute the processes of mixing, melting and homogenizing, and the temperature values are set according to the process requirements. The extrudate is cooled and pressure-filtered to obtain mancozeb, and the product can be dried and stored in the dark. The preparation method is environment-friendly, simple and low in preparation cost, does not pass through physical grinding and other processes, has little change on the current mancozeb preparation process, and has no additional three-waste output.

Description

Technical Field

[0001] This invention belongs to the field of pesticide technology, specifically relating to a method for preparing mancozeb. Background Technology

[0002] In 1940, W.F. Hester of Rohm and Haas prepared dithiocarbamates by reacting ethylenediamine with carbon disulfide. The compound prepared by W.F. Hester, called disodium ethylenebis(dithiocarbamate) (dison), was the first true ethylene dithiocarbamate, but it was unstable as a solid and had to be used in liquid form. Thirteen years after the introduction of mancozeb, it was proven that mancozeb itself did not have bactericidal properties; it only had a bactericidal effect when exposed to the environment, i.e., when it was released into the air, it transformed into an active compound with fungal toxicity. The high water solubility and relative instability of mancozeb meant that its properties were somewhat altered. Huberg and Mans discovered that adding zinc sulfate to the spray can stabilized mancozeb.

[0003] Sodium mancozeb was rapidly adopted by growers and widely used for the management of many vegetable diseases, and is particularly popular among potato growers in the United States, where it quickly replaced Bordeaux mixture. The reaction product formed in a spray tank when zinc sulfate is added to sodium mancozeb is ethylenebis(zinc dithiocarbamate) (zinc mancozeb).

[0004] The development of novel ethylene dibis-dithiocarbamates continued rapidly. DuPont obtained a patent in 1950 for manganous ethylene dithiocarbamate (manganese dithiocarbamate) (Flenner, AL 1950. Manganous ethylene–bis-dithiocarbamate and fungicidal compositions containing the same. US patent 2,504,404.). In 1962, Rohm and Haas registered zinc ion complexes of manganese (manganese dithiocarbamate), which became the most important and commercially significant of all ethylene dithiocarbamates.

[0005]

[0006] Mancozeb is a "surface complex" formed by zinc ions and the surface of mancozeb particles. It is the result of a localized chemical reaction between mancozeb and zinc ions on the particle surface. Non-fully complexed mancozeb contains a large amount of uncomplexed mancozeb, so it rapidly releases excessive manganese ions during the sterilization process, thus damaging crops.

[0007] There are two traditional manganese zinc complexation processes:

[0008] 1. Zinc salt solution is added dropwise during the preparation of mancozeb to form mancozeb zinc;

[0009] 2. First, prepare manganese, then react it with zinc salt to obtain manganese zinc complex.

[0010] Patent CN101962392 A discloses a wet grinding process for preparing mancozeb complexed zinc. It employs a two-stage wet grinding technique to reduce the size of mancozeb particles sufficiently, allowing them to fully complex with zinc ions to obtain mancozeb. This patent essentially uses a colloid mill and a sand mill to grind the slurry, reducing the particle size of mancozeb to 2-5 μm through physical grinding. However, this increases energy consumption and is not environmentally friendly. Patent CN1695449A discloses a mancozeb preparation process where mancozeb, zinc salt, and reaction aids are slurried, and the resulting slurry is then ground in a grinder. During grinding, the materials undergo a complexation reaction to obtain mancozeb with an average particle size of less than 5 μm. Like CN 101962392 A, this process also reduces the product particle size through physical grinding. Patent CN 104412999A discloses a method for preparing mancozeb, which involves complexing and dehydrating mancozeb and zinc in an organic solvent to reduce product decomposition and reduce pollution from harmful impurities and dust. However, this method uses an organic solvent, while water is generally used as a solvent in the synthesis of mancozeb. Therefore, this invention actually exacerbates pollution.

[0011] Patent CN108250245 A discloses a method for preparing nano-sized mancozeb. The method involves mixing ammonium mancozeb, a dispersant, and a buffer solution, then adding a manganese salt aqueous solution dropwise at 30–50°C. After the addition is complete, the mixture is filtered. Water is added to the resulting filter cake I to form a mancozeb suspension, which is stirred until homogeneous. A zinc salt aqueous solution is then added dropwise, and the mixture is filtered again. The resulting filter cake II is dried to obtain nano-sized mancozeb. Patent CN 111333557 A discloses a continuous flow synthesis method for preparing mancozeb. Sodium mancozeb solution and manganese salt solution are simultaneously fed into a continuous flow microreactor for mixing. The reaction solution is then filtered, washed with water, and filtered again. The resulting wet filter cake is directly added to a zinc salt solution, stirred until homogeneous, filtered, and dried to obtain mancozeb.

[0012] In addition, the current production of mancozeb technical grade mainly adopts the emulsification pulping process (Sun Jingquan, Xu Yiwei, Sun Limei, Research, Development and Application of New Generation Complexed Mancozeb New Technology Products, World Pesticides, 2020, 42(1): 36-39). During the production and synthesis process, recalcitrant wastewater with high salt content and high organic matter concentration is generated. Summary of the Invention

[0013] This invention proposes a method for preparing synthetic mancozeb. The method uses a melt extrusion process to prepare mancozeb, achieving high-efficiency preparation of mancozeb without additives and overcoming the shortcomings of existing technologies.

[0014] To address the aforementioned technical problems, this invention proposes a method for preparing mancozeb. The method includes: adding mancozeb and zinc sulfate heptahydrate into a hot-melt extruder. The hot-melt extruder uses a screw for stirring and conveying the materials. The hot-melt extruder is divided into a mixing zone, a melting zone, and a homogenizing zone along the material conveying direction, and the temperature of each zone can be set independently. The molar ratio of mancozeb to zinc sulfate heptahydrate is 1:1-1.1.

[0015] Control the screw speed of the hot melt extruder to 50-300 r / min, control the temperatures of the mixing zone, melting zone, and homogenizing zone, ensuring that the homogenizing zone temperature is higher than the melting zone temperature, the melting zone temperature is higher than the mixing zone temperature, and the melting zone temperature is controlled at 100-110℃.

[0016] The extruded material from the hot melt extruder is cooled to obtain a slurry of mancozeb mixture. The liquid is removed by pressure filtration to obtain mancozeb.

[0017] According to a preferred embodiment of the present invention, the temperature of the mixing zone is controlled at 30-40°C. Preferably, the temperature of the homogenization zone is 110-120°C.

[0018] Preferably, the cooling temperature is 20-40℃. Preferably, the residence time of the material in the mixing zone is 1-10 min, the residence time in the melting zone is 2-10 min, and the residence time in the homogenization zone is 1-3 min.

[0019] Compared with the prior art, the present invention uses zinc sulfate heptahydrate as the zinc salt for preparing mancozeb. Zinc sulfate heptahydrate has a melting point of 100°C. At the melting zone temperature of the hot melt extruder set in the present invention, zinc sulfate heptahydrate can melt. Therefore, the particle size requirement of the zinc salt raw material is low. With the screw rotation, the molten zinc sulfate heptahydrate can react well with mancozeb, improving the raw material utilization rate.

[0020] This invention rationally controls the temperature and residence time of the three zones of the hot melt extruder. The materials are stirred and conveyed in the three zones at the same screw speed. The slurry output from the hot melt extruder only needs to be cooled, filtered and dried to obtain fully complexed mancozeb, which greatly improves the production efficiency of mancozeb.

[0021] The preparation process of this invention does not require the addition of other additives, the waste liquid obtained by slurry filtration does not contain organic matter, and the post-treatment is simple. Attached Figure Description

[0022] Figure 1 This is a schematic flowchart of the method of the present invention;

[0023] Figure 2 The image shows the XRD pattern of the complexed mancozeb obtained in Example 1.

[0024] Figure 3 The infrared spectrum of the complexed mancozeb obtained in Example 1 is shown. Detailed Implementation

[0025] The present invention will be further described and illustrated below with reference to specific embodiments. The technical features of each embodiment of the present invention can be combined accordingly, provided that there is no mutual conflict.

[0026] like Figure 1 As shown, the method of this invention requires the preparation of mancozeb using a hot-melt extruder. The hot-melt extruder needs to achieve material conveying, mixing, melting, reaction, and homogenization. This invention divides the hot-melt extruder into a mixing zone, a melting zone, and a homogenization zone along the material conveying direction, and the temperature of each zone can be set independently. Zinc sulfate heptahydrate has a low melting point, making it an ideal zinc salt suitable for the process of this invention. This invention controls the temperature of the melting zone at 100-110℃ to melt the zinc sulfate. Molten zinc sulfate heptahydrate reacts well with mancozeb. The homogenization zone temperature is higher than the melting zone temperature, and the melting zone temperature is higher than the mixing zone temperature, with the material temperature gradually increasing. The screw speed of the hot-melt extruder can be controlled between 50-300 r / min to ensure good mixing of the reactants.

[0027] The extruded material from the hot melt extruder is at a high temperature. It is first cooled, and the cooled slurry of mancozeb is filtered to remove the liquid, thus obtaining mancozeb.

[0028] The extruder used in the following embodiments of the present invention has at least 10 temperature-adjustable sub-zones along the material conveying direction. The mixing zone, melting zone, and homogenizing zone referred to in this invention include one or more of the aforementioned temperature-adjustable sub-zones. The lengths of the mixing zone, melting zone, and homogenizing zone can be achieved by changing the temperature of the sub-zones. The residence time of the material in the mixing zone, melting zone, and homogenizing zone is achieved by changing the length of each temperature zone and controlling the screw speed.

[0029] Example 1

[0030] use Figure 1The process is as follows: 287.5 kg of zinc sulfate heptahydrate solid and 265.0 kg of mancozeb were weighed and added to the mixing zone. The mixing zone temperature was set to 30℃, the melting zone temperature to 100℃, and the homogenization zone temperature to 110℃. The extruder was started, and the screw speed was controlled at 50 r / min. The residence time of the material in the mixing zone was 10 min, in the melting zone 10 min, and in the homogenization zone 3 min. Zinc sulfate heptahydrate and mancozeb formed a reaction liquid in the extruder. After sufficient reaction, the mixture was cooled at the extruder outlet at 20℃ to form a slurry. This slurry was then filtered through a filter press to obtain 328.1 kg of pale yellow mancozeb powder. The crystal morphology was determined by powder X-ray diffraction, and its structure was verified by infrared spectroscopy. The results are as follows. Figure 2 and 3 As shown.

[0031] Powder X-ray diffraction 2θ angles: 10.5°, 12.0°, 14.3°, 19.5°, 29.8°; IR (cm) -1 )3296, 3153, 2979, 1508, 1400, 1287, 1127, 965, 680. Using acetonitrile-phosphoric acid water as the mobile phase, an Agilent ZORBAX SB-C18 column was used for liquid chromatography analysis at a wavelength of 272 nm. The content of complexed mancozeb was 95.0%.

[0032] Example 2

[0033] use Figure 1 The process is as follows: 316.2 kg of zinc sulfate heptahydrate solid and 265.0 kg of mancozeb were weighed and added to the mixing zone. The mixing zone temperature was set to 40℃, the melting zone temperature to 105℃, and the homogenization zone temperature to 115℃. The extruder was started, and the screw speed was controlled at 290 r / min. The lengths of the mixing zone, melting zone, and homogenization zone were adjusted so that the residence time of the material in the mixing zone was 1 min, in the melting zone was 2 min, and in the homogenization zone was 1 min. Zinc sulfate heptahydrate and mancozeb formed a reaction liquid in the extruder. After sufficient reaction, the mixture was cooled at the extruder outlet at 40℃ to form a slurry. This slurry was then filtered through a filter press to obtain 330.0 kg of light yellow mancozeb powder with a purity of 93.8%.

[0034] Example 3

[0035] use Figure 1The process is as follows: 287.5 kg of zinc sulfate heptahydrate solid and 265.0 kg of mancozeb were weighed and added to the mixing zone. The mixing zone temperature was set to 35℃, the melting zone temperature to 100℃, and the homogenization zone temperature to 110℃. The extruder was started, and the screw speed was controlled at 100 r / min. The residence time of the material in the mixing zone was 5 min, the residence time in the melting zone was 5 min, and the residence time in the homogenization zone was 1.5 min. Zinc sulfate heptahydrate and mancozeb formed a reaction liquid in the extruder. After sufficient reaction, the mixture was cooled at the extruder outlet at 30℃ to form a slurry. This slurry was then filtered through a filter press to obtain 330.0 kg of light yellow mancozeb powder with a purity of 95.2%.

[0036] Comparative Example 1

[0037] use Figure 1 The process is as follows: 287.5 kg of zinc sulfate heptahydrate solid and 265.0 kg of mancozeb were weighed and added to the mixing zone. Compared with Example 1, Comparative Example 1 did not set the temperature of the mixing zone, melting zone, and homogenization zone. That is, the entire area of ​​the extruder operated at room temperature. The extruder was turned on and the screw speed was controlled at 50 r / min to obtain a physical mixture of mancozeb and zinc sulfate heptahydrate with a complexed mancozeb zinc content of 0.2%.

[0038] Comparative Example 2

[0039] use Figure 1 The process is as follows: 287.5 kg of zinc sulfate heptahydrate solid and 265.0 kg of mancozeb were weighed and added to the mixing zone; the mixing zone temperature was set to 30°C, the melting zone temperature to 25°C, and the homogenization zone temperature to 110°C. The extruder was started, and the screw speed was controlled at 50 r / min. The residence time in each temperature zone was the same as in the example, resulting in a physical mixture of mancozeb and zinc sulfate heptahydrate with a complexed mancozeb zinc content of 10.3%.

[0040] Comparative Example 3

[0041] use Figure 1 The process is as follows: 287.5 kg of zinc sulfate heptahydrate solid and 265.0 kg of mancozeb were weighed and added to the mixing zone; the mixing zone temperature was set to 40°C, the melting zone temperature to 105°C, and the homogenization zone temperature to 50°C. The extruder was started, and the screw speed was controlled at 290 r / min. The residence time in each temperature zone was the same as in Example 2, resulting in a physical mixture of mancozeb and zinc sulfate heptahydrate with a complexed mancozeb zinc content of 30.1%.

[0042] Comparative Example 4

[0043] use Figure 1The process is as follows: 287.5 kg of zinc sulfate heptahydrate and 265.0 kg of mancozeb were weighed and added to the mixing zone. The mixing zone temperature was set to 30℃, the melting zone temperature to 100℃, and the homogenization zone temperature to 110℃. The extruder was started, and the screw speed was controlled at 400 r / min. The lengths of the mixing, melting, and homogenization zones were adjusted so that the residence time of the material in the mixing zone was 1 min, the residence time in the melting zone was 1 min, and the residence time in the homogenization zone was 1 min. Zinc sulfate heptahydrate and mancozeb formed a reaction liquid in the extruder. After sufficient reaction, the mixture was cooled at the extruder outlet at 20℃ to obtain a physical mixture of mancozeb, zinc sulfate heptahydrate, and mancozeb zinc, with a complexed mancozeb zinc content of 48.0%.

[0044] Using the exact same operating conditions as in Example 1, but replacing zinc sulfate heptahydrate with zinc chloride, no complexed mancozeb is formed. As can be seen from the above examples and comparative examples, this invention fully utilizes the physical properties of zinc sulfate heptahydrate as a raw material. By setting the temperature at different locations in the hot-melt extruder, the material is thoroughly mixed in the extruder before the reaction, achieving highly efficient preparation of mancozeb. The preparation process requires no addition of zinc sulfate or additives, therefore the waste liquid contains no organic matter, significantly reducing the waste liquid volume compared to existing technologies.

[0045] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for preparing mancozeb, characterized in that, Mancozeb and zinc sulfate heptahydrate are added to a hot melt extruder, which uses a screw to agitate and convey the materials. The hot melt extruder is divided into a mixing zone, a melting zone, and a homogenization zone along the material conveying direction, and the temperature of each zone is set independently. The molar ratio of mancozeb to zinc sulfate heptahydrate is 1:1-1.

1. No other additives are added during the preparation process. The screw speed of the hot melt extruder is controlled, and the material is stirred and conveyed in all three zones at the same screw speed. The temperatures of the mixing zone, melting zone, and homogenization zone are controlled, with the homogenization zone temperature higher than the melting zone temperature, and the melting zone temperature higher than the mixing zone temperature. The melting zone temperature is controlled at 100-110℃. At the melting zone temperature, zinc sulfate heptahydrate can melt, and with the screw rotation, the molten zinc sulfate heptahydrate can react well with manganese. The mixing zone temperature is controlled at 30-40℃; the homogenization zone temperature is 110-120℃; the residence time of the material in the mixing zone is 1-10 min, in the melting zone it is 2-10 min, and in the homogenization zone it is 1-3 min. The extruded material from the hot melt extruder is cooled to a temperature of 20-40℃ to obtain a slurry-like mancozeb mixture. The liquid is removed by pressure filtration to obtain mancozeb.

2. The method for preparing mancozeb according to claim 1, characterized in that, The screw speed of the hot melt extruder is controlled at 50-300 r / min.

Images