阅读说明：本技术 一步合成威百亩的方法 (Method for synthesizing metham in one step ) 是由 武昭华 武子龙 杨新东 于 2020-07-30 设计创作，主要内容包括：本发明公开了一种一步合成土壤熏蒸剂威百亩的方法,将水、一甲胺水溶液,氢氧化钠水溶液搅拌混合,滴加二硫化碳,滴完继续搅拌反应完毕,直接得到外观为黄色至红褐色的威百亩成品,用于土壤熏蒸消毒处理,杀灭根结线虫、有害菌和地下害虫,清除杂草。整个合成方法具有生产效率高,产品含量高、操作安全性高、储存稳定性好和对环境友好的优点。(The invention discloses a method for synthesizing a soil fumigant metam in one step, which comprises the steps of stirring and mixing water, a monomethylamine aqueous solution and a sodium hydroxide aqueous solution, dropwise adding carbon disulfide, continuously stirring after dropwise adding, and directly obtaining a metam finished product with yellow to reddish brown appearance. The whole synthesis method has the advantages of high production efficiency, high product content, high operation safety, good storage stability and environmental friendliness.)

1. The one-step synthesis method of metam is characterized in that water, a monomethylamine aqueous solution and a sodium hydroxide aqueous solution are stirred and mixed, the temperature is reduced, carbon disulfide is dripped, the dripping temperature is controlled to be 5-45 ℃, stirring is continued after dripping, the temperature is controlled to be 5-45 ℃, and the metam product is obtained after reaction.

2. The method of claim 1, wherein monomethylamine is a 30-40% aqueous solution, sodium hydroxide is a 30-50% aqueous solution, and carbon disulfide is present in an amount of 96-98%.

3. The method of claim 2 wherein the monomethylamine is a 40% aqueous solution, the sodium hydroxide is a 32% aqueous solution, and the carbon disulfide is present at 97%.

4. The method according to claim 3, wherein the mass ratio of the water, 40% of monomethylamine, 32% of sodium hydroxide and 97% of carbon disulfide is 0.5-1.2: 1.0: 1.5-2.0: 0.8 to 1.2.

5. The method according to claim 4, wherein the mass ratio of the water, 40% of monomethylamine, 32% of sodium hydroxide and 97% of carbon disulfide is 0.6-1.1: 1.0: 1.6-1.9: 0.9 to 1.1.

6. The method according to claim 1, wherein the dropping time of the carbon disulfide is 1.5-2.5 hours; and after the carbon disulfide is added dropwise, continuing to react for 0.2-1 h.

7. The method according to claim 6, wherein the dropping time of the carbon disulfide is 1.8-2.2 hours; and after dropwise adding, continuously reacting for 0.4-0.8 h.

Technical Field

The invention belongs to the field of chemical pesticide synthesis, and particularly relates to a method for synthesizing metham by a one-step method.

Background

Metham sodium N-methyldithiocarbamate (C)₂NS₂H₄Na) is a dithio with fumigating effectThe carbamate nematicide is decomposed into methyl iso-sulfate in soil to play a fumigating role, and the common dosage form is generally a water agent with the content of sodium N-methyldithiocarbamate of 35 percent, 40 percent and 42 percent. When the metham aqueous solution is diluted, methyl isothiocyanate is chemically decomposed in wet soil to play a role in fumigation, and by inhibiting biological cell division, DNA, RNA and protein synthesis and causing biological respiration obstruction, pests such as root-knot nematodes, harmful bacteria, weeds and the like can be effectively killed, so that clean and healthy soil is obtained. Metham sodium is used as a soil fumigant commonly used at home and abroad and can be used as a substitute product of methyl bromide. The fumigating and sterilizing agent is suitable for soil fumigation of greenhouse, plastic arched shed and open-air planting, and fumigation and sterilization of crop seedbed soil, bonsai soil, edible mushroom bed soil and the like, can prevent diseases and pests caused by root-knot nematodes, harmful bacteria and underground pests and kill weeds such as marshlands, alopecurus, sedge and the like, and is widely applied to soil fumigation treatment of planting crops such as ginger, Chinese yam, cucumber, tomato, watermelon, melon, eggplant, pumpkin, hot pepper, ginseng, strawberry, mushroom, tobacco and the like.

Chinese patent CN102267931A discloses a metam production process, which is a two-step synthesis process, and specifically comprises the steps of reacting a monomethylamine solution with carbon disulfide at 10-30 ℃ for 2-3 hours to obtain N-methyldithiocarbamic acid, then dropwise adding sodium hydroxide to neutralize at 35-60 ℃ for 2 hours, wherein the pH value of the solution is 6-10, and after the reaction is finished, dehydrating under negative pressure, cooling, filtering and drying to obtain metam.

The chemical reaction formula is as follows (two steps):

however, the metham synthesis process has long production time and low production efficiency, and the intermediate (N-methyldithiocarbamate) in the first step is easily decomposed into methyl isothiocyanate and hydrogen sulfide in the production process, so that the content of the product is reduced, and the storage stability of the product is influenced by the generation of byproducts. On the other hand, with the production of the reaction N-methyldithiocarbamic acid, the pH value of the reaction environment is gradually reduced, the reaction speed of the monomethylamine and the carbon disulfide is slowed down, excessive carbon disulfide begins to exist in the reaction system, and the carbon disulfide is easy to escape, so that the yield is reduced, the environment is polluted, and explosion or fire is possibly caused.

The method integrates the problems in the prior art and aims to solve the defects of metam production process and product quality. The high-quality metham is better applied to agricultural production, and the research and development of the production process which has high production efficiency, high product content, high operation safety, good storage stability and environmental friendliness is of great significance.

Disclosure of Invention

Aiming at the problems of low metam production efficiency, low product content, low operation safety, poor product stability and easy pollution to the environment in the prior art, the invention provides a one-step synthesis process for metam.

The invention is realized by the following technical scheme:

the one-step synthesis method of metam sodium comprises the steps of stirring and mixing water, a monomethylamine aqueous solution and a sodium hydroxide aqueous solution, cooling, dropwise adding carbon disulfide, controlling the dropwise adding temperature to be 5-45 ℃, continuing stirring after dropwise adding, controlling the temperature to be 5-45 ℃, and obtaining the metam sodium product after reaction.

The chemical reaction formula is as follows:

further, the monomethylamine is 30-40% aqueous solution, the sodium hydroxide is 30-50% aqueous solution, and the content of carbon disulfide is 96-98%.

Further, the monomethylamine is 40% aqueous solution, the sodium hydroxide is 32% aqueous solution, and the content of the carbon disulfide is 97%.

Further, the mass ratio of the water, 40% of monomethylamine, 32% of sodium hydroxide and 97% of carbon disulfide is 0.5-1.2: 1.0: 1.5-2.0: 0.8 to 1.2.

Further, the mass ratio of the water, 40% of monomethylamine, 32% of sodium hydroxide and 97% of carbon disulfide is 0.6-1.1: 1.0: 1.6-1.9: 0.9 to 1.1.

Further, the dropping time of the carbon disulfide is 1.5-2.5 h; and after the carbon disulfide is added dropwise, continuing to react for 0.2-1 h.

Further, the dropping time of the carbon disulfide is 1.8-2.2 hours; and after the carbon disulfide is added dropwise, continuously reacting for 0.4-0.8 h.

The metam-sodium synthesized in one step has the performance of killing root-knot nematodes, harmful bacteria and underground pests and removing weeds, and is applied to soil fumigation treatment.

The method for synthesizing metham by one step has the following beneficial effects:

1, the synthesis efficiency is improved. The method for synthesizing metham by one step has the advantages that the steps are reduced, the two steps are changed into one step, the synthesizing time is shortened by more than 40%, the production efficiency is improved by more than 40%, the labor is saved, the energy is saved, and the consumption is reduced;

2, the synthesis yield is improved. The metam is synthesized by the one-step method, the side reaction that the intermediate N-methyldithiocarbamic acid is decomposed into methyl iso-sulfate and hydrogen sulfide due to long time in the production process of the two-step method is avoided, the content is increased by 2-4% compared with that of the traditional two-step method, and the calculation yield of the effective components is increased by 5-10% due to the fact that the intermediate is prevented from being decomposed;

and 3, the operation safety is improved. According to the invention, the sodium hydroxide aqueous solution is added before the carbon disulfide is added dropwise, so that not only can a salifying effect be achieved, but also an alkaline environment can be provided for the reaction of monomethylamine and carbon disulfide, the rapid reaction of monomethylamine and carbon disulfide in the forward and reverse reaction directions is promoted, and the synthesis is completed under the condition that a reaction system presents negative pressure, so that no dangerous gas escapes, and the operation safety is greatly improved;

4, being beneficial to protecting the environment. According to the invention, carbon disulfide is dripped into the monomethylamine alkaline solution, the carbon disulfide is excessive, the escape of unreacted carbon disulfide is avoided, the synthesis is completed under the condition that a reaction system presents negative pressure, raw materials are not easy to lose, dangerous gas is not escaped, and the yield reduction and the environmental pollution are not caused;

5, the application effect is good. The metham field synthesized by the one-step method has improved stability, has no odor on the pesticide application site, and is beneficial to protecting the personal safety. After being diluted, the water is irrigated uniformly and enters the soil, and can be decomposed rapidly, so that the water-soluble organic fertilizer has the characteristics of better weeding effect and more thorough killing of nematodes and harmful bacteria, and is beneficial to increasing the yield and income of crops.

Detailed Description

The following examples are further detailed, and the present invention is implemented on the premise of the technical solution of the present invention, and detailed embodiments and specific procedures are given, but the scope of the present invention is not limited to the following examples.