阅读说明：本技术 2-甲基-4-异噻唑啉-3-酮的连续化生产方法 (Continuous production method of 2-methyl-4-isothiazoline-3-ketone ) 是由 刘�英 王慧 朱杰 李瑞涛 陈朋天 于 2021-08-31 设计创作，主要内容包括：本发明涉及一种2-甲基-4-异噻唑啉-3-酮的连续化生产方法。该方法采用连续化生产,可获得高纯度的2-甲基-4-异噻唑啉-3-酮,而且生产收率高,生产过程容易操控、既降低了能耗、又提高了生产效率,同时还实现了生产过程的安全可控。本发明采用的方法步骤为：1)N,N'-二甲基-3,3'-二硫代二丙酰胺与氯仿、N,N-二甲基甲酰胺配制,形成混合液；2)将混合液泵与氯气在第一段管式反应器反应；3)反应物料进入第二段带有夹套的管式反应器反应；4)反应物料进入第三段带有夹套的管式反应器反应；5)管道连续反应完成后,反应液直接进入气液分离器分离出氯化氢,经离心工序,固液分离,再经中和、分层、蒸馏、复配处理工序最终得到2-甲基-4-异噻唑啉-3-酮。(The invention relates to a continuous production method of 2-methyl-4-isothiazoline-3-ketone. The method adopts continuous production, can obtain high-purity 2-methyl-4-isothiazoline-3-ketone, has high production yield, is easy to control the production process, reduces energy consumption, improves production efficiency, and realizes safety and controllability of the production process. The method adopted by the invention comprises the following steps: 1) preparing N, N '-dimethyl-3, 3' -dithiodipropionamide, chloroform and N, N-dimethylformamide to form a mixed solution; 2) reacting a mixed liquid pump with chlorine in a first-stage tubular reactor; 3) the reaction materials enter a second section of tubular reactor with a jacket for reaction; 4) the reaction materials enter a third section of tubular reactor with a jacket for reaction; 5) after the pipeline continuous reaction is finished, the reaction liquid directly enters a gas-liquid separator to separate out hydrogen chloride, and the 2-methyl-4-isothiazoline-3-ketone is finally obtained through the processes of centrifugation, solid-liquid separation, neutralization, layering, distillation and compound treatment.)

The continuous production method of the 2-methyl-4-isothiazoline-3-ketone is characterized by comprising the following steps: the method comprises the following steps:

1) n, N '-dimethyl-3, 3' -dithiodipropionamide, chloroform and N, N-dimethylformamide are mixed according to the weight ratio of 1: 3.0-5.0: 0.2-0.3 to form a mixed solution;

2) pumping the mixed solution into a first section of tubular reactor with a jacket, wherein the mixed solution is contacted with chlorine gas at the inlet of the tubular reactor, the jacket of the first section of tubular reactor is filled with glycol chilled water, the reaction temperature is 10-15 ℃, and the materials are mixed and stay in the tube for 3-5 minutes;

3) the reaction material enters a second section of tubular reactor with a jacket, the reaction liquid is contacted with chlorine gas at the inlet of the tubular reactor, hot water is introduced into the jacket of the second section of tubular reactor, the reaction temperature is 35-45 ℃, and the material is mixed and stays in the tube for 10-20 minutes;

4) the reaction materials enter a third section of tubular reactor with a jacket, the jacket of the third section of tubular reactor is filled with hot water, the reaction temperature is 60-65 ℃, and the materials are mixed and stay in the tube for 3-5 minutes;

5) after the pipeline continuous reaction is finished, the reaction liquid directly enters a gas-liquid separator to separate hydrogen chloride, a solid-liquid mixture is subjected to a centrifugation process after being cooled, solid-liquid separation is carried out, the solid is subjected to chloroform washing to obtain 2-methyl-4-isothiazoline-3-ketone hydrochloride with the purity of more than 99.9%, and the 2-methyl-4-isothiazoline-3-ketone is finally obtained through neutralization, layering, distillation and compounding.

2. The continuous production method of 2-methyl-4-isothiazolin-3-one according to claim 1, characterized in that: the weight ratio of the chlorine used in the step 2) to the N, N '-dimethyl-3, 3' -dithiodipropionamide in the step 1) is 0.1-0.15: 1.

3. the continuous production method of 2-methyl-4-isothiazolin-3-one according to claim 1, characterized in that: the weight ratio of the chlorine used in the step 3) to the N, N '-dimethyl-3, 3' -dithiodipropionamide in the step 1) is 0.72-0.76: 1.

Technical Field

The invention relates to the technical field of continuous production of bactericides, in particular to a continuous production method of 2-methyl-4-isothiazoline-3-ketone.

Background

The 2-methyl-4-isothiazoline-3-ketone (MIT for short, the same below) is a novel isothiazolinone bactericide, has the advantages of high efficiency, broad spectrum, low toxicity, natural degradation in the environment and the like, and has a very wide application range.

In recent years, MIT has been increasingly used in daily chemicals and cosmetics, but its use has been limited to a certain extent because 5-chloro-2-methyl-4-isothiazolin-3-one (CIT, the same shall apply hereinafter) contained in commercial MIT products has strong irritation and mutagenicity. The demand for MIT single components is increasing at present and it is required that the content of impurities CIT is as low as possible.

U.S. Pat. No. 5,54, 818 discloses a method for synthesizing 3-isothiazolinone germicide, which comprises synthesizing CIT/MIT mixture with N-methyl-3-mercaptopropionamide, chlorine and ethyl acetate to obtain CIT/MIT hydrochloride mixture after reaction; because the thermal stability of the CIT hydrochloride and the MIT hydrochloride are different, the CIT hydrochloride is dissociated and dissolved in a solvent by heating to 78-80 ℃ and selectively dissociating the hydrochloride in the process, and the MIT is separately separated as the hydrochloride, so that the separation of the CIT and the MIT is realized. By using the method, the MIT hydrochloride with the purity of 99.6 percent and the CIT content of 0.4 percent can be obtained. The disadvantages of this separation method are: the CIT content in the mixture is still higher; the loss of the main product MIT in the heating dissociation process is large, and the synthesis method is carried out intermittently, so that the operation is complex and the production period is long.

Chinese patent CN110483438A discloses a pipeline type continuous production method of 3-isothiazolinone compounds, N '-dimethyl-3, 3' -dithiodipropionamide, potassium iodide, ethyl acetate and chlorine are subjected to mixed reaction through a pipeline reactor system, and after the reaction is finished, an MIT product is obtained through post-treatment; firstly, mixing and preheating reaction raw materials in proportion, uniformly mixing a solid-liquid mixture by using a static mixer to form slurry, and then sending the slurry into a pipeline reactor for reaction, introducing chlorine gas into the pipeline reactor at multiple points, and controlling the temperature by using a temperature control system, wherein the reaction temperature is 45-50 ℃, and the retention time is 5 minutes; MIT synthesis yield of 90% was described, with CIT content <50 ppm; the continuous production method has the following defects: materials need to enter the tubular reactor through a preheating system and a mixing system, and the operation is still complex; potassium iodide does not play any catalytic role in ethyl acetate; by using ethyl acetate as a solvent, a large amount of CIT hydrochloride byproducts are generated in the reaction process, under the temperature condition mentioned in the patent, CIT hydrochloride cannot be completely dissociated at all, and the CIT content of less than 50ppm cannot be realized.

Chinese patent CN112110870A provides a method for preparing MIT aqueous solution, which comprises mixing N, N '-dimethyl-3, 3' -dithiodipropionamide with solvent uniformly, adding halogenating agent into the mixed solution to perform halogenation ring-closing reaction, filtering, washing with ethyl acetate, and neutralizing to obtain 50% MIT aqueous solution. The patent mentions that the solvent for the reaction consists of a chlorinated solvent and a dipolar aprotic solvent, and the dipolar aprotic solvent is added into the reaction system, so that the high impurity content caused by overhigh local concentration of a chlorinating agent or hydrogen chloride in the system can be avoided; by the method, the preparation yield of MIT is 74-85%, and the content of CIT in 50% MIT aqueous solution is less than 100 ppm; the method is an intermittent preparation method, the operation is complex, the reaction yield is not ideal, a large amount of mixed solvent is generated in the preparation process, and the recycling is difficult.

Disclosure of Invention

In view of the above, the invention provides a continuous production method of 2-methyl-4-isothiazoline-3-ketone, which adopts continuous production to obtain high-purity 2-methyl-4-isothiazoline-3-ketone, has high production yield, is easy to control the production process, reduces energy consumption, improves production efficiency, and realizes safety and controllability of the production process.

In order to achieve the purpose, the invention adopts the technical scheme that: the continuous production method of the 2-methyl-4-isothiazoline-3-ketone is characterized by comprising the following steps: the method comprises the following steps:

1) n, N '-dimethyl-3, 3' -dithiodipropionamide, chloroform and N, N-dimethylformamide are mixed according to the weight ratio of 1: 3.0-5.0: 0.2-0.3 to form a mixed solution;

2) pumping the mixed solution into a first section of tubular reactor with a jacket, wherein the mixed solution is contacted with chlorine gas at the inlet of the tubular reactor, the jacket of the first section of tubular reactor is filled with glycol chilled water, the reaction temperature is 10-15 ℃, and the materials are mixed and stay in the tube for 3-5 minutes;

3) the reaction material enters a second section of tubular reactor with a jacket, the reaction liquid is contacted with chlorine gas at the inlet of the tubular reactor, hot water is introduced into the jacket of the second section of tubular reactor, the reaction temperature is 35-45 ℃, and the material is mixed and stays in the tube for 10-20 minutes;

4) the reaction materials enter a third section of tubular reactor with a jacket, the jacket of the third section of tubular reactor is filled with hot water, the reaction temperature is 60-65 ℃, and the materials are mixed and stay in the tube for 3-5 minutes;

5) after the pipeline continuous reaction is finished, the reaction liquid directly enters a gas-liquid separator to separate hydrogen chloride, a solid-liquid mixture is subjected to a centrifugation process after being cooled, solid-liquid separation is carried out, the solid is subjected to chloroform washing to obtain 2-methyl-4-isothiazoline-3-ketone hydrochloride with the purity of more than 99.9%, and the 2-methyl-4-isothiazoline-3-ketone is finally obtained through neutralization, layering, distillation and compounding.

Further, the weight ratio of the chlorine used in the step 2) to the N, N '-dimethyl-3, 3' -dithiodipropionamide in the step 1) is 0.1-0.15: 1.

further, the weight ratio of the chlorine used in the step 3) to the N, N '-dimethyl-3, 3' -dithiodipropionamide in the step 1) is 0.72-0.76: 1.

compared with the prior art, the invention has the following advantages and effects:

1) according to the method, the proportion of reactants is controlled in a segmented manner, the reaction temperature is controlled in a segmented manner, and a solvent with proper polarity is selected, so that the formation of CIT can be effectively inhibited, and an MIT product with the purity of more than 99.99 percent can be obtained;

2) the invention effectively realizes the continuous production of MIT, the production process is easy to control, the energy consumption is reduced, the production efficiency is improved, and the safety and the controllability of the production process are realized.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The invention relates to a continuous production method of 2-methyl-4-isothiazoline-3-ketone, which comprises the following steps:

1. n, N '-dimethyl-3, 3' -dithiodipropionamide, chloroform and N, N-dimethylformamide (DMF for short) according to the weight ratio of 1: 3.0-5.0: 0.2-0.3 to form a mixed solution of the three components;

2. pumping the mixed solution into a first-stage jacketed pipe type tubular reactor by using a pump, wherein the weight ratio of the mixed solution to chlorine gas in the step 1) is 0.1-0.15: 1 is contacted at the inlet of the tubular reactor, glycol chilled water is introduced into the jacket of the first section of the tubular reactor, the reaction temperature is 10-15 ℃, and the materials are mixed and stay in the tube for 3-5 minutes.

3. The reaction material enters a second section of jacketed tubular reactor, and the weight ratio of the reaction material to chlorine in the step 1) is 0.72-0.76: 1 is contacted at the inlet of the tubular reactor, hot water is introduced into the jacket of the second section of the tubular reactor, the reaction temperature is 35-45 ℃, and the materials are mixed and stay in the tube for 10-20 minutes.

4. The reaction material enters a third section of sleeve type tubular reactor with a jacket, the jacket of the third section of tubular reactor is filled with hot water, the reaction temperature is 60-65 ℃, the material is mixed and stays in the tube for 3-5 minutes, at the moment, CIT hydrochloride is heated and dissociated, and the CIT is dissolved in chloroform mother liquor.

5. After the continuous pipeline reaction is finished, the reaction liquid directly enters a gas-liquid separator to separate hydrogen chloride, a solid-liquid mixture is subjected to a centrifugation process after being cooled, solid-liquid separation is carried out, the solid is subjected to chloroform washing to obtain very pure MIT hydrochloride, and then the treatment processes of neutralization, layering, distillation, compounding and the like are carried out to obtain the MIT final product.

And directly recycling the centrifugal leacheate to the next batch of continuous production, and simply distilling the chloroform mother liquor obtained by centrifugation to recycle chloroform and DMF for recycling to the next batch of continuous production.

The hydrogen chloride separated in the process is removed to the hydrogen chloride absorption system.

The experiment shows that:

the reaction of N, N '-dimethyl-3, 3' -dithiodipropionamide with chlorine to produce MIT proceeds through the following reaction sequence:

if the reaction solvent is not properly selected in the above process, the conditions such as reaction temperature, chlorine gas ratio and the like cannot be well controlled, and the following side reaction processes occur:

in the reaction process, the key intermediate is over-chlorinated to generate an alpha, alpha-dichloro intermediate, and finally dehydrochlorination cyclization is carried out to generate a CIT byproduct.

According to the above reaction mechanism, in order to control the amount of CIT produced in the reaction stage, the amount of the α, α -dichloro intermediate produced must be controlled, and the selection of the reaction solvent, the ratio of the reaction materials, and the reaction temperature can be considered.

When the method is used for synthesizing MIT by taking N, N '-dimethyl-3, 3' -dithiodipropionamide as a raw material, chloroform is used as a solvent, the boiling point of the chloroform is 61.2 ℃, and the chloroform is very easy to recover; CIT hydrochloride can be completely dissociated into free CIT by heating and refluxing in chloroform.

According to the invention, a small amount of polar aprotic solvent DMF is added into chloroform to change the polarity of a reaction system, so that the generation of an alpha, alpha-dichloro intermediate is inhibited, and the generation amount of CIT in the reaction process is greatly reduced, and the addition amount of DMF is determined by experiments, wherein N, N '-dimethyl-3, 3' -dithiodipropionamide, chloroform and Dimethylformamide (DMF) are added into the reaction system according to the weight ratio of 1: 3.8-4.2: preferably in the range of 0.2 to 0.3.

After suspending the N, N '-dimethyl-3, 3' -dithiodipropionamide of the present invention in chloroform (containing DMF) and introducing chlorine gas to a certain amount, at this time, the N, N '-dimethyl-3, 3' -dithiodipropionamide: 100 parts of chlorine gas: 10-15, a clear and transparent complete-dissolution state appears in the reaction system, the chlorination reaction system mainly takes a reaction intermediate generation stage, and the complete-dissolution state disappears along with continuous chlorine introduction reaction to separate out MIT hydrochloride; the early stage of chlorination from suspension to complete dissolution is researched, and comparison and verification are carried out on the two aspects of the chlorine gas aeration speed and the reaction temperature, so that the reaction intermediate is generated in the early stage of chlorination, the proportion of the chlorine gas and the N, N '-dimethyl-3, 3' -dithiodipropionamide is strictly controlled within a certain range, the local concentration is too high during chlorine introduction, and the generation amount of CIT is high; the reaction temperature in this stage is strictly controlled below 20 ℃, the temperature in this stage is high, and the reaction selectivity is poor.

Compared with the comparison of the chlorine introducing temperature after the reaction system is completely dissolved with the CIT generation amount, the invention finds that the chlorine introducing temperature is relatively high, the CIT generation amount is lower, and the high temperature is not beneficial to the generation of the CIT; under the high-temperature condition, the dehydrochlorination and cyclization speed of the generated intermediate is higher than that of the alpha, alpha-dichloro intermediate, so that the generation of the alpha, alpha-dichloro intermediate is inhibited, and the generation amount of CIT is correspondingly reduced.

The research on the chlorination process indicates that the reaction temperature is controlled in a segmented mode in the chlorination synthesis of MIT, the chlorination temperature is lower in the reaction intermediate generation stage in the early chlorination stage, and the chlorination temperature is higher in the product cyclization production stage in the later chlorination stage, which is the key for controlling the generation amount of CIT in the reaction stage.

Experiments show that during the reaction of N, N '-dimethyl-3, 3' -dithiodipropionamide and chlorine to generate MIT, the following consecutive side reactions also occur in the main product MIT:

MIT continues to generate chlorination reaction to generate 4-chloro-2-methyl-3-isothiazolinone and 4, 5-dichloro-2-methyl-3-isothiazolinone (DCMIT); in order to inhibit the above-mentioned consecutive side reactions, the reaction temperature cannot be too high, the chlorine gas ratio cannot be excessive, and the reaction should be quenched in time to remove the MIT product from the reaction system in time.

The continuous synthesis can well solve the problems, and the method uses a tubular reactor, continuously feeds raw materials and continuously discharges products, so that the occurrence of continuous side reactions taking MIT as the raw material can be effectively avoided.

Example (b):

the MIT continuous production uses a special tubular reactor, the tubular reactor is divided into three sections, each section is provided with a jacket with different media, the first section is a low-temperature chlorination section, ethylene glycol chilled water with the temperature controlled at about-10 ℃ is introduced into the reactor jacket, hot water with the temperature of 40 ℃ is introduced into the reactor jacket of the second section, and hot water with the temperature of 90 ℃ is introduced into the reactor jacket of the third section; the porous baffle is arranged in the tubular reactor, so that the mass transfer and heat transfer processes can be effectively enhanced.

Chlorine gas is introduced in two parts, wherein the first part is introduced at multiple points at the inlet of the first section of tubular reactor, and the second part is introduced at multiple points at the inlet of the second section of tubular reactor.

N, N '-dimethyl-3, 3' -dithiodipropionamide, chloroform and DMF were measured in a mass ratio of 1: 4: 0.2 weight ratio drops into in the pulping jar in advance, evenly mixes back and carries into first section tubular reactor with certain velocity of flow of pump control, lets in chlorine at tubular reactor entrance, controls the speed of letting in of chlorine, chlorine: n, N '-dimethyl-3, 3' -dithiodipropionamide 0.12: 1, controlling the temperature of chlorination at 10-15 ℃ in the first stage, and mixing and staying the materials in the tube for 3-5 minutes.

The first-stage chlorination reaction liquid enters a second-stage tubular reactor, chlorine is introduced at the inlet of the tubular reactor, the introduction speed of the chlorine is controlled, and the chlorine: n, N '-dimethyl-3, 3' -dithiodipropionamide 0.75: 1, introducing hot water of 40 ℃ into a jacket of the second-stage tubular reactor, controlling the temperature of 35-45 ℃ in the second-stage chlorination, and mixing and staying the materials in the tube for 10-20 minutes.

The chlorination reaction liquid in the second stage enters a third stage tubular reactor, the temperature of the third stage is controlled at 60-65 ℃, and the materials are mixed and stay in the tube for 3-5 minutes.

The materials after the reaction directly enter a gas-liquid separator to separate hydrogen chloride, the reaction liquid is cooled and centrifuged, a small amount of chloroform is used for washing to obtain MIT hydrochloride, and then procedures of neutralization, delamination, distillation, compounding and the like are carried out to obtain an MIT aqueous solution with the content of 50%; wherein the normalized content of MIT liquid chromatogram (HPLC) is more than 99.99 percent, the content of CIT liquid chromatogram external standard method is less than 40ppm, and the continuous production yield is 92 percent.

The above description is only an example of the present invention, and is not intended to limit the scope of the present invention. The foregoing examples and description have been presented only to illustrate the general principles and features of the invention, and it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made in the details of the embodiments of the invention described herein, which are within the scope of the invention as hereinafter claimed.