A method for preparing small-particle glyphosate

Abstract

The invention discloses a method for preparing small-particle glyphosate, wherein an acidified solution is obtained by a glycine-dimethyl phosphite method, and glyphosate seed powder or seed solution is added to induce crystallization after the acidified solution is concentrated; after the heat preservation reaction is completed, the small-particle glyphosate wet product is obtained by cooling crystallization and neutralization crystallization. The invention solves the problem that it is difficult to directly obtain small-particle glyphosate, and the obtained glyphosate wet product has a small particle size (particle size D97≤180μm) and is evenly distributed, and can be directly applied to the production of downstream soluble granules without the need for additional drying, crushing or screening steps.

Description

Technical Field

[0001] The invention relates to a method for preparing small-particle glyphosate, belonging to the technical field of pesticide production. Background Art

[0002] Glyphosate is a systemic herbicide, an amino acid derivative; its chemical name is N-(phosphomethyl)-glycine, commonly known as "Roundup"; it can be absorbed through the stems and leaves of plants and transmitted to the whole plant, and can control more than 40 families of plants, including monocots and dicots, annuals and perennials, herbs and shrubs. Due to its advantages such as broad spectrum, low toxicity, high efficiency and no residue, it plays an important role in the field of crops. With its excellent weed control properties, it has been vigorously promoted worldwide and quickly became the world's best-selling, largest-volume and most widely used herbicide.

[0003] There are two main production processes for glyphosate: the glycine process and the IDA process. The glycine process in my country is mainly based on the glycine process. The glycine process uses glycine, paraformaldehyde, and dimethyl phosphite as the main raw materials, triethylamine as the catalyst, and methanol as the solvent. It is produced through four steps of depolymerization, addition, condensation, and hydrolysis. The reaction route is as follows: In recent years, with the continuous development of the glyphosate formulation industry, the demand for glyphosate soluble granules has also continued to increase, which has also put forward higher requirements on the physical and chemical properties of glyphosate technical such as particle size, specific surface area, and dissolution rate. Traditional crystallization methods tend to produce glyphosate with large particle size, which is conducive to the preparation of aqueous formulations; however, large particles have small contact areas, poor mass transfer effects and dissolution rates, which are not conducive to the preparation of soluble granules. Therefore, it is particularly important to develop a method that can efficiently prepare small particle size glyphosate. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a method for preparing glyphosate with small particle size. The method prepares glyphosate by a glycine-dimethyl phosphite method, strictly controls the crystallization process, and introduces seed crystals during crystallization to induce rapid nucleation of glyphosate crystals in a reaction solution to obtain a glyphosate product with fine particle size.

[0005] The specific technical solutions of the present invention are as follows: A method for preparing small-particle glyphosate comprises the following steps: (1) Heat the acidified liquid and concentrate it. When the temperature reaches 110-120°C, keep it warm for reaction. (2) adding seed crystals during the heat-keeping reaction and before spontaneous crystallization occurs, and continuing the heat-keeping reaction until the hydrolysis is complete; (3) After hydrolysis, the obtained crystal solution is cooled down to ≤70°C, and then alkali solution is added dropwise to adjust the pH to 0.8-1.2, and then the temperature is further lowered for crystallization; (4) After crystallization is completed, filter to obtain small-sized glyphosate particles.

[0006] Furthermore, the small-particle glyphosate of the present invention is prepared by the glycine-dimethyl phosphite method. The production process of the acidified liquid in step (1) is: using the glycine-dimethyl phosphite method, glycine, polyformaldehyde, and dimethyl phosphite as main raw materials, triethylamine as a catalyst, and methanol as a solvent, depolymerization, addition, and condensation are performed to obtain a condensation liquid, and hydrochloric acid is added to the condensation liquid to obtain an acidified liquid. The hydrolysis reaction in the acidified liquid is not complete, and it contains components such as glyphosate dimethyl ester, glyphosate, methylal, triethylamine hydrochloride, methanol, and water.

[0007] Furthermore, in step (1), the acidified liquid is heated and concentrated to perform desolventization and hydrolysis, and after being concentrated to 110-120°C, the temperature is kept at this temperature for reflux reaction until the hydrolysis is complete. When the temperature is increased and concentrated, the heating speed is fast, the time taken to reach the set temperature is short, and the degree of completion of the hydrolysis reaction is low. Preferably, the temperature is increased to 110-120°C at a rate of 0.5°C / min-2°C / min.

[0008] Furthermore, during the heat preservation reaction of step (1), as the heat preservation time increases, crystals will spontaneously precipitate in the concentrated solution. The present invention controls the crystallization process to ensure that seed crystals are added before spontaneous crystallization to induce crystallization. After adding the seed crystals, the heat preservation reaction is continued until the hydrolysis is complete. During the entire heat preservation reaction, the stirring speed is controlled to be ≥300r / min, such as 300r / min, 400r / min, 500r / min, 600r / min, etc., and any range value therebetween. At this rotation speed, it is beneficial to obtain glyphosate with a small particle size, and the glyphosate particle size is easily increased when the rotation speed is reduced.

[0009] Furthermore, in step (2), the timing of adding seed crystals is determined according to the actual reaction process. Seed crystals are added after a certain period of heat preservation reaction. Adding seed crystals too early or too late is not conducive to the formation of small-sized glyphosate particles. The spontaneous crystallization time is different due to different heating concentration speeds and heat preservation temperatures. After experimental verification, seed crystals are generally added after heat preservation reaction at 110~120℃ for 10~60min, such as 10min, 15min, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min, 60min. After adding seed crystals, in order to ensure the complete hydrolysis reaction, continue to stir and keep warm for 2~5h.

[0010] Furthermore, in step (2), the particle size of glyphosate is reduced by adding seed crystals to the concentrated solution in advance to induce crystallization. The seed crystals may be a small-sized glyphosate solid powder or a glyphosate seed solution containing small-sized glyphosate crystals. The particle size D97 of the small-sized glyphosate solid powder or small-sized glyphosate crystals is ≤120 μm, for example, 120 μm, 100 μm, 50 μm, 40 μm, and any range value therebetween.

[0011] Furthermore, in step (2), the solid seed crystals can be obtained by grinding large-particle glyphosate solid to a particle size of D97≤120μm, or by directly obtaining glyphosate crystals with a particle size of D97≤120μm by recrystallization. The seed crystal solution can be obtained by mixing large-particle glyphosate solid powder with water (or glyphosate mother liquor) and then grinding to a particle size of D97≤120μm; or by uniformly mixing glyphosate solid powder with a particle size of D97≤120μm with water (or glyphosate mother liquor); or by forming a corresponding salt of glyphosate with an alkali in water and then adding an acid to recrystallize to obtain the seed crystal solution. If the crystal particle size D97 in the seed crystal solution is greater than 120μm, the seed crystal solution can be ground to obtain a seed crystal solution with a particle size of D97≤120μm.

[0012] Furthermore, the recrystallization method for preparing seed crystals can be operated in the following manner: glyphosate is mixed with water, alkali solution is added to dissolve (i.e., the alkali reacts with glyphosate to make the glyphosate completely dissolved in water), then the temperature is lowered to 0-15°C, and hydrochloric acid is added dropwise under stirring conditions of a speed of ≥500r / min for recrystallization to obtain a glyphosate seed crystal solution, which can be used directly as a seed crystal, or can be filtered to obtain a glyphosate solid powder, which is then used as a seed crystal, and the obtained glyphosate crystal particle size D97≤60μm.

[0013] In the above-mentioned method for preparing seed crystals by recrystallization, the mass ratio of glyphosate to water is 1:1 to 1:3.

[0014] In the above-mentioned method for preparing seed crystals by recrystallization, the concentration of the alkali solution is 30-40wt%, and the alkali solution component is at least one of a sodium hydroxide solution and a potassium hydroxide solution. The amount of alkali solution added ensures that the glyphosate is completely dissolved, and preferably, the mass ratio of glyphosate to the alkali solution is 1:0.9-1:1.4.

[0015] In the above-mentioned method for preparing seed crystals by recrystallization, the stirring speed can be 500 r / min, 600 r / min, 700 r / min, 800 r / min, etc., and any range value therebetween.

[0016] In the above-mentioned method for preparing seed crystals by recrystallization, the concentration of hydrochloric acid is 30-40wt%, the dropping time is 5-20min, and the molar ratio of base to acid is 1:0.6-1:1.

[0017] Furthermore, in step (2), the amount of seed crystals (in terms of solid) added is 0.5-2.0% of the theoretical mass of glyphosate, for example, 0.5%, 1.0%, 1.5%, 2.0%.

[0018] Further, in step (3), after the hydrolysis reaction in step (2) is completed, a crystal solution is obtained. Turn off the heating, cool down and crystallize, cool down at a rate of 0.5°C / min to 1°C / min, and when the temperature drops to ≤70°C, for example, 70°C, 60°C, or 50°C, add alkali solution to adjust the pH of the reaction solution to 0.8 to 1.2, the alkali solution concentration is 30 to 40wt%, and the alkali solution component can be at least one of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, potassium carbonate solution, sodium bicarbonate solution, and potassium bicarbonate solution, preferably sodium hydroxide solution. The alkali solution is added for 10 to 60 minutes.

[0019] Furthermore, in step (3), after the addition of the alkali solution is completed, the temperature is further lowered to 20-30°C for crystallization. The cooling rate is preferably 0.5°C / min-1°C / min.

[0020] Furthermore, in step (3), the entire cooling and crystallization process is carried out at a stirring speed of 100-300 r / min.

[0021] Furthermore, in step (4), after crystallization is complete, the glyphosate wet product is obtained by filtration. The glyphosate obtained by the method of the present invention has a small particle size, D97≤180μm, and can be directly used in the production of soluble granules. In addition, the crystal-containing solution obtained in step (4) can be used as a seed crystal for step (2) directly or after grinding, and the small-particle glyphosate wet product obtained by filtration can be used as a seed crystal for step (2) directly or after grinding.

[0022] The beneficial effects of the present invention are: (1) The present invention can prepare glyphosate seed crystals by grinding or recrystallization, and the seed crystal particle size D97≤120μm. The seed crystals are added before the concentrated solution spontaneously crystallizes, and the glyphosate crystal particle size is effectively regulated by controlling the seed crystal size, the timing of seed crystal addition, the crystallization process, and the optimization of crystallization conditions, thereby preparing a small-particle glyphosate product with a particle size D97≤180μm, thereby solving the problem of difficulty in directly obtaining small-particle glyphosate.

[0023] (2) The glyphosate crystals prepared by the present invention have a small particle size (particle size D97 ≤ 180 μm) and are evenly distributed, have a larger specific surface area, better dispersibility, and better mass transfer effect, which is conducive to its uniform distribution and rapid dissolution in the pesticide formulation. The small-particle glyphosate crystal wet material obtained by filtration can be directly used in the production of downstream soluble granules without the need for additional drying, crushing or screening steps. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with specific embodiments. The following description is only exemplary and does not limit the scope of protection. Other implementation schemes obtained by those skilled in the art without creative work without departing from the inventive concept of the present invention are also within the scope of protection.

[0025] In the following examples, unless otherwise specified, all raw materials used are commercially available products.

[0026] In the following examples, unless otherwise specified, the concentrations are all mass percentage concentrations.

[0027] Example 1 (1) Take a solid glyphosate sample and grind it to obtain a glyphosate seed powder (particle size D97 = 120 μm) for later use; (2) Mix polyformaldehyde solid (49 g), methanol (52 g), and triethylamine (1 g), heat to 50±10°C, and stir until dissolved to obtain a depolymerization solution; cool the depolymerization solution to 40±5°C, add methanol (228 g), glycine (61 g), and triethylamine (68 g), control the temperature at 40±5°C, keep stirring and react for 1 hour, and obtain a clear and transparent addition solution; add dimethyl ester (108 g) to the addition solution, heat to 52±2°C, keep the temperature for 20 minutes, then add triethylamine (15 g), keep the temperature at 52±2°C for 70 minutes, and obtain a condensation solution; control the temperature of the condensation solution at 30°C, add 32% hydrochloric acid (316 g) dropwise, and stir for 4 hours to obtain an acidified solution; (3) The acidified liquid was distilled at atmospheric pressure and heated to 110°C for 80 minutes to obtain a concentrated liquid. The concentrated liquid was kept refluxed at this temperature under stirring at a speed of 300 r / min. After refluxed for 25 minutes, 1 g of glyphosate seed powder was added to induce crystallization. After adding the seed crystals, stirring and refluxed for 3.5 hours, and heating was stopped to obtain a crystal liquid. (4) Adjust the rotation speed to 200 r / min, and lower the temperature of the crystallization liquid to 50°C at a cooling rate of 1°C / min. Then, add 32% sodium hydroxide solution to adjust the pH to 0.9. The addition takes 20 min. After the addition is completed, continue to cool and crystallize at a cooling rate of 1°C / min and a rotation speed of 200 r / min. After the crystallization is complete, filter to obtain a small-particle glyphosate wet product (particle size D97 = 166 μm), which can be directly used for the preparation of glyphosate soluble granules.

[0028] Example 2 (1) 30 g of glyphosate and 30 g of water were mixed and stirred, and then 27 g of 32% sodium hydroxide solution was added to dissolve the mixture. The mixture was cooled to 5°C and 24.6 g of 32% hydrochloric acid was added dropwise at a speed of 500 r / min for recrystallization. The addition time was 15 min to obtain a glyphosate seed solution (particle size D97 = 37 μm). (2) Obtaining an acidified solution according to the method of step (2) of Example 1; (3) The acidified liquid was distilled at atmospheric pressure and heated to 110°C for 80 minutes to obtain a concentrated liquid. The concentrated liquid was kept refluxed at this temperature under stirring at a speed of 400 r / min. After refluxed for 35 minutes, 4 g of glyphosate seed solution was added to induce crystallization. After adding the seed crystals, stirring and refluxed for 3.5 hours, and heating was stopped to obtain a crystallized liquid. (4) Adjust the rotation speed to 200 r / min, and lower the temperature of the crystallization liquid to 53°C at a cooling rate of 1°C / min. Then, add 32% sodium hydroxide solution and adjust the pH to 0.9. The addition takes 36 min. After the addition is completed, continue to cool and crystallize at a cooling rate of 1°C / min and a rotation speed of 200 r / min to 25°C. After the crystallization is complete, filter to obtain a small-particle glyphosate wet product (particle size D97 = 146 μm), which can be directly used for the preparation of glyphosate soluble granules.

[0029] Example 3 (1) Glyphosate solid sample was taken, and glyphosate seed powder (particle size D97 = 110 μm) was obtained by grinding, and added to the glyphosate mother liquor obtained after filtering out the glyphosate crystals, to prepare a glyphosate seed solution with a mass percentage of 20% for standby use; (2) Obtaining an acidified solution according to the method of step (2) of Example 1; (3) The acidified liquid was distilled at atmospheric pressure, and the temperature was raised to 110°C for 80 minutes to obtain a concentrated liquid. The concentrated liquid was kept refluxed at this temperature under stirring conditions at a speed of 300 r / min. After keeping the temperature at reflux for 25 minutes, 5 g of glyphosate seed solution was added to induce crystallization. After adding the seed crystals, stirring and keeping the temperature at reflux for 3.5 hours were continued, and heating was stopped to obtain a crystallized liquid. (4) Adjust the rotation speed to 200 r / min, and lower the temperature of the crystallization liquid to 50°C at a cooling rate of 1°C / min. Then, add 32% sodium hydroxide solution and adjust the pH to 0.9. The addition time is 20 min. After the addition is completed, continue to cool and crystallize to 30°C at a cooling rate of 1°C / min and a rotation speed of 200 r / min. After the crystallization is complete, filter to obtain a small-particle glyphosate wet product (particle size D97 = 149 μm), which can be directly used for the preparation of glyphosate soluble granules.

[0030] Comparative Example 1 Small-particle glyphosate was prepared according to the method of Example 1, except that in step (1), the particle size of the glyphosate seed powder was D97 = 132 μm. The particle size of the glyphosate wet product finally obtained was D97 = 198 μm, which did not meet the requirements for preparing soluble granules.

[0031] Comparative Example 2 Small-sized glyphosate particles were prepared according to the method of Example 2, except that in step (3), the stirring speed was 200 r / min. The particle size of the glyphosate wet product finally obtained was D97 = 271 μm, which did not meet the requirements for preparing soluble granules.

[0032] Comparative Example 3 Small-sized glyphosate particles were prepared according to the method of Example 1, except that in step (3), after the concentrated solution was kept warm and refluxed for 5 minutes, 1 g of glyphosate seed powder was added to induce crystallization, and after the seed was added, stirring and refluxed for 4 hours. The particle size of the glyphosate wet product finally obtained was D97 = 277 μm, which did not meet the requirements for preparing soluble granules.

Claims

1. A method for preparing small-particle glyphosate, characterized in that The following steps are involved: (1) Heat the acidified liquid and concentrate it. When the temperature reaches 110-120°C, keep it warm for reaction. (2) adding seed crystals during the heat-keeping reaction and before spontaneous crystallization occurs, and continuing the heat-keeping reaction until the hydrolysis is complete; (3) After hydrolysis, the obtained crystal solution is cooled down to ≤70°C, and then alkali solution is added dropwise to adjust the pH to 0.8-1.2, and then the temperature is further lowered for crystallization; (4) After crystallization is completed, filter to obtain small-sized glyphosate particles.

2. The preparation method according to claim 1, characterized in that: In step (1), the acidified liquid refers to the acidified liquid formed by adding hydrochloric acid to the condensation liquid obtained by the glycine-dimethyl phosphite method through depolymerization, addition and condensation.

3. The preparation method according to claim 1, characterized in that: In step (1), the temperature is raised to 110-120°C at a heating rate of 0.5°C / min-2°C / min.

4. The preparation method according to claim 1, characterized in that: In step (2), the seed crystal is a solid glyphosate powder with a particle size D97 ≤ 120 μm, or a glyphosate seed crystal liquid containing glyphosate crystals with a particle size D97 ≤ 120 μm.

5. The preparation method according to claim 4, characterized in that: In step (2), the preparation method of glyphosate seed solution is: mixing glyphosate and water, then adding alkali solution until glyphosate is completely dissolved, then cooling to 0~15°C, and adding hydrochloric acid dropwise under stirring conditions of a speed of ≥500r / min for recrystallization to obtain glyphosate seed solution; preferably, the mass ratio of glyphosate to water is 1:1~1:3; preferably, the alkali solution is 30~40wt% sodium hydroxide solution and / or potassium hydroxide solution, and the mass ratio of glyphosate to the alkali solution is 1:0.9~1:1.4; preferably, the concentration of hydrochloric acid is 30~40wt%, and the molar ratio of alkali to acid is 1:0.6-1.1; preferably, the hydrochloric acid is added dropwise for 5~20min.

6. The preparation method according to claim 1, characterized in that: In step (2), seed crystals are added at a stirring speed of ≥300 r / min; preferably, the amount of seed crystals added is 0.5-2.0% of the theoretical mass of glyphosate.

7. The preparation method according to claim 1, characterized in that: In step (2), after adding the seed crystal, the reaction is stirred and kept warm at 110-120° C. for 2-5 hours.

8. The preparation method according to claim 1, characterized in that: In step (3), the temperature is lowered to ≤70°C at a rate of 0.5°C / min to 1°C / min. Preferably, after the addition of the alkali solution, the temperature is further lowered to 20 to 30°C for crystallization, and the cooling rate is preferably 0.5°C / min to 1°C / min.

9. The preparation method according to claim 1, characterized in that: In step (3), the alkali solution is added dropwise for 10 to 60 minutes; preferably, in step (3), the alkali solution concentration is 30 to 40 wt%, and the alkali solution is at least one of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, potassium carbonate solution, sodium bicarbonate solution, and potassium bicarbonate solution.

10. The preparation method according to claim 1, 8 or 9, characterized in that: In step (3), the entire cooling and crystallization process is carried out at a stirring speed of 100-300 r / min.

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