CS255380B1 - Process for producing alkali metal or alkaline earth metal salt of 2-methyl-4-chlorophenoxyacetic acid - Google Patents

Abstract

The solution relates to chemical technology. It solves the production of salts of 2-methyl-4-chlorophenoxyacetic acid, whereby neutralization is carried out at a temperature of 85 to 100 °C in the melt using a neutralizing agent, which can be a hydroxide, carbonate, oxide of an alkali metal or an alkaline earth metal, and the melt is then cooled after neutralization and processed into the final form: powder, granule, pellet, pill.

Description

3 4 255380

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of an alkali or alkaline earth metal salt of 2-methyl-4-chlorophenoxyacetic acid by neutralization of the 2-ethylphenoxyacetic acid melt, whereupon solid product is obtained upon cooling.

2-Methyl-4-chlorophenoxyacetic acid and its salts are used as very effective herbicides. Most often, it is prepared by chlorination of 2-methylphenoxyacetic acid with gaseous chlorine at 95-105 ° C, as described in MS. No. 91,160. The continuous process of chlorination of the sodium, potassium or sodium potassium salt of 2-methylphenoxyacetic acid in an aqueous solution is described in U.S. Patent No. 8,892, the continuous chlorination process of free 2-methylphenoxyacetic acid by gaseous chlorine is described in U.S. Pat. Patent No. 107,807. Combination of chlorination of 2-methylphenoxyacetic acid with chlorine gas with subsequent chlorination of the chloro compound. Chlorination of 2-methylphenoxyacetic acid with chlorine gas at a pH of 4-6 is described in French Patent No. 116,356. Chlorination with an aqueous solution of sodium hypochlorite prepared or pre-mixed in the reaction mixture at 50 ° C. U.S. Pat. No. 722,625. Chlorination of suspended 2-methylphenoxyacetic acid at a pH equal to 1 in a heterogeneous phase in the presence of hydrochloric acid with sodium hypochlorite at 20 ° C is described by DAS 1,027,680. the sodium salt of 2-methylphenoxyacetic acid chlorine in the presence of a bicarbonate is described in U.S. Pat. UK 855,504. Production of 2-methyl-4-chlorophenoxyacetic acid with sodium hypochlorite in the presence of mineral or carboxylic acid, production of 2-methyl-4-chlorophenoxyacetic acid by chlorination of 2-methylphenoxyacetic acid sodium salt and recovery Of 2-methyl-4-chlorophenoxyacetic acid by precipitation with an aqueous solution of mineral acid described in U.S. Pat. AO 179,200.

A disadvantage of the preparation of 2-methyl-4-chlorophenoxyacetic acid by chlorination of 2-methylphenoxyacetic acid with chlorine gas is that the neutralization of 2-methyl-4-chlorophenoxyacetic acid with an aqueous ammonia solution yields a maximum of 40 ° / other aqueous solution and the 2-methyl-4-chlorophenoxyacetic acid mono-salt. High water content increases packaging and transport costs. Lower heat storage results in the crystallization of the product, causing problems prior to application of the product in the agricultural sector. Similar disadvantages are also found in aqueous solutions of sodium, potassium, amine salts of 2-methyl-4-chlorophenoxyacetic acids whose concentration of aqueous solution is 18 max. 40% by weight.

The aforementioned drawbacks are eliminated by the process of producing the alkali metal or alkaline earth metal salt of 2-methyl-chlorophenoxyacetic acid according to the invention. 2-Methyl-4-chlorophenoxyacetic acid produced by chlorination of 2-methylphenoxyacetic acid (or its sodium or potassium salt) with chlorine gas is recovered from the chlorination step at about 100 degrees Celsius.

The 2-methyl-4-chloro-phenoxyacetic acid melt thus obtained, after separation of the aqueous phase from the organic one, is further neutralized with a 85 to 100 ° C quench with aqueous NaOH or KOH, optionally Na 2 CO 3. A combination of aqueous solutions of alkali hydroxides and carbonates can also be used to neutralize the 2-methyl-4-chlorophenoxyacetic acid melt. Neutralization of the melt at this temperature can be effected by hydroxyl, carbonate, alkali or alkaline earth metal.

During neutralization at 85 to 100 degrees Celsius, the neutralizing water is freely released from the reaction space and leaves the melt of neutralized 2-methyl-4-chlorophenoxyacetic acid in the form of aqueous vapors which are separated and condensed. Neutralization may be carried out continuously or discontinuously in a neutralization vessel at temperatures of 85-100 ° C.

The present invention is simple and the dosage of neutralizing medium is based on the content of 2-methyl-4-chlorophenoxyacetic acid, wherein the molar ratio of neutralizing medium to 2-methyl-4-chlorophenoxyacetic acid is 1-3 to 1. In the case of the use of salt for the production of the combined herbicidal compositions, neutralization can also be carried out in a molar ratio of neutralizing medium to MCPA of 1: 3.

The low-viscosity liquid-forming salt of the 2-methyl-4-chlorophenoxyacetic acid salt is further cooled, solidifying to a brittle mass, which is crushed and milled well, or processed into various final forms in the cooling process ( pulp, pellet, tablet-and-flake, powder). The hard and brittle salt of 2-methyl-4-chlorophenoxyacetic acid salt readily dissolves in water into an aqueous solution of 2-methyl-4-chlorophenoxyacetic acid salt prior to application in the agricultural sector. The advantage of this process is that it yields a solid phase product containing at least 65% of the active substance MCPA, and depending on the conditions of the chlorination of neutralization, as well as depending on the neutralizing medium used, a product containing up to 90% MCPA can be obtained in the form of a solid. salt.

Significantly reduce the cost of product packaging, shipping costs. A product is obtained which may be inexpensive to store and which is water-soluble prior to application. Example 1 2-Methyl-4-chlorophenoxyacetic acid

Claims (1)

Process for producing an alkali metal or alkaline earth metal salt of 2-methyl-4-chlorophenoxyacetic acid obtained by chlorination of 2-methylphenoxyacetic acid, characterized in that the melt of 2-methyl-4-chlorophenoxyacetic acid is separated from the aqueous phase and The molten 2-methyl-4-chlorophenoxyacetic acid is neutralized with a hydroxide, carbonate, alkali metal or alkaline earth metal up to a pH of 7.5-8.5 at 85 to 100 ° C and further smoothed.