CS259207B1 - Method of isolation of 4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine - Google Patents

Abstract

The solution relates to a method for isolating 4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine produced by the reaction of 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine with gaseous ammonia using surfactants which are added before azeotropic distillation and/or before filtration in an amount of 0.05 to 3% by weight.

Description

259207·

The invention relates to a method for isolating 4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine in the presence of a surfactant.

4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine is a herbicide intended primarily for the selective control of weeds in sugar beet /Burex, Pyramin/.

Several methods of producing 4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine are known to date. GB 871 674 describes a method of producing 4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine by reacting 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine with an aqueous ammonia solution under pressure at elevated temperature. This process yields a product containing approximately 80% by weight of 4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine. Furthermore, reactions of 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine with an aqueous ammonia solution under pressure in the presence of a catalyst are known ₍ EP 28 to 359, CS 214 843 and 226 250), in which a product of high purity is obtained.

According to CS 120 858, the production of 4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine is carried out by amination of 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine with gaseous ammonia at a temperature maintaining the reaction mixture in the form of a melt. The technical product thus obtained containing 70 to 75% of 4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine is subjected to extraction with xylene /CS 122 103/, whereby the undesirable isomer 5-amino-1-phenyl-4-chloro-6-oxo-1H-pyridazine is removed. The solvent is removed from the isolated xylene cake of 4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine by azeotropic distillation with water. The product is obtained from the aqueous suspension by filtration in centrifuges.

The disadvantage of the above procedure - in addition to the formation of a foamed suspension, which occurs during the azeotropic distillation of the xylene cake - is that during the amination of less pure 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine, the technical product 4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine contaminated with accompanying impurities is obtained, which creates difficulties in filtering the aqueous suspension on centrifuges due to changes in the physical properties of the product /stickiness, caking/ and leads to losses. Undesirable changes in the physical properties of the product also result in impaired suspendability of the final product after processing into a wettable powder.

Another disadvantage is that after azeotropic distillation, some of the xylene remains in the sintered parts of the product and, when the product is dried, it escapes into the air, which results in a deterioration of the working environment.

We have now found a method for isolating 4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine produced by reacting 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine with ammonia gas at a temperature of 170 to 220°C, followed by extraction of the inactive 5-amino-1-phenyl-4-chloro-6-oxo-1H-pyridazine present and unreacted 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine with xylene, further removing the solvent from the xylene cake of the product by azeotropic distillation with water and filtering the 4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine from the aqueous suspension according to the invention. The essence of the invention lies in the fact that a surfactant is added to the xylene cake before azeotropic distillation and/or before filtration in an amount of 0.05 to 3% by weight relative to technical 4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine.

Surfactants can be Spolion based on dialkyl sulfosuccinate, Abeson based on a combination of an alkaline salt of dodecylbenzenesulfonic acid, alkaline alkyl polyglycol ether sulfate containing solvents, Defoamer T based on resin acids and ethylene oxide, etc.

The advantage of the process according to the invention - in addition to the known effect of defoamers, which consists in preventing foaming of the reaction mixture during azeotropic distillation - is the fact that even in the case of using less pure 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine as the starting product in the amination, the technical product 4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine with high purity is obtained after azeotropic distillation. The product is easily filterable, does not contain xylene residues and impurities of a sticky nature, which tend to cause mechanical losses during filtration. Another advantage lies in the improvement of the physical properties of the active substance, which is manifested mainly in the improvement of the suspendability of the final preparation modified into a wettable powder.

The following examples illustrate, but do not limit, the subject matter of the invention.

Example 1

630 kg of 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine 96% was charged to the reactor, to which 15 kg of technical sulphite liquor (slurry) and 10 kg of benzoic acid were added. Ammonia gas was introduced into the reaction mixture with stirring at a temperature of 200 °C. After the amination was completed, the reaction mixture in the form of a melt was discharged into 3,100 kg of xylene charged in an extraction kettle. After 1 hour of extraction at 60 °C, the xylene suspension was filtered off. Half of the obtained xylene cake of 4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine was charged into a kettle with 900 l of water.

0.5 kg of Spolion was added to the mixture and the xylene was simply azeotropically distilled off without boiling. After the xylene had been distilled off, the product was isolated from the aqueous suspension by filtration on centrifuges. The effluent filtrate contained practically no insoluble fraction of 4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine. The second half of the xylene cake was processed in a similar manner. 4,714 kg of 4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine with a purity of 93.2% was obtained.

Example 2

By the procedure described in Example 1, with the difference that instead of Spolion 1 kg of Defoamer T was used, 479.5 kg of 4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine with a purity of 93.6% was obtained.

A comparison of the purity of 4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine (PCA) obtained using a dialkyl sulfosuccinate surfactant in azeotropic distillation and without the use of a surfactant is shown in Table 1.

The reactions were carried out according to the procedure described in Example 1, except that the starting 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine was 91.8% pure.

Table 1

Effect of Spolion on PCA purity

Attempt No. Without Spolion PCA Purity /%/ With Spolion 1 91.2 94.2 2 89.9 93.1 3 90.1 93.6 4 89.5 94.5 5 88.1 94.9 Average 89.76 94.06

A comparison of the suspension stability of the final formulation prepared into a wettable powder using Spolion in azeotropic distillation and without its use is shown in Table 2.

The stability of a 1% aqueous suspension of the wettable powder was monitored for 30 minutes in water with a hardness of 30 °N.

Experiment 6

Suspension stability

With Spolion

Table 2

Effect of Spolion on suspension stability

Claims (2)

Spolionu 259207 Table 2 Effect of Spolion on Suspension Stability Experiment 6 Suspension Stability With Spolion 1 82.0 86.7 2 82.3 88.0 3 83.1 86.3 4 82.2 87.9 SUBJECT TO 4-amino-1-Isolation phenyl-5-chloro-6-oxo-1H-pyridazine produced by reaction of 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine with ammonia gas at 170-220 ° C, followed by extraction of the non-lime 5- of amino-1-phenyl-4-chloro-6-oxo-1H-pyridazine and unreacted 4,5-dichloro-1-phenyl-6-oxo-1H-pyridazine with xylene, saline removal of xylene cake by azeotropic distillation water and filtering 4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine from an aqueous suspension characterized in that a surfactant in a quantity of 0.05 to 3 is added to the xylene cake prior to azeotropic distillation and / or filtration. % by weight relative to the technical 4-amino-1-phenyl-5-chloro-6-oxo-1H-pyridazine. Severografia, n. P ,, MOST Price 2,40 Kčs