CS221494B1 - Process for preparing benzoguanamine - Google Patents

Abstract

A method for preparing benzoguanamine by condensation of dicyandiamide with benzonitrile using a basic catalyst, in which the base-catalyzed condensation of dicyandiamide with benzonitrile is carried out in an isobutanol environment, the mother liquor being used as part of the isobutanol batch for the subsequent operation and the catalyst being dosed in the form of an isobutanol solution.

Description

The invention relates to a process for the preparation of benzoguanamium. itj. 2!, 4ΐΐΐΐΙΐΙΐΙΌ 6 6-6-ί (βιηγ1Ί, 3,5 * -1: ímazi) and its essence is the reaction of dicyandiindium with benzoniitrileim in isobuitanol in the presence of a caustic bottom catalyst which is fed into the reaction mixture in * Beinzoguainiamine is generally prepared by base-catalyzed condensation of benzoinitrile with dicyanidamide in a suitable solvent, most often in celiosolve according to the following scheme:

NH ₃ -C NHCN + \ i ² II

NH

CN

According to the present invention, benzoguiahamine is prepared by suspending dicyandiamide at room temperature in benzinitrile and part of isobutanol, then heating the mixture to 50 ° C and at this temperature adding ¹ solution of catalyst (KOH) in the remaining amount of isobuitanol. During dosing, the reaction temperature increases due to the heat of reaction. After the batch is complete, the batch is heated to the boiling point of 107-108 ° C and kept under reflux for 3 hours. The reaction mixture is then cooled to 20 ° C and filtered off with suction. The mother liquor (isobutanoil filtrate) is added. It is used as part of the isobutainol charge: for the following operation: The charge for (other operations is always made up of constant amounts of dlkyandlamide and bemzonitrile, only the isobuitanol and potassium hydroxide losses are replenished.

An additional portion of benzoguanamine is isolated from the combined cooled aqueous filtrates after several operations by filtration. The product is dried at 110-120 ° C.

After the end of the series of recycles (at least 6 recycles), isobutanol is recovered by distillation of the isobutanol filtrate.

The preparation of benzoguanamine with the recycle of the mother liquor can be carried out in conventional batch reactors equipped with a duplicator and a bottom outlet. Filtration and washing of the product on hot tub with hot water makes no problems.

Compared to the previous production methods, the new process is characterized by technological simplicity, high yields of benzoguanamine above 93 ° / o, higher product quality, low-temperature solvent is used at low reaction temperature, recirculated mother liquor forms 9/10 batches of total isobutanol catalyst into the reaction system.

The example below illustrates an embodiment of the invention.

Example

200 ml (160.4 g) of isobutanol and 44.7 g of dicyandiamide are introduced into a four-necked Keller flask equipped with a stirrer, reflux condenser, thermometer and addition funnel. After starting the stirrer with reflux condenser, 50 g of benzonitrile are added and the mixture is heated to 90 ° C. Starting from the funnel, dispense 2.4 g of potassium hydroxide dissolved in 100 ml (80.2 g) of isobutanol into the heated batch. It is dosed for 30 minutes, then the reaction mixture is heated to boiling point and kept under reflux with stirring for 3 hours. The reaction mixture was then cooled to 20 ° C, suctioned and suction filtered. The free potassium hydroxide solution was determined in the mother liquor and stored for further processing.

The filter cake is washed in three stages with 200 ml of hot water (100 ° C) each. The aqueous filtrates were collected. The benzoguanamine product was dried at 120 ° C for 3 hours to give 82.2 g (i.e., 90.6%) of benzeguanamine.

In the manufacture with recycle of the mother filtrate, a constant charge of dlcyanediamide and Ibenzonitrile is used as at the start.

The amount of pure isobutanol used is determined from the difference between the total isobutanol used at the start and the volume of the mother filtrate from the previous operation (typically 270 ml). The batch of fresh KOH is replenished to the required 2.4 g KOH by determining the aqueous KOH content of the mother filtrate from the previous operation. Fresh KOH to recover losses was dissolved in fresh isobutanol to be seeded and again added to the reaction mixture over 30 minutes under the same conditions as at the start. Further steps and product isolation are unchanged.

Treatment

The aqueous filtrates were cooled and the benzoguanamine suspension was filtered off. The filter cake is washed in three stages with 200 ml of hot water and after drying forms another part of the product.

The mother liquor from the last operation is distilled to recover isobutanol. Already after six recycles, the average benzoguanamine yield is 93.6% per benzonitrile used and operation.

Claims (1)

Process for the preparation of benzoguanamine by condensation of dicyandiamide with benzonitrile using a basic catalyst, characterized in that the base-catalyzed condensation of dicyandiamide with benzonitrile is carried out in a OF THE INVENTION isobutanol medium, wherein the mother liquor is used as part of the isobutanol batch to the following operation and the catalyst is metered in the form of an isobutanol solution.