Process for the Continuous Production of Alkali Salts of the Dialkyldithiocarbamic Acid

A process for producing alkali metal salts of dialkyldithiocarbamic acids, comprising the steps:

• i) a reaction step in the form of the reaction of one or more dialkylamines, carbon disulphide and one or more alkali metal hydroxides in aqueous solution so as to form an aqueous reaction solution of alkali metal salts of dialkyldithiocarbamic acids;
• ii) a crystallisation step in the form of the introduction of the reaction solution from step i) in an evaporative crystalliser, which is heated by a heater such that a temperature of approximately 30-95, especially 45-80° C. is present at the contact surface of the heating element to the reaction solution, and in which a pressure of approximately 10-800 mbar (a), preferably 50-400 mbar (a) is present, so as to form a crystal suspension of alkali metal salts of dialkyldithiocarbamic acids;
• iii) a separation step in the form of the introduction of the crystal suspension formed in step ii) into a centrifuge and centrifugation of the crystal suspension for solid/liquid separation so as to form crystals of alkali metal salts of dialkyldithiocarbamic acids on the one hand and separated mother liquor on the other hand;
• iv) a recirculation step in the form of the recirculation of the separated mother liquor obtained in step iii) into the crystallisation process;
• and
• v) a drying step in the form of the drying of the alkali metal salts of dialkyldithiocarbamic acids separated off in step iii), wherein the drying step is designed especially such that the separated alkali metal salts of the dialkyldithiocarbamic acids are dried by means of a contact dryer.