Vacuum Drying in a Mixing Reactor to Synthesize Crop Protection Agents

A mixer-drying reactor developed by amixon^® for a manufacturer of pesticides can process substances of varying consistency. Particularly with regard to differing degrees of filling, the reactor described here can be used particularly flexibly. The drug treatment takes place in various stages of synthesis and concludes with a vacuum mixed drying.

In the synthesis of active ingredients in pharmaceutical production or in the production of crop protection agents, the consistency of the product often changes during the mixing and drying process. Systems that also process different active ingredients must therefore have a high degree of flexibility. This requirement is met by a mixer-drying reactor that amixon has developed and manufactured for a well-known manufacturer of pesticides. The plant can process mixes with dusty, flaky and powdery consistency as well as pasty, muddy and viscoplastic goods.

Pumpable, gum-like, friable, dusty
This is particularly important in multi-purpose mixers, as it is safe to pass through tough plastic phases in many drying processes. Typical is the transition from a pumpable suspended mass to a viscoplastic, chewing gum-like substance. With a further reduced liquid phase content, the mass becomes friable and granular, then powdery jamming to free flowing, dusty. In a four step synthesis process, each step starts with dissolving the basic powdery chemical in a suitable liquid phase and concludes with a drying process in the vacuum contact dryer from. The fourth and final stage of the synthesis leads to crystallization. This is followed by several washes. At the end, the centrifuge-moist crystal mixture must be gently dried. This conical vacuum mixer is used in the production of highly pure active ingredients for pesticides. The mixing dryer is used here and also proves to be flexible with regard to the mixing processes: The plant is suitable both for the gentle homogenization of the mixed material and for intensive deagglomeration. In order to exclude foreign reactions and to ensure a constant quality level, the last drying stage takes place under fine vacuum at 0.133 mbar.

High purity and gas-tight
If the powdered material is to be mixed with other powder components before filling, this is done in the same apparatus. In the center of the conical-cylindrical mixing chamber, a mixing tool with a helical outer contour rotates. This conveys the goods along the vessel wall upwards, having reached the top, the goods flow downwards in the center. The mixer-dryer reactor delivers ideal mixing grades at fill levels of approx. 15 to 100%. Complete emptying of the container is achieved using the patented SinConvex^® mixing tool.

The vacuum mixer is capable of producing high-purity active ingredient preparations. The mixer is powered only from above and can be fully heated. The shaft seals of the mixing shaft and the cutting rotor are designed as a mechanical seal and gas-tight. The dead space-free working closure fitting at the end of the mixing space cone also has a particularly high gas-tightness. The mixing space of the reactor is made of Hastelloy C 22. This material has a high strength and is at the same time particularly corrosion resistant. The entire system complies with the principles of Good Manufacturing Practice (GMP) and FDA requirements. All qualification steps were done according to GMP. The complete documentation of development, production and commissioning also meets the high requirements of the pharmaceutical industry. The manufacturer has already developed and produced numerous mixing-drying reactors for chemical and pharmaceutical applications with container sizes from 1 to 25,000 liters, offering equipment for virtually any scale.

Learn more about the vacuum drying process and its applications. 

About the company: Made-to-measure mixers

The requirements for a preparation mixer are always individually shaped. For process testing, amixon^® has more than 30 test mixers in the Technika Paderborn, Memphis (USA), Osaka (Japan), Bangkok (Thailand), Tianjin (China) and Satara (India). As a single contract manufacturer, the manufacturer implements customer requests in detail, with a team of 130 employees at the sole production site in Paderborn realizing a high level of vertical integration.

The after-sales service team is responsible for the maintenance and testing of the equipment after commissioning. The "Amixon Excellent Service" is a worldwide concept with bases in Paderborn, Memphis, Osaka and Bangkok. In addition to the offer of "lifelong" equipment maintenance, the service employees, but also operators and developers are trained here in order to carry out tests and maintenance themselves.

Author: Matthias Böning, Managing Director and Head of Sales department, amixon GmbH