Concentric mixers also known a co-axial mixers offer independently shaft-in-shaft type stable high viscosity mixing. The outer impeller, in this case a Greaves anchor scraper with helical ribbon forces material from the vessel walls and offers positive up-thrust axial flow. The counter-rotating central impellers offer mixing by forcing the viscous fluids under high impeller tip speed and delivering positive axial down-thrust. A flow pattern evolves inside the full vacuum mixing system controlled by variable speed and shafts sealing with two double mechanical wet lubricated seals.
The process involved in the manufacture of high temperature vacuum adhesive mixing reactors requires high levels of mixing knowledge and a detailed technical approach to torque, shaft seals and impeller geometry and speed. Combining this with jacket design temperatures of over 2500C and full vacuum conditions (de-gassing, used to remove air from product) often requires robust engineering, particularly when adhesives aim to bond of the contact parts together.