(102b) Wet Stirred Media Milling of Organic Crystals: Interactions between Product Formulation, Grinding Media Wear and Colloidal Stability | AIChE

(102b) Wet Stirred Media Milling of Organic Crystals: Interactions between Product Formulation, Grinding Media Wear and Colloidal Stability


Flach, F. - Presenter, Technische Universität Braunschweig
Breitung-Faes, S., TU Braunschweig
Kwade, A., Technische Universität Braunschweig
Wet stirred media milling of organic crystals: Interactions between product formulation, grinding media wear and colloidal stability

F. Flach, S. Breitung-Faes, A. Kwade

Institute for Particle Technology, Technische Universität Braunschweig, Volkmaroder Str. 5, 38104 Braunschweig, Germany, f.flach@tu-bs.de

Wet stirred media milling is a common technology to produce fine particles. Recent developments are focused on the production of organic nanoparticles for different applications, e.g. pharmaceuticals, high quality printing inks or fine chemicals. General specifications of those products are well defined particle size distributions and high purity standards. In particular, contaminations, like mill and grinding media wear, represent a critical quality attribute which determines product quality and production costs.

Latest investigations on fine grinding processes of organic particles revealed new insights into the mechanisms of grinding media wear generation. In contrast to former investigations on “hard” inorganic products (minerals, ceramics, …) other specific dependencies were identified. Machine parameters influence wear characteristics, a lower hardness ratio between product and grinding media is less advantageous and especially the young´s modulus of the grinding media has a significant impact [1]. Additionally, the product particles and the used steric stabilization additives provide much potential to reduce wear rates by damping of grinding media collisions. This effect can be enhanced by controlling particle-particle interactions in order to adjust a certain degree of agglomeration. By stressing agglomerated particles more collision energy is transferred into the deformation and breakage of agglomerates and the applied stress intensity is assumed to be closer to the optimum one which is linked to minimum contamination values [2].

Wear particles do not only represent a contamination of the product suspension, they may also lead to the agglomeration of product particles. Investigations have shown that due to different surface charges the formation of heteroagglomerates between product and wear particles is possible. Heteroagglomeration can be controlled by formulation parameters i.e. pH-adjustment or stabilizer choice as well as by adapting the grinding media material [3].

Overall, the results show that especially formulation parameters have great potential for the reduction of product contamination in fine grinding processes of organic crystals. In addition the targeted adjustment of the product formulation enables also the control of interactions between product and wear particles.

[1] F. Flach, C. Konnerth, C. Peppersack, J. Schmidt, C. Damm, S. Breitung-Faes, W. Peukert, and A. Kwade, "Impact of formulation and operating parameters on particle size and grinding media wear in wet media milling of organic compounds – A case study for pyrene," Adv. Powder Technol., 2016.

[2] S. Breitung-Faes and A. Kwade, "Use of an enhanced stress model for the optimization of wet stirred media milling processes," Chem. Eng. Technol., vol. 37, pp. 819-826, 2014.

[3] F. Flach, S. Breitung-Faes, and A. Kwade, "Grinding media wear induced heteroagglomeration of electrosteric stabilized particles," Colloids Surf., A, vol. 522, pp. 140-151, 2017.