Mixing/Dispersion Equipment0 pages

From the La >
totheRealWorld: New Design in Mixing/Dispersion EquipmentAllows More Efficient Development and Scale-Up b >
W ork in a typical coatings lab is aimed atachieving a long list of goals in productdevelopment. But every aspect of busi-ness in the lab is also driven by a col-lection of chronic shortages. Space for equipment inthe lab is always tight, and virtually every lab manager
will tell you that his lab is under-funded.During the last few years, new directions in prod-uct development have added to the challenge ofmanaging R&D. The drive to reduce VOCs, both withwaterborne formulations and with formulations that
require lower solvent content, has introduced manynew variables in raw materials, special-purpose addi-tives, mixing/dispersion equipment, and processtechniques that must be considered in developingnew products.In this environment, any equipment that provides aboost in versatility and efficiency, and enables develop-ment engineers to be more productive, is a welcomeimprovement. A single machine that can do the work oftwo, three or even four machines can save space in the
lab and cut operating costs sharply.When a piece of equipment provides the tools neces-sary to quickly compare the advantages of competingmixing techniques using a method that is controlled,quantifiable, and projectable for scale-up ח its value in
the laboratory is far greater. It allows the developmentengineer to combine two dimensions of laboratory test-ing and development: to refine the formulation and
identify the optimal process for a new product. Rotor/Stator Mixer or High-Speed Disperser: Which is Best? Many coatings manufacturers have found that they canno longer safely presume that a traditional high-speeddisperser (HSD) is the best way to make contemporaryproducts. The rules have changed.Many have found, for example, that waterborne sys-tems require the higher shear of a rotor/stator mixer
to achieve a product with the desired properties
such as droplet size, stability, agglomerate size and
color development.Waterborne products are extremely vulnerable toair entrainment, and the familiar vortex created by
the HSD can cause serious foaming problems. Toreduce the foam, formulators can add a defoamingagent, which adds cost and can also affect otherproperties ח requiring more time and perhaps otheradditives. In such situations, the problem can be
averted by switching to a bottom-vortexing rotor/sta-tor mixer. Compared to the HSD, the rotor/statormixer generates an inverted vortex and much lesssurface violence, sharply reducing the air entrainedin the batch. In the manufacturing of solventborne
flexo and gravure inks, numerous ink makers havefound that a high-speed rotor/stator mixer can out-perform an HSD by a wide margin, saving time andproducing an end-product with superior color devel-opment and consistency.The same is true in many automotive-coatings appli-cations and in other applications where the goal is to By John Paterson / General Manager, Charles Ross & Son Co. size="-5">