Processing, June 2018

Step 1 of old process Step 2 of old process New consolidated process Comments JUNE 2018 www processingmagazine com 41 Prepare liquid pre polymer in a reactor Transfer pre polymer into a mixing vessel Disperse llers plasticizers and other additives into the prepolymer under vacuum Prepare pre polymer and mix nished product in a vacuum rated multishaft mixer reactor see Figure 1 The new process was rst tested in a laboratory setting and later scaled up to a 300 gallon multishaft mixer Mix highly lled epoxy formulation in a double planetary mixer followed by a let down step to lower viscosity Continue mixing using a saw tooth disperser to provide extra shear needed for completion Process the formulation from start to nish in a hybrid planetary mixer equipped with two agitators A rectangular blade and a high speed disperser see Figure 2 The manufacturer was able to move away from a cumbersome two step process that was labor intensive Cycle time was reduced from one hour to 20 minutes Add pigment powders into liquid vehicle Batching tank is equipped with a saw tooth disperser Mill pigment resin premix in a media mill for four hours to achieve an off the gauge dispersion Perform powder wet out and deagglomeration in a single vessel using a batch style ultra high shear mixer The same end point is achieved in 30 minutes total mix time see Figure 3 Prepare medical gel base in a bench top chilled glass reactor Blend active ingredient granular solid into the sterile gel in a single planetary mixer Produce gel and thoroughly mix active ingredient in a laboratory double planetary mixer see Figure 4 Double planetary mixers are ideal for viscous and sticky applications Sanitary design features ensure product purity and easy cleanup between batches Mix thickened solution in a 2000 gallon stirred reactor Cycle time is up to six hours or more because operators have to slowly add gum powders and other thickeners as the batch is vigorously agitated Adding the gums too quickly creates lumps which ruin the product Charge talc powders into the reactor The powders tend to oat on the surface of the thickened solution As a remedy recirculate the material through an inline rotor stator mixer for hours This step allows the powders to gradually fold into the mixture Introduce all powders to the 2000 gallon tank utilizing an inline mixer specially designed for powder injection see Figures 5 and 6 By replacing its inline rotor stator with the powder injection mixer the coatings manufacturer was able to introduce all solids sub surface which eliminated the lumping and oating issues The simple mixer upgrade drastically reduced cycle time by more than 50 percent Figure 6 How a powder induction mixer works The liquid stream blue enters the mixer and immediately encounters the powder addition Drawn by a powerful vacuum generated by the ported rotor powders yellow are injected directly into the high shear zone and dispersed instantaneously The resulting mixture green is expelled centrifugally through the stator openings at high velocity Conclusion It is important to note that mixing results are always formulation dependent Whenever practical perform simulation trials using your own raw materials to con rm a new mixing strategy Ask your mixer supplier about testing and demonstration services or rental equipment which you can use for trial production runs in the convenience of your own plant Lastly a mixers control system plays an important role in optimizing overall e ciency A well speci ed control system minimizes human errors improves batch to batch consistency and lessens downtimes Recipe controls also enable automatic data logging Supervisory control and data acquisition SCADA packages support complete traceability and make it easier to pool statistical information on workloads bottlenecks and maintenance history Source both mixer and controls from the same vendor to ensure seamless execution Christine Banaszek is the sales manager at Charles Ross Son Company manufacturer of specialty mixing and blending equipment As an application engineer at the corporate headquarters in Hauppauge New York she has worked at the Ross Test Development Center and published many articles and white papers in mixing and blending technologies applications and best practices She holds a degree in chemical engineering Charles Ross Son Company www mixers com Figure 5 Inline rotor stator mixer designed for high speed powder induction Table 1 Examples of multiple mixing steps consolidated with a single mixer