Chemical Industry Case Study: High Speed Despersion of Titanium Dioxide

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Find the solution for one of the toughest mixing applications in the chemical industry, high speed dispersion of titanium dioxide. Read this case study on the Process, the Problem and the Solution.

Find the solution for one of the toughest mixing applications in the chemical industry, high speed dispersion of titanium dioxide. Read this case study on the Process, the Problem and the Solution.

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  • 1. High Speed Dispersion of Titanium Dioxide The Advantages Introduction The Process The Problem The Solution HIGH SHEAR MIXERS/EMULSIFIERS CHEMICALS Solutions for Your TOUGHEST MIXING Applications in APPLICATION REPORT
  • 2. Titanium dioxide is most commonly supplied in powder form but may also be predispersed in oil or aqueous systems.The diversity of applications leads to many different methods of processing, however process requirements are basically the same: • TiO2 is usually supplied in powdered/premicronized form and particle size reduction (grinding) is not applicable in most cases. • To maximize opacity and gloss properties,TiO2 must be fully dispersed and evenly distributed throughout the product • Dust/solvent emissions must be minimized The following problems can be encountered when using conventional mixers and agitators: • On addition to the water, solvent, varnish or other media the particles tend to re-agglomerate. • Conventional mixers cannot break these down effectively • Long mixing cycles are required to obtain uniform dispersion. • Extended processing time contributes to solvent emissions. • Conventional systems are difficult to clean. • Powder has to be added under controlled conditions which can be time consuming and leads to increased dust emissions Titanium dioxide (TiO2) is chemically inert and has exceptional opacity and whiteness. These properties have led to its widespread use in many industries, illustrated in table 1 CHEMICALS The Process The Problem High Speed Dispersion of Titanium Dioxide Industry Application Ceramic Colorant, ingredient of glazes Cosmetic Sun protection Paint Used in watercolors, enamels, emulsion, gloss, exterior etc. Paper Paper filler & coating Pharmaceutical Tablet coating Textile Delustrant additive, whitener Table 1: Some uses of titanium dioxide
  • 3. CHEMICALS The high speed, high shear operation of a Silverson mixer provides the solution to these problems. The rotor/stator workhead rapidly disperses the TiO2 particles into the surrounding liquid, leading to a more uniform product and shorter processing times. This can be achieved using a batch mixer immersed in the processing vessel, or by the addition of a Silverson In-Line mixer to an existing process in a recirculation system as illustrated The Solution • The TiO2 is added to the aqueous or organic solvent at a much faster rate, reducing dust emissions. • The rotor/stator workhead provides an intense shearing action capable of breaking down even hard agglomerates. • Operation can be carried out in a closed system, reducing solvent emissions. • It is more energy efficient and economical. • The shorter processing times required to obtain a uniform dispersion reduce wear and therefore maintenance and spare part costs. The batch size, formulation, type of ingredients and the viscosity of the end product dictate which machine from the Silverson product line is best suited to individual processing requirements. See overleaf for details: The Advantages 1.The vessel is charged with water or other solvent. The In-Line mixer is started 2.TiO2 is added to the vessel once circulation of the fluid has started 3. Powder and liquid ingredients are drawn into the In-Line mixer or Multishear mill 4. Particles are “milled” in the gap between each rotor and stator, this progressively reduces particle size and breaks down agglomerates 5.The TiO2 is fully dispersed into the surrounding liquid and returned to the vessel by the self-pumping In-Line mixer Agitator for in-tank uniformity
  • 4. Silverson Machines,Inc. 355 Chestnut Street, East Longmeadow, MA 01028 Ph: (413) 525-4825 • Fax:(413) 525-5804 • Information contained in this report is believed to be correct and is included as a guide only. No warranty is expressed or implied as to fitness for use or freedom from patents. Silverson Machines reserve the right to change product specification without notice. Issue No. 21CA2 Inner rotor subjects materials to initial mixing action and acts as prime mover for the product. 3 or 4 sets of concentric rotor teeth produce intense high shear Rotor Configuration Silverson In-Line Mixer Agitator for in-tank uniformity Pipeline return below fluid level to prevent aeration Centrifugal Pump Powder Feed Hopper Venturi Assembly In-Line Mixer Liquid in Product out High Shear Batch Mixers: • Suitable for batch sizes up to 400 gallons • Can be used on mobile floor stands • Sealed units available to control solvent/dust emissions Flashblend • Ideal for larger batches • Capable of rapidly incorporating large volumes of powder • Minimized aeration. • Minimized cleaning requirements. • Minimum operator input required. • Easily automated. High Shear In-Line Mixers • Ideal for larger batches • Aeration free • Easily retro-fitted to existing plant • Self pumping • Can be used to discharge vessel Multishear Mill and Multi-stage In-Line Mixer Offer the advantages of In-Line mixers plus: • Designed specifically for dispersion of harder pigments and dyestuffs. • The intense high shear imparted by the series of concentric rotors and stators can eliminate the need for conventional milling. • Where conventional milling is required, the product supplied by the Multishear Mill or Multi-stage In-Line mixer allows the mill to operate with greater efficiency and reduces the number of passes required.