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Specialty Mixing Equipment for the Plastics Industry
This article presents just a few examples of specialty mixing equipment used in plastics processing. Mixer selection is always formulation-dependent so partner with a reliable mixer supplier offering testing resources to validate a particular mixing strategy. For established processes, a careful re-evaluation of the mixing procedure will often reveal achievable steps for reducing not only cycle time and energy consumption but also waste/rejects, labor cost, cleaning and maintenance.
Polyvinyl alcohol solutions
Polyvinyl alcohol (PVOH, also referred to as PVA) is a versatile polymer that plays multiple roles in the manufacture of adhesives, sealants, cosmetics, paper, textiles and many other products.
Multi-Shaft Mixers are widely used in the preparation of PVOH solutions. Equipped with two or more independently-driven agitators working in tandem, Multi-Shaft Mixers deliver a robust combination of high shear agitation and laminar bulk flow within a wide viscosity range: from water-like consistency to several hundred thousand centipoise (cP).
The most economical design is the Dual-Shaft Mixer which features an anchor agitator and a high speed disperser. Turning at tip speeds around 5,000 ft/min, the saw-tooth disperser blade creates a vigorous vortex that quickly wets out dry PVOH powders or pellets as they are added into warm or room-temperature water (a defoamer may be pre-blended into the water). The sweeping action of the low-speed anchor agitator enhances the exchange of materials within the vessel, continuously “feeding” the disperser blade with fresh product.
For added versatility and shear capability, a rotor/stator assembly may be supplied in addition to the disperser blade and anchor agitator. This Triple-Shaft Mixer design is particularly ideal for applications where other raw materials are dispersed into the PVOH solution and a very tight particle size distribution is required in the finished product.
Plastisols
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