Bottom spray film coating

Bottom-spray film coating is accomplished by means of the Wurster system, originally developed by Dr. D.E. Wurster (Wurster 1959). A scheme of the bottom-spray fluid bed is given in Figure 16.4. 

Fig. 9. A bottom spray (Wurster) film coating, surface and...

In a spray-coating process, an inert soluble core composed of sugars, salts, polymers, or a combination of these are flnidized within a fluid bed and an enzyme solution is sprayed on the core to make a continuous film on the surface. The process can be carried out either in a top spray mode, that is, where the spray nozzles are placed in the top of the fluid bed chamber or as a bottom spray... 

A butyl rubber sheet, or high temperature plastic film, is held taut aeross two vertieally stacked metal frames or rings, which are themselves sealed between the two platens of a press. The requisite number of prepreg plies is formed into a preform, which is sandwiched between sheets of PTFE coated glass cloth, or a non-perforated PTFE film with a perforated PTFE film next to the preform, and the paek placed on a steel plate sprayed with a fluorocarbon release agent and positioned on the bottom heated platen of the press. The preform... 

Some major applications are thickener in paint industry paper coating, hair sprays shampoos adhesives biodegradable products for the feminine hygiene diapers bottoms water soluble packaging films (detergents, disinfectants, scouring powder, pesticides, fertilizer, laundry, etc.) fibers for concrete reinforcement lubricant for eye drops and contact lenses and material for chemical resistant gloves. 

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