twin screw extruders regarding powder coating manufacturing,
process for manufacturing a powder coating comprising the steps of: Preparing a powder coating premix comprising a resin and optionally a crosslinker therefor; feeding the premix through a melt extruder, wherein the melt extruder conditions comprise a temperature of from 100 DEG to 200 DEG C and a pressure of from 1 to 16 bar; cooling the extruded material; and comminuting it to fine particles, said process being characterized in that from 1 to 25 wt. % (based on the weight of said premix) of a suspension or dispersion of a particulate material in water is added to the melt extruder.
Powder coatings have become widely established due to their ease of use without the need for
solvents, together with high physical strength and a range of surface finishes. Formulations based on
premixes of epoxy, polyester, acrylic and polyurethane thermosetting resins are compounded
with a variety of pigments, fillers, curing agents, flow modifiers etc. to suit specific end-use
requirements. During the compounding process, the resin is melted and the ingredients are mixed
uniformly to produce a homogenous melt which is subsequently cooled and flaked before grinding
into a fine powder and classifying.
The compounding process is well suited to the unique operating and mixing behaviour of the corotating twin screw extruder. This report outlines the main design, performance and operational characteristics of this type of extruder with particular emphasis on processing thermosetting Powder Coating materials. The major advances in
these extruders that have allowed for substantial output improvements are also discussed.