Battenfeld-cincinnati is offering its new PWE 250 planetary roller extruder for production of ethylene vinyl acetate (EVA) sheet for solar panels. Enormous outputs of up to 2tons/h can be achieved, says the Austria-based company.
For the production of EVA sheet, the plastic granulate must be plasticized gently at no more than 150°C and mixed with several additives. A planetary roller extruder is the ideal machine for this purpose, since it already achieves a highly effective dispersion and homogenization performance at low processing temperatures. This is due to its special process technology design, explains battenfeld-cincinnati.
A planetary roller extruder consists of a conventional single screw as feed section and a planetary gear section. The latter consists of a fixed roller cylinder with internal gear teeth, a teethed main spindle driven by a motor, and the revolving planetary spindles. All components of the planetary roller extruder are fitted with helical gears cut at an angle of 45°, with the teething of the planetary spindles being arranged at a counter-pitch to the other components. The machine concept of planetary roller extruders is well known from calender feeding in PVC processing, since, here also, gentle plasticizing at pre-defined low temperatures is a vital prerequisite.
The planetary roller extruder is the optimal equipment for PVC processing as well as numerous alternative processes, such as EVA sheet production due to its high output, the machinery supplier notes. While single screw extruders of comparable size reach up to 800kg/h and twin screw extruders up to 1,200kg/h in output, the planetary roller extruder achieves a performance of up to 2,000kg/h. 15 extrusion lines are already in operation worldwide.
Apart from perfect transparency, optimal mechanical key values and low shrinkage are also important criteria for EVA sheet used in photovoltaic modules. battenfeld-cincinnati says its Multi-Touch roll stack from the complete line supplier meets these requirements. The concept consists of a two-roll roll stack for preliminary calibration and up to seven post-cooling rolls. This ensures even sheet tolerances, a uniform thickness profile, as well as optimal transparency, good flatness with only few orientations, and strong mechanical properties.
Today, EVA has a market share of about 90% in the steadily growing solar energy market, according to battenfeld-cincinnati.