Nordson presents new valve assembly for extrusion coating applications
The adhesives and coating technology experts of the Nordson Corporation, which is based in Westlake (OH), USA, have unveiled the new PolyStream assembly – a hands-free system that uses closed-loop control to maintain back pressure within a desired range for coating and laminating. According to the company, it is the first such system to provide closed-loop control, minimising human error and the possibility of injury when making manual adjustments.
Although extrusion coating operates at higher melt temperatures than other extrusion processes and requires use of a back pressure valve to reach these temperatures, excess back pressure can lead to polymer degradation. Installed between the extruder and the die, the new patent-pending EDI PolyStream motorised valve assembly uses closed-loop control to maintain back pressure within a range targeted to ensure optimal processing. The drive for the valve responds to a controller that receives a continuous flow of signals from a pressure transducer, causing the valve to open at varying degrees in accordance with whether back pressure is trending too high or too low. When the valve reaches its limit of opening as a result of excessive contaminant build-up on the filtration screen, an automated warning indicates that it is time to change the screen.
“The PolyStream valve assembly is the first completely hands-free system for regulating back pressure in extrusion coating,” said Sam G. Iuliano, business development manager for polymer dies. “Back pressure conditions are affected by numerous factors and are in a constant state of flux. By making operator intervention unnecessary, our new system helps to ensure coat weight consistency, adequate adhesion to the substrate, and a high level of product quality.”