Process Control in UV Curing – In-Line Monitoring of the Acrylate Conversion by Near-Infrared Spectroscopy

By Tom Scherzer, Sabine Muller, Reiner Mehnert, Arne Volland, Hartmut Lucht

Process analytical tools have been used in the chemical industry for a long time in order to control the actual state of the process and the quality of the products made. In recent years, such systems have also been increas­ingly employed for the monitoring of various polymerization reactions where they can help to optimize the efficient use of energy and raw materi­als, and also to ensure that the properties of the produced polymers are within the given specification. Process monitoring and control would also be interesting for radiation-induced polymerization reactions.

The most important parameter for process and quality control of UV and electron beam (EB) curing processes is the conversion of the (meth)acrylic double bonds, since that determines all other functional properties of a coat­ing such as scratch and abrasion resistance, hardness, weathering resistance, chemical stability, the content of extractables, etc. Moreover, for further processing of the coating a sufficient conversion is re­quired, and wipe resistance must be attained before stacking or winding.