New Approach to Moisture and Curl Control on Silicone Release Liners, 1993 Polymers, Laminations & Coatings Conference Proceedings

David A. Leeman

Silicone coatings must be cured at elevated temperatures. Curing requires that the coating (and it’s paper substrate) spend more time in the dryer, and at higher temperatures, than would otherwise be required to simply evaporate the silicone’s carrier solvent. Therefore, upon exiting the dryer the paper substrate is often overdried. In addition, a single sided coating causes the web to curl toward the coated side. To combat low moisture levels and coat-side curl, remoisturizing systems apply moisture to the uncoated side, fortunately having the additional benefit of reducing coat-side curl. However, it is not unusual for the lay-flat condition to be reached before the desired moisture level is reached. At this point, adding more moisture to the uncoated side has the undesirable added effect of inducing curl toward the uncoated side. A solution is to add moisture to the coated side as well as the uncoated side. In practice this has not been possible due to the hydrophobic nature of the silicone coating. However, recent pilot line trials, using a new steam application device, the Steam-Foil(R), Coanda actuator have shown steam will penetrate a silicone coating adding up to 1.5% moisture to the paper substrate. Similar moisture increases have been recorded for C2S silicone products. This paper describes the new steam application device and discusses documented system performance.