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E-BEAM DRUM TRANSFER: PROCESS TO ELECTRON IRRADIATE A PSA IN THE ABSENCE OF A BACKING.

James DiZio, Senior Research Specialist, 3M, St. Paul, MN
Douglas Weiss, Senior Research Specialist, 3M, St. Paul, MN

Extruded pressure sensitive adhesives (PSAs) are sometimes post-crosslinked via electron radiation. Crosslinking the PSA by electron radiation increases polymer molecular weight and thereby enhances shear strength. Unfortunately, a problem is encountered when electron irradiating a PSA on a backing; the electrons not only interact with the adhesive but also penetrate into the backing, often degrading the backing. Ionizing (electron) radiation degrades most organic tape backings such as cellulose, PVC, silicone, Teflon, or polypropylene. In the quest to develop a method that would completely eliminate degradation to the backing, we created a process entitled “electron beam drum transfer.” Using the ebeam drum transfer method, the PSA in a tape construction can be crosslinked while completely avoiding radiation exposure and damage to the tape’s backing. An added benefit to this method is that any electron beam voltage and dose can be chosen to elicit a desired level of crosslinking and gradient through the PSA, without harming the backing.