Detackification of Stickies Using Plasma-Spark Technology, 2000 Papermakers Conference Proceedings

Howard Corcoran, Dong-Jin Sung, Sujit Banerjee--A novel process based on plasma-spark technology has been developed that detackifies pressure sensitive adhesives (PSAs), pitch, and hot melts (polyvinyl acetate, PVAc). The proc-ess is based on the discharge of an underwater spark (50,000A, 5,000V, 150 msec) which gener-ates a shock wave, UV, hydroxyl radicals, and other oxidants. The technology is currently used to kill zebra mussels in water intake pipes. A paper mill in the Northeastern US has an operating unit. PSA and PVAc films were made on stainless steel coupons, paper, and board. Samples were placed in either a 130-liter or a 10-liter tank filled with water or whitewater and studied un-der various recycle process conditions. Treated samples and controls were then measured for tack, water drop contact angle, and surface chemical composition. The tack of the PSA films de-creased, as did the water contact angle after only a few sparks. Essentially, sparking removed tackiness. X-ray photoelectron spectroscopy analysis showed that both the PSA and hot melts had significant increases in oxygen bonded to the surface. Sparking also improved the scre-enability of PSA suspensions. The fundamentals of detackification by plasma-spark were investigated, and evidence is presented that free radicals, generated by the shock wave, are available to react on the surface of the PSA and hot melt. The XPS results indicate that the mechanism involves oxidation of the polymer surface. Further experimentation demonstrated that UV and the pressure from the shock wave do not have a major effect on detackification.