Stickies in Recycle Pulp for Use in Fine Paper-The Search for a Precise Method

The use of lower grade recovered paper has increased significantly as general demand for recycle content has increased. These lower grades receive little sorting, and are a mixture of paper products from egg cartons to magazines and Old Corrugated Containers (OCC). This brings in a variety of contaminants, stickies are only one type yet they can cause serious problems on the papermachine. Stickies are defined as anything that becomes tacky when they are heated, generally they are polymer based adhesives. Stickies negatively impact the papermaking process, the quality of the product, and the cost of operation. They are not completely removed during cleaning or deinking (coarse screens - 88% efficient, fine screens - 95% efficient). Water conservation efforts leading to closed water systems cause a build-up of stickies in the water stream. Clogged forming wires, reduced heat and liquid transfer on press and dryer felts, build-up on doctor blades, and sheet tears on the winder are all problems created by stickies. The replacement costs of a papermachine wire or a felt are high, and the 8 hours to replace a felt at $50,000/hr lost production is the most significant. Quality specifications for recycle pulps to be used in fine paper printing and writing grades require stickies to be < 15="" mm="" 2="" g="" of="" od="" pulp.="" a="" search="" for="" a="" method="" to="" quantify="" stickies="" at="" this="" low="" level="" of="" detection,="" in="" a="" precise="" and="" timely="" manner,="" has="" led="" to="" the="" statistical="" evaluation="" of="" three="" methods.="" they="" range="" from="" using="" a="" dissecting="" needle="" to="" count="" stickies="" by="" hand="" to="" the="" use="" of="" sophisticated="" image="" analysis="" systems.="" the="" time="" to="" complete="" one="" test="" can="" range="" from="" 30="" minutes="" (hand="" counting)="" to="" 2="" hours="" (scanner),="" making="" the="" later="" test="" undesirable="" for="" mill="" applications.="" method="" variability="" increases="" when="" stickies="" are="" reported="" in="" units="" of="" area="" per="" weight="" of="" sample="" versus="" the="" number="" of="" stickies="" per="" weight="" of="" sample.="" there="" is="" more="" precision="" in="" reporting="" the="" number="" of="" stickies="" vs.="" area="" of="" stickies,="" while="" the="" area="" is="" a="" better="" representation="" of="" the="" amount="" of="" contamination="" present.="" the="" size="" of="" the="" stickies="" present="" can="" vary="" depending="" on="" the="" raw="" material,="" so="" two="" pulps="" can="" have="" the="" same="">