Mini-Encyclopedia of Papermaking Wet-End
Additives and Ingredients, their Composition, Functions, Strategies for Use
Composition: The most widely used detackifier is talc. The chemical formula of pure talc is magnesium silicate Mg3SiO4O10(OH)2. Talc is a soft mineral with a relatively water-hating surface. These two attributes, softness and hydrophobicity are easy to observe when one pinches some talcum powder and then releases it onto the surface of water in a sink. In addition to talc, there are a number of proprietary chemical products that also are marketed as detackifiers. The common feature of these chemicals is that they are weak polyelectrolytes (sometimes cationic), and they have a tendency to form a film at the surface of tacky or hydrophobic suspended matter.
Function: Reduce the tackiness of pitch-like materials or stickies so that they have less tendency to form agglomerates or deposit onto papermaking equipment or create spots in the product
Strategies for Use: Some of the key rules of thumb for talc are (a) disperse it well, (b) add it the those process streams that are giving the biggest problems, (c) add it early enough to the process with enough agitation, and (d) add enough. If too little talc is used, the talc is merely incorporated into deposits and agglomerates of tacky materials. It makes sense also to use an effective retention aid program in order to retain the talc (and any attached tacky materials), purging the problem from the wet-end system. Similar considerations apply to the use of organic detackifiers. In either case, the best place to start in dealing with deposit problems is chemical analysis. Several major papermaking research groups (including this one) have equipment for lab-scale simulation of pitch and stickies problems.
Cautions: Talc is a potential source of dust. Consult MSDS information for each detackifier. Lock-out procedures and air quality checks are required when tanks and headboxes must be entered to inspect deposits.
|Interaction of talc with tacky, hydrophobic substances suspended in water|
PLEASE NOTE: Users of the information contained on these pages assume complete responsibility to make sure that their practices are safe and do not infringe upon an existing patent. There has been no attempt here to give full safety instructions or to make note of all relevant patents governing the use of additives. Please send corrections if you find errors or points that need better clarification.
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This page is maintained by Martin Hubbe, Associate Professor of Wood and Paper Science, NC State University, firstname.lastname@example.org .