Modified PCC Fillers to Reduce Sizing Demand and Improve Runnability, 1990 Papermakers Conference Proceedings

Robert A. Gill--Adequate internal sizing of alkaline papers is an important issue for most papermakers. Early development of cellulose reactive sizing agents resulted in poor control of sizing and excessive wet end deposits. Present sizing systems have improved greatly but problems still occur, mainly due to the overuse of sizing materials because high surface area materials (e.g., filler and fines) found in the wet end adsorb the size and render it ineffective. Specially modified precipitated calcium carbonate (PCC) fillers, which can be synthesized at an on-site PCC satellite plant, have been developed to make the sizing of filled sheets more efficient. Laboratory results have shown that by using a chemically modified PCC filler, sizing demand can be reduced by one-half. Results show that this type of filler product gives the papermaker the opportunity to increase his filler level in the sheet and reduce the amount of wet end size, thereby alleviating many sizing problems, while still being able to utilize a high opacifying filler. The result is a cleaner wet end system (less sizing agent used), reduced down time (fewer size-related breaks), and improved profitability (filler for fiber substitution, reduced use of sizing materials, increased productivity,...).