Drainage Aids Containing Bound Phosphorus, 2000 Papermakers Conference Proceedings

Peter C. Dalidowicz--The paper industry utilizes starch phosphate derivatives as wet-end additives to attain desired paper properties such as strength, retention, and drainage. One of the major problems associated with the use of drainage aids is overflocculation. Drainage and retention performance is optimal near the point of zero net surface charge on the fiber. Optimization of the drainage process involves an effective balance of the overall system charge. Improved drainage performance can be directly correlated to the bound phosphorus levels in amphoteric starches. It has been shown that increasing the bound phosphorus levels and ultimately the anionic/cationic (A/C) molar ratio in an amphoteric starch affords greater drainage response. Most effectively, amphoteric starch phosphate derivatives should have a molar A/C ratio of from about 0.12 to 0.55 moles of anionic phosphate groups per mole of cationic groups. Furthermore, these derivatives should be substituted with cationic groups to such an extent that their degree of substitution (D.S.-average number of cationic groups per anhydroglucose unit of the starch) ranges from about 0.01 to 0.08.