Fiber surface saturation as a strategy to optimize dual-polymer dry strength treatment, Solutions! & TAPPI JOURNAL, November 2003, Vol. 2(11) (156KB)

ABSTRACT: Adding the first component of a dual-polymer treatment at a level corresponding to saturation of the fiber surface optimized the compression strength of unbleached kraft handsheets. The saturation level of poly-diallyldimethylammonium chloride (poly-DADMAC), determined by streaming current analysis, also coincided with a maximum in water retention value (WRV) and a minimum in the light scattering coefficient of the paper. We propose idealized descriptions of the polymer interactions to explain the observations.
Application: This study reveals a strategy to obtain the maximum strengthening effect of a dual-polymer dry-strength treatment, with benefits extending to the virgin and recycled paper made from the same pulp.
Polymeric wet-end additives help meet customer requirements for the dry strength of paper, especially when recycled kraft fibers are used. This study showed how a dual-polymer dry-strength treatment can compensate for the drying-induced loss of inter-fiber bonding ability of unbleached kraft fibers. The treatment involved sequential addition of a highly cationic, linear polymer, poly-diallyldimethylammonium chloride (poly-DADMAC), followed by anionic carboxymethylcellulose (CMC).
     Titration tests showed that at their level of saturation, the solid surfaces in the pulp slurry were able to adsorb 2-4 times as much poly-DADMAC, compared to the amount just sufficient to neutralize the negative charge at the surfaces of the fiber fines and fibers present in the pulp slurry.
     This same saturation level of poly-DADMAC also resulted in a maximum compression 		strength of the resulting unbleached kraft handsheets, when the second chemical additive, CMC, was applied at a constant level of 2% based on fiber mass. The same benefits were seen when the same fibers were redispersed and formed into a second generation of sheets without further chemical addition. Lower compression strength was observed both at lower and at higher levels of the cationic polymer. The saturation level of poly-DADMAC also coincided with a maximum in water retention value (WRV) of the redispersed pulp and a minimum in the light scattering coefficient of the recycled paper. S!
Martin A. Hubbe and Zhang are with North Carolina State University, Department of Wood and Paper Science, P. O. Box 8005, Raleigh, NC 27695-8005; Jackson is with Tulane University, Department of Civil and Environmental Engineering, MR Box 1551, 31 McAlister Dr., New Orleans, LA 70118, USA. Email Hubbe at m_hubbe@ncsu.edu.

Author: Hubbe, M.A., Jackson, T.L., Zhang, M.
Fiber surface saturation as a strategy to optimize dual-poly
Fiber surface saturation as a strategy to optimize dual-polymer dry strength treatment, Solutions! & TAPPI JOURNAL, November 2003, Vol. 2(11) (156KB)
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