Lignosulfonate adsorption onto recycled unbleached kraft pulps previously treated with poly(allylamine hidrochloride)

GALVÁN, MARÍA V.; MOCCHIUTTI, PAULINA; SCHNELL, CARLA N.; ZANUTTINI MIGUEL A.

San Pablo

Congreso; 45o Congresso e Exposição Internacional de Celulose e Papel; 2012

ABTCP - CIADICYP

The effects of a double polyelectrolyte adsorption of poly(allylamine hydrochloride) (PAH) and lignosulfonates (LS) on a recycled unbleached softwood kraft pulp were studied. The effects of a multilayer adsorption (3 layers) were also studied using PAH as the last layer. The LS was classified by ultrafiltration (cut-off 10kDa), freeze-dried and the charge density was determined using the conductometric titration method. Then, adsorption isotherms of LS on untreated and on previously PAH-treated pulps at neutral pH, and different ionic strengths were built, and the effects of the amount of PAH on LS adsorption were considered. The amount of PAH was indirectly determined using the polyelectrolyte titration method, and the amount of LS was also indirectly determined by UV spectroscopy at 280 nm and by the modified Pearl-Benson method. It was found that a PAH pretreatment was necessary to achieve high levels of LS adsorption at room temperature and short adsorption times. The higher the amount of PAH adsorbed, the higher was the amount of LS adsorbed as the second layer. On the other hand, the addition of LS on a previously PAH treated pulps increased the uniformity of the sheets compared to PAH treated pulps using a PAH dosage corresponding to the saturation level of the fiber charges. Handsheets from the fibrous fraction were prepared and analyzed by scanning electron microscopy (SEM). Then, the effects of low PAH and LS dosages on the papermaking properties were evaluated. It was found that the tensile index, short compression strength (SCT), and concora medium test (CMT) were improved, but these improvements were mainly due to the presence of PAH.