The Effect of Surfactants on Kraft Pulping of Pinus Pinaster

In order to ascertain the influence of surfactants in the delignification of Pinus pinaster wood and the bleachability of the resulting pulps, 17 surfactants from four families of surfactants were tested, namely: cationic, anionic, non-ionic and amphoteric. The best results in terms of improved delignification, lower screen rejects and lighter coloured unbleached pulps were obtained with the non-ionic surfactants. When compared with the reference, these cooks exhibited a decrease of up to 6.2% in Kappa number and 39% in screen rejects, and up to a 9% increase in the unbleached pulps reflectance factor. The most promising surfactants in terms of reflectance factor were poly(ethyleneglycol) 1000-4%, block copolymer poly(ethyleneglycol) - poly(propyleneglycol) 1100- 4% and poly(oxyethylene) 100 stearyl ether-1%. It was also established that the use of surfactants as cooking additives did not influence the bleachability, but allowed savings of chlorine dioxide in the first bleaching stage (about 5.2%), with consequent environmental and economical benefits.