IS THE EXTRACTIVES PLAY ANY ROLE IN COLORING PULPS FROM Pinus pinaster\ulcorner

Pulps from Pinus pinster were obtained using classical and modified kraft processes of pulping with the aim objective of establishing whether the extractives contribute in inducing the dark colour of the unbleached pulps from this specie. The methodology adopted here was based on carrying out two set of experiments. The first one consisted on cooking extractive-free wood chips whereas the second one was devoted to the pulping of wood in the presence of a surfactant. The colour of the pulps thus obtained were compared to that of the pulps prepared from initial wood cooked without any modification. In the first set of experiments, the wood chips were submitted to extraction wit different solvent sand acetone and toluene/ethanol appeared to be the most efficient, since the pulps obtained from wood previously extracted by this solvent showed that the brightness of pulps increased by more than 12% and the kappa number decreased by about 4 points. In second set of experiment, the wood chips were cooked in the presence of non-ionic surfactants from poly(ethlene), PEG, and poly(propylene) glycol, PPG, homopolymers and copolymers with molecular weights ranging from 400 to 10000. The most promising tensio-active compounds were PEG and a block copolymer PEG-PPG-PEG with molecular weight of 1000 and 1100, respectively. The optimal concentration of the surfactants was about 4%. The kappa number of these pulps lowered significantly, i.e. from 50 for the reference to 39 for the pulps obtained by kraft 50 cooking in the presence of 4% of PEG 1000.