Abstract

The effect of different pulping conditions, active alkali (15% and 20% AA), H-factor (130 to 2360) and cooking temperature (155°C and 165°C) on the methylglucuronic (MeGIcA) and hexenuronic (HexA) acid content of kraft pulps of Chilean Eucalyptus globulus were evaluated. The initial amount of MeGlcA in wood chips was 255 mmol/kg wood and after pulping the residual amount of MeGIcA was approximately 110 mmol/kg pulp (on a wood basis). In cookings with 15% AA, the HexA content increased to 70 mmol/kg pulp with no decrease with increasing H-factor. In cookings with 20% AA, the HexA content in pulps reached values of 60 mmol/kg pulp followed by a constant decrease with increasing of H-factor. For bleachable grade pulps (kappa number 15), values higher than 60 mmol/kg pulp of HexA were found. The calculated contribution of the HexA to the kappa number of E. globulus pulps varied from 10% to 50% and was much more significant in pulps with low kappa numbers.