Chemical characteristics and Kraft pulping of tension wood from Eucalyptus globulus labill

María Graciela Aguayo,Miguel Pereira,Paulina Martínez,Regis Teixeira Mendonça,Jaime Rodríguez

doi:10.1590/s0100-67622012000600017

Abstract

Tension (TW) and opposite wood (OW) of Eucalyptus globulus trees were analyzed for its chemical characteristics and Kraft pulp production. Lignin content was 16% lower and contained 32% more syringyl units in TW than in OW. The increase in syringyl units favoured the formation of β-O-4 bonds that was also higher in TW than in OW (84% vs. 64%, respectively). The effect of these wood features was evaluated in the production of Kraft pulps from both types of wood. At kappa number 16, Kraft pulps obtained from TW demanded less active alkali in delignification and presented slightly higher or similar pulp yield than pulps made with OW. Fiber length, coarseness and intrinsic viscosity were also higher in tension than in opposite pulps. When pulps where refined to 30°SR, TW pulps needed 18% more revolutions in the PFI mill to achieve the same beating degree than OW pulps. Strength properties (tensile, tear and burst indexes) were slightly higher or similar in tension as compared with opposite wood pulps. After an OD0(EO)D1 bleaching sequence, both pulps achieved up to 89% ISO brightness. Bleached pulps from TW presented higher viscosity and low amount of hexenuronic acids than pulps from OW. Results showed that TW presented high xylans and low lignin content that caused a decrease in alkali consumption, increase pulp strength properties and similar bleaching performance as compared with pulps from OW.

Highlights

Eucalyptus species are relevant to the forest industry in different parts of the world with E. globulus the most widely planted in regions with Mediterranean climate such as Australia, Chile, Spain and Portugal (PAMPOLINA et al, 2002)
Tension wood is characterized by the development of an extra cell wall layer, the gelatinous layer (G-layer), which replaces the S2 or S3 layer in the cell wall and is made up of crystalline cellulose with a low microfibrilar angle (BABA et al, 1996; RUELLE et al, 2007; HENRIKSSON et al, 2009)
This work presents comparative results for the chemical characterization and Kraft pulping feasibility of tension and opposite wood of E. globulus growing in southern Chile

Summary

Introduction

Eucalyptus species are relevant to the forest industry in different parts of the world with E. globulus the most widely planted in regions with Mediterranean climate such as Australia, Chile, Spain and Portugal (PAMPOLINA et al, 2002). E. globulus trees could present the formation of strongly stressed wood in the upper side of branches, in leaning stems or even in well-growth erected trees (WASHUSEN 2002; WASHUSEN et al, 2003; CLAIR et al, 2006a; AGUAYO et al, 2010). Trees that presented a high amount of tension wood or deformation in its trunk are considered inadequate for use as timber or structural material due to shrinkage and formation of fissures during drying and mechanical processing causing yield losses of lumber (CARVALHO et al, 2010; CLAIR; THIBAUT, 2001; CLAIR et al, 2006b) but could be a suitable raw material for chemical transformation of wood such as pulp for paper or cellulosic bioethanol. This work presents comparative results for the chemical characterization and Kraft pulping feasibility of tension and opposite wood of E. globulus growing in southern Chile

Methods

Results

Conclusion