Chemical Treatment in Mechanical Pulping Part 1: South American Eucalyptus (Process and Properties), 1997 Pulping Conference Proceedings

In this paper an attempt was made to compare results from pilot scale studies on different chemical treatments in mechanical pulping of three South American eucalyptus species: E. grandis from Argentina and E. grandis and E. saligna from Paraguay. The chemical treatments were: alkaline peroxide treatment on chips (APMP), alkaline sulfite on chips (CTMP) and alkaline peroxide post bleaching of pulps from these chemical mechanical processes. The objective of the investigation was to find fundamental characteristics of each process by using intrinsic relationships among pulp handsheet properties, and avoiding effects caused by variations from chemical charge and refining energy conditions, which is important for a fair process comparison and for pulping process selection when pulp properties requirement is defined for its application. The results showed that there was an intrinsically very close correlation between sheet density and bonding strength properties like tensile and burst. The correlation was independent of variations in not only chemical charges and refining energy for a given process, but the different type of the chemical treatment processes as well. The same was also true for relationships among tensile, burst, stretch and T.E.A. Tear/Tensile relation was found to be linear over a wide range of tensile index (20 - 65 N.m/g). Each of the three different chemical treatments was able to produce a pulp with a similar level of strength properties: tensile index of > 60 N.m/g, tear index of > 7.5 mN.m 2 /g, and burst index of > 3.0 kPa.m 2 /g. Under the conditions applied in this study, light scattering coefficient (LSC) was affected less by changes in pulp freeness, fines content, and tensile strength, but more by the type of the chemical treatments. LSC of APMP pulp was found to be constantly higher than both CTMP and the post-bleached pulps when compared, over a wide range, at the same freeness, fines content and the tensile strength levels. Mechanistic explanations were presented for the phenomena observed in this investigation. APMP process was recommended for utilization of these wood species in applications where good brightness, scattering and surface smoothness are desired.