|| STUDY ON THE LMS MODIFICATION OF MASSON PINE TMP AND CHARACTERIZATION OF SURFACE CHEMISTRY AND MORPHOLOGY|
|| Masson Pine TMP, LMS, bio-modification, surface chemistry, surface morphology|
High yield pulps, such as mechanical and chemi thermo mechanical pulp has been increasingly used in paper industry for many paper products by virtue of their high bulk and stiffness, superior optical properties and good printability. However, comparing which chemical pulp, mechanical and chemimechanical pulps have lower capacity of inter fiber bonding because their fiber surface are usually encased by rigid middle lamella and melted lignin which leads to high lignin content on the fiber surface. Such a strength property of mechanical and chemimechanical pulps is limited to replace kraft pulp for making fine paper, and these disadvantages have become drawbacks for the mechanical pulping process.
In this study, a new fiber modification technique: LMS, which is environmentally friendly, consumes less energy and causes damage to the fiber, was used to treat TMP fibers by using remove a minor fraction of lignin and extractives on the fiber surface The purpose of LMS treatment is to improve paper strength properties. Scanning electron microscope, Atomic Force Microscopy, X-ray Photoelectron Spectroscopy were used to investigate the mechanism of fiber LMS modification.
The masson pine unbleached TMP was treated with laccase together with a mediator and thereafter bleached with hydrogen peroxide (H2O2). The effects of such factors as enzyme treatment temperature, pH value, enzyme dosage, and mediator dosage and enzyme treatment time on the pulp whiteness, bulk and strength were analyzed in this paper. At the optimum conditions, the TMP brightness increased 3.11%ISO compared to the sample pulp; the tensile index and the tear index also increase visibly, the bulk decreased. The modification conditions were optimumed: 5LAMU/g laccase dosage, temperature 50℃, ABTS 0.05％dosage, pH 5.0, modification time 90min.
The masson pine unbleached TMP was treated with laccase together with a mediator and thereafter bleached with hydrogen peroxide (H2O2). The influence of such factors as the dosage of H2O2 and the bleaching time on the pulp whiteness, bulk and strength were analyzed in this paper. At the optimum conditions, the TMP brightness increased 4.04%ISO compared to the sample pulp; the opacity, the light absorption coefficient and bulk decreased; the light scattering retained stabilization. The tensile index, the tear index and the PC increased visibly.
The change of fiber characteristics during the refining in the TMP with laccase treatment process by scanning electron microscope (SEM) was investigated in this paper. The results showed that the energy consumption of secondary refining of TMP treated by the laccase treatment was lower than the untreated pulp,the middle lamella even the primary wall were corroded ,The auto-adhesion between fibers occurred,the the tensile index increased 37.30% visibly, the tear index increased 47.33%, the bulk decreased 20.33% and the CA decreased.
The AFM analysis showed that the fiber wall of TMP fiber surface was covered with lignin and extractive which had different shapes and dimension, the surface was coarse. After LMS modification, the lignin and extractive decreased markedly, and their shape and dimension were also decreased. So the surface of fiber became less roughness.
The results of XPS analysis showed that the LMS modified TMP fibers had a higher O/C ratios and lower C1 percentage than that of the control pulp fibers, and the C1s peak shifted to high binding energy direction. This implies that LMS modified fiber had less lignin and extractives, and more hydrophilic groups and carbohydrate of the fiber surface, which helpful to form hydrogen bond.