Abstract
The basic density is the main technical property of the wood due to the fact of the easy determination and correlation with the others wood properties. In this article, it was evaluated wood chips from a five-years-old Eucalyptus grandis in three different silvicultural treatments for pulp and paper production. First, a conventional kraft pulping was executed in the same conditions and then submitted to some elemental chlorine free (ECF) bleaching process to achieve the target brightness of 88 ± 1% ISO. The bleached pulps were refined in a Jokro Mill at 0, 2250, 4500 and 6750 revolutions and their physical, mechanical and optical properties were analyzed. The statistical analysis indicated a difference in the wood basic density from the different silvicultural treatments. The yield of the pulping process was not affected by the variation of the wood basic density. The denser wood had the advantage of a lower specific wood consumption while the disadvantage was a greater difficulty in the delignification and a decrease in the selectivity of the pulping process. The denser wood was the one with the best bleachability and the one that most consumed chlorine in the bleaching process. The increase of the wood density caused gains in the fisical and optical properties of the bleached pulp and losses in the mechanical properties.The optical properties of the pulps from denser woods are more resistant than the negative effects of mechanical properties. Keywords: Kraft pulping; pulp bleaching; paper properties.
Highlights
Brazil is the world's largest producer of bleached eucalyptus pulp, the production of this type of cellulose pulp is intended for production of writing and printing papers besides the production of absorbent paper for hygienic purposes [1]
A conventional kraft pulping was executed in the same conditions and submitted to some elemental chlorine free (ECF) bleaching process to achieve the target brightness of 88 ± 1% ISO
The statistical analysis indicated a difference in the wood basic density from the different silvicultural treatments
Summary
Brazil is the world's largest producer of bleached eucalyptus pulp, the production of this type of cellulose pulp is intended for production of writing and printing papers besides the production of absorbent paper for hygienic purposes [1]. The production processes of these types of papers are distinct and require cellulosic pulps with different technical properties. SANTOS and SANSÍGOLO [2] distinguish the ideal types of cellulose pulps for printing and writing paper and absorbent paper. In the case of absorbent papers manufacturing, the high capacity of water absorption and the increase of softness are important. Pulps from wood with lower basic densities are ideal for production of printing and writing paper, since they have fibers with smaller thickness and smaller mass per length. Pulps from denser hardwoods are ideal for absorbent paper, because they present fibers with greater thickness, a greater potential of liquid absorption, and greater mass per length of fibers [2, 3]
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