Raw material potential of recovered papers for the production of packaging papers in Europe
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Helsinki University of Technology |
Diplomityö
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Date
2004
Department
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Paperitekniikka
Mcode
Puu-21
Degree programme
Language
en
Pages
116
Series
Abstract
During their lifetime, fibers undergo various types of treatments. Wood chips can be cooked with chemicals to release fibers from the wood matrix to get chemical pulps and be finally bleached. Or the fiber separation can be the result of mechanical actions (grinding, refining) to get mechanical pulps and be finally brightened. Finally, fibers are beaten for the production of paper. After web forming, wet paper web is pressed, dried and perhaps calendared. These treatments are detrimental to the fiber structure. With these various treatments, fibers become weaker and shorter resulting in a decrease in paper strength. In Europe, packaging papers are more and more often produced with recovered papers. These raw materials are classified according to the "European List of Standard Grades of Recovered Paper and Board" (EN 643). Humidity, contaminant content, paper and board grades are described whereas fiber qualities and properties are not. Therefore a grade can be composed of almost the same kinds of paper (although there are non-accurate number) but with different kinds of fibers. For this study, four different blends of raw materials have been analysed, after coarse screening, through four European mills. North Europe, with a low utilization rate, had better fiber and paper properties. This can be due to a high content of virgin kraft pulp in the raw material or at least due to a low level of recycling. Raw materials from Central and Southern Europe have lower properties mainly due to higher ash and primary fine contents and a lower water retention value (WRV). Probably, they have been already made of a mixture of recovered papers, which may include graphic papers. Therefore, WRV of high quality raw material, and primary fines and ash contents of low quality raw material are critical to get high paper properties. Various treatments applied on recycled fibers raw material have shown that they can efficiently restore partially some paper properties. After fractionation, the long fiber fraction is often dispersed and refined. Hot dispersion breaks down macro-stickies to smaller size stickies. Cold dispersion has tendency to improve swell ability of fiber and therefore improving paper properties. Refining greatly improves properties under well controlled operation. However, effect of refining on the mixed fractions has only a slight influence due to a too low fraction treated. Paper machine samples were relished and analysed. Northern Kraft liner, through addition of 55% of virgin kraft pulp, shows the best potential to be recycled with high content of long fiber, high 'NRV and low primary fine and filler contents and therefore high strength paper properties. Test liner and medium of Northern and Central Europe shows the opposite characteristics.Description
Supervisor
Paulapuro, HannuThesis advisor
Kemper, MartinKeywords
recovered papers, jätepaperi, recycled fibers, kierrätyskuitu, potential, pakkauspaperi, properties, potentiaali, packaging papers, ominaisuus, OCC, OCC