Development of filler preflocculation technique for newsprint
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Helsinki University of Technology |
Diplomityö
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Date
2007
Department
Major/Subject
Paperi- ja painatustekniikka
Mcode
Puu-21
Degree programme
Language
en
Pages
109+
Series
Abstract
The present study was focused on developing a filler preflocculation technique for newsprint. The objectives were to develop new methods for controlling filler prefloc size to the desired level and to evaluate their influence on paper properties. Filler preflocs were fractionated into the different sizes using different mesh screens to obtain different prefloc fractions with narrower size distribution. However, fractionated preflocs resulted in broader floc size distribution than unfractionated preflocs. Filler coflocs were prepared by two different methods. The first method was to fractionate coflocs of filler-fines using different mesh screens. The second was to fractionate fines and then flocculate the fractionated fines with filler forming coflocs of filler-fines. A smaller-mesh screen produced fractionated coflocs with a smaller mean floc size and narrower floc size distribution than unfractionated flocs. The mean size of the fractionated coflocs composed of larger fines increased as the shear level was increased, while that of smaller fines did not change with shear. Filler coflocs composed of smaller fractionated fines were found to increase the light scattering coefficient more than other coflocs of larger fines when using cationic polyacrylamide, while coflocs with larger fractionated fines increased the light scattering coefficient more than other coflocs of smaller fines when using low molecular weight of cationic starch. However, the tensile strength of filler coflocs with fines of different size remained constant when using both cationic polyacrlyamide and low molecular weight of cationic starch. Coflocs with fractionated fines increased the light scattering coefficient and tensile index more than coflocs with unfractionated fines when using high molecular weight of cationic starch. Coflocs of filler fines improved the relationship between light scattering coefficient and strength properties for both deinked pulp and amixture of deinked pulp and thermomechanical pulp better than conventional filler addition and filler preflocs.Description
Supervisor
Paulapuro, HannuThesis advisor
Kang, TaegeungKeywords
flocculation, flokkaus, filler, täyteaine, fines, hienoaines, flocs, paperin ominaisuudet, paper properties, esiflokkaus, preflocculation, yhteisflokkaus, coflocculation