Use of Primary Fiber Fines as Organic Fillers in Papermaking

Primary fiber fines were screened out of virgin mixed hardwood chemical pulp through a Bauer McNett Fiber Classifier with 2 output materials of fibers and fines. The screened primary fiber fines were blended into the pulp to obtain pulps with no fines, and with 10 and 20% fines. The refining of all pulp samples was carried out in a PFI mill. The pulp with 10 and 20% fines respectively required 10.8 and 28.9% fewer PFI revolutions to obtain a 400 ml CSF level compared to the pulp without fines. At the same freeness level, the opacity of the paper increased with the addition of 10 and 20% fines by 1.7 and 2.6 points, respectively. Similarly, the formation of paper also improved by 2.0, and 10.2% with the respective addition of 10 and 20% fines to the pulp. The bulk and stiffness of the paper improved with the addition of fines up to a 450 ml CSF level. The strength properties, such as the breaking length, burst index, tear index, double fold, and Scott bond, decreased with the addition of fines.