Abstract
In the pulp and paper industry different types of pulp or fiber fines are generated during the pulping (primary fines, mechanical fines), and/or the refining process (secondary fines). Besides fibers, these cellulosic microparticles are a further component of the paper network. Fines, which are defined as the fraction of pulp that is able to pass through a mesh screen or a perforated plate having a hole diameter of 76 μm, are known to influence the properties of the final paper product. To better understand the effect and properties of this material, fines have to be separated from the pulp and investigated as an independent material. In the present study, fines are isolated from the pulp fraction by means of a laboratory pressure screen. To allow for further processing, the solids content of the produced fines suspension was increased using dissolved air flotation. Morphological properties of different types of fines and other cellulosic microparticles, such as microfibrillated celluloses (MFC) are determined and compared to each other. Furthermore, handsheets are prepared from these materials and properties, such as apparent density, contact angle, modulus of elasticity, and strain are measured giving similar results for the analyzed types of fines in comparison to the tested MFC grades. The analysis of the properties of fiber fines contributes on the one hand to a better understanding of how these materials influences the final paper products, and on the other hand, helps in identifying other potential applications of this material.
Highlights
Paper is a non-woven fibrous cellulose based material, which is formed by an interaction of individual fibers to form a network with a complex hierarchy and porosity
The high lignin content in the case of mechanical pulp fines is a result of the production process
Primary fines from unbleached kraft pulp, and to some extent from bleached sulfite pulp have a higher κ number when compared to the secondary fines since they are derived from domains rich in lignin
Summary
Paper is a non-woven fibrous cellulose based material, which is formed by an interaction of individual fibers to form a network with a complex hierarchy and porosity. The large fraction of this network consists of pulp fibers, which have been subjected to a variety of treatments depending on the envisaged application for the final paper products During these treatments in pulping and papermaking processes, cellulosic microparticles are formed, the so-called fines. Secondary fines are generated during the refining of pulp In this case, a mechanical treatment partially induces fibrillation of cell wall fractions, resulting in the formation of a fibrillated material that has microscopic dimensions [3,4]. A mechanical treatment partially induces fibrillation of cell wall fractions, resulting in the formation of a fibrillated material that has microscopic dimensions [3,4] Both types of fines are usually present in a papermaking furnish. Because of their large specific surface area in comparison to pulp fibers, fines consume a high proportion of chemical additives used in pulp and paper production
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