Previous paper (Rahman et al. 2017) showed that the yield of softwood kraft pulp increased by the addition of either polysulfide or sodium borohydride because of higher hemicellulose retention. An increase in hemicellulose content can make dewatering more difficult as WRV of the pulp increases, but instead, an overall increase in pulp yield could improve dewatering as a sheet of a certain weight will contain fewer fibres, giving a more open sheet structure. It was therefore of interest to measure the dewatering properties of low grammage handsheets (20 g/m2) under conditions mimicking the tissue paper machine dewatering processes, and sheet strength properties, WRV, °SR and fibre dimensions were also studied. The results showed that the positive influence of overall yield increase dominated over the negative influence of an increase in hemicellulose content on the dewatering properties, particularly at lower refining energy levels. Moreover, higher yield and higher hemicellulose content pulps had a higher tensile index at the same dryness. A given tensile index was achieved with less refining energy. The results indicate that increased yield and hemicellulose content by modification of the kraft pulping process will result in a pulp with a potential to improve tissue paper quality.
Funding statement: This work was conducted with the support of the Forest as a Resource Industrial College (FORIC) at Mid Sweden University and the Swedish Knowledge foundation in collaboration with SCA Forest Products and Mid Sweden University for financial support of the study.
The authors thanks SCA R&D centre, Sundsvall and Department of Engineering & Chemical Science, Karlstad University for support and guidance in the laboratory. Professor Lars Nilsson, Karlstad University, is thanked for providing the laboratory dewatering facility.
Conflict of interest: The authors declare that there is no conflict of interests related to this article.
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