Nord. Pulp Paper Res. J. 2024; aop
Chemical Pulping
Cláudia V.G. Esteves* Evaluation of oxygen deligni fi ed fi bers with high water absorbency, as a greener alternative to fully bleached fi bers for tissue paper
(de Assis et al. 2018). Those properties are highly dependent on the production process and raw material and they will vary according to the fi nal use. While absorbency and softness are the most required qualities for toilet papers, napkins or facial tissue (Kim et al. 1994), for towel papers, besides the absorption capacity, tensile strength is also a crucial property to take into consideration, especially wet tensile strength (Gigac and Fi š erová 2008). The production and consumption of tissue products have been constantly growing over the years, with the prediction that they will continue to increase, according to CEPI (Central European Paper Industries) statistics. The awareness around health and hygiene issues, population growth and the improved standard of living are some of the causes of the increased demand for tissue. However, the increase in tissue consump- tion leads to some environmental issues. Nowadays, fully bleached fi bers are the ones typically used in tissue and hygiene products due to their good properties: high-level brightness, good water absorption, softness and lower impurity content (Beuther et al. 2010; Fi š erová et al. 2019; Kullander 2012; Rebola et al. 2021). However, fully bleached fi bers require bleaching processes that negatively a ff ect the environment and compromise sustainability. Consumer awareness for sustainability is rising every day and there is an increasing preference for products with lower environmental impact, such as recycled or unbleached products (Brito et al. 2023; Feber et al. 2020; Haller et al. 2020; Zambrano et al. 2022). Unbleached fi bers can be a great alternative to fully bleached fi bers due to their lower carbon footprint (Jour et al. 2013; Man et al. 2020). Depending on the fi nal product prop- erties, unbleached fi bers can probably be tailor-made and eventually replace the fully bleached fi bers used nowadays. Studies have shown that unbleached oxygen deligni fi edpulps can have a great swelling ability due to the fi ber charge increase during their oxidation reactions (Esteves 2022; Mai 2021; Zambrano et al. 2022; Zhang et al. 2005). Besides that, oxygen deligni fi cation tends to result in fi bers with higher curl and a higher number of kinks (Esteves et al. 2021a; Mohlin and Alfredsson 1990), which can be bene fi cial for the bulk of the fi nal product (Rebola et al. 2021). This work aims to
https://doi.org/10.1515/npprj-2024-0024 Received April 5, 2024; accepted July 2, 2024; published online August 27, 2024
Abstract: The potential of oxygen deligni fi ed fi bers to replace fully bleached fi bers in tissue products was investigated on softwood pulps. The absorption, mechanical properties and softness of laboratory tissue hand sheets from one commercial fully bleached pulp and fi ve unbleached oxygen deligni fi edlab pulps were compared. The pulps with di ff erent lignin content and total fi ber charge were evaluated with and without PFI re fi ning. The pulps subjected to oxygen deligni fi cation resulted in pulps with much higher total fi ber charge content that led to higher swelling and higher wet strength when compared to the commercial fully bleached pulp. Some unbleached oxygen deligni fi ed pulps showed great potential in the absorption capacity, while others showed a much higher wet tensile strength when compared to the commercial pulp. Compared to the commercial bleached pulp, a similar softness for a higher wet and dry tensile index in the unbleached fi bers was observed for the oxygen deligni fi ed pulps. Unbleached pulps subjected to an extended oxygen deligni fi cation proved to be a suitable alternative to fully bleached pulps in tissue grades, depending on the desired property (absorption or wet strength). Keywords: absorption capacity; fi ber charges; high lignin content; oxygen deligni fi cation; wet strength 1 Introduction Tissue products are present in our everyday lives for di ff erent purposes, such as personal use as facial tissue, toilet paper, napkins, household towels, packing tissue paper, among others. The primary required properties are generally good liquid absorption capacity, smoothness, bulk and, strength *Corresponding author: Cláudia V.G. Esteves , Sustainable Materials and Packaging Department, RISE Research Institutes of Sweden, Bioeconomy and Health, Drottning Kristinas väg 61, SE-114 28, Stockholm, Sweden, E-mail: claudia.esteves@ri.se
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