Appl. Sci. 2025 , 15 , 875
3of 12
successful products available on the market. Compared to conventional retention systems, it not only provides outstanding retention of wet-end chemical additives, fine fibers, and fillers but also decreases the concentration of white water and boosts the speed of the paper machine, thereby offering both environmental and economic advantages [27,28]. The proper dosing and optimization of retention agents are necessary to ensure the desired benefits without compromising other aspects of the paper manufacturing process. By improving process efficiency and reducing raw material losses, retention aids contribute to both the economic viability and environmental sustainability of paper manufacturing. However, optimizing their use requires careful balancing to avoid adverse effects on the physical and mechanical properties of the paper. While the influence of cationic polyelectrolytes on papermaking processes has been widely studied [29,30], this study focuses on a novel aspect—the optimization of retention aid dosage specifically for recycled pulp under industrial conditions. This study evaluated the impact of a retention aid on the properties of recycled paper and selected the optimal addition of the aid to the recycled fiber stock. This practical application distinguishes our work from previous studies by directly addressing the challenges faced by the paper industry, including balancing the retention efficiency with the mechanical and surface properties of paper. By providing insights into real-world implementation, this research contributes to both academic understanding and practical advancements in sustainable papermaking.
2. Materials and Methods 2.1. Fibrous Materials and Retention Agent
For this research, white wastepaper sourced from a paper mill was selected. This included products made from bleached pulps, specifically scraps of wood-free waterproof paper with minimal print and no adhesive or colored components, classified as grade 3.04 in accordance with the EN643 “List of European standard types of wastepaper” [31]. For comparison, two additional grades of white wastepaper were chosen, labeled as 1.3 and 3.2. Previous analyses on these types of wastepaper [32] demonstrated that it was feasible to eliminate at least 80% of the fine mineral fraction, achieving an average pulp recovery rate of 76.5% along with the best strength properties. These grades also exhibit very similar chemical compositions and impurity levels, as established in earlier studies [32]. The wastepaper delivered from the paper mill was segregated into uniform fractions, manually shredded, and thoroughly mixed to ensure the homogeneity of the sample. The prepared wastepaper was then sealed in polypropylene foil bags and stored in tightly sealed barrels to prevent moisture and contamination. After mechanical shredding, the samples were packed into airtight containers and kept at a stable temperature of around 15 ◦ C. As a retention aid, the study utilized a cationic polyelectrolyte derived from acrylamide and a cationic acrylic acid derivative. This additive was incorporated into the secondary pulp in varying amounts, ranging from 0.1% to 1.0%. 2.2. Preparation of Pulps The preparation process of the pulps for further research involved cleaning, screening, and washing, optimized based on prior studies on wastepaper. These steps enabled the removal of fine mineral fractions and impurities that could negatively impact the washing process of the wastepaper pulp or accelerate wear or damage to the screen. It is worth noting that the pulps used for the tests were free from heavy impurities (such as sand, paper clips, etc.), which were separated during the initial sorting of wastepaper samples. The first step involved defibering the pulp in a laboratory vortex pulper. Rewetted pulp samples (22.5 g dry weight, soaked in water for 24 h) were disintegrated using
Made with FlippingBook interactive PDF creator