Sustainability 2023 , 15 , 2850
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EN 643:2004 standard, contains scraps of wood-free paper with little print, no glue, no waterproof paper, and no colored paper. Cursory analysis of wastepaper revealed that most of the tested samples did not meet the assumed requirements to a greater or lesser extent. Specifically, this wastepaper contained certain amounts of wood paper and paper colored in mass, and most of them contained a significant amount of heavily printed paper. Based on the results of these analyses, the delivered wastepaper to the mill should be formally characterized under category 3.02, that is, mixed wastepaper with scraps of printing and writing paper, slightly dyed in mass, containing at least 90% of wood-free paper, or under category 3.03, that is, wastepaper containing bookbinding scraps of wood-free paper (it may contain 10% wood paper at the most), with little print and glue but no paper colored in mass. In summary, the treatment of white wastepaper as purely type 3 or 04 is a simplification used in the trade of wastepaper. In fact, this type of paper exhibits a spectrum of properties.
Table1. Non-fiberized substances and chemical composition of wastepaper pulps.
Non-Fiberized Substances
Dissolved Substances
Kappa Number
Wastepaper
Ash
Extractives
Holocellulose
DP
[%] 2.55 0.01 0.00 2.61 1.05 0.71 0.79 0.48 2.40 1.35 1.71 0.35
[%]
[%] 1.60 1.47 0.22 1.13 1.10 0.75 1.57 1.41 1.24 1.24 0.50 0.41
[%] 2.67 1.95 3.28 1.98 2.46 1.72 2.44 6.74 3.60 1.35 0.59 0.65
[%]
[–]
[–]
19.97 18.12 16.71 17.60 23.68 27.27 24.60 37.87 22.92 27.48 25.43 16.90
67.67 63.26 78.33 66.68 70.77 73.68 76.73 70.58 76.52 76.95 71.38 79.59
49.67 49.58
376 339 840 832 531 660 673 376 412 377 611 643
White1.1 White1.2 White1.3 White1.4 Mixed1.5 White2.1 White2.2 Mixed2.3 Mixed2.4 Mixed2.5 Mixed3.1 White3.2
5.34 5.28
45.50 45.32 19.38 39.62 39.59 40.15 16.25 13.60
These results confirmed the chemical composition of the examined wastepaper pulp, without simple dependencies on the type of wastepaper. The degree of polymerization affects the strength properties of paper; this is due to the fact that with a decrease in polymerization degree, the mechanical strength of cellulose decreases. Based on the results of our analyses, despite the high degree of cellulose polymerization, the selected wastepaper pulps did not achieve the highest strength properties. Therefore, presence of impurities and many other factors may affect the strength of paper derived from recycled pulp. To determine the critical parameters for obtaining high-quality recycled pulp and ensuring suitability for the production of specific types of paper, papermaking ability was assessed. This analysis covers a wide spectrum of tests aimed at determining whether a given fibrous raw material is suitable for use in paper production. Papermaking ability is determined based on multiple parameters of pulp, including the chemical composition and properties of the finished paper. The assessment of papermaking ability allows compre- hensive comparison of the properties of recycled pulps and determination of the types of wastepaper that may be useful. Most importantly, this assessment identifies the types that cannot certainly be used to obtain products of high utility value. To assess papermaking ability, pulp was refined, the primary purpose of which is the maximum development of surface area bound in the paper. Refining increases the elasticity of cellulose fibers, thereby improving the strength and structural-dimensional properties of the finished paper. Simultaneously, however, it contributes to the reduction of pulp dewatering, which adversely affects the efficiency of the papermaking machine. Moreover, the refining process is highly energy intensive, accounting for nearly 50% of the electricity consumption of the paper mill. Previous studies and industrial experiments have established that the optimum cost, efficiency, and paper product properties could be
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