Document Type : Pulp and Paper
Authors
1 , Associate Prof., Dept. of Wood and Paper Science and Technology, Cha. C., Islamic Azad University, Chalous, Iran
2 Professor, Department of Pulp and Paper Industries, Gorgan University of Agricultural Sciences and Natural Resources. Faculty of Wood and Paper Engineering - Department of Pulp and Paper Industries. Gorgan, Iran
3 Associate Prof., Dept. of Wood and Paper Science and Technology, Tarbiat-Modares University, Faculty of Natural Resources, Noor, Iran
Abstract
Background and aim: Currently, in Iran, CMP pulp for newsprint production is produced from a mixture of about 50% birch, 20% poplar, and 30% mixtures of other wood species. To improve the strength properties and runability of the papers during production and printing, it is necessary to use about 17% imported long fibers. This imported pulp, which is usually coniferous kraft pulp and is imported from other countries (Finland), creates dependency and causes large amounts of foreign exchange to be spent and withdrawn from the country annually. On the other hand, in the Behshahr Linter-Pak factory, which is located at a distance of about 50 kilometers from Mazandaran Wood and Paper industries (MWPI), more than 10,000 tons of purified cotton linter are produced annually. Which is of great importance due to its convenient availability, ease and low cost of transporting the material. For this purpose, this research was conducted with the aim of using cotton linter instead of imported long fiber pulp in newsprint.
Materials and methods: To conduct this research, test samples of purified cotton linter from the Behshahr Linter-Pak factory, imported long fiber pulp and CMP pulp from the MWPI were randomly selected. In the first stage, freeness, fiber classification and biometric properties of their fibers were measured. Then, using a PFI mill laboratory refiner, the imported long fiber pulp and cotton linter were refined to the freeness of 500, 450, and 400 CSF, and CMP pulp was refined to freeness of CSF450, 400, and 350 CSF. In the next step, the refined imported long fibers and cotton linters was mixed separately and in proportions of 10, 15, 20, and 25 percent with the CMP pulp of MWPI. The handsheets with the basis weight of 60 gr/m2 were prepared from selected samples and tested according to TAPPI test procedures. A spectrophotometer was used to measure the optical properties of the prepared papers, accordingly, the brightness, yellowness and opacity
of handsheets was determined. Then, the strength properties, especially the tear strength, burst, tensile and breaking length of the handsheets were measured and compared using standard TAPPI tests.
Results: The results of the fiber classification of cotton linter. and imported long pulp showed that the weight percentage of long fibers (14 and 48 meshes) of cotton linter and its dispersion were higher and its fine particles (fines) were lower than imported long fibers. Biometric characteristics of cotton linter fibers and imported long fibers showed that the average fiber length, felting and flexibility coefficients of cotton linter fibers were higher, and their total diameter, lumen diameter, double wall thickness, and Runkel coefficient were lower than those of imported long fibers. Also, with increasing refining revolutions (rpm), the freeness in long fibers and cotton linter showed a decreasing trend. By increasing the percentage of cotton linter and imported long fibers mixed from 10 to 25 percent, the brightness and yellowness of the handsheets improved and its opacity decreased. By adding long fibers and cotton linter and a mixture of cotton linter + long fibers from 10 to 25% to CMP pulp, tensile, burst, tear strengths, and breaking length increased. This increase is milder with the addition of cotton linter to CMP pulp. The paper made from adding cotton linter to CMP pulp has always had the lowest strength properties, and paper made from adding imported long fibers to CMP pulp has had the highest strength properties.
Discussion: Given that cotton linter does not respond well to refining due to its crystalline structure, beater may be more suitable due to its longer and gentle refining. In this regard, the strength properties of paper made from cotton linters have always been lower than those of imported long- fibers. However, the use of a mixture of cotton linter + long fibers, especially in freeness of 400 and 450 CSF, can replace a portion of imported long fibers in newsprint due to its suitable optical and strength properties comparable to imported long fibers.
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