Optimization of the Use of Recovered OCC/ONP in Mixture with Virgin Hardwoods Kraft Pulp to Produce Kraft Liner Paper

In order to determine the mechanical and optical properties of kraft liner paper made of the mixture of recovered OCC/ONP fibers with mixed local hardwoods virgin kraft pulp, OCC/ONP papers have been repulped in the common method of the paper recycling industry. The initial freeness value of each pulp was measured and they were separately refined to reach the suitable freeness value required to make kraft liner paper. The pulps have been mixed at (85, 10, 5), (80, 10, 10), (75, 10, 15), (70, 10, 20), (70, 15, 15), (65, 15, 20), (50, 25, 25), (25, 50, 25) and (25, 25, 50) percentage rates of virgin kraft pulp, OCC and ONP papers, respectively. Handsheets were made, according to the related TAPPI standard test methods, from each mixture (treatment) and their mechanical and optical properties have been determined. The results were compared with those of control sample (100% virgin kraft pulp) using ANOVA technique. Normalization equation was calculated to determine the best treatment. The results have shown that with increasing the amount of OCC/ONP fibers in the mixture of pulps, tensile, tear and burst indices of the produced kraft liner paper decreased and brightness increased, in comparison to those of the control sample. According to the calculated normalization equation, the score of each treatment showed that 25/25 percent of OCC/ONP fibers (totally 50 percent) can be used in the mixture of local hardwood virgin kraft pulp to produce kraft liner paper with appropriate mechanical and optical properties.