The production of bisulfite pulp from Carpinus betulus species to enhance the strength properties of CMP pulp- Case Study: Mazandaran Wood and Paper Industries

The objective of this study was to investigate the production of bisulfite pulp from Carpinus betulus species to enhance the strength properties of the chemical mechanical pulp (CMP). CMP pulp prepared according to the industrial standards (Mazandaran wood and paper industry) and bisulfite pulp was prepared by direct injection of sulfur dioxide (SO2) gas into a sodium hydroxide solution. The results of cooking bisulfite pulp showed that by increasing of cooking time from 1 to 3 hours the kappa number decreased. The results of mixing bisulfite pulp (10, 30 and 40%) with CMP pulp showed that the mechanical properties of the paper improved with increasing the contribution of bisulfite pulp. By adding 40% bisulfite to CMP, the tensile index, burst index, tear index and folding strength improved by 24%, 16.2%, 13.7% and 84.2%, respectively. Finally, combining 40% bisulfite pulp and 60% CMP pulp showed the highest strength in terms of total paper properties. Therefore, the use of bisulfite pulp up to 40% mixed with CMP paper pulp leads to the desired production of newspaper and is recommended.