Studying the Effect of Using Formaldehyde in Sulfite Pulping Process and Refining Revolutions on the Rice Straw pulp Properties

In the present research, the effect of formaldehyde addition in sulfite pulping process and the refining revolutions on the strength and optical properties of rice straw pulp has been investigated. In order to achieve a final pulp kappa number of 12-13, cooking was done at 20% sodium sulfite in sulfite process and 18% sodium sulfite plus 4% formaldehyde in sulfite-formaldehyde process. The effect of refining revolution values on the pulp properties were investigated in the freeness levels of 500, 400, and 300 mL, CSF. Results indicated that, the addition of formaldehyde in sulfite process led to improve in delignification and increase in tensile and burst strengths. By the increasing of refining revolutions in all pulps, tensile and burst strengths were increased at slightly lower tear strength and optical properties.