Chemical Modification of ECF Softwod Kraft Pulp by Alkaline Peroxide Treatment

摘要

This study characterized the influence of alkaline peroxide treatment of elementally chlorine-free (ECF) softwood kraft pulp. The results after peroxide treatment indicated that fiber charge increased with the increase of peroxide charge, and fiber charge was increased to a maximum of 16.6% increase with 8.0% peroxide charge on oven dried (o.d.) pulp at 60 ℃ treatment. Copper number dropped when peroxide charges were 0.5% and 1.0% under 60℃ and 90℃ treatments, respectively, then increased with the increase of peroxide charge. Two levels of temperature (60℃ and 90 ℃) during peroxide treatment were investigated. The results showed that 90 ℃ for peroxide treatment on a bleached kraft pulp resulted in lower fiber charge and intrinsic viscosity compared to 60 ℃. Sodium borohydride (NaBH_4) pretreatment of fibers was able to protect the fiber from being degraded during peroxide treatment. By comparing fiber charge and copper number after peroxide treatment on ECF kraft pulp versus sodium borohydride reduced ECF kraft pulp, the results indicated that higher carbonyl group content of fibers is favorable for improving fiber charge after peroxide treatment. At the addition of 2.00% cationic starch on the untreated control pulp and peroxide treated pulp, the tensile index of the former pulp increased by 13.7% and that of higher fiber charge pulp increased by 23.7%. The addition of cationic starch onto the control pulp and higher fiber charge pulp exhibited 57.7% and 19.5% higher root-mean square (RMS) roughness values compared to the untreated control pulp and higher fiber charge pulp, respectively.