Abstract:

The chemical composition and fiber morphology from Caragana korshinskii Kom. were analyzed. The twin-screw CMP pulping process of the C. korshinskii and the fiber morphology of the pulp and the physical properties of the handsheet were discussed. The results showed that the contents of cellulose and holocellulose in the raw material of C. korshinskii Kom. were lower than that of softwood and hardwood. The contents of benzene-alcohol extractive and hot water extractive were high. C. korshinskii fibers were generally short; the weight-average lengths of xylem fibers and phloem fibers were 0.621 and 0.819 mm, respectively. There were also some non-fiber cells. The yield of the obtained CMP pulp reached 73% after pretreatment with 3.5% Na₂SO₃ and 1.5% NaOH for 12 h at normal temperature, steaming at 90℃ for 1 h, and then refining with twin-screw at the mass fraction of 35%, and finally refining with high-concentration disc refiner. The CMP pulp from C. korshinskii basically maintained the original length of the fiber with the weight-average length of 0.650 mm. The aspect ratio was 32.7, and the fiber dissociation was better, but the separation of filaments was not ideal, and it contained some fiber bundles and miscellaneous cells. When the Canadian freeness was 300 mL, the ring crush index and bulk of the handsheets were high, reaching 8.67 (N·m)/g and 2.56 cm³/g, respectively. And the tensile index was 19.6 (N·m)/g. The whiteness of the handsheet was high, reaching 50%(ISO). The CMP pulp from C. korshinskii was suitable for packaging paper such as corrugated medium, and could be used for newsprint and whiteboard paper after bleahing.

Key words: Caragana korshinskii Kom., chemical composition, fiber morphology, twin-screw pulping, CMP