Preparation and performance characterization of Lyocell grade dissolving pulp composites from the lignocellulosic materials

Lyocell fiber is known as the green fiber of the twenty-first century for its eco-friendly production and straightforward process. However, the stringent quality requirements for Lyocell grade dissolving pulp are a significant challenge, leading to the current reliance on imported pulp for the production of Lyocell fibers. In this study, corn stover and wheat straw were used as raw materials to prepare the dissolving pulp by formic acid cooking, ClO₂ delignification, H₂SO₄ acidification, and H₂O₂ bleaching; meanwhile, the poplar and pine were used as raw materials to prepare the dissolving pulp by the nucleophiles enhanced formic acid pulping and the subsequent H₂SO₄ acidification. The results showed that the dissolving pulp prepared by poplar and pine pulp reached the standard of the spinning pulp of Lyocell fiber. The optimal treatment conditions were an H₂SO₄ concentration of 5 wt%, a treatment temperature of 95 °C, a time of 240 min, and a pulp concentration of 5%. The α-cellulose content of obtained Lyocell grade dissolving pulp reached 92.2% and 92.0% and the degree of polymerization (DP) of cellulose decreased to 500 and 561 for poplar and pine pulps, respectively. The applied acid treatment significantly reduced the ash content to as low as 0.02%, and the iron ion content was less than 12 ppm. The solubility of the dissolving pulp in N-methylmorpholine-N-oxide (NMMO) was investigated, and the results indicated that the prepared pulp had good spinnability.