Abstract:

Objective Based on the research on using biomass materials (such as bamboo, straw, sorghum straw, mulberry straw, hemp, bagasse, olive, tobacco stem and so on) to prepare acetate grade dissolving pulp and downstream products, this paper proposes the use of rich reed resources in Dongting Lake area to explore the feasibility of preparing acetate reed pulp, and test and analyze the performance of the prepared pulp so as to establish understanding on the preparation of cellulose acetate and acetate fiber.

Method The typical sulfate method was adopted to prepare the Triarrhena lutarioriparia dissolving pulp. Firstly, the water pre-hydrolysis of Triarrhena lutarioriparia slices was carried out in an electrothermal high-pressure boiling pot (Fig. 2) with a liquor ratio of 1∶4. Then, the equipment was used for sulfate boiling (Fig. 3), where the main components of the boiling solution were NaOH and Na₂S. Crude pulp was cleaned with a 45 μm polyester mesh bag and sieved with a sieve machine with a sieve gap of 0.25 mm. Finally, the D₀E_pD₁ three-stage bleaching process (Tab. 2) was used for bleaching, and the bleaching agents were ClO₂ and H₂O₂. The cellulose I content, whiteness, polymerization degree, pentosan content, ash content and iron content of the prepared triarrhena lutarioriparia dissolving pulp were tested, and the apparent morphology, infrared spectroscopy, Raman spectroscopy and X-ray diffraction were employed for analysis.

Results The yield of crude pulp after boiling was 46.31%. The three-stage bleaching process significantly improved the main performance indexes of Triarrhena lutarioriparia pulp. The content of cellulose I increased by 1.24% to 97.70%, the whiteness doubled to 91.42%, and the intrinsic viscosity decreased by 38.01%, which made the average degree of polymerization of pulp reach 1 413. In addition, the pentosan content, ash content and iron content of the pulp after bleaching were 5.76%, 0.004% and 0.000 562%, respectively. The cellulose fibers prepared from Triarrhena lutarioriparia dissolving pulp were long cylindrical with rough surface showing a large number of grooves, cracks, pores and filaments. In the infrared spectra (Fig. 5), the Triarrhena lutarioriparia dissolving pulp showed a typical cellulose characteristic peak, and the intensity of the absorption peak was enhanced compared with that of Triarrhena lutarioriparia. The characteristic peaks of lignin at 1 254 cm^-1 and 1 511 cm^-1 and the characteristic peaks of hemicellulose at 1 726 cm^-1 disappeared, indicating that the pulping process removed the lignin and hemicellulose in Triarrhena lutarioriparia. The characteristic peaks at 1 169 cm^-1 and 1 607 cm^-1 relating to lignin disappeared, and the intensity of the characteristic peak at 2 896 cm^-1 decreased indicating that non-cellulose substances such as lignin in Triarrhena lutarioriparia were removed during pulping (Fig. 6). The Triarrhena lutarioriparia dissolving pulp showed a typical diffraction curve of cellulose I. The small peak at 26.4°disappeared and no peak appeared at 29.4°(Fig. 7), suggesting that the inorganic components such as SiO₂ in Triarrhena lutarioriparia were effectively removed after the pulping process.

Conclusion The acetate grade Triarrhena lutarioriparia dissolving pulp was prepared by water pre-hydrolysis-sulfate cooking-D₀E_pD₁ three-stage bleaching process. The combined action of high temperature and chemical agents during the pulping process effectively removed the lignin, hemicellulose and ash in Triarrhena lutarioriparia, formed irregular microfibril structure on the surface of cellulose fiber, and presented a rough surface full of grooves. The successful preparation of acetate grade Triarrhena lutarioriparia dissolving pulp not only lays a foundation for the preparation of cellulose acetate and acetate fiber, but also helps open up a new way for high-value and efficient utilization of reed resources.

Key words: reed, Triarrhena lutarioriparia, acetate fiber, dissolving pulp, cellulose, lignin, hemicellulose