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Effective separation of various components in biomass is critical for biorefinery. Autohydrolysis is a commercialized unit operation to remove hemicelluloses, such as xylan, in producing high‐quality cellulose (the so‐called dissolving pulp) in the pre‐hydrolysis kraft process. In the present study, the autohydrolysis of eucalyptus woodchips was investigated for the purpose of producing dissolving pulps, with a focus on the production of cellulose acetate grade dissolving pulp. First, the effects of liquid‐to‐solid ratio, maximum temperature, and time on hemicelluloses removal were comprehensively studied, and the total xylose saccharides concentration and total xylose saccharides yield were determined as a function of the P factor and log(Ro). The three‐variable Box–Behnken design of the response surface methodology was followed to optimize the autohydrolysis conditions, aiming to achieving the maximum removal of xylan. The as‐obtained optimal conditions were: liquid‐to‐solid ratio of 5.5 mL · g−1, maximum temperature of 165°C, and time of 120 min, with its P factor of 867 h and log(Ro) of 4.03. Under these conditions, the total xylose saccharides concentration was 16.43 g · L−1. Furthermore, the autohydrolysis yield was investigated. The results showed that the purity of as‐prepared cellulose substrate as a result of autohydrolysis at a P factor of 867 h (log(Ro) of 4.03) can meet the stringent requirement of cellulose acetate grade dissolving pulp. Furthermore, the pre‐hydrolysis liquor compositions were compared between the typical autohydrolysis conditions for rayon grade dissolving pulp (a P factor of 690 h and log(Ro) of 3.91) and the optimal conditions (a P factor of 867 h and log(Ro) of 4.03). [ABSTRACT FROM AUTHOR]

A highly dispersed melamine cyanuric acid (MCA) dispersion with N-methylmorpholine- N-oxide ( NMMO ) aqueous solution as the dispersion medium was prepared using a wet grinding process to address the issues of blockage, wire breakage and flame retardant precipitation in the production process of flame retardant Lyocell fibers using the blending method. The prepared MCA dispersion was used as the flame retardant to prepare flame retardant Lyocell fibers. The stability of MCA dispersion particle size and pH stability, the distribution characteristics of MCA in the spinning solution, the effects of particle size and surface additive content of MCA dispersion on fiber spinnability, thermal stability, mechanical properties and flame retardancy of flame retardant Lyocell fibers were analyzed using laser particle size analyzer, optical microscope, scanning electron microscope, fiber size analyzer, thermogravimetric analyzer, limiting oxygen index analyzer and other equipment. The results show that the particle size and pH value of MCA dispersion have no change. The dissolution degree and dissolution rate of MCA in the spinning solution significantly increase under stirring and vacuum conditions; The particle size of MCA dispersion and the content of surface additives have a significant impact on the spinnability of fibers. For example, when the particle size D90 is 0.5 µm (90% of the particles have a diameter less than 0.5 µm), and the content of surface additives accounts for 6% of the flame retardant, there are no problems such as blocking, fiber breakage, and a large amount of flame retardant precipitation in the coagulation bath during the spinning process; When the MCA content accounts for 40% of the weight of Lyocell fibers, the fibers exhibit good mechanical properties, flame retardancy, and washing resistance. The highest inechanical strength is 2.76 cN/dtex, and the limiting oxygen index (LOI) is 33. 3%. After 12 machine washes, the LOI value of the fibers remains above 30%; In addition, the initial decomposition temperature of the prepared flame retardant Lyocell fiber was significantly increased compared to ordinary Lyocell fibers, and the residual carbon content of cellulose in the fiber (about 24.03%) was higher than that of non flame retardant fibers (about 16.53%) . [ABSTRACT FROM AUTHOR]

In order to explore the performance advantages and application areas of Lyocell filament nonwovens, the performance differences between Lyocell filament nonwoven materials (homemade) and commercially available cellulosic nonwoven materials were comparatively analyzed, Lyocell filament nonwovens were compared with Lyocell staple fiber, viscose staple fiber and copper ammonia filament from the aspects of micro-morphology, crystallinity, water absorption, air permeability, softness and strength. The results show that the crystallinity and strength of Lyocell nonwoven materials are better than that off varicose and copper-ammonia nonwoven materials due to the direct spinning into a web process, and the fibre breakage of Lyocell filament nonwoven materials is less, the inter-fibre entanglement is better, and the rate of chip-out is lower than that of viscose staple fibre and Lyocell staple fibre nonwoven materials due to the direct spinning into a net process. [ABSTRACT FROM AUTHOR]

In this paper, the hydrolysis process of Dichlorohydroxytriazine (NHDT) under alkaline conditions are studied. A qualitative and quantitative method for the determination of HNDT and its hydrolysis products are established, which further clarified the hydrolysis mechanism of NHDT. Under alkaline conditions, the hydrolysis products are mainly compound 4, compound 6 and chloride (Cl−). The hydrolysis rate of NHDT at different NaOH concentration and temperature is studied. This research can be used to guide the high efficiency preparation of low fibrillation Lyocell fiber. According to the quantitative detection of wet abrasion numbers and the qualitative analysis of the fiber by SEM after slapping, it is concluded that the low fibrillation Lyocell fiber is less prone to fibrillation under the combined action of wet state and mechanical force. Due to hydrolysis of the unreacted second chlorine resulting in harmful products on the low fibrillation Lyocell fiber, the fibrillation propensity increased with the increase of storage time. The mechanical properties of low fibrillation Lyocell fiber prepared under different fiber states are studied. The tensile breaking strength of low fibrillation Lyocell fiber prepared in the form of sequentially arranged fiber bundles are better, which is closely related to the fiber surface. [ABSTRACT FROM AUTHOR]