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The production of cellulose diacetate (CDA) faces an ongoing challenge with the formation of insoluble colloidal materials, referred to as insoluble gel particles (IGP). CDA is typically dissolved in solvents like acetone for processing into commercial products. However, IGP presents challenges in the production of commercial CDA-based products, potentially impacting both intermediate processing and quality of the final products. IGP formation is connected to factors such as incomplete acetylation and the presence of hemicellulose acetates, but its root cause is still debated. This study primarily investigates the impact of hemicelluloses on IGP formation during CDA production. To study IGP formation, we proposed scenarios using xylan acetate (XA) as a model impurity. The results show that the precipitation process employed for CDA recovery plays a crucial role in IGP formation, with acetone-soluble CDA also contributing to IGP formation during precipitation. Additionally, the persistence of IGP is influenced by the behavior of XA in redissolution solvents. [ABSTRACT FROM AUTHOR]

Plasticizers depress the glass transition temperature (Tg) of polymers and produce a flowable material at lower temperatures. The use of plasticizers to depress Tg of lignin is important, since at high processing temperatures lignin crosslinks, making it intractable. The goal of this study was to assess plasticizers and polymer blends for the ability to retard a commercial softwood kraft lignin from crosslinking and also serve as thermal and rheological property modifiers during thermal processing in the attempt to produced moldable and spinnable lignin for lignin and carbon fiber products. The Tg of the lignin and the lignin mixed with various amounts of plasticizers and with different thermo-mechanical mixing were determined using differential scanning calorimetry. The Tg and the change in heat capacity at the glass transition (ΔCp) decreased and increased, respectively, about linearly within this plasticizers range with increased plasticizer weight percentage. Gel permeation chromatography results for extruded lignin as well as extruded lignin-plasticizer blends with glycerol, N-allyurea, citric acid with and without sodium hypophosphite, and oleic acid indicate that the presence of these materials reduced the rate of molecular weight increase at temperatures between 100 and 200 °C. Continuous, homogenous films and fibers could be produced by thermal processing with plasticized lignin samples and plasticized lignin-polymer blends, but not with lignin alone. These fibers could be carbonized, yielding up to about 50% of carbon. The present findings have shown the advantages of plasticizers in thermally processing a commercial softwood kraft lignin. [ABSTRACT FROM AUTHOR]

Abstract: Residual hemicellulose in dissolving pulp is known as a reason for deterioration of final product quality and processability problems during cellulose derivative production. However, the issue caused by the residual hemicellulose is not fully understood and is primarily based on industrial experience. To better understand the effect of hemicellulose on cellulose derivative process, hemicellulose in prehydrolysis kraft hardwood dissolving pulp was extracted and its glycosidic linkage structure was thoroughly analysed. Two-stage alkaline extraction, consisting of 24 wt% KOH solution and 18 wt% NaOH with 4 wt% H3BO3 solution, was found effective for the sequential extraction of high purity xylan and glucomannan from the dissolving pulp. Considering the purity and yield of extracted xylan, room temperature for Stage-1 KOH extraction condition was preferred, while 1 °C was preferred for Stage-2 NaOH extraction. Mechanical refining treatment at a mild condition improved the extraction yield of hemicellulose, although the molecular weight of the cellulose was reduced with severe refining condition. Glycosidic linkage analysis showed that native 4-O-methylglucuronic acid side groups were removed during pulping process, resulting in a linearized xylan structure, while a high amount of glucuronic acid was detected in commercial beechwood xylan. The extracted hemicellulose from the second stage showed relatively high number of branched backbone unit e.g., 1,4,6-linked mannose and 1,4,6-linked glucose. The protocol developed in this study should be useful for hemicellulose-related applications.Graphical abstract: [ABSTRACT FROM AUTHOR]

Autohydrolysis is a hot water pretreatment to extract soluble components from wood that can be used prior to converting the woody residuals into paper, wood products, fuel, or other goods. In this study, mixed softwood chips were autohydrolyzed in hot water at 150, 160, 170, and 180 °C for 1 and 2 h residence times. The objective was to understand the tradeoff between the extraction of fermentable sugar and the residual solid total energy of combustion quantitatively. This process strategy will be referred to as 'value prior to combustion'. High-performance liquid chromatography was used to determine chemical compositions (sugars and byproducts such as acetic acid, furfural, and hydroxymethylfurfural) of the extracted liquid and residuals; a bomb calorimeter was used to measure the heating value of original wood and solid residue. As the autohydrolysis temperature increased, material balances of the system indicated higher volatile byproducts loss. More hemicelluloses were solubilized by the hot water extraction process at higher temperatures and longer residence times, and a greater degree of sugar degradation was also observed. The maximum sugar yield was determined to occur at conditions of 170 °C for 2 h, during which 13 g of sugar was recovered from the extract out of 100 g of oven-dried wood. The heating value of the solid residues after extraction was greater than the original wood. The total energy content of the solid residual after extraction ranged from 85 to 98 % of the original energy content of the feed with higher temperatures reducing the total energy content. [ABSTRACT FROM AUTHOR]

In this study, a strategy to reduce enzyme dosage is evaluated by applying two post-treatments, oxygen delignification and mechanical refining. The sugar conversion for GL12 substrates was increased from 51.5% to 77.9% with post-treatments at the enzyme dosage of 10 FPU. When the amount of enzyme was reduced to 5 FPU with post-treatments, the conversion of 71.8% was obtained, which was significant higher than the conversion without any post-treatment using 10 FPU (51.5%). This clearly demonstrates the benefit of post-treatments that allows more than 50% of enzyme reduction at the same level of enzymatic conversion. Enzyme-accessible surface area and pore volume were evaluated by Simons' staining and DSC thermoporometry methods, and strong correlations were found with the sugar conversion. [ABSTRACT FROM AUTHOR]