Kinetics of degradation of cellulose in basic medium

Abstract

Equations are proposed for calculating the kinetics of the change in the degree of polymerization of cellulose in basic medium; they describe the experimental data with sufficiently high accuracy. The dependence of the rate constant of degradation of cellulose in mercerization on the concentration and temperature of the alkali and the content of low-molecular-weight fractions in the reaction mass was established. It was found that degradation of cellulose in the disperse state in mercerization and preripening of alkaline cellulose obey the same rules. The effective concentration of alkali included in the liquid phase of alkaline cellulose was proposed as the criterion for evaluating the occurrence of preripening, identical to the concentration of mercerizing alkali. Using previously established degradation mechanisms and having calculated the residence time of the cellulose in basic medium in different stages of the manufacturing process, it is possible to evaluate and predict the degree of polymerization up to the finished product.Degradation of cellulose, which takes place in viscose technologies primarily in basic medium, is one of the most important stages used to regulate the viscosity of spinning solutions within wide limits and attain the required degree of polymerization (DP) to ensure the necessary strength and elasticity of viscose fibres, filaments, films, and coatings. Z. A. Rogovin also did not abandon the study of degradation of cellulose in different media, publishing the first work on this subject at the beginning of the 1930s in the journals Iskusstvennoe Volokno and Kunstseide (Germany). Studies on cellulose chemistry were subsequently reflected in the well-known seminal monographs of Z. A. Rogovin [1-3] and his many publications.Unfortunately, not all of the scientific ideas and endeavors were realized in this outstanding scientists lifetime. It was possible to theoretically substantiate and implement his idea of increasing the solubility of cellulose xanthate and decreasing the consumption of toxic carbon disulfide by activation of alkaline celluloses before xanthation with a low-concentrated alkali in industry only in the mid-1990s [4-6]. His research on alkaline degradation of cellulose was also not brought to the logical conclusion.It was historically established, so that most of the attention of researchers investigating this process was focused on comparing different hypotheses on the chemical transformations of cellulose in basic medium and developing methods of measuring the degree of polymerization and molecular-weight distribution. The studies in this direction were undoubtedly pressing and made some contribution to the science of cellulose chemistry. However, the fundamental mechanisms of degradation of cellulose in basic medium were not established, and the lack of a mathematical description does not allow controlling the process in industrial practice. And to this day, the temperature-time regime of degradation of cellulose in viscose technologies is actually not regulated, but is ...

Accelerated ageing of paper: effect of lignin content and humidity on tensile properties

“…DP -degree of polymerisation), thereby reducing the strength paper properties [53,54]. This phenomenon is clearly documented in several papers [55][56][57][58][59]. The influence of pH on the strength properties of paper has been analyzed by many researchers [37,38,60].…”