A Novel Method for Analysis of Xanthate Group Distribution in Viscoses

Abstract

Analytical monitoring of xanthation in the viscose process along with xanthate group analysis in the viscose material is a long‐debated problem in cellulose chemistry. The task is rendered extremely intricate by the lability of the starting material and the harshness of the reaction medium, which adds to a lack of suitable analytical approaches. In a four‐years' endeavor in our lab, a method is being developed which allows to analyze the distribution of xanthate groups in viscoses relative to the anhydroglucose units and along the cellulose chain.In a first step the xanthate groups are stabilized by alkylation, which was optimized towards quantitative conversion. In a second step, the remaining free hydroxyl groups are protected by carbanilation, followed by selective removal of the stabilized xanthate groups. Steps two and three thus generate an inverse image of the initial xanthate pattern. In the forth and fifth step, the liberated hydroxyl groups are methylated, and the carbanilates are removed, so that in the overall process the xanthates were replaced by methyl groups. All reaction steps have been comprehensively tested with regard to completeness of conversion and orthogonality of the protecting groups.

Cellulose in NaOH–water based solvents: a review

“…Cellulose carbamate is obtained by the reaction of cellulose with urea and then regenerated in acid (Hill and Jacobsen 1938;Sprague and Noether 1961;Kunze et al 2005). The viscose process is based on cellulose xanthate dissolution in caustic soda followed by regeneration in acid (Russler et al 2005;Russler et al 2006;Musatova et al 1972).…”

Determination of substituent distribution of viscoses by GPC

“…Stabilization of viscose was carried out using N-methyl-N-phenyl-2-iodoacetamide in aqueous solution as previously described (Rußler et al 2005) (Figure 2). For further purification and to achieve a better texture, the stabilized polymer was dissolved in DMAc and subsequently re-precipitated in the three-fold volume of ethyl acetate/hexane (1:1, v/v).…”

“…For instance, the previously described dithiocarbonic acid O-(2-hydroxy-cyclohexyl) ester S-w(Nmethyl-N-phenyl-carbamoyl)-methylx ester (Rußler et al 2005) can be used as a model compound for calibration. The intensity of the signal must be calibrated either with samples of known DS or with low-molecular-weight standards exhibiting the same spectroscopic characteristics corrected for MW-dependant changes in the absorption coefficient.…”