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R. Lehnen, B. Saake, H. H. Nimz
Impact of Pulping Conditions on FORMACELL Aspen Lignin: Investigation of Methoxyl and Ester Groups, Carbohydrates, Molar Mass and Glass Transition Temperatures
The influence of reaction time, reaction temperature and acid concentration on the yield and characteristics of FORMACELL aspen lignins were investigated. 18 samples were quantitatively isolated from the black liquor by precipitation. The samples were analysed regarding their contents of carbohydrates, methoxyl and ester groups. All samples had low carbohydrate contents and the amount of methoxyl and ester groups was continuously reduced under more severe pulping conditions. Molar mass distributions and glass transition temperatures were determined. Molar masses of lignins were continuously reduced during pulping resulting in low weight average molar masses from 2.500–3.200 g/mol. Glass transition temperatures varied from 123.6 to 154.5°C, depending on the reaction conditions. Comparison of the thermograms with those of the lignins from the Kraft or Sulfite process confirmed that in the FORMACELL process a very uniform lignin with few impurities is obtained.
Holzforschung, Walter de Gruyter
Print ISSN: 0018-3830
Volume: 56, 08/2002
Pages: 498 - 506