Reduced Lignin Solubility

Similar difficulties would be encountered using the acid sulfite process on other woods containing stilbenes or polyphenols such as proanthocyanidins containing resorcinol of phloroglucinol moieties. For example, dihydroquercetin has been identified as the cause of inhibition of calcium base sulfite pulping of Pseudo-tsuga menziesii (138). 

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A high proportion of lignin also reduces the solubility of nitrocellulose. According to Bryde and Mnby [3], the solubility in acetone is reduced only when the lignin content approaches 18%.. ... 

It has also been proposed that under the acidic conditions found ia whiskeys, ethanol reacts with lignin (qv) to reduce an alcohol-soluble form of lignin (ethanol lignin). This can be converted into coniferyl alcohol, which can be oxidized to coniferaldehyde. The partial oxidation of ethanol lignin can produce siaapic and coniferyl alcohols that can be converted to syfingaldehyde and vanillin, respectively (8). 

A polymeric composition for reducing fluid loss in drilling muds and well cement compositions is obtained by the free radical-initiated polymerization of a water-soluble vinyl monomer in an aqueous suspension of lignin, modified lignins, lignite, brown coal, and modified brown coal [705,1847]. The vinyl monomers can be methacrylic acid, methacrylamide, hydroxyethyl acrylate, hydroxypropyl acrylate, vinylacetate, methyl vinyl ether, ethyl vinyl ether, N-methylmethacrylamide, N,N-dimethylmethacrylamide, vinyl sulfonate, and additional AMPS. In this process a grafting process to the coals by chain transfer may occur. 

However, in 1939 this difficulty was obviated by Brauns extraction of about 3% lignin from spruce wood by means of the solvent, ethyl alcohol, at room temperature (9). He termed this preparation native lignin. It was found to be soluble in methanol, ethanol, dioxane, dilute sodium hydroxide and pyridine, and insoluble in water, ether, petroleum ether and benzene. Chemically it behaved the same as lignin as it exists in woody tissues. It also reduced Fehling s solution and gave a strong... 

Lignin is water-insoluble and it contains only a few hydrophilic functionalities (primarily the phenolic groups). In order to increase its solubility, aqueous pulping processes therefore seek either to introduce water solubilising groups, or to reduce the degree of polymerisation or both. 

Three laccase preparations (I, II and III) were isolated from the racellular culture medium of Coriolus versicolor by consecutive fractionation through Sephadex G50 and DEAE Sephadex A25 (84). The laccase III preparation at pH 4.0 reduced the apparent molecular weight of a lignin-derived fraction that had been obtained by eluting the water-soluble extract of a cellulase treated ezomatsu wood residue through... 

Chlorination or chlorine dioxide treatment is almost always followed by a caustic extraction. Alkaline extraction neutralizes the pulp and removes the lignin rendered more soluble by chlorine treatment. Removal of this modified lignin opens up the cell wall and allows for milder delignification to be used in later bleaching steps. Caustic extraction is generally performed with most chlorinated chemical pulps at 50-60° with 0.5-5% NaOH for 1 to 2 hr. Consistencies are usually quite high (12 to 16%) to reduce the amount of water and minimize energy requirements. 

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