Softwood Kraft lignin

Kraft Lignin. A softwood kraft lignin (KL) was isolated from a partly evaporated, industrial kraft black liquor by precipitation through the addition of dilute sulfuric acid as described elsewhere (7). The lignin was thereafter fractionated by successive extraction with organic solvents (7). The KL fraction used in the present investigation was the second of five fractions obtained (propanol soluble - methylene chloride insoluble). 

Softwood kraft lignin, 2) NaBH -reduced softwood kraft ligniny (3) Bjorkman spruce milled wood lignin... 

Fig. 5.2.7. Absorption spectrum of softwood kraft lignin in 2% NaOH solution (10%, w/w) and in KBr pellet. The difference spectrum below is obtained by subtraction of the alkaline solution spectrum from the KBr spectrum...

Marton and coworkers (27) estimated that only about 0.30 reactive aromatic sites are available for formaldehyde condensation per every C9 lignin unit of a softwood kraft lignin. Since this is only one-tenth as many available reactive sites as on phenol, it is not surprising that the utilization of lignin for commercial phenolic adhesives is extremely limited. 

Fig. 8.12 Effect of pH on Zeta (( ) potential for samples 1 hardwood Kraft lignin 2 hardwood hydrolysis lignin 3 hardwood steam explosion lignin 4 softwood Kraft lignin 5 softwood organosolv lignin and 6 soda wheat straw lignin...

Elemental and methoxyl analysis data for softwood kraft lignin fractions from Table 9.10 together with data for spruce... 

Kraft lignins contain 1.5—3.0 po- cent sulphur, some of it organically bound and some as elemental sulphur [55]. For softwood kraft lignin, the sulphur content appears to be higho- in low molecular weight fractions [53]. 

Figure 3. Tensile strengths (On x) of cured kraft lignin-polyether triol-polymeric MDI polyurethanes, NCO/OH ratio 0.9. Variation with content of softwood kraft lignin fractions characterized by different molecular weights that were isolated from the parent preparation through solvent extraction. (Data from reference 17.).

Chakar.F. S.,and Ragauskas, A J. (2004). Review of currentand future softwood kraft lignin process chemistry. Ind. Crops Prod., 20,131-141. 

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