Kraft Lignin Fractions

4 Composition of Isolated Lignin 3.3.4.1 Kraft Lignin Fractions 

Fraction pH of precip. Yield (% of total) Ash (%) Acetone solubility (%) Methoxyl (%) Carboxyl (%) 

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Figure 8. Kraft lignin fractionation into two subsets of species during desalting by elution with aqueous 35% diaxane through Sephadex LH20 of an initially 4.5 gL 1 sample solution at 2.3 M ionic strength containing 0.32 M aqueous NaOH.

Figure 14. Variation with molecular weight exhibited by ratios of absorbance values at 230 and 300 nm for paucidisperse kraft lignin fractions in aqueous 0.10 M NaOH from ( ) associated sample after 385 h at 180 gL 1 in 1.0 M ionic strength aqueous 0.40 M NaOH (O) original preparation ( ) dissociated sample precipitated upon acidification to pH 3.0 after 2000 h at 0.50 gL"1 in aqueous 0.10 M NaOH.

Figure 9. Molar mass distribution of pine kraft lignin (fractions 1-IV in Figure 8).

Figure 2. Oxidation of kraft lignin fractions in dilute aqueous alkali dissolved in 0.2N NaOH) 2 mole equivalents alkali based on MW 1000) 70°C.

Kraft Lignin Fractions. 5 grams were dissolved in 50 ml. 0.2N NaOH, corresponding to 2 mole equivalents alkali per 1000 grams lignin. 

The kraft lignin fractions thus obtained are heterogeneous with regard to their chemical properties (see Sect. 3.3.4 for analytical data). When the black liquor contains fibrous materials, it is filtered through a Whatman No. 2 paper prior to the acidification step. 

Table 3.3.1. Analytical data for kraft lignin fractions isolated from pine Kamyr black liquor. (S.Y. Lin 1978, unpubl. data)...

Yoshida, H. Morck, R. Kringstad, K.P. Hatakeyama, H. Fractionation of kraft lignin by successive extraction with organic-solvents, II. Thermal-properties of kraft lignin fractions. Holzforschung 1987, 41 (3), 171-176. 

Additionally, a Kraft lignin fraction (Diwatex XP9), also delivered by Borregaard Lingotech, was studied. The properties of this fraction are summarized in Table 6. The LS and Kraft lignin concentration was 2% on the basis of the external phase weight. The polymer/salt mixture was dissolved in the aqueous phase before emulsifieation, and the emulsions had an internal phase weight of 30%. 

Semilogarithmic plot of weight-average molecular weight versus relative retention volume for paucidisperse kraft lignin fractions eluted from Sephadex G-lOO with aqueous... 

Paucidisperse acetylated methylated and underivatized kraft lignin fractions were selected for absolute molecular weight determinations at 8 x lO g/liter concentrations in DMF and aqueous O.lOMNaOH, respectively, using the Beckman Optima XL-A analytical ultracentrifuge. The partial specific volumes of the solute species (0.744 cm Vg), and densities p of solvent or solution were measured with a Paar 60/602 digital density meter. The sedimentation curves were scaimed at two wavelengths (280 and 320 nm) after equilibrium had been reached at more than one suitable rotor speed the effective baseline at 600 nm was subtracted from each set of sedimentation equilibrium data to correct for... 

Sedimentation equilibrium analyses of (A) acetylated methylated and (B) underivatized kraft lignin fractions. (1) Variation in solute concentration with radial distance from center of rotation monitored in Beckman Optima XL-A ultracentrifuge (2) curve fit to data points achieved by sum of terms of the form expressed in Equation (20). 

Using SigmaPlot 5.0 (Jandel Scientific, San Rafael, CA), the sets of sedimentation equilibrium data for the paucidisperse acetylated methylated and underivatized kraft lignin fractions were successfully curve fit to functions representing sums of terms of the form expressed in Equation (20). In no case were more than four individual terms required for the fits of unprecedented accuracy that were achieved these are exemplified in Figure 6A2 and B2. The sums of the areas under the component exponential curves confirmed that the total mass of solute species observed at equilibrium never differed by more than 1% from that present before the sedimentation process began. 

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

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.).

Figure 8. Dependence of Tg on composition of blends involving the methylated higher molecular weight kraft lignin fraction and either ( ) poly(trimethylene adipate) or (O) poly(trimethylene glutarate) (Data from reference 27).

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