Kraft lignin in aqueous solution

RUDATINETAL. Association of Kraft Lignin in Aqueous Solution 147... 

Fig. 8.11 Particle-size distribution pattern W for kraft lignin in aqueous alkali solution (pH 12.7) at different temperatures [176]...

The spectra of kraft lignin in KBr pellets and in alkaline solutions show striking differences, as clearly illustrated by the difference spectrum (Fig. 5.2.7). The absorbances at 1560, 1494, 1395, and 1305 cm-1 are more intense, whereas the intensities in the spectral ranges 1710-1603 and 1270-900cm-1, and the aromatic skeletal vibration at 1514cm-1, are lower in NaOH solution. Similar qualitative spectral differences are observed when larch (Larix decidua) MWL is measured in KBr and in aqueous alkaline solutions (Fig. 5.2.8) although the magnitude of the differences is smaller with the hardwood MWL. 

The advent of 85% kraft lignin-based thermoplastics was an important development since it had been assumed until then that polymeric materials with such high lignin contents would be extremely weak — if, indeed, they were capable of retaining any measurable cohesiveness at all. However, the kraft lignin components in these new thermoplastics were still partially soluble in aqueous alkaline solution, and thus alternative formulations were sought to obviate dissolution in aqueous solutions of any kind. 

Figure 9. Apparent molecular weight distributions representing a homologous series of kraft lignin samples secured by desalting after association and dissociation in aqueous alkaline solutions for (1) 300 h, (2) 144 h and (3) 48 h at 170 gL1 in 1.0 M ionic strength aqueous 0.40 M NaOH (4) 0 h (5) 144 h and (6) 644 h at 0.50 gL 1 in aqueous 0.10 M NaOH. (Sephadex GlOO/aqueous 0.10 M NaOH elution profiles monitored at 320 nm.)...

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