Physicochemical Studies of Alkali Lignins. I. Preparation and Properties of Fractions

Gupta, P. R.; Goring, D. A. I.

doi:10.1139/v60-034

Cited by 17 publications

(4 citation statements)

References 24 publications

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“…Summarizing the present knowledge, we may conclude that the lignin polymer behaves as a spherical, amorphous (1,(35)(36) macromolecule with a polydisperse molecular weight Colloid and Polymer Science, I/oi. 257 • No.…”

Section: Introductionsupporting

confidence: 57%

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The colloidal behaviour of kraft lignin

Lindströmn¹

1979

Colloid Polymer Sci

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Section: Introductionsupporting

confidence: 57%

“…Gupta and Goring have for example reported molecular weights of alkali-lignins ranging from a few hundred to 5 × 107 (35). Gupta and Goring have for example reported molecular weights of alkali-lignins ranging from a few hundred to 5 × 107 (35).…”

Section: Introductionmentioning

confidence: 99%

The colloidal behaviour of kraft lignin

Lindströmn¹

1979

Colloid Polymer Sci

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“…The second approach concerns the interparticle hydrodynamic and direct potential perturbations to motion, and in the non-free-draining limit of the hard sphere, the Brownian motion has been analyzed by a number of authors.53•56 Since the hydrodynamic effect varies as R"1, where R is the interparticle separation, this influence will dominate in the dilute regime compared with the hard-sphere potentials, which have a significantly sharper distance dependence. This hydrodynamic effect has been treated in detail by Anderson and Reed,57 who calculate the velocity U\ of a particle according to the one-dimensional Langevin equation: dU, M-^= -fUx + Bit) (14) where M is the particle mass, /is the friction factor, and Bit) is the fluctuating force. The velocity is then calculated by integrating over the volume ir.…”

Section: Solvent Diffusionmentioning

confidence: 99%

Hydrodynamics of kraft lignins

Garver¹,

Callaghan²

1991

Macromolecules

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The self-diffusion coefficients of kraft lignin preparations in aqueous and nonaqueous solvents have been measured by using pulsed field gradient NMR (PFGNMR). The diffusion coefficients of kraft lignin fractions conform to the relationship D, -M-', where a is 0.39 for unacetylated lignin in aqueous 1.0 M NaOD and 0.30 for acetylated lignins in CDC13. These exponents and the measured DO values indicate a branched macromolecule. Measurements of the concentration dependence of the self-diffusion coefficients for both the solvent and solute are consistent with an extremely compact and flat conformation for acetylated lignin in CDC13. A diffusion coefficient corresponding to a hydrodynamic radius of 380 A in pH 6.5 aqueous buffer indicated significant association under these conditions. However, there was no evidence of association for unacetylated lignin preparations in pH 9.0 D20, aqueous 1.0 M NaOD, and DMF-d, and for acetylated lignins in CDCl3 and acetone-ds. A kinetic interpretation based on free-volume theory is given for diffusion of branched macromolecules in concentrated solution. IntroductionLignin is a structural macromolecule, found in conjunction with hemicellulose components between cellulose microfibrils, in the cell wall of vascular plants. Although lignin biosynthesis is currently perceived to occur by random coupling of free-radical intermediates derived from phenylpropanoid alcohols, the "polymerization" steps of lignin biosynthesis are poorly understood.' In fact, several recent reports have focused on the extent of order of the lignin macromolecule either in the plant cell wall environment or after removal from the cell wall by various pulpingKraft pulping is currently the most common method used for removal of the unwanted lignin component from wood during recovery of cellulose for the manufacture of paper products. As such, kraft lignins represent a significant potential resource. Kraft pulping cleaves and solubilizes the lignin under relatively severe aqueous conditions at 170 O C in 1 M NaOH and 0.2 M NazS.3 Alder has reviewed the principal structures found in softwood lignin^,^ and Gierer has reviewed structural transformations known to occur during pulping processes.6 Several significant phenylpropanoid structures found in kraft lignins, arising directly from native lignin structures, are depicted in Figure 1. In kraft lignins typically about 42% of the phenolic oxygens are not etherified and may be ionized in alkaline solution. This percentage decreases with increasing molecular eight.^^^ Motivation for PFGNMR Hydrodynamic Studies. Difficulties arising from lignin physical properties have notoriously impeded efforts to apply the techniques of light scattering, chromatography, viscosimetry, and tracer analysis to the systematic study of lignin hydrodynamics. The extent of these difficulties includes problems with fractionation and purification due to association and adsorption on chromatographic media as well as the spectrophotometric properties of lignin, which complicate light scattering...

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“…There is no reason to assume that only one type of bond is responsible for lignin-carbohydrate linkage, in view of the possibilities it appears unlikely that only one type would be involved. Another factor which could limit the solubility is a solubility change of the type noted by Gupta and Goring (1960). In either case it is clear that although alkali treatment after milling is more effective than treatment before milling in rendering P. radiata lignin soluble in cold dilute alkali it does not, because of solubility limitations, lead to any substantially larger yield of milled wood lignin.…”

Section: Resultsmentioning

confidence: 99%

The Effect of Milling and Alkali Treatments on the Accessibility of the Lignins ofPinus radiataandEucalyptus regnans

Bland¹,

Menshun²

1973

Holzforschung

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Keywords Ball milling Lignin accessibility Lignin-carbohydrate linkage Pinus radiata Eucalyptus regnans Schlüsselwörter (Sachgebiete) Schwingmahlung Zuganglichkeit von Lignin Lignin-KohlenhydratBindung The Effect of Milling and Alkali Treatments on the Accessibility of the Lignins of Pinus radiata and Eucalyptus regnans SummaryVibratory ball milling of wood meal produced a large increase in the amount of lignin soluble in cold (20° C) . aqueous sodium hydroxide. This effect was greater for Pinus radiata than for Eucalyptus regnans. These results indicate a mechanical liberation of lignin by the milling and/or cleavage of alkali-sensitive bonds. The yield of milled wood lignin from alkali-treated milled wood of E. regnans was equal to the amount of lignin soluble in cold alkali but was much less from P. radiata apparently because of solubility limitations. Hot (95° C) alkali treatment of milled wood led to a higher amount of alkali soluble lignin and a lower yield of milled wood lignin for both species. About half of the lignin appears to be bound to carbohydrate by bonds resistant to alkali at 20° C. Die Wirkung der Mahlung und Alkali-Behandlung auf die Zugänglichkeit des Lignins von Pinus radiata und Eucalyptus regnans Zusammenfassung Durch Behandlung von Holzmehl in einer Schwingmühle nahm die Menge an Lignin, das in kalter (20° C), wäßriger 0,1 M Natronlauge löslich war, stark zu. Die Wirkung war bei Pinus radiata größer als bei Eucalyptus regnans. Diese Befunde ergaben sich infolge mechanischer Freisetzung von Lignin durch den Mahlvorgang und/oder durch Lösung der alkali-empfindlichen Bindungen. Die Ausbeute an milled wood Lignin aus mit Lauge behandeltem gemahlenem Holz von E. regnans war ebenso groß wie an Lignin, das in kalter Lauge löslich war, aber deutlich geringer bei P. radiata, wahrscheinlich wegen begrenzter Löslichkeit. Wurde gemahlenes Holz mit heißer Lauge (95° C) behandelt, so ergab sich ein höherer Betrag an alkali-löslichem Lignin und eine geringere Ausbeute an milled wood Lignin für beide Holzarten. Etwa die Hälfte des Lignins scheint an Kohlenhydrate durch Bindungen geknüpft zu sein, die Lauge von 20° C widerstehen. IntroductionIsolation of milled wood lignin from Eucalyptus regnans wood was shown by Bland and Menshun (1967) to be assisted by mild alkali pretreatment of the wood before milling. It was suggested that this treatment liberated lignin because it was attached by alkali-sensitive bonds to the polysaccharides. Brownell (1971) has found that while treatment of spruce wood by alkali before milling leads to a higher yield of lignin which is soluble in benzyl alcohol-dimethylformamide, post-treatment of milled wood by alkali gives no enhancement of yield. From this he suggested that the main effect of the alkali pretreatment was that it facilitated grinding by embrittlement of the wood, rather than by bond cleavage. We have observed that alkali pretreated milled wood tends to be more free flowing than untreated and that the mill balls remained bright and clean with no adhering wood pow...

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Physicochemical Studies of Alkali Lignins. I. Preparation and Properties of Fractions

Cited by 17 publications

References 24 publications

The colloidal behaviour of kraft lignin

The colloidal behaviour of kraft lignin

Hydrodynamics of kraft lignins

The Effect of Milling and Alkali Treatments on the Accessibility of the Lignins ofPinus radiataandEucalyptus regnans

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