Lignin milled wood

The polydispersity of softwood milled wood lignin, as measured by M /M = 2.5, is high compared with that of cellulose and its derivatives. 

Milled wood lignin (MWL) is produced by grinding wood in a rotary or vibratory ball mill. Lignin can be extracted from the resulting powder using solvents such as methylbenzene or... 

Comparisons made between unpurified spruce milled-wood lignin fractions and unfractionated poljrmers made from coniferjd alcohol alone already revealed the great qualitative similarity between natural and biosynthetically duplicated lignins [see, for example, K. Freudenberg in 94), pp, 125—126]. When a purified lignin fraction is compared tvith an identical fraction made from a mixture of all three -coumaryl alcohols, the resemblance is of course much greater. 

Kawamura, /., and T, Higuchi Comparative Studies of Milled Wood Lignins from Different Taxonomical Origins by Infrared Spectroscopy. In (10), pp.439--f56. 

Okay, A. Hydrogenation Products of Spruce Milled-Wood Lignin and of Related Model Compounds. Holzforschung J7, 105—110 (1963) J. Org. Chem. 27, 1783-1786 (1962). 

Konishi et al. (4,5) reported that milled wood lignin (MWL) treated with the laccase from C. versicolor suffered oxidative polymerization, depolymerization producing... 

Figure 1. Among the five resonance structures shown, Ra, Rb and Rc will undergo random coupling reactions more readily than Rd and Re, since the radicals Rd and Re are sterically hindered. Indeed, this is what is found experimentally, since only minor amounts of 0-1 structures (derived from Rd) have been found in milled wood lignin (22,23), and demethoxylation does not occur to any appreciable extent during lignin formation (21). The reactivity of the phenoxy radical, Ra, will be affected greatly by pH since it can be masked by protons under acidic conditions, and its reactivity will thus be diminished. On the other hand, the reactivity of Rb and Rc will not be affected appreciably by pH. Thus more frequent coupling of Rb-Rc, Rb-Rb and Rc-Rc can be expected at low pH, and more of Ra-Rb and Ra-Rc coupling at high pH.

The second way consists of hot-water extraction of finely divided wood powder, previously extracted with aqueous dioxane for removing milled wood lignin. The resultant LCC-WE is obtained in 9.3-10.0% yield and does not differ from Bjorkman LCC in relation to chemical composition and molecular weight (11) (see Table I). This fact is very significant in demonstrating that LCC s containing up to 18% lignin are able to be extracted with hot water alone from wood powder. 

Its nature as a lignin component is confirmed by its elemental composition and IR-spectrum compared with corresponding data for a milled wood lignin preparation, Table I and Figure 12. 

Water-insoluble lignin C9H7.4602.47(OCH3)o.83 Milled wood lignin (P. abies) (6) C9H8.8302.37(OCH3)o.96... 

Lignin Samples. Ball-milled (BM) aspen lignin was prepared following the procedure of Lundquist et al. (21). The yield of purified milled wood lignin obtained was usually about 10% w/w that of ethanol/benzene-extracted aspen wood. 

Table II. Some Basic Data of Lignins. Milled Wood Lignin = MWL...

Milled wood lignin was mixed with the crude enzyme solution of Tram-ties versicolor extracellular phenoloxidases produced on spent sulfite liquor in a ratio of approximately 2 1. This comprised the main part of the two-component bio-adhesive. Industrial particles were bonded with 15% bioadhesive under conventional pressing conditions to have 19 mm particle boards (40 x 50 cm) of the properties described in Table IV. The bonding reaction (crosslinking) took place in aqueous solution at room temperature. If conventional pressing technology is applied, the temperature should be elevated in order to maintain water evaporation within a reasonable press time. 

Note The lignins were technical by-product lignins of different polarity, 1 = lignin sulfonates, 2 = milled wood lignin. 

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