Chemically modified lignins

C. D. Williamson. Chemically modified lignin materials and their use in controlling fluid loss. Patent GB 2210888, 1989. 

These data indicate that mechanical, chemical, and biological attack of lignin create radical centers. We turned our attention next to an EPR analysis of chemically modified lignins. Reducing a number of samples (23) with NaBH4 seemed to have very little effect on the spin content. However, when samples were converted to their metal salts, a marked increase in free radical centers was observed. Acidification of the salts returned the spin content to its original level. 

Thus, a small concentration of ortho- or parabenzoquinone species in an environment of phenolic functions could explain the radical enhancement upon basification. The residual spin content of the neutral or acid form of lignin is almost nil in whole wood, very small in native lignins, but significant in kraft and other chemically modified lignins. Such a stable free radical could be attributed to (a) the small equilibrium concentration of I in Equation 1, (b) a semiquinone polymer patterned after synthetic models (4y 25) containing donor and acceptor groups, or (c) radicals entrapped and stabilized in a polymeric matrix (5,15). 

The quinonemethide content of chemically modified lignins may be much higher. If quinonemethide precursors (—e.g. structures of type III) are present in high yield pulps in residues of condensed lignin attached to the fibers, attempts to bleach the pulps with oxidizing agents may lead... 

The institution of fractionated or chemically modified lignin for part or all of the phenol in the synthesis of phenol-formaldehyde resins. This would particularly include the newer forms of lignin recovered with minimum structural alteration and also those representing virtually complete depolymerization to phenylpropane units. 

To improve the processability of the rubber/lignin compound without losing the good mechanical and heat-resistant properties, we used CB-BR, which has hydroxyl groups to make chemical bond with lignin (Fig.l), and a chemically modified lignin whose phenolic hydroxyl groups were converted into aliphatic hydroxides (Fig.2). 

Chemically Modified Lignin and Its Application in Oil and Gas Drilling Industry... 

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