Alkali lignins

Alkali-immobile dye-releasing quinone compounds, 19 293-294 Alkali lignins, 15 19-20 Alkali manganate(VI) salts, 15 596 Alkali manganates(V), 15 592 Alkali-metal alkoxide catalysts, 10 491 Alkali-metal alkoxides, effects of, 14 252 Alkali-metal alkylstannonates, 24 824 Alkali-metal fluoroxenates, 17 329-330 Alkali-metal hydrides, 13 608 Alkali-metal hydroxides, carbonyl sulfide reaction with, 23 622 Alkali-metal metatungstates, 25 383 Alkali-metal perchlorates, 18 211 Alkali-metal peroxides, 16 393... 

Due to the dark color of alkali lignins, their molar masses cannot be determined by means of the light-scattering method. However, as shown by Figure 10, elution with sodium hydroxide also brings about a consistent elution pattern of lignin sulfonates and polypeptides. It is assumed that this also applies to the kraft lignins. 

Table IV. Mn of Black Cottonwood Alkali Lignin Fractions in Different Solvents and at Several Temperatures...

Table V. Mn of Spruce Alkali Lignin Fractions Before and After Acetylation (in 2-methoxyethanol at 60°C)...

Table VII. LALLS Results on Alkali Lignin Fractions from Black Cottonwood ...

Alkali Lignin. Black cottonwood platelets were cooked in a flow-through reactor with 1.0N NaOH at 160°C flowing at a steady rate of about 17.5 ml.min-1 (3). The effluent was collected as several successive fractions from which lignin was precipitated and purified (3). The same procedure was applied, at 170°C, to spruce matchsticks. 

The reaction of formaldehyde with the meta positions of lignin clearly have considerable potential for the use of lignin, particularly heavily condensed alkali lignin, in polymeric applications. 

In this paper an additional approach that can be used for the modification or polymerization of especially alkali lignin is discussed. That is ... 

The suitability of the different conditions found for the meta-hydroxy-methylation and crosslinking of model compounds were subsequently evaluated on three alkali lignins obtained from different industrial spent liquors... 

The alkali lignins used were selected from different industrial origins in order to have a wide variation in their properties. The lignins were a kraft softwood, soda/AQ hardwood and soda bagasse lignin (Table II). 

From the results presented it is evident that the 2- and 6-positions of the phenylpropanoid nuclei can be used for the modification of alkali lignin. The positions can be used for the controlled polymerization of alkali lignin. Secondly, the positions were also used to introduce hydroxymethyl groups. The hydroxymethyl groups are reactive towards nucleophiles such as phenol and resorcinol. The modification of the 2- and 6-positions of the C9 units holds tremendous potential for the utilization of alkali lignin in polymeric applications. 

Van der Klashorst, G. H. The Modification of Lignin at the 2- and 6-Positions of the Phenylpropanoid Nuclei. Part III. Hydroxymethylation of Industrial Alkali Lignin. J. Wood Chem. Technol., in press. 

Oxidation of Alkali Lignin Studies on Oxidation in Alkaline Solution... 

Other preliminary experiments on alkali lignin included oxidations by barium peroxide and alkali (5, 6), alkali fusion, and alkali fusions in the presence of calcium peroxide, sodium borate perhydrate, and monopersulfate compound. Ether extractives and water extractives were examined, but in all cases too many of the oxidation products obtained were new and unidentifiable, and it was impossible to evaluate the experiments adequately with the available techniques. Vanillic acid appeared to be the chief oxidation product under conditions which did not demethylate further or destroy the aromatic nature of the oxidation products. Some oxidation conditions yielded p-hydroxybenzyl moieties as products, and some gave no trace of these products whatever. More detailed studies of the ether-insoluble, water-soluble components of the several oxidation mixtures were postponed until adequate procedures were developed for analytical isolation and identification. 

Alkali lignin was fused with caustic in the presence of sodium sulfide (/, 2) a number of times. Several compounds such as protocatechuic, vanillic, p-hydroxybenzoic, and oxalic acids were obtained, but the degradation of the alkali lignin was relatively low. Alkali fusion in nonaqueous systems 4y 20) also gave only small amounts of desirable products, and most of the starting lignin was recovered undegraded. 

Alkali lignin was oxidized with alkaline cupric oxide at atmospheric and superatmospheric pressure after first etching the lignin with alumi-... 

Oxidation with Barium Dioxide and Alkali. The alkali lignin was boiled in alkaline solution with an excess of barium dioxide and a little cupric hydroxide under conditions reported to give high yields of vanillic acid (5, 6). Analysis indicated only 13.8% ether extractives and the following yields on the basis of the original alkali lignin 2.8% vanillic acid, 0.4% p-hydroxybenzoic acid, 0.1% vanillin, 0.2% acetovanillone, and a trace of />-hydroxybenzaldehyde. 

Alkali Fusion. Several alkali fusions were performed in an attempt to convert the alkali lignin into low molecular weight compounds that could be identified in this exploratory part of the program. 

Fusion with Alkali Alone. Alkali lignin was first fused with potassium hydroxide at 180°-190°C. under standard conditions used previously for converting vanillin to vanillic acid (10) and syringaldehyde to syringic acid (14). Under these conditions, protocatechuic and vanillic acids were the chief oxidation products, but over 70% of the lignin was recovered as a lignin-like polymeric product. Longer fusion times helped... 

Fusion with Alkali and Cupric Oxide in Nonaqueous Solvents. Alkali lignin was fused with potassium hydroxide and cupric oxide in methanol under conditions suggested by Tiemann (20) and in n-amyl alcohol as suggested by Klages (4). These procedures were very effective in earlier model compound studies in our laboratories (12). Ether extracts obtained were less than those from corresponding experiments in aqueous solution, and qualitative compositions were essentially the same. In the case of the amyl alcohol experiments, artifacts with the cupric oxide were obtained. Again, experiments were conducted under more dilute conditions in a bomb under superatmospheric conditions, but results were no better. 

Table I. Representative Schedule for Oxidizing Alkali Lignin with Gaseous Oxygen...

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