Methylolated kraft lignin

Figure 2 shows a difference curve obtained from methylol kraft lignin when untreated lignin was used as reference. The difference curve has a distinct maximum at 590 m/z, characteristic of the phenol alcohol structures formed. By comparing the absorbance at 590 m/z with the molar absorbance (e) of models investigated, the amount of phenol alcohols in lignin can be estimated. The numerical values depend somewhat on the e value of the model chosen. In this study a value of e = 840 was used, the increase found at 590 m/z between the molar absorbances of the dimeric phenol alcohol and its parent phenol of model II. 

Hydroxymethylated lignin, when subjected to thermal cure, becomes insoluble in alkali. If we compare the DTA curves (P) of kraft lignin and methylol kraft lignin (Figure 5) we observe that in the latter a highly exothermic reaction started around 125°C., the material became stabilized over 190°C., and did not melt. Untreated kraft lignin is quite stable only... 

Based on alkali-soluble methylolated kraft lignin which was precipitated by acidification and blended with an acid-curing phenolic resin. 

Characteristics of Methylolated Kraft Lignin. The basic properties of methylolated kraft lignin are summarized as follows ... 

Figure 5. DTA curves of pine kraft lignin and its methylol derivative...

Exploded wood and Kraft methylolated lignins make poor quality binders at 2% loading, but should give better binders at 12%, which is not economical. The bark material is only marginally better. 

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