ALCELL lignins

This black liquor is flashed and then the lignin is recovered by a patented precipitation technique followed by settling, centrifugation (or filtration) and drying. The result is a fine, brown, free-flowing powder. More details on how ALCELL lignin is obtained can be found in the literature (1,2). 

ALCELL lignin has a low moisture content (less than 2% water). It has a bulk density of 0.57 kg/L. The material is soluble in some organic solvents and also in dilute aqueous alkali solutions. It is insoluble in water under neutral or acidic conditions. 

Figure 1. Differential scanning calorimetric analysis of ALCELL lignins.

UV spectra of neutral solutions of ALCELL lignins exhibited maximum at 205-210 nm and at 275-281 nm which are characteristic of other lignin preparations. Alkali-neutral difference spectra exhibited three maxima at about 252-254 nm, 296-300 and 363-366 nm which indicate the presence of aromatic hydroxyl, a-conjugated hydroxyls, and conjugated carbonyl groups. The latter includes carbonyl groups in the a-position as well as those in cinnamaldehyde units mentioned above. The alkali-neutral difference spectrum of ALCELL lignins reduced with sodium borohydride shows an almost complete elimination of the peak at 360-366 nm and an increase... 

Some of the applications for ALCELL lignin that have been explored or considered are shown in T ble II. One application that has been reported... 

Figure 2. FTIR spectra of red oak ALCELL lignin. (Reprinted from ref. 8. Copyright 1987 American Chemical Society.)...

Recent work has concentrated on the use of ALCELL lignin as a substitute for phenol-formaldehyde resins in wood adhesives, particularly wafer-board. Some of the results obtained when a PF resin (Bakelite 9111) was replaced with different levels of hardwood ALCELL lignin in waferboard manufacture will be briefly discussed below. Table III shows the conditions used for waferboard manufacture. 

Initially three ALCELL lignin samples were evaluated acid (pH 3.95), neutral (pH 7.51), and alkaline (pH 8.96). The moisture content of lignin-PF bonded boards ranged from 4.1 to 4.8%, which is well within the 8% allowable limit of commercial grade waferboard. 

The MOR retention, which is the ratio of wet MOR to dry MOR, is shown in Figure 5. ALCELL lignin tends to preserve the MOR strength at... 

Some of the most recent work has focused on evaluations of ALCELL lignins outside the pH range initially shown in Figure 6. When ALCELL lignin replaced 30% of the PF resin and its alkalinity or the acidity were increased, dry MOR values above 90% of the MOR of the control (100% PF resin) were obtained. This shows the importance of pH on performance. Future work will include a more detailed look at formulations, pressing conditions, and derivatization as a way of obtaining a better adhesive. 

Zakzeski J, Jongerius AL, Weckhuysen BM (2010) Transition metal catalyzed oxidation of Alcell lignin, soda lignin, and lignin model compounds in ionic liquids. Green Chem 12 1225... 

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