Lignin based

Nimz, H.H., Lignin-based wood adhesives. In Pizzi, A. (Eds.), Wood Adhesives Chemistry and Technology, Ch. 5. Marcel Dekker Inc., New York, pp. 247-288, 1983. 

S. Schilling. Lignin-based cement fluid loss control additive. Patent US 4926944, 1990. 

The advent of lignin-based polymeric materials as putative engineering plastics represents one of several technological... 

When a new method is reported for synthesis of polymers, in a short time it is also tried on lignins. New lignin-based raw materials are also constantly appearing the use of steam exploded hardwood lignin for making plywood adhesives has recently been explored by Gardner and Sellers (64) and found promising in this intensively competitive area. 

Lignin utilization studies have been conducted in several fields. However, no practical, commercial process has yet emerged for the manufacture of lignin-based polymeric materials. This is undoubtedly related to such factors as product inhomogeneity, reactivity differences, and also with lack of familiarity with this type of raw material. It should be also stressed that lignins are only by-products from pulp manufacture. However, the utilization of lignins in polymeric materials seems to be possible. 

Assume a mole equivalent unit of 200 for organosolv lignin, based on a typical analyzed Cg lignin unit. 

The addition of phenol-formaldehyde precondensate to lignin or methylolated lignin has been known as a way to introduce phenolic reactivity into lignin, and this is usually applied to the preparation of lignin-based... 

Adhesive Formulation. Adhesives for testing consisted of 100 parts resin, 10 parts wheat flour as extender, 4 parts commercial additive, and 2 parts water. This formulation is recommended by Japanese board manufacturers. Adhesives without wheat flour were also formulated to examine the bond strength of the neat lignin based resins. 

Cure Rate of the Phenolated SEL Resins. 13C NMR spectra of the phenolated SEL formaldehyde-treated resins revealed the formation of methylol groups. A similar cure reaction to resole type phenolic resins is expected to occur with the phenolated lignin-based resins. Since cure rate normally determines production capacity of a board mill, it is important that new types of adhesives have at least the same cure rate as the conventional phenolic adhesives. Cure analysis of resins has usually been examined by... 

Relative rigidity vs. temperature curves of LP s are shown in Figure 4 in comparison with a commercial phenolic resin. The pH of these resins was previously adjusted to around 10.8. The phenolic resin is fully cured at around 75°C. By contrast, the curves of the three lignin-based resins exhibit slower cure as compared to the phenolic resin. The retardation increases as the charge ratio of formaldehyde increases. Some retardation had already been found, but neglected, for the phenolated lignin/phenol-formaldehyde resins (12). In this study, the neat phenolated SEL was used for resin preparation. It can be concluded that phenolated steam explosion lignin-based resins have an intrinsically retarded cure behavior as compared to phenolic resin at the same pH. 

Figure 4. Cure behavior of phenolated steam explosion lignin-based resins.

Figure 5. Cure rate dependence on pH for the phenolated steam explosion lignin-based resin LP-B.

This lignin-based bio-adhesive can be applied under conventional pressing conditions. The resulting particle boards meet German performance standards without emission of harmful vapors. An added advantage is the total utilization of lignin from spent pulp liquor. 

Effect of Soft-Segment Content on the Properties of Lignin-Based Polyurethanes... 

Materials. The materials are described in detail in the studies summarized in Table I. Most of these results are based on kraft lignin. The NCO/OH ratio of all of these networks were high greater than 1.5. All of the networks were prepared from homogeneous solutions of the lignin-based polyol, added (soft segment) polyol, and diisocyanate. Films were cast and cured under mild conditions with a controlled loss of solvent. The films were post-cured to insure complete reaction (25). 

KELLEY et al. Soft-Segment Content of Lignin-Based Polyurethanes 407... 

This paper examines two types of hydroxypropyl lignin based macromers, and these are illustrated schematically in Figure 1. Macromers with propylene oxide (PO) are formed by reducing the number of available hydroxyl groups on HPL followed by chain extension with PO and macromers with cellulose triacetate (CTA) are synthesized by attaching a monofunctional CTA chain to a limited number of terminal OH groups on HPL via a suitable grafting reaction. 

Figure 1. Schematic representation of two types of hydroxypropyl lignin-based macromers.

The engineering of lignin-based macromers with propylene oxide to target specifications appears as a useful technique for formulating components for block copolymers and segmented thermosets. 

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