Lignin Binder

Northway Lignin Company USA Sulfur-free lignin Binders Emulsifiers, stabilizers, dispersants Liquid or powder agglomeration... 

Nippon Paper Ind. Steam explosion lignin Binders Chelators... 

The TMP process is carried out at temperatures greater than the transition temperature of the lignin binder, and the processed fibre is lignin coated. In the kraft... 

Lignins are most usually employed as various types of sodium lig-nosulfonate and are products of sulfite pulping. (Kraft lignins from the Kraft pulping process are also available.) They are used as dispersants, binders, sequestrants, and emulsifiers. Sodium lignosulfonate product variables include color, MW, and the degree of carboxylation and sulfonation on the lignin backbone. 

Every year the U.S paper industry produces over 33 million metric tons of kraft lignin (1). Most of this biomass is burned as fuel but small amounts are used as binders, asphalt additives, or cement additives. Larger fractions of this waste would be used in other industrial or commercial processes if an economical way existed to convert lignin into a marketable product with sufficient profit margin to compensate for the loss of the fuel. 

The lignins were separately mixed with PF resin (dry blending) at 30% and 50% levels prior to application as a binder. The formation and testing (9) of the waferboards (30 cm x 30 cm) were done by the Alberta Research Council Panel Testing Laboratory. 

Back (10) has indicated that superior board performance is achieved with covalent bonding of the adhesive to the wood. A binder, then, must have at least the minimum number of reactive sites per molecule. If there is one or fewer such sites, then the lignin should behave as a filler, which may or may not be chemically bound to the resin. In the case of two reactive sites, a linear macromolecule is possible, or the lignin may be considered to behave as an extender for a resin. When three or more sites are available, crosslinking can occur and the lignin could then become a full partner in the crosslinked binder. One may project how the lignin could behave, once the reactive sites on the lignin molecule have been mapped. For this chapter, the interactive sites will be alcohols and benzyl alcohols, to simulate the reaction of PF resins with the carbohydrates in the wood. 

Table II gives a number of derived parameters used to assess the lignin s suitability as a binder. For a full binder, lignins required a minimum of three sites per average molecule for formaldehyde grafting. None of the lignins studied approach this level. At least twice the number of sites found is required for steam exploded lignins and more for the kraft lignin. PF resins have an average of eight sites per molecule, a much higher density than projected, so PF resins are excellent wood binders.

Although the lignins do not perform adequately as full binders, they can be used as extenders. Now the resin supplies the benzylalcohol functionality and the lignins (and wood chips) need only supply alcohol groups to make ether linkages. The results for data on methylolated lignins are expressed in Table II as indices. The index is obtained by dividing the... 

In order to evaluate the method, the three lignins were methylolated, formulated with R-PF resin and waferboards made. The boards were tested for dry MOR, MOE, wet MOR and IB, but only the last term was the pa rameter chosen for quality determinations by the authors. Limited number of testing results are given in Table III. The data are not corrected for board density. The pass level for Canadian requirements is IB = 0.345 MPa, so all of the boards prepared passed, even those containing binder with 50% of the PF resin replaced with methylolated lignin. 

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. 

Non-sulfonated lignins find utility as emulsifiers and stabilizers in water-based asphalt emulsions, as coreactants in phenolic binder applications, as negative plate expanders in lead acid storage batteries, as protein coagulants in fat rendering, and as flocculants in waste water systems. 

The oil embargo of 1973-74 caused the Federal Highway Administration (FHWA) to establish an R D program to investigate the production of asphalt replacements and extenders from essentially non-petroleum sources. Since its inception, this program has examined in detail the use of sulfur in elemental and chemically modified form binders derived from cellulosic materials such as wood wastes and animal manure (JL) and lignins produced as by products of the paper and pulp industries (2) ... 

Both cellulosic wastes and lignins were found to have only limited applicability to the problem at hand. Sulfur, however, has been shown to be a very useful material for this purpose. Elemental sulfur may be used to extend asphalt, as in sulfur extended asphalt (SEA) binders, or chemically modified sulfurs may completely replace asphalt in paving mixtures. 

Pillonel, C., Mulder, M. M., Boon, J. J., Forster, B., and Binder, A., 1991, Involvement of cinnamyl-alcohol dehydrogenase in the control of lignin formation in Sorghum bicolor L. Moench, Planta 185 538-544. 

One technique being used is to bond solid wood with monomeric materials that are highly reactive with hydroxyl groups such as those in the wood fiber wall. For example, Schoring et al. (65) synthesized particleboards using as a binder hexamethylene diamine and polyvinyl chloride at 140°C. They postulated that the polyfunctional amine covalently linked the wood components, especially lignin, to the polyvinyl chloride. 

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