Lignin sulfonates with water

Elution of Lignin Sulfonates with Water. As can be seen from Figures 1, 2, 3, and 4, the fractionation of lignin sulfonates on elution with water through Sephadex G-50 and G-75 takes place in such a way that the logarithms of... 

Hydroxyalkyl lignin derivatives were crosslinked with diisocyanates or with melamine in both solvent and aqueous emulsion-based adhesive formulations for wood products (51) (Figure 7). Adhesive performance was found to be related to component solubility and compatibility (51), The use of kraft lignin in aqueous alkali and that of lignin sulfonates in water has been explored in combination with emulsifiable diisocyanates (52) in wood adhesives. Satisfactory strength properties were reported. 

Why then are these lignin sulfonates not used as a partial replacement for phenol in phenol-formaldehyde-based wood adhesives The first reason is that the presence of the sulfonate groups confers a water sensitivity to the adhesive. This sensitivity is exacerbated by the presence of water-soluble carbohydrates. A second reason is the low reactivity of the lignin sulfonates with formaldehyde and the consequent low level of crosslink density achieved in the final adhesive. A third reason is the molecular size of some of the lignin sulfonates. Large molecular weight material cannot penetrate the cell walls of the wood to form an adhesive continuum between contiguous wood particles. 

In the early 1960s one of the first commercial products Terra Firma (Intrusion-Prepakt, Cleveland) was marketed in the United States and abroad. The patent covering this product [11] defines a calcium lignin sulfonate with reduced sugar content, sodium dichromate and aluminum sulfate catalysts, and copper sulfate and calcium chloride accelerators. The product was marketed as a dry, precatalyzed powder. It was mixed with water in varying proportions for field use. Water content was the only... 

Synthetic examples include the poly(meth)acrylates used as flocculating agents for water purification. Biological examples are the proteins, nucleic acids, and pectins. Chemically modified biopolymers of this class are carboxymethyl cellulose and the lignin sulfonates. Polyelectrolytes with cationic and anionic substituents in the same macromolecule are called polyampholytes. 

Figure 1. Fractionation of lignin sulfonates in spent sulfite liquor on Sephadex G-50. Eluent water. (Reprinted with permission from ref. 1. Copyright 1969 Wiley.)...

Figure 6 shows that the proteins used for calibration elute in the same way as lignin sulfonates, which justifies the use of proteins as calibration standards. A comparison between Figures 4 and 6 shows that elution with an electrolyte solution fractionates lignin sulfonates in the range 3 000-80 000 dalton, but that elution with water fractionates those in the range 20 000-100 000 dalton. 

One disadvantage of using salt solution as eluent is that the lignin sulfonates tend to adsorb onto the gel matrix, resulting in a resolution inferior to that obtained by elution with water. On the other hand, elution behavior with water is adversely affected by the polyelectrolyte properties of the lignin sulfonates. Adsorption, which is caused by the phenolic hydroxyl... 

To eliminate the high pressure resulting from the excessive water, we studied the use of dried SWL solids in several experiments. It was never possible completely to recover pasting oil when the dried solids were used. At 380°C. the paste oil was nearly recovered, but the monophenol yield was low. At 428°C., the paste oil recovery was lower, and the monophenol yield was higher. In one experiment the dried solids were extracted with liquid ammonia so that carbohydrate material would be removed from the calcium lignin sulfonate. Approximately 10% of the solids were removed... 

Methods that attempt to directly measure the sulfonate content of lignin in pulps must overcome the challenge of distinguishing sulfonate from accompanying carboxylate groups. One such method (Sjostrom and Enstrom 1966, Sjostrom et al. 1965) is based on the concept that, under acidic conditions, benzidinium ions form salts only with the sulfonate groups. The pulp is saturated with an aqueous solution of benzidine hydrochloride and washed with water to remove excess reagent the benzidinium ions are eluted with hydrochloric acid and determined by UV spectrophotometry. 

Table IV. Effect of Reaction Temperature on Extent of Phenolysis and Degree of Water Insolubility Conferred upon a Commercial Ammonium Lignin Sulfonate Admixed with Phenol (61.5%) and Heated for 2 Hours...

---