Phenolysis lignin

Wood Adhesives from Phenolysis Lignin A Way To Use Lignin from Steam-Explosion Process Iliro-Kuni Ono and Kenichi Sudo... 

Cure Rate Dependence on pH for the Phenolysis Lignin Resins. Cure behavior at different pH s of the resins was measured at 140°C, which is the usual hot-pressing temperature of phenolic resins. Relative rigidity change curves of LP-B at different pH s are illustrated in Figure 5. Cure advances faster as the pH of the resin increases. When the pH is 11.9, LP-B provides faster cure than the phenolic resin. A similar tendency has been found for LP-C. These findings clearly demonstrate that increasing pH of the resins improves cure rate. 

Table II. Tensile Shear Bond Strength of Adhesives from Phenolysis Lignin in Normal Test and after Repeated Boil Treatment...

Quantitative analysis of phenolysis lignin by 13C NMR has indicated that the amount of phenol bound to the steam exploded lignin is unexpectedly... 

ONO SUDO Wood Adhesives from Phenolysis Lignin... 

Functionality Measurement of Phenolated Lignin. It is important to have knowledge of the functionality of the phenolated lignin from the point of view of further chemical modification. The amount of bound phenol in the phenolysis reaction has been measured by titrating the phenol extracted from the reaction mixture (15). This indirect method measures the unreacted phenol and determines bound phenol as the difference between the initial charge and the titrated phenol. This is sometimes misleading. 1H NMR spectroscopy is another candidate for the determination of the amount of bound phenol. However, this calculation is difficult since the number of protons before and after the phenolysis reaction is unknown. 

Figure 2. Ratio of peak areas of the phenolated lignin to unreacted phenol as an index of phenol consumption during phenolysis.

This might be explained with failure to crosslink sufficiently. Sano et al. have also reported that phenolysis of hardwood lignin sulfonates enhances adhesion properties (22). It is thus clearly demonstrated that the introduction of phenol into lignin improves adhesion properties. 

Although there are still some problems, such as the ineffective methylo-lation of the phenolated SEL and the selection of a suitable extender, it can generally be concluded that phenolysis is a promising method to develop steam explosion lignin into attractive adhesives comparable to commercial phenolic resin. 

Before lignin sulfonates can be usefully incorporated into phenolic wood adhesives, these shortcomings must be remedied in a cost-effective way relative to the price of phenol. The remedial approach selected in this work has been to investigate the phenolysis of commercial lignin sulfonates with commercial grade phenol. 

Choice of the Lignin Modification Reaction. The phenolysis reaction was selected as a means of modifying the structure and reactivity of the ammonium lignin sulfonate for three main practical reasons. First, because this lignin derivative is soluble in (and will ultimately be used in conjunction with) liquid phenol itself second, because unreacted phenol, unlike other reaction solvents, would not have to be removed from the phenolated product after reaction and before conversion to the adhesive resin and third, because lignins and carbohydrates are known to react with phenols under acidic conditions (6,7). 

Phenolysis Reaction Procedure. To explore the concept of phenolation, mixtures of a commercial spray-dried softwood ammonium lignin sulfonate (10 g, Orzan A, 60% ammonium lignin sulfonate (MW0 = 228), 28% sugars, 6.2% sulfur, 2.5% ash, ITT-Rayonier, Shelton, Washington available in bulk at 17 cents a pound (<9) and commercial grade phenol (15 mL, Reichhold Chemicals Inc., Tacoma, Washington) contained in small pressure bombs (30 mL, Parr Instrument Company, Moline, Illinois) were heated by suspension in a hydraulic... 

Solubility of Phenolated Lignin Sulfonates. Since the presence of ammonium sulfonate moieties tends to confer water solubility, their disappearance should be reflected in a reduction of this characteristic. The extent of this effect was assessed by measuring the solubility of a stirred aliquot (1-4 g) of the 200 °C phenolysis product in water (200 mL). The resultant suspension was filtered and the residue dried for about 2 days at 22 °C to constant weight. The results obtained under a variety of reaction conditions are summarized in Table III. 

Another related set of experiments was also carried out to determine the effect of temperature on the insolubilization of the ammonium lignin sulfonate by phenolysis for a period of 2 hours. The results obtained, which are summarized in Table IV, show that more than one-third of the commercial product can be made water-insoluble by this procedure. 

Degradation of Lignin Molecular Weight. In addition to these transformations of the water-sensitive carbohydrates, the phenolysis reaction also affects... 

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...

Kinetic Study of the Phenolysis Reaction. With the demonstration that all of the already outlined deficiencies of ammonium lignin sulfonates as a phenol replacement can be reduced by phenolysis, attention was turned to consideration of the construction of a pilot plant scale continuous tube reactor. This is needed in order to prepare the large amounts of phenolyzed lignin sulfonates required for resin synthesis and testing under plywood production conditions. 

As a prelude to the design of the tube reactor (10), a kinetic study of the phenolysis procedure as a function of temperature was carried out on a larger scale. The equipment used was a stainless steel pressure reactor (Model 4501, Parr Instrument Company, Moline, Illinois). This reactor is fitted with an internal stirrer, an external electric heater, and a continuous sampling device. A mixture of the commercial ammonium lignin sulfonate (668 g) and molten phenol (1000 mL) was sealed into the reactor and heated to the designated temperatures. Approximately 3 hours were needed to heat the reactor from room temperature to 200 °C. A similar period of time was required to cool the reactor and its contents back to 22 °C after completion of a run. After a reaction period nominally lasting 2 hours, the unreacted phenol was steam distilled from the reaction mixture and the amount measured by comparative UV spectroscopy. The results obtained and summarized in Table IV show that a substantial amount of phenol becomes chemically combined with the renewable resource feedstock. 

Table VI. Kinetic Data for the Phenolysis of Ammonium Lignin Sulfonate in Phenol (61.5%)...

Phenolysis Amount of Concentration1 of Rate of Lignin Phenolysis... 

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