Phenolated lignin sulfonates

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. 

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... 

LF lignin sulfonates modified by phenol and formaldehyde and then by 2,4-D (23). 

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. 

Peniston QP, McCarthy JL (1948) Lignin II Liberation of phenolic hydroxyl groups by alkaline cleavage of lignin sulfonic acids J Am Chem Soc 70 1329-1332... 

In contrast, the lignins from the sulfite pulping processes are readily available in commercial quantities from several pulp producers in different countries. More than enough is available annually to replace the entire output of synthetic phenol. In aqueous solution, the price of these lignin sulfonates can be as low as 3 cents a pound on a dry basis. The spray-dried forms sell for about 15 cents a pound (>/). Clearly, the process of spray drying is not inexpensive. 

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. 

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... 

Table I. Effect of Duration of Heating on the Ammonium Ion Content of a Mixture of Ammonium Lignin Sulfonate and Phenol (61.5%)...

Table II. Comparison of Total Pressure Generated by Heated Phenol and a Phenol-Ammonium Lignin Sulfonate (38.5%) Mixture in a Stirred Batch Reactor...

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. 

Lignin Sulfonate in Phenol (61.5%) using the Arrhenius Rate Constant Model (15)... 

Combustion Energy Alkaline Hydrolysis or Direct AoDlications Phenol-Formaldehyde Resins, Epoxy-modified lignin, Aminated Lignin, Sulfonated Lignin, Cement, Ceramics, Emulsions, Fertilisers, Silicon Carbide Pyrolysis CO, H2, Methane, Phenol, Ethene, Benzene Alkaline Melt or Hvdroaenoivsis Phenols... 

Lignin sulfonates are, technically, low-molecular-weight polymers containing a witch s brew of primary and secondary alcohols, phenols, and carboxylic acid functionalities. They are prepared by the sulfonation of lignin byproducts of pulp and paper manufacture, followed by neutralization to the sodium, calcium, or ammonium salt. The resulting materials are useful as dispersing agents for solids and oil/water emulsions, and as stabilizers for aqueous dispersions of dyes, pesticides, and cement. They are very inexpensive relative to other materials and are very... 

Substitution Reactions on Side Chains. Because the benzyl carbon is the most reactive site on the propanoid side chain, many substitution reactions occur at this position. Typically, substitution reactions occur by attack of a nucleophilic reagent on a benzyl carbon present in the form of a carbonium ion or a methine group in a quinonemethide stmeture. In a reversal of the ether cleavage reactions described, benzyl alcohols and ethers may be transformed to alkyl or aryl ethers by acid-catalyzed etherifications or transetherifications with alcohol or phenol. The conversion of a benzyl alcohol or ether to a sulfonic acid group is among the most important side chain modification reactions because it is essential to the solubilization of lignin in the sulfite pulping process (17). 

---