Lignosulfonates

Laboratory methods for isolating lignosulfonates iaclude dialysis (56,57), electro dialysis (58), ioa exclusioa (58,59), precipitatioa ia alcohol (60,61), and extraction with amines (62—64). They can also be isolated by precipitation with long-chain substituted quartemary ammonium salts (65—67). 

Physical and Chemical Properties of Lignosulfonates. Even unmodified lignosulfonates have complex chemical and physical properties. Their molecular polydispersiti.es and stmctures are heterogeneous. They are soluble ia water at any pH but iasoluble ia most common organic solvents. 

Lignosulfonate Uses. Large-volume uses iaclude productioa of vanillin (qv) and DMSO (76). Commercially, softwood spent sulfite Hquors or lignosulfonates can be oxidized ia alkaline media by oxygea or air to produce vanillin [121 -33-5]. Other oxidizing ageats, such as copper(Il) hydroxide, nitrobenzene, and ozone, can also be used. 

Through reaction with sulfide or elemental sulfur at 215°C, lignosulfonates can also be used in the commercial production of dimethyl sulfide and methyl mercaptan (77). Dimethyl sulfide produced in the reaction is further oxidized to dimethyl sulfoxide (DMSO), a useful industrial solvent (see Sulfoxides). 

Water Treatment Industrial CleaningPipplications. Boiler and cooling tower waters are treated with lignosulfonates to prevent scale deposition (78). In such systems, lignosulfonates sequester hard water salts and thus prevent their deposition on metal surfaces. They can also prevent the precipitation of certain iasoluble heat-coagulable particles (79). Typical use levels for such appHcatioas range from 1—1000 ppm. 

Many of the chemical reactions used to modify lignosulfonates are also used to modify kraft lignins. These include ozonation, alkaline—air oxidation, condensation with formaldehyde and carboxylation with chloroacetic acid (100), and epoxysuccinate (101). In addition, cationic kraft lignins can be prepared by reaction with glycidjiamine (102). 

The physical and chemical properties of kraft lignin differ greatly from those of lignosulfonates. A summary of these differences is presented in Table 11. 

Figure 5 illustrates the type of encapsulation process shown in Figure 4a when the core material is a water-immiscible Hquid. Reactant X, a multihmctional acid chloride, isocyanate, or combination of these reactants, is dissolved in the core material. The resulting mixture is emulsified in an aqueous phase that contains an emulsifier such as partially hydroly2ed poly(vinyl alcohol) or a lignosulfonate. Reactant Y, a multihmctional amine or combination of amines such as ethylenediamine, hexamethylenediamine, or triethylenetetramine, is added to the aqueous phase thereby initiating interfacial polymerisation and formation of a capsule shell. If reactant X is an acid chloride, base is added to the aqueous phase in order to act as an acid scavenger. 

Lignites and lignosulfonates can act as o/w emulsifiers, but generally are added for other purposes. Various anionic surfactants, including alkylarylsulfonates and alkylaryl sulfates and poly(ethylene oxide) derivatives of fatty acids, esters, and others, are used. Very Httle oil is added to water-base muds in use offshore for environmental reasons. A nonionic poly(ethylene oxide) derivative of nonylphenol [9016-45-9] is used in calcium-treated muds (126). 

Sacrificial adsorption agents such as lignosulfonates (148—151) can be used to reduce the adsorption of more expensive polymers and surfactants. Other chemicals tested include poly(vinyl alcohol) (152), sulfonated poly(vinyl alcohol) (153), sulfonatedpoly(vinylpyrrohdinone) (153), low molecular weight polyacrylates (154), and sodium carbonate (155). 

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