Sterol ethoxylates

Surface-active compounds can be produced from all wood constituents. For instance, water-soluble cellulose derivatives and lignin, in the form of lignosulfonates, can be used as dispersing agents in many applications. This chapter focuses on the production of resin and fatty acids as well as sterols and sterol ethoxylates as forest-industry by-products, and their use as surface-active components. Moreover, the potential production of hemi-celluloses and their possible utilization as steric stabilizers of oil-in-water emulsions is also outlined. 

Sterols and Sterol Ethoxylates 3.3.1 Production and Uses of Phytosterols... 

Phytosterol ethoxylates (Figure 3.6) obtained by reaction of sterols with ethylene oxide in the presence of catalysts were produced in the early 1980s, for use mainly as emulsifiers in cosmetics [34, 35, 37]. Plant sterol ethoxylates are produced with an average degree of ethoxylation from 5 to 30 [38], but with a very broad homologue distribution. 

The CMC values of sterol ethoxylates at room temperature are very low, in the range of 3-lOpM, which is much lower than those of corresponding ethoxylated nonylphenols. 

Figure 3.7 Surface tension of plant sterol ethoxylates with different ethoxylation degrees, 150 minutes after addition of the surfactant.

FIG. 11. Transmission electron micrographs of freeze fractured oily droplets dispersed (a) in a hexagonal and (b) in a cubic liquid crystalline phase, bar 100 nm. From Mueller-Goymann, C., Liquid crystals in emulsions, creams and gels, containing ethoxylated sterols as surfactant, Pharm. Res. 1 154-158 (1984). 

The extremely large number of lanolin derivatives has been reviewed by Barnett8 and Steel.16 Lanolin derivatives can be formed by acetylation, ethoxylation, propoxylation, alkoxylation, and isobutylation of hydroxy groups, as well as hydroxylation of the double bond in the sterol ester component. Hydrolysis of lanolin can also produce lanolin alcohols and lanolin acids, which like lanolin can be ethoxylated, acetylated, and hydoxylated. 

Mileller-Goymann, C. Liquid crystals in emulsions, creams and gels, containing ethoxylated sterols as surfactant. Pharm. Res. 1984,1, 154-158. 

Pulp and paper mill sludge is a complex and changeable mixture of dozens or even hundreds of compounds. Some are well known, like natural wood extractives, organochlorines, organosulfides, and dioxins. Priority pollutants and chemicals of concern that must be analyzed in pulp mill residues include heavy metals, chlorinated hydrocarbons, chlorobenzenes, PAHs, chlorinated phenols, chlorinated catechols, chlorinated guaiacols, phthalates, resin acids, alkylphenols and alkylphenol ethoxylates, and plant sterols. 

This synthesis is usually carried out in the presence of alkaline catalysts. The catalyst is neutralized and at least partially remains in the final product. Primary Cg-Cig long-chain alcohols are generally used for ethoxylation. The alcohols may be of synthetic (Ziegler or oxo alcohols), vegetable and animal origin. Other hydroxo compounds can be subjected to ethoxylation, for example diols, such as 2,4,7,9- tetramethyl-5-decyne-4,7-diol ( Surfinol ), vegetable sterols, lanoline fractions enriched by sterols and fatty alcohols [34]. Ethoxylated alcohols and mercaptanes modified by a subsequent addition of propylene oxide or ethoxylated and propoxylated alcohols mentioned before (section 1.2.2) are of some industrial importance. 

The aggregation behavior of these surfactants appears to be unusual and requires a deeper analysis. A comparison of the CMC values reported for different polyoxyethylene sterols and polyoxyethylene octylphenols, which have lipophilicities similar to that of cholesterol, is shown in Fig. 2. As the hydrophilicity of the surfactant increases, the trend in the CMC values is quite opposite the CMC values for sterol surfactants are reduced when the number of oxyethylene units is increased, which is contrary to that found for other polyoxyethylene surfactants. The observation of lanolin alcohols can be viewed as an intermediate behavior. At lower numbers of oxyethylene units the CMC trend follows the behavior of sterols, whereas at a higher degree of ethoxylation the behavior becomes dominated by the ethoxylated alcohols. These comprise only about 20% of the weight but approximately 40% of the molar composition. 

The solubility and phase behavior of ethoxylated sterols can be expected to be different from that of nonionic surfactants with straight or branched hydro-phobic moieties. The rigid and bulky hydrophobic group is believed to hinder the packing of surfactant monomers into spherical or rod-like micelles [11]. 

Description. This class of surfactants essentially covers ethoxylated derivatives of lanolin (wool fat) and castor oil. Lanolin is the generic name of a wax containing a complex mixture of esters and polyesters of high-molecular-weight alcohols (aliphatic, steroid, and triterpenoid) and fatty acids (saturated, unsaturated, hydroxylated, and non-hydroxylated). The ethoxylation is carried out on fractionation products of lanolin (lower aliphatic alcohols and sterols). 

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