Ethoxylates fatty acids

8 Sorbitan esters and their ethoxylated derivatives (Spans and Tweens) 

The fatty acid esters of sorbitan (generally referred to as Spans, an Atlcis commercial trade name) and their ethoxylated derivatives (generally referred to as Tweens) are perhaps one of the most commonly used nonionics. The sorbitan esters are produced by reaction of sorbitol with a fatty acid at a high temperature ( 200 C). The sorbitol dehydrates to 1,4-sorbitan and then esterification takes place. If one mole of fatty acid is reacted with one mole of sorbitol, one obtains a mono-ester (some di-ester is also produced as a byproduct). Thus, sorbitan mono-ester has the following general formula. 

The free OH groups in the molecule can be esterified, producing di- and tri-esters. Several products are available depending on the nature of the alkyl group of the acid and whether the product is a mono-, di- or tri-ester. Some examples are given below, 

The ethoxylated derivatives of Spans (Tweens) are produced by reaction of ethylene oxide on any hydroxyl group remaining on the sorbitan ester group. Alternatively, the sorbitol is first ethoxylated and then esterified. However, the final product has different surfactant properties to the Tweens. Some examples of Tween surfactants are given below, 

The sorbitan esters are insoluble in water, but soluble in most organic solvents (low HLB number surfactants). The ethoxylated products are generally soluble in water and they have relatively high HLB numbers. One of the main advantages of the sorbitan esters and their ethoxylated derivatives is their approval as food additives. They are also widely used in cosmetics and some pharmaceutical preparations. 

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The physical properties of the fatty acid ethoxylates depend on the nature of the fatty acid and even more on ethylene oxide content. As the latter increases, consistencies of the products change from free-flowing Hquids to slurries to firm waxes (qv). At the same time, odor, which is characteristic of the fatty acid, decreases in intensity. Odor and color stabiUty are important commercial properties, particularly in textile appHcations. Oleic acid esters, though possessing good functional properties, cannot be used because they tend to yellow on exposure to heat and air. 

At room temperature, ca 60 wt % ethylene oxide is needed to solubilize the fatty acids. Surface activity of the ethoxylates is moderate and less than that of alcohol or alkylphenol ethoxylates (84). The ethoxylates are low foamers, a useful property in certain appHcations. Emulsification is the most important function. Its importance is reflected in the wide range of lipophilic solubiHties available in the commercial products. Like all organic esters, fatty acid ethoxylates are susceptible to acid and alkaline hydrolysis. 

The principal constituents of rosin (qv) are abietic and related acids. Tall oil (qv) is a mixture of unsaturated fatty and aHcycHc acids of the abietic family. Refined tall oil may be high in rosin acids or unsaturated acids, depending on the refining process. Ethoxylates of rosin acids, eg, dehydro abietic acid, are similar to fatty acid ethoxylates in surfactant properties and manufacture, except for thek stabiHty to hydrolysis. No noticeable decomposition is observed when a rosin ester of this type is boiled for 15 min in 10% sulfuric acid or 25% sodium hydroxide (90). Steric hindrance of the carboxylate group associated with the aHcycHc moiety has been suggested as the cause of this unexpectedly great hydrolytic stabiHty. 

Fatty alcohol and fatty acid ethoxylates are amphiphilic compounds that are commonly used as nonionic surfactants and emulsifiers in many applications, such as cosmetic and care products and in textile fabrication. They serve as antistatic lubricants and viscosity regulators. 

Fatty acid esters, 9 142 Fatty acid ester sulfonates, 23 528-529 Fatty acid ethoxylates, 24 149-150 Fatty acid methyl esters (FAME), 12 429 13 26t... 

In order to study the effect of substituents near the hydrolyzable bond, four fatty acid ethoxylates with different degrees of steric hindrance near the ester bond, see Fig. 4, have been synthesized [18]. The homologue pure surfactants were prepared by reacting the appropriate acid chlorides with a large excess of tetra(ethylene glycol) in the presence of pyridine. 

Fig. 4 Four fatty acid ethoxylates with different substituents on the acyl carbon next to the ester bond, i.e., the a-carbon...

Fatty acid ethoxylates are used extensively in the textile industry as emulsifiers for processing oils, antistatic agents (qv), softeners, and fiber lubricants, and as detergents in scouring operations. They also find application as emulsifiers in cosmetic preparations and pesticide formulations. Fatty acid ethoxylates are manufactured either by alkali-catalyzed reaction of fatty acids with ethylene oxide or by acid-catalyzed esterification of fatty acids with preformed poly(ethylene glycol). Deodorization steps are commonly incorporated into the manufacturing process. 

The most common nonionic surfactants are those based on ethylene oxide, referred to as ethoxylated surfactants. Several classes can be distinguished alcohol ethoxylates, alkyl phenol ethoxylates, fatty acid ethoxylates, sorbitan ester ethoxylates, fatty amine ethoxylates, and ethylene oxide-propylene oxide copolymers (sometimes referred to as polymer surfactants). Another important class of nonionics are the multihydroxy products such as glycol esters, glycerol (and polyglycerol) esters, glucosides (and polyglucosides), and sucrose esters. Amine oxides and sulfinyl surfactants represent nonionic with a small head group. 

Table 5.4 Typical range of fatty acid ethoxylates ...

Kolb Distribution Ltd Hedipin CFA, PO, PS Fatty acid ethoxylates... 

Esters of phosphoric acid form the largest group of non-durable antistats (Fig. 10.1). The alkyl groups are usually derived from fatty acids. Ethoxylated fatty... 

Ethoxylated fatty acids Ethoxylated fatty amide... 

It may be noted that fatty acid glycerides and fatty acid ethoxylates are well-known surfactants (72). Thus, the DEAD derivatives may possibly be useftil as surfactants as well, with modified properties. 

Typical enulsifiers used in emulsion polymerization of VC are anirmic emulsifiers like sodium alkyl sulfonates, sodium diaUcyl sulfosucdnates, fatty acid soaps and sodium ethoxy sulfates. Neutral emulsifiers like alltyl phenol ethoxylates and fatty acid ethoxylates are often added during after polymerization in Oder b> increase latex stability. The emulsifiers are not only chosen for control of the particle formation and latex stability during polymerization, but for a number of other reasons like mechanical stability, reactor wall build-up, plastisol formation, heat and colour stability and water resistance of the final product [1]. 

Primarily for toxicity reasons, work has focused on the use of nonionic surfactants, particularly Tweens and Spans. Pouton (20) and Wakericy el al. (21) have screened a range of surfactants, finding that in general molecules with unsat-uraced acyl chains were most efficiem emulsifiers, particularly the oleates with an HLB value of approximately II. The authors also reported that the sorbitan esters and ethoxylated triglycerides such as Tagat TO were more efficient than the fatty acid ethoxylates, possibly due to the polydispersity of the latter. 

These include secondary alcohol ethoxylates, tridecyl alcohol ethoxylates, fatty acid ethoxylates, PO-capped ethoxylates and various alcohol propoxylates. 

Hydrocarbons + fatty acid methyl esters, glycerides 4- fatty alcohols + fatty acids, fatty acid ethoxylates + alkylphenol ethoxylates, other ethoxylates, glycerol + high-molecular-weight polyethylene glycols. 

Polyethoxylates may contain polyethylene glycols as well as ethoxylated alcohols, alkylphenols, etc. Both types of component are determined by the Weibull method [10], which has been adopted as an international standard [11], reference to which is advised. The following is an abbreviated version. The method can be used for fatty acid ethoxylates, but the ethyl acetate extract will include any free fatty acid present in the sample. 

Appearance liquid Fatty acid ethoxylate Concentration % 100... 

Defoamers and deaerators are derived from hydrocarbons that contain substituted polar groups. The active substances contained in products suppbed in the form of 25-30% aqueous emulsions are mainly higher fatty alcohols, fatty acids, and fatty add esters and their ethoxylates (Table 3.9). They may contain anionic or nonionic emulsifiers. The active substances contained in so-called oil-type defoamers are mainly fatty alcohol ethoxylates, fatty acid ethoxylates or mixtures of fatty alcohols. They can also contain emulsifiers in order to aid dispersion. It is important to note that the term oil-type defoamer refers to the oily consistency of this group of products, and has nothing to do with the use of mineral oil as an active substance. Emulsion-type defoamers account for half of the worldwide consumption of defoamers and deaerators, expressed as soHds. Synthetic oils represent 40% and mineral oils 10%. It seems that mineral oils are no longer in use in Europe. 

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