Direct ethoxylation of a longer‐chain aliphatic ester

Abstract

2-Ethylhexyl laurate, as an exemplary longerchain aliphatic ester, was subjected to direct ethoxylation. The synthesis was described and the obtained products were analyzed qualitatively by means of the mass spectrometry and chromatographic methods. Solubility of the obtained ethoxylates was studied by determination of their cloud points in selected model solutions. It was shown that longer-chain aliphatic esters are feasible as raw materials for ethoxylation in the presence of an appropriate catalyst. They undergo effective and selective reaction with ethylene oxide without formation of excessive amounts of by-products. The obtained products exhibit typical properties of ethoxylate-type nonionic surfactants. Their solubility in water and butyldiglycol solution was relatively lower compared to their methyl ester equivalents.Paper no. S1226 in JSD 4, 167-173 (April 2001).KEY WORDS: Aliphatic esters, ethoxylation, 2-ethylhexyl laurate.The common definition of ethoxylation requires the presence of a labile hydrogen group in the substrate subjected to the reaction, according to Equation (1):where R denotes hydrocarbon chain and X means an intermediate group, such as -O-, -N-, or -S-. However, it was found recently that the reaction can also be performed efficiently with fatty acid methyl ester as the substrate (2,3). Since then several catalysts that allow efficient performance of the reaction have been reported (4-6). Ethoxylation of fatty methyl esters was also carried out using the conventional alkaline catalysts (7), although the rate of ethylene oxide (EO) addition was slow and the product distribution obtained was broad. It was proven that during ethoxylation of fatty methyl ester, EO was inserted selectively between the carbonyl carbon and the methoxy group (8).RCOOCH 3 + nCH 2 CH 2 O → RCO(OCH 2 CH 2 ) n OCH 3[2] Substrate Adduct Ethoxylation product Propoxylation of fatty acid methyl esters was also reported in the literature (9). Earlier studies described the impact of methyl ester chain length, degree of unsaturation, and EO content on the physical properties and performance of methyl ester ethoxylates (7,10,11). However, in considering the more recently described effective ethoxylation of the ester bond, a wide spectrum of additional raw materials appears to be relevant for the manufacture of nonionic surfactants. Some of them are already available commercially. They include longer aliphatic esters applied as ecological organic solvents, lubricants, modern bio-fuel additives, or other auxiliary agents. The aim of this work was to present the results from direct ethoxylation of 2-ethylhexyl laurate as an exemplary longer-chain aliphatic ester subjected to the reaction and to study the solubility of the products obtained in water and in 2-(2-butoxyethoxy)ethanol (butyldiglycol: BDG) solution. EXPERIMENTAL PROCEDURESThe following materials were used: oxirane (Mazovian Petrochemical Works, P / lock, Poland); 2-ethylhexyl laurate, marked as Polcet L (CHEMCO Production and Trade Company, Sobowidz, Poland); and ...

Surfactants Based on Natural Fatty Acids

“…Thratnig [63] later described how a similar effect in the distribution of ethylene oxide (EO)units can be obtained with ethoxylation of fatty acids rather than the methyl ester. Furthermore, the technique has also been shown to be applicable to ethoxylation of several types of fatty acid esters like triglycerides or branched alkyl esters [62,64], as well as for propoxylation of fatty acid esters [65]. Alejski et al [66,67] and Bialowas and Szymanowski [68] have contributed to the understanding of how the oxyethylation reaction of fatty acid methyl esters proceeds in stepwise incorporation of the ethylene oxide units.…”

“…Several researchers have described properties of methyl ester ethoxylates [64,70]. In general, polyoxyethylene esters of fatty acid methyl esters have been found to have good emulsifying, lubricating, dispersing and suspending power and these properties, combined with detergent and antistatic characteristics, provide a potential in a variety of textile processing applications.…”

“…Various tests have showed that methyl ester ethoxylates have an improved mildness to human skin compared to ordinary alcohol ethoxylates [62,64]. From the standpoint of environmental properties, fatty acid methyl ester ethoxylates are readily biodegradable and an order of magnitude less toxic than alcohol ethoxylates [70,75].…”

Separation of nonionic surfactants according to functionality by hydrophilic interaction chromatography and comprehensive two-dimensional liquid chromatography

“…Similar molecules can also be obtained by ethoxylation of alkyl phenols of fatty esters [3], especially the methyl esters (FAME). If these samples are synthesized from pure starting materials, they can be characterized quite easily [4][5][6][7][8]: the required information is the molar mass distribution of the ethoxylates and the content of polyethylene glycol (PEG), which results from chain transfer to water.…”

Nonionic ortho ester surfactants as cleavable emulsifiers

“…There exist surfactants that degrade by UV light, ozone treatment or temperature [6][7][8], but the most common types of cleavable surfactants are those that degrade by hydrolysis. Surface active esters are the prime examples and numerous studies that deal with fatty acid esters of poly(ethylene glycol) (ethoxylated fatty acids) [9,10], ester quats [11,12] and betaine esters [13,14]. All these surfactant classes degrade under alkaline conditions.…”