Sorbitan esters contents

Sorbitan esters of fatty acids are well known. Similar products can be made from ether carboxylic acids and sorbitol without an acid catalyst with a good color [39]. The advantage of these products is that the hydrophilicity can be adjusted by the polyethylene glycol content in the ether carboxylic acid. 

The reaction product with monoethanolamine acts as a thickening agent [41,101] and with alcohols as an emollient [40]. Also reaction products with amino acids and oligo- or polypeptides for use in cosmetic formulations are known [43]. Sorbitan esters from ether carboxylates are described as emulsifiers or mild surfactants in cosmetic formulations [39] and alkyl ether carboxylic acid taurides as nonirritant anionic surfactants for cosmetic cleaners in particular [44]. Using unsaturated ether carboxylates it is possible to make viscous formulations based on combinations of unsaturated and saturated ether carboxylates [111]. Highly purified alkyl ether carboxylates based on alcohol ethoxylates with low free alcohol content have also been described [112]. 

Table 6.1 Total fatty acid contents of pure sorbitan esters...

The saponification values of sorbitan esters do not by themselves characterise the esters very well. The total fatty acid content, however, is more useful, even when allowance is made for the fact that each nominal type contains a proportion of its neighbours, e.g. monoesters contain some diester. The total fatty acid contents of some pure compounds are shown in Table 6.1. The figures are for the esters with single homologue acids. The values for oleates are almost identical with those for stearates. 

The fundamental studies discussed below were performed on fairly dilute systems (monomer content 10%), in order to facilitate the comparison with well-established theories and to avoid problems encountered with concentrated systems (e.g. coagulation). The emulsifiers used were in most cases fatty acid esters of sorbitan. 

Stern and Shapiro (1954) incubated the intact mesenteric fat of starved rats with serum and observed a deerease in the total serum esterified fatty acid content but no decrease in the phospholipid or cholesterol ester fraction. When mesenteric adipose tissue was incubated with sodium stearate-1-C or sodium oleate, a significant uptake could be demonstrated and the fatty acids that disappeared from the medium could be recovered in good yield inside the tissue. Of the stearate absorbed, 20-30% was found in the tissue in a combined form, presumably in ester linkage. Stern and Shapiro (1954) also showed that adipose tissue can absorb fatty acids from emulsions of triolein, sorbitan-monolaurate, sorbitan-monopalmitate, and... 

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