Surfactants Alkyl Ether Sulfates

COSTEC INC. Industrial Surfactants Alkyl Ether Sulfates SULFOCHEM ES-2  

Sodium Lauryl Ether (2) Sulfate Water-White Liquid Activity, % 25-27 

Flash foamer and detergent for use in specialty cleaning products. 

High-active surfactant for use in specialty compounds. SULFOCHEM 25-3A  

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Other Anionic Surfactants Alkyl Ether Sulfates... 

High-performance liquid chromatography is performed using a Hewlett-Packard 1090 chromatograph equipped with a ternary-solvent delivery system, an autoinjector with a 0 -20- u.L injection loop, an oven compartment, and a diode-array UV detector. An ELS detector (Alltech Associates, Deerfield, IL) is connected in series to the UV detector. Hexane, 2-propanol, and water were used for the analysis of nonionic surfactants. Water and tetrahydrofuran (THF) are used for the analysis of anionic surfactants. No preliminary sample preparation is used other than dilution. The nonionic surfactants are diluted 1 40 (v/v) with hexane. The anionic surfactants (alkyl ether sulfates and synthetic and petroleum sulfonates) are diluted 1 20 (v/v) with water-THF (50 50). The calcium sulfonate surfactants were diluted 1 20 (v/v) with a THF-38% hydrochloric acid solution of pH 1. Hydrochloric add is required to prevent salt precipitation by converting any excess water-insoluble caldum carbonate into water-soluble calcium chloride. All diluted samples are... 

Shampoos based on lauryl sulfates can range from 6—17% of the active surfactant. However, though they are effective cleansers, the alkyl sulfates tend to be defatting. In an effort to make these shampoos more mild, many shampoos are now based on blends of amphoterics and alkyl sulfates or the less irritating alkyl ether sulfates. 

A.lkylSulfoacetates. These surfactants are prepared by esterification of sulfoacetic acid or by sulfonation of the alkyl chloroester. They are considered to produce good foaming and are less irritating to the eyes than the alkyl and alkyl ether sulfates (10). 

It has been found that the CMC values are higher and the micelle aggregation numbers smaller than those of the corresponding nonionic surfactants. The CMC increases with increasing EO chain, which is, according to the authors, opposite to the results for sodium alkyl ether sulfate. 

These higher foaming properties are very useful for such cosmetic formulations as shampoos, showerbaths, and so on. This is the same with the forming of fine bubbles and the improving of foam stability of other surfactants such as, for example, alkyl ether sulfates due to the combination with ether carboxylates [57,67-69] (Table 9). 

Although by 1957 [9] the use of ether carboxylates also in combination with other surfactants such as alkyl ether sulfates for shampoos had been described,... 

All of the aspects and applications described in papers can be traced back to the patent literature [73]. The special or synergistic effect of ether carboxylates in combination with other surfactants is very often the basis, like combinations with alkyl ether sulfates or alkyl sulfates, for shampoos, foambaths, showerbaths, and liquid soaps [9,70,81-85], and the same for amidether carboxylates [71]. 

Alkyl ether sulfates are/after alkyl benzene sulfonates(LAS),the group of technically important anionic surfactants with the largest production voluJne and product value. They have in comparison with other anionic surfactants special properties which are based on the particular structure of the molecule. These are expressed,for example,in the general adsorption properties at different interfaces, and in the Krafft-Point. Alkyl ether sulfates may be used under conditions, at which the utilization of other surfactant classes is very limited. They possess particularly favorable interfacial and application properties in mixtures with other surfactants. The paper gives a review of all important mechanisms of action and properties of interest for application. 

Alkyl ether sulfates with chain lengths ranging from to Cw are quantitatively the most important products currently based on fatty alcohols. It is estimated, that about 20 % of all surfactant alcohols -about 40 % of all fatty alcohols in the coconut range (C,2 Ci,) - are used in the form of alkyl ether suirateg ( ). Alkyl ether sulfates are the most important group of anionic surfactants after linear alkyl-benzenesulfonate (LAS) (2). 

In 1980, the total consumption of alkyl ether sulfates in Western Europe equaled that of all other anionic surfactants with the exception of alkyIbenzene-sulfonates (Fig. 1). Since alkyl ether sulfates are the most expensive group of anionic surfactants, which are produced in larger quantities, their importance on a... 

An especially effective reduction of the Krafft Point results from the insertion of ether groups into the molecule of the anionic surfactant. In table I this is examplified with Na dodecyl sulfate and Na-tetra-decyl sulfate in comparison to various n-alkyl ether sulfates of the same chain length (10). As a measure of the Krafft Point, a temperature is deTined at which a 1 7o solution dissolves clearly. By the incorporation of oxyalkylene groups into the molecule, the Krafft -Point and the melting point are greatly depressed. This depression is especially effective if there is branching in the oxyalkylene groups. 

The lower Krafft Points resulting from the incorporation of oxyethylene groups into the surfactant molecule is an essential, but not sufficient, property for the utilizationof alkyl ether sulfates. 

The dissociation of the counter-ions of micelles is a characteristic feature of ionic surfactants. For alkyl ether sulfates the degree of dissociation a of the counter-ions of the micelles has been determined by several authors by various methods (2, 26), With... 

Therefore, the hypothesis of an increasing nonionic character of alkyl ether sulfates with increasing number of oxyethylene groups is not tenable. Some time ago (30), it was suggested that a certain hydrophobic nature can be attributed to the polyoxyethylene chain of alkyl ether sulfates. At first, this appears to be in contradiction to the decidedly hydrophilic character of the polyoxyethylene chain for nonionic surfactants. However, the possibility of EO group hydration impairment by the sulfate group cannot be excluded. 

Washing and Cleaning Action. The properties of alkyl ether sulfates, due to the good solubility and the special hydrophilic/hydrophobic properties of the molecule, are of particular practical interest. From the investigations described in sections 2 and 3, it can be concluded that, in addition to the decrease in the Krafft Point, favorable properties for practical applications can be expected as a result of the inclusion of the oxyethylene groups into the hydrophobic part of the molecule. As is true for other anionic surfactants, the electrical double layer will be compressed by the addition of multivalent cations. By this means, the adsorption at the interface is increased, the surface activity is raised, and, furthermore, the critical micelle concentration decreased. In the case of the alkyl ether sulfates, however these effects can be obtained without encountering undesirable salting out effects. 

Cosmetic Rinse off Preparations. In certain cosmetic products, tor example hair shampoos, it is not possible to use complexing agents because of the irritation of mucous membranes. Here a low sensitivity of surfactants to water hardness is a precondition for their application. Foam formation is generally considered to be a measure of shampoo quality (Table V). With increase in water hardness the foam volume of alkyl sulfates decreases very much, whereas with the corresponding alkyl ether sulfates this decrease is relatively small. For cosmetic applications, the good skin compatibility and low irritation to mucous membranes of alkyl ether sulfates is of high importance (37). 

In most products,alkyl ether sulfates are used in form of mixtures with other surfactants. Alkyl benzene sulfonate (LAS) is the most important anionic surfactant used in combination with alkyl ether sulfates. 

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