Ether sulphates

Marli nats Fatty alcohol ether sulphates Huls... 

Sulphate Sulphonate Ether sulphate Ether phosphate Ether carboxylate Carboxylate Primary ammonium Secondary ammonium Tertiary ammonium Quaternary ammonium Amine oxide Betaine... 

Lightweight concrete and cement and production of gypsum plasterboard Alcohol ether sulphates Betaines Alkylphenol ether sulphates Foaming agents... 

Shampoos, bubble baths and Alcohol and alcohol ether sulphates De te rge n cy/foa m i ng... 

Dishwashing liquids Alkyl benzene sulphonates Alcohol ether sulphates Fatty alcohol ethoxylates Detergency/foaming... 

Hard surface cleaners Alkyl benzene sulphonates Alkanolamides Fatty alcohol ethoxylates Potassium oleic acid sulphonate Shorter chain alcohol ether sulphates Detergency high/low foaming... 

Polyglycol ethers Alkanolamides Alkyl ether sulphates Alkylbenzene sulphonates (amine salts) Alkylphenol ethoxylates Alkanolamides Alkylbenzene sulphonates (amine salts)... 

Resin emulsifiers Alkylphenol ether sulphates Fatty alcohol ether sulphates Fatty alcohol ethoxylates Emulsifiers... 

Alcohol ether sulphates (AES) and alcohol sulphates (AS) are shown combined in Figure 1.9 since it is rarely possible to differentiate when products are formulated to contain both materials. Cost competition and producer preferences show their effect on the often erratic consumption of the surfactants over time. 

Ci2 i4 olefin sulphonates are also used in personal care formulations since they are less aggressive than LAS and will not over-strip (i.e. degrease to leave an excessively dry or squeaky feel) the skin or hair although some care maybe required in formulating to compensate for a dry feel to the foam. AOS-based formulations are also more difficult to thicken than products based on alkyl sulphates or alkyl ether sulphates but use of alkanolamides or sarcosinates as secondary surfactants can overcome both problems and give a product more acceptable to the consumer. 

In manual dishwash, a high-SME product (such as Alpha-Step MC48 from Stepan, SME SFA 5 1) based on a distilled coconut methyl ester is used as a partial replacement for LAS and alkyl ether sulphate. Substitution of SME for LAS/AES can give enhanced... 

This class of surfactants has possibly the widest range of use of any anionic surfactant. It is found in almost every product where foaming is desirable, in industrial, household and personal care applications. Alkyl ether sulphates are described in terms of their parent alcohol and the degree of ethoxylation. Thus, sodium laureth-2 is the sodium salt of a sulphated (predominantly) C12 alcohol, with an average of 2 mol of ethylene oxide added. Often, the alcohol is assumed to be the typical C12-14 and the surfactant simply called a 2-or 3-mol ether sulphate. 

Chemistry and general properties. The chemistry of ether sulphates is very similar to that of alkyl sulphates. The backbone of the molecule is a fatty alcohol and often the same alcohols are used as feedstocks for alkyl sulphates, and alkyl ether sulphates and, with higher degrees of ethoxylation, as non-ionic surfactants. The ethoxylation process is more fully described in Chapter 5. 

The addition of an ethylene oxide chain to what is essentially an alkyl sulphate changes its properties in several important ways. Firstly the Kraft point is very significantly reduced. Low active solutions of ether sulphates are clear are fluid at temperatures close to 0°C, and the Kraft point reduces with increasing levels of ethoxylation. Secondly, the nature of foam changes, from the dense stable foam of an alkyl sulphate to a much more open foam structure. The tolerance of the surfactant to water hardness is also improved, with ether sulphates showing better foaming in the presence of moderate hardness. 

Raw materials. Feedstocks for ethoxylated alcohols are made from a large number of alcohols and practically every fatty alcohol used to make alkyl sulphates is also ethoxylated to make non-ionic surfactants, or feedstock for ether sulphates. 

Composition vs. performance. Formulators often do not fully appreciate the complex composition of ether sulphates. Without taking into account formulating aids such as buffers, etc., a typical 3 mol ether sulphate will be a blend of over 50 chemical species, all contributing to the overall performance of the surfactant. Formulators often treat all ether sulphates as equal and will switch suppliers only to find that some of their formulations are no longer stable or that the performance changes. 

It is possible to draw some general trends and it is certainly true to say that the differences between ether sulphates are less than the difference between ether sulphate and its corresponding alkyl sulphate. Figure 4.19 shows the foaming properties of a series of alkyl sulphates and their corresponding 2 and 3 mol ether sulphates. 

Ether sulphates show a strong salt effect - that is an increase in viscosity on addition of salt (or other electrolyte). The response to electrolyte (the salt curve ) can be very different between ether sulphates, even from different suppliers of the same product. Generally, the more soluble the surfactant, the lower the salt response but higher degrees of ethoxylation reduce salt response, as does branching in the alcohol as shown in Figure 4.20. 

Figure 4.20 Salt response of alkyl ether sulphates.

Applications. Alkyl ether sulphates are almost ubiquitous in cleaning products but are rarely found as the primary surfactant as they bring only some detergency but mainly contribute to foaming and viscosity building. 

Alkyl ether sulphates are used relatively little in laundry products, especially in solid ones. The surfactant has a very poor solid form, the pure product being amorphous, somewhat hygroscopic and sticky. Commercial dry ether sulphates are unknown other than as blends of 50% with carrier solids, such as sodium carbonate. In liquid formulations, 3-mol ether sulphates can be used to give improved solubility and hard water tolerance in unbuilt liquids and amine salts are occasionally used. 

Manual dishwash liquids are a major area of application. Whether the primary surfactant is LAS or SLS, ether sulphate is usually present as the secondary surfactant. The foaming generated by the ether sulphate is often the visual cue used by the consumer to judge the effectiveness of a product. This is reflected by the use of the loss of foam as the endpoint in many protocols used to evaluate dishwashing performance. 

They are a versatile surfactant type, with some properties analogous to those of ether sulphates. Unlike sulphate (which is a sulphuric acid mono alkyl ester), phosphate can form di- and triester, giving a wider range of structures and, with them, the ability to tailor the product to a greater number of application areas. 

Raw materials. The base materials for ether carboxylates are typically ethoxylated alcohols, although ethoxylated aromatics or alkanolamides may also be used but a wider range of alkyl chains and degrees of ethoxylation are used in ether carboxylates than in ether sulphates. Carbon chains from C4 to C20 and degrees of ethoxylation from 2 to 20 may be combined to give the required properties in the surfactant. 

Sources and properties of alcohol ethoxylates are covered in more detail under alkyl sulphates and alkyl ether sulphates. 

Composition vs. properties. With such a wide pallet of raw materials, it is possible to produce a very wide range of attributes in the surfactant and the HLB may be varied from 8 (low C number, low EO), to give surfactants soluble in organic media, to >20 (very good aqueous solubility). Ether sulphates (laureth-2 or laureth-3) would have HLB values of 20. 

---