Sulphosuccinates

These are sulphonates with some atypical properties and are more complex in that they are polyfunctional, containing sulphonate, ester and, in the case of the half-ester, carboxylate groups. Sulphosuccinates are valued as very mild surfactants in personal care applications and, as the diester, also as highly effective oil-soluble wetting agents. 

The ring opening is moderately exothermic and the reaction is initially controlled by limiting the addition rate of the alcohol to the molten maleic anhydride. The reaction proceeds similarly for both mono and diester products. 

Both stages of the reaction are ideally carried out in nitrogen atmosphere as oxidation can lead to yellowing of the final product, which is undesirable, particularly in personal care 

Half-ester sulphosuccinates are highly water soluble and are usually sold as 40-50% solutions. With care, alkylsulphosuccinates may also be spray dried to give a free flowing powder of 90% active matter. Diesters have low aqueous solubility but are highly soluble in organic solvents. A typical product, di-isooctyl sulphosuccinate, is sold as a 70% solution in a mixture of water and isopropanol. 

As a class of surfactants, sulphosuccinates differ from most other sulphonates in their chemical stability and, due to the presence of the ester linkages, sulphosuccinates will hydrolyse at extremes of pH and with elevated temperature. Monoesters are more sensitive than diesters, with optimal stability of pH 6-8, whilst diesters are more stable and will tolerate pH of 1-10 at room temperature. This allows the use of diesters in a much wider range of environments, particularly under moderately acidic conditions. 

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Aerosol is also a trade name for certain wetting agents, most of which are esters of sodium sulphosuccinic acid. 

Quick A, NJ Russell, SG Hales, GF White (1994) Biodegradation of sulphosuccinate direct desulphonation of a secondary sulphonate. Microbiology (UK) 140 2991-2998. 

DIOCTYL SULPHOSUCCINATE SIGMA ENGLAND (CH3(CH2)3CH(C2H5)CH2)2C20ljCljH7S03Na 100 - 100 - - -... 

Sulphosuccinates are of particular interest not only for their technical properties but also because structurally they combine the two hydrophile functions described earlier - the sulphonate and carboxylate moieties - in a single molecule (9.18). The sulphosuccinate diesters, however, are probably of greater commercial importance in textile processing than are the monoesters. The most important example is sodium dioctylsulphosuccinate (9.19), but the dinonyl, dimethylamyl and di-isobutyl analogues are also used commercially. As usual, a wide choice of hydrophobes is available and includes alcohols, lightly ethoxylated alcohols, alkanolamides and combinations of these. 

Many other products can be used as softeners but are less important commercially because of greater cost and/or inferior properties. Examples are anionic surfactants such as long-chain (C16-C22) alkyl sulphates, sulphonates, sulphosuccinates and soaps. These have rather low substantivity and are easily washed out. Nonionic types of limited substantivity and durability, usually applied by padding, include polyethoxylated derivatives of long-chain alcohols, acids, glycerides, oils and waxes. They are useful where ionic surfactants would pose compatibility problems and they exhibit useful antistatic properties, but they are more frequently used as lubricants in combination with other softeners, particularly the cationics. 

In these tests, the mixture of Na2Si03/tall oil was added to the scrubber before desliming. Collector used in the bulk circuit was sulphosuccinate. In the rutile circuit, phosphoric acid ester was used. Silica was rejected in a bulk talking. The overall metallurgical results obtained in the continuous operation are shown in Table 25.12. 

Sodium di(ethylhexyl)sulphosuccinate (Aerosol-OT) [577-11-7] M 444.6. Dissolved in MeOH and inorganic salts which ppted were filtered off. Water was added and the solution was extracted several times with hexane. The residue was evaporated to one fifth its original volume, benzene was added and azeotropic distillation was continued until no water remained. Solvent was then evaporated. The white solid was crushed and dried in vacuum over P2O5 for 48h [El Seoud and Fendler JCSFT 171 452 7 975]. 

A dry packed column with porous material was used for the characterization according to size of the PVAc latex samples. The packing employed was CPG (Controlled Pore Glass), 2000 A, 200-400 mesh size. Deionized water with 0.8 gr/lit Aerosol O.T. (dioctyl sodium sulphosuccinate), 0.8 gr/lit sodium nitrate and 0.4 gr/lit sodium azide served as the carrier fluid under a constant flowrate. The sample loop volume was 10 pC A Beckman UV detector operating at 254 nm was connected at the column outlet to monitor particle size. A particle size-mean retention volume calibration curve was constructed from commercially available polystyrene standards. For reasons of comparison, the samples previously characterized by turbidity spectra were also characterized by SEC. A number of injections were repeated to check for the reproducibility of the method. 

Alkylphenol ethoxylate -formaldehyde condensates Sulphosuccinates Wetting agents... 

Carpet shampoos and Diester sulphosuccinates Detergents/wetti ng... 

Plastisol viscosity modifiers Fatty alcohol ethoxylates Sodium dialkyl sulphosuccinates Viscosity modification... 

Aromatic - alkylbenzene, alkyltoluene, alkylxylene, alkylnaphthalene Aliphatic - a-olefin sulphonates, alkane sulphonates, sulphosuccinates... 

Chemistry and general properties. Sulphosuccinates are made in a two-stage synthesis. Firstly an ester is made by reacting maleic anhydride with an alcohol or an ethoxylated alcohol (Figure 4.12). If the molar ratio of alcohol to maleic anhydride is 1 1, the product is called the half-ester, but where 2 mol of alcohol is used per mole of anhydride, the product is a diester. 

The second stage is sulphonation with sodium sulphite (Figure 4.13) which adds the sulphonate group across the double bond. This, too, is an exothermic reaction and care must be taken to limit the temperature rise to avoid discolouration of the sulphosuccinate. 

Sulphosuccinates are not particularly effective detergents but they are good wetting agents and the monoesters are favoured in personal care formulations because of their very low irritancy. 

Sulphosuccinates are prepared using a wide variety of alcohols and the choice of alcohol is a major determinant of the properties of the surfactant. In some instances, the consumers view of what materials are acceptable limits the choice of alcohol source with one example of this being the preference for oleochemical alcohols for personal care applications. 

Monoester sulphosuccinates use a wider variety of alcohols than diesters and tend to use longer carbon chain alcohols to obtain the required HLB value from a single alkyl group. A typical product for cleansing applications would use a C12-14 alcohol derived from coconut or palm kernel oil. These materials are easily available due to their use as raw materials for sulphation (see later). Effective sulphosuccinates can also be prepared from petrochemical alcohols but these seem to be less popular. Ethoxylated alcohols (typically 3 mol of EO) are also used and can provide additional benefits in personal care applications. In some cases, alkanolamides or ethoxylated alkanolamides are used as the alcohol, such as ethoxylated cocomonoethanolamide, but they are relatively uncommon, since they are difficult to manufacture and are prone to colouration. 

Composition vs. performance. The greatest effect of the properties of a sulphosuccinate is undoubtedly the degree of esterification. All monoesters are water soluble, with diesters being very much less so. Variation of the alcohol used in the sulphosuccinate has the expected effect - higher molecular weights give reduced solubility and this is particularly so in diesters, where the dihexyl product is up to 30% soluble in water, but the dioctyl is only 1% soluble. 

Syndet bars contain no soap and, again, often rely on SCI to give mild cleansing, often in combination with sulphosuccinate and alkyl sulphates. Syndets have a small share of the cleansing bar market and are often marketed as a care product, rather than as a simple cleansing bar. 

Empimin Series Sulphosuccinates, Alcohol sulphates and ether sulphates... 

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