Sulphonates Sulphosuccinates

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. 

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

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

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. 

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 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. 

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. 

A special class of sulphonates are sulphosuccinates which are esters of sulpho-succinic acid ... 

All the systems described thus far require relatively high salinity, which is considered to be critical in soil remediation processes [60]. Another approach for effective microemulsification of organic liquids is the use of co-surfactants. Sodium mono- and dimethyl naphthalene sulphonate were found to be effective co-surfactants in formulations with Aerosol OT (sodium bis(2-ethylhexyl) sulphosuccinate) for diverse chlorinated hydrocarbons and their mixtures between 15 and 25°C [60, 61]. All types of microemulsions could be obtained with this approach. 

Watkinson [1988] lists some surfactants used for their dispersing action in organic liquids. He includes amongst them organic and metal sulphonates metal phenolates metal dialkyl dithiophosphates sodium dialkyl sulphosuccinates polyoxyethylene alkyl and alicyclic amines monethanol ammonium phosphate salts co-polymers of N-substituted formamide fatty acid phosphates... 

Water content is adjusted to the total surfactant concentration of 30-42 % wt. The residual sulphite in the product may be oxidised to sulphate. The sulphonation proceeds also well when using partially hydrated crystalline sodium sulphite in a jacketed shear-stress reactor. This process modification is especially appropriate for manufacturing concentrated sulphosuccinate monoesters as flakes or vermicelli (often with plasticisers and fillers added in situ) suitable in mild synthetic soap bars [78]. The Cn-ig alcohols (I), ethoxylated (x2-4 mole EO) alcohols (II), and fatty monoethanolamides (III) esters of sulphosuccinic acid, mainly as sodium and alkanolamine salts, are of most practical importance as very mild high-foaming surfactants useful for personal care products and in wool, fur, and leather treatment. Very mild disodium PEG-5 laurylcitrate sulphosuccinate (in combination with sodium lauryl ethersulphate) serve for cosmetics produced by Witco as "Rewopol SB CS 50". 

Dealing with the sulphosuccinate diester synthesis, the esterification procedure is performed very similar to that described above for monoesters but the feed of hydroxyl-bearing material (generally Ce-u alcohols) should be twice more with respect to maleic anhydride. The first step is performed under a gradually increasing temperature to 120-150 °C and with continuous vacuum distillation of water from esterification. At that step esterification catalyst may be used, such as /7-toluenesulphonic acid or ABSA. The sulphonation with sodium bisulphite proceeds as described above. A representative example of diesters is sodium bis(2-ethylhexyl) sulphosuccinate known as Aerosol OT of the formula ... 

Acid. Conversion to carboxylic acid and alcohol takes place. The sulphonate group may be on either of these. Thus acyl isethionates yield a fatty acid and isethionate ions, mono- and di-alkyl sulphosuccinates yield fatty alcohols and sulphosuccinic acid, and a-sulphonated fatty esters yield the a-sulphonated fatty acid and a low-molecular-weight alcohol. 

The non-extractable hydrolysis products are characteristic of the surfactant type, and include hydrogen ions, sulphate ions, glycerol, alkanolamines, sulphonated amino acids and sulphosuccinic acid. 

Similar groups of ions to those described above (L , L Na -iL Na Jj. i) are seen in the spectra of a-olefin sulphonates, alkyl ether sulphates, sarcosinates and sulphosuccinates. Fatty acid salts do not give rise to strong positive ions but do give good anion signals in negative-ion spectra. 

Stearate soaps Dodecyl sulphate Dodecylbenzene sulphonate Dioctyl sulphosuccinate Nonyl phenol polyether sulphate Dodecyl polyether phosphate Polyethoxylated alkanol Polyethoxylated nonyl phenol Polyethoxylated polypropylene glycol (pluronic) Glyceryl monolaurate... 

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