Sulfonated surfactants hydrotropes

A special application of a-sulfo fatty acid esters is for highly concentrated hard surface cleaners which are used after dilution in a pail of water. Normally hydrotropes are needed to increase the solubility of the surfactants in water and assure clear, homogeneous, and storage-stable products. If the LAS, which are typical surfactants in hard surface cleaners, are replaced by ester sulfonates the hydrotrope can be deleted from the formula [62]. 

Cocoimidazoline sulfobetaine. See Sodium cocoamphohydroxypropyl sulfonate Cocoiminodiglycinate CAS 97659-51-3 EINECS/ELINCS 307-456-2 Properties Amphoteric Uses Surfactant, hydrotrope, detergent for industrial applies. 

All lnaphthalenesulfonic Acids. The aLkyLnaphthalenesulfonic acids can be made by sulfonation of aLkyLnaphthalenes, eg, with sulfuric acid at 160°C, or by alkylation of naphthalenesulfonic acids with alcohols or olefins. These products, as the acids or their sodium salts, are commercially important as textile auxiUaries, surfactants (qv), wetting agents, dispersants (qv), and emulsifying aids, eg, for dyes (qv), wettable powder pesticides, tars, clays (qv), and hydrotropes. 

The DATs present in LAB will readily sulfonate to form dialkyltetralin-sulfonate or DATS. The foam and detergency performance properties of individual C DATS homologs are very similar to that of the corresponding C j LAS homologs [21]. Thus, even at a level of 10% DATS in the LAB, no decrease in foam or detergency performance is observed. In some liquid formulations, the presence of DATS can provide a beneficial hydrotropic effect to LAS [22]. Figure 8 illustrates that DATS are indeed surfactants, as evidenced by their surface tension vs. concentration plot. 

Hydrotropes (LD, DW, HC) Maintain product homogeneity Ability to increase surfactant solubility Color and odor Cumene sulfonate Ethyl alcohol Toluene sulfonates 0-10% 0-10%... 

Choose alkylnaphthalene sulfonates and sulfosuccinate esters as hydrotropes in formulations where foaming needs to be controlled, as they enhance solubility of anionic surfactants without increasing foam amount [20],... 

Sulfonated toluene, xylene, and cumene, neutralized to the corresponding ammonium or sodium salts, are important industrially as hydrotropes or coupling agents in die manufacture of liquid cleaners and other surfactant compositions. 

A preferred mode of adding magnesium to a dishwashing liquid is to use the MgO or Mg(OH)2 to neutralize the surfactants after they are formed by sulfonation or sulfation [89], This method is preferred because adding magnesium from salt generally requires additional hydrotrope. Magnesium is typically preferred for use over calcium, since calcium surfactant salts are much less soluble. However, one series of patents discloses the use of calcium added to the formulation in the form of calcium xylene sulfonate for improved stability [90],... 

Petro . [Witco/Otganics] AO l nq)h-dialene sulfonates hydrotrope, surfactant, germicide, detergent, dispersant, wetting agent for agtic., industrial and... 

Vander Mey, Phenol free and chlorinated hydrocarbon free photoresist stripper comprising surfactant and hydrotropic aromatic sulfonic acids, U.S. Patent No. 4,165,294. 

Aqueous solutions of certain salts, such as those of benzoic, salicylic, benzene-sulfonic, naphthoic, and various hydroaromatic acids, possess the power of dissolving certain substances otherwise not soluble in water. These substances, known as hydrotropes, are structurally similar to surfactants in that they have hydrophilic and hydrophobic moieties in the same molecule, but the alkyl chain is shorter. A few typical hydrotropes are listed in Figure 26.8. When solubilization... 

Definition Potassium salt of xylene sulfonic acid Empiricai CsHgOsS K Properties M.w. 224.33 anionic Toxicoiogy TSCA listed Uses Hydrotrope, solubilizer, coupling agent, vise, modifier in liq. formulations hydrotrope in light-duty liq. detergents cloud pt. depressant in detergent formulations surfactant in cosmetics Trade Name Synonyms Eltesol PX 40 [Huntsman Surf. Sciences http //www. huntsman. com/surface sciences] Eltesol PX 93 [Huntsman Surf. Sciences http //www. huntsman. com/surface sciences]... 

Hydrotropes have been proven to be surface-active. The surface tensions for anionic hydrotropes such as sodium salicylate, sodium xylene sulfonate, sodium p-toluene sulfonate, sodium cumene sulfonate and sodium butyl monoglycol sulfate decrease as a function of the concentration in water, until a plateau is reached (17) (see Figure 18.5). The same behaviour is also observed for the nonionic hydrotropes resorcinol, catechol, and pyrogallol (18). This means that they exhibit the same behaviour as surfactants, even though the drop in surface tension is not as dramatic but more gradual for hydrotropes when compared to surfactants. The concentration for the onset of self-aggregation of the anionic hydrotropes in non-covalent assemblies determined from... 

Hydrotropes do not perform so generally as surfactants do, i.e. the solubility will not increase for all organic compounds in hydrotropic solutions. The efficacy will also vary among the different hydrotropes, even though very small structural differences may be present. This has been reported for the solubilities in aqueous sodium o-y m- and /7-xylene sulfonate solutions of solutes such as acetophenone, aniline, benzaldehyde, c7-cresol, etc. It was found that the meta structure was more effective, particularly at lower temperatures since it had a higher water solubility (5). Another example is... 

Surfactant solubilization in liquid cleaners may be limited due to a high concentration of the surfactant or a high amount of electrolytes present in the formulations. In order to enhance the solubility and to increase the cloud point for nonionic-based systems, hydrotropes are often added. This phenomenon has already been pointed out in Section 3.5 above, where the cloud points of solutions with nonionic surfactants were elevated upon the addition of alkyl polyglucosides (16). Hydrotropic activity can be evaluated by determining the amount of hydrotrope required to clarify a cloudy solution or the cloud point elevation obtained for a specific concentration of a hydrotrope. The efficacy of hydrotropes varies for different classes of compounds. This has been observed for short-chain alkylbenzene and alkylnaph-thalene sulfonates when added to a number of detergent formulations (21). The alkylnaphthalene sulfonates were found to be more efficient than the alkylbenzene sulfonates in elevating the cloud point. 

A variety of isomeric or closely related mixtures of organic compounds are often found when manufacturing chemical and pharmaceutical products. However, it is usually necessary to separate these molecules in order to obtain the expected functionality of the products. Conventional methods such as distillation, extraction and crystallization might be difficult to use since the molecules to be separated might have very close chemical and physical properties. Hydrotropes are known to be selective in the solubilization of compounds and as mentioned earlier, do not perform so generally as surfactants. It has been found that the solubility enhancement in water by adding the hydrotrope sodium xylene sulfonate (SXS) will vary for different isomers such as o- and /7-nitrochlorobenzene, as well as for o- and p-dichlorobenzene (24). In this case, the c -isomer is more soluble than the p-isomer. Higher solubilities have also been reported for aromatic compounds when compared to aliphatic and alicyclic compounds (24). This selective... 

Aqueous solutions of hydrotropes have proven to be powerful systems for preparing vesicles. In this case, the vesicle-forming compound has been mixed with water and the hydrotrope, and dilution with water resulting in the vesicles (33). Vesicles formed by the nonionic surfactant Laureth 4 (Brij 30) from an aqueous solution of sodium xylene sulfonate (SXS) were more stable and smaller than vesicles prepared from the suspension of the lamellar liquid crystal in water. 

Often the phase diagram of an oil-water-surfactant system is such that the domain of a single isotropic phase contains both regions with normal micelles and those with inverse micelles. Inversion between the two microstructures is continuous and does not involve the formation of the lamellar phase when v lal is approximately equal to 1.0. Such behavior is facilitated by the presence of amphiphilic compounds with short hydrocarbon chains, such as short-chain alcohols and sodium xylene sulfonate. The latter compound and others with similar properties are called hydrotropes and have many practical applications (Friberg, 1997). 

Hydrotropes Aromatic sulfonates, some miionic surfactants or other additives <15... 

Alkylbenzene sulfonates and alkylnaphthalene sulfonates act as hydrotropes to modify solubilities, viscosities, and other properties of surfactants and surfactant formulations. Sodium toluenesulfo-nate (STS) and sodium xylene sulfonate (SXS) are the best-known hydrotropes, however, alkylnaphthalene snlfonates also possess hydrotropic properties. Hydrotropicity is the amount of different hydrotropes required to achieve clear solutions. The amount of different hydrotropes, for example, SXS, STS, sodium cumene sulfonate (SCS), and others, in light-duty liquid (LDL) detergent formulations is given in Figure 14.1. There seems to be no trend different hydrotropes are (more or less) similarly efficient in different formulations. 

---