Phosphorous-containing anionic surfactants

Derivatives of phosphonic acid and phosphorous acid are of marginal importance as special P-containing anionics. Their chemistry, along with phosphates, was reviewed comprehensively by Wasow [96]. 

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Because polarity is a dominant factor in solubility, phosphorus-containing anionic surfactants can be tested by solving them in a line of different liquids, e.g., heptane, toluene, propanone-2, ethanol, and water. From the behavior in those liquids the surfactants can be classified for an overall view on the solubility of phosphoric acid esters based on alcohols and ethoxylated alcohols in different surroundings. 

Phosphate Containing Anionic Surfactants Both alkyl phosphates and alkyl ether phosphates are made by treating the fatty alcohol or alcohol ethoxylates with a phophor-ylating agent, usually phosphorous pentoxide, P40io- The reaction yields a mixture of mono- and di-esters of phosphoric acid. The ratio of the two esters is determined by the ratio of the reactants and the amount of water present in the reaction mixture. The physicochemical properties of the alkyl phosphate surfactants depend on the ratio of the esters. Phosphate surfactants are used in the metal working industry due to their anticorrosive properties. 

The heat exchanger fins from aluminum or its alloy are coated with aqueous solution containing a water-soluble cellulose resin or polyvinyl alcohol and a surfactant to form a hydrophilic film. Phosphoric acid ester was used as anionic surfactant (0.05-4.5%) in aqueous solution to form a hydrophilic film showing contact angle with water of 5-32° [288]. 

Monoalkyl phosphate and phosphate esters are special types of phosphoms-contain-ing anionic surfactants that are of great industrial importance. They are used for flameproofing, as antistatic for textiles, for foam inhibition, as an extreme pressure (EP) lubricant additive, as a surfactant component for alkaline, and as acid cleaners and for special cosmetic preparations (5). The commercially available phosphate ester products are complex mixtures of monoester and diester, free phosphoric acid, and free nonionic. 

The resulting product is a mixture of dialkyl and monoalkyl phosphate esters. These products also contain small amounts of condensed phosphates and phosphoric acid. Neutralization of the acids with bases like alkali hydroxides, ammonia, or amines produces water-soluble anionic surfactants and emulsifiers. 

Although in most cases the bulk of anionic surfactants on the market are of the sulfonate, sulfate, or carbonate type, derivatives of phosphoric acid also show surface activity, with very interesting properties. The proportion of phosphorus-containing surfactants reaches about 1% of total surfactant production. It can be fundamentally stated that surfactants covering nearly all applications can be derived from phosphoric acid. It is often only the somewhat higher price which blocks the same... 

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