Fluorinated surfactants electrochemical fluorination process

PFCA salts (e.g., the sodium and ammonium salts) are an industrially important class of anionic PFCA surfactants. Electrochemical fluorination has been employed to manufacture APFO, an emulsifier used in the production of fluoropolymers and other PFCAs. Hydrolysis of the acid fluorides obtained by electrochemical fluorination results either in the free carboxylic acids or the respective salts. A major problem associated with the hydrolysis of PFCA fluorides is the presence of HF from the electrochemical fluorination and the hydrolysis of the PFCA fluorides with water." The technical process of isolating fluoride-free PFCA derivatives has, therefore, been optimized to reduce the fluoride content of the final product to trace amounts. An example of such a process is shown in Figure 18.6. °... 

The perfluorosulfonyl fluorides obtained by the electrochemical fluorination process can be readily converted into the corresponding acids and salts used as surfactants (Fig. 2.4). Hydrolysis yields the perfluoroalkane sulfonic acid (I) or its salt (II). Primary or secondary amines yield sulfonamides (III), which can be converted to a carboxylic acid (IV) or an alcohol (V). The alcohol is an intermediate for nonionic surfactants (VI), phosphates (VII), or sulfates (VIII). The tertiary aminosulfonamide (IX) can form a cationic surfactant (X), a amphoteric surfactant (XI), or an amine salt (XII). 

In addition to the electrolytic preparation of fluorine, the electrochemical fluorination of carboxylic acid and sulfonic acid derivatives have also become important industrially. The Simons process (Ni anodes, HF as solvent) has been realized industrially by 3 M 69). The most important products are perfluorooctanecarboxylic and perfluorooctanesulfonic acids, which are used as surfactants and for surface treatments. 

Fluorinated surfactants have been commercially available since the 1950s. The first available were perfluoroalkyl sulfonates (e.g., perfluorooctane sulfonate, CgFisSOs, PFOS) and perfluoroalkyl carboxylic acids (e.g., perfluorooctanoic acid, C7F15COOH, PFOA) manufactured using the electrochemical fluorination (ECF) process [10]. The unique properties (e.g., surface tension lowering in aqueous systems, high chemical and thermal stability) of these acids and their derivatives when used at low concentrations resulted in their widespread use in industrial processes and consumer uses [11-13]. The most common commercially produced perfluorinated surfactants are the perfluoroalkyl acids (PFAAs) ... 

As shown in Figure 18.5, l//,l//-perfluoroalkanols are an important group of intermediates that can be obtained from PFCA fluorides obtained by electrochemical fluorination (or, alternatively, by a telomerization process ). These alcohols are readily converted into polydisperse nonionic polyoxyethylene surfactants by reaction with oxirane (or analogues) in the presence of a catalyst (Scheme 18.13). Borontrifluoride etherate is the classical catalyst for this oxyethylation reaction, but there are claims for the utilization of other catalysts such as aluminum alkoxides, sodium hydroxide, and acidic catalysts. ... 

The perfluorinated carbonyl fluorides, prepared by electrochemical fluorination, are converted to nonionic fluorinated surfactants via the amide by a similar process ... 

Ammonium perfluoropolyether carboxylates are effective emulsifiers for perfluoropolyether oils [116]. Microemulsions of the oil-in-water type, consisting of perfluoropolyethers emulsified by fluorinated surfactants, are used as catholytes in electrochemical processes [117-119]. 

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