Carboxylated surfactants, properties

Carboxylate, sulfonate, sulfate, and phosphate ate the polar, solubilizing groups found in most anionic surfactants. In dilute solutions of soft water, these groups ate combined with a 12—15 carbon chain hydrophobe for best surfactant properties. In neutral or acidic media, or in the presence of heavy-metal salts, eg, Ca, the carboxylate group loses most of its solubilizing power. 

The principal constituents of rosin (qv) are abietic and related acids. Tall oil (qv) is a mixture of unsaturated fatty and aHcycHc acids of the abietic family. Refined tall oil may be high in rosin acids or unsaturated acids, depending on the refining process. Ethoxylates of rosin acids, eg, dehydro abietic acid, are similar to fatty acid ethoxylates in surfactant properties and manufacture, except for thek stabiHty to hydrolysis. No noticeable decomposition is observed when a rosin ester of this type is boiled for 15 min in 10% sulfuric acid or 25% sodium hydroxide (90). Steric hindrance of the carboxylate group associated with the aHcycHc moiety has been suggested as the cause of this unexpectedly great hydrolytic stabiHty. 

Some special salts of ether carboxylic acids are also described. Chloro-hexidine salts are made by neutralization of chlorohexidine base by an ether carboxylic acid having antibacterial and surfactant properties [47]. Chitosan salts of ether carboxylic acids which are tolerant of anionics and can be used as hair conditioners are also mentioned [48]. 

Enhanced oil recovery by alkaline flooding was proposed some years ago as an inexpensive way to take advantage of the acid components that occur naturally in some crude oils [80,81]. The stabilization of oil-in-water emulsions can also be attained this way. In these cases the carboxylic acid contained in the crude oil adsorbs at the O/W interface, where it is neutralized into a carboxylic salt with surfactant properties such as interfacial tension lowering or emulsification. Fatty amines and their cationic counterparts at low pH are routinely used to stabilize asphalt emulsions for roads and pavement. 

Esterification with poly(carboxylic anhydrides) can be controlled to minimize diesterification and crosslinking to produce carboxylated cellulosic esters. Eastman Kodak in a recent patent claimed the succinylation of cellulose to different degrees 1 per 3 anhydroglucose rings [182] and 1 per 2 rings [183]. Henkel [184] also has a patent for a surfactant by the esterification of cellulose with alkenylsuccinic anhydride, presumably substitution degree governs the hydrophile-hydrophobe balance of the product and its surfactant properties. 

Further studies have demonstrated that PFPE-based surfactants can form microemulsions (with water cores) in supercritical CO2 (21). At higher water loadings, the CO2 was saturated with water and micelles began to solubilize water, which demonstrated bulk-like properties using spectroscopic probes. Although the PFPE-ammonium carboxylate surfactant was able to aggregate in CO2 at low water concentrations, a double-tailed surfactant, Mn(PFPE)2, was not soluble in CO2 without water. However, in the presence of water, Mn(PFPE)2-based micelles formed and the water core was able to ionize the manganese. 

This chapter will cover recent developments in the production, use and characterization of fatty acids and their derivatives as surface-active materials. However, the chapter will be limited to surfactants where the original, native, fatty acid plays an evident role in the properties of the surfactant and will not include the many surfactant classes in which the hydrocarbon backbone or carboxylic group have been modified (e.g. by epoxidation, hydrogenation, amidation) or where the surfactant properties are mostly decided by the variations in the polar head group (e.g. carbohydrate derivatives, amino acids). 

The alkali carboxylate will be a reasonably good surfactant for many applications, but if the hydrocarbon chain length were increased to 16 or 18 carbons, many of the surfactant properties would be even better, illustrating the importance of obtaining the proper balance between the hydrophilic and hydrophobic portions of the molecule. 

Some of the physical properties of fatty acid nitriles are Hsted in Table 14 (see also Carboxylic acids). Eatty acid nitriles are produced as intermediates for a large variety of amines and amides. Estimated U.S. production capacity (1980) was >140, 000 t/yr. Eatty acid nitriles are produced from the corresponding acids by a catalytic reaction with ammonia in the Hquid phase. They have Httie use other than as intermediates but could have some utility as surfactants (qv), mst inhibitors, and plastici2ers (qv). 

In this study we examined the influence of concentration conditions, acidity of solutions, and electrolytes inclusions on the liophilic properties of the surfactant-rich phases of polyethoxylated alkylphenols OP-7 and OP-10 at the cloud point temperature. The liophilic properties of micellar phases formed under different conditions were determined by the estimation of effective hydration values and solvatation free energy of methylene and carboxyl groups at cloud-point extraction of aliphatic acids. It was demonstrated that micellar phases formed from the low concentrated aqueous solutions of the surfactant have more hydrophobic properties than the phases resulting from highly concentrated solutions. The influence of media acidity on the liophilic properties of the surfactant phases was also exposed. 

Until the 1950s ether carboxylates were almost in very limited amounts in the textile industry. It was only in 1957 [9] that the first ethercarobxylates were mentioned, in combination with other surfactants such as alkyl sulfates and ether sulfates, for use in shampoos. In spite of the special properties of ether carboxylates, their use was low in the industry as well as in cosmetics at that time. This was also due to the fact that at that time properties such as toxicity, biodegradability, and mildness to the skin did not have the high priority they do now. 

However, in a 1963 lecture it was pointed out that ether soaps had special characterics [10], i.e., good biodegradability, mildness to the skin, and less corrosiveness to metals, and that we should expect these soaps to play an important role in the future. However, the real breakthrough of the ether carboxylates came in the 1980s, when environmental properties of surfactants became even more important along with other properties of ether carboxylates such as chlorine stability, anticorrosiveness, lime soap dispersibility, electrolyte stability, alkaline stability, and so on. 

The surface-active properties of ether carboxylates have been compared with soaps as well as with those of nonionic and anionic surfactants in addition, the influence of fatty chain and degree of ethoxylation has been investigated. 

Van Paassen [57] describes the CMC of some polyether carboxylates with different fatty chains and EO degrees (Fig. 2). In an extensive study, Binana-Limbele et al. [59] investigated the micellar properties of the alkylpolyether carboxylates of the general formula CnH + OCF CH OCI COONa with n = 8, x = 5, and n = 12 and x = 5,1, and 9, by means of electrical conductivity (CMC, apparent micellar ionization degree) and time-resolved fluorescence probing (micelle aggregation number A7) as a function of temperature and surfactant concentration (Table 1). 

These higher foaming properties are very useful for such cosmetic formulations as shampoos, showerbaths, and so on. This is the same with the forming of fine bubbles and the improving of foam stability of other surfactants such as, for example, alkyl ether sulfates due to the combination with ether carboxylates [57,67-69] (Table 9). 

Due to the good lime soap dispersing properties it is possible to improve the foaming properties of hard water-susceptible surfactants. Improvement of the formulation of a fatty acid soap by laureth-17 carboxylic acid, sodium salt [57,62], and an amidether carboxylate [62] has been described. 

In a patent survey [76] about shampoos over the period 1968-1978 the so-called cryptoanionic alkyl ether carboxylate based on tridecyl alcohol with 6.5 mol EO has been mentioned for a conditioning shampoo in combination with an amphoteric and cationic surfactant [77]. Because of the low interference with cationic surfactants no negative effect on the conditioning properties has been found [78]. 

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