Soap Ether

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. 

Ether Soap,—Another form of medicated soap made by a few firms is a liquid ether soap containing mercuric iodide, and intended for surgeons use. This, as a rule, consists of a soap made from olive oil and potash, dissolved in alcohol and mixed with ether, the mercuric iodide being dissolved in a few drops of water containing an equal weight of potassium iodide, and this solution added to the alcohol-ether soap. ... 

Poly(tetramethylene ether) glycols were found to have low oral toxicity in animal tests. The approximate lethal oral dose, LD q, for Terathane 1000 has been found to be greater than 11,000 mg/kg (272). No adverse effects on inhalation have been observed. The polymer glycols are mild skin and eye irritants, and contact with skin, eyes, and clothing should be avoided. Goggles and gloves are recommended. In case of contact with the skin, wash thoroughly with water and soap. If swallowed, no specific intervention is indicated, because the compounds are not hazardous. However, a physician should be consulted (260). 

Anionic surfactants are the most commonly used class of surfactant. Anionic surfactants include sulfates such as sodium alkylsulfate and the homologous ethoxylated versions and sulfonates, eg, sodium alkylglycerol ether sulfonate and sodium cocoyl isethionate. Nonionic surfactants are commonly used at low levels ( 1 2%) to reduce soap scum formation of the product, especially in hard water. These nonionic surfactants are usually ethoxylated fatty materials, such as H0CH2CH20(CH2CH20) R. These are commonly based on triglycerides or fatty alcohols. Amphoteric surfactants, such as cocamidopropyl betaine and cocoamphoacetate, are more recent surfactants in the bar soap area and are typically used at low levels (<2%) as secondary surfactants. These materials can have a dramatic impact on both the lathering and mildness of products (26). 

Suitable organic solvents, such as ether, benzene, naphtha and the like, are more soluble than in water. This makes it possible to separate them from other substances which may accompany them in the water solution but which are not soluble in the solvents employed. Hence, one application of solvent extraction is the analytical determination of unsaponifiable oils and waxes in admixture with fatty material by submitting the mixture to vigorous saponification with alcoholic potash or, if necessary, sodium ethylate, and to dilute the product with water and extract with petroleum ether. The soaps remain in the aqueous solution while the unsaponifiable oils and waxes dissolved in the ether. The addition of a salt to an aqueous solution prior to extraction is sometimes practiced in some processes. In older processes, SOj is employed in the separation of aromatic and highly saturated hydrocarbons, taking advantage of the much greater solubility of the solubility of the aromatics and... 

Generally ether carboxylates are not suitable for a syndet soap because they are waxy due to the ethylene oxide distribution. The solid ether carboxylates with a long alkyl chain and a low degree of ethoxylation have a bad foam. By use of nonethoxylated ether carboxylates, e.g., a carboxymethylated fatty acid monoethanolamide with the structure... 

A cooling, lubricating, and cleaning agent for use by the metalworking industry has been patented. It is produced by the condensation reaction of an excess diethanolamine or monoethanolamine with boric acid and an ether carboxylic acid or mixtures of ether carboxylic acids and fatty acids [46]. An advantage of these products is that they prevent the deposition of lime soaps. 

A major part of the physicochemical properties of ether carboxylic acids can be ascertained from the structure by comparing it with that of fatty acid soap, ethoxylated alcohol, and other anionics [64,73] ... 

A fatty acid soap in which a polyglycol ether group has been introduced between the fatty chain and the carboxylic group, which transforms some unfavorable properties of soaps into positive characteristics without decreasing the overall positive effects, and... 

Several investigators therefore compared the properties of ether carboxylates with different fatty chains and ethoxylation degrees with soaps based on different fatty chains [2,51,52,57,59,61,62,64,65]. 

With ether carboxylates the above-mentioned problems do not arise due to the polyglycol ether group in the molecule. Therefore ether carboxylates show good hard water stability as well as good detergent and foam properties in hard water. It is even possible to disperse lime soaps [61,62,64]. However, the ether carboxylates have the same creamy foaming properties as soap. 

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. 

Schulze [51] described an extensive study on C12-C14 ether carboxylic acid sodium salt (4.5 mol EO) in terms of surface tension, critical micelle concentration (CMC), wetting, detergency, foam, hardness stability, and lime soap dispersing properties. He found good detergent effect compared to the etho-xylated C16-C18 fatty alcohol (25 mol EO) independent of CaCl2 concentration, there was excellent soil suspending power, low surface tension, and fewer Ca deposits than with alkylbenzenesulfonate. 

The COONa group in the ether carboxylate has a positive effect on the lime soap dispersing properties [61,64] (Table 4). Stroink [61] and Meijer [64] also describe the good acid, alkali, and electrolyte stability of some ether carboxy-... 

FIG. 3 Lime soap dispersing power of some alkyl ether carboxylates compared to other surfactants (DIN 53903). AEC, alkyl ether carboxylate AMEC, amidether carboxylate CAPB, cocamidoproplylbetaine OEC, oleyl ether carboxylate SLES, sodium lauryl ether sulfate. % surfactant soap = % surfactant calculated on the soap needed to disperse the lime soap. (From Refs. 61 and 64.)... 

TABLE 4 Lime Soap Dispersing Power of Some Oleyl Ether Carboxylates Compared to Oleyl Ethoxylate (DIN 53903)... 

Because of improved mildness and lime soap dispersing properties ether carboxylates are also used in fatty acid soap-containing products like soap bars and liquid soaps [57,62] a foam improvement in hard water takes place. 

All of the aspects and applications described in papers can be traced back to the patent literature [73]. The special or synergistic effect of ether carboxylates in combination with other surfactants is very often the basis, like combinations with alkyl ether sulfates or alkyl sulfates, for shampoos, foambaths, showerbaths, and liquid soaps [9,70,81-85], and the same for amidether carboxylates [71]. 

For example, compared to alkylbenzenesulfonate the lauryl ether carboxylate based on C12-C14 alcohol and 4.5 mol EO shows good wetting, lime soap... 

Ether carboxylates are used not only in powdered detergents but in liquid laundry detergents for their hard water stability, lime soap dispersibility, and electrolyte stability they improve the suspension stability and rheology of the electrolyte builder [130,131]. Formulations based particularly on lauryl ether carboxylate + 4.5 EO combined with fatty acid salt and other anionic surfactants are described [132], sometimes in combination with quaternary compounds as softeners [133,163]. Ether carboxylates show improved cleaning properties as suds-controlling agents in formulations with ethoxylated alkylphenol or fatty alcohol, alkyl phosphate esters or alkoxylate phosphate esters, and water-soluble builders [134]. 

Low-foaming liquid or powdered machine detergents are described using a surfactant system prepared from naturally based raw materials with good biodegradability and detergent properties [135]. These formulations are based on 5-30% alkylpolyglucoside, 5-30% alkyl ether carboxylate, 5-35% soap, and 0-3% of another surfactant. 

The lime soap dispersing properties are very important for the dispersal of Ca soap, which is used to achieve among others, lower foam [60,64,66,181]. In addition, nontoxicity as well as good dermatological properties and biodegradability have been factors in the increased use of ether carboxylates [60,66]. 

A special application of the ether carboxylic acid in metalworking has been described by Schuster [46] a boric acid ester has been produced by condensation of boric acid, alkanolamine, and alkyl ether carboxylic acid, eventually combined with a fatty acid. This condensation product gives less Ca soap precipitation, good anticorrosion effect, better removability of residues, and cleaner apparatus than the condensation product using only fatty acid. 

One of the longest known synthetically prepared surfactants are the fatty alcohol sulfates, which were prepared on technical scale before 1940. Along with their ethoxylated counterparts, the fatty alcohol ether sulfates, which appeared on the stage shortly after, their use in toiletries is very popular but they can also be found in products for textile industry and auxiliaries in emulsion polymerization. With the exception of soaps, the mentioned anionic surfactants all have a sulfur-containing functional group. Denying the differences between these, their skin irritancy potential is remarkably high. 

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