Cationic surfactants esterquats

The toxicity of these compounds [ 173,175] can be relatively high compared to other surfactants, but their poor solubility and their tendency to adsorb to solids or to complex with anionic substances considerably reduce the real risk and adverse effects for the aquatic environment. [30,31,176]. The use of alkylquats has been substituted by the more easily biodegradable and less toxic esterquats that are nowadays the cationic surfactants produced in higher volumes. 

Taking into consideration its physico-chemical properties, removal efficiencies, low biodegradability, predicted environmental levels, toxicity, and the need to provide sufficient safety margins for aquatic organisms, the demand for alternative cationic surfactants arose. Since 1991, DTDMAC has been replaced in some European countries due to producer s voluntary initiatives with new quaternary ammonium compounds, the esterquats. These contain an ester function in the hydrophobic chain (Table 1.3) that can be easily cleaved, releasing intermediates that are susceptible to ultimate degradation [24-26]. The effects of the phasing-out and replacement of DTDMAC can be demonstrated by the results of a Swiss study, where the surfactant... 

Fig. 2.12.1. Chemical structure of different classes of cationic surfactants (a) quaternary ammonium surfactants (quats) (b) dialkylcarboxyethyl hydroxyethyl methyl ammonium surfactants (esterquats) (c) alkyl polyglycol amine surfactants (d) quaternary perfluoro-alkyl ammonium surfactants (e) N, N, N1, JV -tetramethyl-iV, iV -didodecyle-l,3-propane-diyle-diammonium dibromide (cationic gemini surfactant). R = alkyl or benzyl group.

Fig. 2.12.6. Identification of esterquat compounds FIA-APCI-MS-MS(+) (CID) product ion mass spectrum of selected [M — RCO]+ base peak ion of cationic surfactant blend of di-hydrogenated tallowethyl hydroxyethyl ammonium methane sulfate type (mlz 692 general formula (R(C0)0CH2CH2)2-N (CH3)-CH2CH2(0H)CH30S03) fragmentation behaviour under CID...

Various classes of cationic surfactants, including quats, esterquats, alkyl ethoxy amines, quaternary perfluoroalkyl ammoniums and gemini surfactants have been analysed extensively with LC—MS and LC—MS—MS techniques, and their spectra have been fully characterised. Different ionisation methods have been applied for the detection of such surfactants, including API techniques (APCI and ESI) in negative and positive modes of operation. In addition, detailed examples regarding MS—MS fragmentation of these compounds have been reported and presented in this chapter. 

The anaerobic biodegradability and toxicity on anaerobic bacteria of cationic surfactants such as ditallow dimethylammonium chloride (DTDMAC) and two esterquats have been investigated in a recent study [52], For the esterquats studied, high biodegradation levels were obtained and no toxic effects on anaerobic bacteria were observed even... 

In the last years the behavior of chemical substances in the environment gained increasing importance for nearly all kinds of consumer products. Therefore the industry has developed new raw materials with a better environmental profile. For cosmetic products the biodegradation, toxicity, and dermatological behavior (especially for leave-on products) are the major issues. New classes of cationic surfactants that fulfill the new demands are the esterquats [107]. 

Triethanolamine based esterquats are a mixture of mono- di- and tries-terquats. It is claimed that for softeners and hair conditioners an esterquat with at least 50% diester content is preferred [49]. Methyldiethanolamine-based esterquats are mainly diesterquats with only slight amounts of mono-esterquat. Monoesterquats are useful as cationic surfactants in hair care formulations [124]. Solid esterquats with improved dispersibility and emulsifying properties are obtained by quaternization of fatty acid triethanolamine esters in the presence of a dispersing agent or nonionic emulsifier [125-127]. Esterquats can be used in sprayable conditioning systems for hair care [128]. 

As shown in the literature, esterquats have also received attention for other industrial applications. However, for many processes, their hydrolytic instability may be a limiting factor for their use as substitutes for the common cationic surfactants employed. Examples of successful applications are mentioned below. 

For many processes the hydrolytic instability for the esterquats in water solutions is a limiting factor for using them as substitutes for the traditional cationic surfactants employed. In some appHcations the hydrolytic instability is an advantage. An example where use is made of spontaneous decomposition into substances that are nontoxic is betaine esters which exhibit high... 

Another type of esterquats in the family of cleavable surfactants makes use of ortho-e ter linkages. It has been demonstrated recently in the literature that not only nonionic [193] but also cationic surfactants with ortho-e ter links can be prepared [194]. The ortho-e ter amine is prepared from a fatty alcohol, a short-chain ortho-e ter, and dimethylaminoethanol (Fig. 20). 

The trend of discovering the analytical field of environmental analysis of surfactants by LC-MS is described in detail in Chapters 2.6-2.13 and also reflected by the method collection in Chapter 3.1 (Table 3.1.1), which gives an overview on analytical determinations of surfactants in aqueous matrices. Most methods have focused on high volume surfactants and their metabolites, such as the alkylphenol ethoxylates (APEO, Chapter 2.6), linear alkylbenzene sulfonates (LAS, Chapter 2.10) and alcohol ethoxylates (AE, Chapter 2.9). Surfactants with lower consumption rates such as the cationics (Chapter 2.12) and esterquats (Chapter 2.13) or the fluorinated surfactants perfluoro alkane sulfonates (PFAS) and perfluoro alkane carboxylates (PFAC) used in fire fighting foams (Chapter 2.11) are also covered in this book, but have received less attention. 

During the last decade, the dialkyl esterquats have to a large extent replaced the stable dialkyl quats as rinse cycle softener, which is the single largest application for quaternary ammonium compounds. The switch from stable dialkyl quats to dialkyl esterquats represents one of the most dramatic changes of product type in the history of surfactants and it is entirely environment driven. Unlike stable quats, esterquats show excellent values for biodegradability and aquatic toxicity. Esterquats have also fully or partially replaced traditional quats in other applications of cationics, such as hair care products and various industrial formulations. Normal esterquats are covered in a special chapter of this book and are not discussed further here. 

Jaeger et al. have studied the kinetics of hydrolysis of cationic ketal-based surfactants [41], A comparison was made between acid hydrolysis of surfactants in nonaggregated form and in the form of either micelles or vesicles. (Ketal surfactants with one hydrophobic tail formed micelles and those with two hydrophobic tails formed vesicles.) It was found that both types of aggregation caused about two orders of magnitude reduction of the hydrolysis rate. Aggregation is evidently a way to protect these acid-labile cationic species from acid hydrolysis just as aggregation is a way to speed up alkaline hydrolysis of cationic alkali-labile surfactants, such as esterquats. 

Chem. Descrip. Esterquat Ionic Nature Cationic Uses Textile softener surfactant... 

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