Ester quats

Ester quat Alkyl quat Imidazolinium quat... 

The development of an easy-to-handle method for the qualitative and quantitative determination of surfactants in consumer products was the goal for applying ESI in the FIA-MS(+/—) mode by direct infusion into the mass spectrometer. In this way Ci2, Ci4, Ci6 and Ci8 ASs could be determined besides other anionics (LASs, alkylcarboxylates), nonionics (alkyl polyglucosides (APGs)) and cationics (quats and ester-quats). The methods applied for concentration and determination (MS-MS) helped to identify the compounds and in addition deuterated internal standards were applied for confirmation [57]. 

A third and more recent example of where readily biodegradable surfactants have replaced surfactants that are more long-lived in the environment is the taking over of the market for textile softener surfactants by the ester quats from the stable quats. This transition is still in progress today but for several years the big soapers all base their softener formulations for the US and Western Europe markets on ester quats instead of traditional, stable quats. The change from stable quats to ester quats is probably the best example of the concept of introducing a cleavable bond in a given surfactant structure because the two types of products are very similar in structure and physical chemical charac-... 

Fig.1 A Stable quat (top) and three ester quats of the type that is used for textile softening...

The three transitions mentioned above, replacement of branched alkylben-zene sulfonates by linear alkylbenzene sulfonates, replacement of alkylphenol ethoxylates by alcohol ethoxylates and substitution of ester quats for stable quats are all driven by environmental concerns. Rate of biodegradation and aquatic toxicity are the major parameters taken into account, and, in order to pass the regulations that the European Union has adopted, a surfactant must pass the criteria of showing ... 

It is common practice to put the experimentally obtained values for biodegradation and aquatic toxicity into a kind of matrix, as is illustrated by Fig. 2. The shaded areas in the matrix are the approved areas . Out of the six product types discussed above linear alkylbenzene sulfonates, alcohol ethoxylates, and ester quats lie within the shaded areas, while branched alkylbenzene sulfonates, alkylphenol ethoxylates and stable quats do not. 

When present in micelles, ester quats hydrolyze faster than free unimers in the bulk phase. This is due to an increased hydroxyl ion concentration around the micelle, i.e., the local pH in the vicinity of the micelle surface is higher than in the bulk. The phenomenon is referred to as micellar catalysis and is further discussed in the Betaine esters section. 

Ester quats with one, two, or three fatty acid ester moieties exist in the molecule, but the dominating type are the diester quats, i.e., products that contain two fatty acid ester chains and two short alkyl groups. These are synthesized by reaction of two moles of fatty acid with one mole of alkanolamine using an acid catalyst under conditions where water is stripped off The fatty... 

The dominating use of ester quats is as fabric softener and the transition from the traditional di(hydrogenated tallow)dimethylammonium chloride, which had been the work-horse softener for more than three decades, to ester quats was made in Europe in the early 1990s as a response to pressure from environmental authorities in the European Union [23]. The transition has been less rapid in the United States, but ester quats have gradually replaced the traditional quats in most of the major softener products there as well. The same trend is ongoing in the rest of the world. 

The diester quats used for fabric softening are hydrophobic species with very limited water solubility. In water they form lamellar phases and liposomes at low concentration. The low water solubility in combination with the hydrolytic instability makes formulation of softener products a demanding task, and a plethora of patents and patent applications related to ester quat formulations have been published during the last decade [21], The diester... 

TEA Based Ester Quat Tallow dimethylammonium Chloride... 

Therefore, commercially available hydrophilic silicone finishes are nondurable. The hand changes considerably after one washing cycle, and the typical silky silicone character of the textile is lost. The additional use of ester quat-based rinse additives does not solve this problem. Ester quats provide a nondurable hydrophobic character. 

Following the same routine, 38% of the durable hydrophilic softener WARO 739 is removed over five washing cycles. The hydrophilic silicone soft hand is maintained over all cycles despite the silicone loss. An addition of ester quat-based rinse additives is not necessary. 

At present, triethanolamine ester quats (TEAEQ), with a formal structure of (RC02CH2CH2)2N+(CH3)CH2CH2OH-CH3SC>4 are the fabric softeners of choice in Europe and elsewhere, replacing the imidazolinium and dialkyldimethyl ammonium types. 

IV. Ester Quaternary Ammonium Salts (Ester Quats)... 

Silicone after Silicone after 5 Silicone after 5 Ester quat add. over S... 

Ester quaternaries have been known since the 1930s, but found limited commercial use in earlier years. However, their commercial relevance took a quantum leap forward in 1991, when European detergent manufacturers reformulated their rinse-added softeners because of pressure from environmental authorities in some European Union member states. A major benefit or feature of the ester quat structure is its decomposition into nonsurface-active fragments upon hydrolysis. However, this benefit, i.e. hydrolytic instability, also posed a challenge to the formulator. Ester quaternaries are stable in aqueous solutions only over a narrow pH range, unlike the traditional alkyl quaternaries. Softener dispersions based on ester quaternaries are typically adjusted to pH < 4 to maintain hydrolytic stability. 

M Ester quat M Dialkyl quat B Monoalkyl quat ... 

During the last decade, the dialkylester quats have to a large extent replaced the stable dialkyl quats as rinse-cycle softeners, which is the single largest application for quaternary ammonium compounds. The switch from stable dialkyl quats to dialkylester quats may represent the most dramatic change of product type in the history of surfactants, and is entirely environment-driven. Unlike stable quats, ester quats show excellent values for biodegradability and aquatic toxicity. Ester quats have also fully or partially replaced traditional quats in other applications of cationics, such as hair care products and various industrial formulations. 

The cationic charge close to the ester bond renders normal ester quats unusually stable to acid and labile... 

Figure 17.17. Structures of one conventional quaternary ammonium surfactant (I) and three ester quats (II-IV) (R is a long-chain alkyl, and X is Cl, Br or CH3SO4)...

The active surfactant in a fabric softener is an ester quat (quaternary ammonium compound with ester links to improve biodegradability). These active ingredients are supplied to the product manufacturers as a mobile liquid which contains isopropanol. Other solvents, such as glycol ethers, can be used but, mainly for cost reasons, over 90% of the market uses isopropanol. 

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