Detergent formulations, anionic surfactants

The described mechanisms of detergency are put into practice by using synthetic micelle-forming surfactants, among which the mixtures of anionic and nonionic surfactants (particularly alkylsulfates and oxyethylenated alcohols) make 10 to 40 % of the total detergent formulation. Cationic surfactants (alkylamines) that are also included into synthetic detergent formulations may contribute up to 5% of the total amount of formulation. These substances reveal biocidal action and control micelle formation by forming mixed micelles. 

In acidic media, amine oxides and anionic surfactants form precipitates the CMC is much greater than in neutral or alkaline media. Change in CMC parallels change from ionic to nonionic form. Amine oxides are stable in formulated detergent products and do not act as oxidizing agents. Composition and function of representative commercial amine oxides are given in Table 26. 

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]. 

This chapter deals with sodium a-olefinsulfonate (AOS) and with sodium internal olefmsulfonate (IOS). AOS is a well-established product and is being applied in many household and industrial formulations. IOS of a sufficiently high quality has only recently been made on laboratory scale and pilot plant scale and has not yet been applied in commercial formulations. AOS and IOS have not only good wetting and detergency properties, but also good tolerance toward water hardness ions, a combination not always observed for other anionic surfactants. 

From the anionic surfactants (Table 1.1) the most relevant is LAS with an annual global production volume of more than 3 X 1061 in 2001. LAS has a wide application because of its excellent detersive properties and cost-performance ratio. Commercial LAS is applied mainly in the formulation of powder and liquid laundry detergents. The calcium salts are used as an emulsifier in pesticide formulations their amine salts are used in dry cleaning and as degreasing agents in the metal industry [14]. 

As an example of an anionic surfactant mixture frequently contained in detergent formulations, an AES blend with the general formula C H2 i i—O—(CH2—CH2—O) —SO3 was examined in the negative FLAMS mode. Because of the considerable differences observed between both API ionisation mode overview spectra, the ESI—FIA—MS(—) and the APCI—FIA—MS(—) spectra are reproduced in Fig. 2.5.3(a) and (b), respectively. Ionisation of this blend in the positive APCI—FIA—MS mode, not presented here, leads to the destruction of the AES molecules by scission of the O—SO3 bond. Instead of the ions of the anionic surfactant mixture of AES, ions of AE can then be observed imaging the presence of non-ionic surfactants of AE type. 

Since this material is cationic, it is generally incompatible with anionic surfactants unless special proprietary formulation approaches are used. Therefore, fabric care detergents, especially liquids, often use nonionic surfactants. 

Sulfonation and sulfation processes are utilized in the production of wateT-soluble anionic surfactants as principal ingredients in formulated light-duty and heavy-duty detergents, liquid hand cleansers, general household and personal care products, and dental care products. Other commercially significant product applications include emulsifiers, lube additives, sweeteners, pesticides, medicinals. ion-exchange resins, dyes and pigments. 

Anionic Surfactants. PVP also interacts with anionic detergents, another class of large anions. The addition of PVP results in the formation of micelles at lower concentration than the critical micelle concentration (CMC) of the free surfactant the mechanism is described as a necklace" of hemimicelles along the polymer chain, the hemimicelles being surrounded to some extent with PVP, The effective lowering of the CMC increases the surfactant s apparent activity at interfaces. PVP will increase foaming of anionic surfactants for this reason, Because of this interaction, PVP has found application in surfactant formulations. 

The characteristic effect of surfactants is their ability to adsorb onto surfaces and to modify the surface properties. Both at gas/liquid and at liquid/liquid interfaces, this leads to a reduction of the surface tension and the interfacial tension, respectively. Generally, nonionic surfactants have a lower surface tension than ionic surfactants for the same alkyl chain length and concentration. The reason for this is the repulsive interaction of ionic surfactants within the charged adsorption layer which leads to a lower surface coverage than for the non-ionic surfactants. In detergent formulations, this repulsive interaction can be reduced by the presence of electrolytes which compress the electrical double layer and therefore increase the adsorption density of the anionic surfactants. Beyond a certain concentration, termed the critical micelle concentration (cmc), the formation of thermodynamically stable micellar aggregates can be observed in the bulk phase. These micelles are thermodynamically stable and in equilibrium with the monomers in the solution. They are characteristic of the ability of surfactants to solubilise hydrophobic substances. 

The worldwide consumption of surfactants in 2003 is shown in Table 36.5. In many parts of the world, soap is still the primary surfactant for textile washing and personal care. Synthetic detergents are widely used in the devolved regions of the world including North America, Western Europe, and Japan. Anionic surfactants dominate the world surfactant market. Common anionic surfactants include LAS, AS, and AES. The second largest class of surfactants is the nonionics of which AE and APE are most common. The use of APE is in decline because of concerns with biodegradability and endocrine disruption. Quats are commonly used in antibacterial formulations because of their ability to lyse the cell membrane of... 

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