Detergency liquid soil removal

The importance of a surfactant - rich phase, particularly a lamellar one, to detergency performance was noted for liquid soils such as C16 and mineral oil (3.6). Videomicroscopy experiments indicated that middle phase microemulsion formation for C12E04 and Cjg was enhanced at 30 °C, while at 18 °C, oil - in - water, and at 40 °C, water - in - oil microemulsions were found to form at the oil - bath interface (3.6). A strong temperature dependence of liquid soil removal by lamellar liquid crystals, attributed to viscosity effects, has been noted for surfactant - soil systems where a middle - phase microemulsion was not formed (10). 

The mechanisms underlying the detergency and soil removal process have been reviewed by many authors [164-172], This section briefly summarizes the test methods used to characterize the performance of liquid laundry detergents. There are typically three stages of testing during product development (1) laboratory evaluation, (2) practical evaluation, and (3) consumer tests. 

Detergency, or the power of a detergent product to remove soil, depends on the ability of surfactants to lower the interfacial tension between different phases. This can be explained for a typical case where removal of liquid soil is aided by surfactant adsorption onto the soil and substrate surfaces from the cleaning bath (Figure 2) using Young s equation,... 

Light-duty liquid or gel dishwashing detergent compositions having controller pH and desirable food soil removal, rheological, and sudsing characteristics... 

Studies of the soil removal properties of polyoxyethylenated straight-chain primary alcohols on cotton and Dacron-cotton permapress fabric indicate that this detergency maximum with change in the number of oxyethylene units in the POE chain is also shown on these fabrics. In liquid no-phosphate formulations built only with diethanolamine to provide an alkaline pH, optimum removal of both sebum and clay soils from Dacron-cotton permapress at 49°C in 150 ppm hard water occurs with about 5, 9, and 10 oxyethylene units for POE C9-11, C12-15, and C16-18 alcohol mixtures, respectively. For removal of the same soils from cotton at the same temperature, the optimum POE chain lengths are about two oxyethylene units larger (Albin, 1973). 

Figure 8.13 Soil removal (5) by a surfactant phase microemulsion (ME) and by a 1 wt.% aqueous liquid detergent solution (L. Det) from different fabrics. (From Ref. [81 ], reprinted with permission of Taylor Francis.)...

In the USA, this surfactant is a well established product used in many household and industrial formulations. In particular, in light-duty liquid detergents the water solubility and soil removal ability of a-olefinesulfonates are excellent. In addition, o -olefinesulfonates are compatible with many other surfactants on the market, including alkyl sulfates, alkylbenzene sulfonates and alcohol ethoxylates. Therefore, o -olefinesulfonates can be used to obtain synergistic effects in binary or ternary mixtures. 

For example, surfactant systems have been changed to provide optimum performance. The introduction of new builder systems—enzymes, bleach activators, and new polymers for reduced soil redeposition—has also maximized soil removal from mixed fabric bundles during lower temperature washes in less wash water. In addition, new product forms such as concentrated liquids and powders with in-wash dosing containers have resulted in better usage and dispersion of detergent at low wash temperatures. 

To formulate a good detergent, one has to understand the various processes involved Wetting, removal of dirt, liquid soiling, prevention of redeposition of dirt. 

Enzymes. Proteolytic and amyolytic enzymes have been designed for use as adjuvants in detergent systems to remove stains. These complete proteinaceous molecules act as catalysts and tend to break down particular soils and stains to a form more readily removed from fabrics. These ingredients are used in presoak detergent systems and some liquid and powdered laundry detergents. 

Another mechanism of oily soil removal involves the formation of liquid crystalline phases at the detergent solution/oil interface. " After formation the intermediate phase is broken off by agitation and emulsified into the aqueous solution, allowing fiesh contact of the remaining soil with the detergent solution. 

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