Detergents fabric, soil removal from

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. 

As with the case of energy input, detergency generally reaches a plateau after a certain wash time as would be expected from a kinetic analysis. In a practical system, each of its numerous components has a different rate constant, hence its rate behavior generally does not exhibit any simple pattern. Many attempts have been made to fit soil removal (50) rates in practical systems to the usual rate equations of physical chemistry. The rate of soil removal in the Launder-Ometer could be reasonably well described by the equation of a first-order chemical reaction, ie, the rate was proportional to the amount of removable soil remaining on the fabric (51,52). In a study of soil removal rates from artificially soiled fabrics in the Terg-O-Tometer, the percent soil removal increased linearly with the log of cumulative wash time. 

The principles outlined in Section 3.6.6 apply to both the removal and anti-redeposi-tion of soils, and to detergency in both industrial and personal care situations. There are, however, some differences between the application of detergency in an industrial setting (Section 12.2.1) and in a household setting. For example, whereas industrial cleaning usually involves hard surfaces that cannot mechanically hold soil, fabrics can hold soil mechanically, even after the soil has been removed from the fibre surfaces. In addition, fabrics can usually swell in aqueous solution, are permeable to small molecules, and may contain charged or polar surface groups that can interact with soil. An effective shampoo or skin cleaner needs to displace dirt and keep it dispersed so it does not redeposit before the hair or skin can be rinsed. 

This behaviour has a particular importance for the soil removal process in detergency. During the oil removal from stained fabrics or hard surfaces, ternary systems occur where three phases coexist in equilibrium. As already pointed out above, in this region the interfacial tension is particularly low. Because the interfacial tension is generally the restraining force,... 

A number of excellent studies have used a variety of radiolabeled soils to investigate the removal of small amounts of colorless soils such as oils (128-130). By proper use of different radiolabels (such as and " C), the preferential removal of various components in a soil mixture can be followed. In these cases in particular, detergency can also be calculated from measurements of the amount of radioactivity that is removed from the fabric and is found in the wash hquor. 

The function of the detergent is to remove the dirt and dust particles and other constituents of the size such as china clay from the cotton fabric. The detergent keeps the soils in dispersed or suspended form in scouring solution and prevents redeposition on the fabric. Fig. 4-10 illustrates the sequence of events of soil removal. Adventitious dirt adhere to the fabric because the oil acts as an adhesive towards it. The fabric/soil/water interfaces not soluble in water is shown in... 

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.)...

Lipases contribute to the detergency at wash temperatures of 30-60°C by catalyzing the hydrolysis of oily and greasy soils. Not only sebum, the stubborn stain of collars, cuffs, and underarm areas, but also fatty residues of various food products (frying fats, butter, tallow, salad oils, and sauces) and of certain cosmetics (lipstick and mascara) are better removed from fabrics by detergents containing lipases. Of course, lipases have no effect on triglyceride-free fatty material such as motor oils. 

The second procedure is used for assessing the ability of detergent products to remove soils from fabric. The difference between this procedure and the preceding one is the type of soil used for testing. The only soil used in this test is standard soil. 

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. 

Anionic surfactants account for about 50% of surfactant use in Europe and about 60% in the United States. Most are high-foaming but sensitive to hard water and therefore require the addition of substances to complex calcium and magnesium ions (i.e., detergent builders). They are more effective than other surfactants in particulate soil removal, especially from natural fabrics. As a rule, they are easily spray-dried and thus are favored for detergent powders. 

Proteia and starch stains are removed by proteases and amylases, respectively. Fats and oils are generally difficult to remove at low wash temperatures by conventional detergents. By usiag Upases, it is possible to improve the removal of fats/oils of animal and vegetable origin even at temperatures where the fatty material is ia a soUd form. Particulate soils can be difficult to remove, especially if the particle sise is small. Removal of particulate soil from cotton fabric can be improved by use of a ceUulase which removes cellulose fibrils from the surface of the yam. 

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