Detergency solid soil removal

Time - resolved spectra of a solid hydrocarbon layer on the surface of an internal reflection element, interacting with an aqueous solution of a nonionic surfactant, can be used to monitor the detergency process. Changes in the intensity and frequency of the CH2 stretching bands, and the appearance of defect bands due to gauche conformers indicate penetration of surfactant into the hydrocaibon layer. Perturbation of the hydrocarbon crystal structure, followed by displacement of solid hydrocaibon from the IRE surface, are important aspects of solid soil removal. Surfactant bath temperature influences detergency through its effects on both the phase behavior of the surfactant solution and its penetration rate into the hydrocaibon layer. 

Solid Soil Type and Size. Different soHd soils differ greatly in ease of removal and redeposition behavior. These differences can be traced to particle size and soil—substrate bonding. The effect of particle size variation on detergency has been studied with soil removal and redeposition techniques. 

Adsorption of bath components is a necessary and possibly the most important and fundamental detergency effect. Adsorption is the mechanism whereby the interfacial free energy values between the bath and the sohd components (solid soil and substrate) of the system are lowered, thereby increasing the tendency of the bath to separate the solid components from one another. Furthermore, the sohd components acquire electrical charges that tend to keep them separated, or acquire a layer of strongly solvated radicals that have the same effect. If it were possible to follow the adsorption effects in a detersive system, in all their complex ramifications and interactions, the molecular picture of soil removal would be greatly clarified. 

Oily soils containing amphiphilic species, such as fatty acids or fatty alcohols, can also be removed from substrates as a result of the formation of liquid crystal or mesomorphic phases between the amphiphile and a detergent. The liquid crystals are then broken up by subsequent osmotic penetration by water [140-142], Removal of solid soils by mesophase formation can be accelerated by increasing the temperature. This has been reported for stearyl alcohol [143] and for lauric, palmitic, and stearic acids [128, 129] and is likely due at least in part to the increased penetration of the soils at higher temperatures [128,129,143],... 

Removal of solid soils by penetration without liquid crystal formation has been reported for tripalmitin, octadecane, and tristearin [143-145]. In these cases penetration of detergents occurred at crack and dislocation sites of soils. 

Unwanted materials (or soils as they are referred to in detergency) to be removed from the substrate are normally classified as oily, particulate, or solid non-... 

Short-chain methyl ester ethoxylates appear to be outstanding detergents for removing solid soils from hard surfaces, but only when surfactant use concentration is significant (>1%). At lower use concentrations, higher carbon chain length methyl ester ethoxylates are more effective. 

Since methyl ester ethoxylates are moderate foamers, and undergo significant hydrolysis at a pH greater than 9, they will not likely be used as the main surfactant in either hand or machine dish detergents. However, because of their ability to remove solid soil, methyl ester ethoxylates may find use not as a foam stabilizers or foam-generating surfactants but for enhancement of soil removal properties. 

In general, there are two types of soil encountered in detergency simations liquid, oily substances, and solid particulate material. Many stains on textiles such as blood, wine, mustard, catsup, and the like involve proteins, carbohydrates, and relatively high-molecular-weight pigmentlike materials that pose special problems in terms of the interfacial interactions involved. The interactions of each class of soil or stain with the solid substrate can be quite complex, and the mechanisms of soil removal may be correspondingly complex. 

Since the detergent power of many surfactants cannot be directly related to their efficacy as emulsifiers, there exists some question as to the importance of emulsification as a primary soil removal mechanism and redeposition control. Certainly, for efficient solubilization to occur, the area of surfactant solution—soil interface must be maximized, which implies a reduction in the solid substrate-oil interface. 

We also describe the spreading of a thin surfactant laden aqueous film on a hydrophilic solid, i.e., one in which the dynamic contact angle is small. In such a case, the osmotic pressure gradient generated by the nonuniform distribution of surfactant micelles in the liquid film can drive fhe spreading process. The mofivation for this study comes from the need to understand the detergent action involved in the removal of an oily soil from a soiled surface. This paper presents an overview of our recent work. 

Protein 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 using lipases, it is possible to improve the removal of fats/oils of animal and vegetable origin even at temperatures where the fatty material is in a solid form. Particulate soils can be difficult to remove, especially if the particle size is small. Removal of particulate soil from cotton fabric can be improved by use of a cellulase which removes cellulose fibrils from the surface of the yam. 

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