Alpha olefin sulfonates (AOS) have been used successfully for many years in laundry and personal-care products throughout Asia. Among their documented positive attributes are good cleaning and high foaming in both soft and hard water, rapid biodegradability, and good skin mildness. AOS has commonly been marketed as approximately 40%-active aqueous solutions. However, with the increased importance of compact powder detergents produced by processes other than spray drying, high-active forms of AOS including 70%-active pastes and 90+%-active powders are now being utilized for that product sector. In this regard, the rheological properties of non-Newtonian AOS and AOS/additive pastes at relevant process temperatures were measured and found potentially suitable for agglomeration processes. Also, the relationship of AOS powder particle size to surfactant solubility at various wash conditions was examined to allow determination of the optimal size for both detergency and processing of laundry powders. Both paste rheology and powder morphology are critical factors for the successful use of high-active AOS in compact powder detergents. JSD 1, 361-369 (1998). KEY WORDS:Alpha olefin sulfonate, detergent, powder, surfactant.Alpha olefin sulfonates (AOS) are obtained by direct sulfonation of alpha olefins (AO) of varying chain lengths to form complex mixtures of alkene and hydroxyalkane sulfonate isomers. Several references describe the process chemistry for AOS production (1,2). Purity of the commercial AO feedstock is critical for obtaining high-quality AOS. For example, trace impurities such as di-olefins can lead to color formation during the sulfonation process. Also, high levels of paraffins lower the yield of active surfactant. Of particular importance for AOS used in powder detergent formulations, high levels of branched and internal olefins lead to reduced detergency and powder formulations with reduced flowability (2). Table 1 shows a comparison of olefin compositions obtained from three different ethylene-based olefin production processes and their positive and negative attributes when used as feedstock for AOS production. The advantages of using feedstocks containing high levels of normal AO are clearly evident. A detailed description of the three AO production processes may be found elsewhere (3).The sodium salts of AOS have been used for many years as anionic surfactants in a variety of industrial, personalcare, and household-cleaning applications. Beneficial attributes of AOS include good cleaning and foaming properties in both soft and hard water, mildness to skin, and rapid biodegradability. Household applications include laundry and dish detergents, and personal-care applications include shampoos and liquid hand soaps. In Asia, particularly Japan and Korea, AOS has commonly been used in laundry powders. For production of low-density powders in spray towers, 40%-active aqueous solutions are suitable for use. However, with the increasing market share of compact powder detergents, new high-active forms of AOS w...
Proposed regulations by the U.S. Department of Energy have spurred development of energy-efficient washing machines that utilize less water and operate with lower energy requirements than conventional machines. As a result, major changes in washing machine design are required. Among expected changes are increased use of a horizontal-axis wash tub, an increase in fabric-to-wash liquor ratio, greater surfactant concentration in the wash water, and reduced average washing temperatures. As a result, surfactants used in future detergent formulations will be required to clean effectively in this new regime while producing minimal foam. Detergency test methods utilizing radiotracer techniques have been developed to study the detergency process in energy-efficient washing machines. Detergency and redeposition of radiolabeled oily soils can be determined in a full-size horizontal-axis washing machine through scintillation counting of wash and rinse water samples. Measurements can be made after each wash process step and combined to determine total cycle detergency. This is a distinct advantage over conventional reflectance detergency methods where only total detergency at the end of the entire washing and rinsing process can be conveniently measured. Also, in contrast to indirect reflectance methods, measurements of absolute soil removal are obtained with the radiotracer method. In this study, soil redeposition was determined by measuring residual radioactivity on fabric swatches and then performing a material balance on the oily soil.
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