Sodium Xylene Sulfonate

Info Lkf Liquid Detergents

FIG. 7.4 Effect of sodium xylene sulfonate on the clear point of a premium LDLD blend. (From Drozd, J.C., Chemical Times & Trends, 8, 49, 1985. Reproduced with permission.)

The cloud and clear points of an LDLD can be adjusted using hydrotropes [83,84] such as sodium xylene sulfonate (SXS), sodium cumene sulfonate (SCS), alcohols, or urea. Figure 7.4 illustrates the significant effect of SXS on the clear point of an LDLD formulation.

(b) Viscosity. The viscosity of an LDLD is very important for its consumer acceptability and its dispersibility on dilution [85]. The viscosity of an LDLD is typically in the range 100 to 500 cP. In some markets such as Malaysia, Singapore, and Hong Kong, consumers prefer a much thicker product with viscosity in the range 2000 to 3000 cP. Consumers generally associate a thicker product with more "ingredients" in the product. However, technically, the viscosity of an LDLD is a strong function of not only its active ingredient level but also the isomer distribution in the surfactant, the relative amount of different surfactants, and the salt levels. Salt can be both a viscosity builder and a viscosity reducer, depending on where the formulation is on its salt curve, as mentioned above. An example of a simple system is sodium dodecylether sulfate (2.8EO) at 15% concentration. The viscosity first increases with the addition of NaCl and then decreases with further increase of the amount of NaCl [86]. AEOS with a narrow EO distribution thickens much more than AEOS with a conventional, broad EO distribution. Other factors that affect salt thickening are carbon chain length and carbon chain distribution [86].

Salt also has a significant effect on LAS. Depending on the cation of the LAS, salt in the range 0 to 2% can have a modest or large effect on the viscosity.

Fatty alkanolamides are mainly used as foam stabilizers, but they can also have a large effect on the viscosity of an LDLD formulation, usually increasing it. Other viscosity modifiers include hydrotropes such as alcohol, SXS, SCS, urea, and water-soluble polymers. However, not all of these have the same magnitude of effect, which depends on the surfactant system in the product.

(c) Physical Stability. Physical stability is another important product attribute that cannot be overlooked. Consumers would not want to purchase a product that changes physically over time. This may include precipitation, phase separation, or microbial contamination.

Industrial surfactants

Journal of the American Chemical Society

Pulping coniferous wood with sodium xylene sulfonate

Advanced Cleaning Product Formulations

Handbook of green chemicals