Volume 44, Issue 1

A wide range of test methods are used worldwide for testing the performance of laundry detergents. Principally, all methods need tracer stains. Uniformly stained standard tracer stains are occasionally considered ‘artificial’ while manually prepared or circular stains are at the same time accepted as ‘natural’. This distinction is not helpful, it is even incorrect. Uniformly stained tracer stains were developed to improve reproducibility. Only few existing stains are additionally heat treated or represent combinations of several stain substances ((effect stains)). All tests are supposed to provide performance results reflecting reality (i. e. consumer perception); suitability of any of the model systems depends solely on their ability to provide results for reliable performance assessment. Extensive comparative tests using different stain systems confirmed that preparation of small batches using different fabric substrates, finish and pre-treatment is beneficial for testing e. g. soil release polymer performance. Apart from that, uniformly soiled standard stains in general showed better reproducibility while providing comparable performance results. We could confirm that standard stains are a good solution for addressing issues with dissatisfactory reproducibility.

The Metrohm NIO surfactant electrode has been used as end-point indicator for potentiometric titration of low concentration level of polyethoxylated nonionic surfactants. This can be achieved by using of a diluted titrant concentration, thus reducing the amount of precipitate formed during titration and preventing the electrode deterioration. The solutions of low levels (down to 10 −6 mol/L) of selected nonionic surfactants containing 5 to 23 EO groups were successfully titrated with diluted (as low as 10 −4 mol/L) sodium tetraphenylborate as standard anionic titrant, increasing up to 20 times the sensitivity of the method. The low surfactant concentration has been determined in synthetic formulations of widely used detergent products and industrial waste waters. The titration end-point has been determined by applying extended Savitzky-Golay least-squares regression. The accuracy and precision has been evaluated by using the standard addition method. Relative standard deviation within results was between 3.4 and 12.8 % depending on the sample complexity and the surfactant concentration level.

This paper provides a generic overview of the relative contribution of different sources to the load of phosphorus (P) in surface waters in 18 European countries. Based on the current P-inputs into surface waters, future scenarios reflecting further reductions of P from municipal waste water are presented. A significant P-reduction can be achieved by improving the wastewater treatment situation and by introducing P-free product alternatives for laundry detergents. The remaining fraction of P in surface waters originating from automatic dishwashing detergents (ADD) only has a minor relevance for the aquatic ecosystem and may be reduced to a maximum of <1–4% when sewage treatment situation is improved. It can be concluded that ADD as P-source in the aquatic environment may not significantly contribute to the nutrient status, especially in eutrophication sensitive areas, where efficient P removal from sewages is regulated by the Urban Wastewater Directive (91/271/EEC). With respect to a requested evaluation of potential legislative steps by the EUDetergent Regulation (648/2004/EEC), a total ban of P in detergents seems not an appropriate measure to achieve significant reductions of P-concentrations in surface waters.

Two series of cationic dimeric ((gemini)) surfactants are presented with respect to key surfactant properties, such as surface activity and micellization. The influence of the dimerization and of the spacer group are examined, in order to establish structure-property relationships. Importantly, the addition of organic anions strongly modifies the solution properties and aggregate morphology. The surface tension and critical micellar concentration can be markedly reduced compared to the dimeric surfactants in the pure state. Moreover, dimeric surfactants with an appropriate spacer group can produce viscoelastic solutions after addition of certain organic anions even when bearing only dodecyl chains, whereas no effect is observed for such mixtures involving the analogous (monomeric) surfactant. Also, first results on the use of polymerizable counterions and their polymerization in such mixtures are presented.

δ layered sodium disilicate (δ-Na 2 Si 2 O 5 ) is a single layer silicate and has good properties as detergent builder. However, it is difficult to synthesize high pure δ-Na 2 Si 2 O 5 . In this paper, a feasible and simple technology was found by decreasing Na content in liquid sodium silicate (water glass). The crystalline time was short and no seed needed. The suitable synthesis conditions were Si/Na = 1.05–1.10, calcining at 720 °C for 5 minutes. The synthesis conditions are of industrial value. XRD and 29 Si NMR data proved that synthesized samples were δ-Na 2 Si 2 O 5 without impure phase. High pure δ-Na 2 Si 2 O 5 exhibited good ions binding ability and reached 312 to 338 mg CaCO 3 /g.