Suds generation is an important signal to the consumer that a hand dishwashing detergent is effective in removing soils and in particular, greasy oily residues. Suds longevity as it pertains to mileage, increased number of items cleaned per session, is also a signal to the consumer of the detergent’s efﬁcacy and value. Therefore, the challenge is to develop an effective dishwashing detergent that removes both particulate and greasy soils that is effective during the entire the course of a hand dishwashing cycle independent of number of items and level/type of soils on dishes, pots, pans, glasses, etc.
Optimal charge density was identiﬁed by using suds cylinder testing in the presence of polymer, formulated detergent and sequential soil additions (Figure 4, 5). These studies included rheology measurements, pH titrations of polymers with varying compositions of amine and non-ionic monomers, streaming potential measurements of wash solutions containing the polymers, and varying molecular structure and molecular weight of the polymer to facilitate formulation and solubility. Roughly 200 polymers were designed to optimize polymer efﬁciency taking into account performance, formulation ﬂexibility, and commercialization requirements.
The weakly charged polymer signiﬁcantly lowers the interfacial tension at the oil/water interface more that at the air/water interface which suggests why suds beneﬁts are observed despite heavy soil additions (simulating adding a food particulates to the wash solution). Increased suds mileage from the detergent formulation containing the polymer mimics was observed rheologically. Surface and interfacial tension measurements alone indicate polymer air/water surface activity is minimal up to 20 ppm polymer in solution (Figure 8). Polymer surface activity at the oil/ water interface occurs as low as 1 ppm concentration. Suds stabilization occurs via interactions (electrostatic and hydrophobic) with greasy soils, reducing soil antifoam effects.
The efﬁciency and efﬁcacy of the dishwashing process is determined by several factors including the type of surfactant chassis the formulation is built on. These detergents are generally designed to facilitate soil removal and make the dishwashing job easier and more enjoyable for the consumer. Second, the amount of mechanical action is highly variable in the dishwashing process. For difﬁcult to remove soils, consumers generally apply a large amount of mechanical action by scrubbing, often with the help of an implement. High performance dishwashing detergents (Figure 1) are generally carefully formulated to work with all the key factors or variables in the dishwashing process.