Seeking Chelating Agents (Sequestrants) for Concentrated Liquid Laundry Detergent Compositions

Need a chelating agent (Sequestrant) that can be incorporated into a concentrated laundary detergent without inducing any instability. The Sequestrant must effectively bind transition metal ions like Fe, Mn and Cu in high Ca/Mg environments during the washing process.

Chelating agents (more commonly known as Sequestrants) are an important class of technology for Laundry detergents. They are important in controlling levels of transition metals present during the laundry wash process and in also product (in trace levels). Such metal ions can have a detrimental effect of the cleaning performance of laundry detergents.

Numerous sequestrants have been utilised in laundry detergent powders (and are predominately phosphonate based chelators). However, such materials are not readily incorporated into concentrated liquid detergents.

Therefore, there is a need to identify sequestrant technology that can effectively bind transition metal ions during the washing process, but can readily be incorporated into a concentrated laundry liquid detergent without inducing any liquid instability.

A desired solution should demonstrate selective complexation of transition metal ions (e.g., Fe, Mn, Cu) in high Ca/Mg environments. It should also show compatibility with other detergent materials. It should not alter phase behavior and stability of concentrated surfactant mixtures.

Conventionally used sequestrants are highly charged small molecules (for example phosphonates) and are widely used in powder detergents. However, they have very limited incorporation potential in concentrated liquid detergents. Such molecules often require high levels of solvents to prevent unwanted changes in formulation microstructure and stability, and can only be incorporated at low levels. It is believed that the highly charged nature of these materials induce phase instability in liquid detergents.

There is a requirement to identify materials which effectively sequester such transition metals during the wash process, but are readily incorporable into concentrated liquid laundry detergents. Such liquid detergents typically contain amongst other ingredients between 20-50% surfactants, hydrotope solvent (typically propylene glycol or ethanol) and water. The typical microstructure of a concentrated liquid is isotropic micellar, although other microstructures such as lamellar phases can also be formulated.

Typically available Laundry sequestrants include:

Phosphonate based (e.g.Dequest series):

• HEDP ( 1-Hydroxyethylidene -1,1,-diphosphonic acid)
• Diethylenetriamine penta(methylene phosphonic acid)

Typical examples of other sequestrants previously tested include:

• IDS (2,2’-Iminodisuccinic acid (Na salt))
• HIDS (3-Hydroxy-2,2’-iminodisuccinic acid (Na salt))
• s,s-EDDS (S,S-ethylenediamine N,N’-disuccinic acid (Na salt))

All these materials either are not readily incorporated into concentrated liquid detergents, and / or do not effectively bind transition metals selectively.

Minimum expectations:

• Must be able to selectively bind first row transition metal ions (e.g., Fe, Mn, Cu) in the presence of high levels of competing ions such as Ca and Mg.
• Ideally would have similar sequestration behaviour as currently utilised phosphonates, but would be readily incorporated into concentrated liquid detergents
• Must not induce instability in concentrated liquid detergents
• Preferably materials with low-levels / zero charge

Better Ifs:

• Solution is non-phosphorus based
• Solution is biodegradable
• Solution is incorporable and stable over a range of formulation pHs (6-9)
• Solutions would provide more than benefit, or amplify the effectiveness of other formulation ingredients

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