The major detergent companies have been working towards effective zero-phosphate laundry powders for several decades now. Regulatory pressure first began over 40 years ago in Germany, parts of Italy and the United States. It seemed a huge challenge to deliver effective cleaning without the use of sodium triphosphate, which had been incorporated for many years as a detergent builder that not only removed water hardness ions, but also performed useful secondary functions in the cleaning process, for example buffering, soil suspension and anti-redeposition.
Alternative water softeners
Formulations were developed with large amounts of zeolite or sodium carbonate replacing the traditional phosphate builder. The zeolite powders, in particular, tended to cake in the pack and were slow to disperse in water, lessening the efficacy of the water softening function. The stability of some of the more reactive components of the formulation, such as low temperature bleach and enzymes, was also sub-optimum. Cleaning performance was only adequate, and consumer reaction was mixed. Complaints were received concerning residues on clothes and around drain outlets from washing machines.
All these years later, is the move away from phosphate still a challenge? Meeting the performance targets of phosphate products has been helped by a general dilution of formulations, owing to cost pressures. Moreover, a better appreciation of consumer requirements has led to the understanding that for many consumers, carrying out the laundry chores is more about freshening and conditioning the laundry items such that they are a pleasure to wear again. Hence it is just as important to deliver the right sensory performance to the consumer as adequate cleaning. Zero-phosphate powders can now be marketed that tick all these boxes.
Lest anyone worry that these products do not clean well enough, and consumers are being short-changed, they only need to look at the success of laundry cleaning liquids that satisfy millions of consumers everyday, without the use of phosphates, or any strong builders, at all.
Opportunities for polymer suppliers
So what are the implications for raw material usage? Firstly, when zeolite is used to replace sodium triphosphate, sodium silicate levels are reduced to around 25% of the original. However, sodium carbonate levels are typically about 30% higher than in the phosphate formulations. Many zeolite formulations contain acrylic/maleic co-polymers at 1 to 2%. Where carbonate is used to replace sodium triphosphate, low molecular-weight polyacrylates are usually included at around 1%. So the move out of phosphates could be good news for polymer suppliers.