If it weren't for the environmental needs to use less energy and fewer chemicals, getting the laundry really clean would be a breeze. All it would take is a hot wash and lots of detergent.
Over the last few decades, detergent and washing machine manufacturers have responded to sustainability imperatives. Effective washing temperatures have fallen dramatically, and the detergents themselves have changed radically.
Still consumers’ top priority (stain and dirt removal) is being met, thanks to the huge strides made in detergent laboratories all over the world.
In fact, one of the first breakthroughs came very early on in the century with the discovery that sodium perborate bleaches stains extremely well by releasing active oxygen (through the intermediary of hydrogen peroxide) into the wash. At the same time, it is gentle and safe. But alone, it works only in hot washes—about 140°F (60°C) and above.
The answer to the low-temperature perborate challenge came in the 1970s, when researchers discovered that the performance of sodium perborate under 140°F could be restored by the use of activators. These ingredients—with catchy names such as tetraacetylethylenediamine (TAED) and sodium nonanoyloxy-benzenesulfonate (NOBS)—interact with the perborate to release peracids and are even more effective active oxygen sources than hydrogen peroxide. Even so, perborate activated in this way still had a working floor of about 104°F (40°C).
Finding another agent that encourages perborate to bleach stains and fugitive dyes (red sock plus white shirt equals pink shirt) at even lower temperatures came with some difficult conditions attached. The solution had to not only work effectively but also be kind to fabrics and dyes, have a good shelf-life, last through the wash cycle, be both safe and environmentally sound—AND be affordable.
Activators or Catalysts?
There it is—useful oxygen, locked away in the perborate molecules. With activators, the active oxygen appears after a number of distinct chemical reactions involving them. But is there another way?
Catalysts offer another route. They work in a completely different way to enhance bleaching and are not used up in the chemical reactions like activators. They do their work on the perborate molecules and are then available to do it again so there is less chemical use.
Chemists know that some of the transition metals such as manganese, iron, and cobalt form complexes that can enhance perborate bleaching at lower temperatures by catalysis.
A manganese-based system did, in fact, come on to the market in the mid-1990s. It was spectacularly effective as an oxygen bleach catalyst, but sadly was found to damage fabrics and dyes. As a household product, it was unsuccessful but was still a big step forward in the understanding of these mechanisms.
Higher Performance, Lower Temperature
At U.S. Borax, scientists researched systems for enhancing perborate-containing detergents with catalysts and more effective activators for a number of years resulting in the development of a new catalytic system in the early 2000s. Exhaustive washing trials in the laboratory confirmed that effective bleaching is achieved well below the 104°F floor and the formulation cares for fabrics and dyes, is stable, environmentally benign, and can be manufactured in a simple one-pot industrial process.
U.S. Borax's “Designer” Catalyst
Knowledge of the behavior of molecular structures enables today's research chemists to answer many questions—including that challenging task: “Find me a chemical, out of the millions possible, that does this.”
The U.S. Borax detergent catalyst is a fine example of biomimetic chemistry. Essentially, scientists have recognized that over millions of years nature has evolved extremely efficient ways of carrying out chemical reactions. The biomimetic approach is to develop synthetic analogues of nature's chemical toolbox. Borax applied these principles and the resultant catalyst is not unlike a biological enzyme in the way it behaves, possessing a so-called active site where key reactions in the stain bleaching process occur.
Washing tests demonstrated the catalyst perborate's impressive bleaching effectiveness and laundry-care combination—a performance the U.S. Borax development team ascribed to its stability—harnessing the inherent reactivity of the active site and putting it to useful effect, while at the same time suppressing any unwanted chemical reactions.