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Polymer bead cleaning - A new revolution in clothes laundering

Polymer bead cleaning - A new revolution in clothes laundering

Polymers play an important part in so much of modern living, and laundry is no exception. A UK company delivers revolutionary clothes laundering technology in which the use of water is largely replaced by polymer beads, due to their ability to agitate, attract and transport away stain and soil from textile surfaces. In any textile cleaning process the combination of mechanical action on the cloth, chemistry from detergents and temperature to activate this, all act together over the wash cycle. The higher the action, the more detergent and the higher the temperature used, generally the better the cleaning. Large amounts of water are required too, to allow the suspension of the soil and its removal, and then again during rinsing. Xeros takes these elements required for good cleaning, and completely reinvents them. The polymer beads provide a gentle, uniform mechanical action on the cloth, aiding the removal of stain and soil. Their hydrophobic nature allows better removal of oily and greasy stains than with water based systems, and their polar surface chemistry attracts and retains all types of stain as it is transported away from the cloth surface. Some polymers even have the ability to absorb stains into their molecular structure. As a result, great cleaning can be achieved at lower temperatures, and with less detergent than has previously been possible. Water acts as a lubricant in the Xeros process rather than as the main wash medium, and hence much less water is required. Rinse water too is reduced, as there is less detergent to be rinsed away. The use of polymer beads provides a whole new platform for research into cleaning processes.

Xeros is a six-year-old spinoff from the University of Leeds, where textile chemist Stephen Burkinshaw had the original inspiration to reverse the dyeing process. As per Amanda Alvarez, instead of adding pigment to textiles, Burkinshaw and his students experimented with removing pigment (stains). Nylon readily takes up dye, and forming the polymer into round beads yielded the most effective stain extractor. The beads' surface area, weight, and chemistry have since been engineered with regard to four independent factors- temperature, chemistry, time, and mechanics - that affect the washing process. The proprietary Xeros washer looks like a standard front-loading machine (the domestic version, slated for a 2015 US launch, will have a smaller footprint than the current commercial instantiation). About 50 kgs of beads, held in a wet sump below the machine, are pulsed in with water through the top of the drum. The beads fall out of the drum and then recirculate. The company's Chief Science Officer, Stephen Jenkins, likens the process to laundry taking a shower - not a bath - in beads. The process claims a 70% reduction in water usage compared with standard washing. And because bead cleaning works in cold water (20 °C), heating is not required, which cuts energy use by an estimated 50%. The amount of special detergent used in the wash is also about 50% of what would normally be used. The one and a half million or so beads used per load constitute the fundamental ingredient in the cleaning cocktail. Xeros now has two main bead compositions—polyester (specifically, polyethylene terephthalate) and nylon (nylon 6,6). The mechanical action of the beads passing over clothing removes soil, and the weight of the beads reduces creasing by pinning the fabric down. But it is the beads' polymeric structure that attracts and traps dirt. Thanks to the presence of polar groups, the beads adsorb solubilizable stains. Nylon excels at “vagrant dye capture” because of a negative glass transition temperature that creates free volume within the polymer’s structure and allows absorption and diffusion of stains into the bead itself. In that way, Xeros washes are also resistant to dye transfer between colors and whites. In retail dry cleaning, "the ability to mix colors and whites can save considerable sorting time,” says Jenkins. “With the chemistry that we are developing for generation-two beads, we can get the dye capture to be almost perfect.” Because the beads are particularly good at clinging to dirt and grease, they might require a periodic wash themselves - perhaps once a month when used in lightly soiled washes. The beads are reusable and have been tested to last through 500 washes. G-force, the drum size, the washload size, and the beads all work together so that the bead can interact with the cloth but then also fall away from it. No more than 20 beads should be left at the end of a washload.


Environmental Benefits
The core of the Xeros proposition is that the polymer beads provide a superior cleaning medium to water. Water remains an essential part of the process, but not in the same way as conventional washing where using plenty of water is unavoidable for an acceptable cleaning result. The obvious next question is whether replacing water with polymer beads is a good thing for the environment. Is this cleaning just moving the problem from using too much fresh water to using too much plastic (i.e. polymer)? Xeros beads can be used hundreds of times before they need to be replaced and they never go down the drain. Better still, after replacement, the used beads will never be thrown away, and can be re-used in other industries that already deal with recycled polymer.

Direct Savings

Cost Factor Conventional Washing Xeros Cleaning Saving
       
Water (litres per kg washload)  20.0 5.6 72%
       
Heat (KwH per kg of wash load) 0.17 0.09 47%
       
Detergent (g/kg of wash load) 16.0  8.0 50%

Indirect Savings
The power of Xeros cleaning means trialists have been able to reduce pre-treatment without any decrease in cleaning performance. This is especially true for greasy collar and cuff stains that Xeros polymer beads are particularly tuned to remove. Due to the low temperature cleaning and polymer beads there is less need to sort mixed colours saving labour and complexity in your operation. Heat, detergent and conventional mechanical action can all lead to garments losing their “new look” colour and even wearing out. The bead cleaning provides a more uniform, gentle cleaning action. Garments crease less in the wash, lower detergent chemistry is spread evenly, and all the cleaning is conducted at lower temperatures. This all leads to clothes looking newer for longer and can extend garment and flatwork life.

Xeros, the company formed to commercialise ground breaking polymer bead technology developed at the University of Leeds, is now a member of the Sustainable Apparel Coalition (SAC), which also includes household names such as Adidas, Burberry, Coca Cola and Levi Strauss.

(Amanda Alvarez is a science writer at the Institute of Molecular Biology in Mainz, Germany)

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