Just the Right Amount of Foam
No matter where you are in the world, nothing says clean and hygienic like a thick, white foam. Detergents that foam too much, however, require an unnecessarily large amount of water to rinse them out. WACKER has now developed SILFOAM® SD 9019, a foam-control agent especially for hand washing that strikes the perfect balance between fluffy white bubbles and responsible use of resources.
The washing machine has become an essential household appliance in industrialized countries; according to Germany’s Federal Statistical Office, over 96% of German homes have one. It is much less common in emerging economies, however, and for reasons that are fairly obvious: in some cases, the technical infrastructure is not available, and in others, it’s simply a question of money. That’s why roughly half of the world’s population still performs the laborious process of washing clothes by hand. Maids and housewives soak the clothes, scrub them by hand, rinse out the suds and then wring out the laundry – a step that requires a great deal of strength.
Foam without Function
The SILFOAM® brand unites a broad portfolio of highly effective antifoams. SILFOAM® products control foam formation and ensure a smooth and therefore efficient production process. In modern detergents, they control foam formation to prevent washing machines from foaming over. In the textile industry, SILFOAM® foam-control systems must withstand temperatures of up to 130 °C, as well as acidic and alkaline environments.
And washing by hand does not exactly conserve resources: the method consumes roughly two to three times as much water as machine washing. This issue is particularly acute in those parts of the world where water is already a scarce resource. The amount of clean water used for rinsing out the suds at the end of the process is especially large. This is arduous and time-consuming work.
“The foam itself doesn’t make laundry any cleaner – it’s a by-product that consumers want. After all, we automatically associate soap suds with cleanliness,” notes Dr. Klaus Pohmer, director of business development for WACKER’s Performance Silicones business unit. Studies have shown that soap with good foam-forming properties is automatically perceived as more effective by consumers, even though the suds are nothing more than the air bubbles that form when a detergent containing a surfactant is mixed with water. Surfactants form a thin film on the surface of the water, which reduces the surface tension of the water.
The huge amount of water needed to get rid of foam from hand-washed laundry is a major environmental problem.
Whereas the hydrophilic ends of the surfactant molecules project into the water, the hydrophobic ends extend into the air, resulting in the formation of entrapped air. Within the water, individual surfactant molecules arrange to form small, spherical aggregates – bubbles in other words – with the polar, hydrophilic end directed outward and the hydrophobic end on the inside. This is what we know as soap suds.
Even though the consumer generally associates foam with cleanliness, it does have a disadvantage: too many suds can cause a washing machine to overflow.
How Silicone Defoamers Work: A defoamer spreads over the entire surface of the foam lamella, causing the surface tension to fall and hence the foam bubble to burst.
As a result, foam-control agents are added to laundry detergents to prevent excessive foaming. Antifoam agents are an indispensable process aid in detergents for washing machines. In 2016, the sector for foam-control agents generated sales of three billion US dollars – with the upward trend intact. The largest gains were seen in emerging markets such as China and India, not to mention Japan and Latin America. Besides water- and oil-based products and polyethylene oxide and polypropylene oxide copolymers, silicones are among the key foam-control technologies with a market share of some 40%.
In large parts of Africa and Asia, water does not come out of a tap in the kitchen, but has to be fetched in buckets from central wells or bodies of flowing water.
WACKER has now developed a foam-control agent that makes it a lot easier to rinse hand-washed laundry and thus significantly reduce water consumption. SILFOAM® SD 9019 is an anhydrous, low-viscosity, silicone-based antifoam agent that results in a fine dispersion in water or other highly polar systems. The remarkable feature of this new foam-control agent is its delayed defoamer technology, which does not immediately begin inhibiting foam formation. Unlike a machine wash, where the foam-control agent prevents the detergent from foaming over from the start, SILFOAM® SD 9019 only takes effect when the pH value of the detergent liquor drops. In hand washing, this is typically the case when the detergent is diluted, i.e. rinsed. Once the defoaming agent starts to work, the foam immediately collapses.
“50% of the world’s population still washes its laundry by hand – a laborious task.”
Silicone defoamers are thoroughly tested at WACKER’s laboratory in Burghausen: foam collapse is recorded and analyzed photoelectronically.
The result is amazing: instead of being rinsed three to four times, the wash now only needs one or two rinse cycles, thereby reducing water consumption by 50%. This can save up to 20 liters of water per wash load. “That allows us to find a middle ground between the perception of cleanliness and behavior that protects the environment,” explains Amit Paul, who developed the product for India-based Wacker Metroark Chemicals, a WACKER joint venture headquartered in Kolkata.
Silicones Combat Foam
SILICONE AS AN INTERNATIONALLY POPULAR DEFOAMER
Silicone defoamers are used in a diverse range of industrial applications such as in the household and personal-care sectors, pulp and textile manufacturing, agrochemicals, the life sciences, paints, surface coatings and printing inks, as well as in adhesives and construction materials, not to mention industrial and municipal wastewater treatment. The pharmaceutical industry also uses foam-control agents, for instance in the manufacture of drugs or as active ingredients (e.g. in antiflatulents). Some 40% of all silicone defoamers are sold in the Americas, followed by Europe, including the Middle East, and Asia-Pacific. WACKER has an extensive portfolio of defoamers to suit a wide variety of industrial applications. For example, PULPSIL® foam-control agents are tailored to the pulp industry. SILFAR® defoamers are especially pure and have no known harmful effects, and are thus ideal for the pharmaceutical industry and medical applications.
Thanks to their good wetting properties, silicones are highly effective foam-control agents. Due to their extremely low surface tension – even lower than that of a surfactant molecule – they spread out at the interface between the liquid and air, thereby displacing the foam-stabilizing surfactant molecules. This results in a local weakening of the foam lamella – a chemist would call it a stabilizing, surfactant-containing liquid layer – which ultimately causes the lamella to rupture and the foam to collapse. SILFOAM® SD 9019 is chemically stable and can be combined with many non-silicone-based defoamers. Thanks to their high thermal stability, they are ideal for critical temperature profiles.
Obtaining drinking water from a safe source requires more than a 30 minute round trip for 263 million people. Source: WHO/UNICEF Joint Monitoring Programme for Water Supply, Sanitation and Hygiene (JMP) 2017
“Delayed defoamer technology is a true advancement in countries where people primarily wash by hand and water is a scare resource,” emphasizes Pohmer. It makes hand washes easier and, at the same time, directly helps to conserve water, an increasingly important resource. Delayed defoamer hand-laundry detergents have been on the market in Africa since 2016 and are currently being rolled out successively in certain Asian countries.