Breathable backsheet films: serving the growing hygiene market more efficiently
Backsheet films are a growth market. Around 590,000 tons are used each year and the number is on the rise. Breathable films used in products such as diapers make up some 50% of this total. “Experts estimate a CAGR of around 4.4% for the hygiene market up to 2020,” explains Ali Hassan, Hygiene Market Specialist at engineering firm W&H. Diaper and incontinence products seem to have a particularly high potential. “Factors such as our aging society, the growing acceptance of these kinds of products and higher global availability, particularly in developing regions, are the driving forces behind this,” adds his colleague Dirk Dreier. Where breathable backsheet films have traditionally been made predominately using cast film extrusion, the experts at W&H are now advising customers to convert to blown film extrusion systems. “We are seeing a clear trend of companies moving to blown film extrusion technology for their backsheet films”, says Hassan.
According to the experts, there are a great number of benefits associated with producing breathable backsheet films using blown film extrusion. These include a lower weight per square meter, and therefore lower raw material usage, and better mechanical properties despite a comparable output rate and speed. “Diaper backsheet films made using cast film extrusion tend to have a base weight of around 16 g/m². The thinner, breathable diaper backsheet films made using blown film extrusion with inline stretching [MDO] on the other hand have a base weight of just 12 g/m². This represents a downgauging potential of around 25 percent with equivalent or even improved product performance,” explains Hassan. By stretching the film and using special materials and parameter configurations on the VAREX II with inline MDO, companies can generate the specific level of breathability they need for their individual applications.
Before, thick spots at the edges (the “neck-in effect”) and tapering at the center of the film (the “smiley effect”) would affect the net output of a production run. With cast film manufacturing, the neck-in effect occurs twice as frequently as in the blown film process. After going through the chill roll and inline stretching systems, thick spots would have to be removed by trimming up to 150 mm off of each side in order to ensure problems would not occur further down the line. The integrated OPTIFIL P-MDO thickness profile control for the VAREX II guarantees a consistent thickness across the entire width of the stretched film. The result: 50% less edge trimming required, and therefore a significantly higher net output from the blown film extrusion system.
High speeds are another important factor that a blown film extrusion line and subsequent winder have to deal with. “The VAREX II can achieve outputs of up to 700 kg per hour at a machine speed of up to 300 m/min. This means that its speed is comparable to that of cast film technology", explains Dreier.
As a system provider, W&H also ensures this level of performance continues on into the next stage in the process, printing. “Our customers appreciate the fact that our expertise covers the entire process chain. We can adapt extrusion and printing lines to ensure that they work together perfectly. The highly automated VISTAFLEX flexographic printing press, for example, can achieve speeds of up to 800 m/min, which makes it a powerful machine for printing breathable backsheet films”, says Dreier.
Both experts are confident that blown film extrusion processes will continue to increase in popularity in backsheet film production. “Competition is fierce, especially in growth markets like the hygiene market. In the diaper product area, brand manufacturers are competing with own-brand labels. As a high-performance blown film extrusion line, the VAREX II offers significant efficiency increases that could prove the key to success here by making the whole process more cost-effective", summarizes Hassan.