Breathable backsheet films: For a more efficient hygiene market

A market for breathable backsheet films, used for hygiene products such as diapers, is a hot one. Blown film extrusion enables producers to reduce film thickness by some 25% or even to improve its performance.

Around 600 thousand tons of breathable films are used annually and the figure is growing. These are used in mass products such as diapers, the market reaching a half of the said figure. Ali Hassan, Hygiene Market Specialist at W&H engineering company, comments on this: "Experts estimate a CAGR of around 4.4% for the hygiene market up to 2020." Incontinency and diaper products do seemingly have a truly 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 Hassan's co-worker Dirk Dreier. Conventionally, breathable backsheet films have been generally produced by cast film extrusion. However, experts at W&H are today committed to converting customers to blown film extrusion. "We are seeing a clear trend of companies moving to blown film extrusion technology for their backsheet films", adds Hassan.

As the experts say, a considerable number of benefits is associated with the manufacture of breathable backsheet films by blown film extrusion. The approach enables a lower weight per m2, reducing thus raw material consumption, as well as increased mechanical performance, while keeping output rate and speed comparable. Hassan is confident when it comes to the new approach: "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 only 12 g/m². This represents a downgauging potential of around 25 percent with equivalent or even improved product performance." Stretching the film and/or using special materials and parameter configurations for producing on VAREX II with inline MDO, manufacturers can reach the desired breathability level as per individual specifications.

With the traditional technology, lumps at web edges (the so-called "neck-in effect") and tapering at web center ("smiley effect") affected the net production output. Blown film technology cuts neck-ins in two. With cast film extrusion, after the chill roll and inline stretching systems, lumps are removed by trimming up to 150 mm from each web edge, in order to avoid downstream issues. The integrated system for profile thickness control, OPTIFIL P-MDO for VAREX II, keeps the thickness reproducible throughout the entire stretched film width. The result is trimming requirement cut in two, and a much higher net output of the system.

Increased production speeds are equally important result of using blown film extrusion approach; downstream winders have to deal with it. "VAREX II can achieve outputs of up to 700 kg/h 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.

Following the system approach, W&H keeps the performance level intact until the next process phase, printing. Dreier continues, "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."

Both company experts are positive as for the growing popularity of blown film extrusion processes in the manufacture of backsheet films. Summing it up, Hassan says: "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, VAREX II offers significant efficiency increases that could prove the key to success here by making the whole process more cost-effective".