A combination of improved polyethylenes and high-precision winding technology could open up a vast new range of applications to films made using machine-direction orientation, or MDO.
Blown film extrusion equipment maker Kiefel Extrusion GmbH (Booth S1515) said MDO films are set to break out of their traditional territories of diaper liners and tapes, and take on biaxially oriented polypropylene and possibly even oriented PET films in numerous packaging applications. MDO also can yield significant savings in the use of barrier resins such as ethylene vinyl alcohol.
MDO units work with regular film and stretch it to several times its original length. Kiefel's new Kirion MDO line can stretch films to 10 times their original size. The line will sell for as much as $1.5 million, depending on configuration.
The technology is set to debut to the public at NPE 2006 in Chicago, but Kiefel presented it for the first time at a news briefing in mid-April at its headquarters in Worms. The event was co-hosted by its Wintech unit, a maker of specialty winding equipment. Another presenter was resin supplier Equistar Chemicals LP, a Houston unit of Lyondell Chemical Co. that has been working on the application of bimodal high density PE resins to MDO technology for more than four years and is cooperating on a nonexclusive basis with Kiefel.
``MDO technology is going to change the packaging world very soon,'' said Kiefel Chief Executive Officer Edgar Gandelheidt.
Kiefel will show a running stand-alone Kirion MDO unit at the show. The unit also can be configured to work in-line, although its speed - up to almost 1,000 feet per minute, or more than 2,000 pounds an hour for a roll width of 102 inches - is well in excess of any blown film line that could feed it.
``We have designed it so that it can take the output from two blown film lines,'' Gandelheidt said. MDO lines also can be used with cast films, he noted.
Kiefel has yet to sell any units, but expectations are high. Sales director Kurt Freye said seven or eight potential buyers were scheduled to do trials in Worms before the unit is dismantled in early May to be shipped to NPE.
Blown PE film accounts today for about one-third of all flexible packaging materials. About 14 percent of the market still is in paper, 22 percent in BOPP and 14 percent in aluminum. ``MDO technology will give us the chance to go into all these markets,'' Gandelheidt said.
Although a large part of the BOPP market is open to MDO PE films, material suppliers are likely to aim for higher-added-value applications, such as laminates, since BOPP overcapacity worldwide has turned much of the market into commodities not worth fighting for.
Kiefel joins a growing list of extrusion equipment suppliers offering MDO technology in one form or another. But Eberhard Wenger, the firm's winding business manager, said the Kirion equipment stands out in its ability to provide accurate and precise control over roll speeds and temperatures. He said those capabilities, along with choosing the right resins, make it possible to produce films without defects in tear and impact strength that generally characterize MDO films. It also is possible to take multilayer films with EVOH barrier layers and stretch them to four times their original length - and, critically, to one-quarter of their original thickness - with no loss of barrier, he said. And, clarity is improved, he added.
``We have stretched the film up to 5½ times before it broke,'' said technical director Jochen Hennes. ``You can get barrier layers down to 0.7 micron when you need only a medium barrier like cookie packs. Nobody uses EVOH for cookies today; it's too expensive. Shelf lives will improve dramatically because of the much better water barrier.''
Hennes said he expects similar results with other barrier materials, but he does not yet have trial results as proof.
Kiefel's new unit has 11 rollers with individual heating or cooling, divided into four zones, devoted to heating, stretching, annealing and cooling. Each roller has its own drive. ``Each film structure reacts in a different way to machine settings, and very slight changes in settings can have a huge impact in film properties, so we need the flexibility in temperature and speed control,'' Gandelheidt said.
Steve Imfeld, a Lyondell research specialist in product development in Cincinnati, said some of the firm's resins are ideal for MDO, although it continues to work on new resins specifically for that application. ``They have a combination of properties that will allow MDO to go into areas where it was not previously possible,'' Imfeld said.
Imfeld's colleague Ryan Breese, who heads Lyondell's MDO project, highlighted some features of the new MDO technology. ``As you increase the draw ratio, a film that starts out hazy becomes very clear, very glossy,'' he said. ``The film also becomes very stiff in both the machine and cross directions, which is critical for applications like stand-up pouches. Strength increases significantly, too, which means that the film can hold a larger weight prior to failure. That's critical for many applications, such as can liner draw tape.''
MDO film disadvantages, including low machine-direction tear strength and impact strength, are being addressed via developments in materials and film structures, he said.
``MDO has a unique fit with our bimodals,'' Breese said. The resins have relatively high molecular weight, allowing the firm to stretch the films to ratios of 13-1, which he said is two to three times more than is possible with conventional MDO or biaxially oriented films. Films orient more uniformly over a wider range of draw ratios, with no evidence of ``tiger striping,'' or periodic variations in thickness. ``So the converter can use draw ratio as another variable in the product development process to adjust the properties of the film,'' he said. ``Converters will be able to use MDO films to replace more expensive structures where polyethylenes could not possibly have participated before.''
Imfeld said a recent U.S. study has shown potential for the new types of MDO films in a range of applications, either replacing more expensive structures or down-gauging existing PE structures. He cites sealant webs in laminates for pouches, films for supermarket sacks, and draw tapes. The use of MDO films will help accelerate the current shift from paper to plastics in pressure-sensitive adhesive labels, he said.
Pressure-sensitive types also are replacing glue-applied labels, while shrink sleeves, which currently account for 10 percent of the labels market, are growing at 20 percent a year.
Imfeld also sees potential in heavy-duty shipping sacks - a 520 million-pound market for PE - as well as thicker films for food packaging, replacing BOPP or oriented PET films that need to be laminated to barrier or heat-seal layers. MDO coextruded films would need no separate heat-seal layer.
Lyondell and Kiefel are banking on converters installing their own MDO units rather than relying on oriented film suppliers. ``They can improve their margin, while payback times on their investment can be under six months,'' Imfeld said.
``Some customers may go for in-line MDO if they have long production runs,'' Hennes said.
But Bob Hawkins, president of Wrentham, Mass.-based Kiefel Inc., said that is becoming less and less the case in North America. ``Film suppliers need to be just as flexible here as in Europe these days,'' Hawkins said. ``All U.S. manufacturers are looking for their own niche.''