Battenfeld Gloucester: Boosting of cast film productivity with air knife/soft box combo

Cast polypropylene film lines use either an air knife or a soft box to pin the web to the chill roll immediately after it exits the die. Each component is suitable for a different range of web thicknesses, and every cast polypropylene (CPP) line uses one or the other separately - until now. Battenfeld Gloucester Engineering Co. has developed a combination air knife and soft box attachment that handles a broad range of CPP film thicknesses with no tradeoff in performance and substantial reductions in downtime for product changeover.

The air knife/soft box component handles a web thickness range of 20 to 150 microns, says Allen F. Hall, group product sales manager for cast, sheet and foam technology at Battenfeld Gloucester Engineering, in Gloucester, Massachusetts. ‘This lets processors run essentially the full range of cast polypropylene film thicknesses used in products,’ he notes.

An air knife expels air in a concentrated stream at high velocity. Its power makes it effective with webs of 30 microns and more in thickness. A soft box usually has a screened opening that expels a higher volume of air at lower velocity and over a wider area of the web than with an air knife. It works best with films that are less than 30 microns.

The design, which Hall believes is unique to Battenfeld Gloucester, features the air knife mounted on top of the soft box. The component is attached in the same general area as a conventional air knife or soft box (i.e., between the die and chill roll). When a processor changes product and needs a different flow of air to pin the web to the chill roll, he makes a mechanical adjustment to the component and indexes the correct side into place. Since the air knife/soft box unit does not have to be removed, processors eliminate the downtime associated with disconnecting one device and installing the other.

The first air knife/soft box component was installed on a Battenfeld Gloucester CPP line in the People’s Republic of China late in 2003. Hall says the device is available for sale on new lines or for retrofit worldwide.

Cast polypropylene is a huge and growing market in China, Japan, and other parts of Asia, where its primary use is in metallized or laminated food packaging. Battenfeld Gloucester is a major supplier of advanced CPP lines in China. CPP use is increasing in Western Europe and Latin America, also in food packaging and in laminations. The U.S. lags the rest of the world in CPP use, but experts say the material is finding a market in laminated structures.

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