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NEW SLOT DIE PROVIDES HIGH-SPEED, STREAK-FREE APPLICATION OF PRESSURE SENSITIVE ADHESIVES USED IN MEDICAL DEVICES

Rotary Rod Slot Coating Die

EDI System Provides Thinner, More Accurate Application than Conventional Roll Coating, Opening the Possibility of Using Less Adhesive

CHIPPEWA FALLS, WI, U.S.A., February 20, 2012: A new slot die for coating continuous-web substrates provides consistent, streak-free application of pressure sensitive adhesives (PSAs) for skin-contact products such as wound coverings, surgical drapes, electrode mounts, and ostomy mounts, it was announced today by EDI.

The die provides the clean appearance and precision valued by medical manufacturers while enabling them to achieve higher line speeds and thinner coatings with less environmental impact than conventional roll coating, according to William Kays, technical account manager.

EDI developed the die specifically for PSAs, a hot melt adhesive subgroup. While roll coating speeds for hot melt application usually do not exceed 365 meters/min., the new EDI die accommodates line speeds up to 610 meters/min. and achieves coat weights as low as 10 g/m2. This is well below the conventional lower limit for hot melts of around 18 to 20 g/m2, noted Mr. Kays, and because of the accuracy of slot die coating, the ability to run thinner coatings opens the possibility of reducing adhesive consumption

“As a completely enclosed, pre-metered system, slot die coating is more efficient and controllable than roll coating and other conventional open systems, in which only part of the adhesive delivered to the substrate is actually applied while the rest is re-circulated,” Mr. Kays said. “By avoiding this exposure of the adhesive to the environment, slot die coating prevents workplace emissions and contamination of the coating material.”

Besides being available as a stand-alone system, the new EDI die can be supplied as part of a completely integrated, PLC- (programmable logic controller-) controlled coating system, incorporating adhesive delivery systems from ITW Dynatec and slot die equipment from EDI. “Resulting from a cooperative program between EDI and ITW Dynatec, the new coating system provides turnkey capabilities for tight-tolerance, high-speed application of virtually any type of hot melt adhesive, including PSAs and other UV-curable hot melt adhesives,” said Mr. Kays. “Its performance is guaranteed by the partner companies.”

How EDI’s New Slot Die for PSA Coating Works

In roll coating, a series of rollers wipes PSAs onto continuous-web substrates such as plastic films. This method has limitations that sacrifice coat weight accuracy and create an increased opportunity for visual defects that are unsightly and inappropriate for a clinical setting.

In EDI’s slot die coating method, the lip of the die applies the adhesive directly to the substrate. The keys to the advanced performance of the die are: 1) an innovative system for adjusting the cross-direction coat weight profile and 2) incorporation of a device that eliminates streaking and makes possible clear application of coatings, with increased coat weight accuracy.

Streaking is caused by gels or solid particles that lodge in the narrow lip opening and the interface between the die lip and substrate. In the new die, a motorized rotating rod in the lip area allows gels to pass through lip opening and coating interface.

At the same time, the new slot coating die includes a mechanism for adjusting the coat weight profile by selectively adjusting the flexible lip at regular intervals along the width of the die.

PHOTO CAPTION: New EDI die for applying pressure sensitive adhesives is shown with lip area facing right. Easily visible in the lip area is a motorized rotary rod that allows gels to pass through the lip opening, preventing buildups that cause streaking.

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EDI is a leading international supplier of flat dies for sheet, film, extrusion coating, fluid coating, and pelletizing. The company designs and manufactures dies, feedblocks, deckling systems, vacuum boxes, and related equipment. Its subsidiaries include EDI GmbH in Reichshof-Wehnrath, Germany, and EDI China in Shanghai. In the U.S.A., Germany, and China, EDI operates facilities dedicated to reworking its own dies and those built by other suppliers, and it has licensed a fourth rework facility in Japan. Headquartered in Chippewa Falls, Wisconsin, U.S.A., EDI is focused on supplying the global market. Visit www.extrusiondies.com and www.reworkdies.com. E-mail: sales@extrusiondies.com.