Filtration Transformation

Out of an engineer's introspection and some solid supplier relationships comes "a breakthrough" for one contract converter's final filtration of hot melts.

Quiet revelations are transforming our world. Though Archimedes may not have subscribed to this notion (the eminent Greek mathematician/inventor is noted, by Webster's, for exclaiming “Eureka!” when he discovered the method for determining the purity of gold), the quiet proof of technological advancement is ubiquitous.

The converting industry, especially, is adept at these subtle transformations. From high-barrier packaging to rheological advances, collaboration (among converters and their suppliers) yields products every day that transform the way we purchase salad, apply stamps to our letters, clean floors (think Swiffer), and so much more.

One such converter, Great Lakes Coating and Laminating (GLCL) Inc., White Bear Lake, MN, contracts converting jobs from a variety of industries, transforming products that may (or may not) change your everyday life. But this independent coater of hot melt adhesives and polymers, collaborating with May Coating Technologies, a div. of Acumeter Laboratories, recently found a way to transform an aspect of its production — consequently improving its bottom line — through quiet, yet unrelenting, exploration.

Output Odyssey
“[Our] business objective causes GLCL to handle, melt, and slot-die coat many different chemistries, viscosities, and rheologies of hot melt polymer systems,” reports president Larry Kraus. Though GLCL's production is proprietary, Kraus does note the operation services several industries. Because of this diversity, adds Kraus, “we have become experienced at many different aspects of coating thin to thick films.” He says this has enabled the company to learn what works well and, of course, what doesn't. “While there are many obstacles to overcome when you work with so many different chemistries,” he explains, “none has been more challenging or costly than the filtration of the hot melt fluid stream prior to slot-die coating.”

With a coating line and inverted-drum unloaders built by May Coating Technologies and platen-drum unloaders supplied by Industrial Machine, GLCL converts in a 10,000-sq-ft facility located in the St. Paul suburb with a full-time workforce of six and a part-time staff of three.

“Think about our production in terms of a glue gun,” describes Kraus, “except on an industrial scale. Instead of having a gun that puts out a little bead, we're spreading the adhesive, or the polymer, through a slot die onto paper, film, or fabric. Sometimes we wind it up on itself, or we might laminate-in a liner or a second substrate.” In addition to its coating equipment, GLCL utilizes a web cleaning system from Teknek, an NDC Infrared gamma backscatter-gauging system (for thickness measurement), and a sheeter supplied by Rosenthal.

But even with its plethora of quality equipment and supplier expertise, GLCL struggled with the difficult challenge — and high costs — of maintaining a robust filtration system prior to slot-die coating. “Slot-die coating requires high but consistent pressure for uniform coating,” Kraus explains. “Final filtration of the molten fluid stream, immediately prior to entering the die, is critical to producing a smooth coating that's streak- and char-free. [Our] ‘old’ system used two parallel, stainless steel cartridges in a filter block that was mounted one to two feet ahead of the die inlet. While this did an admirable job, the cartridges were prone to seal leakage and collapse, particularly when faced with high flow rates and viscosities. And when one cartridge failed, both had to be thrown out.”

GLCL wasn't interested in reusing cartridges by cleaning with solvent or burning them clean. “We didn't use the salvage approach for three reasons,” states Kraus. “First, there's the solvent-waste issue. Secondly, the cartridge structural strength is marginal when new; we felt the cleaning steps would reduce strength further. And third, we felt replacing the grommet seals at the cartridge ends could make them even more vulnerable at high pressures and flow rates. When a seal comes off the filter and gets in the die, you can be down for hours.”

So, says Kraus, the company searched for many years to find a better alternative. “Multiple cartridge canisters were proposed but aren't appropriate for high pressures and are costly for multiple, short-run changeovers,” he explains. “Screen changers have too many issues such as leakage and air entrapment. [Thus] our objectives remained: [we wanted] filtration attached directly to the die; elimination of seals that can fail; a stainless-steel cartridge design that can sustain high pressure and long life; and a cartridge change that's operator-safe and quick.”

Eureka Indeed!
Like many of Archimedes's geometrical findings, GLCL's answer to its filtration problem was demonstrated, at first, mechanically to Kraus, who is trained as a chemical engineer. “Every trip to the gas station brought the issue to mind,” he says. “When you put the nozzle into your gas tank, there's a filter right at the nozzle — that's exactly what I wanted to do. But it had to be able to deal with hot melts.”

One day, during a conversation with Acumeter's Ted Loranz, something finally “clicked,” reports Kraus. “Ted recalled they did something like that with a cylindrical filter housing, using band heaters as a heat source, in conjunction with small Acumeter coating dies. He thought we could use a high-pressure cartridge filter, sealed on one end, with O-shaped rings on the other end, instead of seals. He sent us a sketch, and the idea started to take shape. Our consulting engineer then started working with shapes, angles, and coater-operator issues on a CAD system.”

Additional industry relationships brought the project to full fruition, says Kraus. “Ted brought May Coating into the project. They refined and detailed the mechanical design, abandoned the band heaters in favor of cartridge-style electrical heaters, and finalized a design that met all of [our] goals.”

Kraus says the device is a real breakthrough for the final filtration of hot melts, and it's adding to GLCL's bottom line, too. “While each new high-pressure cartridge filter costs more, there's only one in the fluid stream — in place of the two lower-pressure cartridge filters — and they last longer. Plus, they're much easier to change, which makes the whole process safer and more efficient for operators,” he adds.

“Overall,” says Kraus. “it was a fun and rewarding collaborative effort, combining manufacturing-process experiences with electro-mechanical engineering design and manufacturing.” A quiet transformation but certainly one that could make Archimedes — who considered among his own most significant accomplishments those concerning a cylinder circumscribing a sphere — exclaim “Eureka!”

Great Lakes Coating and Laminating Inc.

1835 Buerkle Rd.
White Bear Lake, MN 55110

Acumeter Laboratories
, Shrewsbury, MA; 508/842-9200;

May Coating Technologies, St. Paul, MN; 651/765-9686;

Industrial Machine Mfg. Inc., Richmond, VA; 804/271-6979;

Teknek, Elk Grove Village, IL; 888/2-TEKNEK;

NDC Infrared Engineering, Irwindale, CA; 626/960-3300;

Rosenthal Mfg., Northbrook, IL; 847/714-0404; 800/621-1266;

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