Printing adhesive coatings

A sterile medical packaging converter is using flexographic printing to coat lidstock in a single pass. 

SteriPax Inc. (www.steripax.com) is streamlining the adhesive-coating process for savings. The company has developed a  single-pass process for coating zones with six layers of adhesive in a single pass, explains Jack Roten, business development manager. Launched about 3 years ago, the patent-pending process utilizes a flexographic printing press to “print” the six layers.

The first three stations of the nine-color press print ink, followed by six that “print” adhesive, explains Roten. “At the end of the machine we have a die-cutter that separates the lidstock, and then it is stacked and poly bagged. We can process up to 100 feet per minute.”

Roten says he had envisioned such a process for years, but needed a special formulation and company support. “Achieving this with a flexographic press is tricky,” Roten says. “Adhesive tends to run, and it can be messy. We had to find a viscosity that would not bleed out and could be stacked upon itself. We chose a hot-melt acrylic hybrid material that allows us to layer it.”

Design Coat generally consists of three slightly different adhesives, with each one put on twice, he says. “There are various ingredients in each layer. The first layer adheres to the substrate, the second layer adheres to the first, the third adheres to the second, but the fourth does not adhere as much as the other layers do. (The fourth, fifth, and sixth layers do adhere to each other firmly.) This allows Design Coat lidstock to peel open smoothly between the third and fourth layers,” he says.

The adhesive can be clear, blue, or any color, really, says Roten, because the process uses a printer. The formulation can support peel strengths up to 5 lb/in., and it can also be adjusted to create a weld seal. In addition to coating lidstock, the company can also coat rollstock. All grades of Tyvek and paper can be coated, he adds. 

With Design Coat, the size of the strip in header bags can be reduced given the increase in breathable area, says Roten. The company is even experimenting with a header bag with a paper strip.

Roten says that the process reduces the likelihood of missing adhesive. With typical coated materials, missing adhesive is “not common, but it is not a rarity, either. It can affect seal strength,” he says.

Roten adds that there should be no concerns about sole sourcing or lack of redundancy. “We have the formula. If there is a flexographic press anywhere in the world, we can rent the machine to produce Design Coat. And if the customer is big enough, we can always go to their local printer,” he says.

SteriPax currently runs Design Coat on two in-house flexographic printers. The company is currently supporting a number of already marketed applications, including over-the-counter medical devices. “Validation has been pretty fast,” he reports. 

Photography by Harte Robba.

Article updated September 11, 2015.