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May 1, 2001 12:00 AM
In the sticky world of adhesives for the perfect binding industry, Tyrone Adams, national product manager for finishing systems at MAN Roland (Westmont, IL), says polyurethane reactive (PUR) is clearly where the industry is headed.
“It's flexible, so you don't have a high rate of tear in terms of loosening sheets, and it has a higher durability over time,” Adams explains.
“Everyone wants to have the capability of doing PUR so that when they are bidding on jobs, they can be competitive. If binders don't have the capability of PUR, they might lose out on an opportunity,” Adams says.
In the past, PUR was used primarily for binding difficult products, such as highly coated stocks or products that would be exposed to extreme temperature ranges. Today there is broader use of PUR, says Bob Shafer, president of Kolbus America (Mahwah, NJ). Shafer believes that use of PUR will increase as binders become more familiar with it.
“PUR requires different equipment and a different method of use. As suppliers have become more comfortable with the equipment and their operator's skills levels, they have become more inclined to use it when they might otherwise use a hot melt.”
Bill Turoczy, owner of Steffen Bookbinders (Macedonia, OH), says he favors PUR for two reasons: “First, it's designed specifically for coated stock, which we use on annual reports and trade magazines. Second, I know when I put PUR on a book, it won't fall apart.”
Eighty percent of the company's work is with PUR adhesive. He adds that PUR is environmentally safe and makes the books easier to recycle than those with hot melt.
The increased interest in PUR, says RIT's Professor Werner Rebsamen, is a direct result of paper now being used in many perfect-bound publications. “Paper today has more filler. There's also more coated stock with more porcelain, clay and other ingredients in the paper where it used to be fiber,” he notes.
While filler content averaged 20 percent in the past, Rebsamen says that now it is not unusual to have paper with filler as high as 54 percent. “This causes a lot of problems in perfect binding. With less fibers, the bond is not as good,” he explains.
Rebsamen says that while PUR has helped address this problem, “the real secret is roughing and spine preparation. Müller Martini, for example, developed a fiber rougher that rakes out the fiber in the sheet. It exposes more and gives a better chance to seal the sheets and adhesive.”
John Morgenstern, director of product planning and management at Heidelberg Web Systems (Dover, NH), also sees growing interest in twin-flex, a cold-glue formulation. “Existing cold-glues require a fair amount of drying. The new twin-flex adhesives, which are used only to adhere signatures together, require significantly less glue use, provide more strength and less drying time.
“Using two adhesives is not typical in the U.S., but we may see a shift if costs come in line,” Morgenstern says.
The exec explains that the current drawback of PUR is it requires a significant amount of drying time before you can check a book, do a page pull or trim it. “As glue technology changes and drying time shortens, we may see a shift because PUR has significant advantages and is stronger than hot melt,” Morgenstern says.