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PUR success

Jul 1, 2010 12:00 AM

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Binding strength, stock range and spine flexibility make polyurethane reactive (PUR) adhesive an ideal solution for a variety of applications. With these benefits come a few important considerations before switching from traditional hotmelt adhesives.

Bob Flinn, director of business development for Andover, MA-based Standard Finishing Systems ( explains that printers typically use PUR to bind coated or digitally imaged stock when they want layflat quality or when their books need to tolerate temperature extremes. Once the user has determined if PUR is right for their binding operation, Flinn says the next consideration should be determining what percentage of their binding volume requires PUR. “If it's 100%, a dedicated PUR system might be the best fit,” he says. “If you want to retain the ability to do EVA, too, you should consider a binding platform that allows you to swap tanks.”

Tom Kane, industry specialist for Nordson Corp. (Duluth, GA) stresses that knowing the difference between PUR and ethylene vinyl acetate (EVA) adhesives is critical. “End users need to understand the differences in how the two adhesives create a bond, the amount of time before a book can be trimmed, when a book is fully cured and what handling practices are recommended prior to a fully cured book.

“Additionally, the capability and commitment of being able to properly maintain a PUR application system should be considered,” Kane continues. “While the performance benefits of PUR typically far exceed the ‘hassle,’ regular maintenance is needed to get the maximum performance and production benefits.”

Run lengths are another consideration. “A binder with four or more clamps would be recommended for run lengths of 1,000 or more, while a single-clamp binder will probably do for shorter runs,” says Flinn. “If your book format and thickness are changing often, you should consider a high level of automation so you can perform changeovers quickly and easily.”

Just as important as the PUR system is the binder it is installed on. “A customer purchasing a new binder will need to evaluate the merits of a closed system or an open wheel pot system,” Kane advises. “If they are retrofitting an existing binder, the binder must be evaluated to ensure suitable spine preparation can be implemented, mounting space is available and proper book handling features are in place.”

Dollars and cents

With PUR more expensive than conventional glue, there has been a misconception that it isn't practical for smaller binders and shorter runs. But today's systems are allowing smaller operations to invest in it.

“PUR reacts to air, so in the past it required closed premelt systems and slot applicators,” Flinn explains. “These requirements added considerable cost and made PUR binding cost-prohibitive for short-run work. Today, new open-tank, low-waste binding systems, coupled with new PUR formulations, have brought efficiency to short-run PUR binding.”

“Smaller users need to be aware that the most efficient use of PUR might actually be to buy the smallest quantity/form available, even if it is more expensive to purchase,” adds Kane. “The waste of disposing unused but cured PUR, along with the problem of using older PUR with diminished bonding capability, will make purchasing larger quantities more expensive in the long run.

“While PUR is more expensive than EVA, with the proper application system you can precisely control the adhesive thickness to achieve an excellent bond with a thinner spine glue thickness,” Kane continues. “So, the actual cost isn't the increased price of PUR over EVA, but is lower because you can use less PUR — at least one-third less.”

As for larger users, Kane says they should consider maximum equipment utilization: “Startup and shutdown of open-pot PUR applicators can be a consideration as that can be an hour or more each day. A closed system can be started up and shutdown in 5 or 10 minutes for daily operation.”

Kane credits digital print with an upswing in PUR. “The typical EVA does not adhere well to some of the toners, oils, inks or even paper used in digital printing. PUR is not impacted by these variables.”

Next Page: What's next for PUR?

What's next for PUR?

Kane says, “The demand for PUR adhesives has crept into every facet of binding, so it is safe to say that every current adhesive application is being evaluated to see if the benefits of PUR can be implemented.”

“PUR is moving down market in terms of price point, machine size and throughput, so PUR is now a practical option for ultra-short runs,” says Flinn. “Adhesive manufacturers also are working hard to develop hybrid PUR formulations in pellet or pillow form that won't require the cost or maintenance of the closed pre-melt systems that are needed today.”

Nsenga Thompson is associate editor for AMERICAN PRINTER. Contact her at

Binding perfect books

With 30 employees and 41,000 sq. ft, of operating space, Steffen Bookbinders (Macedonia, OH) is a midsize bindery specializing in otabind, perfect bind, saddlestitch, cut, fold and shrink wrap.

Steffen relied on Nordson's ( PB 90 Wheel System for several years before seeking an alternative to the glue system's time-intensive wheel pots.

“Startup with wheel pots was up to 11/2 hours every morning, and the old glue showed up throughout the day,” explains owner Bill Turoczy. “Each wheel pot required $1,000 in maintenance and resurfacing with Teflon every 3-4 months, and you had to have a backup for use while one was being [maintained].”

Steffen turned to Nordson's EP 48 V application heads for its two perfect binders. Nordson developed this closed hotmelt PUR application system to offer substantial advantages in product quality, efficiency and production reliability.

The EP 48 V applies adhesive directly to the spine of the book. Better wetting of the paper fibers ensures good adhesion with high pull values and improved layflat properties. The positive adhesive application pressure and clean cutoff enables production speeds of up to 18,000 books/hr. with a spine coating thickness of 0.3 mm (0.01 inch).

With the EP 48 V, Steffen now has faster startups and shutdowns, which plant manager Ron Myers says has been a key benefit of changing to PUR: “With the EP 48 V, there is no need for coating as in the pot. We've experienced large savings from not wasting 3-7 lbs of glue per binder, per day.”


PUR alternatives

Glue pots made simple

Elizabeth, NJ-based On Demand Machinery's ( Sticker XXL features a touchscreen LCD control panel. Operation consists of placing the book on the wing and depressing a foot switch. A servomotor brings the glue stations in contact with the book while the wing travels upward, applying a uniform coating of hotmelt adhesive. Heated joint irons aid in forming the cover by reactivating the adhesive in the joint area and softening hardcover materials. The Smasher XXL has an adjustable dwell timer that controls how long the book remains under pressure.

Layflat binder

Spiel Associates' (Long Island City, NY) Sterling Doublebinder will bind up to 300 books/hr. with no messy cleanup. The books dry instantly, and this new technology produces a layflat book by gluing not only the spine but between the sheets. Spiel boasts it will bind coated stock stronger than any other machine. See