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Company develops line of cost-saving packaging

A Pennsylvania packager responds to the diaper industry's growing demands for high-performance compression diaper bags. These bags, which are tightly sealed around the diapers, allow for a reduction in product size. This translates into savings in the areas of freight and handling costs.

Within the last several years, diaper manufacturers have continued to make their requirements for diaper-bag packaging more demanding.

Compression packaging, where the bag is tightly sealed around the diapers, is now preferred due to the application's smaller size advantages. These benefits translate into a savings in freight charges and make handling easier for the manufacturer and consumer.

Hargro Packaging's, Boyertown, PA, plant had a request from one of its customers, who supplies the private-label diaper market, to develop these high-performance compression diaper bags for their customers.

As a leading film-laminating packager for the food and diaper industry, the company was confident it had the experience to satisfy these demanding diaper packaging requirements.

Through various acquisitions in the 1980s, Hargro has incorporated a number of diverse packaging companies into one unit under the name Hargro Packaging. The backgrounds of each of these companies provides Hargro with the expertise it needs to manufacture flexible packaging for food and related industries, health care packaging and industrial packaging.

This broad range of experience was utilized when faced with the task at hand. In addition to the films themselves, the technical staff at Hargro knew the key component for this particular application would be finding a flexible-laminating adhesive that could meet the application's stringent performance requirements.

After trials using other adhesives, Hargro contacted the flexible-laminating adhesives team at Bostik, Middleton, MA, to provide a solution to the adhesion challenges this application presented.

The Production Process

This demanding application involves the lamination of white and clear linear low-density polyethylene film. The adhesive is gravure applied to the printed web which is then dry bonded to the secondary web. After the webs are laminated, the rolls are placed in a warm room to allow the two-part adhesive to cure for several days.

The film is then converted into sideweld handle bags and shipped to the diaper manufacturer who inserts compressed diapers and closes the bag with another heat seal.

Other Variables

Hargro's requirements were quite demanding for this application because linear low-density polyethylene required a low-effective glue-line temperature. This necessitated careful evaluation of the adhesive for flow and wet out onto the secondary web.

Hargro developed its own series of bond tests that predicted the performance of an adhesive under these strict performance controls. Due to the low-nip temperatures, some adhesives were difficult to liquefy on a consistent basis.

There was often an unacceptable penetration of adhesive into the secondary film interrupting production.

Another consideration was diaper bags require a slip agent in the polyethylene film to reduce friction when loading diapers into the bags. This can present a problem for many adhesives with certain polymer structures because they can't resist slip migration into the glue line. This would result in a change in the coefficient of friction of the film.

Adhesive Meets Demanding Task

Bostik 7896, a US Food and Drug Administration-approved two-component medium-solids solventborne-polyester adhesive, achieved the green strength and cured-bond strength necessary while satisfying the demands of the application's other variables. The ethyl acetate-based 7896 was crosslinked with Boscodur 21 curing agent which upgrades the basic adhesive properties.

Bostik was able to formulate its 7896 polymer to maintain its high-bond strength even under the stress brought on by compression.

"The Bostik 7896 adhesive provided us with tight bonds that passed our stringent high-temperature tests," Bud Leef, manufacturing manager, Boyer-town plant, said.

"The area around the gusset seal didn't fail even when tested at temperatures of 140 [degrees] F. The adhesive was also particularly creep resistant."

The green strength of the 7896 initially off the line gave Hargro the confidence to maximize line speeds, thereby increasing production efficiencies.

These benefits were achieved while nipping at the low temperature described in earlier paragraphs, a testament to the flexibility inherent in the adhesive. "The 7896 product allows us to fine tune our own process without the adhesive itself being a variable," Leef said. For example, the characteristics of an adhesive can vary when a slip agent is allowed to migrate.

The 7896 is a polymer with a high molecular weight formulated with a tightly crosslinked crystalline structure, it resists slip migration.

By synthesizing polyester and polyurethane resins with high-molecular weights ranging from 15,000 to 30,000, manufacturers can formulate flexible-laminating adhesives to meet specific user requirements.

Bostik is working closely with the company to modify the 7896 so it can run at higher solids. This will offer the company additional economic and environmental benefits.

About Hargro

In addition to its Boyertown facility, Hargro has plant locations in Harrisburg, PA, Flemington, NJ, Edinburgh, IN, and Chicago, IL.

The company has direct sales representation throughout the US, as well as in the Caribbean, Mexico, South and Central America. Geographically distributed technical service representation is also available for on-site customer support.

Hargro's capabilities include flexographic printing, rotogravure printing, adhesive laminating, extrusion laminating, in-line polyvinylidene-chloride laminating, polyvinylidene-chloride coating, extrusion coating, coextruded-film extrusion, and extruded-monofilm extrusion.

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