Hot-fill closures are hot stuff.
Various factors are driving the use of plastic containers and closures for hot-fill applications, including: the continuing migration of beverages and other products from glass to plastic, the increasing use of single-serve sizes, and the proliferation
Many hot-fill bottlers continue to use steam to soften caps. However, new hot-fill closure systems are designed to perform without presteaming. There are several advantages to doing without cap steaming, says John Greiner, marketing manager for Alcoa Closure Systems International.
"First and foremost, you don't have to have one more variable affecting your performance, like a steam box," Greiner says. "Secondly, if you were starting from scratch, the cost of installing steam and maintaining the system is an ongoing expense for you."
The ongoing expense is indeed something that bottlers want to avoid, says Jim Wilmington, project engineer for Crown Zeller USA.
"What I'm hearing throughout the juice industry is that this is a practice they're trying to get away from," Wilmington says. "They have to have a boiler going, they have to have the gas to heat the boilers, they've got to continually being boiling water."
That view was echoed by Bob Reay, director of marketing for Silgan Closures, whose White Cap division pioneered the use of plastic closures for hot fill.
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"When we introduced the first all-plastic hot-fill vacuum-holding 43-millimeter closure in 1986, the initial customers and most that followed were ones that had previously been running metal closures on glass where the metal closures required heat to soften the plastisol gasket. Therefore, they all had 'heat' available," Reay says. "In today's world, many new packers are starting out with plastic closures and don't have or don't want to add heat to their capping lines. Also, some existing packers would like to eliminate heat from their operations."
Getting the T-E band to work without pre-steaming is primarily a matter of getting it to slip
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论坛over the lip of the bottle--known as the "A dimension"--without having to be softened. Crown Zeller and other manufacturers are accomplishing this by tweaking the resin they use for closures. Certain polypropylene copolymers give just the right degree of flexibility. Another strategy is to tweak the "bridges" between the T-E band and the cap by altering the number and size of the slits.Crown Zeller's BevGuard Plus closure also boasts another improvement in the T-E band: tiny holes in the "J-hook," the bottom edge of the band that fits over the lip. When the bottles travel through a cooler bath, the drop in temperature creates a slight vacuum in the headspace. This can suck minute amounts of water into the underside of the cap. The holes drain this water, removing potentially troublesome moisture that could otherwise allow bacteria to breed.
Separate seal
One step that is often debated in hot-fill applications is whether to use separate induction seals. Some hot-fill bottlers use foil or film induction seals as an added barrier against mic
robial intrusion, which would compromise the sterility needed for additional shelf life.
日本参议院选举The key to induction sealing in a hot-fill application is using the right kind of sealing head, or coil--the component that emits a pulse of electromagnetic energy that binds the seal to the bottle's lip. Pillar Technologies markets systems with interchangeable coils that can handle a variety of bottle types and sizes with the same base power supply. Both Pillar and Enercon Industries market tunnel sealing heads that allow the container to travel through the sealing head while the electromagnetic pulse is directed to the foil liner for sealing.
Enercon is touting capless sealing as a possibility for hot-fill applications. (In most induction sealing, the seal arrives at the bottling plant already inserted into the cap, and the sealing takes place after the cap is applied. "Capless" sealing refers to a process of attaching the seal to the bottle's mouth and then applying the cap.) The big advantage of capless sealing is that it allows the bottles to be cooled before the caps go on. This cuts down on the liability of misapplied caps and the danger of cooling water collecting betwee
n the cap and seal.
But induction sealing in hot-fill has its detractors. It adds expense and can be perceived by consumers as a nuisance, says Clint Haynes, president of Stress Engineering Services, a consultant engineering firm that specializes in closures.
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