Induction sealing

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Induction sealing, otherwise known as cap sealing, is a non-contact method of heating a metallic disk to hermetically seal the top of plastic and glass containers.

A Hand Held induction sealer
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A Hand Held induction sealer

Contents

[edit] How does it work?

An induction sealer with a conveyor
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An induction sealer with a conveyor

The closure is supplied to the bottler with foil liner already inserted (sealing without a cap is possible but is not used as frequently). Although there are various liners to choose from, a typical induction liner is multi-layered. The top layer is a paper pulp that is generally spot-glued to the cap. The next layer is wax that is used to bond the foil to the pulp. The bottom layer is a polymer film laminated to the foil. After the cap or closure is applied, the container passes under an induction coil, which emits a varying electromagnetic field. As the container passes under the induction coil (sealing head) the conductive aluminum foil liner begins to heat. The heat melts the wax, which absorbs into the pulp backing and releases the foil from the cap. The polymer film also heats and flows onto the lip of the container. When cooled, the polymer creates a bond with the container resulting in a hermetically sealed product. Neither the container nor its contents are affected, and this all happens in a matter of seconds.

It is possible to overheat the foil causing damage to the seal layer and to any protective barriers. This could result in faulty seals, even weeks after the initial sealing process, so proper kilowatt (kW) ratings are vital to determine the exact system necessary to run a particular product.

Sealing can be done with either a hand held unit or on a conveyor system.

[edit] Why seal?

An induction sealed bottle
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An induction sealed bottle

There are a variety of reasons companies choose to use induction sealing:

  • Tamper evidence
  • Leak prevention
  • Freshness
  • Pilferage protection

[edit] Tamper evidence

With the FDA regulations concerning tamper-resistant packaging, pharmaceutical packagers must find ways to comply as outlined in Sec. 450.500 Tamper-Resistant Packaging Requirements for Certain over-the-counter (OTC) Human Drug Products (CPG 7132a.17).

Induction sealing systems meet or exceed these government regulations. As stated in section 6 of Packaging Systems:

“…6. CONTAINER MOUTH INNER SEALS. Paper, thermal plastic, plastic film, foil, or a combination thereof, is sealed to the mouth of a container (e.g., bottle) under the cap. The seal must be torn or broken to open the container and remove the product. The seal cannot be removed and reapplied without leaving visible evidence of entry. Seals applied by heat induction to plastic containers appear to offer a higher degree of tamper-resistance than those that depend on an adhesive to create the bond…”

[edit] Leak prevention/protection

Some shipping companies require liquid chemical products to be sealed prior to shipping to prevent hazardous chemicals from spilling on other shipments.

[edit] Freshness

Induction sealing keeps unwanted pollutants from seeping into food products, and may assist in extending shelf life of certain products.

[edit] Pilferage protection

Induction-sealed containers help prevent the product from being broken into by leaving a noticeable residue from the liner itself. Pharmaceutical companies purchase liners that will purposely leave liner film/foil residue on bottles. Food companies that use induction seals do not want the liner residue as it could potentially interfere with the product itself upon dispensing. They, in turn, put a notice on the product that it has been induction-sealed for their protection; letting the consumer know there was a liner on the plastic bottle prior to purchase.

[edit] Variety of products that use induction sealing

[edit] History

  • Mid-1960s - Induction sealing is used worldwide
  • 1973 – First solid state cap sealer introduced
  • 1982 - U.S. Tylenol scare
  • 1983 – First transistorized air-cooled power supply for induction cap sealing
  • 1985 – Universal coil technology debuted
  • 1992 – Water-cooled, IGBT-based sealer introduced
  • 1997 – Waterless cap sealers introduced (half the size and relatively maintenance free)
  • 2004 – 6 kW system introduced

[edit] External links

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