Induction sealing

Induction sealing is a non-contact heating process that accomplishes the hermetic sealing of a container with a closure that includes a heat-sealable foil laminate. The typical induction innerseal begins as a multi-laminate liner inside a closure made up of the following layers:

• layer of pulpboard
• a layer of wax
• aluminum foil
• layer of polymer

When the closure is applied to the container, the container and closure are passed under an induction coil at high frequency. This process is accomplished by induction heating.

Process

The induction sealing process involves an induction current being applied to a metal liner in a plastic cap. The bottle is first filled, then the cap is applied. The cap already has the liner inside. The liner includes the sealing material that is going to bond with the bottle. After the cap is applied, the bottle passes under an induction coil, which emits a varying electromagnetic field. As the bottle passes under the induction coil (sealing head) the conductive aluminum foil liner begins to heat due to eddy currents. The heat melts the wax, which is absorbed into the pulp board, releasing the foil from the pulp board, and the polymer coating melts, hermetically sealing the foil to the lip of the container. The container now has a hermetically sealed foil liner, which will be pierced by a sharp object (straw) or torn open to access the product.

Applications

Induction sealing is used in many types of manufacturing. In packaging it is used for package fabrication such as forming tubes from flexible materials, attaching plastic closures to package bodies, securing plastic films, paperboard or molded plastic parts/tops. Some of the products that benefit from this type of seal include granulated coffee, milk powders, soup mixes, sauces, pharmaceuticals, and chemicals.

Advantages

Induction sealing has many advantages. It provides a seal that is not only strong but also leak proof. It can be used to extend product shelf life, prevent leakage and enhance product value. It is also a method of providing evidence of tampering to the consumer.

See also

• Packaging and labeling
• Tamper-evident technology
• Induction heating

References

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