Induction Heat Sealing is a packaging process that does not physically touch the product.
Making use of the near magical properties of magnetic fields, without any physical contact, an induction machine is able to heat and seal a specially formulated sealing material to the rim of a bottle or container.
Often referred to as induction machines, bottle sealing machines offer the manufacturer and consumer alike a level of product integrity that cannot be achieved with a plastic cap alone.
The induction process is achieved using high levels of current passing through a sealing head coil back and forth at a high frequency. This process creates a localised magnetic field that goes up and down at high frequency. This magnetic field can pass through the air and through plastic but when it gets to metal it “induced a current back and forth in that metal. This induced current mirrors the current in the sealing head coil that created the magnetic field in the first place.
A bottle sealing machine relies on the bottles being fitted with caps or closures which have had an induction heat sealing material placed into them prior the cap being applied to the bottle. This induction heat sealing material usually comprises layers that include a backing to give the seal some rigidity, a layer of aluminium to “catch” the magnetic field and a sealing layer which is heated by the aluminium. The sealing layer is heated and then, having passed the area of the cap sealing machine, given a chance to cool and “set” onto the top rim of the bottle.
What keeps the induction cap sealing material in the cap or lid prior to the cap or lid being placed onto the bottle or jar?
The most common technique is where the cap is designed to have retaining clips or a retaining ring above top cap threads. The liner is pushed into the cap and it “flicks passed” the retaining feature in the cap. Usually, enough room is left for the liner so when the cap is twisted off the liner does not have to twist with the cap.
How does the liner come out of the cap after it has been induction sealed to the bottle?
After the induction sealing process the sealing layer melts and then sets to form a bond between the lining material and the bottle or jar rim. When the consumer twists the cap off container, the retaining feature of the cap effectively “flicks passed” the foil bonded to the container.
Bottle sealing with the induction process avoids the need to handle the product or packaging films during the production process. It is a process that avoids direct heat and surfaces too hot to touch and bottle sealing machines can be set and adjusted very easily – especially if they are like the MeRo induction machines with energy transfer feedback or if you use a Line-Patrolman which provides this feedback measure for your cap sealing machine setting.
Often the first place a product will spoil is just under the cap due to ingress or escape of gases and/or liquid. The metal layer within the induction sealing material serves the dual purposes of a conduit to take the magnetic energy from the bottle sealing machine and convert it to heat energy required to activate and set the sealing layer and it serves as a packaging sealing layer with barrier qualities of near zero levels for transmission of gases and liquids. The barrier properties of foil are what saves large shipments of product from being cosmetically damaged by leakage and they are also what keeps products smelling so fresh and fine powders remaining so dry.