Inductionย Heating Aluminum Foil For Cap Sealing with IGBT inductive heater
Objective An induction heater is used to heat a polymer laminatedย aluminum foil in 0.5 to 2.0 seconds. The heat produced in theย aluminum foil melts the polymer that bonds to the neck of aย plastic container.
Material Aluminum foil, polyethylene, polypropylene, polyvinylchloride,ย polystyrene, polyethylene terephthalate, styrene acrylonitrile
Temperature 300 – 400 (ยบF), 149 – 204 (ยบC)
Frequency 50 to 200 kHz
Equipment DAWEIย solid-state induction powerย supplies operating between 1 & 10 kW at frequencies of 50-ย 200 kHz. These units operate with remote sealing heads whichย allows the main power cabinet of the equipment to be locatedย away from the immediate production area. Distances of up toย 100 meters are possible. The microprocessor is used to control
and protect the system and ensures that the optimal operatingย frequency is maintained at all times and that each container
receives the same amount of heat energy from cycle to cycle.
Process Two different types of aluminum foil laminates are available forย this application. The first assembly includes backing
board/reseal, a wax layer, aluminum foil, and a heatseal filmย for supported systems (Figure 1). The second assemblyย includes a high temperature film, aluminum foil, and a heatsealย film for unsupported systems (Figure 2). The procedure is to fitย the foil membrane into the cap and to fit the cap to theย container after the product is filled.
Results For the aluminum foil assembly as shown in Figure 1, heatย induced in the metallic foil by the induction coil almost
instantaneously melts the polymer coating and the neck of theย container forming a hermetic seal between the heat seal film
and the rim of the container. The heat also melts the waxย between the aluminum foil and the back board. The wax is
absorbed into the back board. This results in an air tight bondย between the aluminum foil/membrane and the rim of the
container, the back board is released and remains in the cap.
Process (contโd) In the case of unsupported membranes in Figure 2, one side ofย the aluminum foil is coated with a heat sealable polymer filmย and this face that will be in contact with and sealed to theย container. The other side of the foil that will be in contact withย the cap has a higher melting-point film that prevents adhesionย of the aluminum to the cap allowing the end user to unscrewย the cap. Unsupported membranes are typically used where theย end user pierces the tamper evident membrane prior toย dispensing the product.ย The aluminum foil acts as a vapor barrier preserving theย freshness of the product and prevents it from drying.
