The adhesive lamination relates to a process for manufacturing a flexible laminate for packaging, in which process at lease one plastic film and at least one further plastic film, metal foil as laminate layers are bonded together by means of polyurethane laminating adhesive and subsequently energy is applied to the laminate to cure the adhesive.
In the manufacturing of flexible packaging laminates consisting of plastic films, aluminum foils as laminate layers, mostly bi-component polyurethane adhesives are used in bonding together the individual laminate layers. After laminating these adhesives need to be stored up days in high temperature rooms at a temperature of 45-50 ℃ to reach a complete curing of the adhesive. These conditions apply particularly to packaging materials that have to withstand thermal cycle processes, e.g. in retort applications.
The long curing time has a negative impact both on delivery time and storage capacity needed. Moreover, the conventional curing process requires a high energy consumption to maintain the required temperature. A fast curing solution would allow substantially reducing the time from laminating to shipping the laminate. A substantial advantage of the use of microwave energy for curing adhesives according to the present lamination results in a significant reduction of curing time for polyurethane solvent-based adhesives, especially used in high-performance laminate applications such as retort flexible packaging, without raw material technology or cost impact.
