Print Finishing: the adhesive system for film lamination has to meet special requirements
In the manufacture of superior product packaging, the available technologies for print finishing are pushed to their limit to develop their full potential. Print sheets undergo numerous finishing steps before the process is completed: printing, film lamination, grooving, notching, embossing and then assembling. Alternatively to film lamination, surfaces may be finished with a layer of UV varnish. The used adhesives and varnishes have a major impact on the quality of the finished packaging and the requirements they have to meet are high. They must be compatible to the most diverse materials and surface qualities, provide high performance at very fast processing speeds, ensure reliable bonding of substrates with high restoring forces, and deliver packaging that is durable and visually appealing.
Film lamination on printed sheets
Print sheets are laminated with a film to preserve the highly finished aspect of the packaging for a longer time. The adhesive system for this application has to meet special requirements. It must provide excellent bonding properties to the printed substrate as well as to the most diverse types of laminating films. The compound must be strong enough to prevent any delamination during downline processing steps like grooving, notching or embossing. In addition, high gloss lamination is used to create optical effects, which places the highest demands on the optical qualities of the adhesive film. Therefore, the laminating adhesive has to possess a high degree of purity and cleanliness.
In recent years, the properties of film laminating adhesives for highly superior packaging have been improved continuously. An innovative dispersion adhesive of the Jowacoll® product family developed by Jowat last year is particularly suitable for the highest requirements in the lamination of printed sheets. The optimised mechanical processing characteristics, a smooth wetting pattern and the minimal foaming of this 1-component dispersion facilitate a high optical quality of the laminated product. A high compound strength, cut resistance and stability ensure reliable downline processing. Since no crosslinker needs to be added to this dispersion, dosing and mixing becomes obsolete, which leads to significant benefits from a more efficient and faster manufacturing process.
Another product group used in print finishing apart from the adhesives are the Jowat® UV varnishes. Due to perfect adhesion properties, the UV-curing top coating adheres to all standard print inks and facilitates magnificent brilliance. High scratch resistance, a homogeneous application pattern, good processing characteristics and minimal odour provide a superior quality of the final product as well as very efficient manufacturing processes.
One crucial processing benefit of UV varnishes is provided in combination with a specially adapted adhesive. Jowat® UV varnishes and closing adhesives are complementary products which provide an optimal interaction. For instance, print sheets can be coated completely during finishing without recessed areas for the subsequent application of adhesive. The closing flaps will bond perfectly on the coated surface, even in short process cycles and with little pressure. Durable packaging that is resistant to mechanical stress requires adhesives which can provide an excellent compound strength.
The professional article is published in the magazine "Deutscher Drucker Nr. 8/2016" in German language. You can download the original article below.