Adhering to principles

13 April 2010



The latest hotmelts make an attractive proposition, says Gunter Hoffman, manager, product development hotmelts at Henkel.


Modern hotmelt adhesives in the packaging industry are used for high-performance bonding of cartons, trays and folding boxes, and for labelling. They make it possible to produce packages with a variety of different material combinations. However, for packaging manufacturers it is not only consumers’ expectations of the finished package that are hugely important, but also the adhesive’s processing characteristics.

Hotmelts belong to the group of physically setting adhesives. Having a high molecular weight, they are solid at room temperature. They are also free from solvents.

The working principle of hotmelts involves a two-fold change of physical state without any chemical modification of the adhesive. Since the adhesive hardens by cooling, setting can be achieved in a matter of seconds. High and cost-effective production speeds are therefore possible.

Along with the ongoing refinement of hotmelt formulations, the past few years have seen improvements in the handling of hotmelts. Hotmelts in granulate form can be handled today by automatic feed systems. Pressure-sensitive hotmelts, which used to be packaged in silicone-coated papers, are now supplied in film packages. These eliminate the need to unwrap the adhesive, as it is simply placed, still packaged, in the melt container. This not only simplifies the process but also avoids waste.

Low temperature adhesives

An important trend in hotmelts is the development of new low temperature hotmelts. Whereas working temperatures of 160°C to 180°C used to be standard, today’s ‘low-temperature’ hotmelts can be processed at between 100°C and 140°C. The advantages for packaging manufacturers are manifold. Because of the low temperatures to which the adhesive is exposed, its thermal stressing is appreciably reduced. This results in improved viscosity stability, and the colour remains unchanged for days. Because of the low application temperature, applicators are subject to less wear and tear, which extends their service life and decreases energy use.

So far, however, low temperature hotmelts have only been available based on ethylene-vinyl acetate (EVA). Although they show sufficiently good adhesion on many substrates, they score less well than hotmelts based on polyolefins (PO) in

terms of performance range. This applies particularly to the latter’s improved thermal stability, with the result that their viscosity and processing properties remain unchanged even if kept for extended periods in hotmelt applicators. Furthermore, supplemented with other raw materials, marked improvements are possible both in the low-temperature range, eg, for bonds on deep-freeze packages, and in terms of the bond’s heat resistance. In the adhesive melter, they also demonstrate much better cracking resistance than conventional EVA systems.

Highest performance at 130°C

Henkel has developed a hotmelt that unites the best of both adhesives technologies. With Technomelt Supra Cool 130, Henkel has reduced the application temperatures for a PO hotmelt by an average of 40°C to 130°C, without compromising on performance. This gives savings of up to 40% in energy costs and cuts adhesive consumption values of between 20% and 35% compared with EVA-based hotmelts.

This almost odourless adhesive, in addition to exceptional bonding strength, also features great consistency in terms of viscosity and colourfastness. Compared with conventional hotmelts, it is thermally much more stable and flows more evenly without stringing or cracking. Its self-cleaning properties ensure good processability.

Using the new adhesive avoids the problem of clogged modules and blocked nozzles, again reducing machine and equipment attrition and cutting cleaning time. As a result, the outlay for spare parts is reduced. Outages and set-up times can be significantly decreased, with production restarting at an earlier point in the proceedings. The new adhesives technology is suitable for a range of applications considerably wider than that of conventional EVA hotmelts.


New adhesives technology from Henkel is suitable for a wider range of applications than conventional EVA hotmelts. Henkel

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