What actually are cool melts? Low-temperature adhesives, as cool melts are also called, are hot melt adhesives that become liquid at temperatures from around 90 °C and are applied at 100 °C to 150 °C. Therefore they need less heating than conventional hot melts, which are applied at temperatures of
180 °C to 200 °C. This offers a lot of advantages:
Low-temperature adhesives are made of the same raw materials as high-temperature adhesives, namely different thermoplastic polymers. They should therefore not be confused with organically based adhesives, which are partly produced from renewable raw materials. Nevertheless, cool melts contribute to increased sustainability in production, as not only do they consume less energy when being applied, but they also enable higher machine speeds and help to boost the productivity of your packaging line.
Robatech tests its adhesive application systems with different adhesives from different manufacturers. Cool melts are also regularly tested here. When comparing the energy consumption of low-temperature adhesives and conventional hot melts, we found that the adhesives required an average of up to 8.5% less energy per 10 °C temperature drop. This means that you can save around 40% of energy by reducing the application temperature from, for example, 170 °C to 120 °C with a cool melt, or even more in some cases.
«By switching to the new low-temperature adhesive, we were able to reduce power consumption by almost 50% while maintaining the same performance and functionality of the adhesive application. An interesting win-win situation for us.»
Daniel Brack, Coordinator Production and Logistics
at Oel-Brack AG, Switzerland
Cool melts are offered by different manufacturers in granular form. Aside from their lower application temperatures, they are processed in the same way as conventional hot-melt adhesives. Robatech adhesive application systems have no temperature restrictions, meaning they can also be used for the processing of cool melts. Set the temperature according to the adhesive data sheet – as usual for the melter about 10°C below the application temperature, the hose plus 5°C, and the application head the desired application temperature. Test out new adhesives before making the switch and don’t forget to clean your adhesive application system thoroughly every time you change your adhesive.
Let’s start with the bad news: cool melts are not equally suitable for all substrates. Since the adhesive is heated less, it does not penetrate as deeply into the substrate. This makes it more difficult to achieve adhesion on smooth surfaces. But here’s the good news: for many substrates, especially in the field of end-of-line packaging, there are proven cool melts that bond just as well as conventional hot-melt adhesives.
Keep in mind that low-temperature adhesives are not only applied at lower temperatures, but also soften again at lower temperatures. The ‘softening point’ refers to the temperature at which the adhesive passes from the solid to the liquid state. This also applies, of course, to adhesives that have already been processed. Products glued with cool melt should therefore not be exposed to temperatures higher than the softening point temperature, which needs to be taken into account when storing or transporting the products.