Cool melt: Is it worth switching?

18. April 2024 8 min.

Medea Schnyder, Marketing Copywriter

Have you ever considered replacing your hot melt with a cool melt that can be processed at lower temperatures? In this blog post, I explore what cool melts actually are, whether they are sustainable, and what advantages and disadvantages they bring. And I can already let you know that these questions are certainly worth considering, especially within the packaging industry.

Bead application in green and icon for reduced application temperature (coolmelt)

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:

adhesive application with cool melts requires less energy than with conventional hot melt adhesives, making production cheaper and more sustainable.
Cool melts require less time to heat up as they are applied between 95 °C and 150 °C. This helps make production more efficient.
Cool melts have short bonding times, which allows for higher machine speeds. This contributes to increased productivity at the packaging plant.
The low temperatures reduce the risk of burns for line staff. Work safety benefits from this.
Low processing temperatures mean less wear on the adhesive application system, enabling maintenance costs to be minimized. That, too, is efficient.
Better thermal stability: hot melt adhesives that are heated less coke up less quickly. As a result there is less to clean and downtime is reduced.

Icon with two hands forming a bowl open at the top, with a green leaf in the middle to symbolize sustainability Are cool melts green?

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.

HOW MUCH ENERGY YOU CAN SAVE WITH COOL MELTS?

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

Icon representing coins falling into a cupped hand Low-temperature adhesives use up to 50% less energy

CAN I ALSO USE MY ADHESIVE MELTER FOR COOL MELTS?

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.

Vision adhesive melter, Performa heated hose, and two SX jetting heads applying beads to Robatech cartons (demo situation) Robatech adhesive application systems are also suitable for applying cool melts

WHAT ARE COOL MELTS SUITABLE FOR?

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.

WHY COOL MELT?

Depending on the application and the product to be glued, cool melts are a sustainable alternative to conventional hot melts. They can help save energy and in doing so, contribute to sustainable production. We therefore advise companies in the packaging industry, in particular, to consider making the switch. Talk to your adhesive manufacturer about your options. If you’d like to test a cool melt on your substrate, we’d be happy to help.

What do you think about cool melts? Will you try one out? Why? Or why not? Let us know in the comments!

Medea Schnyder, Marketing Copywriter

Medea Schnyder, Marketing Copywriter at Robatech’s headquarters, writes articles about Robatech and its adhesive application systems that are published online or in print format. In the Robatech blog, she collaborates with colleagues to highlight current topics from the world of gluing.