Troubleshooting: Optimising hot melt tank pressure

May 20, 2021 | Adhesives, News

The food and beverage market are seeing continued growth and demand as consumers want more options with their products, and packaging is a huge part to play in the decision process. Using hotmelt adhesives for case and carton sealing is hugely successful, reducing material waste and single use plastic consumption. It is an effective method which can work to demanding speeds of production, while maintaining packaging quality for maximum shelf appeal. To utilise the full effect of high-quality production at increased speeds, it is important to have the adhesives and equipment working together. This will achieve the best results, minimising the risk of costly downtime or pop opens. To optimise your hotmelt equipment, you need to look at 3 key areas:

  • Determine pressure settings.
  • Integrate applications set speed.
  • Avoid adhesives overspray and build-up.

Pressure settings

It is common to see tank pressures set between 20 and 50 psi within packaging applications. There are a few variants to determine a suitable tank pressure for your application. Running at a pressure that is too low can cause inaccurate and inconsistent bead applications. Running at pressures too high can cause adhesive splashing off the substrate and cause problems later in production. Typical reasons to increase tank pressure include:

  • Adhesive application beads are too small.
  • Potential clogged nozzles, no adhesive being applied at all.

Where increasing the tank pressure can add benefit the performance of your application. It is important to be cautious and increase slowly at 3-5 psi increments at a time. As too much pressure without any other adjustments across the equipment can increase consumption by up to 15% per application which can be costly.

Initial Pressure Final Pressure % Adhesive Increase
30 PSI / 2.0 BAR 35 PSI / 2.4 BAR 11%
25 PSI / 1.7 BAR 30 PSI / 2.0 BAR 13%
20 PSI / 1.4 BAR 25 PSI / 1.7 BAR 15%

 

A common misconception is when pop opens occur to increase the amount of adhesive applied. This is not the case, adding more adhesive affects compression time and by putting more adhesive on increases the amount of compression time needed. Generally, the issue is not how much adhesive is applied but something else like temperature, a change in substrate or even the wrong adhesive for the job.

Set Speed

Set speed is the time it takes for hot melt adhesives to cool and set, becoming stronger than the substrate to produce fibre tear. This is a critical variable to consider during any production as if the equipment does not accommodate the correct set time, it can cause pop open and rejects which can be very costly, especially during a fast production line. There is a direct correlation with tank pressure and set speed. The higher the tank pressure, the slower the set time is, due to increased amounts of adhesive per application needing a longer time to cool and adhere to the substrate.  Equally if the tank pressure is too low, the application can set too quickly, preventing a true adhesion to the substrate, causing problems later in production.

Overspray & Build-up

Hot melt adhesives such as Technomelt, are applied via a continuous stream of material. Increasing the tank pressure means more material is dispensed at a time causing overspray. This is a common problem in carton and case sealing applications and can end up spraying onto the production line or machinery. Equally with high pressured tanks and heavy bead applications, this can cause a build-up of adhesive around the application area, effecting the packaging aesthetics as well as the potential to coat the production line belts or machinery. Specialist cleaners are available such as Melt-O-Clean to help clean affected areas.

To conclude, using high quality adhesive such as Technomelt Supra can only get you so far during hotmelt applications. Your machinery and equipment settings are just as important to ensure you have both variables working together to achieve the best quality results. Prior to any changes to your tank pressure, it is important to do a thorough investigation into the cause of your adhesion problems to identify the source of the issue.

Interlock Adhesives Ltd have an extremely knowledgeable technical team with over 60 years of combined experience to be able to assist in identifying adhesion problems across the application settings. For further info on how we could help, contact us today.

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