Hot melt adhesive performance, price or changes in production process could mean you’re considering a switch.

 

In this quick guide Intact’s Laboratory Assistant, Dan Griffiths shares his tips for a successful switch.

 

 
When you introduce a new hot melt adhesive to an existing system, there are a few things to keep in mind.
 
Although hot melts can look similar in colour or shape the specifications and raw materials can be completely different.
 
Even hot melts that are chemically tolerant can still cause issues which can lead to failed tests or unsatisfactory results.
 
We’ve put together this short guide to help you prepare your equipment for switching. Follow these steps to ensure your trials reflect your new hot melt adhesive’s true performance:
 

Remember to Use PPE

Remember to take safety precautions due to the high temperature of the glue. Use appropriate PPE including plastic googles, heat-proof gloves and suitable clothing or work-wear.

 

Hot melt Adhesive Switch in 4 Easy Steps.

 
Step One:
 
First, reduce pump pressure to 0 bar. Now, remove as much adhesive from your hot melt system as possible. You can use the drainage point on your tank.
 
It is worth checking the main filter to see if it’s in good working order. If the filter is heavily polluted you should change it. Refer to the instructions in your equipment manual.
 
Step Two:
 
Once the tank is empty, set the temperature to about 20°C higher than the softening point of the new adhesive being tested. You can find the softening point on the technical data sheet for the adhesive.
 
It is also worth removing any visible areas of burnt-on-glue inside the tank with a wooden spatula or similar tool. Try and avoid a metal tool as you may damage the inside of the tank.
 
You can now fill your tank with the new hot melt sample and allow it to melt.
 
Step Three:
 
Now return the pump pressure to 1 bar. Pump the new hot melt through the hoses and nozzles.
 
What can happen at this point is existing burnt particles in the equipment can come loose and be pushed through the system.
 
Don’t be too concerned if you see small, black specks in the extruding glue.
 
Burnt particles in the glue

It’s normal to find burnt particles when purging glues

This effect is more noticeable if moving from an EVA to one of our Optimise® ranges.

Optimise® hot melts keep equipment clean as they are being used and eliminate problems caused by char and nozzle blockages.

 
Step Four:
 
Refill the tank and pump through the system again. This may need more than two purges, depending on the size of your equipment or the volume of substrates that your trial dictates. If you’re unsure then we can advise.
 

Check for Marbling.

The best way to see if the original glue has been purged, correctly is to look at the extruding sample and check for marbling. This effect (as shown in the image below) is a visible sign of different glues mixing. If you can still see marbling then repeat step four.
Hot melt adhesives mixing together

Marbling effect caused by glues mixing together

A Note on Cleaning Products.

We discourage the use of cleaning products as part of the switching process. Whilst generally useful, these products are best avoided during the changing of a hot melt adhesive.

This previous post explains why.

 

If you have questions or need advice or guidance please get in touch by phone, live chat or send a message using the enquiry form on our contact page.
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