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Changing the Hot Melt

EXCHANGING A HOT MELT – DO’S AND DON’T’S

When exchanging a hot melt, for example to perform a temporary test or conversion to a new adhesive, there are some things to be taken into account, to prevent problems in the long term.
Although hot melts can seem very similar in shape and colour, the formulations and used raw materials differ greatly. The appearance at room temperature does not tell you much about the chemical composition and although in practice a mixture of two similar looking hot melts generally does not cause problems, an intolerance reaction can be the cause of major (and costly) problems.
Even chemically tolerant (compatible) hot melts, can be the cause of a failed test or non-representative evaluation of the bonding results, because of their differences in viscosity.
Cleaning and flushing agents are regularly used for cleaning a hot melt system before exchanging formulations and although these agents can be very effective in specific cases, their use in most cases is not recommendable.


Glue Exchange - what should be checked ?
Before the exchange procedure, it is recommended to have the compatibility of old and new formulation checked. The adhesive manufacturer is able to run a relatively simple laboratory test with a small sample of both hot melts which will confirm the chemical tolerance of hot melts.
When the outcome of these tests demonstrate an intolerance, the next steps should be performed with extra care.

The adhesives are compatible – what’s next ?
Step 1;
The current hot melt should firstly be removed from the system. The tank can be drained from the main plug (with care because of the release of hot glue!).
It is recommendable to check the main filter for excessive dirt. If heavily soiled, it should be replaced.

Step 2;
When the tank is empty, the entire system should be set to a low temperature.
A setting temperature of around 20-30C above the melting point (also called "Ring & Ball temperature") of the new hot melt.
Now the tank can be filled with the new hot melt.

Step 3;
To avoid dirt (carbonized particles, etc.) that is presently in the system ends up in the small channels of the nozzles and cause blockages, it is recommended that the heads are disconnected from the hoses.
Flushing can be started as soon as the new hot melt in the tank is melted.
Because of the low temperature at which the system has been set, the new hot melt’s viscosity is now high (thicker), which allows it to flush (push) out the existing old glue. Increase pump pressure is often required here.

Step 4;
When the flushed hot melt that is released at the end of the disconnected hoses looks clean and consistent, depressurize the system and connect the hoses.

Step 5;
When in-line filters are installed, it is recommended to replace these.
After installing the nozzles, these should also be flushed with the new hot melt.

We have carefully carried out this procedure, but blockages still occur.

Especially in hoses, existing contamination and sediments can often not completely be removed.
A change in using new, clean and clear hot melts, can cause this old contamination to slowly be released and cause blockages. In that case it will be necessary to install new hoses.
It also happens that moving and bending the hoses during the exchange process cause old contamination to be released, blocking the nozzles during the days after the hot melt exchange.
In that case it is advisable to again flush clean hot melt at low temperatures. Should this not help, new hoses have to be installed.

If you do not want to carry out this procedure or might not have the availability of a skilled workforce to perform this, please contact us to discuss the possibilities of make alternative arrangements.

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Contact Intercol

  • Intercol BV
    Marconistraat 7
    NL- 6716 AK, Ede
    The Netherlands
  • +31 (0) 318 63 63 63
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  • +62 81 769 69 212