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Slot-die Hotmelt Coater

hotmelt
Hotmelt coater of HIP-MITSU, Spresiano, installed at Centexbel

Hotmelt

Hotmelts are 100% polymers containing neither water nor organic solvents. The application of hotmelts in coating and lamination is hence very economical: drying/curing in an oven is not required in contrast to conventional coating pastes based on water or solvents.

Hotmelts are melted and applied onto textiles (or other substrates as melt. The melting of polymers is carried out in a conventional or a drum melter according to the type of polymer.

There are two types of hotmelt polymers: thermoplastic polymers and reactive polymers requiring different curing methods: thermoplastic polymers are cured by cooling, whereas reactive polymers need a reaction with e.g. moisture in order to be cured.

  • Thermoplastic polymers become liquid (=melt) in contact with heat (varying temperatures according to the chemical composition of the polymer) and become hard (=solid form) when cooled. This is a reversible process that can be repeated.
    Examples: PE (polyethylene) and PP (polypropylene), EVA (ethylene vinylacetate), TPU (thermoplastic polyurethane)…
  • Reactive polymers cannot be melted again, once they have been cured, because the reaction with e.g. moisture results into a permanent solidification.
    Examples: moisture curing PU, moisture curing APAO (amorphous poly-alpha-olefines), UV-curing acrylates...

Applicatication techniques

The melted polymer can be applied by means of various "applicators". Centexbel disposes of a "slot-die" hotmelt coater. The melted polymer is pushed through a slot and thus applied onto the substrate. The appliance with an operational width of 45 cm is appropriate for both coating and lamination trial runs.

Applications

The present configuration is appropriate to apply thermoplastic hotmelt polymer layers between 2 and 300 g/m² (depending on the polymer characteristics).

Moreover it enables us to apply both a closed "continuous" and an open "discontinuous" coating layer (cfr. to preserve breathability).

In principle all flexible materials may serve as a substrate, provided they can be processed from roll to roll.

Research & Industry

The new appliance is destined for research projects but is also available to the industry to perform specific applications on the "slot-die" hotmelt-coater.