Technology
The application of the adhesive
Slot die BASICS
- A slot die coating head is used in various industrial coating processes to apply a thin, uniform layer of adhesive onto paper, films, foils and more.
- The main body of the die is typically made from high-strength steel. It houses the internal flow channels and the exit slot through which the adhesive dispensed.
- The slot is a narrow opening at the end of the die from which the coating material is extruded. The width of the slot is carefully controlled to determine the thickness of the coating. The slot typically runs the entire width of the substrate to ensure even coverage.
- The slot die usually has adjustable lips, which allow fine-tuning of the gap size at the exit slot. This adjustment controls the thickness of the coating layer.
- Open loop systems are simpler and require adjustment during intitial set-up, then only minor adjustments if needed during the run.
- Closed loop systems automatically adjust make adjustments to the die via pumps or motors to regulate the coat weight across the width.
Slot die against roll
In this method, the adhesive is extruded from the lips of the slot die directly onto a moving web or substrate, which is supported by a coating roll.
Slot die against roll with smoothing bar
The slot die is fitted with rotating bar instead of standard slot lips. This bar is used for smoothing adhesive on the web when coating at lower coat weights and for optical films or clear-on-clear applications.
Slot Die curtain coating
This is a technique where a continuous “curtain” or sheet of adhesive falls vertically onto a moving substrate. The substrate passes through this curtain, picking up a uniform layer of adhesive.
