Requesting a Product Quote or Equipment Proposal
So you’ve decided to purchase some coating equipment and you are not sure where to start. Don’t feel overwhelmed with the information required, it really boils down to a few key concepts:
Rheology is the study of flow. In our case, we are concerned with what happens to the viscosity of the fluid as shear is applied. This knowledge can be developed by doing capillary or parallel plate rheometry. Shear based testing does need to be run and the information has to cover 1-10,000 1/sec. If shear based data is not provided, the slot die design work cannot commence. With an understanding of the coating process, system influence, rheological basis and technique of coating based off the final product construction, Coating Tech Slot Dies has all they will need to design and manufacture your precision coating station.
Typically you understand the product that you are trying to create, but not much thought goes into the process of manufacturing the product. So we have to start with the end and work our way back. What coating thickness does your product need to be? Discounting the thickness of the substrate, how much dried fluid should be left on the web? People usually know this final coated and cured thickness, and if we know the percent solids we can calculate the wet coated thickness. Both are not necessary, but at least one and the percent solids is. Some products require a set width of coated product for the final converted and saleable roll of material. From here, you can coat multiples of this width. As an example, if a final roll of adhesive on the shelf sells at 10 inch (254 mm) wide, then the coat width could be 10, 20, 30, etc. inches wide to be cut down to the final product for sale.
There are five main components required to develop precision coating:
- Slot die. To properly design the slot die all the variables listed are required, but the fluid rheology and coat weight are paramount.
- Positioner. The equipment that places the slot die requires information about the wet coating thickness. This determines the gap that the slot die and substrate should have for proper coating.
- Backing roll. The backing roll is subject to line speed and operating temperature concerns because the temperature of the fluid may need to be maintained outside the coating head.
- Fluid delivery system. To decide between various positive displacement pumps, knowing whether the fluid is shear sensitive, has particles and requires temperature all play a role. In addition, compatibility with solvents can determine materials of construction. Density and viscosity of the fluid are critical for both the pump and the slot die design.
- Substrate. Understanding both the thickness of the substrate and the roughness of the morphology help the equipment designer understand what technique would be required.
The coating technique is based off thickness of coating, temperature of application and roughness of the substrate. Coating below 1 mil (25.4 microns) may lead the equipment supplier to provide a vacuum assist coating system or tensioned web over slot die arrangement. Coating thin at high line speeds may lead to curtain coating. Operating at temperatures above 300°F (149°C) may point to a flexible lip slot die over a fixed lip slot die. It is also good to know if the coating will always be full width or coated with dry areas in-between lanes of coating. Do you require dray areas down web in addition? And ultimately how many coated layers form the functional product?
With an understanding of the coating process, system influence, rheological basis and technique of coating based off the final construction, Coating Tech Slot Dies has all they will need todesign and manufacture your precision coating line.