Curtain Coating (Questionnaire)

A Curtain Coating Questionnaire from TSE Troller AG.

1. How do you judge pros and cons of curtain coating? In particular, with respect to the materials applied (i.e. organic solvent, hotmelt, waterborne coating)? Also, regarding the coated web (film, paper, ..) and web thickness?
From our point of view single and multilayer curtain coating can be used for a wide range of coating applications applying waterborne coating liquids, fluids with organic solvents or solvent-free coating solutions in a temperature range up to 70-80°C.

Of course curtain coating has - as every other coating method too - its own limits of operation in regard to operating conditions and liquid properties such as curtain stability, wet coat weight, web speed, rheological behavior, surface tension of the fluids and others. Curtain coating is applicable to coat a large variety of different substrates such as paper webs, films, metal webs, fabrics and others with varying substrate thickness.

Pros for curtain coating:

• Contact free coating application: no heavy stresses to the substrate (risk for web breaks) and no wear out
• Premetered coating process:
  • No recirculation, no excess fluid.
  • Constant fluid properties over entire coating run.
  • Possibilities to apply multilayer coatings in one pass.
  • Possibility to run 2- component systems.
• Constant quality during entire coating run.
• Very small risk for line defects in coating.
• Even coating thickness also on uneven substrates ("contour coating") both in cross-web and in machine direction.
• Allows high coating speeds (>2000m/min, exact limits are not known at the moment)
• Large variability in coat weight, speeds and liquid properties
• Fluid distribution crosswise and application to the substrate decoupled

Cons for curtain coating:

• Applying thin coatings at low speeds not possible
• Requirements on education and training of operating personnel relatively high regarding handling

2. How do you view future evolution of curtain coating as compared to other coating process types?
Curtain coating will have a large potential between different coating methods due to the followings requirements and/or developments.

• Environmental aspect: "only the required amount of liquid is used".
• An increased quality requirement of the final product requires a higher precision of the coating method too.
• Complex structures of coatings will be economically available due to multilayer possibilities.
• Very low risk of web breaks due to contact free operation with large gap between applicator head and substrate.
• Reasonable short payback due to excellent cross-web uniformity and very small risk for interruptions of a coating run.

3. (For machine manufacturers): What kind of technology improvements do you expect within the near future? What particular feature does your company provide in order to increase your market share or to seize new market segments for this technology?

Since curtain coating is a fairly new coating process in the most of the industrial coating applications there is a potential for improvements in the following areas:

• Optimization of several accessories (curtain edge guides, removal of air boundary layer ...) required for new coating applications.
• Increased number of pilot facilities with curtain coating possibilities for different product families.
• Education and guidance of application and R+D- engineers through scientific and commercial institutions.
• Increased number of well educated experts in curtain coating to improve experience exchange.
• Development and optimization of appropriate coating liquids due to improved process know-how.