The OptiCoat Layer multilayer curtain coater applies extremely thin – or thick - and uniform layers simultaneously all within one, compact coating station. It is equally suitable for both board and paper machines, regardless of their speeds and widths. The multilayer concept offers several advantages over single-layer curtain coating and other conventional coating methods.
Curtain coating slide die has an expandable design, which gives a possibility to upgrade the coating station by adding coating layers. The ability to coat both very thin and thick coating layers gives a possibility for a wide end product assortment. The fierce competition forces paper and board producers to rethink their processes and products.
In multilayer coating, either one, two or even three layers can be applied. All the coating layers remain separate. This allows the use of functional layers, e.g. thermal or barrier coating colors. The thickness of a more expensive coating substance can be optimized, and a less expensive coating layer can function as carrier layer.
OptiCoat Layer gives excellent profiles since the peak-to-peak coat weight variation is very low. There is no need for profiling; profiles are stable within a wide operation window. Due to an even coating thickness, coating layer has a uniform brightness. Even with lower coat weights, coating coverage is good, and total coating amount can be reduced.
Well-functioning air removal and fully sheltered coating process gives even and stable curtain coating. Excellent runnability and efficiency are the results from contactless coating method.
Because of the curtain coating method, the base paper can be produced with less or completely without white fibers. Each coating layer can be adjusted to desired function and cost. This enables the optimizing of the base paper and coating layer to reach the most cost-effective solution. There are no coating color losses because of the dry-edge running mode and careful recovery of the coating color. OptiCoat Layer curtain coating station is very compact in size and can easily be fitted in most paper or board machines.
With its numerous features, OptiCoat Layer brings a number of grade development possibilities. For coated white top testliners, there is a possibility to produce with less or no white fibers. For white lined chipboard, there is a possibility to reduce white fibers on top layer. Expensive ingredients in coating color can be minimized, and there can be an additional layer with protective function.
One of the most interesting ways to use curtain coating is to first apply a blade coating layer, the the curtain coating in the middle, and again a blade coating layer. This brings out the best features of both coating methods. The uniform coating layers and good coverage of curtain coating combined with the smooth surface of blade coating gives excellent results. Furthermore, the profiles are stable and even in curtain coating.
All the targets for the coater section rebuild project were achieved at the Mayr-Melnhof Kolicevo mill in Slovenia. Runnability and efficiency were improved. A multilayer curtain coater and a blade coater started up at the board machine 3 (BM 3) after a very short shutdown period in the summer of 2015. A supply system for the two layers of the curtain coater was also installed.