A simple coating process typically involves coating and drying (or curing) a single layer. Multi-layer products typically require multiple single layer coating stations placed in series or multiple passes through a single coating station machine. In instances where a product requires more than two coated layers at multiple stations, conversion to a multi-layer coating approach at one station can be more economical. There are even cases where adding an additional layer actually improves speed and/or manufacturability. For example, adding a tie layer between two singly coated layers will drive up costs (additional raw materials or need for another coating station), but if it is used to enable a multi-layer coating methodology and an enhanced coating window, it can demonstrably increase product manufacturability, coating speed, and the quality of the finished good. As a result, the additional layer and raw materials enable a net gain.
Carestream Contract Manufacturing has helped several customers convert their multi-pass operation into a more efficient single pass process. Although there are many considerations when designing the product and choosing a coating method, Carestream has multiple coating type choices that include the following multilayer methods:
- Curtain Coating: The Colorado facility features two coating stations that can work in series (tandem) with each other, enabling coating of up to 20 layers at one time as each coating station is capable of coating up to 10 layers. The second tandem coating station can be used either on the same side or on the opposite side of the film if the web is flipped in between.
- Multi-layer Slot and Slide Coating: The Oregon facility has used these robust techniques for customers in a variety of industries. As in Colorado, multi-layer methods can be used at tandem coating stations to create many layer structures on both sides of a conveyed substrate. In addition, lamination is available at the end of the line to add yet another layer for functional or protective purposes.
The economics of high-precision coating are dependent on a number of variables. In fact, there are over a dozen that matter in getting to a final per square meter cost, including coating method, speed, and drying rate.
Line speed can be limited by a number of factors ranging from solution rheology to solids concentration. Speed ranges for the coating processes employed at Carestream Contract Manufacturing range from 50 to 1750 fpm.
Drying rate is equally important. Often sensitive products require gentle drying (e.g., for low stress-based curl or proper morphology development) and / or low final residual solvents (e.g., for food packaging or medical applications). Short, high temperature dryers are not often used for multi-layer structures that are sensitive to drying. Carestream has complex drying “profiles” (time, humidity, temperature, air flows) that allow for customized drying tailored for unique product creation. The dryers on our equipment in both Colorado and Oregon are some of the longest in the world, allowing for an uncommon combination of coating speed and custom drying methodology for multi-layer products. The combination of tailored drying, speed, and high precision multi-layer coating lends itself to strong economics for customers desiring complex, multi-layer structures that can be used in a variety of industries.
As mentioned above, coating method selection is another key component in the economics of coated media. Product formulation is important for proper coating method selection. It is not uncommon to commercialize a product with one coating method and formula only to change methods and formulations to enhance productivity. Carestream has a wide variety of coating methods in the lab (for product development), on the pilot (for product scale up, and at the manufacturing scale (for commercialized products). Our experience with productivity enhancements via tailored coating methods and formulations is an important key to our customers’ successes.
At Carestream, our coating professionals build on over 100 years of coating leadership to deliver knowledge and problem-solving expertise in multi-layer precision coating applications. We have helped a wide variety of customers pinpoint the most efficient and economical way to optimize the coating process as a whole.
In conclusion, improving economics in coating is a function of many variables. By working with Carestream, customers can determine tradeoffs and even convert a single-layer, multi-pass operation into a more efficient, multi-layer coating process for productivity gains and improved manufacturing robustness.