By Dr. Edward D. Cohen
A: There are two important elements that that need to be considered in the selection of the appropriate coating method for a web-processed product at each of the specific coating-application steps in the overall web-coating process. These elements are the coating-method operating range and the specific product coating-application requirements. The coating applicator must reproducibly and effectively meet all product requirements; if it cannot, then a different, appropriate method must be used.
The same coating method typically cannot be used in each of the four coating-application steps:
1. Initial concept development
2. R&D product development
because each step has its own requirements for the coating application and final product requirements. Currently, there is no coating method that can meet all of the requirements for all of the steps, therefore multiple coating methods must be used in the overall web-coating process. It would certainly simplify and improve the effectiveness if available coating methods could coat a wide range of requirements and satisfy all current and potential product requirements.
But that is just not possible. It often requires different coating methods in eachof the coating-process steps. The prime process requirement is to produce an excellent quality, cost-efficient product, and each coating application step needs to use the method that meets coating quality, productivity and economic objectives for each product. Forcing a product to coat in a specific step with a coating method that is not adequate may result in some initial satisfactory results, but in normal production it will have poor quality, poor reproducibility, high costs and will not result in a commercially successful product. If the coater has a wide range of coated-product variables, it will require the ability to use multiple methods at some specific steps.