SINGLE-PASS CURTAIN COATING

Abstract

This paper provides a general explanation of the fundamentals involved in the process of curtain coaling a thin liquid film onto a web or web-transported product. Coatings may consist of a single homogeneous layer or multiple, dissimilar layers applied simultaneously in a single coating pass. Advantages of curtain coating include very high coating speeds, adaptability to a wide range of fluids, high quality product, avoidance of ribbing instability associated with roll-type coaters, and the flexibility of a multi-layer-single-pass process. Unique process problems include minimum web speeds due to coating thickness limitations, significant viscosity changes in the delivery system, drying of multi-layer liquid films, controlling air currents and air boundary layers, and the need for a high precision, non-pulsing, pump system. Despite the special requirements of curtain coating, its flexibility and efficiency make it a very attractive manufacturing process.