Application Technologies

With knife systems, the coating paste is applied onto the carrier or the substrate with a knife. Depending on the counterpiece to the knife, roller knives and air knives are distinguished. The knife bar of modern coating plant is equipped with several coating knives and is turnable according to the socalled revolver principle. This facilitates a quick change of the knives, especially of the roller and the air knife. All application systems are equipped with either manually or powered adjustable side scrapers.

The Meyer rod is a stainless steel rod that is wound tightly with stainless steel wire of varying diameter or with a milled winding (screw thread). The rod is used to doctor of the excess coating solution and control the coating weight. The wet thickness after doctoring is controlled by the diameter of the wire used to wind the roll and is approximately 0.1 times the wire diameter. Rods are available in a wide variety of wire sizes to give a range of coating weights.

The application of the coating raw material by a die system is another alternative. A die is a closed application system, consisting of a die chamber, into which the coating raw material is pumped. For each coating raw material, the design of the die is evaluated regarding the raw material´s flow behavior. This guarantees the raw material´s even outflow out of the die lips.
A special micro pump feeds highly precise meterings of the coating material to the die. The coating weight can be precisely defined by the speed of the pump. Also the die lips and the speed of the web influence the coating weight.

The Gravure Coater has become one of the most popular types of coaters in use today due to its ability to apply less coating with more precision than other methods. There are three types of Gravure coaters: direct gravure, reverse gravure, and differential offset gravure. All three apply a uniform amount of coating across and down the web. In addition, each has its own distinct advantages and disadvantages. The coatweights produced by the gravure roll varies with the type of coater used. The coatweight is dependent upon the coating solids, coating surface tension, gravure pattern, gravure cell depth, coater configuration and operating speed.

The application roller moves in the opposite direction to the web´s moving direction. Principally, this system consists of three rollers that are either arranged vertically align or in an S-shape. The coating raw material is placed between the two upper rollers and is kept in the roller gap by double-sided limiting knives. The Reverse-Roll-Coater is used for the processing of pastes with a low viscosity and a good flow behavior, very thin applications can be realised with this technology.

The coating is passed through a screen giving a uniform and even surface. This technology is often used to coat only parts of the web, for example stripes and patches.