Coaters

Transfer roll coaters are typically used for applying thin coating layers, particularly as required for 100% solid coatings. These coaters typically use 4, 5 or 6 rolls, with each consecutive roll running in the opposite direction of the previous one. The rolls in the stack alternate from rubber covered to steel surface rolls (typically chrome plated). The web is supported by the last roll in the series, which is referred to as the backing roll and runs at web speed. The web passes between the backing roll and the next to last roll, referred to as the applicator roll, which also typically runs at web speed. The coating is typically placed in the gap between the first two rolls, with the first roll, referred to as the metering roll and the second roll both rotating away from the coating puddle. Each roll from the metering roll through the applicator roll runs faster than the previous one, with the coating continuing to be reduced in thickness by the combination of the gap between the rolls and the increase in speed. The coating is transferred from the applicator roll to the web as it passes through the gap with the backing roll. The transfer roll coater has a very good speed range and has fairly wide coating thickness and viscosity ranges.