| 摘要 |
Process and apparatus for applying a flowable coating medium to a travelling web by a reverse applicator roll technique in which the peripheral velocity of the applicator roll (U) is maintained at less than 0.4 of the forward speed of the web, and the dynamic viscosity of the coating medium ( eta ) is selected in accordance with the relationship h=k eta 0.5U0.5, wherein k is from 0.01 to 100, such that a layer of coating medium of equilibrium thickness (h) not exceeding 5.0 mm is entrained on the surface of the applicator roll for transfer to the web. The technique avoids the use of a doctor blade to meter the amount of coating medium on the applicator roll, and is suitable for the high speed application of a heat sealable coating layer onto a polymeric packaging film. Coating quality can be improved by stabilizing the web downstream of the applicator roll. |
