Film Coated Offset Grades - Theoretical Aspects And Practical Experience, 1995 Coating Conference Proceedings

Dr.-Ing. Michael Trefz

Voith Sulzer Paper Technology

Film coated offset grades (FCO) have become an important issue in the paper industry during the last few years. (1,2,3) Production of FCO grades began in Germany in 1992/93. Due to the recession in the paper industry, some mills were forced to find a way to improve paper quality with minimum investment costs. The easiest way was to rebuild old size presses into metering type size presses and to apply an amount of coat weight which improved the paper quality. Depending on basepaper properties and desired quality, the minimum coat weight for sufficient fiber coverage and satisfying printability was found to be between 6 and 8 g/m 2 . Table 1 shows data from two mills that started FCO production in 1992/93. In both mills, old size presses were rebuilt. The width of the paper machines is 3,1 m in both cases. Mill A is producing a coated woodcontaining paper with approximately 20 % bleached kraft pulp at a maximum speed of 900 m/min (40 g/m 2 basepaper). Coat weight is 9 g/m 2 per side, applied at 60 % solids with chrome-plated grooved rods. The dull grades are calendered on-line with a soft nip calender. Mill B specializes in recycled base using 100 % deinked pulp. They are running 450 - 650 m/min and also apply 9 g/m 2 per side, premetered with chrome-plated grooved rods (55 % solids). Both mills started their product development with pilot trials, testing different coating formulations and evaluating the optimum coat weight.