Effect of Wavelength of Infrared Radiators on the Drying Rate of Coating Machines, 1991 Coating Conference Proceedings

The use of infrared drying for control of binder migration has been standard practice in Europe since the mid 1960’s. By the beginning of the 1980’s the use of heaters with temperature between 1.100 k and 1.400 k operating at wavelengths of 2.5 to 2.8 um was commonplace. Today’s driers, with temperatures of 2.400 kat 1 um wavelength offer a fifteen fold increase in drying capacity over the older low temperature units.

The extent to which infrared heaters influence drying rate depends not only on the properties of the heating element, but also on the native of the modiated material. The reflecting and absorbing power of many materials is wavelength dependent and to the design of an I.R. heater can be critical in determining the drying efficiency of the unit.

The relationship between radiation wavelength and drying rate are discussed both from the theoretical standpoint and in the light of practical experience on coating equipment. Questions of efficiency, economy and the requirements of papermakers addressed.