Foam forming under dynamic conditions

Abstract

Using foam as a carrier fluid in papermaking gives interesting new opportunities. Foam as a more viscous fluid than water is expected to behave differently in a dynamic process. This study presents results obtained under dynamic forming conditions in a semi-pilot scale research environment. Effects of process configurations and running conditions on increased forming speed, web properties, and difference between water-laid and foam-laid processes are shown. The studies were carried out using a water-laid former and the same environment modified for foam forming. In order to achieve increased forming speed, the open headbox was replaced with a closed headbox, and the former geometry was updated. The process foam was boosted with an additional foam pulper. The foam pulper was used as a machine chest for improving the dispersion of fibers into the foam. A much broader tensile strength ratio range (~3 to 8) was achieved with foam forming than with water-laid forming. Foam-laid paper had a broader pore size distribution and higher mean pore size. Formation and the formation spectra of foam-laid sheets were more uniform, leading to improvements in the properties of the fiber network.