Unique steel belt press technology for high strength papers from high yield pulp

Abstract

The dry strength properties of hot-pressed moist paper improved as stiff high-yield pulp fibers soften and the sheet density increased. Very high wet strength was also achieved without adding strengthening agents. This research focuses on a new hot-pressing methodology based on a steel belt-based pilot cylinder press with infrared heating. The heated steel belt transports the moist paper into the cylinder nip with two adjacent steel rollers with adjustable nip pressure. The temperature ranges up to 300 °C, maximum speed is 5 m/min, maximum pulling force from the steel belt is 70 kN and the line load in the two press nips is 15 kN/m each. High peak pressures are possible due to the hard press nip between steel rolls and steel belt, allowing a good heat transfer to the paper. The long dwell time allows strained drying of the paper which results to high density and high wet strength. Paper samples from high-yield pulps were tested at different nip pressures, temperatures and machine speeds while the dry content was kept constant at about 63%. High nip pressure showed the largest effect on densification and dry strength. While high temperature and long dwell time seem to be most important in achieving high wet strength.

Utilizing and Valorizing Oat and Barley Straw as an Alternative Source of Lignocellulosic Fibers

“…As the lignin content of the straw was relatively high, we decided to use heat treatment to enhance the bonding of the fibers. Hot pressing [ 31 , 32 , 33 ] has been shown to lead to high dry and wet tensile strength for lignin-containing wood pulps. In that case, the strength increase is caused by the interdiffusion mechanism [ 37 , 38 ] that occurs at temperatures exceeding the softening temperature of lignin (c.a.…”

“…This was probably caused by the larger dimensions, smoother and less fibrillated surfaces, and different surface chemistry of straw fibers when compared to chemical or mechanical wood pulp. However, similar strength as for paperboard could be achieved with hot pressing, which has been shown to increase lignin-rich wood fibers’ dry and wet strength [ 31 , 32 , 33 ]. The most potential application opportunities and logistics requirements that are important when utilizing straw materials as an alternative source of lignocellulosic fibers are discussed based on these observations.…”

A method for chemical and physical modification of oriented pulp fibre sheets

“…Selected samples from sheet steeping were densified by hot pressing to explore the possibility to further enhance the mechanical performance. Samples were compressed in a continuous press manufactured by IPCO AB, described in detail by Joelsson (Joelsson et al 2021). The press is designed with an infraredheated steel belt carrying the sample into a roll nip pressure point, applying a line pressure across the sample as it passes through.…”

A method for chemical and physical modification of oriented pulp fibre sheets

“…Selected samples from sheet steeping were densi ed by hot pressing to explore the possibility to further enhance the mechanical performance. Samples were compressed in a continuous press manufactured by IPCO AB, described in detail in (Joelsson et al 2021). The press is designed with an infrared-heated steel belt carrying the sample into a roll nip pressure point, applying a line pressure across the sample as it passes through.…”