One way to increase the export value for the Swedish forest industry of wood based paperboard by means of sustainable development, is to use more of fibre materials produced at high yield (>90%) as in chemi-mechanical pulping (CTMP) processes.
In Sweden; spruce is by far the most common wood species as raw material in production of CTMP for manufacturing of paperboard. CTMP is also manufactured from hardwoods (aspen and birch) as market pulp but is so far not commonly used as a component in high quality paperboards. However, especially birch fibres have some morphological advantages in comparison to softwood fibres, which might be possible to take advantage of.
The project goal is to develop and demonstrate technologies, which will make it favourable to use high yield pulps, (HYP), as low energy chemimechanical pulp CTMP based on hardwoods, particularly birch, in manufacturing of high quality paperboard. The total energy consumption in refining of such hardwood CTMP should be lower than 700 kWh/ton, to be compared to about 1200 kWh/ton in standard CTMP manufacturing from birch at yield >90%. The CTMP should preferably be used in middle plies in paperboards, which will offer opportunities to reduce grammage at given bending stiffness and improve brightness as well as surface smoothness in final products in comparison at use of softwood CTMP. The extractives of birch CTMP should be reduced to such a low level that they do not cause any problems regarding taste and odour.