Identification of Fibre and Fibril Properties Giving Good Pulp Properties with Low Energy Requirements, 1999 International Mechanical Pulping Conference Proceedings

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Knut Roar Braaten
The Norwegian Pulp & Paper Research Institute

Groundwood processes are known to consume less energy than refiner processes. During the last years so called “high intensity” refiner processes have proven to consume less energy than ordinary refiner processes.

The aim of this investigation has been to examine if fibres and fibrillar material from these low energy processes feature other properties than fibres and fibrillar material from ordinary refiner processes.

The specific surface area of the pulp is important for the sheet properties. The most usual way to increase the specific surface area of the pulp is to increase the specific energy consumption. This applies to all kinds of pulps, but the high intensity refiner processes and in particular the groundwood processes create a lot more specific surface area at a given specific energy consumption than the ordinary refiner processes.

For tensile strength and surface smoothness it is very important to have well fibrillated fibres. Just a slightly increased specific surface area of the pulp in form of a rich fibre fibrillation will give a pronounced increase in the tensile strength and surface smoothness. Since the energy consumption is presumed to be closely related to the creation of specific surface area it is therefore cost effective to have the fibrils sitting on the fibres instead of separating them from the fibres as fines.

The high intensity refiner processes and the groundwood processes in particular, give more fibre fibrillation at a given specific energy consumption than the low intensity refiner processes.

For light scattering purposes it does not matter whether the specific surface area is located on the fibres as fibrils or separately as fines. But the high intensity refiner processes and the groundwood processes in particular yield more fines and hence a bigger specific surface area at a given specific energy consumption. Usually, increased fines content increases the relative bonded area of the fines and hence a reduced ability of the fines fraction to scatter light. High intensity refiner processes and groundwood processes on the contrary remain the same relative bonded area as the low intensity refiner processes even at very high fines contents and hence a high light scattering coefficient.