In the production of cellulosic fibres it is known to use as raw material wood pulp wound in stock rolls of sheet material, to break up the sheet material in a mechanical pulp mill and to convey the broken pieces of sheet material from the mill to a subsequent processing station. The subsequent processing can be critically dependent on the aggregate properties of the mass of broken pieces. This invention, in its different aspects, relates to a novel way of feeding individual layers of sheet material as a pluri-layer web of raw material capable, on comminution in the mill, of producing a mass of broken pieces of the required aggregate properties.
In the case of stock rolls of sheet-formed wood pulp, suppliers grade the sheet-formed material on a roll, inter alia, on the basis of the viscosity of a liquid product produced in a pre-determined manner from the wood pulp and supply the roll to the end user with a viscosity rating. The end user can then select from the range of stock rolls available those having viscosity ratings which he wishes to use for a particular feedstock material.
In accordance with this invention, prior to creating the feedstock material from a plurality of different stock rolls of selected viscosity rating, the sheet materials from a number of stock rolls are drawn together to create a pluri-layer web which is fed as such to a pulp mill for comminution to create the required feedstock material .