Distribution of Chemical Woodpulp and Groundwood Through the Thickness of Newsprint

Abstract

A papermaking furnish may be regarded as potential paper. The extent to which this potential is exploited depends upon the design and operation of the papermachine . The degree of useful utilisation of the furnish is largely determined by the orientation and distribution of the fibres and fines or filler particles in the finished sheet, both across the sheet and through its thickness . However, the structure of paper is the result of an extremely complex interplay between the intrinsic properties of a pulp and the manner in which the formation process is conducted. Consequently, the way individual components of the furnish are put together in the finished sheet is only indirectly and by no means completely under the papermaker’s control. In such a situation, analysis of the structure of paper, both on a microscopic and on a bulk level, provides the most direct link between the formation process and the characteristics of the finished paper.

Recently, the study of paper structure has taken a new turn. Theoretical approaches are being explored in an effort to relate a geometrically defined arrangement of fibres to the properties of the resultant sheet.^{(1, 2)} This approach is as yet in its infancy, but already promises to be a powerful one. The theoretical formulation of paper structure requires the use of an idealized model, however, in order that the problem can be set up in a manageable mathematical form. The choice of a model must depend on a knowledge of the structure of real paper. The analysis of the structure of commercially produced paper is therefore indispensable not only in its own right as an evaluation tool, but also as a complement to the theoretical studies.

The present investigation deals with the structure of newsprint. It was undertaken to obtain information on the manner and sequence in which the components of the newsprint furnish are deposited on the papermachine wire, also to establish the fibrous compositions of the top and wire side surfaces of newsprint . The work forms part of a general investigation of groundwood and newsprint evaluation, aimed at predicting the behaviour of a pulp on the papermachine wire in terms of parameters of the pulp that can be measured in the laboratory.