Analysis of the influence of grinding the short-fiber fraction on the quality indicators of waste containerboard

The research was conducted in three stages. At the first stage, the influence of the nature of the action of shortening and fibrillating grinding was determined, at the second stage – the optimal degree of grinding of the SFF, at the third – the optimal composition of the paper pulp by fiber. To solve the first task of the study, the range of the degree of grinding of the short-fiber fraction of 42 ... 51 °ShR with a step of 3 °ShR was selected. For shortening grinding, an NDM mill with a concentration of 3.5% during grinding was used, for fibrillating – a Yokro mill with a concentration of 6%. At the next stage, to determine the optimal degree of grinding of the SFF, laboratory samples were made from 100% SFF with a weight of 1 m² 120 g to determine the compression resistance at a short distance. The maximum increase in the SCT indicator (by 25%) was noted for samples with a grinding degree of 48 °ShR. With an increase in the degree of grinding of SFF by 8 °SR, a 10% increase in the SCT index is observed in the composition with LFF. The composition by fiber is LFF: KVF = 42: 58%. For the composition of 60% SFF and 40% LFF, the maximum values of resistance to planar compression and resistance to compression over a short distance were found, an increase of 10%. The maximum values of punching resistance are observed in samples of 65% SFF and 35% LFF, an increase of 4%. The optimal composition option should be considered to be 60% SFF and 40% LFF, since an increase of 10% was found for both indicators for this composition. Under production conditions, a pilot production of finished products with a composite composition of 65% SFF and 35% LFF and additional grinding of SFF was carried out. Pilot-industrial tests were conducted with an increase in the SCT index of 0.3 units, in addition, an additional favorable factor is that the variation in SCT and fluctuations in humidity across the width of the paper web with SFF refining are lower than without refining, i.e. the indicators have become more stable. The uniformity of humidity across the width and length of the paper web plays a huge role in the technological efficiency of processing raw materials in the production of corrugated cardboard.

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