INORGANIC IMPURITIES IN CATIONISED STARCH GRANULES

When cationised starch containing inorganic water-soluble salts is use d in manufacture papermaking, salts that are not retained in the fibre web will accumulate in the white water of the paper machine. When the white water is recirculated, the inorganic salts are carried into the paper machine's process water. The presence of these salts in the pro cess water constitutes a potential detrimental factor in paper-making. Point analysis of cross-sections of granules of dry and wet-cationise d starch with a scanning electron microscope (SEM) and an energy-dispe rsive X-ray microanalyser (EDXA) revealed that the Cl content in dry-c ationised granules was lowest in the central part of the granule (0.8% ), higher at the layer under the surface (1.3%) and highest in the sur face of the granule (2.5%). The starch sample contained on average (ch emical analysis) 1.21% Cl, 0.43% Si and 058% Ca. The Cl content in cro ss sections of starch granules cationised in a water slurry proved to be the same in both the centre and the surface of the granule (0.4%). Chemical analysis of the starch sample revealed no Si and Ca, but 0.2% S.