Effect of deinking on optical and physical properties of secondary fibre after pulping and flotation

Furnishes of mixed magazines and newsprint and all-magazines and all-newsprint were used to investigate changes in properties of secondary fibre during deinking. In most cases, optical and physical properties showed reverse trends after pulping and flotation stages. These differences can be explained by the change in proportions of mechanical and chemical fibres, filler, fines and ink during flotation. After the pulping stage, trends in strenght properties were influenced by detrimental effects of filler from magazines. However, after the flotation stage, due to loss of most of the filler and fines, an enhancement in all strenght properties occured. Brightness and light absorption coefficient appeared to be more influenced by ink content, when large amounts of filler are present. The light scattering coefficient was dominated by the fibre type. After flotation, despite the highest brightness value, the all-magazine furnish had the highest ink speck count. Extended periods of flotation (greater than ten minutes) had no significant effect on properties of the waste paper investigated.