| Popis: |
Laboratory tests were performed to assess the influence of various digital prints and packaging paper products on the quality of deinked pulp. Boards and digital prints were dosed to a certain percentage in basic mixtures of offset printed newspapers and offset and rotogravure printed magazines. After pulping, the fiber suspensions were treated in a single step flotation process and the deinked pulp was characterized by optical properties. Effects on optical properties of deinked pulp are presented. Each proportion of 4% corrugated board in a basic mixture of recovered paper results in a 1 point loss in luminosity of the deinked pulp. The luminosity decrease corresponds with increasing degree of printing ink on the board. With increasing proportions of corrugated board, a shift in the color locus and increased filtrate darkening were observed, simultaneously. All effects were smaller for boxboard than for corrugated board. The negative impact of digital prints in a basic recovered paper mixture in terms of luminosity of deinked pulp was greatest with inkjet printed newspapers. A proportion of 30% inkjet printed newsprint results in a luminosity drop of almost 7 points, combined with a shift of the color locus into the green area. Regarding liquid toner prints in the basic mixture of recovered paper, a significant increase of the total dirt speck area from 200 mm²/m² to 1100 mm²/m² was observed after a single laboratory flotation process. |
