Dust and Lint

Loose material on the surface of paper can be especially troublesome for printing and various other converting operations. Some common strategies to evaluate the degree of the problem include wiping the product with a black cloth or performing an operation equivalent to vacuuming the surface of paper and collecting the dust on filter paper.

To solve problems associated with dust or lint, it is recommended first to analyze the loose material on the paper. Dust may include fiber fragments (including vessel segments, fines, or fibers), pitch particles, sizing agent material, size-press starch, fillers, and various other materials. Once the main source of the dust has been determined, the solution to the problem sometimes becomes clear. Sometimes dust is transferred onto the paper surface from rolls or fabrics, so it makes sense to inspect the surfaces in the wet-press, dryer, and calender sections of the paper machine. Tacky materials in the wet-press area or on the early dryer cans sometimes pull fibers and other solid materials from the sheet, and these materials can appear later as dust.

One of the most effective ways to reduce dust due to fibrous material is to increase the level of refining of the furnish. Increased bonding within the paper will help to keep fine materials from being released. On the other hand, higher dusting tendency is expected if the bonding within the paper is weakened by having a high filler content.

One of the biggest justifications for use of a size press often is to increase the surface strength and minimize dusting. This justification has tended to become increasingly important with the advent of alkaline papermaking and the increase in filler content of many paper grades. However, it is important that the starch be prepared with care, avoiding either uncooked grains of starch (insufficient time or temperature) or recrystallized, retrograded amylose from the starch solution (too long holding time of underivatized size-press starch, especially if it is allowed to cool).

