Similar to virgin fibres, recycled-fibre stock must meet defined quality criteria for a given furnish. ln this sense, quality refers to the fibre characteristics, such as the type and condition of fines, and to additives and contaminants. Recycled fibre processing systems are significantly more complex than virgin-fibre systems for two reasons. First, the recovered paper…
One basic characterisation of the rheology of a fluid is the description of the correlation between the forces acting on a fluid,f.i. in form of a pressure gradient, and the shear forces or the shear stress occurring in the fluid. If we consider a simple pipe flow as sketched in Figure 1, the driving force of…
Paper for Recycling (PfR) today is a mixture of different paper grades and each piece of paper in this mixture consists of different fibres. lt may also contain pigments or fillers, binder or additives and other components. ln addition, the paper products in the recovered paper mixture may have been coated, printed or upgraded by…
The assessment of the removability of adhesive applications from graphic paper products is in principle adopted to the assessment of the deinkability score. For an assessment method under laboratory conditions not only the screening but also the pulping process has to be defined because it is essential for the fragmentation of the stickies. That is…
The removal ability of adhesive applications is another product related quality aspect of paper products. Adhesive applications may form tacky particles, so-called stickies, in the paper recycling process. In graphic paper, the most visible components are glued spines of books, catalogues and magazines, glued inserts in magazines, labels of all kinds and the sealing of…
Inkjet printers spray ink as tiny particles onto paper through electronically controlled fine jets. Inkjet inks need to have a low viscosity and contain a high proportion of vehicle, typically 60 % to 90 %. For printing on paper, water-based inks are most commonly used.1 There are different ways to create the image on the paper surface: thermal inkjet, piezoelectric…
Dry toner printing processes have their widest use in laser printers and copiers. There are different ways to create the latent image but without significant influence on deinkability. These electrophotographic processes commonly use powdered toners with a particle size of typically 5 µm to 10 microns.1,2 Most toners contain the general components listed in Table 1.3 Table 1.…
As already seen in the overview on printing technologies, rotogravure prints are easily deinkable in general, as shown in Figure 1. From almost 100 tests, 95 % achieved a positive deinkability result. The few which failed in the test were uncoated magazines and failed due to dirt particles. Red discolouration was in some cases visible but just…
Offset printed products represent by far the largest group in the investigations, comprising 56 % of all tests, mainly newspapers and magazines. Newspapers generally correspond to coldset printing, in which drying occurs primarily by absorption. Flyers printed on newsprint-type papers as well as magazines and flyers printed on SC and LWC papers normally use heatset printing systems for print runs…
A scientific evaluation of the factors influencing deinkability has to consider the printing technology and the printing conditions. The results of the deinkability survey in Figure 1 give a general average overview. Detailed technical data of the printing process are not always available. In this average documentation of deinkability results, all relevant parameters are shown with its…
