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Title
Quality requirements in graphic paper recycling
Authors
Andreas M. Faul
Received
September 25, 2009
Published
Volume 44 Issue 10 November-December
Keywords
recovered paper, recycling, deinking, deinkability, printed products, flotation, inks, recyclability,
Abstract
Paper recycling has a long history. The use of recovered paper in white grades received a boost since the 1970s, with the introduction and spreading of flotation deinking. The paper analyzes two main aspects related to the quality of recovered paper for deinking: one is related to the characteristics of delivery, in terms of contamination, moisture and composition, and the other to the recyclability of the paper products in delivery. The first aspect is in close connection with the collection system, handling and storage of the recovered paper. It is essential for the paper industry that paper and board should be collected separately from other recyclables. The deinking process is designed to remove inks, but not to whiten unbleached fibres. Therefore, the deinking industry favours a separate collection of graphic papers from households, for reducing the contamination with non-deinkable paper and board. The content of brown packaging papers and boards is therefore one of the most important parameters in the entry inspection of recovered paper deliveries. INGEDE, the International Association of the Deinking Industry, has developed methods for entry inspection and runs a database for its members. Deinkability mainly depends on the characteristics of the inks and, therefore, on the printing process. Flotation deinking, the dominant process, developed to remove letterpress and rotogravure inks, works well on mineral-based offset inks and dry toners. Flexographic and inkjet ink particles are too hydrophilic and too small for an efficient flotation. Cured systems and some toners, particularly liquid toners, form agglomerates, which are too big to float. The acknowledged assessment scheme for deinkability, the removal ability of inks, uses INGEDE Method 11 for testing. The results are converted into “deinkability scores”. The second product-related quality aspect is the ability to remove adhesive applications. This depends not only on the chemical characteristics of the adhesive, but also on its type of application. INGEDE’s database on the recyclability behaviour of adhesive applications is considerably smaller than the one on deinkability. The tests focused on glued spines and labels. Glued spines often show sufficient recyclability, if they are made with hot-melt adhesives. Of them, polyurethane glues are generally the best option. Labels are much more critical; one of the reasons is the low film thickness. Not enough is known yet on the way feasible chemical nature can compensate for this disadvantage. In order to find out more about how adhesive applications can improve their recyclability, INGEDE with some co-sponsors launched a survey on the recycling behaviour of about 200 printed products containing adhesive applications.
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