The challenge to deink inkjet prints together with recovered paper from households, 2010 TAPPI PEERS Conference

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Graphic papers collected from households are by far the most important raw materials for deinking in Europe. They consist mainly of newspapers and magazines. In addition to these main components the deliveries often contain certain quantities of higher grade papers originating from mailings, transactional and SOHO prints. Among these print products, digital prints and particularly inkjet have a high share and will increase in the future.

The deinkability is mainly depending on the characteristics of the inks and therefore on the printing process. Flotation deinking, the dominant process, was developed to remove letterpress and rotogravure inks and it works well on mineral oil based offset inks and dry toners. Current waterbased flexographic and inkjet ink particles are too hydrophilic and too small for an efficient flotation. Cured systems and some toners, particularly liquid toners can form agglomerates that are too big to be floated in a single stage process.

Theoretically, inkjet would need a different approach to the deinking process and its chemistry. The degrees of freedom are, however, limited due to the objective to achieve a proper deinking result for the main components – offset and rotogravure prints. The task is to develop inkjet prints which are deinkable under standard deinking conditions. INGEDE Method 11 represents these conditions and the deinkability test results are converted to “Deinkability Scores”. The ink itself plays a key role but also interactions with auxiliary chemicals or the paper surface are possible. Some improvements can already be seen in that field.