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Press Release 2/2000

Reducing Costs and Conserving Resources
with the "Waste Paper Filing Tray"

Research Project "ÖKOPAP 2000" of the German Research Ministry completed successfully

More and more recovered paper shall be used as raw material for graphic paper production, but even this resource is limited. A source of recovered paper that barely has been used yet is hidden in huge office buildings: with copiers and laser printers, today a flood of short-lived documents is created – and a large part of them ends up in the waste-paper basket the next day. There it mixes with yoghurt remnants, paper cups, board and banana peels.

Can white office paper be collected separately in higher amounts? The Institute for Paper Science and Technology of the Darmstadt Technical University examined this question for INGEDE within the scope of "ÖKOPAP 2000" (ECOPAP). This project, funded by the German Research Ministry, has recently been completed. The target of eight related practical project parts was to improve the composition of recovered paper as a raw material as well as to improve waste paper processing.

The research object for paper collection was a office building of Siemens in Erlangen, Germany. The employees were told to return their "white" waste paper to central collection containers that had been positioned close to the copiers of the different departments. This way, no additional walking was necessary. At their desks they were told to collect the office waste paper in separate files.

The test showed that the separate collection of high-grade office papers is possible – and, depending on the quantity collected, can also reduce the disposal costs of a company. But the employees have to be motivated again and again to change their attitude towards the waste-paper basket and to cooperate: Any white paper does not belong underneath the table any more but into the "Waste Paper Filing Tray".

Artificial Intelligence in recovered paper processing

Recovered paper is not uniform – in the material delivered to the paper mills the fraction of printing ink varies often as well as the impurities do. The optical properties of the deinked pulp play an important role for the processing of recovered paper to become new graphical paper. A novel type of soft-sensors for the evaluation of these optical properties was another ÖKOPAP 2000 project. At the "Kübler & Niethammer" mill in Kriebstein, Saxony, the researchers investigated the current processing plant for recovered paper and developed models for every process parameter by means of artificial intelligence. Sensors before and after the flotation plant, where the printing ink is removed from the fibres, supervise the process. Continuously the pulp properties are analysed. Depending on these data, a novel controlling concept proposes how to run the plant optimally. Thus despite variations in the raw material the quality of the deinked pulp can be improved.

Cooperation for the first time allows a integrated view

The project "Production integrated environmental protection by improving paper recycling for the production of high-grade graphical paper", which is ÖKOPAP 2000's full title, has been completed successfully after running for three years, funded by the German Federal Ministry for Education and Research (BMBF). Besides the BMBF, the International Research Association Deinking Technology (INGEDE) and a couple of industrial partners have financed the research project.

University and industry worked together in close collaboration in the eight parts of the project. Among the industry partners were not only Siemens and the Kübler & Niethammer mill, but also BASF Printing Systems and Voith Paper Fiber Systems, Ravensburg. This close cooperation for the first time allowed an integrated approach toward the recycling of graphical papers. The results provide solutions for problems relevant in the practical environment. They can be transferred immediately, e. g. to improve recovered paper quality or the management of the process. The data gained also form a basis for further discussions with everybody involved in the paper chain. In 1994, there had been a voluntary agreement of all members of the paper chain to improve among others the recyclability of graphical papers.

Measuring adhesives and red discolouration

Sticky contaminants are still the major problem of the paper mills utilising deinked pulp. What makes sense for certain applications often leads to problems during recycling: Many adhesives dissolve and then pass the whole process to end up at the paper machine. New paper is formed on synthetic wires, on which the dissolved adhesives may deposit as small sticky particles, so-called stickies. They can settle in the paper mat, but also at various places of the paper machine, where they cause a variety of problems: from breaks of the paper web or contaminated paper machine screens to problems at the end user of the paper – when the stickies re-appear in the copier and stick or burn to black crumbs there.

In order to better investigate the causes of such sticky contraries and to react better towards them during the process, at first the exact amount of sticky material has to be determined. Scientists at the Institute for Paper Science and Technology, Darmstadt Technical University, have now developed a new, quantitative method for sticky determination.

The aim of the deinking process is to remove printing ink – but the result is more or less incomplete. Sometimes a red discolouration remains that can hardly be avoided with conventional means. Not only the deinked pulp keeps a red shade, in most cases also the corresponding process water carries this discolouration. In a basic study the cause for this red shade has been found –the red colouring materials in question as well as their applications in printing inks.

In the first place azo pigment lakes were responsible for the red discolouration of the samples examined. Other than yellow and blue standard pigments, these red printing inks dissolve during the deinking process. Therefore the intensity of the red shade depends on the amount of ink involved as well as on the efficiency of the ink removal. It is difficult to avoid as these pigments represent the quantitatively most important red pigments for printing inks. In some cases also colours based on rhodamine, which are used in rotogravure printing processes only, were found to be responsible for a red shade. These colours lead to very bright and clear tones. Replacing azo pigments and inks based on rhodamine would be possible, but this would not only lead to more expensive inks, they would also worsen in their optical properties.

Other projects dealt with the improvement of ink removal by optimised dosage of chemicals, the influence of chemicals, which are used for paper manufacturing, on the deinkability, and with the improvement of printability of lightweight printing paper containing a high amount of recovered paper.

INGEDE is an association of leading European paper manufacturers founded in 1989. INGEDE aims at promoting utilisation of recovered graphic paper (newsprint and magazines) and improving the conditions for an extended use of recovered paper for the production of graphic and hygiene papers.

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Last update: 11 January 2007