The deinking industry has faced some serious issues in the last decade, but one association has helped avert disaster

by Axel Fischer and Erwin Krauthauf

A prize fighter for the deinking industry

It's a fact of life, more and more paper
is being recycled. In the past, newspapers were the mainstay raw material for the recovered paper industry, but today office and household papers are ending up in the recycled paper chain in almost every industrialized country. While this may seem like an ideal situation, the effect is that the quality of the recovered paper is deteriorating.

Today's paper recycling industry must face up to this challenge and others, such as the effects of new printing technologies, printing inks and defending itself against accusations made by certain environmental organizations.

These types of problem have led to the founding of the International Research Association Deinking Technology, Ingede, based in Germany, to help to deal with the issues which have an impact on the deinking industry.

More wastepaper is getting recycled but its quality is decreasing

While many paper mills often have to install and develop new machinery to keep up with the growing number of unwanted substances found in household recovered paper, the association approaches the problem from a different angle. It tries to create more awareness among publishers, printers, printing ink and adhesive manufacturers to make their products better suited for recycling. And the association has been involved in a number of battles in its 10-year lifetime.

Battle for flotation

At around the same time Ingede was established, a new printing technology had started to worry paper recyclers. The use
of the flexographic process in the print-
ing of newspapers was emerging and it was considered to be a cheaper, better quality replacement for old fashioned letter-
press printing.

Printers paid very little attention to the fact that flexo inks were a threat to successful deinking using the flotation process, even though this effect was already well known. In Europe, flotation deinking is the most common process used to produce secondary fibers for the manufacture of graphical paper, while in the USA washing is the preferred method. Washing is only used in Europe for the manufacture of tissue. The flotation process does not work with flexo inks because when the binder dissolves in the alkaline fiber suspension it releases pigment particles which are too small to be removed by flotation.

In response to growing concern, printing paper and tissue manufacturers around Europe joined together to form Ingede. Their common goal was to prevent the spread of flexo printing until flexo inks were developed which could be removed from recovered paper pulp as well as off-
set inks.

So far, this target has been met in Germany, but other European countries are lagging behind. Flexo ink manufacturers have tried to overcome the resistance to their product by developing new deinkable varieties, but have not yet fully succeeded. For example, Sun Chemical Inks tested a new development a few years ago, but it did not meet certain printers' demands regarding printability, as it dried too fast.

Coates Lorilleux is also attempting to develop deinkable flexo inks at a price that can compete with the price of standard flexo inks, but the group has yet come up with a marketable product.

Soybean silenced

Since the fight to prevent the spread of flexo inks began, other issues have appeared, which Ingede is tackling. In recent years, the American Soybean Association (ASA) launched an extensive marketing campaign to increase sales of soybean oil. With consumers demanding more products made from renewable resources and publishers hurrying to satisfy these claims, soybean oil was promoted as a replacement for mineral oils in printing inks.

As well as campaigners from ASA, a study by Western Michigan University in the USA was released which testified that inks based on soybeans had good deinking properties. Unfortunately this study neglected the fact that deinking processes differ in Europe and the United States and once more European paper mills have failed to obtain similar results.

A series of studies sponsored by Ingede and other organizations have revealed that soybean oil undergoes changes in its chemical structure as it ages. Oxidative drying forms a network which binds the pigments in newsprint ink tightly to the fiber. This pigment is then difficult to remove during flotation, especially when newsprint is more than four weeks old, which is a common occurance. Only some 50% of the newsprint reaching German pulpers is less than one month old.

Technical concerns aren't the only threats to the deinking world, though. Environmental issues have also had to be contended. When German Greenpeace activist, Manfred Krautter, demanded that all substances used in Greenpeace's vast number of publications should be chlorine- free, this included yellow rotogravure inks.

In a radio interview Krautter claimed that during the reductive bleaching process within most deinking plants, carcinogenic amines were formed, originating from chlorinated aromatic yellow pigments. Krautter went on to say that there were some 600 tons of aromatic amines released into effluent water by paper mills every year.

Krautter had used a calculated figure based on theoretical assumptions, but it had not been backed up by any study. Despite this, the claim led to a series of actions. Firstly, a research project was started with the German Association of Printing Ink Manufacturers (Mineralfarbenverband) within the German Chemical Industry (Verband der Chemischen Industrie, VCI) and Ingede. The intense studies used normal deinked pulp and, as a worst case scenario, all-yellow printed paper. The results showed that no aromatic amines were found at all, under both laboratory conditions and in operational deinking plants. Greenpeace has never repeated any of its original claims since.

At the same time, Ingede offered Greenpeace the chance to join a pilot project to develop a chlorine-free ink - if the research institutes working with Ingede were supplied with sufficient samples to examine the deinkability of such a product. Though Greenpeace never responded to this idea, a major German publisher, Axel Springer Verlag, did take notice.

Springer's head of central purchasing department, Herbert Woodtli, invited representatives of major pigment manufacturers such as BASF and Hoechst, printing ink manufacturers such as Gebrüder Schmidt and the major German mail-order company, Otto Versand, whose catalogue is printed at Springer's large rotogravure site in Ahrensburg, to form a working group together with Ingede on dealing with chlorine-free inks.

The initial question was, "Would there be an environmental benefit by using chlorine free rotogravure inks?" From the recovered paper processing paper mills' point of view any measure to reduce chlorine input to the paper recycling process would be beneficial because the less chlorine compounds that are brought into the process, the less adsorbable chlorinated organic compounds (AOX) leave the plant via effluent water or deinking sludge.

High chlorine contents in deinking sludge already rule out certain pathways to dispose of sludge or the chance to use it as a resource rather than as waste. One example where sludge can be used is in the cement industry. The high kaolin content of deinking sludge makes it a welcome source of aluminum oxide. But a high chlorine input is undesirable as it can lead to a build-up of alkali chlorides which are volatile in the high-temperature region of the cement furnace and deposit in colder upstream regions. This means that deinking sludge would have to be added continuously in smaller amounts rather than the current practice, which is just to add the sludge to the process in bulk.

The cement industry is not willing to use a dosage utility unless the deliverer of deinking sludge pays for it. So it tries to limit chlorine contents to 0.05% in the raw material mixture and to a maximum of 0.1% in deinking sludge.

Another more obvious reason for chlorine limitation in cement is the stability of the final product, as higher chlorine concentrations could lead to the corrosion of iron reinforcement.

Chlorine is also unwelcome in the brick industry. Deinking sludge is used as a loam additive and can increase the porosity of the brick's structure as pulp fibers disappear during the burning process. Chlorine can lead to the formation of dioxins during the sintering stage preceding the actual burning process.

With this in mind, new chlorine-free yellow inks seemed to be a promising alternative. But further investigations revealed that, although it would be technically feasible to produce and use chlorine-free yellow pigments, they require a complicated synthesis and a lot more energy to be dispersed with a binder to the final ink.

To conduct a trial, some chlorine-free ink was produced. The results showed that handling on the printing machine and the quality of the final product did not differ from inks used today. Although a complete life cycle analysis has not been made, the ecological advantages due to lower AOX emissions of recovered paper treatment plants might be negated by higher energy demands and a more complex synthesis of the pigment.

A sticky problem

The problem that has caused the most intense research activity supported by Ingede are residues of adhesives in the recycling process. Out of the DM 4.8 ($2.71 million) it has spent on research in the last nine years, some 10% has been invested in research projects dealing with adhesives, both at Papiertechnische Stiftung (PTS) in Munich and at the Institut für Papierfabrikation (IfP) at the Technical University of Darmstadt.

Adhesives that cannot be separated by the initial screening equipment (which is the case for a wide variety of today's adhesives, mostly those used in labels and envelopes), are dispersed in the fiber slurry and transported through the whole manufacturing process. When the water finally evaporates on the paper machine, the adhesives remain as little sticky knots on the dryer screen. The consequence of this is believed to be holes or shiny spots in the final product and it is also believed to be a major contributing factor for paper breaks during the manufacturing process.

Though denied by adhesive manufacturers, the most striking evidence for this correlation are results achieved at At Perlen Paper in Switzerland. At this mill envelopes are sorted out of the recovered paper by hand before recycling. Perlen found that significantly fewer changes of the dryer screen were necessary and they also they had less paper breaks within this section. This lead Perlen to urge local households, through community recycling instruction leaflets, not to put envelopes into the recovered paper - but into the trash.

Some hope that this problem can be improved in the long run comes from the USA. In cooperation with all major manufacturers, the US Mail is putting significant effort into the search for a new pressure sensitive adhesive (PSA) for stamps. The main condition for this PSA is that it must be 100% screenable. As soon as satisfactory results are available, this technology will be adapted to labels and stickers used by the US Mail. It could also prove to be the answer to Europe's sticky problem.