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This paper examines various ways of combining paper and glass as a laminate and the effects on transparency. Laminate in this context means a layer of paper sandwiched in between layers of glass held together with an adhesive. Different kinds of papers and adhesives were used to study the potentials of glass-paper-laminates as related to transparency and translucency. These laminates may find applications in building construction, safety glass, printed electronics and more. Utilizing a variety of adhesives and papers, qualitative evidence found that epoxy achieves the best with regards to transparency and adheres most effectively.

Im Rahmen des folgenden Beitrags werden Untersuchungen zur Eignung des Wasserlinsen-Tests zur Bestimmung der phytotoxischen Effekte von Papierfabriksabwässern beschrieben. Innerhalb dieser Untersuchungen wurde eine standardisierte Methode zur Durchführung des Wasserlinsen-Tests in Papierfabriksabwässern erarbeitet. Die Abwasserproben müssen nach der Entnahme entweder direkt analysiert werden oder sofort eingefroren werden. Die gefrorene Abwasserprobe kann bis zu zwei Wochen gelagert werden. Die Testdurchführung für die Endabläufe wird mit vier Verdünnungsstufen empfohlen. Proben müssen vor dem Test schwarzbandfiltriert und der pH-Wert der Proben auf 5,5 eingestellt werden. Die Darstellung der Ergebnisse der Abwasserproben erfolgt als Gw-Wert, der die nominell erste Verdünnungsstufe (höchste Konzentration an Abwasserprobe) beschreibt, bei der eine Wachstumshemmung von 10 % nicht überschritten wird. Der Wasserlinsen-Test wurde unter definierten Bedingungen in demselben Labor dreimal für die Endabläufe aus sieben Papierfabriken wiederholt und damit die Reproduzierbarkeit der Ergebnisse quantifiziert. Im Laufe dieser Untersuchung zeigten 6 von 7 untersuchten Proben einen Gw-Wert von 1 oder 2. Die innerhalb der Reproduzierbarkeitsuntersuchungen bestimmten Gw-Werte entsprechen denen einer unbedenklichen Abwasserprobe. Für die ARA-Zuläufe und die teilgereinigten Abwässer ergeben sich höhere Werte für den CSB, den AOX und die Trübung. Die höheren Belastungen dieser Abwässer sind mit höheren Wachstumshemmungen im Wasserlinsen-Test verbunden. Ob einer dieser Faktoren oder ein Zusammenspiel mehrerer Faktoren für die höhere Wachstumshemmung verantwortlich ist, konnte in dieser Untersuchung nicht geklärt werden.

Around 60% of the paper worldwide is made from recovered paper. Especially adhesive contaminants, so called stickies, reduce paper quality. To remove stickies but at the same time keep as many valuable fibers as possible, multi-stage screening systems with several interconnected pressure screens are used. When planning such systems, suitable screens have to be selected and their interconnection as well as operational parameters have to be defined considering multiple conflicting objectives. In this contribution, we present a Mixed-Integer Nonlinear Program to optimize system layout, component selection and operation to find a suitable trade-off between output quality and yield.

Paper for recycling is an important fiber source for the production of corrugated base paper. The change in production capacity toward more and more packaging papers affects the composition of paper for recycling and influences the paper quality. This research project investigated the influence of the multiple recycling of five different corrugated base papers (kraftliner, neutral sulfite semichemical [NSSC] fluting, corrugating medium, testliner 2, and testliner 3) on suspension and strength properties under laboratory conditions. The corrugated board base papers were repulped in a low consistency pulper and processed into Rapid-Köthen laboratory sheets. The sheets were then recycled up to 15 times in the same process. In each cycle, the suspension and the paper properties were recorded. In particular, the focus was on corrugated board-specific parameters, such as short-span compression test, ring crush test, corrugating medium test, and burst. The study results indicate how multiple recycling under laboratory conditions affects fiber and paper properties.

Journal of CO2 utilization : JCOU 62, 102067 (2022). doi:10.1016/j.jcou.2022.102067, Published by Elsevier, Amsterdam [u.a.]

The effects of fibre orientation and laminate stacking sequence on the mechanical anisotropy of paper-based all-cellulose composites produced via a partial dissolution route is examined. As part of this work, the fibre architecture and microstructure of the paper precursor is controlled and characterised in order to follow the anisotropy of the materials through from precursor to final composite material. The fibre orientation of the precursor was found to strongly influence the mechanical anisotropy of the final composite material. The ultimate tensile strength and Young’s modulus of the paper-based all-cellulose composite laminates was 191 MPa and 17.5 GPa in the fibre direction, respectively, compared with 104 MPa and 10.4 GPa in the transverse direction, respectively. The ACC crystal structure was assessed with powder and transmission mode Wide-angle X-ray diffraction (WAXD) to measure the changes in crystallinity and crystal orientation due to the dissolution process. The mechanical response of multi-axial all-cellulose composite laminates was also determined experimentally and compared with analytical predictions by Classical Lamination Theory, demonstrating the utility of CLT for the prediction of the elastic properties of ACC laminates.

The well-known McKee formula was derived in 1963 for symmetric fluting constructions. This paper presents investigations showing the influence of asymmetric properties, either geometric or concerning the elastic moduli. Paper properties of the base papers used are taken to calculate the panel properties of corrugated boards. From these results, the box failure is predicted. To do this, a model approximating the corrugated medium by triangles is presented. With this assumption, the bending stiffness of corrugated board, no matter how many flutes, can be predicted from paper data. Machine direction and cross direction are treated separately. The theoretical considerations are verified by measuring paper parameters such as short compression test (SCT), thickness, and bending stiffness, as well as edge compression test (ECT) and bending stiffness of corrugated board and box compression test (BCT) of the boxes. It can be stated that the prediction of using paper data instead of corrugated board data may lead to even better prediction results, as the measuring of bending stiffness at the board may sometimes be influenced by sampling inconveniences. Finally, thickness of the used base papers, as well as thickness of the manufactured board, appear to be the main influencing parameters. The McKee formula is robust enough to be applied for asymmetric corrugated board as well.

In diesem Jahr wird ein Überblick zu den wichtigsten und aktuell laufenden Forschungsprojekten am Fachgebiet Papierfabrikation und Mechanische Verfahrenstechnik (PMV) gegeben.

Paper has been used intensively for thousands of years, and it is a material made from renewable resources. It consists of a highly porous, bendable and foldable, flat structure of randomly arranged and connected fiber-like basic building blocks. The possibility to transport fluids without pumps and sophisticated dosing systems is attractive, and microfluidic paper for diagnostic applications has gained increasing interest, in particular, throughout the last decade. Although a number of interesting demonstrator devices for such easy-to-use diagnostic systems have been reported, still only a very limited number of devices made it into the market. The latter is mainly caused by the geometric and chemical complexity of the paper material itself. Whereas chemical functionalization (e.g., for defining hydrophobic barriers for spatially resolved fluid transport) is well advanced and will be covered by other groups in this book, understanding the impact of the paper material itself on the performance of paper-based diagnostic devices is still a challenge. Yet, only if we understand the latter from a fundamental point of view, more advanced and successful paper materials for such applications may become available. This book chapter outlines principles of paper manufacture; it thereafter reviews important paper chemistry aspects, and finally highlights recent developments on how engineering the morphology and chemistry of paper sheets gives us more insight into fundamentals on the role of the material itself in paper-based diagnostic applications.

A flotation process and two different heat treatment processes prior to pulping were investigated according to their ability to remove mineral oils. For flotation, a correlation between removal of mineral oils and inorganic particles could be found for all process chemicals used in this study. By optimization of chemical concentration and dosing sequence, up to 80% of mineral oils could be removed while keeping the total losses smaller than 15%. The heat treatment processes achieved mineral oil removal rates that were in some cases even higher than those for flotation. For these processes, the most important parameters appeared to be the specific energy applied, the temperature, and the particle size distribution of recovered paper components. However, the specific energy consumption was quite high.

We study the dielectric relaxation in paper of different density and in microcrystalline cellulose in a temperature range between 150 K and 350 K. Qualitatively the spectra display the same relaxations α, β, γ. An additional relaxation, βwet, is found in humidified samples. The adsorption of water is determined and related to the humidity of the surrounding. Two adsorption processes are identified as primary and secondary adsorption at the hydroxyl groups in the amorphous domains of the cellulose. The γ process in the dielectric spectrum is found to be directly related to the amount of water adsorbed in the sample. While qualitatively the differences to unprocessed, microcrystalline cellulose are negligible, quantitatively the less localised β-relaxation shows an increased relaxation strength induced by the geometrical confinement and orientation effects due to the processing into cellulose fibres. While the manufacturing process leads to paper with different density and porosity there is no significant change in water uptake, structure or dynamics.

The paper industry is the industry with the third highest energy consumption in the European Union. Using recycled paper instead of fresh fibers for papermaking is less energy consuming and saves resources. However, adhesive contaminants in recycled paper are particularly problematic since they reduce the quality of the resulting paper-product. To remove as many contaminants and at the same time obtain as many valuable fibres as possible, fine screening systems, consisting of multiple interconnected pressure screens, are used. Choosing the best configuration is a non-trivial task: The screens can be interconnected in several ways, and suitable screen designs as well as operational parameters have to be selected. Additionally, one has to face conflicting objectives. In this paper, we present an approach for the multi-criteria optimization of pressure screen systems based on Mixed-Integer Nonlinear Programming. We specifically focus on a clear representation of the trade-off between different objectives.

Calcium carbonate provides good optical properties to graphic paper and is relatively inexpensive. Therefore, the use of calcium carbonate for the production of paper has steadily increased. But the high amount of calcium carbonate in paper for recycling and the closure of water circuits leads to a high concentration of calcium ions in the process water of paper mills. The consequence can be undesired precipitation and deposition of calcium carbonate in machines and plant components of the mills. Enhanced knowledge about the precipitation potential of calcium carbonate is needed to avoid or reduce undesired precipitation and deposition. The potential can be described using the Langelier saturation index (LSI). Our investigations showed that a deposition of calcium carbonate only happens if the LSI value is higher than 0.5. An LSI value above 0.5 often exists in process water that is treated in a biological effluent treatment plant. Reasons for such values are the increase in hydrogen carbonate concentration (m-alkalinity) by carbon dioxide production and the increase of the pH value by reduction of fatty acids. With the knowledge about the precipitation potential of calcium carbonate in a process water line, suitable measures could be implemented.

Optical microscopy has long been recognized as a method to characterize the heterogeneous and complex structure of paper. With fluorescence detection, the functionality has even been extended to provide chemical selectivity, e.g. to determine the distribution of secondary modifications like coatings and fillers throughout a sheet of paper. The full spectrum of capabilities offered by fluorescence microscopy, which is able to deliver information with high spatial, spectral, radiometric, and temporal resolution simultaneously and non-destructively, however has yet to be exploited. With paper more and more coming into focus as a versatile platform for the development of functional devices, static structural and compositional information is no longer sufficient to describe the properties of these systems. Rather, a likewise versatile method is required that delivers spatially resolved, quantitative, sensitive, and, most importantly, also dynamic measurements. Here we show that quantitative widefield and confocal fluorescence microscopy are able to meet this set of demands. In a proof of concept analysis on PMMA-modified microfluidic paper substrates, we exploit all four types of resolution provided by fluorescence microscopy, by analyzing the distribution of rhodamine labeled polymer in relation to calcofluor white labeled cellulose fibres with high selectivity and spatial resolution and by imaging the static and dynamic distribution of a FITC labeled dextran solution inside the polymer coated fibre network.

Laboratory tests were performed to assess the influence of various digital prints and packaging paper products on the quality of deinked pulp. Boards and digital prints were dosed to a certain percentage in basic mixtures of offset printed newspapers and offset and rotogravure printed magazines. After pulping, the fiber suspensions were treated in a single step flotation process and the deinked pulp was characterized by optical properties. Effects on optical properties of deinked pulp are presented. Each proportion of 4% corrugated board in a basic mixture of recovered paper results in a 1 point loss in luminosity of the deinked pulp. The luminosity decrease corresponds with increasing degree of printing ink on the board. With increasing proportions of corrugated board, a shift in the color locus and increased filtrate darkening were observed, simultaneously. All effects were smaller for boxboard than for corrugated board. The negative impact of digital prints in a basic recovered paper mixture in terms of luminosity of deinked pulp was greatest with inkjet printed newspapers. A proportion of 30% inkjet printed newsprint results in a luminosity drop of almost 7 points, combined with a shift of the color locus into the green area. Regarding liquid toner prints in the basic mixture of recovered paper, a significant increase of the total dirt speck area from 200 mm²/m² to 1100 mm²/m² was observed after a single laboratory flotation process.

The need for deinking mills to reduce their fresh water consumption has resulted in higher loads of various contaminants in the process water. Lower recovered paper quality also leads to higher contamination levels in the mills. This higher load has an influence on achievable target brightness. The objective of the work was to determine and explain the main reasons for relatively poor deinked pulp quality or poor deinking potential based on the influence of recovered paper composition and process water quality. The process water parameters significantly affect the deinking potential of recovered paper. The test results showed the negative effects of increased water hardness. For standard recovered paper mixtures, flotation selectivity is higher with increasing flotation pH-value. Good results were realized for standard recovered paper with low hardness, low surface tension, and high pH-value. The results for recovered paper containing flexo newsprint could be slightly improved with low hardness, low surface tension, and low pH-value. The results of the test program using design of experiments showed interacting effects of pH-value and surface tension on luminosity and flotation selectivity.

Zusammenfassung Die interne Strukturbeschaffenheit von Papier spielt in den meisten Anwendungen eine wichtige Rolle. Um die Struktureigenschaften von Papier zu untersuchen messen wir die totale Reflexion sowie die totale Transmission im MIR mit Hilfe einer Ulbrichtkugel. Die modellbasierte Auswertung der Messdaten liefert die optischen Strukturparameter μ s und μ a . Diese zeigen deutliche Unterschiede zwischen den Proben, was durch die Quecksilberporosimetriemessdaten bestätigt wird. Die Kombination der beiden Messtechniken ermöglicht die Einsicht in die Strukturveränderungen von Papier während der Trocknung.

In the present study, we introduce a novel approach to control and modulate fluid transport inside microfluidic papers using lab-engineered paper sheets. Lab-sheets consisting of different fiber sources (eucalyptus sulfate and cotton linters pulp) and varying porosities were designed and further modified with small millimeter-scaled channels using hydrophobic barriers consisting of fiber-attached, hydrophobic polymers. The capillary-driven transport of an aqueous solution was monitored visually, and the influence of parameters such as fiber source, paper grammage, and channel width on the flow rates through the channel was investigated. The experimental results were compared with those obtained with commercially available filter papers. Our findings suggest that accurate control of fluid transport processes with standard filter papers is complex. Additionally, if the channel width is smaller than the mean fiber length, flow rates become dependent on the geometric parameters of the channel because of the formation of dead-end pores at the hydrophobic barriers. Finally, control of the paper sheets porosity, by varying the fiber density of the lab-made paper, affords the fabrication of chemically identical sheets whereby capillary flow is largely influenced and can be modulated accordingly by simple papermaking processes.

A test method for simultaneous contactless measurement of lateral contraction and change in thickness of paper in tensile testing is presented. All the investigated paper samples showed transverse shrinkage as well as an increase in thickness during loading. Consequently, in-plane Poisson’s ratios for different tested papers were positive, whereas Poisson’s ratios in thickness direction had negative values. In general, the transverse shrinkage proved to be detectable while the resolution and accuracy of the thickness determination in some cases still requires optimization.

The material behavior of two different types of paperboard was characterized in tensile tests and in a new test device called paperboard bulge test. A particularly adapted hydroforming process was used to produce three-dimensional paperboard structures. Furthermore, an online measurement device to describe the mold-filling behavior is introduced. The experimental results were compared to the results obtained with an FEA investigation. The investigations showed the possibilities of the new forming process, as well as the advantages of FEA methods used to pre-define the process parameters.

Beim Recycling von graphischem Altpapier bilden Druckfarben einen wichtigen Anteil an den zu entfernenden Verunreinigungen. Vor allem die wasserbasierten Druckfarben stellen hier eine Herausforderung dar. Ziel dieser Untersuchung war die Entwicklung einer neuen Flotationstechnologie, die diese Druckfarben entfernen konnen. Es wurde untersucht, ob spezielle Schaume, die als Mikroblasen bezeichnet werden, zu nutzen sind. Die Mikroblasen wurden durch Rotation einer Scheibe in einem Gefas mit speziellen Stromstorerstrukturen erzeugt. Dadurch wurden die optischen Eigenschaften von Prozesswassern deutlich verbessert und es konnten zwischen 60 – 90 % der enthaltenen Feststoffe abgetrennt werden. During the recycling of graphic paper products printing inks make an important part of the impurities which must be removed. Especially water based printing inks are challenging. The aim of this investigation was the development of a new flotation technology that can remove water based printing inks. It has been investigated if special foams, called micro bubbles, can be used. The micro bubbles are generated by a rotating disk in a beaker with special baffles included. By using this technology the optical quality of process water samples could be improved and between 60 – 90 % of all solids could be removed.

As opposed to effluents from chemical pulp production, very little is known about the endocrine potential of papermaking effluents. To evaluate the endocrine potential of biologically treated effluents from the main grades produced in Germany (fine, graphic and packaging papers), 16 samples were studied by means of the Recombinant Yeast Estrogen Assay (R-YEA). 10 samples were tested positive; seven of them were effluents from recovered paper processing mills. Possible sources of endocrine disruptors in addition to wood components include papermaking chemicals, paper converting chemicals, if recovered paper is used, and/or detrimental substances introduced by impurities in these chemicals. Six of the above samples were subjected to individual substance analyses to detect endocrinologically active or potentially endocrinologically active substances. Even though phthalate compounds were detected in concentrations between 0.46 and 2.36 μg/L, only two of the six samples were tested positive in the R-YEA, because the test fails to adequately detect this compound's class. Despite this drawback, the R-YEA will be used for further studies because of the great variety of potential endocrine substances present in paper mill effluents. In particular, mechanical and recycled fibre pulps as well as the constituents of chemical additives must be investigated in more detail.

Klebende Verunreinigungen, sogenannte Stickies, stellen ein erhebliches Problem beim Altpapierrecycling dar und fuhren zu Ablagerungen an Maschinenteilen, Produktionsausfallen und steigenden Ausschussanteilen. Zur Reduzierung dieser Probleme soll ein neuer Prozess etabliert werden, der Stickies mithilfe von Pflanzenolen oder Olsaure aus der Faserstoffsuspension entfernt. Zudem sollen die Kenntnisse aus den diskontinuierlichen Laborversuchen auf einen kontinuierlichen halbtechnischen Prozess ubertragen werden. Tacky contaminants, the so-called stickies, cause considerable problems during paper recycling, e.g., deposits on machinery, production downtimes and increased production waste. In order to reduce these problems, a new process will be implemented which is able to remove stickies by means of vegetable oils or oleic acid. Furthermore, the potential for a continuous process in pilot plant scale is investigated.

The scattering of focused laser beams by arbitrarily shaped dielectric bodies is investigated theoretically. The beam description is based on Davis third-order beam approximation for the field components. The scattering problem can be solved on a spherical basis by the extended boundary condition method or by the so-called modified version of the extended boundary condition method. For spheroidal particles with small eccentricities, a perturbation technique for the internal subproblem of the extended boundary condition method is described. This procedure is applied to analyse the influence of the particle shape and orientation on the response of a phase-Doppler system.

The objective of this paper is the development of a pattern classification system for the automatic analysis of the composition of samples from paper for recycling. The system uses a colour video camera and dynamic scales as sensors. An overall number of 26 features of the categories weight, shape, colour, texture and amount of optical brighteners are extracted to distinguish between ten classes of paper for recycling. Five classifiers of different types are trained and tested with industrial samples. During testing a piece of paper is assigned to the class most common among the five classifiers, but the classification success rates lie under 50% for some classes and are therefore not acceptable. For this reason, the system is modified to discriminate only between six of the ten classes. For those classes, the classification success rates lie between 94% and 100% which is suitable for the analysis of samples from paper for recycling.

Paper for recycling is the most important fibre raw material of the German paper industry. 16.3 Mio t of paper for recycling was utilised in 2010 corresponding to 72% of the total fibre raw material input for paper and board production. In comparison to the used virgin fibre-based chemical and mechanical pulp, the utilised amount of paper for recycling is about 2.6 times higher.

Thanks to multiple recirculation of process water, the German paper industry has succeeded in decreasing the specific fresh water demand from an average of 50 m3/t thirty years ago to 13 m3/t today. Although the increasing closure of white water loops creates many problems, it is bound to be part of the German paper industry's ongoing development. For a few years, in the production of packaging paper, two paper mills have been running with a totally closed water system including different process water treatment plants as ‘kidneys’. This paper presents a comprehensive survey of the pros and cons of closed process water systems followed by significant examples of effluent-free production of corrugating medium and test liner. Additionally, operation experiences and economic aspects are discussed.

Sedimentation of organic fibres and inorganic particles can be observed in several industrial applications. Fibres are involved not only in wastewater treatment but also in other separation applications. In the paper industry, the separation of inorganic filler and coating particles from short cellulose fibres is still a challenge in the recycling process. During that process, particles have to be removed to obtain a purified fibre suspension. These fibres can be used again to produce new paper. With the currently applied techniques, like screening and flotation, the efficiency of short fibre separation is very poor. Moreover, also separation by sedimentation fails due to similar settling velocities of heavy-small particles and the light and larger fibres. This paper concentrates on the sedimentation of organic fibres and inorganic particles in water. The investigated suspensions are made by resolving two different and specially produced papers a coated and an uncoated one, as well as the single components used for its production. We observe a different sedimentation behaviour according to the concentration of fibres and particles in the suspension and the pH-value of it. The main result is that, according to the fibre rate, the sedimentation behaviour is particle dominant or fibre dominant.

We explore the application of terahertz spectroscopic techniques for the remote determination of the water content of paper. The aim is the development of a rapid diagnostic imaging tool applicable in paper fabrication processes. THz radiation offers a high sensitivity for water, a good spatial resolution, and insensitivity to scattering at the paper surface. The advent of THz cameras makes fast large-area image detectors feasible. In this paper, we show for the case of a 0.6-THz fixed-frequency system, that the water content of paper can be determined with high accuracy. We demonstrate a quantitative (calibrated) method for determining the moisture content in paper based on extinction and phase measurements in the lower THz range with a spatial resolution in the mm-range and scanning times below two minutes.

In the present study, the surface chemistry of fibres from different sources (groundwood, cotton linters, eucalyptus sulphate and a mixture of pine sulphate and spruce sulphate) was initially assessed via inverse gas chromatography. Significant differences were revealed among the four fibre types, especially between groundwood and the other three with regard to the surface energy and to the specific component of the work of adhesion of different polar probes. Moreover, the freeness value and the specific surface area of the diverse fractionated and unfractionated fibrous materials were investigated. In addition, the porosity and the pore size distribution of lab engineered paper sheets produced with the previously mentioned fibre sources were studied while modifying the fibre length and grammage. Novel approaches to modulate and control fluid transport in the lab-engineered paper substrates were introduced by using different fibre sources with the same freeness value, by fractionating the fibres before fabricating the paper substrates, and by changing the orientation of the fibres. The experimental results for our lab-engineered paper substrates and commercially available filter paper were compared with each other. Our findings suggest a considerable improvement in liquid transport velocity of tailor-made microfluidic paper based analytical devices with lab-engineered paper substrates. By altering the mentioned fibre and paper values, we managed to reduce or raise the capillary rise, which eventually allows us to modulate and control fluid flow in a more accurate and desirable way. Finally, changes in the fluid transport for paper substrates laid on materials with different water contact angles were tested. The obtained information thereby provides an alternative method to increase or decrease the capillary rise.