Volume 27, Issue 4

Birch sawdust was extracted using pressurized hot water (PHW), with the ultimate aim of maximizing the yield of large and intact non-cellulosic heteropolysaccharides, i.e. hemicellulose molecules. The extractions were performed using a flow-through vessel. Effects of different extraction temperatures between 140 and 200°C were evaluated. The amount of extracted xylans, as weil as monosaccharides, increased as the temperature rose to 1 90°C, accordingly the degree of polymerization of the xylans decreased. The extracted xylans retained most of the native acetyl groups and were thereby water-soluble after the extraction. The PHW extract contained not only xylan and other hemicellulose-derived oligomers, but fragmented Iignin molecules and some extractives as well. Only trace amounts of furfurals were found in the extract at lower extraction temperatures. An optimal yield of water-soluble, polymeric xylans with the smallest amount of unwanted impurities and degradation products was thus achieved at an extraction temperature of 1 80°C using the flow-through vessel

A novel fractionation method was developed to characterize nanocellulose in terms of particle size. The fractionation device ues screens or membranes with known size. The scale is in the range of micro to nano, so that NFCs can be size- or shapefractionated accordingly. The procedure is somewhat analogaus to the Sauer-MeNett fiber classifier. The reproducibility of the obtained size profile was very good. The device can also produce size specific nanocelluloses, which could be applied for scientific research purposes, e.g. nano risk assessment. Fractionation with membrane filters was able to screen out almost all particles. However, the membrane permeate contained significant amounts of dissolved substances.

We introduce a new method of processing irregular data rrom any rotating machine, in particular high-consistency pulp refiners. Refiner plate bar forces and rotor absolute angle are acquired synchronously, and a fuzzy gate is exploited to filter instantaneous force events from background noise. Fuzzy gate parameters are partially justified by plate geometry. The method enables the acquisition of quantified and detailed spatial information on refiner plate bar forces, thus supporting the design of more energy efficient refiner plates and bar patterns. The study identifie.s key areas of application for synchronized force analysis in high-consistency pulping research.

The aim of this study was to investigate the influence of lang fibre concentration on Ioadability and pulp properties during LC refming of mechanical pulp. Lang fibre concentration was adjusted to three different Ievels by screen fractionation of the pulp. The three pulps were refined in a single disc pilot scale LC refiner at simi1ar process conditions. Increased lang fibre concentration suppmied a larger refiner gap and resulted in less fibre . cutting at a given specific energy consumption. The higher lang fibre concentration probably contributed to a stronger fibre network that maintained a !arger refining gap at certain specific energy consumption. Increased long fibre concentration also enabled a higher tensile index increase in the LC refmer at certain fibre length reduction. The study supports a process combining LC refining with screen fractionation, where the lang fibre fraction is recycled to the refiner feed. This enables a . higher Ioadability and a more effective utilisation of the LC refiner. By using this technology, overall specific energy consumption can be reduced if a !arger share of the refining is performed in LC rather than HC refining.

Softwood-based kraft mill bleaching effluents from the initial bleaching stages D0 and E1 (the bleaching sequence being D0E 1D 1 E2D2) were treated by the oxidative Fenton method (H20rFeS04) to decompose organic pollutants contammg adsorbable organic halogens (AOX). Experiments designed using the Taguchi method were applied to predict the process conditions that would result in a cost-effective and adequate removal of AOX. In addition to the composition and concentration of the reagents (H202 and Fe2+), the main process parameters selected were temperature and reaction time, while pH was adj usted to an approximate value of 4 (the volumetric ratio of the mixed effluents D0:E 1 was 3 :2). The results indicated that an AOX removal of about 70% for this mixture ( corresponding to about 50% for the mill) was achieved when the eftluent samples were treated for 60 min at 70°C with H202 and Fe2+ at a concentration of 1 600 mg/1 and 28 mg/1, respectively.

The crack area on a coated board was measured after creasing and folding and the crack area on a coated copy paper was measured after folding. A clay pigment and two Ground Calcium Carbonate (GCC) pigments were used. The GCC pigments differed in their particle size distribution. The binder was either an S/B Iatex or an S/B Iatex combined with starch. The type of pigment seemed to have the greatest intluence on the crack area in creased and folded board. Clay showed a !arger crack area than the GCC with a broad particle size distribution. The GCC with a narrow particle size distribution showed a considerably larger crack area than both the clay pigment and the GCC with a broad particle size distribution. The coatings containing starch generally showed a larger crack area than the coatings that only contained the S/8 latex. After the folding of the copy paper, the crack area showed a slightly different pattem. Here, it seemed that the binder was of greater irnportance than the type of pigment, with the coatings containing only latex showing a considerably lower crack area than the coatings containing starch. The coatings that were based on the clay pigment showed similar values as the coatings based on the GCC pigment with the broad particle size distribution. The coatings based on the GCC with the narrow particle size distribution showed displayed considerably higher crack areas than the coatings based on the other two pigments. The cracking tendency of the coatings, based on the GCC with the narrow particle size distributions was probably due to a greater demand for latex, i.e. smaller particles in the GCC with broad particle size distribution would probably fill in the voids and the GCC with the broad particle size distribution will therefore demand less binder. lt was further suggested that the different loadings on the coating layer during the creasing and folding of the board, compared to the folding of copy paper, explain the different results obtained with the two base-substrates.

The aim of this research was to investigate the influence of natural zeolite clinoptilolite used as a filler on the printabi1ity of paper and its print quality. Paper handsheets were prepared with the addition of 20% of fillers, where natural zeolite was added to calcium carbonate in different u.w.% (i.e. 20, 40, 60). Zeolite originates from the sedimentary deposit in Donje Jesenje, Croatia. Zeolite tuff is mainly composed of clinoptilolite. lts particle size distribution is broad and the structure is micro- and mezzo-porous. The addition of natural zeolite as a filler resulted in higher bulk of paper sheets and a more porous structure. Moreover, the absorption capacity and the absorption rate slightly increased. The surface roughness increased, leading to a more hydrophobic surface. Natural zeolite with its broad particle size distribution, higher amount of large particles and yellowgreen colour resulted in slightly lower opacity and ISO brightness of sheets. When used for ink jet printing, the increased amount of zeolite showed a positive influence on the print quality. Smaller wicking and bleeding effects were noticed. Paper hue did not influence the colour density of CMYK prints.

This study examines the impact of paper and printer type on the quality of xerographic prints. Ten different uncoated paper substrates were printed using three different commercial xerographic printers. The print quality of the samples (print microgloss, print microgloss nonuniformity, print density, print and gloss mottle, and visual ranking) and the physical and surface characteristics of the papers were measured. It was found that relationship between print mottle and print gloss nonuniformity was dominated by the printer type. While for some printers, these two parameters were positively correlated, in other cases printer appeared to "mask" variations in the paper properties. Multivariate analysis also showed that brightness, opacity, basis weight, 7 5 ° Tappi gloss, and roughness were the top five paper properties that had the most significant effect on the visual ranking and print mottle. Finally, as expected, print roughness was found to be a better predictor of the perceived print quality, however, paper roughness was poorly correlated with the visual ranking of printed samples (R 2 0.5).

The moist heat (80°C and 65% relative humidity) and light (xenon arc lamp) treatments of accelerated ageing were applied to investigate the colour stability of offset and electrophotographic prints on papers made of virgin and I 00% recycled fibres. The prints were evaluated using spectrophotometric measurements and additional colour differences calculations. In addition to the colour differences, the 2D and 3D colour gamuts are presented. The results reveal the different colour stability of prints. The effect depends on the type of accelerated ageing, printing technique, composition of ink and paper characteristics. Moist heat ageing has less influence on colour stability than light ageing. The electrophotographic prints show better ageing resistance than offset prints. The intluence of ink on print light fastness is considerable. Azo pigments in magenta and yellow have lower light fastness than phthalocyanine pigments in cyan or carbon black. The surface coating has an intluence on light fastness of prints. Meanwhile, prints on recycled papers show similar colour stability compared to prints on papers made of virgin fibres

This work examines the effect of coating pore structure on the evaporation behaviour of mineral oil, as a typical heatset web-offset ink solvent. Two different kinds of coating pigments are compared, a standard ground calcium carbonate (GCC) and a highly porous modified calcium carbonate (MCC) with fine intraparticle pores. The aim is to identify relevant pore structure parameters and their effect on the drying rate. Two internal stages of drying were identified for both structures : a rising drying rate period and a falling rate period. In the rising rate period, the effect of film tlow was of particular relevance for the case of GCC based structures : binder, filling the pore structure decreases the detail of geometry and thus reduces the film flow tendency, progressively depressing the drying rate. At the onset of the falling rate period the liquid phase is in the form of disconnected liquid clusters. Therefore, the diffusion resistance becomes a dominant factor. Because of the high permeability of MCC systems the evaporation rate proofed to be largely unsusceptible to the binder concentration. However, the GCC pigment systems exhibited an extended peak of the drying rate as a result of the increasing diffusion resistance with increasing binder content.

The absorption of liquid into a pore network structure depends on porosity, pore size distribution, surface free energy of the involved phases, and external pressure. In the case of ink setting on coated paper, significant decrease of accessible pore volume can take place due to swelling of latex binder particles when contacted with the vehicle of oil-based ink. The reduction in pore network connectivity can be detected by an optical retlectance measurement procedure based on the refractive index differences between the coating components and the surrounding medium present in the interparticle pores. In this study, GCC mode l coatings with latices displaying differing oil uptake and swelling characteristics were exposed to liquid supersource imbibition without external pressure. Effects of both linseed oil and minerat oil were studied. In the case of free liquid propagation, i.e. in coatings with low content of binders, a linearly increasing trend of logarithmic retlectance gradient in the coating thickness is observed as a function of time, indicating deceleration of the wetting front propagation in consequence of the establishment of the flow resistive viscous factors at long timescales, and the subsequent approach of the saturation point at the wetting front. In contrast, in the case of restricted propagation, due to high binder content of swelling Iatex particles, a deviation of the logarithmic retlectance gradient from the linear trend is observed as saturation is approached. However, the relationship between spatial logarithmic retlectance gradient and liquid uptake per unit cross-sectional porosity continues to follow linear trends irrespective of the binder if the porosity is corrected for the loss due to swelling, thus enabling the effect of the binder on the structure to be studied in isolation.

In the case of ink setting on coated paper, s1gmficant decrease of accessible pore volume of the coating matrix can occur due to structural changes caused by swelling of latex hinder particles when contacted with the vehicle of oil-based ink. The impact of latex swelling, reduced network connectivity and the subsequent effects on the dynamic of spatial liquid distribution characteristics within the expanded pore network were examined by a recently established optical retlectance measurement procedure based on the refractive index differences between the coating components and the surrounding medium present in the interparticle pores. GCC model coatings with latex binders displaying differing swelling characteristics were exposed to liquid supersource imbibition without application of external pressure. Effects of both linseed oil and mineral oil on binder swe lling and consequent structural expansion were studied. lt is proposed that the linear retlectance behaviour in the saturated region is related to the mechanical restriction on expansion at the transition between the saturated and partially filling regions of the porous structure, and is consistent with an approximate catenary form in the macroscopic coating dimensional change as a function of depth. A conceptual structural change factor based on the change of retlectance in the saturated region is introduced, and is shown to correlate with the porosity loss values. The results suggest differences in the structural change factors in relation to the equilibrium oil uptake, coating porosity loss, and liquid propagation. The structural change factor also correlates the reflectance gradient within the coating thickness with regard to oil uptake with hinder content as the binder Ievel is increased.

Model-based optimization is a sophisticated design tool for papermaking processes. In this paper, the method is extended from the unit process design and single-level optimization to the simultaneaus design of the process structure and operations. This is enabled by using a bi-level optimization formulation which allows to avoid unnecessary iterations between the process and automation designs. The bi-level optimization approach is studied here from the perspective of multiobj ective optimization and decision making. The method is illustrated by a case study in which the broke and water system structures and the papermaking process operations are optimized simultaneously.

The three-dimensional velocity field in the single phase approach flow to a multiple layer woven forming fabric was measured using PIV. The measurements were conducted on a scaled-up model of a forming fabric in a water/glycerin flow loop. Each strand on the paper side of the model forming fabric had a filament diameter ( d) of 1 5 mm, and the flow loop test section was 3 1 0 mm squared, permitting the measurement of detailed velocity distributions over multiple strands of the fabric. The flow speed in the loop test section was varied to achieve screen Reynolds numbers between 12 and 6 5 . PIV measurements showed that when the distance t o the paper side of the fabric changes from 0.25d to 1 . 5d, the normalized ZD, CMD and MD velocity deviation decreases from 1 9 .7% to 4 .2%, 1 5 . 3 % to 1 .9% and 1 4 . 5 % t o 2 . 3 %, respectively; the ratio between maximum and minimum ZD velocity decreases from 3 .3 to 1 .2 . These findings indicate that the flow non-uniformity caused by the fabric weave is confined to a short distance above the fabric. CFD simulations of the same flow were consistent with the PIV measurements.

The dewatering ability and wet sheet structure after pressing was studied using a dynamic wet pressing simulator in combination with electron microscopy and image analysis. Deinked pulp (DIP) that contains 5% ash dewaters more easi ly than thermomechanical pulp (TMP) when pressed with single roll pulse. The in-plane moisture flow ( crushing) in DIP samples started at higher peak pressure and higher solids content compared to TMP samples. The TMP sample showed higher springback after wet pressing compared to DIP samples. When both TMP and DIP samples were designed to have a higher amount of small pores at the dewatering side surface layers, the samples with coarser TMP pulp could achieve similar dryness as DIP samples when pressed with higher nip pressure. In addition, the DIP samples with higher number of small pores in the outermost I 0 11m thick surface layer in the dewatering side resulted in lower dryness after pressing with a single roll pulse. The effect of filler distribution in paper zdirection on dryness and sheet structure after wet pressing using an 8 milliseconds roll pulse was also studied. In this study the distribution of filler does not affect the maximum achievable dryness (4 1 %) after wet pressing when the total amount of filler in the sheets remains constant, 1 3 .5%. In addition, the samples with more filler in the dewatering layer dewater more easily and yield the maximum achievable dryness ( 40%) after wet pressing at lower nip pressure (2 . 5 MPa) when compared to samples made from TMP (3 6% at 4.4 MPa) and DIP pulps (40% at 4 . 9 MPa).

This study shows that wet-pressing TMP and DIP with a shoe press pulse may yield similar afterpress solids, provided that an adequate shoe pulse length with similar pressure profile is applied. A wet web with more porous structure in the sheet dewatering (felt) layer seems to contribute to the increased dewatering during wet pressing. In addition, a shoe press pulse with high peak pressure at the end yields higher solids content after wet-pressing and higher bulk compared to a pulse with a peak pressure in the beginning. The increased dewatering during wet-pressing implies a reduction of steam consumption in the dryer.

Calculation of Box Compression Resistance (BCR) is a challenging task and here the possibility of an engineering approach is considered. The strive has been towards obtaining a simple and generat predictive tool with as few parameters as possible and still obtaining an accurate estimate of the BCR. The model proposed is based on the concept of dividing the package into panels and corner panels. With these remarkably few structural elements it is possible to obtain simple explicit formulas where the only material parameters are given by standard tests in terms of short span compression test and bending resistance. The BCR for different packages is then obtained by a simply summation of the load from the panels and corner panels. A validation agairrst experimental data indicates that, despite its remarkably simplicity, the predictions are very accurate for a wide range of package types, package dimensions, board qualities and loading directions.

In this paper, we demoostrate proof-ofprinciple for a low cost paper-based Chromatographie device capable of pre-concentrating a target analyte by a factor of three thousand fold (assessed using confocal Iaser scanning microscopy (LSCM)). The device consists of a capture zone and a passive pump. The capture zone was created by immobilizing biotinylated microgel particles onto a selected area of filter paper. Due to the presence of biotin on their surface, these particles have the ability to specifically bind streptavidin, which was the target analyte selected for this study. With the incorporation of a superabsorbent passive pump, created using cross-linked poly(acrylic acid), partial sodium saltgra. fi-poly(ethylene oxide), the paper-based device was able to process a volume of dilute solution much larger than that associated with paper porosity. Flow through the device, including the passive pump, could be modeled using Darcy' s law. A simple equation was also developed to relate the concentration in the pre-concentration device to the concentration in the dilute sample. This type of device can be useful for sample pre-concentration before analysis using other methods, such as mass spectrometry.