A thermally active polymer, ethyl hydroxyethyl cellulose (EHEC), was evaluated with respect to its ability to generate temperature-induced interactions between components in coating colors. At low temperatures the polymer is water soluble, providing a good flow behavior to the color. As the temperature is raised a phase separation of the polymer takes place, inducing an interaction between the components in the color. Rheological measurements showed that using EHEC as thickener resulted in a significant temperature-induced viscosity increase of the coating color. The increase in viscosity was found to be a result of interactions taking place between the three-component system consisting of EHEC, latex and pigment. The increase in viscosity with increasing temperature was further shown to correlate with the styrene/butadiene ratio in the latex. It was also found that a higher amount of EHEC was adsorbed on English clay than on ground calcium carbonate. This affected the degree of interaction within the three-component system EHEC-latex-pigment, in that the increase in viscosity with temperature was lower when English clay was used. However, when delaminated US clay was used, a strong temperature effect was detected.

An Ultrasound Velocity profiling (UVP) technique is used in this study to investigate the pipe flow of pulp suspensions in the near wall region. Four flow rates and two consistencies were investigated: 1.9 and 4.8% (w/w) consistency. The mean velocity profiles showed a distinct plug at the centre of the pipe, surrounded by a sharp velocity gradient. The plug size increased with increasing consistency or decreasing bulk velocity. The demodulated echo amplitude (DMEA) profile slowly rises from low values near the wall to a distinct maximum at the plug front before slowly decaying towards the pipe centre. Since only the fibres and fines contribute to the attenuation of ultrasound, the demodulated echo amplitude profiles thus indicate and support the hypothesis of the existence of a consistency profile in the near wall area, with a decreasing amount of fines and fibres close to the pipe wall.

The effect of the contact time between cationic polymers (polyacrylamides and cationic starches) and stock on retention and dewatering has been studied using a new type of equipment. Dewatering is carried out under low pressure and the addition of chemicals and other operations are controlled by a microprocessor. The retention often shows a maximum after a polymer contact time of 10-20 s. It is found that long contact times drastically reduce the effect of the added polymer. This is explained as being due to floc rupture, degradation of the polymer and poor reflocculation. The dewatering time is extremely sensitive to the polymer contact time and increases steadily with increasing contact time.

The ionic nature of the components in coating colors is of great importance for the presence or absence of interparticle interactions, which in turn largely govern coating rheology, machine runnability and final paper properties. In the present study two types of starch have been evaluated with repect to their effect on these properties. The aim was to generate different association conditions in coating colors by using anionic or cationized starch, which show clear differences what comes to interaction with anionic clay pigment. Another objective with the study was to evaluate the influence of temperature on the pigment suspensions. Rheological and dewatering measurements were performed and correlated to results from pilot scale coating. It was found that the anionic starch caused a stabilization effect originating from the repulsive forces created between the starch and the equally anionic clay pigment. This colloidally stable system caused no problems in the levelling of coating on the paper, but resulted in a relatively dense coating layer. Starch with substituted cationic groups showed a strong electrostatic interaction with the clay pigment resulting in an aggregated coating system and deteriorated runnability. This was reflected in the final coating as blade streaks due to build-up of coating deposits on the blade during levelling. However, the aggregated coating system resulted in a structured coating layer with a high porosity, which may be desired when printing the coated paper. An increased temperature had a marked effect on the aggregated coating color in terms of a significant decrease in viscosity, while the temperature had a more limited effect on the stable system containing anionic starch. This behavior was also seen in the properties of the dry coated layers, where the open structure of the aggregated color was more affected by a higher temperature than the stable color.

Model studies on a dried ink particle suspension without fibres show that the kinetics of the ink agglomeration are totally dependant on the soap particle precipitation and formation. The calcium soap has to precipitate before the ink and soap particles can agglomerate. Calcium ions have two important effects on ink agglomeration: the precipitation of soap and the reduction of the surface potential on the ink particle surface. The importance of free fatty acid anions adsorbed onto the ink particle surface is negligible, since the fatty acid is almost completely precipitated as calcium soap.

Methods combining micro scale resolution x-ray shadow graphs, computerised x-ray micro-tomography and advanced image analysis were developed to study connections between the structure of void space and raw edge imbibition in liquid packaging board. Imbibition roughening was analyzed from 2D shadow graphs by a dynamic interface recognition algorithm. An idea of investigating flow paths in cardboard samples using potassium iodine in water solution as contrast enhancement substance was introduced. For demonstrating the potential of the tomographic methods, numerical lattice Boltzmann permeability simulations were performed. Experimental measurements were conducted to compare and support the results extracted from tomographic data. A 3D void space segmentation algorithm was utilized to analyze structure of void space in tomographic reconstructions. Tentative results indicate that the new methods can be used to find correlation between pore size heterogeneity and imbibition roughening. Finally, water absorption coefficients of the test samples were calculated utilizing results extracted from the void space segmentation analysis.

The local film formation of latex in model paper coating suspensions of low latex to CaCO3 volume fraction ratio, 0.27, has been studied using both topographic and phase images of atomic force microscopy. Local film formation is believed to work concurrently with latex migration. Both the dosage and molecular weight of carboxymethylcellulose (CMC) have a visible effect on latex film formation. A greater dosage of CMC retards latex migration and a higher molecular weight of CMC prolongs the film-formation process. Another thickener, ethyl(hydmxyethyl)cellulose (EHEC), was compared to CMC, and EHEC creates a composite where deformed latex particles are encapsulated in EHEC. A higher Tg latex increases the amount of latex in the upper region of the coating. It is suggested that a lower Tg latex halts migration, which leads to film formation at an earlier stage, further down in an evaporating pore

The compressional rheology of cellulose fibre suspensions has been studied using a pressure filtration technique. The dewatering of these systems is thus described in terms of various key properties of the suspension, including the compressive yield stress, permeability and solids diffusivity, permitting a quantitative characterisation of the consolidation process. We investigate as a particular example the effect of a commercial debonding agent additive on the compressional properties of a fibre suspension. Such agents are commonly used in the production of hygiene products where they are added to decrease the strength of fibre-fibre bonds. Here we investigate their effect on the compressive response of fibre suspensions as an example of how measurements of this type can be used to characterise the effect of additives on bulk properties. The results indicate that addition of debonder causes a somewhat higher dewatering tendency as the solids level is increased.

Experimental papers with varying alkylketene dimer load were prepared and characterized with respect to size retention, reaction and hydrolysis. The characterization was done by using extraction studies, in combination with X-ray photoelectron spectroscopy and gas chromatography. The surface energy of the produced papers was evaluated using the Good–Oss method. It was shown that by stepping up size additions, both the polar and van der Waals components of the surface energy are reduced.

Dynamic Fourier Transform Infra-Red (FT-IR) spectroscopy was used to examine the effect of a low sulphonation treatment on the ultrastructure of the primary cell wall of spruce wood. Sheets made from enriched primary cell wall material coming from a low sulphonated thermomechanical pulp were used for studying the viscoelastic response of the polymers using dynamic FT-IR spectroscopy. The overall ultrastructure of the primary cell wall remained largely unaltered, due to the exceptionally low degree of sulphonation used. However, an increased softening of the material as well as a weakening of the lignin;pectin, lignin;protein and pectin;protein interactions were observed. The suggestion is that, together with a structural modification of the lignin, it is the increased viscoelasticity of the material, resulting from the breaking down of the interactions among the polymers, that is the cause for the lower energy demand, when refining correspondingly low sulphonated chips.

The surface energetic properties of different areas of the offset printing plate are the key factors of this printing process, since they control the ink transfer during printing. The importance of these factors is discussed for both waterless offset and conventional offset. The printing process is highly dynamic. New surfaces are created and their lifetimes are short. From recent theories of dynamic wetting, it has been concluded that spontaneous removal of ink films from nonimage areas is a very slow due to the high ink viscosity and the low dynamic contact angle. Thus it is of less importance.

The wetting and absorption properties of internally sized paper sheets with differing alkyl ketene dimer (AKD) load were investigated using a numberof wetting and absorption tests, including dynamic contact-angle measurements and dynamic surface-penetration and edge-penetration measurements. Special attention was paid to the spontaneous spreading dynamics of water drops at the surface of the paper. Pure water and aqueous surfactant solutions were used as wetting liquids. The experiments were carried out at several different temperatures. It was shown that AKD-sized papers revealed a large wetting hysteresis indicative of nonuniform size distribution.Wettability of both sized and unsized paper increased with temperature, but the effect was significantly smaller than expected. At elevated temperatures, gas-phase vapour transport played a significant role in water pickup by paper. Surfactant-enhanced wetting and sizing loss are discussed. The experimental results obtained are scrutinized within a theoretical framework developed to model the absorbency of paper.

The feasibility of a novel type of surfactant-templated mesoporous silica particles as pigments in inkjet paper has been evaluated. The surfactant-templated mesoporous silica pigments with small pores and narrow pore size distribution were investigated, and compared to a typical silica gel with larger pores and broader size distribution. The surfactant-templated pigments required significantly lower amounts of binder and gave improvements in colour richness and sharpness, relative to the silica gel pigment.

This paper discusses the effect of alkyd resin composition on the emulsification of fountain solution into heat-set printing ink oil. Data on interfacial tension and initial droplet size are reported. The initial droplet size of emulsions formed by mixing fountain solution and printing ink oil containing alkyd resin is strongly dependent on concentration and type of alkyd resin. Addition of non-ionic surfactant to the aqueous solution decrease the fountain solution - oil interfacial tension but have no significant effect on droplet size. Addition of isopropyl alcohol to the aqueous phase resulted in smaller droplets. Higher concentrations of isopropyl alcohol gave smaller droplets. The interfacial tension between water and oil containing alkyd resin decreases with alkyd resin concentration and polarity. This suggests that the alkyd resin orients at the interface with polar groups in the water and apolar segments in the oil. The alkyd resin then acts as an emulsifier and stabilises the emulsion.