Showing papers in "Appita Journal in 2006"

Papermaking potential of Acacia dealbata and Acacia melanoxylon

Abstract: The pulping and papermaking potential of Acacia dealbata and Acacia melanoxylon were studied using Eucalyptus globulus as a reference. Pulp yield, alkali consumption and delignification in the kraft process, of both species, compare very well with the reference. Pulp yield can be higher than that of E. globulus and the residual lignin content lower after cooking, which is in good agreement with the lower lignin and extractives content of the wood samples used. Pulps produced from Acacia have slightly lower fibre length and coarseness and higher fibre width and wet fibre flexibility than E. globulus pulps. As a consequence of fibre characteristics, the paper produced from Acacia is denser and exhibits higher tensile and burst strength, and lower tear resistance than that from E. globulus, at a given PFI revolution.

Enzymatic Treatment to Increase the Reactivity of a Dissolving Pulp for Viscose Preparation

Abstract: Enzymatic treatment to increase the reactivity of a dissolving pulp for viscose preparation

Estimation of Whole-tree Wood Quality Traits Using 'Near Infrared Spectra' from Increment Cores

Abstract: There is worldwide interest in the potential of eucalypts for fibre production. Selection of the most suitable stock for propagation is important and many wood quality traits related to pulp production are measured. Effective evaluation requires rapid, inexpensive and preferably non-destructive techniques. Near infrared (NIR) spectroscopy provides a rapid method for evaluating a range of wood quality traits but studies are generally limited to the evaluation of whole-tree properties requiring destructive sampling. In this study we compare calibrations for wood quality traits obtained using whole-tree data and NIR spectra obtained from milled wholetree composite chip samples, and 5mm diameter increment cores non-destructively sampled from 0.65m and 1.30 m. Increment core and whole-tree composite calibrations provided similar results indicating that calibrations based on increment cores can be used to estimate wood quality traits on a whole-tree basis. Of the two heights investigated 1.30m was identified as the most suitable height for nondestructive sampling.

Alkaline peroxide mechanical pulping (APMP) of oil palm lignocellulosics : Part 2. empty fruit bunch (EFB) responses to pretreatments

Abstract: Selected properties of oil palm empty fruit bunch, EFB, and modified EFB were studied in order to prepare EFB for Alkaline peroxide mechanical pulping, APMP. The EFB surface was first desilicated - mechanically without washing, mechanically with subsequent washing and mechanically with subsequent washing and demineralisation, yielding EFB-1, EFB-2 and EFB-3, respectively. For treatment leading to EFB-3 84% silica was removable, apparently by dislodging the silica at metal-localised areas. EFB-2 was examined for its responses to soaking in both mild sodium hydroxide and water Ultraviolet-visible spectrophotometric analysis of the spent liquor revealed complementary results to spectrophotocolorimetry of the treated EFB-2 in terms of changes in the chromophoric behaviour.

Specific contact area and the tensile strength of paper

Abstract: The Page equation for tensile strength of paper is widely and successfully used but has the disadvantage of having a number of variables that cannot easily be estimated or measured. Whilst it is possible to separate tensile strength into fibre strength and bonding strength components, the problem of whether a change in strength is due to increased bonded area or increased bond strength is still difficult to address. This paper suggests a variable change in the Page equation allowing existing measurement methods to be used effectively to separate these effects. A series of experiments using standard papermaking treatments to influence tensile strength are described. Data from these experiments are used to illustrate how the change made to the Page equation can be applied to provide insights into the mechanism of strength development.

The potential for bagasse pulping in Australia

Abstract: Despite the large quantity of sugar cane grown in Australia, no bagasse is pulped in the country. This is largely because of an established pulp industry based on the abundant native hardwood resources. However, increasing demand for fibre and the limited availability of additional forest areas make bagasse pulping attractive. Technical issues relating to manufacture, infrastructure and pulp quality are discussed and scenarios of acceptable risk identified. It is shown that there should be scope for the production of market bleached bagasse pulp in Australia.

Studies on three new environmentally friendly chelating ligands

Abstract: In a search for environmentally friendly metal chelating ligands the protonation and complex formation equilibria of N-bis [2-(1,2-dicarboxyethoxy)ethyl] aspartic acid, N-bis[2-(1,2-dicarboxyethoxy)ethyl]-glycine and N-bis[2-(1,2-dicarboxyethoxy)ethyl]-methylglycine with Mg(II), Ca(II), Mn(II), Fe(III), Cu(II), and Zn(II) in aqueous 0.1 M NaCl solution were studied at 25 C by potentiometric titration. The model of the complexation and the stability constants of the different complexes were determined for each metal ion using the computer program SUPERQUAD. With all metals the complex formation was dominated by stable MLn-6 or MLn-5 complexes. The performance of these new complexing agents was studied in a TCF bleaching of eucalyptus pulp (E. Globulus) via a sequence O-Q-P1-PAA-P2.

The Effect of an Anionic Polymer Additive on Fractionation of Paper Pulp

Abstract: The effects of a fibre surface modification by a CMC chemical on fractionation of LWC furnish in pressure screen and hydrocyclone were studied. CMC adsorbs on the fibres and modifies their fibrillar surface, which affects their mechanical and hydrodynamic behavior. Due to the adsorption on fibres and the small amounts of CMC used, the effect of CMC on the pulp water viscosity was negligible. The fractionation results showed that long chained, low charge density CMC changed the operation point of the pressure screen (i.e. changed the reject thickening factor at constant volumetric reject rate) toward less fractionating conditions and increased capacity. The reason for the capacity increase was suggested to be the decrease of the friction in fibre-fibre contacts, which caused a decrease in fibre network strength and consequent easier break up of flocs, facilitating the passage of fibres. The operation point of hydrocyclone fractionation was changed toward more thickening and thus more fractionating conditions. The efficiency of fractionation was also increased, because CMC enhanced the specific surface differences of fibres by selective sorption to cellulose surfaces. Due to fibre surface modification, the addition of an anionic polymer enhances the pressure screen and hydrocyclone fractionation by increasing capacity or fractionation efficiency. If CMC is used, it may be beneficial to dose the chemical prior to fractionation at a paper or board mill.

Fibre and sheet properties of Acacia and Eucalyptus

Abstract: Three market hardwood pulps; one acacia of Indonesian origin (Acacia mangium) and two eucalyptuses of Iberian and Brazilian origin were refined in an industrial conical refiner. Fibre properties were evaluated using image analysis and microscopy and the drainage characteristics and handsheet properties were related to the differences in fibre properties. The main difference between the acacia and the eucalyptus was that the acacia had thinner fibre walls. The acacia fibres also had fewer defects. The water retention value, WRV, (but not the SR-number) was a good measure for fibre bonding and correlated with the Z-strength. WRV and fibre defects explained the differences observed in strength and stiffness. Acacia showed a higher apparent sheet density, a higher surface smoothness and a lower air permeability than the eucalyptus. In spite of the lower bulk of the acacia the bending stiffness was similar for all three pulps. The light scattering ability of the acacia was about 10 units higher, due to its thinner fibre walls.

Removal of Non-process Elements from Hardwood Chips Prior to Kraft Cooking

Abstract: The major part of the intake of non-process elements (NPEs) to the pulp mill is via the wood chips. Some of the problems associated with NPEs are for example, precipitation of sparingly soluble calcium salts in the fibre line and in the recovery department. In order to investigate the possibilities of reducing the intake of NPEs via hardwood chips to the pulp mill, laboratory studies on the acidic leaching of birch and eucalypt chips were carried out. The results showed that potassium, magnesium and manganese were removed from both wood species at similar rates. The removal of calcium was however significantly slower from eucalypt than from birch. Removal of NPEs from birch wood chips prior to cooking resulted in a higher rate of delignification, a higher unbleached brightness and a higher viscosity. In the case of eucalypt, acidic leaching had no effect on the rate of delignification. The positive effect of acidic leaching of birch chips was found to be due to a lower content of calcium in the cooking stage.

White pitch deposition and styrene-butadiene- rubber binder content in paper mill process waters

Abstract: In order to investigate the mechanisms behind white pitch deposition in actual mill environments we developed two program-monitoring techniques: A spectrophotometric method for styrene-butadiene-rubber qualification and an acoustic technique. We are able to access the mechanisms by using these techniques.

A Novel Method to Evaluate Fibre Hornification by High Resolution Thermogravimetric Analysis

Abstract: Fibre hornification was evaluated by a parameter termed 'hard-to-remove (HR) water content', which was defined as the ratio of water mass to fibre mass at the transition between the constant rate zone and the falling rate zone from the isothermal TGA experiments. The results indicated that the HR water content could be used as a measurement technique for fibre hornification, showing a close correlation with the WRV over repeated drying and wetting cycles. As expected, fully bleached kraft pulp fibres demonstrated a much larger decrease in the HR water content upon experiencing multiple drying and wetting cycles than did mechanical pulp fibres. This thermogravimetric analysis could be used as a convenient and insightful characterization technique for a fibrewater system and allows for the direct comparison of fibres at small amount of sample size, about 10 mg of dried mass.

Controlled penetration of starch and hydrophobic sizing agent in surface sizing of porous materials

Abstract: Controlled penetration of starch and hydrophobic sizing agent in surface sizing of porous materials

Bleaching, Brightness Stability and Chemical Characteristics of Eucalyptus grandis-bio-TMP Pulps Prepared in a Biopulping Pilot Plant

Abstract: Biopulping brings several benefits including pulp strengthening and energy savings in mechanical pulping However, during mechanical pulping, biotreated wood chips undergo some thermal degradation reactions resulting in the darkening of the biopulps In this work, E grandis was biotreated in a 50-ton biopulping pilot plant and used to produce TMP pulps Bio-TMP pulps were significantly darker (44% ISO) than control-TMP pulps (60% ISO) Optimization of bleaching indicated that, despite being darker than control pulps, bio-TMP pulps gained more brightness points at a defined peroxide charge However, the final brightness of biopulps was always lower than the brightness of control pulps, whatever the peroxide charge used (73% and 68% ISO for control and biopulps, respectively, by using one-stage-bleaching with 5% hydrogen peroxide) Photo- and thermal-reversion tests were performed on bleached TMP and bio-TMP Bio-TMP was more stable during the first hours of photo yellowing than control-TMP (Figure 2A) For example, bleached bio-TMP with initial brightness of 63% lost 18 brightness points after 1 hour of photo-reversion, while control-TMP with the same initial brightness lost 24 points during the same period However, prolonged photo-reversion resulted in similar brightness values for both pulps Milled wood lignins extracted from studied samples were analyzed for molecular weight distribution, Mw values for bio-TMP (6390 gmol{-1}) being lower than control-TMP (8264 gmol{-1}) UV/Visible spectra of MWL samples showed increased contents of quinone-like groups in MWL from biotreated wood and bio-TMP {1}H-NMR data on these lignins indicated a higher abundance of protons from aromatic and/or alpha-beta unsaturated structures in bio-TMP than in control-TMP In general, data on characterization of MWLs from biotreated wood and bio-TMP pulps indicated that the chromophores responsible for the lower initial brightness of bio-TMP pulps were quinone or alpha-beta unsaturated-type structures that are susceptible to H{2}O{2} bleaching, which could explains the easy restoring of biopulp brightness using only slightly higher H{2}O{2} dosages

Visualization and characterization of high resolution 3D images of paper samples

Abstract: X-ray micro-(computed) tomography (X-{Mu}CT) combined with image analysis allows visualization and characterisation of the 3D structure of porous materials such as paper and board. This study applied high resolution (res. - 1{Mu}m) phase contrast synchrotron radiation. 3D images of three distinctly different paper grades were obtained to test the applicability of the technique. The applied high resolution phase contrast mode allows 3D imaging of the detailed paper structure in both dry and soaked conditions. The paper samples were visualized and characterized by a variety of image analysis routines. The visualization and characterization confirm that the technique does have a resolution sufficient for preservation of the topology and thus obtaining reasonable measures of 3D characteristics. The measurements rank the paper grades correctly for all measured properties and reveal detailed information of the 3D structure and transport properties.

Quantification of macro and micro stickies and their control by flotation in OCC recycling process

Abstract: Stickies contained in the recycled waste paper cause serious deterioration of product quality and paper machine runnability if they are not removed or controlled appropriately. To understand the stickies problem it is necessary to determine the amounts of macro and micro stickies in samples taken from various places in the papermaking processes. The effect of process modification or chemical additives on stickies control can then be evaluated. In this study, macro and micro stickies contained in linerboard stocks were measured to evaluate stickies removal efficiency of various process units, especially flotation, and to evaluate the benefits of using 3-ply forming technology to overcome sticky deposits on a Condebelt dryer. A reliable test procedure for measuring micro stickies was developed for the study. Screens and cleaners were found to be best for removing macro stickies and flotation was found to be best for removing micro stickies. Application of 3-ply forming with flotation for micro stickies removal enhanced linerboard quality and paper machine runnability.

Potential of Acacia Species as Pulpwood in Thailand

Abstract: The available Acacia plantations in Thailand are based on Acacia mangium, Acacia crassicarpa and Acacia aulacocarpa. For this study 4 to 8 years old A. mangium and 7 years old A. crassicarpa and A. aulacocarpa were selected. Basic densities of Acacias were mostly in the range of 400 to 530 kg/m3. Density is slightly increasing with ageing, but the formation of heartrot is reducing it often. The fibre length (length weighted) of A. mangium was typically in the range of 0.60 mm for 4-year old trees to 0.75 mm for 8-year-old trees while the fibre lengths of A. crassicarpa and A. aulacocarpa were somewhat higher (0.98 mm). The coarseness was typically 0.065 to 0.075 mg/m. The lignin contents of all Acacia samples were 26 to 28 %. The total extractives were rather high (5 to 6 %).

The effect of wood extractives on pulp properties of maritime pine kraft pulp

Abstract: The effect of wood extraction before pulping on pulp properties, namely the unbleached pulp colour and its bleachability, was evaluated by carrying out kraft cookings after extractive removal of maritime pinewood. The colour of the pulps thus obtained was compared to a reference pulp prepared without any wood extraction. The wood chips were extracted using different non-swelling and swelling organic solvents, as well as an alkaline solution. In the case of organic solvent extractions, acetone and ethanol-toluene appeared to be the most efficient, since ensuing pulps showed an increase in the reflectance factor by up to 7.5%. For wood alkaline extraction, the results obtained showed improvements of 10% in the reflectance factor of unbleached pulp. The pulp bleachability was studied by applying a short DE bleaching sequence. The pulps from extracted woods showed increments in the reflectance factor of more than 30% compared with the reference.

Fractionation of CMC-modified hardwood pulp

Abstract: ECF-bleached hardwood pulp was treated with carboxymethyl cellulose (CMC) under specified conditions. The CMC-modified pulps were then fractionated in a hydrocyclone and DDJ (Dynamic Drainage Jar) apparatus and the different fibre dimensional properties of the reject and accept fibre fractions were determined with three commercial analysers. The reject fibre fractions in general had greater fibre length, width and coarseness than the accept fibre fractions. In addition, the cell wall thickness and curl value of the accept fractions were lower than those of the corresponding reject fractions. The internal strength of handsheets made from the reject fractions was about twice the strength of sheets made from the accept fractions, although the CMC contents of the accept fibre fractions were higher. One explanation for the differences in strength properties between the fractions could be that the reject fibres, in spite of their greater coarseness, are more flexible due to their higher fibre width to cell wall thickness ratio. Another important observation was that sodium and calcium salts should be added to pulp prior to the sorption of CMC to obtain the strongest possible handsheets.

Characterising the floc size distribution of flowing pulp suspensions : from fibre flocculation to sheet formation

Abstract: The floc size distribution of pulp suspensions flowing in a flat channel is determined by image analysis (binary morphology). Among tested statistical distributions, the Weibull distribution is the best descriptor for floc size distribution, over a wide range of papermaking conditions: hardwood/softwood mixtures with consistency ranging from 3.5 to 9.5 g/L and estimated shearing level ranging from 240 to 960 s-1. Results are analysed in terms of shape and scale factor of the model distribution and floc coverage in the image. Then, the corresponding sheet formation index is calculated, using the Farnood et al floc layering model at various inspection sizes. It is shown that the relationship between the flocculation index and the calculated sheet formation index is not expected to be linear.

Comparison of size distributions of lint particles from different printing operations

Abstract: Linting is the removal of material from the surface of newsprint grades during offset printing. Excessive linting leads to a reduction in image quality and can reduce press productivity. In this paper, the length and size distributions of lint from a large four-colour commercial web offset press, a small single-colour commercial sheet fed offset press and a laboratory pick test were measured. The lint removed on the large commercial press at the first colour was smaller in both area and length than at application of the last colour. The lint removed in the last printing station of the large commercial press had similar distributions in area and length to the lint removed in the small commercial printing press. The area and length of the lint removed in the small commercial press did not depend on the tack of the ink. As was expected, the pick test removed far more lint than either commercial press. The length and area of the lint was also far larger than the material removed as lint on the commercial press. This disparity between the size distributions of the lint produced in the commercial and laboratory pick test suggests that the results of the pick test cannot be assumed automatically to be relevant to linting in commercial offset printing.

The Characterization of Polyamide Epichlorohydrin Resin in Paper - Relationship between Beating Degree of Pulp and Wet Strength

Abstract: The polyamide epichlorohydrin resin (PAE) in paper was characterized by confocal laser scanning microscope (CLSM), scanning electron microscope equipped with energy dispersive X-ray (SEM-EDX) and Xray photoelectron spectroscopy (XPS). PAE in paper sheet was selectively stained with sulforhodamine 101 acid chloride. Pulp fibres were stained with acridine orange. The distribution of PAE in the paper could be observed by CLSM with this double stain technique for the first time. The amount of PAE in paper was quantified as the relative intensity (Os Mα/C Kα) by SEM-EDX after PAE was selectively modified with osmium tetra-oxide (OsO4). The amount of PAE on paper surface was estimated from the relative intensity (N1s/C1s) by XPS. The amount of PAE in paper hardly changes in spite of increasing the beating degree. However, the amount of PAE on paper surface decreased with the increase in beating degree.

Addition of Dissolved Wood Components to Improve the Delignification Rate and Pulp Yield in Hardwood Kraft Pulping

Abstract: This study investigates the effects on the rate of delignification, HexA content and pulp yield of dissolved wood components (DWC) in the cooking liquor during the kraft pulping of Eucalyptus urograndis. The cooking was carried out with and without the addition of 50% DWC, in the form of black liquor, and also with and without the addition of a lignin-like model compound using a so-called constant composition cooking technique. The results show that the presence of DWC leads to an increase in the rate of delignification which makes it possible to reach kappa number 18 with an H-factor 40% less. Due to the faster delignification, 20% less HexA was formed at kappa number 18 when DWC was added than in the absence of added DWC. The presence of DWC also leads to a yield increase of up to two percentage points measured as lignin-free yield.

Influences of Fatty Acid Anhydride Components Present in AKD Wax on Emulsion Stability and Paper Sizing Performance

Abstract: The role of fatty acid anhydrides present as one of the by-products in commercial alkylketene dimer (AKD) waxes was studied in terms of AKD emulsion stability and paper sizing performance. Wax emulsions were prepared from mixtures of AKD waxes synthesized under different conditions and fatty acid anhydrides with various weight ratios, and subjected to stability tests and handsheet-making. Content of fatty acid anhydrides in total waxes varied from 5 to 45%. The presence of fatty acid anhydrides had little influence on ζ-potentials of the emulsion particles, sizing performance or AKD retention behavior in producing handsheets containing AKD emulsions. However, the emulsion stability as measured by a temperature-shock destabilization treatment clearly decreased with increasing content of fatty acid anhydrides in the waxes, and there were clear increases in emulsion viscosity, particle size and scum weight.

A New Method for Determining the Shear Stiffness of Corrugated Board

Abstract: Amethod has been developed to evaluate the quality of the board used in the manufacture of corrugated boxes. This method can be used by the board manufacturer to monitor and minimise damage occurring during the board and box manufacturing processes. The MD shear stiffness of corrugated board has been shown to be a good measure of damage to the fluted medium in corrugated board. It has also been used as an indicator of the general performance of the corrugated box. This new method of measuring shear stiffness is based on torsional stiffness and is quick, reliable and repeatable. The torsional parameter is termed 'Dynamic Stiffness' and the instrument called a 'Dynamic Stiffness Tester' (DST). The board torsional stiffness has been shown to be directly proportional to MD shear stiffness. This paper outlines the theory behind the tester, gives typical results for a range of corrugated board grades and demonstrates the effect of various degrees of board damage.

Control of Bagasse Pulp Quality by Fractionation and Refining

Abstract: This study examines the possibilities of using fractionation followed by refining as a tool to improve the homogeneity of bagasse pulp quality and to overcome its drawbacks in papermaking, for instance its poor drainability. In pressure screen fractionation, long and coarse fibres go to the reject fraction, while short fibres and fines tend to be directed to the accept fraction. The reject fraction was compared to original unfractionated pulp in terms of fibres properties and the consolidation of the fibre network during filtration. The reject fraction forms a more open fibre network, reaches higher consistency faster during filtration and carries a higher structural pressure compared to the original unfractionated bagasse pulp. The reject fraction and unfractionated pulp were refined in a Voith laboratory refiner at the same refining levels. Fibres (R100) separated from the refined reject fraction were found to display greater swelling ability (measured as FSP) and more external fibrillation than similar fibres separated from unfractionated refined pulp. Sheets made from the reject fraction have a higher tear index than sheets made from unfractionated pulp when compared at a certain sheet density. On the other hand, due to their lower fines content, sheets made from the reject fraction show low light scattering potential. A small amount of the accept fraction was added to softwood fibres before refining to enhance the Scott bond - light scattering combination of softwood pulp.

Performance of sericite as a pigment for coating paper

Abstract: Sericite is one of the rare naturally swelling layered minerals that expands its volume when immersed in polar liquids. It possesses a high degree of negative charges on its platy surfaces and a high aspect ratio. These traits could make the mineral a suitable water retention agent and viscosity modifier for coating colours. Because of its platy structure and the swelling and delaminating characteristics, coated paper containing the pigment has greater surface strength, faster ink drying times, and improved opacity. The purpose of the study was to investigate the effects of substituting sericite for a portion of the delaminated clay in an art paper coating colour formulation on the optical and printing properties of the coated paper, so as to understand the role it plays in coating colour formulation and the characteristics of sericite-containing coated paper. The experimental design simulated a typical art paper coating colour formulation, with 2 variables of sericite types (oxalic acidtreated, SA; and plain water-washed sericite, SB) and various replacement levels of sericite for delaminated clay in the formula.

The Appearance of 'White' Papers

Abstract: When attempting to rank the appearance of 'white' papers, technicians and marketers alike are confronted by at least four combinations of ISO-sanctioned measurement options. One can measure either whiteness or brightness as the colour parameter, and the equipment can be calibrated to emulate either Illuminant C or Illuminant D65. This has been a subject of debate for many years, but measurement of a set of 36 office papers showed the choice of parameter and illuminant actually made little difference to ranking. Overall assessment of appearance requires consideration of a third variable, such as red-green tint. When the entire sample set was laid out in whiteness rank order, the variations from sample in lightness and tint were sufficient to almost over-ride any sense of ranked order. In the context of product design, these observations raise the choice of colour from a simplistic pursuit of CIE Whiteness value to a consideration of which colours actually look attractive in a range of lighting conditions. Paradoxically, the product design problem becomes both more technically sophisticated, and more subjective.

Imbibition into Model Calcium Carbonate Coatings of Fluids with Different Dipole Moments

Abstract: A model calcium carbonate coating has been developed for the study of fluid imbibition in paper coatings. Using four different coating color formulations, four model coatings were created under continuous shear and vacuum dewatering in a rheometer. The characterization of the model coatings shows that they mimic commercial coatings well with respect to pore size, porosity and surface roughness. Imbibition trials were performed with six different fluids. Contact angle measurements enabled volume changes, spreading diameter and penetration depth of the fluids to be studied. It was shown that the filling of the pore matrix is dependent on the dipole moment of the fluid and that some voids in the matrix remain unfilled. A fluid with a high dipole moment penetrated further into the pore matrix than a fluid with a low dipole moment.

Optimising High-consistency Refining Conditions for Good Sack Paper Quality

Abstract: High-consistency refining theory originally developed for mechanical pulps can also give insight into how process and refining variables affect the paper-making potential of chemical pulps. We carried out a well-controlled high-consistency refining trial to Examine the impact of both refining intensity and refining energy on tensile energy absorption (TEA) and air permeability, properties that are essential for good end-use performance of sack kraft papers. The results showed that target requirements for both high TEA as well as good air permeability can be met when refining intensity is kept within the range of 0.025 - 0.061 kW h/odt per impact and specific refining energy is in the range of 350-500 kW h/odt.