Bleached Kraft Research Articles

"EFFECTS OF DIFFERENT RATIOS OF STARCH-CONTAINING AKD ON PAPER PROPERTIES IN INTERNAL SIZING OF VARIOUS PULP TYPES "

The main objective of this study is to determine the effects of different ratios of starch-containing AKD emulsion in various pulp types sizing processes on paper properties. A secondary objective of the study is to evaluate the influences of starch content in AKD emulsion and AKD dosage applied to pulps. Three different pulp types were sized: unbleached kraft, bleached kraft and chemithermomechanical pulps. In preparation of AKD emulsions, three different ratios of starch were used. AKD was applied to all pulps under the same conditions at four different dosages based on oven-dried fiber weight. Test papers were produced and Cobb values (water absorptiveness), some mechanical and optical properties of the papers were determined. In addition, SEM, XRD and contact angle analyses were applied to papers produced with optimal sizing parameters. As a result of the study, it was found that the effects of AKD cause different behaviors depending on the pulp types. AKD was highly efficient in sizing chemithermomechanical pulp, decreasing the Cobb value by 90.9%. Depending on the pulp type, the starch content used in the emulsion preparation and the AKD dosage applied to the papers have various effects on the paper properties.

RECYCLING OF WET-STRENGTH TISSUE PAPER. PART 2. BASIC PROPERTIES OF SECONDARY FIBERS

The present investigation focuses on morphological characteristics, tensile and optical properties of secondary fibers obtained in various conditions of batch low-consistency repulping process for wet-strength tissue paper with 100% of bleached softwood kraft pulp. It was found that length-weighted fiber length and fiber width values as well as fiber length and fiber width distributions remained almost unchanged regardless of the repulping time and the presence of persulfates. The shortened repulping cycle due to the use of persulfates lead to an increase in the shape factor from 83.0% to 84.1–84.4%, decrease in the number of fiber kinks from 0.84 to 0.72–0.74 and an increase in zero-span tensile strength of recycled handsheets by 10–12%. At the same time, the shortened repulping cycle resulted in increase in the coarseness of secondary fibers from 190 mg/m to 230–235 mg/m leading to a slight increase in the bulk of the paper and a decrease in its internal bond strength by an average of 8%. The use of persulfates during wet-strength tissue paper repulping improves the color of recycled handsheets and its brightness by up to 3%.

Bacterial nanocellulose and softwood pulp for composite paper

Abstract: Scaling biosynthesis of bacterial nanocellulose (BNC) allowed samples of composite paper with an increased proportion of BNC to be obtained. This work aims to study BNC samples and bleached soft wood kraft pulp (BSKP) composite paper with a ratio of components varying across a wide range: 10:90, 30:70, 50:50, 60:40, 70:30, 90:10. The method of paper manufacturing was chosen based on the determinations of strength and deformation properties of composite samples with the BNC:BSKP ratio of 20:80. Surface application of BNT on BSKP handsheet provided for an increase in the strength values (tear resistance – by 37%, burst index – by 17%) and deformation characteristics (tension stiffness – by 66%, fracture work – by 8%, breaking length – by 4%) compared to a reference sample. The formation of composites is confirmed in all samples. Scanning electron spectroscopy revealed that paper composites comprise interlaced micro BSKP and nano BNC fibres. As the proportion of BNC in composites elevated, densification of the structure was observed due to an increased fraction of cross-linked nanosized elements. IR spectroscopy indicated the resemblance of cellulose structure in all samples. It was found that an increase in the degree of polymerisation of composite paper is directly proportional to an increase in the BNC amount in the samples. The filtering ability of composite paper samples against microorganisms in the culture liquid of the Medusomyces gisevii Sa-12 producer was studied. It should be noted that yeast retention is achieved with 70% BNC in the paper composite. The presented properties of the new material determine prospects for its use in filtering microorganisms.

Evaluation and Optimization of Kraft Delignification and Single Stage Hydrogen Peroxide Bleaching for Ethiopian Sugarcane Bagasse

ABSTRACT The current study investigated the Ethiopian sugarcane bagasse during its delignification using the Kraft pulping process and bleaching by single stage hydrogen peroxide process. The multilevel categoric experimental design was used to appraise the effects of the independent process variables (temperature, NaOH concentration, and time) on the pulp yield and kappa number during the Kraft pulping process. The central composite experimental design of response surface methodology was used to appraise the effects of independent bleaching variables (bleaching temperature, H2O2 concentration, and time) on the pulp yield, brightness, and whiteness during the bleaching process. The optimal pulp yield was 38.41% with 17.68 kappa number. The bleached pulp yield for the pulp with kappa number of 17.68 and the pulp with kappa number of 8.41 were 84.12% and 83.91%, respectively. The brightness and whiteness for the pulp with kappa number of 17.68 were 61.92% and 85.36%, respectively. Similarly, for the pulp with a kappa number of 8.41, the brightness and whiteness were 68.35% and 91.43%, respectively. Paper from the pulp with kappa number of 17.68 has higher tensile, burst, and tear strength. The study shows the promising utilization of the Ethiopian sugarcane bagasse for paper production via the Kraft delignification and single stage hydrogen peroxide bleaching.

Potential of bleached eucalyptus kraft pulp for applications in nonwoven fibrous fabrics

A series of six industrial bleached hardwood kraft pulps produced from Eucalyptus globulus (BEKPs) under variable process conditions were dry-defiberized on a pilot scale hammermill at 3500 rpm and the nonwoven air-laid fabrics evaluated for their specific volume, absorption capacity/absorption rate and fiber network strength. The effect of non-defiberized fiber aggregates (knots) on the former properties was evaluated. Processual variations in pulping and bleaching conditions revealed variability within 15% in the absorption capacity of fluff pulps and within 25% in the network strength of the air-laid formulations. These variations were attributed to changes in the chemical composition of BEKPs and fiber morphology. The importance of pulp bleaching sequence on the quality of BEKPs for fluff applications was highlighted. BEKPs, having a high residual xylan content with a greater amount of uronic/hexenuronic moieties and coarser/deformed fibers, revealed the best performance in fluff applications. The coarseness was considered a critical morphological parameter of the fibers, strongly affecting the porosity of air-laid formulations, which determined the absorption capacity and the network strength. The absorption capacity of fluffed BEKP was comparable of commercial bleached softwood kraft pulp (BSKP), although the latter showed almost triple the network strength of air-laid formulations produced with BEKP. BSKP proved to be much more vulnerable to dry defiberization conditions than BEKP and suffered a pronounced cut of fibers, producing larger amounts of fines (dust) and stronger undesirable peeling and straightening of fibers. BEKPs can be considered a promising raw material for fluff applications, whose basic properties can be adjusted according to the needs by varying conditions in the pulping and bleaching process steps.

The effect of reaction wood on bleached eucalypt kraft pulp production – Part I

The effect of reaction wood on bleached eucalypt kraft pulp production – Part I

Biochemical methane potential of kraft bleaching effluent and codigestion with other in-mill streams

A biochemical methane potential assay was conducted to investigate the anaerobic digestibility of bleaching effluent from hardwood kraft pulping and the potential of codigestion with other effluents from an integrated pulp and paper mill. Four in-mill streams were tested individually and in combination: total bleaching effluent, alkaline bleaching effluent, kraft evaporator condensate, and chemithermomechanical pulping effluent. The total bleaching effluent, consisting of the chlorine dioxide bleaching and alkaline bleaching effluents, exhibited the highest potential for organic matter degradation and methane generation. Chemical oxygen demand (COD) removal ranged from 57%–76%, and methane generation was 220–280 mL/g COD contained in the wastewater, depending on the degree of dilution. When codigestion was tested, the composite consisting of total bleaching effluent, chemithermomechanical pulping effluent, and kraft condensate was most efficient in terms of COD removal (51%) and methane generation (200 mL/g COD contained in the wastewater). The total bleaching effluent is the largest contributor to the overall amount of wastewater at this mill; it contains relatively low concentrations of anaerobic inhibitors such as adsorbable organic halogens (36 mg/L), total sulfur (170 mg/L), and resin and fatty acids (3.2 mg/L). Therefore, the total bleaching effluent from hardwood kraft pulping may be considered for full-scale anaerobic wastewater treatment, either as a singular stream or as part of a composite stream including other in-mill effluents.

Study of Paper Transverse Shrinkage During Thermal Drying

The z-direction shrinkage of laboratory papers made of bleached softwood kraft pulp subjected to drying was studied. The results showed that shrinkage was dependent on the beating level of the pulp and independent of wet pressing in the range explored. The low-basis-weight sheets had greater specific volumes than the higher-basis-weight ones due to the greater relative importance of the superficial layers compared to the bulk, but their transverse shrinkage was smaller.Empirical correlations were proposed to model the thickness results as a function of moisture content for their interest in computational simulation of drying including shrinkage.

Study on Application as Cigarette Paper Dry Strengthening Agent of CPAM Emulsion

Homemade water in water cationic polyacrylamide (CPAM) emulsion was applied in cigarette paper pulp as dry strengthening agent with other strengthening agent. Good collaborative effect was achieved when CPAM was used in bleached wheat straw pulp with strengthening agent E and with cationic additives L as paper pulp strengthening agent. It was also showed that distinct strengthening effect was obtained when CPAM emulsion was applied in mixture of bleached needle kraft pulp (NBKP) and wheat straw pulp, breaking length and tearing index of cigarette handsheet made of mix pulp was respectively increased by 22.2% and17.0% when the dosage of CPAM was 0.8% of dry fiber. Through analysis of cigarette handsheet section scanning electron microscopy (SEM) photos, strengthening mechanism of CPAM emulsion to cigarette paper pulp was preliminary studied.

Conductive pulp fiber sheet-prepared waste newspaper pulp fibers treated by electroless nickel plating and its electric field shielding effect

In order to explore new applications of recovered waste paper, we prepared electrically conductive fibers by plating waste newspaper pulp (WNP) fibers. Further, we mixed them with unplated WNP fibers and filtered the mixture to obtain a conductive pulp fiber sheet, which was to be used for electromagnetic compatibility (EMC) purposes. For the plating of WNP fibers, we used an electroless nickel plating method. We also plated pulp fibers recovered from fine paper, pulp fibers recovered from milk carton, and bleached softwood kraft pulp fibers, which were used for comparison with the plated WNP fibers. All of the four types of plated, recovered waste paper pulp fibers had high conductivity, i.e., an electrical conductivity of 0.1 S/m or more and a conductance of 0.02 S or more. The conductive pulp fiber sheet made of WNP fibers had an electric field shielding effect of 30 dB or more at 10–1000 MHz, provided that the ratio of the plated WNP fibers in the sheet was 40 % or more. Therefore, our conductive WNP fiber sheet is effective in EMC.

Study on the Acrylic Resin Coating Agent Modified by Nanocrystalline Cellulose

In this paper, nanocrystalline cellulose (NCC) was prepared from bleached aspen kraft pulp by the method of sulfuric acid hydrolysis. The morphology and the size of NCC were characterized by atomic force microscopy(AFM) and X-ray diffraction(XRD). The acrylic resin /NCC composite was prepared by physical blends of acrylic resin and NCC. The physical-mechanical properties of the film from acrylic resin /NCC composite were measured . The results show that the resulting NCC has a rigid rod-shape structure with crystallinity of more than 80%, 26.51 nm in diameter and 200―400 nm in length. The dosage of NCC has important influnce on the physical-mechnical properties of the film from acrylic resin /NCC composite. The tensile strength, the moisture permeability and water absorption of the film increase with the dosage of NCC notably, the elongation at break of the resulting film decreases compared to the control sample..

Pengaruh Penambahan Substrat Organik Pada Limbah Klorinasi Pabrik Kertas Terhadap Pembentukan Gas Methan Dan Penurunan Senyawa Klorin

Kraft mill bleaching process is some significant source of chlorinated organic compounds. In this process, wood pulp is bleached using plant specific sequence of chlorination with chlorine and extraction with alkali. The waste water from chlorination of Kraft bleaching contains many toxic compounds that very difficult to be removed by conventional activated sludge treatment. Adding an organic substrate will affect the methanogenesis. The aims of this study are: (1). To remove adsorbable organichalide (AOX) by anaerobic treatment, (2). Toexamine the effect co-substrates to methanogenesis, such as methanol and glucose, (3). To know the effect of sterilization to decrease of AOX. The result is AOX can be removed anaerobically with or without co-substrate.

Advanced oxidation process H2 O2 /UV combined with anaerobic digestion to remove chlorinated organics from bleached kraft pulp mill wastewater

This study investigated the application of an advanced oxidation process combining hydrogen peroxide with ultraviolet radiation (H2 O2 /UV) to remove recalcitrant compounds from Kraft bleaching effluent. Anaerobic pre-treatment was performed to remove easily degraded organics using a horizontal-flow anaerobic immobilized biomass (HAIB) reactor. Bleaching plant effluent was treated in the HAIB reactor processed over 19 h of hydraulic retention time (HRT), reaching the expected removal efficiencies for COD (61 ± 3%), TOC (69 ± 9%), BOD5 (90 ± 5%) and AOX (55 ± 14%). However, the anaerobic treatment did not achieve acceptable removal of UV254 compounds. Furthermore, there was an increase of lignin, measured as total phenols. The H2 O2 /UV post-treatment provided a wide range of removal efficiencies depending on the dosage of hydrogen peroxide and UV irradiation: COD ranged from 0 to 11%, UV254 from16 to 35%, lignin from 0 to 29% and AOX from 23 to 54%. All peroxide dosages applied in this work promoted an increase in the BOD5 /COD ratio of the wastewater. The experiments demonstrate the technical feasibility of using H2 O2 /UV for posttreatment of bleaching effluents submitted to anaerobic pre-treatment.

High-throughput prediction of physical and mechanical properties of paper from Raman chemometric analysis of pulp fibres1This article is a contribution to the series The Role of Sensors in the New Forest Products Industry and Bioeconomy.

Better pulp quality control, especially relating to product sheet strength, can offer an important means to improve the market superiority of a pulp. However, aside from lignin content, few pulp properties can be easily measured in a timely manner for process control. The present report proves a principle on a novel Raman system and a systematic chemometric approach, allowing for rapid spectral data acquisition and definitive spectrochemical analysis of wet pulp under harsh manufacturing conditions. By incorporating sophisticated chemometrics strategies that combine wavelet transform with a template-oriented genetic algorithm feature selection and partial least squares multivariate classification, this instrument system extracts maximum analytical information from raw Raman spectra to accurately predict the physicomechanical properties of sheet products. Our work has tested and refined these routines by drawing upon the systematic analysis of 26 bleached softwood kraft pulps formulated to yield challenges representative of those encountered in common pulp fibre and sheet analyses. Satisfactory calibration results suggest that a Raman gauge can be developed that has the capacity to continuously assay pulp to predict the physicomechanical properties of sheet paper in real time.

Action Mechanism Analysis of Enzymatic Refining for Bleached Simao Pine Kraft Pulp

Cellulase is potential tool for modification of pulp properties to save energy requirement during refining process. In this paper, bleached Simao Pine kraft pulp was treated with NOV476 cellulase under different enzyme dosage for action mechanism analysis. Pulp viscosity was measured to evaluate the damage of fiber by enzyme. Fourier transform infrared spectroscopy (FT-IR) was performed to study the enzyme treatment on the pulp chemical structure and crystallinity index. The fiber morphology difference before and after treatment was also revealed by the SEM and AFM observation. When the cellulase dosage was lower than 1u/g, the fiber mean length slightly increased. With the further increase of cellulase dosage beyond 1u/g, the fiber mean length was less reduced than the control sample. The fiber mean width increased steadily after enzyme treatment in the dosage range of 0~0.1 u/g. Enzyme treatment did change the fiber chemical structure and crystallinity index through FT-IR analysis. With the increase of NOV476 cellulase dosage, the pulp viscosity decreased steadily. The SEM analysis showed the surface of cellulase treated fiber had some fluffing phenomenon and there was obvious intertexture between fiber and fiber. AFM images further demonstrated that the fiber surface of controlled pulp was covered by primary layer. After enzyme treatment, the primary layer of fiber cell wall was peeled off.

Effect of Ultrasound and Xylanase Treatment on the Physical-Mechanical Properties of Bleached Eucalyptus Kraft Pulp

The modification on the fiber structure of bleached eucalyptus kraft pulp is a very attractive alternative for improve- ments in the properties of paper production. The enzymatic treatment by xylanases and ultrassonic treatments modify the characteristics of the fibers, has been reported. Therefore, the purpose of this study was to evaluate the influence of ultrasonic waves as a facilitator of the action of enzymes (hemicellulase) by modifying the physicochemical nature of fiber eucalyptus Kraft pulp, in order to improve the physical and mechanical properties of the paper. But it was observed the that idea of ultrasound acts as facilitator for action of enzymes can’t be affirmed, since in most properties XA-1 and XA-2 were equal statistically. It may be noted that the junction of ultrasound and xylanase provided improves on tensile index, specific elastic modulus and tensile energy absorption and a decrease of tear index on the mechanical properties of handsheet and it increased the opacity when the ultrasound was applied before xylanase.

Chemical components of bleached eucalypt kraft pulp effluent COD and treatment removal efficiency during normal mill operation and maintenance shutdowns

In order to meet increasingly strict Brazilian COD emissions limits, mills must understand the components that contribute to effluent COD, how these vary between normal mill operation and maintenance shutdowns, and how this variation affects treatment efficiency. To this end, primary and secondary effluents from a Brazilian bleached eucalypt kraft pulp mill activated sludge system were analyzed for COD, lignin, extractives, carbohydrates and AOX over a sixth month period that included two general maintenance shutdowns and four months of normal operation. Primary effluent presented significantly different compositions during periods of normal operation and mill shutdowns. During normal operation, the main components of effluent COD (909 mg/l average) were carbohydrates, followed by lignin. However, the lignin fraction was the main component of secondary effluent COD during both normal operation and mill shutdowns. Higher removal efficiencies for COD carbohydrates and AOX were observed during normal operation compared to shutdowns, while no difference in removal efficiencies of lignin and extractives was observed. Carbohydrate removal efficiency was significantly lower in one of the parallel treatment lines. The different removal efficiencies reflect not only variations in effluent composition, but possibly differences in system operational control which should be explored in greater detail.

Analysis of printing and writing papers by using direct analysis in real time mass spectrometry

A quick and direct method for identifying organic components of papers in library and archival collections with minimal destructive sampling is needed for preservation, forensic, and general purposes. Direct analysis in real time mass spectrometry (DART-MS) is used for characterizing 16 reference papers of known manufacture in terms of their pulp composition and pitch contaminants. Unique mass spectra are obtained from bleached kraft, chemithermomechanical, and stone groundwood pulp papers in real time without extractions, derivatizations, chromatographic separations, and other time- and chemical-consuming sample preparations. Phytosteroids are volatilized from bleached hardwood kraft but not from bleached softwood kraft papers, which differentiates the two of them. The kraft papers are in turn differentiated from chemithermomechanical pulp papers by lignin-derived thermolyis products: syringyl products arise from hardwood, but guaiacyl and coumaryl products arise from softwood, chemithermomechanical pulp papers. Stone groundwood papers contain a number of extractives that are volatilized, which serve to differentiate them from all the other papers. Papers that contain rosin vs. alkyl ketene dimer (AKD) sizings are immediately differentiated. The DART-MS methodology is fast and simple, and the spectra are repeatable. Microsamples as small as ∼10 μg tweezed from the paper surface may be analyzed. These benchmark spectra are the prelude to further applications of DART-MS in paper research and the beginning of the development of a searchable library of DART-MS spectra of printing and writing papers by the Library of Congress.

Preparation and application of cationized pulp fiber as a papermaking wet-end additive

Cationized pulp fibers (CPF) were prepared by the adsorption of a novel biodegradable cationic ester quaternary ammonium salt (31441) on bleached softwood kraft pulp fibers. The optimized conditions for the CPF preparation were: 4% of 31441 (based on oven-dry pulp), 80°C and 30 min. The CPF was characterized by FT-IR, SEM and XPS. Experimental results showed that the CPF improved the retention of precipitated calcium carbonate (PCC) filler significantly. With 0.9% CPF (based on oven-dry pulp), the retention of PCC increased from 57.53% to 72.21%. The physical properties of paper were also slightly improved. The tensile strength and burst strength of the paper with CPF were higher than those with CPAM. CPF addition had no effect on the stock drainage.

The effect of sizing and paper structure on paperboard for retortable packaging

This thesis reports on an investigation of the mechanisms of edge wicking in retortable paperboard. Retortable board is used for packaging preserved food, a process which requires that the package and its contents be sterilised by exposure to high temperature steam for up to three hours. The board used must thus have higher water repellence than traditional liquid packaging. Water vapour that condenses on the cut edges on the outside of the board causes particular concern. The paperboards studied were made from refined and unrefined bleached softwood kraft pulp and from refined unbleached softwood kraft pulp in one or two plies with different sizing levels and structures. Samples of each of the boards were immersed in a water bath at 95 °C. Other samples from the same boards were exposed to a combination of saturated steam at 130 °C and condensed steam in a special apparatus developed for this purpose. The board samples were placed on a cooling plate to simulate the temperature gradient when a container of cold food is sterilised with heated steam. Still other samples were exposed to heated steam in the absence of condensation by hanging them freely in the apparatus. The extent of edge wicking in the boards was determined by gravimetric measurements and also by near-infrared (NIR) spectroscopy, a technique that yields more information about the moisture content profiles and the mechanisms of liquid sorption. The moisture content profiles of boards exposed to saturated steam in the absence of condensation show more uniform water uptake. This phenomenon can be explained by rapid vapour phase transport throughout the pore structure, followed by slower water uptake in the fibres. By contrast, in samples exposed to both heated steam and condensed steam, there was both liquid sorption in the fibre network and rapid vapour phase transport of the steam. The moisture content in those samples was much higher close to the edge and lower behind the liquid frontier. The edge wicking of high temperature water was greatest in board that was not fully sized, in low density board, and in board made from unrefined pulp. The greater edge wicking in board made from unbleached pulp can be accounted for in terms of its greater swelling potential. In the low density board and the board made from unrefined pulp, the lumens at the unsized edge and the weaker bonding strength are suggested to affect the results. Capillary sorption takes place in lumens and delaminated bonds at the edge and then any further propagation takes place entirely by fibre diffusion. Capillary sorption may also be important in damaged areas where broken fibre-fibre bonds are exposed to liquid. The weaker bonded area in low density board therefore also contributes to water sorption. Edge wicking in the boards placed on the cooling plate and exposed to a combination of saturated and condensed steam was of a different nature. For these samples, density was not an important factor. The difference is due to the different mechanism at work in this case, where the relative area of the edge exposed to condensed steam was larger in the high density boards than in the low density boards. In the high density boards, condensed steam was sorbed in the structure by diffusion in the fibre structure, whereas in low density boards, the dominant effect was vapour phase transport in the void spaces followed by water uptake in the fibres.