Properties Of Handsheets Research Articles

Vapor-phase diethyl oxalate pretreatment of wood chips: Part 1. Energy savings and improved pulps

AbstractDiethyl oxalate (DEO) was injected into a digester containing wood chips (pine, spruce, or aspen) preheated to 130–140°C and held for 30 min at the same temperature. When mechanical pulps were produced from these pretreated chips, savings in electrical refiner energy could be achieved. For southern yellow pine (Pinus taeda), the electrical refiner energy required to produce pulps with Canadian standard freeness (CSF) of 100 ml was 38– 55% less than for an untreated control. Energy savings were also observed for aspen (Populusspp.) and spruce (Piceaspp.). DEO-treated pine handsheets showed a 26% improvement in tear index compared with a control at 100 ml CSF. Under the pretreatment conditions de-scribed, DEO rapidly vaporizes, reacts with water already present in the chip, and forms an oxalic acid (OA) solution. Reported handsheet properties and energy savings for pine chips treated with a solution of OA are similar to DEO-treated handsheets. It can be concluded that the effect of DEO treatment is due to reactions catalyzed by OA.

Modelling the role of paper microstructure in electrophotography

We study how paper microstructure heterogeneity affects the electrostatic field acting on toner particles during xerographic printing. We use an efficient multigrid Poisson solver to simulate electrostatic fields. The dielectric distribution of paper is obtained either analytically or input numerically using a recently developed 3D fibre network model of paper. Simulations are used to elucidate the relative importance of paper surface, filler and porosity variations in establishing spatial variations of the electrostatic field. It is found that only long wavelength variations of surface height, bulk filler or porosity variations affect variations in electrostatic transfer forces to any relevant degree. Furthermore, we show that the effect of these long wavelength perturbations can be modelled using a new 1D effective capacitor model. When surface variations and surface filler are mixed together, we found the interesting result that mode mixing can decrease the spatial fluctuations of the electric field. Finally, using simulated 3D paper webs, which mimic the properties of laboratory handsheets, we find that to lowest order surface roughness and not formation is responsible in controlling variations of the electrostatic transfer field, a result of importance in digital printing onto stochastic printing substrates, such as commercial paper.

Kraft pulp from budworm-infested Jack pine

Abstract This study evaluated the quality of kraft pulp from budworm-infested jack pine. The logs were classified as merchantable live, suspect, or merchantable dead. Raw materials were evaluated through visual inspection, analysis of the chemical composition, SilviScan measurement of the density, and measurement of the tracheid length. Unbleached pulps were then refined using a laboratory disk refiner. The mechanical and optical properties of handsheets made from the refined pulps were evaluated. Although budworm galleries may affect the physical integrity of the wood, they have no effect on pulp quality. Blue stain did not affect the handsheet brightness. The results indicate that merchantable dead jack pine trees are acceptable for kraft pulp production, with equivalent pulp yield.

Enhancing Dry-Strength Properties of Kenaf (Hibiscus cannabinus) Paper Through Chitosan

The present study was focused on the effect of chitosan, a linear amino-polysaccharide, on the properties of handsheets made from bleached kenaf kraft pulp. Chitosan was incorporated into the sheets by three distinct techniques, equilibrium adsorption (pH 5), precipitation (pH 10), and spray application. The chitosan dosages tested were 0.5%, 1%, 1.5%, and 2% based on oven dry pulp. Chitosan was found to increase the dry-strength properties of paper such as tear, burst, and tensile index, but its effectiveness was strongly dependent on the method of addition. Spray application gives superior strength properties, followed by equilibrium adsorption. Chitosan is less effective under alkaline conditions. The results showed that chitosan addition improved the mechanical properties of sheets, but the rate of increase in strength properties was higher from 0% to 0.5% compared to 1% to 1.5% regardless of the treatment techniques.

The Optical Properties of Deinked Pulp

Optical properties of handsheets made from pulp resulting from deinking flotation of multicolored and desaturated prints from digital and conventional offset printing have been observed. The prints were made on different models of digital offset machines. One series of prints was naturally aged for the period of one year and the other was accelerated aged in a climatic chamber. The results show that the model of the printing machine, even with the same technology, can affect the size of particles and the optical properties of the handsheet. The quality of deinking pulp and the efficacy of the ink removal in relation to the optical parameters such as brightness, reflectance in the determined areas of wavelengths and color are discussed in this work.

Improvement of paper strength with starch modified clay

AbstractIn order to improve the strength properties of high filler filled papers, a new technique of coating starch on the clay surface was developed. The stability of the coated starch and its effects on paper properties were studied. It was found that the starch coated on the clay surface swelled in water. This swelled starch film on the filler surface contributes significantly to the filler–filler bonding. The strength properties of handsheets made from starch coated clay, even with unmodified corn starch, could be increased by more than 15% versus those from the traditional method of adding cationic or amphoteric potato starch directly to 50% bleached softwood pulp/50% bleached hardwood pulp. This research suggests that the starch coated filler can be used to make high filler content paper products. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 44–50, 2005

Effect of pulping variables with dimethyl formamide on the characteristics of bagasse-fiber

Organosolv pulping of bagasse was conducted following a central composite design using a two-level factorial plan involving three pulping variables (temperature: 190–210 °C, time: 120–180 min, organic solvent ratio: 40–60% dimethyl formamide). Responses of pulp and handsheets properties to the process variables were analyzed using statistical software (MINITAB 14). Using values of the independent variables the variation ranges considered provided the following optimum values of the dependent variables: 82.7% (yield), 92.9 (kappa number), 1.403% (ash), 370 ml (freeness), 6290 m (breaking length), 9.4 (folding endurance), 5.955 mN m 2 g −1 (Tear index) and 2.811 kNg −1 (Burst index) for pulps and handsheets. Results showed that acceptable physical and mechanical properties of pulps and papers similar the pulp used for bleaching could be achieved at 210 °C for 150 min and 50% DMF. These are the most suitable conditions for obtaining paper sheets with a high breaking length, tear and burst indices. Also bagasse could be pulped with ease to about 55.72% yield with kappa number ∼35. The cooking temperature was a significant factor while the DMF ratio and cooking time were not as important in term of the properties of the resultant pulps and papers.

In-mill removal of TMP whitewater contaminants by biological treatment in an aerobic biokidney used in conjunction with microfiltration and laccase treatment

SUMMARY: The suitability of an aerobic in-mill biokidney for purification of TMP newsprint white water was investigated. The effects of microfiltration and laccase treatment on the quality of biologically treated white water were also studied. The biokidney showed high (71-92%) removal efficiency for COD, BOD, carbohydrates and lignans. The removal efficiency was moderate (50-66%) for TOC and TS, and low (25-35%) for lipophilic extractives and lignin-like material while the amount of suspended solids (SS) increased by 67% as some of the biomass from the biokidney went into the white water. Microfiltration of biologically treated white water removed a minor part of the remaining contaminants of TMP origin and the bulk of the biomass from the biokidney. The treatment of biologically treated white water with laccase before microfiltration gave a large improvement in removal efficiency for all contaminants originating from the TMP but the material present in the laccase solution caused an increase in COD, BOD and TS. The biomass-based SS from the biokidney and the dissolved material in the laccase solution had a more detrimental effect on the mechanical and optical properties of handsheets prepared with untreated and treated white water than the wood-based contaminants.

Effect of sorbed galactoglucomannans and galactomannans on pulp and paper handsheet properties, especially strength properties

Effect of sorbed galactoglucomannans and galactomannans on pulp and paper handsheet properties, especially strength properties

The Effect of Mill Closure on Properties of Mechanical Fines

The effect of dissoloved and colloidal substances (DCS) in TMP (thermomechanical pulp) white water on the strength properties of handsheets and the flocculation capability of fines with retention aids were investigated.For this experiment, two types of fines were prepared. One is water-washed TMP fines and the other is white-water TMP fines which were fractionated with TMP white water. Breaking length and surface strength of the handsheets containing water-washed TMP fines were higher than that of the handsheets containing white water TMP fines. It is suggested that DCS adsorbed on white water TMP, fines had a detrimental influence on fiber bonding.The extent of flocculation of fines in the white water of a newsprint machine was measured by Photometric Dispersion Analyzer (PDA). The results of flocculation experiments showed that fines extracted with acetone were more easily flocculated with cationic retention aids than fines in white water. The molecular weight of retention aids affected the flocculation of the fines in white water.It is concluded that DCS has negative effects on sheet strength and on the flocculation of fines with retention aids.

Improvement in pulping and bleaching properties of xylem from transgenic tobacco plants

AbstractIn an attempt to improve the pulping properties of xylem pieces and the bleaching properties of the resultant pulp, we compared two lines of transgenic tobacco in which the biosynthesis of lignin had been altered by suppression of the activity of 4‐coumarate: CoA ligase (4CL). The results of Kraft pulping on a laboratory scale indicated that the xylem of transgenic tobacco exhibited a higher delignification efficiency than that of corresponding controls subjected to the same conditions. This facilitated delignification was accompanied by a high pulp yield, but there was no excessive degradation of cellulose in the pulp fibres. The unbleached pulps from the 4CL‐suppressed tobacco plants were easily bleached with a lower consumption of chemicals than was required for the controls. Furthermore, the strength and optical properties of handsheets prepared from the 4CL‐suppressed tobacco plants were similar to those of handsheets prepared from the controls. Our observations suggest that modification of lignin by genetic engineering of the suppression of 4CL activity should result in both an increased pulping yield and a saving of bleaching reagent.© 2002 Society of Chemical Industry

Direct Effects of Wood Characteristics on Pulp and Handsheet Properties of Eucalyptus globulus

Summary Fibre length, microfibril angle and wood density were measured in eight-year-old Eucalyptus globulus clones planted on three different sites. Samples were chipped and pulped, and the pulps beaten prior to preparation of 60g/m2 handsheets. Eleven physical handsheet properties, together with pulp freeness, were measured using standard methods. Direct relationships between wood properties and pulp/paper properties were studied using path analysis. Fibre length had a strong, direct effect on tear index, bending stiffness, freeness, pulp yield and active alkali consumption. Wood density was a strong predictor of most handsheet properties: high density woods produced bulkier, more porous sheets with higher bending stiffness, while lower density woods produced smoother, denser sheets with higher tensile strength.The effect of microfibril angle was small and more evident in handsheets made from beaten pulp.

リサイクルによる古紙パルプの物性変化について

The utilization rate of wastepaper in Japan has reached 58.0% in 2001. However, the use for printing and communication papers has been limited due to concerns about appearance, strength and brightness. To promote the use of recovered paper for higher-quality grades, it is necessary to understand the fundamental aspects on recycled fiber. This paper describes papermaking potentials of recycled pulp fiber.When a kraft pulp is repeatedly defibrated in water, dewatered and dried for several times, the strength properties of papers, as well as the micro-structure of the pulp fibers, are considerably deteriorated. Morphological changes such as delamination and crack formation in cell wall of pulp fiber are enhanced by recycling treatment. On the other hand, the pore volume in cell wall of pulp fibers determined by the solute exclusion method decreases with recycling. Therefore, the shrinkage of internal pore structure under recycling is not easily reversed. The kraft pulp with a significant decrease in handsheet tensile strength during recycling tends to swell less and reduce their bonding potential.Variations in strength properties of papers during recycling are closely related to the fiber morphological characteristics. The fiber lumen diameter : fiber width ratio is an important predictive factor of strength properties of handsheet during recycling.Remarkable increase in water contact angle of kraft pulp fiber is observed by recycling. The recycled fiber is clearly much less hydrophilic than the virgin fiber. This relates to inactivation of the fiber surface by recycling, which is known as “irreversible hornification”.The deterioration of neutralized recycled paper prepared from hardwood bleached kraft pulp by accelerated aging is similar to that of conventional neutralized paper.

The Importance of Xylan for the Strength Properties of Spruce Kraft Pulp Fibres

Summary In this work the role of xylan in spruce kraft pulp fibres was investigated by selectively removing the pulp fibre xylan and also by sorbing xylan onto the pulp fibres. The effects of xylan removal and sorption on fibre properties were measured and the chemical composition of the fibres and also that of the selectively removed xylans was analyzed. According to the results the xylanase could act on both sorbed and native xylan located on accessible fibre surfaces. Xylan was found to affect the strength properties of handsheets. The location and the charge of xylan had a considerable impact on the formation of interfibre bonds. Scott Bond-values correlated with the amount of surface xylan on fibre surfaces, whereas tensile strength was affected by the total amount of xylan and particularly by the total charge of the fibres. The fracture energy was determined by the combined effect of interfibre bonding ability and effective fibre length.

Lightweight, high-opacity paper by fiber loading: filler comparison

SUMMARY:To comparetheeffects ofcommercialcalciumcar­ bonate fillers on handsheet properties with that of fiber loading, we obtained rhombohedral and scalendrohedral precipitated cal­ cium carbonates (PCCs) and wet and dry ground calcium carbo­ nates (GCCs). These commercial calcium carbonate fillers were selected to cover a wide range of particle diameter and shape. The properties of fiber-loaded handsheets, at 25% filler level, were compared to that of five commercial calcium carbonate samples at the same filler level for two fully bleached market pulps, eucalyptus and pine kraft pulps. Fiber-loaded pulps were shown to be stronger than similar direct -loaded pulps at the same calcium carbonate levels as a result of (1) precipitation of calci­ um carbonate within the fiber wall and lumen and (2) the low energy input refining of the pulp at high pH and consistency. Our results show that fiber loading results in somewhat higher free­ ness values than does direct loading along with higher strength. Brightness values were slightly lower or the same for fiber-loa­ ded handsheets compared to direct-loaded handsheets. Opacity and scattering coefficients were slightly lower for fiber-loaded handsheets, but the higher strengths of fiber-loaded pulps permit an increase in the filler level in the fiber -loaded pulps. Production of fiber-loaded PCC (FLPCC) pulp can be a key factor in develo­ ping lightweight, high-opacity printing papers.

Cellulose Depolymerisation and Paper Properties in E. Globulus Kraft Pulps

The aim of this work was to study the impact of cellulose depolymerisation on the beating potential and handsheet properties of the portuguese E. globulus kraft pulp. A homogeneous sample of eucalypt wood chips was cooked using different kraft pulping conditions (cooking temperatures and times, and sodium hydroxide and sodium sulphide concentrations) in order to obtain a wide variation for intrinsic viscosity of the pulps. In the range of industrial cooking conditions, this property was found to be linearly dependent on the effective alkali charge, for a given cooking time and temperature. Unbeaten and beaten (at 2000 rev. PFI) pulp properties were evaluated and the results confirm that the higher the pulp intrinsic viscosity the better the pulp beatability and the paper properties. However, the differences in the latter cannot be exclusively explained by the differences in viscosity, since pulps with the same viscosity may exhibit distinct papermaking potentials. It was then necessary to scan other pulp chemical characteristics that could also influence the development of paper properties such as lignin, pentosan content and polysaccharides relative composition.

Effects of the laccase-mediator system on the handsheet properties of two high kappa kraft pulps

It has been suggested that the laccase-mediator system (LMS), an oxidative enzyme system, could be used to delignify kraft pulp. A series of scoping experiments found that this enzyme system could have a range of effects on the physical properties of two high kappa kraft pulps, kappa 70 and kappa 94. The mediator itself (1-hydroxybenzotriazole) was found to modify pulp properties. At a low dose, the mediator alone increased handsheet densification. This effect was negated in both pulps when either a low LMS dose or a high mediator dose was applied. There was, however, an increase in the stretch of the handsheets at a given apparent density that may indicate a change in fiber wall structure. For the kappa 70 pulp, the low LMS dose also increased tensile strength at a given handsheet density. All these changes to the physical properties of pulp, along with changes to optical properties, indicated that a degree of lignin modification had occurred during LMS treatment. Most of the LMS-derived effects were masked by subsequent peroxide extraction. Future work should consider examining the effects of laccase without the mediator.

The effect of mannan on physical properties of ECF bleached softwood kraft fibre handsheets

The effect of mannan on physical properties of ECF bleached softwood kraft fibre handsheets

A composite representation of pulp quality

Principal component analysis (PCA) performed on data from pilot scale chemimechanical (CMP) pulping trials indicates that over 90% of the variation in 11 handsheet properties can be expressed in terms of only 4 composite variables. The relaionships between the original properties and the new composite properties are displayed graphically using a biplot of the PCA scores. These techniques are combined to construct a chart capable of monitoring changes in a large number of quality responses simultaneously. Model accuracy can be monitored on the same chart resulting in a tool which will self-diagnose as well as offer a powerful overview of the process.

電子線照射の紙質に及ぼす影響

Low energy electron beam irradiating instruments are applied for surface treatment and paint cure because of their compactness compared with corresponding high energy instruments. As electron beam has higher transmittance than UV light, it is supposed to be suitable for high-speed curing of relatively thick ink film such as intaglio ink film.However, electron beam irradiation causes degradation of organic high-polymer induced by radical reaction, involving the main chain scission and crosslinking reaction of the polymer. In the case of paper, electron beam irradiation decreases degree of polymerization of cellulose and sheet strength.In this paper the effects of electron beam irradiation on the physical and chemical properties of handsheets were studied.Following results were obtained.(1) The fiber strength of the handsheets, given by the wet zero-span breaking length, decreased with electron beam irradiation, while the fiber bonding strengths, as given by Pulmac B factor, wet breaking length and Young's modulus, increased. Besides, the microphotographs of the fractured areas of the handsheets showed that the sheet fracture pattern shifted from the inter-fiber bond breakage mode to the fiber breakage mode.(2) The contributions of the fiber strength and fiber bonding strength to the double folds and tensile strength were determined by multiple regression analysis using the equation T=kFaBbLc (T : Physical property of handsheet, F : Fiber strength, B : Fiber bonding strength, L : Fiber length, k, a, b, c : Parameter). It was found that the decreases of double folds and tensile strength caused by electron beam irradiation are mainly attributed to the decrease of fiber strength.(3) The GPC analysis of the irradiated handsheets showed that the decrease of fiber strength is caused by the decrease of degree of polymerization of cellulose.(4) With high dose of irradiation different kinds of pulp sheets showed similar values of probability of main chain scission, while with low dose of irradiation each pulp sheet showed different value of that.(5) Amount of chemical groups such as aldehyde and carboxyl groups and copper number of the handsheets increased with irradiation.