Surface analysis of explosion pulps by ESCA

Summary The oxygen (1s) ESCA peak for aspen explosion pulp consists of two components, O1 and O2. A tentative assignment was made for them. O1 with lower binding energy is assigned to oxygen in lignin; while O2 comes mainly from the oxygen elements in carbohydrates. Thus, an O1 area percentage might be viewed as a measure of lignin exposed on the fiber surface. Sulfur (2p) spectra show that the sulfur on the fiber surface of the pulps studied here is in the form of sulfonate groups. Compared to conventional pulps, the lower percentage of O1 and higher sulfur-to-carbon ratio for explosion pulps imply higher number of hydrophilic groups exposed on their fiber surface.     

Explosion pulping of eucalyptus: a comparison with CTMP and CMP

Summary Explosion pulping results in strong pulp with breaking length at 100 ml CSF (Canadian standard freeness) higher than 6.5 kg and burst index approaching 4 KPa m²/g. The real advantage of eucalyptus explosion pulp over conventional CMP (chemical-mechanical pulp) and CTMP (chemical-thermo-mechanical pulp) is observed when the impregnation solution contains less than 2% NaOH along with 8% Na₂SO₃, and when the liquor/chips ratio equals 3. The strength of eucalyptus explosion pulp obtained by using a pretreatment solution consisting of 8% Na₂SO₃ and 1% NaOH is comparable with that of eucalyptus kraft pulp. The concentration of NaOH present in the pretreatment solution has a very important effect on the specific refining energy of eucalyptus explosion pulp as well as of CMP and CTMP. The explosion pulp obtained from eucalyptus pretreated with a solution containing an appropriate quantity of caustic along with Na₂SO₃ not only requires a minimum specific refining energy but also provides the highest strength values in comparison to that of CMP and CTMP.     

Sulfuric acid bleaching of kraft pulp II: Behavior of lignin and carbohydrate during sulfuric acid bleaching

The purpose of this study was to investigate the behavior of lignin and carbohydrates in kraft pulps during sulfuric acid bleaching. Beech kraft pulp and red pine kraft pulp were bleached with dilute sulfuric acid at pH 1.3 with addition of sodium nitrate and sodium nitrite at 100°C for 1 h. The pulps were then extracted with aqueous sodium hydroxide solution at 70°C for 1 h. Lignin and carbohydrates in the acid effluents and the alkali effluents were analyzed. The carbohydrate compositions of unbleached and bleached kraft pulps were also determined. The residual lignin in kraft pulp was degraded to a molecular size similar to that of milled wood lignin during sulfuric acid bleaching without additives, and it was further degraded to a much smaller molecular size during sulfuric acid bleaching with additives. It was found that the amount of carbohydrate dissolved in the bleach effluents were only about 1 of the dry weight of the kraft pulp under these bleaching conditions. The carbohydrates dissolved during bleaching were mostly of hemicellulose origin.Part of this report was presented at the 8th International Symposium on Wood and Pulping Chemistry, Helsinki, July 1995     

Fiber swelling favoured by lignin softening

Summary The effect of temperature on the uptake of water by various pulps has been studied at temperatures from 20 to 95°C. In the case of lignin-containing pulps, i.e. pulps which have been chlorite-delignified to various degrees, the swelling increases rapidly above a temperature of 60 to 75°C. For a CTMP where the softening temperature of the lignin has been lowered, a maximum in swelling is obtained at 50 to 60°C. When no lignin is present, as in cotton linters and holocellulose, the temperature has no effect on the swelling but the level of swelling in the holocellulose pulp is very high. It is suggested that the increase in swelling above 60 to 75°C is due to the softening of the lignin, the flow of which makes swelling possible. Below its softening temperature, the stiff lignin restricts the swelling which is primarily promoted by water uptake in the hemicelluloses. Some implications for pulping processes are discussed.The authors thank Miss Madeleine Ansén for skilful experimental assistance and Dr. J. A. Bristow for the linguistic revision     

Fate and influence of western red cedar extractives in mechanical pulping

The methanol extractives from western red cedar mechanical pulps were found to be radically different in composition to the extractives obtained from the heartwood. The major heartwood extractive components, the tropolones and lignans, were not present in the extractives from the pulps. However, the proportion of a brown polymer doubled. The low and high molecular weight methanol extractives components from the pulps were separated using methyl tert-butyl ether. The low molecular fraction contained mostly guaiacyl-based compounds with dihydroquercetin, thujic acid, 3-hydroxy-1-(4′-hydroxy-3′-methoxyphenyl)-2-oxopropane and 4-ethyl-2-methoxy-6-hydroxyphenol being positively identified. The brown polymeric portion had molecular weights ranging from 1,000 to 10,000. Infrared analysis indicated that the polymers were formed from lignans. Examination of the changes in diffuse reflectance UV-visible and infra red spectra of the pulps on extraction with methanol, suggested that the colour resides in insoluble polymers formed from plicatic acid/plicatin during refining. Received 18 December 1998     

Industrial utilization of tobacco stalks II: preparation and characterization of tobacco pulp by steam explosion pulping

Our previous paper showed tobacco stalks to posses the characteristics of a raw material for pulp and paper application. It contains the major biomass constituents and cell components common to wood species. In this study, preparation and characterization of tobacco stalk pulp by steam explosion (SE) pulping at two chemical pretreatments were attempted. Chemical pretreatment prior to SE pulping improved the brightness, yield, and strength properties of the resulting tobacco SE pulps in the order: 6% Na₂SO₃ + 1% NaOH > 6% Na₂SO₃ > control (untreated). The 6% Na₂SO₃ + 1% NaOH-impregnated tobacco stalks produced SE pulps of good fiber length distribution and considerable properties that compare well with pulps from other raw materials obtained from previous studies, and the nonimpregnated ones showed strength properties superior to those of their poplar counterpart. Prior to bleaching, pretreating the tobacco stalk SE pulps with two stages, 2% NaOH at 90°C, improved the initial pulp brightness by about 5 points. Two-stage 6% H₂O₂ bleaching gave a comparable effect with hypochlorite bleaching for both tobacco and poplar, giving a 29–34 brightness point increase for tobacco SE pulp and 61 for the poplar samples. The differences in the bleaching responses for untreated tobacco and poplar SE pulps were attributed to the differences in their lignin structure, as shown in the total yield of their respective nitrobenzene oxidation products and FT-IR spectra. Tobacco SE pulps contain more of the guaiacyl-type lignin and poplar the syringyl-type lignin.This paper was presented in part during the 1998 CORESTA (Cooperation Centre for Scientific Research Relative to Tobacco) Congress, Brighton, UK, October 1998     

Steam explosion pretreatment used to remove hemicellulose to enhance the production of a eucalyptus organosolv dissolving pulp

The steam explosion (SE) pretreatment associated with the organosolv process was investigated to produce dissolving pulp from eucalyptus. Prehydrolysis Kraft (PHK) pulping was also done to produce viscose and acetate grade pulps as reference. The organosolv pulps were delignified in two steps with sodium chlorite. Viscose and acetate grade PHK pulps were bleached by OD₀(EH)D₁P and OD₀(EP)D₁PCCE sequences, respectively. Dilute acid-catalyzed (with acid addition) SE pretreatment dissolved more xylan than auto-catalyzed (no acid addition) SE pretreatment. Steam-exploded unbleached organosolv pulps showed lower residual lignin content and screened yield than unbleached organosolv pulps without SE pretreatment. Steam explosion pretreatment helped to decrease lignin content and damaged fiber length of unbleached organosolv pulps. The 1.0% H₂SO₄ organosolv pulp (organosolv dissolving pulp at bioconversion conditions) showed the highest reactivity. Even showing low viscosity for some applications, in general, the organosolv dissolving pulps produced in this study can be used for making lyocell fibers.     

Antibody-based assay for galacturonan deesterification on wood pulp fibers during bleaching

Antibodies recognizing galacturonan were used in immunoassays for industrial unbleached and hydrogen peroxide-bleached chemithermomechanical pulp (CTMP). The assays were based on a colorimetric method using specific monoclonal antibody recognition of acidic and methylated homogalacturonan, respectively, on the pulp fiber surfaces. Alkaline phosphatase-conjugated antibodies were linked to the galacturonan specific antibodies, and an alkaline phosphatase substrate (p-nitrophenylphosphate) was used to develop a yellow reaction product that can be followed spectrophotometrically. Together the newly developed immunoassays were able to describe the deesterification, specifically, of surface-localized galacturonan on CTMP, induced by alkaline hydrogen peroxide bleaching. Unbleached CTMP showed relatively more labeling by methylated galacturonan recognizing antibodies, whereas bleached CTMP was relatively more labeled for acidic galacturonan. The increase in negative charge of the bleached pulp was also shown by polyelectrolyte titration; the negative surface charge was 9.3 μeq g⁻¹ in unbleached CTMP and 21.7 μeq g⁻¹ in bleached pulp.     

Distribution of methyl-esterified galacturonan in chemical and mechanical pulp fibers

The effects of chemithermomechanical pulping (CTMP), high-temperature (HT)-CTMP pulping, and kraft pulping on the distribution of the pectin polymer, methyl-esterified polygalacturonan have been qualitatively evaluated using immunocytochemistry. Pectin was immunolocalized using an antibody (JIM7) specific for partly methyl-esterified polygalacturonan. A fluorescent antibody was linked to JIM7 and analyzed by epifluorescence microscopy. Pectin was found in both chemithermomechanical pulps in similar uneven patterns: Some fibers showed no labeling, whereas others showed extensive labeling in patches restricted to the fiber surfaces. Pectin labeling of bleached and unbleached kraft pulps did not show any presence of pectin. Labeling was correlated to the presence of compound middle lamella tissue left on the CTMP-treated surfaces. Pectin on pulp-fiber surfaces may affect the interfiber bonds and thereby the pulp properties.     

13C CP/MAS nuclear magnetic resonance study of the peroxide bleaching of ultra high yield chemimechanical pulp produced from sound and spruce budworm killed balsam fir

Summary The chemimechanical pulping (CMP) of sound balsam fir and the subsequent peroxide bleaching of the CMP pulp were investigated using solid state ¹³C CP/MAS NMR. A parallel study was made of a CMP pulp produced from spruce budworm killed balsam fir. Changes in the lignin and hemicellulose components were readily evident. The residual lignin and carbohydrate macromolecules in dead balsam fir CMP appeared to be the same as those in the sound wood CMP, before and after bleaching.We are indebted to Mr. S. S. Johal and Dr. J. V. Hatton of PAPRICAN, Vancouver, B.C., for generously supplying the wood and pulp samples. We also appreciate the assistance of Dr. N. R. Jagannathan with the ¹³C CP/MAS NMR measurements. Financial support from NSERC, in the form of a Postdoctoral Fellowship (JMW) and operating grants (FGH), is gratefully acknowledged     

On the selectivity of ozone delignification of softwood kraft pulps

Summary Ozonation of kraft pulp and oxygen-delignified kraft pulp in acetic acid/water mixtures has been studied at different pulp consistencies with and without an inhibitor to obtain information about the limitations of the selectivity of the ozone treatment. The experiments have been performed according to a full factorial design and data have been analysed by stepwise regression analysis. The results show that a better delignification selectivity can be achieved when ozone is applied in acetic acid media instead of conventional aqueous media. By combining conventional oxygen delignification and ozonation in acetic acid, pulps with equal strength properties and better optical properties compared to those of conventional O(DC)E prebleached pulps can be obtained. This study has also revealed that the reagent is utilized far more efficiently in ozonation at high pulp consistency (35%) than in ozonation at low consistency (1%), and that a similar selectivity can be achieved in both types of ozonation by choosing appropriate conditions. The greater selectivity of ozonation in acetic acid than in water is interpreted in terms of different stabilities of the oxidant in these reaction media. The relation between the formation of hydroxyl radicals and the extent and selectivity of delignification during ozonation has been investigated. The final bleaching of pulps prebleached with ozone in acetic acid medium has been studied. Two final bleaching sequences are presented, by which pulps with ISO brightness levels of 79% and 90% can be produced.The authors are indebted to the Swedish National Board for Technical Development (Styrelsen för Teknisk Utveckling) for financial support for this work and to STORA Technology for pulp tests and analyses     

黑荆木材及其KP、CTMP的纤维形态研究

研究表明黑荆木材１—３年生密度为０．５９—０．６５ｇ／ｃｍ３，５—１０年生为０．７２ｇ／ｃｍ３；１—７年生木材成分变化不大，纤维素在４５％以上，半纤维素在２５％以下，木素在２１％以下。比较６年生黑荆木材及其ＫＰ、ＣＴＭＰ的纤维形态，纤维长度在０．７６ｍｍ以上的，木材为７２．０４％、Ｋｐ为７２．２２％、ＣＴＭＰ为８２．５８％；平均纤维长度木材为０．８５６ｍｍ、ＫＰ为０．８４５ｍｍ、ＣＴＭＰ为１．１６５ｍｍ；纤维宽度在１２一２４μｍ，木材为９２．６２％、ＫＰ为９２．８６％、ＣＴＭＰ为３４．６３％；平均纤维宽度木材为１５．６μｍ、ＫＰ为１５．８μｍ、ＣＴＭＰ为３０．７μｍ；长宽比木材为５４．９、ＫＰ为５３．３、ＣＴＭＰ为３７．９。     

Evaluation of paper permanence

Summary The thermal stability of papermaking pulps under conditions of accelerated aging and at pyrolytic temperatures was examined. Degradation was found to be extremely complex and influenced by both the technical processes of papermaking and by the experimental methods used. At moderate temperatures, as used for accelerated aging, the folding endurance test was found to be a sensitive measure of degradation. Methods of reducing the variability of the test were considered, and a new technique capable of handling widely different results was developed and evaluated.Several papermaking pulps were artificially aged and the resultant loss of strength attributed to the interaction between a gradual fiber strength reduction and a rapid increase in interfiber bonding. Excessive initial inter-fiber bonding decreased handsheet stability. Softwood sulfite and kraft pulps were more stable than a birch kraft pulp, but the behavior of sulfite pulps varied greatly. The presence of lignin or a high hemicellulose content was not of itself sufficient to cause rapid aging.The pyrolytic behavior of pulps was investigated using thermogravimetric analysis. Papermaking pulps had mean pyrolytic activation energies between 30–45 kcal/mole. The activation energy decreased as the reaction proceeded. Correlation of these activation energies with the rate of loss of physical properties during accelerated aging was not good. The results indicated that the rate determining reactions for pyrolysis and for low temperature degradation are different but that the pyrolytic behavior is partially determined by the supramolecular structure. Empirical stability indices, based on both the integral and differential thermograms, were calculated, and these correlated well with the relative rates of loss of physical properties.A large part of this paper is based on the thesis of R. D. Carwell. Contributions were also made by L. Lyon and M. C. Varshney. This work was partially funded by the National Bureau of Standards     

Limitation of XPS for analysis of wood species containing high amounts of lipophilic extractives

Chemical composition of Norway spruce and pine, two softwood species, has been investigated by X-ray Photoelectron Spectroscopy (XPS). Contrary to results previously obtained with beech wood, which allow to obtain information on bulk chemical composition from surface composition analysis, XPS analysis appears to be unsuitable for the characterisation of Norway spruce and pine wood chemical composition. Indeed, chemical compositions calculated from XPS data differ strongly from those obtained from microanalyses which are in good agreement with theoretical composition described in the literature. XPS analysis of both the softwood surfaces indicated high carbon contents explained by migration of lipophilic extractives to the surface under the influence of the vacuum necessary for XPS analysis. Nonvolatile extractives contained in wood were extracted and deposited on glass plates and analysed. Survey and detailed C1s spectra indicated similar signals to those recorded on wood surfaces. This phenomenon was not observed when samples had been previously extracted before analysis. These results strongly evidenced that extractives present in both species are able to migrate through resin canals from the bulk of the sample to the surface when put into ultra high vacuum. XPS presents, therefore, some limits in the case of the analysis of softwood species containing extractives able to migrate to the surface during analysis. This behaviour, difficult to control, could lead to erroneous interpretations due to extractives enrichment of the surface under the effect of vacuum.     

锯木屑蒸汽爆破预处理制备糠醛的研究

以锯木屑为原料,采用蒸汽爆破进行预处理,然后酸催化提取糠醛。探讨了预处理温度、爆破压力、预处理时间及液料比等因素对糠醛得率的影响。采用响应面法建立二次回归模型,并对预处理工艺进行了优化。研究结果表明:预处理能有效的促进锯木屑的降解,提高糠醛的得率。在预处理温度为216℃、爆破压力1.8 MPa、预处理时间6 min、液料比3∶1(mL∶g)时,糠醛的得率(79.13%)比相同条件下未进行蒸汽爆破预处理的试样(55.35%)提高了23.78个百分点。     

木聚糖酶预处理对麦草化学机械浆可漂性及白度的改善

探讨了以玉米芯片为碳源制备木聚糖酶及麦草化学机械浆经该木聚糖酶预处理后可漂性和白度的改善效果。结果表明，直接以玉米芯为底物、里氏木霉为菌种产酶效果较好，当底物浓度为18g/L时，木聚糖酶活力可达38．34IU／mL。木聚糖酶预处理有利于改善麦草化机浆的可漂性，促进其过氧化氢漂白，有提高漂白浆白度，降低漂剂消耗。研究表明，当经单段H2O2漂至相同白度时，木聚糖酶预处理后可节约50％的H2O2用量。若麦草CMP酶处理后采用高浓度两段过氧化氢漂白，即XP3P3漂序（H2O2总量为6％0时，白度可达60％（ISO）以上。     

Lignin-carbohydrate bonds in a residual soda spruce pulp lignin

Summary The behaviour of lignin-polysaccharide complex of spruce wood in soda pulping was studied by the characterization of lignin-saccharide fractions isolated from a series of soda pulps. The dioxane pulp lignins contain 8–14% of carbohydrates in which glucose was the predominant component. Its content increased with increasing degree of delignification indicating the formation of secondary lignin-carbohydrate linkage. Both glycosidic and ether type of bond between residual lignin and cellulose in pulp was proved by methylation analysis of the pulp dioxane lignin.The work was supported by the Slovak Academy of Sciences grant number 2/999389/92.     

High-yield pulping of aspen wood: Relation between pulp properties and fibre characteristics by multiple linear regression

Summary High-yield pulps have been obtained by means of steam explosion pulping. This process was carried out as follows: 1) chips soak impregnation (60 °C, 24 h, L/C = 6) in solutions containing 8% Na₂SO₃ and a variable concentration of either Na₂CO₃ or NaHCO₃, ranging from 0 to 2%; 2) cooking at high temperature (190–200 °C) for short time (2-1 min); 3) rapid pressure release. This work shows that mechanical properties were substantially improved when adding a second chemical to the Na₂SO₃ impregnation solution. Moreover, refining energy requirement was significantly reduced. However, the higher chemical charge used made the optical properties drop. In this paper, mathematical models have been proposed in order to accurately predict specific refining energy and paper properties from sulfonate content and pulp yield. In addition, the relative importance of these two parameters has been studied.Thanks are due to the Natural Science and Engineering Council of Canada (NSERC) and Fonds pour la Formation de chercheurs et l'aide à la recherche of Quebec (FCAR) for their financial support.     

Location and fate of carboxyl groups in aspen alkaline peroxide-impregnated chemithermomechanical pulp fibres during alkaline peroxide bleaching

The origin and kinetic changes of carboxyl groups in aspen chemithermomechanical pulp (CTMP) fibres during alkaline peroxide bleaching were evaluated. The results showed that the major contributors of carboxyl groups in aspen CTMP fibres were the 4-O-methylglucuronic acid, galacturonic acid and the carboxyl groups in oxidized lignin. Alkaline peroxide bleaching could increase the total carboxyl groups, surface charge and dissolved anionic substances. However, the excess degradation by superfluous hydroxide and peroxide could result in the reduction of carboxyl groups in fibres because of the production and dissolution of low-molar-mass substances. The total carboxyl groups from polysaccharides in fibres remained constant, and the increase of carboxyl groups in fibres should result from the carboxyl groups newly formed by the lignin oxidation during peroxide bleaching. Alkaline peroxide bleaching could also result in the removal of a large part of extractives and a small fraction of lignin on the fibre surface.