Adsorption behavior of aluminum compounds on pulp fibers at wet-end

Various aluminum compounds were added to pulp suspensions, and the adsorption behavior of their aluminum components on pulp fibers was studied. Aluminum contents in the handsheets were determined using an energy dispersive X-ray analyzer attached to a scanning electron microscope and an X-ray fluorescence analyzer. Although aluminum contents in the handsheets increased with increasing additions of the aluminum compounds, the detailed adsorption patterns varied among the aluminum compounds used. Their chemical structures and the pH values of the pulp suspensions greatly influence the adsorption behavior. When fines are present in the pulp suspensions, the aluminum components are predominantly adsorbed on the fines, probably due to their larger surface areas or the higher carboxyl contents compared to those of coarse fibers. Not only aluminum flocs but also far smaller components such as various aluminum cations seemed to be adsorbed on pulp fibers. Most aluminum flocs, which are formed in pulp suspensions by reacting with OH and entrapped in a fiber matrix by filtration effects, are removable by repeated mechanical agitation of the pulp suspensions.     

Factors influencing retention behavior of aluminum compounds on handsheets

Handsheets were prepared with aluminum sulfate under various conditions of pulp suspension, and factors influencing retention behavior of aluminum components on the handsheets were studied on the basis of their aluminum contents. When deionized water was used in the handsheet-making process, aluminum contents in the handsheets had a plateau level of 0.7mg/g in the range of 1%–8% Al₂(SO₄)₃ addition levels on dry weight of pulp. On the other hand, when tap water was used aluminum contents increased up to 5.6 mg/g, increasing the Al₂(SO₄)₃ addition levels to 8%. The high aluminum contents in the handsheets are explained in terms of pH and the presence of calcium ions from the tap water used. Cationic aluminum species, which are formed from aluminum sulfate added to pulp suspensions, are primarily adsorbed on pulp fibers by electrostatic interactions with carboxyl groups in the pulp, competing with OH^– ions in water. These aluminum components, once adsorbed on pulp fibers by ionic interactions, are not removed from the fibers by extending the stirring time of the pulp suspensions.This research was presented in part at the 48th annual meeting of the Japan Wood Research Society in Shizuoka, April 1998     

Mechanism of size retention on handsheets prepared in rosin soap size-alum systems

The mechanism of rosin size retention in rosin soap size-alum systems was studied on the basis of sizing behavior and the rosin size and aluminum contents of handsheets prepared under normal and particular conditions. Rosin size, aluminum, and calcium contents of handsheets prepared with various stirring times of pulp suspensions after pH adjustment suggested that rosin size components adsorbed on pulp fibers predominantly have the structure of free rosin acid rather than rosin aluminum or calcium salt. When a carboxyl group-blocked pulp was used, the rosin size content clearly decreased. This result shows that pulp carboxyl groups play a significant role in rosin size retention. Electrostatic interactions between dissociated carboxyl groups of pulps and anionic rosin size components through cationic aluminum compounds must be present in pulp suspensions. On the other hand, nonionic interactions in pulp suspensions, which occur particularly around pH 6.2–6.5, may also contribute to rosin size retention and appearance of sizing features. When the carboxyl group blocked pulp was used, some rosin size components were retained in the handsheets in largely coagulated form, resulting in no or quite low sizing levels, when the handsheets were dried at 20°C.This research was presented in part at the 64th pulp and paper research conference of Japan TAPPI, Tokyo, June 1997     

Solid-state13C-NMR analysis of size components in handsheets prepared by fatty acid soap size-alum systems

The mechanism of paper sizing in fatty acid soap size-alum systems was studied by structural analyses of the size components in handsheets prepared with¹³C-labeled fatty acid soap size. Patterns of sizing performance and aluminum content of the handsheets were similar to those for the rosin soap size-alum sizing systems, although the patterns of calcium content were different. Solid-state¹³C-nuclear magnetic resonance analysis of the handsheets revealed that fatty acid calcium salt was the predominant size component in the handsheets prepared using tap water. This calcium salt is formed from the fatty acid soap size (fatty acid potassium salt) by ion exchange with calcium ion in pulp suspensions and retained on pulp fibers through aluminum compounds originating from alum added. On the other hand, when deionized water was used, free fatty acid was the major component in the handsheets. Fatty acid aluminum salt was present as a minor component in the handsheets prepared in both tap water and deionized water systems. Therefore, all size components (i.e., fatty acid calcium salt, free fatty acid, fatty acid aluminum salt) seem to contribute to the appearance of sizing features.This research was presented in part at the 64th Pulp and Paper Research Conference of Japan TAPPI, Tokyo, June 1997     

Retention behavior of size and aluminum components in handsheets prepared in rosin soap size-alum systems

Handsheets were prepared with rosin soap size and aluminum sulfate under various conditions, and the retention behavior of the rosin size and aluminum components in the handsheets was studied. Pyrolysis-gas chromatography and X-ray fluorescence analysis were used to determine the size and aluminum contents in the handsheets, respectively. When the addition level of rosin soap size varied from 0% to 4% and that of aluminum sulfate was fixed at 2%, the rosin size content increased with the increase in the size addition level, whereas aluminum and calcium contents were roughly constant. Under these conditions, handsheets prepared from fines-free pulp had aluminum contents less than those for the original beaten pulp, probably because the former pulp had a carboxyl content less than that of the latter pulp. Not only the conventional rosin retention mechanism but also mechanism proposed below must exist in the rosin soap size-alum systems. That is, some aluminum compounds originating from aluminum sulfate are adsorbed on pulp fibers immediately after the aluminum sulfate addition. These adsorbed aluminum compounds form cationic sites on pulp fibers, and free rosin acid components with anionic charges are then adsorbed onto the cationic sites of pulp fibers at the wet-end.This research was presented in part at the 46th annual meeting of the Japan Wood Research Society, Kumamoto, April 1996     

Retention behavior of size and aluminum components on handsheets in rosin-ester size/alum systems

Anionic emulsion sizes consisting of rosin triglyceride esters and partly fortified rosin acids (i.e., rosin-ester sizes), have recently been used as internal sizes for alkaline papermaking. In this study, handsheets were prepared from pulp suspensions with alum and a rosin-ester size under various conditions, and sizing degree and size and aluminum contents of the handsheets were determined. Aluminum compounds originating from alum added to the pulp suspensions behave as retention aids of the rosin-ester size even in alkaline papermaking under limited conditions. Carboxyl groups in pulp are the primary retention sites of aluminum compounds in pulp suspensions. They form cationic sites on pulp fibers, and thus the anionic size emulsion particles are adsorbed on pulp fibers by electrostatic interactions. However, the cationic charges of aluminum compounds on pulp fibers decrease and finally disappear completely with the lapse of time after the alum addition by forming ionic bonds between the cationic sites and OH^– ions. Thus, pH values of the pulp suspensions and timing of the size addition strongly influence the retention values of the rosin-ester size and the resultant sizing features.This research was presented in part at the 1995 autumn meetings of the Society of Fiber Science and Technology Japan in Hamamatsu, October 1995     

Studies on interactions between aluminum compounds and cellulosic fibers in water by means of27Al-NMR

Interactions between pulp fibers and aluminum compounds in pulp suspensions were studied using fibrous cellulose (FC) and fibrous carboxymethylcellulose (FCMC) powders as models of pulp fibers by X-ray fluorescence analysis and²⁷Al nuclear magnetic resonance. When deionized water was used at pH 4–5, water-soluble cationic aluminum species (Al³⁺, aluminum oligomer, and polyaluminum species) were adsorbed on the solid FCMC, forming carboxylic acid aluminum salts by cation exchange. The formation of these nondissociated pulp-COOAl type structures in paper sheets may contribute to some decreases in hydrophilic property. On the other hand, the water-soluble cationic aluminum species had nearly no interactions with hydroxyl groups of solid cellulose in the suspensions at pH 4–5. When tap water was used at pH 5–7, some aluminum components were retained on not only FCMC but also the FC sample. Probably, water-insoluble Al(OH)₃ flocs are formed in the suspensions at pH 5–7 and retained on the FC sample by simple filtration effect. Therefore, two mechanisms of the aluminum retention (i.e., electrostatic interactions and a simple filtration effect) may exist between pulp fibers and aluminum components in the practical papermaking process.This research was presented in part at the 5th annual meeting of the Japan Cellulose Society, Kyoto, July 1998     

Modification of softwood kraft pulp with carboxymethyl cellulose and cationic surfactants

An elemental chlorine-free (ECF)-bleached soft-wood kraft pulp was treated first with a carboxymethyl cellulose (CMC, degree of substitution 0.3, 1% on pulp) and then with alkyltrimethylammonium bromides (alkyl chain lengths of C₁₀ to C₁₆). Surprisingly, the treatment with dodecyltrimethylammonium bromide (C₁₂TAB) markedly increased the internal and tensile strengths of the handsheets prepared from the modified pulp. Environmental scanning electron microscopy (ESEM) showed that these properties could be partly explained by the “rope/gum-like” bridges that were formed between the fibers.     

Fiber charge characteristics of pulp suspension containing aluminum sulfate

Fiber charge characteristics of pulp suspensions containing aluminum sulfate were investigated with relation to adsorption behavior of aluminum components on the pulp fibers by streaming potential measurement using a particle charge detector, X-ray photoelectron spectroscopy, and X-ray fluorescence analysis. When aluminum sulfate was added to a pulp suspension prepared using deionized water, a streaming potential of the suspension went from negative to slightly negative according to the adsorption of aluminum components on the pulp fibers. Subsequent addition of a dilute NaOH solution to the suspension drastically cationized the fibers in the pH range of around 5 by predominant and homogeneous adsorption of cationic aluminum complexes on the fiber surfaces. However, the aluminum flocs that formed heterogeneously on the fiber surfaces at higher pH by further alkali addition made nearly no contribution to cationization of the fibers, although the abundant aluminum components were retained in the pulp sheets. Therefore, only aluminum cations adsorbed uniformly on the fiber surfaces perform well to control the charge properties of the pulp fibers at the wet end; and the preferential aluminum adsorption behavior on the fiber surfaces, by utilizing the required amounts of hydroxyl ions, probably accounts for the effective cationization of the fibers under acidic to neutral papermaking conditions.This research was presented in part at the presymposium of the International Symposium on Wood and Pulping Chemistry, Seoul, June 1999; at the International Symposium on Environmentally Friendly and Emerging Technologies for a Sustainable Pulp and Paper Industry, Taipei, April 2000; and at the 2000 annual meeting of the Society of Fiber Science and Technology, Japan, Kyoto, June 2000     

Behavioural analysis of a nonionic detergent in the kraft pulp washing process using cryo-time-of-flight secondary ion mass spectrometry and cryo-scanning electron microscopy

In order to understand the kraft pulp decolouring mechanism on using a nonionic detergent, the pulp washing process and the resulting pulp handsheets were investigated by examining the brightness, kappa number, thioacidolysis product yield, and dewatering efficiency in the pressing sheet making process. The pulp decolouring could be attributed to a decrease in the lignin content and an improvement in the dewatering efficiency. Furthermore, the detergent distribution in the aqueous pulp suspension obtained during the pulp washing process was visualised using cryo-time-of-flight secondary ion mass spectrometry/scanning electron microscopy (cryo-TOF-SIMS/SEM). The detergent was clearly observed at the transverse surface of the pulp fibre cell wall and was also detected in the lumen of the fibres, suggesting the permeation of the detergent into the pulp fibre cell wall. Based on these results, the pulp decolouring mechanism can be proposed as follows: the detergent permeates into the pulp fibre cell wall and promotes the solution-exchange between the inside and the outside parts of the fibre cell wall, finally washing away the chromophoric substances such as lignin and its degradation products owing to the enhanced dewatering efficiency.     

A method for visualizing cesium ions adsorbed on wood charcoal using SEM–EDX

A new method based on scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX) was developed for visualizing the distribution of cesium ions (Cs⁺) adsorbed by Japanese cedar charcoal. After being soaked in saturated aqueous CsCl solutions, wood charcoal and regular wood samples were embedded in resin, and thin sections of sample were prepared for the Cs⁺ observations. The Cs⁺ ions on charcoal could be seen in EDX mapping images and also in line profiles with enough contrast to identify differences between the various carbonized cell wall regions. On the other hand, Cs⁺ could not be observed in the EDX mapping images of wood samples, despite having been soaked in a saturated aqueous CsCl solution. These results indicate that Cs⁺ adsorbed on charcoal can be visualized using this method, but not Cs⁺ in wood. Additionally, oxygen detected on the charcoal by EDX can be regarded as an indicator of the presence of surface functional groups.     

Two-dimensional linear viscoelasticity of paper

Summary Linear viscoelastic properties of laboratory handsheets have been investigated from the two dimensional aspect. According to the linear theory of viscoelasticity, the behavior of transverse isotropic materials such as handsheets subjected to plane stresses is fully described by the two in-plane relaxation functions G₁₁ (t) and G₁₂ (t). In the present paper, some viscoelastic characteristic functions describing responses to in-plane deformation histories are derived from G₁₁ (t) and G₁₂ (t) determined by strip biaxial stress relaxation testing. The predicted uniaxial relaxation function curve was in good agreement with the experimental one, and the viscoelastic Poisson's ratios in uniaxial stress relaxation and in uniaxial constant strain rate extension were decrease functions of time. Effects of beating on the areal dilatation and shear relaxation functions are discussed by introducing the classical concept of relaxation spectrum.     

Acetic acid pulping of wheat straw under atmospheric pressure

Atmospheric acetic acid pulping of wheat straw was carried out. Pulping conditions and their effects on pulp properties were investigated in detail, and a comparison between acetic acid (AcOH) pulp and soda-anthraquinone (AQ) pulps of wheat straw was made of the chemical composition, strength, and fiber morphology of the pulps. Wheat straw was successfully pulped and fractionated into pulp (cellulose), acetic acid lignin, and sugars (monosaccharides from hemicellulose), making it easy to utilize them. It was found that among the pulping conditions the dosage of H₂SO₄ as catalyst was the most notable, and the extent and rate of delignification could be controlled by varying the amount of the catalyst. The results also showed that acetic acid pulp was quite different from soda-AQ pulp. About 70% of the ash or 90% of the silica in wheat straw were kept in AcOH pulp. The ash might function as filler and be beneficial to the printability of paper. It was known that many epidermal cells existed in AcOH pulp in bundles or in single cells. These ash-rich nonfiber cells seemed to hinder the bonding between fibers. AcOH pulp had lower strength than soda-AQ pulp, which might result mainly from the chemical damage of fibers caused by acid, not from the depolymerization of cellulose.Part of this paper was presented at the 65th Pulp and Paper Research Conference of Japan TAPPI, Tokyo, June 1998     

Effects of site on fibre, kraft pulp and handsheet properties of Eucalyptus globulus

? Eight-year old trees from two Eucalyptus globulus Labill. clones planted across three different sites in Tasmania, Australia, were sampled for wood and kraft pulp/handsheet properties.

? Site had a significant effect on all measured properties. Compared with the poor site (Parkham) the wood from the good site (West Ridgley) had on average 11 % lower wood density. The poor site had also greater microfibril angles, shorter fibres at lower pulp yields.

? The handsheets produced with pulp from the poor site resulted in comparatively higher bulkiness, lower burst, lower tear and tensile indices, lower zero span tensile strength, but higher opacity, higher light scattering and higher surface roughness. Significant height effects were found with all wood properties, and also with tear index, zero span tensile strength and opacity.

? Discriminant analysis showed that for 76 out of 100 handsheets the raw material source, i.e. growth site, could be predicted correctly using a set of handsheet properties with tear index and bulk index being most prominent.

? This is unique evidence that site conditions are strongly reflected in handsheet properties produced from Eucalyptus pulp.

     

阳离子聚丙烯酰胺乳液对木浆增强作用的研究

以丙烯酰胺和二甲基二烯丙基氯化铵(DDAC)为主单体通过自由基共聚反应合成了水包水型阳离子聚丙烯酰胺(CPAA)乳液增强剂,并探讨了在漂白木浆中的应用条件如CPAA乳液用量、反应时间、硫酸铝用量、浆料pH值、搅拌速度对其增强效果的影响。结果表明,当CPAA乳液用量为0.8%(对绝干浆)、pH值7.0、反应时间10 m in、硫酸铝用量为0.5%(对绝干浆)、搅拌速度150 r/m in时,纸页裂断长和撕裂指数与未加助剂时相比依次增加28.7%和12.4%。红外光谱分析表明,合成的CPAA乳液具有预期设计结构。分析添加乳液前后纸页的环境扫描电镜照片对CPAA乳液的增强机理作了初步探讨。     

相思木EMCC硫酸盐浆氧脱木质素前后酶处理的影响研究

研究了酶处理对相思木EMCC(延伸改良连续蒸煮)硫酸盐浆(KP浆)氧脱木质素效果的影响。结果表明,由白腐菌直接合成的漆酶/木聚糖酶体系(LXS)预处理相思木EMCC硫酸盐浆的的适宜酶用量为7 IU/g;LXS预处理后浆料氧脱木质素的适宜反应时间、最高反应温度及用碱量分别为60 min、100℃和2.5%;利用LXS进行氧脱木质素后处理的适宜反应时间及酶用量分别为2 h和5 IU/g。SEM观察到经过酶处理后纤维表面及横切面出现大量的裂隙及孔隙,其中以酶后处理最为明显,为后续漂白中化学药品的渗透和漂白降解产物的溶出创造条件。     

Morphological changes of ramie fiber during mercerization

Morphological changes of ramie fibers due to swelling in alkali solution were investigated. The observed twisting and changes in the cross-sectional shape of the fibers could be explained as a geometrical alteration caused by lateral expansion of coiling fibrils, as the unmercerized ramie fiber showed an S-helix structure. The fibril angle of ramie fibers was estimated to be 3°. Although the swollen fiber untwisted to some extent on washing with water, the shape of the twisted ribbons as observed by scanning electron microscopy was retained even after drying. Concentrated 8N NaOH produced only a moderate change in morphology, whereas swelling with 3.5N NaOH at 0°C expanded the cross sections about 30 times over the initial ones accompanied by a drastic change in the shape of the fiber.Part of this paper was presented at the annual meeting of the Wood Research Society of Japan in Kumamoto, April 1996     

麦草低温氧碱蒸煮黑液降黏技术

麦草经碱法蒸煮后,所得浆料不经洗涤,直接通入氧气进行处理。以黑液黏度,浆料卡伯值为考核指标,设置4因素3水平正交试验,对试验结果作极差分析发现,在用碱量0～2%、氧压0.2～0.6 MPa、温度70～100℃和时间30～90 min内得到较适宜的工艺条件为:用碱量1%,氧压0.6 MPa,温度85℃,时间60 min。氧碱蒸煮结果为:黑液黏度3.4 mPa.s,浆料卡伯值17.9。与第一段碱法蒸煮相比,黑液黏度降低33.3%,浆料卡伯值降低11.8%。     

Decontamination of Cs from Japanese cedar (<Emphasis Type="Italic">Cryptomeria japonica</Emphasis>) via kraft cooking

To investigate the possibility of decontaminating ¹³⁷Cs-contaminated Cryptomeria japonica wood, kraft pulping was conducted and the Cs behavior in the reaction process was examined. ¹³³Cs-treated or ¹³⁷Cs-contaminated bark, sapwood, and heartwood chips of Cryptomeria japonica were digested using an aqueous solution of NaOH and Na₂S. The pulp was washed with ultrapure water and filtered, after which the filtrate (black liquor) was collected. The black liquor was acidified to separate the supernatant and precipitation. The Cs (¹³³Cs and ¹³⁷Cs) concentrations in the chip and reaction products were measured. As for wood samples, the majority of Cs was present in black liquor, while only a minor amount of Cs was retained in the pulp (<1%). In the case of bark, although the majority of Cs was present in the black liquor, the proportion of Cs in the pulp was much higher than that in the wood pulp. In addition, the Cs in the precipitation of the bark was higher than that in the wood, possibly because the Cs in the bark was combined with some components, which is insoluble in alkaline solution. Our results suggest that ¹³⁷Cs-contaminated Cryptomeria japonica wood can be used in the pulp and paper industries.     

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.