Influence of the chemical composition of kenaf bast and core on the alkaline pulping response

The bast and core of kenaf,Hibiscus cannabinus L., have markedly different chemical components and alkaline cooking responses. The bast had about double the hot-water extractives content and only about half the lignin content of the core. The core contained a large amount of hemicellulose, mostly composed of xylan. The lignin structures of bast and core were also quite different: The former had a significant abundance of syringyl structures. Evidence showed that the bast was much more easily delignified than the core. When the bast and core were cooked together in alkaline condition, the pulp yields at the same kappa number were higher than those of the individual pulpings of bast and core. The bast-core pulping gave a positive effect on the yield of bast pulp in the sodaanthraquinone and kraft pulpings. On the other hand, kenaf was abundant in the hot water extractives. These extractives consumed alkali during cooking to a relatively large extent but acted as a protector of hemicellulose and slightly increased the pulp yields.Part of this paper was presented at the 48th and 49th Annual Meetings of the Japan Wood Research Society, Shizuoka, April 3–5, 1998 and Tokyo, April 3–5, 1999     

Combination treatment of kenaf bast fiber for high viscosity pulp

The viscosity of kenaf bast fiber has been found to be highly sensitive and variable with different pulping methods; therefore, it is important to choose proper chemicals and conditions for pulping and bleaching of kenaf bast fiber. From several pulping experiments, a nonconventional pulping method with a combination of ammonium oxalate pretreatment followed by soda pulping at normal pressure and then acidic chlorite delignification was developed to obtain high-viscosity pulp (162 centipoise). The optimum level of alkali dosage of soda pulping for high-viscosity pulp was found to be 15% (on pulp as NaOH). Pulps showed linear relations between viscosity and xylose or glucose contents, but the combination pulping method gave extremely high pulp viscosity, beyond the relations. The highest viscosity pulp from kenaf bast fiber demonstrated a tear index about twofold and a folding endurance 6.2-fold higher than those of Manila hemp pulp with comparable tensile and burst indexes. The high-viscosity pulp could be used in the production of high-quality currency paper or longevity paper for special uses.Part of this paper was presented at the 43rd Lignin Symposium, Fuchu, Tokyo, October 26–27, 1998     

Comparative study of Kenaf varieties and growing conditions and their effect on kraft pulp quality

Kenaf (Hibiscus cannabinus L.) is an annual plant which produces a very high fiber yield per hectare and has demonstrated to be a suitable material for pulping. The crop conditions influence fiber production, but there is no information about their effect on pulp quality. The aim of this work was to study the effect of kenaf varieties and crop conditions (watering dose and harvesting time) on sulfate pulp quality. The study has been made on bast fiber sulfate pulps due to their high added value. The quality criteria were fiber dimensions, chemical composition and pulp quality. Kenaf variety or crop conditions have significant effect on fiber dimensions, holocellulose content, kappa number and breaking strength. To obtain high fiber yield and good delignified pulps it is recommended to grow the Salvador variety and to employ advance harvesting. Received: 20 January 1999     

Structural characteristics of cell walls of kenaf (<Emphasis Type="Italic">Hibiscus cannabinus </Emphasis>L.) and fixation of carbon dioxide

 Kenaf (Hibiscus cannabinus) plants are widely known for their contribution to the global and regional environment because of their ability to fix CO₂. On the other hand, some scientists have doubts about CO₂ fixation by kenaf and have misgivings about the effect of kenaf on the ecosystem. We have characterized the structural characteristics of cell walls of bast fibers, cores, roots, and leaves of kenaf during the maturation of plants and investigated the rate of photosynthesis. During maturation of the kenaf plant the cellulose (bast fiber 52–59%, core 44–46%) and lignin (bast fiber 9.3–13.2%, core 18.3–23.2%) contents increased significantly. The aromatic composition of the lignin of bast fiber was significantly different from that of the core lignin and of other plants. The lignin of bast fiber appears similar to pure syringyl lignin. Fixation of CO₂ by kenaf plants and their contribution to the global environment are discussed. A significatly high rate of photosynthesis of kenaf plants was observed compared to that of woody plants in Japan, but the amount of CO₂ fixation depends on the characteristics of the plantation. If the kenaf was planted in high density, about twice as much CO₂ was fixed as was fixed by trees in a tropical rain forest. Received: April 22, 2002 / Accepted: July 24, 2002 Acknowledgments This project was supported by the Science and Technology Agency (STA) fellowship of the Japan International Science and Technology Exchange Center (JISTEC), which has been successfully applied by Dr. Shuji Hosoya, Forestry and Forest Products Research Institute. We thank Dr. Toshio Sumizono and Mr. Masao Sakurai, Forestry and Forest Products Research Institute, for their kind help in determining the rate of photosynthesis and cultivating the kenaf plants, respectively. We also express our appreciation to Dr. Quang Hung Le, College of Agriculture and Forestry, Ho Chi Minh City, Vietnam for offering information about the cultivation of kenaf at Thu Duc District, Ho Chi Minh City.     

Lignin characteristics of bast fiber and core in kenaf, bark and wood of paper mulberry and mulberry

The structural features of bast fiber and core lignins in kenaf (Hibiscus cannabinus), bark and wood lignin of paper mulberry (Broussonetia papyrifera (L.) Vent × Broussonetia kazinoki Sieb.) and mulberry (Morus bombycis) were characterized by alkaline nitrobenzene oxidation, ozonation and methoxyl group determination. Bj?rkman lignins were isolated from bast fiber and core, and bark and wood fractions of the plant samples, and structural characteristics were investigated by ¹H NMR and ¹³C NMR spectroscopies. Kenaf bast fiber gave very high molar ratio of syringaldehyde to vanillin (S/V) of alkaline nitrobenzene oxidation products, while methoxyl content was about the same as that of the core fraction. Results of ¹H NMR and ¹³C NMR of Bj?rkman lignin suggested the presence of aliphatic fragments in lignins isolated from paper mulberry and mulberry bark, but not in kenaf bast fiber. The lower yield of alkaline nitrobenzene oxidation products from bast fiber and bark might be due to the higher content of condensed structure of lignin compared to core fraction. Total yield of erythronic (E) and threonic (T) acids of ozonation products and the molar ratio of erythronic acid to threonic acid (E/T) of the bast fibers and bark were lower than the corresponding core and wood fractions, suggesting that the contents of arylglycerol-β-aryl ether intermonomer linkages in the bast fiber and bark lignin were lower than those of the core and wood fractions. Methoxyl content of bark lignin was lower than the corresponding wood lignin. The methoxyl content of the extract-free kenaf bast fiber was similar to that of the core fraction, while the values of paper mulberry and mulberry bark were about one-half of the corresponding wood fractions, respectively. In bark lignins, the methoxyl contents of Klason lignin and Bj?rkman lignin from bark were lower than those of the extract-free barks. This result suggests that the purity of Klason lignin and Bj?rkman lignins of bark may be rather low.     

两个桉树无性系木材材性的年龄效应

以桉树主栽区雷州林业局的2个桉树无性系为研究对象,研究其木材材性的年龄效应.结果发现:尾细桉LH1和ZU6无性系,其纤维长度、宽度和长宽比均随林龄呈增加趋势,纤维长度在0.6 ～ 0.8 mm之间,长宽比在34.4 ～ 42.4之间,同龄LH1的长宽比高于ZU6;随林龄增加木材质量和制浆造纸性能提高.     

Properties of kenaf core binderless particleboard reinforced with kenaf bast fiber-woven sheets

Kenaf composite panels were developed using kenaf bast fiber-woven sheets as top and bottom surfaces, and kenaf core particles as core material. During board manufacture, no binder was added to the core particles, while methylene diphenyldiisocyanate resin was sprayed to the kenaf bast fiber-woven sheet at 50 g/m² on a solids basis. The kenaf composite panels were made using a one-step steam-injection pressing method and a two-step pressing method (the particleboard is steam pressed first, followed by overlaying). Apart from the slightly higher thickness swelling (TS) values for the two-step panels when compared with the one-step panels, there was little difference in board properties between the two composite panel types. However, the two-step pressing operation is recommended when making high-density composite panels (>0.45 g/cm³) to avoid delamination. Compared with single-layer binderless particleboard, the bending strengths in dry and wet conditions, and the dimensional stability in the plane direction of composite panels were improved, especially at low densities. The kenaf composite panel recorded an internal bond strength (IB) value that was slightly low because of the decrease of core region density. The kenaf composite panel with a density of 0.45 g/cm³ (one-step) gave the mechanical properties of: dry modulus of rupture (MOR) 14.5 MPa, dry modulus of elasticity (MOE) 2.1 GPa, wet MOR 2.8 MPa, IB 0.27 MPa, TS 13.9%, and linear expansion 0.23%.     

Studies on the effect of prehydrolysis and amine in cooking liquor on producing dissolving pulp from jute (Corchorus capsularis)

Dissolving pulps are the raw materials for the production of many different end-products. Jute is a very good source of cellulose. In this investigation, jute fiber was subjected to pulping in soda process in order to produce dissolving pulp under different prehydrolysis conditions and compared with prehydrolysed kraft pulp from jute. An increase of the prehydrolysis temperature or H₂SO₄ in prehydrolysis liquor increased the α-cellulose content and decreased the viscosity of pulp. The effect of ethylenediamine in soda liquor was also investigated when producing dissolving pulp. Jute fiber produced pulp having 90–97% α-cellulose. Ethylenediamine in soda liquor produced pulp of higher yield, viscosity and higher α-cellulose content than that of prehydrolysis soda or kraft pulp. The α-cellulose content and viscosity were increased with the increase of amine in soda liquor. The kappa number of dissolving pulp from jute was very low (9–5), which indicated that less bleaching chemicals are required for bleaching. The bleachability of soda-ethylenediamine pulp was lower than prehydrolysed soda and kraft pulp in ECF bleaching sequences. The bleachability of soda-ethylenediamine pulp was improved at the sacrifice of pulp yield when prehydrolysis was done prior to pulping. The alkali solubility S ₁₀ and S ₁₈ were 4–9 and 2–4%, respectively.     

Sawn-timber and kraft pulp properties of Pinus elliottii × Pinus caribaea var. hondurensis and Pinus patula × Pinus tecunumanii hybrids and their parental species

A study was undertaken to evaluate the quality of the timber produced by Pinus elliottii × Pinus caribaea var. hondurensis (PECH) and the Pinus patula × Pinus tecunumanii low elevation (PPTL) and high elevation (PPTH) hybrids and their parent species for both kraft pulp and sawn-timber production. Trees were taken from unthinned tree improvement trials managed for pulpwood, ranging in age between 15 and 19 years. All sawn boards produced by study trees met the minimum wood density requirement for S5-grade structural timber (360 kg m^?3), but approximately 17% of the boards failed to meet the other requirements for the grade, largely due to knot-related defects. Results of dynamic modulus of elasticity assessments performed on all of the boards suggested that a large percentage of boards would not meet the specified average stiffness (7 800 MPa). This was confirmed by the results of static bending tests performed on a subsample of boards. All boards tested for all species and hybrids met the required fifth percentile bending strength value for grade S7 (15.8 MPa) according to SANS 6122 (2008) specifications. The kraft pulping results indicated that the samples taken from the upper part of the stem yielded slightly better results on average than the samples representing the whole tree with respect to uniformity in the kappa vs charge and temperature, and yield vs kappa traits, with slight improvement of pulp yield (52% vs 50%) and some strength properties compared with whole tree pulping. Samples from the upper part of the stem had a close delignification rate in the 60–80 kappa range. The delignification rate for PPTL in the 60–80 kappa range was slower and the yield was slightly lower than P. patula (53.17% vs 52.72%) despite a higher kappa number. The pulp strengths short-span compressive test, breaking length and tearing strength of PECH were similar to those of P. elliottii, which were in turn generally lower than those of P. patula. The pulp strengths of PPTL and PPTH were similar to those of P. patula, whereas P. caribaea strengths were intermediate between those of P. patula and P. elliottii. With the exception of a slightly lower pulp yield, PPTL emerged as the best all-round hybrid for both pulp and sawn-timber properties.     

Influence of prior land use on wood quality of Pinus radiata in New South Wales,Australia

Wood quality data from 33 sites aged between 15 and 18 years old were analysed to determine the effect of prior land use (pasture, cleared grazing land or timber) on wood density, wood stiffness, fibre length and kraft pulp yield. Sampling sites covered 6 different forest areas within the estate. Prior land use (PLU) significantly affected wood stiffness, density and fibre length but not the kraft pulping traits. In contrast, differences were found between different forest areas for the kraft pulping traits plus fibre length but not for stiffness or density.     

Influence on pulping yield and pulp properties of wood density of Acacia melanoxylon

Wood density and pulp yield are key parameters in the evaluation of tree productivity and quality for pulping and their relationships are of high practical importance. The influence of wood density on pulp yield and other pulp quality parameters was investigated using Acacia melanoxylon and its natural variability as a case study. Twenty trees were harvested (five trees in each of four sites in Portugal), and wood discs taken at different height levels, from the base to the top of the tree, providing 100 wood samples, covering the natural variability of wood density ranging from 449?kg?m^?3 to 649?kg?m^?3. Under the same experimental conditions of kraft pulping, screened pulp yield ranged 47.0?C58.2?%, Kappa number 10.9?C18.4, ISO brightness 14.9?C45.6, fibre length 0.660?C0.940?mm and fibre width 16.2?C22.9???m. The pulp yield and Kappa number were not correlated with wood density. Higher pulp yields were associated with lower Kappa numbers and alkali consumption, suggesting the important role of chemical composition of wood on kraft cooking. The results confirm the high pulping potential of Acacia melanoxylon trees grown in Portugal and suggest the possibility of tree selection using both wood density and pulp yield.     

Manufacture of Light-weight Composite Panel from Kenaf

Light-weight composite panels were manufactured using kenaf core particles as core material and kenaf bast fiber-woven sheets as top and bottom surfaces. Methylene diphenyldiisocyanate （MDI） resin was used as the adhesive with the resin content of 4% for core particles and 50 g/m^2 for bast fiberwoven sheets. The target board densities were set at 0.35.0.45 and 0.55 g/cm^3. The composite panels were evaluated With Japanese Industrial Standard for Particleboards （JIS A 5908- 2003）.The results show that the composite panel has high modulus of rupture and internal bonding strength. The properties of 0.45 g/cm^3 density composite panel are： MOR 20.4 MPa. MOE 1.94 MPa, IB 0.36 MPa, WA142%, TS 21%. Kenaf is a good raw material for making light-weight composite panels.     

马尾松硫酸盐浆两段氧脱木质素最佳工艺条件的研究

研究了马尾松硫酸浆两段氧脱木质素的最佳工艺条件。结果表明，第一段氧脱木质素的条件为：氧压0．6MPa，温度100℃，时间80min,NaOH 量5％，MgSO4用量0．5％，浆浓10％；第二段氧脱木质素的条件为：氧压0．4MPa，温度90℃，时间60min，NaOH用量3％，MgSO4用量0．5％，浆浓10％。在此条件下，OIOⅡ木质素脱除率达到72．5％，粘度775．2cm^3/g,得率90．5％。经过氧脱木质素后浆的裂断长5．8km，耐破指数5．3kPa.m^2/g，撕裂指数12．7mN.m^2/g。     

长白落叶松工业纤维林立地控制技术的研究

通过室外样地调查和室内木材材性分析及硫酸盐制浆实验,研究了不同立地条件下长白落叶松工业纤维林的生长过程、木材纤维特性、化学组成、物理性质和制浆特点,指出了立地条件对林分生长、木材纤维含量、纤维长度、纤维长宽比、得浆率、纸浆物理强度的影响。结果表明,长白落叶松工业纤维林生长最佳的立地条件是山地下部Ⅰ、Ⅱ地位级。立地条件对木材材性和纸浆特性有直接影响。在研究的林分密度和立地条件范围内,立地条件越差,木材纤维含量越少,纤维长度越短,纤维长宽比越小,1%NaOH提取物越多。而且这种现象有随林龄增长而加重的趋势。但立地条件对得浆率和纸浆的物理强度影响不明显。综合林分生长和木材材性,长白落叶松工业纤维林的培育最好在山地下部Ⅰ地位级和Ⅱ地位级的立地条件下进行。表4参17。     

竹子深度脱木质素蒸煮与常规硫酸盐法蒸煮的比较

为了提高竹浆性能和减少环境污染,对福建丛生小径竹进行了实验室模拟延伸改良连续蒸煮(EMCC)和常规硫酸盐法蒸煮(CKC)的研究。结果表明,EMCC蒸煮通过分段加入蒸煮药液和在逆流段进行药液置换,比CKC具有更高的脱木质素选择性。在蒸煮相同卡伯值的竹浆时,EMCC浆比常规硫酸盐浆(CK浆)具有更高细浆得率、较低粗渣率、更高粘度和更好强度性能。在相同的打浆度下,EMCC浆抗张指数、耐破指数和撕裂指数都比常规硫酸盐浆高。     

Nondestructive sampling of Eucalyptus globulus and E. nitens for wood properties. III. Predicted pulp yield using Near Infrared Reflectance Analysis

  Within-tree variation in kraft pulp yield, predicted using near infrared reflectance analysis, was studied in thirty trees of E. globulus and fifty trees of E. nitens to develop a non-destructive sampling strategy. Trees, aged 5 to 9 years, were sampled across a range of sites in southern Australia. Simulated core samples were removed at six fixed heights easily accessible from the ground (0.5, 0.7, ... 1.5 m) and at seven percentage heights (0, 20, 30, ... 70%). Whole-tree values, calculated from percentage height data, were correlated with the core data to determine the optimal sampling height. Core samples were found to be good predictors of whole-tree pulp yield for E. globulus, with simulated cores taken from the recommended sampling height (1.1 m) explaining more than 50% of variation in whole-tree pulp yield. Results for E. nitens were variable with large site differences apparent. On high quality sites, core samples from the recommended sampling height (0.9 m) were good predictors of whole-tree pulp yield, explaining around 60% of the variation. On poor quality sites, cores were poor predictors of whole-tree pulp yield. Radial orientation of cores was not important and predicted pulp yield was not related to tree size, basic density or fibre length. To estimate stand mean pulp yield to an accuracy of ±1% would require sampling 6 trees of E. globulus and 4 trees for E. nitens using either multiple discs or core samples. A single sampling height (1.1 m) is recommended for sampling for basic density, fibre length, fibre coarseness and predicted pulp yield in E. globulus. For E. nitens the recommended sampling height for basic density and fibre length is 0.7 m and 0.9 m is recommended for predicted pulp yield on good quality sites. Received 17 September 1998     

白腐菌预处理对杨木硫酸盐法制浆性能的影响

以杨木和白腐菌为研究对象,测定白腐菌预处理前后杨木化学组成与纤维形态的变化,找出合适菌株和最佳的预处理时间,进行硫酸盐法制浆前的预处理,比较制浆后浆料的卡伯值、得率、黏度和纸张的物理性能.结果表明:对木质素降解程度由大到小为香菇菌、云芝菌、杂色木云芝菌、脉射菌、佛罗里达侧耳和糙皮侧耳,香菇菌对综纤维素的降解程度最大,杂色木云芝菌的降解最小;预处理后,杨木纤维平均长度略有降低,纤维的长宽比得到了提高,壁腔比下降;与参照样相比,经脉射菌、杂色木云芝菌和佛罗里达侧耳预处理后制得的浆料,卡伯值降低、得率增加、黏度增加、脱木素选择性提高,纸张的撕裂指数和抗张指数均增加;经过香菇菌预处理后得到的浆料,虽然卡伯值降低、脱木素选择性增加,但是黏度和得率却在下降,纸张的撕裂指数和抗张指数减小.经过这4种白腐菌预处理后,纸张的耐折度和白度均大于对照.     

Effects site conditions on industrial fiber plantations of Lar/x olgensis

Plot sampling was conducted in the second cultivation areas ofLarix olgensis in Heilongjiang Province, China. By analyzing plot investigation data, wood properties, and kraft pulps of 840 plots and 248 sample trees in industrial plantations of L. olgensis on different sites, we examined the growth process of L. olgensis industrial plantation with suitable structure, the wood fiber feature, chemical composition, physical performance and pulp characteristics. It is suggested that site conditions have major effects on plantation growth, fiber contains, fiber length, rate between fiber length and fiber width, pulping rate and pulp physics intensity. The best site for L. olgensis industrial plantation growth is site class Ⅰ and site class Ⅱ, which are on lower locations. Site condition has an obvious influence on the wood characteristics. Within the range of site conditions and stand densities studied, the worse the site condition, the less the fiber contains, the shorter the fiber length, and the more the 1% NaOH extraction. This kind of relationship becomes more obvious as stand age increases. However, the influence of site condition on pulping rate and pulp physics intensity is not obvious. The result provides theoretical base for cultivation of industrial fiber plantation of L. olgensis.     

Sulfuric acid bleaching of kraft pulp 1: Bleaching of hardwood and softwood kraft pulps

To develop a new nonchlorine bleaching technology, hardwood and softwood kraft pulps, before and after oxygen-alkali predelignification, were treated with dilute sulfuric acid solutions (pH 1.0-1.8) at 100°C for 1 h and then extracted with aqueous sodium hydroxide at 70°C for l h. Hardwood kraft pulp was successfully bleached. The delignification selectivity was similar to that seen with oxygen-alkali bleaching; and it was greatly enhanced by the addition of sodium nitrate and sodium nitrite. The sulfuric acid bleaching can replace the presently adopted oxygen and chlorine stages if the additives are allowed. This bleaching process was also effective for oxygen-bleached hardwood kraft pulp, but it was less effective for softwood kraft pulp and oxygen-bleached softwood kraft pulp. The effectiveness of the addition of sodium nitrate and sodium nitrite was more apparent for softwood kraft pulp than for hardwood kraft pulp.Part of this report was presented at the 7th International Symposium on Wood and Pulping Chemistry, Beijing, July 1993     

越南甜竹纤维形态特征的研究

对甜竹原料、甜竹浆的纤维形态进行了研究。结果表明:甜竹原料纤维平均长度为2.37 mm、平均宽度17.91μm、长宽比值132.40;纤维平均壁厚为8.13μm、平均腔径为2.57μm、壁腔比值6.33。研究了在蒸煮过程中纤维形态的变化。结果表明,在蒸煮过程中甜竹纤维长度不断变小,从2.37 mm(原料)到1.79 mm(全浆),减少24%;蒸煮过程中纤维长宽比值也不断缩小,从132.40(原料)到98.89(全浆)。与青皮竹浆、桉木浆(阔叶木)、马尾松浆(针叶木)和麦草浆(草类)的纤维形态相比,甜竹浆纤维长度大于麦草浆纤维,小于马尾松浆纤维,与青皮竹浆和桉木浆纤维长度基本相近,因此甜竹浆纤维属于长纤维范围,是一种优良的造纸原料。