Influence of reaction atmosphere on the liquefaction and depolymerization of wood in an ionic liquid, 1-ethyl-3-methylimidazolium chloride

The influence of reaction atmosphere on the liquefaction and depolymerization of wood in an ionic liquid, 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]), has been systematically studied. The wood samples were treated with [C2mim][Cl] at 120°C under various atmospheres such as oxygen, nitrogen, and carbon dioxide, both dried and humidified. The percentage of residue after the treatment shows that oxygen considerably accelerates the liquefaction of wood in [C2mim][Cl], and humidity hardly affects liquefaction under any atmosphere. Gel permeation chromatography (GPC) and high performance liquid chromatography (HPLC) analyses on the solubilized compounds in [C2mim][Cl] indicate that oxygen and humidity enhance the depolymerization of the wood component. Thus, the reaction atmosphere was revealed to influence, and 1be capable of controlling, the reaction of wood in [C2mim][Cl].     

Reaction behavior of wood in an ionic liquid, 1-ethyl-3-methylimidazolium chloride

Reaction of Japanese beech (Fagus crenata) in an ionic liquid, 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]), which can dissolve cellulose, was investigated. Although both lignin and polysaccharides such as cellulose and hemicelluloses can be liquefied at a treatment temperature of around 100°C, the liquefaction of polysaccharides mainly occurs at the beginning of the treatment with [C2mim][Cl]. Cellulose crystallinity in the wood was gradually broken down as the treatment continued. The solubilized polymers were depolymerized to low molecular weight compounds. The results indicate that [C2mim][Cl] is an effective solvent and reagent for the liquefaction of wood components and subsequent depolymerization of them. Part of this report was presented at the 58th Annual Meeting of the Japan Wood Research Society, Tsukuba, April 2008     

Reaction behavior of cellulose in an ionic liquid, 1-ethyl-3-methylimidazolium chloride

We investigated the reaction behavior of cellulose in an ionic liquid, 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]), which can dissolve cellulose. The cellulose samples were treated with [C2mim][Cl] at 100, 120 and 140 °C. At the beginning of the treatment, the solubilized cellulose in [C2mim][Cl] is depolymerized into various low molecular weight compounds such as cellobiose, cellobiosan, glucose, levoglucosan and 5-hydroxymethylfurfural. As the treatment continued, some of the low molecular weight compounds reacted with the ionic liquid to form new polymers, which were black and contained nitrogen. [C2mim][Cl] is, therefore, not only a solvent for cellulose, but also a reagent for both depolymerization to produce various low molecular weight compounds, and subsequent polymerization of those compounds.     

Manufacture of plywood bonded with kenaf core powder

Kenaf (Hibiscus cannabinus L.) core powder was used as a binder to manufacture three-ply plywoods of sugi (Cryptomeria japonica D. Don) by conventional hot pressing under various manufacturing conditions: hot-pressing conditions (pressure, temperature, and time) and powder conditions (grain size, spread volume, and moisture content). The adhesive shear strength and wood failure of plywoods were measured in accordance with the Japanese Agricultural Standard (JAS) for plywood. The result showed that fine kenaf core powder played a role as an effective binder when plywoods were pressed at high pressure, which caused extreme compression of veneer cells. In addition, the adhesive shear strength of plywoods in dry conditions was high regardless of pressing temperature and time, but it was sensitive to pressing temperature and time in wet conditions. The highest adhesive shear strength was obtained from plywoods manufactured with kenaf core powder (grain size 10 μm, spread volume 200 g/m², moisture content 8.6%) under hot-pressing conditions (pressure 5.0 MPa using distance bars 4 mm thick, temperature 200°C, time 20–30 min). However, the plywood could not meet the requirement for the second grade of plywood by JAS because of its low water-resistance properties. Part of this article was presented at the 58th Annual Meeting of the Japan Wood Research Society, Tsukuba, March 2008, and the 10th World Conference on Timber Engineering, Miyazaki, June 2008     

Morphological changes in sugi (Cryptomeria japonica) wood after treatment with the ionic liquid, 1-ethyl-3-methylimidazolium chloride

We investigated morphological changes in wood tissues of sugi (Cryptomeria japonica) resulting from treatment with the ionic liquid 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]), which dissolves cellulose. Treatment with [C2mim][Cl] caused dissociation and distortion of tracheids in latewood, but not in earlywood. This difference was due to the difference in swelling behavior of the cell wall between earlywood and latewood. Many pit membranes in bordered pits were broken by treatment with [C2mim][Cl]. In addition, some chemical changes in wood components, such as cellulose and lignin, occurred before significant disruption or destruction of the cell wall. Our results show that the reaction of wood liquefaction by [C2mim][Cl] treatment is not homogeneous, both from chemical and morphological viewpoints.     

Comparative study of morphological changes in hardwoods treated with the ionic liquid, 1-ethyl-3-methylimidazolium chloride

Three hardwoods of varying vessel arrangement were treated with the ionic liquid, 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]), which can dissolve cellulose, to investigate its influence on wood tissue morphology. Characterization was carried out by light and scanning electron microscopy. The wood fibers of all species swelled significantly during [C2mim][Cl] treatment. The swelling behavior varied according to wood species and differed from other cell types such as ray parenchyma cells. Morphological changes of the pits also varied between wood species. Treatment with [C2mim][Cl] affects wood tissues differently depending on wood species and cell type. These differences are not due to the vessel arrangement and its presence, but possibly from the chemical component and the microfibril angle of various wood tissues.     

Morphological changes of Japanese beech treated with the ionic liquid, 1-ethyl-3-methylimidazolium chloride

The morphological changes in wood tissues of Japanese beech (Fagus crenata) upon treatment with the ionic liquid, 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]), which can dissolve cellulose, were investigated. Treatment with [C2mim][Cl] induced significant swelling of all wood tissues. However, the swelling behavior of wood fibers was different from that of vessels. Intervascular pits were occluded, and pit membranes in ray-vessel pits were broken after treatment with [C2mim][Cl]. No significant differences in swelling behavior were found between latewood and earlywood, although different morphological changes for latewood and earlywood during [C2mim][Cl] treatment were seen in our previous studies on sugi (Cryptomeria japonica). We have found that the effects of [C2mim][Cl] on Japanese beech tissues are inhomogeneous and different from those found for other wood species.     

阻燃桉树胶合板的初步研究

以磷酸二氢铵（MAP）溶液为阻燃剂,通过浸泡尾叶桉单板,研究了单板的载药量;以Ⅱ类胶合强度为指标,利用正交试验对常规胶合板生产工艺进行了优选。在此基础上,选取浸泡时间和最优生产工艺试制了阻燃桉树胶合板,并对其Ⅱ类胶合强度和燃烧性能进行了检测。结果表明：不同厚度尾叶桉单板的载药量随浸泡时间的延长呈现相似的增长规律;试验所得常规尾叶桉胶合板最优生产工艺为施胶量210 g.m-2、热压温度130℃、热压时间8 min,该条件下胶合板的Ⅱ类胶合强度达到了2.01 MPa;单板浸泡8h后,单板平均载药量为32.05 kg.m-3,所制得阻燃胶合板氧指数提高了13.9%,炭化长度减少了8.3 mm（26.2%）,阻燃性能明显提高,而胶合强度也达到了Ⅱ类胶合板的国家标准。研究初步证明利用常规桉树胶合板生产工艺生产阻燃桉树胶合板是可行的。     

无醛大豆胶制备胶合板工艺及性能探究

采用生物基无醛大豆胶,通过胶合板厂现有设备对大豆胶合板的制备工艺参数进行系列实验表明:杨木胶合板最佳涂胶量为340g/m~2(双面涂胶,下同)、热压温度105℃;桉木胶合板最佳涂胶量为380g/m~2、热压温度110℃;在1～6h闭口陈化时间内,杨木、桉木胶合板的胶合强度均略有降低,但均可制备出满足国家二类板强度要求的胶合板材。实际应用过程中,我们可以根据实际情况调整上述制备工艺,以达到最佳效果。同时,利用生物基无醛大豆胶制备的板材具有较好的耐久性。     

Evaluation of the self-bonding ability of sugi and application of sugi powder as a binder for plywood

Binderless particleboards were manufactured from sugi (Cryptomeria japonica D. Don) heartwood and sapwood by hot-pressing (pressure: 5 MPa; temperatures: 180°, 200°, and 220°C; times: 10, 20, and 30 min), and the board properties [internal bonding (IB), thickness swelling (TS), water absorption (WA)] were investigated to evaluate the self-bonding ability. The IB, TS, and WA of the boards from sugi heartwood were better than those of the boards from sugi sapwood at any hot-pressing condition. Therefore, it was suggested that the self-bonding ability of sugi heartwood was superior to that of sugi sapwood. Then, sugi heartwood and sapwood powder with grain size 10 βm were used as a binder for plywoods. Four kinds of plywood were manufactured from the combination of powder and veneer, both of which were prepared from sugi heartwood and sapwood under the same hot-pressing conditions as the binderless particleboard, and the adhesive shear strength and wood failure of the plywood were investigated. As a result, the plywood composed of sugi heartwood veneer met the second grade of JAS for plywood, when either powder was used as a binder, when they were pressed at 200°C for 20–30 min and 220°C for 10 min.     

三种松木单板的胶合工艺条件和胶合性能的改善

用ＵＦ、ＭＵＦ胶制作三种松木胶合板，分别就单板厚度、涂胶量及抽提物含量对胶合性能的影响，松木与柳安混合树种组坯、特殊添加剂对改善胶合性能的作用进行了研究。结果表明：除了老挝松边材ＭＵＦ胶合板以外，１．５和２．０ｍｍ厚的单板胶合强度均达到或超过日本ＪＡＳ普通胶合板的要求。合板胶合强度随单板厚度增加而下降，在一定范围内增加涂胶量可以提高合板胶合强度，混合组坯及施加特殊添加剂具有改善松木单板胶合性能的作用。     

工艺参数对大豆基木质刨花板性能的影响

大豆蛋白类胶黏剂具有绿色、环保等特点,已成功应用于胶合板生产,但在刨花板领域应用较少。采用不同热压工艺参数,以改性双组份大豆基胶黏剂制备木质刨花板;通过正交试验研究密度、热压温度、热压时间、热压压力等因素对大豆基木质刨花板性能的影响,结果表明:密度对其性能影响最为显著,热压压力次之,而热压温度和热压时间影响不显著。生产性试验表明:大豆基木质刨花板的主要物理力学性能满足GB/T 4897—2015《刨花板》标准要求,可作为基材广泛应用于家具、墙体板等领域。     

杉木胶合板热压工艺研究

采用涂胶量、热压温度、热压压力、加压时间等4因素3水平的L9(34)正交试验,探讨以杉木间伐材和非规格材为原料制作杉木胶合板的热压工艺。结果表明:采用涂胶量280 g.m-2、热压温度125℃、热压压力1.0 MPa、热压时间1 m in.mm-1,制作出的杉木胶合板胶合强度达到GB/T 9846-2004中Ⅱ类胶合板的指标要求。     

桉树木材旋切单板质量以及制造胶合板工艺的研究

对福建省主要桉树木材材性及其旋切单板厚度偏差、背面裂隙率进行检测分析,探讨木材旋切单板的适应性和制造胶合板的工艺并采用正交法优选最佳工艺参数。结果表明:尾叶桉单板背面裂隙率和单板厚度变动系数比尾巨桉小,尾叶桉用于旋切1.5 mm厚度单板质量较佳。尾叶桉木材制造胶合板较佳工艺参数:热压温度为130℃、单位压力为1.4 MPa、热压时间为1.35 min·mm-1、涂胶量为320 g·m-2。工艺条件对板材性能均有影响,桉树木材龄级对板材性能影响显著,随着桉树龄级的增大,板材性能有较大幅度提高,特别是静曲强度、弹性模量影响最为明显。     

Prediction of the optimum veneer drying temperature for good bonding in plywood manufacturing by means of artificial neural network

Veneer drying is one of the most important stages in the manufacturing of veneer-based composites such as plywood and laminated veneer lumber. Due to the high drying costs, increased temperatures are being used commonly in plywood industry to reduce the overall drying time and increase capacity. However, high drying temperatures can alter some physical, mechanical and chemical characteristics of wood and cause some drying-related defects. In this study, it was attempted to predict the optimum drying temperature for beech and spruce veneers via artificial neural network modeling for optimum bonding. Therefore, bonding shear strength values of plywood panels manufactured from beech and spruce veneers dried at temperatures of 20, 110, 150 and 180 °C were obtained experimentally. Then, the intermediate bond strength values based on veneer drying temperatures were predicted by artificial neural network modeling, and the values not measured experimentally were evaluated. The optimum drying temperature values that yielded the highest bonding strength were obtained as 169 °C for urea formaldehyde and 125 °C for phenol formaldehyde adhesive in beech plywood panels, while 162 °C for urea formaldehyde and 151 °C for phenol formaldehyde in spruce plywood panels.     

水性异氰酸酯胶合板与细木工板的研究

以水性异氰酸酯胶粘剂试制胶合板和细木工板。研究结果表明,单板的材种和施胶量等对异氰酸酯胶合的板材性能有较大影响;采用异氰酸酯,胶合板用胶量较少,在施胶量为200g/m~2时,马尾松、杨木、荷木、枫木单板制成的胶合板胶合强度均能达到GB/T5849-1999的要求,枫木作中板的细木工板在施胶量为250g/m~2时胶合强度和横向静曲强度均达到国家标准;根据试验结果并结合生产实际的成本分析表明,胶合板成本增加了81～189元/m~3,细木工板的成本增加了120元/m~3和104元/m~3。     

Micromechanical properties of the interphase in pMDI and UF bond lines

Micromechanical properties of cured polymeric diphenylmethane diisocyanate (pMDI) and urea formaldehyde (UF) adhesive and wood cell walls (beech) in adhesive contact compared with cell walls without adhesive contact were measured in situ by means of nanoindentation. Using UV-microphotometry obtained absorbance spectra of micromechanical investigated cell wall regions gave a strong indicator for the presence of pMDI compounds in wood cell walls. Nanoindentation results reveal that both pure UF and UF-penetrated cell walls show a very brittle character. In contrast, pMDI adhesive is very tough and soft at the same time, and when diffused in cell walls, it does not mechanically embrittle the cell structure.     

生产工艺对巨尾桉/聚乙烯膜复合材料质量的影响

采用巨尾桉基材、胶合剂聚乙烯膜制备三层木塑复合材料,分析热压温度、热压时间、热压压力、施胶量这四个因素对复合材料胶合强度的影响。结果表明：在热压温度160℃、热压时间50s/mm、热压压力0.7MPa、施胶量为119g/m2的工艺条件下,巨尾桉/聚乙烯膜复合材料的胶合性能最优,能够达到II类胶合板标准。     

蔗糖-三聚氰胺-甲醛共缩聚树脂胶黏剂的合成研究

以蔗糖、三聚氰胺、甲醛为原料,在碱性条件下合成了外观为黄色、透明、均一、无沉淀且水溶性好的蔗糖-三聚氰胺-甲醛(SMF)共缩聚树脂木材胶黏剂。采用均匀试验设计对合成反应体系的蔗糖、交联剂用量和甲醛与三聚氰胺的摩尔比进行了优化,通过正交试验设计对桉树胶合板热压工艺参数进行了优化。结果表明:最佳合成条件为:蔗糖与三聚氰胺的摩尔比为0.7,甲醛与三聚氰胺的摩尔比为2.7,交联剂用量为树脂的0.33%;桉树胶合板最佳胶合工艺参数为:双面施胶量为340g/m~2、热压压力为0.9MPa、热压温度为150℃、热压时间为60s/mm。     

Acceleration of the cure of phenolic resin adhesives VII: Influence of extractives of merbau wood on bonding

The influence of merbau wood extractives on the gelation rate of a phenolic adhesive and the effects of some cure accelerators on the bond performance of merbau plywood were investigated. The addition of merbau wood extractives slightly increased the gelation rate of the phenolic resin. This increase in the gelation rate was revealed to be due to a fall in the resin pH caused by addition of the extractives. The addition of cure accelerators, sodium carbonate and propylene carbonate, caused a considerable reduction in the hot-pressing time required for the merbau plywood to achieve sufficient bond qualities. Brushing veneer surfaces caused an increase in bond qualities. The combination of the cure acceleration and the surface brushing greatly improved the bondability of merbau wood. The main factor of gluing difficulty is considered to be the poor wettability of the veneer surfaces resulted from the accumulation of migrating extractives.Part of this work was presented at the 47th annual meeting of The Japan Wood Research Society, Kochi, April 3–5, 1997