酚化木质素改性酚醛树脂胶黏剂的制备及性能表征

在碱性条件下,酸性木质素先经苯酚处理,再用于对酚醛树脂进行改性,制备得到木质素改性酚醛树脂(LPF)胶黏剂,考察了木质素用量、苯酚处理时间及温度、苯酚处理木质素时氢氧化钠水溶液用量(第一批次氢氧化钠)、酚醛物质的量比对LPF胶黏剂性能的影响。研究结果表明:在木质素用量25%、苯酚处理时间2 h、苯酚处理温度80℃、第一批次氢氧化钠水溶液用量8%、苯酚与甲醛的物质的量比1.0∶2.0时,LPF胶黏剂的胶合强度为1.57 MPa,较未经改性的酚醛树脂(PF)胶黏剂的1.35 MPa提高了16.3%,游离苯酚为0.58%,比PF的0.72%降低了19.4%,游离甲醛0.16%、固体质量分数51.2%、pH值11.4、黏度80 mPa·s、贮存期为60天。FT-IR分析表明:LPF在2893和1213 cm~(-1)处吸收峰明显减弱,表明木质素分子中甲氧基部分脱落;在1505、1320、1114和875 cm~(-1)处吸收峰消失,表明合成酚醛树脂过程中,木质素中的磺酸基消失;在1018 cm~(-1)处的吸收峰明显增强,表明有新的醚键生成。     

纤维素乙醇木质素改性酚醛树脂胶黏剂的初步研究

以纤维素乙醇木质素、苯酚、甲醛为原料,氢氧化钠为催化剂,制备了纤维素乙醇木质素改性酚醛树脂胶黏剂,研究了木质素替代苯酚的工艺以及对胶黏剂性能的影响。研究发现:当木质素替代率为30%时,纤维素乙醇木质素改性酚醛树脂胶黏剂胶合强度达到国家Ⅰ类板要求,甲醛释放量达到Eo级,且成本低、胶合强度好、低毒环保,可广泛用于制备室外级人造板。     

酶解木质素改性酚醛树脂胶黏剂的研究

利用秸秆发酵制备能源酒精的残渣中提取的酶解木质素(EHL),部分代替苯酚合成改性酚醛树脂胶,并热压制得胶合板.测定了胶合板的胶合强度,改性树脂胶的黏度、固含量、水混合比、可被溴化物、游离酚、游离醛等性能指标.结果表明:木质素替代量达20%时,各项性能仍能基本达到国家标准Ⅰ类板的要求,特别是耐水性十分良好,水煮两次后胶合强度仍远大于国家标准Ⅰ类板≥0.7MPa的要求.     

酸木质素改性酚醛树脂胶粘剂的研究

分别用硫酸、硝酸和盐酸从造纸黑液中提取木质素,用酸木质素来替代部分苯酚合成酚醛树脂胶粘剂,对产物进行了固体含量、游离甲醛含量和胶合强度的测定,并用红外光谱对其进行了结构表征。作者考察了酚醛比(物质的量比)和酸木质素的替代量对胶粘剂性能的影响。结果表明:当n(苯酚):n(甲醛)=1:1.5,硝酸木质素的替代量为20%时,胶粘剂的综合性能最优。     

环保型改性酚醛树脂胶的制备与性能

利用自制助剂，在酚醛树脂(PF)合成过程中对其进行改性，并通过喷雾干燥工艺研制出环保型无毒酚醛粉状树脂；同时探讨了升温速度、改性荆、助剂、干燥系统参数等试验条件对该改性酚醛树脂胶性能的影响,测试结果表明,制备的改性酚醛树脂胶的性能可满足国标GB14732-93规定的要求。     

低游离甲醛羟甲基化木质素磺酸盐-酚醛复合胶黏剂研究

以工业木质素为原料,采用羟甲基化反应提高木质素反应活性,确定了羟甲基化反应木质素和催化剂的最佳配比:木质素与甲醛质量比为3:1、催化剂用量为0.25%(以木质素原料计).并用FT-IR和13C NMR对羟甲基化反应结果进行了分析.通过羟甲基化木质素磺酸盐(HLF)与酚醛树脂(PF)共混制得木质素酚醛树脂(LPF)胶黏剂.实验结果表明,该胶具有制备工艺简单、游离甲醛低的特点,用HLF替代40%的PF时,其胶合强度达到国家Ⅰ类胶合板的要求.     

生物质酚醛树脂木材胶黏剂的研发和应用

为了缓解石化资源紧缺带来的尖锐矛盾,探索生物质酚醛树脂(BPF)工业生产和应用的可行途径。与生产单位密切合作的初始工业水平下的研发/试产结果表明:BPF的固体含量和出釜粘度是影响树脂生产/使用技术经济期望的重要因素;BPF的生产技术条件和BPF对结构用胶合板的胶合条件和胶合效果与常规纯酚醛树脂(PF)基本相当,但具较好的环保效益和经济效益;生物质酚醛树脂具切实的技术经济可行性和广阔的开发应用前景,但须继续作出艰苦的努力和深入的探索。同时建议政府给取代性生物质材料研发、生产和使用以切实的鼓励政策。     

酚化木质素-糠醛胶黏剂及其复合腻子研究

研究利用高反应活性酚化木质素制备高性能酚化木质素-糠醛胶黏剂。木质素酚化后,在756 cm^-1和695 cm^-1处新增了两个峰,证实了木质素侧链位的羟基和酚环的活性位点发生了取代反应。在糠醛和苯酚的摩尔比为1.4/1,糠醛和木质素的质量比为0.05/1,缩合时间为3.5 h,氢氧化钠的用量为11%条件下,所制备的酚化木质素-糠醛胶黏剂各项性能良好。该胶黏剂的固体含量为56.25%,pH为11.2,黏度为1 525 m Pa·s,游离糠醛含量为0.04%,游离苯酚含量为0.05%,胶合强度为1.67 MPa。采用六亚甲基四胺优化,胶层均匀分布,与木材面紧密结合,有效胶钉较多,改善了胶合强度。该酚化木质素-糠醛胶黏剂与桉木粉复配所得复合腻子,应用于胶合板表面缝隙填充和平整度调控,不含甲醛,与胶合板相容性好,干燥速度快,耐水性好,打磨性好,粘结强度高,为胶合板可直接饰面和提高饰面高光性提供了技术支撑。     

利用苯酚液化大豆粉制备耐水性木材胶黏剂

以硫酸/磷酸为催化剂和苯酚液化,将大豆粉转化为胶黏剂的制备原料,并制备得到耐水性木材胶黏剂。采用GPC,HPLC,FTIR等手段结合胶合板压制,对豆粉苯酚液化产物及其与甲醛缩聚得到的胶黏剂进行表征。结果表明:以苯酚/豆粉质量比为3/1～2/1、5%硫酸为催化剂下,将豆粉在130～150℃下液化90min,90%以上的豆粉转化成相对分子质量为250～7250的产物,部分苯酚以1,4-取代和1,2-取代方式与豆粉反应形成结合酚;苯酚液化不仅破坏大豆蛋白的紧密球形结构,还使液化豆粉的活性基团增加,由此通过苯酚液化豆粉与甲醛缩聚,制得低游离甲醛释放的、胶接性能满足国家标准要求的Ⅰ类胶黏剂,由此所制备胶合板的28h煮-烘-煮湿强度在1.24～1.81MPa之间,达到耐候胶合板要求;苯酚/豆粉的比例对液化产物以及苯酚液化豆粉-甲醛胶黏剂的许多特性都有不同的影响,其中以苯酚/豆粉比例为3的胶黏剂胶接强度最好。     

液化木薯淀粉对改性酚醛树脂的性能影响及结构表征

以苯酚为液化剂,在酸性条件下液化木薯淀粉,将所得液化产物用于制备淀粉基改性酚醛(APF)树脂胶黏剂。采用单因素条件探讨液化过程中木薯淀粉添加量对改性树脂性能的影响,并通过FT-IR和SEM表征改性树脂结构。结果表明:随着木薯淀粉添加量的增大,改性树脂胶合强度逐渐下降,当液固比从2.4∶1降至1.0∶1时,制备的胶合板胶合强度由1.85 MPa降至1.14 MPa,降幅达到38.4%,但仍高于国家标准要求的0.7 MPa。同时,随着木薯淀粉添加量的增大,胶合板甲醛释放量逐渐减小,由0.279 mg/L降至0.095 mg/L,远低于国家标准E0级(0.5 mg/L)要求。FT-IR分析表明,在1014 cm^(-1)和1147 cm^(-1)处分别出现芳香醚C—O和芳香醚C—O—C的伸缩振动峰。SEM结果显示,木薯淀粉经液化后细胞壁形态遭到严重破坏,结晶度降低,但仍可观察到APF树脂的表面存在颗粒,说明APF树脂产生了更多的活性芳核衍生物,总体活性增强,易于发生化学交联反应。     

生物质溶剂液化研究进展

本文阐述了生物质液化溶剂的种类和特性、原料适应性、液化作用原理和液化产物等,总结了国内外在液化溶剂选择、应用等方面的研究情况,探讨了生物质溶剂液化发展趋势,旨在为生物质能的高效利用提供参考.     

酚醛树脂胶粘剂的改性

介绍利用三聚氰胺,尿素,木质素,聚乙烯醇缩醛,间苯二酚等物质对酚醛树脂胶粘剂改性研究的最新进展。     

Attempts to understand the nature of phenolic and etherified components of wood lignin

Summary Periodate oxidation, because of its high selectivity in degrading phenolic nuclei, has been combined with nitrobenzene oxidation and phenyl nucleus exchange techniques to investigate the nature of wood lignin in situ. For both softwood and hardwood, the phenolic and etherified components of wood lignin have been shown to differ significantly in chemical composition, and the etherified lignin structure appears to be substantially more condensed.Financial support from the Empire State Paper Research Associate (ESPRA) and by the NRICGP of USDA (No. 93-37103-9318) is greatly appreciated     

Analysis of progress of oxidation reaction during oxygen-alkali treatment of lignin I: method and its application to lignin oxidation

A new method is applied to evaluate the progress of the oxidation reaction of lignin during oxygen-alkali treatment. This method employs the difference in permanganate consumption of the sample before and after the oxygen-alkali treatment as an indication for the lignin oxidation. When kraft lignin and residual lignin isolated from unbleached softwood kraft pulp were subjected to oxygen-alkali treatment up to 6000min, the progress of the oxidation expressed by this method was separated into clearly distinguished three phases. During the first and second phases, the progress of oxidation was well correlated to the loss of methoxyl group and to the decrease in the yield of nitrobenzene oxidation products. The addition of Mn⁺ to the oxygen-alkali treatment depressed oxidation during the second phase partly and that during the third phase almost completely. Calculations based on the change in the permanganate consumption revealed that the oxidation during the first phase corresponded to 4.2 electrons abstracted from one lignin structural unit on average. The oxidation process by oxygen-alkali treatment was hypothetically attributed to the direct reaction between molecular oxygen and the phenolic unit of lignin, which mainly took place during the first phase, and to the autooxidation-type oxidation during the second and third phases.Part of this paper was presented at the 9th ISWPC, Montreal, June 1997; and at the 42nd Lignin Symposium, Sapporo, October 1997     

Research on utilizing recycled plastic to make environment-friendly plywood

In our study, we replaced traditional adhesives with compounds made with recycled plastic shopping bags in order to make hot-melt plywood using various amounts of plastic film, different hot-pressing temperatures and hot-pressing times.All three variables have an effect on the intensity and water-resistance of plywood.The results show that the bonding strength of plywood does not increase with increasing amounts of plastic film.When the hot-pressing temperature is increased to 150°C, the bonding strength do...     

Factors affecting bleedthrough of phenolic resin adhesive in hardwood plywood

Summary Some variables affecting the bleedthrough of phenolic resin adhesives in hardwood plywood were studied quantitatively. Variables included resin age, age of adhesive mix, extender/water ratio, amount of glue spread, aseembly time, veneer moisture content, species differences, grain angle, platen pressure, pressure cycle, platen temperature and rate of temperature rise.A technique was developed for evaluating bleedthrough numerically. This permitted the use of statistical analysis in a series of two- and three-factor experiments that resulted in some conclusions about the important interactions of variables, the combinatinos of which affect the amount of bleedthrough. Generally those combinations of variables that result in a high volume of glue in the glueline at the time of pressing, with a minimum of penetration into the veneer surfaces, permitted the phenolic adhesive to move through open vessel segments, that were inclined to the panel surface during the period of highest fluidity, when a pronounced lowering of viscosity is caused by the temperature rise in the glueline. These results generally confirmed other research on bleedthrough where urea resin adhesives were used as well as a different evaluating technique. A general concept of the mechanism of glue bond development in the manufacture of plywood is proposed in the light of the experimental results.

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Zusammenfassung Verschiedene Faktoren, die das Durchschlagen von Phenolharzleimen bei der Herstellung von Sperrholz aus Laubhölzern verursachen, wurden quantitativ untersucht. Sie betrafen das Alter des Harzes, das Alter der Leimmischung, das Verhältnis Streckmittel zu Wasser, die Menge des Leimauftrages, die Zeit zwischen Leimauftrag und Erreichen des Preßdruckes, den Feuchtigkeitsgehalt des Furniers, die Unterschiede zwischen den verschiedenen Holzarten, den Faserrichtungswinkel, den Preßdruck, den Preßzyklus, die Preßplattentemperatur und die Temperatur-Anstiegsgeschwindigkeit. Ein Verfahren zur numerischen Bewertung des Durchschlages wurde entwickelt. Dadurch konnte eine statistische Analyse bei einer Reihe von Versuchen mit zwei oder drei Einflußgrößen angewendet werden, die Stärke des Durchschlagens Wechselwirkungen zwischen Faktoren gaben, die gemeinsam die Stärke des Durchschlagens bestimmen. Im allgemeinen ließen jene Faktoren-Kombinationen, die durch eine große Leimmenge kurz vor dem Verpressen, bei gliechzeitig verhältnismäßig geringer Leimeindringung in die Furnieroberfläche gekennzeichnet waren, den Phenolharzleim durch die schräg durch das Furnier hindurchlaufenden, angeschnittenen Gefäße hindurchtreten. Dies geschah zum Zeitpunkt der höchsten Leim-Verflüssigung, d. h. dann, wenn die Leim-Viskosität durch die erhöhte Temperatur in der Leimfuge am niedrigsten war. Diese Ergebnisse bestätigten andere Forschungsergebnisse, bie denen Harnstoffharzleime, aber auch ein anderes Bewertungsschema verwendet wurden. Aufgrund der experimentellen Ergebnisse wird eine allgemeine Hypothese über die Entstehung der Leimverbindung bei der Sperrholzerzeugung aufgestellt.

     

Progress of oxidation of non-phenolic lignin moiety in an oxygen bleaching process via the conversion of non-phenolic into phenolic lignin moiety

To examine whether non-phenolic lignin moiety is converted into the new phenolic counterpart by the participation of active oxygen species (AOS) under oxygen bleaching conditions, a β-O-4 type dimeric lignin model compound, 2-(2-methoxyphenoxy)-1-(3,4-dimethoxyphenyl)propane-1,3-diol (I), 2-(3,5-difluorophenoxy)-1-(4-hydroxy-3-methoxyphenyl)propane-1,3-diol (III), or 2-(3,5-difluorophenoxy)-1-(3,4-dimethoxyphenyl)propane-1,3-diol (IV), was treated under conditions similar to those for oxygen bleaching. A phenolic compound, 4-hydroxy-3-methoxybenzyl alcohol, was added together to generate AOS in the reaction of compound I or IV. The results obtained suggested that AOS attack the side chains of compounds I, III, and IV accompanied by the β-O-4 bond cleavages and the liberations of the corresponding phenolic compounds, 2-methoxyphenol (II), 3,5-difluorophenol (V), and compound V, respectively. However, the rapid liberation of compound V in the oxygen-alkali treatment of compound III may mainly be caused by alkaline-induced reactions and/or some oxidation reactions of the primary degradation product of compound III, a muconic acid derivative.     

Performance of Sugi lamina impregnated with low-molecular weight phenolic resin

This study was conducted to evaluate the performance of Sugi lamina impregnated with low-molecular weight phenolic (LMWP) resin using the full cell process followed by curing at high temperature. In this study, penetration of LMWP resin into finger-jointed lamina was examined. Physical and mechanical properties, such as surface hardness, dimensional stability, bending and shear strength of LMWP-resin-treated and untreated lamina were investigated. In addition, the bonding quality and nail-withdrawal resistance of 3-ply assembly specimen made from LMWP-resin-treated and untreated lamina bonded using resorcinol–phenol formaldehyde resin adhesive were also investigated. The main results were as follows: LMWP resin was found to have penetrated sufficiently into finger-jointed lamina. The physical properties of LMWP-resin-treated lamina were found to have improved significantly in comparison with untreated lamina. However, no significant difference was found between LMWP-resin-treated and untreated lamina in terms of their mechanical properties. There was an improvement in bonding quality of the assembly made from LMWP-resin-treated lamina when compared with that made from untreated lamina. In the assembly made from untreated lamina, a significant decrease in nail-withdrawal resistance was observed between dry conditions test and after humidity conditioning test. However, the same tendency was not found in the assembly made from LMWP-resin-treated lamina.     

Characterisation of phenolic resin and nanoclay admixture and its effect on impreg wood

Wood Science and Technology - Bulking treatment with low molecular weight phenol formaldehyde (LmwPF) resin has been found to successfully enhance the properties of low-density wood but emit higher...     

Experimental and theoretical studies of the thermal degradation of a phenolic dibenzodioxocin lignin model

A large part of biphenyl structures in lignin are etherified by α- and β-carbons of another phenylpropane unit to give an eight-member ring called dibenzodioxocin. The behavior of a phenolic dibenzodioxocin lignin model, 4-(4,9-dimethoxy-2,11-n-dipropyl-6,7-dihydro-5,8-dioxa-dibenzo[a,c]cycloocten-6-yl)-2-methoxyphenol (DBDOH, 1), was studied by different mass spectrometry and thermal methods, leading to the conclusion that dibenzodioxocins are thermally unstable products. Both semi-empirical and density functional theory quantum calculations show that both C–O bonds, which connect the biphenyl part of the dibenzodioxocin molecule to the phenolic group, can be broken under increasing temperature. However, they do not play the same role since their dissociation occurs through different barrier heights. The C–O bond directly connected to the phenolic group (α–O-4) will dissociate first since its barrier energy for scission is lower than the other one (β–O-4), by roughly 12 kcal mol^–1 (≈50 kJ mol^?1). This conclusion is likely applicable to thermal degradation of DBDO units in lignin polymer.