乙酰化木材的制备及其热塑性研究

利用乙酰化改性反应使木材获得热塑性，利用ＩＲ，ＤＳＣ，ＳＥＭ等对乙酰化木材的化学结构及热塑性进行了研究和表征。常规乙酰化方法不能使木材热塑化，而经三氟乙酸预处理制得的乙酰化木材在２９０－３００℃熔融，可在１１０－１３０℃单独或与其他合成高聚物共混热压成半透明薄片。     

近红外光谱快速预测乙酰化木材的增重率

采用近红外光谱技术对乙酰化大青杨和樟子松木材的增重率进行快速预测。在近红外波长780～2500 nm范围内,利用偏最小二乘法( PLS)建立木材横切面原始光谱及不同预处理(一阶导数、二阶导数、归一化处理和消噪)光谱乙酰化木材增重率数学模型,并进行比较分析。结果表明：乙酰化大青杨和樟子松木材分别选用归一化处理光谱和消噪光谱建立的增重率校正模型预测效果较好,预测模型相关系数( R)分别为0.90和0.70,预测标准差(RMSEP)分别为1.0072和1.3012,其中乙酰化大青杨木材增重率预测模型实测能力较佳,表明利用木材横切面近红外光谱建立的数学模型可以实现乙酰化木材增重率的快速预测。     

英国木材企业推出低成本改性木材产品

英国木材企业Kumwood公司推出了一种叫做“Acetowood”的改性木材产品系列。这种产品使用了该公司在广为人知的木材乙酰化技术的基础上自行开发的加工工艺。Acetowood是一种适用于地面的改性木材，堪与Vecowood媲美。     

国外木材乙酰化研究及应用进展

木材乙酰化是木材化学改性中研究最多的,并且已经开始商品化.用乙酸酐对木材进行乙酰化的反应可以用下面的式子表: Wood-OH+(CH3CO)2O=Wood-OOCCH3+CH3COOH     

乙酰化木材用作家具材料的性能分析北大核心

为改善杨木、樟子松等人工速生林木材的材质松软等缺陷,对其进行乙酰化处理,并进行性能检测分析。结果表明:经过乙酰化处理后,木材的热塑性提高,尺寸稳定性增强,漆膜附着力无显著变化,但胶合强度有所下降。建议对乙酰化木材进一步进行压缩处理,以提升其密度和表面硬度等性能,满足家具,特别是厨卫家具用材料的要求。     

乙酰化木材用作家具材料的性能分析

为改善杨木、樟子松等人工速生林木材的材质松软等缺陷,对其进行乙酰化处理,并进行性能检测分析。结果表明:经过乙酰化处理后,木材的热塑性提高,尺寸稳定性增强,漆膜附着力无显著变化,但胶合强度有所下降。建议对乙酰化木材进一步进行压缩处理,以提升其密度和表面硬度等性能,满足家具,特别是厨卫家具用材料的要求。     

乙酰化处理对樟子松木材耐光性和热稳定性的影响

【目的】探讨乙酰化处理对人工林木材耐光性和热稳定性的影响,为木材颜色调控技术及高耐光染色木材的研发提供理论依据。【方法】以樟子松木粉为试样,加入乙酸酐和二甲苯溶液,在120℃条件下分别反应5,10,20,40,60 min,测试乙酰化处理时间对木粉增重率的影响;分别称取1 g经不同时间乙酰化处理的木粉和未处理木粉,置于 UV老化试验箱内辐射100 h,利用红外光谱分析 UV辐射前后乙酰化木粉化学官能团的变化,通过热重和扫描电镜分析乙酰化木粉的热稳定性及其形貌变化。【结果】随着乙酰化处理时间的延长,樟子松木粉的增重率呈现先增加后降低的趋势,在处理40 min 时木粉增重率最大;乙酰化木粉在1741 cm －1和1385 cm －1处的CO,C—H特征吸收峰强度均大于原木粉,处理时间40 min 时木粉的吸收峰强度最大;UV 辐射后,乙酰化木粉在1508 cm －1处木质素苯环特征吸收峰强度明显大于原木粉,处理时间40 min 时木粉的吸收峰强度最大,表明木粉经乙酰化处理后光稳定性得到提升;热重分析显示,经乙酰化处理后,木粉热分解所需的温度明显提高,表明乙酰化木粉的热稳定性好于原木粉;扫描电镜分析表明,乙酰化处理可增强木粉微观构造抵抗光劣化的能力。【结论】乙酰化处理能有效抑制樟子松木材的光降解反应并提升其热稳定性。     

木材丙酰化及其它酰化研究进展

木材乙酰化是木材化学改性中研究最多的,并且已经商品化,而木材丙酰化和其它长碳链酰化的研究只是近年来的事.     

无催化条件下乙酰化杨木的工艺与性能

采用纯乙酸酐为处理液,在无催化剂条件下,分析反应温度和反应时间对乙酰化杨木增重率和反应速率的影响,并测试乙酰化杨木的性能.结果表明:随反应时间的延长和反应温度的升高,乙酰化杨木的增重率增大,密度略增,抗胀率增大,吸湿率减小;乙酰化对杨木弹性模量和抗弯强度的影响不显著.红外光谱分析表明,乙酰化木材中亲水性的羟基被乙酰基所取代,形成巯水性基团酯基,从而提高处理木材的尺寸稳定性.     

Kurawood公司推出采用低成本处理技术的新型木材产品

英国:木材企业Kurawood公司推出了一种叫做"Acetowood"的改性木材产品系列。这种产品使用了该公司在广为人知的木材乙酰化技术的基础上自行开发的加工工艺。Acetowood是一种适用于地面的改性木材,堪与Vecowood媲美。     

Potassium acetate-catalyzed acetylation of wood: extraordinarily rapid acetylation at 120°C

The catalytic effect of potassium acetate (KAc) on wood acetylation was investigated. Spruce wood specimens were impregnated with KAc and then heated in acetic anhydride at 120°C. The degree of acetylation was evaluated by the weight percent gain (WPG). In the presence of KAc, the reaction time to achieve a 20% WPG decreased by a factor of 200: 2 min was required in the KAc-catalyzed acetylation, while the uncatalyzed acetylation required at least 5 h. The hygroscopicity and dimensional stability of acetylated wood depended on the WPG irrespective of the treatment methods. This fact proved that KAc had no adverse influence on the dimensional stability of acetylated wood. As KAc is a cheap, water-soluble and non-toxic salt it can be a useful catalyst for the extraordinarily rapid acetylation of wood.     

木材表面非极性化原理的研究 I.木材乙酰化过程中化学官能团的变化

对杉木和“三北”一号杨两种木材的各主要组成进行了酯化处理,研究其在乙酰化过程中木材各主要组成的化学官能团的变化特征和结构的稳定性。结果表明：磨木木质素、纤维素、半纤维素经乙酸酐处理后,红外光谱上的１７４２ｃｍ－１附近均出现了表示酯类ＣＯ伸缩振动的新的吸收峰,表明在乙酰化过程中这些组分的化学结构都有新的非极性酯类化学官能团产生;而极性的羟基官能团的数量均有不同程度的减少;芳香基和脂肪基的结构上均有乙酸酯生成。纤维素酯化程度较低,半纤维素化学结构在乙酰化过程中会发生降解,而木质素和纤维素较为稳定。乙酰化处理是降低木材表面极性的一种有效方法。     

Effects of previous solvent exchange on acetylation of wood

Wood specimens were prepared in a swollen state using solvent exchange (PS) treatment. The swollen wood specimens were acetylated using acetic anhydride by heating at 80–120°C. At the beginning of heating, the weight percent gain (WPG) of PS-treated wood was greater than that of conventionally acetylated wood. This acceleration effect of the PS treatment was explained by the introduction of treating reagent into the wood polymers where the intermolecular hydrogen bonds were previously broken. On the other hand, the PS treatment had no influence on the final WPG and moisture sorption characteristics of acetylated wood. This indicated that the intrinsic reactivity of wood constituents was unaffected by the PS treatment. The acetylation of PS-treated wood produced greater bulking and slightly higher dimensional stability than that in the case of conventional acetylation at the same WPG. It was speculated that the expansion of cell lumina due to the PS treatment resulted in greater bulking on acetylation and lesser swelling of acetylated wood with moisture sorption.     

Swelling of acetylated wood I. Swelling in organic liquids

To investigate the affinity of acetylated wood for organic liquids, acetylated yezo spruce wood specimens were soaked in various liquids, and their swellings were compared to those of untreated specimens. The acetylated wood was rapidly and remarkably swollen in liquids having low hydrogen bonding power such as benzene and toluene in which the untreated wood was swollen only slightly or very slowly. On the other hand, the swollen volume of wood in water, ethylene glycol, and alcohols remained unchanged or slightly decreased after the acetylation. The effect of acetylation was greater in liquids having smaller solubility parameters. The easier penetration of aprotic organic liquids into the acetylated wood was considered to be due to the reduction of polarity and the scission of hydrogen bonds in the amorphous wood constituents where the hydrophilic hydroxyl groups were substituted by hydrophobic acetyl groups.     

Potassium acetate-catalyzed acetylation of wood: reaction rates at low temperatures

Spruce wood blocks were acetylated in the presence of potassium acetate (KAc) at 20, 40, 60, 80 and 120°C. At 20°C, the weight percent gain (WPG) due to the KAc-catalyzed acetylation reached 20% in 18 days, whereas that due to pyridine-catalyzed acetylation did not exceed 8%. The hygroscopicity and dimensional stability of the KAc-acetylated wood were the same as those of conventionally acetylated wood at the same WPG, irrespective of reaction temperature. These facts suggest that the KAc enables simplified acetylation of wood at room temperature. The activation energy (E _a) of the KAc-acetylation in the lower temperature range (20–40°C, 121–131 kJ/mol) was comparable to that of the acetylation of wood meal (140–146 kJ/mol). It was speculated that diffusion became a minor factor at reduced reaction rates in the lower temperature range, thus requiring a greater E _a.     

木材改性技术发展现状及应用前景

系统阐述了木材改性的背景、方法及意义,重点介绍了热改性、乙酰化、糠基化改性,及压密化和热处理组合改性的基本原理和工艺,及其对木材性质的影响;分析了这些改性方法的应用现状及工业化应用前景,并提出了今后需着重研究的关键问题。     

Potassium acetate-catalyzed acetylation of wood at low temperatures I: simplified method using a mixed reagent

Ezomatsu wood blocks were acetylated in a mixture of acetic anhydride and acetic acid containing excess potassium acetate (KAc). The mixture method enabled rapid acetylation at 120°C: a 20% weight gain (weight percent gain; WPG) was achieved within 30 min while the WPG did not exceed 18% after 120 min of conventional uncatalyzed acetylation. At 40°C, however, a satisfactory WPG was not achieved with the mixture method because both the wood swelling and KAc concentration in the reagent solution were limited at that temperature. In addition, the antiswelling efficiency attained by the mixture method was irregularly low, probably because of nonuniform reaction involving shrinkage of the cell lumina. These results suggest that the mixture method is not advantageous for low-temperature acetylation, whereas it enables simple and rapid acetylation at high temperature.     

Potassium acetate-catalyzed acetylation of wood at low temperatures II: vapor phase acetylation at room temperature

Ezomatsu wood blocks were impregnated with potassium acetate (KAc) and then exposed to acetic anhydride vapor at 25°C and 120°C. The KAc-impregnated wood was rapidly acetylated at 120°C, and only 6 min was needed to achieve 20% weight percent gain (WPG). The WPG increased with increasing catalyst loading (CL), but it turned to decrease above 20% CL probably because the diffusion of acetic anhydride vapor was hindered by excess KAc depositing in the cell lumina. Thus, careful control of CL is necessary in the vapor-phase acetylation. KAc was also effective in catalyzing the vapor-phase acetylation at 25°C: the KAc-impregnated wood attained 20% WPG within 7 days, whereas the WPG did not exceed 10% even after 1 month in the uncatalyzed system. Irrespective of treatment methods, the hygroscopicity of wood was reduced and its dimensional stability was improved with an increase of WPG. These results confirm that the use of KAc simplifies the acetylation process at room temperature with minimal loss of acetic anhydride.     

Analysis of the factors influencing the acetylation rate of wood

Factors influencing the rate of acetylation were examined based on the swelling of wood in the reaction solution and the dimensions of the wood sample. The activation energy of acetylation was also estimated. In a swelling test, it was found that wood swells thoroughly in acetic anhydride even without pyridine above 60°C. Therefore, pyridine may facilitate the acetylation process as a catalyst and not as a swelling agent. The weight gain, x (%), attained at reaction time t (h), for various compositions of acetylation solution or dimensions of wood sample were analyzed by applying an original rate equation [x = a × (1 – e^–kt )^1/n ], where a is the ultimate weight gain (%), k is the rate constant (h^–1), and n is a measure of the hindrance against the diffusion of reagent. The optimum volume fraction of pyridine in the pyridine-catalyzed acetylation was about 0.2. Accompanied by a rise in pyridine content, the reaction showed increased diffusion-controlled behavior. The rate constant, which is not affected by the dimensions of the wood sample, was estimated from which an activation energy of about 130kJ/mol was calculated.