苯酚处理液体木质素改性酚醛树脂胶粘剂的制备及性能表征

在碱性条件下,液体木质素先经苯酚处理后替代部分苯酚对酚醛树脂进行改性,制备得到液体木质素改性酚醛树脂(LPF)胶粘剂。考察了催化剂用量(苯酚处理木质素时氢氧化钠用量)、苯酚与甲醛(P/F)的物质的量之比、聚合温度、聚合时间对LPF胶粘剂性能的影响。研究结果表明:当催化剂用量3%、n(苯酚)∶n(甲醛)=1∶1.975、聚合温度90℃、聚合时间50 min时,所制备的LPF胶粘剂的干湿胶合强度分别为3.15、1.46 MPa,较未经改性的PF胶粘剂分别提高了17.5%、8.1%,游离苯酚的含量降低至0.62%;LPF胶粘剂的游离甲醛含量为0.22%,固体含量为52.8%,黏度为125 mPa·s。红外分析结果表明,苯酚处理后的木质素可以代替苯酚与甲醛发生反应生成新的物质,该物质有可能与PF胶粘剂发生接枝共聚产生新的醚键桥接,由此也说明在制备LPF胶粘剂过程中木质素发生了化学反应。     

三步共聚法制备木质素基酚醛树脂胶粘剂

利用木质素部分替代苯酚,三步共聚制备了木质素基酚醛树脂胶粘剂(LPF),研究了碱浓度、醛酚比、木质素添加量对LPF的粘度、固含量、游离甲醛含量、游离苯酚含量和胶合强度的影响,并采用FT-IR、13C-NMR和TG对LPF官能团结构和热固化特性进行了表征。结果表明:采用三步共聚法分步加入甲醛溶液,更有利于羟甲基化反应和后续的缩聚反应,并且可操作性好。胶粘剂的最优制备工艺为:碱的质量分数15%(以木质素和苯酚总质量为基准);醛、酚物质的量比2.0∶1;木质素添加量为苯酚物质的量分数30%。制得的LPF胶粘剂的粘度为183.2 mPa·s,固体质量分数45.05%,游离甲酵质量分数0.22%,胶合强度0.85 MPa,均达到GB/T 14732—2006要求。木质素的添加还改善了酚醛树脂的热固化特性。     

木素基酚醛树脂胶粘剂的应用性能研究

采用热化学酚化技术活化木素得到木素酚化产物,以酚化产物代替苯酚制备低成本的木素酚化液基酚醛树脂(LPF)胶粘剂。采用红外光谱(FT-IR)对LPF和传统PF的结构进行了表征,通过对比试验分析了LPF的应用性能,并对LPF胶粘剂应用性能产生的机理作了一定的探讨。结果表明:酚化后的木素参与了LPF胶粘剂的合成,并具有新的不同取代基的苯环结构;LPF胶粘剂与传统酚醛树脂(PF)胶粘剂具有相似的应用性能,前者比后者具有更低的游离酚(醛)含量(游离酚<0.12%,游离醛<0.08%)、更快的干燥速率和更低的施胶量(固含量29%时施胶量为297g/m2);另外,LPF胶粘剂具有优异的胶合性能(达到了Ⅰ类胶合板的标准要求)和储存稳定性,完全满足高性能环保型胶粘剂的使用要求。     

不同分子量麦草碱木素性能及其对LPF胶性能的影响

应用超滤分级方法,将麦草碱木素分成3种不同分子量范围的级分。分析表明：随着分子量的降低,麦草碱木素的甲氧基含量降低,酚羟基含量升高,其反应活性随之升高;同时,羧基含量降低,其溶液表面活性升高。进一步实验结果表明,随着麦草碱木素分子量的降低,LPF胶的胶黏强度升高,游离甲醛含量和黏度降低,综合性能提高。     

碱性酚化木质素结构表征及在酚醛树脂中的应用研究

采用碱催化酚化改性的方式,增加木质素反应活性位点含量,提高木质素-酚醛树脂木材胶粘剂的反应活性,同时降低树脂中无机盐的含量.将甲醛溶液分三批加入酚化木质素溶液,并在第二批加入的同时加入30％质量分数的氢氧化钠溶液,甲醛加入并反应一定时间后加入尿素,自然降温至40℃以下出料,即得碱性酚化木质素改性酚醛树脂.为证明碱性酚化...     

木质素基酚醛树脂泡沫塑料的结构与性能研究

研究了木质素基可发性酚醛树脂(LPF)及LPF泡沫塑料的结构与性能。结果表明,采用酚化木质素制备的LPF具有比酚醛树脂(PF)更低的游离甲醛(质量分数为0.35%)和更低的游离苯酚(质量分数为0.59%);傅立叶变换红外光谱(FTIR)分析证明了木质素的酚化及参与树脂固化反应;体视显微镜观测结果表明,LPF泡沫塑料具有比PF泡沫塑料更高的闭孔结构;热重分析及氧指数分析结果表明,LPF泡沫塑料具有更好的热稳定性和阻燃性能;压缩强度、导热系数和吸水率测定结果表明,LPF泡沫塑料具有更好的力学性能、保温性能和防水性能。相比于传统的PF泡沫塑料,采用热化学酚化技术制备的LPF泡沫塑料,具有更加优良的力学、保温、防火、防水性能,且更加安全、环保、经济。     

木质素酚醛树脂胶粘剂黏度的研究

木质素胶粘剂高黏度的特征阻碍了其工业化应用,该文考察了木质素酚醛树脂(LPF)胶粘剂的pH、质量分数、氯化钠与尿素的加入、贮存时间等因素对其黏度的影响,作为对比,同时测试了这些因素对酚醛树脂胶粘剂和麦草碱木素(WSSL)碱性溶液黏度的影响。结果表明,LPF胶粘剂的黏度随着尿素的加入降低,而随着其质量分数的增加、pH的降低、氯化钠的加入急剧升高,并分别在w(LPF)=30.0%、pH=10.2、w(NaCl)=8.3%处有一个转折点;LPF胶粘剂的黏度曲线与WSSL碱性溶液相似,而与酚醛树脂胶粘剂相差较大;要制得高含量的LPF胶粘剂,其pH应大于10.2,w(NaCl)<8.3%,并且w(尿素)=2%～3%。     

木素酚醛胶的制造方法

日本公开昭60-22024介绍了一种苯酚-木素-甲醛系胶粘剂的制造方法。该胶粘剂中木素含量为苯酚量的10～50％,这种木素是将pH调至4～10的亚硫酸纸浆废液(SSL),在140～180℃用氧或空气氧化到pH为3～6得到的物质(以下称作改性木素磺酸盐)。改性木素磺酸盐的添加,可使胶粘剂的胶粘性能提高。本专利的特点是解决了苯酚系胶粘剂胶粘性能低的缺点。在本专利中,SSL是针叶材或阔叶材,针叶材最佳。作为SSL的碱用Na、Ca、Mg、NH_4均可,但用碱的情况下,在氧化反应时有淤渣产生,Na或Mg碱较好。反应温度160～180℃最佳。经氧化反应得到的改性木素磺酸盐,在苯酚与甲醛反应时加入,然后进行共缩合反应,或在经过预反应得到的酚醛初期缩合物中混合,以得到苯酚-甲醛-木素系胶粘剂。该胶粘     

相分离条件下楠竹碱木素改性产物的集聚态研究

楠竹经三种条件碱法蒸煮,所得黑液经酸化沉淀干燥,用60％（wt）硫酸、相分离法处理,精制有机相得到三种碱木质素酚,将三种碱木质素酚分别与由竹粉经相分离法直接提取的木质素酚通过红外光谱（FT-IR）、凝胶色谱（GPC）、原子力显微镜（AFM）、动态光散射（DLS）进行结构和分子集聚态的分析与比较.结果表明,在缓和的碱法蒸煮条件下,黑液中的木素还具备一定的酚化改性潜力,所得碱木素酚结构和官能团与竹粉木质素酚未见较大差异,但在分子集聚态上其分散性明显不同于竹粉木质素酚,表现为尺度小,分布密集等特点.     

玉米芯酶解残渣酚化改性工艺及产物结构表征

以玉米芯纤维素酶水解残渣为原料,利用对甲酚和硫酸对其木质素进行酚化改性。采用单因素和正交试验的方法探讨了硫酸浓度、反应温度、反应时间和硫酸用量对酚化改性产物的得率、酚―羟基含量的影响。利用FTIR、1H-NMR和GPC等手段对酚化木质素的结构进行表征。研究结果表明,酚化改性可以有效地提高木质素的酚羟基含量,降低木质素大分子的分子量。正交实验结果表明,反应温度对酚化改性的影响最大,其次是硫酸浓度,酚化改性的最佳工艺条件为:温度40℃,硫酸质量分数60%,时间60 min,硫酸用量20 mL/g(残渣),此条件下木素酚得率达53.85%,酚羟基含量为1.23 mol/C9,相对分子质量(w M)为3388。     

Eucalyptus bark lignin substituted phenol formaldehyde adhesives: A study on optimization of reaction parameters and characterization

The major adhesive resin worldwide used in the manufacture of plywood is phenol formaldehyde resole (PF) resin. The raw material for this kind of adhesive is derived from petroleum oil. Because of rising prices of crude oil and the scarcity of petroleum products, their replacement by natural resource–based raw material has become a necessity. In the present work, the possibility of replacing phenol in PF resin with lignin was explored. The parameters for preparation of bark lignin substituted PF (LPF) adhesive, such as lignin concentration, formaldehyde to phenol molar ratio, catalyst concentration, reaction time, and reaction temperature, were optimized. It was found that up to 50 wt % of phenol can be substituted by lignin to give an LPF adhesive with better bonding strength compared to that of control PF resin. Prepared resins were characterized using IR, DSC, and TGA. IR spectra of LPF adhesive showed structural similarity with that of PF adhesives. Thermal stability of LPF adhesive was found to be lower compared to that of control PF (CPF) adhesive. DSC studies revealed a lower curing temperature for LPF resin than that for CPF resin. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3514–3523, 2004     

Development and characterization of a wood adhesive using bagasse lignin

Bagasse is spent fiber left after extraction of sugar. It is mainly used as a fuel to concentrate sugarcane juice. In the present work, the possibility of preparing wood adhesives from bagasse has been explored. The parameters for the preparation of a lignin phenol formaldehyde (LPF) adhesive, (lignin concentration, formaldehyde to phenol molar ratio, catalyst concentration, reaction time and reaction temperature) have been optimized. It was found that up to 50% of phenol can be substituted by bagasse lignin to give LPF wood adhesive having better bonding strength in comparison to a control phenol formaldehyde (CPF) wood adhesive. Prepared resins were characterized using IR, DSC and TGA. IR spectra of LPF resin showed structural similarity with CPF resin. Thermal stability of LPF resin was found to be lower as compared to CPF resin. DSC studies reveal a lower curing temperature for LPF adhesive in comparison to CPF adhesive. A shelf-life study reveals that LPF exhibits consistent behavior as compared to CPF in respect to adhesive strength.     

Development and characterization of a lignin–phenol–formaldehyde wood adhesive using coffee bean shell

In the present study, the possibility of development of a wood adhesive using coffee bean shell lignin (Cbsl) has been explored. Cbsl-modified phenolic adhesive has been prepared by replacing phenol with lignin at different weight percents. The optimization of weight percent lignin incorporation was carried out with respect to mechanical properties. It was found that up to 50 wt% of phenol could be replaced by Cbsl to give lignin–phenol–formaldehyde adhesive (LPF) with improved bond strength in comparison to control phenol–formaldehyde (CPF). Optimized LPF and CPF adhesives were characterized by IR, DSC and TGA. The IR spectrum of LPF showed structural similarity to CPF. Thermal stability of LPF adhesive was found to be lower as compared to that of CPF. DSC studies revealed a higher rate of curing in the LPF adhesive.     

Properties of plywood panels bonded with ionic liquid-modified lignin–phenol–formaldehyde resin

The aim of this research was to investigate the physical and mechanical properties of plywood panels bonded with ionic liquid-modified lignin–phenol–formaldehyde (LPF) resin. For this purpose, soda bagasse lignin was modified by 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) ionic liquid, and then, various contents of modified lignins (10, 15, and 20 wt%) were added as a substitute of phenol in phenol–formaldehyde (PF) resin synthesis. The properties of the synthesized resin were compared with those of a control PF resin. The changes in curing behavior of the resins prepared were analyzed by differential scanning calorimetry (DSC). The physical properties of the resins prepared, as well as the water absorption, thickness swelling, shear strength, and formaldehyde emission of the plywood panels bonded with these adhesives, were measured according to standard methods. DSC analysis indicated that in comparison with PF resins, curing of the LPF resin occurred at lower temperatures. The physical properties of the synthesized resins indicated that viscosity and solid content increased, while gel time and density decreased by addition of treated lignin to the PF resin. Although the panels containing resins with modified lignin yielded low formaldehyde emission, their dimensional stability was worse than those bonded with a commercial PF adhesive. The plywood prepared using IL-treated lignin PF resins has shear strength, which satisfy the requirements of the relevant standards specifications and significantly better than that of panels prepared with the control PF resin. The mechanical properties of the panels could be significantly enhanced with increased percentage of treated lignin content from 0 to 20 wt%.     

酶解木质素的碱催化温和水热降解

针对木质素相对分子质量大、空间位阻大、反应活性低、难于利用的缺点,以氢氧化钠作催化剂对酶解木质素进行温和水热降解。研究了反应条件对降解木质素产率的影响,并以红外光谱（FT-IR）、核磁共振谱（¹H NMR）、凝胶渗透色谱（GPC）来表征降解木质素产物。优化后的水热降解条件为反应温度200℃,反应时间120 min,氢氧化钠与木质素的质量比值为0.2,木质素的质量分数为8%,此条件下降解木质素的产率为71%。FT-IR分析表明,在温和的水热降解条件下,木质素的芳环结构得以保留。¹H NMR分析结果表明,水热降解使木质素的部分醚键断裂,酚羟基增多。GPC分析表明,木质素相对分子质量明显下降,证明在此过程中木质素发生了降解。     

木质素酚醛树脂的固化动力学及机理研究

通过差示扫描量热法（Dsc）和红外光谱（IR）分别研究了木质素酚醛树脂（LPF）的固化动力学及机理。DSC分析表明,LPF的固化反应起始温度比酚醛树脂高,终止温度及活化能比酚醛树脂低,因此,LPF凝胶点比酚醛树脂高,贮存稳定性比酚醛树脂好,固化速度比酚醛树脂快;IR分析表明,LPF的固化机理与酚醛树脂相似,都是羟基之间及羟基与芳环上的氢之间的缩合反应。不同的是LPF固化后仍有部分醚键结构。     

Acid‐catalyzed liquefaction of waste paper in the presence of phenol and its application to Novolak‐type phenolic resin

Liquefaction of waste paper (WP) was performed in the presence of phenol with an acid catalyst. Newspaper (NP) was liquefied more easily than box paper (BP) or business paper (BNP). Differences in the degree of liquefaction were due to different chemical compositions. That is, NP had a relatively high lignin content, which is known to be easily liquefied, whereas BP and BNP were mainly composed of cellulose with a crystalline structure, which is difficult to liquefy. The acid concentration and phenol/WP ratio were more important factors in the regulation of liquefaction than reaction temperature. The changes in the apparent molecular weight depending on the reaction time were more significant for phenolated NP, with high lignin content, than for phenolated BP. The obtained phenolated products showed thermal flow properties and reactivity as good as those of phenolated wood and commercial Novolak resin. Thermosetting moldings were obtained from phenolated products, and their flexural properties and thermal stability were comparable to those of phenolated wood and commercial Novolak resin. Flexural properties were further improved by the cocondensation reaction between the unreacted phenol of phenolated products and formaldehyde. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1473–1481, 2002