【作者】 胡立红；

【导师】 周永红；

【作者基本信息】 中国林业科学研究院 ， 林产化学加工工程， 2012， 博士

【摘要】 酚醛泡沫是一种具有自阻燃性的新型隔热保温材料，被称为“第三代保温材料”。传统的酚醛泡沫塑料由化石基甲阶酚醛树脂和发泡剂、表面活性剂和酸固化剂共混，在一定温度下发泡制备。随着化石资源的日益枯竭和人们环保意识的逐渐提高，具有可再生的天然生物质资源替代化石资源制备酚醛泡沫的研究受到了广泛的关注。木质素是生物质资源中重要的可再生酚类化合物，利用价格便宜的木质素替代苯酚制备酚醛泡沫保温材料对发挥生物质资源优势、改善生态环境，促进酚醛保温材料行业发展均有明显的促进作用。本论文采用一种新的方法将木质素应用到甲阶酚醛树脂中。通过低温下氧化降解木质素，使降解产物中含有多种低分子量的酚类小分子化合物，提高了木质素的反应活性；采用木质素磺酸钙的氧化降解产物替代苯酚50%制备甲阶酚醛树脂，进一步制备性能良好的酚醛泡沫；研究木质素的引入对甲阶酚醛树脂和酚醛泡沫保温材料性能的影响。论文的主要研究内容和结论如下：1.采用FTIR、UV、¹H NMR、GPC、DSC、TG和元素分析对木质素磺酸钙、玉米秸秆碱木质素和Indulin碱木质素进行结构差异、官能团定性定量分析和热力学性能表征。FTIR结果显示玉米秸秆碱木质素属于典型的GSH型木质素，Indulin碱木质素和木质素磺酸钙以愈创木基结构为主。¹H NMR结果表明，木质素结构单元之间的连接方式有β-1、β-5和β-O-4，以β-O-4和β-5连接方式为主。木质素磺酸钙、玉米秸秆碱木质素和Indulin碱木质素的酚羟基含量分别为2.32%、3.26%和2.66%，有效成分分别为59.82%、85.35%和90.26%，数均分子量分别为17774、1205和1977。DSC表明玉米秸秆碱木质素T_g为124℃，Indulin碱木质素T_g为143℃，木质素磺酸钙在测试温度范围内没有检测到T_g。2.采用响应面法优化木质素氧化降解工艺条件。以双氧水2g，反应时间2h，反应温度60℃，pH=10反应条件为例，木质素磺酸钙、玉米秸秆碱木质素和Indulin碱木质素数均分子量分别降至493、895和1449，酚羟基含量增至2.98%、3.70%和2.91%。结合三种木质素市场供应，选择木质素磺酸钙作为苯酚替代物进行后续研究。3.对木质素磺酸钙氧化降解产物进行结构表征。FTIR结果表明酚羟基含量增加，甲氧基含量降低。氧化降解前后¹H NMR变化显著，8.50ppm处质子吸收峰很强，推测芳香核连接有强吸电子基所致，6.00-8.00ppm之间、5.62-5.25ppm、4.52-4.00ppm和3.80ppm处的质子吸收峰减弱，表明氧化降解过程中发生了醚键断裂，甲氧基部分脱除，木质素大分子发生降解，木质素磺酸钙在β-O-4和β-5处断裂的可能性最大。UV分析表明木质素极少量开环，红移现象表明愈创木基含量增加。GC-MS显示降解产物含有多种小分子酚类化合物。与甲醛反应活性研究表明在反应0.5h时，100g氧化降解木质素磺酸钙消耗甲醛0.59mol，而原料木质素磺酸钙消耗甲醛0.41mol。4.采用木质素磺酸钙氧化降解产物部分替代苯酚，研究不同甲醛苯酚摩尔比（以下简称摩尔比）和不同木质素替代量（指木质素替代苯酚的质量百分含量，以下同）反应条件下甲阶酚醛树脂的性能。结果表明在相同木质素替代量下，游离酚随摩尔比的增加而降低，游离醛随摩尔比的增加而增加；在相同摩尔比下，游离酚和游离醛均随着木质素替代量的增加而降低。低摩尔比和低木质素替代量下树脂黏度增加缓慢，反之黏度增加较快。采用哈克流变仪研究树脂反应活性，以摩尔比1.7:1和不同木质素替代量下的甲阶酚醛树脂为研究对象，结果表明随着木质素替代量的增加，树脂反应活性逐渐下降，初始黏度开始增加的温度逐渐上升，木质素替代量为0%的树脂黏度在125℃开始上升，而木质素替代量为50%的树脂黏度在130℃开始上升。采用DSC研究摩尔比1.7:1、木质素替代量分别为40%和0%条件下制备的两种树脂等温固化反应动力学，并建立动力学模型，反应级数分别为0.838和0.845，固化活化能分别为125.27KJ mol^-1和110.35KJ mol^-1，木质素的引入降低了树脂的反应活性。5.研究不同的摩尔比、不同的木质素替代量和不同的泡沫密度对泡沫性能的影响。结果表明相同的木质素替代量制备的泡沫，在密度相同的情况下，压缩强度随摩尔比的增加而增加。相同摩尔比且相同木质素替代量制备的泡沫，其压缩强度随泡沫密度的增加而增加。例如，在摩尔比1.9:1和20%木质素替代量下，密度60kg/m³的泡沫压缩强度最高，达到0.21MPa。根据Gbison-Ashby方程建立了泡沫密度与泡沫力学性能之间的动力学模型，泡沫力学性能均与密度呈指数关系，压缩性能指数在3.30左右，弯曲性能指数在2.35左右。木质素替代量对泡沫的闭孔率和孔径有影响，闭孔率由纯酚醛泡沫的99.9%降至木质素替代量为50%的86.3%，纯酚醛泡沫孔径为115μm，木质素替代量为50%时孔径增至290μm。泡沫导热系数较低，由纯酚醛泡沫的0.021W/（m·K）增至50%替代量的0.030W/（m·K）。木质素的引入增加了泡沫的韧性，降低了泡沫的热稳定性和临界氧指数，但仍属难燃材料。锥型量热分析显示木质素酚醛泡沫与纯酚醛泡沫相比，点燃时间和持续燃烧时间均缩短，有效燃烧热（EHC）和峰值EHC降低，热释放速率（HRR）和峰值HRR变化不大，CO和CO₂生成速率增加，但增加幅度不大，总释放热（THR）随着木质素的替代量的增加逐渐降低。当摩尔比1.5:1和1.7:1，木质素替代量10%-30%，三种密度的泡沫均达到GB/T20974-2007要求。更多还原

【Abstract】 Phenolic foam is a new kind of flame-retatdant thermal insulation material, it is known as“the third generation of thermal insulation material”. Conventional phenolic foam wassynthesized by incorporating petroleum-based resol resin with several additional chemicals.However, with the rising cost and foreseeable future scarcity of petrochemicals and theimprovement of the environmental protection consciousness, researches on natural renewableresources replacing petrochemicals has attracted more and more attention. Lignin is animportant feedstock for the renewable production of phenolic compounds in forestrymaterials, and technical lignin is available in great quantities. Less expensive lignin can replacephenol to formulate phenolic foam thermal insulation material, which has significantpromotion to make biomass resource advantage, improve ecological environment and developphenolic foam thermal insulation material industry.In the present work, a new method of introducing lignin into resol resin was explored.Lignin was oxidated into fractions containing phenolic compounds at low temperauture, whichimproved its reactive activity. Oxidatively degradated fractions of lignosulfonate replaced50%phenol to formulate resol resin and good properties of the resulted phenolic foam was obtained.The main purpose of the thesis was to reveal effect of replacement percentage of phenol byoxidatively degradated lignin on properties of resol resin and phenolic foam. The main researchand obtained results were summarized as follows.1. Structure difference, qualitative and quantitative analysis of functional group, andthermodynamic properties of lignosulfonate. Corn kraft lignin and indulin kraft lignin werecharacterized by FTIR、UV、¹H NMR、GPC、DSC and TG, corn kraft lignin was a typical GSHtype lignin, lignosulfonate and indulin kraft lignin were mainly guaiacyl structure.¹H NMRanalysis showed three phenylpropanoid monomers were interconnected by a multitude ofinter-unit bonds that include several types of ethers (e.g. β^-1, β-5, and β-O-4) and carbon-carbon linkages, β-O-4and β-5structures constituted the main intermonomericconnections. The contents of phenolic hydroxyl in lignosulfonate, corn kraft lignin, and Indulinkraft lignin were2.32%、3.26%and2.66%, respectively, and effective lignin contents were59.82%、85.35%and90.26%, respectively. DSC analysis indicated T_gof corn kraft lignin andIndulin kraft lignin were124℃and143℃, respectively,lignosulfonate T_gwasn’t foundwithin the range of temperature.2. Optimization of lignin oxidative degradation technology was carried out usingDesign-Exper8.0software. Take reactive conditions of H2O22g, reaction time2h, reactiontemperature60℃, pH=10for example, number molecular weight （Mn） of lignosulfonate,corn kraft lignin and indulin kraft lignin decreased to493、895and1449after oxidativedegradation, versus17774、1205and1977before oxidative degradation, respectively. Thecontents of phenolic hydroxyl of lignosulfonate, corn kraft lignin and indulin kraft ligninincreased to2.98%、3.70%and2.91%after oxidative degradation, respectively. Consideringprices of three lignins, lignosulfonate was selected as phenol substitution to proceed the nextstudy.3. Oxidative degradation fractions of lignosulfonate were characterized. FTIR showedphenolic hydroxyl content increased, while methoxyl content decreased. Great changes in¹HNMR spectrum was observed pre-and post-oxidative degradation. Proton absorption peak at8.5ppm was very strong, while almost none in raw lignosulfonate¹H NMR spectrum, whichwas likely attributed to aromatic proton connected with strong electron-withdrawing group.Proton absorption peak at6-8ppm weakened, and so did peak at5.2ppm,4.5ppm and3.80ppm, which indicated part cleavage of ether bond and methoxy removal, macromoleculelignosulfonate degradated into small fractions. Great possible cleavage occurred at β-O-4andβ-5. UV analysis revealed partial lignosulfonate benzene rings open after oxidative degradation,its spectrum has a little red shift in comparison with raw lignosulfonate, guaiacly monoercontent increased to some extent. GC-MS analysis disclosed there were kinds of phenoliccompounds in oxidative degradation fractions. Reactive activity toward formaldehyde experiment indicated100g oxidative degradation fractions consumed0.59mol formaldehyde,versus0.41mol formaldehyde consumed by raw lignosulfonate.4. Oxidatively degradated lignosulfonate substitute phenol to formulate resol resin,properties of resol resin were effected by different formaldehyde/phenol molar ratio anddifferent lignin replacement. Free phenol content decreased and free formaldehyde contentincreased with the increasing molar ratio under the same replacement percentage of phenol bylignin. Free phenol content and free formaldehyde content both decreased with the increasingreplacement of phenol by lignin under the same formaldehyde/phenol molar ratio. Viscosity ofresol resin increased slowly when both formaldehyde/phenol molar ratio and replacementpercentage of phenol by lignin were low, Whereas it increased rapidly. Take resol resinprepared under the conditions of formaldehyde/phenol molar ratio1.7:1and differentreplacement percentage of phenol by lignin for example, HAAKE Rotational Rheometer isused to evaluate resol resin reactive activity. The results showed that reactive activity decreasedwith the increasing replacement percentage of phenol by lignin, temperature at which viscositybegan to increase tended to rise, for example,125℃was for resol resin with0%replacementpercentage to increase viscosity rose to130℃f or resol resin with50%replacement percentage.Take resol resin prepared under the conditions of formaldehyde/phenol molar ratio1.7:1forexample, differential scanning calorimetry （DSC） was applied to investigate resin resolisothermal curing reaction kinetics at different temperature, when replacement percentage ofphenol by lignin were40%and0%, reaction order were0.838and0.845, and curingactivation energy were125.27KJ mol^-1and110.35KJ mol^-1, respectively, indicating theintroduction of lignin decreased resol resin reactive activity.5. Different replacement percentage of phenol by lignin，different formaldehyde/phenolmolar ratio and different foam density had influence on properties of phenolic foam. Foamcompressive strength increased with the increasing of formaldehyde/phenol molar ratio on thecondition of the same replacement percentage of phenol by lignin and the same foam density.Foam compressive strength increased with the increasing of foam density on the condition of the same formaldehyde/phenol molar ratio and the same replacement percentage of phenol bylignin. When formaldehyde/phenol molar ratio was1.9:1, replacement percentage of phenol bylignin was20%and foam density was60kg/m³, foam compressive strength reached its highestvalue （0.21MPa）. According to Gbison-Ashby equation, foam density-compressive strengthmodels was established. Foam closed hole rate and hole diameter were effected by replacementpercentage of phenol by lignin, when replacement percentage of phenol by lignin increasedfrom0%to50%, closed role rate decreased from99.9%to86.3%, and hole diameter increasedfrom115μm to290μm. Foam thermal conductivity was very low, it ranged from0.021W/（m·K）（0%replacement） to0.030W/（m·K）（50%replacement）. The introduction of lignininto phenolic foam leaded to higher toughness, lower thermal stability, and lower oxygen index.Cone calorimeter analysis indicated lignin phenolic foam possessed shorter igniting time andlasting time, it had a decrease in effective heat of combustion （EHC） and its peak values, heatrelease rate （HRR） and its peak values （PHRR） changed little, CO and CO₂rate increased alittle, heat release results decreased （THR） with the increasing replacement percentage ofphenol by lignin, compared to conventional phenolic foam.更多还原