【作者】 李燕；

【导师】 储富祥；

【作者基本信息】 中国林业科学研究院 ， 木基复合材料科学与工程， 2012， 博士

【摘要】 酶解木质素是从微生物酶解玉米秸秆制备丁醇等能源的残渣中分离得到的新型木质素，与传统的碱木质素和硫酸盐木质素相比，酶解木质素具有多种活性基团和较好的反应活性。本文对酶解木质素的多羟基醇液化以及酶解木质素基聚氨酯发泡材料的制备进行了一系列研究。通过化学改性手段制备酶解木质素基聚氨酯发泡材料，不但可以提高农业废弃物的利用率和生物酶解技术的经济效益，同时也可获得良好的社会效益。论文首先研究了在常压下以硫酸为催化剂，酶解木质素在聚乙二醇和丙三醇的混合溶剂中的液化工艺，并以液化产物的残渣率和羟值作为液化效果的评价指标，考察了液化时间、液化温度、催化剂用量、液固比等对液化反应的影响。提出了酶解木质素在多羟基醇溶剂中液化的最优条件。在液化温度为120°C，液化时间为50min，硫酸用量为0.6%，液固比为5:2的条件下，液化产物的羟值达到397mgKOH/g，残渣率为0.59%，以及粘度为5405mPa·s。当液固比从5:3增加到5:1时，液化产物的相对分子量下降，多分散系数下降，羟值升高，残渣率下降，粘度下降。采用傅里叶变换红外光谱（FT-IR），核磁共振波谱（NMR），气相色谱-质谱联用（GC-MS）及凝胶渗透色谱（GPC）等方法对不同液化时间下的液化产物的官能团、分子结构、相对分子量大小及其分布进行了表征，初步探讨了玉米秸秆酶解木质素在多羟基醇液化溶剂中的液化改性机理。研究表明，在液化前期，液化产物的重均分子量和数均分子量降低，且多分散系数降低。而在液化后期，液化产物的平均分子量出现上升趋势。说明液化过程中同时存在降解反应和缩聚反应。酶解木质素在酸性条件下，首先发生降解反应生成对香豆醇、芥子醇等结构单元，然后发生甲基脱除反应，最后发生氧化和酯化反应。酶解木质素多羟基醇液化产物中主要有三类化合物，第一类是含有苯酚基本单元和苯基的化合物；第二类是含有苯甲氧基的化合物；第三类是酶解木质素衍生物与液化溶剂相互之间的缩合物。利用酶解木质素多羟基醇液化产物与传统聚醚多元醇复配后，与二苯基亚甲基二异氰酸酯反应，制备了改性聚氨酯发泡材料，并研究了液化产物含量对聚氨酯发泡材料各项性能的影响。结果表明，液化改性木质素基聚氨酯发泡材料的最佳合成工艺：聚醚多元醇4110与403复配比为40:60，液化产物含量为30%，异氰酸酯指数为1.2，催化剂含量为2.5%，发泡剂含量为20%，阻燃剂含量为25～30%（水含量为1%，硅油含量为2%）。可以根据聚氨酯发泡材料的最终用途来选择合适的配方。当液化产物含量低于30%时，液化产物的添加可以提高聚氨酯发泡材料的压缩强度。当液化产物含量为30%时，聚氨酯发泡材料的压缩强度达到最大值291kPa，比未添加液化产物的聚氨酯发泡材料的压缩强度高出36%。当液化产物含量继续增加时会导致材料变脆，压缩强度降低。另外，液化产物的添加可以改善聚氨酯发泡材料的热稳定性能和阻燃性能。含有液化产物的聚氨酯发泡材料的开始热分解温度和第一阶段的最大热失重温度明显高于未添加液化产物的聚氨酯发泡材料。当液化产物含量分别为10%和50%时，释热速率峰值分别为200.60kW·m^-2和191.33kW·m^-2，比未添加液化产物的聚氨酯发泡材料的释热速率峰值(263.43kW·m^-2)分别低约23.85%和27.37%。同时，添加了液化产物的聚氨酯发泡材料的失重率显著下降。并且，当液化产物部分替代聚醚多元醇时，聚氨酯发泡材料的导热性能也得到了提高。当液化产物含量为30%时，聚氨酯发泡材料的导热系数达到最低值（0.02517W/mK），比未添加液化产物的聚氨酯发泡材料导热系数（0.03027W/mK）低约36%。当液化产物含量低于70%时，泡沫的泡孔结构规整。采用填充型酶解木质素和液化改性型酶解木质素两种方法制备酶解木质素基聚氨酯发泡材料，探讨了两种制备方法对酶解木质素基聚氨酯发泡材料的化学结构、基本工艺参数、凝胶量、密度和压缩强度、泡孔微观形貌、动态力学性能的影响。结果表明，在液化改性型聚氨酯发泡材料合成过程中，酶解木质素以液相参与发泡反应，起到核化点和稀释剂的作用，反应分子间的间隔加大，因此液化改性型聚氨酯发泡材料的凝胶时间长于填充型聚氨酯发泡材料。随着多元醇替代物含量增多，填充型聚氨酯发泡材料的密度要高于液化改性型聚氨酯发泡材料，凝胶量低于液化改性型聚氨酯发泡材料。液化改性型聚氨酯发泡材料的压缩强度要高于填充型聚氨酯发泡材料。当多元醇替代物含量低于30%时，液化改性型聚氨酯发泡材料的玻璃化转变温度稍高于填充型聚氨酯发泡材料的玻璃化转变温度。液化改性的方法更有利于酶解木质素基聚氨酯发泡材料的合成。更多还原

【Abstract】 Enzymatic hydrolysis lignin （EHL） a novel lignin which is isolated from the enzymatichydrolysis residues of corn stalk for production of butanol.Compared to lignosulfonate or kraftlignin, EHL has various reaction groups and greater chemical reactivity. The polyhydricalcohol liquefaction of EHL and the modified polyurethane （PU） foaming materials derivedfrom the liquefaction product were studied in this dissertation.The preparation of EHL-basedPU foaming materials by chemaical modified method will be favorable to not only improvingthe application of agricultural wastes and the economic benefit of biological enzymolysistechnology, but also gaining better social benefit.Corn stalk EHL was liquefied using the mixed solvents of polyethylene glycol400（PEG400） and glycerol in the presence of sulfuric acid as a catalyst under atmospheric pressure.The liquefaction residue ratio and hydroxyl number as evalution indexes were used to evaluatethe effects of the liquefaction temperature, the liquefaction time, the catalyst dosage and theliquid-solid ratio on the liquefaction. The optimal reaction conditions was proposed.When theliquefaction temperature was at120°C, the liquefaction time for50min, the liquefactionsolvent/corn stalk EHL ratio at5:2and sulfuric acid dosage at0.6%, the liquefied productshowed hydroxyl number of397mgKOH/g, residue ratio of0.59%and viscosity of5405mPa·s.When the liquefaction solvent/corn stalk EHL ratio increased from5:3to5:1, theaverage molecular weights, polydispersities, residue ratio of the liquefied EHL polyolsdecreased while the hydroxyl number increased.The methods such Fourier transform infrared spectroscopy （FT-IR）, Nuclear maggneticresonance spectrum （NMR）, Gas chromatography-mass spectrometry （GC-MS） and Gelpermeation chromatography （GPC） were used to analyze the functional groups, molecularstructure, molecular weight and distribution of liquefaction product from different liquefactiontime to study the EHL modification mechanism in polyhydroxyl acohol.The results showed that at the first stage of liquefaction process, the average molecular weights and polydipersitiesdecreased,while at the latter stage of liquefaction process, they presented the upward trend.Itindicated that the degradation reaction and condensation reaction occurred in the liquefaction.At the presence of sulfuric acid, the EHL was firstly degraded into structural units ofp-coumaric alcohol, erucic alcohol and so on, and then the demethylation reaction occurred,finally, there were oxidation and esterification reaction.There were three kinds of chemicalcompounds in the liquefaction products.The compounds of the first group had phenol andbenzene ring structure;the compounds of the second group had phenylmethoxy structure;thecompounds of the third group stemmed from condensation reaction between the EHLdeviatives and liquefaction solvents.Polyurethane foams were made from the liquefied product and diphenylmethanediisocynane diisocyanates （MDI）. Furthermore,the impacts of liquefaction product additioncontent on properties of PU foaming materials were investigated. The result showed that theoptimal conditions for preparing EHL-based PU foaming materials were the ratio of4110/40340:60, the liquefaction product30%, catalyst dosage2.5%, foaming dosage20%, isocyanateindex1.2, flame retardant dosage25%～30%, water content1%and silicone surfactant2%.The preparation formulations were choosed according to the end use purpose of PU foamingmaterials.The foams with bio-polyol presented better compressive strength than conventionalpolyurethane foams. When the bio-polyol content was30%, the compressive strength reachedits maximum value of291kPa, which was36%higher than that of conventional PU foamingmaterials. It indicated that a high dosage of bio-polyol in the foaming mixture would lead tobrittle foams. The addition of liquefied EHL polyol into the foaming mixture resulted inimproved the thermal stability and flame resistance.The initial degradation temperature and themost rapid degradation temperature during the first degradation stage of the PU foamingmaterials with bio-polyol were higher than those of conventional PU foaming materials.Whenthe contents of bio-polyol were10%and50%, the peak of heat release rate were200.60kW·m^-2and191.33kW·m^-2, respectively, which were23.85%and27.37%lower thanthat of conventional PU foaming materials (263.43kW·m^-2). In addition, mass loss rate of PU foaming materials based on bio-polyol significantly decreased.The thermal conductivity wasimproved when the liquefaction products replaced a part of trational polyether polyol. Thethermal conductivity of polyurethane foams with30%bio-polyol was0.02517W/mK,whichwas significantly36%lower than that of conventional polyurethane foams （0.03027W/mK）.The scanning electron microscopy images indicated that polyurethane foams containing lessthan70%bio-polyol had smooth surface.Corn stalk EHL-based polyurethane foams were prepared by two methods: blending andliquefaction modification. The effects of the two types of preparation methods on the structureof PU foaming materials, process parameters, gel content, density, compressive strength,surface morphology and dynamic mechanical property of EHL-based polyurethane foams werediscussed.The results showed that EHL-based polyol involving in liquid in the foamingreactionand acted as nucleation sites and diluent.The reaction molecular interval became larger.Therefore, the gel time of PU foaming materials derived from liquefaction modification waslonger than that of PU foaming materials from the blending modification.The density ofpolyurethane foams from liquefaction modification method was lower than that from blendingmethod. The gel content and compressive strength of polyurethane foams based on liquefactionproduct were higher than those from blending method. When the substitution for polyol waslower than30%, the glass transition temperature of the polyurethane foams from liquefactionmethod was higher than those from blending method. The liquefaction modification wassuperior to the synthesis of EHL-bassed PU materials.更多还原