【作者】 张连红；

【导师】 田彦文；

【作者基本信息】 东北大学 ， 冶金物理化学， 2010， 博士

【摘要】 硫酸钙晶须是一种细小纤维状的亚纳米材料,具有十分优良的力学性能和物理性能。目前,硫酸钙晶须的制备主要采用天然石膏为原料,对原料纯度和粒度要求较高,生产设备要求苛刻。硫酸钙晶须不进行表面修饰改性在有机材料中的应用受到很大限制。为了降低硫酸钙晶须制备成本,扩大硫酸钙晶须的应用范围,研究制备硫酸钙晶须的新方法和硫酸钙晶须表面改性及其在胶粘剂改性、有机合成中的应用,具有重要的理论和实践意义。本论文对硫酸钙晶须的制备、表面改性及其应用进行较系统的研究。常压下制备了(半水)硫酸钙晶须和改性硫酸钙晶须,通过多种研究手段对它们的结构和性能进行了表征,考察了晶须表面性质与改性剂种类、添加量的关系;进行了硫酸钙晶须在胶粘剂的改性和催化羧酸酯制备中的应用研究,获得满意的结果；进行硫酸钙晶须催化酯合成的反应动力学研究,确定了硫酸钙晶须为理想的非均相催化剂,拓宽了硫酸钙晶须研究与应用领域。论文的主要工作及结果如下：1.硫酸钙晶须的制备研究(1)通过引入晶化导向剂,以水热结晶法实现了常压下半水硫酸钙晶须的制备。确定了合适的工艺条件为：氢氧化钙悬浊液和硫酸溶液的浓度均为0.2mmo1·L-1,硫酸溶液的加入流量为1.5mL·min-1,反应温度100℃,搅拌速度为400r·min-1,反应时间40min,加入质量分数为2.0%的晶化导向剂；合适工艺条件下制备的产品经扫描电镜和X射线衍射确定为半水硫酸钙晶须和无水硫酸钙晶须混合物,平均粒径为200nm,长径比100：与传统的石膏为原料的水热法相比,该工艺制备硫酸钙晶须无需石膏溶解过程；引入晶化导向剂,加快了晶核的形成,缩短了半水硫酸钙晶须的结晶和单晶生长时间,能够有效地控制晶须的粒径。工艺中所用原材料来源广泛、廉价易得,实现工业化将对半水硫酸钙晶须产业的发展有重大意义。(2)以盐泥为原料进行了硫酸钙晶须的制备研究,得到合适的工艺条件为：在硫酸/盐泥质量比为2,盐泥浆液质量分数为6%,常压下反应温度105℃,时间30min。此条件下回收硫酸钙杂质少,形貌最佳,所得样品直径为0.2～4.0μm、长度为35～150μm；利用盐泥在缓和条件下制备硫酸钙晶须的工艺,结合镁盐回收工艺,不仅可以生产出具有较高利用价值的材料,而且大大降低了成本,变废为宝,实现环保与资源节约双赢。2.硫酸钙晶须的表面改性研究通过对改性硫酸钙晶须的吸油值、体系粘度、沉降体积等性能研究表明,硬脂酸、铝酸酯偶联剂和复配改性剂湿法改性硫酸钙晶须,硬脂酸复配改性剂最优；200nm,500nm硫酸钙晶须的改性以复配改性剂添加量分别在3.0%,2.0%时最佳。FT-IR和TG/DTG分析表明,铝酸酯偶联剂与硫酸钙晶须表面发生了化学吸附和物理吸附。XRD分析表明,硬脂酸、铝酸酯偶联剂仅使硫酸钙晶须表面改性,并没有改变硫酸钙晶须的组成和结构。3.硫酸钙晶须对胶粘剂的改性研究在不饱和聚酯腻子中加入硫酸钙晶须替代白炭黑,聚酯腻子性能提高；当加入量2.0%的200nm改性硫酸钙晶须时腻子的抗冲击性提高了25%,硬度提高了13%,收缩率下降了27.8%,腻子的可打磨时间延长；采用原位聚合法,向溶剂型聚氨酯胶粘剂中加入200nm改性硫酸钙晶须,质量分数为3%时,拉伸强度达到了36MPa,初粘强度达到了95N·(25mm)-1,24h剥离强度达到了213N·(25mm)-1,拉伸强度较未加晶须前提高了80%,初粘性提高了126%,终粘剥离强度提高了52%,综合力学性能最优；在聚氨酯密封胶中添加200nm改性硫酸钙晶须,可以改善密封胶的强度、硬度和弹性；200nm改性硫酸钙晶须可以替代气相二氧化硅来改善密封胶的触变性,降低了原材料的成本；硅酮密封胶加入硫酸钙晶须,提高了硅酮密封胶的最大伸长率。200nm改性硫酸钙晶须改性的硅酮密封胶挤出性好,可替代气相白炭黑作为触变剂使用；将硫酸钙晶须加入到白乳胶中,明显提高白乳胶的力学性能。500nm,200nm,500nm改性,200nm改性硫酸钙晶须的最佳添加量分别为填料总量的0.2%,0.3%,0.2%,0.3%。改性硫酸钙晶须提升白乳胶力学性能更显著,最大值压剪强度比改性前提高160%以上；在乳胶漆中添加硫酸钙晶须,改性硫酸钙晶须比未改性的硫酸钙晶须效果更显著,200nm改性硫酸钙晶须改性后,各项指标都提高,在加入量为0.3%时耐擦洗性能提高275%,达到最高7500次；硫酸钙晶须对彩色高分子防水胶泥的性能影响较大。随着硫酸钙晶须添加量增加,粘结强度逐渐增大,抗折及抗压强度均提高,初凝及终凝时间有所缩短,耐碱性不发生变化,当添加0.3%硫酸钙晶须时,抗渗性增加150%,性能最优。工业化后,各项指标符合标准要求,取得了良好的经济效益和社会效益。综合看,硫酸钙晶须对胶粘剂的改性作用明显,选择适当的晶须添加量和规格不仅能够大幅提高胶粘剂的综合性能,还因硫酸钙晶须具有良好触变性,可以替代气相白炭黑等昂贵的触变剂,从而降低产品成本。4.硫酸钙晶须在羧酸酯制备中的应用研究(1)以冰醋酸与正丁醇为原料,硫酸钙晶须作为催化剂制备醋酸正丁酯。硫酸钙晶须是制备醋酸正丁酯反应的优良催化剂。醋酸正丁酯的酯化反应是一可逆的二级反应。动力学方程为：-dcA/dt=2153exp(-418T08/RT)cA·cB-35.94×10-3exp(-13295/RT)cC·cD(2)当酸醇物质的量比为1.1：1,硫酸钙晶须用量为正丁醇质量的3%,反应温度110℃,反应时间为6h,甲苯带水剂用量为正丁醇质量的14.8%时,酯化产率可达到91%以上。通过实验得出,硫酸钙晶须在催化酯制备反应中,几乎不引起副反应,催化作用良好。以硫酸钙晶须作为酯制备催化剂克服了浓硫酸法腐蚀设备、污染环境的缺点,为酯制备的绿色环保方法。(3)通过甲基丙烯酸甲酯与一缩二乙二醇酯交换制备一缩二乙二醇双甲基丙烯酸酯(DEGDMA)考察硫酸钙晶须的催化活性。研究了硫酸钙晶须催化此反应的合适工艺条件为,甲基丙烯酸甲酯与一缩二乙二醇的物质的量比为3.5：1,反应温度为回流温度,硫酸钙晶须、阻聚剂氮氧自由基加入量分别为一缩二乙二醇质量的3.0%,0.1%。此条件下制备的一缩二乙二醇双甲基丙烯酸酯收率大于93.3%,纯度达97%。实验表明,硫酸钙晶须对制备一缩二乙二醇双甲基丙烯酸酯硫酸钙晶须对制备一缩二乙二醇双甲基丙烯酸酯的催化活性由其结构决定,与组成无关；催化性能与离子交换树脂相当,与硫酸、对甲苯磺酸相比,具有无腐蚀、价格低廉,产品质量好,色泽浅,副反应少,反应条件比较缓和等优点。(4)以硫酸钙晶须为催化剂制备三羟甲基丙烷三丙烯酸酯(TMPTA),避免了用硫酸或对甲基苯磺酸作催化剂造成设备腐蚀及后处理等复杂工艺。与传统的硫酸催化法相比,具有催化活性稳定,反应条件温和,选择性好,副反应少,酯化率高,后处理过程简单等优点。通过实验得出硫酸钙晶须催化制备TMPTA的合适工艺条件为：n(丙烯酸)：n(三羟甲基丙烷)=3.4、硫酸钙晶须的质量分数(以三羟甲基丙烷的质量为基准)2.0%、以环己烷和甲苯混合带水剂、以对苯二酚和吩噻嗪作混合阻聚剂；酯化反应的最终温度为98℃；反应时间为5h；空气流量为15mL·min-1。在合适工艺条件下制备的TMPTA酯化率达96.8%以上。更多还原

【Abstract】 Calcium sulphate whiskers are one kind of small fibrous sub-nanometer materials with perfectly mechanical and physical properties. At present, calcium sulphate whiskers is mainly prepared by the natural gypsum, with demanding production equipment, high purity and granularity requirement raw material. The application of unmodified calcium sulphate whiskers in organic material is restricted. In order to reduce preparation cost and expand the application scope, it is necessary that the new methods of calcium sulphate whiskers preparation, surface modification, application in adhesive modification and organic synthesis is researched.The preparation of calcium sulfate whiskers, surface modification and the application were investigated in the thesis. Calcium sulfate whiskers and modified calcium sulfate whiskers were prepared under the atmospheric pressure. The morphologies and properties were characterized by means of many kinds of test methods, and the relationships between surface properties and modifier types and dosage were investigated. The application in adhesive modification and the synthesis of carboxylate was studied and satisfactory results were obtained. In particular, based on the reaction kinetics of catalyzing esterification, calcium sulfate whiskers were identified as the ideal heterogeneous catalyst, broadening the research and the application scope of the whiskers. The main conclusions were as follows:1. Preparation of calcium sulfate whiskers(1)Through adding crystallization directors, hemi-hydrate calcium sulfate whiskers were prepared by hydrothermal crystallization under atmospheric pressure. The optimum process conditions were as follows:Both calcium hydroxide suspension concentration and sulfuric acid solution concentration were O.2mol·L-1, adding speed of sulfuric acid solution was1.5mL·min-1, reaction temperature was100℃, stirring speed was400r·min-1, reaction time was40min,and dosage of crystallization directors was2%. Products obtained under the optimized conditions were determined to the mixture of hemi-hydrate calcium sulfate whiskers and anhydrous calcium sulfate whiskers by means of scanning electron microscope and X-ray diffraction, of which the average particle diameter was200nm with aspect ratio of100. Compared to traditional hydrothermal synthesis using gypsum as raw materials, the procedure of gypsum dissolution was unnecessary. With the introduction of crystallization directors, the formation of nucleation was accelerated, the time of hemihydrate crystallization and single crystal growing was shorten, and the whisker size was effectively controlled. The raw materials with abundance of material supply were low-cost, and the prosess industrialization would be great significant to the development of hemi-hydrate calcium sulfate whiskers.(2)Using salt slurry as raw materials, calcium sulfate whiskers were prepared under optimum conditions as following:mass ratio was2:1(sulfuric acid:salt slurry), salt slurry concentration was6%, temperature was105℃, reaction time was30min, under atmospheric pressure. Whisker product obtained under optimum conditions have a characteristic of low impurity and good aspect, whose diameter and length was0.2-4.0μm and35-150μm, respectively. Considered magnesium recovery process and the preparation of calcium sulfate whiskers from salt slurry, high valuable materials would be produced, not only the cost was great reduced, but also the waste residue was handled, achieving environmental protection and resource conservation win-win.2. Surface modification of calcium sulfate whiskersThe oil absorption of modification of calcium sulfate whiskers, viscosity and settling volume were investigated, and it showed:among stearic acid, aluminate coupling agent and complex modifying agent in modifying calcium sulfate whiskers, stearic acid is the worst, complex modifying agent is optimal. To modify200nm and500nm calcium sulfate whiskers, the optimal amount of complex modifying agent was3.0%and2.0%, respectively.Through FT-IR and TG/DTG analysis, it showed that chemical adsorption and physical adsorption of aluminate coupling agent both occurred on the surface of calcium sulfate whiskers by FT-IR and TG/DTG. Through XRD analysis, it showed that stearic acid, aluminum coupling agent only modified whisker surface with constant composition and strcture of calcium sulfate whiskers. 3. Study on calcium sulfate whiskers in adhesive modificationMixing calcium sulfate whiskers instead of silica could improve performance of unsaturated polyester putty. When200nm calcium sulfate whiskers amount was2.0%, the impact resistance of putty improved by25%, hardness increased by13%, contraction rate decreased by27.8%, and grinding time extended slightly.By in-situ polymerization, when the200nm modified whisker amount was3.0%of solvent-based polyurethane adhesive, the tensile strength of the polyurethane adhesive reached36MPa, initial bonding strength reached95N·(25mm)-1,24h peeling strength arrived213N·(25mm)-1. Thus the tensile strength increased by80%, initial adhesion increased by126%, and the mechanical performance was optimal.Strength of polyurethane sealant improved with200nm modified calcium sulfate whiskers, and hardness and elasticity was changed slightly. Thixotropy increased with the modified whiskers instead of fumed silica, and the cost of raw materials reduced accordingly.The maximum elongation of silicone sealant mixed by calcium sulfate whiskers enhanced, the extrusion of silicone sealant modified by200nm modified whiskers was good, and cost of raw materials was lowered when200nm modified calcium sulfate whiskers substitute for fumed silica as thixotropic agent.The mechanical performance of white latex could significantly improved with calcium sulfate whiskers. The optimal amount of500nm whiskers,200nm whiskers,500nm modified whiskers and200nm modified whiskers was0.2%,0.3%,0.2%and0.3%of total quantity, respectively. Among all, modified calcium sulfate whiskers showed most significant effect that maximum compression-shear strength increased by over160%compared with blank sample.The effect of calcium sulfate whiskers on latex paint was researched, and results indicated that modified calcium sulfate whiskers effected more pronouncedly than unmodified ones. When0.3%200nm modified calcium sulfate whiskers were used, the scrubbing resistance of latex paint increased by275%, arrived7500times.Calcium sulfate whiskers greater impact the performance of colorful polymer water proof clay. With the increase amount of calcium sulfate whiskers, bending and compressive strength increased, bond strength increased, while initial setting and final setting time shortened, alkali resistance kept constant. When adding0.3%calcium sulfate whiskers, impermeability increased by150%, and the performance was optimal. The various indexes of industrialized product were in line with standard requirements, achieving good economic and social benefits.In conclusion, the effect of calcium sulfate whiskers on adhesive modification is obvious. Appropriate specification and dosage of whiskers not only greatly improved the comprehensive performance of adhesive but also replaced expensive thixotropic agent because of their good thixotropy, such as fumed silica, resulting in lower product cost.4. Study on calcium sulfate whiskers in preparation of carboxylic ester(1)The synthesis of n-butyl acetate from glacial acetic acid and n-butanol catalyzed by calcium sulfate whiskers was studied. The esterification of n-butyl acetate is a reversible second-order reaction. The kinetic equation was as follow:-dCA/dt=2153exp (-41808/RT)CA·CB－35.94×10-3exp(-13295/TT)CC·CB(2)When the molar ratio of acetic acid to n-butyl alcohol was1.1:1, the quality of calcium sulfate whiskers was3.0%of n-butanol, reaction temperature was110℃, reaction time was6h, and the quality of toluene(as water carrier) was14.8%of n-butanol, the yield of n-butyl acetate was up to97.6%. The experiments showed that calcium sulfate whiskers almost brought no secondary reaction in this esterifation, and the esterifation catalyzed by calcium sulfate whiskers was green without environmental pollution and corrosion of equipments compared with traditional concentrated sulfurie acid method.(3)The catalytic activity of calcium sulfate whiskers in the synthesis of diethylene glycol dimethacrylate (DEGDMA) via transesterification from methyl methacrylate and glycol ether was investigated, and the optimized conditions were obtained as follows:a molar ratio of methyl methacrylate to diethylene glycol3.5:1, under circumfluence temperature, the amount of calcium sulfate whiskers and nitroxide free radical inhibitor3%,0.1%, respectively. Yield of product ester obtained under above conditions reached above93.3%and its purity was97%. Experimental results indicated:the catalytic activity of calcium sulfate whiskers depended on the structure, not composition. Calcium sulfate whiskers compared with sulfurie acid and p-toluenesulfonic acid showed efficient catalytic activity in the synthesis of diethylene glycol dimethacrylate via transesterification, with no corrosion, low cost, good product quality, light color, less second section, more relaxed reaction conditions, etc. Therefore, the development of the applications of calcium sulfate whiskers in chemical industry has broad market prospects.(4)The synthesis of TMPTA by using calcium sulfate whiskers as catalyst was studied. The optimized conditions were as follows:a molar ratio of acrylate to trimethylolpropane3.4:1, amount of calcium sulfate whiskers2.0%(based on trimethylolpropane), cyclohexane and toluene as water carriers, with hydroquinone and phenothiazines as inhibitors, the final temperature of esterification98℃, a reaction time5h, the air flow15mL·min-1. Under optimized conditions, the yield of TMPTA above96.8%.更多还原