【作者】 李浩；

【导师】 宋文生；

【作者基本信息】 河南科技大学 ， 高分子化学与物理， 2009， 硕士

【摘要】 聚氨酯涂料优异的机械性能、良好的耐磨性和附着力,使其在涂饰领域获得广泛应用。传统溶剂型聚氨酯涂料使用中存在有机溶剂挥发污染环境问题,因而促使水性聚氨酯(WPU)的发展。WPU虽具有不污染环境、安全可靠、使用方便等优点以及优异的机械性能,但高质量的聚氨酯涂层要求耐候性。因此,本文选用脂肪族聚酯、脂环族异氰酸酯、亲水性羧酸型扩链剂为主要原料,通过加成聚合反应合成耐候性羧酸型水性聚氨酯分散液。本文首先探讨了脂环族二异氰酸酯与亲水性羧酸型扩链剂,即异佛尔酮二异氰酸酯( IPDI )与2,2-二羟甲基丙酸(DMPA)在溶剂N-甲基吡咯烷酮(NMP)中的反应动力学。结果表明:IPDI的反应活性较低,其与DMPA反应活化能为Ea=68.7kJ/mol,反应速率常数k遵循Arrhenius方程以聚己二酸丁二醇酯二醇(PBA3000)、IPDI、DMPA为主要原料,按DMPA加料顺序,分别采用一步法和两步法合成-NCO封端、侧链含-COOH基团的聚氨酯预聚物,加丙酮稀释,降温至室温(25～30℃),由三乙胺(TEA)中和预聚物中-COOH基团,水中分散,再由乙二胺(EDA)进一步扩链,之后脱除丙酮,得到耐候性羧酸型水性聚氨酯分散液。分别探讨了,聚氨酯预聚物合成工艺条件、分散与扩链技术;分散液固含量相同时,离子基团含量、R值与水性聚氨酯分散液的电导率、外观、临界聚沉值之间的关系;以及分散液中粒子的微观特性和分散液胶膜的机械性能、热性能和结构特征。研究发现,一步法与两步法合成的分散液胶膜机械性能基本一致,但一步法工艺简单;聚氨酯分子中-COOH基团含量1.09~2.37%时,分散液均很稳定,电导率、分散液临界聚沉值Cc.c随-COOH基团含量的增加而增大;稳定分散液中固含量可达32.15%,透射电镜(TEM)显示分散液中粒子的粒径小于100nm;分散液胶膜的拉伸强度随聚氨酯分子中-COOH含量的增加而增大,而断裂伸长率随-COOH含量的增大而减小,在-COOH含量为2.37%时拉伸强度达29MPa、断裂伸长率达510%;X-射线衍射(XRD)表明羧酸型水性聚氨酯具有较高的结晶性,且在大分子链段中软段的结晶程度高于硬段;差示扫描(DSC)、热重(TG)表明羧酸型水性聚氨酯具有较高的热性能,热分解温度高于330℃。更多还原

【Abstract】 Polyurethane coatings have excellent mechanical, wear-resistance and adhesive properties, and can be widely applied in the finishing field. Traditional solvent-type polyurethane coatings containing volatile organic solvents pollute the environment. So the development of waterborne polyurethane coatings (WPU) is being prompted. Although WPU possesses many advantages, such as non-pollution, safety, convenient use and excellent mechanical properties, high-quality polyurethane coatings should have weathering resistant characteristic. Therefore, weatherable carboxylic acid-type WPU dispersions were synthesized from aliphatic polyester, alicyclic isocyanate and hydrophilic carboxylic acid-type chain extender as raw materials by addition polymerization in this paper.The reaction kinetics between isophorone diisocyanate (IPDI: as alicyclic diisocyanate) and 2, 2-dimethylolpropionic acid (DMPA: as hydrophilic chain extender) in N-methyl-2-pyrrolidone (NMP: as a solvent) were first studied. The results showed that reaction activity of IPDI was lower, activation energy (Ea) was 68.7kJ/mol and reaction rate constant (k) followed Arrhenius equationFirstly, when polybutylene adipate glycol (PBA3000), IPDI and DMPA were used as main raw materials, the synthesis methods of -NCO terminated polyurethane prepolymers with -COOH groups in the side chain of polymers were classified one-step method and two-step method on the basis of feeding order of DMPA. After, prepolymers were diluted with acetone and cooled to 25~30℃, -COOH groups in the prepolymers were neutralized by triethylamine (TEA). Finally, neutralized prepolymers were dispersed in water and further extended by ethylenediamine (EDA: as auxiliary chain extender). After removing acetone, the carboxylic acid-type waterborne polyurethane dispersions were obtained. The synthetic conditions, dispersion and chain extension of polyurethane prepolymers; the relations between ion group content or R value and conductivity or appearance or critical congregating concentration (Cc.c) of WPU dispersions with the same solid content; microscopic characteristics of particles in WPU dispersions, and mechanical properties, thermal properties and structural characteristics of films made from WPU dispersions, were discussed, respectively. The experiment results showed that mechanical properties of films made from WPU dispersions synthesized by one-step method were similar to those by two-step method, but one-step method was more convenient. When–COOH group content of polyurethane molecule was from 1.09% to 2.37%, WPU dispersions were stable and their conductivities and Cc.c increased with the increasing of–COOH group content. The solid content of stable dispersion could achieve 32.15%, transmission electron microscopic (TEM) showed that the size of particles in dispersions was less than 100nm. With the increasing of -COOH group content of polyurethane molecular, tensile strength of films made from WPU dispersions increased but elongation at break declined. When–COOH group content was 2.37%, tensile strength could achieve 29MPa and elongation at break was 510%. X-ray diffraction (XRD) demonstrated that carboxylic acid-type WPU molecule had higher crystallinity and the crystallinity of soft segment in the polymer was higher than that of hard segmeng. Differential scanning calorimetry (DSC) and thermogravimetry (TG) showed that the thermal stability of carboxylic acid-type WPU was higher and thermal decomposition temperature was more than 330℃.更多还原