【作者】 夏春；

【导师】 李远才；

【作者基本信息】 华中科技大学 ， 材料加工工程， 2005， 博士

【摘要】 随着全球经济一体化进程的加快,我国酚醛树脂行业迎来巨大机遇的同时,也面临着前所未有的挑战。为在竞争日益激烈的国际化市场中求生存、求发展,就必须加大力度进行科技创新,在改善树脂生产中存在的合成时间长、效率低、耗能大等缺点的基础上,解决树脂游离酚含量高、聚合速度慢、综合性能差等问题,以满足铸造业日益增长的质量、环保、效率等方面的需求。为此,本课题将高效快速、节能环保的微波加热技术应用于热塑性酚醛树脂的合成中,通过合成工艺的筛选、优化和化学改性等方法,试图开发出综合性能优良的壳法用酚醛树脂,并在此基础上,对树脂微波合成以及改性剂介入树脂分子结构的机理进行研究和分析。为热塑性酚醛树脂微波合成的研究奠定基础,本文首先对热塑性酚醛树脂传统合成工艺进行了研究,并探讨了树脂软化点、聚合速度、流动性等理化性能对覆膜砂强度的影响规律。然后,在对家用微波炉加热原理及热塑性酚醛树脂在微波炉中合成特点进行分析的基础上,基于家用微波炉的改造,开发了一套具有回流、搅拌、测温等功能的适合实验室的微波合成装置。利用该微波合成装置,以传统合成为对比,通过红外光谱(IR)、凝胶渗透色谱(GPC)等手段分别从微波合成反应、微波脱水两个方面系统地分析了微波合成对树脂性能影响的规律及其原因,揭示了微波合成致使流动性、聚合速度等树脂性能改善的原因所在; 并通过实验证实了树脂微波合成中存在着潜在的局部热点,而局部热点和反应体系的过热是致使微波合成时间相比于传统工艺缩短约80%的根本原因。另外,本文也以大量的实验数据为样本,建立了基于热塑性酚醛树脂微波合成的人工神经网络模型,并利用该人工神经网络对树脂的合成配方及工艺进行了进一步的优化。在上述工艺优化的基础上,本文还开展了A 催化剂或其与草酸所组成的复合催化体系、双酚A(BPA)及水杨酸改性的研究,在获得综合性能优良的改性树脂同更多还原

【Abstract】 With the development of global economization, huge opportunities, but unprecedented challenges have been brought for the phenolic resin industry in china. In order to win the international market competition and meet the demand and development in the foundry industry, the technological innovation is required that sloving the problem, such as the high free phenol content, slow cure rate, low general performance and so on, based on the reduction of synthesis time, improvement of efficiency and economization of energy. Therefore, the microwave heating, which is high heating efficiency, rapid heating rate, low consumed energy and protected environment, has been introduced to the synthesis of novolac resins. The purpose of this subject is to develop novolac resins for shell process with excellent general performance, by means of the selection and optimization of the synthesis and chemical modification processes, and besides, investigate and analyze the mechanisms of the microwave-assisted synthesis and modification of the resins. In this paper, firstly, the conventional synthesis processes of novolac resins and the influences of the properties of physics-chemistry of the resins, e.g. softening point, cure rate and flow distance on the strength of the resin coated sands have studied. Secondly, in the laboratory, a microwave-assisted synthesis device, involved with refluxing, agitating and the measurement of the temperature, has been modified based on domestic microwave oven. Compared with conventional synthesis, the rules of the microwave-assisted polymerization and dehydration have been investigated and analysed comparatively in detail by means of the Infrared spectrum (IR), Gel permeation chromatography (GPC). The reasons of the improvement in the performances of novolac resins, e.g. flow distance, cure rate, caused by microwave heating have been disclosed. Furthermore, the existence of local potential ‘hot spots’in course of microwave-assisted synthesis of novolac resins has been identified by the experiment and the results showed that the ‘local hot’and overheating for the reaction system are the main reason for the notable reduction of synthesis time. Thirdly, a model of the Artificial Neural Networks (ANN) based on the experiments of the microwave-assisted synthesis of novolac resins has been built, and the further optimization of the synthesis process parameters was carried on, according to the ANN. On the basis of before-mentioned optimized processes, a series of modification experments, including to catalyst A, the hybrid catalyst of A and oxalic acid, bisphenol A and salicylic have been carried on, and the results showed that the modified novolac resins with high general performances could been obtained. According to the experiments and analyse of the synthesis mechanisms of the modified resins, some points of view have been put forward, as follows: The mechanisms of the ‘high orth’novolac resins under the catalyst A should be concerned about the formation and breaking down of benzyl ethers etc. The mechanisms of bisphenol A introduced into the molecular structure of novolac resins could be attributed to the condensation reaction between prepolymer of bisphenol A and the base resins by means of ‘embedment’or ‘on end’, and for salicylic modified resins, the reasons of improvement in the performance are considered as the introduction of carboxyl into the base of the resins. Finally, for examining the practical effectiveness of the modified resins, the further experiments were done, and the results showed that excellent effect is obtained, on the one hand, the free phenol content is obviously lower than the domesic novolac resins; on the other hand, the cure rate is rapid and the thermal stability is high on the basis of suitable softening point; what’s more, the strength of resin coated sands is high.更多还原