气固相法制备氯化聚氯乙烯的研究

发布时间：2018-10-31 20:13

【摘要】：氯化聚氯乙烯是聚氯乙烯经氯化得到的一种新型树脂,是一种重要的聚氯乙烯改性产品。氯化聚氯乙烯除了拥有一些聚氯乙烯的优良性能以外,还具有很多优良性能如耐腐蚀、耐热寒、阻燃以及较高的机械强度等。其在塑料、建材、医学、电气、农业、涂料、造纸、船舶、包装等方面有着较为广泛的应用。 国内外大都采用水相悬浮法工艺生产氯化聚氯乙烯。通过高温、加压、加氧化剂等手段提高产品氯含量,但同时也会导致分子链断裂,使产品分子量严重减小,导致产品的一些机械性能下降,制约了氯化聚氯乙烯的使用。采用气固相法可以使氯化反应在较低的温度进行,同时可以保证产品的氯含量,更重要的是,气固相法反应条件较为温和,且不添加氧化剂帮助氯化,因此反应中产品分子链的断裂得到了有效的控制,产品分子量指标可以保持在较高的水平,满足实际应用中对其机械性能的要求。另外,气固相法工艺不需要处理大量废水,经济环保,属于绿色反应工艺。 本文的研究内容即为采用气固相法制备氯化聚氯乙烯,考察了反应时间、反应温度、通氯量及搅拌速率等对产品氯含量及产物分子量的影响,并给出了优化后的反应工艺。结果表明：升高温度、延长反应时间均有利于产品的氯含量增加；温度升高会使数均分子量略有所下降,重均分子量有所增加；延长反应时间可以使数均和重均分子量都有所增加；产品的氯含量会随着通氯量的增加而增加,并且在某一值下达到饱和；搅拌速率对产品的影响相对较小。在氯化反应中,增加了预氯化过程,可以提高聚氯乙烯的耐热性能,使其可在较高温度下进行氯化,氯化效果优于一步氯化。优化后的工艺条件为：预氯化时间1h,预氯化温度55℃,氯化温度100℃,氯化时间6h,氯气流量500mL/min,搅拌速率80r/min. 本文还对较为优化的工艺条件下所制得的产品的各项指标进行了测定,如氯含量,表观密度,挥发组分和分子量等。测试结果表明,该方法所得产品的一些性能指标已经满足某些国内企业的水相法的产品指标,部分性能大大超过了相关指标,并十分接近国外的相关工艺指标。 实验中采用了自旋式反应设备应用于气固相法制备氯化聚氯乙烯,代替传统的机械搅拌,可以使产品氯化均匀,性能良好。 本文还进一步考察了常压低温下聚氯乙烯颗粒内部的氯化反应动力学,推导得出该条件下的气固相反应动力学方程。并计算出不同温度下的表观反应速率常数。最后通过阿伦尼乌斯方程计算出反应的表观活化能和指前因子,反应表观活化能为Ea=22.118kJ/mol,指前因子A=0.001355 (mol-m-3)-1·s-1,
[Abstract]:Chlorinated polyvinyl chloride (PVC) is a new type of resin obtained by chlorination of PVC, which is an important modified product of PVC. In addition to some excellent properties of PVC, chlorinated PVC also has many excellent properties such as corrosion resistance, heat resistance and cold resistance, flame retardancy and high mechanical strength. It is widely used in plastics, building materials, medicine, electricity, agriculture, paint, paper making, ship, packaging and so on. Chlorinated polyvinyl chloride (PVC) is produced by aqueous suspension process at home and abroad. By means of high temperature, pressure and oxidant, the chlorine content of the product is increased, but at the same time, the molecular chain breakage will be caused, the molecular weight of the product will be reduced seriously, and some mechanical properties of the product will be decreased, which will restrict the use of chlorinated polyvinyl chloride. The reaction of chlorination can be carried out at a lower temperature by gas-solid method, at the same time, the chlorine content of the product can be guaranteed. More importantly, the reaction conditions of the gas-solid method are mild and the oxidant is not added to help chlorination. Therefore, the molecular chain breakage of the product can be effectively controlled, and the molecular weight index of the product can be kept at a higher level, which can meet the requirements of its mechanical properties in practical application. In addition, the gas-solid process does not need to treat a large number of wastewater, economic and environmental protection, is a green reaction process. In this paper, chlorinated polyvinyl chloride was prepared by gas-solid method. The effects of reaction time, reaction temperature, chlorine flux and stirring rate on the chlorine content and molecular weight of the product were investigated, and the optimized reaction process was given. The results showed that increasing the temperature and prolonging the reaction time were beneficial to the increase of chlorine content, and the molecular weight of the product decreased slightly and the weight average molecular weight increased with the increase of temperature. When the reaction time is prolonged, the number average and weight average molecular weight can be increased, the chlorine content of the product will increase with the increase of chlorine flux, and reach saturation at a certain value, and the effect of stirring rate on the product is relatively small. In the chlorination reaction, the thermal resistance of PVC can be improved by adding prechlorination process, and the chlorination effect is better than that of one-step chlorination. The optimized conditions were as follows: prechlorination time 1 h, prechlorination temperature 55 鈩，

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