废旧涤纶织物再资源化的研究

发布时间：2018-08-25 10:37

【摘要】：我国是纺织工业大国，同时也是纺织品消费大国，每年我国因此而产生的废旧纺织品高达数千万吨之巨。如今，我国的的废旧纺织品再资源化综合利用才刚刚起步，因此，真正得到再资源化利用的还不足十分之一，而未能得到有效再利用的部分既造成了资源浪费，又带来了环保的问题。涤纶（polyester简称PET）织物在废弃的纺织品中占据了相当大的比重，因此，如何通过合理有效的办法使废旧涤纶织物得以再资源化成了摆在我们眼前亟需解决的难题。近些年来，我国的涤纶产量一直呈现有增无减的态势，2013年我国涤纶产量为3327.61万吨，占到了全球总产量的七成以上，但用来生产涤纶的初级原料对二甲苯（PX）却严重依赖进口，2013年我国对二甲苯的对外依存度高达53%，且缺口仍在不断增加。遗憾的是，当前消费掉的涤纶织物几乎全部被当做垃圾掩埋或焚烧，综合利用率不足1%，因此大力开发涤纶聚酯的回收再利用技术已经成为涤纶聚酯工业发展的关键所在。当今，PET再资源化利用的方法主要有酸性水解法、碱性水解法、中性水解法、甲醇醇解法以及乙二醇醇解法等，然而中性水解废旧PET是最具有发展前景的。本实验以经过前处理的废弃涤纶织物为原料，以亚临界状态下的水为溶液，在高压釜内使涤纶织物降解。采用氮氮二甲基甲酰胺（DMF）剥色系统对废弃的涤纶织物进行前期的剥色处理，，讨论了投料比（去离子水与涤纶布料的质量比）、反应温度、保温时间对PET降解率以及产物的白度、纯度、酸度的影响，并对PET在亚临界水条件下的水解机理进行了初步摸索，揭示了聚对苯二甲酸乙二醇酯在水热条件下的水解过程以及反应机理，最后还对降解所得白色固体对苯二甲酸（TPA）的各项质量指标进行了测定。（1）本文讨论明确了废旧涤纶织物的剥色前处理主要分为溶胀剂溶胀、分散染料的剥色以及还原剥色三个过程。本文选用的溶胀剂为二甲基亚砜（DMSO），分散染料的剥色剂选为DMF，还原剂为二氧化硫脲（TDO）。确定了最佳剥色工艺条件为：剥色时间30min，剥色温度控制在140℃。（2）采用中性水解法回收再利用废旧涤纶织物，再资源化产物为TPA和乙二醇（EG），投料比（去离子水和涤纶织物的质量比）、反应温度以及保温时间是涤纶织物水解的最主要的影响因素；明确了最佳的水解条件：投料比10:1，实验温度250℃，反应时间7h。在最佳条件下PET的降解率可以达到92.9%，TPA的产率为86.4%，TPA纯度为98.251%，TPA的酸度可达657.14mgKOH/g。（3）明确了PET的水解机理：在高温高压下水会电离成H+和OH-，H+与-COOR中的羰基作用形成C+，同时水的H进攻-COOR中的C，形成四面体的中间产物。然后，水中的H离去，O上的电子发生转移，酰氧键断裂，最后降解成TPA和EG。（4）明确了PET水解生成的TPA的各项质量指标满足精对苯二甲酸（PTA）标准的实验条件：反应温度≥250℃，反应时间8h，投料比10:1，干燥温度100℃、干燥时间8h。
[Abstract]:China is a big country in textile industry and also a big country in textile consumption. The amount of waste textiles produced in our country is tens of millions of tons every year. Nowadays, the comprehensive utilization of waste textiles has just started. Therefore, less than one tenth of the waste textiles have been reused, but they have not been effectively reused. It not only caused the waste of resources, but also brought about environmental problems.
Polyester (PET) fabrics occupy a considerable proportion in the waste textiles. Therefore, how to reuse waste PET fabrics by reasonable and effective means has become a difficult problem to be solved urgently. In recent years, China's polyester production has been showing an increasing trend, in 2013 China's polyester production. The total output is 33.2761 million tons, accounting for more than 70% of the world's total output. However, the primary raw material for producing polyester fibers is heavily dependent on imports. In 2013, China's dependence on paraxylene was as high as 53%, and the gap is still increasing. Unfortunately, almost all of the polyester fabrics currently consumed were buried or burned as garbage. The comprehensive utilization rate of PET is less than 1%. Therefore, the recycling technology of PET has become the key to the development of PET industry. Nowadays, the recycling methods of PET mainly include acid hydrolysis, alkaline hydrolysis, neutral hydrolysis, methanol alcoholysis and ethylene glycol hydrolysis. It is the most promising one.
In this experiment, the waste polyester fabric treated before is used as raw material, and the water in subcritical state is used as the raw material.
Polyester fabric was degraded by solution in autoclave. The waste polyester fabric was stripped by DMF stripping system. The effects of feed ratio (mass ratio of deionized water to polyester fabric), reaction temperature and holding time on the degradation rate of PET, whiteness, purity and acidity of the product were discussed. The hydrolysis mechanism of polyethylene terephthalate in subcritical water was explored. The hydrolysis process and reaction mechanism of polyethylene terephthalate under hydrothermal condition were revealed. Finally, the quality indexes of white solid terephthalic acid (TPA) were determined.
(1) The pretreatment of waste polyester fabrics is divided into swelling agent, stripping of disperse dyes and reducing stripping. The swelling agent is DMSO, the stripping agent of disperse dyes is DMF and the reducing agent is thiourea dioxide (TDO). The optimum stripping conditions are determined as follows: The color time is 30min, and the stripping temperature is controlled at 140 C.
(2) The neutral hydrolysis method was used to recover and reuse waste polyester fabrics, and the recycled products were TPA and EG. The feed ratio (mass ratio of deionized water to polyester fabrics), reaction temperature and holding time were the main factors affecting the hydrolysis of polyester fabrics. Under the optimum conditions, the degradation rate of PET was 92.9%, the yield of TPA was 86.4%, the purity of TPA was 98.251%, and the acidity of TPA was 657.14 mg KOH/g.
(3) The hydrolysis mechanism of PET is clarified: water will ionize into H + and OH-, and H + will react with carbonyl group of - COOR to form C+, and water will attack C of - COOR to form tetrahedral intermediate. Then, H in water will leave, electrons on O will transfer, and the acyloxy bond will break, and then it will be degraded into TPA and EG.
(4) The experimental conditions of TPA produced by hydrolysis of PET were defined as follows: reaction temperature (> 250), reaction time (> 8 h), feed ratio (> 10:1), drying temperature (> 100) and drying time (> 8 h).
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X791

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