摘要
ABS树脂是丙烯腈(AN)、丁二烯(BDE)、苯乙烯(SM)的三元共聚物。它是由50%以上的苯乙烯和适量的丁二烯和丙烯腈共聚而成。兼有聚苯乙烯的光泽性、电性能、易加工性,聚丁二烯橡胶的韧性、低温耐冲击性以及聚丙烯腈的耐候性、耐热性和耐化学性能。是目前世界范围内用途最广、用量最大的工程塑料,广泛用于汽车、家电、通讯器材及日用品等领域。
与国外ABS树脂生产装置和产品相比,国内ABS装置的生产和产品质量还存在一定的差距。在生产上主要表现为装置的非计划停车次数较多,干燥器等设备清洗时间较长,生产的连续性不稳定,尤其是ABS干燥系统还存在一些安全隐患;而在ABS产品质量上主要表现颜色偏黄,在指标上具体表现为黄度指数偏高。由于以上原因,导致国内ABS装置的生产成本较高,质量的差距也导致产品的价格大大低于国外和台湾同类产品。所以,开展对ABS装置干燥系统的研究,提出有效的解决办法消除安全隐患和提高产品质量是一项具有十分重要意义的研究。
经过研究,发现ABS粉料在干燥过程中与空气接触,粉料在干燥器内停留时间大约120min,容易被空气中的氧气氧化变黄,这样的粉料和SAN掺混造出的ABS颗粒黄度指数达到30以上(国内外先进的黄度指数指标应小于25)。另外在生产过程中如果ABS粉料在干燥器内堆积,就会氧化自燃,引起干燥系统爆燃。空气在干燥系统中的袋式过滤器内流速较快,也容易与袋式过滤器摩擦产生静电,静电放电产生火花,点燃细粉料,引起爆燃。如果系统中没有氧气,粉料不会变黄,干燥系统也不会爆燃。在这个理论基础上本文提出在ABS干燥系统中采用氮气循环干燥代替空气干燥,这样既可以降低粉料的黄度又可以有效避免爆燃事故的发生。
本课题是针对ABS装置干燥系统改为氮气循环的工艺研究,提出将干燥系统中的干燥介质热空气改为热氮气,氮气密闭循环使用,采用水喷淋式冷却塔除去氮气中夹带的水份,冷却塔热量取出采用两级冷却,一级冷却采用循环水,二级冷却采用浅冷水。循环系统内的压力采用分程控制,及时补充和排放氮气,将原干燥器排风机更换成大功率风机,提高风机出口压力,克服冷却塔的阻力,保证干燥系统的风量等措施来解决ABS干燥系统存在的问题。
ABS resin is consist of acrylonitrile(AN).butadiene(BDE) and styrene(SM). It is that be measured by higher 50% of styrene , some butadiene and acrylonitrile . It' s have polystyrene' s nature of chatoyant and electricity, polybutadiene rubber ' s tenacity, low temperature function and easily processing behavior, and polyacrylonitrile's weather ability.heat resistance and endurable chemistry function. Now and within the scope of world it is widest ABS resin is an use, use to measure biggest engineering plastics, extensive used for the car, appliance, communication device and daily necessity etc.
With the abroad ABS product compare, the color of local ABS product exsits some questions, such as yellow degree number is higher, especially the dryer system of ABS contain the safe question, therefore, open the research ABS equip dry system process, and it is a to bring up the valid solution especially very important with the meaningful issues. Pass by the analysis, ABS powder stop over in the dryer in the cent contact of dry process inside and air fully, ABS powder retention retains about 120 minutes, were oxidized by oxygen in the air to become yellow, like this of powder is with the SAN compound , the yellow degree number of ABS should be attain 30. ( yellow degree number of grain should lower 25). If the ASB powder pile up in the dryer , will can oxidized and detonation, Moreover, air is in the bag filter inside the current velocity is very quickly, with the bag filter rub to produce the static electricity, static electricity to turn on electricity to beat the spark, and spark fine ABS powder, and also
cause to detonation.
Known from analysis the oxygen in the air is main factor of the ABS powder change yellow degree and cause to detonation, if have no an oxygen, ABS powder can't become yellow, the dry system also can't detonation. System that yellow degree that adoption nitrogen circulation inliens the air is dry to make the ABS powder in the dry process not the contact air, it' s make ABS powder avoid detonation trouble.
This issues research change water spraying tower detachs water of nitrogen circulation inliens , nitrogen the closeness the circulating usage, water tower adopt two classes cool off, first calss adopt circulating water, second class adopt freezing water. Pressure in the circulatory system adopt cent control, on time complement and discharge nitrogen . replace the bigger power blower, and increase blower outlet pressure, and overcome the cooling tower' s pressure resistance, then guarantee blower amount of the dry system can good solution ABS dry system problem.
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