Production method of polyethylene wax
目前，聚乙烯蜡的生产方法主要有三类：一是由乙烯单体通过低聚反应， 如通过自由基低聚方法合成的聚乙烯蜡； 二是由高聚物的降解制备的聚乙烯蜡；三是在聚乙烯的合成过程中的副产，如高压法聚乙烯合成中的副产物经过分离得到的聚乙烯蜡。
At present, there are three main production methods of polyethylene wax: one is the oligomerization of ethylene monomers, such as polyethylene wax synthesized by free radical oligomerization; the other is the degradation of polymers; the third is the by-product in the synthesis of polyethylene, such as the by-product in the synthesis of high-pressure polyethylene. Separated polyethylene wax.
1. Ethylene polymerization
乙烯聚合法生产聚乙烯蜡主要有3 种方法，一是用自由基催化剂在高温高压下聚合； 二是用齐格勒催化剂在低压下聚合；三是茂金属催化剂聚合。
There are three main methods to produce polyethylene wax by ethylene polymerization, one is polymerization under high temperature and pressure with free radical catalyst, the other is polymerization under low pressure with Ziegler catalyst, and the third is polymerization with metallocene catalyst.
2. Polyethylene pyrolysis method
聚合法生成的聚乙烯蜡分子量分布窄， 相对分子质量大小可以人为控制，但必须在大装置上进行，资金投入大。国内厂家一般采用高分子量聚乙烯的热裂解法生产， 这种方法采用的原料可以是聚乙烯树脂，也可以是聚乙烯废塑料，前者制得的产品等级高，后者制得的产品等级低。高分子量聚乙烯在隔绝空气的条件下可以热裂解为低分子量的聚乙烯蜡， 这样制备的聚乙烯蜡与结构有关的性质（如结晶度、密度、硬度和熔点）都受到裂解原料的影响。裂解加工方法分为裂解釜法和挤出法。裂解釜法是间歇式加工方法，适合于生产量较低，产能较小的厂家；挤出法是连续化生产，适合于生产量大，产能高的企业。
Polyethylene wax produced by polymerization has narrow molecular weight distribution and its relative molecular weight can be controlled artificially, but it must be carried out in a large unit with large investment. Domestic manufacturers generally use high molecular weight polyethylene pyrolysis production, this method can be used as raw materials can be polyethylene resin, can also be polyethylene waste plastic, the former product grade is high, the latter product grade is low. High molecular weight polyethylene (HMWPE) can be pyrolyzed into low molecular weight polyethylene wax (LMWPE wax) in an air-insulated environment. The structure-related properties (such as crystallinity, density, hardness and melting point) of the prepared polyethylene wax are affected by the pyrolysis feedstock. Cracking process is divided into cracking kettle method and extrusion process. Pyrolysis kettle process is a batch process, suitable for low production, small capacity manufacturers; Extrusion process is continuous production, suitable for large production, high capacity enterprises.
3. Polyethylene byproduct purification
从乙烯聚合生产聚乙烯的反应中， 副产得到的低分子量组分和溶剂的混合物中可以回收聚乙烯蜡产品。从聚乙烯装置的副产中脱出溶剂和引发剂后，产物分子量分布仍然很宽，限制了其应用领域，需要采用溶剂分离的方式进行进一步提纯。这种副产的聚乙烯蜡产品中通常含有相对分子质量在1000 左右的分子，所以在机械强度、耐热性能等物理性能上低于乙烯聚合法生产的聚乙烯蜡产品。
Polyethylene wax can be recovered from the mixture of low molecular weight components and solvents obtained by-product in the process of ethylene polymerization to produce polyethylene. After the solvent and initiator are removed from the by-product of polyethylene plant, the molecular weight distribution of the product is still very wide, which limits its application field. Solvent separation is needed for further purification. This by-product of polyethylene wax usually contains molecules with a relative molecular weight of about 1000, so its mechanical strength, heat resistance and other physical properties are lower than those of polyethylene wax produced by ethylene polymerization.