低缠结超高相对分子质量聚乙烯的制备及表征

Preparation and characterization of polyethylene with low entanglement and ultra-high relative molecular mass

为解决传统Ziegler-Natta催化剂(简称Z-N催化剂)制备的超高相对分子质量聚乙烯(UHMWPE)缠结程度较高、加工困难等问题,以MgCl_(2)、TiCl_(4)、异辛醇、正硅酸四乙酯(或邻苯二甲酸二己酯)为主要原料,采用化学反应法制备了氯化镁负载型Z-N催化剂cat1(或cat2)。分别以cat1、cat2为主催化剂、三乙基铝为助催化剂,采用淤浆聚合工艺制备了低缠结UHMWPE,测定了cat1、cat2的粒径分布和金属元素质量分数,考察了聚合温度、时间对催化剂催化活性和UHMWPE的黏均相对分子质量(M_(v))的影响,并使用流变分析法和DSC热力学退火法对UHMWPE的缠结程度进行了表征。结果表明,制备的cat1、cat2与设计相符,在聚合反应温度分别为65和70℃、反应5 h时,cat1、cat2催化活性分别达到27700、37700 g PE/g cat,制备的UHMWPE的Mv分别为6.01×10^(6)、5.03×10^(6),起始储能模量分别为0.21、0.13 MPa,缠结程度低于商品化UHMWPE。

In order to solve the problems of high entanglement and difficult processing of ultra-high relative molecular mass polyethylene(UHMWPE)prepared at the catalysis of traditional Ziegler Natta catalyst(Z-N catalyst),low entanglement UHMWPE was synthesized from slurry polymerization using magnesium dichloride supported Z-N catalyst cat1(or cat2),which was prepared from chemical reaction of MgCl_(2),TiCl_(4),isooctanol,tetraethyl orthosilicate(or dihexyl phthalate),as main catalysts and triethylaluminum as co catalyst.The particle size distribution and metal element mass fraction of cat1 and cat2 were analyzed.And the influence of polymerization temperature and time on the catalytic activity of cat1 and cat2 as well as the viscosity-average relative molecular mass(Mv)of UHMWPE were investigated,with the entanglement degree of UHMWPE characterized by rheological analysis and DSC thermodynamic annealing.The results showed that the cat1 and cat2 obtained were consistent with the design.Under the polymerization reaction temperature of 65 and 70℃,and reaction time of 5 h,the catalytic activity of cat1 and cat2 reached 27700 and 37700 g PE/g cat,respectively.The Mv of prepared UHMWPE was 6.01×10^(6) and 5.03×10^(6),and the initial storage modulus was 0.21 and 0.13 MPa,respectively.The entanglement degree was lower than that of commercial UHMWPE.