PREPARATION OF ULTRA HIGH MOLECULAR WEIGHT POLYETHYLENE USING STRUCTURED NANOPARTICAL ZIEGLER-NATTA CATALYSTS

A structured nanoparticle support was prepared by using diol as precipitant to recrystallize nano-sized MgCl2 on the surface of SiO2.TiCl4 was immobilized on the surface of the resulting structured nanoparticle support, forming structured nanoparticle Ziegler-Natta cataylst. The resulting catalyst was used to catalyze the slurry-phase polymerization of ethylene. Polyethylene produced was characterized with scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and particle size analysis. In order to obtain the proper catalyst, the influence of diol/MgCl2 ratio on support morphology, catalysis features of structured nanoparticle catalyst and characteristics of products were investigated. Results showed that the structured nanoparticle Ziegler-Natta catalyst was an excellent catalyst for producing ultra high molecular weight polyethylene (UHMWPE) because of its special particle morphology. Polymerization activity and molecular weight of products were both sensitive to the temperature. At the optimum temperature, polymerization activity could reach as high as 1261 kg PE.(molTi)(-1).h(-1).10(-5)Pa(-1) and molecular weight of product could reach as high as 5.87 x 10(6). UHMWPE produced with structured nanoparticle Ziegler-Natta catalyst had a high crystallinity degree which could reach 49.5%. It also performed a uniform spherical morphology with an average particle size of 68 similar to 69 mu m and moreover the distribution of particle size was very narrow. These were all beneficial to the processing of UHMWPE.