Abstract:

The synthesis of copolymer with high comonomer incorporation and broadened molecular mass distribution from ethylene with 1-hexene catalyzed by co-catalyst TiCl₄/XROH/MgCl₂ and Et₃Al is described. The influences of the catalyst system composition and the polymerization conditions on the behavior of ethylene/1-hexene copolymerization, the structure, molecular mass and molecular mass distribution(MMD) of the obtained copolymer have been discussed in detail. When the copolymerization was performed under the optimum conditions:n(Ti)∶n(Mg)=10∶1, n(XROH)∶n(MgCl₂)=2.6∶1, n(Al)∶n(Ti)=100∶1, P=0.45 MPa, t=80 ℃, Time=2 h and the comonomer concentration in feed=0.25 mol/L, the catalytic activity reached 23.2 kg/g cat. The catalyst particle shape and the structure and properties of the ethylene/1-octene copolymer are characterized with ¹³C NMR, X-ray, SEM, WAXD, DSC and GPC. These results show that the catalytic activity, molecular mass distribution and higher 1-hexene incorporation were considerably improved when the multi-halogen alcohol(XROH) was added into the catalyst system. By adding XROH in the catalyst system made Ti mass fraction of the catalyst increased up to 4.8%; the molar ratio of MMD of the copolymer became broader, ranging from 15 to 20; 1-hexene incorporation within the copolymer chain was higher, up to 5.1%.

Key words: supported Z-N catalyst, multi-group internal donor, copolymer of olefins, broaden molecular weight distribution