有机/无机复合载体负载复合催化剂用于乙烯聚合时有机载体的作用

采用溶胶-凝胶法,将苯乙烯-丙烯酸(P(S-co-AA))共聚物包覆在以硅胶/MgCl2为载体的TiCl3催化剂(M-1催化剂)上,负载(n-BuCp)2ZrCl2后制得TiCl3/(n-BuCp)2ZrCl2复合催化剂,研究聚合物载体P(S-co-AA)在复合催化剂乙烯聚合中的作用.前期实验结果表明有机载体P(S-c...

EFFECT OF ORGANIC PART OF ORGANIC/INORGANIC HYBRID SUPPORT IMMOBILIZED HYBRID CATALYST ON ETHYLENE POLYMERIZATION

Organic/inorganic support made by poly(styrene-co-acrylic acid) P(S-co-AA) and SiO₂ was prepared for immobilizing (n-BuCp)₂ZrCl₂/M^-1 hybrid catalyst.P(S-co-AA) was first coated on industrialized M^-1 catalyst (SiO₂/MgCl₂-TiCl₃).The hybrid catalyst was achieved after immobilizing (n-BuCp)₂ZrCl₂ on the P(S-co-AA) layer.The barrier property of P(S-co-AA) layer to cocatalyst MMAO was observed by ethylene polymerization.The appearance of the lag phase in the kinetic curve during the first stage polymerization implied that the exterior catalyst ((n-BuCp)₂ZrCl₂) could be activated prior to the interior catalyst (M^-1).In addition,the morphology,short chain branch degree,molecular weight,molecular weight distribution and crystalline property of polymers obtained at different polymerization times were investigated by scanning electron microscopy (SEM),Fourier transform infrared spectroscopy (FTIR),gel permeation chromatography (GPC),and differential scanning calorimetry (DSC),respectively.The results showed that the polymer properties had little variance in the initial polymerization stage.However,two melting peaks gradually generated when the polymerization was conducted for 40 min.Moreover,the molecular weight,molecular weight distribution and short chain branch degree showed obvious changes after 40 min of polymerization time.All of those obvious changes of the polymer properties indicated that M^-1 catalyst was gradually activated by MMAO after the polymerization were conducted for 40 min.The activated M^-1 catalyst led to a decrease in the molecular weight.