Study On Catalytic Copolymerization Of Ethylene And 1-octene

Copolymerization of ethylene and 1-octene to form the polyolefin elastomers and plastics is of significant importance in current time.In this thesis,studies focused on the use of the metallocene catalysts and investigations on the catalytic ethylene and 1-octene copolymerization have been carried out.Three parts of experimental work are studied as follows.1.Study on the ethylene/1-octene copolymerization catalyzed by the metallocene hafnium catalyst system Ml/[Ph3C][B(C6F5)4]/TIBA.With the use of the metallocene hafnium system Ml/[Ph3C][B(C6F5)4]/TIBA,copolymerization of ethylene and 1-octene was studied by means of the high-temperature solution polymerization method.In the polymerization reactions,effects including polymerization temperature,ethylene pressure,1-octene concentration and catalyst amount were studed along with the molecular weight,molecular weight distribution,comonomer insertion amount as well as the melting temperature,crystallizing temperature,maximum degree of the crystallinity parameters of the copolymers.The sequencial microstructure of the copolymers was also illustrated on the basis of the thermomechanic data measured.The best reaction conditions for the M1/[Ph3C]B(C6F5)4/TIBA system were investigated to be such as the catalyst amount of 8.25μmol for Ml,temperature of 110℃,ethylene pressure of 20 bar,concentration of 1-octene of 0.8 M,the Al/Hf molar ratio of 300,the B/Hf molar ratio of 1.46,the toluene volume of 150 mL and the reaction time of 0.33 h.Under these conditions,the best catalytic activity has been achieved to be 9.73 ×106 g/mol·h,comparable to that for the commercial CGC catalyst.The copolymers obtained were measured by GPC,giving Mw of 109776,Mn of 44982 and PDI of 2.44 as well as the Tm of 116.5℃ and 123.76℃ with Xc of 2.77%and 1-octene insertion amount of ca.2.5 mol%by the DSC measurement.The Ml/[Ph3C][B(C6F5)4]/TIBA system exhibits a coordinatively catalytic property by the single-site active center of the metallocene catalysts,which is usefull for preparing the polyolefin plastics.2.Study on the ethylene/1-octene copolymerization catalyzed by the metallocene titanium catalyst system M2/[Ph3C][B(C6F5)4]/TIBA.With the use of the metallocene hafnium system M2/[Ph3C][B(C6F5)4]/TIBA,copolymerization of ethylene/1-octene was studied by means of the high-temperature solution polymerization method.In the polymerization reactions,effects including polymerization temperature,Al/Ti molar ratio,reaction time,solvent,catalyst addition way,and boron cocatalyst were studed along with the molecular weight,molecular weight distribution,comonomer insertion amount as well as the melting temperature,crystallizing temperature,maximum degree of the crystallinity parameters of the copolymers.The sequencial microstructure of the copolymers was also illustrated on the basis of the thermomechanic data measured.The best reaction conditions on the M2/[Ph3C][B(C6F5)4]/TIBA system were investigated to be such as the catalyst amount of 5 μmol for M2,temperature of 110℃,ethylene pressure of 14 bar,concentration of 1-octene of 0.8 M,the Al/Ti molar ratio of 100,the B/Ti molar ratio of 1.46,the toluene volume of 150 mL and the reaction time of 0.33 h.Under these conditions,the best catalytic activity has been achieved to be 1.35×107 g/mol·h,almost equal to that for the commercial CGC catalyst.The copolymers obtained were measured by GPC,giving Mw of 100499,Mn of 29747 and PDI of 3.38 as well as the Tm of 76.95℃ and Tc of 58.81℃ with Xc of 2.27%and 1-octene insertion amount of ca.11.5 mol%measured by the DSC.The catalytic reaction by the use of the isopar E solvent under similar conditions was also carried out,in which the activity compared a little poorer than that by the use of the toluene solvent.Finally,two types of the copolymers P18 and P19 were measured by the high-temperature 13C NMR spectroscopy.The comparison of this data together with those of the GPC and DSC data was performed with those of the commercially available 875L,8605,and 875 copolymers from the SK Company.3.Study on synthesis of the new CGC catalyst compounds and the use for the ethylene/1-octene copolymerization reactionTwo CGC-types of the catalyst compounds[Me2Si(Ind)(NtBu)]TiCl2(M3)and[Me2Si(2-Me-4-tBuC6H4Ind)(NtBu)]TiMe2(M4)were synthesized and characterized by the NMR spectroscopy,of which compound[Me2Si(2-Me-4-tBuC6H4Ind)(NtBu)]TiMeI,similar to M4,was further confirmed by the X-ray crystallography,featuring the constrained geometric structure.The systems by M3/[Ph3C][B(C6F5)4]/TIBA and M4/[Ph3C][B(C6F5)4]/TIBA both are catalytically active for the ethylene/1-octene copolymerization.Under the conditions by the catalyst amount of 5μmol for M3(or M4),temperature of 110℃,ethylene pressure of 14 bar,concentration of 1-octene of 0.8 M,the Al/Ti molar ratio of 100,the B/Ti molar ratio of 1.46,the toluene volume of 150 mL and the reaction time of 0.33 h,the catalytic activity reached up to 2.85×106 g/mol-h for M3 and to 4.67×106 g/mol·h for M4.The copolymers obtained in the former reaction had the Mw of 145575,Mn of 48286 and PDI of 3.01 while those in the latter reaction held the Mw of 257640,Mn of 130380 and PDI of 1.97.Both these polymers have a high amount of 1-octene copolymerized.