The Preparation, Modification Of Supported Titanium Catalyst And The Study On Diolefin Polymerization

The preparation methods of supported titanium catalyst were firstly studied, thetesting methods of water content of catalyst carrier, content of titanium in catalyst.catalytic efficiency and density of catalyst were brought forward. The trans unitcontent of TPI. crystallinity, molecular weight and distribution, physical performanceand ash content were studied, the examination methods of the product were broughtout accordingly in order to control the quality of TPI production and compare withforeign products.In the progress of catalyst preparation, the catalytic efficiency was easily to bedecreased in the presence of crystal water which always appeared because of thestrong absorbent power of MgCl₂. So the crystal water caused by air slaking of MgCl₂should be avoided in the progress of catalyst preparation. The methods of heattreatment at high temperature and adding isobutyl aluminum for MgCl₂ to wipe offcrystal water were tried, but the results showed that the methods used above weredisadvantaged for increasing catalytic efficiency. The vibration mill had largercatalytic efficiency compared with rolling mill and the best time for the preparationwas more than 15 hours.The TPI (poly trans 1, 4-isoprene) synthesized with the catalyst above wascompared with the foreign products, the results showed that the content of trans unit.crystallinity were higher of self-made TPI. but the molecular weight was lower.Moreover. the tensile strength, modulus at definite elongation, hardness, density ofselfmade TPI were better than the foreign products while the breaking elongation was lower. The catalytic system was similar of the two products through ash analysis, butthe foreign product had more ash and lower catalytic efficiency so that influenced theaging of the rubber.IR spectrum was used to analysis the structure of poly butadiene synthesizedwith supported TiCl_x(OC₈H₁₇)_4-x(x=1-3) in order to improve the performance of theproduct made by supported titanium catalyst, the results showed that the content oftrans unit was more than 90%. expect for the trans unit. mostly of the structure was1.2-unit. The content of chloride in the TiCl_x(OC₈H₁₇)_4-x before supporting onlyeffected the catalytic efficiency and had no effect on the polymer structure. Themelting point and crystallinity were studied by DSC. the results showed that therewere two crystal peaks of the polymer, the high temperature peak and low temperaturepeak were 147.7℃and 66.2℃respectively and the crystallinity were 78.3ï¼…and 34ï¼…respectively. The catatytic efficiency increased with the chloride content in theTiCl_x(OC₈H₁₇)_4-x increasing and decreased after increasing with the increasing ofAl/Ti. the suitable Al/Ti was 80. The catalytic efficiency increased when Ti/Bdincreased or temperature increased, but decreased when the temperature was higherthan 40℃. The molecular weight decreased after increasing with the inceasing ofAl/Ti and reach the highest level when the Al/Ti was 80. The molecular weightdecreased with the increasing of catalyst mass and went down after increasing withincreasing the temperature; the highest value was at the temperature of 40℃.IR spectrum was used to analysis the structure of poly isoprene synthesized withsupported TiCl_x(OC₄H₉)_4-x(x=0-3). the results showed that the content of trans unitdecreased with the content of chloride in the catalyst decreasing while the cis-unitincreased. The ¹H-NMR was used to character the sample of poly-isoprenesynthesized with the catalyst of x equals one. The analysis gave the results that themass content of 3, 4-unit was 4.7ï¼…, cis 1, 4-unit was 46.2% and trans1, 4-unit was49.1%. The catalytic efficiency increased with the increasing of chloride in thecatalyst and decreased after increasing with the increasing of Al/Ti. The catalyticefficiency increased with the increasing of Ti/Ip and temperature, but decreased whenthe temperature was too high. the benefit temperature range was 30℃to 40℃. Themolecular weight decreased after increasing with the increasing of Al/Ti andtemperature while decreased with the increasing of catalyst.The mechanism in the progress of modification was studied because of theresults of the two methods that including modification after supporting (done byprevious work) and supporting after modification (said above) in polymer unit were different distinctly. The results showed that titanate generated in the progress ofmodification that adding alcohol after supporting and the content of titanate did notincrease with the increasing of modification agent (alcohol). The polymer synthesizedwith alcohol modified catalyst (modification after supporting) was the mixture. Thesoluble part in the poly butadiene synthesized with the catalyst of modification aftersupporting was mainly 1.2-unit and cis 1.4-unit. the content of trans 1,4-unit in thesoluble part was distinctly lower than that in the insoluble part while the content of 1,2-unit was low in the insoluble part. So the mechanism of catalyst could be describedas follows: supported TiCl₄ reacted with alcohol and gave the active center of titanatethat cooperated with the active center of supported titanium, the two active centerinitiated monomer together and gave the mixture of polymer that contained differentunits: in the case of supporting after modification, the synthesized polymer wasmainly trans 1.4-unit because the orientation of catalytic active center generated bythe interaction of MgCl₂ and TiCl_x(OR)_4-x.