Studies On Preparation And Characterization For Polypropylene In-reactor Alloys

Polypropylene is one of the most important general-purpose resinswhose capacity increases rapidly in recent decades due to its good heatresistance, electrical insulation, chemical resistance, relatively lowspecific gravity, high transparency, acirulence, low cost, etc. However, thepoor impact behavior, especially at low temperatures, owing to itsrelatively high transition temperature (Tg), limits its practical applications.In order to improve the impact properties of isotactic polypropylene (iPP),a rubbery ethylene-propylene copolymer (EP) phase is usuallyincorporated into iPP matrix, forming heterophase impact polypropyleneblends. The so-called high impact polypropylene (hiPP) exhibits superiorrigidity-toughness balance. In particular, with the emergence of "particlereactor technology"(GRT), polypropylene reactor alloys has been greatlydeveloped. In this technology, the architecture and copolymerizationability of catalyst play an important role in determining the properties of PP reactor alloy. This thesis studied the effects of new internal electrondonor on catalyst activity, small scale pilot test conditions, and thepreparation of polypropylene reactor alloys in different sizes aggregationdevices. The effects of electron donor and carrier on the catalystperformance were investigated. The structure and properties of PP reactoralloy prepared were further studied.1. Phosphate organophosphate compounds as internal electron donorswere applied to prepared highly active Ziegler-Natta (MgCl2/TiCl4/ID)catalysts. Effects of the type and amount of electron donors and thepresence of phthalalates (DIBP) on the catalyst activity and isotacticindex of the obtained polymer were investigated. The results indicatedthat both the catalytic activity and isotactic index of PP obtained met theindustrial requirements.2. Spherical MgCl2supported TiCl4catalysts containingorganophosphate/DIBP hybrid electron donor systems were synthesized.Using this catalyst system, a series of PP/EPR alloys having differentethylene contents with low melt flow rates were successfully prepared inbulk-gas phase lab-scale reactor. The alloys were fractionalized byTemperature Rising Elution Fractionation (TREF) and SolventFractionation (SF). The composition and content of the fractions werecharacterized by Nuclear Magnetic Resonance (NMR), DifferentialScanning Calorimetry (DSC), and Fourier Transform Infra Red Spectroscopy (FTIR), and the effects of composition and content on thealloy performance were investigated. The morphologies of the catalystsand resultant alloys were analyzed by transmission electron microscope(TEM) and scanning electron microscope (SEM). The tougheningmechanism was proposed according to the morphology of cyrofracturedsurface of impact samples.3. Through the optimization of catalyst preparation method, sphericalMgCl2supported MgCl2/TiCl4catalysts with Tricresyl phosphate（TMPP）and DIBP electron donor hybrid systems were used for the synthesis ofPP alloys containing different hexane-soluble contents with high MFR inbulk-gas polymerization process. Morphologies and microphasestructures of PP alloys prepared from the spherical catalysts werecompared with those prepared from their spheroidal counterparts, theformer have better capacity of rubber phase and flowability as well ashigher MFR conducive to melt processibility for injection molding.Effects of polymerization conditions on the properties of the productsincluding melt flow rates and hexanle-soluble contents were investigatedin detail. The resultant PP alloys are proved to have higher upgradedimpact strength and hexane-soluable content compared to thecommercialized products such as SP179and AW191alloys.4. The catalyst was synthesized in a pilot plant scale reactor andapplied to produce three kinds of PP alloys in a slurry loop and gas phase fluidized bed reactor in Lanzhou petrochemical Co. whose capacity iskiloton per year. The resultant PP alloys have superior mechanicalstrength and processibility to the commercialized products. Theperformance of the products meets the requirements of the production ofautomobile dashboards and bumpers. The PP in-reactor alloys werefractionalized by solvent fractionation method, and the composition andmorphology of the fractions were characterized by NMR, DSC, TEM,and polarizing optical microscope. The effect of the fraction on impactstrength of PP in-reactor alloy was investigated, and the result indicatesthat synergistic effect of all fractions is the key factor in improvingimpact strength of PP in-reactor alloy.5.The spherical MgCl2supported TiCl4catalyst (TiCl4/MgCl2/DIBP)was applied to bulk polymerization of propylene and1-butene. Theinfluence of comonomer feed ratio on catalyst activity andstereoregularity of the copolymers were studied. The composition andproperties of copolymers were investigated by13C-NMR, DSC, IR andGPC. The results showed that the catalytic activity increased firstly andthen decreased with the increasing1-butene/propylene feed ratio. Theincrease of1-butene content in the copolymers led to decrease in themelting point and narrower the molecular weight distribution of thecopolymers. As the1-butene content in the copolymers increased, themelting point of the copolymers decreased and the molecular weight distribution became narrow. Meanwhile, the mechanical properties of thecopolymers were improved significantly.