Copolymerization factors that affect molecular

Table 12.1 lists the data on the copolymerization of propylene with 1-butene and 1-pentene in liquid propylene medium. It is seen that different initial concentrations of the MC catalyst significantly affect the activity of the MC-MAO catalytic system (experiments 1, 8). A decrease in the concentration of the MC-based complex during its formation, as was shown in Ref. [25], brings about an increase in the activity of the catalytic system by a factor of nearly 2 from 240 kg PP/(mol Zr h) (experiment 1) to 440 kg PP/(mol Zr h) (experiment 8). Addition of the comonomers influences the activity and molecular mass of the polymers. Thus, even at small contents of 1-butene (below 3.4 mol%) and 1-pentene (below 1.4 mol%) in the monomer mixture, the activity of the catalytic system increases appreciably. In the case of copolymerization with 1-butene, the 5deld of the copolymer increases by a factor of 2-3 relative to that for the homopolymerization of propylene for copolymerization with 1-pentene, the 5deld of the copolymer increases by a factor of 1.5. A further increase in the concentration of these comonomers decreases the rate of polymerization. The activation effect of small additives of less reactive comonomers is referred to as the comonomer effect. ... 

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