Propylene polymerization rate

They have shown it to fit propylene polymerization rate data well, when using a MgCl supported TiCl /triethylaluminum (TEA)... 

Fia. 9. Propylene polymerization rate at constant pressure and temperature as function of polymerization time (pciHi = 1,460 mm. Hg, f = 70°). 

In Fig. 9 the characteristic behavior of propylene polymerization rate is plotted vs. polymerization time. The data were obtained by operating at constant pressure with a catalytic system containing a-TiCU crystalshaving initial sizes between 1 and 10 p (a-TiCls sample A). 

PiQ. 10. Propylene polymerization rate at constant pressure and temperature (pciHf = 1,4S0 mm. Hg, t — 70°C) obtained with two samples of unground a-TiCli whose crystals have different sizes (seeFigs. 7 andS). (a-TiCl 1.64 g./l., [AI(CjHb),] 2.94 X 10- mol./l.). 

Fio. 11. Effect of previous physical treatments on a sample of a-TiCl on the propylene polymerization rate, at constant pressure and temperature (t = 70° PciHi = 1,450 mm. Hg). 1 and 2 ground aTiCl (sample A) (sizes <2 it). 3 and 4 unground aTiCU (sample A) (sizes within 1 to 10 it). 

PiQ. 12. Dependency of the Izn index of the adjustment period, on the reciprocal of the propylene polymerization rate in steady. state conditions. Tests performed with unground a-TiCla (sample A). 

Fig. 13. Effect of the variations of the steady-state conditions on the propylene polymerization rate.

Fig. 16. Dependency of propylene polymerization rate in steady-state conditions on the amount of a-TiCls (sample A) in the catalytic system.

Fig. 20. Log of propylene polymerization rate in steady-state conditions as function of l/T (pciH< 1,500 mm. Hg, a-TiCla sample A).

Fig. 42. Variation of the propylene polymerization rate measured at the first minute, with the partial pressure of hydrogen, in the presence of theTiCl /MgClj/AlICjHjIj catalyst 120>. By permission of Hiithig Wepf Verlag.

Fig. 8. Dependence of the relative propylene polymerization rate, Rp/Rp, on the amount of poison consumed, nP, based on published data...

PP (mol-Ti-which is about one-fifth of the activity of 1/MAO. Radiolabeling determination found that about one-fourth of the Ti in the supported catalyst is active. Therefore, the difference in the activities of the heterogeneous and homogeneous catalysts may be attributed to lower utilization of Ti in the former, and that the two catalysts have comparable intrinsic propylene polymerization rates for their active species. 

Eastman Chemical has utilized a unique, high temperature solution process for propylene polymerization. Polymerization temperatures are maintained above 150°C to prevent precipitation of the isotactic polypropylene product in the hydrocarbon solvent. At these temperatures, the high rate of polymerization decreases rapidly, requiring low residence times (127). Stereoregularity is also adversely affected by high temperatures. Consequentiy, the... 

It was found 158,159) that the fall of the rate observed when aluminum-organic compound was added to TiCl2 during ethylene polymerization was due to the decrease in the number of propagation centers. The propagation rate constant remained unchanged. In propylene polymerization the number of atactic propagation centers sharply diminished when the aluminum-... 

The use, in the propylene polymerization, of unground a-TiCU that had been previously maintained, for many hours, in the presence of solutions of A1(C2Hs)3 at temperatures lower than 80°, does not substantially modify the observed reaction rate and its variation during the adjustment period (31). 

Propylene Partial Pressure. The polymerization rate, under steady-state conditions (Figs. 17 and 18) is proportional to the partial pressure of propylene (30, 33). 

If we consider the results reported so far, the polymerization rate of propylene under steady-state conditions, catalyzed by the catalytic system Al(CjHj)3-a-TiCl3-n-heptane, shows the following relation ... 

It must be remembered that several compounds or soluble complexes of titanium which, alone, and also in the presence of AIU3, do not polymerize the propylene, can effect the polymerization rate of the catalytic systems containing a-TiCla and the molecular weight of the polymers obtained (10, 11). 

Temperature effects on the polymerization activity and MWD of polypropylene have been examined in the range of —78 °C to 3 °C 82 The MWD of polypropylene obtained at temperatures below —65 °C was close to a Poisson distribution, while the MWD at higher temperatures above—48 °C became broader (Slw/IWIii = 1.5-2.3). At higher temperatures the polymerization rate gradually decreased during the polymerization, indicating the existence of a termination reaction with deactivation of active centers. It has been concluded that a living polymerization of propylene takes place only at temperatures below —65 °C. 

The alkylaluminum component combined with V(acac)3 has an influence on the kinetic behavior of the propylene polymerization at —78 °C47 82 83). In the polymerization with V(acac)3 and dialkylaluminum monohalide like Al(i-C4H9)2C1, Al(n-C3H7)2C1, A1(C2HS)2C1 or Al(C2H5)2Br, M of polypropylene increased proportionally to the polymerization time, and the polydispersity (M Mj was as narrow as 1.15 0.05 (see Fig. 9). This is the case of living polymerization. As can be seen from Fig. 9, the rate of increase of Mn, i.e. the rate of propagation of living chains as expressed by lvln/(42 t), is influenced by the kind of aluminum component and decreases in the series... 

Figure 12-A shows the relationship between the polymerization rate and the concentration of propylene monomer at — 78 C. The polymerization rate was not simple first order with regard to monomer concentration, but approached a constant value with increasing monomer concentration. Figure 12-B shows the relationship between the number of polymer chains [N] and the concentration of propylene monomer. The value of [N] did not vary with the monomer concentration, confirming that propylene monomer affects the propagation rate. The polymerization rate Rp could be expressed by...

Fig. 12. Dependence of polymerization rate, Rp, and number of polymer chains produced per vanadium atom, [N], on propylene-concentration in the polymerization of propylene with soluble V(acac)3/ A1(C,HS)2C1 catalyst at —78 °C. [V(acac)3] = 0.005, [A1(C2H5)2C1] = 0.05 mol/dm3, toluene (from Ref.ily)...

The reaction of living polypropylene with H2 has been examined by Doi, Ueki and Keii102). Figure 18 shows the results of the polymerization of propylene with the V(acac)3/A1(C2H5)2C1 catalyst at —78 °C in the absence or presence of H2. The yield of polymer as a function of time, i.e. the polymerization rate, was scarcely affected by the presence of H2. Conversely, in the presence of H2, Mn increased toward... 

Fig. 14. Variation of the polymerization rate of propylene with the time (at 50°C) in n-heptane for two different catalyst systems catalyst 1 g/100 ml of n-heptane in each case. From Soga cl al. (98).

After an induction period, the polymerization rate reaches a maximum and then becomes almost constant for over 20 hours. The constant rate of polymerization of the homogeneous system indicates that living polymers are present in this case. Indeed, block copolymers of propylene and ethylene could be obtained with this homogeneous system when ethylene was dissolved in liquid propylene [see also, related experiments with the heterogeneous system (3/)]. 

Figure 11. Multigrain model predictions for propylene polymerization in a semihatch reactor Q = M /Mn, rate = gm polymer/gm cat.-hr, yield = gm polymer/gm-catalyst.

Depressed rates have been observed in Ziegler-Natta systems with monomers other than 4-methylpentene-l. Bier (7) suggested that the slowly decreasing rates of propylene polymerization under polymer precipitating conditions with the catalyst system a-TiCb-Al HsbCl are caused by diffusion control. In another case Burnett and Tait (3) found depressed rates of styrene polymerization under polymer-precipitating conditions with the catalyst system a-TiCb-Al HsU. At styrene concentrations less than 3.5M in heptane (isotactic polystyrene precipitates in this region of monomer concentration) a plot of polymerization rate vs. styrene concentration falls below the extrapolated linear plot by a factor of 2. 

The polymerization rate of propylene and the amorphous polymer content of the polymer produced were used as criteria for the effectiveness of a catalyst combination. In this connection it seemed worthwhile to try to produce a polypropylene of either very low or very high amorphous content, the former being of interest as a plastic and the latter possibly as a material with elastic properties. The molecular weight of the polymer was an additional factor to be considered. 

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