polymerization of propene with organomagnesium–reduced titanium (iv) chloride-based catalyst

Polymerization of Propene With Organomagnesium- Reduced Titanium (IV) Chloride-Based Catalyst

KEVIN GARDNER, IAN W. PARSONS, and ROBERT N. HAWARD, Department of Chemistry, University of Birmingham, Birmingham B15

2TT, England

Synopsis

A kinetic study of the polymerization of propene by use of magnesium-reduced titanium (IV) chloride-based catalyst systems has been carried out and the tacticities and molecular weights of the polymers formed have been investigated. The rate constant for the formation of btactic polymer is estimated to be 69 f 18 dm3/mole sec and that for the atactic polymer to be 12 f 5 cm3/mole sec. The number of active sites producing atactic polymer has been determined as 3 f 1% of the Ti atoms present, whereas sites producing isotactic material amount to 0.36 f 0.13% of the Ti atoms. The overall tacticity of the polymers corresponds to approximately 40% isotactic material. This figure is barely affected by heat treatment of the catalyst.

INTRODUCTION

Recently,l we have published the results of an investigation of the reactivity of certain catalyst systems, based on the reduction of titanium (IV) chloride with alkyl magnesium compounds, in the Ziegler-Natta-type polymerization of ethylene. Thii type of catalyst was originally developed elsewhere: and is described in the patent literature: but most of the earlier studies were of reactions in the presence of hydrogen (as molecular weight modifier). Another group of workers have reported their findings on supported catalysts of this type.4 All groups agree that this class of catalyst is very active towards ethylene, and it now seems that this high activity is due to a high concentration of active sites1 rather than to any abnormally high activity in each site. Importantly, this high activity is sustained over very high polymer yields.

The very high (-50%) proportion of transition metal atoms active in ethylene polymerization has been explained without difficulty as a consequence of the known very low crystallinity of the catalyst material; a particle size of 50 nm has been quoted: and it seems quite possible from the method of preparation of this catalyst and from x-ray studies that there is no real crystallinity-in the sense of extensive ordered Tic13 phases-in the precipitated catalyst at all. This is supported by analysis which has shown that a typical catalyst precipitate has a Mg/Ti ratio of about 1.5,2 so that without extensive phase separation of MgC12 (and in our case MgClBr) from the TiC13, very little ordering of the lattice in the Tic13 form can be envisaged. Thus, only very small aggregates of titanium halide are to be expected. These will have a large surface/volume ratio and thus many more titanium atoms per mole will be available to take part in active site formation than is usual in other systems with TiC13, where the guest ion is A13+ and the lattice is little di~rupted.~

The above arguments depend on the assumption that the active site contains

Journal of Polymer Science: Polymer Chemistry Edition, Vol. 16,1683-1696 (1978) 0 1978 John Wiley & Sons, Inc. 0360-6376/78/0016-1683$01.~

1684 GARDNER, PARSONS, AND HAWARD

at least one titanium atom but do not seek to distinguish between monometallic and bimetallic active sites. It should be said here that the brown color of the catalyst suggests that, insofar as it is a form of TiC13, it is of the /3 type.

In light of the above, it was of interest to study the activity of these catalysts towards other monomers, and we now report the results of a study of propene polymerizations with such magnesium-reduced catalysts. Interest here centers around three main points: first, are these types of catalyst significantly more reactive towards propene than conventional Tic13 combinations? Second, what proportion of the transition metal atoms are involved in active sites? Third, how stereospecific a catalyst is this? A question arising from the third point is the percentage, if any, of the active sites producing isotactic polymer.

Initially, attention was directed towards the selection of a reactive cocatalyst for the magnesium-reduced catalyst and of near-optimum conditions for the polymerization, since only then might a fair comparison be made with the ethylene work. There might, of course, be several sets of optimum conditions, de- pending on whether one was interested in overall polymer yield or catalyst, in maximizing tacticity, or in other points. We find, however, that tacticity is barely affected by changes in conditions in the region where a good yield of polymer on catalyst is obtained.

EXPERIMENTAL

Catalyst Preparation

Catalysts used in this work were made, as previously described,l by addition of a solution of Tic14 to a stirred solution of rz-octylmagnesium bromide. The solvent in each case was pure isooctane (2,2,4-trimethylpentane). These re- ductions were performed under purified nitrogen at the ambient temperature, and the catalyst slurries were aged for at least 48 hr before use. The ratio of alkyl groupsDiC14 used in this reduction step was varied slightly, between 1.5 and 2.0; this variation made little, if any, difference to the activity of the catalysts. The total [Ti] of the catalysts was estimated photometrically by using the method described by Belcher and Nutten.'j

Heat Treatment of the Catalyst

A 200-cm3 portion of a standard magnesium-reduced catalyst slurry, prepared as above, was evaporated to dryness using a vacuum line (0.1 mm Hg pressure), and the pressure adjusted to atmospheric with pure Nz. Freshly distilled decalin (200 cm3) was then added under Nz flow, and the flask equipped with stirrer, thermometer, condenser, and white oil bubbler before being heated to 155 f 2OC for 2 hr, after which it was allowed to cool overnight under Nz. This slurry was assayed and used for polymerizations in the same way as the isooctane slurries described above.

Polymerization Procedure

All polymerizations were carried out in purified isooctane, in either 500- or 1000-cm3 vessels. The apparatus and techniques used have been described

POLYMERIZATION OF PROPENE 1685

beforel: the purification train used for propylene was similar to that previously used for ethylene and the catalyst components were added to the reaction vessel by syringe via a self-sealing rubber cap. Polymerizations were followed via readings of a wet gas meter in the exit gas stream, and the polymer was isolated by stripping of the solvent from the reaction mixture, followed by filtration to give the polymer. The polymer was then dried in a vacuum oven at 5OoC to constant weight.

Polymer Characterization

Viscometry was performed in Ubbelohde suspended level instruments at 135OC with 0.5% or 0.1% decalin solutions. The average of two concordant readings was taken in each case. Molecular weights were calculated as follows: firstly the one-point method of Elliot7 was employed to convert q to [q]; secondly Mu and Mn were estimated8sg from

[q] = 1.4 X Mu 0.76

and

[q] = 0.917 X Mn 0.80

Heptane Extraction

Samples were placed in a stirred vessel and extracted with heptane overnight at the ambient temperature. The insoluble and soluble fractions were obtained by filtration and steam stripping, respectively, before drying to constant weight.

Infrared Spectroscopy

Polymer films were cast from 2% xylene solutions directly onto NaCl disks, and the disk and film dried in an oven at 95°C. Tacticities were estimated by the method of Kissin.lO

13C-NMR 1

NMR spectra were run on a JEOL JNM FX60 spectrometer at 15.03 MHz by FT spectroscopy. Samples were run as solutions in 1,2,4-trichlorobenzene at 130°C, CD3SOCD3 being used as internal lock.

A comparison between the tacticity figures given by the different methods is shown in Table I. While the actual numbers vary widely, the methods generally give the same rank order for different polymers.

Early experiments established that, for the aluminum alkyls examined as cocatalysts and the range of temperatures explored (2O-7O0C), tri-n-octylaluminum and triisobutyl aluminum, both at 4OoC, were easily the best cocatalysts. Triethyl aluminum gave poor yields and diethylaluminum chloride produced very little polymer. Of the two successful cocatalysts, the tri-n-octyl compound was marginally the better, and so further work concentrated on the combination of this with the magnesium-reduced Tic13 used at 4OOC: occasionally some reference will be made to the other catalysts as appropriate.


TABLE I Comparison of Tacticity Measurements

X-ray Insoluble

Sample crystallinity 13C-NMRb in cold after 1 hr/ mm rr mi heptane

code 120°C(%) (%) (%) (%) T m (96) (34)

Shell 36/75 42.W 8EiC 6c 9c 87 f Id - Shell X38 44.9c 93c 2c 5c 88f Id 97d POCG 6/1/16 whole polymer - - - - 6 9 f 3 d 43d

44d POCG 6/1/16 heptane-soluble fraction - -338 -33d -338 - - POCG 6/1/16 heptane-insoluble fraction - 94 3a 38 - - POCG 9/1/2 whole polymer - 5od 2ad 22d 73 f 2 d 45d POCG 9/1/2 heptane-soluble fraction - 39d 2ad 33d 51 f 5 d - POCG 9/1/2 heptane-insoluble fraction - 82d gd gd 81 f 2d -

a Data from Imperial Chemical Industries Ltd. b A referee has pointed out that certain line assignments in the 13C-NMR of polyprbpylene have

been revised.26 However, this seems to make little difference to our own results, and the cited work had not been published when our outside comparisons were made. Accordingly, we have chosen to keep to the earlier system for the calculation of tacticity for the sake of internal consistency of the table.

Data from Shell Co. Ltd. Data from present work.

Two main points now remained to be established: the effect of the aluminum concentration on polymerization yield (qnd rate), and the importance of mass transfer in the experimental system. In order to investigate the first point a series of reactions were performed a t varying [All, and the results are set forth in Figure 1, from which it is clear that a t this value of [Ti] the yield of polymer increases with [All up to a critical level after which the yield remains constant with increasing [Al].lla

The importance of mass transfer was investigated by using the technique previously described,lJ2J3 whereby a series of polymerizations was carried out at different [Ti], and the results plotted as (rate)-l or (yield)-l versus [Ti]-’ (Fig. 2). From this plot a value for the maximum rate of transfer of propene into solution was obtained, as was a value for the “kinetic rate” of the polymerization reaction, i.e., allowing for mass-transfer effects.

In our system, the results can be plotted in two ways, since the polymerization rate-versus time curves decline (see Fig. 3). If the rate is taken as yieldhime over a 3-hr polymerization experiment (our standard experiment), then the plot gives a propene dissolution rate of 33 g/hr and a kinetic rate of 11 (g propene/hr)/ (millimole Ti/dm3) at 40°C, whereas if the rate maxima are taken for the plot, the results are 43 g/hr and 15 (g propene/hr)/(millimole Ti/dm3), respectively. We feel that the lower figures for the rate of dissolution are probably safer to work with, and we have conducted our further experiments under conditions where the average gross polymerization rate is < 20 g/hr.

In order to convert the observed rate into a rate constant, we require the concentration of propene in the solution. A value for the saturated concentration of propene in isooctane has been estimated from the data of Konobeev and Lyapin.14 This value is 13 mole/dm3, and, if it is assumed that the solution is saturated at all times with propene and that this value may be equated with [h&] in the earlier treatment,12J3 then the overall rate constant may be calculated


Rate. dm’/b

15.1

10.1

5

5 10 15 20 2 5 3 0 35 40 [, mmoleldm’

Fig. 1. Plots of (0) maximum rate and (a) stationary rate vs. Al(n-Oct)3 concentration; [Ti] = 3.45 x 10-3 mmoleh.

as 2.0 X lo3 (mole/Ti)/hr on the basis of the 3-hr polymerization data or 2.6 X lo3 (mole/Ti)/hr on the basis of the rate maxima. These will, of course, both be underestimates.

The measured gross activity of this catalyst combination towards propene, = 3 X lo3 g polymedg Tic13 over 3 hr, puts it in the mainstream of the usual activities, albeit towards the more active side. Some comparable figures for aluminum-reduced Ti (1V)-based catalysts are given in Boor’s review,15 where figures of 2-1000 g/g Tic13 are given. Duck et al.4 quote 2 X lo3 g/g Ti/hr/atm as the activity of their supported catalysts; our present combination gives 4.5 X lo2 in the Same units, but we have taken a 3-hr polymerization period, whereas it seems probable that Duck et al. took a 1-hr polymerization and would thus obtain a higher figure for the activity of the catalyst.

The next important parameter studied was the stereoregulating power of the catalyst. Three methods have been employed to study the tacticity of the polymers produced, viz., infrared spectroscopy, heptane extraction, and I3C- NMR. The findings from all the techniques agree: the polymer is neither wholly isotactic nor entirely atactic. The infrared measurements by the method pro- posed by Kissin,lo which depends upon a statistical model of the polymerization coupled with the infrared measurements, suggested that the overall macrotac- ticity T, of the polymer was --60-70% (isotactic); whereas separation in heptane suggested that the material contained about this proportion of material soluble in cold heptane; 13C-NMR16J7 showed that this insoluble portion was almost wholly isotactic whereas the soluble portion was partly random and partly blocky.


0 0.5 1.0 1.5 2.0 2.5 3a 35 [Tit-’, dm’/mmole

Fig. 2. Plot of reciprocal of yield vs. reciprocal of [Ti].

0 50 100 150

Fig. 3. Typical rate vs. time curve. Time. mm

The molecular weights of these fractions were also very different, with the isotactic fraction being much the higher polymer. The relative proportions of isotactic and amorphous material seem to be almost constant with this form of TiC13, but small differences in tacticity were noted; in particular, the reaction using triethyl aluminum as cocatalyst gave an appreciably higher tacticity in the polymer (75% by infrared; 55% by extraction) a t 40°C. Duck et al., using a supported version of this catalyst, report 35% isotactic material in their work.


The occurrence of two different types of polymeric material leads to a model of the catalyst in which there are two rather different types of active site. On the one hand, there seem to be sites which are almost wholly incapable of stereoregulation, and on the other hand there are sites which yield highly isotactic polymer. We shall return to this point later.

One possible method of improving the stereoregulating power of the catalyst is to convert it to one of the sheet-type (a, y) allotropes.18 One standard method for such a conversion is heat treatment. Accordingly, we have attempted to convert our standard magnesium-reduced catalyst material, which we regard for this purpose as a greatly modified p form, to the a form by heating above 15OoC, following Keii et a1.l1'J The results of these experiments were incon- clusive; the catalyst's color did change, but the final product could not be described as either blue or purple in color. Polymerizations conducted using this catalyst were on the whole slightly less rapid than with untreated catalysts, and the overall tacticity changes (Table 11) were either too small to be significant, or, for triethyl aluminum cocatalyzed reactions, slightly adverse. We therefore conclude that this method of improving tacticity is unable to produce marked improvements in the properties of the present catalysts.

The effect of temperature on the overall tacticity of the raw polymer has been studied using tri-n-octyl aluminum as the cocatalyst. In this case, the effect of temperature is small over the temperature range investigated (2O-7O0C), as shown in Figure 4(a), but there does seem to be a slight maximum between 50 and 6OOC. The effect is still smaller in the case of triethyl aluminium cocatalysts,

.

TABLE I1 Effect of Heat Treatment of the Catalyst

Untreated catalyst Heat-treated catalyst

Yield Tacticity Yield Tacticity Activator (g/g TiCM (%) (g/g Ti&) (%)

Al(n-Oct)s 283.2 42.9 94.8 50.9 AlEt3 35.6 55.4 48.0 50.3 AlEtzCl 14.6 37.2 10.4 48.3

Tachcity

T m . 5 8 0

70

60

50

LO

3 0 0 20 LO 60 80 0 20 LO 60 80 T,"C

Fig. 4. Effect of temperature on tacticity T,,, with (a) Al(Et3) activator and (b) Al(n-O~t)~ activator: (a) m = 12; (0) m = 11; (@) rn = 10.


but here the trend [Fig. 4(b)] seems to still be upwards as the temperature falls to its lowest value. Nevertheless, it is clear that temperature has only a marginal effect on tacticity under these conditions.

A significant quantity estimated in this work is the total number of active sites. We have estimated this using the method previously employed for the ethylene reaction,l viz., a study of the variation of molecular weight with time. Clearly, knowing the yield of polymer Yt, and the number-average molecular weight %n,t at any time t enables a calculation of the number of molecules of polymer, and extrapolation of this quality to zero time (or zero yield) gives an estimate of the number of active sites in the particular system. Trivially, this may be compared with the number of (say) titanium atoms in the reaction to give an estimate of the percentage of these which are involved in active polymer growth. The theory of this method is developed more formally elsewherel; it naturally bears a very close resemblance to the more usual methods19 based on a radioactive method of estimation of gn a t zero conversion, i.e., in the absence of transfer reactions.

Accordingly, several polymerizations were carried out for varying times, the polymers were isolated and weighed, and the value of an was estimated for each sample by viscometry. The results of these experiments are plotted in Figure 5, as (yie1d/Mn) versus time, where a reasonable straight line is obtained. From the intercept of this line a value of 3 f 1% is estimated for the proportion of titanium atoms active in polymerization. This figure is rather large for a propene polymerization, but it should be remembered that the present catalyst is of the f i type, not the more usual a or y types, for which figures of, e.g., 14.5% have been quoted. Also, this figure refers to whole polymer, rather than just the isotactic (crystalline) portion.

We have also subjected each whole polymer from the above experiments to heptane extraction and have plotted a similar straight line for the isotactic (insoluble) polymer (Fig. 6). A good straight line is again evident, from which it is possible to calculate that about 0.3 f 0.1% of the titanium atoms are functioning as active sites for the generation of isotactic polymer. This figure is much more in line with literature data20 on a- and y-TiCl3-based catalysts.

0 10 2 0 30 LO 50

Fig. 5. Plot of YJM,,,, vs. Yt for whole polymer.


The errors in these determinations are considerable, since Mn has perforce been estimated via [q] and since the actual numbers obtained are directly de- pendent on Mn. Nevertheless, it seems clear from the data that the following quantitative conclusions must be correct at the beginning of the polymerization, and very probably thereafter: (1) With this catalyst there are many more active sites producing atactic than isotactic polymer (we estimate a tenfold ratio). (2) Since the amounts of isotactic and atactic material in the whole polymer are comparable, the isotactic-producing sites must polymerize propylene faster than the atactic sites do. Our quantitative results are collected in Table 111.

We have. attempted to check these conclusions by a separate study of the atactic portion of the polymers, but as Figure 7 shows, a much worse straight line is obtained here. The reason for this is not clear, but we might speculate that more atactic sites are actually being generated throughout the polymerization up to fairly high yields, when a steady state of some sort is approached. The excellence of the fit of the other two plots to a straight line lends no credence to this, however, and it is equally likely that the low molecular weight ( [ q ] N 0.2) of this fraction has led to difficulties in our estimation of Mn. In this matter, it is particularly noteworthy that our procedure for conversion of [q] to M,, is rather suspect. Nevertheless, the qualitative conclusions clearly must stand.

TABLE I11 Kinetic Data

Isotactic material Atactic material Whole polymer

[C*], mole/dm3 (6.2 f 2.3) X 5.2a x 10-5 a (3.8 f 1.9) x 10-5 Ti atoms active 0.36 f 0.13 3.08 3.0 f 1.4

K,, dm3/mole sec 69 f 18 12.3a 28 f 12 in polymer, %

K t , sec-I (4.1 f 1.1) x 10-5 C (4.7 f 2.8) x 10-5 Mnb 2.0 x 105 5.3 x 104 1.5 x 105 F" 4.9 x 103 1.3 X lo2 3.5 x 103

a Less reliable, see text. From [v]. Not calculated; see text.


0 10 20 30 LO yt.g

Fig. 7. Plot of Y&f,,,t vs. Yt for heptane-soluble polymer.

By using our calculated values for- the concentrations of active sites in this catalyst, it is possible to make numerical estimates of the rate constants for isotactic and atactic polymerizations in the present system. We have made an estimate of the solubility of propene in isooctane based on data for other hy- drocarbon solvents, as previously mentioned. This leads to an overall rate constant for the whole polymer, one for isotactic polymerization, and one for atactic polymerization.

Total rate of polymerization Rptot = ktot [Ctot*] [CBH~] Rate of atactic polymerization R ~ A = kA[CA*] [C&ls] Rate of isotactic polymerization Rp1 = hr[C~*] [C3H8]

where we have assumed

[CA"] = [Ctot*] - [cI*] Values for these constants are collected in Table 111, along with values for the appropriate transfer rate constants. There is no figure for transfer from the atactic sites, since the relevant plot is far from a straight line.

At this point, one of the most interesting features of the present catalyst system reveals itself. This is the contrast between its behavior with ethene and propene and the corresponding behavior of more conventional systems. Thus, the present catalyst shows a very high number of active sites for ethene (-50% of the Ti atoms)l with a rather mundane rate of reaction at each site, whereas the number of active sites for propene polymerization is much the same as that for conventional catalysts, with a rather high reaction rate per site. In particular, these data may be contrasted with those of Schnecko et d.F0,21 who find a ratio of active sites of 1.3 (ethene/propene) and a ratio of rate constants per active site of 4.3 (ethene/propene). In the present work, the corresponding ratios are -19 and


0 5 10 15 2 0 2 5 30 35 L 0 [Al(n-Ocl)il, rnmole/drn’

Fig. 8. Effect of [Al(n-Oct3)] on intrinsic viscosity.

Taclicily

Tm, 70

7 50

70.0

6 5.0

6 OQ

0 5 10 15 2 0 2s 30 3s l+O I A l ( t V W ~ 1 .

mmoleldm’

Fig. 9. Effect of [Al(n-Oct)s] on tacticity T,: (0 ) m = 12; (0) m = 11; (@) rn = 10.

5.2 (data for ethene extracted from Boucher22), so that whereas in ethene polymerizations disorder of the crystal lattice leads to generation of very large numbers of moderately active sites, the effect in propene polymerizations is very much less marked, as if the requirements for an active site are not the same in the two cases. There may, of course, be other explanations of this observation. In particular, it has been suggested23 that polyethylene formation acts to destroy the inorganic lattice more than does polypropene, but we have no evidence on this matter: this differential destruction of the lattice certainly does not operate to a great degree in other cases.20p21

1694

Yield 1 L 0 y. g

120

1 0 0

80

60

60

20

0

GARDNER, PARSONS, AND HAWARD

8 Propen pESS"re.

bars (absolute)

0 2 I 6

Fig. 10. Effect of propene pressure on yield over 3 hr.

In this connection, it is interesting to note the effect of varying the concentration of tri-n-octylaluminum on the tacticity and molecular weight of the polymer. Figures 8 and 9 show these data, and it is interesting to speculate that this is consistent with a higher value of [All being required to activate the isotactic sites than to activate the atactic ones. If this were the case, it would fit in with the idea of stereoregulation of polymerization being a purely steric effect, since the aluminum alkyl dimer, a fairly large molecular species, would be appreciably less likely to get into a sterically crowded environment than into a more open one suitable for the generation of atactic polymer.

If this explanation is accepted, then it need not follow that the observed in- crease in molecular 'weight as [All increases rules out the aluminum alkyl as a transfer agent. This process might be occurring, but be swamped by the generation of a comparatively small number of (highly reactive) isotactic sites since the isotactic polymer is observed, in the cases studied, to be of higher molecular weight than the atactic material (this seems to be a general effect).24

Some comment is perhaps justified on the results reported here: it was commonly assumed that polymerization on an atactic site would be faster than polymerization on an isotactic site, since monomer access to the less sterically crowded position should be easier. Recently, several authors25 have adduced data which contradict this, as does our own. We see no difficulty here, since it is clear that rapid polymerization depends on the balance of various forces in the reaction pathway. In particular, it is quite likely that free access to a polymerization site will lead to the formation of a metal-olefin bond so strong as to be somewhat difficult to break (as it must be broken) in the next (insertion) step along the polymerization pathway. Extreme, and hence trivial, cases of this formation of "too strong" bonds are to be found in the many abortive attempts to polymerize acetylenes with transition metal complexes; in many such cases


the bond is so strong that a metal-acetylene complex is easily isolable, and no polymerization (even to a benzene or a cyclooctatetraene) is observed.

A final variable we have studied is the pressure of propene. These experiments were run in the same volume of solvent (1 dm3) as the majority of the earlier ones (including all the experiments to estimate the active site concentration) so as to keep variation to a minimum. The effect of increased pressure is to produce increased yields of polymer, at least up to 7 bar, the maximum pressure we could conveniently generate in our system. These results are set forth in Figure 10. . In conclusion, this work has shown that magnesium-reduced titanium-based

catalysts polymerize propylene by involving at least two rather different types of active site. The sites producing nonisotactic polymer are the more numerous by a factor of about 10, but polymerization upon them is slower by about a factor of 5. The stereospecific (isotactic) polymer produced is of much higher molecular weight than the nonisotactic, and this difference is mainly due to faster chain propagation upon these sites. The finding of a high percentage of Ti atoms which function as active sites for ethylene polymerization is not repeated here.

The authors acknowledge the advice and practical help they have received from Dr. A. Caunt of ICI Plastics Division Ltd, Welwyn Garden City, England; and from Dr. W. Wagner of Koninklijke/ Shell Lab., Amsterdam, Holland. One of the authors (K.G.) thanks SRC and Charles Thackray Ltd. for the award of a CASE studentship.

References

1. D. G. Boucher, I. W. Parsons, and R. N. Haward, Makromol. Chem., 175,3461 (1974). 2. R. N. Haward, A. N. Roper, and K. L. Fletcher, Polymer, 14,15 (1973). 3. Brit. Pat. 1,299,862. 4. E. W. Duck, D. Grant, A. V. Butcher, and D. G. Timms, Eur. Polym. J., 10,77 (1974). 5. E. G. M. Tornquist, J. T. Richardson, Z. W. Wilchinsky, and R. W. Loony, J. Catal., 8,189

6. R. Belcher and A. J. Nutten, Quantitative Inorganic Analysis, 2nd ed., Butterworths, London,

7. J. H. Elliot, K. H. Horowitz, and T. Hoodock, J. Appl. Polym. Sci., 14,2947 (1970). 8. J. Boor, Jr., in First Biannual American Chemical Society Symposium (J. Polym. Sci. C,

9. P. Parrini, F. Sebastiano, and G. Messina, Makromol. Chem., 38,27 (1960).

(1967).

1960, p. 328.

1) H. W. Starkweather, Jr., Ed., Interscience, New York, 1963, p. 237.

10. Y. V. Kissin, V. I. Tsvetkova, and N. M. Chirkov, Eur. Polym. J., 8,529 (1972). 11. T. Keii, Kinetics of Ziegler-Natta Polymerisations, Chapman and Hall, London, 1972, (a)

12. G. Boocock and R. N. Haward, SOC. Chem. Znd. (London) Monogr., 20,3 (1966). 13. T. Keii, Y. Doi, and H. Kobayashi, J. Polym. Sci. A-2, 11,1881 (1973). 14. B. I. Konobeev and V. V. Lyapin, Khim. Prom., 43,114 (1967). 15. J. Boor, Jr., Macromol. Rev., 2,115 (1967). 16. A. Zambelli, D. E. Dorman, A. I. R. Brewster, and F. A. Bovey, Macromolecules, 6 , 925

17. A. D. Caunt, private communication. 18. G. Natta, P. Corradini, and G. Allegra, J. Polym. Sci., 51,399 (1961). 19. P. J. T. Tait, in Coordination Polymerization, a Memorial to Karl Ziegler, J. C . W. Chien,

20. H. Schnecko, M. Reinmoller, W. Lontz, K. Weirauch, and W. Kern, Makromol. Chem., 84,

21. K. A. Jung and H. Schnecko, Makromol. Chem., 154,227 (1972). 22. D. G. Boucher, M. Sc. Thesis, University of Birmingham, Birmingham, England, 1973. 23. H. Schnecko, K. A. Jung, and W. Kern, in Coordination Polymerization, a Memorial to Karl

24. G. Natta and I. Pasquon, Adu. Catal., 11,1(1959), and references therein.

p. 35; (b) p. 44.

(1973).

Ed., Academic, New York, 1975, p. 168.

156 (1965).

Ziegler, J. C. W. Chien, Ed., Academic, New York, 1975, p. 85 ff, and references therein.


25. D. F. Hoeg, in The Stereochemistry of Macromolecules, Vol. 1, A. D. Ketley, Ed., Edward

26. A. Zambelli, P. Locatelli, G. Bajo, and F. A. Bovey, Macromolecules, 5,687 (1975). Arnold, London, 1967, p. 123 ff, and references therein.

Received October 27,1976 Revised February 23,1977

polymerization of propene with organomagnesium–reduced titanium (iv) chloride-based catalyst

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