Macromol React Eng 2009 3 257262_Controlled Catalyst Dosing An Elegant

Full Paper

Controlled Catalyst Dosing: An ElegantApproach in Molecular Weight Regulation forUHMWPEa

Sudhakar Padmanabhan,* Krishna R. Sarma, Shashikant Sharma, Viral Patel

Ethylene polymerization using Ziegler-Natta catalysts comprising TiCl4 supported on MgCl2with aluminum alkyls as co-catalyst produce UHMWPE through a mediated proportionalreduction of the Ti oxidation states. We observe the molecular weight regulation to be acombined function of hydrogen and the co-cata-lyst through experimental evidences. The role ofunavoidable chain transfer reactions for molecu-lar weight regulation has been observed duringthe production of UHMWPE along with H2

through controlled catalyst dosing. Process optim-ization studies at 7.5 atm ethylene pressure couldabsorb small deviations in the catalyst systems tomaintain the desired molecular weights.

Introduction

Ultrahigh-molecular-weight polyethylene (UHMWPE)

belongs to the specialty grade of polyethylene (PE) having

an average molecular weight greater than

3� 106 g �mol�1.[1] UHMWPE is unique and is distinctly

different from its homologs as can be seen from the

‘‘ultrahigh’’ molecular weight. For a polymer, its molecular

weight is an important characteristic and plays a key role in

the application properties. Because of its ultrahigh mole-

cular weight, UHMWPE has excellent wear resistance,

outstanding impact strength and very good chemical

S. Padmanabhan, K. R. Sarma, S. Sharma, V. PatelResearch Centre, Vadodara Manufacturing Division, RelianceIndustries Limited, Vadodara 391 346, IndiaFax: þ91 265 669 3934;E-mail: [email protected]

a : Supporting information for this article is available at the bottomof the article’s abstract page, which can be accessed from thejournal’s homepage at , or from the author.

Macromol. React. Eng. 2009, 3, 257–262

� 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

resistance.[2] Consequently it finds applications in diversi-

fied areas with unique requirements.[3]

More than two thirds of the commercial processes

employed for manufacturing UHMWPE are based on

continuous stirred tank reactor using conventional Zieg-

ler-Natta catalysts.[4] Few plants are also using metallo-

cene-based catalyst systems at very limited capacities.[5]

Among the various grades of UHMWPE, the grade with

molecular weight 4–5� 106 g �mol�1 is unique because of

the optimum abrasion resistance, impact strength, and

chemical resistance.[6] Hence, the 4� 106 g �mol�1 mole-

cular weight grade is having maximum business volume.

At higher molecular weights, though the abrasion resis-

tance is slightly better than that of the lower molecular

weight polymers, the impact strength drops down con-

siderably.[6]

Most of the PE produced based on the market needs are

manufactured using traditional Ziegler-Natta catalysts

which typically comprise titanium halides (TiX4 where X

is generally Cl) supported on magnesium chloride (MgCl2) –

through various chemical modifications.[7] The activity of

these catalysts not only depend on the total titanium

DOI: 10.1002/mren.200900001 257

S. Padmanabhan, K. R. Sarma, S. Sharma, V. Patel

258

present in the system but also depend on the percentage of

the reduced titanium species.[4] In general, when alkyl

aluminum is added to the catalyst system containing

titanium in the 4þ oxidation state, it gets transformed to

lower oxidation states depending on the amount of alkyl

aluminum which basically functions as a reducing agent.

The production of UHMWPE using these catalyst systems is

again a big task taking in to account the possible

termination reactions which can kill the propagating active

species. The presence of excess aluminum alkyls brings

about the termination via transfer of polymer chain to

aluminum, reducing the length/molecular weight of the

polymer chain. It also results in broadening the molecular

weight distribution.[8,9] Apart from the termination reac-

tions described above which brings down the molecular

weight of the growing polymer chain, the presence of

excess aluminum alkyl takes part in eliminating the

impurities which are detrimental to olefin polymerization.

This is especially true when carrying out laboratory

experiments in 5 L scale and above as the catalyst can

easily be killed by the presence of small amounts of

impurities in the solvent. Hence, optimization of Al content

with respect to catalyst quantity is inevitable and is of

prime importance especially in the case of UHMWPE, where

the molecular weight is of paramount importance.

Here, in this paper, we have demonstrated the capability

of using aliphatic hydrocarbon as a polymerization

medium for producing UHMWPE having controlled poly-

mer properties. We have also developed laboratory process

and catalyst recipes for making UHMWPE of higher

molecular weights namely 6, 8, and 10� 106 g �mol�1.

We have demonstrated the effective utilization of side

reactions such as termination due to alkyl aluminum in

regulating the molecular weight of the growing polymer

chains.

Experimental Part

General Considerations

All glassware was scrupulously cleaned and oven dried prior to use.

All manipulations like handling/transfer of catalysts and pyr-

ophoric aluminum alkyls were carried out in a nitrogen glove bag.

Catalyst designated C-00, was prepared by treating Mg(OEt)2 with

TiCl4 in hexane as the medium at high temperature, washed with

hexane to remove dissolved impurities, dried under N2 and used as

a hexane slurry. The other catalyst batches with different Ti3þ

contents were synthesized from C-00 by adjusting the AlRR02

quantity and are designated C-16 (Ti3þ 16%), C-21 (Ti3þ 21%), C-25

(Ti3þ25%), C-32 (Ti3þ32%), and C-50 (Ti3þ50%). The Ti content in the

catalysts was evaluated as per standard procedures using spectro-

scopic techniques. The average particle size (APS) of the catalysts

was in the range of 8–16mm in the order of C-16>C-21>C-25>

C-32>C-50.



Preparation of Catalyst, C-00

10 g of Mg(OEt)2 was added to 150 mL of Varsol, a high boiling

kerosene fraction under an atmosphere of nitrogen and mechanical

stirring. The temperature was increased to 85 8C and maintained.

Subsequently 35 g (20 mL) of TiCl4 was added to the Mg(OEt)2

suspension under a gentle atmosphere of nitrogen slowly over a

period of 5–6 h. The molar ratio of Mg/Ti was 1:2. After the TiCl4

addition was complete the temperature was increased to 120 8Cand maintained for 60 h to temper the catalyst. The Varsol

contained the precatalyst as a pale yellow to white suspension. The

titanium in this system is present in the 4þ state. The composition

approximately works out to Mg/Ti/Cl as 1:1.4:3.5.

Preparation Activated Catalysts

The actual catalyst for UHMWPE was prepared from the C-00 by

reducing the same using an equal volume mixture of triisobuty-

laluminum and isoprenylaluminum. The molar ratio employed

between the Ti catalyst and the aluminum alkyl was adjusted as

per the catalyst synthesized. The aluminum alkyl was gently added

at 25 8C to the C-00 under a stream of nitrogen and mechanical

agitation over a period of 5 h. The color of the slurry changed to

grayish black and hence the catalyst is also referred to as the ‘‘black

catalyst.’’ Here, the titanium is present as a mixture of 4þ and 3þtitanium. The trivalent titanium varied from about 16–50% based

on the catalyst system.

General Polymerization Procedure

The polymerization was carried out in a 5 L laboratory Buchi

reactor. Calculated amounts of the catalyst slurry and aluminum

alkyls were transferred under nitrogen to 3 L of dry hexane in a

standard catalyst charging vessel. The same was then transferred

under a gentle stream of nitrogen into the 5 L laboratory Buchi

reactor which was already baked at 80 8C for 4 h and cooled under

dry nitrogen to ambient temperature. Agitation was started to keep

the slurry homogeneous and thus preventing the catalyst particles

from settling down. The required quantity of ethylene was allowed

to enter at 75 8C. The reaction was stopped by cutting off the

ethylene supply after 2 h from the time the reactor temperature

registered 75 8C. The polymer was isolated after cooling down

the reactor, washed with acidic methanol, methanol, and acetone

followed by drying under reduced pressure.

Results and Discussion

Catalyst Systems for UHMWPE

In general, the typical Ziegler catalyst namely titanium

supported on MgCl2 employing a unique combination of

aluminum alkyls, AlRR02 (an equal mixture of triisobutyl-

aluminum and isoprenylaluminum) as the activator and

hydrogen as the molecular weight regulator has been used

for the generation of UHMWPE.[10] Essentially such

DOI: 10.1002/mren.200900001

Controlled Catalyst Dosing: An Elegant Approach in Molecular . . .

Scheme 1. UHMWPE process overview.

Figure 1. Optimization of Al/Ti under specified process conditions.

catalysts (C-00) were used for making HDPE upon activation

with TEAL.[11] Tailoring the precatalyst to produce

UHMWPE through process optimization in hydrocarbon

media with rigid polymer specifications has been a

challenge in industrial arena. The process overview is

shown in Scheme 1.

The catalyst batches with different Ti3þ contents were

synthesized from C-00 (Ti3þ 0%) by adjusting the AlRR02

quantity and are C-16 (Ti3þ 16%), C-21 (21%), C-25 (25%),

C-32 (32%), and C-50 (50%).

For a particular ethylene pressure (PC2) and catalyst

system (C-21) ethylene polymerization were carried out at

different Al/Ti ratios for its optimization and the results are

given in Figure 1.

It was observed that when ethylene pressure was 2 atm,

the optimum value of Al/Ti was �7–8 under the specified

operating conditions. This exercise needed optimization

when ethylene pressure was changed during polymeriza-

tion. At an ethylene pressure of about 5 atm we found that

the Al/Ti ratio of 4–8 showed an increase in catalyst activity

but further increase in Al/Ti ratio from 8 to 16 did not show a

significant difference in the yield of the polymer obtained.

At different Al/Ti ratios, besides yield the other polymer

properties like bulk density (BD) and average molecular

weight changed, thus providing a lever to alter the polymer

Table 1. Effect of Al/Ti over polymer properties. General conditions: PC2 7.5 atm, Cocatallaluminum and isoprenylaluminum), Al/Ti¼4, 75 8C, 500 rpm and different catalyst con

Runa) Catalyst (Ti) Al/Tib) PC2 Yield (Ti) BD APS

Type Amount atm g �mL�1 g �mL�1 mm

mmol

1 C-21 3.64 5 2.0 19 0.22 100

2 C-21 3.64 10 2.0 92 0.26 80

3 C-21 3.64 15 2.0 66 0.25 83

4 C-00 1.20 4 7.5 617 0.4 125

5 C-00 1.20 8 7.5 767 0.39 110

6e) CPP 0.13 40 7.5 4850 0.37 100

7e) CPP 0.13 60 7.5 6100 0.35 113

8e) CPP 0.13 100 7.5 6560 0.40 105

9e) CPP 0.13 20 7.5 2190 0.26 185

a)Extracted from extensive studies carried out in the laboratory for making UHMWPE; b)Fi

by both Malvern PSA and traditional sieve shaker methods; d)Viscosity-average molecula

[(5.37�104�RSV1.49)/106]; e)CPP, commercially available PP catalyst.



characteristics at the cost of yield. The

efficacies of catalyst and process condi-

tions are shown in Table 1. We have

exploited a commercial Ziegler-Natta

catalyst which is routinely used for

making poly(propylene) (PP) to give

UHMWPE of very high molecular weights and different

polymer characteristics. As seen from Table 1, changing the

Al concentration resulted in tailored polymers with diverse

properties.

Besides AlRR02 we have also evaluated triethylaluminum

(TEAL) as the activator for selected catalyst batches. Under

the experimental conditions employed, namely with

0.24 mmol Ti catalyst and Al/Ti ratio of 4, we found that

TEAL activated catalyst showed better productivity com-

pared to that of AlRR02 but the molecular weight of the

UHMWPE obtained was comparatively on the lower side to

that of the counter part as shown in Table 2. These results

yst used AlRR02 (an equal mixture of triisobuty-

centrations with no H2.

c) %< 63c) % >250c) Mvd)

mm mm 106 g �mol�1

12 2 2.7

52.3 0.1 3.8

52.7 0.1 5.7

11 3.1 15.0

9.7 1 10.1

8.6 1.4 13.3

6.2 2.1 13.6

10.9 2.5 13.1

38.4 14 13.6

xed based on catalyst performance; c)Analyzed

r weight calculated using Margolie’s equation

www.mre-journal.de 259


Table 2. Effect of cocatalyst over polymer properties. General conditions: PC2 7.5 atm, AlRR02 is an equal mixture of triisobutylaluminum and

isoprenylaluminum, Al/Ti¼4, 75 8C, 500 rpm and different catalyst concentration with no H2.

Run Catalyst C-25 (Ti) Co-catalyst Al/Tia) Yield (Ti) BD APSb) Mvc)

mmol g �mmol�1 g � cm�3 mm 106 g �mol�1

5 0.24 AlRR02 4 617 0.41 125 15

4 0.24 AlRR02 8 767 0.39 110 10.1

10 0.24 TEAL 4 630 0.39 108 6.4

11 0.24 TEAL 8 670 0.34 100 4.6

a)Fixed based on catalyst performance; b)Analyzed by both Malvern PSA and traditional sieve shaker methods; c)Viscosity-average

molecular weight calculated using Margolie’s equation.

Figure 2. Effect of Ti3þ oxidation state over polymer molecularweight at (a) 5 atm and (b) 7.5 atm ethylene pressures.

260

indicate that TEAL acts as a better chain transfer agent than

that of the other aluminum alkyls. The use of TEAL as the

activator for UHMWPE formation is very limited because in

conjunction with hydrogen we end up with high-density PE

(HDPE).

Under similar operating conditions (PC2-5 atm; PH2-NIL;

75 8C) catalyst systems C-16, C-21, C-25, C-32, and C-50 were

screened for polymerization. The results indicated that

polymer obtained from C-25 catalyst system gave the

maximum reduced specific viscosity (RSV) as shown in

Figure 2a. At subsequent stages we realized that we could

get UHMWPE with desired molecular weight with other

catalyst systems as well, by suitable optimization on the

catalyst, activator and hydrogen concentrations.

The trend when ethylene pressure was 7.5 atm can be

seen in Figure 2b. Unlike the ethylene pressure at 5 atm

(Figure 2a), ethylene pressure of 7.5 atm does not change the

polymer characteristics as seen from the steady RSV values

(Figure 2b) over a range of trivalent Ti content in the

catalysts. At 7.5 atm ethylene pressure the process proceeds

smoothly maintaining the same molecular weight even

with marginal variations in trivalent Ti content in the

catalyst. This could be very favorable for polymerization

processes in the plant level.

Molecular Weight Regulation Using Hydrogen forUHMWPE Polymerization

Hydrogen is a well known molecular weight regulator used

in polyolefin industry during polymerization of ethy-

lene.[12] We studied the effect of hydrogen on the solubility

of ethylene in different process solvents over a wide range

of temperature and pressure.[13] It is interesting to note that

the presence of hydrogen reduces the solubility of ethylene

in hexane significantly at 30 8C. The extent of decrease in

the solubility of ethylene with 5 vol.-% hydrogen over no

hydrogen is nearly 50%. It can be further noted that the

extent of decrease in ethylene solubility with increase in



hydrogen is not linear. The extent of drop in solubility of

ethylene in hexane with 5% hydrogen and with 10%

hydrogen is not significantly different, while the amount of

decrease in solubility due to 5% hydrogen against 0%

hydrogen is significant. Similar trends in solubility were

seen at 55 8C also. Experiments were also carried out at 75 8Cat 6 atm ethylene pressure with 5 vol.-% hydrogen. The

solubility (mole fraction) of ethylene in the presence of

hydrogen was 0.032 while the ethylene solubility (mole

fraction) in the absence of hydrogen was 0.044. This implies

that presence of hydrogen, under polymerization condi-

tions, not only deactivates the active polymerization sites of

the catalyst[14] but also effectively brings down the

DOI: 10.1002/mren.200900001

Controlled Catalyst Dosing: An Elegant Approach in Molecular . . .

Table 3. Molecular weight regulation using controlled catalystdosing at specified hydrogen dosage. General conditions: PC27.5 atm, Al/Ti¼4, 75 8C, 500 rpm and different catalyst concen-trations with PH2 34 mL in 100 mL bomb.

Run Catalyst

C-25

Yield (Ti) BD APSa) Mvb)

g g �mmol�1 g � cm�3 mm 106 g �mol�1

12 0.17 716 0.40 106 8.0

13 0.31 915 0.41 107 7.3

14 0.34 855 0.41 111 6.9

15 0.36 890 0.41 108 6.1

16 0.41 980 0.40 109 5.1

a)Analyzed by both Malvern PSA and traditional sieve shaker

methods; b)Viscosity-based average molecular weight calculated

using Margolie’s equation.

ethylene available for polymerization thus altering the

polymerization rate.

Knowing the fact that hydrogen can act as a chain

terminating agent as well as affect the polymerization rate

by decreasing the solubility of ethylene in hexane. We have

opted to keep the hydrogen concentration constant and

vary the catalyst concentration to get UHMWPE of different

molecular weights.[9]

Molecular Weight Regulation Using ControlledCatalyst Dosing at Specified Hydrogen Dosage forUHMWPE Polymerization

As mentioned earlier, we require process conditions better

than that of 5 atm ethylene operating conditions to achieve

better polymer properties like BD, APS with controlled

amount of coarse and fine materials. Experiments at 7.5 atm

ethylene pressure gave us most of the desired polymer

properties. We found that it was an excellent recipe for

making the 4–5 million molecular weight grade with

enhanced productivity, desired BD and particle size distribu-

Table 4. Molecular weight regulation using other catalyst systems, Cconditions: catalyst 1 mmol Ti, PC2 7.5 atm, PH2 34 mL in 100 mL bom

Run Catalysta) PH2 Productivity

atm (g PE) � (g cat)�1

17 C-16 0.34 680

18 C-32 0.34 860

19 C-50 0.34 660

a)Prepared by activation C-00 with different amounts of AlRR02; b)Ana

c)Viscosity-average molecular weight calculated using Margolie’s equ



tion (PSD)/APS (Table 3). It was then realized the necessity to

tailor this process for producing higher molecular weight

grades namely >6� 106 g �mol�1. Limitations using hydro-

gen for achieving this objective has been already explained in

terms of the different solubility characteristics of ethylene,

hydrogen, and their mixtures in process solvents. It was at

this juncture, we realized that the molecular weight of the

polymer produced also depended on the catalyst to hydrogen

ratio. Thus, reducing the catalyst concentration for the same

hydrogen dosage level and keeping all other parameters

constant resulted in UHMWPE with the desired character-

istics of BD, APS/PSD, and molecular weight – albeit at a

marginal loss of productivity – which is in order. The results

are tabulated in Table 3.

It can be observed from the above results that besides

hydrogen, the concentration of the catalyst also plays a

major role in regulating the molecular weight.Prima facie it

may be misleading that how the molecular weight

decreases with decrease in effective hydrogen concentra-

tion per unit Ti (Table 3).

From Table 3 it can be seen that the experiments have been

performed keeping the same ratio of Al/Ti and concentration

of hydrogen. If hydrogen alone was responsible for molecular

weight regulation the trend in molecular weight as depicted

in the Table 3 should have been reversed viz. an increase in

the molecular weight with increase in catalyst to hydrogen

ratio. In other words the effective hydrogen available in the

system reduces as catalyst concentration increases. Since,

this phenomenon was not observed it is clear that the apart

from hydrogen, the other competing termination reaction

namely transfer to aluminum is responsible for regulating

the molecular weight. This is a vivid example of two

competing termination reactions which are prominent in

the area of olefin polymerization.

Using this approach we could get different grades of

UHMWPE with desired molecular weights of 5–

8� 106 g �mol�1 (Table 3). The BD and APS/PSD were also

optimal. During the process of fine tuning, we also realized

that, other catalyst systems under identical optimized

process conditions could give desired polymer characteristics

(Table 4).

-16, C-32, and C-50 at specified hydrogen dosage. General reactionb, Al/Ti¼4, 3 L hexane, 75 8C, 500 rpm, 2 h.

BD APS RSV, hb) Mvc)

g � cm�3 mm dL � g�1 106 g �mol�1

0.4138 104 26 6.9

0.397 115 21.2 5.1

0.396 113 25.3 6.6

lyzed by both Malvern PSA and traditional sieve shaker methods;

ation.

www.mre-journal.de 261


262

Conclusion

In this paper, we have demonstrated the regulation of

molecular weight through controlled catalyst dosing which

provided a convenient handle to tune the molecular weight

especially on larger operating scales. We have highlighted

the significance of moderating competing chain termina-

tion reactions mediated through hydrogen and aluminum

alkyls through process optimization studies.

Acknowledgements: We sincerely thank Dr. A.B. Mathur andDr. R.V. Jasra for their continuous encouragement to carry out thiswork.

Received: January 10, 2009; Revised: March 25, 2009; Accepted:March 25, 2009; DOI: 10.1002/mren.200900001

Keywords: catalysts; chain termination; molecular weight reg-ulation; polyethylene; polymerization; titanium; transfer toaluminum; Ziegler-Natta catalysis

[1] S. M. Kurtz, UHMWPE Handbook, 1st edition, Elsevier Aca-demic Press, Amsterdam 2004.

[2] For more information visit: www.dsm.com/en_US/html/dep/stamylanuh.htm.

[3] [3a] A. Keller, M. Hikosaka, A. Toda, S. Rastogi, P. J. Barham,G. J. Gooldbeck-Wood, J. Mater. Sci. 1994, 29, 2579; [3b] P. S. M.Barbour, M. H. Stone, J. Fisher, Biomaterials 1999, 20, 2101.

[4] Patent search results related to UHMWPE: [4a] US 3910870(1975), invs: L. Siegfried, H. W. Birnkraut, H. Moser;[4b] US 5292837 (1994), invs: A. Heinrich, L. Bohm, H. A.Scholz; [4c] US 5587440 (1996), invs: J. Ehlers, J. Walter;[4d] US 6114271 (2000), invs: D. Bilda, L. Bohm;[4e] US 7157532 (2007), invs: W. Payer, J. Ehlers;[4f] US 7141636 (2006), invs: J. Ehlers, S. Haftka, L. Wang.

[5] Novel catalysts reported in the scholarly literature demon-strated to produce ultrahigh molecular weight polyethy-lenes: [5a] M. Tamm, S. Randoll, E. Herdtweck, N.Kleigrewe, G. Kehr, G. Erker, B. Rieger, Dalton Trans. 2006,459; [5b] K. A. O. Starzewski, B. S. Xin, N. Steinhauser, J.Schweer, J. Benet-Buchholz, Angew. Chem. 2006, 118, 1831;[5c] A. Karam, E. Casas, E. Catarı, S. Pekerar, A. Albornoz, B.Mendez, J. Mol. Catal. A: Chem. 2005, 238, 233; [5d] K. Michiue,R. F. Jordan, Organometallics 2004, 23, 460; [5e] A. S. Ionkin,W. J. Marshall, Organometallics 2004, 23, 3276; [5f] M. Fujita,Y. Seki, T. Miyatake, J. Polym. Sci., Part A: Polym. Chem. 2004,42, 1107; [5g] H. Makio, N. Kashiwa, T. Fujita, Adv. Synth.Catal. 2002, 344, 477; [5h] H. Mori, K. Ohnishi, M. Terano,Macromol. Chem. Phys. 1999, 200, 2320; [5i] K. Kageyama, J.



Tamazawa, T. Aida, Science 1999, 285, 2113; [5j] U. Peucker, W.Heitz, Macromol. Rapid Commun. 1998, 19, 159; [5k] Y.-X.Chen, C. L. Stern, T. J. Marks, J. Am. Chem. Soc. 1997, 119, 2582;[5l] M. Frediani, D. Semeril, A. Comucci, L. Bettucci, P. Frediani,L. Rosi, D. Matt, L. Toupet, W. Kaminsky, Macromol. Chem.Phys. 2007, 208, 938.

[6] [6a] S. M. Kurtz, O. K. Muratoglu, M. Evans, A. A. Edidin,Biomaterials 1999, 20, 1659; [6b] K. Nakayama, A. Furumiya,T. Okamot, K. Yag, A. Kaito, C. R. Choe, L. Wu, G. Zhang, L. Xiu,D. Liu, T. Masuda, A. Nakajima, Pure Appl. Chem. 1991, 63,1793; [6c] R. M. Rose, W. R. Cimino, Wear 1982, 77, 89; [6d] B.Weightman, D. Light, Biomaterials 1985, 6, 177.

[7] [7a] A. Munoz-Escalona, J. G. Hernandez, J. A. Gallardo, J. Appl.Polym. Sci. 1984, 29, 1187; [7b] K. Soga, K. Shiono, Prog. Polym.Sci. 1997, 22, 1503.

[8] [8a] V. A. Zakharov, G. D. Bukatov, Y. I. Yermakov, Die Mak-romol. Chem. 1975, 176, 1959; [8b] V. A. Zakharov, G. D.Bukatov, N. B. Chumaevskii, Y. I. Yermakov, Die Makromol.Chem. 1977, 178, 967; [8c] G. D. Bukatov, N. B. Chumaevskii,V. A. Zakharov, G. I. Kuznetsova, Y. I. Yermakov, Die Makro-mol. Chem. 1977, 178, 953.

[9] B. M. Grieveson, Die Makromol. Chem. 1965, 84, 93.[10] For synthesis of the catalyst recipes MgOEt2 þTiCl4 see:

[10a] US 4447587 (1984), invs: J. Berthold, B. Diedrich,R. Franke, J. Hartlapp, W. Schafer, W. Strobel;[10b] US 4448944 (1984), invs: J. Berthold, B. Diedrich, R.Franke, J. Hartlapp, W. Schafer, W. Strobel.

[11] [11a] L. L. Bohm, Angew. Chem., Int. Ed. 2003, 42, 5010;[11b] L. L. Bohm, Macromol. Symp. 2001, 173, 53; [11c] T. I.Koranyi, E. Magni, G. A. Somorjai, Top. Catal. 1999, 7, 179.

[12] [12a] A. Toyota, T. Tsutsui, N. Kashiwa, J. Mol. Catal. 1989, 56,237; [12b] K. Peng, S. Xiao, J. Mol. Catal. 1994, 90, 201;[12c] S. S. Reddy, S. Sivaram, Prog. Polym. Sci. 1995, 20, 309;[12d] J. Huang, G. L. Rempel, Prog. Polym. Sci. 1995, 20, 459;[12e] Y. Imanishi, N. Naga, Prog. Polym. Sci. 2001, 26, 1147; Forheterogeneous systems: [12f] Y. V. Kissin, R. I. Mink, T. E.Nowlin, J. Polym. Sci., Part A: Polym. Chem. 2000, 37, 4255;[12g] K. J. Chu, J. B. P. Soares, A. Penlidis, Macromol. Chem.Phys. 2000, 201, 552; [12h] Y. V. Kissin, J. Polym. Sci., Part A:Polym. Chem. 2001, 39, 1681; [12i] Y. V. Kissin, R. I. Mink, T. E.Nowlin, A. J. Brandolini, J. Polym. Sci., Part A: Polym. Chem.1999, 37, 4281; [12j] Y. V. Kissin, L. A. Rishina, J. Polym. Sci.,Part A: Polym. Chem. 2002, 40, 1353; [12k] A. Schindler, DieMakromol. Chem. 1964, 70, 94; [12l] I. A. Jaber, W. H. Ray,J. Appl. Polym. Sci. 1993, 49, 1695; [12m] K. Czaja, M. Bialek,J. Appl. Polym. Sci. 2001, 79, 361; [12n] Y. V. Kissin, L. A.Rishina, E. I. Vizen, J. Polym. Sci., Part A: Polym. Chem. 2002, 40,1899.

[13] G. Sivalingam, V. Natarajan, K. R. Sarma, U. Parasuveera, Ind.Eng. Chem. Res. 2008, 47, 8940.

[14] N. P. Khare, K. C. Seavey, Y. A. Liu, S. Ramanathan, S. Lingard, C.Chen, Ind. Eng. Chem. Res. 2002, 41, 5601.

DOI: 10.1002/mren.200900001

Macromol React Eng 2009 3 257262_Controlled Catalyst Dosing An Elegant

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