nonstereospecific centers. This leads to an increase in polymer isotacticity and to a
decrease in polymerization rate. The k p value increases because of an increase in the
proportion of stereospecific active centers with higher reactivity. A similar effect of
the influence of stereospecificity of the catalyst on k p values has been found [183]
using a catalyst containing an internal donor (dibutylphtalate, DBP) (see Table 8,
experiments 4–6). In this case, the stereospecificity of the catalyst was changed by
its preliminary treatment with triethylaluminum, which leads to partial removal of
DBP from the catalyst. It is seen that in this case the k p values also increase with an
increase in stereospecificity of the catalyst (i.e., in the content of meso-pentads in
polypropylene).
In work [189], data on the influence of the composition of organoaluminum
cocatalyst on C p and k p values were obtained for propylene polymerization on ТМC
containing an internal donor (Table 9, SF method). In Table 9, the data both for total
polymer and the isotactic fraction insoluble in boiling heptane are presented. The
values calculated for total polymer (K
tot
p ) depend on AlR 3 composition and this
dependence correlates with changes in isotacticity of polypropylene (the content of
Table 8 Data on the effect of internal and external donors on C p and k p values for propylene
polymerization [183, 187, 188] (SF method)
Experiment
number
Catalyst
Isotacticity,
mmmm (mol%)
C p (mol/mol Ti)
k p (L/mol s)
1
TiCl 4 /MgCl 2 + AlEt 3 (I)
56
0.1
1,100
2
I + M e 2 Si(OEt) 2
66
0.064
1,500
3
I + CMDMS
a
66
0.038
1,600
4
TiCl 4 /MgCl 2 ÁnDBP
b +
AlEt 3 (II-A)
94
0.008
3,000
5
II-B
c
85
0.0075
2,500
6
II-C
c
78
0.0072
2,300
a
External donor, CMDMS cyclohexyl(methyl)dimethoxysilane
b
Internal donor, DBP dibutylphtalate
c
Catalysts II-B and II-C were prepared by pretreatment of catalyst II-A by AlEt 3 at 30
C for 5 and
30 min, respectively, to remove DBP from catalyst II-A
Table 9 Data on the effect of AlR 3 cocatalysts on the C p and k p values for propylene polymerization over catalyst TiCl 4 /MgCl 2 /DBP [189] (SF method)
Parameter
Cocatalyst
ТEА
TNBA
TNHA
TNOA
TIBA
C
tot
p (mol/mol Ti)
0.056
0.036
0.027
0.016
0.02
K
tot
p (L/mol s)
3,900
4,000
3,700
3,400
2,800
mmmm (mol%)
92.8
92.9
91.8
89.3
87.8
C
i
p (mol/mol Ti)
0.03
0.028
0.016
0.008
0.008
K
i
p (L/mol s)
4,700
4,800
4,900
4,900
4,900
ТEА AlEt 3 , TNBA Al(n-Bu) 3 , TNHA Al(n-hexyl) 3 , TNOA Al(n-oktyl) 3 , TIBA Al(i-Bu) 3
126
L.A. Novokshonova and V.A. Zakharov
decrease in polymerization rate. The k p value increases because of an increase in the
proportion of stereospecific active centers with higher reactivity. A similar effect of
the influence of stereospecificity of the catalyst on k p values has been found [183]
using a catalyst containing an internal donor (dibutylphtalate, DBP) (see Table 8,
experiments 4–6). In this case, the stereospecificity of the catalyst was changed by
its preliminary treatment with triethylaluminum, which leads to partial removal of
DBP from the catalyst. It is seen that in this case the k p values also increase with an
increase in stereospecificity of the catalyst (i.e., in the content of meso-pentads in
polypropylene).
In work [189], data on the influence of the composition of organoaluminum
cocatalyst on C p and k p values were obtained for propylene polymerization on ТМC
containing an internal donor (Table 9, SF method). In Table 9, the data both for total
polymer and the isotactic fraction insoluble in boiling heptane are presented. The
values calculated for total polymer (K
tot
p ) depend on AlR 3 composition and this
dependence correlates with changes in isotacticity of polypropylene (the content of
Table 8 Data on the effect of internal and external donors on C p and k p values for propylene
polymerization [183, 187, 188] (SF method)
Experiment
number
Catalyst
Isotacticity,
mmmm (mol%)
C p (mol/mol Ti)
k p (L/mol s)
1
TiCl 4 /MgCl 2 + AlEt 3 (I)
56
0.1
1,100
2
I + M e 2 Si(OEt) 2
66
0.064
1,500
3
I + CMDMS
a
66
0.038
1,600
4
TiCl 4 /MgCl 2 ÁnDBP
b +
AlEt 3 (II-A)
94
0.008
3,000
5
II-B
c
85
0.0075
2,500
6
II-C
c
78
0.0072
2,300
a
External donor, CMDMS cyclohexyl(methyl)dimethoxysilane
b
Internal donor, DBP dibutylphtalate
c
Catalysts II-B and II-C were prepared by pretreatment of catalyst II-A by AlEt 3 at 30
C for 5 and
30 min, respectively, to remove DBP from catalyst II-A
Table 9 Data on the effect of AlR 3 cocatalysts on the C p and k p values for propylene polymerization over catalyst TiCl 4 /MgCl 2 /DBP [189] (SF method)
Parameter
Cocatalyst
ТEА
TNBA
TNHA
TNOA
TIBA
C
tot
p (mol/mol Ti)
0.056
0.036
0.027
0.016
0.02
K
tot
p (L/mol s)
3,900
4,000
3,700
3,400
2,800
mmmm (mol%)
92.8
92.9
91.8
89.3
87.8
C
i
p (mol/mol Ti)
0.03
0.028
0.016
0.008
0.008
K
i
p (L/mol s)
4,700
4,800
4,900
4,900
4,900
ТEА AlEt 3 , TNBA Al(n-Bu) 3 , TNHA Al(n-hexyl) 3 , TNOA Al(n-oktyl) 3 , TIBA Al(i-Bu) 3
126
L.A. Novokshonova and V.A. Zakharov