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Synthesis of Polypropylene in the Liquid Monomer in the Presence of a Titanium—Magnesium Catalyst: Effect of Various Internal Donors

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The influence of supported titanium-magnesium catalysts with various internal and external donors on the propylene polymerization in the liquid monomer medium and the characteristics of the polypropylene formed were studied. The following internal donors were used: dibutyl phthalate, diisobutyl phthalate, 9,9′-bis(methoxymethyl) fluorene, and diethyl 2,3-diisopropylsuccinate. The catalysts studied allow synthesis of polypropylene with high isotacticity (>96%) and different molecular-mass distribution (Mw/Mn from 3.3 to 6.3). The influence of external donors (alicyclic, amine) in combination with phthalate and nonphthalate electron-donor compounds on the stereospecificity and activity of the catalysts and on their sensitivity to hydrogen was studied. The optimum catalytic systems for preparing polypropylene for various purposes can be found by varying pairs of internal and external donors.
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ISSN 1070-4272, Russian Journal of Applied Chemistry, 2019, Vol. 92, No. 6, pp. 796808. © Pleiades Publishing, Ltd., 2019.
Russian Text © The Author(s), 2019, published in Zhurnal Prikladnoi Khimii, 2019, Vol. 92, No. 6, pp. 767780.
Polymerization of propylene in the presence of
supported titanium–magnesium catalysts (TMCs)
attracts interest owing to high activity and high
stereospeci city of the catalytic systems. It is known
that the catalytic system based on TMC with internal
phthalate donors proved to be effective and in the
2000s was the most widely used catalytic system for
commercial production of polypropylene throughout
the world [1–5]. These TMCs with phthalate electron-
donor compounds in combination with alkoxysilanes
were named catalysts of fourth generation. The
catalytic system has the general composition TiCl4/
ID/MgCl2 + TEA/ED (ID is an internal donor, ED is
an external donor, and TEA is triethylaluminum). The
mechanism of the action of electron-donor compounds
consists in blocking of nonstereospeci c active sites,
or their conversion to stereospeci c active sites, and
or an increase in the propagation rate constant for
stereospeci c active sites [1–3].
Catalytic systems based on phthalate catalysts
without external donor exhibit low stereospeci city
[5]. This is caused by the fact phtalates are desorbed
from the MgCl2 surface after interaction with alkyl-
aluminium and require substitution by an external
donor (usually alkoxysilane) to preserve high stereo-
speci city of the catalytic system. Search for new in-
ternal donors led to the discovery of a new family of
internal donors belonging to the class of 1,3-diethers
(e.g., 2,2-diisopropyl-1,3-dimethoxypropane), which
ensure high stereospeci city of TMC in propylene po-
lymerization without external donor [6]. Such catalysts
are sometimes named catalysts of fth generation. The
polypropylene obtained is characterized by narrower
molecular-mass distribution (MMD) compared to that
obtained with phthalate TMCs (Mw/Mn = 3–4 against
4–6, respectively). On the other hand, such internal
donors as 2,3-substituted succinates were also found
[7]; their use in TMC allowed synthesis of polypropyl-
MACROMOLECULAR COMPOUNDS
AND POLYMERIC MATERIALS
Synthesis of Polypropylene in the Liquid Monomer in the
Presence of a Titanium–Magnesium Catalyst: Effect of Various
Internal Donors
I. I. Salakhova,*, G. D. Bukatovb, A. Z. Batyrshina, M. A. Matskob, A. A. Barabanovb,
A. N. Tavtorkinc, E. V. Temnikovaa, and A. G. Sakhabutdinova
a PAO Nizhnekamskneftekhim, Nizhnekamsk, Tatarstan, 423553 Russia
b Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia
c Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow, 119991 Russia
*e-mail: i.i.salahov@gmail.com
Received May 7, 2019; revised May 8, 2019; accepted May 8, 2019
AbstractThe in uence of supported titanium–magnesium catalysts with various internal and external donors on the
propylene polymerization in the liquid monomer medium and the characteristics of the polypropylene formed were
studied. The following internal donors were used: dibutyl phthalate, diisobutyl phthalate, 9,9-bis(methoxymethyl)
uorene, and diethyl 2,3-diisopropylsuccinate. The catalysts studied allow synthesis of polypropylene with high
isotacticity (>96%) and different molecular-mass distribution (Mw/Mn from 3.3 to 6.3). The in uence of external
donors (alicyclic, amine) in combination with phthalate and nonphthalate electron-donor compounds on the stereo-
speci city and activity of the catalysts and on their sensitivity to hydrogen was studied. The optimum catalytic systems
for preparing polypropylene for various purposes can be found by varying pairs of internal and external donors.
Keywords: titanium–magnesium catalyst, propylene polymerization, electron donors, isotacticity, molecular
characteristics, thermal characteristics
DOI: 10.1134/S1070427219060090
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 92 No. 6 2019
797SYNTHESIS OF POLYPROPYLENE IN THE LIQUID MONOMER
ene with high isotacticity and broader molecular-mass
distribution (Mw/Mn > 6) compared to the polypropylene
prepared in the presence of phthalate catalysts [8, 9].
In production processes, phthalate TMCs are now
gradually replaced by nonphthalate TMCs because of
restrictions of REACH-2015 regulations, associated
with the data on harmful effect of phthalates on human
health. Consumers prefer more and more frequently
nonphthalate polypropylene grades for food packing
and storage and for fabrication of children’s toys and
hygienic means. Therefore, TMCs with 1,3-diethers and
succinates as internal donors are of indubitable interest
as nonphthalate catalysts. Studies of nonphthalate cata-
lysts are more and more topical, which is con rmed by
an increase in the number of patents and publications on
this subject [10–14]. New nonphthalate catalysts open
possibilities for producing new polypropylene items
with improved properties. Systematic studies of pairs
of donors with evaluation of the complete set of physi-
comechanical properties of polymers, allowing choice
of optimum catalytic systems for producing polypro-
pylene for various purposes, are lacking, especially for
nonphthalate TMCs.
In this work we studied how various combinations of
internal and external donors in uence the activity and ste-
reospeci city of titanium–magnesium catalytic systems
for propylene polymerization and the characteristics of
the polypropylene obtained. Such data would allow suc-
cessful synthesis of polymers with preset properties and
control of their commercial production process.
EXPERIMENTAL
Data on the composition and morphology (average
particle size, d50
cat) of the titanium–magnesium catalysts
studied are given in Table 1. TMC-1 and TMC-4
Table 1. Titanium–magnesium catalysts with different internal donors, used in this study
Catalyst
sample
Internal
donor ID structure
Titanium
content
Magnesium
content ID content d50
cat,
μm
wt %
TMC-1 DBP 2.5 17.7 10.2 47
TMC-2 DIBP 2.6 16.7 8.9 55
TMC-3 DEDIPS 2.6 17.0 11.0 41
TMC-4 BMMF 2.9 15.8 14.8 49
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 92 No. 6 2019
798 SALAKHOV et al.
catalysts were prepared according to [15]. TMC-3 was
a commercial catalyst; data for TMC-2 were obtained
previously [5]. Titanium–magnesium catalysts TMC-
1, TMC-2, TMC-3, and TMC-4 contain internal
donors: dibutyl phthalate (DBP), diisobutyl phthalate
(DIBP), diethyl 2,3-diisopropylsuccinate (DEDIPS),
and 9,9-bis(methoxymethyl) uorene (BMMF),
respectively.
We used propylene and hydrogen produced by PJSC
Nizhnekamskneftekhim. To remove polymerization
catalytic poisons, propylene and hydrogen were
subjected to deep puri cation on heterogeneous
catalysts with chemical sorption promoters and on
molecular sieves 3А and 4А. TEA cocatalyst ( PJSC
Nizhnekamskneftekhim) with no less than 96% main
substance content was used.
The following external donors were used (main
substance content no less than 98%): cyclohexylmeth-
yldimethoxysilane (CHMDMS, Wacker ChemieAG),
dicyclopentyldimethoxysilane (DCPDMS, USI Chemi-
cal), and diethylaminotriethoxysilane (DEATES, Toho
Titanium Company).
The procedures for catalytic complex preparation,
propylene polymerization in the liquid monomer, and
stabilization of the polypropylene (PP) powder obtained
were similar to those described in [5]. The catalyst
activity was evaluated by the polymer yield (kg PP/g
catalyst).
The molecular characteristics of polypropylene
samples were analyzed with a Polymerlab 220 high-
temperature gel permeation chromatograph [5]. The
polymer melt ow index (MFI) was determined in
accordance with ASTM 1238 with a Ray-Ran extrusion
plastometer. The polypropylene isotacticity index
(I.I.) was determined by dissolution of the sample in
o-xylene, followed by slow cooling of the solution to
25°С under controllable conditions, separation of the
solid phase by ltration, о-xylene evaporation from
the solution, and determination of the relative content
of xylene-soluble atactic polypropylene fraction (X.S.,
wt %); I.I. was determined as I.I. = 100 – X.S. (wt %).
Polypropylene samples were studied by differential
scanning calorimetry (DSC) under argon with a
DSC 204F1 Phoenix device in accordance with ASTM
D 3418 [5]. The degree of crystallinity was calculated
by the formula χ = (Нm/Н100%) × 100%, where χ
is the degree of the sample crystallinity (%); Н100%,
enthalpy of melting of fully crystalline isotactic PP
(χ = 100%) (J g–1); and Нm, enthalpy of melting of the
given sample (J g–1).
The following elastic, strain, and strength
characteristics of cast polypropylene samples were
determined: bending elastic modulus E (according to
ASTM D 790), tensile strength σt, relative elongation at
break εb (both according to ASTM D 638), and Charpy
notch impact strength at +23°С А23°С (according to
ASTM D 256).
RESULTS AND DISCUSSION
The following electron-donor compounds were used
as internal donors: dibutyl phthalate, diisobutyl phthalate,
diethyl 2,3-diisopropylsuccinate (diethyl ester of
substituted succinic acid), and 9,9-bis(methoxymethyl)
uorene (1,3-diether).
Table 2 shows that the stereospeci city of the
catalytic system TiCl4/ID/MgCl2 + TEA/CHMDMS in
Table 2. Properties of polypropylene synthesized on the catalytic system TiCl4/ID/MgCl2 + TEA/CHMDMS with different
internal donors (70°С, 2 h)
Catalyst
sample
Internal donor
ID
Isotacticity
I.I., %
Activity, kg
PP/g cat
Melt ow
index, g/10
min
Weight-
average
molecular mass
Mw, kg mol–1
Polydispersity,
Mw/Mn
TMC-1 DBP 98.0 57 3.9 390 4.3
TMC-2 DIBP 96.8 50 7.0 300 4.1
TMC-3 DEDIPS 97.5 45 2.0 450 6.3
TMC-4 BMMF 98.3 46 8.0 280 3.1
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 92 No. 6 2019
799SYNTHESIS OF POLYPROPYLENE IN THE LIQUID MONOMER
propylene polymerization decreases depending on the
internal donor in the following order:
ID BMMF DBP DEDIPS DIBP
I.I., % 98.3 > 98.0 > 97.5 > 96.8
The polypropylene formed under the action of
titanium–magnesium catalysts with different internal
donors in the presence of an external donor (CHMDMS)
has high isotacticity (>96%). The isotacticity is the
highest (98.3%) for the polypropylene synthesized on
TMC-4 with uorene internal donor and the lowest
(96.8%) for the propylene synthesized in the presence
of TMC-2 with DIBP, in agreement with the results of
experiments with 1,3-diethers [16, 17].
Without external donor, the stereospeci city of
the catalytic system for the propylene polymerization
decreases in the following series of internal donors:
ID BMMF DEDIPS DIBP
I.I., % 96.7 > 93.6 > 66.3
As can be seen, the TMC with DIBP exhibits low
stereospeci city because of removal of phthalate from
the catalyst under the action of TEA in the course of
polymerization. High isotacticity of polypropylene
obtained in the presence of BMMF agrees with the
published data, according to which the 1,3-diether as
an internal donor ensures high stereospeci city without
external donor. This is caused by the fact that the
1,3-diether, in contrast to phthalates, is not removed from
the catalyst under the action of TEA. The isotacticity of
the polypropylene obtained in the presence of TMC with
succinate is lower than in the case of the 1,3-diether but
considerably higher than in the case of DIBP. These data
allow a conclusion that the sensitivity of catalysts to
external donors will be maximal in the case of phthalates
and minimal in the case of the 1,3-diether. Table 3 shows
that the polypropylene isotacticity varies in the series of
external donors DCPDMS, CHMDMS, and DEATES as
follows: 98.1, 96.8, and 95.3% with DIBP, 97.8, 97.5,
and 97.5% with the succinate, and 98.5, 98.3, and 98.4%
with BMMF, respectively. That is, the sensitivity of the
TMC stereospeci city to the external donor is noticeable
in the case of the phthalate and insigni cant in the case of
the 1,3-diether and succinate. Slightly lower isotacticity
of polypropylene in the case of the succinate compared
to BMMF (~97.6 against ~98.4%) is consistent with
the results of the polypropylene polymerization without
external donor.
The activity of the catalytic system in polypropylene
polymerization depends on the internal and external
donors as follows:
Activity, kg PP/g cat.
ED\ID DIBP DEDIPSСBMMF
No ED 34 58 63
DCPDMS 56 50 47
CHMDMS 50 45 46
DEATES 40 36 40
As can be seen, the activity of the phthalate catalyst
is low without external donor (34 kg PP/g cat.) and
signi cantly increases in the presence of an external
donor: to a greater extent with DCPDMS (56 kg PP/g
cat.) and to a lesser extent with DEATES (40 kg PP/g
cat.). Enhancement of the activity of the catalytic system
based on phthalate catalysts on introducing an external
donor agrees with the data of [18, 19]. The external
donor also signi cantly enhances the stereospeci city
of the catalytic system (from 66 to 95–98%). The
activity of nonphthalate catalysts, on the contrary, is
maximal without external donor (58 and 63 kg PP/g cat.
in the case of the succinate and 1,3-diether, respectively)
and noticeably decreases in the presence of an external
donor: to 47–50 kg PP/g cat. with DCPDMS and to
36–40 kg PP/g cat. with DEATES. The stereospeci city
of the catalytic system slightly increases (from 93.6
to 97.5% and from 96.7 to 98.4% in the case of the
succinate and 1,3-diether, respectively). In the case
of phthalate TMC, the external donor substitutes the
removed phthalate and supports high activity and
high stereospeci city of the active sites. In the case of
internal donors that are removed to a small extent, the
external donor can be partially adsorbed on the active
sites, reducing the activity of the catalytic system.
The melt ow index of polyole ns is one of the most
important parameters of the polymer rheology, related
to the weight-average molecular mass Mw. The MFI
values of PP obtained by propylene polymerization on
the catalytic system with different internal and external
donors are compared, as the hydrogen sensetivity of
TMCs, below (data from Table 3):
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 92 No. 6 2019
800 SALAKHOV et al.
Table 3. Properties of polypropylene synthesized on the catalytic system TiCl4/ID/MgCl2 + TEA/ED with different internal and external donors
Catalyst
sample
Ixternal
donor ED
Isotacticity
I.I., %
Activity, kg
PP/g cat
Melt ow
index,
g/10 min
Weight-average
molecular mass
Mw, kg mol–1
Polydispersity,
Mw/Mn
Melting
point
Tm, °C
Crystallization
point Tcr, °C
Crystallinity
χ, %
TMC-2
(DIBP)
No ED 66.3 34 50 180 4.2 161.9
156.0
109.9 27.5
DCPDMS 98.1 56 2.0 441 4.3 170.5 116.9 47.0
CHMDMS 96.8 50 7.0 300 4.1 169.1 118.0 46.6
DEATES 95.3 40 30 200 4.5 167.0 117.6 49.4
TMC-3
(DEDIPS)
No ED 93.6 58 2.7 490 7.2 165.7 112.7 45.2
DCPDMS 97.8 50 2.0 500 5.7 171.7 117.7
111.2
47.8
CHMDMS 97.5 45 2.0 450 6.3 170.0
154.9
148.7
109.5 48.3
DEATES 97.5 36 3.3 410 5.9 172.5
154.2
148.1
111.7 47.1
TMC-4
(BMMF)
No ED 96.7 63 12.0 240 3.4 165.2
154.6
148.7
113.2 46.3
DCPDMS 98.5 47 5.1 360 3.3 170.7 110.5 48.5
CHMDMS 98.3 46 8.0 280 3.1 169.7 109.8 48.8
DEATES 98.4 40 6.0 350 3.6 169.3 110.0 46.1
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 92 No. 6 2019
801SYNTHESIS OF POLYPROPYLENE IN THE LIQUID MONOMER
Melt ow index, g/10 min
ED\ID DIBP DEDIPS BMMF
No ED 50 2.7 12.0
DCPDMS 2.0 2.0 5.1
CHMDMS 7.0 2.0 8.0
DEATES 30 3.3 6.0
As can be seen, in the case of the phthalate catalyst
the MFI values for polypropylene depend signi cantly
on the internal donor (from 2 to 30 g/10 min), whereas
for nonphthalate TMC with the 1,3-diether and succinate
as internal donor the MFI values depend on the external
donor insigni cantly (5.1–8.0 and 2.0–3.3 g/10 min,
respectively). When replacing DCPDMS as external
donor by the amine (DEATES), MFI sharply increases
(by a factor of 15) in the case of the phthalate TMC and
only slightly changes for the nonphthalate TMCs. As
already noted, this is associated with high sensitivity of
phthalate TMCs, compared to nonphthalate TMCs, to
external donors.
The width of the molecular-mass distribution depends
on the TMC internal donor. Table 2 shows that Мw/Mn
is 4.1–4.3 for phthalate TMCs, 6.3 for TMC-3 with
the succinate donor (i.e., the polydispersity becomes
higher), and 3.1 for TMC-4 with the uorene donor
(i.e., the molecular-mass distribution, on the contrary,
becomes narrower). The shape of the curves in Fig. 1
con rms the effect of the internal donor on the width of
the molecular-mass distribution.
Variation of external donors does not lead to signi -
cant changes in the polydispersity index (Table 3, Fig. 2).
As with CHMDMS, with DCPDMS and DEATES as
external donors the Мw/Mn values for polypropylene
are determined by the kind of the internal donor used
in TMC. In particular, with different external donors the
Мw/Mn values are in the interval 4.1–4.5 for phthalate
(Fig. 2a), 5.7–6.3 for the succinate (Fig. 2b), and 3.1–
3.6 for the 1,3-diether (Fig. 2c).
Differential scanning calorimetry is a simple and
informative method for studying the supramolecular
structure of polypropylene. Isotactic PP has several
polymorphic modi cations: α1, α2, β, and γ [20, 21]. Such
polymorphic structures of polypropylene can be readily
revealed by DSC in several heating–cooling cycles. It
is well known [22] that samples of highly stereoregular
isotactic polypropylene at common crystallization rates
form mainly crystallites of α1-modi cation.
The results of calorimetric measurements of
polypropylene samples obtained using various external
and internal donors are presented in Figs. 3–6 and in
Tables 3 and 4.
Table 4 shows that the thermal properties of
polypropylene synthesized on the catalytic system
TiCl4/ID/MgCl2 + TEA/CHMDMS vary depending on
the internal donor as follows:
ID DBP DIBP DEDIPS BMMF
Тm, °С169.3 ~ 169.1 170.0
154.9
148.7
~ 169.7
Тcr, °С116.7 ~ 118.0 > 109.5 ~ 109.8
χ, % 46.9 ~ 46.6 48.3 ~ 48.8
As can be seen, the polypropylene samples prepared
on nonphthalate catalysts with CHMDMS external
donors are characterized by higher values of Тm and
crystallinity but lower crystallization points compared
to the polymers prepared on phthalate catalysts.
Analysis of the DSC melting curves at second heating
shows that the polypropylene samples synthesized on
TMC-1, TMC-2, and TMC-4 are characterized by a
single phase transition in the range from 169 to 170°C.
The use of catalysts with the phthalate and 1,3-diether as
internal donors leads to the formation of polypropylene
Fig. 1. Gel chromatograms of polypropylene samples obtained
on catalysts with different internal donors (TMC-1, DBP;
TMC-2, DIBP; TMC-3, DEDIPS; TMC-4, BMMF).
log M
TMC-1
TMC-2
TMC-3
TMC-4
Relative content of polymer fractions, wt %
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 92 No. 6 2019
802 SALAKHOV et al.
Table 4. Thermal properties of polypropylene synthesized on the catalytic system TiCl4/ID/MgCl2 + TEA/CHMDMS with
different internal donors
Catalyst
sample
Internal
donor
ID
Melting
point
Tm, °C
Enthalpy
of melting
ΔHm,
J g–11
Extrapolat-
ed crystal-
lization
onset
tempera-
ture
Tcr.onset, °C
Crystalliz-
ation point
Tcr, °C
Difference
between the
temperatures
of the
crystallization
onset and
crystallization
point Tcr.onset
Tcr, °C
Difference
between the
melting and
crystallization
points Tm
Tcr, °C
Enthalpy
of crystal-
lization
ΔHcr, J g–1
Crystal-
linity
χ, %
TMC-1 DBP 169.3 98.1 121.1 116.7 4.4 52.6 99.8 46.9
TMC-2 DIBP 169.1 97.3 122.0 118.0 4.0 51.1 106.1 46.6
TMC-3 DEDIPS 148.7
154.9
170.0
101.0 118.6 109.5 9.1 60.5 113.0 48.3
TMC-4 BMMF 169.7 102.0 119.4 109.8 9.6 59.9 111.5 48.8
with the α1-modi cation of the crystalline phase.
However, when using the succinate as an internal donor
(TMC-3), additional low-temperature melting peaks
at 148.7 and 154.9°C, corresponding to melting of the
less stable β-modi cation [23], appear in the DSC curve
(Fig. 3). The temperature characteristics (Тm, Тcr) can be
clearly subdivided into two groups corresponding to the
phthalate donors (TMC-1 and TMC-2) and succinate and
uorene donors (TMC-3 and TMC-4). Similar pattern
is observed for the crystallinity of the polypropylene
samples. It is clearly seen that the polypropylene
samples synthesized on TMC-4 and TMC-3 exhibit
the highest crystallinity (on the level of 48.8%) and the
crystallinity of the polypropylene samples synthesized
using phthalate donors (TMC-1, TMC-2) is slightly
lower (46–47%).
The polypropylene samples can also be characterized
by the crystallization curves. These data supplement the
melting curve data. For example, the crystallization pa-
rameters given in Table 4 demonstrate noticeable dif-
ference in the crystallization onset temperature between
the polypropylene sample synthesized using TMC-3
(succinate) and the samples synthesized using the other
TMCs (118.6 against 121–122°C). The former sample
is also characterized by low crystallization ability (Т
= ТmТcr = 60.5°C is maximal) and minimal crystal-
lization point (Тcr = 109.5°C). Furthermore, the crystal-
lization peak for the polypropylene sample prepared on
TMC with the succinate is broader than the crystallization
peaks of the other polymer samples studied. These dif-
ferences are due to factors in uencing the crystallite for-
mation, such as the stereoregularity of the polymer chain
and molecular-mass characteristics. In this case, at high
isotacticity of the polypropylene sample (TMC-3), an
increase in its polydispersity (to Мw/Mn = 6.3, Table 2)
and viscosity (MFI = 2 g/10 min) leads to a decrease in
the crystallization rate (decrease in Тcr) and favors the
formation of crystals of different thicknesses. This is
manifested in the DSC thermogram in the appear-
ance of the melting peak of β-modi cation crystals
[17]. The same phenomenon was noted in [18, 22]. The
polypropylene samples synthesized in the presence of
phthalate catalysts (TMC-1 and TMC-2) are character-
ized by high crystal growth rate [(Тcr.onsetТcr) = 4°C],
maximal intensity of crystallization peaks (Fig. 4, cool-
ing curves, Тcr.onset = 121–122°C), and maximal crys-
tallization point (Table 4). The PP samples prepared on
TMC-4 with the 1,3-diether and on TMC-3 are charac-
terized by slightly lower temperatures (on the level of
109°C) and heights of the crystallization peaks.
For the same internal donors, we performed a series
of experiments with variation of the external donors
(Table 3).
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 92 No. 6 2019
803SYNTHESIS OF POLYPROPYLENE IN THE LIQUID MONOMER
Fig. 2. Gel chromatograms of polypropylene samples obtained on catalysts with different internal and external donors. Internal donor:
(a) DIBP, (b) DEDIPS, and (c) BMMF.
log M
TMC-3/DCPDMS
Relative content of polymer fractions, wt %
log M
Relative content of polymer fractions, wt %
Relative content of polymer fractions, wt %
log M
(a)
(c)
(b)
TMC-3/CHMDMS
TMC-3/DEATES
TMC-2/CHMDMS TMC-2/DCPDMS
TMC-2/DEATES
TMC-4/DEATES TMC-4/DCPDMS
TMC-4/CHMDMS
TMC-1
TMC-2
TMC-3
TMC-4
TMC-1 TMC-2
TMC-3
TMC-4
Fig. 3. DSC thermograms (heating curves) of polypropylene sam-
ples obtained on catalysts with different internal donors (TMC-1,
DBP; TMC-2, DIBP; TMC-3, DEDIPS; TMC-4, BMMF).
Fig. 4. DSC thermograms (cooling curves) of polypropylene sam-
ples obtained on catalysts with different internal donors (TMC-1,
DBP; TMC-2, DIBP; TMC-3, DEDIPS; TMC-4, BMMF).
0.2 mW mg–1
0.2 mW mg–1
Temperature, °C Temperature, °C
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 92 No. 6 2019
804 SALAKHOV et al.
For the TMCs with different internal donors (phthalate,
succinate, uorene), dicyclopentyldimethoxysilane as
an external donor exhibits the highest stereoregulating
ability. Table 3 and Figs. 5 and 6 show that the
polypropylene samples obtained on the phthalate catalyst
with different external donors have the crystallinity
of 46.6–49.4% with Тm = 167–170.5°C (Figs. 5a, 6a).
The polypropylene samples obtained on the succinate
catalyst with different silanes have the crystallinity of
47.1–48.3% with Тm = 170–172.5°C (Figs. 5b, 6b).
The polypropylene samples obtained on the catalyst
with the 1,3-diether and external donors have the
crystallinity of 46.1–48.8% with Тm = 169.3–170.7°C
(Figs. 5c, 6c). On the whole, the Тm values are relatively
close and maximal in the case of the succinate; the
polypropylene crystallinity is close in the cases of the
phthalate and succinate and slightly lower in the case of
the 1,3-diether. Without external donor, the crystallinity
of the polypropylene obtained with the phthalate,
succinate, and 1,3-diether as internal donors is 27.5, 45.2,
and 46.3%, and Тm of the polymer is 159, 165.7, and
165.2°C, respectively. The maximal Тcr is reached when
using DCPDMS as an external donor on TMC with the
phthalate and succinate internal donors. It suggests high
TMC-2/DCPDMS
(a)
(c)
(b)
TMC-2/CHMDMS
TMC-2/DEATES
TMC-2/No external donor
Fig. 5. DSC thermograms (heating curves) of polypropylene samples obtained on catalysts with different internal and external donors.
Internal donor: (a) DIBP, (b) DEDIPS, and (c) BMMF.
TMC-3/No external donor
TMC-3/CHMDMS
TMC-3/DEATES
TMC-3/DCPDMS
TMC-4/No external donor
TMC-4/DEATES
TMC-4/CHMDMS
TMC-4/DCPDMS
0.2 mW mg–1
Temperature, °C
0.2 mW mg–1
Temperature, °C
Temperature, °C
0.2 mW mg–1
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 92 No. 6 2019
805SYNTHESIS OF POLYPROPYLENE IN THE LIQUID MONOMER
(b)
(a)
(c)
stereoregularity of the polypropylene samples studied.
As can be seen, variation of Тm and crystallinity (Figs.
6a, 6c) show that the TMCs with the phthalate internal
donor are more sensitive than the nonphthalate TMCs to
the chemical structure of the external donor. In the case
of the succinate internal donor, high values of Тm, Тcr,
and crystallinity are reached simultaneously only with
DCPDMS as an external donor (Fig. 6).
It can also be noted that, for all the TMCs studied
with different internal donors, the maximal values of
the isotacticity, degree of crystallinity, and molecular
characteristics of polypropylene samples are reached
when using DCPDMS as an external donor (with two
cyclopentyl substituents and two methoxy groups). For
the polypropylene samples obtained using the internal
donor based on the 1,3-diether, the kind of the external
donor (among those we studied) does not signi cantly
in uence the properties of the polymer obtained.
Thus, according to the DSC data, the polypropylene
samples prepared on the succinate catalyst with external
donors exhibit high crystallinity (47–48%) and the
highest Тm. The polymers prepared on TMC with the
1,3-diether and different external donors have somewhat
lower values of the crystallinity and Тm. In the case of
the phthalate catalyst, the values of Тm and crystallinity
depend on the external donor.
The results of studying the elastic, strain, and
strength characteristics of polypropylene samples
synthesized on the catalytic systems TiCl4/ID/MgCl2
+ TEA/ED with different internal and external
donors are given in Table 5. As can be seen, when
comparing catalysts with different internal donors,
the highest values of the bending elastic modulus of
polypropylene were reached when using the succinate
catalyst with DCPDMS and CHMDMS (Е = 1260 and
1210 MPa, respectively) as external electron donors.
The lowest values of the elastic modulus were obtained
when using the uorene catalyst with DEATES as an
external donor (Е = 1080 MPa). In the case of the
phthalate catalyst with different external donors, the
Е values are close (1140–1160 MPa). Without external
donor, Е decreases slightly for nonphthalate TMCs
(Е = 975–1000 MPa) and sharply for the phthalate
catalyst (Е = 270 MPa), which is associated with a sharp
Fig. 6. (a) Melting point, (b) crystallization point, and (c) crystallinity of polypropylene samples obtained on catalysts with different
internal and external donors.
Tm, °C Tcr, °C
DEATES
DIBP DEDIPS BMMF DIBP DEDIPS BMMF
DIBP DEDIPS BMMF
No
ED
No
ED
No
ED
No
ED
No
ED
No
ED
No
ED
No
ED
No
ED
DCPDMS
DCPDMS DCPDMS
DCPDMS DCPDMS DCPDMS
CHMDMS
CHMDMS CHMDMS CHMDMS
DEATES DEATES
DCPDMS DCPDMS
DCPDMS
CHMDMS
CHMDMS
CHMDMS
CHMDMS
CHMDMS
CHMDMS
DEATES DEATES
DEATES
DEATES
DEATES
DEATES
X
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 92 No. 6 2019
806 SALAKHOV et al.
decrease in the PP isotacticity and crystallinity in the
latter case.
The Charpy impact resistance of the polypropylene
samples obtained with different donors correlates to a
greater extent with the polymer molecular mass than
with its crystallinity. In the case of TMC with DIBP,
polypropylene with different levels of impact resistance
depending on the molecular mass range is formed, with
the highest value reached when using the phthalate cata-
lyst with DCPDMS (8.7 kJ m–2 at Mw = 441 kg mol–1),
and the lowest, with DEATES (5.3 kJ m–2 at Mw =
200 kg mol–1). In the case of the succinate, the impact
resistance of the polypropylene samples obtained with
DCPDMS, CHMDMS, and DEATES as external do-
nors was close (6.0, 6.1, and 5.5 kJ m–2, respectively),
with the molecular mass being also close (Mw = 500,
450, and 410 kg mol–1, respectively). In the case of the
TMC with the 1,3-diether in the presence of CHMDMS
as an external donor, the impact resistance of polypro-
pylene was 5.7 kJ m–2, being lower than for the poly-
propylene samples obtained on the catalysts with DIBP
(7.9 kJ m–2) and DEDIPS (6.1 kJ m–2).
The relative elongation of polypropylene at break
also signi cantly depends on the kind of internal and
external donors. In the case of DIBP with DCPDMS and
CHMDMS as external donors, the relative elongation of
the polypropylene samples at break is 63–76%, and with
DEATES as an external donor εb is 3.5–4 times higher,
270%. With the succinate catalyst, the polypropylene
synthesized in the presence of DCPDMS and DEATES
as external donors has the lowest εb (43–44%), and that
synthesized in the presence of CHMDMS, the highest
εb (67%). As for the tensile strength, the maximal value
(22.4 MPa) is reached on TMC-2 catalyst with DEATES
as an external donor.
Apparently, with an increase in the molecular mass
of polypropylene and with a decrease in the relative
content of the low-stereoregularity fraction, the elastic
modulus and impact resistance of the polymer increase,
but the polymer becomes rigid and less elastic (more
brittle), which is manifested when using the succinate
irrespective of the kind of the external donor. An
increase in the amorphous phase content of the polymer
favors an increase in the relative elongation at break.
The results of the elastic, strength, and strain studies of
polypropylene samples show that the polymers obtained
have different values of the bending elastic modulus,
impact resistance, strength, and relative elongation at
break depending on the combinations of the internal and
external donors in the TMC. The data obtained allow
the polypropylene properties to be controlled in a wide
Table 5. Physicomechanical properties of polypropylene synthesized on the catalytic system TiCl4/ID/MgCl2 + TEA/ED with
different internal and external donors
Catalyst
sample
External
donor ED
Flexural modulus
E, MPa
Charpy impact strength at
+23°C A23°C, kJ m–2
Tensile at break σb,
MPa
Elongation at
break εb, %
TMC-2
(DIBP)
No ED 270 19.0 15.9 670
DCPDMS 1150 8.7 10.5 63
CHMDMS 1140 7.9 17.9 76
DEATES 1160 5.3 22.4 270
TMC-3
(DEDIPS)
No ED 975 8.7 14.7 122
DCPDMS 1260 6.0 20.8 43
CHMDMS 1210 6.1 11.4 67
DEATES 1100 5.5 13.6 44
TMC-4
(BMMF)
No ED 1000 6.2 18.5 613
CHMDMS 1100 5.7 16.2 90
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 92 No. 6 2019
807SYNTHESIS OF POLYPROPYLENE IN THE LIQUID MONOMER
range by varying electron-donor compounds of different
structures, and optimum TMC-based catalytic systems
can be chosen for preparing polymers for different
purposes. For example, polypropylene with narrow
molecular-mass distribution, prepared on TMC with the
diether internal donor, is more suitable for producing
bers and threads, whereas polypropylene with broad
molecular-mass distribution, formed on TMC with the
succinate donor, is preferred by producers of plastic
pipes.
CONCLUSIONS
Our study shows that the structure of the internal
electron-donor compound as a component of the
titanium–magnesium catalyst largely determines the
course of the propylene polymerization and the nal
characteristics of the polypropylene formed. A study
of the in uence exerted by phthalates, 1,3-diether,
and substituted succinate as internal donors in the
titanium–magnesium catalyst on the polypropylene
synthesis in the liquid monomer revealed trends in the
stereospeci city and activity of the catalytic system
and in the melt ow index, polydispersity, and thermal
properties of the polymer. The use of the titanium–
magnesium catalysts with diethers and diesters as
internal donors leads to the formation of polypropylene
samples with different values of isotacticity and melt
ow index and different molecular-mass distribution.
In particular, the polypropylene synthesized using the
titanium–magnesium catalyst with the succinate or
1,3-diether has broader or narrower molecular-mass
distribution, respectively, than the polymer synthesized
on the phthalate catalyst. Introduction of external
donors (alicyclic, amine) into the polymerization system
containing the catalysts studied leads to the formation
of catalytic systems with different levels of activity and
sensitivity to hydrogen.
Data on the bending elastic modulus, Charpy
impact resistance, and relative elongation at break
of the polypropylene samples obtained on the
titanium–magnesium catalyst with different internal
donors show that the physicomechanical properties
of polypropylene largely correlate with its degree of
crystallinity and weight-average molecular mass. The
nonphthalate catalysts compared to phthalate catalysts
are characterized by weaker in uence of the kind of
external donor on the properties of the polypropylene
obtained.
Thus, variation of the internal donors based on
diethers and diesters (1,3-diether, substituted succinate,
phthalate) in the titanium–magnesium catalyst
formulation allows control of the isotacticity, molecular
and thermal characteristics, and impact resistance of
the polypropylene obtained. The results of experiments
on variation of combinations of internal and external
electron donors in the catalyst are useful for nding
catalytic systems for the production of polymers with
the required properties.
CONFLICT OF INTEREST
The authors declare that they have no con ict of
interest.
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... The increase in the M evaluated with the elemental analysis of the samples shows that this increase is es due to the cleavage of the chain and not to oxidation, as has been evidenced in oth ies [26][27][28]. The increase in MFI in the samples of polymers synthesized in the presence nal compounds has been evaluated by various authors, where it has been determi this phenomenon occurs due to the interaction between the ZN catalyst and the d The increase in MFI in the samples of polymers synthesized in the presence of external compounds has been evaluated by various authors, where it has been determined that this phenomenon occurs due to the interaction between the ZN catalyst and the different compounds that may be present during polymerization (poisons or external donors), causing a decrease in the molecular weight of the resin obtained [25,[29][30][31], which translates into an increase in the MFI according to the relationship between the average molecular weight and the MFI proposed by Bremner [32,33]. ...
... This analysis also demonstrates how the temperature range at which the resin's mass decreases shift, with the lowest concentration of iron oxide having a range of mass loss varying between 270 and 540 • C, while the resin with the highest iron oxide content had a degradation that began at 100 • C and stopped losing mass at 580 • C. At the temperature where they lost 50% of the mass, it was determined that it decreased as the concentration of iron oxide increased, obtaining the highest concentration of FeO when the mass was reduced to 50% when it reached a temperature of around 414 • C, while the same percentage of weight loss was reached at around 450 • C for the lowest concentration. compounds that may be present during polymerization (poisons or external donors), causing a decrease in the molecular weight of the resin obtained [25,[29][30][31], which translates into an increase in the MFI according to the relationship between the average molecular weight and the MFI proposed by Bremner [32,33]. ...
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