close

Вход

Забыли?

вход по аккаунту

?

Copolymers of ethylene with bicyclic dienes.

код для вставкиСкачать
D i e Angewandte Makromolekulare Chemie 20 (1971) 141-152 ( N r . 283)
From the Dunlop Forschung, D-645 Hanau, Germany
Copolymers of Ethylene with Bicyclic Dienes
By H. SCHNECKO,
R. CASPARYand G. DEGLER
Dedicated to Professor Dr. K. HAMANN
on occasion of his 65th birthday
(Eingegangen am 1. April 1971)
SUMMARY:
The copolymerization of ethylene (E) with dicyclopentadiene (DCP), ethylidene
norbornene (ENB) or methyl endomethylene hexahydronaphthalene (MEHN) by
ZIEGLER-NATTA
catalysts in presence of Hz affords low-mo1.-wt. products over a
wide range of unsaturation. I n this paper some characteristic features of the copolymerization and some physical properties of the raw products are discussed.
For the catalytic system VOC13-Al~Et3C13differences in catalyst efficiency,
copolymer composition, diene incorporation and viscosity can be seen as a function
of type and amount of diene monomer.
Physical properties of the copolymers are strongly dependent on composition.
Incorporation of dienes results in lowered melting points of the parent PE. I n case
of E-DCP and E-ENB the materials become amorphous beyond 15-20 mole-%
diene. At this composition minimum glass transition temperatures are seen.
ZUSAMMENFASSUNG :
Bei der Copolymerisation von Athylen (E) mit Dicyclopentadien (DCP), Pithy(MEHN)
lidennorbornen (ENB) oder Methyl-Endomethylen-Hexahydronaphthalin
durch ZIEGLER-NATTA-Katalysatorenin Gegenwart von Hz entstehen niedermolekulare Produkte uber einen weiten Bereich an Ungesattigtheit. I n dieser Arbeit
wird uber einige charakteristische Einzelheiten dieser Copolymerisationen und
einige physikalische Eigenschaften der Rohpolymeren berichtet.
Diskutiert werden fur das Katalysatorsystem VOC13-AIzEt3C13 Unterschiede in
Katalysatorwirksamkeit, Copolymerzusammensetzung, Dieneinbauverhaltnis und
Viskositat in Abhangigkeit von der Art und der Menge des Diens.
Die physikalischen Eigenschaften der Copolymeren hangen stark von der Zusammensetzung ab. Der Einbau des Comonomeren aul3ert sich in einer Erniedrigung des Polyathylenschmelzpunktes. I m Fall von E-DCP und E-ENB werden die
Produkte bei 15-20 Mol-yo Dien amorph und zeigen ein Minimum im Glasiibergangspunkt .
141
H. SCHNECKO,
R. CASPARYand G. DEGLER
1. Introduction
Whereas the terpolymers of ethylene (E) with propylene (P) and unsaturated bicyclic compounds have found wide scientific attention1 and commercial
applicationz, the corresponding copolymers are scarcely found in the literature
with the exception of EP-copolymers. Thus, in the compositional triangle for
E, P and DM (diene) the 2 corners E and P are well-known as homopolymers
(Fig. 1 ) ; for the E-P-side of the triangle and for a relatively small area inside
(E and P roughly equimolar, DM < 5 mole-o/o)there is a host of information.
A few reports exist on the third corner, i. e. homopolymerization of DM, and
less knowledge is available along the 2 other sides of the triangle, i. e. E-DM
and P-DM, as well as for the residual space inside. One of the main reasons for
this fact is the experimental problem of preparing polymers in these regions.
In these laboratories a number of investigations has been conducted in these
direction$; this report is concerned only with results obtained along the straight)
line E-DM. The 3 DMs used here are:
Dicyclopentadiene (DCP)
&
4)
Ethylidene norbornene (ENB)
and methyl endomethylene hexahydronaphthalene (MEHN),
6)
WISMERand PRUCNAL7 have recently published results on some properties and
coating applications of low mo1.-wt. E-DCP copolymers ; the experimental
background, however, is only given for EPDM, i. e. for the respective terpolymers with propyleneg.
E
Fig. 1. Triangle of composition for the 3 components E (ethylene), P (propylene)
and DM (diene).
142
Ethylene Copolymers
2 . Experimental
Reactions were conducted in a stirred 5 1 pressurizable steel autoclave with 3 1
cyclohexane as solvent at 20°C. Each component had a separate entry into the
head of the vessel and was measured during the reaction except for Hz which was
precharged only, at a constant pressure of 2 atm. The compounds were added in
the sequence: solvent; comonomer (- 25% of total amount) ; AlzEt3C13-VOC13
(constant Al/V-ratio = 5/1); about 20% of the total amount required; E. Total E
pressurization was about 35 1 (1.32 moles) in most cases; a constant monomer feed
was read at the flow-meters, the valves working a t constant pre-pressure from the
line. Thus, the overall E concentration in the experiments was constant and only
comonomer concentration varied. I n most cases the internal pressure rose
somewhat depending on the rate of polymerization and of catalyst and DM addition. The initial Hz-pressure was attained again at the end of a 60 min post-reaction period (with stirring) ; the period during which continuous addition of catalysts
and monomers took place was 30 min.
Copolymers were isolated by repeated precipitation into alcohol-HC1 mixtures.
I n case of high ethylene contents the copolymers were insoluble at room temperature
and could only be dissolved at < 100 "C in solvents like decalin, xylene, toluene etc.
Polymer composition was determined by pyrolysis - gas chromatography and
calibrated by independent analysis of residual unsaturation in comonomers with
IC19 or pyridinium bromide perbromidelo.
Intrinsic viscosities were determined from measurements in cyclohexane at 32 "C.
Samples for modulus-temperature measurements11 were pressed at elevated temperatures ; in these cases slight crosslinking was fostered by peroxide addition.
For X-ray and DTA, powdered polymers could be used as they were obtained.
It should be noted that due to the difference in mo1.-wts. between E and DM
there is a large discrepancy between molar and wt.-compositional values of copolymers. This can be seen by comparing columns 4 and 5 of Table 1.
Monomer and polymer abbreviations :
DCP
DM
Dicyclopentadiene
Diene monomer (although, in the ASTM-nomenclature12 the M refers to a
saturated polymethylene chain)
E
Ethylene
E-DM Copolymers of ethylene with respective diene (DCP, ENB, MEHN)
ENB
Ethylidene norbornene
EPDM Ethylene propylene terpolymer
MEHN Methyl endomethylene hexahydronaphthalene
P
Propylene
P-DM Copolymers of propylene with diene
PE
Polyethylene
VAc
Vinyl acetate
143
H. SCHNECKO,
R. CASPARY
and G. DEGLER
3. Results
3.1 Copolymer Synthesis
Table 1 contains a selection of typical copolymerization results. Obviously,
for the three dienes DCP, ENB and MEHN, a broad spectrum of copolymers
with E can be prepared.
-
voc13
No.
Comonomer
Yield
(g)
mmole/l
TYPe
D1
D2
D3
D4
D5
D6
D7
D8
D9
2.50
1.60
1.41
1.12
0.81
1.14
2.11
0.80
0.80
DCP
DCP
E l
E2
E 3
E4
E5
E6
2.50
2.50
2.10
1.50
1.80
1.20
ENB
M1
4.45
6.90
3.12
3.00
MEHN
171
(100 ml/g)
-
M2
M3
M4
a) E
c) E
=
=
DCP
DCP
DCP
J
b)
ENB
ENB
MEHNJ
503
378
252
226
125
88
50
8
0
100
95
85
68
50
48
37
6
0
100
80
54
31
18
17
11
1.3
0
7
150
125
105
57
70
33
7
0.39
0.145
0.127
0.145
0.200
0.255
0.125
cryst.
cryst.
555
695
250
186
87
28
100
73
55
49
37
18
100
39
22
19
12
5
48
142
122
96
82
67
0.088
0.197
0.312
0.382
0.315
cryst.
250
750
375
125
100
95
70
50
100
77
29
15
62
6
29
45
nd
0.213
0.148
0.865
12.3 g/l (0.44 mole/l); b) Homopolymerization of E
20.0 g/1 (0.71 mole/l).
=
6.7 g/l (0.24 mole/l);
There are certain differences in the behaviour of the dienes. Fig. 2 shows that
catalyst consumption is much higher in case of E-MEHN copolymers as compared to E-ENB and E-DCP which are about the same. I n all 3 cases, a slight
decrease in catalytic amounts towards higher E containing polymers is seen.
However, this latter effect is artificial because, due to the experimental conditions which provide constant E concentration, the total monomer concentration is increased towards the left side of the plot.
144
Ethylene Copolymers
Fig. 2. VOC13 consumption vs. wt.-fraction of E
for the three DMs. Curve
1 : DCP, C a v e 2 : ENR,
Curve 3 : MEHN.
This picture is partly confirmed by efficiency curves where the ratio of
polymer yield/cat. is plotted vs. composition, Fig. 3. Here DCP has the highest
curve, followed by ENB, and MEHN giving the lowest efficiency. The DM sequence DCP > ENB > MEHN parallels that of these monomers in terpolymerization3. The best figures for E-DCP obtained are in the region of 170-240 g
polymer/g VOC13 whereas in EPDM-terpolymerizations under comparable conditions (i. e. with 5 15 wt.-% DCP) average values of 375 are obtained and
can go as high as 6003. This certainly indicates that other parts of the triangle
in Fig. 1 are more favourable for polymerization with this system than the
base line E-DM chosen for this study.
On the other hand, it can be seen from Fig. 3 that maximum curves are
obtained in all three cases and that catalyst efficiency is very low for homopolymerizations on either end of the plot. I n case of E-DCP the curve is unsymmetrical and the maximum shifted towards low E-contents.
It might be inferred from this behaviour that there is a tendency for the
growing chain end t o incorporate a comonomer unit, i. e. copolymerization
145
H. SCHNECKO,
R. CASPARYand G. DEGLER
parameters r might be < 1 ; attempts were made to calculate r-values, but did
not appear significant in view of the operational conditions, i. e. a ) high conversion, b) nonequilibrium conditions with respect to monomer or catalyst concentration.
\
0
A
0
A
7
I?'
%
0
'A
A
'/
/ x
/
-
- x
x -x-
I
\
1
.
0
X
0
I
I
I
20
40
60
I
wt-% E
Catalyst efficiency vs. wt.-fraction of E for the three DMs. Curve 1 : DCP,
Curve 2 : ENB, Curve 3 : MEHN.
Fig. 3.
Average comonomer incorporation is shown in Fig. 4 for DCP; there is some
scatter in the sample points but the average value is around 80% of DM charged
(from Fig. 4 the incorporation is 79.9 & 9.7%).
DCP
-
incorp.
Fig. 4.
DCP-incorporation (amount of DCP in
polymer/amount of DCP
charged) vs. wt.-fraction
of E.
0
146
20
60 wt-% E
Ethylene Copolymers
Viscosities are generally in the range of [q] = 0.1 - 0.3 which is due to the
regulating power of H2. Higher mo1.-wts. can be prepared in absence of H2, but
there is the danger of crosslinking occurence, in particular for high comonomer
containing products.
If intrinsic viscosities are plotted vs. composition their highest values are
found towards the 1 : l wt.-yo copolymers, Fig. 5 . In case of E-DCP there is
again a large scatter ; the least square parabola drawn as curve 1 was calculated
by the computer using the experimental points. One could be tempted to again
infer higher termination rates for the respective homopolymers, but on the E
side the decrease in intrinsic viscosity is due to lower solubility in the solvent;
products with < 10 mole-% DM were partly insoluble due to E-crystallinity
(cf. Section 3 ) .
x
I
0
20
60
wt
-
Ole
E
Fig. 5 . Change of intrinsic viscosity vs. wt.-fraction of E for DCP (Curve
ENB (Curve 2).
1) and
Gel chromatographic curves of copolymers were found similar to those published7 indicating a broad molecular weight distribution ; homopolymers as
Poly-DCP gave a somewhat narrower GPC trace.
147
H. SCHNECKO,
R. CASPARYand G. DEGLER
3.2 Physical Investigation
Contrary to PE, the homopolymer-DMs are amorphous and brittle materials ;
this latter property might of course be due to the low mo1.-wts. Their softening areas range from 120 to 200°C, as shown in Table 2.
Table 2. Softening Data.
at mole-% DM
DCP
200
18
ENB
120
MEHN
155
13
15
+ 14
5
+ 30
-
18-20
12-13
ca. 15
Starting with pure P E (made with this catalyst system) one might expect a
decrease in crystallinity for copolymers with increasing DM content. This has
already been inferred from solubility data and is proven by X-ray measurements. Fig. 6 shows the curves for E-DCP and E-ENB. It becomes clear that
for both systems products become amorphous beyond 10-20 mole-% (40-50
wt.-yo, Table 2 ) . For E-MEHN there were not sufficient samples available to
0
20
40
Wt-OIoDM
Fig. 6. X-ray crystallinity (yo)vs. wt.-fraction of D M for DCP (Curve 1) and ENB
(Curve 2).
148
Ethylene Copolymers
.construct a curve; a t 15 mole-% (sample M 4 of Table 1) the copolymer was
amorphous. This is corroborated by DTA measurements (Fig. 7) where it is
shown that a decrease of the P E melting point occurs by incorporation
of DM (DCP). From the shape of the DTA-traces it can be inferred that indeed
random copolymers have been formed and that no block structure is present.
h
0
W
L3
100
z
Y
n
E
a8
I-
60
40
Fig. 7.
\
I
0
I
1
20
1
40
I
Wt-OIo
DCP
DTA-peak temperature position of melting vs. wt.-yo DCP.
This is again seen from modulus-temperature plots (Fig. 8). In the series of
E-DCP copolymers of varying composition, there is no indication of two different transitions for any compound which would be expected for block or
homopolymers. Instead, the broad transition for P E is becoming steeper and
the transition temperature is lowered, going through a minimum for compositions of 10-20 mole-yo DM (50-60 wt.-yo E ) and then increases again. The
slight broadening in the transition observed a t high DCP contents might be due
to crosslinking (cf. Section 2), but could also stem from DCP-sequences of
variable length.
The described modulus-temperature dependence on DM-content is also reflected in Fig. 9 where the temperature position of the 109 dynes/cm2 modulus
is plotted vs. the E-DM-composition. Again, there were not sufficient amounts
of pressed samples for MEHN to construct the corresponding curve.
4.Discussion
The experiments reported in this paper show that over the entire range of
composition copolymers are formed between E and three bicyclic dienes respec149
H. SCHNECKO,
R. CASPAFCYand G. DEGLER
7
Nr. in table 1
DX (YIZ~%crystallin.
wt -% DCP
c
-
- TI
%
-m
-
e
-
0
.-c
--30
0
100
50
Temperature ('C)
Fig. 8. Torsional modulus G vs. temperature for various E-DCP copolymers.
Explanation of numbers in upper right hand corner, cf. Table 1 .
Fig. 9. Temperature position of torsional modulus G = 109 dynes/cmZ vs. wt.-%
E for E-DCP (Curve 1) and E-ENB copolymers (Curve 2).
150
Ethylene Copolymers
tively. Although no direct structural investigations have been conducted, the
physical properties indicate a random structure and there is no rationale to
assume an alternating structure as has been claimed in an Italian patentl5.
The synthesis is not as facile as in case of the respective terpolymers (EPDMs).
The two practical criteria applied here are a ) catalyst consumption or rather
catalyst efficiency, and b) incorporation of diene charged.
With respect to a), DCP is the best of the three monomers investigated; as
regards b), all three monomers behave similar although MEHN seems to be
generally somewhat lower in its incorporation percentage.
There are also differences in copolymer properties as compared to the respective terpolymers. The materials are no good elastomeric polymers (aside of the
intentional mo1.-wt. restrictions), due to their higher glass transitiohs and greater hardness. If one looks a t the materials from the side of E , this is to be expected. In case of our E-DM copolymers, modifications are achieved only by the
diene, whereas there is the additional influence of P in EPDM terpolymers.
Thus, both types of polymers (E-DM and EPDM) can be seen in a more general way to affect P E properties from two opposite sides: a ) increase of main
chain mobility by reduction of crystallinity, b) decrease of main chain flexibility and promotion of chain stiffening by introduction of bulky monomers.
The contradiction between a ) and b) is an apparent one only because the
actual chain mobility of the homopolymer P E does not occur below the melting point of 125"C; amorphous PE on the other hand, which should be a highly
elastomeric and flexible material, is not existent.
With respect to a) all unsaturated monomers will be effective. As for b)
there will be differences between a-olefins like propylene or vinyl monomers as
vinyl acetate (VAc), acrylic acid on one hand and the DM monomers on the
other which are incorporated with the olefinic site of the norbornyl ring, thus
providing a rigid unit in the polymer chain. The effect is enhanced in case of an
additional condensed ring as in DCP and MEHN. Column 4 of Table 2 supports
this contention: in accordance with the structure the position of the lowest
glass transition temperature increases in the sequence ENB < DCP < MEHN.
Thus, only E-ENB copolymers with 12-13 mole-% ENB might be useful as
elastomeric material a t or around room temperature, but even then the
Tc-values are higher than those of some other E-copolymers. In E-VAc,
the lowest value is a t about -20 to -25OC17 and EP copolymers come down
as far as -6O0C16. On the other hand, other polar comonomers like acrylic
acid, maleic anhydride etc., which are in a position to exert H-bonding or
other intermolecular forces, again give higher Tc-values17 comparable to those
found with our nonpolar but rigid dienes.
151
H. SCHNECKO,
R. CASPARYand G. DEGLER
Minimum curves similar to those shown in Fig. 9 have been found for EP
from DTA measurements16. Such curves do not represent true changes in the
main TGover the whole range of composition, in particular towards both ends,
i. e. for the respective homopolymers. The modulus behaviour of PE is determined by its crystalline cohesion forces and that of the amorphous E-DMs by
their high Tc-values (cf. Table 2).
With respect to coating applications of these materials7, the autoxidation is
certainly slower than that of corresponding EPDMs, again pointing to the
particular role of P incorporated in the chains>l3. However, the apparent
sequence of oxidative crosslinking as judged from insolubilization is MEHN
> DCP > ENB which is again parallel to the respective EPDMsl3>l4. Solution cast films can be readily prepared from E-DCP copolymers (about 30
wt.-% DCP) ; they exhibit transparency and flexibility, but also hardness and
could be useful due to their insolubility.
We would like to acknowledge the skillful experimental assistance of Msrs.
F. DRESCHER,
J. WENDE,and J. HESKE.We would also like t o thank Dr. H.
GERHARTof PPG INDUSTRIES
PITTSBURGH
for making available a paper7 in
advance and DUNLOP
LTD.for permission to publish.
1
2
and E. G. M.
G. NATTA,A. VALVASSORI,
and G. SARTORI,in J. P. KENNEDY
TORNQVIST,
Polymer Chemistry of Synthetic Elastomers, 11, Interscience Publ.,
N. Y. 1969, p. 679.
B. MULLIGAN,
Rubber World 158/5 (1968) 49; Chem. Engng. News, June 23
(1969) 26.
3
5
8
9
10
11
12
13
14
l5
16
17
Unpublished work of this laboratory.
Brit. P. 880 904 (1961), Dunlop Co., Ltd.
Rubber J., 151/3 (1969) 16 (Union Carbide).
Franz. P. 1 511 441 (Jan. 16,1968), I C I ; Inv.: N. CAMELI,
A. VALVASSORI,
and C.
TOSI,Materie Plast. Elast. 34 (1968) 1433.
M. WISMERand P. PRUCNAL,
Ind. Engng. Chem., Product Research & Development, in press.
US.P. 3 496 129 (Feb. 17,1970), Pittsburgh Plate Glass Comp. ; Inv. : M. WISMER
and P. J. PRUCNAL.
M. E. ,TUNNICLIFFE,
D. A. MacKILLoP, and R. HANK,European Polymer J. 1
(1965) 259.
M. E . TUNNICLIFFE,
J. appl. Polymer Sci. 14 (1970) 827.
R. CASPARY,
Kautschuk u. Gummi 20 (1967) 587; Materialpruf. 12 (1970) 41.
ASTM D 1418-67 28 (1968) 676, ASTM, Philadelphia.
R. D. SINGER,G. T. WILLIAMS,
and G. ANGERER,
Ind. Engng. Chem., Product
Research & Development, in press.
H. SCHNECKO
and J. S. WALKER,
European Polymer J., in press.
Brit. P. 951 022 (March 4, 1964) MONTECATINI.
J. J. MAURER,
Rubber Chem. Technol. 42 (1969) 110; ibid. 38 (1965) 979.
N. L. ZUTTY,J. A. FAUCHER,
and S. BONOTTO,
Encyclopedia Polymer Sci. 8~
Technol. 6 (1967) 387.
152
Документ
Категория
Без категории
Просмотров
1
Размер файла
484 Кб
Теги
diener, bicyclic, ethylene, copolymers
1/--страниц
Пожаловаться на содержимое документа