Thermoplastic propylene block copolymer containing 1-alkene-propylene-diene copolymer block

The invention relates to a thermoplastic propylene block copolymer comprising one or more substantially crystalline polypropylene blocks and one or more 1-alkene-propylene copolymer blocks, in at least one of which 1-alkene-propylene copolymer blocks diene units are present, and to a process for preparing such a propylene block copolymer. According to the invention, as diene, a cyclic hydrocarbon compound is used wherein at least one double bond forms part of a strained structure, particularly a polycyclic compound with 7 to 20 carbon atoms containing at least one 4- and/or 5-ring, with one or more double bonds in or to the ring. The invention offers the advantage that it is possible to prepare block copolymers which can otherwise not or hardly be made, while at the same time only a small quantity is formed of byproducts which are soluble in the dispersant.

The invention relates to a thermoplastic propylene block copolymer 
comprising one or more substantially crystalline polypropylene blocks, and 
one or more 1-alkene-propylene copolymer blocks, in at least one of which 
1-alkene-propylene copolymer blocks diene units are present. 
From the Derwent abstract 35725 Q (Japanese patent publication No. 
20751/69) a thermoplastic propylene block copolymer is known consisting of 
a polypropylene block, a poly-ethylene-propylene-octadiene-1,7-block and a 
polyethylene block. A similar block copolymer with cyclooctadiene-1,5 as 
the diene could possibly be formed in the process according to Chemical 
Abstracts 71 (24), 113670 c (Japanse patent publication No. 19542/69). 
In the preparation of such block copolymers the problem arises that during 
the step in which the poly-ethylene-propylene-octadiene block is made, a 
large quantity of byproduct is obtained that is soluble in the dispersant. 
This has a number of disadvantages. In the first place it means a loss of 
raw materials, because the fraction dissolved in the dispersant does not 
form a usable product. 
This already immediately indicates the second problem, formed by the fact 
that the fraction dissolved in the dispersant must eventually be carried 
off. 
A third disadvantage concerns the fact that the fraction which dissolves in 
the dispersant strongly increases the viscosity thereof. The viscosity of 
the dispersant may even become so high as to make sufficient mixing 
impossible. This means a considerable reduction of the capacity of the 
installation, because on account of this it is possible only to operate at 
relatively low slurry concentrations. 
Moreover, there is a need of products combining reasonable to good 
flowability with a high impact resistance. Such a combination of 
properties cannot be obtained in the propylene block copolymer according 
to the Japanese patent publications. 
The object of the invention is to provide a thermoplastic block copolymer 
in which these problems do not occur. 
The block copolymer according to the invention is characterized in that, as 
diene, a cyclic hydrocarbon compound is used wherein at least one double 
bond forms part of a strained structure. A strained structure means in 
this connection that the valence angles of at least one of the two carbon 
atoms of the said double bond differ from the sp.sup.2 hybridization 
state. 
The invention also relates to a process for the preparation of a 
thermoplastic propylene block copolymer, in which process propylene is 
polymerized in one or more first steps under conditions in which 
substantially crystalline polypropylene is formed, in one or more 
subsequent steps a mixture of a 1-alkene and propylene is polymerized, in 
at least one of which 1-alkene-propylene polymerization steps a diene is 
present, and finally propylene or ethylene is possibly polymerized in one 
or more final steps. 
This process is characterized in that, as diene, a cyclic hydrocarbon 
compound is used wherein at least one double bond in the ring forms part 
of a strained structure. 
In this connection the term `1-alkene` means a 1-alkene other than 
propylene, for instance a 1-alkene having 2 or 4-12 carbon atoms. 
Preference is given to ethylene. 
As cyclic diene various dienes can be used. Strained structures are 
particularly present in polycyclic compounds. Generally, these compounds 
have 7 to 20 carbon atoms. 
Preference is given to using as diene a compound containing one or more 4- 
and/or 5-rings, with one or more double bonds in or to the ring. 
Preferably the double bonds are not conjugated. Very useful dienes are 
those that possess the bicyclo[2.2.1.]heptene skeleton. 
Preference is given in particular to dienes having both double bonds in the 
4- and/or 5-rings. 
It has been found that with these compounds, the quantity required to 
obtain the desired effect is very small indeed. 
Suitable dienes for application in the present invention are norbornadiene, 
dicyclopentadiene, tricyclopentadiene, 5-ethylidenenorbornene-2, 
5-methylenenorbornene-2, 5-vinylnorbornene-2, 5-(2-propenyl)norbornene-2, 
isopropylidenetetrahydroindene and 4, 7, 8, 9-tetrahydroindene. 
Very suitable compounds are ethylidenenorbornene, dicyclopentadiene and 
norbornadiene. In particular with norbornadiene the desired effect is 
reached already with very small quantities. 
Surprisingly it has been found that, according to the invention, a 
thermoplastic block copolymer can be obtained having a combination of 
properties which has so far not been possible before, namely the 
combination of reasonable to good flowability and a very high impact 
resistance, also at low temperatures. According to the invention block 
copolymers can be made combining an impact resistance of 40-60 (Izod, 
notched, according to ASTM D 256, 296 K) with a melt index of 1-4 (dg/min, 
ISO R 1133, 503 K/21.6 N). 
Moreover, these block copolymers have the advantage that in the preparation 
substantially fewer byproducts are formed that are soluble in a 
dispersant. 
Hence, with the present invention it is possible to make block copolymers 
which can otherwise not or hardly be made, while at the same time no 
problems arise in consequence of the formation of byproducts, such as 
capacity reduction resulting from the high viscosity, purification of the 
dispersant and processing of the byproduct. 
According to a preferred mode of realizing the invention the block 
copolymer is built up of a first polypropylene block, one or more 
polyethylene-propylene-diene blocks and possibly a polyethylene block. 
In this connection it is noted that the term polypropylene means those 
propylene polymers most of which (.gtoreq.90 % wt, preferably .gtoreq.95 % 
wt, more specifically 100 % wt) is built up of propylene units. It is 
possible to use ethylene or higher 1-alkenes as comonomers. The quantities 
thereof are so small, however, that the propylene polymers are still 
always substantially crystalline (`disordered` polypropylene). 
The block copolymer is preferably built up with 10-90 % wt polypropylene 
blocks, 10-90 % wt poly-ethylene-propylene-diene blocks and 0-50 % wt 
polyethylene blocks. 
The content of diene units in the poly-ethylene-propylene-diene blocks is 
preferably between 0.1 and 25 % wt, but particularly between 0.1 and 5 % 
wt. Within these limits a block copolymer is obtained having optimum 
processing characteristics and a very good impact resistance. 
The overall composition of the block copolymer may vary within very wide 
limits. The block copolymer, however, must retain thermoplastic 
properties. The composition may e.g. be 50-95 % wt propylene, 5-49.99 % wt 
ethylene, 0.01-10 % wt diene and 0-15 % wt other monomers. 
In the polyethylene-propylene-diene block preference is given to taking the 
ethylene-propylene molar ratio between 0.1 and 10, more specifically 
between 0.5 and 3, because with such ratios the highest impact resistances 
are obtained. Such ethylene-propylene molar ratios can be incorporated in 
the block copolymer by taking the ethylene-propylene molar ratio in the 
feed between 0.5 and 5, more specifically between 0.5 and 3.0. In practice 
the ratio in the feed will be regulated on the basis of the composition of 
the gas mixture over the liquid in the reactor. 
For the preparation of the present block copolymers the known 
high-stereospecific catalyst systems can be used, for instance those based 
on a TiCl.sub.3 -containing component prepared by reduction of TiCl.sub.4 
with aluminium or an organic aluminium compound, such as 
aluminiumdiethyl-chloride or aluminimethylsesquichloride and, if required, 
subjected to a thermal after-treatment. A TiCl.sub.3 component subjected 
to an after-treatment with complex-forming compounds can be used also. It 
is possible also to use a catalyst system based on a titanium compound on 
a carrier, such as MgCl.sub.2, SiO.sub.2 or Al.sub.2 O.sub.3, an organic 
aluminium compound, as well as an electron donor compound, for instance an 
organic ester or amine. 
If desired the stereospecificity of the catalyst system can be increased by 
an addition of so-called third components (complex-forming compounds) to 
the polymerization mixture. Suitable complexforming compounds are, for 
instance, ethers, thioethers, thiols, phosphines, amines, amides, ketones, 
esters, more in particular ethers having the formula R--O--R, where R is 
an alkyl group having 1-15 carbon atoms. Suitable third components for 
increasing the stereospecificity are further, for instance, cyclopolyenes 
and phosphoric acid amides, in particular cycloheptatriene and 
hexamethylphosphoric acid triamides. 
The catalyst system may contain an activator. Preference is given to using, 
as activator, organometallic compounds having the formula MeR.sub.q 
X.sub.p-q, where Me is a metal from the first, second or third main group 
or the second subgroup of the Periodic System, preferably aluminium or 
zinc, in particular aluminium, R is a hydrocarbon residue having 1-16 
carbon atoms, preferably an alkyl group having 1-16 carbon atoms, in 
particular an alkyl group having 2-12 carbon atoms, X is hydrogen, a 
halogen atom or an alkoxy or dialkylamine group having 1-8 carbon atoms, p 
is the valence of Me and q is an integer corresponding with 
1.ltoreq.q.ltoreq.p. 
Particularly suitable are chlorine-containing organo-aluminium compounds, 
such as dialkylaluminiummonochlorides having the formula AlR.sub.2 Cl or 
alkylaluminiumsesquichloride having the formula Al.sub.2 R.sub.3 Cl.sub.3, 
where R has the meaning given above. Examples are: Al(C.sub.2 
H.sub.5).sub.2 Cl, Al(i-C.sub.4 H.sub.9).sub.2 Cl, Al.sub.2 (C.sub.2 
H.sub.5).sub.3 Cl.sub.3. 
Aluminiumtrialkyls AlR.sub.3 or aluminiumdialkylhydrides having the formula 
AlR.sub.2 H can also be used, where R has the meaning given above. In that 
case preference is given to taking Al(C.sub.2 H.sub.5).sub.3, Al(C.sub.2 
H.sub.5).sub.2 H, Al(C.sub.3 H.sub.7).sub.3, Al(C.sub.3 H.sub.7).sub.2 H, 
Al(i-C.sub.4 H.sub.9).sub.3 or Al(iC.sub.4 H.sub.9).sub.2 H. 
The circumstances under which the polymerization reaction with the 
catalytic titanium component according to the invention is performed do 
not differ from those known in the art. The reaction is performed 
preferably in the presence of a dispersant. The dispersant may be inert or 
also a monomer in liquid form. Examples of suitable dispersants are 
aliphatic, cycloaliphatic, aromatic and mixed aromatic/aliphatic 
hydrocarbons having 3-8 carbon atoms per molecule, such as propylene, 
butylene-1, butane, isobutane, n-hexane, n-heptane, cyclohexane, benzene, 
toluene and the xylenes. More specifically propylene, n-hexane or 
n-heptane are used. titanium compound should preferably be about 0.001-0.5 
mmole, calculated as titanium atom, and the concentration of the 
organometallic compound about 0.1-50 mmoles, both per liter dispersant. 
The polymerization temperature is mostly between 190 and 475 K., preferably 
between 310 and 375 K. The pressure may, for instance, be between 1 and 30 
bar. 
If so desired, the molecular weight of the polymer can be regulated during 
the polymerization, for instance by operating in the presence of hydrogen 
or another known molecular weight regulator. 
The polymerization reaction can be effected both batchwise and continuously 
.

The invention is elucidated by means of the following nonrestrictive 
examples and the comparative examples. 
EXAMPLE I 
To a 5-1 autoclave, provided with a mechanical stirrer, 2.5 l heptane is 
added, followed by 2 g diethylaluminiumchloride (20 % wt solution in 
heptane) and 1.0 g TiCl.sub.3.1/3 AlCl.sub.3. With propylene the pressure 
is brought to 8 bar and the temperature to 343 K. 
The polymerization is effected in the presence of hydrogen having a 
concentration of 2 % vol in the gas phase over the liquid. After 3 hours 
the pressure is relieved to 1 bar. After addition of 10 ml EN 
(5-ethylidenenorbornene-2) to the autoclave, a mixture of ethylene, 
propylene and hydrogen is passed in continuously in an ethylene-propylene 
molar ratio of 3. After that, polymerization is effected for 2.5 hours at 
a pressure of 2 bar. After the pressure has been relieved, the slurry 
obtained is removed from the reactor, treated with n-butanol and extracted 
with water. The slurry is subsequently centrifuged off. 
The dissolved polymer content is 4.8 % wt. The powder is dried, stabilized 
and granulated. The mechanical properties are: melt index (ISO R 1133, 
21.6 N, 503 K)=3.1 dg/min, Izod (ASTM D 256, 296 K)=42.5 kJ/m.sup.2 and 
E-modulus (ASTM D790)=1110 N/mm.sup.2. 
COMATIVE EXAMPLE I 
The polymerization is effected in the same way as described in example I, 
except that no EN is added this time. The dissolved polymer content now 
amounts to 7.2 % wt. The mechanical properties are: melt index=3.1 dg/min; 
Izod=13.0 kJ/m.sup.2 ; E-modulus=1325 N/mm.sup.2. 
EXAMPLE II 
The polymerization is effected analogously to example I. Now 10 ml DCPD 
(dicyclopentadiene) is added instead of EN and an ethylene-propylene molar 
ratio of 5 is applied. 
The dissolved polymer content is now 4.6 % wt. The viscosity of the 
polymerization medium after the polymer has been centrifuged off is 4.9 
cSt. 
COMATIVE EXAMPLE II 
The polymerization is effected analogously to example II, except that no 
DCPD is used this time. The dissolved polymer content is 8.0 % wt and the 
viscosity of the polymerization medium centrifuged off is 35.9 cSt. 
EXAMPLE III 
The polymerization is effected analogously to example I, except that 10 ml 
DCPD is added this time instead of EN and that the ethylene-propylene 
molar ratio is 5. The dissolved polymer content is 4.0 % wt and the 
viscosity of the polymerization medium centrifuged off as function of 
temperature and shear rate is: 
______________________________________ 
shear rate (s.sup.-1) 
.eta. (mPa .multidot. s) 293 K 
.eta. (mPa .multidot. s) 343 K 
______________________________________ 
5194 -- 2.6 
2597 4.8 2.9 
1298 5.5 3.3 
649 6.7 4.2 
325 7.5 5.2 
162 8.0 6.0 
81 9.0 -- 
______________________________________ 
COMATIVE EXAMPLE III 
The polymerization is effected analogously to example III, except that no 
DCPD was added this time. The dissolved polymer content is 6.2 % wt. The 
viscosity of the polymerization medium, after centrifuging off, as 
function of the temperature and shear rate is: 
______________________________________ 
shear rate (s.sup.-1) 
.eta. (mPa .multidot. s) 293 K 
.eta. (mPa .multidot. s) 343 K 
______________________________________ 
1298 -- 9.8 
698 21.2 11.6 
325 25.9 13.2 
162 31.4 15.5 
81 37.9 18.9 
41 45.9 25.9 
______________________________________ 
EXAMPLE IV 
The polymerization is effected analogously to example I, except that an 
ethylene-propylene molar ratio of 2.25 is taken this time and 1 ml 
norbornadiene is added instead of EN. The dissolved polymer content is 5.0 
% wt and the polymerization medium is low-viscous. 
COMATIVE EXAMPLE IV 
The polymerization is effected analogously to example IV, except that no 
norbornadiene was added this time. The dissolved polymer content is now 
9.0 % wt and the polymerization medium is viscously thick. 
EXAMPLE V 
The polymerization is effected analogously to example IV, except that this 
time 5 ml 5-vinylnorbornene-2 is added instead of norbornadiene. The 
dissolved polymer content is 5.4 % wt and the polymerization medium is 
low-viscous.