Propylene polymers and process for the preparation thereof

Details Propylene polymers and process for the preparation thereof Propylene polymers and process for the preparation thereof

2002-01-18

2004-03-09

Rabago, Roberto (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S113000, C526S114000, C526S115000, C526S117000, C526S127000, C526S160000, C526S170000, C526S348000, C526S351000

Reexamination Certificate

active

06703457

ABSTRACT:

The present invention relates to propylene polymers, optionally containing up to 5 mol % of ethylene, having a number of internal vinylidene unsaturations per polymer chain greater than or equal to 2; these polymers are obtained by removing at least a part of hydrogen present in the polymerization apparatus during the process.
It is known that polypropylene, although possessing good physicomechanical properties and excellent chemical resistance, lack highly desirable properties, such as varnishability, dyeing adhesion and compatibility with other polymers or inorganic substrates because of the apolar and saturated nature. Introducing a high number of unsaturations in the polymer chain therefore could be a way for obtaining a functionalizable polymer and for eliminating these disadvantages. It is known that the polymerization of olefins carried out with metallocene complexes gives rise to evolution of molecular hydrogen. For instance J. Am. Chem. Soc. 1998, 120, 2174-2175 shows that gas-phase reactions between ethylene or an alpha-olefin and Cp
2
ZrCH
3
+
during mass spectroscopic studies result in elimination of molecular hydrogen with concomitant formation of an eta-3-allyl complex. This evolution has been associated with the formation of unsaturations in the polymer chain. Formation of internal unsaturations in the polymer chain in ethylene/alpha-olefin copolymers produced with metallocenes is reported in Polymers Preprints 1998, 39(2), 425. However these documents do not relate to propylene polymerization and moreover, in these documents, there is no indication that the nature and the number of internal unsaturation in a propylene polymer may be controlled. Chain transfer reactions in polypropylene polymerization have been investigated by Resconi at al. in Topics in Catalyst 1999, 7, 145-163, but he does not relate to hydrogen produced during the polymerization reactions.
EP 778293 relates to a process for producing an olefin polymer where an olefin is polymerized in the presence of a metallocene complex; by forced removing hydrogen during the polymerization process, it is possible to obtain an olefin polymer having a desired melt index. In this document the presence of hydrogen in the process is explained by the formation of unsaturated bonds at the terminal end of olefin polymer, no reference being made to internal unsaturations; moreover only ethylene/1-hexene is polymerized in the examples. The Applicant has now unexpectedly found a new propylene polymer, optionally containing up to 5 mol % of ethylene, having the following characteristics:
i) molecular weight distribution (M
W
/M
n
)≦4;
ii) number of internal vinylidene per polymer chain ≧2.
The propylene polymer object of the present invention is obtainable with a polymerization process carried out in the presence of a metallocene-based catalyst system, by selectively removing at least part of hydrogen present in the polymerization apparatus during the polymerization process. More specifically, it is another object of the present invention a process for preparing the above described propylene polymers comprising contacting, under polymerization conditions, propylene and optionally ethylene, with a catalyst system comprising:
a) a metallocene complex of formula (I)
 wherein:
M is titanium zirconium or hafnium; preferably M is zirconium;
the groups X equal to or different from each other, are monoanionic sigma ligands selected from the group consisting of hydrogen, halogen, —R, —OR, —OCOR, —OSO
2
CF
3
, —SR, —NR
2
and —PR
2
, wherein R is a linear or branched C
1
-C
20
alkyl, C
2
-C
20
alkenyl C
3
-C
20
cycloalkyl, C
6
-C
20
aryl, C
7
-C
20
alkylaryl or C
7
-C
20
arylalkyl radical; preferably R is methyl, ethyl, propyl, butyl or phenyl; preferably X is halogen or C
1
-C
20
alkyl;
the groups R
1
, R
2
, R
3
and R
4
, equal to or different from each other, are selected from the group consisting of hydrogen, linear or branched C
1
-C
20
alkyl, C
2
-C
20
alkenyl, C
3
-C
20
cycloalkyl, C
6
-C
20
aryl, C
7
-C
20
alkylaryl or C
7
-C
20
arylalkyl radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table; two or four adjacent groups R
1
, R
2
, R
3
and R
4
may form together one or more 3-6 membered aromatic or aliphatic rings, optionally substituted with hydrocarbyl radicals optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table; preferably R
1
, R
2
, R
3
and R
4
are hydrogen or C
1
-C
20
alkyl; optionally containing nitrogen, phosphorus or sulfur, or R
1
and R
2
form a six-membered aromatic or aliphatic ring;
with the proviso that either R
1
is different from R
4
or R
2
is different from R
3
;
Z is a carbon or silicon atom; preferably Z is a carbon atom;
the groups R
1
and R
6
, equal to or different from each other, are selected from the group consisting of hydrogen, linear or branched C
1
-C
20
alkyl, C
2
-C
20
alkenyl, C
3
-C
20
cycloalkyl, C
6
-C
20
aryl, C
7
-C
20
alkylaryl and C
7
-C
20
arylalkyl radical optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table; R
5
and R
6
optionally form together a 3 to 6-membered ring; preferably R
5
and R
6
are selected from the group consisting of hydrogen, methyl, ethyl, propyl and phenyl; and
b) a suitable activating cocatalyst;
said process being characterized by reducing the concentration of hydrogen formed during the polymerization reaction
DETAILED DESCRIPTION OF THE INVENTION
The number of internal vinylidenes per polymer chain is defined as the number of internal vinylidene bonds over the total number of unsaturated end groups. More precisely, the number of internal vinylidenes per polymer chain is the ratio between the number of bonds in a polymer chain having the following structure:
over the total number of unsaturated end groups in a polymer chain, having the following structures:
Using N.M.R. techniques, the skilled man in the art can carry out the analysis of the polymer in order to determine the content of internal vinylidene per polymer chain. Examples of N.M.R. assignments can be found in Topics in Catalysis 1999, 7, 145 and Journal of Molecular Catalysis 1999, 146, 167.
The propylene polymer, optionally containing up to 5 mol % of ethylene, object of the present invention has the following characteristics:
(i) molecular weight distribution (M
W
/M
n
) ≦4, preferably ≦3,
 more preferably ≦2.5;
(ii) number of internal vinylidene per polymer chain ≧2, preferably ≧2.5, more preferably ≧3.
Moreover, according to a preferred embodiment, the propylene polymers of the invention have the following characteristic:
iii) the isotactic pentads (mmmm), as determined by
13
C-NMR analyses, are ≧80%.
According to another preferred embodiment, the propylene polymer of the invention, have the following characteristic:
iv) less than 0.5% of the CH
2
groups in the polymeric chain are in sequences (CH
2
)
n
wherein n is an even number. The structure of the propylene polymer according to the invention appears to be highly regioregular. In fact, from the
13
C-N.M.R. analysis (125.7 MHz) no signals are revealed as deriving from the (CH
2
)
n
sequence where n is an even number.
Preferably the propylene polymers, object of the present invention, are obtainable by a process comprising contacting, under polymerization conditions, propylene and optionally ethylene with a catalyst system comprising:
a) a metallocene complex of formula (II)
 wherein
M, X, R
3
, R
4
, R
5
and R
6
have the meaning reported above and the groups R
7
, R
8
, R
9
and R
10
, equal to or different from each other, are selected from the group consisting of hydrogen, linear or branched C
1
-C
20
alkyl, C
2
-C
20
alkenyl, C
3
-C
20
cycloalkyl, C
6
-C
20
aryl, C
7
-C
20
alkylaryl and C
7
-C
20
arylalkyl radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table; preferably R
7
, R
8
, R
9
and R
10
are hydrogen, C
1
-C
20
alkyl or C
6
-C
20
aryl;
preferably R
3
is a group SiR
3
or CR
3
, wherein R has t

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