U.S. patent application number 14/042799 was filed with the patent office on 2014-01-30 for polyolefin gas phase polymerization with 3-substituted c4-10-alkene.
This patent application is currently assigned to Evonik Oxeno GmbH. The applicant listed for this patent is Pal Bentzrod, Stefan Buchholz, Tore Dreng, Gerhard Ellermann, Michael GRASS, Jarmo Lindroos, Ted M. Pettijohn. Invention is credited to Pal Bentzrod, Stefan Buchholz, Tore Dreng, Gerhard Ellermann, Michael GRASS, Jarmo Lindroos, Ted M. Pettijohn.
Application Number | 20140031505 14/042799 |
Document ID | / |
Family ID | 42062723 |
Filed Date | 2014-01-30 |
United States Patent
Application |
20140031505 |
Kind Code |
A1 |
GRASS; Michael ; et
al. |
January 30, 2014 |
POLYOLEFIN GAS PHASE POLYMERIZATION WITH 3-SUBSTITUTED
C4-10-ALKENE
Abstract
An alkene interpolymer is prepared by polymerizing at least one
3-substituted C.sub.4-10 alkene and at least one C.sub.2-8 alkene
in a gas phase polymerization using a Ziegler Natta polymerization
catalyst system.
Inventors: |
GRASS; Michael; (Haltern am
See, DE) ; Pettijohn; Ted M.; (Magnolia, TX) ;
Buchholz; Stefan; (Hanau, DE) ; Ellermann;
Gerhard; (Marl, DE) ; Bentzrod; Pal; (Stavern,
NO) ; Dreng; Tore; (Larvik, NO) ; Lindroos;
Jarmo; (Ulefoss, NO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GRASS; Michael
Pettijohn; Ted M.
Buchholz; Stefan
Ellermann; Gerhard
Bentzrod; Pal
Dreng; Tore
Lindroos; Jarmo |
Haltern am See
Magnolia
Hanau
Marl
Stavern
Larvik
Ulefoss |
TX |
DE
US
DE
DE
NO
NO
NO |
|
|
Assignee: |
Evonik Oxeno GmbH
Marl
DE
|
Family ID: |
42062723 |
Appl. No.: |
14/042799 |
Filed: |
October 1, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
13145013 |
Oct 13, 2011 |
8604142 |
|
|
PCT/EP10/50264 |
Jan 12, 2010 |
|
|
|
14042799 |
|
|
|
|
61146915 |
Jan 23, 2009 |
|
|
|
Current U.S.
Class: |
526/159 |
Current CPC
Class: |
C08F 4/52 20130101; C08F
210/16 20130101; C08F 210/16 20130101; C08F 210/16 20130101; C08F
210/16 20130101; C08F 210/16 20130101; C08F 210/16 20130101; C08F
210/16 20130101; C08F 4/65916 20130101; C08F 4/65912 20130101; C08F
210/16 20130101; C08F 210/16 20130101; C08F 210/16 20130101; C08F
210/16 20130101; C08F 2500/12 20130101; C08F 4/65925 20130101; C08F
210/16 20130101; C08F 2500/17 20130101; C08F 2500/12 20130101; C08F
2500/12 20130101; C08F 2500/17 20130101; C08F 2500/12 20130101;
C08F 210/08 20130101; C08F 210/14 20130101; C08F 210/14 20130101;
C08F 2500/12 20130101; C08F 2500/12 20130101; C08F 2500/26
20130101; C08F 2500/26 20130101; C08F 210/08 20130101; C08F 2500/12
20130101; C08F 2/001 20130101; C08F 2500/04 20130101; C08F 2/34
20130101; C08F 210/14 20130101; C08F 210/14 20130101; C08F 210/14
20130101; C08F 210/08 20130101; C08F 210/14 20130101; C08F 2500/11
20130101; C08F 210/14 20130101; C08F 2500/17 20130101; C08F 2500/12
20130101; C08F 2500/08 20130101 |
Class at
Publication: |
526/159 |
International
Class: |
C08F 4/52 20060101
C08F004/52 |
Claims
1. A process for the preparation of an alkene interpolymer,
comprising: polymerizing at least one 3-substituted C.sub.4-10
alkene and at least one C.sub.2-8 alkene in a gas phase
polymerization using a Ziegler Natta polymerization catalyst
system.
2. The process as claimed in claim 1, wherein said catalyst system
is in particulate form.
3-5. (canceled)
6. The process as claimed in claim 1, wherein said C.sub.2-8 alkene
is ethylene or propylene.
7. The process as claimed in claim 1, wherein said 3-substituted
C.sub.4-10 alkene is a compound of formula (I) ##STR00002## wherein
R.sup.1 is a substituted or unsubstituted, preferably
unsubstituted, C.sub.1-6 alkyl group and n is an integer between 0
and 6.
8. The process as claimed in claim 1, wherein said 3-substituted
C.sub.4-10 alkene is 3-methyl-1-butene.
9. The process as claimed in claim 1, wherein said process is
continuous.
10. The process as claimed in claim 1, wherein a total productivity
of the catalyst system is at least 1000 g polymer per g solid
catalyst.
11. The process as claimed in claim 1, wherein said alkene
interpolymer comprises 3-substituted C.sub.4-10 alkene comonomer in
an amount of 0.01-40 wt % based on the total weight of the
interpolymer.
12. The process as claimed in claim 1, wherein said alkene
interpolymer comprises C.sub.2-8 alkene monomer in an amount of at
least 60 wt % based on the total weight of the interpolymer.
13. The process as claimed in claim 1, wherein said alkene
interpolymer comprises two C.sub.2-8 alkene monomers and at least
one 3-substituted C.sub.4-10 alkene monomer.
14. The process as claimed in claim 1, wherein said alkene
interpolymer has a MFR.sub.21 of greater than 0.01 g/10 min.
15. The process as claimed in claim 1, wherein said alkene
interpolymer is unimodal.
16. The process as claimed in claim 1, wherein said process is
carried out in condensed or supercondensed mode.
17. The process as claimed in claim 1, wherein said alkene
interpolymer comprises less than 1200 ppm by weight of ash.
18. The process as claimed in claim 1, wherein said polymerization
is carried out in a concentration of C.sub.3-8 alkane of lower than
10 mol %.
19. The process as claimed 1, wherein said 3-substituted C.sub.4-10
alkene constitutes more than 5 wt % of a liquid that is
continuously fed to a gas phase polymerization reactor.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of prior U.S.
application Ser. No. 13/145,013, filed Oct. 13, 2011, the
disclosure of which is incorporated herein by reference in its
entirety. The parent application is the National Stage of
PCT/EP10/050,264, filed Jan. 12, 2010, the disclosure of which is
incorporated herein by reference in its entirety. The parent
application claims priority to U.S. Provisional Application No.
61/146,915, filed Jan. 23, 2009, the disclosure of which is
incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a novel, efficient, process
for the preparation of an alkene interpolymer comprising
polymerizing at least one 3-substituted C.sub.4-10 alkene and
another C.sub.2-8 alkene in a gas phase polymerization using a
polymerization catalyst system. The invention also relates to
interpolymers obtainable from the process.
[0004] 2. Description of the Related Art
[0005] Alkenes, such as ethylene, are often copolymerized with
comonomers in order to obtain polymers having particular
properties. Thus it is common to copolymerize ethylene with
comonomers such as 1-hexene or 1-octene in order to obtain a
polymer having, for example, decreased density relative to ethylene
homopolymer. Decreasing the density of the interpolymer generally
impacts positively on a number of its mechanical properties,
potentially making the polymer more useful in a number of end
applications. Thus comonomers are generally used to tailor the
properties of a polymer to suit its target application. There are
vast numbers of commercially available ethylene interpolymers, e.g.
comprising 1-butene, 1-hexene or 1-octene as comonomers.
[0006] A significant proportion of alkene polymer, e.g.
polyethylene, is produced industrially using gas phase
polymerization. Gas phase polymerization has several advantages
over slurry polymerization. First there is no need for a slurry
diluent, which in slurry polymerization is a component that is
present in a large amount in the production plant, but which must
be separated from the polymer at the end of the polymerization
process and recovered and purified for reuse. Second the drying of
the polymer after a gas phase polymerization compared to a slurry
phase polymerization is much simpler. Third polymer powders that
are too sticky to handle in slurry polymerization may behave well
in gas phase polymerization, e.g. polymers having a density of 920
kg/m.sup.3 may be too sticky and soluble to be produced in slurry
polymerization, while corresponding polymers having a density of
910 kg/m.sup.3 may be easily produced in gas phase polymerization.
Fourth, in the case of a multistage process wherein much less
comonomer were to be required in the second step, in the case of a
gas phase reactor, there would be no need to remove comonomer from
the polymer flow between reactors.
[0007] Gas phase polymerization may be carried out using any
conventional polymerization catalyst system, e.g. a Ziegler Natta,
single site or chromium oxide (Phillips-type) containing catalyst
system. The catalyst system chosen is largely dictated by what
properties are desired in the final interpolymer. For example, if
an interpolymer with good processing properties is desired, the
skilled man is likely to choose a Ziegler Natta catalyst or a
chromium oxide catalyst. On the other hand, if the key desired
property of the interpolymer is that it be homogenous, the skilled
man would probably choose a catalyst system comprising a single
site catalyst.
[0008] Regardless of the nature of the polymerization catalyst
system used, when gas phase polymerization is carried out
industrially it is usually conducted as a continuous process
because this is economically most attractive. Thus the
polymerization catalyst system is continuously introduced into the
gas phase reactor along with the appropriate monomers, whilst the
desired polymer is continuously removed. The continuous addition of
fresh catalyst system is necessary because when the desired
polyalkene is removed from the reactor system, a certain amount of
catalyst system is also removed. It is thus important to provide
additional catalyst system in order to maintain the polymerization
reaction.
[0009] A disadvantage of this manufacturing set up, however, is
that the catalyst system that is removed from the reactor with the
desired polymer cannot usually be separated therefrom. Rather the
catalyst system will typically be present within the polymer in the
form of a partially modified residue. In other words, the catalyst
system is present in the polyalkene as an impurity.
[0010] The presence of catalyst system residues in polymers such as
polyethylene is undesirable for a number of reasons, e.g. [0011]
they make processing, e.g. to fibers or films difficult if the
residues make particles of the same size or greater than the fiber
or film thickness [0012] they reduce the performance of the polymer
in its end use, e.g. it can reduce the optical performance of films
made using the polymer by making visually observable
inhomogeneities in the film, often called gels, specs or fish eyes
[0013] they can render polymers unsuitable for use in applications
where the level of impurities present therein is required to be
below a certain standard, e.g. in food and/or medical applications
[0014] they, through their content of transition metals, can act as
accelerators for polymer degradation resulting eventually in
discoloration and loss of mechanical strength.
[0015] It is thus generally desirable to try to minimize the amount
of catalyst system needed to make a given amount of polymer. This
helps overcome the above-mentioned problems in processing and use
and also decreases the production cost of the polymer through
reduced catalyst system cost per ton polymer. It also minimizes any
safety risks associated with the handling of catalytic materials.
Additionally the ability to use a lesser amount of catalyst system
per kg of final polymer in some cases enables production plants to
increase their production rate without having to increase their
reactor size.
[0016] There are a number of known methods that usually would
increase catalyst system productivity (i.e. ton polymer/kg catalyst
system) for a given catalyst system. These include increasing the
residence time in the reactor, increasing the polymerization
temperature, increasing the partial pressure of monomer and/or the
partial pressure of comonomer. All of these approaches, however,
suffer from serious drawbacks.
[0017] Increasing the residence time can only be done by decreasing
production rate, which is economically unfavorable, or by
increasing polymer concentration in the reactor which may easily
lead to fouling and/or lumps in the reactor and ultimately to a
long stop for cleaning. Increasing the partial pressure of monomer
has a negative effect on production economy by reducing the
relative conversion of monomer. Increasing the partial pressure of
comonomer increases the incorporation of comonomer and thus, in
effect, leads to the production of a different interpolymer to the
one targeted. Increasing the polymerization temperature from the
usual operation temperature is probably the most common strategy
employed to date, but as with increasing the residence time it can
lead to reactor sheeting or lumping or chunking in the reactor and
again to a long stop for cleaning the reactor system.
BRIEF DESCRIPTION OF DRAWINGS
[0018] FIG. 1 is a plot of catalyst system activity coefficient
versus polyethylene density for a polymerization carried out with a
single site catalyst.
[0019] FIG. 2 is a plot of catalyst system activity coefficient
versus polyethylene density for a polymerization carried out with a
Ziegler Natta catalyst.
DETAILED DESCRIPTION OF THE INVENTION
[0020] In view of the drawbacks of the background art, there is a
need for alternative polymerization processes for the preparation
of alkene polymers and, in particular, alkene interpolymers that
enable the amount of catalyst system needed to make a given amount
of polymer to be minimized. Processes that enable the reaction to
be carried out under conventional gas phase polymerization
conditions (i.e. typical temperature and pressure conditions) as
well as in existing gas phase reactors are especially desired.
[0021] It has now been surprisingly found that the productivity
(i.e. ton polymer/kg catalyst system) of polymerization catalyst
system in the gas phase polymerization of 1-alkenes such as
ethylene is significantly increased by using a 3-substituted
C.sub.4-10 alkene as comonomer rather than a conventional
non-substituted, linear C.sub.4-10 alkene. As a result, a
significantly lower amount of catalyst system can be used to
manufacture a given amount of an interpolymer comprising the
3-substituted C.sub.4-10 alkene (i.e. catalyst system productivity
is significantly increased). Advantageously the major properties of
a 1-alkene/3-substituted C.sub.4-10 alkene interpolymer (e.g.
MFR.sub.2, density, melting point, Mw, Mn and molecular weight
distribution) may be maintained on a comparable level to the
properties of the conventional 1-alkene/non-substituted, linear
C.sub.4-10 alkene interpolymer. Thus the process herein described
offers an economically attractive approach for making interpolymers
that can be used as substitutes for the ethylene/1-hexene and
ethylene/1-octene copolymers commercially available.
[0022] Copolymers comprising ethylene and 3-methyl-but-1-ene have
previously been described in the prior art, e.g. in WO2008/006636,
EP-A-0058549 and WO2008/003020. None of these documents, however,
specifically disclose a gas phase copolymerisation of
3-methyl-but-1-ene with another C.sub.2-8 alkene. Rather
WO2008/006636 is focused on the slurry polymerization of ethylene
and 3-methyl-but-1-ene and, in particular, on slurry polymerization
using a non-supported catalyst system. Slurry polymerization with a
non-supported catalyst system is preferred because the catalyst
system has a higher activity in slurry conditions and the need for
a support can be avoided.
[0023] EP-A-0058549 describes a Ziegler Natta catalyst for the
polymerization of ethylene including its copolymerisation with
other olefins. A list of comonomers is mentioned in the description
of EP-A-0058549 but there is no disclosure therein of a
3-substituted C.sub.4-10 alkene such as 3-methyl-1-butene.
Nevertheless one of the examples in the experimental section
(example 51) of EP-A-0058549 illustrates the slurry phase
copolymerisation of ethylene and 3-methyl-1-butene. The results in
Table 5, however, show that the Ziegler Natta catalytic activity is
less when 3-methyl-1-butene is used as comonomer relative to the
use of 1-hexene or 1-octene as comonomer.
[0024] WO 2008/003020 is focused on the production of films having
specific properties such as dart drop impact strength and moisture
vapor transmission rate. Few details are given in the examples of
WO 2008/003020 as to how the polymers processed into films are
prepared. Certainly there is no mention in the examples of WO
2008/003020 of the manufacture of the polymers by gas phase
polymerization.
[0025] Accordingly, none of the above-mentioned documents teach or
disclose that the catalytic productivity of a polymerization
catalyst system in a gas phase copolymerisation of a C.sub.2-8
alkene such as ethylene may be significantly increased by utilizing
3-methyl-but-1-ene as comonomer, rather than conventional
comonomers such as 1-butene, 1-hexene or 1-octene.
[0026] In a first aspect, the present invention provides a process
for the preparation of an alkene interpolymer comprising
polymerizing at least one 3-substituted C.sub.4-10 alkene and at
least one C.sub.2-8 alkene in a gas phase polymerization using a
polymerization catalyst system.
[0027] In a preferred embodiment of the process of the present
invention the polymerization catalyst system is in particulate
form. Particularly preferably the catalyst system comprises a
carrier.
[0028] In a further preferred embodiment of the process of the
present invention the polymerization catalyst system comprises a
single site catalyst or a Ziegler Natta catalyst, especially a
single site catalyst.
[0029] In a further aspect, the present invention provides an
alkene interpolymer obtainable by a process as hereinbefore
described.
[0030] In a further preferred embodiment, the present invention
provides a process of increasing the productivity of a gas phase
polymerization comprising polymerizing at least one 3-substituted
C.sub.4-10 alkene with another C.sub.2-8 alkene.
[0031] In another aspect, the present invention provides the use of
a 3-substituted C.sub.4-10 alkene in the preparation of a C.sub.2-8
alkene interpolymer by gas phase polymerization.
[0032] In a further preferred embodiment, the present invention
provides a process of gas phase polymerization comprising
polymerizing a 3-substituted C.sub.4-10 alkene and optionally
another C.sub.2-8 alkene using a polymerization catalyst system,
wherein said polymerization is carried out in a concentration of
C.sub.3-8 saturated hydrocarbon (e.g. C.sub.3-8 alkane) of lower
than 10 mol %.
[0033] In a preferred embodiment, the polymerization is carried out
in condensed mode or supercondensed mode.
[0034] In a further preferred embodiment, the present invention
provides a process of 3-substituted C.sub.4-10 alkene in a gas
phase polymerization, wherein said alkene constitutes more than 5
wt % of a liquid (e.g. a vaporizable liquid) that is continuously
fed to the gas phase polymerization reactor.
DEFINITIONS
[0035] As used herein, the term "alkene interpolymer" refers to
polymers comprising repeat units deriving from at least one
3-substituted C.sub.4-10 alkene monomer and at least one other
C.sub.2-8 alkene. Preferred interpolymers are binary (i.e.
preferred interpolymers are copolymers) and comprise repeat units
deriving from one type of 3-substituted C.sub.4-10 alkene comonomer
and one other type of C.sub.2-8 alkene monomer. Other preferred
interpolymers are ternary, e.g. they comprise repeat units deriving
from one type of 3-substituted C.sub.4-10 alkene comonomer and two
types of C.sub.2-8 alkene monomer. Particularly preferred
interpolymers are copolymers. In preferred interpolymers at least
0.01% wt, still more preferably at least 0.1% wt, e.g. at least
0.5% wt of each monomer is present based on the total weight of the
interpolymer.
[0036] In contrast the term "alkene homopolymer" as used herein,
refers to polymers which consist essentially of repeat units
deriving from one type of C.sub.2-8 alkene, e.g. ethylene.
Homopolymers may, for example, comprise at least 99.9% wt e.g. at
least 99.99% wt of repeat units deriving from one type of C.sub.2-8
alkene based on the total weight of the polymer.
[0037] As used herein, the term "3-substituted C.sub.4-10 alkene"
refers to an alkene having: (i) a backbone containing 4 to 10
carbon atoms, wherein the backbone is the longest carbon chain in
the molecule that contains an alkene double bond, and (ii) a
substituent (i.e. a group other than H) at the 3 position.
[0038] Gas phase polymerization is a term of the art and is readily
understood by the skilled man. As used herein, the terms "condensed
mode" and "supercondensed mode" refer to gas phase polymerization
wherein a vaporizable liquid is continuously fed to the
reactor.
[0039] As used herein, the term "catalyst system" refers to the
total active entity that catalyses the polymerization reaction.
Typically the catalyst system is a coordination catalyst system
comprising a transition metal compound (the active site precursor)
and an activator (sometimes referred to as a cocatalyst) that is
able to activate the transition metal compound. The catalyst system
of the present invention preferably comprises an activator, at
least one transition metal active site precursor and a particle
building material that may be the activator or another material.
Preferably, the particle building material is a carrier.
[0040] As used herein, the term "multisite catalyst system" refers
to a catalyst system comprising at least two different active sites
deriving from at least two chemically different active site
precursors. Examples of a multisite catalyst system are one
comprising two or three different metallocene active sites
precursors, one comprising two or three different Ziegler Natta
active site precursors or one comprising a Ziegler Natta active
site and a metallocene active site. If there are only two active
sites in the catalyst system, it can be called a dual site catalyst
system. Particulate multisite catalyst systems may contain its
different active sites in a single type of catalyst particle.
Alternatively, each type of active site may each be contained in
separate particles. If all the active sites of one type are
contained in separate particles of one type, each type of particles
may enter the reactor through its own inlet.
[0041] As used herein, the term "single site catalyst" refers to a
catalyst having one type of active catalytic site. An example of a
single site catalyst is a metallocene-containing catalyst. A
typical Ziegler Natta (ZN) catalyst made from, e.g. impregnation of
TiCl.sub.4 into a carrier material, or chromium oxide (Philips)
catalyst made from, e.g. impregnation of chromium oxide into
silica, are not single site catalysts as they contain a mixture of
different types of sites that give rise to polymer chains of
different composition.
[0042] As used herein, the term "Ziegler Natta (ZN)" catalyst
refers to a catalyst that preferably comprises a transition metal
component (e.g. Ti) which is sigma bonded to its ligands and an
activator (e.g. an Al containing organometallic compound).
Preferred Ziegler Natta catalysts additionally comprise a particle
building material.
[0043] As used herein, the term "polymerization section" refers to
all of the polymerization reactors present in a multistage
polymerization. The term also encompasses any prepolymerization
reactors that are used.
[0044] As used herein, the term "multimodal" refers to a polymer
comprising at least two components, which have been produced under
different polymerization conditions and/or by a multisite catalyst
system in one stage and/or by using two or more different catalyst
systems in a polymerization stage resulting in different (weight
average) molecular weights and molecular weight distributions for
the components. The prefix "multi" refers to the number of
different components present in the polymer. Thus, for example, a
polymer consisting of two components only is called "bimodal". The
form of the molecular weight distribution curve, i.e. the
appearance of the graph of the polymer weight fraction as a
function of its molecular weight, of a multimodal polyalkene will
show two or more maxima or at least be distinctly broadened in
comparison with the curves for the individual components. In
addition, multimodality may show as a difference in melting or
crystallisation temperature of components.
[0045] In contrast a polymer comprising one component produced
under constant polymerization conditions is referred to herein as
unimodal.
[0046] C.sub.2-8 Alkene
[0047] In order to produce an interpolymer the C.sub.2-8 alkene
should be a different alkene to the alkene used as the
3-substituted C.sub.4-10 alkene. One or more (e.g. two or three)
C.sub.2-8 alkenes may be used. Preferably, however, one or two,
e.g. one, C.sub.2-8 alkene is used.
[0048] Preferably, the C.sub.2-8 alkene is a monoalkene. Still more
preferably the C.sub.2-8 alkene is a terminal alkene. In other
words, the C.sub.2-8 alkene is preferably unsaturated at carbon
numbers 1 and 2. Preferred C.sub.2-8 alkene are thus C.sub.2-8
alk-1-enes.
[0049] The C.sub.2-8 alkene is preferably a linear alkene. Still
more preferably the C.sub.2-8 alkene is an unsubstituted C.sub.2-8
alkene.
[0050] Representative examples of C.sub.2-8 alkenes that are
suitable for use in the process of the present invention include
ethylene, propylene, 1-butene, 1-pentene, 4-methyl-1-pentene,
1-hexene and 1-octene. Preferably, the C.sub.2-8 alkene is selected
from ethylene, propylene, 1-butene, 4-methyl-1-pentene or mixtures
therefore. Particularly preferably the C.sub.2-8 alkene is ethylene
or propylene, e.g. ethylene.
[0051] C.sub.2-8 alkenes for use in the present invention are
commercially available. Alternatively, ethylene, propylene and
but-1-ene may be prepared by thermal cracking. Higher linear
olefins are available from catalytic oligomerization of ethylene or
by Fischer Tropsch synthesis.
[0052] 3-Substituted C.sub.4-10 Alkene
[0053] It has been found that the gas phase polymerization of the
above-described C.sub.2-8 alkene with 3-substituted C.sub.4-10
alkene occurs with unexpectedly high efficiency (i.e. excellent
catalytic productivity). It has also been found that to provide a
polymer of any given density, less 3-substituted C.sub.4-10 alkene
needs to be included therein than 1-hexene or 1-octene. This is
advantageous as the cost of comonomers such as 1-hexene, 1-octene
or 3-substituted C.sub.4-10 alkene is much greater than the cost of
ethylene or propylene.
[0054] Preferably, the substituent present at carbon 3 of the
3-substituted C.sub.4-10 alkene is a C.sub.1-6 alkyl group. The
alkyl group may be substituted by non-hydrocarbyl substituents or
unsubstituted. Representative examples of non-hydrocarbyl
substituents that may be present on the alkyl group include F and
Cl. Preferably, however, the C.sub.1-6 alkyl group is
unsubstituted. Particularly preferably the substituent group
present at carbon 3 is a C.sub.1-3 alkyl group such as methyl,
ethyl or iso-propyl. Methyl is an especially preferred substituent
group.
[0055] Preferably, the 3-substituted C.sub.4-10 alkene is solely
substituted at carbon 3. If, however, a substituent is present at
another position it is preferably a C.sub.1-6 alkyl group as
described above for the substituent present at carbon 3.
[0056] The 3-substituted C.sub.4-10 alkene is preferably a
monoalkene. Still more preferably the 3-substituted C.sub.4-10
alkene is a terminal alkene. In other words, the 3-substituted
C.sub.4-10 alkene is preferably unsaturated at carbon numbers 1 and
2. Preferred 3-substituted C.sub.4-10 alkenes are thus
3-substituted C.sub.4-10 alk-1-enes.
[0057] Preferred 3-substituted C.sub.4-10 alkenes for use in the
process of the present invention are those of formula (I):
##STR00001##
wherein R.sup.1 is a substituted or unsubstituted, preferably
unsubstituted, C.sub.1-6 alkyl group and n is an integer between 0
and 6.
[0058] In preferred compounds of formula (I) R.sup.1 is methyl or
ethyl, e.g. methyl. In further preferred compounds of formula (I) n
is 0, 1 or 2, still more preferably 0 or 1, e.g. 0.
[0059] Representative examples of compounds of formula (I) that can
be used in the process of the present invention include
3-methyl-1-butene, 3-methyl-1-pentene, 3-methyl-1-hexene,
3-ethyl-1-pentene and 3-ethyl-1-hexene. A particularly preferred
3-substituted C.sub.4-10 alkene for use in the process of the
present invention is 3-methyl-1-butene.
[0060] 3-substituted C.sub.4-10 alkenes for use in the invention
are commercially available, e.g. from Sigma-Aldrich.
3-methyl-1-butene can be made, e.g. according to WO
2008/006633.
[0061] Catalyst System
[0062] The polymerization catalyst system used in the gas phase
polymerization is preferably in the form of a particulate.
Preferably, the catalyst system is in the form of particles having
a weight average particle size of 0.5 to 250 microns, preferably 4
to 150 microns. Particularly preferably the polymerization catalyst
system comprises a carrier. Suitable carrier materials are known to
the skilled man in the art but are discussed in more detail
below.
[0063] The polymerization catalyst system used in the gas phase
polymerization preferably comprises a Ziegler Natta catalyst, a
single site catalyst or a chromium oxide catalyst, more preferably
a single site catalyst. Preferred single site catalysts comprise a
metallocene.
[0064] Single Site Catalyst System
[0065] The catalyst system comprising a single site catalyst that
may be used in the process of the present invention is preferably a
metallocene-containing catalyst system. Such catalyst systems are
well known in the art, e.g. from WO98/02246, the contents of which
are hereby incorporated herein by reference.
[0066] The catalyst system may be supported or unsupported, but is
preferably supported. Supported catalyst systems may be prepared by
impregnating the active site precursors into it. Alternatively, the
catalyst system may be synthesized by producing the solid particles
from liquid starting material components directly, without a
separate impregnation step. Preferred catalyst systems comprising a
single site catalyst comprise a carrier.
[0067] The catalyst system comprising a single site catalyst
preferably comprises a carrier, an activator and at least one
transition metal active site precursor (e.g. a metallocene). The
activator may be aluminoxane, borane or borate but preferably is
aluminoxane. Preferably, the active site precursor is a
metallocene.
[0068] Catalyst Morphology and Carrier
[0069] The catalyst system comprising a single site catalyst used
in the process of the present invention is preferably in
particulate form. Preferably, the catalyst system is in the form of
particles having a weight average particle size of 1 to 250
microns, preferably 4 to 150 microns. Preferably, the catalyst
system is in the form of a free-flowing powder.
[0070] Suitable carrier materials for use in the catalyst system
comprising a single site catalyst are well known in the art. The
carrier material is preferably an inorganic material, e.g. an oxide
of silicon and/or of aluminium or MgCl.sub.2. Preferably, the
carrier is an oxide of silicon and/or aluminium. Still more
preferably the carrier is silica.
[0071] Preferably, the carrier particles have an average particle
size of 1 to 500 microns, preferably 3 to 250 microns, e.g. 10 to
150 microns. Particles of appropriate size can be obtained by
sieving to eliminate oversized particles. Sieving can be carried
out before, during or after the preparation of the catalyst system.
Preferably, the particles are spherical. The surface area of the
carrier is preferably in the range 5 to 1200 m.sup.2/g, more
preferably 50 to 600 m.sup.2/g. The pore volume of the carrier is
preferably in the range 0.1 to 5 cm.sup.3/g, preferably 0.5-3.5
cm.sup.3/g.
[0072] Preferably, the carrier is dehydrated prior to use.
Particularly preferably the carrier is heated at 100 to 800.degree.
C., more preferably 150 to 700.degree. C., e.g. at about
250.degree. C. prior to use. Preferably, dehydration is carried out
for 0.5-12 hours.
[0073] Carriers that are suitable for the preparation of the
catalyst systems herein described are commercially available, e.g.
from Grace and PQ Corporation.
[0074] Activator
[0075] Aluminoxane is preferably present in the catalyst system as
activator. The aluminoxane is preferably oligomeric. Still more
preferably the aluminoxane is a cage-like (e.g. multicyclic)
molecule, e.g. with an approximate formula
(Al.sub.1.4R.sub.0.8O).sub.n where n is 10-60 and R is an alkyl
group, e.g. a C.sub.1-20 alkyl group. In preferred aluminoxanes R
is a C.sub.1-8 alkyl group, e.g. methyl. Methylaluminoxane (MAO) is
a mixture of oligomers with a distribution of molecular weights,
preferably with an average molecular weight of 700 to 1500. MAO is
a preferred aluminoxane for use in the catalyst system.
[0076] The aluminoxane may be modified with an aluminium alkyl or
aluminium alkoxy compound. Especially preferred modifying compounds
are aluminium alkyls, in particular, aluminium trialkyls such as
trimethyl aluminium, triethyl aluminium and tri isobutyl aluminium.
Trimethyl aluminium is particularly preferred.
[0077] Aluminoxanes, such as MAO, that are suitable for the
preparation of the catalyst systems herein described are
commercially available, e.g. from Albemarle and Chemtura.
[0078] It is also possible to generate the activator in situ, e.g.
by slow hydrolysis of trimethylaluminium inside the pores of a
carrier. This process is well known in the art.
[0079] Alternatively, activators based on boron may be used.
Preferred boron based activators are those wherein the boron is
attached to at least 3 fluorinated phenyl rings as described in EP
520 732.
[0080] Alternatively, an activating, solid surface as described in
U.S. Pat. No. 7,312,283 may be used as a carrier. These are solid,
particulate inorganic oxides of high porosity which exhibit Lewis
acid or Bronsted acidic behavior and which have been treated with
an electron-withdrawing component, typically an anion, and which
have then been calcined.
[0081] Transition Metal Active Site Precursor
[0082] Generally the metal of the transition metal precursors are
16-electron complexes, although they may sometimes comprise fewer
electrons, e.g. complexes of Ti, Zr or Hf.
[0083] The active site transition metal precursor is preferably a
metallocene.
[0084] The metallocene preferably comprises a metal coordinated by
one or more .eta.-bonding ligands. The metal is preferably Zr, Hf
or Ti, especially Zr or Hf. The .eta.-bonding ligand is preferably
a .eta..sup.5-cyclic ligand, i.e. a homo or heterocyclic
cyclopentadienyl group optionally with fused or pendant
substituents.
[0085] The metallocene preferably has the formula:
(Cp).sub.mL.sub.nMX.sub.p
wherein Cp is an unsubstituted or substituted cyclopentadienyl
group, an unsubstituted or substituted indenyl or an unsubstituted
or substituted fluorenyl (e.g. an unsubstituted or substituted
cyclopentadienyl group);
[0086] the optional one or more substituent(s) being independently
selected from halogen (e.g. Cl, F, Br, I), hydrocarbyl (e.g.
C.sub.1-20 alkyl, C.sub.2-20 alkenyl, C.sub.2-20 alkynyl,
C.sub.6-20 aryl or C.sub.6-20 arylalkyl), C.sub.3-12 cycloalkyl
which contains 1, 2, 3 or 4 heteroatom(s) in the ring moiety,
C.sub.6-20 heteroaryl, C.sub.1-20 haloalkyl, --SiR''.sub.3,
--OSiR''.sub.3, --SR'', --PR''.sub.2 or --NR''.sub.2,
[0087] each R'' is independently a H or hydrocarbyl, e.g. e.g.
C.sub.1-20 alkyl, C.sub.2-20 alkenyl, C.sub.2-20 alkynyl,
C.sub.6-20 aryl or C.sub.6-20 arylalkyl; or in the case of --NR'',
the two R'' can form a ring, e.g. a 5 or 6 membered ring, together
with the nitrogen atom to which they are attached;
[0088] L is a bridge of 1-7 atoms, e.g. a bridge of 1-4 C atoms and
0-4 heteroatoms, wherein the heteroatom(s) can be, e.g. Si, Ge
and/or O atom(s), wherein each of the bridge atoms may
independently bear substituents (e.g. C.sub.1-20 alkyl,
tri(C.sub.1-20 alkyl)silyl, tri(C.sub.1-20alkyl)siloxy or
C.sub.6-20 aryl substituents); or a bridge of 1-3, e.g. one or two,
heteroatoms, such as Si, Ge and/or O atom(s), e.g. --SiR'''.sub.2,
wherein each R''' is independently C.sub.1-20 alkyl, C.sub.6-20
aryl or tri(C.sub.1-20alkyl)silyl residue such as
trimethylsilyl;
[0089] M is a transition metal of Group 3 to 10, preferably of
Group 4 to 6, such as Group 4, e.g. titanium, zirconium or hafnium,
preferably hafnium,
[0090] each X is independently a sigma ligand such as halogen (e.g.
Cl, F, Br, I), hydrogen, C.sub.1-20 alkyl, C.sub.1-20 alkoxy,
C.sub.2-20 alkenyl, C.sub.2-20 alkynyl, C.sub.3-12 cycloalkyl,
C.sub.6-20 aryl, C.sub.6-20 aryloxy, C.sub.7-20 arylalkyl,
C.sub.7-20 arylalkenyl, --SR'', --PR''.sub.3, --SiR''.sub.3,
--OSiR''.sub.3, --NR''.sub.2, or CH.sub.2--Y wherein Y is
C.sub.6-20 aryl, C.sub.6-20 heteroaryl, C.sub.1-20 alkoxy,
C.sub.6-20 aryloxy, --NR''.sub.2, --SR'', --PR''.sub.3,
--SiR''.sub.3 or --OSiR''.sub.3; alternatively, two X ligands are
bridged to provide a bidentate ligand on the metal, e.g.
1,3-pentadiene;
[0091] each of the above mentioned ring moieties alone or as part
of another moiety as the substituent for Cp, X, R'' or R''' can be
further substituted, e.g. with C.sub.1-20 alkyl which may contain
Si and/or O atom(s);
[0092] m is 1, 2 or 3, preferably 1 or 2, more preferably 2;
[0093] n is 0, 1 or 2, preferably 0 or 1;
[0094] p is 1, 2 or 3 (e.g. 2 or 3); and the sum of m+p is equal to
the valence of M (e.g. when M is Zr, Hf or Ti, the sum of m+p
should be 4).
[0095] Preferably, Cp is a cyclopentadienyl group, especially a
substituted cyclopentadienyl group. Preferred substituents on Cp
groups, including cyclopentadienyl, are C.sub.1-20 alkyl.
Preferably, the cyclopentadienyl group is substituted with a
straight chain C.sub.1-6 alkyl group, e.g. n-butyl.
[0096] If present L is preferably a methylene, ethylene or silyl
bridge whereby the silyl can be substituted as defined above, e.g.
a (dimethyl)Si.dbd., (methylphenyl)Si.dbd. or
(trimethylsilylmethyl)Si.dbd.; n is 1; m is 2 and p is 2. When L is
a silyl bridge, R'' is preferably other than H. More preferably,
however, n is 0.
[0097] X is preferably H, halogen, C.sub.1-20 alkyl or C.sub.6-20
aryl. When X are halogen atoms, they are preferably selected from
fluorine, chlorine, bromine and iodine. Most preferably X is
chlorine. When X is a C.sub.1-20 alkyl group, it is preferably a
straight chain or branched C.sub.1-8 alkyl group, e.g. a methyl,
ethyl, n-propyl, n-hexyl or n-octyl group. When X is an C.sub.6-20
aryl group, it is preferably phenyl or benzyl. In preferred
metallocenes X is a halogen, e.g. chlorine.
[0098] Suitable metallocene compounds include:
[0099] bis(cyclopentadienyl)metal dihalides,
bis(cyclopentadienyl)metal hydridohalides,
bis(cyclopentadienyl)metal monoalkyl monohalides,
bis(cyclopentadienyl)metal dialkyls and bis(indenyl)metal dihalides
wherein the metal is zirconium or hafnium, preferably hafnium,
halide groups are preferably chlorine and alkyl groups are
preferably C.sub.1-6 alkyl.
[0100] Representative examples of metallocenes include:
[0101] bis(cyclopentadienyl)ZrCl.sub.2,
bis(cyclopentadienyl)HfCl.sub.2, bis(cyclopentadienyl)ZrMe.sub.2,
bis(cyclopentadienyl)HfMe.sub.2, bis(cyclopentadienyl)Zr(H)Cl,
bis(cyclopentadienyl)Hf(H)Cl,
bis(n-butylcyclopentadienyl)ZrCl.sub.2,
bis(n-butylcyclopentadienyl)HfCl.sub.2,
bis(n-butylcyclopentadienyl)ZrMe.sub.2,
bis(n-butylcyclopentadienyl)HfMe.sub.2,
bis(n-butylcyclopentadienyl)Zr(H)Cl,
bis(n-butylcyclopentadienyl)Hf(H)Cl,
bis(pentamethylcyclopentadienyl)ZrCl.sub.2,
bis(pentamethylcyclopentadienyl)HfCl.sub.2,
bis-(1,3-dimethylcyclopentadienyl)ZrCl.sub.2,
bis(4,5,6,7-tetrahydro-1-indenyl)ZrCl.sub.2 and
ethylene-[bis(4,5,6,7-tetrahydro-1-indenyl)ZrCl.sub.2.
[0102] Alternatively, the metallocene may be a constrained geometry
catalyst (CGC). These comprise a transition metal, M (preferably
Ti) with one eta-cyclopentadienyl ligand and two X groups, i.e. be
of the formula CpMX.sub.2, wherein X is as defined above and the
cyclopentadienyl has a --Si(R'').sub.2N(R'')-- substituent wherein
R'' is as defined above and the N atom is bonded to M. Preferably,
R'' is C.sub.1-20 alkyl. Preferably, the cyclopentadienyl ligand is
substituted with 1 to 4, preferably 4, C.sub.1-20 alkyl groups.
Examples of metallocenes of this type are described in US
2003/0022998, the contents of which are hereby incorporated by
reference.
[0103] The preparation of metallocenes can be carried out according
to, or analogously to, the methods known from the literature and is
within the skills of a polymer chemist.
[0104] Other types of single site precursor compounds are described
in:
[0105] G. J. P. Britovsek et al.: The Search for New-Generation
Olefin Polymerization Catalysts: Life beyond Metallocenes, Angew.
Chemie Int. Ed., 38 (1999), p. 428.
[0106] H. Makio et al.: FI Catalysts: A New Family of High
Performance Catalysts for Olefin Polymerization, Advanced Synthesis
and Catalysis, 344 (2002), p. 477.
[0107] Dupont-Brookhart type active site precursors are disclosed
in U.S. Pat. No. 5,880,241.
[0108] Catalyst System Preparation
[0109] To form the catalyst systems for use in the present
invention, the carrier, e.g. silica, is preferably dehydrated (e.g.
by heating). The further preparation of the catalyst system is
preferably undertaken under anhydrous conditions and in the absence
of oxygen and water. The dehydrated carrier is then preferably
added to a liquid medium to form a slurry. The liquid medium is
preferably a hydrocarbon comprising 5 to 20 carbon atoms, e.g.
pentane, isopentane, hexane, isohexane, heptane, octane, nonane,
decane, dodecane, cyclopentane, cyclohexane, cycloheptane, toluene
and mixtures thereof. Isomers of any of the afore-mentioned
hydrocarbons may also be used. The volume of the liquid medium is
preferably sufficient to fill the pores of the carrier, and more
preferably to form a slurry of the carrier particles. Typically the
volume of the liquid medium will be 2 to 15 times the pore volume
of the support as measured by nitrogen adsorption method (BET
method). This helps to ensure that a uniform distribution of metals
on the surface and pores of the carrier is achieved.
[0110] In a separate vessel, the metallocene may be mixed with
aluminoxane in a solvent. The solvent may be a hydrocarbon
comprising 5 to 20 carbon atoms, e.g. toluene, xylene,
cyclopentane, cyclohexane, cycloheptane, pentane, isopentane,
hexane, isohexane, heptane, octane or mixtures thereof. Preferably,
toluene is used. Preferably, the metallocene is simply added to the
toluene solution in which the aluminoxane is present in its
commercially available form. The volume of the solvent is
preferably about equal to or less than the pore volume of the
carrier. The resulting mixture is then mixed with the carrier,
preferably at a temperature in the range 0 to 60.degree. C.
Impregnation of the metallocene and aluminoxane into the carrier is
preferably achieved using agitation. Agitation is preferably
carried out for 15 minutes to 12 hours. Alternatively, the carrier
may be impregnated with aluminoxane first, followed by metallocene.
Simultaneous impregnation with aluminoxane and metallocene is,
however, preferred.
[0111] The solvent and/or liquid medium are typically removed by
filtering and/or decanting and/or evaporation, preferably by
evaporation only. Optionally, the impregnated particles are washed
with a hydrocarbon solvent to remove extractable metallocene and/or
aluminoxane. Removal of the solvent and liquid medium from the
pores of the carrier material is preferably achieved by heating
and/or purging with an inert gas. Removal of the solvent and liquid
medium is preferably carried out under vacuum. Preferably, the
temperature of any heating step is below 80.degree. C., e.g.
heating may be carried out at 40-70.degree. C. Typically heating
may be carried out for 2 to 24 hours. Alternatively, the catalyst
system particles may remain in a slurry form and used as such when
fed to the polymerization reactor, however, this is not
preferred.
[0112] The metallocene and aluminoxane loading on the carrier is
such that the amount of aluminoxane (dry), on the carrier ranges
from 10 to 90% wt, preferably from 15 to 50% wt, still more
preferably from 20 to 40% wt based on the total weight of dry
catalyst. The amount of transition metal on the carrier is
preferably 0.005-0.2 mmol/g of dry catalyst, still more preferably
0.01-0.1 mmol/g of dry catalyst.
[0113] The molar ratio of Al:transition metal in the catalyst
system (dry) may range from 25 to 10,000, usually within the range
of from 50 to 980 but preferably from 70 to 500 and most preferably
from 100 to 350.
[0114] Particulate catalyst system can also be made using a boron
activator instead of aluminoxane activator, e.g. as described in
U.S. Pat. No. 6,787,608. In its example 1, an inorganic carrier is
dehydrated, then surface modified by alkylaluminum impregnation,
washed to remove excess alkylaluminum and dried. Subsequently the
carrier is impregnated with an about equimolar solution of boron
activator and trialkylaluminum, then mixed with a metallocene
precursor, specifically a CGC metallocene, then filtered, washed
and dried.
[0115] Also U.S. Pat. No. 6,350,829 describes the use of boron
activator, but using mainly bis metallocene complexes as active
site precursors. The dried metal alkyl-treated carrier is
co-impregnated with a mixture of the metallocene and the boron
activator (without additional metal alkyl), and then the volatiles
removed.
[0116] The support material may also be mixed with the metallocene
solution just before polymerization. U.S. Pat. No. 7,312,283
describes such a process. A porous metal oxide particulate material
is impregnated with ammonium sulphate dissolved in water, and then
calcined in dry air, kept under nitrogen, then mixed with a
hydrocarbon liquid. Separately a solution was prepared by mixing
metallocene with 1-alkene, and then mixing in metal alkyl.
Polymerization was done in a continuous slurry reactor, into which
both the sulphated particulate metal oxide and the metallocene
solution were fed continuously, in such a way that the two feed
streams were mixed immediately before entering the reactor. Thus
the treated metal oxide functions both as an activator as well as a
catalyst support.
[0117] Alternative methods of supporting single site catalysts via
a preformed carrier and aluminoxane are given in EP 279 863, WO
93/23439, EP 793 678, WO 96/00245, WO 97/29134
[0118] Alternative methods of supporting single site catalysts via
preformed carriers and boron activators are given in WO 91/09882
and WO 97/31038.
[0119] Methods of obtaining particulate catalyst systems without
employing preformed carriers are given in EP 810 344 and EP 792
297.
[0120] Ziegler Natta Catalyst System
[0121] The Ziegler Natta catalyst system preferably comprises a
transition metal component and an activator. Preferably, the
transition metal component, when added to the polymerization
reaction is contained within solid particles. Still more
preferably, at least some activator (sometimes referred to as a
cocatalyst) is added to the polymerization as a liquid or
solution.
[0122] Catalyst System Particles
[0123] Transition Metal Component
[0124] The active site of the catalyst system is a transition
metal. Group 4 or 5 transition metals are preferred, particularly
Group 4 metals, and especially Ti. In particularly preferred
Ziegler Natta catalysts only Group 4 transition metals (e.g. Ti)
are present.
[0125] During preparation of the catalyst system it is preferred to
use transition metals in the form of alkoxy or halide compounds,
especially chlorides. Particularly preferably Ti, at the stage of
its introduction into the catalyst system preparation process, is
provided as TiCl.sub.4.
[0126] The content of transition metal in the final solid catalyst
based on the weight of dry, solid, catalyst component is preferably
0.1-5 mmol/g.
[0127] Preferably, the final solid catalyst particles also comprise
a group 2 metal, preferably a magnesium compound, still more
preferably a Mg--Cl compound, e.g. MgCl.sub.2.
[0128] The magnesium compound may be introduced into the catalyst
preparation as the Mg--Cl (e.g. MgCl.sub.2 compound itself), but it
is preferred to make it in situ within the catalyst preparation
procedure to endure a high degree of dispersion, contact with the
transition metal and porosity. The skilled man is aware of how to
carry out such an in situ reaction.
[0129] The content of Mg in the final solid catalyst based on the
weight of dry, solid, catalyst component is preferably 1-25 wt
%.
[0130] Particle Building Material
[0131] The particle building material present in the catalyst
system comprising a Ziegler Natta catalyst may be an inorganic
oxide support such as silica, alumina, titania, silica-alumina and
silica-titania or may be Mg or Ca compounds such as chlorides,
oxychlorides, alkyls or alkoxides or metal salts with organic
anions. Preferably, however, the material is silica or MgCl.sub.2
with optional other components.
[0132] The particle building material preferably comprises 30-90 wt
% of the final, dry, solid catalyst. If the particle building
material comprises Mg--Cl compounds, then typically the building
material will also function as the magnesium compound hereinbefore
described. If the particle building material is a metal oxide, the
metal oxide particles typically define the final catalyst system
outer morphology and the other components of the catalyst system
will be synthesized inside its pores.
[0133] Preformed carriers that are suitable for the preparation of
Ziegler Natta catalyst systems are commercially available, e.g.
from Grace and PQ Corporation. Preferred preformed carriers are
those described above in section 4.4.1.1 entitled "Catalyst
morphology and carrier".
[0134] Activator and Additional Components
[0135] The activator is a compound that is capable of activating
the transition metal component. It is sometimes referred to as a
cocatalyst. Useful activators are, amongst others, aluminium alkyls
and aluminium alkoxy compounds. Especially preferred activators are
aluminium alkyls, in particular, aluminium trialkyls (e.g.
trimethyl aluminium, triethyl aluminium and tri-isobutyl
aluminium). The activator is preferably used in excess to the
transition metal component. For instance, when an aluminium alkyl
is used as an activator, the molar ratio of the aluminium in the
activator to the transition metal in the transition metal component
is from 1 to 500 mol/mol, preferably 2 to 100 mol/mol, e.g. 5 to 50
mol/mol. The activator is typically not part of the solid,
particulate catalyst but added to the polymerization reactor as a
liquid.
[0136] The catalyst system comprising a Ziegler Natta catalyst may
additionally comprise co-activators and/or modifiers. Thus, for
example, two or more alkyl aluminium compounds as described above
may be used and/or the catalyst system components may be combined
with different types of ethers, esters, silicon ethers etc to
modify the activity and/or selectivity of the catalyst system as is
known in the art.
[0137] Catalyst System Preparation
[0138] The catalyst system comprising a Ziegler Natta catalyst may
be prepared by procedures known in the art, e.g. as disclosed in
U.S. Pat. No. 5,332,793, U.S. Pat. No. 6,187,866, U.S. Pat. No.
5,290,745, U.S. Pat. No. 3,901,863, U.S. Pat. No. 4,292,200, U.S.
Pat. No. 4,617,360, WO 91/18934.
[0139] The solid catalyst system particles may optionally be washed
prior to use to remove non bonded transition metal. In the final
catalyst system particle added to the polymerization, only very
minor amounts of transition metal should be extractable in alkanes
at 80.degree. C.
[0140] The average particle size of the catalyst system particles
is preferably in the range 1 to 250 .mu.m, more preferably 4 to 100
.mu.m, still more preferably 6 to 30 .mu.m, e.g. 10 to 25 .mu.m.
The particles are preferably spherical.
[0141] The surface area of the catalyst system particles is
preferably in the range 1-500 m.sup.2/g, more preferably 2-300
m.sup.2/g. The pore volume of the catalyst system particles is
preferably in the range 0.1-5 cm.sup.3/g, preferably 0.2-1.5
cm.sup.3/g.
[0142] Chromium Oxide Catalyst Systems
[0143] Procedures for making chromium oxide catalyst systems are
well known in the art. Chromium oxide catalysts, also called
Phillips catalysts, are typically made by calcining a porous powder
of silica, silica-alumina or aluminium phosphate together with a Cr
compound that is not heat stable, in a flow of dry,
oxygen-containing gas at a temperature of 500-900.degree. C. The Cr
content is preferably 0.1-2% wt. They are preferably used without
cocatalysts or activators, but sometimes minor amounts of Al or B
alkyls are added to the polymerization reactor. The molecular
weight of the polymer to be produced may be highly influenced by
the temperature chosen for the calcination. Generally the higher
the calcination temperature used, the lower the molecular weight of
the resulting polymer.
[0144] The molecular weight of the polymer also depends on
polymerisation conditions: The higher the polymerisation
temperature, the lower the molecular weight. The higher the
productivity (kg polymer/g catalyst), the higher the molecular
weight. The higher the polymer density (less comonomer), the higher
the molecular weight. (M. P. McDaniel: Supported Chromium Catalysts
for Ethylene Polymerization, Adv. Catal., 33 (1985), 48.
[0145] Still, there is a limitation on how low molecular weight
(how high MFR2) can be made by particle form (slurry or gas phase)
commercial polymerisation process. This limitation means that only
a fraction of the injection moulding polymer application market can
be supplied by chromium oxide catalyst. Also, bimodal polymer
grades are not produced by chromium due to the catalyst's inability
to produce a low molecular weight fraction.
[0146] Multisite Catalyst Systems
[0147] Multisite catalyst systems may be used in the gas
polymerization of the present invention.
[0148] Multisite catalyst systems for use in the polymerization may
be hybrids from two (or more) different catalyst families. For
instance, Ziegler Natta and single site catalytic sites may be used
together, e.g. by impregnating metallocene site precursor and
activator for the metallocene into the pores of a particulate
Ziegler Natta catalyst. Alternatively, chromium oxide may be used
together with a metallocene, e.g. by impregnating, under inert
conditions, metallocene site precursor and activator for the
metallocene into the pores of a particulate, thermally activated
chromium oxide catalyst. Ziegler Natta and chromium oxide catalysts
may also be used, e.g. as a system where the solid component of
each of these catalysts are fed as separate particles to the
polymerization reactor, and a relatively minor amount of the
cocatalyst needed for the Ziegler Natta component is used.
Alternatively, multisite catalyst systems comprising two different
ZN sites, e.g. both Hf and Ti active sites, may be prepared.
[0149] Single site catalysts are particularly useful in the
preparation of multisite catalyst systems. A preferred multisite
catalyst system is one comprising two metallocenes, e.g. one having
a tendency to make higher molecular weight polymer and one having a
tendency to make lower molecular weight polymer or one having a
tendency to incorporate comonomer and one having a lesser tendency
to do so. The two metallocenes may, for instance, be isomeric
metallocenes in about the same ratio as made in their synthesis.
Preferably, however, the multisite catalyst system comprises one
active site making a polymer component of both lower molecular
weight and lower comonomer incorporation than another site. Dual
site catalyst systems (multisite catalyst systems with two sites)
containing such sites are particularly preferred.
[0150] Alternatively, chromium oxide catalysts may, in some cases,
behave as dual site catalyst systems, e.g. if they are supported on
aluminum phosphate (with a surplus of Al vs. P). This is believed
to be due to the effect of the support influencing the properties
of the active site.
[0151] High Catalyst Activity/Productivity
[0152] An important feature of the process of the present invention
is that the above-described gas phase polymerization has a high
activity coefficient in the copolymerisation of 3-substituted
C.sub.4-10 alkene and another C.sub.2-8 alkene at a polymerization
temperature of about 80.degree. C. Preferably, the activity
coefficient of the catalyst system is at least 100 g polyalkene/(g
solid cat, h, bar), still more preferably the activity coefficient
of the catalyst system is at least 200 g polyalkene/(g solid cat,
h, bar), e.g. at least 250 g polyalkene/(g solid cat, h, bar).
There is no upper limit on the activity coefficient, e.g. it may be
as high as 10 000 g polyalkene/(g solid cat, h, bar).
[0153] Based on the total catalyst system, e.g. including liquid
adjuvants such as activator added in liquid form, e.g. triethyl
aluminium, preferably the activity coefficient of the catalyst
system is at least 25 g polyalkene/(g total cat. system, h, bar),
still more preferably the activity coefficient of the catalyst
system is at least 40 g polyalkene/(g total cat. system, h, bar),
e.g. at least 60 g polyalkene/(g total cat. system, h, bar). There
is no upper limit on the activity coefficient, e.g. it may be as
high as 500 g polyalkene/(g total cat. system, h, bar).
[0154] If a catalyst system comprising a single site catalyst is
used, its activity coefficient is preferably least 5 000 g
polyalkene/(mmol transition metal, h, bar), still more preferably
the activity coefficient of the catalyst system is at least 8 000 g
polyalkene/(mmol transition metal, h, bar), e.g. at least 12 000 g
polyalkene/(mmol transition metal, h, bar).
[0155] The high activity coefficient, and therefore catalytic
productivity of the process of the present invention, has many
advantages. For instance, it decreases the production cost of the
polymer and minimizes any safety risks associated with the handling
of catalytic materials as less are required. Additionally the
ability to use a lesser amount of catalyst system per kg of final
polymer in some cases enables production plants to increase their
production output without having to increase their reactor size or
catalyst system material feed systems.
[0156] The high activity coefficient based on total catalyst system
also means that the catalyst system residues may be left in the
polymer without removal since they will not cause trouble in the
further use of the polymer if the polymer is properly pretreated,
e.g. several of the invention polymers were made into films, which
is a rather critical application, without observing negative
effects of the catalyst system residues, neither on the processing
nor on the film itself.
[0157] Polymerization and Downstream Process
[0158] Polymerization Process
[0159] Commercial Processes
[0160] The gas phase polymerization is preferably carried out in a
conventional gas phase reactor such as a bed fluidized by gas feed
or in a mechanically agitated bed, or in a circulating bed process.
Suitable gas phase polyalkene processes for polyethylene are, for
example, Unipol PE gas feed fluidized single reactor process and
Unipol PE II gas feed fluidized staged reactor process by
Univation, Evolue gas feed fluidized staged reactor process by
Mitsui, Innovene gas fed fluidized single reactor process by Ineos,
Lupotech G gas fed fluidized single reactor process and Spherilene
gas feed fluidized staged reactor process by LyondellBasell and
last part of Borstar PE staged reactor process by Borealis.
Suitable gas phase polyalkene processes for polypropylene are, for
example, Innovene PP by Ineos, Dow/Unipol PP by Dow, Spherizone
circulating bed by LyondellBasell, Chisso/JPP mechanically agitated
reactor process by Japan Polypropylene, Novolen gas phase by Lummus
and last polymerization part of Spheripol process by
LyondellBasell.
[0161] Gas Phase Reactor Parameters and Operation
[0162] The high activity of the polymerization catalyst systems
with 3-substituted C.sub.4-10 alkene comonomer allow for efficient
gas phase polymerization to be carried out. Preferably, the
productivity of the solid catalyst is at least 1000 g polymer per g
of solid catalyst system. Still more preferably the productivity of
the solid catalyst is at least 1800 g polymer/g catalyst system,
e.g. at least 2000 g polymer/g solid catalyst system. The upper
limit is not critical but might be in the order of 100 000 g
polymer/g solid catalyst system. Preferably, the productivity of
the total catalyst system is at least 250 g polymer per g of total
catalyst system. Still more preferably the productivity of the
solid catalyst is at least 400 g polymer/g catalyst total system,
e.g. at least 1000 g polymer/g catalyst system. The upper limit is
not critical but might be in the order of 20000 g polymer/g solid
catalyst.
[0163] Advantageously, the process typically proceeds without
reactor fouling.
[0164] The conditions for carrying out gas phase polymerization are
well established in the art. The reaction temperature is preferably
in the range 30 to 120.degree. C., e.g. 50 to 100.degree. C. The
total gauge pressure is preferably in the range 1 to 100 bar, e.g.
10 to 40 bar. The total monomer partial pressure is preferably in
the range 2 to 20 bar, e.g. 3 to 10 bar. The residence time in each
gas phase reactor is preferably in the range 0.3 to 7 hours, more
preferably 0.5 to 4 hours, still more preferably 0.7 to 3 hours,
e.g. 0.9 to 2 hours.
[0165] Hydrogen is also preferably fed into the reactor to function
as a molecular weight regulator. In the case of single site
catalysts and especially for catalysts with Group 4 metallocenes
with at least one cyclopentadienyl group, the molar ratio between
the feed of hydrogen and the feed of the C.sub.2-8 alkene into the
reactor system is preferably 1:10 000-1:2000. In the case of ZN
catalysts, the H.sub.2/C.sub.2-8 alkene molar ratio within the gas
phase of the polymerization reactor is preferably 1:5 000-1.0
[0166] The concentration in the gas in the reactor of the major
monomer, the C.sub.2-8 alkene, is preferably is 10-70 mol %,
preferably 20-50 mol %, while the 3-substituted C.sub.4-10 alkene
comonomer concentration preferably is 1-70 mol %, more preferably
5-50 mol %.
[0167] Preferably, nitrogen is also fed into the reactor. It
functions as a flushing gas.
[0168] Preferably, a C.sub.3-8 saturated hydrocarbon is also fed
into the reactor. Particularly preferably a C.sub.3-6 alkane (e.g.
propane, n-butane) is fed into the reactor. It functions to
increase heat transfer efficiency, thereby removing heat more
efficiently from within the reactor.
[0169] Preferably, the gas phase polymerization reaction is carried
out as a continuous or semi-continuous process. Thus the monomers,
hydrogen and other optional gases are preferably fed continuously
or semi-continuously into the reactor. Preferably, the catalyst
system is also fed continuously or semi-continuously into the
reactor. Still more preferably polymer is continuously or
semi-continuously removed from the reactor. By semi-continuously is
meant that addition and/or removal is controlled so they occur at
relatively short time intervals compared to the polymer residence
time in the reactor, e.g. between 20 seconds to 2 minutes, for at
least 75% (e.g. 100%) of the duration of the polymerization.
[0170] Thus in a preferred process of the present invention the
catalyst components or catalyst system is preferably injected into
the reactor at a rate equal to its rate of removal from the
reactor. An advantage of the invention herein described, however,
is that because less catalyst system can be used per kg of polymer
produced, less catalyst system is removed from the reactor along
with polymer. The interpolymers obtained directly from the
polymerization reactor(s) therefore comprise less impurities
deriving from the catalyst system.
[0171] When used in a gas phase polymerization of a 3-substituted
C.sub.4-10 alkene comonomer, the polymerization catalyst system
herein described, particularly the single site catalyst system,
gives a very high activity, enabling a high productivity (g
polymer/g catalyst system). Consequently relatively low
concentrations of catalyst system are required in the reactor.
Preferably, the concentration of the total catalyst system in the
gas phase polymerization is less than 3 kg/ton polymer, still more
preferably less than 1.0 kg/ton polymer, e.g. less than 0.8 kg/ton
polymer. Preferably, the concentration of catalyst system is at
least 0.01 kg/ton polymer.
[0172] The above-described gas phase polymerization may be combined
with one or more further polymerizations, i.e. in a multistage
process. Thus, for example, two gas phase polymerizations can be
carried out in sequence (e.g. UNIPOL II, Evolue, Spherilene,
Novolen processes, Spheripol process option) or a gas
polymerization can be preceded by a slurry phase polymerization
(e.g. in Borstar or Spheripol processes). Alternatively, a gas
phase polymerization may be followed by a slurry phase
polymerization.
[0173] When a polymer is produced in a multistage process, the
reactors may be in parallel or in series but arrangement in series
is preferred. If the polymer components are produced in a parallel
arrangement, the powders are preferably mixed and extruded for
homogenization.
[0174] When a polymer is produced in a sequential multistage
process, using reactors coupled in series and using different
conditions in each reactor, the polymer components produced in the
different reactors will each have their own molecular weight
distribution and weight average molecular weight. When the
molecular weight distribution curve of such a polymer is recorded,
the individual curves from these fractions are superimposed into
the molecular weight distribution curve for the total resulting
polymer product, usually yielding a curve with two or more distinct
maxima. The product of a multistage polymerization is usually a
multimodal polyalkene.
[0175] If a slurry phase polymerization is additionally employed
then the conditions are preferably as follows: [0176] the
temperature is within the range of 30-120.degree. C., preferably
50-100.degree. C. [0177] the reaction pressure is within the range
of 1-100 bar, preferably 10-70 bar [0178] the residence time is
typically 0.5 to 6 hours, e.g 1 to 4 hours [0179] the diluent used
is preferably an aliphatic hydrocarbon having a boiling point in
the range -70 to 100.degree. C., e.g. n-hexane, isobutane, propane
[0180] hydrogen may be added for controlling the molar mass in a
manner known in the art.
[0181] Monomer (e.g. ethylene) and optionally a 3-substituted
C.sub.4-10 alkene comonomer is fed to the slurry reactor.
Alternatively, another comonomer may be added together with the
3-substituted C.sub.4-10 alkene comonomer. Alternatively, no
comonomer may be added. When no comonomer is added in the slurry
phase polymerization, the polymer component from the slurry phase
polymerization is an alkene homopolymer.
[0182] The polymerization may be conducted in a manner known in the
art such as in a conventional loop or tank reactor.
[0183] Staged processes for polyethylene preferably produce a
combination of a major component A of lower molecular weight and
lower (especially preferred is zero when producing final products
of density higher than 940 g/dm.sup.3) comonomer content and one
major component B of higher molecular weight and higher comonomer
content. Component A is preferably made in a reactor A' wherein the
hydrogen level is higher and the comonomer level lower than in the
reactor B' where component B is made. If reactor A' precedes B', it
is preferred that hydrogen should be stripped off from the polymer
flow from A' to B'. If reactor B' precedes A', then preferably no
extra comonomer is added to reactor B', and it is preferred to
remove a significant part of the non converted comonomer from the
polymer flow from B' to A'. It is also preferred that the
3-substituted C.sub.4-10 alkene is used in the reactor where the
polymer with highest incorporation of comonomer is produced, and
especially preferred in all the reactors of the process where
comonomer is used.
[0184] When a two stage polymerization is utilized, the lower
molecular weight polymer component is preferably produced in a
slurry reactor as described above and the higher molecular weight
component produced in a gas phase reactor. The higher molecular
weight component is typically produced using a lower
hydrogen/monomer feed. The reactors are preferably connected in
series. Preferably, the same catalyst system is used in both
reactors. The lower molecular weight component may be an
interpolymer (e.g. copolymer) or homopolymer.
[0185] A prepolymerization may be employed as is well known in the
art. In a typical prepolymerization less than about 5% wt of the
total polymer is produced. A prepolymerization does not count as a
stage with regard to consideration of whether a process is a single
or multistage process.
[0186] Preferably, however, the process of the present invention is
a single stage polymerization in a gas phase reactor.
[0187] Multimodal polymers may alternatively be prepared by using
two or more different single site catalysts in a single
reactor.
[0188] Alternatively, multisite catalyst systems, as described
above, may be used to prepare multimodal polymers. In this case, in
order to achieve the optimum polymer properties, especially in a
single reactor system, it is preferably for the multisite catalyst
system to have as high a ratio as possible between the
incorporation of comonomer on a site I and on another site II. It
has been surprisingly found that the 3-substituted C.sub.4-10
alkene comonomer as hereinbefore described, for numerous
combinations of active sites, gives a higher ratio compared to the
corresponding reaction using conventional comonomers like 1-butene
and 1-hexene. Utilizing 3-substituted C.sub.4-10 alkene with a
multisite catalyst system is therefore especially favorable.
[0189] Multimodal polymer may therefore be obtained in a single
reactor or in a system of two or more reactors, e.g. in a staged
reactor process. Preferably, however, a single reactor process
(except optional prepolymerization reactors making less than 7% of
the total polymer) is used. Preferably, a multisite catalyst system
comprising two or more (e.g. two) metallocene active site
precursors is used.
[0190] A further possibility is to blend different interpolymers as
hereinbefore described, e.g. prior to pelletization. Blending is,
however, less preferable to the production of multimodal polymer,
e.g. by multistage polymerization or by the use of two or more
different single site catalysts in a single reactor.
[0191] Multimodal and Unimodal Polymers
[0192] Multimodal interpolymers as hereinbefore described, and
especially those wherein the higher molecular weight polymer
component A has a higher comonomer content than the lower molecular
weight component B, may in some instances possess some advantages
over unimodal interpolymers.
[0193] Compared to unimodal interpolymer, at the same density and
at the same high ease of extrusion as regards extruder screw and
die processes, a multimodal interpolymer comprising, e.g. ethylene
and a 3-substituted C.sub.4-10 alkene, may be prepared having a
higher stress crack, brittle crack hoop stress failure and/or slow
crack growth resistance. Such interpolymers are particularly useful
for moulding and pipe applications where they give improved
resistance to stress crack and slow crack propagation as well as in
film applications wherein they enable improved impact resistance
and often improved tear resistance.
[0194] Additionally, multimodal interpolymers as hereinbefore
described also have higher melt strength, equivalent to sagging
resistance, which is an advantage in extrusion of large pipes and
blow moulding of articles, especially of large pieces.
[0195] Multimodal interpolymers as hereinbefore described may also
exhibit improved sealing properties (e.g. lower minimum sealing
temperature, sealing temperature range broadness) compared to an
unimodal polymer of the same density and ease of extrusion. This is
particularly useful in the manufacture of films.
[0196] On the other hand, unimodal interpolymers as hereinbefore
described often have a lower viscosity at very low shear stress
compared to multimodal interpolymers. This is useful, for example,
in rotomoulding processes where better mechanical strength of the
product can be achieved with the same cycle time. Furthermore such
interpolymers may possess a low degree of warpage making them
advantageous for injection moulding.
[0197] 3-Substituted C.sub.4-10 Alkene in Heat Removal
[0198] As mentioned above, the gas phase polymerization reaction
preferably comprises a C.sub.3-8 saturated hydrocarbon such as a
C.sub.3-6 alkane. The function of the C.sub.3-8 saturated
hydrocarbon is to increase the heat removal efficiency in the gas
phase reactor. Cooling of particles is achieved by circulating the
C.sub.3-8 saturated hydrocarbon within the reactor through the
polymerization zone where it picks up heat from the particles, to a
cooling surface, where it is cooled, and then recycled. This
process is important, since if any particle overheats sufficiently,
it will melt and stick together with another particle or with the
reactor wall, i.e. agglomerate. C.sub.3-C.sub.6 hydrocarbons have
higher specific heat capacity than nitrogen and have been found to
function more efficiently for heat removal than e.g. nitrogen.
[0199] Thus in a typical gas phase polymerization, in addition to
the monomers, there is usually added a substantial concentration of
C.sub.3-8 saturated hydrocarbon, e.g. C.sub.3-6 alkane. For
instance, the concentration of C.sub.3-8 saturated hydrocarbon in
the reactor may be in the order of 5-60 mol %.
[0200] It has now been found, however, that 3-substituted
C.sub.4-10 alkenes such as 3-methyl-but-1-ene can act as an
effective in situ means for removing heat. It is possible, and in
many cases preferable, to utilize a relatively high partial
pressure of 3-substituted C.sub.4-10 alkene in gas phase
polymerization and it has been found that it serves as a means to
remove heat from the reactor. This is a further advantage of using
a 3-substituted C.sub.4-10 alkene comonomer instead of e.g. a
linear 1-butene or 1-hexene. In this way, the cooling can be
improved and the amount of C.sub.3-8 saturated hydrocarbon, e.g.
C.sub.3-C.sub.6 alkane, can be reduced. The advantage of
eliminating addition of C.sub.3-8 saturated hydrocarbon, e.g.
C.sub.3-6 alkane, is that this alkane must be acquired, purified,
added, controlled, removed from the reactor and the polymer and
separated from the gas mixture, especially in quantities.
[0201] An advantage of the above-described gas phase polymerization
is therefore that it can be carried out with no additional
C.sub.3-8 saturated hydrocarbon or with less additional C.sub.3-8
saturated hydrocarbon. In preferred gas phase polymerizations the
concentration of C.sub.3-8 saturated hydrocarbon, e.g. C.sub.3-6
alkane, is therefore less than 20% mol, more preferably less than
10% mol, still more preferably less than 5% mol. In some cases
substantially no C.sub.3-8 saturated hydrocarbon, e.g. C.sub.3-6
alkane may be present.
[0202] In a further preferred gas phase polymerization the molar
ratio of C.sub.3-8 saturated hydrocarbon, e.g. C.sub.3-6 alkane, to
3-substituted C.sub.4-10 alkene is less than 2:1, preferably less
than 1:1, more preferably less than 1:2, e.g. less than 1:9.
[0203] The partial pressure of 3-substituted C.sub.4-10 alkene
present in the gas phase reactor is preferably at least 10% of the
total pressure, more preferably at least 20% of the total pressure,
e.g. at least 40% of the total pressure.
[0204] For instance, a gas phase polymerization may be carried out
under the following conditions: [0205] a concentration of C.sub.3-6
alkane of 0.01-5 mol % [0206] a concentration of nitrogen, 10-40
mol %, [0207] a concentration of ethylene of 10-50 mol %, [0208] a
partial pressure of 3-substituted C.sub.4-10 alkene (e.g. 3-methyl
but-1-ene) of more than 20% of the total pressure in the reactor,
and [0209] a concentration of hydrogen of, e.g. 1-5 mol % for ZN or
chromium oxide catalysts and 5 to 1000 ppm mol for single site
catalysts.
[0210] Thus viewed from a further aspect the present invention
provides a method of carrying out a gas phase polymerization
comprising polymerizing a 3-substituted C.sub.4-10 alkene and
optionally another C.sub.2-8 alkene using a polymerization catalyst
system, wherein said polymerization is carried out at a
concentration of C.sub.3-8 saturated hydrocarbon (e.g. C.sub.3-8
alkane) of less than 5 mol %.
[0211] Preferably, the feed of C.sub.3-8 saturated hydrocarbon
(e.g. C.sub.3-6 alkane) into the gas phase reactor system
(reactor+recirculation system) is less than 100 kg/ton
polyethylene, preferably less than 30 kg/ton polyethylene, more
preferably less than 10 kg/ton polyethylene.
[0212] Condensed/Supercondensed Mode, Optionally with Comonomer as
Condensable
[0213] It has been found that the increased catalytic activity
discussed above that is achieved using the 3-substituted C.sub.4-10
alkene comonomer is most significant at relatively short residence
times (e.g. within the first hour). Of course, it is at short
residence times that the need for high catalytic activity is
greatest, since then is the greatest amount of catalyst system or
catalyst residue incorporated into the polymer.
[0214] However gas phase reactors, especially when fed non
polymerized catalyst systems, sometimes encounter operational
difficulties if operated in a conventional manner with short
residence times due to local overheating by insufficient control
over local cooling. Short residence times in gas phase
polymerization reactors are therefore achieved by using what is
called condensed or supercondensed operation mode. A preferred gas
phase polymerization of the invention is therefore carried out in
condensed or supercondensed mode. This is an operational mode
wherein a vaporizable liquid is continuously fed to the fluidized
bed polymerization reactor (U.S. Pat. No. 453,399, U.S. Pat. No.
4,588,790, U.S. Pat. No. 5,352,749, U.S. Pat. No. 5,405,922), in
order to increase cooling efficiency and cooling control.
Supercondensed mode usually refers to a situation of fluid feed of
more than about 20% wt liquid of total fluid feed. The condensed
mode may be used by partial condensing of the comonomer only, but
the amount of condensibles and the dewpoint of the recirculation
gas is very often adjusted by added alkanes, such as
C.sub.3-C.sub.6, especially C.sub.5 into the reactor system, so the
alkane in or from the recirculation gas will also be partially
condensed. Thus the combination of continuous gas phase
polymerization with continuous vaporizable liquid feed to the
reactor bed is favorable and especially preferred.
[0215] It has been found that 3-substituted C.sub.4-6 alkenes, and
in particular those with 5-7 carbon atoms in total (e.g.
3-methyl-1-butene and 3-methyl-1-pentene, especially
3-methyl-1-butene) are ideal vaporizable liquids for condensed mode
operation. In comparison to the standard linear comonomers, the
3-substituted C.sub.4-6 alkenes may be used in a much higher
concentration in the reactor without impacting on the nature of the
interpolymer obtained which enables a much higher degree of
condensation of the recirculation gas. It is possible to run
operation in condensed mode with essentially no added saturated
C.sub.3-6 alkanes.
[0216] Thus viewed from a still further aspect the invention
provides the use of 3-substituted C.sub.4-10 alkene in a gas phase
polymerization, wherein said alkene constitutes more than 5 wt % of
a vaporizable liquid that is continuously fed to the gas phase
polymerization reactor.
[0217] When operating in condensed mode, the concentration of
3-substituted C.sub.4-10 alkene gas in the gas in the reactor is
preferably more than 10 mol %, more preferably more than 20 mol %,
e.g. more than 30 mol %. Preferably, the concentration of
3-substituted C.sub.4-10 alkene in condensed liquid feed flow to
the gas phase reactor is 10-99 mol %, more preferably 25-98 mol %,
e.g. 50-96 mol %. The condensed liquid flow to the reactor of total
recirculation gas out from reactor is preferably 3-60 wt %, e.g.
5-40 wt %.
[0218] The optimum comonomer strategy may be to use a mixture of a
3-substituted C.sub.4-6 alkene with a linear alkene comonomer, e.g.
butene. At a relatively high density, there is preferred a high
proportion of the 3-substituted C.sub.4-6 alkene for a high
concentration of condensibles, product properties and activity. At
very low density polymer, the balance is shifted to the linear
comonomer in order that the total comonomer concentration does not
get excessively high, e.g. so the dew point in the reactor gets too
close, and there must be some partial pressure left for ethylene
and the indispensable part of nitrogen also.
[0219] Downstream Requirements and Process
[0220] When the final polymer product is obtained from a slurry
reactor, the polymer is removed therefrom and the diluent
preferably separated from it by flashing or filtration. The major
part of the diluent and unconverted comonomer is recycled back to
the polymerization reactor(s). Preferably, the polymer is then
dried (e.g. to remove residues of liquids and gases from the
reactor). Due to its relatively low content of catalyst system
residues, preferably the polymer is not subjected to a deashing
step, i.e. to washing with an alcohol, optionally mixed with a
hydrocarbon liquid, or water.
[0221] The polymer obtained from gas phase polymerization is
preferably dried. Otherwise the final polymer is obtained from a
gas phase reactor is preferably used without removing catalyst
system residues or polymer components.
[0222] In order that the polymer can be handled without difficulty,
both within and downstream of the polymerization process, the
polymer powder from the reactor(s) should be in a free-flowing
state, preferably by having relatively large particles of high bulk
density, e.g. less than 10% wt of the polymer being smaller than
100 size, and the loose bulk density being higher than 300
kg/m.sup.3.
[0223] Preferably, the processes from the polymerization until the
pelletization extruder outlet, are carried out under an inert (e.g.
N.sub.2) gas atmosphere.
[0224] Antioxidants are preferably added (process stabilizers and
long term antioxidants) to the polymer. As antioxidant, all types
of compounds known for this purpose may be used, such as sterically
hindered or semi-hindered phenols, aromatic amines, aliphatic
sterically hindered amines, organic phosphates and
sulphur-containing compounds (e.g. thioethers).
[0225] Preferably, the antioxidant is selected from the group of
organic phosphates and sterically hindered or semi-hindered
phenols, i.e. phenols which comprise two or one bulky residue(s),
respectively, in ortho-position to the hydroxy group, and sulphur
containing compounds.
[0226] Representative examples of sterically hindered phenolic
compounds include 2,6-di-tert.-butyl-4-methyl phenol;
pentaerythrityl-tetrakis(3-(3',5'-di-tert.-butyl-4-hydroxyphenyl)-propion-
ate; octadecyl 3-(3',5'-di-tert.-butyl-4-hydroxyphenyl)propionate;
1,3,5-trimethyl-2,4,6-tris-(3,5-di-tert.-butyl-4-hydroxyphenyl)benzene;
2,2'-thiodiethylene-bis-(3,5-di-tert.-butyl-4-hydroxyphenyl)-propionate;
calcium-(3,5-di-tert.-butyl-4-hydroxy benzyl
monoethyl-phosphonate);
1,3,5-tris(3',5'-di-tert.-butyl-4'-hydroxybenzyl)-isocyanurate;
bis-(3,3-bis-(4'-hydroxy-3'-tert.-butylphenyl)butanoic
acid)-glycolester; 4,4'-thiobis(2-tert.-butyl-5-methylphenol);
2,2'-methylene-bis(6-(1-methyl-cyclohexyl)para-cresol);
n,n'-hexamethylene bis(3,5-di-tert.
Butyl-4-hydroxy-hydrocinnamamide;
2,5,7,8-tetramethyl-2-(4',8',12'-trimethyltridecyl)chroman-6-ol;
2,2'-ethylidenebis(4,6-di-tert.-butylphenol);
1,1,3-tris(2-methyl-4-hydrosy-5-tert.-butylphenyl)butane;
1,3,5-tris(4-tert.-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4-
,6-(1h,3h,5h)-trione;
3,9-bis(1,1-dimethyl-2-(beta-(3-tert.-butyl-4-hydroxy-5-methylphenyl)prop-
ionyloxy)ethyl)-2,4,8,10-tetraoxaspiro(5,5) undecane;
1,6-hexanediyl-bis(3,5-bis(1,1-dimethylethyl)-4-hydroxybenzene-propanoate-
); 2,6-di-tert.-butyl-4-nonylphenol;
di-tert.-butyl-4-hydroxyhydrocinnamic acid triester with
1,3,5-tris(2-hydroxyethyl)-s-triazine-2,4,6(1h,3h,5h)-trione;
4,4'-butylidenebis(6-tert.butyl-3-methylphenol); 2,2'-methylene
bis(4-methyl-6-tert.-butylphenol);
2,2-bis(4-(2-(3,5-di-t-butyl-4-hydroxyhydrocinnamoyloxy))ethoxyphenyl))pr-
opane;
triethyleneglycole-bis-(3-tert.-butyl-4-hydroxy-5-methylphenyl)prop-
ionate; benzenepropanoic acid,
3,5-bis(1,1-dimethylethyl)-4-hydroxy-c.sub.13-15-branched and
linear alkyl esters; 6,6'-di-tert.-butyl-2,2'-thiodi-p-cresol;
diethyl((3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl)methyl)
phosphonate; 4,6-bis(octylthiomethyl)o-cresol; benzenepropanoic
acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-c.sub.7-9-branched and
linear alkyl esters;
1,1,3-tris[2-methyl-4-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propiony-
loxy]-5-t-butylphenyl]butane; and a butylated reaction product of
p-cresol and dicyclopentadiene.
[0227] Among those compounds, the following phenolic-type
antioxidant compounds are especially preferred to be included:
pentaerythrityl-tetrakis(3-(3',5'-di-tert.-butyl-4-hydroxypheyl)-propiona-
te; octadecyl 3-(3',5'-di-tert.-butyl-4-hydroxyphenyl)propionate;
1,3,5-trimethyl-2,4,6-tris-(3,5-di-tert.-butyl-4-hydroxyphenyl)benzene;
1,3,5-tris(3',5'-di-tert.-butyl-4'-hydroxybenzyl)isocyanurate,
bis-(3,3-bis-(4'-hydroxy-3'-tert.-butylphenyl)butanoic
acid)-glycolester; and
3,9-bis(1,1-dimethyl-2-(beta-(3-tert.-butyl-4-hydroxy-5-methylphenyl)-
propionyloxy)ethyl)-2,4,8,10-tetraoxaspiro(5,5)undecane.
[0228] Preferred organic phosphate antioxidants contain a phosphite
moiety or a phosphorite moiety. Representative examples of
preferred phosphite/phosphonite antioxidants include
tris(2,4-di-t-butylphenyl)phosphite;
tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylen-di-phosphonite,
bis(2,4-di-t-butylphenyl)-pentaerythrityl-di-phosphite;
di-stearyl-pentaerythrityl-di-phosphite; tris-nonylphenyl
phosphite;
bis(2,6-di-t-butyl-4-methylphenyl)pentaerythrityl-di-phosphite;
2,2'-methylenebis(4,6-di-t-butylphenyl)octyl-phosphite;
1,1,3-tris(2-methyl-4-ditridecyl phosphite-5-t-butylphenyl)butane;
4,4'-butylidenebis(3-methyl-6-t-butylphenyl-di-tridecyl)phosphite;
bis(2,4-dicumylphenyl)pentaerythritol diphosphite;
bis(2-methyl-4,6-bis(1,1-dimethylethyl)phenyl)phosphorous acid
ethylester; 2,2',2''-nitrilo
triethyl-tris(3,3'5,5'-tetra-t-butyl-1,1'-biphenyl-2,2'-diyl)phosphite);
phosphorous acid, cyclic butylethyl propandiol,
2,4,6-tri-t-butylphenyl ester;
bis(2,4,6-tri-t-butylphenyl)-pentaerythrityl-di-phosphite;
2,2'-ethylidenebis(4,6-di-t-butylphenyl)fluorophosphonite,
6-(3-tert-butyl-4-hydroxy-5-methylphenyl)propoxy)-2,4,8,10-tetra-tert.but-
-yldibenz(d,t)(1.3.2)dioxaphosphepin; and
tetrakis-(2,4-di-t-butyl-5-methyl-phenyl)-4,4'-biphenylen-di-phosphonite.
[0229] Among the above-mentioned compounds, the following
phosphite/phosphonite antioxidant compounds are preferred to be
included:
tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylen-di-phosphonite;
bis(2,6-di-t-butyl-4-methylphenyl)pentaerythrityl-di-phosphite;
di-stearyl-pentaerythrityl-di-phosphite; and
bis(2,4-dicumylphenyl)pentaerythritol diphosphite.
[0230] As antioxidant either a single compound or a mixture of
compounds may be used. Particularly preferably a sterically
hindered phenolic compound and a phosphite/phosphonite compound may
be used in combination. The sterically hindered phenolic compound
typically acts as a long term stabilizer. The phosphite/phosphonite
compound typically acts as a process stabilizer.
[0231] The skilled man can readily determine an appropriate amount
of antioxidant to include in the polymer. As discussed above,
however, the polymers produced by the process of the present
invention comprise less catalyst system residues than conventional
polymers thus it is possible to add less antioxidant thereto. Thus
a sterically hindered phenolic antioxidant may be used in an amount
of 200-1000 ppmwt, more preferably 300-800 ppmwt, e.g. 400-600
ppmwt or about 500 ppmwt. The amount of organic
phosphite/phosphonite antioxidant present in the polymer is
preferably 50-500 ppmwt, more preferably 100-350 ppmwt and most
preferably 150-200 ppmwt.
[0232] The above-mentioned antioxidants are particularly preferred
when the amount of transition metal present in the polymer is
sufficient to accelerate oxidation reactions, e.g. when the level
of transition metal in the polymer is more than 1 .mu.mol
transition metal per kg polymer, more typically more than 2 .mu.mol
transition metal per kg polymer, e.g. more than 6 .mu.mol
transition metal per kg polymer. Such levels of transition metals
may occur as the interpolymers are often prepared without a washing
(e.g. deashing) step.
[0233] Other additives (antiblock, color masterbatches,
antistatics, slip agents, fillers, UV absorbers, lubricants, acid
neutralizers and fluoroelastomer and other polymer processing
agents) may optionally be added to the polymer.
[0234] Prior to introduction into the plastic converter, the
polymer is preferably further processed to achieve less than 10% wt
of the polymer being smaller than 2 mm in average size (weight
average) and a loose bulk density of higher than 400
kg/m.sup.3.
[0235] The polymer or polymer mix is preferably extruded and
granulated into pellets. Prior to extrusion, the polymer preferably
contacts less than 1 kg/ton, still more preferably less than 0.1
kg/ton, water or alcohol. Prior to extrusion, the polymer
preferably does not contact acid.
[0236] Additives (e.g. polymer processing agents or antiblock) may
be added after pelletization of the polymer. In this case the
additives are preferably used as masterbatches and pellets mixed
therewith before being extruded or moulded into films or
articles.
[0237] Polymer Composition and Properties
[0238] The amount of C.sub.2-8 alkene (e.g. ethylene) monomer
present in the interpolymer of the invention is preferably
60-99.99% wt, still more preferably 80-99.9% wt, e.g. 90-99.5% wt.
In interpolymers wherein the largest amount of C.sub.2-8 alkene is
propylene, preferably at least 3-10% wt of ethylene is additionally
present. If the interpolymer comprises two types of C.sub.2-8
alkenes (e.g. ethylene and 1-butene), the C.sub.2-8 alkene in the
minor amount (e.g. 1-butene) is preferably present in an amount
0.1-20% wt, still more preferably 0.5-10% wt, e.g. 1-7% wt.
[0239] The amount of 3-substituted C.sub.4-10 alkene (e.g.
3-methyl-1-butene) monomer present in the interpolymer of the
invention is preferably 0.01 to 40% wt, more preferably 0.1-20% wt,
e.g. 0.5-10% wt, more preferably less than 7% wt.
[0240] When it is stated herein that the amount of a given monomer
present in a polymer is a certain amount, it is to be understood
that the monomer is present in the polymer in the form of a repeat
unit. The skilled man can readily determine what is the repeat unit
for any given monomer.
[0241] The density of the interpolymer of the invention is
preferably in the range 835-970 kg/m.sup.3. When the C.sub.2-8
alkene is ethylene, the density is preferably in the range 880-950
kg/m.sup.3, still more preferably in the range 900-940 kg/m.sup.3,
e.g. 915-930 kg/m.sup.3.
[0242] When the C.sub.2-8 alkene is propylene, the density is
preferably in the range 880-910 kg/m.sup.3, still more preferably
in the range 885-910 kg/m.sup.3, e.g. 890-910 kg/m.sup.3. When the
C.sub.2-8 alkene is propylene, the xylene solubles of the
interpolymer is preferably in the range 0.5-30% wt, more preferably
1-10% wt, e.g. 3-8% wt.
[0243] The MFR.sub.2 of the interpolymer of the invention is
preferably in the range 0.01-1000 g/10 min. When the C.sub.2-8
alkene is ethylene, the MFR.sub.2 of the polymer is preferably in
the range 0.01-1000 g/10 min, more preferably in the range 0.05-500
g/10 min, e.g. 0.1-5 g/10 min. When the C.sub.2-8 alkene is
propylene, the MFR.sub.2 of the polymer is preferably in the range
0.1-1000 g/10 min, more preferably in the range 1-150 g/10 min,
e.g. 10-50 g/10 min.
[0244] The MFR.sub.21 of the interpolymer of the invention is
preferably greater than 0.01 g/10 min. When the C.sub.2-8 alkene is
ethylene, the MFR.sub.21 of the polymer is preferably greater than
0.05 g/10 min, more preferably greater than 0.1 g/10 min, e.g.
greater than 1 g/10 min. The upper limit of MFR.sub.21 is not
critical and might be 300 g/10 min.
[0245] The melting temperature of the interpolymer of the invention
is preferably in the range 90-240.degree. C. When the C.sub.2-8
alkene is ethylene, the melting temperature is more preferably in
the range 100-140.degree. C., still more preferably in the range
110-130.degree. C., e.g. 115-125.degree. C. When the C.sub.2-8
alkene is propylene, the melting temperature is more preferably in
the range 120-160.degree. C., still more preferably in the range
130-155.degree. C., e.g. 135-150.degree. C.
[0246] The Mn of the interpolymer of the invention is preferably in
the range 4000-500 000 g/mol. When the C.sub.2-8 alkene is
ethylene, the Mn is more preferably in the range 7000-250 000
g/mol, still more preferably in the range 10 000-150 000 g/mol,
e.g. 20 000-70 000 g/mol. When the C.sub.2-8 alkene is propylene,
the Mn is more preferably in the range 6000-100 000 g/mol, still
more preferably in the range 8000-70 000 g/mol, e.g. 15 000-50 000
g/mol.
[0247] The weight average molecular weight (Mw) of the interpolymer
of the invention is preferably in the range 20 000-1000 000 g/mol.
When the C.sub.2-8 alkene is ethylene, the weight average molecular
weight is more preferably in the range 30 000-700 000 g/mol, still
more preferably in the range 50 000-150 000 g/mol, e.g. 70 000-140
000 g/mol. When the C.sub.2-8 alkene is propylene, the weight
average molecular weight is more preferably in the range 30 000-700
000 g/mol, still more preferably in the range 50 000-400 000 g/mol,
e.g. 80 000-200 000 g/mol.
[0248] The Mw/Mn of the interpolymer of the invention is preferably
in the range 1.5-50. When the C.sub.2-8 alkene is ethylene, the
Mw/Mn of the interpolymer is preferably in the range 1.5-50, more
preferably in the range 2-30, e.g. 2-5. When the C.sub.2-8 alkene
is propylene, the Mw/Mn is more preferably in the range 1-10, more
preferably in the range 2-10, e.g. 2-5. When the polymer is
multimodal, each component made using a single site catalyst
preferably has a M.sub.w/M.sub.n in the range 2-5, more preferably
in the range 2-4, most preferably in the range 2-3.5. When the
polymer is multimodal, each component made with a Ziegler-Natta
catalyst preferably has a M.sub.w/M.sub.n in the range 4-12, more
preferably in the range 5-10, most preferably in the range 6-9.
[0249] Preferably, the interpolymer of the present invention is
unimodal.
[0250] The polymer chains of the interpolymer of the present
invention may be linear in the sense that they have no measurable
long chain branching. Alternatively, they may have some degree of
long chain branching, which may be made e.g. by certain catalytic
sites, especially metallocene such as CGC metallocenes, or by
polymerization with dienes or by post reactor modification, e.g.
via radicals. If present, however, long chain branching is
preferably introduced during polymerization without adding extra
reactants, e.g. by using a mono-Cp metallocene as discussed above
or metallocenes with two Cp rings (including indenyl and fluorenyl)
and having a single bridge between the Cp rings. Long chain
branching gives useful rheological properties similar to broader
molecular weight polymers (and thereby improved processing
behavior) while in reality maintaining a relatively narrow
molecular weight distribution, e.g. as measured by GPC.
[0251] The interpolymer of the present invention is obtained with
high purity. It may, for example, be used without a deashing or
washing step. Thus the interpolymer contains only very low amounts
of catalyst system or catalyst residues (i.e. ash). Preferably, the
amount of catalyst system residue (i.e. ash) in the interpolymer of
the invention is less than 1200 ppm wt ash, still more preferably
less than 600 ppm wt ash, e.g. less than 500 ppm wt ash. By the
catalyst system ash is meant the ash from the active site
precursor, activator, carrier or other catalyst particle
construction material and any other components of the catalyst
system that are present after polymerization and prior to any
deashing, washing or additivation step.
[0252] Transition metals are harmful in films in far lower
concentrations since they act as accelerators for degradation of
the polymer by oxygen and temperature, giving discoloration and
reducing or destroying mechanical properties. A particular
advantage of the process of the present invention is that it yields
polymers containing very low amounts of transition metal. Polymers
produced by the process of the invention preferably comprise less
than 500 .mu.mol transition metal per kg polymer, more preferably
less than 400 .mu.mol transition metal per kg polymer, still more
preferably less than 200 .mu.mol transition metal per kg polymer,
e.g. less than 100 .mu.mol transition metal per kg polymer.
[0253] Applications
[0254] The interpolymer of the present invention is therefore
useful in a wide range of applications. It may be used, for
example, in medical applications, for the manufacture of packaging
for food or for electrical applications wherein it is important
that the amount of impurities present in the polymer is
minimized.
[0255] The interpolymer may also be used in moulding as well as in
pipe applications.
[0256] Moulding
[0257] The interpolymer of the present invention may be
advantageously used in moulding applications. It may, for example,
be used in blow moulding, injection moulding or rotomoulding.
[0258] Representative examples of blow moulded articles that may be
prepared include bottles or containers, e.g. having a volume of 200
ml to 300 liters. Preferred interpolymers for blow moulding have a
density of more than 945 g/dm.sup.3, e.g. 945-970 g/dm.sup.3.
Preferred interpolymers for blow moulding have a MFR.sub.21 of 1-40
g/10 min.
[0259] Particularly preferred interpolymers for use in blow
moulding are prepared using a Ziegler Natta or chromium oxide
catalyst. The interpolymers preferably have a MFR.sub.21/MFR.sub.2
of 50-150. If made using a Ziegler Natta catalyst, the interpolymer
is preferably multimodal. If made using a chromium oxide catalyst,
the interpolymer is preferably unimodal.
[0260] Representative examples of injection moulded articles that
may be prepared include boxes, crates, thin walled packaging,
plastic housing, buckets, toys, racks, rail pads, trash cans, caps
and closures. Preferred interpolymers for injection moulding have a
density of more than 955 g/dm.sup.3, e.g. 955-970 g/dm.sup.3.
Preferred interpolymers for injection moulding have a MFR.sub.2 of
0.5-100 g/10 min.
[0261] Particularly preferred interpolymers for use in injection
moulding are prepared using a Ziegler Natta catalyst. The
interpolymers preferably have a MFR.sub.21/MFR.sub.2 of 20-40. The
interpolymers used for injection moulding may be unimodal or
multimodal.
[0262] Representative examples of rotomoulded articles that may be
prepared include water tanks, bins, containers and small boats.
Preferred interpolymers for rotomoulding have a density of 915-950
g/dm.sup.3. Preferred interpolymers for rotomoulding have a
MFR.sub.2 of 0.5-5 g/10 min.
[0263] Pipe
[0264] The interpolymer of the present invention may be
advantageously used in pipe applications. Preferably, it is used in
HDPE pipes, e.g. according to PE80 or PE100 standards. The pipes
may be used e.g. for water and gas distribution, sewer, wastewater,
agricultural uses, slurries, chemicals etc.
[0265] The interpolymer used in pipe applications may be prepared
using a chromium oxide catalyst in, e.g. a single stage
polymerization. Alternatively, the interpolymer may be prepared in
a multireactor process, preferably a staged polymerization, still
more preferably in two or three stages, e.g. using a Ziegler Natta
catalyst. Single site catalysts may, however, also be used.
[0266] Preferred interpolymers for use in pipe applications have a
density of 930-960 g/dm.sup.3, preferably 940-954 g/dm.sup.3, more
preferably 942-952 g/dm.sup.3. Preferred interpolymers for use in
pipe applications also have a MFR.sub.5 of 0.1-0.5 g/10 min, more
preferably 0.15-0.4 g/10 min. Preferred interpolymers for use in
pipe applications have a MFR.sub.21/MFR.sub.5 of 14-45, more
preferably 16-37, most preferably 18-30. Preferred interpolymers
for use in pipe applications have a comonomer content of 0.8-5% wt,
more preferably 1-3% wt. If used with added carbon black, the
density of the interpolymer with the carbon black is preferably
940-970 g/dm.sup.3, more preferably 948-966 g/dm.sup.3, still more
preferably 953-963 g/dm.sup.3.
[0267] If the interpolymer comprises of more than one component,
and especially if it is prepared using a Ziegler Natta catalyst, it
preferably comprises:
[0268] A. A polymer component(s) which is 25-65% wt, more
preferably 35-60% wt of the interpolymer and comprises less than 1%
wt of comonomer, more preferably less than 0.5 wt comonomer and has
a MFR.sub.2 of 50-5000 g/10 min, more preferably 100-1000 g/10
min.
[0269] B. A polymer component(s) which is 25-65% wt, more
preferably 35-60% wt of the interpolymer and comprises more than
0.5% wt of comonomer, more preferably more than 1% wt of comonomer
and has a MFR.sub.2 of 50-5000 g/10 min, more preferably 100-1000
g/10 min.
[0270] Having generally described this invention, a further
understanding can be obtained by reference to certain specific
examples which are provided herein for purposes of illustration
only, and are not intended to be limiting unless otherwise
specified.
EXAMPLES
[0271] The present invention will now be described with reference
to the following non-limiting examples wherein:
[0272] Determination Methods
[0273] General Methods
[0274] Unless otherwise stated, the following parameters were
measured on polymer samples as indicated in the Tables.
[0275] MFR.sub.2, MFR.sub.5 and MFR.sub.21 were measured according
to ISO 1133 at loads of 2.16, 5.0, and 21.6 kg respectively. The
measurements were at 190.degree. C. for polyethylene interpolymers
and at 230.degree. C. for polypropylene interpolymers.
[0276] Molecular weights and molecular weight distribution, Mn, Mw
and MWD were measured by Gel Permeation Chromatography (GPC)
according to the following method: The weight average molecular
weight Mw and the molecular weight distribution (MWD=Mw/Mn wherein
Mn is the number average molecular weight and Mw is the weight
average molecular weight) is measured by a method based on ISO
16014-4:2003. A Waters 150CV plus instrument, equipped with
refractive index detector and online viscosimeter was used with
3.times.HT6E styragel columns from Waters (styrene-divinylbenzene)
and 1,2,4-trichlorobenzene (TCB, stabilized with 250 mg/L 2,6-Di
tert butyl-4-methyl-phenol) as solvent at 140.degree. C. and at a
constant flow rate of 1 mL/min. 500 .mu.l of sample solution were
injected per analysis. The column set was calibrated using
universal calibration (according to ISO 16014-2:2003) with 15
narrow molecular weight distribution polystyrene (PS) standards in
the range of 1.0 kg/mol to 12 000 kg/mol. These standards were from
Polymer Labs and had Mw/Mn from 1.02 to 1.10. Mark Houwink
constants were used for polystyrene and polyethylene
(K:9.54.times.10.sup.-5 dL/g and a: 0.725 for PS and K:
3.92.times.10.sup.-4 dL/g and a: 0.725 for PE). All samples were
prepared by dissolving 0.5-3.5 mg of polymer in 4 mL (at
140.degree. C.) of stabilized TCB (same as mobile phase) and
keeping for 3 hours at 140.degree. C. and for another 1 hour at
160.degree. C. with occasional shaking prior to sampling into the
GPC instrument.
[0277] Melting temperature was measured according to ISO 11357-1 on
Perkin Elmer DSC-7 differential scanning calorimetry. Heating
curves were taken from -10.degree. C. to 200.degree. C. at
10.degree. C./min. Hold for 10 min at 200.degree. C. Cooling curves
were taken from 200.degree. C. to -10.degree. C. at 10.degree. C.
per min. Melting temperature was taken as the peak of endotherm of
the second heating.
[0278] Comonomer content (wt %) was determined based on Fourier
transform infrared spectroscopy (FTIR) determination (using a
Perkin Elmer Spectrum GX instrument) calibrated with C13-NMR.
[0279] Density of materials is measured according to ISO 1183:1987
(E), method D, with isopropanol-water as gradient liquid on pieces
from compression moulded plaques. The cooling rate of the plaques
when crystallizing the samples was 15 C/min. Conditioning time was
16 hours.
[0280] Xylene solubles were determined according to ISO-6427, annex
B1992.
[0281] Rheology of the polymers was determined by frequency sweep
at 190.degree. C. under nitrogen atmosphere according to ISO
6721-10, using Rheometrics RDA II Dynamic Rheometer with parallel
plate geometry, 25 mm diameter plate and 1.2 mm gap. The
measurements gave storage modulus (G'), loss modulus (G'') and
complex modulus (G*) together with the complex viscosity (.eta.*),
all as a function of frequency (.omega.). These parameters are
related as follows: For any frequency .omega.: The complex modulus:
G*=(G'.sup.2+G'.sup.'2).sup.1/2. The complex viscosity:
.eta.*=G*/.quadrature..omega.. The denomination used for modulus is
Pa (or kPa) and for viscosity Pa s and for frequency (1/s).
.eta.*.sub.0.05 is the complex viscosity at a frequency of 0.05
s.sup.-1 and .eta.*.sub.300 is the complex viscosity at 300
s.sup.-1.
[0282] According to the empirical Cox-Merz rule, for a given
polymer and temperature, the complex viscosity as function of
frequency measured by this dynamic method is the same as the
viscosity as a function of shear rate for steady state flow (e.g. a
capillary).
[0283] The activity coefficient for the bench scale polymerization
runs is calculated by the following equation:
Activity_coefficient ( kg / ( g , bar , h ) = ( Yield_of _polymer _
( kg ) ) ( Catalyst_amount _ ( g ) ) ( Partial_pressure _of
_ethylene _ ( bar ) ) ( Polymerisation_time - ( h ) )
##EQU00001##
[0284] For continuous polymerizations, the activity coefficient is
analogous by using production rate of polymer instead of yield of
product and feed rate of catalyst system instead of amount fed
catalyst, and using the average residence time in the continuous
reactor.
Mechanical Properties on Compression Moulded Specimens
[0285] Secant modulus is measured according to ASTM D 882-A at a
temperature of 23.degree. C. and a speed of 1 mm/min. Tensile
properties (tensile stress at yield, tensile strain at yield,
tensile strength at break, tensile strain at break) on compression
moulded samples are measured at 23.degree. C. according to ISO
527-2, the modulus is measured at a speed of 1 mm/min, while yield
and break point properties at 50 mm/min. The specimens for this
test are made according to ISO 1872-2 with cooling rate 15.degree.
C./min. For Charpy impact are used compression moulded specimens
made according to ISO 10350-1 (1998-11-15)--option ISO 179-1 with
V-notch type A. These are tested on impact according to ISO 179 at
23.degree. C.
Films
[0286] Unless otherwise stated, the following parameters were
measured at 23.degree. C. on 40 .mu.m thick films prepared as
described in the examples. Dart drop is measured according to ISO
7765/1. Haze is measured according to ASTM D 1003. Gloss is
measured according to ASTM D 2457. Measured at light angle of
60.degree.. Puncture resistance is measured according to ASTM
D5748. Secant modulus: is measured according to ASTM D 882-A, and
calculated from the values at 0.05 and 1.05% strain. Tensile
stress, tensile strain and tensile strength is measured according
to ISO 527-3. Tear strength (Elmendorf) is measured according to
ISO 6383/2
EXAMPLES
[0287] Raw materials [0288] Ethylene: Polymerization grade. [0289]
Hydrogen: Grade 6.0. [0290] 1-hexene: Sasol. Stripped of volatiles
and dried with 13.times. molecular sieve. [0291] 1-butene:
Polymerization grade (99.5%). N.sub.2 bubbled and dried with
13.times. molecular sieve. [0292] 3-methyl-1-butene: Produced by
Evonik Oxeno. Purity >99.7%. N.sub.2 bubbled and dried with
13.times. molecular sieve. [0293] Propane and isobutane:
Polymerization use quality. [0294] Nitrogen: <0.7 ppm oxygen,
dew point<-98.degree. C.
Example 1
Gas Phase Polymerization Using a Particulate Single Site
Catalyst
[0295] The catalyst system ((n-Bu-Cp).sub.2HfCl.sub.2 and MAO
supported on calcined silica) was prepared according to example 1
of WO 98/02246, except Hf was used as transition metal instead of
Zr and the calcination (dehydration) temperature of silica was
600.degree. C.
[0296] Polymerization Method
[0297] Polymerization was carried out in an 8 liter reactor fitted
with a stirrer and a temperature control system. The same comonomer
feeding system was used for all runs. The procedure consisted of
the following steps:
1. Catalyst system was fed into the reactor. 2. Stirring was
started (280 rpm). 3. The reactor was heated to the polymerization
temperature of 70.degree. C. 4. Propane (400 ml) was added. 5.
Ethylene, comonomer and hydrogen were added into the reactor. The
pressure was maintained at 21 bar gauge pressure by supply of
ethylene via a pressure control valve. Hydrogen had been previously
mixed with ethylene in the ethylene supply cylinder. Comonomer was
also added continuously into the reactor, proportional to the
ethylene flow. 6. The polymerization was stopped by venting the
reactor of volatiles and reducing the temperature. 7. The polymer
was further dried at 70.degree. C. in the reactor with N.sub.2
flow.
[0298] Further details of the polymerization procedure and details
of the resulting interpolymers are provided in Table 1 and FIG.
1a.
[0299] Results
TABLE-US-00001 TABLE 1A Gas phase polymerization with particulate
single site catalyst Run no 1 2 3 4 5 6 7 8 9 10 11 12
POLYMERIZATION Catalyst feed g 1.12 0.95 0.74 0.68 0.58 0.40 1.45
1.45 1.45 1.40 1.31 1.04 Hydrogen in ppm 520 520 520 520 510 510
530 520 520 520 520 520 ethylene feed Comonomer -- M1B M1B M1B M1B
M1B MIB 1- 1- 1- 1- 1- 1- type * hexene hexene hexene hexene butene
butene Comonomer ml 8 8 25 40 40 60 10 40 30 30 6 20 start Feed
ratio g/g 0.024 0.063 0.125 0.199 0.310 0.367 0.026 0.108 0.076
0.079 0.019 0.057 comonomer/ ethylene Run time min 62 60 68 64 54
60 80 74 74 68 70 72 Yield g 1330 1250 1060 1160 1150 910 1250 1290
1400 1360 1260 1250 Productivity kg PE/g 1.19 1.32 1.43 1.71 1.98
2.28 0.86 0.89 0.97 0.97 0.96 1.20 cat. Activity g PE/(g 185 212
204 258 355 367 104 116 126 138 133 162 coefficient cat., h, bar)
POLYMER ANALYSES POWDER MFR2 g/10 min 1.10 1.10 1.1 0.89 0.78 0.76
1.4 0.97 0.91 0.83 0.97 1.29 MFR21 g/10 min n.a. n.a. 21.0 17.0
n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. .eta.*.sub.0.05 Pa s 6 556
6 728 6 519 11 789 10 617 7 960 5 021 9 253 11 117 n.a. 8 063 5 336
.eta.*.sub.300 Pa s 1 314 1 305 1 209 1 386 1 288 1 216 1 143 1 043
1 229 n.a. 1 378 1 206 Comon. wt % 2.8 3.8 5.2 6.1 7.4 7.8 2.9 8.8
6.6 6 1.9 4.2 content (FT-IR) Density kg/dm.sup.3 930.9 926.4 921.8
918.7 912.9 908.0 931.7 912.8 919.6 924.6 935.7 923.1 * M1B:
3-methyl-1-butene
[0300] The results in Table 1a show that for the production of
comparable ethylene interpolymers the use of 3-methyl-1-butene in
conjunction with a particulate catalyst system comprising a
metallocene catalyst in a gas phase polymerization enables a much
high catalytic activity to be achieved than when 1-hexene or
1-butene is used as comonomer. This can be seen, for example, by
comparing the results obtained in runs 4 and 9 (comparative) of
Table 1b.
TABLE-US-00002 TABLE 1b Run 4 Run 9 Comonomer 3-methyl but-1-ene
1-hexene Catalyst activity coefficient 258 126 MFR2 0.89 0.91 MFR21
17.0 n.a. .eta.*.sub.0.05 11 789 11 117 .eta.*.sub.300 1 386 1 229
Comonomer content (FT-IR) 6.1 6.6 Density 918.7 919.6
Some of the results from Table 1a are also presented in FIG. 1.
[0301] FIG. 1, a plot of catalyst system activity coefficient
versus polyethylene density, shows that in order to produce a
polyethylene of a given density, the polymerization utilizing
3-methyl-1-butene as comonomer is significantly more efficient
compared to using 1-hexene or 1-butene. This is particularly the
case for polyethylene having a density of less than about 920
kg/m.sup.3. Furthermore, the activity coefficients obtained here
are relatively close to those that by experience has been achieved
in slurry polymerizations with the same catalyst to give the same
polymer density.
Example 2
Gas Phase Polymerization Using a Ziegler Natta Catalyst
[0302] A conventional Ziegler Natta catalyst, with Ti as transition
metal, was used.
[0303] TEAL (triethyl aluminium): 1 M in heptane
[0304] Polymerization Method
[0305] Polymerization was carried out in a 5.3 liter reactor fitted
with a stirrer and a temperature control system. The same comonomer
feeding system was used for all runs. The procedure consisted of
the following steps: [0306] 1. 260 ml propane was added to the
reactor and stirring started (300 rpm). The reactor temperature was
85.degree. C., which temperature was maintained during the
polymerization. [0307] 2. Hydrogen, ethylene and comonomer were
added into the reactor. Hydrogen was added as a batch. The pressure
was maintained at the required pressure by supply of ethylene via a
pressure control valve. Comonomer was also added continuously into
the reactor, proportional to the ethylene flow. [0308] 3. Catalyst
system was added. The cocatalyst triethylaluminum (TEAL) was fed as
1M in heptane solution. [0309] 4. The polymerization was stopped by
venting the reactor of volatiles and reducing the temperature.
[0310] 5. The polymer was further dried in a vacuum oven at
70.degree. C. for 30 minutes.
[0311] Further details of the polymerization procedure and details
of the resulting interpolymers are provided in Tables 2a and 2b as
well as in FIG. 2.
[0312] Polymers were also mixed with antioxidant, 1500 ppm Irganox
B561 from Ciba (contains 20 w % Irgafos 168
(Tris(2,4-di-t-butylphenyl) phosphate) and 80 wt % Irganox 1010
(Pentaerythrityl-tetrakis(3-(3',5'-di-tert
butyl-4-hydroxyphenyl)-propionate)) and then pelletized by a Prism
16 extruder at 200.degree. C. extruder temperature.
[0313] Results
TABLE-US-00003 TABLE 2A Gas phase polymerization with Ziegler Natta
catalyst Run no 1 2 3 4 5 6 7 8 9 POLYMERIZATION Catalyst feed g
0.254 0.254 0.262 0.258 0.234 0.246 0.272 0.245 0.253 TEAL (1 M)
solution ml 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 Total pressure bar
g 21 23 22 22 22 22 22 22 22 Hydrogen partial bar g 0.5 0.5 0.5 0.5
0.5 0.5 0.3 0.5 0.7 pressure start Comonomer type * M1B M1B M1B M1B
M1B M1B M1B M1B Butene / M1B # Comonomer start ml 10 10 10 10 10 10
5 30 Comonomer g/100 g 5 10 15 20 5 40 2.5 20 (continuous) ethylene
Run time min 180 180 180 180 180 180 180 180 180 Yield g 515 920 1
410 1 490 520 1 065 510 1 300 940 Productivity kg PE/ 2.0 3.6 5.4
5.8 2.2 4.3 1.9 5.3 3.7 (g solid cat.) Activity coefficient g PE/(g
cat 123 161 276 296 114 222 93 272 197 solid,h, bar) POLYMER
ANALYSES OF POWDER MFR2 g/10 min 0.96 1.9 0.64 0.48 1.1 0.52 0.16
0.69 0.84 MFR21 g/10 min 22 46 15 12 26 13 3.2 Mw g/mol 135 000 115
000 140 000 Mn g/mol 32 000 26 000 33 000 Mw/Mn -- 4.2 4.4 4.2
Comon. content wt % 2.9 3.2 1.4 0.4 1.4 / 2.5 (FT-IR) Density
kg/dm3 941 937 934.4 933 945 935 950 934 934 Ash wt ppm 490 410 270
260 700 350 790 280 400 POLYMER ANALYSES OF PELLETS MFR2, g/10 min
0.72 0.55 Density kg/dm.sub.3 935.5 934 * M1B: 3-methyl-l-butene; #
Feed blend of 78 volume % M1B and 22 volume % 1-butene.
TABLE-US-00004 TABLE 2B Gas phase polymerization with Ziegler Natta
catalyst (comparative examples) Run no 10 11 12 14 17 15 19 20 21
23 24 POLYMERIZATION Catalyst g 0.230 0.259 0.271 0.256 0.258 0.245
0.241 0.253 0.253 0.250 0.242 feed TEAL ml 3.2 3.3 3.4 3.4 3.4 3.3
3.3 3.4 3.4 3.4 3.3 (1 M) solution Total bar g 21 21 21 21 21 21 21
21 21 21 21 pressure Hydrogen bar g 0.5 0.5 0.6 0.5 0.5 0.47 0.5
0.5 0.5 0.5 0.5 partial pressure start Comono- Hexene Hexene Hexene
Hexene Hexene Hexene Butene Butene Butene Butene Butene mer type*
Comono- ml 10 10 0 5 5 5 5.6 5.5 8.25 8.25 8.25 mer start Comono-
g/100 g 3 3 3 3/ 2.0/ 2.5/3/ Man. 5/7/ 10/10/ 10/5/ 10/ mer
ethylene 2.5/ 1.5/ 2.5/ feed 5/7/ 5/ 5/ (contin- 2/ 1.0/ 2.0/ 10/
10/ 7/ uous) 1.5 0.5/ 1.5/ 7 10/ 10/ 0.3 1.0/ 10 15 0.5 Run time
min 165 180 180 115 180 180 150 180 180 180 140 Yield g 227 922 600
630 627 555 347 542 382 457 317 Product- kg PE/ 1.0 3.6 2.2 2.5 2.4
2.3 1.4 2.1 1.5 1.8 1.3 ivity (g cat.) Activity g PE/(g 65 216 134
233 147 137 102 127 91 109 101 coefficient cat.,h, bar) Ash wt ppm
1590 420 680 620 630 680 1100 730 1030 860 1190 POLYMER ANALYSES OF
POWDER MFR2 g/10 min 1.3 0.31 1.9 0.6 0.66 0.95 0.43 0.79 0.96 0.54
0.98 MFR21 g/10 min 33 6.2 46 13 14 22 9 18 22 11 22 Mw g/mol 135
007 194 113 122 954 163 939 162 310 146 576 188 733 153 864 171 503
144 771 Comon. wt % 3.5 6.5 4.5 6.0 3.8 4.9 2.8 2.8 3.1 3.0 3.7
content (FT-IR) Density kg/dm3 935 926 930 927 931.7 929.7 935.1
935 934.4 934 933 *M1B: 3-methyl-l-butene
[0314] The results in Tables 2a and 2b show that for the production
of comparable ethylene interpolymers the use of 3-methyl-1-butene
in conjunction with a catalyst system comprising a Ziegler Natta
catalyst in a gas phase polymerization enables a much higher
catalytic activity to be achieved than when 1-hexene or 1-butene is
used as comonomer. This can be seen, for example, by comparing the
results obtained in runs 3 and 8 to run 17 (comparative), see Table
2c.
TABLE-US-00005 TABLE 2c Run 3 Run 8 Run 17 Comonomer 3-methyl
but-1-ene 3-methyl 1-Hexene but-1-ene Catalyst activity 828 816 147
coefficient MFR2 0.64 0.69 0.66 MFR21 15 14 Mw 140 000 162 310 Mn
33 000 Mw/Mn 4.2 Comon. Content (FT-IR) 3.8 Density 934.4 934
931.7
Some of the results of Tables 2a and 2b are also presented in FIG.
2. This shows that run 9 has an activity close to that typical of
the use of 3-methyl-1-butene alone, in spite of using a substantial
amount of 1-butene blended with the 3-methyl-1-butene.
Example 3
Use of 3-Methyl-but-1-Ene as an In Situ Means to Remove Heat
[0315] A polymerization was performed as in Example 1 except that
no propane was added and different reactor temperatures were used
as detailed in the Table 3 below.
TABLE-US-00006 TABLE 3 Polymerisation with particulate single site
catalyst, without propane Run no 1 2 POLYMERIZATION Catalyst feed g
0.37 0.41 Total pressure bar g 10.2 8.5 Hydrogen in ethylene feed
ppm 510 510 Comonomer type -- M1B M1B Comonomer start ml 300 150
Feed ratio comonomer/ethylene g/g 0.044 0.042 Temperature .degree.
C. 70 85 Run time min 55 40 Yield g 360 450 Productivity kg PE/g
cat. 0.97 1.10 Activity g PE/(g cat., h, bar) 171 284 ANALYSES MFR2
g/10 min 0.21 0.72 Density kg/dm.sup.3 894 903.2
[0316] The temperature control during these polymerizations was
satisfactory. The large density decrease was surprising.
Example 4
Use of 3-Methyl-but-1-Ene in Staged Polymerization
[0317] The same raw materials as in example 1 were used when
applicable, including the same catalyst.
[0318] Polymerization was carried out in an 8 liter reactor fitted
with a stirrer and a temperature control system. The same comonomer
feeding system was used for all runs. The procedure consisted of
the following steps: [0319] 1. Catalyst system was fed into the
reactor. [0320] 2. 3.8 liter isobutane was added to the reactor and
stirring started (300 rpm). [0321] 3. The reactor was heated to the
desired polymerization temperature of 85.degree. C. [0322] 4.
Ethylene, comonomer and hydrogen were added into the reactor. The
pressure was maintained at the required pressure by the supply of
ethylene via a pressure control valve. Hydrogen had been previously
mixed with ethylene in the ethylene supply cylinder. Comonomer was
also added continuously into the reactor, proportional to the
ethylene flow. [0323] 5. The consumption of monomer was followed.
When about 1200 g polymer had been produced, the reactor was
vented, stirring reduced to 30 rpm, the polymer dried with N.sub.2
at 70.degree. C. and 40 g polymer sample removed. [0324] 6. The
temperature was adjusted to the desired polymerization temperature.
400 ml propane was added and stirring adjusted to 280 rpm. [0325]
7. Ethylene, comonomer and hydrogen were added into the reactor.
The pressure was maintained at the desired pressure by supply of
ethylene via a pressure control valve. Hydrogen had been previously
mixed with ethylene in the ethylene supply cylinder. Comonomer was
also added continuously into the reactor, proportional to the
ethylene flow. [0326] 8. The polymerization was stopped by venting
the reactor of volatiles and reducing the temperature. [0327] 9.
The polymer was further dried at 70.degree. C. in the reactor with
N.sub.2 flow.
[0328] Further details of the polymerization procedure and details
of the resulting interpolymers are provided in Table 4.
[0329] Results
TABLE-US-00007 TABLE 4 3-methyl-1-butene with single site catalyst
polymerisation in 2 stages Run no 1 2 POLYMERIZATION STAGE 1 -
SLURRY Catalyst feed g 2.91 1.93 Total pressure bar g 21 21 Reactor
temperature .degree. C. 85 85 Hydrogen in ethylene feed molppm 3550
3550 Comonomer type -- 1-hexene 3-methyl-1- butene Comonomer start
ml 30 50 Feed ratio g/g 0.09 0.27 comonomer/ethylene Fraction in
stage 1 wt % 50 50 Yield in stage 1 g 1190 1180 Run time min 47 31
Activity coefficient g PE/(g cat, 245 368 h, bar) MFR.sub.2 g/10
min 170 150 Density g/dm.sup.3 937 941 POLYMERIZATION STAGE 2 - GAS
PHASE Total pressure bar g 21 21 Reactor temperature .degree. C. 70
70 Hydrogen in ethylene feed molppm 300 300 Comonomer type --
1-hexene 3-methyl-1- butene Comonomer start ml 30 50 Feed ratio
comonomer/ethylene g/g 0.09 0.29 Fraction in stage 2 wt % 50 50
Yield in stage 2 only g 1150 1140 Run time min 66 33 Activity
coefficient g PE/(g cat, 169 334 h, bar) TOTAL RUN POLYMER Fraction
made in stage 2 wt % 50 50 MFR.sub.2 g/10 min 2.1 1 Density
g/dm.sup.3 924 920
[0330] The results in Table 4 show that when comparing
3-methyl-1-butene and 1-hexene in a staged process of one slurry
and one gas phase polymerization stage to produce relatively equal
products, 3-methyl-1-butene is superior on activity in the slurry
as well as in the gas phase stage. Thus multistage polymerization
can be advantageously carried out using 3-substituted C.sub.4-10
alkene, including cases where a gas phase polymerization is
followed by a slurry polymerization.
Example 5
Cr Polymerisation
[0331] Grade EP352 Cr catalyst from Ineos Silicas was used. This is
chromium acetate on a support of porous particles of synthetic
silica with some titania. This was activated by fluidizing it in a
flow of dry air at a temperature of 600.degree. C. for 15 hours
before use. Polymerisation was carried out in a 3.4 litre reactor
fitted with a stirrer and a temperature control system. The
procedure consisted of the following steps: [0332] 1. 90 ml
isobutane, a given amount of nitrogen, the start amount of
isobutane and some ethylene were fed to the reactor. The amount of
nitrogen added was the amount necessary give 16 bar partial
pressure in reactor during polymerisation. The stirring speed was
set to 475 rpm. [0333] 2. Reactor temperature was increased to the
polymerisation temperature set point of 95.degree. C. The catalyst
was injected when temperature passed 70.degree. C. [0334] 3. The
pressure was maintained at 36 bar gauge pressure by supply of
ethylene via a pressure control valve. Comonomer was also added
continuously to the reactor, proportional to the ethylene flow.
[0335] 4. The polymerisation was stopped by venting the reactor of
volatiles and reducing the temperature, and polymer taken out.
[0336] 5. The polymer powder was further dried in a vacuum oven at
70.degree. C. for 2 hours.
Results
TABLE-US-00008 [0337] TABLE 5 Polymerisation with Cr catalyst Run
no 1 2 3 5 7 8 9 10 POLYMERISATION Catalyst feed g 0.849 0.840
0.855 0.826 0.827 0.820 0.82 0.82 Comonomer type .sup.1 -- M1B M1B
M1B M1B Hexene Hexene Hexene Hexene Comonomer start ml 15 15 15 10
5 5 10 10 Feed ratio g/g 0.033 0.083 0.011 0.011 0.030 0.016 0.059
0.103 comonomer/ethylene Run time min 46 50 46 30 50 45 53 60 Yield
g 413 398 412 409 412 402 292 207 Productivity kg PE/g cat. 0.49
0.47 0.48 0.50 0.50 0.49 0.36 0.25 Activity coefficient g PE/(g
cat, 42 39 40 62 37 41 25 16 h, bar) POLYMER ANALYSES POWDER Mw
g/mol n.a. 140 000 170 000 150 000 175 000 190 000 150 000 140 000
Mn g/mol n.a. 6 800 8 800 7 400 7 400 7 500 7 100 6 300 Mw/Mn --
n.a. 21 19 20 23 25 21 22 MFR2 g/10 min 0.28 0.46 0.33 0.34 0.18
0.14 0.37 0.5 MFR21 g/10 min 34 60 38 42 22 22 53 69 .eta..sub.0.05
Pa s 55 942 36 278 47 418 48 254 85 141 107 371 47 924 36 151
.eta..sub.300 Pa s 605 453 576 548 670 693 475 416 Comon. content
wt % 2.6 5.3 2.9 2 4.9 3.4 8.1 11.6 by FT-IR Density kg/dm.sup.3
939 928.5 939.4 943 942.6 947.3 934.3 923.6 .sup.1 M1B:
3-methyl-l-butene
The polymerisation data and polymer analyses are shown in Table 5.
The activity data are plotted in FIG. 3. This shows that the
activity to reach a certain density with 3-methyl-1-butene as
comonomer was significantly higher than with 1-hexene. MFR2 is
shown against productivity in FIG. 4. One observes that MFR2 is
higher for runs with 3-methyl-1-butene than for runs with 1-hexene.
The combined effect of productivity and density on MFR2 is shown in
FIG. 5. This figure shows that the observation referred to is not
caused by disturbance from variation of the density. At about equal
productivity and density, the MFR2 with 3-methyl-1-butene is about
double that with 1-hexene (0.34 versus 0.18). Further on, it should
be borne in mind that with a given Cr chromium oxide polymerisation
system, the lowest MFR2's should be found near the upper right
corner of the figure, while the highest would be found near the
lower left corner. In spite of higher productivities of runs with
3-methyl-1-butene versus the runs with 1-hexene at similar
densities, the MFR2 values for 3-methyl-1-butene still are higher
than for 1-hexene. Thus, 3-methyl-1-butene is able to give higher
MFR2 polymer at given density and productivity. This surprising
property will enable higher MFR2 polymers to be made with
3-methyl-1-butene comonomer than with 1-hexene.
Example 6
Ziegler Natta Co- and Ter-Polymerisation
[0338] Ziegler Natta catalyst was synthesised in laboratory scale
according to Example 1 of US 2006/0014897.
Polymerisation
[0339] Polymerisation was carried out in an 8 litre reactor fitted
with a stirrer and a temperature control system. 0.15 bar H.sub.2
had been added to the reactor. Polymerisation was done at
85.degree., at a total pressure of 21 bar gauge, and with 15 bar
N.sub.2 partial pressure in the reactor. No alkane was added. 1 M
triethylaluminum (TEAL) in heptane was added as given in Table 6a
and polymerised for a period as shown in Table 6a. Table 6a and
FIG. 6 show that the runs gave essentially the same density. The
activity coefficient with 3-methyl-1-butene as comonomer is about
1.7 higher than with the linear alkenes 1-butene and 1-hexene in
order to reach this density. Using a mixture of 3-methyl-1-butene
and 1-butene, surprisingly gives almost no loss in activity
coefficient in comparison to using 3-methyl-1-butene alone to reach
this density. This was achieved by adding about half the amount of
1-butene used alone, and about half of the 3-methyl-1-butene used
alone. Thus, a mixture of 3-methyl-1-butene and a linear 1-alkene
gives a combination of essentially the high activity achieved with
3-methyl-1-butene alone, at the same time that it needs a much
lower total concentration of comonomer in the reactor than
3-methyl-1-butene alone as comonomer to reach a given density.
Pelletisation
[0340] The dried polymer powders from polymerisations were mixed
with 1500 ppm Irganox B561 antioxidant from Ciba (contains 20 w %
Irgafos 168 (Tris(2,4-di-t-butylphenyl) phosphate) and 80 wt %
Irganox 1010 (Pentaerythrityl-tetrakis(3-(3',5'-di-tert
butyl-4-hydroxyphenyl)-propionate)) and 10% wt of a Ziegler Natta
bimodal PE of density 937 g/dm.sup.3 and MFR2 of 0.4. The mixture
was blended pelletised by a Prism 16 extruder at 210.degree. C.
extruder temperature. It was observed that the maximum output rate
achievable before getting operational problems was highest for
polymers with 3-methyl-1-butene only as comonomer and next highest
for polymers with a blend of 3-methyl-1-butene and 1-butene, see
Table 6a. The polymers with only linear alkenes (1-butene and
1-hexene) as comonomer were inferior.
TABLE-US-00009 TABLE 6A Ziegler Natta co-and ter-polymerisation,
pelletisation and moulded specimens tests Run no 1 2 3 4 5 6 7 8 9
10 11 POLYMERISATION Catalyst feed g 0.84 0.81 0.88 0.91 0.91 0.71
0.95 0.94 0.93 0.93 0.93 TEAL solution ml 11.4 11.0 11.9 12.3 12.3
12.9 12.8 12.6 12.6 12.6 Comonomer M1B M1B M1B M1B / M1B/ Hexene
Hexene Hexene Butene Butene Butene type .sup.1 Butene Butene
Comonomer ml 90 75 80 60 60 13 22 25 20 25 24 start Comonomer g/100
g 72 64 59 52 52 32 28 30 26 29 24 (continuous) 0-10 min ethylene
Comonomer g/100 g 1.9 1.8 1.8 1.5 1.5 0.5 0.6 0.6 0.5 0.6 0.5
(continuous) 10 min - end ethylene Run time min 126 122 111 117 119
177 158 160 157 154 155 Yield g 2060 1790 1900 1800 1820 1400 1700
1900 1630 1760 1800 Productivity kg PE/g 2.5 2.2 2.2 2.0 2.0 2.0
1.8 2.0 1.8 1.9 1.9 cat. Activity g PE/(g 234 217 233 203 202 134
136 152 134 147 150 coefficient cat., h, bar) POLYMER ANALYSES
POWDER MFR2 g/10 min 0.24 0.22 0.2 0.21 0.23 0.14 0.18 0.15 0.17
0.18 0.18 Mw g/mol 155 000 145 000 n.a. n.a. 150 000 155 000 n.a.
n.a. n.a. 170 000 170 000 Mn g/mol 48 000 46 000 n.a. n.a. 41 000
42 000 n.a. n.a. n.a. 53 000 52 000 Mw/Mn -- 3.2 3.2 n.a. n.a. 3.7
3.7 n.a. n.a. n.a. 3.2 3.2 Comonomer wt % 2.4 2.2 n.a. n.a. n.a.
1.8 n.a. n.a. n.a. 2.6 2.6 content Density kg/dm3 935 935 934 934
934 936 935 935 934 935 935 PELLETISATION Maximum % 45 42 45 40 40
35 40 38 33 40 40 feed screw rotation speed Maximum rate kg/h 2.3
2.3 2.3 2.0 2.0 1.7 1.8 1.5 1.7 2.0 2.0 POLYMER ANALYSES PELLETS
MFR2 g/10 min 0.16 0.17 0.17 0.19 0.20 0.14 0.15 0.10 0.11 0.13
0.13 Density kg/dm3 936.2 936.4 936.6 936.9 936.9 939.4 939.5 938.7
938.5 937.0 937.9 COMPRESSION MOULDED SPECIMENS TESTS Secant
modulus MPa 560 625 610 640 630 690 700 680 650 600 620 Tensile
stress MPa 18.5 18.4 18.5 19.3 19.1 20.6 20.6 20.1 19.7 19.0 19.4
at yield Tensile strain % 12.0 12.0 11.9 12.3 12.1 11.6 11.5 11.8
12.1 12.3 10.5 at yield Tensile strength MPa 25.7 26.7 26.8 29.0
28.8 27.0 28.1 25.9 28.3 29.4 33.4 Tensile strain % 650 680 710 727
750 630 710 590 700 775 885 at break Charpy impact strenght
kJ/m.sup.2 89 87 87 77 76 72 74 90 80 82 77 .sup.1 Mix M1B/Butene:
75 vol%/25 vol%. M1B: 3-methyl-1-butene
TABLE-US-00010 TABLE 6B Ziegler-Natta polymer film blowing and film
properties Polymerisation run material 1 2 3 4 5 9 10 11 Comonomer
type .sup.1 M1B M1B M1B M1B/Butene M1B/Butene Butene Butene Butene
FILM BLOWING .sup.2 Bubble stability Stable Stable Stable Stable
Stable Pumping Pumping Pumping Output kg/h kg/h 4.38 4.38 4.38 3.92
4.21 2.81 3.05 na Take off speed nn/min 3.3 3.3 3.3 3.1 3.1 2.6 2.6
na FILM TESTING General Density (film material) kg/dm.sup.3 935.2
935.4 935.2 935.7 935.5 936.7 936.1 937.1 Dart drop g 180 170 160
175 160 125 115 100 Puncture resistance Max force N 69 76 75 69 74
64 61 51 Deformation at max mm 75 84 87 78 80 62 64 58 force
Optical properties Gloss % 23 25 26 38 41 21 22 29 Haze % 43 43 42
34 30 48 48 41 Tests transverse direction (TD) Secant modulus MPa
465 490 495 485 445 510 515 525 Tensile stress at yield MPa 20.2
20.9 21.4 21.5 21 21.8 21.5 22 Tensile strain at yield % 9.6 9.1
9.9 9.3 10.5 8.2 7.2 7.6 Tensile strength MPa 48.5 51 52.6 57.5
58.6 52 48 41 Tensile strain at break % 720 715 735 755 790 745 725
730 Elmendorf tear N 6.2 6.1 6.2 4.5 4.9 4 4.7 3.9 resistance Tests
machine direction (MD) Secant modulus MPa 420.0 445 420 415 410 435
425 425 Tensile stress at yield MPa 18.6 18.8 18.6 18.8 18.6 19.1
18.8 18.5 Tensile strain at yield % 12.0 11.2 12.3 11.5 11.7 10.5
9.8 na Tensile strength MPa 55 60 61 57 54 58.7 58 58 Tensile
strain at break % 610 620 620 660 625 560 590 560 Elmendorf tear N
1.4 1.3 1.2 1.3 1.2 0.9 1.1 0.5 resistance .sup.1 M1B:
3-methyl-1-butene. Mix M1B/Butene: 75 vol %/25 vol % .sup.2 Less
wrinkles were seen on films during extrusion of films with
3-methyl-1-butene than on the other films.
Film Blowing and Film
[0341] Pellets were blown into film on a Collin monolayer film line
with screw diameter 25 mm, length/diameter ratio of 25, die
diameter 50 mm and with die gap adjusted to 1.5 mm. The polymers
were run at a blow up ratio (BUR) of 3.5 and screw speed of 90 rpm.
The temperature zones settings were set to (increasing towards
extruder head) 200-230.degree. C. By varying take off speed, the
film thickness was adjusted to approximately 40 .mu.m in each run.
Films for testing were selected to be 40 .mu.m. The film blowing
parameters and analytical results are shown in Table 6b. Table 6b
shows that in spite of the constant screw rotational speed, the
output rate, and therefore also the take off speed, varied quite
much between runs. The polymers with 3-methyl-1-butene only as
comonomer had the highest production rate, those with 1-butene only
the lowest rates, while the polymers with blend of
3-methyl-1-butene and 1-butene had intermediate rates. Furthermore,
the polymers with 1-butene only showed unstable bubble (indicating
that a slightly higher production rate would result in bubble
failure), while the runs with 3-methyl-1-butene gave good
stability. It was found that that the polymers with
3-methyl-1-butene as comonomer compared with polymers with 1-butene
only as comonomer gave significantly improved properties (Table 3):
Better impact properties (higher dart drop), better puncture
resistance (higher maximum force and deformation at maximum force),
better optical properties (higher gloss, lower haze), and higher
Elmendorf tear resistance in both TD and MD direction. It should be
noted that for optical properties, gloss and haze, the terpolymers
having both 3-methyl-1-butene and 1-butene together were
surprisingly the superior.
[0342] U.S. provisional patent application 61/146,915 filed Jan.
23, 2009, is incorporated herein by reference.
[0343] Numerous modifications and variations on the present
invention are possible in light of the above teachings. It is
therefore to be understood that within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described herein.
* * * * *