U.S. patent application number 14/634120 was filed with the patent office on 2015-06-18 for pe mib film zn/cr.
This patent application is currently assigned to EVONIK OXENO GmbH. The applicant listed for this patent is Anne Britt BJALAND, Stefan BUCHHOLZ, Gerhard ELLERMANN, Arild FOLLESTAD, Michael GRASS, Jarmo LlNDROOS, Ted M. PETTIJOHN. Invention is credited to Anne Britt BJALAND, Stefan BUCHHOLZ, Gerhard ELLERMANN, Arild FOLLESTAD, Michael GRASS, Jarmo LlNDROOS, Ted M. PETTIJOHN.
Application Number | 20150166749 14/634120 |
Document ID | / |
Family ID | 41818460 |
Filed Date | 2015-06-18 |
United States Patent
Application |
20150166749 |
Kind Code |
A1 |
PETTIJOHN; Ted M. ; et
al. |
June 18, 2015 |
PE MIB FILM ZN/CR
Abstract
A film containing an interpolymer of ethylene and a
3-substituted C.sub.4-10 alkene is prepared using a catalyst system
comprising a Ziegler Natta or chromium oxide catalyst.
Inventors: |
PETTIJOHN; Ted M.;
(Magnolia, TX) ; GRASS; Michael; (Haltern am See,
DE) ; BUCHHOLZ; Stefan; (Hanau, DE) ;
ELLERMANN; Gerhard; (Marl, DE) ; BJALAND; Anne
Britt; (Porsgrunn, NO) ; FOLLESTAD; Arild;
(Stathelle, NO) ; LlNDROOS; Jarmo; (Ulefoss,
NO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PETTIJOHN; Ted M.
GRASS; Michael
BUCHHOLZ; Stefan
ELLERMANN; Gerhard
BJALAND; Anne Britt
FOLLESTAD; Arild
LlNDROOS; Jarmo |
Magnolia
Haltern am See
Hanau
Marl
Porsgrunn
Stathelle
Ulefoss |
TX |
US
DE
DE
DE
NO
NO
NO |
|
|
Assignee: |
EVONIK OXENO GmbH
Marl
DE
|
Family ID: |
41818460 |
Appl. No.: |
14/634120 |
Filed: |
February 27, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13145043 |
Oct 7, 2011 |
9012564 |
|
|
PCT/EP10/50252 |
Jan 12, 2010 |
|
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14634120 |
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61146948 |
Jan 23, 2009 |
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Current U.S.
Class: |
524/579 ;
264/564; 525/240; 526/348.5; 526/348.6 |
Current CPC
Class: |
C08F 210/16 20130101;
C08F 210/16 20130101; C08J 5/18 20130101; C08J 2323/08 20130101;
C08J 2323/04 20130101; C08F 2500/17 20130101; C08F 210/08 20130101;
C08F 2500/17 20130101; C08F 210/14 20130101; C08F 2500/17 20130101;
C08F 210/14 20130101; C08F 210/16 20130101; C08F 210/14 20130101;
C08F 210/16 20130101 |
International
Class: |
C08J 5/18 20060101
C08J005/18 |
Claims
1. A film comprising an interpolymer of ethylene and a
3-substituted C.sub.4-10 alkene, wherein said interpolymer is made
using a catalyst system comprising a Ziegler Natta or chromium
oxide catalyst.
2. A film 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.
3. A film as claimed in claim 1, wherein said 3-substituted
C.sub.4-10 alkene is 3-methyl-1-butene.
4. A film as claimed in claim 1, wherein said catalyst system is in
particulate form.
5. A film as claimed in claim 1, wherein said catalyst system
comprises a Ziegler Natta catalyst.
6. A film as claimed in claim 1, wherein said 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.
7. A film as claimed in claim 1, wherein said interpolymer
comprises ethylene in an amount of at least 60 wt % based on the
total weight of the interpolymer.
8. A film as claimed in claim 1, wherein said interpolymer
comprises two types of C.sub.2-8 alkene monomers and at least one
3-substituted C.sub.4-10 alkene monomer.
9. A film as claimed in claim 1, wherein said alkene interpolymer
has a Mw of 20 000 to 900 000.
10. A film as claimed in claim 1, wherein said alkene interpolymer
has a MFR.sub.2 of 0.01-5000.
11. A film as claimed in claim 1, wherein said alkene interpolymer
is unimodal.
12. A film as claimed in claim 1, further comprising another
polyethylene.
13. A film as claimed in claim 1, further comprising
antioxidant.
14. A film as claimed in any one of claim 1 which is a blown film
or multilayer film or an industrial film.
15. A process for the preparation of a film as claimed in claim 1
comprising blowing an interpolymer of ethylene and a 3-substituted
C.sub.4-10 alkene as defined in claim 1.
16. A laminate or an article or a packaging, comprising a film as
claimed in claim 1.
17. The film as claimed in claim 1, wherein said interpolymer is
prepared using a catalyst system comprising a chromium oxide
catalyst.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a film comprising an
interpolymer of ethylene and 3-substituted C.sub.4-10 alkene,
wherein the interpolymer is made using a catalyst system comprising
a Ziegler Natta or chromium oxide catalyst. The invention also
relates to a process for the preparation of the film and to
laminates and articles comprising the film.
[0003] 2. Description of the Related Art
[0004] Polyethylene is widely used in the manufacture of films,
often for use in packaging applications.
[0005] The use of films to form laminates for use in the packaging
industry is, for instance, well known. Laminates are used to form a
range of articles, for example, food containers, stand up pouches
and product labels. Films used for this purpose need to possess a
certain combination of properties. Specifically the films need
excellent tear strength in order that during production, and in
use, articles made from the film, do not fail. The films should
also possess impact strength and tensile strength to make the films
usable. Without adequate mechanical properties such as impact
strength, thicker films have to be made which is economically
unattractive and in some cases less aesthetically appealing. It is
also important that films have adequate optical properties such as
low haze and high gloss. Stiffness is also an important property,
particularly if they are to be used in the preparation of stand up
pouches. Obtaining films having a desirable combination of tear
strength and stiffness is often a challenge.
[0006] Another common application of polyethylene films in the
packaging industry is in the formation of bags or sacks. These are
used, for example, in the packaging of food stuffs such as cereals
and crisps, as well as much heavier materials such as sand, cement
mix, compost, stones etc. It is often desirable for the bags to be
transparent in order that their content can be easily determined.
More significantly, however, and especially in the case of heavy
duty sacks (e. g. bags and sacks designed for the packaging of
materials up to 25 kg, or even 50 kg in weight) the key requirement
is that they possess good mechanical properties such as impact
strength and tensile strength, and tear strength. This is necessary
as bags and sacks are usually transported on pallets, one on top of
the other. Hence the total load on at least some of the sacks is
extremely high, e. g. in the region of 1000 kg or more, in some
instances. Moreover such sacks are rarely handled with care and
must be able to withstand conventional transportation conditions
without tearing. Additionally a certain level of stiffness, e. g.
for stability on pallets, is usually desirable.
[0007] Films having attractive combinations of properties,
especially tear strength and mechanical strength, particularly
impact strength and tensile strength, as well as reasonable optical
performance are therefore highly desired for use in the packaging
industry. The difficulty often encountered, however, is that those
polymer properties that minimize, e. g. haze, are often those that
are detrimental to, e. g. impact strength. Additionally those
polymers possessing low haze and reasonable impact strength, often
have poor stiffness whilst those polymers possessing high tear
strength often have poor stiffness and in addition tend to have
high melt viscosities making melt processing difficult.
[0008] It is therefore common to utilize interpolymers and/or
blends of polymers in the manufacture of films to try to provide
the desired balance of film properties. Thus ethylene may be
copolymerized with a comonomer such as 1-butene in order to obtain
a polymer yielding films having increased dart drop strength and
tear resistance. In other words comonomers are generally used to
tailor the properties of a polymer to suit its target film
application. There are vast numbers of commercially available films
that are made from ethylene and 1-butene copolymers that provide
advantages over ethylene homopolymer films.
[0009] A film manufactured from ethylene/1-butene, for example,
typically has improved impact strength (e. g. dart drop) compared
to an ethylene homopolymer of the same density as dart drop
strength generally increases with the increasing molecular weight
of the comonomer. Its optical properties are also usually
excellent. On the other hand, however, films made from
ethylene/1-butene copolymers often do not have as high a tear
strength or as strong mechanical properties as desired. Often this
is disadvantage is compensated for by making films thicker than is
desirable. There is therefore a trade off between polymer
properties such as impact strength, tensile strength, tear strength
and melt viscosity and the thickness of the film that is
usable.
DETAILED DESCRIPTION OF THE INVENTION
[0010] Based on the drawbacks of the background art, there remains
a need for polymer films that are suitable for making packaging
items such as laminate films and bags or sacks with an appropriate
combination of mechanical properties, in particular impact strength
and tensile strength, tear strength and optical properties,
especially transparency and gloss. As always there is also a need
for the film to be capable of being manufactured cost effectively.
Since the margins on many packaging products are small, it is
important that packaging costs are kept to a minimum.
[0011] It has now been surprisingly found that films comprising an
interpolymer of ethylene and a 3-substituted C.sub.4-10 alkene,
wherein said interpolymer is made using a catalyst system
comprising a Ziegler Natta or chromium oxide catalyst, have
excellent tear strength and high tensile strength as well as
reasonable impact strength and optical properties (e. g. haze).
More specifically it has been unexpectedly found that such
interpolymers yield films having tear strength and tensile strength
that are better than those of conventional ethylene/1-butene
copolymers and comparable impact strength and optical properties.
In other words, the films of the present invention possess a very
attractive balance of properties and may, e. g. be used at thinner
gauges than conventional ethylene/1-butene films.
[0012] Films comprising an interpolymer of ethylene and a
3-substituted C.sub.4-10 alkene have been generically disclosed in
the background art but it has never been realized before that a
polyethylene interpolymer with a 3-substituted C.sub.4-10 alkene
made using a catalyst system comprising a Ziegler Natta or chromium
oxide catalyst would provide film with such an advantageous
combination of tear strength, tensile strength, impact strength and
optical properties.
[0013] In a first aspect, the present invention provides a film
comprising an interpolymer of ethylene and a 3-substituted
C.sub.4-10 alkene, wherein said interpolymer is made using a
catalyst system comprising a Ziegler Natta or chromium oxide
catalyst.
[0014] In a preferred embodiment of the present invention, said
interpolymer is made using a catalyst system comprising a Ziegler
Natta catalyst.
[0015] In a further preferred embodiment of the present invention,
the film is a blown film.
[0016] In a further preferred embodiment of the present invention,
the film is an industrial film.
[0017] In a further aspect, the present invention provides a
process for the preparation of a film as hereinbefore described
comprising blowing an interpolymer of ethylene and a 3-substituted
C.sub.4-10 alkene, wherein said interpolymer is made using a
catalyst system comprising a Ziegler Natta or chromium oxide
catalyst.
[0018] In a still further aspect, the present invention provides a
laminate comprising a film as hereinbefore described.
[0019] In yet another aspect, the present invention provides an
article comprising a film as hereinbefore described (e. g. for use
in packaging).
[0020] In yet another aspect, the present invention provides the
use of a film as hereinbefore described in packaging.
DEFINITIONS
[0021] As used herein the term "interpolymer" refers to polymers
comprising repeat units deriving from ethylene and a 3-substituted
C.sub.4-10 alkene monomer. The interpolymer may also contain repeat
units deriving from other monomers, e. g. C.sub.3-10 alkenes.
Preferred interpolymers are binary (i. e. preferred interpolymers
are copolymers) and comprise repeat units deriving from ethylene
and one type of 3-substituted C.sub.4-10 alkene comonomer. Other
preferred interpolymers are ternary, e. g. they comprise repeat
units deriving from ethylene, one type of 3-substituted C.sub.4-10
alkene comonomer and another C.sub.3-10 alkene. 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.
[0022] The term "alkene homopolymer" as used herein refers to
polymers which consist essentially of repeat units deriving from
one type of C.sub.2-6 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.2-6 alkene based on
the total weight of the polymer.
[0023] 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.
[0024] 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.
[0025] 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. A multisite catalyst system used in the present
invention comprises at least one Ziegler Natta or chromium oxide
catalyst. Examples of a multisite catalyst system are one
comprising two or three different Ziegler Natta active sites
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.
[0026] 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.
[0027] As used herein the term particulate catalyst system means a
catalyst system that when fed to the polymerization reactor or into
the polymerization section, has its active sites or active site(s)
precursors within solid particles, preferably porous particles.
This is in contrast to catalyst systems with active sites, or
precursor compounds, which are liquid or are dissolved in a liquid.
It is generally presumed that when carrying out a polymerization
using a particulate catalyst system the particles of the catalyst
will be broken down to catalyst fragments. These fragments are
thereafter present within polymer particles whenever the
polymerization is carried out in conditions whereby solid polymer
forms. The particulate catalyst system may be prepolymerized during
the catalyst preparation production process or later. The term
particulate catalyst system also includes the situation wherein an
active site or active site precursor compound contacts a carrier
just before, or at the same time, as the active site or active site
precursor compound contacts the monomer in the polymerization
reactor.
[0028] As used herein the term "slurry polymerization" refers to a
polymerization wherein the polymer forms as a solid in a liquid.
The liquid may be a monomer of the polymer. In the latter case the
polymerization is sometimes referred to as a bulk polymerization.
The term slurry polymerization encompasses what is sometimes
referred to in the art as supercritical polymerization, i. e. a
polymerization wherein the polymer is a solid suspended in a fluid
that is relatively close to its critical point, or if the fluid is
a mixture, its pseudocritical point. A fluid may be considered
relatively close to its critical point if its compressibility
factor is less than double its critical compressibility factor or,
in the case of a mixture, its pseudocritical compressibility
factor.
[0029] Gas phase polymerization is a term of the art and is readily
understood by the skilled man.
[0030] As used herein the term "solution polymerization" refers to
a polymerization wherein, in the polymerization reactor, the
polymers are dissolved in a solvent.
[0031] 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.
[0032] 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 using a multisite
catalyst system in a single reactor 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
crystallization temperature of components.
[0033] In contrast a polymer comprising one component produced
under constant polymerization conditions is referred to herein as
unimodal.
[0034] As used herein the term laminate refers to a film structure
comprising at least one film layer and a substrate. The film
structure is prepared by adhering said film layer(s) to said
substrate. During the adhesion process, the film layer(s) and the
substrate are solid (i. e. they do not form a melt or liquid during
the adhesion process).
[0035] As used herein the term lamination film refers to the film
layer(s) that are used in the lamination process. The lamination
film may comprise 1 or more (e. g. 3, 5, 7) layers.
[0036] As used herein the term substrate refers to the material to
which at least one lamination film is adhered. It may, for example,
comprise a polymer, a metal or paper. If the substrate is
polymeric, it preferably has a higher melting/softening point than
the lamination film.
[0037] Ethylene
[0038] Ethylene for use in preparation of films of the invention is
commercially available from numerous suppliers, e. g. from Sigma
Aldrich.
[0039] 3-Substituted C.sub.4-10 alkene
[0040] 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.
[0041] 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.
[0042] 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.
[0043] Preferred 3-substituted C.sub.4-10 alkenes for use in the
interpolymers 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.
[0044] 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.
[0045] Representative examples of compounds of formula (I) that can
be used in the interpolymers include 3-methyl-1-butene,
3-methyl-1-pentene, 3-methyl-1-hex ene, 3-ethyl-1-pentene and
3-ethyl-1-hexene. A particularly preferred 3-substituted C.sub.4-10
alkene is 3-methyl-1-butene.
[0046] 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.
Other C.sub.3-8 Alkene
[0047] The interpolymer may comprise one or more additional
C.sub.3-8 alkene. Preferably, the amount of additional C.sub.3-8
alkene present in the interpolymer is 0.01-15% wt, more preferably
0.1-10% wt, e. g. 1-5% wt.
[0048] Preferably, the additional C.sub.3-8 alkene is a monoalkene.
Still more preferably the C.sub.3-8 alkene is a terminal alkene. In
other words, the C.sub.3-8 alkene is preferably unsaturated at
carbon numbers 1 and 2. Preferred C.sub.3-8 alkenes are thus
C.sub.3-8 alk-1-enes.
[0049] The C.sub.3-8 alkene is preferably a linear alkene. Still
more preferably the C.sub.3-8 alkene is an unsubstituted C.sub.3-8
alkene.
[0050] Representative examples of C.sub.3-8 alkenes that may be
present in the interpolymer include propylene, 1-butene, 1-pentene,
4-methyl-1-pentene, 1-hexene and 1-octene. Preferably, the
C.sub.3-8 alkene is selected from propylene, 1-butene,
4-methyl-1-pentene or mixtures therefore.
[0051] C.sub.3-8 alkenes for use in the present invention are
commercially available. Alternatively, propylene and but-1-ene may
be prepared by thermal cracking. Linear olefins are available from
catalytic oligomerization of ethylene or by Fischer Tropsch
synthesis.
[0052] Preferably, the interpolymer does not comprise an alkene
other than ethylene or 3-substituted C.sub.4-10 alkene.
[0053] Catalyst System
[0054] The polymerization catalyst system used in the preparation
of the interpolymer comprises a Ziegler Natta or chromium oxide
catalyst, preferably a Ziegler Natta catalyst.
[0055] Catalyst systems comprising a Ziegler Natta catalyst may be
used in solution form or particulate form but is preferably in
particulate form. Catalyst systems comprising a chromium oxide
catalyst are in the form of particulates.
[0056] The particles preferably have a weight average particle size
of 0.5 to 250 microns, preferably 4 to 150 microns.
[0057] Ziegler Natta Catalyst System
[0058] 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.
[0059] Catalyst System Particles
[0060] Transition Metal Component
[0061] 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.
[0062] 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.
[0063] 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.
[0064] Preferably, the final solid catalyst system particles also
comprise a group metal, preferably a magnesium compound, still more
preferably a Mg--Cl compound, e. g. MgCl.sub.2.
[0065] The magnesium compound may be introduced into the catalyst
system preparation as the Mg--Cl (e. g. MgCl.sub.2 compound
itself), but it is preferred to make it in situ within the catalyst
system 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.
[0066] The content of Mg in the final solid catalyst based on the
weight of dry, solid, catalyst component is preferably 1-25 wt
%.
[0067] Particle Building Material
[0068] The particle building material present in the Ziegler Natta
catalyst system 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.
[0069] 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.
[0070] Preformed carriers that are suitable for the preparation of
Ziegler Natta catalyst systems are commercially available, e. g.
from Grace and PQ Corporation. A preferred preformed carrier
material for use in the catalyst system is 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] If a metal oxide is the carrier, 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] If the catalyst is to be used for solution polymerization,
preferably no carrier is used. For solution polymerization, it is
preferred that the majority (e. g. all) of the particle building
material is identical to the group 2 compound associated with the
transition metal.
[0074] Activator and Additional Components
[0075] 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 a part of the solid,
particulate catalyst, but added to the polymerization reactor as a
liquid.
[0076] The Ziegler Natta catalyst system 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 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.
[0077] Catalyst System Preparation
[0078] The Ziegler Natta catalyst system 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. 390,1863, No. 4,294,2200, No. 4,617,360, WO 91/18934.
[0079] 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.
[0080] 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
for slurry and gas phase polymerization and 2 to 20 .mu.m for
solution phase polymerization. In all cases, the particles are
preferably spherical.
[0081] 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.
[0082] Chromium Oxide Catalyst Systems
[0083] 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.
[0084] Multisite Catalyst Systems
[0085] Multisite catalyst systems may be used in the preparation of
interpolymers present in the films of the present in the films of
the invention.
[0086] Multisite catalyst systems for use in the polymerization may
be hybrids from two (or more) different catalyst families but must
include at least one Ziegler Natta or chromium oxide active site.
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.
[0087] Alternatively, chromium oxide catalysts may, in some cases,
behave as dual site catalysts, 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.
[0088] High Catalyst Activity/Productivity
[0089] A feature of the above-described catalyst system,
particularly in gas and slurry phase polymerization, is that it has
a high activity coefficient in the copolymerization of ethylene and
3-substituted C.sub.4-10 alkene at a polymerization temperature of
about 80.degree. C. Preferably, the activity coefficient of the
catalyst system is at least 60 g polyalkene/(g cat. system, h,
bar), still more preferably the activity coefficient of the
catalyst system is at least 80 g polyalkene/(g cat. system, h,
bar), e. g. at least 110 g polyalkene/(g cat. system, h, bar).
There is no upper limit on the activity coefficient, e. g. it may
be as high as 1000 g polyalkene/(g cat. system, h, bar).
[0090] The high catalytic productivity 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 materials feed systems.
[0091] Even more significantly, however, the fact that a lesser
amount of catalyst system can be used per kg of final polymer means
that less catalyst and/or catalyst system residues are present in
the polymer as impurities and films made therefrom are much less
prone to degradation. This can be achieved without washing (e. g.
deashing) the polymer as described below.
[0092] Polymerization and Downstream Process
[0093] The interpolymer present in the films of the present
invention may be prepared by any conventional polymerization
process, e. g. gas phase polymerization and/or slurry
polymerization and/or solution polymerization. Preferably, the
interpolymer is made using slurry and/or gas phase polymerization,
e. g. slurry polymerization.
[0094] A prepolymerization may also 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.
[0095] Gas Phase Polymerization
[0096] Commercial Processes
[0097] 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 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
feed 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 polymerization
part of Borstar PE staged reactor process by Borealis.
[0098] Gas Phase Reactor Parameters and Operation
[0099] The high activity of the polymerization catalyst system 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 2500 g polymer per g
of solid catalyst system. Still more preferably the productivity of
the solid catalyst is at least 3500 g polymer/g catalyst system, e.
g. at least 5000 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 1000 g polymer per g of total catalyst
system. Still more preferably the productivity of the solid
catalyst is at least 1500 g polymer/g total catalyst system, e. g.
at least 2000 g polymer/g total catalyst system. The upper limit is
not critical but might be in the order of 20000 g polymer/g total
catalyst system.
[0100] Advantageously, the process typically proceeds without
reactor fouling.
[0101] 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.
[0102] Hydrogen is also preferably fed into the reactor to function
as a molecular weight regulator. The molar ratio between the
concentration of hydrogen and the feed of ethylene into the reactor
system is preferably 1: 1000-1:1.
[0103] The concentration in the gas in the reactor of the major
monomer, ethylene, is preferably 10-70 mol %, more 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
%.
[0104] Preferably, nitrogen is also present in the reactor. It
functions, e. g. as a flushing gas.
[0105] 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.
[0106] 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.
[0107] Thus in a preferred process the catalyst components or
catalyst system is injected into the reactor at a rate equal to its
rate of removal from the reactor. An advantage of the process
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.
[0108] When used in a gas phase polymerization of a 3-substituted
C.sub.4-10 alkene comonomer, the polymerization catalyst system
herein described 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 1 kg/ton polymer, still more
preferably less than 0.8 kg/ton polymer, e. g. less than 0.5 kg/ton
polymer.
[0109] 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.
[0110] 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 %.
[0111] 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 gas must be acquired, purified,
added, controlled, removed from the reactor and the polymer and
separated from the gas mixture, especially in quantities.
[0112] 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.
[0113] 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.
[0114] 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.
[0115] For instance, a gas phase polymerization may be carried out
under the following conditions: [0116] a concentration of C.sub.3-6
alkane of 0.01-5 mol % [0117] a concentration of nitrogen, 10-40
mol %, [0118] a concentration of ethylene of 10-50 mol %, [0119] 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 [0120] a concentration of hydrogen of 1-5 mol %.
[0121] Preferably, the feed of 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.
[0122] Slurry Phase Polymerization
[0123] The slurry polymerization reaction is preferably carried out
in conventional circulating loop or stirred tank reactors. Suitable
polyalkene processes are, for example, Hostalen staged (where
catalyst system and polymer sequentially pass from reactor to
reactor) tank slurry reactor process for polyethylene by
LyondellBasell, LyondellBasell-Maruzen staged tank slurry reactor
process for polyethylene, Mitsui staged tank slurry reactor process
for polyethylene by Mitsui, CPC single loop slurry polyethylene
process by Chevron Phillips, Innovene staged loop slurry process by
Ineos and in part the Borstar staged slurry loop and gas phase
reactor process for polyethylene by Borealis.
[0124] The high activity of the catalyst systems hereinbefore
described allow for efficient slurry polymerization to be carried
out. Preferably, the productivity achieved based on the total (dry)
weight of the catalyst system in the polymerization process is at
least 1 ton polymer/kg of catalyst system. Still more preferably
the productivity of the total catalyst system is at least 2 ton
polymer/kg catalyst system, e. g. at least 3 ton polymer/kg
catalyst system. The upper limit is not critical but might be in
the order of 30 ton polymer/kg catalyst system. Advantageously, the
process typically proceeds without reactor fouling.
[0125] Slurry Reactor Parameters and Operation
[0126] The conditions for carrying out slurry polymerizations 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
reaction pressure will preferably be in the range 1 to 100 bar, e.
g. 10 to 70 bar. The residence time in the reactor or reactors (i.
e. in the polymerization section) is preferably in the range 0.5 to
6 hours, e. g. 1 to 4 hours. The diluent used will generally be an
aliphatic hydrocarbon having a boiling point in the range -50 to
100.degree. C. Preferred diluents include n-hexane, isobutane and
propane, especially isobutane.
[0127] Hydrogen is also preferably fed into the reactor to function
as a molecular weight regulator. The molar ratio between the feed
of hydrogen and the feed of the ethylene into the reactor system is
1:10 000-1:10.
[0128] Preferably, the polymerization reaction is carried out as a
continuous or semi-continuous process. Thus the monomers, diluent
and hydrogen 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 slurry 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.
[0129] Thus in a preferred process the 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 therefore comprise less impurities
deriving from the catalyst system.
[0130] When used with a 3-substituted C.sub.4-10 alkene comonomer,
the catalyst systems herein described gives a very high activity,
enabling a high productivity (ton polymer/kg catalyst system).
Consequently relatively low concentrations of catalyst system are
required in the reactor. Preferably, the concentration of catalyst
system in the slurry polymerization is less than 0.3 kg/ton slurry,
still more preferably less than 0.2 kg/ton slurry, e. g. less than
0.1 kg/ton slurry. Preferably, the concentration of catalyst system
is at least 0.01 kg/ton slurry. Preferably, the concentration of
polymer present in the reactor during polymerization is in the
range 15 to 55% wt based on total slurry, more preferably 25 to 50%
wt based on total slurry. Such a concentration can be maintained by
controlling the rate of addition of monomer, the rate of addition
of diluent and catalyst system and, to some extent, the rate of
removal of polymer slurry from the slurry reactor.
[0131] Solution Phase Polymerization
[0132] Polymerization may be conducted in solution (i. e. with the
polymer in solution in a solvent), particularly when a catalyst
system comprising a Ziegler Natta catalyst is used. The conditions
for carrying out solution phase polymerization are well established
in the art. The reaction temperature is preferably 120-250.degree.
C. The solvent is preferably a saturated C.sub.6-10 hydrocarbon or
a mixture thereof. The residence time in the reactor(s) is
preferably in the range 1-30 minutes. The partial pressure of
monomer is preferably 20-150 bar. The concentration of polymer is
preferably 5-20% wt. In addition to solvent, comonomer(s) and
catalyst system components, hydrogen may optionally be fed to the
reactor.
[0133] Multireactor systems may optionally be employed. When used,
multistage reactor systems are preferably in a parallel
arrangement.
[0134] After polymerization, the liquids (solvent and comonomer)
are preferably vaporized from the polymer. The polymer is
preferably mixed with additives and pelletized as discussed in more
detail below.
[0135] Multistage Polymerization
[0136] The interpolymer may be prepared in a single stage
polymerization or in a multistage polymerization.
[0137] When a polymer is produced in a multistage process, the
reactors may be in parallel or in series but arrangement in series
is preferred, e. g. for slurry and gas phase polymerization. For
solution polymerization, a parallel arrangement is preferred. If
the polymer components are produced in a parallel arrangement in
solution polymerization, their solutions are preferably mixed for
homogenization before extrusion.
[0138] A multistage polymerization may comprise the above-described
slurry polymerization in combination with one or more further
polymerizations. Thus, for example, two slurry polymerizations can
be carried out in sequence (e. g. in Mitsui, Hostalen or Innovene
slurry processes) or a slurry polymerization stage can be followed
by a gas phase polymerization stage as described above (e. g. in
Borstar or Spheripol processes). Alternatively, a slurry
polymerization may be preceded by a gas phase polymerization. A
still further possibility is that two gas phase polymerizations are
carried out in sequence.
[0139] 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 or at least a broadening of the molecular weight
distribution of each polymer component by itself. The product of a
multistage polymerization is usually a multimodal polyalkene.
[0140] Preferred conditions for the slurry and gas phase
polymerizations in a multistage process are the same as those
described above. It is possible, however, not to add comonomer to
one stage of a multistage polymerization. When no comonomer is
present in a stage of a multistage polymerization, the polymer
component from that stage is an ethylene homopolymer.
[0141] 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.
[0142] When a two stage polymerization is utilized, the lower
molecular weight polymer component is preferably produced in the
slurry reactor as described in detail above. The higher molecular
weight component may be produced in another slurry reactor or in a
gas phase reactor. The higher molecular weight component is
typically produced using a lower hydrogen/monomer feed. The
reactors may be connected in parallel or in series, but preferably
they are connected in series, especially if they are slurry or gas
phase reactors or a combination of the two. Preferably, the same
catalyst system is used in both reactors. Preferably, the catalyst
system is only fed into the first reactor and flows from this,
along with polymer, to the next reactor(s) in sequence. The higher
molecular weight component may be an interpolymer (e. g. copolymer)
or homopolymer. Preferably, it is a copolymer, and more preferably,
it is a copolymer comprising a 3-substituted C.sub.4-10 alkene as
hereinbefore described.
[0143] Preferably, however, the interpolymer is made in a single
stage polymerization. Still more preferably the interpolymer is
made in a slurry phase polymerization.
[0144] Multimodal polymers may alternatively be prepared by using
two or more different Ziegler Natta and/or chromium oxide catalysts
in a single reactor or by using a multisite catalyst as described
above.
[0145] 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 a more incorporating comonomer on a site I and on
another less incorporating 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.
[0146] 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.
[0147] A further possibility is to blend different interpolymers as
hereinbefore described, e. g. prior to pelletisation. Blending is,
however, less preferable to the production of multimodal polymer,
e. g. by multistage polymerization.
[0148] Multimodal and Unimodal Polymers
[0149] 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.
[0150] Compared to unimodal interpolymer, at the same density
(stiffness) and at the same high ease of extrusion as regards
extruder screw and die processes, a multimodal interpolymer
comprising 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 in film applications wherein they enable
improved impact resistance and often improved tear resistance.
[0151] 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
useful in the manufacture of films.
[0152] Downstream Requirements and Process
[0153] When the final polymer product is obtained from the
reactor(s), the polymer is removed therefrom and liquid and/or
volatile components are preferably separated from it by stripping,
flashing and/or filtration. For instance, for slurry and gas phase
processes, the polymer is removed from the reactor section and to
remove volatiles, is preferably filtered or flashed. For slurry
processes, the diluent is also preferably separated from the
polymer by flashing or filtration.
[0154] 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.
[0155] Preferably, the polymer is dried (e. g. to remove residues
of liquids and gases from the reactor).
[0156] In slurry and gas phase processes, 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 .mu.m size, and the dry, loose bulk
density being higher than 300 kg/m.sup.3.
[0157] For solution processes, the solvent is preferably removed by
flashing and the melt conveyed directly to the pelletizer after
additivation.
[0158] The major part of the liquid and gaseous components that
leave the reactor(s) with the polymer, including unconverted
comonomer, is recycled back to the polymerization section.
[0159] Preferably, these processes, from the polymerization until
the pelletisation extruder outlet, are carried out under an inert
(e. g. N.sub.2) gas atmosphere. Prior to pelletisation, 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.
[0160] Additives and Pelletisation
[0161] Antioxidants are preferably added (process stabilizers and
long term antioxidants) to the polymer, e. g. prior to
pelletisation. Other additives (antiblocking agents, color
masterbatches, antistatics, slip agents, fillers, UV absorbers,
lubricants, acid neutralizers, fluoroelastomer and other polymer
processing aids (PPA), UV stabilizers, acid scavengers, nucleating
agents) may optionally be added to the polymer.
[0162] 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 phosphites/phosphonites and sulphur-containing compounds
(e. g. thioethers).
[0163] Preferably, the antioxidant(s) is selected from the group of
organic phosphites/phosphonites 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.
[0164] 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;
3,5-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))p-
ropane;
triethyleneglycole-bis-(3-tert.-butyl-4-hydroxy-5methylphenyl)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.
[0165] Among those compounds, the following phenolic-type
antioxidant compounds are especially preferred to be included in
the polymers:
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.
[0166] Preferred organic phosphite/phosphonite antioxidants contain
a phosphite moiety or a phosphonite 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.
[0167] Among the above-mentioned compounds, the following
phosphite/phosphonite antioxidant compounds are preferred to be
included in the polymers:
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.
[0168] As antioxidant either a single compound or a mixture of
compounds may be used. Particularly preferably the polymer
comprises a sterically hindered phenolic compound and a
phosphite/phosphonite compound.
[0169] The skilled man can readily determine an appropriate amount
of antioxidant to include in the polymers. As discussed above,
however, the polymers comprise less catalyst system residues than a
film of the same density and MFR made with 1-butene as comonomer
thus it is possible to add less antioxidant thereto (i. e. the
polymer possess increased inherent stability). Thus a sterically
hindered phenolic antioxidant may be used in an amount of 200-1000
ppm wt, more preferably 300-800 ppm wt, e. g. 400-600 ppm wt or
about 500 ppm wt. The amount of organic phoshite/phosphonite
antioxidant present in the polymer is preferably 50-500 ppm wt,
more preferably 100-350 ppm wt and most preferably 150-250 ppm
wt.
[0170] 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.
[0171] Further preferred polymers comprise a lubricant. Preferred
lubricants include fatty acid salts (e. g. Ca or Mg stearate) and
polymer processing aids (PPAs). A preferred PPA is a fluoropolymer,
e. g. as available from Dyneon as FX 5922. The amount of lubricant
present in the polymer is preferably 100-500 ppm wt, more
preferably 300-450 ppm wt.
[0172] The polymer or polymer mix is preferably extruded and
granulated into pellets, preferably after addivation. In this step,
any extruder known in the art may be used, however, twin screw
extruders are preferred. A preferred twin screw extruder is a
counter rotating twin screw extruder. Preferably, the resulting
pellets have a high bulk density, e. g. more than 500 kg/m.sup.3
and a low amount of fines, e. g. less than 10% wt of the polymer is
smaller than 2 mm in size.
[0173] Interpolymer Production Advantage
[0174] As discussed above, it is known that the mechanical
performance of polymer films is improved by increasing the
molecular weight of comonomer in the order propylene, butene,
hexene and octene. The higher the molecular weight of the
comonomer, however, the harder it is to produce the copolymer
economically.
[0175] To obtain pure polymer, the non-incorporated comonomer
residues therein should be low. The higher the molecular weight of
the comonomer, however, the higher its solubility in the polymer at
a given partial pressure. For particle form polymerization
processes (slurry and gas phase polymerization processes), the
removal of non-incorporated monomer is typically done by counter
current drying of the polymer powder with N.sub.2, a process in
which there is typically close to equilibrium between the comonomer
in the gas and comonomer dissolved within the polymer phase.
Thereafter an increase in the molecular weight of the comonomer
makes the drying much more difficult and in practice, octene is not
used in particle form polymerization for this reason. 1-hexene and
1-butene are therefore most commonly used, especially 1-butene,
which can be stripped off relatively easily, i. e. with reasonable
low feed of N.sub.2 compared to the polymer flow, at a temperature
somewhat below the lumping temperature of the polymer powder.
[0176] A further advantage of the films of the invention is
therefore that they comprise a 3-substituted C.sub.4-10 alkene such
as 3-methyl-1-butene that is more volatile than hexene and octene
and is therefore easier to strip from the polymer product.
[0177] Interpolymer Composition and Properties
[0178] The amount of ethylene monomer present in the interpolymer
is preferably 60-99.99% wt, more preferably 70-99.9% wt, still more
preferably 80-99.5% wt, e. g. 93-99.0% wt.
[0179] The amount of 3-substituted C.sub.4-10 alkene (e. g.
3-methyl-1-butene)monomer present in the interpolymer is preferably
0.01 to 40% wt, more preferably 0.1-30% wt, still more preferably
0.5-20% wt, e. g. 0.5-6.5% wt or less than 7% wt.
[0180] 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.
[0181] 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.
[0182] Preferably, the interpolymer has a crystallinity as measured
by DSC of 10-90%, more preferably 15-75%, most preferably
25-70%.
[0183] The density of the interpolymer is preferably in the range
890-965 kg/m.sup.3, still more preferably in the range 915-950
kg/m.sup.3, e. g. 925-940 kg/m.sup.3.
[0184] The MFR.sub.2 of the interpolymer is preferably in the range
0.002-2000 g/10 min, more preferably in the range 0.05-500 g/10
min, still more preferably 0.15-49 g/10 min, e. g. 0.3-5 g/10
min.
[0185] The MFR.sub.21 of the interpolymer is preferably greater
than 0.05 g/10 min, more preferably greater than 0.1 g/10 min,
still more preferably greater than 1 g/10 min.
[0186] The melting temperature of the interpolymer is preferably in
the range 110-140.degree. C., still more preferably in the range
115-135.degree. C., e. g. 120-130.degree. C.
[0187] The Mn of the interpolymer of the invention is preferably in
the range 5000-200 000 g/mol, still more preferably in the range 8
000-100 000 g/mol, e. g. 12 000-50 000 g/mol.
[0188] The Mw of the interpolymer is preferably in the range 30
000-800 000 g/mol, still more preferably in the range 50 000-150
000 g/mol, e. g. 90 000-130 000 g/mol.
[0189] The Mw/Mn of the interpolymer is preferably in the range
4-50, more preferably in the range 5-30, e. g. 6-15.
[0190] Preferably, the interpolymer of the present invention is
unimodal.
[0191] The interpolymer as hereinbefore described is also
particularly suited for crosslinking compared to other single site
or Ziegler Natta polymers made using conventional, linear alkenes
as comonomers. Crosslinking may be carried out on the articles in
their final geometric form, e. g. through the use of radicals,
either by radiation, primarily gamma radiation or at high
temperature by peroxides decomposition.
[0192] The interpolymer is obtained with high purity. Thus the
interpolymer contains only very low amounts of catalyst or catalyst
system residues (i. e. ash). Preferably, the amount of catalyst
system ash in the interpolymer, and therefore film, is less than
1000 ppm wt, still more preferably less than 500 ppm wt, e. g. less
than 300 ppm wt. 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 present in the polymer after polymerization and
prior to any washing, deashing or additivation step.
[0193] 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 films of the present invention is that they
contain very low amounts of transition metal. The interpolymers,
and therefore films, preferably comprise less than 300 .mu.mol
transition metal per kg polymer, more preferably less than 200
.mu.m transition metal per kg polymer, still more preferably less
than 150 .mu.mol transition metal per kg polymer, e. g. less than
100 .mu.mol transition metal per kg polymer.
[0194] Film Preparation
[0195] Optional further polymer components and/or additives may be
added to the polymer at the film extrusion stage, especially
polymer processing aids, external lubricants and antiblocking
agents. Preferably, further polymer components are added as is
discussed in more detail below.
[0196] The films of the present invention may be monolayer or
multilayer films. To form multilayer films, the interpolymer
composition hereinbefore described may be coextruded, i. e. the
interpolymer composition as hereinbefore described is fed into the
film extrusion die with at least one other film material, each from
a separate feed extruder, to make a multilayer film, containing two
or more layers. After the extrusion process itself (whether to
produce a monolayer or multilayer film), the film can be
monoaxially or biaxially stretched to improve mechanical and
optical properties.
[0197] Alternatively, films may be prepared by lamination.
Multilayer films may, for example, be prepared by lamination of a
coextruded multilayer film.
[0198] The films of the present invention may be prepared by any
conventional procedure, e. g. casting or blowing. Preferably, the
films are prepared by blowing.
[0199] Cast Film
[0200] The films of the present invention may be prepared by using
casting techniques, such as a chill roll casting process. For
example, a composition comprising the interpolymer hereinbefore
described can be extruded in a molten state through a flat die and
then cooled to form a film. The skilled man is aware of typical
casting conditions. Typically, however, extrusion is carried out at
a temperature in the range 150 to 350.degree. C., the die gap is in
the range 500-1300 .mu.m and the draw down ratio is in the range
50-200. Cooling is preferably carried out at a temperature of
0-35.degree. C.
[0201] As a specific example, cast films can be prepared using a
pilot scale commercial cast film line machine as follows. Pellets
of the interpolymer composition are melted at a temperature ranging
from about 200 to 260.degree. C., with the specific melt
temperature being chosen to match the melt viscosity of the
particular polymers. In the case of a multilayer cast film, the two
or more different melts are conveyed to a co-extrusion adapter that
combines the two or more melt flows into a multilayer, coextruded
structure. This layered flow is distributed through a single
manifold film extrusion die to the desired width. The die gap
opening is typically about 600 .mu.m. The material is then drawn
down to the final gauge. The material draw down ratio is typically
about 21:1 for 40 .mu.m films. A vacuum box or air knife may then
be used to pin the melt exiting the die opening to a primary chill
roll maintained at about 32.degree. C. The resulting polymer film
is collected on a winder. The film thickness may be monitored by a
gauge monitor and the film may be edge trimmed by a trimmer. One or
more optional treaters can be used to surface treat the film, if
desired.
[0202] A chill roll casting process and apparatus that can be used
to form a film of the present invention suitably modified in
accordance with the above-described processing parameters is in The
Wiley Encyclopedia of Packaging Technology, Second Edition, A. L.
Brody and K. S. Marsh, Ed., John Wiley and Sons, Inc., New York
(1997).
[0203] Although chill roll casting is one example, other forms of
casting can be used.
[0204] Blown Film
[0205] The films of the invention are preferably prepared by
blowing according to procedures well known in the art. Thus the
film may be produced by extrusion through an annular die and
blowing (e. g. with air) into a tubular film by forming a bubble
which is collapsed between nip rollers after solidification. The
film can then be slit, cut or converted (e. g. sealed) as required.
Conventional film production techniques may be used in this
regard.
[0206] The skilled man is aware of typical blowing conditions.
Typically, however, extrusion is carried out at a temperature in
the range 160 to 240.degree. C. and cooled by blowing gas (e. g.
air) at a temperature of 10 to 50.degree. C. to provide a frost
line height of up to 10 times, typically 2 to 8 times the diameter
of the die. The blow up ratio should generally be in the range 2 to
5, preferably 2.5 to 4.
[0207] As a specific example, blown films can be prepared as
follows. The interpolymer composition hereinbefore described is
introduced into a feed hopper of an extruder, such as a 63.5 mm
Egan extruder that is water-cooled, resistance heated, and has an
L/D ratio of 24:1. The film can be produced using a 15.24 cm Sano
die with a 2.24 mm die gap, along with a Sano dual orifice
non-rotating, non-adjustable air ring. The film is extruded through
the die into a film that is cooled by blowing air onto the surface
of the film. The film is drawn from the die typically forming a
cylindrical film that is cooled, collapsed and optionally subjected
to a desired auxiliary process, such as slitting, treating, sealing
and/or printing. The finished film can be wound into rolls for
later processing or can be fed into a bag machine and converted
into bags.
[0208] Apparatus for making a blown film according to the present
invention is available from e. g. Windmoller & Holscher and
from Alpine. Of course, other blown film forming equipment and
corresponding methods can also be used.
[0209] Film Structure and Composition
[0210] The product from the film forming process may be a monolayer
film or a film comprising two or more layers (i. e. a multilayer
film). In a multilayer film, the polymer composition of one layer
is typically different from that of adjacent layers, e. g. it
comprises different components or the same components in different
ratios.
[0211] In the case of monolayer films, they may consist of the
above-described interpolymer composition, i. e. it may not comprise
any other polyalkene component. Alternatively, the interpolymer
composition may be blended with one or more polymer components.
[0212] In the case of a multilayer film, one or more of its layers
may consist of the above-described interpolymer composition, i. e.
said layer may not comprise any other polyalkene component.
Alternatively, the interpolymer composition may be blended with one
or more polymer components.
[0213] Other Polymer Components
[0214] The films (monolayer and multilayer) of the present
invention may therefore comprise one or more polyalkene components.
The film may, for example, comprise a low density polyethylene
(LDPE). In the case of a multilayer film, the LDPE may be present
in one or more (e. g. all) of its layers.
[0215] LDPE is prepared using a well known high pressure radical
process using a radical generating compound such as peroxide. The
skilled polymer chemist appreciates that LDPE is a term of the art.
Both LDPE made in tubular and in autoclave reactors may be used,
including its copolymers, e. g. Ethylene vinyl acrylate (EVA),
ethylene methyl acrylate (EMA), ethylene butyl acrylate (EBA) and
ethylene ethyl acrylate (EEA)copolymers.
[0216] The LDPE present in the films of the present invention
preferably has a density in the range 915-937 kg/m.sup.3, still
more preferably 918-930 kg/m.sup.3, e. g. 920-924 kg/m.sup.3.
[0217] The LDPE present in the films of the present invention
preferably has a MFR.sub.2 in the range 0.2-4 g/10 min, still more
preferably 0.5-2 g/10 min, e. g. 0.7-1.0 g/10 min.
[0218] The amount of LDPE present in a monolayer film of the
invention may be 2 to 60% wt, more preferably 3 to 50% wt, still
more preferably 4-25% wt, e. g. 6-15% wt.
[0219] In the case of multilayer films, the amount of LDPE present
in any given layer may be 2 to 60% wt, more preferably 3 to 50% wt,
still more preferably 4-25% wt, e. g. 6-15% wt.
[0220] Further Additives
[0221] The films of the present invention may additionally comprise
conventional additives such as antioxidants, antiblocking agents,
color masterbatches, antistatics, slip agents (external
lubricants), fillers, UV absorbers, internal lubricants, acid
neutralizers, fluoroelastomer and other polymer processing aids
(PPA), UV stabilizers, acid scavengers, nucleating agents, etc. In
the case of a multilayer film, the additives may be present in one
or more (e. g. all) of its layers.
[0222] Preferred films may comprise external lubricants (slip
agents), e. g. erucamide or oleamide, to decrease film friction.
External lubricant should preferably be present in an amount of
300-1500 ppm wt.
[0223] Film Thickness
[0224] In the case of a multilayer film, each film layer may have a
thickness of, e. g. 2-200 .mu.m, preferably 5-70 .mu.m, more
preferably 15-40 .mu.m e. g. 20-35 .mu.m.
[0225] The total thickness of the film (monolayer or multilayer) is
not critical and depends on the end use. Thus films may have a
thickness of, e. g. 10-300 .mu.m, preferably 15-150 .mu.m, more
preferably 20-70 .mu.m, e. g. 30-60 .mu.m.
[0226] Film Properties
[0227] The films of the invention have a desirable balance of
properties.
[0228] The films of the invention exhibit reasonable dart impact
strength. Dart drop (ISO 7765/1) may be at least 1 g/.mu.m,
preferably at least 1.1 g/.mu.m, still more preferably at least 1.2
g/.mu.m, e. g. at least 1.3 g/.mu.m. The upper limit of dart drop
is not critical and may be, e. g. 10 g/.mu.m. In particular for a
40 .mu.m blown film consisting of an interpolymer as hereinbefore
described and particularly in the case of a film prepared according
to example 1 below, dart drop (ISO 7765/1) is preferably at least 1
g/.mu.m, preferably at least 1.1 g/.mu.m, still more preferably at
least 1.2 g/.mu.m, e. g. at least 1.3 g/.mu.m.
[0229] The films of the invention exhibit excellent tensile
strength. MD (machine direction) tensile strength (ISO 527-3) may
be at least 29 MPa, preferably at least 32 MPa, still more
preferably at least 34 MPa, e. g. at least 36 MPa. The upper limit
of MD tensile strength is not critical and may be, e. g. 100 MPa.
In particular for a 40 .mu.m blown film consisting of an
interpolymer as hereinbefore described and particularly in the case
of a film prepared according to example 1 below, MD tensile
strength (ISO 527-3) is preferably at least 29 MPa, preferably at
least 32 MPa, still more preferably at least 34 MPa, e. g. at least
36 MPa.
[0230] TD (transverse direction) tensile strength (ISO 527-3) may
be at least 27 MPa, preferably at least 30 MPa, still more
preferably at least 32 MPa, e. g. at least 34 MPa. The upper limit
of TD tensile strength is not critical and may be, e. g. 100 MPa.
In particular for a 40 .mu.m blown film consisting of an
interpolymer as hereinbefore described and particularly in the case
of a film prepared according to example 1 below, TD tensile
strength (ISO 527-3) is preferably at least 27 MPa, preferably at
least 30 MPa, still more preferably at least 32 MPa, e. g. at least
34 MPa.
[0231] The films of the invention exhibit excellent tear strength.
MD (machine direction) Elmendorf tear resistance (ISO 6383/2) may
be at least 0.018 N/.mu.m, preferably at least 0.022 N/.mu.m, still
more preferably at least 0.025 N/.mu.m, e. g. at least 0.027
N/.mu.m. The upper limit of tear resistance is not critical and may
be, e. g. 0.2 N/.mu.m. In particular for a 40 .mu.m blown film
consisting of an interpolymer as hereinbefore described and
particularly in the case of a film prepared according to example 1
below, MD tear strength (ISO 6383/2) is preferably at least 0.7 N,
preferably at least 0.8 N, still more preferably at least 0.95 N,
e. g. at least 1.05 N.
[0232] TD (transverse direction) Elmendorf tear resistance (ISO
6383/2) may be at least 0.03 N/.mu.m, preferably at least 0.04
N/.mu.m, still more preferably at least 0.05 N/.mu.m, e. g. at
least 0.06 N/.mu.m. The upper limit of tear resistance is not
critical and may be, e. g. 4 N/.mu.m. In particular for a 40 .mu.m
blown film consisting of an interpolymer as hereinbefore described
and particularly in the case of a film prepared according to
example 1 below, TD tear strength (ISO 6383/2) is preferably at
least 1.7 N, preferably at least 1.9 N, still more preferably at
least 2.1 N, e. g. at least 2.3 N.
[0233] Particularly preferred films (e. g. 40 .mu.m thick) of the
invention satisfy the following equation:
Tear>A(Thickness)10.sup.B(Density-935)MFR2.sup.C
wherein tear is Elmendorf tear measured according to ISO 6383/2 and
given in N, thickness is in .mu.m, density is measured according to
ISO 1183:1987 (E), method D and is in g/dm.sup.3, MFR.sub.2 is
measured according to ISO 1133 and is given in g/10 min and. In MD
direction, B is -0.045, C is -0.2 and A is 0.015 and in
particularly preferred films A is 0.017, more preferably 0.19 and
still more preferably 0.021. In TD direction, B is -0.02, C is -0.3
and A is 0.04 and in particularly preferred films A is 0.045, more
preferably 0.050 and still more preferably 0.055.
[0234] The films of the invention additionally exhibit high tensile
modulus properties (0.05-1.05%, ASTM D 882-A) in the machine and
transverse directions. These are preferably 250-600 MPa, more
preferably 320-450 MPa, e. g. 360-400 MPa, particularly for a 40
.mu.m blown film consisting of the interpolymer as hereinbefore
described, and especially in the case of a film prepared according
to example 1 below.
[0235] The films of the invention also preferably have a high
strain at break in both machine and transverse directions, e. g. at
least 600% in either direction (MD/TD), particularly for a 40 .mu.m
blown film consisting of the interpolymer as hereinbefore described
and especially in the case of a film prepared according to example
1 below.
[0236] The films of the invention preferably exhibit low haze. Haze
(ASTM D 1003) may be less than 40%, preferably less than 45%, e. g.
less than 30%, particularly for a 40 .mu.m blown film consisting of
the interpolymer as hereinbefore described and especially in the
case of a film prepared according to example 1 below. The lower
limit of haze is not critical and may be, e. g. 1%.
[0237] The films of the invention preferably exhibit high gloss.
Gloss (ASTM D 2457) may be greater than 60%, preferably greater
than 65%, e. g. greater than 70%, particularly for a 40 .mu.M blown
film consisting of the interpolymer as hereinbefore described and
especially in the case of a film prepared according to example 1
below. The upper limit of gloss is not critical and may be, e. g.
120%.
[0238] Film Applications
[0239] Industrial Films
[0240] The films of the present invention may be used as industrial
films, e. g. as industrial packaging films and as non packaging
industrial films. Examples of industrial packaging films include,
for example, shipping sacks e. g. heavy duty shipping sacks (HDSS),
stretch hoods, stretch wraps, liners and industrial shrink film.
Examples of non packaging industrial films include, for example,
building and constructing films (e. g. air and moisture membranes,
barrier films and geomembranes), agricultural films, protection
films and technical films.
[0241] Preferably, the films of the invention are used in
packaging. Heavy duty shipping sacks may, for example, be used for
packaging sand, cement, stones, compost, polymer pellets etc.
[0242] The film used for the production of industrial film may be a
monolayer film. In this case, the MFR.sub.2 of the interpolymer
composition from which it is formed is preferably 0.2-3 g/10 min,
more preferably 0.4-2.5 g/10 min and still more preferably 0.5-2
g/10 min. The density of the interpolymer composition is preferably
900-950 g/dm.sup.3, more preferably 915-945 g/dm.sup.3 and more
preferably 920-940 g/dm.sup.3.
[0243] More preferably, however, the film used for the production
of industrial film is a multilayer film, preferably obtained by
coextrusion. By utilizing more than one layer, the properties of
the overall film may be optimized to a greater extent than with a
single layer (monolayer) structure. This means that the film can be
made thinner without sacrificing important properties.
[0244] A preferred multilayer film for use in industrial film has
the structure aba wherein:
[0245] (a): outer layer
[0246] (b): core layer or core layers (b1b2b3)
[0247] (a): outer layer
[0248] Layers (a) preferably comprises 10-100% wt of the
interpolymer composition hereinbefore described, more preferably
50-100% wt and still more preferably 70-95% wt. Still more
preferably at least one of the layers (a) and more preferably both
additionally comprise 3-30% wt, more preferably 5-20% wt LDPE as
hereinbefore described. Preferably, the LDPE component has a
density of 880-930 kg/dm.sup.3 and a MFR.sub.21/MFR.sub.2 greater
than 30.
[0249] The interpolymer as hereinbefore described that is present
in the layers (a) preferably has a MFR.sub.2 of 0.2-3 g/10 min,
more preferably 0.5-2 g/10 min and still more preferably 0.7-1.5
g/10 min. The density of the interpolymer is preferably 900-945
g/dm.sup.3, more preferably 910-940 g/dm.sup.3 and still more
preferably 920-937 g/dm.sup.3.
[0250] A LDPE polymer optionally present in layers (a) preferably
has a MFR.sub.2 of 0.2-3 g/10 min, more preferably 0.5-2 g/10 min
and still more preferably 0.7-1.5 g/10 min. The density of the LDPE
is preferably 905-930 g/dm.sup.3, more preferably 910-926
g/dm.sup.3 and still more preferably 917-924 g/dm.sup.3.
[0251] The polymer composition of the layers (a) preferably has a
MFR.sub.2 of 0.2-3 g/10 min, more preferably 0.5-2 g/10 min and
still more preferably 0.7-1.5 g/10 min. The density of the polymer
composition of the layers (a) is preferably 890-940 g/dm.sup.3,
more preferably 900-935 g/dm.sup.3, still more preferably 910-930
g/dm.sup.3.
[0252] Layers (a) may optionally contain further polymer
components.
[0253] The layers (a) may have the same or different compositions,
but it is preferred if the layers (a) have the same
composition.
[0254] One or both of layers (a) may be used for printing. Layer(s)
(a) preferably has good sealing properties.
[0255] Layer (b) may be any polymer that can be formed into a film.
It may function e. g. to provide mechanical properties (impact
strength and stiffness) or barrier properties. It may consist of
several layers, e. g. 3, 5, 7 or 9 layers.
[0256] The following polymers are especially well suited for
inclusion in layer (b): Polyethyleneterephtalate (PET), polyamides
(PA), ethylene vinyl alcohol (EVOH), polypropylene (including
oriented polypropylene (OPP) and biaxially oriented polypropylene
(BOPP)) and polyethylene (included oriented polyethylene (OPE).
[0257] The layer(s) (b) may also comprise a polyethylene,
particularly a polyethylene interpolymer as hereinbefore described.
The interpolymer composition present in this layer preferably has a
MFR.sub.2 of 0.1-4 g/dm.sup.3, more preferably 0.3 to 2 g/10 min,
and still more preferably 0.2 to 1.5 g/10 min. The density of the
interpolymer composition is preferably 900 g/dm.sup.3 to 955
g/dm.sup.3, more preferably 920 to 945 g/dm.sup.3 and still more
preferably 920-940 g/dm.sup.3. Preferably, the interpolymer
composition present in layer(s) (b) has a lower MFR.sub.2 and a
lower density than the average of the polyethylene polymer present
in the layer.
[0258] The total thickness of the film of this embodiment (i. e. an
industrial film) is preferably 15-300 .mu.m, more preferably 25-250
.mu.m, still more preferably 40-200 .mu.m.
[0259] If the film has 3 or more layers, then preferably layers (a)
should each be 5-30% of the total thickness of the multilayer film,
and layer or layers (b) totally 25-90% of the total thickness. Thus
the thickness of each layer (a) is preferably 10-30 .mu.m. The
thickness of layer (b) is preferably 25-60 .mu.m.
[0260] Laminates
[0261] The film of the invention may also be incorporated into a
laminate. In the process of lamination a film is adhered to a
substrate. The film that is used in the lamination process is
herein referred to as a lamination film. The resulting product is
referred to herein as a laminate.
[0262] Lamination Film
[0263] The lamination film may be a monolayer film or a multilayer
film. Preferably, the lamination film is a multilayer film,
preferably formed by coextrusion.
[0264] The lamination film may, for example, have a coextruded
layer structure AC:
[0265] A outer layer; and
[0266] C inner layer,
wherein the inner layer is adjacent to the substrate.
[0267] More preferably the lamination film may have a coextruded
structure ABC:
[0268] A outer layer;
[0269] B core layer;
[0270] C inner layer,
wherein the inner layer is adjacent to the substrate.
[0271] The inner layer C preferably comprises 10-100% wt of the
interpolymer composition hereinbefore described, more preferably
50-100% wt and most preferably 70-95% wt. Still more preferably the
inner layer C additionally comprises 3-30% wt, more preferably
5-20% wt LDPE as hereinbefore described. Preferably, the LDPE
component has a density of 880-930 kg/dm.sup.3 and a
MFR.sub.21/MFR.sub.2 greater than 30. The inclusion of such a
component typically improves the processability of the polymer
composition.
[0272] The interpolymer as hereinbefore described that is present
in the inner layer C preferably has a MFR.sub.2 of 0.2-3 g/10 min,
more preferably 0.5-2 g/10 min and still more preferably 0.7-1.5
g/10 min. The density of the interpolymer is preferably 900-950
g/dm.sup.3, more preferably 910-945 g/dm.sup.3 and still more
preferably 920-940 g/dm.sup.3.
[0273] A LDPE polymer optionally present in inner layer C
preferably has a MFR.sub.2 of 0.2-3 g/10 min, more preferably 0.5-2
g/10 min and still more preferably 0.7-1.5 g/10 min. The density of
the LDPE is preferably 905-930 g/dm.sup.3, more preferably 910-926
g/dm.sup.3 and still more preferably 917-924 g/dm.sup.3.
[0274] The polymer composition of the inner layer C preferably has
a MFR.sub.2 of 0.2-3 g/10 min, more preferably 0.5-2 g/10 min and
still more preferably 0.7-1.5 g/10 min. The density of the polymer
composition of the inner layer C is preferably 890-940 g/dm.sup.3,
more preferably 900-935 g/dm.sup.3, still more preferably 910-930
g/dm.sup.3.
[0275] Layer C may optionally contain further polymer
components.
[0276] The outer layer A preferably has good sealing properties
since this side of the laminate is typically subjected to a sealing
process, e. g. in the production of pouches and bags. Preferably,
outer layer A also has good optical properties, namely haze and
gloss, especially gloss. Optionally, there is an additional
substrate on top of layer A, but preferably, A is a free
surface.
[0277] In AC lamination films, the layers A and C must be
different. In ABC lamination films, preferably outer layer A is
identical to inner layer C. Thus preferred features of layer C are
also preferred features of layer A. A preferred lamination film
structure is therefore ABA.
[0278] The core layer B may be any polymer that can be formed into
a film. It may function e. g. to provide mechanical properties
(rupture properties and stiffness) and barrier properties (oxygen,
water, flavor). It may consist of several layers.
[0279] The following polymers are especially well suited for
inclusion in layer B: polyethyleneterephtalate (PET), polyamides
(PA), ethylene vinyl alcohol (EVOH), polypropylene (including
oriented polypropylene (OPP) and biaxially oriented polypropylene
(BOPP)) and polyethylene (included oriented polyethylene
(OPE)).
[0280] If the core layer B consists of more than one layer, it
preferably consists of 3, 5, 7 or 9 layers. In such a case, the
layers preferably are symmetric so that in a 3 layer composition
B1B2B3, layers B1 and B3 are identical.
[0281] The total thickness of the lamination film is preferably
10-150 .mu.m, more preferably 15-90 .mu.M and still more preferably
20-70 .mu.m.
[0282] If the film has 3 or more layers, then preferably layer A
and C should each be 5-30% of the total thickness of the multilayer
film, and layer or layers B totally 25-90% of the total thickness.
Thus the thickness of layers A and C is preferably 10-30 .mu.m. The
thickness of layer B is preferably 25-60 .mu.m.
[0283] If the film has 2 layers A and B, then preferably each layer
should be 10-90% of the total thickness of the film, more
preferably 20-80% and most preferably 30-70%. Thus the thickness of
layer A is preferably 20-60 .mu.m. The thickness of layer B is
preferably 50-120 .mu.m.
[0284] Substrate
[0285] The substrate used in the preparation of the laminate
preferably comprises polyethyleneterephtalate (PET), polyamides
(PA), ethylene vinyl alcohol (EVOH), polypropylene, polyethylene,
metal, especially aluminium, paper or cardboard. The substrate may
also comprise more than one layer, e. g. metalized (aluminized)
polymer, or aluminium foil coated with polyethylene. The thickness
of the substrate is preferably 3-100 .mu.m, more preferably 4-50
.mu.m, still more preferably 5-30 .mu.m.
[0286] Print may optionally be applied on the surface of the
lamination film, preferably to a layer A therein, before the
lamination process. Alternatively, print may be applied to the
surface of the substrate. In the latter case the print is protected
from mechanical influence and from solvent/chemical action by the
lamination film, but is still visible through a transparent
lamination film.
[0287] Laminate and Lamination
[0288] The lamination film is preferably laminated onto the
substrate after the lamination film has been formed. Lamination
film may optionally be adhered to both sides of a substrate.
[0289] Lamination may be carried out by a continuous process where
lamination film(s) and substrate are pressed against each other at
elevated temperature. Typical temperatures used may be
150-300.degree. C. Neither the lamination film nor the substrate
melts during the lamination process. Often, in addition to the
layers previously mentioned, a layer (e. g. 0.5-5 .mu.m thick) of
adhesive is applied to the surface of at least one of the surfaces
to be laminated together. Suitable equipment for lamination can be
bought from Windmoller & Holscher and from Macchi.
[0290] The laminates of the invention have a wide variety of
applications but are of particular interest in packaging of food
and drink as well as packaging of consumer and industrial goods. In
food packaging the laminates of the invention may, for example, be
used for the packaging of pasta, milk powder, snack food, coffee
bags, margarine and frozen food. In consumer goods packaging, the
laminates of the invention may be used for packaging detergent
powder and toothpaste as well for the manufacture of stand-up
pouches for, e. g. for pet food, beverages etc.
[0291] 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
Determination Methods
[0292] Polymers
[0293] Unless otherwise stated, the following parameters were
measured on polymer samples as indicated in the Tables below.
[0294] 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.
[0295] 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.
[0296] 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 the endotherm
of the second heating. The degree of crystallinity was calculated
by dividing the observed melting peak with the heat of melting of a
perfectly crystalline polyethylene, i. e. 290 J/g.
[0297] Comonomer content (wt %) was determined based on Fourier
transform infrared spectroscopy (FTIR) determination (using a
Perkin Elmer Spectrum GX instrument) calibrated with C13-NMR.
[0298] Methyl groups (1/10 000 C) was determined by C13-NMR.
[0299] Density of materials is measured according to ISO 1183:1987
(E), method D, with isopropanol-water as gradient liquid. The
cooling rate of the plaques when crystallizing the samples was 15
C/min. Conditioning time was 16 hours.
[0300] 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*/a).
The denomination used for modulus is Pa (or kPa) and for viscosity
Pa s and 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.
[0301] 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).
[0302] 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##
[0303] 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 system, and using the average residence time in the
continuous reactor.
Mechanical Properties on Compression Moulded Specimens
[0304] Secant modulus is measured according to ASTM D 882-A at a
temperature of 23.degree. C. and a speed of 1 mm/min.
[0305] 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.
[0306] For Charpy impact are used compression moulded specimens
made according to ISO 10350-1 (1998 Nov. 15)--option ISO 179-1 with
V-notch type A. These are tested on impact according to ISO 179 at
23.degree. C.
[0307] Films
[0308] Unless otherwise stated, the following parameters were
measured at 23.degree. C. on 40 .mu.M thick films prepared as
described in the examples.
[0309] Dart is measured according to drop: ISO 7765/1.
[0310] Haze is measured according to ASTM D 1003.
[0311] Gloss is measured according to ASTM D 2457. Measured at
light angle of 60.degree..
[0312] Minimum fusion temperature (sealing property): Minimum
fusion temperature (cold sealing) of film was measured using a
CeraTek welding equipment. Film is welded in 8 welding zones with
5.degree. C. differences between zones for 1 second at 2 bar
pressure. After cooling, films are cut in 15 mm breadth and weld
manually pulled apart. Minimum fusion temperature is the minimum
temperature at which weld survives until the film itself
stretches.
[0313] Puncture resistance is measured according to ASTM D5748.
[0314] Secant modulus is measured according to ASTM D 882-A, and
calculated from the values at 0.05 and 1.05% strain.
[0315] Tensile stress, tensile strain and tensile strength is
measured according to ISO 527-3.
[0316] Elmendorf tear strength is measured according to ISO
6383/2
EXAMPLES
Example 1
Gas Phase Polymerization Using a Ziegler Natta Catalyst System
[0317] A conventional Ziegler Natta catalyst, with Ti as transition
metal, was used.
[0318] TEAL (triethyl aluminium): 10% wt in heptane
[0319] Polymerization Method
[0320] 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:
[0321] 1. 260 ml liquid 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.
[0322] 2. Hydrogen, ethylene and comonomer were added into the
reactor.
[0323] 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.
[0324] 3. Catalyst system was added. The cocatalyst
triethylaluminum (TEA) was fed as 1M solution in heptane.
[0325] 4. The polymerization was stopped by venting the reactor of
volatiles and reducing the temperature.
[0326] 5. The polymer was further dried in a vacuum oven at
70.degree. C. for 30 minutes.
[0327] Further details of the polymerization procedure and details
of the resulting interpolymers are provided in Table 1 below.
TABLE-US-00001 TABLE 1 Polymerization Polymerization run no. 1 2 3
4 POLYMERIZATION Solid catalyst feed G 0.262 0.258 0.253 0.253 TEA
(1M) solution M1 3.2 3.2 3.4 3.4 Total pressure bar g 22 22 21 21
Hydrogen partial bar g 0.5 0.5 0.5 0.5 pressure start Comonomer
type* M1B M1B Butene Butene Comonomer start M1 10 10 5.5 8.25
Comonomer g/100 g 15 20 5/7/5/7/ 10/10/5/ (continuous) ethylene
10/7 10/10/ 10 Run time Min 180 180 180 180 Yield G 1 410 1 490 542
382 Productivity 1 kg PE/(g 5.4 5.8 2.1 1.5 solid cat.)
Productivity 2 kg PE/(g cat. 2.3 2.4 0.8 0.6 system) Activity g
PE/(g solid 276 296 127 91 coefficient 1 cat, h, bar) Activity g
PE/(g cat 115 123 51 36 coefficient 2 system, h, bar) POLYMER
ANALYSES POWDER MFR2 g/10 min 0.64 0.48 0.79 0.96 MFR21 g/10 min 15
12 18 22 Mw g/mol 140 000 -- 153 864 -- Mn g/mol 33 000 -- -- Mw/Mn
-- 4.2 -- -- Methyl groups 1/1000 C. 1.8 Comon. content wt % -- 3.2
2.8 3.1 (FT-IR) Density kg/dm3 934.4 933 935 934.4 Ash wt ppm 270
260 650 980 *M1B: 3-methyl-1-butene
[0328] Surprisingly, the activity coefficients were higher with
3-methyl-1-butene than with 1-butene. This is advantageous in
films, as it would result in purer films with either less tendency
to degradation or less consumption of costly antioxidant for the
same life time of the film.
[0329] Polymers were also mixed with antioxidant, 1500 ppm Irganox
B561 from Ciba (contains 20 w % Irgafos 168
(tris(2,4-di-t-butylphenyl)phosphite) 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. Powders of
parallel runs were partially mixed before pelletisation as can be
seen in Table 2 below.
[0330] Preparation of Polymer Films
[0331] 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 screw speed of 60 rpm, melt temperature 175.degree.
C., blow up ratio (BUR) of 3.5 and take off speed 1.9 m/min. The
film thickness was adjusted to approximately 40 .mu.m. Films for
testing were selected to be 40 .mu.m.
TABLE-US-00002 TABLE 2 Pellets and film Material A B D
Polymerization runs 1 2 3 + 4 Comonomer M1B M1B 1-butene ANALYSES
OF PELLETS MFR.sub.2 g/10 0.72 0.55 0.89 min .eta.*(0.05 s.sup.-1)
Pa s 10 713 .eta.*(300 s.sup.-1) Pa s 986 M.sub.w g/mol 120 000 135
000 125 000 M.sub.n g/mol 31 800 33 200 28 900 M.sub.w/M.sub.n --
3.8 4.1 4.3 M.sub.z g/mol 365 000 465 000 425 000 M.sub.v g/mol 100
000 115 000 100 000 Density kg/dm.sup.3 935.5 934.0 935.7 FILM
TESTING General Film thickness .mu.m 40 40 40 Dart Drop g 70 70 70
Haze % 29 30 30 Tensile tests machine direction (MD) Secant modulus
MPa 375 360 375 Tensile stress at yield MPa 17.2 17.6 19 Tensile
strain at yield % 9.9 10.9 12 Tensile strength MPa 37 43 35 Tensile
strain at break % 715 705 765 Elmendorf tear N 1.3 1.1 0.62
resistance Tensile tests transverse direction (TD) Secant modulus
MPa 400 355 390 Tensile stress at yield MPa 17.6 18.5 21.4 Tensile
strain at yield % 6.7 7.7 8.8 Tensile strength MPa 35 36 33 Tensile
strain at break % 745 730 780 Elmendorf tear N 2.4 3.2 1.7
resistance
[0332] Surprisingly the tear resistance of the films made with a
copolymer comprising 3-methyl-1-butene were much better than those
made with a copolymer comprising butene. Also the tensile strength
was higher for the films with 3-methyl-1-butene than those with
butene. Both of these mechanical properties are vital to have at a
high value for films for industrial use as well as for lamination
film.
5.2.2 Example 2
Ziegler Natta Co- and Ter-Polymerisation
[0333] Ziegler Natta catalyst was synthesised in laboratory scale
according to Example 1 of US 2006/0014897.
Polymerisation
[0334] 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 3a
and polymerised for a period as shown in Table 3a.
[0335] Table 3a shows 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
[0336] 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.
TABLE-US-00003 TABLE 3a 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 type .sup.1 M1B M1B M1B M1B/
M1B/ Hexene Hexene Hexene Butene Butene Butene Butene Butene
Comonomer start ml 90 75 80 60 60 13 22 25 20 25 24 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 ethylene min - end 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 cat. 2.5 2.2 2.2 2.0 2.0
2.0 1.8 2.0 1.8 1.9 1.9 Activity g PE/(g cat., h, 234 217 233 203
202 134 136 152 134 147 150 coefficient 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 feed % 45 42 45
40 40 35 40 38 33 40 40 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 at MPa 18.5 18.4 18.5 19.3 19.1 20.6 20.6 20.1 19.7 19.0
19.4 yield Tensile strain at % 12.0 12.0 11.9 12.3 12.1 11.6 11.5
11.8 12.1 12.3 10.5 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 at % 650 680 710
727 750 630 710 590 700 775 885 break Charpy impact kJ/m.sup.2 89
87 87 77 76 72 74 90 80 82 77 strenght .sup.1 Mix M1B/Butene: 75
vol %/25 vol %. M1B: 3-methyl-1-butene
TABLE-US-00004 TABLE 3b 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 n.a. Take off speed m/min 3.3 3.3 3.3 3.1 3.1 2.6
2.6 n.a. 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 force mm 75 84 87 78 80 62 64 58
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 resistance N 6.2 6.1 6.2 4.5 4.9 4 4.7 3.9 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 n.a. 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
resistance N 1.4 1.3 1.2 1.3 1.2 0.9 1.1 0.5 .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.
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 3a. The
polymers with only linear alkenes (1-butene and 1-hexene) as
comonomer were inferior.
Film Blowing and Film
[0337] 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 3b.
[0338] Table 3b 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.
[0339] 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.
[0340] 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.
[0341] U.S. provisional patent application 61/146,948 filed Jan.
23, 2009, is incorporated herein by reference.
[0342] 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.
* * * * *