U.S. patent application number 11/544129 was filed with the patent office on 2010-07-01 for method for forming flame-retardant clay-polyolefin composites.
Invention is credited to Brian Peoples, Susannah Scott, Cathleen M. Yung.
Application Number | 20100168310 11/544129 |
Document ID | / |
Family ID | 39738930 |
Filed Date | 2010-07-01 |
United States Patent
Application |
20100168310 |
Kind Code |
A1 |
Scott; Susannah ; et
al. |
July 1, 2010 |
METHOD FOR FORMING FLAME-RETARDANT CLAY-POLYOLEFIN COMPOSITES
Abstract
A method for forming polyolefin/clay composites by olefin
polymerization which can be used as flame retardants in which at
least one filler is combined with an early or late transition metal
first catalyst component that becomes activated for olefin
polymerization when in contact with the treated filler. An olefin
is contacted by the activated catalyst--filler combination either
(a) in the absence of an alkylaluminum second catalyst component or
(b) in the presence an alkylaluminum second catalyst component when
the first catalyst component is an early transition metal catalyst,
whereby to form an clay-polyolefin composite incorporating
platelets of said filler. The filler is preferably clay,
exemplified by montmorillonite and chlorite. The first catalyst
component is preferably a non-metallocene catalyst. A predetermined
amount of one or more olefinic polymers can also be blended with a
masterbatch to obtain a composite having a desired amount of
loading.
Inventors: |
Scott; Susannah; (Goleta,
CA) ; Peoples; Brian; (Goleta, CA) ; Yung;
Cathleen M.; (Goleta, CA) |
Correspondence
Address: |
BERLINER & ASSOCIATES
555 WEST FIFTH STREET, 31ST FLOOR
LOS ANGELES
CA
90013
US
|
Family ID: |
39738930 |
Appl. No.: |
11/544129 |
Filed: |
October 6, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11451199 |
Jun 12, 2006 |
|
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11544129 |
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Current U.S.
Class: |
524/445 |
Current CPC
Class: |
C08F 4/659 20130101;
C09D 5/18 20130101; C08F 210/00 20130101; C08F 110/06 20130101;
C08F 210/00 20130101; C08F 210/00 20130101; C08F 10/00 20130101;
B82Y 30/00 20130101; C08F 210/00 20130101; C08F 110/02 20130101;
C08F 4/65912 20130101; C08F 110/06 20130101; C08F 10/00 20130101;
C08F 4/025 20130101; C08F 2500/15 20130101; C08F 4/80 20130101;
C08F 4/65916 20130101; C08F 2/44 20130101 |
Class at
Publication: |
524/445 |
International
Class: |
C08K 3/34 20060101
C08K003/34 |
Claims
1. A method for forming a flame retardant composite polymer by
olefin polymerization, comprising: treating at least one filler,
selected from the group consisting of layered silicates and
non-silicate compounds; combining said filler with an early or late
transition metal first catalyst component that becomes activated
for olefin polymerization when in contact with the filler, and
contacting an olefin with the activated catalyst--filler
combination either (a) in the absence of an alkylaluminum second
catalyst component or (b) in the presence an alkylaluminum or an
alkylaluniinoxane second catalyst component when the first catalyst
component is an early transition metal catalyst, whereby to form an
filler-polyolefin composite incorporating platelets of said filler,
and having flame retardant properties.
2. The method of claim 1 in which said filler is a layered
filler.
3. The method of claim 1 in which said filler is clay.
4. The method of claim 3 in which said clay is chlorite or
montmorillonite.
5. The method of claim 4 in which said montmorillonite is treated
by acid whereby to partly disrupt its layered structure.
6. The method of claim 1 in which said filler is treated with a
Bronsted base or a silylating agent.
7. The method of claim 1 in which said olefin is a) ethylene, b)
propylene or c) a combination of ethylene and an
.alpha.-olefin.
8. The method of claim 1 in which sufficient filler is used to
constitute greater than 0.5 weight % of the composite.
9. The method of claim 1 in which sufficient filler is used to
constitute at least 30 weight % of the composite to prepare a high
clay-loaded composite masterbatch incorporating platelets of said
layered filler.
10. The method of claim 9 including the step of blending a
predetermined amount of one or more olefinic polymers with said
masterbatch to obtain a composite having a desired amount of
loading.
11. The method of claim 1 in which said early or late transition
metal catalyst is a non-metallocene catalyst.
12. The method of claim 11 in which said catalyst is a nickel
complex bearing an .alpha.-iminocarboxamidato ligand.
13. The method of claim 12 in which said complex has the general
formula I, II, III, IV or V: ##STR00002## wherein: M is Ni, Pt, Pd;
A is a a substituted .pi.-allyl, a .pi.-benzyl, a substituted
.pi.-benzyl, benzoyl or picolino ligand; X is N, P or CH; Y is O,
CH.sub.2, or S; L is N or P or a structure that is capable of being
a neutral two electron donor ligand; L.sup.1 is a neutral
monodentate ligand and L.sup.2 is a monoanionic monodentate ligand,
or L.sup.1 and L.sup.2 taken together are a monoanionic bidentate
ligand, provided that said monoanionic monodentate ligand or said
monoanionic bidentate ligand is capable of adding to said olefin; B
is a bridge connecting covalently an unsaturated carbon and L;
R.sup.1, R.sup.2, R.sup.3A and R.sup.3B are the same or different
and are each independently hydrogen, hydrocarbyl group, or
substituted hydrocarbyl bearing functional group; the designation:
is a single or double bond; and R.sup.3B is nothing when B is
connected to L by a double bond.
14. The method of claim 12 in which said .alpha.-iminocarboxamidato
catalyst is
(N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)propanamidato)Ni-
(.quadrature..sup.3-CH.sub.2Ph).
15. The method of claim 12 in which said .alpha.-iminocarboxamidato
ligand is N-phenyl-2-(2,6-dimethylphenylimino)propanamidate.
16. The method of claim 11 in which said catalyst has the formula
MR.sub.x where M is an early transition metal, R is an alkyl or
substituted alkyl ligand, and x is from 3 to 6.
17. The method of claim 16 in which the metal component is selected
from titanium, zirconium, hafnium, vanadium, niobium, tantalum,
chromium, molybdenum, and tungsten, the alkyl or substituted alkyl
ligand lacks an alpha-hydrogen, and x is 4.
18. The method of claim 17 in which the alkyl or substituted alkyl
ligand is selected from neopentyl, neosilyl, benzyl, and adamantyl
groups.
19. The method of claim 16 in which said catalyst is
tetrabenzylzirconium.
20. The method of claim 1 in which the filler is propylene and the
amount of filler being used constitutes at least 30% weight % of
the composite to prepare a highly clay-loaded composite masterbatch
incorporating platelets of said clay.
21. A flame retardant polymer composite prepared by the method of
treating at least one filler, selected from the group consisting of
layered silicates and non-silicate compounds, combining said filler
with an early or late transition metal first catalyst component
that becomes activated for olefin polymerization when in contact
with the filler, and contacting an olefin with the activated
catalyst--filler combination either (a) in the absence of an
alkylaluminum second catalyst component or (b) in the presence an
alkylaluminum or an alkylaluminoxane second catalyst component when
the first catalyst component is an early transition metal catalyst,
whereby to form an filler-polyolefin composite incorporating
platelets of said filler, and having flame retardant properties,
wherein the silicate's layered structure is disrupted and the flame
retardant properties are a result of including the filler.
22. A flame retardant composite comprised of at least a polyolefin,
a layered filler, selected from the group consisting of silicates
and non-silicate compounds, and a component derived from a complex
containing a metal ion and a ligand containing a heteroatom,
wherein the filler's layered structure is disrupted and the flame
retardant properties are a result of including the filler.
23. A flame retardant composite comprised of at least a polyolefin,
a layered filler, selected from the group consisting of layered
compounds other than silicates and silicates, and an organic
compound that can form a radical via pyrolysis or other
decomposition process, wherein the filler's layered structure is
disrupted and the flame retardant properties are a result of
including the filler.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part application of
U.S. patent application Ser. No. 11/451,199, filed Jun. 12,
2006.
FIELD OF INVENTION
[0002] The invention relates to the formation of flame-retardant
clay-polyolefin composites, and more particularly, to the formation
of flame-retardant clay-polyolefin composites using non-metallocene
catalysts.
BACKGROUND OF THE INVENTION
[0003] Nanocomposites are materials containing two or more
chemically dissimilar phases in which at least one of the phases
has a nanoscale dimension. Nanocomposites consisting of exfoliated
clay lamellae dispersed in an organic polymer matrix exhibit
enhanced physical properties relative to virgin polymer, or to
conventional macro- or microcomposites containing other inorganic
fillers (e.g., glass fiber, talc, mica, carbon black) [1]. The
enhancements may include improved tensile and flexural properties,
increased storage modulus, increased heat distortion temperature,
decreased flammability [32], decreased gas permeability, reduced
visual defects and improved optical transparency [2].
[0004] The clay filler achieves these improvements at very low clay
loadings (.ltoreq.5 wt %), thus the material retains desirable
polymer properties such as light weight, low cost, solution/melt
processability and recyclability. Uses for these nanocomposite
materials include molded automotive and appliance components (such
as body panels, under hood components, electrical/electronic parts
and insulation, power tool housings) and furniture (such as seat
components, consoles), medical tubing, abrasion and chemical
resistant coatings, food packaging materials (such as transparent
stretch films) and barrier layers for beverage bottles.
[0005] Clays such as kaolinite, hectorite and montmorillonite (MMT)
have been investigated as mechanical supports for single-site
ethylene polymerization catalysts [3]. Usually the support is also
treated with an organoaluminum co-catalyst, such as a
trialkylaluminum or an alkylaluminoxane, which serves to remove
adsorbed water and passivate the clay surface. It has also been
suggested that alkylaluminum compounds can cause delamination of
kaolinite [4]. In general, the catalyst is adsorbed onto the
co-catalyst-modified clay, where it is activated in situ by the
co-catalyst surface layer [5], [6]. Olefin uptake by the supported
catalyst results in controlled particle growth, which is a
desirable behavior in polymerization reactor engineering.
[0006] Supporting metallocene catalysts on clays results in modest
activity for ethylene polymerization [7], even in the absence of
alkylaluminum co-catalysts [8]. However these catalyst systems do
not generate high quality nanocomposites; the polyethylene they
produce contains small clumps of unexfoliated clay.
[0007] The desirable physical properties of nanocomposites are
observed only when clay sheets are highly dispersed in the
polyolefin matrix. The difficulty in making exfoliated
clay-polyolefin nanocomposites originates in the immiscibility of
strongly associated hydrophilic clay sheets and hydrophobic
polyolefin chains. In many varieties of clay, clay layers are
negatively charged due to isomorphic substitution of framework
ions, generally cations. Interlayer cations provide charge
compensation and promote strong interlayer adhesion, which simple
mixing with a polyolefin cannot effectively disrupt.
[0008] One strategy to make the components of the nanocomposite
compatible is to render the clay hydrophobic, by replacing the
interlayer ions with surfactants such as long chain alkylammonium,
imidazolium or alkylphosphonium cations (typically C18). This
procedure generates an organically-modified layered silicate
(OMLS). Methods employing an OMLS in the preparation of polyolefin
nanocomposites include: [0009] In situ intercalative
polymerization, in which a catalyst adsorbed onto the OMLS, causes
spontaneous delamination upon addition of monomer. This strategy
has been successfully applied to propylene polymerization using a
zirconocene catalyst supported on methylaluminoxane (MAO)-treated
OMLS [9], and to ethylene polymerization using a Brookhart Pd
catalyst supported on OMLS [10]. The Ziegler catalyst TiCl.sub.4,
grafted onto a hydroxyl-containing surfactant intercalated into
MMT, was used for in situ polymerization of ethylene upon
activation with triethylaluminum [11]. Silica or titania
nanoparticles synthesized in the interlayer spaces of an OMLS by a
sol-gel method were treated with an alkylaluminum and a metallocene
to create a catalyst system for in situ polymerization [12]. In
situ polymerization filling was achieved using MAO-treated clay and
metallocene or constrained geometry catalysts with [13] and even
without [14], [15] surfactant modification of the clay. In the
absence of surfactant, the clay was swollen using an organic
solvent. [0010] Solution intercalation, in which high density
polyethylene (HDPE) dissolved in a hot xylene/benzonitrile mixture
is stirred with dispersed OMLS [16]; [0011] Melt intercalation, in
which the OMLS is annealed with polymer above the softening point
of the latter, either statically or under shear. Since mixing is
driven by interactions between the polymer and the clay, this
method typically requires a compatibilizer consisting of polymers
or oligomers modified with polar sidechains or endgroups. For
example, nanocomposite formation was achieved by melt intercalation
of propylene oligomers with telechelic OH groups, followed by
melt-mixing with unmodified PP [17]. Melt blending of PP and OMLS
was achieved using a twin screw extruder in the presence of
maleated PP (i.e., functionalized with maleic anhydride side
chains, PP-g-MA) as the compatibilizer [18, 19, 20, 21]. A similar
strategy was used to make nanocomposites by melt blending of
PE-g-MA [22], [23] or EPR-g-MA [23] with OMLS. A semifluorinated
surfactant was used to create an OMLS with weaker clay-surfactant
interactions and a greater propensity to intercalate unmodified PP
[24]. A method involving functionalized surfactants which react to
form chemical bonds with the maleated compatibilizer has been
described [25]. Direct melt intercalation of
ammonium-functionalized polypropylene chains into unmodified MMT
was achieved, presumably by direct cation exchange, without
intermediate functionalization of the clay with surfactant
[26].
[0012] Recently, the formation of nanocomposites with unmodified
clay was achieved by making the polyolefin component more
hydrophilic. In the presence of the surfactant
cetyltrimethylammonium bromide, micelles containing polystyrene
were formed and adsorbed from solution onto dispersed clay
[27].
[0013] Also recently, nanocomposite materials have been produced by
adding an olefin to a suspension of acid-treated layered silicate
treated with a solution of a metallocene polymerization catalyst,
causing olefin polymerization to form the nanocomposite polymer
[28]. Although described in broad encompassing terms, the specific
preparations described by the reference all require the use of a
tripropylaluminum co-catalyst added to the slurry formed by mixing
4-tetradecylanilinium-exchanged or HCl-treated clay to dry
toluene.
[0014] A flame retardant is a material that exhibits either a delay
in the start, or a decrease in the rate of propagation, of a fire
[30, 31]. Organic polymers can be made flame retardant by
incorporating a large quantity (ca. 50 wt %) of an inorganic (e.g.,
Mg(OH).sub.2) or organic (e.g., brominated polystyrene) filler.
Flame retardant properties may be obtained at much lower filler
content with nanocomposites. Potential uses for flame retardant
nanocomposite materials include molded furniture, automotive parts
(such as body panels, under hood components) and appliance
components (such as electrical/electronic parts, power tool
housings).
[0015] The first report of improved thermal stability in a
polymer-clay composite involved a polymethylmethacrylate
(PMMA)--montmorillonite (MMT) clay system. At 10 wt % clay loading,
this material exhibits an increase of 40-50.degree. C. in its
thermal decomposition temperature relative to pure PMMA [33]. A
nanocomposite prepared by sonication of silanol-terminated
polydimethylsiloxane (PDMS) with montmorillonite (10 wt %)
decompose at a temperature 140.degree. C. higher than pure PDMS
[34]. An increase in the decomposition temperature was observed
upon melt intercalation of aliphatic polyimide (PEI-10) into clay
[35]. An increase in the thermal decomposition temperature was
observed for organically-modified layer silicate (OMLS)
nanocomposites with polypropylene-graft-maleic anhydride (PP-g-MA)
[30,37], PP [38], and polystyrene (PS) [39,40], when compared to
their pure polymer counterparts. In particular, thermogravimetric
analysis (TGA) experiments performed under N.sub.2 showed the onset
temperatures for decomposition of polyethylene (PE)/OMLS
nanocomposites are approximately 20-30.degree. C. higher than for
pure PE [41].
[0016] Flammability properties: Cone calorimetry measurements have
demonstrated decreased flammability for many types of polymer-clay
nanocomposites. The heat release rate (HRR), especially the peak
HRR, is an important parameter in evaluating fire safety [42,43].
The reduction in HRR and peak HRR shown by many polymer-clay
nanocomposites suggest a decrease in their flammability relative to
the pure polymers. Delaminated clay-nylon-6 and -nylon-12
nanocomposites, as well as intercalated clay-PS and --PP
nanocomposites, have shown substantial decreases in HRR [44].
Several PP and PP-g-MA nanocomposites also exhibit a reduction in
HRR as measured by cone calorimetry [30, 37, 38, 45]. The peak HRR
of PE nanocomposites was reduced by 54% [41].
[0017] A more severe test of non-flammability is the capacity of a
burning material to self-extinguish. Self-extinguishing behavior of
PEI-clay nanocomposites has been reported [36], however there is no
report of this behavior in polyolefin-clay nanocomposites.
Similarly, no report has shown that a polyolefin/clay nanocomposite
has achieved a UL94 VO rating, which is a practical flame retardant
material according to the Underwriter's Laboratory's fire test
protocol [46].
BRIEF SUMMARY OF THE INVENTION
[0018] The present invention provides a flame retardant composite
and a method for forming flame retardant composite materials
containing a filler, which is accomplished with either an early or
late transition metal first catalyst component, without the use of
alkylammonium modifiers to separate the filler layers, and without
the use of an alkylaluminum second catalyst component. In other
embodiments, an alkylaluminum second catalyst component can be used
with an early transition metal first catalyst component.
[0019] The filler is selected from the group consisting of
silicates and non-silicate compounds. The invention proceeds by
combining the filler with a first catalyst component that becomes
activated for olefin polymerization when in contact with the
filler. An olefin is contacted by the activated catalyst--filler
combination in the absence of an alkylaluminum second catalyst
component to form a composite polymer containing the filler. The
first catalyst component can be selected to provide a high or low
melting point polymer. One class of preferred first catalyst
components used particularly without the need or use of an
alkylaluminum second catalyst component is a non-metallocene
catalyst, most preferably a nickel complex bearing an
.alpha.-iminocarboxamidato ligand. Another preferred first catalyst
component, one that can be used with or without an alkylaluminum
second catalyst component, is tetrabenzylzirconium.
[0020] In a particular embodiment, sufficient silicate is used to
constitute at least 30 weight % of the composite material to
prepare a high silicate-loaded composite masterbatch. A
predetermined amount of one or more polyolefins can then be blended
with the masterbatch to obtain a composite polymer having a desired
amount of silicate loading. In this invention, the method to
prepare a composite by blending the said masterbatch with a
predetermined amount of polyolefins is defined as the "masterbatch
method."
[0021] In specific embodiments, the silicate material is a clay. In
a more specific embodiment, the invention achieves high dispersion
of montmorillonite clay platelets in a polyethylene or
polypropylene matrix by in situ polymerization of ethylene or
propylene. The clay may first be acid-treated, causing disruption
of its layered structure. The acid-treated clay is then treated
with an organic solvent solution of a polymerization catalyst,
which contains Ni, an .alpha.-iminocarboxamidato ligand and an
alkyl ligand. Upon exposure to olefin, a polyolefin matrix is
formed in which the embedded clay layers are mostly separated.
[0022] In particular embodiments, capped clay can be used to
polymerize olefin in the presence or absence of an organoaluminum
second catalyst component. The capping of the Bronsted acid sites
on the clay essentially passivates the clay surface prior to the
deposition of catalyst.
[0023] The invention allows a new flame retardant composite and
preparation of flame retardant clay-polyolefin composites which
self-extinguish after ignition, and represents a simple,
inexpensive, one-pot procedure for making silicate-polymer
composites without the need for time-consuming organic modification
of the filler material or the use of expensive surfactants. The
flame retardant composite in the invention is not limited to a
nanocomposite, and a flame retardant composite is also allowed in
which the dimension of the dispersed filler is not nano-scale but
micron-scale.
[0024] With the invention, the use of organic solvents to swell the
clay and/or dissolve the polymer is also greatly reduced or
eliminated. There is no need for compatibilizers, such as maleated
polymers, whose lower molecular weights and lower stability
relative to the polyolefin component may result in degradation of
composite performance [1]. The composite material can be prepared
with or without additional added flame retardants. With late
transition metal catalysts, there is no need for organoaluminum
activators or other co-catalyst modification or passivation of the
surface of the layered filler, since the layered filler itself
serves as catalyst activator. The improvements as described herein
lead to higher quality and less expensive flame retardant composite
polymers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] For a more complete understanding of the present invention,
reference is now made to the following descriptions taken in
conjunction with the accompanying drawing in which:
[0026] FIG. 1 is a TGA graph showing decomposition of PE/clay
composites in air; and
[0027] FIG. 2 shows a table of char tests on PE-clay composites;
and
[0028] FIG. 3 shows a photograph of char test for PE-clay
composites, recorded 1:20 min after ignition. Sample numbers
correspond to run numbers in FIG. 2; and
[0029] FIG. 4 shows a table of char tests on PP-clay composites;
and
[0030] FIG. 5 shows a photograph of char tests for PP-clay
composites prepared by in situ polymerization, recorded 1:50 mins
after ignition. Sample numbers correspond to run numbers in FIG. 4;
and
[0031] FIG. 6 shows a photograph of char tests for PP-clay
composites, recorded 3:00 mins after ignition. Sample numbers
correspond to run numbers in FIG. 4.
[0032] FIG. 7 shows TEM images of a 5.4 wt % LiMMT/PE composite
prepared by in situ polymerization; and
[0033] FIG. 8 shows TEM images of a 15 wt % LiMMT/PP composite
prepared by in situ polymerization; and
[0034] FIG. 9 shows an X-ray diffraction pattern of acid-treated
montmorillonite; and
[0035] FIG. 10 shows TEMs of polyethylene-clay composites with (A)
2.6 wt. % clay, (B) 10.6 wt. % clay, and (C) ethylene/1-hexene
copolymer with 2.4 wt. % clay; and
[0036] FIG. 11 shows TEM images of an 11.1 wt % clay-polyethylene
composite produced with a trimethylaluminum-modified clay.
DETAILED DESCRIPTION OF THE INVENTION
[0037] The invention provides a flame retardant composite comprised
of at least a polyolefin, a layered filler, selected from the group
consisting of layered silicates and non-silicate compounds, and a
component derived from a complex containing a metal ion and a
ligand containing a heteroatom (i.e., the said complex itself, or
resulting products that are formed in a process in which the said
complex undergoes some chemical reactions), or a complex in which
the said complex has the formula MR, where M is an early transition
metal, R is an alkyl or substituted alkyl ligand, and x is from 3
to 6.
[0038] The invention also provides a flame retardant composite
comprised of at least a polyolefin, a layered filler, selected from
the group consisting of layered silicates and non-silicate
compounds, and an organic compound that can form a radical via
pyrolysis or other decomposition process.
[0039] The invention provides a method for forming flame retardant
clay-polyolefin composites by olefin polymerization in the presence
of a filler. Highly exfoliated nanocomposites can also be formed as
disclosed in U.S. patent application Ser. No. 11,451,199, filed
Jun. 12, 2006, the entirety of which is incorporated herein by
reference. However, exfoliation is not necessary for the production
of flame retardant composites of the present invention.
[0040] The filler is selected from the group consisting of
nonlayered or layered silicates and non-silicate compounds, and is
combined with a catalyst that becomes activated for olefin
polymerization when in contact with the filler. The activated
catalyst--filler combination is then contacted with olefin whereby
to form a polyolefin composite material incorporating platelets of
the filler. The polymerization step can be accomplished without the
use of an alkylaluminum second catalyst component. In other
embodiments, an alkylaluminum second catalyst component may be used
with an early transition metal first catalyst component.
[0041] More particularly, the filler and a late transition metal
first catalyst component are added to a reactor followed by the
addition to the reactor of the olefin. As stated above, in an
advantageous departure from the art, the polymerization reaction
can be carried out in the absence of an alkylaluminum second
catalyst component. This allows significant savings and
simplification of the process. Indeed, where the late transition
metal first catalyst component is a nickel complex bearing an
.alpha.-iminocarboxamidato ligand, when trimethylaluminum (a second
catalyst component, present in 60-fold excess relative to the first
catalyst component) is added as a scavenger to the reactor after
addition of the filler and first catalyst component, reactor
fouling occurs. A larger excess of trimethylaluminum (350-fold
relative to catalyst) inhibits the polymerization. Moreover, when
the second catalyst component is added to the clay prior to the
addition of the late transition metal first catalyst component,
incorporation of the clay into the polymer matrix is compromised,
and the material is obtained is not a highly exfoliated
nanocomposite.
[0042] In particular embodiments, sufficient layered filler is used
to constitute at least 30 weight % of the composite material, to
prepare a high loaded composite masterbatch. A predetermined amount
of one or more olefinic polymers can be blended with the
masterbatch to obtain a composite having a desired amount of
loading.
[0043] As the filler, clay, clay minerals or compounds having a
layered crystal structure of e.g. a hexagonal densely packed-type,
antimony-type, CdCl.sub.2-type or Cdl.sub.2-type, may be used.
Specific examples of clay, clay minerals and layered compounds
useful as fillers include kaolin, bentonite, kibushi clay, gairome
clay, allophane, hisingerite, pyrophyllite, talc, a mica group, a
montmorillonite group, vermiculite, a chlorite group, palygorskite,
kaolinite, nacrite, dickite and halloysite.
[0044] The silicates to be used as a filler in the present
invention may be synthesized products or naturally produced
minerals. Specific examples of the silicates include alkaline
silicates such as lithium silicate, sodium silicate, and potassium
silicate, alkaline earth silicates such as magnesium silicate,
calcium silicate, and barium silicate, metal silicates such as
aluminium silicate, titanium silicate and zirconium silicate, and
natural silicates such as an olivine group such as forsterite and
fayalite, a garnet group such as garnet, a phenacite group such as
phenacite and willemite, zircon, tricalcium silicate, merrillite,
gehlenite, benitoite, beryl, cordierite, a pyroxene group such as
enstatite, hypersthene, diopside, spondumene, rhodonite and
wollastonite, an amphibole group such as anthophyllite, tremolite
and actinolite.
[0045] Particularly preferred as fillers are clay or clay minerals,
and most preferred are montmorillonite and chlorite. Fillers may be
used alone or in combination as a mixture of two or more of them.
Flame retardant nano-composites can be formed using
montmorillonite, while micro-composites can be formed using
chlorite.
[0046] The fillers used in this invention may be acid treated.
Further, they may be used as they are without subjecting them to
any treatment, or they may be treated by ball milling, sieving,
acid treatment or the like before use. They may be treated to have
water added and adsorbed or may be treated for dehydration by
heating before use. They may also be treated to exchange their
interlayer cation by organic cation such as onium cations having
aliphatic chains. Specific examples of the onium cations include
primary to quaternary ammonium cation and phosphonium cation.
Specific examples of the aliphatic chains are aliphatic chains
which have 6-20 carbon atoms including hexyl, octyl, 2-ethylhexyl,
dodecyl, hexadecyl, octadecyl and the like, also the mixture of
them such as hydrogenated tallow. Specific examples of the organic
cation include hexylammonium, octylammonium, 2-ethylhexylammonium,
dodecylammonium, trioctylammonium, dioctadecyldimethylammonium,
trioctadecylammonium and the like. They may be used alone or in
combination as a mixture of two or more of them.
[0047] In one embodiment, the filler material is acidified by
contacting it with a Bronsted acid (such as hydrochloric acid,
sulfuric acid, or any material which forms a strong acidic aqueous
solution). The acid dissolves some of the aluminum present in the
clay and thereby partly disrupts the layered structure.
[0048] The acid-treated filler is dispersed with a small quantity
of solvent (such as toluene), which can be done by any suitable
technique, and can use mechanical means if desired or needed such
as by sonication or by high shear mixing or wet ball milling.
[0049] As indicated, the first catalyst component is preferably a
non-metallocene catalyst. A non-metallocene catalyst is comprised
of a transition metal ion and a ligand that does not contain a
cyclopentadienyl ring. The ligand for the said non-metallocene
catalyst preferably contains at least one heteroatom. Preferred
heteroatoms are the atoms in group 15 and/or group 16 in the
Periodic Table. In more detail, nitrogen, oxygen, sulfur,
phosphorus, arsenic, and selenium atom are preferred for the
heteroatom in the said ligand. There is no limitation to the
transition metal ion as long as the said complex based on the metal
ion has a function to polymerize .alpha.-olefins. An early
transition metal or a late transition metal can be used in this
invention. A mixture of non-metallocene catalysts can also be used
in this invention.
[0050] In a particular embodiment, the first catalyst component is
a late transition metal catalyst, a nickel complex bearing an
.alpha.-iminocarboxamidato ligand. The acid-treated clay activates
late transition metal catalysts containing
.alpha.-iminocarboxamidato ligands, i.e., catalysts from the family
LNi(R)(S), where L is an .alpha.-iminocarboxamidato ligand, R is an
alkyl group (e.g., CH.sub.2Ph) and S is an ancillary ligand (e.g.,
PMe.sub.3) [28].
[0051] Most preferably, the nickel catalyst is a complex having the
general formula I, II, III, IV or V:
##STR00001##
[0052] wherein:
[0053] M is Ni, Pt, Pd;
[0054] A is a n-allyl, a substituted .pi.-allyl, a .pi.-benzyl, a
substituted .pi.-benzyl, benzoyl or picolino ligand;
[0055] X is N, P or CH;
[0056] Y is O, CH.sub.2, or S;
[0057] Z is O or S
[0058] L is N or P or a structure that is capable of being a
neutral two electron donor ligand;
[0059] L.sup.1 is a neutral monodentate ligand and L.sup.2 is a
monoanionic monodentate ligand, or L.sup.1 and L.sup.2 taken
together are a monoanionic bidentate ligand, provided that said
monoanionic monodentate ligand or said monoanionic bidentate ligand
is capable of adding to said olefin;
[0060] B is a bridge connecting covalently an unsaturated carbon
and L;
[0061] R.sup.1, R.sup.2, R.sup.3A and R.sup.3B are the same or
different and are each independently hydrogen, hydrocarbyl group,
or substituted hydrocarbyl bearing functional group;
[0062] the designation:
[0063] is a single or double bond; and
[0064] R.sup.3B is nothing when B is connected to L by a double
bond.
[0065] A particularly preferred catalyst is
(N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)propanamidato)Ni-
(.eta..sup.3-CH.sub.2Ph).
[0066] With late transition metal complexes, such as the nickel
complex, no second catalyst components are required to achieve
typical polymerization activities of 1000-15,000 kg
polyethylene/mol catalyst/hr at 30.degree. C. The filler does not
need to be dried, although better activities are obtained with
filler dried in vacuo for 12 hours at 100.degree. C. In a typical
procedure, a solution of 8 .mu.mol of the catalyst in toluene or
hexane is stirred with 85 mg of dried filler under a N.sub.2
atmosphere. This catalyst suspension can be loaded directly into
the reactor, or filtered, washed and resuspended in fresh, dry
solvent prior to use. Hereinafter, the case using clay as filler
will be explained, because clay is one of the typical fillers.
[0067] In other embodiments, early transition metal catalysts can
be used as the first catalyst component to generate composites,
where the metal component of the catalyst can be any early
transition metal, such as titanium, zirconium, hafnium, vanadium,
niobium, tantalum, chromium, molybdenum, tungsten. Any of a variety
of alkyl or substituted alkyl ligands can be used, particularly
those which lack alpha-hydrogens, such as neopentyl, neosilyl,
benzyl, adamantyl, which are stable in the form MR.sub.x (where M
is the metal, R is the alkyl ligand, and x is the number of alkyl
ligands (from 3 to 6, usually 4).
[0068] In a preferred embodiment, an alkylaluminum second catalyst
component can be advantageously used, that is active in olefin
polymerization when supported on clay, in combination with early
transition metal first catalyst components, as disclosed above.
Preferred second catalyst components are trialkylaluminum or an
alkyaluminoxane. A particularly preferred second catalyst component
is triisobutylaluminum (TIBA). The second catalyst component can be
added first to filler to remove adsorbed water and passivate the
clay surface. The second catalyst component is also able to cap
many of the silanol groups on the clay surface, which would
otherwise catalyze polymer decomposition and deactivate early
transition metal catalysts.
[0069] More extensive and more robust capping of the silanol groups
can be achieved by converting them to trimethylsilyl groups to
yield TMS-capped-LiMMT (TMS-clay). This achieved by stirring a
suspension of LiMMT in neat chlorotrimethylsilane for 2 hours under
N.sub.2. The volatiles can be removed either under vacuum at
100.degree. C. for 16 hours, or by washing with fresh solvent.
Activities for ethylene and propylene polymerization remain the
same order of magnitude when TMS-LiMMT treated with the second
catalyst component is substituted for the second catalyst
component-non-TMS modified LiMMT. Polymerization with TMS-LiMMT and
either early or late transition metal first catalyst components can
also proceed without the use of the second catalyst component,
although activities are not as high. The clay can also be capped
with other silylating agents or treated with Bronsted bases (e.g.,
tertiary amines or phosphines).
[0070] When an olefin is contacted with the activated first
catalyst component--filler combination, the olefin polymerizes to
form a composite material containing platelets of an acid-treated
filler dispersed in the polyolefin matrix. It is believed that
Lewis acid sites, on certain acid-treated layered fillers, activate
the catalyst to produce polymer between the layers of the layered
filler and thereby separate or exfoliate such layers to a greater
degree into the developing polymer matrix.
[0071] Preferably, the olefin used in the instant invention is
selected from the group of olefins having from two to ten carbon
atoms. Such olefins include, for example, styrene, divinylbenzene,
norbornene, ethylene, propylene, hexene, octene, butadiene and
mixtures thereof. Thus, the polymer product of or by way of the
instant invention may be, for example, a polyethylene, a
polypropylene, a thermoplastic elastomer, or a synthetic rubber. It
is also possible that larger monomers (macromonomers) are formed in
situ and incorporated into the polymer.
[0072] In a preferred embodiment, the olefin is ethylene or
propylene. In another preferred embodiment, the olefin is a
combination of ethylene and an .alpha.-olefin, e.g., 1-hexene.
[0073] Preferably, the weight % of layered filler in the composite
material is at least 0.5%. In a preferred embodiment, sufficient
silicate is used to constitute at least 30 weight % of the
composite to prepare a highly silicate-loaded composite
masterbatch. A predetermined amount of one or more olefinic
polymers can be blended with the composite masterbatch to obtain a
composite material having a desired amount of silicate loading,
e.g., from 0.1 to 20 weight %.
[0074] In a particularly preferred embodiment, a flame retardant
polyethylene composite is formed by treating montmorillonite with
an alkylaluminum second catalyst component, and then with a
tetrabenzylzirconium first catalyst component, that becomes
activated for ethylene polymerization when in contact with the
clay, and contacting ethylene with the activated catalyst--clay
combination.
[0075] Polymerization of ethylene or copolymerization of ethylene
with an .alpha.-olefin such as 1-hexene occurs at temperatures from
10 to 70.degree. C., preferably between 20 and 50.degree. C. Since
the polymerization is highly exothermic, it is desirable to control
the temperature with a heat exchanger to prevent overheating and
decomposition of the catalyst above 70.degree. C. The
polymerization can be terminated by exhaustion of monomer, by
venting unreacted monomer, or by quenching the reaction with a
chain-terminating agent, such as hydrogen gas, carbon monoxide or a
polar comonomer.
[0076] Thermal stability of polyolefin/clay composites: The thermal
stability of polyethylene (PE)/clay composites was assessed by
thermogravimetric analysis (TGA). The TGA experiments were
performed in air as the temperature was ramped from 25 to
600.degree. C. at a rate of 20.degree. C./min (FIG. 1). The onset
of decomposition for the composite materials occurs at temperatures
similar to that seen for pure PE made using the same catalyst
activated by a homogeneous Lewis acid, B(C.sub.6F.sub.5).sub.3, in
the absence of clay. The TGA graphs show that aerobic polymer
decomposition occurs in at least two stages. For pure PE, the first
stage is barely detectable; most of the mass loss occurs in the
second stage. For the composites, the first stage extends to higher
temperatures, resulting in slightly more mass loss for materials
with <10 wt % clay, and considerably more for materials with
>10 wt % clay. The second stage of decomposition occurs at
substantially higher temperatures for all PE/clay composites,
indicating that they are more thermally stable than pure PE, even
at low clay loadings.
[0077] Flammability of polyolefin/clay composites: A modified char
test was used to evaluate flammability. Compression-molded bars
(60.times.6.times.3 mm) were clamped vertically and ignited at the
top with a butane lighter for 7 sec. The amount of time required to
either self-extinguish or burn completely was recorded.
[0078] The results of char tests with PE/clay composites are
summarized in FIG. 2, and a photograph of a char test with a
variety of TMS-clay-containing PE samples is shown in FIG. 3.
Samples 1-5 are composites prepared by in situ polymerization,
while samples 7-10 are composite materials made by the masterbatch
blending method. Samples 7-8 were blended from a 52.8 wt % LiMMT/PE
masterbatch, sample 9 was made with a 57.0 wt % masterbatch
containing TIBA-treated TMS-LiMMT, and sample 10 was blended from a
50.8 wt. % masterbatch containing only TMS-LiMMT (no TIBA).
[0079] All of the PE composites, whether made by in situ
polymerization or by the masterbatch method, resisted ignition
compared to PE containing no clay. Materials made by in situ
polymerization, with or without TMS-capping (samples 1-5),
self-extinguished. Samples 1-4 formed char on the surface of the
bar. The formation of char prevents diffusion of combustible
volatiles that sustain the flame [2]. The material with the lowest
clay loading (sample 1) had the shortest self-extinguishing time.
However, the blended materials (samples 7-10) burned faster than PE
alone (sample 6) and generated a lot of black smoke.
[0080] The results of char tests with polypropylene (PP)/clay
composites are summarized in FIG. 4. Representative photographs of
the char tests are presented in FIGS. 5 and 6. Samples 11a and 11b
were performed with bars of isotactic PP containing no clay. Two
bars with high clay loadings, 20 wt % LiMMT/TIBA (sample 12) and 30
wt % TMS-LiMMT (sample 13), were made by in situ polymerization.
Three bars were made by the masterbatch method, blended with
isotactic PP to 5 wt % clay: sample 14 was blended from a 42.3 wt %
LiMMT/TIBA/PP composite; sample 15 was blended from a 76.9 wt %
TMS-LiMMT/PP composite; and sample 16 was blended from a 35.1 wt %
TMS-LiMMT/TIBA/PP composite.
[0081] After ignition, sample 11a began to melt, causing liquid
polymer to drip down the side. The sample burned continuously for
1:44 min, until the flame reached the base and was extinguished
manually. The LiMMT/TIBA-containing composite (sample 12) did not
drip but took only slightly longer (2:38 min) for the flame to
reach the base, when it was extinguished manually. On the other
hand, the TMS-LiMMT/TIBA/PP composite (sample 13) self-extinguished
1:04 min after ignition. At the end of the experiment, char was
observed covering the top of both composites formed by in situ
polymerization. Capping of the Bronsted acid sites, either by TIBA
or TMS, retards catalytic decomposition of the polymer to smaller
hydrocarbon fragments. The isotactic PP bar (sample 11b) took the
shortest time to burn to the bottom of samples 11b and 14-16 in
FIG. 6.
[0082] Unlike the blended PE composites, the blended PP composites
showed flame retardant properties. All of the PP-masterbatch blends
(samples 14-16) burned slower than PP containing no clay. In
addition, the material containing TMS-LiMMT/TIBA self-extinguished
after 3:22 min.
[0083] As evident from the above, the flame retardant composites
can be made directly, or using a masterbatch with high clay loading
(e.g., >50 wt %) which is subsequently blended with pure polymer
(polyethylene, polypropylene, copolymers of ethylene with other
.alpha.-olefins, etc) to create composites with the desired clay
loading. The method can be used for composites of homopolymers such
as ethylene and propylene, copolymers of ethylene with other
.alpha.-olefins or with functionalized monomers such as styrenes or
norbornenes.
[0084] The following examples will illustrate best practices of the
invention.
Example 1
[0085] A solution of TIBA (2.0 g of 1.0 M in hexanes), a second
catalyst component, was added to LiMMT (1.3 g) in 15 g toluene, and
a yellow solution of the air-sensitive first catalyst component,
Zr(CH.sub.2Ph).sub.4 (50 mg in 10 g toluene) was mixed with the
LiMMT/TIBA slurry for 15 mins at 20.degree. C. The slurry was
washed twice, by removal of excess solvent, resuspension in 20 g of
fresh toluene, and stirring for 15 mins. After the final removal of
excess solvent, the slurry was resuspended in 70 g fresh toluene,
and placed inside a batch polymerization reactor. The reactor was
pressurized with 100 psi ethylene at 25.degree. C. and
prepolymerized for 15 min. The temperature was increased to
40.degree. C. and the polymerization allowed to proceed for an
additional 45 mins. The reaction yielded 23.9 g of PE with a clay
content of 5.4 wt %.
[0086] Typical polymerization activities are 150 kg PE/mol
catalyst/hr at 40.degree. C. and 30 kg PP/mol catalyst/hr at
50.degree. C. Polymerization of ethylene is conducted between 25
and 60.degree. C., preferably between 40 and 50.degree. C. Since
the polymerization is highly exothermic, it is desirable to control
the reactor temperature with a heat exchanger to prevent
overheating and decomposition of the catalyst above 70.degree. C.
Ethylene is added on demand at 100 psi once the temperature is
equilibrated. Typical clay loading after a 30 min polymerization at
40.degree. C. is 15 wt %. In order to achieve a lower clay loading
material (<10 wt %), a pre-polymerization step is implemented.
Ethylene is added at 25.degree. C. for 15 min, then the temperature
is raised to 40.degree. C. for 45 min to obtain a 5 wt % PE/clay
composite. Exfoliation of the clay layers is shown in the
transmission electron microscopy (TEM) images, FIG. 7. Individual
clay sheets are visible in profile as dark lines against the light
gray PE background.
Example 2
[0087] The procedure of Example 1 can be repeated except that
polymerization is carried out using propylene. Polymerization is
conducted between 30 and 60.degree. C., preferably between 40 and
50.degree. C. Since the polymerization is highly exothermic, it is
desirable to control the reactor temperature with a heat exchanger
to prevent overheating and decomposition of the catalyst above
70.degree. C. Typical clay loading for a 30 min polymerization at
50.degree. C. is 40 wt %, but loadings as low as 15 wt % have been
obtained. Partial exfoliation of the clay layers at 15 wt % loading
is shown in the TEM images in FIG. 8.
Example 3
[0088] LiMMT (2.5 g) was suspended in chlorotrimethylsilane (10
mL), and stirred at 20.degree. C. for 2 hours. The volatiles were
removed by heating at 100.degree. C. under dynamic vacuum (16 hours
at .ltoreq.10-4 Torr), then the solid was transferred to a
N.sub.2-filled glove box. A solution of TIBA (2.0 g of 1.0 M in
hexanes) was added to the TMS-capped clay in 15 g hexanes, and a
yellow solution of the air-sensitive first catalyst component,
Zr(CH.sub.2Ph).sub.4 (200 mg in 10 g hexanes) was mixed with the
TMS-capped clay/TIBA slurry for 15 mins at 20.degree. C. The slurry
was washed twice, by removal of excess solvent, resuspension in 20
g of fresh hexanes, and stirring for 15 mins. After the final
removal of excess solvent, the slurry was resuspended in 70 g fresh
hexanes, and placed inside a batch polymerization reactor, whose
temperature was equilibrated at 50.degree. C. The reactor was
pressurized with 140 psi propylene and polymerization was allowed
to proceed for 60 mins. The reaction yielded 8.9 g of polypropylene
with a clay content of 30 wt %.
Example 5
[0089] PP/clay composites prepared by the masterbatch blending
method are flame retardant materials. The masterbatch was made
using the method described above for the PP/LiMMT composite, but
with a TMS-clay treated with TIBA and 30 min polymerization time. A
physical mixture of the 35.1 wt % TMS-clay-TIBA/PP composite (0.57
g) and pure PP (3.43 g) was blended in a twin screw extruder at
170.degree. C. for 8 min then extruded.
Example 6
[0090] The clay can be ion-exchanged with cations other than Li.
Thus, the procedure of Example 1 can be repeated except that the
clay is cation-exchanged with Na.
Example 7
[0091] The acid treatment can be applied to clays other than
montmorillonite, or to layered non-clay materials. Thus, the
procedure of Example 1 can be repeated except that the acid
treatment can be applied to layered aluminum phosphate.
Example 8
[0092] In manner similar to Example 6, the procedure of Example 1
can be repeated except that the acid treatment can be applied to
zirconium phosphate.
Example 9
[0093] The method can be used for composites of copolymers of
ethylene with other .alpha.-olefins or with functionalized
monomers. Thus, the procedure of Example 1 can be repeated except
that the olefin is styrene.
Example 10
[0094] In manner similar to Example 7, the procedure of Example 1
can be repeated except that the olefin is norbornene.
Example 11
[0095] The ethylene pressure can be varied in order to alter the
branch content of the polymer. Thus, the procedure of Example 1 can
be repeated except that the ethylene pressure is increased to 3500
kPa.
Example 12
[0096] Chlorite was treated with TIBA (2.0 g of 1.0M in hexanes)
prior to the deposition of tetrabenzylzirconium. Chlorite requires
less tetrabenzylzirconium catalyst (10 mg/1.3 g clay) for
polymerization compared to LiMMT (50 mg/1.3 g clay). The reactor
was pressurized with 100 psi ethylene. Polymerization at 40.degree.
C. for 30 min yielded a white shred like material (10.1 g) with 13%
clay loading. The activity for that polymerization is 918 kg/mol/h.
The clay layers in the chlorite activated materials are not
exfoliated. The chlorite material did not form any char during the
char test but it self-extinguished after 1:28.
Example 13
[0097] A 5.7 wt % PE/LiMMT composite made with the eta-3 Ni
catalyst by in situ polymerization was also shown to
self-extinguish. It self-extinguished after 3:51. [not shown in
Figures]. To make the composite, catalyst solution (9.6 micromol in
1 g of toluene) was added to a slurry of 200 mg of LiMMT in 100 g
of toluene. The slurry was placed inside a batch polymerization
reactor. The temperature was equilibrated at 40.degree. C. and
ethylene (100 psi) was added on demanded for 30 min. The reaction
yielded 5.3 g of PE with a clay content of 5.7 wt %.
Example 14
[0098] Acid-treated lithium montmorillonite was prepared by
stirring a suspension of untreated clay in a solution of
Li.sub.2SO.sub.4 and concentrated H.sub.2SO.sub.4 for 5 hours. This
material retains its sheet-like structure but the interlayer
association is greatly disrupted, as shown by the absence of an XRD
(001) reflection at 2.theta.=7.degree., as shown in FIG. 9.
[0099] 85 mg Acid-treated lithium montmorillonite was partially
dehydrated by heating at 100.degree. C. under a dynamic vacuum (12
hours at .ltoreq.10-4 Torr) and then transferred to a
N.sub.2-filled glove box. A dark orange solution of the
air-sensitive catalyst, LNi(.eta..sup.3-CH2Ph) where
L=N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)propanamidato
(4 mg in 1 g toluene) was mixed with a slurry of 85 mg clay
suspended in 26 g toluene for 30 mins at room temperature inside a
batch polymerization reactor thermostated at 25.degree. C. The
reactor was pressurized with 689 kPa C.sub.2H.sub.4 and
polymerization proceeded for 70 mins. The reaction yielded 3.2 g of
polyethylene with Mw=1,089,000 g/mol, a polydispersity index of 2.8
and a clay content of 2.6 wt %.
[0100] Evidence for nanocomposite formation is shown in the
transmission electron microscopy (TEM) image of FIG. 10A.
Individual clay sheets are visible in profile as dark lines against
the light gray polyethylene background.
Example 15
[0101] The procedure of Example 14 was repeated except that 500 mg
acid-treated lithium montmorillonite was used. The result was a
yield of 4.7 g of polyethylene Mw=1,146,000 g/mol, a polydispersity
index of 2.7 and a clay content of 10.6 wt %. Evidence for
nanocomposite formation is shown in the transmission electron
microscopy (TEM) image of FIG. 10B.
Example 16
[0102] The procedure of Example 14 was repeated except that 4 g of
the solvent, toluene, was replaced with 4 g of 1-hexene, and
polymerization proceeded for 30 mins. The reaction yielded 3.6 g of
polyethylene with a clay content of 2.4 wt %. Evidence for
nanocomposite formation is shown in the transmission electron
microscopy (TEM) image of FIG. 10C.
[0103] The images of FIG. 2 show that most of the clay is
exfoliated. Groups of less than 5 associated, possibly
intercalated, clay sheets are also present. High clay dispersion
was observed up to 11 wt % loading, and in the presence of
co-monomer.
Example 17
[0104] The clay can be cation-exchanged with cations other than Li.
Thus, the procedure of Example 14 can be repeated except that the
clay is cation-exchanged with Na.
Example 18
[0105] The acid treatment can be applied to clays other than
montmorillonite, or to layered non-clay materials. Thus, the
procedure of Example 14 can be repeated except that the acid
treatment can be applied to layered aluminum phosphate.
Example 19
[0106] In manner similar to Example 18, the procedure of Example 14
can be repeated except that the acid treatment can be applied to
zirconium phosphate.
Example 20
[0107] The structure of the catalyst can be varied via the nature
of the donor atoms and the substituents on the ligand L, the
initiating group R and the ancillary ligand S. Thus, the procedure
of Example 14 can be repeated except that the late transition metal
Pd may be substituted for the late transition metal Ni.
Example 21
[0108] In manner similar to Example 20, the procedure of Example 14
can be repeated except that the late transition metal Pt may be
substituted for the late transition metal Ni.
Example 22
[0109] In manner similar to Example 20, the procedure of Example 14
can be repeated except that the late transition metal Fe may be
substituted for the late transition metal Ni.
Example 23
[0110] In manner similar to Example 20, the procedure of Example 14
can be repeated except that the late transition metal Co may be
substituted for the late transition metal Ni.
Example 24
[0111] The method can be used for composites of homopolymers other
than polyethylene. Thus, the procedure of Example 14 was repeated
except that the olefin was propylene and the catalyst was
LNi(.eta..sup.1-CH.sub.2Ph)(PMe.sub.3) where
L=2-methylene-3-(2,6-diisopropylphenylimino)propoxide. A mixture of
the catalyst (8 mg in 1 g toluene) and
bis(1,5-cyclooctadiene)nickel (30 mg in 2 g toluene) was added to a
slurry of 450 mg clay suspended in 55 g toluene. The reactor was
pressurized with 937 kPa C.sub.3H.sub.6 and the polymerization
proceeded for 180 mins. The reaction yielded 1.4 g of a
polypropylene composite with a clay loading of 32%.
Example 25
[0112] The method can be used for composites of copolymers of
ethylene with other .alpha.-olefins or with functionalized
monomers. Thus, the procedure of Example 14 can be repeated except
that the olefin is styrene.
Example 26
[0113] In manner similar to Example 25, the procedure of Example 14
can be repeated except that the olefin is norbornene.
Example 27
[0114] The ethylene pressure can be varied in order to alter the
branch content of the polymer. Thus, the procedure of Example 14
can be repeated except that the ethylene pressure is increased to
3500 kPa.
Example 28
[0115] The procedure of Example 14 can be used to make a
masterbatch with high clay loading which then can be blended with
pure polymer (polyethylene, polypropylene, copolymers of ethylene
with other alpha-olefins, etc) to create composites with the
desired clay loading. Thus, the procedure of Example 14 can be
repeated except that a slurry of 0.25 g clay suspended in 40 g
toluene can be treated with 1 mg of the catalyst of Example 14 (in
1 g toluene). The reactor can be pressurized with 689 kPa
C.sub.2H.sub.4 and polymerization can proceed for 4 mins, to yield
polyethylene having a clay content of at least 40 wt. %.
Example 29
[0116] 500 mg of neat second catalyst component trimethylaluminum
(TMA) was added dropwise to a rapidly stirred suspension of 3 g
acid-treated montmorillonite in 10 g toluene. The clay was then
filtered and washed three times with fresh toluene to remove
unreacted TMA. A portion of the clay (626 mg) was resuspended in 70
g toluene and transferred to a 300 mL Parr reactor. 1 g of catalyst
solution (16 mg LNi(.eta..sup.3-CH.sub.2Ph) catalyst where
L=N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)propanamidato
in 3 g toluene) was added, the reactor was sealed and removed from
the glove box. After thermal equilibration at 40.degree. C. with
stirring, ethylene was added on demand at 100 psi for 35 minutes.
The activity is similar to that of the catalyst supported on
unmodified clay, under similar conditions in the same reactor. 5.6
g of material (containing 11.1 wt % clay) was recovered. It
appeared fluffier (i.e., less granular) than materials previously
produced using clay without TMA modification.
[0117] FIG. 11 shows TEM images of an 11.1 wt % clay-polyethylene
composite produced with TMA-modified clay catalyst. While the clay
is well-distributed in the polymer matrix, it is not highly
exfoliated. This may be a consequence of TMA-induced catalyst
leaching, resulting in polymerization other both on and off the
surface of the clay. The fluffy appearance of the polymer is
consistent with this explanation, since it resembles materials
produced by homogeneous acid-activated catalysts.
Example 30
[0118] 31.1 g Acid-treated lithium montmorillonite was partially
dehydrated by heating at 200.degree. C. under a dynamic vacuum (12
hours at .ltoreq.10-4 Torr). The clay was then suspended in toluene
(100 g) and transferred, under N.sub.2, to a 2 L autoclave reactor
containing 1 L toluene. A solution of the catalyst,
LNi(.eta..sup.3-CH.sub.2Ph) where
L=N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)propanamidato
(16 mg in 5 g toluene) was transferred to the burst valve of the
reactor. The reactor was thermostatted at 40.degree. C. The
catalyst solution was pushed into the reactor with ethylene at 1800
kPa, creating the clay-supported catalyst in situ. The
polymerization was allowed to proceed isothermally for 30 mins. The
reaction yielded 242 g polyethylene with a clay content of 13.2 wt.
%.
Example 31
[0119] 0.5 g Acid-treated lithium montmorillonite was partially
dehydrated by heating at 100.degree. C. under a dynamic vacuum (12
hours at .ltoreq.10-4 Torr) and then transferred to a
N.sub.2-filled glove box. A solution of the catalyst,
tetrabenzylzirconium (140 mg in 2 g toluene) was mixed with a
slurry of 2.5 g clay suspended in 80 g toluene for 30 mins at room
temperature inside a batch polymerization reactor thermostated at
55.degree. C. The reactor was pressurized with 965 kPa
C.sub.3H.sub.6 and polymerization was allowed to proceed for 60
mins. The reaction yielded 8.65 g polypropylene with a clay content
of 28.9 wt. % and a melting point of 148.degree. C.
Example 32
[0120] 430 mg Acid-treated lithium montmorillonite was partially
dehydrated by heating at 100.degree. C. under a dynamic vacuum (12
hours at .ltoreq.10.sup.4 Torr) and then transferred to a
N.sub.2-filled glove box. A solution of the catalyst
LNi(.eta..sup.1-CH.sub.2Ph)PMe.sub.3 where
L=3-(2,6-diisopropylphenylimino)-butan-2-one (16 mg in 2 g toluene)
and Ni(COD).sub.2 (37 mg in 1.5 g toluene) were mixed with a slurry
of 430 mg clay suspended in 40 g toluene for 30 mins at room
temperature. The clay-supported catalyst was allowed to settle and
the solvent decanted. 60 g fresh toluene and additional
Ni(COD).sub.2 (38 mg in 1.5 g toluene) was then added. The catalyst
suspension was then transferred to a batch polymerization reactor
and thermostatted at 25.degree. C. The reactor was pressurized with
965 kPa C.sub.3H.sub.6 and polymerization allowed to proceed for
180 mins. The reaction yielded 1.3 g polypropylene with a clay
content of 33.1 wt. %.
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[0168] Although the present invention has been described in
connection with the preferred embodiments, it is to be understood
that modifications and variations may be utilized without departing
from the principles and scope of the invention, as those skilled in
the art will readily understand. Accordingly, such modifications
may be practiced within the scope of the following claims.
* * * * *