U.S. patent application number 11/454950 was filed with the patent office on 2006-12-28 for heterogeneous polymer blend and process of making the same.
Invention is credited to Armenag H. Dekmezian, Sunny Jacob, Peijun Jiang, Aspy K. Mehta, Andrew G. Narvaez, Pradeep P. Shirodkar, Weiqing Weng.
Application Number | 20060293455 11/454950 |
Document ID | / |
Family ID | 34956812 |
Filed Date | 2006-12-28 |
United States Patent
Application |
20060293455 |
Kind Code |
A1 |
Jiang; Peijun ; et
al. |
December 28, 2006 |
Heterogeneous polymer blend and process of making the same
Abstract
A heterogeneous polymer blend comprises a continuous phase
comprising a thermoplastic first polymer having a crystallinity of
at least 30% and a dispersed phase comprising particles of a second
polymer different from the first polymer dispersed in said
continuous phase, the second polymer having a crystallinity of less
than 20% and being at least partially cross-linked, and the average
particle size of the particles of the second polymer being less
than 1 micron.
Inventors: |
Jiang; Peijun; (League City,
TX) ; Dekmezian; Armenag H.; (Kingwood, TX) ;
Mehta; Aspy K.; (Humble, TX) ; Jacob; Sunny;
(Akron, OH) ; Narvaez; Andrew G.; (Pasadena,
TX) ; Shirodkar; Pradeep P.; (Stow, OH) ;
Weng; Weiqing; (Houston, TX) |
Correspondence
Address: |
ExxonMobil Chemical Company;Law Technology
P.O. Box 2149
Baytown
TX
77522-2149
US
|
Family ID: |
34956812 |
Appl. No.: |
11/454950 |
Filed: |
June 16, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60693030 |
Jun 22, 2005 |
|
|
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Current U.S.
Class: |
525/191 |
Current CPC
Class: |
C08F 210/06 20130101;
C08L 2205/22 20130101; C08L 23/10 20130101; C08L 23/083 20130101;
C08L 2308/00 20130101; C08L 23/16 20130101; C08L 2666/06 20130101;
C08L 2666/04 20130101; C08L 2666/06 20130101; C08L 23/04 20130101;
C08L 2312/00 20130101; C08L 23/145 20130101; C08F 210/18 20130101;
C08L 91/00 20130101; C08L 23/12 20130101; C08L 23/10 20130101; C08F
110/06 20130101; C08L 2666/06 20130101; C08F 236/20 20130101; C08F
2500/20 20130101; C08F 2/001 20130101; C08L 2666/02 20130101; C08L
23/16 20130101; C08L 23/12 20130101; C08L 2205/03 20130101; C08L
23/145 20130101; C08F 210/06 20130101; C08F 210/06 20130101; C08L
23/12 20130101 |
Class at
Publication: |
525/191 |
International
Class: |
C08F 8/00 20060101
C08F008/00 |
Claims
1. A heterogeneous polymer blend comprising: (a) a continuous phase
comprising a thermoplastic first polymer having a crystallinity of
at least 30%; and (b) a dispersed phase comprising particles of a
second polymer different from the first polymer dispersed in said
continuous phase, the second polymer having a crystallinity of less
than 20% and being at least partially cross-linked, and the average
particle size of the particles of the second polymer being less
than 1 micron.
2. The polymer blend of claim 1 wherein said thermoplastic first
polymer is a homopolymer of a C.sub.2 to C.sub.20 olefin.
3. The polymer blend of claim 1 wherein said thermoplastic first
polymer is a copolymer of a C.sub.2 to C.sub.20 olefin with less
than 15 wt % of at least one comonomer.
4. The polymer blend of claim 1 wherein said thermoplastic first
polymer comprises a polymer of propylene.
5. The polymer blend of claim 1 wherein the second polymer is
produced from a plurality of comonomers comprising at least one
C.sub.3 to C.sub.20 olefin and at least one polyene.
6. The polymer blend of claim 5 wherein said at least one polyene
has at least two polymerizable unsaturated groups.
7. The polymer blend of claim 5 wherein said plurality of
comonomers comprise propylene and ethylene.
8. The polymer blend of claim 1 wherein the average particle size
of the particles of the second polymer is between about 50
nanometers and about 0.5 microns.
9. The polymer blend of claim 1 wherein said dispersed phase
comprises more than 50 wt % of the total heterogeneous polymer
blend.
10. A heterogeneous polymer blend comprising (a) a continuous phase
comprising a thermoplastic first polymer having a crystallinity of
at least 30%; and (b) a dispersed phase comprising particles of a
second polymer different from the first polymer dispersed in said
continuous phase, the second polymer having a crystallinity of less
than 20% and being at least partially cross-linked, and the average
particle size of the particles of the second polymer being less
than 10 microns, wherein said polymer blend is substantially free
of processing oil.
11. The polymer blend of claim 10 wherein said thermoplastic first
polymer is a homopolymer of a C.sub.2 to C.sub.20 olefin.
12. The polymer blend of claim 10 wherein said thermoplastic first
polymer is a copolymer of a C.sub.2 to C.sub.20 olefin with less
than 15 wt % of at least one comonomer.
13. The polymer blend of claim 10 wherein the second polymer is
produced from a plurality of comonomers comprising at least one
C.sub.3 to C.sub.20 olefin and at least one polyene.
14. The polymer blend of claim 10 wherein the average particle size
of the particles of the second polymer is less than 1 micron.
15. The polymer blend of claim 10 wherein the average particle size
of the particles of the second polymer is between about 50
nanometers and about 0.5 microns.
16. A heterogeneous polymer blend comprising (a) a continuous phase
comprising a thermoplastic first polymer that is at least partially
crystalline; and (b) a dispersed phase comprising particles of a
second polymer different from the first polymer dispersed in said
continuous phase, wherein said dispersed phase comprises at least a
fraction which is insoluble in xylene and which comprises less than
2,500 ppm of a curative.
17. The polymer blend of claim 16 wherein said fraction insoluble
in xylene comprises less than 100 ppm of a curative.
18. The polymer blend of claim 16 wherein said fraction insoluble
in xylene comprises at least is at least 4% of said dispersed
phase.
19. A process for producing a heterogeneous polymer blend
comprising (a) a continuous phase comprising a thermoplastic first
polymer that is at least partially crystalline; and (b) a dispersed
phase comprising particles of a second polymer different from the
first polymer dispersed in said continuous phase, the second
polymer having a crystallinity less than that of the first polymer
and being at least partially cross-linked, the process comprising:
(i) polymerizing at least one first monomer to produce a
thermoplastic first polymer that is at least partially crystalline;
and (ii) contacting at least part of said first polymer with at
least one second monomer and at least one polyene under conditions
sufficient to polymerize said second monomer to produce said second
polymer and simultaneously cross-link said second polymer such that
the dispersed phase produced by said contacting (ii) comprises at
least a fraction which is insoluble in xylene.
20. The process of claim 19 wherein said polymerizing (i) is
conducted in the presence of a catalyst and said contacting (ii) is
conducted in the presence of the same catalyst.
21. The process of claim 19 wherein said polymerizing (i) is
conducted in the presence of a first catalyst and said contacting
(ii) is conducted in the presence of a second catalyst different
from the first catalyst.
22. A process for producing a heterogeneous polymer blend, the
process comprising: (a) selecting a catalyst capable of
polymerizing a C.sub.2 to C.sub.20 olefin to produce a first
polymer having at least 30% crystallinity; (b) contacting said
catalyst with one or more C.sub.2 to C.sub.20 olefins at a
temperature of at least 50.degree. C. to produce a first polymer
having at least 30% crystallinity; (c) contacting said first
polymer and said catalyst with at least one C.sub.3 to C.sub.20
olefin and at least one polyene under conditions sufficient to
polymerize said at least one C.sub.3 to C.sub.20 olefin to produce
a second polymer and simultaneously cross-link said second polymer,
whereby the product of said contacting (c) is a heterogeneous
polymer blend comprising a continuous phase of the first polymer
having at least 30% crystallinity and a discontinuous phase of
particles of said second polymer having an average particle size
less than 10 microns, said second polymer being at least partially
cross-linked and comprising at least 15 wt % of said C.sub.3 to
C.sub.20 olefin and at least 0.0001 wt % of said polyene.
23. The process of claim 22 wherein the first polymer produced in
said contacting (b) has at least 0.01% terminal unsaturation.
24. The process of claim 22 wherein said C.sub.2 to C.sub.20 olefin
comprises propylene.
25. The process of claim 22 wherein said first polymer is contacted
with ethylene together with said at least one C.sub.3 to C.sub.20
olefin and said at least one polyene in said contacting (c).
26. The process of claim 22 wherein said polyene has at least two
polymerizable unsaturated groups.
27. The process of claim 22 wherein said catalyst selected in (a)
is a single site catalyst comprising at least one catalyst
component and at least one activator.
28. The process of claim 27 wherein said catalyst component is a
bridged bis-indenyl metallocene catalyst having a substituent on
one or both of the 2- and 4-positions on each indenyl ring.
29. A process for producing a heterogeneous polymer blend, the
process comprising: (a) selecting a catalyst capable of
polymerizing a C.sub.2 to C.sub.20 olefin to produce a first
polymer having at least 30% crystallinity; (b) contacting said
catalyst with one or more C.sub.2 to C.sub.20 olefins at a
temperature of at least 50.degree. C. to produce a first polymer
having at least 30% crystallinity; (c) contacting said first
polymer together with at least one C.sub.3 to C.sub.20 olefin and
at least one polyene with a catalyst capable of polymerizing bulky
monomers under conditions sufficient to polymerize said at least
one C.sub.3 to C.sub.20 olefin to produce a second polymer and
simultaneously cross-link said second polymer, whereby the product
of said contacting (c) is a heterogeneous polymer blend comprising
a continuous phase of the first polymer having at least 30%
crystallinity and a discontinuous phase of particles of said second
polymer having an average particle size less than 3 microns, said
second polymer being at least partially cross-linked and comprising
at least 15 wt % of said C.sub.3 to C.sub.20 olefin and at least
0.0001 wt % of said polyene.
30. The process of claim 29 wherein the first polymer produced in
said contacting (b) has at least 0.1% terminal unsaturation.
31. The process of claim 29 wherein said C.sub.2 to C.sub.20 olefin
comprises propylene.
32. The process of claim 29 wherein said first polymer is contacted
with ethylene together with said at least one C.sub.3 to C.sub.20
olefin and said at least one polyene in said contacting (c).
33. The process of claim 29 wherein said polyene has at least two
polymerizable unsaturated groups.
34. The process of claim 29 wherein the particles of said second
polymer blend produced in step (c), prior to any subsequent curing
step, have a melting temperature of at least 100.degree. C.
35. The process of claim 29 wherein the catalyst selected in (a) is
different from the catalyst employed in said contacting (c).
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. Provisional
Application Ser. No. 60/693,030 filed Jun. 22, 2005.
BACKGROUND
[0002] Heterogeneous polymer blends comprising a second polymer
dispersed in a matrix of a first polymer are very useful and,
depending on the properties and the relative amounts of the first
and second polymers, a wide variety of such polymer blends can be
produced. Of particular interest are polymer blends, also referred
to as thermoplastic elastomers, in which the first polymer is a
thermoplastic material, such as polypropylene, and the second
polymer is an elastomeric material, such as an ethylene-propylene
elastomer or an ethylene-propylene-diene (EPDM) rubber. Examples of
such thermoplastic elastomers include polypropylene impact
copolymers, thermoplastic olefins and thermoplastic
vulcanizates.
[0003] Unlike conventional vulcanized rubbers, thermoplastic
elastomers can be processed and recycled like thermoplastic
materials, yet have properties and performance similar to that of
vulcanized rubber at service temperatures. For this reason,
thermoplastic elastomers are useful for making a variety of
articles such as weather seals, hoses, belts, gaskets, moldings,
boots, elastic fibers and like articles. They are also particularly
useful for making articles by blow molding, extrusion, injection
molding, thermo-forming, elasto-welding and compression molding
techniques. In addition, thermoplastic elastomers are often used
for making vehicle parts, such as but not limited to, weather
seals, brake parts including, but not limited to cups, coupling
disks, diaphragm cups, boots such as constant velocity joints and
rack and pinion joints, tubing, sealing gaskets, parts of
hydraulically or pneumatically operated apparatus, o-rings,
pistons, valves, valve seats, and valve guides.
[0004] One method of making the aforementioned polymer blends is by
mixing two different polymers after they have been polymerized to
achieve a target set of properties. However, this method is
relatively expensive making it much more desirable to make blends
by direct polymerization. Blending by direct polymerization
typically uses multiple reactors in series, where the product from
one reactor is fed to a second reactor having a different
polymerizing environment, resulting in a final product that is an
intimate mix of two different products. Examples of such processes
employing vanadium catalysts in series reactor operation to produce
different types of EPDM compositions are disclosed in U.S. Pat.
Nos. 3,629,212, 4,016,342, and 4,306,041.
[0005] U.S. Pat. No. 6,245,856 discloses a thermoplastic olefin
composition comprising polypropylene, an ethylene-alpha olefin
elastomer and a compatabilizer comprising an ethylene-propylene
copolymer having a propylene content of greater than 80 weight
percent. According to this patent, the individual components of the
composition can be separately manufactured and mechanically blended
together in a mechanical mixer or two or more of the components can
be prepared as a reactor blend using a series of reactors where
each component is prepared in a separate reactor and the reactant
is then transferred to another reactor where a second component is
prepared. In the absence of the compatabilizer, the elastomer phase
is said to be uneven with particles greater than 5 microns in size,
whereas the addition of the compatabilizer is said to improve
dispersion such that the elastomer phase has a particle size of
about 1 micron. The elastomer phase of this polymer blend is not
cross-linked.
[0006] U.S. Pat. No. 6,207,756 describes a process for producing a
blend of a continuous phase of a semi-crystalline plastic, such as
polypropylene, and a discontinuous phase of an amorphous elastomer,
such as a terpolymer of ethylene, a C.sub.3-C.sub.20 alpha olefin
and a non-conjugated diene. The blends are produced in series
reactors by producing a first polymer component in a first reactor,
directing the effluent to a second reactor and producing the second
polymer component in solution in the second reactor in the presence
of the first polymeric component. U.S. Pat. No. 6,319,998 also
discloses using series solution polymerizations to produce blends
of ethylene copolymers. U.S. Pat. No. 6,770,714 discloses the use
of parallel polymerizations to produce different polymeric
components that are then blended through extrusion or using other
conventional mixing equipment. One polymeric component is a
propylene homopolymer or copolymer and the second polymeric
component is an ethylene copolymer.
[0007] One particularly useful form of thermoplastic elastomer is a
thermoplastic vulcanizate ("TPV"), which comprises a thermoplastic
resin matrix, such as polypropylene, within which are dispersed
particles of a cured elastomeric material, such as an EPDM rubber.
TPVs are normally produced by a process of "dynamic vulcanization",
which is a process of vulcanizing or cross-linking the elastomeric
component during intimate melt mixing with the thermoplastic resin,
together with plasticizers (e.g. process oils), fillers,
stabilizers, and a cross-linking system, under high shear and above
the melting point of the thermoplastic. The mixing is typically
done in a twin-screw extruder, to create a fine dispersion of the
elastomeric material within the thermoplastic resin while the
elastomeric material is cured. The levels of thermoplastic resin
and plasticizer (oil) can be adjusted to produce grades having
different profiles of hardness, rheology and engineering
properties, although in general it is difficult to produce TPVs by
dynamic vulcanization in which the content of the elastomeric phase
is greater than 50 wt % of the overall polymer blend. Examples of
dynamic vulcanization are described in the U.S. Pat. Nos. 4,130,535
and 4,311,628.
[0008] However, while dynamic vulcanization is effective in
producing TPVs with a unique profile of properties, it is expensive
and suffers from a number of disadvantages. Thus the production of
quality product is technically challenging and specialized
equipment is needed. Moreover, the process involves many steps,
each one critical to the eventual quality of the final product.
Forming the polymer blend normally involves separately comminuting
bales of the elastomeric polymer (which is typically how EPDM
rubber is commercially distributed), mechanically mixing it with
the thermoplastic resin along with the processing oils, curatives,
and other ingredients in a suitable high shear mixing device to
comminute the rubber particles and cure them to generate cured
rubber particles embedded in a continuous thermoplastic resin
matrix. The cured rubber particles in the finished products have an
averaged particle size of 1 to 10 microns. Careful injection of
processing oil helps manage the rheological characteristics of the
fluid in the reactive extruder (to minimize pressure buildup) as
well as product properties such as hardness. Precise control over
the size and distribution of the cross-linked elastomer particles
is sought, as it affects properties such as elastic recovery (as
measured through compression set). While the products produced with
existing technology have many desirable properties, there are gaps
in the overall properties profile. Some of these are the need for
higher service temperatures, improved elastic recovery, softer
products, higher tensile strength, easier processability, oil-free
compositions, and/or colorless products.
[0009] An improved process for producing TPVs is disclosed in U.S.
Pat. No. 6,388,016, incorporated herein in its entirety, in which a
polymer blend is produced by solution polymerization in series
reactors employing metallocene catalysts and the resultant blend is
subjected to dynamic vulcanization. In particular, the process
involves feeding a first set of monomers selected from ethylene and
higher alpha-olefins, and a solvent, to a first continuous flow
stirred tank reactor, adding a metallocene catalyst to the first
reactor in an amount of 50 to 100 weight % of the total amount of
catalyst added to all reactors, operating the first reactor to
polymerize the monomers to produce an effluent containing a first
polymer, feeding the effluent from the first reactor to a second
continuous flow stirred tank reactor, feeding a second set of
monomers selected from ethylene, higher alpha-olefins and
non-conjugated dienes, and optionally additional solvent, to the
second reactor, operating the second reactor to polymerize the
second monomers to produce a second polymer containing diene,
recovering the resulting first and second polymers and blending
them with a curing agent under conditions of heat and shear
sufficient to cause the blend to flow and to at least partially
crosslink the diene-containing polymer and form a dispersion of
cured diene-containing particles in a matrix of the first polymer.
It will, however, be seen that this improved process still relies
on dynamic vulcanization to cure the elastomeric component. As a
result the cured diene-containing particles have an average
particle size in the range of 1 to 10 microns
SUMMARY
[0010] In one aspect, the present invention relates to a
heterogeneous polymer blend comprising: [0011] (a) a continuous
phase comprising a thermoplastic first polymer having a
crystallinity of at least 30%; and [0012] (b) a dispersed phase
comprising particles of a second polymer different from the first
polymer dispersed in said continuous phase, the second polymer
having a crystallinity of less than 20% and being at least
partially cross-linked, and the average particle size of the
particles of the second polymer being less than 1 micron.
[0013] In a further aspect, the present invention resides in a
heterogeneous polymer blend comprising: [0014] (a) a continuous
phase comprising a thermoplastic first polymer having a
crystallinity of at least 30%; and [0015] (b) a dispersed phase
comprising particles of a second polymer different from the first
polymer dispersed in said continuous phase, the second polymer
having a crystallinity of less than 20% and being at least
partially cross-linked, and the average particle size of the
particles of the second polymer being less than 10 microns, wherein
said polymer blend is substantially free of processing oil.
[0016] Preferably, said thermoplastic first polymer is a
homopolymer of a C.sub.2 to C.sub.20 olefin or a copolymer of a
C.sub.2 to C.sub.20 olefin with less than 15 wt % of at least one
comonomer.
[0017] Preferably, the second polymer is produced from a plurality
of comonomers comprising at least one C.sub.3 to C.sub.20 olefin
and at least one polyene. Conveniently, the polyene has at least
two polymerizable unsaturated groups and preferably is a diene.
[0018] Preferably, the average particle size of the particles of
the second polymer is between about 50 nanometers and about 0.5
microns.
[0019] Conveniently, said dispersed phase comprises more than 50 wt
%, such as more than 60 wt %, for example more than 70 wt % of the
total heterogeneous polymer blend.
[0020] In a another aspect, the present invention resides in a
heterogeneous polymer blend comprising: [0021] (a) a continuous
phase comprising a thermoplastic first polymer that is at least
partially crystalline; and [0022] (b) a dispersed phase comprising
particles of a second polymer different from the first polymer
dispersed in said continuous phase, wherein said dispersed phase
comprises at least a fraction which is insoluble in xylene and
which comprises less than 10,000 ppm, such as less than 2,500 ppm,
such as less than 1,000 ppm, such as less than 100 ppm, such as
less than 10 ppm, (preferably in the absence) of a curative.
[0023] Conveniently, said fraction insoluble in xylene comprises at
least is at least 4%, such as at least 10%, such as at least 20%,
such as at least 40%, such as at least 50%, of said dispersed
phase.
[0024] In yet a further aspect, the invention resides in a process
for producing a heterogeneous polymer blend comprising (a) a
continuous phase comprising a thermoplastic first polymer that is
at least partially crystalline; and (b) a dispersed phase
comprising particles of a second polymer different from the first
polymer dispersed in said continuous phase, the second polymer
having a crystallinity less than that of the first polymer and
being at least partially cross-linked, the process comprising:
[0025] (i) polymerizing at least one first monomer to produce a
semi-crystalline thermoplastic first polymer that is at least
partially crystalline; and [0026] (ii) contacting at least part of
said first polymer with at least one second monomer and at least
one polyene under conditions sufficient to polymerize said second
monomer to produce said second polymer and also (preferably
simultaneously) cross-link said second polymer such that the
dispersed phase produced by said contacting (ii) comprises at least
a fraction which is insoluble in xylene.
[0027] In still a further aspect, the present invention resides in
a process for producing a heterogeneous polymer blend, the process
comprising: [0028] (a) selecting a catalyst capable of polymerizing
a C.sub.2 to C.sub.20 olefin to produce a first polymer having at
least 30% crystallinity; [0029] (b) contacting said catalyst with
one or more C.sub.2 to C.sub.20 olefins at a temperature of at
least 50.degree. C. to produce a first polymer having at least 30%
crystallinity; [0030] (c) contacting said first polymer and said
catalyst with at least one C.sub.3 to C.sub.20 olefin and at least
one polyene under conditions sufficient to polymerize said at least
one C.sub.3 to C.sub.20 olefin to produce a second polymer and
simultaneously cross-link said second polymer, whereby the product
of said contacting (c) is a heterogeneous polymer blend comprising
a continuous phase of the first polymer having at least 30%
crystallinity and a discontinuous phase of particles of said second
polymer having an average particle size less than 3 microns, said
second polymer being at least partially cross-linked and comprising
at least 15 wt % of said C.sub.3 to C.sub.20 olefin and at least
0.0001 wt % of said polyene.
[0031] Conveniently, said polyene has at least two polymerizable
unsaturated groups.
[0032] Conveniently, said catalyst selected in (a) is a single site
catalyst comprising at least one catalyst component, normally a
metallocene, and at least one activator.
[0033] In still yet a further aspect, the present invention resides
in a process for producing a heterogeneous polymer blend, the
process comprising: [0034] (a) selecting a catalyst capable of
polymerizing a C.sub.2 to C.sub.20 olefin to produce a first
polymer having at least 30% crystallinity; [0035] (b) contacting
said catalyst with one or more C.sub.2 to C.sub.20 olefins at a
temperature of at least 50.degree. C. to produce a first polymer
having at least 30% crystallinity; [0036] (c) contacting said first
polymer together with at least one C.sub.3 to C.sub.20 olefin and
at least one polyene with a catalyst capable of polymerizing bulky
monomers under conditions sufficient to polymerize said at least
one C.sub.3 to C.sub.20 olefin to produce a second polymer and
simultaneously cross-link said second polymer, whereby the product
of said contacting (c) is a heterogeneous polymer blend comprising
a continuous phase of the first polymer having at least 30%
crystallinity and a discontinuous phase of particles of said second
polymer having an average particle size less than 3 microns, said
second polymer being at least partially cross-linked and comprising
at least 15 wt % of said C.sub.3 to C.sub.20 olefin and at least
0.0001 wt % of said polyene.
[0037] Conveniently, said catalyst employed in contacting (c) is
capable of producing a polymer having an Mw of 20,000 or more and a
crystallinity of less than 20%.
[0038] In one embodiment, the catalyst employed in contacting (c)
is the same as the catalyst employed in contacting (b).
[0039] In another embodiment, the catalyst employed in contacting
(c) is the different from the catalyst employed in contacting (b)
and catalyst quenching is applied between the contacting (b) and
the contacting (c).
DESCRIPTION OF THE DRAWINGS
[0040] FIGS. 1A and 1B are atomic force micrographs (AFM) of the
polymer blend produced in Example 1A and 1B, respectively.
[0041] FIG. 1C is a transmission electron micrograph (TEM) of a
molded part cross-section produced from the polymer blend of
Example 1A.
[0042] FIG. 1D is a histogram of particle sizes for the polymer
blend of Example 1A obtained from an AFM image.
[0043] FIG. 1E is a histogram of particle sizes for the polymer
blend of Example 1A obtained from a TEM image.
[0044] FIG. 1F is a DSC trace of the xylene insolubles of Example
1B.
[0045] FIG. 1G is a transmission electron micrograph (TEM) of a
molded part cross-section produced from the polymer blend of
Example 1C
[0046] FIG. 1H are transmission electron micrographs (TEM) of
molded part cross-sections produced from Santoprene 201-55 and
201-55F.
[0047] FIG. 2A is an atomic force micrograph (AFM) of the polymer
blend produced in Example 2C.
[0048] FIG. 2B is a transmission electron micrograph (TEM) of a
molded part cross-section produced from the polymer blend of
Example 2C.
[0049] FIG. 2C is a Van Gurp-Palmen plot for Examples 1A and 2C,
and Santoprene 201-55 and 201-73.
DETAILED DESCRIPTION
[0050] For purposes of this invention and the claims thereto when a
polymer or oligomer is referred to as comprising an olefin, the
olefin present in the polymer or oligomer is the polymerized or
oligomerized form of the olefin, respectively. Likewise the use of
the term polymer is meant to encompass homopolymers and copolymers.
In addition the term copolymer includes any polymer having 2 or
more monomers. Thus, as used herein, the term "polypropylene" means
a polymer made of at least 50 weight % propylene units, preferably
at least 70% propylene units, more preferably at least 80%
propylene units, even more preferably at least 90% propylene units,
even more preferably at least 95% propylene units or 100% propylene
units.
[0051] As used herein the term "substantially free of processing
oil" means that the relevant product contains little or no of the
oil-based processing aids, such as extender oils, synthetic
processing oils, oligomeric extenders, or a combination thereof,
that are added to conventional polymer blends to control the
rheological characteristics of the blends during dynamic
vulcanization. Preferably the relevant product contains less than 1
weight % processing oil, more preferably less than 0.5 weight %,
preferably less than 0.1 weight % processing oil. The amount of oil
in the polymer blend is determined using solvent extraction as
described the example section. By virtue of the fact that the
second polymer of the polymer blend of the invention is formed as
at least partially cross-linked particles dispersed in the first
polymer phase in the polymerization reactor, the need for a
subsequent dynamic vulcanization step and hence the need for
addition of processing oil is avoided. It is, however, to be
appreciated that in some cases the polymer blend of the invention
may be subjected to post-polymerization curing and/or vulcanization
to produce additional cross-linking of the second polymer.
[0052] As used herein the term "curative" means any of the
additives conventionally added to polymer blends to effect curing
of one or more components of the blend during a
post-polymerization, dynamic vulcanization step. Examples of known
curatives include sulfur, sulfur donors, metal oxides, resin
systems, such as phenolic resins, peroxide-based systems,
hydrosilation with platinum or peroxide and the like, both with and
without accelerators and coagents.
[0053] As used herein the term "bulky monomer" means an olefin
monomer that is not a linear C.sub.2 to C.sub.20 alpha olefin.
Bulky monomers include cyclic olefin monomers, such as
5-ethylidene-2-norbornadiene, (ENB), 5-vinyl-2-norbornene (VNB) and
cyclopentadiene; branched olefin monomers, such as 3,5,5 trimethyl
hexene-1; and macromonomers, such as terminally unsaturated
oligomers or terminally unsaturated polymers.
[0054] As used herein, the term "terminal unsaturation" is defined
to mean vinyl unsaturation, vinylene unsaturation or vinylidene
unsaturation, with vinyl unsaturation being preferred.
[0055] As used herein, the term "heterogeneous blend" means a
composition having two or more morphological phases in the same
state. For example a blend of two polymers where one polymer forms
discrete packets such as finely divided domains dispersed in a
matrix of another polymer is said to be heterogeneous in the solid
state. Also a heterogeneous blend is defined to include
co-continuous blends where the blend components are separately
visible, but it is unclear which is the continuous phase and which
is the discontinuous phase. Such morphology is determined using
scanning electron microscopy (SEM) or atomic force microscopy
(AFM). In the event the SEM and AFM provide different data, then
the AFM data are used. By continuous phase is meant the matrix
phase in a heterogeneous blend. By discontinuous phase is meant the
dispersed phase in a heterogeneous blend.
[0056] In contrast, a "homogeneous blend" is a composition having
substantially one morphological phase in the same state. For
example a blend of two polymers where one polymer is miscible with
another polymer is said to be homogeneous in the solid state. Such
morphology is determined using scanning electron microscopy. By
miscible is meant that that the blend of two or more polymers
exhibits single-phase behavior for the glass transition
temperature, e.g. the Tg would exist as a single, sharp transition
temperature on a dynamic mechanical thermal analyzer (DMTA) trace
of tan .delta. (i.e., the ratio of the loss modulus to the storage
modulus) versus temperature. By contrast, two separate transition
temperatures would be observed for an immiscible blend, typically
corresponding to the temperatures for each of the individual
components of the blend. Thus a polymer blend is miscible when
there is one Tg indicated on the DMTA trace. A miscible blend is
homogeneous, while an immiscible blend is heterogeneous.
[0057] The heterogeneous polymer blend of the invention comprises
particles of an "at least partially cross-linked polymer". These
partially cross-linked polymers are believed to be formed by
in-situ reaction between the polyene and the second polymers. The
presence and amount of such partially cross-linked polymers in the
blend can be determined by a multi-step solvent extraction process.
In this process the direct product of the polymerization process,
without undergoing any additional curing steps, is first contacted
with cyclohexane at 25.degree. C. for 48 hours to dissolve the
uncured and lightly branched elastomeric components of the blend
and then the remaining solids are refluxed at the boiling
temperature of xylene for 24 hours with xylene to isolate the "at
least partially cross-linked polymer". The "at least partially
cross-linked polymer" is also referred to herein as "xylene
insolubles". Details of the solvent extraction procedure are given
in the Examples.
[0058] Melting temperature (T.sub.m) and crystallization
temperature (T.sub.c), referred to herein, are measured using
Differential Scanning Calorimetry (DSC) according to ASTM E 794-85.
Details of the DSC test are given in the Examples. Heat of fusion
(.DELTA.H.sub.f) is measured according to ASTM D 3417-99, and
percentage crystallinity is calculated using heat of fusion as
described below.
[0059] This invention relates to a heterogeneous polymer blend
comprising a semi-crystalline (at least 30% crystalline)
thermoplastic first polymer that constitutes the continuous phase
and particles of a second polymer different from, and less
crystalline than, the first polymer dispersed within the continuous
phase. The dispersed particles have an average size of less than 10
micron, normally less than 3 micron, preferably less than 2
microns, more preferably less than 1 micron, and most preferably
between about 50 nanometers and about 0.5 microns.
[0060] The inventive heterogeneous blends are believed to contain
hybrid polymer. While not wishing to bound by theory, it is
believed that some or all of the discrete particles of the second
polymer are produced by means of an in-situ cross-linking chemistry
that takes place concurrently with the synthesis of the second
polymer and conveniently in the same polymerization reaction
zone.
[0061] This invention also relates to a process for making the
above polymer blend. In a reactor, a semi-crystalline polymer phase
is produced in a first polymerization step. In a second
polymerization step, the elastomeric phase is synthesized, in the
presence of the semi-crystalline polymer phase. The elastomer phase
takes the form of a fine particle size dispersion in the
semi-crystalline phase. The elastomer phase is crosslinked through
the use of multifunctional monomers, particularly a polyene having
at least two polymerizable unsaturated groups, with the degree of
crosslinking being controlled by the reaction environment during
the polymerization. While not wishing to bound by theory, it is
believed that reactive intermediates generated in the first reactor
engage in the polymerization processes taking place in the second
reactor, producing hybrid polymers (also known as branch-block
copolymers) that combine the characteristics of the polymers formed
in the first and second reactor zones, such as the melting
temperature of the first polymer and the lower glass transition
temperatures of the second polymer.
[0062] Following the two polymerization steps, the product
composition, direct from the polymerization reactor, can undergo a
typical polymer finishing operation, where suitable additives are
incorporated and the polymer is melt homogenized. The finished
product displays easy processability, high elastic recovery, high
tensile strength and elongation. Heretofore, such properties were
only possible via dynamic vulcanization.
The First Polymer
[0063] The matrix of the heterogeneous polymer blend of the present
invention may be any crystalline or semi-crystalline thermoplastic
polymer or a mixture thereof. Useful thermoplastic polymers have a
crystallinity of at least 30%, more preferably at least 40% as
determined by differential scanning calorimetry (DSC). The first
polymer provides the composition with required tensile strength and
temperature resistance. Accordingly, semi-crystalline polymers with
a melting temperature, as measured by DSC, above 100.degree. C.,
preferably above 120.degree. C., preferably above 140.degree. C.
are desired. Typically, the first polymer has a crystallization
temperature (T.sub.c) between about 20 and about 120.degree. C.,
such as between about 70 and about 110.degree. C. Polymers with a
high glass transition temperature to provide the elevated
temperature resistance are also acceptable as the thermoplastic
matrix.
[0064] Exemplary thermoplastic polymers include the family of
polyolefin resins, polyesters (such as polyethylene terephthalate,
polybutylene terephthalate), polyamides (such as nylons),
polycarbonates, styrene-acrylonitrile copolymers, polystyrene,
polystyrene derivatives, polyphenylene oxide, polyoxymethylene, and
fluorine-containing thermoplastics. The preferred thermoplastic
resins are crystallizable polyolefins that are formed by
polymerizing C.sub.2 to C.sub.20 olefins such as, but not limited
to, ethylene, propylene and C.sub.4 to C.sub.12 .alpha.-olefins,
such as 1-butene, 1-hexene, 1-octene, 2-methyl-1-propene,
3-methyl-1-pentene, 4-methyl-1-pentene, 5-methyl-1-hexene, and
mixtures thereof. Copolymers of ethylene and propylene or ethylene
or propylene with another .alpha.-olefin, such as butene-1;
pentene-1,2-methylpentene-1,3 -methylbutene-1; hexene-1,3
-methylpentene-1,4-methylpentene-1,3,3-dimethylbutene-1; heptene-1;
hexene-1; methylhexene-1; dimethylpentene-1 trimethylbutene-1;
ethylpentene-1; octene-1; methylpentene-1; dimethylhexene-1;
trimethylpentene-1; ethylhexene-1; methylethylpentene-1;
diethylbutene-1; propylpentane-1; decene-1; methylnonene-1;
nonene-1; dimethyloctene-1; trimethylheptene-1; ethyloctene-1;
methylethylbutene-1; diethylhexene-1 and dodecene-1, may also be
used.
[0065] In one embodiment, the thermoplastic polymer comprises a
propylene homopolymer, a copolymer of propylene, or a mixture of
propylene homopolymers and copolymers. Typically, the propylene
polymer is predominately crystalline, i.e., it has a melting point
generally greater than 110.degree. C., alternatively greater than
115.degree. C., and preferably greater than 130.degree. C. The term
"crystalline," as used herein, characterizes those polymers that
possess high degrees of inter- and intra-molecular order in the
solid state. Heat of fusion, a measure of crystallinity, greater
than 60 J/g, alternatively at least 70 J/g, alternatively at least
80 J/g, as determined by DSC analysis, is preferred. The heat of
fusion is dependent on the composition of the polypropylene. A
propylene homopolymer will have a higher heat of fusion than a
copolymer or blend of a homopolymer and copolymer.
[0066] Where the thermoplastic polymer matrix is polypropylene, the
matrix can vary widely in composition. For example, substantially
isotactic polypropylene homopolymer or propylene copolymer
containing 10 weight percent or less of a comonomer can be used
(i.e., at least 90% by weight propylene). Further, polypropylene
segments may be part of graft or block copolymers having a sharp
melting point above 110.degree. C. and alternatively above
115.degree. C. and alternatively above 130.degree. C.,
characteristic of the stereoregular propylene sequences. The
continuous phase matrix may be a combination of homopolypropylene,
and/or random, and/or block copolymers as described herein. When
the matrix is a random copolymer, the percentage of the
copolymerized alpha-olefin in the copolymer is, in general, up to
9% by weight, alternatively 0.5% to 8% by weight, alternatively 2%
to 6% by weight. The preferred alpha-olefins contain 2 or from 4 to
12 carbon atoms. One, two or more alpha-olefins can be
copolymerized with propylene.
The Second Polymer
[0067] The dispersed second polymer phase of the heterogeneous
polymer blend of the invention is generally an elastomeric
copolymer and is polymerized and also cross-linked in the presence
of the first polymer. The second polymer is generally an amorphous
or low crystallinity (having a crystallinity of less than 20%)
polymer and in particular may include any elastomer or mixture
thereof that is capable of forming a cross-linked system during the
polymerization. Some non-limiting examples of these elastomers
include olefin copolymers, butyl rubber, styrene-butadiene
copolymer rubber, butadiene rubber, acrylonitrile rubber,
halogenated rubber such as brominated and chlorinated
isobutylene-isoprene copolymer rubber, butadiene-styrene-vinyl
pyridine rubber, urethane rubber, polyisoprene rubber,
epichlolorohydrin terpolymer rubber, and polychloroprene. The
second polymer of the heterogeneous polymer blend of the invention
can also comprise atactic polymers such as atactic polypropylene.
The preferred second polymers are elastomeric olefin
copolymers.
[0068] Suitable elastomeric copolymers for use in the present
invention are rubbery copolymers produced by copolymerizing two or
more alpha olefins with at least one polyene, normally a diene.
More typically, the elastomeric component is a copolymer of
ethylene with at least one alpha-olefin monomer, and at least one
diene monomer. The alpha-olefins may include, but are not limited
to, C.sub.3 to C.sub.20 alpha-olefins, such as propylene, butene-1,
hexene-1, 4-methyl-1 pentene, octene-1, decene-1, or combinations
thereof. The preferred alpha-olefins are propylene, hexene-1,
octene-1 or combinations thereof. Thus, for example, the second
polymer can be an ethylene-propylene-diene (commonly called
"EPDM"). Typically, the second polymer contains at least 15 wt % of
the C.sub.3 to C.sub.20 olefin and at least 0.0001 wt % of the
diene.
[0069] In one embodiment, the polyene has at least two unsaturated
bonds that can readily be incorporated into polymers to form
cross-linked polymers. Examples of such polyenes include
.alpha.,.omega.-dienes (such as butadiene, 1,4-pentadiene,
1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, 1,8-nonadiene,
1,9-decadiene, 1.10-undecadiene, 1,11-dodecadiene,
1,12-tridecadiene, and 1,13-tetradecadiene) and certain multi-ring
alicyclic fused and bridged ring dienes (such as tetrahydroindene;
norbomdiene; methyl-tetrahydroindene; dicyclopentadiene;
bicyclo-(2.2.1)-hepta-2,5-diene; and alkenyl-, alkylidene-,
cycloalkenyl-, and cylcoalkyliene norbornenes [including, e.g.,
5-methylene-2-norbornene, 5-ethylidene-2-norbornene,
5-propenyl-2-norbornene, 5-isopropylidene-2-norbornene,
5-(4-cyclopentenyl)-2-norbornene, 5-cyclohexylidene-2-norbornene,
and 5-vinyl-2-norbornene]).
[0070] In further embodiment, the polyene has at least two
unsaturated bonds wherein one of the unsaturated bonds is readily
incorporated into a polymer. The second bond may partially take
part in polymerization to form cross-linked polymers but normally
provides at least some unsaturated bonds in the polymer product
suitable for subsequent functionalization (such as with maleic acid
or maleic anhydride), curing or vulcanization in post
polymerization processes. Examples of polyenes according to said
further embodiment include, but are not limited to butadiene,
pentadiene, hexadiene, heptadiene, octadiene, nonadiene, decadiene,
undecadiene, dodecadiene, tridecadiene, tetradecadiene,
pentadecadiene, hexadecadiene, heptadecadiene, octadecadiene,
nonadecadiene, icosadiene, heneicosadiene, docosadiene,
tricosadiene, tetracosadiene, pentacosadiene, hexacosadiene,
heptacosadiene, octacosadiene, nonacosadiene, triacontadiene, and
polybutadienes having a molecular weight (M.sub.w) of less than
1000 g/mol. Examples of straight chain acyclic dienes include, but
are not limited to 1,4-hexadiene and 1,6-octadiene. Examples of
branched chain acyclic dienes include, but are not limited to
5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene, and
3,7-dimethyl-1,7-octadiene. Examples of single ring alicyclic
dienes include, but are not limited to 1,4-cyclohexadiene,
1,5-cyclooctadiene, and 1,7-cyclododecadiene. Examples of
multi-ring alicyclic fused and bridged ring dienes include, but are
not limited to tetrahydroindene; norbornadiene;
methyl-tetrahydroindene; dicyclopentadiene;
bicyclo-(2.2.1)-hepta-2,5-diene; and alkenyl-, alkylidene-,
cycloalkenyl-, and cylcoalkyliene norbornenes [including, e.g.,
5-methylene-2-norbornene, 5-ethylidene-2-norbornene,
5-propenyl-2-norbornene, 5-isopropylidene-2-norbornene,
5-(4-cyclopentenyl)-2-norbornene, 5-cyclohexylidene-2-norbornene,
and 5-vinyl-2-norbornene]. Examples of cycloalkenyl-substituted
alkenes include, but are not limited to vinyl cyclohexene, allyl
cyclohexene, vinyl cyclooctene, 4-vinyl cyclohexene, allyl
cyclodecene, vinyl cyclododecene, and tetracyclo
(A-11,12)-5,8-dodecene.
[0071] According to one aspect of the invention, during the second
polymerization step to produce the elastomeric phase, it is
believed that a distribution of cross-products are formed emanating
principally from the grafting of the first thermoplastic polymer to
the second elastomeric polymer. These hybrid cross-products, also
known as branch-block copolymers, form when reactive intermediates
from the first polymerization step cross-over into the second
polymerization step and participate in the polymerization of the
second polymer. The presence of branch-block copolymers is believed
to influence the events occurring during the polymerization as well
as product properties. The extent of influence depends on the
population distribution of the branch-block copolymer fraction.
[0072] The amount of second polymer relative to the first polymer
may vary widely depending on the nature of the polymers and the
intended use of the final polymer blend. In particular, however,
one advantage of the process of the invention is the ability to be
able to produce a heterogeneous polymer blend in which the discrete
particles of the second polymer comprise more than 50 wt %, such as
more than 60 wt %, for example more than 70 wt % of the total
heterogeneous polymer blend. For TPV applications, the weight ratio
of the second polymer to the first polymer is generally from about
90:10 to about 50:50, more preferably from about 80:20 to about
60:40, and most preferably from about 75:25 to about 65:35. For TPO
or impact copolymer applications, the weight ratio of the second
polymer to the first polymer is generally from about 49:51 to about
10:90, more preferably from 35:65 to about 15:85.
Production of the Polymer Blend
[0073] According to the invention, the polymer composition is
produced by a novel two-step process. In the first step, a
crystalline thermoplastic polymer is produced by polymerizing at
least one first monomer in one or more polymerization zones. The
effluent from the first step is then fed into a second
polymerization step where an elastomer is produced in the presence
of the polymer produced in the first step. The elastomer is in-situ
cross-linked, at least partially, in the second polymerization
zone. After removal of the polymerization medium, the cross-linked
elastomer forms finely dispersed particles embedded within the
crystalline thermoplastic matrix.
[0074] In an alternative embodiment, the first step of
polymerization is replaced with addition of pre-made crystalline
thermoplastic polymer. The pre-made polymer can be produced in a
separate system or can be a commercially available product. The
crystalline thermoplastic polymer can be dissolved in a solvent and
then added into a reaction medium for the second polymerization
step. The crystalline thermoplastic polymer can be also ground into
fine powder and then added into the reaction medium for the second
polymerization step.
[0075] Any known polymerization process may be used to produce the
thermoplastic polymer. For example, the polymer may be a propylene
homopolymer obtained by homopolymerization of propylene in a single
stage or multiple stage reactor. Copolymers may be obtained by
copolymerizing propylene and an alpha-olefin having 2 or from 4 to
20 carbon atoms in a single stage or multiple stage reactor.
Polymerization methods include high pressure, slurry, gas, bulk,
suspension, supercritical, or solution phase, or a combination
thereof, using a traditional Ziegler-Natta catalyst or a
single-site, metallocene catalyst system, or combinations thereof
including bimetallic (i.e, Z/N and/or metallocene) catalysts.
Preferred catalysts are those capable of polymerizing a C.sub.2 to
C.sub.20 olefin to produce a first polymer having at least 30%
crystallinity and at least 0.01% terminal unsaturation. The
catalysts can be in the form of a homogeneous solution, supported,
or a combination thereof. Polymerization may be carried out by a
continuous, a semi-continuous or batch process and may include use
of chain transfer agents, scavengers, or other such additives as
deemed applicable. By continuous is meant a system that operates
(or is intended to operate) without interruption or cessation. For
example a continuous process to produce a polymer would be one
where the reactants are continually introduced into one or more
reactors and polymer product is continually withdrawn.
[0076] Where the thermoplastic matrix comprises a polyolefin, such
as a propylene polymer or copolymer, the polyolefin will generally
be produced in the presence of a single site catalyst, preferably a
metallocene catalyst, with an activator and optional scavenger.
Preferred metallocene catalysts are those capable of polymerizing a
C.sub.2 to C.sub.20 olefin to produce a first polymer having at
least 30% crystallinity.
[0077] Preferred metallocene catalysts useful for producing the
thermoplastic first polymer in the process of the invention are not
narrowly defined but generally it is found that the most suitable
are those in the generic class of bridged, substituted
bis(cyclopentadienyl) metallocenes, specifically bridged,
substituted bis(indenyl) metallocenes known to produce high
molecular weight, high melting, highly isotactic propylene
polymers. Particularly suitable catalysts are bridged bis-indenyl
metallocene catalysts having a substituent on one or both of the 2-
and 4- positions on each indenyl ring or those having a substituent
on the 2-, 4-, and 7- positions on each indenyl ring. Generally
speaking, those of the generic class disclosed in U.S. Pat. No.
5,770,753 (fully incorporated herein by reference) should be
suitable, however, it has been found that the exact polymer
obtained is dependent on the metallocene's specific substitution
pattern, among other things. A specific list of useful catalyst
compounds is found at WO 2004/026921 page 29 paragraph [00100] to
page 66, line 4. In another embodiment, the catalyst compounds
described at WO 2004/026921 page 66, paragraph [00103] to page 70,
line 3 may also be used in the practice of this invention.
[0078] Particularly preferred are racemic metallocenes, such as
rac-dimethylsiladiyl(2-isopropyl,4-phenylindenyl).sub.2 zirconium
dichloride; rac-dimethylsiladiyl(2-
isopropyl,4-[1-naphthyl]indenyl).sub.2 zirconium dichloride;
rac-dimethylsiladiyl(2-
isopropyl,4-[3,5-dimethylphenyl]indenyl).sub.2 zirconium
dichloride;
rac-dimethylsiladiyl(2-isopropyl,4-[ortho-methyl-phenyl]indenyl).sub.2
zirconium dichloride; rac-dimethylsilyl bis-(2-methyl,
4-phenylindenyl)zirconium dichoride, rac dimethylsiladlyl
bis-(2-methyl, 4-napthylindenyl) zirconium dichloride, rac-dimethyl
siladiyl(2-isopropyl, 4-[3,5 di-t-butyl-phenyl]indenyl).sub.2
zirconium dichloride; rac-dimethyl siladiyl(2-isopropyl,
4-[orthophenyl-phenyl]indenyl).sub.2 zirconium dichloride,
rac-diphenylsiladiyl(2-methyl4-[1-naphthyl]indenyl).sub.2 zirconium
dichloride and rac-biphenyl siladiyl(2-isopropyl, 4-[3,5
di-t-butyl-phenyl]indenyl).sub.2 zirconium dichloride. Alkylated
variants of these metallocenes (e.g. di-methyl instead of
dichloride) are also useful, particularly when combined with a
non-coordinating anion type activator. These and other metallocene
compositions are described in detail in U.S. Pat. Nos. 6,376,407,
6,376,408, 6,376,409, 6,376,410, 6,376,411, 6,376,412, 6,376,413,
6,376,627, 6,380,120, 6,380,121, 6,380,122, 6,380,123, 6,380,124,
6,380,330, 6,380,331, 6,380,334, 6,399,723 and 6,825,372.
[0079] The manner of activation of the catalyst used in the first
polymerization step can vary. Alumoxane and preferably methyl
alumoxane (MAO) can be used. Non-or weakly coordinating anion
activators (NCA) may be obtained in any of the ways described in
EP277004, EP426637. Activation generally is believed to involve
abstraction of an anionic group such as the methyl group to form a
metallocene cation, although according to some literature
zwitterions may be produced. The NCA precursor can be an ion pair
of a borate or aluminate in which the precursor cation is
eliminated upon activation in some manner, e.g. trityl or ammonium
derivatives of tetrakis pentafluorophenyl boron (See EP277004). The
NCA precursor can be a neutral compound such as a borane, which is
formed into a cation by the abstraction of and incorporation of the
anionic group abstracted from the metallocene (See EP426638).
[0080] The alumoxane activator may be utilized in an amount to
provide a molar aluminum to metallocene ratio of from 1:1 to
20,000:1 or more. The non-coordinating compatible anion activator
may be utilized in an amount to provide a molar ratio of
metallocene compound to non-coordinating anion of 10:1 to 1:1.
[0081] Particularly useful activators include
dimethylaniliniumtetrakis (pentafluorophenyl) borate and dimethyl
anilinium tetrakis(heptafluoro-2-naphthyl) borate. For a more
detailed description of useful activators please see WO 2004/026921
page 72, paragraph [00119] to page 81 paragraph [00151]. A list of
particularly useful activators that can be used in the practice of
this invention may be found at page 72, paragraph [00177] to page
74, paragraph [00178] of WO 2004/046214.
[0082] Preferably, the first polymerization step is conducted in a
continuous, stirred tank reactor. Tubular reactors equipped with
the hardware to introduce feeds, catalysts and cross-linking agents
in staged manner can also be used. Generally, polymerization
reactors are agitated (stirred) to reduce or avoid concentration
gradients. Reaction environments include the case where the
monomer(s) acts as diluent or solvent as well as the case where a
liquid hydrocarbon is used as diluent or solvent. Preferred
hydrocarbon liquids include both aliphatic and aromatic fluids such
as desulphurized light virgin naphtha and alkanes, such as propane,
isobutane, mixed butanes, hexane, pentane, isopentane, cyclohexane,
isooctane, and octane. In an alternate embodiment a perfluorocarbon
or hydrofluorocarbon is used as the solvent or diluent.
[0083] Suitable conditions for the first polymerization step
include a temperature from about 50 to about 250.degree. C.,
preferably from about 50 to about 150.degree. C., more preferably
from about 70 to about 150.degree. C. and a pressure of 0.1 MPa or
more, preferably 2 MPa or more. The upper pressure limit is not
critically constrained but is typically 200 MPa or less,
preferably, 120 MPa or less, except when operating ins
supercritical phase then the pressure and temperature are above the
critical point of the reaction media in question (typically over
95.degree. C. and 4.6 MPa for propylene polymerizations). For more
information on running supercritical polymerizations, please see WO
2004/026921. Temperature control in the reactor is generally
obtained by balancing the heat of polymerization with reactor
cooling via reactor jackets or cooling coils, auto refrigeration,
pre-chilled feeds, vaporization of liquid medium (diluent, monomers
or solvent) or combinations of all three. Adiabatic reactors with
pre-chilled feeds may also be used.
[0084] In the second polymerization step, some or all of the first
polymer formed in the first polymerization step are contacted with
at least one second monomer, typically ethylene and a C.sub.3 to
C.sub.20 olefin, and at least one cross-linking agent, typically a
diene, under conditions sufficient to polymerize the second
monomer(s) to produce the second polymer and also cross-link said
second polymer. As a result of the cross-linking that occurs with
the second polymerization step, the product of the second
polymerization step contains at least a fraction which is insoluble
in xylene. Preferably, the amount of said xylene insoluble fraction
by weight of the second polymer, also referred to herein as the
degree of cross-link of the second polymer, is at least 4%, such as
at least 10%, such as at least 20%, such as at least 40%, such as
at least 50%.
[0085] Any known polymerization process, including solution,
suspension, slurry, supercritical and gas phase polymerization
processes, and any known polymerization catalyst can be used to
produce the second polymer component. Generally, the catalyst used
to produce the second polymer component should be capable of
polymerizing bulky monomers and also be capable of producing a
polymer having an Mw of 20,000 or more and a crystallinity of less
than 20%.
[0086] In one embodiment, the catalyst employed to produce the
second polymer component is the same as, or is compatible with, the
catalyst used to produce the thermoplastic matrix. In such a case,
the first and second polymerization zones can be in a multiple-zone
reactor, or separate, series-connected reactors, with the entire
effluent from the first polymerization zone, including any active
catalyst, being transferred to the second polymerization zone.
Additional catalyst can then be added, as necessary to the second
polymerization zone. In a particularly preferred embodiment, the
process of the invention is conducted in two or more
series-connected, continuous flow, stirred tank or tubular reactors
using metallocene catalysts.
[0087] In another embodiment, catalyst quenching is applied between
the two polymerization zones and a separate catalyst is introduced
in the second reaction zone to produce the elastomer component.
Catalyst quenching agents (such as air or an alcohol) may be
introduced into the effluent from the first polymerization zone
right after the reactor exit to deactivate the catalyst used for
the first polymerization. Scavenger may be useful and can be fed
into the effluent downstream of the catalyst quenching agent
injection point or the second polymerization zone.
[0088] Where a separate catalyst is used to produce the elastomeric
second polymer, this is conveniently one of, or a mixture of,
metallocene compounds of either or both of the following types:
[0089] 1) Cyclopentadienyl (Cp) complexes which have two Cp ring
systems for ligands. The Cp ligands form a sandwich complex with
the metal and can be free to rotate (unbridged) or locked into a
rigid configuration through a bridging group. The Cp ring ligands
can be like or unlike, unsubstituted, substituted, or a derivative
thereof such as a heterocyclic ring system which may be
substituted, and the substitutions can be fused to form other
saturated or unsaturated rings systems such as tetrahydroindenyl,
indenyl, or fluorenyl ring systems. These cyclopentadienyl
complexes are represented by the formula
(Cp.sup.1R.sup.1.sub.m)R.sup.3.sub.n(Cp.sup.2R.sup.2.sub.p)MX.sub.q
[0090] wherein Cp.sup.1 of ligand (Cp.sup.1 R.sup.1.sub.m)and
Cp.sup.2 of ligand (Cp.sup.2 R.sup.2.sub.p) are the same or
different cyclopentadienyl rings, R.sup.1 and R.sup.2 each is,
independently, a halogen or a hydrocarbyl, halocarbyl,
hydrocarbyl-substituted organometalloid or halocarbyl-substituted
organometalloid group containing up to about 20 carbon atoms, m is
0, 1, 2, 3, 4, or 5, p is 0, 1, 2, 3, 4 or 5, and two R.sup.1
and/or R.sup.2 substituents on adjacent carbon atoms of the
cyclopentadienyl ring associated there with can be joined together
to form a ring containing from 4 to about 20 carbon atoms, R.sup.3
is a bridging group, n is the number of atoms in the direct chain
between the two ligands and is 0, 1, 2, 3, 4, 5, 6, 7, or 8,
preferably 0, 1, 2, or 3, M is a transition metal having a valence
of 3, 4, 5 or 6, preferably from Group 4, 5, or 6 of the Periodic
Table of the Elements and is preferably in its highest oxidation
state, each X is a non-cyclopentadienyl ligand and is,
independently, a halogen or a hydrocarbyl, oxyhydrocarbyl,
halocarbyl, hydrocarbyl-substituted organometalloid,
oxyhydrocarbyl-substituted organometalloid or
halocarbyl-substituted organometalloid group containing up to about
20 carbon atoms, q is equal to the valence of M minus 2. [0091] 2)
Monocyclopentadienyl complexes which have only one Cp ring system
as a ligand. The Cp ligand forms a half-sandwich complex with the
metal and can be free to rotate (unbridged) or locked into a rigid
configuration through a bridging group to a heteroatom-containing
ligand. The Cp ring ligand can be unsubstituted, substituted, or a
derivative thereof such as a heterocyclic ring system which may be
substituted, and the substitutions can be fused to form other
saturated or unsaturated rings systems such as tetrahydroindenyl,
indenyl, or fluorenyl ring systems. The heteroatom containing
ligand is bound to both the metal and optionally to the Cp ligand
through the bridging group. The heteroatom itself is an atom with a
coordination number of three from Group 15 or 16 of the periodic
table of the elements. These mono-cyclopentadienyl complexes are
represented by the formula (Cp.sup.1R.sup.1.sub.m)R.sup.3.sub.n(Y
R.sup.2)MX.sub.s [0092] wherein R.sup.1 is, each independently, a
halogen or a hydrocarbyl, halocarbyl, hydrocarbyl-substituted
organometalloid or halocarbyl-substituted organometalloid group
containing up to about 20 carbon atoms, m is 0, 1, 2, 3, 4 or 5,
and two R.sup.1 substituents on adjacent carbon atoms of the
cyclopentadienyl ring associated therewith can be joined together
to form a ring containing from 4 to about 20 carbon atoms, R.sup.3
is a bridging group, n is 0, 1, 2 or 3, M is a transition metal
having a valence of from 3, 4, 5, or 6, preferably from Group 4, 5,
or 6 of the Periodic Table of the Elements and is preferably in its
highest oxidation state, Y is a heteroatom containing group in
which the heteroatom is an element with a coordination number of
three from Group 15 or a coordination number of two from Group 16
preferably nitrogen, phosphorous, oxygen, or sulfur, R.sup.2 is a
radical selected independently from the group consisting of C.sub.1
to C.sub.20 hydrocarbon radicals, substituted C.sub.1 to C.sub.20
hydrocarbon radicals, wherein one or more hydrogen atoms is
replaced with a halogen atom, and when Y is three coordinate and
unbridged there may be two R.sub.2 groups on Y each independently a
radical selected from a group consisting of C.sub.1 to C.sub.20
hydrocarbon radicals, substituted C.sub.1 to C.sub.20 hydrocarbon
radicals, wherein one or more hydrogen atoms is replaced with a
halogen atom, and each X is a non-cyclopentadienyl ligand and is,
independently, a halogen or a hydrocarbyl, oxyhydrocarbyl,
halocarbyl, hydrocarbyl-substituted organometalloid,
oxyhydrocarbyl-substituted organometalloid or
halocarbyl-substituted organometalloid group containing up to about
20 carbon atoms, s is equal to the valence of M minus 2; and
Cp.sup.1 is a Cp ring.
[0093] Examples of suitable biscyclopentadienyl metallocenes of the
type described in Group 1 above for the invention are disclosed in
U.S. Pat. Nos. 5,324,800; 5,198,401; 5,278,119; 5,387,568;
5,120,867; 5,017,714; 4,871,705; 4,542,199; 4,752,597; 5,132,262;
5,391,629; 5,243,001; 5,278,264; 5,296,434; and 5,304,614, all of
which are incorporated by reference herein.
[0094] Illustrative, but not limiting examples of preferred
biscyclopentadienyl metallocenes of the type described in Group 1
above for the invention are the racemic isomers of: [0095]
.mu.-(CH.sub.3).sub.2Si(indenyl).sub.2M(Cl).sub.2 [0096]
.mu.-(CH.sub.3).sub.2Si(indenyl).sub.2M(CH.sub.3).sub.2 [0097]
.mu.-(CH.sub.3).sub.2Si(tetrahydroindenyl).sub.2M(Cl).sub.2 [0098]
.mu.-(CH.sub.3).sub.2Si(tetrahydroindenyl).sub.2M(CH.sub.3).sub.2
[0099]
.mu.-(CH.sub.3).sub.2Si(indenyl).sub.2M(CH.sub.2CH.sub.3).sub.2
[0100] .mu.-(C.sub.6H.sub.5).sub.2C(indenyl).sub.2M(CH.sub.3).sub.2
wherein M is chosen from a group consisting of Zr and Hf.
[0101] Examples of suitable unsymmetrical cyclopentadienyl
metallocenes of the type described in Group 1 above for the
invention are disclosed in U.S. Pat. Nos. 4,892,851; 5,334,677;
5,416,228; and 5,449,651; and are described in publication J Am.
Chem. Soc. 1988, 110, 6255, all of which are incorporated by
reference herein.
[0102] Illustrative, but not limiting examples of preferred
unsymmetrical cyclopentadienyl metallocenes of the type described
in Group 1 above for the invention are: [0103]
.mu.-(C.sub.6H.sub.5).sub.2C(cyclopentadienyl)(fluorenyl)M(R).sub.2
[0104]
.mu.-(C.sub.6H.sub.5).sub.2C(3-methylcyclopentadienyl)(fluorenyl)-
M(R).sub.2 [0105]
.mu.-(CH.sub.3).sub.2C(cyclopentadienyl)(fluorenyl)M(R).sub.2
[0106]
.mu.-(C.sub.6H.sub.5).sub.2C(cyclopentadienyl)(2-methylindenyl)M(R).sub.2
[0107]
.mu.-(C.sub.6H.sub.5).sub.2C(3-methylcyclopentadienyl)(2-methyli-
ndenyl)M(R).sub.2 [0108]
.mu.-(p-triethylsilylphenyl).sub.2C(cyclopentadienyl)(3,8-di-t-butylfluor-
enyl)M(R).sub.2 [0109]
.mu.-(C.sub.6H.sub.5).sub.2C(cyclopentadienyl)(2,7-dimethylindenyl)M(R).s-
ub.2 [0110]
.mu.-(CH.sub.3).sub.2C(cyclopentadienyl)(2,7-dimethylindenyl)M(R).sub.2.
wherein M is chosen from the group consisting of Zr and Hf and R is
chosen from the group consisting of Cl and CH.sub.3.
[0111] Examples of suitable monocyclopentadienyl metallocenes of
the type described in group 2 above for the invention are disclosed
in U.S. Pat. Nos. 5,026,798; 5,057,475; 5,350,723; 5,264,405;
5,055,438 and are described in publication WO 96/002244, all of
which are incorporated by reference herein.
[0112] Illustrative, but not limiting examples of preferred
monocyclopentadienyl metallocenes of the type described in group 2
above for the invention are: [0113]
.mu.-(CH.sub.3).sub.2Si(cyclopentadienyl)(1-adamantylamido)M(R).sub.2
[0114]
.mu.-(CH.sub.3).sub.2Si(3-tertbutylcyclopentadienyl)(1-adamantyla-
mido)M(R).sub.2 [0115]
.mu.-(CH.sub.3).sub.2Si(tetramethylcyclopentadienyl)(1-adamantylamido)M(R-
).sub.2 [0116]
.mu.-(CH.sub.3).sub.2C(tetramethylcyclopentadienyl)(1-adamantylamido)M(R)-
.sub.2 [0117]
.mu.-(CH.sub.3).sub.2Si(tetramethylcyclopentadienyl)(1-tertbutylamido)M(R-
).sub.2 [0118]
.mu.-(CH.sub.3).sub.2Si(fluorenyl)(1-tertbutylamido)M(R).sub.2
[0119]
.mu.-(CH.sub.3).sub.2Si(tetramethylcyclopentadienyl)(1-cyclododecylamido)-
M(R).sub.2 [0120]
.mu.-(CH.sub.3).sub.2C(tetramethylcyclopentadienyl)(1-cyclododecylamido)M-
(R).sub.2 wherein M is selected from a group consisting of Ti, Zr,
and Hf and wherein R is selected from Cl and CH.sub.3.
[0121] Another class of organometallic complexes that are useful
catalysts for producing the second polymer component are those with
diimido ligand systems such as those described in WO 96/23010
assigned to Du Pont. These catalytic polymerization compounds are
incorporated here by reference.
[0122] In a preferred processing mode, the conditions in the second
polymerization zone are arranged not only to copolymerize the
elastomer monomers with the bifunctional monomer, such as a diene,
but also to cause at least partial cross-linking of resultant
elastomer. Typical conditions in the second polymerization zone
include a temperature of about 10.degree. C. to about 250.degree.
C. and a pressure of about 0.1 MPa to about 200 MPa.
[0123] The second polymer, which is at least partially cross-linked
in the copolymerization reaction of olefins and dienes, may be
prepared by solution, suspension or slurry polymerization of the
olefins and diene under conditions in which the catalyst site
remains relatively insoluble and/or immobile so that the polymer
chains are rapidly immobilized following their formation. Such
immobilization is affected, for example, by (1) using a solid,
insoluble catalyst, (2) maintaining the polymerization below the
crystalline melting point of thermoplastic polymers made in the
first step and (3) using low solvency solvent such as a fluorinated
hydrocarbon.
[0124] In a solution process, the uncrosslinked second polymers are
preferably dissolved (or are soluble) in the polymerization media.
The second polymers are then phase separated from the reaction
media to form micro-particles when the polymers are cross-linked.
This in-situ cross-link and phase separation facilitates the
process to produce polymers of high molecular weight.
[0125] By selecting the catalysts, the polymerization reaction
conditions, and/or by introducing a diene modifier, some molecules
of the first polymer(s) and the second polymer(s) can be linked
together to produce branch-block structures. While not wishing to
be bound by theory, the branch-block copolymer is believed to
comprise an amorphous backbone having crystalline side chains
originating from the first polymer.
[0126] To effectively incorporate the polymer chains of the first
polymer into the growing chains of the second polymer, it is
preferable that the first polymerization step produces
macromonomers having reactive termini, such as vinyl end groups. By
macromonomers having reactive termini is meant a polymer having
twelve or more carbon atoms (preferably 20 or more, more preferably
30 or more, more preferably between 12 and 8000 carbon atoms) and
having a vinyl, vinylidene, vinylene or other terminal group that
can be polymerized into a growing polymer chain. By capable of
polymerizing macromonomer having reactive termini is meant a
catalyst component that can incorporate a macromonomer (which tend
to be molecules larger than a typical single monomer such as
ethylene or propylene), having reactive termini into a growing
polymer chain. Vinyl terminated chains are generally more reactive
than vinylene or vinylidene terminated chains. Generally, it is
desirable that the first polymerization step produces a first
polymer having at least 0.01% terminal unsaturation.
[0127] Optionally the thermoplastic first polymers are copolymers
of one or more alpha olefins and one or more of monomers having at
least two olefinically unsaturated bonds. Both of these unsaturated
bonds are suitable for and readily incorporated into a growing
polymer chain by coordination polymerization using either the first
or second catalyst systems independently such that one double bond
is incorporated into the first polymer segments while another
double bond is incorporated into the second elastomeric polymer
segments for form a branched block copolymer. In a preferred
embodiment these monomers having at least two olefinically
unsaturated bonds are di-olefins, preferably di-vinyl monomers.
[0128] A polymer can be recovered from the effluent of either the
first polymerization step or the second polymerization step by
separating the polymer from other constituents of the effluent
using conventional separation means. For example, polymer can be
recovered from either effluent by coagulation with a non-solvent
such as isopropyl alcohol, acetone, or n-butyl alcohol, or the
polymer can be recovered by stripping the solvent or other media
with heat or steam. One or more conventional additives such as
antioxidants can be incorporated in the polymer during the recovery
procedure. Possible antioxidants include phenyl-beta-naphthylamine;
di-tert-butylhydroquinone, triphenyl phosphate, heptylated
diphenylamine, 2,2'-methylene-bis (4-methyl-6-tert-butyl)phenol,
and 2,2,4-trimethyl-6-phenyl-1,2-dihydroquinoline. Other methods of
recovery such as by the use of lower critical solution temperature
(LCST) followed by devolatilization are also envisioned. The
catalyst may be deactivated as part of the separation procedure to
reduce or eliminate further uncontrolled polymerization downstream
the polymer recovery processes. Deactivation may be effected by the
mixing with suitable polar substances such as water, whose residual
effect following recycle can be counteracted by suitable sieves or
scavenging systems.
Properties of the Polymer Blend
[0129] By virtue of the novel polymerization process used in its
production, the heterogeneous polymer blend of the invention not
only comprises particles of the second polymer dispersed within a
matrix of the first thermoplastic polymer but also at least a
portion the dispersed phase is cross-linked and preferably
comprises a hybrid species of said first and second polymers having
characteristics of the first and second polymers such as a melting
temperature, preferably of at least 100.degree. C., in the xylene
insoluble fraction. In addition, it is found that the particles of
the second polymer tend be more evenly distributed and
significantly smaller, typically having an average diameter of less
than 1 micron, than products obtained by conventional reactive
extrusion techniques.
[0130] In addition, since at least some cross-linking of the
dispersed phase occurs during the second polymerization step,
rather than all the cross-linking being effected in a subsequent
dynamic extrusion step, the dispersed phase of the heterogeneous
polymer blend of the invention comprises at least a fraction which
is insoluble in xylene and which is substantially free of the
curatives normally added to polymers blends to effect cross-linking
during post-polymerization, dynamic extrusion. By substantially
free is meant that the dispersed phase contains less than 10,000
ppm, such as less than 1,000 ppm, such as less than 1000 ppm, such
as less than 10 ppm, of a curative.
[0131] Polymers with bimodal distributions of molecular weight and
composition can be produced by the polymerization process of the
invention, by, for example, controlling the polymerization
conditions in the first and the second polymerization zones and
selecting the catalysts for the first and the second
polymerizations, such as by using multiple catalysts in each
polymerization zone. Some of the polymer chains produced in the
first polymerization zone are still live in the second
polymerization zone. The polymer chains so produced in the second
polymerization zone contain crystalline polymer segments and
amorphous polymer segments and form blocky structures. The blocky
compositions have characteristics of both the first and second
polymers.
[0132] Generally, olefins are present in the elastomeric dispersed
phase of the heterogeneous polymer blend of the invention at levels
from about 95 to about 99.99 wt %, whereas the diene content of the
elastomeric copolymer is from about 0.01 wt % to about 5 wt %. But
specific embodiments can have a variety of diene contents. Some
embodiments have two or more different olefin units in the
elastomeric component, with at least one monomer being selected
from ethylene, propylene and C.sub.4 to C.sub.20 alpha-olefins.
Typically, said at least one monomer unit comprises ethylene and a
further monomer is selected from propylene and C.sub.4 to C.sub.12
alpha-olefins, especially propylene. These embodiments typically
have one olefin present in amounts of from 12 to 88 wt %, for
example from 30 to 70 wt %, of the copolymer whereas the other
olefin is present in amounts of from 88 to 12 wt %, for example
from 70 to 30 wt %, of the copolymer.
[0133] Still more desirably, the copolymer includes: ethylene units
in the range from 12 wt % to 88 wt % of the copolymer; propylene or
other .alpha.-olefin(s) units in the range from 88 wt % to 12 wt %,
desirably ethylene units in the range from 30 to 70 wt % and
propylene or other .alpha.-olefin(s) units in the range from 70 to
30 wt %; more desirably ethylene units in the range from 40 wt % to
60 wt % and propylene or other .alpha.-olefin(s) units in the range
from 60 to 40 wt % of the copolymer.
[0134] The individual components of the heterogeneous polymer blend
of the invention can readily be separated by solvent extraction. In
a suitable solvent extraction regime, the blend, without undergoing
any additional processing steps, is contacted with cyclohexane at
25.degree. C. for 48 hours to dissolve the uncured and branched
elastomeric components of the blend and then the remaining solids
are refluxed at the boiling temperature of xylene for 24 hours with
xylene to dissolve the continuous thermoplastic phase material. The
remaining xylene insolubles comprise the cross-linked hybrid
copolymers of the first and second polymers. These hybrid
copolymers typically exhibit a melting temperature in excess of
100.degree. C.
[0135] In one embodiment, the polymer blend described herein has a
tensile strength at break (as measured by ISO 37 at 23.degree. C.)
of 0.5 MPa or more, alternatively 0.75 MPa or more, alternatively
1.0 MPa or more, alternatively 1.5 MPa or more, alternatively 2.0
MPa or more, alternatively 2.5 MPa or more, alternatively 3.0 MPa
or more, alternatively 3.5 MPa or more.
[0136] In another embodiment, the polymer blend described herein
has a Shore hardness of 30A to 90D, preferably 15A to 90D (as
measured by ISO 868).
[0137] In another embodiment, the polymer blend described herein
has an ultimate elongation (as measured by ISO 37) of 20% or more,
preferably 30% or more, more preferably 40% or more.
[0138] In another embodiment, the polymer blend described herein
has a compression set (as measured by ISO 815A) of 90% or less,
preferably 70% or less, more preferably 50% or less, more
preferably 30% or less, more preferably 10% or less.
[0139] In another embodiment, the polymer blend described herein
has a tension set (as measured by ISO 2285) of 100% or less,
preferably 80% or less, more preferably 60% or less, more
preferably 20% or less, more preferably 5% or less, more preferably
1% or less.
[0140] In another embodiment, the polymer blend described herein
has an oil swell (as measured by ASTM D471) of 500% or less,
preferably 250% or less, more preferably 100% or less.
Additives
[0141] The heterogeneous polymer blend according to the invention
may optionally contain reinforcing and non-reinforcing fillers,
plasticizers, antioxidants, stabilizers, rubber processing oils,
extender oils, lubricants, antiblocking agents, antistatic agents,
waxes, foaming agents, pigments, flame retardants and other
processing aids known in the rubber compounding art. Such additives
may comprise up to about 70 weight percent, more preferably up to
about 65 weight percent, of the total composition. Fillers and
extenders which can be utilized include conventional inorganics
such as calcium carbonate, clays, silica, talc, titanium dioxide,
carbon black and the like. The rubber processing oils generally are
paraffinic, naphthenic or aromatic oils derived from petroleum
fractions. The oils are selected from those ordinarily used in
conjunction with the specific rubber or rubber component present in
the composition.
[0142] The additives such as fillers and oils can be introduced
into the heterogeneous polymer blend during the polymerization in
either the first polymerization zone or the second polymerization
zone. The additives can be added into the effluent from the second
polymerization zone and are preferably added into the polymer blend
after removal of solvent or diluent through melt blending.
[0143] Additional polymers can also be added to form blends. In one
or more embodiments, the additional polymers include thermoplastic
resins. Exemplary thermoplastic resins include crystalline and
crystallizable polyolefins. Also, suitable thermoplastic resins may
include copolymers of polyolefins with styrene, such as a
styrene-ethylene copolymer. In one or more embodiments, the
thermoplastic resins are formed by polymerizing ethylene or
.alpha.-olefins such as propylene, 1-butene, 1-hexene, 1-octene,
2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene,
5-methyl-1-hexene, and mixtures thereof. Copolymers of ethylene and
propylene and ethylene and propylene with another .alpha.-olefin
such as 1-butene, 1-hexene, 1-octene, 2-methyl-1-propene,
3-methyl-1-pentene, 4-methyl-1-pentene, 5-methyl-1-hexene or
mixtures thereof are also contemplated. Specifically included are
homopolypropylene, impact, and random copolymers of propylene with
ethylene or the higher .alpha.-olefins, described above, or with
C.sub.10-C.sub.20 diolefins. Preferably, the homopolypropylene has
a melting point of at least 130.degree. C., for example at least
140.degree. C. and preferably less than or equal to 160.degree. C.,
a heat of fusion of at least 75 J/g, alternatively at least 80 J/g,
as determined by DSC analysis, and weight average molecular weight
(Mw) of at least 100,000, alternatively at least 500,000. Comonomer
contents for these propylene copolymers will typically be from 1 to
about 30% by weight of the polymer, for example, See U.S. Pat. Nos.
6,268,438, 6,288,171, and 6,245,856. Copolymers available under the
tradename VISTAMAXX.TM. (ExxonMobil) are specifically included.
Blends or mixtures of two or more polyolefin thermoplastics such as
described herein, or with other polymeric modifiers, are also
suitable in accordance with this invention. These homopolymers and
copolymers may be synthesized by using an appropriate
polymerization technique known in the art such as, but not limited
to, the conventional Ziegler-Natta type polymerizations, and
catalysis employing single-site organometallic catalysts including,
but not limited to, metallocene catalysts.
Uses of the Polymer Blends
[0144] The heterogeneous polymer blends described herein may be
shaped into desirable end use articles by any suitable means known
in the art. They are particularly useful for making articles by
blow molding, extrusion, injection molding, thermoforming, gas
foaming, elasto-welding and compression molding techniques.
[0145] Thermoforming is a process of forming at least one pliable
plastic sheet into a desired shape. An embodiment of a
thermoforming sequence is described, however this should not be
construed as limiting the thermoforming methods useful with the
compositions of this invention. First, an extrudate film of the
composition of this invention (and any other layers or materials)
is placed on a shuttle rack to hold it during heating. The shuttle
rack indexes into the oven which pre-heats the film before forming.
Once the film is heated, the shuffle rack indexes back to the
forming tool. The film is then vacuumed onto the forming tool to
hold it in place and the forming tool is closed. The forming tool
can be either "male" or "female" type tools. The tool stays closed
to cool the film and the tool is then opened. The shaped laminate
is then removed from the tool.
[0146] Thermoforming is accomplished by vacuum, positive air
pressure, plug-assisted vacuum forming, or combinations and
variations of these, once the sheet of material reaches
thermoforming temperatures, typically of from 140.degree. C. to
185.degree. C. or higher. A pre-stretched bubble step is used,
especially on large parts, to improve material distribution. In one
embodiment, an articulating rack lifts the heated laminate towards
a male forming tool, assisted by the application of a vacuum from
orifices in the male forming tool. Once the laminate is firmly
formed about the male forming tool, the thermoformed shaped
laminate is then cooled, typically by blowers. Plug-assisted
forming is generally used for small, deep drawn parts. Plug
material, design, and timing can be critical to optimization of the
process. Plugs made from insulating foam avoid premature quenching
of the plastic. The plug shape is usually similar to the mold
cavity, but smaller and without part detail. A round plug bottom
will usually promote even material distribution and uniform
side-wall thickness.
[0147] The shaped laminate is then cooled in the mold. Sufficient
cooling to maintain a mold temperature of 30.degree. C. to
65.degree. C. is desirable. The part is below 90.degree. C. to
100.degree. C. before ejection in one embodiment. For the good
behavior in thermoforming, the lowest melt flow rate polymers are
desirable. The shaped laminate is then trimmed of excess laminate
material.
[0148] Blow molding is another suitable forming means, which
includes injection blow molding, multi-layer blow molding,
extrusion blow molding, and stretch blow molding, and is especially
suitable for substantially closed or hollow objects, such as, for
example, gas tanks and other fluid containers. Blow molding is
described in more detail in, for example, CONCISE ENCYCLOPEDIA OF
POLYMER SCIENCE AND ENGINEERING 90-92 (Jacqueline I. Kroschwitz,
ed., John Wiley & Sons 1990).
[0149] In yet another embodiment of the formation and shaping
process, profile co-extrusion can be used. The profile co-extrusion
process parameters are as above for the blow molding process,
except the die temperatures (dual zone top and bottom) range from
150.degree. C. to 235.degree. C., the feed blocks are from
90.degree. C. to 250.degree. C., and the water cooling tank
temperatures are from 10.degree. C. to 40.degree. C.
[0150] One embodiment of an injection molding process is described
as follows. The shaped laminate is placed into the injection
molding tool. The mold is closed and the substrate material is
injected into the mold. The substrate material has a melt
temperature between 200.degree. C. and 300.degree. C., such as
between 215.degree. C. and 250.degree. C. and is injected into the
mold at an injection speed of between 2 and 10 seconds. After
injection, the material is packed or held at a predetermined time
and pressure to make the part dimensionally and aesthetically
correct. Typical time periods are from 5 to 25 seconds and
pressures from 1,380 kPa to 10,400 kPa. The mold is cooled between
10.degree. C. and 70.degree. C. to cool the substrate. The
temperature will depend on the desired gloss and appearance
desired. Typical cooling time is from 10 to 30 seconds, depending
on part on the thickness. Finally, the mold is opened and the
shaped composite article ejected.
[0151] Likewise, molded articles may be fabricated by injecting
molten polymer into a mold that shapes and solidifies the molten
polymer into desirable geometry and thickness of molded articles.
Sheet may be made either by extruding a substantially flat profile
from a die, onto a chill roll, or alternatively by calendaring.
Sheet will generally be considered to have a thickness of from 10
mils to 100 mils (254 .mu.m to 2540 .mu.m), although sheet may be
substantially thicker. Tubing or pipe may be obtained by profile
extrusion for uses in medical, potable water, land drainage
applications or the like. The profile extrusion process involves
the extrusion of molten polymer through a die. The extruded tubing
or pipe is then solidified by chill water or cooling air into a
continuous extruded articles. The tubing will generally be in the
range of from 0.31 cm to 2.54 cm in outside diameter, and have a
wall thickness of in the range of from 254 cm to 0.5 cm. The pipe
will generally be in the range of from 2.54 cm to 254 cm in outside
diameter, and have a wall thickness of in the range of from 0.5 cm
to 15 cm. Sheet made from the products of an embodiment of a
version of the present invention may be used to form containers.
Such containers may be formed by thermoforming, solid phase
pressure forming, stamping and other shaping techniques. Sheets may
also be formed to cover floors or walls or other surfaces.
[0152] In an embodiment of the thermoforming process, the oven
temperature is between 160.degree. C. and 195.degree. C., the time
in the oven between 10 and 20 seconds, and the die temperature,
typically a male die, between 10.degree. C. and 71.degree. C. The
final thickness of the cooled (room temperature), shaped laminate
is from 10 .mu.m to 6000 .mu.m in one embodiment, from 200 .mu.m to
6000 .mu.m in another embodiment, and from 250 .mu.m to 3000 .mu.m
in yet another embodiment, and from 500 .mu.m to 1550 .mu.m in yet
another embodiment, a desirable range being any combination of any
upper thickness limit with any lower thickness limit.
[0153] In an embodiment of the injection molding process, wherein a
substrate material is injection molded into a tool including the
shaped laminate, the melt temperature of the substrate material is
between 230.degree. C. and 255.degree. C. in one embodiment, and
between 235.degree. C. and 250.degree. C. in another embodiment,
the fill time from 2 to 10 seconds in one embodiment, from 2 to 8
seconds in another embodiment, and a tool temperature of from
25.degree. C. to 65.degree. C. in one embodiment, and from
27.degree. C. and 60.degree. C. in another embodiment. In a
desirable embodiment, the substrate material is at a temperature
that is hot enough to melt any tie-layer material or backing layer
to achieve adhesion between the layers.
[0154] In yet another embodiment of the invention, the compositions
of this invention may be secured to a substrate material using a
blow molding operation. Blow molding is particularly useful in such
applications as for making closed articles such as fuel tanks and
other fluid containers, playground equipment, outdoor furniture and
small enclosed structures. In one embodiment of this process,
Compositions of this invention are extruded through a multi-layer
head, followed by placement of the uncooled laminate into a parison
in the mold. The mold, with either male or female patterns inside,
is then closed and air is blown into the mold to form the part.
[0155] It will be understood by those skilled in the art that the
steps outlined above may be varied, depending upon the desired
result. For example, an extruded sheet of the compositions of this
invention may be directly thermoformed or blow molded without
cooling, thus skipping a cooling step. Other parameters may be
varied as well in order to achieve a finished composite article
having desirable features.
[0156] The thermoplastic elastomer blends of this invention are
useful for making a variety of articles such as weather seals,
hoses, belts, gaskets, moldings, boots, elastic fibers and like
articles. Foamed end-use articles are also envisioned. More
specifically, the blends of the invention are particularly useful
for making vehicle parts, such as but not limited to, weather
seals, brake parts including, but not limited to cups, coupling
disks, diaphragm cups, boots such as constant velocity joints and
rack and pinion joints, tubing, sealing gaskets, parts of
hydraulically or pneumatically operated apparatus, o-rings,
pistons, valves, valve seats, valve guides, and other elastomeric
polymer based parts or elastomeric polymers combined with other
materials such as metal, plastic combination materials which will
be known to those of ordinary skill in the art. Also contemplated
are transmission belts including V-belts, toothed belts with
truncated ribs containing fabric faced V's, ground short fiber
reinforced Vs or molded gum with short fiber flocked V's. The cross
section of such belts and their number of ribs may vary with the
final use of the belt, the type of market and the power to
transmit. They also can be flat made of textile fabric
reinforcement with frictioned outside faces. Vehicles contemplated
where these parts will find application include, but are not
limited to passenger autos, motorcycles, trucks, boats and other
vehicular conveyances.
[0157] In alternate embodiments the invention also relates to:
[0158] 1. A heterogeneous polymer blend comprising: [0159] (a) a
continuous phase comprising a thermoplastic first polymer having a
crystallinity of at least 30%; and [0160] (b) a dispersed phase
comprising particles of a second polymer different from the first
polymer dispersed in said continuous phase, the second polymer
having a crystallinity of less than 20% and being at least
partially cross-linked, and the average particle size of the
particles of the second polymer being less than 1 micron. [0161] 2.
The polymer blend of paragraph 1 wherein said thermoplastic first
polymer is a homopolymer of a C.sub.2 to C.sub.20 olefin. [0162] 3.
The polymer blend of paragraph 1 or 2 wherein said thermoplastic
first polymer is a copolymer of a C.sub.2 to C.sub.20 olefin with
less than 15 wt % of at least one comonomer. [0163] 4. The polymer
blend of paragraph 1, 2 or 3 wherein said thermoplastic first
polymer comprises a polymer of propylene. [0164] 5. The polymer
blend of paragraph 1, 2, 3, or 4 wherein the second polymer is
produced from a plurality of comonomers comprising at least one
C.sub.3 to C.sub.20 olefin and at least one polyene. [0165] 6. The
polymer blend of paragraph 5 wherein said at least one polyene has
at least two polymerizable unsaturated groups. [0166] 7. The
polymer blend of paragraph 5 or 6 wherein said plurality of
comonomers comprise propylene and ethylene. [0167] 8. The polymer
blend of paragraph 1, 2, 3, 4, 5, 6, or 7 wherein the average
particle size of the particles of the second polymer is between
about 50 nanometers and about 0.5 microns. [0168] 9. The polymer
blend of paragraph 1, 2, 3, 4, 5, 6, 7, or 8 wherein said dispersed
phase comprises more than 50 wt % of the total heterogeneous
polymer blend. [0169] 10. A heterogeneous polymer blend comprising
[0170] (a) a continuous phase comprising a thermoplastic first
polymer having a crystallinity of at least 30%; and [0171] (b) a
dispersed phase comprising particles of a second polymer different
from the first polymer dispersed in said continuous phase, the
second polymer having a crystallinity of less than 20% and being at
least partially cross-linked, and the average particle size of the
particles of the second polymer being less than 10 microns, [0172]
wherein said polymer blend is substantially free of processing oil.
[0173] 11. The polymer blend of paragraph 10 wherein said
thermoplastic first polymer is a homopolymer of a C.sub.2 to
C.sub.20 olefin. [0174] 12. The polymer blend of paragraph 10 or 11
wherein said thermoplastic first polymer is a copolymer of a
C.sub.2 to C.sub.20 olefin with less than 15 wt % of at least one
comonomer. [0175] 13. The polymer blend of paragraph 10, 11, or 12
wherein the second polymer is produced from a plurality of
comonomers comprising at least one C.sub.3 to C.sub.20 olefin and
at least one polyene. [0176] 14. The polymer blend of paragraph 10,
11, 12, or 13 wherein the average particle size of the particles of
the second polymer is less than 1 micron. [0177] 15. The polymer
blend of paragraph 10, 11, 12, 13, or 14 wherein the average
particle size of the particles of the second polymer is between
about 50 nanometers and about 0.5 microns. [0178] 16. A
heterogeneous polymer blend comprising [0179] (a) a continuous
phase comprising a thermoplastic first polymer that is at least
partially crystalline; and [0180] (b) a dispersed phase comprising
particles of a second polymer different from the first polymer
dispersed in said continuous phase, wherein said dispersed phase
comprises at least a fraction which is insoluble in xylene and
which comprises less than 2,500 ppm of a curative. [0181] 17. The
polymer blend of paragraph 16 wherein said fraction insoluble in
xylene comprises less than 100 ppm of a curative. [0182] 18. The
polymer blend of paragraph 16 or 17 wherein said fraction insoluble
in xylene comprises at least is at least 4% of said dispersed
phase. [0183] 19. A process for producing a heterogeneous polymer
blend (preferably the blends described in paragraphs 1 to 18)
comprising (a) a continuous phase comprising a thermoplastic first
polymer that is at least partially crystalline; and (b) a dispersed
phase comprising particles of a second polymer different from the
first polymer dispersed in said continuous phase, the second
polymer having a crystallinity less than that of the first polymer
and being at least partially cross-linked, the process comprising:
[0184] (i) polymerizing at least one first monomer to produce a
thermoplastic first polymer that is at least partially crystalline;
and [0185] (ii) contacting at least part of said first polymer with
at least one second monomer and at least one polyene under
conditions sufficient to polymerize said second monomer to produce
said second polymer and simultaneously cross-link said second
polymer such that the dispersed phase produced by said contacting
(ii) comprises at least a fraction which is insoluble in xylene.
[0186] 20. The process of paragraph 19 wherein said polymerizing
(i) is conducted in the presence of a catalyst and said contacting
(ii) is conducted in the presence of the same catalyst. [0187] 21.
The process of paragraph 19 or 20 wherein said polymerizing (i) is
conducted in the presence of a first catalyst and said contacting
(ii) is conducted in the presence of a second catalyst different
from the first catalyst. [0188] 22. A process for producing a
heterogeneous polymer blend (such as the blends of paragraphs
1-18), the process comprising: [0189] (a) selecting a catalyst
capable of polymerizing a C.sub.2 to C.sub.20 olefin to produce a
first polymer having at least 30% crystallinity; [0190] (b)
contacting said catalyst with one or more C.sub.2 to C.sub.20
olefins at a temperature of at least 50.degree. C. to produce a
first polymer having at least 30% crystallinity; [0191] (c)
contacting said first polymer and said catalyst with at least one
C.sub.3 to C.sub.20 olefin and at least one polyene under
conditions sufficient to polymerize said at least one C.sub.3 to
C.sub.20 olefin to produce a second polymer and simultaneously
cross-link said second polymer, whereby the product of said
contacting (c) is a heterogeneous polymer blend comprising a
continuous phase of the first polymer having at least 30%
crystallinity and a discontinuous phase of particles of said second
polymer having an average particle size less than 10 microns, said
second polymer being at least partially cross-linked and comprising
at least 15 wt % of said C.sub.3 to C.sub.20 olefin and at least
0.0001 wt % of said polyene. [0192] 23. The process of paragraph 22
wherein the first polymer produced in said contacting (b) has at
least 0.01% terminal unsaturation. [0193] 24. The process of
paragraph 22 or 23 wherein said C.sub.2 to C.sub.20 olefin
comprises propylene. [0194] 25. The process of paragraph 22, 23 or
24 wherein said first polymer is contacted with ethylene together
with said at least one C.sub.3 to C.sub.20 olefin and said at least
one polyene in said contacting (c). [0195] 26. The process of
paragraph 22, 23, 24 or 25 wherein said polyene has at least two
polymerizable unsaturated groups. [0196] 27. The process of
paragraph 22, 23, 24, 25, or 26 wherein said catalyst selected in
(a) is a single site catalyst comprising at least one catalyst
component and at least one activator. [0197] 28. The process of
paragraph 27 wherein said catalyst component is a bridged
bis-indenyl metallocene catalyst having a substituent on one or
both of the 2- and 4- positions on each indenyl ring. [0198] 29. A
process for producing a heterogeneous polymer blend (such as the
blends of paragraphs 1 to 18), the process comprising: [0199] (a)
selecting a catalyst capable of polymerizing a C.sub.2 to C.sub.20
olefin to produce a first polymer having at least 30%
crystallinity; [0200] (b) contacting said catalyst with one or more
C.sub.2 to C.sub.20 olefins at a temperature of at least 50.degree.
C. to produce a first polymer having at least 30% crystallinity;
[0201] (c) contacting said first polymer together with at least one
C.sub.3 to C.sub.20 olefin and at least one polyene with a catalyst
capable of polymerizing bulky monomers under conditions sufficient
to polymerize said at least one C.sub.3 to C.sub.20 olefin to
produce a second polymer and simultaneously cross-link said second
polymer, whereby the product of said contacting (c) is a
heterogeneous polymer blend comprising a continuous phase of the
first polymer having at least 30% crystallinity and a discontinuous
phase of particles of said second polymer having an average
particle size less than 3 microns, said second polymer being at
least partially cross-linked and comprising at least 15 wt % of
said C.sub.3 to C.sub.20 olefin and at least 0.0001 wt % of said
polyene. [0202] 30. The process of paragraph 29 wherein the first
polymer produced in said contacting (b) has at least 0.1% terminal
unsaturation. [0203] 31. The process of paragraph 29 or 30 wherein
said C.sub.2 to C.sub.20 olefin comprises propylene. [0204] 32. The
process of paragraph 29, 30 or 31 wherein said first polymer is
contacted with ethylene together with said at least one C.sub.3 to
C.sub.20 olefin and said at least one polyene in said contacting
(c). [0205] 33. The process of paragraph 29, 30, 31, or 32 wherein
said polyene has at least two polymerizable unsaturated groups.
[0206] 34. The process of paragraph 29, 30, 31, 32, or 33 wherein
the particles of said second polymer blend produced in step (c),
prior to any subsequent curing step, have a melting temperature of
at least 100.degree. C. [0207] 35. The process of paragraph 29, 30,
31, 32, 33, or 34 wherein the catalyst selected in (a) is different
from the catalyst employed in said contacting (c).
EXAMPLES
[0208] The invention will now be more particularly described with
reference to the Examples and the accompanying drawings.
[0209] In the Examples, molecular weights (number average molecular
weight (Mn), weight average molecular weight (Mw), and z-average
molecular weight (Mz)) were determined using a Waters 150 Size
Exclusion Chromatograph (SEC) equipped with a differential
refractive index detector (DRI), an online low angle light
scattering (LALLS) detector and a viscometer (VIS). The details of
these detectors as well as their calibrations have been described
by, for example, T. Sun, P. Brant, R. R. Chance, and W. W.
Graessley, in Macromolecules, Volume 34, Number 19, 6812-6820,
(2001), incorporated herein by reference. Solvent for the SEC
experiment was prepared by adding 6 grams of butylated hydroxy
toluene (BHT) as an antioxidant to a 4 liter bottle of 1,2,4
Trichlorobenzene (TCB) (Aldrich Reagent grade) and waiting for the
BHT to solubilize. The TCB mixture was then filtered through a 0.7
micron glass pre-filter and subsequently through a 0.1 micron
Teflon filter. There was an additional online 0.7 micron glass
pre-filter/0.22 micron Teflon filter assembly between the high
pressure pump and SEC columns. The TCB was then degassed with an
online degasser (Phenomenex, Model DG-4000) before entering the
SEC. Polymer solutions were prepared by placing dry polymer in a
glass container, adding the desired amount of TCB, then heating the
mixture at 160.degree. C. with continuous agitation for about 2
hours. All quantities were measured gravimetrically. The TCB
densities used to express the polymer concentration in mass/volume
units were 1.463 g/ml at room temperature and 1.324 g/ml at
135.degree. C. The injection concentration ranged from 1.0 to 2.0
mg/ml, with lower concentrations being used for higher molecular
weight samples.
[0210] The branching index in the Examples was measured using SEC
with an on-line viscometer (SEC-VIS) and is reported as g' at each
molecular weight in the SEC trace. The branching index g' is
defined as: g ' = .eta. b .eta. l ##EQU1## where .eta..sub.b is the
intrinsic viscosity of the branched polymer and .eta..sub.1 is the
intrinsic viscosity of a linear polymer of the same
viscosity-averaged molecular weight (M.sub.v) as the branched
polymer. .eta..sub.1=KM.sub.v.sup..alpha., K and .alpha. were
measured values for linear polymers and should be obtained on the
same SEC-DRI-LS-VIS instrument as the one used for branching index
measurement. For polypropylene samples presented in this invention,
K=0.0002288 and .alpha.=0.705 were used. The SEC-DRI-LS-VIS method
obviates the need to correct for polydispersities, since the
intrinsic viscosity and the molecular weight were measured at
individual elution volumes, which arguably contain narrowly
dispersed polymer. Linear polymers selected as standards for
comparison should be of the same viscosity average molecular
weight, monomer content and composition distribution. Linear
character for polymer containing C2 to C10 monomers is confirmed by
Carbon-13 NMR using the method of Randall (Rev. Macromol. Chem.
Phys., C29 (2&3), p. 285-297). Linear character for C11 and
above monomers is confirmed by GPC analysis using a MALLS detector.
For example, for a copolymer of propylene, the NMR should not
indicate branching greater than that of the co-monomer (i.e. if the
comonomer is butene, branches of greater than two carbons should
not be present). For a homopolymer of propylene, the GPC should not
show branches of more than one carbon atom. When a linear standard
is desired for a polymer where the comonomer is C9 or more, one can
refer to T. Sun, P. Brant, R. R. Chance, and W. W. Graessley,
Macromolecules, Volume 34, Number 19, 6812-6820, (2001) for
protocols on determining standards for those polymers. In the case
of syndiotactic polymers, the standard should have a comparable
amount of syndiotacticty as measured by Carbon 13 NMR. The
viscosity averaged g' was calculated using the following equation:
g vis ' = C i .function. [ .eta. i ] b C i .times. KM i .alpha.
##EQU2##
[0211] Where C.sub.i is the polymer concentration in the slice i in
the polymer peak, and [.eta..sub.i].sub.b is the viscosity of the
branched polymer in slice i of the polymer peak, and M.sub.i is the
weight averaged molecular weight in slice i of the polymer peak
measured by light scattering, K and .alpha. are as defined
above.
[0212] Peak melting point (Tm) and peak crystallization temperature
(Tc) were determined using the following procedure according to
ASTM E 794-85. Crystallinity was calculated using heat of fusion
determined using ASTM D 3417-99. Differential scanning calorimetric
(DSC) data were obtained using a TA Instruments model Q100 machine
or a Perkin-Elmer DSC-7. Samples weighing approximately 5-10 mg
were sealed in aluminum sample pans. The DSC data were recorded by
first cooling the sample to -100.degree. C. and then gradually
heating it to 200.degree. C. at a rate of 10.degree. C./minute. The
sample was kept at 200.degree. C. for 5 minutes before a second
cooling-heating cycle was applied. Both the first and second cycle
thermal events were recorded. Areas under the melting curves were
measured and used to determine the heat of fusion and the degree of
crystallinity. The percent crystallinity is calculated using the
formula, [area under the curve (Joules/gram)/B (Joules/gram)]*100,
where B is the heat of fusion for the homopolymer of the major
monomer component. These values for B were obtained from the
Polymer Handbook, Fourth Edition, published by John Wiley and Sons,
New York 1999. A value of 189 J/g (B) was used as the heat of
fusion for 100% crystalline polypropylene. A value of 290 J/g is
used for the heat of fusion for 100% crystalline polyethylene. For
polymers displaying multiple cooling and melting peaks, all the
peak crystallization temperatures and peaks melting temperatures
were reported. The heat of fusion for each melting peak was
calculated individually.
[0213] The glass transition temperature (Tg) was measured by ASTM E
1356 using a TA Instruments model Q100 machine.
[0214] Morphology data were obtained using an Atomic Force
Microscope (AFM) in tapping phase. All specimens were analyzed
within 8 hours after cryofacing to prevent specimen relaxation.
During cryofacing, the specimens were cooled to -130.degree. C. and
cut with diamond knives in a Reichert cryogenic microtome. They
were then stored in a dissector under flowing dry nitrogen gas to
warm up to ambient temperatures without condensation being formed.
Finally, the faced specimens were mounted in a miniature steel vise
for AFM analysis. The AFM measurements were performed in air on a
NanoScope Dimension 3000 scanning probe microscope (Digital
Instrument) using a rectangular 225-mm Si cantilever. The stiffness
of the cantilever was .about.4 N/m with a resonance frequency of
.about.70 kHz. The free vibration amplitude was high, in the range
of 80 nm to 100 nm, with a RMS setting of 3.8 volts. While the set
point ratio was maintained at a value equal to or lower than 0.5,
the contact set point was adjusted routinely to ensure repulsive
contacts with positive phase shifts. The cantilever was running at
or slightly below its resonance frequency.
[0215] AFM phase images of all specimens were converted into a TIFF
format and processed using PHOTOSHOP (Adobe Systems, Inc.). The
image processing tool kit (Reindeer Games, Inc.) was applied for
image measurements. Results of image measurements were written into
a text file for subsequent data processing using EXCEL (Microsoft)
or MATLAB (MathWorks, Inc.) for computing sizes/shapes of dispersed
phases, co-continuity factor of co-continuous phases, or
nearest-neighbor inter-particle distances.
[0216] Transmission Electron Microscopy (TEM) was used to study
details of the interface between the ethylene/propylene/diene
rubber and the semi-crystalline polypropylene phases. The
instrument used was the JEOL 2000FX microscope. A heavy metal
staining technique was employed to provide contrast to delineate
the details of the sample morphology. Ruthenium tetroxide provides
excellent contrast between amorphous and crystalline regions and
was used. Lower density and amorphous polymers take up more stain
than do higher density and more crystalline components. Thus
heavily stained components appear darker in TEM amplitude contrast
images whereas less heavily stained materials appear lighter. The
TEM analytical method used involved: [0217] Setting the orientation
of the plane of analysis. Typically the MD-ND (machine
direction/normal direction) plane is preferred for samples that may
be oriented in the machine direction. [0218] Creating a
deformation-free face through the bulk polymer sample using a
cryomicrotome. [0219] Staining with ruthenium tetroxide vapor for
about 8 hours. [0220] Cutting and collecting ultrathin (about 100
nm) sections from the stained face using an ultramicrotome. The
cutting is done using a diamond knife. Sections are floated onto
TEM grids. [0221] Loading sections into the TEM for examination at
the appropriate accelerating voltage (typically 160 to 200 kV).
[0222] Examining the sections to determine level of sampling
needed. [0223] Acquiring digital images using appropriate vendor
software.
[0224] The ethylene content of ethylene/propylene copolymers was
determined using FTIR according to the following technique. A thin
homogeneous film of polymer, pressed at a temperature of about
150.degree. C., was mounted on a Perkin Elmer Spectrum 2000
infrared spectrophotometer. A full spectrum of the sample from 600
cm.sup.-1 to 4000 cm.sup.-1 was recorded and the area under
propylene band at .about.1165 cm.sup.-1 and the area of ethylene
band at .about.732 cm.sup.-1 in the spectrum were calculated. The
baseline integration range for the methylene rocking band is
nominally from 695 cm.sup.-1 to the minimum between 745 and 775
cm.sup.-1. For the polypropylene band the baseline and integration
range is nominally from 1195 to 1126 cm.sup.-1. The ethylene
content in wt. % was calculated according to the following
equation: ethylene content(wt. %)=72.698-86.495X+13.696X.sup.2
where X=AR/(AR+1) and AR is the ratio of the area for the peak at
.about.1165 cm.sup.-1 to the area of the peak at .about.732
cm.sup.-1.
[0225] Solvent extraction was used to isolate the different polymer
species of the in-reactor polymer blends. The fractionations were
carried out in a two-step successive solvent extraction when the
polymer blend did not contain any oil: one involves cyclohexane
extraction, the other xylene Soxhlet extraction. In the cyclohexane
solvent extraction, about 0.3 gram of polymer was dissolved in
about 60 ml of cyclohexane to isolate the uncured and lightly
branched elastomeric components of the polymer blend. The mixture
was continuously stirred at room temperature for about 48 hours.
The soluble fraction (referred as cyclohexane solubles) was
separated from the insoluble material (referred as cyclohexane
insolubles) using filtration under vacuum. The insoluble material
was then subjected to the xylene soxhlet extraction procedure. In
this step, the insoluble material from the room temperature
cyclohexane extraction was first extracted for about 24 hours with
xylene. The xylene insoluble portion (referred as xylene
insolubles) was recovered by filtration and is the extract
containing the at least partially cross-linked second polymer. The
remaining portion was cooled down to room temperature and retained
in a glass container for 24 hours for precipitation. The
precipitated component (referred as xylene precipitate) was
recovered through filtration and the soluble component (referred as
xylene soluble) was recovered by evaporating the xylene solvent.
The xylene precipitate fraction is where the thermoplastic
crystalline component resides. In the case of blends containing
paraffinic oil, plasticizer and the like, another Soxhlet solvent
extraction step was performed on the sample for 24 hours to isolate
the oil from the blend before the cyclohexane extraction and xylene
Soxhlet extraction using an azeoptrope of acetone and cyclohexane
in the ratio 2:1 by volume. The soluble fraction is referred as to
azeoptrope solubles.
[0226] In order to measure the physical properties of the polymer
blends, samples were first mixed in a Brabender melt mixer with
.about.45 mL mixing head. The polymer was stabilized with
antioxidant during mixing in the Brabender. The Brabender was
operated at 100 rpm and at temperature of 180.degree. C. Mixing
time at temperature was 5-10 minutes, after which the sample was
removed from the mixing chamber. The homogenized samples were
molded under compression into film on a Carver hydraulic press for
analysis. About 7 grams of the homogenized polymer were molded
between brass platens lined with Teflon.TM. coated aluminum foil. A
0.033 inch (0.08 cm) thick chase with a square opening 4
inch.times.4 inch (10.2.times.10.2 cm) was used to control sample
thickness. After one minute of preheat at 170.degree. C. or
180.degree. C., under minimal pressure, the hydraulic load was
gradually increased to 10,000 to 15,000 lbs, at which it was held
for three minutes. Subsequently the sample and molding plates were
cooled for three minutes under 10,000 to 15,000 lbs load between
the water-cooled platens of the press. Plaques were allowed to
equilibrate at room temperature for a minimum of 24 hours prior to
physical property testing.
[0227] .beta. relaxation, Loss Modulus (E'') and Storage Modulus
(E') were measured by dynamic mechanical thermal analysis (DMTA).
The instrument used was the RSA II, Rheometrics Solid Analyzer II
from TA Instruments, New Castle, Del. The instrument was operated
in tension mode and used molded rectangular samples. Sample
conditions were: 0.1% strain, 1 Hz frequency, and 2.degree. C. per
minute heating rate, covering the temperature range from
-135.degree. C. to the melting point of the sample. Samples were
molded at about 200.degree. C. Typical sample dimensions were 23 mm
length.times.6.4 mm width.times.thickness between 0.25 mm and 0.7
mm, depending on the sample. Tan .delta. is the ratio of E''/E'.
The output of these DMTA experiments is the storage modulus (E')
and loss modulus (E''). The storage modulus measures the elastic
response or the ability of the material to store energy, and the
loss modulus measures the viscous response or the ability of the
material to dissipate energy. The ratio of E''/E' (=tan .delta.)
gives a measure of the damping ability of the material. Energy
dissipation mechanisms (i.e., relaxation modes) show up as peaks in
tan .delta., and are associated with a drop in E' as a function of
temperature. The uncertainty associated with reported values of E'
is expected to be on the order of .+-.10%, due to variability
introduced by the molding process.
[0228] Shore hardness was determined according to ISO 868 at
23.degree. C. using a Durometer.
[0229] Stress-strain properties such as ultimate tensile strength,
ultimate elongation, and 100% modulus were measured on 2 mm thick
compression molded plaques at 23.degree. C. by using an Instron
testing machine according to ISO 37.
[0230] Compression set test was measured according to ISO 815A.
[0231] Tension set was measured according to ISO 2285.
[0232] Oil swell (oil gain) was determined after soaking a die-cut
sample from compression molded plaque in IRM No. 3 fluid for 24
hours at 125.degree. C. according to ASTM D 471.
[0233] Viscosity was measured using LCR (Laboratory Capillary
Rheometer) according to ASTM D 3835-02 using a Dynisco Capillary
rheometer at 30:1 L/D (length/diameter) ratio, a shear rate of 1200
l/s and a temperature of 204.degree. C. The entrance angle of the
laboratory capillary rheometer is 180.degree., barrel diameter is
9.55 mm. The heat soak time is 6 minutes.
Examples 1A to 1C
[0234] Three polymer blends were produced in a two-stage
polymerization reaction by polymerizing propylene in a first stage
to make homopolymer, and copolymerizing propylene and ethylene as
well as a diene cross-linking agent in a second stage in the
presence of the homopolymer produced in the first stage. The
polymerization was carried out in an autoclave reactor equipped
with a stirrer, an external water/steam jacket for temperature
control, a regulated supply of dry nitrogen, ethylene, propylene,
and a septum inlet for introduction of other solvents, catalysts
and scavenger solutions. The reactor was first washed using hot
toluene and then dried and degassed thoroughly prior to use. All
the solvents and monomers were purified by passing through a
1-liter basic alumina column activated at 600.degree. C., followed
by a column of molecular sieves activated at 600.degree. C. or
Selexsorb CD column prior to transferring into the reactor.
[0235] In the first stage of polymerization, triisobutyl aluminum
(TIBAL) (25 wt % in hexane, purchased from Sigma-Aldrich) solution
was first added to the reactor. Then the catalyst solution was
cannulated into the reactor using solvent. In succession, solvent
(diluent) and propylene were added into the reactor. All of these
were conducted at room temperature. The mixture was then stirred
and heated to a desired temperature. The first stage of
polymerization was ended when the desired amount of polypropylene
was produced, determined by monitoring the reactor pressure during
the reaction. Thereafter, the reactor was depressurized by venting
the unreacted propylene and solvent to the atmosphere until the
reactor pressure reached about 5 psig (34.5 kPa) to maintain an
inert atmosphere in the reactor for the continuation of
polymerization in the second stage.
[0236] In the second stage of polymerization, propylene was added
into the mixture produced in the first stage. The mixture was then
stirred and heated to a desired reaction temperature. In
succession, diene and ethylene were added into the reactor. The
ethylene was fed on demand to maintain a relative constant reactor
pressure during the polymerization reaction. The ethylene
consumption was monitored during the reaction using a mass flow
meter. The polymerization reaction was terminated when desired
amount of rubber was produced. Thereafter, the reactor was cooled
down and unreacted monomer and solvent (diluent) were vented to the
atmosphere. The resulting mixture, containing mostly solvent,
polymer and unreacted monomers, was collected in a collection box
and first air-dried in a hood to evaporate most of the solvent, and
then dried in a vacuum oven at a temperature of about 90.degree. C.
for about 12 hours.
[0237] 1,9-decadiene was used as the diene cross-linking agent in
the second polymerization stage. The 1,9-decadiene was obtained
from Sigma-Aldrich and was purified by first passing through an
alumina column activated at high temperature under nitrogen,
followed by a molecular sieve activated at high temperature under
nitrogen.
[0238] Rac-dimethylsilyl bis(2-methyl, 4-phenylindenyl)zirconium
dimethyl catalyst preactivated with N,N-dimethylanilinium tetrakis
(pentafluorophenyl) borate (both obtained from Albemarle) at a
molar ratio of about 1:1 in toluene was fed into the reactor in
Stage 1. Example 1A and 1C were conducted in a 0.5-liter autoclave
reactor with no additional catalyst being added in Stage 2. Example
1B was produced in a 1-liter autoclave reactor with additional
catalyst added in the second stage of polymerization. No reactor
depressurization was used at the end of stage 1 and no additional
propylene was added into the reactor in the second stage in Example
1B. Details of the experimental conditions, catalysts employed and
the properties of the resultant polymer blends are listed in Table
1A below. TABLE-US-00001 TABLE 1A Example # 1A 1B 1C Polymerization
in Stage 1 Reaction temperature (.degree. C.) 70 70 70 Amount of
catalyst (mg) 2 0.5 2 Propylene #1 (ml) 125 500 125 Hexane (ml) 125
700 125 TIBAL (25 wt. %) (ml) 0.5 4 0.5 Reaction time in stage 1
(min) 15 3.2 15 Polymerization in Stage 2 Reaction temperature
(.degree. C.) 70 85 70 Amount of catalyst (mg) 0 0.72 0 Propylene
#2 (ml) 100 0 70 Ethylene head pressure (psi) 100 180 100 1,9
decadiene (ml) 0.3 6 100 Hexane (ml) 0 100 0.1 Reaction time in
stage 2 (min) 60 28 60 Yield (g) 78.8 151.7 99.9 Tc (.degree. C.)
119.8 109.4 121.5 Tm (.degree. C.) 155.9 156.9 155.6 Heat of fusion
(J/g) 36.3 24.6 60.4 Tg (.degree. C.) -50.1 -35.4 -46.6 Ethylene
content (wt %) 22.6 19.1 19.5 Xylene precipitate (wt %) 44.4 27.3
76.4 Xylene insolubles (wt %) 27.2 40.2 1.0 Xylene solubles (wt %)
10.2 7.7 7.5 Cyclohexane solubles (wt %) 18.2 24.9 15.1 Degree of
cross-link (%) 48.9 55.3 4.1
[0239] Degree of cross-link is defined as: Degree of
cross-link=Percent of xylene insoluble/100-percent of xylene
precipitate.times.100
[0240] The Tg values shown in the table above refer to the
elastomer component in the reactor-produced blend examples. The
values provide an indication of the amorphous nature of the
elastomer component; thus Example 1A which contains a higher level
of ethylene comonomer appears more amorphous than Example 1B with a
higher Tg. The Tg of the polypropylene component--located primarily
in the xylene precipitate fraction--is generally about 0.degree.
C., typical for semi-crystalline propylene homopolymers.
[0241] The two polymer blends produced in Examples 1A and 1B were
subjected to solvent extraction. The amount of each extracted
fraction is expressed as the weight percent of the total polymer
blend and is listed in Table 1A. Some of the physical properties of
these fractionated components are listed in Table 1B and 1C.
TABLE-US-00002 TABLE 1B Physical properties for the fractions
obtained through solvent extraction for Example 1A Cyclohexane
Xylene Xylene Xylene Fraction solubles Insolubles Precipitates
Solubles Tc (.degree. C.) 15.0 Tm (.degree. C.) 146 154 Tg
(.degree. C.) -50.9 Heat of 35 fusion (J/g) Mn (kg/mol) 26.4 Mw
(kg/mol) 72.8 Mz (kg/mol) 273.5 g'vis 0.84 Ethylene content (wt
%)
[0242] TABLE-US-00003 TABLE 1C Physical properties for the
fractions obtained through solvent extraction for Example 1B xylene
cyclohexane cyclohexane xylene precip- xylene Fraction solubles
insolubles insolubles itates solubles Tc (.degree. C.) 12.8 Tm
(.degree. C.) 65.0 Tg (.degree. C.) -40.5 Heat of 3.3 fusion (J/g)
Mn (kg/mol) 11.4 196.5 69.8 Mw (kg/mol) 34.0 432.5 225.1 Mz
(kg/mol) 92.6 877.9 955.9 g'vis Ethylene 25.7 16.9 content (wt
%)
[0243] The polymer blends produced in Examples 1A and 1B were melt
mixed and molded under compression into plaques, and tested for
thermoplastic elastomer applications. Examples 1B was also
compounded with about 30% of Sunpar 150 M oil at an elevated
temperature in a Brabender mixer, and molded under compression into
plaques, and tested for thermoplastic elastomer applications. The
performance data are listed in Table ID. TABLE-US-00004 TABLE 1D
Performance data for Examples 1A and 1B Polymer 1A 1B 1B Polymer
(%) 100 100 70 Oil (Sunpar 150 M) (%) 0 0 30 Hardness (SHORE) 33D
72A 49A Ultimate tension strength (psi) 2101 1144 542 (ISO37)
Ultimate elongation (%) (ISO37) 153 332 340 100% Modulus (psi) 1953
673 274 Viscosity (Pa-s) 135 179.6 75.6 Tension set (%) (ISO2285)
7.5 19.75 15.75 Compression set, 70.degree. C./22 Hrs (%) 62.18
62.74 48.47 (ISO815A) Weight gain, 121.degree. C./24 hrs (%) 330.16
495.15 380.2
[0244] The morphology of each of the blends produced in Examples 1A
and 1B was examined using AFM according to the procedure described
above and the results are shown in FIGS. 1A and 1B. It was observed
that the rubber was in the discrete particle phase embedded in
polypropylene matrix. The particle size of the dispersed phase
varied in a range of 0.04 to 3 .mu.m with an average particle size
of about 0.48 .mu.m for the dispersed phase of the blend of Example
1A (see FIG. 1D). The particle size at the lower end was estimated
due to the limitation of AFM image resolution. The presence of
sub-micrometer particles is illustrated in the TEM image shown in
FIG. 1C. The particle size distribution of the dispersed phase at
the lower end of particle size was analyzed using TEM image. As an
example, FIG. 1E shows the data obtained from the TEM image of
Example 1A.
[0245] DSC melting and crystallization on the xylene insoluble
fraction from Example 1B is shown in FIG. 1F. The xylene insoluble
fraction is mainly crosslinked elastomer produced in the reactor.
The DSC first heating shows the presence of an exotherm starting at
about 175.degree. C. This exotherm is unexpected, because it occurs
during heating and because the sample fraction contains primarily
crosslinked rubber. Generally, crystallization (of a propylene
polymer in this case) would be suspected from the presence of an
exotherm. This is however unlikely, given that it occurs at such a
high temperature. It is believed that this exotherm reflects
shrinkage in the sample. Some of the crosslinked elastomer appears
to be linked to a small amount of polypropylene, which constrains
its movement. Following the melting of the polypropylene (complete
by about 175.degree. C.), mobility is regained and the elastomer is
able to shrink. Subsequent crystallization and 2nd heating of this
fraction also exhibit a response, as is seen by baseline changes at
about this temperature. This observation points to the capability
of the process to produce cross products, which offer novel product
features (in this case unexpected high levels of shrinkage).
[0246] In addition to the capability offered by the process to form
novel cross products, unique morphologies are noted in the
polypropylene matrix. An example of such a morphology is shown in
FIG. 1G. This TEM micrograph is of Example 1C. FIG. 1G shows the
uniform, fine-sized rubber particles delivered by the process
(largest dimension .about.0.2 .mu.m). This is to be compared
against a size generally 0.5 .mu.m or larger for current commercial
TPVs via dynamic vulcanization, as shown in FIG. 1H, which is are
TEM representations for Santoprene grade 201-55 (available from
Advanced Elastomer Systems in Akron, Ohio). Additionally, the
micrograph of FIG. 1G shows the presence of spherulites with
transverse oriented lamellae, different from the more usual
radially-oriented lamellae. The presence of these transverse
spherulites in metallocene polypropylene has been related to the
gamma phase or polymorph of polypropylene crystals (reference: R.
G. Alamo and coworkers, Polymer, 45, 3441-3455, 2004). The presence
of gamma phase crystallites, along with the more common alpha form,
provides a broadened melting range. This offers benefits for the
blends of this invention in certain thermoplastic fabricating
operations (e.g. thermoforming).
Examples 2A to 2C
[0247] These three samples were produced in a 2-liter autoclave
reactor equipped similarly to the 0.5 liter reactor described in
Examples 1A and 1B. These examples demonstrate a two-stage
polymerization reaction with the use of rac-dimethylsilyl
bis(2-methyl-4-phenylindenyl)zirconium dimethyl catalyst (Catalyst
A) in the first stage to produce polypropylene and
[di(p-triethylsilylphenyl)methylene](cyclopentadienyl)
(3,8-di-t-butylfluorenyl)haffiium dimethyl catalyst (Catalyst B)
(obtained from Albemarle) in the second stage to produce ethylene
propylene diene rubber. Both catalysts were preactivated by
dimethylanilinum tetrakis(heptafluoro-2-naphthyl) borate at a molar
ratio of 1:1 in toluene. The general procedure described above in
Examples 1A and 1B was followed with the following exceptions: (1)
tri-n-octylaluminum (TNOA) (25 wt. % in hexane, Sigrna Aldrich) was
used as a scavenger; (2) no reactor depressurization at the end of
stage 1; (3) about 6 ml of air was injected into the reactor at the
end of stage 1 to deactivate the Catalyst A and then additional 5
ml of TNOA was injected at about 10 minutes after; (4) the second
stage polymerization started with ethylene addition and diene was
injected after ethylene introduction; (5) Catalyst B was injected
into reactor in stage 2 right after diene addition. The detailed
reaction condition and polymer properties are listed in Table 2A.
TABLE-US-00005 TABLE 2A Example # 2A 2B 2C Polymerization in Stage
1 Reaction temperature (.degree. C.) 75 75 75 Amount of catalyst A
(mg) 0.60 0.50 0.50 Propylene #1 (ml) 700 700 700 Toluene (ml) 500
500 500 TNOA (25 wt %) (ml) 8.0 8.0 8.0 Reaction time in stage 1
(min) 11.0 7.0 7.0 Polymerization in Stage 2 Reaction temperature
(.degree. C.) 75 75 80 Amount of catalyst B (mg) 1.20 1.00 1.10
Propylene #2 (ml) 0 0 0 Ethylene head pressure (psi) 230 250 250
1,9 decadiene (ml) 47.0 50.0 50.0 Toluene (ml) 300 300 300 Reaction
time in stage 2 (min) 22 8 19 Yield (g) 57.3 53.1 119.0 Tc
(.degree. C.) 109.3 111.4 102.4 Tm (.degree. C.) 157.8 155.3 150.6
Heat of fusion (J/g) 50.6 40.0 22.8 Tg (.degree. C.) -46.4 -48.1
-44.0 Ethylene content (wt %) 22.4 Xylene precipitate (wt %) 45.03
45.03 22.73 Xylene insolubles (wt %) 23.12 29.73 60.08 Xylene
solubles (wt %) 22.43 18.39 11.23 Cyclohexane solubles (wt %) 9.42
6.85 5.97 Degree of cross-link (%) 42.1 54.1 77.8
[0248] The polymer blends produced in Examples 2A to 2C were
subjected to solvent extraction. The amount of each fraction is
listed in Table 2A. Some of the physical properties of the
fractionated components for the polymer blend of Example 2C are
listed in Table 2B. TABLE-US-00006 TABLE 2B Physical properties for
the fractions obtained through solvent extraction for Example 2C
Xylene Insoluble film Cyclohexane without Xylene Xylene Fraction
Solubles filler Precipitate Solubles Tc (.degree. C.) 117.46 Tm
(.degree. C.) 154.98 Tg (.degree. C.) Heat of 114.10 fusion (J/g)
Ethylene 27.7 content (wt %)
[0249] The polymer blends produced in Examples 2A to 2C were melt
mixed and molded under compression into plaques, and tested for
thermoplastic elastomer applications. Example 2C was also
formulated with Paralux 6001R oil during the melt mixing. The
performance data are listed in Table 2C. TABLE-US-00007 TABLE 2C
Performance data for Examples 2A to 2C Polymer 2A 2B 2C 2C Polymer
(%) 100.0 100.0 100.0 69.93 Oil (Paralux 6001R) (%) 0 0 0 30.07
Hardness (SHORE) 88A 91A 75A 57A Ultimate tension strength 2037
2330 1255 617.4 (psi) (ISO37) Ultimate elongation 286 364 125 203.8
(%) (ISO37) 100% Modulus (psi) 1517 1704 1138 356.1 Viscosity
(Pa-s) NA NA NA 198.7 Tension set (%) 36.5 39.2 15 8.5 (ISO2285)
Compression set, 55.1 56.9 29.4 27.6 70.degree. C./22 Hrs (%)
(ISO815A) Weight gain, 121.degree. C./ 171.3 186.1 254.9 235.0 24
hrs (%)
[0250] A transmission electron micrograph of a molded part
cross-section produced from the polymer blend of Example 2C is
shown in FIG. 2A.
[0251] Reactor blend Examples 1A and 2C were analyzed by small
angle oscillatory shear experiments. This rheological analysis
provides data on the viscoelastic properties of the polymer blends.
Measurements include those of the storage and loss modulii (G',
G'') over a range of frequencies, at a given melt temperature. The
Theological data were analyzed using the Van Gurp-Palmen treatment
(reference: M. Van Gurp and J. Palmen, Rheology Bulletin, 67, 5,
1998), whereby the phase angle .delta.(=tan.sup.-1 (G''/G')) is
plotted against the absolute value of the complex modulus
|G*|=(G'.sup.2+G''.sup.2).sup.1/2. This representation of linear
viscoelastic data is a powerful means of characterizing molecular
and structural features of polymers. For example, low levels of
long chain branching in polyolefins can be detected and quantified
on a relative basis, using this methodology. The data are shown in
FIG. 2C. The figure shows the region of .delta. vs |G*| where
current commercial Santoprene grades (from Advanced Elastomer
Systems in Akron, Ohio) reside. These products are TPVs produced
via dynamic vulcanization.
Example 3A
[0252] This example demonstrates a series dual-reactor continuous
solution process with the use of rac-dimethylsilyl
bis(2-methyl-4-phenylindenyl)zirconium dimethyl catalyst (Catalyst
A) in the first reactor to produce polypropylene and
[di(p-triethylsilylphenyl)methylene](cyclopentadienyl)
(3,8-di-t-butylfluorenyl)haffium dimethyl catalyst (Catalyst B) in
the second reactor to produce ethylene/propylene/diene copolymer.
Polymerization was performed in a series dual-reactor continuous
solution process. Both of the reactors were 0.5-liter stainless
steel autoclave reactors and were equipped with a stirrer, a
water-cooling/steam-heating element with a temperature controller,
and a pressure controller. Solvents, monomers such as ethylene and
propylene were first purified by passing through a three-column
purification system. The purification system consisted of an
Oxiclear column (Model # RGP-R1-500 from Labclear) followed by a 5A
and a 3A molecular sieve columns. Purification columns were
regenerated periodically whenever there was evidence of lower
activity of polymerization. Both the 3A and 5A molecular sieve
columns were regenerated in-house under nitrogen at a set
temperature of 260.degree. C. and 315.degree. C., respectively. The
molecular sieve material was purchased from Aldrich. Oxiclear
column was regenerated in the original manufacture.
[0253] The solvent feed to the reactors was measured by a mass-flow
meter. A Pulsafeed pump controlled the solvent flow rate and
increased the solvent pressure to the reactors. The compressed,
liquefied propylene feed was measured by a mass flow meter and the
flow was controlled by a Pulsafeed pump. The diene was fed into the
reactor through an Eldex pump and the flow rate was measured using
a Micro-Motion Coriolis-type flow meter. The solvent, monomers and
diene were fed into a manifold first. Ethylene from in-house supply
was delivered as a gas solubilized in the chilled solvent/monomer
mixture in the manifold. The mixture of solvent and monomers were
then chilled to about -15.degree. C. by passing through a chiller
prior to feeding into the reactor through a single tube. Ethylene
flow rate was metered through a Brookfield mass flow
controller.
[0254] Catalyst A was preactivated with dimethyl anilinium
tetrakis(heptafluoro-2-naphthyl) borate. The catalyst B was
preactivated with N,N-dimethylanilinium tetrakis(pentafluorophenyl)
borate. Both of them were preactivated at a molar ratio of 1:1 in
700 ml of toluene. All catalyst solutions were kept in an inert
atmosphere with <1.5 ppm water content and fed into reactors by
metering pumps. Tri-n-octylaluminum (TNOA) solution was used as a
scavenger.
[0255] The reactors were first cleaned by continuously pumping
solvent (e.g., hexane) and scavenger through the reactor system for
at least one hour at a maximum allowed temperature (about
150.degree. C.). After cleaning, the reactors were heated/cooled to
the desired temperature using water/steam mixture flowing through
the reactor jacket and controlled at a set pressure with controlled
solvent flow. Monomers and catalyst solutions were then fed into
the reactor. An automatic temperature control system was used to
control and to maintain the reactors at set temperatures. Onset of
polymerization activity was determined by observations of a viscous
product and lower temperature of water-steam mixture. Once the
activity was established and system reached steady state, the
reactors were lined out by continuing operating the system under
the established condition for a time period of at least five times
of mean residence time prior to sample collection. The resulting
mixture from the second reactor, containing mostly solvent, polymer
and unreacted monomers, was collected in a collection box. The
collected samples were first air-dried in a hood to evaporate most
of the solvent, and then dried in a vacuum oven at a temperature of
about 90.degree. C. for about 12 hours. The vacuum oven dried
samples were weighed to obtain yields. All the reactions were
carried out at a pressure of about 2.41 MPa-g.
[0256] Propylene, solvent, Catalyst A solution and scavenger were
fed into the first reactor. The content of the first reactor flows
into the second reactor. Catalyst B solution, ethylene and diene
were fed into the second reactor. The detailed reaction conditions
and polymer properties are listed in Table 3A. TABLE-US-00008 TABLE
3A 1st reactor 2nd reactor Polymerization 80 110 temperature (C.)
Propylene feed 14 0 rate (g/min) Ethylene feed 0 6 rate (SLPM) 1,9
decadiene 0 0.108 feed rate (ml/min) Toluene feed 80 rate (ml/min)
Catalyst B feed 0 4.61 .times. 10.sup.-8 rate (mole/min) Catalyst A
feed 4.16 .times. 10.sup.-8 0 rate (mole/min) Yield (g/min) 11.5 Tc
(.degree. C.) 111.3 Tm (.degree. C.) 157.1 Tg (.degree. C.) -49.0
Heat of 25.8 fusion (J/g)
Examples 4A to 4C
[0257] These three samples were produced in a 2-liter autoclave
reactor equipped similarly to the 0.5-liter reactor described in
Example 1A. Catalysts used were rac-dimethylsilyl
bis(2-methyl-4-phenylindenyl)zirconium dimethyl catalyst (Catalyst
A) in the first stage to produce polypropylene and
[di(p-triethylsilylphenyl)methylene](cyclopentadienyl)
(3,8-di-t-butylfluorenyl)hafniium dimethyl catalyst (Catalyst B) in
the second stage to produce ethylene propylene diene rubber. Both
catalysts were preactivated by dimethylanilinum
tetrakis(heptafluoro-2-naphthyl) borate at a molar ratio of about
1:1 in toluene. The procedure described above in Example 2A to 2C
was followed except that 5-vinyl-2-norbornene (VNB) was used as the
cross-linking agent in the second stage of polymerization. VNB was
obtained from Sigma-Aldrich and was purified by first passing
through an alumina column activated at high temperature under
nitrogen, followed by a molecular sieve activated at high
temperature under nitrogen. The detailed reaction conditions and
polymer properties are listed in Table 4A. TABLE-US-00009 TABLE 4A
Example # 4A 4B 4C Polymerization in Stage #1 Reaction temperature
(.degree. C.) 75 75 75 Amount of catalyst A (mg) 0.5 0.5 0.5
Propylene #1 (ml) 600 600 600 Toluene (ml) 500 500 500 TNOA (25 wt
%) (ml) 3 3 3 Reaction time in stage 1 (min) 8 5.5 3 Polymerization
in Stage #2 Reaction temperature (.degree. C.) 75 75 75 Amount of
catalyst B (mg) 1.5 1.6 2 Propylene #2 (ml) 100 100 100 Ethylene
head pressure (psi) 230 230 230 VNB (ml) 10 20 40 Toluene (ml) 300
300 300 TNOA (25 wt. %) (ml) 10 10 10 Reaction time in stage 2
(min) 48 37 20 Yield (g) 56 101 104 Tc (.degree. C.) 113.7 111.0
111.1 Tm (.degree. C.) 157.4 158.6 157.7 Heat of fusion (J/g) 28.8
35.5 49.0 Tg (.degree. C.) -52.5 -51.2 -51.5 Xylene precipitate
(wt. %) 61.5 45.1 51.2 Xylene insolubles (wt. %) 2.0 18.9 27.3
Xylene solubles (wt. %) 8.2 28.3 17.1 Cyclohexane solubles (wt. %)
28.3 7.6 4.5 Degree of cross-link (%) 5.1 34.5 56.0 (TNOA is
tri-n-octyl-aluminum)
[0258] The polymer blends produced in Examples 4A to 4C were
subjected to solvent extraction using the procedure described
above. The amount of each fraction expressed as weight percent and
the calculated degree of cross-link are listed in Table 4A.
[0259] The polymer blends produced in Examples 4A to 4C were melt
mixed and molded under compression into plaques, and tested for
thermoplastic elastomer applications. The performance data are
listed in Table 4B. TABLE-US-00010 TABLE 4B Performance data for
polymer blends produced in Examples 4A to 4C Polymer blend 4A 4B 4C
Hardness 76A 87A 94A Ultimate tension strength (MPa) 3.90 11.14
17.54 Ultimate elongation (%) 292 403 468 100% Modulus (MPa) 3.72
8.78 11.60 Tension Set (%) 36.75 31.75 37.25 Compression set,
70.degree. C./22 Hrs (%) 68.9 60.6 55.5 Weight gain, 121.degree.
C./24 hrs (%) 511.3 354.9 200.4
[0260] All documents described herein are incorporated by reference
herein, including any priority documents and/or testing procedures
to the extent they are not inconsistent with this text. While there
have been described what are presently believed to be the preferred
embodiments of the present invention, those skilled in the art will
realize that other and further embodiments can be made without
departing from the spirit of the invention, and is intended to
include all such further modifications and changes as come within
the true scope of the claims set forth herein.
* * * * *