U.S. patent application number 09/827222 was filed with the patent office on 2001-11-22 for elastic polypropylenes and catalysts for their manufacture.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Duerr, Brook F., Kolpe, Vasant V., Misemer, David K., Siedel, Allen R..
Application Number | 20010044515 09/827222 |
Document ID | / |
Family ID | 25498808 |
Filed Date | 2001-11-22 |
United States Patent
Application |
20010044515 |
Kind Code |
A1 |
Siedel, Allen R. ; et
al. |
November 22, 2001 |
Elastic polypropylenes and catalysts for their manufacture
Abstract
A propylene polymeric composition with elastic character that is
soluble in at least one nonpolar organic solvent selected from the
group consisting of toluene, xylene, heptane, and hexane, comprises
greater than 3 weight percent and up to 45 weight percent
homotactic sequences each having only r or m diads, all of which
homotactic sequences have a helical length in the range of 20 to
150 .ANG., and in the range of 55 to 97 weight percent of the sum
of homotactic sequences of less than 20 .ANG. in helical length,
each homotactic sequence having only r or m diads and having fewer
than 10 repeat units with mmmm pentads being present in the range
of 0 to 35 weight percent of the total composition, and
heterotactic sequences having r and m diads of unequal number, the
polymer having a molecular weight (M.sub.w) of at least 70,000.
Inventors: |
Siedel, Allen R.; (Lake
Elmo, MN) ; Misemer, David K.; (Maplewood, MN)
; Kolpe, Vasant V.; (Mendote Heights, MN) ; Duerr,
Brook F.; (Lake Elmo, MN) |
Correspondence
Address: |
Office of Intellectual Property Counsel
3M Innovative Properties Company
PO Box 33427
St. Paul
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
25498808 |
Appl. No.: |
09/827222 |
Filed: |
April 5, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09827222 |
Apr 5, 2001 |
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08956880 |
Oct 23, 1997 |
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6265512 |
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Current U.S.
Class: |
526/351 ;
526/127; 526/160 |
Current CPC
Class: |
C08L 2314/06 20130101;
C08F 210/06 20130101; C07F 7/081 20130101; C08F 4/65912 20130101;
Y10S 526/943 20130101; C08F 10/06 20130101; C08L 23/10 20130101;
C08F 110/06 20130101; C08L 2205/02 20130101; C08F 10/00 20130101;
C08F 10/00 20130101; C08F 4/65927 20130101; C08L 23/10 20130101;
C08L 2666/04 20130101; C08F 110/06 20130101; C08F 2500/03 20130101;
C08F 2500/20 20130101; C08F 2500/21 20130101; C08F 210/06 20130101;
C08F 210/14 20130101; C08F 2500/03 20130101; C08F 2500/20 20130101;
C08F 2500/21 20130101 |
Class at
Publication: |
526/351 ;
526/127; 526/160 |
International
Class: |
C08F 110/06 |
Claims
We claim:
1. A propylene homopolymer, said polymer being elastomeric and
being soluble in at least one nonpolar organic solvent selected
from the group consisting of toluene, xylene, heptane, and hexane,
said polymer comprising a) greater than 3 weight percent and up to
45 weight percent homotactic sequences each having only r or m
diads, all of which homotactic sequences have a helical length in
the range of 20 to 150 .ANG., and b) in the range of 55 to 97
weight percent of the total composition being the sum of 1)
homotactic sequences, each having only r or m diads, and being less
than 20 .ANG. in helical length, and having fewer than 10 repeat
units with mmmm pentads being present in the range of 0 to 35
weight percent of the total composition, and 2) heterotactic
sequences having unequal numbers of r and m diads, said polymer
having a molecular weight (M.sub.w) of at least 70,000.
2. The polymer according to claim 1 wherein said homotactic
sequences are syndiotactic.
3. The polymer according to claim 1 wherein said homotactic
sequences are isotactic.
4. The polymer according to claim 1 having one or more of the
following characteristics: i) a stereoregularity index between 1.30
and 10.00, ii) a heat of fusion (.DELTA.H.sub.fus) that is less
than 50% of the .DELTA.H.sub.fus of 100% isotactic polypropylene
when mm>rr; or less than 50% of the .DELTA.H.sub.fus of 100%
syndiotactic polypropylene when rr>mm, and iii) optical
clarity.
5. The polypropylene polymers according to claim 1 prepared by a
metallocene catalyst having the formula
{ligand1-bridge-ligand2}MX.sub.2 wherein ligand1 and ligand2 are
different and are selected from the group consisting of
cyclopentadienyl (Cp), indenyl (ind), fluorenyl (flu),
4,5-dihydrocyclopentaphenathryl (H.sub.2CPA), and
cyclopentaphenanthryl (CPA) ring groups, wherein, the ring groups
can be substituted by groups selected from the class consisting of
i) C.sub.1-C.sub.4 straight-chain or branched alkyl, ii)
C.sub.6-C.sub.20 aryl, iii) C.sub.7-C.sub.20 alkylaryl, iv)
C.sub.4-C.sub.7 cycloalkyl, v) (--CH.sub.2--).sub.n wherein n=3, 4,
or 5, or (--CH.dbd.CH--).sub.m wherein m is 1, 2, 3, or 4,
connecting adjacent or non-adjacent ring carbon atoms in the same
ring structure, vi) fused aromatic rings, and vii) fused aromatic
rings substituted by any one of groups i)-iv); bridge is a linking
group joining ligand 1 and ligand2 at C-1 position of Cp and ind
ligands or C-9 position of flu and CPA ligands and is selected from
the group consisting of i) >CR.sup.1R.sup.2 ii)
>SiR.sup.1R.sup.2 iii) --CR.sup.1R.sup.2--CR.sup.3R.sup.4--iv)
--SiR.sup.1R.sup.2--SiR.sup.3R.su- p.4--v)
--CR.sup.1R.sup.2--SiR.sup.3R.sup.4--vi) --SiR.sup.1R.sup.2--CR.su-
p.3R.sup.4--, wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4 can be
the same or different and are selected from the group consisting of
H, C.sub.1-C.sub.20 straight-chain or branched alkyl,
C.sub.6-C.sub.20 aryl, and C.sub.3-C.sub.8 cycloalkyl; M is a metal
atom selected from the group consisting of Zr, Hf, and Ti,
preferably is zirconium, and X is selected from the group
consisting of Cl, Br, I, C.sub.1-C.sub.20 straight-chain or
branched alkyl, C.sub.6-C.sub.20 aryl, C.sub.7-C.sub.20 alkaryl,
and C.sub.7-C.sub.20 aralkyl.
6. The polypropylene polymer according to claim 1 having an rr
triad content in the range of 29% to 73%.
7. The polymer according to claim 1 having an S.I. index in the
range of 1.30 to 10.00.
8. The polymer according to claim 1 having an S.I. index in the
range of 1.30 to 7.00.
9. The polymer according to claim 1 further comprising rr and mm
sequences wherein the % rr sequences>% mm sequences.
10. A blend of polymers comprising one or more propylene polymers
according to claim 1.
11. The blend according to claim 8 comprising one or more propylene
polymers and at least one polymer selected from the group
consisting of crystalline propylene having a melting point greater
than 100.degree. C., polyhexene, and polyoctene.
12. The composition according to claim 1 comprising one or more
propylene polymers and tackifying resin.
13. The composition according to claim 1 comprising one or more
propylene polymers and an antioxidant.
14. The composition according to claim 13 further comprising a
tackifying resin.
15. A method of controlling the stereostructure of polypropylene in
accordance with claim 1, said polypropylene having a
steroregularity index (S.I.) in the range of 1.30 and 10.00,
comprising the step of: polymerizing propylene in the presence of a
metallocene catalyst and an activating cocatalyst, said metallocene
having the formula {ligand1-bridge-ligand2}MX.sub.2 wherein ligand1
and ligand2 are different and are selected from the group
consisting of cyclopentadienyl (Cp), indenyl (ind), fluorenyl
(flu), 4,5-dihydrocyclopentaphenanthryl, and cyclopentaphenanthryl
(CPA) ring groups, wherein, the ring groups can be substituted by
groups selected from the class consisting of i) C.sub.1-C.sub.4
straight-chain or branched alkyl, ii) C.sub.6-C.sub.20 aryl, iii)
C.sub.7-C.sub.20 alkylaryl, iv) C.sub.4-C.sub.7 cycloalkyl v)
(--CH.sub.2--).sub.n or (--CH.dbd.CH--).sub.m connecting adjacent
or non-adjacent ring carbon atoms in the same ring structure,
wherein n is 3, 4, or 5, and m is 1, 2, 3, or 4, vi) fused aromatic
rings, and vii) fused aromatic rings substituted by any one of
groups i)-iv); bridge is a linking group joining ligand 1 and
ligand2 at C-1 position of Cp and ind ligands or C-9 position of
flu and CPA ligands and is selected from the group consisting of i)
>CR.sup.1R.sup.2 ii) >SiR.sup.1R.sup.2 iii)
--CR.sup.1R.sup.2--CR.sup.3R.sup.4--iv)
--SiR.sup.1R.sup.2--SiR.sup.3R.su- p.4--v)
--CR.sup.1R.sup.2--SiR.sup.3R.sup.4--vi) --SiR.sup.1R.sup.2--CR.su-
p.3R.sup.4--, wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4 can be
the same or different and are selected from the group consisting of
H, C.sub.1-C.sub.20 straight-chain or branched alkyl,
C.sub.6-C.sub.20 aryl, and C.sub.3-C.sub.8 cycloalkyl; M is a metal
atom selected from the group consisting of Zr, Hf, and Ti,
preferably is zirconium, and X is selected from the group
consisting of Cl, Br, I, C.sub.1-C.sub.20 straight-chain or
branched alkyl, C.sub.1-C.sub.20 straight-chain or branched
oxyalkyl, C.sub.6-C.sub.20 aryl, C.sub.7-C.sub.20 alkylaryl, and
C.sub.7-C.sub.20 arylalkyl. said catalyst having an asymmetry
parameter in the range of 1.03 and 1.69, wherein the
stereoregularity index of said polypropylene increases with an
increase in asymmetry parameter of said catalyst.
16. The method according to claim 15 wherein said propylene is
polymerized in the presence of an olefin comonomer having 2 to 20
carbon atoms.
17. A metallocene catalyst and an activating cocatalyst for olefin
polymerization, said metallocene having the structure
{ligand1-bridge-ligand2}MX.sub.2, wherein ligand1 and ligand2 are
different and are selected from the group consisting of substituted
and unsubstituted cyclopentadienyl, indenyl, fluorenyl, and
cyclopentaphenanthryl ring groups, wherein, when present, ring
group substituents are selected from the group consisting of i)
C.sub.1-C.sub.4 straight-chain or branched alkyl, ii)
C.sub.6-C.sub.20 aryl, iii) C.sub.7-C.sub.20 alkylaryl, iv)
C.sub.4-C.sub.7 cycloalkyl v) (--CH.sub.2--).sub.n or
(--CH.dbd.CH--).sub.m connecting adjacent or non-adjacent ring
carbon atoms in the same ring structure, wherein n is 3, 4, or 5,
or m=1, 2, 3, or 4, vi) fused aromatic rings, and vii) fused
aromatic rings substituted by any one of groups i)-v); bridge is
selected from the group consisting of i) >CR.sup.1R.sup.2 ii)
>SiR.sup.1R.sup.2 iii) --CR.sup.1R.sup.2--CR.sup.3R.sup.4--iv)
--SiR.sup.1R.sup.2--SiR.sup.3R.sup.4--v)
--CR.sup.1R.sup.2--SiR.sup.3R.su- p.4--vi)
--SiR.sup.1R.sup.2--CR.sup.3R.sup.4--, wherein R.sup.1, R.sup.2,
R.sup.3, and R.sup.4 can be the same or different and are selected
from the group consisting of H, C.sub.1-C.sub.20 straight-chain or
branched alkyl, C.sub.6-C.sub.20 aryl, and C.sub.3-C.sub.8
cycloalkyl; M is a metal atom selected from the group consisting of
Zr, Hf, and Ti, and X is selected from the group consisting of Cl,
Br, I, C.sub.1-C.sub.20 straight-chain or branched alkyl,
C.sub.6-C.sub.20 aryl, C.sub.7-C.sub.20 alkylaryl, and
C.sub.7-C.sub.20 arylalkyl, wherein the metallocene catalyst
exhibits an asymmetry parameter of 1.30 to 1.69, with the proviso
that when M=Zr, and bridge=C.sub.2H.sub.4, then component (v) is
(--CH.sub.2--).sub.n or (--CH.dbd.CH).sub.m', wherein n=3, 4, or 5
and m' is 2, 3 or 4.
18. The metallocene catalyst and activating cocatalyst according to
claim 17 which provides propylene polymers according to claim
1.
19. The metallocene catalyst and activating cocatalyst according to
claim 17 wherein at least one of ligand 1 and ligand 2 comprises a
4,5-H-dihydrocyclopentaphenanthrene which includes a fluorenyl
group.
20. The metallocene catalyst and activating cocatalyst according to
claim 17 wherein bridge is 8and wherein R.sup.1and R.sup.2 are
selected from the group consisting of phenyl and methyl.
21. The metallocene catalyst and activating cocatalyst according to
claim 17 wherein bridge is 9and wherein Me=methyl.
22. The metallocene catalyst and activating cocatalyst according to
claim 17 wherein M=Zr.
23. The metallocene catalyst and activating cocatalyst according to
claim 22 wherein when X=an alkyl or aralkyl group, and said
activator cocatalyst is a (C.sub.6H.sub.5).sub.3C(+) salt of a
noncoordinating anion or an onium compound having the formula
R.sub.1R.sub.2R.sub.3QH(+) wherein Q=N or P and R.sub.1, R.sub.2,
R.sub.3 are as previously defined.
24. The metallocene catalyst according to claim 22 wherein
X=halogen, said activating cocatalyst is an aluminoxane
compound.
25. The metallocene catalyst according to claim 22 selected from
the group consisting of
{flu-C.sub.2H.sub.4-2-methyl-4,5-benzindenyl}ZrCl.sub.2
{flu-SiMe.sub.2-CPA}ZrCl.sub.2 {flu-SiPh.sub.2-CPA}ZrCl.sub.2
{flu-C.sub.2H.sub.4--H.sub.2CPA}ZrCl.sub.2
{flu-SiMe.sub.2--H.sub.2CPA}Zr- Cl.sub.2
{flu-SiPh.sub.2--H.sub.2CPA}ZrCl.sub.2 {perhydrocylopentaphenanth-
ryl-C.sub.2H.sub.4-perhydrofluorenyl}ZrCl.sub.2, wherein
CPA=4H-cyclopentaphenanthryl,
H.sub.2CPA=4,5-dihydrocyclopentaphenanthryl- , flu=fluorenyl,
Me=methyl, and Ph=phenyl.
26. A composition of matter having a formula selected from the
group consisting of H{flu-C.sub.2H.sub.4--H.sub.2CPA}H
H{flu-C.sub.2H4-2-CH.sub- .3-4,5-benzindene}H H{flu-SiR.sub.2-CPA}H
H{flu-SiR.sub.2--H.sub.2CPA}H wherein R is a methyl or phenyl
group.
27. A method of making chemical compounds having the formula
H{ligand1-CH.sub.2CH.sub.2-ligand2}H wherein ligand1 and ligand2
are different and are selected from the group consisting of
substituted and unsubstituted cyclopentadienyl, indenyl, fluorenyl,
and cyclopentaphenanthrene ring groups, wherein, when present, ring
group substituents are selected from the group consisting of i)
C.sub.1-C.sub.4 straight-chain or branched alkyl, ii)
C.sub.6-C.sub.20 aryl, iii) C.sub.7-C.sub.20 alkylaryl, iv)
C.sub.4-C.sub.7 cycloalkyl v) (--CH.sub.2--).sub.n or
(--CH.dbd.CH--).sub.m connecting to adjacent or non-adjacent ring
carbon atoms in the same ring structure, wherein n is 3, 4, or 5,
and m=1, 2, 3, or 4, vi) fused aromatic rings, and vii) fused
aromatic rings substituted by any one of groups i)-v), comprising
the steps: 1) deprotonating the hydroxyl group of a compound of the
type H{ligand1-CH.sub.2CH.sub.2OH}; 2) reacting the deprotonated
compound with highly fluorinated alkyl sulfonyl fluoride to obtain
a highly fluorinated alkyl sulfonate of the type
H{ligand1-CH.sub.2CH.sub.2--OSO.sub.2R.sub.f}- ; wherein R.sub.f is
a straight chain, branched, or cyclic alkyl group containing 1 to
20 carbon atoms and optionally O, N, or S heteroatoms, with more
than 50% of the H atoms being replaced by fluorine atoms; 3)
condensing the trifluoromethanesulfonate with the conjugate base of
a compound of the type ligand2-H.
28. The method according to claim 27 wherein R.sub.f is a
perfluorinated alkyl group.
29. The method according to claim 27 wherein said catalyst is
{flu-C.sub.2H.sub.4-ind}ZrCl.sub.2.
30. A method of producing polypropylene in the presence of a
metallocene catalyst and an activating cocatalyst, said
metallocene, comprising contacting propylene with a catalyst having
the structure {ligand1-bridge-ligand2}MX.sub.2, wherein ligand1 and
ligand2 are different and are selected from the group consisting of
substituted and unsubstituted cyclopentadienyl, indenyl, fluorenyl,
and cyclopentaphenanthrene ring groups, wherein, when present, ring
group substituents are selected from the group consisting of i)
C.sub.1-C.sub.4 straight-chain or branched alkyl, ii)
C.sub.6-C.sub.20 aryl, iii) C.sub.7-C.sub.20 alkylaryl, iv)
C.sub.4-C.sub.7 cycloalkyl v) (--CH.sub.2--).sub.n or
(--CH.dbd.CH--).sub.m connecting adjacent or non-adjacent ring
carbon atoms in the same ring structure, wherein n is 3, 4, or 5,
and m=1, 2, 3, or 4, vi) fused aromatic rings, and vii) fused
aromatic rings substituted by any one of groups i)-v); bridge is
selected from the group consisting of i) >CR.sup.1R.sup.2 ii)
>SiR.sup.1R.sup.2 iii) --CR.sup.1R.sup.2--CR.sup.3R.sup.4--iv)
--SiR.sup.1R.sup.2--SiR.sup.3R.sup.4--v)
--CR.sup.1R.sup.2--SiR.sup.3R.su- p.4--vi)
--SiR.sup.1R.sup.2--CR.sup.3R.sup.4--, wherein R.sup.1, R.sup.2,
R.sup.3, and R.sup.4 can be the same or different and are selected
from the group consisting of H, C.sub.1-C.sub.20 straight-chain or
branched alkyl, C.sub.6-C.sub.20 aryl, and C.sub.3-C.sub.8
cycloalkyl; M is a metal atom selected from the group consisting of
Zr, Hf, and Ti, and X is selected from the group consisting of Cl,
Br, I, C.sub.1-C.sub.20 straight-chain or branched alkyl,
C.sub.6-C.sub.20 aryl, C.sub.7-C.sub.20 alkylaryl, and
C.sub.7-C.sub.20 arylalkyl, wherein the metallocene catalyst
exhibits an asymmetry parameter of 1.03 to 1.69.
31. The method according to claim 30 wherein said catalyst is
{ind-C.sub.2H.sub.4-flu}ZrCl.sub.2 and said polypropylene polymer
is elastomeric.
32. The method according to claim 30 further comprising the step of
adding hydrogen gas to modify the product molecular weight.
33. The method according to claim 30 wherein said polypropylene is
polymerized in the presence of an olefin comonomer having 2 to 20
carbon atoms.
34. The article according to claim 33 comprising a pressure
sensitive adhesive.
35. The polypropylene according to claim 1 wherein the storage
modulus vs. temperature up to 175.degree. C. produces a tracing
that is essentially flat.
36. The polypropylene according to claim 35 wherein elongation
without break exceeds 4,000%.
37. A propylene copolymer, said copolymer being elastomeric and
being soluble in at least one nonpolar organic solvent selected
from the group consisting of toluene, xylene, heptane, and hexane,
said polymer comprising a) greater than 3 weight percent and up to
45 weight percent homotactic sequences each having only r or m
diads, all of which homotactic sequences have a helical length in
the range of 20 to 150 .ANG., and b) in the range of 55 to 97
weight percent of the total composition being the sum of 1)
homotactic sequences, each having only r or m diads, and being less
than 20 .ANG. in helical length, and 2) heterotactic sequences
having unequal numbers of r and m diads, said polymer having a
molecular weight (M.sub.w) of at least 35,000.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a novel class of polypropylenes
that possess elastic character and are hybrid polymers having
stereregularity intermediate between those that are highly
syndiotactic (or highly isotactic) and those that are atactic, as
well as catalysts that produce these hybrid polymers.
BACKGROUND OF THE INVENTION
[0002] Elastic polypropylene was first isolated by solvent
extraction of polypropylene obtained by Ziegler-Natta
polymerization of propylene (inter alia, U.S. Pat. No. 3,175,999).
A process for preparing primarily isotactic, fractionable,
elastomeric polyolefins has been described (U.S. Pat. No.
4,335,225), using a catalyst prepared by reacting a solid support
such as alumina with, e.g., a tetraalkylzirconium compound. U.S.
Pat. No. 5,594,080 discloses preparation of a stereoblock
elastomeric polypropylene using a metallocene catalyst containing
two unbridged phenylindenyl ligands connected to zirconium, i.e.
(phenylindenyl).sub.2ZrCl.sub.2. Chien et al. (J. Am. Chem. Soc.,
112, 2030 (1990); Macromolecules, 25, 1242 (1992); Macromolecules,
24, 850 (1991)) prepared a thermoplastic, elastomeric polypropylene
containing about 30% crystalline isotactic polypropylene, using a
metallocene catalyst.
[0003] Collins et al. (Macromolecules, 28, 3771 (1995); Macromol.
Symp., 98, 223 (1995)) describe the use of zirconium and hafnium
metallocene catalysts to prepare elastic polypropylene. These
polymers had 29-54% mmmm pentads, i.e. they were predominantly
isotactic. Significantly, elastic polypropylene could only be
obtained when the molecular weight was greater than 50,000 and when
the mmmm content of the polymer exceeded 38%, using exclusively
hafnium complexes.
[0004] European Patent Application No. 666,267 describes the use of
a metallocene catalyst of the type
{fluorenyl-C.sub.2H.sub.4-indenyl}ZrCl.s- ub.2 to prepare
polypropylene in the presence of hydrogen. Polymer properties are
not described. The same catalyst was used (Organometallics, 13, 647
(1994)) to polymerize propylene in toluene in the absence of
hydrogen; highly isotactic polymers having mmmm contents ranging
from 38 to 64% and melting points of 104-110.degree. C. were
obtained. When the C.sub.2H.sub.4 bridging group was replaced by
--SiMe.sub.2-- (U.S. Pat. No. 5,391,789), only a viscous, tacky oil
was obtained.
[0005] European Patent Application No. EP 707,016 describes a
catalyst system comprising
{2-Me-4-naphthyl-indenyl-SiMe.sub.2-fluorenyl}ZrCl.sub.- 2, a Lewis
acid compound and an organoaluminum compound, to prepare
elastomeric polypropylene. U.S. Pat. No. 5,516,848 describes a
process for making elastomeric polypropylenes employing a mixture
of two different metallocene catalysts, one of which was a
monocyclopentadienyl transition metal compound.
[0006] Metallocene catalysts generally can be defined as catalysts
comprising one or more cyclopentadienyl groups, including
substituted cyclopentadienyl groups, in combination with a
transition metal, typically a metal of Group IVB of the Periodic
Chart (i.e., titanium, zirconium, and hafnium). Useful metallocenes
have been described comprising two cyclopentadienyl-type rings, in
which both rings are identical (symmetrical metallocenes) and in
which the two rings are different, due either to differing
substitution patterns on identical ring systems or to the presence
of two different ring systems (unsymmetrical metallocenes). The
first reports of the use of cyclopentadienyl metallocenes to
catalyze the polymerization of 1-olefins appeared in 1957. British
Patent Application GB 934,281 first described metallocene catalysts
of the type (R-indenyl).sub.2MX.sub.2 and
(R-fluorenyl).sub.2MX.sub.2, where R represents an alkyl or aryl
substitutent on the aromatic ring, M represents titanium, zirconium
or hafnium, and X represents a halide or an alkyl or alkoxy group,
or the like, having from 1 to 12 carbon atoms. Since then, numerous
patents and other publications have provided ample evidence of the
commercial interest in these materials.
[0007] Four limiting cases illustrate the possibilities for
stereoregularity in polypropylene. The isotactic structure is
typically described as having the methyl side groups oriented so
that they are all on the same side of the plane containing the
polymer backbone. Another way of describing the isotactic structure
employs Bovey's NMR (nuclear magnetic resonance) nomenclature: An
isotactic diad, represented by m (for meso), is a pair of propylene
units placed in the polymer chain so that both methyl side groups
lie on the same side of the plane containing the polymer backbone.
Similarly, a mmmm pentad represents five monomer units with their
methyl groups all oriented the same way. .sup.13C NMR can be used
to determine the relative amounts of the various pentads present in
a propylene polymer.
[0008] In contrast, in the syndiotactic structure, the methyl
groups are oriented alternately above and below the plane
containing the polymer backbone. A pair of propylene units with
this up-down arrangement comprises an r (for racemic) diad, and
rrrr would correspond to five similarly arranged monomer units.
[0009] Hemi-isotactic polypropylene is similar to the isotactic
kind except that every other methyl side group has a random
orientation.
[0010] Finally, in the atactic polymer, the orientation of the
methyl groups with respect to the plane containing the polymer
backbone is random and the number of r and m diads is the same.
[0011] The physical properties of polypropylene depend greatly on
polymer stereoregularity. For example, isotactic and syndiotactic
polypropylene are crystalline polymers that are insoluble in
hydrocarbon solvents such as cold xylene. Because of the presence
of crystallites that scatter light, they are often opaque or
translucent. Additionally, these polymers are stiff, inelastic, and
high-melting, their melting points being 171 and 138.degree. C.,
respectively.
[0012] In contrast, hemi-isotactic and atactic polymers are
non-crystalline and soluble in cold xylene. Atactic polypropylene
is transparent, flexible and elastomeric.
[0013] Because isotactic and syndiotactic polypropylenes are such
useful materials, their preparation has been the object of
extensive research. For example, catalysts that produce isotactic
polypropylene are disclosed in U.S. Pat. Nos. 4,794,096 and
4,975,403; catalysts that lead to syndiotactic polyolefins are
described in U.S. Pat. Nos. 3,258,455, 3,305,538, 3,364,190,
4,892,851, 5,155,080 and 5,225,500.
[0014] The precise effect of changes in catalyst structure on
catalyst activity and polymer stereoregularity is difficult to
predict. For example, U.S. Pat. No. 5,459,218 describes catalysts
of the type {flu-bridge-Cp}ZrCl.sub.2, wherein flu=fluorenyl,
bridge=Me.sub.2Si or Ph.sub.2Si, and wherein Me=methyl, Ph=phenyl,
and Cp=cyclopentadienyl. It is broadly stated and claimed that the
propylene polymers contain at least 50% rr content, whereas the
syndiotactic content actually achieved ranged from 74 to 82%. The
highest molecular weight given for the propylene polymers is
66,000. No unusual properties of these polymers were disclosed nor
were any clues provided as to how the catalysts could be modified
to produce polymers having a lesser or greater syndiotactic
content. By comparison, U.S. Pat. No. 4,892,851 describes a
catalyst of a very similar type, namely
{flu-CMe.sub.2-Cp}ZrCl.sub.2, which is reported to produce even
more highly syndiotactic (92% rr) polypropylene.
[0015] A relationship between catalyst symmetry and polypropylene
stereostructure has been proposed (Trends in Polymer Science, 2,
158 (1994)). Symmetry elements, typically described in terms of
"point groups" of a bis(fluorenyl)MX.sub.2-type catalyst are shown
in FIGS. 1 and 2 (comparative). FIG. 1 illustrates the different
symmetry elements that can occur in metallocene catalysts and FIG.
2 provides illustrative examples. A catalyst (FIG. 1 and, e.g.,
FIG. 2 entry 20) having point group C.sub.2v has three symmetry
elements: the structure is unchanged after a 180 degree rotation
about the bisector of the MX.sub.2 plane and there are two mirror
planes of symmetry, reflections in which leave the structure
unchanged. One contains the MX.sub.2 plane .sigma..sub.h and the
other is orthogonal to and bisects the MX.sub.2 plane
.sigma..sub.v. Looking straight on at the MX.sub.2 plane, one sees
that the top and bottom as well as the left and right hand side of
the catalyst molecule are the same. A catalyst 21 having point
group C.sub.2 (entry 21 in FIG. 2) contains only a C.sub.2 axis:
the top and bottom of the molecule are the same, so that 180 degree
rotation about the bisector of the MX.sub.2 plane leaves the
structure unchanged. Catalyst 22 having point group C.sub.S
contains only a mirror plane of symmetry orthogonal to and
bisecting the MX.sub.2 plane. Viewed as described above, the left-
and right hand sides of the catalyst are the same but the top and
bottom are different. Catalyst 25 of C.sub.1 point group symmetry
contain none of these three symmetry elements.
[0016] According to FIG. 2, catalysts of point group C.sub.2v are
said to produce atactic polypropylene, except that
Cp.sub.2TiPh.sub.2 (24) atypically produces a stereoblock isotactic
polymer (perhaps by a different polymerization mechanism) at low
temperatures. Metallocenes having C.sub.2 and C.sub.S point group
symmetry are said to produce isotactic and syndiotactic polymers,
respectively. However, U.S. Pat. No. 4,769,510 describes catalysts
of the type {ind-bridge-ind}MX.sub.2, which exists in two isomeric
forms. One form is chiral and consists of a d,l pair of
enantiomers; it produces isotactic polypropylene. The second (meso)
form is achiral and produces atactic polypropylene
(Organometallics, 14, 1256 (1995)). Catalysts with C.sub.1 symmetry
are said to produce either hemi-isotactic 23 (in FIG. 2) or
stereoblock isotactic-atactic 25 (in FIG. 2) polypropylene.
[0017] European Patent Application No. 537,130 describes the effect
of the size of an organic group attached to a cyclopentadienyl ring
in metallocenes of the type {Cp-CMe.sub.2-flu}ZrCl.sub.2 (C.sub.s
point group symmetry), which was shown to produce syndiotactic
polypropylene. Introduction of a methyl group into the 3-position
of the cyclopentadienyl ring led to
{3-MeCp-CMe.sub.2-flu}ZrCl.sub.2 (C.sub.1 point group symmetry),
which produced a hemi-isotactic polymer. When the 3-CH.sub.3 group
was replaced by a t-butyl group to form
{3-t-BuCp-CMe.sub.2-flu}ZrCl.sub.2 (also C.sub.1 point group),
isotactic polypropylene was obtained instead.
[0018] U.S. Pat. No. 5,459,218 relates to syndiotactic
polypropylene prepared using silyl bridged metallocenes and having
molecular weights up to 66,000. U.S. Pat. No. 5,668,230 discloses
certain specific ethylene bridged fluorenyl-containing metallocenes
to catalyze olefins polymerization.
[0019] One skilled in the art can only conclude that there are no
reliable, general correlations between the structure of a
metallocene catalyst and the stereospecificity or the
stereoregularity of polymers produced thereby.
SUMMARY OF THE INVENTION
[0020] Briefly, the present invention provides propylene
homopolymers that are elastomeric and are soluble in at least one
nonpolar organic solvent selected from the group consisting of
toluene, xylene, heptane, and hexane, the polymer comprising
[0021] a) greater than 3 weight percent and up to 45 weight percent
of homotactic sequences, each having only r or m diads, all of
which homotactic sequences have a helical length in the range of
about 20 to 150 .ANG., and
[0022] b) in the range of 55 to 97 weight percent of the total
composition being the sum of
[0023] 1) homotactic sequences, each having only r or m diads, and
being less than 20 .ANG. in helical length and having fewer than 10
repeat units with mmmm pentads being present in the range of 0 to
35 (preferably 0 to 31) weight percent of the total composition,
and
[0024] 2) heterotactic sequences having unequal numbers of r and m
diads,
[0025] the polymer having a weight average molecular weight
(M.sub.w) of at least about 70,000, preferably greater than 70,000
and up to 2,000,000, more preferably 75,000 to 1,000,000, and most
preferably 80,000 to 500,000. The two b) components can be present
in any amount so long as their sum amounts to 55 to 97 weight
percent of the total composition.
[0026] The propylenes of the invention include homotactic sequences
of length as specified above having all r or all m diads. As is
appreciated by those skilled in the art, these homotactic sequences
can assume a helical configuration. Connecting these homotactic
sequences are similar homotactic sequences of less than 20 .ANG. in
helical length and having less than 10 repeat units as well as
heterotactic sequences having both r and m diads present in unequal
numbers. These polymers exhibit elastomeric character that varies
from a stiff rubber to that of a very stretchy rubber band. The
homotactic sequences can be all r or all m and preferably they are
all r, i.e., syndiotactic. In general, the polymers comprise
discontinuous small (20 .ANG. to 150 .ANG. in length) hard segments
in a continuous softer matrix.
[0027] The length of the homotactic sequences can be estimated in
the following way. Helical chains of polypropylene run
approximately parallel to the c-axis of the unit cell of
orthorhombic syndiotactic polypropylene. Four monomer units are
contained in the unit cell which is 7.6 .ANG. long. Therefore, each
molecule of propylene contributes 7.6/4 or 1.9 .ANG. to the chain
length. This is a reasonable estimate because if the chain were
fully extended, each propylene would contribute the distance of two
C--C bonds or 3 .ANG. to the chain length.
[0028] The heterotactic sequences comprise both r and m diads and
are of variable lengths and are randomly dispersed as to size and
distribution in the polymer chain.
[0029] Preferably, the propylene polymers of the invention also
have one or more of the following characteristics:
[0030] i) a stereoregularity index between 1.30 and 10.0,
preferably 1.30 to 7.00 and more preferably 1.60 to 6.40.
[0031] ii) a heat of fusion (.DELTA.H.sub.fus) that is less than
50% of the .DELTA.H.sub.fus of 100% isotactic polypropylene when
mm>rr; or less than 50% of the .DELTA.H.sub.fus of 100%
syndiotactic polypropylene when rr>mm, (.DELTA.H.sub.fus values
are as given in J. Brandrup et al., POLYMER HANDBOOK, 3d Edition,
John Wiley & Sons, NY (1989), section V, p. 29); and
[0032] iii) optical clarity.
[0033] In another aspect, this invention provides blends of two or
more different propylene polymers, at least one of which exhibits
the properties described above. Blends of one or more propylene
polymers as described above can further comprise crystalline or
amorphous polypropylene, tackifying resins, antioxidants, fillers,
and other adjuvants known in the art.
[0034] In yet another aspect, this invention provides copolymers of
propylene wherein the propylene sequences are as defined above, and
wherein the comonomers can be olefins having 2 to 20, preferably 2
to 8, carbon atoms. Copolymers can be blended with one another as
well as with homopolymers which provides a way to tailor or modify
polypropylene properties. Molecular weight of copolymers (M.sub.w)
can be in the range of 35,000 to 2,000,000, preferably 50,000 to
1,000,000, more preferably 70,000 to 500,000.
[0035] In a further aspect, this invention provides metallocene
catalysts for propylene polymerization, having the structure
{ligand1-bridge-ligand2}MX.sub.2,
[0036] wherein
[0037] ligand1 and ligand2 are different and are selected from the
group consisting of substituted and unsubstituted cyclopentadienyl
(Cp), indenyl (ind), fluorenyl (flu),
4,5-dihydrocyclopentaphenanthryl (H.sub.2CPA), and
cyclopentaphenanthryl (CPA) ring groups, wherein, when present,
ring group substituents can be selected from the group consisting
of
[0038] i) C.sub.1-C.sub.4 straight-chain or branched alkyl,
[0039] ii) C.sub.6-C.sub.20 aryl,
[0040] iii) C.sub.7-C.sub.20 alkylaryl,
[0041] iv) C.sub.4-C.sub.7 cycloalkyl,
[0042] v) (--CH.sub.2--).sub.n, wherein n is 2, 3, 4, or 5, or
(--CH.dbd.CH--).sub.m wherein m is 1, 2, 3, or 4, connecting two
positions (i.e., adjacent or non-adjacent ring carbon atoms) in the
same ring structure, preferably the 4 and 5 positions in fluorenyl
or indenyl,
[0043] vi) fused aromatic rings, and
[0044] vii) fused aromatic rings substituted by any one of groups
i)-v);
[0045] bridge is a linking group joining ligand1 and ligand2 at C-1
of Cp or ind ligands or C-9 of flu and CPA ligands and is selected
from the group consisting of
[0046] i) >CR.sup.1R.sup.2,
[0047] ii) >SiR.sup.1R.sup.2,
[0048] iii) --CR.sup.1R.sup.2--CR.sup.3R.sup.4--,
[0049] iv) --SiR.sup.1R.sup.2--SiR.sup.3R.sup.4--,
[0050] v) --CR.sup.1R.sup.2--SiR.sup.3R.sup.4--,
[0051] wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4 can be the
same or different and are selected from the group consisting of H,
C.sub.1-C.sub.20 straight-chain or branched alkyl groups,
C.sub.6-C.sub.20 aryl groups, and C.sub.3-C.sub.8 cycloalkyl
groups;
[0052] M is a metal atom selected from the group consisting of Zr,
Hf, and Ti, preferably is zirconium or hafnium, and most preferably
zirconium, and
[0053] X is selected from the group consisting of Cl, Br, I,
C.sub.1-C.sub.20 straight-chain or branched alkyl groups,
C.sub.6-C.sub.20 aryl groups, C.sub.7-C.sub.20 alkaryl groups, and
C.sub.7-C.sub.20 aralkyl groups,
[0054] wherein the metallocene catalyst exhibits an asymmetry
parameter of 1.03 to 1.69, preferably 1.03 to 1.45, more preferably
1.05 to 1.35,
[0055] with the proviso that the metallocene catalyst provides
propylene polymers described above.
[0056] In a still further aspect, this invention also provides a
method of making novel catalyst precursor compounds of the type
H{ligand1-CH.sub.2CH.sub.2-ligand2}H
[0057] wherein ligand1 and ligand2 are as previously defined,
[0058] the method comprising the steps:
[0059] 1) deprotonating the hydroxyl group of a compound of the
type
ligand1-CH.sub.2CH.sub.2OH;
[0060] 2) reacting the deprotonated compound with a
perfluoroalkylsulfonyl fluoride of the type R.sub.fSO.sub.2F to
obtain a stable perfluoroalkylsulfonate of the type
ligand1-CH.sub.2CH.sub.2--OSO.sub.2R.sub.f;
[0061] wherein R.sub.f means an alkyl group having 1-20 carbon
atoms or an aryl group having 5 to 12 carbon atoms in which at
least 75% of H atoms have been replaced by F atoms;
[0062] 3) condensing the perfluoroalkylsulfonate with the conjugate
base of a compound of the type
ligand2-H;
[0063] wherein ligand1 and ligand2 are as previously defined and
R.sub.f is independently selected from the group consisting of
highly fluorinated or perfluorinated alkyl radicals containing from
1-20 carbon atoms.
[0064] In yet a further aspect, there is provided a novel class of
metallocene catalysts that are particularly useful to prepare
hybrid polymers of the present invention, i.e. those having
intermediate stereoregularity between those that are highly
syndiotatic (or highly isotactic) and those that are atactic, the
novel catalysts of the present invention having the formula: 1
[0065] wherein
[0066] strap can be a (--CH.sub.2--)n group or a
(--CH.dbd.CH--).sub.m group,
[0067] bridge is as previously defined,
[0068] M.sup.a is Zr or Hf,
[0069] n is 1, 2, 3, or 4 and m is 1, 2, 3, or 4, and
[0070] X is as previously defined,
[0071] with the proviso that when M.sup.a=Zr, X=Cl, and
bridge=C.sub.2H.sub.4, then strap can (--CH.sub.2--)n or
(--CH.dbd.CH--).sub.m, wherein n=3, 4 or 5, and m=2, 3, or 4,
preferably m is 2, 3, or 4 and can be designated m'.
[0072] In yet another aspect, this invention also provides a method
of controlling the stereostructure of polypropylene by choosing the
shape of a metallocene catalyst, as defined by its asymmetry
parameter, from the class of catalysts having the structure
{ligand1-bridge-ligand2}MX.sub.2,
[0073] wherein
[0074] ligand1 and ligand2, bridge, M, and X are as previously
defined, and wherein the metallocene catalyst exhibits an asymmetry
parameter of 1.03 to 1.69, and the stereoregularity index of said
polypropylene increases from about 1.30 to about 10.00 with an
increase in the asymmetry parameter of the catalyst.
[0075] Preparation of the hybrid polypropylenes of the invention is
accomplished by combining propylene with a metallocene catalyst,
preferably in the absence of solvent for the monomer, in an inert
atmosphere at a pressure in the range of 69 to 6890 Kpa at a
temperature in the range of -20.degree. C. to about 120.degree. C.
When a solvent is used, it can be a hydrocarbon, preferably
aliphatic, cycloaliphatic, or aromatic, more preferably it is
toluene or cyclohexane. Activation of the metallocene is
accomplished by activators known in the art, preferably
methylaluminoxane alone or in combination with trialkylaluminum
compounds such as trimethylaluminum, triethylaluminum, or
triisobutylaluminum.
[0076] As used herein:
[0077] "asymmetry parameter (A.P.)" is defined as the ratio of the
van der Waals surface area of the larger ligand to that of the
smaller ligand, wherein the van der Waals surface area can be
calculated by CAChe.TM. Satellite molecular modeling program
(version 3.8) (Oxford Molecular Ltd., Oxford, United Kingdom) on a
Macintosh computer; this is a measure of the asymmetric character
of a molecule;
[0078] "atactic" means "polypropylene having no dominant tacticity
and having 25% mm triads and 25% rr triads, as determined by NMR
spectroscopy;
[0079] "Cp or cp" means cyclopentadienyl;
[0080] "CPA" means cyclopentaphenanthryl;
[0081] "elastomeric" or "elastic" means a material that at room
temperature can be stretched repeatedly to at least twice its
original length and, immediately upon release of the stress,
returns with force to its approximate original length;
[0082] "entanglement molecular weight ({overscore (M)}.sub.e)"
means average molecular weight of chains between entanglements in a
polymer;
[0083] "film" means a self-supporting layer;
[0084] "flu" means fluorenyl;
[0085] "group" or "radical" or "compound" or "ligand" or "monomer"
or "polymer" means a chemical species that allows for substitution
or which may be substituted by conventional substituents which do
not interfere with the desired product; e.g., substituents can be
alkyl, aryl, phenyl, etc.; and
[0086] "H.sub.2CPA" means 4,5-dihydrocyclopentaphenanthryl;
[0087] "helical length" means the length of a segment in a coiled
configuration in contrast to the filly extended polymer
segment;
[0088] "heterotactic" sequences are those having both r or m
diads;
[0089] "highly fluorinated" (R.sub.f) means having at least 75% of
H atoms in an alkyl cycloalkyl, or aryl group substituted by
fluorine atoms;
[0090] "highly isotactic" means polypropylene having an mm content
of at least 80%, as determined by NMR spectroscopy;
[0091] "highly syndiotactic" means polypropylene having an rr
content of at least 80%, as determined by NMR spectroscopy;
[0092] "homotactic" sequences are those having diads which are all
r or all m.
[0093] "ind" means indenyl;
[0094] "isotactic" or "isotactic-rich" means polypropylene having
tacticity shown in FIG. 2 (second entry) and having an mm content
of greater than the rr triad content, as determined by NMR
spectroscopy;
[0095] "Me" means methyl;
[0096] "metallocene" means a metal-organic compound characterized
by .pi.-bonds between a transition metal and a cyclopentadienyl,
indenyl, or fluorenyl ligand, or such substituted ligands;
[0097] "mm triads" refers to an isotactic structure having three
propylene units placed in a polypropylene backbone such that all
three methyl side groups lie on the same side of the plane
containing the polymer backbone, as determined by NMR
spectroscopy;
[0098] "mr triads" refers to a stereoregular polypropylene
structure having three successive propylene units placed in a
polypropylene backbone such that, relative to the first propylene
unit, the methyl group of the second propylene lies on the same
side of the plane containing the polymer backbone and the methyl
group of the third propylene lies on the opposite side of the plane
containing the polymer backbone, as determined by NMR
spectroscopy;
[0099] "nanocystalline" means having crystallites in the nanometer
size range (largest length), preferably 2 to 200 nm;
[0100] "optical clarity" means transmittance of greater than 80% of
light of wavelengths of 400-750 nm;
[0101] "peak molecular weight," M.sub.p, means the maximum
molecular weight in a curve relating molecular weight and the
abundance of a species of a given molecular weight determined by
gel phase (or size exclusion) chromatography;
[0102] "Ph" means phenyl;
[0103] "rr triads" refers to a syndiotactic structure having three
propylene units placed in a polypropylene backbone such that each
successive methyl side group is alternately above and below the
plane containing the polymer backbone, as determined by NMR
spectroscopy;
[0104] "soluble" means dissolves to an extent of greater than 98
weight percent at a temperature up to the boiling point of the
stated solvent;
[0105] "stereoregularity index (S.I.)" of a propylene polymer is
defined as the ratio of the percentage of mm triads to rr triads,
wherein the ratio represents the larger of mm or rr over the
smaller of mm or rr (i e., the ratio is positive and greater than
1); and
[0106] "syndiotactic" or "syndiotactic-rich" means polypropylene
having tacticity shown in FIG. 2 (third entry) and having an rr
content of greater than the mm triad content, as determined by NMR
spectroscopy.
[0107] Metallocene catalysts that produce highly isotactic or
highly syndiotactic polymers exhibit a number of chemical and/or
structural similarities:
[0108] 1) These catalysts very often contain a MX.sub.2 unit (M=Ti,
Zr, or Hf, X=Cl, Br or CH.sub.3, most commonly Cl) bonded to two
variously substituted cyclopentadienyl-type ligands such as
cyclopentadienyl itself, 1-indenyl or 9-fluorenyl.
[0109] 2) The two cyclopentadienyl-type ligands may be connected by
a bridging group joined at the C-1 position in the indenyl moiety
or the C-9 position in the fluorenyl moiety. The groups
--CH.sub.2--CH.sub.2-- and --SiMe.sub.2--, wherein Me=methyl, are
common examples.
[0110] 3) During the course of activation by an organoaluminum
compound such as methylaluminoxane or mixtures of methylaluminoxane
and other co-catalysts, Cl is replaced by one or two alkyl groups
derived from the organoaluminum compound so that equivalent results
for compounds containing a MCl.sub.2 or M(Me.sub.2) moiety are
often seen.
[0111] 4) Once a basic catalyst structural type that provides
isotactic or syndiotactic polymer has been recognized,
stereoregularity can be increased by further adjustments of the
structure through introduction of organic groups on the
cyclopentadienyl-type ligands.
[0112] However, prior to the present invention it was not possible
to predict the physical properties of polypropylene of intermediate
stereoregularity based on the shape of the metallocene
catalyst.
[0113] Metallocene catalysts of the invention produce novel
propylene polymers, herein sometimes referred to as hybrid
polymers, whose stereoregularity lies between highly syndiotactic
(or highly isotactic) and atactic. Polymers thus obtained exhibit
novel and useful properties, for example resistance to creep at
high temperatures or extreme extensibility, which properties have
not been previously observed in polypropylene.
BRIEF DESCRIPTION OF THE DRAWINGS
[0114] FIG. 1 shows the symmetry elements of an unsubstituted,
bridged bisfluorenyl metallocene catalyst that is known in the
art.
[0115] FIG. 2 shows the relationship between metallocene catalyst
symmetry and polypropylene stereostructure for selected catalysts
(20, 21, 22, 23, 24, 25) as is known in the art.
[0116] FIG. 3 shows the relationship between stereoregularity index
(S.I.) and asymmetry parameter (A.P.) for metallocene
catalyst-polypropylene pairs of the invention; preferred pairs fall
within area II, IV, V, VII; more preferred pairs fall within area
II, III, VI, VII.
[0117] FIG. 4 shows the dynamic mechanical analysis spectrum and
the variation of tensile storage modulus E', loss modulus E" and
loss tangent (tan delta) with temperature for a polypropylene
prepared using a metallocene catalyst in accordance with the
invention (see Example 19, below).
[0118] FIG. 5 shows the variation of tensile modulus E' with
temperature, after 28 days of aging at 23.degree. C., for a
polypropylene prepared using a metallocene catalyst in accordance
with the invention (see Example 20, below).
[0119] FIG. 6 shows Raman scattering traces of polypropylenes of
the invention (18T and 18N) and comparative polypropylenes (18A and
18E).
DETAILED DESCRIPTION OF THE INVENTION
[0120] The present invention presents a simple, quantitative
(numerical) means of describing the shape of metallocene catalysts,
even those which have yet to be made. Using this simple metrical
parameter, and noting the symmetry planes present in the structure
of the catalyst molecule, it is possible to predict whether the
catalyst will produce a highly isotactic polypropylene, one that is
highly syndiotactic, or atactic. Polymers of the invention have
properties that are not adequately described by any of the
conventional designations, and may be referred herein as a hybrid
polymer. The invention also presents a numerical measure of the
stereoregularity of a poly(1-olefin).
[0121] As described above, propylene homopolymers can be divided
according to their stereoregularity into three broad categories:
isotactic, syndiotactic and atactic. The former two materials are
crystalline, high melting, insoluble in (and resistant to) common
organic solvents, stiff, tough and nontacky. They are particularly
well suited to engineering applications where their high strength
is beneficial.
[0122] These are, as has been mentioned, limiting cases and they
are describable in essentially statistical terms. Commercially
available isotactic polypropylene can have an mm content of 90% or
higher and commercial syndiotactic polypropylene can have an rr
content of 70% or higher. Atactic polypropylene is not at present
commercially available but descriptions of it in the art refer to
tacky material in which the mm and rr content are each about
25%.
[0123] The present invention is directed toward preparation of
novel propylene polymers whose mm (or rr) content exceeds 25%
(which can be characterized as constituting a flexible, tacky
polymer) to greater than 65% (where a high degree of structure can
contribute significantly to the physical properties such as modulus
and resistance to flow). Polymers of intermediate stereregularity
can be hybrids, i.e. they can combine some of the properties of
both highly crystalline and amorphous polymers, such as, for
example, a material that is both tough and tacky.
[0124] In order to obtain such hybrid polymers, hybrid catalysts,
intermediate in structure between those used to make highly
isotactic (or highly syndiotactic) polypropylene and atactic
polypropylene, are required. Unfortunately, as described above, the
necessary features of such a hybrid catalyst have been difficult or
impossible to identify by study of the art. What is needed, and
provided by the present invention, are low symmetry catalysts (low
A.P.) as well as a means of describing their shape, e.g., molecules
that could not be adequately described by point group symmetry.
[0125] Metallocene catalysts in which two cyclopentadienyl-type
ligands are connected by a bridging group are known. Such a bridge
holds the two ligands in fixed positions relative to one another.
Rotation of the ligands is prevented, substituents on the ligands
are fixed in the molecular structure, and the catalyst has,
therefore, a permanent and definite shape.
[0126] When bridged metallocene catalysts are used, polymerization
activity, i.e., joining an entering monomer molecule to the growing
polymer chain, takes place in a very specific region of the
metallocene catalyst molecule. For example, in a metallocene
catalyst of the type (ligand).sub.2ZrCl.sub.2, polymerization
activity takes place around the --ZrCl.sub.2 region. Numerous
metallocene catalysts have been described having substituent groups
at every conceivable free site of the ligand ring groups. However,
many positions at which substituents could be introduced are so
distant from the polymerization site (i.e., metal center) that
substituents placed there have little or no effect on the
stereochemical outcome of the polymerization. In the present
invention, substituents located more than about 5 .ANG. from the
metal center are ignored. For example, in fluorenyl ligands
connected at C-9 to a bridge, substituents placed at the C-1, C-2,
C-7 or C-8 ring positions are of essentially no stereochemical
significance. In contrast, the C-4 and C-5 positions are quite
close to the metal atom at which polymerization occurs so the size
and nature of substituents located there are critical determinants
of the catalyst's stereospecificity. Similarly, in bridged
metallocenes containing a cyclopentadienyl-bridge-indenyl moiety
(with the bridge being connected at C-1 of the indenyl ring group),
substituents located at C-3 or C-4 in the cyclopentadienyl ligand;
or at C-2, C-3, C-4, or C-5 in the indenyl ligand are considered of
primary importance.
[0127] The numbering systems for cyclopentadienyl, indenyl,
fluorenyl, and cyclopentaphenanthryl ligands are shown below: 2
[0128] Unsymmetrical bridged metallocene catalysts of the invention
can be characterized by an asymmetry parameter (A.P.) as follows.
For a metallocene catalyst of the type
{ligand1-bridge-ligand2}MX.sub.2, wherein M is selected from the
group consisting of Ti, Zr, and Hf and each X is as previously
defined, A.P. is the ratio area of the van der Waals surface of the
larger ligand to that of the smaller, as determined by
computer-assisted molecular modeling, such as, for example, the
CAChe.TM. suite of programs from Oxford Molecular Inc. It is always
continuous, positive and equal to or greater than 1. The surface
areas of the ligand includes contributions from substituents at the
critically important positions described above (i.e., those that
are less than about 5 .ANG. from the metal center). Substituents at
other positions are ignored and hydrogen atoms are assumed to
reside at those positions. The A.P. provides a numerical measure of
the degree of asymmetry of a catalyst. The larger the value of A.P.
for a metallocene, the more unsymmetrical it is. Surface areas for
the individual ligands are the areas comprising the constituent
atoms at their van der Waals radii. They can be readily calculated
using, e.g., the CAChe.TM. molecular modeling program. This program
also permits placement of a substituent at a given position in an
optimized geometry that minimizes non-bonded repulsions. For
example, in calculating the surface area of a
3-phenylcyclopentadieny- l ligand fragment, the five- and
six-membered rings are not coplanar. The phenyl ring is allowed to
rotate out of the plane of the cyclopentadienyl ring so as to
reduce unfavorable steric interactions between hydrogen atoms.
Several examples that illustrate how A.P. values are calculated
follow.
[0129] A.P. for {flu-C.sub.2H.sub.4-flu}ZrCl.sub.2 is 1.00 by
definition because both ligands are the same. Because the bulky but
distant t-butyl groups are ignored, it is 1.00 as well for the
analogous {2,7-di-t-butyl-flu-C.sub.2H.sub.4-flu}ZrCl.sub.2.
Surface areas of fluorenyl and indenyl groups are calculated to be
151 and 112 square Angstroms, respectively. Therefore, A.P. for
both of the catalysts {flu-C.sub.2H.sub.4-ind}ZrCl.sub.2 and
{flu-SiMe.sub.2-ind}ZrCl.sub.2 is 151/112, or 1.35.
[0130] We have found that one effective way of altering the shape
(and A.P.) of catalysts is to connect the 4 and 5 positions of one
of the fluorene rings by means of (--CH.sub.2--).sub.n or
(--CH.dbd.CH--).sub.m, wherein n=2, 3, 4, or 5, and m=1, 2, 3, or
4, methylene or vinylene groups that are connected to one another
so as to form a ring. Relative to an unsubstituted fluorene ring,
these substituents increase the van der Waals surface areas thus
making the substituted fluorene portion of the ligand larger and so
increase the asymmetry parameter. In Table 2, these moieties are
referred to as a STRAP. The two halves of the ligand molecule are
connected with a BRIDGE which serves to inhibit rotation or
movement of the different parts of the catalyst molecule and
imparts to it a permanent and persistent shape.
[0131] Another effective means of providing asymmetrical catalysts
is to use a ligand of the type flu-bridge-ind. This is related to
the symmetrical flu-bridge-flu ligand by replacement of one
(CH).sub.4 benzo rings by two hydrogen atoms. Again, the catalyst
molecule has a persistent shape in contrast with asymmetrical,
unbridged catalyst molecules. Unlike
(ind(1)-bridge-ind(2))MCl.sub.2 catalysts, wherein (1) and (2)
indicate nonequivalent indenyl-type ligands and which exist as d,I
and meso isomers (the former gives isotactic and the latter atactic
polypropylene), such isomerism is not possible.
[0132] In order to correlate A.P. with stereoregularity, a
numerical measure of stereoregularity, called the stereoregularity
index, or S.I., is defined as follows: In a perfectly atactic
polymer, the two homotactic triads, mm and rr, are present in equal
amounts, 25% each. As the polymer becomes increasingly
stereoregular, the relative amounts of mm and rr change so that one
increases to be greater than the other. S.I. is the ratio of the
larger of mm or rr to the smaller of mm or rr and is always
positive and greater than 1. S.I. expresses in a numerical way how
the stereochemical arrangement of monomer sequences shifts away
from 1.00 for a random, atactic polymer to larger values
characteristic of more stereoregular polymers. For example,
.sup.13C NMR analysis of polypropylene made using the catalyst
{flu-C.sub.2H.sub.4-ind}ZrCl.sub.2 (activated with
methylaluminoxane) showed that the mm:mr:rr ratio is 26:31:43, so
the S.I. is 43/26, or 1.65.
[0133] The S.I. does not indicate whether a particular polymer is
isotactic or syndiotactic but this can be shown by adding the
letter S or I after the S.I. value. In the example above, one would
have 1.65S, indicating that the polymer is syndiotactic-rich.
However, this distinction matters little when S.I. values are
large, because highly iso- or syndiotactic-rich polymers share
properties outside of the scope of the present invention: high
crystallinity, opacity, high melting points, stiffness and
insolubility in aromatic and aliphatic hydrocarbons. These
properties begin to occur in polypropylenes whose stereoregularity
indices are greater than about 6.6.
[0134] The asymmetry parameter of a metallocene catalyst can be
related to the stereoregularity index of the polypropylene that it
produces and therefore to the physical and mechanical properties of
the polymer. Polypropylenes produced with metallocene catalysts
whose asymmetry parameters are about 1.0 are essentially atactic
with stereoregularity indices between about 1.0 and about 1.3.
[0135] The stereochemical irrelevance of large bulky groups that
are placed in positions far removed (i.e., greater than 5 .ANG.)
from the reaction center is illustrated by the metallocene
catalysts {(2,7-R.sub.2flu)-C.sub.2H.sub.4-(flu)}ZrCl.sub.2
(wherein R=t-butyl or p-tolyl). These produced polypropylenes with
S.I. values of 1.26 and 1.08, respectively, and whose NMR spectra
were consistent with that of an atactic polymer.
[0136] Asymmetry in the bridging element has little effect on the
stereochemical outcome of the polymerization. For example,
polypropylene obtained with the catalyst
{flu-CH.sub.2-SiMe.sub.2-flu}ZrCl.sub.2 is atactic and has an S.I.
value of 1.04.
[0137] When the asymmetry parameter of a metallocene catalyst is
above about 1.69, both stereoregularity and crystallinity of the
product polypropylene rise sharply. This is illustrated by FIG. 3
and Table 1. For example, the catalyst
{4-(1-naphthyl)-2,7-di-t-butyl-flu-C.sub.2H.sub- .4-flu}ZrCl.sub.2
(18H, below, A.P.=1.70) produced crystalline, very isotactic-rich
polypropylene with mm:mr:rr 80:14:6 (stereoregularity index=13.3).
The catalyst {flu-CMe.sub.2-Cp}ZrCl.sub.2 is even more asymmetric
and has a very large A.P. value of 2.09 (18E, below). It is
reported (Ewen, et al., in Catalytic Olefin Polymerization, T. Keii
and K. Soga, eds., Elsevier (1990), p. 439) to produce highly
isotactic polypropylene with an S.I. value of 27.3.
[0138] Thus, the shape of a metallocene catalyst, reflected in its
asymmetry parameter, is a critical determinant of polymer
stereoregularity and crystallinity. Catalysts whose A.P. values lie
between about 1.03 and 1.69 have been found to be useful in the
preparation of hybrid polypropylenes, that is, polypropylenes
having physical and mechanical properties that are not
characteristic of the extremes represented by either atactic or
very stereoregular materials, but rather are intermediate between
the two limiting cases. Such catalysts enable synthetic access to a
continuum of new polypropylenes, with a continuum of properties,
that lies between these two extremes. Hybrid polymers can have a
wide variety of microstructures and their S.I. values can vary from
1.30 to 10.00. In FIG. 3, area II, IV, V, VII indicates the range
of asymmetry parameters and stereoregularity indices found to be
associated with these new, hybrid polymers of the present
invention.
[0139] While many of the catalysts of this invention contain
fluorenyl moieties, their presence is not necessary in order to
obtain polypropylenes in the range of S.I. values claimed. This is
illustrated by Example 18-V, below, in which the 6-membered benzene
rings have been catalytically hydrogenated; in this way, they
become tetramethylene, (CH.sub.2).sub.4, moieties connected to
cyclopentadienyl rings. This example underscores the fact that it
is not the specific nature of the cyclopentadienyl-type rings in
the catalysts that determines steroregularity. Rather, it is the
shape of the catalyst (taken as a single molecular unit) expressed
through its asymmetry parameter (A.P.) that controls the
stereoregularity index.
[0140] Metallocene catalysts useful in the invention can be
represented generally by { (ligand1)-bridge-(ligand2}MX.sub.2,
wherein
[0141] ligand1, ligand2, bridge, M, and X are as previously defined
and
[0142] wherein the metallocene catalyst exhibits an asymmetry
parameter of 1.03 to 1.69. The metallocene catalysts provide
propylene polymers as defined above. Preferably, the catalysts
exhibit one or more of
[0143] i) a stereoregularity index between 1.30 and 10.00,
[0144] ii) a heat of fusion (.DELTA.H.sub.fus) that is less than
50% of the .DELTA.H.sub.fus of either isotactic or syndiotactic
polypropylene, and
[0145] iii) optical clarity.
[0146] Preferably, metallocene catalysts of the invention comprise
the structure
{ligand1-bridge-ligand2}MX.sub.2,
[0147] wherein ligand1 and ligand2 are different and are selected
from the group consisting of fluorenyl, indenyl,
4,5-dihydrocyclopentaphenanthryl, and cyclopentaphenanthryl,
optionally having substituents as described above, bridge is
selected from the group consisting of C.sub.2H.sub.4, SiPh.sub.2
and Si(CH.sub.3).sub.2, M is Zr, X is individually selected from
the group previously defined, and the catalyst asymmetry parameter
is between 1.03 and 1.50.
[0148] Preferably, metallocene catalysts comprise various
substituent groups on the ligand rings, typically alkyl or alkenyl
groups, preferably C.sub.1-C.sub.20 alkyl, are placed near the
metal-containing reactive center in the catalyst (i.e., within 5
.ANG.).
[0149] Metallocene catalysts of the present invention having
asymmetry parameters between about 1.03 and 1.50 can be subdivided
into two classes, designated A and B, below, depending on whether
or not they possess a mirror plane of symmetry bisecting the
MX.sub.2 angle. This mirror plane is represented by sigma v
(.sigma..sub.v) in FIG. 1.
[0150] Catalysts of Type A have such a symmetry plane. They produce
novel polypropylenes whose molecular weight distributions, as
assessed by gel permeation chromatography (GPC) of toluene
solutions, typically are monomodal. These polymers are
syndiotactic-rich, that is %rr>%mm, and they are optically clear
and transparent. They may be noncrystalline or only slightly
crystalline. That is, they may either exhibit no melt endotherm by
differential scanning calorimetry (DSC) analysis or may exhibit an
endotherm corresponding to less than 50% crystallinity, preferably
less than 40% crystallinity.
[0151] The percentage of crystallinity of an isotactic-rich
polypropylene approximately equals the ratio of the observed heat
of fusion (.DELTA.H.sub.fus) to the literature heat of fusion of
100% crystalline isotactic polypropylene. The percent crystallinity
of a syndiotactic-rich polypropylene is calculated similarity but
using instead the literature value of .DELTA.H.sub.fus for 100%
crystalline syndiotactic polypropylene. Furthermore, polypropylenes
of the invention can exhibit melting transitions at temperatures at
least 50.degree. C. below the melting temperature for any known
purely crystalline form of polypropylene. All show a glass
transition at about 0.degree. C., consistent with a substantially
noncrystalline character. In addition, the X-ray diffraction (XRD)
patterns can show weak, sharp lines due to a very minor crystalline
component superimposed upon a broad, structureless peak arising
from the predominant, noncrystalline component.
[0152] Depending on the catalyst design and polymerization
conditions (see below), the rr content of polypropylenes of the
invention resulting from use of Type A catalysts can range from
about 35% to greater than 65%. Stereoregularity indices can vary
between 1.30 and 10.00 preferably in the range of 1.30 to 7.00, and
most preferably 1.80 to 6.30. These polymers are soluble in toluene
at room temperature. Films made by the latter technique are
transparent, elastomeric and show no evidence of haze. It is now
appreciated that the properties of the propylene polymers such as
modulus, particularly modulus at 150.degree. C., crystallinity, and
tensile strength, are very sensitive to, and increase sharply with,
small changes in rr content. This has not been taught in the prior
art.
[0153] The weight average molecular weight of the polymers of the
invention can be in the range of 70,000 to 1,000,000 preferably
80,000 to 750,000.
[0154] When the weight average molecular weight of these polymers
is between about 70,000 and 200,000, more preferably 80,000 to
200,000, and when the S.I. is in the range of 2.5 to 4.0,
preferably about 3.0, the materials are both elastic and tacky.
They may be used, e.g., to make pressure sensitive adhesives.
[0155] As molecular weight increases, an unexpected property,
resistance to flow at elevated temperature, develops in these
elastomers. As an illustrative example, a novel polypropylene
having an S.I. of 2.6 was prepared using the metallocene catalyst
{CPA-C.sub.2H.sub.4-flu}ZrCl.sub.- 2 (A.P.=1.08) (I) (referred to
in Table 1, below, as 18Q). 3
[0156] This compound has one ligand in which a vinylene or
--CH.dbd.CH-- "strap" joins the 4 and 5 positions of a fluorene
ring group, which has the systematic name
4H-cyclopenta{d,e,f}phenanthrene, abbreviated as CPA. In FIG. 4, it
can be seen that dynamic mechanical analysis of the resulting
polypropylene shows that the polymer resists flow up to about
170.degree. C. The curve relating storage modulus (E') and
temperature exhibits a broad, rubbery plateau between about
25.degree. C. and 170.degree. C. One interpretation of the DMA
spectrum can be that the material behaves as though it were
crosslinked or contained a hard structural, load bearing phase in a
softer continuous matrix. However, the polymer is completely
soluble in toluene at room temperature, which is inconsistent with
crosslinking, and it exhibits neither a melt endotherm nor sharp
X-ray diffraction lines, which indicates the absence of
crystallinity. In contrast, both atactic polypropylene and
commercial syndiotactic polypropylene begin to flow at about
100.degree. C. The shear modulus is 6.0.times.10.sup.5 Pa between
25 and 150.degree. C. and is much higher than that of atactic
polypropylene, 3.0.times.10.sup.5 Pa at 150.degree. C. The polymer
is highly elastic and exhibits only a 4.5% inelastic deformation
after 10% of strain (ASTM D1774-90).
[0157] As polymer stereoregularity increases, room temperature
shear storage modulus (E') increases significantly. For example, a
novel polypropylene prepared using the novel metallocene catalyst
{H.sub.2CPA-SiMe.sub.2-flu}ZrCl.sub.2(II) (the abbreviation
H.sub.2CPA indicates hydrogenation of the vinylene "strap" of CPA),
having an A.P. of 1.13 (18T, below), yields polypropylene having an
rr content of 59% and an S.I. of 5.9. 4
[0158] The subtle changes in catalyst design lead to a polymer that
is considerably stiffer at room temperature, with a E' value for
pressed films of 13.0.times.10.sup.6 Pa. It exhibits a melt
endotherm at 48.degree. C.; the heat of fusion, 12 J/g, corresponds
to a crystallinity content of 12/50 or 24 weight % (50 J/g is the
literature heat of fusion (.DELTA.H.sub.fus) of totally
syndiotactic polypropylene). The crystallinity is due to small
amounts of an oriented syndiotactic polypropylene phase.
Significantly, both DSC and X-ray diffraction show that the
crystalline phase has disappeared at a temperature of about
60.degree. C., yet a plot of E' versus temperature (FIG. 5) again
demonstrates a broad, rubbery plateau, with a value of
2.20.times.10.sup.6 Pa, from about 50.degree. to about 170.degree.
C., at which temperature the material begins to flow. Between
50.degree. and 170.degree. C., the plot of E' versus temperature
strongly resembles that of FIG. 4, trace A, 18Q, in Table 2, below,
where the polypropylene had an S.I. of 2.8. Therefore, resistance
to flow at elevated temperatures displayed by these two polymers
cannot be attributed to crystallinity, the presence of which has
heretofore been assessed, as it is here, by DSC and X-ray
diffraction. Without wishing to be bound by theory, it is proposed
that this phenomena, which to our knowledge has never before been
reported for non-crystalline polypropylene, may be due to
nanocrystallinity, that is, crystalline or structurally-ordered
domains that are very much smaller, perhaps 150 .ANG., than has
previously been considered as important. Small angle light
scattering experiments disclose that additional orientation of
large crystallites (i.e., those melting at about 48.degree. C.) in
this polymer may be achieved by stretching and which diffract
X-rays.
[0159] This polymer is exceptionally elastic and exhibits
essentially no inelastic deformation following extension to 10%
strain. The presence of a low-melting component confers heat
sealability upon the polymer. Films of the material may be fused
together above about 50.degree. C.
[0160] Raman spectra can be used to characterize the hybrid nature
of propylene polymers. Spectra in the 200-500 cm.sup.-1 skeletal
stretching region are shown in FIG. 6. Atactic polypropylene
(Example 18A below) has a broad scattering peak at about 400
cm.sup.-1 and crystalline syndiotactic polypropylene (Example 18E)
has a sharp peak at 313 cm.sup.-1. The spectra of polymers from
(Examples 18 N and 18 T, below) show bands at both about 400 and
310 cm.sup.-1 due both heterotactic and homotactic sequences,
respectively, in the same chain. That is, a single chain, if it
were extracted from the polymer mass, would be seen to contain both
types of sequences.
[0161] Table 7, below, summarizes some of the physical properties
of polypropylenes obtained with the novel catalysts of the
invention.
[0162] A noteworthy result is that crystallinity (as detected by
DSC and XRD) is present generally when the S.I. index is about 3.9
or greater.
[0163] Table 2, below, presents data that show how S.I. (and % rr
content) change with catalyst design and with polymerization
conditions. It reveals how changes in catalyst structure and
polymerization temperature may be used to change the polymer
stereoregularity index and polymer physical properties.
[0164] Several trends can be found:
[0165] (1) Connecting the 4 and 5 positions of a fluorene ligand
(i.e., dihydrocylopentaphenanthrenes of Examples 18S, 18T, and 18U,
below) via a --CH.sub.2--CH.sub.2-- unit provides a catalyst that
is more stereoregulating (higher S.I. and % rr content) than one
having a --CH.dbd.CH-- unit in the same position (i.e.,
cyclopentaphenanthrenes of Examples 18Q and 18R). Both groups are
more effective in controlling stereoregularity than is a single
methyl group at the 4 position (18W) or even two methyl groups at
the 4 and 5 positions as found, for example, in compounds having
the general formula shown in Table 2 but in which the
4,5-dimethylfluorenyl group replaces (strap)flu;
[0166] (2) Stereoregularity and polymer molecular weight both
decrease with increasing polymerization temperature (Examples
18Q.sub.1 vs. 18Q.sub.2; 18T.sub.1 vs. 18T.sub.2; 18S.sub.1 vs
18S.sub.2); the temperature effect on M.sub.w is much larger than
on S.I.;
[0167] (3) Otherwise identical metallocenes with a SiMe.sub.2
bridge connecting the two ligands (Examples 18R, 18T, and 18U)
wherein Me=methyl are more stereoregulating than those having a
--CH.sub.2--CH.sub.2-- bridge (18Q and 18S);
[0168] Small changes in stereoregularity index (and % rr content)
bring with them substantial changes in polymer properties, as
explained above. Thus, catalysts of the invention make possible
synthesis of a wide variety of new polypropylenes whose %rr content
varies from 29 to 73%, preferably 29 to 65%, a range of 36% when
considering both Type A and Type B catalysts. This is in
advantageous contrast with prior art catalysts, which enabled a
range of only 8% (from 74-82%) in rr content (U.S. Pat. No.
5,459,218).
[0169] The pentad intensities of polypropylenes produced by Type A
metallocenes of the invention can be described in terms of a single
catalytic site. They follow Bernoullian statistics based upon a
single, unique value of P.sub.r, the probability of obtaining a
syndiotactic insertion each time a propylene monomer is added to
the growing polymer chain. P.sub.r values can be used in a Monte
Carlo calculation to determine the length distributions of all-r
sequences and their weight percent abundances.
[0170] Metallocenes of type B have the general structure
{R.sup.1-ligand1-bridge-ligand2}ZrCl.sub.2, wherein ligand1,
ligand2, bridge, and R.sup.1 have been previously defined. The
mirror plane of symmetry bisecting the Cl--Zr--Cl angle is absent
in Type B metallocenes; in fact, these metallocenes have C.sub.1
point group symmetry. The microstructure of polymers obtained using
Type B metallocenes of the invention, as deduced from .sup.13C NMR
analysis, cannot be described in terms of a single catalytically
active site.
[0171] Polypropylenes obtained using Type B catalysts of the
invention can be either syndiotactic- or isotactic-rich. They are
elastomeric but lack the resistance to flow at elevated
temperatures found in high molecular weight polymers obtained using
Type A catalysts. Table 3 summarizes results obtained using Type B
catalysts. It can be seen that the polymer microstructure, i.e.
whether syndiotactic- or isotactic rich, appears to vary
unpredictably depending on the nature of the substituent on the
indenyl ring and, more surprisingly, on the nature of the bridging
moiety connecting the indenyl and fluorenyl moieties of the ligand.
Unlike the polypropylene elastomers prepared by Collins et al.
(supra), which had a mmmm content of 38% or greater, the maximum
mmmm content in elastomeric polymers prepared using catalysts of
the invention is 31%, and the mm triad content was in range of 24
to 50 percent. This indicates that materials have been obtained
that are distinguishable and very different.
[0172] Polymers listed in Table 3, below, also exhibit large
polydispersity (PD) values (i.e., greater than 2.5), that is, the
weight average molecular weight M.sub.w divided by the number
average molecular weight M.sub.n. In fact, GPC analysis discloses
that the molecular weight distributions of polymers obtained using
Type B catalysts are actually bimodal and in the case of catalysts
18B and 18I, possibly trimodal. In Table 3, the values given in
parentheses represent the percent composition of each major
constituent. That is, these catalysts appear to produce two
different kinds of polypropylene. The two kinds are differentiable
by their distribution of molecular weights and peak molecular
weights, M.sub.p. Neither of the two kinds of polymers corresponds
to a highly stereoregular, e.g., crystalline, component because all
of the polymers are soluble in or completely extractable by
hydrocarbons such as toluene or heptane. In other words, the two
kinds of polypropylene produced by a given catalyst of the
invention cannot be fractionated according to solubility. Lack of
significant levels of crystallinity is affirmed by the transparency
of pressed films of the novel polymers.
[0173] A particularly interesting elastomer is produced using the
class B metallocene {ind-C.sub.2H.sub.4-flu}ZrCl.sub.2 (Examples 3,
4 and 18N). It has a tensile strength at break and modulus (at
small strain) of 718 and 2300 KPa, respectively. The material is
exceptionally elastic or stretchy: elongations without break of
4,000% or more were achieved and a maximum elongation of 5200% has
been achieved and the sample did not break. U.S. Pat. No. 5,595,080
describes a different homopolymer of propylene obtained by a
catalyst of a different class having an ultimate elongation of
3000% that was reported as the highest known value for
elongation.
[0174] This invention also encompasses heteropolymers, that is,
co-polymers of propylene with up to 25 mole per cent of 1-olefins
containing up to 18 carbon atoms, such as 1-hexene, 1-octene or
1-octadecene, which serve to render the polymers softer and more
flexible, lower the glass transition temperature, or to facilitate
their flow and extrusion at elevated temperatures. One or more
tackifiers known in the art may be added to the polymers in order
to lower their glass transition temperatures. Two or more polymers
of this invention may be mixed together to provide blends having
intermediate properties. A similar result can be achieved by
polymerizing propylene, along with optional comonomers as described
above, in the presence of two or more catalysts of this invention.
Additionally, various antioxidants, such as Irganox 1010.TM., may
be added to enhance thermal stability of the polymers.
[0175] Metallocenes of the type {ligand1-bridge-ligand2}MX.sub.2
require treatment with an activating cocatalyst in order to produce
an active catalyst. When X is CH.sub.3, CH.sub.2C.sub.6H.sub.5 or
other alkyl or aralkyl groups, (C.sub.6H.sub.5).sub.3C(+) salts of
various noncoordinating anions can be used. Also useful are onium
salts of the type R.sup.5R.sup.6R.sup.7QH(+), wherein Q=N or P, and
R.sup.5, R.sup.6, and R.sup.7 can be the same or different and are
selected from the group consisting of C.sub.1-C.sub.20
straight-chain group or branched alkyl group, C.sub.6-C.sub.20
aryl, and C.sub.3-C.sub.8 cycloalkyl groups. Illustrative are
(n-C.sub.4H.sub.9).sub.3NH(+), PhN(CH.sub.3).sub.2H(+) and
Ph.sub.3PH(+). Effective noncoordinating anions include, but are
not limited to, (C.sub.6F.sub.5).sub.4B(-),
(C.sub.6F.sub.5).sub.3BCH.sub.3(-- ) and B.sub.11CH.sub.12(-).
[0176] When X=halogen, the preferred activator compound is an
aluminoxane. Aluminoxanes are prepared by the partial, controlled
hydrolysis of trialkylaluminums, See, for example, U.S. Pat. No.
4,752,597, col. 10, line 6 ff, which is incorporated herein by
reference. Particularly preferred is methylaluminoxane,
(CH.sub.3AlO).sub.x which is obtained by controlled hydrolysis of
trimethylaluminum. Unreacted trimethylaluminum may be removed from
commercially available methylaluminoxane by vacuum distillation or
other methods known in the art, but such removal may not be
necessary in order to obtain highly active catalysts. Indeed,
trialkylaluminum compounds may be optionally added to the catalyst
solution or monomer to scavenge harmful impurities such as
adventitious oxygen or water. Methylaluminoxane can be used in
excess so that the Al:M (wherein M=Zr or Hf) ratio is 2:1 to 2000:1
with the preferred range being 10:1 to 1000:1.
[0177] The active catalyst is prepared by combining the metallocene
and the activator component in a nonreactive solvent such as
toluene or xylenes and, optionally, nonreactive hydrocarbons such
as heptane or cyclohexane. The active catalyst may be used directly
or it may be impregnated onto a solid carrier such as silica. It is
also possible to combine two or more metallocenes and to then treat
this mixture with an activator component and to produce in this way
a catalyst blend that, when contacted with propylene, will produce
a polymer blend.
[0178] It has been found that polymer properties such as
stereoregularity and molecular weight are greatly affected by the
propylene concentration in the polymerizing reaction mixture and
also by how it changes during the course of the reaction. Thus,
although catalysts of this invention may be used under a wide
variety of conditions, they are preferably used to prepare
polypropylene in the absence of solvent. Propylene then serves as
both monomer and diluent; its initial concentration, about 12M,
changes little until high conversions to polymer have occurred.
This was the case in Examples 4 and 18N, below.
[0179] Polymerization may be carried out as a batchwise slurry,
solution or bulk reaction, or as a continuous process. In
continuous polymerization, propylene, comonomer (if any) (as
described above), and catalyst are continually supplied to a
reactor in amounts equal to those removed from the reaction zone in
the product stream. When the catalyst is supported on a solid
carrier, gas phase polymerization in a fluidized bed can be
conducted.
[0180] Processes for preparation of polypropylene in which no
solvent is added, i.e., in which propylene serves as both monomer
and diluent, are preferred. When solvents are used, preferably they
are hydrocarbons, more preferably toluene or cyclohexane.
Polymerization to produce new polypropylenes of this invention may
be carried out at a pressure of 69 to 6890 Kpa (about 10-1000 psi).
A wide range of reaction temperatures is possible but the range
-20.degree. to about 120.degree. C. is preferred. Optionally,
hydrogen gas may be added to modify the product molecular weight.
For example, as is known in the olefin-polymerization art,
controlled addition of hydrogen gas to a catalytic olefin
polymerization reaction can lower the molecular weight of the
polymer thus obtained, relative to the same polymerization
procedure carried out in the absence of hydrogen. See, for example,
U.S. Pat. No. 3,051,690, entire document, particularly Examples
1-32.
[0181] After processing at elevated temperatures, e.g., pressing
films at about 170.degree. C., mechanical strength develops at
rates dependent on thermal treatment. The process may be hastened
by brief cooling, e.g., in ice water, or by passing the polymers
over a chill roll or by the addition of a small amount of
crystallization aid such as Millad.TM. 3905 (Milliken Chemical Co.,
Spartanburg, N.C.).
[0182] Unsymmetrical metallocenes, i.e., those having an A.P.
greater than 1.03, can be prepared using dissimilar ligands, e.g.,
ligand1 and ligand2. Such metallocenes containing an --SiMe.sub.2--
bridge may be prepared from the reaction of a compound such as
{ligand1}SiMe.sub.2Cl (prepared as described in U.S. Pat. No.
5,026,798, Example C, Part 2) with the conjugate base of
ligand2.
[0183] The present invention also describes a novel process for the
synthesis of compounds of the type
H{ligand1-C.sub.2H.sub.4-ligand2}H. For example,
2-(9-fluorenyl)ethanol, abbreviated as
H{flu-CH.sub.2--CH.sub.2--OH}, in a hydrocarbon solvent such as
toluene, heptane or cyclohexane or mixtures of such solvents, is
treated with exactly one equivalent of a base having sufficient
basicity to deprotonate the hydroxyl group. n-Butyllithium is
preferred. Next, reaction with a highly fluorinated alkyl sulfonyl
fluoride wherein alkyl has 1 to 20 carbon atoms, preferably a
perfluoroalkyl sulfonyl fluoride R.sub.fSO.sub.2F wherein R.sub.f
is an alkyl group having 1 to 20 carbon atoms, e.g.,
trifluoromethanesulfonyl fluoride, yields
H{flu-CH.sub.2--CH.sub.2--OSO.sub.2R.sub.5}. In a second step, the
conjugate base of ligand2 is used to displace
R.sub.fSO.sub.3.sup.-. Thus, for example, reaction of
flu-C.sub.2H.sub.4--OSO.sub.2CF.sub.3 with the lithium salt of
cyclopentaphenathrene produces
1-(9-fluorenyl)-2-(cyclopentaphenanthrenyl)ethane which can be
abbreviated as H{CPA-C.sub.2H.sub.4-flu}H.
[0184] In the above reaction sequence, R.sub.f is independently
selected from the group consisting of highly fluorinated or
perfluorinated alkyl radicals.
[0185] The R.sub.f alkyl group may contain from 1-20 carbon atoms,
with 1- 12 carbon atoms preferred. The R.sub.f groups chains may be
straight, branched, or cyclic and preferably are straight.
Heteroatoms or radicals such as divalent oxygen, trivalent nitrogen
or hexavalent sulfur may interrupt the skeletal chain, as is well
recognized in the art. When R.sub.f is or contains a cyclic
structure, such structure preferably has 5 or 6 ring members, 1 or
2 of which can be heteroatoms. The radical R.sub.f is also free of
ethylenic or other carbon-carbon unsaturation: e.g., it is a
saturated aliphatic, cycloaliphatic or heterocyclic radical. By
"highly fluorinated" is meant that the degree of fluorination on
the chain is sufficient to provide the chain with properties
similar to those of a perfluorinated chain, i.e., at least 75
percent fluorination. More particularly, a highly fluorinated alkyl
group will have more than half the total number of hydrogen atoms
on the chain replaced with fluorine atoms. Although hydrogen atoms
may remain on the chain, it is preferred that all hydrogen atoms be
replaced with fluorine to form a perfluoroalkyl group, and that any
hydrogen atoms beyond the at least half replaced with fluorine that
are not replaced with fluorine be replaced with bromine and or
chlorine. It is more preferred that at least two out of three
hydrogens on the alkyl group be replaced with fluorine, still more
preferred that at least three of four hydrogen atoms be replaced
with fluorine and most preferred that all hydrogen atoms be
replaced with fluorine to form a perfluorinated alkyl group.
[0186] Surprisingly, the trifluoromethane sulfonate prepared by the
method of the present invention is stable for at least 2 days at
room temperature (about 23.degree. C.), in contrast to the
previously-reported method (Rieger et al., Organometallics 13, 647
(1994)), wherein the same compound was obtained in a form that
decomposed rapidly above 0.degree. C.
[0187] Other perfluoroalkylsulfonyl fluorides, such as
C.sub.4F.sub.9SO.sub.2F, which is a liquid at room temperature, can
be used in place of low boiling CF.sub.3SO.sub.2F.
[0188] Compounds of the type H{ligand1-bridge-ligand2}H can be
converted into to their titanium, zirconium or hafnium dihalide
complexes by methods long known in the art. As an illustrative
example, reaction of H{CPA-C.sub.2H.sub.4-flu}H with two
equivalents of butyllithium yields the salt
Li.sub.2(CPA-C.sub.2H.sub.4-flu) which, when allowed to react with
ZrCl.sub.4 or ZrCl.sub.4.circle-solid.2(tetrahydrofuran) or
ZrCl.sub.4.circle-solid.CH.sub.3OC.sub.2H.sub.4OCH.sub.3, affords
{CPA-C.sub.2H.sub.4-flu}ZrCl.sub.2. The metallocene is obtained as
a finely divided powder. It may be freed from lithium chloride and
other byproducts and impurities by extraction with a nonreactive
solvent such as dichloromethane. However, this purification step
typically is not necessary and the crude metallocene can be used as
such to prepare a catalyst. Other metal alkyls, such as butylsodium
or dibutylmagnesium, or benzylpotassium, or metal hydrides such as
potassium hydride may be used in place of butyllithium.
[0189] Polypropylenes of this invention provide thermoplastic
elastomers which can be used as adhesives, binders, and films.
These polymers may be used alone or admixed with fillers or
adjuvants, such as carbon black, glass fibers, metal particles or
whiskers, or cellulose. They may be used in combination with
colorants and pigments such as iron oxide. They may be incorporated
into blends with other polymers, such polyhexene or polyoctene, or
with crystalline or amorphous polypropylenes, or as multilayer,
laminated construction with these same polymers. Amounts of
adjuvants or fillers added can vary depending on the application
desired.
[0190] Objects and advantages of this invention are further
illustrated by the following examples, but the particular materials
and amounts thereof recited in these examples, as well as other
conditions and details, should not be construed to unduly limit
this invention.
EXAMPLES
[0191] Methylaluminoxane was obtained from Albemarle Corp., Baton
Rouge, La., as a 30% solution in toluene. This was diluted 1:2
(v/v) with dry, oxygen-free toluene (vacuum distilled from
triisobutyl aluminum) to produce a solution having an aluminum
concentration of 1.7M.
[0192] Unless otherwise indicated, reactions were carried out in an
atmosphere of dry, oxygen free nitrogen. Solvents, when used, were
dried with molecular sieves or purified by distillation from
sodium-benzophenone. Uncomplexed, organic ligands were handled and
purified in air but metallocenes, which usually exhibited some
degree of sensitivity to atmospheric moisture, were purified and
stored in a nitrogen-filled drybox.
[0193] Unless otherwise indicated, all chemicals were obtained from
Aldrich Chemical Co., Milwaukee, Wis. The compounds 1-methyl- and
1-trimethylsilylindene were prepared according to the method of
Ready et al., J. Organomet. Chem., 21, 519 (1996), and
1-phenylindene was prepared according to the method of Greifenstein
et al., J. Org. Chem., 46, 5131 (1981).
[0194] Polymerization Grade propylene (Matheson Gas Products,
Seacaucus, N.J.) was passed through two Matheson model 6406A
purifiers, connected in series, before use.
[0195] .sup.13C NMR analyses to determine microstructure of
polymers at the pentad level were obtained at 100.degree. C. using
1,2-dichlorobenzene solutions of the polymers with a Varian XL-500
spectrometer (Varian Associates, Inc., Palo Alto, Calif.) according
to the method of Tonelli, "NMR Spectroscopy and Polymer
Microstructure: The Conformational Connection", VCH, Deerfield
Beach, Fla. (1989).
[0196] NMR chemical shifts are expressed in ppm relative to
external Me.sub.4Si (.sup.1H and .sup.13C) or CFCl.sub.3
(.sup.19F), positive shifts being downfield of the reference.
[0197] Positive ion mass spectra were obtained in electron impact
mode using 70 eV electron beam energy. A Finnigan FT/MS dual-cell
Fourier transform mass spectrometer (Finnigan, San Jose, Calif.)
with a 3.0 Tesla magnet was utilized to obtain the high resolution
exact mass measurements. The samples were introduced into the mass
spectrometer by using a direct insertion probe that was heated to
350.degree. C. The electron impact (El) mass spectral data was
obtained using standard EI conditions. All mass spectra were
acquired with a minimum resolving power of 3,000.
[0198] Number average molecular weights, M.sub.n, weight average
molecular weights, M.sub.w, and peak molecular weights, M.sub.p,
for polymers were determined by gel phase permeation chromatography
(GPC) on filtered solutions using a Waters 150C system (Waters
Corp., Milford, Mass.) equipped with Jordi Associates Inc.
(Bellingham, Mass.) 500 A and mixed bed columns which were
calibrated with polystyrene standards. Toluene at room temperature
was used as solvent unless otherwise noted.
[0199] Wide angle X-ray scattering (WAXS) data was collected in a
reflection geometry using a Philips vertical diffractometer
(Philips Electronic Instruments Co., Mahwah, N.J.) equipped with
variable entrance slits, graphite diffracted beam monochromator,
and proportional registry of the scattered radiation. The radiation
employed was copper K alpha with generator settings of 45 kV and 35
mA. Step scans were conducted between 5 and 55 degrees (2Theta)
using a 0.04 degree step size and 4 second count time. For elevated
temperature scans, a similar diffractometer fitted with a platinum
strip furnace and Paar HTK temperature controller (Paar, Anton,
USA, Ashland, Va.) was used. Software used to analyze the
diffraction data was Philips PC-APD.
[0200] DSC data were obtained using a TA Instruments Model 2920
modulated differential scanning calorimeter (TA Instruments, Inc.,
New Castle, Del.). A linear heating rate of 5.degree. C./min was
applied with a perturbation amplitude of +1.degree. C. every 60
sec. Samples were subjected to a cyclic heat-cool-heat profile
ranging from -120.degree. to 200.degree. C. in a nitrogen
atmosphere. Heats of fusion (.DELTA.H.sub.fus) were determined by
integrating heat flow curves.
[0201] Molecular modeling programs employed CAChe.TM. Satellite,
ProjectLeader and molecular mechanics programs (all version 3.8)
(Oxford Molecular Ltd., Oxford, United Kingdom) which were run on a
Macintosh computer.
[0202] Counterions for the catalyst can be varied as is known in
the art. Metallocene catalysts can also include Ti metal centers as
is known in the art.
Example 1
2-(9-fluorenyl)ethyl Trifluoromethane Sulfonate
[0203] A 2.5M solution of n-butyllithium in hexane was added with
stirring to 5 g 2-(9-fluorenyl)ethanol, flu-CH.sub.2--CH.sub.2--OH
(prepared by the method disclosed in Organometallics 13, 647
(1994)), in 90 mL toluene. Addition was terminated when the
reaction mixture became light orange; about 10 mL was required. The
resulting solution of Li {flu-CH.sub.2--CH.sub.2--O} was cooled in
a dry ice-acetone bath and 3.8 g trifluoromethanesulfonyl fluoride,
CF.sub.3SO.sub.2F (prepared according to U.S. Pat. No. 2,732,398,
Example 1), was added by vacuum transfer. After warming to room
temperature, any unreacted CF.sub.3SO.sub.2F was removed by
pumping. The desired compound was obtained as a colorless oil, 7.7
g (95%) by filtration of the reaction mixture followed by
evaporation of solvents. Spectroscopic and chemical analysis
confirmed the identity of the desired compound.
Example 2
{flu-C.sub.2H.sub.4-ind}
1-(9-fluorenyl)-2-(1-indenyl)ethane
[0204] To a solution of 21.0 g 2-(9-fluorenyl)ethanol, in 495 mL
toluene was added dropwise with stirring 40 mL of a 2.5M solution
of n-butyllithium in hexane. The resulting solution of
Li{flu-CH.sub.2--CH.sub.2--O} was cooled to below -25.degree. C.
Then, 16.7 g CF.sub.3SO.sub.2F was condensed into the reaction
mixture. The temperature was allowed to rise to 25.degree. C. and
the reaction mixture was stirred for 6 h. Unreacted
CF.sub.3SO.sub.2F was removed by pumping about 10 mL of liquid into
a dry ice-cooled trap. To the solution of
flu-CH.sub.2--CH.sub.2--OSO.sub.2CF.sub.3 thus obtained was added a
solution of 0.1 mole indenyllithium in 100 mL diethyl ether. After
stirring for 12 h, solvents were removed under vacuum and the
residue recrystallized in air from boiling heptane. The yield of
white microcrystalline solid, mp 79-80.degree. C., was 8.9 g (29%).
Spectroscopic and chemical analysis confirmed the identity of the
desired compound.
Example 3
{flu-C.sub.2H.sub.4-ind}ZrCl.sub.2(Designated 18N in Table 1,
Below)
[0205] A solution of 1.54 g 1-(9-fluorenyl)-2-(1-indenyl)ethane
(Example 2) in 70 mL diethyl ether was treated with 4 mL 2.5M
n-butyllithium in hexane. The resulting orange solution was stirred
overnight, after which solvents were pumped away on a vacuum line.
Zirconium chloride (1.17 g) and 75 mL hexane were added. The
reaction mixture was vigorously stirred for 18 h then filtered. The
solids were extracted with 350 mL dichloromethane. The filtered
extract was evaporated and the residue slurried with 10 mL portions
of 1:1 (v/v) dichloromethane-hexane to produce 0.61 g (26%) bright
orange, powdery product that was collected on a filter and vacuum
dried. Spectroscopic and chemical analysis confirmed the identity
of the desired compound.
Example 4
Propylene Polymerization using
{flu-C.sub.2H.sub.4-ind}ZrCl.sub.2
[0206] A 0.017 g quantity of {flu-C.sub.2H.sub.4-ind}ZrCl.sub.2
(Example 3) was dissolved in 16 mL methylaluminoxane solution.
After 1 h, the solution was diluted with 10 mL toluene and
transferred to a 100 mL stainless steel cylinder fitted with a
valve. The cylinder was pressurized to about 5520 KPa (800 psi)
with nitrogen gas, inverted and attached to a reactor containing
1816 g propylene at a temperature of 8.degree. C. This reactor had
a volume of about 8 L and was equipped with a thermocouple, an
agitator and a jacket through which coolant could be circulated as
needed in order to control the polymerization temperature. It was
evacuated with a vacuum pump then backfilled with nitrogen prior to
charging with propylene. Upon opening the cylinder valve, the
catalyst solution was injected into the reactor. Over a 1 h period,
the temperature rose to 28.degree. C. and was maintained at that
temperature for 4 more hours. Then, the reaction was terminated by
venting unreacted propylene. The yield of polymer was 533 g.
.sup.13C NMR analysis: 8.7% mmmm, 9.4% mmmr, 7.6% rmmr, 17.3% mmrr,
10.3% rmrr/mmrm, 3.8% rmrm, 22.0% rrrr, 14.1% mrrr, 6.9% mrrm,,
25.7% mr, 31.4% mr and 43.0% rr. Spectroscopic and chemical
analysis confirmed the identity of the desired product.
Example 5
{flu-C.sub.2H.sub.4-ind}HfCl.sub.2
[0207] A solution of 1.54 g flu-C.sub.2H.sub.4-ind (Example 2) in
70 mL diethyl ether was treated dropwise with 4 mL 2.5 M
n-butyllithium in hexane. The reaction mixture was stirred
overnight, after which solvents were removed under vacuum. A slurry
of 1.6 g HfCl.sub.4 in 75 mL hexane was added and the reaction
mixture was stirred for an additional 72 hours at 23.degree. C.,
then filtered. Retained solids were extracted with 300 mL
dichloromethane, and the extracts were evaporated to give a crude
solid that was washed with five 20 mL portions of hexane, 20 mL 2:1
hexane:dichloromethane, then 20 mL hexane. After vacuum drying, the
orange powdery solid product, {flu-C.sub.2H.sub.4-ind}HfCl.sub.2,
weighed 1.32 g (47%).
[0208] Spectroscopic and chemical analysis confirmed the identity
of the desired compound.
Example 6
CPA-SiMe.sub.2-flu
[0209] A solution of lithium cyclopentaphenanthrene (Li(CPA)) was
prepared by adding 6.0 mL 2.5M n-butyllithium in hexane to 2.85 g
cyclopentaphenanthrene dissolved in 50 mL tetrahydrofuran. The
reaction mixture was stirred for 12 hr then treated with a solution
of 3.87 g (9-fluorenyl)dimethylchlorosilane, flu-SiMe.sub.2Cl
(prepared according to the method of U. S. Pat. No. 5,026,798,
Example C, incorporated herein by reference), in 50 mL diethyl
ether. After stirring overnight, 1.5 mL methanol was added.
Solvents were removed under vacuum and the residue extracted with
dichloromethane. The extracts were filtered through diatomaceous
earth, 10 mL heptane was added, and the solution then slowly
concentrated on a rotary evaporator. After nearly all the
dichloromethane had been removed, the product separated as a white
microcrystalline solid that was isolated by filtration. The yield
was 3.9 g (63%), mp 153-154.degree. C. Spectroscopic and chemical
analysis confirmed the identity of the desired compound.
Example 7
{CPA-SiMe.sub.2-flu}ZrCl.sub.2(Designated Example 18R, Below)
[0210] Li.sub.2{CPA-SiMe.sub.2-flu} was prepared by treating a
solution of 1.65 g CPA-SiMe.sub.2-flu (prepared as in Example 6) in
40 mL diethyl ether with 3.2 mL 2.5M butyllithium in hexane. After
stirring overnight, solvents were removed on a vacuum line.
Zirconium tetrachloride (0.93 g) was added and the mixture cooled
to -79.degree. C. with a dry ice-acetone bath. Dichloromethane, 75
mL, precooled to -78.degree. C., was added and the reaction mixture
was vigorously stirred overnight as the cooling bath warmed to room
temperature. The red solid phase was separated and extracted with
five 100 mL portions of dichloromethane. The filtered extracts were
evaporated and the residue was washed with hexanes to give 0.48 g
(24%) red microcrystals. Spectroscopic and chemical analysis
confirmed the identity of the desired compound.
Example 8
Copolymerization of Propylene and 1-Octene
[0211] A catalyst prepared by stirring 0.018 g
{CPA-SiMe.sub.2-flu}ZrCl.su- b.2 (Example 7) and 21 mL
methylaluminoxane solution was added to a mixture of 48 g 1-octene
and 1816 g propylene which were contained in the reactor as
described in Example 4. The polymerization temperature was
maintained between 15.degree. and 20.degree. C. for 4 h, after
which the reaction was terminated. The copolymer product weighed
950 g and contained 1.1 wt. % (0.4 mole %) octene. .sup.13C NMR
analysis showed 4.6% mmmm, 8.6% mmmr, 6.2% rmmr, 12.6% mmrr, 19.1%
rmmr/mmrm, 9.5% rmrm, 20.6% rrrr, 14.2% mrrr, 4.6% mrrm, 19.4 % mm,
41.2% mr and 39.4% rr. Spectroscopic and chemical analysis
confirmed the identity of the desired product.
[0212] Copolymers of propylene and ethylene, butene, hexene or
mixtures thereof can be prepared as in this Example by substituting
one or more of them for the octene used herein.
Example 9
Dihydrocyclopentaphenanthrene, H.sub.2CPA
[0213] A mixture of 2 g cyclopentaphenanthrene, 0.2 g 10% palladium
on carbon and 50 mL toluene was stirred under hydrogen (69 kPa)
until hydrogen uptake ceased, about 48 h. Catalyst was removed by
filtration through diatomaceous earth and the filtrate evaporated.
The crude product remaining weighed 1.97 g. It was further purified
by recrystallization from heptane at -40.degree. C. to give 1.8 g
colorless plates. Spectroscopic and chemical analysis confirmed the
identity of the desired compound.
Example 10
{H.sub.2CPA-SiMe.sub.2-flu}ZrCl.sub.2(Designated 18T in Table 1,
Below)
[0214] H.sub.2CPA-SiMe.sub.2-flu was prepared from
dihydrocyclopentaphenan- threne (Example 9) and 9-flu-SiMe.sub.2Cl
by the method described in Example 6. The crude product was
recrystallized by slow rotary evaporation from solution in
dichloromethane-acetone. The yield of white powdery solid, mp.
155-156.degree. C., was 58%. Spectroscopic and chemical analysis
confirmed the identity of the desired compound.
[0215] This compound was converted to the metallocene catalyst
{H.sub.2CPA-SiMe.sub.2-flu}ZrCl.sub.2 by the method described in
Example 3. The mass spectrum showed a cluster of molecular ions
having the correct distribution of Cl and Zr isotopomers.
Example 11
{2-Methylbenzindene-C.sub.2H.sub.4-flu}ZrCl.sub.2 (Designated 18D
in Table 1, Below)
[0216] A mixture of isomeric 2-methylbenzindenes was prepared by
the method described by Stehling et al., Organometallics, 13, 964
(1994). A solution of 3.6 g of this material was dissolved in 90 mL
diethyl ether and converted to the lithium salt by dropwise
addition of 8 mL 2.5M butyllithium in hexane. This was added to 20
mmole flu-CH.sub.2--CH.sub.2--OSO.sub.2CF.sub.3 (Example 1) in 100
mL toluene. After stirring overnight , the reaction mixture was
filtered and evaporated. The residual gum was extracted with 300 mL
boiling heptane. The extract was cooled to -5.degree. C. and the
yellow solids which separated were collected on a filter. Further
purification of the solids was carried out by chromatography on an
20.3.times.3.8 cm silica gel column, eluting with 1:1 (v/v) toluene
- heptane. Evaporation of the eluate gave 3.6 g crude
methylbenzindene-C.sub.2H.sub.4-flu as an amber resin.
[0217] A 3.48 g quantity of this crude adduct was dissolved in 50
mL ether and treated with 7.5 mL 2.5M butyllithium in hexane. After
stirring overnight, most of the liquid phase was removed with a
hypodermic syringe. The residue was dried by pumping on a vacuum
line then washed with hexane, after which 50 mL hexane and 0.98 g
zirconium tetrachloride were added. After stirring for 48 h, the
reaction mixture was filtered and the solids extracted with five 50
mL portions of dichloromethane. The filtered extracts were
evaporated and washed with hexane to leave 0.73 g of product as a
bright orange powder. Spectroscopic and chemical analysis confirmed
the identity of the desired compound.
Example 12
Propylene Polymerization with
{2-Methylbenzindene-C.sub.2H.sub.4-flu}ZrCl.- sub.2
[0218] A catalyst solution was prepared by stirring 0.04 g of the
metallocene catalyst obtained in Example 11 with 15 mL
methylaluminoxane solution. The catalyst solution was injected into
1816 g propylene held at 8.degree. C. After 40 min, the temperature
inside the reactor had risen to 26.degree. C. and maintained at
that temperature for 4.5 h, after which the polymerization reaction
was terminated. The yield of polymer product was 1534 g. .sup.13C
NMR analysis gave 30.9% mmmm, 14.2% mmmr, 4.9% rmmr, 16.2% mrr,
8.3% rmrr/mmrm, 3.7% rmrm, 7.1% rrrr, 7.8% mrrr, 7.8% mrrm, 50.0%
mm, 28.2% mr and 21.8% rr. Spectroscopic and chemical analysis
confirmed the identity of the desired product. The polymer was
extracted with hot heptane (at about 95.degree. C.) in a Soxhlet
apparatus. No material remained unextracted. Recovery was about 95%
with 5% attributed to mechanical losses. The .sup.13C NMR spectrum
of the recovered polymer matched that of the starting material
within experimental error, indicating that an insoluble,
crystalline phase was not present.
Example 13
{H.sub.2CPA-C.sub.2H.sub.4-flu}ZrCl.sub.2 (Designated 18S in Table
1, Below)
[0219] A slurry of Li(H.sub.2CPA) was prepared by treating 15 mmole
(2.88 g) dihydrocyclopentaphenanthrene (Example 9) in 50 mL diethyl
ether with 6 mL 2.5M n-butyllithium in hexane. Toluene, 50 mL, was
added to reduce the viscosity. This slurry was added to 15 mmole
flu-CH.sub.2--CH.sub.2--- OSO.sub.2CF.sub.3 in 75 mL toluene
(Example 2). The desired adduct, H.sub.2CPA-C.sub.2H.sub.4-flu was
obtained as colorless crystals. After recrystallization from
CH.sub.2Cl.sub.2-acetone 50% yield was obtained. Spectroscopic and
chemical analysis confirmed the identity of the desired
compound.
[0220] The adduct was converted to the metallocene
{H.sub.2CPA-C.sub.2H.su- b.4-flu}ZrCl.sub.2 by the method described
in Example 3. The yield of carmine colored microcrystals was 50%.
Spectroscopic and chemical analysis confirmed the identity of the
desired compound.
Example 14
Propylene Polymerization using
{H.sub.2CPA-C.sub.2H.sub.4-flu}ZrCl.sub.2
[0221] A. Polymerization at 68.degree. C. A catalyst prepared by
stirring 0.022 g {H.sub.2CPA-C.sub.2H.sub.4-flu}ZrCl.sub.2 with 15
ml, methylaluminoxane solution was added to 1816 g propylene at
1.degree. C., according to the method described in Example 4.
Within 7 min, the temperature rose to 23.degree. C. and circulation
of coolant was started. The temperature continued to rise until it
reached 68.degree. C., then declined slowly. After about 3 h, the
reactor was vented and 1435 g colorless, tacky, elastic
polypropylene was removed. .sup.13C NMR showed 2.4% mmmm, 6.0%
mmmr, 5.7% rmmr, 12.2% mmrr, 20.8% rmrr/mmrm, 10.7% rmrm, 20.8%
rrrr, 15.8% mrrr, 5.7% mrrm, 14.0% mm, 43.8% mr and 42.3% rr.
[0222] B. Polymerization at 28.degree. C. The polymerization
reaction in Run A was repeated but the amount of metallocene used
was reduced to 0.008 g. The reaction temperature was kept at about
28.degree. C. by circulation of coolant through the jacket
surrounding the reactor. After 3 hr, unreacted propylene was vented
and 1748 g nontacky, elastic polymer was removed from the reactor.
.sup.13C NMR analysis showed 0.9% mmmm, 3.3% mmmr, 6.0% rmmr, 11.4%
mmrr, 12.3% rmrr/mmrm, 4.8% rmrm, 42.0% rrrr, 17.1% mrrr, 2.2%
mrrm, 10.2% mm, 28.5% mr and 61.3% rr. Spectroscopic and chemical
analysis confirmed the identity of the desired product.
Example 15
{CPA-C.sub.2H.sub.4-flu}HfCl.sub.2
[0223] The ligand CPA-C.sub.2H.sub.4-flu was obtained as colorless
needles from toluene-heptane, m.p. 225-227.degree. C., in 51% yield
by the reaction of the lithium salt of cyclopentaphenanthrene with
flu-C.sub.2H.sub.4--OSO.sub.2CF.sub.3 according to the method
described in Example 2. Spectroscopic and chemical analysis
confirmed the identity of the desired compound.
[0224] A 1.0 g quantity of the above adduct, suspended in 50 mL
ether, was treated with 2.1 mL 2.5M butyllithium in hexane. After
12 h, solvents were removed on a vacuum line. Solid hafnium
tetrachloride, 0.83 g and 50 mL hexane were added. The reaction
mixture was stirred vigorously for 24 h. The finely divided, crude,
orange product was isolated by centrifugation and washed with
hexane then toluene and vacuum dried. The yield was 0.8 g. The
metallocene was used without further purification in subsequent
polymerization reactions. Spectroscopic and chemical analysis
confirmed the identity of the desired compound.
Example 16
Propylene Polymerization using
{CPA-C.sub.2H.sub.4-flu}HfCl.sub.2
[0225] A 0.025 g quantity of the metallocene obtained in Example 15
was stirred for 38 min with 18 mL methylaluminoxane solution. This
mixture was added to 1816 g propylene held at 0.degree. C. The
reactor was allowed to warm to room temperature, then vented and
opened. The polymer thus obtained, 43 g, was removed. .sup.13C NMR
analysis gave 4.4% mmmm, 6.3% mmmr, 5.7% rmmr, 12.3% mmrr, 15.9%
rmrr/mmrm, 8.4% rmrm, 27.7% rrrr, 14.1% mrrr, 5.2% mrrm, 16.4% mm,
36.6% mr and 47.0% rr. Spectroscopic and chemical analysis
confirmed the identity of the desired product. GPC analysis gave
M.sub.w 9.5E5, M.sub.n3.2E5, and M.sub.w/M.sub.n2.84.
Example 17
{CPA-C.sub.2H.sub.4-flu}ZrCl.sub.2 (Designated 18Q in Table 1,
Below)
[0226] To a suspension of 1.91 g CPA-C.sub.2H.sub.4-flu (Example
15) in 70 mL diethyl ether was slowly added 4 mL 2.5 M
n-butyllithium in hexane. An orange crystalline solid separated.
The reaction mixture was stirred overnight at 23.degree. C., after
which solvents were removed in a vacuum line. The reaction flask
containing the solid dilithium salt thus obtained was cooled in a
acetone-dry ice bath, and 1.17 g solid ZrCl.sub.2 was added,
followed by 70 mL dichloromethane that had been precooled to
-78.degree. C. The reaction mixture was stirred overnight as the
cold bath warmed to 23.degree. C. The solid phase was isolated by
centrifugation, then washed successively with hexane, absolute
ethanol, and hexane. The bright red solid product, dried under
vacuum, weighed 1.53 g (57%). Spectroscopic and chemical analysis
confirmed the identity of the desired compound.
Example 18
Propylene Polymerization Reactions
[0227] Propylene was polymerized at 25.+-.10.degree. C. by the
method described in Example 4. A 20.+-.10 mg quantity of
metallocene was employed; the exact amount was chosen so as to
enable maintenance of temperature and prevent too vigorous a
reaction. These catalysts, their A.P. values, and the S.I. of the
product polymers, are summarized in Table 1, below. Table 2, below
summarizes stereochemical and molecular weight data for some
polypropylenes prepared with Class A catalysts. Table 2 also
includes results from polymerization reactions carried out at
higher and lower temperatures. This has been denoted by subscripts
(i.e. 1 or 2) indicating reaction at different temperatures.
[0228] Table 3, below, presents stereochemical analyses of
polypropylenes prepared using Class B catalysts. This Table
illustrates how the stereochemical preference of these
metallocenes, i.e. whether a syndio- or isotactic-rich polymer is
formed, varies unpredictably with the structural details of the
catalyst. The data also show brimodal molecular weight
distributions and peak molecular weight, M.sub.p, of each of the
two distributions which are given in the last two columns in Table
3.
1TABLE 1 Exam- ple A.P. S.I rr/mm 18A*
(fluorenyl-C.sub.2H.sub.4-fluorenyl)ZrCl.sub.2 1.00 1.13 23/26 18B
(fluorenyl-C.sub.2H.sub.4-3-phenylindenyl)ZrCl.sub.- 2 1.16 1.50
36/24 18C (fluorenyl-C.sub.2H.sub.4-2-pbenylindenyl)ZrC- l.sub.2
1.16 2.73 22/60 18D (fluorenyl-C.sub.2H.sub.4-2-methyl-4,5- 1.22
2.27 22/50 benzoindenyl)ZrCl.sub.2 18E* (fluorenyl-CMe.sub.2-cyclo-
2.09 27.30 82/3 pentadienyl)ZrCl.sub.2 18F
(fluorenyl-C.sub.2H.sub.4-3,4-benzo- 1.18 1.33 24/32
fluorenyl)ZrCl.sub.2 18G (fluorenyl-C.sub.2H.sub.4-4-phenyl- 1.44
1.68 22/37 fluorenyl)ZrCl.sub.2 18H*
(fluorenyl-C.sub.2H.sub.4-4-(1-naphthy1)- -2,7- 1.70 13.30 6/80
di-t-butylfluorenyl)ZrCl.sub.2 18I
(fluorenyl-C.sub.2H.sub.4-3-methylindenyl)ZrCl.sub.2 1.16 1.12
29/26 18J (fluorenyl-C.sub.2H.sub.4-3-trimethylsilylin- 1.30 2.19
21/46 denyl)ZrCl.sub.2 18K
(fluorenyl-C.sub.2H.sub.4-3-trimethylsilyli- n- 1.30 1.44 25/36
denyl)HfCl.sub.2 18L* (fluorenyl-C.sub.2H.sub.4-2,7-di-para- 1.00
1.08 28/26 tolylfluoreflyl)ZrCl.sub.2 18M*
(fluorenyl-C.sub.2H.sub.4-2,7-di-t- ert- 1.00 1.26 23/29
butylfluorenyl)ZrCl.sub.2 18N
(fluorenyl-C.sub.2H.sub.4-indenyl)ZrCl.sub.2 1.35 1.65 43/26 18O*
(fluorenyl-CH.sub.2SiMe.sub.2-fluorenyl)ZrCl.sub.2 1.00 1.04 25/24
18P* (fluorenyl-SiMe.sub.2-fluorenyl)ZrCl.sub.2 1.00 1.31 29/22 18Q
(fluorenyl-C.sub.2H.sub.4-cyclopentaphen- 1.08 1.84 35/19
anthryl)ZrCl.sub.2 18R (fluorenyl-SiMe.sub.2-cyclopentaphen- 1.08
2.47 42/17 anthryl)ZrCl.sub.2 18S (fluorenyl-C.sub.2H.sub.- 4-4,5-
1.13 6.10 61/10 dihydrocyclopentaphenanthryl)ZrCl.sub.2 18T
(fluorenyl-SiMe.sub.2-4,5- 1.13 5.90 59/10
dihydrocyclopentaphenanthryl)ZrCl.sub.2 18U
(fluorenyl-SiPh.sub.2-4,5- 1.13 5.09 56/11
dihydrocyclopentaphenanthryl)ZrCl.sub.2 18V
(perhydrocyclopentaphenanthryl-C.sub.2H.sub.4- 1.10 3.92 51/13
perhydrofluorenyl)ZrCl.sub.2 18W* (fluorenyl-C.sub.2H.sub.4-4-meth-
yl- 1.11 1.03 38/37 fluorenyl)ZrCl.sub.2 18X
(cyclopentaphenanthryl-SiMe.sub.2- 1.46 6.36 11/70
indenyl)ZrCl.sub.2 18Y (3,4-Dimethylfluorenyl-SiMe.sub.2-3,4- 1.00
1.28 32/25 dimethylfluorenyl)ZrCl.sub.2 18Z*
(fluorenyl-SiMe.sub.2-indenyl)ZrCl.sub.2 1.35 1.88 24/45 18AA
(fluorenyl-SiPh.sub.2-indenyl)ZrCl.sub.2 1.35 1.23 37/30
*Comparative Example (both catalyst and polypropylene known in the
art)
[0229]
2TABLE 2 Polypropylenes Prepared with Some Type A Catalysts 5 Rx
Example Strap Bridge Temp % rrrr % rr/% mm M.sub.w/M.sub.n PD*
18Q.sub.1 --CH.dbd.CH-- CH.sub.2--CH.sub.2 -20 21 42/15 7.2E5/4.2E5
1.71 18Q.sub.2 --CH.dbd.CH-- CH.sub.2--CH.sub.2 +10 16 35/19
6.3E5/3.3E5 1.3 18T.sub.1 CH.sub.2--CH.sub.2 SiMe.sub.2 +25 40
59/10 6.6E5/4.1E5 1.6 18T.sub.2 CH.sub.2--CH.sub.2 SiMe.sub.2 +50
34 56/11 2.9E5/1.1E5 2.6 18R --CH.dbd.CH-- SiMe.sub.2 +15 25 42/17
1.4E6/4.9E5 2.85 18U CH.sub.2--CH.sub.2 SiPh.sub.2 +25 33 57/12
1.4E6/5.8E5 2.4 18S.sub.1 CH.sub.2--CH.sub.2 CH.sub.2--CH.sub.2 +65
21 42/14 8.0E4/1.9E4 4.2 18S.sub.2 CH.sub.2--CH.sub.2
CH.sub.2--CH.sub.2 +28 42 61/10 7.1E5/2.5E5 2.84 *PD means
polydispersity, i.e., M.sub.w/M.sub.n.
[0230]
3TABLE 3 Polypropylenes Prepared with Some Type B Catalysts 6 Ex. R
M AP S.I. mm:mr:rr M.sub.p (%) M.sub.p (%) 18N* H Zr 1.35 1.65
26:31:43 7.1E4 (20) 8.2E4 (80) 18B 3-Ph Zr 1.16 1.50 24:41:36 6.2E5
(69) 1.3E5 (11) 18J 3-SiMe.sub.3 Zr 1.30 2.19 46:33:21 4.3E5 (50)
8.9E4 (50) 18K 3-SiMe.sub.3 Hf 1.30 1.44 36:39:25 5.1E5 (50) 8.1E4
(50) 18I 3-CH.sub.3 Zr 1.16 1.12 26:45:29 6.3E5 (78) 1.6E5 (18) 18D
2-Me-4,5-benzo Zr 1.22 2.27 50:28:22 6.2E5 (100) .dagger. 7 Ex.
Bridge mm:mr:rr A.P. S.I. M.sub.p (%) M.sub.p (%) 18N*
C.sub.2H.sub.4 26:31:43 1.35 1.65 7.5E5 (20) 8.2E4 (80) 18Z*
SiMe.sub.2 45:32:24 1.35 1.88 3.5E5 (15) 9.6E4 (85) 18AA SiPh.sub.2
30:33:37 1.35 1.23 5.8E5 (76) 9.6E4 (24) .dagger.sample had single
peak *Catalyst is known in the art
Example 19
Polypropylene Properties
[0231] Polypropylene was prepared by the method described in
Example 4, using catalyst 18Q.sub.1
((fluorenyl-C.sub.2H.sub.4-cyclopentaphenanthryl- )ZrCl.sub.2),
except that the reaction temperature was kept at -20.degree. C. As
shown in Table 2, the S.I. for the resulting polymer was 42/15=2.8,
indicating that the lower-temperature reaction (compared to the
polymer resulting from the use of catalyst 18Q.sub.2 (reaction
temperature=+10.degree. C., S.I.=1.84) produced a polypropylene
having a higher percentage of syndiotacticity.
[0232] A sample of the low-temperature polymer, from catalyst
18Q.sub.1 was pressed into a thin film using a Carver hydraulic
press (Fred S. Carver, Inc., Model 2699, Wabash, Ind.) by pressing
at 170.degree. C. for two minutes. When cooled to 23.degree. C.,
two samples of the film were subjected to Dynamic Mechanical
Analysis at 1 Hz using a Rheometrics Model RSAII rheometer
(Rheometric Scientific, Piscataway, N.J.) at -60.degree. C. and
+250.degree. C., respectively, in order to avoid thermal
equilibrium or annealing effects on transitions. Thermal expansion
of the sample was compensated for by adjustment of the dynamic
oscillatory strain amplitude.
[0233] FIG. 4 shows the tensile storage modulus (Trace A), the loss
modulus (Trace B), and the loss tangent or tan delta (Trace C), of
the sample. As can be seen in FIG. 4, Trace A, the polypropylene of
the invention, from catalyst 18Q.sub.1, exhibited a sharp drop in
elastic modulus between -3.degree. and +8.degree. C., followed by a
surprising essentially flat tracing up to about 175.degree. C.,
more particularly between +8.degree. and +174.degree. C., a
property that is unprecedented for a polypropylene having no
measurable gross crystallinity by WAXS or detectable melting point
by DSC.
[0234] Trace B shows the loss modulus for this sample, which is a
measurement of the ability of the material to dissipate heat when
deformed. The slight rise in loss modulus with temperature is an
indication of loss of structural order as the temperature
increases, at about 180.degree. C., an abrupt change in slope of
Trace B is indicative of a physical change, such as melting. Trace
C shows the ratio of loss modulus to tensile storage modulus
(E"/E'), also known as tan delta, for the sample, and is wholly
derived from the two previous traces.
[0235] The tensile storage modulus shown in FIG. 4 corresponding to
the elastic flat plateau allows calculation of an entanglement
molecular weight ({overscore (M)}e) for the polypropylene of this
Example of 3620 g/mole, a value less than that predicted for pure
atactic polypropylene, i.e., 4650 g/mole (Z. Xu, et al., Advances
in Polymer Science, Vol. 120, Springer Verlag, Berlin (1995), pp.
1-50).
[0236] A sample of the polypropylene of the invention was further
annealed at 150.degree. C. for 60 minutes, then slowly cooled to
23.degree. C. at 1.degree. C./minute prior DMA analysis. The DMA
analysis indicated that the polymer behaved like an uncrosslinked
polypropylene, that is, fine structure that may contribute to a
plateau in the elastic modulus was prevented from forming by the
slow cooling process. This shows that the source of elastic
behavior over an extended temperature range was not due to the
relatively high molecular weight of the polypropylene alone, but
was reasonably attributed to the nanocrystallinity of the sample
before annealing.
[0237] This experiment shows that polypropylene prepared, for
example, using catalysts 18Q, 18Q.sub.1, 18R, 18S, 18T, 18U, of the
invention exhibited physical properties that have not been
described previously, that is, rubbery elastic behavior over an
extended temperature range, without evidence of gross
crystallinity. Without wishing to be bound by theory, it is
postulated that this behavior, coupled with the calculated low
entanglement molecular weight, is indicative of a near perfect
infinite network structure generated by extremely fine scale
crystallinity.
Example 20
Time Dependence of Modulus for Polypropylene
[0238] Polypropylene was prepared according to the method of
Example 4 using catalyst 18T.sub.1
((fluorenyl-dimethylsilyl-4,5-dihydrocylopentaph-
enanthryl)ZrCl.sub.2; polymerization at 25.degree. C., per Table
3). A melting point of 48.degree. C. was found via Modulated
Differential Scanning Calorimetry (MDSC) methods (Model 2980, TA
Instruments, Inc., New Castle Del.). Analysis by WAXS methods
established the presence of crystallinity in the sample by
comparison with spectra of commercially-available polypropylene:
Rexene.TM. D-100 (isotactic polypropylene from metallocene
catalyst, Rexene Corp., Dallas, Tex.); Exxon.TM. 3505 (isotactic
polypropylene from Ziegler-Natta catalyst, Exxon Chemicals Co.,
Houston, Tex.).
[0239] A film sample was prepared by pressing the polymer in a
Carver press at 176.degree. C., then allowing the film to cool to
23.degree. C. The tensile storage modulus of a portion of the film
was then determined over a lengthy time period by Dynamic
Mechanical Analysis using a Rheometrics RSA II analyzer. Results of
the analysis are shown in Table 4, below.
4TABLE 4 Modulus as a Function of Time at 23.degree. C. Time after
preparation, Tensile Storage Modulus, hours MPa Loss Tangent 0.5
2.23 0.16 2.5 2.68 0.15 4.5 4.36 0.15 23 3.14 0.12 100 10.2 0.14
120 10.3 0.14
[0240] The data of Table 4 show surprising polypropylene behavior,
that is, an increase in tensile storage modulus by a factor of 5
over a 5-day period while the loss tangent remained unchanged.
Measurement of tensile storage modulus of the sample after aging
for 28 days, using a Rheometrics RSAII instrument, revealed the
data shown in FIG. 5, which clearly shows the newly-developed
shoulder in the trace between about 15.degree. and 45.degree. C.,
corresponding to the increase in tensile modulus shown in Table 4.
Using this first "step" modulus, an entanglement molecular weight
of 545 was calculated, indicating a higher degree of structural
order than shown for the final, higher temperature equilibrium
tensile modulus plateau to 170.degree. C. A higher molecular weight
for the aged sample can be indicative of a tightly crosslinked
polymer.
[0241] In a related study, a portion of the same polypropylene
(from catalyst 18T.sub.1) was annealed at 170.degree. C. for 7-10
minutes under nitrogen, then cooled at 10.degree. C./minute to
simulate a supercooling process that wipes out previous heating and
cooling history without thermal degradation of the sample. The
growth in tensile modulus for the annealed material was followed at
45.degree. C. for 70 hours, during which time the tensile modulus
increased from 6.5 to 30 MPa. MDSC analysis of the aged sample
showed a melt endotherm at 48.degree. C., and a crystallinity of
24% was estimated from the melting enthalpy. WAXS and MDSC data was
consistent with syndiotactic crystallinity in the aged
material.
[0242] The ability of polypropylenes of the invention to organize
over time was demonstrated for polymers prepared from catalysts 18T
(polymerization at 50.degree. C.), 18S (polymerization at
65.degree. C.), and 18Q, as well as from the hafnium metallocene
catalyst prepared in Example 5.
Example 21
Permanent Set Properties of Polypropylenes
[0243] The two polypropylenes prepared as described in Examples 19
and 20 (i.e., polypropylene from catalyst 18Q.sub.1 and 18T.sub.1,
Table 2) were further characterized by their permanent set
properties, by methods described in the art, in comparison to
commercially-available rubbery polypropylene (Rexene.TM. D-100). In
these characterizations, "permanent set" of a given percentage
means that, after stretching the material at a specified percent
elongation for a specified time, the material equilibrates at a
length longer than its original length by the given percentage.
Thus, a permanent set of 10% means that the final length of the
material was 10% longer than its original length, and a permanent
set of "nil" means that the final length was the same as the
original length. The data for the characterizations is shown in
Table 5, below. Methods described in U.S. Pat. No. 5,549,080,
Example 33, which employed an initial 300% elongation, and European
Patent Application No. 707,016, p. 19, which employed an initial
100% elongation, as well as an initial elongation of 200%, were
used.
[0244] Data in Table 5, below, show that polypropylenes of the
invention exhibit less permanent set, i.e., more elasticity, by any
of three methods, than a commercial "elastic" polypropylene. The
75% permanent set in the commercial material can be interpreted as
plastic deformation of crystallites, which was not observed in
polypropylenes of the present invention. Elasticity is an important
and useful characteristic in polymers used, e.g., for
adhesives.
5TABLE 5 Permanent Set in Polypropylenes Sample % Permanent Set
Rexene D-100 Method 18-Q.sub.1 18T (Comparative) A: Immediate Test
0 5.0 17.5 A: 10 Minutes Rest and Test 0 2.5 17.5 B: Immediate Test
2.5 10.0 85.0 B: 10 Minutes Rest and Test 2.5 7.5 75.0 C: Immediate
Test 0 7.5 50.0 C: 10 Minute Rest and Test 0 5.0 42.5 Method A: EP
707016, p.19 Sample was stretched to 100% extension; held for one
minute. Test set evaluated immediately after relaxation and 10
minutes after relaxation Method B: US 5,594,080 Sample was
stretched to 300% and allowed to relax immediately. Evaluated
immediately after relaxation and 10 minutes after relaxation Method
C: Data were collected at 200% extension.
Example 22
Tack and Adhesion of Polypropylenes
[0245] Polymers prepared by the method described in Example 4 from
catalysts 18S.sub.1 and 18S.sub.2 (Table 2), that is, the same
catalyst but polymerization is carried out at +65.degree. C.
(catalyst 18S.sub.1) and at +28.degree. C. (catalyst 18S.sub.2)
were isolated, then blended as described below.
[0246] The polypropylene from catalyst 18S.sub.1 (hereinafter
referred to as `polymer A`) was a tacky, film forming material
having a weight average molecular weight of 80,000 and an S.I. of
3.0. The polypropylene from catalyst 18S.sub.2 (hereinafter
referred to as `polymer B`) had a weight average molecular weight
of 710,000 and an S.I. of 6.1. As noted in Example 14, polymer B
was found to have twice as many rrrr pentads as polymer A. Blends
of 70:30 A:B and 70:30 B:A were prepared and coated at two
thicknesses onto poly(butylene terephthalate) (PBT) that had been
sputter plasma etched to provide increased adhesiveness to
coatings. Shear adhesion data for the four formulations are shown
in Table 6, below, for a 1 Kg load on a 1 inch.times.1/2 inch (2.5
cm.times.1.3 cm) tape.
[0247] Blends were prepared in a Haake-Brabender mixing apparatus
(C. W. Brabender Co., South Hackensack, N.J.) at 210.degree. C.,
then fused to the PBT using a Carver press at 177.degree. C. and
575 kPa for 3 minutes. Shear adhesion tests were performed
according to ASTM Method D3654M-88. The data of Table 6 show that
moderate to good pressure sensitive adhesives were formed from
polypropylenes of the invention, and that failure-resistant bonding
occurred when the majority of the polymer had a higher weight
average molecular weight. Polypropylenes of the invention were
blended with numerous other polymers, such as crystalline
polypropylene(s), tacky poly-1-hexene and poly-1-octene to tailor
the adhesive performance of the mixtures as well as the rheology of
the mixtures (i.e., hot-melt type adhesives were prepared from
polypropylene and/or the mixtures noted above).
6TABLE 6 Shear Adhesion PSTC Test Method Adhesive Blend Shear
Adhesion 23.degree. C. Composition Minutes to Failure; Polymer
Polymer Adhesive Thickness 2.5 .times. 1.3 cm tape Sample S.sub.1
S.sub.2 (Substrate, PBT)* 1 Kg Load 22A 70 30 0.0035 407 22B 30 70
0.0035 1895 22C 70 30 0.0015 200 (partial cohesive failure) 22D 30
70 0.0015 3380 *Sputter plasma etched polybutyleneterephthalate
Example 23
Polypropylene Physical Properties Based On Catalysts Having C.sub.S
Symmetry
[0248] A synopsis of physical properties observed for
polypropylenes of the invention, prepared using catalysts having
C.sub.S symmetry, also referred to as Type A catalysts, is
presented in Table 7, below. Samples were prepared by pressing the
polypropylene into a film in a Carver press at 175.degree. C., then
allowing the film to cool to 23.degree. C. over a short period of
time. In the Table, Tensional Modulus values were obtained using a
Rheometrics RSA II instrument. Extrusion viscosity values were
obtained at 230.degree. C. (except for sample 23G, at 175.degree.
C.), using a 1 mm diameter capillary having a length/diameter ratio
of 50:1 on a Series 4200 Instron Capillary Rheometer (Instron
Corp., Canton, Mass.), Tensile strength and elongation at break
values were obtained using an Material Test System Model 880
servohydraulic tester (MTS Systems Corp., Minneapolis, Minn.) at a
crosshead speed of 30.5 cm/minute. Inelasticity figures refer to a
protocol of stretching a sample to 10% (ASTM D1774-90 using MTS
Model 880 machine, also) and 15%, respectively, of its original
length, holding for 3 minutes at 23.degree. C., then releasing
tension and allowing the sample to recover to an equilibrium
length. The figure reported is the percent permanent elongation of
the sample after release of tension.
[0249] Data shown in Table 7, below, support the observation that
polypropylenes of the invention are highly elastic, having tensile
strengths below 8.90 MPa with no observable yield point. The lack
of a yield point indicated lack of measurable gross crystalline
structure, further supporting the conclusion that these elastic
polymers possessed a near perfect infinite network structure
generated by nanocrystals of polypropylene.
7TABLE 7 Type A Catalysts: Synopsis of Physical Properties of
Polypropylene Tensional Extrusion Tensile Modulus, Inelasticity
Viscosity Catalyst Strength Elongation Mpa 10% 15% @ sec-1, Ex.
(Table 2) MPa at Break % 23.degree. C. 150.degree. C. Strain Strain
Pa-sec 23A 18Q.sub.1 2.14 545 2.21 1.69 4.5 0 1.1 .times. 10.sup.4
23B 18Q.sub.2 1.45 1100 1.76 0.90 0 2.7 1.0 .times. 10.sup.4 23C
18T.sub.1 2.21 710 13.0 2.21 0 2.8 1.0 .times. 10.sup.4 23D
18T.sub.2 3.04 1700 2.41 0.23 * * 6 .times. 10.sup.3 23E 18R 0.59
1200 2.65 1.93 * * 1 .times. 10.sup.4 23F 18U 2.55 345 1.04 * * *
1.1 .times. 10.sup.4 23G 18S.sub.1 .about.0.72 >1000 ** * * *
2.1 .times. 10.sup.2 (175.degree. C.) 23H 18S.sub.2 8.90
.gtoreq.1000 8.14 0.31 * * 3.5 .times. 10.sup.3 *not measured **not
measurable in tension mode
Example 24
Polypropylene Physical Properties Based On Catalysts Having C.sub.1
Symmetry
[0250] A synopsis of physical properties observed for
polypropylenes of the invention, prepared using catalysts having
C.sub.1 symmetry, also referred to as Type B catalysts, is
presented in Table 8, below. Measurements were taken as described
in Example 23. Some of the polypropylenes of Table 8 exhibited very
large extensibility (elongated at break), characteristic of
polymers that were uncrosslinked or slightly crosslinked or having
an irregular structure. In contrast to the data of Table 7 (Type A
catalysts), polypropylenes described in Table 8 exhibited a yield
point. Generally, polymers prepared using Type B catalysts had
lower (peak) molecular weights than those from Type A catalysts,
which were reflected in the generally lower extrusion viscosity
values of Table 8 vs. Table 7.
[0251] The data of Table 8 also show another instance of the
influence of catalyst molecular structure on polypropylene
properties. Comparing the polymer obtained using catalyst 18B with
that obtained using catalyst 18N, a significant decrease in the
yield point and tensile strength was noted. The molecular structure
of catalyst 18B comprised a large, bulky phenyl group at the
3-position of the indenyl ligand, where it can significantly
interact sterically with the incoming propylene monomer, whereas
catalyst 18N had only a small hydrogen atom at the 3-position. It
is believed that the decrease in the yield point and tensile
strength of the polymer prepared using catalyst 18B was due to a
decrease in structural order of the polymer, relative to that of
the polymer prepared using catalyst 18N.
8TABLE 8 Synopsis of Physical Properties of Polypropylenes Made
with Class B Catalysts Shear Tensile Yield Tensile Viscosity
Catalyst Strength Elongation Point Modulus at 10 sec.sup.-1, (Table
1) MPa at Break % MPa MPa Pa-sec 18N* 0.93 @ 5200 0.62 2.30 480
5200% (no break) 18D 0.80 @ 1000 0.34 9.90 3000 1000% (no break)
18B 0.27 @ 2000 0.07 2.10 280 2000% (no break) 18I 0.02 550 0.45
2.10 295 18AA 0.39 985 0.14 0.34 5000 18J 2.58 @ 1000 1.30 7.25
1800 1000% (no break) 18K 3.30 500 1.69 7.25 4440 Ex 5 2.65 430
1.90 14.30 8000 *catalyst is known in the art
[0252] Various modification and alterations of this invention will
become apparent to those skilled in the art without departing from
the scope and intent of this invention, and it should be understood
that this invention is not to be unduly limited to the following
illustrative embodiments set forth herein.
* * * * *