U.S. patent application number 09/897687 was filed with the patent office on 2002-01-31 for catalyst composition and process for controlling the characteristics of conjugated diene polymers.
Invention is credited to Luo, Steven.
Application Number | 20020013435 09/897687 |
Document ID | / |
Family ID | 23887164 |
Filed Date | 2002-01-31 |
United States Patent
Application |
20020013435 |
Kind Code |
A1 |
Luo, Steven |
January 31, 2002 |
Catalyst composition and process for controlling the
characteristics of conjugated diene polymers
Abstract
A catalyst composition that is the combination of or the
reaction product of ingredients including an iron-containing
compound, a hydrogen phosphite, and a mixture of two or more
organoaluminum compounds. This catalyst composition is particularly
useful for polymerizing conjugated dienes. When this catalyst
composition is used to polymerize 1,3-butadiene into syndiotactic
1,2-polybutadiene the ratio of the organoaluminum compounds can be
adjusted to vary the melting temperature and molecular weight of
the polymer product.
Inventors: |
Luo, Steven; (Akron,
OH) |
Correspondence
Address: |
John H. Hornickel, Chief I. P. Counsel
Bridgestone/Firestone, Inc.
1200 Firestone Parkway
Akron
OH
44317
US
|
Family ID: |
23887164 |
Appl. No.: |
09/897687 |
Filed: |
July 2, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09897687 |
Jul 2, 2001 |
|
|
|
09475345 |
Dec 30, 1999 |
|
|
|
6288183 |
|
|
|
|
Current U.S.
Class: |
526/139 ;
526/337; 526/338; 526/339; 526/340 |
Current CPC
Class: |
C08F 4/70 20130101; C08F
36/04 20130101; C08F 36/04 20130101; C08F 4/70 20130101 |
Class at
Publication: |
526/139 ;
526/337; 526/338; 526/339; 526/340 |
International
Class: |
C08F 004/44; C08F
236/00 |
Claims
What is claimed is:
1. A process for preparing conjugated diene polymers with desired
characteristics comprising the step of: polymerizing conjugated
diene monomers in the presence of a catalytically effective amount
of a catalyst composition formed by combining: (a) an
iron-containing compound; (b) a hydrogen phosphite; and (c) a blend
of two or more sterically distinct organoaluminum compounds.
2. The process of claim 1, where the conjugated diene monomers are
1,3-butadiene, 1,3-pentediene, 1,3-hexadiene, or mixtures thereof,
thereby forming a crystalline conjugated diene polymer.
3. The process of claim 2, where the conjugated diene monomers are
1,3-butadiene, thereby forming syndiotactic 1,2-polybutadiene.
4. The process of claim 3, where the hydrogen phosphite is an
acyclic hydrogen phosphite.
5. The process of claim 4, where the acyclic hydrogen phosphite is
defined by the following keto-enol tautomeric structure: 6where
R.sup.1 and R.sup.2, which may be the same or different, are
mono-valent organic groups.
6. The process of claim 1, where the blend of two or more
sterically distinct organoaluminum compounds includes at least one
sterically hindered organoaluminum compound and at least one
sterically non-hindered organoaluminum compound.
7. The process of claim 4, where the blend of two or more
sterically distinct organoaluminum compounds includes at least one
sterically hindered organoaluminum compound and at least one
sterically non-hindered organoaluminum compound.
8. The process of claim 7, where the at least one sterically
hindered organoaluminum compound is triisopropylaluminum,
triisobutylaluminum, tri-t-butylaluminum, trineopentylaluminum,
tricyclohexylaluminum, tris(1-methylcyclopentyl)aluminum,
tris(2,6-dimethylphenyl)aluminum, or mixtures thereof.
9. The process of claim 7, where the at least one sterically
non-hindered organoaluminum compound is trimethylaluminum,
triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum,
tri-n-hexylaluminum, tri-n-octylaluminum, or mixtures thereof.
10. The process of claim 7, where the at least one sterically
hindered organoaluminum compound is isopropylaluminoxane,
isobutylaluminoxane, t-butylaluminoxane, neopentylaluminoxane,
cyclohexylaluminoxane, 1-methylcyclopentylaluminoxane,
2,6-dimethylphenylaluminoxane, or mixtures thereof.
11. The process of claim 7, where the at least one sterically
non-hindered organoaluminum compound is methylaluminoxane,
ethylaluminoxane, n-propylaluminoxane, n-butylaluminoxane,
n-hexylaluminoxane, n-octylaluminoxane, or mixtures thereof.
12. A method for controlling the melting temperature of a
crystalline conjugated diene polymer that is prepared by
polymerizing conjugated diene monomers with a catalyst composition
that is formed by combining (a) an iron-containing compound, (b) a
hydrogen phosphite, and (c) a blend of two or more sterically
distinct organoaluminum compounds, the method comprising the steps
of: selecting at least one sterically hindered organoaluminum
compound; selecting at least one sterically non-hindered
organoaluminum compound; combining the selected organoaluminum
compounds to form ingredient (c) of the catalyst composition; and
thereafter polymerizing the conjugated diene monomers with the
catalyst composition.
13. The method of claim 12, where the conjugated diene monomers are
1,3-butadiene, 1,3-pentediene, 1,3-hexadiene, or mixtures thereof,
thereby forming a crystalline conjugated diene polymer.
14. The method of claim 13, where the conjugated diene monomers are
1,3-butadiene, thereby forming syndiotactic 1,2-polybutadiene.
15. The method of claim 14, further comprising the step of
increasing the molar ratio of the sterically hindered
organoaluminum compounds to the sterically non-hindered
organoaluminum compounds in order to increase the melting
temperature of the syndiotactic 1,2-polybutadiene.
16. The method of claim 14, further comprising the step of
decreasing the molar ratio of the sterically hindered
organoaluminum compounds to the sterically non-hindered
organoaluminum compounds in order to decrease the melting
temperature of the resulting polymer.
17. The method of claim 14, where the hydrogenphosphite is an
acyclic hydrogen phosphite.
18. The method of claim 12, where the at least one sterically
hindered organoaluminum compound is triisopropylaluminum,
triisobutylaluminum, tri-t-butylaluminum, trineopentylaluminum,
tricyclohexylaluminum, tris(1-methylcyclopentyl)aluminum,
tris(2,6-dimethylphenyl)aluminum, or a mixture thereof.
19. The method of claim 12, where the at least one sterically
non-hindered organoaluminum compound is trimethylaluminum,
triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum,
tri-n-hexylaluminum, tri-n-octylaluminum, or a mixture thereof.
20. A catalyst composition formed by a process comprising the step
of combining: (a) an iron-containing compound; (b) a hydrogen
phosphite; and (c) a blend of two or more sterically distinct
organoaluminum compounds.
Description
FIELD OF THE INVENTION
[0001] The present invention generally relates to a process for
polymerizing conjugated dienes. More particularly, the process of
the present invention employs a catalyst composition that is formed
by combining an iron-containing compound, a hydrogen phosphite, and
a blend of two or more sterically distinct organoaluminum
compounds. By utilizing this catalyst composition, the
characteristics, such as the melting temperature, of the resulting
conjugated diene polymers can be manipulated. The preferred
embodiments of the present invention are directed toward a process
for polymerizing 1,3-butadiene into syndiotactic 1,2-polybutadiene
whereby the melting temperature of the resulting polymer can be
controlled.
BACKGROUND OF THE INVENTION
[0002] Syndiotactic 1,2-polybutadiene is a crystalline
thermoplastic resin that has a stereoregular structure in which the
side chain vinyl groups are located alternately on the opposite
sides in relation to the polymeric main chain. Syndiotactic
1,2-polybutadiene is a unique material that exhibits the properties
of both plastics and rubber, and therefore it has many uses. For
example, films, fibers, and various molded articles can be made
from syndiotactic 1,2-polybutadiene. It can also be blended into
and co-cured with natural or synthetic rubber.
[0003] Syndiotactic 1,2-polybutadiene can be made by solution,
emulsion or suspension polymerization. The physical properties of
syndiotactic 1,2-polybutadiene are largely determined by its
melting temperature and molecular weight. Generally, syndiotactic
1,2-polybutadiene has a melting temperature within the range of
about 195.degree. C. to about 215.degree. C., but due to
processability considerations, it is generally desirable for
syndiotactic 1,2-polybutadiene to have a melting temperature of
less than about 195.degree. C. Accordingly, there is a need for
means to regulate the melting temperature and molecular weight of
syndiotactic 1,2-polybutadiene.
[0004] Various transition metal catalyst systems based on cobalt,
titanium, vanadium, chromium, and molybdenum for the preparation of
syndiotactic 1,2-polybutadiene have been reported. The majority of
these catalyst systems, however, have no practical utility because
they have low catalytic activity or poor stereoselectivity, and in
some cases they produce low molecular weight polymers or partially
crosslinked polymers unsuitable for commercial use.
[0005] The following two cobalt-based catalyst systems are well
known for the preparation of syndiotactic 1,2-polybutadiene on a
commercial scale: (1) a system containing cobalt
bis(acetylacetonate), triethylaluminum, water, and
triphenylphosphine (U.S. Pat. Nos. 3,498,963 and 4,182,813), and
(2) a system containing cobalt tris(acetylacetonate),
triethylaluminum, and carbon disulfide (U.S. Pat. No. 3,778,424).
These cobalt-based catalyst systems also have disadvantages.
[0006] The first cobalt catalyst system referenced above yields
syndiotactic 1,2-polybutadiene having very low crystallinity. Also,
this catalyst system develops sufficient catalytic activity only
when halogenated hydrocarbon solvents are used as the
polymerization medium, and halogenated solvents present toxicity
problems.
[0007] The second cobalt catalyst system referenced above uses
carbon disulfide as one of the catalyst components. Because of its
low flash point, obnoxious smell, high volatility, and toxicity,
carbon disulfide is difficult and dangerous to use, and requires
expensive safety measures to prevent even minimal amounts escaping
into the atmosphere. Furthermore, the syndiotactic
1,2-polybutadiene produced with this cobalt catalyst system has a
very high melting temperature of about 200-210.degree. C., which
makes it difficult to process the polymer. Although the melting
temperature of the syndiotactic 1,2-polybutadiene produced with
this cobalt catalyst system can be reduced by employing a catalyst
modifier as a fourth catalyst component, the presence of this
catalyst modifier has adverse effects on the catalyst activity and
polymer yields. Accordingly, many restrictions are required for the
industrial utilization of these cobalt-based catalyst systems.
[0008] Coordination catalyst systems based on iron-containing
compounds, such as the combination of iron(III) acetylacetonate and
triethylaluminum, have been known for some time, but they have
shown very low catalytic activity and poor stereoselectivity for
the polymerization of 1,3-butadiene. The product mixture often
contains oligomers, low molecular weight liquid polymers, and
partially crosslinked polymers. Therefore, these iron-based
catalyst systems have no industrial utility.
[0009] Because syndiotactic 1,2-polybutadiene is useful and the
catalysts known heretofore in the art have many shortcomings, it
would be advantageous to develop a new and significantly improved
catalyst composition that has high activity and stereoselectivity
for polymerizing 1,3-butadiene into syndiotactic 1,2-polybutadiene.
It would be additionally advantageous if that catalyst system was
versatile enough to control the melting temperature and molecular
weight of the polymerization product.
SUMMARY OF THE INVENTION
[0010] In general, the present invention provides a process for
preparing conjugated diene polymers with desired characteristics
comprising the step of polymerizing conjugated diene monomers in
the presence of a catalytically effective amount of a catalyst
composition formed by combining (a) an iron-containing compound,
(b) a hydrogen phosphite, and (c) a blend of two or more sterically
distinct organoaluminum compounds.
[0011] The present invention also provides a method for controlling
the melting temperature of a crystalline conjugated diene polymer
that is prepared by polymerizing conjugated diene monomers with a
catalyst composition that is formed by combining (a) an
iron-containing compound, (b) a hydrogen phosphite, and (c) a blend
of two or more sterically distinct organoaluminum compounds, the
method comprising the steps of selecting at least one sterically
hindered organoaluminum compound; selecting at least one sterically
non-hindered organoaluminum compound; combining the selected
organoaluminum compounds to form ingredient (c) of the catalyst
composition; and thereafter polymerizing the conjugated diene
monomers with the catalyst composition.
[0012] The present invention also provides a catalyst composition
formed by a process comprising the step of combining (a) an
iron-containing compound, (b) a hydrogen phosphite, and (c) a blend
of two or more sterically distinct organoaluminum compounds.
[0013] Advantageously, the catalyst composition utilized in the
present invention has very high catalytic activity and
stereoselectivity for polymerizing conjugated diene monomers such
as 1,3-butadiene. This activity and selectivity, among other
advantages, allows conjugated diene polymers, such as syndiotactic
1,2-polybutadiene, to be produced in very high yields with low
catalyst levels after relatively short polymerization times.
Significantly, the catalyst composition of this invention is very
versatile. By blending sterically distinct organoaluminum
compounds, it is possible to produce crystalline conjugated diene
polymers, such as syndiotactic 1,2-polybutadiene, with a wide range
of melting temperatures and molecular weights, thus eliminating the
need to add a melting temperature regulator or a molecular weight
regulator that adversely affects the catalyst activity and the
polymer yield. In addition, the catalyst composition utilized in
this invention does not contain carbon disulfide. Therefore, the
toxicity, objectionable smell, dangers, and expense associated with
the use of carbon disulfide are eliminated. Further, the catalyst
composition utilized in this invention is iron-based, and iron
compounds are generally stable, inexpensive, relatively innocuous,
and readily available. Furthermore, the catalyst composition
utilized in this invention has a high catalytic activity in a wide
variety of solvents including the environmentally-preferred
nonhalogenated solvents such as aliphatic and cycloaliphatic
hydrocarbons.
[0014] Other advantages and features of the present invention will
be apparent from a consideration of the following detailed
description of the present invention.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0015] The present invention is generally directed toward a process
for synthesizing conjugated diene polymers by using an iron-based
catalyst composition. The preferred embodiments of this invention
are directed toward the synthesis of crystalline conjugated diene
polymers, such as syndiotactic 1,2-polybutadiene. The iron-based
composition is formed by combining (a) an iron-containing compound,
(b) a hydrogen phosphite, and (c) a blend of two or more sterically
distinct organoaluminum compounds. It has now been found that the
characteristics of the resulting conjugated diene polymer can be
adjusted by selecting certain sterically distinct organoaluminum
compounds. For example, the melting temperature of crystalline
conjugated diene polymers can be adjusted by selecting certain
sterically distinct organoaluminum compounds or by varying the
molar ratio of the sterically distinct organoaluminum
compounds.
[0016] As noted above, the catalyst composition of the present
invention is formed by combining (a) an iron-containing compound,
(b) a hydrogen phosphite, and (c) a blend of two or more sterically
distinct organoaluminum compounds. In addition to the three
catalyst ingredients (a), (b), and (c), other organometallic
compounds or Lewis bases can also be added, if desired.
[0017] Various iron-containing compounds or mixtures thereof can be
employed as ingredient (a) of the catalyst composition of this
invention. It is generally advantageous to employ iron-containing
compounds that are soluble in a hydrocarbon solvent such as
aromatic hydrocarbons, aliphatic hydrocarbons, or cycloaliphatic
hydrocarbons. Hydrocarbon-insoluble iron-containing compounds
however, can be suspended in the polymerization medium to form the
catalytically active species and are therefore also useful.
[0018] The iron atom in the iron-containing compounds can be in
various oxidation states including but not limited to the 0, +2,
+3, and +4 oxidation states. It is preferable to use divalent iron
compounds (also called ferrous compounds), wherein the iron is in
the +2 oxidation state, and trivalent iron compounds (also called
ferric compounds), wherein the iron is in the +3 oxidation state.
Suitable types of iron-containing compounds that can be utilized
include, but are not limited to, iron carboxylates, iron
carbamates, iron dithiocarbamates, iron xanthates, iron
.beta.-diketonates, iron alkoxides, iron aryloxides, and organoiron
compounds.
[0019] Some specific examples of suitable iron carboxylates include
iron(II) formate, iron(III) formate, iron(II) acetate, iron(III)
acetate, iron(II) acrylate, iron(III) acrylate, iron(II)
methacrylate, iron(III) methacrylate, iron(II) valerate, iron(III)
valerate, iron(II) gluconate, iron(III) gluconate, iron(II)
citrate, iron(III) citrate, iron(II) fumarate, iron(III) fumarate,
iron(II) lactate, iron(III) lactate, iron(II) maleate, iron(III)
maleate, iron(II) oxalate, iron(III) oxalate, iron(II)
2-ethylhexanoate, iron(III) 2-ethylhexanoate, iron(II)
neodecanoate, iron(III) neodecanoate, iron(II) naphthenate,
iron(III) naphthenate, iron(II) stearate, iron(III) stearate,
iron(II) oleate, iron(III) oleate, iron(II) benzoate, iron(III)
benzoate, iron(II) picolinate, and iron(III) picolinate.
[0020] Some specific examples of suitable iron carbamates include
iron(II) dimethylcarbamate, iron(III) dimethylcarbamate, iron(II)
diethylcarbamate, iron(III) diethylcarbamate, iron(II)
diisopropylcarbamate, iron(III) diisopropyl-carbamate, iron(II)
dibutylcarbamate, iron(III) dibutylcarbamate, iron(II)
dibenzyl-carbamate, and iron(III) dibenzylcarbamate.
[0021] Some specific examples of suitable iron dithiocarbamates
include iron(II) dimethyldithiocarbamate, iron(III)
dimethyldithiocarbamate, iron(II) diethyl-dithiocarbamate,
iron(III) diethyldithiocarbamate, iron(II)
diisopropyldithio-carbamate, iron(III) diisopropyldithiocarbamat-
e, iron(II) dibutyldithiocarbamate, iron(III)
dibutyldithiocarbamate, iron(II) dibenzyldithiocarbamate, and
iron(III) di-benzyldithiocarbamate.
[0022] Some specific examples of suitable iron xanthates include
iron(II) methylxanthate, iron(III) methylxanthate, iron(II)
ethylxanthate, iron(III) ethyl-xanthate, iron(II)
isopropylxanthate, iron(III) isopropylxanthate, iron(II)
butyl-xanthate, iron(III) butylxanthate, iron(II) benzylxanthate,
and iron(III) benzyl-xanthate.
[0023] Some specific examples of suitable iron .beta.-diketonates
include iron(II) acetylacetonate, iron(III) acetylacetonate,
iron(II) trifluoroacetylacetonate, iron(III)
trifluoroacetylacetonate, iron(II) hexafluoroacetylacetonate,
iron(III) hexafluoroacetylacetonate, iron(II) benzoylacetonate,
iron(III) benzoylacetonate, iron (II)
2,2,6,6-tetramethyl-3,5-heptanedionate, and iron (III)
2,2,6,6-tetramethyl-3,5-heptanedionate.
[0024] Some specific examples of suitable iron alkoxides or
aryloxides include iron(II) methoxide, iron(III) methoxide,
iron(II) ethoxide, iron(III) ethoxide, iron(II) isopropoxide,
iron(III) isopropoxide, iron(II) 2-ethylhexoxide, iron(III)
2-ethylhexoxide, iron(II) phenoxide, iron(III) phenoxide, iron(II)
nonylphenoxide, iron(III) nonylphenoxide, iron(II) naphthoxide, and
iron(III) naphthoxide.
[0025] The term organoiron compound refers to any iron compound
containing at least one iron-carbon bond. Some specific examples of
suitable organoiron compounds include bis(cyclopentadienyl)iron(II)
(also called ferro-cene), bis(pentamethylcyclopentadienyl)iron(II)
(also called decamethylferrocene), bis (pentadienyl) iron (II), bis
(2,4-dimethylpentadienyl) iron (II), bis (allyl) dicarbonyl-iron
(II), (cyclopentadienyl) (pentadienyl) iron (II), tetra(1-norbomyl)
iron (IV), (tri-methylenemethane) tricarbonyliron(II), bis
(butadiene) carbonyliron(0), butadienetricarbonyliron(0), and
bis(cyclooctatetraene)i- ron(0).
[0026] Useful hydrogen phosphite compounds that can be employed as
ingredient (b) of the catalyst composition of this invention are
acyclic hydrogen phosphites, cyclic hydrogen phosphites, and
mixtures thereof.
[0027] In general, the acyclic hydrogen phosphites may be
represented by the following keto-enol tautomeric structures: 1
[0028] Where R.sup.1 and R.sup.2, which may be the same or
different, are mono-valent organic groups. Preferably, R.sup.1 and
R.sup.2 are hydrocarbyl groups such as, but not limited to, alkyl,
cycloalkyl, substituted cycloalkyl, alkenyl, cycloalkenyl,
substituted cycloalkenyl, aryl, allyl, substituted aryl, aralkyl,
alkaryl, and alkynyl groups, with each group preferably containing
from 1 carbon atom, or the appropriate minimum number of carbon
atoms to form the group, up to 20 carbon atoms. These hydrocarbyl
groups may contain heteroatoms such as, but not limited to,
nitrogen, oxygen, silicon, sulfur, and phosphorus atoms. The
acyclic hydrogen phosphites exist mainly as the keto tautomer
(shown on the left), with the enol tautomer (shown on the right)
being the minor species. The equilibrium constant for the
above-mentioned tautomeric equilibrium is dependent upon factors
such as the temperature, the types of R.sup.1 and R.sup.2 groups,
the type of solvent, and the like. Both tautomers may be associated
in dimeric, trimeric or oligomeric forms by hydrogen bonding.
Either of the two tautomers or mixtures thereof can be
employed.
[0029] Some representative and non-limiting examples of suitable
acyclic hydrogen phosphites are dimethyl hydrogen phosphite,
diethyl hydrogen phosphite, dibutyl hydrogen phosphite, dihexyl
hydrogen phosphite, dioctyl hydrogen phosphite, didecyl hydrogen
phosphite, didodecyl hydrogen phosphite, dioctadecyl hydrogen
phosphite, bis(2,2,2-trifluoroethyl) hydrogen phosphite,
diisopropyl hydrogen phosphite, bis(3,3-dimethyl-2-butyl) hydrogen
phosphite, bis(2,4-dimethyl-3-pentyl) hydrogen phosphite,
di-t-butyl hydrogen phosphite, bis(2-ethylhexyl) hydrogen
phosphite, dineopentyl hydrogen phosphite, bis(cyclopropylmethyl)
hydrogen phosphite, bis(cyclobutylmethyl) hydrogen phosphite,
bis(cyclopentylmethyl) hydrogen phosphite, bis(cyclohexylmethyl)
hydrogen phosphite, dicyclobutyl hydrogen phosphite, dicyclopentyl
hydrogen phosphite, dicyclohexyl hydrogen phosphite, dimethyl
hydrogen phosphite, diphenyl hydrogen phosphite, dinaphthyl
hydrogen phosphite, dibenzyl hydrogen phosphite, bis
(1-naphthylmethyl) hydrogen phosphite, diallyl hydrogen phosphite,
dimethallyl hydrogen phosphite, dicrotyl hydrogen phosphite, ethyl
butyl hydrogen phosphite, methyl hexyl hydrogen phosphite, methyl
neopentyl hydrogen phosphite, methyl phenyl hydrogen phosphite,
methyl cyclohexyl hydrogen phosphite, methyl benzyl hydrogen
phosphite, and the like. Mixtures of the above dihydrocarbyl
hydrogen phosphites may also be utilized.
[0030] In general, cyclic hydrogen phosphites contain a divalent
organic group that bridges between the two oxygen atoms that are
singly-bonded to the phosphorus atom. These cyclic hydrogen
phosphites may be represented by the following keto-enol tautomeric
structures: 2
[0031] Where R.sup.3 is a divalent organic group. Preferably,
R.sup.3 is a hydrocarbylene group such as, but not limited to,
alkylene, cycloalkylene, substituted alkylene, substituted
cycloalkylene, alkenylene, cycloalkenylene, substituted alkenylene,
substituted cycloalkenylene, arylene, and substituted arylene
groups, with each group preferably containing from 1 carbon atom,
or the appropriate minimum number of carbon atoms to form the
group, up to 20 carbon atoms. These hydrocarbylene groups may
contain heteroatoms such as, but not limited to, nitrogen, oxygen,
silicon, sulfur, and phosphorus atoms. The cyclic hydrogen
phosphites exist mainly as the keto tautomer (shown on the left),
with the enol tautomer (shown on the right) being the minor
species. The equilibrium constant for the above-mentioned
tautomeric equilibrium is dependent upon factors such as the
temperature, the types of R.sup.3 group, the type of solvent, and
the like. Both tautomers may be associated in dimeric, trimeric or
oligomeric forms by hydrogen bonding. Either of the two tautomers
or mixtures thereof can be used.
[0032] The cyclic hydrogen phosphites may be synthesized by the
transesterification reaction of an acyclic dihydrocarbyl hydrogen
phosphite (usually dimethyl hydrogen phosphite or diethyl hydrogen
phosphite) with an alkylene diol or an arylene diol. Procedures for
this transesterification reaction are well known to those skilled
in the art. Typically, the transesterification reaction is carried
out by heating a mixture of an acyclic dihydrocarbyl hydrogen
phosphite and an alkylene diol or an arylene diol. Subsequent
distillation of the side-product alcohol (usually methanol or
ethanol) that results from the transesterification reaction leaves
the new-made cyclic hydrogen phosphite.
[0033] Some specific examples of suitable cyclic alkylene hydrogen
phosphites are 2-oxo-(2H)-5-butyl-5-ethyl-1,3,2-dioxaphosphorinane,
2-oxo-(2H)-5,5-dimethyl-1,3,2-dioxaphosphorinane,
2-oxo-(2H)-1,3,2-dioxap- hosphorinane,
2-oxo-(2H)-4-methyl-1,3,2-dioxaphosphorinane,
2-oxo-(2H)-5-ethyl-5-methyl-1,3,2-dioxaphosphorinane,
2-oxo-(2H)-5,5-diethyl-1,3,2-dioxaphosphorinane,
2-oxo-(2H)-5-methyl-5-pr- opyl-1,3,2-dioxaphosphorinane,
2-oxo-(2H)-4-isopropyl-5,5-dimethyl-1,3,2-d- ioxaphosphorinane,
2-oxo-(2H)-4,6-dimethyl-1,3,2-dioxaphosphorinane,
2-oxo-(2H)-4-propyl-5-ethyl-1,3,2-dioxaphosphorinane,
2-oxo-(2H)-4-methyl-1,3,2-dioxaphospholane,
2-oxo-(2H)-4,5-dimethyl-1,3,2- -dioxaphospholane,
2-oxo-(2H)-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane, and the
like. Mixtures of the above cyclic alkylene hydrogen phosphites may
also be utilized.
[0034] Some specific examples of suitable cyclic arylene hydrogen
phosphites are 2-oxo-(2H)-4,5-benzo-1,3,2-dioxaphospholane,
2-oxo-(2H)-4,5-(3'-methylbenzo)-1,3,2-dioxaphospholane,
2-oxo-(2H)-4,5-(4'-methylbenzo)-1,3,2-dioxaphospholane,
2-oxo-(2H)-4,5-(4'-tert-butylbenzo)-1,3,2-dioxaphospholane,
2-oxo-(2H)-4,5-naphthalo-1,3,2-dioxaphospholane, and the like.
Mixtures of the above cyclic arylene hydrogen phosphites may also
be utilized.
[0035] As noted above, ingredient (c) of the catalyst composition
of the present invention includes a blend of two or more
organoaluminum compounds that have distinct steric hindrance. In is
generally advantageous to employ organoaluminum compounds that are
soluble in hydrocarbon solvent. As used herein, the term
"organoaluminum compound" refers to any aluminum compound
containing at least one aluminum-carbon bond. In a preferred
embodiment, ingredient (c) of the catalyst composition utilized in
this invention is formed by combining at least one organoaluminum
compound that is sterically hindered with at least one
organoaluminum compound that is sterically less hindered or, more
simply stated, non-hindered.
[0036] The organoaluminum compounds employed to form ingredient (c)
are generally characterized by containing at least one organic
group that is attached to an aluminum atom via a carbon atom. The
structure of these organic groups determines whether the
organoaluminum compound is sterically hindered or non-hindered for
purposes of this invention. The structures of these organic groups
are best explained with reference to the following figure, which
shows an organic group attached to an aluminum atom: 3
[0037] where C.sup..alpha. will be referred to as the .alpha.
carbon and C.sup..beta. will be referred to as the p carbon. In
general, the steric hindrance of an organoaluminum compound is
determined by the substitution patterns of the .alpha. and .beta.
carbons. An organoaluminum compound is sterically hindered where
the a carbon is secondary or tertiary, i.e., has only one or no
hydrogen atom bonded thereto. Also, an organoalurninum compound is
hindered where the .beta. carbon has only one or no hydrogen atom
bonded thereto. On the other hand, an organoaluminum compound is
non-hindered where the a carbon is primary, i.e., has two hydrogen
atoms bonded thereto, and the .beta. carbon has at least two
hydrogen atoms bonded thereto. Other non-hindered organic groups
include CH.sub.3 or CH.sub.2F.
[0038] Non-limiting examples of sterically hindered organic groups
include isopropyl, isobutyl, t-butyl, neopentyl, cyclohexyl,
1-methylcyclopentyl, and 2,6-dimethylphenyl groups. Non-limiting
examples of non-hindered organic groups include methyl, ethyl,
n-propyl, n-butyl, n-hexyl, and n-octyl groups.
[0039] Those skilled in the art will understand that an
organoaluminum compound may include both hindered and non-hindered
organic groups because the aluminum atom generally has a valence of
three as shown in the foregoing figure. In the event that the
organoaluminum compound includes both hindered and non-hindered
organic groups, then, for purposes of this specification, the
compound will be deemed to be both sterically hindered and
non-hindered because it is believed that both the hindered and
non-hindered organic groups will have an impact on the
characteristics of the resulting polymer.
[0040] A preferred class of organoaluminum compounds that can be
utilized to form ingredient (c) is represented by the general
formula AlR.sub.nX.sub.3-n, where each R, which may be the same or
different, is a mono-valent organic group that is attached to the
aluminum atom via a carbon atom, where n is an integer of 1 to 3,
and where each X, is selected from a hydrogen atom, a carboxylate
group, an alkoxide group, or an aryloxide group. Preferably, each R
is a hydrocarbyl group such as, but not limited to, alkyl,
cycloalkyl, substituted cycloalkyl, alkenyl, cycloalkenyl,
substituted cycloalkenyl, aryl, allyl, substituted aryl, aralkyl,
alkaryl, and alkynyl groups, with each group preferably containing
from 1 carbon atom, or the appropriate minimum number of carbon
atoms to form the group, up to about 20 carbon atoms. Also, these
hydrocarbyl groups may contain heteroatoms such as oxygen, sulfur,
nitrogen, silicon, and phosphorous atoms. Preferably, each X is a
carboxylate group, an alkoxide group, or an aryloxide group, with
each group preferably containing from 1 carbon atom, or the
appropriate minimum number of carbon atoms to form the group, up to
about 20 carbon atoms.
[0041] Thus, some suitable types of organoaluminum compounds that
can be utilized include, but are not limited to,
trihydrocarbylaluminum, dihydrocarbylaluminum hydride,
hydrocarbylaluminum dihydride, dihydrocarbylaluminum carboxylate,
hydrocarbylaluminum bis(carboxylate), dihydrocarbylaluminum
alkoxide, hydrocarbylaluminum dialkoxide, dihydrocarbylaluminum
aryloxide, hydrocarbylaluminum diaryloxide, and the like, and
mixtures thereof. Trihydrocarbylaluminum compounds are generally
preferred.
[0042] Some specific examples of organoaluminum compounds that can
be utilized include trimethylaluminum, triethylaluminum,
triisobutylaluminum, tri-n-propylaluminum, triisopropylaluminum,
tri-n-butylaluminum, tri-t-butylaluminum, tri-n-hexylaluminum,
tri-n-octylaluminum, tricyclohexylaluminum, triphenylaluminum,
tri-p-tolylaluminum, tribenzylaluminum, trineopentylaluminum,
tris(1-methylcyclopentyl)aluminum,
tris(2,6-dimethylphenyl)aluminum, diethylphenylaluminum,
diethyl-p-tolylaluminum, diethylbenzylaluminum,
ethyldiphenylaluminum, ethyldi-p-tolylaluminum,
ethyldibenzylaluminum, diethylaluminum hydride, di-n-propylaluminum
hydride, diisopropylaluminum hydride, di-n-butylaluminum hydride,
diisobutylaluminum hydride, di-n-octylaluminum hydride,
diphenylaluminum hydride, di-p-tolylaluminum hydride,
dibenzylaluminum hydride, phenylethylaluminum hydride,
phenyl-n-propylaluminum hydride, phenylisopropylaluminum hydride,
phenyl-n-butylaluminum hydride, phenylisobutylaluminum hydride,
phenyl-n-octylaluminum hydride, p-tolylethylaluminum hydride,
p-tolyl-n-propylaluminum hydride, p-tolylisopropylaluminum hydride,
p-tolyl-n-butylaluminum hydride, p-tolylisobutylaluminum hydride,
p-tolyl-n-octylaluminum hydride, benzylethylaluminum hydride,
benzyl-n-propylaluminum hydride, benzylisopropylaluminum hydride,
benzyl-n-butylaluminum hydride, benzylisobutylaluminum hydride, and
benzyl-n-octylaluminum hydride, ethylaluminum dihydride,
n-propylaluminum dihydride, isopropylaluminum dihydride,
n-butylaluminum dihydride, isobutylaluminum dihydride,
-octylaluminum dihydride, dimethylaluminum hexanoate,
diethylaluminum octoate, diisobutylaluminum 2-ethylhexanoate,
dimethylaluminum neodecanoate, diethylaluminum stearate,
diisobutylaluminum oleate, methylaluminum bis (hexanoate),
ethylaluminum bis (octoate), isobutylaluminum
bis(2-ethylhexanoate), methylaluminum bis(neodecanoate),
ethylaluminum bis(stearate), isobutylaluminum bis(oleate),
dimethylaluminum methoxide, diethylaluminum methoxide,
diisobutylaluminum methoxide, dimethylaluminum ethoxide,
diethylaluminum ethoxide, diisobutylaluminum ethoxide,
dimethylaluminum phenoxide, diethylaluminum phenoxide,
diisobutylaluminum phenoxide, methylaluminum dimethoxide,
ethylaluminum dimethoxide, isobutylaluminum dimethoxide,
methylaluminum diethoxide, ethylaluminum diethoxide,
isobutylaluminum diethoxide, methylaluminum diphenoxide,
ethylaluminum diphenoxide, isobutylaluminum diphenoxide, tris
(fluromethyl) aluminum, and the like, and mixtures thereof.
[0043] Another class of organoaluminum compounds that can be
utilized to form ingredient (c) of the catalyst composition of this
invention is aluminoxanes. Aluminoxanes are well known in the art
and comprise oligomeric linear aluminoxanes that can be represented
by the general formula: 4
[0044] and oligomeric cyclic aluminoxanes that can be represented
by the general formula: 5
[0045] where x is an integer of 1 to about 100, preferably about 10
to about 50; y is an integer of 2 to about 100, preferably about 3
to about 20; and each R.sup.4, which may be the same or different,
is a mono-valent organic group that is attached to the aluminum
atom via a carbon atom. Preferably, each R.sup.4 is a hydrocarbyl
group such as, but not limited to, alkyl, cycloalkyl, substituted
cycloalkyl, alkenyl, cycloalkenyl, substituted cycloalkenyl, aryl,
allyl, substituted aryl, aralkyl, alkaryl, and alkynyl groups, with
each group preferably containing from 1 carbon atoms, or the
appropriate minimum number of carbon atoms to form the group, up to
about 20 carbon atoms. These hydrocarbyl groups may contain
heteroatoms such as, but not limited to, nitrogen, oxygen, silicon,
sulfur, and phosphorus atoms. It should be noted that the number of
moles of the aluminoxane as used in this application refers to the
number of moles of the aluminum atoms rather than the number of
moles of the oligomeric aluminoxane molecules. This convention is
commonly employed in the art of catalysis utilizing
aluminoxanes.
[0046] In general, aluminoxanes can be prepared by reacting
trihydrocarbylaluminum compounds with water. This reaction can be
performed according to known methods, such as (1) a method in which
the trihydrocarbylaluminum compound is dissolved in an organic
solvent and then contacted with water, (2) a method in which the
trihydrocarbylaluminum compound is reacted with water of
crystallization contained in, for example, metal salts, or water
adsorbed in inorganic or organic compounds, and (3) a method in
which the trihydrocarbylaluminum compound is added to the monomer
or monomer solution that is to be polymerized, and then water is
added.
[0047] Some specific examples of suitable aluminoxane compounds
that can be utilized include methylaluminoxane (MAO), modified
methylaluminoxane (MMAO), ethylaluminoxane, n-propylaluminoxane,
isopropylaluminoxane, -butylaluminoxane, n-hexylaluminoxane,
n-octylaluminoxane, isobutylaluminoxane, t-butylaluminoxane,
neopentylaluminoxane, cyclohexylaluminoxane,
1-methylcyclopentylaluminoxane, 2,6-dimethylphenylaluminoxane, and
the like, and mixtures thereof. Isobutylaluminoxane is particularly
useful on the grounds of its availability and its solubility in
aliphatic and cycloaliphatic hydrocarbon solvents. Modified
methylaluminoxane can be formed by substituting about 20-80% of the
methyl groups of methylaluminoxane with C.sub.2 to C.sub.12
hydrocarbyl groups, preferably with isobutyl groups, by using
techniques known to those skilled in the art.
[0048] The catalyst composition of this invention has very high
catalytic activity over a wide range of total catalyst
concentrations and catalyst ingredient ratios. The polymers having
the most desirable properties, however, are obtained within a
narrower range of total catalyst concentrations and catalyst
ingredient ratios. Further, it is believed that the three catalyst
ingredients (a), (b), and (c) can interact to form an active
catalyst species. Accordingly, the optimum concentration for any
one catalyst ingredient is dependent upon the concentrations of the
other catalyst ingredients. The molar ratio of the hydrogen
phosphite to the iron-containing compound (P/Fe) can be varied from
about 0.5:1 to about 50:1, more preferably from about 1:1 to about
25:1, and even more preferably from about 2:1 to about 10:1. The
molar ratio of the aluminum in the blend of two or more
organoaluminum compounds to the iron-containing compound (Al/Fe)
can be varied from about 1:1 to about 100:1, more preferably from
about 3:1 to about 50:1, and even more preferably from about 5:1 to
about 25:1.
[0049] As discussed above, the catalyst composition of the present
invention is preferably formed by combining the three catalyst
ingredients (a), (b), and (c). Although an active catalyst species
is believed to result from this combination, the degree of
interaction or reaction between the various ingredients or
components is not known with any great degree of certainty.
Therefore, it should be understood that the term "catalyst
composition" has been employed to encompass a simple mixture of the
ingredients, a complex of the various ingredients that is caused by
physical or chemical forces of attraction, a chemical reaction
product of the ingredients, or a combination of the foregoing.
[0050] The catalyst composition of the present invention can be
formed by combining or mixing the catalyst ingredients or
components by using, for example, one of the following methods.
[0051] First, the catalyst composition may be formed in situ by
adding the three catalyst ingredients to a solution containing
monomer and solvent, or simply bulk monomer, in either a stepwise
or simultaneous manner. When adding the catalyst ingredients in a
stepwise manner, the sequence in which the ingredients are added is
not critical. Preferably, however, the iron-containing compound is
added first, followed by the hydrogen phosphite, and finally
followed by the blend of two or more organoalurninum compounds.
[0052] Second, the three catalyst ingredients may be pre-mixed
outside the polymerization system at an appropriate temperature,
which is generally from about -20.degree. C. to about 80.degree.
C., and the resulting catalyst composition is then added to the
monomer solution.
[0053] Third, the catalyst composition may be pre-formed in the
presence of monomer. That is, the three catalyst ingredients are
pre-mixed in the presence of a small amount of monomer at an
appropriate temperature, which is generally from about -20.degree.
C. to about 80.degree. C. The amount of monomer that is used for
the catalyst pre-forming can range from about 1 to about 500 moles
per mole of the iron-containing compound, and preferably should be
from about 4 to about 100 moles per mole of the iron-containing
compound. The resulting catalyst composition is then added to the
remainder of the monomer that is to be polymerized.
[0054] Fourth, the catalyst composition may be formed by using a
two-stage procedure. The first stage involves combining the
iron-containing compound and the blend of two or more
organoaluminum compounds in the presence of a small amount of
monomer at an appropriate temperature, which is generally from
about -20.degree. C. to about 80.degree. C. In the second stage,
the foregoing reaction mixture and the hydrogen phosphite are
charged in either a stepwise or simultaneous manner to the
remainder of the monomer that is to be polymerized.
[0055] Fifth, an alternative two-stage procedure may also be
employed. An iron-ligand complex is first formed by pre-combining
the iron-containing compound with the hydrogen phosphite. Once
formed, this iron-ligand complex is then combined with the blend of
two or more organoaluminum compounds to form the active catalyst
species. The iron-ligand complex can be formed separately or in the
presence of the monomer that is to be polymerized. This
complexation reaction can be conducted at any convenient
temperature at normal pressure, but for an increased rate of
reaction, it is preferable to perform this reaction at room
temperature or above. The temperature and time used for the
formation of the iron-ligand complex will depend upon several
variables including the particular starting materials and the
solvent employed. Once formed, the iron-ligand complex can be used
without isolation from the complexation reaction mixture. If
desired, however, the iron-ligand complex may be isolated from the
complexation reaction mixture before use.
[0056] With respect to the catalyst ingredient (c), i.e., the blend
of two or more organoaluminum compounds, it is advantageous to
preform this blend by combining two or more organoaluminum
compounds prior to mixing the blend with the other catalyst
ingredients and the monomers that are to be polymerized.
Nevertheless, the blend of two or more organoaluminum compounds can
also be formed in situ. That is, the two or more organoaluminum
compounds are combined at the time of polymerization in the
presence of the other catalyst ingredients and the monomers that
are to be polymerized.
[0057] When a solution of the iron-based catalyst composition or
one or more of the catalyst ingredients is prepared outside the
polymerization system as set forth in the foregoing methods, an
organic solvent or carrier is preferably employed. Useful solvents
include hydrocarbon solvents such as aromatic hydrocarbons,
aliphatic hydrocarbons, and cycloaliphatic hydrocarbons.
Non-limiting examples of aromatic hydrocarbon solvents include
benzene, toluene, xylenes, ethylbenzene, diethylbenzene,
mesitylene, and the like. Non-limiting examples of aliphatic
hydrocarbon solvents include n-pentane, n-hexane, n-heptane,
n-octane, n-nonane, n-decane, isopentane, isohexanes, isopentanes,
isooctanes, 2,2-dimethylbutane, petroleum ether, kerosene,
petroleum spirits, and the like. Non-limiting examples of
cycloaliphatic hydrocarbon solvents include cyclopentane,
cyclohexane, methylcyclopentane, methylcyclohexane, and the like.
Commercial mixtures of the above hydrocarbons may also be used. For
environmental reasons, aliphatic and cycloaliphatic solvents are
highly preferred. The foregoing organic solvents may serve to
dissolve the catalyst composition or ingredients, or the solvent
may simply serve as a carrier in which the catalyst composition or
ingredients may be suspended.
[0058] As described above, the catalyst composition utilized in the
present invention exhibits a very high catalytic activity for the
polymerization of conjugated dienes. Some specific examples of
conjugated diene that can be polymerized include 1,3-butadiene,
isoprene, 1,3-pentadiene, 1,3-hexadiene,
2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene,
2-methyl-1,3-pentadiene, 3-methyl-1,3-pentadiene,
4-methyl-1,3-pentadiene, and 2,4-hexadiene. Mixtures of two or more
conjugated dienes may also be utilized in co-polymerization. The
preferred conjugated dienes are 1,3-butadiene, isoprene,
1,3-pentadiene, and 1,3-hexadiene. The most preferred monomer is
1,3-butadiene inasmuch as the catalyst composition of this
invention advantageously has very high catalytic activity and
stereoselectivity for polymerizing 1,3-butadiene into syndiotactic
1,2-polybutadiene, and, as noted above, the melting temperature of
the syndiotactic 1,2-polybutadiene can be adjusted.
[0059] The production of conjugated diene polymers, such as
syndiotactic 1,2-polybutadiene, according to this invention is
accomplished by polymerizing conjugated diene monomers in the
presence of a catalytically effective amount of the foregoing
catalyst composition. There are available a variety of methods for
bringing the ingredients of the catalyst composition into contact
with conjugated dienes as described above. To understand what is
meant by a catalytically effective amount, it should be understood
that the total catalyst concentration to be employed in the
polymerization mass depends on the interplay of various factors
such as the purity of the ingredients, the polymerization
temperature, the polymerization rate and conversion desired, and
many other factors. Accordingly, specific total catalyst
concentration cannot be definitively set forth except to say that
catalytically effective amounts of the respective catalyst
ingredients should be used. Generally, the amount of the
iron-containing compound used can be varied from about 0.01 to
about 2 mmol per 100 g of conjugated diene monomers, with a more
preferred range being from about 0.02 to about 1.0 mmol per 100 g
of conjugated diene monomers, and a most preferred range being from
about 0.05 to about 0.5 mmol per 100 g of conjugated diene
monomers.
[0060] The polymerization of conjugated diene monomers according to
this invention is preferably carried out in an organic solvent as
the diluent. Accordingly, a solution polymerization system may be
employed in which both the monomer to be polymerized and the
polymer formed are soluble in the polymerization medium.
Alternatively, a precipitation polymerization system may be
employed by choosing a solvent in which the polymer formed is
insoluble. In both cases, an amount of the organic solvent in
addition to the organic solvent that may be used in preparing the
iron-based catalyst composition is usually added to the
polymerization system. The additional organic solvent may be either
the same as or different from the organic solvent contained in the
catalyst solutions. It is normally desirable to select an organic
solvent that is inert with respect to the catalyst composition
employed to catalyze the polymerization. Suitable types of organic
solvents that can be utilized as the diluent include, but are not
limited to, aliphatic, cycloaliphatic, and aromatic hydrocarbons.
Some representative examples of suitable aliphatic solvents include
n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane,
isopentane, isohexanes, isopentanes, isooctanes,
2,2-dimethylbutane, petroleum ether, kerosene, petroleum spirits,
and the like. Some representative examples of suitable
cycloaliphatic solvents include cyclopentane, cyclohexane,
methylcyclopentane, methylcyclohexane, and the like. Some
representative examples of suitable aromatic solvents include
benzene, toluene, xylenes, ethylbenzene, diethylbenzene,
mesitylene, and the like. Commercial mixtures of the above
hydrocarbons may also be used. For environmental reasons, aliphatic
and cycloaliphatic solvents are highly preferred.
[0061] The concentration of conjugated diene monomers to be
polymerized is not limited to a special range. Generally, however,
it is preferred that the concentration of the monomer present in
the polymerization medium at the beginning of the polymerization be
in a range of from about 3% to about 80% by weight, more preferably
from about 5% to about 50% by weight, and even more preferably from
about 10% to about 30% by weight.
[0062] The polymerization of conjugated diene monomers according to
this invention may also be carried out by means of bulk
polymerization, which refers to a polymerization environment where
no solvents are employed. Bulk polymerization can be conducted
either in a condensed liquid phase or in a gas phase.
[0063] In performing the polymerization of conjugated diene
monomers according to this invention, a molecular weight regulator
may be employed to control the molecular weight of the conjugated
diene polymers to be produced. As a result, the scope of the
polymerization system can be expanded in such a manner that it can
be used for the production of conjugated diene polymers having a
wide range of molecular weights. Suitable types of molecular weight
regulators that can be utilized include, but are not limited to,
a-olefins such as ethylene, propylene, 1-butene, 1-pentene,
1-hexene, 1-heptene, and 1-octene; accumulated diolefins such as
allene and 1,2-butadiene; nonconjugated diolefins such as
1,6-octadiene, 5-methyl-1,4-hexadiene, 1,5-cyclooctadiene,
3,7-dimethyl-1,6-octadiene, 1,4-cyclohexadiene, 4-vinylcyclohexene,
1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 1,6-heptadiene,
1,2-divinylcyclohexane, 5-ethylidene-2-norbomene,
5-methylene-2-norbornen- e, 5-vinyl-2-norbornene,
dicyclopentadiene, and 1,2,4-trivinylcyclohexane; acetylenes such
as acetylene, methylacetylene and vinylacetylene; and mixtures
thereof. The amount of the molecular weight regulator used,
expressed in parts per hundred parts by weight of the conjugated
diene monomers (phm), is from about 0.01 to about 10 phm,
preferably from about 0.02 to about 2 phm, and more preferably from
about 0.05 to about 1 phm.
[0064] The molecular weight of the conjugated diene polymers to be
produced can also be effectively controlled by polymerizing
conjugated diene monomers in the presence of hydrogen gas. In this
case, the preferable partial pressure of hydrogen gas is within the
range of about 0.01 to about 50 atmospheres.
[0065] The polymerization of conjugated diene monomers according to
this invention may be carried out as a batch process, a continuous
process, or even a semi-continuous process. In the semi-continuous
process, monomer is intermittently charged as needed to replace
that monomer already polymerized. In any case, the polymerization
is desirably conducted under anaerobic conditions by using an inert
protective gas such as nitrogen, argon or helium, with moderate to
vigorous agitation. The polymerization temperature employed in the
practice of this invention may vary widely from a low temperature,
such as -10.degree. C. or below, to a high temperature such as
100.degree. C. or above, with a preferred temperature range being
from about 20.degree. C. to about 90.degree. C. The heat of
polymerization may be removed by external cooling, cooling by
evaporation of the monomer or the solvent, or a combination of the
two methods. Although the polymerization pressure employed may vary
widely, a preferred pressure range is from about 1 atmosphere to
about 10 atmospheres.
[0066] Once a desired conversion is achieved, the polymerization
can be stopped by the addition of a polymerization terminator that
inactivates the catalyst. Typically, the terminator employed is a
protic compound, which includes, but is not limited to, an alcohol,
a carboxylic acid, an inorganic acid, water, or a mixture thereof.
An antioxidant such as 2,6-di-tert-butyl-4-methylphenol may be
added along with, before or after the addition of the terminator.
The amount of the antioxidant employed is preferably in the range
of 0.2% to 1% by weight of the polymer product. When the
polymerization reaction has been stopped, the polymer can be
recovered from the polymerization mixture by conventional
procedures of desolventization and drying. For instance, the
polymer may be isolated from the polymerization mixture by
coagulation of the polymerization mixture with an alcohol such as
methanol, ethanol, or isopropanol, or by steam distillation of the
solvent and the unreacted monomer, followed by filtration. The
polymer product is then dried to remove residual amounts of solvent
and water.
[0067] As noted above, a preferred embodiment of this invention is
directed toward a process for the synthesis of crystalline
conjugated diene polymers such as syndiotactic 1,2-polybutadiene.
Advantageously, the melting temperature of the resulting
crystalline conjugated diene polymers produced according to this
invention can be manipulated by employing a blend of two or more
organoaluminum compounds that have distinct steric hindrance. In
general, it has been found that the use of a sterically hindered
organoaluminum compound within the iron-based catalyst composition
gives rise to a polymer having a relatively high melting
temperature, and that the use of a sterically non-hindered
organoaluminum compound within the iron-based catalyst composition
gives rise to a polymer having a relatively low melting
temperature. Surprisingly, it has been discovered that by employing
a blend of sterically dissimilar organoaluminum compounds, one can
tailor the melting temperature of the resulting polymer. In other
words, by using a blend of a sterically hindered organoaluminum
compound that yields a polymer having a relatively high melting
temperature and a sterically non-hindered organoaluminum compound
that yields a polymer having a relatively low melting temperature,
one can obtain a polymer whose melting temperature is somewhere
between the relatively high and relative low temperatures.
[0068] For example, when an acyclic hydrogen phosphite is employed
within the iron-based catalyst composition, the use of a sterically
non-hindered organoaluminum compound generally yields a
syndiotactic 1,2-polybutadiene polymer having amelting temperature
of from about 90.degree. C. to about 130.degree. C. On the other
hand, the use of a sterically hindered organoaluminum compound
generally yields a syndiotactic 1,2-polybutadiene polymer having a
melting temperature of from about 180.degree. C. to about
210.degree. C. By using a blend of a sterically hindered
organoaluminum compound and a sterically non-hindered
organoaluminum compound, one can obtain a syndiotactic
1,2-polybutadiene polymer whose melting temperature is somewhere
between about 90.degree. C. and about 210.degree. C. when an
acyclic hydrogen phosphite is used within the catalyst composition.
Advantageously, the process of this invention allows for the
synthesis of syndiotactic 1,2-polybutadiene having a melting
temperature from about 130.degree. C. to about 170.degree. C., more
advantageously from about 140.degree. C. to about 170.degree. C.,
and even more advantageously from about 150.degree. C. to about
160.degree. C.
[0069] Moreover, the desired melting temperature of the resulting
crystalline conjugated diene polymer can be achieved by adjusting
the molar ratio of the hindered to non-hindered organoaluminum
compounds. In general, the melting temperature of the resulting
polymer can be increased by increasing the molar ratio of the
hindered to non-hindered organoaluminum compounds. Likewise, the
melting temperature of the resulting polymer can be decreased by
decreasing the molar ratio of the hindered to non-hindered
organoaluminum compounds.
[0070] In addition to adjusting the molar ratio of the hindered to
non-hindered organoaluminum compounds, the melting temperatures of
the resulting crystalline conjugated diene polymer can be
manipulated by selecting certain organoaluminum compounds within
the class of hindered compounds, by selecting certain
organoaluminum compounds within the class of non-hindered
compounds, or by selecting one or more from each class. The
selected organoaluminum compounds are then combined to form
ingredient (c) of the catalyst composition.
[0071] It has also been found that the molecular weight,
1,2-linkage content, and syndiotacticity of the syndiotactic
1,2-polybutadiene can be increased by increasing the molar ratio of
the hindered to non-hindered organoaluminum compounds within the
blend two or more sterically distinct organoaluminum compounds.
[0072] The syndiotactic 1,2-polybutadiene produced with the
catalyst composition of this invention has many uses. It can be
blended with various rubbers in order to improve the properties
thereof. For example, it can be incorporated into elastomers in
order to improve the green strength of those elastomers,
particularly in tires. The supporting or reinforcing carcass of
tires is particularly prone to distortion during tire building and
curing procedures. For this reason, the incorporation of the
syndiotactic 1,2-polybutadiene into rubber compositions that are
utilized in the supporting carcass of tires has particular utility
in preventing or minimizing this distortion. In addition, the
incorporation of the syndiotactic 1,2-polybutadiene into tire tread
compositions can reduce the heat build-up and improve the tear and
wear characteristics of tires. The syndiotactic 1,2-polybutadiene
is also useful in the manufacture of films and packaging materials
and in many molding applications.
[0073] In order to demonstrate the practice of the present
invention, the following examples have been prepared and tested as
described in the General Experimentation Section disclosed
hereinbelow. The examples should not, however, be viewed as
limiting the scope of the invention. The claims will serve to
define the invention.
GENERAL EXPERIMENTATION
EXAMPLE 1
[0074] An oven-dried 1-liter glass bottle was capped with a
self-sealing rubber liner and a perforated metal cap. After the
bottle was thoroughly purged with a stream of dry nitrogen gas, the
bottle was charged with 73 g of hexanes and 177 g of a
1,3-butadiene/hexanes blend containing 28.3% by weight of
1,3-butadiene. The following catalyst ingredients were added to the
bottle in the following order: (1) 0.050 mmol of iron(III)
2-ethylhexanoate, (2) 0.20 mmol of bis(2-ethylhexyl) hydrogen
phosphite, and (3) 0.75 mmol of triethylaluminum. The bottle was
tumbled for 4 hours in a water bath maintained at 50.degree. C. The
polymerization was terminated by addition of 10 mL of isopropanol
containing 1.0 g of 2,6-di-tert-butyl-4-methylphenol. The
polymerization mixture was coagulated with 3 liters of isopropanol.
The resulting syndiotactic 1,2-polybutadiene was isolated by
filtration and dried to a constant weight under vacuum at
60.degree. C. The yield of the polymer was 45.3 g (91%). As
measured by differential scanning calorimetry (DSC), the polymer
had a melting temperature of 133.degree. C. The .sup.1H and
.sup.13C nuclear magnetic resonance (NMR) analysis of the polymer
indicated a 1,2-linkage content of 88.3% and a syndiotacticity of
76.1%. As determined by gel permeation chromatography (GPC), the
polymer had a weight average molecular weight (Mw) of 512,000, a
number average molecular weight (M.sub.n) of 226,000, and a
polydispersity index (M.sub.w/M.sub.n) of 2.3. The monomer charge,
the amounts of the catalyst ingredients, the polymer yield, and the
properties of the resulting syndiotactic 1,2-polybutadiene are
summarized in Table I.
1TABLE I Example No. 1 2 3 4 5 Hexanes (g) 73 73 73 73 73 28.3%
1,3-Bd/hexanes 177 177 177 177 177 (g) Fe(2-EHA).sub.3 (mmol) 0.050
0.050 0.050 0.050 0.050 HP(O)(OCH.sub.2CH(Et) 0.20 0.20 0.20 0.20
0.20 (CH.sub.2).sub.3CH.sub.3).sub.2 (mmol) i-Bu.sub.3Al/Et.sub.3Al
0:100 30:70 50:50 70:30 100:0 molar ratio Total AlR.sub.3 (mmol)
0.75 0.75 0.75 0.75 0.75 Fe/P/Al molar ratio 1:4:15 1:4:15 1:4:15
1:4:15 1:4:15 Polymer yield (%) after 91 98 97 98 96 4 hr at
50.degree. C. Melting temperature 133 144 157 179 188 (.degree. C.)
M.sub.w 512,000 580,000 629,000 719,000 773,000 M.sub.n 226,000
264,000 299,000 359,000 381,000 M.sub.w/M.sub.n 2.3 2.2 2.1 2.0 2.0
1,2-Linkage content (%) 87.3 88.0 89.2 89.8 90.9 Syndiotacticity
(%) 76.9 81.0 87.5 90.1 93.3
EXAMPLES 2-5
[0075] In Examples 2-5, the procedure described in Example 1 was
repeated except that triisobutylaluminum/triethylaluminum mixtures
having various molar ratios, i.e., 30:70, 50:50, 70:30, and 100:0
were substituted for the triethylaluminum. Table I summarizes the
monomer charge, amounts of the catalyst ingredients, polymer
yields, and the properties of the resulting syndiotactic
1,2-polybutadiene produced in each example.
[0076] As shown in Table I, the melting temperature, molecular
weight, 1,2-linkage content, and syndiotacticity of the
syndiotactic 1,2-polybutadiene can be increased by increasing the
molar ratio of triisobutylaluminum to triethylaluminum.
EXAMPLES 6-10
[0077] In Examples 6-10, the procedure described in Example 1 was
repeated except that triisobutylaluminum/tri-n-butylaluminum
mixtures having various molar ratios, i.e., 0:100, 30:70, 50:50,
70:30, and 100:0 were substituted for the triethylaluminum. The
monomer charge, the amounts of the catalyst ingredients, the
polymer yields, and the properties of the resulting syndiotactic
1,2-polybutadiene are summarized in Table II.
2TABLE II Example No. 6 7 8 9 10 Hexanes (g) 73 73 73 73 73 28.3%
1,3-Bd/hexanes 177 177 177 177 177 (g) Fe(2-EHA).sub.3 (mmol) 0.050
0.050 0.050 0.050 0.050 HP(O)(OCH.sub.2CH(Et) 0.20 0.20 0.20 0.20
0.20 (CH.sub.2).sub.3CH.sub.3).sub.2 (mmol)
i-Bu.sub.3Al/n-Bu.sub.3Al 0:100 30:70 50:50 70:30 100:0 molar ratio
Total AlR.sub.3 (mmol) 0.75 0.75 0.75 0.75 0.75 Fe/P/Al molar ratio
1:4:15 1:4:15 1:4:15 1:4:15 1:4:15 Polymer yield (%) after 96 98 99
98 96 4 hr at 50.degree. C. Melting temperature 133 146 158 171 188
(.degree. C.) M.sub.w 424,000 561,000 625,000 700,000 773,000
M.sub.n 191,000 278,000 298,000 320,000 381,000 M.sub.w/M.sub.n 2.2
2.0 2.1 2.2 2.0 1,2-Linkage content (%) 87.0 88.2 89.6 90.2 90.9
Syndiotacticity (%) 77.7 81.4 87.0 89.6 93.3
[0078] As shown in Table II, the melting temperature, molecular
weight, 1,2-linkage content, and syndiotacticity of the
syndiotactic 1,2-polybutadiene can be increased by increasing the
molar ratio of triisobutylaluminum to tri-n-butylaluminum.
[0079] Various modifications and alterations that do not depart
from the scope and spirit of this invention will become apparent to
those skilled in the art. This invention is not to be duly limited
to the illustrative embodiments set forth herein.
* * * * *