TITLE: Process for producing styrenic polymer
European Patent EP0591841
 B1

ABSTRACT:
Abstract of EP0591841
There is disclosed a process for producing a styrenic polymer which
comprises polymerizing at least one styrenic monomer by the use of a
polymerization catalyst comprising in combination (A) at least one
transition metal compounds, (B) an aluminoxane, (C) a coordination
complex compound comprising a cation and an anion in which a plurality
of radicals are bonded to a metal and (D) an organoaluminum compound.
The above process is capable of producing a styrenic polymer which has
high degree of syndiotactic configuration and a wide range of molecular
weight distribution and is minimized in residual metallic components at
a low production cast with a high efficiency.

INVENTORS:
Tomotsu, Norio (4-2, Yushudai-nishi, 2-chome, Ichihara-shi, Chiba-ken,
JP)
Takeuchi, Mizutomo (2189-1, Anesaki, Ichihara-shi, Chiba-ken, JP)

APPLICATION NUMBER: EP19930115786
PUBLICATION DATE: 04/09/1997
FILING DATE: 09/30/1993

ASSIGNEE: IDEMITSU KOSAN COMPANY LIMITED (1-1, Marunouchi 3-chome Chiyoda-ku,
Tokyo, 100, JP)
INTERNATIONAL CLASSES: C08F4/602; C08F4/60; C08F4/642; C08F4/645; C08F4/646; C08F4/659;
C08F4/6592; C08F12/00; C08F12/04; (IPC1-7): C08F12/04
EUROPEAN CLASSES: C08F12/04+4/62

DOMESTIC PATENT REFERENCES:
EP0389981 Process for producing styrene-based polymer.
EP0493678 Process for producing a styrene polymer and a catalyst for
 use therein
Attorney, Agent or Firm:
Türk, Gille Hrabal Leifert (Brucknerstrasse 20, Düsseldorf, 40593, DE)

CLAIMS:
1. A process for producing a styrenic polymer which comprises
polymerizing at least one styrenic monomer by the use of a
polymerization catalyst comprising in combination (A) a transition
metal compound, wherein the transition metal is selected from the group
consisting of Ti, Zr and Hf, (B) an aluminoxane, selected from the
group consisting of a chain aluminoxane represented by the general
formula (VI): wherein R^11 is an alkyl group having 1 to 20 carbon
atoms, is preferably a methyl group and p is a number from 0 to 50,
preferably 5 to 30; and a cyclic aluminoxane represented by the general
formula (VII): Wherein R^11 is as previously defined and q is a number
from 2 to 50, preferably 5 to 30, (C) a coordination complex compound
comprising a cation and an anion in which a plurality of radicals are
bonded to a metal selected from the group consisting of coordination
complex compounds represented by the following general formula (VIII)
or (IX): ([L^1-H]^g+)[h]([M^1X^1X^2 --- X^n]^(n-m)-)i or
([L^2]^g+)[h]([M^2X^1X^2---X^n]^(n-m)-)i wherein L^2 is M^3,
R^12R^13M^4 or R^14[3]C as hereinafter described; L^1 is a Lewis base;
M^1 and M^2 are each a metal selected from Groups 5 to 15 of the
Periodic Table; M^3 is a metal selected from Groups 8 to 12 of the
Periodic Table; M^4 is a metal selected from Groups 8 to 10 of the
Periodic Table; X^1 to X^n are each a hydrogen atom, dialkylamino
group, alkoxy group, aryloxy group, alkyl group having 1 to 20 carbon
atoms, aryl group having 6 to 20 carbon atoms, alkylaryl group,
arylalkyl group, substituted alkyl group, organometalloid group or
halogen atom; R^12 and R^13 are each a cyclopentadienyl group,
substituted cyclopentadienyl group, indenyl group or fluorenyl group;
R^14 is an alkyl group; m is the valency of each of M^1 and M^2,
indicating an integer of 1 to 7; n is an integer of 2 to 8; g is the
ion valency of each of [L^1-H] and [L^2], indicating an integer of 1 to
7; h is an integer of 1 or more; and i=hxg/(n-m), and (D) an
organoaluminum compound which is represented by the formula (X): R^15 
[r]Al(OR^16)[s]H[t]Y^1  [u] wherein R^15 and R^16 each independently
represent an alkyl group having 1 to 8 carbon atoms, preferably 1 to 4
carbon atoms; Y^1 represents a halogen; r, s, t and u are 0<r≦3, 0≦s<3
and 0≦t<3, respectively, and r+s+t+u=3.
2. A process for producing a styrenic polymer which comprises
polymerizing at least one styrenic monomer by the use of a
polymerization catalyst comprising in combination (A) a plurality of
transition metal compounds, (B) an aluminoxane, (C) a coordination
complex compound comprising a cation and an anion in which a plurality
of radicals are bonded to a metal and (D) an organoaluminum compound,
wherein compounds (A), (B), (C) and (D) are defined as in claim 1.
3. A Catalyst for polymerizing a styrenic monomer into a syndiotactic
polystyrene which comprises in combination (A) a transition metal
compound, (B) an aluminoxane, (C) a coordination complex compound
comprising a cation and an anion in which a plurality of radicals are
bonded to a metal and (D) an organoaluminum compound, wherein compounds
(A), (B), (C) and (D) are defined as in claim 1.
4. A Catalyst for polymerizing a styrenic monomer into a syndiotactic
polystyrene which comprises in combination (A) a plurality of
transition metal compounds, (B) an aluminoxane, (C) a coordination
complex compound comprising a cation and an anion in which a plurality
of radicals are bonded to a metal and (D) an organoaluminum compound,
wherein compounds (A), (B), (C) and (D) are defined as in claim 1.

DESCRIPTION:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improved process for producing a
styrenic polymer. More particularly it pertains to a process for
producing a styrenic polymer which has high degree of syndiotactic
configuration and a wide range of molecular weight distribution and is
reduced in residual metallic components at a low production cost with a
high efficiency.
2. Description of Related Art
There have heretofore been known the processes for producing
high-performance styrenic polymer having high degree of syndiotactic
configuration in high yield by allowing a reaction product of an
aluminoxane with a transition metal complex to act on styrene. (Refer
to Japanese Patent Application Laid-Open Nos. 187708/1987, 179906/1988,
241009/1988). However, the styrenic polymer produced by any of the
above-disclosed processes involves the problem of moldability due to
the usually narrow range of molecular weight distribution. Accordingly
there is desired a styrenic polymer which has high degree of
syndiotactic configuration and besides a wide range of molecular weight
distribution.
In order to produce such a styrenic polymer having a wide range of
molecular weight distribution, there has heretofore been employed a
method in which a high molecular styrenic polymer and a low molecular
styrenic polymer are mixed with each other by melt kneading or the like
to expand the range of molecular weight distribution. However, the
aforesaid method involves the problem of requiring much labor and
effort for uniform mixing.
There is also known a method of expanding the molecular weight
distribution by the use of a plurality of transition metal compounds
and an aluminoxane. (Refer to Japanese Patent Application Laid-Open No.
119006/1991). Nevertheless the above-mentioned method suffers the
disadvantage that a large requirement of an aluminoxane increases the
catalyst cost and the amount of residual metallic components is
excessive making it unserviceable unless deashing is put into practice.
Under such circumstances it is an object of the present invention to
provide a process for producing a styrenic polymer which has high
degree of syndiotactic configuration and a wide range of molecular
weight distribution and is reduced in residual metallic components at a
low production cost with a high efficiency.

SUMMARY OF THE INVENTION
As the result of intensive research and investigation accumulated by
the present inventors in order to attain the above-mentioned object, it
has been found, in the combined polymerization catalyst comprising a
transition metal compound, an aluminoxane, a specific ion complex and
an organoaluminum compound, that the incorporation of said
organoaluminum compound causes the polymer portion produced by the
aluminoxane to shift to the side of the lower molecular weight but does
not cause the polymer portion produced by the ion complex to shift to
said side and therefore the combined use of the aluminoxane, the ion
complex and the organoaluminum compound can expand the range of
molecular weight distribution; the combined use of the aluminoxane and
the ion complex can reduce the requirement of the expensive aluminoxane
as compared with the conventional methods; the use of a plurality of
transition metal compounds can set the molecular weight distribution at
a desired value thereby enabling the range of said distribution to be
expanded; and after all the use of said polymerization catalyst can
attain the object of the present invention. The present invention has
been accomplished on the basis of the above-mentioned finding and
information.
Specifically the present invention provides a process for producing a
styrenic polymer which comprises polymerizing at least one styrenic
monomer by the use of a polymerization catalyst comprising in
combination (A) a transition metal compound, wherein the transition
metal is selected from the group consisting of Ti, Zr and Hf, (B) an
aluminoxane, selected from the group consisting of a chain aluminoxane
represented by the general formula (VI): wherein R^11 is an alkyl group
having 1 to 20 carbon atoms, is preferably a methyl group and p is a
number from 0 to 50, preferably 5 to 30; and a cyclic aluminoxane
represented by the general formula (VII): Wherein R^11 is as previously
defined and q is a number from 2 to 50, preferably 5 to 30, (C) a
coordination complex compound comprising a cation and an anion in which
a plurality of radicals are bonded to a metal selected from the group
consisting of coordination complex compounds represented by the
following general formula (VIII) or (IX): ([L^1-H]^g+)[h]([M^1X^1X^2
--- X^n]^(n-m)-)i or ([L^2]^g+)[h]([M^2X^1X^2---X^n]^(n-m)-)i wherein
L^2 is M^3, R^12R^13M^4 or R^14[3]C as hereinafter described; L[1] is a
Lewis base; M^1 and M^2 are each a metal selected from Groups 5 to 15
of the Periodic Table; M^3 is a metal selected from Groups 8 to 12 of
the Periodic Table; M^4 is a metal selected from Groups 8 to 10 of the
Periodic Table; X^1 to X^n are each a hydrogen atom, dialkylamino
group, alkoxy group, aryloxy group, alkyl group having 1 to 20 carbon
atoms, aryl group having 6 to 20 carbon atoms, alkylaryl group,
arylalkyl group, substituted alkyl group, organometalloid group or
halogen atom; R^12 and R^13 are each a cyclopetnadienyl group,
substituted cyclopentadienyl group, indenyl group or fluorenyl group;
R^14 is an alkyl group; m is the valency of each of M^1 and M^2,
indicating an integer of 1 to 7; n is an integer of 2 to 8; g is the
ion valency of each of [L^1-H] and [L^2], indicating an integer of 1 to
7; h is an integer of 1 or more; and i=hxg/(n-m), and (D) an
organoaluminum compound which is represented by the formula (X): R^15 
[r]Al(OR^16)[s]H[t]Y^1  [u] wherein R^15 and R^16 each independently
represent an alkyl group having 1 to 8 carbon atoms, preferably 1 to 4
carbon atoms; Y^1 represents a halogen; r, s, t and u are 0<r≦3, 0≦s<3
and 0≦t<3, respectively, and r+s+t+u=3.
At the same time, a process for producing a styrenic polymer which
comprises polymerizing at least one styrenic monomer by the use of a
polymerization catalyst comprising in combination (A) a plurality of
transition metal compounds and the aforesaid components (B) an
aluminoxane, (C) a coordination complex compound comprising a cation
and an anion in which a plurality of radicals are bonded to a metal and
(D) an organoaluminum compound wherein compounds (A), (B), (C) and (D)
are defined as in claim 1.
DESCRIPTION OF PREFERRED EMBODIMENT
In the process according to the present invention, the combination of
the components (A), (B), (C) and (D) is employed as the polymerization
catalyst. Various transition metal compounds are available as the
component (A), and (A) is selected from the group consisting of
titanium, zirconium, hafnium. Various titanium compounds can be used
and a preferred example is at least one compound selected from the
group consisting of titanium compounds and titanium chelate compounds
represented by the general formula: TiR^1  [a]R^2  [b]R^3  [c]R^4 
[4-(a+b+c)] or TiR^1  [d]R^2  [e]R^3  [3-(d+e)] wherein R^1, R^2, R^3
and R^4 are each a hydrogen atom, an alkyl group having 1 to 20 carbon
atoms, an alkoxy group having 1 to 20 carbon atoms, an aryl group
having 6 to 20 carbon atoms, an alkylaryl group, an arylalkyl group, an
acyloxy group having 1 to 20 carbon atoms, a cyclopentadienyl group, a
substituted cyclopentadienyl group, an indenyl group or a halogen atom;
a, b and c are each an integer from 0 to 4; and d and e are each an
integer from 0 to 3.
R^1, R^2, R^3 and R^4 in the general formulae (I) and (II) each
represent a hydrogen atom, an alkyl group having 1 to 20 carbon atoms
(specifically, methyl group, ethyl group, propyl group, butyl group,
amyl group, isoamyl group, isobutyl group, octyl group and 2-ethylhexyl
group), an alkoxy group having 1 to 20 carbon atoms (specifically,
methoxy group, ethoxy group, propoxy group, butoxy group, amyloxy
group, hexyloxy group, and 2-ethylhexyloxy group), an aryl group having
6 to 20 carbon atoms, an alkylaryl group, an arylalkyl group
(specifically, phenyl group, tolyl group, xylyl group and benzyl
group), an acyloxy group having 1 to 20 carbon atoms (specifically,
heptadecylcarbonyloxy group), a cyclopentadienyl group, a substituted
cyclopentadienyl group (specifically, methylcyclopentadienyl group,
1,2-dimethylcyclopentadienyl group and pentamethylcyclopentadienyl
group), an indenyl group or a halogen atom (specifically, chlorine,
bromine, iodine and fluorine). These R^1, R^2, R^3, R^4 may be the same
as or different from each other. Furthermore, a, b and c are each an
integer from 0 to 4, and d and e are each an integer from 0 to 3.
More desirable titanium compounds include a titanium compound
represented by the formula: TiRXYZ wherein R represents a
cyclopentadienyl group, a substituted cyclopentadienyl group or an
indenyl group; X, Y, and Z, independently of one another, are a
hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy
group having 1 to 12 carbon atoms, an aryl group having 6 to 20 carbon
atoms, an aryloxy group having 6 to 20 carbon atoms, an arylalkyl group
having 6 to 20 carbon atoms or a halogen atom.
The substituted cyclopentadienyl group represented by R in the above
formula is, for example, a cyclopentadienyl group substituted by at
least one of an alkyl group having 1 to 6 carbon atoms, more
specifically, methylcyclopentadienyl group,
1,3-dimethylcyclopentadienyl group, 1,2,4-trimethylcyclopentadienyl
group, 1,2,3,4-tetramethylcyclopentadienyl group, or
pentamethylcyclopentadienyl group. In addition, X, Y, and Z are each
independently a hydrogen atom, an alkyl group having 1 to 12 carbon
atoms (specifically, methyl group, ethyl group, propyl group, n-butyl
group, isobutyl group, amyl group, isoamyl group, octyl group and
2-ethylhexyl group), an alkoxy group having 1 to 12 carbon atoms
(specifically, methoxy group, ethoxy group, propoxy group, butoxy
group, amyloxy group, hexyloxy group, octyloxy group and 2-ethylhexyl
group), an aryl group having 6 to 20 carbon atoms (specifically, phenyl
group and naphthyl group), an aryloxy group having 6 to 20 carbon atoms
(specifically, phenoxy group), an arylalkyl group having 6 to 20 carbon
atoms (specifically, benzyl group) or a halogen atom (specifically,
chlorine, bromine, iodine and fluorine).
Specific examples of the titanium compound represented by the general
formula (III) include
  cyclopentadienyltrimethyltitanium,
  cyclopentadienyltriethyltitanium,
  cyclopentadienyltripropyltitanium,
  cyclopentadienyltributyltitanium,
  cyclopentadienyltrichlorotitanium,
  methylcyclopentadienyltrimethyltitanium,
  1,3-dimethylcyclopentadienyltrimethyltitanium,
  pentamethylcyclopentadienyltrimethyltitanium,
  pentamethylcyclopentadienyltriethyltitanium,
  pentamethylcyclopentadienyltripropyltitanium,
  pentamethylcyclopentadienyltributyltitanium,
  pentamethylcyclopentadienyltrichlorotitanium,
  cyclopentadienylmethyltitanium dichloride,
  cyclopentadienylethyltitanium dichloride,
  pentamethylcyclopentadienylmethyltitanium dichloride,
  pentamethylcyclopentadienylethyltitanium dichloride,
  cyclopentadienyldimethyltitanium monochloride,
  cyclopentadienyldiethyltitanium monochloride,
  cyclopentadienyltitanium trimethoxide,
  cyclopentadienyltitanium triethoxide,
  cyclopentadienyltitanium tripropoxide,
  cyclopentadienyltitanium triphenoxide,
  pentamethylcyclopentadienyltitanium trimethoxide,
  pentamethylcyclopentadienyltitanium triethoxide,
  pentamethylcyclopentadienyltitanium tripropoxide,
  pentamethylcyclopentadienyltitanium tributoxide,
  pentamethylcyclopentadienyltitanium triphenoxide,
  cyclopentadienyltitanium trichloride,
  pentamethylcycloentadienyltitanium trichloride,
  cyclopentadienylmethoxyltitanium dichloride,
  cyclopentadienyldimethoxytitanium chloride,
  pentamethylcyclopentadienylmethoxytitanium dichloride,
  cyclopentadienyltribenzyltitanium,
  pentamethylcyclopentadienylmethyldiethoxytitanium,
  indenyltitanium trichloride, indenyltitanium trimethoxide,
  indenyltitanium triethoxide, indenyltrimethyltitanium and
  indenyltribenzyltitanium.
Of these titanium compounds, a compound not containing a halogen atom
is preferred and a titanium compound having one π electron type ligand
is particularly desirable.
Furthermore, a condensed titanium compound represented by the general
formula may be used as the titanium compound. wherein R^5 and R^6 each
represent a halogen atom, an alkoxy group having 1 to 20 carbon atoms
or an acyloxy group; and k is an integer from 2 to 20.
Furthermore, the above titanium compounds may be used in the form of a
complex formed with an ester, an ether or a phosphine.
The trivalent titanium compound represented by the formula (IV)
typically includes a trihalogenated titanium such as titanium
trichloride; and a cyclopentadienyltitanium compound such as
cyclopentadienyltitanium dichloride, and also those obtained by
reducing a tetravalent titanium compound. These trivalent titanium
compounds may be used in the form of a complex formed with an ester, an
ether or a phosphine.
In addition, examples of the zirconium compound used as the transition
metal compound include tetrabenzylzirconium, zirconium tetraethoxide,
zirconium tetrabutoxide, bisindenylzirconium dichloride,
triisopropoxyzirconium chloride, zirconium benzyl dichloride and
tributoxyzirconium chloride. Examples of the hafnium compound include
tetrabenzylhafnium, hafnium tetraethoxide and hafnium tetrabutoxide.
Examples of the vanadium compound include vanadyl bisacetylacetonato,
vanadyl triacetylacetonato, vanadyl triethoxide and vanadyl
tripropoxide. Of these transition metal compounds, the titanium
compounds are particularly suitable.
Aside from the foregoing, the transition metal compounds constituting
the component (A) of the catalyst include the transition metal compound
with two ligands having conjugated π electrons, for example, at least
represented by the general formula: MR^7R^8R^9R^10 wherein M is
titanium, zirconium or hafnium; R^7 and R^8 are each a cyclopentadienyl
group, substituted cyclopentadienyl group, indenyl group or fluorenyl
group; and R^9 and R^10 are each a hydrogen atom, a halogen atom,
hydrocarbon radical having 1 to 20 carbon atoms, alkoxy group having 1
to 20 carbon atoms, amino group or thioalkoxyl group having 1 to 20
carbon atoms, but R^7 and R^8 may be each crosslinked by a hydrocarbon
radical having 1 to 5 carbon atoms, alkylsilyl group having 1 to 20
carbon atoms and 1 to 5 silicon atoms or germanium-containing
hydrocarbon group having 1 to 20 carbon atoms and 1 to 5 germanium
atoms.
In more detail, each of R^7 and R^8 in the general formula (V)
designates a cyclopentadienyl group, substituted cyclopentadienyl
group, more specifically,
  methylcyclopentadienyl group;
  1,3-dimethylcyclopentadienyl group;
  1,2,4-trimethylcyclopentadienyl group;
  1,2,3,4-tetramethylcyclopentadienyl group;
  pentamethylcyclopentadienyl group;
  trimethylsilylcyclopentadienyl group;
  1,3-di(trimethylsilyl)cyclopentadienyl group;
  1,2,4-tri(trimethylsilyl)cyclopentadienyl group;
  tert-butylcyclopentadienyl group;
  1,3-di(tert-butyl)cyclopentadienyl group; or
  1,2,4-tri(tert-butyl)cyclopentadienyl group, indenyl group,
substituted indenyl group, more specifically, methylindenyl group;
dimethylindenyl group or trimethylindenyl group, fluorenyl group, or
substituted fluorenyl group such as methylfluorenyl group, and may be
the same or different and crosslinked by a alkylidene group having 1 to
5 carbon atoms, more specifically, methine group; ethylidene group;
propylidene group or dimethylcarbyl group, or an alkylsilyl group
having 1 to 20 carbon atoms and 1 to 5 silicon atoms, more
specifically, dimethylsilyl group; diethylsilyl group or dibenzylsilyl
group. Each of R^9 and R^10 independently indicates, as described above
but more specifically, a hydrogen atom; an alkyl group having 1 to 20
carbon atoms such as methyl group, ethyl group, propyl group, n-butyl
group, isobutyl group, amyl group, isoamyl group, octyl group or
2-ethylhexyl group; an aryl group having 6 to 20 carbon atoms such as
phenyl group or naphthyl group; an arylalkyl group having 7 to 20
carbon atoms such as benzyl group; an alkoxyl group having 1 to 20
carbon atoms such as methoxyl group, ethoxyl group, propoxyl group,
butoxyl group, amyloxyl group, hexyloxyl group, octyloxyl group or
2-ethylhexyloxyl group; an aryloxyl group having 6 to 20 carbon atoms
such as phenoxyl group; an amino group; or a thioalkoxyl group having 1
to 20 carbon atoms.
Specific examples of the transition metal compounds represented by the
general formula (V) include
  bis(cyclopentadienyl)dimethyltitanium;
  bis(cyclopentadienyl)diethyltitanium;
  bis(cyclopentadienyl)dipropyltitanium;
  bis(cyclopentadienyl)dibutyltitanium;
  bis(methylcyclopentadienyl)dimethyltitanium;
  bis(tert-butylcyclopentadienyl)dimethyltitanium;
  bis(1,3-dimethylcyclopentadienyl)dimethyltitanium;
  bis(1,3-di-tert-butylcyclopentadienyl)dimethyltitanium;
  bis(1,2,4-trimethylcyclopentadienyl)dimethyltitanium;
  bis(1,2,3,4-tetramethylcyclopentadienyl)dimethyltitanium;
  bis(pentamethylcyclopentadiemyl)dimethyltitanium;
  bis(trimethylsilylcyclopentadienyl)dimethyltitanium;
  bis(1,3-di(trimethylsilyl)cyclopentadienyl)dimethyltitanium;
  bis(1,2,4-tri((trimethylsilyl)cyclopentadienyl) dimethyltitanium;
bis(indenyl)dimethyltitanium;
  bis(fluorenyl)dimethyltitanium;
  methylenebis(cyclopentadienyl)dimethyltitanium;
  ethylidenebis(cyclopentadienyl)dimethyltitanium;
  methylenebis(2,3,4,5-tetramethylcyclopentadienyl) dimethyltitanium;
ethylidenebis(2,3,4,5-tetramethylcyclopentadienyl)dimethyltitanium;
  dimethylsilylbis(2,3,4,5-tetramethylcyclopentadienyl)
  dimethyltitanium; methylenebisindenyldimethyltitanium;
  ethylidenebisindenyldimethyltitanium;
  dimethylsilylbisindenyldimethyltitanium;
  methylenebisfluorenyldimethyltitanium;
  ethylidenbisfluorenyldimethyltitanium;
  dimethylsilylbisfluorenyldimethyltitanium;
methylene(tert-butylcyclopentadienyl)(cyclopentadienyl)dimethyltitanium
;
  methylene(cyclopentadienyl)(indenyl)dimethyltitanium;
  ethylidene(cyclopentadienyl)(indenyl)dimethyltitanium;
  dimethylsilyl(cyclopentadienyl)(indenyl)dimethyltitanium;
  methylene(cyclopentadienyl)(fluorenyl)dimethyltitanium;
  ethylidene(cyclopentadienyl)(fluorenyl)dimethyltitanium;
  dimethylsilyl(cyclopentadienyl)(fluorenyl)dimethyltitanium;
  methylene(indenyl)(fluorenyl)dimethyltitanium;
  ethylidene(indenyl)(fluorenyl)dimethyltitanium;
  dimethylsilyl(indenyl)(fluorenyl)dimethyltitanium;
  bis(cyclopentadienyl)dibenzyltitanium;
  bis(tert-butylcyclopentadienyl)dibenzyltitanium;
  bis(methylcyclopentadienyl)dibenzyltitanium;
  bis(1,3-dimethylcyclopentadienyl)dibenzyltitanium;
  bis(1,2,4-trimethylcyclopentadienyl)dibenzyltitanium;
  bis(1,2,3,4-tetramethylcyclopentadienyl)dibenzyltitanium;
  bis(pentamethylcyclopentadienyl)dibenzyltitanium;
  bis(trimethylsilylcyclopentadienyl)dibenzyltitanium;
  bis[1,3-di-(trimethylsilyl)cyclopentadienyl]dibenzyltitanium;
  bis[1,2,4-tri(trimethylsilyl)cyclopentadienyl]dibenzyltitanium;
bis(indenyl)dibenzyltitanium;
  bis(fluorenyl)dibenzyltitanium;
  methylenebis(cyclopentadienyl)dibenzyltitanium;
  ethylidenebis(cyclopentadienyl)dibenzyltitanium;
  methylenebis(2,3,4,5-tetramethylcyclopentadienyl)dibenzyltitanium;
ethylidenebis(2,3,4,5-tetramethylcyclopentadienyl)dibenzyltitanium;
  dimethylsilylbis(2,3,4,5-tetramethylcyclopentadienyl)
dibenzyltitanium; methylenebis(indenyl)dibenzyltitanium;
  ethylidenebis(indenyl)dibenzyltitanium;
  dimethylsilylbis(indenyl)dibenzyltitanium;
  methylenebis(fluorenyl)dibenzyltitanium;
  ethylidenebis(fluorenyl)dibenzyltitanium;
  dimethylsilylbis(fluorenyl)dibenzyltitanium;
  methylene(cyclopentadienyl)(indenyl)dibenzyltitanium;
  ethylidene(cyclopentadienyl)(indenyl)dibenzyltitanium;
  dimethylsilyl(cyclopentadienyl)(indenyl)dibenzyltitanium;
  methylene(cyclopentadienyl)(fluorenyl)dibenzyltitanium;
  ethylidene(cyclopentadienyl)(fluorenyl)dibenzyltitanium;
  dimethylsilyl(cyclopentadienyl)(fluorenyl)dibenzyltitanium;
  methylene(indenyl)(fluorenyl)dibenzyltitanium;
  ethylidene(indenyl)(fluorenyl)dibenzyltitanium;
  dimethylsilyl(indenyl)(fluorenyl)dibenzyltitanium;
  biscyclopentadienyltitanium dimethoxide;
  biscyclopentadienyltitanium diethoxide;
  biscyclopentadienyltitanium dipropoxide;
  biscyclopentadienyltitanium dibutoxide;
  biscyclopentadienyltitanium dipheoxide;
  bis(methylcyclopentadienyl)titanium dimethoxide;
  bis(1,3-dimethylcyclopentadienyl)titanium dimethoxide;
  bis(1,2,4-trimethylcyclopentadienyl)titanium dimethoxide;
  bis(1,2,3,4-tetramethylcyclopentadienyl)titanium dimethoxide;
  bispentamethylcyclopentadienyltitanium dimethoxide;
  bis(trimethylsilylcyclopentadienyl)titanium dimethoxide; bis
[1,3-di(trimethylsilyl)cyclopentadienyl]titanium dimethoxide;
  bis[1,2,4-tri(trimethylsilyl)cyclopentadienyl]titanium
  dimethoxide; bisindenyltitanium dimethoxide;
  bisfluorenyltitanium dimethoxide;
  methylenebiscyclopentadienyltitanium dimethoxide;
  ethylidenebiscyclopentadienyltitanium dimethoxide;
  methylenebis(2,3,4,5-tetramethylcyclopentadienyl)titanium
dimethoxide; ethylidenebis(2,3,4,5-tetramethylcyclopentadienyl)titanium
dimethoxide;
  dimethylsilylbis(2,3,4,5-tetramethylcyclopentadienyl)titanium
dimethoxide; methylenebisindenyltitanium dimethoxide;
  methylenebis(methylindenyl)titanium dimethoxide;
  ethylidenebisindenyltitanium dimethoxide;
  dimethylsilylbisindenyltitanium dimethoxide;
  methylenebisfluorenyltitanium dimethoxide;
  methylenebis(methylfluorenyl)titanium dimethoxide;
  ethylidenebisfluorenyltitanium dimethoxide;
  dimethylsilylbisfluorenyltitanium dimethoxide;
  methylene(cyclopentadienyl)(indenyl)titanium dimethoxide;
  ethylidene(cyclopentadienyl)(indenyl)titanium dimethoxide;
  dimethylsilyl(cyclopentadienyl)(indenyl)titanium dimethoxide;
  methylene(cyclopentadienyl)(fluorenyl)titanium dimethoxide;
  ethylidene(cyclopentadienyl)(fluorenyl)titanium dimethoxide;
  dimethylsilyl(cyclopentadienyl)(fluorenyl)titanium
  dimethoxide; methylene(indenyl)(fluorenyl)titanium
  dimethoxide; ethylidene(indenyl)(fluorenyl)titanium
  dimethoxide; dimethylsilyl(indenyl)(fluorenyl)titanium dimethoxide,
  isopropylidene(cyclopentadienyl)(fluorenyl)titanium dichloride, and
  isopropylidene(cyclopentadienyl)(fluorenyl)titanium dimethoxide.
Examples of the transition metal compounds represented by the formula
(V) wherein M is zirconium include
ethylidenebiscyclopentadienylzirconium dichloride,
ethylidenbiscyclopentadienylzirconium dimethoxide,
dimethylsilylbiscyclopentadienylzirconium dimethoxide, and
isopropylidene(cyclopentadienyl)(fluorenyl)zirconium dichloride.
Examples of the hafnium compounds according to the general formula (V)
include ethylidenebiscyclopentadienylhafnium dimethoxide, and
dimethylsilylbiscyclopentadienylhafnium dimethoxide. Particularly
desirable transition metal compounds among them are titanium compounds.
The transition metal compound as the component (A) of the catalyst
according to the present invention may be used alone or in combination
with at least one of them. In the case of the combined use, it is
preferable that the transition metal compounds be properly selected on
the basis of the chemical shift in ^13C-NMR of the carbon in the
methoxy group as the index when at least one σ-bonded ligand in the
transition metal compound is methoxized. Since the weight-average
molecular weight of the styrenic polymer to be produced decreases with
increase in the chemical shift value of the ^13C-NMR, it is possible to
set the range of the molecular weight distribution of the styrenic
polymer to the desired value by properly selecting a plurality of
transition metal compounds each having a different chemical shift value
from one another.
The aluminoxane which is the component (B) of the polymerization
catalyst is a compound obtained by bringing an organoaluminum compound
into contact with a condensation agent, and is selected from the group
consisting of a chain aluminoxane represented by the general formula
(VI): wherein R^11 is an alkyl group having 1 to 20 carbon atoms, is
preferably a methyl group and p is a number from 0 to 50, preferably 5
to 30; and a cyclic aluminoxane represented by the general formula
(VII): Wherein R^11 is as previously defined and q is a number from 2
to 50, preferably 5 to 30.
The organoaluminum compound is exemplified by a trialkylaluminum such
as trimethylaluminum, triethylaluminum and triisobutylaluminum, of
which is preferable trimethylaluminum.
The condensation agent is typified by water and exemplified by an
arbitrary substance which undergoes condensation reaction with a
trialkylaluminum such as copper sulphate pentahydrate, water adsorbed
in an inorganic or organic substance.
In general, the contact product of an organoaluminum compounds such as
trialkylaluminum and water contains the above-mentioned chain
alkylaluminoxane and cyclic alkylaluminoxane together with unreacted
trialkylaluminum, various mixture of condensates and further the
molecules resulting from association in an intricate manner thereof.
Accordingly, the resultant contact product varies widely depending upon
the conditions of contact of trialkylaluminum with water as the
condensation agent.
The reaction of the alkylaluminum compound and water is not
specifically limited in the above case but may be effected according to
the publicly known methods, which are exemplified by (1) a method in
which an organoaluminum compound is dissolved in an organic solvent an
then brought into contact with water, (2) a method in which an
organoaluminum compound is first added to the reaction system at the
time of polymerization and thereafter water is added thereto, and (3) a
method in which an organoaluminum compound is reacted with the water of
crystallization contained in metal salts, or the water adsorbed in
inorganic or organic materials. The above-mentioned water may contain
up to about 20% of ammonia, amine such as ethylamine, sulfur compound
such as hydrogen sulfide, phosphorus compound such as phosphite. The
above-mentioned reaction proceeds even in the absence of a solvent but
is preferably carried out in a solvent. Examples of the suitable
solvent to be used here include aliphatic hydrocarbons such as hexane,
heptane and decane, aromatic hydrocarbons such as benzene, toluene and
xylene. The aluminoxane (e.g. an alkylaluminoxane) is preferably
obtained by a method wherein the solid residue produced after contact
reaction in the case of a water-containing compound being used is
removed by means of filtration and the filtrate is heat treated under
atmospheric or reduced pressure at 30 to 200°C, preferably 40 to 150°C
for 20 minutes to 8 hours, preferably 30 minutes to 5 hours while
distilling away the solvent used.
The temperature in the aforementioned heat treatment may be pertiently
determined according to the various conditions, but should be usually
within the above-described range. The temperature lower than 30°C fails
to bring about the prescribed effect, whereas that exceeding 200°C
causes thermal decomposition of aluminoxane itself, each resulting in
unfavorable consequence.
The reaction product is obtained in the form of colorless solid or
solution depending upon the heat treatment conditions, and can be used
as the catalyst solution by dissolving in or diluting with a
hydrocarbon solvent according to the demand.
Suitable examples of the aluminoxane, that is, the contact product of
organoaluminum compound and a condensation agent which is used as the
component of the catalyst, especially an alkylaluminoxane are those in
which the area of the high magnetic field component in the methyl
proton signal region due to the aluminum-methyl group (Al-CH[3]) bond
as observed by the proton nuclear magnetic resonance method is not more
than 50% of the total signal area. That is, in a proton nuclear
magnetic resonance (^1H-NMR) spectral analysis of the alkylaluminoxane
in toluene solvent at room temperature, the methyl proton signal due to
Al-CH[3] is observed in the region of 1.0 to -0.5 ppm
(tetramethylsilane (TMS) standard). Since the proton signal of TMS (0
ppm) is in the region of the methyl proton signal due to Al-CH[3], the
methyl proton signal due to Al-CH[3] is measured with 2.35 ppm methyl
proton signal of toluene in TMS standard. The methyl proton signal due
to Al-CH[3] is divided into two components: the high magnetic field
component in the -0.1 to -0.5 ppm region and the other magnetic field
component in the 1.0 to -0.1 ppm region. In alkylaluminoxane preferably
used as component (B) of the catalyst in the present invention, the
area of the high magnetic field component is not more than 50%,
preferably 45 to 5% of the total signal area in the 1.0 to -0.5 ppm
region.
As the coordination complex compound comprising a cation and an anion
in which a plurality of radicals are bonded to a metal, that is, the
component (C) of the polymerization catalyst, there are used the
coordination complex compounds represented by the following general
formula (VIII) or (IX): ([L^1-H]^g+)[h]([M^1X^1X^2 --- X^n]^(n-m)-)i or
([L^2]^g+)[h]([M^2X^1X^2---X^n]^(n-m)-)i wherein L^2 is M^3,
R^12R^13M^4 or R^14[3]C as hereinafter described; L[1] is a Lewis base;
M^1 and M^2 are each a metal selected from Groups 5 to 15 of the
Periodic Table; M^3 is a metal selected from Groups 8 to 12 of the
Periodic Table; M^4 is a metal selected from Groups 8 to 10 of the
Periodic Table; X^1 to X^n are each a hydrogen atom, dialkylamino
group, alkoxy group, aryloxy group, alkyl group having 1 to 20 carbon
atoms, aryl group having 6 to 20 carbon atoms, alkylaryl group,
arylalkyl group, substituted alkyl group, organometalloid group or
halogen atom; R^12 and R^13 are each a cyclopentadienyl group,
substituted cyclopentadienyl group, indenyl group or fluorenyl group;
R^14 is an alkyl group; m is the valency of each of M^1 and M^2,
indicating an integer of 1 to 7; n is an integer of 2 to 8; g is the
ion valency of each of [L^1-H] and [L^2], indicating an integer of 1 to
7; h is an integer of 1 or more; and i=hxg/(n-m).
Specific examples of M^1 and M^2 include B, Al, Si, P, As, and Sb;
those of M^3 include Ag and Cu; and those of M^4 include Fe, Co and Ni.
Specific examples of X^1 to X^n include dialkylamino group such as
dimethylamino and diethylamino; alkoxyl group such as methoxyl, ethoxyl
and n-butoxyl; aryloxyl group such as phenoxyl, 2,6-dimethylphenoxyl
and naphthyloxyl; alkyl group having 1 to 20 carbon atoms such as
methyl, ethyl, n-propyl, iso-propyl, n-butyl, n-octyl and 2-ethylhexyl;
aryl group having 6 to 20 carbon atoms, alkylaryl group or arylalkyl
group such as phenyl, p-tolyl, benzyl, pentafluorophenyl,
3,5-di(trifluoromethyl)phenyl, 4-tert-butylphenyl, 2,6-dimethylphenyl,
3,5-dimethylphenyl, 2,4-dimethylphenyl and 1,2-dimethylphenyl; halogen
such as F, Cl, Br and I; and organometalloid such as
pentamethylantimony group, trimethylsilyl group, trimethylgermyl group,
diphenylarsine group, dicyclohexylantimony group and diphenylboron
group. Specific examples of substituted cyclopentadienyl group of R^12
and R^13 include methylcyclopentadienyl, butylcyclopentadienyl and
pentamethylcyclopentadienyl.
Among the compounds represented by the general formula (VIII) or (IX),
specific examples of preferably usable compounds include, as the
compound of general formula (VIII), triethylammonium tetraphenylborate,
tri(n-butyl)ammonium tetraphenylborate, trimethylammonium
tetraphenylborate, triethylammonium tetra(pentafluorophenyl)borate,
tri(n-butyl)ammonium tetra(pentafluorophenyl)borate, and
triethylammonium hexafluoroarsenate, pyridinium
tetra(pentafluorophenyl)borate, pyrrolinium
tetra(pentafluorophenyl)borate, N,N-dimethylanilinium
tetra(pentafluorophenyl)borate, methyldiphenylammonium
tetra(pentafluorophenyl)borate, and as the compound of general formula
(IX) ferrocenium tetraphenylborate, dimethylferrocenium
tetra(pentafluorophenyl)borate, ferrocenium
tetra(pentafluorophenyl)borate, decamethylferrocenium
tetra(pentafluorophenyl)borate, acetylferrocenium
tetra(pentafluorophenyl)borate, formylferrocenium
tetra(pentafluorophenyl)borate, cyanoferrocenium
tetra(pentafluorophenyl)borate, silver tetraphenylborate, silver
tetra(pentafluorophenyl)borate, trityl tetraphenylborate, trityl
tetra(pentafluorophenyl)borate, silver hexafluoroarsenate, silver
hexafluoroantimonate, and silver tetrafluoroborate.
On the other hand, various organometallic compounds are available as
the component (D) of the polymerization catalyst, and those represented
by the general formula (X) are used : R^15  [r]Al(OR^16)[s]H[t]Y^1  [u]
wherein R^15 and R^16 each independently represent an alkyl group
having 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms; Y^1
represents a halogen; r, s, t and u are 0<r≦3, 0≦s<3 and 0≦t<3,
respectively, and r+s+t+u=3.
The activity of the catalyst is further improved by adding the above
compound.
The organoaluminum compound represented by the above formula (X) can be
exemplified as shown below. Those corresponding to t=u=o are
represented by the formula: R^15[r]Al(OR^16)[3-r] (wherein R^15 and
R^16 are as previously defined and r is preferably a number of
1.5≦r≦3). Those corresponding to s=t=0 are represented by the formula:
R^15[r]AlY^1[3-r] (wherein R^15 and Y^1 are as previously defined and r
is preferably a number of 0<r<3). Those corresponding to s=u=0 are
represented by the formula: R^15[r]AlH[3-r] (wherein R^15 is as
previously defined and r is preferably a number of 2≦r<3). Those
corresponding to t=0 are represented by the formula:
R^15[r]Al(OR^16)[s]Y^1[u] (wherein R^15, R^16 and Y^1 are as previously
defined and 0<r≦3, 0≦s<3, 0≦u<3 and r+s+u=3.
In the organoaluminum compound represented by the formula (X), the
compound wherein t=u=0 and r=3 is selected from, for example,
trialkylaluminum such as triethylaluminum and tributylaluminum, or
combination thereof, and those preferred are triethylaluminum,
tri-n-butyl-aluminum and triisobutylaluminum. In the case of t=u=o and
1.5≦r<3, included are dialkylaluminum alkoxide such as diethylaluminum
ethoxide and dibutylaluminum butoxide; alkylaluminum sesquialkoxide
such as ethylaluminum sesquiethoxide and butylaluminum sesquibutoxide;
as well as partially alkoxylated alkylaluminum having an average
composition represented by R^15[2.5]Al(OR^16)[0.5]. Examples of the
compound corresponding to the case where s=t=0 include a partially
halogenated alkylaluminum including dialkylaluminum halogenide (r=2)
such as diethylaluminum chloride, dibutylaluminum chloride and
diethylaluminum bromide; alkylaluminum sesquihalogenide (r=1.5) such as
ethylaluminum sesquichloride, butylaluminum sesquichloride and
ethylaluminum sesquibromide; and alkylaluminum dihalogenide (r=1) such
as ethylaluminum dichloride, propylaluminum dichloride and
butylaluminum dibromide. Examples of the compound corresponding to the
case in which s=u=0 includes a partially hydrogenated alkylaluminum
including dialkylaluminum hydride (r=2) such as diethylaluminum hydride
and dibutylaluminum hydride; alkylaluminum dihydride (r=1) such as
ethylaluminum dihydride and propylaluminum dihydride. Examples of the
compound corresponding to the case in which t=0 include a partially
alkoxylated and halogenated alkylaluminum such as ethylaluminumethoxy
chloride, butylaluminumbutoxy chloride and ethylaluminumethoxy bromide
(r=s=u=1).
The catalyst to be used in the process of the present invention
comprises the components (A), (B), (C) and (D). A variety of procedures
are applicable to the preparation of the catalyst, including (1) a
method in which the component (D) is added to the reaction product
among the components (A), (B) and (C) to prepare the polymerization
catalyst, which is brought into contact with monomer/s to be
polymerized; (2) a method in which the components (B) and (C) are added
to the reaction product between the components (A) and (D) to prepare
the catalyst, which is brought into contact with monomer/s to be
polymerized; and (3) a method in which the components (A), (B), (C) and
(D) are added one by one to monomer/s to be polymerized to bring each
of the components into contact with the monomer/s. There may be
employed the reaction product among the components (A), (B) and (C)
which has been isolated and purified in advance.
The addition and contact of each of the components (A), (B), (C) and
(D) may be carried out, of course, at the polymerization temperature
and besides at a temperature in the range of 0 to 100°C.
In producing the styrenic polymer according to the process of the
present invention, at least one styrenic monomer such as styrene and/or
a derivative thereof exemplified by alkylstyrene, alkoxy styrene,
halogenated styrene or vinyl benzoate ester is polymerized or
copolymerized in the presence of the combined catalyst comprising the
above-mentioned components (A), (B), (C) and (D). As described
hereinbefore, there are available various methods of bringing the
catalyst of the present invention into contact with the styrenic
monomer.
The polymerization of the styrenic monomer may be carried out in bulk
or in a solvent such as an aliphatic hydrocarbon exemplified by
pentane, hexane and heptane; an alicyclic hydrocarbon exemplified by
cyclohexane; or an aromatic hydrocarbon exemplified by benzene, toluene
and xylene. The polymerization temperature is not specifically limited,
but is usually 0 to 90°C, preferably 20 to 70°C.
For the purpose of modifying the molecular weight of the styrenic
polymer to be produced, it is effective to proceed with the
polymerization reaction in the presence of hydrogen.
The styrenic polymer obtained by the process according to the present
invention has a high degree of syndiotactic configuration.
Here, the styrenic polymer which has a high degree of the syndiotactic
configuration means that its stereochemical structure is mainly the
syndiotactic configuration, i.e. the stereostructure in which phenyl
groups or substituted phenyl groups as side chains are located
alternately at opposite directions relative to the main chain
consisting of carbon-carbon bonds. Tacticity is quantitatively
determined by the nuclear magnetic resonance method (^13C-NMR method)
using carbon isotope. The tacticity as determined by the ^13C-NMR
method can be indicated in terms of proportions of structural units
continuously connected to each other, i.e., a diad in which two
structural units are connected to each other, a triad in which three
structural units are connected to each other and a pentad in which five
structural units are connected to each other. "The styrenic polymers
having such a high degree of syndiotactic configuration" as mentioned
in the present invention means polystyrene, poly(alkylstyrene),
poly(halogenated styrene), poly(alkoxystyrene), poly(vinyl benzoate),
the mixtures thereof, and copolymers containing the above polymers as
main components, having such a syndiotacticity that the proportion of
racemic diad is at least 75%, preferably at least 85%, or the
proportion of racemic pentad is at least 30%, preferably at least 50%.
Poly(alkylstyrene) include poly(methylstyrene), poly(ethylstyrene),
poly(isopropylstyrene) and poly(tert-butylstyrene), poly(halogenated
styrene) include poly(chlorostyrene), poly(bromostyrene),
poly(fluorostyrene), etc, and poly(alkoxystyrene) include
poly(methoxystyrene, and poly(ethoxystyrene).
The most desirable styrene polymers among them are polystyrene,
poly(p-methylstyrene), poly(m-methylstyrene),
poly(p-tert-butylstyrene), poly(p-chlorostyrene),
poly(m-chlorostyrene), poly(p-fluorostyrene), and the copolymer of
styrene and p-methylstyrene.
In summary, the process according to the present invention exhibits
remarkable effect in that the range of the molecular weight
distribution of the product styrenic polymer is expanded, since the
incorporation of the organoaluminum compound causes the polymer portion
produced by the aluminoxane to shift to the side of lower molecular
weight without causing the polymer portion produced by the ion complex
to shift to said side; the molecular weight distribution thereof can be
regulated to a desired value by the use of a plurality of transition
metal compounds; and the resultant polymer is minimized in residual
metallic components even when deashing treatment is omitted. After all,
highly syndiotactic styrenic polymer with a wide and arbitrary range of
molecular weight distribution can be efficiently produced at a low
production cost by the process according to the present invention.
In the following, the present invention will be described in more
detail with reference to examples.
  Example 1
In a 20 mL vessel which had been dried and purged with nitrogen were
successively placed 10 mL of styrene and 15 µmol of
triisobutylaluminum, 10 µmol of methylaluminoxane, 0.50 µmol of
dimethylanilinium tetra(pentafluorophenyl)borate(DMAB) and, 0.50 µmol
of pentamethylcyclopentadienyltrimethyltitanium to proceed with
polymerization at 70°C for 4 hours. After the completion of the
reaction, the reaction product was dried to afford 3.79 g of a polymer.
The resultant polymer was cut into slices of 1 mm or less in thickness,
which were subjected to Soxhlet extraction for 6 hours by the use of
methyl ethyl ketone (MEK) as the solvent to produce MIP (MEK-insoluble
portion). As the result, syndiotactic polystyrene (SPS) was obtained at
a yield of 3.60 g. As the result of analysis by gel permeation
chromatography, the SPS had a weight-average molecular weight
(Mw)/number-average molecular weight (Mn) ratio (Mw/Mn) of 5.2.
  Example 2
In a 20 mL vessel which had been dried and purged with nitrogen were
successively placed 10 mL of styrene and 15 µmol of
triisobutylaluminum, 100 µmol of methylaluminoxane, 0.50 µmol of
dimethylanilinium tetra(pentafluorophenyl)borate(DMAB) and, 0.25 µmol
of 1,2,3,4-tetramethylcyclopentadienyltrimethyltitanium to proceed with
polymerization at 70°C for 4 hours. After the completion of the
reaction, the reaction product was dried to afford 3.11 g of a polymer.
The resultant polymer was cut into slices of 1 mm or less in thickness,
which were subjected to Soxhlet extraction for 6 hours by the use of
methyl ethyl ketone (MEK) as the solvent to produce MIP (MEK-insoluble
portion). As the result, syndiotactic polystyrene (SPS) was obtained at
a yield of 3.16 g. As the result of analysis by gel permeation
chromatography, the SPS had a weight-average molecular weight
(Mw)/number-average molecular weight (Mn) ratio (Mw/Mn) of 8.3.
  Example 3
In a 20 mL vessel which had been dried and purged with nitrogen were
placed 10 mL of styrene and 15 µmol of triisobutylaluminum, 100 µmol of
methylaluminoxane, and 0.50 µmol of ferrocenium
tetra(pentafluorophenyl)borate (FCB) and, after one (1) minute, were
further added 0.25 µmol of pentamethylcyclopentadienyltitanium
trimethoxide and 0.25 µmol of
1,2,3,4-tetramethylcyclopentadienyltitanium trimethoxide to proceed
with polymerization at 70°C for 4 hours. After the completion of the
reaction, the reaction product was dried to afford 4.80 g of a polymer.
The resultant polymer was cut into slices of 1 mm or less in thickness,
which were subjected to Soxhlet extraction for 6 hours by the use of
methyl ethyl ketone (MEK) as the solvent to produce MIP (MEK-insoluble
portion). As the result, syndiotactic polystyrene (SPS) was obtained at
a yield of 4.68 g. As the result of analysis by gel permeation
chromatography, the SPS had a weight-average molecular weight
(Mw)/number-average molecular weight (Mn) ratio (Mw/Mn) of 13.2.