U.S. patent application number 11/585810 was filed with the patent office on 2008-05-01 for process for producing modified conjugated diene based polymer, modified conjugated diene based polymer produced by the process, rubber composition, and tire.
This patent application is currently assigned to BRIDGESTONE CORPORATION. Invention is credited to Terrence E. Hogan, Koji Masaki, Yoichi Ozawa, Christine M. Rademacher, Eiju Suzuki, Ken Tanaka.
Application Number | 20080103261 11/585810 |
Document ID | / |
Family ID | 39324629 |
Filed Date | 2008-05-01 |
United States Patent
Application |
20080103261 |
Kind Code |
A1 |
Tanaka; Ken ; et
al. |
May 1, 2008 |
Process for producing modified conjugated diene based polymer,
modified conjugated diene based polymer produced by the process,
rubber composition, and tire
Abstract
The invention provides a process for producing a modified
conjugated diene based polymer which attains favorable interaction
between a rubber component and carbon black and/or silica, thereby
improving dispersibility of the fillers, and which exhibits
excellent properties such as heat-buildup-suppressing performance,
fracture characteristics, and wear resistance; a modified
conjugated diene based polymer produced through the process; a
rubber composition containing the diene polymer; and a tire
produced from the rubber composition and exhibiting the above
properties. The process for producing a modified conjugated diene
based polymer includes a step (a) of reacting a silicon compound
with a conjugated diene based polymer having an active end so that
the reaction takes place at the active end, the silicon compound
having a protected primary amino group in the molecule thereof and
a bi-functional silicon atom to which a hydrocarbyloxy group and a
reactive group including a hydrocarbyloxy group are bonded, to
thereby modify the active end, and a step (b) of performing
condensation reaction which involves the compound having a
bi-functional silicon atom, in the presence of a titanium compound
serving as a titanium-based condensation-accelerating agent.
Inventors: |
Tanaka; Ken; (Tokyo, JP)
; Masaki; Koji; (Tokyo, JP) ; Ozawa; Yoichi;
(Tokyo, JP) ; Suzuki; Eiju; (Cuyahoga Falls,
OH) ; Rademacher; Christine M.; (Akron, OH) ;
Hogan; Terrence E.; (Akron, OH) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
BRIDGESTONE CORPORATION
|
Family ID: |
39324629 |
Appl. No.: |
11/585810 |
Filed: |
October 25, 2006 |
Current U.S.
Class: |
525/331.9 ;
525/342; 525/374 |
Current CPC
Class: |
C08K 3/36 20130101; B60C
1/0016 20130101; C08L 15/00 20130101; C08K 3/04 20130101; B60C
1/0025 20130101; C08C 19/44 20130101; C08L 21/00 20130101; C08C
19/25 20130101; C08L 9/00 20130101; C08L 15/00 20130101; C08L
2666/08 20130101; C08L 21/00 20130101; C08L 2666/08 20130101; C08L
15/00 20130101; C08K 3/04 20130101; C08L 9/00 20130101; C08L 15/00
20130101; C08K 3/36 20130101; C08L 9/00 20130101; C08L 21/00
20130101; C08L 15/00 20130101 |
Class at
Publication: |
525/331.9 ;
525/342; 525/374 |
International
Class: |
C08F 136/00 20060101
C08F136/00 |
Claims
1. A process for producing a modified conjugated diene based
polymer, the process comprising a step (a) of reacting a silicon
compound with a conjugated diene based polymer having an active end
so that the reaction takes places at the active end, the silicon
compound having a protected primary amino group in the molecule
thereof and a bi-functional silicon atom to which a hydrocarbyloxy
group and a reactive group including a hydrocarbyloxy group are
bonded, to thereby modify the active end, and a step (b) of
performing condensation reaction which involves the compound having
a bi-functional silicon atom, in the presence of a titanium
compound serving as a titanium-based condensation-accelerating
agent.
2. A process for producing a modified conjugated diene based
polymer as described in claim 1, which further includes a
deprotection step (c) of hydrolyzing a group which is bonded to the
active end of the conjugated based polymer and which has been
derived from the compound having a bi-functional silicon atom,
whereby the protected primary amino group contained in the group
bonded to the active end is converted to a free amino group.
3. A process for producing a modified conjugated diene based
polymer as described in claim 1, wherein the compound having a
bi-functional silicon atom employed in the step (a) is a silicon
compound represented by formula (1): ##STR00009## (wherein each of
R.sup.1 and R.sup.2 represents a hydrocarbon group having 1 to 20
carbon atoms, each of R.sup.3 to R.sup.5 represents a hydrocarbon
group having 1 to 20 carbon atoms, R.sup.6 represents a alkylene
group having 1 to 12 carbon atoms, A represents a reactive group,
and f is an integer of 1 to 10); a silicon compound represented by
formula (II): ##STR00010## (wherein each of R.sup.7 to R.sup.11
represents a hydrocarbon group having 1 to 20 carbon atoms, and
R.sup.12 represents a alkylene group having 1 to 12 carbon atoms);
or a silicon compound represented by formula (III): ##STR00011##
(wherein each of R.sup.1 and R.sup.2 represents a hydrocarbon group
having 1 to 20 carbon atoms, each of R.sup.3 to R.sup.5 represents
a hydrocarbon group having 1 to 20 carbon atoms, R.sup.6 represents
a alkylene group having 1 to 12 carbon atoms, R.sup.13 represents a
alkylene group having 1 to 12 carbon atoms, A represents a reactive
group, and f is an integer of 1 to 10).
4. A process for producing a modified conjugated diene based
polymer as described in claim 3, wherein the group A in formula (I)
is a halogen atom or a alkoxyl group having 1 to 20 carbon
atoms.
5. A process for producing a modified conjugated diene based
polymer as described in claim 1, wherein the conjugated diene based
polymer having an active end is produced through anionic
polymerization, in the presence of an organic alkali metal compound
serving as a polymerization initiator, of a conjugated diene
compound singly or of a conjugated diene compound and an aromatic
vinyl compound in combination.
6. A process for producing a modified conjugated diene based
polymer as described in claim 5, wherein the conjugated diene
compound is at least one species selected from the group of
1,3-butadiene, isoprene, and 2,3-dimethyl-1,3-butadiene.
7. A process for producing a modified conjugated diene based
polymer as described in claim 5, wherein the aromatic vinyl
compound is styrene.
8. A process for producing a modified conjugated diene based
polymer as described in claim 5, wherein the conjugated diene based
polymer has a polymer unit derived from an aromatic vinyl compound
in an amount of 0 to 55 mass % based on the total polymer unit
present in the conjugated diene based polymer and a vinyl bond
content of 7 to 65 mass % based on the total conjugated diene
portion.
9. A process for producing a modified conjugated diene based
polymer as described in claim 1, wherein the
condensation-accelerating agent employed in the step (b) is at
least one species selected from among a titanium alkoxide, a
titanium carboxylate salt, a titanium acetylacetonate complex salt,
and a salt mixture thereof.
10. A modified conjugated diene based polymer produced by a process
as recited in claim 1.
11. A rubber composition comprising a modified conjugated diene
based polyner as recited in claim 10.
12. A rubber composition as described in claim 11, which comprises
a rubber component containing 20 mass % or more of the modified
conjugated diene base polymer in an amount of 100 parts by mass and
silica and/or carbon black in the total amount of 20 to 120 parts
by mass.
13. A rubber composition as described in claim 11, wherein the
rubber component comprises the modified conjugated diene based
polymer in an amount of 15 to 100 mass % and at least one species
selected from among a natural rubber, a synthetic isoprene rubber,
a butadiene rubber, a styrene-butadiene rubber, an
ethylene-.alpha.-olefin copolymer rubber, an
ethylene-.alpha.-olefin-diene copolymer rubber, a chloroprene
rubber, a halogenated butyl rubber, and a styrene-isobutylene
copolymer having a halomethyl group, in an amount of 85 to 0 mass
%.
14. A pneumatic tire employing a rubber composition as recited in
claim 11.
15. A pneumatic tire employing a rubber composition as recited in
claim 11 as a tread, a base tread, or a sidewall thereof.
Description
TECHNICAL FIELD
[0001] The present invention relates to a process for producing a
modified conjugated diene based polymer, to a modified conjugated
diene based polymer produced through the process, to a rubber
composition, and to a tire. More particularly, the invention
relates to a process for producing a modified conjugated diene
based polymer which attains favorable interaction between a rubber
component and carbon black and/or silica, thereby improving
dispersibility of the fillers, which exhibits excellent properties
such as heat-buildup-suppressing performance, fracture
characteristics, and wear resistance, and which is remarkably
consistent in quality; to a modified conjugated diene based polymer
produced through the process; to a rubber composition containing
the diene polymer; and to a tire produced from the rubber
composition and exhibiting the above properties.
BACKGROUND ART
[0002] In recent years, social demand with respect to energy
conservation and concerns about environmental problems have
increased, and emission of carbon dioxide is now controlled more
and more rigorously throughout the world. In the midst of such a
trend, demand has increased for reducing fuel consumption of
automobiles. In order to satisfy such demands, performance of tires
must be enhanced; particularly, rolling resistance must be reduced.
Previously, optimization of the structure of tires was investigated
for reducing rolling resistance. However, at present, rolling
resistance is generally reduced through employment of a
low-heat-buildup rubber composition.
[0003] In order to produce such a low-heat-buildup rubber
composition, a variety of modified rubbers containing silica or
carbon black serving as a filler have been developed. Among the
techniques for producing such modified rubbers, Japanese Patent
Publication (kokoku) Nos. 6-53763 and 6-57767 and other documents
disclose particularly effective approaches in which the
polymerization active end of a conjugated diene based polymer
produced through anionic polymerization in the presence of an
organic lithium is modified with an alkoxysilane derivative having
a functional group interacting with a filler.
[0004] Although, these approaches are generally effective for
polymers having a stable polymerization living end, modification of
a rubber composition containing silica or carbon black has not been
satisfactorily attained. In addition, when a conventional
modification technique is employed, in many cases, branching of the
backbone of the polymer is insufficient. Therefore, when such a
modified rubber is used in practice, problematic cold flow occurs.
In this case, partial coupling is performed so as to prevent cold
flow and, as a result, the effect of modification is reduced.
[0005] Thus, an approach for overcoming the above drawbacks and
enhancing the effect of modification has been proposed. WO
03/087171 discloses a method in which a condensation-accelerating
agent is added to a reaction system during modification of the
active end of a conjugated diene based polymer with an
alkoxysilane. Although the method successfully prevents loss of a
silica filler in the rubber composition, loss of a carbon black
filler cannot be satisfactorily prevented.
DISCLOSURE OF THE INVENTION
[0006] Under such circumstances, an object of the present invention
is to provide a process for producing a modified conjugated diene
based polymer which attains favorable interaction between a rubber
component and carbon black and/or silica, thereby improving
dispersibility of the fillers, and which exhibits excellent
properties such as heat-buildup-suppressing performance, fracture
characteristics, and wear resistance. Another object of the
invention is to provide a modified conjugated diene based polymer
produced through the process. Still another object of the invention
is to provide a rubber composition containing the diene polymer.
Yet another object is to provide a tire produced from the rubber
composition and exhibiting the above properties.
[0007] The present inventors have carried out extensive studies in
order to attain the above objects, and have found that the objects
can be attained by two-part process, including the step of
modification reaction in which the active end of a conjugated diene
based polymer is modified with a compound containing a
bi-functional silicon atom, which compound has at least an amino
group of a specific structure in the molecule thereof and a
hydrocarbyloxy group bonded to the silicon atom; and the step of
condensation reaction performed in the presence of a specific
titanium compound serving as a condensation-accelerating agent. The
present invention has been accomplished on the basis of this
finding.
[0008] Accordingly, in a first aspect of the present invention,
there is provided
[0009] a process for producing a modified conjugated diene based
polymer, the process comprising
[0010] a step (a) of reacting a silicon compound with a conjugated
diene based polymer having an active end so that the reaction takes
places at the active end, the silicon compound having a protected
primary amino group in the molecule thereof and a bi-functional
silicon atom to which a hydrocarbyloxy group and a reactive group
including a hydrocarbyloxy group are bonded, to thereby modify the
active end, and
[0011] a step (b) of performing condensation reaction which
involves the compound having a bi-functional silicon atom, in the
presence of a titanium compound serving as a titanium-based
condensation-accelerating agent.
[0012] The process may further include a deprotection step (c) of
hydrolyzing a group which is bonded to the active end of the
conjugated diene based polymer and which has been derived from the
compound having a bi-functional silicon atom, whereby the protected
primary amino group contained in the group bonded to the active end
is converted to a free amino group.
[0013] The compound having a bi-functional silicon atom employed in
the step (a) is a silicon compound represented by formula (I):
##STR00001##
(wherein each of R.sup.1 and R.sup.2 represents a hydrocarbon group
having 1 to 20 carbon atoms, each of R.sup.3 to R.sup.5 represents
a hydrocarbon group having 1 to 20 carbon atoms, R.sup.6 represents
a alkylene group having 1 to 12 carbon atoms, A represents a
reactive group, and f is an integer of 1 to 10);
[0014] a silicon compound represented by formula (II):
##STR00002##
(wherein each of R.sup.7 to R.sup.11 represents a hydrocarbon group
having 1 to 20 carbon atoms, and R.sup.12 represents a alkylene
group having 1 to 12 carbon atoms); or
[0015] a silicon compound represented by formula (III):
##STR00003##
(wherein each of R.sup.1 and R.sup.2 represents a hydrocarbon group
having 1 to 20 carbon atoms, each of R.sup.3 to R.sup.5 represents
a hydrocarbon group having 1 to 20 carbon atoms, R.sup.6 represents
a alkylene group having 1 to 12 carbon atoms, R.sup.13 represents a
alkylene group having 1 to 12 carbon atoms, A represents a reactive
group, and f is an integer of 1 to 10).
[0016] The group A in formula (I) is a halogen atom or a alkoxyl
group having 1 to 20 carbon atoms.
[0017] The conjugated diene based polymer having an active end may
be produced through anionic polymerization, in the presence of an
organic alkali metal compound serving as a polymerization
initiator, of a conjugated diene compound singly or of a conjugated
diene compound and an aromatic vinyl compound in combination.
[0018] The conjugated diene compound is at least one species
selected from the group of 1,3-butadiene, isoprene, and
2,3-dimethyl-1,3-butadiene.
[0019] The aromatic vinyl compound is styrene.
[0020] The conjugated diene based polymer has a polymer unit
derived from an aromatic vinyl compound in an amount of 0 to 55
mass % based on the total polymer unit present in the conjugated
diene based polymer and a vinyl bond content of 7 to 65 mass %
based on the total conjugated diene portion.
[0021] The condensation-accelerating agent employed in the step (b)
is at least one species selected from among a titanium alkoxide, a
titanium carboxylate salt, a titanium acetylacetonate complex salt,
and a salt mixture thereof.
[0022] In a second aspect of the present invention, there is
provided a modified conjugated diene based polymer produced by the
above process.
[0023] In a third aspect of the present invention, there is
provided a rubber composition comprising the modified conjugated
diene based polymer.
[0024] The rubber composition may comprise a rubber component
containing 20 mass % or more of the modified conjugated diene based
polymer in an amount of 100 parts by mass and silica and/or carbon
black in the total amount of 20 to 120 parts by mass.
[0025] The rubber component may comprise the modified conjugated
diene based polymer in an amount of 15 to 100 mass % and at least
one species selected from among a natural rubber, a synthetic
isoprene rubber, a butadiene rubber, a styrene-butadiene rubber, an
ethylene-.alpha.-olefin copolymer rubber, an
ethylene-.alpha.-olefin-diene copolymer rubber, a chloroprene
rubber, a halogenated butyl rubber, and a styrene-isobutylene
copolymer having a halomethyl group, in an amount of 85 to 0 mass
%.
[0026] In a fourth aspect of the present invention, there is
provided a pneumatic tire employing the rubber composition.
[0027] The pneumatic tire may employ the rubber composition as a
tread, a base tread, or a sidewall thereof.
[0028] According to the present invention, there can be provided a
process for producing a modified conjugated diene based polymer
which attains favorable interaction between a rubber component and
carbon black and/or silica, thereby improving dispersibility of the
fillers, which exhibits excellent properties such as
heat-buildup-suppressing performance, fracture characteristics, and
wear resistance, and which is remarkably consistent in quality; a
modified conjugated diene based polymer produced through the
process; a rubber composition containing the diene polymer; and a
tire produced from the rubber composition and exhibiting the above
properties.
BEST MODE FOR CARRYING OUT THE INVENTION
[0029] The process of the present invention for producing a
modified conjugated diene base polymer includes
[0030] a step (a) of reacting a silicon compound with a conjugated
diene based polymer having an active end so that the reaction takes
places at the active end, the silicon compound having a protected
primary amino group in the molecule thereof and a bi-functional
silicon atom to which a hydrocarbyloxy group and a reactive group
including a hydrocarbyloxy group (hereinafter the compound may be
referred to as "an alkoxysilane compound") are bonded, to thereby
modify the active end, and
[0031] a step (b) of performing condensation reaction which
involves the compound having a bi-functional silicon atom, in the
presence of a titanium compound serving as a titanium-based
condensation-accelerating agent.
[0032] The condensation-accelerating agent is generally added after
modification reaction in which the alkoxysilane compound is reacted
with the active end of the conjugated diene based polymer, and
before condensation reaction. Alternatively, the
condensation-accelerating agent may be added before addition of the
alkoxysilane compound (i.e., before modification reaction),
followed by adding the alkoxysilane compound for modification and
performing condensation reaction.
[0033] No particular limitation is imposed on the method for
producing a conjugated diene based polymer having an active end
employed in the present invention, and a conjugated diene based
polymer may be produced from a diene monomer or a diene monomer and
another comonomer. Examples of the mode of polymerization include
solution polymerization, gas-phase polymerization, and bulk
polymerization. Of these, solution polymerization is particularly
preferred. The polymerization may be performed in a batch manner or
a continuous manner.
[0034] The active site in the molecule of a conjugated diene based
polymer is preferably at least one metal species selected from
alkaline metals and alkaline earth metals. Of these, alkali metals
are preferred, with lithium being particularly preferred.
[0035] In the solution polymerization, the polymer of interest may
be produced through, for example, anionically polymerizing a
conjugated diene compound alone or a conjugated diene compound with
an aromatic vinyl compound in the presence of an organic alkali
metal compound, particularly an organic lithium compound as a
polymerization initiator. In the specification, the term
"conjugated diene based polymer" refers not only to a polymer
formed from a conjugated diene but also to a polymer formed from a
conjugated diene and an aromatic vinyl compound.
[0036] In addition, in an effective manner, a halogen-containing
monomer is employed, and a halogen atom contained in the formed
polymer is activated by an organic metal compound. For example, a
bromine site of a copolymer containing an isobutylene unit, a
p-methylstylene unit, or a p-bromomethylstylene unit is lithiated
to thereby provide an active site.
[0037] Examples of the aforementioned conjugated diene compound
includes 1,3-butadiene, isoprene, 1,3-pentadiene,
2,3-dimethyl-1,3-butadiene, 2-phenyl-1,3-butadiene, and
1,3-hexadiene. These dienes may be used singly or in combination of
two or more species. Among them, 1,3-butadiene, isoprene, and
2,3-dimethyl-1,3-butadiene are particularly preferred.
[0038] Examples of the aromatic vinyl compound used in
copolymerization with these conjugated diene compounds includes
styrene; .alpha.-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene,
ethylvinylbenzene, divinylbenzene, 4-cyclohexylbenzene, and
2,4,6-trimethylstyrene. These compounds may be used singly or in
combination of two or more species. Among them, styrene is
particularly preferred.
[0039] In the case where the conjugated diene compound and the
aromatic vinyl compound are used as comonomers, use of
1,3-butadiene and styrene are particularly preferred, from the
viewpoint of practical aspects including availability, and anionic
polymerization characteristics including a living property.
[0040] When solution polymerization is employed, the monomer
concentration of the solution is preferably 5 to 50 mass %, more
preferably 10 to 30 mass %. When the conjugated diene compound and
the aromatic vinyl compound are used as comonomers, the monomer
mixture preferably has an aromatic vinyl compound content falling
within a range 0 to 55 mass %.
[0041] No particular limitation is imposed on the lithium compound
serving as a polymerization initiator, and hydrocarbyllithium and a
lithiumamide compound are preferably used. When hydrocarbyllithium
is used, a conjugated diene based polymer which has a hydrocarbyl
group at a polymerization-initiating end and a polymerization
active site at the other end is produced, whereas when the
lithiumamide compound is used, a conjugated diene based polymer
which has a nitrogen-containing group at a
polymerization-initiating end and a polymerization active site at
the other end is produced.
[0042] The hydrocarbyllithium is preferably a compound having a C2
to C20 hydrocarbyl group. Specific examples include ethyllithium,
n-propyllithium, isopropyllithium, n-butyllithium,
sec-butyllithium, tert-octyllithium, n-decyllithium, phenyllithium,
2-naphthyllithium, 2-butyl-phenyllithium, 4-phenyl-butyllithium,
cyclohexyllithium, cyclopentyllithium, and a reaction product of
diisopropenylbenzene with butyllithium. Among them, n-butyllithium
is preferred.
[0043] Examples of the lithium amide compound includes, for
example, lithium hexamethyleneimide, lithium pyrrolidide, lithium
piperidide, lithium heptamethyleneimide, lithium
dodecamethyleneimide, lithium dimethylamide, lithium diethylamide,
lithium dibutylamide, lithium dipropylamide, lithium diheptylamide,
lithium dihexylamide, lithium dioctylamide, lithium
di-2-ethylhexylamide, lithium didecylamide, lithium
N-methylpiperazide, lithium ethylpropylamide, lithium
ethylbutylamide, lithium ethylbenzylamide, and lithium
methylphenethylamide. Among them, cyclic lithium amides such as
lithium hexamethyleneimide, lithium pyrrolidide, lithium
piperidide, lithium heptamethyleneimide and lithium
dodecamethyleneimide are preferred in terms of interaction with
carbon black and polymerization initiating ability. Particularly
preferred are lithium hexamethyleneimide and lithium
pyrrolidide.
[0044] Generally, these lithium amide compounds for use in
polymerization may be prepared in advance from a secondary amine
and a lithium compound. Alternatively, the amide compounds may also
be prepared in the polymerization system (in-situ). The
polymerization initiator is preferably employed in an amount 0.2 to
20 mmol per 100 g of the monomer.
[0045] No particular limitation is imposed on the method for
producing a conjugated diene based polymer through anionic
polymerization employing the aforementioned lithium compound
serving as a polymerization initiator, and any conventionally known
methods may be employed.
[0046] In a specific procedure, a conjugated diene compound or a
mixture of a conjugated diene compound and an aromatic vinyl
compound is anionically polymerized in the presence of the lithium
compound serving as a polymerization initiator and an optional
randomizer in an organic solvent which is inert to the reaction, to
thereby produce a conjugated diene based polymer of interest.
Examples of the hydrocarbon solvent include aliphatic, alicyclic,
and aromatic hydrocarbon compounds.
[0047] The hydrocarbon solvent is preferably a C3 to C8
hydrocarbon. Specific examples include propane, n-butane,
isobutane, n-pentane, isopentane, n-hexane, cyclohexane, propene,
1-butene, isobutene, trans-2-butene, cis-2-butene, 1-pentene,
2-pentene, 1-hexene, 2-hexene, benzene, toluene, xylene, and
ethylbenzene. These hydrocarbons may be used singly or in
combination of two or more species.
[0048] The randomizer, which may be used in accordance with needs,
is a compound which is capable of controlling a microstructure of a
conjugated diene based polymer (e.g., increasing 1,2-butadiene
units in a butadiene-styrene copolymer or 3,4-bonds in an isoprene
polymer) or controlling of the monomer unit composition
distribution profile of a conjugated diene compound-aromatic vinyl
compound copolymer (e.g., randomization in butadiene units and
styrene units in a butadiene-styrene copolymer). No particular
limitation is imposed on the type of randomizer, and any of
compounds known as a randomizer may appropriately employed.
Specific examples of the randomizer include ethers and tertiary
amines such as dimethoxybenzene, tetrahydrofuran, dimethoxyethane,
diethylene glycol dibutyl ether, diethylene glycol dimethyl ether,
oxoranylpropane oligomers (particularly
2,2-bis(2-tetrahydrofuryl)propane), triethylamine, pyridine,
N-methylmorpholine, N,N,N',N'-tetramethylethylenediamine and
1,2-piperidinoethane. Further, potassium salts such as potassium
t-amylate and potassium t-butoxide and sodium salts such as sodium
t-amylate may also be employed.
[0049] These randomizers may be used singly or in combination of
two or more species. The randomizer is preferably employed in an
amount 0.01 to 1000 mole equivalents per mole of the lithium
compound.
[0050] The polymerization reaction is preferably carried out at 0
to 150.degree. C., more preferably 20 to 130.degree. C. The
polymerization reaction may be carried out under generated
pressure. In a general procedure, the pressure is preferably
selected such that the monomer is maintained virtually as a liquid
phase. That is, a higher pressure may be employed in accordance
with needs, although depending on the individual substances to be
polymerized, polymerization solvent, and polymerization
temperature. Such pressure may be obtained through an appropriate
method such as applying pressure to a reactor by use of gas inert
to the polymerization reaction.
[0051] In the polymerization, all the raw materials involved in
polymerization such as a polymerization initiator, a solvent,
monomers, etc. are preferably employed after removing
reaction-inhibiting substances such as water, oxygen, carbon
dioxide, and protic compounds.
[0052] In order to produce an elastomeric polymer, the formed
polymer or copolymer preferably has a glass transition temperature
(Tg) of -95 to -15.degree. C., as determined through differential
thermal analysis. Through controlling of the glass transition
temperature to fall within the above range, increase in viscosity
is prevented, whereby a polymer which can be easily handled can be
obtained.
[0053] In the present invention, the active end of the
thus-produced conjugated diene based polymer is modified through
reaction with a silicon compound having a protected primary amino
group in the molecule thereof and a bi-functional silicon atom to
which a hydrocarbyloxy group and a reactive group including a
hydrocarbyloxy group are bonded.
[0054] Examples of the silicon compound having a protected primary
amino group in the molecule thereof and a bi-functional silicon
atom to which a hydrocarbyloxy group and a reactive group including
a hydrocarbyloxy group are bonded (hereinafter the compound may be
referred to as "a modifying agent") include the following
compounds:
[0055] a silicon compound represented by formula (I):
##STR00004##
(wherein each of R.sup.1 and R.sup.2 represents a hydrocarbon group
having 1 to 20 carbon atoms, each of R.sup.3 to R.sup.5 represents
a hydrocarbon group having 1 to 20 carbon atoms, R.sup.6 represents
a alkylene group having 1 to 12 carbon atoms, A represents a
reactive group, preferably a halogen atom or a alkoxyl group having
1 to 20 carbon atoms, and f is an integer of 1 to 10);
[0056] a silicon compound represented by formula (II):
##STR00005##
(wherein each of R.sup.7 to R.sup.11 represents a hydrocarbon group
having 1 to 20 carbon atoms, and R.sup.12 represents a alkylene
group having 1 to 12 carbon atoms); and
[0057] a silicon compound represented by formula (III):
##STR00006##
(wherein each of R.sup.1 and R.sup.2 represents a hydrocarbon group
having 1 to 20 carbon atoms, each of R.sup.3 to R.sup.5 represents
a ydrocarbon group having 1 to 20 carbon atoms, R.sup.6 represents
a alkylene group having 1 to 12 carbon atoms, R.sup.13 represents a
alkylene group having 1 to 12 carbon atoms, A represents a reactive
group, and f is an integer of 1 to 10).
[0058] In the above formulas (I) to (III), examples of preferred
alkylene groups having 1 to 12 carbon atoms represented by R.sup.6
or R.sup.12 include a methylene group, an ethylene group, and a
propylene group. Examples of the hydrocarbon group having 1 to 20
carbon atoms include alkyl groups such as methyl, ethyl, and
propyl; and aryl groups such as aralkyl groups including phenyl,
toluyl, naphthyl, and benzyl.
[0059] In formula (I), any two groups of R.sup.3, R.sup.4, and
R.sup.5 may be linked to each other, to thereby form, together with
the silicon atom bonded thereto, a 4- to 7-membered ring.
Similarly, in formula (II), any two groups of R.sup.9, R.sup.10,
and R.sup.11 may be linked to each other, to thereby form, together
with the silicon atom bonded thereto, a 4- to 7-membered ring.
R.sup.13 represents a alkylene group having 1 to 12 carbon
atoms.
[0060] Examples of the silicon compound having a protected primary
amino group and a bi-functional silicon atom to which at least an
alkoxy group is bonded include
N,N-bis(trimethylsilyl)aminopropylmethyldimethoxysilane,
N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane,
N,N-bis(trimethylsilyl)aminoethylmethyldimethoxysilane,
N,N-bis(trimethylsilyl)aminoethylmethyldiethoxysilane, and
1-trimethylsilyl-2-ethoxymethyl-1-aza-2-cyclopentane.
[0061] Examples of such compounds in which A is a halogen atom
include
N,N-bis(trimethylsilyl)aminopropylmethylmethoxychlorosilane,
N,N-bis(trimethylsilyl)aminopropylmethylethoxychlorosilane,
N,N-bis(trimethylsilyl)aminoethylmethylmethoxychlorosilane, and
N,N-bis(trimethylsilyl)aminoethylmethylethoxychlorosilane.
[0062] Of these,
N,N-bis(trimethylsilyl)aminopropylmethyldimethoxysilane,
N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane, and
1-trimethylsilyl-2-ethoxymethyl-1-aza-2-cyclopentane are
preferred.
[0063] These modifying agents may be used singly or in combination
of two or more species, and may be a partial condensate.
[0064] As used herein, the term "partial condensate" means a
condensation product in which a part (not entirety) of SiOR
moieties are condensed to form Si--O--Si bonds.
[0065] The polymer subjected to the modification reaction
preferably contain at least 10% of living polymer chains.
[0066] Reaction between a living polymerization end, for example,
P.sup.-Li.sup.+ and a modifying agent represented by formula (I)
(f=1) is represented by the following scheme:
##STR00007##
[0067] (wherein P represents a polymer chain of a conjugated diene
compound chain or a copolymer chain of a conjugated diene compound
and an aromatic vinyl compound.
[0068] Similarly, reaction between a living polymerization end, for
example, P.sup.-Li.sup.+ and a modifying agent represented by
formula (II) is represented by the following scheme.
##STR00008##
[0069] During modification reaction, the above modifying agent is
preferably employed in an amount of 0.5 to 200 mmol/kg (conjugated
diene based polymer), more preferably 1 to 100 mmol/kg (conjugated
diene based polymer), particularly preferably 2 to 50 mmol/kg
(conjugated diene based polymer). In the unit of the amount, the
"conjugated diene based polymer" means the mass of polymer not
containing additives such as an anti-aging agent added during or
after the production of the diene polymer. Through controlling the
amount of the modifying agent employed so as to fall within the
above ranges, high dispersibility of fillers can be attained, and
mechanical characteristics, wear resistance, and
heat-buildup-suppressing performance after vulcanization can be
enhanced.
[0070] No particular limitation is imposed on the method of adding
the above modifying agent, and one batch addition, divided
addition, continuous addition, etc. may be employed. Among them,
one batch addition is preferred.
[0071] The modifying agent may act on any of a
polymerization-initiating end, a polymerization-terminating end, a
polymer backbone, and a polymer side chain. From the viewpoint of
improvement of the heat-buildup-suppressing performance by
preventing energy loss from a polymer end, the modifying agent is
preferably introduced into the polymerization-initiating end or the
polymerization-terminating end.
[0072] In the present invention, a specific
condensation-accelerating agent is employed in order to accelerate
condensation reaction involving the aforementioned alkoxysilane
compound serving as a modifying agent.
[0073] The condensation-accelerating agent employed in the
invention may be added to the reaction system before the
aforementioned modification reaction. However, preferably, the
agent is added to the reaction system after modification reaction
and before condensation reaction. When the agent is added before
modification reaction, in some cases, the agent is directly reacted
with the active end, thereby failing to introduce a hydrocarbyloxy
group to the active end.
[0074] When the agent is added after initiation of condensation
reaction, in some cases, the condensation-accelerating agent is not
uniformly dispersed in the reaction system, thereby deteriorating
the catalyst performance.
[0075] The timing of addition of the condensation-accelerating
agent is generally 5 minutes to 5 hours after initiation of
modification reaction, preferably 15 minutes to one hour after
initiation of modification reaction.
[0076] The condensation-accelerating agent employed in the step (b)
of the present invention is preferably an alkoxide, carboxylate
salt (including titanium (Ti) dioleate), or acetylacetonate complex
salt.
[0077] Specific examples of the condensation-accelerating agent
include titanium ethylhexyldioleate, titanium 2-ethylhexylhexoxide,
titanium di-n-butoxide (bis-2,4-pentadionate), titanium
isobutoxide, titanium stearyloxide, titanium oxide
bis(tetramethylheptanedionate), titanium oxide bis(pentanedionate),
and titanium lactate. Of these, titanium ethylhexyl dioleate,
titanium 2-ethylhexoxide, and titanium di-n-butoxide
(bis-2,4-pentanedionate) are preferred.
[0078] The condensation-accelerating agent is preferably employed
at a mole ratio of the agent to the total amount of hydrocarbyloxy
groups present in the reaction system of 0.1 to 10, particularly
preferably 0.5 to 5. Through controlling the amount of the
condensation-accelerating agent so as to fall within the above
range, condensation reaction is effectively proceeds.
[0079] In the present invention, condensation reaction is
preferably carried out in an aqueous solution. The condensation
reaction temperature is preferably 85 to 180.degree. C., more
preferably 100 to 170.degree. C., particularly preferably 110 to
150.degree. C.
[0080] Through controlling the temperature during condensation
reaction to fall within the above range, condensation reaction can
be effectively completed, whereby aging reaction as elapse of time
or other deterioration in quality of the produced modified
conjugated diene based polymer can be prevented.
[0081] The condensation reaction is generally about 5 minutes to 10
hours, preferably about 15 minutes to 5 hours. Through controlling
the condensation reaction time to fall within the above range,
condensation reaction can be smoothly completed.
[0082] The pressure of the reaction system during condensation
reaction is generally 0.01 to 20 MPa, preferably 0.05 to 10
MPa.
[0083] No particular limitation is imposed on the mode of
condensation reaction, and a batch-type reactor may be employed.
Alternatively, the reaction may be carried out in a continuous
manner by means of an apparatus such as a multi-step continuous
reactor. In the course of condensation reaction, removal of solvent
may be simultaneously performed.
[0084] The amino group derived from a modifying agent for producing
the modified conjugated diene based polymer of the present
invention may be protected, or deprotected to be a primary amine.
Both cases are preferred. In the case where a protected group is
deprotected, the following procedure is performed.
[0085] Specifically, silyl protective groups on the protected amino
group are hydrolyzed, to thereby form the corresponding free amino
group. Through removal of the solvent from the thus-deprotected
polymer, the corresponding dried polymer having a primary amino
group is obtained. Needless to say, in any step from a step
including the condensation to a step of removing solvent to produce
a dried polymer, deprotection of the protected primary amino group
derived from the modifying agent may be performed in accordance
with needs.
[0086] In the present invention, after completion of the
condensation, a deprotection step (c) may be performed. In the step
(c), a group which is bonded to the active end of the conjugated
diene based polymer and which has been derived from a compound
having a bi-functional silicon atom is hydrolyzed, whereby the
protected primary amino group in the end group is converted to a
free amino group. Thus, a modified conjugated diene based polymer
of interest can be produced.
[0087] The modified conjugated diene based polymer produced in the
present invention preferably has a Mooney viscosity (ML.sub.1+4,
100.degree. C.) of 10 to 150, more preferably 15 to 100. Though
controlling the Money viscosity to fall within the above range, a
rubber composition exhibiting excellent kneadability and mechanical
strength after vulcanization can be produced.
[0088] The rubber composition of the present invention preferably
contains, as a rubber component, the aforementioned modified
conjugated diene based polymer in an amount at least 20 mass %. The
rubber component more preferably contains the modified conjugated
diene based polymer in an amount of 30 mass % or more, particularly
preferably 40 mass % or more. Through controlling the modified
conjugated diene based polymer content of the rubber component to
be 15 mass % or more, the rubber composition is endowed with a
physical property of interest.
[0089] The modified conjugated diene based polymer species may be
used singly or in combination of two or more species. Examples of
the additional rubber component employed in combination with the
modified conjugated diene basedpolymer include natural rubber,
synthetic isoprene rubber, butadiene rubber, styrene-butadiene
rubber, ethylene-.alpha.-olefin copolymer rubbers,
ethylene-.alpha.-olefin-diene copolymer rubbers,
acrylonitrile-butadiene copolymer rubber, chloroprene rubber,
halogenated butyl rubbers, and mixtures thereof. These rubber
species may be treated with a multi-functional modifying agent such
as tin tetrachloride or silicon tetrachloride, to thereby have a
branch structure.
[0090] The rubber composition of the present invention preferably
contains, as a filler, silica and/or carbon black.
[0091] No particular limitation is imposed on the type of silica,
and any of the silica species conventionally employed as rubber
reinforcing fillers may be used.
[0092] Examples of the silica species include wet silica (hydrous
silicic acid), dry silica (anhydrous silicic acid), calcium
silcate, and aluminum silicate. Among them, wet silica is
preferred, since the silica can remarkably improve both fracture
characteristics and wet grip performance.
[0093] No particular limitation is imposed on the type of carbon
black, and SRF, GPF, FEF, HAF, 1SAF, SAF, etc. may be employed. The
carbon black employed in the invention preferably has an iodine
absorption (IA) of 60 mg/g or more and a dibutyl phthalate oil
absorption (DBP) of 80 mL/100 g or more. By use of carbon black,
grip performance and fracture characteristics can be greatly
improved. From the viewpoint of wear resistance, HAF, ISAF, and SAF
are particularly preferred.
[0094] The silica and/or carbon black may be used singly or in
combination of two or more species.
[0095] The rubber composition preferably contains silica and/or
carbon black in an amount of 20 to 120 parts by mass with respect
to 100 parts by mass of the rubber component. From the viewpoint of
reinforcing effects and improvement of physical properties, the
amount is more preferably 25 to 100 parts by mass. Through
controlling the amount of carbon black and/or silica to fall within
the above range, a rubber composition exhibiting excellent
operability in factories such as kneadability and fracture
characteristics of interest can be produced.
[0096] The rubber composition of the present invention, when silica
is employed as a reinforcing filler, a silane coupling agent may be
incorporated into the composition in order to further enhance
reinforcing performance and heat-buildup-suppressing
performance.
[0097] Examples of the silane coupling agent includes
bis(3-triethoxysilylpropyl)tetrasulfide,
bis(3-triethoxysilylpropyl)trisulfide,
bis(3-triethoxysilylpropyl)disulfide,
bis(2-triethoxysilylethyl)tetrasulfide,
bis(3-trimethoxysilylpropyl)tetrasulfide,
bis(2-trimethoxysilylethyl)tetrasulfide,
3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane,
2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane,
3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide,
3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide,
2-triethoxysilylethyl-N,N-dimethylthiocarbamonyl tetrasulfide,
3-trimethoxysilylpropylbenzothiazolyl tetrasulfide,
3-triethoxysilylpropylbenzolyl tetrasulfide, 3-triethoxysilylpropyl
methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate
monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide,
3-mercaptopropyldimethoxymethylsilane,
dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide,
and dimethoxymethylsilylpropylbenzothiazolyl tetrasulfide. Among
them, bis(3-triethoxysilylpropyl)polysulfide and
3-trimethoxysilylpropylbenzothiazyl tetrasulfide are preferred from
the viewpoint of an effect for improving the reinforcing
property.
[0098] These silane coupling agents may be used singly or in
combination of two or more species.
[0099] The rubber composition of the present invention employs, as
a rubber component, a modified polymer in which a functional group
having a high affinity to silica is introduced into an active site
of the molecule thereof. Therefore, the amount of the silane
coupling agent can be reduced as compared to the general cases. The
amount of the silane coupling agent, which varies depending on the
type of the agent, is preferably 1 to 20 mass % based on the
silica. When the amount is less than 1 mass %, the effect of the
coupling agent cannot sufficiently be attained, whereas when the
amount is in excess of 20 mass %, the rubber component may be
gelated. From the viewpoint of fully attaining the effect of
coupling agent and prevention of gelation, the amount of the silane
coupling agent is preferably 5 to 15 mass %.
[0100] So long as the object of the present invention is not
impeded, the rubber composition of the present invention may
further contain, in accordance with needs, a variety of chemicals
usually used in the rubber industry. Examples of the chemicals
include vulcanizing agents, vulcanization-accelerating agents,
process oils, anti-aging agents, antioxidants, scorch preventives,
zinc oxide, and stearic acid.
[0101] The rubber composition of the present invention is produced
through kneading by means of an open kneader such as a roller or a
closed kneader such as a Banbury mixer. The kneaded rubber
composition is molded and, subsequently, vulcanized, to thereby
provide a wide range of rubber product. Examples of such rubber
products include tire-related uses such as tire treads, under
treads, carcass sidewalls, and bead portion; vibration-insulating
rubber; fenders; belts; hoses; and other industrial products.
Particularly, the rubber composition of the invention, exhibiting
well-balanced heat-buildup-suppressing performance, wear
resistance, and fracture strength, is suitably employed as
fuel-saving tires, large-scale tires, and treads for
high-performance tires.
EXAMPLES
[0102] Next, the present invention will be described more
specifically with reference to examples in the following. However
the present invention is not limited to the examples.
[0103] In the Examples, physical properties of the samples were
determined by the following procedures.
(1) Vinyl Content of Conjugated Diolefin Portion (% Based on the
Entirety of the Diolefin Portion)
[0104] Vinyl content was determined by 270 MHz .sup.1H-NMR.
(2) Bonded Styrene Content (Mass % in Polymer)
[0105] Bonded styrene content was determined by 270 MHz
.sup.1H-NMR.
(3) Weight Average Molecular Weight
[0106] Weight average molecular weight was determined, by gel
permeation chromatography (GPC) (by means of a chromatograph,
HLC-8220GPC, product of Tosoh Corporation). The result was
expresses as the value of corresponding polystyrene as the
reference.
(4) Mooney Viscosity (ML.sub.1+4, 100.degree. C.)
[0107] Mooney viscosity was determined in accordance with JIS K6300
(use of an L rotor, preheating for one minute, rotor operation for
four minutes, and temperature of 100.degree. C.).
(5) Evaluation of Physical Properties of Vulcanized Rubber
[0108] Physical properties of vulcanized rubber samples were
determined by the following methods (i) and (ii). [0109] (i)
tan.delta. (50.degree. C.): By means of a dynamic spectrometer
(product of Rheometrix Co., Ltd.), tan.delta. (50.degree. C.) was
determined under a tensile strain of 1%, a frequency of 10 Hz, and
50.degree. C., and represented by an index. The higher the index,
the smaller the rolling resistance (the better the quality). [0110]
(ii) Wear resistance (Lanborn wear index): By means of a Lanborn
type abrasion tester, the wear resistance at a percent slip of 25%
was measured and represented by an index. The measurement was
performed at room temperature. The higher the index, the better the
wear resistance.
<Synthesis of Modifying Agent>
Synthesis Example 1
Synthesis of
N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane
[0111] Under nitrogen, 3-aminopropylmethyldiethoxysilane (product
of Gelest) (36 g) for forming an aminosilane moiety was added to
dichloromethane (solvent) (400 mL) placed in a glass flask equipped
with an agitator. Subsequently, trimethylsilane chloride (product
of Aldrich) (48 mL) and triethylamine (53 mL) for forming a
protective moiety were added to the solution, followed by stirring
the mixture at room temperature for 17 hours. The reaction mixture
was evaporated by means of an evaporator, to thereby remove solvent
from the mixture. The thus-obtained reaction mixture was distilled
under reduced pressure (5 mm/Hg), to thereby yield 40 g of
N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane as a
130-135.degree. C. fraction.
Synthesis Example 2
Synthesis of
1-trimethylsilyl-2-ethoxymethyl-1-aza-2-sila-cyclopentane
[0112] The procedure of Synthesis Example 1 was repeated, except
that 2-ethoxymethyl-l-aza-2-cyclopentane (28 g) for forming an
aminosilane moiety and trimethylsilane chloride (24 mL) for forming
a protective moiety were employed, to thereby yield
1-trimethylsilyl-2-ethoxymethyl-1-aza-2-sila-cyclopentane.
Synthesis Example 3
Synthesis of
3-(2,2,5,5-tetramethyl(1-aza-2,5-disilacyclopentane)-1-il)-propylmethyldi-
ethoxysilane
[0113] The procedure of Synthesis Example 1 was repeated, except
that 1,2-bis(chloro-dimethylsilyl)-ethane (product of Gelest) (44
mL) for forming a protective moiety was employed, to thereby yield
3-(2,2,5,5-tetramethyl(1-aza-2,5-disilacyclopentane)-1-yl)-propylmethyldi-
ethoxysilane.
Synthesis Example 4
Synthesis of
N,N-bis(trimethylsilyl)aminopropyldimethylethoxysilane
[0114] The procedure of Synthesis Example 1 was repeated, except
that 3-aminopropyldimethylethoxysilane (product of Gelest) (30 g)
for forming an amino moiety was employed, to thereby yield
N,N-bis(trimethylsilyl)aminopropyldimethylethoxysilane.
Synthesis Example 5
Synthesis of
N-methyl(trimethylsilyl)aminopropylmethyldiethoxysilane
[0115] The procedure of Synthesis Example 1 was repeated, except
that N-methyl-3-aminopropylmethyldiethoxysilane (33 g), which had
been synthesized through a procedure disclosed in Organic letters
(2002), 4(13), 2117 to 2119, for forming an aminosilane moiety and
trimethylsilane chloride (24 mL) for forming a protective moiety
were employed, to thereby yield
N-methyl(trimethylsilyl)aminopropylmethyldiethoxysilane.
Synthesis Example 6
Synthesis of N,N-dimethyl-3-aminopropylmethyldiethoxysilane
[0116] The compound was synthesized in accordance with a procedure
disclosed in Japanese Patent Application Laid-Open (kokai) No.
2003-155381.
Synthesis Example 7
Synthesis of N,N-bis(trimethylsilyl)aminopropyltriethoxysilane
[0117] Under nitrogen, 3-aminopropyltriethoxysilane (product of
Gelest) (41 g) for forming an aminosilane moiety was added to
dichloromethane (solvent) (400 mL) placed in a glass flask equipped
with an agitator. Subsequently, trimethylsilane chloride (product
of Aldrich) (48 mL) and triethylamine (53 mL) for forming a
protective moiety were to the solution, followed by stirring the
mixture at room temperature for 17 hours. The reaction mixture was
evaporated by means of an evaporator, to thereby remove solvent
from the mixture. The thus-obtained crude reaction mixture was
distilled under reduced pressure (5 mm/Hg), to thereby yield 40 g
of N,N-bis(trimethylsilyl)aminopropyltriethoxysilane as a
125-130.degree. C. fraction.
Example 1
(Synthesis of Copolymer A)
[0118] To an autoclave reactor (inner volume: 5 L) whose atmosphere
had been purged with nitrogen, cyclohexane (2,750 g),
tetrahydrofuran (41.3 g), styrene (125 g), and 1,3-butadiene (375
g) were placed. The content of the reactor was adjusted to
10.degree. C., and n-butyllithium (215 mg) was added thereto, to
thereby initiate polymerization. The polymerization was carried out
under adiabatic conditions. The temperature of the polymerization
reached 85.degree. C. (maximum).
[0119] When percent conversion in polymerization reached 99%,
butadiene (10 g) was added to the polymerization system, followed
by polymerization for a further 5 minutes. The resultant polymer
solution was removed from the reactor, and a small aliquot of the
solution was sampled and added to a methanol (1 g) in cyclohexane
(30 g). N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane
(1,129 mg), obtained in Synthesis Example 1, was added thereto, and
modification reaction was performed for 15 minutes. Subsequently,
titanium ethylhexyl dioleate (8.11 g) was added to the reaction
mixture, followed by stirring for 15 minutes. Finally, after
completion of reaction, 2,6-di-tert-butyl-p-creasol was added
thereto. The mixture was subjected to steam stripping, to thereby
remove solvent. The thus-formed rubber was dried by means of a hot
roller (maintained at 110.degree. C.), to thereby yield copolymer
A. Table 1 shows the polymerization formula for producing copolymer
A, and Table 2 shows physical properties of the copolymer.
Example 2
(Synthesis of Copolymer B)
[0120] The procedure of Example 1 was repeated, except that
titanium ethylhexyl dioleate was replaced by titanium
di-n-butoxide(bis-2,4-pentanedionate), to thereby yield copolymer
B. Table 1 shows the polymerization formula for producing copolymer
B, and Table 2 shows physical properties of the copolymer.
Example 3
(Synthesis of Copolymer C)
[0121] The procedure of Example 1 was repeated, except that
titanium ethylhexyl dioleate was replaced by titanium
2-ethylhexoxide, to thereby yield copolymer C. Table 1 shows the
polymerization formula for producing copolymer C, and Table 2 shows
physical properties of the copolymer.
Example 4
(Synthesis of Copolymer D)
[0122] The procedure of Example 1 was repeated, except that
N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane was replaced
by 1-trimethylsilyl-2-ethoxymethyl-1-aza-2-silacyclopentane,
obtained in Synthesis Example 2, to thereby yield copolymer D.
Table 1 shows the polymerization formula for producing copolymer D,
and Table 2 shows physical properties of the copolymer.
Example 5
(Synthesis of Copolymer E)
[0123] The procedure of Example 1 was repeated, except that
N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane was replaced
by
3-(2,2,5,5-tetramethyl(1-aza-2,5-disilacyclopentane)-1-yl)-propylmethyldi-
ethoxysilane, obtained in Synthesis Example 3, to thereby yield
copolymer E. Table 1 shows the polymerization formula for producing
copolymer E, and Table 2 shows physical properties of the
copolymer.
Comparative Example 1
(Synthesis of Copolymer F)
[0124] The procedure of Example 1 was repeated, except that no
titanium ethylhexyl dioleate was added, to thereby yield copolymer
F. Table 1 shows the polymerization formula for producing copolymer
F, and Table 2 shows physical properties of the copolymer.
Comparative Example 2
(Synthesis of Copolymer G)
[0125] The procedure of Example 1 was repeated, except that
titanium ethylhexyl dioleate was replaced by tin 2-ethylhexanoate,
to thereby yield copolymer G. Table 1 shows the polymerization
formula for producing copolymer G, and Table 2 shows physical
properties of the copolymer.
Comparative Example 3
(Synthesis of Copolymer H)
[0126] The procedure of Example 1 was repeated, except that
N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane was replaced
by N,N-bis(trimethylsilyl)aminopropyldimethylethoxysilane, obtained
in Synthesis Example 4, to thereby yield copolymer H. Table 1 shows
the polymerization formula for producing copolymer H, and Table 2
shows physical properties of the copolymer. Comparative Example 4
(Synthesis of copolymer I)
[0127] The procedure of Example 1 was repeated, except that
N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane was replaced
by N-methyl(trimethylsilyl)aminopropylmethyldiethoxysilane,
obtained in Synthesis Example 5, to thereby yield copolymer I.
Table 1 shows the polymerization formula for producing copolymer I,
and Table 2 shows physical properties of the copolymer.
Comparative Example 5
(Synthesis of Copolymer J)
[0128] The procedure of Example 1 was repeated, except that
N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane was replaced
by N,N-dimethyl-3-aminopropylmethyldiethoxysilane, obtained in
Synthesis Example 6, to thereby yield copolymer J. Table 1 shows
the polymerization formula for producing copolymer J, and Table 2
shows physical properties of the copolymer.
Comparative Example 6
(Synthesis of Copolymer K)
[0129] The procedure of Example 1 was repeated, except that,
N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane was replaced
by N,N-bis(trimethylsilyl)aminopropyltriethoxysilane, obtained in
Synthesis Example 7, to thereby yield copolymer K. Table 1 shows
the polymerization formula for producing copolymer K, and Table 2
shows physical properties of the copolymer.
TABLE-US-00001 TABLE 1 Comp. Comp. Comp. Comp. Comp. Comp. Ex. 1
Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6
Modified conjugated diene A B C D E F G H I J K based polymer
Polymerization formula Solvent: cyclohexane (g) 2750 2750 2750 2750
2750 2750 2750 2750 2750 2750 2750 Vinyl content regulator
:tetrahydrofuran (g) 41.3 41.3 41.3 41.3 41.3 41.3 41.3 41.3 41.3
41.3 41.3 Monomers :styrene (g) 125 125 125 125 125 125 125 125 125
125 125 :butadiene (g) 375 375 375 375 375 375 375 375 375 375 375
Polymerization initiator :n-Butyllithium (mg) 215 215 215 215 215
215 215 215 215 215 215 Modifying agent :N--Si-1*.sup.1 (mg) 1129
1129 1129 -- -- 1129 1129 -- -- -- -- :N--Si-2*.sup.2 (mg) -- -- --
699 -- -- -- -- -- -- -- :N--Si-3*.sup.3 (mg) -- -- -- -- 1075 --
-- -- -- -- -- :N--Si-4*.sup.4 (mg) -- -- -- -- -- -- -- 1027 -- --
-- :N--Si-5*.sup.5 (mg) -- -- -- -- -- -- -- -- 902 -- --
:N--Si-6*.sup.6 (mg) -- -- -- -- -- -- -- -- -- 675 --
:N--Si-7*.sup.7 (mg) -- -- -- -- -- -- -- -- -- -- 1231
Condensation-accelerating -- -- -- -- agent :Ti(EHDO).sub.4*.sup.8
(g) 8.11- -- 8.11 8.11 -- -- 8.11 8.11 8.11 8.11
:Ti(nObu).sub.2(acac).sub.2*.sup.9 (g) -- 4.30 -- -- -- -- -- -- --
-- :Ti(OEH).sub.4*.sup.10 (g) -- -- 6.19 -- -- -- -- -- -- --
:Sn(EHA).sub.2*.sup.11 (g) -- -- -- -- 4.09 -- -- -- -- Note:
<Modifying agents> *.sup.1N--Si-1:
N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane
*.sup.2N--Si-2:
1-trimethylsilyl-2-methylethoxy-1-aza-2-cyclopentane
*.sup.33-(2,2,5,5-tetramethyl(1-aza-2,5-disilacyclopentane)-1-yl)-propylme-
thyldiethoxysilane *.sup.4N--Si-3:
N,N-bis(trimethylsilyl)aminopropyldimethylethoxysilane
*.sup.5N--Si-4:
N-methyl(trimethylsilyl)aminopropylmethyldiethoxysilane
*.sup.6N--Si-5: N,N-dimethyl-3-aminopropylmethyldiethoxysilane
*.sup.7N--Si-6: N,N-bis(trimethylsilyl)aminopropyltriethoxysilane
*.sup.8Ti(EHDO).sub.4: titanium ethylhexyl dioleate
*.sup.9Ti(nOBu).sub.2(acac).sub.2: titanium di-n-butoxide
(bis-2,4-pentanedionate) *.sup.10Ti(0EH).sub.4: titanium
2-ethylhexoxide *.sup.11Sn(EHA).sub.2: tin 2-ethylhexanoate
TABLE-US-00002 TABLE 2 Comp. Comp. Comp. Comp. Comp. Comp. Ex. 1
Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6
Modified conjugated diene A B C D E F G H I J K based copolymer
Molecular characteristics of polymers Bonded styrene content (%) 20
20 21 20 20 20 20 21 21 20 20 Vinyl content (%) 56 56 55 55 55 55
56 56 55 55 55 Mooney viscosity 32 31 41 33 34 25 71 18 30 30
36
Examples 6 to 10 and Comparative Examples 7 to 12
[0130] Each of the modified diene polymers A to K shown in Table 1,
produced in Examples 1 to 5 and Comparative Examples 1 to 6, was
blended with additives shown in Table 3 (formulation I), to thereby
prepare a carbon-black-blended rubber composition through the
below-described procedure. The rubber composition was vulcanized at
160.degree. C. for 15 minutes, and physical properties of the
vulcanized rubber were determined.
[0131] The results are shown in Table 4. In Table 4, each of
heat-buildup-suppressing performance (tan.delta.: 50.degree. C.)
and wear resistance is shown by an index with respect to the
corresponding value of the sample of Comparative Example 7, which
is taken as 100. The greater the value of an index, the more
excellent the corresponding property.
<Formulation I: Carbon-Black-Blend Formulation>
[0132] To a blend (100 parts) containing each modified conjugated
diene based polymer of the present invention shown in Table 2 (80
parts) and polyisoprene rubber (20 parts), carbon black, aromatic
oil, stearic acid, and an anti-aging agent 6C were added at the
corresponding proportions shown in Table 3 (formulation I), to
thereby prepare a master batch. To the master batch, zinc oxide,
vulcanization-accelerators DPG, DM, and NS, and sulfur were added,
to thereby prepare a carbon-black-blended rubber composition.
TABLE-US-00003 TABLE 3 Formulation Formulation Formulation (parts
by mass) I II 1st stage Modified conjugated diene 80 80 based
polymer*.sup.1 Polyisoprene rubber*.sup.2 20 20 Aromatic oil*.sup.3
10 10 Carbon black*.sup.4 50 -- Silica*.sup.5 -- 55 Silane coupling
agent*.sup.6 -- 5.5 Stearic acid 2.0 2.0 Anti-aging agent 6C*.sup.7
1.0 1.0 2nd stage Zinc Oxide 3.0 3.0 Vulcanization DPG*.sup.8 0.5 1
accelerator DM*.sup.9 0.5 1 NS*.sup.10 0.5 1 Sulfur 1.5 1.5 Note:
*.sup.1Modified conjugated diene based polymer: Shown in Table 1
*.sup.2Polyisoprene rubber: IR2200, product of JSR *.sup.3Aromatic
oil: Aromax #3, product of Fuji Kosan Co., Ltd. *.sup.4Carbon
black: DIABLACK N339, product of Mitsubishi Chemical Corporation
*.sup.5Silica: AQ, product of Tosoh Silica *.sup.6Silane coupling
agent: Si69, product of Degussa *.sup.7Anti-aging agent 6C: Nocrac
6C, product of Ouchi Shinko Chemical Industrial Co., Ltd.
*.sup.8Vulcanization accelerator DPG: Nocceler D, product of Ouchi
Shinko Chemical Industrial Co., Ltd. *.sup.9Vulcanization
accelerator DM: Nocceler DM, product of Ouchi Shinko Chemical
Industrial Co., Ltd. *.sup.10Vulcanization accelerator NS: Nocceler
NS-F, product of Ouchi Shinko Chemical Industrial Co., Ltd.
TABLE-US-00004 TABLE 4 Comp. Comp. Comp. Comp. Comp. Comp. Ex. 6
Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12
Modified conjugated diene A B C D E F G H I J K based polymer
Vulcanizate characteristics (carbon black blend) tan.delta.
(50.degree. C.) (index) 131 121 108 129 125 100 97 84 70 48 79 Wear
resistance (index) 128 116 107 127 121 100 96 83 69 46 74
Examples 11 to 15 and Comparative Examples 13 to 18
[0133] Each of the modified diene polymers A to K shown in Table 1,
produced in Examples 1 to 5 and Comparative Examples 1 to 6, was
blended with additives shown in Table 3 (formulation II), to
thereby prepare a silica-blended rubber composition through the
below-described procedure. The rubber composition was vulcanized at
160.degree. C. for 15 minutes, and physical properties of the
vulcanized rubber were determined.
[0134] The results are shown in Table 5. In Table 5, each of
heat-buildup-suppressing performance (tan.delta.: 50.degree. C.)
and wear resistance is shown by an index with respect to the
corresponding value of the sample of Comparative Example 13, which
is taken as 100. The more the value of an index, the more excellent
the corresponding property.
<Formulation II: Silica-Blend Formulation>
[0135] To a blend (100 parts) containing each modified conjugated
diene based polymer of the present invention shown in Table 2 (80
parts) and polyisoprene rubber (20 parts), silica, aromatic oil,
stearic acid, a silane coupling agent, and an anti-aging agent 6C
were added at the corresponding proportions shown in Table 3
(formulation II), to thereby prepare a master batch. To the master
batch, zinc oxide, vulcanization-accelerators DPG, DM, and NS, and
sulfur were added, to thereby prepare a silica-blended rubber
composition.
TABLE-US-00005 TABLE 5 Comp. Comp. Comp. Comp. Comp. Comp. Ex. 11
Ex. 12 Ex. 13 Ex. 14 Ex. 15 Ex. 13 Ex. 14 Ex. 15 Ex. 16 Ex. 17 Ex.
18 Modified conjugated diene A B C D E F G H I J K based polymer
Vulcanizate characteristics (silica blend) tan.delta. (50.degree.
C.) (index) 126 112 119 124 124 100 94 72 98 89 91 Wear resistance
(index) 124 109 117 121 120 100 92 69 97 84 90
[0136] As is clear from Tables 4 and 5, the rubber composition
samples of the present invention (Examples 6 to 10) containing
carbon black serving as a filler and the modified conjugated diene
based polymer produced through a step (a) of modifying a conjugated
diene based polymer with a silicon compound essentially having a
protected primary amino group and a bi-functional silicon atom to
which an alkoxy group is bonded, and a step (b) of performing
condensation reaction in the presence of a titanium compound
serving as a condensation-accelerating agent exhibit excellent
heat-buildup-suppressing performance (low loss property) and wear
resistance, as compared with the rubber composition sample
(Comparative Example 7) produced through the step (a) (not
including the step (b)); the rubber composition sample (Comparative
Example 8) produced through the step (a) and the step (b) but
employing a different condensation accelerator; and the rubber
composition samples (Comparative Examples 9 to 12) produced through
the step (b) and the step (a) but employing a different modifying
agent.
[0137] Particularly, the effect of the invention is remarkable, as
compared with the rubber composition samples of Comparative
Examples 9 to 12 produced from a modifying agent differing from the
modifying agent employed in the invention.
[0138] The compositions shown in Table 5 were prepared from silica
serving as a filler, instead of carbon black. As is clear from
Table 5, use of silica instead of carbon black can also provide
excellent heat-buildup-suppressing performance and wear
resistance.
INDUSTRIAL APPLICABILITY
[0139] The rubber composition of the invention containing a
modified copolymer produced through the method of the present
invention attains excellent interaction between the rubber
component and carbon black and/or silica, whereby dispersibility of
carbon black and/or silica in the composition can be improved, and
tires exhibiting excellent heat-buildup-suppressing performance,
fracture characteristics, wear resistance, etc. can be provided.
Particularly, the rubber composition cab be effectively employed as
tire tread coating for rubber low-fuel-consumption automobiles.
* * * * *