U.S. patent application number 10/560099 was filed with the patent office on 2007-07-12 for hysteresis elastomeric compositions comprising polymers terminated with isocyanato alkoxysilanes.
Invention is credited to Terrence E. Hogan, David F. Lawson, Christine Rademacher.
Application Number | 20070161757 10/560099 |
Document ID | / |
Family ID | 33551660 |
Filed Date | 2007-07-12 |
United States Patent
Application |
20070161757 |
Kind Code |
A1 |
Rademacher; Christine ; et
al. |
July 12, 2007 |
Hysteresis elastomeric compositions comprising polymers terminated
with isocyanato alkoxysilanes
Abstract
A functionalized polymer terminated by using an isocyanato
alkoxysilane terminating agent. A method of preparing a
functionalized polymer comprising the step of contacting a living
polymer with an isocyanato alkoxysilane terminating agent.
Inventors: |
Rademacher; Christine;
(Akron, OH) ; Lawson; David F.; (Uniontown,
OH) ; Hogan; Terrence E.; (Akron, OH) |
Correspondence
Address: |
Bridgestone Americas Holding Inc;Chief Intellectual Property Counsel
1200 Firestone Parkway
Akron
OH
44317-0001
US
|
Family ID: |
33551660 |
Appl. No.: |
10/560099 |
Filed: |
June 9, 2004 |
PCT Filed: |
June 9, 2004 |
PCT NO: |
PCT/US04/18285 |
371 Date: |
January 29, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60477012 |
Jun 9, 2003 |
|
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|
Current U.S.
Class: |
525/333.6 ;
525/331.9; 525/333.3; 525/342; 525/374 |
Current CPC
Class: |
C08C 19/44 20130101;
C08F 212/08 20130101; C08K 3/04 20130101; C08F 8/42 20130101; C08F
212/14 20130101; C08K 3/36 20130101; C08K 3/013 20180101; C08L
19/006 20130101; C08F 236/10 20130101; C08K 3/04 20130101; C08L
19/006 20130101; C08K 3/36 20130101; C08L 19/006 20130101; C08L
19/006 20130101; C08L 2666/08 20130101; C08F 212/08 20130101; C08F
4/48 20130101; C08F 236/10 20130101; C08F 4/48 20130101 |
Class at
Publication: |
525/333.6 ;
525/331.9; 525/333.3; 525/342; 525/374 |
International
Class: |
C08F 8/30 20060101
C08F008/30; C08F 12/00 20060101 C08F012/00; C08F 36/00 20060101
C08F036/00 |
Claims
1. A method for preparing a functionalized polymer, the method
comprising: contacting an anionically-polymerized living polymer
with an isocyanato alkoxysilane or isothiocyanato alkoxysilane.
2. The method of claim 1, where the anionically-polymerized polymer
is a prepared from at least one monomer comprising 1,3-butadiene,
isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene,
1,3-hexadiene, myrcene, styrene, .A-inverted.-methyl styrene,
p-methylstyrene, and vinylnaphthalene.
3. The method of claim 1, where the anionically-polymerized polymer
is a copolymer of styrene and 1,3-butadiene.
4. The method of claim 1, vulcanizate of claim 2, where the
anionically-polymerized polymer is formed by using an initiator
comprising at least one element from Group 1 or Group 2 of the
Periodic Table.
5. The method of claim 1, where the anionically-polymerized polymer
is contacted with from about 0.3 to about 1 equivalent of
terminating agent per equivalent of initiator.
6. The method of claim 4, where the initiator includes a
lithium-containing initiator.
7. The method of claim 3, where the anionically-polymerized polymer
is formed by using a lithium-containing initiator in the presence
of a polar coordinator.
8. The method of claim 7, where the anionically-polymerized polymer
includes from about 10 to about 50 percent mer units deriving from
styrene, and where from about 8 to about 99 percent of the mer
units deriving from 1,3-butadiene are in the 1,2-vinyl
microstructure.
9. The method of claim 8, where the anionically-polymerized polymer
includes from about 18 to about 40 percent mer units deriving from
styrene, and where from about 10 to about 60 percent of the mer
units deriving from 1,3-butadiene are in the 1,2-vinyl
microstructure.
10. The method of claim 9, where the remaining mer units deriving
from 1,3-butadiene are in the 1,4-cis microstructure or the
1,4-trans microstructure at a relative ratio of about 3 cis-units
to about 5 trans-units.
11. The method of claim 1, where the isocyanato alkoxysilane
compound or isothiocyanato alkoxysilane compound comprises
gamma-isocyanatopropyl-triethoxysilane,
gamma-isothiocyanatopropyl-triethoxysilane, gamma-isocyanatopropyl
-trimethoxysilane, and
gamma-isothiocyanatopropyl-trimethoxysilane.
12. The method of claim 1, where the isocyanato alkoxysilane
comprises gamma-isocyanatopropyl-trimethoxysilane.
13. A functionalized polymer that is defined by the formula
##STR4## where is an anionically-polymerized polymer, A is oxygen
or sulfur, R.sup.1 is a divalent organic group, each R.sup.2 and R3
is a monovalent organic group, and m is an integer from 0 to 2.
14. The functionalized polymer of claim 13, where the
anionically-polymerized polymer is a copolymer of styrene and
1,3-butadiene.
15. The functionalized polymer of claim 13, where the
anionically-polymerized polymer is contacted with from about 0.3 to
about 1 equivalent of terminating agent per equivalent of
initiator.
16. The functionalized polymer of claim 14, where the
anionically-polymerized polymer is formed by using a
lithium-containing initiator in the presence of a polar
coordinator.
17. The functionalized polymer of claim 16, where the
anionically-polymerized polymer includes from about 10 to about 50
percent mer units deriving from styrene, and where from about 8 to
about 99 percent of the mer units deriving from 1,3-butadiene are
in the 1,2-vinyl microstructure.
18. The functionalized polymer of claim 17, where the
anionically-polymerized polymer includes from about 18 to about 40
percent mer units deriving from styrene, and where from about 10 to
about 60 percent of the mer units deriving from 1,3-butadiene are
in the 1,2-vinyl microstructure.
19. The functionalized polymer of claim 18, where the remaining mer
units deriving from 1,3-butadiene are in the 1,4-cis microstructure
or the 1,4-trans microstructure at a relative ratio of about 3
cis-units to about 5 trans-units.
20. A vulcanizate prepared by employing the functionalized polymer
of claim 11, and further comprising carbon black, silica, or a
mixture thereof.
Description
This application gains benefit from U.S. Provisional Patent
Application No. 60/477,012, filed Jun. 9, 2003.
FIELD OF THE INVENTION
[0001] This invention relates to functionalized polymers terminated
with isocyanato alkoxysilane and methods for making the same. The
functionalized polymers are particularly useful in fabricating
tires.
BACKGROUND OF THE INVENTION
[0002] In the art of making tires, it is desirable to employ rubber
vulcanizates that demonstrate reduced hysteresis loss, i.e., less
loss of mechanical energy to heat. Hysteresis loss is often
attributed to polymer free ends within the cross-linked rubber
network, as well as the disassociation of filler agglomerates.
[0003] Functionalized polymers have been employed to reduce
hysteresis loss. The functional group of the functionalized polymer
is believed to interact with a filler particle and thereby reduce
the number of polymer free ends. Also, the interaction between the
functional group and the filler particles reduces filler
agglomeration, which thereby reduces hysteretic losses attributable
to the disassociation of filler agglomerates (i.e., Payne
effect).
[0004] Conjugated diene monomers are often anionically polymerized
by using alkyllithium compounds as initiators. Selection of certain
alkyllithium compounds can provide a polymer product having a
functionality at the head of the polymer chain. A functional group
can also be attached to the tail end of an anionically-polymerized
polymer by terminating a living polymer with a functionalized
compound.
[0005] For example, trialkyltin chlorides, such as tributyl tin
chloride, have been employed to terminate the polymerization of
conjugated dienes, as well as the copolymerization of conjugated
dienes and vinyl aromatic monomers, to produce polymers having a
trialkyltin functionality at the tail end of the polymer. These
polymers have proven to be technologically useful in the
manufacture of tire treads that are characterized by improved
traction, low rolling resistance, and improved wear.
[0006] Because functionalized polymers are advantageous, especially
in the preparation of tire compositions, there exists a need for
additional functionalized polymers. Moreover, because precipitated
silica has been increasingly used as a reinforcing particulate
filler in tires, functionalized elastomers having affinity to
silica filler are needed.
SUMMARY OF THE INVENTION
[0007] In general the present invention provides a method for
preparing a functionalized polymer, the method comprising
contacting an anionically-polymerized living polymer with an
isocyanato alkoxysilane or isothiocyanato alkoxysilane.
[0008] The present invention also includes a vulcanizate prepared
by vulcanizing a rubber formulation comprising at least one
vulcanizable rubber and a filler, where the at least one
vulcanizable rubber is a functionalized polymer that is formed by
contacting an anionically-polymerized living polymer with an
isocyanato alkoxysilane or isothiocyanato alkoxysilane.
[0009] The present invention further includes a functionalized
polymer that is defined by the formula ##STR1## where is an
anionically-polymerized polymer, A is oxygen or sulfur, R.sup.1 is
a divalent organic group, each R.sup.2 and R.sup.3 is a monovalent
organic group, and m is an integer from 0 to 2.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0010] The functionalized polymers of this invention are preferably
prepared by contacting anionically-polymerized living polymers with
isocyanato alkoxysilane compounds. Useful isocyanato alkoxysilane
compounds include those represented by the formula:
A=C.dbd.N--R.sup.1--Si(R.sup.2).sub.m(OR.sup.3).sub.3-m where A is
oxygen or sulfur, R.sup.1 is a divalent organic group, each R.sup.2
and R.sup.3 is independently a monovalent organic group, and m is
an integer from 0 to 2. Each R.sup.2 and R.sup.3 is preferably an
alkyl group having 1 to 4 carbon atoms. Where A is sulfur, the
above formula represents an isothiocyanato alkoxysilane compound.
For purposes of this specification, the term "isocyanato
alkoxysilane" will also refer to isothiocyanato alkoxysilane
compounds. Isocyanato alkoxysilane compounds are described, for
example, in U.S. Pat. No. 4,146,585, which is incorporated herein
by reference.
[0011] The divalent organic group is preferably a hydrocarbylene
group such as, but not limited to, alkylene, cycloalkylene,
substituted alkylene, substituted cycloalkylene, alkenylene,
cycloalkenylene, substituted alkenylene, substituted
cycloalkenylene, arylene, and substituted arylene groups, with each
group preferably containing from 1 carbon atom, or the appropriate
minimum number of carbon atoms to form the group, up to about 20
carbon atoms. These hydrocarbylene groups may contain heteroatoms
such as, but not limited to, nitrogen, oxygen, silicon, sulfur, and
phosphorus atoms.
[0012] The monovalent organic groups are preferably hydrocarbyl
groups such as, but not limited to alkyl, cycloalkyl, substituted
cycloalkyl, alkenyl, cycloalkenyl, substituted cycloalkenyl, aryl,
allyl, substituted aryl, aralkyl, alkaryl, and alkynyl groups, with
each group preferably containing from 1 carbon atom, or the
appropriate minimum number of carbon atoms to form the group, up to
20 carbon atoms. These hydrocarbyl groups may contain heteroatoms
such as, but not limited to, nitrogen, oxygen, silicon, sulfur, and
phosphorus atoms. The preferred monovalent organic groups will not
react with a living polymer.
[0013] Particularly preferred isocyanato alkoxysilane compounds
include gamma-isocyanatopropyl-triethoxysilane,
gamma-isothiocyanatopropyl-triethoxysilane,
gamma-isocyanatopropyl-trimethoxysilane, and
gamma-isothiocyanatopropyl-trimethoxysilane. Commercially available
isocyanato alkoxysilane compounds include, for example,
gamma-isocyanatopropyl-trimethoxysilane, which is available under
the tradename Silquest A-Link 35 (General Electric OSi Corp.).
[0014] Anionically-polymerized living polymers can be formed by
reacting anionic initiators with certain unsaturated monomers to
propagate a polymeric structure. Throughout formation and
propagation of the polymer, the polymeric structure is anionic and
"living." A living polymer, therefore, is a polymeric segment
having a living or reactive end. For example, when a lithium (Li)
containing initiator is employed to initiate the formation of a
polymer, the reaction produces a reactive polymer having a Li atom
at its living end. A new batch of monomer subsequently added to the
reaction can add to the living ends of the existing chains and
increase the degree of polymerization. For further information
respecting anionic polymerizations, one can refer to George Odian,
Principles of Polymerization, ch. 5 (3.sup.rd Ed. 1991), or Panek,
94 J. Am. Chem. Soc., 8768 (1972).
[0015] Monomers that can be employed in preparing an
anionically-polymerized living polymer include any monomer capable
of being polymerized according to anionic polymerization
techniques. These monomers include those that lead to the formation
of elastomeric homopolymers or copolymers. Suitable monomers
include, without limitation, conjugated C.sub.4-C.sub.12 dienes,
C.sub.8-C.sub.8 monovinyl aromatic monomers, and C.sub.6-C.sub.20
trienes. Examples of conjugated diene monomers include, without
limitation, 1,3-butadiene, isoprene, 1,3-pentadiene,
2,3-dimethyl-1,3-butadiene, and 1,3-hexadiene. A non-limiting
example of trienes includes myrcene. Aromatic vinyl monomers
include, without limitation, styrene, .alpha.-methyl styrene,
p-methylstyrene, and vinylnaphthalene. When preparing elastomeric
copolymers, such as those containing conjugated diene monomers and
aromatic vinyl monomers, the conjugated diene monomers and aromatic
vinyl monomers are normally used at a ratio of 95:5 to 50:50, and
preferably 95:5 to 65:35.
[0016] One preferred type of living polymer is a copolymer of
styrene and 1,3-butadiene (SBR). Preferably, the styrene content of
the SBR copolymer is from about 10 to about 50 percent by weight of
the total polymer, and more preferably from about 18 to about 40
percent by weight of the total polymer. From about 8 to about 99
percent of the units derived from the 1,3-butadiene are preferably
of the 1,2-vinyl microstructure, more preferably from about 10 to
about 60 percent of the units derived from the 1,3-butadiene are of
the 1,2-vinyl microstructure. Preferably, the remaining units
derived from the 1,3-butadiene are in the 1,4-cis-or 1,4-trans-
microstructure at a relative ratio of about 3 cis-units to 5
trans-units.
[0017] Any anionic initiator can be employed to initiate the
formation and propagation of the living polymers. Preferably, the
anionic initiator comprises at least one element from Group 1 or
Group 2 of the Periodic Table, according to the new notation of the
IUPAC, as reported in Hawley's Condensed Chemical Dictionary,
(13.sup.thEd. 1997). The elements in Groups 1 and 2 are commonly
referred to as alkali metals and alkaline earth metals,
respectively. More preferably, the anionic initiator comprises
lithium.
[0018] Exemplary initiators include, but are not limited to, alkyl
lithium initiators such as n-butyl lithium, arenyllithium
initiators, arenylsodium initiators, N-lithium dihydrocarbon
amides, aminoalkyllithiums, and alkyl tin lithiums. Other useful
initiators include N-lithiohexamethyleneimide,
N-lithiopyrrolidinide, and N-lithiododecamethyleneimide as well as
organolithium compounds such as the alkyl lithium adducts of
substituted aldimines and substituted kethnines, N-lithio salts of
substituted secondary amines, and organosulfur compounds such as
sulfur-containing heterocycles. Exemplary initiators are also
described in the following U.S. Pat. Nos.: 5,332,810, 5,329,005,
5,578,542, 5,393,721, 5,698,646, 5,491,230, 5,521,309, 5,496,940,
5,574,109, and 5,786,441, which are incorporated herein by
reference. Preferably, the anionic polymerization is conducted in
the absence of lanthanide compounds such as those used in
coordination catalysis.
[0019] The amount of initiator employed in conducting anionic
polymerizations can vary widely based upon the desired polymer
characteristics. In one embodiment, it is preferred to employ from
about 0.1 to about 100, and more preferably from about 0.33 to
about 10 mmol of lithium per 100 g of monomer.
[0020] Anionic polymerizations are typically conducted in a polar
solvent such as tetrahydrofuran (THF) or a nonpolar hydrocarbon
such as the various cyclic and acyclic hexanes, heptanes, octanes,
pentanes, their alkylated derivatives, and mixtures thereof, as
well as benzene.
[0021] In order to promote randomization in copolymerization and to
control vinyl content, a polar coordinator may be added to the
polymerization ingredients. Amounts range between 0 and 90 or more
equivalents per equivalent of lithium. The amount depends on the
amount of vinyl desired, the level of styrene employed and the
temperature of the polymerization, as well as the nature of the
specific polar coordinator (modifier) employed. Suitable
polymerization modifiers include, for example, ethers and
amines.
[0022] Compounds useful as polar coordinators include those having
an oxygen or nitrogen heteroatom and a non-bonded pair of
electrons. Examples include dialkyl ethers of mono and oligo
alkylene glycols; "crown" ethers, tertiary amines such as
tetramethylethylene diamine CIMEDA), linear THF oligomers, and the
like. Specific examples of compounds useful as polar coordinators
include tetrahydrofuran (THF), linear and cyclic oligomeric
oxolanyl alkanes such as 2,2-bis 2'-tetrahydrofuryl) propane,
dipiperidyl ethane, dipiperidyl methane, hexamethylphosphoramide,
N-N'-dimethylpiperazine, diazabicyclooctane, dimethyl ether,
diethyl ether, tributylamine and the like. The linear and cyclic
oligomeric oxolanyl alkane modifiers are described in U.S. Pat. No.
4,429,091, which is incorporated herein by reference.
[0023] Anionically-polymerized living polymers can be prepared by
either batch or continuous methods. A batch polymerization is begun
by charging a blend of monomer(s) and normal alkane solvent to a
suitable reaction vessel, followed by the addition of the polar
coordinator (if employed) and an initiator compound. The reactants
are heated to a temperature of from about 20 to about 200.degree.
C. and the polymerization is allowed to proceed for from about 0.1
to about 24 hours. This reaction produces a reactive polymer having
a lithium atom at its reactive or living end. Preferably, at least
about 30 percent of the polymer molecules contain a living end.
More preferably, at least about 50 percent of the polymer molecules
contain a living end.
[0024] A continuous polymerization is preferably begun by charging
monomer(s), initiator and solvent at the same time to a suitable
reaction vessel. Thereafter, a continuous regime is typically
followed that removes product after a suitable residence time and
replenishes the reactants.
[0025] The isocyanato alkoxysilane terminating compounds react with
the living polymer end. The reaction can be achieved by simply
mixing the isocyanato alkoxysilane compound with the living
polymer. In a preferred embodiment, these terminating compounds are
added once a peak polymerization temperature is observed, which is
indicative of nearly complete monomer conversion. Because live ends
may self terminate, it is especially preferred to add the
terminating agent within about 25 to about 35 minutes of the peak
polymerization temperature.
[0026] The living polymer is typically contacted with terminating
agent in a solvent or diluent. The solvent is preferably one in
which both the polymer and terminating agent are soluble. In one
embodiment, the reaction can occur in the same medium in which the
polymerization occurred.
[0027] The amount of terminating agent is not limited, and can vary
widely depending upon the terminating agent and the amount of
functionalization desired. In one embodiment, it is preferred to
employ from about 0.3 to about 1 equivalent of terminating agent
per equivalent of initiator, more preferably, from about 0.4 to
about 0.9 equivalents of terminating agent, and even more
preferably from about 0.5 to about 0.8 equivalents of terminating
agent per equivalent of initiator. It will be appreciated that
these numbers are based upon the amount of initiator added to the
system, and may or may not reflect the amount of initiator that is
associated with the polymer.
[0028] Preferably, at least about 40 percent of the polymer
molecules are functionalized with the terminating agent. More
preferably, at least about 50 percent of the polymer molecules are
functionalized with the terminating agent of the present
invention.
[0029] It is believed that this reaction results in a terminated
polymer having both an amide and an alkoxysilane functionality, as
set forth in the following reaction mechanism: ##STR2## where Li is
an anionically-polymerized polymer and A, R.sup.1, R.sup.2,
R.sup.3, and m are as described above. Other structures, however,
are also possible as the result of side reactions or coupling
reactions.
[0030] When a functionalized initiator is employed, the result is
believed to be a multi-functionalized polymer such as that
described by the general formula: ##STR3## where init is a
functional residue from a functional initiator and A, R.sup.1,
R.sup.2, R.sup.3, and m are as described above. Preferably, init is
a functionality or functional group that reacts or interacts with
rubber or rubber fillers or otherwise has a desirable impact on
filled rubber compositions or vulcanizates. Those groups or
substituents that react or interact with rubber or rubber fillers
or otherwise have a desirable impact on filler rubber compositions
or vulcanizates are known and may include trialkyl tin
substituents, cyclic amine groups, or sulfur-containing
heterocycles. Exemplary trialkyl tin substituents are disclosed in
U.S. Pat. No. 5,268,439, which is incorporated herein by reference.
Exemplary cyclic amine groups are disclosed in U.S. Pat. Nos.
6,080,853, 5,786,448, 6,025,450, and 6,046,288, which are
incorporated herein by reference. Exemplary sulfur-containing
heterocycles are disclosed in WO 200/020475, which is incorporated
herein by reference.
[0031] After formation of the functionalized polymer, a processing
aid and other optional additives such as oil can be added to the
polymer cement. The functionalized polymer and other optional
ingredients are then isolated from the solvent and preferably
dried. Conventional procedures for desolventization and drying may
be employed. In one embodiment, the functionalized polymer may be
isolated from the solvent by steam desolventization or hot water
coagulation followed by filtration. Residual solvent may be removed
by using conventional drying techniques such as oven drying or drum
drying. Alternatively, the cement may be directly drum dried.
[0032] The functionalized polymers of this invention are
particularly useful in preparing tire components. These tire
components can be prepared by using the functional polymers of this
invention alone or together with other rubbery polymers. Other
rubbery elastomers that may be used include natural and synthetic
elastomers. The synthetic elastomers typically derive from the
polymerization of conjugated diene monomers. These conjugated diene
monomers may be copolymerized with other monomers such as vinyl
aromatic monomers. Other rubbery elastomers may derive from the
polymerization of ethylene together with one or more
.alpha.-olefins and optionally one or more diene monomers.
[0033] Useful rubbery elastomers include natural rubber, synthetic
polyisoprene, polybutadiene, polyisobutylene-co-isoprene, neoprene,
poly(ethylene-co-propylene), poly(styrene-co-butadiene),
poly(styrene-co-isoprene), and
poly(styrene-co-isoprene-co-butadiene),
poly(isoprene-co-butadiene), poly(ethylene-co-propylene-co-diene),
polysulfide rubber, acrylic rubber, urethane rubber, silicone
rubber, epichlorohydrin rubber, and mixtures thereof. These
elastomers can have a myriad of macromolecular structures including
linear, branched and star shaped. Other ingredients that are
typically employed in rubber compounding may also be added.
[0034] The rubber compositions may include fillers such as
inorganic and organic fillers. The organic fillers include carbon
black and starch. The inorganic fillers may include silica,
aluminum hydroxide, magnesium hydroxide, clays (hydrated aluminum
silicates), and mixtures thereof.
[0035] A multitude of rubber curing agents may be employed,
including sulfur or peroxide-based curing systems. Curing agents
are described in 20 Kirk-Othmer, Encyclopedia of Chemical
Technology, 365-468, (3.sup.rd Ed. 1982), particularly
Vulcanization Agents and Auxiliary Materials, 390-402, and A. Y.
Coran, Vulcanization in Encyclopedia of Polymer Science and
Engineering, (2.sup.nd Ed. 1989), which are incorporated herein by
reference. Vulcanizing agents may be used alone or in
combination.
[0036] Other ingredients that may be employed include accelerators,
oils, waxes, scorch inhibiting agents, processing aids, zinc oxide,
tackifying resins, reinforcing resins, fatty acids such as stearic
acid, peptizers, and one or more additional rubbers.
[0037] These stocks are useful for forming tire components such as
treads, subtreads, black sidewalls, body ply skins, bead filler,
and the like. Preferably, the functional polymers are employed in
tread formulations, and these tread formulations will include from
about 10 to about 100% by weight of the functional polymer based on
the total rubber within the formulation. More preferably, the tread
formulation will include from about 35 to about 90% by weight, and
more preferably from about 50 to 80% by weight of the functional
polymer based on the total weight of the rubber within the
formulation. The preparation of vulcanizable compositions and the
construction and curing of the tire is not affected by the practice
of this invention.
[0038] Preferably, the vulcanizable rubber composition is prepared
by forming an initial masterbatch that includes the rubber
component and filler. This initial masterbatch is preferably mixed
at a starting temperature of from about 25.degree. C. to about
125.degree. C. with a discharge temperature of about 135.degree. C.
to about 180.degree. C. To prevent premature vulcanization (also
known as scorch), this initial masterbatch generally excludes any
vulcanizing agents. Once the initial masterbatch is processed, the
vulcanizing agents may be introduced and blended into the initial
masterbatch at low temperatures in a final mix stage, which does
not initiate the vulcanization process. Optionally, additional
mixing stages, sometimes called remills, can be employed between
the masterbatch mix stage and the final mix stage. Rubber
compounding techniques and the additives employed therein are
generally known, as disclosed in the in Stephens, The Compounding
and Vulcanization of Rubber, in Rubber Technology (2.sup.nd Ed.
1973). The mixing conditions and procedures applicable to
silica-filled tire formulations are also well known as described in
U.S. Pat. Nos. 5,227,425, 5,719,207, 5,717,022, as well as European
Patent No. 890,606, all of which are incorporated herein by
reference.
[0039] Where the vulcanizable rubber compositions are employed in
the manufacture of tires, these compositions can be processed into
tire components according to ordinary tire manufacturing techniques
including standard rubber shaping, molding and curing techniques.
Typically, vulcanization is effected by heating the vulcanizable
composition in a mold; e.g., it is heated to about 140 to about
180.degree. C. Cured or crosslinked rubber compositions may be
referred to as vulcanizates, which generally contain
three-dimensional polymeric networks that are thermoset. The other
ingredients, such as processing aides and fillers, are generally
evenly dispersed throughout the vulcanized network. Pneumatic tires
can be made as discussed in U.S. Pat. Nos. 5,866,171, 5,876,527,
5,931,211, and 5,971,046, which are incorporated herein by
reference.
[0040] In order to demonstrate the practice of the present
invention, the following examples have been prepared and tested.
The examples should not, however, be viewed as limiting the scope
of the invention. The claims will serve to define the
invention.
EXAMPLES
Example 1
[0041] To a 18.9 L reactor equipped with turbine agitator blades
was added 4.8 kg hexane, 1.22 kg (33 wt %) styrene in hexane, and
7.39 kg (22.1 wt %) 1,3-butadiene in hexane. To the reactor was
charged 11 mL of 1.68 M butyllithium in hexane and 3.83 mL of 1.6 M
2,2'-di(tetrahydrofuryl)propane in hexane and the batch temperature
was controlled at from 50.degree. C. to about 58.degree. C. After
approximately 45 minutes, the batch was cooled to 32.degree. C. and
a measured amount of live poly(styrene-co-butadiene)cement was then
transferred to a sealed nitrogen purged 800 mL bottle. The bottle
contents were then terminated with isopropanol, coagulated and drum
dried. The Tg of the polymer was -32.degree. C.
Example 2
[0042] A second measured amount of live
poly(styrene-co-butadiene)cement prepared in Example 1 was
transferred to a sealed nitrogen purged bottle, and to this was
added 1 equivalent of isocyanatopropyl trimethoxysilane
(Silquest.RTM. A-Link 35) per equivalent of butyllithium. The
contents of the bottle were agitated at about 50.degree. C. for
about 30 minutes. The bottle contents were then coagulated and drum
dried. The polymers of Examples 1 and 2 were characterized as set
forth in Table I. TABLE-US-00001 TABLE I Example No. 1 2 M.sub.n
(kg/mol) 111 238 M.sub.w/M.sub.n 1.06 1.78
[0043] The rubber of Examples 1 and 2 were employed in carbon black
and carbon black/silica tire formulations. The formulations are
presented in Table II. More specifically, the rubber of Example 1
was incorporated in the formulations of Examples 3 and 5. The
rubber of Example 2 was incorporated in the formulations of
Examples 4 and 6. TABLE-US-00002 TABLE II Example No. (weight
parts) 3 4 5 6 Initial Rubber Sample 100 100 100 100 Carbon Black
55 55 35 35 Silica 0 0 30 30 Wax 1 1 0 0 Antiozonant 0.95 0.95 0.95
0.95 Zinc Oxide 2.5 2.5 0 0 Stearic Acid 1.5 1.5 1.5 1.5 Aromatic
Oil 10 10 10 10 Total 177.45 177.45 177.45 177.45 Intermediate
Initial N/A N/A 177.45 177.45 Silane Shielding Agent N/A N/A 4.57
4.57 Total 177.45 177.45 182.02 182.02 Final Formulation Initial
171.45 171.45 182.02 182.02 Sulfur 1.3 1.3 1.7 1.7 Zinc Oxide 0 0
2.5 2.5 Pre-Vulcanization Inhibitor 0 0 0.25 0.25 Accelerators 1.9
1.9 2.0 2.0 Total 174.65 174.65 188.47 188.47
Examples 3 and 4
[0044] Each carbon black rubber compound was prepared in two
stages, which are named Initial (Masterbatch) and Final. In the
initial stage, the polymer from Example 1 or 2 was mixed with
carbon black, an antioxidant, stearic acid, wax, aromatic oil, and
zinc oxide, in a 65 g Banbury mixer operating at 60 RPM and
133.degree. C. Specifically, the polymer was first placed in the
mixer, and after 0.5 minutes, the remaining ingredients except the
stearic acid were added. The stearic acid was then added after 3
minutes. The initials were mixed for 5-6 minutes. At the end of the
mixing the temperature was approximately 165.degree. C. The sample
was transferred to a mill operating at a temperature of 60.degree.
C., where it was sheeted and subsequently cooled to room
temperature.
[0045] The finals were mixed by adding the initials and the
curative materials to the mixer simultaneously. The initial mixer
temperature was 65.degree. C. and it was operating at 60 RPM. The
final material was removed from the mixer after 2.25 minutes when
the material temperature was between 100 and 105.degree. C.
[0046] Test specimens of each rubber formulation were prepared by
cutting out the required mass from an uncured sheet (about 2.5 mm
to 3.81 mm thick), and cured within closed cavity molds under
pressure for 15 minutes at 171.degree. C. The test specimens were
then subjected to various physical tests, and the results of these
tests are reported in Table III. Modulus at 300% and tensile
strength were measured according to ASTM D 412 (1998) Method B.
Dynamic properties were determined by using a Rheometrics Dynamic
Analyzer (RDA).
[0047] Bound rubber, a measure of the percentage of rubber bound,
through some interaction, to the filler, was determined by solvent
extraction with toluene at room temperature. More specifically, a
test specimen of each uncured rubber formulation was placed in
toluene for three days. The solvent was removed and the residue was
dried and weighed. The percentage of bound rubber was then
determined according to the formula % bound
rubber=(100(W.sub.d-F))/R where W.sub.d is the weight of the dried
residue, F is the weight of the filler and any other solvent
insoluble matter in the original sample, and R is the weight of the
rubber in the original sample.
Examples 5 and 6
[0048] Each carbon black/silica rubber compound was prepared in
three stages named Initial, Intermediate and Final. In the initial
part, the polymer from Examples 1 or 2 was mixed with carbon black,
silica, an antioxidant, stearic acid, and aromatic oil in a 65 g
Banbury mixer operating at 60 RPM and 133.degree. C. Specifically,
the polymer was first placed in the mixer, and after 0.5 minutes,
the remaining ingredients except the stearic acid were added. The
stearic acid was then added after 3 minutes. The initials were
mixed for 5-6 minutes. At the end of the mixing the temperature was
approximately 165.degree. C. The sample was cooled to less that
about 95.degree. C. and transferred to a remill mixer.
[0049] In the intermediate stage, the initial formulation and a
silane shielding agent were simultaneously added to a mixer
operating at about 60 RPM. The shielding agent employed in these
examples was EF(DiSS)-60, available from Rhein Chemie Corp. The
starting temperature of the mixer was about 94.degree. C. The
intermediate material was removed from the mixer after about 3
minutes, when the material temperature was between 135 and
150.degree. C.
[0050] The finals were mixed by adding the intermediate, zinc oxide
and the curative materials to the mixer simultaneously. The initial
mixer temperature was 65.degree. C. and it was operating at 60 RPM.
The final material was removed from the mixer after 2.25 minutes
when the material temperature was between 100 and 105.degree. C.
The test specimens were prepared and subjected to various physical
tests as for Examples 3-4 above. The results of these tests are
reported in Table III. TABLE-US-00003 TABLE III Sample No. 3 4 5 6
ML.sub.1+4@130.degree. C. 24.3 63.7 54.2 85.4 t.sub.50 (min) 3.13
3.11 6.84 5.45 300% Modulus @ 23.degree. C. (MPa) 14.08 15.55 10
12.7 Tensile @ Break @23.degree. C. (MPa) 17.15 20.58 12.3 14.9 tan
.delta. 0.5% E (0.degree. C.) 0.2539 0.2969 0.2266 0.3238 .DELTA.G'
(50.degree. C.) (MPa)** 3.9008 2.1052 6.304 1.892 tan .delta. 0.5%
E (50.degree. C.) 0.2665 0.2221 0.2431 0.1766 Bound Rubber (%) 14.5
44.4 22.8 72.3 **.DELTA.G' = G' (@0.25% E) - G' (@14.5% E)
[0051] In some embodiments, the functionalized polymers of this
invention advantageously provide carbon black, carbon black/silica,
and silica filled-rubber vulcanizates having reduced hysteresis
loss, reduced wear, and improved wet traction. Also, certain
filled-rubber vulcanizates prepared with the functionalized
polymers of this invention exhibit a reduced Payne effect, and good
polymer processability. These functionalized polymers can be
readily prepared by terminating living polymers.
[0052] Various modifications and alterations that do not depart
from the scope and spirit of this invention will become apparent to
those skilled in the art. This invention is not to be duly limited
to the illustrative embodiments set forth herein.
* * * * *