U.S. patent application number 12/666146 was filed with the patent office on 2010-12-23 for one-pot synthesis of nanoparticles and liquid polymer for rubber applications.
Invention is credited to Xiaorong Wang, Sandra Warren.
Application Number | 20100324167 12/666146 |
Document ID | / |
Family ID | 39650519 |
Filed Date | 2010-12-23 |
United States Patent
Application |
20100324167 |
Kind Code |
A1 |
Warren; Sandra ; et
al. |
December 23, 2010 |
ONE-POT SYNTHESIS OF NANOPARTICLES AND LIQUID POLYMER FOR RUBBER
APPLICATIONS
Abstract
A method for performing a one-pot synthesis of a blend of
nanoparticles and liquid polymer includes polymerizing a first
monomer and optionally a second monomer in a hydrocarbon solvent to
form the liquid polymer. The polymerization is terminated before
completion with a quenching agent. Then a charge of polymerization
initiator, and a mixture of cross-linking agent and mono-vinyl
aromatic monomer are added. This causes further polymerization
whereby nanoparticles are formed having a core including the
cross-linking agent, and a shell including the first monomer or the
first monomer and the second monomer. Nanoparticle/liquid polymer
blends resulting from the method and rubber compositions
incorporating the blends are also disclosed.
Inventors: |
Warren; Sandra; (Gradignan,
FR) ; Wang; Xiaorong; (Wilshire Park Drive Hudson,
OH) |
Correspondence
Address: |
BRIDGESTONE AMERICAS, INC.
1200 FIRESTONE PARKWAY
AKRON
OH
44317
US
|
Family ID: |
39650519 |
Appl. No.: |
12/666146 |
Filed: |
June 30, 2008 |
PCT Filed: |
June 30, 2008 |
PCT NO: |
PCT/US2008/068838 |
371 Date: |
January 29, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11771659 |
Jun 29, 2007 |
7829624 |
|
|
12666146 |
|
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Current U.S.
Class: |
523/150 |
Current CPC
Class: |
C08L 51/003 20130101;
C08F 279/02 20130101; C08L 2666/02 20130101; C08L 51/003 20130101;
C08L 2666/04 20130101; C08L 51/003 20130101; C08F 257/02 20130101;
C08F 297/04 20130101 |
Class at
Publication: |
523/150 |
International
Class: |
C08J 5/14 20060101
C08J005/14 |
Claims
1. A method for preparing a one-pot synthesized blend of
nanoparticles and liquid polymer in a solvent, the method
comprising the steps of: (a) in a reaction vessel, polymerizing
either a first monomer to form a liquid polymer, or copolymerizing
the first monomer and a second monomer to form the liquid polymer;
(b) partially terminating the polymerization with a quenching
agent; and (c) adding a polyfunctional comonomer, a mono-vinyl
aromatic monomer, and an optional charge of polymerization
initiator; wherein said nanoparticles have a core including the
mono-vinyl aromatic monomer and a shell comprising the first
monomer or the first and the second monomer.
2. The method of claim 1, wherein the quenching agent partially
terminates the polymerization such that 20 to 95% of the polymers
chains are terminated.
3. The method of claim 1, further comprising the step of filtering
and drum drying the one-pot synthesized blend of nanoparticles and
liquid polymer.
4. The method of claim 1, wherein the second monomer is selected
from the group consisting of styrene, .alpha.-methyl styrene,
1-vinyl naphthalene, 2-vinyl naphthalene, 1-.alpha.-methyl vinyl
naphthalene, 2-.alpha.-methyl vinyl naphthalene, vinyl toluene,
methoxystyrene, t-butoxystyrene, and alkyl, cycloalkyl, aryl,
alkaryl, and aralkyl derivatives thereof in which the total number
of carbon atoms in the derivative is not greater than 18, or any
di- or tri-substituted aromatic hydrocarbons, and mixtures
thereof.
5. The method of claim 1, wherein the first monomer is a conjugated
diene.
6. The method of claim 5, wherein the first monomer is selected
from the group consisting of C.sub.4-C.sub.8 conjugated dienes and
mixtures thereof.
7. The method of claim 1, wherein the nanoparticles are crosslinked
with the polyfunctional comonomer.
8. The method of claim 1, wherein the cross-linking agent is
selected from the group consisting of diisopropenylbenzene,
divinylbenzene, divinyl ether, divinyl sulphone, diallyl phthalate,
triallyl cyanurate, triallyl isocyanurate, 1,2-polybutadiene,
N,N'-m-phenylenedimaleimide, N,N'-(4-methyl-m-phenylene)dimaleimide
and/or triallyl trimellitate. acrylates and methacrylates of
polyhydric, C.sub.2-C.sub.10 alcohols, acrylates and methacrylates
of polyethylene glycol having from 2 to 20 oxyethylene units and
polyesters composed of aliphatic di- and/or polyols, or maleic
acid, fumaric acid and/or itaconic acid.
9. The method of claim 8, wherein the cross-linking agent is
divinylbenzene.
10. The method of claim 1, wherein the first monomer is butadiene
and the second monomer is styrene.
11. The method of claim 1, wherein the core of the nanoparticle has
a Tg of about 60.degree. C. or higher.
12. The method of claim 1, wherein the shell of the nanoparticle
has a Tg lower than about 0.degree. C.
13. The method of claim 1, wherein the shell of the nanoparticle
has a Tg between about 0.degree. C. and about -70.degree. C.
14. The method of claim 1, wherein the core of the nanoparticle has
a Tg of at least about 60.degree. C. higher than the Tg of the
shell.
15. The method of claim 1, wherein the liquid polymer has an Mw of
about 10,000 to about 120,000.
16. The method of claim 1, wherein the nanoparticles are formed by
micelle self-assembly.
17. The method of claim 15, wherein the nanoparticles have a core
comprising styrene cross-linked with divinylbenzene and a shell
comprising butadiene.
18. The method of claim 1, wherein the cross-linking agent is added
before the polymerization initiator and mono-vinyl aromatic
monomer.
19. The method of claim 1, wherein the quenching agent is selected
from the group consisting of methanol, ethanol, propanol, and
isopropanol.
20. The method of claim 1, wherein the quenching agent is a
functionalizing agent.
21. The method of claim 20, wherein the functionalizing agent is
tin tetrachloride.
22. The method of claim 1, wherein the polymerizing or
copolymerizing of step (a) are initiated with an anionic
initiator.
23. The method of claim 1, wherein the steps are performed in the
same reaction vessel.
24. A method for making a rubber composition, the method
comprising: making a blend of nanoparticles and liquid polymer
according of claim 1; and adding the blend to a rubber
composition.
25. A method for making a tire with nanoparticles and liquid
polymer, the method comprising: making a blend of nanoparticles and
liquid polymer according to claim 1; adding the blend to a rubber
composition; molding the rubber composition into a tire tread; and
constructing a tire using the tire tread.
26. A composition of matter consisting essentially of: core-shell
type, micellar nanoparticles; and a liquid polymer having a Mw of
about 10,000 to about 120,000; wherein the nanoparticles are
dispersed and blended within the liquid polymer.
27. The composition of matter of claim 26, wherein the
nanoparticles and liquid polymer are present in a ratio of 25:75 to
40:60.
Description
[0001] This application is the national stage of International
Application No. PCT/U.S. 08/068,838, filed on Jun. 30, 2008, which
claims the benefit of U.S. application Ser. No. 11/771,659, filed
Jun. 29, 2007.
FIELD
[0002] The technology discussed herein relates generally to rubber
compositions. In particular, it relates to methods for synthesizing
nanoparticle and liquid polymer blends in a single polymerization
reaction vessel.
BACKGROUND
[0003] As depicted in the example shown in FIG. 1, the
nanoparticles described herein are each made up of a group or a
collection of several polymer chains that are organized around a
center 1. The polymer chains are linked together at one end at a
core formed from cross-linked monomer units on each polymer chain.
The polymer chains extend from the core 2 outwardly to form a shell
3. The shell 3 includes the monomer units and optionally co-monomer
units of the polymers that are not in the core 2. It should be
understood that the shell 3 is not limited to a single monomer unit
in each polymer chain, but may include several monomer units.
Additionally, the shell 3 may be separated into sublayers, and the
sublayers may include blocks of various homopolymer or copolymer.
For example, a sublayer may include a block of randomized
styrene-butadiene copolymer or a homopolymer such as butadiene. The
outermost layer portion of the shell 4, is comprised of the monomer
units or functionally or non-functionally initiated polymer chain
heads at the outer terminal ends of each polymer. The shell 4 is
the outermost portion of the nanoparticle. The living polymer
chains form micelles due to the aggregation of ionic chain ends and
the chemical interactions of the polymer chains in hydrocarbon
solvent. When the cross-linking agent is added, the polymer chains
forming the micelle(s) become crosslinked and the stable
nanoparticle(s) is formed.
[0004] Nanoparticles and liquid polymers for use in rubber
compositions are described in commonly owned U.S. patent
application Ser. No. 11/305,279, which is hereby incorporated by
reference. The combination of nanoparticle and liquid polymer
improves important properties of rubber articles, such as vehicle
tires, and in particular, the tread portion of vehicle tires. For
example, wet/dry traction and rolling resistance of tire tread can
be improved with the addition of nanoparticles and liquid polymers
while maintaining good reinforcement for tread durability. A
reduction or elimination of the amount of processing oils used in a
composition for vehicle tires is desirable, and this is made
possible by use of combination of nanoparticles and liquid polymer
in such compositions.
[0005] However, there are difficulties in synthesizing and
processing the previously disclosed nanoparticles and liquid
polymers. Previously known methods involve synthesizing
nanoparticles and liquid polymer separately, drying them
separately, and then separately adding each component into a rubber
composition. Processing problems stem from the fact that the liquid
polymer is a highly viscous substance that is very difficult to
remove from solvent and dry. Additionally, the nanoparticles and
liquid polymer are stored separately, thereby consuming valuable
inventory space.
SUMMARY
[0006] The technology disclosed herein provides for the synthesis
of nanoparticles and liquid polymer in the same reaction vessel,
without the removal of either the nanoparticles or liquid polymer
(hereinafter "one-pot synthesis"). The resulting blend is easier to
process and dry than a separately synthesized liquid polymer. The
blend also facilitates dispersion of the nanoparticles in a rubber
composition. An additional benefit is a savings in inventory space
for the nanoparticle/liquid polymer blend, as opposed to the
individual components.
[0007] A method for performing a one-pot synthesis of a blend of
nanoparticles and liquid polymer includes polymerizing a first
monomer and optionally a second monomer in a hydrocarbon solvent to
form the liquid polymer. The polymerization is partially quenched
or terminated with a quenching agent. A quenching agent may also be
referred to as a terminating agent, and the terms are used
interchangeably herein. Then a charge of polymerization initiator,
cross-linking agent and mono-vinyl aromatic monomer are added. This
initiates further polymerization whereby nanoparticles are formed
in situ having a core including the multiple-vinyl aromatic
monomer, and a shell including the first monomer or the first
monomer and the second monomer.
[0008] A composition of matter consists essentially of a blend of
core-shell type nanoparticles and a liquid polymer. The
nanoparticles are dispersed and blended within the liquid
polymer.
[0009] The blends of nanoparticle and liquid polymer made by the
methods disclosed herein may be added to a rubber composition to
produce a nanoparticle/liquid polymer rubber composition. As an
example, a tire that incorporates the nanoparticle/liquid polymer
rubber composition can be formed by a tire tread comprising the
rubber composition, and constructing a tire using the tire
tread.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 shows a diagram of an example nanoparticle.
[0011] FIG. 2 shows a rubber article with improved reinforcement
and controllable hysteresis in an embodiment of the present
invention.
DETAILED DESCRIPTION
[0012] Methods for performing a one-pot synthesis for making a
blend of nanoparticles and liquid polymer are disclosed herein. A
first illustrative method involves polymerization of the liquid
polymer, wherein a first monomer and optionally a second monomer
are polymerized in a hydrocarbon solvent in a reaction vessel. The
polymerization is allowed to proceed, and is then partially
quenched (terminated) with a quenching agent. The amount of
terminated polymer chains can vary according to the application.
The amount of terminated polymer chains may be about 1-99 wt % of
total polymer chains in the reaction vessel, alternatively about
15-85 wt %, or alternatively about 30-75 wt %.
[0013] As part of this example method, in a second step an addition
of polymerization initiator and a mixture of cross-linking agent
and a mono-vinyl aromatic monomer are added to the reaction vessel
containing the liquid polymer. In this step, living polymer chains
remaining from the liquid polymer synthesis step copolymerize with
the mono-vinyl aromatic monomer. The resulting copolymers assemble
into micelle structures in the hydrocarbon solvent. The
cross-linking agent functions to cross-link the micelles resulting
in nanoparticles.
[0014] As used herein, unless otherwise stated, a charge or
addition of material, including monomer, into the reaction vessel
may be simultaneous or stepwise. Stepwise means that either the
addition of one ingredient is completed before the addition of
another ingredient is begun, or the addition of one ingredient is
begun (but not necessarily completed) before the addition of
another ingredient.
[0015] A second illustrative method involves a liquid
polymerization step as described above. However, in this method the
nanoparticle synthesis process differs in that there is a step-wise
addition of mono-vinyl aromatic monomer, followed by the addition
of cross-linking agent and initiator to the pot. The resulting
copolymers self-assemble into core-shell type micelles in the
hydrocarbon solvent, and the cross-linking agent functions to
cross-link the micelles, resulting in the formation of
nanoparticles.
[0016] The nanoparticles that result from the first method and the
second method can have differing physical properties. Under similar
conditions, the first method results in polymer nanoparticles with
a core relatively less densely crosslinked, but crosslinked
throughout the entire core, while the second method results in
polymer nanoparticles with a core densely crosslinked at the center
of the core.
[0017] The cross-linking density can be defined as the number of
crosslinks per monomer (Xd). In an example where the nanoparticle
comprises styrene and divinyl benzene (DVB), the Xd is determined
by the ratio of moles of DVB to moles of DVB and styrene. This
number may range from 0.01 to 1, for example 0.1 to 0.8, such as
0.2 to 0.4. In the example first method described above the
cross-linking density may be 0.2-0.4, for example 0.3, and in the
example second method described above the cross-linking density may
be 0.8-1.0, for example 0.9.
[0018] The one-pot synthesis processes described herein yield a
nanoparticle/liquid polymer blend that is easier to process and dry
compared to the synthesis of those materials separately. The
resulting blends also save inventory space for manufacturers of
products incorporating such blends.
[0019] The first step of the methods described above results in the
polymerization of the liquid polymer. A first monomer, and
optionally a second monomer, are added to a reaction vessel along
with an anionic initiator to start the polymerization of the
monomer(s), resulting in a liquid polymer. The liquid polymer may
comprise a homopolymer, such as polybutadiene, or a copolymer, such
as styrene-butadiene.
[0020] The first monomer may be any monomer capable of being
anionically polymerized. The first monomer may be selected from one
or more of conjugated diene monomers. In one embodiment, the first
monomer is selected from C.sub.4-C.sub.8 conjugated diene monomers.
Specific examples of the conjugated diene monomers include, but are
not limited to 1,3-butadiene, isoprene (2-methyl-1,3-butadiene),
cis- and trans-piperylene (1,3-pentadiene),
2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, cis- and
trans-1,3-hexadiene, cis- and trans-2-methyl-1,3-pentadiene, cis-
and trans-3-methyl-1,3-pentadiene, 4-methyl-1,3-pentadiene,
2,4-dimethyl-1,3-pentadiene, and the like, and the mixture thereof.
In exemplary embodiments, isoprene or 1,3-butadiene or mixtures
thereof are used as the conjugated diene monomer(s).
[0021] The optional second monomer may be a vinyl aromatic monomer,
and may be selected from the group consisting of styrene,
ethylvinylbenzene, .alpha.-methyl-styrene, 1-vinyl naphthalene,
2-vinyl naphthalene, vinyl toluene, methoxystyrene,
t-butoxystyrene, and the like; as well as alkyl, cycloalkyl, aryl,
alkaryl, and aralkyl derivatives thereof, in which the total number
of carbon atoms in the monomer is generally not greater than about
20; and mixtures thereof. In exemplary embodiments, the conjugated
diene monomer and vinyl aromatic monomer are normally used at the
weight ratios of from about 99:1 to about 1:99, or from about 30:70
to about 90:10, or from about 85:15 to about 60:40.
[0022] In one or more embodiments, the anionic initiator employed
is a functional initiator that imparts a functional group at the
head of the polymer chain (i.e., the location from which the
polymer chain is started). In certain embodiments, the functional
group includes one or more heteroatoms (e.g., nitrogen, oxygen,
boron, silicon, sulfur, tin, and phosphorus atoms) or heterocyclic
groups.
[0023] Exemplary anionic initiators include organolithium
compounds. In one or more embodiments, organolithium compounds may
include heteroatoms. In these or other embodiments, organolithium
compounds may include one or more heterocyclic groups.
[0024] Types of organolithium compounds include alkyllithium,
aryllithium compounds, and cycloalkyllithium compounds. Specific
examples of organolithium compounds include ethyllithium,
n-propyllithium, isopropyllithium, n-butyllithium,
sec-butyllithium, t-butyllithium, n-amyllithium, isoamyllithium,
and phenyllithium. Other examples include alkylmagnesium halide
compounds such as butylmagnesium bromide and phenylmagnesium
bromide. Still other anionic initiators include organosodium
compounds such as phenylsodium and 2,4,6-trimethylphenylsodium.
Also contemplated are those anionic initiators that give rise to
di-living polymers, wherein both ends of a polymer chain is living.
Examples of such initiators include dilithio initiators such as
those prepared by reacting 1,3-diisopropenylbenzene with
sec-butyllithium. These and related difunctional initiators are
disclosed in U.S. Pat. No. 3,652,516, which is incorporated herein
by reference. Radical anionic initiators may also be employed,
including those described in U.S. Pat. No. 5,552,483, which is
incorporated herein by reference.
[0025] In particular embodiments, the organolithium compounds
include a cyclic amine-containing compound such as
lithiohexamethyleneimine. These and related useful initiators are
disclosed in the 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. In other
embodiments, the organolithium compounds include alkylthioacetals
such as 2-lithio-2-methyl-1,3-dithiane. These and related useful
initiators are disclosed in U.S. Publ. Nos. 2006/0030657,
2006/0264590, and 2006/0264589, which are incorporated herein by
reference. In still other embodiments, the organolithium compounds
include alkoxysilyl-containing initiators, such as lithiated
t-butyldimethylpropoxysilane. These and related useful initiators
are disclosed in U.S. Publ. No. 2006/0241241, which is incorporated
herein by reference.
[0026] In one or more embodiments, the anionic initiator employed
is trialkyltinlithium compound such as tri-n-butyltinlithium. These
and related useful initiators are disclosed in U.S. Pat. Nos.
3,426,006 and 5,268,439, which are incorporated herein by
reference.
[0027] Optionally, the liquid polymer synthesis step may be
conducted in the presence of a modifier or a 1,2-microstructure
controlling agent, so as to, for example, increase the reaction
rate, equalize the reactivity ratio of monomers, and/or control the
1,2-microstructure in the conjugated diene monomers. Suitable
modifiers include, but are not limited to, triethylamine,
tri-n-butylamine, hexamethylphosphoric acid triamide,
N,N,N',N'-tetramethylethylene diamine, ethylene glycol dimethyl
ether, diethylene glycol dimethyl ether, triethylene glycol
dimethyl ether, tetraethylene glycol dimethyl ether,
tetrahydrofuran, 1,4-diazabicyclo [2.2.2]octane, diethyl ether,
tri-n-butylphosphine, p-dioxane, 1,2 dimethoxy ethane, dimethyl
ether, methyl ethyl ether, ethyl propyl ether, di-n-propyl ether,
di-n-octyl ether, anisole, dibenzyl ether, diphenyl ether,
dimethylethylamine, bix-oxolanyl propane, tri-n-propyl amine,
trimethyl amine, triethyl amine, N,N-dimethyl aniline,
N-ethylpiperidine, N-methyl-N-ethyl aniline, N-methylmorpholine,
tetramethylenediamine, oligomeric oxolanyl propanes (OOPs),
2,2-bis-(4-methyl dioxane), bistetrahydrofuryl propane, and the
like.
[0028] Other modifiers or 1,2-microstructure controlling agents
used in the present invention may be linear oxolanyl oligomers
represented by the structural formula (IV) and cyclic oligomers
represented by the structural formula (V), as shown below:
##STR00001##
[0029] wherein R.sup.14 and R.sup.15 are independently hydrogen or
a C.sub.1-C.sub.8 alkyl group; R.sup.16, R.sup.17, R.sup.18, and
R.sup.19 are independently hydrogen or a C.sub.1-C.sub.6 alkyl
group; y is an integer of 1 to 5 inclusive, and z is an integer of
3 to 5 inclusive.
[0030] Specific examples of modifiers or 1,2-microstructure
controlling agents include, but are not limited to, oligomeric
oxolanyl propanes (OOPs); 2,2-bis-(4-methyl dioxane);
bis(2-oxolanyl)methane; 1,1-bis(2-oxolanyl)ethane;
bistetrahydrofuryl propane; 2,2-bis(2-oxolanyl) propane;
2,2-bis(5-methyl-2-oxolanyl) propane;
2,2-bis-(3,4,5-trimethyl-2-oxolanyl) propane;
2,5-bis(2-oxolanyl-2-propyl) oxolane; octamethyl
perhydrocyclotetrafurfurylene (cyclic tetramer);
2,2-bis(2-oxolanyl) butane; and the like. A mixture of two or more
modifiers or 1,2-microstructure controlling agents also can be
used.
[0031] After the reaction has had time to proceed to form the
liquid polymer, a quenching agent is added in an amount that
results in partial quenching (termination) of the living polymer.
By partial termination, living (un-terminated) polymers remain, and
are subsequently copolymerized to form the shell of the
nanoparticle in the subsequent nanoparticle synthesis step. The
liquid polymer synthesis step is relatively fast, and may for
example, be completed in about 15 minutes. As used herein, partial
termination means less than 100% of the living polymer chains are
terminated.
[0032] Suitable quenching agents include, but are not limited to,
alcohols such as methanol, ethanol, propanol, and isopropanol.
Optionally, a quenching agent may be employed to provide terminal
functionality. Exemplary functionality-providing quenching agents
include, but are not limited to, SnCl.sub.4, R.sub.3SnCl,
R.sub.2SnCl.sub.2, RSnCl.sub.3, carbodiimides, N-methylpyrrolidine,
cyclic amides, cyclic ureas, isocyanates, Schiff bases,
4,4'-bis(diethylamino) benzophenone, N,N'-dimethylethyleneurea, and
mixtures thereof, wherein R is selected from the group consisting
of alkyls having from about 1 to about 20 carbon atoms, cycloalkyls
having from about 3 to about 20 carbon atoms, aryls having from
about 6 to about 20 carbon atoms, aralkyls having from about 7 to
about 20 carbon atoms, and mixtures thereof.
[0033] The liquid polymer can be made by batch, semi-batch or
continuous processes. Typically, a hydrocarbon solvent is used,
although it may be possible to use other solvents or combinations
of solvents provided that the solvent/combination would not
interfere in the formation of the micelles. The hydrocarbon solvent
may be selected from any suitable aliphatic hydrocarbons, alicyclic
hydrocarbons, or mixture thereof, with a proviso that it exists in
liquid state during the polymerizations. Exemplary aliphatic
hydrocarbons include, but are not limited to, pentane, isopentane,
2,2 dimethyl-butane, hexane, heptane, octane, nonane, decane,
mixtures of such hydrocarbons and the like. Exemplary alicyclic
hydrocarbons include, but are not limited to, cyclopentane, methyl
cyclopentane, cyclohexane, methyl cyclohexane, cycloheptane,
cyclooctane, cyclononane, cyclodecane, and the like. In one
embodiment, the liquid hydrocarbon medium comprises hexanes.
[0034] According to the process disclosed herein there are some
advantages to synthesizing the liquid polymer in a batch process.
However, it is also possible to perform the method described herein
by a continuous process in a single reaction vessel. In a
continuous process the monomers and an initiator are continuously
fed into the reaction vessel with solvent.
[0035] The pressure in the reaction vessel should be sufficient to
maintain a substantially liquid phase under the conditions of the
polymerization reaction. The reaction medium may generally be
maintained at a temperature that is within the range of about
20.degree. C. to about 140.degree. C. throughout the
polymerization.
[0036] The liquid polymer may comprise polyisoprene, polybutadiene,
styrene-butadiene copolymer, styrene-isoprene-butadiene copolymer,
styrene-isoprene copolymer, butadiene-isoprene copolymer, liquid
butyl rubber, liquid neoprene, ethylene-propylene copolymer,
ethylene-propylene-diene copolymer, acrylonitrile-butadiene
copolymer, liquid silicone, ethylene acrylic copolymer, ethylene
vinyl acetate copolymer, liquid epichlorohydrin, liquid chlorinated
polyethylene, liquid chlorosulfonated polyethylene rubbers, liquid
hydrogenated nitrile rubber, liquid tetrafluoroethylene-propylene
rubber, liquid hydrogenated polybutadiene and styrene-butadiene
copolymer, and the like, and the mixture thereof.
[0037] In one embodiment, the number average molecular weight (Mn)
of the resulting liquid polymer is within the range of from about
10,000 to about 120,000, within the range of from about 20,000 to
about 110,000, or within the range of from about 25,000 to about
75,000.
[0038] The weight average molecular weight of the liquid polymer
can range from about 20,000 to 100,000, for example 70,000 to
90,000.
[0039] The glass transition temperature (Tg) of the liquid polymer
is, for example, within the range of from about -100.degree. C. to
about -20.degree. C., such as within the range of from about
-95.degree. C. to about -40.degree. C., or from about -90.degree.
C. to about -50.degree. C. The liquid polymer may exhibit only one
glass transition temperature.
[0040] Since the remaining polymers with living ends are later used
to form the shell layer of the nanoparticles, the amount of
quenching agent also determines the ratio of liquid polymer to
nanoparticles in the nanoparticle/liquid polymer blend.
[0041] The formation of the liquid polymer is complete after the
reaction is partially terminated with the quenching agent. In the
illustrative methods described herein a charge is then added that
begins the nanoparticle synthesis step.
[0042] In one embodiment, for the nanoparticle synthesis step an
anionic initiator is first added to the reaction vessel (i.e.
before adding the mono- and coupling agent). In other embodiments,
the initiator can also be added at the same time as the mono-vinyl
aromatic monomer and coupling agent. Anionic initiators may be
those described above.
[0043] After addition of the initiator or concurrently with the
addition of the initiator the mono-vinyl aromatic monomer and
cross-linking agent are added to the same reaction vessel that the
liquid polymer was formed in. The living polymer chains from the
liquid polymer synthesis step copolymerize with the mono-vinyl
aromatic monomer. The copolymer chains then self-assemble in the
hydrocarbon solvent into micelles. The cross-linking agent serves
to cross-link the micelles resulting in nanoparticles.
[0044] Optionally, the nanoparticle synthesis step may be conducted
in the presence of a modifier or a 1,2-microstructure controlling
agent, such as those described above.
[0045] In one embodiment, the copolymers are di-block copolymers
comprising a polyconjugated diene block and a mono-vinyl aromatic
block, such as poly(butadiene-b-styrene). The mono-vinyl aromatic
blocks are typically at least partially crosslinked by the
cross-linking agent. In one embodiment, the polymer nanoparticles
retain their discrete nature with little or no polymerization
between each other. In some embodiments, the nanoparticles are
substantially monomodal and uniform in shape, in others the
nanoparticles have a polymodal size distribution.
[0046] The copolymerization of the nanoparticle chains may last as
long as necessary until the desired monomer conversion, degree of
polymerization (DP), and/or block polymer molecular weight are
obtained. The polymerization reaction of this step may last
typically from about 0.5 hours to about 20 hours, from about 0.5
hours to about 10 hours, or from about 0.5 hours to about 5 hours.
The polymerization reaction of this step may be conducted at a
temperature of from about 30.degree. F. to about 300.degree. F.,
from about 100.degree. F. to about 250.degree. F., or from about
150.degree. F. to about 210.degree. F.
[0047] The polymerization reaction used to prepare the polymer
nanoparticles may be terminated with a quenching agent. Suitable
quenching agents include those described above In exemplified
embodiments, the nanoparticle reaction mixture was cooled and
dropped in an isopropanol/acetone solution containing an
antioxidant such as butylated hydroxytoluene (BHT). The
isopropanol/acetone solution may be prepared, for example, by
mixing 1 part by volume of isopropanol and 4 parts by volume of
acetone.
[0048] In one embodiment, the nanoparticle synthesis is conducted
in the same solvent as was used for the liquid polymer synthesis.
During synthesis of the nanoparticles, the liquid polymer can also
be considered a solvent. Without being bound to theory, it is
believed that during the nanoparticle synthesis the liquid polymer
also intercalates itself between the living polymer chains when
they are in the micelle formation. This may result in the
isolatation of the inside of the micelle from the hydrocarbon
solvent. Consequently, the resulting micelle will be more stable
and the chances of two or more micelles meeting each other and
potentially linking, resulting in the creation of much larger
particles, is decreased. The liquid polymer causes the resulting
nanoparticle to swell, and the resulting mixture is softer and more
easily mixed into rubber compositions.
[0049] Without being bound to theory, it is believed that during
the nanoparticle synthesis the poly(conjugated diene) block is more
soluble or miscible in a selected hydrocarbon solvent, than the
mono-vinyl aromatic block. This facilitates the subsequent
formation of micelles and ultimately nanoparticles, from the block
copolymer chains.
[0050] Depending on their miscibility, polymer chains in a solution
or suspension system can be self-assembled into domains of various
structures. Without being bound to any theory, it is believed that
a micelle-like structure may be formed by aggregating the block
copolymer chains comprising the poly(conjugated diene) block and
the aromatic block. The mono-vinyl aromatic blocks are typically
directed toward the center of the micelle and the poly(conjugated
diene) containing blocks are typically extended away from the
center.
[0051] The nanoparticles are formed from cross-linked micelle
structures having a core made from the mono-vinyl aromatic blocks,
and a shell made from the poly(conjugated diene) containing blocks.
It is believed that the cross-linking agents crosslink the center
core of the micelle to stabilize and hold together the
nanoparticles.
[0052] In one example the liquid polymer of the nanoparticle/liquid
polymer blend is a styrene-butadiene copolymer. The
styrene-butadiene has an Mn of about 80,000 to 120,000 and is
comprised of repeat units that are derived from about 5 weight
percent to about 95 weight percent styrene and correspondingly from
about 5 weight percent to about 95 weight percent 1,3-butadiene,
wherein the repeat units derived from styrene and 1,3-butadiene are
in essentially random order. In this example, in the liquid
polymerization process of the illustrative methods, the first
monomer is styrene and the second monomer is butadiene. Vinyl
percentages of 50-60% are preferred for some applications because
this range results in a compatible liquid polymer/nanoparticle
phases. However, lower vinyl levels are also possible.
[0053] In another example, the liquid polymer comprises a liquid
isoprene-butadiene rubber (IBR) with Mn of about 35,000 to 70,000,
which is comprised of repeat units that are derived from about 5
weight percent to about 95 weight percent isoprene and
correspondingly from about 5 weight percent to about 95 weight
percent 1,3-butadiene, wherein the repeat units derived from
isoprene and 1,3-butadiene are in essentially random order. In this
example, the first monomer is isoprene and the second monomer is
butadiene according to the illustrative methods described
above.
[0054] The polymer nanoparticles synthesized in the one-pot methods
described herein may include a vulcanizable shell and a crosslinked
core. The monomers that comprise the shell may be curable by
vulcanization by sulfur or peroxide. Examples of suitable sulfur
vulcanizing agents include "rubber maker's" soluble sulfur;
elemental sulfur (free sulfur); sulfur donating vulcanizing agents
such as organosilane polysulfides, amine disulfides, polymeric
polysulfides or sulfur olefin adducts; and insoluble polymeric
sulfur. Related prior patents and publications U.S. Pat. No.
6,437,050 (Bridgestone Corp.) and Macromol. Symp. 118, 143-148
(1997) disclose some suitable sulfur vulcanizing agents.
[0055] In a variety of exemplary embodiments, the shell may be made
up of any suitable conjugated diene or mixture thereof.
C.sub.4-C.sub.8 1,3-conjugated diene monomers are the most
preferred. Specific examples of the shell monomers include, but are
not limited to 1,3-butadiene, isoprene (2-methyl-1,3-butadiene),
cis- and trans-piperylene (1,3-pentadiene),
2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, cis- and
trans-1,3-hexadiene, cis- and trans-2-methyl-1,3-pentadiene, cis-
and trans-3-methyl-1,3-pentadiene, 4-methyl-1,3-pentadiene,
2,4-dimethyl-1,3-pentadiene, and the like, and the mixture thereof.
In certain embodiments, isoprene or 1,3-butadiene or mixture
thereof is used as the shell monomer.
[0056] The crosslinked core of the nanoparticles is typically
formed when mono-vinyl aromatic monomers are cross-linked with a
cross-linking agent. The weight ratio between the mono-vinyl
aromatic monomers and cross-linking agent may broadly range from
about 95:5 to about 0:100, from about 90:10 to about 25:75, or from
about 85:15 to about 60:40.
[0057] Suitable mono-vinyl aromatic monomers include, but are not
limited to those generally containing from 8 to 20, preferably from
8 to 12 carbon atoms, and may be selected, for example, from:
styrene; 1-vinylnaphthalene; 2-vinylnaphthalene; various alkyl,
cycloalkyl, aryl, alkylaryl or arylalkyl derivatives of styrene
such as, for example, .alpha..-methylstyrene, 3-methylstyrene,
4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene,
2-ethyl-4-benzylstyrene, 4-p-tolylstyrene,
4-(4-phenylbutyl)styrene, or mixtures thereof. In certain
embodiments, the mono-vinyl aromatic monomer comprises styrene.
[0058] In certain embodiments, the micelles formed by the
polymerization of mono-vinyl aromatic monomers and conjugated diene
monomers are cross-linked to enhance the uniformity and permanence
of shape and size of the resultant nanoparticle. In such
embodiments, cross-linking agents comprise polyfunctional
comonomers. In certain embodiments, cross-linking agents which are
at least bifunctional, wherein the two functional groups are
capable of reacting with vinyl-substituted aromatic hydrocarbon
monomers are acceptable. Suitable polyfunctional comonomers are
compounds having at least 2, preferably from 2 to 4 copolymerizable
carbon-carbon double bonds, e.g. diisopropenylbenzene,
divinylbenzene, divinyl ether, divinyl sulphone, diallyl phthalate,
triallyl cyanurate, triallyl isocyanurate, 1,2-polybutadiene,
N,N'-m-phenylenedimaleimide, N,N'-(4-methyl-m-phenylene)dimaleimide
and/or triallyl trimellitate.
[0059] Other compounds which can also be used are the acrylates and
methacrylates of polyhydric, preferably di- to tetrahydric
C.sub.2-C.sub.10 alcohols, e.g. ethylene glycol, 1,2-propanediol,
1,4-butanediol, 1,6-hexanediol, neopentyl glycol, glycerol,
trimethylolpropane, pentaerythritol and sorbitol. It is also
possible to use acrylates and methacrylates of polyethylene glycol
having from 2 to 20, preferably 2 to 8, oxyethylene units. Examples
of the acrylate containing cross-linking agents include bisphenol A
ethoxylate diacrylate, (diethylene glycol) diacrylate, glycerol
propoxylate triacrylate, poly(ethylene glycol) diacrylate, and
trimethylol propane ethoxylate triacrylate. It is also possible to
use polyesters composed of aliphatic di- and/or polyols, or else
maleic acid, fumaric acid and/or itaconic acid.
[0060] The polymer nanoparticle synthesized in the one-pot methods
described herein may be substantially spherical. The mean diameter
of the spheres may be broadly within the range of from about 1 nm
to about 200 nm, within the range of from about 5 nm to about 100
nm, within the range of from about 10 nm to about 80 nm, or within
the range of from about 15 nm to about 70 nm.
[0061] The average molecular weight Mn of the poly(conjugated
diene) block of the shell portion may be controlled within the
range of from about 5,000 to about 500,000, or within the range of
from about 5,000 to about 200,000, and most preferably within the
range of from about 10,000 to about 100,000. The average molecular
weight Mn of the uncrosslinked aromatic block may be controlled
within the range of from about 5,000 to about 500,000, within the
range of from about 5,000 to about 200,000, or within the range of
from about 10,000 to about 100,000.
[0062] The number average molecular weight (Mn) of the entire
nanoparticle may be controlled within the range of from about
10,000 to about 200,000,000, within the range of from about 50,000
to about 1,000,000, or within the range of from about 100,000 to
about 500,000. The polydispersity (the ratio of the weight average
molecular weight to the number average molecular weight) of the
polymer nanoparticle may be controlled within the range of from
about 1 to about 1.5, within the range of from about 1 to about
1.3, or within the range of from about 1 to about 1.2.
[0063] The Mn may be determined by using Gel Permeation
Chromatography (GPC) calibrated with polystyrene standards and
adjusted for the Mark-Houwink constants for the polymer in
question. The Mn values used in the examples below were measured by
GPC methods calibrated with linear polymers.
[0064] In one example, the core of the synthesized nanoparticles is
relatively hard. That is, the core has a Tg of about 60.degree. C.
or higher. In another example, the nanoparticles have a core that
is relatively harder than the shell, for example, at least about
60.degree. C. higher than the Tg of the shell layer. In one
example, the shell layer is soft. That is, the shell layer has a Tg
lower than about 0.degree. C. In one embodiment, the Tg of the
shell layer is between about 0.degree. C. and about -100.degree. C.
Nanoparticles with hard cores and soft shells are particularly
useful for reinforcing rubber compounds used for tire treads.
[0065] As known by those of skill in the art, the Tg of the
polymers can be controlled by the selection of monomers and their
molecular weight, styrene content, and vinyl content.
[0066] An illustrative composition comprising a liquid
polymer/nanoparticle blend also includes (a) a rubber matrix, (b)
an optional oil, and (c) one or more components selected from the
group consisting of carbon black, silica, vulcanizing agent,
vulcanization accelerator, tackifier resin, antioxidant, fatty
acids, zinc oxide, wax, peptizer, vulcanization retarder,
activator, processing additive, plasticizer, pigments, and
antiozonant. Various rubber products such as tires and power belts
may be manufactured based on this composition.
[0067] The nanoparticle/liquid polymer blend may be compounded with
rubber by methods generally known in the rubber compounding art,
such as mixing the rubbery matrix polymer and the
nanoparticle/liquid polymer blend with conventional amounts of
various commonly used additive materials, using standard rubber
mixing equipment and procedures.
[0068] A vulcanized rubber product may be produced from the
composition of the present invention by thermomechanically mixing
the nanoparticle/liquid polymer blend, a rubbery matrix polymer,
and conventional amounts of various commonly used additive
materials in a sequentially step-wise manner in a rubber mixer,
followed by shaping and curing the composition. Rubber articles
such as tires may be manufactured from the composition made with
the nanoparticle/liquid polymer blend described supra. Reference
for this purpose may be made to, for example, U.S. Publication No.
2004/0143064 A1, which is hereby incorporated by reference.
[0069] Polymers that may comprise the rubber matrix 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.
[0070] Useful 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.
[0071] Oil has been conventionally used as a compounding aid in
rubber compositions. Examples of oil include, but are not limited
to, aromatic, naphthenic, and/or paraffinic processing oils. In
some examples, it may be preferable to use low-polycyclic-aromatic
(PCA) oils, particularly oils that have a PCA content of less than
3%. In certain embodiments, the liquid polymer portion of the blend
described above is used along with the oil, is used to replace a
portion of the oil, or is used to replace the entirety of the oil
in a rubber compound. As such, a typical amount of oil may broadly
range from about 0 phr to about 100 phr, from about 0 phr to about
70 phr, or from about greater than 0 phr to about 50 phr, based on
100 phr rubbery matrix in the rubber composition.
[0072] As a skilled artisan can appreciate, reinforcement of a
rubber product may be reflected by a low strain dynamic modulus G',
as can be measured according to ASTM-D 412 at 22.degree. C. In
certain embodiments, reinforcement of rubber products such as tires
made from the composition of the present invention may be achieved
by (i) incorporation of the nanoparticle/liquid polymer blend; (ii)
partially replacing the oil with the nanoparticle/liquid polymer
blend; or (iii) entirely replacing the oil with the
nanoparticle/liquid polymer blend.
[0073] The nanoparticle/liquid polymer blend provides various
rubber products with improved reinforcement and controllable
hysteresis. By controllable hysteresis, it is meant that the
hysteresis is increased or decreased, or remains roughly unchanged,
comparing to the situation where oil is present in the composition,
but no nanoparticle/liquid polymer blend is included in the
composition. For example, G'(MPa) may be increased by at least
about 0.3, alternatively at least about 1.5, or at least 3.0.
[0074] The energy loss of an elastomer is termed hysteresis, which
refers to the difference between the energy applied to deform an
article made from the elastomer and the energy released as the
elastomer returns to its initial and undeformed state. Hysteresis
is characterized by a loss tangent, tangent delta (tan .delta.),
which is a ratio of the loss modulus to the storage modulus (i.e.,
the viscous modulus to the elastic modulus) as measured under an
imposed sinusoidal deformation. The tan .delta. value can be
measured, for example, with a TA Instrument ARES Rheometer.
[0075] Rubber products with improved reinforcement and suitable
hysteresis may comprise with the nanoparticle/liquid polymer blend,
in which the phr ratio between the component (a) liquid polymer and
component (b) polymer nanoparticles is within the range of from
about 1:99 to about 99:1, in another embodiment within the range of
from about 20:80 to about 80:20, and in another embodiment within
the range of from about 25:75 to about 40:60.
[0076] The illustrative rubber compositions described herein can be
used for various purposes. For example, they can be used for
various rubber compounds, such as a tire treadstock, sidewall stock
or other tire component stock compounds. Such tires can be built,
shaped, molded and cured by various methods that are known and will
be readily apparent to those having skill in the art. In an
embodiment, a molded unvulcanized tire is charged into a
vulcanizing mold and then vulcanized to produce a tire, based on
the composition and the procedure as described above.
[0077] The following examples are included to provide additional
guidance to those skilled in the art in practicing the claimed
invention. The examples provided are merely representative of the
work that contributes to the teaching of the present application.
Accordingly, these examples are not intended to limit the
invention, as defined in the appended claims, in any manner.
EXAMPLES
Preparation of Nanoparticle/Liquid Polymer Blend
[0078] A two-gallon jacketed reactor was used as the reaction
vessel. The following ingredients were used: 19.3% butadiene in
hexane, 33% styrene in hexane, hexane, n-butyl lithium (1.6 M),
oligomeric oxalanyl propane (1.6 M) (OOPs), isopropanol, butylated
hydroxytoluene (BHT), and 80% divinylbenzene (DVB) purchased from
Aldrich.
[0079] The reactor was sequentially charged with 4.96 lbs of
hexane, 0.59 lbs of 33% styrene, and 3.58 lbs of 19.3% butadiene.
This reactor was heated to 120.degree. F. over about 15 minutes.
When the reactor reached 117.degree. F., 2.3 mL of n-butyl lithium
(1.6 M) and 0.76 mL of OOPs (1.6 M), diluted with about 20 mL of
hexane were added. The polymerization exothermed at 126.7.degree.
F. after three minutes. After one hour, the jacket of the reactor
was set to 100.degree. F. and 0.14 mL of isopropanol was added.
After dropping a sample for analysis, additional n-butyl lithium
(2.3 mL) was added to the reactor. A mixture of 140.2 g styrene
blend and 28.5 mL of DVB was prepared and added to the reactor. The
jacket temperature of the reactor was increased to 180.degree. F.
After three hours, the reactor temperature was brought down to
90.degree. F. and the mixture was dropped in isopropanol containing
BHT. The resulting solid was then filtered through cheesecloth and
drum dried.
[0080] The liquid polymer portion was determined to have an Mn of
73,000 to 80,000. The nanoparticle portion was determined to have a
Mn of 83,700. The synthesized blend contained 55 wt % liquid
polymer and 45 wt % nanoparticles.
[0081] The nanoparticle/liquid polymer blend was much easier to
isolate from solvent and dry than previously known methods of
separately synthesizing the liquid polymer. However, with a
sufficient amount of nanoparticles in the liquid polymer blend, a
substantially solid blend results after coagulation, which can be
drum-dried very easily.
Preparation and Analysis of Example Rubber Compounds
[0082] Six rubber compositions were prepared according to the
formulation shown in Tables 1 and 2. The first example was a
control that contained no nanoparticles or liquid polymer to serve
as a comparison with the test compounds. The second example was
made using synthesized nanoparticles to replace 10 phr of
styrene-butadiene rubber (SBR) in the compound formulation. The
third example was made using nanoparticles and liquid polymer to
replace 10 phr of SBR and about 15 phr of aromatic oil. Because the
synthesized MNP/LP blend contained 55 wt % of the liquid polymer
and 45 wt % of the nanoparticles, 22.2 phr of the MNP/LP blend and
2.8 phr of additional LP were used in the formulation in order to
correctly match the desired composition.
[0083] To illustrate that the additional amount of LP is not a
necessary component of the examples described herein, a fourth
prophetic example is also presented. In the prophetic example 4, 25
phr of 40:60 MNP/LP blend is used. This prophetic example replaces
the 10 phr of SBR with 10 phr of blended MNP and replaces the 15
phr of LP with 15 phr of blended LP without using additional LP by
itself.
[0084] Three comparative examples were also prepared. Each of these
examples use polybutadiene as the matrix rubber and use
nanoparticles that were synthesized in a separate pot from the
liquid polymer. Comp. Example 1 contained 15 phr of aromatic oil,
but did not contain any nanoparticles or liquid polymer. Comp.
Example 1 was used as a control (Control 2) and the results of the
other comparative examples were normalized in relation to Comp.
Example 1. Comp. Example 2 differs from Comp. Example 1 in that it
replaces 15 phr of the polybutadiene with 15 phr of nanoparticles.
Comp. Example 3 differs from Comp. Example 1 in that it replaces 15
phr of polybutadiene and 15 phr of aromatic oil with 15 phr of
nanoparticles and 15 phr of butadiene liquid polymer.
TABLE-US-00001 TABLE 1 Composition of Example Master Batches (in
phr) Comp. Example 1 Prophetic Example 1 Comp. Comp. (Control 1)
Example 2 Example 3 Example 4 (Control 2) Example 2 Example 3
Polybutadiene.sup.1 0 0 0 0 100 85 85 SBR.sup.2 100 90 90 90 0 0 0
Carbon Black 50 50 50 50 50 50 50 (N343) Aromatic Oil 15 15 0 0 15
15 0 Zinc Oxide 3.0 3.0 3.0 3.0 3.0 3.0 3.0 Hydrocarbon Resin 2.0
2.0 2.0 2.0 2.0 2.0 2.0 (tackifiers) Santoflex 13 0.95 0.95 0.95
0.95 0.95 0.95 0.95 (antioxidants) Stearic Acid 2.0 2.0 2.0 2.0 2.0
2.0 2.0 Wax 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Nanoparticles 0 10 0 0 0 15
15 (100 wt % MNP).sup.3 Liquid 0 0 22.2 0 0 0 0
Polymer/Nanoparticle.sup.4 Liquid 0 0 0 25 0 0 0
Polymer/Nanoparticle.sup.5 Liquid Polymer.sup.6 0 0 2.8 0 0 0 15
.sup.1Trade Name HX301 from Firestone Polymers (Mw of 150,000, 12%
vinyl, 40 Mooney viscosity) .sup.2Trade Name HX263 from Firestone
Polymers (Mw of 261 kg/mol, Mw/Mn of 2.30, 23.8% styrene by weight,
35% cis 1,4, 52% trans 1,4, and 13% 1,2 vinyl) .sup.3Nanoparticles
prepared as described in U.S. 2007/0142550 A1, which is hereby
incorporated by reference. .sup.445% nanoparticles and 55% liquid
polymer .sup.540% nanoparticles and 60% liquid polymer
.sup.6Polybutadiene with Mn of 80,000, prepared as described in
U.S. 2007/0142550 A1
TABLE-US-00002 TABLE 2 Additional Additives to Final Batch
Composition (in phr) Comp. Example 1 Prophetic Example 1 Comp.
Comp. (Control 1) Example 2 Example 3 Example 4 (Control 2) Example
2 Example 3 Sulfur ~1.3 ~1.3 ~1.3 ~1.3 ~1.3 ~1.3 ~1.3 Cyclohexyl-
1.4 1.4 1.4 1.4 1.4 1.4 1.4 benzothiazole sulfenamide (accelerator)
Diphenylguanidine 0.20 0.20 0.20 0.20 0.20 0.20 0.20
(accelerator)
[0085] In each example, a blend of the ingredients was kneaded by
the method listed in Table 3. The final stock was sheeted and
molded at 165.degree. C. for 15 minutes.
TABLE-US-00003 TABLE 3 Mixing Conditions Mixer: 300 g Brabender
Agitation Speed: 60 rpm Master Batch Stage Initial 110.degree. C.
Temperature 0 min charging polymers 0.5 min charging oil and Carbon
Black 5.0 min drop sample for analysis Final Batch Stage Initial
75.degree. C. Temperature 0 min charging master stock 0.5 min
charging curing agent and accelerators 1.25 min Drop sample for
analysis
TABLE-US-00004 TABLE 4 Analysis of Examples Comp. Example 1 Example
5 Comp. Comp. (control 1) Example 2 Example 3 (control 2) Example 6
Example 7 Ring Tensile Strength Tensile Break Stress 100 118 129
100 110 115 23.degree. C. Tb (Normalized) Elongation at Break 100
105 94 100 100 90 23.degree. C. (Eb %) (Normalized) 300% Modulus
100 113 145 100 112 134 23.degree. C. (M300) (Normalized) 50%
Modulus 100 114 144 100 115 139 23.degree. C. (M50) (Normalized) Tg
of Compound -45.degree. C. -43.degree. C. -40.degree. C.
(extropolated from tan .delta.) Rolling Resistance tan .delta.
50.degree. C. 100 110 98 100 105 96 (Normalized) G' 50.degree. C.
100 135 156 100 122 129 (Normalized)
[0086] Measurement of the tensile strength and hysteresis loss were
taken of the example vulcanized rubber compositions. The results
are shown in Table 4. Measurement of tensile strength was performed
according ASTM-D 412.
[0087] For examples 1, 2, and 3, the test specimen geometry was in
the form of a ring of a width of 0.05 inches and of a thickness of
0.075 inches. The specimen was tested at a specific gauge length of
1.0 inch. Hysteresis loss was measured with a Dynastat Viscoelastic
Analyzer set at a frequency of 1 Hz and 1% strain. The geometry of
the specimen for this test was a cylinder of a length of 15 mm and
a diameter of 10 mm.
[0088] For examples 5, 6, and 7 the test specimen geometry was
taken in the form of a ring of a width of 0.05 inches and of a
thickness of 0.075 inches. The specimen was tested at a specific
gauge length of 1.0 inches. The hysteresis loss was measured with a
TA Instrument ARES Rheometer. Test specimen geometry was taken in
the form of a cylinder of a length of 15 mm and of a diameter of 9
mm. The following testing conditions were employed: frequency 5 Hz,
1% strain.
[0089] While the invention has been illustrated and described in
typical embodiments, it is not intended to be limited to the
details shown, since various modifications and substitutions can be
made without departing in any way from the spirit of the present
invention. As such, further modifications and equivalents of the
invention herein disclosed may occur to persons skilled in the art
using no more than routine experimentation, and all such
modifications and equivalents are believed to be within the spirit
and scope of the invention as defined by the following claims.
* * * * *