U.S. patent application number 09/794447 was filed with the patent office on 2001-12-27 for rubber composition containing a silica coated with a liquid low molecular weight epoxidized butadiene polymer.
Invention is credited to Agostini, Giorgio, Materne, Thierry Florent Edme, Visel, Friedrich.
Application Number | 20010056151 09/794447 |
Document ID | / |
Family ID | 22693431 |
Filed Date | 2001-12-27 |
United States Patent
Application |
20010056151 |
Kind Code |
A1 |
Visel, Friedrich ; et
al. |
December 27, 2001 |
Rubber composition containing a silica coated with a liquid low
molecular weight epoxidized butadiene polymer
Abstract
There is disclosed a rubber composition particularly suited for
use in tires. The rubber composition is composed of 100 parts by
weight of at least one rubber containing olefinic unsaturation; and
from 1 to 150 parts per 100 parts by weight of rubber, of a silica
having predispersed on the surface of the silica a liquid
epoxidized butadiene polymer having a number average molecular
weight of from 500 to 10,000.
Inventors: |
Visel, Friedrich;
(Bofferdange, LU) ; Materne, Thierry Florent Edme;
(Viville, BE) ; Agostini, Giorgio; (Colmar-Berg,
LU) |
Correspondence
Address: |
The Goodyear Tire & Rubber Company
Patent & Trademark Department - D/823
1144 East Market Street
Akron
OH
44316-0001
US
|
Family ID: |
22693431 |
Appl. No.: |
09/794447 |
Filed: |
February 27, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60188505 |
Mar 10, 2000 |
|
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|
Current U.S.
Class: |
524/493 |
Current CPC
Class: |
C08L 21/00 20130101;
Y10S 152/905 20130101; C08K 9/08 20130101; C08K 9/08 20130101 |
Class at
Publication: |
524/493 |
International
Class: |
C08L 001/00 |
Claims
What is claimed is:
1. A rubber composition comprising: (a) 100 parts by weight of at
least one rubber containing olefinic unsaturation; and (b) from 1
to 150 phr of a silica having predispersed on the surface of the
silica a liquid epoxidized butadiene polymer having a number
average molecular weight of from 500 to 10,000.
2. The rubber composition of claim 1 wherein the apparent density
of the silica, prior to dispersement of the polymer, is less than
300 g/cm.sup.3, as determined by ASTM D-1575.
3. The rubber composition of claim 1 wherein the weight ratio of
polymer to the silica ranges from 0.2:1 to 1:1.
4. The rubber composition of claim 1 wherein the backbone of said
epoxidized butadiene polymer contains at least 50 percent by weight
of polymeric units derived from butadiene and has an epoxide oxygen
content of from 1 percent to 8 percent by weight.
5. The rubber composition of claim 2 wherein the apparent density
ranges from 50 to 200 g/cm.sup.3.
6. The rubber composition of claim 1 wherein from 1 to 150 phr of
additional filler is present.
7. The rubber composition of claim 6 wherein said filler is
selected from the group consisting of silica, carbon black and
mixtures thereof.
8. The rubber composition of claim 1 wherein the silica having the
predispersed polymer is selected from the group consisting of
pyrogenic and precipitated silicas.
9. The sulfur cured rubber composition of claim 8 wherein the
silica has an ultimate particle size in a range of from about 50 to
1,000 angstroms and a BET surface area in the range of from about
40 to 600.
10. The rubber composition of claim 1 wherein a bifunctional sulfur
containing organosilane is present.
11. A pneumatic tire having a rubber containing component made from
a rubber composition comprising (a) 100 parts by weight of at least
one containing olefinic unsaturation; and (b) from 1 to 150 phr of
a silica having predispersed on the surface of the silica, an
epoxidized butadiene polymer having a number average molecular
weight of from 500 to 10,000.
12. The pneumatic tire of claim 11 wherein the apparent density of
the silica prior to dispersement of the polymer, is less than 300
g/cm.sup.3 as determined by ASTM D-1573.
13. The pneumatic tire of claim 12 wherein the apparent density of
the silica ranges from 50 to 200 g/cm.sup.3.
14. The pneumatic tire of claim 11 wherein the backbone of said
epoxidized butadiene polymer contains at least 50 percent by weight
of polymeric units derived from butadiene and has an epoxide oxygen
content of from 1 percent to 8 percent by weight.
15. The pneumatic tire of claim 11 wherein from 1 to 150 phr of
additional filler is present.
16. The pneumatic tire of claim 15 wherein said filler is selected
from the group consisting of silica, carbon black and mixtures
thereof.
17. The pneumatic tire of claim 11 wherein the silica having the
predispersed polymer is selected from the group consisting of
pyrogenic and precipitated silicas.
18. The pneumatic tire of claim 11 wherein the silica has an
ultimate particle size in a range of from about 50 to 1,000
angstroms and a BET surface area in the range of from about 40 to
600.
19. The pneumatic tire of claim 11 wherein a bifunctional sulfur
containing organosilane is present.
20. The pneumatic tire of claim 11 wherein the weight ratio of
polymer to silica ranges from 0.2:1 to 1:1.
Description
BACKGROUND OF THE INVENTION
[0001] A pneumatic tire is a polymeric composite and is a complex
system of interacting components, each with specific properties for
maximum effectiveness. One of the more important components of a
tire is the tread. Since the tread of a tire comes into contact
with the road, it is particularly compounded for abrasion and tear
resistance. For example, abrasion resistance can correlate to tread
wear and tear resistance can correlate to the tread's ability to
resist chunking or tearing of the ground contacting tread elements.
With the ever present need to improve the performance of tires,
there is a continuous need for a rubber composition which improves
both abrasion resistance and tear values. One current approach to
this problem is the use of silica filler in the tread compounds.
Unfortunately, the rubber environment and silica are very
dissimilar and there needs to be improved methods to compatibilize
this interface to yield better properties.
SUMMARY OF THE INVENTION
[0002] The present invention relates to a rubber composition
particularly suited for the tread of a pneumatic tire. The rubber
comprises 100 parts by weight of at least one rubber containing
olefinic unsaturation; and from 1 to 150 phr of a silica having
dispersed thereon a liquid epoxidized butadiene polymer having a
number average molecular weight of from 500 to 10,000.
DETAILED DESCRIPTION OF THE INVENTION
[0003] There is disclosed a rubber composition comprising
[0004] (a) 100 parts by weight of at least one rubber containing
olefinic unsaturation; and
[0005] (b) from 1 to 150 phr of a silica having predispersed on the
surface of the silica, a liquid epoxidized butadiene polymer having
a number average molecular weight of from 500 to 10,000.
[0006] In addition, there is disclosed a pneumatic tire having a
rubber containing component made from a rubber composition
comprising
[0007] (a) 100 parts by weight of at least one rubber containing
olefinic unsaturation; and
[0008] (b) from 1 to 150 phr of a silica having predispersed on the
surface of the silica, a liquid epoxidized butadiene polymer having
a number average molecular weight of from 500 to 10,000.
[0009] The present invention may be used with rubbers or elastomers
containing olefinic unsaturation. The phrase "rubber or elastomer
containing olefinic unsaturation" is intended to include both
natural rubber and its various raw and reclaim forms as well as
various synthetic rubbers. In the description of this invention,
the terms "rubber" and "elastomer" may be used interchangeably,
unless otherwise prescribed. The terms "rubber composition",
"compounded rubber" and "rubber compound" are used interchangeably
to refer to rubber which has been blended or mixed with various
ingredients and materials and such terms are well known to those
having skill in the rubber mixing or rubber compounding art.
Representative synthetic polymers are the homopolymerization
products of butadiene and its homologues and derivatives, for
example, methylbutadiene, dimethylbutadiene and pentadiene as well
as copolymers such as those formed from butadiene or its homologues
or derivatives with other unsaturated monomers. Among the latter
are acetylenes, for example, vinyl acetylene; olefins, for example,
isobutylene, which copolymerizes with isoprene to form butyl
rubber; vinyl compounds, for example, acrylic acid, acrylonitrile
(which polymerize with butadiene to form NBR), methacrylic acid and
styrene, the latter compound polymerizing with butadiene to form
SBR, as well as vinyl esters and various unsaturated aldehydes,
ketones and ethers, e.g., acrolein, methyl isopropenyl ketone and
vinylethyl ether. Specific examples of synthetic rubbers include
neoprene (polychloroprene), polybutadiene (including
cis-1,4-polybutadiene), polyisoprene (including
cis-1,4-polyisoprene), butyl rubber, halobutyl rubber such as
chlorobutyl rubber or bromobutyl rubber, styrene/isoprene/butadiene
rubber, copolymers of 1,3-butadiene or isoprene with monomers such
as styrene, acrylonitrile and methyl methacrylate, as well as
ethylene/propylene terpolymers, also known as
ethylene/propylene/diene monomer (EPDM), and in particular,
ethylene/propylene/dicyclopentadiene terpolymers. Additional
examples of rubbers which may be used include alkoxy-silyl end
functionalized solution polymerized polymers (SBR, PBR, IBR and
SIBR), silicon-coupled and tin-coupled star-branched polymers. The
preferred rubber or elastomers are polybutadiene and SBR.
[0010] In one aspect the rubber is preferably of at least two of
diene based rubbers. For example, a combination of two or more
rubbers is preferred such as cis 1,4-polyisoprene rubber (natural
or synthetic, although natural is preferred), 3,4-polyisoprene
rubber, styrene/isoprene/butadiene rubber, emulsion and solution
polymerization derived styrene/butadiene rubbers, cis
1,4-polybutadiene rubbers and emulsion polymerization prepared
butadiene/acrylonitrile copolymers.
[0011] In one aspect of this invention, an emulsion polymerization
derived styrene/butadiene (E-SBR) might be used having a relatively
conventional styrene content of about 20 to about 28 percent bound
styrene or, for some applications, an E-SBR having a medium to
relatively high bound styrene content, namely, a bound styrene
content of about 30 to about 45 percent.
[0012] The relatively high styrene content of about 30 to about 45
for the E-SBR can be considered beneficial for a purpose of
enhancing traction, or skid resistance, of the tire tread. The
presence of the E-SBR itself is considered beneficial for a purpose
of enhancing processability of the uncured elastomer composition
mixture, especially in comparison to a utilization of a solution
polymerization prepared SBR (S-SBR).
[0013] By emulsion polymerization prepared E-SBR, it is meant that
styrene and 1,3-butadiene are copolymerized as an aqueous emulsion.
Such are well known to those skilled in such art. The bound styrene
content can vary, for example, from about 5 to about 50 percent. In
one aspect, the E-SBR may also contain acrylonitrile to form a
terpolymer rubber, as E-SBAR, in amounts, for example, of about 2
to about 30 weight percent bound acrylonitrile in the
terpolymer.
[0014] Emulsion polymerization prepared
styrene/butadiene/acrylonitrile copolymer rubbers containing about
2 to about 40 weight percent bound acrylonitrile in the copolymer
are also contemplated as diene based rubbers for use in this
invention.
[0015] The solution polymerization prepared SBR (S-SBR) typically
has a bound styrene content in a range of about 5 to about 50,
preferably about 9 to about 36, percent. The S-SBR can be
conveniently prepared, for example, by organo lithium catalyzation
in the presence of an organic hydrocarbon solvent.
[0016] A purpose of using S-SBR is for improved tire rolling
resistance as a result of lower hysteresis when it is used in a
tire tread composition.
[0017] The 3,4-polyisoprene rubber (3,4-PI) is considered
beneficial for a purpose of enhancing the tire's traction when it
is used in a tire tread composition. The 3,4-PI and use thereof is
more fully described in U.S. Pat. No. 5,087,668 which is
incorporated herein by reference. The Tg refers to the glass
transition temperature which can conveniently be determined by a
differential scanning calorimeter at a heating rate of 10.degree.
C. per minute.
[0018] The cis 1,4-polybutadiene rubber (BR) is considered to be
beneficial for a purpose of enhancing the tire tread's wear, or
treadwear. Such BR can be prepared, for example, by organic
solution polymerization of 1,3-butadiene. The BR may be
conveniently characterized, for example, by having at least a 90
percent cis 1,4-content.
[0019] The cis 1,4-polyisoprene and cis 1,4-polyisoprene natural
rubber are well known to those having skill in the rubber art.
[0020] The term "phr" as used herein, and according to conventional
practice, refers to "parts by weight of a respective material per
100 parts by weight of rubber, or elastomer."
[0021] The compositions of the present invention contain a silica
that is coated or has predispersed on its surface a liquid low
molecular weight epoxidized butadiene polymer. The amount of this
silica may vary. Generally speaking, the level ranges from 1 to 150
phr. Preferably, the level of silica coated with the polymer ranges
from 10 to 80 phr.
[0022] In the context of this invention, polybutadienes are
understood above all to be the various structurally isomeric
homopolymers of 1,3-butadiene. However, they are also understood to
include copolymers to the type in which butadiene determines the
chemical character of the compound. Butadiene homopolymers may
exist as two isomers, namely, as 1,4-polybutadiene and as
1,2-polybutadiene. 1,4-polybutadienes are linear, unbranched and
contain in the main chain double bonds in the "cis" or "trans"
configuration, the 1,2-polybutadiene contain side groups having one
vinylic double bond.
[0023] The epoxidation products of all the isomers mentioned above
are suitable for the present invention.
[0024] In one embodiment of the invention, it is possible to use
partially epoxidized cis-1,4-polybutadienes. Thus,
1,4-polybutadienes containing more than 70 percent of their double
bonds in the cis configuration are suitable. Commercially available
products of this type containing 80 percent or even 98 percent of
their double bonds in the cis configuration are particularly
suitable.
[0025] In another embodiment of the invention, it is possible to
use 1,4-polybutadienes containing more than 20 percent, preferably
more than 50 percent, most preferably 60 to 98 percent of their
double bonds in the trans configuration.
[0026] Another embodiment of the invention is characterized by the
use of 1,2-polybutadienes, i.e. materials containing vinylic double
bonds. One particularly suitable starting material of this type
contains from 20 to more than 80 percent, preferably 20 to more
than 90 percent, most preferably from 20 to 98 lateral ethylenic
bonds.
[0027] In the majority of cases, one may use an isomeric mixture of
polybutadienes i.e. 1,4-polybutadienes containing from 20 to 70
percent of their double bonds in the cis configuration and/or from
20 to 50 percent of their double bonds in the trans configuration
which, in addition, may contain from 0 to 3 percent, from 3 to 30
percent or even more side groups containing vinylic double bonds.
Polybutadienes of different configuration may be produced by any of
the methods generally known in polymer chemistry, see for example,
the book by H. G. Elias entitled "Makromolekuele," 4.sup.th
Edition, Huethig und Wepf-Verlag (pub.), Basel/Heidelberg/New York,
Pages 676 (change in configuration from "cis" to "trans") and Pages
744 through 746 and 1012, et seq.
[0028] The liquid epoxidized butadiene polymer used in the
invention include not only from epoxidized homopolymers of
1,3-butadiene, but also from epoxidized copolymers. Suitable
copolymers are those of butadiene with styrene and/or
acrylonitrile. Regardless the copolymer used, the butadiene content
should predominate, i.e. not be less than 50 percent by weight.
Stated in the alternative, the polymeric backbone of the liquid
epoxidized butadiene polymer contains at least 50 percent by weight
of polymeric units derived from butadiene.
[0029] The epoxidation process used to produce the epoxidized
polybutadienes on which the polyolefins are based is not critical.
Any standard epoxidation process may be used, including epoxidation
with peracids, such as peracetic acid.
[0030] The epoxidized butadiene polymers containing from 1 to 8
percent by weight of epoxide oxygen, preferably 2 to 6 percent by
weight, most preferably 3 to 5 percent by weight.
[0031] Accordingly, for every 10 double bonds originally present,
up to 50 percent or even less may be subjected to epoxidation. The
percentages quoted are based on polybutadienes. Where the above
copolymers of butadiene are used, necessarily resulting in fewer
double bonds in the polymer chain, a correspondingly higher
conversion percentage, based on double bonds, is necessary in order
to keep the total epoxide oxygen content between 1 and 8 percent.
The low molecular weight epoxidized butadiene polymers are liquid
at room temperature (22.degree. C.). Accordingly, the epoxidized
butadiene polymers have a number average molecular weight of 500 to
10,000, preferably 500 to 5,000, most preferably 1,000 to
2,000.
[0032] Commercially available liquid low molecular weight
epoxidized butadiene polymers may be used in the present invention.
One example is Polyol Huels 110 which has from 8.6-3.1 percent by
weight of epoxide oxygen, 70 to 77 percent cis-1,4, 29-24 percent
trans-1,4 and 1 percent 1,2 (vinyl) isomer distribution, and a
molecular weight (wgt average) of 1500. Polyol Huels 110 is
available from Huels.
[0033] The above liquid low molecular weight epoxidized butadiene
polymers are dispersed on a siliceous pigment (alternatively
referred to herein as silica filler). The silica filler that can be
used include both pyrogenic and precipitated finely-divided silicas
of the type heretofore employed for rubber compounding. The silica
filler, however, is preferably of the type obtained by
precipitation from a soluble silicate, such as sodium silicate. For
example, silica fillers produced according to the method described
in U.S. Pat. No. 2,940,830 can be used. These precipitated,
hydrated silica pigments have a SiO.sub.2 content of at least 50%
and usually greater than 80% by weight on anhydrous basis. The
silica filler may have an ultimate particle size in the range of
from about 50 to 10,000 angstroms, preferably between 50 and 400
and, more preferably, between 100 and 300 angstroms. The silica may
be expected to have an average ultimate particle size in a range of
about 0.01 to 0.05 microns as determined by electron microscope,
although the silica particles may even be smaller in size. The BET
surface area of the filler as measured using nitrogen gas is
preferably in the range of 40 to 600 square meters per gram,
usually 50 to 300 square meters per gram. The BET method of
measuring surface area is described in the Journal of the American
Chemical Society, Vol. 60, page 304 (1930). The silica also has a
dibutyl (DBP) absorption value in a range of about 200 to about
400, with a range of from about 220 to 300 being preferred.
[0034] The silica (before the polymer is applied) preferably has an
apparent density of below 300 g/cm.sup.3 as measured by ASTM
D-1573. Preferably, the silica has an apparent density ranging from
50 to 200 g/cm.sup.3.
[0035] Powdery forms or slurries of various commercially available
silicas may be considered, for example, silicas commercially
available from PPG Industries under the Hi-Sil trademark such as,
for example, those with designations 210, 243, etc.; silicas
available from Rhone-Poulenc, with designations of Z1165MP and
Z165GR and silicas available from Degussa AG with designations VN2
and VN3, etc. The Rhone-Poulenc Z1165MP silica is a preferred
silica which is reportedly characterized by having a BET surface
area of about 160 to 170 and by a DBP value of about 250 to 290.
Additional commercially available fumed or pyrogenic silicas may be
used, for example Aerosel 200.TM. from Degussa and Cab-O-Sil.TM.
from Cabot.
[0036] The liquid low molecular weight epoxidized butadiene polymer
may be dispersed on the silica at a variety of levels. For example,
the amount of polymer to silica may range in a weight ratio of from
0.2:1 to 1:1. Preferably, the ratio ranges from 0.3:1 to 0.7:1.
[0037] The liquid low molecular weight polymer may be dispersed
onto the silica by a number of means. One mean would be to place
the low molecular weight epoxidized butadiene polymer in an organic
solvent and suspend the silica in solvent solution. Representative
examples of suitable solvents include aliphatic C.sub.6-C.sub.12
hydrocarbons, aromatic or haloaromatic (C.sub.6-C.sub.9)
hydrocarbons, or a C.sub.6-C.sub.9 aliphatic halohydrocarbon.
Examples of suitable solvents include hexane, heptane, cyclohexane,
benzene, toluene, xylene and chlorobenzene. The preferred solvents
are hexane and heptane.
[0038] After the polymer cement and silica have been adequately
mixed, the solvent is removed and treated silica is dried.
[0039] In compounding a silica filled rubber composition, one may
use a coupling agent. Such coupling agents, for example, may be
premixed, or pre-reacted, with the treated silica particles or
added to the rubber mix during the rubber/treated silica
processing, or mixing, stage. If the coupling agent and treated
silica are added separately to the rubber mix during the
rubber/treated silica mixing, or processing stage, it is considered
that the coupling agent then combines in situ with the silica.
[0040] In particular, such coupling agents are generally composed
of a silane which has a constituent component, or moiety, (the
silane portion) capable of reacting with the epoxy groups on the
treated silica surface and, also, a constituent component, or
moiety, capable of reacting with the rubber, particularly a sulfur
vulcanizable rubber which contains carbon-to-carbon double bonds,
or unsaturation. In this manner, then the coupler acts as a
connecting bridge between the treated silica and the rubber and
thereby enhances the rubber reinforcement aspect of the silica.
[0041] The rubber-reactive group component of the coupler may be,
for example, one or more of groups such as mercapto, amino, vinyl,
epoxy, and sulfur groups, preferably a sulfur or mercapto moiety
and more preferably sulfur.
[0042] Representative examples of suitable coupling agents are
sulfur containing organosilicon compounds. Specific examples of
suitable sulfur containing organosilicon compounds are of the
formula:
Z-Alk-S.sub.n-Alk-Z I
[0043] in which Z is selected from the group consisting of 1
[0044] where R.sup.1 is an alkyl group of 1 to 4 carbon atoms,
cyclohexyl or phenyl; R.sup.2 is alkoxy of 1 to 8 carbon atoms, or
cycloalkoxy of 5 to 8 carbon atoms; Alk is a divalent hydrocarbon
of 1 to 18 carbon atoms and n is an integer of 2 to 8.
[0045] Specific examples of sulfur containing organosilicon
compounds which may be used in accordance with the present
invention include: 3,3'-bis(trimethoxysilylpropyl) disulfide,
3,3'-bis (triethoxysilylpropyl) disulfide, 3,3'-bis
(triethoxysilylpropyl) tetrasulfide, 3,3'-bis(triethoxysilylpropyl)
octasulfide, 3,3'-bis(trimethoxysilylpropyl) tetrasulfide,
2,2'-bis(triethoxysilylethy- l) tetrasulfide,
3,3'-bis(trimethoxysilylpropyl) trisulfide,
3,3'-bis(triethoxysilylpropyl) trisulfide,
3,3'-bis(tributoxysilylpropyl) disulfide,
3,3'-bis(trimethoxysilylpropyl) hexasulfide,
3,3'-bis(trimethoxysilylpropyl) octasulfide,
3,3'-bis(trioctoxysilylpropy- l) tetrasulfide,
3,3'-bis(trihexoxysilylpropyl) disulfide,
3,3'-bis(tri-2"-ethylhexoxysilylpropyl) trisulfide,
3,3'-bis(triisooctoxysilylpropyl) tetrasulfide,
3,3'-bis(tri-t-butoxysily- lpropyl) disulfide, 2,2'-bis(methoxy
diethoxy silyl ethyl) tetrasulfide, 2,2'-bis(tripropoxysilylethyl)
pentasulfide, 3,3'-bis(tricyclohexoxysilyl- propyl) tetrasulfide,
3,3'-bis(tricyclopentoxysilylpropyl) trisulfide,
2,2'-bis(tri-2"-methylcyclohexoxysilylethyl) tetrasulfide,
bis(trimethoxysilylmethyl) tetrasulfide, 3-methoxy ethoxy
propoxysilyl 3'-diethoxybutoxy-silylpropyltetrasulfide,
2,2'-bis(dimethyl methoxysilylethyl) disulfide, 2,2'-bis(dimethyl
sec.butoxysilylethyl) trisulfide, 3,3'-bis(methyl
butylethoxysilylpropyl) tetrasulfide, 3,3'-bis(di
t-butylmethoxysilylpropyl) tetrasulfide, 2,2'-bis(phenyl methyl
methoxysilylethyl) trisulfide, 3,3'-bis(diphenyl
isopropoxysilylpropyl) tetrasulfide, 3,3'-bis(diphenyl
cyclohexoxysilylpropyl) disulfide, 3,3'-bis(dimethyl
ethylmercaptosilylpropyl) tetrasulfide, 2,2'-bis(methyl
dimethoxysilylethyl) trisulfide, 2,2'-bis(methyl
ethoxypropoxysilylethyl) tetrasulfide, 3,3'-bis(diethyl
methoxysilylpropyl) tetrasulfide, 3,3'-bis(ethyl
di-sec.butoxysilylpropyl) disulfide, 3,3'-bis(propyl
diethoxysilylpropyl) disulfide, 3,3'-bis(butyl
dimethoxysilylpropyl) trisulfide, 3,3'-bis(phenyl
dimethoxysilylpropyl) tetrasulfide, 3-phenyl ethoxybutoxysilyl
3'-trimethoxysilylpropyl tetrasulfide,
4,4'-bis(trimethoxysilylbutyl) tetrasulfide,
6,6'-bis(triethoxysilylhexyl- ) tetrasulfide,
12,12'-bis(triisopropoxysilyl dodecyl) disulfide,
18,18'-bis(trimethoxysilyloctadecyl) tetrasulfide,
18,18'-bis(tripropoxysilyloctadecenyl) tetrasulfide,
4,4'-bis(trimethoxysilyl-buten-2-yl) tetrasulfide,
4,4'-bis(trimethoxysilylcyclohexylene) tetrasulfide,
5,5'-bis(dimethoxymethylsilylpentyl) trisulfide,
3,3'-bis(trimethoxysilyl- -2-methylpropyl) tetrasulfide,
3,3'-bis(dimethoxyphenylsilyl-2-methylpropy- l) disulfide.
[0046] The preferred sulfur containing organosilicon compounds are
the 3,3'-bis(trimethoxy or triethoxy silylpropyl) sulfides. The
most preferred compounds are 3,3'-bis (triethoxysilylpropyl)
disulfide and 3,3'-bis(triethoxysilylpropyl) tetrasulfide.
Therefore, as to Formula I preferably Z is 2
[0047] where R.sup.2 is an alkoxy of 2 to 4 carbon atoms, with 2
carbon atoms being particularly preferred; Alk is a divalent
hydrocarbon of 2 to 4 carbon atoms, with 3 carbon atoms being
particularly preferred; and n being an integer of from 2 to 4 being
particularly preferred.
[0048] The amount of the sulfur containing organosilicon compound
of Formula I in a rubber composition may vary. Generally speaking,
the amount of the organosilicon compound of formula I will range
from 0.5 to 15 phr. Preferably, the amount will range from 1 to 10
phr.
[0049] The sulfur cured rubber composition may also contain
conventional additives including reinforcing agents, fillers,
peptizing agents, pigments, stearic acid, accelerators, sulfur
vulcanizing agents, antiozonants, antioxidants, processing oils,
activators, initiators, plasticizers, waxes, prevulcanization
inhibitors, extender oils and the like. Representative of
reinforcing agents or fillers include untreated silica as described
above (prior to treatment with the polymer). Such silica may be
used in an amount ranging from 1 to 150 phr. Additional fillers
include carbon black, which is typically added in amounts ranging
from about 5 to 100 parts by weight based on 100 parts by weight of
total rubber (phr). Preferably, carbon black is used in amounts
ranging from about 15 to 85 phr. Typical carbon blacks that are
used include N110, N121, N220, N231, N234, N242, N293, N299, N326,
N330, M332, N339, N343, N347, N351, N358, N375, N472, N539, N550,
N660, N683, N754, and N765. Depending on the particular use of the
compound, the appropriate carbon black may be selected.
Representative of conventional accelerators are amines, guanidines,
thioureas, thiols, thiurams, sulfenamides, dithiocarbamates and
xanthates which are typically added in amounts of from about 0.2 to
about 5 phr. Representative of sulfur vulcanizing agents include
element sulfur (free sulfur) or sulfur donating vulcanizing agents,
for example, an amine disulfide, polymeric polysulfide or sulfur
olefin adducts. The amount of sulfur vulcanizing agent will vary
depending on the type of rubber and particular type of sulfur
vulcanizing agent but generally range from about 0.1 phr to about 5
phr with a range of from about 0.5 phr to about 2 phr being
preferred. Representative of the antidegradants which may be in the
rubber composition include monophenols, bisphenols, thiobisphenols,
polyphenols, hydroquinone derivatives, phosphites, phosphate
blends, thioesters, naphthylamines, diphenol amines as well as
other diaryl amine derivatives, para-phenylene diamines, quinolines
and blended amines. Antidegradants are generally used in an amount
ranging from about 0.1 phr to about 10 phr with a range of from
about 2 to 6 phr being preferred. Representative of a peptizing
agent that may be used is pentachlorophenol which may be used in an
amount ranging from about 0.1 phr to 0.4 phr with a range of from
about 0.2 to 0.3 phr being preferred. Representative of processing
oils which may be used in the rubber composition of the present
invention include aliphatic-naphthenic aromatic resins,
polyethylene glycol, petroleum oils, ester plasticizers, vulcanized
vegetable oils, pine tar, phenolic resins, petroleum resins,
polymeric esters and rosins. These processing oils may be used in a
conventional amount ranging from about 0 to about 50 phr with a
range of from about 5 to 35 phr being preferred. Representative of
an initiator that may be used is stearic acid. Initiators are
generally used in a conventional amount ranging from about 1 to 4
phr with a range of from about 2 to 3 phr being preferred.
[0050] Accelerators may be used in a conventional amount. In cases
where only a primary accelerator is used, the amounts range from
about 0.5 to 2.5 phr. In cases where combinations of two or more
accelerators are used, the primary accelerator is generally used in
amounts ranging from 0.5 to 2.0 phr and a secondary accelerator is
used in amounts ranging from about 0.1 to 0.5 phr. Combinations of
accelerators have been known to produce a synergistic effect.
Suitable types of conventional accelerators are amines, disulfides,
guanidines, thioureas, thiazoles, thiurams, sulfenamides,
dithiocarbamates and xanthates. Preferably, the primary accelerator
is a sulfenamide. If a secondary accelerator is used, it is
preferably a guanidine, dithiocarbamate or thiuram compound.
[0051] Pneumatic tires are conventionally comprised of a generally
toroidal shaped carcass with an outer circumferential tread adapted
to the ground contacting space beads and sidewalls extending
radially from and connecting said tread to said beads. The tread
may be built, shaped, molded and cured by various methods which
will be readily apparent to those skilled in the art.
[0052] The rubber composition may be used in a variety of rubber
containing tire components. Such components include the tread,
sidewall, apex, chafer, innerliner and wirecoat. Preferably, the
rubber composition is used to form a tread rubber which can then be
applied in the building of a green tire in which the uncured,
shaped tread is built unto the carcass following which the green
tire is shaped and cured. Alternatively, the tread can be applied
to a cured tire carcass from which the previously tread has been
buffed or abraded away and the tread cured thereon as a
retread.
[0053] While certain representative embodiments and details have
been shown for the purpose of illustrating the invention, it will
be apparent to those skilled in this art that various changes and
modifications may be made therein without departing from the spirit
or scope of the invention.
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