U.S. patent application number 12/971326 was filed with the patent office on 2012-06-21 for tire having rubber component containing short fiber reinforcement with compatablizer.
Invention is credited to Martin Paul Cohen, Junling Zhao.
Application Number | 20120152423 12/971326 |
Document ID | / |
Family ID | 45093547 |
Filed Date | 2012-06-21 |
United States Patent
Application |
20120152423 |
Kind Code |
A1 |
Zhao; Junling ; et
al. |
June 21, 2012 |
TIRE HAVING RUBBER COMPONENT CONTAINING SHORT FIBER REINFORCEMENT
WITH COMPATABLIZER
Abstract
The invention relates to a tire having a rubber component which
contains short fiber reinforcement with a compatabilizer for the
fiber reinforcement. Desirably said short fiber reinforcement is an
aramid pulp. Desirably said compatabilizer is an epoxy
functionalized natural rubber.
Inventors: |
Zhao; Junling; (Hudson,
OH) ; Cohen; Martin Paul; (Fairlawn, OH) |
Family ID: |
45093547 |
Appl. No.: |
12/971326 |
Filed: |
December 17, 2010 |
Current U.S.
Class: |
152/458 ;
523/157; 523/351; 524/502; 524/535 |
Current CPC
Class: |
C08K 7/02 20130101; Y10T
152/10513 20150115; C08L 9/06 20130101; C08K 7/02 20130101; C08L
15/00 20130101; C08L 2666/08 20130101; C08L 2666/08 20130101; C08L
15/00 20130101; C08L 9/06 20130101; C08L 15/00 20130101 |
Class at
Publication: |
152/458 ;
523/351; 524/502; 524/535; 523/157 |
International
Class: |
B60C 9/12 20060101
B60C009/12; C08K 3/36 20060101 C08K003/36; C08K 3/04 20060101
C08K003/04; C08J 3/22 20060101 C08J003/22 |
Claims
1. A tire having a component of a rubber composition containing a
dispersion therein of short organic fibers comprised of, based on
parts by weight per 100 parts by weight rubber (phr): (A) 100 phr
of conjugated diene-based elastomers comprised of: (1) from zero to
about 95 phr of at least one of polymers and copolymers of isoprene
and 1,3-butadiene and copolymers of styrene with at least one of
isoprene and 1,3-butadiene as non-functionalized elastomers, and
(2) about 5 to about 100 phr of functionalized sulfur curable
elastomer as a compatiblizer for said short organic fibers within
said rubber composition comprised of at least one of polymers and
copolymers of isoprene and 1,3-butadiene and copolymers of styrene
with at least one of isoprene and 1,3-butadiene having at least one
functional group interactive with said organic fibers comprised of
at least one of epoxy groups, amine groups, hydroxyl groups,
carboxyl groups, maleic group and maleimide group; (B) about 30 to
about 100 phr of particulate reinforcement comprised of: (1) rubber
reinforcing carbon black, or (2) synthetic amorphous precipitated
silica, or (3) combination of rubber reinforcing carbon black and
synthetic amorphous precipitated silica containing up to about 80
phr of said precipitated silica together with a silica coupler for
said precipitated silica; (C) about 0.5 to about 30 phr of said
short organic fibers wherein said short organic fibers are
comprised of at least one of aramid fiber, polyester fiber, nylon
fiber and rayon fiber.
2. The tire of claim 1 wherein said rubber composition also
contains up to about 50 phr of at least one of clay and calcium
carbonate.
3. The tire of claim 1 wherein said rubber compositions contains at
least one of clay and calcium carbonate in amounts of up to about
10 phr of clay and up to about 50 phr of calcium carbonate.
4. The tire of claim 1 wherein said short organic fiber is
comprised of short aramid fiber pulp.
5. The tire of claim wherein said functionalized sulfur curable
elastomer is comprised of expoxidized cis 1,4-polyisoprene
rubber.
6. The tire of claim 1 wherein said functionalized sulfur curable
elastomer is comprised of expoxidized cis 1,4-polyisoprene rubber
having an expoxidation in a range of from about 5 to about 60
percent and said short organic fiber is comprised of short aramid
fiber pulp.
7. The tire of claim 1 wherein said rubber composition is comprised
of from about 10 to about 95 phr of at least one of cis
1,4-polyisoprene rubber, cis 1,4-polybutadiene rubber and
styrene/butadiene rubber and from about 5 to about 90 phr of at
least one of functionalized cis 1,4-polyisoprene rubber and
functionalized styrene/butadiene rubber functionalized with at
least functional group reactive with said organic fibers comprised
of at least one of epoxy groups, amine groups, hydroxyl groups and
carboxyl groups.
8. The tire of claim 7 wherein said functionalized sulfur curable
elastomer is comprised of expoxidized cis 1,4-polyisoprene rubber
having an expoxidation in a range of from about 5 to about 60
percent and said short organic fiber is comprised of short aramid
fiber pulp.
9. The tire of claim 1 wherein said particulate reinforcement is
comprised of rubber reinforcing carbon black.
10. The tire of claim 1 wherein said particulate reinforcement is
comprised of synthetic amorphous precipitated silica.
11. The tire of claim 1 wherein said particulate reinforcement is
comprised of said combination of rubber reinforcing carbon black
and synthetic amorphous precipitated silica.
12. The tire of claim 1 wherein said short organic fiber is
comprised of at least one of aramid and polyester fiber.
13. The tire of claim 7 wherein said particulate reinforcement is
comprised of said combination of rubber reinforcing carbon black
and synthetic amorphous precipitated silica and wherein said short
organic fiber is comprised of at least one of aramid and polyester
fiber.
14. A method of preparing a rubber composition comprised of, based
on parts by weight per 100 parts by weight rubber (phr): (A) 100
phr of conjugated diene-based elastomers comprised of: (1) from
zero to about 95 phr of at least one of polymers and copolymers of
isoprene and 1,3-butadiene and copolymers of styrene with at least
one of isoprene and 1,3-butadiene as non-functionalized elastomers,
and (2) about 5 to about 100 phr of functionalized sulfur curable
elastomer as a compatiblizer for said short organic fibers within
said rubber composition comprised of at least one of polymers and
copolymers of isoprene and 1,3-butadiene and copolymers of styrene
with at least one of isoprene and 1,3-butadiene having at least one
functional group interactive with said organic fibers comprised of
at least one of epoxy groups, amine groups, hydroxyl groups,
carboxyl groups, maleic group and malemide group; (B) about 30 to
about 100 phr of particulate reinforcement comprised of: (1) rubber
reinforcing carbon black, or (2) synthetic amorphous precipitated
silica, or (3) combination of rubber reinforcing carbon black and
synthetic amorphous precipitated silica containing up to about 80
phr of said precipitated silica together with a silica coupler for
said precipitated silica; (C) about 0.5 to about 30 phr of said
short organic fibers wherein said short organic fibers are
comprised of at least one of aramid fiber, polyester fiber, nylon
fiber and rayon fiber; wherein said method is comprised of: (1)
mixing said short organic fibers and said compatiblizer elastomer
with said rubber composition to enable said compatiblizer elastomer
to compatiblize said short organic fibers with said elastomers of
said rubber composition in situ with said rubber composition, or
(2) mixing a pre-formed masterbatch with said rubber composition
wherein said master batch is comprised of a dispersion of said
organic short fibers blended with as least one of said
functionalized elastomers, or (3) mixing a pre-formed masterbatch
with said rubber composition wherein said masterbatch is comprised
of at least one of said organic short fibers and least one of said
functionalized elastomer as: (a) a coagulated functionalized
elastomer from a latex thereof, or (b) a recovered functionalized
elastomer from an organic solution thereof.
15. The method of claim 14 wherein said functionalized elastomer is
an epoxidized cis 1,4-polyisoprene having an epoxidation in a range
of from about 5 to about 60 percent and said short organic fiber is
comprised of aramid fiber pulp.
16. A rubber composition prepared by the method of claim 14.
17. A tire having a component comprised of the rubber composition
of claim 16.
18. The method of claim 14 comprised of mixing said short organic
fibers and said compatiblizer elastomer with said rubber
composition to enable said compatiblizer elastomer to compatiblize
said short organic fibers with said elastomers of said rubber
composition in situ with said rubber composition.
19. The method of claim 14 comprised of mixing a pre-formed
masterbatch with said rubber composition wherein said master batch
is comprised of a dispersion of said organic short fibers blended
with as least one of said functionalized elastomers.
20. The method of claim 14 comprised of mixing a pre-formed
masterbatch with said rubber composition wherein said masterbatch
is comprised of at least one of said organic short fibers and at
least one of said functionalized elastomers as a coagulated
functionalized elastomer from a latex thereof.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a tire having a rubber component
which contains short fiber reinforcement with a compatabilizer for
the fiber reinforcement. Such short fibers may be, for example,
aramid fiber particularly aramid fiber pulp, nylon fiber, polyester
fiber and/or rayon fiber. Desirably said short fiber reinforcement
is an aramid pulp. Such compatabilizer is a functionalized sulfur
curable elastomer such as, for example, epoxidized natural
rubber.
BACKGROUND AND PRESENTATION OF THE INVENTION
[0002] Pneumatic rubber tires have various rubber components for
which sometimes enhanced stiffness of the rubber composition is a
desirable feature.
[0003] Enhanced stiffness of the rubber composition might be
accomplished, for example, by an inclusion of a dispersion of a
small content, or amount, of short fiber reinforcement.
[0004] Sometimes aramid short fibers in a form of a pulp are used
to promote an increase of stiffness for a rubber composition, a
practice which is well known by those having skill in such art.
[0005] For such practice, where the short fiber is a short aramid
fiber pulp, natural cis 1,4-polyisoprene rubber is used to aid in
dispersing the aramid short fiber pulp in a rubber composition.
[0006] For this invention, it is desired to evaluate an effect of
substituting at least a portion of such natural cis
1,4-polyisoprene rubber with a functionalized sulfur curable
elastomer such as, for example, an epoxidized natural rubber
(epoxidized natural cis 1,4-polyisoprene rubber).
[0007] A challenge is therefore presented for enhancing short fiber
reinforcement, particularly aramid short fiber pulp reinforcement
of rubber compositions.
[0008] In the description of this invention, the terms "rubber" and
"elastomer" where used, are used interchangeably, unless otherwise
prescribed. The terms "rubber composition", "compounded rubber" and
"rubber compound", where used, are used interchangeably to refer to
"rubber which has been blended or mixed with various ingredients"
and the term "compound" relates to a "rubber composition" unless
otherwise indicated. Such terms are well known to those having
skill in the rubber mixing and rubber compounding art.
[0009] In the description of this invention, the term "phr" refers
to parts of a respective material per 100 parts by weight of
rubber, or elastomer. The terms "cure" and "vulcanize" are used
interchangeably unless otherwise indicated.
SUMMARY AND PRACTICE OF THE INVENTION
[0010] In accordance with this invention, a tire is provided having
a component of a rubber composition containing a dispersion therein
of short organic fibers comprised of, based on parts by weight per
100 parts by weight rubber (phr):
[0011] (A) 100 phr of conjugated diene-based elastomers comprised
of: [0012] (1) from zero to about 95, alternately from about 10 to
about 95, phr of at least one of polymers and copolymers of
isoprene and 1,3-butadiene and copolymers of styrene with at least
one of isoprene and 1,3-butadiene, (non-functionalized elastomers),
and [0013] (2) about 5 to about 100, alternately from about 5 to
about 90, phr of a functionalized sulfur curable elastomer as a
compatabilizer for said short organic fibers within said rubber
composition comprised of at least one of polymers and copolymers of
isoprene and 1,3-butadiene and copolymers of styrene with at least
one of isoprene and 1,3-butadiene, preferably comprised of at least
one of functionalized cis 1,4-polyisoprene elastomer and
functionalized styrene/butadiene elastomer (functionalized SBR),
with functional groups interactive with said organic fibers
comprised of at least one of epoxy groups, amine groups (e.g. amine
functionalized SBR), hydroxyl groups (e.g. hydroxyl functionalized
SBR), carboxyl groups, maleic group and maleimide group (e.g.
maleated SBR), preferably epoxy groups and preferably expoxy
functionalized natural cis 1,4-polyisoprene rubber having an
epoxidation in a range of from about 5 to about 60 percent;
[0014] (B) about 30 to about 100 phr of particulate reinforcement
comprised of: [0015] (1) rubber reinforcing carbon black, or [0016]
(2) synthetic amorphous silica (e.g. precipitated silica), or
[0017] (3) combination of rubber reinforcing carbon black and
synthetic amorphous silica (e.g. precipitated silica) containing up
to about 80 phr of said precipitated silica together with a silica
coupler for said silica;
[0018] (C) about 0.5 to about 30 phr of said short organic fibers
wherein said short organic fibers are comprised of at least one of
aramid fiber (e.g. short aramid fiber pulp), polyester fiber nylon
fiber and rayon fiber, preferably said aramid fiber pulp.
[0019] In practice, said rubber composition may also contain up to
about 50 phr of at least one of clay and calcium carbonate,
alternately up to about 10 phr of clay and up to about 50 phr of
calcium carbonate.
[0020] A purpose of the compatabilizer elastomer is to
compatabilize said organic short fiber, particularly said short
aramid fiber pulp, with said rubber composition.
[0021] Accordingly, said short organic fiber may be, for example,
short aramid fiber pulp.
[0022] Said compatabilizer elastomer may be, for example,
expoxidized cis 1,4-polyisoprene rubber.
[0023] In further accordance with this invention, a method of
preparing a rubber composition is comprised of:
[0024] (A) mixing said short organic fibers (e.g. said aramid short
fiber pulp) and said compatabilizer elastomer (as a solid
compatibilzer elastomer) with said rubber composition (comprised of
solid elastomer or elastomers) rubber to enable said compatibilzer
elastomer to compatabilize said short organic fibers (e.g. said
aramid short fiber pulp) with said elastomers of said rubber
composition in situ with said rubber composition, or
[0025] (B) mixing a pre-formed masterbatch with said rubber
composition wherein said masterbatch is comprised of a dispersion
of said organic short fibers (e.g. said aramid short fiber pulp)
blended with as least one of said functionalized elastomers as a
(solid) functionalized elastomer (e.g. solid epoxidized cis
1,4-polyisoprene rubber or solid functionalized SBR elastomer),
or
[0026] (C) mixing a pre-formed masterbatch with said rubber
composition wherein said masterbatch is comprised of at least one
of said organic short fibers (e.g. aramid short fiber pulp) and
least one of said functionalized elastomer as: [0027] (1) a
coagulated functionalized elastomer from a latex (aqueous latex)
thereof (e.g. an epoxidized cis 1,4-polyisoprene rubber latex or
functionalized SBR latex), or [0028] (2) a recovered functionalized
elastomer from an organic solution thereof (e.g. an epoxidized cis
1,4-polyisoprene rubber or functionalized SBR).
[0029] In additional accordance with this invention, a tire is
provided having a tread comprised of the rubber composition
prepared by said method.
[0030] In further accordance with this invention, said method
further comprises preparing a tire with a tread comprised of the
rubber composition prepared by said method.
[0031] A significant aspect of this invention is promoting an
improved bonding strength between the short fiber and sulfur cured
rubber matrix through the inclusion of the functionalized elastomer
in the rubber composition, particularly, for example, by use of an
epoxidized natural rubber as a compatabilizer for aramid short
fiber pulp.
[0032] This is considered herein to also be significant in a sense
of promoting improved (increased) de-bonding strength between the
short fibers and associated rubber composition and, also for
promoting higher (greater) stiffness of the cured rubber
composition. Various rubber reinforcing carbon blacks might be
used. Representative of various rubber reinforcing blacks are found
in The Vanderbilt Rubber Handbook (1978), Page 417.
[0033] In practice, the rubber composition may be prepared, for
example, in at least one preparatory (non-productive) mixing step
in an internal rubber mixer, often a sequential series of at least
one, usually two, separate and individual preparatory internal
rubber mixing steps, or stages, in which the diene-based elastomer
is first mixed with the prescribed silica (if used) and carbon
black, aramid short fibers, and compatabilizer elastomer, or aramid
short fiber masterbatch with said compatabilizer elastomer,
followed by a final mixing step (productive mixing step) in an
internal rubber mixer, or optionally on an open mill mixer, where
curatives (sulfur and sulfur vulcanization accelerators) are
blended at a lower temperature and for a substantially shorter
period of time.
[0034] It is conventionally required after each internal rubber
mixing step that the rubber mixture (rubber composition) is
actually removed from the rubber mixer and cooled to a temperature
below 40.degree. C., perhaps to a temperature in a range of about
20.degree. C. to about 40.degree. C. and then added back to an
internal rubber mixer for the next sequential mixing step, or
stage.
[0035] Such non-productive mixing, followed by productive mixing is
well known by those having skill in such art.
[0036] The forming of a tire component is contemplated to be by
conventional means such as, for example, by extrusion, or by
calendering, of rubber composition to provide a shaped,
unvulcanized rubber component such as a tire tread layer. Such
forming of a tire tread (layers) is well known to those having
skill in such art.
[0037] It is understood that a tire, as a manufactured article, is
prepared by shaping and curing the assembly of its components at an
elevated temperature (e.g. 140.degree. C. to 170.degree. C.) and
elevated pressure in a suitable mold. Such practice is well known
to those having skill in such art.
[0038] It is readily understood by those having skill in the
pertinent art that the rubber composition would be compounded by
methods generally known in the rubber compounding art, such as
mixing the various sulfur-vulcanizable constituent rubbers with
various commonly used additive materials, as herein before
discussed, such as, for example, curing aids such as sulfur,
activators, retarders and accelerators, processing additives, such
as rubber processing oils, resins including tackifying resins,
silicas, and plasticizers, fillers, pigments, fatty acid, zinc
oxide, waxes, antioxidants and antiozonants, peptizing agents and
reinforcing materials such as, for example, carbon black. As known
to those skilled in the art, depending on the intended use of the
sulfur vulcanizable and sulfur vulcanized material (rubbers), the
additives mentioned above are selected and commonly used in
conventional amounts.
[0039] Typical amounts of fatty acids, if used, which can include
stearic acid, comprise about 0.5 to about 3 phr. Typical amounts of
zinc oxide comprise about 1 to about 5 phr. Typical amounts of
waxes comprise about 1 to about 5 phr. Often microcrystalline waxes
are used. Typical amounts of peptizers comprise about 0.1 to about
1 phr. Typical peptizers may be, for example, pentachlorothiophenol
and dibenzamidodiphenyl disulfide.
[0040] The vulcanization is conducted in the presence of a sulfur
vulcanizing agent. Examples of suitable sulfur vulcanizing agents
include elemental sulfur (free sulfur) or sulfur donating
vulcanizing agents, for example, an amine disulfide, polymeric
polysulfide or sulfur olefin adducts. Preferably, the sulfur
vulcanizing agent is elemental sulfur. As known to those skilled in
the art, sulfur vulcanizing agents are used in an amount ranging
from about 0.5 to about 4 phr, or even, in some circumstances, up
to about 8 phr, with a range of from about 1.5 to about 2.5,
sometimes from about 2 to about 2.5, being preferred.
[0041] Accelerators are used to control the time and/or temperature
required for vulcanization and to improve the properties of the
vulcanizate. In one embodiment, a single accelerator system may be
used, i.e., primary accelerator. Conventionally and preferably, a
primary accelerator(s) is used in total amounts ranging from about
0.5 to about 4, preferably about 0.8 to about 2.5, phr. In another
embodiment, combinations of a primary and a secondary accelerator
might be used with the secondary accelerator being used in smaller
amounts (of about 0.05 to about 3 phr) in order to activate and to
improve the properties of the vulcanizate. Combinations of these
accelerators might be expected to produce a synergistic effect on
the final properties and are somewhat better than those produced by
use of either accelerator alone. In addition, delayed action
accelerators may be used which are not affected by normal
processing temperatures but produce a satisfactory cure at ordinary
vulcanization temperatures. Vulcanization retarders might also be
used. Suitable types of accelerators that may be used in the
present invention are amines, disulfides, guanidines, thioureas,
thiazoles, thiurams, sulfenamides, dithiocarbamates and xanthates.
Preferably, the primary accelerator is a sulfenamide. If a second
accelerator is used, the secondary accelerator is preferably a
guanidine, dithiocarbamate or thiuram compound.
[0042] The mixing of the rubber composition can preferably be
accomplished by the aforesaid sequential mixing process. For
example, the ingredients may be mixed in at least two stages,
namely, at least one non-productive (preparatory) stage followed by
a productive (final) mix stage. The final curatives are typically
mixed in the final stage which is conventionally called the
"productive" or "final" mix stage in which the mixing typically
occurs at a temperature, or ultimate temperature, lower than the
mix temperature(s) of the preceding non-productive mix stage(s).
The terms "non-productive" and "productive" mix stages are well
known to those having skill in the rubber mixing art.
[0043] The following example is presented to further illustrate the
practice of this invention. The parts and percentages are by weight
unless otherwise indicated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] The invention will be described by way of example and with
reference to accompanying drawings in which:
[0045] FIG. 1 and FIG. 2 graphically present Stress (MPa) versus
dynamic Strain (%) at 23.degree. C. for FIG. 1 and at 150.degree.
C. for FIG. 2 for curves A, B, C, D, E and F for the Samples in
Table 2 of Example I.
[0046] FIG. 3 graphically presents hysteresis in term of a
hysteresis loop test at a constant maximum stress of 5 MPa for
curves A, B, C, D, E and F for the Samples in Table 2 of Example
I.
[0047] FIG. 4 and FIG. 5 are graphical presentations of Stress
(MPa) versus dynamic Strain (%) at test temperature of 23.degree.
C. for FIG. 4 and 150.degree. C. for FIG. 5 for rubber Samples G, H
and I in Table 2 of Example I.
[0048] FIG. 6 and FIG. 7 are graphical presentations of Stress
(MPa) versus dynamic Strain (%) for rubber Sample J (Control) and K
(Experimental) at 23.degree. C. and 150.degree. C., respectively,
of Table 7 in Example II.
EXAMPLE I
[0049] Rubber compositions were prepared for evaluating an effect
of providing short fiber aramid pulp reinforcement in a rubber
composition together with an epoxy functionalized natural rubber as
a compatibilzer for the short aramid fiber pulp reinforcement.
[0050] Control rubber Samples A and B are rubber compositions which
contain natural cis 1,4-polyisoprene rubber (NR) and epoxidized
natural rubber (ENR), respectively, without aramid fiber pulp
reinforcement.
[0051] Comparative rubber Sample C contained cis 1,4-polyisoprene
natural rubber with an inclusion of 3 phr of a dispersion of short
aramid fiber pulp reinforcement.
[0052] Experimental rubber Samples D, E and F contained epoxidized
natural rubber with an inclusion of 3 phr, 6 phr and 12 phr,
respectively, of short aramid fiber pulp reinforcement.
[0053] The rubber compositions were prepared by mixing the
ingredients in sequential non-productive (NP) and productive (PR)
mixing steps in one or more internal rubber mixers.
[0054] The basic formulation for the rubber Samples is presented in
the following Table 1 and presented in terms of parts by weight
unless otherwise indicated.
TABLE-US-00001 TABLE 1 Parts Non-Productive Mixing Step (NP),
(mixed to 160.degree. C.) Natural cis 1,4-polyisoprene rubber.sup.1
100 and 0 Epoxidized natural rubber.sup.2 0 and 100
Antioxidant.sup.3 2 Carbon black (N330).sup.4 50 Processing
oil.sup.5 5 Fatty acid.sup.6 3 Zinc oxide 5 Aramid pulp, short
fiber.sup.7 0 and variable Productive Mixing Step (PR), (mixed to
110.degree. C.) Sulfur and sulfur cure accelerators.sup.8 4
.sup.1Natural cis 1,4-polyisoprene rubber .sup.2Expoxidized cis
1,4-polyisoprene rubber as ENR50 .TM., a 50 percent expoxidized
natural rubber from Malaysia company .sup.3Antoxidant of the
diamine type .sup.4Rubber reinforcing carbon black as N330, an ASTM
designation .sup.5Rubber processing oil, primarily aromatic rubber
processing oil .sup.6Fatty acid comprised primarily of stearic acid
and a minor amount of other fatty acids comprised primarily of
palmitic and oleic acids. .sup.7Aramid short fiber pulp (not a
natural rubber/aramid pulp masterbatch) from du Pont de Nemours.
.sup.8Sulfur and sulfur cure accelerators of the sulfenamide and
thiuram types
[0055] The rubber Samples were prepared to evaluate the inclusion
of short aramid fiber pulp with the expoxidized natural rubber
compatabilizer, as illustrated in the following Table 2 with the
rubber and aramid fiber pulp reported in terms of parts per 100
parts by weight of rubber (phr) for the rubber Samples A through
F.
[0056] Table 2 also reports a summary of various physical
properties.
TABLE-US-00002 TABLE 2 Rubber Samples A B C D E F Short aramid
fiber pulp (phr) 0 0 3 3 6 12 Natural cis 1,4-polyisoprene rubber
(phr) 100 0 100 0 0 0 Epoxidized natural rubber (phr) 0 100 0 100
100 100 Summary of Various Physical Properties Rubber Processing
Characteristic RPA.sup.1 100.degree. C., 0.83 Hertz, 15% strain
Uncured rubber, elastic modulus G' (kPa) 153 126 135 107 117 113
Storage Modulus RPA.sup.1, 100.degree. C., 11 Hertz Elastic storage
modulus G' at 1% strain, (kPa) 2688 2072 3002 3326 3825 4266
Percent increase with 3 phr of short aramid fiber -- -- 12 24 -- --
Elastic storage modulus G' at 10% strain, (kPa) 1662 1191 1851 1913
2190 2171 Percent increase with 3 phr of short aramid fiber -- --
12 15 -- -- Tan Delta, RPA.sup.1 100.degree. C., 11 Hertz Tan delta
at 10% strain 0.107 0.175 0.108 0.165 0.160 0.168 Percent increase
with 3 phr of short aramid fiber -- -- 0 54 -- -- .sup.1Rubber
Process Analyzer
[0057] From the Summary of Various Physical Properties reported in
Table 2 it can be seen that physical interaction of the short
aramid fiber pulp with the ENR (epoxidized natural rubber)
containing rubber composition is considerably greater than with the
natural rubber composition without the expoxidized natural
rubber.
[0058] This phenomenon can be readily seen that for the rubber
compositions containing 3 phr of the short aramid fiber pulp that
the storage modulus (G') at 1 percent strain increased by 24
percent for the ENR rubber and only 12 percent for the natural
rubber which is indicative of beneficially increased interaction of
the fiber in the ENR rubber composition.
[0059] This phenomenon can also be seen for the rubber compositions
containing 3 phr of the short aramid fiber pulp that the storage
modulus (G') at 10 percent strain increased by 15 percent for the
ENR rubber and only 12 percent for the natural rubber which is
indicative of beneficially increased interaction of the fiber in
the ENR rubber composition.
[0060] This phenomenon can further be seen for the rubber
compositions containing 3 phr of the short aramid fiber pulp that
the Tan delta property at 10 percent strain increased by 54 percent
for the ENR rubber and virtually no increase in the Tan delta value
for the natural rubber which is further indicative of beneficially
increased interaction of the fiber in the ENR rubber
composition.
In the Drawings
[0061] For the physical properties reported for the rubber Samples
in the above Table 2:
[0062] (A) FIGS. 1 and 2 (FIG. 1 and FIG. 2) graphically present
Stress (MPa) versus dynamic Strain (%) at 23.degree. C. for FIG. 1
and at 150.degree. C. for FIG. 2.
[0063] (B) FIG. 3 (FIG. 3) graphically presents hysteresis in terms
of a hysteresis loop test at a constant maximum stress of 5
MPa.
[0064] In particular, it can be seen from FIG. 1 (Stress versus
Strain at 23.degree. C. using an Instron.TM. analytical instrument,
ASTM D412) that, compared to the curves for the natural rubber
(curve A) and the ENR (curve B) that, while the inclusion of 3 phr
of the short aramid fiber in the natural rubber (curve C) increased
its stiffness, namely that it increased the rubber's stress value,
the inclusion of 3 phr of the short aramid fiber in the ENR rubber
(curve D) increased the rubber's stiffness (stress value) by a
significantly greater margin which is indicative of significantly
greater interaction of the short aramid fiber with the ENR
rubber.
[0065] It can further be seen from FIG. 1 that, as the loading of
the short aramid fiber in the ENR rubber increased from the 3 phr
level (curve D) to levels of 6 phr (curve E) and 12 phr (curve F),
the stiffness (stress value) of the ENR rubber increased
dramatically to thereby further indicate a greater interaction of
the short aramid fibers with the ENR.
[0066] This is considered herein to be significant in a sense that
FIG. 1 demonstrates that the interaction of the short aramid fibers
had a significantly greater interaction effect for the ENR than for
the natural rubber composition.
[0067] In particular, it can be seen from FIG. 2 (Stress versus
Strain at an increased temperature of 150.degree. C. using an
Instron.TM. analytical instrument, ASTM D412) that, compared to the
curves for the natural rubber (curve A) and the ENR (curve B) that
the inclusion of 3 phr of the short aramid fiber in the natural
rubber (curve C) and in the ENR (curve D) similarly increased their
stiffness values, namely their stress values, the fiber-containing
ENR (curve D) extended further until the rubber sample broke (a
longer curve D line compared to the curve C line) thereby
suggesting a greater elongation durability short aramid
fiber-containing ENR (curve D).
[0068] It can further be seen from FIG. 2 that, similar to FIG. 1,
as the loading of the short aramid fiber in the ENR rubber
increased from the 3 phr level (curve D) to levels of 6 phr (curve
E) and 12 phr (curve F), the stiffness (stress value) of the ENR
rubber increased dramatically to thereby further indicate a greater
interaction of the short aramid fibers with the ENR.
[0069] It can be seen from FIG. 3 (Hysteresis at Constant Stress of
5 MPa versus Number of Cycles for the dynamic test) that hysteresis
values for all of the natural rubber (curve A), ENR rubber (curve
B) and 3 phr short aramid fiber containing ENR (curve C), were
significantly higher than hysteresis values for the 3 phr and 6 phr
short aramid fiber containing ENR rubber which is a further
indication of better interaction of the short aramid fibers with
the ENR. The reduction in hysteresis is considered to be a
particularly beneficial effect for the short aramid fiber loaded
ENR rubber in a sense that, as the hysteresis effect is reduced,
significantly beneficially less internal heat build up in the ENR
based rubber composition is expected.
EXAMPLE II
[0070] Additional rubber compositions were prepared for evaluating
an effect of providing epoxidized natural rubber as a
compatabilizer for short fiber aramid pulp reinforcement in a
rubber composition comprised of cis 1,4-polybutadiene rubber,
natural cis 1,4-polybutadiene rubber and isoprene/butadiene rubber
(IBR) containing 1.6 phr of the aramid short fiber pulp.
[0071] Control rubber Sample G contains elastomers composed of cis
1,4-polybutadiene rubber, natural cis 1,4-polyisoprene rubber and
IBR together with reinforcing filler as rubber reinforcing carbon
black without the ENR compatabilizer.
[0072] Experimental rubber Samples H and I contained elastomers
provided an inclusion of the 1.6 phr of the short aramid fiber pulp
together with 6 and 12 phr, respectively, of epoxidized natural
compatabilizer for the short aramid fiber pulp.
[0073] The rubber compositions were prepared by mixing the
ingredients in sequential non-productive (NP) and productive (PR)
mixing steps in one or more internal rubber mixers.
[0074] The basic formulation for the rubber Samples is presented in
the following Table 3 and recited terms of parts by weight unless
otherwise indicated.
TABLE-US-00003 TABLE 3 Parts Non-Productive Mixing Step (NP),
(mixed to 160.degree. C.) Isoprene/butadiene (IBR) rubber.sup.9
36.75 Cis 1,4-polybutadiene rubber.sup.10 36.75 Natural cis
1,4-polyisoprene rubber 26.5, 20.5, 14.5 Epoxidized natural rubber
(ENR50) 0, 6, 12 Antioxidant 3 Carbon black (N550) 51 Resin.sup.11
1.2 Fatty acid 0.5 Zinc oxide 5 Aramid pulp 1.6 Productive Mixing
Step (PR), (mixed to 110.degree. C.) Sulfur and sulfur cure
accelerators 9.5 .sup.9Tin coupled IBR rubber as a 30/70
isoprene/butadiene rubber from The Goodyear Tire and Rubber Company
.sup.10Cis 1,4-polybutadiene rubber as BUD1208 .TM. from The
Goodyear Tire and Rubber Company .sup.11non staining, unreactive
100 percent phenol formaldehyde resin
[0075] The rubber Samples were prepared to evaluate the inclusion
of short aramid fiber pulp with the expoxidized natural rubber
compatiblizer, as illustrated in the following Table 4 with the
rubber and aramid fiber pulp reported in terms of parts per 100
parts by weight of rubber (phr) for the rubber Samples G, H, and
I.
TABLE-US-00004 TABLE 4 G H I Natural cis 1,4-polyisoprene rubber
(phr) 26.5 20.5 14.5 Epoxidized natural rubber (phr) 0 6 12 Short
aramid fiber pulp (phr) 1.6 1.6 1.6 Sulfur (phr) 3 3 3 Accelerators
(phr) 6.5 6.5 6.5 Summary of Various Physical Properties Rubber
Processing Characteristic RPA.sup.1 100.degree. C., 0.83 Hertz, 15%
strain Uncured rubber, elastic modulus G' (kPa) 197 199 213 Elastic
Storage Modulus RPA.sup.1 100.degree. C., 11 Hertz Modulus G', 1%
strain (kPa) 3464 3522 3857 Modulus G', 10% strain (kPa) 2781 2789
2991 Tan delta, RPA.sup.1 100.degree. C., 11 Hertz Tan delta at 10%
strain 0.06 0.07 0.08 .sup.1Rubber Process Analyzer
[0076] In Table 4, from the Summary of Various Physical Properties
it can be seen that the cured modulus G' increased progressively
for rubber Samples H and I as the amount of ENR compatabilizer
increased from 6 phr to 12 phr for both the 1 percent and 10
percent test conditions as compared to modulus G' values of 3464
kPa and 2781 kPa, respectively, for rubber Sample G with no ENR
being added.
[0077] This is considered herein to be significant in a sense
showing the beneficial effect of the increasing presence of the ENR
in the rubber composition as a compatabilizer for the fiber/rubber
composite to enable an indication of greater filler/rubber
interaction which is a desirable effect.
In the Drawings
[0078] For the rubber Samples reported in the above Table 4:
[0079] FIGS. 4 and 5 (FIGS. 4 and 5) are graphical presentations of
Stress (MPa) versus dynamic Strain (%) at test temperatures of
23.degree. C. and 150.degree. C., respectively, for the aforesaid
rubber Samples G, H and I.
[0080] In both FIGS. 4 and 5 Yield "Points" are shown which are
represented by inflections in the curves for each of rubber Samples
G, H and I where the ENR content increased from zero percent
(Sample G) to 6 and 12 phr for Samples H and I, respectively.
[0081] In FIG. 4 (23.degree. C. test condition) the Yield Points
(cure inflection regions) progressively and significantly increased
with both higher Stress and Strain values as the ENR contents
progressed from zero (Sample G) to 6 phr (Sample H) to 12 phr
(Sample I).
[0082] The advancing Yield Points in FIG. 4 (23.degree. C. test
condition) for Samples H and I is indicative of progressively
increasing bonding strength between the short fibers and rubber
which is envisioned as evidence of an increasing fiber/rubber
compatabilizing effect of the increasing ENR content which is a
desirable effect.
[0083] Advancing Yield Points in FIG. 5 (150.degree. C. test
condition) can similarly be seen for Samples H and I which is also
indicative of progressively increasing bonding strength between the
short fibers and rubber which is also envisioned as evidence of an
increasing fiber/rubber compatabilizing effect of the increasing
ENR content at the higher temperature which is a desirable
effect.
EXAMPLE III
Use of Aramid Fiber Masterbatch
[0084] A fiber masterbatch was prepared by dry blending aramid
fiber pulp and epoxidized natural rubber for use in evaluating an
effect of using epoxidized natural rubber to aid in compatabilizing
the aramid fiber pulp with the rubber composition and to promote
bonding strength to the aramid fibers.
[0085] The aramid fiber/epoxidized natural rubber masterbatch is
shown in the following Dry Fiber Masterbatch Table where the
amounts are presented in parts of weight per 100 parts of rubber
(phr) unless otherwise indicated.
TABLE-US-00005 TABLE Dry Fiber Masterbatch Ingredients Dry Fiber
Masterbatch Epoxidized natural rubber (phr) 100 Rubber reinforcing
carbon black (N550) (phr) 60 Aramid short fiber pulp (phr)
26.65
[0086] Rubber compositions were prepared for evaluation an effect
of providing short aramid fibers as a pre-formed masterbatch with
epoxidized natural rubber with the epoxidized natural rubber being
used as a compatiblizer for the aramid fiber to promote improved
bonding strength to the aramid fiber.
[0087] Control rubber Sample J is prepared without the epoxidized
natural rubber and Experimental rubber Sample K is prepared with a
combination of epoxidized natural rubber and the Fiber Masterbatch
rubber sample.
[0088] The rubber Samples were prepared by mixing the ingredients
in sequential non-productive (NP) and productive (P) mixing steps
in internal rubber mixers.
[0089] The formulations are shown in the following Table 6 for
Samples J and K with parts and percentages presented in terms of
weight unless otherwise indicated.
TABLE-US-00006 TABLE 6 Basic Formulations J K Non-Productive Mixing
Step (NP) to about 160.degree. C. Isoprene/Butadiene (IBR) rubber
(phr) 36.75 36.75 Cis 1,4-polybutadiene rubber (phr).sup.10 36.75
36.75 Natural cis 1,4-polyisoprene rubber (NR) (phr) 26.5 0
Epoxidized natural rubber (ENR50) (phr) 0 20.5 Antioxidant 4 4
Rubber reinforcing carbon black (N550) 56 47.9 Resin11 1.2 1.2
Fatty acid 0.5 0.5 Zinc oxide 5 5 Dry Fiber masterbatch 0
11.1.sup.a Productive Mixing Step (P) to about 110.degree. C.
Sulfur 4 3 Sulfur cure accelerator(s) 8 6.5 .sup.aParts by weight
composed of 1.5 phr of fiber, 3.6 phr of carbon black, and 6 phr of
ENR
[0090] The following Table 7 illustrates a summary of rubber
Samples followed by a cure behavior as various physical properties
of the Rubber Samples based on the basic formulations presented in
preceding Table 6 with the parts and percentages presented in terms
of weight unless otherwise indicated.
TABLE-US-00007 TABLE 7 J K Epoxidized natural rubber (phr) 0 20.5
Carbon black (N550) (phr) 56 47.9 Fiber Masterbatch (Table 5)
(parts by weight) 0 11.1 Summary of Various Physical Properties
Rubber Processing Characteristic RPA.sup.1 100.degree. C., 0.83
Hertz, 15% strain Uncured rubber, elastic modulus G' (kPa) 204 230
Elastic Storage Modulus RPA.sup.1 100.degree. C., 11 Hertz Modulus
G', 1% strain (kPa) 4569 3857 Modulus G', 10% strain (kPa) 3196
2931 Tan delta, RPA.sup.1 100.degree. C., 11 Hertz Tan delta at 10%
strain 0.1 0.07 K @ P K @ L J With Grain Against Grain
Stress-Strain Test at 23.degree. C. 25% Modulus (MPa) 0.96 1.11
0.88 50% Modulus (MPa) 2.29 3.28 2.71 100% Modulus (MPa) 6.11 9.26
6.86 Tensile strength (MPa) 6.47 14.7 13.7 Elongation at break (%)
104 173 185 Energy at break (J) (joules) 0.43 1.89 1.64
Stress-Strain Test at 150.degree. C. 25% Modulus (MPa) 0.59 0.54
0.47 50% Modulus (MPa) 1.89 2.09 1.88 Tensile strength (MPa) 2.96
5.83 4.84 Elongation at break (%) 68.6 95.3 96.3 Energy at break
(J) (joules) 0.15 0.33 0.29 .sup.1Rubber Process Analyzer
[0091] From Table 7 it can be seen that the tensile strength at
break (stress at break) of rubber Sample K, with the masterbatch of
ENR compatiblizer and aramid pulp, increased to a value of over 13
MPa (13.7 MPa for K@L and 14.7 MPa for K@P), which is an increase
of about 100 percent compared to a value of about 6.5 MPa for
rubber Sample J which did not contain the ENR or fiber/natural
rubber masterbatch.
[0092] Elongation at break for rubber Sample K increased to a value
of at least about 170 percent (185 percent for K@L and 173 percent
for K@P), an increase of at least about 66 percent compared to a
value of about 104 percent for rubber Sample J which did not
contain the ENR or fiber/natural rubber masterbatch.
[0093] Energy at break at 23.degree. C. for rubber Sample K
(prepared with the pre-formed masterbatch of aramid fiber and ENR)
increased to a value of about 1.9 joules (an increase of about 150
percent) as compared to a value of about 0.4 joules for rubber
Sample J (which did not contain the inclusion of the pre-formed
masterbatch of aramid fiber and ENR).
[0094] These observations are considered herein to be significant
as they are indicative of greater durability of rubber Sample K
with the inclusion of the pre-formed aramid fiber/ENR masterbatch
as compared to rubber Sample J without the aramid fiber/ENR
masterbatch.
In the Drawings
[0095] For the rubber Samples reported in the above Table 7:
[0096] FIGS. 6 and 7 (FIGS. 6 and 7) are graphical presentations of
Stress (MPa) and Strain (%) for rubber Samples J (Control) and K
(Experimental) at 23.degree. C. and 150.degree. C.,
respectively.
[0097] The K@L curves in FIGS. 6 and 7 represent Stress versus
Strain curve for the Stress measurement for Experimental rubber
Sample K taken laterally (about 90 degrees or at a right angle) and
the K@P curves for the measurement taken in a parallel direction
(about 0 degrees) to its grain.
In the Drawings: For the 23.degree. C. Test shown in FIG. 6
[0098] (A) For Control Rubber Sample J
[0099] Control rubber Sample J (without both ENR compatiblizer and
short fiber reinforcement) broke at a strain (elongation) of about
100 percent at a stress (tensile strength) of about 6 MPa, prior to
its intended completion of the tests.
[0100] (B) For Experimental Rubber Sample K@P
[0101] In contrast, for Experimental rubber Sample K, the K@P
Stress value at about 100 percent strain (where rubber Sample J
broke) increased to about 9.3 MPa without breaking, as reported in
Table 7, representing an increase in Stress value at 100 percent
strain, or elongation, of over 50 percent--without breaking.
[0102] Further, Experimental rubber Sample K@P broke at a strain
(elongation) of 173 percent and a stress of about 14.7 MPa, an
increase in strain (elongation) of at least 70 percent and in
ultimate stress, or tensile strength, of over 120 percent, compared
to rubber Sample J.
[0103] (C) For Experimental Rubber Sample K@L
[0104] In further contrast, for Experimental rubber Sample K, the
K@L Stress value at about 100 percent strain (where rubber Sample J
broke) increased to about 6.9 MPa without breaking, as reported in
Table 7, representing an increase in Stress value at 100 percent
strain, or elongation, of about 15 percent--without breaking.
[0105] Further, Experimental rubber Sample K@L broke at a strain
(elongation) of 185 percent and a stress (tensile strength) of
about 13.7MPa, an increase in strain (elongation) of about 85
percent and in ultimate stress, or tensile strength, of at least
110 percent, compared to rubber Sample J.
In the Drawings: For the 150.degree. C. Test Shown in FIG. 7:
[0106] (A) For Control Rubber Sample J
[0107] Control rubber Sample J (without both ENR compatiblizer and
short fiber reinforcement) broke at a strain (ultimate elongation
at break) of about 69 percent at a stress (tensile strength) of
about 3 MPa, prior to its intended completion of the tests.
[0108] (B) For Experimental Rubber Sample K@P
[0109] In contrast, for Experimental rubber Sample K, the K@P
Stress value at about 69 percent strain (where rubber Sample J
broke) increased to about 3.4 MPa without breaking, representing an
increase in Stress value at 100 percent strain, or elongation, of
about 13 percent--without breaking.
[0110] Further, Experimental rubber Sample K@P broke at a strain
(elongation) of about 95 percent and a stress (tensile strength) of
about 5.8 MPa, an increase in strain (elongation) of at least 70
percent and in ultimate stress, or tensile strength, of over 90
percent, compared to rubber Sample J.
[0111] (C) For Experimental Rubber Sample K@L
[0112] For additional contrast, for Experimental rubber Sample K,
the K@L Stress value at about 70 percent strain (where rubber
Sample J broke) increased to about 3.1 MPa without breaking, as
reported in Table 7, representing an increase in Stress value at
100 percent strain, or elongation, of about 3 percent--without
breaking.
[0113] Further, Experimental rubber Sample K@L broke at a strain
(ultimate elongation) of about 96 percent and a stress (tensile
strength) of about 4.8 MPa, an increase in strain (increase in
ultimate elongation at break) of about 39 percent and in ultimate
stress, or tensile strength, of about 60 percent, compared to
rubber Sample J.
[0114] These observations are considered herein to be additionally
significant as they are further indicative of greater durability of
rubber Sample K with the inclusion of the pre-formed aramid fiber
masterbatch together with the ENR as compared to rubber Sample J
without the aramid fiber masterbatch and the ENR.
[0115] While certain representative embodiments and details have
been shown for the purpose of illustrating the subject invention,
it will be apparent to those skilled in this art that various
changes and modifications can be made therein without departing
from the scope of the subject invention.
* * * * *