U.S. patent application number 17/134698 was filed with the patent office on 2021-08-19 for cured guayule rubber containing compositions and method for preparing same.
This patent application is currently assigned to Bridgestone Corporation. The applicant listed for this patent is Bridgestone Corporation. Invention is credited to Sheel P. Agarwal, Yingyi Huang.
Application Number | 20210253832 17/134698 |
Document ID | / |
Family ID | 1000005568362 |
Filed Date | 2021-08-19 |
United States Patent
Application |
20210253832 |
Kind Code |
A1 |
Agarwal; Sheel P. ; et
al. |
August 19, 2021 |
Cured Guayule Rubber Containing Compositions And Method For
Preparing Same
Abstract
Provided herein are cured rubber compositions containing guayule
natural rubber with 2.5-4 weight % resin and fillers. By the use of
a specified cure package that contains increased amounts of sulfur
and accelerator, the cured rubber compositions are found to exhibit
strain induced crystallization (as can be observed by X-ray
diffraction). Also provided are related methods for preparing the
rubber compositions.
Inventors: |
Agarwal; Sheel P.; (Solon,
OH) ; Huang; Yingyi; (Hudson, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bridgestone Corporation |
Chuo-ku |
|
JP |
|
|
Assignee: |
; Bridgestone Corporation
Chuo-ku
JP
|
Family ID: |
1000005568362 |
Appl. No.: |
17/134698 |
Filed: |
December 28, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16564058 |
Sep 9, 2019 |
10875989 |
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17134698 |
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15894278 |
Feb 12, 2018 |
10407564 |
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16564058 |
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13787644 |
Mar 6, 2013 |
9890268 |
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15894278 |
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61607494 |
Mar 6, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08L 21/00 20130101;
C08K 3/013 20180101; C08L 7/00 20130101 |
International
Class: |
C08L 7/00 20060101
C08L007/00; C08L 21/00 20060101 C08L021/00; C08K 3/013 20060101
C08K003/013 |
Claims
1. A cured rubber composition comprising: a. 100 phr of guayule
natural rubber, where the guayule natural rubber contains 2.5-4
weight % resin or 10-90 phr of guayule natural rubber, where the
guayule natural rubber contains 2.5-4 weight % resin, and 90-10 phr
of at least one conjugated diene monomer containing polymer or
copolymer; b. 5-100 phr of at least one filler selected from the
group consisting of carbon black and silica; wherein the cure
package used to prepare the cured rubber composition comprises: (i)
1.2 to 4 phr sulfur, (ii) 0.5 to 5 phr of at least one antioxidant,
(iii) 0.5 to 5 phr zinc oxide, (iv) 0.5 to 4 phr stearic acid, (iv)
1.05 to 3 phr of at least one accelerator and the cured rubber
composition exhibits strain induced crystallization (as can be
observed by X-ray diffraction).
2. A cured rubber composition according to claim 1, wherein the at
least one conjugated diene monomer containing polymer or copolymer
contains at least one monomer selected from the group consisting of
1,3-butadiene, isoprene, 1,3-pentadiene, 1,3-hexadiene,
2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene,
2-methyl-1,3-pentadiene, 3-methyl-1,3-pentadiene,
4-methyl-1,3-pentadiene and 2,4-hexadiene; and optionally at least
one monomer selected from the group consisting of styrene,
.alpha.-methyl styrene, p-methylstyrene, o-methylstyrene,
p-butylstyrene and vinylnaphthalene.
3. The rubber composition of claim 1, wherein the cured rubber
composition has a max stress at break, a 300% MPa and an elongation
at break that is no more than +/-15% as compared to a comparative
rubber composition that contains Hevea natural rubber instead of
guayule natural rubber.
4. The rubber composition of claim 1, wherein the cured rubber
composition has a max stress at break, a 300% MPa and an elongation
at break that is no more than +/-10% as compared to a comparative
rubber composition that contains Hevea natural rubber instead of
guayule natural rubber.
5. The rubber composition of claim 1, wherein the cured rubber
composition has a max stress at break, a 300% MPa and an elongation
at break that is no more than +/-5% as compared to a comparative
rubber composition that contains Hevea natural rubber instead of
guayule natural rubber.
6. A tire component made from the rubber composition of claim
1.
7. A tire component made from the rubber composition of claim 1
where the tire component is selected from the group consisting of
treads, sidewalls, and body skim plies.
8. A method of providing a cured guayule natural rubber containing
composition with strain induced crystallization comprising: a.
utilizing a rubber mixture that comprises (i) either 100 phr of
guayule natural rubber that contains 2.5-4 weight % resin, or a
combination of 10-90 phr of guayule natural rubber that contains
2.5-4 weight % resin and 90-10 phr of at least one conjugated diene
monomer containing polymer or copolymer, and (ii) 5-100 phr of at
least one filler selected from the group consisting of carbon black
and silica, and b. utilizing a cure package comprising (i) 1.2 to 4
phr sulfur, (ii) 0.5 to 5 phr of at least one antioxidant, (iii)
0.5 to 5 phr zinc oxide, (iv) 0.5 to 4 phr stearic acid, (iv) 1.05
to 3 phr of at least one accelerator to produce a cured guayule
natural rubber containing composition wherein the cured guayule
natural rubber containing composition exhibits strain induced
crystallization (as evidenced by X-ray diffraction).
9. A method according to claim 8, wherein the cured guayule rubber
composition has a max stress at break, a 300% MPa and an elongation
at break that is no more than +/-15% as compared to a comparative
rubber composition that contains Hevea natural rubber instead of
guayule natural rubber.
10. A method according to claim 8, wherein the cured guayule rubber
composition has a max stress at break, a 300% Mpa and an elongation
at break that is no more than +/-10% as compared to a comparative
rubber composition that contains Hevea natural rubber instead of
guayule natural rubber.
11. A method according to claim 8, wherein the cured guayule rubber
composition has a max stress at break, a 300% Mpa and an elongation
at break that is no more than +/-5% as compared to a comparative
rubber composition that contains Hevea natural rubber instead of
guayule natural rubber.
12. A cured rubber composition according to claim 8, wherein the at
least one conjugated diene monomer containing polymer or copolymer
contains at least one monomer selected from the group consisting of
1,3-butadiene, isoprene, 1,3-pentadiene, 1,3-hexadiene,
2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene,
2-methyl-1,3-pentadiene, 3-methyl-1,3-pentadiene,
4-methyl-1,3-pentadiene and 2,4-hexadiene; and optionally at least
one monomer selected from the group consisting of styrene,
.alpha.-methyl styrene, p-methylstyrene, o-methylstyrene,
p-butylstyrene and vinylnaphthalene.
13. A method of providing a cured guayule natural rubber containing
composition with strain induced crystallization comprising: a.
utilizing a rubber mixture comprising (i) either 100 phr of guayule
natural rubber that contains 2.5-4 weight % resin, or a combination
of 10-90 phr of guayule natural rubber that contains 2.5-4 weight %
resin and 90-10 phr of at least one conjugated diene monomer
containing polymer or copolymer, and (ii) 5-100 phr of at least one
filler selected from the group consisting of carbon black and
silica, and b. curing the rubber mixture by increasing the amount
of sulfur in the cure package by 30-300% and increasing the amount
of accelerator by 30-200% each as compared to a comparative rubber
composition that contains Hevea natural rubber instead of guayule
natural rubber wherein the cured guayule natural rubber containing
composition and the comparative rubber composition both exhibit
strain induced crystallization (as can be observed by X-ray
diffraction) and have a max stress at break, a 300% Mpa and an
elongation at break that are no more than +/-15% different and a
tan delta at 0.degree. C. and 50.degree. C. (obtained from
temperature sweep experiments conducted with a frequency of 31.4
rad/sec using 0.5% strain for temperatures ranging from
-100.degree. C. to -10.degree. C., and with 2% strain for
temperatures ranging from -10.degree. C. to 100.degree. C.) that is
no more than 5% different that the tan delta at 0.degree. C. and
50.degree. C. of the comparative rubber composition.
14. A method according to claim 13, wherein the amount of sulfur in
the cure package is 1.2 to 4 phr and the amount of accelerator in
the cure package is 1.05 to 3 phr.
15. A method according to claim 13, wherein the at least one
conjugated diene monomer containing polymer or copolymer contains
at least one monomer selected from the group consisting of
1,3-butadiene, isoprene, 1,3-pentadiene, 1,3-hexadiene,
2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene,
2-methyl-1,3-pentadiene, 3-methyl-1,3-pentadiene,
4-methyl-1,3-pentadiene and 2,4-hexadiene; and optionally at least
one monomer selected from the group consisting of styrene,
.alpha.-methyl styrene, p-methylstyrene, o-methylstyrene,
p-butylstyrene and vinylnaphthalene.
16. A method according to claim 13, wherein the cured guayule
rubber composition has a max stress at break, a 300% Mpa and an
elongation at break that is no more than +/-10% as compared to a
comparative rubber composition that contains Hevea natural rubber
instead of guayule natural rubber.
17. A method according to claim 13, wherein the cured guayule
rubber composition has a max stress at break, a 300% Mpa and an
elongation at break that is no more than +/-5% as compared to a
comparative rubber composition that contains Hevea natural rubber
instead of guayule natural rubber.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 16/564,058, filed Sep. 9, 2019 and assigned
U.S. Pat. No. 10,875,989, which is a continuation of U.S. patent
application Ser. No. 15/894,278, filed Feb. 12, 2018, which issued
on Sep. 10, 2019 under U.S. Pat. No. 10,407,564, which is a
continuation of U.S. patent application Ser. No. 13/787,644, filed
Mar. 6, 2013, which issued on Feb. 13, 2018 under U.S. Pat. No.
9,890,268, which claims priority to and any other benefit of U.S.
Provisional Patent Application Ser. No. 61/607,494, filed Mar. 6,
2012, and entitled "CURED GUAYULE RUBBER CONTAINING COMPOSITIONS
AND METHODS FOR PREPARING SAME," the entire disclosures of which
are incorporated by reference herein.
BACKGROUND
[0002] Natural rubber sourced from the guayule shrub is well-known
to contain a significant amount of resin. The common understanding
among those skilled in the art has been that the resin has
detrimental effects on rubber compositions for use in tire-related
components and to attempt to remove as much of the resin as
possible.
SUMMARY
[0003] Provided herein are cured guayule-rubber containing
compositions which exhibit strain induced crystallization and
methods for preparing those compositions. It was surprisingly found
that cured rubber compositions containing guayule natural rubber
with 2.5-4 weight % resin exhibited strain induced crystallization
when the cure package was adjusted to increase the amount of sulfur
and accelerator but without any need to increase the amount of
stearic acid. This discovery was contrary to previous teachings
which were directed at removing as much resin as possible from the
guayule natural rubber (thereby increasing processing time and cost
in the guayule natural rubber production process) in an attempt to
limit crack growth propagation in rubber compositions containing
the guayule natural rubber. Because the raw plant matter from the
guayule shrub can contain a considerable amount of resin that is
difficult to separate from the natural rubber also contained
therein, the ability to use guayule natural rubber containing as
much as 4 weight % resin has the potential to decrease processing
complexity and costs associated with isolation of natural rubber
from the guayule shrub.
[0004] In a first embodiment is provided a cured rubber composition
comprising: (a) 100 phr of guayule natural rubber, where the
guayule natural rubber contains 2.5-4 weight % resin and (b) 5-100
phr of at least one filler selected from the group consisting of
carbon black and silica. The cure package used to prepare the cured
rubber composition comprises: (i) 1.2 to 4 phr sulfur, (ii) 0.5 to
5 phr of at least one antioxidant, (iii) 0.5 to 5 phr zinc oxide,
(iv) 0.5 to 4 phr stearic acid, (iv) 1.05 to 3 phr of at least one
accelerator and the cured rubber composition exhibits strain
induced crystallization (as can be observed by X-ray
diffraction).
[0005] In a second embodiment is provided a cured rubber
composition comprising: (a) 10-90 phr of guayule natural rubber,
where the guayule natural rubber contains 2.5-4 weight % resin, (b)
90-10 phr of at least one conjugated diene monomer containing
polymer or copolymer, and (c) 5-100 phr of at least one filler
selected from the group consisting of carbon black and silica. The
cure package used to prepared the cured rubber composition
comprises: (i) 1.2 to 4 phr sulfur, (ii) 0.5 to 5 phr of at least
one antioxidant (standard), (iii) 0.5 to 5 phr zinc oxide, (iv) 0.5
to 4 phr stearic acid, (iv) 1.05 to 3 phr of at least one
accelerator and the cured rubber composition exhibits strain
induced crystallization as can be observed by X-ray
diffraction.
[0006] In a third embodiment is provided a method of providing a
cured guayule natural rubber containing composition with strain
induced crystallization. In the method, a rubber composition is
utilized that contains (i) 100 phr of guayule natural rubber that
contains 2.5-4 weight % resin and (ii) 5-100 phr of at least one
filler selected from the group consisting of carbon black and
silica and a cure package is utilized that contains (i) 1.2 to 4
phr sulfur, (ii) 0.5 to 5 phr of at least one antioxidant, (iii)
0.5 to 5 phr zinc oxide, (iv) 0.5 to 4 phr stearic acid, (iv) 1.05
to 3 phr of at least one accelerator to produce a cured guayule
natural rubber containing composition. The cured guayule natural
rubber containing composition exhibits strain induced
crystallization (as evidenced by X-ray diffraction).
[0007] In a fourth embodiment is provided a method of providing a
cured guayule natural rubber containing composition with strain
induced crystallization. In the method, a rubber composition is
utilized that contains (i) 1-90 phr of guayule natural rubber that
contains 2.5-4 weight % resin, (ii) 90-10 phr of at least one
conjugated diene monomer containing polymer or copolymer, and (iii)
5-100 phr of at least one filler selected from the group consisting
of carbon black and silica and a cure package is utilized that
contains (i) 1.2 to 4 phr sulfur, (ii) 0.5 to 5 phr of at least one
antioxidant, (iii) 0.5 to 5 phr zinc oxide, (iv) 0.5 to 4 phr
stearic acid, (iv) 1.05 to 3 phr of at least one accelerator to
produce a cured guayule natural rubber containing composition. The
cured guayule natural rubber containing composition exhibits strain
induced crystallization (as evidenced by X-ray diffraction).
[0008] In a fifth embodiment is provided a method of providing a
cured guayule natural rubber containing composition with strain
induced crystallization comprising: utilizing a rubber mixture
comprising (i) 100 phr of guayule natural rubber that contains
2.5-4 weight % resin and (ii) 5-100 phr of at least one filler
selected from the group consisting of carbon black and silica, and
curing the rubber mixture by increasing the amount of sulfur in the
cure package by 30-300% and increasing the amount of accelerator by
30-200% each as compared to a comparative rubber composition that
contains Hevea natural rubber instead of guayule natural rubber.
The cured guayule natural rubber containing composition and the
comparative rubber composition both exhibit strain induced
crystallization (as can be observed by X-ray diffraction) and have
a max stress at break, a 300% MPa and an elongation at break that
are no more than +/-15% different. The tan delta at 0.degree. C.
and 50.degree. C. (obtained from temperature sweep experiments
conducted with a frequency of 31.4 rad/sec using 0.5% strain for
temperatures ranging from -100.degree. C. to -10.degree. C., and
with 2% strain for temperatures ranging from -10.degree. C. to
100.degree. C.) of the cured guayule natural rubber containing
composition is no more than 5% different that the tan delta at
0.degree. C. and 50.degree. C. of the comparative rubber
composition.
[0009] In a sixth embodiment is provided a method of providing a
cured guayule natural rubber containing composition with strain
induced crystallization comprising: utilizing a rubber mixture
comprising (i) 1-90 phr of guayule natural rubber that contains
2.5-4 weight % resin, (ii) 90-10 phr of at least one conjugated
diene monomer containing polymer or copolymer, and (iii) 5-100 phr
of at least one filler selected from the group consisting of carbon
black and silica, and curing the rubber mixture by increasing the
amount of sulfur in the cure package by 30-300% and increasing the
amount of accelerator by 30-200% each as compared to a comparative
rubber composition that contains Hevea natural rubber instead of
guayule natural rubber. The cured guayule natural rubber containing
composition and the comparative rubber composition both exhibit
strain induced crystallization (as can be observed by X-ray
diffraction) and have a max stress at break, a 300% MPa and an
elongation at break that are no more than +/-15% different. The tan
delta at 0.degree. C. and 50.degree. C. (obtained from temperature
sweep experiments conducted with a frequency of 31.4 rad/sec using
0.5% strain for temperatures ranging from -100.degree. C. to
-10.degree. C., and with 2% strain for temperatures ranging from
-10.degree. C. to 100.degree. C.) of the cured guayule natural
rubber containing composition is no more than 5% different that the
tan delta at 0.degree. C. and 50.degree. C. of the comparative
rubber composition.
DESCRIPTION OF THE FIGURES
[0010] FIG. 1 is a graph showing tensile properties of rubber
compositions containing Hevea natural rubber and varying amounts of
guayule-sourced resin at various elongations and at break.
[0011] FIG. 2 is a graph showing crosslink density of rubber
compositions.
[0012] FIG. 3 is a graph showing tensile properties of rubber
compositions containing either Hevea natural rubber with varying
amounts of curatives or guayule natural rubber with varying amounts
of resin at various elongations and at break.
[0013] FIG. 4 is a graph showing crack growth resistance for rubber
compositions containing either Hevea natural rubber with varying
amounts of curatives or guayule natural rubber with varying amounts
of resin.
[0014] FIG. 5 shows the results of x-ray diffraction analysis of
guayule natural rubber containing compositions with either 1% or
2.5% resin versus Hevea natural rubber and is evidence of the
presence of strain induced crystallization in the guayule natural
rubber containing compositions.
DETAILED DESCRIPTION
[0015] Provided herein are cured guayule-rubber containing
compositions which exhibit strain induced crystallization and
methods for preparing those compositions.
Definitions
[0016] The terminology as set forth herein is for description of
the embodiments only and should not be construed as limiting the
invention as a whole.
[0017] As used herein the term "resin" means the naturally
occurring non-rubber chemical entities present in non-Hevea plants
such as guayule shrubs matter. These chemical entities include, but
are not limited to, resins (such as terpenes), fatty acids,
proteins, and inorganic materials, and include both polar and
non-polar moieties.
Rubber Compositions and Methods
[0018] In a first embodiment is provided a cured rubber composition
comprising: (a) 100 phr of guayule natural rubber, where the
guayule natural rubber contains 2.5-4 weight % resin and (b) 5-100
phr of at least one filler selected from the group consisting of
carbon black and silica. The cure package used to prepare the cured
rubber composition comprises: (i) 1.2 to 4 phr sulfur, (ii) 0.5 to
5 phr of at least one antioxidant, (iii) 0.5 to 5 phr zinc oxide,
(iv) 0.5 to 4 phr stearic acid, (iv) 1.05 to 3 phr of at least one
accelerator and the cured rubber composition exhibits strain
induced crystallization (as can be observed by X-ray
diffraction).
[0019] In a second embodiment is provided a cured rubber
composition comprising: (a) 10-90 phr of guayule natural rubber,
where the guayule natural rubber contains 2.5-4 weight % resin, (b)
90-10 phr of at least one conjugated diene monomer containing
polymer or copolymer, and (c) 5-100 phr of at least one filler
selected from the group consisting of carbon black and silica. The
cure package used to prepared the cured rubber composition
comprises: (i) 1.2 to 4 phr sulfur, (ii) 0.5 to 5 phr of at least
one antioxidant (standard), (iii) 0.5 to 5 phr zinc oxide, (iv) 0.5
to 4 phr stearic acid, (iv) 1.05 to 3 phr of at least one
accelerator and the cured rubber composition exhibits strain
induced crystallization as can be observed by X-ray
diffraction.
[0020] In a third embodiment is provided a method of providing a
cured guayule natural rubber containing composition with strain
induced crystallization. In the method, a rubber composition is
utilized that contains (i) 100 phr of guayule natural rubber that
contains 2.5-4 weight % resin and (ii) 5-100 phr of at least one
filler selected from the group consisting of carbon black and
silica and a cure package is utilized that contains (i) 1.2 to 4
phr sulfur, (ii) 0.5 to 5 phr of at least one antioxidant, (iii)
0.5 to 5 phr zinc oxide, (iv) 0.5 to 4 phr stearic acid, (iv) 1.05
to 3 phr of at least one accelerator to produce a cured guayule
natural rubber containing composition. The cured guayule natural
rubber containing composition exhibits strain induced
crystallization (as evidenced by X-ray diffraction).
[0021] In a fourth embodiment is provided a method of providing a
cured guayule natural rubber containing composition with strain
induced crystallization. In the method, a rubber composition is
utilized that contains (i) 1-90 phr of guayule natural rubber that
contains 2.5-4 weight % resin, (ii) 90-10 phr of at least one
conjugated diene monomer containing polymer or copolymer, and (iii)
5-100 phr of at least one filler selected from the group consisting
of carbon black and silica and a cure package is utilized that
contains (i) 1.2 to 4 phr sulfur, (ii) 0.5 to 5 phr of at least one
antioxidant, (iii) 0.5 to 5 phr zinc oxide, (iv) 0.5 to 4 phr
stearic acid, (iv) 1.05 to 3 phr of at least one accelerator to
produce a cured guayule natural rubber containing composition. The
cured guayule natural rubber containing composition exhibits strain
induced crystallization (as evidenced by X-ray diffraction).
[0022] In a fifth embodiment is provided a method of providing a
cured guayule natural rubber containing composition with strain
induced crystallization comprising: utilizing a rubber mixture
comprising (i) 100 phr of guayule natural rubber that contains
2.5-4 weight % resin and (ii) 5-100 phr of at least one filler
selected from the group consisting of carbon black and silica, and
curing the rubber mixture by increasing the amount of sulfur in the
cure package by 30-300% and increasing the amount of accelerator by
30-200% each as compared to a comparative rubber composition that
contains Hevea natural rubber instead of guayule natural rubber.
The cured guayule natural rubber containing composition and the
comparative rubber composition both exhibit strain induced
crystallization (as can be observed by X-ray diffraction) and have
a max stress at break, a 300% MPa and an elongation at break that
are no more than +/-15% different. The tan delta at 0.degree. C.
and 50.degree. C. (obtained from temperature sweep experiments
conducted with a frequency of 31.4 rad/sec using 0.5% strain for
temperatures ranging from -100.degree. C. to -10.degree. C., and
with 2% strain for temperatures ranging from -10.degree. C. to
100.degree. C.) of the cured guayule natural rubber containing
composition is no more than 5% different that the tan delta at
0.degree. C. and 50.degree. C. of the comparative rubber
composition.
[0023] In a sixth embodiment is provided a method of providing a
cured guayule natural rubber containing composition with strain
induced crystallization comprising: utilizing a rubber mixture
comprising (i) 1-90 phr of guayule natural rubber that contains
2.5-4 weight % resin, (ii) 90-10 phr of at least one conjugated
diene monomer containing polymer or copolymer, and (iii) 5-100 phr
of at least one filler selected from the group consisting of carbon
black and silica, and curing the rubber mixture by increasing the
amount of sulfur in the cure package by 30-300% and increasing the
amount of accelerator by 30-200% each as compared to a comparative
rubber composition that contains Hevea natural rubber instead of
guayule natural rubber. The cured guayule natural rubber containing
composition and the comparative rubber composition both exhibit
strain induced crystallization (as can be observed by X-ray
diffraction) and have a max stress at break, a 300% MPa and an
elongation at break that are no more than +/-15% different. The tan
delta at 0.degree. C. and 50.degree. C. (obtained from temperature
sweep experiments conducted with a frequency of 31.4 rad/sec using
0.5% strain for temperatures ranging from -100.degree. C. to
-10.degree. C., and with 2% strain for temperatures ranging from
-10.degree. C. to 100.degree. C.) of the cured guayule natural
rubber containing composition is no more than 5% different that the
tan delta at 0.degree. C. and 50.degree. C. of the comparative
rubber composition.
[0024] In certain embodiments according to the first and fourth
embodiments described herein, the cured rubber composition has a
max stress at break, a 300% MPa and an elongation at break that is
no more than +/-15% as compared to a comparative rubber composition
that contains Hevea natural rubber instead of guayule natural
rubber. (The comparative rubber composition containing Hevea rubber
has all other ingredients the same as the composition containing
guayule natural rubber but simply replaces the guayule natural
rubber with the same amount of Hevea natural rubber. In addition,
the methods used to mix the ingredients of the Hevea rubber
composition and the guayule natural rubber composition are the
same.) In other embodiments according to the first and fourth
embodiments described herein, the cured rubber composition has a
max stress at break, a 300% MPa and an elongation at break that is
no more than +/-10% as compared to a comparative rubber composition
that contains Hevea natural rubber instead of guayule natural
rubber. In yet other embodiments according to the first and fourth
embodiments described herein, the cured rubber composition has a
max stress at break, a 300% MPa and an elongation at break that is
no more than +/-5% as compared to a comparative rubber composition
that contains Hevea natural rubber instead of guayule natural
rubber.
[0025] It is specifically contemplated that a tire component may be
made from any of the rubber formulations according to the first and
fourth embodiments disclosed herein. Non-limiting examples of tire
components that may be made from the rubber formulations according
to the first and fourth embodiments disclosed herein include
treads, sidewalls and body skim plies.
[0026] In certain embodiments according to the second and fifth
embodiments disclosed herein, the cured rubber composition has a
max stress at break, a 300% MPa and an elongation at break that is
no more than +/-15% as compared to a comparative rubber composition
that contains Hevea natural rubber instead of guayule natural
rubber. (The comparative rubber composition containing Hevea rubber
has all other ingredients the same as the composition containing
guayule natural rubber but simply replaces the guayule natural
rubber with the same amount of Hevea natural rubber. In addition,
the methods used to mix the ingredients of the Hevea rubber
composition and the guayule natural rubber composition are the
same.) In other embodiments according to the second and fifth
embodiments described herein, the cured rubber composition has a
max stress at break, a 300% MPa and an elongation at break that is
no more than +/-10% as compared to a comparative rubber composition
that contains Hevea natural rubber instead of guayule natural
rubber. In yet other embodiments according to the second and fifth
embodiments described herein, the cured rubber composition has a
max stress at break, a 300% MPa and an elongation at break that is
no more than +/-5% as compared to a comparative rubber composition
that contains Hevea natural rubber instead of guayule natural
rubber.
[0027] In certain embodiments according to the third and sixth
embodiments disclosed herein, the cured rubber composition has a
max stress at break, a 300% MPa and an elongation at break that is
no more than +/-10% as compared to a comparative rubber composition
that contains Hevea natural rubber instead of guayule natural
rubber. In yet other embodiments according to the third and sixth
embodiments described herein, the cured rubber composition has a
max stress at break, a 300% MPa and an elongation at break that is
no more than +/-5% as compared to a comparative rubber composition
that contains Hevea natural rubber instead of guayule natural
rubber.
[0028] In certain embodiments according to the fourth, fifth and
sixth embodiments disclosed herein, the at least one conjugated
diene monomer containing polymer or copolymer is selected from the
group consisting of 1,3-butadiene, styrene-butadiene copolymer and
polyisoprene. In other embodiments according to the third and sixth
embodiments disclosed herein, the at least one conjugated diene
monomer containing polymer or copolymer contains at least one
monomer selected from the group consisting of 1,3-butadiene,
isoprene, 1,3-pentadiene, 1,3-hexadiene,
2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene,
2-methyl-1,3-pentadiene, 3-methyl-1,3-pentadiene,
4-methyl-1,3-pentadiene and 2,4-hexadiene; and optionally at least
one monomer selected from the group consisting of styrene,
.alpha.-methyl styrene, p-methylstyrene, o-methylstyrene,
p-butylstyrene and vinylnaphthalene.
[0029] In certain embodiments according to the first-sixth
embodiments disclosed herein, the silica utilized (silicon dioxide)
includes wet-process, hydrated silica produced by a chemical
reaction in water, and precipitated as ultra-fine spherical
particles. In certain of the foregoing embodiments, the silica has
a surface area of about 32 to about 400 m.sup.2/g, in another
embodiment about 100 to about 250 m2/g, and in yet another
embodiment, about 150 to about 220 m.sup.2/g. The pH of the silica
filler in certain of the foregoing embodiments is about 5.5 to
about 7 and in another embodiment about 5.5 to about 6.8.
Commercially available silicas include Hi-Sil.TM. 215, Hi-Sil.TM.
233, Hi-Sil.TM. 255LD, and Hi-Sil.TM. 190 (PPG Industries;
Pittsburgh, Pa.), Zeosil.TM. 1165MP and 175GRPlus (Rhodia),
Vulkasil.TM. (Bary AG), Ultrasil.TM. VN2, VN3 (Degussa), and
HuberSil.TM. 8745 (Huber).
[0030] In certain embodiments according to the first-sixth
embodiments disclosed herein, the carbon black(s) utilized may
include any of the commonly available, commercially-produced carbon
blacks. These include those having a surface area (EMSA) of at
least 20 m.sup.2/gram and in other embodiments at least 35
m.sup.2/gram up to 200 m.sup.2/gram or higher. Surface area values
include those determined by ASTM test D-1765 using the
cetyltrimethyl-ammonium bromide (CTAB) technique. Among the useful
carbon blacks are furnace black, channel blacks and lamp blacks.
More specifically, examples of the carbon blacks include super
abrasion furnace (SAF) blacks, high abrasion furnace (HAF) blacks,
fast extrusion furnace (FEF) blacks, fine furnace (FF) blacks,
intermediate super abrasion furnace (ISAF) blacks, semi-reinforcing
furnace (SRF) blacks, medium processing channel blacks, hard
processing channel blacks and conducting channel blacks. Other
carbon blacks that may be utilized include acetylene blacks.
Mixtures of two or more of the above blacks can be used. Exemplary
carbon blacks include those bearing ASTM designation (D-1765-82a)
N-110, N-220, N-339, N-330, N-351, N-550, and N-660. In one or more
embodiments, the carbon black may include oxidized carbon
black.
[0031] In certain embodiments according to the first-sixth
embodiments disclosed herein, other conventional rubber additives
may also be added to the rubber compositions. These include, for
example, process oils, plasticizers, anti-degradants such as
antioxidants and anti-ozonants, curing agents and the like.
[0032] Typically, process oils are added to tread rubber
compositions as a softener. Non-limiting examples of process oils
used in the tread rubber compositions disclosed herein include
paraffinic, naphthenic, and aromatic process oils, and the like. In
one or more embodiments according to the first-sixth embodiments
disclosed herein, the process oil is an aromatic process oil. In
other embodiments, the process oil is a low polycyclic aromatic
content ("low PCA") oil containing less than 2%. Other useful oils
include those containing less than 3 wt %, less than 2 wt % or less
than 1 wt % of polycyclic aromatic compounds (as measured by IP346)
("low PCA oils"). Such low PCA oils are increasingly used in an
effort to reduce the amount of polycyclic aromatic compounds
present in rubbers used in tires. Commercially available low PCA
oils include various naphthenic oils, mild extraction solvates
(MES) and treated distillate aromatic extracts (TDAE).
[0033] In certain embodiments according to the first-sixth
embodiments disclosed herein, where the rubber compositions are
used for treads, the rubber compositions preferably contain between
1 and 100 phr process oil. In one or more embodiments, the amount
of process oil is between 2 and 100 phr; in other embodiments,
between 1 and 50 phr; in others, between 2 and 50 phr. In still
other embodiments, the amount of process oil is between 1 and 20
phr; in others, between 2 and 20 phr; in others, between 1 and 10
phr; in still others, between 2 and 10 phr.
[0034] When forming a tread rubber composition, generally all
ingredients may be mixed with standard equipment such as, e.g.,
Banbury or Brabender mixers. Typically, mixing occurs in two or
more stages. During the first stage (also known as the masterbatch
stage), mixing typically is begun at temperatures of about
100.degree. to about 130.degree. C. and increases until a so-called
drop temperature, typically about 165.degree. C., is reached.
[0035] Where a rubber composition includes fillers other than (or
in addition to) carbon black, a separate re-mill stage often is
employed for separate addition of the other fillers. This stage
often is performed at temperatures similar to, although often
slightly lower than, those employed in the masterbatch stage, i.e.,
ramping from about 90.degree. C. to a drop temperature of about
150.degree. C. For purposes of this application, the term
"masterbatch" means the composition that is present during the
masterbatch stage or the composition as it exists during any
re-mill stage, or both.
[0036] Curatives, accelerators, etc., are generally added at a
final mixing stage. To avoid undesirable scorching and/or premature
onset of vulcanization, this mixing step often is done at lower
temperatures, e.g., starting at about 60.degree. to about
65.degree. C. and not going higher than about 105.degree. to about
110.degree. C. For purposes of this application, the term "final
batch" means the composition that is present during the final
mixing stage.
[0037] As previously discussed above, with respect to the first,
second, fourth and fifth embodiments, the cured rubber composition
or rubber mixture utilizes a cure package comprising 1.2-4 phr
sulfur, 0.5 to 5 phr of at least one antioxidant, 0.5 to 5 phr of
zinc oxide, 0.5-4 phr of stearic acid, and 1.05 to 3 phr of at
least one accelerator. As also discussed above, with respect to the
third and sixth embodiments, the amount of sulfur and accelerator
in the cured guayule rubber containing composition is increased by
30-300% and 30-200% as compared to a comparative rubber composition
that contains Hevea natural rubber instead of guayule natural
rubber, respectively, in order to compensate for the resin content
of the guayule natural rubber. As used herein, a 100% increase
should be understood to be a doubling in amount. In certain
embodiments of the third and sixth embodiments disclosed herein,
the amount of sulfur in the cured guayule rubber composition is
increased by 30-200%. As a non-limiting example of the increased
amount of sulfur and accelerator, if the amount of sulfur and
accelerator in the comparative rubber composition was 1.3 and 0.8,
respectively, the amount of sulfur and accelerator in the guayule
rubber containing composition could be 1.7-2.6 and 1.0-1.6,
respectively.
[0038] Subsequently, the compounded mixture is processed (e.g.,
milled) into sheets prior to being formed into any of a variety of
components and then vulcanized, which typically occurs at about
5.degree. to about 15.degree. C. higher than the highest
temperatures employed during the mixing stages, most commonly about
170.degree. C.
Examples
[0039] The following examples are for purposes of illustration only
and are not intended to limit the scope of the claims which are
appended hereto.
[0040] Unless otherwise defined, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which the technology of this
application belongs. While the present application has been
illustrated by the description of embodiments thereof, and while
the embodiments have been described in considerable detail, it is
not the intention of the applicants to restrict or in any way limit
the scope of the appended claims to such detail. Additional
advantages and modifications will readily appear to those skilled
in the art. Therefore, the application, in its broader aspects, is
not limited to the specific details, the representative
embodiments, and illustrative examples shown and described.
Accordingly, departures may be made from such details without
departing from the spirit or scope of the applicant's general
inventive concept.
[0041] In order to investigate the effect of various resin levels
on the physical properties of cured guayule natural rubber
containing rubber compositions, rubber formulations containing 100
phr of guayule natural rubber along with varying amounts of resin
were prepared according to the formulas provided below in Table 1.
The resins that were added were obtained from material that
resulted from other work done on isolating natural rubber from
guayule shrub using organic solvent based processes. This material
represented the dried fraction (i.e., solvent removed) of material
isolated in the polar organic solvent phase from the process. The
amounts of resin added are weight % based upon the total weight of
the natural rubber ((in other words, the stock indicated as
containing 1% resin utilized natural rubber that contained 1 weight
% rubber so that the rubber was 99 parts rubber and 1 part resin).
The same convention is used in Table 2 below for the Yulex 1% and
2.5% rubbers.
TABLE-US-00001 TABLE 1 Ingredient/Amount (in phr) Stock A Stock B
Stock C Stock D Stock E Stock F Rubber 100 (#4RSS).sup.1 100
(Yulex).sup.2 100 (Yulex) 100 (Yulex) 100 (Yulex) 100 (Yulex)
Amount of resin 0 1.0 2.0 4.0 12.0 (weight %) Carbon black 50 50 50
50 50 50 Stearic acid 2 2 2 2 2 2 Antioxidant (6PPD) 1 1 1 1 1 1
Zinc oxide 3 3 3 3 3 3 Accelerator (TBBS).sup.3 0.8 0.8 0.8 0.72
0.64 0.56 Sulfur 1.3 1.3 1.3 1.17 1.04 0.91 .sup.1Hevea rubber in
the form of #4 rubber smoked sheet (RSS) .sup.2Yulex guayule rubber
containing approximately 1 weight % resin
.sup.32-(tert-butylaminothio)benzothiazole
[0042] After formulating, samples of each stock were subjected to
testing to determine the physical properties of the resulting
stocks. Data obtained is illustrated in FIGS. 1 and 2. As can be
seen from FIGS. 1 and 2, the physical properties of the rubber
compositions generally decrease with an increasing amount of resin
(compare stocks A and B to control stock C). FIG. 1 also shows that
a rubber composition containing guayule natural rubber with
approximately 0% resin still shows lower modulus at 300% than
#4RSS. Notably, FIG. 1 also shows that the stock containing guayule
rubber with approximately 0% resin is still lower than those rubber
compositions containing #4RSS. FIG. 2 shows cross link density of
the guayule rubber containing compositions with 1% and 2.5% resin
to be essentially equivalent.
[0043] In order to investigate the effect of the cure package
components upon physical rubber properties, rubber formulations
containing 100 phr of either guayule natural rubber of Hevea
natural rubber were prepared according to the formulas provided
below in Table 2. As can be seen from Table 2, the amount of sulfur
and accelerator was adjusted in Hevea-containing stocks D, E and F
to be 90%, 80% and 70% of the amount in control stock C. Guayule
natural rubber obtained from Yulex Corporation was used in Stocks A
and B.
TABLE-US-00002 TABLE 2 Ingredient/Amount (in phr) Stock A Stock B
Stock C Stock D Stock E Stock F Rubber 100 (Yulex 100 (Yulex 100
(RSS).sup.3 100 (RSS).sup.3 100 (RSS).sup.3 100 (RSS).sup.3
2.5%).sup.1 1.0%).sup.2 Carbon black 50 50 50 50 50 50 Stearic acid
2 2 2 2 2 2 Antioxidant (6PPD) 1 1 1 1 1 1 Zinc oxide 3 3 3 3 3 3
Accelerator (TBBS).sup.4 0.8 0.8 0.8 0.72 0.64 0.56 Sulfur 1.3 1.3
1.3 1.17 1.04 0.91 .sup.1Yulex guayule rubber containing
approximately 2.5 weight % resin .sup.2Yulex guayule rubber
containing approximately 1 weight % resin .sup.3Hevea rubber in the
form of #4 rubber smoked sheet (RSS)
.sup.42-(tert-butylaminothio)benzothiazole
[0044] After formulating, samples of each stock were subjected to
testing to determine the physical properties of the resulting
stocks. Data obtained is reported in Table 3 below and illustrated
in FIGS. 3 and 4. As can be seen from FIGS. 3 and 4, the physical
properties of the rubber compositions can be manipulated by
adjusting the cure package to reduce the amount of sulfur and
accelerator. Based upon the data obtained from the experiments done
using varying amounts of resin content in guayule natural rubber
containing compositions and adjusting the cure package in Hevea
natural rubber containing compositions, it is postulated that the
physical properties of guayule natural rubber containing
compositions can be adjusted by changing the cure package to
increase the amounts of sulfur and accelerator by 30-300% and
30-200%, respectively, (as further detailed herein, including in
the claims).
TABLE-US-00003 TABLE 3 Yulex~2.5% Yulex~1.0% #4RSS #4RSS (w/90%)
#4RSS (w/80%) #4RSS (w/70%) CMPD MOONEY (130.degree. C., FINAL) MS1
+ 4 (MU): 48.8 56.5 >200 46.0 59.7 57.3 ML1 + 4 (MU): 47.0 59.5
MDR2000 (145.degree. C., FINAL) ML (kg cm): 3.4 3.8 4.0 4.1 3.8 3.6
MH (kg cm): 16.0 16.2 17.6 17.5 15.0 13.5 MH - ML (kg cm): 12.6
12.4 13.6 13.5 11.3 9.9 ts2 (min): 5.7 5.9 5.7 5.9 6.6 7.2 ts5
(min): 6.9 7.2 6.9 7.0 8.3 9.5 t50 (min): 7.5 7.7 7.7 7.8 8.7 9.4
t90 (min): 12.5 13.2 12.7 13.1 14.6 15.8 t100 (min): 23.7 24.4 22.5
22.8 24.8 26.7 MICRO DUMBELL TENSILE (23.degree. C., FINAL, UNAGED)
Max. Stress (MPa) 28.50 30.30 29.60 29.10 29.20 28.10 100% (MPa)
3.21 3.46 4.35 4.29 3.86 3.46 200% (MPa) 9.45 10.45 13.13 12.50
11.62 10.63 300% (MPa) 16.89 18.79 23.00 21.48 20.20 18.91 Brk
Strain % 474 457 380 401 429 434 Toughness (MPa) 60.73 62.04 49.79
52.95 57.59 55.06 LAMBOURN (MULTI-PT, 65%) Avg. Wt. Loss: 0.1231
0.1214 0.1342 0.1284 0.1213 0.1172 Avg. Intercept: 7.9433 8.0111
8.1611 8.1738 8.0729 8.0070 Avg. Slope: -0.0017 -0.0016 -0.0018
-0.0017 -0.0016 -0.0016 Avg. Correlation: -0.999 -0.999 -0.999
-0.998 -0.999 -0.998
[0045] To the extent that the term "includes" or "including" is
used in the specification or the claims, it is intended to be
inclusive in a manner similar to the term "comprising" as that term
is interpreted when employed as a transitional word in a claim.
Furthermore, to the extent that the term "or" is employed (e.g., A
or B) it is intended to mean "A or B or both." When the applicants
intend to indicate "only A or B but not both" then the term "only A
or B but not both" will be employed. Thus, use of the term "or"
herein is the inclusive, and not the exclusive use. See Bryan A.
Garner, A Dictionary of Modern Legal Usage 624 (2d. Ed. 1995).
Also, to the extent that the terms "in" or "into" are used in the
specification or the claims, it is intended to additionally mean
"on" or "onto." Furthermore, to the extent the term "connect" is
used in the specification or claims, it is intended to mean not
only "directly connected to," but also "indirectly connected to"
such as connected through another component or components.
[0046] While the present application has been illustrated by the
description of embodiments thereof, and while the embodiments have
been described in considerable detail, it is not the intention of
the applicants to restrict or in any way limit the scope of the
appended claims to such detail. Additional advantages and
modifications will readily appear to those skilled in the art.
Therefore, the application, in its broader aspects, is not limited
to the specific details, the representative apparatus, and
illustrative examples shown and described. Accordingly, departures
may be made from such details without departing from the spirit or
scope of the applicant's general inventive concept.
* * * * *