U.S. patent application number 10/335922 was filed with the patent office on 2003-07-03 for rubber composition.
This patent application is currently assigned to The Yokohama Rubber Co., Ltd.. Invention is credited to Kawazoe, Masayuki, Kawazura, Tetsuji, Nakamura, Masao.
Application Number | 20030125461 10/335922 |
Document ID | / |
Family ID | 26391160 |
Filed Date | 2003-07-03 |
United States Patent
Application |
20030125461 |
Kind Code |
A1 |
Kawazura, Tetsuji ; et
al. |
July 3, 2003 |
Rubber composition
Abstract
A rubber composition comprising (i) an incompatible polymer
blend of at least two diene rubbers selected from rubbers
containing a conjugated diene and, optionally, an aromatic vinyl
monomer and forming two polymer phases (A) and (B), and (ii) 0.1 to
20 parts by weight, based upon 100 parts by weight of the total
polymer component including the block copolymer, of a block
copolymer having at least two mutually incompatible blocks (a) and
(b), wherein the block (a) is compatible with the polymer phase (A)
and incompatible with the polymer phase (B) and the block (b) is
compatible with the polymer phase (B) and incompatible with the
polymer phase (A), and composed of a conjugated diene and,
optionally, an aromatic vinyl monomer, and wherein the molecular
weights of the polymers forming the polymer phases (A) and (B)
satisfy the specified equations (I) and (II) mentioned in the
specification.
Inventors: |
Kawazura, Tetsuji;
(Hiratsuka-shi, JP) ; Kawazoe, Masayuki;
(Hiratsuka-shi, JP) ; Nakamura, Masao;
(Kawasaki-shi, JP) |
Correspondence
Address: |
ARENT FOX KINTNER PLOTKIN & KAHN
1050 CONNECTICUT AVENUE, N.W.
SUITE 400
WASHINGTON
DC
20036
US
|
Assignee: |
The Yokohama Rubber Co.,
Ltd.
|
Family ID: |
26391160 |
Appl. No.: |
10/335922 |
Filed: |
January 3, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10335922 |
Jan 3, 2003 |
|
|
|
09506443 |
Feb 18, 2000 |
|
|
|
Current U.S.
Class: |
525/88 |
Current CPC
Class: |
C08L 9/06 20130101; C08L
21/00 20130101; C08L 7/00 20130101; C08L 21/00 20130101; C08L
2666/02 20130101; C08L 2666/02 20130101; C08L 2666/04 20130101;
C08L 9/06 20130101; C08L 2666/02 20130101; C08L 53/02 20130101;
C08L 9/00 20130101; B60C 1/0016 20130101; C08L 53/02 20130101; B60C
1/0025 20130101; B60C 1/00 20130101; C08L 7/00 20130101 |
Class at
Publication: |
525/88 |
International
Class: |
C08L 053/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 26, 1999 |
JP |
11050710 |
Feb 15, 2000 |
JP |
2000-41396 |
Claims
1. A method for producing a rubber composition having an improved
abrasion resistance and tensile strength by controlling a molecular
weight distribution of a rubber composition comprising (i) an
incompatible polymer blend comprising at least two diene rubbers
selected from the group consisting of rubbers containing at least
one conjugated diene monomer and, optionally, at least one aromatic
vinyl monomer and forming two incompatible polymer phases (A) and
(B) and (ii) 0.1 to 20 parts by weight, based upon 100 parts by
weight of the total polymer component including the block
copolymer, of a block copolymer having at least two mutually
incompatible blocks (a) and (b) in which the block (a) is
compatible with the polymer phase (A) and incompatible with the
polymer phase (B) and the block (b) is compatible with the polymer
phase (B) and incompatible with the polymer phase (A), and
comprising at least one conjugated diene monomer and, optionally,
at least one aromatic vinyl monomer, such that the polymers forming
the polymer phases (A) and (B) satisfy the following equations (I)
and (II): Mw.sub.30(A)/Mw(a).ltoreq.1- .2 (I)
Mw.sub.30(B)/Mw(b).ltoreq.1.2 (II) wherein Mw.sub.30(A): a value of
molecular weight corresponding to 30% of the cumulative area when
converting the curve of the distribution of the molecular weight
measured by GPC to the integrated molecular weight curve of the
polymer forming the polymer phase (A), Mw30(B): a value of
molecular weight corresponding to 30% of the cumulative area when
converting the curve of the distribution of the molecular weight
measured by GPC to the integrated molecular weight curve of the
polymer forming the polymer phase (B), Mw(a): weight average
molecular weight of block (a) of block copolymer, and Mw(b): weight
average molecular weight of block (b) of block copolymer.
2. A method as claimed in claim 1, wherein (iii) 5 to 200 parts by
weight, based upon 100 parts by weight of the block copolymer of
polymer (.alpha.) compatible with the block (a) and the polymer
phase (A) and/or polymer (.beta.) compatible with the block (b) and
polymer phase (B) are further blended and the weight average
molecular weights of the polymer (.alpha.) and (.beta.) satisfy the
following equations (III) and (IV):
S.sub..alpha.=Mw(.alpha.)/Mw(a).ltoreq.1.2 (III)
S.sub..beta.=Mw(.beta.)- /Mw(b).ltoreq.1.2 (IV) wherein
Mw(.alpha.): weight average molecular weight of polymer (.alpha.),
Mw(.beta.): weight average molecular weight of polymer (.beta.)
Mw(a): weight average molecular weight of block (a) of block
copolymer, and Mw(b): weight average molecular weight of block (b)
of block copolymer.
3. A method as claimed in claim 1, wherein said diene rubbers are
NR, IR, BR, SBR, SIR and SIBR.
4. A method as claimed in claim 3, wherein a weight ratio of
polymer phase (A)/polymer phase (B) is 90/10 to 10/90.
5. A method as claimed in claim 1, wherein said block copolymer
contains at least two blocks selected from the group consisting of
BR block, SBR block, IR block, SIR block, BIR block and SBIR
block.
6. A method as claimed in claim 5, wherein a weight ratio of block
(a)/block (b) is 80/20 to 20/80.
7. A method as claimed in claim 2, wherein said polymers (.alpha.)
and (.beta.) are selected from IR, BR, SBR and SIBR.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a rubber composition, more
specifically relates to a rubber composition suitable for use for a
tire tread, sidewalls, or other rubber parts and having improved
tensile strength, elongation, and abrasion resistance.
[0003] 2. Description of the Related Art
[0004] In recent years, improvements in various types of
performance have been sought in the rubber compositions for
automobile and other tires etc. Therefore, in tire tread rubber and
the like, several types of polymers have been used by blending
together. However, when these polymers are incompatible with each
other, phase separated interfaces are present. In most cases, these
interfaces become starting points for breakage and are believed to
have a detrimental effect on the tensile strength, tear strength,
abrasion resistance, etc. However, in tire and other rubber
products, since the special process of vulcanization is included,
it is not possible to apply as is the molecular design of the block
copolymer for control of the phase structure as is normally done in
rubber/resin blends or resin/resin blends. Therefore, the problem
of the phase separation interface of rubber/rubber blends has not
been sufficiently studied and no method for solving this problem
had been found yet.
[0005] In the past, the decrease in the breaking strength due to
the incompatibility of polymer blends obtained by blending block
copolymers has not been sufficiently studied. Blending, into a
blend of natural rubber (NR)/polybutadiene rubber (BR), a small
amount of a block copolymer of polybutadiene (BR) and polyisoprene
(IR) has only been described slightly in J. Apply. Polym. Sci., 49
(1993) and RCT. 66 (1993). However, the compositions of the block
copolymers used in these references have insufficient compatibility
with BR, and therefore, are not satisfactory in performance for
practical use. Further, attempts have been made to add cis-BR into
an incompatible polymer blend of cis-BR/SBR so as to improve the
abrasion resistance, but the wet braking performance is decreased,
and therefore, there is a limit to the amount of addition of cis-BR
and there were consequently problems in practical use. In addition,
except for the proposals made by the inventors of the present
invention (Japanese Unexamined Patent Publication (Kokai) Nos.
7-188510, 8-134267, 8-193147, 8-193146, 8-193145, 8-283465,
8-302071, 10-007844, and 10-036465), examples of blending a block
polymer into a rubber composition as a compatibilizing agent have
not been known. The previous proposals by the present inventors did
not clarify the relationship between the rubber component forming
the matrix of the rubber composition and the molecular weight of
the block polymer added. Later study resulted in clarification of
this point and the present invention has been completed.
SUMMARY OF THE INVENTION
[0006] Accordingly, the object of the present invention is to
provide a rubber composition capable of eliminating the,
above-mentioned problems in the prior art and improving the tensile
strength, elongation, abrasion resistance, etc. thereof.
[0007] In accordance with the present invention, there is provided
a rubber composition comprising (i) an incompatible polymer blend
comprising at least two diene rubbers selected from the group
consisting of rubbers containing at least one conjugated diene
monomer and optionally at least one aromatic vinyl monomer, such as
natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber
(BR), styrene-butadiene copolymer rubber (SBR), styrene-isoprene
copolymer rubber (SIR) and styrene-isoprene-butadiene rubber (SIBR)
and forming two incompatible polymer phases (A) and (B) and (ii)
0.1 to 20 parts by weight, based upon 100 parts by weight of the
total polymer component including the block copolymer, of a block
copolymer having at least two mutually incompatible blocks (a) and
(b), the block (a) being compatible with the polymer phase (A) and
being incompatible with the polymer phase (B) and the block (b)
being compatible with the polymer phase (B) and incompatible with
the polymer phase (A), and comprising at least one conjugated diene
monomer (e.g., isoprene, butadiene) and, optionally, at least one
aromatic vinyl monomer (e.g., styrene), wherein the molecular
weights of the polymers forming the polymer phases (A) and (B)
satisfy the following equations (I) and (II):
S.sub.A=Mw.sub.30(A)/Mw(a).ltoreq.1.2 (I)
S.sub.B=Mw.sub.30(B)/Mw(b).ltoreq.1.2 (II)
[0008] wherein
[0009] Mw.sub.30(A): molecular weight of the low molecular weight
portion of the polymer forming the polymer phase (A),
[0010] Mw.sub.30(B): molecular weight of the low molecular weight
portion of the polymer forming the polymer phase (B),
[0011] Mw(a): weight average molecular weight of block (a) of block
copolymer, and
[0012] Mw(b): weight average molecular weight of block (b), of
block copolymer.
[0013] In accordance with the present invention, there is also
provided a rubber composition, wherein 5 to 200 parts by weight,
based upon 100 parts by weight of the block copolymer, of a polymer
(.alpha.) compatible with the block (a) and the polymer phase (A)
and/or a polymer (.beta.) compatible with the block (b) and polymer
phase (B) are further blended and the weight average molecular
weights of the polymers (.alpha.) and (.beta.) satisfy the
following equations (III) and (IV):
S.sub..alpha.=Mw(.alpha.)/Mw(a).ltoreq.1.2 (III)
S.sub..beta.=Mw(.beta.)/Mw(b).ltoreq.1.2 (IV)
[0014] wherein
[0015] Mw(.alpha.): weight average molecular weight of polymer
(.alpha.),
[0016] Mw(.beta.): weight average molecular weight of polymer
(.beta.),
[0017] Mw(a): weight average molecular weight of block (a) of block
copolymer, and
[0018] Mw(b): weight average molecular weight of block (b) of block
copolymer.
[0019] In accordance with the present invention, there is further
provided a rubber composition comprised of a block copolymer having
at least two mutually incompatible blocks (a) and (b) and
comprising at least one conjugated diene and, optionally, at least
one aromatic vinyl monomer based upon 100 parts by weight of the
same, 5 to 200 parts by weight of a polymer (.alpha.) compatible
with the block (a) and/or a polymer (.beta.) compatible with the
block (b), the weight average molecular weights of the polymers
(.alpha.) and (.beta.) satisfying the following equations (III) and
(IV):
S.sub..alpha.=Mw(.alpha.)/Mw(a).ltoreq.1.2 (III)
S.sub..beta.=Mw(.beta.)/Mw(b).ltoreq.1.2 (IV)
[0020] wherein
[0021] Mw(.alpha.): weight average molecular weight of polymer
(.alpha.),
[0022] Mw(.beta.): weight average molecular weight of polymer
(.beta.),
[0023] Mw(a): weight average molecular weight of block (a) of block
copolymer, and
[0024] Mw(b): weight average molecular weight of block (b) of block
copolymer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The present invention will be better understood from the
description set forth below with reference to the accompanying
drawings, wherein
[0026] FIG. 1 is a view of an example of a molecular weight
distribution curve (integrated molecular weight curve) of molecular
weights measured by GPC forming the basis for finding the molecular
weights of the low molecular weight portions of the polymers of the
polymer phases (A) and (B) of equations (I) and (II);
[0027] GPC Measurement Conditions
[0028] GPC: HLC-8020 made by Toso
[0029] Column: GMH-HR-H, 2
[0030] Temperature: 40.degree. C.
[0031] Mobile phase: THF
[0032] Standard substance: 10 points used between standard
polystyrene 1000 to 10,000,000
[0033] Approximation method: By tertiary method.
[0034] Preparation of polymer sample: 50 mg of the polymer was
dissolved in 10 cc of THF. The mixture was stirred at room
temperature for about 168 hours so as to dissolve. This was then
filtered by a 0.5 micron filter (H25-5 made by Toso) to remove the
insolubles. The result was used as the sample. The amount injected
into the GPC was made 400 .mu.l.
[0035] FIG. 2 is a view of an integrated molecular weight curve
obtained by converting the molecular weight distribution curve of
FIG. 1, wherein Mw.sub.30(A) and Mw.sub.30(B) of equations (I) and
(II) are found from the molecular weight of the cumulative area 30%
as shown in FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] The present inventors found that the above-mentioned object
can be achieved by compounding, into a rubber composition formed
from at least two rubber phases comprising at least two
incompatible rubbers, a block polymer comprising at least two
incompatible blocks having molecular weights which are defined by
two types of relationships with the molecular weights of the
rubbers forming the two rubber phases.
[0037] The tire rubber composition according to the present
invention can be obtained by blending (i) an incompatible polymer
blend of two polymer phases (A) and (B) comprising at least two
types of incompatible rubbers of NR, IR, BR, SBR, SIR, and SIBR,
preferably in the weight ratio of (A)/(B) of 90/10 to 10/90, more
preferably 85/15 to 15/85) and (ii) 0.1 to 20 parts by weight,
preferably 1 to 15 parts by weight, based upon 100 parts by weight
of the entire rubber component including a block copolymer, of the
block copolymer having at least two blocks comprising monomers
selected from isoprene, butadiene, and styrene, wherein the blocks
(a) and (b) are mutually incompatible, the block (a) is compatible
with the polymer phase (A) and incompatible with the polymer phase
(B), and the block (b) is compatible with the polymer phase (B) and
incompatible with the polymer phase (A), preferably the weight
ratio of (a)/(b) of 80/20 to 20/80, more preferably 60/40 to 40/60,
and wherein the molecular weights of the polymers forming the
polymer phases (A) and (B) satisfy the equations (I) and (II). Note
that SA and SB preferably are 0.1 to 1.2, more preferably 0.3 to
1.0.
[0038] If the value of S.sub.A and the value of S.sub.B are more
than 1.2, the block copolymer added while mixing the rubber
component does not disperse well and the effect as a
compatibilizing agent cannot be sufficiently exhibited.
[0039] Note that the molecular weights of the low molecular weight
portions of the polymers forming the polymer phases (A) and (B)
mean those found as values of molecular weights (i.e., Mw.sub.30(A)
and Mw.sub.30(B)) corresponding to 30% of the cumulative area when
converting the curve of the distribution of the molecular weight
measured by GPC such as shown in FIG. 1 to the integrated molecular
weight curve, as shown in FIG. 2. The GPC is measured by, for
example, dissolving the polymer sample into THF, removing the
insoluble gel component by a 0.5 micron filter, then calculating
the molecular weight by an equation obtained from the amount of
elution of standard polystyrene.
[0040] Further, it is possible to previously blend a block
copolymer having at least two mutually incompatible blocks (a) and
(b) and comprising a conjugated diene and/or aromatic vinyl monomer
with a polymer (.alpha.) compatible with the block (a) and the
polymer phase (A) and/or a polymer (.beta.) compatible with the
block (b) and the polymer phase (B), which satisfies the following
equations (III) and (IV):
S.sub..alpha.=Mw(.alpha.)/Mw(a).ltoreq.1.2 (III)
S.sub..beta.=Mw(.beta.)/Mw(b).ltoreq.1.2 (IV)
[0041] wherein
[0042] Mw(.alpha.): weight average molecular weight of polymer
(.alpha.),
[0043] Mw(.beta.): weight average molecular weight of polymer
(.beta.),
[0044] Mw(a): weight average molecular weight of block (a) of block
copolymer, and
[0045] Mw(b): weight average molecular weight of block (b) of block
copolymer,
[0046] so as to improve the dispersion of the block copolymer
during mixing of the rubber and obtain the better mechanical
strength.
[0047] Note that S.sub..alpha. and S.sub..beta. are preferably 0.1
to 1.2, more preferably 0.3 to 1.0.
[0048] In particular, (.alpha.) should be added when the low
molecular weight portion of the polymer forming the polymer phase
(A) is small and (.beta.) should be added when the low molecular
weight portion of the polymer forming the polymer phase (B) is
small. Therefore, even when the above equations (I) and/or (II) are
not satisfied, it is possible to obtain the effect of the present
invention by blending in the polymer (.alpha.) or (.beta.).
[0049] Here, as the polymer (.alpha.) or (.beta.), rubbers such as
IR, BR, SBR, SIBR having a suitable molecular weight are
preferable, but it is not limited to a rubber so long as the object
of improving the dispersion at the time of mixing the block polymer
is achieved without impairing the vulcanized physical properties of
the rubber composition finally obtained. Other polymers may also be
used.
[0050] The amount of the polymer (.alpha.) or (.beta.) blended
should be 5 to 200 parts by weight, preferably 20 to 100 parts by
weight, based upon 100 parts by weight of the block copolymer. If
the amount is less than 5 parts by weight, the anticipated effect
is not manifested, while if more than 200 parts by weight, the
elasticity or mechanical strength is decreased, and therefore,
there is a detrimental effect on the physical properties or the
Mooney viscosity of the starting rubber is decreased and handling
becomes difficult.
[0051] The process of production of the block copolymer used in the
present invention is not particularly limited, but, for example,
this may be produced by polymerizing isoprene, butadiene, or
styrene monomers in a hydrocarbon solvent using an organoactive
metal as an initiator. As the organoactive metal, for example, an
anionic polymerizable organoactive metal such as an organoalkali
metal compound, organoalkali earth metal compound, or
organolanthanoid based rare earth metal compound may be mentioned.
Among these, an organoalkali metal compound is particularly
preferable.
[0052] According to the present invention, it is possible to
further blend low molecular weight polymers (for example, IR, BR,
SBR, or SIBR) as parts of the polymers forming the polymer phases
so as to satisfy the above equations (I) and (II). The amounts of
the low molecular weight polymers blended are preferably 1 to 50
parts by weight, based upon 100 parts by weight of the rubber
component, as a whole. If the amounts blended are too great, this
leads to the decrease in the tensile strength etc., and therefore,
this is not preferred.
[0053] The incompatible polymer blend comprising the polymer phases
(A) and (B) used in the present invention is not particularly
limited so long as two or more types of polymers selected from
polymers containing conjugated dienes and/or aromatic vinyl
monomers such as NR, IR, BR, SBR, are selected and constitute two
incompatible polymer phases (A) and (B). Further, the block
copolymer comprising the blocks (a) and (b) used in the present
invention may be made any polymer provided with the above
conditions. For example, a BR block, SBR block, IR block, SIR
(i.e., styrene isoprene rubber) block, BIR (i.e., butadiene
isoprene) block, SBIR (i.e., styrene butadiene isoprene) block,
etc. may be suitably combined for use.
[0054] Representative examples of combinations of such incompatible
polymers and block copolymers are as follows:
1 TABLE I Matrix polymer (A)/(B) Block copolymer ((a)/(b)) NR/SBR
(wherein, amount of IR/SBR (amount of vinyl of vinyl of Bd part is
not Bd part not more than about more than about 60 mol %) 60 mol %)
or SBR/SBR (amount of St about 20% by weight, amount of vinyl of Bd
part about 70 mol %) NR/BR (cis content not less IR/SBR (amount of
St about than 90 mol %) 20% by weight, amount of vinyl of Bd part
about 50 mol %)
[0055] Of course, the present invention is not limited to the above
examples.
[0056] The rubber composition according to the present invention
may suitably use various conventional additives according to its
application, for example, various reinforcing fillers generally
used in the prior art such as carbon black and silica, softeners,
antioxidant, wax, resin, vulcanization agent, vulcanization
accelerator, vulcanization accelerator activator, etc. Further,
blowing agent, low moisture plasticizer, short fibers, etc. may be
used.
[0057] In blending the rubber composition according to the present
invention, it is preferable to first mix the rubber (i.e., matrix
rubber and block copolymer) and the additives other than, for
example, vulcanization agent and vulcanization accelerator
according to an ordinary method, then blend them. Of course, even
if some of these ingredients are separately mixed, the resultant
mixture, needless to say, falls in the technical scope of the
present invention so long as the object of the present invention is
not impaired. Further, the blending may be carried out in any means
used in the past.
[0058] The rubber composition of the present invention may be
vulcanized by a general method. The amount of the above additives
blended may be the general amounts. Further, the vulcanization
conditions may be made the general conditions.
EXAMPLES
[0059] The present invention will be further illustrated with
reference to Examples, but the present invention is of course by no
means limited in scope by these Examples.
Standard Examples 1 to 6, Examples 1 to 12, and Comparative
Examples 1 to 7
[0060] The ingredients of the formulations of Tables II to IV,
Table V, and Table VI (parts by weight) (wherein the
characteristics of the polymers used as the phase (A) and phase (B)
are shown in Table VII, the characteristics of the block polymers
are shown in Table VIII, and the characteristics of the polymers
(.alpha.) and (.beta.) are shown in Table IX) were mixed in 1.5
liter Bambury mixers for 4 minutes, then the vulcanization
accelerators and sulfur were mixed with the mixtures by 8-inch
test-use roll mill to obtain the rubber compositions. These rubber
compositions were press vulcanized at 160.degree. C. for 20 minutes
to prepare the desired test pieces which were then subjected to
various tests and measured in physical properties. The physical
properties of the vulcanates obtained were as shown in Tables II,
III and IV.
[0061] Mixing Method
[0062] The mixing methods used in the Examples and the Comparative
Examples were all according to the following mixing
specifications:
[0063] 1) Rotor speed: 60 rpm
[0064] 2) Temperature adjustment: 50.degree. C.
[0065] 3) Charging specifications:
[0066] 0' . . . rubber ingredients (matrix rubber, block
copolymer)
[0067] 1' . . . carbon black in half amount, zinc white, stearic
acid
[0068] 2'30" . . . carbon black in half amount, antioxidant,
wax
[0069] 3'30" . . . raising and lowering of ram (cleaning ram
portion)
[0070] 4'00" . . . discharge
[0071] The "yes" in the compatibility section of Tables II, III and
IV indicates a compatible relationship, while the "no" indicates an
incompatible relationship.
2 TABLE II Standard Comp. Ex. Comp. Ex. 1 1 Ex. 2 Ex. 1 phase (A)
polymer NR-2 50 45 45 45 phase (B) polymer SBR 50 45 45 45 Block
polymer BP-1 -- 10 -- -- BP-2 -- -- 10 -- BP-3 -- -- -- 10
Compatibility Block (a) block (b) -- No No No Block (a) phase (A)
-- Yes Yes Yes polymer Block (a) phase (B) -- No No No polymer
Block (b) phase (A) -- No No No polymer Block (b) phase (B) -- Yes
Yes Yes polymer Relation with molecular weight S.sub.A = Mw.sub.30
(A)/Mw (a) -- 1.8 1.7 0.8 S.sub.B = Mw.sub.30 (B)/Mw (b) -- 1.2 0.6
0.6 Physical properties of rubber composition Tensile strength
(MPa) 23.2 23.5 24.0 26.3 Elongation (%) 370 378 380 418 Abrasion
resistance 100 102 101 120 index (index)
[0072]
3 TABLE III Standard Standard Standard Ex. 2 Ex. 3 Ex. 4 phase (A)
polymer NR-1 80 -- -- NR-2 -- 80 -- NR-3 -- -- 80 phase (B) polymer
BR 20 20 20 Physical properties of rubber composition Tensile
strength (MPa) 29.9 28.1 26.6 Elongation (%) 568 578 579 Abrasion
resistance index 100 100 100 (index) Times to breakage in 2195900
2320300 2342100 fatigue test Comp. Ex. 3 Comp. Ex. 4 Ex. 2 phase
(A) polymer NR-2 78 78 78 phase (B) polymer BR 19 19 19 Block
polymer BP-4 3 -- -- BP-5 -- 3 -- BP-6 -- -- 3 Compatibility Block
(a) block (b) No No No Block (a) phase (A) polymer Yes Yes Yes
Block (a) phase (B) polymer No No No Block (b) phase (A) polymer No
No No Block (b) phase (B) polymer Yes Yes Yes Relation with
molecular weight S.sub.A = Mw.sub.30 (A)/Mw (a) 1.7 1.7 0.9 S.sub.B
= Mw.sub.30 (B)/Mw (b) 0.7 0.3 0.3 Physical properties of rubber
composition Tensile strength (MPa) 28.4 28.3 30.6 Elongation (%)
581 580 586 Abrasion resistance index 101 102 106 (index) Times to
breakage in fatigue 2310000 2298700 3212400 test Comp. Ex. 5 Ex. 3
phase (A) polymer NR-1 78 -- NR-3 -- 78 phase (B) polymer BR 19 19
Block polymer BP-5 -- 3 BP-6 3 -- Compatibility Block (a) block (b)
No No Block (a) phase (A) polymer Yes Yes Block (a) phase (B)
polymer No No Block (b) phase (A) polymer No No Block (b) phase (B)
polymer Yes Yes Relation with molecular weight S.sub.A = Mw.sub.30
(A)/Mw (a) 1.3 1.2 S.sub.B = Mw.sub.30 (B)/Mw (b) 0.3 0.3 Physical
properties of rubber composition Tensile strength (MPa) 29.9 29.1
Elongation (%) 572 599 Abrasion resistance index (index) 102 107
Times to breakage in fatigue test 2188800 3400200
[0073]
4 TABLE IV Standard Comp. Ex. Ex. 5 6 Ex. 4 Ex. 5 phase (A) polymer
NR-1 60 58 55 57.85 NR-2 -- -- -- -- phase (B) polymer BR 40 39 39
39 Block polymer BP-7 -- 3 3 3 Polymer (.alpha.) .alpha.-1 -- -- 3
-- .alpha.-2 -- -- -- 0.15 .alpha.-3 -- -- -- -- .alpha.-4 -- -- --
-- Polymer (.beta.) .beta.-1 -- -- -- -- Compatibility Block (a)
block (b) -- No No No Block (a) phase (A) -- Yes Yes Yes polymer
Block (a) phase (B) -- No No No polymer Block (b) phase (A) -- No
No No polymer Block (b) phase (B) -- Yes Yes Yes polymer Polymer
(.alpha.) block (a) -- -- Yes Yes Polymer (.alpha.) phase -- -- Yes
Yes (A) polymer Polymer (.beta.) block (b) -- -- -- -- Polymer
(.beta.) phase (B) -- -- -- -- polymer Relation with molecular
weight S.sub.A = Mw.sub.30 (A)/Mw (a) -- 2.2 2.2 2.2 S.sub.B =
Mw.sub.30 (B)/Mw (b) -- 0.3 0.3 0.3 S.sub..alpha. = Mw (.alpha.)/Mw
(a) -- -- 0.7 1 S.sub..beta. = Mw (.beta.)/Mw (b) -- -- -- -- Rate
of polymers (.alpha.) and -- -- 100 5 (.beta.) added/wt % (to block
polymer) Physical properties of rubber composition Tensile strength
(MPa) 27.9 28.3 29.2 28.7 Elongation (%) 550 560 588 575 Abrasion
resistance 100 102 110 103 index (index) Comp. Ex. 6 Ex. 7 Ex. 8
Ex. 7 phase (A) polymer NR-1 55 52 55 55 NR-2 -- -- -- -- phase (B)
polymer BR 39 39 39 39 Block polymer BP-7 3 3 3 3 Polymer (.alpha.)
.alpha.-1 -- -- -- -- .alpha.-2 3 6 .alpha.-3 -- -- 3 -- .alpha.-4
-- -- -- 3 Polymer (.beta.) .beta.-1 -- -- -- -- Compatibility
Block (a) block (b) No No No No Block (a) phase (A) Yes Yes Yes Yes
polymer Block (a) phase (B) No No No No polymer Block (b) phase (A)
No No No No polymer Block (b) phase (B) Yes Yes Yes Yes polymer
Polymer (.alpha.) block (a) Yes Yes Yes Yes Polymer (.alpha.) phase
Yes Yes Yes Yes (A) polymer Polymer (.beta.) block (b) -- -- -- --
Polymer (.beta.) phase (B) -- -- -- -- polymer Relation with
molecular weight S.sub.A = Mw.sub.30 (A)/Mw (a) 2.2 2.2 2.2 2.2
S.sub.B = Mw.sub.30 (B)/Mw (b) 0.3 0.3 0.3 0.3 S.sub..alpha. = Mw
(.alpha.)/Mw (a) 1 1 1.2 1.4 S.sub..beta. = Mw (.beta.)/Mw (b) --
-- -- -- Rate of polymers (.alpha.) and 100 200 100 100 (.beta.)
added/wt % (to block polymer) Physical properties of rubber
composition Tensile strength (MPa) 29.7 28.5 28.8 28.4 Elongation
(%) 585 588 577 562 Abrasion resistance 108 103 105 102 index
(index) Stand- ard Ex. Ex. 9 Ex. 10 6 Ex. 11 Ex. 12 phase (A)
polymer NR-1 58 56 -- -- -- NR-2 -- -- 60 58 57.4 phase (B) polymer
BR 38 38 40 39 39 Block polymer BP-6 -- -- -- 3 3 Block polymer
BP-7 3 3 -- -- -- Polymer (.alpha.) .alpha.-1 -- -- -- -- --
.alpha.-2 -- 2 -- -- 0.6 .alpha.-3 -- -- -- -- -- .alpha.-4 -- --
-- -- -- Polymer (.beta.) .beta.-1 1 1 -- -- -- Compatibility Block
(a) block (b) No No -- No No Block (a) phase (A) Yes Yes -- Yes Yes
polymer Block (a) phase (B) No No -- No No polymer Block (b) phase
(A) No No -- No No polymer Block (b) phase (B) Yes Yes -- Yes Yes
polymer Polymer (.alpha.) block (a) -- Yes -- -- Yes Polymer
(.alpha.) phase -- Yes -- -- Yes (A) polymer Polymer (.beta.) block
(b) Yes Yes -- -- -- Polymer (.beta.) phase (B) Yes Yes -- -- --
polymer Relation with molecular weight S.sub.A = Mw.sub.30 (A)/Mw
(a) 2.2 2.2 -- 0.9 0.9 S.sub.B = Mw.sub.30 (B)/Mw (b) 0.3 0.3 --
0.3 0.3 S.sub..alpha. = Mw (.alpha.)/Mw (a) -- 1.0 -- -- 0.6
S.sub..beta. = Mw (.beta.)/Mw (b) 0.3 0.3 -- -- -- Rate of polymers
(.alpha.) and 33 100 -- -- 20 (.beta.) added/wt % (to block
polymer) Physical properties of rubber composition Tensile strength
(MPa) 28.4 30 26.8 27.7 29.8 Elongation (%) 570 590 520 566 602
Abrasion resistance 103 107 100 101 111 index (index)
[0074]
5TABLE V NR/SBR Blend Formulation (Parts by Weight) Rubber
component 100 Carbon black (N339)*1 50 Zinc white 3 Stearic acid 2
Antioxidant (6C)*2 3 Wax 2 Vulcanization accelerator (NS)*3 1
Sulfur 1.7 *1: Seast KH, made by Tokai Carbon Co. *2: Santoflex 13,
made by Flexis Co. *3: Santocure NS, made by Flexis Co.
[0075]
6TABLE VI NR/BR Blend Formulation (Parts by Weight) Rubber
component 100 Carbon black (N110)*1 50 Zinc white 5 Stearic acid 2
Antioxidant (6C)*2 3 Vulcanization accelerator (NS)*3 1.2 Sulfur 1
*1: Diablack I (made by Mitsubishi Chemical) *2: Santoflex 13 (made
by Flexis Co.) *3: Santocure NS (made by Flexis Co.)
[0076]
7TABLE VII Characteristics of Polymers Used as Phase (A) and Phase
(B) Overall (MW) 30% (Mw) NR-1*1 7.57 .times. 10.sup.5 3.9 .times.
10.sup.5 NR-2*2 1.19 .times. 10.sup.6 2.6 .times. 10.sup.5 NR-3*3
4.65 .times. 10.sup.5 1.8 .times. 10.sup.5 SBR*4 3.72 .times.
10.sup.5 1.9 .times. 10.sup.5 BR*5 3.51 .times. 10.sup.5 1.1
.times. 10.sup.5 (Note) *1: Masticated natural rubber RSS #3.
Masticated by 8-inch roll mill at 80.degree. C. for 3 minutes. *2:
Notural rubber SMR-L *3: Masticated natural rubber RSS #3.
Masticated by 8-inch roll mill at 80.degree. C. for 15 minutes. *4:
NS 114 (SBR made by Nippon Zeon) *5: BR 1220 (BR made by Nippon
Zeon)
[0077]
8TABLE VIII Characteristics of Block Polymer Block (a) Block (b)
Microstructure Mw Microstructure Mw BP-1 Polyisoprene 1.48 .times.
SBR (St = 18 wt %, 1.61 .times. (cis/trans/vn = 10.sup.5 Vn = 11
mol %) 10.sup.5 77/16/7) BP-2 Polyisoprene 1.52 .times. SBR (St =
18 wt %, 3.12 .times. (cis/trans/vn = 10.sup.5 Vn = 11 mol %)
10.sup.5 77/16/7) BP-3 Polyisoprene 3.10 .times. SBR (St = 18 wt %,
3.21 .times. (cis/trans/vn = 10.sup.5 Vn = 11 mol %) 10.sup.5
77/16/7) BP-4 Polyisoprene 1.51 .times. SBR (St = 19 wt %, 1.47
.times. (cis/trans/vn = 10.sup.5 Vn = 46 mol %) 10.sup.5 77/16/7)
BP-5 Polyisoprene 1.49 .times. SBR (St = 19 wt %, 3.22 .times.
(cis/trans/vn = 10.sup.5 Vn = 46 mol %) 10.sup.5 77/16/7) BP-6
Polyisoprene 3.01 .times. SBR (St = 19 wt %, 3.21 .times.
(cis/trans/vn = 10.sup.5 Vn = 46 mol %) 10.sup.5 77/16/7) BP-7
Polyisoprene 1.80 .times. SBR (St = 19 wt %, 3.22 .times.
(cis/trans/vn = 10.sup.5 Vn = 46 mol %) 10.sup.5 77/16/7) (Note)
BP-1 to BP-7 were obtained by 2-stage polymerization by butyl
lithium initiator in n-hexane solvent.
[0078]
9TABLE IX Characteristics of Polymers Used as (.alpha.) and
(.beta.) Microstructure Mw .alpha.-1 Polyisoprene (cis/trans/vn =
77/16/7) 1.2 .times. 10.sup.5 .alpha.-2 Polyisoprene (cis/trans/vn
= 77/16/7) 1.8 .times. 10.sup.5 .alpha.-3 Polyisoprene
(cis/trans/vn = 77/16/7) 2.2 .times. 10.sup.5 .alpha.-4
Polyisoprene (cis/trans/vn = 77/16/7) 2.5 .times. 10.sup.5 .beta.-1
SBR (St = 19 wt %, Vn = 46 mol %) 1.0 .times. 10.sup.5 (Notes)
.alpha.-1 to .alpha.-4 and .beta.-1 were obtained by polymerization
in organic solvents using organometallic compounds as
initiators.
[0079] The physical properties evaluated in the above Examples were
measured by the following methods:
[0080] Tensile strength (Mpa): Measured according to JIS K6251.
[0081] Elongation (%): Measured according to JIS K6251.
[0082] Abrasion resistance test: Measured using a Lambourn abrasion
tester at conditions of a slip rate of 25% and a load of 5 kg. The
results are shown indexed to the formulation of the corresponding
Standard Examples as 100 (abrasion resistance index). The larger
the figure, the better the abrasion resistance shown.
[0083] Times to breakage in fatigue test: Shown by number of times
to breakage of a JIS No. 3 dumbbell shaped sample after being given
repeated deformation at a cycle rate of 400 rpm at an elongation
stress of 100% (average for four tests).
[0084] The incompatibility of polymers was judged by the following
method:
[0085] 1) The incompatibility of the polymer phases (A) and (B) of
the polymer blend was judged by vulcanizing the polymer blend,
preparing ultrathin slice samples by the freezing method, then
dyeing these in a gas phase with a benzene solution of osmium
tetraoxide at room temperature for about 15 hours. The presence of
phase (a) separated structure was examined by observation through a
transmission type electron microscope at magnifications of about
5000 to 10,000.
[0086] 2) The incompatibility of the blocks (a) and (b) of the
block copolymer was judged by preparing samples in the same way as
above from the block copolymer in the unvulcanized state, then
observing them through a transmission type electron microscope at a
magnification of about 60,000 to examine the presence of a phase
separated structure.
[0087] 3) The incompatibility of the blocks of the block copolymer
and the polymer phases of the polymer blend was judged by
separating polymerizing and preparing the polymers corresponding to
the polymers constituting the blocks, mixing these with the matrix
polymers, vulcanizing them, then proceeding in the same way as
above to prepare samples for observation through an electron
microscope and observing these at magnifications of about 5000 to
10,000 to examine the presence of phase separated structures.
[0088] In addition, the compatibilities and incompatibilities may
be decided by judging the presence of bimodal or not from the
temperature dependence curve of tan .delta. or by judging the
presence of plurality of glass transition temperatures or not of
the blend polymers can be observed by DSC measurement and further
may be judged by an optical microscope if the phase separated
structure reaches as much as several dozen microns. Among these,
the above direct observation by an electron microscope is the most
sensitive method.
[0089] As explained above and as shown in Examples 1 to 12, the
rubber compositions according to the present invention are improved
in mechanical strength such as tensile strength, elongation,
abrasion resistance, and fatigue resistance compared with the
rubber compositions of Comparative Examples 1 to 7.
* * * * *