U.S. patent application number 10/529549 was filed with the patent office on 2006-03-23 for orientated carbon nanotube composite, process for producing orientated carbon nanotube, and, produced using orientated carbon nanotube composite, pneumatic tire, wheel for vehicle, tire wheel assembly and disk brake.
Invention is credited to Satoshi Aizawa, Yukio Aoike, Iki Harada, Masami Kikuchi, Keiichiro Mizuno, Masao Ogawa, Takahisa Shizuku, Itsuo Tanuma.
Application Number | 20060061011 10/529549 |
Document ID | / |
Family ID | 32074819 |
Filed Date | 2006-03-23 |
United States Patent
Application |
20060061011 |
Kind Code |
A1 |
Kikuchi; Masami ; et
al. |
March 23, 2006 |
Orientated carbon nanotube composite, process for producing
orientated carbon nanotube, and, produced using orientated carbon
nanotube composite, pneumatic tire, wheel for vehicle, tire wheel
assembly and disk brake
Abstract
A carbon nanotube orientated composite formed by orientating
carbon nanotubes in a given direction in a matrix having a heat
conductivity lower than that of carbon nanotube, in which at least
a part of carbon nanotubes are contacted with each other to be
continuous from one end to the other end between both ends in the
orientated direction, is provided as a material having a heat
conductivity considerably higher than that of copper, aluminum or
the like or a material to be disposed in rubber material having a
low heat releasing characteristic to considerably improve the heat
conduction, and also there are provided a method of producing the
same as well as a pneumatic tire, a wheel for a vehicle, a
tire-wheel assembly and a disc brake using this material.
Inventors: |
Kikuchi; Masami; (Tokyo,
JP) ; Harada; Iki; (Tokyo, JP) ; Mizuno;
Keiichiro; (Tokyo, JP) ; Tanuma; Itsuo;
(Tokyo, JP) ; Ogawa; Masao; (Tokyo, JP) ;
Aizawa; Satoshi; (Tokyo, JP) ; Aoike; Yukio;
(Tokyo, JP) ; Shizuku; Takahisa; (Tokyo,
JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Family ID: |
32074819 |
Appl. No.: |
10/529549 |
Filed: |
September 25, 2003 |
PCT Filed: |
September 25, 2003 |
PCT NO: |
PCT/JP03/12267 |
371 Date: |
March 29, 2005 |
Current U.S.
Class: |
264/289.3 |
Current CPC
Class: |
F16D 65/092 20130101;
B60C 9/0007 20130101; C08K 7/06 20130101; F16D 2065/1328 20130101;
B60C 19/00 20130101; F16D 65/125 20130101; F16D 2200/0052 20130101;
B60C 9/20 20130101; F16D 2200/006 20130101; B60C 15/06 20130101;
B82Y 30/00 20130101; C08K 7/06 20130101; C08K 7/24 20130101; B60C
9/00 20130101; B60C 11/01 20130101; C08K 2201/011 20130101; F16D
65/128 20130101; F16D 65/78 20130101; C08L 21/00 20130101 |
Class at
Publication: |
264/289.3 |
International
Class: |
D02J 1/22 20060101
D02J001/22 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 30, 2002 |
JP |
2002-285466 |
Oct 8, 2002 |
JP |
2002-294943 |
Oct 8, 2002 |
JP |
2002-295042 |
Oct 8, 2002 |
JP |
2002-295047 |
Oct 8, 2002 |
JP |
2002-295202 |
Oct 9, 2002 |
JP |
2002-296346 |
Claims
1. A carbon nanotube orientated composite in which carbon nanotubes
are orientated in a matrix having a heat conductivity lower than
that of the carbon nanotube in a given direction, and at least a
part of the carbon nanotubes are contacted with each other to
become continuous from one end to the other end between both ends
in the orientated direction.
2. A carbon nanotube orientated composite according to claim 1,
wherein a length of the carbon nanotube is 0.1-30 pm and a diameter
10 thereof is 10-300 nm.
3. A carbon nanotube orientated composite according to claim 1,
wherein the matrix is a metallic material,
4. A carbon nanotube orientated composite according to claim 3,
wherein a compounding ratio of the metallic material and the carbon
nanotube is 0.1-5 parts by mass of the carbon nanotube to 100 parts
by mass of the metallic material.
5. A carbon nanotube orientated composite according to claim 3,
wherein the metallic material is one or more of a metal selected
from Al, Cu and Mg or an alloy containing the selected metal.
6. A carbon nanotube orientated composite according to claim 3,
wherein a heat conductivity of the carbon nanotube in the
orientated direction is not less than 300 W/mK.
7. A carbon nanotube orientated composite according to claim 1,
wherein the matrix contains a rubber component.
8. A carbon nanotube orientated composite according to claim 7,
wherein a compounding ratio of the rubber component and the carbon
nanotube is 5-100 parts by mass based on 100 parts by mass of the
rubber component.
9. A carbon nanotube orientated composite according to claim 7,
wherein the rubber component is butyl rubber.
10. A carbon nanotube orientated composite according to claim 7,
wherein a heat conductivity of the carbon nanotube in the
orientated direction is not less than 0.15 W/mK.
11. A method of producing carbon nanotube orientated composite as
claimed in claim 3, which comprises fluidizing a melt dispersed
carbon nanotubes into a molten metallic material and cooling and
solidifying the melt on the way of the fluidization to orientate
the carbon nanotubes.
12. A method of producing carbon nanotube orientated composite as
claimed in claim 7, which comprises milling a rubber component and
carbon nanotubes, extruding the milled mass through an extruder and
drawing the extruded mass at a drawing rate faster than an
extrusion rate.
13. A pneumatic tire in which carbon nanotube orientated composites
as claimed in claim 7 are arranged in parallel to each other and
covered with a coating rubber to form a heat releasing member, and
the heat releasing member is arranged so that one end of the carbon
nanotube orientated composite is exposed at an outer surface of the
tire and the other end thereof is positioned in an interior of the
tire.
14. A pneumatic tire according to claim 13, wherein the heat
releasing member is arranged in the vicinity of at least one of an
end of a belt and an turnup end of a carcass.
15. A pneumatic tire according to claim 13, wherein the heat
releasing member has a thickness of 1-5 mm.
16. A wheel for a vehicle provided with a rim enclosing an interior
portion of a tire in consort with the tire, in which the carbon
nanotube orientated composite as claimed in claim 3 is arranged so
as to pass through the rim in its thickness direction, and an end
of the carbon nanotube orientated composite is positioned in a
portion contacting with the tire or a portion exposing to the
interior portion of the tire and the other end thereof is
positioned in a portion exposing to an atmosphere.
17. A wheel for a vehicle according to claim 16, wherein a high
heat conductive member having a heat conductivity of not less than
300 W/mK is coated onto a surface of the rim, and the high heat
conductive member is extended from a first portion contacting with
the tire or exposing to the interior portion of the tire to a
second portion exposing to the atmosphere.
18. The invention is a wheel for a vehicle according to claim 17,
wherein the high heat releasing member is an alloy of a metal
selected from the group consisting of Al, Mg and Cu or a sintered
body of the selected metal and a diamond.
19. A wheel for a vehicle according to claim 17, wherein a cooling
means is arranged on an exposed surface of the second portion of
the high heat conductive member.
20. A wheel for a vehicle according to claim 19, wherein a cooling
fin is arranged on the surface as the cooling means.
21. A wheel for a vehicle according to claim 16, wherein a heat
collecting fin is arranged on a portion contacting with the
interior of the tire.
22. A tire-wheel assembly comprising a wheel for a vehicle as
claimed in claim 16 and a tire mounted on the wheel for the vehicle
and a gas inclusive of at least helium gas filled in an interior of
the tire defined between the tire and the wheel.
23. A tire-wheel assembly comprising a wheel for a vehicle as
claimed in claim 16 and a tire mounted on the wheel for the vehicle
and clastic balls filled in an interior of the tire defined between
the wheel and the tire.
24. A disc brake comprising a rotor and a pad decelerating the
rotor while sliding to the rotating rotor, in which a carbon
nanotube orientated composite as claimed in claim 3 is arranged on
at least one part of the rotor and the pad, and an end of the
carbon nanotube orientated composite is exposed to a sliding
surface of the part or located in the vicinity of the sliding
surface and the other end thereof is exposed to a surface other
than the sliding surface of the part.
25. A disc brake according to claim 24, which further comprises a
cooling means for cooling the surface of the part exposing the
other end.
26. A disc brake according to claim 25, wherein the cooling means
is a cooling fin disposed on the surface.
Description
TECHNICAL FIELD
[0001] This invention relates to a carbon nanotube orientated
composite formed by orientating carbon nanotubes in a matrix and a
method of producing the same as well as a pneumatic tire, a wheel
for a vehicle, a tire-wheel assembly and a disc brake having a heat
dissipation improved by using the carbon nanotube orientated
composite.
BACKGROUND ART
[0002] As a general-purpose heat conductive material for thermal
machine accompanied with a phenomenon of heat exchange and heat
conduction, or for heat dispersion have hitherto been used a cast
iron, stainless steel, copper and copper alloy, aluminum and
aluminum alloy, nickel and nickel alloy, titanium and titanium
alloy, zirconium alloy and the like. Particularly, copper, aluminum
and the like having a highest heat conductivity over a temperature
range from room temperature to higher temperature are used in
thermal machines requiring a high heat conductivity such as heat
exchangers and the like.
[0003] However, thermal machines having a higher heat conductivity
or heat efficiency are demanded with an increasing requirement to
energy saving in recent years, and hence it is required to develop
general-purpose heat conductive materials having a heat
conductivity higher than that of copper, aluminum or the like.
Also, in the parts such as a brake, a wheel for a vehicle and the
like, it is desired to further improve heat releasing
characteristics of these parts for improving the braking
performance or controlling the temperature rise of the tire during
the running at higher speed to ensure the durability of the
tire.
[0004] On the other hand, since elastic bodies such as rubber and
the like are generally materials having a low heat conductivity,
they generate heat through repetitive deformation, and store the
generated heat and hence the temperature of rubber itself becomes
higher to promote heat deterioration thereof. In the parts
including rubber portion subjected to repetitive deformation such
as tire and the like, therefore, it is required to rapidly release
the generated heat. As a countermeasure therefor, it is attempted
to improve the heat conduction by compounding a rubber component
with a filler or the like having a heat conductivity higher than
that of the rubber component. However, in order to obtain a
satisfactory effect, it is required to fairly increase the
compounding amount of the filler or the like, and as a result,
there are caused problems that the dispersion of the filler becomes
non-uniform and dynamic properties are lowered.
[0005] The invention is made considering such problems and is to
provide materials having a heat conductivity considerably higher
than that of copper aluminum or the like and capable of
considerably improving a heat conducting property in the
incorporation into rubber material having low heat releasing
characteristics and a method of producing these materials. Also, it
is to provide parts capable of improving the heat releasing
characteristics by using such a material.
DISCLOSURE OF THE INVENTION
[0006] The invention is made for achieving the above objects, and
the summary, construction and functions are as follows.
[0007] (1) The invention is a carbon nanotube orientated composite
in which carbon nanotubes are orientated in a matrix having a heat
conductivity lower than that of the carbon nanotube in a given
direction, and at least a part of the carbon nanotubes are
contacted with each other to become continuous from one end to the
other end between both ends in the orientated direction.
[0008] The carbon nanotube is a structural body made of carbon atom
having a diameter of about few nm to few hundreds nm and has an
extremely fine tubular structure of an order corresponding to
10.sup.-3 times of usual carbon fiber (CF)(average diameter: not
less than 5 .mu.m, length: about 100 .mu.m). Although the heat
conductivity of the carbon nanotube itself is not clear because the
measuring method is not established, it is theoretically guessed
from the crystal structure that the heat conductivity is very high.
In the carbon nanotube orientated composite according to the
invention, the carbon nanotubes orientated in the matrix are
contacted with each other and connected from one end to the other
end between both the ends in the orientated direction to form a
carbon nanotube continuous body, so that when the carbon nanotube
orientated composite is arranged in a part to be heat-released so
as to locate one end of the continuous body at a high temperature
side and the other end thereof at a low temperature side, the heat
releasing characteristics of this part can be improved.
[0009] (2) The invention is a carbon nanotube orientated composite
according to the item (1), wherein a length of the carbon nanotube
is 0.1-30 .mu.m and a diameter thereof is 10-300 nm.
[0010] When the length is shorter than 0.1 .mu.m, the heat
conductive length of the carbon nanotube itself is short and it is
difficult to form a continuous body by contacting the carbon
nanotubes with each other because the number of end portions of
nanotubes becomes large, while when it exceeds 30 .mu.m, the carbon
nanotubes are hardly orientated due to the tangling and it is
difficult to produce the continuous body.
[0011] When the diameter is less than 10 nm, the production yield
is bad and the productivity is poor and the cost is high, and hence
the use as a general-purpose good becomes difficult, while when it
exceeds 300 nm, the surface area is small and the heat conduction
is poor.
[0012] (3) The invention is a carbon nanotube orientated composite
according to the item (1) or (2), wherein the matrix is a metallic
material.
[0013] According to this invention, since the matrix is a metallic
material having a high heat conductivity, a higher heat
conductivity can be guaranteed.
[0014] (4) The invention is a carbon nanotube orientated composite
according to the item (3), wherein a compounding ratio of the
metallic material and the carbon nanotube is 0.1-5 parts by mass of
the carbon nanotube to 100 parts by mass of the metallic
material.
[0015] In order to guarantee the heat conductivity considerably
higher than that of aluminum as the conventionally known high heat
conductive material, it is necessary to include not less than 0.1
part by mass of the carbon nanotube per 100 parts by mass of the
metallic material, while when the amount of the carbon nanotube
exceeds 5 parts by mass, the carbon nanotubes can not be
sufficiently dispersed in the metallic material, and hence the
consolidated portion of the carbon nanotube or the cavity portion
due to the entrapping of air is undesirably caused.
[0016] (5) The invention is a carbon nanotube orientated composite
according to the item (3) or (4), wherein the metallic material is
one or more of a metal selected from Al, Cu and Mg or an alloy
containing the selected metal.
[0017] According to this invention, a higher heat conductivity can
be given because any one of Al, Cu and Mg is included as the
metallic material. Further, these metals are low in the melting
point, so that a melt dispersing the carbon nanotubes can be formed
at a lower temperature, and also they are soft and high in the
ductility and rich in the processability, which are preferable in
view of the production.
[0018] (6) The invention is a carbon nanotube orientated composite
according to any one of the items (3)-(5), wherein a heat
conductivity of the carbon nanotube in the orientated direction is
not less than 300 W/mK.
[0019] According to this invention, the heat conductivity is
considerably higher than the heat conductivity: 240 W/mK of
aluminum as a high heat conductive material, so that an excellent
heat releasing characteristics can be obtained by properly setting
a direction of the carbon nanotube orientated composite and
arranging in the part to be heat-released.
[0020] (7) The invention is a carbon nanotube orientated composite
according to the item (1) or (2), wherein the matrix contains a
rubber component.
[0021] According to this invention, the matrix contains the rubber
component, so that if it is intended to dispose the carbon nanotube
orientated composite in rubber such as a tire or the like to
improve the heat releasing characteristics of the tire, since the
composite is high in the affinity with the surrounding rubber and
the rubber component has a flexibility, it can deform following to
the surrounding rubber without obstructing the deformation of the
surrounding rubber, and also the breakage of the composite itself
is not caused.
[0022] (8) The invention is a carbon nanotube orientated composite
according to the item (7), wherein a compounding ratio of the
rubber component and the carbon nanotube is 5-100 parts by mass
based on 100 parts by mass of the rubber component.
[0023] When the amount of the carbon nanotube is less than 5 parts
by mass, the effect of improving the heat conduction is low because
the contact between the carbon nanotubes is less, while when it
exceeds 100 parts by mass, the processability in the mixing,
shaping or the like lowers.
[0024] (9) The invention is a carbon nanotube orientated composite
according to the item (7) or (8), wherein the rubber component is
butyl rubber.
[0025] According to this invention, butyl rubber is used as the
rubber component, so that the balance between the coat and the
performance is good, and further there are merits that the tensile
strength is low for facilitating the milling, and the gas
permeability is low, and the resistance to permeation and
resistance to corrosion of magnetic powder are excellent, and the
viscosity is low for facilitating the kneading and the like.
[0026] (10) The invention is a carbon nanotube orientated composite
according to any one of the items (7)-(9), wherein a heat
conductivity of the carbon nanotube in the orientated direction is
not less than 0.15 W/mK.
[0027] According to this invention, since the heat conductivity of
the carbon nanotube in the orientated direction is made not less
than 0.15 W/mK, there can be provided a heat conductivity
considerably higher than the heat conductivity of rubber, and hence
the excellent heat releasing characteristics can be obtained by
properly setting a direction of the carbon nanotube orientated
composite and arranging in the rubber part to be heat-released.
[0028] (11) The invention is a method of producing carbon nanotube
orientated composite according to any one of the items (3)-(6),
which comprises fluidizing a melt dispersed carbon nanotubes into a
molten metallic material and cooling and solidifying the melt on
the way of the fluidization to orientate the carbon nanotubes.
[0029] According to this invention, the melt is cooled and
solidified on the fluidizing stage, the carbon nanotubes can be
easily orientated and also there can be prevented the breakage of
the orientation of the carbon nanotubes after the orientation.
[0030] (12) The invention is a method of producing carbon nanotube
orientated composite according to any one of the items (7)-(10),
which comprises milling a rubber component and carbon nanotubes,
extruding the milled mass through an extruder and drawing the
extruded mass at a drawing rate faster than an extrusion rate.
[0031] According to this invention, the carbon nanotubes can be
orientated in a longitudinal direction by applying a tension
corresponding to the drawing rate faster than the extrusion rate (a
length of the extruded mass per unit time) to the extruded
mass.
[0032] (13) The invention is a pneumatic tire in which carbon
nanotube orientated composites according to any one of the items
(7)-(10) are arranged in parallel to each other and covered with a
coating rubber to form a heat releasing member, and the heat
releasing member is arranged so that one end of the carbon nanotube
orientated composite is exposed at an outer surface of the tire and
the other end thereof is positioned in an interior of the tire.
[0033] The tire absorbs energies through vibration of a vehicle,
impact and the like based on a large deformation during the running
to contribute to ride comfort and safety of the vehicle, but the
heat generation is large owing to the large energy absorbability
and hence it is an important matter to efficiently release the heat
generated in the tire for ensuring the improvement of tire
durability and the safety. In order to enhance the property of
releasing the heat generated in the tire, it is important to
improve heat conduction from a heat-generated site in the interior
of the tire to a surface of the tire.
[0034] According to the invention, one end of the carbon nanotube
orientated composite in the heat releasing member is exposed to the
outer surface of the tire, so that even if heat is generated in the
tire through the deformation during the running, the generated heat
moves from one end of the carbon nanotube orientated composite
located inside the tire through the carbon nanotube orientated
composite to the other end thereof exposed to the outer surface,
and can be efficiently released from the tire because the exposed
portion is always cooled by air outside the tire.
[0035] Also, the heat releasing member is formed by covering the
carbon nanotube orientated-composites with the coating rubber, so
that the affinity of the carbon nanotube orientated composite with
rubber in the tire can be enhanced to ensure the durability.
[0036] (14) The invention is a pneumatic tire according to the item
(13), wherein the heat releasing member is arranged in the vicinity
of at least one of an end of a belt and an turnup end of a
carcass.
[0037] The term "turnup end of carcass" used herein means an end of
the carcass wound around a bead core from an inside of the tire
toward an outside thereof. The vicinity of the belt end and the
vicinity of the carcass turnup end are portions most easily causing
the heat generation in the interior of the tire during the running
of the tire. According to the invention, an end of the heat
releasing member is arranged in the vicinity of at least one of
these ends, so that there can be effectively prevented the lowering
of the durability due to the heat deterioration.
[0038] (15) The invention is a pneumatic tire according to the item
(13) or (14), wherein the heat releasing member has a thickness of
1-5 mm.
[0039] When the thickness of the heat releasing member is less than
1 mm, a sectional area for heat release is small and the heat
release is insufficient, while when it exceeds 5 mm, a ratio of the
surrounding reinforced rubber decreases to cause problems in the
durability and peeling.
[0040] (16) The invention is a wheel for a vehicle provided with a
rim enclosing an interior portion of a tire in consort with the
tire, in which the carbon nanotube orientated composite according
to any one of the items (3)-(6) is arranged so as to pass through
the rim in its thickness direction, and an end of the carbon
nanotube orientated composite is positioned in a portion contacting
with the tire or a portion exposing to the interior portion of the
tire and the other end thereof is positioned in a portion exposing
to an atmosphere.
[0041] In order to effectively release the heat generated in the
tire, it is important to lower a temperature in the interior
portion of the tire raised by the heat generation of the tire in
addition to the rise of the heat conductivity form the interior of
the tire to the surface thereof. According to the invention, the
carbon nanotube orientated composite is arranged so as to pass
through the rim in the thickness direction, so that heat can be
moved from a side of the rim contacting in the interior portion of
the tire to a side opposite thereto in the thickness direction and
contacting with an atmosphere at a short pass and hence the
temperature of the interior portion of the tire can be efficiently
lowered.
[0042] (17) The invention is a wheel for a vehicle according to the
item (16), wherein a high heat conductive member having a heat
conductivity of not less than 300 W/mK is coated onto a surface of
the rim, and the high heat conductive member is extended from a
first portion contacting with the tire or exposing to the interior
portion of the tire to a second portion exposing to the
atmosphere.
[0043] According to this invention, the high heat conductive member
has a heat conductivity of not less than 300 W/mK and is higher
than the heat conductivity of a main part constituting the rim such
as aluminum or the like, and the first portion of the high heat
conductive member is exposed to the tire or the interior portion of
the tire being a high temperature side and the second portion
thereof is exposed to the atmosphere being a low temperature side,
respectively, so that the heat of the tire or in the interior
portion of the tire can be transmitted to the high heat conductive
member and rapidly discharged to the atmosphere side and further
the heat in the tire or the interior portion of the tire can be
efficiently released, whereby the wheel for the vehicle having more
excellent heat releasing performance can be constructed.
[0044] (18) The invention is a wheel for a vehicle according to the
item (17), wherein the high heat releasing member is an alloy of a
metal selected from the group consisting of Al, Mg and Cu or a
sintered body of the selected metal and a diamond.
[0045] According to this invention, the high heat conductive member
is made of the alloy of the selected metal or the sintered body of
the metal and diamond, so that heat from the tire can be more
effectively released by easily making the heat conductivity of the
high heat conductive member larger than that of the remaining
member constituting the wheel.
[0046] (19) The invention is a wheel for a vehicle according to the
item (17) or (18), wherein a cooling means is arranged on an
exposed surface of the second portion of the high heat conductive
member.
[0047] According to this invention, the cooling means is arranged
on the exposed surface of the second portion of the high heat
conductive member constituting the low temperature side, so that
the temperature difference between both the portions of the high
heat conductive member can be made large and hence the heat
releasing can be further promoted. In this case, the cooling means
includes a cooling fin provided on the heat releasing surface, a
cooling fin provided on an exterior, all means for promoting the
heat releasing of the heat releasing surface inclusive of the
covering of the heat releasing surface with a high heat releasing
member.
[0048] (20) The invention is a wheel for a vehicle according to the
item (19), wherein a cooling fin is arranged on the surface as the
cooling means.
[0049] According to this invention, the cooling means is
constructed with the cooling fin, so that the cooling can be simply
attained in a higher efficiency.
[0050] (21) The invention is a wheel for a vehicle according to any
one of the items (16)-(20), wherein a heat collecting fin is
arranged on a portion contacting with the interior of the tire.
[0051] According to this invention, the heat collecting fin is
arranged on the surface contacting with the interior of the tire,
so that heat inside the tire can be absorbed efficiently and the
cooling can be attained simply in a higher efficiency.
[0052] (22) The invention is a tire-wheel assembly comprising a
wheel for a vehicle according to any one of the items (16)-(21) and
a tire mounted on the wheel for the vehicle and a gas inclusive of
at least helium gas filled in an interior of the tire defined
between the tire and the wheel.
[0053] A heat conductivity of helium gas is 0.18 W/mK, which is
considerably higher than a heat conductivity: 0.026 W/mK of air
usually filled in the interior of the tire. According to this
invention, the gas inclusive of helium gas is filled, so that the
heat of the tire can be efficiently transmitted to the wheel as
compared with the conventionally used gas, and hence the heat
releasing from the tire can be more promoted.
[0054] (23) The invention is a tire-wheel assembly comprising a
wheel for a vehicle according to any one of the items (16)-(22) and
a tire mounted on the wheel for the vehicle and elastic balls
filled in an interior of the tire defined between the wheel and the
tire.
[0055] According to this invention, the elastic balls are filled in
the interior of the tire, so that the elastic balls bound about
inner wall face of the tire or the wheel in the interior of the
tire during the running of the tire to efficiently convect the gas
in the interior of the tire and hence the flowing ratio of heat
from the tire to the wheel can be improved to further release heat
from the tire.
[0056] (24) The invention is a disc brake comprising a rotor and a
pad decelerating the rotor while sliding to the rotating rotor, in
which a carbon nanotube orientated composite according to any one
of the items (3)-(6) is arranged on at least one part of the rotor
and the pad, and an end of the carbon nanotube orientated composite
is exposed to a sliding surface of the part or located in the
vicinity of the sliding surface and the other end thereof is
exposed to a surface other than the sliding surface of the
part.
[0057] The disc brake used in the vehicle or the like comprises a
rotating rotor and a pad sandwiching both surfaces of the rotor and
sliding to these surfaces to lower a rotating speed of the rotor
through a friction force, but even if the rotor is sandwiched by
the pads at the same force, a friction coefficient of the sliding
surface is largely affected by a temperature at this place.
Therefore, it is important to make the temperature constant for
stably ensuring the braking performance, but the brake is not
particularly provided with a cooling device, so that it is
important to rapidly lower the temperature of the sliding surface
to the surrounding temperature as far as possible.
[0058] According to this invention, the carbon nanotube orientated
composite is extended from the sliding surface or the vicinity
thereof to the surface as a heat releasing surface other than the
sliding surface, so that heat generated at the sliding surface can
be transmitted through the carbon nanotube orientated composite and
rapidly released from the heat releasing surface and hence the disc
brake having a higher heat releasing performance can be
constructed. Moreover, the feature that one end of the carbon
nanotube orientated composite is terminated in the vicinity of the
sliding surface means that the end is terminated at a position
shallowest from the sliding surface in a depth direction within a
range that the end is not exposed to the sliding surface even if
the sliding surface is worn.
[0059] (25) The invention is a disc brake according to the item
(24), which further comprises a cooling means for cooling the
surface of the part exposing the other end.
[0060] According to this invention, the cooling means is disposed
on the surface exposing the other end of the carbon nanotube
orientated composite as a heat releasing surface, so that the
temperature difference can be made large between both ends of the
carbon nanotube orientated composite and further heat releasing can
be promoted. In this case, the cooling means includes a cooling fin
provided on the heat releasing surface, a cooling fin provided on
an exterior, all means for promoting the heat releasing of the heat
releasing surface inclusive of the covering of the heat releasing
surface with a high heat releasing member.
[0061] (26) The invention is a disc brake according to the item
(25), wherein the cooling means is a cooling fin disposed on the
surface.
[0062] According to this invention, the cooling means is
constituted with the cooling fin, so that the cooling can be
attained simply in a high efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
[0063] FIG. 1 is a schematically perspective view of the carbon
nanotube orientated composite according to a first embodiment of
the invention;
[0064] FIG. 2 is a schematically side view illustrating a portion
of contacting carbon nanotubes with each other;
[0065] FIG. 3 is a schematically perspective view of a carbon
nanotube orientated composite extending along a curve;
[0066] FIG. 4 is a view illustrating a method of producing a carbon
nanotube orientated composite;
[0067] FIG. 5 is a schematically perspective view of the carbon
nanotube orientated composite according to a second embodiment of
the invention;
[0068] FIG. 6 is a section view of an embodiment of the pneumatic
tire according to the invention;
[0069] FIG. 7 is a section view taken along an arrow A-A of FIG.
6;
[0070] FIG. 8 is a section view taken along an arrow B-B of FIG.
6;
[0071] FIG. 9 is a schematically section view of a half part of a
wheel for a vehicle;.
[0072] FIG. 10 is a schematically section view illustrating a
portion C of FIG. 9;
[0073] FIG. 11 is a section view taken along a line D-D of FIG.
9;
[0074] FIG. 12 is a schematically section view of a disc brake;
and
[0075] FIG. 13 is a schematically perspective view of a rotor.
BEST MODE FOR CARRYING OUT THE INVENTION
[0076] An embodiment of the carbon nanotube orientated composite is
described with reference to the drawings. FIG. 1 is a schematically
perspective view of a first embodiment of the carbon nanotube
orientated composite 1, and FIG. 2 is a schematically side view of
a portion contacting carbon nanotubes 2 with each other.
[0077] The carbon nanotube orientated composite 1 comprises many
carbon nanotubes 2 orientated in a given direction in a matrix 4
made of a metal, in which at least a part of the carbon nanotubes 2
contact with each other and continuously extend from one end face
6a to the other end face 6b between the end faces 6a, 6b of the
carbon nanotube orientated composite 1.
[0078] The carbon nanotube 2 is a structural body made of a carbon
atom having a diameter of about few nm to few hundreds nm and has
an extremely fine tubular structure of an order corresponding to
10-2 times of usual carbon fiber (average diameter: not less than 5
.mu.m, length: about 100 .mu.m). A heat conductivity of the carbon
nanotube 2 itself is not clear in the accurate numerical value
though the measuring method is not established, but is known to be
very high as theoretically guessed from its structure.
[0079] The carbon nanotube 2 used in the invention is preferable to
have a length of 0.1-30 .mu.m, more preferably 0.1-10 .mu.m. When
the length is shorter than 0.1 .mu.m, the heat conductive length of
the carbon nanotube itself is short and it is difficult to form a
continuous body by contacting the carbon nanotubes with each other
because the number of end portions of nanotubes becomes large,
while when it exceeds 30 .mu.m, the carbon nanotubes are hardly
orientated due to the tangling and it is difficult to produce the
continuous body.
[0080] The carbon nanotube 2 is preferable to have a diameter of
10-300 nm, more preferably 100-250 nm. When the diameter is less
than 10 nm, the production yield is bad and the productivity is
poor and the cost is high, and hence the use as a general-purpose
good becomes difficult, while when it exceeds 300 nm, the surface
area is small and the heat conduction is poor.
[0081] The carbon nanotube is preferable to be synthesized by a
plasma CVD (chemical vapor deposition) process, a thermal CVD
process, a surface decomposition process, a fluidized vapor
synthesis process, an arc discharge process or the like. Among
them, the fluidized vapor synthesis process is particularly
preferable from a viewpoint of mass production.
[0082] As the carbon nanotube orientated composite 1 can be used
anyone of single layer nanotube and multi-layer nanotube. The
single layer nanotube has a bundle structure, but the number of
tubes per one bundle is not particularly limited. Also, the number
of tube layers in the multi-layer nanotube is not particularly
limited.
[0083] Furthermore, commercially available carbon nanotube can be
properly used as the carbon nanotube orientated composite 1. For
example, there can be used vapor process carbon fiber VGCF (trade
mark) made by Showa Denko Co., Ltd. and carbon nanotube made by
Materials Technologies Research (MTR) in USA.
[0084] In this case, the size of the carbon nanotube orientated
composite 1 is about 0.1-2.0 nm and the length thereof can be
freely selected if necessary.
[0085] As the metal of the matrix can be used aluminum, copper,
magnesium and the like. In the embodiment of the invention, a
mixing ratio of the carbon nanotube per 100 parts by mass of
aluminum is 0.1-5 parts by mass. As a result, the heat conductivity
is 300-12000 W/mK, which is higher by 50 times at maximum than the
heat conductivity of usual aluminum of 240 W/mK.
[0086] FIG. 3 is a schematically perspective view of a carbon
nanotube orientated composite 1A according to another embodiment of
the invention. In this case, the carbon nanotube orientated
composite 1A extends along a curve and comprises many carbon
nanotubes 2 orientated in the extending direction in a matrix 4A
made of a metal likewise the carbon nanotube orientated composite
1, in which these carbon nanotubes 2 communicate with each other
and continuously extend from one end face 7a to the other end face
7b so as to open at both end faces 7a, 7b of the carbon nanotube
orientated composite 1A.
[0087] The method of producing the carbon nanotube orientated
composite 1 shown in FIG. 1 is explained with reference to FIG. 4.
There is provided a melt 21 of aluminum mixed and dispersed with
carbon nanotubes 2 in a container 25, and the carbon nanotubes 2
are not orientated at this state. Then, a valve 26 disposed at an
outlet of the container 25 is opened and the melt 21 is flowed out
from the container 25 at a given flow rate.
[0088] The flowed melt 21 is poured into a groove 28 formed in a
cooling drum 27 rotating in an anti-clockwise direction in the
figure. In this case, the peripheral rate of the cooling drum is
set to be faster than the flow rate of the melt 21, so that the
melt 21 id drawn out by the groove 28 in the cooling drum 27 and
hence the carbon nanotubes 2 can be orientated in the flowing
direction by the drawing. Also, the melt 21 is rendered into a
semi-solidified state by the cooling action of the cooling drum 27
before it is discharged from the groove of the cooling drum 27, and
the orientation of the carbon nanotubes 2 is never turned back at
such a semi-solidified state. After the discharge from the cooling
drum 27, the melt is further cooled and solidified to form a solid
body 23. The solid body 23 is shaped into a circle at section
through rolling rolls 29 and cut into a given length by a cutter to
form a carbon nanotube orientated composite 1.
[0089] In the above production method, the carbon nanotubes 2 are
orientated in the flowing direction at a stage of flowing the melt
21. In this case, the carbon nanotubes 2 can be orientated in a
given direction by making the peripheral rate of the cooling drum
27 faster than the flow rate of the melt 21, and also can be
continuously formed.
[0090] In case of producing the carbon nanotube orientated
composite 1A extending along the curve, it can be produced by
pouring the melt 21 into a cylindrical mold having a radius of
curvature corresponding to the carbon nanotube orientated composite
1A instead of the cylindrical mold 28 and cooling the melt 21
flowing therein.
[0091] Next, a carbon nanotube orientated composite 11 according to
a second embodiment of the invention is described. FIG. 5 is a
schematically perspective view of the carbon nanotube orientated
composite 11 of the second embodiment.
[0092] The carbon nanotube orientated composite 11 comprises many
carbon nanotubes 2 orientated in a given direction in a matrix 14
containing a rubber component, in which at least a part of carbon
nanotubes 2 contact with each other and continuously extend from
one end face 16a to the other end face 16b between end faces 16a,
16b of the carbon nanotube orientated composite 11. The mutually
adjoining carbon nanotubes 2 are contacted on their outer
peripheral faces with each other at L1, L2 or L3 as shown in FIG. 2
to form a heat conductive pass in which substances having a high
heat conductivity are connected in series.
[0093] The details of the carbon nanotube 2 used in the carbon
nanotube orientated composite 11 are explained as in the first
embodiment and omitted here.
[0094] As the rubber component constituting the carbon nanotube
orientated composite 11 are mentioned natural rubber;
general-purpose synthetic rubbers such as emulsion-polymerized
styrene-butadiene rubber, solution-polymerized styrene-butadiene
rubber, high cis-1,4 polybutadiene rubber, low cis-1,4
polybutadiene rubber, high cis-1,4 polyisoprene rubber and the
like; diene-based specific rubbers such as nitrile rubber,
hydrogenated nitrile rubber, chloroprene rubber and the like;
olefinic specific rubbers such as ethylene-propylene rubber, butyl
rubber, halogenated butyl rubber, acrylic rubber, chlorosulfonated
polyethylene and the like; and other specific rubbers such as
hydrine rubber, fluorine rubber, polysulfide rubber, urethane
rubber and the like. Among them, the natural rubber and
general-purpose synthetic rubbers are preferable from a viewpoint
of a balance between cost and performances, and the butyl rubber is
preferable from viewpoints that the tensile strength is low and the
kneading is easy and the gas permeability is low and the resistance
to permeability is advantageous in the corrosion of magnetic powder
and the viscosity is low to facilitate the kneading and the
like.
[0095] The amount of the carbon nanotubes 2 compounded in the
carbon nanotube orientated composite 11 is preferable to be 5-100
parts by mass per 100 parts by mass of the rubber component. When
the amount is less than 5 parts by mass, the contact between the
carbon nanotubes is less and the effect of improving the heat
conduction is low, while when it exceeds 100 parts by mass, the
operability in the mixing, shaping and the like lowers.
[0096] The carbon nanotube orientated composite 11 may be properly
compounded with additives usually used in the rubber industry such
as filler, vulcanizing agent, vulcanization accelerator,
reinforcing member, antioxidant, softening agent and the like in
addition to the rubber component and carbon nanotubes.
[0097] In the carbon nanotube orientated composite 11, the heat
conductivity in the orientated direction of the carbon nanotubes is
not less than 0.15 W/mK, more preferably not less than 0.5
W/mK.
[0098] The carbon nanotube orientated composite 11 can be produced
as follows. At first, the rubber component is kneaded with the
carbon nanotubes. In this case, the kneading can be conducted by
properly compounding the additives usually used in the rubber
industry.
[0099] Then, the kneaded mass is heated to lower the viscosity and
extruded through an extruder to a low temperature side and the
extruded mass is drawn by applying tension and solidified at the
low temperature side. In this case, tension corresponding to a
drawing rate (length of the drawn mass per unit time) faster than
an extrusion rate (length of the extruded mass per unit time) is
applied to the extruded mass to orientate the carbon nanotubes in a
longitudinal direction. The upper limit of the tension is a level
preventing the cut of the extruded mass due to the drawing.
[0100] Then, an embodiment of the pneumatic tire using the carbon
nanotube orientated composite 11 of the second embodiment is
explained with reference to the drawings. FIG. 6 is a section view
of the pneumatic tire according to an embodiment of the invention,
and FIG. 7 is a section view corresponding to an arrow A-A of FIG.
6 and FIG. 8 is a section view corresponding to an arrow B-B of
FIG. 6. A tire 30 comprises a pair of bead portions 31, a pair of
sidewall portions 32, a tread portion 33, a carcass 35 toroidally
extending between ring-shaped bead cores 34 embedded in the
respective bead portions 31 and wound at both ends around the bead
cores 34 from an inside toward an outside, a belt 36 arranged on an
outer periphery of the carcass 35 located at the tread portion 33
and comprised of at least two belt layers, and a pair of
cone-shaped heat releasing members 37 and a pair of cone-shaped
heat releasing members 38 having a central axis of the tire as an
axial center, in which the heat releasing member 37 is arranged so
as to extend from the vicinity of a belt end to an outer surface of
the tire and the heat releasing member 38 is arranged so as to
extend from the vicinity of a turnup end of the carcass 35 to the
outer surface of the tire.
[0101] Moreover, it is preferable that these heat releasing members
37, 38 are directed to such a direction that the distance to the
outer surface of the tire becomes shortest from a viewpoint of the
heat conduction.
[0102] Each of the heat releasing members 37, 38 is constructed
with a plurality of the carbon nanotube orientated composites 11
and a coating rubber 39 covering these carbon nanotube orientated
composites 11, in which the carbon nanotube orientated composite is
arranged so as to expose its both ends to both the end faces of the
cone-shaped member.
[0103] The width of the heat releasing member 37, 38 corresponds to
a distance from the vicinity of the belt end or carcass turnup end
to the outer surface of the tire determined in correspondence with
a size of the target tire. Also, the carbon nanotube orientated
composites 11 have a diameter of 0.1-2.0 mm, preferably 0.1-1.0 mm
and are arranged at a given interval in the circumferential
direction.
[0104] Moreover, the pneumatic tire 30 are provided with both of
the heat releasing members 37 and 38, but may be provided with only
one of the heat releasing members 37, 38.
[0105] Next, an embodiment of the wheel for a vehicle using the
carbon nanotube orientated composite 1 of the first embodiment is
explained with reference to the drawings. FIG. 9 is a schematically
section view of a half part of a wheel 41 for a vehicle, and FIG.
10 is a schematically section view showing details of a portion C
in FIG. 9 and FIG. 11 is a section view taken along a line D-D of
FIG. 9. The wheel 41 for the vehicle comprises a rim 42 supporting
a tire 45 and defining a tire interior 41 together with the tire
45, and a disc 43 connected to the rim 42 and attached to a hub of
the wheel. Also, a plurality of ribs 44 reinforcing the rim 42 are
arranged on the circumference of the rim.
[0106] A plurality of carbon nanotube orientated composites 1 are
arranged so as to pass through the rim 42 in a thickness direction,
in which one end of the composite is arranged at a portion of the
rim 42 contacting with the tire 45 or exposing to the tire interior
46 and the other end thereof is arranged on a portion exposing to
an atmosphere at an opposite side in the thickness direction of the
rim 42.
[0107] Also, a high heat conductive member 48 is coated on surfaces
of the rim 42, disc 43 and rib 44 constituting the wheel 41 over
their full surfaces. When the surface contacting with the tire 45
and surface exposing to the tire interior 46 are a first portion N
of high temperature side and the surface other than the surfaces N
is a second portion T of low temperature side, heat is moved from
the first portion through the carbon nanotube orientated composites
1 and high heat conductive members 48 to the second portion and
released therefrom.
[0108] Since the carbon nanotube orientated composite 1 and high
heat conductive member 48 is higher in the heat conductivity than a
matrix 47 as a main member of the wheel 41, heat from the tire 45
or the tire interior 46, which has been discharged to the
atmosphere only through the matrix 47 in the prior art, is mainly
released to the atmosphere through the carbon nanotube orientated
composites 1 and the high heat conductive member 48 and hence the
considerably excellent heat releasing characteristic can be
provided. It is preferable that the carbon nanotube orientated
composite 1 and the high heat conductive member 38 have a heat
conductivity of not less than 300 W/mK.
[0109] Also, a plurality of convex heat-collecting fins 51 are
disposed on the surface N of the high heat conductive member 48
exposing to the tire interior 46, whereby heat from the tire
interior 46 can be efficiently collected, while a plurality of
convex cooling fins 52 are disposed on the surface T of the high
heat conductive member 48 exposing to the atmosphere. These cooling
fins 52 constitute a cooling device for efficiently releasing heat
transmitted through the carbon nanotube orientated composites 1 and
the high heat conductive member 48 to the atmosphere.
[0110] As the high heat conductive member 48 can be used an alloy
of a metal selected from the group consisting of Al, Mg and Cu
having a high heat conductivity or a sintered body of the selected
metal and diamond, or the like.
[0111] The carbon nanotube orientated composites 1 are arranged
over a full surface of a portion of the rim 42 that is not provided
with the rib 44 so as to uniformly expose to the tire interior 46
and in this case, it is preferable that an exposed area ratio is
5-50%. When the ratio is less than 5%, the effect of sufficiently
improving the heat releasing is not obtained, while when it exceeds
50%, the strength required as the wheel can not be satisfied. Also,
when the carbon nanotube orientated composites 1 are arranged in
the matrix 47, a hole receiving the carbon nanotube orientated
composite 1 is first formed in the rim 42 and the carbon nanotube
orientated composites are inserted and fixed in the hole. In the
fixation can be used a method using an adhesive, a method utilizing
interference fit or the like.
[0112] In order to more improve the heat releasing from the tire
45, it is effective to enhance the heat conductivity of the tire
interior 46 constituting a part of a heat releasing path. For this
end, the tire interior 46 is preferable to be filled with a helium
gas 53 having a heat conductivity higher than air instead of air,
and also a mixture of the helium gas 53 and other gas such as air
can be used.
[0113] In order to randomly move elastic balls 54 in the tire
interior 46, it is preferable to use elastic balls 54 easily
bounding on wall face of the tire 45 or the rim 42. For this end,
the elastic ball 54 is required to have a high elasticity. For
example, there can be used sponge ball, rubber ball, a hollow ball
filled under an internal pressure higher than an internal pressure
filled in the tire interior 46 and made of rubber or resin, and the
like. Also, if irregularities or fins for stirring are formed on
the surface of the elastic ball 54, the stirring efficiency can be
improved.
[0114] The elastic ball 54 is preferable to have a diameter of 5-10
mm. When the diameter exceeds 10 mm, heat generation becomes large
due to the impact on the wall face or the friction with the gas,
while when it is less than 5 mm, the sufficient stirring is not
obtained. Also, the number of the elastic balls 54 filled in the
tire interior 46 is preferable to be 10. When the number of the
balls exceeds 10, the heat generation becomes large likewise the
above case.
[0115] Next, an embodiment of the disc brake using the carbon
nanotube orientated composite 1 of the first embodiment is
explained with reference to the drawings. FIG. 12 is a
schematically section view of a disc brake 61, and FIG. 13 is a
schematically perspective view illustrating a rotor 62. The disc
brake 61 comprises a disc-shaped rotor 62 attached to an axle and
rotated therewith, and a pair of plate-shaped pads 63 sandwiching
the rotor from both sides and sliding along a sliding face 72 of
the rotor 62 to decelerate the rotating speed of the rotor 62
through friction force. The pads 63 are supported by a hydraulic
piston 64 and a caliper 65, respectively, and driven in forward and
rearward directions on the rotor 62 by these members.
[0116] A peripheral face 71 of the rotor 62 constitutes a heat
releasing face releasing friction heat generated at the sliding
face 72, and a plurality of convex cooling fins 73 are formed on
the periphery of the face for improving s heat releasing
efficiency. As a main member 66 of the rotor 62 us generally used a
cast iron considering mechanical strengths, abrasion resistance and
the like. In the rotor 62 according to the invention, however, a
plurality of carbon nanotube orientated composites 1 exposing at
one end to the sliding face 72 and exposing at the other end to the
peripheral face 72 are embedded and arranged in the member 66.
[0117] The carbon nanotube orientated composites 1 can enhance the
heat releasing effect of the rotor 62 because the heat conductivity
in the orientated direction of the carbon nanotube is 300-1200 W/mK
as previously mentioned and is higher by about 164 times at maximum
that the heat conductivity of the cast iron of 73 W/mK constituting
the member 66 around the carbon nanotube orientated composite
1.
[0118] The carbon nanotube orientated composites 1 are arranged so
as to uniformly expose over a whole of the sliding face 72, and in
this case the exposing area ratio is preferable to be 5-30%. When
the ratio is less than 5%, the effect of sufficiently improving the
heat releasing is not obtained, while when it exceeds 30%, the
strength required as the sliding face can not be satisfied. Also,
in order to arrange the carbon nanotube orientated composites 1 in
the member 66, holes receiving the carbon nanotube orientated
composites 1 are first formed in the member 66 and then the carbon
nanotube orientated composites 1 are inserted and fixed in the
holes. In the fixation can be used a method using an adhesive, a
method utilizing interference fit or the like.
[0119] An edge face 74 of the plate-shaped pad 63 constitutes a
heat releasing face releasing friction heat generated at the
sliding face 75. Also, this face is provided with a plurality of
convex cooling fins 76 for improving the heat releasing efficiency
over the periphery of the edge face 74. As a main member 68 of the
pad 63 is generally used a material such as a sintered body of a
metal or the-like considering the mechanical strengths, friction
coefficient and the like. In the pad 63 according to the embodiment
of the invention, however, a plurality of the carbon nanotube
orientated composites 1 exposing at one end to the sliding face 75
and exposing at the other end to the edge face 74 are embedded and
arranged in the member 68.
[0120] The carbon nanotube orientated composite 1 having a heat
conductivity of 300-1200 W/mK has a heat conductivity considerably
higher than the heat conductivity of not more than 100 W/mK in the
main member 68 of the pad 63 and can enhance the heat releasing
effect of the pad 63.
EXAMPLES
[0121] The carbon nanotube orientated composite of the second
embodiment and the pneumatic tire using the same are explained in
detail with reference to the following examples but the invention
is not limited to these examples.
Examples 1-15
[0122] There are prepared various rubber compositions having a
compounding recipe shown in Table 1. Then, each of these rubber
composition after the kneading is extruded through an extruder at
an extrusion rate of 10 m/min and drawn at a drawing rate of 15
m/min under a tension of 0-200 N/mm.sup.2 and vulcanized to prepare
a rod-shaped carbon nanotube orientated composite having a diameter
of 1 mm in which carbon nanotubes are orientated therein.
Conventional Examples 1-3
[0123] A rubber composition is kneaded in the same manner as in
Example 3, 8 or 12 except that carbon nanotubes are not compounded,
and extruded without applying tension and vulcanized to prepare a
thread-shaped vulcanized rubber.
Comparative Examples 1-3
[0124] A rubber composition having the same compounding recipe as
in Example 3, 8 or 12 is prepared and kneaded and extruded through
the extruder without applying tension and vulcanized to obtain a
rod-shaped carbon nanotube orientated composite.
[0125] The heat conductivities of the carbon nanotube orientated
composites obtained in the examples and comparative examples and
the vulcanized rubbers obtained in the conventional examples are
measured by means of a rapid heat conductivity meter QTM-500 made
by Kyoto Densi Co., Ltd. to obtain results shown in Table 1.
[0126] Then, a plurality of rod-shaped carbon nanotube orientated
composites in each of Examples 1, 2, 3 and 7 or the vulcanized
rubbers in Conventional Example 1 are coated with rubber to prepare
a heat releasing member, which is used to prepare a tire shown in
FIG. 1 except that the heat releasing member 38 is not arranged at
a position in the vicinity of the carcass turnup end. Such a tire
is run on a drum at 100 km/hr over 300 km in an indoor drum test
under an atmosphere of 30.degree. C., and thereafter a temperature
of a shoulder portion of the tire is measured to obtain a result as
shown in Table 1. Also, for the comparison, a rubber composition
containing no carbon nanotube is prepared, which is used to prepare
a tire having the same structure as in the above example and then
the heat conductivity and temperature of shoulder portion of the
tire are measured. The measured results are also shown in Table 1.
Moreover, in the tires of Examples 1, 2, 3 and 7 using the carbon
nanotube orientated composite, the breakage of the composite is not
observed after the running on the drum. TABLE-US-00001 TABLE 1
Conven- Compar- Example Example Example Example Example Example
Example tional ative 1 2 3 4 5 6 7 Example 1 Example 1 Compounding
butyl rubber (IIR) 100 100 100 100 100 100 100 100 100 recipe
carbon nanotube *1 100 80 50 40 30 20 5 0 50 (part by mass) carbon
black *2 0 10 0 10 20 30 50 50 0 aromatic oil 10 10 10 10 10 10 10
10 10 zinc white 3 3 3 3 3 3 3 3 3 stearic acid 1 1 1 1 1 1 1 1 1
antioxidant *3 1 1 1 1 1 1 1 1 1 vulcanization 1 1 1 1 1 1 1 1 1
accelerator *4 sulfur 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Heat
conductivity (W/m K) 6.0 5.0 3.7 3.2 2.3 1.6 1.3 0.3 0.9
Temperature of shoulder portion (.degree. C.) 61 65 73 -- -- -- 85
90 -- Conven- Compar- tional ative Example 8 Example 9 Example 10
Example 11 Example 2 Example 2 Compounding NR 100 100 100 100 100
100 recipe carbon nanotube *1 50 40 30 20 0 50 (part by mass)
carbon black *2 0 10 20 30 50 0 aromatic oil 10 10 10 10 10 10 zinc
white 3 3 3 3 3 3 stearic acid 1 1 1 1 1 1 antioxidant *3 1 1 1 1 1
1 vulcanization 1 1 1 1 1 1 accelerator *4 sulfur 1.5 1.5 1.5 1.5
1.5 1.5 Heat conductivity (W/m K) 3.4 2.8 2.1 1.5 0.3 0.8 Conven-
Compar- tional ative Example 12 Example 13 Example 14 Example 15
Example 3 Example 3 Compounding NR 50 50 50 50 50 50 recipe BR 50
50 50 50 50 50 (part by mass) carbon nanotube *1 50 40 30 20 0 50
carbon black *2 0 10 20 30 50 0 aromatic oil 10 10 10 10 10 10 zinc
white 3 3 3 3 3 3 stearic acid 1 1 1 1 1 1 antioxidant *3 1 1 1 1 1
1 vulcanization 1 1 1 1 1 1 accelerator *4 sulfur 1.5 1.5 1.5 1.5
1.5 1.5 Heat conductivity (W/m K) 3.5 3.0 2.1 1.6 0.3 0.8 *1: vapor
process carbon fiber VGCF (trade mark) made by Showa Denko Co.,
Ltd. *2: carbon black HAF *3:
N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine *4:
N-cyclohexyl-2-benzothiazyl sulfenamide
[0127] Moreover, there is provided a conventional tire having the
same structure as in the tire shown in FIG. 6 except that the heat
releasing member is not arranged, which is subjected to the indoor
drum test in the same manner as in Example 1 and the temperature of
the shoulder portion of the tire is measured to be 90.degree.
C.
INDUSTRIAL APPLICABILITY
[0128] As seen from the above, according to the invention, there
can be provided materials having a heat conductivity considerably
higher than that of copper, aluminum or the like, and the heat
conduction can be considerably improved by arranging it in a rubber
material, and heat can be efficiently released from a tire or a
brake requiring a severe heat durability.
* * * * *