Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
1998-06-30
2001-02-13
Henderson, Christopher (Department: 1713)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S209500, C525S349000
Reexamination Certificate
active
06186204
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire which exhibits excellent stability and controllability on wet roads (hereinafter referred to as controllability) or a combination of excellent controllability on wet roads and excellent comfort of ride even when a vehicle is vibrating (hereinafter referred to as ride comfort) throughout the life of the pneumatic tire including the initial, intermediate, and final periods of tire use.
2. Description of the Related Art
In recent years, as the higher power, higher performance, and longer life have been desired of automobiles, tires have been increasingly required to have more excellent controllability or a combination of more excellent controllability and ride comfort than hitherto throughout the life of the pneumatic tire. Particularly for passenger tires, highly excellent controllability or a combination of highly excellent controllability and ride comfort is strongly required as the tire structure changes from a bias structure to a radial structure and the aspect ratio of radial tires changes from 82 to 72 and further to 65.
To satisfy the requirement, various compounding ingredients used in rubber compositions for tire treads have been examined. As for the vulcanization accelerator, it is disclosed in Japanese Patent Application Laid-Open No. 58-87138 that a rubber composition comprising a specific vulcanization accelerator and a specific antioxidant shows improved resistance to hardening under heating and provides a tire showing improved appearance in the final period of tire use. However, performances of the tire during driving are not examined at all. It is disclosed in Japanese Patent Application Laid-Open No. 56-139542 that scorching in mixing to prepare a rubber composition can be improved by the use of a rubber composition comprising a specific vulcanization accelerator. However, performances of a tire are not described or suggested at all. With respect to inorganic fillers, it is disclosed in Japanese Patent Application Laid-Open No. 10-53003 that a rubber composition comprising alumina provides a tire showing improved controllability in the initial period of tire use. However, the improved controllability cannot be maintained in the intermediate to final periods of tire use.
SUMMARY OF THE INVENTION
The present invention has been made under the above circumstances, and the object of the present invention is to provide a pneumatic tire exhibiting excellent controllability or a combination of excellent controllability and excellent ride comfort throughout the life of the pneumatic tire including the initial, intermediate, and final periods of tire use.
As the result of extensive studies by the present inventors in which attention was paid on polymers and compounding ingredients, the present inventors found that the object could be achieved by the following means, and thus, the inventors arrived at the present invention.
Accordingly, the present invention provides (1) a pneumatic tire comprising a tread portion formed by using a rubber composition which comprises:
a rubber component comprising 50 parts by weight or more of SBR in 100 parts by weight of the rubber component;
per 100 parts by weight of the rubber component, 20 parts by weight or more of a softener which comprises 5 to 55 parts by weight of at least one resin softener having a softening point of 35 to 150° C. and selected from the group consisting of coumarone resins, phenol-terpene resins, and petroleum hydrocarbon resins; and
per 100 parts by weight of the rubber component, 0.2 to 10.0 parts by weight of at least one dithiophosphoric acid compound type vulcanization accelerator selected from the group consisting of O,O′-dialkyldithiophosphoric acid disulfides, O,O′-dialkyldithiophosphoric acid tetrasulfides, and metal dithiophosphates represented by following general formula (I):
wherein R
1
and R
2
each independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 10 carbon atoms, the alkyl group being a linear, branched, or cyclic group; M
1
represents a Zn atom, an Sb atom, an Fe atom, or a Cu atom; and n represents a valency of the metal represented by M
1
.
(2) It is preferable that the metal dithiophosphate represented by general formula (I) which is described in (1) is a dithiophosphoric acid compound type vulcanization accelerator which is represented by following general formula (II):
wherein M
2
represents a Zn atom or an Sb atom; and n represents a valency of the metal represented by M
2
.
The present invention also provides (3) a pneumatic tire comprising a tread portion formed by using a rubber composition which comprises:
a rubber component comprising 50 parts by weight or more of SBR in 100 parts by weight of the rubber component;
per 100 parts by weight of the rubber component, 20 parts by weight or more of a softener which comprises 5 to 55 parts by weight of at least one resin softener having a softening point of 35 to 150° C. and selected from the group consisting of coumarone resins, phenol-terpene resins, and petroleum hydrocarbon resins; and
per 100 parts by weight of the rubber component, 0.2 to 10.0 parts by weight of at least one benzothiazole compound type vulcanization accelerator selected from the group consisting of compounds represented by following general formulae (III), (IV), (V), and (VI):
wherein R
3
and R
4
each independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group having 6 to 10 carbon atoms, excluding the case in which R
3
and R
4
both represent hydrogen atoms; R
5
represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group, or a cycloalkyl group; R
6
represents a hydrogen atom or an amino group represented by —N(R
7
)R
8
, wherein R
7
and R
8
each independently represents a hydrogen atom, an alkyl group having 2 to 4 carbon atoms, or cyclohexyl group, excluding the case in which R
7
and R
8
both represent hydrogen atoms; R
9
and R
10
each independently represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group, or a cycloalkyl group; X represents a Zn atom, a Cu atom, or an amino group represented by >N—R
13
, wherein R
13
represents an alkyl group having 2 to 4 carbon atoms or cyclohexyl group; and R
11
and R
12
each independently represents the same group as that represented by R
9
.
(4) It is preferable that, in general formula (III) representing the benzothiazole compound type vulcanization accelerator which is described in (3), R
3
and R
4
each independently represents a hydrogen atom, methyl group, ethyl group, or phenyl group, excluding the case in which R
3
and R
4
both represent hydrogen atoms.
(5) It is preferable that the benzothiazole compound type vulcanization accelerator represented by general formula (III) which is described in (3) is at least one compound selected from the group consisting of bis(4-methylbenzothiazolyl-2) disulfide, bis(5-methyl-benzothiazolyl-2) disulfide, mercapto-4-methyl-benzothiazole, and mercapto-5-methylbenzothiazole.
(6) It is preferable that, in general formulae (IV), (V), and (VI) representing the benzothiazole compound type vulcanization accelerator which are described in (3), the alkoxy group is bonded to the 4-position or the 6-position, more preferably to the 4-position, of the aromatic single ring.
(7) It is preferable that, in general formulae (IV), (V), and (VI) representing the benzothiazole compound type vulcanization accelerator which are described in (3), the alkoxy group is a group selected from the group consisting of methoxy group, ethoxy group, and butoxy group, and more preferably ethoxy group.
(8) It is preferable that the resin softener described in any of (1) and (3) has a softening point of 70 to 130° C.
(9) It is preferable that, in any of (1) and (3), the coumarone resin used as the resin softener is a coumarone-indene resin having a softening point of 70 to 130° C.
(10) It is preferable that, in any of (1) and
Kimura Shigeo
Sasaka Naohiro
Yagawa Kazuo
Bridgestone Corporation
Henderson Christopher
Sughrue Mion Zinn Macpeak & Seas, PLLC
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