Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1996-06-19
2001-02-13
Mulcahy, Peter D. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S098000, C524S100000, C524S236000, C524S248000
Reexamination Certificate
active
06187843
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a rubber composition for a tire tread developing an excellent gripping performance as well as a pneumatic tire using the same.
2. Description of Related Art
Recently, it is strongly demanded to provide pneumatic tires having higher running performances accompanied with improvement of automobile performances, pavement of roads and development of expressway networks. As the running performances of the tire become higher, the automobile can be run accurately and safely at a higher speed. Particularly, the gripping performance exemplified by acceleration performance and braking performance is an important requirement in the tire.
In order to obtain a high gripping performance, there has hitherto been proposed a method wherein styrene-butadiene copolymer rubber having a high bound styrene content as a rubber having a high glass transition temperature was used in the rubber composition for the tire tread.
According to this method, however, the improvement of the gripping performance is obtained, but there is caused a problem that the value of tan &thgr; lowers with the rise of rubber temperature during the running of the tire and hence the gripping performance rapidly lowers.
In order to prevent the degradation of the gripping performance due to the temperature rise, there is proposed a technique of using a copolymer rubber obtained by copolymerizing a monomer such as 1,3-butadiene, styrene, isoprene or the like with a methacrylate compound or acrylate compound containing diphenyl phosphate group such as diphenyl-2-methacryloyloxyethyl phosphate, diphenyl-2-acryloyloxyethyl phosphate or the like (see JP-A-59-187011). However, this technique can not be applied to natural rubber, but also undesirably damages properties inherent to a polymer such as styrene-butadiene copolymer rubber or polybutadiene rubber in accordance with the production conditions.
On the other hand, there is a method of increasing the value of tan &thgr; in the rubber composition by using a compounding system filled with great amounts of process oil and carbon black. According to this method, the gripping performance is improved, but the fracture properties and wear resistance are considerably degraded, so that the filling amount is critical and hence it is difficult to render the gripping performance into the required high level.
There is another method wherein particular amount of particular imidazole compound or imidazoline compound and particular proton acid derivative are compounded with the rubber ingredient to increase the value of tan &thgr; and the resulting rubber composition is used in the tire tread to improve the gripping performance (see JP-A-63-139931). In this method, the antiscorching property is somewhat improved as compared with a method described in JP-A-63-10645, but does not yet arrive at a practical level.
SUMMARY OF THE INVENTION
It is, therefore, an object of the invention to solve the aforementioned problems of the conventional techniques and to provide rubber compositions having a good scorch time and developing an excellent gripping performance as well as pneumatic tires using the same.
According to the invention, there is the provision of a rubber composition for use in a tire tread developing an excellent gripping performance, comprising 0.1-50 parts by weight of at least one nitrogen-containing compound selected from the group consisting of the following compounds (1)-(4):
(1) a lactam having a carbon number of 4-19 in a hetero-cyclic ring and represented by the following formula:
(wherein each of R
1
and R
2
is a straight or branched chain alkyl group having a carbon number of 1-8, a hydrogen atom, a phenyl group, or a phenyl group substituted with an alkyl group having a carbon number of 1-8 and they are the same or different);
(2) a tertiary amine represented by the following formula:
(R
3
)
3
N
(wherein R
3
is a straight or branched chain alkyl group having a carbon number of 1-8, a phenyl group, or a phenyl group substituted with an alkyl group having a carbon number of 1-8);
(3) an isoquinoline represented by the following formula:
(wherein R
4
is a straight or branched chain alkyl group having a carbon number of 1-8, a hydrogen atom, a phenyl group, or a phenyl group substituted with an alkyl group having a carbon number of 1-8); and
(4) a cyclic dipeptide represented by the following formula:
(wherein each of R
5
and R
6
is a straight or branched chain alkyl group having a carbon number of 1-8, a hydrogen atom, a phenyl group, or a phenyl group substituted with an alkyl group having a carbon number of 1-8 and they are the same or different); and 0.1-50 parts by weight of at least one compound selected from the group consisting of proton acids and derivatives thereof, based on 100 parts by weight of rubber ingredient consisting of natural rubber and/or synthetic rubber.
In the rubber composition according to the invention, the proton acid and derivative thereof include acetic acid, succinic acid, oleic acid, resin acid, maleic acid, benzoic acid, p-methoxybenzoic acid, p-chlorobenzoic acid, p-nitrobenzoic acid, cinnamic acid, d-naphthylcarboxylic acid, phthalic acid, trimellitic acid, pyromellitic acid, anhydrous phthalic acid, naphthoic acid and phenolic derivatives thereof.
In a pneumatic tire according to the invention, the above-defined rubber composition is used in a tread portion of the tire.
REFERENCES:
patent: 4638026 (1987-01-01), Sambuis et al.
patent: 5064905 (1991-11-01), Stamhuis et al.
patent: 5187236 (1993-02-01), Coolbaugh et al.
patent: 5536774 (1996-07-01), Segatta
patent: 271522 (1989-09-01), None
patent: 139602 (1985-05-01), None
patent: 251760 (1988-01-01), None
patent: 59-187011 (1984-10-01), None
patent: 63-10645 (1988-01-01), None
patent: 63-139931 (1988-06-01), None
Chemical Abstracts, vol. 98, No. 14, 1983, Columbus, Ohio, US; Abstract No. 108679, XP002016622 Abstract and SU-A-979 530 (VP Bukalov et al.) Dec. 7, 1982.
Hatakeyama Kazuya
Nohara Daisuke
Bridgestone Corporation
Mulcahy Peter D.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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