Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-07-17
2002-04-30
Jagannathan, Vasu (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S495000, C152S450000
Reexamination Certificate
active
06380288
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a rubber composition providing rubber products which are excellent in aging resistance, and a pneumatic tire.
BACKGROUND ART
In order to prevent aging of rubber products using rubber compositions comprising natural rubber and/or synthetic rubber, various antioxidants have so far been developed.
Further, in order to meet social demands for saving resources and energy in recent years, low heat generation property rubber compositions have actively been developed in the rubber industry.
In general, diphenyldiamine based and hindered phenol based compounds have so far been used as antioxidants. These compounds give H of >NH and —OH to peroxy radicals produced in a process of auto-oxidative degradation to deactivate them, and the compounds themselves turn to stable compounds through more stable radicals. Widely known is such a method that peroxy radicals are deactivated to cut off a radical chain reaction, whereby aging is prevented.
However, both the conventional diphenyldiamine based and hindered phenol based antioxidants described above have an aging-resistant action. In general, the aging-resistant effect increases according as the compounding amount is increased in a range where the compounding amount thereof is small. However, when they are used in large quantities, an increase in the effect gets slow gradually, and the effect is reduced by blooming in a certain case. Accordingly, amount to be used has to be properly restricted.
Further, the diphenyldiamine based antioxidants cause a large change rate of an elastic modulus of rubber before and after degradation of the rubber, and in a certain case, they harden the rubber markedly and deteriorate the rubber properties depending on the ingredients of the rubber composition and the conditions of degradation.
On the other hand, with respect to the aging-resistant characteristics of hydrazide compounds, known are dihydrazide compounds displaying a green strength-improving effect (U.S. Pat. No. 4,124,750), compounds which elevate ozone resistance and in which hydrogen parts of hydrazide and hydrazine are substituted (British Pat. No. 909753) and compounds having an effect as stabilizers for oil extended rubber (British patent 1330393).
Further, it is described in Japanese Pat. No. Publication No. Hei 7-57828 that specific hydrazide compounds can provide a rubber product with a low heat generation property effect and among these compounds, particularly isophthalic dihydrazide (IDH) and 3-hydroxy-2-naphthoic hydrazide can reveal a low heat generation property effect in small amounts.
However, the hydrazide compounds described in these publications, which are compounded into rubber compositions comprising a general sulfur-vulcanizing base rubber, shorten initiation of vulcanization reaction to a large extent and elevate the Mooney viscosity, so that the workability is damaged to a large extent. Accordingly, the compounding amount is restricted only to a small amount, and the satisfactory aging resistant effect is not obtained.
In light of the conventional problems described above, the present invention intends to solve them, and an object thereof is to provide a rubber composition providing rubber products having an excellent aging resistant characteristic and a rubber composition in which workability is not reduced when blended with sulfur vulcanizing agents used extensively in the rubber industry including tire.
Another object of the present invention is to provide a low heat generation property rubber composition which can control an increase in the Mooney viscosity and enhance the workability while maintaining the low heat generation property.
In addition, a further object of the present invention is to provide a pneumatic tire having an excellent aging-resistant characteristic as well as an excellent low heat generation property.
DISCLOSURE OF THE INVENTION
Intensive investigations of the conventional problems described above continued by the present inventors have resulted in newly finding that specific hydrazide compounds obtained as a result of modifying a hydrazide group by various methods so that an influence is not exerted on a vulcanization reaction can achieve the objects described above while maintaining an aging-resistant capability and that some of these compounds have a low heat generation property effect as well, and thus the present invention has come to complete.
That is, the present invention has the following constituents of (1) to (17):
(1) A rubber composition prepared by compounding 0.05 to 20 parts by weight of at least one selected from the group consisting of hydrazide compounds represented by the following Formulas (I) to (IV) per 100 parts by weight of a rubber component comprising at least one rubber selected from the group consisting of natural rubber and synthetic rubber:
wherein A represents one selected from the group consisting of an aromatic group which may be substituted with at least one substituent containing at least one atom of carbon, sulfur, oxygen and nitrogen atoms, a hydantoin ring which may be substituted with at least one substituent containing at least one atom of carbon, sulfur, oxygen and nitrogen atoms, and a saturated or unsaturated linear hydrocarbon having 1 to 18 carbon atoms; R
1
to R
4
each represent hydrogen, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group or an aromatic group which may be substituted with at least one substituent containing at least one atom of carbon, sulfur, oxygen and nitrogen atoms, and each of R
1
to R
4
may be the same or different, and when R
1
and R
2
and/or R
3
and R
4
are alkyl groups, R
1
may be bonded to R
2
and R
3
may be bonded to R
4
to form rings;
wherein Y represents hydrogen, an amino group, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group, an alkenyl group, an aromatic group which may be substituted with at least one substituent containing at least one atom of carbon, sulfur, oxygen and nitrogen atoms, a pyridyl group or hydrazino group, R
5
and R
6
each represent hydrogen, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group, an alkenyl group or an aromatic group which may be substituted with at least one substituent containing at least one atom of carbon, sulfur, oxygen and nitrogen atoms, and each of R
5
and R
6
may be the same or different, and when R
5
and R
6
are alkyl groups, R
5
may be bonded to R
6
to form a ring;
wherein R
7
and R
8
each represent an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group, an aromatic group which may be substituted with at least one substituent containing at least one atom of carbon, sulfur, oxygen and nitrogen atoms, an alkenyl group, an amino group or an alkylamino group and each of R
7
and R
8
may be the same or different; and X represents a single bond or any of the groups represented by the following formulas;
wherein R
9
represents hydrogen, an alkoxy group, an amino group, a substituted amino group, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group, an alkenyl group or an aromatic group which may be substituted with at least one substituent containing at least one atom of carbon, sulfur, oxygen and nitrogen atoms; and R
10
and R
11
each represent hydrogen, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group, an alkenyl group or an aromatic group which may be substituted with at least one substituent containing at least one atom of carbon, sulfur, oxygen and nitrogen atoms, and each of R
10
and R
11
may be the same or different, and when R
10
and R
11
are alkyl groups, R
10
may be bonded to R
11
to form a ring.
(2) The rubber composition as described in the above item (1), containing 30 phr or more of natural rubber (which may be polyisoprene rubber) as the rubber component.
(3) The rubber composition as described in the above item (1) or (2), prepared by further compounding 20 to 150 parts by weight of a reinforcing filler.
(4) The rubber composition as described in the above item (3), wherein the reinforcing filler is carbon black.
(5)
Hirayama Ken
Hojo Masahiro
Kamo Shigeki
Kusano Tomohiro
Matsue Akihiko
Bridgestone Corporation
Jagannathan Vasu
Shasho Callie E.
Sughrue & Mion, PLLC
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