Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2002-11-25
2003-12-23
Egwim, Kelechi C. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
Reexamination Certificate
active
06667356
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rubber composition which is excellent in heat aging resistance.
2. Description of the Related Art
Heat aging of rubber is caused according to an auto-oxidation mechanism of polymers which is generally known, and therefore it is effective for preventing heat aging to inactivate peroxy radicals produced in this course.
In general, diphenyldiamine based compounds and hindered phenol based compounds have so far been used as an antioxidant. These compounds give “H” in “>NH” and “—OH” to peroxy radicals produced in the course of auto-oxidative degradation to inactivate them, and the compounds themselves change to stable compounds through more stable radicals. Thus, widely known is a method in which peroxy radicals are inactivated to terminate a radical chain reaction to thereby prevent aging.
Both the conventional diphenyldiamine based antioxidants and hindered phenol based antioxidants described above have an aging preventing action. In general, as the blending amount thereof is increased, an aging preventing effect grows large correspondingly in an area where the blending amount is small, but when they are used in a large amount, an increment in the effect becomes gradually small. The effect is even reduced due to bloom in a certain case, and therefore involved is the problem that the optimum use amount has to be set.
Further, a rubber composition using a diphenylamine based antioxidant has a large change rate in an elastic modulus before and after degradation, and the rubber composition is notably hardened and reduced in its physical properties in a certain case depending on the blending recipe of the rubber composition and the conditions of degradation.
In light of the problems of the conventional techniques described above, an object of the present invention is to solve the problems and to provide a rubber composition which is excellent in heat aging resistance without causing a reduction in physical properties.
SUMMARY OF THE INVENTION
Intensive researches repeated by the present inventors in order to solve the problems of the conventional technique described above have resulted in successfully obtaining a rubber composition meeting the object described above by blending a specific amount of a specific compound with a rubber component comprising at least one selected from the group consisting of natural rubber and synthetic rubbers, and thus the invention has been completed.
That is, the rubber composition of the present invention relates to the following compositions (1) to (8):
(1) A rubber composition comprising 100 parts by weight of a rubber component comprising at least one selected from the group consisting of natural rubber and synthetic rubbers and 0.05 to 20 parts by weight of at least one selected from compounds (A) represented by the following Formula (I):
wherein A
1
and A
2
each represent R—, R—NH—, R—X—NH—, R—NH—NH— or R—X—NH—NH—, and A
1
and A
2
may be the same or different; R represents any one of a hydrogen atom, an alkyl group having 1 to 18 carbon atoms which may be branched, a cycloalkyl group, an aryl group, an alkylaryl group or an alkenyl group, each group of which may include at least one substituent containing a sulfur atom, a nitrogen atom and an oxygen atom, and two R's may be combined in a molecule to form a ring containing a >C═NH bond; and X represents any one of those shown below:
(2) The rubber composition as described in the above item (1), wherein the compound (A) represented by Formula (I) described above is a compound represented by the following Formula (II):
wherein B
1
and B
2
each represent:
a hydrogen atom or an alkyl group having 1 to 18 carbon atoms which may be branched, and B
1
and B
2
may be the same or different.
(3) The rubber composition as described in the above item (2), wherein the compound represented by Formula (II) is N′-(N-benzoylamidino)benzoic acid hydrazide.
(4) The rubber composition as described in the above item (3), wherein the compound (A) represented by Formula (I) described above is a compound represented by the following Formula (III):
wherein B
1
and B
2
each represent:
a hydrogen atom or an alkyl group having 1 to 18 carbon atoms which may be branched, and B
1
and B
2
may be the same or different.
(5) The rubber composition as described in the above item (4), wherein the compound represented by Formula (III) is N-amidinobenzamide.
(6) The rubber composition as described in any of the above items (1) to (5), further comprising an antioxidant, wherein the antioxidant is at least one selected from the group consisting of antioxidants of a naphthylamine base, a p-phenylenediamine base, a hydroquinone derivative, a monophenol base, a bisphenol base, a trisphenol base, a polyphenol base, a diphenylamine base, a quinoline base, a thiobisphenol base and a hindered phenol base.
(7) The rubber composition as described in the above item (6), wherein the antioxidant described above is at least one selected from the group consisting of antioxidants of a p-phenylenediamine base and a diphenylamine base.
(8) The rubber composition as described in the above item (5) or (6), wherein an amount of the antioxidant described above is 0.1 to 5.0 parts by weight per 100 parts by weight of the rubber component.
A rubber composition which is better in heat aging resistance is provided by using at least one selected from the compounds (A) represented by Formula (I) in combination with an antioxidant.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention shall be explained below in detail.
The rubber composition of the present invention is characterized by comprising 100 parts by weight of a rubber component comprising at least one selected from the group consisting of natural rubber and synthetic rubbers and 0.05 to 20 parts by weight of at least one selected from the compounds (A) represented by the following Formula (I):
wherein A
1
and A
2
each represent R—, R—NH—, R—X—NH—, R—NH—NH— or R—X—NH—NH—, and A
1
and A
2
may be the same or different.
Above R is any one of a hydrogen atom, an alkyl group having 1 to 18 carbon atoms which may be branched, a cycloalkyl group, an aryl group, an alkylaryl group or an alkenyl group (these groups include a group having at least one substituent containing a sulfur atom, a nitrogen atom and an oxygen atom), and two R's may be combined in a molecule to form a ring containing a >C═NH bond.
X represents any one of those shown below:
The compound (A) represented by Formula (I) used in the present invention is used as a novel heat aging preventive. Although an action mechanism thereof is not sufficiently made clear, it is considered that “>NH” is contained in the structure thereof as is the case with conventional diphenylamine base antioxidants and therefore gives a proton to peroxy radicals produced in the course of an auto-oxidation of the rubber composition to stabilize, whereby the aging preventing action is displayed (this point shall further be explained in examples described later).
The compound (A) represented by Formula (I) includes, for example, various compounds shown in the following items (1) to (14).
(1) When A
1
and A
2
are R—, included are, for example, ethaneimine, benzylimine, acetoneimine, acetophenoneimine and benzophenoneimine.
(2) When A
1
is R— and A
2
is R—NH—, included are, for example, benzoamidine, acetoamidine, 1-phenylbenzoamidine, 1-methylbenzoamidine and 1-phenylacetoamidine.
(3) When A
1
is R— and A
2
is R—X—NH—, included are, for example, 1-benzoylbenzoamidine, 1-acetylbenzoamidine and 1-benzoylacetoamidine.
(4) When A
1
and A
2
are R—NH—, included are, for example, guanidine, 1-phenylguanidine, 1-methylguanidine, 1,3-diphenylguanidine, 1,3-dipropylguanidine and 1-phenyl-3-methylguanidine.
(5) When A
1
is R—NH— and A
2
is R—X—NH—, included are, for example, N-amidinobenzamide, N-amidinoacetoamide, N′-(N-phenylamidino)benzamide, N′-(N-phenylamidino)acetoamide, N′-(N-phenylamidino)stear
Nohara Daisuke
Oka Akinori
Shirasaka Jingo
Sonogi Ken
Tokuda Hiroaki
Bridgestone Corporation
Egwim Kelechi C.
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