JP5420224B2 - Rubber composition for anti-vibration rubber, anti-vibration rubber and method for producing the same - Google Patents

Description

  The present invention relates to a rubber composition for vibration-proof rubber, and in particular, a rubber composition for vibration-proof rubber that can be suitably used as a vibration-proof member for automobile engine mounts, vibration-proof rubber using the same, and vibration-proof rubber The present invention relates to a method for producing rubber.

  In general, an anti-vibration rubber is used for an automobile to absorb vibrations of an engine and a vehicle body to improve riding comfort and prevent noise. In particular, anti-vibration rubbers such as engine mounts used in engine rooms and exhaust systems of automobiles are required to have high heat resistance with the recent increase in engine output.

  Conventionally, natural rubber or blends of natural rubber and diene-based synthetic rubber are generally used as the rubber component of the vibration-proof rubber, and the heat resistance of the vulcanized rubber of the rubber composition containing these rubber components is improved. As a technique for reducing the amount of sulfur in the rubber composition, a technique for vulcanizing by adding a large amount of a vulcanization accelerator (EV (Efficient Vulcanization)) is known.

  However, when the amount of sulfur in the rubber composition and the blending amount of the vulcanization accelerator are optimized as described above, for example, by increasing the crosslinking form by monosulfide bonds, the heat resistance of the vulcanized rubber is improved. Although the heat resistance is improved to some extent, the rubber composition has insufficient number of sulfur molecules, and sufficient crosslinks are not formed, resulting in a decrease in rubber hardness and a decrease in static spring constant (Ks) indicating the vibration-proof rubber support performance. At the same time, since the dynamic spring constant (Kd) indicating the vibration and noise damping performance increases, the value of the dynamic magnification (dynamic spring constant / static spring constant), which is an index as a dynamic characteristic, increases. There is a problem that the vibration performance decreases. Further, there is a problem that the strength and rigidity of the rubber composition cannot be obtained, the fatigue resistance is lowered, and the durability of the anti-vibration rubber is deteriorated.

  On the other hand, when producing anti-vibration rubber from the rubber composition, vulcanization may be performed in a short time in order to improve the productivity, and as a technique, vulcanization is performed at a high temperature (170 to 190 ° C.). The method is known. However, when vulcanization is performed at a high temperature, the polymer molecules are cleaved, and the polysulfide bonds that are bonded between the rubber polymers are easily cleaved. As a result, the rubber is softened, the breaking strength is lowered, the elongation at break is increased, and there is a tendency to be in a state of insufficient vulcanization, so-called reversion. Due to the effect of this vulcanization return (torque reduction), due to slight fluctuations in vulcanization time, the rubber's tensile properties (breaking strength, breaking elongation), rubber hardness, etc. decrease, or the static spring constant (Ks) increases. There are difficulties such as lowering. However, even with such difficulties, there is a great demand for improving the productivity of vulcanized rubber, and it is strongly desired to reduce the cost of products.

  As described above, the tensile properties (breaking strength, breaking elongation), rubber hardness, and static spring constant (Ks) of the anti-vibration rubber are sufficiently suppressed and have excellent anti-sag and durability properties. However, it is difficult to efficiently produce anti-vibration rubber having excellent heat resistance.

  In the following Patent Document 1, by vulcanizing a rubber composition for anti-vibration rubber containing sulfur and bismaleimide as a rubber vulcanizing agent, a decrease in static spring constant (Ks) is suppressed, and heat resistance is improved. It describes that an excellent vibration-proof rubber can be obtained. However, such anti-vibration rubber does not have sufficient durability, and not all of the properties required for anti-vibration rubber are improved in a balanced manner.

  Moreover, in the following patent document 2, with respect to 100 parts by weight of a rubber component mainly composed of a diene rubber, sulfur is 0.2 parts by weight or more and less than 0.5 parts by weight, and the following (2) is used as a crosslinking agent. By vulcanizing a rubber composition for anti-vibration rubber containing 0.1 to 2.0 parts by weight of at least one of the compounds shown and 0.5 to 4.0 parts by weight of an imidazole compound, It is described that a vibration-proof rubber that suppresses a decrease in the static spring constant (Ks) and is excellent in durability and heat resistance can be obtained.

(Where R = —S— (C═S) —N (CH ₂ C ₆ H ₅ ), or

X = 6)

  However, the anti-vibration rubber has room for further improvement in terms of the effect of suppressing aging deterioration.

Further, in Patent Document 3 below, a diene rubber and a sulfur vulcanizing agent are essential components, and 1,3-bis (citraconimidomethyl) benzene, 1,6-hexamethylenedithiosulfate sodium, and dialkyldithiophospho By vulcanizing rubber composition for anti-vibration rubber containing zincate salt, the tensile properties (breaking strength, breaking elongation) and rubber hardness of anti-vibration rubber and static spring constant (Ks) are reduced. It is described that it is possible to obtain a vibration-proof rubber that can be sufficiently suppressed and has excellent anti-sagging properties. However, such anti-vibration rubber does not have sufficient heat resistance, and not all the characteristics required for anti-vibration rubber are improved in a balanced manner.
Japanese Patent Laid-Open No. 03-258840 JP 2004-307621 A JP 2007-146035 A

  The present invention has been made in view of the above circumstances, and its purpose is to provide tensile properties (breaking strength, breaking elongation), rubber hardness, etc. due to reversion even when vulcanized at a high temperature (170 to 190 ° C.). Rubber composition for anti-vibration rubber, in which the reduction of the lowering of the static spring constant (Ks) and the reduction of the static spring constant (Ks) are sufficiently suppressed, and the effects of suppressing heat resistance, sag resistance, durability, and aging deterioration are improved in a balanced manner, and An object of the present invention is to provide a vibration-proof rubber obtained by using a rubber composition for vibration rubber and a method for producing the same.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by the rubber composition for vibration-proof rubber shown below, and have completed the present invention.

That is, the rubber composition for vibration-proof rubber according to the present invention is a rubber composition for vibration-proof rubber containing a rubber component mainly composed of a diene rubber and a sulfur-based vulcanizing agent.
(A) a bismaleimide compound,
(B) Compound represented by the following formula (1):

(Wherein x is an integer of 2 to 12, and R is a thiocarbamoyl group or benzothiazole group having an aromatic hydrocarbon group or fatty acid hydrocarbon in the molecular structure), and (C) a hydrazide compound,
It contains at least two compounds selected from the group consisting of:

  Rubber composition for anti-vibration rubber containing a rubber component mainly composed of a diene rubber and a sulfur-based vulcanizing agent, and containing only a bismaleimide compound, the heat and anti-slip properties of the anti-vibration rubber obtained Although the effect of suppressing aging deterioration is improved, the durability of the anti-vibration rubber tends to deteriorate. Further, when only the compound (B) is contained, an increase in the dynamic spring constant (Kd) of the vibration-proof rubber obtained is suppressed, and the heat resistance, durability, and sag resistance of the vibration-proof rubber are improved. However, the anti-vibration rubber tends to deteriorate over time. On the other hand, when only the hydrazide compound is contained, an increase in the dynamic spring constant (Kd) of the obtained vibration-proof rubber is suppressed and the durability of the vibration-proof rubber is improved. There is a tendency for the property to deteriorate, and there is a tendency for the anti-vibration rubber to deteriorate over time.

  However, the rubber composition for an anti-vibration rubber according to the present invention contains at least two compounds selected from the group consisting of the compounds (A) to (C), so that the anti-vibration rubber comprising the vulcanized rubber is contained. In vibration rubber, it suppresses the decrease in breaking strength, breaking elongation, rubber hardness, etc., improves vibration damping performance such as dynamic magnification, etc., and has a good balance of heat resistance, sag resistance, durability, and the effects of suppressing aging deterioration Can be improved.

  In the rubber composition for vibration-proof rubber according to the present invention, when the bismaleimide compound is contained, the content is preferably 0.2 to 4 parts by weight when the rubber component is 100 parts by weight. More preferably, it is 5 to 2 parts by weight. If the content of the bismaleimide compound is less than 0.2 parts by weight, the effect of suppressing the heat resistance, sag resistance, or aging resistance of the obtained vibration-proof rubber may not be sufficiently improved. On the other hand, if it exceeds 4 parts by weight, the mold may be contaminated when the rubber composition for vibration-proof rubber is vulcanized, and in addition, the processability of the rubber composition for vibration-proof rubber may be deteriorated. Furthermore, when the content of the bismaleimide compound exceeds 4 parts by weight, the cost of the entire vibration-proof rubber increases, which is not preferable.

  Moreover, in the rubber composition for vibration-proof rubber according to the present invention, when the compound (B) is contained, the content is 0.2 to 4 parts by weight when the rubber component is 100 parts by weight. Is preferable, and 0.5 to 2 parts by weight is more preferable. When the content of the compound (B) is less than 0.2 parts by weight, the effect of suppressing an increase in the dynamic spring constant (Kd) of the vibration-proof rubber obtained, or the heat resistance and durability of the vibration-proof rubber, Alternatively, the settling resistance may not be sufficiently improved. On the other hand, if the amount exceeds 4 parts by weight, the heat resistance or sag resistance of the vibration-proof rubber may deteriorate. In addition, when the content of the compound (B) exceeds 4 parts by weight, the cost of the entire vibration-proof rubber is increased, which is not preferable.

  Furthermore, in the rubber composition for vibration-proof rubber according to the present invention, when the hydrazide compound is contained, the content is preferably 0.2 to 4 parts by weight when the rubber component is 100 parts by weight, More preferably, it is 0.5 to 2 parts by weight. When the content of the hydrazide compound is less than 0.2 parts by weight, the effect of suppressing an increase in the dynamic spring constant (Kd) of the obtained vibration-insulating rubber or the durability of the vibration-insulating rubber may not be sufficiently improved. Yes, if it exceeds 4 parts by weight, the heat resistance of the anti-vibration rubber may deteriorate. In addition, when the content of the hydrazide compound exceeds 4 parts by weight, the cost of the entire vibration-proof rubber increases, which is not preferable.

  The anti-vibration rubber according to the present invention is obtained by vulcanizing and molding the rubber composition for anti-vibration rubber described above. Such anti-vibration rubber has the effect of suppressing the decrease in breaking strength, elongation at break, rubber hardness, etc., improving the anti-vibration performance such as dynamic magnification, and having the effects of heat resistance, sag resistance, durability, and aging deterioration suppression. The balance is improved. For this reason, it can be suitably used as an anti-vibration rubber for automobiles such as engine mounts, torsional dampers, body mounts, cap mounts, member mounts, strut mounts, and muffler mounts.

  The method for producing vibration-proof rubber according to the present invention is characterized in that the rubber composition for vibration-proof rubber described above is vulcanized at 170 to 190 ° C. According to such a production method, since the rubber composition for vibration-proof rubber described above is vulcanized at a high temperature of 170 to 190 ° C., the vulcanization can be performed in a short time, thereby improving productivity and reducing cost. Can be realized.

  In the rubber composition for vibration-proof rubber according to the present invention, natural rubber alone or a blend of natural rubber and diene synthetic rubber is used as the rubber component. When natural rubber and diene synthetic rubber are blended, the diene synthetic rubber includes polyisoprene rubber (IR), polybutadiene rubber (BR), styrene butadiene rubber (SBR), butyl rubber (IIR), and acrylonitrile butadiene rubber. (NBR) and the like. The polymerization method and microstructure of the diene-based synthetic rubber are not limited, and one or more of these can be used by blending with natural rubber.

  When natural rubber and diene synthetic rubber are blended, the blend ratio is not particularly limited, but natural rubber is contained in the rubber component in an amount of 50% by weight or more in order to maintain the fatigue resistance of natural rubber. It is preferable to contain 90% by weight or more. In addition to natural rubber and diene synthetic rubber, examples of rubber that can be used as a rubber component include olefin rubber such as ethylene propylene rubber (EPM) and halogenated butyl rubber such as brominated butyl rubber (Br-IIR). And other synthetic rubbers including polyurethane rubber, acrylic rubber, fluorine rubber, silicon rubber, chlorosulfonated polyethylene, and the like. However, the rubber other than the diene rubber is preferably less than 40% by weight in the rubber component, and more preferably less than 20% by weight.

  Sulfur should just be normal sulfur for rubber | gum, For example, powder sulfur, precipitated sulfur, insoluble sulfur, highly dispersible sulfur etc. can be used. The sulfur content in the rubber composition for vibration-proof rubber according to the present invention is preferably 0.1 to 3 parts by weight with respect to 100 parts by weight of the rubber component. If the sulfur content is less than 0.1 parts by weight, the crosslinking density of the vulcanized rubber will be insufficient and the rubber strength will be reduced. If it exceeds 3 parts by weight, both heat resistance and durability will be deteriorated. . In order to ensure good rubber strength of the vulcanized rubber and to further improve the heat resistance and durability, the sulfur content is 0.1 to 2.0 parts by weight with respect to 100 parts by weight of the rubber component. Is more preferably 0.1 to 1.2 parts by weight.

The rubber composition for vibration-proof rubber according to the present invention is a rubber composition for vibration-proof rubber containing a rubber component mainly composed of a diene rubber and a sulfur-based vulcanizing agent.
(A) a bismaleimide compound,
(B) Compound represented by the following formula (1):

(Wherein x is an integer of 2 to 12, and R is a thiocarbamoyl group or benzothiazole group having an aromatic hydrocarbon group or fatty acid hydrocarbon in the molecular structure), and (C) a hydrazide compound,
Containing at least two compounds selected from the group consisting of:

  The (A) bismaleimide compound is specifically represented by the following formula (3).

(Wherein X is a hydrocarbon group or aromatic hydrocarbon group having an aromatic ring in the molecular structure, or an aliphatic hydrocarbon group. R _{1 to} R ₄ are a hydrogen atom, an alkyl group, —NH ₂ or —NO _2. And may be the same as or different from each other.)

  As the (A) bismaleimide compound, N, N′-phenylenebismaleimide represented by the following formula (4):

4,4'-diphenylmethane bismaleimide represented by the following formula (5):

Bis (3-ethyl-5-methyl-4-maleimidophenyl) methane, 2,2′-bis (4- (4-maleimidophenoxy) phenyl) propane and the like are preferable, and in particular, N, N′-phenylenebismaleimide or 4,4′-diphenylmethane bismaleimide is preferred.

  The compound of the above (B) is represented by the following formula (1):

(Wherein x is an integer of 2 to 12, and R is a thiocarbamoyl group having an aromatic hydrocarbon group or a fatty acid hydrocarbon or a benzothiazole group in the molecular structure). In addition, as the compound of the above (B), 1,6-bis (N, N′-dibenzylthiocarbamoyldithio) -hexane represented by the following formula (6):

Or 1,6-bis (benzothiazyl sulfide) -hexane represented by the following formula (7):

Are preferred.

  The (C) hydrazide compound is specifically represented by the following formula (8), (9) or (10).

(In the formula, A is a single bond, a divalent group derived from an aromatic group, a divalent group derived from a hydantoin ring which may have a substituent, or a saturated or unsaturated linear carbon atom having 1 to 18 carbon atoms. A divalent group derived from hydrogen, B is a monovalent group derived from an aromatic group having a substituent X, X is a hydroxyl group or an amino group, Y is a pyridyl group or a hydrazide group, R ₁ to R ₄ are each independently, hydrogen, alkyl group having 1 to 18 carbon atoms, a cycloalkyl group or a monovalent aromatic ring group). In addition, as said (C) hydrazide compound, the isophthalic acid dihydrazide represented by following formula (11):

Or adipic acid dihydrazide represented by the following formula (12):

Is preferred.

  The rubber composition for vibration-proof rubber of the present invention comprises the rubber component, the compounds (A) to (C), and a sulfur vulcanizing agent, a vulcanization accelerator, carbon black, silica, a silane coupling agent, and zinc oxide. Compounding agents usually used in the rubber industry, such as stearic acid, vulcanization accelerator, vulcanization retarder, organic peroxide, anti-aging agent, softener such as wax and oil, processing aid, etc. In the range which does not impair the effect, it can mix | blend and use suitably.

  As carbon black, for example, SAF, ISAF, HAF, FEF, GPF and the like are used. Carbon black can be used within a range in which rubber properties such as hardness, reinforcement and low heat build-up of the rubber after vulcanization can be adjusted. The compounding amount of carbon black is in the range of 20 to 120 parts by weight, preferably 30 to 100 parts by weight, and more preferably 30 to 60 parts by weight with respect to 100 parts by weight of the rubber component. If the blending amount is less than 20 parts by weight, the reinforcing effect of carbon black cannot be sufficiently obtained. If the blending amount exceeds 120 parts by weight, exothermic property, rubber mixing property, workability during processing, and the like deteriorate.

  As the vulcanization accelerator, sulfenamide vulcanization accelerator, thiuram vulcanization accelerator, thiazole vulcanization accelerator, thiourea vulcanization accelerator, guanidine vulcanization, which are usually used for rubber vulcanization. Vulcanization accelerators such as accelerators and dithiocarbamate vulcanization accelerators may be used alone or in admixture.

  As an anti-aging agent, an aromatic amine-based anti-aging agent, an amine-ketone-based anti-aging agent, a monophenol-based anti-aging agent, a bisphenol-based anti-aging agent, a polyphenol-based anti-aging agent, dithiocarbamic acid, which are usually used for rubber Anti-aging agents such as a salt-based anti-aging agent and a thiourea-based anti-aging agent may be used alone or in admixture as appropriate.

  The rubber composition for vibration-proof rubber of the present invention comprises the compounds (A) to (C), a sulfur vulcanizing agent, a vulcanization accelerator, and, if necessary, carbon black, zinc oxide, stearic acid, vulcanization acceleration. It can be obtained by kneading agents, anti-aging agents, waxes and the like using a kneader used in a normal rubber industry such as a Banbury mixer, a kneader, and a roll.

  In addition, the blending method of each of the above components is not particularly limited, and a blending component other than the vulcanization component such as a sulfur vulcanizing agent and a vulcanization accelerator is previously kneaded to form a master batch, and the remaining components are added Any of a method of further kneading, a method of adding and kneading the components in an arbitrary order, a method of adding all the components simultaneously and kneading may be used.

  By kneading, molding, and vulcanizing the above components, sufficient reduction in tensile properties (breaking strength, breaking elongation), rubber hardness, and static spring constant (Ks) due to reversion It is possible to obtain an anti-vibration rubber which is suppressed in a well-balanced manner and has an excellent effect of suppressing heat resistance, settling resistance, durability, and aging deterioration. Such anti-vibration rubber includes anti-vibration rubber for automobiles such as engine mounts, torsional dampers, body mounts, cap mounts, member mounts, strut mounts, muffler mounts, anti-vibration rubbers for railway vehicles, and anti-vibration rubbers for industrial machinery. It can be suitably used for vibration isolation of rubber, seismic isolation rubber for construction, seismic isolation rubber support, etc., and is particularly useful as a component of automotive anti-vibration rubber that requires heat resistance such as engine mounts. is there.

  Hereinafter, the present invention will be described in more detail with reference to examples.

(Preparation of rubber composition)
The rubber compositions of Examples 1 to 3 and Comparative Examples 1 to 4 are blended with 100 parts by weight of the rubber component according to the formulation of Table 1, and kneaded using a normal Banbury mixer to prepare the rubber composition did. Each compounding agent described in Table 1 is shown below.

a) Rubber component (1) Natural rubber RSS # 3
(2) Polybutadiene rubber ("BR01", manufactured by JSR)
b) Sulfur 5% oil treated sulfur c) Vulcanization accelerator (1) Sulfenamide vulcanization accelerator N-tert-butyl-2-benzothiazolylsulfenamide ("Noxeller NS-P (NS)", Ouchi Shinsei Chemical Co., Ltd.)
(2) Thiuram-based vulcanization accelerator Tetramethylthiuram monosulfide (“Noxeller TS (TS-P), manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.)
d) Zinc oxide No. 3 zinc white e) Stearic acid Industrial stearic acid f) Anti-aging agent (1) Aromatic amine-based anti-aging agent N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylene Diamine ("ANTAGE 6C", manufactured by Kawaguchi Chemical Co., Ltd.)
(2) Amine-ketone-based anti-aging agent 2,2,4-trimethyl-1,2-dihydroquinoline polymer Nocrack 224 (224-S) ("Nocrack 224 (224-S)", Ouchi Shinsei Chemical Co., Ltd. Made)
g) Carbon Black FEF ("Seast SO", manufactured by Tokai Carbon Co., Ltd.)
h) Process oil ("Process X-140", manufactured by Japan Energy)
i) (A) Bismaleimide compound (1) 4,4′-diphenylmethane bismaleimide (“BMI-HS”, manufactured by KAI Kasei Co., Ltd.)
(2) N, N′-phenylene bismaleimide (“Barnock PM-P”, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
j) (B) Compound represented by the following formula (1):

(Wherein x is an integer of 2 to 12, and R is a thiocarbamoyl group having an aromatic hydrocarbon group or a fatty acid hydrocarbon or a benzothiazole group in the molecular structure).
(1) 1,6-bis (N, N′-dibenzylthiocarbamoyldithio) -hexane (manufactured by LANXESS)
(2) 1,6-bis (benzothiazyl sulfide) -hexane (manufactured by LANXESS)
k) (C) Hydrazide compound (1) Isophthalic acid dihydrazide ("IDH", manufactured by Otsuka Chemical Co., Ltd.)
(2) Adipic acid dihydrazide (“ADH”, manufactured by Otsuka Chemical Co., Ltd.)

  About each rubber composition, each vulcanized rubber was produced and the characteristic evaluation was performed.

(Evaluation)
The evaluation was performed on rubbers obtained by heating and vulcanizing each rubber composition using a predetermined mold under the following conditions.

<Tensile properties and rubber hardness>
Each rubber composition was press-molded while being vulcanized at 180 ° C. for 5 minutes to prepare a vulcanized rubber sheet. Similarly, each rubber composition was press-molded while being vulcanized at 180 ° C. for 10 minutes to prepare a vulcanized rubber sheet. These samples were punched with a JIS No. 5 dumbbell to produce rubber samples having a thickness of 2 mm. Each rubber sample was measured for breaking strength (TB), breaking elongation (EB), and rubber hardness (Hs: JIS-A) according to JIS-K 6251. Regarding the breaking strength (TB), elongation at break (EB) and rubber hardness (Hs: JIS-A), the rate of change of the measured value of the rubber sample vulcanized for 10 minutes with respect to the rubber sample vulcanized at 180 ° C. for 5 minutes (rubber The change amount was calculated for the hardness. The lower the rate of change of the measured value (the amount of change with respect to rubber hardness), the lower the vulcanization return. The evaluation results are shown in Table 1.

<Vibration characteristics>
(Static spring constant (Ks))
Each rubber composition was press-molded while being vulcanized at 180 ° C. for 10 minutes or at 180 ° C. for 15 minutes to produce a vulcanized rubber sample having a cylindrical shape (diameter 50 mm, height 25 mm), and then subjected to such addition. A test piece was prepared by bonding a pair of cylindrical metal fittings (diameter 60 mm, thickness 6 mm) to the upper and lower surfaces of the vulcanized rubber sample using an adhesive. After the prepared test piece is compressed 7 mm twice in the axial direction of the cylinder, the deflection load of 1.5 mm and 3.5 mm is measured from the deflection curve when the strain is restored, and the static spring is determined from these values. A constant (Ks) was calculated. For the static spring constant (Ks), the change rate of the measured value of the rubber sample vulcanized for 15 minutes relative to the rubber sample vulcanized at 180 ° C. for 10 minutes was calculated. The lower the rate of change of the static spring constant (Ks), the lower the vulcanization return.
(Dynamic spring constant (Kd))
The test piece used for measuring the static spring constant (Ks) was compressed 2.5 mm in the direction of the cylinder axis, and a constant of 0.05 mm in amplitude at a frequency of 100 Hz from the bottom centered on this 2.5 mm compressed position. Displacement harmonic compression vibration was applied, the dynamic load was detected in the upper load cell, and the dynamic spring constant (Kd) was calculated according to JIS-K 6394. For the dynamic spring constant (Kd), the change rate of the measured value of the rubber sample vulcanized for 15 minutes relative to the rubber sample vulcanized at 180 ° C. for 10 minutes was calculated. The lower the rate of change of the dynamic spring constant (Kd), the lower the vulcanization return.
(Dynamic magnification: Kd / Ks)
The dynamic magnification was calculated from the following formula.
(Dynamic magnification) = (Dynamic spring constant (Kd)) / (Static spring constant (Ks))
About dynamic magnification, the change rate of the measured value of the rubber sample vulcanized for 15 minutes to the rubber sample vulcanized at 180 ° C. for 10 minutes was determined. It means that the lower the rate of change of the measured value, the more the reversion is suppressed. The evaluation results are shown in Table 1.

<Suppression effect of spring constant change (effect of suppressing aging degradation)>
Similarly to the calculation of the static spring constant (Ks) and the dynamic spring constant (Kd), each rubber composition was press-molded while vulcanized to add a cylindrical shape (diameter 50 mm, height 25 mm). After producing a vulcanized rubber sample, a test piece was produced by adhering a pair of cylindrical metal fittings (diameter 60 mm, thickness 6 mm) to the upper and lower surfaces of the vulcanized rubber sample using an adhesive. This test piece was heat-aged in a gear oven at 100 ° C. for 500 hours. The test piece after heat aging was taken out from the gear oven and allowed to stand at room temperature for at least 8 hours, and then the static spring constant (Ks) and dynamic spring constant (Kd) were measured under the same conditions as described above. Based on these measurement results, the rate of change of the static spring constant (Ks) and the dynamic spring constant (Kd) before and after thermal aging was calculated. It means that the lower the change rate of the measured value, the better the effect of suppressing aging degradation. The evaluation results are shown in Table 1.

<Heat resistance (compression set)>
Each rubber composition was press-molded while being vulcanized at 180 ° C. for 5 minutes or 180 ° C. for 10 minutes to prepare a vulcanized rubber sample having a cylindrical shape (diameter 29 mm, height 12.5 mm). Using this vulcanized rubber sample, compression set was measured under predetermined conditions (100 ° C., test time 240 hours, compression rate 25%) according to JIS-K 6262. It means that the smaller the compression set, the better the settling resistance. The evaluation results are shown in Table 1.

<Heat resistance>
Each rubber composition was press-molded while being vulcanized at 180 ° C. for 5 minutes or at 180 ° C. for 10 minutes, and then punched with a JIS No. 5 dumbbell to prepare a rubber sample having a thickness of 2 mm. Using this rubber sample, a heat aging test was conducted in accordance with JIS-K 6257. In the heat aging test, a gear oven (manufactured by Toyo Seiki Co., Ltd.) was used, and the rubber sample was heat aged at 100 ° C. for 1000 hours. The elongation at break (EB) of each rubber sample before and after heat aging was measured, and the rate of change was calculated. The lower the change rate of the measured value, the better the heat resistance. The evaluation results are shown in Table 1.

<Durability>
Each rubber composition is injection-molded so as to have a predetermined square shape (length 30 mm, width 50 mm, height 40 mm) and vulcanized at 180 ° C. for 10 minutes or 180 ° C. for 15 minutes. A vulcanized rubber sample was prepared. Using this vulcanized rubber sample, a constant load vertical vibration test was conducted. The retention of the measured value (constant load vertical vibration test) of the rubber sample vulcanized for 15 minutes relative to the rubber sample vulcanized at 180 ° C. for 10 minutes was calculated. The closer the measured value retention rate is to 100%, the better the durability. The evaluation results are shown in Table 1.

From the results shown in Table 1, the vulcanized rubbers of the rubber compositions of Examples 1 to 3 have tensile properties (breaking strength, breaking elongation) due to reversion and rubber even when vulcanized at a high temperature (170 to 190 ° C.). It can be seen that a decrease in hardness or the like and a decrease in the static spring constant (Ks) are sufficiently suppressed, and the balance is improved in terms of the effects of heat resistance, sag resistance, durability, and aging deterioration suppression. On the other hand, the vulcanized rubbers of the rubber compositions of Comparative Examples 1 to 4 are inferior to the vulcanized rubbers of the rubber compositions of Examples 1 to 3 in any of heat resistance, durability, and resistance to sag. I understand.

Claims (3)

In a rubber composition for a vibration-proof rubber containing a rubber component mainly composed of a diene rubber and a sulfur vulcanizing agent,
(A) a bismaleimide compound, and (B) a compound represented by the following formula (1):


(Wherein x is an integer of 2 to 12, and R is a thiocarbamoyl group or benzothiazole group having an aromatic hydrocarbon group or fatty acid hydrocarbon in the molecular structure ) (provided that the hydrazide compound is A rubber composition for anti-vibration rubber.   An anti-vibration rubber obtained by vulcanization and molding using the rubber composition for anti-vibration rubber according to claim 1.   A rubber composition for vibration-proof rubber according to claim 1 is vulcanized at 170 to 190 ° C.