JP2011111532A - Rubber composition for vibration-proof rubber and vibration-proof rubber - Google Patents

Abstract

An object of the present invention is to provide a rubber composition for a vibration-proof rubber and a vibration-proof rubber that have particularly excellent heat resistance while improving durability and anti-sag property.
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 bismaleimide compound, a compound represented by the following formula (1):



(Wherein, x is an integer from 2 to 12, R represents a thiocarbamoyl group having an aromatic hydrocarbon group or a fatty acid hydrocarbon group in the molecular structure, benzothiazole group or -SO _3, ^- Na ⁺ group) , And a radical generator.
[Selection figure] None

Description

  The present invention relates to a rubber composition for vibration proof rubber and vibration proof rubber, and more particularly to a rubber composition for vibration proof rubber that can be suitably used as a vibration proof member for an engine mount for automobiles, and a vibration proof rubber using the same. Is.

  In recent years, automobiles are required to have high output while being quiet. Furthermore, since the airtightness of the engine room tends to increase, heat is likely to accumulate, and it is a severe condition for the vibration isolating rubber, which is a vibration isolating member for automobiles, such as an increase in the frequency of traffic congestion and an increase in the outside air temperature. In addition, it is necessary to consider use in overseas countries with high outside temperatures, such as Southeast Asia and Middle East countries, and the heat resistance requirements for anti-vibration rubber are increasing year by year. From such a background, there has been a demand for an anti-vibration rubber for automobiles that has improved heat resistance while maintaining anti-vibration properties.

  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 of the vulcanized rubber is lowered because the number of sulfur molecules in the rubber composition is insufficient and the cross-linking is not sufficiently formed. For this reason, there is a problem that the anti-vibration resistance of the anti-vibration rubber is lowered and the durability of the anti-vibration rubber is deteriorated.

  In Patent Document 1 described below, by vulcanizing a rubber composition for vibration-proof rubber that contains sulfur and a bismaleimide compound as a rubber vulcanizing agent, a decrease in vibration-proof performance is suppressed, and the heat-proof performance is excellent. The point that a vibration rubber is obtained is described. Further, in Patent Document 2 below, a vibration-proof rubber having excellent vibration-proof performance is obtained by vulcanizing a rubber composition for vibration-proof rubber that does not contain sulfur as a rubber vulcanizing agent while using a bismaleimide compound as an essential component. The point from which is obtained is described. However, these anti-vibration rubbers do not have sufficient durability, and not all of the properties required for anti-vibration rubbers are improved in a balanced manner.

Moreover, in the following patent document 3, sulfur, at least one compound represented by the following formula (2), and an imidazole compound are contained with respect to 100 parts by weight of a rubber component mainly composed of a diene rubber. It is described that, by vulcanizing the rubber composition for vibration-proof rubber, a vibration-proof rubber excellent in durability can be obtained while suppressing a decrease in vibration-proof performance.


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

  However, the anti-vibration rubber has room for further improvement in terms of heat resistance and anti-slip properties of the anti-vibration rubber.

  Furthermore, in the following Patent Document 4, a diene rubber and a sulfur vulcanizing agent are essential components, and 1,3-bis (citraconimidomethyl) benzene, 1,6-hexamethylenedithiosulfate sodium, and dialkyldithiophospho It is described that by vulcanizing a rubber composition for an anti-vibration rubber containing a nate zinc salt, a decrease in the anti-vibration performance of the anti-vibration rubber can be suppressed. However, such anti-vibration rubber does not have sufficient heat resistance and sag resistance, and all the characteristics required for the anti-vibration rubber are not improved in a well-balanced manner.

  As described above, there is no anti-vibration rubber that has improved heat resistance to a level that satisfies market demands while improving durability and anti-sag properties.

Japanese Patent Laid-Open No. 03-258840 JP 2006-273940 A JP 2004-307621 A JP 2007-146035 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rubber composition for vibration-proof rubber and a vibration-proof rubber having particularly excellent heat resistance while improving durability and anti-sag property. There is to do.

  As a result of intensive studies to solve the above problems, the present inventor has found that the above object can be achieved by the rubber composition for vibration-proof rubber shown below, and has 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. Compound represented by 1):


(Wherein, x is an integer from 2 to 12, R represents a thiocarbamoyl group having an aromatic hydrocarbon group or a fatty acid hydrocarbon group in the molecular structure, benzothiazole group or -SO _3, ^- Na ⁺ group) And a radical generator.

  The inventor of the present invention is a vibration-proof rubber obtained by using a rubber composition for vibration-proof rubber containing both the bismaleimide compound and the compound represented by the above formula (1). Alternatively, it has been found that all of durability, sag resistance, and heat resistance are improved in a well-balanced manner as compared with a compound containing only the compound represented by the above formula (1). However, as a result of further investigation by the inventor, the rubber composition for vibration-proof rubber contains both the bismaleimide compound and the compound represented by the above formula (1), and a radical generator. It has been found that when it is contained, all of durability, sag resistance, and heat resistance are dramatically improved. The reason why such an effect can be obtained is that the introduction of a crosslinked structure into the diene rubber by the bismaleimide compound and the compound represented by the above formula (1) is considered to be promoted.

  In the rubber composition for vibration-proof rubber according to the present invention, the content of the bismaleimide compound is preferably 0.2 to 4 parts by weight, and 0.5 to 3 parts by weight when the rubber component is 100 parts by weight. More preferably, it is a part. If the content of the bismaleimide compound is less than 0.2 parts by weight, the heat resistance and sag resistance of the resulting vibration-proof rubber may not be sufficiently improved. On the other hand, if it exceeds 4 parts by weight, the durability of the vibration-proof rubber tends to deteriorate. On the other hand, when the amount 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.

  In the rubber composition for vibration-proof rubber according to the present invention, the content of the compound represented by the above formula (1) is 0.5 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 represented by the formula (1) is less than 0.5 parts by weight, the heat resistance, durability, or sag resistance of the obtained vibration-proof rubber 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 the rubber composition for an anti-vibration rubber, the content of the radical generator is preferably 0.1 to 1.5 parts by weight with respect to 100 parts by weight of the rubber component. If the content of the radical generator is less than 0.1 parts by weight relative to 100 parts by weight of the rubber component, the formation of a crosslinked structure with the diene rubber may be insufficient, and 1.5 parts by weight If it exceeds, the deterioration of the diene rubber will progress, and the heat resistance and settling resistance of the anti-vibration rubber may deteriorate. In consideration of the durability, sag resistance, and heat resistance of the vibration-proof rubber obtained, the content of the radical generator is preferably 0.3 to 1 part by weight with respect to 100 parts by weight of the rubber component.

  The anti-vibration rubber according to the present invention is obtained by vulcanizing and molding the rubber composition for anti-vibration rubber described above. With such an anti-vibration rubber, heat resistance, durability and anti-slip properties are improved in a well-balanced manner. 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.

  In the rubber composition for vibration-proof rubber according to the present invention, a natural rubber alone or a diene rubber comprising a blend of natural rubber and a diene synthetic rubber is mainly used as a 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, and chlorosulfonated polyethylene. 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 as the sulfur-based vulcanizing agent may be normal sulfur for rubber, and for example, powdered sulfur, precipitated sulfur, insoluble sulfur, highly dispersible sulfur and the like 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 1.0 part by weight.

The rubber composition for vibration-proof rubber according to the present invention includes a bismaleimide compound and a compound represented by the following formula (1):


(Wherein, x is an integer from 2 to 12, R represents a thiocarbamoyl group having an aromatic hydrocarbon group or a fatty acid hydrocarbon group in the molecular structure, benzothiazole group or -SO _3, ^- Na ⁺ group) And containing.

The 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 hydrogen atoms, alkyl groups, —NH ₂ groups or —NO ₂ groups, which may be the same or different.)

As the bismaleimide compound, N, N′-m-phenylene dimaleimide represented by the following formula (4):

N, N′-phenylenebismaleimide 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 N, N′-m-phenylenedimaleimide is particularly preferable. Or N, N'-phenylene bismaleimide is preferable.

Compound represented by the following formula (1):

(Wherein, x is an integer from 2 to 12, R represents a thiocarbamoyl group having an aromatic hydrocarbon group or a fatty acid hydrocarbon in the molecular structure, benzothiazole group or -SO _3, ^- Na ⁺ group) as Is a hydrate of 1,6-hexamethylene-sodium dithiosulfate represented by the following formula (6):


1,6-bis (N, N′-dibenzylthiocarbamoyldithio) -hexane represented by the following formula (7):

1,6-bis (benzothiazyl sulfide) -hexane represented by the following formula (8):


Is preferred.

  In the present invention, an organic peroxide having a one-minute half-life temperature of 130 to 200 ° C. can be suitably used as the radical generator in consideration of the vulcanization temperature and vulcanization time of the rubber composition. . Specific examples of the organic peroxide having a 1-minute half-life temperature of 130 to 200 ° C. include disuccinic acid peroxide, t-hexylperoxy-2-ethylhexanate, and t-butylperoxy-2- Ethyl hexanate, di (3-methylbenzoyl) peroxide / benzoyl (3-methylbenzoyl) peroxide / dibenzoyl peroxide mixture, dibenzoyl peroxide, 1,1-di (t-butylperoxy) -2- Methylcyclohexane, 1,1-di (t-hexylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di (t-hexylperoxy) cyclohexane, 1,1-di (t-butylperoxy) ) Cyclohexane, 2,2-di (4,4-di- (t-butylperoxy) cyclohexyl) propane t-hexylperoxyisopropyl monocarbonate, t-butylperoxymaleic acid, t-butylperoxy-3,5,5-trimethylhexanate, t-butylperoxylaurate, t-butylperoxyisopropylmonocarbonate Nate, t-butylperoxy-2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, 2,5-di-methyl-2,5-di (benzoylperoxy) hexane, t-butylperoxyacetate, 2 , 2-Di- (t-butylperoxy) butane, t-butylperoxybenzoate, n-butyl-4,4-di- (t-butylperoxy) valerate, di (2-t-butylperoxy) Isopropyl) benzene, dicumyl peroxide, di-t-hexyl peroxide, 2,5 Dimethyl-2,5-di (t-butylperoxy) hexane, t-butylcumyl peroxide, di-t-butyl peroxide, p-menthane hydroperoxide, 2,5-dimethyl-2,5-di ( t-butylperoxy) hexyne-3. Among these, 1,1-di (t-butylperoxy) cyclohexane and 2,2-di (4,4-di- (t-butylperoxy) cyclohexyl having a 1 minute half-life temperature of 150 to 180 ° C. ) Propane, t-hexylperoxyisopropyl monocarbonate, t-butylperoxymaleic acid, t-butylperoxy-3,5,5-trimethylhexanate, t-butylperoxylaurate, t-butylperoxy Isopropyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, 2,5-di-methyl-2,5-di (benzoylperoxy) hexane, t-butylperoxy Acetate, 2,2-di- (t-butylperoxy) butane, t-butylperoxybenzone N-butyl-4,4-di- (t-butylperoxy) valerate, di (2-t-butylperoxyisopropyl) benzene, dicumyl peroxide, di-t-hexyl peroxide, 2,5 -Dimethyl-2,5-di (t-butylperoxy) hexane and t-butylcumyl peroxide are preferable, and dicumyl peroxide is particularly preferable.

  The rubber composition for vibration-proof rubber of the present invention comprises a vulcanization accelerator, carbon black, together with the rubber component, sulfur-based vulcanizing agent, bismaleimide compound, compound represented by the above formula (1), and radical generator. , Silica, silane coupling agent, zinc oxide, stearic acid, vulcanization acceleration aid, vulcanization retarder, anti-aging agent, softener such as wax and oil, processing aid etc. An agent can be appropriately blended and used as long as the effects of the present invention are not impaired.

  Examples of carbon black include SAF, ISAF, HAF, FEF, and GPF. 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 obtained sufficiently.

  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 appropriate.

  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 an appropriate mixture.

  The rubber composition for vibration-proof rubber of the present invention comprises a rubber component, a sulfur-based vulcanizing agent, a bismaleimide compound, a compound represented by the above formula (1), a radical generator, and, if necessary, carbon black, zinc oxide. , Stearic acid, vulcanization accelerator, anti-aging agent, wax and the like can be obtained by kneading using a kneader used in a normal rubber industry such as a Banbury mixer, a kneader, or a roll.

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

  Anti-vibration rubber having particularly excellent heat resistance can be produced by kneading and molding each of the above components, followed by vulcanization, while improving durability and resistance to sag. Such anti-vibration rubber includes anti-vibration rubber for automobiles such as engine mounts, torsional dampers, body mounts, cap mounts, member mounts, strut mounts, and muffler mounts, as well as anti-vibration rubbers for railway vehicles and industrial machines. It can be suitably used for vibration isolation and isolation rubber for rubber, building isolation rubber, and isolation rubber bearings, and is particularly useful as a component for automotive vibration isolation 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 4, Comparative Examples 1 and 2 and Reference Example are blended with 100 parts by weight of the rubber component in accordance with the formulation of Table 1, and kneaded using a normal Banbury mixer to obtain a rubber composition. I adjusted things. Each compounding agent described in Tables 1-2 is shown below.

a) Rubber component Natural rubber RSS # 3
b) Sulfur 5% oil treated sulfur c) Vulcanization accelerator (A) Sulfenamide vulcanization accelerator N-cyclohexyl-2-benzothiazolylsulfenamide ("Noxeller CZ-G (CZ)", Ouchi Shinsei Chemical Industry)
(B) Thiazole vulcanization accelerator di-2-benzothiazolyl disulfide ("Noxeller DM-P (DM)", manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.)
(C) Thiuram-based vulcanization accelerator tetramethylthiuram disulfide ("Noxeller TT-P (TT), manufactured by Ouchi Shinsei Chemical Co., Ltd.)"
d) Zinc oxide No. 3 zinc white e) Stearic acid Industrial stearic acid f) Wax Microcrystalline wax g) Anti-aging agent (A) Aromatic amine-based anti-aging agent N- (1,3-dimethylbutyl) -N ′ -Phenyl-p-phenylenediamine ("ANTAGE 6C", manufactured by Kawaguchi Chemical Co., Ltd.)
(B) 2,2,4-trimethyl-1,2-dihydroquinoline polymer ("Nonflex RD", manufactured by Seiko Chemical Co., Ltd.)
h) Bismaleimide compound N, N′-m-phenylenedimaleimide (“Barnock PM-P”, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
i) Compound represented by formula (1) (A) 1,6-hexamethylene-sodium dithiosulfate dihydrate (“HTS”, manufactured by Flexis)
(B) 1,6-bis (N, N′-dibenzylthiocarbamoyldithio) -hexane (“KA9188”, manufactured by Bayer)
j) Radical generator Dicumyl peroxide ("Park mill D", manufactured by NOF Corporation)

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

<Heat resistance>
Each rubber composition was press-molded while vulcanizing at 160 ° C. for 20 minutes, and then punched with a JIS No. 3 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, the rate of change was calculated, and the index was evaluated with the rate of change of the reference example as 100. The larger the index, the better the heat resistance. 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 20 minutes to prepare a vulcanized rubber sample having a cylindrical shape (diameter 29 mm, height 12.5 mm). Using such a vulcanized rubber sample, compression set was measured in accordance with JIS-K 6262 under predetermined conditions (100 ° C., test time 240 hours, compression rate 25%), and compression permanent of reference example. Index evaluation was performed with the measurement result of strain as 100. The smaller the index, the better the settling resistance. The evaluation results are shown in Table 1.

<Durability>
As a test piece for the durability test, a thick cylindrical metal fitting having an outer diameter of 16 mm and a height of 70 mm is positioned at the axial center of the thin cylindrical metal fitting in an inner hole of a thin cylindrical metal fitting having an outer diameter of 81 mm and a height of 49 mm. In addition, the cylindrical metal fittings having a structure in which both the cylindrical metal fittings are integrally connected with a new vulcanized rubber were used. In these test pieces, the vulcanized rubber connecting the two cylindrical fittings has a length of 38 mm, the width of the portion connecting the two cylindrical fittings is 22 mm, and the width of the portion fixed to the thick cylindrical fitting is 36 mm. Was set to be. The test piece having such a structure is subjected to a constant vibration at a frequency of 3 Hz with a load equivalent to an initial displacement of ± 14 mm, and the number of times of vibration until the vulcanized rubber breaks is measured. The index was evaluated with the number of vibrations in the example set to 100. It shows that durability is excellent, so that an index | exponent is large. The evaluation results are shown in Table 1.

  From the results shown in Table 1, the anti-vibration rubber obtained by vulcanization and molding using the rubber composition for anti-vibration rubber according to Examples 1 to 3 is more durable and less resistant to resistance than the reference example. It can be seen that it is improved and has excellent heat resistance. The anti-vibration rubber obtained from the rubber composition for anti-vibration rubber according to Example 4 includes only the anti-vibration rubber of Comparative Example 1 containing the maleimide compound and the compound represented by the formula (1), and the maleimide compound. Although heat resistance, durability, and anti-slip properties are improved as compared with the anti-vibration rubber of Comparative Example 2 to be contained, the polymer main chain is likely to be deteriorated due to a large content of the radical generator. As a result, it can be seen that the heat resistance and settling resistance are inferior to those of the reference example. From this result, it is understood that the content of the radical generator is preferably 1.5 parts by weight or less.

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,
Bismaleimide compound, compound represented by the following formula (1):


(Wherein, x is an integer from 2 to 12, R represents a thiocarbamoyl group having an aromatic hydrocarbon group or a fatty acid hydrocarbon group in the molecular structure, benzothiazole group or -SO _3, ^- Na ⁺ group) And a rubber composition for vibration-proof rubber, comprising a radical generator.   The rubber composition for vibration-proof rubber according to claim 1, wherein the content of the radical generator is 0.1 to 1.5 parts by weight with respect to 100 parts by weight of the rubber component.   Anti-vibration rubber obtained by vulcanization and molding using the rubber composition for anti-vibration rubber according to claim 1.