JP2011132413A - Vibration-damping rubber composition and vibration-damping rubber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vibration-damping rubber composition that gives a cured rubber material having a largely improved creep resistance while retaining heat resistance, strength and low dynamic-to-static modulus ratio and a vibration-damping rubber obtained by curing the rubber composition. <P>SOLUTION: The vibration-damping rubber composition includes natural rubber (NR) and ethylene/propylene/diene rubber (EPDM) as a rubber component in a mass ratio of NR/EPDM=70/30 to 45/55, only a peroxide as a vulcanization agent, and (X) zinc acrylate or zinc methacrylate and (Y) trimethylolpropane trimethacrylate as crosslinking agents. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heat-resistant and vibration-proof rubber composition that can be suitably used in a high-temperature environment, and a vibration-proof rubber obtained by curing the composition. In particular, the present invention relates to an anti-vibration rubber composition and an anti-vibration rubber that can be suitably used at high temperature sites such as automobile torsional dampers, engine mounts, and muffler hangers.

  Conventionally, in various vehicles such as automobiles, in order to improve the comfort of passengers, various anti-vibration materials have been arranged at sites that are sources of vibration and noise to reduce the intrusion of vibration and noise into the room. Attempts have been made. For example, for engines that are the main source of vibration and noise, vibrations during engine drive are absorbed by using anti-vibration rubber for components such as torsional dampers, engine mounts, and muffler hangers. Reduces the intrusion of vibration and noise and the spread of noise to the surrounding environment.

  As a basic characteristic of such an anti-vibration rubber, a strength characteristic that supports a heavy object such as an engine and an anti-vibration performance that absorbs and suppresses the vibration are required. Furthermore, when used in high-temperature environments such as engine rooms, it has excellent strength characteristics, low dynamic magnification and excellent vibration-proof performance, as well as heat resistance, ozone resistance, and creep resistance. It is required to have high performance.

  Until now, natural rubber (NR), which has excellent physical properties such as fracture characteristics, has been often used as the rubber component of the vibration-proof rubber. However, although NR is excellent in destructive properties and the like, heat resistance and ozone resistance are inferior to that of synthetic rubber, so that heat resistance and ozone resistance are insufficient when used in a high temperature environment.

  Moreover, in the conventionally proposed technology, in order to greatly improve the creep resistance, one of heat resistance, strength, and low dynamic magnification must be sacrificed. In addition, in Japanese Patent Application No. 2008-156225 (Japanese Patent Laid-Open No. 2009-298949) previously proposed by the present applicant, natural rubber (NR) and ethylene / propylene / diene rubber (EPDM) are used as a rubber component in a mass ratio of NR. An anti-vibration rubber composition containing / EPDM = 70/30 to 45/55 and premixed with zinc acrylate and a fatty acid ester is described.

  However, the rubber composition using zinc acrylate or zinc methacrylate as a co-crosslinking agent as described above is excellent in heat resistance and tensile physical properties, but inferior in creep resistance.

  In order to solve the above problems, Japanese Patent Application No. 2009-195021 proposes to use zinc acrylate and a bismaleimide compound together as a co-crosslinking agent for the rubber component (NR / EPDM). In the composition, a slight decrease in elongation was observed in the tensile properties, and the vibration-insulating rubber performance was not sufficiently satisfactory.

JP 2009-298949 A

  The present invention has been made in view of the above circumstances, and an anti-vibration rubber composition capable of obtaining a rubber cured product capable of greatly improving creep resistance while maintaining heat resistance, strength and low dynamic magnification, and the rubber composition An object is to provide a vibration-proof rubber obtained by curing a product.

  As a result of intensive studies to achieve the above object, the present inventor has blended NR and EPDM at a specific ratio to form a rubber component, and blends only a peroxide as a vulcanizing agent and a co-crosslinking agent. In order to significantly improve the creep resistance in the conventional technology by containing (X) zinc acrylate or zinc methacrylate and (Y) trimethylolpropane trimethacrylate or trimethylolpropane triacrylate One of the heat resistance, strength, and low dynamic magnification had to be sacrificed, but the rubber composition of the present invention greatly improved creep resistance while maintaining heat resistance, strength, and low dynamic magnification. The present invention has been found and the present invention has been made.

Accordingly, the present invention provides the following rubber composition for vibration-proof rubber and vibration-proof rubber.
[1] Natural rubber (NR) and ethylene / propylene / diene rubber (EPDM) are contained as a rubber component in a mass ratio of NR / EPDM = 70/30 to 45/55, and only a peroxide is used as a vulcanizing agent. And (X) zinc acrylate or zinc methacrylate and (Y) trimethylolpropane trimethacrylate or trimethylolpropane triacrylate as a co-crosslinking agent.
[2] X parts by mass of zinc acrylate or zinc methacrylate with respect to 100 parts by mass of rubber component, Y parts by mass of trimethylolpropane trimethacrylate or trimethylolpropane triacrylate, and total parts of co-crosslinking agent Is X + Y = Z parts by mass,
1.0 ≦ X ≦ 4.0
0.2 ≦ Y ≦ 6.0
4.0 ≦ Z ≦ 7.0
The anti-vibration rubber composition according to [1], wherein
[3] A vibration-proof rubber obtained by curing the rubber composition according to [1] or [2].

  The anti-vibration rubber composition of the present invention can greatly improve creep resistance while maintaining heat resistance, strength and low dynamic magnification.

  The anti-vibration rubber composition of the present invention contains natural rubber (NR) and ethylene / propylene / diene rubber (EPDM) in a predetermined ratio as rubber components, contains only peroxide as a vulcanizing agent, and is a co-crosslinking agent. As (X) zinc acrylate or zinc methacrylate and (Y) trimethylolpropane trimethacrylate or trimethylolpropane triacrylate.

  The rubber component includes NR and EPDM. At that time, the blending ratio of NR and EPDM is usually in the range of NR / EPDM = 70/30 to 45/55 in terms of mass ratio. If the ratio of EPDM is less than the above range, ozone resistance and heat resistance may be reduced, and if it is too high, dynamic magnification may be increased, and durability and strength may be reduced. The NR and EPDM may be appropriately selected from known ones and are not particularly limited.

  Further, in the present invention, the rubber component containing NR and EPDM is used as described above. However, as long as it does not deviate from the purpose, other rubbers such as a known synthetic rubber are used in addition to the rubber component as necessary. May be used in combination. Specific examples thereof include butadiene rubber, styrene / butadiene rubber, isoprene rubber, chloroprene rubber, isobutylene / isoprene rubber, acrylonitrile / butadiene rubber, silicone rubber, acrylic rubber, epoxidized natural rubber, acrylate butadiene rubber and the like, and these Examples include synthetic rubbers or natural rubbers whose molecular chain ends are modified, and one or more of them may be appropriately selected and used. When blending the rubber, it is preferably 20% by mass or less (0 to 20% by mass) based on the total amount of the rubber components.

  As the vulcanizing agent, only peroxide is used in the present invention. In the present invention, by peroxide-crosslinking the rubber component using only a peroxide as a vulcanizing agent, heat resistance and creep resistance at high temperatures are excellent as compared with the case of crosslinking using sulfur. Therefore, the heat resistance and durability of the anti-vibration rubber can be improved. As the peroxide, those normally used in this field can be blended, and specific examples thereof include dicumyl peroxide, benzoyl peroxide, 1,1-bis (t-butylperoxy) -3, 5,5-trimethylcyclohexane, diisobutyryl peroxide, cumylperoxyneodecanoate, di-n-propylperoxydicarbonate, diisopropylperoxydicarbonate, di-sec-butylperoxydicarbonate, 1,1, 3,3-tetramethylbutylperoxyneodecanoate, di (4-t-butylcyclohexyl) peroxydicarbonate, di (2-ethylhexyl) peroxydicarbonate, t-hexylperoxyneodecanoate, t-butyl peroxyneodecanoate, t-butyl peroxy Oxyneoheptanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, di (3,5,5-trimethylhexanoyl) peroxide, dilauroyl peroxide, 1,1,3,3- Tetramethylbutylperoxy-2-ethylhexanoate, disuccinic acid peroxide, 2,5-dimethyl-2,5-di (2-ethylhexanoylperoxy) hexane, t-hexylperoxy-2-ethylhexa Noate, di (4-methylbenzoyl) peroxide, t-butylperoxy-2-ethylhexanoate, di (3-methylbenzoyl) peroxide, benzoyl (3-methylbenzoyl) peroxide, dibenzoyl peroxide 1,1-di (t-butylperoxy) -2-methylcyclohex 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-trimethylhexanoate, t-butyl peroxylaurate, t-butyl peroxyisopropyl monocarbonate, t-butyl peroxy 2-ethylhexyl monocarbonate, t-hexyl peroxybenzoate, 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) Oxyisopropyl) benzene, 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, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydro Peroxide, t-butyl hydroperoxide and the like. In the present invention, di (2-t-butylperoxy) is used. An isopropyl) benzene, can be suitably used dicumyl peroxide. These can be used individually by 1 type or in mixture of 2 or more types. The compounding amount of these vulcanizing agents is usually 1 to 10 parts by mass, preferably 2 to 8 parts by mass with respect to 100 parts by mass of the rubber component. When the blending amount exceeds 10 parts by mass, the rubber is excessively cured, which may cause a decrease in elongation at break and a decrease in durability. When the amount is less than 1 part by mass, the crosslinking density decreases and the breaking strength decreases. There is a risk of lowering, deterioration of dynamic magnification, deterioration of compression set, deterioration of durability, and the like.

  In addition, in the range which does not deviate from the objective of this invention, sulfur can also be mix | blended as a crosslinking adjuvant. When mix | blending this crosslinking adjuvant, it is preferable to make the compounding quantity into the range of 0.1-0.5 mass part with respect to 100 mass parts of rubber components.

  The co-crosslinking agent is not itself capable of generating a crosslinking point, but is an additive that causes a crosslinking reaction in the rubber when used in combination with the above-described peroxide, in order to obtain the desired effect of the present invention. , (X) zinc acrylate or zinc methacrylate, and (Y) trimethylolpropane trimethacrylate or trimethylolpropane triacrylate as essential components.

  (X) Although there is no restriction | limiting in particular in the compounding quantity of zinc acrylate or zinc methacrylate, Preferably it is 1.0 mass part or more with respect to 100 mass parts of said rubber components, More preferably, it is 2.0 mass parts or more. The upper limit is preferably 4.0 parts by mass or less, more preferably 3.5 parts by mass or less. If the blending amount exceeds the above range, the rubber may be cured too much, leading to a decrease in elongation at break, and if the blending amount is less than the above range, the rubber is not sufficiently crosslinked, resulting in a decrease in breaking strength and a dynamic ratio. May increase, compression set may increase.

  In the present invention, the fatty acid ester can be blended with the rubber component together with the (X) zinc acrylate or zinc methacrylate, thereby dispersibility of the zinc acrylate or zinc methacrylate with respect to the rubber component during kneading. And the mechanical properties of the rubber after vulcanization can be improved. Here, the fatty acid and alcohol constituting the fatty acid ester may both have a linear structure or a branched structure, may be either saturated or unsaturated, and the number of carbon atoms is not particularly limited. . In the present invention, a known fatty acid ester composed of a fatty acid having a chain length of 1 to 30 carbon atoms and an alcohol having a chain length of 1 to 30 carbon atoms can be used. May be ethyl stearate, propyl stearate, butyl stearate, ethyl palmitate, propyl palmitate, butyl palmitate and the like. These can be used alone or in combination of two or more. The amount of the fatty acid ester is preferably 0.02 to 1.2 parts by mass, more preferably 0.2 to 0.6 parts by mass with respect to 100 parts by mass of the rubber component. If the blending amount exceeds 1.2 parts by mass, the rubber may be softened, the workability may be deteriorated, and the dynamic magnification may be deteriorated. If the blending amount is less than 0.02 parts by mass, the dispersibility improvement effect may not be obtained. is there.

  This fatty acid ester exhibits the effect of improving dispersibility even when blended separately with the zinc acrylate or zinc methacrylate when kneaded with the rubber component. By premixing with zinc methacrylate, the dispersibility of zinc acrylate or zinc methacrylate in the rubber component can be further improved.

  In the present invention, (Y) trimethylolpropane trimethacrylate or trimethylolpropane triacrylate is used as an essential component as a co-crosslinking agent, and is used in combination with the above (X) zinc acrylate or zinc methacrylate. (Y) Although there is no restriction | limiting in particular in the compounding quantity of a trimethylol propane trimethacrylate or a trimethylol propane triacrylate, Preferably it is 0.2 mass part or more with respect to 100 mass parts of said rubber components, More preferably, it is 0.5 mass. The upper limit is preferably 6.0 parts by mass or less, and more preferably 4.5 parts by mass or less. If the blending amount exceeds the above range, the breaking strength may be lowered and the dynamic magnification may be increased. If the blending amount is less than the above range, the compression set may be increased.

  Further, the blending amount of zinc acrylate or zinc methacrylate with respect to 100 parts by weight of the rubber component is X parts by weight, the blending amount of trimethylolpropane trimethacrylate or trimethylolpropane triacrylate is Y parts by weight, and the total weight part of the co-crosslinking agent is When X + Y = Z parts by mass, it is preferable to satisfy 4.0 ≦ Z ≦ 7.0, more preferably 4.5 ≦ Z ≦ 5.5 from the viewpoint of effectively exhibiting the effects of the present invention. is there. Deviating from this range may lead to an increase in dynamic magnification, a decrease in elongation at break and strength, and an increase in compression set.

  In addition, for the rubber component, a vulcanizing agent, a vulcanization accelerator, an anti-aging agent, carbon, silica, zinc white, which are usually used in the rubber industry, are used as long as the effects of the present invention are not impaired. Additives such as (ZnO), waxes, antioxidants, fillers, foaming agents, plasticizers, oils, lubricants, tackifiers, petroleum resins, ultraviolet absorbers, dispersants, compatibilizers, homogenizers, etc. Can be appropriately blended.

  As the oil, known oils can be used, and are not particularly limited. Specifically, process oils such as aromatic oils, naphthenic oils, paraffin oils, vegetable oils such as palm oil, alkylbenzene oils, etc. Synthetic oil, castor oil, etc. can be used. In the present invention, paraffin oil can be preferably used. These can be used alone or in combination of two or more. The blending amount of these oils is not particularly limited, but can be approximately 15 to 45 parts by mass with respect to 100 parts by mass of the rubber component. If the blending amount deviates from the above range, the kneading workability may be deteriorated. When oil-extended rubber is used for the rubber component, the total amount of oil contained in the rubber and oil added separately during mixing may be adjusted within the above range.

  Known carbon can be used, and is not particularly limited. Examples thereof include carbon black such as SRF, GPF, FEF, HAF, ISAF, SAF, FT, MT, In the present invention, FEF can be preferably used. Moreover, these carbon blacks may be used individually by 1 type, and may use 2 or more types together. The blending amount of these carbon blacks is usually 15 to 60 parts by mass, preferably 20 to 50 parts by mass with respect to 100 parts by mass of the rubber component. When the amount exceeds 60 parts by mass, workability may be deteriorated, and when it is less than 15 parts by mass, adhesion may be deteriorated.

  In the present invention, from the viewpoint of promoting vulcanization, a vulcanization acceleration aid such as zinc white (ZnO) or a fatty acid can be blended. The fatty acid may be a saturated, unsaturated, linear or branched fatty acid, and is not particularly limited as the carbon number of the fatty acid. For example, the fatty acid has 1 to 30 carbon atoms, preferably 15 to 15 carbon atoms. 30 fatty acids, more specifically naphthenic acid such as cyclohexane acid (cyclohexanecarboxylic acid), alkylcyclopentane having a side chain, hexanoic acid, octanoic acid, decanoic acid (including branched carboxylic acid such as neodecanoic acid), Saturated fatty acids such as dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid (stearic acid), unsaturated fatty acids such as methacrylic acid, oleic acid, linoleic acid, linolenic acid, resin acids such as rosin, tall oil acid, abietic acid, etc. Is mentioned. These may be used alone or in combination of two or more. In the present invention, zinc white and stearic acid can be preferably used. The compounding amount of these vulcanization acceleration aids is preferably 1 to 10 parts by mass, more preferably 2 to 7 parts by mass with respect to 100 parts by mass of the rubber component. If the blending amount exceeds 10 parts by mass, workability and dynamic magnification may be degraded, and if it is less than 1 part by mass, vulcanization delay may occur.

  As the anti-aging agent, known ones can be used, and are not particularly limited, and examples thereof include a phenol type anti-aging agent, an imidazole type anti-aging agent and an amine type anti-aging agent. The blending amount of these anti-aging agents is usually 2 to 10 parts by mass, preferably 3 to 7 parts by mass with respect to 100 parts by mass of the rubber component.

  When obtaining the rubber composition of the present invention, there is no particular limitation on the blending method of each of the above components, and all the component raw materials may be blended and kneaded at once, and each component may be divided into two or three stages. You may mix | blend and knead | mix. At that time, by premixing with the fatty acid ester before kneading the (meth) zinc acrylate with the rubber component, the dispersibility of the (meth) zinc acrylate in the rubber component is further improved, and the resulting rubber The mechanical properties can be further improved. In the kneading, a kneader such as a roll, an internal mixer, a Banbury rotor or the like can be used. Furthermore, when forming into a sheet shape or a belt shape, a known molding machine such as an extrusion molding machine or a press machine may be used.

  Moreover, there are no particular limitations on the vulcanization conditions for curing the rubber composition, but vulcanization conditions can be generally employed at 140 to 180 ° C. for 5 to 120 minutes.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not restrict | limited to the following Example.

[Examples 1-27, Comparative Examples 1-3]
The rubber composition for vibration-proof rubber of each of Examples 1 to 27 and Comparative Examples 1 to 3 is vulcanized and cured under predetermined conditions by kneading and vulcanizing with the blending compositions shown in Tables 1 to 3 below. A sheet molded product of 120 mm × width 120 mm × thickness 2 mm was produced. This sheet was used as an evaluation body of the vibration-proof rubber of the present invention. About the obtained rubber sheet, hardness (Hd), tensile elongation (Eb), tensile strength (Tb), heat resistance (thermal aging test), compression set (%), static spring constant (Ks), dynamic spring constant (Kd) and dynamic magnification (Kd / Ks) were measured and evaluated according to the following JIS standards. The results are also shown in Tables 1-3.

[Hardness (Hd)]
Conforms to JIS K 6253 (Type A) [Tensile elongation (Eb)]
Conforms to JIS K 6251. When Eb was 500% or more, it was judged as “good”.
[Tensile strength (Tb)]
Conforms to JIS K 6251. When Tb was 15 MPa or more, it was judged as “good”.
[Heat resistance (heat aging test)]
In accordance with JIS K 6257, the test piece was allowed to stand under the conditions of 100 ° C. and 96 hours, and then the hardness (Hd), tensile elongation (Eb), and tensile strength (Tb) were measured. For hardness (Hd), change values (degrees) are shown, and for tensile elongation (Eb) and tensile strength (Tb), retention (%) is shown.
[Compression set]
Conforms to JIS K 6262. The target value was within 30% of compression set (CS).
[Static spring constant (Ks), dynamic spring constant (Kd), and dynamic magnification (Kd / Ks)]
According to JIS K 6385, Kd was measured at 100 Hz. The dynamic magnification (Kd / Ks) was set to a target value within 1.4.

Details of the above formulation are as follows.
(1) NR: Natural rubber, “RSS # 1”
(2) EPDM: “EP96” manufactured by JSR, ENB content 6.0% by mass, ethylene content 66% by mass (polymer component: 30 phr, oil component: 15 phr)
(3) FT grade carbon black: "Asahi Thermal" made by Asahi Carbon
(4) Anti-aging agent: 2,2,4-trimethyl-1,2-dihydroquinoline polymer, “NOCRACK 224” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
(5) Peroxide: Di (2-t-butylperoxyisopropyl) benzene, “Peroximon F-40” manufactured by NOF Corporation
(6) Trimethylolpropane trimethacrylate: manufactured by Seiko Chemical Co., Ltd., trade name “Hi-Cross MP” (manufactured by NOF Corporation, trade name “Blemmer PTT”)
(7) Trimethylolpropane triacrylate: NOF Corporation, trade name “Blemmer ATT”
(8) Zinc acrylate (ZA), “SR633” manufactured by Sartomer

  As shown in Tables 1 to 3 above, the rubber compositions of the examples according to the present invention blend NR and EPDM at a specific ratio to form a rubber component, and blend only peroxide as a vulcanizing agent. As the crosslinking agent, (X) zinc acrylate or zinc methacrylate and (Y) trimethylolpropane trimethacrylate or trimethylolpropane triacrylate are combined. As a result, it was confirmed that the rubber compositions of these examples can significantly improve the creep resistance (compression set) while maintaining good heat resistance, strength and low dynamic magnification. .

Claims (3)

  Natural rubber (NR) and ethylene / propylene / diene rubber (EPDM) are contained as a rubber component in a mass ratio of NR / EPDM = 70/30 to 45/55, and only a peroxide is contained as a vulcanizing agent. A vibration-proof rubber composition comprising (X) zinc acrylate or zinc methacrylate and (Y) trimethylolpropane trimethacrylate or trimethylolpropane triacrylate as a co-crosslinking agent. The blending amount of zinc acrylate or zinc methacrylate to 100 parts by weight of the rubber component is X parts by weight, the blending amount of trimethylolpropane trimethacrylate or trimethylolpropane triacrylate is Y parts by weight, and the total weight part of the co-crosslinking agent is X + Y = When it is Z parts by mass,
1.0 ≦ X ≦ 4.0
0.2 ≦ Y ≦ 6.0
4.0 ≦ Z ≦ 7.0
The anti-vibration rubber composition according to claim 1 satisfying   Anti-vibration rubber obtained by curing the rubber composition according to claim 1.