JP2018095810A - Rubber composition for vibration-proof rubber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for vibration-proof rubber serving as a raw material for vibration-proof rubber having low dynamic magnification and excellent vibration-proof performance while excellent in creep resistance at high temperature.SOLUTION: A rubber composition for vibration-proof rubber includes ethylene-α-olefin-nonconjugated diene copolymer rubber, a silica, a silane coupling agent, and sulfur. The ethylene-α-olefin-nonconjugated diene copolymer rubber has an ethylene content of 50 wt.% or more, and Mooney viscosity (ML1+4(125°C)) of 65 or more. If a total amount of rubber constituents including the ethylene-α-olefin-nonconjugated diene copolymer rubber is 100 pts.wt., a blend amount of the silica is 12-24 pts.wt., a blend amount of the sulfur is 0.75-2.5 pts.wt.SELECTED DRAWING: None

Description

  The present invention relates to a rubber composition for an anti-vibration rubber containing an ethylene-α-olefin-nonconjugated diene copolymer rubber, silica, a silane coupling agent, and sulfur.

  As characteristics required for the vibration-proof rubber, strength characteristics for supporting a heavy object such as an engine and vibration-proof performance for absorbing and controlling the vibration are required. In automotive applications, for example, when used in an engine room, the anti-vibration rubber is exposed to high temperatures, so it is required to have excellent creep resistance at high temperatures in addition to strength properties and anti-vibration performance. The

  Generally, ethylene-α-olefin-nonconjugated diene copolymer rubber (hereinafter also referred to as “EPDM”) is said to be a rubber material having excellent heat resistance, and is a vibration-proof rubber used in a high-temperature environment. May be used as a rubber material that constitutes. For example, in the following Patent Document 1, an object is to produce an anti-vibration rubber having a low dynamic magnification by using EPDM having a high ethylene content and performing organic peroxide crosslinking while blending carbon black.

JP 2006-193621 A

  However, as a result of intensive studies by the inventor, the technique described in Patent Document 1 has a certain effect in reducing the dynamic ratio of the vibration-proof rubber, but has seen improvement in terms of creep resistance at high temperatures. It turned out not to be. An object of the present invention is to provide a rubber composition for an anti-vibration rubber, which is a raw material for an anti-vibration rubber having a low dynamic magnification, excellent anti-vibration performance, and excellent creep resistance at high temperatures.

The above problem can be solved by the following configuration. That is, the present invention contains an ethylene-α-olefin-nonconjugated diene copolymer rubber, silica, a silane coupling agent, and sulfur, and the ethylene-α-olefin-nonconjugated diene copolymer rubber contains ethylene. The total amount of the rubber component having a content of 50% by weight or more and a Mooney viscosity (ML _{1 + 4} (125 ° C.)) of 65 or more and containing the ethylene-α-olefin-nonconjugated diene copolymer rubber is 100 parts by weight. In addition, the present invention relates to a rubber composition for vibration-proof rubber, wherein the amount of silica is 12 to 24 parts by weight and the amount of sulfur is 0.75 to 2.5 parts by weight.

  In this invention, specific EPDM is mix | blended as a rubber component in the rubber composition for anti-vibration rubber | gum, A silica and a silane coupling agent are added to this, and sulfur bridge | crosslinking is performed. As a result, the anti-vibration rubber obtained by vulcanizing the rubber composition for anti-vibration rubber according to the present invention can improve the anti-vibration performance without deteriorating the creep resistance at high temperature. The reason why such an effect is obtained is not clear, but by crosslinking the specific EPDM with sulfur, the crosslinking density is increased, and the elastic term is dominant over the viscous term with respect to viscoelasticity when used as a vibration-proof rubber. Become. As a result, the reduction in dynamic magnification can be achieved, and coupled with the presence of silica, the decrease in elastic modulus at high temperature is suppressed, and the creep resistance at high temperature is improved.

  In the rubber composition for an anti-vibration rubber, the ethylene-α-olefin-nonconjugated diene copolymer rubber is preferably a non-oil-extended type, and the ethylene-α-olefin-nonconjugated diene copolymer rubber is The Mooney viscosity (ML1 + 4 (125 ° C.)) is more preferably less than 100. In this case, since the Mooney viscosity of EPDM is kept low even in non-oil-extended, the anti-vibration performance of the obtained anti-vibration rubber is improved while improving the processability of the rubber composition for anti-vibration rubber. Can be improved.

  The rubber composition for vibration-proof rubber according to the present invention contains ethylene-α-olefin-nonconjugated diene copolymer rubber (EPDM), silica, a silane coupling agent, and sulfur.

  EPDM is a ternary copolymer in which an unsaturated bond is introduced by copolymerizing a small amount of a copolymer of ethylene and propylene and a non-conjugated diene monomer, which is a third component as a crosslinking monomer, as a non-conjugated diene. Include dicyclopentadiene, 1,4-hexadiene, 5-ethylidene-2-norbornene, and the like.

In the present invention, EPDM satisfying at least the following conditions is used as EPDM.
(1) The ethylene content is 50% by weight or more, and (2) the Mooney viscosity (ML _{1 + 4} (125 ° C.)) is 65 or more.
Regarding (1), it is preferably 60 to 70% by weight, more preferably 62 to 64% by weight. In the present invention, two or more types of EPDM can be used in combination, and the ethylene content of EPDM in that case means an average value in consideration of the amount used. The ethylene content of EPDM can be calculated based on ASTM D 3900. Moreover, regarding (2), a preferable lower limit is 68 or more, and a preferable upper limit is less than 100. When two or more types of EPDM are used, it means an average value in consideration of the amount used. The Mooney viscosity (ML _{1 + 4} (125 ° C.)) of EPDM can be calculated based on ASTM D 1646.

In the present invention, commercially available products can also be suitably used as EPDM satisfying (1) ethylene content of 50% by weight or more and (2) Mooney viscosity (ML _{1 + 4} (125 ° C.)) of 65 or more. IP5565 (ethylene content 50% by weight, ML1 + 4 (125 ° C.) 65, diene content (hereinafter abbreviated as “DN”) 7.5% by weight) and IP4770 (ethylene content 70% by weight, ML1 + 4 (125 C) 70, DN 4.9% by weight). In the present invention, an embodiment in which these two types of EPDM are used in combination is also preferable, and the combined ratio is a ratio of IP5565 having an ethylene content of 50% by weight and IP4770 having an ethylene content of 70% by weight. It is preferable to set it as 70-50 / 50, and it is preferable to set it as 35 / 65-45 / 55.

  In the present invention, “oil-extended rubber” means rubber obtained by adding mineral oil, paraffin oil, naphthenic oil or the like as an oil-extended component to rubber. For example, “oil-extended 50 type” means the total amount of rubber component. Of 100% by weight means that 50% by weight of an oil component such as oil is blended. In the present invention, an oil-extended EPDM may be used. However, when an EPDM that is a non-oil-extended EPDM and satisfies the above (1) and (2) is used, a rubber composition is used. This is preferable because the processing stability of the rubber and the dynamic ratio of the vulcanized rubber can be improved in a balanced manner. In the present invention, “non-oil-extended EPDM” means “the blending amount of oil components such as oil is 0 wt% when the total amount of rubber components is 100 wt%”.

  As the silica, wet silica, dry silica, sol-gel silica, surface-treated silica or the like used for usual rubber reinforcement is used. Of these, wet silica is preferable. These may be used alone or in combination of two or more. The compounding amount of silica in the rubber composition is preferably 12 to 24 parts by weight, and more preferably 12 to 15 parts by weight, when the total amount of rubber components including EPDM is 100 parts by weight.

  In the present invention, a silane coupling agent is blended in order to improve the dispersibility of silica in the rubber composition. Examples of the silane coupling agent include sulfide systems such as bis- (3- (triethoxysilyl) propyl) tetrasulfide, mercapto systems such as 3-mercaptopropyltrimethoxysilane, amino systems such as 3-aminopropyltrimethoxysilane, A vinyl-based silane coupling agent such as vinyltriethoxysilane is usually used. These may be used singly or in combination of two or more. The compounding amount of the silane coupling agent in the rubber composition part is preferably 8 to 12% by weight when the total amount of silica is 100% by weight.

  In the present invention, in addition to silica, carbon black may be blended in the rubber composition. Examples of carbon black include SAF, ISAF, HAF, FEF, GPF, and SRF. These may be used singly or in combination of two or more. The blending amount of carbon black is not particularly limited, but for example, about 30 to 90 parts by weight can be exemplified when the total amount of rubber components including EPDM is 100 parts 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 0.5 to 2.5 parts by weight with respect to 100 parts by weight of the rubber component. If the sulfur content is less than 0.5 parts by weight, the dynamic ratio of the vulcanized rubber increases and the durability tends to deteriorate. On the other hand, when the sulfur content exceeds 2.5 parts by weight, the heat resistance tends to deteriorate. In order to further improve the dynamic magnification, heat resistance and durability of the vulcanized rubber in a well-balanced manner, the sulfur content relative to 100 parts by weight of the rubber component is preferably 0.75 to 1.2 parts by weight.

  In the present invention, oil may be blended in the rubber composition. The hardness of the vibration-proof rubber finally obtained can be adjusted by appropriately adjusting the blending amount of the oil. As the oil, paraffinic, naphthenic and aromatic types can be used. The amount of oil blended can be varied according to the hardness of the finally obtained anti-vibration rubber. For example, when the total amount of rubber components including EPDM is 100 parts by weight, it is appropriately adjusted within the range of 21 to 74 parts by weight. Is possible.

  The rubber composition for vibration-proof rubber according to the present invention comprises carbon rubber, oil, zinc oxide, stearic acid, vulcanization accelerator, vulcanization accelerator together with the rubber component containing the above EPDM, silica, silane coupling agent and sulfur. Additives usually used in the rubber industry such as auxiliary agents, vulcanization retarders, anti-aging agents, reversion inhibitors, softening agents such as waxes, processing aids, etc., as long as the effects of the present invention are not impaired. It can be blended and used.

  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. In consideration of rubber physical properties and durability after vulcanization, the blending amount of the vulcanization accelerator with respect to 100 parts by weight of the rubber component is preferably 0.5 to 2 parts by weight.

  As an anti-aging agent, an aromatic amine-based anti-aging agent, an amine-ketone-based anti-aging agent, a dithiocarbamate-based anti-aging agent, a thiourea-based anti-aging agent, etc., which are usually used for rubber in addition to the phenol-based anti-aging agent May be used as needed. The blending amount of the anti-aging agent with respect to 100 parts by weight of the rubber component is preferably 0 to 3 parts by weight.

  The rubber composition for vibration-proof rubber according to the present invention comprises carbon rubber, oil, zinc oxide, stearic acid, vulcanization accelerator, vulcanization accelerator together with the rubber component containing the above EPDM, silica, silane coupling agent and sulfur. Additives normally used in the rubber industry such as auxiliaries, vulcanization retarders, anti-aging agents, vulcanization reversion inhibitors, softeners such as waxes, processing aids, ordinary ingredients such as Banbury mixers, kneaders, rolls, etc. It can be obtained by kneading using a kneader used in the rubber industry.

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

  By kneading and molding each of the above components, followed by vulcanization, it is possible to obtain a vibration-proof rubber that improves both heat resistance and durability in a well-balanced manner. 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)
According to the formulation of Table 1, the rubber compositions of Examples 1 to 7 and Comparative Examples 1 to 5 are blended with 100 parts by weight of the rubber component and kneaded using a normal Banbury mixer to prepare a rubber composition. did. Each compounding agent described in Table 1 is shown below.

a) EPDM
EP33 (ethylene content 52% by weight, ML _{1 + 4} (125 ° C.) 28, DN 8.1% by weight) manufactured by JSR EP57C (ethylene content 67% by weight, ML _{1 + 4} (125 ° C.) 58, DN 4.5% by weight) JSR EPT3072 (ethylene content 64 wt%, ML _{1 + 4} (125 ° C) 51, DN 5.4 wt%, oil extended 40 parts by weight) Mitsui Chemicals Co., Ltd. EP96 (ethylene content 66 wt%, ML _{1 + 4} (125 ° C) 61, DN 5.8% by weight, oil extended 50 parts by weight) IPSR 5565 (ethylene content 50% by weight, ML _{1 + 4} (125 ° C.) 65, DN 7.5% by weight) manufactured by JSR IP4770 (ethylene content 70% by weight) _{%, ML 1 + 4 (125} ℃) 70, DN4.9 wt%) Dow Inc. b) carbon black GPF Tokai carbon Co. SR C) Paraffinic oil "Process Oil PW-380", Idemitsu Kosan Co., Ltd. d) Silica "Nipseal AQ", Tosoh Silica Co., Ltd. e) Sulfur 5% oil-treated sulfur, Tsurumi Chemical F) Zinc oxide "Zinc oxide 3 types", Sakai Chemical Industry Co., Ltd. g) Stearic acid, NOF Corporation h) Vulcanization accelerator (A) Vulcanization accelerator (CZ) Sulfenamide vulcanization accelerator Agent N-cyclohexyl-2-benzothiazolylsulfenamide “Noxeller CZ”, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. (B) Vulcanization accelerator (M) Thiazole vulcanization accelerator 2-mercaptobenzothiazole “Noxeller M- P (M), manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. (C) Vulcanization accelerator (TT) Thiuram compound Tetramethylthiuram disulfide “Noxeller TT”, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. (D Vulcanization accelerator (PX) Dithiocarbamate-based zinc N-ethyl-N-phenyldithiocarbamate “Noxeller PX”, manufactured by Ouchi Shinsei Chemical Co., Ltd. i) Vulcanizing agent (R) “Varnock R”, Ouchi Emerging Chemical J) Vulcanization retarder (CTP) “Retarder CTP”, manufactured by Toray Industries, Inc.

(Evaluation)
The evaluation was performed on rubber obtained by heating and vulcanizing each rubber composition at 170 ° C. for 20 minutes using a predetermined mold.

(Physical properties of unvulcanized rubber)
Based on JIS-K 6300-1, the Mooney viscosity (ML _{1 + 4} (100 ° C.)) of the unvulcanized rubber after blending was measured. The results are shown in Table 1.

(Vulcanized rubber spring characteristics)
(Static spring constant (Ks))
Each rubber composition is press-molded while vulcanized to prepare a vulcanized rubber sample having a cylindrical shape (diameter 50 mm, height 25 mm), and then a cylindrical metal fitting (diameter on the upper and lower surfaces of the vulcanized rubber sample. A test piece was prepared by bonding a pair of 60 mm and a thickness of 6 mm using an adhesive. After compressing the prepared test piece twice in the cylinder axis direction for 5 mm, the deflection load of 1.25 mm and 3.75 mm is measured from the load deflection curve when the strain is restored, and the static spring is determined from these values. Constant (Ks) (N / mm) was calculated.
(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, dynamic load was detected in the upper load cell, and dynamic spring constant (Kd) (N / mm) was calculated according to JIS-K 6394.
(Dynamic magnification: Kd / Ks)
The dynamic magnification was calculated from the following formula.
(Dynamic magnification) = (Dynamic spring constant (Kd)) / (Static spring constant (Ks))
The dynamic magnification was calculated based on the calculated dynamic spring constant and static spring constant.
In addition, the dynamic magnification of the Example with respect to each comparative example was evaluated as a dynamic magnification INDEX. Specifically, for Examples 1 to 3, index evaluation is performed when the dynamic magnification of Comparative Example 1 is 100, and for Example 4, index evaluation is performed when the dynamic magnification of Comparative Example 2 is 100. For Example 5, index evaluation is performed when the dynamic magnification of Comparative Example 3 is 100, for Example 6, index evaluation is performed when the dynamic magnification of Comparative Example 4 is 100, and for Example 7, Index evaluation was performed when the dynamic magnification of Comparative Example 5 was set to 100. The results are shown in Table 1.

(Physical properties of vulcanized rubber)
Based on JIS-K 6251, TB (MPa) and EB (%) of vulcanized rubber were evaluated. The results are shown in Table 1.

(Resistance to vulcanized rubber)
Based on JIS-K 6262, the vulcanized rubber was evaluated for its stickiness resistance (CS (%) @ 125 ° C., 72 h). The results are shown in Table 1.

(Creep resistance of vulcanized rubber at high temperature)
Comparison of room temperature and high temperature (100 ° C.) of dynamic viscoelastic properties (storage modulus: E ′). The degree of decrease in elastic modulus (%) relative to room temperature at high temperature was determined. The measurement conditions were a frequency of 0.5 Hz, an initial strain of 10%, and a strain amplitude of ± 5%. The results are shown in Table 1.

(Dynamic magnification and creep resistance evaluation at high temperature)
As for the dynamic magnification, when the dynamic magnification INDEX of the example for each comparative example is (X), 100 <(X) ≦ 120, ◯, and (X)> 120, ◎. Regarding creep resistance at high temperature, when (Y)>-20, the elastic modulus decrease rate (%) at high temperature is (Y)>-20, and if -25 ≦ (Y) ≦ −20 ○, if (Y) <− 25, × The results are shown in Table 1.

Claims (3)

Containing ethylene-α-olefin-nonconjugated diene copolymer rubber, silica, silane coupling agent, and sulfur;
The ethylene-α-olefin-nonconjugated diene copolymer rubber has an ethylene content of 50% by weight or more and a Mooney viscosity (ML _{1 + 4} (125 ° C.)) of 65 or more.
When the total amount of the rubber component including the ethylene-α-olefin-nonconjugated diene copolymer rubber is 100 parts by weight, the amount of silica is 12 to 24 parts by weight and the amount of sulfur is 0.75 to 2. A rubber composition for vibration-proof rubber, characterized by being 5 parts by weight.   The rubber composition for vibration-proof rubber according to claim 1, wherein the ethylene-α-olefin-nonconjugated diene copolymer rubber is a non-oil-extended type. The rubber composition for vibration-proof rubber according to claim 1 or 2, wherein the ethylene-α-olefin-nonconjugated diene copolymer rubber has a Mooney viscosity (ML _{1 + 4} (125 ° C)) of less than 100.