JP2006193621A - Vibration-proof rubber composition and vibration-proof rubber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vibration-proof rubber composition improved in dynamic-to-static modulus ratio and resistance to loss of bulkiness without impairing the other properties including mechanical strength and fatigue resistance. <P>SOLUTION: The vibration-proof rubber composition comprises 100 pts.wt. of a rubber component, i.e. at least one kind selected from the group consisting of diene rubber and ethylene-propylene-diene copolymer(EPDM), and 1-20 pts.wt. of particulate zinc oxide 10-200 m<SP>2</SP>/g in specific surface area determined by BET method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  In general, an anti-vibration rubber such as a mount, a bush, or a damper is used in an automobile in order to absorb vibrations of an engine and a vehicle body and improve riding comfort and prevent noise in the passenger compartment.

  In order to enhance the vibration-proof performance of the vibration-proof rubber, it is necessary that the value of the dynamic magnification (dynamic spring constant (Kd) / static spring constant (Ks)) of the vibration-proof rubber composition is sufficiently small. Accordingly, the smaller the dynamic spring constant in the vibration state for transmitting the vibration of the engine, the better the anti-vibration performance as the static rigidity indicating the support performance of the engine and the vehicle body, that is, the greater the static spring constant.

  This anti-vibration rubber composition includes a natural rubber having a low dynamic magnification and high strength, a natural rubber mainly blended with a diene rubber such as butadiene rubber or styrene butadiene rubber, or ethylene- Conventionally, a propylene-diene copolymer (EPDM) is used as a rubber component, and the use of specific carbon black or increasing the amount of zinc white is used to lower the dynamic magnification.

For example, JP-A-2002-97307 proposes a rubber composition in which 8 to 30 parts by weight of zinc oxide and carbon black having an average particle diameter of 40 nm or less are blended with 100 parts by weight of rubber. In 2001-240703, a rubber composition excellent in vibration-proof characteristics is disclosed in which a diene rubber such as natural rubber or an ethylene-α-olefin copolymer rubber is blended with a reinforcing agent such as carbon black and zinc oxide. (Patent Documents 1 and 2).
JP 2002-97307 A JP 2001-240703 A

  By the way, with the recent high performance, high output, and high grade of automobiles, the demand for improvement in ride comfort and quietness of the passenger compartment is gradually increased, and such vibration-proof rubber using such a conventional rubber composition is like this. It is difficult to sufficiently respond to the demand, and further improvement of the vibration isolating characteristics is required for the vibration isolating rubber composition.

  In view of these points, the present invention improves the dynamic magnification and sag resistance without reducing other properties such as strength and fatigue resistance, and enables wide application to vibration-proof members. An object of the present invention is to provide a vibration rubber composition and a vibration-proof rubber using the same.

  In order to achieve the above object, the present inventors pay attention to the fact that the addition of zinc white can lower the dynamic ratio of the rubber composition, and in earnest study on the particle structure of zinc white, The inventors have found that the formation of fine particles is extremely effective in reducing the dynamic magnification, and have completed the present invention.

That is, the anti-vibration rubber composition of the present invention comprises at least one selected from the group consisting of a diene rubber and an ethylene-propylene-diene copolymer as a rubber component, and BET with respect to 100 parts by weight of the rubber component. It contains 1 to 20 parts by weight of finely divided zinc white having a specific surface area measured by the method of 10 to 200 m ² / g.

  In the anti-vibration rubber composition, it is preferable that an average particle size of the fine particle zinc white is 0.001 to 0.3 μm.

 The present invention also relates to an anti-vibration rubber using the anti-vibration rubber composition.

  In the anti-vibration rubber composition of the present invention, by containing highly active zinc white composed of fine particles, zinc white has a role as a reinforcing filler and a role as a cross-linking accelerating agent. The effect is demonstrated by dispersing in.

  In particular, its function as a crosslinking accelerator is important and affects dynamic properties and reinforcing properties. It is possible to disperse the crosslinking uniformly by highly dispersing fine particles of zinc oxide, and the distribution of the number of sulfur involved in the crosslinking. It is presumed that good dynamic characteristics and sag resistance could be obtained by these effects. Even in organic peroxide crosslinking, although the mechanism is not clear, there is an effect of improving characteristics.

  According to the anti-vibration rubber composition of the present invention, the vibration ratio is reduced and the sag resistance is improved without affecting other properties of the rubber composition, and the anti-vibration rubber using this anti-vibration rubber composition The vibration-proof performance and durability can be improved.

  The anti-vibration rubber composition of the present invention improves the anti-vibration characteristics by reducing the dynamic spring constant of the rubber composition by reducing the dynamic spring constant of the rubber composition by containing specific fine zinc oxide with respect to 100 parts by weight of the rubber component. At the same time, the heat resistance is improved.

  As the rubber component used in the present invention, one kind selected from the group consisting of a diene rubber and an ethylene-propylene-diene copolymer (EPDM), or a blend of two or more kinds thereof is used as the rubber component. can do.

  As the diene rubber component, natural rubber (NR) or diene synthetic rubber is used. Examples of the diene synthetic rubber include butadiene rubber (BR), styrene butadiene rubber (SBR), polyisoprene rubber (IR), acrylonitrile-butadiene rubber (NBR), isobutylene-isoprene rubber (IIR), and chloroprene rubber (CR). Etc.

  In particular, in an anti-vibration rubber composition that requires heat resistance, it is preferable to use EPDM or a blend of EPDM and a diene rubber having excellent heat resistance as a rubber component.

The fine zinc white used in the present invention is zinc white consisting of fine particles having a specific surface area of 10 to 200 m ² / g measured by the BET method. If the BET specific surface area is less than 10 m ² / g, fine dispersion in the rubber is not sufficient, and the cross-linking structure distribution between the polymer and sulfur is not uniform as in the case of ordinary zinc white, and the dynamic magnification reduction effect Cannot be obtained. In addition, since the cross-linked structure is not uniform, bonds between sulfur are easily broken, and sufficient reinforcement cannot be obtained, and improvement in sag resistance cannot be expected. On the other hand, if the BET specific surface area exceeds 200 m ² / g, the zinc white particles may aggregate to easily cause poor dispersion.

  The average particle size of the fine zinc oxide is preferably 0.001 to 0.3 μm in order to obtain the effect that the zinc oxide is finely and uniformly dispersed in the rubber. When the average particle diameter exceeds 0.3 μm, the fine dispersibility in the polymer is lowered, and when it is less than 0.001 μm, the particles are aggregated to easily cause poor dispersion.

The finely divided zinc oxide is a highly dispersible powdered zinc oxide made of extremely fine primary particles produced using a metal zinc ingot as a raw material, and as its production method, the metal zinc was melted and vaporized. Oxidize and dry method to produce zinc white powder by cooling, wet method to produce fine powdered zinc oxide by obtaining precipitate after dissolving zinc in acid such as sulfuric acid The production method is not particularly limited as long as fine particles having a BET specific surface area of 10 to 200 m ² / g can be obtained.

In the present invention, fine zinc oxide having a BET specific surface area of 10 to 200 m ² / g and preferably an average particle diameter of 0.001 to 0.3 μm may be used alone, or two or more kinds may be used. You may use it in combination. The content of fine zinc oxide is 1 to 20 parts by weight with respect to 100 parts by weight of the rubber component. If the content of zinc white is less than 1 part by weight, the homogenization of the cross-linking distribution becomes unstable and dynamic magnification reduction and improvement in sag resistance cannot be obtained, and even if contained in excess of 20 parts by weight, No further effect can be obtained.

  In addition, in the vibration-proof rubber composition of the present invention, a conventional normal zinc white can be used in combination with the fine particle zinc white. The amount used in this case is preferably about 1 to 30 parts by weight with respect to 100 parts by weight of the rubber component as the total amount of zinc white. When the amount is less than 1 part by weight, the reinforcing property and the elastic modulus are lowered.

  In addition, the measurement of the BET specific surface area of zinc white is calculated | required by the nitrogen gas adsorption amount based on ASTMD3037, and an average particle diameter is measured from the 20,000-100,000 times photograph with a scanning electron microscope. It is.

  The vibration-proof rubber composition of the present invention preferably further contains a reinforcing filler. The reinforcing filler can be arbitrarily selected from those conventionally used in anti-vibration rubber compositions, but carbon black and silica are mainly preferred.

As the carbon black, those having a nitrogen adsorption specific surface area (N ₂ SA) of 100 m ² / g or less, preferably 60 m ² / g or less, and a DBP oil absorption of 80 to 150 ml / 100 g are preferable. For example, HAF, FEF And carbon black such as GPF grade, and the content thereof is about 20 to 80 parts by weight with respect to 100 parts by weight of the rubber component.

  In the blending range of the carbon black, it is possible to promote a reduction in the dynamic magnification of the vibration-proof rubber composition and to maintain rubber properties such as strength, rigidity, and fatigue resistance and workability.

  In the anti-vibration rubber composition of the present invention, the rubber component and fine zinc oxide, and various known compounding agents blended in a normal anti-vibration rubber composition, that is, filler reinforcing agents such as carbon black and silica, Vulcanizing agents such as sulfur and organic peroxides, vulcanization accelerators, stearic acid, softeners, anti-aging agents, processing aids, and the like can be appropriately blended within a range that does not impair the object of the present invention.

  The anti-vibration rubber composition of the present invention can be prepared by kneading using an ordinary Banbury mixer or kneader in the rubber industry. If this rubber composition is vulcanized as a vibration isolator under known vulcanization conditions, the rubber properties such as strength and fatigue resistance are maintained, the dynamic magnification is reduced, and the heat resistance (sag resistance) is improved. Anti-vibration rubber with excellent anti-vibration performance is obtained.

  Anti-vibration rubbers for automobiles such as engine mounts, torsional dampers, strut mounts, etc. that use this anti-vibration rubber composition have both excellent anti-vibration performance and durability performance. It becomes possible to cope with sophisticated and diversified demand characteristics.

  An example of a strut mount using the vibration-proof rubber composition of the present invention is shown in FIG. The strut mount 1 includes a main body 15 attached to a front end of a rod 12 of a strut via a bearing 14 at a front end of the rod 12 of the strut, and an attachment 17 attached to the automobile main body by a bolt 16. And an anti-vibration rubber 11 that is interposed between the main body metal fitting 15 and the mounting metal fitting 17 and elastically connects the two. The anti-vibration rubber composition of the present invention and the metal fittings 15 and 17 It is formed by vulcanization molding.

  It is also possible to use a liquid-filled strut mount that includes a liquid chamber in which the vibration-proof rubber forms a part of the chamber wall and attenuates vibrations by the elastic force of the vibration-proof rubber and the fluid flow effect.

  Hereinafter, the vibration-insulating rubber composition according to the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

  Natural rubber (NR, RSS # 3) as a rubber component in the blending contents (parts by weight) shown in Table 1 for the anti-vibration rubber compositions of each Example and Comparative Example, the following ordinary zinc white A, the present invention Examples 1 to 4 and Comparative Example 1 were prepared by blending the following fine zinc oxides B to D and various kinds of the following compounding agents (parts by weight) as common components and kneading using a 20 liter closed Banbury mixer. ~ 3 rubber compositions were prepared.

[Zinc flower]
Zinc flower-A: BET specific surface area = 4 m ² / g, average particle size = 0.6 μm (Mitsui Metal Mining Co., Ltd., Zinc Flower No. 1)
Zinc flower-B: BET specific surface area = 10 m ² / g, average particle diameter = 0.1 μm
Zinc flower-C: BET specific surface area = 25 m ² / g, average particle size = 0.05 μm
Zinc flower-D: BET specific surface area = 70 m ² / g, average particle size = 0.01 μm

[Common ingredients and blending amounts]
Carbon black (CB): 35 parts by weight (Showa Cabot Co., Show Black N550)
・ Stearic acid: 2 parts by weight (Kao Soap Co., Ltd., stearic acid for rubber)
Anti-aging agent 6C: 2 parts by weight (Ouchi Shinsei Chemical Co., Ltd., NOCRACK 6C)
Anti-aging agent RD: 1 part by weight (Ouchi Shinsei Chemical Co., Ltd., Nocrack 224)
・ Sulfur: 1.8 parts by weight (Hosoi Chemical Co., Ltd., powdered sulfur for rubber)
・ Vulcanization accelerator TT: 0.2 parts by weight (Sanshin Chemical Industry Co., Ltd., Sunseller TT)
・ Vulcanization accelerator CZ: 1.5 parts by weight (Ouchi Shinsei Chemical Co., Ltd. Noxeller CZ)

  Next, these rubber compositions were vulcanized under vulcanization conditions of 150 ° C. × 25 minutes to prepare each test piece, and the tensile strength (TB), static spring constant (Ks), dynamic spring constant (Kd), The compression set (CS) was measured according to the following measurement method, and the dynamic magnification was determined from Ks and Kd. The results are shown in Table 1.

[Measurement method]
・ Tensile strength (TB)
TB (MPa) was measured according to JIS K6251 (using No. 3 dumbbell). The larger the value, the higher the strength and the better.

・ Static spring constant (Ks)
Tensilon manufactured by Orientec Co., Ltd. was used as a measuring machine, and compression between 0 and 5 mm was repeated twice at a crosshead speed of 10 mm / min for a vulcanized test piece of 50 mmφ × 25 mm. Second load-deflection line The figure was drawn and the static spring constant was calculated based on the following equation (1). Static spring constant (N / mm) = (w2-w1) / (δ2-δ1) (1)
Here, w1 is a load (N) when the deflection amount δ1 is 1.3 mm, and w2 is a load (N) when the deflection amount δ2 is 3.8 mm.

・ Dynamic spring constant (Kd)
The dynamic servo constant (N / mm) was calculated | required by the calculation method described in JISK6394, using the dynamic servo by Kashiwamiya Seisakusho Co., Ltd. for a measuring machine, performing initial distortion 10%, frequency 100Hz, and amplitude ± 0.05mm.

Dynamic magnification is defined as the ratio of the dynamic spring constant to the static spring constant measured by the above method (dynamic spring constant (Kd) / static spring constant (Ks)). It is good.

・ Compression set (CS)
According to JIS K6262, heat treatment was performed at 120 ° C. for 500 hours, and CS (%) was measured. The smaller the value, the better the heat resistance (sag resistance).

  As shown in the results of Table 1, in Comparative Example 2 in which the amount of zinc white was increased, no improvement in dynamic magnification and heat resistance was observed with respect to Comparative Example 1, and Comparative Example with a small content of fine zinc white 3 does not exhibit the effect of dispersion, but Examples 1 to 3 according to the present invention contain fine-particle zinc white, thereby lowering the dynamic magnification compared with Comparative Example 1 and providing anti-vibration performance of the anti-vibration rubber composition. In addition, it has excellent heat resistance (sag resistance) by reducing compression set distortion. It can be seen that this improvement effect is more effective as the BET specific surface area of zinc white is larger and the average particle size is smaller, and from the results of Examples 3 and 4, the effect is increased as the amount is increased within the specified range.

  The anti-vibration rubber composition of the present invention can be used as an anti-vibration member for an anti-vibration rubber of an automobile to effectively absorb vibrations of the engine and the vehicle body, reduce in-vehicle vibration and noise, and improve quietness during running. In addition to automobiles, the present invention can also be applied to anti-vibration rubbers for railway vehicles and building structures, seismic isolation rubbers, anti-vibration products such as bridges and road supports, and seismic isolation rubber products.

It is sectional drawing which shows an example of the strut mount which uses the vibration-proof rubber composition of this invention.

Explanation of symbols

1 …… Strut mount 11 …… Vibration-proof rubber composition 15 …… Body bracket 17 …… Mounting bracket

Claims (3)

The rubber component is at least one selected from the group consisting of a diene rubber and an ethylene-propylene-diene copolymer,
An anti-vibration rubber composition comprising 1 to 20 parts by weight of fine zinc oxide having a specific surface area measured by the BET method of 10 to 200 m ² / g based on 100 parts by weight of the rubber component. The anti-vibration rubber composition according to claim 1, wherein an average particle diameter of the fine zinc oxide particles is 0.001 to 0.3 μm. An anti-vibration rubber comprising the anti-vibration rubber composition according to claim 1.

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