JPH08269237A - Vibration-proofing rubber composition - Google Patents

Abstract

PURPOSE: To obtain a vibration-proofing rubber composition improved in, dynamic fatigue resistance and strengths by kneading a terminal-modified butadiene rubber and a natural rubber. CONSTITUTION: This composition is prepared by mixing 100 pts.wt. rubber component prepared by blending a terminal-modified butadiene rubber and a natural rubber in a weight ratio of 1:9 to 4:6 with 20-80 pts.wt. high-structure carbon black having a dibutyl phthalate absorption of 140ml/100g or above and optionally 0.5-5 pts.wt. vulcanizer, 0.5-5 pts.wt. vulcanization accelerator, 100 pts.wt. or below curing agent, a processing aid, an age resister, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-vibration rubber composition, and more particularly to an anti-vibration rubber composition which can be widely used as an anti-vibration member for automobiles and an anti-vibration rubber using the same.

[0002]

2. Description of the Related Art Generally, in automobiles, anti-vibration rubber is used for strut mounts, suspension bushes, engine mounts, etc. for the purpose of reducing vibration and noise. For the purpose of reducing vibration and noise,
It is desirable that the rubber composition that constitutes the anti-vibration rubber be soft with low rigidity. However, on the other hand, if it is too soft, it will bend due to the weight of the mounted object and its supporting position will change, and the performance of the entire structure including the supporting object, and by extension, the basic performance related to steering stability such as running, stopping, and bending of the vehicle will be improved. It will have a bad effect.

That is, the anti-vibration rubber is required to have antinomic properties of reduction of vibration and noise and ensuring of steering stability. Here, vibration / noise is a dynamic element having a relatively high frequency, whereas steering stability is a static element with little movement. Therefore, the vibration damping performance is better as the spring constant (dynamic spring constant) in the vibration state transmitting the vibration is smaller, while the support performance (strength) is better as the static spring constant indicating the support rigidity is larger. Therefore, the ratio of the dynamic spring constant to the static spring constant,
That is, it can be said that a rubber having a smaller value of dynamic magnification (dynamic spring constant / static spring constant) is superior as a vibration-proof rubber.

On the other hand, attempts have been made to modify the ends of rubber molecules to improve their dynamic properties. For example, it has been reported that when tin coupling is applied to the molecular end of SBR rubber, a rubber material having low rolling resistance and high wet skid resistance and favorable properties as a rubber for tires can be obtained (Tsumi et al. Journal "Vol. 63, No. 5 (1990), pp. 27-33). Attempts have also been made to modify the molecular terminals with aminobenzophenone, lactam and the like, but vibration-proof rubbers with sufficient strength have not been obtained.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to improve strength and dynamic magnification of a vibration-proof rubber so that it can be widely used as a vibration-proof member for automobiles.

Means for Solving the Problems The present inventor has studied to solve the above problems, and by blending a natural rubber (NR) and a terminal-modified butadiene rubber (BR), a dynamic ratio is small and a protective strength is high. The inventors have found that a vibrating rubber can be obtained, and have completed the present invention.

That is, the present invention provides the following anti-vibration rubber composition and anti-vibration rubber: 1) Anti-vibration rubber composition obtained by kneading terminal-modified butadiene rubber and natural rubber. 2) The vibration-insulating rubber composition as described in 1 above, wherein the terminal-modified butadiene rubber is obtained by modifying butadiene rubber with a lactam. 3) The vibration-insulating rubber composition as described in 1 or 2, wherein the compounding ratio (weight ratio) of the terminal-modified butadiene rubber and the natural rubber is 1: 9 to 4: 6. 4) The above-mentioned 1 to 3 further containing carbon black
The anti-vibration rubber composition according to any one of 1. 5) Carbon black has a dibutyl phthalate oil absorption of 14
5. The vibration-insulating rubber composition as described in 4 above, which is 0 ml / 100 g or more of high-structure carbon. 6) An anti-vibration rubber comprising the anti-vibration rubber composition according to any of 1 to 5 above. Hereinafter, the anti-vibration rubber composition of the present invention will be described in detail.

[0007]

[Rubber Polymer] In the present invention, as a rubber polymer matrix (base), a butadiene rubber (B
A blend rubber of R) and natural rubber (NR) is used.
The terminal-modified BR is obtained by modifying the molecular end of BR with an appropriate compound. As a modifier, a metal salt such as tin tetrachloride has been conventionally used (the above-mentioned "Journal of the Rubber Society of Japan" Vol. 63, No. 5 (199
0) See pages 27 to 33) and the like are known. It is also known to use a lactam compound as a modifier (for example, Nagata "Magazine of Japan Rubber" Vol. 62, No. 10 (1
989) pp. 38-48). In the present invention, the modifier is not particularly limited, but particularly excellent improvement of the vibration damping property is observed by blending the lactam-modified BR with NR.

Since the modified BR polymer alone has low strength and poor durability, it cannot be used alone.
R is N, which has excellent workability and mechanical strength characteristics (durability)
Used by blending with R. The compounding ratio of the terminal modified BR and NR is preferably in the range of 1: 9 to 4: 6, and 1: 9 to 3:
The range of 7 is more preferable.

[0009]

[Carbon Black] In the anti-vibration rubber composition of the present invention, it is preferable to use carbon black in the above rubber polymer matrix. In addition to its normal function as a reinforcing material, carbon black is considered in the present invention to react with the modified end groups of the above-mentioned end-modified BR in the rubber matrix to form a kind of composite. To be For example, in the case of lactam modification,
There is an iminium ion generated by the conversion of the amino group of lactam at the end of the rubber molecule. This is an O in the phenolic hydroxyl group or carboxyl group on the carbon black surface.
^- it is believed that binds to. As the carbon black, any ordinary carbon black can be used, but a carbon black called a high structure having a highly developed secondary structure is particularly preferable. Practically, carbon black having a DBP (dibutyl phthalate) oil absorption of 140 ml / 100 g or more can be preferably used. The blending amount of carbon black cannot be unconditionally specified because it depends on the use of the anti-vibration rubber, but generally, the weight ratio is 20 to 80 parts by weight (phr) of carbon black with respect to 100 parts by weight of rubber.

[0010]

[Other Additives] Further, the anti-vibration rubber composition of the present invention may be added with a processing aid, an antioxidant, a vulcanizing agent, a vulcanization accelerator, a softening agent, a filler and the like. . As the vulcanizing agent, any commonly used vulcanizing agent can be used. Examples of such compounds include sulfur, morpholine disulfide, tetramethylthiuram disulfide and the like. Among them, sulfur is preferable, and 100 parts by weight of the rubber component is used.
About 0.5 to 5 parts by weight can be used.

The vulcanization accelerator is an additive for suppressing radical cleavage of the rubber polymer and improving the crosslinking effect, and can be used in an amount of about 0.5 to 5 parts by weight per 100 parts by weight of the rubber component. Examples of the vulcanization accelerator include sulfinamide such as N-cyclohexyl-2-benzothiazole sulfenamide, N-oxydiethylene-2-benzothiazole sulfenamide, N, N-diisopropyl-2-benzothiazole sulfenamide. Phenamide compounds; 2-mercaptobenzothiazole, 2- (2,4-dinitrophenyl) mercaptobenzothiazole, 2- (2,6-
Thiazole-based compounds such as diethyl-4-morpholinothio) benzothiazole and dibenzothiazyl disulfide;
Guanidine compounds such as diphenylguanidine, dioltotolylguanidine, triphenylguanidine, orthotolylbiguanide, diphenylguanidine phthalate;
Acetaldehyde-aniline reaction products, butyraldehyde-aniline condensates, hexamethylenetetramine, acetaldehyde-ammonia reaction products and other aldehyde-amine or aldehyde-ammonia compounds; 2-mercaptoimidazoline and other imidazoline compounds; thiacarbamide, diethylthiourea, Thiourea compounds such as dibutylthiourea, trimethylthiourea and diortotolylthiourea; thiuram compounds such as tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, pentamethylenethiuram tetrasulfide; dimethyl Zinc dithiocarbamate, zinc diethyldithiocarbamate, zinc dibutylthiocarbamate, ethylphenyldithio Rubamin zinc, butylphenyl dithiocarbamate, zinc, sodium dimethyl dithiocarbamate, dimethyl dithiocarbamate selenium dithiocarbamate compound tellurium diethyldithiocarbamate and the like; Compound of xanthate-based compounds such as dibutyltin xanthate acid zinc.

The softening agent is used up to about 100 parts by weight based on 100 parts by weight of the above rubber component. Examples of softening agents include petroleum-based softening agents such as procell oil, lubricating oil, paraffin, liquid paraffin, petroleum asphalt, and vaseline; fatty oil-based softening agents such as castor oil, linseed oil, rapeseed oil, and coconut oil; tall oil. Waxes such as sub; beeswax, carnauba wax, lanolin; linoleic acid, palmitic acid, stearic acid, lauric acid, etc., and process oil is particularly preferably used. Examples of fillers other than carbon black include calcium carbonate, talc, silica and the like. In addition to the above additives, plasticizers, stabilizers,
Conventional compounding agents such as processing aids and colorants may be used.

[0013]

[Manufacturing Method] The anti-vibration rubber composition of the present invention can be manufactured by a conventional method using the above rubber component, carbon black and other additives.

[0013]

The anti-vibration rubber composition of the present invention has a lower dynamic magnification than that of the conventional rubber composition, as will be concretely shown in the examples described later. The reason for this is not clear, but it is considered that the modified BR molecule ends interact with the carbon black surface to form a kind of complex structure and affect the vibration characteristics. The anti-vibration rubber composition of the present invention has a small compression set and improved dynamic fatigue resistance, which also suggests the formation of the above composite.

The anti-vibration rubber of the present invention is a composition in which carbon black as a reinforcing material is blended with a blended rubber of a low vibration-transmitting natural rubber (NR) and a terminal-modified butadiene rubber (BR), and vibration and noise It has excellent prevention properties and the necessary rigidity. Starting with engine mounts, body mounts, cab mounts, member mounts, strut bar cushions, center bearing supports,
It can be used as a component of various anti-vibration rubbers for automobiles such as torsional damper, steering rubber coupling, tension rod bush, lower ring bush, arm bush, bump trapper, FF engine roll stopper and muffler hanger.

[0015]

The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following description. In each of the examples and comparative examples, the following materials were used as raw materials and additives.

(1) Rubber component (i) Natural rubber, (ii) Terminal modified BR (modifier: ε-caprolactam, polymer viscosity: 50, cis-1,4 / trans-1,4 / vinyl ratio = 39 / 49/12), (iii) unmodified BR ("Ubepol 150" manufactured by Ube Industries, Ltd.,
Polymer viscosity: 43, cis-1,4 / trans-1,4
/ Vinyl ratio = 98/1/1). (2) Carbon black (i) FEF carbon black, (ii) high-structure carbon (DBP oil absorption: 180 ml / 100 g; Asahi Carbon Co., Ltd. "Asahi F-200").

(3) Vulcanizing agent Sulfur. (4) Vulcanization accelerator (i) CZ: N-cyclohexyl-2-benzothiazolylsulfenamide (Sanshin Chemical Co., Ltd. “Sanserra CZ”), (i
i) Zinc white (ZnO). (5) Softener (i) naphthenic process oil, (ii) stearic acid. (6) Anti-aging agent An amine anti-aging agent.

Examples 1 to 5 and Comparative Examples 1 to 4 The above components were compounded in the proportions shown in Table 1 (numerical values represent weights) to prepare compounded rubber compositions. The obtained compounded rubber composition was molded and crosslinked as described below to give a test piece, and the normal state characteristics (tensile strength, elongation at break, hardness), compression set and dynamic ratio were measured by the following methods. did. The results are shown in Table 1.

1) Normal State Physical Properties A compounded rubber composition was molded, heated at 150 ° C. for 20 minutes and crosslinked to obtain a dumbbell type test piece (JIS K6301). Using this test piece, the measuring temperature is 25 according to the method described in JIS K6301.
Tensile test was carried out under conditions of ℃ and tensile speed of 500 mm / min., 100% modulus (M100), tensile strength (T
B) (kgf / cm ² ) and elongation at break (EB) (%) were measured. The hardness (HS) is also JIS K6.
According to the method described in 301, the spring hardness was measured with a JIS A hardness meter.

2) Compression set The compounded rubber composition was heated at 150 ° C. for 30 minutes to apply a load to the crosslinked test piece and compress it to 25%.
After maintaining the temperature at 22 ° C. for 22 hours, the load was removed and the temperature was returned to room temperature to measure the amount of deformation (compression set). The size and shape of the test piece and the magnitude of the load were in accordance with JIS K6301. 3) Dynamic Magnification A cylindrical test piece having a diameter of 50 mm and a height of 25 mm is cross-linked by heating the compounded rubber composition at 150 ° C. for 30 minutes, and a circular metal fitting having a diameter of 60 mm and a thickness of 6 mm is provided on the upper and lower surfaces thereof. Was attached, and the static spring constant (Ks) and the dynamic spring constant (Kd100) were measured to obtain the dynamic magnification (Kd100 / Ks). The static spring constant is 1.5 mm and 3.5 mm from the second load deflection curve obtained by compressing the cylindrical test piece in the axial direction of the cylinder by 7 mm in the axial direction.
The load at the time of bending was read and calculated. The dynamic spring constant is that the test piece is compressed 2.5 mm in the axial direction, and the amplitude is ± 0.
A constant displacement harmonic vibration of 05 mm was applied, the dynamic load was measured with a load cell attached above the test piece, and calculation was performed according to JIS K6394. Dynamic magnification is the ratio of these values.

[0021]

[Table 1]

As shown in Table 1, in Examples 2 to 4 using the terminal-modified BR and NR according to the present invention, the dynamic magnification was 1.4.
This is less than the above, and an excellent effect is obtained as compared with the comparative example using NR (Comparative Example 1) or unmodified BR (Comparative Example 3) alone. In particular, the characteristics of Example 5 using high structure carbon are greatly improved. Also,
In Example 1, a remarkable effect is not always observed as compared with the comparative example, but from the comparison between Examples 1 and 2, when the addition amount of the unmodified BR with respect to NR exceeds 1/9, the dynamic magnification of the present invention is improved. It can be seen that the effect clearly appears.

[0023]

INDUSTRIAL APPLICABILITY According to the present invention, carbon black and end-modified B
An NR-based anti-vibration rubber composition having a low dynamic magnification is provided when used in combination with R. This composition also has excellent dynamic fatigue resistance.
Therefore, the engine or the like can be stably supported with high accuracy in actual use. On the other hand, since the composition of the present invention has a low dynamic spring constant, it has an excellent effect of absorbing noise and vibration. Therefore, the anti-vibration rubber composition of the present invention can be widely used for anti-vibration members for automobiles such as engine mounts and suspension bushes.

Claims (6)

[Claims] 1. An anti-vibration rubber composition obtained by kneading an end-modified butadiene rubber and a natural rubber. 2. The anti-vibration rubber composition according to claim 1, wherein the terminal-modified butadiene rubber is obtained by modifying butadiene rubber with a lactam. 3. The antivibration rubber composition according to claim 1, wherein the compounding ratio (weight ratio) of the terminal-modified butadiene rubber and the natural rubber is 1: 9 to 4: 6. 4. The anti-vibration rubber composition according to claim 1, further comprising carbon black. 5. The anti-vibration rubber composition according to claim 4, wherein the carbon black is a high-structure carbon having a dibutyl phthalate oil absorption of 140 ml / 100 g or more. 6. An anti-vibration rubber comprising the anti-vibration rubber composition according to any one of claims 1 to 5.