JPH0415819B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a rubber composition excellent in both vibration-proofing and sound-proofing properties. In recent years, energy saving measures have been sought from various fields, and in response to this, the automobile industry has been investigating various aspects such as making automobiles smaller and lighter, improving engines, etc., and putting them into practical use. On the other hand, the demands of automobile users are becoming more sophisticated, and automobiles with even less vibration and noise are required. These automobile vibrations
Noise is reduced and improved by engine mounts that absorb engine vibrations and vibrations from tires.
It is a vibration isolating rubber for bushings, etc., and the development of a vibration isolating rubber with these characteristics is awaited. In this regard, the present inventors have discovered that polymer surfaces,
As a result of various studies from the viewpoint of formulation technology, we found that styrene polymerized using a lithium-based catalyst
A butadiene copolymer with (i) a bound styrene content of 3 to 20% by weight (ii) a vinyl bond content of the butadiene moiety of 25% or more60
Less than % (iii) Molecular weight distribution (w/n) measured by gel permeation chromatography (GPC)
Contains 30% by weight or more of a styrene-butadiene copolymer with a molecular weight of 1.3 to 4.0 as a rubber component, and contains 20 to 60 parts by weight of carbon black and 0 to 50 parts by weight of rubber extender oil per 100 parts by weight of the rubber component. , a vulcanized rubber composition characterized in that the loss coefficient (tan δ) measured at 23°C and 11 Hz is 0.18 or more, They discovered that it has excellent vibration performance and completed the present invention. The vibration-proofing and sound-proofing properties referred to here can be explained in terms of the dynamic properties of vulcanized rubber as follows. In other words, from a one-dimensional vibration system, the function between the vibration transmissibility τ of the anti-vibration rubber and the vibration frequency ω of the excitation force is expressed as where m: Weight of support K _D : Dynamic spring constant tan δ: Loss coefficient Equation (1) is illustrated as shown in Fig. 1 (ω is the natural frequency). In the L region of Fig. 1, it is expressed as τ∝1/tanδ...(2), and in the H region, τ∝K _D ...(3). For automobile engine mounts, etc., vibration isolation is important when the vibration frequency is 10 to 20Hz, such as during low-speed driving or idling (region L in Figure 1), and when the vibration frequency is 75Hz or higher, such as during high-speed driving. In this region (region H in FIG. 1), soundproofing is important. Therefore, considering the balance between vibration and soundproofing,
From formulas (2) and (3), it is best to use a rubber compound in which tan δ is as large as possible in the L region and K _D is as small as possible in the H region. In the figure, a indicates natural rubber,
b represents butyl rubber, c represents natural rubber-butyl rubber, and d represents the composition of the present invention. As is clear from FIG. 1, composition d of the present invention exhibits a behavior similar to b in the low frequency L region and similar to a in the high frequency H region, and exhibits an excellent balance of vibration and sound insulation. Regarding existing rubbery polymers, the present inventors have
As a result of various studies on the above-mentioned vibration-proofing properties and sound-proofing properties, we found that in the case of existing rubber-like polymers or compositions that combine them, the above two properties are inversely correlated, and that it is possible to improve one without deteriorating the other. It became clear that this could not be measured. For this reason, as a result of intensive research into polymers with new structures, we found that styrene with a specific structure
The present invention was achieved by discovering that a butadiene copolymer has a better relationship than the inverse correlation between vibration damping properties and sound proofing properties. The styrene-butadiene copolymer used as the rubber component in the present invention will be explained below. The amount of bound styrene in the styrene-butadiene copolymer of the present invention is 3 to 20% by weight, preferably 8 to 20% by weight.
Weight%. If the amount of bound styrene is less than 3% by weight, the vibration-proofing performance of the vibration-proof rubber will be poor, and if the amount of bound styrene exceeds 20% by weight, the soundproofing performance will be poor, which is undesirable. In terms of the balance between vibration-proofing performance and sound-proofing performance, a particularly preferable range is 8 to 20% by weight. Furthermore, the amount of vinyl bonds in the butadiene moiety of the styrene-butadiene copolymer of the present invention is 25% or more.
%, preferably 30-58%. If the amount of vinyl bonding is less than 25%, the anti-vibration performance of a vibration-proof rubber will be poor, and if the amount of vinyl bonding is 60% or more, problems will occur in terms of soundproofing performance. Furthermore, the Mooney viscosity of the styrene-butadiene copolymer of the present invention is preferably 20 to 130,
More preferably 25 to 100. Mooney viscosity is 20
If the Mooney viscosity is less than 30, the durability as a vibration-proof rubber will be poor, while if the Mooney viscosity exceeds 30, the processability of the compound will be poor. In addition, the molecular weight distribution (ratio of weight average molecular weight (w) to number average molecular weight (n) (w/ n) ranges from 1.3 to 4.0;
When w/n is less than 1.3, the sound insulation properties are good but the vibration isolation properties are poor, while when w/n exceeds 4.0, the sound insulation properties are poor and the strength is poor. Note that w and n of the styrene-butadiene copolymer of the present invention are measured values calculated by creating a calibration curve based on standard polystyrene having different molecular weights. The styrene-butadiene copolymer can be obtained by a method based on a conventional general polymerization method using a lithium-based compound as a catalyst, but in order to obtain the polymer defined in the present invention, some ingenuity is required. is necessary. In order to obtain a polymer having a vinyl content within the range of the present invention, for example, ether compounds such as tetrahydrofuran, diethyl ether, dimethoxyethane, diglyme, veratrol, amine compounds such as triethylamine, tetramethylethylenediamine, dimethylformamide, etc. , dimethyl sulfoxide, hexamethylphosphortriamide, etc., are added to the polymerization system, and the vinyl content is adjusted by adjusting the amount of these compounds added and the polymerization temperature. In addition, in order to obtain a polymer having a molecular weight distribution within the range of the present invention, 1,2-butadiene,
A method of adding a chain transfer agent such as propadiene, during the progress of the polymerization reaction or at the end of the polymerization reaction.
It can be obtained by adding 0.2 to 1.0 equivalents of a functional or higher-functional coupling agent per mole of active lithium. The method of using a trifunctional or higher-functional coupling agent as a coupling agent is effective for obtaining a desired molecular weight distribution, and furthermore, this method can produce rubber with improved vibration-proofing and sound-proofing properties, which is the object of the present invention. A polymer to be used as a composition is obtained. Among them, silicon or tin compounds are preferred, and examples of these compounds include silicon tetrachloride, methyl 3
Examples include silicon chloride, bis-(trichlorosilyl)-ethane, tin tetrachloride, and butyltin trichloride. In particular, when coupled with a tin compound, as shown in Japanese Patent Publication No. 44-4996, the processability of the compounded composition is improved, and the processability is improved compared to other coupling agents. The relationship with soundproofing properties is also improved. When the trifunctional or more functional coupling agent is used, the polymer of the present invention contains a branched polymer. It is expressed as a scale of the ratio of the Mooney viscosity of the polymer before coupling (ML ₁₊₄ -I) and the Mooney viscosity of the polymer after coupling (ML ₁₊₄ -C).
It is preferable for the ratio (ML ₁₊₄ −C/ML ₁₊₄ −I) to be 1.3 or more in terms of the balance of vibration-proofing and sound-proofing properties, especially w/n+ML ₁₊₄ −C/ML ₁₊₄ − By satisfying I≧3.5, vibration-proofing and sound-proofing properties can be improved.
Compared to the case where existing rubber-like polymers are used, it is possible to achieve a significant improvement, and a useful rubber composition can be obtained. The polymerization process for obtaining the above polymer may be any method as long as it yields a polymer with a predetermined structure, but in order to obtain a molecular weight distribution within the scope of the present invention, a continuous polymerization method is preferred. This is preferred, and reactors having various structures with different mixing characteristics can be used. The styrene-butadiene copolymer of the present invention is used in an amount of 30% by weight or more, preferably 50% by weight or more of the rubber component, and can be used alone. As the rubber component of the composition of the present invention, it is possible to use a blend of other rubbery polymers together with the above-mentioned specific styrene-butadiene copolymer. Examples of these rubbery polymers include natural rubber, polyisoprene rubber, high cis polybutadiene rubber, low cis polybutadiene rubber, styrene-butadiene copolymer rubber other than the above-mentioned specific styrene-butadiene rubber, such as emulsion polymerized styrene rubber.
Examples include butadiene copolymers and solution-polymerized styrene-butadiene copolymers with a vinyl bond content of about 10%, with natural rubber and polyisoprene rubber being particularly preferred. Further, it is possible to add liquid rubber to the vulcanized composition of the present invention if necessary, and preferably one having a number average molecular weight of 500 to 30,000 is used, and liquid polybutadiene, liquid polyisoprene, etc. are representative examples. It is also possible to use compounds whose molecular terminals are hydroxylated or carboxylated. The carbon black used in the rubber composition of the present invention is usually used in the rubber industry.
Various types of FEF, GPF, HAF, ISAF, etc. with different particle sizes and structures are used, preferably 20 to 60 parts by weight per 100 parts by weight of the rubber component.
20-50 parts by weight are used. Furthermore, as the rubber extender oil used in the present invention, petroleum oils such as aromatic, naphthenic, and paraffinic oils, vegetable oils such as coconut oil, and coconut oil are used, and the rubber component is 100 parts by weight. 0 to 50 parts by weight, preferably 0 to 35 parts by weight. The amounts of the above carbon black and rubber extension oil are as follows:
It is used in consideration of the hardness of the resulting vulcanized rubber composition and the vibration-proofing properties and sound-proofing properties described below. If the amount used is other than the above, it is difficult to obtain the target vibration-proofing and soundproofing properties. The vulcanized rubber composition of the present invention contains carbon black and rubber extender oil as a rubber component, and further contains various rubber chemicals such as vulcanizing agents such as sulfur, vulcanization accelerators, vulcanization aids, and anti-aging agents. It is obtained by adding, kneading and blending, and vulcanizing. In addition to limiting the structure of the styrene-butadiene copolymer used as the rubber component, the vulcanized rubber composition of the present invention is characterized by the fact that the composition obtained by vulcanization is
A loss coefficient (tan δ) measured at 23°C and 11 Hz is required to be 0.18 or more in order to satisfy the vibration damping performance, and the range of such vibration damping performance is limited to the styrene-butadiene copolymer with the specific structure mentioned above. This can be achieved by using coalescence and adjusting the amounts of carbon black and rubber extender oil and the amount of vulcanizing agent. If the loss factor is less than 0.18, even if the specific styrene-butadiene copolymer is used, a vulcanized rubber composition having the desired vibration-proofing properties and sound-proofing properties cannot be obtained. As mentioned above, the rubber composition of the present invention is compounded and kneaded using an internal mixer such as a mixing roll or a Banbury mixer commonly used in the rubber industry, and then molded and then subjected to a vulcanization operation to obtain the desired protective properties. This is a vibration-proof rubber product with vibration and soundproof properties. EXAMPLES Hereinafter, the present invention will be explained in detail with reference to Examples, but the scope of the present invention is not limited. [Preparation of copolymer] A styrene-butadiene copolymer (sample A) having a specific structure used in the present invention was obtained by the continuous polymerization method shown below. Internal volume 10, with stirrer and jacket
Two reactors with L/D = 3 are connected in series, and at the bottom of the first reactor, 17 g/min of butadiene, 3 g/min of styrene, 120 g/min of cyclohexane,
1g/1g of tetrahydrofuran as a vinylizing agent
min, 0.5% by weight of n-butyllithium as a catalyst
Containing cyclohexane was continuously supplied at a rate of 3 g/min, the reactor internal temperature was adjusted to 85-90°C, the reactor internal pressure was adjusted to 5.0 Kg/G, and the overflowing polymer solution was poured from the top of the reactor. Continuously extract,
It was fed to the bottom of the second reactor. After the polymerization reaction reached a steady state, the polymer solution was sampled at the inlet of the second reactor and analyzed. The Mooney viscosity (ML ₁₊₄ ) was 24, and the residual viscosity was determined by gas chromatography. The reaction rate calculated from the amounts of butadiene and styrene is 98.8 for butadiene.
%, and styrene was 97.1%. Then add tin tetrachloride to the bottom of the second reactor.
1.5g of cyclohexane solution containing 0.5% by weight/
The coupling reaction was carried out while maintaining the internal temperature of the reactor at 85 to 90°C. Butylated hydroxytoluene was added as a stabilizer to the overflowing polymer solution from the top of the second reactor.
1 part by weight per part was added, the solvent was removed on a heated roll, and the polymer was recovered. Analysis of the polymer solution by gas chromatography showed that the reaction rate of butadiene was 99.9% and that of styrene was 99.7%. The obtained polymer had a Mooney viscosity of 45, a bound styrene content of 15% by infrared spectroscopy, and a vinyl content of the butadiene moiety of 50% (both
Hampton's method), gel permeation chromatography (GPC) (Shimadzu LC-3A column HSG-60, 50, 40, 1 each,
W/n = 2.7 was measured using a calibration curve using standard polystyrene at a temperature of 42°C, using THF as a solvent, and using a detector and a differential refractometer. Furthermore, by the same method as that used to obtain sample A, the vinyl content regulator, molecular weight distribution regulator, type and amount of coupling agent, catalyst amount, amount of styrene supplied, etc. were varied, and the polymerization temperature and residence time were also varied. Styrene-butadiene copolymers having various structures shown in Table 1 were obtained. In addition, samples E, F, J, and K were obtained by batch polymerization under increasing temperature, and a coupling agent was added immediately before the end of polymerization, and sample O was obtained through batch polymerization under increasing temperature. . The analytical values for each polymer are shown in Table 1. Examples 1 to 14 B with an internal volume of 1.7 and a case temperature of 50°C
The specific styrene-butadiene copolymer used in the present invention, and if necessary, other polymers or liquid rubber, zinc white, and stearic acid were added to a Banbury mixer at the proportions shown in Table 2, and kneaded. did. After 30 seconds, oil and carbon black were added to continue kneading, and 3 minutes after the start, sulfur and vulcanization accelerator were added, and 3 minutes and 30 seconds after the start, the mixture was dumped out. . The temperature of the formulation at dumpout was approximately 120-140°C. These compositions were vulcanized at 160°C for 20 minutes,
A sheet with a thickness of 2 mm was obtained. A sample with a width of 3 mm and a length of 40 mm was cut out from this sheet, and the dynamic loss coefficient (tan δ) at 23°C and 11 Hz was measured using a viscoelastic spectrometer (manufactured by Iwamoto Seisakusho).
The dynamic modulus of elasticity K _D at 100 Hz and the static modulus of elasticity Ks at 0.5 Hz were measured at 23° C., and the vibration-proofing and sound-proofing properties were measured, and the results are shown in Table 2. Comparative Examples 1 to 12 Comparative Examples 1 to 8 used styrene-butadiene copolymers with structures other than those limited by the present invention, and Comparative Example 9 used a specific polymer usage amount outside the scope of the present invention, Comparative Example 10 is a composition in which tan δ is outside the range of the present invention, Comparative Examples 10 to 12 are commercially available rubbery polymers (natural rubber...RSS No. 3, SBR1502...emulsion polymerized SBR manufactured by Nippon Synthetic Rubber, Diene 35R (polybutadiene manufactured by Asahi Kasei) was used, and kneaded and mixed in the same manner as in the example.
It was vulcanized and the anti-vibration rubber performance was measured. The results are shown in Table 3. In the results of the above examples and comparative examples, the vibration isolation performance is expressed by tanδ, and the soundproof performance is expressed by the value of K _D /Ks, taking into account slight variations in Ks between samples. The better the performance, the smaller K _D /Ks, the better the soundproofing performance. From the results in Tables 2 and 3, it can be seen that a vulcanized rubber composition containing the specific styrene-butadiene copolymer of the present invention in Examples as a rubber component and having a limited tan δ,
It is clear that the balance between vibration-proof performance and sound-proof performance is better than that of the vulcanized rubber composition of the comparative example.

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【table】 [Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the vibration transmissibility of vibration isolating rubber and the vibration frequency of excitation force.

Claims (1)

[Scope of Claims] 1. A styrene-butadiene copolymer polymerized using a lithium-based catalyst, wherein (i) the amount of bound styrene is 3 to 20% by weight, and (ii) the amount of vinyl bonds in the butadiene moiety is 25 or more and 60% by weight. %
Less than (iii) Molecular weight distribution (w/n) measured by gel permeation chromatography is 1.3~
Contains 30% by weight or more of a styrene-butadiene copolymer with a molecular weight of 4.0 as a rubber component, and per 100 parts by weight of the rubber component, 20 to 60 parts by weight of carbon black and 0 to 50 parts by weight of rubber extension oil are blended and vulcanized. A vibration-proof and sound-proof vulcanized rubber composition characterized in that the loss coefficient (tan δ) measured at 23°C and 11 Hz is 0.18 or more. 2 A styrene-butadiene copolymer containing a molecular polymer component coupled with a trifunctional or higher polyfunctional coupling agent,
Mooney viscosity before coupling (ML ₁₊₄ −
I) and Mooney viscosity after coupling (ML ₁₊₄
-C) (ML ₁₊₄ -C/ML ₁₊₄ -I) is 1.3
Claim 1 characterized in that:
The anti-vibration and sound-insulating rubber composition described in Section 1. 3 Said w/n and ML ₁₊₄ −C/ML ₁₊₄ −
The vibration-proof and sound-proof rubber composition according to claim 2, wherein I satisfies the following formula. w/n+ML ₁₊₄ −C/ML ₁₊₄ −I≧3.5