JPH07119319B2 - Anti-vibration rubber composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vibration damping rubber composition, and more specifically, it comprises a blend of natural rubber and / or isoprene rubber and polyvinyl chloride, and has a loss coefficient in the low frequency region. The present invention relates to a rubber composition having a large value, a small frequency dependence from a low frequency region to a high frequency region, a small dynamic elastic modulus at a high frequency, and a small static-dynamic ratio, and an excellent vibration damping effect.

(Prior Art) Generally, regarding the vibration transmissibility indicating the performance of the vibration damping rubber, the vibration transmissibility T using the degree-of-freedom model and the vibration frequency ω
It is well known that there is a predetermined relational expression between and, and from this relational expression, in the region where the frequency ω of the exciting force is small, T = 1 / tanδ ··· (1) In the region where is large, T = Kd / (mω ² −Kd) (2) (where Kd is the dynamic elastic modulus, tan δ is the loss coefficient, and m is the weight of the support). .

That is, it can be seen that the material having excellent vibration damping has a large tan δ and a small dynamic elastic modulus.

By the way, the anti-vibration rubber generally used for vehicles etc.
In the low frequency range of 20 (Hz), it has vibration control that suppresses shake phenomenon, while in the high frequency range of 75 Hz and above, it needs sound insulation to suppress muffled noise in the room.
It is said that the ideal state is that tan δ is large and the static-dynamic ratio (dynamic spring constant / static spring constant) is small in the high frequency region.

Therefore, conventionally, blends of natural rubber and polybutadiene rubber having excellent soundproofing properties and styrene-butadiene copolymer having excellent vibration damping properties have been used. Above all, cis
The average chain length of 1,4 bonds is 110 to 4 when the content of 1,4 bonds is 80% or more.
It is known that a polybutadiene having a weight average molecular weight to a number average molecular weight of 50 or more and a ratio of 8 or more is blended with a natural rubber or a diene rubber containing synthetic isoprene as a main component.

(Problems to be Solved by the Invention) However, the conventional anti-vibration rubber composition also lacks the balance of anti-vibration and sound-insulating properties, and further, with the development of the automobile industry and the like, anti-vibration rubber composition The target value of the vibration absorption characteristics required for products has become stricter year by year, and there has been a demand for the development of a more excellent vibration damping rubber composition.

The present inventors have found that the vibration-damping rubber composition has a large loss coefficient at low frequencies, has little frequency dependence from the low-frequency region to the high-frequency region, has a small dynamic elastic modulus at high frequencies, and has a small static-dynamic ratio. As a result of the purpose of product development, rubber that has excellent vibration damping performance by mechanically mixing natural rubber (including isoprene rubber) and polyvinyl chloride at a specific blending ratio and then filling with carbon black. It has been found that a composition is obtained.

(Means for Solving the Problems) That is, the feature of the present invention is to add polyvinyl chloride to natural rubber and / or isoprene rubber within a rubber / polyvinyl chloride weight ratio range of 70/30 to 30/70. A vibration damping rubber composition is obtained by mixing 100 parts by weight of this mixture with 30 to 70 parts by weight of carbon black having an average particle diameter of 30 to 120 nm.

That is, according to the anti-vibration rubber composition of the present invention, it was obtained by filling the carbon black having a specific particle size with a specific blend ratio of natural rubber and / or isoprene rubber and polyvinyl chloride. The rubber composition has a large loss coefficient (tan δ) in the low frequency region, low frequency dependence, and has a small dynamic elastic modulus in the high frequency region and a small static-dynamic ratio. There is a shaking effect.

The polymer used in the vibration damping rubber composition of the present invention is a blend of natural rubber and / or isoprene rubber and polyvinyl chloride, and the blending ratio (weight ratio) of rubber / polyvinyl chloride is 70/30. Within the range of ~ 30/70. Rubber / polyvinyl chloride blend ratio 100 / 0-80 /
In the range of 20 the loss factor (ta
nδ) is small, while tanδ in the range of 20/80 to 0/100
Has a drawback that its frequency dependence is large and its static-dynamic ratio is large, so that the desired rubber composition having vibration and soundproofing cannot be obtained.

The natural rubber or isoprene rubber used here is a commonly used one, and the polyvinyl chloride has a degree of polymerization in the range of 800 to 3000 and may be a linear or graft polymer.

Incidentally, various plasticizers such as DOP are mixed in polyvinyl chloride, and the addition amount is 100% of polyvinyl chloride.
It is 30 to 150 parts by weight with respect to parts by weight.

Further, the carbon black used in the present invention has an average particle size of 30 to 120 nm, preferably 50 to 100 nm, and is selected from, for example, commonly used furnace black type, acetylene black type, thermal black type, channel black type and the like. . The carbon black is added in an amount of 30 to 70 parts by weight based on 100 parts by weight of a polymer composed of a blend of natural rubber and / or isoprene rubber and polyvinyl chloride.

If you use carbon black with an average particle size of less than 30 nm,
The reinforcing property of the rubber composition tends to be too high, and the dynamic elastic modulus in a high frequency region (70 to 100 Hz) tends to be large. On the other hand, carbon black having an average particle size of more than 120 nm has a small loss coefficient in the low frequency region (1 to 10 Hz). Further, if the filling amount of carbon black is less than 30 parts by weight, the loss coefficient in the low frequency region tends to be small, and if it exceeds 70 parts by weight, the dynamic elastic modulus in the high frequency region tends to increase.

Further, the vibration-damping rubber composition of the invention contains a softening agent, an antioxidant, a vulcanization aid, a vulcanization accelerator, etc., which are used in ordinary rubber, and is vulcanized and molded to obtain a vibration-damping material. It is used, but in this case there is no particular limitation on the method of mixing the components, for example, using a Banbury mixer, kneader, roll, etc.,
The sheet can be kneaded by a known means or method as appropriate to form a sheet.

(Example) Next, the present invention will be described in more detail with reference to specific examples.

The measured values of the dynamic elastic modulus E ′ and the loss coefficient tan δ were measured with a rheological solid manufactured by Toyo Seiki Co., Ltd.
It is measured by applying a sinusoidal extensional compression strain of 0.05 to 0.08% to the sample at 25 ° C. ± 2 ° C. and a frequency of 1 to 100 Hz.
The static-dynamic ratio was calculated by E '(100Hz) / E' (1Hz).

Example 1 / Comparative Example 1 Based on the formulation shown in Table 1, a rubber compound was kneaded with a Banbury mixer and then formed into a sheet by using a roll.
Vulcanization was performed at 20 ° C for 20 minutes to prepare various samples of thickness 2 mm x width 8 mm x length 20 mm. Polyvinyl chloride (PVC) used here
Was 110 parts by weight of a plasticizer with respect to 100 parts by weight of PVC and had a degree of polymerization of 1300. The dynamic elastic modulus E ′ and the loss coefficient tan δ were measured for these samples.

FIG. 1 shows the frequency dependence of the loss coefficient tan δ of Examples 1-1, 1-4, 1-5, 1-6 and Comparative Examples 1-1, 1-4, 1-5. Comparative Example 1-1 has a small frequency dependence but a small tan δ value, and in particular has a small tan δ at low frequencies and is not suitable for a vibration damping material. Comparative Example 1-5 has a very large frequency dependency, and uniform performance cannot be maintained from a low frequency to a high frequency. Examples 1-1 to 1-6 have excellent frequency dependence.

In addition, the ratio of the loss coefficient of frequency 1Hz and 100Hz (tan δ (100H
z) / tan δ (1Hz)) and the relationship between NR / PVC blend ratio, and
Ratio of dynamic modulus of 1Hz and 100Hz (E '(100Hz) / E' (1H
The relationship between z)) and the blend ratio of NR / PVC is also shown in Table 1. Static / dynamic ratio (E '(100Hz) / E' (1Hz)) is NR / PVC = 10
It is low in the range of 0/0 to 50/50, sharply increases in the range of 50/50 to 30/70, and further decreases in 0/100. The ratio of loss factors is NR /
It has a low value in the range of PVC = 70/30 to 30/70, and has favorable performance as a vibration damping material. As a characteristic of the vibration damping material, in the range of NR / PVC = 70/30 to 30/70, the static-dynamic ratio and loss coefficient show good values that are well balanced from the low frequency region to the high frequency region.

Example 2 / Comparative Example 2 Based on the formulations shown in Table 2, the dynamic elastic modulus E ′ and the loss coefficient tan δ were obtained by the same sample preparation and measurement method as those of the above-mentioned examples. The PVC used here had a degree of polymerization of 2700 in which 60 parts by weight of a plasticizer was filled with 100 parts by weight of PVC.

Fig. 2 shows the ratio of the loss factor at frequencies of 1 Hz and 100 Hz (tan δ (100
Hz) / tan δ (1Hz)) and the blend ratio of NR / PVC, and the ratio of the dynamic elastic modulus between 1Hz and 100Hz (E '(100Hz) / E' (1
Hz)) and the NR / PVC blend ratio. Static / dynamic ratio (E '(100Hz) / E' (1Hz)) is NR / PVC = 100 / 0-80 /
Low in the range of 20, increased in the range of 80 / 20-30 / 70, and also 30
It showed a constant high value from / 70 to 0/100. The ratio of loss factors is
The value was low in the range of NR / PVC = 70/30 to 30/70, and the change in tanδ with frequency was small. As the characteristics of the vibration damping material, the static-dynamic ratio and the loss coefficient were well balanced in the range of NR / PVC = 70/30 to 30/70 from low frequency to high frequency.

Example 3 Based on the formulation shown in Table 3, the dynamic elastic modulus E ′ and the loss coefficient tan δ were obtained by the same sample preparation and measurement method as those of the above-mentioned Example. In Table 3, tan δ at 1 Hz, 100 Hz E'is also shown. The same PVC used in Example 2 was used, and the NR / PVC blend ratio was 60/40. Table 4 shows the particle size of the carbon black used in Example 3 and the DBP oil absorption.

Example 3 filled with ISAF carbon black having a particle size of 20 nm
-1 has a high E'at high frequency (100 Hz) and is not preferable as a vibration damping material. On the other hand, in Examples 3-2 to 3-4, a material having a high loss coefficient in a low frequency range, a low E ′ in a high frequency range, and a carbon black filled particle diameter of 38 nm to 100 nm is used as a vibration damping material. Was excellent.

Example 4 / Comparative Example 4 Based on the formulations shown in Table 5, the sample preparation and measurement method similar to those of Example 1 were used to determine the dynamic elastic modulus E ′ and the loss coefficient tan δ. Table 5 also shows tan δ at 1 Hz and E'at 100 Hz. The PVC used here was the same as in Example 1, and the blend ratio of NR / PVC was 40/60. Comparative Example 4-
1 and 4-2 have small tan δ at 1 Hz, and Comparative Example 4-3 has 10
The E'at 0 Hz is large, and both do not satisfy the performance required for the vibration damping material from the low frequency region to the high frequency region. Examples 4-1 to 4-4 have a good balance of tan δ at 1 Hz and E'at 100 Hz, and carbon black with excellent protection in the range of 36 to 63 parts by weight per 100 parts by weight of polymer. The damping characteristics are shown.

(Effect) As described above, the anti-vibration rubber composition of the present invention is obtained by blending natural rubber and / or isoprene rubber and polyvinyl chloride in a rubber / polyvinyl chloride weight ratio of 70/30 to 30/70. , Carbon black having a particle diameter of 30 to 120 nm is filled in an amount of 30 to 70 parts by weight with respect to 100 parts by weight of the polymer,
As a result, tan δ at low frequencies is large, and tan δ with low frequency dependence from low frequencies to high frequencies is shown.
It is a material that has a small E'at high frequencies and an excellent vibration damping effect.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the frequency and the loss coefficient (tan δ) of the vibration damping rubber compositions according to Example 1 and Comparative Example 1, and FIG. 2 is the natural rubber and poly in Example 2 and Comparative Example 2. Blend ratio of vinyl chloride and loss coefficient ratio of frequency 1Hz and 100Hz ta
nδ (100Hz) / tanδ (1Hz) and the above blend ratio and 1Hz
It is a figure showing the relation of ratio E '(100Hz) / E' (1Hz) of the dynamic elastic modulus of 100Hz.

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Claims (2)

[Claims] 1. A rubber comprising natural rubber and / or isoprene rubber and polyvinyl chloride are mixed in a rubber / polyvinyl chloride weight ratio of 70/30 to 30/70, and the mixture has an average particle diameter of 30 to 30. A vibration-damping rubber composition, characterized by being filled with carbon black of 120 nm. 2. The carbon black is added in an amount of 30 to 70 parts by weight based on 100 parts by weight of a mixture of natural rubber and / or isoprene rubber and polyvinyl chloride. Anti-vibration rubber composition.