JPH11100474A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition capable of forming a rubber member having damping performances which does not change depending upon temperature change and is approximately constant in a temperature range of -30 to 20 deg.C at which instruments are supposed to work. SOLUTION: This rubber composition comprises a block copolymer of styrene and isoprene, a polymer composed of an isoprene part containing a vinyl isoprene unit and a polymer which is a partially brominated substance of a copolymer of isobutylene and p-methylstyrene. The composition after vulcanization has difference between the minimum and the maximum of dissipation factor tan δat - 30 to 20 deg.C of <=0.5 and the minimum of tan δ of >=0.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel rubber composition suitably used for rubber members for vibration control and vibration control.

[0002]

2. Description of the Related Art Electronic information storage media such as optical disks [CD (compact disk), LD (laser disk), DVD (digital video disk or digital versatile disk)] and magneto-optical disks [MO, MD (mini disk)]. From consumer applications such as AV (audiovisual) devices and OA (office automation) devices such as storage devices for personal computers, to various types of industrial precision devices such as electron microscopes and microfabrication devices. 2. Description of the Related Art Rubber members for vibration isolation are used in a wide range in order to block external vibration and prevent malfunctions of devices and the like.

[0003] In a wide range of applications from home washing machines to various machine tools, vibrations generated by the apparatus itself are prevented from being transmitted to the outside, and vibration damping of the apparatus itself is attenuated. Rubber member is used. Among these, the rubber member for vibration isolation has (a) a natural frequency lower than the natural frequency of the object to be subjected to vibration isolation, and (b) a vibration magnification (resonance magnification T) when both resonate. Is required. In addition, rubber members for damping
(c) It is required to have characteristics such as a large attenuation with respect to the frequency of the vibration object to be damped.

[0004] In particular, in a rubber member for vibration isolation,
When the resonance magnification is reduced, there is a problem that the vibration isolation ability in a high frequency region is reduced. Depending on the application, it is necessary to select whether to give priority to the resonance magnification or to give priority to the vibration isolation ability in the high frequency region.If priority is given to the low resonance magnification, a rubber member for vibration suppression and Similarly, high damping performance is required.

[0005] As a parameter for defining the resonance magnification T of the rubber member, a loss tangent tan δ expressed by a tangent of a phase difference δ between strain and stress in the measurement of dynamic viscoelasticity is given. That is, the resonance magnification T [dB] and tan δ
Equation (1):

[0006]

(Equation 1)

[0007] The larger the tan δ, the smaller the resonance magnification T and the more excellent the damping performance of the rubber member. As a rubber member excellent in damping performance, a rubber member having a tan δ peak value of about 2 is known at present.

[0008]

However, according to studies by the inventors, the conventional special rubber member having a peak value of tan δ of about 2 as described above is a device which is an object to be subjected to vibration isolation and vibration suppression. It has been clarified that the damping performance in a temperature range of -30 to 20 ° C., in which the use of a kind is assumed, is not constant and greatly fluctuates depending on a temperature change.

That is, the rubber member exhibits high damping performance only in a very narrow temperature range near the peak temperature showing the peak value, and the temperature deviates from the peak temperature by about 10 to 20 ° C. In this range, tan δ is reduced to a fraction of the peak value (to about 0.3 when the peak value is 2). When this is converted into the resonance magnification T, it varies from 0.96 dB to 10.8 dB.

It is generally known that the rubber member tends to have a higher vibration transmissibility in a high frequency range exceeding the resonance frequency as the resonance magnification T becomes smaller. , Ta in a narrow temperature range
A rubber member having a large nδ, that is, a small resonance magnification T,
The vibration transmissibility in the above-mentioned temperature range is significantly larger than in other temperature ranges.

For this reason, when such a rubber member is used for vibration control and vibration control, there is a problem that it is difficult to design equipment (weight distribution, dimensions, shape, etc.). The purpose of the present invention is
In a temperature range of −30 to 20 ° C. in which the use of equipment is assumed, a novel rubber composition capable of forming a substantially constant rubber member whose damping performance does not fluctuate depending on a temperature change is provided. To provide.

[0012]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have proposed, as a base polymer constituting a rubber composition, a block copolymer of styrene and isoprene exhibiting excellent damping performance especially at around normal temperature. A polymer A which is a polymer and the isoprene part contains vinyl isoprene units, and a polymer B which is a partially brominated copolymer of isobutylene and p-methylstyrene, which exhibits excellent damping performance especially at low temperatures. As a result of studying that the rubber member formed by vulcanizing the rubber composition is specified to define a range of tan δ that defines the damping performance in a temperature range of −30 to 20 ° C. It was completed.

That is, the rubber composition of the present invention is a rubber composition containing the above polymers A and B, wherein the difference between the minimum value and the maximum value of tan δ in the above temperature range after vulcanization is 0. 0.5 or less, and the minimum value of the tan δ is 0.5 or more. According to the rubber composition of the present invention, it is possible to form a rubber member whose damping performance in the temperature range is substantially constant, which is assumed to be used for devices to be subjected to vibration damping and vibration damping. There is an advantage that the kind of design becomes easy.

The reason that the minimum value of tan δ in the above temperature range is limited to 0.5 or more is that, when the tan δ is less than this range, the resonance magnification T of the rubber member used in the above-mentioned precision equipment is particularly reduced. This is because the vibration exceeds the required range of 7 dB or less, which makes it difficult to prevent vibration. Further, the difference between the minimum value and the maximum value of the tan δ is limited to 0.5 or less. If the difference exceeds this range, the rubber member greatly fluctuates in the damping performance in the temperature range, and the This is because it makes it difficult to design such types.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below. The rubber composition of the present invention contains two components of polymers A and B as the base polymer as described above. Among the above, in the polymer A which is a block copolymer of styrene and isoprene, in which the isoprene portion contains vinyl isoprene units, the content ratio of vinyl isoprene units to the total amount of isoprene portions (vinyl isoprene content) is Although not particularly limited, 50%
More preferably, it is 50 to 75%, especially 65 to 75%.
More preferably, it is 75%.

If the vinyl isoprene content falls below such a range, the damping performance may decrease. On the other hand, those having a vinyl isoprene content exceeding the above range are not known at present. Incidentally, the vinyl isoprene unit means that isoprene is not a normal 1,4-bond but has the following formula (i)
And a 3,4-bonded portion represented by the following formula (ii).

[0017]

Embedded image

As described above, the polymer A exhibits excellent damping performance especially at around normal temperature, exhibits thermoplasticity, and can be molded at a temperature higher than the melting point. In addition, since it has a double bond in the side chain, it can be vulcanized with sulfur or a peroxide in the same manner as a normal rubber. Generate. In addition, the polymer A includes a polymer obtained by adding hydrogen to a double bond present in the main chain. In this case, the ozone resistance is improved as compared with the non-hydrogenated one.

Specific examples of the polymer A include, for example, HYBRAR VS-1 (vinyl isoprene content: 70%) manufactured by Kuraray Co., Ltd., and HYBRAR VS-3 manufactured by Kuraray Co., Ltd.
(Vinyl isoprene content 55%), HYBRA manufactured by the company
RHVS-3 (vinyl isoprene content 55%) and the like. In the polymer B, which is a partially brominated copolymer of isobutylene and p-methylstyrene, used in combination with the polymer A, the weight ratio of p-methylstyrene is preferably 3 to 20% by weight, More preferably, it is 10% by weight.

If the proportion of p-methylstyrene exceeds the above range, the glass transition point will increase, and the rubber may become too hard or the damping performance may decrease. Conversely, when the value falls below the above range, the crosslinking point decreases and the polymer A
There is a possibility that the co-crosslinking property with the polymer may decrease. In polymer B, the bromine is believed to have replaced one of the hydrogens of the methyl group. The bromine content is preferably 0.5 to 2% by weight, and more preferably 1.2 to 2% by weight, expressed as a percentage of brominated p-methylstyrene in the total weight of polymer B. Is more preferred. If the bromine content exceeds the above range, the crosslinking density may increase, and the rubber may become too hard. Conversely, if it is less than the above range, the crosslinking does not proceed, and the creep may be too large.

The polymer B is butyl rubber (IIR)
Due to the action of the isobutylene unit having the same structure as described above, it has excellent damping performance especially at low temperatures as described above. Further, since the polymer B does not have a double bond in the main chain that causes ozone deterioration or aging, it has excellent ozone resistance and aging resistance. Specific examples of the polymer B include, but are not limited to, EXXPRO MDX 90-10 manufactured by Exxon Chemical Co., Ltd., EXXPRO MDX89-4 manufactured by the company, EXXPR manufactured by the company.
O MDX 89-5, EXXPROMDX manufactured by the company
89-1 and EXXPRO MDX 93-4 manufactured by the company.

The difference between the minimum value and the maximum value of tan δ at a temperature of -30 to 20 ° C. after vulcanization of the rubber composition containing both polymers is limited to 0.5 or less.
The minimum value of δ is limited to 0.5 or more. The reason is as described above. The difference between the minimum value and the maximum value of tan δ is preferably 0.3 or less, more preferably 0.2 or less, within the above range in order to make the damping performance in the above temperature range substantially constant. Is more preferred. Since it is most ideal that there is no difference, the lower limit value is obviously 0.

The minimum value of tan δ is preferably 0.6 or more in the above range in order to reduce the resonance magnification T of the rubber member and improve the damping performance.
More preferably, it is 7 or more. The upper limit of the minimum value of tan δ is not particularly limited, and the higher the minimum value, the better the damping performance. However, the practical upper limit of the minimum value of tan δ is about 0.8.

The most basic factors that define the difference between the minimum value and the maximum value of tan δ and the minimum value of tan δ in the above range are the types and blend ratios of the polymers A and B. For example, as is clear from the results of Examples and Comparative Examples described later, HYBRAR VS-1 as Polymer A
And EXXPRO MDX 90- as polymer B
When combining with 10, the weight ratio is 20:
By blending within the range of 80 to 28:72, ta
The difference between the minimum value and the maximum value of nδ, and the minimum value of tanδ are defined in the above ranges.

The rubber composition of the present invention comprises a vulcanizing agent for vulcanizing the above-mentioned polymers A and B, a vulcanization accelerator, a vulcanization accelerating aid and, if necessary, a vulcanization retarder, Reinforcing agents, softening agents, fillers, lubricants, tackifiers, antioxidants, pigments and the like may be added. Among them, examples of the vulcanizing agent and vulcanization accelerator include a combination of sulfur capable of vulcanizing the polymer A and a thiazole-based, thiuram-based or dithiocarbamate-based vulcanization accelerator.

Specific examples of the vulcanization accelerator include dibenzothiazyl disulfide (DM), tetramethylthiuram disulfide (TMT), tetraethylthiuram disulfide (TET), tetrabutylthiuram disulfide (TBT), iron dimethyldithiocarbamate, Zinc dimethyldithiocarbamate (PZ), copper dimethyldithiocarbamate, zinc diethyldithiocarbamate (E
Z), zinc dibutyldithiocarbamate (BZ), N-
Zinc ethyl-N-phenyldithiocarbamate (P
X), 2-mercaptobenzothiazole (M), dipentamethylenethiuram tetrasulfide (TRA) and the like.

The total addition amount of sulfur and the vulcanization accelerator is 0.5 to 20 with respect to 100 parts by weight of the total amount of the polymers A and B.
Preferably, the amount is from 2 to 5 parts by weight. Further, the polymer B is vulcanized by zinc oxide and stearic acid as vulcanization accelerators used in combination with the above vulcanizing agents and vulcanization accelerators.

The amount of zinc oxide to be added is preferably 0.5 to 10 parts by weight based on 100 parts by weight of the total of the polymers A and B. The amount of stearic acid to be added is as follows: polymer A,
It is preferably 0.1 to 5 parts by weight based on 100 parts by weight of the total amount of B. Examples of the reinforcing agent include carbon black and silica, and inexpensive carbon black is particularly preferably used. Examples of the carbon black include SRF, GPF, FEF, HAF, and ISAF.

The amount of carbon black to be added varies depending on the type of carbon black to be used and the like, but is generally 20 parts by weight based on 100 parts by weight of the total amount of the polymers A and B.
0 parts by weight or less, preferably 10 to 100 parts by weight.
About parts by weight are used. Examples of the softening agent include various conventionally known vegetable oils, mineral oils, and synthetic oils such as fatty acids (such as stearic acid and lauric acid), cottonseed oil, tall oil, asphalt substances, paraffin oil, naphthenic oil, and mineral oil. Any of the above softeners can be used. In particular, paraffin oil having an excellent affinity for the polymer B is preferably used.

The amount of the softening agent to be added varies depending on the kind of the softening agent to be used and the like, but generally it is preferably 100 parts by weight or less based on 100 parts by weight of the total amount of the polymers A and B. . In the present invention, following the types and blending ratios of the above-described polymers A and B, the types and amounts of the carbon black and the softener are determined by the difference between the minimum value and the maximum value of tan δ, and the minimum value of tan δ. This is an important factor for defining the above range.

For example, the types and mixing ratios of the polymers A and B are as described above, and SRF-
When LM is used and paraffin oil is used as a softening agent, the SR based on 100 parts by weight of the total amount of the polymers A and B is used.
When the addition amount of F-LM is about 15 parts by weight and the addition amount of paraffin oil is about 30 parts by weight, tan δ is 0.8
It can be about ± 0.1.

The rubber composition may contain other reinforcing agents and fillers other than carbon black within a range that does not affect the above-mentioned range of tan δ. Examples of such other reinforcing agents and fillers include, in addition to the silica, calcium carbonate, magnesium silicate, clay, zeolite, barium sulfate, lithopone, titanium oxide and the like.

The total amount of these other reinforcing agents and fillers is 10 parts by weight based on 100 parts by weight of the total amount of the polymers A and B.
It is preferably at most 0 parts by weight, more preferably at most 50 parts by weight. As the antioxidant, for example, a phenol-based antioxidant can be used. The compounding amount of the antioxidant is 0.5 to 100 parts by weight of the total amount of the polymers A and B.
It is desirable to adjust within the range of from 10 to 10 parts by weight according to the amount of the polymer A.

The rubber composition may further contain, for example, a resin, a rubber powder, hollow particles, a liquid rubber, etc. in addition to the above. In particular, the resin works together with the softener to increase tan δ. It can be suitably used. Such resins include, for example, coumarone-indene resin, phenol resin, terpene resin, high styrene resin, petroleum hydrocarbon resin (eg, dicyclopentadiene resin, aliphatic cyclic hydrocarbon resin, unsaturated hydrocarbon resin, etc.), polybutene , Rosin derivatives and hydrogenated products thereof.

The amount of the resin is preferably set so that a part of the added amount of the softener can be replaced. That is, it is preferable to adjust the addition amounts of both the resin and the softening agent so that the total addition amount of the resin and the softening agent falls within the above-described range of the preferable addition amount of the softening agent alone. Addition of the hollow particles can reduce the weight of the rubber member. Liquid rubbers such as polybutadiene and polyisoprene have the function of plasticizing the rubber member, but are co-crosslinked and integrated with the base polymer, depending on the molecular weight, so they are used as unextractable plasticizers and softeners. it can. The amount of the liquid rubber to be added is as follows:
It is preferably at most 50 parts by weight, more preferably at most 30 parts by weight, per 100 parts by weight of the total amount of B.

[0036]

The present invention will be described below based on examples and comparative examples. Example 1 Polymer A (HYBRAR VS- manufactured by Kuraray Co., Ltd.)
1, vinyl isoprene content 70%) 20 parts by weight, polymer B (EXXPRO MDX manufactured by Exxon Chemical Co., Ltd.)
90-10) 80 parts by weight, carbon black (SRF-
LM) 15 parts by weight, paraffin oil (Idemitsu Kosan Co., Ltd.)
Diana Process Oil PW-380), 30 parts by weight, zinc white 2 parts by weight, stearic acid 1 part by weight, sulfur 1 part by weight, vulcanization accelerator (DM) 2 parts by weight and vulcanization accelerator (TET) 0. 5 parts by weight were kneaded to produce a rubber composition.

Examples 2 and 3, Comparative Examples 1 and 2 A rubber composition was produced in the same manner as in Example 1 except that the amounts of the polymers A and B were set to the values shown in Table 1. Measurement of tan δ The rubber compositions of Examples and Comparative Examples were each vulcanized and molded to prepare strip-shaped test pieces.

The tan δ of this test piece was measured using a test device manufactured by Rheology Co., Ltd. under the following measurement conditions, and the maximum value tan δ (MAX) and tan δ (MAX) of tan δ in a temperature range of −30 to 20 ° C. The minimum value tanδ (MIN) was determined, and the difference Δtanδ between the two values was determined. Measurement conditions Test temperature: From -75 ° C to 75 ° C Test frequency: 10 Hz Type of deformation: Tensile Type of dynamic strain: Sine wave Strain amplitude: ± 0.1% The results are shown in Table 1. FIG. 1 shows measured values of tan δ from -75 ° C. to 75 ° C. in Examples 1 and 2 and Comparative Example 2 among Examples and Comparative Examples.

[0039]

[Table 1]

From the results shown in Table 1 and FIG. 1, when the blending ratio of the polymers A and B is in the range of 20:80 to 28:72, the damping performance does not fluctuate depending on the temperature change. It was found that a constant rubber member could be formed. Example 4 A rubber composition was produced in the same manner as in Example 2, except that 30 parts by weight of aroma oil was used instead of paraffin oil.

Example 5 A rubber composition was produced in the same manner as in Example 1 except that 20 parts by weight of mineral oil and 10 parts by weight of coumarone-indene resin were used instead of paraffin oil. Example 6 A rubber composition was produced in the same manner as in Example 1 except that 20 parts by weight of mineral oil and 10 parts by weight of dicyclopentadiene resin were used instead of paraffin oil.

The same test as described above was conducted for the rubber compositions of the above examples. Table 2 shows the results.

[0043]

[Table 2]

From the results shown in Table 2, it was found that a rubber member having similar characteristics can be formed even when a softener and a resin are used in combination.

[0045]

As described in detail above, according to the present invention,
In a temperature range of −30 to 20 ° C. where use of equipment is assumed, a novel rubber composition can be provided in which a damping performance can form a substantially constant rubber member without fluctuating depending on a temperature change. This produces a unique effect.

[Brief description of the drawings]

FIG. 1 is a graph showing the temperature dependence of tan δ in vulcanizates formed from rubber compositions of Examples and Comparative Examples of the present invention.

Claims (1)

[Claims] 1. A polymer which is a block copolymer of styrene and isoprene, wherein the isoprene part is a polymer A containing vinyl isoprene units and a partial bromide of a copolymer of isobutylene and p-methylstyrene. A rubber composition containing B, wherein the difference between the minimum value and the maximum value of the loss tangent tan δ at a temperature of −30 to 20 ° C. after vulcanization is 0.5 or less, and the minimum tan δ A rubber composition having a value of 0.5 or more.