JP5043310B2 - Low repulsion rubber composition and seismic isolation structure using the same - Google Patents

Description

  The present invention relates to a rubber composition having high initial rigidity, excellent low repulsion and damping, and very effective in absorbing vibration energy such as seismic isolation, vibration isolation or vibration isolation, and a seismic isolation structure using the same About.

In recent years, a seismic isolation method using a seismic isolation structure has attracted attention for the purpose of reducing the input acceleration of vibrations to structures generated by an earthquake.
This insulates the ground and the structure with a soft layer and reduces the natural frequency of the structure relative to the frequency of the ground during an earthquake, that is, minimizes damage to the structure by reducing the input acceleration of vibration. It is something that is limited.

  The seismic isolation structure used here is a combination of soft layers (rubbers) and hard layers (steel plates, etc.) alternately and is hard in the vertical direction to support the structure, while mitigating vibration input acceleration. Therefore, it is soft in the horizontal direction and does not break even during large deformations.

  However, since the conventional seismic isolation rubber composition has a small hysteresis loss, the seismic isolation structure using this rubber composition itself has a drawback that it has a poor ability to reduce the vibration of the superstructure. It was.

On the other hand, there are various examples of seismic isolation structures in which vibration energy absorption capacity is greatly improved by imparting low repulsion (high damping function) to the soft layer (rubber) (see, for example, Patent Document 1). is there. In patent document 1, it is the content of the invention specified for the area | region with a low elastic modulus for buildings. On the other hand, seismic isolation structures in the high elastic modulus region are required for bridge isolation applications. An object of the present invention is to provide a low repulsion rubber composition that can be applied to seismic isolation structures such as bridges in general.
Patent No.2949671

Further, although a highly damped elastomer composition containing a thermoplastic elastomer as a rubber component is disclosed (see Patent Document 2), in the present invention, as a seismic isolation structure such as a tensile strength of a soft layer (rubber). Necessary properties are not described and are unknown. In general, reinforcing fillers (carbon black, silica) are not blended, and a large amount of softener is blended. In addition, tensile strength is extremely low, Mooney viscosity is low, and processing is difficult. It is estimated that.
JP 2003-261717 A

Similarly, in Patent Document 3, it is presumed that the attenuation characteristic does not have an excellent characteristic.
JP 2004-269839 A

  An object of the present invention is to provide a low-repulsion rubber composition having excellent low-repellency and high-damping properties, high elastic modulus and excellent low-temperature characteristics, and a seismic isolation structure using the composition. For the purpose.

In order to solve the above problems, the present invention has the following configuration.
The gist of the invention of claim 1 is the sum of 55 to 90 parts by weight of diene rubber, one or more thermoplastic polymers selected from ethylene / butene copolymers and ethylene / methyl methacrylate copolymers, and polyoctenemers. The total amount of carbon black and silica is 50 to 120 parts by weight with respect to 100 parts by weight of rubber consisting of 10 to 45 parts by weight, and the silica has an amorphous surface area in the range of 100 to 210 m ² / g. silica or in the amorphous silica in a hydrophobic treated silica strained facilities hydrophobic processing state, and are not blended singly or in an arbitrary ratio, the diene rubber, the group consisting of natural rubber, isoprene rubber, butadiene rubber, One or more types are selected from the above, and each of them is used alone or in an arbitrary ratio .
The gist of the invention described in claim 2 is characterized in that the hydrophobically treated silica is obtained by subjecting amorphous silica to a hydrophobic treatment with an organosilicon compound, and an adsorption amount of DBA (dibutylamine) is 19 m-mol / kg or less. It exists in the low repulsion rubber composition of Claim 1 or 2.
The gist of the invention described in claim 3 resides in a seismic isolation structure in which the low repulsion rubber composition according to any one of claims 1 to 3 is used as a soft rubber layer, and hard plates are alternately laminated.

  According to the present invention, it is possible to provide a low repulsion rubber composition having an excellent low rebound, that is, a high damping property, a high elastic modulus and an excellent low temperature characteristic. Moreover, the low rebound rubber composition of the present invention has a low Mooney viscosity and is excellent in processability.

  In addition to diene rubbers such as natural rubber, isoprene rubber, low cis isoprene rubber, butadiene rubber, low cis butadiene rubber, and terminal modified butadiene rubber, the present inventors have added ethylene / butene copolymer to the rubber component in the rubber composition. By blending at least one thermoplastic polymer selected from a polymer, an ethylene / methyl methacrylate copolymer and a polyoctenemer, carbon black, amorphous silica and / or hydrophobic silica, it has a high elastic modulus and excellent low repulsion. A low-repulsion rubber composition that has excellent properties and high damping properties, has a low temperature dependency of rubber performance, and is balanced in many properties, and has completed the seismic isolation structure. In addition, the low repulsion rubber composition of the present invention is excellent in processability because the Mooney viscosity at the time of processing is kept low by adding a thermoplastic polymer.

The low repulsion rubber composition of the present invention is composed of 55 to 90 parts by weight of a diene rubber and 45 to 10 parts by weight of a thermoplastic polymer as 100 parts by weight of a rubber component.
Examples of the diene rubber component include natural rubber, isoprene rubber, polyisoprene rubber having a cis-1.4 bond content (weight%) of 92% or less, butadiene rubber, cis- 1.4 Low cis-butadiene rubber and terminal-modified butadiene rubber having a bond content (% by weight) of 35 to 40% can be used, either alone or in a blended ratio.
The butadiene rubber is preferably used at a weight ratio of 67% or less in the whole diene rubber, more preferably 30 to 50% by weight. The combined use of butadiene rubber, low cis butadiene rubber and end-modified butadiene rubber does not sacrifice the breaking strength of the base isolation structure made of the rubber composition, and the characteristics of the base isolation structure are affected by the operating temperature environment. Without making it easy, for example, roll processing of unvulcanized rubber.
Further, the terminal-modified butadiene rubber is a polymer in which a specific functional group is introduced into a polymer molecule, and can improve the dispersibility of silica particles in the compound. Therefore, it is used when compounding silica in the present invention. Is preferred.

In the low repulsion rubber composition of the present invention, a thermoplastic polymer is blended as a rubber component in addition to the diene rubber. Examples of the thermoplastic polymer include a styrene / butadiene block copolymer, an ethylene / vinyl acetate copolymer, an ethylene / butene copolymer, an ethylene / methyl methacrylate copolymer, and a polyoctenemer. It is desirable to use a butene copolymer, an ethylene / methyl methacrylate copolymer and a polyoctenemer.
Styrene / butadiene block copolymers and ethylene / vinyl acetate copolymers have excellent low repulsion, but the temperature dependence of the rubber compound characteristics is large and the balance of the characteristics is lacking. On the other hand, ethylene-butene copolymer, ethylene-methyl methacrylate copolymer, and polyoctenemer have excellent low repulsion, and the influence of the ambient temperature on the loss coefficient and shear modulus is small, and the balance of characteristics is good. It is suitable because it is taken.

  The ethylene / butene copolymer, the ethylene / methyl methacrylate copolymer, and the polyoctenemer may be used alone or in any desired ratio.

  In the low repulsion rubber composition of the present invention, the total amount of diene rubber (A) and the total amount of the thermoplastic polymer (B) are A part: 55 to 90 parts by weight, B part: 45 to 10 parts by weight. The total of A part + B part is 100 parts by weight. Since the Mooney viscosity during processing is kept low by blending the thermoplastic polymer, it is excellent in processability.

In the low repulsion rubber composition of the present invention, 50 to 120 parts by weight of the total of carbon black and silica having a specific particle diameter is blended with 100 parts by weight of the polymer component. As the carbon black, the nitrogen adsorption specific surface area is preferably in the range of 93m ² / g~142m ² / g. When the nitrogen specific surface area is 92 m ² / g or less, excellent low repulsion cannot be obtained. On the other hand, when the nitrogen specific surface area is 143 m ² / g or more, it is difficult to obtain good dispersion in rubber.

In general, silica is classified into crystalline silica having a certain crystal structure and amorphous silica having no crystal structure typified by hydrous succinic acid and synthetic succinic acid.
The low repulsion rubber composition of the present invention, silica or within a specific surface area a amorphous silica of 100m ² / g~210m ² / g, or, respectively of the hydrophobic treated silica the amorphous silica hydrophobically treated people It is blended alone or in combination at any ratio.

  The hydrophobic silica is obtained by subjecting the amorphous silica to a hydrophobic treatment with an organosilicon compound. The degree of hydrophobic treatment of the hydrophobic treated silica is generally represented by the DBA (dibutylamine) adsorption amount, that is, the DBA value. When the DBA value is small, there are few silanol groups, and the silanol groups of amorphous silica are treated with hydrophobic treatment. Show.

  The total amount of carbon black and silica added is less than 49 parts by weight, and excellent low repulsion, that is, high damping properties cannot be obtained, while 121 parts by weight or more increases the viscosity of unvulcanized rubber significantly. The carbon black and silica cannot be evenly dispersed, and it is difficult to produce a seismic isolation structure.

  In the composition of the present invention, in addition to the above-mentioned diene rubber, resin, carbon black, and silica, in a range that does not impair the characteristics of the composition of the present invention, a tackifier generally used in the rubber industry, Compounding agents such as a vulcanizing agent, a vulcanization accelerator, an anti-aging agent, a peptizer, a plasticizer, various fillers, a processing aid, and various resins can be appropriately blended within a normal blending amount range.

  The low repulsion rubber composition of the present invention can be obtained by mixing the above components with a rubber kneader generally used in the rubber industry such as a Banbury mixer and a kneader.

The seismic isolation structure of the present invention is a seismic isolation structure in which the low-rebound rubber composition is a soft rubber layer, and hard plates such as steel plates are alternately laminated. FIG. 1 shows an example of a seismic isolation structure.
This seismic isolation structure 10 is a laminated body in which metal flanges 1 and 2 are provided on the upper and lower surfaces, and a soft rubber layer 3 and a hard plate 4 are alternately laminated between the upper and lower surfaces. It can be obtained by vulcanization molding of the repellent rubber composition.
Further, the outer periphery of the laminate is the same rubber composition as that of the soft rubber layer 3, natural rubber, or chloroprene rubber, ethylene / propylene rubber, butyl rubber, chlorosulfone having better weather resistance than the diene rubber specified in the present invention. You may coat | cover with the covering rubber layer 5 which consists of a general carbon black compounded rubber composition similar to the vulcanized rubber of the low repulsion rubber composition of the present invention, such as chlorinated polyethylene.
As a material of the hard plate 4, a metal ceramic or plastic can be used, and a steel plate is particularly preferably used.

  The manufacturing method of the seismic isolation structure is a method of manufacturing a sheet-like rubber member obtained by molding and vulcanizing a low repulsion rubber material, and laminating a hard plate or a flange and bonding them together with an adhesive to manufacture them. Alternatively, it can be manufactured by laminating an unvulcanized low-rebound rubber material formed into a sheet shape and a hard plate or a flange and vulcanizing and bonding them.

  This seismic isolation structure has a stable effect on the absorption of vibration energy such as base isolation for buildings and detached buildings, seismic isolation for bridges and road bearings, seismic isolation, vibration isolation, etc. I can do it.

  The following examples illustrate the invention in more detail.

  To the various rubber components in which the combination of the diene rubber and the thermoplastic polymer shown in Table 1 was changed, the same type of a certain amount of carbon black, silica, and tackifier were blended with the contents shown in Table 1.

<Diene rubber>
The diene rubbers listed in Table 1 are shown below.
Natural rubber (NR): CV-60 (constant viscosity rubber)
Isoprene rubber (IR): IR-2200
Low cis-isoprene rubber (low cis IR): Low cis-isoprene rubber with a cis-1.4 bond content (wt%) of 92% or less Butadiene rubber (BR): 96% cis-1.4 bond content (wt%) High cis butadiene rubber Low cis butadiene rubber (low cis BR): Low cis butadiene rubber having a cis-1.4 bond content (wt%) of 35 to 40% End-modified butadiene rubber (terminal-modified BR): Dispersion of silica particles Butadiene rubber with specific functional groups introduced in the polymer

<Thermoplastic polymer>
The thermoplastic polymers listed in Table 1 are shown.
Styrene / butadiene system: Styrene / butadiene block copolymer with a styrene / butadiene ratio (weight ratio) of 40/60 Ethylene / vinyl acetate system: Ethylene / vinyl acetate copolymer with a vinyl acetate content (weight ratio) of 14%・ Butene series: Ethylene / butene copolymer Ethylene / methyl methacrylate series: Ethylene / methyl methacrylate copolymer with a methyl methacrylate content of 20% (wt%) or less Polyoctenemer: A polymer of cyclooctene Transpolyoctenemer

<Common essential ingredients>
Carbon black: Carbon black with a small particle diameter of nitrogen adsorption specific surface area of 140 m ² / g Amorphous silica: Amorphous silica with nitrogen adsorption specific surface area of 205 m ² / g

<Addable ingredients>
The low repulsion rubber composition of the present invention includes a vulcanizing agent such as sulfur, a vulcanization accelerator, an anti-aging agent, a wax and an activator which are usually used in the rubber industry in addition to the essential rubber component and the essential compounding component. Well-known compounding agents such as zinc white, softener, plasticizer, stearic acid, peptizer, various fillers, processing aids, and various resins can be appropriately blended within the range of ordinary blending amounts.

<Measurement test method of tensile strength, elongation, hardness, Mooney viscosity>
The tensile strength and elongation of each low repulsion rubber composition were measured according to JIS K6251 (using dumbbell-shaped test piece No. 3). Hardness was measured according to JISK6253.
Mooney viscosity (ratio): Measured according to JISK6300, with Comparative Example 1 as the standard (100), and expressed as a ratio to that.

<Measurement test method for low rebound (loss factor) and shear modulus>
Obtained by vulcanizing and molding the “2-block lap shear type” specimen of FIG. 2 (rubber part: width 25 mm, length 25 mm, thickness 4 mm) using each compounded rubber composition at 140 ° C. for 30 minutes. .

<Strain excitation conditions>
Frequency: 0.05Hz
Distortion rate: 175%
Measurement temperature: 23 ℃
Measurement of shear elastic modulus (G) and loss factor: 11 times of continuous excitation, 2nd to 11th arithmetic average values are adopted.
Loss coefficient (ratio): Comparative example 1 was used as a reference (100), and the ratio was expressed as a ratio.
G (−10 ° C.) / G (23 ° C.): The ratio of the shear elastic modulus (G) measured at −10 ° C. and 23 ° C., respectively.

  An example of a stress-strain curve is shown in FIG.

In Table 1, Comparative Example 1 is a general compounding system in which natural rubber is blended with SAF grade carbon black and a tackifier used in a normal rubber industry. Comparative Example 2 is a blending system in which most of the carbon black is replaced with amorphous silica. Although Comparative Example 2 has a larger loss factor than Comparative Example 1, the Mooney viscosity increased to a level at which processing was hindered because of a large amount of amorphous silica.
For these comparative examples, in Comparative Examples 3 to 15 and Examples 1 and 2 in which a diene rubber and a thermoplastic polymer are used in combination, any compound except Comparative Example 15 which is a low cis butadiene rubber alone as a diene rubber. The system is also greatly improved in loss factor. Further, Comparative Examples 3 to 14 have a Mooney viscosity lower than that of Comparative Example 2 although a large amount of amorphous silica is blended in the same manner as Comparative Example 2. However, among the thermoplastic polymers, the ratio of G (−10 ° C.) / G (23 ° C.) of the styrene / butadiene copolymer of Comparative Example 3 and the ethylene vinyl acetate copolymer of Comparative Example 4 is 1.70. As described above, the influence of the temperature setting environment of the support body is greatly unfavorable.
Further, in Comparative Example 15 where the butadiene rubber is used alone as the diene rubber, the effect of improving the loss factor is small. In the combined use of butadiene rubber, it is desirable that the ratio of diene rubber is 67% or less as in Comparative Example 8 . Accordingly, natural rubber and isoprene rubber are preferable as the diene rubber, and combined use with butadiene rubber is preferred from the viewpoint of improving roll adhesion during kneading.
As for the thermoplastic polymer, Comparative Examples 5 to 12 in which an ethylene / butene copolymer, an ethylene / methyl methacrylate copolymer and a polyoctenemer were blended, and a polyoctenemer and an ethylene / butene copolymer, a polyoctenemer and an ethylene / methyl methacrylate In Examples 1 and 2 using a copolymer together, the ratio of G (−10 ° C.) / G (23 ° C.) is relatively small, the loss factor is improved, and a balanced composition is obtained.
Moreover, since the Mooney viscosity is also reduced, the processability is excellent, and a composition preferable as a low repulsion rubber composition can be provided. That is, as the thermoplastic polymer, it is preferable to use an ethylene / butene copolymer, an ethylene / methyl methacrylate copolymer and a polyoctenemer alone or in combination.

  Carbon blacks having different nitrogen specific surface areas were blended with the contents shown in Table 2 with respect to the fixed rubber components of the diene rubber and the thermoplastic polymer shown in Table 2. The amorphous silica and tackifier were fixed.

The carbon black described in Table 2 is shown below.
Carbon black A: Nitrogen specific surface area 79m ² / g (HAF grade)
Carbon black B: Nitrogen specific surface area 109m ² / g (ISAF class)
Carbon Black C: Nitrogen specific surface area 140m ² / g (SAF class)

<Common essential ingredients>
Diene rubber: Isoprene rubber (IR / 2200)
Thermoplastic polymer: Polyoctenemer Amorphous silica: Amorphous silica with a nitrogen specific surface area of 205 m ² / g

<Addable ingredients>
The low repulsion rubber composition of the present invention includes a vulcanizing agent such as sulfur, a vulcanization accelerator, an anti-aging agent, a wax and an activator which are usually used in the rubber industry in addition to the essential rubber component and the essential compounding component. Well-known compounding agents such as zinc white, softener, plasticizer, stearic acid, peptizer, various fillers, processing aids, and various resins can be appropriately blended within the range of ordinary blending amounts.

<Measurement conditions>
Various characteristics were measured under the same experimental conditions as in Example 1.

In Table 2, Comparative Example 16 is HAF grade carbon black generally used in the rubber industry.
On the other hand, in the present invention, carbon black having a particle size smaller than that of HAF grade carbon black, that is, a nitrogen specific surface area, specifically, Comparative Example 17 having a nitrogen specific surface area in the range of 93 to 142 m ² / g, Comparative Example By using the carbon black shown in FIG. 18 , a large loss factor was obtained for repeated shear deformation. When carbon black having a nitrogen specific surface area of 143 m ² / g or more is used, good dispersion in the rubber composition cannot be obtained, resulting in a non-uniform composition.

    Different types of silica were blended with the contents shown in Table 4 with respect to the diene rubber and thermoplastic rubber fixed rubber component shown in Table 4. Carbon black and tackifier were fixed.

    The silica listed in Table 4 is shown in Table 3. Hydrophobic treated silica A in Table 3 is obtained by subjecting amorphous silica B to a hydrophobic treatment with an organosilicon compound.

  The method for measuring the DBA adsorption amount is shown below.

Measurement method of DBA (dibutylamine) adsorption amount Weigh accurately 250 mg of dry sample into a 250 ml Erlenmeyer flask with a stopper, add 50 ml of N / 500-n dibutylamine solution (petroleum benzine solvent) to this with a pipette, and shaker Shake for about 1 hour.
Carefully suck out 25 ml of this supernatant with a pipette, transfer to a 100 ml beaker, add 10 ml of ethanol, and titrate with a potentiometric automatic titrator. (Aml)
Separately, 25 ml of N / 500-n dibutylamine solution and 10 ml of ethanol are placed in a beaker, titrated with a potentiometric automatic titrator, blanked (B ml), and the DBA adsorption amount is calculated by the following formula.
DBA adsorption amount (m-mol / kg) = 80 (BA) f
However, f is the titer of N / 100 perchloric acid. Note) Electrode used: Glass electrode / reference electrode (double external liquid: potassium chlorate solution)

<Common essential ingredients>
Diene rubber: Isoprene rubber (IR / 2200)
Thermoplastic polymer: Polyoctenemer Carbon black: Carbon black with a nitrogen specific surface area of 140m ² / g

<Addable ingredients>
The low repulsion rubber composition of the present invention includes a vulcanizing agent such as sulfur, a vulcanization accelerator, an anti-aging agent, a wax and an activator which are usually used in the rubber industry in addition to the essential rubber component and the essential compounding component. Well-known compounding agents such as zinc white, softener, plasticizer, stearing agent, peptizer, various fillers, processing aids, and various resins can be appropriately blended within the range of ordinary blending amounts.

<Measurement conditions>
Various characteristics were measured under the same experimental conditions as in Example 1.

In Table 4, Comparative Example 19 is a blend using amorphous silica having a particle size generally used in the rubber industry.
In Comparative Example 20 , crystalline silica having a secondary particle size smaller than that of amorphous silica was used in combination, but the loss factor (attenuation) was significantly reduced by the combined use. In Comparative Example 21 , since the amorphous silica having a smaller secondary particle size than that in Comparative Example 19 was blended, the loss factor decreased. In Comparative Example 22 , since amorphous silica having a small secondary particle diameter was blended, the loss factor was the same level as in Comparative Example 19 , but the Mooney viscosity was remarkably increased.
On the other hand, in Comparative Examples 23 and 24 , Mooney viscosity is kept low by using hydrophobically treated silica while obtaining a high loss factor. Hydrophobic-treated silica has an effect of suppressing an increase in Mooney viscosity of unvulcanized rubber, and a high loss factor can be obtained by either a simple substance or a combination with amorphous silica.
However, since Comparative Examples 25 and 27 were blended with the total addition amount of carbon black and silica being 45 parts by weight, the loss factor decreased, and Comparative Examples 26 and 28 were of the addition amount of carbon black and silica. Since the total was 120 parts by weight, a significant increase in Mooney viscosity was observed.
In the low repulsion rubber composition of the present invention, the effect of improving the loss factor is greatly reduced when the total amount of carbon black and silica is 49 parts by weight or less with respect to the rubber component, and when it is 121 parts by weight or more, the effect of the unvulcanized rubber is reduced. A significant increase in viscosity occurs, which is not preferable.

As described above, the low repulsion rubber composition according to the present invention uses a total blended in an appropriate ratio of a diene rubber and a specific thermoplastic polymer as a polymer component, and includes a specific carbon black and silica. As a result, it has good workability during kneading, good rubber properties, excellent low rebound (high damping property), and balanced rubber performance with little temperature dependence of damping properties.
Therefore, the seismic isolation structure to which this low repulsion rubber composition is applied is excellent in breaking strength and seismic isolation performance, and can stably exhibit vibration energy absorption capacity during an earthquake over a long period of time.

... Laminated rubber structure to which the low repulsion rubber composition of the present invention is applied ・ ・ ・ Cross section of “2-block lap-shear” specimen ... Explanation of stress-strain curve during shear deformation

Explanation of symbols

1, 2 ... Flange 3 ... Soft rubber layer (low repulsion rubber)
4 ・ ・ ・ Hard plate 5 ・ ・ ・ Covered rubber layer 10 ・ ・ ・ Seismic isolation structure

Claims (3)

55 to 90 parts by weight of diene rubber,
A total of 10 to 45 parts by weight of a thermoplastic polymer selected from one or more of an ethylene / butene copolymer and an ethylene / methyl methacrylate copolymer, and a polyoctenemer;
A total of 50 to 120 parts by weight of carbon black and silica with respect to 100 parts by weight of rubber comprising
The silica is an amorphous silica having a specific surface area of 100 to 210 m ² / g, or a hydrophobized silica obtained by subjecting the amorphous silica to a hydrophobizing treatment, each of which is incorporated alone or in an arbitrary ratio. The
One or more types of said diene rubber are selected from the group consisting of natural rubber, isoprene rubber, and butadiene rubber, and each of them is blended alone or in an arbitrary ratio . The hydrophobic treated silica is obtained by hydrophobic treatment of the amorphous silica with an organosilicon compound, characterized in that DBA (dibutylamine) adsorption amount is less 19 m-mol / kg, low according to claim 1 Rebound rubber composition. A base-isolated structure in which the low repulsion rubber composition according to claim 1 or 2 is used as a soft rubber layer, and hard plates are alternately laminated.

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