JP5621183B2 - Rubber composition for seismic isolation structure - Google Patents

Description

  The present invention relates to a rubber composition for a base-isolated structure having a high damping property and a small Mullins effect.

  In recent years, attaching seismic isolation structures to buildings as a countermeasure against earthquakes has become widespread. This seismic isolation structure generally has a structure in which a rubber layer and a hard plate layer are alternately laminated, and natural rubber is generally used for the rubber layer because of its excellent fracture property (for example, Patent Document 1 below) etc).

  However, in vulcanized rubber, a phenomenon that the elastic modulus decreases due to repeated deformation, commonly called the Malins effect, the high damping rubber using natural rubber has a large Malins effect, and the durability as a seismic isolation structure is not Not always enough. In particular, the drop in elastic modulus (history dependence) due to the Mullins effect has already occurred during large deformations, which has a significant effect when a large earthquake is assumed.

  Therefore, it is desired to develop a rubber material for a seismic isolation structure that can reliably maintain good performance with a small Mullins effect and that can reliably exhibit a highly reliable seismic isolation function.

In addition, the following are mentioned as prior art documents relevant to the present invention.
JP-A-2-32135 JP-A-5-59219 JP 2002-340089 A

  The present invention has been made in view of the above circumstances, and provides a rubber composition for a seismic isolation structure that is small in the decrease in elastic modulus due to repeated deformation and can reliably maintain the desired performance over a long period of time. Objective.

  As a result of diligent studies to achieve the above object, the present inventor, when preparing a rubber composition for forming a rubber layer of a seismic isolation structure, a cis-form content instead of natural rubber as a base rubber By using a high cis-isoprene rubber with a proportion of 90% by mass or more, it is possible to obtain a rubber layer of a seismic isolation structure having a small decrease in elastic modulus due to repeated deformation and a small so-called Mullins effect. The present invention has been completed by finding that a highly reliable seismic isolation structure that can be maintained well over a long period of time can be obtained.

Accordingly, the present invention includes a lithium isoprene rubber having a cis-form content of 90 to 99% by mass as a rubber component, containing 50% by mass or more of all rubber components, butadiene rubber , and a phenol resin and dicyclopentadiene. A rubber composition for a base-isolated structure comprising a resin .

  The rubber composition of the present invention has a small decrease in elastic modulus due to repeated deformation, and can reliably maintain the desired performance over a long period of time. Using this rubber composition, the rubber layer of the seismic isolation structure can be formed. By forming, a highly reliable seismic isolation structure can be obtained.

Hereinafter, the present invention will be described in more detail.
As described above, the rubber composition of the present invention contains a high cis-isoprene rubber as a rubber component.

  This high cis-isoprene rubber refers to an isoprene rubber having a cis-form content of 90% by mass or more. In this case, although not particularly specified, the cis-form content is preferably 90 to 99 mass% and 91 to 95 mass%.

  Examples of the high cis-isoprene rubber include lithium catalyst-based isoprene rubber (cis-form content ratio: about 92% by mass) and Ziegler catalyst-based isoprene rubber (cis-form content ratio: about 98% by mass). The lithium catalyst-based isoprene rubber is particularly suitable for the cis-form content ratio, and the Malins effect can be more effectively reduced.

  Here, the reason why the Malins effect can be reduced by using such a high cis-isoprene rubber is not necessarily clear, but can be presumed as follows. That is, the Malins effect of natural rubber is due to stretch crystallinity, and the presence of this stretch crystallinity raises the elastic modulus in a high strain region, which increases the Malins effect. On the other hand, since isoprene rubber has less stretched crystallinity than natural rubber, the rise in elastic modulus does not occur, and it is presumed that the Malins effect is reduced. In particular, lithium-catalyzed isoprene rubber, as described above, has a moderately lower cis-form content than Ziegler-catalyzed isoprene rubber, more effectively inhibits stretched crystals, and is considered preferable for reducing the Malins effect. It is done.

  The rubber composition of the present invention is based on high cis-isoprene rubber as described above, and the rubber component in the composition may be used by mixing other rubber together with this high cis-isoprene rubber. Good.

  Other rubbers include natural rubber (NR), styrene butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber, butyl rubber (IIR), halogenated butyl rubber, ethylene-propylene rubber (EPR, EPDM), fluorine rubber, Examples thereof include silicone rubber and urethane rubber, and one or more of these can be used in combination. Of these, natural rubber and butadiene rubber are particularly preferably used from the viewpoint of mechanical properties of vulcanized rubber.

  When a high cis-isoprene rubber and another rubber are mixed and used as the rubber component, the proportion of the high cis-isoprene rubber is 50% by mass or more, preferably 60% by mass or more of the total rubber component.

  Although it does not restrict | limit in particular in the rubber composition of this invention, a synthetic resin can be mix | blended with the said rubber component.

  Examples of the synthetic resin blended in the rubber composition of the present invention include phenol resin, dicyclopentadiene resin, xylene resin, aliphatic (C5) petroleum resin, aromatic (C9) petroleum resin, and alicyclic. -Based petroleum resins, those obtained by copolymerization of C5-based petroleum resins and C9-based petroleum resins, terpene-based resins, ketone resins, modified products of these resins, etc., and using one or more of these Can do.

  The blending amount of these synthetic resins is appropriately selected according to the type of resin to be blended and is not particularly limited, but is usually 2 to 60 parts by weight, particularly 100 parts by weight of the total rubber component. It is preferable to set it as 5-40 mass parts. In this case, if the blending amount is less than 2 parts by mass, the high damping performance by these synthetic resins may not be sufficiently obtained. On the other hand, if it exceeds 60 parts by mass, the fracture characteristics and workability of the unvulcanized rubber are deteriorated. May cause inconvenience such as.

  In addition to the above-mentioned synthetic resin, a known compounding agent that is usually compounded in a rubber composition can be blended with the rubber composition of the present invention in addition to the above synthetic resin. For example, carbon black, silica, silane coupling agent, sulfur as a vulcanizing agent, vulcanization accelerator, vulcanization acceleration aid, various process oils, zinc white, stearic acid, various softening agents, wax, anti-aging agent, An appropriate amount of known compounding agents such as petroleum hydrocarbons, rosin, various fillers such as clay and calcium carbonate can be blended.

  As said vulcanization accelerator, dithiocarbamates such as thiurams such as TMTD (tetramethyldisulfide) and EZ (zinc diethyldithiocarbamate) can be used.

  In addition, organic peroxides, quinone dioximes, polyfunctional acrylic monomers [for example, trimethylol ethane triacrylate (TMETA), trimethylol propane triacrylate (TMPTA), dipentaerythritol ether hexaacrylate (DPEHA) ), Pentaerythritol tetraacrylate (DPEHA), dimethylolpropane diacrylate (TMPTA), stearyl acrylate (SA), etc.], triazine thiol can be used.

  Sulfur-based vulcanizing agents and vulcanization accelerators include powder sulfur, highly dispersible sulfur, insoluble sulfur, etc., which are generally used as rubber vulcanizing agents, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutyl Thiurams such as thiuram disulfide, tetramethylthiuram monosulfide, dipentamethylene thiuram tetrasulfide, pentamethylenedithiocarbamic acid piperidine salt, pipecolyldithiocarbamic acid pipecoline salt, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, Zinc N-ethyl-N-phenyldithiocarbamate, zinc N-pentamethylenedithiocarbamate, zinc dibenzyldithiocarbamate, sodium dimethyldithiocarbamate, diet Dithiocarbamates such as sodium dithiocarbamate, sodium dibutyldithiocarbamate, copper dimethyldithiocarbamate, ferric dimethyldithiocarbamate, tellurium diethyldithiocarbamate, xanthates such as zinc butylxanthate, zinc isopropylxanthate, sodium isopropylxanthate N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazole sulfenamide, N-oxydiethylene-2-benzothiazole sulfenamide, N, N-diisopropyl-2-benzothiazole Examples include sulfenamides such as sulfenamide, and thiazoles such as 2-mercaptobenzothiazole and dibenzothiazyl disulfide.Two or more of these may be used in combination. The amount used is preferably 0.5 to 10 parts by mass, more preferably 1 to 6 parts by mass with respect to 100 parts by mass of the rubber component.

  Examples of carbon black include standard varieties such as SAF, ISAF, HAF, FEF, GPF, SRF (hereinafter, furnace for rubber), and MT carbon black (pyrolytic carbon). The compounding amount is preferably 20 to 70 parts by mass, and more preferably 25 to 65 parts by mass with respect to 100 parts by mass of the rubber component. In addition to carbon black, a plasticizer such as dioctyl sebacate may be added.

  Examples of the antioxidant include N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine (6C), N-phenyl-N′-isopropyl-p-phenylenediamine (3C), 2, Examples include 2,4-trimethyl-1,2-dihydroquinoline polymer (RD). These can use about 0.5-5 mass parts with respect to 100 mass parts of rubber components.

  The rubber composition of the present invention can be produced by kneading the above components using a kneading apparatus such as a known Banbury mixer, roll, kneader or the like. In this case, although not particularly limited, usually, the rubber component, the resin component, the filler, the oil and the like are first mixed and kneaded, and then the vulcanizing agent and the accelerator are added and further kneaded. It is preferable to perform the kneading operation.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not restrict | limited to the following Example.

[Examples 1 to 10 and Comparative Examples 1 to 4]
Each of the blending components A shown in Tables 1 to 3 below is kneaded, and then blended with B zinc white mixed sulfur and accelerator CZ and further kneaded, and rubber compositions of Examples 1 to 10 and Comparative Examples 1 to 4 A product was prepared. Each obtained rubber composition was rolled to a thickness of 2 mm to produce a rubber sheet, and the following physical properties were measured and evaluated. The results are shown in Tables 1 and 2.

(1) Hardness (Hd)
The hardness was determined according to JIS K 6301.
(2) Elongation at break (Eb)
The elongation at break was determined according to JIS K 6301.
(3) Tensile strength (Tb)
The tensile strength was determined according to JIS K 6301.
(4) 100% modulus (Md100)
It calculated | required based on JISK6301.
(5) 200% modulus (Md200)
It calculated | required based on JISK6301.
(6) 300% modulus (Md300)
It calculated | required based on JISK6301.

(7) Shear elastic modulus (G), equivalent damping constant (Heq) and Mullins effect (G1st / G3rd)
[Preparation of shear elastic modulus measurement sample]
One rectangular rubber sheet was produced by punching the rubber sheet into a 25 mm × 25 mm square, and this was sandwiched between two iron plates of 25 mm × 60 mm × 2.3 mm in thickness. That is, as shown in FIG. A rectangular rubber sheet 20 was sandwiched between two iron plates 22 coated with an adhesive so as to have a cross-sectional crank shape. In this way, vulcanization was performed in a state where the iron plate 22 and the surface of the rubber sheet 20 in contact with the iron plate 22 were bonded, and the iron plate 22 and the rubber sheet 20 surface were bonded. As a result, a sample having the shape shown in FIG.
[Measurement of shear modulus]
The sample was placed in a spring stiffness / loss energy measuring device (manufactured by Kakimiya Seisakusho, model: EFH-26-8-10). The shear rate of 50% → 100% → 200% → 300% at a frequency of 0.2 Hz in the outer and inner directions with respect to the rubber sheet 20 with respect to the two iron plates 22 described above (see FIG. 1B). The shear force was applied by changing. At the same shear rate, a shear force was applied three times.
And in each shear rate, the measured value (3 times) was averaged and G and Heq were computed. “G” means a shear elastic modulus (sometimes referred to as equivalent spring stiffness), and “Heq” is an equivalent damping constant, which is an index of the magnitude of hysteresis loss. Further, the Malins effect was calculated from the ratio (G1st / G3rd) of the first shear modulus (G1st) and the third shear modulus (G3rd) at the same shear rate.

In addition, the detail of the mixing | blending component in each table | surface is as follows.
NR: RSS # 4
BR: Asahi Kasei Corporation “Asahi Kasei Diene NF35R”
High Transform IR: Kuraray Co., Ltd. “High Transform IR”
Ziegler IR: JSR Corporation “JSR IR2200” (cis-form ratio 98% by mass)
Lithium IR: Kraton Polymer Japan Co., Ltd. “IR307” (cis-form ratio 92% by mass)
Carbon: Asahi Carbon Co., Ltd. “Asahi # 80-N”
Phenol resin: Sumitomo Bakelite Co., Ltd. “Sumilite Resin 217”
Dicyclopentadiene resin: Nippon Zeon Co., Ltd. “Quinton 1325”
Xylene resin: Fudou "L5"
Aromatic petroleum resin: Nippon Oil Corporation “E-130”
Aroma oil: Idemitsu Kosan Co., Ltd. “Diana Process Oil AH-58”
Zinc flower mixed sulfur: Tsurumi Chemical Co., Ltd. “Z Sulfur”
Accelerator CZ: Ouchi Shinsei Chemical Co., Ltd. “Noxeller CZ”

  From the results of Tables 1 to 3, it was found that the rubber sheet made of the rubber composition of the example had a smaller Mullins effect than the comparative example and was practically superior. The workability was also good.

It is a schematic perspective view which shows the sample produced in the Example.

Explanation of symbols

20 Rubber sheet 22 Iron plate

Claims (2)

As a rubber component, a lithium isoprene rubber having a cis-type content ratio of 90 to 99% by mass contains 50% by mass or more of the total rubber component, butadiene rubber , and a phenol resin and a dicyclopentadiene resin. A rubber composition for a seismic isolation structure. Amount of the phenolic resin and dicyclopentadiene resins, claim 1 Symbol mounting base isolation structure for a rubber composition 2 to 60 parts by weight per 100 parts by weight total rubber component.

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