JP5674690B2 - Anti-vibration rubber composition and anti-vibration rubber member - Google Patents

Description

  The present invention relates to an anti-vibration rubber member used for automobile engine mounts and the like, and an anti-vibration rubber composition of the material.

  In a vehicle such as an automobile, a vibration-proof rubber member is disposed at a site that is a source of vibration and noise to reduce vibration transmission and noise diffusion. This type of anti-vibration rubber member is required to have a strength for supporting heavy objects such as an engine and an anti-vibration performance that absorbs and suppresses vibration. One of the characteristics showing the anti-vibration performance is dynamic magnification. The dynamic magnification is the ratio of the dynamic spring constant to the static spring constant (dynamic spring constant (Kd) / static spring constant (Ks)), and the smaller the dynamic magnification, the higher the anti-vibration performance.

  As a material for the vibration-proof rubber member, natural rubber is mainly used because of its high tensile strength and low heat generation due to vibration. And in order to improve the intensity | strength and durability of natural rubber, carbon black, a silica, etc. are mix | blended as a reinforcing material. However, when a reinforcing material is blended, the dynamic magnification of the vibration isolating rubber member increases. Silica is a naturally-derived material compared to carbon black, and therefore has a large amount, and has the advantage that the product is not colored black. However, the surface of silica is covered with hydrophilic silanol groups. On the other hand, natural rubber is hydrophobic. Therefore, when silica is kneaded with natural rubber, the affinity between the two is low, and peeling tends to occur at the interface between the natural rubber and silica. Thereby, there existed a problem that sufficient reinforcement was not acquired.

  In order to improve the affinity between natural rubber and silica, a method of blending silica particles treated with a silane coupling agent into natural rubber is known (see, for example, Patent Documents 1 and 2). Patent Document 3 discloses a method in which a diene rubber latex is modified with a silane coupling agent, an alkoxysilane compound is added, and silica particles are generated and dispersed by a sol-gel method.

JP 2011-174034 A JP 2008-7770 A JP-A-9-176385

  By treating the surface of silica with a silane coupling agent, the affinity for natural rubber is improved. However, as described in Patent Documents 1 and 2, the rubber composition before vulcanization and the surface-treated silica are kneaded by a Banbury mixer or the like. Silica tends to aggregate due to hydrogen bonding of the remaining silanol groups. For this reason, in the conventional kneading method, it is difficult to uniformly disperse silica in the rubber material, and there is a limit to the improvement of the reinforcing property. In order to advance the reaction between the surface-treated silica and the rubber composition, it is necessary to knead at a temperature of 120 ° C. or higher. However, when kneaded for a long time at a high temperature, the rubber component may be deteriorated. Also, since heat is generated during kneading, it is difficult to control the reaction.

  On the other hand, in the method described in Patent Document 3, silica particles are generated and dispersed in a liquid (modified diene rubber latex). Specifically, first, a diene rubber latex and a silane coupling agent are reacted to graft bond the silane coupling agent to the rubber particles. Next, an alkoxysilane compound is added to the diene rubber latex modified with the silane coupling agent to produce and disperse silica particles in the latex. Thus, in the method described in Patent Document 3, in order to improve the affinity between the generated silica particles and rubber particles, a silane coupling agent is bonded to the rubber particles in advance.

  In the method described in Patent Document 3, the reaction is a two-stage reaction: (1) generation of silica particles by a sol-gel reaction, and (2) reaction of the generated silica particles and a silane coupling agent grafted to rubber particles. is necessary. For this reason, it is difficult to react with the silane coupling agent in a state where the generated silica particles are uniformly dispersed. Therefore, as in the above kneading method, the dispersibility of the silica particles is not sufficient. It is also difficult to reliably bond all the generated silica particles to rubber particles. There is also a possibility that unreacted alkoxysilane compounds may remain around the rubber particles. Therefore, even in the rubber material obtained by the method described in Patent Document 3, the reinforcing property is not sufficient.

  The present invention has been made in view of such a situation, and both improvement in strength and reduction in dynamic magnification are realized by reliably bonding silica with natural rubber particles in a uniformly dispersed state. An object of the present invention is to provide an anti-vibration rubber member and an anti-vibration rubber composition capable of producing the same.

  (1) In order to solve the above problems, the vibration-insulating rubber composition of the present invention includes a silica-containing modified natural rubber material and a crosslinking agent, and the silica-containing modified natural rubber material contains an alkoxysilane in the natural rubber latex. It is produced by adding a vinyl monomer having a natural rubber particle to graft copolymerize the vinyl monomer, generating silica by hydrolysis and condensation of the alkoxysilane, and then drying the obtained latex. It is characterized by.

In the vibration-proof rubber composition of the present invention, a silica-containing modified natural rubber material is used as a raw rubber material. The silica-containing modified natural rubber material is produced by reacting a natural rubber latex with a vinyl monomer having an alkoxysilane. Here, as natural rubber latex, latex of deproteinized natural rubber from which protein has been removed can be used in addition to natural rubber. In the present specification, alkoxysilane means a structure in which 1 to 3 alkoxy groups (—OR, R: alkyl group) are bonded to a silicon atom. The vinyl monomer means a monomer having a vinyl structure. In addition to the vinyl group (—CH═CH ₂ ), the vinyl structure has a mode in which the hydrogen atom of the vinyl group is substituted with a substituent such as a methyl group (—CH ₃ ) (—C (CH ₃ ) ═CH ₂ ). Including.

  A vinyl monomer having an alkoxysilane is grafted to natural rubber particles by a vinyl structure. At the same time, silica is produced by hydrolysis and condensation of the grafted vinyl monomer alkoxysilane. Thus, the silica-containing modified natural rubber material is produced by a one-step reaction in which a natural rubber latex is reacted with a vinyl monomer having an alkoxysilane. That is, it is not necessary to treat the natural rubber latex with a silane coupling agent in advance.

  In the silica-containing modified natural rubber material, the produced silica is reliably bonded to the natural rubber particles as part of the grafted vinyl monomer. For this reason, silica hardly peels from the natural rubber particles, and the reinforcing effect is high. Therefore, according to the vibration-insulating rubber composition of the present invention using the silica-containing modified natural rubber material, a strong crosslinked product (vibration-insulating rubber member) can be produced. Further, since silica and natural rubber particles are firmly bonded, friction between silica and natural rubber particles due to vibration is reduced. For this reason, in the anti-vibration rubber member to be manufactured, the energy loss is reduced and the dynamic magnification is reduced.

  Further, according to the silica-containing modified natural rubber material, silica is less likely to aggregate as compared with the case where silica is kneaded with natural rubber or silica is reacted with and bonded to silane-coupled natural rubber. For this reason, silica can be uniformly dispersed around the natural rubber particles. That is, in the silica-containing modified natural rubber material, since there are few silica agglomerates, the fracture starting point is small. Moreover, when the dispersibility of silica improves, the surface area of silica increases. Thereby, a reinforcement property improves. Therefore, according to the anti-vibration rubber composition of the present invention using the silica-containing modified natural rubber material, a strong anti-vibration rubber member can be produced. Moreover, since the dispersibility of silica is high, friction between silica due to vibration is reduced. For this reason, in the anti-vibration rubber member to be manufactured, the energy loss is reduced and the dynamic magnification is reduced.

  (2) The anti-vibration rubber member of the present invention is obtained by crosslinking the anti-vibration rubber composition of the present invention having the constitution (1).

  As described in (1) above, the vibration-insulating rubber member of the present invention has high strength. Moreover, according to the vibration-insulating rubber member of the present invention, the energy loss and the dynamic magnification can be reduced as compared with the conventional vibration-insulating rubber member having the same static spring constant.

A TEM photograph of the silica-containing modified natural rubber material is shown (magnification: 10,000 times). An enlarged TEM photograph of the same material is shown (magnification: 30,000 times). It is a graph which shows the value of 100% modulus with respect to the compounding quantity of a silica powder. It is a graph which shows the value of the tensile strength with respect to the compounding quantity of a silica powder. It is a graph which shows the value of the dynamic magnification with respect to a static spring constant. It is a graph which shows the value of tan-delta with respect to a static spring constant.

  Hereinafter, the anti-vibration rubber composition and anti-vibration rubber member of the present invention will be described in detail.

<Anti-Vibration Rubber Composition>
The anti-vibration rubber composition of the present invention includes a silica-containing modified natural rubber material and a crosslinking agent. Silica-containing modified natural rubber material is made by adding vinyl monomer having alkoxysilane to natural rubber latex and graft copolymerizing the vinyl monomer to natural rubber particles, and generating silica by hydrolysis and condensation of alkoxysilane. And then dried. As natural rubber latex, latex of deproteinized natural rubber from which protein has been removed can be used in addition to natural rubber. When deproteinized natural rubber is used, the reaction rate in graft copolymerization can be improved.

As the natural rubber, for example, field latex, latex treated by adding ammonia to field latex (high ammonia latex), or the like may be used. Various known methods can be adopted for deproteinization of natural rubber. For example, (i) a method of degrading protein by adding a proteolytic enzyme or bacteria to natural rubber latex (see JP-A-6-56902), and (ii) natural rubber latex by a surfactant such as soap. (Iii) A protein denaturant selected from the group consisting of the urea compound represented by the following general formula (1) and NaClO is added to natural rubber latex to denature the protein in the latex. The method of removing after processing (refer to JP 2004-99696 A) and the like.
RNHCONH ₂ (1)
[In formula (1), R is H, a C1-C5 alkyl group.]
The rubber content (dry rubber mass, hereinafter the same) concentration of natural rubber latex is not particularly limited. If the rubber concentration is too low, the amount of rubber material obtained is small, which is not economical. On the other hand, when the rubber concentration is too high, the rubber component in the latex becomes unstable. For this reason, aggregation of rubber particles tends to occur, and it becomes difficult to cause the graft copolymerization reaction to proceed uniformly. For example, the rubber concentration is desirably 10% by mass or more and 60% by mass or less.

  As a vinyl monomer having alkoxysilane (hereinafter, simply referred to as “vinyl monomer” as appropriate), one having an alkoxysilane at one end of the main chain and a vinyl structure at the other end is desirable. In this case, the alkoxysilane and the vinyl structure may be directly bonded, and a carbon chain (which may contain an oxygen atom), an aromatic ring, or the like is interposed between the alkoxysilane and the vinyl structure. Also good. Specifically, vinyltrimethoxysilane, vinyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3 -Methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, etc. are mentioned.

  The addition amount of the vinyl monomer is desirably 5 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the rubber content in the natural rubber latex. When the addition amount of the vinyl monomer is less than 5 parts by mass, a desired reinforcing effect cannot be obtained. More preferably, it is 10 parts by mass or more. On the other hand, when the addition amount of the vinyl monomer exceeds 60 parts by mass, the viscoelasticity inherent to natural rubber may be inhibited. More preferably, it is 30 parts by mass or less.

When the vinyl monomer is graft copolymerized with the natural rubber latex, a polymerization initiator is used. The polymerization initiator may be added to the natural rubber latex before adding the vinyl monomer. Examples of the polymerization initiator include potassium persulfate (KPS), ammonium persulfate (APS), benzoyl peroxide (BPO), hydrogen peroxide, cumene hydroperoxide, tert-butyl hydroperoxide (TBHPO), and di-tert. -Peroxides such as butyl peroxide and 2,2-azobisisobutyronitrile. From the viewpoint of lowering the polymerization temperature, a redox polymerization initiator may be used. Examples of the reducing agent combined with the peroxide as a redox polymerization initiator include tetraethylenepentamine (TEPA), mercaptans, acidic sodium sulfite, reducing metal ions, ascorbic acid, and the like. Examples of suitable combinations as redox-based polymerizable initiators include TBHPO and TEPA, hydrogen peroxide and Fe ²⁺ salt, KPS and sodium acid sulfite, and the like. The addition amount of the polymerization initiator is preferably 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the rubber content in the natural rubber latex.

  The pH of the natural rubber latex is not particularly limited. For example, a pH of about 8 to 10 is suitable. An emulsifier may be added in advance to the natural rubber latex. As the emulsifier, any of various known anionic surfactants, nonionic surfactants, and cationic surfactants can be used. Examples of the anionic surfactant include carboxylic acid type, sulfonic acid type, and sulfuric acid ester type. Examples of nonionic surfactants include polyoxyalkylene ethers and polyhydric alcohol fatty acid esters. Examples of the cationic surfactant include alkylamine salt type and imidazolinium salt type. For example, an anionic surfactant such as sodium dodecyl sulfate is suitable.

  The reaction between the natural rubber latex and the vinyl monomer may be performed with stirring at room temperature for about 0.5 to 12 hours. As a result, the vinyl monomer is graft copolymerized with the natural rubber particles, and silica is generated by hydrolysis and condensation of the alkoxysilane. The produced silica is bonded to the natural rubber particles as a part of the graft-bonded vinyl monomer in a state of being dispersed around the natural rubber particles.

  By drying and solidifying the obtained latex, a silica-containing modified natural rubber material is produced. For example, a coating film formed by applying latex on the substrate surface or immersing the substrate in latex may be heated and dried. In the produced silica-containing modified natural rubber material, the vinyl monomer (graft chain) graft-copolymerized to the natural rubber particles forms a matrix. The matrix consisting of graft chains contains the produced silica and surrounds the natural rubber particles. That is, the silica-containing modified natural rubber material has a nanomatrix structure in which natural rubber particles are dispersed in a matrix composed of a graft chain containing silica.

  From the viewpoint of increasing the surface area of silica and enhancing the reinforcing effect, the particle diameter of silica in the matrix is desirably 150 nm or less. It is more preferable that it is 100 nm or less. On the other hand, from the viewpoint that the hydrolysis and condensation reaction of alkoxysilane can be controlled, the silica particle diameter is desirably 10 nm or more. It is more preferable that it is 15 nm or more. As the particle diameter of silica, for example, the length of the longest part of silica in an image observed with a transmission electron microscope (TEM) may be adopted.

  The anti-vibration rubber composition of the present invention contains a crosslinking agent in addition to the silica-containing modified natural rubber material. As the cross-linking agent, sulfur (powder sulfur, precipitated sulfur, insoluble sulfur, etc.) or organic peroxide usually used for cross-linking of natural rubber may be used. When sulfur is used as the crosslinking agent, the amount of sulfur is preferably 0.3 parts by mass or more and 7 parts by mass or less with respect to 100 parts by mass of the silica-containing modified natural rubber material. More preferably, it is 1 part by mass or more and 5 parts by mass or less. If the amount of sulfur is too small, it cannot be sufficiently cross-linked, and the dynamic magnification may increase. On the other hand, if the amount of sulfur is too large, the heat resistance decreases.

  The anti-vibration rubber composition of the present invention may further contain additives such as a vulcanization accelerator, zinc oxide, a processing aid, an antiaging agent, and a softening agent. Moreover, the anti-vibration rubber composition of the present invention may contain carbon black, silica powder or the like as a reinforcing material. However, even if a reinforcing material is not blended, the strength of the vibration-insulating rubber member produced from the vibration-insulating rubber composition of the present invention is large. Moreover, when a reinforcing material is blended, the dynamic magnification of the vibration isolating rubber member may be increased. Therefore, it is not necessary to positively add a reinforcing material to the vibration-proof rubber composition of the present invention. That is, a preferred embodiment of the vibration-proof rubber composition of the present invention includes an embodiment that does not contain carbon black and silica powder. Of course, a small amount of carbon black may be blended for the purpose of coloring and the like, not for the purpose of reinforcement. When the anti-vibration rubber composition of the present invention is prepared without including silica powder, the silica powder addition step which is difficult to handle can be omitted.

  The anti-vibration rubber composition of the present invention is prepared by blending a silica-containing modified natural rubber material with a crosslinking agent and, if necessary, an additive, and kneading using a Banbury mixer, kneader, roll or the like. do it.

<Anti-vibration rubber member>
The anti-vibration rubber member of the present invention is obtained by crosslinking the anti-vibration rubber composition of the present invention. That is, the anti-vibration rubber member of the present invention is manufactured by holding the prepared anti-vibration rubber composition at, for example, a temperature of 150 to 170 ° C. for 5 to 30 minutes to crosslink and molding it into a predetermined shape. The The anti-vibration rubber member of the present invention includes an engine mount, a mission mount, a body mount, a cab mount, a member mount, a differential mount, a connecting rod, a torque rod, a strut bar cushion, a center bearing support, and a torsional damper disposed in a vehicle such as an automobile. Suitable for steering rubber coupling, tension rod bush, bound stopper, FF engine roll stopper, muffler hanger, stabilizer ring rod, radiator support, control arm bush, suspension arm bush, etc.

  Next, the present invention will be described more specifically with reference to examples.

<Production of deproteinized natural rubber latex>
As natural rubber latex, high ammonia latex (rubber content concentration 60.2 mass%, ammonia content concentration 0.7 mass%) manufactured by Golden Hope (Malaysia) was used. First, the high ammonia latex was diluted so that the rubber concentration was 30% by mass. Next, 1.2 g of sodium dodecyl sulfate (SDS: anionic surfactant) was added to 1200 g of the diluted latex to stabilize the latex. Subsequently, 12 g of urea was added to the latex, and the mixture was stirred at room temperature for 10 minutes at a rotation speed of 200 rpm to perform proteolytic treatment. Thereafter, the latex after the proteolytic treatment was centrifuged at a rotational speed of 8000 rpm for 45 minutes. Then, the separated cream of the upper layer was redispersed in an aqueous SDS solution and stirred at a rotational speed of 300 rpm for 30 minutes. Such centrifugation and redispersion were repeated three times to produce a deproteinized natural rubber latex. The concentration of the SDS aqueous solution used for redispersion was 1% by mass for the first time, 0.5% by mass for the second time, and 0.1% by mass for the third time.

<Manufacture of silica-containing modified natural rubber material>
First, 200 g of deproteinized natural rubber latex prepared with a rubber concentration of 20% by mass is placed in a stainless steel container and subjected to nitrogen replacement for 1 hour while stirring at 30 ° C. at a rotation speed of 200 rpm. The dissolved oxygen was removed. Next, 0.238 g of a polymerization initiator TBHPO and 0.500 g of TEPA were added to the latex at room temperature. Further, 8 g of vinyltriethoxysilane (BTES) was added dropwise and stirred for 2 hours to carry out graft copolymerization. The obtained latex was transferred to a petri dish and dried at 50 ° C. to produce a sheet-like silica-containing modified natural rubber material.

<TEM observation>
The produced silica-containing modified natural rubber material was observed using TEM (Hitachi H-800, acceleration voltage 200 kV). Ultrathin sections were prepared at −90 ° C. using an ultramicrotome (Sorvall MT-6000). FIG. 1 shows a TEM photograph of the silica-containing modified natural rubber material (magnification: 10,000 times). FIG. 2 shows an enlarged TEM photograph of the same material (magnification: 30,000 times).

  As shown in FIG. 1, a matrix layer containing silica particles (black portion) was observed around the natural rubber particles (white portion). That is, it was confirmed that the silica-containing modified natural rubber material has a nanomatrix structure in which natural rubber particles are dispersed in a matrix composed of a graft chain containing silica. Further, as shown in an enlarged view in FIG. 2, large particles having a particle size of about 150 nm and small particles having a particle size of about 20 nm were confirmed as silica.

<Preparation of anti-vibration rubber composition of Example 1>
First, 100 parts by mass of silica-containing modified natural rubber material, 5 parts by mass of zinc oxide (made by Sakai Chemical Industry Co., Ltd.), and a processing aid stearic acid ("Lunac (registered trademark)" made by Kao Corporation 1 part by mass of S30) and 2 parts by mass of carbon black (“Seast S” manufactured by Tokai Carbon Co., Ltd.) were kneaded in a lab plast mill set at 120 ° C. Next, the obtained kneaded product, 1 part by mass of a vulcanization accelerator (“Sunseller (registered trademark) CZ-G” manufactured by Sanshin Chemical Industry Co., Ltd.) and sulfur (“Saru” manufactured by Tsurumi Chemical Industry Co., Ltd.) The anti-vibration rubber composition was prepared by kneading 2.5 parts by mass of Fax T-10 ") using a roll. The prepared anti-vibration rubber composition was used as the anti-vibration rubber composition of Example 1.

<Preparation of anti-vibration rubber composition of comparative example>
[Comparative Example 1]
In place of the silica-containing modified natural rubber material, a deproteinized natural rubber that is a raw material of the silica-containing modified natural rubber material is used, and silica powder (“Nipsil (manufactured by Tosoh Silica Co., Ltd.) as a reinforcing material is used. (Registered trademark) VN3 ") 20 parts by mass and silane coupling agent (" Si75 "manufactured by Evonik Degussa Japan Co., Ltd.) 1 part by mass, except that the same as the anti-vibration rubber composition of Example 1. Thus, an anti-vibration rubber composition of Comparative Example 1 was prepared.

[Comparative Examples 2 to 4]
In place of the silica-containing modified natural rubber material, natural rubber (RSS # 3) is used, and 10 to 30 parts by mass of silica powder (same as above) and silane coupling agent (same as above) 1 or 2 parts as a reinforcing material The anti-vibration rubber compositions of Comparative Examples 2 to 4 were prepared in the same manner as the anti-vibration rubber composition of Example 1 except that the parts were blended. Table 1 summarizes the raw materials of the anti-vibration rubber compositions of Example 1 and Comparative Examples 1 to 4.

<Production and evaluation of cross-linked product>
The anti-vibration rubber compositions of Example 1 and Comparative Examples 1 to 4 were vulcanized under conditions of 160 ° C. × 30 minutes to produce a crosslinked product. And the test piece using the said crosslinked material was produced for every following evaluation items, and the characteristic of the crosslinked material was evaluated.

[Tensile properties]
The anti-vibration rubber composition was press-molded under the above conditions to produce a rubber sheet (crosslinked product) having a thickness of 2 mm. The rubber sheet was punched out to produce a dumbbell-shaped No. 5 test piece defined in JIS K 6251 (2010). Using the prepared test piece, 100% elongation tensile stress (100% modulus) and tensile strength (TS) were measured according to the tensile test method specified in the JIS. The measurement results are shown in FIGS. FIG. 3 shows a value of 100% modulus with respect to the amount of silica powder. FIG. 4 shows the value of tensile strength with respect to the amount of silica powder.

  The cross-linked product prepared from the vibration-proof rubber composition of Example 1 (hereinafter referred to as “cross-linked product of Example 1”) does not contain silica powder as a reinforcing material. However, as shown in FIG. 3, the 100% modulus of the crosslinked product of Example 1 is a crosslinked product prepared from the vibration-proof rubber compositions of Comparative Examples 1 to 4 containing silica powder (hereinafter referred to as “crosslinked product of Comparative Example”). It was larger than the 100% modulus). Moreover, as shown in FIG. 4, the tensile strength of the crosslinked product of Example 1 was larger than the tensile strength of the crosslinked product of the comparative example. From the above, it was confirmed that the anti-vibration rubber composition of the present invention can produce a crosslinked product having a high strength without blending a reinforcing material as in the prior art. That is, it was confirmed that the vibration-proof rubber member of the present invention has a large strength.

[Dynamic characteristics]
(1) Dynamic magnification A cylindrical rubber piece (diameter 50 mm, height 25 mm) was produced from the vibration-proof rubber composition. By placing disc-shaped metal fittings (diameter 60 mm, thickness 6 mm) one by one on the two bottom surfaces of the rubber pieces and pressing them under the above conditions, the rubber pieces are vulcanized and the metal fittings are attached to both bottom surfaces. Glued. In this manner, a test piece in which a columnar cross-linked product was sandwiched between a pair of metal fittings was produced. Using the prepared test piece, the static spring constant and the dynamic spring constant of the crosslinked product were calculated according to the test method defined in JIS K6385 (2001). That is, a load was applied from the axial direction, the test piece was compressed by 7 mm, and then unloaded and restored. Then, the load was applied again and the test piece was compressed 7 mm. At that time, a load-deflection curve in the process of applying the load is created, and the static spring constant (Ks) is calculated by reading the load value when the deflection is 1.5 mm and 3.5 mm from the load-deflection curve. did. Further, in a state where the test piece was compressed 2.5 mm in the axial direction, constant displacement harmonic compression vibration having an amplitude of 0.05 mm centered on the compression position was applied at a frequency of 100 Hz. Then, the dynamic spring constant (Kd ₁₀₀ ) at ₁₀₀ Hz was calculated by a non-resonant method (cited JIS K6394) defined in the above JIS. The dynamic magnification was calculated by dividing the dynamic spring constant by the static spring constant (Kd ₁₀₀ / Ks).

(2) Loss coefficient (tan δ)
In a state where the test piece produced in the above (1) was compressed 2.5 mm in the axial direction, constant displacement harmonic compression vibration having an amplitude of ± 0.5 mm centered on the compression position was applied at a frequency of 15 Hz. Then, the loss coefficient (tan δ) at 15 Hz of the crosslinked product was calculated by a non-resonant method (cited JIS K6394) defined in JIS K6385 (2001).

(3) Results FIG. 5 shows the value of the dynamic magnification with respect to the static spring constant. As shown in FIG. 5, among the cross-linked products of Example 1 and Comparative Example, the dynamic ratio of the cross-linked product of Example 1 was the smallest. That is, the dynamic magnification of the crosslinked product of Example 1 was smaller than the dynamic magnification of the crosslinked products of Comparative Examples 1 and 2 having a static spring constant smaller than that of the crosslinked product of Example 1.

  FIG. 6 shows the value of tan δ with respect to the static spring constant. As shown in FIG. 6, tan δ of the crosslinked product of Example 1 was the smallest among the crosslinked products of Example 1 and Comparative Example. That is, the tan δ of the crosslinked product of Example 1 was smaller than the tan δ of the crosslinked product of Comparative Examples 1 and 2 in which the static spring constant was smaller than that of the crosslinked product of Example 1.

  In the crosslinked product of Example 1, silica and natural rubber particles are firmly bonded. Silica is uniformly dispersed around the natural rubber particles. For this reason, it is considered that the friction between silica and natural rubber particles due to vibration and the friction between silica are reduced, the low energy loss is improved, and the dynamic magnification is reduced. From the above, it was confirmed that the vibration-insulating rubber composition of the present invention can produce a crosslinked product having a small energy loss and dynamic magnification. Further, it was confirmed that the vibration-proof rubber member of the present invention can realize low energy loss and low dynamic magnification.

Claims (5)

Including a silica-containing modified natural rubber material and a crosslinking agent;
The silica-containing modified natural rubber material is obtained by adding a vinyl monomer having an alkoxysilane to natural rubber latex and graft copolymerizing the vinyl monomer to natural rubber particles, and at the same time hydrolyzing and condensing the alkoxysilane. An anti-vibration rubber composition produced by drying the resulting latex after the production.   The anti-vibration rubber composition according to claim 1, wherein the vinyl monomer having an alkoxysilane has an alkoxysilane at one end of the main chain and a vinyl structure at the other end.   The vibration-insulating rubber composition according to claim 1 or 2, wherein the addition amount of the vinyl monomer having an alkoxysilane is 5 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the rubber content of the natural rubber latex. .   The silica-containing modified natural rubber material is obtained by dispersing the natural rubber particles in a matrix comprising a graft chain containing the silica, and the particle diameter of the silica is 10 nm or more and 150 nm or less. The anti-vibration rubber composition according to any one of the above. An anti-vibration rubber member obtained by crosslinking the anti-vibration rubber composition according to any one of claims 1 to 4.