JP2020075945A - Rubber composition for vibrationproof rubber, vibrationproof rubber, and method for producing rubber composition for vibrationproof rubber - Google Patents

Abstract

To provide a rubber composition for vibrationproof rubber that is a raw material for a vibrationproof rubber capable of attaining the compatibility of a decreased dynamic magnification with an improved set-in fatigue resistance; a method for producing the composition; and a vibrationproof rubber.SOLUTION: A rubber composition for vibrationproof rubber comprises a natural rubber wet masterbatch comprising carbon black. When the total amount of rubber components is 100 pts.mass, a compound of the following formula is contained by 0.1-5 pts.mass, where Rand Reach represent a hydrogen atom, and an alkyl group, alkenyl group or alkynyl group that has 1 to 20 carbon atoms, and Mrepresents an alkali metal ion.SELECTED DRAWING: None

Description

  TECHNICAL FIELD The present invention relates to a rubber composition for a vibration-proof rubber, and particularly to a rubber composition for a vibration-proof rubber, a vibration-proof rubber, and a rubber composition for a vibration-proof rubber that can be suitably used as a vibration-proof member such as an automobile engine mount. The present invention relates to a manufacturing method.

  BACKGROUND ART Anti-vibration rubber is used in vehicles such as automobiles in order to absorb vibrations of an engine and a vehicle body, improve riding comfort and prevent noise. In such an anti-vibration rubber, it is required to reduce the dynamic magnification (dynamic spring constant / static spring constant) and improve the sag resistance at a high level. The dynamic ratio is an index of vehicle interior noise, and the lower the better, the better. Further, since the sag resistance is an abnormal sound such as a tapping sound, the lower this is, the better.

  In Patent Document 1, in order to achieve such an object, in a rubber composition for anti-vibration rubber, while the particle size of carbon black is optimized, natural rubber latex and a slurry containing carbon black are mixed in a liquid phase and dried. It is disclosed to use a rubber wet masterbatch.

  Patent Document 2 discloses that the kinetic magnification of the anti-vibration rubber is reduced by blending a thiosulfate compound such as S- (3-aminopropyl) thiosulfate or a salt thereof.

  In addition, as a technique relating to a rubber wet masterbatch, Patent Document 3 discloses carbon black to which natural rubber latex particles are attached by adding at least a part of natural rubber latex when dispersing carbon black in a dispersion solvent. It is disclosed that after the contained slurry is produced, the slurry and the rest of the natural rubber latex are mixed, coagulated and dried.

JP, 2009-292465, A JP, 2016-117843, A Japanese Patent No. 4738551

  The present invention has been made in view of the above circumstances, and an object thereof is a rubber composition for a vibration-proof rubber which is a raw material of a vibration-proof rubber capable of achieving both low dynamic magnification and improved sag resistance, and the same. It is to provide a manufacturing method and an anti-vibration rubber.

  In order to solve the above-mentioned problems, the present inventor has added a specific compound in a rubber composition containing a natural rubber wet masterbatch, thereby reducing the dynamic ratio and improving the sag resistance of the vulcanized rubber. We found that and can be compatible. The present invention has been made as a result of the above studies, and achieves the above object by the following configurations.

（式（Ｉ）中、Ｒ^１およびＲ^２は、水素原子、ならびに炭素数１〜２０のアルキル基、アルケニル基またはアルキニル基を示し、Ｒ^１およびＲ^２は同一であっても異なっていてもよい。Ｍ^＋はナトリウムイオン、カリウムイオンまたはリチウムイオンを示す。）を０．１〜５質量部含有することを特徴とする。 That is, the rubber composition for vibration damping rubber according to the present invention is a rubber composition for vibration damping rubber containing a natural rubber wet masterbatch containing 5 to 100 parts by mass of carbon black with respect to 100 parts by mass of natural rubber. hand,
When the total amount of the rubber component is 100 parts by mass, the compound represented by the following formula (I):

(In the formula (I), R ¹ and R ² represent a hydrogen atom and an alkyl group, an alkenyl group or an alkynyl group having 1 to 20 carbon atoms, and R ¹ and R ² may be the same or different. M ⁺ represents sodium ion, potassium ion or lithium ion) in an amount of 0.1 to 5 parts by mass.

  The rubber composition for a vibration-proof rubber according to the present invention contains a natural rubber wet masterbatch containing 5 to 100 parts by mass of carbon black with respect to 100 parts by mass of natural rubber, and the compound represented by the formula (I). .. In general, when a natural rubber wet masterbatch is mixed in a rubber composition for vibration-proof rubber, the kinetic ratio of the vulcanized rubber can be lowered. Similarly, when the compound described in the above formula (I) is blended in the rubber composition for vibration proof rubber, the dynamic ratio of the vulcanized rubber can be lowered. However, when the natural rubber wet masterbatch and the compound represented by the formula (I) are both compounded in the rubber composition for vibration damping rubber, a high synergistic effect is obtained as compared with the case where each compound is compounded alone. It turned out to be obtained. Although the reason why such a synergistic effect is obtained is not clear, in the natural rubber wet masterbatch, carbon black is well dispersed in the rubber in advance. It is considered that the compound described in (I) acts efficiently so that a higher synergistic effect can be obtained as compared with the case where each of them is blended alone.

  In the rubber composition for anti-vibration rubber, when the total amount of the rubber component is 100% by mass, it is preferable to contain 10% by mass or more of the natural rubber derived from the natural rubber wet masterbatch. Further, when the total amount of the carbon black is 100% by mass, it is preferable to contain 15% by mass or more of the carbon black derived from the natural rubber wet masterbatch. The present invention also relates to a vibration damping rubber obtained by vulcanizing and molding the rubber composition for vibration damping rubber. The anti-vibration rubber obtained by vulcanizing and molding the rubber composition for anti-vibration rubber has both reduced dynamic magnification and improved sag resistance.

（式（Ｉ）中、Ｒ^１およびＲ^２は、水素原子、ならびに炭素数１〜２０のアルキル基、アルケニル基またはアルキニル基を示し、Ｒ^１およびＲ^２は同一であっても異なっていてもよい。Ｍ^＋はナトリウムイオン、カリウムイオンまたはリチウムイオンを示す。）を０．１〜５質量部配合することを特徴とする。かかる製造方法では、まず工程（ｉ）〜（ｉｉｉ）において、特にカーボンブラックの分散性に優れた天然ゴムウエットマスターバッチを製造する。さらに、工程（ｉ）〜（ｉｖ）の少なくとも一工程において、前記式（Ｉ）に記載の化合物を配合する。これにより、優れた分散状態にあるカーボンブラックに対し、前記式（Ｉ）記載の化合物がさらに効率よく作用する。その結果、本発明に係る製造方法により製造された防振ゴム用ゴム組成物を原料として防振ゴムを製造した場合、動倍率の低減と耐へたり性の向上とを、さらに高いレベルで両立することができる。 Further, the method for producing a rubber composition for a vibration isolating rubber according to the present invention is a rubber composition for a vibration isolating rubber containing at least carbon black, a dispersion solvent, and a natural rubber wet masterbatch obtained from a natural rubber latex solution as raw materials. A method for producing a product, wherein when the carbon black is dispersed in the dispersion solvent, at least a part of the natural rubber latex solution is added to contain the carbon black to which natural rubber latex particles are attached. A step (ii) of producing a slurry solution, and a step (ii) of mixing the slurry solution and the rest of the natural rubber latex solution to produce the carbon black-containing rubber latex solution having natural rubber latex particles attached thereto. When,
A step (iii) of producing a natural rubber wet masterbatch by coagulating and drying the carbon black-containing rubber latex solution having the natural rubber latex particles adhered thereto, and the natural rubber wet masterbatch and various compounding agents are dry mixed. And a step (iv) in which at least one step of the steps (i) to (iv) is 100 parts by mass of the rubber component, the compound represented by the following formula (I):

(In the formula (I), R ¹ and R ² represent a hydrogen atom and an alkyl group, an alkenyl group or an alkynyl group having 1 to 20 carbon atoms, and R ¹ and R ² may be the same or different. M ⁺ represents sodium ion, potassium ion or lithium ion) in an amount of 0.1 to 5 parts by mass. In such a manufacturing method, first, in steps (i) to (iii), a natural rubber wet masterbatch having particularly excellent dispersibility of carbon black is manufactured. Further, in at least one step of steps (i) to (iv), the compound represented by the formula (I) is blended. As a result, the compound represented by the formula (I) acts more efficiently on the carbon black in an excellent dispersed state. As a result, when a vibration-proof rubber is manufactured by using the rubber composition for vibration-proof rubber manufactured by the manufacturing method according to the present invention as a raw material, both reduction of dynamic ratio and improvement of sag resistance are achieved at a higher level. can do.

  The rubber composition for a vibration-proof rubber according to the present invention contains a natural rubber wet masterbatch containing carbon black and the compound represented by the formula (I).

  The natural rubber wet masterbatch is obtained by using at least carbon black, a dispersion solvent, and a natural rubber latex solution containing natural rubber latex as a main component as raw materials. The natural rubber wet masterbatch can be manufactured by a known manufacturing method, or a commercially available product can be used. However, in the present invention, it is preferable to use a natural rubber wet masterbatch produced by steps (i) to (iii) in the method for producing a rubber composition for a vibration-proof rubber shown below.

As carbon black, for example, SAF class (N100 series by ASTM number), ISAF class (N200 series), HAF class (300 series), FEF class (N500 series), GPF class (N600 series), SRF class Carbon black used in the usual rubber industry, such as the same 700 series, can be used. The carbon black may be a granulated carbon black or a non-granulated carbon black that has been granulated in consideration of its handling property in the usual rubber industry.

  As the dispersion solvent, it is particularly preferable to use water, but water containing an organic solvent may be used.

  The natural rubber latex solution is a natural product of the metabolic action of plants, and is preferably a natural rubber / water system in which the dispersion solvent is water. The number average molecular weight of the natural rubber in the natural rubber latex used in the present invention is preferably 2,000,000 or more, more preferably 2.5,000,000 or more. For natural rubber latex solution, concentrated latex and fresh latex called field latex can be used without distinction.

  Hereinafter, an example of the method for producing the rubber composition for vibration-proof rubber will be specifically described. Such a production method is a step of producing a slurry solution containing carbon black to which natural rubber latex particles are adhered by adding at least a part of the natural rubber latex solution when dispersing carbon black in a dispersion solvent ( i), a slurry solution, and the rest of the natural rubber latex solution are mixed to produce a carbon black-containing rubber latex solution to which natural rubber latex particles adhere, and (ii) carbon to which the natural rubber latex particles adhere. The method includes a step (iii) of coagulating and drying the rubber latex solution containing black to produce a natural rubber wet masterbatch, and a step (iv) of dry mixing the natural rubber wet masterbatch and various compounding agents.

(1) Step (i)
In the step (i), when the carbon black is dispersed in the dispersion solvent, at least a part of the natural rubber latex solution is added to obtain a slurry solution containing the carbon black to which the natural rubber latex particles are attached. To manufacture. The natural rubber latex solution may be mixed with a dispersion solvent in advance, and then carbon black may be added to disperse the solution. Further, carbon black may be added to the dispersion solvent, and then the carbon black may be dispersed in the dispersion solvent while adding the natural rubber latex solution at a predetermined addition rate, or the carbon black may be added to the dispersion solvent. Then, the carbon black may be dispersed in the dispersion solvent while adding a fixed amount of the natural rubber latex solution in several batches. By dispersing carbon black in a dispersion solvent in the presence of the natural rubber latex solution, a slurry solution containing carbon black to which the natural rubber latex particles adhere can be manufactured.

  In the step (i), the amount of solid content (rubber) of the natural rubber latex solution to be added is preferably 0.25 to 15%, and preferably 0.5 to 6% by mass ratio with carbon black. preferable. Further, the solid content (rubber) concentration in the natural rubber latex solution to be added is preferably 0.2 to 5% by mass, and more preferably 0.25 to 1.5% by mass. In these cases, it is possible to manufacture the tire member in which the dispersion degree of the carbon black is enhanced while surely attaching the natural rubber latex particles to the carbon black. The concentration of carbon black in the slurry solution is not particularly limited and may be, for example, 1 to 20% by mass, or 3 to 10% by mass.

  In the step (i), the method of mixing the carbon black and the dispersion solvent in the presence of the natural rubber latex solution includes a high shear mixer, a high shear mixer, a homomixer, a ball mill, a bead mill, a high pressure homogenizer, an ultrasonic homogenizer and a colloid mill. A method of dispersing carbon black using a general disperser of

  The "high shear mixer" is a mixer including a rotor and a stator, and the rotor rotates with a precise clearance provided between the rotor capable of high-speed rotation and a fixed stator. Means a mixer with high shear. In order to produce such a high shearing action, it is preferable that the clearance between the rotor and the stator is 0.8 mm or less and the peripheral speed of the rotor is 5 m / s or more. As such a high shear mixer, a commercially available product can be used, and examples thereof include "High Shear Mixer" manufactured by SILVERSON.

  In the present invention, when carbon black and a dispersion solvent are mixed in the presence of a natural rubber latex solution to produce a slurry solution containing carbon black having natural rubber latex particles attached, an interface for improving the dispersibility of carbon black is provided. Activators may be added. As the surfactant, known surfactants in the rubber industry can be used, and examples thereof include nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants and the like. Be done. Further, alcohol such as ethanol may be used instead of the surfactant or in addition to the surfactant. However, when a surfactant is used, it is feared that the rubber physical properties of the final vulcanized rubber may be deteriorated. Therefore, the compounding amount of the surfactant is 100 parts by mass of the solid content (rubber) of the rubber latex solution. On the other hand, it is preferably 2 parts by mass or less, more preferably 1 part by mass or less, and it is preferable that substantially no surfactant is used.

(2) Step (ii)
In the step (ii), the slurry solution and the remaining natural rubber latex solution are mixed to produce a carbon black-containing rubber latex solution having natural rubber latex particles attached thereto. The method for mixing the slurry solution and the remaining natural rubber latex solution in the liquid phase is not particularly limited, and the slurry solution and the remaining natural rubber latex solution are mixed with a high shear mixer, a high shear mixer, a homomixer, a ball mill. , A bead mill, a high-pressure homogenizer, an ultrasonic homogenizer, a colloid mill and the like can be used for mixing. If necessary, the entire mixing system such as a disperser may be heated during mixing.

  Considering the drying time and labor in the next step (iii), the remaining natural rubber latex solution preferably has a higher solid content (rubber) concentration than the rubber latex solution added in step (i). The solid content (rubber) concentration is preferably 10 to 60% by mass, more preferably 20 to 30% by mass.

(3) Step (iii)
In the step (iii), the carbon black-containing rubber latex solution to which the natural rubber latex particles are attached is coagulated and dried to produce a natural rubber wet masterbatch. Examples of the coagulation method include a method in which a coagulant is contained in a carbon black-containing rubber latex solution to which rubber latex particles are attached. In this case, as the coagulant, an acid such as formic acid or sulfuric acid which is usually used for coagulating a rubber latex solution, or a salt such as sodium chloride can be used. For drying, for example, using a single screw extruder, it is possible to perform dehydration while applying a shearing force to the carbon black-containing rubber coagulated product while heating at 100 to 250 ° C.

  After the step (iii), a drying step may be separately provided, if necessary, in order to further reduce the moisture content of the natural rubber wet masterbatch. As a method for drying the natural rubber wet masterbatch, various drying devices such as a single screw extruder, an oven, a vacuum dryer and an air dryer can be used.

(4) Step (iv)
In the step (iv), the natural rubber wet masterbatch and various compounding agents are dry mixed. Examples of usable compounding agents include additional rubber, additional carbon black, sulfur-based vulcanizing agents, vulcanization accelerators, antioxidants, silica, silane coupling agents, zinc oxide, methylene acceptors and methylene donors, Examples thereof include compounding agents usually used in the rubber industry such as stearic acid, vulcanization accelerating aids, vulcanization retarders, organic peroxides, softening agents such as waxes and oils, and processing aids. The compound represented by the formula (I) may be added in the step (iv) or in the steps (i) to (iii) for producing a natural rubber wet masterbatch. The compound represented by the formula (I) will be described later.

  The rubber component contained in the rubber composition for vibration-proof rubber of the present invention may be only the natural rubber derived from the above-mentioned natural rubber wet masterbatch, or an additional rubber may be blended separately. However, when the total amount of the rubber component is 100% by mass, the natural rubber derived from the natural rubber wet masterbatch is preferably contained in an amount of 10% by mass or more, more preferably 25% by mass or more, and 50% by mass or more. It is preferably 70% by mass or more, and particularly preferably 70% by mass or more. Natural rubber Wet masterbatch derived natural rubber may be compounded in addition to natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), butyl rubber (IIR). , And a diene synthetic rubber such as acrylonitrile-butadiene rubber (NBR); halogenated butyl rubber such as brominated butyl rubber (BR-IIR); other polyurethane rubber, acrylic rubber, fluororubber, silicone rubber, chlorosulfonated polyethylene, etc. Synthetic rubbers included are included. Among these, it is preferable to use at least one selected from the group consisting of natural rubber (NR), butadiene rubber (BR), and styrene butadiene rubber (SBR) as the additional rubber.

  The carbon black contained in the rubber composition for a vibration-proof rubber of the present invention may be only the carbon black derived from the natural rubber wet masterbatch, or an additional carbon black may be blended separately. However, when the total amount of carbon black is 100% by mass, the content of carbon black derived from the natural rubber wet masterbatch is preferably 15% by mass or more, more preferably 40% by mass or more, and 70% by mass or more. Is particularly preferable. Similarly, when the total amount of carbon black is 100% by mass, the additional carbon black is preferably 85% by mass or less, more preferably 60% by mass or less, and particularly preferably 30% by mass or less. .. The total carbon black content contained in the rubber composition for vibration-proof rubber according to the present invention is preferably 20 to 100 parts by mass, and 25 to 80 parts by mass, when the total amount of the rubber component is 100 parts by mass. It is more preferably part by mass, and particularly preferably 30 to 60 parts by mass.

（式（Ｉ）中、Ｒ^１およびＲ^２は、水素原子、ならびに炭素数１〜２０のアルキル基、アルケニル基またはアルキニル基を示し、Ｒ^１およびＲ^２は同一であっても異なっていてもよい。Ｍ^＋はナトリウムイオン、カリウムイオンまたはリチウムイオンを示す。）を０．１〜５質量部含有する。 The rubber composition for a vibration-proof rubber according to the present invention is a compound represented by the following formula (I) when the total amount of rubber components is 100 parts by mass:

(In the formula (I), R ¹ and R ² represent a hydrogen atom and an alkyl group, an alkenyl group or an alkynyl group having 1 to 20 carbon atoms, and R ¹ and R ² may be the same or different. 0.1 to 5 parts by mass of M ⁺ represents sodium ion, potassium ion or lithium ion.

を使用することが特に好ましい。 In order to increase the affinity for carbon black, a compound represented by the following formula (I ′) in which R ¹ and R ² in the formula (I) are hydrogen atoms and M ⁺ is a sodium ion:

Is particularly preferably used.

  When the total amount of the rubber component is 100 parts by mass, the content of the compound represented by the formula (I) is 0.1 to 5 parts by mass, preferably 0.3 to 3 parts by mass, and 0. It is particularly preferably 5 to 2 parts by mass.

  The rubber composition for a vibration-proof rubber of the present invention comprises a natural rubber wet masterbatch and the compound represented by the formula (I), an additional rubber, an additional carbon black, a sulfur-based vulcanizing agent, a vulcanization accelerator, silica and a silane. The compounding agents usually used in the rubber industry, such as coupling agents, stearic acid, vulcanization accelerating aids, vulcanization retarders, antioxidants, softeners such as waxes and oils, processing aids, etc. Can be appropriately blended and used within a range that does not impair.

  The rubber composition for a vibration-proof rubber according to the present invention preferably contains a sulfur-based vulcanizing agent. Sulfur as the sulfur-based vulcanizing agent may be ordinary sulfur for rubber, and for example, powdered sulfur, precipitated sulfur, insoluble sulfur, highly dispersible sulfur and the like can be used. The content of sulfur in the rubber composition for a vibration-proof rubber according to the present invention is 0.2 to 5 parts by mass with respect to 100 parts by weight of the rubber component, in consideration of the dynamic ratio and heat resistance of the manufactured vibration-proof rubber. Is preferable, and more preferably 0.5 to 3 parts by mass.

  As the vulcanization accelerator, usually used for rubber vulcanization, sulfenamide-based vulcanization accelerator, thiuram-based vulcanization accelerator, thiazole-based vulcanization accelerator, thiourea-based vulcanization accelerator, guanidine-based vulcanization Vulcanization accelerators such as accelerators and dithiocarbamate vulcanization accelerators may be used alone or in an appropriate mixture. It is preferable to use a sulfenamide-based vulcanization accelerator from the viewpoint of lowering the dynamic expansion ratio of the produced vibration-insulating rubber. Further, the compounding amount of the vulcanization accelerator is preferably 0.1 to 5 parts by mass, and more preferably 0.2 to 3 parts by mass with respect to 100 parts by mass of the rubber component.

  As the anti-aging agent, usually used for rubber, aromatic amine anti-aging agent, amine-ketone anti-aging agent, monophenol anti-aging agent, bisphenol anti-aging agent, polyphenol anti-aging agent, dithiocarbamic acid Antiaging agents such as salt antiaging agents and thiourea antiaging agents may be used alone or in admixture.

  The rubber composition for vibration-proof rubber of the present invention comprises a natural rubber wet masterbatch and the compound represented by the formula (I), a sulfur-based vulcanizing agent, a vulcanization accelerator, silica, a silane coupling agent, stearic acid, Vulcanization accelerating aids, vulcanization retarders, antioxidants, softeners such as waxes and oils, processing aids and other compounding agents usually used in the rubber industry, such as Banbury mixers, kneaders, rolls, etc. It is obtained by kneading using a kneader used in the rubber industry.

  Further, the mixing method of each of the above components is not particularly limited, and a sulfur-based vulcanizing agent, and a compounding component other than the vulcanizing system component such as a vulcanization accelerator are kneaded in advance to form a master batch, and the remaining components are added. And further kneading, a method of adding each component in an arbitrary order and kneading, a method of simultaneously adding all components and kneading, and the like.

  By kneading the above-mentioned components, molding and processing, and then performing vulcanization, it is possible to manufacture a vibration-proof rubber in which both reduction in dynamic ratio and improvement in durability are achieved. The vulcanization temperature may be, for example, 120 to 200 ° C, preferably 140 to 180 ° C.

Specific examples of the anti-vibration rubber application according to the present embodiment include mounts such as engine mounts, strut mounts, body mounts, cab mounts, member mounts, differential mounts, suspension bushes, arm bushes, torque bushing bushes, and torsion. Various anti-vibration rubbers for automobiles such as dampers, muffler hangers, damper pulleys, dynamic dampers, etc. can be mentioned. Further, in addition to automobiles, it can be suitably used for anti-vibration rubber for railway vehicles, anti-vibration rubber for industrial machines, anti-vibration rubber for construction, anti-vibration rubber for anti-vibration rubber, etc.

  Hereinafter, the embodiments of the present invention will be described in more detail.

(Preparation of rubber composition)
The rubber compositions of Examples 1 to 6 and Comparative Examples 1 to 4 were compounded with 100 parts by weight of the rubber component according to the compounding recipe of Table 1 and kneaded using a normal Banbury mixer to prepare the rubber composition. did. Each compounding agent shown in Table 1 is shown below.

・ NR: Natural rubber, RSS # 3
-Compound of formula (I) ((2Z) -4-[(4-aminophenyl) amino] -4-oxo-2-butenoate sodium): "Sumilink 200" manufactured by Sumitomo Chemical Co., Ltd.
・ Carbon black FEF (N550): "Seast SO" manufactured by Tokai Carbon Co., Ltd.
・ Carbon black HAF (N339): "Seast KH" manufactured by Tokai Carbon Co., Ltd.
・ Zinc oxide: Mitsui Mining & Smelting Co., Ltd. "Zinc oxide type 1"
-Stearic acid: "Lunack S-20" manufactured by Kao Corporation
・ Wax: "OZOACE2701" manufactured by Nippon Seiro Co., Ltd.
・ Anti-aging agent 6C: "SANTOFLEX6PPD" manufactured by Flexsys
・ Anti-aging agent RD: "Nocrac 224" manufactured by Ouchi Shinko Chemical Co., Ltd.
・ Sulfur: Hosoi Chemical Co., Ltd. "Rubber powder sulfur 150 mesh"
・ Vulcanization accelerator CZ: "Nox Cellar DM-P" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
・ Vulcanization accelerator TS: Sansan Chemical Co., Ltd. "Suncellar TS"

Examples 1 to 6 and Comparative Example 3
Using a natural rubber concentrated latex (Dry Rubber Content = 60%) manufactured by Resitex Co., carbon black was added to the diluted natural rubber aqueous latex solution adjusted to a concentration of 0.5% by mass so as to have the blending amount shown in Table 1. (The concentration of carbon black with respect to water is 1% by mass), and the carbon black is dispersed therein by using Robomix manufactured by PRIMIX (conditions of the Robomix: 9000 rpm, 30 minutes), whereby natural rubber latex particles are obtained. An adhered carbon black-containing slurry solution was produced (step (i)). Next, the natural rubber latex solution (25% by mass) was added to the carbon black-containing slurry solution to which the natural rubber latex particles produced in step (i) were attached so that the blending amount shown in Table 1 was obtained, Then, the mixture was mixed using a SANYO household mixer SM-L56 type (mixer conditions 11300 rpm, 30 minutes) to produce a carbon black-containing rubber latex solution having natural rubber latex particles attached thereto (step (ii)).

  Carbon black-containing natural rubber was prepared by adding formic acid (10% by mass) as a coagulant to the carbon black-containing natural rubber latex solution to which the natural rubber latex particles produced in step (ii) were adhered until the pH of the entire solution reached pH 4. A natural rubber wet master batch (GMB-1 or GMB-2) is produced by producing a coagulated product, and then adding the obtained carbon black-containing natural rubber coagulated product to a screw press V-01 type manufactured by Suehiro EPM Co., Ltd., and drying. Was produced (step (iii)).

  The obtained natural rubber wet masterbatch was mixed with various compounding agents containing the compound represented by the formula (I) and dry-mixed with a Banbury mixer to produce a rubber composition (step (iv)). ). The compounding ratios in Table 1 are shown in parts by mass (phr) when the total amount of rubber components is 100 parts by mass.

Comparative Examples 1-2, 4-5
Instead of using a natural rubber wet masterbatch, natural rubber, carbon black, the compound represented by formula (I) and various compounding agents are blended and dry-blended using a Banbury mixer to produce a rubber composition. did.

  The obtained vulcanized rubber was evaluated according to the following evaluation criteria.

[Moving ratio]
The static spring constant Ks and the dynamic spring constant Kd of the vulcanized rubber sample (50 mmΦ × 25 mm) obtained by vulcanizing each rubber composition at 150 ° C. for 25 minutes using a predetermined mold were measured by the following method. And the ratio (Kd / Ks) was calculated to obtain the dynamic magnification. For Examples 1 to 4 and Comparative Example 2, index evaluation was performed with the result of Comparative Example 1 as 100, and for Examples 5 to 6 and Comparative Example 5, index evaluation was performed with the result of Comparative Example 4 as 100. .. The smaller the index, the lower the dynamic ratio of the vulcanized rubber and the better the dynamic characteristics.

-Static spring constant (Ks): Tensilon manufactured by Orientec Co., Ltd. was used as a measuring machine, and a vulcanized rubber sample was compressed at a crosshead speed of 10 mm / min between 0 and 5 mm (compression up to 20%) to 2. It was repeated twice, and a second load-deflection diagram was drawn and calculated based on the following formula.
Static spring constant (N / mm) = (w2-w1) / (δ2-δ1)
(In the formula, w1 is the load (N) when the deflection amount δ1 is 1.3 mm, and w2 is the load (N) when the deflection amount δ2 is 3.8 mm.)

-Dynamic spring constant (Kd): Dynamic servo manufactured by Sagimiya Seisakusho Co., Ltd. is used as a measuring machine, and initial strain (compression) is 10%, frequency is 100 Hz, and amplitude is ± 0.05 mm (± 0.2%). Was calculated by the calculation method described (unit is N / mm).

[Settling resistance]
Based on JIS-K 6262, the settling resistance (CS (%) @ 100 ° C., 250 h) of the vulcanized rubber was evaluated. Regarding the evaluation, for Examples 1 to 4 and Comparative Example 2, index evaluation was performed with the result of Comparative Example 1 as 100, and for Examples 5 to 6 and Comparative Example 5, index evaluation was performed with the result of Comparative Example 4 as 100. I went. The smaller the index, the better the sag resistance of the vulcanized rubber.

The results are as shown in Table 1. Comparative example 1 in which natural rubber, carbon black, the compound described in formula (I) and various compounding agents were dry-mixed in comparison with comparative example 1 as a control, and natural rubber wet master In Comparative Example 3 using the batch and not using the compound represented by the formula (I), it can be seen that the sag resistance is not improved although the dynamic magnification is lowered. On the other hand, in Examples 1 to 4 in which both the natural rubber wet masterbatch and the compound represented by the formula (I) were used, the sag resistance was significantly improved, and in comparison with Comparative Examples 2 and 3. It can be seen that the dynamic magnification is remarkably reduced. It is understood that the same effect can be obtained in Examples 5 to 6 in which carbon black is changed as compared with Examples 1 to 4.

Claims (5)

A rubber composition for anti-vibration rubber, comprising a natural rubber wet masterbatch containing 5 to 100 parts by mass of carbon black with respect to 100 parts by mass of natural rubber,
When the total amount of the rubber component is 100 parts by mass, the compound represented by the following formula (I):

(In the formula (I), R ¹ and R ² represent a hydrogen atom and an alkyl group, an alkenyl group or an alkynyl group having 1 to 20 carbon atoms, and R ¹ and R ² may be the same or different. M ⁺ represents sodium ion, potassium ion or lithium ion) in an amount of 0.1 to 5 parts by mass.   The rubber composition for a vibration-proof rubber according to claim 1, containing 10% by mass or more of the natural rubber derived from the natural rubber wet masterbatch, when the total amount of the rubber component is 100% by mass.   The rubber composition for a vibration-proof rubber according to claim 1 or 2, containing 15% by mass or more of carbon black derived from the natural rubber wet masterbatch, when the total amount of the carbon black is 100% by mass.   An anti-vibration rubber obtained by vulcanizing and molding the rubber composition for anti-vibration rubber according to claim 1. At least carbon black, a dispersion solvent, and a method for producing a rubber composition for anti-vibration rubber containing a natural rubber wet masterbatch obtained by using a natural rubber latex solution as a raw material,
A step of producing a slurry solution containing the carbon black having the natural rubber latex particles attached thereto by adding at least a part of the natural rubber latex solution when the carbon black is dispersed in the dispersion solvent (i )When,
A step (ii) of mixing the slurry solution and the rest of the natural rubber latex solution to produce the carbon black-containing rubber latex solution having natural rubber latex particles attached thereto;
A step (iii) of producing a natural rubber wet masterbatch by coagulating and drying the carbon black-containing rubber latex solution to which the natural rubber latex particles adhere,
And a step (iv) of dry-mixing the natural rubber wet masterbatch and various compounding agents,
In at least one of the steps (i) to (iv), when the total amount of the rubber component is 100 parts by mass, the compound represented by the following formula (I):

(In the formula (I), R ¹ and R ² represent a hydrogen atom and an alkyl group, an alkenyl group or an alkynyl group having 1 to 20 carbon atoms, and R ¹ and R ² may be the same or different. M ⁺ represents sodium ion, potassium ion or lithium ion) in an amount of 0.1 to 5 parts by mass.