JP2007224085A - Cross-linking rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cross-linking rubber composition which can control the occurrence of vulcanization reversion and can prevent the deterioration of cross-link density due to the long period storage of a rubber. <P>SOLUTION: This cross-linking rubber composition is characterized by containing the following components (A) to (C) and not containing sulfur element as a cross-linking agent. (A) A dienic rubber. (B) Fullerene. (C) A benzothiazole-based vulcanization promoter excluding mercaptobenzothiazole. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rubber composition for cross-linking, and more particularly to a rubber composition for cross-linking used in an engine mount or the like for suppressing the vibration supporting function of an engine such as an automobile and vibration transmission.

Conventionally, rubber materials such as natural rubber and synthetic rubber have been used as vibration-insulating rubber compositions used for engine mounts, suspension bushes, and the like for suppressing support functions and vibration transmission of engines such as automobiles. ing. As a crosslinking agent for such a rubber material, a sulfur vulcanizing agent or a peroxide crosslinking agent is usually used (for example, see Patent Document 1).
JP 2004-231905 A

  When the above sulfur vulcanizing agent is used, monosulfide bonds, disulfide bonds, polysulfide bonds, etc. are formed by sulfur. However, when vulcanized at a high temperature (about 180 ° C), polysulfide bonds, etc. are broken during vulcanization. There is a drawback that reversion occurs. In addition, when the above peroxide crosslinking agent is used, crosslinking at a higher temperature is possible than when using a sulfur vulcanizing agent. However, when the rubber after crosslinking is stored for a long period of time, the peroxide sublimates. Thus, there are difficulties such as a decrease in crosslink density.

  The present invention has been made in view of such circumstances, and its object is to provide a rubber composition for cross-linking that can suppress the occurrence of reversion and can suppress a decrease in cross-linking density due to long-term storage of rubber. To do.

In order to achieve the above object, the rubber composition for crosslinking according to the present invention has a constitution in which the following (A) to (C) are essential components and no sulfur element is contained as a crosslinking agent.
(A) Diene rubber.
(B) Fullerene.
(C) A benzothiazole vulcanization accelerator excluding mercaptobenzothiazole.

  That is, the present inventor has conducted extensive research in order to obtain a rubber composition for cross-linking that can suppress the occurrence of reversion and suppress the decrease in cross-linking density due to long-term storage of rubber. And as a result of repeated studies on a crosslinking system that replaces the conventional sulfur crosslinking system and peroxide crosslinking system, focusing on fullerenes with excellent radical scavenging properties, radicals are fed to this fullerene and diene rubber (polymer). It has been found that the intended purpose can be achieved when used in combination with a benzothiazole structure type vulcanization accelerator having a function to be generated, and the present invention has been achieved. The reason for this is not clear, but is presumed as follows. That is, as shown in the schematic diagram of FIG. 1, when the diene rubber A and the benzothiazole structure type vulcanization accelerator C react with each other, radicals R are generated from the vulcanization accelerator C, and this is the diene rubber A. The radical R is trapped by the fullerene B to be three-dimensionalized, and a crosslinked structure by a three-dimensional network is formed between the polymers of the diene rubber A via the fullerene B. Since this fullerene functions as a cross-linking agent, this cross-linked structure is a very stable structure compared to sulfur cross-linked structures such as polysulfide bonds. Therefore, even when the reaction is performed at a high temperature (about 180 ° C.), the crosslinked chain of the diene rubber A is not broken, and the physical property change due to the change in the crosslinked structure due to heat aging is small. Further, since it can be vulcanized at a high temperature, rubber can be vulcanized in a short time, and production efficiency is improved.

  Since the rubber composition for crosslinking of the present invention contains diene rubber (component A), fullerene (component B), and benzothiazole vulcanization accelerator (component C) excluding mercaptobenzothiazole, As described above, a crosslinked structure by a three-dimensional network can be formed between polymers of diene rubber (A component) via fullerene (B component). Since this fullerene is considered to function as a cross-linking agent, this cross-linked structure is a very stable structure compared to a sulfur cross-linked structure such as a polysulfide bond. Therefore, even when the reaction is carried out at a high temperature (about 180 ° C.), the crosslinked chain of the diene rubber A is not broken, and the effect that the physical property change due to the change of the crosslinked structure due to heat aging is small is obtained. Further, since it can be vulcanized at a high temperature, rubber can be vulcanized in a short time, and the effect of improving production efficiency can be obtained.

  Moreover, the vulcanization accelerator after vulcanization | cure that the compounding quantity of the said specific vulcanization accelerator (C component) is 1-8 weight part with respect to 100 weight part of said diene rubber (A component). The effect that the residue of (C component) does not bleed on the rubber surface is also obtained.

  Furthermore, when the blending amount of the fullerene (component B) is 0.1 to 8 parts by weight with respect to 100 parts by weight of the diene rubber (component A), the rubber material cost can be kept low. Can also be obtained.

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

  The rubber composition for crosslinking of the present invention can be obtained using a diene rubber (component A), fullerene (component B), and a specific vulcanization accelerator (component C).

  In the present invention, fullerene (component B) is used as a crosslinking agent, a benzothiazole vulcanization accelerator excluding mercaptobenzothiazole is used as a specific vulcanization accelerator (component C), and elemental sulfur is used as a crosslinking agent. The biggest feature is not using.

  In the present invention, “does not contain elemental sulfur as a crosslinking agent” means that a sulfur vulcanizing agent used for vulcanizing ordinary rubber is not blended in the rubber composition for crosslinking, that is, sulfur-free. Means.

  In the present invention, the reason for removing mercaptobenzothiazole (MBT) from the benzothiazole vulcanization accelerator is that mercaptobenzothiazole (MBT) is hydrogen in the X part of -SX that is bonded to the carbon of the thiazole ring. Therefore, it is estimated that the crosslinking reactivity is inferior.

  The diene rubber (component A), which is an essential component of the crosslinking rubber composition of the present invention, is not particularly limited. For example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene -Butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), ethylene-propylene-diene rubber (EPDM) and the like. These may be used alone or in combination of two or more. Among these, NR is preferably used in terms of versatility, vibration isolation performance, and durability.

  In the rubber composition for crosslinking according to the present invention, fullerene (B component) is used together with the diene rubber (A component).

In the present invention, fullerene is a generic term for a carbon atom having a spherical network structure. A typical fullerene, C _60, has 12 five-membered rings and 20 six-membered rings that surround the five-membered ring. Each vertex of the network has the same shape as a soccer ball (60). It has a structure in which a carbon atom is located. Its diameter is 1 nm (0.7 nm as a carbon skeleton). The fullerene of the present invention is not limited to the above C _60, is composed of 70 C ₇₀ composed of carbon atoms, 82 carbon C ₈₂ composed of carbon atoms, 124 carbon atoms _C124 etc. are mentioned, and these are used alone or in combination of two or more.

  The blending amount of the fullerene (component B) is preferably 0.1 to 8 parts, particularly preferably 0.1 to 2 parts, with respect to 100 parts by weight (hereinafter abbreviated as “part”) of the diene rubber. That is, if the amount of the fullerene is less than 0.1 part, the crosslinking may not proceed sufficiently, and if it exceeds 8 parts, the viscosity and cost of the kneaded rubber may be increased.

  Next, the specific vulcanization accelerator (C component) used together with the diene rubber (A component) and fullerene (B component) has a benzothiazole skeleton represented by the following structural formula (A). A benzothiazole vulcanization accelerator (excluding MBT) is used.

  As the specific vulcanization accelerator (component C), specifically, N-cyclohexyl-2-benzothiazolylsulfenamide (CBS) represented by the following structural formula (1), the following structural formula Dibenzothiazyl disulfide (MBTS) represented by (2), N-oxydiethylene-2-benzothiazolylsulfenamide (OBS) represented by the following structural formula (3), and the following structural formula (4) Mercaptobenzothiazole sodium salt (NaMBT) represented by the following structural formula (5), zinc salt of mercaptobenzothiazole (ZnMBT) represented by the following structural formula (6), 2- (4 -Morpholinodithio) benzothiazole, 2- (2,4-dinitro-phenyl) mercaptobenzothiazole represented by the following structural formula (7), represented by the following structural formula (8) Mercaptobenzothiazole cyclohexylamine salt (CMBT), N, N′-diethylthiocarbamoyl-2-benzothiazoyl sulfide represented by the following structural formula (9), represented by the following structural formula (10) N-tert-butyl-2-benzothiazoylsulfenamide (BBS), N, N′-dicyclohexyl-2-benzothiazoylsulfenamide represented by the following structural formula (11) and the like can be mentioned. These may be used alone or in combination of two or more. Among these, MBTS is preferable because it has a benzothiazole skeleton at both ends and is excellent in cross-linking reactivity.

  The amount of the specific vulcanization accelerator (component C) is preferably 1 to 8 parts, particularly preferably 2 to 5 parts, per 100 parts of the diene rubber (component A). That is, when the C component is less than 1 part, the crosslinking reactivity tends to be inferior. Conversely, when the C component exceeds 8 parts, a residue of the vulcanization accelerator (C component) is formed on the rubber surface after vulcanization. This is because there is a risk of bleeding.

  In addition to the above components A to C, the crosslinking rubber composition of the present invention contains carbon black, an antioxidant, a processing aid, a softener, an acid acceptor, a peptizer (shacking agent), and the like. It is also possible to mix | blend suitably as needed.

  The carbon black is not particularly limited, and examples thereof include various grades of carbon black such as SAF class, ISAF class, HAF class, MAF class, FEF class, GPF class, SRF class, FT class, and MT class. . These may be used alone or in combination of two or more.

  The compounding amount of such carbon black is preferably 10 to 100 parts, particularly preferably 30 to 80 parts with respect to 100 parts of the diene rubber. That is, if the blending amount of the carbon black is less than 10 parts, the supporting performance of the rubber is reduced. Conversely, if the blending amount of the carbon black exceeds 100 parts, the Mooney viscosity increases and the processability tends to deteriorate. This is because of

  Examples of the anti-aging agent include carbamate-based anti-aging agents, phenylenediamine-based anti-aging agents, phenol-based anti-aging agents, diphenylamine-based anti-aging agents, quinoline-based anti-aging agents, imidazole-based anti-aging agents, and waxes. can give.

  The blending amount of such an anti-aging agent is preferably 1 to 7 parts, particularly preferably 2 to 5 parts, with respect to 100 parts of the diene rubber (component A).

  Examples of the processing aid include stearic acid, fatty acid esters, fatty acid amides, hydrocarbon resins, and the like.

  The amount of such a processing aid is preferably 1 to 5 parts, particularly preferably 1 to 3 parts, per 100 parts of the diene rubber (component A).

  The acid acceptor is not particularly limited, and examples thereof include zinc white (ZnO) and magnesium oxide.

  As described above, the crosslinking rubber composition of the present invention does not contain elemental sulfur as a crosslinking agent and uses a specific benzothiazole vulcanization accelerator (component C). It is also possible to make a composition in which no acid agent is blended (acid acceptor-free). In the crosslinking rubber composition of the present invention, when the acid acceptor is free, effects such as an increase in crosslinking density and an improvement in rubber strength can be obtained. This is because, when an acid acceptor such as ZnO is used in combination, a part of the radical generated by the vulcanization accelerator (component C) is trapped by ZnO or the like, resulting in poor crosslinking efficiency. It is presumed that this problem is reduced when the acid agent is free.

  The rubber composition for crosslinking of the present invention includes, for example, carbon black, a processing aid (if necessary) in the diene rubber (component A), fullerene (component B) and a specific vulcanization accelerator (component C). It can be prepared by appropriately blending additives such as stearic acid and the like and kneading them using a closed kneader, roll, biaxial kneader or the like.

  A rubber product obtained by crosslinking the crosslinking rubber composition of the present invention can be produced, for example, by crosslinking the crosslinking rubber composition prepared as described above by applying heat under predetermined conditions. . In this case, since there is no vulcanization return due to high temperature vulcanization as in the case of using sulfur as a vulcanizing agent, it is possible to crosslink at a high crosslinking temperature, shortening the crosslinking time and increasing production efficiency. Can do.

  In this rubber product, a crosslinked structure is formed between the polymers of the diene rubber via fullerene. Since the crosslinked structure is a very stable structure as described above, even when the reaction is performed at a high temperature (about 180 ° C.), the crosslinked chain of the diene rubber A is not broken, and is caused by heat aging. Little change in physical properties due to change in cross-linked structure.

  The rubber composition for cross-linking of the present invention is suitably used for vibration-proof materials such as engine mounts, stabilizer bushes, suspension bushes and the like used for automobiles, and hoses that require heat resistance.

  Next, examples will be described together with comparative examples. However, the present invention is not limited to these examples.

  First, prior to the examples and comparative examples, the following materials were prepared.

[Natural rubber]
RSS # 3 [ML _{1 + 4} (100 ° C.): 65]

[Mixed fullerene]
Frontier Carbon Co., nanom mix MF-S [Main component: Mixture of C ₆₀ and C ₇₀ (85 wt%), other higher fullerenes (15 wt%)]

〔Carbon black〕
FEF grade carbon black (manufactured by Tokai Carbon Co., Seast SO)

[Zinc oxide]
Mitsui Metal Mining Co., Ltd., zinc oxide

〔stearic acid〕
Made by Kao, Lunac S30

[Vulcanization accelerator (CBS)]
N-cyclohexyl-2-benzothiazolylsulfenamide represented by the structural formula (1) (manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., Noxeller CZ-G)

[Vulcanization accelerator (MBTS)]
Dibenzothiazyl disulfide represented by the structural formula (2) (Ouchi Shinsei Chemical Co., Ltd., Noxeller DM)

[Vulcanization accelerator (OBS)]
N-oxydiethylene-2-benzothiazolylsulfenamide represented by the structural formula (3) (Ouchi Shinsei Chemical Co., Ltd., Noxeller MSA-G)

[Vulcanization accelerator (ZnMDC)]
Zinc dimethyldithiocarbamate represented by the following structural formula (a) (Ouchi Shinsei Chemical Co., Ltd., Noxeller PZ)

[Vulcanization accelerator (TMTM)]
Tetramethylthiuram monodisulfide represented by the following structural formula (b) (Ouchi Shinsei Chemical Co., Ltd., Noxeller TS)

[Vulcanization accelerator (DOTG)]
Diortolyl guanidine represented by the following structural formula (c) (Sokushinol DT, manufactured by Sumitomo Chemical Co., Ltd.)

[Vulcanization accelerator (MBT)]
Mercaptobenzothiazole represented by the following structural formula (d) (Ouchi Shinsei Chemical Co., Ltd., Noxeller M)

[Examples 1-8, Comparative Examples 1-6]
The components shown in Table 1 and Table 2 below were blended in the proportions shown in the same table, and these were kneaded using a closed kneader to prepare a rubber composition.

  Using the rubber compositions of Examples and Comparative Examples thus obtained, each characteristic was evaluated according to the following criteria. These results are shown in Tables 1 and 2 below.

[Initial physical properties]
Each rubber composition was cross-linked by applying heat at 160 ° C. for 20 minutes, and punched with a JIS No. 5 dumbbell to prepare a rubber sheet having a thickness of 2 mm. And using this rubber sheet, based on JISK6251, tensile strength (TB), elongation at break (EB), and hardness (Hs) were measured, respectively.

(Heat aging characteristics)
The rubber compositions of Example 7 and Comparative Example 6 were cross-linked by applying heat at 160 ° C. for 20 minutes to produce a rubber sheet having a thickness of 2 mm. Then, a JIS No. 5 dumbbell was punched from this rubber sheet, and tensile strength (TB), elongation at break (EB), and hardness (Hs) were measured. Next, the heat aging characteristic was calculated | required based on the accelerated aging test A-2 method of JISK6257 (test condition: implemented at 100 degreeC x 70 hours).

  From the result of the said table | surface, all the Example goods were excellent in normal state physical property.

  On the other hand, Comparative Examples 1 to 5 were not worthy of measuring physical properties without sufficient crosslinking. This can be seen from the crosslinking curves shown in FIGS. Further, when the comparative example 6 product and the example 7 product were compared, the comparative example 6 product was inferior in heat aging characteristics to the example 7 product. The reason for this is that in Example 7 product, a cross-linked structure is formed by a three-dimensional network between natural rubber via mixed fullerene, whereas Comparative Example 6 product is a sulfur cross-linked structure such as polysulfide bond. The product of Example 7 is presumed to be because, even when reacted at a high temperature, the crosslinked chain of the natural rubber is not broken, and the physical property change due to the change of the crosslinked structure due to heat aging is small.

  Next, the crosslinked state was evaluated according to the following criteria using the rubber compositions of Examples and Comparative Examples.

[Crosslinked state]
For the rubber compositions of Example 1 and Comparative Example 5, the crosslinking state at a temperature of 150 ° C. was measured using a crosslinking state measuring machine (manufactured by ALPHA TECHNOLOGIES, RUBBER PROCESS ANALYZER RPA2000P), and the crosslinking state was evaluated. The results are shown in FIG.

  From the results shown in FIG. 2, the product of Example 1, which used both the mixed fullerene and the vulcanization accelerator (CBS), had a rapid increase in torque and was excellent in crosslinking reactivity. In contrast, in Comparative Example 5 using only mixed fullerene and not using a vulcanization accelerator (CBS), the increase in torque was very slow and the crosslinking reactivity was poor.

  Moreover, also about the rubber composition of Examples 1, 2 and Comparative Examples 1-3, the crosslinked state was evaluated similarly to the above. The results are shown in FIG.

  From the results shown in FIG. 3, all of the examples had a rapid increase in torque and were excellent in crosslinking reactivity. On the other hand, since all of Comparative Examples 1 to 3 used a vulcanization accelerator having no benzothiazole skeleton, the torque was hardly increased and the crosslinking reactivity was poor.

  Further, for the rubber compositions of Examples 1 to 3 and Comparative Example 4, the crosslinking state at a temperature of 180 ° C. was measured using a crosslinking state measuring machine (manufactured by ALPHA TECHNOLOGIES, RUBBER PROCESS ANALYZER RPA2000P) to evaluate the crosslinking state. Went. The results are shown in FIG.

  From the results shown in FIG. 4, all of the products according to the examples showed a rapid increase in torque, excellent cross-linking reactivity, and no reversion occurred even when vulcanized at a high temperature (180 ° C.). In contrast, the product of Comparative Example 4 uses a vulcanization accelerator (MBT) having a benzothiazole skeleton, and in this product, the X part of -SX bonded to the carbon of the thiazole ring is hydrogen. Therefore, it is estimated that the crosslinking reactivity is inferior.

  The specific benzothiazole vulcanization accelerator (component C) is represented by the structural formulas (4) to (11) instead of the structural formulas (1) to (3). It was confirmed that the same excellent effects as those of the examples using the structural formulas (1) to (3) can be obtained even when using.

  The rubber composition for cross-linking of the present invention is suitably used for vibration-proof materials such as engine mounts, stabilizer bushes, suspension bushes and the like used for automobiles, and hoses that require heat resistance.

It is a schematic diagram for demonstrating the crosslinked structure in the rubber composition for bridge | crosslinking of this invention. It is a graph which shows the bridge | crosslinking state in 150 degreeC about the rubber composition of Example 1 and Comparative Example 5. FIG. It is a graph which shows the bridge | crosslinking state in 150 degreeC about the rubber composition of Examples 1, 2 and Comparative Examples 1-3. It is a graph which shows the crosslinked state in 180 degreeC about the rubber composition of Examples 1-3 and the comparative example 4. FIG.

Claims (4)

A rubber composition for crosslinking comprising the following (A) to (C) as essential components and not containing sulfur element as a crosslinking agent.
(A) Diene rubber.
(B) Fullerene.
(C) A benzothiazole vulcanization accelerator excluding mercaptobenzothiazole. The vulcanization accelerator of the above (C) is N-cyclohexyl-2-benzothiazolylsulfenamide represented by the following structural formula (1), dibenzothiazyl disulfide represented by the following structural formula (2) N-oxydiethylene-2-benzothiazolylsulfenamide represented by the following structural formula (3), a sodium salt of mercaptobenzothiazole represented by the following structural formula (4), the following structural formula (5 ), A zinc salt of mercaptobenzothiazole represented by the following formula, 2- (4-morpholinodithio) benzothiazole represented by the following structural formula (6), 2- (2, represented by the following structural formula (7), 4-dinitro-phenyl) mercaptobenzothiazole, a cyclohexylamine salt of mercaptobenzothiazole represented by the following structural formula (8), N represented by the following structural formula (9) N′-diethylthiocarbamoyl-2-benzothiazoyl sulfide, N-tert-butyl-2-benzothiazoylsulfenamide represented by the following structural formula (10) and the following structural formula (11) The rubber composition for crosslinking according to claim 1, which is at least one selected from the group consisting of N, N'-dicyclohexyl-2-benzothiazoylsulfenamide.

  The rubber composition for crosslinking according to claim 1 or 2, wherein the blending amount of the vulcanization accelerator (C) is 1 to 8 parts by weight with respect to 100 parts by weight of the diene rubber (A).   The amount of the fullerene (B) is 0.1 to 8 parts by weight based on 100 parts by weight of the diene rubber (A). Rubber composition.

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