JP5501812B2 - Rubber composition and pneumatic tire - Google Patents

Description

  The present invention relates to a rubber composition and a pneumatic tire using the same.

  In order to improve the fuel efficiency of a pneumatic tire, it is known that it is effective to reduce the hysteresis loss of the rubber composition constituting the tire so as to reduce heat generation. As the demand for lower fuel consumption of automobiles increases, it is required to improve the low heat build-up of the rubber composition.

  By the way, conventionally, diamine carbamate is generally used as a vulcanizing agent and a crosslinking agent for halogen-containing rubber, carboxyl group-containing rubber, epoxy group-containing rubber and the like. For example, in Patent Document 1 below, a polyamine compound such as hexamethylenediamine carbamate is used as a vulcanizing compound in a polymer obtained by dissolving or swelling a fluorine-containing polymer in an acrylic monomer and then polymerizing the acrylic monomer. The point which mix | blends is disclosed. Patent Document 2 below discloses an acrylic rubber composition obtained by blending an acrylic rubber such as a carboxyl group-containing acrylic rubber with an alkylsulfonic acid metal salt, a stearic acid metal salt, and a vulcanizing agent. It is disclosed that hexamethylenediamine carbamate is used as a vulcanizing agent.

Japanese Patent No. 3256971 JP 2008-201903 A

  As mentioned above, amine carbamate reacts with polymer by using acid acceptor such as red lead in combination with polymer having polar group such as halogen, carboxyl group, epoxy group in molecular chain. It is said that it is not effective for general-purpose rubbers such as natural rubber and styrene butadiene rubber.

  In contrast, the present inventor improved dispersibility of carbon black by blending diamine carbamate with carbon black as a reinforcing agent in a system for sulfur vulcanizing general-purpose rubber, and further, carbon black and rubber. It has been found that the characteristics of vulcanized rubber such as low heat build-up can be improved by chemically linking these.

  That is, the present invention provides a rubber composition capable of improving characteristics such as low heat build-up by blending diamine carbamate in a sulfur vulcanization system using a general-purpose rubber, and a pneumatic tire using the same. The purpose is to do.

The rubber composition according to the present invention is at least one selected from the group consisting of natural rubber, polyisoprene rubber, polybutadiene rubber, and a copolymer rubber of two or more monomers selected from isoprene, butadiene and styrene. Carbon rubber, diamine carbamate of more than 0.1 parts by weight and less than 2 parts by weight with respect to 100 parts by weight of the rubber component , sulfur, and a vulcanization accelerator are blended with the rubber component made of diene rubber. Is.

  Moreover, the pneumatic tire according to the present invention uses the rubber composition at least in part.

  According to the present invention, in the rubber composition to be sulfur vulcanized, the characteristics of the vulcanized rubber such as low heat build-up can be improved by blending diamine carbamate with carbon black as a reinforcing agent. Therefore, the fuel efficiency of the tire can be improved by using the rubber composition for at least a part of the pneumatic tire.

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

  In the rubber composition according to the present invention, the rubber component includes a natural rubber (NR), a polyisoprene rubber (IR), a polybutadiene rubber (BR), and a copolymer of two or more monomers selected from isoprene, butadiene and styrene. Polymer rubber is mentioned, and these sulfur vulcanizable diene rubbers can be used either alone or in a blend of two or more.

  Examples of the copolymer rubber include styrene butadiene rubber (SBR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer, and styrene-isoprene-butadiene copolymer rubber.

  As the rubber component, natural rubber, polyisoprene rubber, polybutadiene rubber, and styrene butadiene rubber are preferably used, and these are preferably used alone or in combination of two or more.

  In the rubber composition according to the present invention, carbon black is blended as a reinforcing agent (that is, a reinforcing filler). Carbon black is not particularly limited, and is, for example, ASTM grade, SAF class (N100 series), ISAF class (N200 series), HAF class (N300 series), FEF class (N500 series), GPF class ( N600 series), SRF class (N700 series), and the like, and a blend of two or more thereof may be used.

  For example, when the rubber composition is used for a tread rubber of a pneumatic tire, the iodine adsorption amount (IA) is 105 to 165 mg / g, and the DBP absorption amount (dibutyl phthalate) is 95 to 140 ml / 100 g. Some carbon black is preferably used. When the rubber composition is used as a sidewall rubber or bead filler for a pneumatic tire, the iodine adsorption amount (IA) is 30 to 100 mg / g, and the DBP absorption amount (dibutyl phthalate) is 95 to 160 ml / g. Carbon black of 100 g is preferably used. Here, the iodine adsorption amount is a value measured according to JIS K6217-1, and the DBP absorption amount is a value measured according to JIS K6217-4.

  Although the compounding quantity of carbon black is not specifically limited, It is preferable that it is 20-200 mass parts with respect to 100 mass parts of said rubber components, More preferably, it is 30-120 mass parts, More preferably, it is 40-100. Part by mass.

  The rubber composition according to the present invention contains sulfur as a vulcanizing agent. Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and oil-treated sulfur, and are not particularly limited.

  Although the compounding quantity of sulfur is not specifically limited, It is preferable that it is 0.5-10 mass parts with respect to 100 mass parts of said rubber components, More preferably, it is 1-5 mass parts.

  A vulcanization accelerator is blended in the rubber composition according to the present invention. A vulcanization accelerator is a chemical compounded in this type of rubber composition in order to accelerate the sulfur vulcanization reaction to accelerate vulcanization or to improve the degree of crosslinking of diene rubber with sulfur. . The vulcanization accelerator is not particularly limited. For example, N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N-tert-butyl-2-benzothiazolylsulfenamide (BBS), N- Oxydiethylene-2-benzothiazolylsulfenamide (OBS), N, N-diisopropyl-2-benzothiazolylsulfenamide (DPBS), N, N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS) Sulfenamide vulcanization accelerators such as tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetrabutylthiuram disulfide (TBTD), dipentamethylenethiuram tetrasulfide ( DP T), thiuram vulcanization accelerators such as dipentamethylene thiuram hexasulfide; 2-mercaptobenzothiazole (MBT), di-2-benzothiazolyl disulfide (MBTS), salt of 2-mercaptobenzothiazole (zinc salt) (ZnMBT), sodium salt (NaMBT), cyclohexylamine salt (CMBT), etc.), thiazole vulcanization accelerators such as 2- (4′-morpholinodithio) benzothiazole; sodium dimethyldithiocarbamate (NaMDC), diethyldithiocarbamic acid Sodium (NaEDC), sodium di-n-butyldithiocarbamate (NaBDC), zinc dimethyldithiocarbamate (ZnMDC), zinc diethyldithiocarbamate (ZnEDC), zinc di-n-butyldithiocarbamate (Z BDC), zinc N-pentamethylenedithiocarbamate (ZnPDC), zinc ethylphenyldithiocarbamate (ZnEPDC), zinc dibenzyldithiocarbamate, tellurium diethyldithiocarbamate (TeEDC), copper dimethyldithiocarbamate (CuMDC), iron dimethyldithiocarbamate ( Dithiocarbamate vulcanization accelerators such as FeMDC); guanidine vulcanizations such as 1,3-diphenylguanidine (DPG), 1,3-di-orthotolylguanidine (DOTG), 1-ortho-tolylbiguanide (OTBG) Accelerators: thiourea vulcanization accelerators such as trimethylthiourea (TMU), N, N′-diphenylthiourea, N, N′-diethylthiourea and the like. These may be used alone or in combination of two or more. Among these, it is preferable to use at least one selected from a sulfenamide vulcanization accelerator, a thiuram vulcanization accelerator, and a thiazole vulcanization accelerator, and particularly preferably a sulfenamide vulcanization accelerator. Is to use.

  Although the compounding quantity of a vulcanization accelerator is not specifically limited, It is preferable that it is 0.05-5 mass parts with respect to 100 mass parts of said rubber components, More preferably, it is 0.1-3 mass parts. Since the diamine carbamate described below does not have a function as a crosslinking agent for improving the degree of crosslinking with respect to the general-purpose diene rubber, the degree of crosslinking of the rubber becomes insufficient unless a vulcanization accelerator is blended. Sufficient rubber properties cannot be obtained.

  Diamine carbamate is blended in the rubber composition according to the present invention. By incorporating diamine carbamate, the dispersibility of carbon black can be improved, and diamine carbamate is considered to act as a coupling agent that binds carbon black and diene rubber. Hysteresis loss can be reduced and low heat build-up can be improved.

  As the diamine carbamate, a compound represented by the following general formula (1) is preferably used.

H ₃ N ⁺ —R—NHCO ₂ ⁻ (1)
In the formula, R is an alkyl group having 2 to 20 carbon atoms, and may be a linear alkyl group, a branched alkyl group, or an alkyl group having a cyclic structure. Preferably, it is a C4-C16 alkyl group, More preferably, it is a linear alkyl group or an alkyl group with a cyclic structure. Specific examples of the diamine carbamate include hexamethylene diamine carbamate and 4,4′-methylenebiscyclohexylamine carbamate. These may be used alone or in combination.

  The blending amount of the diamine carbamate is preferably more than 0.1 parts by weight and less than 2 parts by weight, more preferably 0.2 parts by weight to 1.5 parts by weight with respect to 100 parts by weight of the rubber component. . If the blending amount of diamine carbamate is 0.1 parts by mass or less, the effect of improving the low heat build-up may not be sufficiently obtained. On the other hand, when the blending amount is 2 parts by mass or more, the scorch property is deteriorated and there is a possibility that burns may occur during mixing of the rubber composition.

  In the rubber composition according to the present invention, in addition to the above components, various compounding agents generally blended into the rubber composition can be arbitrarily blended. Examples of such compounding agents include fillers other than carbon black such as silica, zinc white, stearic acid, oil, anti-aging agents, waxes, processing aids, resins, and the like. It can mix | blend suitably in the range which is not warped.

  The rubber composition according to the present invention is prepared by kneading according to a conventional method using a rubber mixer such as a commonly used Banbury mixer or kneader, and vulcanized and molded according to a conventional method to obtain tread rubber or It can be used as a rubber member for pneumatic tires such as sidewall rubber, bead filler, rim strip rubber, or for various rubber products such as anti-vibration rubber and belt. Preferably, since a low heat-generating rubber is obtained, it is used as a rubber member of a pneumatic tire, and the fuel efficiency can be improved by using it in a tire.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

[First embodiment]
Using a Banbury mixer, a rubber composition for bead filler was prepared according to a conventional method according to the formulation shown in Table 1 below. Specifically, first, in the first mixing stage, other compounding agents excluding sulfur and a vulcanization accelerator are added to the diene rubber and kneaded, and then the obtained kneaded product is sulfurated in the final mixing stage. And a vulcanization accelerator was added and kneaded to prepare a rubber composition. Each component in Table 1 is as follows.

・ Natural rubber: RSS # 3
Carbon black 1: HAF, “Seast 3” manufactured by Tokai Carbon Co., Ltd. (IA = 80 mg / g, DBP = 101 ml / 100 g)
・ Zinc flower: "Zinc flower 3" manufactured by Mitsui Mining & Smelting Co., Ltd.
・ Stearic acid: "Industrial stearic acid" manufactured by Kao Corporation
・ Sulfur: “5% oil-treated powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.
・ Vulcanization accelerator 1: N-tert-butyl-2-benzothiazolylsulfenamide, “Noxeller NS-P” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Diamine carbamate 1: hexamethylene diamine carbamate, “Cheminox AC-6” manufactured by Unimatec Corporation, structural formula: H ₃ N ^+. (CH ₂ ) ₆ NHCO ₂ ⁻
Diamine carbamate 2: 4,4′-methylenebiscyclohexylamine carbamate, “Cheminox AC-9” manufactured by Unimatec Co., Structural formula: Formula (2) below

  Each rubber composition was evaluated for the presence or absence of burns, as well as scorch (t5), degree of crosslinking (MH), and low heat build-up (tan δ). Each evaluation method is as follows.

-Generation of burns: The presence or absence of a phenomenon in which vulcanization partially progresses in a processing step such as mixing and becomes a polymer gel was examined.

Scorch property (t5): Based on JIS K6300-1 (2001), using a Mooney scorch tester, preheating for 1 minute, t5 value when measured at a temperature of 125 ° C (time until vulcanization torque increases by 5 points) ) And was displayed as an index with the value of Comparative Example 1 being 100. The smaller the index, the more likely burns occur.

-Crosslinking degree (MH): Based on JIS K6300-2 (2001), the maximum torque (MH) at the time of vulcanization | cure at 150 degreeC x 45 minutes was calculated | required using the vibration type vulcanization test machine, The value was expressed as an index with a value of 100. The larger the index, the more vulcanized and the higher the degree of crosslinking.

Low exothermic property (tan δ): For a test piece vulcanized at 150 ° C. for 30 minutes, the loss coefficient tan δ is set in accordance with JIS K6394 under conditions of a temperature of 70 ° C., a frequency of 10 Hz, a static strain of 10%, and a dynamic strain of 2%. Measured and displayed as an index with the value of Comparative Example 1 as 100. The smaller the index, the smaller the tan δ, the smaller the hysteresis loss, and the less the heat generation, that is, the lower the heat generation.

  The results are as shown in Table 1. Compared to Comparative Example 1 which is a control in which sulfur and a vulcanization accelerator are blended as a vulcanization system, Comparative Example 2 in which diamine carbamate is blended in place of the vulcanization accelerator is low. An exothermic improvement effect was not obtained. Further, in Comparative Example 2, the action of accelerating vulcanization due to the basicity of diamine carbamate (t5 is small) was recognized, but the degree of crosslinking MH was low, so that diamine carbamate is used for general-purpose rubber such as natural rubber. Thus, it can be seen that it has no effect as a crosslinking agent.

On the other hand, in Examples 1 to 4 in which diamine carbamate is blended with sulfur and a vulcanization accelerator, the diamine carbamate improves the dispersibility of carbon black as a reinforcing agent, and the coupling agent binds carbon black and rubber. The low exothermicity was remarkably improved as compared with Comparative Example 1.

[Second Embodiment]
Using a Banbury mixer, a rubber composition for a tread was prepared according to a conventional method in the same manner as in Example 1 according to the formulation shown in Table 2 below. Each component in Table 2 is the same as in the first example except for the following components.

・ Styrene butadiene rubber: “SBR1502” manufactured by Sumitomo Chemical Co., Ltd.
・ Polybutadiene rubber: “BR150B” manufactured by Ube Industries, Ltd.
Carbon black 2: ISAF, “Seast 6” manufactured by Tokai Carbon Co., Ltd. (IA = 119 mg / g, DBP = 101 ml / 100 g)
・ Vulcanization accelerator 2: N-cyclohexyl-2-benzothiazolylsulfenamide, “Noxeller CZ-G” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

  Each rubber composition was evaluated in the same manner as in Example 1 for the presence or absence of burns, scorch property (t5), degree of crosslinking (MH), and low exothermic property (tan δ). However, the evaluation of t5, MH and tan δ was expressed as an index with the value of Comparative Example 3 as 100.

The results are shown in Table 2. Even when styrene butadiene rubber / polybutadiene rubber is used as the rubber component, the low heat build-up is remarkably improved in Examples 5 and 6 as in the first example. It was.

[Third embodiment]
Using a Banbury mixer, a rubber composition for a sidewall was prepared according to a conventional method in the same manner as in Example 1 according to the formulation shown in Table 3 below. Each component in Table 3 is the same as in the first and second examples except for the following components.

Carbon black 3: HAF, “Seast 3” manufactured by Tokai Carbon Co., Ltd. (IA = 80 mg / g, DBP = 101 ml / 100 g)
Vulcanization accelerator 3: N-tert-butyl-2-benzothiazolylsulfenamide, “Noxeller NS-P” manufactured by Ouchi Shinsei Chemical Co., Ltd.

  Each rubber composition was evaluated in the same manner as in Example 1 for the presence or absence of burns, scorch property (t5), degree of crosslinking (MH), and low exothermic property (tan δ). However, the evaluation of t5, MH and tan δ was expressed as an index with the value of Comparative Example 4 being 100.

The results are shown in Table 3. Even when natural rubber / polybutadiene rubber was used as the rubber component, the low heat build-up was remarkably improved in Examples 7 and 8 as in the first example. .

  The rubber composition of the present invention can be used for various rubber products, and can be suitably used as a rubber member for various tires such as tires for passenger cars and large tires for trucks and buses.

Claims (3)

A rubber component comprising at least one diene rubber selected from the group consisting of natural rubber, polyisoprene rubber, polybutadiene rubber, and a copolymer rubber of two or more monomers selected from isoprene, butadiene and styrene, A rubber composition comprising carbon black, a diamine carbamate of more than 0.1 parts by weight and less than 2 parts by weight with respect to 100 parts by weight of the rubber component , sulfur, and a vulcanization accelerator.   The rubber composition according to claim 1, wherein the diamine carbamate is at least one selected from hexamethylene diamine carbamate and 4,4'-methylenebiscyclohexylamine carbamate. Pneumatic tire using at least in part according to claim 1 or 2 rubber composition.