JP2013203918A - Coupling agent for rubber-carbon black, and rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coupling agent for a rubber-carbon black suitable as the raw material of a tire that exhibits excellent wet grip performance and low fuel consumption performance, and a rubber composition in which the coupling agent is blended.SOLUTION: A coupling agent for rubber-carbon black includes a mercaptobenzimidazole compound expressed by chemical formula (I) as a component. A rubber composition for a tire includes the coupling agent.

Description

  The present invention relates to a coupling agent for rubber and carbon black and a rubber composition containing the same.

  In recent years, as the interest in the environment has increased, there has been an increasing demand for lower fuel consumption for automobiles. A tire rubber composition suitable for such a purpose is strongly desired because the characteristics of the tire have a great influence on the reduction in fuel consumption of automobiles. On the other hand, in terms of running safety, the grip force on a wet road surface, that is, “wet grip force” is also emphasized. In order to improve the low fuel consumption characteristics, it is necessary to reduce the rolling resistance of the tire. However, when the rolling resistance is reduced, the wet grip force is reduced.

  As one of the means to reduce rolling resistance while maintaining wet grip, improve dispersibility of carbon black compounded as a rubber reinforcing agent and strengthen the chemical bond between rubber molecules and carbon black Investigation of coupling agents for rubber and carbon black is underway.

Many of the compounds that have been developed as coupling agents for rubber and carbon black are amine compounds, and it is expected that carbonyl groups and carboxyl groups present on the surface of carbon black will be bonded by acid-base interaction. It is.
For example, Patent Document 1 reports that a dialkylamino group-containing sulfur compound is used as a coupling agent for rubber and carbon black.
In addition, Patent Document 2 discloses that an organic sulfide compound having a quaternary ammonium salt structure is used as a rubber by utilizing an action in which an iminium ion group, which is one of quaternary ammonium groups, is firmly bonded to the surface of carbon black.・ It has been reported to be used as a coupling agent for carbon black.

  However, in any case, the effect of reducing the rolling resistance of the tire obtained by vulcanization and molding has not yet been satisfactory.

JP-A-9-278742 JP 2000-239446 A

  An object of the present invention is to provide a rubber / carbon black coupling agent suitable as a tire raw material that exhibits excellent wet grip performance and low fuel consumption performance, and a rubber composition containing the same.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have used a mercaptobenzimidazole compound represented by the chemical formula (I) of Chemical Formula 1 as a coupling agent for rubber and carbon black. It has been found that the intended purpose is achieved, and the present invention has been completed.
That is, the first invention is a coupling agent for rubber and carbon black characterized by comprising a mercaptobenzimidazole compound represented by the chemical formula (I) of Chemical Formula 1 as a component.
The second invention is a rubber composition comprising the rubber / carbon black coupling agent of the first invention.

（式中、Ｒ_１は、炭素数１〜６の直鎖状または分岐状のアルキル基を表わす。Ａは、ＮＨまたはＮＲ_２を表わす。Ｒ_２は、炭素数１〜６の直鎖状または分岐状のアルキル基もしくはベンジル基を表わす。Ｙは、炭素数１〜１０の直鎖状または分岐状の二価の脂肪族炭化水素基、炭素数３〜７の二価の脂環式炭化水素基もしくは炭素数６〜１０の二価の芳香族炭化水素基を表わす。）

(Wherein R ₁ represents a linear or branched alkyl group having 1 to 6 carbon atoms. A represents NH or NR _2. R ₂ represents a linear or 1 to 6 carbon atom or Represents a branched alkyl group or a benzyl group, Y represents a linear or branched divalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a divalent alicyclic hydrocarbon group having 3 to 7 carbon atoms. Represents a group or a divalent aromatic hydrocarbon group having 6 to 10 carbon atoms.)

The mercaptobenzimidazole compound, which is a component of the coupling agent for rubber and carbon black of the present invention, has a benzimidazole structure in the molecule. In addition to the bond due to the acid-base interaction, the bond due to the π-electron interaction with the benzene ring on the carbon black surface is expected.
As a result, when the rubber composition containing the coupling agent for rubber and carbon black of the present invention is used as a raw material for tires, rolling resistance is reduced while maintaining excellent wet grip force, and fuel efficiency performance is reduced. The tire can be improved.

  The present invention will be described in detail below.

  The mercaptobenzimidazole compound, which is a component of the coupling agent for rubber and carbon black of the present invention, is represented by the chemical formula (I), and has a bilaterally symmetric structure (bis structure) having a benzimidazole structure as a main skeleton. Have.

As the compound, for example,
1,2-bis (mercaptobenzimidazolyl-2) ethane,
1,2-bis (mercapto-4-methylbenzimidazolyl-2) ethane,
1,2-bis (mercapto-5-methylbenzimidazolyl-2) ethane,
1,3-bis (mercaptobenzimidazolyl-2) propane,
1,3-bis (mercapto-1-methylbenzimidazolyl-2) propane,
1,3-bis (mercapto-1-ethylbenzimidazolyl-2) propane,
1,4-bis (mercaptobenzimidazolyl-2) butane,
1,5-bis (mercaptobenzimidazolyl-2) pentane,
1,6-bis (mercaptobenzimidazolyl-2) hexane,
1,6-bis (mercapto-1-benzylbenzimidazolyl-2) hexane,
1,8-bis (mercaptobenzimidazolyl-2) octane,
1,10-bis (mercaptobenzimidazolyl-2) decane,
1,4-bis (mercaptobenzimidazolyl-2) 2-cis-butene,
1,4-bis (mercaptobenzimidazolyl-2) 2-trans-butene,
1,4-bis (mercapto-1-methylbenzimidazolyl-2) 2-cis-butene,
1,4-bis (mercapto-1-methylbenzimidazolyl-2) 2-trans-butene,
1,4-bis (mercapto-1-ethylbenzimidazolyl-2) 2-cis-butene,
1,4-bis (mercapto-1-ethylbenzimidazolyl-2) 2-trans-butene,
1,4-bis (mercapto-1-n-propylbenzimidazolyl-2) 2-cis-butene,
1,4-bis (mercapto-1-n-propylbenzimidazolyl-2) 2-trans-butene,
1,4-bis (mercapto-1-isopropylbenzimidazolyl-2) 2-cis-butene,
1,4-bis (mercapto-1-isopropylbenzimidazolyl-2) 2-trans-butene,
1,4-bis (mercapto-1-n-butylbenzimidazolyl-2) 2-cis-butene,
1,4-bis (mercapto-1-n-butylbenzimidazolyl-2) 2-trans-butene,
1,4-bis (mercaptobenzimidazolyl-2) 2-methylbutane,
1,4-bis (mercaptobenzimidazolyl-2) benzene,
α, α′-bis (mercaptobenzimidazolyl-2) metaxylene,
α, α′-bis (mercaptobenzimidazolyl-2) paraxylene and the like can be mentioned. A combination of these mercaptobenzimidazole compounds may be used as a component of the coupling agent for rubber and carbon black.

  Such a mercaptobenzimidazole compound, for example, as shown in the reaction formula (i) of Chemical Formula 2, can be obtained by trapping a precursor 2-mercaptobenzimidazole compound and a dihalogen compound in water or an organic solvent. It can be easily synthesized by reacting in the presence of an agent.

（式中、Ａ、Ｒ_１及びＹは前記と同じであり、Ｘは塩素原子、臭素原子またはヨウ素原子を表わす。）

(In the formula, A, R ₁ and Y are the same as defined above, and X represents a chlorine atom, a bromine atom or an iodine atom.)

  Examples of 2-mercaptobenzimidazole compounds include 2-mercaptobenzimidazole, 2-mercapto-4-methylbenzimidazole, 2-mercapto-5-methylbenzimidazole, 2-mercapto-1-methylbenzimidazole, 2- Mercapto-1-ethylbenzimidazole, 2-mercapto-1-propylbenzimidazole, 2-mercapto-1-isopropylbenzimidazole, 2-mercapto-1-n-butylbenzimidazole, 2-mercapto-1-benzylbenzimidazole, etc. Is mentioned.

  Examples of the dihalogen compound include 1,2-dichloroethane, 1,3-dibromopropane, 1,4-dichlorobutane, 1,4-dichloro-2-cis-butene, 1,4-dichloro-2-trans-butene. 1,5-dichloropentane, 1,6-dichlorohexane, 1,6-dibromohexane, 1,4-dichlorocyclohexane, 1,7-dichloropentane, 1,8-dichlorooctane, 1,9-dichlorononane, Examples include 1,10-dichlorodecane, 1,4-dichloro-2-methylbutane, α, α′-dichlorometaxylene, α, α′-dichloroparaxylene and the like.

  Halogen scavengers include organic amine compounds such as sodium methoxide, sodium ethoxide, sodium propoxide, triethylamine, diazabicycloundecane, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, sodium carbonate Inorganic alkaline compounds such as potassium carbonate may be used, and these may be used in combination.

In the reaction between the 2-mercaptobenzimidazole compound and the dihalogen compound, the reaction temperature is preferably 50 to 110 ° C, and more preferably 60 to 80 ° C. The reaction time is preferably 2 to 48 hours, and more preferably 6 to 18 hours.
The amount of the halogen scavenger used is preferably 0.5 to 3 moles, more preferably 1.5 to 2.5 moles, with respect to the 2-mercaptobenzimidazole compound.
As the organic solvent, methanol, ethanol, isopropanol, butanol, toluene, xylene, monochlorobenzene, dimethylformamide, dioxane, tetrahydrofuran and the like can be used.

  The mercaptobenzimidazole compound produced by the reaction precipitates when the reaction solution is cooled to room temperature. Then, it is isolated and purified by filtering it and washing with a solvent. The solvent used in this washing is not particularly limited as long as the product is difficult to dissolve. For example, water, methanol, ethanol, isopropanol, acetone, toluene, acetonitrile, dioxane, monochlorobenzene, etc. should be used. Can do.

  The rubber composition of the present invention can be prepared by blending the rubber / carbon black coupling agent of the present invention together with carbon black in a diene rubber and kneading.

  As the diene rubber compounded in the rubber composition of the present invention, those conventionally used in the field of rubber industry can be used without particular limitation. For example, natural rubber (NR), isoprene rubber (IR ), Butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), butyl rubber (IIR), chloroprene rubber (CR) and the like can be preferably used. Moreover, you may use combining these.

For example, furnace black, acetylene black, thermal black, channel black, and the like can be used as the carbon black to be blended in the rubber composition of the present invention. From the viewpoint of a raw material for tires, furnace black is preferably used. Can do.
As the furnace black, commercially available products such as Asahi # 70 manufactured by Asahi Carbon Co., Ltd. and Seest 3G manufactured by Tokai Carbon Co. can be used.

  In the rubber composition of the present invention, carbon black is preferably blended at a rate of 10 to 100 parts by weight, more preferably 30 to 80 parts by weight, with respect to 100 parts by weight of diene rubber. . If the blending amount of carbon black is less than 10 parts by weight, the abrasion resistance of the vulcanized and molded rubber will be reduced. Decreases.

  In the rubber composition of the present invention, the rubber / carbon black coupling agent of the present invention is preferably compounded in an amount of 1 to 30 parts by weight with respect to 100 parts by weight of carbon black. It is more preferable to mix in proportions. When the blending amount of the coupling agent is less than 1 part by weight, the effect of sufficiently reducing the rolling resistance of a tire obtained by vulcanization and molding cannot be obtained. Moreover, even if the blending amount of the coupling agent exceeds 30 parts by weight, the reduction effect is almost flattened, and the amount of the coupling agent used is increased, which is not economical.

  The timing of blending the rubber / carbon black coupling agent of the present invention with the diene rubber is added before mixing the carbon black with the diene rubber or while mixing the carbon black with the diene rubber. Things are preferable.

  Further, in the rubber composition of the present invention, soluble sulfur or insoluble sulfur is used as a vulcanizing agent with respect to 100 parts by weight of the diene rubber, and either one or both of them is combined to 0.5 to 10 weights. It is preferable to mix part, more preferably 2 to 5 parts by weight.

  In addition, the rubber composition of the present invention can be blended with reinforcing agents and fillers such as silica, clay and talc that have been conventionally used for rubber. These compounding amounts can be general amounts, but are preferably 40 to 120 parts by weight with respect to 100 parts by weight of the diene rubber.

  In addition, vulcanization accelerators such as sulfenamides, vulcanization accelerators such as zinc white (zinc oxide) and magnesium oxide, process oils such as naphthenic oil and aroma oil, dispersants (wax) such as stearic acid, Besides antioxidants, antioxidants, ozone cracking inhibitors, peptizers, adhesive resins, vulcanization retarders, and the like can be used as long as the effects of the present invention are not impaired.

  The rubber composition of the present invention can be obtained by kneading the above-described raw materials using a Banbury mixer or a kneader such as an open roll. Then, for example, it is vulcanized and molded as a tire rubber member such as a carcass, a belt, a bead, or a tread.

  Hereinafter, the present invention will be described in detail with reference to control tests, examples and comparative examples, but the present invention is not limited thereto. The main raw materials used in these are as follows.

[raw materials]
・ NR: (Product name “SMR-CV60” manufactured by Chong Hutton)
・ SBR: (Nippon Zeon, product name "Nipol 1723")
・ BR: (Nippon Synthetic Rubber Co., Ltd., trade name “BR01”)
Carbon black: (Asahi Carbon Co., Ltd., trade name “# 70”, BET specific surface area 77 m ² / g, DBP oil supply 101 ml / 100 g)
・ Process oil: (made by Idemitsu Kosan Co., Ltd., trade name “Aromax 3”)
・ Stearic acid: (Miyoshi Oil & Fats, trade name “MXST”)
・ Zinc Hana: (Made by Shodo Chemical Industry Co., Ltd., trade name “Zinc oxide 2 types”)
・ Vulcanizing agent: (manufactured by Shikoku Kasei Kogyo Co., Ltd., insoluble sulfur content: 80% as sulfur content, trade name “Muclon OT20”)
・ Vulcanization accelerator: (Ouchi Shinsei Chemical Co., Ltd., trade name “Noxeller CZ-G”)
・ Anti-aging agent: (Ouchi Shinsei Chemical Co., Ltd., trade name “NOCRACK 6C”)

  The coupling agents for rubber and carbon black used in the examples are as follows, and these synthesis examples are shown in Reference Examples 1 to 4.

[Rubber / Carbon Black Coupling Agent in Examples]
1,4′-bis (mercaptobenzimidazolyl-2) butane (abbreviated as “C4SBZ”)
1,6′-bis (mercaptobenzimidazolyl-2) hexane (abbreviated as “C6SBZ”)
Α, α'-bis (mercaptobenzimidazolyl-2) metaxylene (abbreviated as "CmXSBZ")
1,4′-bis (mercaptobenzimidazolyl-2) 2-trans-butene (abbreviated as “C4SVBZ”)

[Reference Example 1]
<Synthesis of C4SBZ>
1 L of ethanol, 136 g (2.0 mol) of sodium ethoxide, 300 g (2.0 mol) of 2-mercaptobenzimidazole, and 216 g (1.0 mol) of 1,4-dibromobutane are charged into a 2 L flask. After stirring at an internal temperature of 40 for 1 hour, stirring was performed at 70 ° C. for 3 hours. After the reaction solution was cooled to room temperature, the precipitate in the system was separated, washed with water and dried to obtain 312 g (0.88 mol, yield 88%) of the desired product C4SBZ.

[Reference Example 2]
<Synthesis of C6SBZ>
1 L of ethanol, 136 g (2.0 mol) of sodium ethoxide, 300 g (2.0 mol) of 2-mercaptobenzimidazole, and 155 g (1.0 mol) of 1,6-dichlorohexane were charged into a 2 L flask. After stirring at an internal temperature of 40 for 1 hour, the mixture was stirred at 80 ° C. for 5 hours. After the reaction solution was cooled to room temperature, the precipitate in the system was separated, washed with water and dried to obtain 309 g (0.81 mol, yield 81%) of the desired product C6SBZ.

[Reference Example 3]
<Synthesis of CmXSBZ>
2 L of ethanol, 136 g (2.0 mol) of sodium ethoxide, 300 g (2.0 mol) of 2-mercaptobenzimidazole, and 175 g (1.0 mol) of α, α′-dichlorometaxylene were charged into a 3 L flask. A reaction solution was prepared and stirred at an internal temperature of 40 for 1 hour, and then stirred at 75 ° C. for 7 hours. After cooling the reaction solution to room temperature, the precipitate in the system was separated, washed with water and dried to obtain 350 g (0.87 mol, yield 87%) of the desired product CmXSBZ.

[Reference Example 4]
<Synthesis of C4SVBZ>
In a 3 L flask, 2 L of ethanol, 136 g (2.0 mol) of sodium ethoxide, 300 g (2.0 mol) of 2-mercaptobenzimidazole, and 125 g (1.0 mol) of 1,4-dichloro-2-trans-butene The reaction mixture was added to prepare a reaction solution, which was stirred at an internal temperature of 40 for 1 hour, and then stirred at 70 ° C. for 7 hours. After the reaction solution was cooled to room temperature, the precipitate in the system was separated, washed with water and dried to obtain 295 g (0.84 mol, yield 84%) of the desired product C4SVBZ.

The coupling agents for rubber and carbon black used in the comparative examples are as follows.
[Coupling agent for rubber and carbon black of comparative example]
Bis (dimethylaminoethyl) tetrasulfide (abbreviated as “DME”, synthesized according to the method described in Patent Document 1)
Bis (dimethylaminopropyl) tetrasulfide (abbreviated as “DMP”, synthesized according to the method described in Patent Document 1)
Bis (dimethylaminopyridinium hexyl chloride) tetrasulfide (abbreviated as “DPH”, synthesized according to the method described in Patent Document 2)

  The evaluation test methods employed in the control tests, examples and comparative examples are as follows.

[Internal loss measurement test]
The unvulcanized rubber composition processed into a sheet is vulcanized by heating at 160 ° C. for 20 minutes in a 200 × 200 × 2 mm mold, and a strip of 5 × 20 × 2 mm is formed from this vulcanized rubber sheet. The test piece was cut out. This test piece was set on a viscoelastic spectrometer (Model Rheosol-G5000, manufactured by UBM Co.) with a gripping tool spacing of 15 mm, torsional deformation with an ambient temperature of 0 ° C. and 60 ° C., a frequency of 10 Hz, and a dynamic strain of 5 °. The internal loss [Tanδ] of the test piece was measured.
The internal loss [Tan δ (0 ° C.)] at 0 ° C. is an index of the wet grip force, and it is determined that the wet grip force of the tire is larger as the numerical value is larger.
The internal loss [Tan δ (60 ° C.)] at 60 ° C. is an index of rolling resistance. The smaller the numerical value, the smaller the rolling resistance of the tire and the better the fuel efficiency characteristics.

  The results of the internal loss measurement test are all shown in Table 1 as relative values when the value of the wet grip index of the control test 1 and the rolling resistance index is 100, and in Table 2, all of the wet grip index of the control test 2 The relative value when the value of the rolling resistance index is 100 is shown.

[Control study 1]
NR, carbon black, process oil, and stearic acid were weighed so as to have the composition shown in Table 1, and kneaded using a Banbury mixer to prepare a master batch. To this, zinc oxide, vulcanizing agent, vulcanization accelerator, and anti-aging agent are added so as to have the composition shown in Table 1, kneaded using a two-roll mixer with a surface temperature of 70 ° C., and processed into a sheet form An unvulcanized rubber composition was prepared.
When this rubber composition was subjected to an internal loss measurement test, the test results obtained were as shown in Table 1.

[Examples 1 to 6]
An unvulcanized rubber composition processed into a sheet having the composition shown in Table 1 was prepared in the same manner as in Control Test 1 except that a rubber / carbon black coupling agent was used.
When this rubber composition was subjected to an internal loss measurement test, the test results obtained were as shown in Table 1.

[Comparative Examples 1-3]
In the same manner as in Examples 1 to 6, unvulcanized rubber compositions processed into sheets having the compositions shown in Table 1 were prepared.
When this rubber composition was subjected to an internal loss measurement test, the test results obtained were as shown in Table 1.

[Control study 2]
An unvulcanized rubber composition processed into a sheet having the composition shown in Table 2 was prepared in the same manner as in Control Test 1 except that SBR was used instead of NR.
When this rubber composition was subjected to an internal loss measurement test, the test results obtained were as shown in Table 2.

[Examples 7 to 12]
An unvulcanized rubber composition processed into a sheet having the composition shown in Table 2 was prepared in the same manner as in Control Test 2 except that the coupling agent for rubber and carbon black was used.
When this rubber composition was subjected to an internal loss measurement test, the test results obtained were as shown in Table 2.

[Comparative Examples 4 to 6]
In the same manner as in Examples 7 to 12, unvulcanized rubber compositions processed into sheets having the compositions shown in Table 2 were prepared.
When this rubber composition was subjected to an internal loss measurement test, the test results obtained were as shown in Table 2.

  According to the test results shown in Tables 1 and 2, in the case of the rubber composition containing the rubber / carbon black coupling agent of the present invention, the conventional rubber / carbon black coupling agent was added. Compared to the case of the rubber composition, it is recognized that the rolling resistance is drastically improved while maintaining the same wet grip index.

  According to the present invention, it is possible to provide a fuel-efficient tire that has excellent wet grip performance and reduced rolling resistance.

Claims (2)

A rubber / carbon black coupling agent comprising a mercaptobenzimidazole compound represented by the chemical formula (I) of Chemical Formula 1 as a component.

(Wherein R ₁ represents a linear or branched alkyl group having 1 to 6 carbon atoms. A represents NH or NR _2. R ₂ represents a linear or 1 to 6 carbon atom or Represents a branched alkyl group or a benzyl group, Y represents a linear or branched divalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a divalent alicyclic hydrocarbon group having 3 to 7 carbon atoms. Represents a group or a divalent aromatic hydrocarbon group having 6 to 10 carbon atoms.)   A rubber composition comprising the rubber / carbon black coupling agent according to claim 1.