JP2014080535A - Coupling agent for rubber-carbon black and rubber composition for tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coupling agent for a rubber-carbon black suitable as raw material of a tire exhibiting excellent wet grip performance and low fuel consumption performance, and to provide a rubber composition for a tire.SOLUTION: There are provided a coupling agent for a rubber-carbon black containing a disulfide compound represented by the following formula as a component, and raw material for a tire capable of exhibiting excellent wet grip performance and low fuel consumption performance by using the rubber composition for a tire containing the coupling agent. (I), where Rrepresents a hydrogen atom or a linear or a branched alkyl group having 1 to 6 carbon atoms.

Description

  The present invention relates to a rubber / carbon black coupling agent and a tire 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 methods to develop tires with low rolling resistance while maintaining wet grip strength, the chemical bond between carbon black and rubber molecules compounded as a rubber reinforcing agent is strengthened, and in rubber compositions Studies are underway on coupling agents for rubber and carbon black that improve the dispersibility of carbon black.

Many of the coupling agents for rubber and carbon black that have been studied so far are amino group-containing compounds, and the effect of acid-base interaction between the carbonyl group, carboxyl group and amino group present on the carbon black surface. This is because it is expected.
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 an organic sulfide compound having a quaternary ammonium salt structure as a rubber by utilizing the property that an iminium ion group, which is one of quaternary ammonium salts, 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 and a tire rubber composition that are suitable as a raw material for tires that exhibit excellent wet grip performance and low fuel consumption performance.

As a result of intensive studies in order to solve the above problems, the present inventors have used the disulfide compound represented by the chemical formulas (I) to (III) as a coupling agent for rubber and carbon black. The inventors have found that the purpose of the period can be achieved and have completed the present invention.
That is, the first invention is a coupling agent for rubber and carbon black characterized in that one or more selected from disulfide compounds represented by chemical formulas (I) to (III) are used as components.
According to a second invention, 10 to 100 parts by weight of carbon black is blended with 100 parts by weight of the diene rubber, and the rubber / carbon black cup according to the first invention is added with respect to 100 parts by weight of the carbon black. A rubber composition containing 0.5 to 30 parts by weight of a ring agent.

（式中、Ｒ_１は、水素原子または炭素数１〜６の直鎖状、もしくは分岐状のアルキル基を表わす。）

(Wherein R ₁ represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms.)

（式中、Ｒ₂は、水素原子または炭素数１〜６の直鎖状、もしくは分岐状のアルキル基を表わす。）

(Wherein R ₂ represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms.)

Since the disulfide compound which is a component of the coupling agent for rubber and carbon black of the present invention has a heterocyclic ring having an amino group in the molecule, the carbon black surface and In addition to the acid-base interaction, a bond with carbon black is expected due to the π-electron interaction with the benzene ring on the surface of carbon black.
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.

  Hereinafter, the present invention will be described in detail.

  The disulfide compound that is a component of the coupling agent for rubber and carbon black of the present invention is represented by the chemical formulas (I) to (III), and is bilaterally symmetrical with both ends of the molecule having an aromatic heterocyclic ring as the main skeleton. It has a disulfide structure (bis structure).

As the compound, for example,
Bisbenzimidazolyl-2-disulfide,
Bis 5-methylbenzimidazolyl-2-disulfide,
Bis 5-ethylbenzimidazolyl-2-disulfide,
Bis 5-aminothiadiazolyl-2-disulfide,
Bis 5-methylaminothiadiazolyl-2-disulfide,
Bis 5-ethylaminothiadiazolyl-2-disulfide,
Examples thereof include bis1,2,4-triazolyl-3-disulfide. These disulfide compounds may be used in combination as a component of the coupling agent for rubber / carbon black.

  Such a disulfide compound can be easily synthesized by oxidizing a thiol group-containing heterocyclic compound as a precursor with hydrogen peroxide.

  Examples of the thiol group-containing heterocyclic compound include 2-mercaptobenzimidazole, 2-mercapto-5-methylbenzimidazole, 2-mercapto-5-ethylbenzimidazole, 2-mercapto-5-aminothiadiazole, 2-mercapto- Examples include 5-methylaminothiadiazole, 2-mercapto-5-ethylaminothiadiazole, 3-mercapto-1,2,4-triazole and the like.

  In the reaction between the thiol-containing heterocyclic compound and the hydrogen peroxide solution, the reaction time and reaction temperature are not particularly limited, but the reaction temperature is preferably 20 to 110 ° C, more preferably 40 to 80 ° C. preferable. The reaction time is preferably 0.5 to 8 hours, more preferably 1 to 4 hours. Although it does not specifically limit as a solvent used by reaction, In an industrial manufacturing method, water or methanol is preferable.

  The said disulfide compound produced | generated by reaction precipitates in a reaction liquid. 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, and examples thereof include water, methanol, ethanol, isopropyl alcohol, acetone, toluene, acetonitrile, and dioxane.

  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.

  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 is lowered, which is not preferable. On the other hand, if it exceeds 100 parts by weight, the rubber composition at the time of kneading before vulcanization is thickened and the processability is lowered.

  In the rubber composition of the present invention, the rubber / carbon black coupling agent of the present invention is preferably blended at a ratio of 0.5 to 30 parts by weight with respect to 100 parts by weight of carbon black, and 1 to 20 parts by weight. More preferably, it is blended at a ratio of parts. When the blending amount of the rubber / carbon black coupling agent is less than 0.5 parts by weight, the effect of sufficiently reducing the rolling resistance of the tire obtained by vulcanization and molding cannot be obtained. Further, even if the blending amount of the rubber / carbon black coupling agent exceeds 30 parts by weight, the effect of the reduction is almost flat, and the amount of use of the rubber / carbon black coupling agent increases, which is not economical.

  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. These diene rubbers can be used alone or in combination.

The carbon black compounded in the rubber composition of the present invention, preferably has a nitrogen adsorption specific surface area (BET method) is 50 to 250 m ² / g, more preferably 70~230m ² / g. When the nitrogen adsorption specific surface area is less than 50 m ² / g, the abrasion resistance of the vulcanized and molded rubber is lowered, and when it exceeds 250 m ² / g, the rubber composition before vulcanization is thickened and the workability is lowered. To do.
Moreover, in order to maintain the reinforcing property and processability of the rubber composition satisfactorily, the DBP oil supply amount of the carbon black is preferably 60 to 150 ml / 100 g, more preferably 80 to 140 ml / 100 g. . When the DBP oil supply amount is less than 60 ml / 100 g, the reinforcing property of the vulcanized and molded rubber is lowered, and when it exceeds 150 ml / 100 g, the processability of the rubber composition before vulcanization is lowered.

The carbon black to be blended in the rubber composition of the present invention is not particularly limited. For example, furnace black, acetylene black, thermal black, channel black, and the like can be used. From the viewpoint of tire use, furnace black is preferable. Can be used.
As the furnace black, commercially available products such as Asahi # 70 manufactured by Asahi Carbon Co., Ltd. and Seast G-3 manufactured by Tokai Carbon Co., Ltd. can be used.

  The rubber / carbon black coupling agent of the present invention is preferably added before carbon black is mixed with diene rubber or during mixing of diene rubber and carbon black.

  The rubber composition of the present invention preferably contains 0.5 to 10 parts by weight of a sulfur component such as soluble sulfur or insoluble sulfur as a vulcanizing agent with respect to 100 parts by weight of the diene rubber. It is more preferable to blend by weight. These sulfur components can be used alone or in combination.

  In addition to the coupling agent for rubber and carbon black of the present invention, diene rubber, and carbon black, the rubber composition of the present invention includes silica, clay, talc and the like that have been conventionally used for rubber. Reinforcing agents and fillers can be blended. The compounding amount of these reinforcing agents and fillers can also be a general amount, but it is preferably compounded at a ratio of 40 to 120 parts by weight with respect to 100 parts by weight of the diene rubber.

  Further, the rubber composition of the present invention includes a vulcanization accelerator such as a sulfenamide generally used as a rubber compounding component of this type, a vulcanization accelerator such as zinc oxide (zinc white), and magnesium oxide. Agent, process oil such as naphthenic oil and aroma oil, dispersant (wax) such as stearic acid, anti-aging agent, antioxidant, ozone crack inhibitor, peptizer, adhesive resin, vulcanization delay An agent etc. can be mix | blended in the range which does not impair the effect of this invention.

  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. For example, it is vulcanized and molded as a tire rubber member such as a carcass, a belt, a bead, or a tread.

  Hereinafter, although this invention is demonstrated with a control test, an Example, and a comparative example, this invention is not restrict | limited to these. The main raw materials used in these are as follows.

[raw materials]
・ NR: Product name “SMR-CV60” manufactured by Chong Hutton
・ SBR: Product name “Nipol 1723” manufactured by ZEON Corporation
Carbon black: manufactured by Asahi Carbon Co., Ltd., trade name “Asahi # 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: manufactured by Miyoshi Oil & Fats Co., Ltd., trade name “MXST”
・ Zinc flower: Made by Shodo Chemical Industry Co., Ltd., trade name "Zinc oxide 2 types"
・ Vulcanizing agent: Shikoku Kasei Kogyo Co., Ltd., insoluble sulfur, trade name "Muclon OT20"
・ Vulcanization accelerator: Ouchi Shinsei Chemical Co., Ltd., trade name “Noxeller CZ-G”
・ Anti-aging agent: Product name “NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

  The disulfide compounds (rubber and carbon black coupling agents) used in the examples are as follows, and these synthesis examples are shown in Reference Examples 1 to 3. In addition, these synthesis | combination was performed according to the well-known synthesis | combining method of disulfide. That is, the target disulfide compound can be obtained by adding hydrogen peroxide water dropwise while stirring an equivalent amount of thiol compound in water, filtering the produced disulfide compound, washing with water and drying.

[Disulfide compound]
Bisbenzimidazolyl-2-disulfide (abbreviated as “BBZ”)
Bis 5-aminothiadiazolyl-2-disulfide (abbreviated as “BAT”)
Bis 1,2,4-triazolyl-3-disulfide (abbreviated as “BTZ”)

[Reference Example 1]
<Synthesis of BBZ>
1500 mL of water and 300.4 g (2.0 mol) of 2-mercaptobenzimidazole were added to a 3 L flask to prepare a reaction solution. While stirring the reaction solution at 60 ° C., 100 g (1.0 mol) of 30% aqueous hydrogen peroxide was added dropwise over 2 hours. After completion of dropping, the mixture was further heated and stirred for 4 hours. Next, the reaction solution was cooled to room temperature, and the precipitate was separated, washed with water, and dried to obtain the target BBZ 268.0 g (0.90 mol, yield 90%).

[Reference Example 2]
<Synthesis of BAT>
Into a 3 L flask, 1200 ml of water and 266.4 g (2.0 mol) of 2-mercapto-5-aminothiadiazole were added to prepare a reaction solution. While stirring the reaction liquid at 70 ° C., 100 g (1.0 mol) of 30% aqueous hydrogen peroxide was added dropwise over 2 hours. After completion of dropping, the mixture was further heated and stirred for 4 hours. Next, the reaction solution was cooled to room temperature, and the precipitate was separated, washed with water, and dried to obtain 235.0 g (0.89 mol, yield 89%) of the target BAT.

[Reference Example 3]
<Synthesis of BTZ>
Into a 3 L flask, 1500 ml of water and 202.2 g (2.0 mol) of 3-mercapto-1,2,4-triazole were added to prepare a reaction solution. While stirring the reaction solution at 60 ° C., 100 g (1.0 mol) of 30% aqueous hydrogen peroxide was added dropwise over 2 hours. After completion of dropping, the mixture was further heated and stirred for 4 hours. Next, the reaction solution was cooled to room temperature, and the precipitate was separated, washed with water, and dried to obtain 170.2 g (0.85 mol, yield 85%) of the intended BTZ.

The tetrasulfide compound (rubber / carbon black coupling agent) used in the comparative examples is as follows.
[Tetrasulfide compound]
Bis (dimethylaminoethyl) tetrasulfide: Abbreviated as “DME”. The compound was synthesized according to the method described in Patent Document 1.
Bis (dimethylaminopropyl) tetrasulfide: Abbreviated as “DMP”. Same as above.
Bis (dimethylaminopyridinium hexyl chloride) tetrasulfide: abbreviated as “DPH”. The compound was 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 heated in a mold having an internal size of 200 × 200 × 2 mm at 160 ° C. for 20 minutes to produce a vulcanized rubber sheet, and 5 × from this vulcanized rubber sheet A 20 × 2 mm strip-shaped 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 °. Given, the internal loss (Tan δ) 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, and the smaller the value, the smaller the tire rolling resistance 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 an internal loss measurement test was performed on the obtained unvulcanized rubber composition, the test results obtained were as shown in Table 1.

[Examples 1 to 6]
A sheet-like unvulcanized rubber composition having the composition shown in Table 1 was prepared and an internal loss measurement test was performed in the same manner as in Control Test 1 except that a coupling agent for rubber and carbon black was used. It was. The test results obtained were as shown in Table 1.

[Comparative Examples 1-3]
In the same manner as in Examples 1 to 6, a sheet-like unvulcanized rubber composition having the composition shown in Table 1 was prepared, and an internal loss measurement test was performed. The test results obtained were as shown in Table 1.

[Control study 2]
Except that SBR was used instead of NR, a sheet-like unvulcanized rubber composition having the composition shown in Table 2 was prepared in the same manner as in Control Test 1, and an internal loss measurement test was performed. The test results obtained were as shown in Table 2.

[Examples 7 to 12]
A sheet-like unvulcanized rubber composition having the composition shown in Table 2 was prepared and an internal loss measurement test was performed in the same manner as in Control Test 2 except that a coupling agent for rubber and carbon black was used. It was. 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, a sheet-like unvulcanized rubber composition having the composition shown in Table 2 was prepared, and an internal loss measurement test was performed. The test results obtained were as shown in Table 2.

  According to the test results shown in Tables 1 and 2, when the rubber composition containing the rubber / carbon black coupling agent of the present invention is used, the rubber composition containing the conventional rubber / carbon black coupling agent is used. Compared to the case of using a product, it is possible to obtain a vulcanized rubber having a drastically improved rolling resistance while maintaining a wet grip property equivalent or higher.

  As described above, according to the present invention, it is possible to provide a fuel-efficient tire having excellent wet grip performance and reduced rolling resistance.

Claims (2)

A rubber / carbon black coupling agent comprising one or more disulfide compounds represented by chemical formulas (I) to (III) as components.

(Wherein R ₁ represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms.)

(Wherein R ₂ represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms.)

  10 to 100 parts by weight of carbon black is blended with 100 parts by weight of diene rubber, and 0.5 to 30 of the coupling agent for rubber and carbon black according to claim 1 with respect to 100 parts by weight of carbon black. A rubber composition characterized by blending parts by weight.