JP2014118526A - Coupling agent for rubber and carbon black and rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coupling agent for rubber and carbon black and a rubber composition suitable as a raw material of a tire exhibiting excellent wet grip performance and low fuel consumption performance.SOLUTION: There are provided a coupling agent for rubber and carbon black containing a metal salt of benzimidazolyl alkylthio sulfuric acid represented by the chemical formula (I) as a component and a rubber composition made by blending the same.

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 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 effects of acid-base interaction between the carbonyl group, carboxyl group, and amino group existing on the surface of carbon black. Is used.
For example, Patent Document 1 reports that a dialkylamino group-containing sulfur compound is used as a coupling agent for rubber and carbon black.
Patent Document 2 reports that an organic sulfide compound having a quaternary ammonium salt structure is used as a coupling agent for rubber and carbon black.
Patent Document 3 reports that 3-aminopropylthiosulfuric acid and its metal salt are used as a coupling agent for rubber and 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 JP 2012-126923 A

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

As a result of intensive studies to solve the above-mentioned problems, the present inventors have used a metal salt of benzimidazolylalkylthiosulfuric acid represented by the chemical formula (I) 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 metal salt of benzimidazolylalkylthiosulfuric acid represented by the chemical formula (I) as a component.
According to a second aspect of the present invention, 10 to 100 parts by weight of carbon black is blended with 100 parts by weight of diene rubber, and the rubber / carbon black cup according to the first aspect of the invention is added to 100 parts by weight of the carbon black A rubber composition comprising 0.2 to 30 parts by weight of a ring agent.

（式中、Ｒは炭素数１〜６の直鎖状または分岐状のアルキレン基を表す。Ｍ^ｎ＋は金属イオンを表し、ｎはその価数を表す。）

(In the formula, R represents a linear or branched alkylene group having 1 to 6 carbon atoms. M ^{n +} represents a metal ion, and n represents its valence.)

Since the metal salt of benzimidazolylalkylthiosulfuric acid, which is a component of the coupling agent for rubber and carbon black of the present invention, has a benzimidazole group in the molecule, in addition to acid-base interaction with the carbon black surface, Bonding with carbon black is caused by π-electron interaction with the benzene ring on the surface of carbon black.
As a result, when the rubber composition blended with the rubber / carbon black coupling agent of the present invention is used as a tire raw material, the rolling resistance is reduced and the fuel efficiency performance is reduced while maintaining excellent wet grip force. An improved tire can be obtained.

  Hereinafter, the present invention will be described in detail.

  The metal salt of benzimidazolylalkylthiosulfuric acid, 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 an alkyl group having a thiosulfate group is substituted at the 2-position of benzimidazole. It has a feature in that it has a structure.

As the metal ion represented by M ^{n +} in the chemical formula (I), lithium ion, sodium ion, potassium ion, magnesium ion, cesium ion, cobalt ion, copper ion or zinc ion are preferable, and sodium ion, potassium ion or magnesium ion is preferable. More preferred.
n represents the valence of a metal ion, n is 1 in the case of lithium ion, sodium ion, potassium ion, and cesium ion, n is 2 or 3 in the case of cobalt ion, and n in the case of copper ion In the case of magnesium ion or zinc ion, n is 2.

As the metal salt, for example,
S-((benzimidazolyl-2) methyl) thiosulfate sodium salt,
S- (2- (benzimidazolyl-2) ethyl) thiosulfate sodium salt,
S- (3- (benzimidazolyl-2) n-propyl) thiosulfate sodium salt,
S- (2- (benzimidazolyl-2) isopropyl) thiosulfate sodium salt,
S- (4- (benzimidazolyl-2) n-butyl) thiosulfate sodium salt,
S- (5- (benzimidazolyl-2) n-pentyl) thiosulfate sodium salt,
S- (6- (benzimidazolyl-2) n-hexyl) thiosulfate sodium salt,
S-((benzimidazolyl-2) methyl) thiosulfate potassium salt,
S- (2- (benzimidazolyl-2) ethyl) thiosulfate potassium salt,
S-((benzimidazolyl-2) methyl) thiosulfate magnesium salt,
And S- (2- (benzimidazolyl-2) ethyl) thiosulfate magnesium salt.
These metal salts of benzimidazolylalkylthiosulfuric acid may be used alone or in combination of two or more as a component of a rubber / carbon black coupling agent.

  Such a metal salt of benzimidazolylalkylthiosulfuric acid can be easily synthesized by reacting a precursor haloalkylbenzimidazole compound with a metal salt of thiosulfuric acid in an appropriate solvent. Although there is no restriction | limiting in particular in reaction time or reaction temperature, it is preferable that reaction temperature is 20-110 degreeC, and it is more preferable that it is 40-80 degreeC. The reaction time is preferably 0.5 to 8 hours, more preferably 1 to 4 hours. Examples of the solvent used for the reaction include water, methanol, ethanol, 2-propanol and the like. These solvents can be used alone or in combination of two or more.

  The metal salt of benzimidazolylalkylthiosulfuric acid produced by the reaction is isolated and purified by extracting the reaction solution with a suitable solvent after concentrating to dryness. Examples of the solvent used for this extraction include methanol, ethanol, and 2-propanol.

  Examples of the haloalkylbenzimidazole compound include 2-chloromethylbenzimidazole, 2-chloroethylbenzimidazole, 2-chloropropylbenzimidazole, 2-chloroisopropylbenzimidazole, 2-chlorobutylbenzimidazole, and 2-chloropentyl. Examples include benzimidazole, 2-chlorohexylbenzimidazole, 2-bromomethylbenzimidazole, 2-bromoethylbenzimidazole, and the like. These benzimidazole compounds can be synthesized by a known method in which a haloalkylcarboxylic acid and o-phenylenediamine are reacted in dilute hydrochloric acid.

  Examples of the metal salt of thiosulfuric acid include lithium thiosulfate, sodium thiosulfate, potassium thiosulfate, magnesium thiosulfate, cesium thiosulfate, cobalt thiosulfate, copper thiosulfate, and zinc thiosulfate.

  In the implementation of the rubber composition of the present invention, it is preferable to blend carbon black at a ratio of 10 to 100 parts by weight, preferably 30 to 80 parts by weight, with respect to 100 parts by weight of the diene rubber. More preferred. 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.

  And it is preferable to mix | blend the coupling agent for rubber | gum and carbon black of this invention in the ratio of 0.2-30 weight part with respect to 100 weight part of carbon black, and mix | blend in the ratio of 0.5-20 weight part. More preferably. If the blending amount of the rubber / carbon black coupling agent is less than 0.2 parts by weight, the effect of reducing the rolling resistance of the tire obtained by vulcanization and molding cannot be obtained sufficiently. 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.

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

  As the diene rubber, 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 of two or more.

For the carbon black, it is preferable that the 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.

Carbon black is not particularly limited, and for example, furnace black, acetylene black, thermal black, channel black, and the like can be used. From the viewpoint of tire use, furnace black can be preferably 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 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 of two or more.

  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. Although these compounding quantities can also be made into a general quantity, it is preferable to mix | blend in the ratio of 40-120 weight part with respect to 100 weight part of diene rubbers.

  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, the present invention will be described 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: Product name “Nipol 1723” manufactured by ZEON Corporation
Carbon black: manufactured by Asahi Carbon Co., Ltd., trade name “Asahi # 70”, nitrogen adsorption 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.

  In the examples, the metal salts of benzimidazolylalkylthiosulfuric acid used as a coupling agent for rubber and carbon black are as follows, and these synthesis examples are shown in Reference Examples 1 and 2. In addition, these synthesis | combination was performed according to the well-known synthesis | combining method.

[Metal salt of benzimidazolyl alkylthiosulfate]
S-((benzimidazolyl-2) methyl) thiosulfate sodium salt (abbreviated as “BZMTS”)
S- (2- (benzimidazolyl-2) ethyl) thiosulfate sodium salt (abbreviated as “BZETS”)

[Reference Example 1]
<Synthesis of BZMTS>
Into a 1 L flask was charged 203 g (1.0 mol) of 2-chloromethylbenzimidazole hydrochloride, 284.2 g (1.1 mol) of sodium thiosulfate pentahydrate, 400 mL of methanol and 400 mL of water, and the reaction solution. Was prepared. The reaction solution was heated to reflux at 70 ° C. for 8 hours and then allowed to cool, and methanol was distilled off under reduced pressure. Next, 45.0 g (1.1 mol) of sodium hydroxide was added, and the mixture was stirred at room temperature for 1 hour. After concentrating the reaction solution under reduced pressure, 800 mL of ethanol was added, and the mixture was heated to reflux for 1 hour, and sodium chloride as a by-product was removed by hot filtration. The filtrate was concentrated under reduced pressure, and the precipitated crystals were separated and dried to obtain 230 g (yield: 86.4%) of the intended BZMTS.

[Reference Example 2]
<Synthesis of BZETS>
Into a 1 L flask was charged 217 g (1.0 mol) of 2-chloroethylbenzimidazole hydrochloride, 284.2 g (1.1 mol) of sodium thiosulfate pentahydrate, 400 mL of methanol and 400 mL of water, and the reaction solution. Was prepared. The reaction solution was heated to reflux at 70 ° C. for 8 hours and then allowed to cool, and methanol was distilled off under reduced pressure. Next, 45.0 g (1.1 mol) of sodium hydroxide was added, and the mixture was stirred at room temperature for 1 hour. After concentrating the reaction solution under reduced pressure, 800 mL of ethanol was added, and the mixture was heated to reflux for 1 hour, and sodium chloride as a by-product was removed by hot filtration. The filtrate was concentrated under reduced pressure, and the precipitated crystals were separated and dried to obtain 248 g of the target BZETS (yield 88.6%).

The coupling agents for rubber and carbon black used in the comparative examples are as follows.
[Coupling agent for rubber and carbon black]
Bis (dimethylaminoethyl) tetrasulfide (abbreviated as “DME”, synthesized according to the method described in Patent Document 1)
Bis (dimethylaminopropyl) tetrasulfide (abbreviated as “DMP”).
Bis (dimethylaminopyridinium hexyl chloride) tetrasulfide (abbreviated as “DPH”, synthesized according to the method described in Patent Document 2)
S- (3-aminopropyl) thiosulfate sodium salt (abbreviated as “ATS”, synthesized according to the method described in Patent Document 3)

  The evaluation test methods employed in the control test, 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 is set on a viscoelastic spectrometer (Model Rheosol-G5000, manufactured by UBM) with a gripping tool spacing of 15 mm, and is subjected to torsional deformation at 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 shown in Table 1 as relative values when the value of the wet grip index and the rolling resistance index of Control Test 1 is 100. In Table 2, the wet grip index of 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 white, a vulcanizing agent, a vulcanization accelerator and an anti-aging agent were blended so as to have the composition shown in Table 1. Next, after preparing an unvulcanized rubber composition kneaded using a two-roll mixer having a surface temperature of 70 ° C. and processed into a sheet shape, an internal loss measurement test was performed.

[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 1-4]
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]
A sheet-like unvulcanized rubber composition 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 and the blending amount of carbon black was changed. A measurement test was conducted.

[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 5 to 8]
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 Table 1 and Table 2, when the rubber composition containing the rubber / carbon black coupling agent of the present invention is used, a rubber composition containing a known 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.

  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 metal salt of benzimidazolylalkylthiosulfuric acid represented by the chemical formula (I) as a component.

(In the formula, R represents a linear or branched alkylene group having 1 to 6 carbon atoms. M ^{n +} represents a metal ion, and n represents its valence.)   10 to 100 parts by weight of carbon black is blended with 100 parts by weight of diene rubber, and the coupling agent for rubber and carbon black according to claim 1 is added to 0.2 to 30 with respect to 100 parts by weight of carbon black. A rubber composition characterized by blending parts by weight.