JP2014218614A - 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 a raw material of a tire which exhibits excellent wet grip performance and low fuel consumption performance without deteriorating processability during kneading of an unvulcanized rubber, and to provide a rubber composition in which the coupling agent is blended.SOLUTION: There is provided: a coupling agent for a rubber-carbon black containing a sulfide compound which has a median diameter of 0.1 to 5.0 μm and is represented by the chemical formula (I) as a component; and a rubber composition for a tire containing the same. There is provided a rubber composition in which 10 to 100 pts.wt. of carbon black is blended based on 100 pts.wt. of a dien-based rubber and 0.2 to 3.0 pts.wt. of the coupling agent for a rubber-carbon black is blended based on 100 pts.wt. of the carbon black.

Description

  The present invention relates to a rubber / carbon black coupling agent and a rubber composition suitable as a raw material of a tire.

  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, from the viewpoint of running safety, the grip force on a wet road surface, that is, “wet grip force” is also emphasized. In order to improve the fuel consumption characteristics, it is necessary to reduce the rolling resistance of the tire. However, if the rolling resistance is reduced, the wet grip force is reduced.

  As one of the means to develop tires with low rolling resistance while maintaining wet grip, it improves the dispersibility of carbon black compounded as a rubber reinforcing material, and chemistry between carbon black and rubber molecules Studies are underway on coupling agents for rubber and carbon black that strengthen the bond.

The bond strength of aromatic condensed heterocyclic compounds, which have been developed as coupling agents for rubber and carbon black, is based on the acid-base interaction between the carbonyl group and carboxyl group present on the carbon black surface and the compound. ing.
The present applicant has proposed in Patent Document 1 that the sulfide compound according to the present application is used as a coupling agent for rubber and carbon black.

However, when this sulfide compound is used, the fuel consumption characteristics are improved, but there is a problem that processability (scorch resistance and rubber viscosity) in the kneading process of the unvulcanized rubber is deteriorated.
Moreover, if the compounding amount of the sulfide compound is reduced, processability can be maintained, but this does not provide a sufficient effect of improving fuel consumption characteristics.

JP 2013-23610 A

  The present invention relates to a rubber / carbon black coupling agent suitable as a raw material for tires that exhibits excellent wet grip performance and low fuel consumption performance without deteriorating processability in the kneading process of unvulcanized rubber, and It aims at providing the compounded rubber composition.

As a result of intensive studies to solve the above problems, the inventors of the present invention pulverized the median diameter of the sulfide compound represented by the chemical formula (I) to be in the range of 0.1 to 5.0 μm. As a result, it was found that the intended purpose was achieved by using it as a component of a coupling agent for rubber and carbon black, and the present invention was completed.
That is, the first invention is a rubber / carbon black coupling agent comprising a sulfide compound represented by the chemical formula (I) having a median diameter of 0.1 to 5.0 μm as a component.
2nd invention mix | blends 10-100 weight part of carbon black with respect to 100 weight part of diene rubbers, and coupling agent for rubber | gum and carbon black of 1st invention with respect to 100 weight part of this carbon black 0.2 to 3.0 parts by weight of a rubber composition.

（式中、ｘは２〜４の整数を表す。）

(In the formula, x represents an integer of 2 to 4.)

The rubber / carbon black coupling agent of the present invention has a contact area with the rubber or carbon black per unit weight of the sulfide compound by setting the median diameter of the sulfide compound as a component to 0.1 to 5.0 μm. Can be made sufficiently large, so that the chemical bond between carbon black and rubber molecules can be strengthened.
As a result, when a rubber composition containing this rubber / carbon black coupling agent is used as a raw material for a tire, the rolling resistance is reduced and the fuel consumption characteristics are improved while maintaining excellent wet grip force. It can be.
In addition, in the kneading step of the unvulcanized rubber composition, it is possible to prevent deterioration of processability (scorch resistance and rubber viscosity).

  Hereinafter, the present invention will be described in detail.

  The sulfide compound used in the practice of the present invention is represented by the above chemical formula (I), and the median diameter of this sulfide compound (sometimes simply referred to as a sulfide compound) is 0.1 to 5.0 μm. It is a range.

This sulfide compound is
2,2′-bis (benzimidazolyl-2) ethyl disulfide,
It represents 2,2′-bis (benzimidazolyl-2) ethyl trisulfide and 2,2′-bis (benzimidazolyl-2) ethyl tetrasulfide, and can be synthesized according to the method described in Patent Document 1.
These may be used alone or in combination of two or more.

  The median diameter according to the present invention refers to a 50% particle diameter in an integrated particle size distribution measured by a laser diffraction scattering method.

  In the coupling agent for rubber / carbon black of the present invention, the median diameter of the sulfide compound is preferably in the range of 0.1 to 5.0 μm, and more preferably in the range of 0.5 to 2.0 μm. If the median diameter is less than 0.1 μm, the effect of reducing the rolling resistance of the tire obtained by vulcanization / molding has reached its peak, which only increases the pulverization cost and is not economical. If the median diameter exceeds 5.0 μm, a large amount of sulfide compound is required to obtain the same reduction effect, and the processability is deteriorated.

  The sulfide compound used in the practice of the present invention can be made into particles having a median diameter of 0.1 to 5.0 μm by a known pulverization method and classification method.

  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. . When the blending amount of carbon black is less than 10 parts by weight, the abrasion resistance of the vulcanized and molded rubber is lowered, and when it exceeds 100 parts by weight, the viscosity is increased at the time of kneading the unvulcanized rubber and the workability is deteriorated.

  In the rubber composition of the present invention, the rubber / carbon black coupling agent of the present invention is preferably blended in an amount of 0.2 to 3.0 parts by weight per 100 parts by weight of carbon black. It is more preferable to mix | blend in the ratio of 5-2.0 weight part. 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. Moreover, even if the blending amount of the coupling agent for rubber / carbon black exceeds 3.0 parts by weight, the effect of the reduction has almost reached its peak, and the amount of coupling agent for rubber / carbon black has only increased. Absent.

  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 may be used alone or in combination of two or more.

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 unvulcanized rubber at the time of kneading is thickened and the workability is deteriorated. 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 rubber is lowered, and when it exceeds 150 ml / 100 g, the unvulcanized rubber at the time of kneading is thickened and the workability is deteriorated.

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 Seast G-3 manufactured by Tokai Carbon Co., Ltd. can be used.

  In the rubber composition of the present invention, soluble sulfur or insoluble sulfur is preferably blended at a ratio of 0.5 to 10 parts by weight as a vulcanizing agent with respect to 100 parts by weight of the diene rubber, and 2 to 5 parts by weight. More preferably, it is blended at a ratio of parts.

  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. 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.

  The rubber composition of the present invention includes a vulcanization accelerator such as sulfenamide, a vulcanization accelerator such as zinc oxide (zinc white) and magnesium oxide, a process oil such as naphthenic oil and aroma oil, and stearic acid. A dispersing agent (wax) such as anti-aging agent, antioxidant, ozone cracking inhibitor, peptizer, adhesive resin, vulcanization retarder and the like can be blended within a range not impairing the effects of the present invention.

  The rubber composition of the present invention is prepared by mixing the aforementioned 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 specifically described with reference to control tests, examples and comparative examples, but the present invention is not limited thereto. The main raw materials and equipment used for these are as follows.

  The sulfide compound was synthesized according to the method described in JP 2013-23610 A, and particles having a predetermined median diameter were prepared with a jet mill pulverizer. The sulfide compound used in the comparative example was used without being pulverized. The median diameter was measured by a laser diffraction method.

[raw materials]
• 2,2′-bis (benzimidazolyl-2) ethyl disulfide median diameter 1.0 μm product (abbreviated as “2EBZ (D50: 1 μm)”)
• 2,2′-bis (benzimidazolyl-2) ethyl disulfide median diameter 3.0 μm product (abbreviated as “2EBZ (D50: 3 μm)”)
• 2,2′-bis (benzimidazolyl-2) ethyl tetrasulfide median diameter 2.0 μm product (abbreviated as “4EBZ (D50: 2 μm)”)
・ Product of 2,2′-bis (benzimidazolyl-2) ethyl tetrasulfide having a median diameter of 5.0 μm (abbreviated as “4EBZ (D50: 5 μm)”)
• 2,2′-bis (benzimidazolyl-2) ethyl disulfide median diameter 10.4 μm product (abbreviated as “2EBZ (D50: 10 μm)”)
・ Product of 2,2′-bis (benzimidazolyl-2) ethyl tetrasulfide having a median diameter of 153.0 μm (abbreviated as “4EBZ (D50: 153 μm)”)
・ Natural rubber (product name “SMR-CV60”, abbreviated as “NR”, manufactured by Chong Hutton)
Styrene-butadiene rubber (manufactured by Nippon Zeon Co., Ltd., trade names “Nipol 1723”, “SBR”)
Carbon black (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 (manufactured by Sankyo Oil Chemical Co., Ltd., trade name “Naphten Oil SNH-22”)
・ Stearic acid (made by Miyoshi Yushi Co., Ltd., trade name “MXST”)
・ Zinc flower (manufactured by Shodo Chemical Industry Co., Ltd., trade name “Zinc oxide”)
・ Vulcanizing agent (Shikoku Kasei Kogyo Co., Ltd., insoluble sulfur, trade name "Muclon OT20")
・ Vulcanization accelerator (made by Ouchi Shinsei Chemical Co., Ltd., trade name “Noxeller NS”)
・ Anti-aging agent (trade name “NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.)
[apparatus]
・ Jet mill grinder (manufactured by Seishin Enterprises, Model FS-4)
・ Laser diffraction type particle size distribution measuring device (SALD-2000J, manufactured by Shimadzu Corporation)

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

[Workability test]
Using an unvulcanized rubber sheet, using an automatic Mooney viscometer (model AM-3, manufactured by Toyo Seiki Seisakusho Co., Ltd.), conforming to JIS-K6300-1, scorch time (T5) of 125 ° C. and Mooney of 100 ° C. The viscosity (M _{L1 + 4} ) was measured. In Table 1, the measured data are shown as relative values when the value of Control Test 1 is 100, and in Table 2, are shown as relative values when the value of Control Test 2 is 100.
Regarding the scorch time (T5) and Mooney viscosity ( _{ML1 + 4} ), the closer these values are to 100, the better the workability.

[Internal loss measurement test]
An unvulcanized rubber sheet is heated in a 200 × 200 × 2 mm mold at 160 ° C./15 minutes to prepare a vulcanized rubber sheet, and a strip test of 5 × 20 × 2 mm is made from this vulcanized rubber sheet. A piece was cut out.
This test piece was set on a viscoelastic spectrometer (Model Rheosol-G5000, manufactured by UBM Co., Ltd.) with a gripping tool spacing of 15 mm, and twisted with a frequency of 10 Hz / dynamic strain of 5 ° at an ambient temperature of 0 ° C. and 60 ° C. And the internal loss (Tan δ) of the test piece was measured. In Table 1, the measured data are shown as relative values when the value of Control Test 1 is 100, and in Table 2, are shown as relative values when the value of Control Test 2 is 100.
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.

[Control study 1]
A master batch is prepared by kneading a predetermined amount of each NR, carbon black, process oil and stearic acid using a Banbury mixer. Subsequently, a predetermined amount of this master batch and a predetermined amount of each zinc oxide, A vulcanizing agent, a vulcanization accelerator, and an anti-aging agent are kneaded using a two-roll mixer having a surface temperature of 70 ° C. to form a sheet-like unvulcanized rubber composition (hereinafter referred to as an unvulcanized rubber sheet). ) Was prepared.
The composition (mixing ratio) of the obtained unvulcanized rubber sheet is as shown in Table 1.
When the processability test of the unvulcanized rubber sheet and the internal loss measurement test of the vulcanized rubber sheet were performed, the test results obtained were as shown in Table 1.

[Examples 1 to 6]
An unvulcanized rubber sheet having the composition (mixing ratio) shown in Table 1 was prepared in the same manner as in Control Test 1 except that a coupling agent for rubber and carbon black was used. The processability test and the internal loss measurement test of the vulcanized rubber sheet were conducted.
The test results obtained were as shown in Table 1.

[Comparative Examples 1-4]
In the same manner as in the above examples, an unvulcanized rubber sheet having the composition (mixing ratio) shown in Table 1 was prepared, the workability test of the unvulcanized rubber sheet, and the internal loss of the vulcanized rubber sheet. A measurement test was conducted.
The test results obtained were as shown in Table 1.

[Control study 2]
Except that SBR was used instead of NR, an unvulcanized rubber sheet having the composition (mixing ratio) shown in Table 2 was prepared in the same manner as in Control Test 1, and the processability of the unvulcanized rubber sheet The test and the internal loss measurement test of the vulcanized rubber sheet were conducted.
The test results obtained were as shown in Table 2.

[Examples 7 to 12]
An unvulcanized rubber sheet having the composition (mixing ratio) shown in Table 2 was prepared in the same manner as in Control Test 2 except that a coupling agent for rubber and carbon black was used. The processability test and the internal loss measurement test of the vulcanized rubber sheet were conducted.
The test results obtained were as shown in Table 2.

[Comparative Examples 5 to 8]
In the same manner as in the above examples, an unvulcanized rubber sheet having the composition (mixing ratio) shown in Table 2 was prepared, the processability test of the unvulcanized rubber sheet, and the internal loss of the vulcanized rubber sheet A measurement test was conducted.
The test results obtained were as shown in Table 2.

According to the test results shown in Tables 1 and 2, the rubber composition containing the coupling agent for rubber and carbon black of the present invention has a median diameter of particles of the coupling agent of 0.1 to 5.0 μm. By adjusting to this range, the rolling resistance was drastically improved while maintaining the same wet grip property.
Moreover, the workability at the time of kneading unvulcanized rubber was good.

  As described above, according to the present invention, it is possible to provide a fuel-efficient tire having good wet grip performance and rolling resistance, which has good processability when kneaded unvulcanized rubber.

Claims (2)

A rubber / carbon black coupling agent comprising a sulfide compound represented by chemical formula (I) having a median diameter of 0.1 to 5.0 μm as a component.

(In the formula, x represents an integer of 2 to 4.)   10 to 100 parts by weight of carbon black is blended with 100 parts by weight of diene rubber, and 0.2 to 3 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 containing 0.0 part by weight.