阅读说明：本技术 轮胎用橡胶组合物 (Rubber composition for tire ) 是由 清水克典 尾崎诚人 于 2019-11-22 设计创作，主要内容包括：本发明提供一种轮胎用橡胶组合物,该轮胎用橡胶组合物意图主要用于充气轮胎的底胎面部,其滚动阻力低且制成轮胎后的操纵稳定性和耐久性优异。该轮胎用橡胶组合物中是在100质量份的包含50质量％以上的天然橡胶和15～50质量％的末端改性丁二烯橡胶的橡胶组分中配合包含炭黑和二氧化硅的填充剂而成,前述二氧化硅的配合量相对于前述填充剂的配合量的质量比率为0.1～0.5,橡胶组合物的硬度设定为73以上,40℃时的回弹弹性模量设定为60％以上。(The present invention provides a rubber composition for a tire, which is intended to be mainly used for an undertread portion of a pneumatic tire, and which has low rolling resistance and excellent steering stability and durability after the tire is produced. The rubber composition for a tire is obtained by blending a filler containing carbon black and silica into 100 parts by mass of a rubber component containing 50% by mass or more of natural rubber and 15 to 50% by mass of a terminal-modified butadiene rubber, wherein the mass ratio of the blending amount of the silica to the blending amount of the filler is 0.1 to 0.5, the hardness of the rubber composition is 73 or more, and the modulus of elasticity at 40 ℃ is 60% or more.)

1. A rubber composition for a tire, characterized in that 100 parts by mass of a rubber component comprising 50% by mass or more of a natural rubber and 15 to 50% by mass of a terminal-modified butadiene rubber is blended with a filler comprising carbon black and silica, the mass ratio of the blending amount of the silica to the blending amount of the filler is 0.1 to 0.5,

the hardness is 73 or more, and the modulus of elasticity at 40 ℃ is 60% or more.

2. The rubber composition for a tire according to claim 1, wherein Mw/Mn, which is a molecular weight distribution determined from the weight average molecular weight Mw and the number average molecular weight Mn, of the terminal-modified butadiene rubber, is 2.0 or less.

3. The rubber composition for a tire according to claim 1 or 2, wherein the functional group at the terminal of the terminal-modified butadiene rubber is at least 1 selected from the group consisting of a hydroxyl group, an amino group, an amide group, an alkoxy group, an epoxy group, and a siloxane bond group.

4. The rubber composition for a tire according to any one of claims 1 to 3, wherein the amount of the filler blended is 55 parts by mass or more per 100 parts by mass of the rubber component.

5. A pneumatic tire according to any one of claims 1 to 4, wherein 1.0 to 4.0 parts by mass of an amine-based antioxidant is blended with respect to 100 parts by mass of the rubber component.

6. A pneumatic tire according to any one of claims 1 to 5, wherein more than 0 part by mass and not more than 2.0 parts by mass of wax are blended with respect to 100 parts by mass of the rubber component.

7. A pneumatic tire, characterized in that the rubber composition for a tire as set forth in any one of claims 1 to 6 is used for a tread portion.

Technical Field

The present invention relates to a rubber composition for a tire intended to be mainly used for a tread portion (undercut) of a pneumatic tire.

Background

In a pneumatic tire, performance for improving fuel efficiency during running is required in order to reduce environmental load. Therefore, suppression of heat generation of the rubber composition constituting each portion of the pneumatic tire is carried out. In recent years, in order to further improve fuel efficiency performance, for example, suppression of heat generation has been required even for a rubber composition constituting an undertread portion disposed on the inner side of a crown portion forming a tread surface of a pneumatic tire.

As an index of heat generating properties of a rubber composition, tan δ at 60 ℃ (hereinafter referred to as "tan δ (60 ℃)") measured by dynamic viscoelasticity is generally used, and as tan δ (60 ℃), heat generating properties of a rubber composition become smaller. Further, as a method for reducing the tan δ (60 ℃) of the rubber composition, for example, a method of reducing the amount of a filler such as carbon black or a method of increasing the particle diameter of carbon black can be mentioned. Alternatively, it has been proposed to incorporate silica (see, for example, patent document 1). However, these methods do not always provide sufficient rubber hardness and fatigue resistance, and there is a concern that the rubber hardness and fatigue resistance may be affected when used in a tire (particularly, when used in a tread portion). Therefore, in the rubber composition for a tire intended to be used as a tread portion, a further measure is sought to improve low rolling property while maintaining good steering stability and durability after the tire is manufactured.

Documents of the prior art

Patent document 1: japanese patent laid-open publication No. 2015-059181

Disclosure of Invention

The purpose of the present invention is to provide a rubber composition for a tire, which is intended to be used mainly for a tread portion of a pneumatic tire, and which has low rolling resistance and excellent steering stability and durability after being manufactured into a tire.

The rubber composition for a tire according to the present invention for achieving the above object is characterized in that a filler containing carbon black and silica is blended per 100 parts by mass of a rubber component containing 50% by mass or more of a natural rubber and 15% by mass to 50% by mass of a terminal-modified butadiene rubber, the mass ratio of the amount of the silica blended to the amount of the filler is 0.1 to 0.5, and the rubber composition for a tire has a hardness of 73 or more and a modulus of elasticity at rebound at 40 ℃ of 60% or more.

The rubber composition for a tire of the present invention is obtained by using a terminal-modified butadiene rubber in combination with a natural rubber as a rubber component and carbon black and silica as fillers, and the hardness and the modulus of elasticity in rebound of the rubber composition are sufficiently improved as described above, so that the rolling resistance can be reduced and the steering stability and durability after the tire is produced can be improved. In particular, since carbon black and silica are used in combination with the terminal-modified butadiene rubber and the amount of silica added to the total amount of carbon black and silica is set as described above, steering stability and durability after tire production can be effectively improved without deteriorating heat generation, and these properties can be improved in a well-balanced manner.

In the present invention, the "hardness" is the hardness of the rubber composition measured at a temperature of 20 ℃ by type A Shore durometer in accordance with JIS K6253. The "modulus of elasticity at 40 ℃ is the modulus of elasticity at 40 ℃ of the rubber composition measured by a Lupulg's formula (リュプケ formula) resilience elasticity tester in accordance with JIS K6255.

In the present invention, it is preferable that the molecular weight distribution (Mw/Mn), which is determined from the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the terminal-modified butadiene rubber, is 2.0 or less. By narrowing the molecular weight distribution in this way, the rubber properties become better, and the rolling resistance is reduced, and at the same time, the rubber composition is advantageous in improving the steering stability and durability after the tire is manufactured. In the present invention, "weight average molecular weight Mw" and "number average molecular weight Mn" are measured by Gel Permeation Chromatography (GPC) in terms of standard polystyrene.

In the present invention, the functional group at the end of the end-modified butadiene rubber is preferably at least 1 of a hydroxyl group, an amino group, an alkoxy group, and an epoxy group. This improves the affinity with carbon black and silica, and further improves the dispersibility of carbon black and silica, and therefore, it is advantageous in that the rubber hardness and the adhesiveness can be improved while maintaining the heat generating property at a low level more effectively, and these properties can be balanced well.

In the present invention, the amount of the filler blended is preferably 55 parts by mass or more per 100 parts by mass of the rubber component. By blending carbon black and silica in such a sufficient amount, the rubber hardness can be effectively increased while maintaining the heat generation property at a low level, and it is advantageous in terms of the balance between the above properties.

In the present invention, it is preferable to add 1.0 to 4.0 parts by mass of the amine antioxidant to 100 parts by mass of the rubber component. Further, it is preferable to add more than 0 part by mass and not more than 2.0 parts by mass of wax to 100 parts by mass of the rubber component. By thus blending an anti-aging agent and wax, crack resistance and processability can be improved.

The rubber composition for a tire of the present invention is preferably used for an under tread portion of a pneumatic tire, and a pneumatic tire using the rubber composition for a tire of the present invention for an under tread portion can improve fuel efficiency performance while maintaining good steering stability and durability.

Detailed Description

In the rubber composition for a tire of the present invention, the rubber component is a diene rubber, and it is necessary to contain a natural rubber and a terminal-modified butadiene rubber.

As the natural rubber, rubbers generally used in rubber compositions for tires can be used. By blending natural rubber, sufficient rubber strength can be obtained as a rubber composition for a tire. The amount of the natural rubber is 50% by mass or more, preferably 50% by mass to 85% by mass, and more preferably 60% by mass to 85% by mass, based on 100% by mass of the total diene rubber. When the amount of the natural rubber is less than 50% by mass, the rubber strength is lowered.

The terminal-modified butadiene rubber is a butadiene rubber modified with an organic compound having a functional group at one or both ends of a molecular chain. By blending such a terminal-modified butadiene rubber, the affinity with carbon black and silica described later is improved, and the dispersibility is improved, so that the heat generating property is maintained low, and the action effect of carbon black and silica is further improved, whereby the rubber hardness can be improved. Examples of the functional group at the terminal of the modified molecular chain include an alkoxysilyl group, a hydroxyl group, an aldehyde group, a carboxyl group, an amino group, an amide group, an imino group, an alkoxy group, an epoxy group, an amide group, a mercapto group, an ether group, and a siloxane bond group. Among them, at least one selected from the group consisting of a hydroxyl group, an amino group, an amide group, an alkoxy group, an epoxy group and a siloxane bond group is preferable. Here, the siloxane bond group is a functional group having a structure of-O-Si-O-.

The blending amount of the terminal-modified butadiene rubber is 15 to 50% by mass, preferably 30 to 40% by mass, based on 100% by mass of the total diene rubber. If the blending amount of the terminal-modified butadiene rubber is less than 15 mass%, the low fuel efficiency is deteriorated. When the blending amount of the terminal-modified butadiene rubber exceeds 50 mass%, the rubber strength is lowered.

The molecular weight distribution (Mw/Mn) of the terminal-modified butadiene rubber is preferably 2.0 or less, more preferably 1.1 to 1.6. By using a molecule having a narrow molecular weight distribution as the terminal-modified butadiene rubber in this way, the rubber properties become better, the rolling resistance is reduced, and the steering stability and durability after the tire is manufactured can be effectively improved. When the molecular weight distribution (Mw/Mn) of the terminal-modified butadiene rubber exceeds 2.0, the hysteresis loss becomes large, the heat generating property of the rubber increases, and the compression set resistance decreases.

The glass transition temperature Tg of the terminal-modified butadiene rubber used in the present invention is preferably-85 ℃ or lower, more preferably-90 ℃ to-100 ℃. By setting the glass transition temperature Tg in this manner, the heat generating property can be effectively reduced. When the glass transition temperature Tg exceeds-80 ℃, the effect of reducing the heat generating property cannot be sufficiently obtained. The glass transition temperature Tg of the natural rubber is not particularly limited, and may be set to, for example, from-70 ℃ to-80 ℃.

The vinyl content of the terminal-modified butadiene rubber used in the present invention is preferably 0.1 to 20% by mass, more preferably 0.1 to 15% by mass. If the vinyl content of the terminal-modified butadiene rubber is less than 0.1 mass%, the affinity with carbon black and silica is insufficient and it is difficult to sufficiently reduce heat generation. When the vinyl content of the terminal-modified butadiene rubber exceeds 20 mass%, the glass transition temperature Tg of the rubber composition increases, and rolling resistance and abrasion resistance cannot be sufficiently improved. The vinyl unit content of the terminal-modified butadiene rubber was measured by an infrared spectroscopic analysis method (Hampton method). The increase or decrease in the vinyl unit content in the terminal-modified butadiene rubber can be appropriately adjusted by a usual method such as a catalyst.

The rubber composition for a tire of the present invention may contain other diene rubbers in addition to the natural rubber and the terminal-modified butadiene rubber. Examples of the other diene rubber include terminal-unmodified butadiene rubber, styrene butadiene rubber, isoprene rubber, acrylonitrile-butadiene rubber, and the like. These diene rubbers may be used alone or as an arbitrary mixture.

The rubber composition for a tire of the present invention must contain both carbon black and silica as fillers. The strength of the rubber composition can be improved by blending these fillers. In particular, by blending silica in combination with the modified butadiene rubber, the rubber hardness can be effectively improved while keeping the heat build-up low. The filler is blended so that the mass ratio of silica to the total amount of carbon black and silica is 0.1 to 0.5, preferably 0.15 to 0.3. If the mass ratio of silica deviates from this range, the heat generation property can be kept low, but the effect of improving the rubber hardness or adhesiveness cannot be obtained. In particular, if the mass ratio of silica is too large, the adhesiveness of the rubber composition may be reduced, and the durability during tire running may be deteriorated.

The amount of the filler containing carbon black and silica is not particularly limited as long as the above-mentioned mass ratio is satisfied, and the amount of the filler to be added is preferably 55 parts by mass or more, and more preferably 70 parts by mass to 90 parts by mass, per 100 parts by mass of the diene rubber. If the amount of the filler is less than 55 parts by mass, the hardness of the rubber composition decreases. From the viewpoint of the relationship between the amount of the filler and the mass ratio of the silica, the amount of the silica is preferably 20 to 50 parts by mass, more preferably 20 to 40 parts by mass, per 100 parts by mass of the diene rubber, and the amount of the carbon black is preferably 30 to 60 parts by mass, more preferably 35 to 50 parts by mass, per 100 parts by mass of the diene rubber.

In the carbon black used in the present invention, nitrogen adsorbs to the specific surface area N₂SA is preferably 140m²A ratio of 100m or less per gram²/g～130m²The ratio is/g. By combining carbon black having a large particle diameter with the modified butadiene rubber, the heat generation property can be maintained to be low, and the rubber hardness can be effectively increased. If the nitrogen adsorption specific surface area N of the carbon black₂SA exceeds 150m²The heat generating property is deteriorated. Here, in the present invention, the nitrogen adsorption specific surface area N of the carbon black₂SA was measured according to JIS 6217-2.

In the silica used in the present invention, the CTAB adsorption specific surface area is preferably 140m²/g～250m²A/g, more preferably 150m²/g～220m²The ratio is/g. By using such silica, heat generation properties can be improved. If the CTAB adsorption specific surface area of the silica is less than 130m²The rubber strength decreases per gram. If the CTAB adsorption specific surface area of the silica exceeds 250m²The heat generating property is deteriorated. In the present invention, the CTAB adsorption specific surface area of silica is measured in accordance with ISO 5794.

When silica is used in this manner, a silane coupling agent is preferably used in combination. The amount of the silane coupling agent to be blended is preferably 5 to 10 mass%, more preferably 7 to 9 mass% based on the mass of silica. By blending the silane coupling agent in this manner, the dispersibility of silica can be improved and the reinforcing property with respect to the rubber component can be further improved. If the amount of the silane coupling agent blended is less than 5 mass% of the mass of the silica, the effect of improving the dispersibility of the silica cannot be sufficiently obtained. If the amount of the silane coupling agent is more than 10 mass% based on the mass of the silica, polycondensation occurs between the silane coupling agents, and the desired effect cannot be obtained. The type of silane coupling agent is not particularly limited, and examples of preferable sulfur-containing silane coupling agents include bis- (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, 3-trimethoxysilylpropylbenzothiazoletetrasulfide, γ -mercaptopropyltriethoxysilane, and 3-octanoylthiopropyltriethoxysilane.

The rubber composition of the present invention may contain other inorganic fillers than the above-mentioned carbon black and silica. Examples of the other inorganic filler include clay, talc, calcium carbonate, mica, and aluminum hydroxide.

In the present invention, it is preferable to add an amine-based antiaging agent and/or wax. By blending these components, crack resistance and workability can be improved. The amount of the amine antioxidant blended is preferably 1.0 to 4.0 parts by mass, more preferably 1.5 to 3.5 parts by mass, per 100 parts by mass of the rubber component. The amount of the wax blended is preferably more than 0 part by mass and 2.0 parts by mass or less, more preferably 0.1 part by mass or more and 2.0 parts by mass or less, per 100 parts by mass of the rubber component. The amine-based antiaging agent and the wax may be used alone or in combination. If the amount of the amine-based antioxidant is less than 1.0 part by mass, the effect of improving the crack resistance or processability, particularly the crack resistance is not expected to be reduced. If the amount of the amine-based antioxidant added exceeds 4.0 parts by mass, the processability is lowered. If the amount of wax added exceeds 2.0 parts by mass, the processability is lowered.

The rubber composition for a tire of the present invention may contain other compounding agents than those described above. Examples of the other compounding agents include various compounding agents used for a usual pneumatic tire, such as a vulcanization or crosslinking agent, a vulcanization accelerator, an antioxidant other than amine, a liquid polymer, a thermosetting resin, and a thermoplastic resin. The compounding amount of these compounding agents can be a conventional usual compounding amount as long as the object of the present invention is not violated. The kneading machine may be a general rubber kneading machine, such as a banbury mixer, a kneader, a roll, or the like.

The rubber composition for a tire of the present invention comprising these components has a hardness of 73 or more, preferably 75 to 80, and more preferably 76 to 78. The rubber composition for a tire of the present invention has a modulus of elasticity at 40 ℃ of rebound of 60% or more, preferably 60% to 65%, more preferably 62% to 65%. The rubber composition of the present invention has such physical properties that the rubber composition can reduce rolling resistance and improve steering stability and durability after being formed into a tire. If the hardness is less than 73, the steering stability after the tire is manufactured is deteriorated. If the modulus of elasticity in springback is less than 60%, heat generation is deteriorated and rolling resistance cannot be reduced. The hardness and the modulus of elasticity in springback are not limited to the above-mentioned compounding, but are physical properties that can be adjusted depending on, for example, kneading conditions and a kneading method.

The rubber composition for a tire of the present invention can reduce rolling resistance and improve steering stability and durability after production into a tire by the above-mentioned compounding and physical properties. Specifically, the terminal-modified butadiene rubber may be used in combination with a natural rubber as a rubber component, and carbon black and silica may be used as fillers in an appropriate mass ratio to use the filler and the terminal-modified butadiene rubber in combination, so that the hardness and the modulus of elasticity of resilience of the rubber composition are sufficiently improved as described above, whereby the rolling resistance can be reduced, the steering stability and the durability after the tire is produced can be improved, and the performances can be improved in a well-balanced manner. Therefore, the rubber composition for a tire of the present invention is preferably used for an under tread portion (undercut) of a pneumatic tire, and a pneumatic tire using the rubber composition for a tire of the present invention for an under tread portion can improve fuel efficiency performance while maintaining good steering stability and durability.

The present invention will be further described with reference to the following examples, but the scope of the present invention is not limited to these examples.

Examples

The compounding ingredients other than the vulcanization accelerator and sulfur in 28 rubber compositions (reference example 1, comparative examples 1 to 11, and examples 1 to 16) having the compounding ingredients shown in tables 1 to 3 were weighed, kneaded for 5 minutes in a 1.8L internal Banbury mixer, discharged at a temperature of 150 ℃ and cooled at room temperature. Then, the master batch was supplied to a 1.8L internal Banbury mixer, and a vulcanization accelerator and sulfur were added thereto and mixed for 2 minutes to prepare a rubber composition. Subsequently, the obtained rubber composition was press-vulcanized in a predetermined mold at 160 ℃ for 20 minutes to prepare a vulcanized rubber test piece.

In tables 1 to 3, the hardness of the rubber compositions was measured at a temperature of 20 ℃ by Shore Durometer type A in accordance with JIS K6253. The modulus of resilience of the rubber composition was measured at a temperature of 40 ℃ by a Lupock type resilience elasticity tester in accordance with JIS K6255.

The obtained rubber composition was evaluated for low fuel efficiency performance, steering stability, durability, crack resistance, and processability by the following methods.

Low fuel efficiency performance

A test tire (tire size 215/45R17) in which the obtained rubber composition was used for a tread portion was prepared, assembled to a standard rim (rim size 7JJ) with an air pressure of 230kPa, and a load corresponding to 85% of the maximum load under the air pressure described in the 2009 edition of JATMA was applied to the tire using an indoor drum tester (drum diameter: 1707mm), and the rolling resistance during running was measured at a speed of 80km/h in a state of being pressed against a drum. The evaluation results were expressed by using the reciprocal of the measurement value and an index obtained when the value of reference example 1 was taken as index 100. The larger the index value, the smaller the rolling resistance, meaning the more excellent the low fuel efficiency performance.

Steering stability

A test tire (tire size 215/45R17) using the obtained rubber composition for a tread portion was prepared, mounted on a standard rim (rim size 7JJ), mounted on a test vehicle with an air pressure of 230kPa and an air displacement of 2000cc, and on a test road formed by a paved road surface, road surface responsiveness at the time of lane change when running at 80km/h was functionally evaluated by a test driver. The evaluation results are shown as index values when the standard example 1 is set as index 100. The larger the index value, the better the road surface responsiveness at the time of changing the road surface, meaning the more excellent the steering stability.

Durability

A test tire (tire size 215/45R17) using the obtained rubber composition for a tread portion was prepared, mounted on a standard rim (rim size 7JJ), mounted on a test vehicle with an air pressure of 230kPa and an air displacement of 2000cc, run on an 8-turn test road under conditions of a cornering acceleration of 0.8G and 500 cycles, and a wear amount of the tread portion after running was measured. The evaluation results were expressed as an index when the index of standard example 1 was 100, using the reciprocal of the measurement value. The larger the index value, the smaller the wear amount means the more excellent the durability.

Crack resistance

From the test piece thus obtained, a dumbbell type test piece No. JIS3 based on JIS K6251 was cut. The test piece was evaluated by the following A to C, after measuring the length of crack growth by repeating the bending under the conditions of a temperature of 23 ℃, a stroke of 40mm, a speed of 300. + -. 10rpm, and a number of times of bending of 10 ten thousand using a Demosia bending crack tester based on JIS K6260, and visually observing the presence or absence of cracks (cracks) on the surface of the test piece. The results are shown in the columns of "crack resistance" in tables 1 to 3.

A: few cracks (less than about 10)

B: the number of cracks is large (about 10 or more but less than 100)

C: there are numerous cracks (more than about 100)

Workability

The obtained rubber composition was extruded into a sheet form, and 2 sheets of the extruded product (pressure-bonding sample) 3 hours after extrusion were pressure-bonded under conditions of a pressure-bonding load of 0.98N, a pressure-bonding time of 0 second, and a pressure-bonding speed of 50cm/min, and then peeled off at a peeling speed of 125cm/min, and the adhesive force at that time was measured by a PICMA type viscometer (manufactured by Toyo Seiki Seisaku-Sho Ltd.). The evaluation results are shown in the following A to C. The "adhesion index" used for the evaluation of a to C is an index obtained by using the measured value and setting the index of reference example 1 to 100.

A: the processability was very good (adhesion index over 95)

B: good processability (adhesion index of more than 80 and 95 or less)

C: poor processability (adhesion index of 80 or less)

The kinds of the raw materials used in tables 1 to 3 are shown below.

NR: natural rubber, TSR20 (glass transition temperature Tg: -65 ℃ C.)

SBR: styrene butadiene rubber, Nipol 1502 (glass transition temperature: -60 ℃ C., manufactured by Zeon corporation, Japan)

Modified S-SBR: terminal-modified solution-polymerized styrene butadiene rubber, Nipol NS612 manufactured by Zeon corporation of Japan (non-oil-extended, glass transition temperature Tg: -65 ℃, functional group: hydroxyl group)

BR: butadiene rubber, Nipol BR1220 (glass transition temperature Tg: -105 ℃ C., manufactured by Zeon corporation, Japan)

Modified BR 1: terminal-modified butadiene rubber, BR54 manufactured by JSR corporation (glass transition temperature Tg: -107 ℃, functional group: silanol group, molecular weight distribution 2.5)

Modified BR 2: terminal-modified butadiene rubber (glass transition temperature Tg: -93 ℃, functional group: polyorganosiloxane group) synthesized by the following method

Modified BR 3: terminal-modified butadiene rubber, Nipol BR1250H manufactured by Zeon corporation of Japan (glass transition temperature Tg: -96 ℃, functional group: N-methylpyrrolidinone group, molecular weight distribution 1.1)

CB 1: carbon Black, Niteron #300IH manufactured by Nippon カーボン (Nitrogen adsorption specific surface area N2 SA: 115 m)²/g)

CB 2: carbon Black, Niteron #430 manufactured by Nikkiso カーボン (nitrogen adsorption specific surface area N2 SA: 134 m)²/g)

Silica 1: ultrasil VN3(CTAB adsorption specific surface area: 153m, manufactured by Degussa²/g)

Silica 2: zeosil premix 200MP (CTAB adsorption specific surface area: 210 m) manufactured by Rhodia²/g)

Silane coupling agent: si69 manufactured by Evonik Degussa

Zinc oxide: 3 kinds of zinc oxide produced by the same chemical industry society

Stearic acid: manufactured by Kao corporation ルナック S-25

Anti-aging agent 1: amine antioxidant サントフレックス 6PPD manufactured by フレキシス

Anti-aging agent 2: amine-ketone type antiaging agent ノクラック 224 from Dai-Nei-Shi chemical industry Co Ltd

Wax: サンノック manufactured by Dainio new chemical industry Co., Ltd

Sulfur: ミュークロン OT-20, manufactured by four nationality chemical industry Co., Ltd

Vulcanization accelerators: ノクセラー CZ manufactured by Dainio new chemical industries

Synthetic method of modified BR2

After 5670g of cyclohexane, 700g of 1, 3-butadiene and 0.17mmol of tetramethylethylenediamine were charged into an autoclave equipped with a stirrer under a nitrogen atmosphere, n-butyllithium in an amount necessary for neutralizing impurities contained in cyclohexane and 1, 3-butadiene and inhibiting polymerization was added, and 8.33mmol of n-butyllithium in an amount used in the polymerization reaction was further added to start the polymerization at 50 ℃. After 20 minutes passed from the start of polymerization, 300g of 1, 3-butadiene was continuously added over 30 minutes. The maximum temperature in the polymerization was 80 ℃. After the completion of the continuous addition, the polymerization reaction was further continued for 15 minutes, and it was confirmed that the polymerization conversion rate was in the range of 95% to 100%, and then a small amount of the polymerization solution was sampled. An excess of methanol was added to a small amount of the sampled polymerization solution to stop the reaction, and then air-dried to obtain a polymer, which was then used as a sample for Gel Permeation Chromatography (GPC) analysis. Using this sample, the peak molecular weight and the molecular weight distribution of the polymer (corresponding to the conjugated diene polymer chain having an active end) were measured, and as a result, "23 ten thousand" and "1.04", respectively.

Immediately after sampling the small amount of the polymerization solution, 0.288mmol of 1, 6-bis (trichlorosilyl) hexane (equivalent to 0.0345 times mol based on n-butyllithium used for polymerization) was added to the polymerization solution in the form of a 40 wt% cyclohexane solution, and the mixture was reacted for 30 minutes. Further, 0.0382mmol (corresponding to 0.00459 times mol of n-butyllithium used for polymerization) of polyorganosiloxane A was added in the form of a 20 wt% xylene solution, and the mixture was reacted for 30 minutes. Then, methanol was added as a polymerization terminator in an amount of 2 times by mol as much as the n-butyllithium used. Thus, a solution containing a modified butadiene rubber was obtained. To this solution, 0.2 part of 2, 4-bis (n-octylthiomethyl) -6-methylphenol as an antiaging agent was added per 100 parts of the rubber component, and then the solvent was removed by steam stripping, followed by vacuum drying at 60 ℃ for 24 hours to obtain a modified butadiene rubber (modified BR2) in a solid form. The weight average molecular weight, molecular weight distribution, coupling ratio, vinyl content, and Mooney viscosity were measured for the modified butadiene rubber (modified BR2) and were "51 ten thousand", "1.46", "28%", "11% by mass", and "46", respectively.

As is apparent from tables 1 to 3, the rubber compositions (tires) of examples 1 to 16 are improved in low fuel efficiency performance, steering stability and durability in a well-balanced manner with respect to the rubber composition of reference example 1. Further, the steel sheet exhibited excellent crack resistance and workability equal to or higher than those of standard example 1.

On the other hand, the rubber composition (tire) of comparative example 1 is compounded with styrene butadiene rubber instead of the terminal-modified butadiene rubber, and therefore the fuel efficiency performance is deteriorated. In the rubber composition (tire) of comparative example 2, since the terminal-modified solution-polymerized styrene butadiene rubber was blended in place of the terminal-modified butadiene rubber, the fuel efficiency performance and durability were deteriorated. The rubber composition (tire) of comparative example 3 had poor durability because the amount of the terminal-modified butadiene rubber blended was too small. The rubber composition (tire) of comparative example 4 is not compounded with silica, and therefore, the fuel efficiency performance and durability are deteriorated. With the rubber composition (tire) of comparative example 5, since the hardness is too small, the steering stability and durability are deteriorated. The rubber composition (tire) of comparative example 6 had an excessively low elastic modulus of resilience, and therefore had poor heat generation properties. The rubber composition (tire) of comparative example 7 is inferior in durability because not only natural rubber and terminal-modified butadiene rubber are blended, but also styrene butadiene rubber is blended. The rubber composition (tire) of comparative example 8 did not contain the terminal-modified butadiene rubber, and therefore did not exhibit the effect of improving the low fuel efficiency performance and the steering stability performance, and further, contained only an antioxidant other than an amine-based one, and therefore, the crack resistance and the durability were deteriorated. The rubber composition (tire) of comparative example 9 did not contain the terminal-modified butadiene rubber, and therefore, the effects of improving the low fuel efficiency performance, the steering stability performance and the durability were not obtained, and further, the processability was deteriorated because the amount of the antioxidant added was too large. The rubber composition (tire) of comparative example 10 did not contain the terminal-modified butadiene rubber, and therefore, the effects of improving the low fuel efficiency performance, the steering stability performance, and the durability were not obtained, and further, the processability was deteriorated because the amount of the wax added was too large. The rubber composition (tire) of comparative example 11 did not contain the terminal-modified butadiene rubber, and therefore did not exhibit the effects of improving the low fuel efficiency performance, the steering stability performance and the durability, and further, contained a large amount of an antioxidant other than an amine antioxidant, and therefore, the crack resistance and the processability were deteriorated.