JP2012062408A - Rubber composition for tire and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for a tire, with which low fuel consuming properties and destruction characteristics are improved with good balance between them, and to provide a pneumatic tire using the composition.SOLUTION: The rubber composition for a tire includes a liquid coumarone-indene resin of which the softening point is -20 to 20°C, and a liquid rosin-based resin of which the softening point is -20 to 20°C, wherein the total content of the liquid coumarone-indene resin and the liquid rosin-based resin is 3-40 pts.mass with respect to 100 pts.mass of the rubber components.

Description

The present invention relates to a rubber composition for tires and a pneumatic tire using the same.

Conventionally, vehicle fuel efficiency has been reduced by reducing the rolling resistance of tires (improving rolling resistance performance). In recent years, there has been an increasing demand for low fuel consumption of vehicles, and excellent low heat generation (low fuel consumption) for rubber compositions for producing treads with a high occupation ratio of tires among tire components. Sex) is required.

As a method for improving the low fuel consumption of the rubber composition, a method of reducing the reinforcing filler is known. However, when the amount of reinforcing filler is reduced, the fracture characteristics of the rubber composition tend to deteriorate. For this reason, there is a possibility that wear appearance defects (chipping), tread groove bottom cracks (TGC), and the like may occur. Therefore, it has been desired to develop a rubber composition that achieves both low fuel consumption and fracture characteristics.

Patent Document 1 discloses that grip performance can be improved by blending a rubber composition with a rosin ester resin having a softening point of 125 ° C. or more and an acid value of 20 or less. However, there is still room for improvement in terms of improving fuel economy and destruction characteristics in a well-balanced manner.

JP 2005-2448056 A

An object of the present invention is to solve the above problems and provide a rubber composition for a tire that can improve fuel economy and fracture characteristics in a well-balanced manner, and a pneumatic tire using the same.

The present invention includes a liquid coumarone indene resin having a softening point of -20 to 20 ° C and a liquid rosin resin having a softening point of -20 to 20 ° C. It is related with the rubber composition for tires whose total content of resin and liquid rosin-type resin is 3-40 mass parts.

The liquid rosin resin preferably has an acid value of 10 to 100 mgKOH / g and a hydroxyl value of 50 to 150 mgKOH / g.

The liquid rosin resin is preferably a rosin ester resin.

The tire rubber composition preferably contains 8 parts by mass or more of the liquid coumarone indene resin and 8 parts by mass or more of the liquid rosin resin with respect to 100 parts by mass of the rubber component.

The tire rubber composition is preferably used as a tread rubber composition.

The present invention also relates to a pneumatic tire produced using the rubber composition.

According to the present invention, a liquid coumarone indene resin having a specific softening point and a liquid rosin resin having a specific softening point are used. Since the total rubber content of the tire is a specific amount, the use of the rubber composition for tire components (especially treads) improves the fuel efficiency and fracture characteristics in a well-balanced manner. Provided tires.

The rubber composition for tires of the present invention includes a liquid coumarone indene resin having a specific softening point (hereinafter also simply referred to as liquid coumarone indene resin) and a liquid rosin resin having a specific softening point (hereinafter simply referred to as liquid). The total content of the liquid coumarone indene resin and the liquid rosin resin is a specific amount with respect to the rubber component. By using a liquid coumarone indene resin and a liquid rosin resin in combination, and setting the total content of these to a specific amount, fuel economy and destruction characteristics are improved in a well-balanced manner. Accordingly, it is possible to suppress the occurrence of wear appearance defects (chipping), tread groove bottom cracks (TGC) and the like while having excellent fuel efficiency.

Examples of the rubber component used in the present invention include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), and ethylene propylene diene rubber. Examples thereof include diene rubbers such as (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), and butyl rubber (IIR). A rubber component may be used independently and may use 2 or more types together. Among these, NR, SBR, and BR are preferable, and NR, SBR, and BR are more preferably used in combination because fuel efficiency and destruction characteristics are improved in a well-balanced manner.

The NR is not particularly limited, and for example, SIR20, RSS # 3, TSR20, deproteinized natural rubber (DPNR), high-purity natural rubber (HPNR), and the like can be used in the tire industry.

The content of NR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 7% by mass or more. If it is less than 5% by mass, the fracture characteristics tend to be lowered. The NR content is preferably 20% by mass or less, more preferably 15% by mass or less. If it exceeds 20% by mass, sufficient fuel economy may not be obtained.

It is not particularly limited as BR, for example, BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B manufactured by Ube Industries, Ltd., BR150B having high cis content such as BR150B, VCR412, VCR617 manufactured by Ube Industries, Ltd. Commonly used in the tire industry, such as BR containing syndiotactic polybutadiene crystals, can be used. Among them, the cis content is preferably 95% by mass or more because it has excellent fracture characteristics.

The content of BR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 15% by mass or more. If it is less than 10% by mass, the fracture characteristics tend to be lowered. The BR content is preferably 30% by mass or less, more preferably 25% by mass or less. If it exceeds 30% by mass, sufficient fuel economy may not be obtained.

The SBR is not particularly limited, and those generally used in the tire industry such as emulsion polymerization styrene butadiene rubber (E-SBR) and solution polymerization styrene butadiene rubber (S-SBR) can be used. Among these, from the viewpoint that the effect of improving fuel economy is great, modified SBR modified with a polyfunctional compound having two or more epoxy groups in the molecule and introduced with a hydroxyl group or an epoxy group is preferable. As such modified SBR, Asaprene E15 manufactured by Asahi Kasei Chemicals Corporation can be used.

The vinyl content of SBR is preferably 5% by mass or more, more preferably 10% by mass or more. If the vinyl content is less than 5% by mass, sufficient grip performance may not be obtained. The vinyl content is preferably 90% by mass or less, more preferably 80% by mass or less, and still more preferably 70% by mass or less. When the vinyl content exceeds 90% by mass, the fracture characteristics tend to decrease.
In the present invention, the vinyl content of SBR can be measured by infrared absorption spectrum analysis.

The styrene content of SBR is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 20% by mass or more. If the styrene content is less than 5% by mass, sufficient grip performance may not be obtained. The styrene content is preferably 90% by mass or less, more preferably 80% by mass or less, and still more preferably 60% by mass or less. When the styrene content exceeds 90% by mass, the exothermic property is remarkably increased and the fuel efficiency tends to be deteriorated.
In the present invention, the styrene content of SBR is calculated by H ¹ -NMR measurement.

The content of SBR in 100% by mass of the rubber component is preferably 50% by mass or more, more preferably 60% by mass or more, and further preferably 65% by mass or more. If it is less than 50% by mass, sufficient fuel economy may not be obtained. The content of SBR is preferably 80% by mass or less, more preferably 75% by mass or less. When it exceeds 80 mass%, there exists a tendency for a fracture characteristic to fall.

The rubber composition of the present invention uses a liquid coumarone indene resin having a specific softening point and a liquid rosin resin having a specific softening point. By using the liquid coumarone indene resin and the liquid rosin resin as oil substitutes so that the total content of these resins becomes a specific amount, fuel economy and destruction characteristics can be improved in a well-balanced manner. This effect is considered due to the high compatibility of the liquid coumarone indene resin and the rubber component of the liquid rosin resin and the viscosity characteristics of the liquid coumarone indene resin and liquid rosin resin.

In the present invention, the fracture characteristics can be improved by blending the liquid coumarone indene resin.
In the present invention, the liquid coumarone indene resin is a coumarone indene resin in a liquid state, and specifically means a coumarone indene resin having the following softening points. In the present invention, the coumarone indene resin means a resin containing coumarone and indene as a monomer component constituting the resin skeleton (main chain), and as a monomer component contained in the skeleton other than coumarone and indene, Examples thereof include styrene, α-methylstyrene, methylindene, vinyltoluene and the like.

The softening point of the liquid coumarone indene resin is −20 ° C. or higher, preferably −5 ° C. or higher, more preferably 0 ° C. or higher. When the temperature is lower than -20 ° C, the viscosity of the liquid coumarone indene resin becomes too low, and the kneadability with the rubber component is deteriorated, so that the dispersibility in the rubber composition is lowered, and the fracture energy (breaking characteristics) ) Gets worse. The softening point of the liquid coumarone indene resin is 20 ° C. or lower, preferably 18 ° C. or lower, more preferably 17 ° C. or lower. If it exceeds 20 ° C., sufficient fuel efficiency cannot be obtained.
The softening point of the liquid coumarone indene resin is a temperature at which the sphere descends when the softening point specified in JIS K 6220 is measured with a ring and ball softening point measuring device.

The content of the liquid coumarone indene resin is preferably 4 parts by mass or more, more preferably 8 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 4 parts by mass, the fracture characteristics may not be sufficiently improved. Further, the content of the liquid coumarone indene resin is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and further preferably 12 parts by mass or less with respect to 100 parts by mass of the rubber component. When it exceeds 20 mass parts, there exists a tendency for a fracture characteristic and a low fuel consumption to deteriorate.

In the present invention, fuel efficiency can be improved by blending a liquid rosin resin.
In the present invention, the liquid rosin resin is a liquid rosin resin, and specifically means a rosin resin having the following softening point.

In the present invention, as the rosin resin, raw rosin such as gum rosin, wood rosin, tall oil rosin; disproportionate of raw rosin; stabilized rosin obtained by hydrogenating raw rosin; rosins such as polymerized rosin; Various known products such as esterified rosins (rosin ester resin), phenol-modified products, unsaturated acid (maleic acid, etc.)-Modified rosins, and formylated rosins obtained by reducing rosins can be used. Among these, rosin ester resin is preferable because it can achieve both low fuel consumption and fracture characteristics. The rosin ester resin is produced by an esterification reaction between the rosin and a polyol (polyhydric alcohol such as glycerin or pentaerythritol). The esterification reaction can be performed by a known method, for example, by heating the rosins and polyol to 200 to 300 ° C. in an inert gas atmosphere and removing the generated water out of the system.

The softening point of the liquid rosin resin is −20 ° C. or higher, preferably −5 ° C. or higher, more preferably 0 ° C. or higher. When the temperature is lower than -20 ° C, the viscosity of the liquid rosin resin becomes too low, and the kneadability with the rubber component is deteriorated, so that the dispersibility in the rubber composition is lowered, and the fracture energy (breakage characteristics). Gets worse. The softening point of the liquid rosin resin is 20 ° C. or lower, preferably 18 ° C. or lower, more preferably 17 ° C. or lower. If it exceeds 20 ° C., sufficient fuel efficiency cannot be obtained.
The softening point of the liquid rosin-based resin is a temperature at which the sphere descends when the softening point specified in JIS K 5902 is measured with a ring and ball softening point measuring device.

The acid value (mgKOH / g) of the liquid rosin resin is preferably 10 or more, more preferably 20 or more, and still more preferably 30 or more. The acid value is preferably 100 or less, more preferably 80 or less, and still more preferably 50 or less. When the acid value is within the above range, fuel efficiency can be further improved.
In the present invention, the acid value is the amount of potassium hydroxide required to neutralize the acid contained in 1 g of resin, expressed in milligrams, and is a value measured by potentiometric titration (JIS K0070). is there.

The hydroxyl value (mgKOH / g) of the liquid rosin resin is preferably 50 or more, more preferably 60 or more.
The hydroxyl value is preferably 150 or less, more preferably 100 or less. When the hydroxyl value is within the above range, the fuel efficiency can be further improved.
In the present invention, the hydroxyl value is the amount of potassium hydroxide required to neutralize acetic acid bonded to a hydroxyl group when 1 g of the resin is acetylated, expressed in milligrams, and potentiometric titration (JIS K0070). ).

The content of the liquid rosin resin is preferably 4 parts by mass or more, more preferably 8 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 4 parts by mass, the fuel economy may not be sufficiently improved. The content of the liquid rosin resin is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 12 parts by mass or less with respect to 100 parts by mass of the rubber component. When it exceeds 20 mass parts, there exists a tendency for a fracture characteristic and a low fuel consumption to deteriorate.

The total content of the liquid coumarone indene resin and the liquid rosin resin is 3 parts by mass or more, preferably 5 parts by mass or more, more preferably 15 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 3 parts by mass, the fuel efficiency and the destructive properties cannot be sufficiently improved. Moreover, the said total content is 40 mass parts or less with respect to 100 mass parts of rubber components, Preferably it is 35 mass parts or less, More preferably, it is 25 mass parts or less. When it exceeds 40 mass parts, there exists a tendency for a fracture characteristic and a low fuel consumption to deteriorate.

In the present invention, it is preferable to use silica. By blending silica, good low heat build-up and high rubber strength can be obtained, and both low fuel consumption and breaking characteristics can be achieved. The silica is not particularly limited, and examples thereof include dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid), and the like, but wet process silica is preferable because of its large number of silanol groups.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 40 m ² / g or more, more preferably 50 m ² / g or more. If it is less than 40 m < ² > / g, there exists a tendency for a fracture characteristic to fall. Further, N ₂ SA of silica is preferably 220 m ² / g or less, more preferably 200 m ² / g or less. If it exceeds 220 m ² / g, fuel economy and kneading processability tend to deteriorate.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

The content of silica is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and further preferably 45 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 10 parts by mass, there is a tendency that a sufficient effect due to silica blending cannot be obtained. Further, the content of silica is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, and still more preferably 85 parts by mass or less. When it exceeds 150 parts by mass, silica is difficult to disperse and the fracture characteristics tend to deteriorate.

Silica is preferably used in combination with a silane coupling agent. As the silane coupling agent, any silane coupling agent conventionally used in combination with silica can be used in the rubber industry. For example, bis (3-triethoxysilylpropyl) disulfide, bis (3-triethoxy Silylpropyl) sulfide type such as tetrasulfide, mercapto type such as 3-mercaptopropyltrimethoxysilane, vinyl type such as vinyltriethoxysilane, amino type such as 3-aminopropyltriethoxysilane, γ-glycidoxypropyltri Examples include glycidoxy type of ethoxysilane, nitro type such as 3-nitropropyltrimethoxysilane, and chloro type such as 3-chloropropyltrimethoxysilane. These may be used alone or in combination of two or more. Among these, sulfide type is preferable, and bis (3-triethoxysilylpropyl) tetrasulfide is more preferable.

The content of the silane coupling agent is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, and still more preferably 10 parts by mass or more with respect to 100 parts by mass of the silica. If it is less than 5 mass parts, there exists a tendency for a fracture characteristic to fall large. Further, the content of the silane coupling agent is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, with respect to 100 parts by mass of the silica. When it exceeds 20 parts by mass, there is a tendency that effects such as improvement of fracture characteristics and reduction of rolling resistance (improvement of fuel efficiency) due to addition of the silane coupling agent cannot be obtained.

You may mix | blend carbon black with the said rubber composition. Thereby, better reinforcing properties can be obtained, and the fracture characteristics can be further improved. As the carbon black, for example, those generally used in the tire industry such as GPF, HAF, ISAF, and SAF can be used.

When carbon black is used, the nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 30 m ² / g or more, more preferably 70 m ² / g or more. If N ₂ SA is less than 30 m ² / g, sufficient reinforcing properties cannot be obtained, and the fracture characteristics may not be sufficiently improved. Also, _N 2 SA of carbon black is preferably 250 meters ² / g or less, and more preferably not more than 150m ² / g. When N ₂ SA exceeds 250 m ² / g, the viscosity of the unvulcanized rubber composition becomes very high and the kneading processability tends to deteriorate or the fuel efficiency tends to deteriorate.
Note that N ₂ SA of carbon black is obtained by JIS K6217, method A on page 7.

The content of carbon black is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, and still more preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 5 parts by mass, sufficient reinforcing properties cannot be obtained, and the fracture characteristics may not be sufficiently improved. The carbon black content is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and still more preferably 30 parts by mass or less with respect to 100 parts by mass of the rubber component. If it exceeds 60 parts by mass, the fuel efficiency tends to deteriorate.

In addition to the above components, the rubber composition of the present invention includes compounding agents generally used in the production of rubber compositions, such as reinforcing fillers such as clay, zinc oxide, stearic acid, various anti-aging agents, aromas Oils such as oil, waxes, vulcanizing agents such as sulfur, vulcanization accelerators and the like can be appropriately blended.

The liquid coumarone indene resin and the liquid rosin resin have an action of softening the rubber composition. Therefore, by using the liquid coumarone indene resin and the liquid rosin resin, the content of oil in the rubber composition can be reduced and the fuel efficiency can be further improved.

The oil content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 12 parts by mass or less with respect to 100 parts by mass of the rubber component.

The rubber composition of the present invention can be used for each member used in a tire, and among them, it is preferably used for a tread (cap tread and base tread), and more preferably used for a cap tread. The cap tread is an outer layer portion of a tread having a multilayer structure, and is a surface layer in a tread having a two-layer structure [a surface layer (cap tread) and an inner surface layer (base tread)].

As a method for producing the rubber composition of the present invention, a known method can be employed, and examples thereof include a method of kneading the above components using a rubber kneading device such as a Banbury mixer or an open roll.

Using the rubber composition of the present invention, the pneumatic tire of the present invention can be produced by an ordinary method. That is, a tire member such as a tread can be produced using the rubber composition, bonded together with other members, and heated and pressurized on a tire molding machine. A tread can be produced by a method of pasting a rubber composition in a sheet shape into a predetermined shape, a method of charging two or more extruders, and forming two layers at the head outlet of the extruder. it can.

The pneumatic tire of the present invention can be used for passenger cars, trucks, buses and the like.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
NR: SIR (made in Indonesia)
SBR: Asaprene E15 manufactured by Asahi Kasei Chemicals Corporation (S-SBR modified with a polyfunctional compound having two or more epoxy groups in the molecule (coupling), styrene content: 23% by mass, vinyl content: 63% by mass) )
BR: Nippon 1220 manufactured by Nippon Zeon Co., Ltd. (Hicis BR, cis content: 96.5% by mass)
Silica: Ultrasil VN3 manufactured by Evonik Degussa (N ₂ SA: 175 m ² / g)
Carbon black: N220 (N ₂ SA: 111 m ² / g) manufactured by Cabot Japan
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Evonik Degussa
Zinc oxide: Zinc oxide stearic acid manufactured by Mitsui Mining & Smelting Co., Ltd .: Stearic acid “Kashiwa” manufactured by NOF Corporation
Liquid coumarone indene resin: NOVARES C10 manufactured by Rutgers Chemicals (liquid coumarone indene resin, softening point: 5 to 15 ° C.)
Liquid rosin resin: ke-364c (rosin ester resin, acid value: 35 mgKOH / g, hydroxyl value: 97 mgKOH / g, softening point: 5 to 15 ° C.) manufactured by Arakawa Chemical Co., Ltd.
Rosin resin: KR-85 manufactured by Arakawa Chemical Co., Ltd. (Rosin resin having a carboxyl group, acid value: 170 mgKOH / g, softening point: 80 to 87 ° C.)
Aroma oil: Diana Process AH-24 manufactured by Idemitsu Kosan Co., Ltd.
Anti-aging agent: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd.
Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Sulfur: Powder sulfur vulcanization accelerator CZ manufactured by Karuizawa Sulfur Co., Ltd .: Noxeller CZ manufactured by Ouchi Shinsei Chemical Co., Ltd.
Vulcanization accelerator DPG: NOCELLER D manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-5 and Comparative Examples 1-6
According to the formulation shown in Table 1, using a 1.7 L Banbury mixer, materials other than sulfur and a vulcanization accelerator were kneaded for 5 minutes at 150 ° C. to obtain a kneaded product. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 3 minutes at 80 ° C. using a biaxial open roll to obtain an unvulcanized rubber composition. Furthermore, the vulcanized rubber composition was obtained by vulcanizing the obtained unvulcanized rubber composition at 150 ° C. for 30 minutes.

The following evaluation was performed using the obtained vulcanized rubber composition. The results are shown in Table 1.

(Low fuel consumption)
Using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), tan δ of each vulcanized rubber composition was measured under the conditions of a temperature of 70 ° C., an initial strain of 10%, and a dynamic strain of 2%. The tan δ was set to 100, and the index was expressed by the following calculation formula. The larger the index, the better the rolling resistance (low fuel consumption).
(Rolling resistance index) = (tan δ of Comparative Example 1) / (tan δ of each formulation) × 100

(Tensile test)
A tensile test was carried out from the vulcanized rubber composition using a No. 3 dumbbell according to JIS-K6251, and the breaking strength (TB) and elongation at break (EB) were measured. TB × EB / 2 was defined as the fracture characteristic, and the fracture characteristic of Comparative Example 1 was expressed as an index with the fracture characteristic as 100. The larger the index, the better the fracture characteristics.

As shown in Table 1, in the examples in which the liquid coumarone indene resin and the liquid rosin resin were used in combination and the total content thereof was a specific amount, the fuel economy and the breaking characteristics were improved in a well-balanced manner. In particular, from the results of Comparative Examples 1 to 3 and Example 1, it has been clarified that the above-described combined use synergistically improves fuel efficiency and destruction characteristics. On the other hand, Comparative Examples 1 to 5 in which the liquid coumarone indene resin and the liquid rosin resin are not used in combination, and Comparative Example 6 in which the total content of the combined use exceeds the specific amount are low fuel consumption and destruction characteristics. Could not improve in a balanced manner.

Claims (6)

A liquid coumarone indene resin having a softening point of -20 to 20 ° C and a liquid rosin resin having a softening point of -20 to 20 ° C, and the liquid coumarone indene resin and liquid rosin with respect to 100 parts by mass of the rubber component The rubber composition for tires whose total content of a system resin is 3-40 mass parts. The tire rubber composition according to claim 1, wherein the liquid rosin resin has an acid value of 10 to 100 mgKOH / g and a hydroxyl value of 50 to 150 mgKOH / g. The tire rubber composition according to claim 1 or 2, wherein the liquid rosin resin is a rosin ester resin. The rubber composition for a tire according to any one of claims 1 to 3, comprising 8 parts by mass or more of the liquid coumarone indene resin and 8 parts by mass or more of the liquid rosin resin with respect to 100 parts by mass of the rubber component. The tire rubber composition according to any one of claims 1 to 4, which is used as a tread rubber composition. The pneumatic tire produced using the rubber composition in any one of Claims 1-5.