JP6787022B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire.

As a method for improving the grip performance of a tire, a method of blending a tackifier resin such as a phenol resin is generally known (see, for example, Patent Document 1). However, when the tackifier resin is blended, the temperature dependence of the rubber hardness becomes large, so that good grip performance cannot be exhibited over a wide temperature range. For example, even if the dry grip performance is improved, it is wet. Grip performance may deteriorate. Further, if the tackifier resin is blended, the abrasion resistance is deteriorated, and good durability may not be ensured. Therefore, it is required to provide a tire that can exhibit good grip performance over a wide temperature range and has excellent durability.

Japanese Unexamined Patent Publication No. 2008-163108

An object of the present invention is to solve the above problems and to provide a pneumatic tire having improved wet grip performance and dry grip performance while maintaining good durability.

The present invention has a tread prepared using a rubber composition containing a rubber component, a thermoplastic elastomer, a carbon black and / or white filler, and a softening agent, and the thermoplastic elastomer has one end. The first block component having a difference in SP value from the rubber component of 0.3 or less is placed at the other end, and the difference from the SP value from the rubber component is 0.4 to 0.9. With respect to pneumatic tires having a two-block component.

The content of the thermoplastic elastomer with respect to 100 parts by mass of the rubber component is preferably 2 to 15 parts by mass.

The melting point of the second block component is preferably 40 to 150 ° C.

The softener is preferably an oil and / or a liquid diene rubber.

According to the present invention, it is a pneumatic tire having a tread made by using a rubber composition containing a rubber component, a specific thermoplastic elastomer, a carbon black and / or white filler, and a softening agent. Wet grip performance and dry grip performance can be improved while maintaining good durability.

The pneumatic tire of the present invention has a tread prepared by using a rubber composition containing a rubber component, a thermoplastic elastomer, a carbon black and / or white filler, and a softener, and the thermoplastic elastomer is At one end, the first block component having an SP value difference of 0.3 or less from the rubber component is placed, and at the other end, the difference from the SP value from the rubber component is 0.4 to 0. It has a second block component of 9.

The tackifier resin (highly compatible resin) having high compatibility with the polymer (rubber component) is inferior in the effect of improving the grip performance as compared with the tackifier resin (low compatibility resin) having low compatibility with the polymer. Tend. It is considered that this is because, in the case of a highly compatible resin, the resin is finely dispersed in the rubber composition, and energy loss is less likely to occur. Therefore, in order to further improve the grip performance, it is preferable to use a low compatibility resin, but since the low compatibility resin tends to generate bloom, the adhesiveness between the rubbers is lost due to the bloom, and good durability is obtained. May not be secured. Further, when a low compatibility resin is used, the abrasion resistance tends to be deteriorated.

On the other hand, the thermoplastic elastomer used in the present invention has a first block component having a difference in SP value of 0.3 or less from the rubber component and having high compatibility with the rubber component at one end. At the end of, the difference between the SP value and the rubber component is 0.4 to 0.9, and the second block component, which has low compatibility with the rubber component, is contained. Grip performance can be improved by the second block component while suppressing. This makes it possible to improve the grip performance while maintaining good durability (wear resistance, rubber adhesiveness).

Further, since the rubber composition containing the thermoplastic elastomer has a smaller temperature dependence of rubber hardness than the conventional rubber composition containing a tackifier resin, it has a good grip over a wide temperature range. It is possible to demonstrate the performance. As a result, both dry grip performance and wet grip performance can be improved.

Examples of the rubber component that can be 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 ( EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), butyl rubber (IIR) and other diene rubbers. The rubber component may be used alone or in combination of two or more. Of these, NR, BR, and SBR are preferable, and SBR is more preferable, because grip performance, wear resistance, and adhesiveness can be obtained in a well-balanced manner.

The SBR is not particularly limited, and for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), and the like can be used.

The styrene content of SBR is preferably 20% by mass or more, more preferably 25% by mass or more, and further preferably 30% by mass or more. If it is less than 20% by mass, sufficient grip performance tends not to be obtained. The styrene content is preferably 60% by mass or less, more preferably 50% by mass or less, and further preferably 40% by mass or less. If it exceeds 60% by mass, the wear resistance tends to decrease. In addition, the temperature dependence of the grip performance increases, and the dry grip performance and the wet grip performance tend to be unbalanced.
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 10% by mass or more, more preferably 15% by mass or more, and further preferably 60% by mass or more. If it is less than 10% by mass, sufficient grip performance, wear resistance and adhesiveness tend not to be obtained. The upper limit of the SBR content is not particularly limited, and may be 100% by mass.

In the present invention, a thermoplastic elastomer having a first block component having a high compatibility with a rubber component at one end and a second block component having a low compatibility with a rubber component at the other end is used. As a result, the grip performance can be improved while maintaining the durability. A thermoplastic elastomer having a block component having a high compatibility with the rubber component at both ends does not sufficiently improve the grip performance, and heat having a block component having a low compatibility with the rubber component at both ends. With a plastic elastomer, the adhesiveness between rubbers is deteriorated, which may cause a problem in durability.

The difference in solubility parameter (SP value) between the first block component and the rubber component is 0.3 or less, preferably 0.2 or less. When the difference in SP value is within the above range, the bloom of the thermoplastic elastomer is effectively suppressed, and good durability can be obtained. The lower limit of the difference between the SP values of the first block component and the rubber component is not particularly limited, and the smaller the difference, the more preferable, and it may be 0.

The difference in SP value between the second block component and the rubber component is 0.4 to 0.9. When the difference in SP value is within the above range, energy loss is effectively generated and good grip performance can be obtained. The lower limit of the difference in SP value is preferably 0.6 or more from the viewpoint of grip performance. Further, the upper limit of the difference in SP value is preferably 0.8 or less because the bloom of the thermoplastic elastomer can be satisfactorily suppressed.

In the present invention, the SP value means a solubility parameter (Solubility Parameter) calculated by the Hoy method based on the structure of the compound. The Hoy method is, for example, K.K. L. Hoy "Table of Solubility Parameters", Solvent and Coatings Materials Research and Development Department, Union Carbites Corp. It is a calculation method described in (1985).

The melting point of the first block component is preferably 40 ° C. or higher, more preferably 50 ° C. or higher, and preferably 150 ° C. or lower, more preferably 120 ° C. or lower. If the temperature is lower than 40 ° C or higher than 150 ° C, sufficient grip performance may not be obtained.

The melting point of the second block component is preferably 40 ° C. or higher, more preferably 50 ° C. or higher, and preferably 150 ° C. or lower, more preferably 120 ° C. or lower. If the temperature is lower than 40 ° C or higher than 150 ° C, sufficient grip performance may not be obtained.

In the present specification, the melting point is the peak temperature in DSC (differential scanning calorimetry), and when there are a plurality of peaks, the peak temperature having the largest heat of fusion ΔH (J / g) is defined as the melting point.

The content of the first block component in 100% by mass of the thermoplastic elastomer is preferably 10% by mass or more, more preferably 15% by mass or more, because good wear resistance and adhesiveness can be obtained. Further, it is preferably 80% by mass or less, more preferably 70% by mass or less.

The content of the second block component in 100% by mass of the thermoplastic elastomer is preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 10% by mass or more, because good grip performance can be obtained. It is 80% by mass or less, more preferably 70% by mass or less.

The constituent units of the first block component and the second block component can be appropriately changed according to the rubber component used. For example, when SBR is used as the rubber component, styrene is used as the constituent unit of the first block component. , Butden, etc., and as the second block component, a constitutional unit based on ethylene, urethane, nylon, vinyl acetate, etc. can be used. Further, in order to adjust the SP value, a polar group such as phenol may be introduced into these constituent units.

The thermoplastic elastomer may be composed of only the first block component and the second block component, but it is preferable that the thermoplastic elastomer has another component between the first block component and the second block component (main chain portion). Examples of other components include structural units based on isoprene, butadiene, ethylene, butylene, urethane, nylon, vinyl acetate and the like. Among them, a structural unit based on at least one selected from the group consisting of ethylene, butylene, and urethane is preferable because a highly flexible thermoplastic elastomer can be obtained and the temperature dependence of grip performance can be further reduced. And butylene-based building blocks are more preferred.

The content of the thermoplastic elastomer is preferably 2 parts by mass or more, more preferably 3 parts by mass or more, still more preferably 5 parts by mass or more, and preferably 15 parts by mass with respect to 100 parts by mass of the rubber component. Hereinafter, it is more preferably 10 parts by mass or less. If it is less than 2 parts by mass, a sufficient effect of improving the grip performance cannot be obtained, and if it exceeds 15 parts by mass, the wear resistance may be lowered.

In the present invention, a tackifier resin (resin) may be used together with the thermoplastic elastomer. Examples of the tackifying resin that can be used include resins commonly used in conventional rubber compositions for tires, such as aromatic petroleum resins. Examples of the aromatic petroleum resin include phenol-based resin, Kumaron inden resin, terpene resin, styrene resin, acrylic resin, rosin resin, dicyclopentadiene resin (DCPD resin) and the like. Examples of the phenolic resin include kolesin (manufactured by BASF) and tackyrol (manufactured by Taoka Chemical Co., Ltd.). Examples of the Kumaron inden resin include Esclon (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.) and Neopolymer (manufactured by Nippon Petrochemicals Co., Ltd.). Examples of the styrene resin include Sylvatraxx4401 (manufactured by Arizona chemical). Examples of the terpene resin include TR7125 (manufactured by Arizona chemical) and TO125 (manufactured by Yasuhara Chemical Co., Ltd.).

The softening point of the tackifier resin is preferably 60 to 170 ° C. If it is less than 60 ° C., stable grip performance during running may not be obtained, and if it exceeds 170 ° C., the initial grip performance may be deteriorated.
In the present invention, the softening point of the tackifier resin is the temperature at which the ball drops when the softening point defined in JIS K 6220-1: 2001 is measured by a ring-ball type softening point measuring device.

As the softener used in the present invention, oil and liquid diene polymer are preferable, and oil is more preferable.

Examples of the oil include process oils such as paraffin-based, aroma-based, and naphthenic-based process oils.

When the oil is blended, the content of the oil is preferably 15 parts by mass or more, more preferably 30 parts by mass or more, still more preferably 50 parts by mass or more, and particularly preferably 60 parts by mass with respect to 100 parts by mass of the rubber component. The above is more preferably 120 parts by mass or less, and more preferably 100 parts by mass or less. If it is less than 15 parts by mass, the effect of the addition may not be sufficiently obtained, and if it exceeds 120 parts by mass, the wear resistance tends to deteriorate.
In the present specification, the oil content also includes the amount of oil contained in the oil spread rubber.

The liquid diene polymer is a diene polymer in a liquid state at room temperature (25 ° C.). Examples of the liquid diene polymer include a liquid styrene-butadiene copolymer (liquid SBR), a liquid butadiene polymer (liquid BR), a liquid isoprene polymer (liquid IR), and a liquid styrene isoprene copolymer (liquid SIR). Be done. Of these, liquid SBR is preferable because it provides a good balance between wear resistance and stable grip performance during running.

Liquid diene polymer preferably has a weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC) (Mw) is a ^{1.0 × 10 3 ~2.0 × 10 5} , 3.0 More preferably, it is × 10 ^{3 to} 1.5 × 10 ⁴ . If it is less than 1.0 × 10 ^3, the wear resistance, fracture properties is reduced, sufficient durability may not be secured. On the other hand, 2.0 if × exceeds ^105, there is a possibility that the viscosity of the polymerization solution becomes too productivity is deteriorated high.
In the present invention, Mw of the liquid diene polymer is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

In the present invention, carbon black and / or white filler is used as the reinforcing filler. Carbon black is preferable as the reinforcing filler because the effects of the present invention can be obtained satisfactorily.

Examples of the carbon black include carbon black produced by the oil furnace method, and two or more kinds of carbon blacks having different colloidal characteristics may be used in combination. Specific examples thereof include GPF, HAF, ISAF, and SAF, and among them, SAF is preferable.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 100 m ² / g or more, more preferably 105 m ² / g or more, further preferably 110 m ² / g or more, and preferably 600 m ² / g or less. , 250 m ² / g or less is more preferable, and 180 m ² / g or less is further preferable. If it is less than 100 m ² / g, the grip performance tends to decrease, and if it exceeds 600 m ² / g, it is difficult to obtain good dispersion and the wear resistance tends to decrease.
The nitrogen adsorption specific surface area of carbon black is determined in accordance with JIS K 6217-2: 2001.

The oil absorption of carbon black (DBP) is preferably 50 ml / 100 g or more, more preferably 100 ml / 100 g or more, preferably 250 ml / 100 g or less, more preferably 200 ml / 100 g or less, still more preferably 135 ml / 100 g or less. .. If it is less than 50 ml / 100 g, sufficient wear resistance may not be obtained, and if it exceeds 250 ml / 100 g, the grip performance may be deteriorated.
The amount of DBP oil absorbed by carbon black is measured in accordance with JIS K6217-4: 2001.

White fillers commonly used in the rubber industry, such as silica, calcium carbonate, mica such as cericite, aluminum hydroxide, magnesium oxide, magnesium hydroxide, clay, talc, alumina, titanium oxide. Etc. can be used, and silica is preferable from the viewpoint of reinforcing property and low fuel consumption.

The silica used in the present invention may be any generally used silica. For example, dry silica (silicic anhydride), wet silica (hydrous silicic acid) and the like can be mentioned, but wet silica is preferable because it has a 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, further preferably 100 m ² / g or more, still more preferably 130 m ² / g or more. 160 m ² / g or more is particularly preferable. If it is less than 40 m ² / g, the fracture strength after vulcanization tends to decrease. The _N 2 SA of the silica is preferably 500 meters ² / g or less, more preferably ^{300m 2 / g, 250m 2 /} g more preferably or less, and most preferably 200m ² / g. If it exceeds 500 m ² / g, low heat generation and rubber workability tend to decrease. The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

In addition to the above components, the rubber composition of the present invention contains a compounding agent generally used in the tire industry, for example, a vulcanizing agent such as wax, zinc oxide, an antioxidant, sulfur, and a vulcanization accelerator. Etc. may be appropriately blended.

The zinc oxide used in the present invention is not particularly limited, and examples thereof include those used in the rubber field such as tires. Here, among the zinc oxide, fine particle zinc oxide can be preferably used. Specifically, it is preferable to use zinc oxide having an average primary particle diameter of 200 nm or less, and more preferably 100 nm or less. The lower limit of the average primary particle size is not particularly limited, but is preferably 20 nm or more, more preferably 30 nm or more.
The average primary particle size of zinc oxide represents the average particle size (average primary particle size) converted from the specific surface area measured by the BET method by nitrogen adsorption.

When zinc oxide is blended, the content of zinc oxide is preferably 0.5 to 10 parts by mass, and more preferably 1 to 5 parts by mass with respect to 100 parts by mass of the rubber component. When the content of zinc oxide is within the above range, the effect of the present invention can be obtained more preferably.

Examples of the vulcanization accelerator include sulfenamide-based, thiazole-based, thiuram-based, and guanidine-based vulcanization accelerators. Among them, thiazole-based and thiuram-based vulcanization accelerators can be preferably used in the present invention. ..

Examples of the thiazole-based vulcanization accelerator include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and the like, among which di-2-benzothia. Zolyl disulfide is preferred. Examples of the thiuram-based vulcanization accelerator include tetramethylthiuram disulfide (TMTD), tetrabenzyl thiuram disulfide (TBzTD), tetrakis (2-ethylhexyl) thiuram disulfide (TOT-N), and among them, TOT-N. preferable.

When the vulcanization accelerator is blended, the content of the vulcanization accelerator is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and preferably 15 parts by mass with respect to 100 parts by mass of the rubber component. Parts or less, more preferably 10 parts by mass or less. If it is less than 1 part by mass, a sufficient vulcanization rate cannot be obtained, and good grip performance and wear resistance tend not to be obtained. If it exceeds 15 parts by mass, blooming occurs and the grip performance and wear resistance are deteriorated. It may decrease.

The tire of the present invention is produced by a usual method using the above rubber composition.
That is, the rubber composition containing the above components is extruded according to the shape of the tread at the unvulcanized stage, and is molded together with other tire members by a normal method on a tire molding machine. Form a vulcanized tire. A tire is obtained by heating and pressurizing this unvulcanized tire in a vulcanizer.

The present invention will be specifically described based on Examples, but the present invention is not limited thereto.

The various chemicals used in the examples will be described below.
SBR: T3830 (S-SBR, styrene content: 33% by mass, vinyl bond amount: 34% by mass, SP value: 8.6 to 8.7, rubber solid content 100 parts by mass, manufactured by Asahi Kasei Corporation Contains 37.5 parts by mass of oil)
Thermoplastic Elastomer (1): Hybler 7311 manufactured by Kuraray Co., Ltd. (Styrene block at both ends (SP value: 8.7))
Thermoplastic elastomer (2): Dynaron 4600 manufactured by JSR Co., Ltd. (one end is a styrene block (first block component, SP value: 8.7, melting point: 100 ° C., content: 20% by mass), one end is Ethylene block (second block component, SP value: 8.0, melting point: 100 ° C.), copolymer composed of structural units based on ethylene and butylene in the main chain)
Thermoplastic Elastomer (3): Dynaron 6100 manufactured by JSR Corporation (ethylene blocks at both ends (SP value of ethylene block: 8.0))
Resin: BASF's koresin (pt-butylphenol acetylene resin, softening point: 145 ° C)
Oil: VIVATEC500 manufactured by H & R
Carbon Black: Tokai Carbon Co., Ltd. Seest 9SAF (N ₂ SA: 142m ² / g, DBP: 115ml / 100g)
Zinc oxide: Zinc oxide type 2 stearic acid manufactured by Mitsui Mining & Smelting Co., Ltd .: Stearic acid "Tsubaki" manufactured by Nichiyu Co., Ltd.
Anti-aging agent: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd.
Wax: Sunknock N manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Sulfur: Powdered sulfur vulcanization accelerator manufactured by Karuizawa Sulfur Co., Ltd. (1): Noxeller DM (di-2-benzothiazolyl disulfide) manufactured by Ouchi Shinko Kagaku Co., Ltd.
Vulcanization accelerator (2): Noxeller TOT-N (Tetrakis (2-ethylhexyl) thiuram disulfide) manufactured by Ouchi Shinko Kagaku Co., Ltd.

<Examples and Comparative Examples>
According to the compounding formula shown in Table 1, the compounding materials other than sulfur and the vulcanization accelerator were kneaded for 5 minutes under the condition of the discharge temperature of 150 ° C. using 4.0 L Banbury manufactured by Kobe Steel, Ltd. Sulfur and a vulcanization accelerator were added to the obtained kneaded product, and the mixture was kneaded using an open roll under the condition of an discharge temperature of 95 ° C. for 4 minutes to obtain an unvulcanized rubber composition.
The obtained unvulcanized rubber composition was press-vulcanized under the condition of 160 ° C. for 20 minutes to obtain a vulcanized rubber composition.

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

<Grip performance>
A strip-shaped test piece having a width of 1 mm or 2 mm and a length of 40 mm was punched out from the sheet-shaped vulcanized rubber composition and used for the test. Using a spectrometer manufactured by Ueshima Seisakusho Co., Ltd., tan δ (wet grip performance) at 0 ° C. and tan δ (dry grip performance) at 50 ° C. were measured under the conditions of dynamic strain amplitude 1% and frequency 10 Hz. .. Then, the tan δ of Comparative Example 1 was set to 100, and the tan δ of each formulation was expressed as an exponential notation. The larger the index, the better the grip performance.

<Abrasion resistance index>
In accordance with JIS K6251 "Vulcanized rubber and thermoplastic rubber-How to determine tensile properties", a tensile test was conducted using a No. 3 dumbbell type test piece made of vulcanized rubber sheet, and the breaking strength (TB) and breaking time were obtained. The elongation (EB) was measured and the fracture energy (TB × EB / 2) was calculated. Then, the destructive energy of Comparative Example 1 was set to 100, and the destructive energy of each compound was expressed as an index. The larger the index, the better the wear resistance and the higher the durability.

<Adhesiveness of rubber>
The rubbers were vulcanized and adhered to each other, and the peeling force was measured according to JIS K 6854-2: 1999 and evaluated according to the following criteria.
◯: The index is 90 or more when the peeling force of Comparative Example 1 is 100. ×: The index is less than 90 when the peeling force of Comparative Example 1 is 100.

From Table 1, Examples 1 and 2 containing a rubber component, a specific thermoplastic elastomer (thermoplastic elastomer (2)), a carbon black and / or white filler, and a softener have good wear resistance. , Wet grip performance and dry grip performance were improved while maintaining the adhesiveness of rubber. In particular, in Example 2 in which the content of the thermoplastic elastomer is 5 parts by mass or more, the wet grip performance and the dry grip performance are greatly improved.

Claims (4)

It has a tread prepared using a rubber composition containing a rubber component, a thermoplastic elastomer, a carbon black and / or white filler, and a softener.
The thermoplastic elastomer has a first block component having a difference in SP value of 0.3 or less from the rubber component at one end, and a difference in SP value from the rubber component of 0 at the other end. At least a second block component of 4 to 0.9 is selected between the first block component and the second block component from the group consisting of isoprene, butadiene, ethylene, butylene, urethane, nylon and vinyl acetate. have a structural units based on a kind,
Wherein the first block component, styrene block der Ru pneumatic tire. The pneumatic tire according to claim 1, wherein the content of the thermoplastic elastomer with respect to 100 parts by mass of the rubber component is 2 to 15 parts by mass. The pneumatic tire according to claim 1 or 2, wherein the melting point of the second block component is 40 to 150 ° C. The pneumatic tire according to any one of claims 1 to 3, wherein the softener is an oil and / or a liquid diene rubber.