JP2015034219A - Tread rubber composition for high-performance wet tire and high-performance wet tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tread rubber composition for a high-performance wet tire, which can improve both of wet grip performance and stable wet grip performance during traveling to a higher level while improving or maintaining good wear resistance, and to provide a high-performance wet tire having a tread manufactured by using the composition.SOLUTION: The tread rubber composition for a high-performance wet tire comprises a rubber component, a solvent-free acrylic resin, and a low-temperature plasticizer. The solvent-free acrylic resin has a glass transition point (Tg) of 20 to 100°C. The composition contains 1 to 5 parts by mass of the solvent-free acrylic resin and 5 to 50 parts by mass of the low-temperature plasticizer with respect to 100 parts by mass of the rubber component.

Description

The present invention relates to a tread rubber composition for a high performance wet tire and a high performance wet tire having a tread produced using the tread rubber composition.

Tread rubber used in high performance wet tires is strongly required to have good wet grip performance, and a method of blending silica into a tread rubber composition has been widely used.

As other methods for improving wet grip performance, in a tread rubber composition, a method of increasing the blending amount of a low softening point resin or a liquid polymer, a method of blending a cold-resistant plasticizer, a method of blending a low-temperature softening agent Is being considered. On the other hand, a method of blending a low softening point resin with a tread rubber composition has been studied particularly for the purpose of obtaining stable wet grip performance during running. However, these methods still have room for improvement in terms of both wet grip performance and stable wet grip performance during running.

Further, in order to further improve wet grip performance, a method of blending aluminum hydroxide has been studied, but there is a problem that wear resistance is lowered. In particular, the low wear resistance when the road surface dries (when dried up) is remarkable. Therefore, there is a need for development of a technology that improves wet grip performance and stable wet grip performance while traveling at the same time, while improving or maintaining good wear resistance.

JP-A-5-9336 JP-A-5-9338

The present invention provides a tread rubber composition for a high-performance wet tire capable of simultaneously improving the wet grip performance and a stable wet grip performance during traveling at a high level while solving the above-mentioned problems and improving or maintaining good wear resistance. And it aims at providing the high-performance wet tire which has a tread produced using this.

The present invention contains a rubber component, a solventless acrylic resin and a cold-resistant plasticizer, the glass transition point (Tg) of the solventless acrylic resin is 20 to 100 ° C., and relative to 100 parts by mass of the rubber component In addition, the present invention relates to a tread rubber composition for a high-performance wet tire in which the content of the solventless acrylic resin is 1 to 5 parts by mass and the content of the cold-resistant plasticizer is 5 to 50 parts by mass.

The solventless acrylic resin is preferably a solventless acrylic resin and / or a solventless styrene acrylic resin.

The cold-resistant plasticizer is preferably an ester plasticizer.

The tread rubber composition further contains carbon black, silica, and an inorganic reinforcing agent represented by the following formula, and the content of the carbon black is 10 to 50 with respect to 100 parts by mass of the rubber component. It is preferable that the content of the mass part, the silica is 30 to 100 parts by mass, and the content of the inorganic reinforcing agent is 5 to 30 parts by mass.
kM ₁ · xSiO _y · zH ₂ O
(Wherein M ₁ is at least one metal selected from the group consisting of Al, Mg, Ti and Ca, an oxide or hydroxide of the metal, k is an integer of 1 to 5, and x is 0 to 0) 10 is an integer, y is an integer of 2 to 5, and z is an integer of 0 to 10.)

The inorganic reinforcing agent is preferably aluminum hydroxide.

The present invention also relates to a high performance wet tire having a tread produced using the tread rubber composition for a high performance wet tire.

According to the present invention, since the tread rubber composition for a high-performance wet tire includes a predetermined amount of a rubber component, a solventless acrylic resin having a predetermined glass transition point, and a cold-resistant plasticizer, it has good wear resistance. It is possible to provide a high-performance wet tire in which wet grip performance and stable wet grip performance during running are simultaneously improved in a high dimension while improving or maintaining the performance.

The tread rubber composition for high performance wet tires of the present invention contains a predetermined amount of a rubber component, a solventless acrylic resin having a predetermined glass transition point, and a cold resistant plasticizer.

Conventionally, resins, aluminum hydroxide, and cold-resistant plasticizers have been blended to improve wet grip performance, but these components that have been blended in the past improve viscoelastic properties by blending these components. It is estimated that the wet grip performance is improved. Therefore, there is room for improvement in terms of both wet grip performance and stable wet grip performance during traveling.

On the other hand, in the present invention, by adding a solventless acrylic resin, in addition to improving the wet grip performance by improving the viscoelastic properties, the wet grip performance can also be provided by being able to impart the adhesion to the road surface of the tread rubber. It is estimated that the wet grip performance and stable wet grip performance during running can be improved at the same time to a higher level by using the solvent-free acrylic resin within the specified range and using a cold-resistant plasticizer. Is done.

In addition, the performance improvement effect obtained when a solventless acrylic resin having a predetermined glass transition point and a cold-resistant plasticizer are used in combination is simply the performance improvement effect obtained when each is used alone. More than an addition. That is, by using a solvent-free acrylic resin having a predetermined glass transition point in combination with a cold-resistant plasticizer, wet grip performance and stable wet grip performance during running can be improved. When used alone, the wear resistance is lowered, but when used in combination, good wear resistance can be improved or maintained.

Examples of rubber components 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), ethylene propylene diene rubber ( EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), diene rubber such as butyl rubber (IIR). A rubber component may be used independently and may use 2 or more types together. Among these, NR, BR, and SBR are preferable, and SBR is more preferable because wet grip performance and wear resistance can be obtained in a well-balanced manner.

The SBR is not particularly limited, and for example, emulsion polymerization styrene butadiene rubber (E-SBR), solution polymerization 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. If it is less than 20% by mass, sufficient wet grip performance tends to be not obtained. The styrene content is preferably 60% by mass or less, and more preferably 50% by mass or less. If it exceeds 60% by mass, not only the wear resistance will be lowered, but also the temperature dependence will increase, and the performance change with respect to the temperature will increase, and the stable wet grip performance during running will tend not to be obtained well. There is.
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 heat resistance, wet grip performance and wear resistance tend to be not obtained. Further, the upper limit of the SBR content is not particularly limited, and may be 100% by mass.

The tread rubber composition of the present invention contains a solventless acrylic resin having a predetermined glass transition point and a cold-resistant plasticizer. Thereby, the wet grip performance and the stable wet grip performance during traveling can be improved at a high level at the same time while improving or maintaining good wear resistance.

The glass transition point (Tg) (° C./DSC) of the solventless acrylic resin is 20 to 100 ° C. Preferably it is 40 degreeC or more. The Tg is preferably 80 ° C. or lower. If the temperature is lower than 20 ° C, an effect of improving wet grip performance can be obtained, but there is a possibility that stable wet grip performance and wear resistance during running may not be obtained well. Although the effect of improving the wet grip performance can be obtained, there is a possibility that the wet grip performance and the wear resistance cannot be obtained satisfactorily.
In the present invention, the glass transition point of the solventless acrylic resin is a value measured by differential scanning calorimetry (DSC) according to JIS-K7121 under the condition of a heating rate of 10 ° C./min.

The above solvent-free acrylic resin is a high temperature continuous polymerization method (high temperature continuous mass polymerization method) (U.S. Pat. No. 4,414,370) without using a polymerization initiator, chain transfer agent, organic solvent, or the like as auxiliary materials as much as possible. No., JP-A-59-6207, JP-B-5-58005, JP-A-1-313522, US Pat. No. 5,010,166, Toa Gosei Research Annual Report TREND2000 No. 3 p42 (Meth) acrylic resin (polymer) synthesized by the method described in -45 etc.). In the present invention, (meth) acryl means methacryl and acryl.

The (meth) acrylic resin does not substantially contain a polymerization initiator, a chain transfer agent, an organic solvent, or the like, which are auxiliary materials, due to the production method. Moreover, since the said (meth) acrylic-type resin is obtained by continuous polymerization, composition distribution and molecular weight distribution are comparatively narrow. It is presumed that the effects of the present invention can be suitably obtained by such properties of the (meth) acrylic resin.

Examples of the monomer component constituting the (meth) acrylic resin include (meth) acrylic acid, (meth) acrylic acid ester (alkyl ester, aryl ester, aralkyl ester, etc.), (meth) acrylamide, and (meth) ) (Meth) acrylic acid derivatives such as acrylamide derivatives. (Meth) acrylic acid is a general term for acrylic acid and methacrylic acid.

In addition, as a monomer component constituting the (meth) acrylic resin, together with (meth) acrylic acid or a (meth) acrylic acid derivative, styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, Aromatic vinyl such as divinylnaphthalene may be used.

The solvent-free acrylic resin may be a resin (solvent-free acrylic resin) composed only of a (meth) acrylic component, or styrene containing a component derived from styrene together with the (meth) acrylic component. A resin having a component other than the (meth) acrylic component such as an acrylic resin (solvent-free styrene acrylic resin) may also be used. Thus, it is also one of the preferred embodiments of the present invention that the solventless acrylic resin is a solventless acrylic resin and / or a solventless styrene acrylic resin.

The solventless acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group, and the like. Among them, the solvent-free acrylic resin has a hydroxyl group and a carboxyl group because the effects of the present invention can be more suitably obtained. Preferably it is.

Examples of commercially available solventless acrylic resins include ARUFON series UP-1150, UH-2170, UHE-2012, UC3000, UC3900, UC3910, and UF-5022 manufactured by Toagosei Co., Ltd.

The acid value (OH value) of the solventless acrylic resin is preferably 15 mgKOH / g or more, more preferably 30 mgKOH / g or more, still more preferably 50 mgKOH / g or more, particularly preferably 70 mgKOH / g or more, and most preferably 100 mgKOH. / G or more. The OH value is preferably 250 mgKOH / g or less, more preferably 200 mgKOH / g or less, still more preferably 170 mgKOH / g or less, and particularly preferably 150 mgKOH / g or less. If it is less than 15 mgKOH / g, there is a possibility that both wet grip performance and stable wet grip performance during running cannot be obtained at a high level, and if it exceeds 250 mgKOH / g, the compatibility with the diene rubber component is deteriorated. Therefore, sufficient fracture characteristics cannot be obtained, and the wear resistance may be significantly deteriorated.
In the present invention, the acid value (OH value) of the solventless acrylic resin is the amount of potassium hydroxide required to neutralize acetic acid bonded to a hydroxyl group when 1 g of the solventless acrylic resin is acetylated. Is expressed in milligrams, and is a value measured by potentiometric titration (JIS K 0070: 1992).

The weight average molecular weight (Mw) of the solventless acrylic resin is preferably 1000 or more, more preferably 2000 or more. The Mw is preferably 25000 or less, more preferably 20000 or less, still more preferably 15000 or less, and particularly preferably 12000 or less. If it is less than 1000, the effect of improving wet grip performance can be obtained, but there is a possibility that stable wet grip performance during running may not be obtained satisfactorily, and if it exceeds 25000, the softening point may be high and the polymer may not be mixed. is there.
In the present invention, Mw of the solventless acrylic resin is a polystyrene equivalent value measured by gel permeation chromatography (GPC).

As described above, the solventless acrylic resin has a high purity because it does not substantially contain a polymerization initiator, a chain transfer agent, an organic solvent, or the like, which are auxiliary materials. The purity of the solventless acrylic resin (ratio of resin contained in the resin) is preferably 95% by mass or more, more preferably 97% by mass or more.

The content of the solventless acrylic resin is 1 part by mass or more, preferably 2 parts by mass or more with respect to 100 parts by mass of the rubber component. The content is 5 parts by mass or less, preferably 4 parts by mass or less. If it is less than 1 part by mass, sufficient adhesive effect cannot be obtained, and both wet grip performance and stable wet grip performance improvement effect during running cannot be obtained, and if it exceeds 5 parts by mass, sufficient fracture characteristics are obtained. It cannot be obtained, and the wear resistance is remarkably deteriorated. Further, sufficient wet grip performance and stable wet grip performance during running cannot be obtained.

Examples of the cold resistant plasticizer used in the present invention include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), di-2-ethylhexyl azelate (DOZ), dibutyl sebacate (DBS), Diisononyl adipate (DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), diundecyl phthalate (DUP), dibutyl phthalate (DBP), dioctyl sebacate (DOS), tributyl phosphate (TBP), phosphorus Ester plasticizers (plasticizers having ester groups) such as trioctyl acid (TOP), triethyl phosphate (TEP), trimethyl phosphate (TMP), tricresyl phosphate (TCP), trixylenyl phosphate (TXP), and thymidine Triphosphoric acid (TTP) It is. Among them, an ester plasticizer having a plurality of octyl ester groups such as dioctyl adipate (DOA), dioctyl phthalate (DOP), dioctyl sebacate (DOS), and trioctyl phosphate (TOP) is preferable, and a plasticizing effect at a low temperature. DOS, DOS, and TOP are more preferable from the balance of wear resistance.

The freezing point of the cold resistant plasticizer is preferably −100 ° C. or higher, more preferably −80 ° C. or higher. The freezing point is preferably 0 ° C. or lower, more preferably −20 ° C. or lower, and further preferably −40 ° C. or lower. Although the wet grip performance can be improved when the temperature is lower than -100 ° C, there is a possibility that the stable wet grip performance during driving may not be obtained. When the temperature exceeds 0 ° C, the stable wet grip performance during driving is improved. However, good wet grip performance may not be obtained.
In the present invention, the freezing point of the cold resistant plasticizer is a value measured by the following method.
A sample (plasticizer) is sealed in an aluminum cell, and the aluminum cell is inserted into a sample holder of a differential scanning calorimeter (manufactured by Shimadzu Corporation, DSC-60A), and then the sample holder is placed in a nitrogen atmosphere. An endothermic peak was observed while heating to 150 ° C. at 10 ° C./min, and the obtained endothermic peak was taken as the freezing point.

When the cold resistant plasticizer is blended, the content of the cold resistant plasticizer is preferably 5 parts by mass or more, more preferably 7 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. . The content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and still more preferably 30 parts by mass or less. If the amount is less than 5 parts by mass, the plastic effect at low temperature is not sufficiently exhibited, the wet grip performance is deteriorated, and if it exceeds 50 parts by mass, the wear resistance is remarkably reduced.

In the present invention, resins commonly used in rubber compositions for tires such as coumarone resins, aromatic petroleum resins, and aromatic vinyl polymers can be used together with the solventless acrylic resin and the cold resistant plasticizer.

The resin that can be used is not particularly limited. For example, coumarone resin, aromatic petroleum resin, phenol resin, aromatic vinyl polymer (resin obtained by polymerizing α-methylstyrene and / or styrene), Examples include terpene phenol resins and rosin resins. Among these, a coumarone-based resin is preferable because wet grip performance and stable wet grip performance during running can be obtained better.

The coumarone resin is not particularly limited as long as it is a resin having coumarone as a constituent component, and examples thereof include coumarone resin and coumarone indene resin. Of these, coumarone indene resin is preferable.

The softening point of the resin is preferably 60 ° C. or higher, more preferably 70 ° C. or higher. The softening point is preferably 120 ° C. or lower, more preferably 110 ° C. or lower. If it is lower than 60 ° C, stable wet grip performance during running may be reduced, and if it exceeds 120 ° C, wet grip performance may be reduced.
In the present invention, the softening point of the resin is the temperature at which the sphere descends when the softening point specified in JIS K 6220-1: 2001 is measured with a ring and ball softening point measuring device.

When mix | blending the said resin, content of the said resin becomes like this. Preferably it is 10-50 mass parts or less with respect to 100 mass parts of rubber components, More preferably, it is 20-40 mass parts. When the content of the resin is within the above range, wet grip performance and stable wet grip performance during traveling can be improved to a higher level.

In the present invention, from the viewpoints of wet grip performance, stable wet grip performance during traveling, etc., the above resins (solvent-free acrylic resins, if necessary, resins commonly used in the tire rubber composition (especially coumarone). It is preferable to add one or more softeners in addition to the cold-resistant plasticizer. Although it does not specifically limit as a softening agent, Oil, a liquid diene polymer, etc. are mentioned.

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

When oil is blended, the oil content is preferably 20 parts by mass or more, more preferably 40 parts by mass or more with respect to 100 parts by mass of the rubber component. Moreover, this content becomes like this. Preferably it is 80 mass parts or less, More preferably, it is 60 mass parts or less. If the amount is less than 20 parts by mass, the effect of the addition may not be obtained. If the amount exceeds 80 parts by mass, the wear resistance tends to deteriorate. In the present specification, the oil content includes the amount of oil contained in the oil-extended rubber.

The liquid diene polymer is a diene polymer in a liquid state at normal temperature (25 ° C.).
The liquid diene polymer preferably has a polystyrene-equivalent weight average molecular weight (Mw) of 1.0 × 10 ^{3 to} 2.0 × 10 ⁵ measured by gel permeation chromatography (GPC), 3.0 It is more preferable that it is * 10 < ³ > -1.5 * 10 < ⁴ >. If it is less than 1.0 × 10 ³ , the wear resistance and fracture characteristics are lowered, and sufficient durability may not be ensured. On the other hand, if it exceeds 2.0 × 10 ⁵ , the viscosity of the polymerization solution becomes too high, and the productivity may be deteriorated.
In the present invention, Mw of the liquid diene polymer is a polystyrene conversion value measured by gel permeation chromatography (GPC).

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), a liquid styrene isoprene copolymer (liquid SIR), and the like. It is done. Among these, liquid SBR is preferable because durability, wear resistance, and stable wet grip performance during running can be obtained in a well-balanced manner.

When the liquid diene polymer is blended, the content of the liquid diene polymer is preferably 20 parts by mass or more, more preferably 30 parts by mass or more with respect to 100 parts by mass of the rubber component. Moreover, this content becomes like this. Preferably it is 120 mass parts or less, More preferably, it is 80 mass parts or less. If it is less than 20 parts by mass, sufficient wet grip performance tends to be not obtained, and if it exceeds 120 parts by mass, the wear resistance tends to deteriorate.

The total content of the solventless acrylic resin, the cold resistant plasticizer, the resin (particularly coumarone resin), the oil, and the liquid diene polymer is preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component. More preferably, it is 100 mass parts or more, More preferably, it is 120 mass parts or more. Moreover, Preferably it is 250 mass parts or less, More preferably, it is 200 mass parts or less, More preferably, it is 180 mass parts or less. The effect of this invention is acquired more suitably as the said content is in the said range.

The rubber composition of the present invention preferably contains silica from the viewpoints of wet grip performance and wear resistance. Examples of the silica include dry method silica (anhydrous silica), wet method silica (hydrous silica), and the like. Of these, wet-process silica is preferred because it has many silanol groups.

The cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of silica is preferably 100 to 300 m ² / g because good wet grip performance, wear resistance and durability can be obtained. Moreover, it is preferable that the dibutyl phthalate oil absorption (DBP) of a silica is 150-300 mL / 100g for the same reason.
In addition, the cetyltrimethylammonium bromide adsorption specific surface area of silica is a value measured according to ASTM D3765-80, and the dibutyl phthalate oil absorption is a value measured according to the method described in JIS K 6221 6.1.2 A method.

When silica is blended, the content of silica is preferably 30 parts by mass or more, more preferably 40 parts by mass or more with respect to 100 parts by mass of the rubber component. When the amount is less than 30 parts by mass, there is a tendency that a sufficient wet grip performance improvement effect cannot be obtained. The content is preferably 100 parts by mass or less, more preferably 80 parts by mass or less. If it exceeds 100 parts by mass, sufficient processability, wear resistance and durability may not be obtained.

The rubber composition of the present invention is carbon black from the viewpoint that the durability and kneadability are good and the effects of the present invention are sufficiently obtained, although it does not reach silica and inorganic reinforcing agents described later in terms of wet grip performance. May be included. In the present invention, workability is dramatically improved by blending carbon black. Examples of carbon black include carbon black produced by an oil furnace method, and two or more types having different colloidal characteristics may be used in combination. Specific examples include GPF, HAF, ISAF, and SAF. Among these, SAF is preferable.

Nitrogen adsorption specific surface area _(N 2 SA) of carbon black is preferably not less than 70m ² / g, more preferably at least 100 m ² / g, more preferably not less than 105m ² / g, more 110m ² / g is particularly preferred, 130m ² / g or more is most preferable. If it is less than 70 m < ² > / g, there exists a tendency for wet grip performance to fall. The N ₂ SA is preferably 250 m ² / g or less, more preferably 200 m ² / g or less, and still more preferably 180 m ² / g or less. When it exceeds 250 m < ² > / g, favorable dispersion | distribution is difficult to be obtained and there exists a tendency for abrasion resistance to fall.
In addition, the nitrogen adsorption specific surface area of carbon black is calculated | required based on JISK6217-2: 2001.

Carbon black has a dibutyl phthalate (DBP) oil absorption of preferably 50 ml / 100 g or more, and more preferably 100 ml / 100 g or more. If it is less than 50 ml / 100 g, sufficient wear resistance may not be obtained. The DBP of carbon black is preferably 250 ml / 100 g or less, more preferably 200 ml / 100 g or less, and still more preferably 135 ml / 100 g or less. If it exceeds 250 ml / 100 g, the wet grip performance may be lowered.
The DBP of carbon black is measured according to JIS K6217-4: 2001.

When carbon black is blended, the content thereof is preferably 10 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 10 parts by mass, good workability, sufficient wear resistance, and wet grip performance may not be obtained. The content is preferably 50 parts by mass or less, more preferably 35 parts by mass or less. If it exceeds 50 parts by mass, the processability improvement width at the time of unvulcanization tends to be small, and the contribution to wet grip performance tends to be small.

In this invention, it is preferable to mix | blend the inorganic reinforcing agent represented by a following formula from the point that wet grip performance improves and the effect of this invention is acquired favorably.
kM ₁ · xSiO _y · zH ₂ O
(Wherein M ₁ is at least one metal selected from the group consisting of Al, Mg, Ti and Ca, an oxide or hydroxide of the metal, k is an integer of 1 to 5, and x is 0 to 0) 10 is an integer, y is an integer of 2 to 5, and z is an integer of 0 to 10.)

As the inorganic reinforcing agent represented by the above formula, alumina, alumina hydrate, aluminum hydroxide, magnesium hydroxide, magnesium oxide, talc, titanium white, titanium black, calcium oxide, calcium hydroxide, aluminum magnesium oxide, clay Pyrophyllite, bentonite, aluminum silicate, magnesium silicate, calcium silicate, aluminum calcium silicate, magnesium silicate and the like. These inorganic compounds may be used alone or in combination of two or more. Among them, M ₁ is a hydroxide of at least one metal selected from the group consisting of Al, Mg, Ti and Ca in the above formula because the effect of the present invention can be obtained more suitably. And M ₁ is more preferably an Al hydroxide (aluminum hydroxide). As the inorganic reinforcing agent, aluminum hydroxide is particularly preferable.

The average primary particle diameter of the inorganic reinforcing agent is preferably 0.5 μm or more, more preferably 0.8 μm or more. If it is less than 0.5 μm, it becomes difficult to disperse the inorganic reinforcing agent, and the wear resistance tends to deteriorate. The average primary particle size is preferably 10 μm or less, more preferably 5 μm or less. When the thickness exceeds 10 μm, the inorganic reinforcing agent serves as a fracture nucleus and wear resistance tends to deteriorate.
In addition, in this invention, the average primary particle diameter of the said inorganic compound is a number average particle diameter, and is measured with a transmission electron microscope.

When mix | blending the said inorganic reinforcement agent, content of the said inorganic reinforcement agent becomes like this. Preferably it is 5 mass parts or more with respect to 100 mass parts of rubber components, More preferably, it is 10 mass parts or more. If it is less than 5 mass parts, there exists a possibility that the improvement effect of wet grip performance may be small. The total content is preferably 30 parts by mass or less, more preferably 25 parts by mass or less. If it exceeds 30 parts by mass, poor dispersion may occur and the wear resistance may deteriorate.

The total content of carbon black, silica and the inorganic reinforcing agent is preferably 60 parts by mass or more, more preferably 90 parts by mass or more, with respect to 100 parts by mass of the rubber component. The total content is preferably 170 parts by mass or less, more preferably 140 parts by mass or less. When the total content is within the above range, the effects of the present invention can be more suitably obtained.

In addition, when mix | blending a silica with the rubber composition of this invention, it is preferable to use a silane coupling agent together with a silica. The silane coupling agent is not particularly limited. For example, bis (3-triethoxysilylpropyl) polysulfide, bis (2-triethoxysilylethyl) polysulfide, bis (3-trimethoxysilylpropyl) polysulfide, bis (2- Trimethoxysilylethyl) polysulfide, bis (4-triethoxysilylbutyl) polysulfide, bis (4-trimethoxysilylbutyl) polysulfide and the like. Of these, bis (3-triethoxysilylpropyl) polysulfide and bis (2-triethoxysilylethyl) polysulfide are preferable, and bis (3-triethoxysilylpropyl) tetrasulfide and bis (2-triethoxysilylethyl) tetrasulfide are preferable. Is more preferable.

When mix | blending the said silane coupling agent, content of a silane coupling agent becomes like this. Preferably it is 5 mass parts or more with respect to 100 mass parts of silica, More preferably, it is 7 mass parts or more. If it is less than 5 parts by mass, the wear resistance tends to decrease. The content of the silane coupling agent is preferably 20 parts by mass or less, more preferably 15 parts by mass or less. If it exceeds 20 parts by mass, there is a tendency that an improvement effect commensurate with the increase in cost cannot be obtained.

In addition to the above components, the rubber composition of the present invention includes compounding agents generally used in the tire industry, such as waxes, zinc oxide, anti-aging agents, vulcanizing agents such as sulfur, and vulcanization accelerators. You may mix | blend materials, such as these, suitably.

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, fine zinc oxide can be suitably used among zinc oxides. Specifically, it is preferable to use zinc oxide having an average primary particle diameter of 200 nm or less, and more preferably 120 nm or less. Although the minimum of this average primary particle diameter is not specifically limited, Preferably it is 20 nm or more, More preferably, it is 30 nm or more.
In addition, the average primary particle diameter of zinc oxide represents the average particle diameter (average primary particle diameter) converted from the specific surface area measured by the BET method by nitrogen adsorption.

When blending zinc oxide, the content of zinc oxide is preferably 0.5 to 10 parts by mass or less, more preferably 1 to 5 parts by mass with respect to 100 parts by mass of the rubber component. The effect of this invention is acquired more suitably as content of zinc oxide exists in the said range.

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

Examples of thiazole-based vulcanization accelerators include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and the like. Among them, di-2-benzothia Zolyl disulfide is preferred. Examples of the thiuram-based vulcanization accelerator include tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), tetrakis (2-ethylhexyl) thiuram disulfide (TOT-N), etc. 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. Part or less, more preferably 10 parts by weight or less. If it is less than 1 part by mass, a sufficient vulcanization rate cannot be obtained, and good wet grip performance and wear resistance tend to be not obtained. If it exceeds 15 parts by mass, blooming occurs and wet grip performance and wear resistance are deteriorated. May decrease.

The rubber composition of the present invention is produced by a general method. That is, it can be produced by a method of kneading the above components with a Banbury mixer, a kneader, an open roll or the like and then vulcanizing. The rubber composition of the present invention is used for a tread rubber of a high-performance wet tire that can be suitably used on a wet road surface.

The high-performance wet tire of the present invention is produced by a normal method using the rubber composition. That is, the rubber composition containing the above components is extruded in accordance with the shape of the tread at an unvulcanized stage and molded together with other tire members on a tire molding machine by a normal method. Form a vulcanized tire. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire. The high-performance wet tire in the present invention is a tire that is particularly excellent in wet grip performance, and is a concept that includes a competition tire used in a competition vehicle. The high-performance wet tire is used for competition such as a race. The present invention can be suitably applied to tires, particularly wet tires for competition used on wet road surfaces.

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.
SBR: Toughden 4850 manufactured by Asahi Kasei Corporation (styrene content: 40% by mass, containing 50 parts by mass of oil with respect to 100 parts by mass of rubber solid content)
Carbon black: Seast 9 (SAF, N ₂ SA: 142 m ² / g, DBP oil absorption: 115 ml / 100 g) manufactured by Tokai Carbon Co., Ltd.
Silica: Nipsil VN3 manufactured by Tosoh Silica Co., Ltd. (CTAB: 168 m ² / g, DBP: 183 ml / 100 g, N ₂ SA: 177 m ² / g)
Aluminum hydroxide: Heidilite H-43 (average primary particle size: 1 μm) manufactured by Showa Denko KK
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Cold resistant plasticizer: TOP (trioctyl phosphate, freezing point: -70 ° C) manufactured by Daihachi Chemical Industry Co., Ltd.
Liquid diene polymer: L-SBR-820 manufactured by Kuraray Co., Ltd. (liquid SBR, Mw: 10,000)
Resin 1: Escron G-90 (Coumarone Indene resin (low softening point resin) manufactured by Nikko Chemical Co., Ltd., softening point: 90 ° C.)
Solvent-free acrylic resin 1: Solvent-free acrylic polymer UC3510 manufactured by Toagosei Co., Ltd. (solvent-free acrylic resin (solvent-free all acrylic resin), carboxyl group-containing resin, purity: 98% by mass or more, Tg: − (50 ° C., acid value: 70 mg KOH / g, Mw: 2000)
Solvent-free acrylic resin 2: Solvent-free acrylic polymer UC3900 (solvent-free acrylic resin (solvent-free styrene acrylic resin), carboxyl group-containing resin, manufactured by Toagosei Co., Ltd., purity: 98% by mass or more, Tg: 60 (C, acid value: 108 mgKOH / g, Mw: 4600)
Solvent-free acrylic resin 3: Solvent-free acrylic polymer UC3000 (solvent-free acrylic resin (solvent-free all acrylic resin), carboxyl group-containing resin, manufactured by Toagosei Co., Ltd., purity: 98% by mass or more, Tg: 65 C, acid value: 74 mg KOH / g, Mw: 10,000)
Solvent-free acrylic resin 4: Solvent-free acrylic polymer UC3920 (solvent-free acrylic resin (solvent-free styrene acrylic resin), carboxyl group-containing resin, manufactured by Toagosei Co., Ltd., purity: 98% by mass or more, Tg: 102 (C, acid value: 240 mg KOH / g, Mw: 15500)
Zinc oxide: Zinccock Super F-1 (average primary particle size: 100 nm) manufactured by Hakusui Tech Co., Ltd.
Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Anti-aging agent 1: Antigen 6C (N-phenyl-N ′-(1,3-dimethyl) -p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Anti-aging agent 2: Antigen RD (2,2,4-trimethyl-1,2-dihydroquinoline polymer) manufactured by Sumitomo Chemical Co., Ltd.
Stearic acid: Stearic acid “椿” manufactured by NOF Corporation
Sulfur: Powder sulfur vulcanization accelerator manufactured by Karuizawa Sulfur Co., Ltd. 1: Noxeller DM (di-2-benzothiazolyl disulfide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Vulcanization accelerator 2: Noxeller TOT-N (tetrakis (2-ethylhexyl) thiuram disulfide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

<Examples and Comparative Examples>
In accordance with the formulation shown in Table 1, compounding materials other than sulfur and a vulcanization accelerator were kneaded using 1.7 L Banbury manufactured by Kobe Steel Co., Ltd. Sulfur and a vulcanization accelerator were added to the obtained kneaded product and kneaded using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was molded into a tread shape, bonded together with other tire members on a tire molding machine, vulcanized at 150 ° C. for 30 minutes, and a test tire (tire size: 215). / 45R17).

The following evaluation was performed about the test tire obtained by the said manufacture. The results are shown in Table 1.

(Wet grip performance)
The test tire was mounted on a 2000 cc domestic FR vehicle, and the vehicle was run for 10 laps on a wet asphalt road test course. The test driver evaluated the stability of the control at the time of the best lap, and the comparative example 1 was set to 100 and displayed as an index. The larger the value, the higher the grip performance on the wet road surface. When the index value was 110 or more, it was judged to be particularly good.

(Stable wet grip performance while driving)
The test tire was mounted on a 2000 cc domestic FR vehicle, and the vehicle was run for 10 laps on a wet asphalt road test course. At that time, the test driver compared and evaluated the stability of control during steering of the best lap and the final lap. The larger the value, the smaller the decrease in grip performance during traveling on the wet road surface, and the better the stable wet grip performance during traveling is obtained. When the index value was 110 or more, it was judged to be particularly good.

(Abrasion resistance)
The test tire was mounted on a domestic FR vehicle with a displacement of 2000 cc, and the vehicle was run on a wet asphalt road test course. The remaining groove amount of the tire tread rubber at that time was measured (15 mm at the time of a new article), and the index was displayed with the remaining groove amount of Comparative Example 1 as 100 (wear resistance index). It shows that abrasion resistance is so high that a numerical value is large. When the index value was 100 or more, it was judged to be good.

From Table 1, with respect to 100 parts by mass of the rubber component, 1 to 5 parts by mass of a solventless acrylic resin having a glass transition point of 20 to 100 ° C. and 5 to 50 parts by mass of a cold resistant plasticizer are blended. It was revealed that the wet grip performance and the stable wet grip performance during running can be simultaneously improved to a high level while improving or maintaining good wear resistance.

Moreover, from the comparison of Comparative Example 3, Comparative Example 8, and Example 2, by using a solvent-free acrylic resin having a glass transition point of 20 to 100 ° C. and a cold-resistant plasticizer, Stable wet grip performance during running can be improved, and when each is used alone, wear resistance will be reduced. I found out that I could do it.

Claims (6)

Contains rubber component, solvent-free acrylic resin and cold-resistant plasticizer,
The solvent-free acrylic resin has a glass transition point (Tg) of 20 to 100 ° C.,
A tread rubber composition for a high-performance wet tire in which the content of the solventless acrylic resin is 1 to 5 parts by mass and the content of the cold-resistant plasticizer is 5 to 50 parts by mass with respect to 100 parts by mass of the rubber component. object. The tread rubber composition for a high-performance wet tire according to claim 1, wherein the solventless acrylic resin is a solventless acrylic resin and / or a solventless styrene acrylic resin. The tread rubber composition for a high-performance wet tire according to claim 1 or 2, wherein the cold-resistant plasticizer is an ester plasticizer. The tread rubber composition further contains carbon black, silica, and an inorganic reinforcing agent represented by the following formula:
The content of the carbon black is 10 to 50 parts by mass, the content of the silica is 30 to 100 parts by mass, and the content of the inorganic reinforcing agent is 5 to 30 parts by mass with respect to 100 parts by mass of the rubber component. The tread rubber composition for high performance wet tires in any one of Claims 1-3.
kM ₁ · xSiO _y · zH ₂ O
(Wherein M ₁ is at least one metal selected from the group consisting of Al, Mg, Ti and Ca, an oxide or hydroxide of the metal, k is an integer of 1 to 5, and x is 0 to 0) 10 is an integer, y is an integer of 2 to 5, and z is an integer of 0 to 10.) The tread rubber composition for a high-performance wet tire according to claim 4, wherein the inorganic reinforcing agent is aluminum hydroxide. The high performance wet tire which has a tread produced using the tread rubber composition for high performance wet tires in any one of Claims 1-5.