JP5571921B2 - Rubber composition for snow tire tread and pneumatic snow tire - Google Patents

Description

  The present invention relates to a rubber composition for a tire tread, and more particularly to a rubber composition for a tire tread formed by blending specific hollow fine particles and a pneumatic tire using the same.

  With the recent high performance and high speed of automobiles, the required performance for each tire has become severe. Among them, improvement of high-speed durability and improvement of grip performance on a wet road surface (hereinafter sometimes referred to as “wet performance”) are very important characteristics from the viewpoint of safety.

  In order to achieve both tire rolling resistance and wet performance, new materials such as silica and aluminum hydroxide, which are white fillers, have been developed, and rubber compositions using them have been studied (for example, Patent Document 1). 2). In addition, studies have been made to improve hydroplaning performance, which is one of the wet performances, without changing the rubber composition (see, for example, Patent Documents 3 and 4).

  On the other hand, in order to improve the braking / driving performance (on-ice performance) of a tire on an icy and snowy road surface, research on a tire tread has been actively conducted. On ice and snow road surfaces, a water film is likely to be generated due to frictional heat of the tire and the like, and this water film causes a decrease in the coefficient of friction between the tire and the ice and snow road surface. For this reason, various proposals have been made to improve the water film removal ability and edge effect of the tire tread.

For example, in a rubber composition used in a tread (rubber composition for a tire tread), the rubber composition composed of a rubber component and a foaming agent is used until the temperature reaches the maximum temperature vulcanization temperature of the rubber component during vulcanization. It has been proposed to improve the above performance and effects by blending organic fibers whose viscosity is lower than that of the components (see, for example, Patent Document 5).
By using foamed rubber for the tread rubber, it is possible to improve on-ice performance and road noise performance. There was a problem that the edge effect and the drainage effect were not sufficient, and the wear resistance and running performance on general roads were reduced.

  In order to solve the above problems, it has been proposed to incorporate hollow fine particles into tread rubber (for example, see Patent Documents 6 to 9). However, since the conventional hollow fine particles have low pressure strength, there is a problem that a part of the hollow fine particles collapses in the course of compounding into rubber, and as a result, the effect as hollow fine particles is reduced.

Japanese Patent Laid-Open No. 2005-8824 JP 11-227409 A JP 2003-63213 A JP 2005-34328 A Japanese Patent Laid-Open No. 11-48264 JP 2001-279020 A Japanese Patent No. 3189128 Japanese Patent No. 3215467 JP-A-4-198241

  The object of the present invention relates to a rubber composition for tires particularly used for high-speed running, and is excellent in wet grip performance, wear resistance, durability, etc., and further improved on-ice performance. It is to provide a pneumatic tire using the same.

  As a result of intensive investigations to achieve the above object, the present inventors have applied a rubber composition containing specific hollow fine particles to the tread portion of the tire, so that the braking performance on the ice and the wet road surface braking of the tire can be achieved. The present inventors have found that the performance (wet performance) is greatly improved and have completed the present invention.

That is, the present invention
<1> With respect to 100 parts by mass of at least one rubber component selected from natural rubber and diene-based synthetic rubber , the number average particle size in rubber is 1 μm or more and 100 μm or less, and the particle size distribution index (PDI) in rubber is 1. so that 50 or less, Ri Na and at least blended 30 parts by mass or less than 1 part by weight hollow particles have a closed cell, and foaming rate after vulcanization Ru der 5% to 40% snow tires It is a rubber composition for treads.

<2> The rubber composition for a snow tire tread according to <1>, wherein the rubber particle size distribution index (PDI) is 1.35 or less.

<3> The rubber composition for a snow tire tread according to <1> or <2>, wherein the rubber component contains 50% by mass or more of styrene-butadiene copolymer rubber.

<4> The snow tire tread rubber composition according to <3>, wherein a styrene content in the styrene-butadiene copolymer rubber is 10% by mass or more and 50% by mass or less.

<5> The rubber component is at least one diene selected from natural rubber, polyisoprene rubber, polybutadiene rubber, ethylene-propylene-diene rubber, chloroprene rubber, butyl rubber, halogenated butyl rubber, and acrylonitrile-butadiene rubber. The rubber composition for a snow tire tread according to <1> or <2>, which is a mixture with synthetic rubber.

<6> The snow tire tread rubber composition according to <5>, wherein a mass ratio of natural rubber and diene synthetic rubber (natural rubber / diene synthetic rubber) in the mixture is in a range of 80/20 to 40/60. It is.

<7> The rubber composition for a snow tire tread according to any one of <1> to <6>, wherein a blending amount of the hollow fine particles is 3 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the rubber component. .

<8> Carbon black, silica and general formula (I) as fillers
_{nM · xSiO y · zH 2 O} ········ (I)

[Wherein, M is selected from metals selected from aluminum, magnesium, titanium, calcium and zirconium, and oxides or hydroxides of these metals, hydrates thereof, and carbonates of the metals. It is at least one, and n, x, y, and z are an integer of 1 to 5, an integer of 0 to 10, an integer of 2 to 5, and an integer of 0 to 10, respectively. ]

The rubber composition for a snow tire tread according to any one of <1> to < 7 >, comprising at least one selected from inorganic fillers represented by the formula:

< 9 > The rubber composition for a snow tire tread according to < 8 >, wherein the filler content is 10 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the rubber component.

< 10 > The rubber composition for a snow tire tread according to < 8 > or < 9 >, wherein a total amount of the hollow fine particles and the filler is 1 part by mass or more and 130 parts by mass or less with respect to 100 parts by mass of the rubber component. It is a thing.

< 11 > The rubber composition for a snow tire tread according to any one of <1> to < 10 >, further comprising a silane coupling agent.

<12> comprises a tread portion, a pneumatic snow tires with snow tire tread rubber composition according to any one of <1> to <11> in the tread portion.

< 13 > The pneumatic snow tire according to < 12 >, wherein the tread surface has an arithmetic average roughness Ra of 5 μm or more and 50 μm or less, and a roughness deviation Rsk of −0.5 or more and less than 0.

  According to the present invention, particularly for a tire rubber composition used for high-speed running, a tire tread rubber composition having excellent wet grip performance, wear resistance, durability, etc., and further improved on-ice performance, and A pneumatic tire using the same can be provided.

Hereinafter, the present invention will be described by way of embodiments.
<Rubber composition for tire tread>
The rubber composition for a tire tread of the present embodiment is such that the number average particle size in rubber is 1 μm or more and 100 μm or less and the particle size distribution index (PDI) in rubber is 1.50 or less with respect to 100 parts by mass of the rubber component. At least 1 part by mass and 30 parts by mass or less of hollow fine particles are blended.

  In the tire tread rubber composition of the present embodiment, since hollow fine particles are blended, unevenness is formed on the tread surface, and the hollow fine particles fall off from the tread surface or are broken on the tread surface. In the tread surface, a concave hole is formed, and water on the road surface can escape to the concave hole when traveling on an icy and snowy road surface, so that the grip force to the road surface is increased and the frictional force on ice can be improved. Even when traveling on a wet road, the water on the road surface is well absorbed in the concave holes on the tread surface, and the absorbed water is immediately drained when the tread surface is separated from the road surface, so the running performance is improved. It will not be damaged.

(Hollow particles)
Since the hollow fine particles in the present embodiment have a large compressive strength, they are present in the rubber or on the rubber surface in a state where they are not destroyed even when an operation such as kneading is performed after being blended with the rubber component.

  The hollow fine particles in the present embodiment are required to have a number average particle diameter in rubber of 1 μm or more and 100 μm or less. If the number average particle diameter in the rubber is less than 1 μm, even if the particle diameter is too small and a concave hole is formed on the rubber surface or the like, an effective effect on the water on the road surface is not exhibited. On the other hand, if it exceeds 100 μm, it becomes a fracture nucleus in the rubber and the wear resistance of the compounded rubber is lowered.

  The number average particle diameter of the hollow fine particles in the rubber in the present embodiment is preferably 5 μm or more and 80 μm or less, and more preferably 10 μm or more and 50 μm or less.

Further, the hollow fine particles in the present embodiment are required to have a rubber particle size distribution index (PDI) of 1.50 or less, preferably 1.45 or less, and more preferably 1.35 or less. preferable.
When the particle size distribution of the hollow fine particles in the rubber becomes broad and the PDI exceeds 1.5, the strain input to the tire cannot be uniformly dispersed and the wear resistance is lowered. Further, the diameter distribution of the concave holes formed on the tread surface becomes broad, and the water cannot be effectively drained within the tire contact surface, so that the wet performance and the friction performance on ice are reduced.

The rubber particle size distribution was determined by cutting a block-shaped rubber from a tread rubber of a test tire with a double-blade razor using a stereomicroscope with a magnification of 100 to 400 times (manufactured by Keyence Corporation, VH-6300). It can be determined by measuring the diameter of the hollow fine particles.
The number average particle size in rubber was determined as a value of 50% on the basis of the number from the particle size distribution in rubber obtained here.
Further, the particle size distribution index in rubber (abbreviated as “PDI”) was calculated from the following formula (1) using the half width W of the particle size distribution obtained here and the number average particle size M in the rubber. .
PDI = W / M (1)

Although it does not restrict | limit especially as a hollow microparticle which satisfy | fills said each conditions, It is preferable at the point which can obtain the said required compressive strength and the preferable particle size distribution to use a glass bubble.
As the glass microbubbles used in the present embodiment, for example, the ratio of the mass of alkaline earth metal oxide to the mass of alkali metal oxide in the glass composition (alkaline earth metal oxide / alkali metal oxide mass) is 1.2. In the range of at least 97% by mass of the combined mass of the alkaline earth metal oxide and the alkali metal oxide, SiO ₂ is 70 to 80% by mass and CaO is 8%. 15 wt%, Na ₂ O 3 to 8% by weight, and B ₂ O ₃ is desirably that contains 2 to 6 wt%. Glass microbubbles can also be prepared in devices such as those described in US Pat. No. 3,230,064 or US Pat. No. 3,129,086.

  Examples of commercially available glass bubbles that can be used in the present embodiment include Scotchlite (Glass Bubbles) S60HS (manufactured by soda-lime borosilicate glass) as a high-strength type. be able to. The hollow fine particles have a density of 0.60 g / cc and a number average particle diameter of about 30 μm.

The compounding amount of the hollow fine particles in a rubber component described later is 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the rubber component. If the blending amount is less than 1 part by mass, the amount of hollow fine particles is so small that a sufficient concave hole cannot be formed particularly in the vicinity of the rubber composition surface in order to exhibit the effective effect. When the amount exceeds 30 parts by mass, the wear resistance decreases.
The blending amount is preferably 1 part by mass or more and 20 parts by mass or less, and more preferably 3 parts by mass or more and 10 parts by mass or less.

(Rubber component)
Examples of the rubber component that can be used in the rubber composition of the present embodiment include at least one selected from natural rubber (NR) and various synthetic rubbers. Specific examples of the synthetic rubber include polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), Examples include ethylene-propylene-diene rubber (EPDM), crosslinked polyethylene rubber, chloroprene rubber, and nitrile rubber. These rubber components may be used alone or in a combination of two or more.

  As the rubber component used in the present embodiment, the following three tire tread rubber compositions (hereinafter referred to as “first tire tread rubber composition”), which are suitable for the performance required for a tire, And “second rubber composition for tire tread” and “third rubber composition for tire tread”).

[Rubber component of first rubber composition for tire tread]
The first rubber composition for a tire tread is intended to improve driving performance on a wet road surface (wet road surface), in particular, wet performance such as wet brake performance, in addition to handling stability on a dry road surface when used as a tire. As the rubber component, a rubber component containing 50% by mass or more of styrene-butadiene copolymer rubber (hereinafter sometimes simply referred to as “SBR”) is used.
SBR, which has a relatively high glass transition temperature, is used to place emphasis on wet skidability and handling stability on wet road surfaces. By combining the hollow fine particles with this, the braking performance on wet road surfaces can be improved. Can do.

  As described above, the rubber component contains 50% by mass or more of styrene-butadiene copolymer rubber, but preferably contains 80% by mass or more. Examples of the rubber component other than the styrene-butadiene copolymer rubber include natural rubber (NR) and butadiene rubber (BR).

The styrene-butadiene copolymer used for the SBR preferably has a Mooney viscosity at 100 ° C. of 30 or more, more preferably 40 or more. If the Mooney viscosity is less than 30, the heat resistance may deteriorate. The Mooney viscosity can be obtained, for example, by measuring ML _{1 + 4} at 100 ° C. using a Mooney viscosity tester, for example, a rotorless Mooney tester manufactured by Toyo Seiki.

The amount of styrene in the styrene-butadiene copolymer rubber is preferably 10% by mass or more and 50% by mass or more, and more preferably 15% by mass or more and 40% by mass or less. When the amount of styrene is 10% by mass or more and 50% by mass or more, a decrease in hysteresis loss and an increase in storage elastic modulus (E ′) at a low temperature (−10 ° C.) can be suppressed, and a decrease in wet performance can only be prevented. In addition, it is possible to sufficiently follow the unevenness of the road surface at low temperatures. The amount of styrene can be calculated from the integration ratio of the H-NMR spectrum.
As the styrene-butadiene copolymer, a commercially available product can be used, and it may be oil-extended.

[Rubber component of second rubber composition for tire tread]
The second rubber composition for a tire tread is intended to improve frictional force on icy and snowy roads, particularly on ice, without sacrificing wear resistance when used as a tire. A mixture of rubber and a specific diene synthetic rubber is used.
When the rubber component of the tread rubber is natural rubber and diene synthetic rubber, in addition to suppressing the decrease in the complex elastic modulus in the dry road surface running temperature region, the tread rubber is sufficiently free in the road running temperature region on ice. Therefore, it is easy to achieve both on-ice performance and wear resistance. By combining the hollow fine particles with this, the frictional force particularly on ice can be improved.

Specific examples of the specific diene-based synthetic rubber used with natural rubber include polyisoprene rubber (IR), polybutadiene rubber (BR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), and butyl rubber (IIR). ), One or more selected from halogenated butyl rubber and acrylonitrile-butadiene rubber (NBR). Polyisoprene rubber (IR), polybutadiene rubber (BR), and halogenated butyl rubber are preferable.
In particular, as a rubber component, polybutadiene rubber (BR) is preferable in terms of low heat buildup, wear resistance, crack growth resistance, tear resistance, and the like.

Also, rubber latex or rubber solution can be used as the rubber component. Examples of the rubber latex include natural rubber latex and synthetic rubber latex, or an organic solvent solution of synthetic rubber obtained by solution polymerization. Among these, the performance of the master batch obtained and ease of production can be mentioned. From the viewpoint, natural rubber latex and synthetic rubber latex are preferable.
As the natural rubber latex, any of field latex, ammonia-treated latex, centrifugal concentrated latex, deproteinized latex treated with an enzyme, latex having a functional group introduced, and a combination of the above-mentioned ones can be used. . Natural rubber latex is a colloidal sol having fine particles of rubber hydrocarbon as a dispersoid, and is electrically negatively charged. Usually, it is stored at pH 9 to 10 with ammonia and other alkalis as a stabilizer. The latex contains about 30% rubber, and the concentrated latex is concentrated to 60%.
As the synthetic rubber latex, for example, latex such as styrene-butadiene polymer rubber, nitrile rubber, polychloroprene rubber and the like can be used.

  The natural rubber and the specific diene synthetic rubber preferably have a mass ratio (natural rubber / specific diene synthetic rubber) in the range of 80/20 to 40/60. If the mass ratio is within this range, the decrease in the complex elastic modulus in the dry road surface travel temperature region is suppressed, and the tread rubber has sufficient flexibility in the ice road surface travel temperature region. It is easy to achieve both wear characteristics. The mass ratio is more preferably in the range of 60/40 to 40/60.

[Rubber component of third rubber composition for tire tread]
The third rubber composition for a tire tread is intended to improve frictional force on icy and snowy roads, particularly on ice, without sacrificing wear resistance when used as a tire. At least one selected from rubber and diene-based synthetic rubber is used, and it has independent foaming.
It is known that by imparting roughness to the tread surface, water melted on the ice can be drained and the frictional force on the ice can be improved, and foamed rubber has been used as the tread. By combining the foamed rubber with the hollow fine particles, it becomes possible to control the surface roughness aimed at the tread surface, and the frictional force can be further improved by the scratching effect of the hollow fine particles.

The rubber component may include only natural rubber, only diene synthetic rubber, or both. The diene synthetic rubber is not particularly limited and may be appropriately selected from known ones according to the purpose. For example, styrene-butadiene copolymer rubber (SBR), polyisoprene rubber (IR), Polybutadiene rubber (BR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), halogenated butyl rubber, acrylonitrile-butadiene rubber (NBR) and the like can be mentioned. Among these diene-based synthetic rubbers, cis-1,4-polybutadiene is preferable, and those having a cis content of 90% or more are particularly preferable in that the glass transition temperature is low and the effect on performance on ice is large.
In addition, when using the said rubber composition for tire treads for a tread etc. of a tire, as said rubber component, what has a glass transition temperature of -60 degrees C or less is preferable. When a rubber component having such a glass transition temperature is used, the tread or the like is advantageous in that it maintains sufficient rubber elasticity even in a low temperature range and exhibits good performance on ice.

(filler)
The rubber composition for tire treads of this embodiment may contain a filler. Examples of the filler include carbon black, silica, clay, talc, calcium carbonate, aluminum hydroxide and the like. The type of these fillers is not particularly limited, and any one of those conventionally used as a filler for rubber can be selected and used. Moreover, when using inorganic fillers, such as a silica, you may use a silane coupling agent together.

In this embodiment, the filler is carbon black, silica, and general formula (I).
nM · xSiO _y · zH ₂ O (I)
[Wherein, M is selected from metals selected from aluminum, magnesium, titanium, calcium and zirconium, and oxides or hydroxides of these metals, hydrates thereof, and carbonates of the metals. N, x, y, and z are at least 1 type, an integer of 1-5, an integer of 0-10, an integer of 2-5, and an integer of 0-10, respectively. ]
Is preferably at least one selected from the group consisting of inorganic fillers
By using the inorganic filler represented by the above general formula (I) in addition to carbon black and silica, the reinforcing effect can be enhanced efficiently, and the wear resistance and low heat build-up when used as a tire ( (Low fuel consumption) can be achieved.

Here, as the carbon black, those usually used in the rubber industry can be used. For example, various grades of carbon black such as SAF, HAF, ISAF, FEF, GPF can be used alone or in combination. .
The silica is not particularly limited, but wet silica, dry silica, and colloidal silica are preferable. These can be used alone or in combination.
When carbon black is used for the third tire tread rubber composition, the blending amount is desirably 20 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the rubber component. By setting the blending amount within the above range, it is possible to achieve both wear resistance and on-ice performance.

Specific examples of the inorganic filler represented by the general formula (I) include alumina (Al ₂ O ₃ ) such as γ-alumina and α-alumina, alumina monohydrate such as boehmite and diaspore (Al ₂ O ₃ · H ₂ O), Gibbsite, Bayerite, etc. Aluminum hydroxide [Al (OH) ₃ ], Aluminum carbonate [Al ₂ (CO ₃ ) ₂ ], Magnesium hydroxide [Mg (OH) ₂ ], oxidation magnesium (MgO), magnesium carbonate (MgCO _3), talc _{(3MgO · 4SiO 2 · H 2} O), attapulgite _{(5MgO · 8SiO 2 · 9H 2} O), titanium white (TiO _2), titanium black (TiO _2n-1 ), calcium oxide (CaO), calcium hydroxide [Ca (OH) _2], magnesium aluminum oxide _{(MgO · Al 2 O 3)} , clay _{(Al 2 O 3 · 2SiO 2} ), Olin _{(Al 2 O 3 · 2SiO 2} · 2H 2 O), pyrophyllite _{(Al 2 O 3 · 4SiO 2} · H 2 O), bentonite _{(Al 2 O 3 · 4SiO 2} · 2H 2 O), aluminum silicate (Al ₂ SiO ₅ , Al ₄ · 3SiO ₄ · 5H ₂ O, etc.), magnesium silicate (Mg ₂ SiO ₄ , MgSiO ₃ etc.), calcium silicate (Ca ₂ · SiO ₄ etc.), aluminum calcium silicate (Al ₂ O ₃ · CaO · 2SiO ₂ etc.), magnesium calcium silicate (CaMgSiO ₄ ), calcium carbonate (CaCO ₃ ), zirconium oxide (ZrO ₂ ), zirconium hydroxide [ZrO (OH) ₂ · nH ₂ O], carbonic acid zirconium _{[Zr (CO 3) 2]} , hydrogen to correct electric charge as various zeolites, crystalline aluminosilicates containing alkali metal or alkaline earth metal And the like can be used.
The inorganic filler represented by the general formula (I) includes at least one selected from M selected from aluminum metal, aluminum oxide or hydroxide, hydrates thereof, and aluminum carbonate. preferable. Among these, carbon black, silica and aluminum hydroxide are preferable as the filler.

As content of the said filler, it is preferable to use a filler in 10 mass parts or more and 100 mass parts or less with respect to 100 mass parts of rubber components. By making the addition amount in the above range, it is possible to achieve both the reinforcing property and the low heat generation property (low fuel consumption) when used in a tire, and the workability and the like can be improved.
The content is preferably 15 parts by mass or more and 95 parts by mass or less, more preferably 20 parts by mass or more and 90 parts by mass or less.

  Moreover, in this embodiment, it is preferable that the total compounding quantity of the said hollow fine particle and a filler shall be 1 to 130 mass parts with respect to 100 mass parts of said rubber components. By setting the total blending amount within this range, it is possible to achieve both wear resistance and the wet performance and on-ice performance. The total blending amount is more preferably 30 parts by mass or more and 80 parts by mass or less.

(Other ingredients)
The tire tread rubber composition of the present embodiment includes the above rubber component, filler such as carbon black, oil such as process oil, vulcanizing agent, vulcanization accelerator, anti-aging agent, softening agent, zinc oxide. This embodiment is a blending material for rubber that is normally used in the rubber industry, such as ozone deteriorating agent, coloring agent, antistatic agent, lubricant, antioxidant, coupling agent, foaming agent, foaming aid and stearic acid. Can be appropriately selected and blended within a range that does not impair the purpose. As these compounding agents, commercially available products can be suitably used.

  There is no restriction | limiting in particular as oils, such as the said process oil, According to the objective, it can select suitably and can be used. Examples of the oil include aromatic oils, naphthenic oils, paraffinic oils, ester oils, solution conjugated diene rubbers, solution hydrogenated conjugated diene rubbers, and the like. When the oil component is contained in the rubber composition, the fluidity of the rubber composition can be controlled. Therefore, by reducing the viscosity of the rubber composition before vulcanization and increasing the fluidity, the rubber composition can be improved very well. This is advantageous in that it can be extruded.

  Further, as the vulcanizing agent, in addition to conventional sulfur, at least one of an organic thiosulfate compound (for example, 1,6-hexamethylenedithiosulfate sodium dihydrate) and a bismaleimide compound (for example, phenylene bismaleimide) Seeds can be used in combination.

  Examples of the vulcanization accelerator include thiuram compounds such as tetrakis-2-ethylhexyl thiuram disulfide, tetrakis-2-isopropyl thiuram disulfide, tetrakis-dodecyl thiuram disulfide, and tetrakis-benzyl thiuram disulfide; Dithiocarbamate compounds such as zinc hexyldithiocarbamate, zinc dodecyldithiocarbamate, and zinc benzyldithiocarbamate; and dibenzothiazyl disulfide, 4,4′-dimethyldibenzothiazyl disulfide, N-cyclohexyl-2-benzothiazyl- Sulfenamide, Nt-butyl-2-benzothiazyl-sulfenamide, Nt-butyl-2-benzothiazyl-sulfenimide, N-oxydiethylene-benzothia Le - sulfenamide, and N, hexyl N'- dicyclohexyl-2-benzothiazyl - benzothiazolyl vulcanization accelerator such as sulfenamide; and the like.

  Furthermore, examples of the anti-aging agent include 3C (N-isopropyl-N′-phenyl-p-phenylenediamine, 6C [N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine], Examples thereof include AW (6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline), a high-temperature condensate of diphenylamine and acetone.

In the case of the third rubber composition for a tire tread, since it is necessary to use foamed rubber, a foaming agent is blended together with other compounding agents in the rubber component in order to form air bubbles after the addition. To do.
Examples of the foaming agent include dinitrosopentamethylenetetramine (DPT), azodicarbonamide (ADCA), dinitrosopentastyrenetetramine, a benzenesulfonyl hydrazide derivative, oxybisbenzenesulfonylhydrazide (OBSH), and a heavy gas that generates carbon dioxide. Ammonium carbonate, sodium bicarbonate, ammonium carbonate, nitrososulfonylazo compound generating nitrogen, N, N′-dimethyl-N, N′-dinitrosophthalamide, toluenesulfonylhydrazide, p-toluenesulfonyl semicarbazide, p, p ′ -Oxy-bis (benzenesulfonyl semicarbazide) etc. are mentioned.

  Among these foaming agents, in consideration of production processability, dinitrosopentamethylenetetramine (DPT) and azodicarbonamide (ADCA) are preferable, and azodicarbonamide (ADCA) is particularly preferable. These may be used individually by 1 type and may use 2 or more types together. By the action of the foaming agent, the obtained vulcanized rubber becomes a foamed rubber having a high foaming rate.

In the case of foamed rubber, from the viewpoint of efficient foaming, it is preferable to use a foaming aid as the other component and use it together with the foaming agent. Examples of the foaming aid include urea, zinc stearate, zinc benzenesulfinate, zinc white, and the like, which are usually used in the production of foamed products. Among these, urea, zinc stearate, zinc benzenesulfinate and the like are preferable. These may be used individually by 1 type and may use 2 or more types together.
The content of the foaming agent may be appropriately determined according to the purpose, but is generally preferably about 1 to 10 parts by mass with respect to 100 parts by mass of the rubber component.

It is preferable to further mix a silane coupling agent in the tire tread rubber composition of the present embodiment. By blending a silane coupling agent, wear resistance is further improved and tan δ is further reduced. The amount of the silane coupling agent is preferably in the range of 1 to 20 parts by mass with respect to 100 parts by mass of the filler.
As silane coupling agents, vinyltrichlorosilane, vinyltriethoxysilane, vinyltris (β-methoxy-ethoxy) silane, β- (3,4-epoxycyclohexyl) -ethyltrimethoxysilane, γ-glycidoxypropyl Trimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-methacryloxypropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, N- (β-aminoethyl)- γ-aminopropyltrimethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, bis (3- (tri Ethoxysilyl) propi ) Tetrasulfide, bis (3- (triethoxysilyl) propyl) disulfide, .gamma.-trimethoxysilylpropyl dimethylthiocarbamoyl tetrasulfide, .gamma.-trimethoxysilylpropyl benzothiazyl tetrasulfide and the like.

  The tire tread rubber composition of the present embodiment can be produced by kneading, heating, extruding, and vulcanizing, etc., a rubber component, a resin, and the other compounding agents that are appropriately selected as necessary. .

  The kneading conditions are not particularly limited and depend on various conditions such as the amount of each component charged into the kneading apparatus, the rotational speed of the rotor, the ram pressure, the kneading temperature, the kneading time, and the type of the kneading apparatus. It can be selected as appropriate. Examples of the kneading apparatus include a single-screw kneading extruder and a multi-shaft kneading extruder (continuous kneading apparatus) generally used for kneading rubber compositions, a meshing type such as a Banbury mixer, an intermix, and a kneader. Examples thereof include a kneader and a roll (batch type kneader) having a meshing rotary rotor. You may use combining these two or more.

  In addition, the heating or extrusion is not particularly limited with respect to various conditions such as heating or extrusion time, heating or extrusion apparatus, and can be appropriately selected according to the purpose. A commercially available product can be suitably used as the heating or extrusion device. In addition, when the said foaming agent exists, heat-insertion or extrusion temperature is suitably selected in the range which does not raise | generate the foaming. The extrusion temperature is desirably about 90 to 110 ° C.

In the present embodiment, as the third rubber composition for a tire tread, the foaming ratio of the rubber composition after vulcanization is preferably 5% or more and 40% or less. By setting the foaming rate (Vs) within this range, it is possible to achieve both on-ice braking and wear resistance due to the softening effect of foaming. The foaming rate is more preferably 15% or more and 30% or less.
In addition, a foaming rate (Vs) can be calculated | required by following formula (2).
Vs = (ρ ₀ / ρ ₁ −1) × 100 (%) (2)
(Wherein, ρ ₁ is the foam rubber density (g / cm ³ ), and ρ ₀ is the density of the solid phase part of the foam rubber (g / cm ³ )).

<Pneumatic tire>
The pneumatic tire of this embodiment includes a tread portion, and the above-described rubber composition for a tire tread is used for the tread portion. The structure of the tread portion of the tire is not particularly limited, and may have a single layer structure or a multilayer structure depending on the application. When the tread portion is composed of multiple layers, the desired effect is exhibited by using the rubber composition for a tire tread in at least one layer. When the tread portion has a two-layer structure (cap / base structure) of a cap rubber layer located on the tread surface portion and a base rubber layer adjacent to the belt-covered rubber, the base rubber layer is a rubber composition for a tire tread. It is preferable that it is comprised with a thing. In this case, the block rigidity increases as the groove height when the base rubber layer is exposed decreases.

In the present embodiment, it is desirable that the arithmetic average roughness Ra of the tread surface in the tire is 5 μm or more and 50 μm or less, and the roughness deviation Rsk is −0.5 or more and less than 0. By making Ra and Rsk within the above ranges, the drainage within the ground plane can be improved. The Ra and Rsk are defined in JIS B0601: 2001.
The Ra is more preferably 10 μm or more and 30 μm or less, and Rsk is more preferably −0.4 or more and −0.1 or less.

In addition, said Ra and Rsk prepare the tread rubber same as what was affixed on the tread part, and measure it using surface roughness measuring device NH-120S (made by Mitaka Kogyo Co., Ltd.).
Further, Ra and Rsk are particularly preferably applied to a tire using the first tire tread rubber composition as a tread.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
First, tire performance was evaluated by the following methods for tires obtained using the rubber composition for tire treads obtained in the following examples.

<Tire performance evaluation>
(Abrasion resistance)
A test tire (tire size 195 / 65R15) was prototyped, and after running on a paved road surface for 20,000 km on an actual vehicle, the remaining groove was measured, and the running distance required for 1 mm of wear on the tread was relatively compared. The index is shown with 1 being 100. The larger the index, the better the wear resistance.

(Wet performance)
Four test tires (tire size 195 / 65R15) were mounted on a 2000 cc passenger car, and the braking distance from an initial speed of 70 km / hr was measured on the wet asphalt road surface of the test course. The measured value of Comparative Example 1 was set to 100, and for the values of other examples, an index was calculated and displayed as an index by the braking distance of Comparative Example 1 / the braking distance of the test tire × 100. Therefore, the larger the numerical value, the better.

(Performance on ice)
Four test tires (tire size 195 / 65R15) were mounted on a 2000 cc passenger car and the braking performance on ice at an ice temperature of −1 ° C. was confirmed. The tire of Comparative Example 1 was used as a control tire, and performance on ice = (braking distance of control tire / braking distance of other examples) × 100. Larger values indicate better performance on ice.

< Reference Examples A1 to A4 and Comparative Examples A1 to A4>
Eight types of rubber compositions for tire treads having the composition shown in Table 1 were prepared using a Banbury mixer. Next, for each rubber composition, a vulcanized rubber sample was produced under the conditions of a vulcanization temperature of 145 ° C. and a vulcanization time of 45 minutes.
A summer tire (tire size: 195 / 65R15) using the above-prepared eight types of rubber compositions as tread rubber was prototyped and the tire performance was evaluated. The results are summarized in Table 1.

[note]
* 1) SL563 (JSR, styrene content: 20% by mass)
* 2) Glass Bubbles manufactured by Sumitomo 3M, trade name “Scotchlite S60” (number average particle size in rubber: 30 μm, PDI: 1.33, average wall thickness: 1.5 μm)
* 3) Glass Bubbles manufactured by Sumitomo 3M, trade name “Scotchlite S32” (number average particle diameter in rubber: 35 μm, PDI: 1.43, average wall thickness: 0.89 μm)
* 4) Glass Bubbles manufactured by Sumitomo 3M, trade name “Scotchlite S15” (number average particle diameter in rubber: 30 μm, PDI: 1.83)
* 5) Product name “SEAST 7HM” manufactured by Tokai Carbon Co., Ltd.
* 6) Product name “Nip Seal AQ” manufactured by Nippon Silica Kogyo Co., Ltd.
* 7) Product name “Si75” manufactured by Degussa
* 8) N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine, manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name “NOCRACK 6C”
* 9) N-cyclohexyl-2-benzothiazolylsulfenamide, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., trade name “Noxeller CZ”
* 10) 1,3-diphenylguanidine, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., trade name “Noxeller D”

As can be seen from the results shown in Table 1, in the tire using the rubber composition of the reference example using glass bubbles with a predetermined content of PDI at a certain value or less, compared to the case of using the rubber composition of the comparative example Thus, it can be seen that the wet performance (braking performance) is improved without reducing the wear resistance.

< Reference Examples B1 to B3 and Comparative Examples B1 to B7>
Ten types of rubber compositions for tire treads having the composition shown in Table 2 were prepared using a Banbury mixer. Next, for each rubber composition, a vulcanized rubber sample was produced under the conditions of a vulcanization temperature of 145 ° C. and a vulcanization time of 45 minutes.
Snow tires (tire size: 195 / 65R15) using the above-prepared 10 types of rubber compositions as tread rubbers were prototyped and the tire performance was evaluated. The results are summarized in Table 2.

[note]
* 1) Ube Industries' cis-1,4-polybutadiene rubber, trade name “UBEPOL 150L”
* 2) Glass Bubbles manufactured by Sumitomo 3M, trade name “Scotchlite S60” (number average particle size in rubber: 30 μm, PDI: 1.33, average wall thickness: 1.5 μm)
* 3) Glass Bubbles manufactured by Sumitomo 3M, trade name “Scotchlite S32” (number average particle diameter in rubber: 35 μm, PDI: 1.43, average wall thickness: 0.89 μm)
* 4) Glass Bubbles manufactured by Sumitomo 3M, trade name “Scotchlite S15” (number average particle diameter in rubber: 30 μm, PDI: 1.83)
* 5) Glass balloon manufactured by Asahi Glass Co., Ltd., trade name “Cell Star” (number average particle diameter in rubber: 29 μm, PDI: 1.85, average wall thickness: 3 μm, average specific gravity: 0.68 g / cc)
* 6) Glass balloon manufactured by Asahi Glass Co., Ltd., trade name “Cell Star” (number average particle diameter in rubber: 25 μm, PDI: 1.60, average wall thickness: 2 μm, average specific gravity: 0.90 g / cc)
* 7) Expansion microcapsules manufactured by Matsumoto Yushi Co., Ltd., trade name “Microsphere F100D” (number average particle diameter in rubber: 26 μm, PDI: 1.54)
* 8) Expanded graphite manufactured by UCAR, trade name “GRAFGuard160-50N” (number average particle diameter in rubber: 250 μm, PDI: 2.3)
* 9) Product name “N134” (N2SA: 146 m ² / g) manufactured by Asahi Carbon Co., Ltd.
* 10) Product name "Nip Seal AQ", manufactured by Nippon Silica Kogyo Co., Ltd.
* 11) Product name “Si69” manufactured by Degussa
* 12) N-isopropyl-N′-phenyl-p-phenylenediamine, manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name “NOCRACK 6C”
* 13) Di-2-benzothiazyl-disulfide, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., trade name “Noxeller DM”
* 14) N-cyclohexyl-2-benzothiazolylsulfenamide, manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name “Noxeller CZ”

As can be seen from the results shown in Table 2, in the tire using the rubber composition of the reference example using glass bubbles with a predetermined content of PDI of a certain value or less, compared to the case of using the rubber composition of the comparative example Thus, it can be seen that the performance on ice (braking performance) is greatly improved without reducing the wear resistance.

<Examples C1- C7, Reference Examples C1- C2 and Comparative Examples C1-C4>
Thirteen types of rubber compositions for tire treads having the composition shown in Table 3 were prepared using a Banbury mixer. Next, for each rubber composition, a vulcanized rubber sample was produced under the conditions of a vulcanization temperature of 145 ° C. and a vulcanization time of 45 minutes.
Snow tires (tire size: 195 / 65R15) using the 13 types of rubber compositions produced above as tread rubbers were prototyped and the tire performance was evaluated. The results are summarized in Table 3.

[note]
* 1) Ube Industries' cis-1,4-polybutadiene rubber, trade name “UBEPOL 150L”
* 2) Glass Bubbles manufactured by Sumitomo 3M, trade name “Scotchlite S60” (number average particle size in rubber: 30 μm, PDI: 1.33, average wall thickness: 1.5 μm)
* 3) Glass Bubbles manufactured by Sumitomo 3M, trade name “Scotchlite S32” (number average particle diameter in rubber: 35 μm, PDI: 1.43, average wall thickness: 0.89 μm)
* 4) Glass Bubbles manufactured by Sumitomo 3M, trade name “Scotchlite S15” (number average particle diameter in rubber: 30 μm, MDI: 1.83)
* 5) Product name “N134” manufactured by Asahi Carbon Co., Ltd. (N2SA: 146 m ² / g)
* 6) Product name “Nip Seal AQ” manufactured by Nippon Silica Kogyo Co., Ltd.
* 7) Product name “Si69” manufactured by Degussa
* 8) N-isopropyl-N′-phenyl-p-phenylenediamine, manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name “NOCRACK 6C”
* 9) Di-2-benzothiazyl-disulfide, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., trade name “Noxeller DM”
* 10) N-cyclohexyl-2-benzothiazolylsulfenamide, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., trade name “Noxeller CZ”
* 11) Dinitrosopentamethylenetetramine

  As can be seen from the results shown in Table 3, in the tire using the rubber composition of the example using glass bubbles with a predetermined content of PDI of a certain value or less, compared with the case of using the rubber composition of the comparative example Thus, it can be seen that the performance on ice (braking performance) is greatly improved without reducing the wear resistance.

  According to the present invention, it is possible to obtain a pneumatic tire excellent not only in wear resistance but also in wet performance and on-ice performance, so that air for passenger cars, light cars, light trucks, trucks and buses, and off-the-roads is used. It is suitably used as a tread member such as a cap tread of an entering tire.

Claims (13)

With respect to 100 parts by mass of at least one rubber component selected from natural rubber and diene synthetic rubber , the number average particle size in rubber is 1 μm or more and 100 μm or less, and the particle size distribution index (PDI) in rubber is 1.50 or less. so as to, Ri Na and at least blended 1 part by mass or less than 30 parts by weight hollow particles have a closed-cell, and after vulcanization of the foaming rate of 5% to 40% der Ru rubber snow tire tread Composition. The rubber composition for a snow tire tread according to claim 1, wherein the rubber particle size distribution index (PDI) is 1.35 or less. The rubber composition for a snow tire tread according to claim 1 or 2, wherein the rubber component comprises 50% by mass or more of styrene-butadiene copolymer rubber. The rubber composition for a snow tire tread according to claim 3, wherein the styrene content in the styrene-butadiene copolymer rubber is 10 mass% or more and 50 mass% or less. The rubber component is natural rubber and at least one diene-based synthetic rubber selected from polyisoprene rubber, polybutadiene rubber, ethylene-propylene-diene rubber, chloroprene rubber, butyl rubber, halogenated butyl rubber, and acrylonitrile-butadiene rubber. The rubber composition for a snow tire tread according to claim 1, wherein the rubber composition is a mixture of The rubber composition for a snow tire tread according to claim 5, wherein a mass ratio (natural rubber / diene synthetic rubber) of natural rubber and diene synthetic rubber in the mixture is in a range of 80/20 to 40/60. The rubber composition for a snow tire tread according to any one of claims 1 to 6 , wherein a blending amount of the hollow fine particles is 3 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the rubber component. Carbon black, silica and general formula (I) as fillers
nM · xSiO _y · zH ₂ O (I)
[Wherein, M is selected from metals selected from aluminum, magnesium, titanium, calcium and zirconium, and oxides or hydroxides of these metals, hydrates thereof, and carbonates of the metals. It is at least one, and n, x, y, and z are an integer of 1 to 5, an integer of 0 to 10, an integer of 2 to 5, and an integer of 0 to 10, respectively. ]
The rubber composition for a snow tire tread according to any one of claims 1 to 7 , comprising at least one selected from inorganic fillers represented by: The rubber composition for a snow tire tread according to claim 8 , wherein the filler content is 10 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the rubber component. The rubber composition for a snow tire tread according to claim 8 or 9 , wherein the total amount of the hollow fine particles and the filler is 1 part by mass or more and 130 parts by mass or less with respect to 100 parts by mass of the rubber component. Furthermore, the rubber composition for snow tire treads of any one of Claims 1-10 formed by mix | blending a silane coupling agent. Comprising a tread portion, the pneumatic snow tires with snow tire tread rubber composition according to any one of claims 1 to 11, the tread portion. The pneumatic snow tire according to claim 12 , wherein the arithmetic average roughness Ra of the tread surface is 5 µm or more and 50 µm or less, and the roughness bias Rsk is -0.5 or more and less than 0.