JP4785388B2 - Rubber composition for tread and pneumatic tire using the same - Google Patents

Description

  The present invention relates to a rubber composition for a tread and a pneumatic tire using the same, and particularly to a rubber composition for a tread that can exhibit excellent grip performance in both a low temperature region and a high temperature region when used in a tire. It is.

  High grip performance is required for tread rubber of pneumatic tires used in high-speed running. Conventionally, in order to impart high grip performance to a tire, a rubber composition containing a styrene-butadiene copolymer rubber (SBR) having a high styrene content is used for a tread, and hysteresis loss between polymers is utilized in the grip. A method in which a rubber composition highly filled with resin is applied to the tread and the adhesion effect of the resin is applied to the grip, and a rubber composition highly filled with carbon black is applied to the tread and the hysteresis of the rubber composition is applied to the grip For example, a method of applying a rubber composition containing carbon black having a small particle diameter to a tread has been adopted. In order to improve grip performance at low temperatures, a rubber composition containing a low freezing point plasticizer and having a reduced elastic modulus at low temperatures has been used for tire treads.

  However, since SBR with a high styrene content has a high glass transition temperature, when a rubber composition containing the SBR is used for a tire tread, the temperature dependence of various physical properties of the tire increases in the vicinity of the tire temperature during running. There has been a problem that the performance change of the tire with respect to the temperature change becomes large.

  In addition, increasing the blending amount of carbon black or softener in the rubber composition or blending carbon black with a small particle size reduces the dispersibility of the carbon black in the rubber composition. When is used for a tire tread, there is a problem that the wear resistance of the tire is lowered.

  Furthermore, when a large amount of resin is blended, there is a problem that the performance change with respect to the temperature of the tire becomes large due to the influence of the resin.

In contrast, high styrene content, in a system using a high glass transition temperature is SBR as a rubber component, a petroleum resin and the softening point of the main component process oil and C ₉ aromatic resin is less than 40 ° C. A method of blending a coumarone indene resin mixture (for example, see Patent Document 1), a method of using carbon black having a small particle size and an alkylphenol-based resin in combination (for example, see Patent Document 2), a naphtha with respect to a diene rubber a method of blending the copolymer resin with C ₅ fraction and styrene or vinyl toluene obtained by thermal decomposition (e.g., see Patent Document 3), a method of blending the isoprene rubber and a low freezing point plasticizers (e.g., Patent Document 4 For example). Further, in order to reduce temperature dependency, a method of blending a large amount of natural resin / synthetic resin in a system using SBR having a low styrene content and a low glass transition temperature as a rubber component (see, for example, Patent Document 5) ) Etc. have been tried. However, even with these methods, the grip performance cannot be sufficiently improved, and there is still room for improvement.

JP-A-5-214170 JP-A-6-200078 Japanese Patent Laid-Open No. 9-328577 Japanese Patent Laid-Open No. 10-273560 JP 2003-253051 A

  Accordingly, the object of the present invention is to solve the above-mentioned problems of the prior art and to exhibit excellent grip performance when used for a tire tread, particularly excellent grip performance in both a low temperature region and a high temperature region. An object of the present invention is to provide a rubber composition for a tread that can be used. Another object of the present invention is to provide a pneumatic tire using such a tread rubber composition and having excellent grip performance.

  As a result of intensive studies to achieve the above-mentioned object, the present inventor has obtained a rubber composition comprising a phenolic resin having a softening point and an OH value within a specific range and a plasticizer having a freezing point below a certain level. It has been found that the grip performance of a tire can be improved in a wide temperature range by using it for a tire tread, and the present invention has been completed.

That is, the rubber composition for a tread of the present invention has a filler (B) of 30 to 200 parts by mass and a pt-butylphenol acetylene resin (C) of 10 parts by mass or more with respect to 100 parts by mass of the rubber component (A). And tri (2-ethylhexyl) phosphate (TOP), tributyl phosphate (TBP), di (2-ethylhexyl) sebacate (DOS), diisooctyl sebacate (DIOS), di (2-ethylhexyl) adipate (DOA), It is characterized by blending at least 10 parts by mass of at least one plasticizer (D) selected from the group consisting of diisooctyl adipate (DIOA) .

  In a preferred example of the rubber composition for a tread of the present invention, the rubber component (A) contains a styrene-butadiene copolymer rubber having a styrene content of 20 to 70% by mass.

  In another preferred embodiment of the rubber composition for a tread of the present invention, the filler (B) contains carbon black.

In another preferred embodiment of the rubber composition for a tread of the present invention, the filler (B) is silica and / or the following general formula (I):
wM · xSiO _y · zH ₂ O (I)
(Wherein, M is a metal selected from the group consisting of aluminum, magnesium, titanium, calcium, and zirconium, oxides or hydroxides of these metals, and hydrates thereof, or carbonates of these metals. And w, x, y, and z are each 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) including.

  The pneumatic tire according to the present invention is characterized in that the tread rubber composition is used as a tread rubber. Here, it is preferable that the pneumatic tire is a tire for a high-speed competition vehicle.

According to the present invention, a rubber composition comprises a pt-butylphenol acetylene resin, tri (2-ethylhexyl) phosphate (TOP), tributyl phosphate (TBP), di (2-ethylhexyl) sebacate (DOS), diiso By blending at least one plasticizer selected from the group consisting of octyl sebacate (DIOS), di (2-ethylhexyl) adipate (DOA), and diisooctyl adipate (DIOA) , a low temperature region and a high temperature region Any of the above can provide a rubber composition for a tread capable of exhibiting excellent grip performance in a tire. Moreover, the pneumatic tire which has the outstanding grip performance in the wide temperature range using this rubber composition for treads can be provided.

The present invention is described in detail below. The rubber composition for a tread of the present invention has a filler (B) of 30 to 200 parts by mass, a pt-butylphenol acetylene resin (C) of 10 parts by mass or more, with respect to 100 parts by mass of the rubber component (A). Tri (2-ethylhexyl) phosphate (TOP), tributyl phosphate (TBP), di (2-ethylhexyl) sebacate (DOS), diisooctyl sebacate (DIOS), di (2-ethylhexyl) adipate (DOA), diiso It is characterized by comprising at least one plasticizer (D) selected from the group consisting of octyl adipate (DIOA) and at least 10 parts by mass. The pt-butylphenol acetylene resin (C) is softened at the softening point to cause hysteresis loss, and the grip performance in a high temperature region after the softening point is greatly improved. In addition, the plasticizer (D) reduces the elastic modulus of the rubber composition at low temperatures, increases the real contact area between the tread and the road surface, and increases the adhesive frictional force, greatly improving the grip performance in the low temperature region. To improve.

In addition, by using the pt-butylphenol acetylene resin (C) and the plasticizer (D) in combination, the pt-butylphenol acetylene resin (C) or the plasticizer (D) is blended alone. In addition to further improving the grip performance of the tire, the grip performance in the low temperature region and the grip performance in the high temperature region are highly compatible. Note that the rubber composition for a tread of the present invention cannot be improved even when a resin having a too low softening point (so-called tackifier such as tackifier) is used in combination with the plasticizer (D). , A pt-butylphenol acetylene resin (C) having a softening point of 110 ° C. or higher is used . Further, in the rubber composition for a tread of the present invention, the grip improving effect obtained by using the pt-butylphenol acetylene resin (C) and the plasticizer (D) has a conventional low glass transition point. It is higher than the combined effect of the polymer and the resin, and the combined effect of the polymer having a high glass transition point and the low melting point softener.

  Examples of the rubber component (A) used in the tread rubber composition of the present invention include natural rubber (NR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), polyisoprene rubber (IR) and other dienes. A system rubber can be illustrated. These rubber components may be used alone or in a blend of two or more. The rubber component (A) preferably contains styrene-butadiene copolymer rubber having a styrene content of 20 to 70% by mass. By using SBR having a styrene content of 20% by mass or more, an appropriately high tan δ can be obtained, and an appropriate grip performance can be exhibited as a tread compound. On the other hand, if the styrene content exceeds 70% by mass, the Tg of the polymer (SBR) is too high, so that a good grip cannot be obtained even when using this composition. Here, the content of SBR having a styrene content of 20 to 70% by mass in the rubber component (A) is preferably 80% by mass or more.

  There is no restriction | limiting in particular as a filler (B) used for the rubber composition for treads of this invention, Carbon black and an inorganic filler can be used. Here, as the inorganic filler, silica and inorganic compounds represented by the above general formula (I) are preferable. These fillers (B) may be used alone or in combination of two or more. The filler (B) is blended in an amount of 30 to 200 parts by mass with respect to 100 parts by mass of the rubber component (A), and is blended in an amount of 50 to 150 parts by mass from the viewpoints of reinforcing properties and effects of improving various physical properties. Is preferred. When the blending amount of the filler (B) is less than 30 parts by mass, sufficient grip performance of the tire cannot be ensured, and when it exceeds 200 parts by mass, the workability of the rubber composition tends to be lowered.

The carbon black is not particularly limited, and grades such as SRF, GPF, FEF, HAF, ISAF, and SAF can be used. The iodine adsorption amount (IA) is 60 mg / g or more, and dibutyl phthalate (DBP). ) Carbon black having an oil absorption of 80 mL / 100 g or more is preferred. By using carbon black, the improvement effect of the grip performance and fracture resistance of the tire can be improved. In order to further improve the wear resistance of the tire, it is particularly preferable to use HAF, ISAF, or SAF grades. Moreover, the external surface area by the cetyltrimethylammonium bromide (CTAB) adsorption method is in the range of 130 to 200 m ² / g, and the 24M4DBP oil absorption is preferably 80 mL / 100 g or more. The 24M4 DBP oil absorption is the DBP oil absorption after four times of compression at a pressure of 24,000 psi.

The silica is not particularly limited, and examples include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, and the like. Wet silica is preferred in terms of the most remarkable effect of achieving both grip properties and low rolling resistance. Further, the silica is preferably the specific surface area measured by the nitrogen adsorption method is in the range of 80~300m ² / g, and still more preferably in the range of 100~220m ² / g. When the specific surface area of silica is 80 m ² / g or more, sufficient reinforcement is exhibited, and when it is 300 m ² / g or less, workability can be prevented from being lowered. Usually, fine powdered silicic acid or hydrous silicic acid used as a white reinforcing filler for rubber is used. As the silica, specifically, "Nipsil" [manufactured by Nippon Silica Industrial Co., Ltd.] having a specific surface area of about 200 meters ² / g, "Zeosil 1115MP" having a specific surface area of about 117m ² / g [Rhodia] etc. Commercial products can be used.

Specific examples of the inorganic compound include alumina monohydrate (Al ₂ O ₃ .H ₂ O), aluminum hydroxide [Al (OH) ₃ ] such as gibbsite, bayerite, and alumina (Al ₂ O ₃ ). , Aluminum carbonate [Al ₂ (CO ₃ ) ₃ ], magnesium hydroxide [Mg (OH) ₂ ], magnesium oxide (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 ], aluminum magnesium oxide (MgO. Al ₂ O _3), clay _{(Al 2 O 3 · 2SiO 2} ), kaolin _{(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], zirconium carbonate [Zr (CO ₃ ) ₂ ], various zeolites, feldspar, mica, montmorillonite, etc. Among these, M is aluminum. Those are preferred. The inorganic compound may further contain a metal such as potassium, sodium, iron and magnesium, an element such as fluorine, and a group such as —NH ₄ .

The pt-butylphenol acetylene resin (C) used in the rubber composition for a tread of the present invention has a softening point (measurement method: ASTM E28-58-T) of 110 to 150 ° C. and an OH value (measurement method: JIS K0070). ) Is 180 mgKOH / g or more, and the OH value is preferably in the range of 180 to 300 mgKOH / g. The pt-butylphenol acetylene resin (C) has a tackifying property to the rubber composition and softens at the softening point to cause hysteresis loss, thereby greatly improving the grip performance of the tire after the softening point. be able to. If the softening point of the pt-butylphenol acetylene resin (C) is less than 110 ° C, the grip performance of the tire may be deteriorated. If it exceeds 150 ° C, the temperature dependence of the hysteresis loss characteristic may become too high. In addition, the processability of the rubber composition may deteriorate. In addition, when the pt-butylphenol acetylene resin (C) has an OH value of less than 180, the effect as adhesion is small and the merit is very small. On the other hand, if the OH value exceeds 300, workability is greatly deteriorated, and it becomes difficult to use.

The pt-butylphenol acetylene resin (C) is generally a thermoplastic resin having a molecular weight of several hundred to several thousand, and is a resin that imparts tackiness when blended with natural rubber or synthetic rubber. Here, as the pt-butylphenol acetylene resin , trade name cholecin (OH value = 193.4 mgKOH / g, manufactured by BASF) can be mentioned. In the present invention, pt-butylphenol acetylene resin is used from the viewpoint of the wear resistance and grip characteristics of the blended rubber composition.

The amount of the p-t-butylphenol acetylene resin (C) is the rubber component (A) 10 parts by mass or more with respect to 100 parts by weight of the amount of p-t-butylphenol acetylene resin (C) is 10 If it is less than the mass part, the effect of improving the grip performance of the tire after the softening point is small.

  The plasticizer (D) used in the rubber composition for a tread of the present invention needs to have a freezing point of -50 ° C or lower. The plasticizer (D) reduces the elastic modulus of the rubber composition at low temperature (high frequency), increases the real contact area between the tread and the road surface, improves the adhesive friction force, and greatly improves the grip performance of the tire. Has the effect of improving. When the freezing point of the plasticizer (D) exceeds -50 ° C., the elastic modulus of the rubber composition at low temperature (high frequency) cannot be sufficiently reduced, and the real contact area and adhesive frictional force between the tread and the road surface. The effect of improving the tire is small, and the grip performance of the tire cannot be sufficiently improved.

The plasticizer (D) is tri (2-ethylhexyl) phosphate (TOP), tributyl phosphate (TBP) , di (2-ethylhexyl) sebacate (DOS), diisooctyl sebacate (DIOS) , di (2-ethylhexyl) . ) Selected from the group consisting of adipate (DOA) and diisooctyl adipate (DIOA). These plasticizers may be used alone or in combination of two or more.

  The compounding amount of the plasticizer (D) is 10 parts by mass or more with respect to 100 parts by mass of the rubber component (A), preferably in the range of 10-50 parts by mass, and more preferably in the range of 15-40 parts by mass. The range of 20 to 30 parts by mass is even more preferable. When the blending amount of the plasticizer (D) is less than 10 parts by mass, the elastic modulus of the rubber composition at low temperature (high frequency) is lowered, and the true contact area between the tread and the road surface and the adhesive frictional force are improved. The effect of improving grip performance is reduced.

The rubber composition for a tread of the present invention is usually used in the rubber industry in addition to the rubber component (A), filler (B), pt-butylphenol acetylene resin (C), and plasticizer (D). For example, oils, anti-aging agents, vulcanizing agents, vulcanization aids, vulcanization accelerators, scorch preventing agents, and the like are appropriately selected and blended within a range that does not impair the object of the present invention. be able to. As these compounding agents, commercially available products can be suitably used. The rubber composition includes a rubber component (A), a filler (B), a pt-butylphenol acetylene resin (C) and a plasticizer (D), and various compounding agents appropriately selected as necessary. And kneading, heating, extruding, and the like.

  The pneumatic tire of the present invention is characterized by using the above-described tread rubber composition as a tread rubber. Further, the pneumatic tire is particularly suitable as a tire for a high-speed competition car that emphasizes high-speed running. Since the pneumatic tire of the present invention uses the rubber composition as a tread rubber, the grip performance is particularly excellent in a wide temperature range. The pneumatic tire of the present invention is not particularly limited except that the above rubber composition is used for the tread, and can be produced according to a conventional method. Further, as the gas filled in the pneumatic tire, an inert gas such as nitrogen, argon, helium, or the like can be used in addition to normal or air whose oxygen partial pressure is adjusted.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

  According to the formulation shown in Table 1 or Table 2, the rubber composition for tire treads was prepared by kneading using a Banbury mixer. The hysteresis loss characteristic was evaluated by the following method with respect to the obtained rubber composition for treads. The results are shown in Tables 1 and 2.

(1) Hysteresis loss characteristics For vulcanized rubbers obtained by vulcanizing each rubber composition, using a rheometrics viscoelasticity measuring tester at a dynamic strain of 1%, 50 ° C In Table 1, the tan δ of the rubber composition of Comparative Example 1 was expressed as 100, and in Table 2, the tan δ of the rubber composition of Comparative Example 3 was expressed as 100. The larger the index value, the larger the tan δ and the better the grip performance.

  Next, using the rubber composition for a tread as a tread rubber, a JY tire (competition tire) having a size of 225 / 40R18 was prototyped. The grip characteristics of the obtained tire were evaluated by the following method. The results are shown in Tables 1 and 2.

(2) Actual vehicle grip characteristics The actual vehicle equipped with the tire was actually run on a dry circuit, and the dry grip performance of the tire was evaluated. Specifically, the reciprocal of the average value of the lap times from the 10th lap to the 20th lap is obtained. In Table 1, the tire of Comparative Example 1 is displayed as an index, and in Table 2, the tire of Comparative Example 3 is displayed. The index is shown as 100. The larger the index value, the smaller the average value of the lap time, and the better the grip performance.

* 1 Emulsion polymerization SBR, styrene content = 35% by mass, vinyl bond content = 18%, oil extended with 37.5 parts by mass of aroma oil for 100 parts by mass of rubber component.
* 2 Emulsion polymerization SBR, styrene content = 45% by mass, vinyl bond content = 18%, oil extended with 37.5 parts by mass of aroma oil for 100 parts by mass of rubber component.
* 3 External surface area by CTAB adsorption method = 148m ² / g, 24M4DBP oil absorption = 102mL / 100g.
* 4 “Aromax # 3” manufactured by Fuji Kosan Co., Ltd.
* 5 Daihachi Chemical Co., Ltd., Di (2-ethylhexyl) sebacate (DOS), Freezing point = -65 ° C or less.
* 6 Manufactured by Daihachi Chemical Co., Ltd., tri (2-ethylhexyl) phosphate (TOP), freezing point = -70 ° C or less.
* 7 The CP Hall, adipic acid diisooctyl ester (DIOA), freezing point = -60 ℃.
* 8 Made by BASF, “Cholecin”, softening point = 110 to 130 ° C., OH group = 193.4 mgKOH / g.
* 9 C ₉ fraction (co) polymer obtained by aromatic petroleum resin, Nippon Petrochemicals Co., Ltd., "Neo Polymer 140", softening point = 145 ° C..
* 10 C ₉ fraction (co) polymerization to obtained aromatic petroleum resin, Nippon Petrochemicals Co., Ltd., "Neo polymer 170S", softening point = 160 ° C..
* 11 YShara Chemical Co., Ltd., YS Polyster S145, OH group = 100.4 mgKOH / g.
* 12 N- (1,3-Dimethylbutyl) -N'-phenyl-p-phenylenediamine.
* 13 1,3-Diphenylguanidine.
* 14 Dibenzothiazyl disulfide.

From Table 1, the rubber composition and tire of Example 1 which used pt-butylphenol acetylene resin (C) and a plasticizer (D) in combination are represented by pt-butylphenol acetylene resin (C) and plasticizer (D ) In combination with the rubber composition and tire of Comparative Example 1 blended with the plasticizer (D), and the rubber composition and tire of Comparative Example 2 blended with the pt-butylphenol acetylene resin (C). It can be seen that the hysteresis loss and the actual vehicle grip performance are greatly improved.

Moreover, it turns out from the result of the comparative example 3 of Table 2 that the compounding quantity of a plasticizer (D) needs to be 10 mass parts or more. Furthermore, from the results of Examples 2 to 4, various plasticizers (D) whose freezing point satisfies the upper limit defined by the present invention, and pt-butylphenol acetylene satisfying the ranges defined by the present invention for softening point and OH number It can be seen that the tire grip performance can be greatly improved by using the resin (C). Incidentally, although containing C ₉ aromatic resins, tire of Comparative Example 4-7 not containing p-t-butylphenol acetylene resin (C), compared with the tires of Examples 2-4, improved width of the actual vehicle grip performance Is small. The tire of Comparative Example 8 containing a phenolic resin having an OH value of less than 180 did not improve the actual vehicle grip performance as compared with the tire of Comparative Example 3.

Claims (6)

For 100 parts by mass of rubber component (A),
30-200 parts by weight of filler (B),
10 parts by mass or more of pt-butylphenol acetylene resin (C),
Tri (2-ethylhexyl) phosphate (TOP), tributyl phosphate (TBP), di (2-ethylhexyl) sebacate (DOS), diisooctyl sebacate (DIOS), di (2-ethylhexyl) adipate (DOA), diiso A rubber composition for a tread comprising: at least one plasticizer (D) selected from the group consisting of octyl adipate (DIOA) and at least 10 parts by mass.   The rubber composition for a tread according to claim 1, wherein the rubber component (A) contains a styrene-butadiene copolymer rubber having a styrene content of 20 to 70 mass%.   The rubber composition for a tread according to claim 1, wherein the filler (B) contains carbon black. The filler (B) is silica and / or the following general formula (I):
wM · xSiO _y · zH ₂ O (I)
(Wherein, M is a metal selected from the group consisting of aluminum, magnesium, titanium, calcium, and zirconium, oxides or hydroxides of these metals, and hydrates thereof, or carbonates of these metals. And w, x, y, and z are each 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) The rubber composition for a tread according to claim 1, comprising: A pneumatic tire using the tread rubber composition according to claim 1 as a tread rubber. The pneumatic tire according to claim 5 , wherein the pneumatic tire is a tire for a high-speed competition vehicle.