JP5344662B2 - Rubber composition and pneumatic tire using the same - Google Patents

Description

  The present invention relates to a rubber composition and a pneumatic tire using the same, and more particularly to a rubber composition for a tread of a high performance passenger car tire and a pneumatic tire using the same.

  In recent years, with the improvement of automobile performance, road paving and the development of highway networks, there is an increasing demand for pneumatic tires with high movement performance. The higher this characteristic, the faster and more accurately and safely it is possible to travel. In particular, grip performance represented by acceleration performance and brake performance is an important required characteristic.

  Conventionally, in order to obtain high grip performance, there has been a method of using a styrene-butadiene copolymer rubber having a high styrene content, which is a rubber having a high glass transition temperature, in a tire tread rubber composition. However, this method has a disadvantage that the tan δ value decreases as the rubber temperature increases due to running, so that the grip performance decreases as the tire temperature increases.

Therefore, in order to eliminate this inconvenience, a monomer such as 1,3-butadiene, styrene or isoprene and a diphenyl phosphate group such as diphenyl-2-methacryloyloxyethyl phosphate or diphenyl-2-acryloyloxyethyl phosphate are included. A technique (Patent Document 1) using a copolymer rubber obtained by copolymerizing a methacrylate compound or an acrylate compound has been proposed.
JP 59-187011 A

  However, this method is not only applicable to natural rubber, but also has the disadvantage of impairing the inherent properties of polymers such as styrene / butadiene copolymer rubber and polybutadiene rubber depending on the production conditions.

  On the other hand, there is also a method to increase the tan δ value of the rubber composition by using a compound system that is highly filled with process oil and carbon black, but this method improves the grip performance, but it also has fracture characteristics and wear resistance. Therefore, there is a limit to high filling, and it is difficult to obtain a required level of high grip performance.

  Furthermore, there is a method of improving the grip performance by adding a certain kind of resin to improve adhesion between the rubber and the road surface. Generally, a resin having a higher grip performance has a metal mixer existing in the manufacturing process and Adhesiveness with a metal roll becomes high and tends to inhibit factory workability. Therefore, it is actually difficult to improve the grip performance by improving the resin.

  Accordingly, an object of the present invention is to provide a rubber composition and a pneumatic tire using the same, which can obtain high grip performance without deteriorating fracture resistance and wear resistance.

  As a result of intensive studies to achieve the above object, the present inventors have found that it is effective to add a p-tertbutylphenol-formaldehyde resin having a high softening point to the rubber composition, and complete the present invention. It came to.

That is, the rubber composition of the present invention comprises carbon black and a p-tertbutylphenol-formaldehyde resin having a softening point of 143 ° C. or more and 180 ° C. or less with respect to a rubber component containing 40 parts by mass or more of styrene / butadiene copolymer rubber. The p-tertbutylphenol-formaldehyde resin is contained in 3 to 50 parts by mass with respect to 100 parts by mass of the rubber component.

  The rubber composition of the present invention preferably contains 10 to 40 parts by mass of the p-tertbutylphenol / formaldehyde resin with respect to 100 parts by mass of the rubber component. Moreover, it is preferable that the weight average molecular weight (Mw) of the said p-tert butylphenol formaldehyde resin is 1000 or more. Furthermore, it is preferable to contain 30 to 200 parts by mass of the carbon black with respect to 100 parts by mass of the rubber component, and the carbon black has a cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of 100 to 160 m 2 / g, And it is preferable that dibutyl phthalate oil absorption (DBP) is 90-150 mL / 100g. The styrene / butadiene copolymer rubber preferably contains 20 to 70% by mass of styrene.

  The pneumatic tire of the present invention is characterized by using the rubber composition as a tread member.

  According to the present invention, it is possible to provide a rubber composition and a pneumatic tire using the rubber composition capable of greatly improving high grip performance without deteriorating the fracture resistance and wear resistance.

Embodiments of the present invention will be specifically described below.
The rubber composition of the present invention contains 40 parts by mass or more of styrene / butadiene copolymer rubber as a rubber component, and other rubber components may be used alone or in combination with natural rubber and synthetic rubber. And synthetic polyisoprene rubber, polybutadiene rubber, styrene / butadiene copolymer rubber, halogenated butyl rubber, EPDM rubber, acrylic rubber and the like. If the styrene / butadiene copolymer rubber is less than 40 parts by mass, the desired effect cannot be obtained. The styrene / butadiene copolymer rubber is preferably 50 parts by mass or more.

  The styrene / butadiene copolymer rubber used in the present invention preferably has a styrene content of 20 to 70% by mass. If the styrene content of the styrene-butadiene copolymer rubber is less than 20% by mass, the grip at high temperature may be insufficient, and if it exceeds 70% by mass, the grip at low temperature may be insufficient. Such styrene / butadiene copolymer rubber may be a commercially available product, and may be oil-extended.

  In the rubber composition of the present invention, the carbon black is preferably contained in an amount of 30 to 200 parts by mass with respect to 100 parts by mass of the rubber component, and is used as a reinforcing filler in the rubber composition. If the carbon black content is less than 30 parts by mass, high grip performance may not be obtained, and if it exceeds 200 parts by mass, the fracture characteristics and wear resistance may be remarkably lowered.

There is no restriction | limiting in particular as carbon black, According to the objective, it can select suitably. Carbon black may be used singly or in combination of two or more, and commercially available products can be used, but carbon black cetyltrimethylammonium bromide adsorption specific surface area (CTAB) Is preferably 100 to 160 m ² / g. If the cetyltrimethylammonium bromide adsorption specific surface area (CTAB) is less than 100 m ² / g, the wear resistance of the rubber composition may not be sufficient, and if it exceeds 160 m ² / g, the workability and elongation properties are reduced. Sometimes.

The cetyltrimethylammonium bromide adsorption specific surface area (CTAB) is defined in ASTM-D 3765-80 or JIS K6217-3: 2001, and the cetyltrimethylammonium bromide adsorption specific surface area per unit mass (m ² / g). Means.

  Moreover, as dibutyl phthalate oil absorption (DBP) of carbon black, 90-150 mL / 100g is preferable. If the dibutyl phthalate oil absorption (DBP) is less than 90 mL / 100 g, heat resistance may not be sufficiently secured. If it exceeds 150 mL / 100 g, the processability and elongation characteristics are inferior, and the general properties as rubber deteriorate. There are things to do.

  In addition, dibutyl phthalate oil absorption (DBP) is a value measured according to JIS K6217-4: 2001, and means the amount (mL) of dibutyl phthalate absorbed per 100 g of carbon black.

  In the rubber composition of the present invention, the p-tertbutylphenol-formaldehyde resin is not particularly limited as long as it contains a softening point of 135 ° C. or higher, and can be appropriately selected according to the purpose. If the softening point of the p-tertbutylphenol-formaldehyde resin is less than 135 ° C., the desired effect cannot be obtained. The softening point is preferably 140 to 180 ° C. Furthermore, p-tertbutylphenol-formaldehyde resin may be used individually by 1 type, and may use 2 or more types together.

  The rubber composition of the present invention preferably contains 3 to 50 parts by mass, more preferably 10 to 40 parts by mass of p-tertbutylphenol / formaldehyde resin with respect to 100 parts by mass of the rubber component. When the content of the p-tertbutylphenol / formaldehyde resin is less than 3 parts by mass, sufficient performance may not be exhibited. When the content exceeds 50 parts by mass, workability is extremely deteriorated and sufficient performance cannot be exhibited. There is.

  In the rubber composition of the present invention, the p-tertbutylphenol / formaldehyde resin preferably has a polystyrene-equivalent weight average molecular weight of 1000 or more obtained by gel permeation chromatography.

  In the rubber composition of the present invention, it is important to contain a p-tertbutylphenol-formaldehyde resin having a softening point of 135 ° C. or higher, but other softeners may be used depending on the purpose as long as the effects of the present invention are not impaired. Can be used together as appropriate. Other softeners are not particularly limited, and specifically, aromatic oils, low-temperature softeners, thermoplastic resins, and the like can be used. Such a softener may be composed of one kind of substance or may be composed of two or more kinds in combination. The latter case is preferable in that the temperature dependence of the hardness of the rubber composition can be widened.

  As the low-temperature softener, those having a softening point of 0 ° C. or lower, preferably −10 ° C. or lower are suitable. As such a low-temperature softener, those conventionally used as rubber softeners, for example, process oils such as paraffinic process oil, naphthenic process oil, aromatic process oil, polymerized high boiling strong aromatic Appropriate selection from mineral softeners such as oil, liquid paraffin and white oil, castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, peanut oil, tall oil and other plant softeners Can be used.

  There is no restriction | limiting in particular as a thermoplastic resin, Although it can select suitably according to the objective, C5-type petroleum resin, C9-type petroleum resin, etc. are mentioned suitably.

  C5 petroleum resin is a resin of C5 fraction obtained by thermal decomposition of naphtha. Examples of the C5 fraction include olefinic hydrocarbons and diolefinic hydrocarbons. Examples of the olefinic hydrocarbon include pentene, 2-methyl-1-butene, 3-methyl-1-butene, 2-methyl-2-butene and the like. Commercially available products can be suitably used as the C5 petroleum resin, and examples of commercially available products include Stratokol TS30 (manufactured by Straktor), TX-500 (manufactured by Mitsui Chemicals, Inc.) and the like. .

  The C9 petroleum resin is a C9 fraction resin obtained by thermal decomposition of naphtha. Examples of the C9 fraction include diolefin hydrocarbons. Examples of the diolefin hydrocarbon include benzene, toluene, xylene, styrene, α-methylstyrene, 1,2-pentadiene and the like. Commercially available products can be suitably used as the C9 petroleum resin. Examples of commercially available products include Neopolymer (manufactured by Nippon Oil Co., Ltd.), Petcoal (manufactured by Tosoh Corporation), PetroTac (Tosoh Corporation). Manufactured by Toho Chemical Co., Ltd.).

  As melting | fusing point of a thermoplastic resin, 60-160 degreeC is preferable and 120-160 degreeC is more preferable. When the melting point of the thermoplastic resin is less than 60 ° C., the rigidity of the rubber at high temperatures may be insufficient, and when it exceeds 160 ° C., the flexibility of the rubber at low temperatures may be insufficient.

  The other components contained in the rubber composition can be appropriately selected and used within a range not impairing the object of the present invention, such as inorganic fillers, vulcanizing agents such as sulfur, dibenzothiazyl disulfide, etc. Vulcanization accelerators, vulcanization aids, anti-aging agents such as N-cyclohexyl-2-benzothiazyl-sulfenamide, N-oxydiethylene-benzothiazyl-sulfenamide, zinc oxide, stearic acid, ozone degradation inhibitor, In addition to additives such as colorants, antistatic agents, lubricants, antioxidants, coupling agents, foaming agents and foaming aids, various compounding agents usually used in the rubber industry can be mentioned. These can use a commercial item suitably.

  Moreover, the rubber composition of this invention can be used as a tread member for a pneumatic tire. Thereby, high grip performance can be obtained without deteriorating operability and wear resistance at low temperatures.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by this example.

(P-tert-butylphenol / formaldehyde resin synthesis method (resin C))
1000 parts by mass of p-tertbutylphenol, 432 parts by mass of 37% formalin, 1 part by mass of a surfactant and 5 parts by mass of oxalic acid were charged into a reaction flask in which a stirrer, a thermometer and an aggregator were set. Next, the contents of the flask were reacted for 90 minutes under reflux with stirring and mixing. The aggregator was removed and connected to a dehydration vessel, and the contents were dehydrated by raising the temperature under normal pressure. The temperature was raised under reduced pressure (80 mmHg) to perform dehydration and demonomerization, and after reaching 200 ° C., the contents were taken out of the flask and cooled to obtain a solid resin.

(Method for preparing rubber composition)
A rubber composition for tire treads was prepared by kneading using a Banbury mixer according to the formulation shown in Tables 1 and 2. The obtained rubber composition was vulcanized at 160 ° C. for 15 minutes, and the grip performance was evaluated. The tire grip performance was evaluated by the following method. The obtained evaluation results are shown in Table 1 and Table 2 below.

(Hysteresis characteristics)
For vulcanized rubber obtained by vulcanizing each rubber composition, tan δ at 50 ° C. was measured under a dynamic strain of 1% using a rheometrics viscoelasticity measuring tester, and compared. The rubber composition of Example 1 was expressed as an index with tan δ of 100. The larger the index value, the larger the tan δ, indicating that the grip performance is excellent.

(Dry skid property)
The evaluation was made on a dry road surface by a skid tester (manufactured by Stanley London Co.), and a numerical value with Comparative Example 1 as 100 was shown. The larger this value, the better.

(Grip property)
The grip property of the tire was evaluated by producing a tire having a tire size of 225 / 40R18 using the above rubber composition as a tread. Four passenger tires were mounted on a passenger car and evaluated by running on a dry asphalt road test course, and the grip performance was evaluated by a test driver in seven stages.
7 stages 7: Very good, 6: Good, 5: Somewhat good, 4: Normal, 3: Somewhat bad, 2: Bad, 1: Very bad,-: Not rated

＊１ 旭化成製タフデン４３５０（結合スチレン含有率３９％、ビニル結合量３８％、ゴム成分１００質量部に対し５０質量部のアロマチックオイルで油展）
＊２ カーボンブラック（ＣＴＡＢ吸着法による外部表面積１４８ｍ^２／ｇ、２４Ｍ４ＤＢＰ吸油量１０２ｍＬ／１００ｇ）
＊３ コレシン（ＢＡＳＦ社製）
＊４ Ｄｕｒｅｚ３２３３３（Ｄｕｒｅｚ社製、ｐ−ｔｅｒｔブチルフェノール・ホルムアルデヒド樹脂、軟化点１３０℃）
＊５ ｐ−ｔｅｒｔブチルフェノール・ホルムアルデヒド樹脂（合成品、軟化点１４３℃）
＊６ Ｎ−１，３−ジメチル−ブチル−Ｎ’−フェニル−ｐ−フェニレンジアミン
＊７ Ｎ−ｔ−ブチル−２−ベンゾチアジル−スルフェンアミド
＊８ テトラキス−２−エチルヘキシルチウラムジスルフィド

* 1 Toughden 4350 manufactured by Asahi Kasei Co., Ltd. (bonded styrene content 39%, vinyl bond amount 38%, 50 parts by weight of aromatic oil for 100 parts by weight of rubber component)
* 2 Carbon black (external surface area by CTAB adsorption method: 148m ² / g, 24M4DBP oil absorption: 102mL / 100g)
* 3 Colesin (BASF)
* 4 Durez32333 (Durez, p-tertbutylphenol / formaldehyde resin, softening point 130 ° C.)
* 5 p-tertbutylphenol-formaldehyde resin (synthetic product, softening point 143 ° C)
* 6 N-1,3-dimethyl-butyl-N'-phenyl-p-phenylenediamine * 7 Nt-butyl-2-benzothiazyl-sulfenamide * 8 tetrakis-2-ethylhexylthiuram disulfide

Claims (7)

For a rubber component containing 40 parts by mass or more of styrene / butadiene copolymer rubber, carbon black and p-tertbutylphenol / formaldehyde resin having a softening point of 143 ° C. or higher and 180 ° C. or lower to 100 parts by mass of the rubber component A rubber composition comprising 3 to 50 parts by mass of the p-tertbutylphenol / formaldehyde resin.   The rubber composition according to claim 1, comprising 10 to 40 parts by mass of the p-tertbutylphenol-formaldehyde resin with respect to 100 parts by mass of the rubber component.   The rubber composition according to claim 1 or 2, wherein the p-tertbutylphenol-formaldehyde resin has a weight average molecular weight (Mw) of 1000 or more.   The rubber composition according to any one of claims 1 to 3, comprising 30 to 200 parts by mass of the carbon black with respect to 100 parts by mass of the rubber component. The cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of the carbon black is 100 to 160 m ² / g, and the dibutyl phthalate oil absorption (DBP) is 90 to 150 mL / 100 g. The rubber composition according to claim 1.   The rubber composition according to any one of claims 1 to 5, wherein the styrene-butadiene copolymer rubber contains 20 to 70% by mass of styrene.   A pneumatic tire using the rubber composition according to any one of claims 1 to 6 for a tread member.