JPH10330541A - Modified polybutadiene rubber and rubber composition containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber which, when used as a rubber composition for treads of pneumatic tires, can give treads having high abrasion resistance and good wet grip by selecting a modified polybutadiene rubber comprising butadiene repeating units and (substituted) phenyl sulfide skeleton bonded butadiene repeating units. SOLUTION: This rubber is a modified polybutadiene rubber comprising butadiene repeating units of formula I and (substituted) phenyl sulfide skeleton bonded butadiene repeating units of formula II (wherein R is H, NH2 , a 1-4C alkyl, OH, COOH or NCO; and m:n is 99:1 to 10:90). This is obtained by reacting a polybutadiene rubber with a thiophenol (derivative). When this rubber is used in a composition for e.g. tire treads, it is used in an amount of at least 1 wt.% based on the total weight of the stock rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modified polybutadiene rubber and a rubber composition containing the same, and more particularly to a modified polybutadiene rubber having a high abrasion resistance and a wet grip when used as a rubber composition for a tire tread (wet grip). ) Relates to a good modified polybutadiene rubber.

[0002]

2. Description of the Related Art When cis-polybutadiene rubber (cis-BR) is used in a rubber composition for a pneumatic tire or the like, there is a problem that grip force, particularly wet grip, is low despite high abrasion resistance. there were. Conversely, styrene
Butadiene copolymer rubber (SBR) has a problem in that although it has a high grip force, it is inferior in abrasion resistance.

[0003]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the problems of conventional cis-polybutadiene rubber when used for a tire tread of a pneumatic tire, for example, to provide a high wear resistance and a high wettability. An object of the present invention is to provide a modified polybutadiene rubber having a high gripping force (wet grip) and a rubber composition using the same.

[0004]

According to the present invention, there is provided a modified compound comprising a butadiene unit of the formula (I) and a butadiene unit to which an optionally substituted phenylsulfide skeleton of the formula (II) is bonded as a repeating unit. A polybutadiene rubber is provided.

Embedded image

Embedded image (In the formula, R represents H, NH ₂ , C ₁ -C ₄ alkyl (preferably methyl or ethyl), OH, COOH or NCO, and m: n is 99: 1 to 10:90.)

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Conventionally, cis-polybutadiene rubber (cis-BR) has low gripping force despite its high abrasion resistance, and conversely, styrene-butadiene copolymer rubber (SB)
It is known that R) has low abrasion resistance but high grip force. The present inventors believe that this is due to the low cis content of the butadiene repeating unit of the SBR, and synthesize an SBR-like polymer having a high content of the cis polybutadiene repeating unit having high abrasion resistance. Cis
-An aromatic ring, particularly a thiophenol skeleton, was introduced into a part of BR to successfully obtain a desired modified polybutadiene rubber having high abrasion resistance and high gripping power.

The modified polybutadiene rubber according to the present invention has a repeating unit ratio (m: n) of the repeating unit (m) of the formula (I) and the repeating unit (n) of the formula (II) of 99: 1 to 99: 1.
10:90 (molar ratio), preferably 99: 1 to 70: 3
0. If the proportion of the repeating unit (II) is less than 1 mol%, the desired improvement effect cannot be obtained, and conversely, it is practically impossible to modify the content to more than 90 mol%. The modified polybutadiene rubber according to the present invention has a degree of polymerization (m + n) of 200.
0 to 50,000, preferably 10,000 to 30,000, and the number average molecular weight corresponding to this is substantially 100,000 to
It is preferably 3,000,000, more preferably 500,000-
2 million.

[0007] The modified polybutadiene according to the present invention can be obtained, for example, by reacting cis polybutadiene rubber and thiophenol or a derivative thereof with a suitable radical initiator such as azobisisobutyronitrile (AIBN) as shown in the following reaction formula. In a solution of a suitable solvent such as benzene, under a nitrogen stream, for example, while heating and stirring at a temperature of about 60 ° C., for example, after 24 hours, the reaction solution is precipitated in a poor solvent such as methanol, It can be manufactured by drying under reduced pressure.

[0008]

Embedded image

(Wherein, R, m and n are as defined above)

In the above reaction formula, examples of the thiophenol derivative include the following compounds.

[0011]

Embedded image

The modified polybutadiene rubber according to the present invention comprises:
For example, it can be added to a rubber composition for a tire tread of a pneumatic tire to enhance the wear resistance and wet grip of the pneumatic tire.

In the case where the modified polybutadiene rubber according to the present invention is used as a vulcanizable rubber composition for a tread of a pneumatic tire, other rubber components have been conventionally compounded in various rubber compositions. Any rubber, such as natural rubber (NR), polyisoprene rubber (IR), various styrene-butadiene copolymer rubbers (SBR), various polybutadiene rubbers (BR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR)
Such as diene rubber or ethylene-propylene copolymer rubber (EPR, EPDM) can be used alone or as an arbitrary blend. The content of the modified polybutadiene rubber according to the present invention in the rubber component is 1% by weight or more based on the total weight of the raw rubber, preferably 1 to 50% by weight, although it depends on the content of the phenyl sulfide skeleton in the modified polybutadiene rubber. It is. If the content of the modified polybutadiene is less than 1% by weight, the desired effects, that is, excellent abrasion resistance and wet grip cannot be obtained. Conversely, if the content is too large, the same tendency is not preferred.

In the rubber composition according to the present invention, in addition to the above-mentioned essential components, carbon black, a vulcanizing or crosslinking agent,
Vulcanization or crosslinking accelerators, various oils, anti-aging agents, fillers, tires such as plasticizers, can be blended with various additives that are generally blended for other general rubber,
Such a composition can be kneaded and vulcanized in a conventional manner into a composition, which can be used for vulcanization or crosslinking. The compounding amounts of these additives can also be conventional general compounding amounts as long as they do not contradict the object of the present invention.

[0015]

EXAMPLES The present invention will be further described below with reference to Examples and Comparative Examples, but it goes without saying that the scope of the present invention is not limited to these Examples.

Examples 1 to 4 and Comparative Examples 1 to 6 The components used in Examples and Comparative Examples shown in Table I are as follows. Ingredients NR: RSS # 1 BR: Nipol BR1220 Nippon Zeon SBR: Nipol 1502 Nippon Zeon Modified BR: cis-BR (cis content = 98%), benzene solution containing thiophenol and AIBN at 60 ° C. under a nitrogen stream. BR carbon black obtained by reacting for 24 hours with: SHOBTEC N339 (Grade: HAF-HS, manufactured by Showa Cabot) ZnO: Zinc Flower (Toho Zinc) Stearic acid: Beads stearic acid (Nippon Oil & Fat) Antioxidant: Santoflex 13 (dimethylbutyl)
-N'-phenyl-p-phenylenediamide) Sulfur: oil-treated sulfur (produced by Karuizawa Seirakusho) (oil 5 phr)
) Vulcanization accelerator: Noxeller CZ-G (Ouchi Shinko Chemical N
-Cyclohexyl-2-benzothiazylsulfenamide)

Of the components shown in Table I, the components excluding the vulcanization accelerator and sulfur were mixed in a 1.8-liter closed mixer.
The mixture was kneaded for about 5 minutes, and the masterbatch released when the temperature reached 165 ± 5 ° C. was kneaded with an 8-inch open roll with a vulcanization accelerator and sulfur to obtain a rubber composition. Next, this composition was press-vulcanized in a mold of 15 × 15 × 0.2 cm at 160 ° C. for 20 minutes to prepare a target test piece (rubber sheet), and the vulcanization properties were evaluated.

The vulcanization properties of the compositions obtained in the examples are as follows, and the results are shown in Table I. Measurement method of vulcanization properties Tensile strength: JIS K-5261 No. 3, dumbbell, pulling speed 500 mm / min Lambourn test: 25% slip rate, 5 kg load, measured for 5 minutes Wet grip (μ): wet skid test Use a silicon carbide cloth From the BPN value, μ = (3 ×
(BPN) / (330-BPN)

[0019]

[Table 1]

[0020]

As described above, according to the present invention, the wet grip is significantly improved as compared with any of the polybutadiene rubber and the styrene-butadiene copolymer rubber, and the abrasion resistance is equal to that of the styrene-butadiene copolymer rubber. Good value and good tensile strength.

Claims (5)

[Claims] 1. A modified polybutadiene rubber comprising, as repeating units, a butadiene unit of the formula (I) and a butadiene unit having an optionally substituted phenylsulfide skeleton of the formula (II). Embedded image Embedded image (Wherein R is H, NH ₂ , C ₁ -C ₄ alkyl, OH,
Represents COOH or NCO, and m: n is 99: 1 to 10:
90. ) 2. The polybutadiene rubber has a cis content of 1 to 2.
98% of the modified polybutadiene rubber of claim 1. 3. The modified polybutadiene rubber according to claim 1, which is obtained by reacting the polybutadiene rubber with thiophenol or a derivative thereof. 4. A rubber composition comprising a raw rubber containing 1% by weight or more of the modified polybutadiene rubber according to claim 1. 5. The rubber composition for a pneumatic tire according to claim 4.