JP2005146076A - Rubber composition for tire side and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a rubber composition for side tread, that has high hardness, strength and elongation and controls rise in tanδ. <P>SOLUTION: The rubber composition for tire side comprises (A) 100 parts wt. of vulcanizable rubber containing ≥65 wt.% total of (i) natural rubber (NR) and (ii) polybutadiene rubber (BR), (B) 30-80 parts wt. of the total of silica and/or carbon black having 20-85 m<SP>2</SP>/g nitrogen adsorption specific surface area (N<SB>2</SB>SA) and (C) 0.1-10 parts wt. of a cyclic polysulfide represented by formula (I) (x is a number of 2-6 on the average; n is an integer of 1-15; R a substituted or nonsubstituted 2-20C alkylene group, a substituted or nonsubstituted 2-20C oxyalkylene group or an aromatic ring-containing alkylene group). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rubber composition having high hardness, high strength and elongation, and capable of suppressing an increase in tan δ, and a pneumatic tire using the rubber composition for a side tread.

  In recent years, various improvements have been made on pneumatic tires. Among such various improvements, as a rubber for a side tread, a rubber composition exhibiting high tensile strength and elongation at break is required for improving fatigue resistance (see, for example, Patent Document 1). ). On the other hand, high-hardness side treads for improving steering stability and low tan δ side treads for improving fuel efficiency are also demanded (see, for example, Patent Documents 2 and 3). Was in a relationship. From such a viewpoint, a rubber composition having high hardness, high strength and elongation, and no increase in tan δ is desired.

Japanese Patent Laid-Open No. 9-324075 JP 2003-113270 A JP 2001-123025 A

  Accordingly, the present invention eliminates the problems of the prior art described above, and has a high hardness, high strength, high elongation, no increase in tan δ, excellent fatigue resistance, and improved handling stability. The purpose is to provide.

（式中、ｘは平均２〜６の数、ｎは１〜１５の整数、Ｒは置換もしくは非置換のＣ₂〜Ｃ₂₀アルキレン基、置換もしくは非置換のＣ₂〜Ｃ₂₀オキシアルキレン基又は芳香族環を含むアルキレン基を示す）
で表される環状ポリスルフィド０．１〜１０重量部を含んでなるタイヤサイド用ゴム組成物が提供される。 According to the present invention, (A) 100 parts by weight of vulcanizable rubber containing (i) natural rubber (NR) and (ii) polybutadiene rubber (BR) in an amount of 65% by weight or more, (B) silica and / or nitrogen adsorption 30 to 80 parts by weight of carbon black having a specific surface area (N ₂ SA) of 20 to 85 m ² / g and formula (I):

(Wherein x is an average of 2 to 6, n is an integer of 1 to 15, R is a substituted or unsubstituted C _{2 to} C ₂₀ alkylene group, a substituted or unsubstituted C _{2 to} C ₂₀ oxyalkylene group, or Represents an alkylene group containing an aromatic ring)
The rubber composition for tire side which comprises 0.1-10 weight part of cyclic polysulfide represented by these is provided.

  According to the present invention, there is also provided a pneumatic tire using the rubber composition on a tire side.

  The rubber composition according to the present invention can improve durability without impairing rolling resistance and steering stability by using the cyclic polysulfide as a vulcanizing agent, and further improve viscoelastic properties. it can.

  The vulcanizable rubber used as component (A) in the present invention contains (i) natural rubber (NR) and (ii) polybutadiene rubber (BR) in an amount of 65% by weight or more, preferably 70% by weight or more. As the rubber component, tires, and any rubber generally used for other purposes, such as various polyisoprene rubbers (IR), various styrene-butadiene copolymer rubbers (SBR), and acrylonitrile-butadiene copolymers Examples include diene rubbers such as rubber, styrene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, butyl rubber, halogenated butyl rubber, ethylene-propylene-diene copolymer rubber, and the like. Or it can be used as any blend. The blending ratio of NR and BR is not limited, but is preferably NR / BR (weight ratio) 10 to 90 / 90-10. If the total amount of NR and BR is too small, it is not preferable because the fatigue resistance is insufficient.

(I) Silica and / or (ii) N ₂ SA of 20 to 85 m ² / g, preferably 25 to 80 m ² / g of carbon black used as component (B) in the rubber composition used in the present invention is rubber. 30 to 80 parts by weight, preferably 32 to 75 parts by weight, is added as a total amount of (i) and (ii) with respect to 100 parts by weight. If the blending amount is too small, the hardness becomes too low, which is not preferable. On the other hand, if the blending amount is too large, tan δ increases and the fuel efficiency is not improved. The blending ratio of components (i) and (ii) is not necessarily limited, but the ratio of (i) / (ii) is 0 to 90/100 to 10 from the viewpoint of fatigue resistance and fuel efficiency. Is preferred.

The silica used in the present invention may be any silica conventionally used for tires, such as natural silica, synthetic silica, more specifically dry silica and wet silica. On the other hand, as the carbon black used in the present invention, any carbon black conventionally used for tires and the like can be used, but the nitrogen specific surface area (N ₂ SA) must be 20 to 85 m ² / g. In other words, it is preferable to use one of 25 to 80 m ² / g. If this N ₂ SA is too low, the tensile strength and elongation at break are too low, which is not preferable. On the other hand, if N ₂ SA is too high, the fuel efficiency is impaired.

The cyclic polysulfide of the above formula (I) to be blended as the component (C) in the rubber composition of the present invention has the formula: X—R—X (where X is independently fluorine, chlorine, bromine, iodine, Preferably, it represents a halogen atom of chlorine or bromine, and R represents an alkylene group containing a substituted or unsubstituted C _{2 to} C ₂₀ alkylene group or a substituted or unsubstituted C _{2 to} C ₂₀ oxyalkylene group, preferably substituted or unsubstituted C ₂ -C _20, more preferably dihalide and in polysulfide M-S _x -M (wherein the alkali metal.) which indicates an alkylene group or an aromatic ring of C ₄ -C _10, M is an alkali metal such as sodium, potassium, lithium and the like, and x is an integer of 2 to 6, preferably 4 to 6) in an incompatible mixed solvent of hydrophilic and lipophilic solvents. To react in a phase system Therefore or M-S _x -M solution (as the solvent can be water and C ₁ -C ₄ aliphatic alcohols, the use of water is most preferable) the X-R-X in M-S It is produced by adding _x- M and X-R-X at a rate such that they react at the interface and reacting them (see Japanese Patent Application Laid-Open No. 2002-293783). If the addition rate of X-R-X is too fast in the latter method, the concentration of X-R-X will increase, and reactions other than at the interface will occur, giving priority to intermolecular reactions and becoming chained. It is not preferable. Therefore, it is preferable to obtain a cyclic polysulfide by reacting the reaction of M-S _x -M and X-M-X as heterogeneously as possible only at the interface.

Examples of the group R in the general formula X-R-X and the formula (I) include linear or branched alkylene such as ethylene, propylene, butylene, pentylene, hexylene, octylene, nonylene, decylene and 1,2-propylene. These alkylene groups may be substituted with a substituent such as a phenyl group or a benzyl group. The group R further includes an alkylene group containing an oxyalkylene group, for example, a group (CH ₂ CH ₂ O) p and a group (CH ₂ ) q (wherein p is an integer of 1 to 5, and q is 0 to 2). (Which is an integer) can be an alkylene group including an oxyalkylene group optionally bonded thereto. Preferred group R is

—CH ₂ CH ₂ OCH ₂ OCH ₂ CH ₂ —, and x is preferably 3 to 5 on average, and n is preferably 1 to 10, more preferably 1 to 5.

  There are no particular limitations on the hydrophilic solvent and lipophilic solvent used in the above reaction, and any solvent that is incompatible and forms two phases in the actual reaction system can be used. Specifically, examples of the hydrophilic solvent include water and alcohols such as methanol, ethanol, ethylene glycol, and diethylene glycol, and these can also be used as an arbitrary mixture. Examples of the lipophilic solvent include aromatic hydrocarbons such as toluene, xylene and benzene, aliphatic hydrocarbons such as pentane and hexane, ethers such as dioxane and dibutyl ether, and esters such as ethyl acetate. These can be used as any mixture.

  The reaction at the interface between the dihalogen compound and the alkali metal polysulfide is an equivalent reaction. Practically, both compounds are reacted at 0.95: 1 to 1: 0.95 (equivalent ratio), The reaction temperature is preferably 50 to 120 ° C, more preferably 70 to 100 ° C.

In the reaction, a catalyst is not necessary, but in some cases, a quaternary ammonium salt, a phosphonium salt, a crown ether, or the like can be used as a catalyst. For example, (CH ₃ ) ₄ N ⁺ Cl ⁻ , (CH ₃ ) ₄ N ⁺ Br ⁻ , (C ₄ H ₉ ) ₄ N ⁺ Cl ⁻ , (C ₄ H ₉ ) ₄ N ⁺ Br ⁻ , C ₁₂ H _{25 ^{N + (CH 3) 3 Br}} -, (C 4 H 9) 4 P + Br -, CH 3 P + (C 6 H 5) 3 I -, C 16 H 33 P + (C 4 H 9) 3 Br ^- , 15-crown-5, 18-crown-6, benzo-18-crown-6, and the like can be used. In particular, when a cyclic polysulfide (I) having an average x exceeding 4 to 6 or less is used, a catalyst is preferably used.

  In the rubber composition of the present invention, the cyclic polysulfide (C) is blended in an amount of 0.1 to 10 parts by weight, preferably 0.2 to 9 parts by weight, based on 100 parts by weight of the rubber. If the amount is too small, the desired effect cannot be obtained. On the other hand, if the amount is too large, the fatigue resistance deteriorates, which is not preferable.

  The rubber composition according to the present invention can be used together with the cyclic polysulfide (C) as a vulcanizing agent by using any conventionally used sulfur as a vulcanizing agent. When sulfur (D) is used in combination with component (C), (D) / (C) (weight ratio) is preferably used in an amount of 8 or less, more preferably 6 or less. If this ratio is too large, the desired effect of the present invention may be difficult to obtain.

  In addition to the above-described essential components, the rubber composition according to the present invention includes reinforcing agents (fillers) such as carbon black and silica, various oils, anti-aging agents, plasticizers, various vulcanization accelerators, and silane coupling agents. Various additives generally blended for tires and other general rubbers can be blended, and such blends are kneaded by a general method into a composition and used for vulcanization. be able to. As long as the amount of these additives is not contrary to the object of the present invention, the conventional general amounts can be used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, it cannot be overemphasized that the scope of the present invention is not limited to these Examples.

Synthesis of cyclic polysulfide 1 30% sodium polysulfide (Na ₂ S ₄ ) aqueous solution 89.76 g (0.15 mol), water 80 g, sulfur 48 g (0.15 mol) and tetrabutylammonium bromide 1.16 g (0.0045 mol) as catalyst ) And then reacted at 80 ° C. for 2 hours, 100 g of toluene was added, and 23.3 g (0.15 mol) of 1,6-dichlorohexane was added dropwise at 90 ° C. for 1 hour, followed by further reaction for 4 hours. After completion of the reaction, the organic phase was separated and concentrated under reduced pressure at 90 ° C., and then 35.2 g of cyclic polysulfide having the formula (I), R = (CH ₂ ) ₆ , x = 5 and n = 1 to 4 on average. (Yield 95%).
¹ HNMR (270 MHz, CDCl ₃ ) δ (ppm): 1.4-1.9 (8H, —CH ₂ —), 2.9-3.3 (4H, —S—CH ₂ —).

Synthesis of cyclic polysulfide 2 100 g of toluene was added to 89.76 g of a 30% sodium polysulfide (Na ₂ S ₄ ) aqueous solution, and 28.1 g (0.15 mol) of 1,2-bis (2-chloroethoxy) ethane was added at 90 ° C. The solution was added dropwise for 1 hour and further reacted for 4 hours. After completion of the reaction, the organic phase was separated and concentrated at 90 ° C. under reduced pressure. Then, in formula (I), R = (CH ₂ ) ₂ O (CH ₂ ) O (CH ₂ ) ₂ , x average 4 and n = 1 to 2 cyclic polysulfides were obtained in 35.0 g (yield 96%).
¹ HNMR (270 MHz, CDCl ₃ ) δ (ppm): 2.9-3.2 (4H, CH ₂ Sx), 3.7-4.0 (8H, CH ₂ O).

Examples 1-4 and Comparative Examples 1-3
According to the formulation shown in Table I, kneading was carried out for 5 minutes by a Banbury mixer, excluding sulfur and a crosslinking accelerator. Subsequently, the obtained kneaded material, sulfur, and a crosslinking accelerator were kneaded with an open roll to obtain a rubber composition. The obtained rubber composition was press-crosslinked at 160 ° C. for 20 minutes and subjected to physical property evaluation. The test method is as follows.

Test method Rupke JIS hardness Hs (20C): Durometer A hardness was shown in accordance with JIS K6253.
100% and 300% modulus: measured in accordance with JIS K6251.
Breaking strength TB (MPa): Measured according to JIS K6251.
Elongation at break EB (%): Measured according to JIS K6251.
tan δ (60 ° C.): Measured using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho under conditions of an initial strain of 10%, an amplitude of ± 2%, and a frequency of 20 Hz.

A tire of size 195 / 65R15 using each of the compounds shown in the table above was prepared for a 50 mm high hardness reinforcing rubber extending from the bead portion along the tire sidewall inside the tire sidewall, and subjected to the following test. It was used for.
Load endurance test Drum diameter 1707 mm, JIS D 4230, JATMA Y / B 2003 edition Specified load endurance test , the load was accelerated every 20% / 5 hr, and the test was continued until the tire broke down. The results are shown as an index with Comparative Example 1 as 100. The larger the number, the longer the mileage and the better.
It was measured by an indoor drum type tire rolling resistance tester having a rolling resistance drum diameter of 1707 mm. As the measurement conditions, JATMA Y / B 2003 edition was applied mutatis mutandis. Larger numbers indicate lower rolling resistance and better results.
Steering stability The vehicle was run on a slalom test road where pylons were set up at regular intervals, and the steering stability was evaluated based on the average speed. The larger the index value, the better the steering stability.

Table I Footnote * 1: Natural rubber TSR20: SIR20
* 2: Polybutadiene rubber NIPOL 1220 manufactured by Nippon Zeon Co., Ltd.
* 3: Carbon black DIA I (N ₂ SA = 114 m ² / g) manufactured by Mitsubishi Chemical Corporation
* 4: Carbon black DIA E (N ₂ SA = 41 m ² / g) manufactured by Mitsubishi Chemical Corporation
* 5: SANTOFLEX 6PPD made by FLEXSYS
* 6: Sannok, manufactured by Ouchi Shinsei Chemical Co., Ltd. * 7: Three types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd. * 8: Bead stearic acid manufactured by Nippon Oil & Fats Co., Ltd. * 9: manufactured by Showa Shell Sekiyu K.K. Process oil Desolex No. 3 * 10: SANTOCURE NS made by FLEXSYS
* 11: Tsurumi Chemical Co., Ltd. Jinhua stamped fine powdered sulfur * 12: See the above synthesis example * 13: See the above synthesis example

  As is apparent from the results in Table I, Examples 1 and 2 use only cyclic polysulfide, and have substantially the same durability as rolling resistance and steering stability compared to Comparative Example 1 using only sulfur. Has improved. Example 3 is an example in which a cyclic polysulfide and sulfur are used in combination, and the durability is greatly improved while the rolling resistance and steering stability are equivalent to those of Comparative Example 1 using only sulfur. Example 4 is an example in which the blending amount of the cyclic polysulfide is increased, and is excellent in rolling resistance and steering stability while being as durable as Comparative Example 1.

  As described above, the rubber composition according to the present invention improves the balance of durability, rolling resistance, and steering stability, and thus is useful for, for example, a side tread of a pneumatic tire.

Claims (3)

(A) (i) 100 parts by weight of vulcanizable rubber containing at least 65% by weight of natural rubber (NR) and (ii) polybutadiene rubber (BR), (B) silica and / or nitrogen adsorption specific surface area (N ₂ SA ) Is ²⁰ to 85 m ² / g of carbon black in a total amount of 30 to 80 parts by weight and (C) Formula (I):

(Wherein x is an average of 2 to 6, n is an integer of 1 to 15, R is a substituted or unsubstituted C _{2 to} C ₂₀ alkylene group, a substituted or unsubstituted C _{2 to} C ₂₀ oxyalkylene group, or Represents an alkylene group containing an aromatic ring)
A rubber composition for a tire side, comprising 0.1 to 10 parts by weight of a cyclic polysulfide represented by: The cyclic polysulfide is represented by the formula: X—R—X (wherein each X independently represents a halogen atom, and R includes a substituted or unsubstituted C _{2 to} C ₂₀ alkylene group, oxyalkylene group or aromatic ring). A dihalogen compound of an alkylene group) and an alkali metal polysulfide of the formula M ₂ S _x (wherein M is an alkali metal and x is an integer of 2 to 6), hydrophilic and parent The rubber composition according to claim 1, wherein the rubber composition is reacted in a two-phase system in an incompatible mixed solvent of an oily solvent.   The pneumatic tire which comprised the tire side using the rubber composition of Claim 1 or 2.