JP2007284645A - Rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silica-containing diene rubber composition that enhances the storage elastic modulus E' at a high temperature and improve the dispersibility of silica. <P>SOLUTION: The rubber composition comprises a diene rubber including a hydroxyl group-containing diene rubber having a hydroxyl group which has an aromatic vinyl content of 15-50 wt.%, a 1,2-bond content of a conjugated diene polymer of 10-80 wt.% and a glass transition temperature of -50 to -10°C, a silane compound represented by formula (I), a reinforcing filler comprising silica and a sulfur-containing silane coupling agent. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rubber composition. More specifically, the present invention is useful as a tread for a pneumatic tire obtained by containing a specific modified SBR as a rubber component, and particularly excellent in both silica dispersibility and steering stability performance. The present invention relates to a rubber composition.

  In the past, especially when blending a rubber composition for a pneumatic tire, silica has been blended as a filler in order to obtain low rolling resistance and high wettability (see, for example, Patent Document 1). However, when silica is blended, the silica tends to aggregate due to the characteristics of the silica surface, and there is a problem that the mixing property with a rubber component or the like deteriorates. In order to solve such a problem, silica is mixed with good dispersibility by using a silane coupling agent in combination, but further improvement in dispersibility has been desired.

  In recent years, a silica-containing rubber composition has been proposed which is excellent in low rolling resistance and wet grip by introducing a hydroxyl group having high affinity with silica into the main chain of the rubber polymer and does not cause burns during processing (patent) Reference 2). However, this proposal still has problems such as the functional group to be modified is limited in the reaction process.

Japanese Patent Laid-Open No. 11-124474 JP 2004-175993 A

  Accordingly, an object of the present invention is to improve the high temperature E ′ in the silica-containing rubber composition, improve the dispersibility of silica in the rubber, and control the rubber composition as compared with a rubber composition using a conventional modified SBR. An object of the present invention is to provide a rubber composition that increases E ′ (60 ° C.), which is an index of stability, and is excellent in ΔG ′, which is an index of silica dispersion.

で表されるシラン化合物、シリカを含む補強性充填剤並びにイオウ含有シランカップリング剤を含んでなるゴム組成物が提供される。 According to the present invention, the aromatic vinyl content is 15-50% by weight, the 1,2 bond content of the conjugated diene polymer is 10-80% by weight, and the glass transition temperature is -50 ° C to -10 ° C. A diene rubber including a hydroxyl group-containing diene rubber having a hydroxyl group, and a formula (I):

A rubber composition comprising a reinforcing filler containing silica and a sulfur-containing silane coupling agent is provided.

  According to the present invention, when the rubber composition is further produced, 0.1 to 10 parts by weight of the silane compound represented by the formula (I) is preliminarily mixed with 100 parts by weight of the hydroxyl group-containing diene rubber. Thereafter, a method for producing the rubber composition is provided, wherein the silica and the sulfur-containing silane coupling agent are added and mixed.

  According to the present invention, it is possible to modify any kind of modifying group to a rubber polymer, improve the silica dispersibility without deteriorating the properties of various rubbers, and tire tread rubber excellent in handling stability. A composition can be obtained.

  As a result of researches to solve the above problems, the present inventors have made it possible to modify any type of modifying group, improve silica dispersibility without deteriorating various physical properties, and improve steering stability. The present inventors have also found an excellent rubber composition for tire treads.

  The diene rubber containing a hydroxyl group used in the present invention is a polymer with an alkylene oxide such as ethylene oxide or propylene oxide, particularly an aromatic vinyl compound such as a styrene-butadiene copolymer (SBR) whose terminal is modified with —OH and a conjugated diene. And a copolymer rubber modified with a hydroxyl group. This hydroxyl group-containing diene rubber has an aromatic vinyl content of 15 to 50% by weight, preferably 20 to 40% by weight, and 1,2 bonds of the conjugated diene polymer are 10 to 80% by weight, preferably 20 to 75% by weight. The glass transition temperature measured according to ASTM: D-3418-82 using a Shimadzu differential thermal analyzer (DSC-EOA) is -50 ° C to -10 ° C, preferably -50 ° C to -20 ° C. is there. If the aromatic vinyl content is low, the strength of the rubber is lowered, which is not preferable. When the 1,2 bond of the conjugated diene polymer is small, the heat generation becomes high, which is not preferable. On the contrary, when the bond is large, the elongation becomes small. A low glass transition temperature is not preferable because dry grip deteriorates. On the other hand, a high glass transition temperature is not preferable because wear resistance deteriorates.

  The hydroxyl group-containing diene rubber according to the present invention is prepared by using, for example, an aromatic vinyl compound such as styrene and a diene monomer such as butadiene as a solvent using an organic alkali metal catalyst such as n-butyllithium according to a conventional method. After polymerization in an aromatic vinyl-conjugated diene copolymer such as SBR, a metal catalyst such as n-butyllithium and an amine compound such as TMEDA (tetramethylethyldiamine) are added and reacted. It can be obtained by reacting an alkylene oxide such as ethylene oxide or propylene oxide. The hydroxyl group thus obtained is preferably introduced at the end of the polymer molecule, but a part thereof may be introduced into the molecule. The amount of hydroxyl group introduced is not particularly limited, but is preferably from 0.1 to 10 mmol%, more preferably from 0.5 to 10 mmol%, based on the weight of the hydroxyl group-containing diene rubber. The amount of hydroxyl group introduced can be measured by H-NMR or the like.

The diene rubber constituting the rubber composition of the present invention contains the hydroxyl group-containing diene rubber in an amount of 5% by weight or more, preferably 10% to 100% by weight of the diene rubber, and the others can be used for pneumatic tires. Any diene rubber such as natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer rubber, butyl rubber and the like can be used.
In the rubber composition of the present invention, the silane compound represented by the formula (I) is preferably blended in an amount of 0.1 to 10% by weight, more preferably 1 to 10% by weight, based on the hydroxyl group-containing diene rubber. When the amount of the silane compound is small, the desired effect is small and it is difficult to improve the dispersion of the silica. On the other hand, when the amount is large, the condensation reaction between silanes may start preferentially, and scorching may be easily performed. is there.

  The rubber composition of the present invention contains a reinforcing filler containing silica, preferably 10 to 150 parts by weight, more preferably 30 to 90 parts by weight, per 100 parts by weight of the diene rubber. If the compounding amount of the reinforcing filler is small, it is not preferable because the rubber has a low degree of reinforcement and may become soft. On the contrary, if the amount is too large, the mixing property may be deteriorated. The amount of silica in the reinforcing filler is preferably 10% by weight or more, more preferably 20 to 90% by weight. As the reinforcing filler other than silica, carbon black, clay, aluminum hydroxide, titanium oxide, magnesium oxide, and the like commonly used for rubber can be used, and carbon black is particularly preferable.

  The sulfur-containing silane coupling agent used in the present invention is a known compound, for example, SI69 and SI75 (manufactured by Degussa), alkoxysilanes such as NXT silane (manufactured by GE Silicone), KBM-903 (manufactured by Shin-Etsu Chemical), and the like. Commercial products such as alkoxymercaptosilane can be used. Although the compounding quantity of a sulfur containing silane coupling agent does not have limitation in particular, It is preferable that it is 2 to 20 weight% with respect to the silica weight. If the blending amount is small, silica dispersion is poor, while if the blending amount is large, burns may occur and the cost increases.

The method for producing the rubber composition according to the present invention is not particularly limited, but preferably 0.1 to 10 silane compounds represented by the formula (I) with respect to 100 parts by weight of the hydroxyl group-containing diene rubber. It is preferable to add and mix the silica and sulfur-containing silane coupling agent after previously mixing parts by weight, more preferably 0.5 to 10 parts by weight.
By previously mixing the silane compound, it is possible to prevent the isocyanate silane from reacting with the hydroxyl group of silica. When mixing in advance, a reaction promoting catalyst such as dibutyltin dilaurate may be added.

  In addition to the components described above, the rubber composition according to the present invention includes other reinforcing agents (fillers) such as carbon black, vulcanization or crosslinking agents, vulcanization or crosslinking accelerators, various oils, anti-aging agents, plastics Various additives that are generally blended for tires such as additives and other rubber compositions can be blended, and these additives are kneaded into a composition by a general method to be vulcanized or crosslinked. Can be used to do. As long as the amount of these additives is not contrary to the object of the present invention, a conventional general amount 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.

Examples 1-4 and Comparative Examples 1-3
Sample preparation In the formulation shown in Table I, the blended components are first kneaded according to the first non-pro production step, and then 1.8 liters of components excluding the vulcanization accelerator and sulfur are sealed according to the formulation of the second non-pro production step. The mixture was kneaded with a mold mixer for 6 minutes and discharged when the temperature reached 155 ° C. to obtain a master batch. A vulcanization accelerator and sulfur were kneaded with this masterbatch with an open roll in accordance with the formulation of the product production process to obtain a rubber composition.

  Next, the obtained rubber composition was vulcanized in a 15 × 15 × 0.2 cm mold at 160 ° C. for 25 minutes to prepare a vulcanized rubber sheet, and the physical properties of the vulcanized rubber were measured by the following test methods. It was measured. The results are shown in Table I.

Rubber physical property evaluation test method
Storage elastic modulus E '(60 ° C)
Using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho, measurement was performed at a static strain of 10%, a dynamic strain of ± 2%, and a frequency of 20 Hz, and E ′ (60 ° C.) was measured. The result was expressed as an index with the value of Comparative Example 1 as 100. Higher values indicate better rubber reinforcement.

ΔG '
The strain shear stress G ′ was measured using RPA2000 manufactured by α Technology. Vulcanization was performed at 160 ° C. for 20 minutes using unvulcanized rubber, and G ′ was measured from a strain of 0.28% to 30.0%. The difference ΔG ′ (G′0.28 (MPa) − G′30.0 (MPa)) was expressed as an index with the value of Comparative Example 1 being 100. The smaller this value, the better the silica dispersion in the rubber.

Table I Footnote SBR1: Novel terminal-modified solution polymerization SBR (terminal OH-modified) (see the synthesis method below)
SBR2: SBR (NS116) manufactured by Nippon Zeon Co., Ltd.
KBE-9007: Shin-Etsu Chemical Co., Ltd. triethoxysilylpropyl isocyanate (in formula (I), n = 0, R ¹ = C ₃ H ₆ , R ³ = C ₂ H ₅ )

SBR3: SBR manufactured by LANXESS (VSL5025)
SiO2: Rhodia silica (Zeosil 1165MP)
Carbon black: Tokai Carbon Co., Ltd. carbon black (Seast H)
SI69: Degussa silane coupling agent SI69 (sulfur chain length average 4)
Stearic acid: manufactured by Nippon Oil & Fats Co., Ltd. Beads stearic acid Anti-aging agent 6PPD: Anti-aging agent 6PPD manufactured by Flexis
Zinc Hana: 3 types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd. Aroma oil: Process X-140 manufactured by Japan Energy

Accelerator CBS: Vulcanization accelerator (Noxeller CZ-G) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Accelerator DPG: Vulcanization accelerator (Noxeller D) manufactured by Ouchi Shinsei Chemical Industry
Sulfur: Tsurumi Chemical Industry Co., Ltd. oil processing sulfur

Into an autoclave equipped with a stirrer of SBR1, 8000 g of cyclohexane, 460 g of styrene and 700 g of butadiene were added, and 3.5 mmol of TMEDA and 11 mmol of n-butyllithium were further added and polymerized at 50 ° C. Ten minutes after the start of the polymerization, the remaining 840 g of butadiene was continuously added to the autoclave. After confirming that the polymerization conversion was 100%, equimolar methanol was added to the active terminal (Li) of the produced polymer to terminate the polymerization. To the obtained solution, 60 mmol of sec-butyllithium and 60 mmol of TMEDA were added and reacted at 70 ° C. for 1 hour, and then 60 mmol of ethylene oxide (EO) was added, and the mixture was further stirred for 20 minutes. After completion of the stirring, 120 mmol of methanol was added to stop the reaction, and then the polymer (SBR1) was recovered by a steam stopping method (aromatic vinyl content: 22.7% by weight, 1,2 bond content: 10. 1 wt%, glass transition temperature: -30 ° C).

  As described above, according to the present invention, a rubber composition having a high high temperature E ′ and excellent filler dispersibility can be obtained, and it is particularly suitable for use as a tire tread for a pneumatic tire.

Claims (5)

Hydroxyl group having a hydroxyl group, wherein the aromatic vinyl content is 15 to 50% by weight, the 1,2 bond content of the conjugated diene polymer is 10 to 80% by weight, and the glass transition temperature is −50 ° C. to −10 ° C. A diene rubber including a diene rubber and a formula (I):

A rubber composition comprising a silane compound represented by formula (I), a reinforcing filler containing silica, and a sulfur-containing silane coupling agent.   The silane compound represented by the formula (I) corresponds to 0.1 to 10% by weight based on the weight of the hydroxyl group-containing diene rubber with respect to 100 parts by weight of the diene rubber containing 5% by weight or more of the hydroxyl group-containing diene rubber. The rubber according to claim 1, wherein 10 to 150 parts by weight of a reinforcing filler containing silica and 10 to 150 parts by weight of a sulfur-containing silane coupling agent are blended in an amount corresponding to 2 to 20% by weight with respect to the silica weight. Composition.   In producing the rubber composition according to claim 1, after previously mixing 0.1 to 10 parts by weight of the silane compound represented by the formula (I) with respect to 100 parts by weight of the hydroxyl group-containing diene rubber, The method for producing a rubber composition according to claim 1 or 2, wherein silica and a sulfur-containing silane coupling agent are added and mixed.   A pneumatic tire using the rubber composition according to claim 1 or 2 as a tire member.   A pneumatic tire using the rubber composition produced by the production method according to claim 3 as a tire member.