JP2009155444A - Rubber composition and tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition which is excellent in workability, is improved in storage modulus (G') and loss tangent (tanδ) at low temperature, and is further improved in wear resistance. <P>SOLUTION: The rubber composition is prepared by blending 100 pts.mass of a high molecular weight polymer component (A) having a bonding amount of an aromatic vinyl compound of ≤80 mass% and a weight average molecular weight (expressed in terms of polystyrene) of ≥1.5×10<SP>5</SP>with >1 to <30 pts.mass of a low molecular weight polymer component (B) having a bonding amount of an aromatic vinyl compound of <30 mass% and a weight average molecular weight (expressed in terms of polystyrene) of 0.2×10<SP>4</SP>-8.0×10<SP>4</SP>and ≥5 pts.mass of a filler (C). The sum of the bonding amounts of the aromatic vinyl compounds of the high molecular weight polymer component (A) and the low molecular weight polymer component (B) is ≤5 mass%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rubber composition and a tire using the rubber composition, and in particular, a rubber composition that is excellent in processability and can improve wear resistance while highly balancing the wet performance and on-ice performance of the tire. It is about things.

  In recent years, demands for low fuel consumption and safety of automobiles have become more severe. In addition to the wear resistance and fracture characteristics conventionally required for rubber materials for automobile tire treads, ice, wet, dry, etc. A rubber composition excellent in grip performance has been strongly desired. Conventionally, as a technique for improving wear resistance and fracture characteristics, a technique using a low molecular weight liquid aromatic vinyl compound-conjugated diene compound copolymer instead of a softening agent such as aroma oil has been performed. When a styrene-butadiene copolymer is used as the compound-conjugated diene compound copolymer, there is a problem that the glass transition point (Tg) of the rubber composition is increased and the on-ice performance of the tire is lowered.

  In response to this problem, Japanese Patent Application Laid-Open No. 9-194640 discloses a high coefficient of friction on ice, a high degree of flexibility at low temperatures, grip performance on wet roads (wet performance), and grip performance on ice and snow (performance on ice). As a rubber composition that can be balanced, 100 to 50 parts by mass of a specific type of rubber component is blended with 2 to 50 parts by mass of a low molecular weight styrene-butadiene copolymer having a controlled microstructure. A rubber composition containing foamable cells in a rubber matrix is disclosed.

  Japanese Patent No. 3457469 discloses a rubber composition that has excellent flexibility at low temperatures, good workability, can achieve both on-ice performance and wet performance of a tire, and has improved shrinkage. The amount of bonded styrene is 30 to 120 parts by mass of a low molecular weight polymer component having an amount of bonded styrene of 30% by mass or less to 100 parts by mass of high molecular weight polymer component having an amount of bonded styrene of 30% by mass or less. And a rubber composition in which the vinyl content satisfies a specific relational expression.

JP-A-9-194640 Japanese Patent No. 3457469

  However, as a result of studies by the present inventors, the rubber compositions disclosed in JP-A-9-194640 and Japanese Patent No. 3457469 are known to have grip performance (wet performance) on wet road surfaces and grip performance on ice and snow (on ice). It was found that there is still room for improvement with regard to the effect of improving the wear resistance.

  Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art, to improve workability, to improve storage elastic modulus (G ′) and loss tangent (tan δ) at low temperature, and to improve wear resistance. It is to provide a rubber composition. Another object of the present invention is to provide a tire using such a rubber composition in a tread portion and having improved wear resistance while highly balancing wet performance and on-ice performance.

  As a result of intensive studies to achieve the above object, the inventors of the present invention have found that the amount of a specific aromatic vinyl compound bonded to a high molecular weight polymer component having a specific amount of aromatic vinyl compound and a weight average molecular weight. In addition, by blending a specific amount of a low molecular weight polymer component having a weight average molecular weight and a filler, and further controlling the microstructure of the high molecular weight polymer component and the low molecular weight polymer component, the processability is excellent. It has been found that a rubber composition capable of improving wet performance, performance on ice and wear resistance can be obtained, and the present invention has been completed.

That is, the rubber composition of the present invention is an aromatic vinyl compound-conjugated diene compound copolymer or a conjugated diene compound polymer having an aromatic vinyl compound bond amount (S ₁ ) of 80% by mass or less, and converted to polystyrene. Aromatic vinyl compound-conjugated diene compound having a binding amount (S ₂ ) of the aromatic vinyl compound of less than 30% by mass with respect to 100 parts by mass of the high molecular weight polymer component (A) having a weight average molecular weight of 1.5 × 10 ⁵ or more A copolymer or a conjugated diene compound polymer having a polystyrene-reduced weight average molecular weight of 0.2 × 10 ^{4 to} 8.0 × 10 ⁴ exceeding 1 part by mass and less than 30 parts by mass The filler (C) is blended with 5 parts by mass or more,
The total of the binding amount (S ₁ ) of the aromatic vinyl compound and the binding amount (S ₂ ) of the aromatic vinyl compound is 5% by mass or less.

  In a preferred example of the rubber composition of the present invention, the amount of chloroform extracted after vulcanization is 15% by mass or more based on the mass of the low molecular weight polymer component (B).

In the rubber composition of the present invention, the low molecular weight polymer component (B) preferably has a polystyrene equivalent weight average molecular weight of 4.0 × 10 ^{4 to} 8.0 × 10 ⁴ .

  The rubber composition of the present invention preferably contains 5 to 25 parts by mass of the low molecular weight polymer component (B) with respect to 100 parts by mass of the high molecular weight polymer component (A).

  The tire of the present invention is characterized by using the above rubber composition in a tread portion.

  According to the present invention, a high molecular weight polymer component having a specific aromatic vinyl compound binding amount and a weight average molecular weight, a low molecular weight polymer component having a specific aromatic vinyl compound binding amount and a weight average molecular weight; In addition, by blending a specific amount of filler and further controlling the microstructure of the high molecular weight polymer component and the low molecular weight polymer component, it has excellent processability, storage modulus (G ′) and loss tangent at low temperature A rubber composition with improved (tan δ) and further improved wear resistance can be provided. Another object of the present invention is to provide a tire using such a rubber composition in the tread portion and having improved wear resistance while highly balancing wet performance and on-ice performance.

The present invention is described in detail below. The rubber composition of the present invention is an aromatic vinyl compound-conjugated diene compound copolymer or conjugated diene compound polymer having an aromatic vinyl compound bond amount (S ₁ ) of 80% by mass or less, and is a polystyrene-converted weight average. on the molecular weight of the high molecular weight polymer component (a) 100 parts by mass of at 1.5 × 10 ⁵ or more, bonds of the aromatic vinyl compound (S ₂₎ is less than 30% by weight aromatic vinyl compound - conjugated diene compound copolymerization A polymer or conjugated diene compound polymer, having a polystyrene-reduced weight average molecular weight of 0.2 × 10 ^{4 to} 8.0 × 10 ⁴ exceeding 1 part by mass and less than 30 parts by mass, and filling Agent (C) is blended with 5 parts by mass or more, and the total of the binding amount of aromatic vinyl compound (S ₁ ) and the binding amount of aromatic vinyl compound (S ₂ ) is 5% by mass or less. Features.

As a result of the study by the present inventors, the aromatic vinyl compound is used for the high molecular weight polymer component (A) having a bonded amount of the aromatic vinyl compound of 80% by mass or less and a polystyrene equivalent weight average molecular weight of 1.5 × 10 ⁵ or more. A low molecular weight polymer component (B) having a bond weight of less than 30% by mass and a polystyrene-reduced weight average molecular weight of 0.2 × 10 ^{4 to} 8.0 × 10 ⁴ , and further, a high molecular weight polymer component (A) and a low molecular weight By adjusting the total amount of the aromatic vinyl compound in the polymer component (B) to 5% by mass or less, the processability of the rubber composition is improved and the storage elastic modulus (G ′) and loss at low temperature are improved. It was found that the tangent (tan δ) can be improved. Further, the low molecular weight polymer component (B) is more than 1 part by weight and less than 30 parts by weight with respect to 100 parts by weight of the high molecular weight polymer component (A), and the filler (C) is the high molecular weight polymer component. (A) By mix | blending 5 mass parts or more with respect to 100 mass parts, abrasion resistance can be improved further, without deteriorating an above-described effect. Therefore, a tire using such a rubber composition in the tread portion can improve wear resistance while highly balancing wet performance and on-ice performance.

The high molecular weight polymer component (A) used in the rubber composition of the present invention requires a polystyrene-equivalent weight average molecular weight of 1.5 × 10 ⁵ or more, preferably 3.0 × 10 ^{5 to} 1.5 × 10 ^6. . When the polystyrene equivalent weight average molecular weight of the high molecular weight polymer component (A) is less than 1.5 × 10 ⁵ , the Mooney viscosity of the rubber composition decreases when the low molecular weight polymer component (B) is blended, and the fracture characteristics and wear resistance are reduced. Not only deteriorates the workability but also significantly decreases the workability.

The high molecular weight polymer component (A) is an aromatic vinyl compound-conjugated diene compound copolymer or a conjugated diene compound polymer, and the binding amount (S ₁ ) of the aromatic vinyl compound is 80% by mass or less. And is preferably 30% by mass or less. When the binding amount (S ₁ ) of the aromatic vinyl compound exceeds 80% by mass, the workability, storage elastic modulus (G ′) and loss factor (tan δ) cannot be balanced.

  The rubber composition of the present invention requires that the low molecular weight polymer component (B) is contained in an amount exceeding 1 part by weight and less than 30 parts by weight with respect to 100 parts by weight of the high molecular weight polymer component (A). It is preferable to contain 5-25 mass parts, and it is especially preferable to contain 15-20 mass parts. Since the low molecular weight polymer component (B) acts in the same manner as a normal softening agent at the time of kneading, if the polymer component (B) is blended more than a certain amount, no torque is applied at the time of kneading, Reduce the dispersibility of the filler. In particular, when the glass transition temperature (Tg) of the high molecular weight polymer component (A) and the low molecular weight polymer component (B) is low, the polymer component is soft, so that the dispersibility is significantly reduced. Therefore, in the rubber composition of the present invention, by restricting the content of the low molecular weight polymer component (B) to the above specified range, a decrease in the dispersibility of the filler is suppressed, and heat generation and wear resistance are reduced. Property and fracture properties can be improved. In addition, when the content of the low molecular weight polymer component (B) is 1 part by mass or less with respect to 100 parts by mass of the high molecular weight polymer component (A), the effect of improving wet performance and on-ice performance cannot be obtained, whereas 30 mass If it is at least part, the dispersibility of the filler is lowered.

The low molecular weight polymer component (B) used in the rubber composition of the present invention requires a polystyrene-equivalent weight average molecular weight of 0.2 × 10 ^{4 to} 8.0 × 10 ⁴ , and is 1.0 × 10 ^{4 to} 8.0 × 10 ⁴ . Preferably, it is 4.0 × 10 ^{4 to} 8.0 × 10 ⁴ . In general, in a rubber composition highly filled with a filler such as carbon black, the filler is not sufficiently dispersed, resulting in poor dispersion, and exothermicity, wear resistance and fracture characteristics are deteriorated. On the other hand, the low molecular weight polymer component (B) has a molecular weight in the above-specified range and can be blended as a polymer component. Therefore, the low molecular weight polymer component (B) is blended. In the rubber composition, the filler such as carbon black can be sufficiently diluted, the dispersion of the filler can be suppressed, and the heat generation, wear resistance and fracture characteristics can be improved. In addition, when the polystyrene-reduced weight average molecular weight of the low molecular weight polymer component (B) is less than 0.2 × 10 ⁴ , the effect of improving wet performance and on-ice performance cannot be obtained, while when it exceeds 8.0 × 10 ⁴ , the wet performance and In addition to not being able to obtain the effect of improving the performance on ice, the workability deteriorates.

The low molecular weight polymer component (B) is an aromatic vinyl compound-conjugated diene compound copolymer or a conjugated diene compound polymer, and the binding amount (S ₂ ) of the aromatic vinyl compound is less than 30% by mass. Is preferably 15% by mass or less, and particularly preferably does not contain an aromatic vinyl compound. When the binding amount (S ₂ ) of the aromatic vinyl compound of the low molecular weight polymer component (B) is 30% by mass or more, the low molecular weight polymer component (B) is hardly entangled, and the wet performance and the performance on ice are improved. The effect becomes insufficient, and further, flexibility at low temperatures is lowered.

  The low molecular weight polymer component (B) preferably has a vinyl bond content of the conjugated diene compound portion of 80% or less. When the amount of vinyl bonds in the conjugated diene compound portion exceeds 80%, the storage elastic modulus (G ′) at a low temperature increases and the performance on ice tends to deteriorate.

In addition, the amount (S ₁ ) (% by mass) of the aromatic vinyl compound in the high molecular weight polymer component (A) and the amount (S ₂ ) of the aromatic vinyl compound in the low molecular weight polymer component (B) ( Mass%) is required to be 5 mass% or less, and is preferably less than 5 mass%. When the combined amount of the aromatic vinyl compound exceeds 5% by mass, the storage elastic modulus (G ′) at low temperature is significantly increased, and the performance on ice tends to be deteriorated.

  In the rubber composition of the present invention, the amount of chloroform extracted after vulcanization is preferably 15% by mass or more, more preferably 30 to 98% by mass, based on the mass of the low molecular weight polymer component (B). preferable. Here, the chloroform extraction amount after vulcanization is the extraction amount when the vulcanized rubber obtained by vulcanizing the rubber composition of the present invention is extracted with chloroform. When the amount of chloroform extracted after vulcanization is less than 15% by mass relative to the mass of the low molecular weight polymer component (B) contained in the rubber composition, the effect of improving wet performance and on-ice performance can be sufficiently obtained. Absent.

  The high molecular weight polymer component (A) and the low molecular weight polymer component (B) are produced by copolymerizing an aromatic vinyl compound and a conjugated diene compound or polymerizing a conjugated diene compound. Here, the polymerization method of the polymer component is not particularly limited, and examples thereof include anionic polymerization using a lithium-based initiator, coordination polymerization, and emulsion polymerization using dodecyl mercaptan. Aromatic vinyl compounds include styrene, α-methylstyrene, p-methylstyrene, o-methylstyrene, p-butylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4- Examples include cyclohexylstyrene and 2,4,6-trimethylstyrene. On the other hand, the conjugated diene compounds include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 2-phenyl-1,3-butadiene, and 1,3-hexadiene. , Octadiene and the like. Among these monomers, 1,3-butadiene is particularly preferable. In addition, these monomers may be used independently and may be used in combination of 2 or more type.

  When the high molecular weight polymer component (A) or the low molecular weight polymer component (B) is produced by anionic polymerization, an organic alkali metal compound is preferably used as the polymerization initiator, and a lithium compound is further used. preferable. Examples of the lithium compound include alkyllithium such as ethyllithium, propyllithium, n-butyllithium, sec-butyllithium, t-butyllithium and hexyllithium; aryllithium such as phenyllithium and tolyllithium; vinyllithium and propenyl Alkenyl lithium such as lithium; Alkylene dilithium such as tetramethylene dilithium, pentamethylene dilithium, hexamethylene dilithium and decamethylene dilithium; Allylenes such as 1,3-dilithiobenzene and 1,4-dilithiobenzene 1,3,5-trilithiocyclohexane, 1,2,5-trilithionaphthalene, 1,3,5,8-tetralithiodecane, 1,2,3,5-tetralithio-4-hexyl- other than lithium Anthracene etc. are mentioned. Among these, n-butyllithium, sec-butyllithium, t-butyllithium and tetramethylenedilithium are preferable, and n-butyllithium is particularly preferable. The amount of the polymerization initiator used is determined by the polymerization rate in the reaction operation and the molecular weight of the polymer to be produced.

  There is no restriction | limiting in particular as a method of manufacturing the said high molecular weight polymer component (A) or the said low molecular weight polymer component (B) using the said polymerization initiator, For example, the hydrocarbon solvent inactive to a polymerization reaction Among them, a polymer can be produced by polymerizing a monomer. Here, hydrocarbon solvents inert to the polymerization reaction include propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane, propene, 1-butene, isobutene, trans-2-butene, cis -2-butene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, benzene, toluene, xylene, ethylbenzene and the like. These may be used alone or in combination of two or more.

  The anionic polymerization may be performed in the presence of a randomizer. The randomizer can control the microstructure of the conjugated diene compound portion of the polymer. More specifically, the randomizer can control the amount of vinyl bonds in the conjugated diene compound portion of the polymer, or can control the conjugated diene content in the polymer. It has the effect of randomizing the compound unit and the aromatic vinyl compound unit. Examples of the randomizer include dimethoxybenzene, tetrahydrofuran, dimethoxyethane, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, bistetrahydrofurylpropane, triethylamine, pyridine, N-methylmorpholine, N, N, N ′, N′-tetramethylethylenediamine, 1 , 2-dipiperidinoethane, potassium-t-amylate, potassium-t-butoxide, sodium-t-amylate and the like. The amount of these randomizers used is preferably in the range of 0.01 to 100 molar equivalents per mole of polymerization initiator.

  The anionic polymerization is preferably carried out by solution polymerization, and the concentration of the monomer in the polymerization reaction solution is preferably in the range of 5 to 50% by mass, more preferably in the range of 10 to 30% by mass. Further, the polymerization mode is not particularly limited, and may be batch type or continuous type.

  The polymerization temperature of the anionic polymerization is preferably in the range of 0 to 150 ° C, more preferably in the range of 20 to 130 ° C. The polymerization can be carried out under a generated pressure, but it is usually preferred to carry out the polymerization under a pressure sufficient to keep the monomer used in a substantially liquid phase. Here, when the polymerization reaction is carried out under a pressure higher than the generated pressure, it is preferable to pressurize the reaction system with an inert gas. Moreover, it is preferable to use what removed reaction-inhibiting substances, such as water, oxygen, a carbon dioxide, and a protic compound, as raw materials, such as a monomer used for superposition | polymerization, a polymerization initiator, and a solvent.

  On the other hand, when the high molecular weight polymer component (A) or the low molecular weight polymer component (B) is produced by coordination polymerization, a rare earth metal compound is preferably used as the polymerization initiator, and the following component (a): More preferably, the components (b) and (c) are used in combination.

  The component (a) used for the coordination polymerization is selected from a rare earth metal compound, a complex compound of a rare earth metal compound and a Lewis base, and the like. Here, examples of rare earth metal compounds include rare earth element carboxylates, alkoxides, β-diketone complexes, phosphates and phosphites, and Lewis bases include acetylacetone, tetrahydrofuran, pyridine, N, N. -Dimethylformamide, thiophene, diphenyl ether, triethylamine, organophosphorus compound, monovalent or divalent alcohol and the like. As the rare earth element of the rare earth metal compound, lanthanum, neodymium, praseodymium, samarium and gadolinium are preferable, and among these, neodymium is particularly preferable. Specific examples of the component (a) include neodymium tri-2-ethylhexanoate, a complex compound thereof with acetylacetone, neodymium trineodecanoate, a complex compound thereof with acetylacetone, neodymium tri-n-butoxide, and the like. It is done. These (a) components may be used individually by 1 type, or 2 or more types may be mixed and used for them.

The component (b) used for the coordination polymerization is selected from organoaluminum compounds. Specifically, as the organoaluminum compound, a trihydrocarbyl aluminum compound represented by the formula: R ₃ Al, a hydrocarbyl aluminum hydride represented by the formula: R ₂ AlH or RAlH ₂ (wherein R is independently And a hydrocarbylaluminoxane compound having a hydrocarbon group having 1 to 30 carbon atoms. Specific examples of the organoaluminum compound include trialkylaluminum, dialkylaluminum hydride, alkylaluminum dihydride, alkylaluminoxane, and the like. These compounds may be used alone or in combination of two or more. In addition, as (b) component, it is preferable to use aluminoxane and another organoaluminum compound together.

  The component (c) used in the coordination polymerization is a compound having a hydrolyzable halogen or a complex compound thereof with a Lewis base; an organic halide having a tertiary alkyl halide, benzyl halide or allyl halide; a non-coordinating anion And an ionic compound comprising a counter cation. Specific examples of the component (c) include alkylaluminum dichloride, dialkylaluminum chloride, silicon tetrachloride, tin tetrachloride, zinc chloride and Lewis base complexes such as alcohol, magnesium chloride and Lewis such as alcohol. Examples thereof include complexes with bases, benzyl chloride, t-butyl chloride, benzyl bromide, t-butyl bromide, triphenylcarbonium tetrakis (pentafluorophenyl) borate and the like. These (c) components may be used individually by 1 type, or 2 or more types may be mixed and used for them.

  In addition to the components (a), (b), and (c), the polymerization initiator is preliminarily used, if necessary, using the same conjugated diene compound and / or aromatic vinyl compound as the polymerization monomer. May be prepared. Further, part or all of the component (a) or the component (c) may be supported on an inert solid. The amount of each of the above components can be appropriately set depending on the molecular weight of the polymer to be produced. Usually, the component (a) is 0.001 to 0.5 mmol per 100 g of the monomer. The molar ratio of the component (b) / component (a) is preferably 5 to 1000, and the component (c) / component (a) is preferably 0.5 to 10.

  The polymerization temperature in the coordination polymerization is preferably in the range of -80 to 150 ° C, more preferably in the range of -20 to 120 ° C. Moreover, as a solvent used for coordination polymerization, a hydrocarbon solvent inert to the reaction exemplified in the above-mentioned anionic polymerization can be used, and the concentration of the monomer in the reaction solution is the same as in the case of anionic polymerization. . Furthermore, the reaction pressure in coordination polymerization is the same as that in the case of anionic polymerization, and it is desirable that the raw material used for the reaction substantially removes reaction inhibitors such as water, oxygen, carbon dioxide, and protic compounds.

  In the present invention, the polymer solution (A) and the polymer component obtained by drying the reaction solution containing the polymer component (A) or the polymer component (B) to separate each polymer component are obtained. (B) may be mixed, or after the reaction solution containing the polymer component (A) or the polymer component (B) is mixed, it is dried, and the polymer component (A) and the polymer component ( A mixture of B) may be obtained.

  In the rubber composition of the present invention, in addition to the high molecular weight polymer component (A) and the low molecular weight polymer component (B), a general rubber component used in the rubber industry can be blended. Specifically, natural rubber (NR), styrene-butadiene copolymer rubber (SBR), polyisoprene rubber (IR), polybutadiene rubber (BR), ethylene-propylene copolymer, chloroprene rubber (CR), butyl rubber ( IIR), halogenated butyl rubber, acrylonitrile-butadiene rubber (NBR) and the like can be blended.

  The rubber composition of the present invention is required to contain 5 parts by mass or more of filler (C) with respect to 100 parts by mass of the high molecular weight polymer component (A), preferably 20 parts by mass or more, It is more preferable to contain 20-80 parts by mass. When the content of the filler (C) is less than 5 parts by mass, the effect of improving the wear resistance cannot be sufficiently obtained. Here, the filler (C) is preferably carbon black and / or silica.

  The carbon black is not particularly limited, and examples thereof include FEF, SRF, HAF, ISAF, and SAF grades. The carbon black is preferably carbon black having an iodine adsorption amount (IA) of 60 mg / g or more and a dibutyl phthalate (DBP) oil absorption of 80 mL / 100 g or more. By blending carbon black, various physical properties of the rubber composition can be improved, but from the viewpoint of improving the wear resistance, those of HAF, ISAF, and SAF grade are more preferable. On the other hand, the silica is not particularly limited, and examples thereof include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc. Among these, wet silica is preferable. .

  In addition to the high molecular weight polymer component (A), the low molecular weight polymer component (B), the additional rubber component, and the filler (C), the rubber composition of the present invention is usually used in the rubber industry. A compounding agent such as a softening agent, an anti-aging agent, a silane coupling agent, a vulcanization accelerator, a vulcanization accelerator, a vulcanizer, 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 is kneaded by blending the high molecular weight polymer component (A) with the low molecular weight polymer component (B) and the filler (C), and various compounding agents appropriately selected as necessary. , Heating, extruding and the like.

  The tire according to the present invention is characterized in that the rubber composition is used in a tread portion. A tire using the rubber composition in the tread portion is excellent in wet performance, performance on ice and wear resistance. The tire of the present invention is not particularly limited except that the above rubber composition is used for the tread portion, and can be produced according to a conventional method. Moreover, as gas with which this tire is filled, inert gas, such as nitrogen, argon, helium other than normal or the air which adjusted oxygen partial pressure, can be used.

  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.

  The polymer (A-1) and the polymers (B-1) to (B-3) were synthesized by the following method, and the vinyl bond amount and polystyrene-converted weight average molecular weight of the obtained polymer were determined by the following method. It was measured. The results are shown in Table 1.

(1) Microstructure The amount of vinyl bonds in the butadiene portion of the polymer was determined by the infrared method (Morero method).

(2) Weight average molecular weight (Mw)
Gel permeation chromatography [GPC: Tosoh HLC-8020, column: Tosoh GMH-XL (two in series), detector: differential refractometer (RI)], based on monodisperse polystyrene, The weight average molecular weight (Mw) in terms of polystyrene was determined.

<Example of production of polymer (A-1)>
In an 800 mL pressure-resistant glass container that has been dried and purged with nitrogen, 300 g of cyclohexane, 50 g of 1,3-butadiene, and 0.66 mmol of ditetrahydrofurylpropane were injected, and 0.500 mmol of n-butyllithium (n-BuLi) was further added. Thereafter, a polymerization reaction was carried out at 50 ° C. for 1.5 hours. The polymerization conversion rate at this time was almost 100%. Thereafter, 0.5 mL of an isopropanol solution (BHT concentration: 5% by mass) of 2,6-di-t-butyl-p-cresol (BHT) was added to the polymerization reaction system to stop the polymerization reaction, and further according to a conventional method. It dried and the polymer (A-1) was obtained.

<Example of production of polymer (B-1)>
Into a dry, nitrogen-substituted 800 mL pressure-resistant glass container, 300 g of cyclohexane, 50 g of 1,3-butadiene and 0.11 mmol of ditetrahydrofurylpropane were added, and 3.6 mmol of n-butyllithium was further added. The polymerization reaction was performed for 5.0 hours. The polymerization conversion rate at this time was almost 100%. Thereafter, 0.5 mL of an isopropanol solution (BHT concentration: 5% by mass) of 2,6-di-t-butyl-p-cresol (BHT) was added to the polymerization reaction system to stop the polymerization reaction, and further according to a conventional method. The polymer was dried to obtain a polymer (B-1).

<Production Examples of Polymers (B-2) to (B-3)>
Polymers (B-2) to (B-3) were synthesized in the same manner as the polymer (B-1) except that the amount of n-butyllithium used was changed.

  Next, the polymer (A-1) and the polymers (B-1) to (B-3) were blended according to the formulation shown in Table 2, and further using a 250 ml plastmill (manufactured by Toyo Seiki Co., Ltd.), Table 2 A rubber composition having the formulation shown in FIG. The processability of this rubber composition was evaluated by the following method. The obtained rubber composition was vulcanized at 160 ° C. for 15 minutes to obtain a vulcanized rubber. The vulcanized rubber was extracted with chloroform, the storage elastic modulus (G ′) at −20 ° C., 0 ° C. Loss tangent (tan δ) and wear resistance were measured and evaluated by the following methods. The results are shown in Table 3.

(3) Processability In accordance with JIS K6300-1994, the Mooney viscosity [ML _{1 +} 4/130 ° C] of the rubber composition was measured at 130 ° C, and the index of the Mooney viscosity of the rubber composition of Example 1 was taken as 100. displayed. In addition, since the index value is too hard when it exceeds 105 and is too soft when it is less than 95, in either case, it is not preferable for maintaining workability.

(4) Chloroform extraction amount A vulcanized rubber sample was extracted with a Soxhlet extractor for 48 hours using chloroform as a solvent, and the amount of vulcanized rubber relative to the mass of the low molecular weight polymer component (B) was determined from the remaining amount of the vulcanized rubber sample. Chloroform extraction amount (% by mass) was determined.

(5) Storage elastic modulus (G ′)
Storage elastic modulus (G ′) was measured at a temperature of −20 ° C., a frequency of 10 Hz, and a strain of 0.1% using a viscoelasticity measuring device manufactured by Rheometrics, and the storage elastic modulus (G ′) of the rubber composition of Example 1 was measured. ) And the exponent is displayed. The larger the index value, the lower the storage elastic modulus and the better the performance on ice.

(6) Loss tangent (tan δ)
Using a viscoelasticity measuring device manufactured by Rheometrics, tan δ was measured at a temperature of 0 ° C., a frequency of 10 Hz, and a strain of 0.1%, and the tan δ of the rubber composition of Example 1 was expressed as 100. It shows that it is excellent in wet performance, so that an index value is large.

(7) Abrasion resistance Using a Ramborn type abrasion tester, the amount of wear at a slip rate of 40% at room temperature was measured, and the index was displayed with the reciprocal of the amount of wear in Example 1 being 100. The larger the index value, the smaller the wear amount and the better the wear resistance.

* 1 Table 3 shows the polymers (B-1) to (B-3) produced by the above method and the types of polymers used.
* 2 Nippon Sil AQ.
* 3 Si69, manufactured by Degussa.
* 4 ISAF, Seest 3H, manufactured by Tokai Carbon Co., Ltd.
* 5 IPPD, N-isopropyl-N′-phenyl-p-phenylenediamine.
* 6 Di-2-benzothiazolyl disulfide.
* 7 N-cyclohexyl-2-benzothiazolylsulfenamide.

  From Table 3, Examples 1-2 of the compound 2 whose compounding quantity of a low molecular weight polymer component (B) is more than 1 mass part and less than 30 mass parts with respect to 100 mass parts of high molecular weight polymer components (A). The rubber composition of No. 1 is superior in performance on ice, wet performance, workability and wear resistance to the rubber compositions of Comparative Examples 1 to 3 of Formulation 1, and Comparative Examples 5 to 7 of Formulation 3 It is understood that the performance on ice and the wet performance are superior to those of Comparative Example 4, and the workability is superior to Comparative Example 4 of Formulation 3.

Claims (5)

Aromatic vinyl compound-conjugated diene compound copolymer or conjugated diene compound polymer having a binding amount (S ₁ ) of aromatic vinyl compound of 80% by mass or less, and having a polystyrene-equivalent weight average molecular weight of 1.5 × 10 ⁵ or more An aromatic vinyl compound-conjugated diene compound copolymer or conjugated diene compound polymer in which the bond amount (S ₂ ) of the aromatic vinyl compound is less than 30% by mass with respect to 100 parts by mass of a certain high molecular weight polymer component (A). More than 1 part by mass of the low molecular weight polymer component (B) having a polystyrene equivalent weight average molecular weight of 0.2 × 10 ^{4 to} 8.0 × 10 ⁴ and less than 30 parts by mass, and 5 parts by mass or more of the filler (C) And
The rubber composition, wherein the total of the binding amount (S ₁ ) of the aromatic vinyl compound and the binding amount (S ₂ ) of the aromatic vinyl compound is 5% by mass or less.   The rubber composition according to claim 1, wherein the amount of chloroform extracted after vulcanization is 15% by mass or more based on the mass of the low molecular weight polymer component (B). 2. The rubber composition according to claim 1, wherein the low molecular weight polymer component (B) has a polystyrene equivalent weight average molecular weight of 4.0 × 10 ^{4 to} 8.0 × 10 ⁴ .   The rubber composition according to claim 1, wherein the low molecular weight polymer component (B) is contained in an amount of 5 to 25 parts by mass with respect to 100 parts by mass of the high molecular weight polymer component (A).   A tire comprising the rubber composition according to any one of claims 1 to 4 in a tread portion.