AIR TIRES AND THE USE OF A RUBBER COMPOSITION FOR THE MANUFACTURING OF AN AIR TIRES

Abstract

Pneumatic tire, which has been manufactured using a rubber compound containing the following rubber composition: a rubber component, a plasticizer (a) and at least one of a resin and a plasticizer (b), wherein the resin is at least one selected from the group consisting of aromatic petroleum resins, terpene resins and rosin resins, wherein the plasticizer (a) has a glass transition temperature of -50°C or less, wherein the resin and the plasticizer (b) each have a glass transition temperature of -40°C to 20°C, and, wherein the rubber composition for a tire, based on 100 parts by mass of the rubber component, comprises 1 to 30 parts by mass of the plasticizer (a) and a total of 1 to 30 parts by mass of at least one of the resin and the plasticizer (b), wherein the weight-averaged molecular weight (Mw) of the rubber component is 200,000 or more, and in the event that the plasticizer (a) and / or (b) is a diene polymer, the weight-average molecular weight of the diene polymer is 150,000 or less.

Description

TECHNICAL FIELD

[0001] The present invention relates to a pneumatic tire produced using a rubber composition and to a use of a rubber composition for producing a pneumatic tire. STATE OF THE ART

[0002] Renewed concerns about environmental issues such as global warming have led to growing societal demands for lower fuel consumption. To meet the demand for lower-fuel-consumption automobiles, the development of fuel-efficient tires with reduced rolling resistance is necessary. Known methods for reducing tire rolling resistance include replacing carbon black with silica, reducing the amount of filler that causes energy loss, and using modified rubber with a functional group that is highly reactive toward silica.

[0003] Although the above techniques can improve rolling resistance properties, reducing the filler amount and using modified rubber both tend to reduce rubber strength. Furthermore, when using modified rubber, it must be sufficiently kneaded to react with silica. As a result, the surface of the rubber composition becomes rough, reducing the adhesion force (tackiness), resulting in deterioration of tire processability.

[0004] To improve adhesion and rubber strength, the use of aliphatic petroleum resin or aromatic petroleum resin has been investigated; however, these uses disadvantageously impair fuel economy. Patent Document 1 teaches a method for improving fuel economy and braking performance by using natural rubber, white filler, a specific resin, and the like. However, this document does not satisfactorily address fuel economy, processability, adhesion, and rubber strength simultaneously.

[0005] Patent Document 1: JP 2009-7454 A

[0006] WO 2012 / 084847 A1, which is prior art according to Section 3(2) / S.3 of the German Patent Act (PatentG), discloses a tire whose tread comprises a rubber composition. The rubber composition comprises: a diene elastomer, an inorganic reinforcing filler, a thermoplastic poly(alkylene ester) resin, and a plasticizer system comprising: a hydrocarbon resin with a Tg of more than 20°C, according to a content A of 5 to 60 phe; a plasticizer liquid at 20°C with a Tg of less than -20°C, according to a content B of 5 to 60 phe, with the proviso that A+B is more than 40 phe.

[0007] JP 2005 350 535 A describes a rubber composition for a tire. The rubber composition comprises 15 parts by weight or more of a resin with a softening point of 120°C or higher and 5 parts by weight or more of a styrene-butadiene rubber plasticizer.

[0008] JP 2007 277 307 A describes a rubber composition for a tire containing a phenolic resin and / or an aromatic petroleum resin with a softening point of 60 to 180°C and a plasticizer with a freezing point of -50°C or lower. Furthermore, the rubber component contains 60 mass percent or more of solution-polymerized styrene-butadiene copolymer rubber. SUMMARY OF THE INVENTION

[0009] The present invention aims to provide a pneumatic tire made using a rubber composition which can solve the above problem and can improve fuel economy, processability, grip and rubber strength in a balanced manner.

[0010] The present invention relates to a pneumatic tire produced using a rubber composition comprising a rubber component, a plasticizer (a), and at least one of a resin and a plasticizer (b), wherein the resin is at least one selected from the group consisting of aromatic petroleum resins, terpene resins, and rosin resins, wherein the plasticizer (a) has a glass transition point of -50°C or less, wherein the resin and the plasticizer (b) each have a glass transition point of -40°C to 20°C, and wherein the rubber composition for a tire contains, based on 100 parts by mass of the rubber component, 1 to 30 parts by mass of the plasticizer (a) and a total of 1 to 30 parts by mass of the at least one of the resin and the plasticizer (b), wherein the weight-average molecular weight (Mw) of the rubber component is 200.000 or more, and in case the plasticizer (a) and / or (b) is a diene polymer, the weight average molecular weight of the diene polymer is 150,000 or less.

[0011] Preferably, the rubber composition for a tire contains, based on 100 parts by mass of the rubber component, 10 to 120 parts by mass of silica having a specific surface area of ​​50 m measured by nitrogen adsorption 2 / g or more and contains, based on 100 mass% of the rubber component, 10 mass% or more of a modified diene rubber modified by a compound represented by the following formula (1):wherein R 1 , R 2 and R 3 may be the same or different from each other and each represents an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group, a mercapto group or a derivative thereof, R 4 and R 5may be the same or different and each represents a hydrogen atom or an alkyl group and n represents an integer.

[0012] The silica preferably contains a silica (1) with a specific surface area of ​​50 m measured by nitrogen adsorption 2 / g or more, but less than 120 m 2 / g and a silica (2) with a specific surface area of ​​120 m measured by nitrogen adsorption 2 / g or more, wherein the total amount of the silica (1) and the silica (2) is 10 to 120 parts by mass based on 100 parts by mass of the rubber component.

[0013] The silica (1) and the silica (2) preferably satisfy the following relationships: (specific surface area of ​​silica (2) measured by nitrogen adsorption) / (specific surface area of ​​silica (1) measured by nitrogen adsorption)≥1.4 and (Amount of silica (1))×0.06≤(Amount of silica (2))≤(Amount of silica(1))×15.

[0014] The rubber composition for a tire preferably contains a butadiene rubber having a cis double bond content of 50 mol% or less and a butadiene rubber having a cis double bond content of 95 mol% or more.

[0015] The butadiene rubber having a cis double bond content of 95 mol% or more is preferably obtained by polymerization in the presence of a neodymium catalyst.

[0016] At least one of the plasticizer (a) and the plasticizer (b) is preferably a diene polymer having a weight-average molecular weight of 3,000 to 150,000.

[0017] Preferably, the plasticizer (a) is at least one of an ester plasticizer and a diene polymer having a weight-average molecular weight of 3,000 to 150,000 and having a vinyl content of 35 mol% or less, and the diene polymer has been modified by the compound represented by the formula (1).

[0018] At least one of the plasticizer (a) and the plasticizer (b) is preferably a diene polymer having an epoxidation degree of 25 mol% or less.

[0019] Use of a rubber composition for producing a pneumatic tire, the rubber composition comprising: a rubber component, a plasticizer (a), and at least one of a resin and a plasticizer (b), wherein the resin is at least one selected from the group consisting of aromatic petroleum resins, terpene resins, and rosin resins, wherein the plasticizer (a) has a glass transition point of -50°C or less, wherein the resin and the plasticizer (b) each have a glass transition point of -40°C to 20°C, and wherein the rubber composition for a tire contains, based on 100 parts by mass of the rubber component, 1 to 30 parts by mass of the plasticizer (a) and a total of 1 to 30 parts by mass of the at least one of the resin and the plasticizer (b), wherein the weight-average molecular weight (Mw) of the rubber component is 200.000 or more, and in case the plasticizer (a) and / or (b) is a diene polymer, the weight average molecular weight of the diene polymer is 150,000 or less.

[0020] It is also preferred to use the rubber composition for producing a pneumatic tire, wherein the rubber composition is used in a sidewall.

[0021] Since the present invention provides a pneumatic tire produced using a rubber composition, the rubber composition containing predetermined amounts of a plasticizer (a) having a glass transition point in a specific range and at least one of a resin and a plasticizer (b) each having a glass transition point in a specific range, fuel economy, processability, adhesiveness, and rubber strength can be improved in a balanced manner. MODES FOR CARRYING OUT THE INVENTION

[0022] The pneumatic tire according to the present invention is manufactured using a rubber composition containing predetermined amounts of the plasticizer (a) and at least one of the resin and the plasticizer (b), the resin being selected from the group consisting of aromatic petroleum resins, terpene resins, and rosin resins. The glass transition point of the plasticizer (a) is -50°C or less, and the glass transition points of the resin and the plasticizer (b) are -40°C to 20°C. The resin and the plasticizer (b) each have a glass transition point of -40°C to 20°C, and the rubber composition for a tire contains, based on 100 parts by mass of the rubber component, 1 to 30 parts by mass of the plasticizer (a) and a total of 1 to 30 parts by mass of at least one of the resin and the plasticizer (b), wherein the weight-average molecular weight (Mw) of the rubber component is 200.000 or more, and in case the plasticizer (a) and / or (b) is a diene polymer, the weight average molecular weight of the diene polymer is 150,000 or less.

[0023] The use of predetermined amounts of the plasticizer (a) having a glass transition point within a specific range and at least one of the predetermined resin and the plasticizer (b) each having a glass transition point within a specific range greatly enhances the effect of the plasticizer (a) on reducing rolling resistance and the effects of the resin and the plasticizer (b) on improving grip and rubber strength. Therefore, the rolling resistance (fuel economy), processability, grip, and rubber strength properties are synergistically improved, achieving these performance characteristics to a high degree in a balanced manner while also achieving good handling stability. Furthermore, the combined use of materials with different temperature ranges results in excellent rubber strength over a wide temperature range.

[0024] Additionally, lightweight tires can be produced because the durability of the rubber composition is improved. This makes it possible to improve productivity and reduce energy consumption during production, enabling both the tire products and their manufacturing processes to be environmentally friendly.

[0025] The rubber component used in the present invention is not particularly limited. Examples of rubbers that can be included in the rubber component include isoprene-based rubbers such as natural rubber (NR) and isoprene rubber (IR), and diene rubbers such as butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR).

[0026] In particular, isoprene-based rubbers are preferred in terms of achieving good fuel economy, rubber strength, and processability during construction, whereas diene rubbers are preferred in terms of flex fatigue resistance and reversion resistance. Furthermore, the combined use of an isoprene-based rubber and a diene rubber is particularly preferred in terms of achieving good fuel economy, processability, adhesion, and rubber strength.

[0027] Examples of isoprene-based rubber include natural rubber (NR) and isoprene rubber (IR). NR is not particularly limited, and any commonly used rubber in the tire industry, such as SIR20, RSS #3, TSR20, and ENR25, can be used. IR is also not particularly limited, and any commonly used rubber in the tire industry can be used. NR is particularly preferred because it provides good rubber strength.

[0028] The amount of the isoprene-based rubber is preferably 10 mass% or more, and more preferably 30 mass% or more, based on 100 mass% of the rubber component. If the amount is less than 10 mass%, sufficient rubber strength and fuel economy cannot be achieved. The amount is preferably 80 mass% or less, and more preferably 60 mass% or less, based on 100 mass% of the rubber component. If the amount is more than 80 mass%, the viscosity of the unvulcanized rubber composition tends to be high, so kneading processability may be poor, and flexural fatigue resistance tends to be poor.

[0029] The diene rubber is not particularly limited. BR or SBR is preferred, and BR is especially preferred because they contribute to good fuel economy, processability, adhesion, and rubber strength. The diene rubber is preferably one modified by a compound represented by the following formula (1) (modified diene rubber) because it contributes to a high degree of fuel economy, processability, adhesion, and rubber strength.

[0030] In formula (1), R 1 , R 2 and R 3 may be the same or different from each other and each represent an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group (-COOH), a mercapto group (-SH) or a derivative thereof, R 4 and R 5be the same or different and each represent a hydrogen atom or an alkyl group and n represents an integer.

[0031] The cis content of the BR is not particularly limited. Accordingly, low-cis BR with a cis content of 50 mol% or less (but preferably 5 mol% or more) or high-cis BR with a cis content of 95 mol% or more can be used. In particular, the combined use of these BRs is preferred because the effects of the present invention are well achieved. The amount of the low-cis BR is preferably the same as that of the modified low-cis BR mentioned later, and the amount of the high-cis BR is preferably the same as that of the modified high-cis BR mentioned later.

[0032] In the case of combined use, the ratio between the amounts of the low-cis BR and the high-cis BR is preferably the same as that between the amounts of the modified low-cis BR and the modified high-cis BR mentioned later.

[0033] The amount of BR is preferably 10 mass% or more, and more preferably 30 mass% or more, based on 100 mass% of the rubber component. If the amount is less than 10 mass%, adequate flexural fatigue resistance cannot be achieved. The amount is preferably 90 mass% or less, and more preferably 70 mass% or less, based on 100 mass% of the rubber component. If the amount is more than 90 mass%, the cohesion of the rubber composition tends to be poor during kneading, resulting in poor processability and productivity.

[0034] Examples of the modified diene rubber include those disclosed in JP 2010-111753 A.

[0035] In formula (1), R 1 , R 2 and R 3 each preferably contains an alkoxy group (preferably a C1-C6 alkoxy group and particularly preferably a C1-C4 alkoxy group) with a view to achieving a high degree of fuel economy, processability, adhesion, and rubber strength. R 4 and R 5 are each preferably an alkyl group (preferably a C1-C4 alkyl group and particularly preferably a C1-C2 alkyl group). Furthermore, n is preferably 1 to 5, particularly preferably 2 to 4, and most preferably 3. The use of such a preferred compound results in excellent fuel economy, processability, adhesion, and rubber strength.

[0036] Specific examples of the compound represented by formula (1) include 2-dimethylaminoethyltrimethoxysilane, 3-Dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-Dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-Diethylaminopropyltrimethoxysilane, 2-Diethylaminoethyltriethoxysilane and 3-Diethylaminopropyltriethoxysilane. In particular 3-Dimethylaminopropyltrimethoxysilane, 3-Dimethylaminopropyltriethoxysilane and 3-Diethylaminopropyltrimethoxysilane is preferred because it improves the aforementioned performance properties. Each of these can be used alone, or two or more of them can be used in combination.

[0037] The method of modifying a diene rubber with the compound represented by formula (1) can be a conventionally known method such as those disclosed in JP H06-53768 B and JP H06-57767 B. For example, a diene rubber can be modified by bringing it into contact with the compound. Specific examples thereof include a method in which, after producing the diene rubber (e.g., butadiene rubber) by anionic polymerization, a predetermined amount of the compound is added to the resulting rubber solution to cause a reaction between the polymerizing end (active end) of the diene rubber and the compound.

[0038] There are no particular restrictions on the diene rubber to be modified. Butadiene rubber (BR) is preferred in terms of achieving good fuel economy, processability, adhesion, and rubber strength.

[0039] In the case where the diene rubber to be modified is BR, the cis content of the resulting modified diene rubber (modified BR) is not particularly limited. Accordingly, those with a cis double bond content of 50 mol% or less (modified low-cis BR), those with a cis double bond content of 95 mol% or more (modified high-cis BR), and the like can be used. In particular, the combined use of the modified low-cis BR and the modified high-cis BR is preferred because such use leads to high levels of fuel economy, processability, adhesiveness, and rubber strength.

[0040] The cis content of the modified low-cis BR is preferably 50 mol% or less, and more preferably 45 mol% or less, while it is preferably 5 mol% or more, and more preferably 10 mol% or more. When the cis content is within the above range, good processability is achieved and the effects of the present invention are well achieved.

[0041] The amount of cis units (cis content) is measured according to the methods described in the EXAMPLES mentioned below.

[0042] The amount of the modified low-cis BR, based on 100 mass % of the rubber component, is preferably 10 mass % or more, and more preferably 20 mass % or more, while it is preferably 80 mass % or less, and particularly preferably 40 mass % or less. When the amount is within the above range, good fuel economy, processability, adhesion, and rubber strength are achieved.

[0043] The modified high-cis BR is not particularly limited. It is preferably one obtained by polymerization in the presence of a neodymium (Nd) catalyst (such a BR is referred to as Nd-modified high-cis BR) because it effectively improves the balance of the aforementioned performance characteristics.

[0044] Examples of the Nd catalyst include halides, carboxylates, alcoholates, thioalcoholates, and amides of Nd. Nd high-cis BR for use in the preparation of the Nd-modified high-cis BR can be prepared by polymerizing 1,3-butadiene in a reaction-inert organic solvent such as hydrocarbon solvents (e.g., aliphatic, alicyclic, and aromatic hydrocarbon compounds) in the presence of a Nd catalyst and, if necessary, a promoter such as an Al- or B-containing compound. Furthermore, the Nd-modified high-cis BR can be prepared by contacting the polymer obtained by the above polymerization with the aforementioned compound.

[0045] The cis content of the double bonds of the modified high-cis BR is 95 mol% or more, and preferably 97 mol% or more. A cis content of 95 mol% or more results in good flexural fatigue resistance.

[0046] The amount of the modified high-cis BR, based on 100 mass % of the rubber component, is preferably 10 mass % or more, and more preferably 20 mass % or more, while it is preferably 80 mass % or less, and particularly preferably 40 mass % or less. When the amount is within the above range, good fuel economy, processability, adhesion, and rubber strength are achieved.

[0047] The amounts of modified low-cis BR and modified high-cis BR preferably satisfy the following formula: 0.5≤(amount of modified low−cis BR) / (amount of modified high−cis BR)≤10.

[0048] If the ratio of (amount of modified low-cis BR) to (amount of modified high-cis BR) is less than 0.5, adequate kneading processability cannot be achieved. If the ratio is more than 10, adequate flexural fatigue resistance cannot be achieved.

[0049] The amount of the modified diene rubber (the total amount of the modified low-cis BR and the modified high-cis BR in the case of using the modified low-cis BR and the modified high-cis BR in combination) is preferably 10 mass % or more, and more preferably 30 mass % or more, based on 100 mass % of the rubber component. If the amount is less than 10 mass %, the effect of the modified diene rubber on improving fuel economy cannot be sufficiently achieved. The amount is preferably 80 mass % or less, and more preferably 60 mass % or less, based on 100 mass % of the rubber component. If the amount is more than 80 mass %, the polymer and silica tend to react strongly with each other, thereby failing to achieve adequate tensile strength, and kneading processability tends to be poor.

[0050] The weight-average molecular weight (Mw) of the diene rubber is preferably 200,000 or more, and more preferably 300,000 or more. If the Mw is less than 200,000, the tensile strength and flexural fatigue resistance tend to decrease. The Mw is preferably 2,000,000 or less, and more preferably 1,000,000 or less. If the Mw is more than 2,000,000, the processability tends to decrease, causing dispersion defects, resulting in a decrease in tensile strength.

[0051] The weight average molecular weight (Mw) is a value measured according to the method described in the EXAMPLES mentioned below.

[0052] The amount of the diene rubber is preferably 10 mass% or more, and more preferably 30 mass% or more, based on 100 mass% of the rubber component. If the amount is less than 10 mass%, adequate flexural fatigue resistance cannot be achieved. The amount is preferably 90 mass% or less, and more preferably 70 mass% or less, based on 100 mass% of the rubber component. If the amount is more than 90 mass%, the cohesion of the rubber composition tends to be poor during kneading, resulting in poor processability and productivity.

[0053] According to the invention, the weight-average molecular weight (Mw) of the rubber component is 200,000 or more.

[0054] The glass transition point (glass transition temperature (Tg)) of the plasticizer (a) is -50°C or lower, and preferably -60°C or lower. If the Tg is higher than -50°C, fuel economy, processability, adhesion, and rubber strength tend not to be improved in a balanced manner. The Tg is preferably -80°C or higher. If the Tg is lower than -80°C, rubber stiffness tends to be greatly reduced, resulting in a decrease in handling stability, and the Tg of the rubber composition tends to be greatly reduced, resulting in a decrease in rubber strength at ambient temperatures.

[0055] The glass transition point (Tg) is a value measured according to the method described in the EXAMPLES mentioned below.

[0056] The plasticizer (a) is not particularly limited. Examples include ester plasticizers, diene polymers with a weight-average molecular weight (Mw) of 3,000 to 150,000, and aromatic oils.

[0057] In particular, ester plasticizers are preferred for achieving good fuel economy, processability, adhesion, and rubber strength, and diene polymers with a weight-average molecular weight (Mw) of 3,000 to 150,000 are preferred for achieving excellent rubber strength and durability. According to the invention, when the plasticizer (a) and / or (b) is a diene polymer, the weight-average molecular weight of the diene polymer is 150,000 or less.

[0058] Examples of the ester plasticizers include phthalic acid derivatives, long-chain fatty acid derivatives, phosphoric acid derivatives, sebacic acid derivatives and adipic acid derivatives.

[0059] Examples of phthalic acid derivatives include phthalates such as di-2-ethylhexyl phthalate (DOP) and diisodecyl phthalate (DIDP). Examples of long-chain fatty acid derivatives include glycerol esters of long-chain fatty acids. Examples of phosphoric acid derivatives include phosphates such as tri(2-ethylhexyl) phosphate (TOP) and tributyl phosphate (TBP). Examples of sebacic acid derivatives include sebacates such as di-(2-ethylhexyl) sebacate (DOS) and diisooctyl sebacate (DIOS). Examples of adipic acid derivatives include adipates such as di(2-ethylhexyl) adipate (DOA) and diisooctyl adipate (DIOA). In particular, sebacates and adipates are preferred in view of achieving good fuel economy, processability, adhesiveness, and rubber strength, and DOS and DOA are particularly preferred.

[0060] The diene polymer is not particularly limited as long as it meets the above ranges for glass transition point and Mw. In particular, butadiene polymers and styrene-butadiene copolymers are preferred in terms of achieving good fuel economy, processability, adhesion, and rubber strength.

[0061] The weight-average molecular weight (Mw) of the diene polymer is preferably 3,000 or more, and more preferably 20,000 or more. If the Mw is less than 3,000, the effect of improving rubber strength cannot be sufficiently achieved. The Mw is preferably 150,000 or less, and more preferably 120,000 or less. If the Mw is more than 150,000, the effect of improving adhesiveness cannot be sufficiently achieved.

[0062] The vinyl content of the diene polymer is preferably 35 mol% or less, and more preferably 25 mol% or less. If the vinyl content is more than 35 mol%, fuel economy tends to be poor.

[0063] The vinyl content of the diene polymer can be measured by infrared absorption spectrometry.

[0064] In view of achieving excellent fuel economy, as the diene polymer, one modified by the compound represented by the formula (1) or an epoxidized one (one having an epoxy group) can also be used.

[0065] In the compound used for the diene polymer, R 1 , R 2 , R 3 , R 4 , R 5and n is preferably as defined for the aforementioned modified diene rubber. The use of such a preferred compound results in high levels of fuel economy, processability, adhesion, and rubber strength.

[0066] The method for modifying the diene polymer is not particularly limited, and the modification can be carried out similarly to the method for modifying the diene rubber mentioned above. For example, the modification can be carried out by bringing the diene polymer into contact with the compound. Specific examples thereof include a method in which, after producing a diene polymer (e.g., a butadiene polymer) by anionic polymerization, a predetermined amount of the compound is added to the resulting polymer solution to cause a reaction between the polymerizing end (active end) of the diene polymer and the compound.

[0067] The process for epoxidizing the diene polymer is not particularly limited. Examples include a chlorohydrin process, a direct oxidation process, a hydrogen peroxide process, an alkyl hydroperoxide process, and a peracid process (e.g., see JP H04-26617 B, JP H02-110182A, and GB 2113692 B). Examples of the peracid process include a process in which a diene polymer is reacted with an organic peracid, such as peracetic acid or performic acid.

[0068] The degree of epoxidation of the epoxidized diene polymer is preferably 25 mol% or less, more preferably 15 mol% or less, and most preferably 8 mol% or less. If the degree of epoxidation is more than 25 mol%, the Tg may be greatly increased, thereby failing to achieve adequate fuel economy. The lower limit of the degree of epoxidation is not particularly limited and is preferably 2 mol% or more.

[0069] In the present invention, the degree of epoxidation is the ratio (mol%) of the number of epoxidized double bonds to the total number of double bonds in the rubber before epoxidation. In the present invention, the degree of epoxidation is also a value measured according to the method described in the examples mentioned below.

[0070] The amount of the plasticizer (a) is 1 part by mass or more, and preferably 5 parts by mass or more, based on 100 parts by mass of the rubber component. If the amount is less than 1 part by mass, the effect of improving fuel economy cannot be sufficiently achieved. The amount is 30 parts by mass or less, and preferably 20 parts by mass or less, based on 100 parts by mass of the rubber component. If the amount is more than 30 parts by mass, the rigidity of the rubber composition tends to be greatly impaired, resulting in a decrease in driving stability. Furthermore, the adhesiveness tends to be too high, resulting in very poor productivity because the rubber composition sticks to the production equipment during its processing. In addition, bleeding tends to easily occur, resulting in a decrease in adhesiveness.

[0071] The glass transition points (Tg) of the resin and the plasticizer (b) are -40°C or higher, and preferably -30°C or higher. Those with a Tg lower than -40°C cause the plasticizer (a) and a material having properties similar to those of the plasticizer (a) to be combined. Therefore, it tends to be difficult to obtain the effects of the present invention resulting from the combined use of two components with different Tg values. The Tg is 20°C or lower, preferably 0°C or lower, and more preferably -10°C or lower. If the Tg is higher than 20°C, fuel economy tends to be poor.

[0072] The resin used is at least one resin selected from the group consisting of aromatic petroleum resins, terpene resins, and rosin resins. Aromatic petroleum resins are particularly preferred because they have a significant effect on improving rubber strength and contribute to a good balance between fuel economy, processability, adhesion, and rubber strength.

[0073] Aromatic petroleum resins are resins obtained by polymerizing the C9 aromatic fraction (carbon number: 9), which is generally obtained by pyrolysis of naphtha and contains vinyltoluene and indene as the main monomers. Other components of the aromatic fraction include styrene homologues, such as α-methylstyrene and β-methylstyrene. The aromatic petroleum resin may contain a coumarone unit. The aromatic petroleum resin is preferably a coumarone resin, α-methylstyrene resin, or coumarone-indene resin, and particularly preferably a coumarone-indene resin, in order to achieve good fuel economy, processability, adhesion, and rubber strength.

[0074] Examples of commercially available products of these resins include NOVARES C10 (RUTGERS Chemical) and Picco A-10 (Eastman Chemical Company).

[0075] Terpene resins refer to resins obtained by polymerizing terpene compounds contained in essential plant oils, which are generally obtained from leaves, trees, roots, and the like, as the main monomers. Terpene compounds are generally polymers of isoprene (C5H8), have basic terpene skeletons, and are called monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32 ) and the like. Examples include α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol, camphene, tricyclics, sabinene, paramenthadienes, and carenes.

[0076] Terpene resins include terpene resins whose raw material is the aforementioned terpene compound, such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, and β-pinene / limonene resin; as well as aromatic-modified terpene resins whose raw material is a mixture of the terpene compound and an aromatic compound; terpene-phenolic resins whose raw material is a mixture of the terpene compound and a phenolic compound; and hydrogenated terpene resins obtained by hydrogenating terpene resins. Examples of the aromatic compound used as raw material for the aromatic-modified terpene resins include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene.

[0077] Examples of the phenolic compound used as raw materials for terpene phenolic resins include phenol, bisphenol A, cresol, and xylenol. Each of these terpene resins can be used alone, or two or more of them can be used in admixture. The terpene resin is preferably a terpene resin or an aromatic-modified terpene resin. In view of achieving excellent fuel economy, it is particularly preferred to use one obtained from β-pinene as the main raw material.

[0078] Examples of commercially available products of these resins include YS Resin PX300, YS Resin PX300N, Dimerone and YS Polyster T30 (YASUHARA CHEMICAL CO., LTD.).

[0079] Various known rosins can be used as the rosin resin. Examples include: rosins such as raw rosins (e.g., gum rosin, wood rosin, and tall oil rosin), disproportionated products of raw rosins, stabilized rosins obtained by hydrogenating raw rosins, and polymerized rosins; esterified rosins (rosin ester resins); phenol-modified rosins; unsaturated acid (e.g., maleic acid)-modified rosins; and formylated rosins obtained by reducing rosins. In particular, polymerized rosins, phenol-modified rosins, unsaturated acid-modified rosins, and rosin ester resins are preferred, and rosin ester resins are especially preferred because they contribute to a good balance between fuel economy, processability, adhesiveness, and rubber strength.Rosin ester resins are produced by esterifying the aforementioned rosin and a polyol (polyhydric alcohol such as glycerin or pentaerythritol). The esterification can be carried out according to a known method, such as a method in which a rosin and a polyol are heated to 200°C to 300°C in an inert gas atmosphere, and any water formed is removed from the system. The rosin resin can be used in an emulsified form (as an emulsion) formed using a known emulsifier. For example, an emulsion of a stabilized rosin ester resin can be suitably used.

[0080] Examples of commercially available products of these resins include HARIESTER SK-501NS (Harima Chemicals, Inc.).

[0081] The plasticizer (b) is not particularly limited as long as it satisfies the above-mentioned range of Tg, and diene polymers having a weight-average molecular weight (Mw) of 3,000 to 150,000, for example, can be used. When using a diene polymer as the plasticizer (b), the epoxidation degree thereof is preferably 25 mol% or less. In the present invention, when the plasticizer (a) and / or (b) is a diene polymer, the weight-average molecular weight of the diene polymer is 150,000 or less.

[0082] The total amount of the resin and the plasticizer (b) is 1 part by mass or more, and preferably 5 parts by mass or more, based on 100 parts by mass of the rubber component. If the total amount is less than 1 part by mass, the effect of improving rubber strength cannot be sufficiently achieved. The total amount is 30 parts by mass or less, and preferably 20 parts by mass or less, based on 100 parts by mass of the rubber component. If the amount is more than 30 parts by mass, the rigidity of the rubber composition tends to be greatly impaired, resulting in a decrease in driving stability.

[0083] The total amount of the plasticizer (a), the resin, and the plasticizer (b) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, but preferably 50 parts by mass or less, and particularly preferably 35 parts by mass or less, based on 100 parts by mass of the rubber component. When the total amount is within the above range, fuel economy, processability, adhesion, rubber strength, and drivability stability are well achieved.

[0084] In the present invention, it is preferable to use silica. This results in excellent fuel economy. The silica is not particularly limited, and examples include dry silica (anhydrous silica) and wet silica (hydrous silica). Wet silica (hydrous silica) is preferred because it contains many silanol groups.

[0085] The specific surface area (N2SA) of the silica measured by nitrogen adsorption is preferably 50 m 2 / g or more and particularly preferably 100 m 2 / g or more. The N2SA is preferably 250 m 2 / g or less and particularly preferably 120 m 2 / g or less. When the N2SA is within the above range, the effects of the present invention are well achieved.

[0086] In the present invention, the N2SA of silica is a value measured by the BET method according to ASTM D 3037-81.

[0087] In the present invention, it is preferred to use a silica (1) having an N2SA of 50 m 2 / g or more, but less than 120 m 2 / g and a silica (2) with a N2SA of 120 m 2 / g or more in combination.

[0088] The N2SA of silica (1) is 50 m 2 / g or more and preferably 70 m 2 / g or more. If the N2SA is less than 50 m2 / g, adequate reinforcement tends not to be achieved, resulting in poor rubber strength and flexural fatigue resistance. The N2SA is less than 120 m 2 / g and is preferably 100 m 2 / g or less. If the N2SA 120 m 2 / g or more, the improvement effects of the blended silica cannot be achieved.

[0089] The N2SA of silica (2) is 120 m 2 / g or more, preferably 150 m 2 / g or more and particularly preferably 180 m 2 / g or more. If the N2SA is less than 120 m 2 / g, the improvement effects of the mixed silica cannot be achieved. The upper limit of the N2SA is not particularly limited and is preferably 250 m 2 / g or less and particularly preferably 220 m 2 / g or less. If the N2SA is more than 250 m 2 / g, the processability may be poor and the effects of the present invention may not be sufficiently achieved.

[0090] In the case that the silica (1) or the silica (2) independently consists of one or more kinds of silica, the N2SA of each of the silica (1) and the silica (2) is a value obtained by measuring a sample consisting of the corresponding total silica.

[0091] The silica (1) and the silica (2) preferably satisfy the relationship: (N2SA of the silica (2)) - (N2SA of the silica (1)) ≥ 40 m 2 / g and particularly preferably the relationship: (N2SA of silica (2)) - (N2SA of silica (1)) ≥ 100 m 2 / g. They also preferably fulfill the relationship: (N2SA of silica (2)) - (N2SA of silica (1)) ≤ 180 m 2 / g and particularly preferably the relationship: (N2SA of silica (2)) - (N2SA of silica (1)) ≤ 140 m 2 / g. Silicas that satisfy the above relationships can effectively improve the balance of the above performance characteristics.

[0092] The silica (1) and the silica (2) preferably satisfy the relationship: (N2SA of the silica (2)) / (N2SA of the silica (1)) ≥ 1.4, and more preferably the relationship: (N2SA of the silica (2)) / (N2SA of the silica (1)) ≥ 2.0. If this ratio is less than 1.4, the difference between the particle sizes of the silica (1) and the silica (2) is so small that a mixture thereof tends to have no effect on improving dispersibility.

[0093] The amount of silica (1) is preferably 1 part by mass or more, more preferably 10 parts by mass or more, but preferably 80 parts by mass or less, and particularly preferably 50 parts by mass or less, based on 100 parts by mass of the rubber component. When the amount is within the above range, fuel economy, processability, adhesiveness, and rubber strength are greatly improved.

[0094] The amount of silica (2) is preferably 1 part by mass or more, more preferably 10 parts by mass or more, but preferably 80 parts by mass or less, and particularly preferably 50 parts by mass or less, based on 100 parts by mass of the rubber component. When the amount is within the above range, fuel economy, processability, adhesiveness, and rubber strength are greatly improved.

[0095] The amounts of silica (1) and silica (2) preferably satisfy the following formula: (Amount of silica (1))×0.06≤(Amount of silica (2))≤(Amount of silica(1))×15.

[0096] If the amount of silica (2) is less than 0.06 times that of silica (1), adequate rubber strength tends not to be achieved. If the amount of silica (2) is more than 15 times that of silica (1), rolling resistance tends to be increased. The amount of silica (2) is more preferably 0.3 times or more, and particularly preferably 0.5 times or more, that of silica (1), while it is particularly preferably not more than 7 times, and particularly preferably not more than 4 times, that of silica (1).

[0097] The amount of silica (the total amount of silica (1) and silica (2) in the case of using silica (1) and silica (2) together) is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and most preferably 60 parts by mass or more, based on each 100 parts by mass of the rubber component. If the amount is less than 10 parts by mass, the effect of silica on reducing rolling resistance cannot be achieved. The amount is preferably 120 parts by mass or less, and more preferably 80 parts by mass or less, based on 100 parts by mass of the rubber component. If the amount is more than 120 parts by mass, the flexion fatigue resistance tends to be poor. In addition, the rubber stiffness tends to be so high that the damping effect required for tire components such as sidewalls tends to be poor, resulting in tires that provide inferior ride comfort.

[0098] The pneumatic tire according to the present invention is manufactured using a rubber composition, wherein the rubber composition preferably contains a silane coupling agent. Examples of the silane coupling agent include sulfide-type silane coupling agents, mercapto-type silane coupling agents, vinyl-type silane coupling agents, amino-type silane coupling agents, glycidoxy-type silane coupling agents, nitro-type silane coupling agents, and chlorine-type silane coupling agents. In particular, sulfide-type silane coupling agents such as bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, and bis(2-triethoxysilylethyl)disulfide are preferred, and bis(3-triethoxysilylpropyl)disulfide is particularly preferred.

[0099] The amount of the silane coupling agent is preferably 3 parts by mass or more, and more preferably 5 parts by mass or more, based on 100 parts by mass of silica. If the amount is less than 3 parts by mass, the coupling effect tends to be insufficient, so that high dispersion of the silica tends to be unattainable, resulting in a reduction in fuel economy and tensile strength. The amount is preferably 15 parts by mass or less, and more preferably 10 parts by mass or less, per 100 parts by mass of silica. If the amount is more than 15 parts by mass, an excess of the silane coupling agent may remain, resulting in a decrease in the processability and fracture properties of the resulting rubber composition.

[0100] The pneumatic tire according to the present invention is produced using a rubber composition, wherein the rubber composition preferably contains carbon black. The specific surface area (N2SA) of the carbon black, measured by nitrogen adsorption, is preferably 80 m 2 / g or more and particularly preferably 100 m 2 / g or more. If the N2SA is less than 80 m 2 / g, adequate amplification cannot be achieved. The N2SA is preferably 200 m 2 / g or less and particularly preferably 120 m 2 / g or less. If the N2SA is more than 200 m 2 / g, the dispersibility of the soot may be poor and adequate fuel economy may not be achieved.

[0101] The N2SA of carbon black is determined according to JIS K 6217-2:2001.

[0102] The amount of carbon black, based on 100 parts by mass of the rubber component, is preferably 1 part by mass or more, more preferably 3 parts by mass or more, but preferably 50 parts by mass or less, and particularly preferably 10 parts by mass or less. When the amount is within the above range, the aforementioned performance characteristics are well achieved.

[0103] In the case where the rubber composition contains carbon black and silica, the total amount of carbon black and silica is preferably 20 parts by mass or more, and more preferably 60 parts by mass or more, per 100 parts by mass of the rubber component. If the total amount is less than 20 parts by mass, adequate drivability and rubber strength cannot be achieved. The total amount is preferably 120 parts by mass or less, and more preferably 90 parts by mass or less, per 100 parts by mass of the rubber component. If the total amount is more than 120 parts by mass, adequate fuel economy and processability cannot be achieved.

[0104] In the case where the rubber composition contains carbon black and silica, the total content of silica based on 100 mass % of the total amount of silica and carbon black is preferably 50 mass % or more, and more preferably 80 mass % or more. When the total content is 50 mass % or more, the effects of the present invention are sufficiently achieved. Meanwhile, the total content is preferably 95 mass % or less.

[0105] In addition to the above-mentioned components, the rubber composition used in the present invention may contain compounding components generally used in the production of rubber compositions, such as stearic acid, various antioxidants, zinc oxide, vulcanizing agents such as sulfur, and vulcanization accelerators, as appropriate.

[0106] The rubber composition can be prepared by a conventional method. In other words, the rubber composition can be prepared, for example, by kneading the ingredients using a kneading device such as a Bunbury mixer, a kneader, or an open-roll mill, and then vulcanizing the kneaded mixture. The rubber composition can be used for various tire components, such as sidewalls, tread bases, clinch apices, belts, carcasses, inner liners, and insulators. In particular, the rubber composition is preferably used for treads and sidewalls, and particularly preferably for sidewalls.

[0107] The pneumatic tire according to the present invention can be manufactured using the rubber composition according to a conventional method. In other words, the rubber composition containing the components is extruded and processed into the shape of a tire component before vulcanization, and then assembled with other tire components in a tire building machine according to a conventional method to provide an unvulcanized tire. This unvulcanized tire is then subjected to heat pressurization in a vulcanizer to yield a tire.

[0108] Accordingly, the pneumatic tire according to the present invention can be used as a tire for passenger cars, trucks and buses, two-wheeled vehicles, racing cars, and the like; particularly, it is suitably used as a tire for passenger cars. EXAMPLES

[0109] The present invention will be described in detail with reference to, but not limited to, examples.

[0110] The chemicals used in Preparation Examples 1 to 8 are described below: Cyclohexane: Cyclohexane (KANTO CHEMICAL CO., INC.) 1,3-Butadiene: 1,3-Butadiene (Tokyo Chemical Industry Co., Ltd.) Styrene: Styrene (KANTO CHEMICAL CO., INC.) Tetramethylethylenediamine: Tetramethylethylenediamine (KANTO CHEMICAL CO., INC.) n-Butyllithium: 1.6 M solution of n-butyllithium in hexane (KANTO CHEMICAL CO., INC.) Modifying agent (1): 3-(N,N-Dimethylaminopropyl)trimethoxysilane (in the formula (1) R 1 , R 2 and R 3 = methoxy groups, R 4 and R 5 = methyl groups, n = 3, AZmax. co) Modifying agent (2): 3-(N,N-Dimethylaminopropyl)triethoxysilane (in formula (1) R 1 , R 2 and R3 = ethoxy groups, R 4 and R 5 = methyl groups, n = 3, AZmax. co) 2,6-tert-butyl-p-cresol: NOCRAC 200 (OUCHI SHINKO CHEMICAL INDUSTRIAL CO., LTD.) Neodymium 2-ethylhexanoate: Neodymium 2-ethylhexanoate (Wako Pure Chemical Industries, Ltd.) PMAO (Polymethylaluminoxane): PMAO (Al: 6.8% by mass, Tosoh Finechem Corporation) DIBAH solution: 1 M solution of diisobutylaluminum hydride in toluene (Tosoh Finechem Corporation) DEAC solution: 1 M solution of diethylaluminum chloride in hexane (Tosoh Finechem Corporation) TIBA solution: 1 M solution of triisobutylaluminum in hexane (Tosoh Finechem Corporation) (Production example 1)

[0111] A pressure-resistant container sufficiently purged with nitrogen was charged with cyclohexane (1500 mL), 1,3-butadiene (900 mmol), tetramethylethylenediamine (0.2 mmol), and n-butyllithium (0.12 mmol), and the contents were stirred at 40°C for 48 hours. A modifier (1) (0.12 mmol) was then added, and the reaction was terminated. Thereafter, 2,6-tert-butyl-p-cresol (1 g) was added to the reaction solution, and the resulting solution was purified by reprecipitation to yield a BR (2). (Production example 2)

[0112] A 50 mL glass container was purged with nitrogen. The container was charged with a solution of butadiene in cyclohexane (2.0 mol / L, 8 mL), a neodymium 2-ethylhexanoate / toluene solution (0.2 mol / L, 1 mL), and PMAO (8 mL), and the contents were stirred. After 5 minutes, a DIBAH solution (5 mL) was added, and after another 5 minutes, a DEAC solution (2 mL) was added to yield a catalyst solution (1).

[0113] A reactor (a 3-liter pressure-resistant stainless steel container) was purged with nitrogen. While maintaining the nitrogen atmosphere, the reactor was charged with cyclohexane (1,800 ml), butadiene (75 g), and a TIBA solution (1 ml), and then hermetically sealed. After stirring for 5 minutes, the catalyst solution (1) (1.5 ml) was added, and the mixture was stirred while maintaining the temperature at 30°C. After 3 hours, a modifier (2) (1 mmol) was added, and then a 2,6-tert-butyl-p-cresol / isopropanol solution (0.01 M, 10 ml) was added dropwise to the reactor to terminate the reaction. The reaction solution was cooled and added to separately prepared methanol (3 l). The resulting precipitate was air-dried overnight and then dried under vacuum for 2 days to yield BR (3). The yield was approximately 74.2 g. (Production example 3)

[0114] A pressure-resistant container sufficiently purged with nitrogen was charged with cyclohexane (1,500 mL), 1,3-butadiene (900 mmol), tetramethylethylenediamine (0.5 mmol), and n-butyllithium (0.5 mmol), and the contents were stirred at 40°C for 48 hours. Thereafter, 2,6-tert-butyl-p-cresol (1 g) was added to the reaction solution, and the resulting solution was purified by reprecipitation to yield a low-molecular-weight butadiene polymer (1). (Production example 4)

[0115] A pressure-resistant container sufficiently purged with nitrogen was charged with cyclohexane (1,500 mL), 1,3-butadiene (900 mmol), tetramethylethylenediamine (0.8 mmol), and n-butyllithium (0.8 mmol), and the contents were stirred at 70°C for 48 hours. Thereafter, 2,6-tert-butyl-p-cresol (1 g) was added to the reaction solution, and the resulting solution was purified by reprecipitation to yield a low-molecular-weight butadiene polymer (2). (Production example 5)

[0116] A pressure-resistant container sufficiently purged with nitrogen was charged with cyclohexane (1500 mL), 1,3-butadiene (900 mmol), tetramethylethylenediamine (0.5 mmol), and n-butyllithium (0.5 mmol), and the contents were stirred at 70°C for 48 hours. Then, a modifier (1) (0.5 mmol) was added, and the reaction was terminated. Thereafter, 2,6-tert-butyl-p-cresol (1 g) was added to the reaction solution, and the resulting solution was purified by reprecipitation to yield a low-molecular-weight butadiene polymer (3). (Production example 6)

[0117] A pressure-resistant container sufficiently purged with nitrogen was charged with n-hexane (1500 mL), styrene (10 g), 1,3-butadiene (92 g), tetramethylethylenediamine (0.25 mmol), and a solution of n-butyllithium in hexane (0.25 mmol), and the contents were stirred at 70°C for 48 hours. Then, a modifier (1) (0.25 mmol) was added, and the mixture was stirred for 30 minutes. Methanol (1 g) was added to the polymer solution to terminate the reaction. Thereafter, an oil (27 g) and 2,6-tert-butyl-p-cresol (1 g) were added to the reaction solution, and the mixture was dried under vacuum at 50°C for 24 hours to obtain a low-molecular-weight styrene-butadiene copolymer. (Production example 7)

[0118] In a 5-liter container equipped with a stirrer, a dropping funnel, and a condenser, the low-molecular-weight butadiene polymer (1) (300 g) synthesized in Preparation Example 3 was dissolved in toluene (3 l), and formic acid (4 g) was added thereto. Thereafter, an aqueous hydrogen peroxide solution (concentration: 30 mass%, 12 g) was added dropwise, and the reaction was continued with stirring at 40°C for 4 hours. After the reaction, an aqueous calcium carbonate solution was added to adjust the pH of the polymer solution to 7. The polymer solution was then added dropwise to ethanol. The precipitated polymer was separated and dried to obtain an epoxidized low-molecular-weight butadiene polymer (1). (Production example 8)

[0119] An epoxidized low molecular weight butadiene polymer (2) was obtained in the same manner as in Preparation Example 7, except that 60 g of an aqueous hydrogen peroxide solution (concentration: 30 mass%) was added dropwise.

[0120] The chemicals used in the examples and comparative examples are described below: No.: TSR20 (VAT: 1,000,000) BR (1): BR150B (unmodified, cis content: 97 mol%, Mw: 400,000, UBE INDUSTRIES, LTD.) BR (2): prepared in Preparation Example 1 (modified, Mw: 460,000, cis content: 40 mol%) BR (3): prepared in Preparation Example 2 (modified, Mw: 230,000, cis content: 99 mol%) Carbon black: N220 (DBP oil absorption: 115 ml / g, N2SA: 110 m 2 / g, Cabot Japan KK) Silica (1-1): ZEOSIL 1085GR (N2SA: 80 m 2 / g, Rhodia) Silica (1-2): ZEOSIL 115GR (N2SA: 110 m 2 / g, Rhodia) Silica (2-1): ZEOSIL 1165MP (N2SA: 160 m 2 / g, Rhodia) Silica (2-2): ZEOSIL 1205MP (N2SA: 200 m 2 / g, Rhodia) Silane coupling agent: Si75 (bis(3-triethoxysilylpropyl) disulfide, Degussa) Aromatic oil: PROCESS X-140 (Japan Energy Corporation) Ester plasticizer (1): Di(2-ethylhexyl) sebacate (Tg: -65°C, DAIHACHI CHEMICAL INDUSTRY CO., LTD.) Ester plasticizer (2): Di(2-ethylhexyl)adipate (Tg: -70°C, DAIHACHI CHEMICAL INDUSTRY CO., LTD.) Low molecular weight butadiene polymer (1): prepared in Preparation Example 3 (Tg: -72°C, Mw: 130,000, vinyl content: 34 mol%) Low molecular weight butadiene polymer (2): prepared in Preparation Example 4 (Tg: -74°C, Mw: 90,000, vinyl content: 34 mol%) Low molecular weight butadiene polymer (3): prepared in Preparation Example 5 (Tg: -68°C, Mw: 130,000, vinyl content: 34 mol%, modified) Low molecular weight butadiene polymer (4): Ricon 131 (Tg: -76°C, butadiene polymer, Mw: 5,000, vinyl content: 20 mol%, Sartomer) Low molecular weight styrene-butadiene copolymer: prepared in Preparation Example 6 (Tg: -52°C, Mw: 120,000, styrene component content: 10 mass%, vinyl content: 32 mol%, modified) Low molecular weight epoxidized butadiene polymer (1): prepared in Preparation Example 7 (Tg: -72°C, Mw: 130,000, vinyl content: 34 mol%, degree of epoxidation: 4 mol%) Low molecular weight epoxidized butadiene polymer (2): prepared in Preparation Example 8 (Tg: -62°C, Mw: 130,000, vinyl content: 34 mol%, degree of epoxidation: 24 mol%) Aromatic petroleum resin (1): NOVARES C10 (coumarone-indene resin, Tg: -30°C, RUTGERS Chemical) Aromatic petroleum resin (2): NOVARES C30 (coumarone indene resin, Tg: 10°C, RUTGERS Chemical) Aromatic petroleum resin (3): NOVARES C90 (coumarone indene resin, Tg: 90°C, RUTGERS Chemical) Terpene resin: Dimerone (terpene resin obtained from β-pinene as the main component, Tg: -38°C, YASUHARA CHEMICAL CO., LTD.) Rosin resin: HARIESTER SK-501NS (stabilized rosin ester emulsion, Tg: -33°C, Harima Chemicals, Inc.) Antioxidant: Santoflex 13 (Flexsys) Stearic acid: Stearic acid “TSUBAKI” (NOF Corporation) Zinc oxide: Zinc oxide #2 (MITSUI MINING & SMELTING CO., LTD.) Sulfur: Powdered sulfur (TSURUMI CHEMICAL INDUSTRY CO., LTD.) Vulcanization accelerator: NOCCELER NS (N-tert-butyl-2-benzothiazolylsulfenamide, OUCHI SHINKO CHEMICAL INDUSTRIAL CO., LTD.) The chemicals were analyzed as follows: (Measurement of the glass transition point (Tg))

[0121] The glass transition point (Tg) was a value measured at a temperature rise rate of 10°C / min using a differential scanning calorimeter (Q200, TA Instruments Japan Inc.) according to JIS K 7121. (Measurement of weight-average molecular weight Mw)

[0122] The weight-average molecular weight, Mw, of the sample was determined relative to polystyrene standards based on the value measured by gel permeation chromatography (GPC) (GPC-8000 series of TOSOH CORPORATION, detector: differential refractometer, column: TSKgel SuperMultipore HZ-M of TOSOH CORPORATION). (Measurement of the cis content of butadiene units)

[0123] The cis content of the double bonds in the butadiene units of the sample was measured using a JNM-ECA series NMR instrument (JEOL Ltd.). The measurement was performed as follows: a 1 g portion of the sample was dissolved in 15 ml of toluene, and the solution was slowly poured into 30 ml of methanol, purified, and dried. The thus treated sample was subjected to measurement. (Measurement of the content of the styrene component)

[0124] The styrene content was measured using a JNM-ECA series NMR instrument (JEOL Ltd.). (Measurement of the degree of epoxidation)

[0125] The low-molecular-weight epoxidized butadiene polymers (1) and (2) were each dissolved in deuterated chloroform. The ratio between the number of diene units before epoxidation and the number of epoxidized diene units was determined by nuclear magnetic resonance spectrometry (NMR) (JNM-ECA series from JEOL Ltd.), and the degree of epoxidation was calculated based on the following formula: (Degree of epoxidation E%) = (number of epoxy groups in the main chain of the polymer) / (number of diene units (including epoxidized units) in the main chain of the polymer) × 100. <Beispiele und Vergleichsbeispiele>

[0126] Based on the formulations shown in Tables 1 to 3, the chemicals except the sulfur and the vulcanization accelerator were kneaded for 4 minutes using a Bunbury mixer to obtain a kneaded mixture. Thereafter, the sulfur and the vulcanization accelerator were added to the kneaded mixture, and they were kneaded for 4 minutes using an open-roll mill to obtain an unvulcanized rubber composition. A portion of the obtained unvulcanized rubber composition was press-vulcanized at 170°C for 12 minutes to obtain a vulcanized rubber composition. Another portion of the unvulcanized rubber composition was molded into a sidewall, combined with other tire components in a tire building machine, and press-vulcanized at 170°C for 20 minutes to produce a test tire (tire size: 195 / 65R15).

[0127] The obtained unvulcanized rubber compositions, vulcanized rubber compositions, and test tires were evaluated as follows. Tables 1 to 3 show the results. (Processability)

[0128] The Mooney viscosity of the unvulcanized composition of each formulation was measured at 130°C according to JIS K 6300, and the value was converted into an index value based on the value in Comparative Example 1, which was considered to be 100. A larger index value indicates lower viscosity and easier processing. When the index value is 100 or higher, this performance property is good. (Processability index)=(Mooney viscosity in comparative example 1) / (Mooney viscosity of the respective formulation)×100 (adhesion)

[0129] The adhesion force [N] of the unvulcanized rubber composition of each formulation was measured using a PICMA tackifier (Toyo Seiki Seisaku-sho, Ltd.) under conditions of a measurement temperature of 23°C, a load of 4.9 N, a bonding time of 10 seconds, and a separation speed of 30 mm / min according to JIS T 9233. The adhesion index of the rubber composition in Comparative Example 1 was considered to be 100, and the adhesion force was converted into an index value based on the following formula. A higher adhesion index value indicates higher adhesion strength and better properties. When the index value is 105 to 130, this performance property is good. (Adhesion index) = (adhesion of the respective formulation) / (adhesion in comparison example 1) × 100 (Low heat generation)

[0130] The loss tangent (tan δ) of the vulcanized rubber sheet (vulcanized rubber composition) at 70°C was measured using a viscoelasticity spectrometer (manufactured by Iwamoto Seisakusho Co., Ltd.) under conditions of a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 2%. The low heat buildup index in Comparative Example 1 was considered to be 100, and the tan δ of each formulation was converted into an index value based on the following formula. A larger low heat buildup index value indicates lower heat buildup and better low heat buildup properties. When the index value is 100 or higher, this performance characteristic is good. (Low heat development index)=(tan δ in comparative example 1) / (tan δ of the respective formulation)×100 (Rubber strength)

[0131] A tensile test was conducted according to JIS K 6251, and the elongation at break was measured. The measurement result was expressed as an index value relative to the result of Comparative Example 1, which was considered to be 100. A larger index value indicates higher tensile strength. If the index value is 105 or higher, this performance property is good. (Rubber strength index)=(elongation at break of the respective formulation) / (elongation at break in comparative example 1)×100 (driving stability)

[0132] The test tyre was fitted on each wheel of a FF vehicle (front engine, front wheel drive) (2000 cm 3, made in Japan) was applied to the tire, and a test run was conducted on a test track. The handling stability was evaluated sensorially by a driver. The evaluation was based on a 10-point scale, and the handling stability of each formulation was rated relative to the handling stability of Comparative Example 1, which was rated as 6. A higher rating indicates better handling stability. If the rating is 6 or higher, this performance characteristic is good. In the examples in which predetermined amounts of the plasticizer (a) with a glass transition point within a specific range and the resin with a glass transition point within a specific range were used, fuel economy, processability, adhesion, and rubber strength were improved in a balanced manner, and drivability was also good. Particularly in the examples in which the modified BRs (2) and / or (3) were used, and in the examples in which two types of silica with different N2SA values ​​were used, the above performance characteristics were greatly improved.

Claims

[1] A pneumatic tire manufactured using a rubber composition containing the rubber composition: a rubber component, a plasticizer (a) and at least one of a resin and a plasticizer (b), wherein the resin is at least one selected from the group consisting of aromatic petroleum resins, terpene resins and rosin resins, wherein the plasticizer (a) has a glass transition point of -50°C or less, wherein the resin and the plasticizer (b) each have a glass transition point of -40°C to 20°C, and, wherein the rubber composition for a tire contains, based on 100 parts by mass of the rubber component, 1 to 30 parts by mass of the plasticizer (a) and a total of 1 to 30 parts by mass of at least one of the resin and the plasticizer (b), wherein the weight-average molecular weight (Mw) of the rubber component is 200,000 or more, and in the case that the plasticizer (a) and / or (b) is a diene polymer, the weight-average molecular weight of the diene polymer is 150,000 or less. [2] Pneumatic tyre according to claim 1, wherein the rubber composition contains, based on 100 parts by mass of the rubber component, 10 to 120 parts by mass of silica having a specific surface area of ​​50 m measured by nitrogen adsorption 2 / g or more and based on 100 mass% of the rubber component, contains 10 mass% or more of a modified diene rubber modified by a compound represented by the following formula (1): where R 1 , R 2 and R 3may be the same or different from each other and each represents an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group, a mercapto group or a derivative thereof, R 4 and R 5 may be the same or different and each represents a hydrogen atom or an alkyl group and n represents an integer. [3] Pneumatic tyre according to claim 2, wherein the silica is a silica (1) having a specific surface area measured by nitrogen adsorption of 50 m 2 / g or more, but less than 120 m 2 / g and a silica (2) with a specific surface area of ​​120 m measured by nitrogen adsorption 2 / g or more, and, wherein the total content of the silica (1) and the silica (2) is 10 to 120 parts by mass based on 100 parts by mass of the rubber component. [4] Pneumatic tyre according to claim 3, where the silica (1) and the silica (2) satisfy the following relationships: (specific surface area of ​​silica (2) measured by nitrogen adsorption) / (specific surface area of ​​silica (1) measured by nitrogen adsorption)≥1.4 and (Amount of silica (1))×0.06≤(Amount of silica (2))≤(Amount of silica (1))×15. [5] Pneumatic tyre according to claim 1, wherein the rubber composition contains a butadiene rubber having a cis double bond content of 50 mol% or less and a butadiene rubber having a cis double bond content of 95 mol% or more. [6] Pneumatic tyre according to claim 5, wherein the butadiene rubber having a cis double bond content of 95 mol% or more has been obtained by polymerization in the presence of a neodymium catalyst. [7] Pneumatic tyre according to claim 1, wherein at least one of the plasticizer (a) and the plasticizer (b) is a diene polymer having a weight-average molecular weight of 3,000 to 150,000. [8] Pneumatic tyre according to claim 1, wherein the plasticizer (a) is at least one of an ester plasticizer and a diene polymer having a weight-average molecular weight of 3,000 to 150,000 and a vinyl content of 35 mol% or less, and, wherein the diene polymer has been modified by a compound represented by the following formula (1): where R 1 , R 2 and R 3 may be the same or different from each other and each represents an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group, a mercapto group or a derivative thereof, R 4 and R 5may be the same or different and each represents a hydrogen atom or an alkyl group and n represents an integer. [9] Pneumatic tyre according to claim 1, wherein at least one of the plasticizer (a) and the plasticizer (b) is a diene polymer having an epoxidation degree of 25 mol% or less. [10] Use of a rubber composition for producing a pneumatic tire, the rubber composition comprising: a rubber component, a plasticizer (a) and at least one of a resin and a plasticizer (b), wherein the resin is at least one selected from the group consisting of aromatic petroleum resins, terpene resins and rosin resins, wherein the plasticizer (a) has a glass transition point of -50°C or less, wherein the resin and the plasticizer (b) each have a glass transition point of -40°C to 20°C, and, wherein the rubber composition for a tire contains, based on 100 parts by mass of the rubber component, 1 to 30 parts by mass of the plasticizer (a) and a total of 1 to 30 parts by mass of at least one of the resin and the plasticizer (b), wherein the weight-average molecular weight (Mw) of the rubber component is 200,000 or more, and in the case that the plasticizer (a) and / or (b) is a diene polymer, the weight-average molecular weight of the diene polymer is 150,000 or less. [11] Use of a rubber composition for producing a pneumatic tire according to claim 10, wherein the rubber composition is used in a sidewall.