JP2021095464A - Rubber composition for base tread and tire - Google Patents

Abstract

To provide a rubber composition for a base tread which is excellent in steering stability and rolling resistance when being applied to a tire, and can improve passage noise.SOLUTION: A rubber composition for a base tread, which is used for a base tread of a tread part of a tire, has a ratio (0°CE'/30°CE') of storage elastic modulus (0°CE') at 0°C to storage elastic modulus (30°CE') at 30°C in the range of 1.3 to 2.0.SELECTED DRAWING: None

Description

The present invention relates to a rubber composition for a base tread and a tire.

From the viewpoint of improving the fuel efficiency of the vehicle (to reduce the fuel efficiency), a technique for optimizing the rubber member (base tread) constituting the base portion of the tread of the tire is known.
For example, Patent Document 1 discloses a technique for applying a rubber composition having improved low heat generation (with low tan δ) to a base tread by adjusting a rubber component and a filler.

However, when the tan δ (tangent loss) of the rubber composition is kept low as in the base tread disclosed in Patent Document 1, the rolling resistance can be improved and the fuel efficiency can be improved, but the tire when passing through the vehicle. There was a problem that the noise generated from the tire (passing noise) was aggravated. It was also considered that when the tan δ of the rubber composition was kept low, the rigidity of the rubber was lowered and the steering stability when applied to the tire was deteriorated.
Therefore, it has been desired to develop a base tread that is excellent in steering stability and rolling resistance and can also improve passing noise.

Japanese Unexamined Patent Publication No. 2016-6135

Therefore, an object of the present invention is to provide a rubber composition for a base tread which is excellent in steering stability and rolling resistance when applied to a tire and can improve passing noise. Another object of the present invention is to provide a tire which is excellent in steering stability and rolling resistance and has improved passing noise.

As a result of studying to achieve both reduction of rolling resistance and improvement of passing noise when applied to a tire, the present inventor paid attention to the relationship between tire vibration and a rubber factor that affect passing noise. As a result of further diligent research, the ratio of 0 ° C. E'to 30 ° C. E'was within a certain range (specifically, 0 ° C. E'/ 30 ° C. E'was set to 1.3 to 2.0. ) By setting, it is possible to increase the high frequency tan δ that affects the passing noise while maintaining the tire rigidity, and when the rubber composition is applied to the tire, excellent steering stability and rolling resistance can be obtained. It was found that it can be realized and the passing noise can be improved.

The gist structure of the present invention for solving the above problems is as follows.
A rubber composition for base tread used for the base tread of the tread portion of a tire, which is a ratio (0 ° C. E') of a storage elastic modulus (0 ° C. E') at 0 ° C. to a storage elastic modulus (30 ° C. E') at 30 ° C. E'/ 30 ° C. E') is in the range of 1.3 to 2.0.
By providing the above configuration, it is possible to improve steering stability, rolling resistance and passing noise when applied to a tire.

Further, in the rubber composition for base tread of the present invention, the 0 ° C.E'/ 30 ° C.E'is preferably in the range of 1.3 to 1.8, preferably in the range of 1.4 to 1.6. More preferably. This is because the steering stability and rolling resistance when applied to tires and the improvement of passing noise can be achieved at a higher level.

Further, in the rubber composition for base tread of the present invention, the 0 ° C.E'is preferably 15 MPa or less. This is because it is possible to more reliably improve the passing noise when applied to a tire.

Furthermore, in the rubber composition for base tread of the present invention, the 30 ° C.E'is preferably 10 MPa or less. This is because it is possible to more reliably improve steering stability and rolling resistance when applied to tires.

Further, in the rubber composition for base tread of the present invention, the tan δ (0 ° C. tan δ) at 0 ° C. of the rubber composition for base tread is preferably 0.35 or more. This is because it is possible to more reliably improve the passing noise when applied to a tire.

Further, in the rubber composition for base tread of the present invention, the tan δ (30 ° C. tan δ) at 30 ° C. of the rubber composition for base tread is preferably 0.2 or less. This is because it is possible to more reliably improve steering stability and rolling resistance when applied to tires.

Furthermore, the rubber composition for a base tread of the present invention contains a rubber component containing 70% by mass or more of natural rubber, a filler, and a resin of 20% by mass or more with respect to 100 parts by mass of the rubber component. Is preferable. This is because it is possible to more reliably improve steering stability, rolling resistance and passing noise when applied to tires.

The tire of the present invention is characterized in that the rubber composition for a base tread of the present invention described above is used for the base tread of the tread portion.
By providing the above configuration, steering stability and rolling resistance are excellent, and passing noise is also improved.

According to the present invention, it is possible to provide a rubber composition for a base tread which is excellent in steering stability and rolling resistance when applied to a tire and can improve passing noise. Further, according to the present invention, it is possible to provide a tire which is excellent in steering stability and rolling resistance and has improved passing noise.

Hereinafter, the rubber composition for base tread and the tire of the present invention will be described in detail based on the embodiments thereof.
<Rubber composition for base tread>
The rubber composition for base tread of the present invention is a rubber composition for base tread used for the base tread of the tread portion of a tire.
In the rubber composition for base tread of the present invention, the ratio (0 ° C.E'/ 30 ° C.E') of the storage elastic modulus (0 ° C.E') at 0 ° C. to the storage elastic modulus (30 ° C.E') at 30 ° C. ) Is in the range of 1.3 to 2.0.

Examining the rolling resistance of tires, if the rolling resistance of the tire is reduced, the rolling resistance of the tire can be improved, but there is a problem that the passing noise level deteriorates. On the other hand, if the tan δ is increased, the passing noise level is increased. Although it can be suppressed, there is a problem that rolling resistance deteriorates.
On the other hand, with respect to the storage elastic modulus E', although the rolling resistance and steering stability are improved when the storage elastic modulus is increased, the passing noise tends to be deteriorated as the rigidity is increased. Therefore, in the present invention, a technique for increasing only the high-frequency tan δ without increasing the rigidity too much is studied, and attention is paid to the non-linearity of the temperature dispersion of the storage elastic modulus E'.
As a result, in the rubber composition for base tread of the present invention, the ratio (0 ° C. E'/ 30 ° C. E') of the storage elastic modulus (0 ° C. E') at 0 ° C. to the storage elastic modulus (30 ° C. E') at 30 ° C. By setting') to 1.3 to 2.0, it is possible to lower the low frequency tan δ, suppress the decrease in the storage elastic modulus E', and further increase the high frequency tan δ. Therefore, when applied to a tire, it is possible to improve steering stability and rolling resistance, and to improve passing noise.

As described above, in the rubber composition for base tread of the present invention, the 0 ° C.E'/ 30 ° C.E'needs to be 1.3 to 2.0 or more, but the 0 ° C.E'/ 30 When ° C. E'is less than 1.3, tan δ at low temperature cannot be increased (tan δ at high frequency cannot be increased), so that the passing noise can be sufficiently reduced when applied to a tire. I can't plan. On the other hand, when the 0 ° C.E'/ 30 ° C.E'exceeds 2.0, the E'at high temperature becomes small, so that sufficient steering stability and reinforcement when applied to tires should be ensured. I can't.
From the same viewpoint, the 0 ° C.E'/ 30 ° C.E'is preferably 1.3 to 1.8, and more preferably 1.4 to 1.6.

The 0 ° C.E'and the 30 ° C.E'in the present invention are the storage elastic moduli of 0 ° C. and the storage elastic modulus of 30 ° C. after vulcanization of the rubber composition for base tread of the present invention. That is.
Regarding the measurement of 0 ° C.E'and 30 ° C.E', for example, E'at 0 ° C. and 30 ° C. can be measured using a spectrometer manufactured by Ueshima Seisakusho Co., Ltd., and the respective E'values. The method is not particularly limited as long as it can be obtained accurately, and can be obtained by using a known measuring instrument.
Further, as the conditions of the initial input, the dynamic distortion, and the frequency in the measurement of the 0 ° C. tan δ and the 30 ° C. tan δ, for example, the conditions of the initial input of 150 μm, the frequency of 52 Hz, and the dynamic strain of 1% can be mentioned.

Further, the value of the storage elastic modulus (0 ° C. E') at 0 ° C. of the rubber composition for base tread of the present invention is particularly limited as long as the above-mentioned relationship of 0 ° C. E'/ 30 ° C. E'can be satisfied. However, from the viewpoint of further improving the effect of improving passing noise when applied to a tire, it is preferably 15 MPa or less, and more preferably 10 MPa or less. From the viewpoint of not deteriorating steering stability and rolling resistance when applied to tires, it is preferable that the 0 ° C.E'is 5 MPa or more.

Further, the value of the storage elastic modulus (30 ° C.E') at 30 ° C. of the rubber composition for base tread of the present invention is particularly limited as long as the above-mentioned relationship of 0 ° C.E'/ 30 ° C.E'can be satisfied. However, from the viewpoint of further improving the effect of improving passing noise when applied to a tire, it is preferably 10 MPa or less, and more preferably 5 MPa or less. From the viewpoint of not deteriorating steering stability and rolling resistance when applied to tires, it is preferable that the temperature of 30 ° C. E'is 3 MPa or more.

The method for adjusting the value of 0 ° C.E'/ 30 ° C.E'within a predetermined range is not particularly limited. For example, it is possible to optimize the constituent components of the rubber composition for base tread of the present invention. As will be described later, by limiting the type and content of the rubber component and adjusting the type and content of the filler, the value of 0 ° C.E'/ 30 ° C.E'is within the scope of the present invention (1. It is possible to set it to 3 to 2.0).

Further, the rubber composition for a base tread of the present invention has a tan δ (0 ° C. tan δ) of 0 ° C. of 0.35 or more from the viewpoint of further enhancing the effect of suppressing passing noise when applied to a tire. It is preferable to have. From the same viewpoint, the 0 ° C. tan δ is more preferably 0.4 or more.

Further, the rubber composition for a base tread of the present invention has a tan δ (30 ° C. tan δ) of 30 ° C. of 0.2 or less from the viewpoint of further improving steering stability and rolling resistance when applied to a tire. Is preferable. From the same viewpoint, the 0 ° C. tan δ is more preferably 0.15 or less.

The 0 ° C. tan δ and the 30 ° C. tan δ are 0 ° C. tan δ and 30 ° C. tan δ after the rubber composition for base tread of the present invention is vulcanized.
Regarding the measurement of the 0 ° C. tan δ and the 30 ° C. tan δ, for example, the 0 ° C. tan δ and the 30 ° C. tan δ can be measured using a spectrometer manufactured by Ueshima Seisakusho Co., Ltd., but the respective tan δ values are accurate. The method is not particularly limited as long as it can be obtained by using a commonly used measuring instrument.
Further, as the conditions of the initial input, the dynamic distortion, and the frequency in the measurement of the 0 ° C. tan δ and the 30 ° C. tan δ, for example, the conditions of the initial input of 150 μm, the frequency of 52 Hz, and the dynamic strain of 1% can be mentioned.

The components constituting the rubber composition for base tread of the present invention are not particularly limited as long as they can satisfy the above-mentioned relationship of 0 ° C.E'/ 30 ° C.E'.
The type and content of the rubber component and filler can be appropriately adjusted according to the performance required for the base tread.

The rubber composition for a base tread of the present invention easily satisfies the above-mentioned relationship of 0 ° C.E'/ 30 ° C.E', and improves steering stability and rolling resistance and passing noise when applied to a tire. From the viewpoint that the level can be more reliably compatible with each other, a rubber component containing natural rubber, a filler, and a resin can be contained.

The rubber component of the rubber composition for base tread of the present invention preferably contains at least natural rubber (NR). This is because it is easy to satisfy the above-mentioned relationship of 0 ° C.E'/ 30 ° C.E', and excellent passing noise improvement performance can be obtained while maintaining good rolling resistance and steering stability.
Here, the content of the natural rubber in the rubber component is not particularly limited, but when applied to a tire, both steering stability and rolling resistance and improvement of passing noise are compatible at a higher level. From the point of view, it is preferably 70% by mass or more, preferably 75% by mass or more, more preferably 80% by mass or more, and particularly preferably 85% by mass or more.

Further, the rubber component may further contain styrene-butadiene rubber (SBR) and / or butadiene rubber (BR) in addition to the natural rubber. It is preferable in that the tan δ in the high frequency region can be increased and the effect of improving the passing noise when applied to the tire can be further improved.
The total content of the styrene-butadiene rubber and / or the butadiene rubber in the rubber component is not particularly limited, but is preferably smaller than that of the natural rubber, and specifically, 5 to 30% by mass. Is more preferable, and 10 to 20% by mass is more preferable.

The rubber component may be unmodified or modified.
Further, the rubber component may include rubbers other than the above-mentioned NR, SBR and BR (other rubber components) depending on the required performance. Examples of the other rubber components include diene rubbers such as isoprene rubber (IR), styrene isoprene butadiene rubber (SIBR), chloroprene rubber (CR), and acrylonitrile butadiene rubber (NBR), ethylene propylene diene rubber (EPDM), and ethylene. Examples thereof include non-diene rubbers such as propylene rubber (EPM) and butyl rubber (IIR).

Further, the type and content of the inorganic filler contained in the rubber composition for base tread of the present invention are not particularly limited and can be appropriately changed according to the required performance.
For example, the inorganic filler may include carbon black, silica, other inorganic fillers, and the like. Among these fillers, it is preferable that the filler contains carbon black from the viewpoint of obtaining more excellent reinforcing property and wear resistance.

As for the carbon black is preferably a nitrogen adsorption specific surface area _(N 2 SA) is 20 to 80 m ² / g, but more preferably of 40 to 60 ² / g. Since the structure of carbon black can be further optimized, it is possible to further improve the reinforcing property while reducing the rolling resistance.
The nitrogen adsorption specific surface area can be measured by a single-point method in accordance with ISO4652-1. For example, after immersing degassed carbon black in liquid nitrogen, it is adsorbed on the surface of carbon black at equilibrium. ^{The specific surface area (m 2} / g) can be calculated from the measured value by measuring the amount of nitrogen produced.

The content of the carbon black contained in the rubber composition for base tread of the present invention is preferably 25 to 65 parts by mass, preferably 30 to 45 parts by mass with respect to 100 parts by mass of the rubber component. More preferably. By setting the content of the carbon black to 25 parts by mass or more with respect to 100 parts by mass of the rubber component, higher reinforcing properties and cracking resistance can be obtained, and by setting it to 65 parts by mass or less. , It is possible to suppress the deterioration of rolling resistance when applied to tires.

Further, the inorganic filler may include silica and other inorganic fillers.
Examples of the type of silica include wet silica, colloidal silica, calcium silicate, aluminum silicate and the like.

The rubber composition of the present invention may also contain a resin from the viewpoint of further improving the effect of improving passing noise.
Examples of the resin include petroleum hydrocarbon resins, dicyclopentadiene resins, rosin resins, alkylphenol resins, and resins that are hydrogenated thereof. These resins may be used alone. It can be used in combination of more than one species. Further, among these resins, C ₅ resins, C ₅ -C ₉ resins, it is preferable to use at least one of a C ₉ resins and their hydrogenated products.

Wherein A C ₅ resins, refers to C ₅ type synthetic petroleum hydrocarbon resins, examples of the C ₅ resin, for example, a C ₅ fraction obtained by thermal cracking of petroleum chemical industry naphtha, AlCl _3, aliphatic petroleum resins obtained by polymerizing using a Friedel-Crafts catalyst BF _3, and the like. The _C in ₅ fractions, typically, 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, 3-methyl-1-olefin hydrocarbons butene, 2- Diolefin hydrocarbons such as methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene and 3-methyl-1,2-butadiene are included. Incidentally, examples of the C ₅ resin may be commercially available products, for example, an ExxonMobil Chemical Co. aliphatic petroleum resin "Escorez (registered trademark) 1000 Series", Nippon Zeon Co., Ltd. aliphatic Among the "Quinton (registered trademark) 100 series" which are petroleum resins, "A100, B170, M100, R100", "T-REZ RA100" manufactured by Tonen Chemical Corporation and the like can be mentioned.

Wherein A _C 5 -C _{9 resins,} refers to C 5 -C ₉ based synthetic petroleum hydrocarbon resins, and examples of the _C 5 -C ₉ resins, for example, _{C 5} fraction and _{C 9} fraction of petroleum Examples _{thereof include solid polymers obtained by polymerizing fractions using a Friedelcraft type catalyst such as AlCl 3} , BF ₃ , and more specifically, styrene, vinyltoluene, α-methylstyrene, inden and the like. Examples thereof include a copolymer as a main component. As the C ₅ -C ₉ resins, less resin of C ₉ or more components is preferable from the viewpoint of compatibility with the rubber component. Here, " _{there are few components of C 9 or more" means that the components of C 9} or more in the total amount of the resin are less than 50% by mass, preferably 40% by mass or less. Examples of the _C 5 -C ₉ resins, it is possible to use a commercially available product, for example, trade name "Quinton (registered trademark) G100B" (manufactured by Nippon Zeon Co., Ltd.), trade name "ECR213" (ExxonMobil Chemical Company ), Product name "T-REZ RD104" (manufactured by Tonen Chemical Corporation) and the like.

The C _9- based resin is a synthetic petrochemical hydrocarbon resin, for example, vinyl toluene, which is _{a C 9} fraction produced as a by-product together with basic petrochemical raw materials such as ethylene and propylene by thermal decomposition of naphtha in the petrochemical industry. , Alkylstyrene, and inden are the main monomers, and it is a resin obtained by polymerizing an aromatic having 9 carbon atoms. Here, specific examples of the C ₉ fraction obtained by thermal decomposition of naphtha, vinyl toluene, alpha-methyl styrene, beta-methyl styrene, .gamma.-methyl styrene, o- methyl styrene, p- methyl styrene, indene and the like Can be mentioned. The C _9- based resin, _{together with the C 9} fraction, is a C ₈ fraction such as styrene, a C ₁₀ fraction such as methyl indene, 1,3-dimethyl styrene, etc., and further, naphthalene, vinyl naphthalene, vinyl anthracene, p. -Tert-Butylstyrene or the like is also used as a raw material, and these C _{8 to} C ₁₀ fractions and the like can be obtained as a mixture by copolymerization with, for example, a Friedelcraft type catalyst. Also, the C ₉ resin, a compound having a hydroxy group may be a modified modified petroleum resin with an unsaturated carboxylic acid compound or the like. Incidentally, examples of the C ₉ resins, can be utilized commercially, for example, the unmodified C ₉ petroleum resin, trade name "Nisseki Neo Polymer (registered trademark) L-90", "Nisseki Examples thereof include "Neopolymer (registered trademark) 120", "Nippon Oil Neopolymer (registered trademark) 130", and "Nippon Oil Neopolymer (registered trademark) 140" (manufactured by JX Nippon Oil Energy Co., Ltd.).

The dicyclopentadiene resin is a petroleum resin produced by using dicyclopentadiene as a main raw material, which is obtained by dimerizing cyclopentadiene. As the dicyclopentadiene resin, a commercially available product can be used. For example, among the trade names "Quinton (registered trademark) 1000 series", which is an alicyclic petroleum resin manufactured by Nippon Zeon Corporation, "1105, 1325, 1340 ”and the like.

The terpene phenol resin can be obtained, for example, by reacting terpenes with various phenols using a Friedel-Crafts type catalyst, or by further condensing with formalin. The raw material terpenes are not particularly limited, and monoterpene hydrocarbons such as α-pinene and limonene are preferable, those containing α-pinene are more preferable, and α-pinene is particularly preferable. Commercially available products can be used as the terpenphenol resin, for example, trade names "Tamanol 803L", "Tamanol 901" (manufactured by Arakawa Chemical Industry Co., Ltd.), and trade name "YS Polystar (registered trademark) U" series. , "YS Polystar (registered trademark) T" series, "YS Polystar (registered trademark) S" series, "YS Polystar (registered trademark) G" series, "YS Polystar (registered trademark) N" series, "YS Polystar (registered trademark) N" series Examples include the "K" series and the "YS Polystar (registered trademark) TH" series (manufactured by Yasuhara Chemical Co., Ltd.).

The terpene resin is a turpentine oil obtained at the same time as obtaining rosin from a pine tree, or a solid resin obtained by blending a polymerization component separated from the turpentine and polymerizing using a Friedelcrafts type catalyst. Yes, β-pinene resin, α-pinene resin and the like can be mentioned. Commercially available products can be used as the terpene resin. For example, the product name "YS resin" series (PX-1250, TR-105, etc.) manufactured by Yasuhara Chemical Co., Ltd. and the product name "Picolite" series manufactured by Hercules Co., Ltd. (A115, S115, etc.) and the like.

The rosin resin is a residue remaining after collecting balsams such as pine fat (pine yani), which is the sap of Pinaceae plants, and distilling terepine essential oil. Natural resins as the main component, modified resins obtained by modifying them, and processing them by hydrogenation, etc., and hydrogenated resins. Examples thereof include natural resin rosins, their polymerized rosins and partially hydrogenated rosins; glycerin ester rosins, their partially hydrogenated rosins and fully hydrogenated rosins and polymerized rosins; pentaerythritol ester rosins, their partially hydrogenated rosins and polymerized rosins. .. Examples of natural resin rosin include raw pine tar, gum rosin contained in tall oil, tall oil rosin, and wood rosin. As the rosin resin, a commercially available product can be used, for example, the product name "Neotol 105" (manufactured by Harima Kasei Co., Ltd.), the product name "SN Tuck 754" (manufactured by Sannopco Co., Ltd.), and the product name "Lime Resin". No. 1 ”,“ Pencel A ”and“ Pencel AD ”(manufactured by Arakawa Chemical Industry Co., Ltd.), product names“ Polypale ”and“ Pentalin C ”(manufactured by Eastman Chemical Co., Ltd.), product name“ Hyrosin (registered trademark) "S" (manufactured by Taisha Matsu Seiyu Co., Ltd.) and the like.

The alkylphenol resin is obtained, for example, by a condensation reaction of alkylphenol and formaldehyde under a catalyst. Commercially available products can be used as the alkylphenol resin. For example, the product name "Hitanol 1502P" (alkylphenol formaldehyde resin, manufactured by Hitachi Kasei Co., Ltd.) and the product name "Tackiroll 201" (alkylphenol formaldehyde resin, Taoka Chemical Industry Co., Ltd.) can be used. (Company), Product name "Tackiroll 250-I" (brominated alkylphenol formaldehyde resin, manufactured by Taoka Chemical Industry Co., Ltd.), Product name "Tackiroll 250-III" (brominated alkylphenol formaldehyde resin, manufactured by Taoka Chemical Industry Co., Ltd.), Product names such as "R7521P", "SP1068", "R7510PJ", "R7572P" and "R7578P" (manufactured by SI GROUP INC.) Can be mentioned.

Further, the hydrogenated resin such as the C5 resin and the C9 resin is a resin in which unsaturated bonds in the molecule are partially or completely hydrogenated (hereinafter, also referred to as “hydrogenated resin”). .).

Further, the content of the resin in the rubber composition of the present invention is 20 parts by mass with respect to 100 parts by mass of the rubber component in order to increase tan δ in the high frequency region and enhance the effect of reducing passing noise when applied to a tire. It is preferably more than 40 parts by mass, and more preferably 40 parts by mass or less. This is because it is possible to suppress a decrease in reinforcing property and a deterioration in low heat generation, and to maintain good crack resistance and rolling resistance when applied to a tire.

The rubber composition for a base tread of the present invention may contain other components in addition to the above-mentioned rubber components and fillers to the extent that the effects of the present invention are not impaired.
Other components are commonly used in the rubber industry, such as silane coupling agents, softeners, stearic acid, anti-aging agents, vulcanizing agents (sulfur), vulcanization accelerators, vulcanization accelerators, etc. Additives may be included as appropriate.

When the rubber composition for base tread of the present invention contains silica as the filler, it is preferable to further contain a silane coupling agent. This is because the effects of reinforcing property and low heat generation by silica can be further improved. As the silane coupling agent, known ones can be appropriately used.

As the anti-aging agent, known ones can be used and are not particularly limited. For example, a phenol-based anti-aging agent, an imidazole-based anti-aging agent, an amine-based anti-aging agent, and the like can be mentioned. These anti-aging agents may be used alone or in combination of two or more.

As the vulcanization accelerator, known ones can be used and are not particularly limited. For example, thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole and dibenzothiadyl disulfide; N-cyclohexyl-2-benzothiadylsulfeneamide, Nt-butyl-2-benzothiadylsulfenamide and the like. Sulfenamide-based vulcanization accelerator; guanidine-based vulcanization accelerator such as diphenylguanidine (1,3-diphenylguanidine, etc.); tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetradodecyltiuram disulfide, tetraoctyl Thiuram-based vulcanization accelerators such as thiuram disulfide, tetrabenzyl thiuram disulfide, dipentamethylene thiuram tetrasulfide; dithiocarbamate-based vulcanization accelerators such as zinc dimethyldithiocarbamate; zinc dialkyldithiophosphate and the like can be mentioned.

Examples of the vulcanization accelerating aid include zinc oxide (ZnO) and fatty acids. The fatty acid may be a saturated or unsaturated, linear or branched fatty acid, and the number of carbon atoms of the fatty acid is not particularly limited, but for example, a fatty acid having 1 to 30 carbon atoms, preferably 15 to 30 carbon atoms. More specifically, cyclohexaneic acid (cyclohexanecarboxylic acid), naphthenic acid such as alkylcyclopentane having a side chain; hexanic acid, octanoic acid, decanoic acid (including branched carboxylic acid such as neodecanoic acid), dodecanoic acid, tetradecane. Saturated fatty acids such as acids, hexadecanoic acid and octadecanoic acid (stearic acid); unsaturated fatty acids such as methacrylic acid, oleic acid, linoleic acid and linolenic acid; resin acids such as rosin, tall oil acid and avietic acid. These may be used alone or in combination of two or more. In the present invention, zinc oxide and stearic acid can be preferably used.

<Tire>
The tire of the present invention is characterized in that the rubber composition for a base tread of the present invention described above is used for the base tread of the tread portion.
By using the rubber composition for base tread of the present invention as the base tread, it is possible to improve steering stability and rolling resistance, and it is also possible to improve passing noise.

The structure of the cap tread formed on the base tread in the tread portion of the tire of the present invention is not particularly limited. Depending on the performance required of the tire, a cap tread with suitable conditions can be used.
The rubber composition constituting the cap tread can contain, for example, a rubber component, a reinforcing filler, a softener, and an additive commonly used in the rubber industry.

Further, the tire of the present invention may be vulcanized after being molded using an unvulcanized rubber composition, depending on the type of tire to be applied, and may be molded using a semi-vulcanized rubber that has undergone a preliminary vulcanization step or the like. After that, it may be further vulcanized for production.
Further, the tire of the present invention is preferably a pneumatic tire, and the gas to be filled in the pneumatic tire is an inert gas such as nitrogen, argon, helium, etc., in addition to normal or oxygen-participated air. Gas can be used.

Although the tire of the present invention can be used as a tire for various vehicles, it is preferably used as a tire for passenger cars and a tire for trucks and buses. This is because the benefits of reducing rolling resistance and improving passing noise can be further enjoyed.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

<Examples 1 to 3 and Comparative Examples 1 to 2>
A sample rubber composition for base tread was prepared using a normal Banbury mixer according to the formulation shown in Table 1. The blending amount of each component in Table 1 is the amount (parts by mass) with respect to 100 parts by mass of the rubber component.
Further, the obtained rubber composition for base tread was vulcanized at 145 ° C. for 33 minutes, and the obtained vulcanized rubber was subjected to an initial input of 150 μm using a spectrometer manufactured by Ueshima Seisakusho Co., Ltd. Loss vulcanization (tan δ) and storage elastic modulus (E') at 0 ° C. and 30 ° C. were measured at a frequency of 52 Hz and a dynamic strain of 1%. The measured tan δ and E'at 0 ° C and 30 ° C are shown in Table 1.

<Evaluation>
Regarding the obtained sample of the rubber composition for base tread, the sample of Comparative Example 1 was used for the base tread of the tread portion to prepare a sample of a pneumatic radial tire for a passenger car having a size of 205 / 60R16. The tires of the prepared samples were evaluated by the following methods. The results are shown in Table 1.

(1) Rolling resistance The rolling resistance coefficient (RRC) of the tire of Comparative Example 1 was measured in accordance with the international standard (ECE R117). Examples 1 to 3 and Comparative Example 2 were estimated based on the measured rubber physical characteristics and the measurement results of the tire of Comparative Example 1.
The evaluation was expressed as an index when the reciprocal of the estimated RRC was taken and the reciprocal of the RRC of the tire using the sample of Comparative Example 1 was set to 100. The larger the index value, the better the rolling resistance (the rolling resistance is reduced), and if it is 90 or more, it is judged to be good. The evaluation results are shown in Table 1.

(2) Passing noise level The passing noise (dB) of the tire of Comparative Example 1 was measured in accordance with the international standard (ECE R117). Examples 1 to 3 and Comparative Example 2 were estimated based on the measured rubber physical characteristics and the measurement results of the tire of Comparative Example 1.
For the evaluation, the difference in noise level from the passing noise (dB) of Comparative Example 1 was calculated and used as the passing noise level. The smaller the passing noise level, the more the passing noise is reduced, and 110 or less is considered good. The evaluation results are shown in Table 1.
(3) Steering stability The tires of Comparative Example 1 were mounted on the test vehicle, and the steering stability was expressed by the driver's feeling score in the actual vehicle test on a dry road surface. Examples 1 to 3 and Comparative Example 2 were estimated based on the measured rubber physical characteristics and the measurement results of the tire of Comparative Example 1.
Regarding the evaluation, the rubber composition of Comparative Example 1 was also used, and the feeling score of the other tire was displayed as 100. The larger the score value, the better the steering stability.

＊１ ＲＳＳ ＃３
＊２ ＪＳＲ株式会社製「ＢＲ０１」
＊３ ＪＳＲ株式会社製「ＳＬ５２０」、スチレン量：３５質量％
＊４ ＪＸＴＧ株式会社製「スーパーオイル Ｙ２２」
＊５ 脂肪族系炭化水素樹脂、日本ゼオン株式会社製「Ｑｕｉｎｔｏｎｅ Ｇ１００」
＊６ 石油系炭化水素樹脂
＊７ 変性フェノール樹脂、住友ベークライト株式会社製「ＰＲ−１３３４９」
＊８ 東海カーボン株式会社製「シーストＦ」

* 1 RSS # 3
* 2 "BR01" manufactured by JSR Corporation
* 3 "SL520" manufactured by JSR Corporation, styrene amount: 35% by mass
* 4 "Super Oil Y22" manufactured by JXTG Co., Ltd.
* 5 Aliphatic hydrocarbon resin, "Quintone G100" manufactured by Zeon Corporation
* 6 Petroleum-based hydrocarbon resin * 7 Modified phenol resin, "PR-13349" manufactured by Sumitomo Bakelite Co., Ltd.
* 8 "Seast F" manufactured by Tokai Carbon Co., Ltd.

From the results in Table 1, it was found that the samples of Examples 1 to 3 showed well-balanced and excellent effects on rolling resistance, passing noise level, and steering stability as compared with each sample of Comparative Example.
In addition, each sample of the comparative example showed a value inferior to that of the example in at least one evaluation item.

According to the present invention, it is possible to provide a rubber composition for a base tread which is excellent in steering stability and rolling resistance when applied to a tire and can improve passing noise. Further, according to the present invention, it is possible to provide a tire which is excellent in steering stability and rolling resistance and has improved passing noise.

Claims (8)

A rubber composition for base tread used for the base tread of the tread part of a tire.
The ratio (0 ° C.E'/ 30 ° C.E') of the storage elastic modulus (0 ° C.E') at 0 ° C. to the storage elastic modulus (30 ° C.E') at 30 ° C. is in the range of 1.3 to 2.0. A rubber composition for a base tread, which is characterized by being present. The rubber composition for a base tread according to claim 1, wherein the 0 ° C.E'/ 30 ° C.E'is in the range of 1.3 to 1.8. The rubber composition for a base tread according to claim 2, wherein the 0 ° C.E'/ 30 ° C.E'is in the range of 1.4 to 1.6. The rubber composition for a base tread according to claim 1 or 2, wherein the 0 ° C. E'is 15 MPa or less. The rubber composition for a base tread according to any one of claims 1 to 3, wherein the 30 ° C. E'is 10 MPa or less. The rubber composition for base tread according to any one of claims 1 to 4, wherein the tan δ (0 ° C. tan δ) at 0 ° C. of the rubber composition for base tread is 0.35 or more. .. The base tread rubber composition is characterized by containing a rubber component containing 70% by mass or more of natural rubber, a filler, and a resin of 20% by mass or more with respect to 100 parts by mass of the rubber component. , The rubber composition for a base tread according to any one of claims 1 to 6. A tire according to any one of claims 1 to 7, wherein the rubber composition for a base tread is used for the base tread of the tread portion.