JP2009013218A - Rubber composition for tread and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for treads which allows amount of use of raw materials deriving form petroleum resources to be reduced and provides a pneumatic tire excellent in rolling resistance, wet grip performance and dry grip performance, and to provide a pneumatic tire using the same. <P>SOLUTION: The rubber composition for treads is provided which contains at least a rubber component containing ≥10 mass% of a natural rubber component and a filler, wherein ≥80 mass% of the filler is a white filler and the rubber composition contains ≥8 mass% of an acetone-extractable component and has a ratio of non-petroleum resources of ≥75 mass%. The pneumatic tire using the same is also provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rubber composition for a tread and a pneumatic tire using the rubber composition for a tread in at least a part of a tread portion.

  Conventionally, synthetic rubbers such as styrene-butadiene rubber (SBR) have been used in tire tread rubber compositions in order to improve grip performance. However, in recent years, environmental issues have become more important and regulations on carbon dioxide emissions have been strengthened. In addition, since the existing amount of petroleum is limited, the use of raw materials derived from petroleum resources is limited. This environment-oriented orientation is no exception in the field of tires, and the development of a rubber composition for tread that replaces some or all of the raw materials derived from petroleum resources with raw materials derived from non-oil resources. It has been demanded.

  Patent Document 1 discloses an eco-tire in which natural rubber or the like is used as a raw material derived from resources other than petroleum, and dependency on petroleum resources is reduced. However, in the case of using only natural rubber as the rubber component, the rolling resistance is relatively good, but the running performance on the WET road surface and the DRY road surface tends to be inferior compared to the case of using SBR. Although the use of fillers can improve WET performance, it is insufficient for improving DRY performance.

Thus, in a rubber composition in which a raw material derived from petroleum resources is replaced with a raw material derived from resources other than petroleum, a rubber composition that is sufficiently usable for tread rubber and has an excellent balance of rolling resistance, WET performance, and DRY performance is The current situation is that it has not been obtained.
JP 2003-63206 A

  The present invention solves the above-described problems, reduces the amount of raw materials derived from petroleum resources, and provides a rubber composition for a tread that provides a pneumatic tire excellent in rolling resistance, WET grip performance and DRY grip performance, and the same. An object is to provide a pneumatic tire.

  The present invention contains at least a rubber component containing 10% by mass or more of a natural rubber component and a filler, 80% by mass or more of the filler is a white filler, and 8% by mass or more of an acetone extraction component. A rubber composition for a tread is provided that includes a non-petroleum resource ratio of 75% by mass or more.

  Here, the natural rubber component includes an epoxidized natural rubber, and the total epoxidation rate of the natural rubber component is preferably 0.025 or more.

  The white filler is preferably composed of one or more selected from silica, calcium carbonate, and aluminum hydroxide.

  Loss of a vulcanized rubber sheet obtained by vulcanizing the rubber composition for treads of the present invention at 160 ° C. for 20 minutes under conditions of a temperature of 50 ° C., a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 0.5%. The tangent is preferably 0.06 or more and 0.25 or less.

  The present invention also provides a pneumatic tire in which any of the above tread rubber compositions forms at least a part of a tread portion.

  According to the present invention, a rubber composition for a tread that reduces the amount of a raw material derived from petroleum resources and gives a pneumatic tire excellent in rolling resistance, WET grip performance and DRY grip performance, and a pneumatic tire using the same It becomes possible to provide.

<Rubber component>
The rubber component used in the present invention contains 10% by mass or more of a natural rubber component. If the natural rubber component is less than 10% by mass, the ratio of non-petroleum resources in the rubber composition becomes too high. The content of the natural rubber component in the rubber component is preferably 50% by mass or more, and more preferably 100% by mass. However, rubber components other than the natural rubber component may be blended depending on the desired tire characteristics within a range that does not impair the effects of the present invention.

  Examples of the natural rubber component include natural rubber (NR), epoxidized natural rubber (ENR), and modified natural rubber such as hydrogenated natural rubber. As the natural rubber (NR), those conventionally used in the rubber industry can be used, and examples thereof include natural rubber of grades such as RSS # 3 and TSR. Natural rubber in the narrow sense means cis-1,4-polyisoprene as a main component. However, in the present invention, in addition to the above, for example, trans-1,4-polyisoprene is mainly used. Including balata as a component, it means an elastic body derived from an emulsion collected from a plant and containing polyisoprene.

  In the present invention, the natural rubber component preferably contains epoxidized natural rubber (ENR). Epoxidized natural rubber (ENR) is a kind of modified natural rubber in which unsaturated double bonds of natural rubber are epoxidized, and molecular cohesion is increased by epoxy groups that are polar groups. Therefore, the glass transition temperature (Tg) is higher than that of natural rubber, and the mechanical strength and wear resistance are excellent. In particular, when silica is blended in the tread rubber composition, carbon black is blended in the rubber composition due to the reaction between the silanol group on the silica surface and the epoxy group of the epoxidized natural rubber. The same mechanical strength and wear resistance can be obtained.

  The total epoxidation rate of the natural rubber component is preferably 0.025 or more. When the total epoxidation rate is less than 0.15, the glass transition temperature of the natural rubber component is low, and the grip performance of a pneumatic tire using the tread rubber composition as the tread rubber tends to be insufficient. The total epoxidation rate of the natural rubber component is more preferably 0.05 or more, and further preferably 0.1 or more.

  On the other hand, the total epoxidation rate of the natural rubber component is theoretically 1.00 or less, but preferably 0.8 or less. This is because when the epoxidation rate exceeds 0.8, the rubber composition for tread becomes hard and mechanical strength tends to decrease. The total epoxidation rate of the natural rubber component is more preferably 0.65 or less, and further preferably 0.6 or less.

Here, the total epoxidation rate of the natural rubber component is expressed by the following formula:
Total epoxidation rate = A x B
(In the above formula, A represents the mass fraction of the epoxidized natural rubber in the natural rubber component, and B represents the epoxidation rate of the epoxidized natural rubber occupying the mass fraction)
Is calculated by

  The epoxidation rate means the ratio of the number of epoxidized out of the total number of carbon-carbon double bonds in the natural rubber component before epoxidation. For example, by titration analysis or nuclear magnetic resonance (NMR) analysis Desired.

  As the epoxidized natural rubber (ENR), a commercially available product may be used, or an epoxidized natural rubber (NR) may be used. The method for epoxidizing natural rubber (NR) is not particularly limited, and examples thereof include a chlorohydrin method, a direct oxidation method, a hydrogen peroxide method, an alkyl hydroperoxide method, and a peracid method. Examples of the peracid method include a method of reacting an organic peracid such as peracetic acid or performic acid as an epoxidizing agent with an emulsion of natural rubber.

  In the present invention, since the total epoxidation rate of the natural rubber component is preferably 0.025 or more as described above, the epoxidation rate of the epoxidized natural rubber (ENR) itself is also 0.025 or more. Preferably there is. However, for example, when two or more kinds of epoxidized natural rubber are combined, the epoxidation rate may be 0.025 or more in the entire epoxidized natural rubber. In this case, the epoxidation rate is less than 0.025. An epoxidized natural rubber may be included. The epoxidation rate of the epoxidized natural rubber is more preferably 0.05 or more, and further preferably 0.1 or more.

  On the other hand, the epoxidation rate of the epoxidized natural rubber is preferably 0.8 or less. When the epoxidation ratio exceeds 0.8, the tread rubber composition becomes hard and the mechanical strength tends to decrease, or the dispersibility during preparation of the tread rubber composition tends to decrease. . The epoxidation rate is more preferably 0.65 or less, and further preferably 0.6 or less.

  More typically, examples of the epoxidized natural rubber include epoxidized natural rubber having an epoxidation rate of 0.25, and epoxidized natural rubber having an epoxidation rate of 0.50.

  When the rubber component includes a rubber component other than the natural rubber component as long as the effects of the present invention are not impaired, examples of the rubber component other than the natural rubber component include styrene butadiene rubber (SBR), butadiene rubber (BR), Styrene isoprene copolymer rubber, isoprene rubber (IR), butyl rubber (IIR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), halogenated butyl rubber (X-IIR), copolymer of isobutylene and p-methylstyrene Examples thereof include halides of coalescence.

  The content of natural rubber (NR) in the rubber component is preferably 10% by mass or more. When the content of natural rubber (NR) is less than 10% by mass, the non-petroleum resource ratio may be too high. The content of natural rubber (NR) is more preferably 40% by mass or more, and further preferably 50% by mass or more. Further, when the content of the natural rubber (NR) in the rubber component is, for example, 90% by mass or less, and further 80% by mass or less, particularly good grip performance is imparted to the pneumatic tire.

  The content of epoxidized natural rubber (ENR) in the rubber component is preferably 10% by mass or more. When the content of the epoxidized natural rubber (ENR) is less than 10% by mass, the grip performance of the tread rubber composition tends to be low. The content of the epoxidized natural rubber (ENR) is more preferably 20% by mass or more, and more preferably 30% by mass or more.

<Filler>
The rubber composition of the present invention contains a filler. The blending amount of the filler is preferably within a range of 30 to 130 parts by mass with respect to 100 parts by mass of the rubber component. If the blending amount of the filler with respect to 100 parts by mass of the rubber component is less than 30 parts by mass, the reinforcing effect is not sufficient. The blending amount of the filler is preferably 40 parts by mass or more, and more preferably 50 parts by mass or more. On the other hand, if the blending amount of the filler exceeds 130 parts by mass, the effect of reducing rolling resistance cannot be obtained sufficiently. The blending amount of the filler is further preferably 120 parts by mass or less, and more preferably 110 parts by mass or less.

  The rubber composition of the present invention contains a white filler as a filler. The white filler means a white and inorganic filler, and more specifically, silica, calcium carbonate, aluminum hydroxide and the like are exemplified.

  The content rate of a white filler is 80 mass% or more in all the fillers, Preferably it is 90 mass%, More preferably, it is 100 mass%.

  In the present invention, the white filler is preferably silica in terms of reinforcing properties, wet performance, low rolling resistance performance, and the ratio of resources outside of petroleum. By adding silica, the reinforcing effect, the rolling resistance reducing effect, and the grip performance improving effect are particularly good.

Silica may be prepared by a wet method or may be prepared by a dry method. Moreover, as a preferable commercial item, "Ultrasil VN2" (BET specific surface area 125m < ² > / g), "Ultra Gil VN3" (BET specific surface area 210m < ² > / g), etc. made from Degussa can be illustrated, for example.

<Fillers other than white filler>
The rubber composition of the present invention may contain a filler other than a white filler such as carbon black. In this case, it is preferable that the compounding quantity of carbon black with respect to 100 mass parts of rubber components shall be 15 mass parts or less. When the blending amount of the carbon black exceeds 15 parts by mass, the effect of reducing the amount of raw material derived from petroleum resources tends to be small, and the effect of reducing rolling resistance tends to be difficult to obtain. From the viewpoint of reducing the amount of raw material derived from petroleum resources, the blending amount of carbon black is more preferably 10 parts by mass or less, and further preferably 5 parts by mass or less.

<Silane coupling agent>
In the present invention, when silica is used as the white filler, a silane coupling agent may be used in combination. Thereby, the more excellent reinforcement effect is provided with respect to the rubber composition for treads. The blending amount of the silane coupling agent is preferably in the range of 4 to 15 parts by mass with respect to 100 parts by mass of silica. When the blending amount of the silane coupling agent is less than 4 parts by mass, the viscosity tends to increase in the kneading process and the workability tends to decrease. When it exceeds 15 parts by mass, the reinforcing effect is remarkable even if the amount is increased. Such improvement cannot be expected, but the cost increases and tends to be less economical. From the viewpoint of dispersibility and coupling effect, the amount of the silane coupling agent is more preferably 5 parts by mass or more, and more preferably 14 parts by mass or less.

  As the silane coupling agent, a conventionally known silane coupling agent can be used. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4- Triethoxysilylbutyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilylbutyl) tetrasulfide, bis (3-triethoxy Silylpropyl) trisulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (2-trimethoxysilylethyl) ) Resulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3 -Trimethoxysilylpropyl) disulfide, bis (2-trimethoxysilylethyl) disulfide, bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-tri Ethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl-N, N-dimethylthio Sulfide systems such as rubamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-trimethoxysilylpropyl methacrylate monosulfide; 3-mercaptopropyltrimethoxysilane Mercapto series such as 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; Vinyl series such as vinyltriethoxysilane and vinyltrimethoxysilane; 3-aminopropyltriethoxysilane 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxy Amino systems such as silane; glycidoxy systems such as γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane Nitro compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloroethyltri Chloro-based compounds such as ethoxysilane; These silane coupling agents may be used alone or in combination of two or more.

  Of these, Si69 (bis (3-triethoxysilylpropyl) tetrasulfide), Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa are preferably used because of their good processability. It is done.

<Other ingredients>
In addition to the components described above, the rubber composition for treads of the present invention includes other compounding agents conventionally used in the rubber industry, such as vulcanizing agents, stearic acid, vulcanization accelerators, vulcanization accelerators, oils. Further, a curable resin, a wax, an anti-aging agent and the like may be blended.

  As the vulcanizing agent, an organic peroxide or a sulfur-based vulcanizing agent can be used. Examples of the organic peroxide include benzoyl peroxide, dicumyl peroxide, and di-t-butyl peroxide. , T-butyl cumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoyl) Peroxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3 or 1,3-bis (t-butylperoxypropyl) benzene, di-t-butylperoxy- Diisopropylbenzene, t-butylperoxybenzene, 2,4-dichlorobenzoyl peroxide, 1,1-di t- butyl peroxy-3,3,5-trimethyl siloxane, and the like can be used n- butyl-4,4-di -t- butyl peroxy valerate. Of these, dicumyl peroxide, t-butylperoxybenzene and di-t-butylperoxy-diisopropylbenzene are preferred. Moreover, as a sulfur type vulcanizing agent, sulfur, morpholine disulfide, etc. can be used, for example. Of these, sulfur is preferred. These vulcanizing agents may be used alone or in combination of two or more.

  Vulcanization accelerators include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine, aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. Those containing at least one of them can be used. Examples of the sulfenamide system include CBS (N-cyclohexyl-2-benzothiazylsulfenamide), TBBS (N-tert-butyl-2-benzothiazylsulfenamide), N, N-dicyclohexyl-2- Sulfenamide compounds such as benzothiazylsulfenamide, N-oxydiethylene-2-benzothiazylsulfenamide, and N, N-diisopropyl-2-benzothiazolesulfenamide can be used. Examples of the thiazole group include MBT (2-mercaptobenzothiazole), MBTS (dibenzothiazyl disulfide), sodium salt of 2-mercaptobenzothiazole, zinc salt, copper salt, cyclohexylamine salt, 2- (2,4-dinitro). Thiazole compounds such as phenyl) mercaptobenzothiazole and 2- (2,6-diethyl-4-morpholinothio) benzothiazole can be used. Examples of thiurams include TMTD (tetramethylthiuram disulfide), tetraethylthiuram disulfide, tetramethylthiuram monosulfide, dipentamethylenethiuram disulfide, dipentamethylenethiuram monosulfide, dipentamethylenethiuram tetrasulfide, dipentamethylenethiuram hexasulfide. Further, thiuram compounds such as tetrabutylthiuram disulfide and pentamethylenethiuram tetrasulfide can be used. As the thiourea series, for example, thiourea compounds such as thiacarbamide, diethylthiourea, dibutylthiourea, trimethylthiourea, diortolylthiourea and the like can be used. Examples of guanidine-based compounds include guanidine-based compounds such as diphenylguanidine, diortolylguanidine, triphenylguanidine, orthotolylbiguanide, and diphenylguanidine phthalate. Examples of dithiocarbamate include zinc ethylphenyldithiocarbamate, zinc butylphenyldithiocarbamate, sodium dimethyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc diamyldithiocarbamate, zinc dipropyldithiocarbamate , Complex salt of zinc pentamethylenedithiocarbamate and piperidine, zinc hexadecyl (or octadecyl) isopropyldithiocarbamate, zinc dibenzyldithiocarbamate, sodium diethyldithiocarbamate, piperidine pentamethylenedithiocarbamate, selenium dimethyldithiocarbamate, tellurium diethyldithiocarbamate, diamyl Di, such as cadmium dithiocarbamate And the like can be used Okarubamin acid compound. As the aldehyde-amine system or aldehyde-ammonia system, for example, an aldehyde-amine system or aldehyde-ammonia system compound such as acetaldehyde-aniline reaction product, butyraldehyde-aniline condensate, hexamethylenetetramine, acetaldehyde-ammonia reaction product, etc. is used. can do. As the imidazoline-based compound, for example, an imidazoline-based compound such as 2-mercaptoimidazoline can be used. As the xanthate type, for example, a xanthate type compound such as zinc dibutylxanthate can be used. These vulcanization accelerators may be used alone or in combination of two or more. Examples of the vulcanization acceleration aid include zinc oxide.

  As the anti-aging agent, an amine-based, phenol-based or imidazole-based anti-aging agent, a carbamic acid metal salt, or the like can be appropriately selected and used.

  Examples of the oil include process oil, vegetable oil and fat, or a mixture thereof. Examples of the process oil include paraffinic process oil, naphthenic process oil, and aromatic process oil. Vegetable oils include castor oil, cottonseed oil, sesame oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, beet flower oil, sesame oil, Examples include olive oil, sunflower oil, palm kernel oil, cocoon oil, jojoba oil, macadamia nut oil, safflower oil, tung oil, and the like.

  Here, the rubber composition for a tread of the present invention (before vulcanization) contains 8% by mass or more of an acetone extract. By including 8% by mass or more of acetone extract, grip performance can be ensured. The amount of acetone extracted is preferably 9% by mass or more, and more preferably 10% by mass or more. On the other hand, the acetone extract is preferably 35% by mass or less, and more preferably 30% by mass or less. When the amount of acetone extracted exceeds 35% by mass, body wear performance tends to deteriorate.

  In the present invention, the content of acetone extracted is calculated by the following equation after a rubber sample is immersed in acetone all day and night.

(Sample weight before extraction−Sample weight after extraction) / Sample weight before extraction × 100
The rubber composition for a tread of the present invention is a vulcanized rubber sheet obtained by vulcanization at 160 ° C. for 20 minutes under the conditions of a temperature of 50 ° C., a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 0.5%. The loss tangent at is preferably 0.06 or more and 0.25 or less. When the loss tangent is less than 0.06, the grip performance tends to be insufficient. On the other hand, when the loss tangent exceeds 0.25, there is a tendency that physical properties are reduced due to heat generation and wear performance is reduced.

<Pneumatic tire>
The present invention also provides a pneumatic tire in which the rubber composition for a tread as described above forms at least a part of the tread portion. In particular, the tread portion preferably has a cap tread portion and a base tread portion, and the base tread portion and / or the cap tread portion is preferably made of the rubber composition for a tread of the present invention.

  FIG. 1 is a cross-sectional view illustrating the left half of a pneumatic tire according to the present invention. The pneumatic tire 1 includes a tread portion 2, a pair of sidewall portions 3 extending inward in the tire radial direction from both ends of the tread portion 2, and a bead portion 4 positioned at an inner end of each sidewall portion 3. It is common to have a structure with. A carcass 6 is bridged between the bead portions 4, and a belt layer 7 that reinforces the tread portion 2 with a tagging effect is disposed outside the carcass 6 and inside the tread portion 2. .

  The carcass 6 is formed of one or more carcass plies in which the carcass cord is arranged at an angle of, for example, 70 to 90 ° with respect to the tire equator CO. The carcass ply extends from the tread portion 2 to the sidewall portion 3. After that, the periphery of the bead core 5 of the bead portion 4 is folded back from the inner side in the tire axial direction to be locked.

  The belt layer 7 is composed of two or more belt plies in which the belt cords are arranged at an angle of, for example, 40 ° or less with respect to the tire equator CO. The belt layers 7 are stacked in different directions so that the belt cords cross each other. is doing.

  Further, a bead apex rubber 8 extending radially outward from the bead core 5 is disposed in the bead portion 4, and an inner liner rubber 9 forming a tire lumen surface is adjacent to the inside of the carcass 6. The outside of the carcass 6 is protected by clinch rubber 4G and sidewall rubber 3G.

  As shown in FIG. 1, the pneumatic tire of the present invention can include a cap tread portion 2a and a base tread portion 2b, and the cap tread portion 2a and / or the base tread portion 2b is a rubber composition for a tread according to the present invention. It consists of things.

  The pneumatic tire of the present invention is produced by a conventionally known method using the tread rubber composition of the present invention. That is, the rubber composition for a tread of the present invention is kneaded, extruded in accordance with the shape of the tread portion of the tire at an unvulcanized stage, and a normal method on a tire molding machine together with other members of the tire. An unvulcanized tire is formed by molding with. The pneumatic tire of the present invention can be obtained by heating and pressurizing the unvulcanized tire in a vulcanizer.

  Since the pneumatic tire of the present invention includes a tread portion obtained by using the rubber composition for a tread according to the present invention, the pneumatic tire has an excellent balance of rolling resistance, WET performance, and DRY performance, and the amount of raw material derived from petroleum resources. And can be prepared for a future decrease in the supply of oil, and has excellent safety. The pneumatic tire provided by the present invention can be suitably applied to various applications such as a motorcycle, a passenger car, a truck, a bus, and a heavy vehicle as an “eco tire” that is friendly to the global environment.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited to these.

<Example 1 and Comparative Examples 1-3>
According to the formulation shown in Table 1, using a Banbury mixer, the components except for sulfur and the vulcanization accelerator were discharged after kneading at 160 ° C. for 4 minutes to obtain a kneaded product. To this was added sulfur and a vulcanization accelerator in the formulation shown in Table 1, and a biaxial open roll was used and further kneaded at 100 ° C. for 2 minutes to prepare an unvulcanized rubber composition. Next, an unvulcanized rubber composition was extruded to prepare an unvulcanized rubber sheet, which was further vulcanized at 160 ° C. for 20 minutes to obtain a vulcanized rubber sheet. Table 1 shows the acetone extractables of each rubber composition before vulcanization.

(Production of test tires)
An unvulcanized tire was formed by extruding the unvulcanized rubber composition obtained above into a cap tread shape and molding it on a tire molding machine together with other members of the tire including the base tread. . This unvulcanized tire is heated and pressurized at 160 ° C. for 20 minutes in a vulcanizer, whereby a front tire (size: 120 / 80-14 D305) and a rear tire (size: 150/70) having the structure shown in FIG. -13 D305). The base tread was mixed in the same manner as the cap tread.

(Characteristic evaluation of vulcanized rubber sheet and test tire)
[hardness]
The vulcanized rubber sheet was measured for JIS-A hardness at 25 ° C. according to JIS-K6301. The results are shown in Table 1.

[Viscoelastic properties]
The vulcanized rubber sheet was cut with a knife and formed into a 50 mm × 4 mm × 2.5 mm test piece. Using the viscoelastic spectrometer “VES-F-3” manufactured by Iwamoto Seisakusho Co., Ltd., the produced test piece was subjected to loss under conditions of a temperature of 50 ° C., a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 0.5%. Tangent (tan δ) was measured. The results are shown in Table 1.

[Grip performance]
The test tires obtained above were mounted on Yamaha Majesty (250 cc), and sensory evaluation of grip performance on dry asphalt road surfaces and wet asphalt road surfaces was performed. The numerical values in Table 1 are numerical values when the braking performance of Comparative Example 1 is set to a central value of 3.5 points. The larger this value, the better the grip performance.

[Rolling resistance]
The rolling resistance of the test tire obtained above was measured under the conditions of 80 km / h, air pressure 250 kPa, and additional load 4.0 kN. About the obtained measured value, the comparative formula 1 is set to 100, the following calculation formula:
Rolling resistance index = (Rolling resistance of Comparative Example 1) ÷ (Rolling resistance of each example) × 100
Was used to calculate the rolling resistance index. As the rolling resistance index is larger, the rolling resistance is smaller and the heat build-up is smaller, indicating that the tire performance is better.

Note 1: Natural rubber is RSS # 3.
Note 2: The epoxidized natural rubber is “ENR25” (epoxidation rate: 25 mol%) manufactured by Kumpulang Guthrie.
Note 3: Styrene-butadiene rubber (SBR) is “Nipol 1502” manufactured by Nippon Zeon Co., Ltd.
Note 4: Silica is “Ultrazil VN3” (BET specific surface area: 175 m ² / g) manufactured by Degussa.
Note 5: carbon black N330 is, Showa Kyabonetto Co., Ltd. of "small black N330": a (BET specific surface area of 75m ² / g).
Note 6: Carbon black N220 is “Show Black N220” (BET specific surface area: 110 m ² / g) manufactured by Showa Cabonet Co., Ltd.
Note 7: The oil is an aromatic oil made by Idemitsu Kosan.
Note 8: Sulfur is “powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.
Note 9: The vulcanization accelerator NS is “Noxeller NS” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Note 10: The vulcanization accelerator DPG is “Noxeller D” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Note 11: The anti-aging agent is “6C” (N-1,3-dimethylbutyl-N′-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Note 12: Wax is “Sannok S” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Note 13: Stearic acid is stearic acid manufactured by NOF Corporation.
Note 14: Zinc Hana is “Zinc Hana 1” manufactured by Mitsui Mining & Smelting Co., Ltd.
Note 15: Silane coupling agent is “Si266” manufactured by Degussa.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is sectional drawing which illustrated the left half of the pneumatic tire which concerns on this invention.

Explanation of symbols

  1 tire, 2 tread part, 2a cap tread part, 2b base tread part, 3 side wall part, 4 bead part, 5 bead core, 6 carcass, 7 belt layer, 8 bead apex rubber, 9 inner liner rubber, 3G side wall Rubber, 4G clinch rubber.

Claims (5)

Containing at least a rubber component containing 10% by mass or more of a natural rubber component, and a filler;
80% by mass or more of the filler is a white filler,
Containing 8% by mass or more of acetone-extracted components,
A rubber composition for tread having a non-petroleum resource ratio of 75% by mass or more. The natural rubber component includes epoxidized natural rubber,
The rubber composition for a tread according to claim 1, wherein a total epoxidation rate of the natural rubber component is 0.025 or more.   The rubber composition for a tread according to claim 1 or 2, wherein the white filler comprises one or more selected from silica, calcium carbonate, and aluminum hydroxide.   The loss tangent of the vulcanized rubber sheet obtained by vulcanization at 160 ° C. for 20 minutes under the conditions of temperature 50 ° C., frequency 10 Hz, initial strain 10%, dynamic strain 0.5% is 0.06 or more and 0.00. The rubber composition for tread according to any one of claims 1 to 3, which is 25 or less.   A pneumatic tire, wherein the tread rubber composition according to claim 1 forms at least a part of a tread portion.

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