JP2009001681A - Rubber composition for bead apex and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for bead apexes, which can reduce the usage of raw materials originated from petroleum resources and simultaneously enables both the maintenance of physical characteristics such as hardness and the improvement of processability, and to provide a pneumatic tire having bead apexes using the rubber composition. <P>SOLUTION: This rubber composition for the bead apexes comprises a rubber component, and ≥60 pts.mass of silica, ≤5 pts.mass of carbon black, and 0.1 to 0.8 pt.mass of a peptizer, on the basis of 100 pts.mass of the rubber component, wherein the rubber component contains a natural rubber component comprising at least one of natural rubber and a modified natural rubber in an amount of 10 to 100 mass%, and the pneumatic tire has the bead apexes using the rubber composition. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rubber composition for bead apex and a pneumatic tire provided with a bead apex made of the rubber composition.

  In recent years, with the improvement of automobile performance, high maneuvering stability is also required for tires. In order to obtain a tire having high steering stability, it is necessary to improve the hardness of the bead apex rubber, and a rubber composition for bead apex in which a larger amount of carbon black is blended than before has been developed.

  However, in the bead apex rubber composition, it is possible to increase the hardness of the bead apex by blending a large amount of carbon black, but the bead apex is increased during the running of the vehicle due to an increase in loss tangent (tan δ). There is a problem in that heat is easily generated, durability of the bead apex is impaired due to heat aging, and rolling resistance of the tire (resistance acting in the direction opposite to the traveling direction of the tire when the tire rotates) increases.

  The bead apex is installed after the bead apex rubber composition is molded into a predetermined shape. If the bead apex rubber composition has poor processability, the bead apex is used. As a result, there is a problem that the bead apex characteristics also vary.

  On the other hand, in recent years, methods for reducing the amount of raw materials derived from petroleum resources have been studied in various technical fields due to increasing interest in environmental problems. Currently, commercially available tires are composed of raw materials in which more than half of the total weight is petroleum resources. For example, a general tire for a passenger car contains about 20% by mass of synthetic rubber, about 20% by mass of carbon black, a softener, a synthetic fiber, and the like, so that about 50% by mass or more of the entire tire is derived from raw materials of petroleum resources. It is configured. The rubber composition for tires is mixed with a tackifier for the purpose of improving the tackiness and improving the workability by reducing the viscosity. As the tackifier, a C5 resin, a C9 series can be used. Resins derived from petroleum resources such as resins and phenolic resins are generally used. Accordingly, it is desired to develop a rubber for tires using a raw material derived from a natural resource that satisfies the same or more required characteristics as when using a raw material derived from a petroleum resource.

  Here, 100 to 150 parts by weight of a terpene resin is blended with 100 parts by weight of a diene rubber for the purpose of providing a tread rubber composition that satisfies industrial workability and has excellent grip properties. A tread rubber composition is known. In addition, it contains 50 parts by weight or more of natural rubber or polyisoprene rubber among diene rubber components, and contains 1 to 50 parts by weight of a terpene resin having a specific kinematic viscosity. There is also known a technique capable of providing a rubber composition for a tire with a small amount of addition. Further, for the same purpose, a phenol-modified terpene having a specific softening point, hydroxyl value and kinematic viscosity, including a reinforcing filler containing 50 parts by weight or more of natural rubber and 60% by weight or more of silica among diene rubber components. A rubber composition for a tire tread obtained by blending 0.5 to 15 parts by weight of a resin is also known. However, these rubber compositions contain a large amount of natural resource materials without blending petroleum-based resins and reduce the burden on the environment, but there is nothing about the bead apex and the performance required for this. It is not taken into consideration and the processability is not sufficient.

  JP-A-11-11106 (Patent Document 1) describes that 1 to 10 parts by weight of a tackifier is added to 100 parts by weight of a rubber component comprising a diene rubber and a bromide of an isobutylene / p-methylstyrene copolymer. A tubeless tire without an inner liner using a rubber composition for containing a case cord covering rubber layer is disclosed, and examples of the tackifier include terpene resins and rosin derivatives. According to Patent Document 1, it is described that the adhesiveness with other tire members is excellent by using such a rubber composition.

  JP 2004-2584 A (Patent Document 2) discloses a rubber composition for a tire in which 40 to 500 parts by weight of a filler and 15 parts by weight or more of a resin are blended with 100 parts by weight of a rubber component. Examples of the resin include terpene resins and rosin resins. According to Patent Document 2, it is described that, by using such a composition, both wet grip performance and wear resistance can be achieved using the tread portion.

  Furthermore, Japanese Patent Application Laid-Open No. 2006-63093 (Patent Document 3) discloses a resin and white filler of 8 parts by weight or more with respect to 100 parts by weight of a rubber component containing 80% by weight or more of natural rubber and / or epoxidized natural rubber. A rubber composition for a tread containing a filler composed of 80% by weight or more is disclosed, and examples of the resin include terpene resins, aromatic modified terpene resins, and rosin resins. According to Patent Document 3, it is disclosed that the content of non-petroleum resources can be increased and the conventional performance can be maintained equally.

However, none of the inventions disclosed in Patent Documents 1 to 3 considers the bead apex and the performance required for this, and it is difficult to say that the workability is sufficient.
Japanese Patent Laid-Open No. 11-11106 JP 2004-2584 A JP 2006-63093 A

  The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to maintain the physical properties such as hardness and improve the workability while reducing the amount of raw materials derived from petroleum resources. It is to provide a rubber composition for a bead apex that can be compatible with the above, and a pneumatic tire including the bead apex using the same.

  The rubber composition for bead apex of the present invention comprises a rubber component, 60 parts by mass or more of silica, 5 parts by mass or less of carbon black, 0.1 to 0.8 parts by mass with respect to 100 parts by mass of the rubber component. It contains a disintegrating agent, and the rubber component contains a natural rubber component comprising at least one of natural rubber and modified natural rubber within a range of 10 to 100% by mass.

  The modified natural rubber used in the rubber composition for bead apex of the present invention is preferably an epoxidized natural rubber.

  Moreover, it is preferable that the rubber composition for bead apex of this invention further contains at least any one of 0.5 mass parts or more of terpene resin and rosin resin with respect to a rubber component.

  The rubber component in the rubber composition for bead apex of the present invention is preferably composed of a natural rubber component.

  The present invention also provides a pneumatic tire provided with a bead apex made of the rubber composition of the present invention described above.

  According to the present invention, a rubber composition for bead apex capable of achieving both maintenance of physical properties such as hardness and improvement of workability while reducing the amount of a raw material derived from petroleum resources, and a bead using the same A pneumatic tire provided with an apex can be provided.

  The rubber composition for bead apex of the present invention comprises a rubber component, 60 parts by mass or more of silica, 5 parts by mass or less of carbon black, 0.1 to 0.8 parts by mass with respect to 100 parts by mass of the rubber component. Contains a demulcent. The rubber component used in the present invention is a natural rubber component (hereinafter also simply referred to as “natural rubber component”) composed of at least one of natural rubber (NR) and modified natural rubber within the range of 10 to 100% by mass. Contains.

<Rubber component>
In the rubber composition for bead apex of the present invention, the rubber component contains a natural rubber component composed of at least one of natural rubber and modified natural rubber (ENR). That is, the natural rubber component in the present invention may be composed only of natural rubber, may be composed only of modified natural rubber, or may include both.

  The natural rubber used in the present invention includes any rubber as long as it is known as natural rubber, and the place of origin is not limited. Such natural rubber mainly contains cis 1,4 polyisoprene, but can also contain trans 1,4 polyisoprene according to required characteristics. Therefore, the natural rubber includes natural rubber mainly containing trans 1,4 isoprene, such as balata, which is a kind of rubber from the South American Acatecaceae family, in addition to natural rubber mainly containing cis 1,4 polyisoprene. It is. The natural rubber component in the present invention may contain one or more of such natural rubbers (that is, one component or two or more components). As such natural rubber, for example, natural rubber of grades such as RSS # 3 and TSR can be suitably used.

  The modified natural rubber used in the present invention refers to a product obtained by modifying or purifying the above-described natural rubber, and examples thereof include epoxidized natural rubber (ENR), deproteinized natural rubber (DPNR), and hydrogenated natural rubber. The natural rubber component in the present invention may contain one or more of such modified natural rubbers. Among the above, the natural rubber component in the present invention preferably contains epoxidized natural rubber as the modified natural rubber.

  Epoxidized natural rubber 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, wear resistance, and air permeation resistance are excellent. Examples of such epoxidized natural rubber include commercially available products such as ENR25 (manufactured by Clamp-Lance Gully) (epoxidation rate: 25%), ENR 50 (made by Clamp-Lance Gully) (epoxidation rate: 50%), and the like. You may use what was used and what epoxidized natural rubber may be used. The method for epoxidizing natural rubber 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.

  The epoxidation rate of the epoxidized natural rubber (ENR) is preferably 5 mol% or more, and more preferably 25 mol% or more. Here, the epoxidation rate is the ratio of the number of epoxidized to the total number of double bonds in natural rubber before epoxidation ((number of epoxidized double bonds) / (two before epoxidation). The number of double bonds)), and is determined by titration analysis, nuclear magnetic resonance (NMR) analysis, or the like. When the epoxidation rate of the epoxidized natural rubber (ENR) is less than 5 mol%, the glass transition temperature of the epoxidized natural rubber (ENR) is low, so that the bead apex using the bead apex rubber composition is used. In the pneumatic tire provided, high hardness, high durability, high fatigue resistance and high rolling resistance tend to be difficult to obtain. The epoxidation rate of the epoxidized natural rubber (ENR) is preferably 50 mol% or less, and more preferably 30 mol% or less. When the epoxidation rate of the epoxidized natural rubber (ENR) exceeds 50 mol%, the hardness is excessively increased, and the bending fatigue resistance of the pneumatic tire including the bead apex using the bead apex rubber composition. Tend to decrease.

  More typical examples of the epoxidized natural rubber (ENR) include an epoxidized natural rubber having an epoxidation rate of 25 mol% and an epoxidized natural rubber having an epoxidation rate of 50 mol%.

  In this invention, the content rate of the natural rubber component in a rubber component shall be 10 mass% or more. This is because if the content of the natural rubber component in the rubber component is less than 10% by mass, the effect of reducing the amount of raw material derived from petroleum resources cannot be obtained sufficiently. The content of the natural rubber component in the rubber component is preferably 20% by mass or more, and more preferably 50% by mass or more. The content of the natural rubber component in the rubber component is preferably 100% by mass (that is, the rubber component is made of a natural rubber component) in that the effect of reducing the amount of raw material derived from petroleum resources is good.

  Further, the rubber component may contain a petroleum resource-derived rubber as long as the effects of the present invention are not impaired. Examples of rubbers derived from petroleum resources include styrene butadiene rubber (SBR), butadiene rubber (BR), styrene isoprene copolymer rubber, isoprene rubber (IR), butyl rubber (IIR), chloroprene rubber (CR), and acrylonitrile butadiene rubber. Examples thereof include (NBR), halogenated butyl rubber (X-IIR), and halides of copolymers of isobutylene and p-methylstyrene. Among these, SBR, BR, and IR are preferable because the pneumatic tire using the bead apex rubber composition as a bead apex can impart high hardness, high durability, high fatigue resistance, and high rolling resistance. .

<Silica>
The rubber composition for bead apex of the present invention contains silica in addition to the rubber component described above. Silica functions as a reinforcing filler, and the tensile strength of the resulting bead apex can be improved by blending silica. In addition, since silica is derived from non-petroleum resources, the amount of raw material derived from petroleum resources in the rubber composition is reduced compared to the case where a reinforcing agent derived from petroleum resources such as carbon black is blended as a main reinforcing agent. Can be reduced.

  The rubber composition for bead apex of the present invention contains 60 parts by mass or more of silica with respect to 100 parts by mass of the rubber component described above. When the content of silica is less than 60 parts by mass with respect to 100 parts by mass of the rubber component, there is a tendency that sufficient hardness is not obtained in the obtained bead apex, and particularly sufficient tensile strength may not be obtained. There is. In order to keep the hardness sufficiently, the content of silica is preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component.

  Moreover, it is preferable that it is 120 mass parts or less with respect to 100 mass parts of rubber components mentioned above, and, as for content of the silica in the rubber composition for bead apex of this invention, it is more preferable that it is 100 mass parts or less. This is because when the silica content exceeds 120 parts by mass with respect to 100 parts by mass of the rubber component, the breaking strength tends to decrease.

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

<Carbon black>
The rubber composition for bead apex of the present invention further contains carbon black as a reinforcing agent as long as the effects of the present invention are not impaired. By blending carbon black, good mechanical strength is imparted to the rubber composition for bead apex. However, since carbon black is generally derived from petroleum resources, the amount of raw materials derived from petroleum resources is reduced. The amount of carbon black is preferably 5 parts by mass or less, further 3 parts by mass or less, and further 2 parts by mass or less with respect to 100 parts by mass of the rubber component. On the other hand, the amount of carbon black is preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component in that the effect of improving the mechanical strength due to the addition of carbon black is favorably obtained. More preferably.

  As a preferable commercial product of carbon black, for example, Show Black N220 (manufactured by Cabonet Japan Co., Ltd.) can be exemplified.

<Funging agent>
The rubber composition for bead apex of the present invention further contains a demulcent. The peptizer, also known as peptizer or peptizer, accelerates the viscosity reduction of the rubber so that the raw unvulcanized rubber can be chemically cut to accelerate plasticization and shorten the puffing time. To be added. As a disintegrant, for example, a conventionally known appropriate disintegrator such as an aromatic mercaptan compound, a disulfide compound and a zinc salt thereof, an organic peroxide, a nitro compound, a nitroso compound, and the like can be used. In the rubber composition for bead apex according to the present invention, 0.1 to 0.8 parts by mass of the demulcent is blended with respect to 100 parts by mass of the rubber component described above.

<Terpene resin, rosin resin>
The rubber composition for bead apex of the present invention preferably contains at least one of a terpene resin and a rosin resin as a resin using a natural material. In this case, the bead apex rubber composition of the present invention may contain only a terpene resin, may contain only a rosin resin, or may contain both of these. Good. Moreover, you may contain multiple types of terpene resin and rosin resin. Among these, it is preferable to contain a terpene resin.

Here, the term “terpene-based resin” as used herein refers to a resin that is polymerized with a terpene compound contained in a plant essential oil generally obtained from plant leaves, trees, roots and the like as a main monomer. The terpene compound is generally a polymer of isoprene (C ₅ H ₈ ), and terpenes classified into monoterpene (C ₁₀ H ₁₆ ), sesquiterpene (C ₁₅ H ₂₄ ), diterpene (C ₂₀ H ₃₂ ), etc. A compound having a basic skeleton, such as α-pinene, β-pinene, dipentene, limonene, myrcene, allocymene, ocimene, α-ferrandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1, Examples include 4-cineole, α-terpineol, β-terpineol, γ-terpineol, camphene, tricyclene, sabinene, paramentadienes, and carenes.

  The terpene resin in the present invention includes, as a raw material, terpene compounds other than terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, β-pinene / limonene resin. And an aromatic modified terpene resin using terpene compound and aromatic compound, terpene phenol resin using terpene compound and phenol compound as raw materials, and hydrogenated terpene resin obtained by hydrogenating terpene resin. Here, as an aromatic compound used as the raw material of the aromatic terpene resin in the present invention, for example, styrene, α-methylstyrene, vinyltoluene, divinyltoluene and the like can be mentioned, and a phenolic compound used as a raw material for the terpene phenol resin. Examples thereof include phenol, bisphenol A, cresol, and xylenol.

  As such a terpene resin, commercially available products such as PX300N (manufactured by Yasuhara Chemical Co., Ltd.) can be suitably used.

  In addition, the “rosin resin” in the present specification is a resin acid such as abietic acid, neoabietic acid, parastrinic acid, levopimaric acid, pimaric acid, isopimaric acid, and dehydroabietic acid obtained by processing pine resin. In addition to natural rosin resin (polymerized rosin) such as gum rosin, wood rosin, tall oil rosin, etc., hydrogenated rosin resin, maleic acid modified rosin resin, modified rosin resin such as rosin modified phenolic resin, rosin glycerin ester Rosin esters such as, disproportionated rosin resins obtained by disproportionating rosin resins, and the like are also included.

  The rubber composition for bead apex of the present invention preferably contains at least one selected from the above-mentioned terpene resin and rosin resin in an amount of 0.5 parts by mass or more based on 100 parts by mass of the rubber component. Here, when both terpene-type resin and rosin-type resin are contained, the total amount shall be 0.5 mass part or more with respect to 100 mass parts of rubber components. When the content of at least one selected from a terpene resin and a rosin resin is less than 0.5 parts by mass with respect to 100 parts by mass of the rubber component, the adhesive force tends to decrease and the processability tends to deteriorate. . From the viewpoint of keeping the adhesive strength optimal, the content of at least one selected from terpene resins and rosin resins is preferably 0.5 parts by mass or more with respect to 100 parts by mass of the rubber component. More preferably, it is at least part.

  In the rubber composition for bead apex of the present invention, the content of at least one selected from the above-mentioned terpene resin and rosin resin is preferably 15 parts by mass or less with respect to 100 parts by mass of the rubber component, More preferably, it is 10 parts by mass or less. This is because the hardness tends to decrease when the content of at least one selected from terpene resins and rosin resins exceeds 15 parts by mass with respect to 100 parts by mass of the rubber component.

<Silane coupling agent>
Although the rubber composition for bead apex of the present invention contains silica as described above, it is preferable to blend a silane coupling agent with this silica. 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-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxy Ethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl-N, N-dimethylthio Rubamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, etc. Sulfide type; mercapto type such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; vinyltriethoxysilane, vinyltrimethoxysilane, etc. Vinyl-based; 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltriethoxy Amino series such as silane, 3- (2-aminoethyl) aminopropyltrimethoxysilane; γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane , Glycidoxy type such as γ-glycidoxypropylmethyldimethoxysilane; nitro type such as 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane; 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane , Chloro-based compounds such as 2-chloroethyltrimethoxysilane and 2-chloroethyltriethoxysilane; These silane coupling agents may be used alone or in combination of two or more.

  Among these, Si69 (made by Degussa) (bis (3-triethoxysilylpropyl) tetrasulfide), Si266 (made by Degussa) (bis (3-triethoxysilylpropyl) because of good processability. ) Disulfide) and the like are preferably used. When a silane coupling agent is further contained, the content is not particularly limited.

<Other ingredients>
In addition to the components described above, the bead apex rubber composition of the present invention includes other compounding agents conventionally used in the rubber industry, such as vulcanizing agents, stearic acid, vulcanization accelerators, and vulcanization acceleration aids. Oils, hardened resins, waxes, anti-aging agents, etc. 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 type 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 Such as cadmium dithiocarbamate And the like can be used thiocarbamate 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.

As the vulcanization acceleration aid, for example, zinc oxide, stearic acid and the like can be used.
As the anti-aging agent, amine-based, phenol-based, imidazole-based, carbamic acid metal salts, and the like can be appropriately selected and used.

  The bead apex rubber composition of the present invention may contain a metal stearate. Examples of metal stearates include magnesium stearate, magnesium 12-hydroxystearate, calcium stearate, calcium 12-hydroxystearate, barium stearate, barium 12-hydroxystearate, zinc stearate, zinc 12-hydroxystearate, and the like. Can be mentioned. Among the metal stearates, alkaline earth metal salts of stearic acid are preferable from the viewpoint of heat resistance improvement effect and compatibility with epoxidized natural rubber, and calcium stearate, 12-hydroxycalcium stearate, barium stearate, 12- More preferred is barium hydroxystearate.

  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, palm oil, peanut oil, pine oil, pineapple, tall oil, corn oil, rice bran oil, bean flower oil, sesame oil, olive oil, Examples include sunflower oil, palm kernel oil, cocoon oil, jojoba oil, macadamia nut oil, safflower oil, tung oil, and the like.

  The rubber composition for bead apex of the present invention is capable of maintaining both physical properties such as hardness and rupture properties and improving processability while reducing the amount of raw materials derived from petroleum resources. is there. Here, the improved “workability” was measured using a Picuma Tack Tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.) in accordance with the provisions of JIS-T 9233 (details such as measurement conditions will be described later). ) It means that the adhesive index calculated by the following formula from the adhesive strength of the unvulcanized rubber composition is 105 or more.

・ Adhesive index = (Adhesive strength of rubber composition of the present invention / Adhesive strength of reference compounded rubber composition) × 100
In addition, the reference | standard mixing | blending rubber composition in the said calculation formula points out the rubber composition mix | blended with the same composition as the rubber composition of this invention except not containing a terpene resin and a rosin resin.

  The present invention also provides a pneumatic tire provided with a bead apex comprising the rubber composition for bead apex of the present invention as described above. Here, FIG. 1 is a schematic sectional view showing an example of the pneumatic tire of 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. Prepare. A carcass 6 is bridged between the bead portions 4 and 4, and a belt layer 7 is provided outside the carcass 6 and inside the tread portion 2 to reinforce the tread portion 2 with a tagging effect.

  The carcass 6 is formed of one or more carcass plies 6a 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 6a extends from the tread portion 2 to the sidewall portion. 3, the periphery of the bead core 5 of the bead portion 4 is folded back and locked from the inner side to the outer side in the tire axial direction.

  The belt layer 7 is composed of two or more belt plies 7a in which the belt cord is arranged at an angle of, for example, 40 ° or less with respect to the tire equator CO. It is location. If necessary, a band layer (not shown) for preventing lifting at both ends of the belt layer 7 may be provided at least outside the belt layer 7. At this time, the band layer is formed of a low modulus organic fiber. The cord is formed of a continuous ply spirally wound substantially parallel to the tire equator CO.

  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. The bead apex rubber composition of the present invention is used for the bead apex rubber 8.

  FIG. 1 illustrates a pneumatic tire for a passenger car, but the present invention is not limited to this, and is used for various vehicles such as a passenger car, a truck, a bus, and a heavy vehicle. Provided pneumatic tires.

  The pneumatic tire of the present invention is produced by a conventionally known method using the rubber composition for bead apex of the present invention. That is, the rubber composition for bead apex containing the above-described essential components and other compounding agents blended as necessary is kneaded and matched to the shape of the tire bead apex in the unvulcanized stage. An unvulcanized tire is formed by extruding and molding together with other members of the tire by a conventional method on a tire molding machine. The tire of the present invention can be obtained by heating and pressurizing the unvulcanized tire in a vulcanizer.

  In the pneumatic tire of the present invention, the content ratio of components derived from petroleum resources in the bead apex rubber is further reduced, sufficient consideration is given to resource saving and environmental protection, and good physical characteristics are maintained. Since a rubber composition that is compatible with improved processability is used, it is an “eco-tyre” that is friendly to the global environment, has improved processability, and has good durability and steering stability performance.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

<Example 1 and Comparative Examples 1 and 2>
In accordance with the formulation shown in Table 1, using a 1.7L Banbury mixer manufactured by Kobe Steel Co., Ltd., the components other than sulfur and vulcanization accelerator were filled so that the filling rate would be 58%, and the rotational speed was 80 rpm. And kneading for 3 minutes until reaching 140 ° C. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded material in the amounts shown in Table 1, and then kneaded for 5 minutes at 80 ° C. using an open roll. Example 1 and Comparative Examples 1 and 2 Thus, an unvulcanized rubber composition blended according to the above was obtained.

The details of various blending components used in Examples and Comparative Examples are as follows.
(1) Natural rubber (NR): RSS # 3 (manufactured by Tech Behang)
(2) Dissolving agent: Noctiizer SD (Ouchi Shinsei Chemical Co., Ltd.)
(3) Resin (1): Petroleum resin (Marcaretz T100AS (manufactured by Maruzen Petrochemical Co., Ltd.))
(4) Resin (2): Terpene resin (PX300N (manufactured by Yasuhara Chemical Co., Ltd.))
(5) Carbon black: Show black N220 (manufactured by Cabot Japan)
(6) Silica: Ultrazil VN3 (manufactured by Degussa)
(7) Silane coupling agent: Si69 (Degussa)
(8) Anti-aging agent: NOCRACK 6C (Ouchi Shinsei Chemical Co., Ltd.) (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine))
(9) Stearic acid: Paulownia (Nippon Yushi Co., Ltd.)
(10) Zinc oxide: Zinc flower (Mitsui Metal Mining Co., Ltd.)
(11) Sulfur: Powdered sulfur (manufactured by Tsurumi Chemical Co., Ltd.)
(12) Vulcanization accelerator: Noxeller NS (Ouchi Shinsei Chemical Co., Ltd.)
The following tests were conducted on the unvulcanized rubber compositions obtained in the examples and comparative examples. Table 1 also shows the test results.

(Adhesion test)
In accordance with the provisions of JIS-T9233, using a Pikuma tack tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.), a measurement temperature of 20 ° C., a load of 4.9 N, a standing time of 10 seconds, and a peeling speed of 30 mm / min Below, the adhesive force [N] of the unvulcanized rubber composition was measured. Furthermore, the adhesive index of the rubber composition of Comparative Example 1 as a reference compounded rubber composition was set to 100, and the adhesive strength was displayed as an index according to the following calculation formula. The greater the tack index, the greater the adhesive strength and the better.

・ Adhesiveness index = (adhesive strength of each example, comparative example / adhesive strength of reference blend) × 100
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 a schematic sectional drawing which shows an example of the pneumatic tire of this invention.

Explanation of symbols

  1 tire, 2 tread part, 3 sidewall part, 4 bead part, 5 bead core, 6 carcass, 7 belt layer, 8 bead apex rubber, 9 inner liner rubber.

Claims (5)

Including 60 parts by mass of silica, 5 parts by mass or less of carbon black, 0.1 to 0.8 parts by mass of a disintegrant with respect to 100 parts by mass of the rubber component,
A rubber composition for bead apex, wherein the rubber component contains a natural rubber component composed of at least one of natural rubber and modified natural rubber within a range of 10 to 100% by mass.   The rubber composition for bead apex according to claim 1, wherein the modified natural rubber is an epoxidized natural rubber.   The rubber composition for bead apex according to claim 1 or 2, further comprising at least one of 0.5 parts by mass or more of a terpene resin and a rosin resin with respect to the rubber component.   The rubber composition for bead apex according to any one of claims 1 to 3, wherein the rubber component comprises the natural rubber component.   A pneumatic tire provided with the bead apex which consists of a rubber composition in any one of Claims 1-4.

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