JP4968732B2 - Rubber composition for bead apex and pneumatic tire using the same - Google Patents

Description

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

  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 rigidity of the bead apex rubber. Conventionally, in order to improve the rigidity of the bead apex rubber, a large amount of carbon black has been added to the bead apex rubber composition.

  Adding a large amount of carbon black is effective in increasing the rigidity of the bead apex, but induces a problem that heat is easily generated during tire running. When heat is generated, the tire's fatigue resistance is reduced and durability is impaired, and the rolling loss of the tire is increased due to an increase in loss tangent (tan δ) of the rubber, resulting in an increase in fuel consumption.

On the other hand, in recent years, environmental issues have become more important and regulations on CO ₂ emissions have been strengthened. In addition, oil resources are limited, and in the future it may become difficult to supply raw materials derived from petroleum resources such as carbon black. is expected. Therefore, it is required to replace raw materials derived from petroleum resources with raw materials derived from resources other than petroleum.

  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. 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.

  In addition, in order to reduce the amount of raw materials derived from petroleum resources and suppress heat generation during running, it has been proposed to replace the filler compounding with the silica compounding from the addition of a large amount of carbon black. A rubber composition that gives rubber having relatively good durability can be obtained by blending silica. However, when silica is blended, a problem of deterioration in workability due to an increase in viscosity is likely to occur during the preparation of the rubber composition. Tend.

  In Patent Document 1, for the purpose of reducing rolling resistance, 5 to 150 parts by weight of an inorganic filler, 0 to 30 parts by weight of a silane coupling agent, and an iodine value of 130 or less with respect to 100 parts by weight of a diene rubber. A rubber composition containing 5 to 100 parts by weight of a certain vegetable oil has been proposed.

Patent Document 2 discloses (A) a diene rubber for the purpose of providing a rubber composition for a tread and a pneumatic tire that can greatly improve wet grip performance without reducing the wear resistance and rolling resistance characteristics of the tire. Or 100 parts by weight of a rubber component comprising a mixture of diene rubber and natural rubber and containing at least 20% by weight of styrene-butadiene rubber, (B) 5 to 50 parts by weight of clay, and (C) a nitrogen adsorption specific surface area. Containing 5 parts by weight or more of silica of 100 to 300 m ² / g and (D) 1 part by weight or more of carbon black having a nitrogen adsorption specific surface area of 70 to 300 m ² / g, (B) clay and (C) silica The total amount of (B) clay, (C) silica and (D) carbon black is 100 parts by weight or less. For tire tread rubber compositions have been proposed.

  In Patent Document 3, for the purpose of providing a rubber composition for a base tread capable of reducing fuel consumption in automobile driving and a tire using the rubber composition, 100 parts by weight of a rubber component composed of natural rubber and butadiene rubber is used. A rubber composition for base treads containing 1 to 20 parts by weight of a composite material composed of starch and a plasticizer has been proposed.

  Patent Document 4 discloses a rubber component made of natural rubber and / or isoprene rubber, and butadiene rubber for the purpose of providing a rubber composition for a sidewall that enables low fuel consumption in automobile driving, and a tire using the rubber composition. A rubber composition for a sidewall containing 1 to 20 parts by weight of a composite material composed of starch and a plasticizer is proposed with respect to 100 parts by weight.

  Patent Document 5 discloses a tire rubber composition that maintains the performance required as a tire member such as air permeation resistance, crack growth resistance and hardness, and further has improved workability, and a tire obtained thereby. For the purpose of providing, 100 parts by weight of a rubber component made of natural rubber and / or a modified product thereof, 30 parts by weight or more of silica, 5 to 15 parts by weight of calcium carbonate, and 5 parts by weight or less of carbon black A rubber composition for tires to be contained has been proposed.

  Patent Document 6 provides a breaker rubber composition having an excellent balance of rigidity, adhesion, wet heat adhesion, elongation performance, and the like, and a pneumatic tire using the rubber composition for a breaker layer or a belt layer. For this purpose, 55 to 65 parts by weight of carbon black, 5 to 15 parts by weight of silica, and 3.5 to 4.5 parts by weight per 100 parts by weight of the rubber component mainly composed of natural rubber and / or isoprene rubber. A rubber composition for a breaker has been proposed that contains a part of sulfur, 0.08 part by weight or more of cobalt, a resorcin-based resin and a methylene donor.

However, in the conventional technology, a rubber composition for bead apex that reduces the amount of raw materials derived from petroleum resources, has high rigidity, low heat generation, and excellent processability during preparation, and pneumatic using the same Tires have not been obtained.
JP 2003-64222 A JP 2002-105245 A Japanese Patent Laid-Open No. 2005-2287 JP 2005-53944 A JP 2006-89526 A JP 2002-338734 A

  The present invention solves the above-mentioned problems, reduces the amount of raw materials derived from petroleum resources, has high rigidity, low heat generation, and excellent processability during preparation, and uses the rubber composition for bead apex. An object of the present invention is to provide a pneumatic tire excellent in handling stability and fuel consumption.

  The present invention contains a rubber component and an inorganic filler containing at least silica and clay, and the rubber component contains a natural rubber component consisting of at least one of natural rubber and epoxidized natural rubber, and the amount of clay added is The bead apex is in the range of 5 to 40 parts by mass with respect to 100 parts by mass of the rubber component, and the total amount of silica and clay is 65 parts by mass or more with respect to 100 parts by mass of the rubber component. A rubber composition is provided.

  In the rubber composition for bead apex of the present invention, the inorganic filler further contains carbon black, and the blending amount of the carbon black can be 5 parts by mass or less with respect to 100 parts by mass of the rubber component.

  In the rubber composition for bead apex of the present invention, the compounding amount of the inorganic filler is preferably 70 parts by mass or more with respect to 100 parts by mass of the rubber component.

  In the rubber composition for bead apex of the present invention, the rubber component is preferably composed of the natural rubber component.

  In the rubber composition for bead apex of the present invention, the durometer hardness is preferably in the range of 70 to 95.

  The present invention also provides a pneumatic tire comprising a bead apex rubber comprising any one of the above-described bead apex rubber compositions.

  According to the present invention, a rubber composition for a bead apex that reduces the amount of raw materials derived from petroleum resources, has high rigidity, low heat build-up, and excellent processability during preparation, and steering stability using the rubber composition. It is possible to provide a pneumatic tire excellent in performance and fuel consumption.

  The rubber composition for bead apex of the present invention contains a rubber component and an inorganic filler containing at least silica and clay. That is, the use amount of raw materials derived from petroleum resources can be reduced by using at least silica and clay derived from resources other than petroleum as inorganic fillers. A pneumatic tire using a bead apex rubber composition containing silica and clay, for example, generates heat like a pneumatic tire using a bead apex rubber composition containing a large amount of carbon black. There is little possibility to cause it. Furthermore, in the present invention, by blending clay, a rubber having excellent mechanical strength can be obtained without deteriorating processability during preparation of the rubber composition.

<Rubber component>
The rubber component used in the present invention includes a natural rubber component composed of at least one of natural rubber and epoxidized 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.

  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, abrasion resistance, and air permeation resistance are excellent. In particular, in the present invention, since silica is blended in the 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.

  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.

  The epoxidation rate of the epoxidized natural rubber (ENR) is preferably 10 mol% or more, and more preferably 20 mol% or more. Here, the epoxidation rate means a ratio of the number of epoxidized out of the total number of double bonds in the natural rubber before epoxidation, and is obtained by, for example, titration analysis or nuclear magnetic resonance (NMR) analysis. . When the epoxidation rate of the epoxidized natural rubber (ENR) is less than 10 mol%, the rubber hardness of the bead apex rubber composition is low because the glass transition temperature of the epoxidized natural rubber (ENR) is low. The durability and fatigue resistance of a pneumatic tire using the apex rubber composition as a bead apex rubber tends to be reduced. The epoxidation rate of the epoxidized natural rubber (ENR) is preferably 70 mol% or less, and more preferably 60 mol% or less. When the epoxidation rate of epoxidized natural rubber (ENR) exceeds 70 mol%, the rubber composition for bead apex tends to be hard and mechanical strength tends 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, it is preferable that the content rate of the natural rubber component in a rubber component shall be 70 mass% or more. When this content rate is less than 70 mass%, there exists a tendency for the reduction effect of the usage-amount of the raw material derived from a petroleum resource to become low. The content of the natural rubber component is more preferably 80% by mass or more, and further preferably 90% by mass or more. It is most preferable that the content of the natural rubber component in the rubber component is 100% by mass, that is, the rubber component is made of a natural rubber component, in that the effect of reducing the amount of the raw material derived from petroleum resources is good. However, depending on the desired tire characteristics, for example, the content of the natural rubber component in the rubber component is 90% by mass or less, further 80% by mass or less, and rubber other than the natural rubber component is blended as the balance in the rubber component. Also good.

  In addition to the natural rubber component defined above, the rubber component of the present invention can contain modified natural rubber such as hydrogenated natural rubber, for example, as rubber derived from non-petroleum resources.

  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 the rubber 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 them, SBR, BR, and IR are preferable in that the hardness of the rubber composition for bead apex can be increased and particularly good durability and fatigue resistance can be imparted to the pneumatic tire.

  The content of natural rubber (NR) in the rubber component is preferably 70% by mass or more. When the content of natural rubber (NR) is less than 70% by mass, the effect of reducing the amount of raw material derived from petroleum resources tends to be small. The content of natural rubber (NR) is more preferably 80% by mass or more, and more preferably 90% by mass or more. Further, the content of the natural rubber (NR) in the rubber component may be 100% by mass, but it is, for example, 90% by mass or less, further 80% by mass or less depending on desired tire characteristics, and the balance is epoxidized natural. Rubber, other modified natural rubber, synthetic rubber and the like can be used.

  The content of epoxidized natural rubber (ENR) in the rubber component is preferably 5% by mass or more. When the content of the epoxidized natural rubber (ENR) is less than 5% by mass, the rigidity of the bead apex rubber composition tends to be low. The content of epoxidized natural rubber (ENR) is more preferably 10% by mass or more, and further preferably 15% by mass or more. The content of epoxidized natural rubber (ENR) in the rubber component is preferably 80% by mass or less. When the content of epoxidized natural rubber (ENR) exceeds 80% by mass, the rubber hardness and rigidity are excessively increased, so that the mechanical strength of the bead apex rubber composition tends to be lowered. The content of epoxidized natural rubber (ENR) is more preferably 70% by mass or less, and further preferably 60% by mass or less.

<Clay>
In the present invention, clay (that is, clay) is a general term for an aggregate of fine particles generated by weathering or metamorphism of rocks or minerals. Means particles. Here, the clay mineral typically means crystalline or amorphous mainly composed of layered silicate.

  Specific examples of the clay include wet kaolin (unfired kaolin), fired kaolin, wet and dry wax stone clay, and the like. Of these, calcined kaolin is preferred because it has a high effect of imparting low heat buildup of the tire during vehicle travel.

  The amount of clay added to 100 parts by mass of the rubber component is in the range of 5 to 40 parts by mass. When the blending amount of the clay is less than 5 parts by mass, the reinforcing effect and the processability improving effect cannot be sufficiently obtained, and when it exceeds 40 parts by mass, the mechanical strength of the bead apex rubber composition is lowered and the bead The durability of the apex rubber tends to decrease. The blending amount of the clay is more preferably 5 parts by mass or more, and further preferably 10 parts by mass or more, and more preferably 40 parts by mass or less, and further preferably 30 parts by mass or less.

  The average particle size of the clay is preferably in the range of 0.3 to 5 μm. When the average particle size of the clay is less than 0.3 μm, the workability tends to be low, and when it exceeds 5 μm, the hardness of the bead apex rubber composition tends to be low and the mechanical strength tends to be low. The average particle size of the clay is more preferably 0.4 μm or more, and further preferably 0.5 μm or more, and more preferably 4 μm or less, and further preferably 3 μm or less.

  Preferable commercial products of clay include, for example, “Union Clay RC-1”, “Gromax LL”, “NN Kaolin Clay”, “No. 5 Clay” manufactured by Takehara Chemical Industries, Ltd., and “KAOKAL” manufactured by THIELE. "J. M.M. An example is “Huber35 (B)” manufactured by Huber.

<Silica>
Silica is blended so that the total blending amount of silica and clay is 65 parts by mass or more with respect to 100 parts by mass of the rubber component. If the total amount of silica and clay is less than 65 parts by mass, a sufficient reinforcing effect cannot be obtained. The total amount of silica and clay is more preferably 70 parts by mass or more. In terms of obtaining a good reinforcing effect, it is preferable that the total amount of silica and clay is large. However, if the total is too large, the bead apex rubber composition tends to be hard and mechanical strength tends to decrease. Therefore, the total amount of silica and clay is preferably 100 parts by mass or less, further 90 parts by mass or less, and further 85 parts by mass or less with respect to 100 parts by mass of the rubber component.

  It is preferable that the compounding quantity of the silica with respect to 100 mass parts of rubber components shall be in the range of 20-70 mass parts. When the blending amount of silica is less than 20 parts by mass, the reinforcing effect due to the blending of silica tends to be small, and when it exceeds 70 parts by mass, the rubber composition for bead apex becomes hard and mechanical strength decreases. Tend. The compounding amount of silica is more preferably 25 parts by mass or more, and further preferably 30 parts by mass or more, and more preferably 65 parts by mass or less, and further preferably 60 parts by mass or less.

The BET specific surface area of silica is preferably in the range of 100 to 300 m ² / g. When the BET specific surface area of silica is less than 100 m ² / g, the hardness of the bead apex rubber composition tends to decrease and mechanical strength tends to decrease, and when it exceeds 300 m ² / g, workability decreases. Tend. The BET specific surface area of silica is more preferably 110 m ² / g or more, further preferably 120 m ² / g or more, more preferably 280 m ² / g or less, and further preferably 260 m ² / g or less.

  In addition, a BET specific surface area can be measured by the method based on ASTM-D-4820-93, for example.

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

<Carbon black>
The inorganic filler blended in the present invention may further contain carbon black. In this case, the blending amount of carbon black with respect to 100 parts by mass of the rubber component is preferably 5 parts by mass or less. When the blending amount of carbon black exceeds 5 parts by mass, the effect of reducing the amount of petroleum resource-derived raw material used tends to be small, and low heat build-up 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 4.5 parts by mass or less, and further preferably 4 parts by mass or less. On the other hand, the compounding amount of the carbon black may be 1 part by mass or more, further 2 parts by mass or more, and further 2.5 parts by mass or more in that the reinforcing effect on the bead apex rubber composition is improved.

The BET specific surface area of carbon black is preferably in the range of 40 to 300 m ² / g. When the BET specific surface area of carbon black is less than 40 m ² / g, the mechanical strength of the bead apex rubber composition tends to decrease. The BET specific surface area of carbon black is more preferably 50 m ² / g or more, and more preferably 60 m ² / g or more. On the other hand, when the BET specific surface area of carbon black exceeds 300 m ² / g, the processability during the preparation of the bead apex rubber composition tends to be lowered. The BET specific surface area of carbon black is more preferably 280 m ² / g or less, and more preferably 260 m ² / g or less.

  Examples of preferable commercially available carbon black include “Show Black N330”, “Show Black N220”, and “Show Black N110” manufactured by Cabonet Japan.

<Silane coupling agent>
In the present invention, silica is blended. Therefore, when a silane coupling agent is used in combination, an excellent reinforcing effect is preferably imparted to the bead apex rubber composition. The compounding amount of the silane coupling agent is preferably in the range of 2 to 12% by mass when the compounding amount of silica is 100% by mass. When the amount of the silane coupling agent is less than 2% by mass, the reinforcing effect tends to be low. When the amount exceeds 12% by mass, a significant improvement in the reinforcing effect cannot be expected even if the amount is increased, while the cost is high. It tends to be uneconomical because it rises. The blending amount of the silane coupling agent is more preferably 3% by mass or more, and further preferably 4% by mass or more, and more preferably 11% by mass or less, and further preferably 10% 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-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxy 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 type such as 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; Vinyl type such as vinyltriethoxysilane, 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 inorganic fillers>
The inorganic filler may contain, for example, titanium oxide, magnesium oxide, calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, clay, talc and the like in addition to the above-mentioned clay, silica, and carbon black. However, more typically, an inorganic filler composed of clay and silica or an inorganic filler composed of clay, silica, and carbon black is blended.

  It is preferable that the compounding quantity of an inorganic filler is 60 mass parts or more with respect to 100 mass parts of rubber components. When the compounding amount of the inorganic filler is less than 60 parts by mass, the reinforcing effect tends to decrease. The blending amount of the inorganic filler is preferably 65 parts by mass or more, and more preferably 70 parts by mass or more. On the other hand, it is possible to prevent a decrease in mechanical strength due to excessively high rigidity of the bead apex rubber composition and to maintain good processability during preparation of the bead apex rubber composition. The blending amount of the filler is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and further preferably 80 parts by mass or less with respect to 100 parts by mass of the rubber component.

<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, curable resins, waxes, anti-aging agents, 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. Further, sulfur may be oil-treated.

  Vulcanization accelerators include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine or 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 (tetramethyl thiuram disulfide), tetraethyl thiuram disulfide, tetramethyl thiuram monosulfide, dipentamethylene thiuram disulfide, dipentamethylene thiuram monosulfide, dipentamethylene thiuram tetrasulfide, dipentamethylene thiuram 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. As the guanidine-based compound, for example, guanidine-based compounds such as diphenylguanidine, diortolylguanidine, triphenylguanidine, orthotolylbiguanide, diphenylguanidine phthalate can be used. 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 such as an acetaldehyde-aniline reaction product, butyraldehyde-aniline condensate, hexamethylenetetramine, an acetaldehyde-ammonia reaction product, or an aldehyde-ammonia system compound 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, amine-based, phenol-based, imidazole-based, carbamic acid metal salts, and 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, palm oil, peanut oil, rosin, pine oil, pineapple, 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.

  It is preferable that the durometer hardness which is the rubber hardness measured according to JIS K6253 after the crosslinking of the rubber composition for bead apex of the present invention is in the range of 70 to 95. If the durometer hardness is less than 70, the rigidity of the bead apex rubber composition tends to be low, and the durability of the pneumatic tire tends to decrease. On the other hand, when the durometer hardness exceeds 95, the bead apex rubber composition tends to be hard and the mechanical strength tends to decrease. The durometer hardness is more preferably 78 or more, and more preferably 80 or more, and more preferably 92 or less, and even more preferably 90 or less.

  In the measurement of the durometer hardness, the measurement range of the type A durometer hardness is 10 to 90. When the type A durometer hardness exceeds 90, the measurement is performed with the type D durometer. When less than 20, it shall be measured with a type A durometer.

  The pneumatic tire of the present invention is a pneumatic tire provided with a bead apex rubber made of the rubber composition for bead apex of the present invention. Hereinafter, the pneumatic tire of the present invention will be described with reference to FIG. 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 thereof, and a bead portion 4 positioned at an inner end of each sidewall portion 3. 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 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. If necessary, a band layer (not shown) for preventing lifting at both ends of the belt layer 7 may be provided on at least the outer side of the belt layer 7. At this time, the band layer is 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 rubber composition for bead apex of the present invention is used for the bead apex rubber 8 of the bead portion 4.

  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, a rubber composition for a bead apex containing the above-described essential components and other additives blended as necessary is kneaded and matched to the shape of the bead apex of the tire at an 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 according to the present invention, in particular, consideration is given to resource saving and environmental protection by reducing the amount of petroleum resource-derived raw materials used for bead apex rubber, as well as handling stability and fuel efficiency. In addition, it is excellent in processability during manufacturing. Therefore, the pneumatic tire provided by the present invention can be suitably applied to various uses such as passenger cars, trucks, buses, heavy vehicles, etc., as “eco-tires” that are 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.

<Examples 1-5 and Comparative Examples 1-5>
(Preparation of unvulcanized rubber sheet)
According to the formulation shown in Tables 1 and 2, the components except for sulfur and the vulcanization accelerator were kneaded at 150 ° C. for 5 minutes using a 1.7 L Banbury mixer manufactured by Kobe Steel to obtain a kneaded product. To this, sulfur and a vulcanization accelerator were added in the formulation shown in Tables 1 and 2, and a biaxial open roll was used and further kneaded at 80 ° C. for 5 minutes to prepare an unvulcanized rubber composition. Was extruded to a predetermined thickness to obtain an unvulcanized rubber sheet and an unvulcanized rubber piece having a predetermined shape.

(Production of rubber sheet for test)
The unvulcanized rubber sheet and the unvulcanized rubber piece of the predetermined shape obtained above were vulcanized at 170 ° C. for 15 minutes to obtain a test rubber sheet and a test rubber piece.

(Production of test tires)
An unvulcanized rubber sheet having a thickness of 10 mm obtained by the above method is extruded into a bead apex shape, and is molded together with other members of the tire by a normal method on a tire molding machine, thereby forming an unvulcanized tire. did. This unvulcanized tire was heated and pressurized at 175 ° C. for 10 minutes in a vulcanizer to produce a size 195 / 60R15 pneumatic tire having the structure shown in FIG. 1 as a test tire.

(Mooney viscosity index)
For the above unvulcanized rubber composition, the Mooney viscosity was measured at 130 ° C. according to JIS K6300, and the Mooney viscosity of Comparative Example 1 was set to 100.
Mooney viscosity index = (Mooney viscosity of each example and comparative example) ÷ (Mooney viscosity of comparative example 1) × 100
The index is indicated by. The smaller the index, the lower the viscosity and the better the workability.

(Rubber hardness)
The rubber hardness was measured in accordance with JIS K6253 for a sample in which three test rubber sheets of 150 mm × 150 mm × 2.0 mm obtained by the above method were stacked.

(Garbage die extrudability)
About said unvulcanized rubber composition, the extrusion was evaluated by setting a garbage die to a lab plast mill. The evaluation was performed by scoring the surface of the extrudate with A to E according to ASTM D2230 method B.

(Extrudability)
When extrudability is evaluated by a method according to ASTM D2230, Method B, the edge of the extrudate is 6 points or more with a score of 1 to 10, and the surface is A or B with a score of A to E Is shown as A, and cases other than the above are shown as B.

(Complex modulus (E *), loss tangent (tan δ))
A rubber piece for test of 4.0 mm × 2.0 mm × 40 mm obtained by the above method was subjected to E using a viscoelastic spectrometer manufactured by Iwamoto under the conditions of a temperature of 70 ° C., an initial strain of 10%, and a dynamic strain of 2%. * And tan δ were measured.

(Tensile strength (TB), elongation at break (EB))
For the No. 3 dumbbell test rubber sheet obtained by the above method, the tensile strength (TB) and elongation at break (EB) were measured according to JIS K6251.

(Maneuvering stability)
The test tire obtained above was mounted on a Toyota Corolla, and an actual vehicle steering stability test was conducted on a tire test course. Steering stability was evaluated as A when the responsiveness was acceptable and B when the responsiveness was unacceptable.

(durability)
The test tire obtained above was run for 30000 km by tabletop evaluation and then disassembled, and the damage state of the bead apex was visually observed. A case where no damage was observed in the bead apex was evaluated as A, and a case where damage was observed was evaluated as B.

Note 1: Natural rubber is TSR.
Note 2: The epoxidized natural rubber is “EPOXYPRENE25” (epoxidation rate: 25%) manufactured by Mu-ang Mai Guthrie Public Company Limited (Thailand).
Note 3: Carbon black is “Show Black N330” (BET specific surface area: 79 m ² / g) manufactured by Cabonet Japan.
Note 4: Silica is “VN2” (BET specific surface area: 125 m ² / g) manufactured by Degussa.
Note 5: The clay is “Satinton W” manufactured by Takehara Chemical Industries.
Note 6: Silane coupling agent is “Si69” manufactured by Degussa.
Note 7: The curable resin is “Sumilite Resin PR12686” manufactured by Sumitomo Durez Co., Ltd.
Note 8: Vegetable oil is “rapeseed oil” manufactured by Nisshinsei Co., Ltd.
Note 9: Stearic acid is “stearic acid” manufactured by NOF Corporation.
Note 10: Zinc oxide is “Zinc Hana 1” manufactured by Mitsui Mining & Smelting.
Note 11: Sulfur is “powder sulfur” manufactured by Tsurumi Chemical Industry.
Note 12: The vulcanization accelerator is “Noxeller NS” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

  As shown in Tables 1 and 2, in Comparative Example 1 in which only carbon black was blended as the inorganic filler, tan δ was high, and in Comparative Examples 2 and 3 in which only carbon black and silica were blended as the inorganic filler, Comparative Example 1 and In comparison, tan δ was reduced, but Mooney viscosity was high and processability was not good. In Comparative Example 4 with a small amount of clay, the processability was not good and E * tended to be low, and in Comparative Example 5 with a large amount of clay, the durability was not good. On the other hand, in Examples 1 to 5 which are examples of the present invention in which silica and clay were combined in combination so as to be the same amount as the silica of Comparative Example 2, rubber physical properties, tire handling stability, tire durability Tended to be good, and tan δ was reduced as compared with Comparative Example 2. Moreover, in Examples 1-5, the Mooney viscosity was reduced compared with the comparative example 2, and the workability evaluated by the garbage die extrudability and the extrudability was a tendency which was favorable. Therefore, according to this invention, it turns out that the rubber composition for bead apex which is high-rigidity, low exothermic property, and is excellent also in the workability at the time of preparation is obtained.

  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.

  The rubber composition for bead apex of the present invention is suitably applied to the bead apex rubber of pneumatic tires for various uses such as for passenger cars, trucks, buses, heavy vehicles, etc. , And can be suitably applied to the various uses described above.

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, 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 (6)

Containing a rubber component and an inorganic filler containing at least silica and clay;
The rubber component includes a natural rubber component consisting of at least one of natural rubber and epoxidized natural rubber,
The amount of the clay is in the range of 5 to 40 parts by mass with respect to 100 parts by mass of the rubber component,
The rubber composition for bead apex, wherein the total amount of the silica and the clay is 65 parts by mass or more with respect to 100 parts by mass of the rubber component. The inorganic filler further includes carbon black,
2. The rubber composition for bead apex according to claim 1, wherein a blending amount of the carbon black is 5 parts by mass or less with respect to 100 parts by mass of the rubber component.   3. The rubber composition for bead apex according to claim 1, wherein the compounding amount of the inorganic filler is 70 parts by mass or more with respect to 100 parts by mass of 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.   The rubber composition for bead apex according to any one of claims 1 to 4, wherein the durometer hardness is in a range of 70 to 95.   A pneumatic tire provided with the bead apex rubber which consists of a rubber composition for bead apex in any one of Claims 1-5.

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