JP5480588B2 - Pneumatic tire - Google Patents

Description

The present invention relates to a pneumatic tire.

In general, raw materials derived from petroleum resources such as butadiene rubber and carbon black are used for the rubber composition for tires. However, in recent years, environmental issues have been emphasized, and regulations for suppressing carbon dioxide emissions have been strengthened. In addition, the existing amount of petroleum is limited, and there is a limit to the use of raw materials derived from petroleum resources. Therefore, assuming that oil will be depleted in the future, it is required to replace some or all of the raw materials derived from petroleum resources with raw materials derived from non-petroleum resources such as natural rubber, silica, white filler such as calcium carbonate. ing.

On the other hand, demands for lowering rolling resistance of tires are becoming stricter, and it is desired to reduce rolling resistance not only in treads but also in other members such as breakers and sidewalls by using a technique such as silica. Yes.

However, when silica is blended in each member of the tire, the silica has high electrical insulation and tends to increase the electrical resistance of the tire, so that there is a drawback that static electricity tends to accumulate in the vehicle. Such accumulation of static electricity may cause, for example, a spark due to static electricity when the vehicle is refueled, and may ignite the fuel.

In order to avoid this drawback, a technique for laying a conductive thin film on the tread part and the side wall part, a technique for lining the tread rubber body with a conductive rubber layer, a technique for providing an outer conductive part made of conductive rubber (patent) However, when silica is used for the tread portion, breaker portion, and sidewall portion, it is very difficult to reduce the electrical resistance of the tire with the conventional technology.

Further, in the structure of the conventional tire proposed for avoiding the above-mentioned drawbacks, cracks are generated starting from the ply winding portion called PTL (ply turn-up loose), and grow on the side wall side or the inner liner side, In some cases, a crack on the sidewall surface or a crack on the inner liner surface may occur.

In order to improve the crack resistance performance, a method of blending butadiene rubber with good flex crack resistance performance in addition to natural rubber exhibiting excellent tear strength has been used, but butadiene rubber is a polymer derived from petroleum. Therefore, it is also desired to improve the crack resistance performance without using butadiene rubber.

JP-A-8-230407 JP 9-71112 A JP 2000-190709 A

An object of the present invention is to provide a pneumatic tire that solves the above-mentioned problems, suppresses rolling resistance, prevents static electricity during running of the tire, and further improves crack resistance.

The present invention includes a tread portion, a sidewall portion, a bead portion, a carcass extending from the tread portion through the sidewall portion to the bead portion, and an air having a breaker portion outside the carcass in the tire radial direction. The volume specific resistance of the tread rubber, breaker rubber, and sidewall rubber formed in the tread portion, the breaker portion, and the sidewall portion, respectively, is 1 × 10 ⁸ Ω · cm or more. The pneumatic tire includes an internal conductive layer disposed between the carcass and the sidewall rubber, a conductive rubber in contact with the internal conductive layer and disposed in a lower region at both ends of the breaker, the conductive rubber And a coated rubber disposed so as to cover the upper side of the breaker part, and a part of the tread that comes into contact with the coated rubber. A conductive rubber embedded in the tread portion so as to be exposed to the inner conductive layer, and a bead portion rubber disposed in a region in contact with the inner conductive layer and in contact with the rim flange of the bead portion, the inner conductive layer, the conductive rubber, and the coating The volume specific resistance values of the rubber, the current-carrying rubber, and the bead rubber are all less than 1 × 10 ⁸ Ω · cm, and the internal conductive layer comprises 30 to 90% by mass of natural rubber and epoxidized natural rubber. A pneumatic tire manufactured using a rubber composition for an internal conductive layer containing 10 to 50 parts by mass of carbon black and 10 to 50 parts by mass of silica with respect to 100 parts by mass of a rubber component containing 70 to 10% by mass. About.

The thickness of the internal conductive layer is preferably 0.2 to 1.0 mm. The bead rubber is preferably clinch rubber or chafer rubber. Furthermore, it is preferable that the current-carrying rubber is formed continuously in the tire circumferential direction.

According to the present invention, the internal conductive layer disposed between the carcass and the sidewall rubber, the conductive rubber disposed in the lower region at both ends of the breaker in contact with the internal conductive layer, the conductive rubber and the contact region A coated rubber arranged to cover the upper side of the breaker portion, a conductive rubber embedded in the tread portion so as to be in contact with the coated rubber and partly exposed on the surface of the tread, and a bead in contact with the internal conductive layer The pneumatic tire is provided with a bead rubber disposed in a region in contact with the rim flange, and a specific composition is used for the inner conductive layer. Therefore, the rolling resistance of the pneumatic tire can be kept low, and the generation of static electricity when the tire is running can be prevented. Furthermore, the crack resistance can be improved.

It is a figure which shows the upper right half of sectional drawing of the pneumatic tire of this invention.

<Basic structure>
The structure of the pneumatic tire of the present invention is exemplified in the upper right half of the tire cross section in FIG. The tire 1 includes a tread rubber 7 constituting a tread portion, a pair of sidewall rubbers 8 constituting a pair of sidewall portions extending inward in the tire radial direction from both ends thereof, and a clinch positioned at an inner end of each sidewall portion. A clinch rubber 3 constituting the part and a chafer rubber 2 constituting the chafer part located at the upper part of the rim. A carcass 10 is bridged between the clinch portion and the chafer portion, and a breaker rubber 9 constituting a breaker portion is disposed on the outer side of the carcass 10 in the tire radial direction. The carcass 10 is formed of one or more carcass plies on which carcass cords are arranged. The carcass ply includes a bead core 13 extending from a tread portion through a sidewall portion, and a bead core 13 extending from the upper end of the bead core 13 toward the sidewall. The area around the apex 11 is folded from the inner side to the outer side in the tire axial direction and is locked by the folded portion. The breaker portion is composed of two or more breaker plies in which breaker cords are arranged, and the breaker cords are stacked in different directions so that the breaker cords intersect each other. In the pneumatic tire of the present invention, a covering rubber (under tread) 5 that covers the upper side of the breaker portion is provided between the tread portion (tread rubber, base tread) and the breaker portion. The conductive rubber 4 is disposed between the carcass ply and both ends of the breaker part and the side wall part, having a contact area with the covering rubber 5. An energizing rubber 6 is disposed in the tread rubber 7 so as to be in contact with the covering rubber 5 and partially exposed to the grounding surface. Further, an inner conductive layer 14 having a contact area with the conductive rubber 4 and extending between at least the conductive rubber 4 and the clinch rubber 3 or the chafer rubber 2 between the carcass 10 and the sidewall rubber 8 is provided. Be placed. In the pneumatic tire 1, the current-carrying rubber 6, the covering rubber 5, the conductive rubber 4, the internal conductive layer 14, the clinch rubber 3 or the chafer rubber 2 are electrically connected.

By adopting the above structure, the bead rubber located in the contact area with the rim during running of the tire or the static electricity generated in the ground contact area is electrically connected to the outside of the tire through the electrically connected conductive rubber member inside the tire. To be released. Therefore, even if silica is used for the tread rubber, breaker rubber, and sidewall rubber, the electrical resistance of the tire can be lowered.

The pneumatic tire of the present invention can be used as tires for various vehicles such as passenger cars, trucks and buses, and heavy machinery.

<Tread rubber, breaker rubber, sidewall rubber>
The volume specific resistances of the tread rubber, breaker rubber, and sidewall rubber constituting the tire are all set to 1 × 10 ⁸ Ω · cm or more. Conventionally, carbon black has been used as a rubber reinforcing agent (filler), but rolling resistance can be reduced by replacing this with silica. Furthermore, since silica is not a petroleum-derived material, it is preferably used from the viewpoint of environmental problems as compared with carbon black, which is a petroleum-derived material. However, when silica is used, the volume resistivity tends to increase. According to the present invention, the volume specific resistance of the rubber composition is 1 by the above-mentioned electrically connected structure while maintaining the basic characteristics such as the reduction of the rolling resistance of the tire and the processability of the rubber by using the silica compound as a base. The problem of high electric resistance of × 10 ⁸ Ω · cm or more can be improved.

In the pneumatic tire of the present invention, it is preferable that 50% by mass or more of the filler contained in each of the tread rubber, breaker rubber, and sidewall rubber is silica. When silica accounts for 50 mass% or more of the filler, the effect of reducing the rolling resistance of the tire is good. The proportion of silica in the filler is more preferably 70% by mass or more, and still more preferably 90% by mass or more. All of the above fillers may be silica, but other fillers may be used in combination for the purpose of adjusting the electrical conductivity and mechanical strength of the tread rubber, breaker rubber and sidewall rubber.

Silica can be blended in an amount of, for example, 5 to 100 parts by mass with respect to 100 parts by mass of the rubber component in each of the tread rubber, breaker rubber, and sidewall rubber. When it is 5 parts by mass or more, the rolling resistance of the tire can be reduced, and when it is 100 parts by mass or less, the workability due to the increase in viscosity of the unvulcanized rubber composition at the production of tread rubber, breaker rubber and sidewall rubber is improved. Reduction and excessive increase in cost can be prevented well.

As silica, those generally used for general-purpose rubber can be used, and examples thereof include dry method white carbon, wet method white carbon, colloidal silica and the like. Of these, wet-type white carbon containing hydrous silicic acid as a main component is preferable.

Tread rubber, breaker rubber and the nitrogen adsorption specific surface area of silica used in the sidewall rubber (BET method), for example 100 to 300 m ² / g, it is preferable that further the range of 150 to 250 ² / g. When it is 100 m ² / g or more, the abrasion resistance of the tire is improved satisfactorily by obtaining a sufficient reinforcing effect. On the other hand, when it is 300 m ² / g or less, the processability during production of each rubber is good, and the steering stability of the tire is also ensured. In the present invention, the nitrogen adsorption specific surface area of silica is measured by the BET method according to ASTM D3037-81.

<Coating rubber>
The covering rubber 5 in the present invention is made of a rubber whose volume resistivity is set to be less than 1 × 10 ⁸ Ω · cm so as to be in contact with the conductive rubber 4 and the energizing rubber 6 and cover the upper part of the breaker portion. Become. If the volume resistance value is less than 1 × 10 ⁸ Ω · cm, a desired degree of improvement in tire conductivity can be obtained. The volume resistivity is preferably 1 × 10 ⁷ Ω · cm or less, more preferably 1 × 10 ⁶ Ω · cm or less, and preferably 1 × 10 ³ Ω · cm or more. Preferably, it is set to 1 × 10 ⁴ Ω · cm or more.

If the thickness of the covering rubber 5 is 0.2 mm or more, the desired effect of improving the tire conductivity is obtained, and if it is 3.0 mm or less, the rolling resistance of the tire is not greatly deteriorated. The thickness of the conductive rubber is preferably 0.5 to 2.0 mm, particularly preferably 0.9 to 1.5 mm. The covering rubber 5 only needs to have a portion in contact with the conductive rubber and the current-carrying rubber, and is provided over the entire surface between the tread portion and the breaker portion, or a range up to or beyond the position where the current-carrying rubber is disposed. Or can be partially provided.

Further, with respect to the portion where the covering rubber is in contact with the conductive rubber and the current-carrying rubber, it is preferable that the conductive rubber has a belt-shaped portion having a width of 5 mm or more in the tire circumferential direction. More preferably. By bringing the conductive rubber and the covering rubber into contact with each other under the above conditions, the conductive effect of the tire can be sufficiently obtained. The contact with the current-carrying rubber is preferably in contact with the entire surface of the current-carrying rubber in the tire width direction.

In this invention, it is preferable that the said covering rubber contains 20-80 mass parts of carbon black with respect to 100 mass parts of rubber components. When carbon black of 20 parts by mass or more is blended, the conductivity of the covering rubber is increased. The blending amount of the carbon black is more preferably 30 parts by mass or more, still more preferably 40 parts by mass or more, more preferably 80 parts by mass or less, still more preferably 60 parts by mass or less.

The nitrogen adsorption specific surface area of carbon black used for the coating rubber is preferably 80 to 140 m ² / g. Thereby, the mechanical strength of the coated rubber is good, which is also preferable in terms of ensuring processability during production. The nitrogen adsorption specific surface area is more preferably 100 m ² / g or more, and more preferably 140 m ² / g or less. In the present invention, the nitrogen adsorption specific surface area of carbon black is determined by A method of JIS K6217, item 7. As the carbon black, wood tar carbon black, which is a resource other than petroleum, is preferably employed.

The coated rubber may contain silica as a filler in addition to carbon black.
In the coated rubber, the content of silica is preferably 20 to 40 parts by mass with respect to 100 parts by mass of the rubber component. When it is 20 parts by mass or more, the rolling resistance of the tire can be reduced, and when it exceeds 40 parts by mass, the rolling resistance tends to deteriorate.

The nitrogen adsorption specific surface area (BET method) of silica used for the coating rubber is preferably in the range of 80 to 120 m ² / g, for example. When it is 80 m ² / g or more, the abrasion resistance of the tire is improved satisfactorily by obtaining a sufficient reinforcing effect.

<Conductive rubber>
The conductive rubber 4 according to the present invention has a volume resistivity provided between the carcass ply constituting the carcass 10 to be described later and the edge portion and side wall portion of the breaker portion so as to have an internal conductive layer 14 and a contact region. It consists of rubber set to less than 1 × 10 ⁸ Ω · cm. If the volume eigenvalue is less than 1 × 10 ⁸ Ω · cm, an effect of improving the conductivity of the tire can be obtained. The volume resistivity of the conductive rubber 4 is preferably set to 1 × 10 ⁷ Ω · cm or less, more preferably 1 × 10 ⁶ Ω · cm or less, and preferably 1 × 10 ³ Ω · cm or more. Preferably, it is set to 1 × 10 ⁴ Ω · cm or more.

The conductive rubber only needs to be formed continuously or discontinuously in the tire circumferential direction between the carcass ply constituting the carcass and the edge portion and side wall of the breaker portion as described above. There is no particular limitation.

The rubber blend of the conductive rubber 4 can be a blend substantially similar to that of the covering rubber, and the same carbon black or silica as described above may be blended.

<Electric rubber>
In the present invention, the current-carrying rubber is embedded in the tread part, and a part thereof is exposed to the tire ground contact surface, and the other part is connected (contacted) with the covering rubber, so that the static electricity generated during the running of the pneumatic tire is connected. Effectively release to the ground. In FIG. 1, the current-carrying rubber 6 is shown as a structure embedded in one central portion of the tread portion, but a plurality of current-carrying rubbers can also be buried. And the width | variety of the electricity supply rubber | gum of a tire width direction is 0.2-10 mm, for example, Preferably it is 0.9-1.5 mm. If the thickness is less than 0.2 mm, the current-carrying effect is small. On the other hand, if it exceeds 10 mm, the grounding area of the current-carrying rubber in the tread portion is relatively increased, which may impair the grounding characteristics. Moreover, although it is preferable to form the current carrying rubber as a continuous layer in the tire circumferential direction, it can also be formed intermittently in the tire circumferential direction.

The volume specific resistance of the current-carrying rubber is set lower than that of the tread rubber, breaker rubber, and sidewall rubber, and is less than 1 × 10 ⁸ Ω · cm. When the volume resistivity is less than 1 × 10 ⁸ Ω · cm, the conductivity of the tire is improved and the effect of discharging static electricity is obtained. The volume specific resistance of the conductive rubber is more preferably 1 × 10 ⁷ Ω · cm or less, and further preferably 1 × 10 ⁶ Ω · cm or less.

The electrically conductive rubber can employ substantially the same composition as the covering rubber, and the same carbon black or silica as described above may be incorporated. Moreover, it is also possible to employ | adopt the compounding design which provides electroconductivity based on the mixing | blending of a tread rubber from a viewpoint of improving a grounding characteristic.

<Internal conductive layer>
The internal conductive layer 14 in the present invention has a contact region with the conductive rubber 4, and is at least a position in contact with the clinch rubber 3 or the chafer rubber 2 from the conductive rubber 4 between the carcass 10 and the sidewall rubber 8. For example, the upper end portion of the internal conductive layer 14 is electrically connected to the conductive rubber 4 and the lower end portion is electrically connected to the clinch rubber 3 or the chafer rubber 2. The volume resistivity of the internal conductive layer 14 is set to less than 1 × 10 ⁸ Ω · cm. If the volume eigenvalue is less than 1 × 10 ⁸ Ω · cm, an effect of improving the conductivity of the tire can be obtained. The volume resistivity of the internal conductive layer 14 is preferably set to 1 × 10 ⁷ Ω · cm or less, more preferably 1 × 10 ⁶ Ω · cm or less. When a rubber composition containing a large amount of a conductive component is employed, the electrical resistance decreases, but on the other hand, the electrochemical reaction in the region where the tire is in contact with the rim is promoted and the rim is likely to rust. In order to avoid this, the volume resistivity of the conductive rubber is preferably set to 1 × 10 ³ Ω · cm or more, more preferably 1 × 10 ⁴ Ω · cm or more.

If the thickness of the internal conductive layer 14 is 0.2 mm or more, the desired effect of improving tire conductivity is obtained, and if it is 1.0 mm or less, the rolling resistance of the tire is not greatly deteriorated. The thickness of the conductive rubber is particularly preferably in the range of 0.5 to 1.0 mm. The internal conductive layer 14 is disposed between the carcass 10 and the sidewall rubber 8 (for example, disposed adjacent to the outside of the carcass 10 and the inside of the sidewall rubber 8), and the conductive rubber and the bead rubber. What is necessary is just to have a part which touches. A part of the inner conductive layer 14 may be disposed between the carcass and the breaker, and may be formed continuously or discontinuously in the tire circumferential direction.

Further, with respect to the portion where the inner conductive layer is in contact with the conductive rubber and the bead rubber, it is preferable that the conductive rubber is in contact with the belt in the tire circumferential direction with a width of 5 mm or more. More preferably. By bringing the internal conductive layer and the conductive rubber into contact with each other under the above conditions, the tire conductive effect can be sufficiently obtained. The contact with the bead rubber is preferably a portion in contact with the width of 5 mm or more along the carcass shape, and more preferably 10 mm or more.

The internal conductive layer is obtained by a rubber composition for an internal conductive layer containing natural rubber (NR), epoxidized natural rubber (ENR) as a rubber component, and further carbon black and silica. The natural rubber includes deproteinized natural rubber (DPNR) and high-purity natural rubber (HPNR).

In the internal conductive layer (rubber composition for internal conductive layer), the content of natural rubber in 100% by mass of the rubber component is 30% by mass or more, preferably 40% by mass or more, and the content of epoxidized natural rubber is 70%. It is not more than mass%, preferably not more than 50 mass%. When the content of the natural rubber is less than 30% by mass or the content of the epoxidized natural rubber exceeds 70% by mass, the rubber strength of the obtained rubber composition is not sufficient. Moreover, the content rate of this natural rubber is 90 mass% or less, Preferably it is 80 mass% or less, The content rate of this epoxidized natural rubber is 10 mass% or more, Preferably it is 20 mass% or more. If the content of the natural rubber exceeds 90% by weight or the content of the epoxidized natural rubber is less than 10% by mass, the bending crack resistance performance deteriorates.

As the epoxidized natural rubber, commercially available epoxidized natural rubber may be used, or natural rubber may be epoxidized. The method for epoxidizing natural rubber is not particularly limited, and can be carried out using a method such as a chlorohydrin method, a direct oxidation method, a hydrogen peroxide method, an alkyl hydroperoxide method, or a peracid method. Examples thereof include a method of reacting natural rubber with an organic peracid such as peracetic acid or performic acid.

The epoxidation rate of the epoxidized natural rubber is preferably 12 to 50 mol%. If the epoxidation rate is less than 12 mol%, the effect of epoxidized natural rubber becomes compatible with natural rubber, and the effect tends to decrease. If it exceeds 50 mol%, the rubber strength of the obtained rubber composition tends to be insufficient. There is.

In the internal conductive layer, as a rubber component, in addition to natural rubber and epoxidized natural rubber, butadiene rubber, styrene butadiene rubber, butyl rubber, halogenated butyl rubber, a halide of a copolymer of isobutylene and p-methylstyrene, and the like. Although it can be used, it is preferably made of only natural rubber and epoxidized natural rubber because it is obtained from resources other than petroleum.

The internal conductive layer includes specific amounts of carbon black and silica.
In the internal conductive layer, the carbon black content is 10 parts by mass or more, preferably 20 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 10 parts by mass, the tear strength is low and the strength of the rubber may be insufficient. The carbon black content is 50 parts by mass or less, preferably 40 parts by mass or less. If it exceeds 50 parts by mass, the resistance to bending cracking is inferior.

The nitrogen adsorption specific surface area of carbon black used for the internal conductive layer is preferably 80 to 140 m ² / g. Thereby, the mechanical strength of an internal conductive layer is favorable, and it is preferable also from the point which ensures the workability at the time of manufacture. The nitrogen adsorption specific surface area is more preferably 100 m ² / g or more, and more preferably 140 m ² / g or less.

The silica is not particularly limited, and examples thereof include the same as described above.
In the internal conductive layer, the content of silica is 10 parts by mass or more, preferably 20 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 10 parts by mass, the tear strength is low and the strength of the rubber may be insufficient. The silica content is 50 parts by mass or less, preferably 40 parts by mass or less. If it exceeds 50 parts by mass, the resistance to bending cracking is inferior.

The nitrogen adsorption specific surface area (BET method) of the silica used for the internal conductive layer is, for example, in the range of 80 to ²⁰⁰ m ² / g, preferably 80 to 120 m ² / g. When it is 80 m ² / g or more, the abrasion resistance of the tire is improved satisfactorily by obtaining a sufficient reinforcing effect.

When silica is blended in the internal conductive layer, it is preferable to use a silane coupling agent in combination. Examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, and bis (2-triethoxy). Silylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane and the like. Of these, bis (3-triethoxysilylpropyl) tetrasulfide is preferable from the viewpoint that processability can be improved.

In the internal conductive layer, the content of the silane coupling agent is preferably 4 to 20 parts by mass with respect to 100 parts by mass of silica. If it is less than 4 parts by mass, the flex crack resistance tends to be inferior, and if it exceeds 20 parts by mass, the flex crack resistance tends to be inferior.

In addition, it is preferable not to use an aroma oil and a petroleum resin for an internal conductive layer from a viewpoint of utilizing resources other than petroleum.

In the present invention, static electricity can be effectively discharged through the electrical connection path as shown in FIG. 1, and crack resistance can be improved by using the rubber composition for an internal conductive layer having the above composition. Therefore, the occurrence of cracks can be prevented starting from the ply winding portion, and the occurrence of cracks on the sidewall surface and the inner liner surface can also be prevented.

<Bead rubber>
In the present invention, the bead rubber disposed in the region of the bead that contacts the rim flange is a concept including clinch rubber, chafer, and rubber chafer. When the tire travels, driving force is transmitted from the rim via the bead rubber, and at this time, static electricity is easily generated due to friction between the rim and the bead rubber. Since the bead rubber has a contact area with the internal conductive layer, static electricity is effectively discharged to the ground plane through the internal conductive layer. In FIG. 1, a clinch rubber, a chafer or a rubber chafer is electrically connected to the internal conductive layer 14.

Here, the volume resistivity of the bead rubber is less than 1 × 10 ⁸ Ω · cm. Good electrical conductivity of the tire can be obtained by setting the volume resistivity to less than 1 × 10 ⁸ Ω · cm. The volume resistivity of the bead rubber is preferably less than 1 × 10 ⁷ Ω · cm, more preferably less than 1 × 10 ⁶ Ω · cm. Since bead rubber, that is, clinch rubber, chafer, and rubber chafer, requires wear resistance, rigidity, and hardness, in addition to such a compounding design, the electric resistance is adjusted by the compounding method of the conductive rubber and the current-carrying rubber. can do.

<Carcass>
The carcass 10 extending from the tread portion to the bead portion through the sidewall portion in the present invention is composed of one or more carcass plies on which carcass cords are arranged. The carcass ply has a configuration in which carcass cords are aligned in parallel and embedded in rubber. Examples of the fiber material constituting the carcass cord include rayon, nylon, polyester, and aramid. These may be used alone or in combination of two or more. Especially, since it is a natural resource material, it is preferable to use rayon, and it is preferable to mix rayon 90 mass% or more with respect to the fiber material which comprises a carcass cord.

Although the volume specific resistance of the ply rubber is not particularly limited, it can be set similarly to the tread rubber, breaker rubber and sidewall rubber. In addition, the volume resistivity of the ply rubber can be set to less than 1 × 10 ⁸ Ω · cm, which, in combination with the adjacent internal conductive layer, improves the conductivity of the tire and provides an effect of discharging static electricity. It is done. In this case, the volume specific resistance of the ply rubber can be set to preferably 1 × 10 ⁷ Ω · cm or less, more preferably 1 × 10 ⁶ Ω · cm or less.

The ply rubber in the present invention can be blended substantially the same as the coating rubber, and may be blended with carbon black or silica similar to the above. Further, from the viewpoint of improving the adhesion with the carcass cord, it is possible to impart conductivity by blending carbon black or the like based on the basic blend of conventional ply rubber.

In the present invention, the volume specific resistance of the tread rubber, breaker rubber, and sidewall rubber is set to 1 × 10 ⁸ Ω · cm or more, while maintaining the tire performance such as rolling resistance and durability, The volume specific resistances of the conductive rubber, the covering rubber, the energizing rubber, and the bead rubber that are electrically connected to each other are adjusted to be lower. Therefore, static electricity generated in the pneumatic tire can be effectively discharged through the electrical connection passage formed by these.

<Rubber compounding>
The inner conductive layer, the covering rubber, the conductive rubber, the energizing rubber, the chafer rubber, the clinch rubber, the tread rubber, the breaker rubber, and the sidewall rubber in the pneumatic tire of the present invention are composed of, for example, the following rubber compositions.

Examples of the rubber component used in these rubber compositions include those listed above for the internal conductive layer. Diene rubber is preferable as the rubber component used in the covering rubber, conductive rubber, conductive rubber, chafer rubber, and clinch rubber. Among them, natural rubber, styrene-butadiene rubber, butadiene rubber, isoprene rubber, epoxidized natural rubber, Deproteinized natural rubber and the like are preferred.

In the rubber composition, the following compounding agents generally employed in tire rubber compounding can be appropriately compounded.

In the present invention, as described above, it is preferable to add silica to the tread rubber, breaker rubber, and sidewall rubber. When silica is blended in the rubber composition, it is preferable to blend 1 to 20 parts by mass of the silane coupling agent with respect to 100 parts by mass of silica, for example. By blending 1 part by mass or more, the wear resistance of the tire is improved and the rolling resistance can be reduced. On the other hand, when the amount is 20 parts by mass or less, there is little risk of scorching in the rubber kneading and extrusion processes. Examples of the silane coupling agent include those similar to the above.

Other fillers, vulcanizing agents, vulcanization accelerators, stearic acid, zinc oxide, softeners, plasticizers, anti-aging agents, foaming agents, anti-scorching agents, and the like can be added to the rubber composition.

As the vulcanizing agent, an organic peroxide or a sulfur-based vulcanizing agent can be used. As the organic peroxide, for example, dicumyl peroxide, t-butylperoxybenzene, di-t-butylperoxy-diisopropylbenzene can be preferably used. Moreover, as a sulfur type vulcanizing agent, sulfur, morpholine disulfide, etc. can be used, for example, and sulfur can be used conveniently.

Examples of vulcanization accelerators include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine or aldehyde-ammonia, imidazoline, and xanthate vulcanization accelerators. It is done.

The pneumatic tire of this invention is manufactured by a normal method using the rubber composition which comprises each tire member. That is, the rubber composition for each tire member blended with the above components is extruded in accordance with the shape of the tire member at an unvulcanized stage, and is molded together with other tire members by a normal method on a tire molding machine. By doing so, an unvulcanized tire is formed. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
<Material>
NR (natural rubber): TSR20
BR (butadiene rubber): BR150B manufactured by Ube Industries, Ltd.
ENR25: manufactured by Kumpulan Guthrie Berhad (Malaysia) (epoxidized natural rubber with an epoxidation rate of 25 mol%)
ENR50: manufactured by Kumpulan Guthrie Berhad (Malaysia) (epoxidized natural rubber with an epoxidation rate of 50 mol%)
SBR1502: SBR1502 manufactured by Sumitomo Chemical Co., Ltd.
SBR1500: SBR1500 manufactured by Sumitomo Chemical Co., Ltd.
Carbon Black N220: Dia Black I (N ₂ SA: 110 m ² / g) manufactured by Mitsubishi Chemical Corporation
Carbon black N330: Dia Black HM manufactured by Mitsubishi Chemical Corporation (N ₂ SA: 80 m ² / g)
Silica: Ultrasil VN3 manufactured by Degussa (N ₂ SA: 175 m ² / g)
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Aroma oil: Process X-140 manufactured by Japan Energy Co., Ltd.
Petroleum-based resin: SP1068 resin wax manufactured by Nippon Shokubai Co., Ltd .: Ozoace 0355 manufactured by Nippon Seiwa Co., Ltd.
Anti-aging agent: Antigen 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.
Stearic acid: Tsubaki stearic acid manufactured by NOF Corporation
Zinc oxide: Zinc oxide cobalt oxide manufactured by Mitsui Mining & Smelting Co., Ltd .: COST-S manufactured by Nikko Metal Co., Ltd.
Sulfur: powder sulfur insoluble sulfur manufactured by Tsurumi Chemical Co., Ltd .: Sanfel EX manufactured by Sanshin Chemical Co., Ltd.
Vulcanization accelerator NS: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfanamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

<Preparation of internal conductive layer, conductive rubber, coating rubber, energizing rubber, clinch rubber>
After knead | mixing the component except a sulfur and a vulcanization accelerator among the compounding components shown in Tables 1-5 using a closed Banbury mixer at 150 ° C for 4 minutes, sulfur and a vulcanization accelerator are added at 95 ° C. Further kneading for 2 minutes, through an extrusion process and a calendar process by a conventional method, internal conductive layer rubber composition A-1 to A-6, conductive rubber composition B, coated rubber composition C (under tread rubber composition) The electrified rubber composition D and the clinch rubber composition E were prepared.

<Preparation of tread rubber, sidewall rubber, breaker rubber>
Ingredients shown in Tables 6 to 8, except for sulfur and vulcanization accelerator, were kneaded at 140 ° C for 4 minutes using a closed Banbury mixer, and then added with sulfur and vulcanization accelerator at 95 ° C. Further kneading was conducted for 2 minutes, and a tread rubber composition F, a sidewall rubber composition G, and a breaker rubber composition H were prepared through an extrusion process and a calendar process by a conventional method.

<Volume specific resistance of rubber composition>
Test pieces having a thickness of 2 mm and 15 cm × 15 cm were prepared using the rubber compositions A-1 to H of Tables 1 to 8, and a voltage of 500 V, an air temperature of 25 ° C., and a humidity of 50 using an electric resistance measurement R8340A manufactured by ADVANTEST. % Was measured. The results are shown in Table 1. The larger the value, the higher the volume resistivity of the rubber composition.

<Dematia test>
According to the test method of “Dematcher bending crack growth test method for vulcanized rubber and thermoplastic rubber” of JIS-K6260, samples (inner conductive layer rubber compositions A-1 to A-6) were used at room temperature of 25 ° C. The number of times until breakage of 1 mm occurred was measured, and the obtained number was expressed logarithmically. The larger the value, the better the flex crack resistance. Note that 70% and 110% represent elongation rates with respect to the length of the original sample. The results are shown in Table 1.

(Examples 1-2, Comparative Examples 1-4)
The rubber compositions prepared by blending the rubbers shown in Tables 1 to 8 are used in the combinations shown in Table 9 and applied to tread rubber, sidewall rubber, breaker rubber, clinch rubber, internal conductive layer, conductive rubber, coating rubber, and conductive rubber. Then, a 195 / 65R15 pneumatic tire having the structure shown in FIG.

Here, the basic structure of the prototype tire is as follows.
<Carcass ply>
Cord angle: 90 degrees in the tire circumferential direction Cord material: Polyester 1670 dtex / 2
<Breaker>
Cord angle: 24 degrees x 24 degrees in the tire circumferential direction Cord material: Steel cord (2 + 2 x 0.25)

In addition, the thickness of the inner conductive layer was 0.5 mm, the thickness of the covering rubber was 1 mm, the thickness of the conductive rubber was 1 mm, the width of the current-carrying rubber was 3 mm, and a continuous structure in the tire circumferential direction was adopted.
Further, the contact between the covering rubber and the conductive rubber is a belt-like 5 mm width in the tire circumferential direction, the contact between the covering rubber and the conductive rubber is the entire surface in the tire width direction of the conductive rubber, and the contact between the internal conductive layer and the conductive rubber is the tire circumferential direction. A belt having a width of 5 mm in the direction and a structure having a width of 5 mm or more along the carcass shape was adopted for the contact between the inner conductive layer and the clinch rubber.

<Tire conductivity>
The pneumatic tire produced above is mounted on a regular rim, filled with a specified internal pressure of 2.0 MPa, the tread portion is grounded to the iron plate with a load of 4.7 kN, and the electric power between the tire rim portion and the iron plate is applied at an applied voltage of 100V. The resistance value was measured. The results are shown in Table 9.

<Rolling resistance>
The pneumatic tire produced above was mounted on a regular rim, filled with a specified internal pressure of 2.0 MPa, and the rolling resistance was measured at a speed of 80 km / h and a load of 4.7 kN using a rolling resistance tester manufactured by STL. . With respect to the rolling resistance coefficient (RRC) obtained by dividing the measured value of rolling resistance by the load, the rolling resistance of each tire was indicated by an index with Comparative Example 1 as 100 by the following formula. The larger the value, the smaller the rolling resistance and the better the performance. The results are shown in Table 9.
(Rolling resistance index) = (Rolling resistance coefficient of Comparative Example 1) / (Rolling resistance coefficient of each tire) × 100
<Crack resistance>
The 195 / 65R15 pneumatic tire produced as described above was mounted, traveled for 30000 km at a speed of 80 km / h and a load of 4.7 kN, the amount of crack growth in the internal conductive layer was measured, and the crack resistance performance was evaluated. In addition, the case where the growth amount was 5 mm or less was rated as ◯, and the case where it exceeded 5 mm was rated as x.

From Tables 1 and 9, the tires of Examples using Formulations A-1 to A-2 containing specific amounts of NR, ENR, carbon black and silica for the inner conductive layer had good conductivity and rolling resistance. It was. At the same time, the crack resistance of the internal conductive layer was good. On the other hand, in the tire of Comparative Example 1-3 in which the blends A-3 to A-5 using only NR as the rubber component and the blend A-6 having a small amount of NR are used for the internal conductive layer, the conductivity and rolling resistance are high. Although it was good, the crack resistance of the internal conductive layer was inferior.

DESCRIPTION OF SYMBOLS 1 Tire 2 Chafer rubber 3 Clinch rubber 4 Conductive rubber 5 Cover rubber 6 Conductive rubber 7 Tread rubber 8 Side wall rubber 9 Breaker 10 Carcass 11 Bead apex 12 Band 13 Bead core 14 Internal conductive layer

Claims (6)

A pneumatic tire comprising a tread portion, a sidewall portion, a bead portion, a carcass from the tread portion through the sidewall portion to the bead portion, and a breaker portion on the outer side in the tire radial direction of the carcass. And
Volume specific resistance of the tread rubber, breaker rubber and sidewall rubber respectively formed in the tread portion, the breaker portion and the sidewall portion is 1 × 10 ⁸ Ω · cm or more,
The pneumatic tire includes an inner conductive layer disposed between the carcass and the sidewall rubber, a conductive rubber disposed in a lower region of both ends of the breaker in contact with the inner conductive layer, the conductive rubber, Coated rubber having a contact region and arranged to cover the upper side of the breaker part, current-carrying rubber embedded in the tread part so as to be in contact with the coated rubber and partly exposed on the surface of the tread, the internal conductive layer A bead portion rubber disposed in a region in contact with the rim flange of the bead portion,
The volume specific resistance values of the internal conductive layer, the conductive rubber, the covering rubber, the energizing rubber, and the bead rubber are all less than 1 × 10 ⁸ Ω · cm,
The internal conductive layer is 10 to 50 parts by mass of carbon black and 10 to 50 parts by mass of silica with respect to 100 parts by mass of a rubber component containing 30 to 90% by mass of natural rubber and 70 to 10% by mass of epoxidized natural rubber. A pneumatic tire produced using the rubber composition for an internal conductive layer contained in part. The pneumatic tire according to claim 1, wherein the inner conductive layer has a thickness of 0.2 to 1.0 mm. The pneumatic tire according to claim 1 or 2, wherein the bead rubber is a clinch rubber or a chafer rubber. The pneumatic tire according to any one of claims 1 to 3, wherein the conductive rubber is formed continuously in a tire circumferential direction. The tread rubber, the breaker rubber, or the sidewall rubber contains at least one selected from the group consisting of natural rubber, butadiene rubber, and styrene butadiene rubber, and silica. Pneumatic tires. The covering rubber, the conductive rubber, the energizing rubber, or the bead rubber is at least selected from the group consisting of natural rubber, styrene-butadiene rubber, butadiene rubber, isoprene rubber, epoxidized natural rubber, and deproteinized natural rubber. The pneumatic tire according to any one of claims 1 to 5, comprising one type and carbon black and / or silica.

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