JP6006603B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire capable of discharging static electricity charged on a vehicle to a road surface.

  In order to improve rolling resistance of pneumatic tires and running performance on wet road surfaces (wet performance), a technique of blending silica as a reinforcing agent in a tread rubber composition instead of conventional carbon black is known. Due to the static electricity charged to the vehicle due to this silica compounding technology, a discharge phenomenon occurs when the tire passes over a manhole or the like, causing radio noise, adverse effects on electronic circuit components, and occurrence of short circuits. .

  Conventionally, in order to solve such a problem, a technique has been proposed in which a conductive member in which carbon black is blended in a part of a tread structure is provided to ensure the conductivity of the tire. For example, the technique of Patent Document 1 below describes that a conductive thin film containing carbon black is laid on the outer surfaces of a tread and sidewalls and discharged through the conductive layer. Further, in the technique of Patent Document 2, a conductive insert is provided in the tire crown portion from the tread surface to the bottom surface, and the conductive strip made of a conductive material in contact with the insert is in contact with the wheel in the conductive bead region. It is disclosed that static electricity is discharged by being in the above.

JP-A-8-230407 JP 2006-143208 A No. 2008-038461 Japanese Patent No. 4738551

  However, in the technique of Patent Document 1, the effect of improving the tread rolling resistance and wet performance due to silica blending is reduced by laying the conductive thin film containing the carbon black, and it is difficult to fully exhibit the original effect. . In addition, since a conductive thin film containing carbon black is laid on the outer surfaces of the tread and sidewalls, additional members and processes are required, and productivity deterioration and cost increase are expected.

  Since the technique of Patent Document 2 requires a separate conductive insert and strip, the number of parts is increased, and it is difficult to say that the structure is easy to manufacture by requiring a special process, and a decrease in productivity is expected. The

  In Patent Document 3, the conductive path in which at least the surface portions of the rim strip, the cushion rubber, and the ground contact end region are continuous is formed of a conductive rubber material obtained by devising the blending amount of carbon black. Tires are described. However, such a conductive rubber material has room for further improvement in terms of low heat generation performance.

  By the way, in Patent Document 4, when a filler is dispersed in a dispersion solvent, a slurry solution containing a filler to which rubber latex particles are adhered is produced by adding at least a part of a rubber latex solution, and then slurry is added. A rubber wet masterbatch obtained by mixing the solution with the remaining rubber latex solution and then coagulating and drying is described. However, in this patent document, the electrical resistance of vulcanized rubber obtained using a rubber wet masterbatch as a raw material is not mentioned, and there is no description limiting the filler, particularly carbon black.

  This invention is made | formed in view of the said situation, The objective is to provide the pneumatic tire which is excellent in the low heat generation performance, and has electroconductivity.

  The above object can be achieved by the present invention as described below. That is, in the pneumatic tire according to the present invention, a sheet-like cushion rubber having a thickness of 1 mm or less is disposed on the tire inner surface side of the sidewall rubber, the cushion rubber contacts the rim strip, and the tread portion of the tread portion passes through the sidewall portion. A pneumatic tire connected to a grounded end region, wherein a conductive path in which at least a surface portion of the rim strip, the cushion rubber, and the grounded end region is continuous is conductive on a circumference of one or both side portions of the tire. It is formed of a rubber material, and only the conductive path is a tire energization path, and other members than the energization path are formed of a conductive rubber material or a non-conductive rubber material, and the conductive rubber material is at least carbon black , Dispersion solvent, and rubber wet master obtained from rubber latex solution A vulcanized rubber of a rubber composition containing a batch, wherein the carbon black is a carbon black having an iodine adsorption amount of 41 mg / g or less, and the rubber wet masterbatch contains the carbon black in the dispersion solvent. When dispersing, at least part of the rubber latex solution is added to produce a slurry solution containing the carbon black to which rubber latex particles are adhered, and then the slurry solution and the remaining rubber latex solution are mixed. And then solidified and dried.

  The pneumatic tire of the present invention uses a cushion rubber disposed on the tire inner surface side of the sidewall as an energization path in order to improve the adhesion between the sidewall rubber and different rubbers such as carcass and rim strip rubber, It has conductivity. Therefore, even when a non-conductive rubber material such as a silica compound is disposed on a tire tread or the like, it is possible to eliminate noise caused by static electricity charged on the vehicle, adverse effects on electronic components, short-circuit problems, and the like.

  Further, the conductive rubber material forming the conductive path is formed of a rubber composition vulcanized rubber containing at least carbon black, a dispersion solvent, and a rubber wet masterbatch obtained using a rubber latex solution as a raw material. When the master batch disperses the carbon black in the dispersion solvent, by adding at least a part of the rubber latex solution, a slurry solution containing the carbon black to which the rubber latex particles are adhered is manufactured, and then the slurry solution and the remaining The rubber latex solution was mixed, and then coagulated and dried. Such a rubber wet masterbatch is a rubber wet masterbatch in which carbon black is uniformly dispersed and is excellent in dispersion stability of carbon black over time, and can be a raw material of a conductive rubber material excellent in low heat generation performance. Further, since carbon black having an iodine adsorption amount of 41 mg / g or less is used as the carbon black, the carbon black is uniformly dispersed in the rubber wet masterbatch so that electron conduction is possible. Will have a reasonably close distance. As a result, in the conductive rubber material using such a rubber wet masterbatch, the electric resistance can be reduced while improving the low heat generation performance. As a result, a pneumatic tire provided with such a conductive rubber material on at least the surface portion of the rim strip, the cushion rubber, and the ground contact end region has excellent low heat generation performance and conductivity.

In the pneumatic tire, the carbon black is preferably DBP absorption is less than 80 cm ^3/100 g. When such carbon black is used, the electric resistance of the conductive rubber material finally obtained can be further reduced.

  In the pneumatic tire, the rubber wet masterbatch preferably contains 40 to 150 parts by mass of the carbon black with respect to 100 parts by mass of rubber. In this case, the low heat generation performance of the conductive rubber material finally obtained and the reduction of electric resistance can be improved in a balanced manner.

In the pneumatic tire, it is preferable that an electric resistance value of the conductive rubber material is less than 10 ⁸ Ω · cm. The real number of loss tangent (tan δ) of the conductive rubber material is preferably 0.120 or less. Moreover, it is preferable that the tire rubber radial outer end portion of the sidewall rubber integrally forms the ground contact end region, and the tip end portion of the cushion rubber is exposed on the surface of the ground contact end region. And a wing disposed at both ends in the tire axial direction of the tread portion and in contact with the sidewall rubber to form a surface portion of the ground contact end region, wherein at least a part of the cushion rubber contacts the wing. It is preferable.

Tire meridian cross-sectional view showing an example of a pneumatic tire according to the present invention Tire meridian cross-sectional view showing another example of a pneumatic tire according to the present invention Schematic showing how to measure the electrical resistance of tires

[First Embodiment]
FIG. 1 is a tire meridian cross-sectional view showing an example of a pneumatic tire according to the present invention.

  A pneumatic tire (hereinafter, a pneumatic tire is simply referred to as a “tire”) 10 includes a pair of bead portions 11 that are assembled into a rim, a sidewall portion 16 that extends outward from the bead portion 11 in the tire radial direction, and the sidewall. A tread portion 13 that contacts the road surface provided between the portions 16 and 16, and the tread portion 13 is positioned on both sides of the crown portion 15 that forms a main contact portion at the center in the tire width direction and the tread portion 13. It consists of a shoulder portion 17 that forms a grounding end region and continues to the sidewall portion 16.

  The tire 10 includes a rim strip 19 that comes into contact with a rim flange disposed on the outer side in the tire axial direction of the bead portion 11, and a lower end portion of the sidewall portion 16 is in contact with an upper end portion of the rim strip 19. .

Further, as shown in FIG. 1, the tire 10 has a sidewall on tread (SWOT) structure in which the end portion in the tire radial direction of the sidewall portion 16 overlaps the end portion of the tread rubber 21. That is, the outer end portion of the sidewall portion 16 forms a shoulder portion 17 that covers both peripheral surfaces of the tread portion 13 and serves as a tread ground contact end region on the tire circumference.

The sidewall portion 16 of the tire 10 is provided with a sidewall cushion rubber 25 on the tire inner surface side of the sidewall rubber 22, and is in contact with the rim strip 19, the carcass 14 and the end portion of the tread rubber 21, and adheres between different types of rubber. A barrier layer that enhances the properties is formed.

In the tire 10 having the SWOT structure, the sidewall portion 16 extends outward from the bead portion 11 in the tire radial direction and integrally forms a shoulder portion 17 that forms a grounding end region, and the tip portion 25a of the cushion rubber 25 is grounded. Exposed on the surface of the edge region.

Further, the tire 10 includes a carcass 14 in which two carcass plies made of cords arranged in a radial direction around the bead cores 12 embedded in the pair of bead portions 11 are folded and locked outward from the inside of the tire. A belt 18 comprising two cross belt plies arranged on the inner side of the tread portion 13, and a cord wound spirally around the outer circumference of the belt 18 at an angle of approximately 0 ° with respect to the tire circumferential direction. A radial tire for a passenger car having a single cap ply 20 is shown.

The carcass ply of the carcass 14 has an organic fiber cord such as polyester, nylon, or rayon, the belt ply of the belt 18 has a rigid cord such as a steel cord or an aramid fiber, and the cap ply 20 has nylon, polyester, or the like. A cord having a relatively large heat shrinkability is used as a reinforcing material.

The tread rubber 21 of the crown portion 15 that constitutes the main grounding portion of the tread portion 13 contributes to the improvement of the rolling resistance and wet performance of the tire 10, so that the tan δ of the rubber composition is reduced, so that the conventional carbon black is used as a reinforcing agent. And a rubber composition using a non-carbon black reinforcing agent such as calcium carbonate, a silica such as precipitated silica and anhydrous silicic acid, a clay such as calcined clay and hard clay, and a calcium carbonate as a reinforcing agent. In particular, silica having a large improvement effect such as rolling resistance is preferably used.

The amount of the non-carbon black reinforcing agent such as silica is usually 30 to 100 parts by mass, preferably 40 to 80 parts by mass with respect to 100 parts by mass of the rubber component, although it depends on the type and substitution amount of the carbon black. Is done.

In the case of silica, the type of silica is not particularly limited, but wet silica having a nitrogen adsorption specific surface area (BET) of 100 to 250 m ² / g and a DBP oil absorption of 100 ml / 100 g or more is preferable from the viewpoint of the reinforcing effect and workability. Commercial products such as Nipsil AQ and VN3 manufactured by Tosoh Silica Industry Co., Ltd., and Ultrazil VN3 manufactured by Degussa Corporation can be used. Further, a combined use of a silane coupling agent such as bis (triethoxysilylpropyl) -tetrasulfide is preferable.

As the carbon black in the tread rubber 21, SAF, ISAF, HAF and the like are preferable from the viewpoint of wear resistance and heat generation.

The rubber composition of the tread rubber 21 is a diene rubber such as natural rubber (NR), isoprene rubber (IR), styrene butadiene rubber (SBR), butadiene rubber (BR), etc. as a rubber component. Generally used. Further, softeners such as oils and waxes for rubber compounding agents, stearic acid, zinc white, resins, anti-aging agents, vulcanizing agents such as sulfur, vulcanization accelerators, and the like are appropriately blended.

Further, in order to improve the improvement effect such as rolling resistance, the tire 10 is applied to the side wall rubber 22 of the side wall part 16 and to 100 parts by mass of the rubber component using the non-carbon black reinforcing agent as a reinforcing agent at the same time as the tread rubber. On the other hand, a rubber composition containing about 30 to 100 parts by mass is used.

As the non-conductive side wall 22, NR, IR, SBR, BR, diene rubber such as butadiene rubber (VCR) containing syndiotactic-1,2-polybutadiene or a blend is used as a rubber component, and nitrogen is used. Carbon black having an adsorption specific surface area (N ₂ SA) of 25 to 100 m ² / g is obtained by containing less than 14% by volume of the entire rubber composition.

Further, when the N ₂ SA of the carbon black is less than 25 m ² / g, the durability is lowered due to the strength reduction of the rubber composition, and when it exceeds 100 m ² / g, the hysteresis loss is increased and the rolling resistance and heat generation are increased.

Examples of the carbon black having N ₂ SA of 25 to 100 m ² / g include HAF, FEF, and GPF grade carbon black.

In addition, silica, clay, calcium carbonate, etc. may be used in combination with carbon black in an appropriate amount as a non-carbon black reinforcing agent, and further, softeners such as oils and waxes for rubber compounding agents, stearic acid, zinc white, resin , Anti-aging agents, vulcanizing agents such as sulfur, vulcanization accelerators and the like are appropriately blended.

As a result, the tread rubber 21 and the side wall rubber 22 improve rolling resistance and wet performance, but on the other hand, the electrical resistivity of the vulcanized rubber becomes 10 ⁸ Ω · cm or more and the non-conductive rubber and Become. As a result, the tire 10 has a non-conductive tread grounding portion and a sidewall portion 16 and becomes a non-conductive tire having an electric resistance of 10 ⁹ Ω or more as a tire due to the combination of each member. It becomes impossible to discharge from the part 13 to the road surface.

In order to solve the problem of static electricity charged in the vehicle, the tire 10 of the present embodiment is electrically conductive to the rim strip rubber 23 and the sidewall cushion rubber 25 on the circumference of the tire 10 in at least one side portion of the tire. Rubber material is applied. As a result, the rim strip rubber 23 and the side wall cushion rubber 25 form a continuous conductive path.

The tire 10 uses only the conductive path as the current-carrying path of the tire, and the static electricity of the vehicle is exposed from the front end portion 25a of the sidewall cushion rubber 25 exposed from the rim to the surface of the ground end region through the rim strip rubber 23 and the sidewall cushion rubber 25. It is discharged on the road surface.

The energization path of the tire 10, that is, the members other than the rim strip rubber 23 and the sidewall cushion rubber 25 can be selected and used from a conductive rubber material or a non-conductive rubber material as long as no energization path is provided. .

For example, when the conductive sidewall cushion rubber 25 is applied to only one side portion of the tire 10, a nonconductive rubber having an electrical resistivity of 10 ⁸ Ω · cm or more is applied to the other side portion. You can also. Thereby, the rolling resistance and wet performance of the tire 10 can be further improved by increasing the amount of non-conductive rubber used. In this case, the electrical resistance of the tire 10 is slightly increased as compared with the case where the conductive rubber is applied to the side wall cushion rubber on both side portions, but the discharge property of static electricity is not greatly reduced, and there is no practical problem. .

As the non-conductive side wall cushion rubber, for example, a rubber composition containing carbon black having 25 to 100 m ² / g of N ₂ SA in less than 14% by volume of the entire rubber composition is obtained as a raw material.

When the conductive rubber is applied only to one side wall cushion rubber 25 of the side portion, the conductive rubber is also applied to the rim strip rubber 23 on the same side. That is, the conductive property of the tire can be ensured by applying a pair of conductive rubbers to the side wall cushion rubber 25 and the rim strip rubber 23 at one or both side portions of the tire 10.

Further, in the tire 10 shown in FIG. 1, the tread rubber 21 shows a tread having a single body structure, but when the tread portion 13 has a cap / base structure, a non-conductive rubber is applied to the cap. The base rubber can be appropriately selected from conductive or non-conductive rubber. In addition, other parts such as the carcass of the tire 10, the topping rubber of the belt, and the bead filler can be appropriately selected from conductive or non-conductive rubber within a range not having a current-carrying path, but the rolling resistance and wet performance are improved. In view of the above, it is preferable to select a nonconductive rubber.

In the present invention, the conductive rubber material preferably has an electric resistance value of less than 10 ⁸ Ω · cm, and the real number of loss tangent (tan δ) is preferably 0.120 or less.

  Below, the rubber wet masterbatch used as the raw material of the conductive rubber material of this invention is demonstrated. Such a rubber wet masterbatch is obtained using at least carbon black, a dispersion solvent, and a rubber latex solution as raw materials. Then, such a rubber wet masterbatch is prepared by adding at least a part of a rubber latex solution when carbon black is dispersed in a dispersion solvent, thereby producing a slurry solution containing carbon black to which rubber latex particles are adhered. The slurry solution and the remaining rubber latex solution were mixed and then coagulated and dried.

In the rubber wet masterbatch used in the present invention, carbon black having an iodine adsorption amount of 41 mg / g or less is used as carbon black. In order to further reduce the electrical resistance of the finally obtained vulcanized rubber, the iodine adsorption amount of the carbon black to be used is preferably 41 mg / g or less, and more preferably 24 mg / g or less. Further, in order to further reduce the electrical resistance of the vulcanized rubber is preferably DBP absorption is less than 160cm ^{3/100 g,} more preferably 100 cm 3/100 g or ^less, is 80 cm 3/100 g or less It is particularly preferred. Furthermore, when considering heat generation performance and the like, the nitrogen specific surface area of carbon black is preferably 40 × 10 ³ m ² / kg or more. The carbon black may be a granulated carbon black or a non-granulated carbon black granulated in the normal rubber industry in consideration of its handleability.

  As the dispersion solvent, it is particularly preferable to use water, but for example, water containing an organic solvent may be used.

  Natural rubber latex solution and synthetic rubber latex solution can be used as the rubber latex solution.

  The natural rubber latex solution is a natural product produced by the metabolic action of plants, and a natural rubber / water system is particularly preferred in which the dispersion solvent is water. The number average molecular weight of the natural rubber in the natural rubber latex used in the present invention is preferably 2 million or more, and more preferably 2.5 million or more. Natural rubber latex can be used without distinction, such as concentrated latex and fresh latex called field latex. Examples of the synthetic rubber latex solution include those produced by emulsion polymerization of styrene-butadiene rubber, butadiene rubber, nitrile rubber, and chloroprene rubber.

  Below, the manufacturing method of the rubber wet masterbatch used by this invention is demonstrated. In particular, in this embodiment, an example in which a natural rubber latex solution is used as the rubber latex solution will be described. In this case, it is possible to produce a rubber wet masterbatch in which the degree of dispersion of carbon black is very high and the low heat generation performance when vulcanized rubber is further improved.

  In this production method, when carbon black is dispersed in a dispersion solvent, at least a part of the natural rubber latex solution is added to produce a slurry solution containing carbon black to which natural rubber latex particles are adhered ( I), the slurry solution and the remaining natural rubber latex solution are mixed to produce a carbon black-containing rubber latex solution with the natural rubber latex particles attached thereto; and the carbon with the natural rubber latex particles attached thereto. And a step (III) of coagulating and drying the black-containing rubber latex solution. In particular, in the present invention, carbon black having an iodine adsorption amount of 41 mg / g or less is used as the carbon black.

(1) Step (I)
In step (I), when carbon black is dispersed in a dispersion solvent, a slurry solution containing carbon black to which natural rubber latex particles are adhered is produced by adding at least a part of the natural rubber latex solution. The natural rubber latex solution may be mixed with a dispersion solvent in advance, and then carbon black may be added and dispersed. Alternatively, carbon black may be added to the dispersion solvent, and then carbon black may be dispersed in the dispersion solvent while adding the natural rubber latex solution at a predetermined addition rate, or carbon black may be added to the dispersion solvent. Then, carbon black may be dispersed in a dispersion solvent while adding a certain amount of natural rubber latex solution in several times. By dispersing carbon black in the dispersion solvent in the presence of the natural rubber latex solution, a slurry solution containing carbon black with natural rubber latex particles attached thereto can be produced. The amount of the natural rubber latex solution added in the step (I) is 0.5 to 50% by mass with respect to the total amount of the natural rubber latex solution used (the total amount added in the step (I) and the step (II)). Illustrated.

  In the step (I), the amount of solid content (rubber) of the natural rubber latex solution to be added is preferably 0.5 to 10% by mass ratio with respect to carbon black, and preferably 1 to 6%. Moreover, it is preferable that the solid content (rubber) density | concentration in the natural rubber latex solution to add is 0.5-5 mass%, and it is more preferable that it is 0.5-1.5 mass%. In these cases, it is possible to produce a rubber wet masterbatch in which the degree of dispersion of carbon black is increased while reliably attaching the natural rubber latex particles to the carbon black.

  In the step (I), as a method of mixing carbon black and a dispersion solvent in the presence of a natural rubber latex solution, a high shear mixer, a high shear mixer, a homomixer, a ball mill, a bead mill, a high pressure homogenizer, an ultrasonic homogenizer, a colloid mill, etc. And a method of dispersing carbon black using a general disperser.

  The "high shear mixer" is a mixer having a rotor and a stator, and the rotor rotates with a precise clearance between a rotor capable of high-speed rotation and a fixed stator. Means a mixer with a high shearing action. In order to produce such a high shearing action, it is preferable that the clearance between the rotor and the stator is 0.8 mm or less and the circumferential speed of the rotor is 5 m / s or more. A commercial item can be used for such a high shear mixer, for example, “High Shear Mixer” manufactured by SILVERSON.

  In the present invention, carbon black and a dispersion solvent are mixed in the presence of a natural rubber latex solution to produce a slurry solution containing carbon black to which natural rubber latex particles are adhered, in order to improve the dispersibility of the carbon black. An activator may be added. As the surfactant, known surfactants in the rubber industry can be used, and examples thereof include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. It is done. Further, alcohol such as ethanol may be used instead of or in addition to the surfactant. However, when a surfactant is used, there is a concern that the rubber properties of the final vulcanized rubber will be lowered. Therefore, the amount of the surfactant to be blended is 100 mass of solid content (rubber) of the natural rubber latex solution. The amount is preferably 2 parts by mass or less, more preferably 1 part by mass or less, and substantially no surfactant is used.

(2) Step (II)
In step (II), the slurry solution and the remaining natural rubber latex solution are mixed to produce a carbon black-containing rubber latex solution to which the natural rubber latex particles are adhered. The method of mixing the slurry solution and the remaining natural rubber latex solution in a liquid phase is not particularly limited, and the slurry solution and the remaining natural rubber latex solution are mixed with a high shear mixer, a high shear mixer, a homomixer, and a ball mill. And a mixing method using a general disperser such as a bead mill, a high-pressure homogenizer, an ultrasonic homogenizer, and a colloid mill. If necessary, the entire mixing system such as a disperser may be heated during mixing.

  The remaining natural rubber latex solution preferably has a higher solid content (rubber) concentration than the natural rubber latex solution added in step (I), considering the drying time and labor in the next step (III). Specifically, the solid content (rubber) concentration is preferably 10 to 60% by mass, and more preferably 20 to 30% by mass.

(3) Step (III)
In step (III), the carbon black-containing rubber latex solution to which the natural rubber latex particles are adhered is coagulated and dried. The coagulation / drying method may be a coagulation drying method in which a coagulant is contained in a carbon black-containing rubber latex solution to which natural rubber latex particles are adhered and dried after coagulation. It may be a method.

  As a coagulant used in the coagulation drying method, an acid such as formic acid and sulfuric acid usually used for coagulation of a rubber latex solution, and a salt such as sodium chloride can be used.

  As a method for drying the carbon black-containing natural rubber latex solution, various drying devices such as an oven, a vacuum dryer, and an air dryer can be used.

  In the step (III), a carbon black-containing rubber latex solution to which natural rubber latex particles obtained by mixing in a liquid phase a slurry solution containing carbon black to which natural rubber latex particles are attached and a natural rubber latex solution is mixed. After the flocculant is contained therein, the obtained agglomerates may be collected and dried. As the flocculant, known rubber flocculant flocculants can be used without limitation, and specific examples thereof include cationic flocculants.

  The rubber wet masterbatch obtained after the step (III) preferably contains 20 to 150 parts by mass of carbon black, more preferably 40 to 90 parts by mass with respect to 100 parts by mass (solid content) of rubber. In this case, the low heat generation performance of the conductive rubber material finally obtained and the reduction of electric resistance can be improved in a balanced manner.

  In the natural rubber wet masterbatch obtained after step (III), the contained carbon black is uniformly dispersed, and the dispersion stability of carbon black over time is excellent.

After the step (III), it may further include a step (IV) of dry-mixing the obtained rubber wet masterbatch and a dry rubber containing a diene rubber as a main component. By passing through this process (IV), the rubber composition in which exothermic property is remarkably improved can be produced. In the present invention, “dry mixing” means mixing, for example, at least two mixed components such as rubber wet masterbatch and dry rubber in a state in which the moisture content of the entire mixed component is 5% or less. . Specific examples of the dry mixing method include a method of mixing using a kneader such as a Banbury mixer, an open roll, or a kneader.

  As the dry rubber mainly composed of diene rubber, diene rubber known to those skilled in the art can be used. However, when the finally obtained vulcanized rubber is used for tires, styrene butadiene rubber (SBR), It is preferable to use at least one of natural rubber (NR) and polyisoprene rubber (IR). Moreover, it is preferable that the compounding ratio of a rubber wet masterbatch and the dry rubber which has a diene rubber as a main component contains 0-30 mass parts of this dry rubber when the rubber component whole quantity is 100 mass parts.

  In the rubber wet masterbatch obtained after the step (III) or (IV), if necessary, a sulfur vulcanizing agent, a vulcanization accelerator, silica, a silane coupling agent, zinc oxide, stearic acid, a vulcanization accelerating aid. Conductivity used in the present invention by blending compounding agents usually used in the rubber industry, such as vulcanization retarders, organic peroxides, anti-aging agents, softeners such as waxes and oils, processing aids, etc. A rubber composition as a raw material for the rubber material can be produced.

  Sulfur as the sulfur-based vulcanizing agent may be normal sulfur for rubber, and for example, powdered sulfur, precipitated sulfur, insoluble sulfur, highly dispersible sulfur and the like can be used. The sulfur content in the rubber composition for tire rubber according to the present invention is preferably 0.3 to 6 parts by mass with respect to 100 parts by mass of the rubber component. When the sulfur content is less than 0.3 part by mass, the crosslinking density of the vulcanized rubber is insufficient and the rubber strength and the like are reduced, and when it exceeds 6.5 parts by mass, the heat resistance is particularly deteriorated. In order to ensure good rubber strength of the vulcanized rubber and further improve heat resistance, the sulfur content is more preferably 1.5 to 5.5 parts by mass with respect to 100 parts by mass of the rubber component. Preferably, it is 2-4.5 mass parts.

  As the vulcanization accelerator, sulfenamide vulcanization accelerator, thiuram vulcanization accelerator, thiazole vulcanization accelerator, thiourea vulcanization accelerator, guanidine vulcanization, which are usually used for rubber vulcanization. Vulcanization accelerators such as accelerators and dithiocarbamate vulcanization accelerators may be used alone or in admixture as appropriate. The content of the vulcanization accelerator is preferably 1 to 5 parts by mass with respect to 100 parts by mass of the rubber component.

  As an anti-aging agent, an aromatic amine-based anti-aging agent, an amine-ketone-based anti-aging agent, a monophenol-based anti-aging agent, a bisphenol-based anti-aging agent, a polyphenol-based anti-aging agent, dithiocarbamic acid, which are usually used for rubber Anti-aging agents such as a salt-based anti-aging agent and a thiourea-based anti-aging agent may be used alone or in an appropriate mixture. The content of the anti-aging agent is more preferably 1 to 5 parts by mass and further preferably 2 to 4.5 parts by mass with respect to 100 parts by mass of the rubber component.

  In the rubber composition used in the present invention, in addition to the rubber wet masterbatch, if necessary, a sulfur vulcanizing agent, a vulcanization accelerator, silica, a silane coupling agent, zinc oxide, stearic acid, vulcanization acceleration. Auxiliaries, vulcanization retarders, organic peroxides, anti-aging agents, softeners such as wax and oil, processing aids, kneading machines used in the normal rubber industry such as Banbury mixers, kneaders and rolls. It is obtained by using and kneading.

  In addition, the blending method of each of the above components is not particularly limited, and a blending component other than a vulcanizing component such as a sulfur vulcanizing agent and a vulcanization accelerator is previously kneaded to obtain a master batch, and the remaining components are added. Any of a method of further kneading, a method of adding and kneading each component in an arbitrary order, a method of adding all components simultaneously and kneading may be used.

  As described above, the rubber wet masterbatch used in the present invention has a uniform dispersion of carbon black contained therein and is excellent in dispersion stability of carbon black over time. Also, the carbon black contained is uniformly dispersed, and the dispersion stability of the carbon black over time is excellent. Further, since carbon black having an iodine adsorption amount of 41 mg / g or less is used as the carbon black, the carbon black is uniformly dispersed in the rubber wet masterbatch so that electron conduction is possible. Will have a reasonably close distance. As a result, in the conductive rubber material using such a rubber wet masterbatch, the electric resistance can be reduced while improving the low heat generation performance.

[Second Embodiment]
FIG. 2 is a tire meridian cross-sectional view showing another example of a pneumatic tire according to the present invention.

The tire 30 includes a pair of bead portions 31 that are assembled into a rim, a sidewall portion 36 that extends outward in the tire radial direction from the bead portion 31, and a tread portion 33 that contacts a road surface provided between the sidewall portions 36 and 36. The tread portion 33 includes a crown portion 35 that forms a main ground contact portion at the center in the tire width direction, and a shoulder portion 37 that is located on both sides of the tread portion 33 and forms a ground contact end region and continues to the sidewall portion 36. It has become.

The tire 30 includes a rim strip 39 that contacts a flange of a rim disposed on the radially outer side of the bead portion 31, and a lower end portion of the sidewall portion 36 is in contact with an upper end portion of the rim strip 39.

As shown in FIG. 2, the tire 30 has a tread over sidewall (TOS) structure in which both end portions of the tread portion 33 are overlapped with and overlapped with outer end portions of the sidewall portions 36.

A wing rubber 44 that is located on a shoulder portion 37 that forms a ground contact end region at both ends in the tire axial direction of the tread portion 33 and that forms a surface of the shoulder portion 37 in contact with the sidewall portion 36 is formed on the tire circumference. It is arranged. That is, the wing rubber 44 is arranged so as to straddle the end portion of the tread rubber 41 and the end portion of the side wall rubber 42 so as to contact both.

The sidewall portion 36 of the tire 30 is provided with a sidewall cushion rubber 45 on the tire inner surface side of the sidewall rubber 42, and is in contact with the rim strip 39, the carcass 34, and the end portion of the tread rubber 41 to bond between different types of rubber. A barrier layer that enhances the properties is formed.

In the tire 30 having the TOS structure, the side wall rubber 42 extends from the bead portion 31 to the outer side in the tire radial direction and is positioned on the inner surface side of the wing rubber 44 in the shoulder portion 37 that forms a ground contact end region.

The method for bringing the sidewall cushion rubber 45 into contact with the wing rubber 44 is not particularly limited as long as the cushion rubber 45 and the wing rubber 44 are in contact with each other.

Further, the tire 30 includes two carcass plies made of cords arranged in a radial direction around bead cores 32 respectively embedded in a pair of bead portions 31, and a carcass 34 that is locked by folding back from the inside to the outside of the tire. A belt 38 formed of two cross belt plies arranged on the inner side of the tread portion 33, and a cord wound spirally around the outer periphery of the belt 38 at an angle of approximately 0 ° with respect to the tire circumferential direction. A tire for a passenger car having a radial structure having a single cap ply 40 is shown.

The carcass ply of the carcass 34 is made of an organic fiber cord such as polyester, nylon or rayon, the belt ply of the belt ply 38 is made of a rigid cord such as steel cord or aramid fiber, and the cap ply 40 is made of nylon or polyester. A cord having a relatively large heat shrinkability, such as, is used as a reinforcing material.

Like the tire 10, the tread rubber 41 is replaced with conventional carbon black as a reinforcing agent to reduce tan δ of the rubber composition in order to contribute to improvement of rolling resistance and wet performance. Silica, clay, calcium carbonate A rubber composition using a non-carbon black reinforcing agent such as a reinforcing agent is used, and an electric resistivity is obtained by using a rubber composition having the same formulation as the tread rubber 21 described in the first embodiment. Is a non-conductive rubber of 10 ⁸ Ω · cm or more.

Furthermore, in order to improve the improvement effect such as rolling resistance, the non-carbon black reinforcing agent is also used as a reinforcing agent at the same time as the tread rubber for the side wall rubber 42 of the side wall part 36 with respect to 100 parts by weight of the rubber component. A rubber composition containing about ~ 100 parts by weight is used.

As the non-conductive side wall 42, diene rubber such as NR, IR, SBR, BR, VCR or the like is used as a rubber component, and carbon black having N ₂ SA of 25 to 100 m ² / g is used as the rubber. It is obtained by containing less than 14% by volume of the entire composition.

Further, if the N2SA of the carbon black is less than 25 m ² / g, the durability is lowered due to the strength reduction of the rubber composition, and if it exceeds 100 m ² / g, the hysteresis loss is increased, and the rolling resistance and heat generation are increased.

Examples of the carbon black having N ₂ SA of 25 to 100 m ² / g include HAF, FEF, and GPF grade carbon black.

In addition, silica, clay, calcium carbonate, etc. may be used in combination with carbon black in an appropriate amount as a non-carbon black reinforcing agent, and further, softeners such as oils and waxes for rubber compounding agents, stearic acid, zinc white, resin , Anti-aging agents, vulcanizing agents such as sulfur, vulcanization accelerators and the like are appropriately blended.

As a result, the tread rubber 41 and the side wall rubber 42 improve rolling resistance and wet performance, but on the other hand, the electrical resistivity of the rubber composition becomes non-conductive with 10 ⁸ Ω · cm or more as a tire. Becomes a non-conductive tire having an electric resistance of 10 ⁹ Ω or more, and discharges static electricity charged on the vehicle from the rim 33 to the road surface through the rim strip rubber 43 of the bead portion 31 and the sidewall rubber 42 of the sidewall portion 36 from the rim. I can't do that.

In order to solve the problem of static electricity charged in the vehicle, the tire 30 of the present embodiment is electrically connected to the rim strip rubber 43, the side wall cushion rubber 45, and the wing rubber 44 in at least one side portion of the tire. A conductive rubber having a resistivity of less than 10 ⁸ Ω · cm is applied. As a result, a continuous conductive path is formed from the rim strip 39 to the wing 44.

The tire 30 uses only the conductive path as a conduction path of the tire, and the static electricity of the vehicle is discharged from the rim to the road surface through the wing rubber 44 that contacts the rim strip rubber 43 and the sidewall cushion rubber 45.

For the conductive side wall cushion rubber 45 and rim strip rubber 43, a rubber composition having the same formulation as that of the side wall rubber 25 and rim strip rubber 23 described in the first embodiment is used, and the electrical resistivity is used. Can be a conductive rubber having a viscosity of less than 10 ⁸ Ω · cm.

Also, the conductive wing rubber 44 uses a rubber composition having the same formulation as the sidewall rubber 25 and rim strip rubber 23 described in the first embodiment, and has an electrical resistivity of 10 ⁸ Ω · The conductive rubber can be less than cm.

The current-carrying path of the tire 30, that is, the members other than the rim strip rubber 43, the side wall cushion rubber 45, and the wing rubber 44 are selected and used from a conductive rubber material or a non-conductive rubber material as long as the current-carrying path is not provided. can do.

For example, when conductive sidewall cushion rubber 45, rim strip rubber 43 and wing rubber 44 are applied to only one side portion of tire 30, a non-carbon black reinforcing agent is blended in the other side portion. Non-conductive rubber having an electrical resistivity of 10 ⁸ Ω · cm or more may be applied. Thereby, the rolling resistance and wet performance of the tire 30 can be improved. In this case, although the electrical resistance of the tire is slightly increased as compared with the case where conductive rubber is disposed on both side portions, the discharge property of static electricity is not greatly reduced and is not practically affected.

Needless to say, the conductive rubber is applied in pairs to the sidewall cushion rubber 45, the rim strip rubber 43, and the wing rubber 44 in order to secure the conductivity of the tire 30.

Further, in the tire 30, when the tread portion 33 has a cap / base structure, a non-conductive rubber is applied to the cap, but the base can be appropriately selected from conductive or non-conductive rubber. In addition, other parts such as the carcass of the tire 30, the topping rubber of the belt, and the bead filler can be appropriately selected from conductive or non-conductive rubber within a range not having a current-carrying path, but the rolling resistance and wet performance are improved. In view of the above, it is preferable to select a nonconductive rubber.

  Hereinafter, the present invention will be described in more detail with reference to examples. The raw materials used and the equipment used are as follows.

(Raw materials used)
a) Carbon black
Carbon black (HAF); "N330" (Seast 3) (iodine adsorption 80 mg / g, DBP absorption 101 cm ^3/100 g, the nitrogen adsorption specific surface area ^{79 × 10 3 m 2 / kg} , manufactured by Tokai Carbon Co., Ltd.)
Carbon black (SRF); "N774" (SEAST S) (iodine adsorption 26 mg / g, DBP absorption 68cm ^3/100 g, the nitrogen adsorption specific surface area ^{27 × 10 3 m 2 / kg} , manufactured by Tokai Carbon Co., Ltd.)
Carbon black (FEF); "N550" (Seast SO) (iodine adsorption 44 mg / g, DBP absorption 115cm ^3/100 g, the nitrogen adsorption specific surface area ^{42 × 10 3 m 2 / kg} , manufactured by Tokai Carbon Co., Ltd.)
Carbon black (ISAF); "N220" (Seast 6) (iodine adsorption amount 121 mg / g, DBP absorption 114 cm ^3/100 g, the nitrogen adsorption specific surface area ^{119 × 10 3 m 2 / kg} , manufactured by Tokai Carbon Co., Ltd.)
b) Dispersion solvent Water c) Rubber latex solution Natural rubber fresh latex solution (NR field latex); manufactured by Golden Hope (DRC (Dry Rubber Content)) = 31.2%, weight average molecular weight 232,000 d) coagulant Formic acid (primary 85%, 10% solution diluted to pH 1.2), (Nacalai Tesque)
e) Zinc oxide “No. 1 Zinc Hana” (Mitsui Metals)
f) Stearic acid “Lunac S-20” (manufactured by Kao Corporation)
g) Wax “Ozoace-0355” (manufactured by Nippon Seiwa Co., Ltd.)
h) Anti-aging agent “NOCRACK 6C” (manufactured by Ouchi Shinsei Chemical Co., Ltd.)
i) Sulfur “5% oil-treated powder sulfur” (manufactured by Hosoi Chemical Co., Ltd.)
j) Vulcanization accelerator "Noxeller NS-P" (Ouchi Shinsei Chemical Co., Ltd.)
k) Boron-containing organic acid cobalt “Manobond C680C” (manufactured by OMG)
l) Resorcin-alkylphenol-formalin resin “SUMIKANOL 620” (manufactured by Sumitomo Chemical Co., Ltd.)
m) Hexamethoxymethyl melamine “Ciretz 963L” (Mitsui Cytec)
n) Diene dry rubber
Polystyrene butadiene rubber (SBR) “1502” (manufactured by JSR)
Polybutadiene rubber (BR) "BR150B" (manufactured by Ube Industries)
o) Silica “Nipseal AQ” (manufactured by Tosoh Silica Industry Co., Ltd.)
p) Silane coupling agent "Si69" (Degussa)
q) Aroma oil “X-140” (manufactured by Japan Energy)

(Evaluation)
The evaluation was performed on rubber obtained by heating and vulcanizing each rubber composition at 150 ° C. for 30 minutes using a predetermined mold.

(Low heat generation performance of vulcanized rubber)
According to JIS K6265, the low heat generation performance of the vulcanized rubber produced was evaluated by loss tangent tan δ. Tan δ was measured using a rheometer E4000 manufactured by UBM in a state of 50 Hz, 80 ° C., and dynamic strain of 2%. The lower the value, the better the low heat generation performance.

(Electric resistance value of vulcanized rubber)
The electrical resistance value was measured according to JIS K6911 (measurement conditions; applied voltage 1000 V, temperature 25 ° C., humidity 50%).

Production Example 1 (Production of natural rubber wet masterbatch)
By adding 50 parts by mass of carbon black (N774) to a dilute natural rubber (NR) latex aqueous solution adjusted to 0.5% by mass and dispersing the carbon black using PRIMIX Robomix (the robot Mixing conditions: 9000 rpm, 30 minutes), a carbon black-containing slurry solution to which natural rubber latex particles were adhered was produced (step (I)).

  Next, water is added to the carbon black-containing slurry solution to which the natural rubber latex particles produced in step (I) are attached, so that the remaining natural rubber latex solution (solid content (rubber) concentration is 25% by mass). And the natural rubber latex solution used in step (I) is added so that the solid content (rubber) amount is 83 parts by mass, and then a household mixer SM-L56 type manufactured by SANYO (Mixer conditions 11300 rpm, 30 minutes) to produce a carbon black-containing natural rubber latex solution (step (II)).

  A 10% by weight aqueous solution of formic acid as a coagulant is added to the carbon black-containing natural rubber latex solution produced in the step (II) until pH 4 is reached, and the coagulated product is 1% moisture content with a screw press V-01 type manufactured by Suehiro EPM. A natural rubber wet masterbatch (WMB) was produced by drying to 5% or less (step (III)).

  40 parts by mass of the polybutadiene rubber (BR) listed in Table 1 and various additives were mixed in the obtained natural rubber wet masterbatch and dry-mixed to obtain a rubber composition (low heat generation / conductive rubber composition for sidewall cushion) The physical properties of the vulcanized rubber were measured. The results are shown in Table 1.

Production Examples 2-5
A rubber composition (non-conductive rubber composition for tread rubber, conductive rubber composition for rim strips, conductive rubber composition for sidewall cushions) by blending and dry-mixing the rubber described in Table 1 and various additives. Non-conductive rubber composition for sidewall cushion), and physical properties of the vulcanized rubber were measured. The results are shown in Table 1.

  Using the obtained rubber composition, the side wall cushion rubber is made of a low heat-generating / conductive rubber for side wall cushions (indicated by “◯” in Table 2) and conductive rubber (in Table 2) by the combinations shown in Table 2. A radial tire (195 / 65R15 88S) having the SWOT structure shown in FIG. 1 changed to “△” or non-conductive rubber (indicated by “x” in Table 2) is manufactured, and electric resistance and rolling resistance are measured. did. As the tread rubber and rim strip rubber, the tread rubber and rim strip rubber shown in Table 1 were commonly used in each tire.

The side wall cushion rubber is formed by extruding the cushion rubber into a sheet having a thickness of 0.3 mm by a rubber extruder using the cushion rubber composition shown in Table 1, and is separately extruded continuously after the cushion rubber extrusion process. A green tire was molded using a member that was bonded and integrated on the tire inner surface side of the side wall rubber.

Also, the carcass is 1670 dtex / 2 polyester cord, the driving density is 22 plies / 25 mm, 1 ply, the belt is 2 + 2 × 0.25 steel cord, the driving density is 18 plies / 25 mm, 2 plies (crossing angle 45 °), cap ply 940 dtex / 2 nylon 66 cord, a single piece structure with a driving density of 28/25 mm was commonly used.

The electrical resistance of the tire is as follows. After the tire 10 is assembled on a standard rim R (15 × 6JJ) at a pneumatic pressure of 200 kPa and mounted on an FF-type domestic passenger car with a displacement of 1600 cc, running for 3 hours at 100 km / h for 3 hours. It was measured based on “Measurement procedure of tire electric resistance under load” defined by German WDK, Blatt 3. That is, as shown in FIG. 3, the rim-assembled tire 10 is vertically grounded with a load of 400 kg on a copper plate 131 installed in an insulated state with respect to the base plate 130, and the central portion of the standard rim R and the copper plate 131 are Was measured using a resistance measuring instrument 132 having an applied voltage of 1000 volts. The temperature during measurement is 25 ° C. and the humidity is 50%. The results are shown in Table 2.

For rolling resistance, a tire was assembled on a standard rim at an air pressure of 200 kPa, and a rolling resistance was measured at a load of 3.92 kN and a speed of 60 km using a uniaxial drum tester for measuring rolling resistance. It represents with the index which sets Comparative Example 1 to 100, and shows that rolling resistance is so high that a fuel consumption performance is inferior, so that a numerical value is large. The results are shown in Table 2.

Claims (7)

Manufacture of a pneumatic tire in which a sheet-like cushion rubber having a thickness of 1 mm or less is arranged on the tire inner surface side of the sidewall rubber, and the cushion rubber contacts the rim strip and is connected to the ground contact end region of the tread portion through the sidewall portion. A method ,
The pneumatic tire is
On the circumference of one or both sides of the tire,
A conductive path in which at least a surface portion of the rim strip, the cushion rubber, and the ground contact end region is continuous is formed of a conductive rubber material, and only the conductive path is used as a tire energization path, and other members other than the energization path include Formed by conductive rubber material or non-conductive rubber material,
When carbon black having an iodine adsorption amount of 41 mg / g or less is dispersed in a dispersion solvent, a slurry solution containing the carbon black to which rubber latex particles are adhered is added by adding at least a part of the rubber latex solution. After the production, the slurry solution and the remaining rubber latex solution are mixed, coagulated and dried to obtain a rubber wet master batch;
Vulcanizing a rubber composition for cushion rubber containing the rubber wet masterbatch,
A method of manufacturing a pneumatic tire. The carbon black manufacturing method of the pneumatic tire according to claim 1 DBP absorption is less than 80 cm ^3/100 g. The said rubber wet masterbatch is a manufacturing method of the pneumatic tire of Claim 1 or 2 containing 40-150 mass parts of said carbon black with respect to 100 mass parts of rubber | gum. The method for producing a pneumatic tire according to any one of claims 1 to 3, wherein the conductive rubber material has an electric resistance value of less than 10 ⁸ Ω · cm. The method for manufacturing a pneumatic tire according to claim 1, wherein a real number of loss tangent (tan δ) of the conductive rubber material is 0.120 or less. In the pneumatic tire, the tire rubber radial outer end portion of the sidewall rubber integrally forms the ground contact end region, and the tip end portion of the cushion rubber is exposed on the surface of the ground contact end region. The method for producing a pneumatic tire according to any one of 5. The pneumatic tire has wings that are disposed at both ends in the tire axial direction of the tread portion and that form a surface portion of the ground contact end region in contact with the sidewall rubber, and at least a part of the cushion rubber is The method for manufacturing a pneumatic tire according to claim 1, wherein the pneumatic tire is in contact with the wing.

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