JP2019104849A - Ply coating rubber composition for run flat tire, ply coating rubber for run flat tire, and run flat tire - Google Patents

Abstract

To provide a run flat tire excellent in run flat durability, a ply coating rubber composition for run flat tire capable of manufacturing the same, and a ply coating rubber for run flat tire.SOLUTION: There is provided a ply coating rubber composition for run flat tire containing a rubber component containing a diene rubber containing a natural rubber of 80 mass% or more, a filling agent, a vulcanizer, and a vulcanization accelerator. and having a 100% modulus value at 180°C M100 of 2.0 MPa or more, and tensile strength Tb at 180°C of 7.0 MPa or more as vulcanization rubber properties.SELECTED DRAWING: None

Description

  The present invention relates to a ply-coated rubber composition for run flat tires, a ply coated rubber for run flat tires, and a run flat tire.

A pneumatic tire (hereinafter referred to as a run flat tire) capable of traveling even when the internal pressure (hereinafter referred to as an internal pressure) of the tire is lowered due to a puncture or the like has been proposed. In the run-flat tire, the rigidity of the sidewall portion is increased so that the vehicle can travel even when the internal pressure of the tire is reduced.
In order to improve run-flat durability, it has been realized by improving the reinforcing rubber of the sidewall portion and improving the adhesion between the ply coating rubber and the reinforcing rubber. For example, in patent document 1, run flat durability improvement is achieved by suppressing the progress of a crack in the side reinforcing rubber and enhancing the peeling resistance between the ply coating rubber and the side reinforcing rubber.

Unexamined-Japanese-Patent No. 2007-145922

However, as the performance of automobiles, particularly passenger cars, is improved, further improvement in run-flat durability is required.
The present invention provides a ply-coated rubber composition for run-flat tires and a ply-coated rubber for run-flat tires capable of producing a run-flat tire having excellent run-flat durability, and a run-flat tire having excellent run flat durability. To be a task.

<1> A ply-coated rubber composition for a run flat tire, comprising a rubber component containing a diene rubber containing 80% by mass or more of a natural rubber, a filler, a vulcanizing agent, and a vulcanization accelerator. It is a ply coated rubber composition for run flat tires having a 100% modulus value M100 at 180 ° C. of 2.0 MPa or more and a tensile strength Tb at 180 ° C. of 7.0 MPa or more as vulcanized rubber properties.

<2> The ply coated rubber composition for run flat tires according to <1>, wherein the content of the styrene-butadiene copolymer rubber in the rubber component is 20% by mass or less.

<3> The ply-coated rubber composition for run flat tires according to <1> or <2>, wherein the vulcanization accelerator contains a sulfenamide vulcanization accelerator.
<4> The ply-coated rubber composition for a run flat tire according to <3>, which contains 0.7 parts by mass or more of the sulfenamide vulcanization accelerator with respect to 100 parts by mass of the rubber component.

<5> The ply-coated rubber composition for run flat tires according to any one of <1> to <4>, further comprising a heat-resistant crosslinking agent.
<6> The heat-resistant crosslinking agent is bismaleimide hexane, 1,1 ′-(methylenedi-4,1-phenylene) bis-maleimide, hexamethylene-1,6-bis (sodium thiosulfate) hydrate, and tetrakis It is a ply coated rubber composition for run flat tires according to <5>, which is at least one selected from the group consisting of (2-ethylhexyl) thiuram disulfide.

<7> The filler according to any one of <1> to <6>, wherein the filler contains 40 to 50 parts by mass of carbon black having an average particle diameter of 30 to 90 nm with respect to 100 parts by mass of the rubber component. It is a ply coating rubber composition for run flat tires as described.

It is ply coating rubber for run flat tires using the ply coating rubber composition for run flat tires as described in any one of <8> <1>-<7>.

It is a run flat tire using the ply coating rubber for run flat tires as described in <9> <8>.

  According to the present invention, a ply-coated rubber composition for run-flat tire and a ply-coated rubber for run-flat tire capable of producing a run-flat tire excellent in run-flat durability, and a run-flat tire excellent in run flat durability Can be provided.

It is a schematic diagram which shows the cross section of one embodiment of the run flat tire of this invention.

<Ply-coated rubber composition for run flat tires>
The ply-coated rubber composition for a run flat tire according to the present invention is a run containing a rubber component containing a diene rubber containing 80% by mass or more of a natural rubber, a filler, a vulcanizing agent and a vulcanization accelerator. A ply-coated rubber composition for flat tires, wherein the 100% modulus value M100 at 180 ° C. is 2.0 MPa or more and the tensile strength Tb at 180 ° C. is 7.0 MPa or more as vulcanized rubber properties.
Hereinafter, the ply-coated rubber composition for run flat tires may be simply referred to as "rubber composition". Also, ply coated rubber for run flat tires may be referred to simply as "ply coated rubber".
Heretofore, in order to improve run-flat durability, improvements have been made mainly to the reinforcing rubber, such as improvement of the reinforcing rubber of the sidewall portion and improvement of adhesion between the ply coating rubber and the reinforcing rubber. However, to further improve run-flat durability, the inner pressure of the tire is lowered, and the ply-coated rubber has the above-mentioned specific physical properties (M100, Tb) under the temperature environment (180 ° C.) of the tire when run-flat. The present inventors have found that it is necessary to be. That is, the run flat tire can be excellent in run flat durability by containing a rubber component containing a diene rubber containing 80% by mass or more of natural rubber and having the above-mentioned physical properties as a vulcanized rubber characteristic. all right.

  The 100% modulus value M100 at 180 ° C. of the vulcanized rubber of the ply coated rubber composition for run flat tires according to the present invention is 100% when the vulcanized rubber is heated to 180 ° C. based on JIS K 6251 (2017). It can be measured as modulus tensile modulus when stretched. From the viewpoint of further improving the run flat durability of the run flat tire, the M100 is preferably 2.1 MPa or more, and more preferably 2.2 MPa or more. The upper limit of the 100% modulus value M100 at 180 ° C. of the vulcanized rubber is not particularly limited, but is preferably 5 MPa or less from the viewpoint of securing the elongation (Eb) as a rubber.

  The tensile strength Tb (Tensile Strength at break) of the vulcanized rubber of the ply-coated rubber composition for run flat tires of the present invention at 180 ° C is based on JIS K 6251 (2017). It can be measured at 100% elongation as the maximum tensile force required to break. The Tb is preferably 7.5 MPa or more, and more preferably 8.0 MPa or more, from the viewpoint of further improving the run flat durability of the run flat tire. The larger the tensile strength Tb of the vulcanized rubber at 180 ° C., the better, and the upper limit is not particularly limited.

Hereinafter, the rubber composition of the present invention will be described in detail.
In the present invention, the "rubber component" is a polymer substance having rubber elasticity at room temperature and means a polymer component in rubber before vulcanization. The "rubber composition" is a mixture containing at least a rubber component and a vulcanizing agent, and one obtained by vulcanizing the rubber composition is referred to as "vulcanized rubber". That is, the rubber component is contained in the unvulcanized rubber composition and is not contained in the vulcanized rubber composition.

[Rubber component]
The rubber composition of the present invention contains a rubber component containing a diene rubber containing 80% by mass or more of natural rubber.
If the diene rubber does not contain 80% by mass or more of natural rubber, run-flat durability can not be improved. From the viewpoint of further improving run-flat durability, the content of the natural rubber in the diene rubber is preferably 83% by mass or more, and more preferably 80% by mass or more as the content in the rubber component, More preferably, it is 83% by mass or more. A diene rubber may contain 100 mass% of natural rubber, and 100 mass% of natural rubber may be contained as a whole rubber component.

The diene rubber may contain synthetic diene rubber in addition to natural rubber (NR).
Synthetic diene rubbers include, for example, polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), butadiene-isoprene copolymer rubber (BIR), styrene-isoprene copolymer rubber (SIR), styrene-butadiene-isoprene copolymer rubber (SBIR) and the like. The synthetic diene rubber may be modified or unmodified.
Among the above, synthetic diene rubbers are preferably polyisoprene rubber, styrene-butadiene copolymer rubber, polybutadiene rubber, and isobutylene isoprene rubber from the viewpoint of improving run-flat durability, and styrene-butadiene copolymer rubber is preferable. More preferable. The synthetic diene rubbers may be used alone or in combination of two or more.
The rubber component may contain non-diene rubber as long as the effects of the present invention are not impaired. The non-diene rubber may be modified or unmodified.

  The rubber component is preferably at least one selected from the group consisting of natural rubber and synthetic diene rubber, and from the viewpoint of improving the fracture characteristics of a run flat tire, the content of synthetic diene rubber in the rubber component Is preferably 0 to 20% by mass, and the content of styrene-butadiene copolymer rubber in the rubber component is more preferably 0 to 20% by mass, and styrene-butadiene copolymer rubber in the rubber component More preferably, the content of is 0 to 17% by mass.

〔filler〕
The rubber composition of the present invention preferably contains a filler in order to increase the rigidity of the vulcanized rubber, and particularly preferably contains a reinforcing filler such as carbon black and silica.

(Carbon black)
As carbon black, for example, SRF, GPF, FEF, HAF, ISAF, SAF, etc., and a mixture thereof (eg, ISAF-HAF etc.) can be used. Among them, it is preferable to use carbon black having an average particle diameter of 30 to 90 nm, such as GPF and FEF, from the viewpoint of reducing run loss and reducing rolling resistance, and using carbon black of 30 to 70 nm. Is more preferred. One type of carbon black may be used, or two or more types may be used.
The average particle size of carbon black is determined as an arithmetic average particle size measured by a transmission electron microscope, and in the case of commercially available carbon black, a catalog value may be referred to.

The content of carbon black in the rubber composition is 30 to 100 parts by mass of the rubber component from the viewpoint of reducing the loss of the run flat tire, further improving the run flat durability and reducing the rolling resistance. The amount is preferably 60 parts by mass, and more preferably 40 to 50 parts by mass.
In particular, 40 to 50 parts by mass of carbon black having an average particle diameter of 30 to 90 nm is preferably contained with respect to 100 parts by mass of the rubber component.
The rubber composition may further contain one or more types of silica.

[Vulcanizing agent, vulcanization accelerator]
The rubber composition of the present invention contains a vulcanizing agent.
The vulcanizing agent is not particularly limited, and usually, sulfur is used, and for example, powder sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, insoluble sulfur and the like can be mentioned.
The content of the vulcanizing agent is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the rubber component. When the content is 0.1 parts by mass or more, vulcanization can be sufficiently advanced, and when the content is 10 parts by mass or less, the aging resistance of the ply coated rubber can be suppressed.
The content of the vulcanizing agent in the rubber composition is more preferably 0.5 to 8 parts by mass, still more preferably 1 to 6 parts by mass with respect to 100 parts by mass of the rubber component.

[Vulcanization accelerator]
The rubber composition of the present invention contains a vulcanization accelerator.
As a vulcanization accelerator, a sulfenamide-based vulcanization accelerator, a thiazole-based vulcanization accelerator, a dithiocarbamate-based vulcanization accelerator, a xanthogenate-based vulcanization accelerator and the like can be mentioned. By containing a vulcanization accelerator, it is easy to achieve vulcanized rubber characteristics such that the 100% modulus value M100 at 180 ° C. is 2.0 MPa or more and the tensile strength Tb at 180 ° C. is 7.0 MPa or more; And the rolling resistance of the run flat tire can be made smaller.

  As a sulfenamide-based vulcanization accelerator, N-cyclohexyl-2-benzothiazolylsulfenamide, N, N-dicyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazole Rusulfenamide, N-oxydiethylene-2-benzothiazolylsulfenamide, N-methyl-2-benzothiazolylsulfenamide, N-ethyl-2-benzothiazolylsulfenamide, N-propyl-2- Benzothiazolylsulfenamide, N-butyl-2-benzothiazolylsulfenamide, N-pentyl-2-benzothiazolylsulfenamide, N-hexyl-2-benzothiazolylsulfenamide, N-pentyl- 2-benzothiazolylsulfenamide, N-octyl-2-benzothia Lylsulfenamide, N-2-ethylhexyl-2-benzothiazolylsulfenamide, N-decyl-2-benzothiazolylsulfenamide, N-dodecyl-2-benzothiazolylsulfenamide, N-stearyl- 2-benzothiazolylsulfenamide, N, N-dimethyl-2-benzothiazolylsulfenamide, N, N-diethyl-2-benzothiazolylsulfenamide, N, N-dipropyl-2-benzothiazole Rusulfenamide, N, N-dibutyl-2-benzothiazolylsulfenamide, N, N-dipentyl-2-benzothiazolylsulfenamide, N, N-dihexyl-2-benzothiazolylsulfenamide, N , N-dipentyl-2-benzothiazolylsulfenamide, N, N-dioctyl-2- Nzothiazolylsulfenamide, N, N-di-2-ethylhexylbenzothiazolylsulfenamide, N-decyl-2-benzothiazolylsulfenamide, N, N-didodecyl-2-benzothiazolylsulfene Amide, N, N-distearyl-2-benzothiazolylsulfenamide and the like, and because of high reactivity, N-cyclohexyl-2-benzothiazolylsulfenamide and N-tert-butyl-2-benzothia Soryl sulfenamide is preferred.

  As a thiazole type vulcanization accelerator, 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, zinc salt of 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, 2- (N, N- Diethylthiocarbamoylthio) benzothiazole, 2- (4'-morpholinodithio) benzothiazole, 4-methyl-2-mercaptobenzothiazole, di- (4-methyl-2-benzothiazolyl) disulfide, 5-chloro-2-mercapto Benzothiazole, 2-mercaptobenzothiazole sodium, 2-mercapto-6-nitrobenzothiazole, 2-mercapto-naphtho [1,2-d] thiazole, 2-mercapto-5-methoxybenzothiazole, 6-amino-2- Mercaptobenzothiazo Le, and the like, because of high reactivity 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide are preferred.

  As a dithiocarbamate-based vulcanization accelerator, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc ethylphenyldithiocarbamate, zinc N-pentamethylenedithiocarbamate, zinc dibenzyldithiocarbamate, sodium dibutyldithiocarbamate And copper dimethyl dithiocarbamate, ferric dimethyl dithiocarbamate, and tellurium diethyl dithiocarbamate.

  Examples of xanthogenate-based vulcanization accelerators include zinc methylxanthogenate, zinc ethylxanthogenate, zinc propylxanthogenate, zinc isopropylxanthogenate, zinc butylxanthogenate, zinc pentylxanthogenate, zinc hexylxanthogenate and heptylxanthogen Acid zinc, zinc octyl xanthate, zinc 2-ethylhexyl xanthate, zinc decyl xanthate, zinc dodecyl xanthate, potassium methyl xanthate, potassium ethyl xanthate, potassium propyl xanthate, potassium isopropyl xanthate, potassium butyl xanthate, Potassium pentyl xanthate, potassium hexyl xanthate, potassium heptyl xanthate, octyl xanthate Sodium, potassium 2-ethylhexylxanthogenate, potassium decylxanthogenate, potassium dodecylxanthogenate, sodium methylxanthogenate, sodium ethylxanthogenate, sodium propylxanthogenate, sodium isopropylxanthogenate, sodium butylxanthogenate, sodium pentylxanthogenate, hexyl Sodium xanthogenate, sodium heptyl xanthogenate, sodium octyl xanthogenate, sodium 2-ethylhexyl xanthogenate, sodium decyl xanthate, sodium dodecyl xanthate and the like can be mentioned.

Among the above, it is selected from the group consisting of sulfenamide-based vulcanization accelerators and dithiocarbamate-based vulcanization accelerators from the viewpoint of suppressing softening of the ply-coated rubber at 180 ° C. and further improving run-flat durability. It is preferable to use at least one amine-based vulcanization accelerator, and more preferably to use a sulfenamide-based vulcanization accelerator. The vulcanization accelerator may be used alone or in combination of two or more.
The rubber composition of the present invention contains a diene rubber containing 80% by mass or more of a natural rubber, and further contains a sulfenamide vulcanization accelerator to suppress the softening of the ply coating rubber, and the run flat durability Sex can be further improved.
The content of the vulcanization accelerator in the rubber composition is preferably 0.1 to 5 parts by mass and more preferably 0.2 to 3 parts by mass with respect to 100 parts by mass of the rubber component. From the viewpoint of further improving run-flat durability, the rubber composition preferably contains 0.7 parts by mass or more of a sulfenamide vulcanization accelerator with respect to 100 parts by mass of the rubber component. The rubber composition contains 0.7 parts by mass or more of a sulfenamide-based vulcanization accelerator with respect to 100 parts by mass of the rubber component to increase mono and disulfide bonds, and a ply at a high temperature (180 ° C. or more) It is possible to further suppress the softening of the coating rubber.

[Heat resistant crosslinking agent]
The rubber composition of the present invention may further contain a heat-resistant crosslinking agent.
When the rubber composition contains a heat-resistant crosslinking agent, the heat-resistant crosslinking agent forms a pseudo-crosslinked form at a high temperature (180 ° C. or more), and easily suppresses the softening of the ply-coated rubber. Therefore, with respect to the ply coated rubber, it is easy to achieve the vulcanized rubber characteristics such that the 100% modulus value M100 at 180 ° C. is 2.0 MPa or more and the tensile strength Tb at 180 ° C. is 7.0 MPa or more. As a result, the durability of the run flat tire can be further improved, and the rolling resistance of the run flat tire can be further reduced.

Examples of the heat-resistant crosslinking agent include bismaleimide compounds, thiuram compounds, and thiosulfates.
As the bismaleimide compound, for example, N, N'-1,2-ethylenebismaleimide, N, N'-1,2-propylenebismaleimide, 4,4'-bismaleimide diphenylmethane, N, N'-m- Phenylene bismaleimide, N, N '-(4,4-diphenyl-methane) bismaleimide, bis (3-ethyl-5-methyl-4-maleimidophenyl) methane, 2,2'-bis [4- (4-) Maleimidophenoxy) phenyl] propane, m-phenylenebis (methylene) bismaleimide, m-phenylenebis (methylene) biscitraconimide, bismaleimide hexane, 1,1 '-(methylenedi-4,1-phenylene) bismaleimide and the like It can be mentioned. Among these, bismaleimide hexane and 1,1 ′-(methylenedi-4,1-phenylene) bismaleimide are preferable.

Examples of the thiuram compound include tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetrakis (2-ethylhexyl) thiuram disulfide, and dipentamethylenethiuram sulfide. Among them, tetrakis (2-ethylhexyl) thiuram disulfide is preferable.
Examples of the thiosulfate include hexamethylene-1,6-bis (sodium thiosulfate) hydrate and the like.
The heat-resistant crosslinking agent may be used alone or in combination of two or more.

Among the above, the vulcanized rubber characteristics that suppress the softening of the ply-coated rubber at 180 ° C. and have a 100% modulus value M100 at 2.0 ° C. of 2.0 MPa or more and a tensile strength Tb at 180 ° C. of 7.0 MPa or more From the viewpoint of making it easier to achieve, the heat-resistant crosslinking agent is bismaleimide hexane, 1,1 ′-(methylenedi-4,1-phenylene) bis-maleimide, hexamethylene-1,6-bis (sodium thiosulfate) hydration And at least one selected from the group consisting of tetrakis (2-ethylhexyl) thiuram disulfide.
The content of the heat-resistant crosslinking agent in the rubber composition suppresses the softening of the ply-coated rubber at 180 ° C., further improves run-flat durability, and reduces rolling resistance, relative to 100 parts by mass of the rubber component. It is preferable that it is 0.1-5 mass parts, and it is more preferable that it is 0.5-3 mass parts.

Further, from the viewpoint of more easily achieving the vulcanized rubber characteristic that the 100% modulus value M100 at 180 ° C. is 2.0 MPa or more and the tensile strength Tb at 180 ° C. is 7.0 MPa or more, the rubber composition It is preferable to use a vulcanization accelerator and a heat-resistant crosslinking agent as follows.
When the rubber composition does not contain a heat-resistant crosslinking agent, that is, when the content of the heat-resistant crosslinking agent is 0 parts by mass with respect to 100 parts by mass of the rubber component, the content of the vulcanization accelerator is 100 parts by mass of the rubber component. Preferably, the amount is 0.7 parts by mass or more.
On the other hand, when the rubber composition contains a heat-resistant crosslinking agent, that is, when the content of the heat-resistant crosslinking agent exceeds 0 parts by mass with respect to 100 parts by mass of the rubber component, the content of the vulcanization accelerator is 100 parts by mass of the rubber component. The amount is preferably 0.3 parts by mass or more. When the rubber composition contains a heat-resistant crosslinking agent, the content of the heat-resistant crosslinking agent is 0.3 parts by mass or more per 100 parts by mass of the rubber component, and the content of the vulcanization accelerator is 100 parts by mass with respect to the rubber component It is preferable that it is 0.3 mass part or more.

  The rubber composition constituting the vulcanized rubber of the present invention may contain, in addition to the above-mentioned components, compounding agents which are blended and used in a normal rubber composition. For example, various fillers other than carbon black and silica (for example, clay, calcium carbonate, etc.), silane coupling agents, vulcanization acceleration assistants, vulcanization retarders, softeners such as various process oils, zinc flower, stearic acid , Various additives such as waxes, anti-aging agents, compatibilizers, workability improvers, lubricants, tackifiers, petroleum resins, ultraviolet absorbers, dispersants, homogenizing agents, etc. be able to.

  As an antiaging agent, a well-known thing can be used, Although it does not restrict | limit in particular, A phenolic anti-aging agent, an imidazole anti-aging agent, an amine anti-aging agent etc. can be mentioned. The content of these antioxidants is usually 0.1 to 5 parts by mass, preferably 0.5 to 3 parts by mass with respect to 100 parts by mass of the rubber component.

  When the rubber composition is obtained, there is no particular limitation on the method of blending the above components, and all the component materials may be blended at one time and kneaded, or the components may be blended in two or three stages. Kneading may be performed. In addition, kneaders, such as a roll, an internal mixer, and a Banbury rotor, can be used in the case of kneading | mixing. Further, when forming into a sheet shape, a band shape or the like, a known forming machine such as an extrusion molding machine or a press machine may be used.

<Ply coated rubber, run flat tire>
The ply-coated rubber for run flat tires of the present invention comprises the ply-coated rubber composition for run flat tires of the present invention and has a 100% modulus value M100 at 180 ° C. of 2.0 MPa or more and a tension at 180 ° C. The strength Tb is 7.0 MPa or more.
The run flat tire of the present invention comprises the ply coated rubber for a run flat tire of the present invention.
The ply-coated rubber for run flat tires of the present invention has a 100% modulus value M100 at 80 ° C. of 2.0 MPa or more and a tensile strength Tb at 180 ° C. of 7.0 MPa or more. By applying rubber to a run flat tire, the run flat tire is excellent in run flat durability.

Hereinafter, an example of the structure of a run flat tire is demonstrated using FIG.
FIG. 1 is a schematic view showing a cross section of one embodiment of the run flat tire of the present invention. Hereinafter, a run flat tire may be simply referred to as a "tire".
In FIG. 1, a preferred embodiment of the tire according to the present invention is continuous in a toroidal shape between a pair of bead cores 1, 1 '(1' is not shown), and both ends of the bead core 1 are wound up from the tire inside to outside. A carcass layer 2 comprising at least one radial carcass ply, a side rubber layer 3 disposed outside in the tire axial direction of the side region of the carcass layer 2 to form an outer part, and a tire of a crown region of the carcass layer 2 A tread rubber layer 4 disposed radially outward to form a ground contact portion, a belt layer 5 disposed between the tread rubber layer 4 and a crown region of the carcass layer 2 to form a reinforcing belt, and the carcass layer An inner liner 6 disposed on the entire inner surface of the tire 2 to form an airtight film, and a carcass layer extending from one of the bead cores 1 to the other of the bead cores 1 ' A bead filler 7 disposed between the main body portion and the winding portion wound up on the bead core 1, the bead filler 7 in the side region of the carcass layer and the shoulder area 10, the carcass layer 2 and the inner The tire is provided with at least one side reinforcing rubber layer 8 having a substantially crescent-shaped cross section along the tire rotation axis with the liner 6.
By using the ply-coated rubber of the present invention as the ply-coated rubber for covering the carcass ply constituting the carcass layer 2 of the tire, the tire of the present invention is excellent in run-flat durability.

  Although the carcass layer 2 of the tire according to the present invention comprises at least one carcass ply, the number of carcass plies may be two or more. Further, the reinforcing cords of the carcass ply can be arranged at an angle of substantially 90 ° with respect to the circumferential direction of the tire, and the number of reinforcement cords driven can be 35 to 65/50 mm. Further, a belt layer 5 comprising two first belt layers and a second belt layer may be disposed on the outer side in the tire radial direction of the crown region of the carcass layer 2, and the number of belt layers 5 is not limited thereto. It is not limited. The first belt layer and the second belt layer may be formed by embedding a plurality of steel cords aligned in parallel in the tire width direction without being twisted together in rubber, for example, The first and second belt layers may be arranged to cross each other between the layers to form a cross belt.

  Furthermore, in the tire of the present invention, a belt reinforcing layer (not shown) may be disposed on the outer side in the tire radial direction of the belt layer 5. The reinforcing cord of the belt reinforcing layer is intended to secure tensile rigidity in the circumferential direction of the tire, and therefore, it is preferable to use a cord made of a highly elastic organic fiber. Organic fiber cords include aromatic polyamide (aramid), polyethylene naphthalate (PEN), polyethylene terephthalate, rayon, Zylon (registered trademark) (polyparaphenylene benzobisoxazole (PBO) fiber), aliphatic polyamide (nylon), etc. Organic fiber cords and the like can be used.

  Furthermore, in the tire of the present invention, although not shown, reinforcing members such as inserts and flippers may be arranged outside the side reinforcing layer. The insert is a reinforcing material in which a plurality of highly elastic organic fiber cords arranged in the tire circumferential direction from the bead core 1 or 1 'to the side rubber layer 3 are arranged and rubber-coated (not shown). The flipper is disposed between the main body portion of the carcass ply extending between the bead cores 1 or 1 ′ and the folded back portion around the bead cores 1 or 1 ′, and the bead cores 1 or 1 ′ and the It is a reinforcing material in which a plurality of highly elastic organic fiber cords including at least a part of the bead filler 7 disposed on the outer side in the tire radial direction are arranged and rubber-coated. The angles of the insert and the flipper are preferably 30 to 60 degrees with respect to the circumferential direction.

  The bead cores 1 and 1 'are embedded in the pair of bead portions, and the carcass layer 2 is folded around the bead cores 1 and 1' from the inside to the outside of the tire and locked. Nor is it limited to this. For example, of the carcass plies constituting the carcass layer 2, at least one carcass ply is folded from the inside in the tire width direction to the outside around the bead cores 1 and 1 ′, and the folded end is folded with the belt layer 5. It may be a so-called envelope structure located between the carcass layer 2 and the crown portion. Furthermore, a tread pattern may be appropriately formed on the surface of the tread rubber layer 4, and an inner liner 6 may be formed on the innermost layer. In the tire according to the present invention, as the gas to be filled in the tire, a normal air or air with a changed partial pressure of oxygen, or an inert gas such as nitrogen can be used.

(Production of tire)
The run flat tire of the present invention is produced by a conventional method of producing a run flat tire using the ply coated rubber of the present invention for the carcass ply of the carcass layer 2.
That is, a rubber composition containing various chemicals is processed as a covering material of a carcass ply in an unvulcanized stage, and is pasted and formed on a tire forming machine by a usual method to form a green tire. The green tire is heated and pressurized in a vulcanizer to obtain a run flat tire.

<Examples 1 to 5, Comparative Examples 1 to 5>
[Preparation of rubber composition]
Each component was kneaded according to the composition shown in the following Tables 1 and 2 to prepare a rubber composition.
The details of each component used for preparation of the rubber composition are as follows.
(Rubber component)
NR: Natural rubber, TSR
SBR: styrene-butadiene copolymer rubber, manufactured by Asahi Kasei Chemicals Corporation, trade name "TUFDENE 3835" (including 37.5 parts by mass of oil with respect to 100 parts by mass of styrene butadiene rubber)

(Carbon black)
HAF: Asahi Carbon Co., Ltd., trade name "Asahi # 70" (average particle diameter = 26 nm)
FEF: Asahi Carbon Co., Ltd., trade name "Asahi # 60" (average particle diameter = 45 nm)

(Heat resistant crosslinking agent)
Heat-resistant cross-linking agent 1: Bismaleimidohexane heat-resistant cross-linking agent 2: 1, 1- (methylene di-4, 1-phenylene) bis-maleimide heat-resistant cross-linking agent 3: Hexamethylene-1, 6-bis (sodium thiosulfate) hydration Product, made by Flexis, product name "DURALINK HTS"

(Vulcanization accelerator)
Sulfenamide accelerator: N-tert-butyl-2-benzothiazolyl sulfenamide, manufactured by Sanshin Chemical Industry Co., Ltd., trade name "Sunseller NS-G"
Non-amine promoter: di-2-benzothiazolyl disulfide, "Noxceler DM" manufactured by Ouchi Shinko Chemical Co., Ltd.

Sulfur: Tsurumi Chemical Co., Ltd., trade name "powdered sulfur"
Stearic acid: Shin Nippon Rika Co., Ltd., trade name "stearic acid 50S"
Zinc flower: manufactured by Hakusui Tech, trade name "No. 3 zinc flower"
Antiaging agent: N-phenyl-N '-(1,3-dimethylbutyl) -p-phenylenediamine, manufactured by Ouchi Emerging Chemical Industry Co., Ltd., trade name "NOCRACK 6C"

[Manufacture of run flat tires, physical property measurement and evaluation of vulcanized rubber]
Then, the obtained rubber composition is disposed on a carcass ply constituting the carcass layer 2 shown in FIG. 1 as a ply-coated rubber composition for covering the carcass ply, and the radial run for a passenger car of a tire size 205/65 R16. Flat tires were manufactured according to a standard method.
The rubber composition is vulcanized under the same vulcanization conditions as the manufactured run flat tire to form a vulcanized rubber test piece, and as the physical properties of the vulcanized rubber, 100% modulus value M100 at 180 ° C. and tension at 180 ° C. The strength Tb was measured to evaluate the rolling resistance. Moreover, run flat durability was evaluated as tire performance using the manufactured run flat tire. The results are shown in Table 2.

100% modulus value M100 at 1.180 ° C.
The vulcanized rubber test piece was processed into a dumbbell-shaped No. 8 test piece, and based on JIS K 6251 (2017), the modulus tensile elastic modulus was determined at 100% elongation at a measurement temperature of 180 ° C.

2. Tension strength Tb at 180 ° C
Vulcanized rubber test pieces are processed into dumbbell-shaped No. 8 test pieces and fractured at a specified speed (500 ± 25 mm / min) at 180 ° C using a tensile testing device based on JIS K 6251 (2017) The maximum tensile force required for breaking was taken as the tensile strength Tb.

3. Run Flat Durability Using the produced run flat tire, the drum was run (speed: 80 km / h) with no internal pressure filled, and the drum travel distance until the tire became unable to run was measured. The run flat travel distance of the run flat tire of Comparative Example 1 is represented by an index of 100. The larger the index, the better the run flat durability.

4. Rolling resistance For a vulcanized rubber test piece, using a spectrometer manufactured by Ueshima Seisakusho, distance between chucks: 10 mm, initial strain: 200 μm, dynamic strain: 1%, frequency: 52 Hz, measurement temperature: 25 ° C. Below, the loss tangent (tan δ) of the vulcanized rubber test piece was measured. The vulcanized rubber test piece of Comparative Example 1 was represented by an index with tan δ being 100. The smaller the index, the smaller the rolling resistance and the better.

From Table 2, the rubber component does not contain a diene rubber containing 80% by mass or more of natural rubber (Comparative Example 1), the 100% modulus value M100 at 180 ° C. is 2.0 MPa or more, and the tensile strength at 180 ° C. It can be seen that the rubber compositions (Comparative Examples 2 to 5) which do not have a vulcanized rubber characteristic having Tb of 7.0 MPa or more have large rolling resistance and are not excellent in run flat durability.
On the other hand, a vulcanized rubber comprising a diene rubber having a rubber component containing 80% by mass or more of natural rubber, a 100% modulus value M100 at 180 ° C. of 2.0 MPa or more, and a tensile strength Tb at 180 ° C. of 7.0 MPa or more All of the run flat tires obtained from the rubber composition of the example having rubber properties were excellent in run flat durability and low in rolling resistance.

1 bead core 2 carcass layer 3 side rubber layer 4 tread rubber layer 5 belt layer 6 inner liner 7 bead filler 8 side reinforcing rubber layer 10 shoulder area

Claims (9)

A rubber component containing a diene rubber containing 80% by mass or more of natural rubber,
With fillers
A vulcanizing agent,
A ply coated rubber composition for a run flat tire, comprising a vulcanization accelerator, comprising:
A ply-coated rubber composition for a run flat tire, wherein the 100% modulus value M100 at 180 ° C. is 2.0 MPa or more and the tensile strength Tb at 180 ° C. is 7.0 MPa or more as the vulcanized rubber properties.   The ply-coated rubber composition for a run flat tire according to claim 1, wherein a content of the styrene-butadiene copolymer rubber in the rubber component is 20% by mass or less.   The ply-coated rubber composition for a run flat tire according to claim 1 or 2, wherein the vulcanization accelerator contains a sulfenamide vulcanization accelerator.   The ply-coated rubber composition for a run flat tire according to claim 3, comprising 0.7 parts by mass or more of the sulfenamide vulcanization accelerator with respect to 100 parts by mass of the rubber component.   The ply coated rubber composition for run flat tires according to any one of claims 1 to 4, further comprising a heat-resistant crosslinking agent.   The heat-resistant crosslinking agent includes bismaleimide hexane, 1,1 ′-(methylenedi-4,1-phenylene) bis-maleimide, hexamethylene-1,6-bis (sodium thiosulfate) hydrate, and tetrakis (2- The ply-coated rubber composition for a run flat tire according to claim 5, which is at least one selected from the group consisting of ethylhexyl) thiuram disulfide.   The run according to any one of claims 1 to 6, wherein the filler contains 40 to 50 parts by mass of carbon black having an average particle diameter of 30 to 90 nm with respect to 100 parts by mass of the rubber component. Ply coated rubber composition for flat tires.   The 100% modulus value M100 at 180 ° C. using the ply coated rubber composition for run flat tires according to any one of claims 1 to 7 is 2.0 MPa or more, and the tensile strength at 180 ° C. Ply coated rubber for run flat tires having Tb of 7.0 MPa or more.   A run flat tire using the ply coated rubber for a run flat tire according to claim 8.