JP6195243B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a high performance pneumatic tire.

  The pneumatic tire is composed of various members such as a sidewall and a case, in addition to the tread in contact with the road surface. Conventionally, in the blending design of the rubber composition used for each member, a laboratory test was performed for each rubber composition of each member, and the best rubber composition was designed for each member (for example, Patent Documents 1 to 3). And based on the evaluation result of this laboratory test, the pneumatic tire was produced combining each member comprised with each best rubber composition. However, there is a problem that the durability of the produced pneumatic tire is often lower than the durability expected from the results of laboratory vulcanization and laboratory tests of the rubber composition alone.

  High-performance pneumatic tires used in sports cars and race cars are strongly required to have excellent durability during continuous running at high speeds, but they were produced based on the results of laboratory tests as described above. There is a problem that the durability of high-performance pneumatic tires is often lower than the durability expected from the results of laboratory tests.

  As one form of tire damage during continuous running in the high speed range of high performance pneumatic tires, the rubber composition near the breaker edge is destroyed by continuous running in the high speed range, and the tire member adjacent to the breaker becomes It may be exfoliated. And there exists a problem that it becomes lower than durability expected from the result of a laboratory test by the damage form of this tire.

JP 2008-24913 A Japanese Patent No. 4246245 Japanese Patent No. 4308289

  An object of the present invention is to solve the above-mentioned problems and to provide a high-performance pneumatic tire that is extremely excellent in durability during continuous running in a high speed region and that is also excellent in handling stability.

  As a result of diligently examining the above problems, the present inventors have found that the sulfur contained in the rubber composition near the breaker edge moves between the members during use of the tire, resulting in a change in the physical properties of the rubber composition of each member. As a result, the inventors have hypothesized that the durability of the produced high performance pneumatic tire is lower than the durability expected from the results of the laboratory test.

  Then, paying attention to the movement of sulfur in the vicinity of the breaker edge, the sulfur content in the rubber composition used for the breaker, and each rubber composition used for the side wall and case adjacent to the breaker satisfies a predetermined relational expression. It has been found that by using a high-performance pneumatic tire, the durability at the time of continuous running in a high speed range is extremely excellent, and the steering stability is also excellent, and the present invention has been completed.

That is, the present invention is a high performance pneumatic tire having a sidewall (A), a breaker (B) and a case (C),
Side wall (A)
A rubber composition for sidewalls containing 3.0 to 7.0 parts by mass of sulfur with respect to 100 parts by mass of a rubber component containing 75 to 100% by mass of natural rubber and / or isoprene rubber,
Breaker (B)
It consists of a breaker cord and a rubber composition for covering the breaker cord,
Case (C)
It consists of a case cord and a rubber composition for case cord coating,
Sulfur content (sulfur A) with respect to 100 parts by mass of the rubber component of the rubber composition for sidewall, sulfur content (sulfur B) with respect to 100 parts by mass of the rubber component of the rubber composition for covering a breaker cord, and case cord coating The sulfur content (sulfur C) with respect to 100 parts by mass of the rubber component of the rubber composition relates to a high performance pneumatic tire satisfying the following formulas (1) and (2).
Formula (1): -0.5 <sulfur A-sulfur B <0.5
Formula (2): -0.5 <sulfur A-sulfur C <0.5

  The rubber composition for sidewalls preferably contains 40 to 70 parts by mass of carbon black (I) with respect to 100 parts by mass of the rubber component.

It is preferable that the nitrogen adsorption specific surface area (N ₂ SA) of the carbon black (I) is 50 to 120 m ² / g.

  The rubber composition for covering a breaker cord and / or the rubber composition for covering a case cord preferably contains 50 to 90 parts by mass of carbon black (II) with respect to 100 parts by mass of each rubber component.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black (II) is preferably 40 to 100 m ² / g.

  According to this invention, it has a side wall (A), a breaker (B), and a case (C), and a side wall (A) is 3.0-7.0 mass with respect to 100 mass parts of predetermined rubber components. The sulfur content of the rubber composition for side walls is the sulfur content of the rubber composition for breaker cord coating and the sulfur of the rubber composition for case cord coating. High-performance pneumatic tire that satisfies the above-mentioned content and a predetermined relational expression, so that it has excellent durability during continuous running in a high speed range and excellent handling stability. can do.

It is a fragmentary sectional view showing one mode of a high performance pneumatic tire concerning the present invention.

The high-performance pneumatic tire of the present invention has a sidewall (A), a breaker (B), and a case (C), and the sidewall (A) contains 75 to 100% by mass of natural rubber and / or isoprene rubber. It consists of a rubber composition for sidewalls containing 3.0 to 7.0 parts by mass of sulfur with respect to 100 parts by mass of the rubber component, and the breaker (B) consists of a breaker cord and a rubber composition for covering a breaker cord, The case (C) is composed of a case cord and a case cord covering rubber composition, the sulfur content of the sidewall rubber composition (sulfur A), and the sulfur content of the breaker cord covering rubber composition (sulfur B). ), And the sulfur content (sulfur C) of the case cord covering rubber composition satisfies the following formulas (1) and (2).
Formula (1): -0.5 <sulfur A-sulfur B <0.5
Formula (2): -0.5 <sulfur A-sulfur C <0.5

  In addition, in this specification, content of the chemical | medical agent contained in each rubber composition means content in the rubber composition before vulcanization | cure all. That is, it means the theoretical content of chemicals contained in each rubber composition. Here, the theoretical content means the amount of chemicals added when preparing the unvulcanized rubber composition.

  The high-performance pneumatic tire of the present invention has a sidewall (A), a breaker (B), and a case (C). A side wall is a member arranged on the outside of the case, and is indicated by A in FIG. The breaker is a member made of a breaker cord and a rubber composition for covering the breaker cord, and is indicated by B in FIG. The case is a member made of a case cord and a rubber composition for covering the case cord, which is also called a carcass, and is indicated by C in the attached FIG.

Side wall (A)
The sidewall (A) constituting the high-performance pneumatic tire of the present invention comprises a rubber composition for sidewall.

  The rubber composition for a sidewall contains a predetermined rubber component and sulfur.

  The rubber component of the rubber composition for a side wall contains natural rubber (NR) and / or isoprene rubber (IR). NR is not particularly limited, and examples thereof include SIR20, RSS3, and TSR20. Moreover, it does not specifically limit as IR, For example, Nippon Zeon Co., Ltd. IR2200 etc. are mentioned. It is preferable to contain NR from the viewpoint of excellent strength.

  The content of NR and / or IR in the rubber component is 75% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 100% by mass. When the content is less than 75% by mass, the strength tends to be insufficient.

  In the rubber composition for a sidewall, the rubber component that can be used in addition to NR and IR is not particularly limited. For example, liquid isoprene rubber (LIR), styrene butadiene rubber (SBR), butadiene rubber (BR), styrene isoprene butadiene rubber Examples thereof include diene rubbers such as (SIBR), chloroprene rubber (CR), and acrylonitrile butadiene rubber (NBR). These diene rubbers may be used alone or in combination of two or more. Among these, BR and SBR are preferable, and BR is more preferable because good durability can be obtained while ensuring good steering stability, low fuel consumption, elongation at break, and crack growth resistance.

  Examples of the SBR include emulsion polymerization SBR (E-SBR) obtained by emulsion polymerization, solution polymerization SBR (S-SBR) obtained by solution polymerization, and modified SBR (modified E-SBR, modified S) obtained by modifying these SBRs. Various SBRs such as -SBR) can be used.

  As the BR, various BR such as high-cis 1,4-polybutadiene rubber (high-cis BR), butadiene rubber containing 1,2-syndiotactic polybutadiene crystals (SPB-containing BR), modified butadiene rubber (modified BR), and the like are used. Can do. Among these, high cis BR is preferable. High cis BR is a butadiene rubber having a cis 1,4 bond content of 90% by mass or more. Examples of such high-sis BR include BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B manufactured by Ube Industries, Ltd., and BR150B.

  The content in the case where BR is contained in the rubber component is preferably 0% by mass or more because it is excellent in flex resistance. Further, the content of the various BRs is preferably 30% by mass or less because of excellent retention of breaking strength.

  The rubber composition for a sidewall contains sulfur as a vulcanizing agent. Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. Among these, insoluble sulfur is preferable because it prevents bloom.

  Content with respect to 100 mass parts of sulfur in the rubber composition for side walls is 3.0 mass parts or more, 3.5 mass parts or more are preferable, 4.0 mass parts or more are more preferable, 4.5 More preferred is part by mass or more. When the amount is less than 3.0 parts by mass, there is a possibility that sufficient sidewall rigidity required for a high-performance pneumatic tire cannot be obtained. Moreover, content of sulfur is 7.0 mass parts or less, and 6.5 mass parts or less are preferable. When it exceeds 7.0 parts by mass, the crosslink density becomes too high, and the crack growth resistance and elongation at break of the sidewall may be significantly deteriorated.

  The rubber composition for sidewalls preferably contains a softening agent. Examples of the softening agent include C5 petroleum resin, C9 petroleum resin, process oil, vegetable oil, and coumarone indene resin. Among these, C5 petroleum resins are preferable, and C9 petroleum resins and process oils are more preferable because they are excellent in adhesiveness, elongation at break, and resistance to ozone deterioration and are inexpensive.

  In the rubber composition for a sidewall, the content with respect to 100 parts by mass of the rubber component when the softener is contained is preferably 0 part by mass or more, and more preferably 1 part by mass or more. Moreover, 10 mass parts or less are preferable, as for content of a softening agent, 5 mass parts or less are more preferable, and 2 mass parts or less are more preferable. When it exceeds 10 mass parts, there exists a possibility that bending resistance may fall.

  The rubber composition for sidewalls preferably contains carbon black (I) as a filler component. By containing carbon black, the reinforcing property of the rubber composition can be enhanced, and the crack growth resistance, durability, steering stability, and UV degradation resistance of the tire can be further improved. In the present specification, the carbon black contained in the rubber composition for the sidewall is referred to as “carbon black (I)”, and the rubber composition for covering a breaker cord and the rubber composition for covering a case cord described later are contained. Although carbon black is described as “carbon black (II)”, the same carbon black is used as carbon blacks (I) and (II), and different carbons are used in a rubber composition for covering a breaker cord and a rubber composition for covering a case cord. It does not exclude the use of black.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black (I) is preferably 50 m ² / g or more, and more preferably 60 m ² / g or more. If it is less than 50 m ² / g, the crack growth resistance, durability and steering stability of the tire tend to be insufficient. Further, N ₂ SA of carbon black (I) is preferably 120 m ² / g or less, and more preferably 100 m ² / g or less. When it exceeds 120 m ² / g, the workability tends to deteriorate. The N ₂ SA of carbon black can be measured according to JIS K 6217-2 “Carbon black for rubber—Basic characteristics—Part 2: Determination of specific surface area—Nitrogen adsorption method—Single point method”. .

  In the rubber composition for a sidewall, the content with respect to 100 parts by mass of the rubber component when carbon black (I) is contained is preferably 40 parts by mass or more, and more preferably 45 parts by mass or more. If the amount is less than 40 parts by mass, sufficient reinforcement cannot be obtained, and there is a risk that the crack growth resistance, durability, and steering stability of the tire will deteriorate. Moreover, 70 mass parts or less are preferable, as for content of carbon black (I), 65 mass parts or less are more preferable, and 60 mass parts or less are more preferable. When the amount exceeds 70 parts by mass, the heat generation of the sidewall is increased, and the durability of the tire may be deteriorated.

  In addition to the above components, the rubber composition for the sidewall is a compounding agent or additive conventionally used in the rubber industry, for example, various reinforcing fillers other than carbon black, coupling agents, waxes, antioxidants. Anti-aging agents, vulcanization accelerators (stearic acid, zinc oxide, etc.), hybrid cross-linking agents (HTS, PK900, etc., manufactured by Flexis Co.), vulcanization accelerators, etc. can be appropriately contained as necessary. .

  Examples of the vulcanization accelerator include guanidine, aldehyde-amine, aldehyde-ammonia, thiazole, sulfenamide, thiourea, thiuram, dithiocarbamate, and zanddate compounds. These vulcanization accelerators may be used alone or in combination of two or more. Among these, from the viewpoint of dispersibility in rubber and stability of vulcanization properties, sulfenamide vulcanization accelerators [N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl 2-benzothiazolylsulfenamide (CBS), N, N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS), N, N-diisopropyl-2-benzothiazolesulfenamide, etc.], N-tert -Butyl-2-benzothiazolylsulfenimide (TBSI) and di-2-benzothiazolyl disulfide (DM) are preferred, and TBBS, CBS, TBSI and DM are more preferred.

  In the rubber composition for a sidewall, the content with respect to 100 parts by mass of the rubber component when the vulcanization accelerator is contained is preferably 0.3 parts by mass or more, and more preferably 0.5 parts by mass or more. Further, the content of the vulcanization accelerator is preferably 2.0 parts by mass or less, and more preferably 1.5 parts by mass or less. When the content of the vulcanization accelerator is within the above range, suitable crosslinking density and crack growth resistance as a rubber composition for a sidewall can be obtained, and the effects of the present invention can be obtained more suitably.

  As a method for producing the rubber composition for a sidewall, a known method can be used. For example, it can be produced by a method of kneading the above components using a rubber kneading apparatus such as an open roll or a Banbury mixer.

Breaker (B)
The breaker (B) constituting the high-performance pneumatic tire of the present invention is a member made of a breaker cord and a rubber composition for covering a breaker cord, and the breaker cord is coated with a rubber composition for covering a breaker cord.

  Examples of the breaker cord include a textile cord and a steel cord. In the present invention, a textile cord is preferable because of excellent grip performance. Moreover, a steel cord is preferable because of its excellent durability.

The textile cord is a cord in which a plurality of filaments made of an organic fiber material are twisted together, and as the organic fiber material, nylon 6, nylon 66, polyethylene terephthalate (PET), polyethylene-2,6-naphthalate (PEN) , Polyparaphenylene terephthalamide (PPTA), polyvinyl alcohol (PVA), Kevlar ^(R) (Kevlar ^(R) is a registered trademark of DuPont) (KEV), etc. And can be used as an organic fiber material. Among them, as a textile cord for a breaker, Kevlar ^(R) is preferable because it has a relatively high modulus and good steering stability.

  Examples of the steel cord include a single-stranded steel cord having a 1 × n configuration and a layer-twisted steel cord having a k + m configuration. Here, the single stranded steel cord having a 1 × n configuration is a one-layer stranded steel cord obtained by twisting n filaments. The k + m layer-twisted steel cord is a steel cord having a two-layer structure with different twist directions and twist pitches, and having k filaments in the inner layer and m filaments in the outer layer. n is an integer of 1 to 27, k is an integer of 1 to 10, and m is an integer of 1 to 3. The surface of the steel cord is preferably plated with brass (Brass), Zn or the like in order to improve adhesion to the rubber composition.

  The rubber component contained in the rubber composition for covering a breaker cord is not particularly limited, and the same diene rubber as that for the sidewall rubber composition can be used. A rubber component may be used independently and may use 2 or more types together. Among these, NR is preferable because good durability can be obtained while ensuring good handling stability and elongation at break.

  It does not specifically limit as NR, The thing similar to the rubber composition for sidewalls can be used. The content of NR in the rubber component is preferably 50% by mass or more, more preferably 80% by mass or more, and further preferably 100% by mass. When the NR content is within the above range, good durability can be obtained while ensuring good handling stability and elongation at break.

  The rubber composition for covering a breaker cord contains sulfur as a vulcanizing agent. Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. Among these, insoluble sulfur is preferable from the viewpoint of preventing bloom.

  The content of sulfur in the rubber composition for covering a breaker cord with respect to 100 parts by mass of the rubber component is preferably 3.0 parts by mass or more, more preferably 3.5 parts by mass or more, further preferably 4.0 parts by mass or more. It is most preferably 5 parts by mass or more. If the amount is less than 3.0 parts by mass, there is a risk of poor adhesion to the breaker cord. Moreover, 7.0 mass parts or less are preferable and, as for sulfur content, 6.5 mass parts or less are more preferable. When it exceeds 7.0 parts by mass, the crosslinking density becomes too high, so that the crack growth resistance and the elongation at break are lowered, and the durability may be deteriorated. When the sulfur content is in the above range, good elongation at break, crack growth resistance, and adhesion to the breaker cord can be obtained while ensuring good handling stability, resulting in good durability. Is obtained.

  The rubber composition for covering a breaker cord preferably contains a softening agent. As the softening agent, the same rubber composition as that for the sidewall can be used.

  In the rubber composition for covering a breaker cord, the content with respect to 100 parts by mass of the rubber component when the softener is contained is preferably 2 parts by mass or more, and more preferably 3 parts by mass or more. When the amount is less than 2 parts by mass, the oil moves during vulcanization from the adjacent rubber composition, and the adhesive strength with the adjacent rubber composition may be reduced. Further, the content of the softening agent is preferably 10 parts by mass or less, and more preferably 7 parts by mass or less. When it exceeds 10 mass parts, there exists a possibility that the fall of the adhesive force with the rubber composition which adjoins at the time of high temperature may arise.

  The rubber composition for covering a breaker cord may contain carbon black (II). By containing carbon black, the reinforcing property of the rubber composition can be enhanced, and the crack growth resistance, durability, and steering stability of the tire can be further improved.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black (II) is preferably 40 m ² / g or more, and more preferably 60 m ² / g or more. If it is less than 40 m ² / g, the steering stability and durability of the tire tend to be insufficient. Also, N ₂ SA of the carbon black (II) is preferably from 150 meters ² / g or less, more preferably 100 m ² / g. If it exceeds 150 m ² / g, the dispersibility is poor, and there is a possibility that sufficient fracture strength and elongation at break cannot be obtained.

  In the rubber composition for covering a breaker cord, the content with respect to 100 parts by mass of the rubber component when carbon black (II) is contained is preferably 30 parts by mass or more, and more preferably 45 parts by mass or more. When the amount is less than 30 parts by mass, sufficient reinforcing properties cannot be obtained, and the durability and steering stability of the tire may be deteriorated. Moreover, 100 mass parts or less are preferable and, as for content of carbon black (II), 90 mass parts or less are more preferable. When the amount exceeds 100 parts by mass, the heat build-up becomes high and the durability of the tire may be deteriorated.

  The rubber composition for coating a breaker cord when using a steel cord as the breaker cord preferably contains an organic acid cobalt for the purpose of improving the adhesion to the steel cord. Since the organic acid cobalt serves to crosslink the rubber composition and the steel cord, the adhesion between the steel cord and the rubber composition can be improved by containing the organic acid cobalt.

  Examples of the organic acid cobalt include cobalt stearate, cobalt naphthenate, cobalt neodecanoate, boron 3 neodecanoate cobalt, and abitienate cobalt. Among these, cobalt stearate is preferable because it is excellent in processability (viscosity) and the vulcanization reaction easily proceeds.

  When the organic acid cobalt is contained, the content with respect to 100 parts by mass of the rubber component is preferably 0.05 parts by mass or more, and more preferably 0.07 parts by mass or more in terms of cobalt. If the amount is less than 0.05 parts by mass, the adhesion between the steel cord and the rubber composition may not be sufficient. Further, the content is preferably 0.35 parts by mass or less and more preferably 0.30 parts by mass or less in terms of cobalt. When it exceeds 0.35 mass part, there exists a possibility that oxidation deterioration resistance, crack growth resistance, and durability may deteriorate.

  In addition to the above components, the rubber composition for covering the breaker cord is a compounding agent or additive conventionally used in the rubber industry, for example, various reinforcing fillers other than carbon black, coupling agents, waxes, antioxidants. If necessary, an agent, an antioxidant, a vulcanization accelerator (such as stearic acid or zinc oxide), a hybrid crosslinking agent (such as HTS or PK900 manufactured by Flexis), or a vulcanization accelerator may be appropriately contained. it can.

  In the case of using a textile cord as the breaker cord, the content with respect to 100 parts by mass of the rubber component when zinc oxide is contained is preferably 2 to 20 parts by mass, and more preferably 4 to 12 parts by mass. When the content of zinc oxide is within the above range, good handling stability and low fuel consumption can be ensured while good elongation at break, resistance to crack growth and adhesion to textile cords can be obtained. Good durability can be obtained.

  In the case of using a steel cord as the breaker cord, the content with respect to 100 parts by mass of the rubber component when zinc oxide is contained is preferably 3 to 20 parts by mass, and more preferably 6 to 12 parts by mass. When the content of zinc oxide is within the above range, good handling stability and low fuel consumption can be secured, and good elongation at break, resistance to crack growth and adhesion to steel cords can be obtained. Good durability can be obtained.

  As the vulcanization accelerator, the same rubber composition as that for the sidewall rubber composition can be used, but DCBS and TBSI are more preferable because of excellent adhesion to the cord.

  In the case of using a textile cord as a breaker cord, the content with respect to 100 parts by mass of the rubber component when the vulcanization accelerator is contained is preferably 0.3 parts by mass or more, and more preferably 0.6 parts by mass or more. . The content is preferably 2.0 parts by mass or less, and more preferably 1.2 parts by mass or less. When the blending amount of the vulcanization accelerator is within the above range, a suitable crosslinking density as a rubber for covering a breaker cord (textile cord) can be obtained, and the amount of sulfur transfer can be adjusted to an appropriate amount, and the effect of the present invention Is more suitably obtained.

  In the case of using a steel cord as a breaker cord, the content with respect to 100 parts by mass of the rubber component when the vulcanization accelerator is contained is preferably 0.3 parts by mass or more, and more preferably 0.5 parts by mass or more. . The content is preferably 2.0 parts by mass or less, and more preferably 1.5 parts by mass or less. When the blending amount of the vulcanization accelerator is within the above range, a suitable crosslinking density as a rubber for covering a breaker cord (steel cord) can be obtained, and the amount of sulfur transfer can be adjusted to an appropriate amount, and the effect of the present invention Is more suitably obtained.

  As a method for producing the rubber composition for covering a breaker cord, a known method can be used, and for example, the same method as that for the sidewall rubber composition can be used.

Case (C)
The case (C) constituting the high-performance pneumatic tire of the present invention is a member made of a case cord and a case cord covering rubber composition, and the case cord is covered with the case cord covering rubber composition.

  The case cord used in the high-performance pneumatic tire of the present invention is a textile cord because of its excellent balance between durability and grip performance. As the textile code, one described as a breaker code can be used. Of these, nylon 66 is preferred because of its good durability and steering stability.

  The rubber component contained in the case cord covering rubber composition is not particularly limited, but the same diene rubber as that of the sidewall rubber composition can be used. A rubber component may be used independently and may use 2 or more types together. Among these, NR is preferable because good durability can be obtained while ensuring good handling stability and elongation at break.

  It does not specifically limit as NR, The thing similar to the rubber composition for sidewalls can be used. The content of NR in the rubber component is preferably 50% by mass or more, more preferably 80% by mass or more, and further preferably 100% by mass. When the NR content is within the above range, good durability can be obtained while ensuring good handling stability and elongation at break.

  The rubber composition for covering a case cord contains sulfur as a vulcanizing agent. Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. Among these, insoluble sulfur is preferable from the viewpoint of preventing bloom.

  The content of sulfur in the rubber composition for covering a case cord with respect to 100 parts by mass of the rubber component is preferably 3.0 parts by mass or more, more preferably 3.5 parts by mass or more, further preferably 4.0 parts by mass or more. It is most preferably 5 parts by mass or more. If it is less than 3.0 parts by mass, there is a risk of poor adhesion to the case cord. Moreover, 7.0 mass parts or less are preferable and, as for sulfur content, 6.5 mass parts or less are more preferable. When it exceeds 7.0 parts by mass, the crosslinking density becomes too high, so that the crack growth resistance and the elongation at break are lowered, and the durability may be deteriorated. When the sulfur content is within the above range, good elongation at break, crack growth resistance, and adhesion to the case cord can be obtained while ensuring good handling stability, resulting in good durability. Is obtained.

  The rubber composition for covering a case cord preferably contains a softening agent. As the softening agent, the same rubber composition as that for the sidewall can be used.

  In the case cord covering rubber composition, the content with respect to 100 parts by mass of the rubber component when the softener is contained is preferably 2 parts by mass or more, and more preferably 3 parts by mass or more. When the amount is less than 2 parts by mass, the oil moves during vulcanization from the adjacent rubber composition, and the adhesive strength with the adjacent rubber composition may be reduced. Further, the content of the softening agent is preferably 10 parts by mass or less, and more preferably 7 parts by mass or less. When it exceeds 10 mass parts, there exists a possibility that the fall of the adhesive force with the rubber composition which adjoins at the time of high temperature may arise.

  The rubber composition for covering a case cord preferably contains carbon black (II). By containing carbon black, the reinforcing property of the rubber composition can be enhanced, and the crack growth resistance, durability, and steering stability of the tire can be further improved.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black (II) is preferably 40 m ² / g or more, and more preferably 60 m ² / g or more. If it is less than 40 m ² / g, the steering stability and durability of the tire tend to be insufficient. Also, N ₂ SA of the carbon black (II) is preferably from 150 meters ² / g or less, more preferably 100 m ² / g. If it exceeds 150 m ² / g, the dispersibility is poor, and there is a possibility that sufficient fracture strength and elongation at break cannot be obtained.

  In the case cord covering rubber composition, the content with respect to 100 parts by mass of the rubber component when carbon black (II) is contained is preferably 30 parts by mass or more, and more preferably 45 parts by mass or more. When the amount is less than 30 parts by mass, sufficient reinforcing properties cannot be obtained, and the durability and steering stability of the tire may be deteriorated. Moreover, 100 mass parts or less are preferable and, as for content of carbon black (II), 90 mass parts or less are more preferable. When the amount exceeds 100 parts by mass, the heat build-up becomes high and the durability of the tire may be deteriorated.

  In addition to the above-mentioned components, the case cord covering rubber composition is a compounding agent or additive conventionally used in the rubber industry, for example, various reinforcing fillers other than carbon black, coupling agents, waxes, antioxidants. If necessary, an agent, an antioxidant, a vulcanization accelerator (such as stearic acid or zinc oxide), a hybrid crosslinking agent (such as HTS or PK900 manufactured by Flexis), or a vulcanization accelerator may be appropriately contained. it can.

  In the case cord covering rubber composition, the content with respect to 100 parts by mass of the rubber component in the case of containing zinc oxide is preferably 2 to 20 parts by mass, and more preferably 4 to 12 parts by mass. When the content of zinc oxide is within the above range, good handling stability and low fuel consumption can be ensured while good elongation at break, resistance to crack growth and adhesion to textile cords can be obtained. Good durability can be obtained.

  As the vulcanization accelerator, the same rubber composition as that for the sidewall rubber composition can be used, but DCBS and TBSI are more preferable because of excellent adhesion to the cord.

  In the case cord covering rubber composition, when the vulcanization accelerator is contained, the content with respect to 100 parts by mass of the rubber component is preferably 0.3 parts by mass or more, and more preferably 0.6 parts by mass or more. The content is preferably 2.0 parts by mass or less, and more preferably 1.2 parts by mass or less. When the blending amount of the vulcanization accelerator is within the above range, a suitable crosslinking density as a case cord covering rubber can be obtained, the amount of sulfur transfer can be adjusted to an appropriate amount, and the effects of the present invention are more suitably achieved. can get.

  As a method for producing the case cord covering rubber composition, a known method can be used. For example, the same method as that for the sidewall rubber composition can be used.

Sulfur content In the high performance pneumatic tire of the present invention, the sulfur content is 100% by mass with respect to 100 parts by mass of the rubber component of the sidewall rubber composition, and the rubber component of the rubber composition for covering a breaker cord is 100% by mass. When the sulfur content relative to the part is “sulfur B”, the relationship between “sulfur A” and “sulfur B” satisfies the following formula (1), thereby improving durability during continuous running in a high speed range. Can be made.
Formula (1): -0.5 <sulfur A-sulfur B <0.5

  When the value obtained by subtracting “sulfur B” from “sulfur A” is −0.5 or less, sulfur contained in the rubber composition for covering the breaker cord moves to the sidewall during traveling in the high speed range. The adhesive strength between the breaker cord covering rubber composition and the sidewall rubber composition is lowered, and the durability of the tire tends to be lowered. When the equivalence is 0.5 or more, sulfur contained in the sidewall rubber composition moves to the breaker cord coating rubber composition, and the breaker cord coating rubber composition and the sidewall rubber composition. There is a tendency for the durability of the tire to decrease due to a decrease in the adhesive strength.

  The lower limit of the formula (1) is preferably -0.4 because the adhesive strength between the breaker cord covering rubber composition and the sidewall rubber composition is less likely to decrease, and the durability of the tire is excellent. -0.2 is more preferable. Further, the upper limit of the formula (1) is preferably 0.4 because the adhesive strength between the breaker cord covering rubber composition and the sidewall rubber composition is less likely to decrease and the tire has excellent durability. 0.2 is more preferable.

Furthermore, in the high performance pneumatic tire of the present invention, the sulfur content with respect to 100 parts by mass of the rubber component of the sidewall rubber composition is “sulfur A”, and the rubber component for 100 parts by mass of the rubber composition for case cord coating is used. When the sulfur content is “sulfur C”, the relationship between “sulfur A” and “sulfur C” satisfies the following formula (2), thereby improving durability during continuous running in a high speed range. Can do.
Formula (2): -0.5 <sulfur A-sulfur C <0.5

  When the value obtained by subtracting “sulfur C” from “sulfur A” is −0.5 or less, sulfur contained in the rubber composition for covering the case cord moves to the sidewall during traveling in the high speed range. In addition, the adhesive strength between the case cord covering rubber composition and the sidewall rubber composition is lowered, and the durability of the tire tends to be lowered. Further, when the equivalence is 0.5 or more, sulfur contained in the sidewall rubber composition moves to the case cord covering rubber composition, and the case cord covering rubber composition and the sidewall rubber composition. There is a tendency for the durability of the tire to decrease due to a decrease in the adhesive strength.

  The lower limit value of the formula (2) is preferably −0.4 because the adhesive strength between the rubber composition for covering a case cord and the rubber composition for a sidewall hardly decreases and the tire has excellent durability. -0.2 is more preferable. Further, the upper limit value of the formula (2) is preferably 0.4 for the reason that the adhesive strength between the rubber composition for covering a case cord and the rubber composition for a sidewall hardly decreases and the tire has excellent durability. 0.2 is more preferable.

Rubber component In the pneumatic tire of the present invention, the above-described diene rubber components can be used for the rubber composition for sidewalls, the rubber composition for covering a breaker cord, and the rubber composition for covering a case cord, respectively. Even when a rubber component is used, a high-performance pneumatic tire excellent in durability and steering stability can be obtained by satisfying the above-described relationship of sulfur content. Furthermore, by unifying the rubber components used in the three rubber compositions and improving the affinity between the rubber compositions, the peel strength of each member is improved and the high-performance pneumatic is superior in durability. A tire is obtained. NR, BR, and SBR are preferable as the rubber component used in a unified manner.

Pneumatic tire The high-performance pneumatic tire of the present invention is produced by a normal method using each rubber composition described above. That is, if necessary, the rubber composition containing various additives, the shape of each component of the tire in the unvulcanized stage (in the case of a sidewall, the rubber composition for the sidewall, the shape of the sidewall, in the case of a breaker Is an unvulcanized sheet-form breaker cord coating rubber composition that is pressure-coated on the breaker cord from above and below to form the shape of the breaker. And then extruded according to the shape of the case), molded on a tire molding machine by a normal method, bonded together with other tire members to form an unvulcanized tire, It can be produced by heating and pressurizing in a vulcanizer (preferably a dome type vulcanizer).

  The vulcanization mold temperature or the steam filling temperature of the vulcanizer when vulcanizing the tire is preferably 130 to 170 ° C, more preferably 140 to 165 ° C. The higher the vulcanization temperature, the thinner the gauge side wall, the more likely it will be vulcanized and reversion will occur, the easier the transition of sulfur from the case and breaker to the side wall will be, and the lower the durability. Here, the reversion refers to a phenomenon in which a sulfur bridge once formed is cut and sulfur hangs in a pendant form on one polymer chain, or a molecular chain of the polymer itself is cut.

  The pneumatic tire of the present invention is used as a high performance tire, and particularly preferably used as a high performance tire for competition. The high-performance tire for competition in this specification is a tire that is particularly excellent in high-speed durability and handling stability. For example, in a circuit on a paved road surface that exceeds 1 km in total length, the maximum speed exceeds 200 km / h. It is a high-performance tire for competition, intended for use in Japan.

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

The various chemicals and codes used in the examples and comparative examples are summarized below.
NR: RSS3
BR: BR150B manufactured by Ube Industries, Ltd. (cis content: 97% by mass)
SBR: SBR1502 (E-SBR) manufactured by Nippon Zeon Co., Ltd.
Carbon black: Dia Black H (N330, N ₂ SA: 78 m ² / g) manufactured by Mitsubishi Chemical Corporation
Process oil: Process oil NM manufactured by Taniguchi Oil Refinery Co., Ltd.
Zinc oxide: Zinc Hana No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Stearic acid “Kashiwa” manufactured by NOF Corporation
Cobalt stearate: cost-F (cobalt content: 9.5% by mass) manufactured by Dainippon Ink & Chemicals, Inc.
Anti-aging agent: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd.
Heat aging inhibitor: Antigen RD manufactured by Sumitomo Chemical Co., Ltd.
Condensate: Sumikanol 620 manufactured by Taoka Chemical Industry Co., Ltd.
Modified etherified methylomelamine resin: Sumikanol 507AP manufactured by Taoka Chemical Co., Ltd.
Sulfur: Seimi OT (10% oil-containing insoluble sulfur) manufactured by Nippon Kiboshi Kogyo Co., Ltd.
Vulcanization accelerator 1: Noxeller NS (TBBS) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Vulcanization accelerator 2: Noxeller DZ (DCBS) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Cord 1: Textile cord used for breaker, Material: Aramid fiber (Kevlar ^(R) manufactured by DuPont), Structure: 800 dtex, Twist number: 60 times / 10 cm, Cord diameter: 0.60 mm
Cord 2: Steel cord used for breaker, Material: Steel, Structure: 1 × 3 × 0.16, Number of twists: 30 times / 10cm, Cord diameter: 0.16mm
Cord 3: Textile cord used for the case, Material: Nylon fiber (Nylon 66 manufactured by Asahi Kasei Corporation), Structure: 1400 dtex, Number of twists: 41 times / 10 cm, Cord diameter: 0.61 mm

Examples 1 and 2 and Comparative Examples 1-16
According to the blending contents shown in Tables 1 and 2, materials other than the vulcanizing agent (sulfur) and the vulcanization accelerator were kneaded for 5 minutes at 160 ° C. using a Banbury mixer to obtain a kneaded product. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 3 minutes at 105 ° C. using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press vulcanized with a 2 mm thick mold at 160 ° C. for 35 minutes to obtain a test vulcanized rubber composition.

  Furthermore, it shape | molded in the shape of each tire member using the obtained unvulcanized rubber composition. Here, the rubber composition for a sidewall is formed into a sidewall shape (the thickness of the sidewall rubber at the maximum width portion in the tire axial direction of the tire is 5 mm), and the rubber composition for covering a breaker cord and the rubber for covering a case cord. The composition was press-coated on the above cords 1 to 3 from above and below and formed into a 0.8 mm sheet. Then, according to the combinations shown in Table 2, each tire member is bonded to another tire member, and press vulcanized at 165 ° C. for 35 minutes with a dome type vulcanizer to produce a test pneumatic tire (255 / 40R20). did.

  Using the obtained test vulcanized rubber composition and test pneumatic tire, evaluation was performed by the following method. The evaluation results are shown in Tables 3 and 4.

<Complex elastic modulus (E *)>
Using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd., the complex elastic modulus (E *) of each vulcanized rubber composition for testing under the conditions of 80 ° C., initial strain 10%, dynamic strain 2%, and frequency 10 Hz. ) Was measured. It shows that it is excellent in steering stability, so that E * is large.

<Tensile test>
Using a No. 3 dumbbell-shaped test piece composed of a vulcanized rubber composition for each test, in accordance with JIS K 6251 “Vulcanized rubber and thermoplastic rubber-Determination of tensile properties” in an atmosphere at 80 ° C. The strength at break (TB) (MPa) and the elongation at break (EB) (%) were measured. It shows that it is excellent in elongation at break, so that EB is large, and it is excellent in strength at break, so that TB is large. Moreover, the fracture energy was calculated | required from the following formula | equation using these values. It shows that it is excellent in a fracture | rupture characteristic and durability, so that fracture energy is large.
Fracture energy = (TB x EB) / 2

<Drum durability (high-speed durability drum test)>
Durability was evaluated by running the tire on a test pneumatic tire at a speed of 230 km / h for 60 minutes under a load condition of 6 kN. Those who completed the run for 60 minutes were accepted, and when they broke during the run for 60 minutes, the time was recorded and the test was terminated there.

<Sulfur migration rate>
For the test pneumatic tire immediately after production and the tire after the drum durability test, a rubber sump in the vicinity of the breaker edge (about 1 cm from the breaker edge) indicated by X in FIG. 1 is cut out, and oxidative decomposition / ultraviolet fluorescence method (based on JIS-K2541) ) To determine the amount of sulfur. From this result, the migration rate of sulfur was determined by the following equation, and it was determined that the migration of sulfur was suppressed as the value increased.
Sulfur migration rate = (sulfur content after drum durability test) / (sulfur content immediately after production) × 100

<Steering stability>
Using a test pneumatic tire (255 / 40R20), the tire was mounted on a domestic FR vehicle with a displacement of 5000 cc on a dry asphalt road test course, and the vehicle traveled for 10 laps. At that time, the test driver compared and evaluated the stability of control during steering of the best lap and the final lap. The larger the value, the better the driving stability on the dry road surface.

  From the results of Table 2, the sidewall is composed of a rubber composition for a sidewall containing 3.0 to 7.0 parts by mass of sulfur with respect to 100 parts by mass of a predetermined rubber component. The sulfur content is a high-performance pneumatic tire that satisfies a predetermined relational expression with the sulfur content of the rubber composition for covering a breaker cord and the sulfur content of a rubber composition for covering a case cord. It can be seen that a high-performance pneumatic tire not only excellent in durability but also excellent in driving stability can be obtained.

A Side wall B Breaker C Case

Claims (5)

A high performance pneumatic tire having a sidewall (A), a breaker (B) and a case (C),
Side wall (A)
A rubber composition for sidewalls containing 3.0 to 7.0 parts by mass of sulfur with respect to 100 parts by mass of a rubber component containing 75 to 100% by mass of natural rubber and / or isoprene rubber,
Breaker (B)
It consists of a breaker cord and a rubber composition for covering the breaker cord,
Case (C)
It consists of a case cord and a rubber composition for case cord coating,
Sulfur content (sulfur A) with respect to 100 parts by mass of the rubber component of the rubber composition for sidewall, sulfur content (sulfur B) with respect to 100 parts by mass of the rubber component of the rubber composition for covering a breaker cord, and case cord coating A high-performance pneumatic tire in which the sulfur content (sulfur C) with respect to 100 parts by mass of the rubber component of the rubber composition satisfies the following formulas (1) and (2).
Formula (1): -0.5 <sulfur A-sulfur B <0.5
Formula (2): -0.5 <sulfur A-sulfur C <0.5 The sidewall rubber composition is
The high-performance pneumatic tire according to claim 1, comprising 40 to 70 parts by mass of carbon black (I) with respect to 100 parts by mass of the rubber component. The high-performance pneumatic tire according to claim 2, wherein the carbon black (I) has a nitrogen adsorption specific surface area (N ₂ SA) of 50 to 120 m ² / g. The rubber composition for covering a breaker cord and / or the rubber composition for covering a case cord,
The high-performance pneumatic tire according to any one of claims 1 to 3, comprising 50 to 90 parts by mass of carbon black (II) with respect to 100 parts by mass of each rubber component. The high-performance pneumatic tire according to claim 4, wherein the carbon black (II) has a nitrogen adsorption specific surface area (N ₂ SA) of 40 to 100 m ² / g.

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