JP2007276620A - Run flat tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a run flat tire having good durability which is capable of reducing the weight of the tire. <P>SOLUTION: The run flat tire has a side part reinforcing rubber layer using a rubber composition containing 5-80 pts.wt. pulverized bituminous coal to 100 pts.wt. rubber component. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a run flat tire.

  In recent years, run-flat tires have been developed with the aim of safely traveling a certain distance even when a tire is punctured.

  A run-flat tire has a thick elastic rubber layer with a high modulus of elasticity inside the sidewall of the tire, maintaining the rigidity of the tire during tire puncture and even when subjected to repeated bending deformation. It reduces rubber breakage and enables long distance running. Furthermore, by using this run-flat tire, there is no need to always load a spare tire on the vehicle, the weight of the entire vehicle can be reduced, and the fuel efficiency is excellent. In the run flat running at the time of puncture of the run flat tire, there is room for improvement in terms of the running speed and the running distance in consideration of the durability of the run flat tire.

  In addition, as an effective means to improve the durability of run-flat tires, there is a method of suppressing the deformation of the tire and preventing the destruction due to the deformation by increasing the thickness of the reinforcing rubber layer disposed inside the sidewall. can give. However, when the durability of the run flat running is improved by increasing the thickness of the reinforcing rubber layer, the tire weight increases as the thickness of the reinforcing rubber layer increases. Therefore, there has been a problem that the effect of weight reduction that would have been obtained by using a run-flat tire would be reduced.

  Further, as a method of increasing the elastic modulus of rubber, there is a method of increasing the amount of carbon black, but heat is easily generated and durability is lowered. By using a butadiene rubber containing syndiotactic crystals without increasing the amount of carbon black, a rubber having a high elastic modulus can be obtained and durability can be improved. However, when butadiene rubber containing syndiotactic crystals is further blended, there is a problem that tensile elongation at break is lowered and durability is also lowered.

  In Patent Document 1, by containing a predetermined amount of a predetermined base rubber component and a predetermined bituminous coal pulverized product, the rolling resistance of the tire is reduced and air permeation prevention and durability are improved. Although the rubber composition used suitably is disclosed, it is not considered about applying this rubber composition to a run flat tire.

Japanese Patent Laid-Open No. 5-43755

  An object of the present invention is to provide a run-flat tire that is light in weight and excellent in durability.

  The present invention relates to a run flat tire having a side portion reinforcing rubber layer using a rubber composition containing 5 to 80 parts by weight of a bituminous coal pulverized product with respect to 100 parts by weight of a rubber component.

  According to the present invention, a run-flat tire that has a rubber layer for reinforcing a side portion using a rubber composition containing a predetermined amount of a rubber component and a bituminous coal pulverized product, reduces the weight of the tire, and is excellent in durability. Can be provided.

  The present invention relates to a run flat tire.

  A run-flat tire is a rubber layer with a high elastic modulus and thick side reinforcement that is placed inside the sidewall of the tire, maintaining the rigidity of the tire during tire puncture, and when it is repeatedly bent and deformed. This also reduces rubber damage and enables long distance running.

  The run flat tire of the present invention includes a side portion reinforcing rubber layer using a specific rubber composition.

  Side reinforcement rubber layer refers to the lining strip layer placed inside the sidewall of the run-flat tire, and the presence of the side reinforcement rubber layer in the run-flat tire allows the air pressure to be lost. The vehicle can be supported and excellent run-flat durability can be imparted.

  The rubber composition for reinforcing side portions includes a rubber component and a bituminous coal pulverized product.

  Examples of the rubber component include natural rubber (NR), butadiene rubber (BR), styrene butadiene rubber (SBR), isoprene rubber (IR), chloroprene rubber (CR), butyl rubber (IIR), and halogenated butyl rubber (X-IIR). And the like, which are commonly used in the rubber industry, may be used alone or in combination of two or more. Among these, NR and / or BR are preferable, and NR and BR are more preferable because of excellent low heat build-up.

  When NR is used, the content of NR in the rubber component is preferably 20% by weight or more, and more preferably 30% by weight or more. If the NR content is less than 20% by weight, the processability tends to deteriorate. The NR content is preferably 90% by weight or less, and more preferably 80% by weight or less. When the content of NR exceeds 90% by weight, reversion is caused and low heat build-up tends to deteriorate.

  When BR is used, as BR, butadiene rubber in which syndiotactic-1,2-polybutadiene is dispersed (SPB-containing BR), butadiene rubber having a high cis content, butadiene rubber having a low cis content, the degree of branching of the molecular structure A linear type butadiene rubber with a reduced amount of SPB is preferred. Among them, SPB-containing BR is preferable because of its excellent physical properties such as rigidity, strength and low heat build-up.

  The SPB-containing BR is one in which syndiotactic-1,2-polybutadiene (SPB) is sufficiently finely dispersed in the matrix BR, and the average particle size of SPB in the BR is very small.

  In the SPB-containing BR, the average particle diameter of SPB in BR is preferably 20 nm or more, and more preferably 40 nm or more. When the average particle size of SPB is less than 20 nm, the dispersibility tends to deteriorate. The average particle size of SPB is preferably 300 nm or less. When the average particle diameter of SPB exceeds 300 nm, the strength tends to decrease.

  The content of SPB in the SPB-containing BR is preferably 1.0% by weight or more, and more preferably 2.0% by weight or more. When the SPB content is less than 1.0% by weight, the effect of containing the SPB-containing BR tends to be small. The SPB content is preferably 25% by weight or less, more preferably 20% by weight or less. When the SPB content exceeds 25% by weight, the hardness of the polymer excessively increases and the processability tends to deteriorate.

  Since SPB in the SPB-containing BR is a crystal, it can provide reinforcement in the tire use temperature range from room temperature.

  The content of SPB-containing BR in the rubber component is preferably 10% by weight or more, and more preferably 15% by weight or more. If the content rate of SPB containing BR is less than 10 weight%, the effect by containing SPB containing BR tends to become small. Moreover, 80 weight% or less is preferable and, as for the content rate of SPB containing BR, 70 weight% or less is more preferable. If the content of SPB-containing BR exceeds 80% by weight, processability tends to deteriorate.

  Bituminous coal includes coal in general, and examples thereof include caking coal and non-caking coal.

  The carbon content of the bituminous coal pulverized product is preferably 60% or more, and more preferably 70% or more. When the carbon content of the bituminous coal pulverized product is less than 60%, the moisture content increases, which tends to be unsuitable for use. The carbon content of the bituminous coal pulverized product is preferably 90% or less, more preferably 85% or less. If the carbon content of the bituminous coal pulverized product exceeds 90%, the cost tends to increase.

  The average particle size of the bituminous coal pulverized product is preferably 0.1 μm or more, and more preferably 0.2 μm or more. If the average particle size of the bituminous coal pulverized product is less than 0.1 μm, the cost tends to increase. The average particle size of the bituminous coal pulverized product is preferably 20 μm or less, and more preferably 10 μm or less. When the average particle size of the bituminous coal pulverized product exceeds 20 μm, the strength tends to decrease.

  The specific gravity of the bituminous coal pulverized product is preferably 1.2 or more, and more preferably 1.3 or more. If the specific gravity of the bituminous coal pulverized product is less than 1.2, the carbon component tends to decrease. Further, the specific gravity of the pulverized bituminous coal is preferably 1.6 or less, and more preferably 1.5 or less. If the specific gravity of the bituminous coal pulverized product exceeds 1.6, it tends to be difficult to reduce the weight.

  The content of the bituminous coal pulverized product is 5 parts by weight or more, preferably 10 parts by weight or more with respect to 100 parts by weight of the rubber component. When the bituminous coal pulverized content is less than 5 parts by weight, the effect of addition is reduced. The content of the bituminous coal pulverized product is 80 parts by weight or less, preferably 70 parts by weight or less. When the content of the bituminous coal pulverized product exceeds 80 parts by weight, workability deteriorates.

  In the present invention, by using a rubber composition for reinforcing a side part containing a predetermined amount of a rubber component and a bituminous coal pulverized product in a side part reinforcing layer of a run flat tire, the weight can be reduced and a highly rigid tire can be obtained. Can be obtained. Furthermore, since the usage-amount of a filler can be reduced by containing SPB containing BR in the said rubber component, the effect that it can further reduce in weight can be acquired.

  Further, the side reinforcing rubber composition of the present invention may contain carbon black.

  There is no restriction | limiting in particular as carbon black, For example, HAF, ISAF, SAF, GPF, FEF, FT etc. can be used.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 30 m ² / g or more, and more preferably 35 m ² / g or more. When N ₂ SA is less than 30 m ² / g, the reinforcing property is insufficient and sufficient durability tends not to be obtained. Further, N ₂ SA is preferably 100 m ² / g or less, more preferably 80 m ² / g or less. When N ₂ SA exceeds 100 m ² / g, the low heat build-up tends to deteriorate.

  The DBP oil absorption (DBP) of carbon black is preferably 50 ml / 100 g or more, and more preferably 80 ml / 100 g or more. If the DBP of the carbon black is less than 50 ml / 100 g, there is a tendency that sufficient reinforcing properties cannot be obtained.

  When carbon black is contained, the content of carbon black is preferably 10 parts by weight or more, more preferably 20 parts by weight or more with respect to 100 parts by weight of the rubber component. When the content of carbon black is less than 10 parts by weight, there is a tendency that sufficient rubber strength cannot be obtained. The carbon black content is preferably 100 parts by weight or less, and more preferably 70 parts by weight or less. When the content of carbon black exceeds 100 parts by weight, processability tends to deteriorate.

  Further, the side reinforcing rubber composition of the present invention may contain sulfur.

As the sulfur used in the present invention, it is preferable to use insoluble sulfur because sulfur surface precipitation (blooming) can be suppressed. Here, the insoluble sulfur refers to sulfur obtained by heating and quenching natural sulfur S ₈ to increase the molecular weight so as to be Sx (x = 100,000 to 300,000).

  The average molecular weight of insoluble sulfur is preferably 10,000 or more, and more preferably 100,000 or more. If the average molecular weight of insoluble sulfur is less than 10,000, decomposition at low frequencies tends to occur, and blooming tends to occur. The average molecular weight of insoluble sulfur is preferably 500,000 or less, and more preferably 300,000 or less. When the average molecular weight of insoluble sulfur exceeds 500,000, the dispersibility in rubber tends to deteriorate.

  The sulfur content is preferably 2 parts by weight or more and more preferably 3 parts by weight or more with respect to 100 parts by weight of the rubber component. If the sulfur content is less than 2 parts by weight, sufficient hardness tends not to be obtained. The sulfur content is preferably 10 parts by weight or less, and more preferably 8 parts by weight or less. If the sulfur content exceeds 10 parts by weight, the storage stability of the unvulcanized rubber composition tends to be impaired.

  In addition to the rubber component, bituminous coal pulverized product, carbon black and sulfur, the side portion reinforcing rubber composition used in the run flat tire of the present invention includes compounding agents conventionally used in the rubber industry, such as silica. Reinforcing agents other than carbon black, stearic acid, zinc oxide, various anti-aging agents, various vulcanization accelerators, and the like can be appropriately blended as necessary.

  As shown in FIG. 1, the side portion reinforcing rubber composition is used for the side portion reinforcing rubber layer 8 of the run flat tire 1. The side portion reinforcing rubber layer 8 is disposed on the sidewall portion 2 so that the rigidity of the tire can be improved. Specifically, the side portion reinforcing rubber layer is arranged in contact with the inside of the carcass ply 3 from the bead portion 7 to the shoulder portion, and a crescent-shaped reinforcing rubber layer 8 that gradually decreases in thickness in both end directions. A reinforcing rubber layer disposed from the bead portion to the end of the tread portion between the carcass ply main body portion and the folded portion, a two-layer side reinforcing rubber layer disposed between the plurality of carcass plies or the reinforcing plies, and the like. .

  The thickness of the side portion reinforcing rubber layer is preferably 0.5 mm or more, and more preferably 1 mm or more. When the thickness of the side portion reinforcing rubber layer is less than 0.5 mm, sufficient reinforcing properties tend not to be obtained. Further, the thickness of the side portion reinforcing rubber layer is preferably 40 mm or less, and more preferably 35 mm or less. When the thickness of the side portion reinforcing rubber layer exceeds 40 mm, the tire weight tends to increase.

  The run flat tire of the present invention can be produced by a normal method using the rubber composition for side part reinforcement. That is, if necessary, the rubber composition for side part reinforcement blended with the compounding agent is extruded in accordance with the shape of the side part reinforcing rubber layer of the tire at an unvulcanized stage, together with other members of the tire Then, an unvulcanized tire is molded by molding in a usual manner on a tire molding machine. This unvulcanized tire is heated and pressurized in a vulcanizer to obtain the run flat tire of the present invention.

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

Next, various chemicals used in Examples and Comparative Examples will be described together.
Natural rubber (NR): RSS # 3
Butadiene rubber (BR): VCR412 manufactured by Ube Industries, Ltd. (SPB-containing BR, SPB average particle size: 250 nm, SPB content: 12% by weight)
Carbon black: Diamond Black E (N ₂ SA: 41 m ² / g, DBP: 115 ml / 100 g) manufactured by Mitsubishi Chemical Corporation
Bituminous coal pulverized product: Austin black made of coal filler (carbon content: 77%, volatile content: 17%, average particle size: 5 μm, specific gravity: 1.3)
Stearic acid: Zinc oxide manufactured by Nippon Oil & Fats Co., Ltd .: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd .: Antigen 6C ((N- (1,3-dimethylbutyl) manufactured by Sumitomo Chemical Co., Ltd. ) -N'-phenyl-p-phenylenediamine))
Insoluble sulfur: Mucron OT (average molecular weight: 200000) manufactured by Shikoku Kasei Kogyo Co., Ltd.
Vulcanization accelerator: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-2 and Comparative Examples 1-2
According to the formulation shown in Table 1, chemicals other than sulfur and a vulcanization accelerator were kneaded for 4 minutes at 150 ° C. with a 1.7 L Banbury mixer manufactured by Kobe Steel Co., Ltd. to obtain a kneaded product. It was. Next, sulfur and a vulcanization accelerator are added to the kneaded material obtained and kneaded for 4 minutes under a condition of 80 ° C. using a biaxial open roll to obtain an unvulcanized rubber sheet of a predetermined size. It was. Using the obtained unvulcanized rubber sheet, it is molded into the shape of a side rubber reinforcing layer of a tire having a thickness of 20 mm, bonded to other tire parts, and vulcanized at 150 ° C. for 35 minutes. Thus, a test tire was manufactured (tire size: 215 / 45ZR17).

(Tensile test)
In accordance with JIS K 6251 “Vulcanized rubber and thermoplastic rubber – Determination of tensile properties”, a tensile test was carried out using a No. 3 dumbbell-shaped test piece, and a sheet having a thickness of 2 mm from the side reinforcing rubber layer of the tire. A test piece was cut out and the breaking strength (MPa) was measured. In addition, it shows that it is excellent in rubber | gum strength, so that breaking strength is large.

(Run flat running test)
With a load of 6.86 kN, running on the drum at an air pressure of 0 kPa at a constant speed of 80 km / h, measuring the distance traveled until the tire breaks, and setting the run-flat running performance index of Comparative Example 1 as 100 The mileage is displayed as an index. The larger the run-flat running performance index, the better the run-flat running performance.
(Run-flat running performance index) = (mileage of each formulation)
÷ (mileage of comparative example 1) x 100

(Tire weight)
The weight of the tire was measured using a lightweight machine, and the tire weight index of Comparative Example 1 was set to 100, and the tire weight of each formulation was displayed as an index by the following formula. The smaller the tire weight index, the lighter the tire.
(Tire Weight Index) = (Tire Weight of Each Formulation) / (Tire Weight of Comparative Example 1) × 100

  The measurement results are shown in Table 1.

It is sectional drawing of the run flat tire of this invention which has a side part reinforcement rubber layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Run flat tire 2 Side wall part 3 Carcass ply 4 Belt layer 5 Tread part 6 Bead core 7 Bead part 8 Side part reinforcement rubber layer 9 Bead apex

Claims (1)

For 100 parts by weight of rubber component
A run-flat tire having a side portion reinforcing rubber layer using a rubber composition containing 5 to 80 parts by weight of a bituminous coal pulverized product.

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