JP2017210094A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire excellent in high-speed steering stability and load durability.SOLUTION: The pneumatic tire has a pair of bead parts and a pair of side wall parts and a tread part communicated with both the side wall parts, and has carcass layers of one or more layers extended toroidally between the pair of bead parts. In the carcass layers are arranged a plurality of cords of aromatic system oxadiazole compounds as a carcass cord. Preferably, in the pneumatic tire, side reinforcing rubber layers with a crescent shape cross section are arranged inside a tire width direction of the carcass layers in the side wall parts.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire using an aromatic oxadiazole compound cord as a carcass cord of a carcass layer, and particularly to a pneumatic tire excellent in high-speed steering stability and load durability.

  In a pneumatic tire, a carcass layer that forms a tire skeleton is disposed in a tread portion, a belt layer is disposed outside the carcass and a belt reinforcing layer is disposed outside the belt layer. The carcass layer is mounted on a pair of left and right bead portions. The carcass layer is formed by covering a reinforcing cord (carcass cord) with a coding rubber.

Various reinforcing cords for the carcass layer have been studied according to the characteristics required for the pneumatic tire such as high-speed steering stability and load resistance, and various types of reinforcing cords for the carcass layer have been used. For example, Patent Document 1 describes that a single twisted rayon cord is used for a carcass cord. A single-strand rayon cord is defined as T × (D / 1.52) ^1/2 when a yarn having a fineness of 1000 to 3600 dtex, a twist number of T (times / 10 cm), and a fineness of D (dtex) is used. And the twist angle of the single twisted rayon cord is 18 ° to 33 °.

Japanese Patent Laying-Open No. 2015-54680

It is known that rayon fibers such as a single twisted rayon cord disclosed in Patent Document 1 have high rigidity but low temperature dependency. However, rayon fibers have a problem that dry heat oxidation deterioration occurs due to heat generated during running of the tire, resulting in a decrease in durability and a decrease in high-speed stability.
In particular, when rayon fibers are used for the carcass cord of the run-flat tire, the carcass cord rayon fiber undergoes dry heat oxidation during run-flat running, leading to a reduction in durability and a reduction in high-speed maneuverability.

  An object of the present invention is to provide a pneumatic tire that solves the above-described problems based on the prior art and has excellent high-speed steering stability and load durability.

In order to achieve the above-described object, the present invention has a pair of bead portions and a pair of sidewall portions, and a tread portion connected to both sidewall portions, and extends in a toroidal shape between the pair of bead portions. A pneumatic tire having one or more carcass layers, wherein the carcass layer has a plurality of aromatic oxadiazole compound cords arranged as a carcass cord. Is.
It is preferable that a side reinforcing rubber layer having a crescent-shaped cross section is disposed on the inner side in the tire width direction of the carcass layer in the sidewall portion.

The carcass cord is a dip treatment cord in which an aromatic oxadiazole compound cord is coated with a first liquid and a second liquid. The first liquid contains (a) an epoxy compound and (b) a styrene / butadiene ratio of 5 / 95-45 / 55 (mass ratio) styrene-butadiene copolymer rubber latex and (c) formula (1)
(In the formula, A represents an isocyanate residue of an organic polyisocyanate compound having 3 to 5 functional groups, Y represents an active hydrogen residue of a blocking agent compound that liberates an isocyanate group by heat treatment, and Z represents at least one in the molecule. An active hydrogen residue of a compound having an active hydrogen atom and at least one anion-forming group, X is an active hydrogen of an ethylene oxide adduct of bisphenol A having two hydroxyl groups and an average molecular weight of 5000 or less A heat-reactive water-soluble polyurethane resin represented by a residue, n is an integer of 2 to 4, p + m is an integer of 2 to 4 (m ≧ 0.25), and component (a) an epoxy compound (B) SBR latex and (c) heat-reactive water-soluble polyurethane resin at a solid content mass ratio of (1) 0.1 ≦ (a) / [(b) + (c)] ≦ 2 and (2) (C) (B) has been formulated in a proportion of ≦ 2, the second solution preferably is made of a resorcinol-formalin condensate and a rubber latex.

  The carcass cord of the carcass layer preferably has an upper twist coefficient of 1800-2200.

  According to the pneumatic tire of the present invention, high-speed steering stability and load durability are excellent. Even when the pneumatic tire of the present invention is applied to a run-flat tire, high-speed steering stability and load durability are excellent, and run-flat durability is excellent.

It is sectional drawing which shows the cross-sectional shape of the pneumatic tire of embodiment of this invention. It is a typical sectional view showing the carcass layer of the pneumatic tire of the embodiment of the present invention.

Hereinafter, a pneumatic tire according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
A pneumatic tire (hereinafter, also simply referred to as a tire) 10 shown in FIG. 1 includes a tread portion 12, a shoulder portion 14, a pair of left and right sidewall portions 16, and a pair of left and right bead portions 18 as main components. Have. The tread portion 12 is connected to both sidewall portions 16.
In the following description, as indicated by arrows in FIG. 1, the tire width direction refers to a direction parallel to a tire rotation axis (not shown), and the tire radial direction is orthogonal to the rotation axis. The direction. Further, the tire circumferential direction refers to the direction of rotation with the rotation axis as the axis serving as the center of rotation.
Further, the tire inner side means the lower side of the tire in FIG. 1 in the tire radial direction, that is, the tire inner surface side facing the cavity region R that applies a predetermined internal pressure to the tire, and the tire outer side means the upper side of the tire in FIG. That is, it means the tire outer surface side that is visible to the user, on the side opposite to the tire inner peripheral surface. 1 denotes a tire equator plane, and the tire equator plane CL is a plane that is orthogonal to the rotational axis of the pneumatic tire 10 and passes through the center of the tire width of the pneumatic tire 10.

  The tire 10 includes a carcass layer 20, a belt layer 22, a belt auxiliary reinforcing layer 24 (belt cover layer), a bead core 28, a bead filler 30, a tread rubber layer 32 constituting the tread portion 12, and a sidewall portion. 16 mainly includes a side wall rubber layer 34, a rim cushion rubber layer 36, and an inner liner rubber layer 38 provided on the inner peripheral surface of the tire.

The tread portion 12 is provided with a land portion 12b constituting a tread surface 12a outside the tire and a tread groove 12c formed in the tread surface 12a. The land portion 12b is partitioned by the tread groove 12c. The tread groove 12c has a main groove formed continuously in the tire circumferential direction and a plurality of lug grooves (not shown) extending in the tire width direction. A tread pattern is formed on the tread surface 12a by the tread groove 12c and the land portion 12b.
The maximum width Wm in the tire width direction of the tire 10 is a distance between the maximum width positions 39a that are positions indicating the maximum length of the tire side 39 in the tire width direction. A region within the range of ± 30 (%) of the tire cross-section height SH in the tire radial direction centering on the maximum width position 39a of the tire is referred to as a side tread.

  The bead portion 18 is provided with a pair of left and right bead cores 28 that function to fold the carcass layer 20 and fix the tire 10 to the wheel, and a bead filler 30 so as to contact the bead core 28. Therefore, the bead core 28 and the bead filler 30 are sandwiched between the main body portion 20a and the folded portion 20b of the carcass layer 20.

The carcass layer 20 extends in a toroidal shape between the pair of left and right bead portions 18, and extends from the portion corresponding to the tread portion 12 to the shoulder portion 14 and the sidewall portion 16 in the tire width direction. It extends to the bead portion 18 and forms a skeleton of the tire 10.
The carcass layer 20 has a configuration in which a plurality of organic fiber cords are arranged as a carcass cord (reinforcing cord) and covered with a cord coating rubber. The organic fiber cord is composed of an aromatic oxadiazole compound cord described later.

The carcass layer 20 is folded back from the tire inner side to the tire outer side by a pair of left and right bead cores 28 and forms an end portion in the region of the side wall portion 16. It is configured. That is, the carcass layer 20 is stretched between the pair of left and right bead portions 18 so as to form a toroid.
Further, the carcass layer 20 may be composed of one sheet material or a plurality of sheet materials. In the case of a plurality of sheet materials, the carcass layer 20 has a joint portion (splice portion). The carcass layer 20 will be described in detail later.

As the cord coating rubber of the carcass layer 20, one or more kinds of rubbers selected from natural rubber (NR), styrene-butadiene rubber (SBR), butadiene rubber (BR), and isoprene rubber (IR) are preferably used. . These rubbers were also end-modified with functional groups containing elements such as nitrogen, oxygen, fluorine, chlorine, silicon, phosphorus, or sulfur, such as amine, amide, hydroxyl, ester, ketone, siloxy, or alkylsilyl. Or those end-modified with epoxy can be used.
The carbon black to be blended into these rubbers, for example, an iodine adsorption amount 20~100 (g / kg), preferably 20~50 (g / kg), DBP absorption amount is 50~135 ^(cm 3 / 100g ), preferably 50~100 ^(cm 3 / 100g), and CTAB adsorption specific surface area of 30 to 90 ^(m 2 / g), preferably those which are 30~45 ^(m 2 / g) is used.
Moreover, the quantity of sulfur to be used is 1.5-4.0 mass parts with respect to 100 mass parts of rubber | gum, for example, Preferably it is 2.0-3.0 mass parts.

The belt layer 22 is a reinforcing layer that is attached in the tire circumferential direction to reinforce the carcass layer 20. The belt layer 22 is provided outside the carcass layer 20 in the tire radial direction. The belt layer 22 is provided in a portion corresponding to the tread portion 12, and includes an inner belt layer 22a and an outer belt layer 22b.
The inner belt layer 22a and the outer belt layer 22b include a plurality of reinforcing cords that are inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords intersect each other between the layers. The inner belt layer 22a and the outer belt layer 22b are configured such that a reinforcing cord is, for example, a steel cord and is covered with the above-described cord coating rubber or the like.
The inner belt layer 22a and the outer belt layer 22b are related to the belt layer 22, and the cord angle of the reinforcing cord with respect to the tire circumferential direction is, for example, 24 to 35 °, and preferably 27 to 33 °. Thereby, high-speed durability can be improved.

  The inner belt layer 22a and the outer belt layer 22b of the belt layer 22 are not limited to the steel cord being the reinforcing cord, and the steel belt may be applied to only one of them, or at least one of them. May be a conventionally known reinforcing cord made of an organic fiber cord made of polyester, nylon, aromatic polyamide or the like.

In the tire 10, a belt auxiliary reinforcing layer 24 that reinforces the belt layer 22 is provided in the tire circumferential direction on the outer belt layer 22 b that is the uppermost layer of the belt layer 22, that is, outside the belt layer 22 in the tire radial direction. Has been placed.
The belt auxiliary reinforcing layer 24 is a belt-shaped member in which, for example, one or a plurality of organic fiber cords are aligned as a reinforcing cord and are covered with the above-described cord coating rubber or the like. The belt auxiliary reinforcing layer 24 is a belt auxiliary reinforcing layer in the tire circumferential direction configured by winding a belt-like member in a spiral shape in the tire circumferential direction. The belt auxiliary reinforcing layer 24 is spirally arranged in the tire circumferential direction.

The belt auxiliary reinforcing layer 24 shown in FIG. 1 includes, for example, a so-called full cover 24a configured to cover the belt layer 22 from end to end in the tire width direction including the end portion 22e of the belt layer 22, and the belt layer. It has what is called the edge cover 24b of the structure which selectively covers 22 edge part 22e.
The belt auxiliary reinforcing layer 24 may be only one of the above-described full cover 24a and edge cover 24b.
Examples of the organic fiber cord of the belt auxiliary reinforcing layer 24 include nylon 66 (polyhexamethylene adipamide) fiber, aramid fiber, composite fiber composed of aramid fiber and nylon 66 fiber (aramid / nylon 66 hybrid cord), PEN Fibers, POK (aliphatic polyketone) fibers, heat-resistant PET fibers, rayon fibers, and the like are used.

The tire 10 is called a run flat tire. A side reinforcing rubber layer 40 having a crescent-shaped cross section made of rubber is provided on the inner side in the tire width direction of the carcass layer 20 in the sidewall portion 16. The side reinforcing rubber layer 40 is set to be harder than the other rubber of the sidewall portion 16. Specifically, the side reinforcing rubber layer 40 is made of rubber having a JIS-A hardness of, for example, 70 to 80, and a modulus at 100% elongation of, for example, 9.0 MPa to 10.0 MPa. . By arranging the side reinforcing rubber layer 40 having a crescent-shaped cross section in this way, the load during run-flat travel is supported based on the rigidity of the side reinforcing rubber layer 40.
An additional reinforcing layer 42 is provided between the carcass layer 20, the sidewall rubber layer 13, and the rim cushion rubber layer 36. Note that the additional reinforcing layer 42 is not always necessary, but by providing the additional reinforcing layer 42, durability during run-flat traveling can be further improved.

Next, the carcass layer 20 will be described in detail. FIG. 2 is a schematic cross-sectional view showing a carcass layer of the pneumatic tire according to the embodiment of the present invention.
As shown in FIG. 2, the carcass layer 20 includes a rubber layer 50 and a plurality of carcass cords 52 as reinforcing cords, and the plurality of carcass cords 52 are arranged to be aligned and covered with the rubber layer 50. It is a strip-shaped member. For example, the rubber layer 50 is made of the above-described cord coating rubber.
The carcass cord 52 is composed of an aromatic oxadiazole compound cord. In the carcass layer 20, a plurality of aromatic oxadiazole compound codes are arranged as carcass codes. The structure of the aromatic oxadiazole compound cord is not limited to one (single yarn), but may be a plurality of twisted ones.

The carcass cord 52 composed of an aromatic oxadiazole compound cord preferably has an upper twist coefficient K of 1800-2200. An upper twist coefficient K of 1800 to 2200 is preferable because load durability and high speed steering stability are further improved.
When the upper twist coefficient K exceeds 2200, the effect of further improving durability cannot be obtained. In addition, since the rigidity is lowered, the steering stability is lowered. On the other hand, if the upper twist coefficient K is less than 1800, the fatigue resistance of the aromatic oxadiazole compound cord is deteriorated, so that the durability of the tire is lowered. Also in the case of a run flat tire, the durability of the tire is reduced.
The upper twist coefficient K is represented by K = N × D ^1/2 . Here, N is the number of twists (times / 10 cm), and D is the total fineness (dtex). The unit of the upper twist coefficient K is (times · (dtex) ^1/2 ) / 10 cm.
The carcass cord 52 of the carcass layer 20 preferably has a carcass angle of 80 ° to 88 ° with respect to the tire circumferential direction when high-speed durability is important.

Next, the aromatic oxadiazole compound code will be described. The aromatic oxadiazole compound code includes an aromatic oxadiazole compound yarn.
The aromatic oxadiazole compound code is composed of an oxadiazole aromatic represented by the following general structural formula.

The aromatic oxadiazole compound code preferably has a heat resistant temperature of 400 ° C. A heat-resistant temperature of 400 ° C. is preferable because sufficient heat resistance can be obtained and a decrease in rigidity due to heat generation of the tire during high-speed running is suppressed.
The aromatic oxadiazole compound code has a rigidity ratio E (120 ° C.) / E (25 ° C.) of rigidity E (120 ° C.) at a temperature of 120 ° C. and rigidity E (25 ° C.) at a temperature of 25 ° C. of 0. It is preferable that it is 7-0.9. By setting the rigidity ratio E (120 ° C.) / E (25 ° C.) to 0.7 to 0.9, it is possible to ensure steering stability during high-speed traveling.
The stiffness E (120 ° C.) at a temperature of 120 ° C. and the stiffness E (25 ° C.) at a temperature of 25 ° C. are the same measurement conditions except for the temperature, and the strength (cN / dtex) and elongation of the aromatic oxadiazole compound cord It can be obtained by seeking the relationship. Based on the relationship between the strength (cN / dtex) of the aromatic oxadiazole compound cord and the elongation, the maximum strength at a temperature of 25 ° C. is defined as stiffness E (25 ° C.), and the maximum strength at a temperature of 120 ° C. is defined as stiffness E. (120 ° C.).

The aromatic oxadiazole compound cord preferably has an elongation at break of 10% or more. If the elongation at break is 10% or more, fatigue resistance can be ensured. On the other hand, if the elongation at break is less than 10%, the fatigue resistance may deteriorate.
The aramid fiber has an elongation at break of about 3%.
Regarding the elongation at break, when determining the relationship between strength (cN / dtex) and elongation for an aromatic oxadiazole compound cord at a temperature of 20 ° C., the strength until the aromatic oxadiazole compound cord breaks is obtained. Thus, elongation at break can be obtained.

It is preferable that the initial stiffness ratio represented by the ratio Eo / En of the stiffness Eo of the aromatic oxadiazole compound and the stiffness En of nylon in the region where the elongation is 0 to 2% is 4.5 or more. By setting the initial rigidity ratio to 4.5 or more, high-speed durability can be ensured.
For the initial stiffness ratio, the relationship between strength (cN / dtex) and elongation is obtained under the same measurement conditions for the aromatic oxadiazole compound cord and the nylon cord, respectively. Using the relationship between the strength (cN / dtex) and elongation of the aromatic oxadiazole compound cord and nylon cord, the rigidity Eo of the aromatic oxadiazole compound in the region of 0 to 2% and the nylon The rigidity En is obtained. The rigidity Eo and the rigidity En correspond to the strength (cN / dtex) in the region where the elongation is 0 to 2%. The nylon cord is made of nylon 66.

In the tire 10, by using an aromatic oxadiazole compound cord for the carcass cord 52 of the carcass layer 20, high-speed steering stability and load durability are excellent. In particular, when applied to a run-flat tire such as the tire 10, the run-flat tire is heavier than a general passenger car tire and generates a large amount of heat during running. However, by using an aromatic oxadiazole compound cord for the carcass cord 52, even run-flat tires can have excellent durability, and excellent high-speed steering stability and load durability can be obtained.
The tire 10 has a structure in which one carcass layer 20 is provided. However, the present invention is not limited to this, and the carcass layer 20 may have one or more layers, and may have a plurality of layers, for example, two layers.
The tire 10 can be manufactured by a general manufacturing method including a vulcanization process.

  The carcass cord 52 may be a dip treatment cord in which an aromatic oxadiazole compound cord is coated with a first liquid and a second liquid in order to further improve the adhesion to the rubber layer 50. The aromatic oxadiazole compound code may be a dip treatment code coated with at least the first liquid of the first liquid and the second liquid.

Hereinafter, the first liquid and the second liquid will be described.
The first liquid is represented by (a) an epoxy compound, (b) a styrene-butadiene copolymer rubber latex having a styrene / butadiene ratio of 5/95 to 45/55 (mass ratio), and (c) the following formula (1). The heat-reactive water-soluble polyurethane resin is composed of the component (a) epoxy compound, (b) SBR latex and (c) heat-reactive water-soluble polyurethane resin in a solid content mass ratio of (1) 0.1 ≦ (a) / [(B) + (c)] ≦ 2 and (2) (c) / (b) ≦ 2.

  In the following formula (1), A represents an isocyanate residue of an organic polyisocyanate compound having 3 to 5 functional groups, Y represents an active hydrogen residue of a blocking agent compound that liberates an isocyanate group by heat treatment, and Z represents a molecule. Among them, an active hydrogen residue of a compound having at least one active hydrogen atom and at least one anion-forming group, X represents two hydroxyl groups, and an average molecular weight of 5,000 or less bisphenol A ethylene oxide It is an active hydrogen residue of the adduct, n is an integer of 2 to 4, and p + m is an integer of 2 to 4 (m ≧ 0.25).

The first liquid is composed of (a) an epoxy compound, (b) SBR latex, and (c) a heat-reactive water-soluble polyurethane resin, and these must satisfy the following composition (solid content mass ratio).
(1) 0.1 ≦ (a) / [(b) + (c)] ≦ 2 and (2) (c) / (b) ≦ 2 Particularly preferred blends are such that each solid content is 100 parts by mass of SBR latex. On the other hand, it is 20-70 mass parts of epoxy compounds, and 10-100 mass parts of heat reaction type water-soluble polyurethane resins.
The epoxy compound is a known epoxy compound having one or more glycidyl groups in the molecule, preferably a polyol-based epoxy compound such as glycerol polyglycidyl ether, diglycerol polyglycidyl ether, sorbitol polyglycidyl ether. If the blending amount of the epoxy compound in the first liquid is too small, sufficient adhesiveness with the rubber layer 50 may not be obtained, and conversely if too large, the stability of the first liquid may be reduced. Absent.

The SBR latex used for the first liquid is a copolymer rubber latex having a styrene / butadiene monomer ratio (mass ratio) of 5/95 to 45/55, preferably 10/90 to 30/70. If the styrene content is too small in the styrene / butadiene mass ratio, processability such as gum-up on rolls during dipping may be reduced, and conversely if too large, the adhesive strength may be reduced. The SBR latex can be produced by any conventionally known emulsion polymerization method, and the preferred solid content is 30 to 60% by mass. If the amount of SBR latex blended in the first liquid is too small, sufficient adhesion may not be obtained. On the other hand, if the amount is too large, workability during dipping may be reduced.
In the heat-reactive water-soluble polyurethane resin blended as the third component in the first liquid, X in the above formula (1) is an active hydrogen residue of an ethylene oxide adduct of bisphenol A having two hydroxyl groups.
If the blending amount of the heat-reactive water-soluble polyurethane resin blended in the first liquid is too small, the adhesive strength with the rubber layer 50 may be reduced, and conversely if too large, the carcass cord becomes hard and fatigue resistance. Since there exists a possibility of a fall, it is not preferable.

  The first liquid can be prepared by mixing the above-mentioned components by a general method, and if necessary, a surfactant such as sodium sulfosuccinate is blended in order to improve the permeability to the cord. Can do. The treatment method of the aromatic oxadiazole compound cord with the first liquid can be performed by dipping roll application in the liquid, spray spraying, etc., as in the general fiber treatment method. The amount of the first liquid attached to the aromatic oxadiazole compound code is preferably 3 to 8% by mass. The treated aromatic oxadiazole compound code is, for example, dried at a temperature of 80 to 150 ° C., and further heat-treated at a temperature of 200 to 250 ° C., for example.

  The second liquid is composed of a resorcin / formalin condensate and rubber latex. The second liquid is also referred to as an RFL mixed liquid. The RFL mixed solution is an aqueous mixed solution of resorcin (R) / formalin (F) initial condensate (RF initial condensate) and rubber latex (L), and includes an aromatic oxadiazole compound code and a rubber layer 50. Adhesiveness is improved.

In the RFL liquid mixture, the RF initial condensate is a resole type in which resorcin and formalin are dissolved in water, and an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide is added thereto to react resorcin with formalin. Alternatively, there is a novolak type obtained by reacting resorcin and formalin under an acidic catalyst such as oxalic acid or hydrochloric acid, and any of them may be used. Preferably, a novolac type is used.
The rubber latex (L) to be mixed with the RF initial condensate can be appropriately selected according to the type of rubber constituting the coated rubber layer. Examples of the rubber latex include vinylpyridine / styrene / butadiene terpolymer (VP) latex, styrene-butadiene copolymer (SBR) latex, and natural rubber latex. In particular, VP latex is preferable from the viewpoint of adhesiveness. In addition, SBR latex or natural rubber latex can be appropriately mixed and used for VP latex.
The second liquid treatment method can be the same as the conventional method. The adhesion amount to the aromatic oxadiazole compound code or the like is preferably 2 to 6% by mass. The treated aromatic oxadiazole compound code or the like is dried, for example, at a temperature of 80 to 150 ° C., and further heat-treated at a temperature of 200 to 250 ° C., for example.

  Aromatic oxadiazole compound cords (dip-treated cords) coated with the first liquid and the second liquid are general-purpose unvulcanized rubbers such as natural rubber, SBR rubber, polyisoprene rubber, and polybutadiene rubber. A carcass layer 20 is obtained by integrally vulcanizing with a rubber compounded with a vulcanizing compounding agent, for example, a vulcanizing agent, a vulcanization accelerator, carbon black, an anti-aging agent, a filler and the like according to a conventional method.

  The aromatic oxadiazole compound code is first immersed in a first liquid composed of a specific epoxy compound, a specific styrene-butadiene rubber, and a specific heat-reactive water-soluble polyurethane resin, dried and heat-treated, It is coated with the first liquid. Next, it is immersed in the second liquid, dried and heat-treated, and coated with the second liquid. As a result, a dip treatment code in which the aromatic oxadiazole compound code is coated with the first liquid and the second liquid is obtained. The dip treated cord has excellent adhesion to the rubber layer 50, and the durability of the carcass layer 20 in which the aromatic oxadiazole compound cord is combined is remarkably enhanced. Further, the peel resistance between the dipping cord and the rubber layer 50 in the carcass layer 20 is improved. A tire using a dip treated cord as a carcass cord further improves load durability.

  The present invention is basically configured as described above. As mentioned above, although the pneumatic tire of this invention was demonstrated in detail, this invention is not limited to the above-mentioned embodiment, Of course, in the range which does not deviate from the main point of this invention, various improvement or a change may be carried out. It is.

Examples of the pneumatic tire of the present invention will be specifically described below.
In this example, pneumatic tires (hereinafter simply referred to as tires) of Examples 1 to 5 and Comparative Example 1 having the configurations shown in Table 2 below were manufactured, and load durability and high-speed steering stability were obtained for each tire. Sex was evaluated. The evaluation results of load durability and high-speed steering stability are shown in Table 2 below.
The tire was a run-flat tire having two carcass layers in which a plurality of aromatic oxadiazole compound cords or a plurality of rayon cords are arranged. The configuration of the run-flat tire is as shown in FIG.

  In Examples 1 to 5 and Comparative Example 1, the tire size was 255 / 40RF18. The arrangement of the aromatic oxadiazole compound cords in the carcass layers of Examples 1 to 5 was all the same, and the implantation density was 33/50 mm. In addition, the arrangement of the rayon cord in the carcass layer of Comparative Example 1 was the same as that of the aromatic oxadiazole compound cord, and the driving density was 33/50 mm. The carcass angle of the carcass layer was 90 °.

The organic fiber cord material of the carcass layer is shown in the column of “organic fiber cord material” in Table 2 below.
In the column of “Organic fiber cord structure” in Table 2 below, “/ 2” indicates that two are twisted.
The column of “Carcass structure” in Table 2 below shows the structure of the carcass layer, and the carcass layer has a two-layer structure. For this reason, two layers are indicated in the “carcass structure” column.

In the column of “Dip prescription” shown in Table 2 below, “epoxy” represents that the above-described first liquid was used for coating treatment, and “RFL” was that the above-described second liquid was used for coating treatment. “Epoxy + RFL” represents that the first liquid and the second liquid were used for coating. “Epoxy”, “RFL” and “epoxy + RFL” will be described in detail later.
The carcass layer uses an unvulcanized rubber compound shown in Table 1 below, and integrally vulcanizes the aromatic oxadiazole compound cord or rayon cord and the unvulcanized rubber compound (vulcanization condition: 170 ° C. × 20 minutes).
As shown in Table 2 below, the aromatic oxadiazole compound cord or rayon cord was coated with the first liquid, the second liquid, or the first liquid and the second liquid.

  “Epoxy” is obtained by immersing an aromatic oxadiazole compound cord or rayon cord in a first liquid containing (a) an epoxy compound, (b) rubber latex and (c) urethane resin, followed by drying and heat treatment (drying 100 degreeC * 1 minute, heat processing 240 degreeC * 1 minute) were given, and the 1st liquid was coat | covered.

The first liquid will be described.
(A) epoxy compound: glycerol polyglycidyl ether, (b) rubber latex: SBR latex having a styrene / butadiene ratio of 23/77 (mass ratio), (c) urethane resin: heat-reactive water-soluble polyurethane resin A
The blending was solid parts by mass, (a) 100 epoxy compound, (b) 100 rubber latex, and (c) 100 urethane resin. The blending ratio was set to (a) / [(b) + (c)] = 0.50 and (c) / (b) = 1.00 in terms of solid content mass ratio.

Next, the thermal reaction type water-soluble polyurethane resin A will be described.
Production of heat-reactive water-soluble polyurethane resin A 100 parts of polymethylene polyphenyl polyisocyanate (NCO content 31.5%) and 31.2 parts of 4-mole ethylene oxide 4-mole adduct were reacted at 85 ° C. for 30 minutes. A urethane prepolymer of 18.7% free isocyanate was obtained. Next, 65 parts of dioxane, 50 parts of ε-caprolactam and 0.2 parts of triethylamine were added, and the reaction was carried out at an internal temperature of 75 ° C. for 120 minutes to give a 4-methylene adduct of polymethylene polyphenyl polyisocyanate and bisphenol A. A partially blocked prepolymer of 5.5% free isocyanate relative to the total was obtained. Next, 84 parts of a 30% aqueous taurine soda solution was added at a system temperature of 40 ° C. and reacted at 40 to 45 ° C. for 30 minutes. Thereafter, dilution with water and removal of dioxane were performed so that the solid content was 30%, and a heat-reactive water-soluble polyurethane resin A was obtained.

“RFL” is a treatment using an RFL treatment liquid (composition: resorcin / formalin condensate / Vp latex (vinylpyridine / styrene / butadiene terpolymer latex (mass ratio) = 1/5) having a solid content of 18%. Aromatic oxadiazole compound cord or rayon coat is immersed in the RFL treatment liquid (second liquid), dried and heat-treated (drying 100 ° C. × 1 minute, heat treatment 240 ° C. × 1 minute) to give the second liquid Covered.
“Epoxy + RFL” was performed by successively performing the above-mentioned “epoxy” and “RFL”, and coating the first and second liquids on the aromatic oxadiazole compound code.

Next, high-speed steering stability and load durability will be described.
High-speed steering stability was measured and evaluated as follows.
Each of the tires of Examples 1 to 5 and Comparative Example 1 was assembled on a rim having a rim size of 18 × 8 JJ at an internal pressure of 250 kPa, and each of the test tires was mounted on a passenger car having a displacement of 2500 cc. Ran the test course and evaluated the feeling.
The results were scored by a 5-point method based on the following criteria in relative comparison with Comparative Example 1, and expressed as an average score. The numerical value in the column of “High Speed Steering Stability” shown in Table 2 below is based on 3.0, and the closer to 5.0, the better the high speed steering stability.
Criteria 5: Excellent, 4: Excellent, 3.5: Slightly excellent, 3: Equivalent to standard, 2.5: Slightly inferior (practical lower limit), 2: Inferior, 1: Very inferior

Load durability was measured and evaluated as follows.
The tires of Examples 1 to 5 and Comparative Example 1 were assembled on a rim having a rim size of 18 × 8JJ, and then mounted on the right side of the rear wheel of a rear-wheel drive vehicle with a displacement of 2500 cc in a state where air was removed. In this state, an elliptical course was run counterclockwise at a speed of 90 km / h, and the distance traveled until the test driver felt abnormal vibration due to a tire failure and stopped running was measured. The load durability was evaluated by an index value with Comparative Example 1 as 100.
In addition, the numerical value of the column of "Load durability" shown in following Table 2 means that load durability is excellent and run flat durability is excellent, so that a numerical value is large.

As shown in Table 2 above, Examples 1 to 5 use aromatic oxadiazole compound cords, and good results were obtained in both high-speed steering stability and load durability. Among Examples 1 to 5, Example 2, Example 4 and Example 5 have a dip formulation of “epoxy + RFL”, which improves the adhesion of an aromatic oxadiazole compound cord (dip treatment cord). , Load durability increased. In Example 4, the upper twist coefficient is 2100, which is in a preferable range. In Example 4, a better result was obtained in terms of load durability than Example 2 having an upper twist coefficient of 1700.
Example 5 had an upper twist coefficient of 2500, and Example 5 gave better results in terms of load durability than Example 2 with an upper twist coefficient of 1700, but the rigidity decreased and high-speed steering stability was obtained. It became comparable as the comparative example 1.
In Example 1 and Example 3, the dip formulation is “epoxy”, and in Example 3, the upper twist coefficient is 2100, which is in a preferable range. In Example 3, a better result was obtained in terms of load durability than Example 1 having an upper twist coefficient of 1700.

10 Pneumatic tire (tire)
12 tread portion 14 shoulder portion 16 sidewall portion 18 bead portion 20 carcass layer 22 belt layer 22a inner belt layer 22b outer belt layer 24 belt auxiliary reinforcing layer 28 bead core 30 bead filler 32 tread rubber layer 34 sidewall rubber layer 36 rim cushion rubber Layer 38 Inner liner rubber layer 50 Rubber layer 52 Carcass cord

Claims (4)

A pneumatic tire having a pair of bead portions, a pair of sidewall portions, and a tread portion connected to both sidewall portions, and having one or more carcass layers extending in a toroid shape between the pair of bead portions. Because
The carcass layer is a pneumatic tire characterized in that a plurality of aromatic oxadiazole compound cords are arranged as a carcass cord.   2. The pneumatic tire according to claim 1, wherein a side reinforcing rubber layer having a crescent-shaped cross section is disposed on an inner side in the tire width direction of the carcass layer in the sidewall portion. The carcass cord is a dip treatment cord in which the aromatic oxadiazole compound cord is coated with a first liquid and a second liquid,
The first liquid is (a) an epoxy compound, (b) a styrene-butadiene copolymer rubber latex having a styrene / butadiene ratio of 5/95 to 45/55 (mass ratio), and (c) Formula (1).

(In the formula, A represents an isocyanate residue of an organic polyisocyanate compound having 3 to 5 functional groups, Y represents an active hydrogen residue of a blocking agent compound that liberates an isocyanate group by heat treatment, and Z represents at least one in the molecule. An active hydrogen residue of a compound having an active hydrogen atom and at least one anion-forming group, X is an active hydrogen of an ethylene oxide adduct of bisphenol A having two hydroxyl groups and an average molecular weight of 5000 or less A heat-reactive water-soluble polyurethane resin represented by a residue, n is an integer of 2 to 4, p + m is an integer of 2 to 4 (m ≧ 0.25), and component (a) an epoxy compound , (B) SBR latex and (c) heat-reactive water-soluble polyurethane resin in solid mass ratio,
(1) 0.1 ≦ (a) / [(b) + (c)] ≦ 2 and (2) (c) / (b) ≦ 2
The pneumatic tire according to claim 1 or 2, wherein the second liquid is made of a resorcin / formalin condensate and a rubber latex.   The pneumatic tire according to any one of claims 1 to 3, wherein the carcass cord of the carcass layer has an upper twist coefficient of 1800 to 2200.