JP2008024190A - Pneumatic run-flat radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a run-flat tire having side reinforcement rubber layers with highly balanced run-flat durability and ride comfort at normal internal pressure. <P>SOLUTION: In this pneumatic run-flat radial tire, the side reinforcement rubber layers are formed in an entire region of both sides along the inner face of a carcass ply 2. The carcass ply 2 has a mono-ply structure, and the number of cord overlapped joint portions of the carcass ply layer is smaller than two. A gap between positions of the cord overlapped joints of inner and outer layer sides of the carcass ply layer is 50 mm or longer in the tire circumferential direction. In the cord overlapped joint part of the carcass ply layer, four or more cords of the carcass ply 2 are not vertically overlapped. The cord of the carcass ply includes 50 mass% of PK fiber. The maximum heat shrinkage stress of the cord is 0.1 to 1.8 cN/dtex, and the heat shrinkage rate of the PK fiber at the time of dry heat treatment at 150°C for 30 minutes is 1 to 5%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a so-called side-reinforced pneumatic run-flat radial tire that is capable of run-flat running when the tire internal pressure is abnormally lowered or punctured, and more specifically, run-flat durability and ride comfort during normal internal pressure. The present invention relates to a pneumatic run-flat radial tire (hereinafter, also referred to as “run-flat tire”) that is highly balanced.

  Many tires that can travel for a certain distance even when the tire internal pressure drops abnormally or are punctured, so-called run-flat tires, have been proposed for summer tires that run on ordinary paved roads. Broadly categorized into two types: core type and side reinforcement type.

  The core type is a run-flat tire in which a support is built in a rim-assembled tire. Such a support body is configured to be able to support a crushed tire from its inner surface side by contacting the inner surface of the tire only when the internal pressure is abnormally lowered or punctured. It is a thing.

  However, such a run-flat tire has a problem that the rim assembling workability is poor and the weight and cost are increased because the support must be incorporated at the time of assembling the rim of the tire. There was also a problem.

The side-reinforced run-flat tire that can eliminate all the problems of the core type is a meridional cross section so that the entire side of the tire has a substantially uniform thickness over the entire area of both sides. Has been proposed as a structure having a crescent-shaped side reinforcing rubber layer (for example, Patent Document 1), and even if the filling pressure of the tire decreases due to puncture or the like, the tire continues to run while supporting the load. Is possible and practical.
Japanese Patent Application Laid-Open No. 2000-309211

  However, in side reinforcement type run-flat tires, the so-called run-flat running in the state where the internal pressure is reduced, the deformation of the side reinforcing rubber layer increases as the deformation of the sidewall portion of the tire increases. The side reinforcing rubber layer generates heat and may reach a high temperature of 200 ° C. or higher in some cases. In such a state, there is a risk that the side reinforcing rubber layer will exceed its failure limit and the tire will fail.

  As a means for delaying the time to failure, there is a means for increasing the volume of the side reinforcing rubber layer, such as increasing the maximum thickness of the side reinforcing rubber layer. Problems such as deterioration in riding comfort, increase in weight, and increase in noise occur.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a side-reinforcement type run-flat tire that eliminates such problems of the prior art and highly balances run-flat durability and riding comfort during normal internal pressure. .

  The present inventor has analyzed in detail the side-reinforced type run-flat tire destroyed by the run-flat running, and found out that the carcass ply cord has a tendency to advance easily in the cord overlap joint portion. It was. Therefore, as a result of further intensive studies focusing on this point, the present inventors have completed the present invention.

That is, the pneumatic run-flat radial tire of the present invention has a bead core provided on a pair of left and right bead parts, and extends from the crown part to both bead parts through both side parts, wound around the bead core and moored to the bead part. In a pneumatic run-flat radial tire comprising a carcass ply made of a radial cord layer, and a belt and a tread arranged on the outer side in the crown portion radial direction of the carcass ply,
Along the inner surface of the carcass ply, over the entire region of both side portions or almost the entire region, the meridional section includes a crescent-shaped side reinforcing rubber layer,
The carcass ply has a monoply structure, and there are no more than two places of the cord lap joint of the carcass ply on the tire circumference,
At the joint position, four or more carcass ply cords do not overlap vertically,
The cord of the carcass ply contains at least 50% by mass of polyketone fiber, the maximum heat shrinkage stress of the cord is in the range of 0.1 to 1.8 cN / dtex, and the polyketone fiber is dried at 150 ° C. for 30 minutes. The heat shrinkage rate during heat treatment is in the range of 1% to 5%.

（ｎは撚り数（回／１０ｃｍ）、Ｄはトータル表示デシテックス数、ρは繊維の比重（ｇ／ｃｍ^３）である）で定義される撚り係数Ｎが下記式（ＩＩ）、
０．６ ≦ Ｎ ≦ ０．９ ・・・ （ＩＩ）
を満たすことが好ましい。 In the present invention, the polyketone fiber preferably has a tensile strength of the raw yarn of 10 cN / dtex or more and an elastic modulus of 200 cN / dtex or more. Moreover, the following formula (I) of the fiber cord forming the carcass ply,

The twist coefficient N defined by (where n is the number of twists (times / 10 cm), D is the total display decitex number, and ρ is the specific gravity (g / cm ³ ) of the fiber) is expressed by the following formula (II):
0.6 ≦ N ≦ 0.9 (II)
It is preferable to satisfy.

  ADVANTAGE OF THE INVENTION According to this invention, the side reinforcement type run flat tire which balanced run flat durability and the riding comfort at the time of normal internal pressure highly can be provided.

  FIG. 1 shows a typical half-section in the width direction of a run flat tire according to a preferred embodiment of the present invention. The run flat tire shown in FIG. 1 is a cord that is substantially radially arranged (specifically, arranged at an angle of 70 to 90 ° with respect to the tire equatorial plane E) between the bead cores 1 embedded in the pair of bead portions. The carcass ply 2 is formed by folding one ply having a bend around the bead core 1 and the bead filler 5 from the inside to the outside.

  Further, in this tire, at least two inclined belt layers (in the illustrated example, two inclined belts) in which cords extending incline with respect to the tire equatorial plane E are arranged in parallel on the outer peripheral side of the crown portion of the carcass ply 2. A tread portion 4 reinforced by a main belt 3 comprising layers 31, 32) is arranged.

  The main belt 3 may constitute an intersecting belt in which at least two inclined belt layers 31 and 32 among the inclined belt layers constituting the main belt 3 are laminated so that the cords intersect with each other across the tire equatorial plane E. preferable.

  Although not shown in the tread portion 4, as in a general tire, a plurality of circumferential grooves extending along the tire circumferential direction and / or a plurality of grooves extending in a direction crossing the circumferential groove are provided. A tread groove such as a transverse groove, a plurality of sipes, and the like are appropriately arranged depending on the application.

  In FIG. 1, a belt protective layer 7 in which a cord is arranged substantially parallel to the tire equatorial plane E is provided between the main belt 3 and the tread portion 4 so as to cover almost the entire width of the main belt 3. Is shown. The belt protective layer 7 is provided to prevent a tire failure due to belt end separation, and can be appropriately disposed as necessary, and may be disposed at least at both ends of the main belt 3. .

  Between the both ends of the tread portion 4 and the bead portion, there is provided a side wall portion for connecting them, and at least on the inner surface side of the carcass ply 2 across the side wall portion, a side having a substantially crescent-shaped cross-sectional shape. A reinforced rubber layer 6 is provided, which is a so-called side reinforcing type run-flat tire structure.

  The carcass ply 2 is composed of a fiber cord and a coating rubber that covers the fiber cord. That is, add a certain twist to the fiber, twist 2 to 3 strands, draw multiples of these as warp yarns, roughly smash thin and weak wefts into a sled, and then adhesive treatment to adhere to rubber I do. Thereafter, a topping rubber having a constant thickness is coated to obtain a rubber-coated cord.

  Next, the warp yarn of the rubber-coated cord is cut so as to have a certain length, and both edge portions other than the cut surface are joined to obtain a carcass material for a radial tire. At the time of tire molding, the carcass material is cut into a cylindrical shape by cutting and joining in the same direction as the warp on a drum molding machine (or similar equipment). The joining in the cutting / molding process includes an overlap joint (FIG. 2) for overlapping the cord and the cord, or a butt joint (FIG. 3) for abutting the cord and the cord. In particular, in the case of a butt joint, the amount of rubber at the ear portion is about ½ of the amount between the cord and the cord (FIG. 3: A / It is important to set 2). A butt joint can be formed by a joint machine having a claw of a mechanism that abuts a topping sheet with a half amount of ear rubber between the cords and pulls the sheet rubber from both sides.

  In the present invention, the number of the cord lap joints of the carcass ply 2 formed as described above is within two, preferably one, and more preferably the cord lap joint. No structure is desirable. If there are three or more cord overlapping joints, the run-flat running durability will be significantly reduced.

  Further, at the cord superposition joint position of the carcass ply 2, the carcass ply cords are prevented from overlapping one another vertically, preferably three or more. If four or more are overlapped, run-flat running durability is also lowered.

  In the present invention, the cord of the carcass ply 2 desirably contains at least 50% by mass of polyketone fibers, preferably 70% by mass or more, and more preferably 100% by mass. If it is less than 50% by mass, the performance of any of the strength, heat resistance, and adhesion to rubber as a tire becomes insufficient.

  The maximum heat shrinkage stress of the carcass ply 2 cord is in the range of 0.1 to 1.8 cN / dtex, preferably 0.4 to 1.6 cN / dtex, more preferably 0.6 to 1.4 cN / dtex. It is desirable to be in When the maximum heat shrinkage stress is less than 0.1 cN / dtex, the run flat running durability cannot be sufficiently improved. On the other hand, when the maximum heat shrinkage stress exceeds 1.8 cN / dtex, the cord is remarkably contracted by heating at the time of tire manufacture, so that there is a concern that the finished tire shape may be deteriorated.

  Further, the polyketone fiber contained in the cord of the carcass ply 2 has a heat shrinkage ratio in the range of 1% to 5%, preferably in the range of 2% to 4% at 150 ° C. for 30 minutes. When the heat shrinkage rate at the time of dry heat treatment at 150 ° C. for 30 minutes is less than 1%, the alignment efficiency by heating at the time of tire production is remarkably lowered, and the strength as a tire becomes insufficient. On the other hand, when the thermal shrinkage rate at the time of dry heat treatment at 150 ° C. for 30 minutes exceeds 5%, the cord is significantly shrunk by heating at the time of manufacturing the tire, so that the finished tire shape may be deteriorated.

  Furthermore, the tensile strength of the polyketone fiber contained in the cord of the carcass ply 2 is preferably 10 cN / dtex or more, more preferably 15 cN / dtex or more. When the tensile strength is less than 10 cN / dtex, the strength as a tire is insufficient.

  Furthermore, as a polyketone fiber contained in the cord of the carcass ply 2, the elastic modulus is preferably 200 cN / dtex or more, more preferably 250 cN / dtex or more. When this elastic modulus is less than 200 cN / dtex, the run-flat running durability cannot be sufficiently improved.

（ｎは撚り数（回／１０ｃｍ）、Ｄはトータル表示デシテックス数、ρは繊維の比重（ｇ／ｃｍ^３）である）で定義される撚り係数Ｎが下記式（ＩＩ）、
０．６ ≦ Ｎ ≦ ０．９ ・・・ （ＩＩ）
を満たすことが好ましく、さらには下記式（ＩＩＩ）、
０．７ ≦ Ｎ ≦ ０．８５ ・・・ （ＩＩＩ）
を満たすことがより好ましい。この撚り係数が０．６未満の場合にはカーカスプライコードに要求される耐疲労性が低下し、結果としてタイヤ耐久性が低下するという問題が生じる。一方、０．９より大きい場合には撚糸の撚り戻りが大きく、作業性が著しく悪化する。 Next, the following formula (I) of the carcass ply 2 cord:

The twist coefficient N defined by (where n is the number of twists (times / 10 cm), D is the total display decitex number, and ρ is the specific gravity (g / cm ³ ) of the fiber) is expressed by the following formula (II):
0.6 ≦ N ≦ 0.9 (II)
Preferably, the following formula (III),
0.7 ≦ N ≦ 0.85 (III)
It is more preferable to satisfy. When the twist coefficient is less than 0.6, the fatigue resistance required for the carcass ply cord is lowered, resulting in a problem that the tire durability is lowered. On the other hand, when it is larger than 0.9, the twist back of the twisted yarn is large, and the workability is remarkably deteriorated.

  Next, fibers containing at least 50% by mass of polyketone fibers (hereinafter abbreviated as “PK fibers”) that can be used in the present invention will be described in detail.

  Examples of fibers other than PK fibers that can be used in the present invention include nylon, ester, rayon, polynosic, lyocell, and vinylon.

The dry heat shrinkage of the PK fiber in the present invention is measured by subjecting the fiber length before and after the heat treatment to 1/30 (cN / dtex) by performing a dry heat treatment at 150 ° C. for 30 minutes in an oven. The value obtained from the following formula.
Dry heat shrinkage (%) = (Lb−La) / Lb × 100
However, Lb is the fiber length before heat treatment, and La is the fiber length after heat treatment. Further, the tensile strength and tensile modulus of the PK fiber are values obtained by measurement according to JIS-L-1013, and the tensile modulus is a load at an elongation of 0.1% and an elongation of 0.2%. It is the value of the initial elastic modulus calculated from the load at.

  Specifically, the carcass ply cord that can be used in the present invention is preferably a PK fiber cord described in detail below. That is, it is a multifilament twisted PK fiber having a total decitex per cord of 1000 to 20000 dtex. If the total decitex per cord is in the range of 1000 to 20000 decitex, it is possible to achieve high rigidity and light weight compared to the steel cord, which is a merit of organic fibers. If the total decitex is less than 1000 decitex, sufficient high rigidity as a carcass ply cannot be obtained. On the other hand, if it exceeds 20000 decitex, the ply gauge becomes thick, resulting in an increase in tire mass and deterioration in tire quality. .

  Further, the maximum heat shrinkage stress of the cord is 177 ° C. obtained by heating a 25 cm long fixed sample of a PK fiber cord before vulcanization subjected to a general dip treatment at a heating rate of 5 ° C./min. It is the maximum stress (unit: cN / dtex) sometimes generated in the cord.

（式中、Ａは不飽和結合によって重合された不飽和化合物由来の部分であり、各繰り返し単位において同一であっても異なっていてもよい）で表される繰り返し単位から実質的になるものが好適であり、その中でも、繰り返し単位の９７モル％以上が１−オキソトリメチレン［−ＣＨ_２−ＣＨ_２−ＣＯ−］であるポリケトンが好ましく、９９モル％以上が１−オキソトリメチレンであるポリケトンが更に好ましく、１００モル％が１−オキソトリメチレンであるポリケトンが最も好ましい。 As a polyketone as a raw material of the PK fiber, the following general formula (IV),

(In the formula, A is a portion derived from an unsaturated compound polymerized by an unsaturated bond, and each repeating unit may be the same or different). Among them, a polyketone in which 97 mol% or more of repeating units is 1-oxotrimethylene [—CH ₂ —CH ₂ —CO—] is preferable, and a polyketone in which 99 mol% or more is 1-oxo trimethylene is preferable. Is more preferable, and a polyketone in which 100 mol% is 1-oxotrimethylene is most preferable.

  In such polyketones, the ketone groups may be partially bonded to each other and the portions derived from the unsaturated compound may be bonded to each other, but the proportion of the portions in which the unsaturated compound-derived portions and the ketone groups are alternately arranged is 90 mass. % Or more, preferably 97% by mass or more, and most preferably 100% by mass.

  In the formula (IV), the unsaturated compound forming A is most preferably ethylene, but propylene, butene, pentene, cyclopentene, hexene, cyclohexene, heptene, octene, nonene, decene, dodecene, styrene, acetylene. , Unsaturated hydrocarbons other than ethylene such as allene, and methyl acrylate, methyl methacrylate, vinyl acetate, acrylamide, hydroxyethyl methacrylate, undecenoic acid, undecenol, 6-chlorohexene, N-vinylpyrrolidone, diethyl ester of sulphonylphosphonic acid Further, it may be a compound containing an unsaturated bond such as sodium styrene sulfonate, sodium allyl sulfonate, vinyl pyrrolidone and vinyl chloride.

（上記式中、ｔおよびＴは、純度９８％以上のヘキサフルオロイソプロパノールおよび該ヘキサフルオロイソプロパノールに溶解したポリケトンの希釈溶液の２５℃での粘度管の流過時間であり、ｃは、上記希釈溶液１００ｍＬ中の溶質の質量（ｇ）である）で定義される極限粘度［η］が、１〜２０ｄＬ／ｇの範囲内にあることが好ましく、３〜８ｄＬ／ｇの範囲内にあることがより一層好ましい。極限粘度が１ｄＬ／ｇ未満では、分子量が小さ過ぎて、高強度のポリケトン繊維コードを得ることが難しくなる上、紡糸時、乾燥時および延伸時に毛羽や糸切れ等の工程上のトラブルが多発することがあり、一方、極限粘度が２０ｄＬ／ｇを超えると、ポリマーの合成に時間およびコストがかかる上、ポリマーを均一に溶解させることが難しくなり、紡糸性および物性に悪影響が出ることがある。 Furthermore, as a polymerization degree of the said polyketone, following formula (V),

(In the above formula, t and T are the flow time of a viscosity tube at 25 ° C. of a diluted solution of hexafluoroisopropanol having a purity of 98% or more and a polyketone dissolved in the hexafluoroisopropanol, and c is the diluted solution. The intrinsic viscosity [η] defined by the mass (g) of solute in 100 mL) is preferably in the range of 1 to 20 dL / g, more preferably in the range of 3 to 8 dL / g. Even more preferred. If the intrinsic viscosity is less than 1 dL / g, the molecular weight is too small to obtain a high-strength polyketone fiber cord, and troubles such as fluff and yarn breakage occur frequently during spinning, drying and stretching. On the other hand, if the intrinsic viscosity exceeds 20 dL / g, it takes time and cost to synthesize the polymer, and it becomes difficult to uniformly dissolve the polymer, which may adversely affect the spinnability and physical properties.

  Furthermore, the PK fiber preferably has a crystal structure with a crystallinity of 50 to 90% and a crystal orientation of 95% or more. If the degree of crystallinity is less than 50%, the structure of the fiber is not sufficiently formed and sufficient strength cannot be obtained, and the shrinkage characteristics and dimensional stability during heating may be unstable. For this reason, the crystallinity is preferably 50 to 90%, more preferably 60 to 85%.

  The polyketone fiberization method includes (1) a method in which unstretched yarn is spun and then subjected to multistage hot stretching and stretched at a specific temperature and magnification in the final stretching step of the multistage hot stretching, (2 ) A method in which after the undrawn yarn is spun, hot drawing is performed, and the fiber after completion of the hot drawing is rapidly cooled with high tension applied. A desired filament suitable for the production of the polyketone fiber cord can be obtained by fiberizing the polyketone by the method (1) or (2).

  Here, the spinning method of the unstretched yarn of the polyketone is not particularly limited, and a conventionally known method can be employed. Specifically, JP-A-2-112413, JP-A-4-228613, Wet spinning method using an organic solvent such as hexafluoroisopropanol and m-cresol as described in JP-A-4-505344, WO99 / 18143, WO00 / 09611, JP2001 -164422, JP-A-2004-218189, JP-A-2004-285221, and the wet spinning method using an aqueous solution of zinc salt, calcium salt, thiocyanate, iron salt, etc. Among these, the wet spinning method using an aqueous solution of the above salt is preferable.

  For example, in a wet spinning method using an organic solvent, a polyketone polymer is dissolved in hexafluoroisopropanol, m-cresol, or the like at a concentration of 0.25 to 20% by mass, extruded from a spinning nozzle to be fiberized, and then toluene, ethanol, isopropanol The unstretched yarn of polyketone can be obtained by removing and washing the solvent in a non-solvent bath such as n-hexane, isooctane, acetone or methyl ethyl ketone.

  On the other hand, in the wet spinning method using an aqueous solution, for example, a polyketone polymer is dissolved in an aqueous solution of zinc salt, calcium salt, thiocyanate, iron salt or the like at a concentration of 2 to 30% by mass, and a spinning nozzle is formed at 50 to 130 ° C. Then, it is extruded into a coagulation bath and subjected to gel spinning, and further desalting and drying can be performed to obtain unstretched polyketone. Here, in the aqueous solution in which the polyketone polymer is dissolved, it is preferable to use a mixture of zinc halide and a halogenated alkali metal salt or a halogenated alkaline earth metal salt. An organic solvent such as an aqueous solution, acetone, or methanol can be used.

  Further, as a drawing method of the obtained undrawn yarn, a hot drawing method in which the undrawn yarn is heated and drawn to a temperature higher than the glass transition temperature of the undrawn yarn is preferable. The method (2) may be carried out in one stage, but it is preferably carried out in multiple stages. There is no restriction | limiting in particular as a method of heat drawing, For example, the method etc. which run a thread | yarn on a heating roll or a heating plate are employable. Here, the heat stretching temperature is preferably in the range of 110 ° C. to (melting point of polyketone), and the total stretching ratio is suitably 10 times or more.

  When polyketone fiberization is carried out by the method of (1) above, the temperature in the final stretching step of the multistage hot stretching is in the range of 110 ° C. to (the stretching temperature of the stretching step one step before the final stretching step). Moreover, the draw ratio in the final drawing step of multistage hot drawing is preferably in the range of 1.01 to 1.5 times. On the other hand, when polyketone fiberization is carried out by the method of (2) above, the tension applied to the fiber after completion of the hot drawing is preferably in the range of 0.5 to 4 cN / dtex, and the cooling rate in rapid cooling is 30 The cooling end temperature in the rapid cooling is preferably 50 ° C. or less. There is no restriction | limiting in particular as a rapid cooling method of the heat-stretched polyketone fiber, A conventionally well-known method can be employ | adopted, Specifically, the cooling method using a roll is preferable. In addition, since the polyketone fiber obtained in this way has a large residual elastic strain, it is usually preferable to perform relaxation heat treatment so that the fiber length is shorter than the fiber length after hot drawing. Here, the temperature of the relaxation heat treatment is preferably in the range of 50 to 100 ° C., and the relaxation ratio is preferably in the range of 0.980 to 0.999 times.

  In order to make the most effective use of the high heat shrinkage characteristics of PK fiber cords, the processing temperature during processing and the temperature of the molded product during use are close to the temperature indicating the maximum heat shrinkage stress (maximum heat shrinkage temperature). It is desirable to be temperature. Specifically, the processing temperature such as the RFL processing temperature and the vulcanization temperature in the adhesive processing performed as necessary is 100 to 250 ° C., and when the tire material generates heat due to repeated use or high speed rotation. Since the temperature can be as high as 100 to 200 ° C, the maximum heat shrink temperature is preferably in the range of 100 to 250 ° C, more preferably in the range of 150 to 240 ° C.

  The coating rubber for covering the carcass ply cord according to the present invention can have various shapes. Typically, it is a film, a sheet or the like. Moreover, a known rubber composition can be appropriately employed as the coating rubber, and it is not particularly limited.

Hereinafter, the present invention will be specifically described based on examples.
(Preparation example of PK fiber)
A polyketone polymer with an intrinsic viscosity of 5.3, which is a completely alternating copolymer of ethylene and carbon monoxide, prepared by a conventional method is added to an aqueous solution containing 65% by weight of zinc chloride / 10% by weight of sodium chloride, and stirred at 80 ° C. for 2 hours. It melt | dissolved and the dope with a polymer concentration of 8 weight% was obtained.

  This dope is heated to 80 ° C., filtered through a 20 μm sintered filter, passed through a 10 mm air gap from a 50-hole nozzle with a diameter of 0.10 mmφ kept at 80 ° C., and 5% by weight of zinc chloride. Was extruded at a rate of discharge of 2.5 cc / min into water at 18 ° C. containing a coagulated yarn while being drawn at a speed of 3.2 m / min.

Subsequently, the coagulated yarn was washed with an aqueous sulfuric acid solution having a concentration of 2% by weight and a temperature of 25 ° C., and further washed with water at 30 ° C., and then the coagulated yarn was wound at a speed of 3.2 m / min.
The solidified yarn was impregnated with IRGANOX 1098 (manufactured by Ciba Specialty Chemicals) and IRGANOX 1076 (manufactured by Ciba Specialty Chemicals) in an amount of 0.05% by weight (with respect to polyketone polymer), and then dried at 240 ° C. A finishing agent was applied to obtain an undrawn yarn.

A finishing agent having the following composition was used.
Oleic acid lauryl ester / bisoxyethyl bisphenol A / polyether (propylene oxide / ethylene oxide = 35/65: molecular weight 20000) / polyethylene oxide 10 mol addition oleyl ether / polyethylene oxide 10 mol addition castor oil ether / sodium stearylsulfonate / dioctyllin Sodium acid = 30/30/10/5/23/1/1 (weight% ratio).

  The obtained undrawn yarn was drawn at 240 ° C. in the first stage, followed by the second stage at 258 ° C., the third stage at 268 ° C., the fourth stage at 272 ° C., and then the second stage at 200 ° C. The film was stretched five times at 1.08 times (stretching tension 1.8 cN / dtex) and wound with a winder. The total draw ratio from the undrawn yarn to the five-stage drawn yarn was 17.1 times. This fiber yarn had high physical properties of strength 15.6 cN / dtex, elongation 4.2%, and elastic modulus 347 cN / dtex.

(Examples 1 to 8, Comparative Examples 1 and 2, Conventional Example)
Tires with a tire size of 225 / 45R17 were prototyped according to the specifications shown in Table 1 and Table 2 below, and actual vehicle evaluation of run-flat durability and ride comfort was performed by the following test methods.

(Run flat durability)
A test tire is mounted on the right front wheel of an FR vehicle with a rim (17 × 7JJ) and an internal pressure of 0 kgf / cm ² , running at a speed of 80 km / h, and compared with the running distance (km) until the tire breaks The tire of the conventional example is indicated by 100 as an index. The higher the number, the better the result. The load applied to the tire during running was 450 kg.
(Ride comfort)
Each prototype tire was mounted on a passenger car, a feeling test of ride comfort was conducted by two specialized drivers, a score of 1 to 10 was assigned, and an average value was obtained.

＊未延伸から５段延伸までの全延伸倍率を９．０倍として得られたＰＫ繊維であり、原糸の強度１１．１ｃＮ／ｄｔｅｘ、伸度１０．５％、弾性率１３８ｃＮ／ｄｔｅｘである。

* PK fiber obtained by setting the total draw ratio from undrawn to 5-stage drawing to 9.0 times, and the strength of the original yarn is 11.1 cN / dtex, the elongation is 10.5%, and the elastic modulus is 138 cN / dtex. .

It is sectional drawing which shows one embodiment of the run flat tire of this invention. FIG. 3 is a cross-sectional view of a joint portion having a cord overlapping joint in a carcass ply. In a carcass ply, it is sectional drawing of the butt | joint joint part without the overlapping joint of a code | cord | chord.

Explanation of symbols

1 Bead core 2 Carcass ply 3 Belt 4 Tread part 5 Bead filler 6 Side reinforcing rubber layer 7 Belt protective layer

Claims (3)

A bead core provided in a pair of left and right bead parts, a carcass ply made of a radial cord layer extending from the crown part to both bead parts via both side parts, wound around the bead core and anchored to the bead part, In a pneumatic run-flat radial tire provided with a belt and a tread arranged on the outer side in the radial direction of the crown portion of the carcass ply,
Along the inner surface of the carcass ply, over the entire region of both side portions or almost the entire region, the meridional section includes a crescent-shaped side reinforcing rubber layer,
The carcass ply has a monoply structure, and there are no more than two places of the cord lap joint of the carcass ply on the tire circumference,
At the joint position, four or more carcass ply cords do not overlap vertically,
The cord of the carcass ply contains at least 50% by mass of polyketone fiber, the maximum heat shrinkage stress of the cord is in the range of 0.1 to 1.8 cN / dtex, and the polyketone fiber is dried at 150 ° C. for 30 minutes. A pneumatic run-flat radial tire having a heat shrinkage rate in the range of 1% to 5% during heat treatment.   The pneumatic run-flat radial tire according to claim 1, wherein in the polyketone fiber, the tensile strength of the raw yarn is 10 cN / dtex or more and the elastic modulus is 200 cN / dtex or more. The following formula (I) of the fiber cord forming the carcass ply,

The twist coefficient N defined by (where n is the number of twists (times / 10 cm), D is the total display decitex number, and ρ is the specific gravity (g / cm ³ ) of the fiber) is expressed by the following formula (II):
0.6 ≦ N ≦ 0.9 (II)
The pneumatic run-flat radial tire according to claim 1 or 2, wherein:

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