JP2008254705A - Run flat tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a run flat tire outstandingly enhancing durability in run flat traveling without impairing ride comfort in normal traveling, and also improving tire uniformity. <P>SOLUTION: The run flat tire is provided with a side reinforcement rubber layer of a crescent-like meridian cross section along an inner surface of a carcass ply. A carcass ply cord includes at least 50 mass% or more of polyketone fiber, and has the maximum thermal contraction stress of 0.1-1.8 cN/dtex as a dip processed cord. Thermal contraction ratio at 150°C×30 min. dry heat processing of polyketone fiber is within a range of 0.3-3%. The hitting number of the polyketone fiber cord at a bead portion of the carcass ply is within a range of 70-120/100 mm, and the carcass ply includes a weft yarn crossing to the cord arranged in an approximately radial direction. Further, the hitting number of the weft yarn is within a range of 3-20/100 mm, and the weft yarn is cut at a plurality of positions in a tire circumferential direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a run-flat tire, and more particularly, to a side-reinforced run-flat tire in which durability during run-flat running is greatly improved without impairing riding comfort during normal running.

  As a so-called run-flat tire, the inner surface of the carcass in the side wall portion of the tire can be safely run over a certain distance without losing the load bearing capacity even when the internal pressure of the tire is reduced due to puncture or the like. In addition, a crescent-shaped side reinforcing rubber layer with a relatively high modulus is arranged to improve the rigidity of the sidewall part so that the load can be borne without excessively increasing the deformation of the sidewall part when the internal pressure decreases. Various types of side-reinforced run-flat tires such as tires and tires whose sidewall portions are reinforced with various reinforcing members have been proposed (see Patent Documents 1 to 4).

  On the other hand, cellulosic fibers such as rayon have been used as a reinforcing material for various rubber articles including tire reinforcing cords because they are highly elastic at room temperature and have high adhesion to rubber. In addition, the cellulosic fibers have a higher Young's modulus at room temperature and higher temperature than polyesters such as polyethylene terephthalate (PET), and a high thermal shrinkage at 177 ° C. of 0.65 to 1.0%. have. Therefore, the cellulosic fiber has been used as a carcass reinforcing cord of the side reinforcing type run-flat tire.

  However, conventional side-reinforced type run-flat tires using cellulosic fiber cords such as rayon as carcass reinforcement cords are not sufficiently high in the elastic modulus of cellulosic fibers, so that the tire is bent during run-flat running. When the tire becomes large due to the run-flat running and the temperature of the tire becomes high, the rigidity of the carcass ply is lowered and the tire is further bent. For this reason, the main cause of tire failure at the end of run-flat driving is due to the cracking of the side-reinforcing rubber layer with a crescent-shaped cross section, and conventional side-reinforced run-flat tires have a long-running running distance. There was a problem of being short.

  On the other hand, if the sidewall is reinforced by increasing the gauge of the side reinforcing rubber layer, etc., in order to extend the durability distance of the tire during run-flat running, the tire weight increases or the tire runs during normal running. There is a problem that the vertical spring rises and the riding comfort during normal running deteriorates.

In order to solve such a problem, the applicant previously used a polyketone fiber cord having specific heat shrinkage stress and elastic modulus as a carcass reinforcement cord of a side reinforcement type run-flat tire in Patent Document 5, It has been reported that tire deflection during run-flat driving can be suppressed without increasing tire weight, and as a result, tire run-flat durability can be greatly improved without deteriorating riding comfort during normal driving. ing.
JP 2000-264012 A Special table 2002-500587 gazette Japanese translation of PCT publication No. 2002-500589 JP 2004-306658 A JP 2006-224952 A

  In the run-flat tire described in Patent Document 5, the run-flat durability of the tire can be greatly improved without deteriorating the riding comfort during normal running. However, since the longitudinal spring of the tire during normal running is large, there is a problem that the uniformity of the tire is worse than that of a general tire.

  Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, greatly improve the durability during run-flat driving without impairing the riding comfort during normal driving, and improve tire uniformity. The object is to provide an improved run-flat tire.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors mainly use polyketone fibers having physical properties such as specific heat shrinkage characteristics and the number of driving as a reinforcing cord for a carcass of a side-reinforced type run-flat tire. By using an organic fiber cord and cutting the wefts intersecting with the carcass reinforcing cord having a specific number of driving at a plurality of locations in the circumferential direction of the tire at specific cutting pitches, without increasing the tire weight, Suppresses tire deflection during flat travel, and as a result, significantly improves tire run-flat durability without deteriorating ride comfort during normal travel, and improves tire circumferential uniformity and uniformity. As a result, it was found that the deterioration of the film can be suppressed, and the present invention has been completed.

That is, the run-flat tire of the present invention is a bead core provided in a pair of left and right bead parts, and extends from the crown part to both bead parts via both side parts, wound around the bead core and moored to the bead part. A carcass ply formed of a cord layer arranged in a substantially radial direction; a belt and a tread disposed radially outward of the crown portion of the carcass ply; In a run flat tire having a crescent-shaped side reinforcing rubber layer,
The carcass ply cord includes at least 50% by mass of polyketone fiber, and has a maximum heat shrinkage stress of 0.1 to 1.8 cN / dtex as a dip-treated cord, and the polyketone fiber is subjected to a dry heat treatment at 150 ° C. for 30 minutes. The thermal shrinkage is in the range of 0.3-3%,
The number of driving of the polyketone fiber cord in the bead portion of the carcass ply is in the range of 70 to 120/100 mm;
The carcass ply includes a weft that intersects with a cord arranged in a substantially radial direction, and the number of driven wefts is within a range of 3 to 20/100 mm,
The weft is cut at a plurality of locations in the tire circumferential direction,
It is characterized by this.

  In the run-flat tire according to the present invention, the cord diameter D1 of the carcass ply cord is preferably in the range of 0.45 to 0.95 mm, and the weft yarn diameter D2 is in the range of 0.1 to 0.3 mm. Further, it is preferable that the weft cutting pitch A is in the range of 5.5 to 60 times D1. The polyketone fiber contained in the fiber cord forming the carcass ply preferably has an original yarn tensile strength of 10 cN / dtex or more and an elastic modulus of 200 cN / dtex or more, and the weft is cut. It is preferable that the elongation is 5 to 20% and the cutting strength is in the range of 200 to 1000 g. Further, the weft is preferably made of cellulosic fiber or vinylon fiber, and the weft is preferably spun yarn.

Here, the maximum heat shrinkage stress of the cord means that a 25 cm long fixed sample of a carcass ply cord before vulcanization subjected to a general dip treatment is heated at a heating rate of 5 ° C./min. It is the maximum stress (unit: cN / dtex) generated in the cord at ° C. In addition, the heat shrinkage rate of the polyketone fiber during the dry heat treatment was measured by measuring the fiber length before and after the heat treatment by applying a load of 1/30 (cN / dtex) in an oven at 150 ° C. for 30 minutes. It is a value obtained by the following formula.
Thermal shrinkage during dry heat treatment (%) = {(Lb−La) / Lb} × 100
However, Lb is the fiber length before heat treatment, and La is the fiber length after heat treatment. The tensile strength and tensile modulus of the polyketone fiber are values obtained by measurement according to JIS-L-1013. The tensile modulus is the load at an elongation of 0.1% and the elongation of 0.2%. It is the value of the initial elastic modulus calculated from the load at.

  According to the present invention, it is possible to provide a run-flat tire that can greatly improve durability during run-flat running without impairing riding comfort during normal running and also has improved tire uniformity.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a partial cross-sectional view of an example of a run flat tire of the present invention. The tire shown in FIG. 1 has a pair of left and right bead portions 1 and a pair of sidewall portions 2 and a tread portion 3 connected to both sidewall portions 2, and extends in a toroidal shape between the pair of bead portions 1. A radial carcass 4 made of one or more carcass plies that reinforce each of these parts 1, 2, and 3, and a pair of crescent-shaped side reinforcing rubber layers 5 disposed inside the radial carcass 4 of the sidewall part 2. Prepare.

  In the illustrated tire, a bead filler 7 is disposed on the outer side in the tire radial direction of the ring-shaped bead core 6 embedded in the bead portion 1, and further, on the outer side in the tire radial direction of the crown portion of the radial carcass 4. In addition to the belt 8 composed of two belt layers, a belt reinforcing layer 9A is arranged so as to cover the entire belt 8 outside the belt 8 in the tire radial direction. A pair of belt reinforcing layers 9B is arranged so as to cover only both end portions of the layer 9A. Here, the belt layer is usually composed of a rubberized layer of a cord extending in an inclined manner with respect to the tire equatorial plane, preferably a rubberized layer of a steel cord, and the two belt layers constitute the belt layer. The belt 8 is formed by laminating the cords so as to cross each other with the equator plane interposed therebetween. The belt reinforcing layers 9A and 9B are usually made of rubberized layers of cords arranged substantially parallel to the tire circumferential direction.

  The radial carcass 4 in the illustrated example is composed of a single carcass ply formed by coating a plurality of reinforcing cords arranged in parallel with a coating rubber, and each of the radial carcass 4 is in the bead portion 1. The present invention comprises a main body portion extending in a toroidal shape between a pair of embedded bead cores 6 and a folded portion wound around each bead core 6 radially outward from the inner side to the outer side in the tire width direction. In the pneumatic tire, the number of plies and the structure of the radial carcass 4 are not limited to this. Furthermore, although the belt 8 in the illustrated example comprises two belt layers, the number of belt layers constituting the belt 8 is not limited to this in the pneumatic tire of the present invention. Furthermore, in the pneumatic tire of the present invention, it is not essential to dispose the belt reinforcing layers 9A and 9B, and a belt reinforcing layer having a different structure can be disposed.

  In the present invention, it is desirable that the carcass ply cord of the radial carcass 4 includes at least 50% by mass, preferably 70% by mass or more, more preferably 100% by mass of polyketone fiber. 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 carcass ply cord of the radial carcass 4 has a maximum heat shrinkage stress of 0.1 to 1.8 cN / dtex, more preferably 0.4 to 1.6 cN / dtex, and still more preferably 0.6 to 1.4 cN. It is desirable to be in the range of / dtex. 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.

  Furthermore, the polyketone fiber contained in the carcass ply cord of the radial carcass 4 has a heat shrinkage ratio in the range of 0.3 to 3%, preferably in the range of 1 to 2% at 150 ° C. for 30 minutes in the dry heat treatment. . When the thermal shrinkage rate at 150 ° C. for 30 minutes during the dry heat treatment is less than 0.3%, 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, if the thermal shrinkage rate during dry heat treatment at 150 ° C. for 30 minutes exceeds 3%, 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 number of carcass ply cords driven in the bead portion of the carcass ply is desirably in the range of 70 to 120/100 mm, and preferably in the range of 85 to 110/100 mm. When the number of driving is less than 70/100 mm, the uniformity in the tire circumferential direction cannot be sufficiently improved. On the other hand, when exceeding 120 pieces / 100 mm, there is a concern that the carcass cord may be damaged in the weft cutting process.

  Furthermore, as shown in FIG. 2, the carcass ply includes a weft 11 intersecting with the carcass ply cord 10 arranged in a substantially radial direction, and the number of driven wefts 11 is within a range of 3 to 20/100 mm. . Further, the weft 11 is cut at a plurality of locations in the tire circumferential direction. If the number of driving is less than 3/100 mm, it will cause a poor quality of the weave fabric, and as a result, the uniformity in the tire circumferential direction cannot be sufficiently improved. On the other hand, when it exceeds 20/100 mm, the weft 11 is difficult to cut, which is not desirable. The means for cutting the weft 11 can be performed by a known method described in Japanese Patent Laid-Open No. 5-208458, but it goes without saying that the weft can be cut by using other methods. It is.

  Furthermore, the cord diameter D1 of the carcass ply cord of the radial carcass 4 is preferably in the range of 0.45 to 0.95 mm. When the cord diameter D1 is less than 0.45 mm, there is a concern that the carcass cord may be damaged in the cutting process. On the other hand, if it exceeds 0.95 mm, it will cause a poor quality of the weave fabric, and as a result, the uniformity in the tire circumferential direction cannot be sufficiently improved.

  Furthermore, the diameter D2 of the weft 11 is preferably in the range of 0.1 to 0.3 mm. When the diameter D2 is less than 0.1 mm, the weft 11 is unexpectedly cut before the step of topping the rubber, and the shape as a weave fabric cannot be maintained. On the other hand, if it exceeds 0.3 mm, it will cause a poor weave fabric property, and as a result, the uniformity in the tire circumferential direction cannot be sufficiently improved.

  Furthermore, as shown in FIG. 2, the cutting pitch A of the weft 11 is preferably in the range of 5.5 to 60 times the cord diameter D1, and more preferably in the range of 8 to 24 times. If the cutting pitch A is less than 5.5 times, the carcass cord may be damaged in the cutting process. On the other hand, when it exceeds 60 times, the uniformity in the tire circumferential direction cannot be sufficiently improved.

  Furthermore, the polyketone fiber contained in the carcass ply cord of the radial carcass 4 preferably has a tensile strength of 10 cN / dtex or more, more preferably 15 cN / dtex or more. When this tensile strength is less than 10 cN / dtex, the strength as a tire is insufficient.

  Furthermore, the polyketone fiber contained in the carcass ply cord of the radial carcass 4 preferably has an elastic modulus of 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.

  Furthermore, the weft 11 preferably has a cutting elongation of 5 to 20% and a cutting strength of 200 to 1000 g. If the cut elongation is less than 5% or the cut strength is less than 200 g, the unexpected weft 11 is cut before the step of topping the rubber, and the shape as a weave fabric cannot be maintained. On the other hand, if the cut elongation is greater than 20% or the cut strength exceeds 1000 g, it becomes difficult to cut the weft 11 in the cutting step, and the uniformity in the tire circumferential direction cannot be sufficiently improved.

  Furthermore, it is desirable that the weft 11 is made of a cellulosic fiber or a vinylon fiber, and more preferably a spun yarn. Such a fiber can be designed to satisfy the above-described cutting elongation and cutting strength.

  Next, a carcass ply cord containing at least 50 mass% or more 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.

（式中、Ｔは撚り数（回／１００ｍｍ）、Ｄはコードの総繊度（ｄｔｅｘ）、ρはコードに使用される繊維素材の密度（ｇ／ｃｍ³）である）で定義される撚り係数αが０．２５〜１．２５の範囲であることが好ましい。ＰＫ繊維コードの撚り係数αが０．２５未満では、熱収縮応力が十分に確保できず、一方、１．２５を超えると、弾性率が十分に確保できず、補強能が小さくなる。 Further, the above code further includes the following formula (I),

(Where T is the number of twists (times / 100 mm), D is the total fineness of the cord (dtex), and ρ is the density of the fiber material used in the cord (g / cm ³ )). α is preferably in the range of 0.25 to 1.25. If the twist coefficient α of the PK fiber cord is less than 0.25, the heat shrinkage stress cannot be sufficiently ensured. On the other hand, if it exceeds 1.25, the elastic modulus cannot be sufficiently ensured and the reinforcing ability is reduced.

（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［−ＣＨ₂−ＣＨ₂−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 (II),

(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 the repeating units is 1-oxotrimethylene [—CH ₂ —CH ₂ —CO—] is preferable, and a polyketone in which 99 mol% or more is 1-oxotrimethylene. 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 (II), 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 (III),

(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.

  The run flat tire of the present invention can be manufactured by a conventional method by applying the above-mentioned carcass ply as the radial carcass 4. In the pneumatic tire of the present invention, as the gas filled in the tire, normal or air with a changed oxygen partial pressure, or an inert gas such as nitrogen can be used.

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 coagulated 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 the polyketone polymer), and then dried at 240 ° C. or higher. A finishing agent was added to obtain an undrawn yarn. The heat shrinkage rate can be adjusted by appropriately controlling the drying temperature.

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. In addition, the heat shrinkage rate during dry heat treatment at 150 ° C. for 30 minutes was 1.9%. The PK fiber thus obtained was used as a cord under the following conditions.

(Examples 1-5, Comparative Examples 1-3, a conventional example)
A cord / rubber composite by arranging fiber cords having the material, structure, elastic modulus, heat shrinkage stress, and the like shown in Table 1 below in parallel with the number of drivings shown in the table, cutting the wefts after coating with coating rubber, etc. The cord / rubber composite was used as a carcass ply, and a side reinforcement type run flat tire having a size 215 / 45ZR17 having the structure shown in FIG. 1 was prototyped. Moreover, the longitudinal spring and run-flat durability of the obtained tire were evaluated by the following methods, and the results shown in Table 1 were obtained.

(1) Longitudinal spring A load-deflection curve of a test tire filled with an internal pressure of 230 kPa is measured, and the inclination of a tangent at a certain load on the obtained load-deflection curve is defined as a longitudinal spring constant with respect to the load. The value of the longitudinal spring constant of the tire was taken as 100 and indicated as an index. A larger index value indicates a larger longitudinal spring constant.

(2) Run-flat durability A drum test was performed in an environment with a load of 4.17kN, a speed of 89km / h, and a temperature of 38 ° C without filling the test tire with internal pressure. The distance measured until the failure of the conventional tire was measured as 100 and indicated as an index. The larger the index value, the longer the distance traveled until failure, and the better the run-flat durability.

(3) Tire uniformity RFV (Radial Force Variation) and LFV (Lateral Force Variation) of the test tire filled with an internal pressure of 230 kPa were measured, and the value of the longitudinal spring constant of the tire of the conventional example was expressed as an index. The smaller the index value, the better the uniformity.

It is sectional drawing of the right half of an example of the pneumatic tire of this invention. FIG. 3 is a cross-sectional view of a portion including a carcass cord and a weft that intersects the carcass ply in the carcass ply.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tread part 4 Radial carcass 5 Side reinforcement rubber layer 6 Bead core 7 Bead filler 8 Belt 9A, 9B Belt reinforcement layer 10 Carcass ply cord 11 Weft A Weft cut pitch

Claims (8)

A pair of left and right bead parts, a carcass ply extending from the crown part to both bead parts through both side parts, and a side reinforcing rubber having a crescent-shaped meridional section over the entire area of the both side parts along the inner surface of the carcass ply In a run flat tire comprising a layer,
The carcass ply cord includes at least 50% by mass of polyketone fiber, and has a maximum heat shrinkage stress of 0.1 to 1.8 cN / dtex as a dip-treated cord, and the polyketone fiber is subjected to a dry heat treatment at 150 ° C. for 30 minutes. The thermal shrinkage is in the range of 0.3-3%,
The number of driving of the polyketone fiber cord in the bead portion of the carcass ply is in the range of 70 to 120/100 mm;
The carcass ply includes a weft that intersects with a cord arranged in a substantially radial direction, and the number of driven wefts is within a range of 3 to 20/100 mm,
The weft is cut at a plurality of locations in the tire circumferential direction,
A run-flat tire characterized by that.   The run-flat tire according to claim 1, wherein a cord diameter D1 of the carcass ply cord is in a range of 0.45 to 0.95 mm.   The run-flat tire according to claim 1 or 2, wherein a diameter D2 of the weft yarn is in a range of 0.1 to 0.3 mm.   The run-flat tire according to any one of claims 1 to 3, wherein the cutting pitch A of the weft is in the range of 5.5 to 60 times D1.   The polyketone fiber contained in the fiber cord forming the carcass ply has a tensile strength of the raw yarn of 10 cN / dtex or more and an elastic modulus of 200 cN / dtex or more. Run flat tires.   The run-flat tire according to any one of claims 1 to 5, wherein the weft has a cutting elongation of 5 to 20% and a cutting strength of 200 to 1000 g.   The run-flat tire according to any one of claims 1 to 6, wherein the weft is made of cellulosic fibers or vinylon fibers.   The run-flat tire according to any one of claims 1 to 7, wherein the weft is a spun yarn.

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