JP2011063071A - Run-flat tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a run-flat tire compatibly achieving durability in run-flat traveling and riding comfort in usual internal pressure traveling. <P>SOLUTION: When a region at the tire width direction inside from a straight line L1 passing a belt end 4a is called a region X, a tire cross section height and a rim-shaped half length are H and RB, respectively, and a region held by a straight line L2 away from a tire center axis CL by RB+0.65H and a straight line L3 away from the tire center axis CL by RB+0.45H is called a region Y, in a cross section passing the tire center axis CL, a ratio S1/S2 of area S1 of a reinforcing rubber layer part 51 included in the region X to area S2 of a reinforcing rubber layer part 52 included in the region Y is ≤0.1. As a reinforcing member of a carcass ply, a cord including at least 50 mass% or more of polyketone fiber having tensile strength of ≥10 cN/dtex and tensile elastic modulus of ≥200 cN/dtex and maximum thermal shrinkage stress of 0.1 to 1.8 cN/dtex is used. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a run flat tire (hereinafter, also simply referred to as “tire”), and more particularly, to an improvement in a reinforcing rubber layer and a carcass cord in a side reinforcing type run flat tire.

  Conventionally, a tread rubber disposed on a tread portion and constituting a ground contact surface, and a pair of bead cores disposed on each bead portion, each side portion is rolled back radially outward in the tire radial direction. A radial carcass made of a carcass ply, a belt made of one or more belt plies disposed between the radial carcass and the tread rubber 1, and at least a portion corresponding to the sidewall portion, and the inner side of the radial carcass in the tire width direction 2. Description of the Related Art A run-flat tire including a reinforcing rubber layer having a substantially crescent-shaped cross section disposed in a tire is known (for example, see Patent Document 1).

  In such a run-flat tire, even in a state in which the air pressure in the tire has dropped or has become zero, the so-called run-flat state, the reinforcing rubber layer disposed on the sidewall portion maintains the shape of the tire. By doing so, it is configured to be able to travel with sufficient durability.

Japanese Patent No. 4104825 (Japanese Patent Publication No. 2002-518231, claims, etc.)

  However, since the reinforcement rubber layer of such a run-flat tire needs to have the above functions, a rubber material with high rigidity is used, the layer thickness is increased, or a fiber reinforcement layer is added. In connection with this, the spring constant during normal internal pressure traveling also increases, and as a result, there is a problem that riding comfort deteriorates.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a run-flat tire that solves the above-described problems and achieves both durability performance during run-flat traveling and riding comfort during normal internal-pressure traveling.

  As a result of intensive studies, the inventors of the present invention have optimized the arrangement of the reinforcing rubber layer in the run-flat tire and used a cord having specific physical properties as a reinforcing member for the carcass ply, so that the run-flat durability and normal running can be achieved. The present invention has been completed by finding that it is possible to achieve a high degree of compatibility with the ride quality of the time.

That is, the present invention includes a tread portion, a pair of sidewall portions extending inward in the tire radial direction from both side portions of the tread portion, and a pair of bead portions continuing to the inner peripheral side of the pair of sidewall portions. A radial carcass including one or more carcass plies extending between the pair of bead portions, and one or more belt plies disposed on the tread portion on the radially outer side of the radial carcass. In a run flat tire comprising a belt and a reinforcing rubber layer having a substantially crescent-shaped cross section disposed at the inner side in the tire width direction of the radial carcass at least at a portion corresponding to the sidewall portion,
In the cross section passing through the tire center axis C when the tire is mounted on a predetermined rim and the internal pressure is atmospheric pressure, the inner side in the tire width direction of the straight line L1 passing through the end face of the belt among the straight lines orthogonal to the tire center axis C The region X is called region X, the tire cross-section height is H, the length of half the rim diameter is RB, and the straight line L2 separated from the tire center axis C by RB + 0.65H and the straight line separated by RB + 0.45H. When the region sandwiched between L3 is referred to as region Y, the ratio S1 / S2 of the area S1 of the reinforcing rubber layer included in region X to the area S2 of the reinforcing rubber layer included in region Y is 0.1 or less. And
The reinforcing member of the carcass ply includes at least 50% by mass or more of polyketone fiber having a tensile strength of 10 cN / dtex or more and a tensile modulus of 200 cN / dtex or more, and a maximum heat shrinkage stress as a dip-treated cord is 0.1 It is characterized by using a code of ˜1.8 cN / dtex.

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

  In the tire of the present invention, the reinforcing rubber having the area S2 of the reinforcing rubber layer included in the region Y in a cross section passing through the tire center axis C when the tire is mounted on a predetermined rim and the internal pressure is atmospheric pressure. The ratio S2 / S3 to the area S3 of the entire layer is preferably 0.5 to 0.65.

  Various studies have been made on the technology for achieving both run-flat durability and ride comfort by applying polyketone fibers to the carcass ply of run-flat tires. Until now, sufficient studies have not been made on combining with carcass cords including. The present invention has been completed by finding that the combination of the optimization of the arrangement of the reinforcing rubber layer and the application of a carcass cord having a predetermined physical property including polyketone fibers can provide performance superior to the previously obtained knowledge. It has been done.

  According to the present invention, the above configuration makes it possible to achieve a run-flat tire that achieves a higher level of both durability performance during run-flat travel and ride comfort during normal internal pressure travel than in the past. became.

It is a width direction one side sectional view showing an example of the run flat tire of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a cross-sectional side view of one example of the run-flat tire of the present invention in the width direction. As shown in the drawing, a run flat tire 10 of the present invention includes a tread portion 11, a pair of sidewall portions 12 extending inward in the tire radial direction from both side portions thereof, and a pair of bead portions 13 continuing to the inner peripheral side thereof. And a tread rubber 1 disposed on the tread portion 11 to form a ground contact surface, and extending between the pair of bead portions 13 and around the pair of bead cores 2 disposed on each bead portion 13. The radial carcass 3 made up of one or more carcass plies with their respective side portions rolled back outward in the tire radial direction, and one or more belts disposed on the outer side in the tire radial direction of the radial carcass 3 in the tread portion 11 A substantially crescent-shaped cross section disposed on the inner side in the tire width direction of the radial carcass 3 at a portion corresponding to the belt 4 made of ply and at least the sidewall portion 12 And a reinforcing rubber layer 5.

  In the run flat tire of the present invention, as shown in the drawing, among the straight lines orthogonal to the tire center axis C in the cross section passing through the tire center axis C when the tire is mounted on a predetermined rim and the internal pressure is atmospheric pressure The region inside the tire width direction from the straight line L1 passing through the end surface (hereinafter also referred to as “belt end”) 4a of the belt 4 is referred to as a region X, the tire cross-sectional height is H, and the length of half the rim diameter is RB. When the region sandwiched between the straight line L2 separated from the tire center axis C by RB + 0.65H and the straight line L3 separated by RB + 0.45H is referred to as a region Y, the area of the reinforcing rubber layer 5 included in the region X The ratio S1 / S2 of S1 to the area S2 of the reinforcing rubber layer 5 included in the region Y needs to be 0.1 or less, particularly 0.01 to 0.05. That is, in the reinforcing rubber layer 5, the ratio S1 / S2 of the area S1 of the portion 51 included in the region X to the area S2 of the portion 52 included in the region Y is 0.1 or less. If the value of S2 / S1 exceeds 0.1, the vertical spring increases and it becomes difficult to achieve both riding comfort.

  Here, the predetermined rim is a standard rim (or “Applied Rim” or “Recommended Rim”) in an applicable size described in a predetermined industrial standard. With regard to such industrial standards, standards that are effective in the regions where tires are produced or used are defined, and these standards include, for example, “The Tire and Rim Association Inc. Year Book (including design guides) in the United States. ) ”(TRA standard), in Europe,“ Standard Manual of The European Tire and Rim Technical Organization ”(ETRTO standard), and in Japan,“ JATMA YEAR BOOK ”by the Japan Automobile Tire Association.

  The inventors have come to recall the above-described configuration as a result of the following studies. That is, the present inventors divided the tire into finite elements, and simulated the normal internal pressure state in which the stress of each element was simulated at the time of normal internal pressure running, with a normal internal pressure and a load of 75% of a predetermined load, As a result of comparison with a zero internal pressure state where the internal pressure is zero and a load of 75% of the predetermined load is applied, which simulates run-flat traveling, in the region X, a higher stress is generated in the normal internal pressure state than in the zero internal pressure state. I got the knowledge that. As a result of further investigation based on this finding, the present inventors have found that, in this region X, the contribution to the load support at normal running is too large for the contribution to the load support in the zero internal pressure state. It was thought that by reducing the rigidity of the region X, the spring constant in the normal internal pressure state can be reduced while minimizing the influence on the durability in the zero internal pressure state.

  In the present invention, by further combining the optimization of the arrangement of the reinforcing rubber layer and the application of the specific carcass ply cord described below, the distortion of the maximum bent portion during run-flat travel is reduced, and the carcass ply Due to the rigidity due to the heat shrinkage stress, it becomes easy to maintain the durability. This is a new effect that is different from that of a tire in which a conventional polyketone is only applied to a carcass ply. In both a flat tire and an SUV heavy duty tire, the carcass rigidity of the side portion during run flat running is obtained. It is effective as a technique for fully exhibiting.

  In the present invention, the belt 4 includes the belt reinforcing layer when there is a belt reinforcing layer. For example, in the illustrated example, the belt 4 has two cords whose inclination angles are opposite to each other with respect to the tire equatorial plane. The cross belt layer 40 includes belt plies 41 and 42, and the belt reinforcing layer 43 is disposed on the outer side in the tire radial direction of the cross belt layer 40. In this case, the end surface 4 a of the belt 4 becomes the outer end of the belt reinforcing layer 43.

  In the present invention, the area S2 of the portion 52 included in the region Y of the reinforcing rubber layer 5 in the cross section passing through the tire center axis C when the tire is mounted on a predetermined rim and the internal pressure is atmospheric pressure. The ratio S2 / S3 to the area S3 of the entire reinforcing rubber layer 5 is preferably 0.5 to 0.65, particularly preferably 0.55 to 0.60. As a result, the riding comfort during normal internal pressure can be further improved while reliably maintaining the durability performance during run-flat travel.

  In the present invention, the reinforcing member of the carcass ply 3 is at least 50% by mass, preferably 70% polyketone fiber having a tensile strength as a raw yarn of 10 cN / dtex or more and a tensile elastic modulus of 200 cN / dtex or more. It is necessary to use a cord containing at least 100% by mass, more preferably 100% by mass. In particular, when a plurality of carcass plies are arranged, the condition relating to the reinforcing member is satisfied for all of the plurality of carcass plies. When the content of the polyketone fiber is less than 50% by mass, any performance of strength as a tire, heat resistance, and adhesion to rubber becomes insufficient. Examples of fibers other than polyketone fibers that can be used in the present invention include nylon, ester, rayon, polynosic, lyocell, and vinylon.

  When the polyketone fiber has a tensile strength of less than 10 cN / dtex, the strength as a tire becomes insufficient. Moreover, since the weight of the fiber to be used can be reduced as the tensile strength is higher, a polyketone fiber having a tensile strength of 15 cN / dtex or more is preferably used. Here, the tensile strength of the polyketone fiber is a value obtained by measurement according to JIS-L-1013.

  Further, the higher the tensile modulus of the polyketone fiber, the smaller the dimensional change under the same load and the better the form stability. Therefore, it is necessary to be 200 cN / dtex or more, and preferably 300 cN / dtex. That's it. Here, the tensile elastic modulus of the polyketone fiber is a value obtained by measurement according to JIS-L-1013. Specifically, the load at an elongation of 0.1% and the elongation at 0.2%. It is the value of the initial elastic modulus calculated from the load.

  Furthermore, in the present invention, as the reinforcing member of the carcass ply 3, the maximum heat shrinkage stress as the dipped cord is 0.1 to 1.8 cN / dtex, preferably 0.4 to 1.6 cN / dtex. It is necessary to use a cord that is preferably 0.6 to 1.4 cN / dtex. Thereby, the bending of the tire at the time of run-flat traveling can be suppressed, and as a result, the run-flat durability of the tire can be improved satisfactorily. If the maximum heat shrinkage stress of the carcass ply cord as a dip-treated cord is less than 0.1 cN / dtex, the run-flat running durability may not 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, and there is a concern that the finished tire shape may be deteriorated.

  The carcass ply cord used in the present invention preferably has a heat shrinkage ratio of 1% or more, particularly 2% or more at 150 ° C. for 30 minutes as a dip-treated cord at the time of dry heat treatment. When the heat shrinkage rate during dry heat treatment at 150 ° C. for 30 minutes is less than 1%, the alignment efficiency due to heating during tire manufacture is significantly reduced, 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 is too large, the dimensional stability after vulcanization is deteriorated and the uniformity as a product is deteriorated. More preferably, it is 5% or less.

  The carcass ply includes a carcass ply cord that satisfies the above conditions and a coating rubber that covers the cord. In producing such a carcass ply, first, a predetermined twist is added to a fiber satisfying the above conditions, and then twisted with two or three strands. Then, an adhesive treatment (dip treatment) for bonding with rubber is performed. Thereafter, it is coated with a topping rubber having a predetermined thickness to form a rubber-coated cord. Next, the rubber-coated cord is cut so that the warp yarn has a certain length, and both edge portions other than the cut surface are joined to form a carcass ply of the tire. At the time of tire molding, the carcass ply is cut in the same direction as the warp on a drum molding machine (or similar equipment) and joined to form a cylinder.

（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。本発明においては、繰り返し単位の９５モル％以上が１−オキソトリメチレンであることが好ましく、より好ましくは９９モル％以上であり、１００モル％が最も好ましい。 In the present invention, the polyketone used for the polyketone fiber is represented by the following general formula (I),

(In the formula, A is a portion derived from an unsaturated compound polymerized by an unsaturated bond, and may be the same or different in each repeating unit). In the present invention, 95 mol% or more of the repeating units are preferably 1-oxotrimethylene, more preferably 99 mol% or more, and most preferably 100 mol%.

  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 (I), 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 (II),

(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 cords made of polyketone fibers, the processing temperature during processing and the temperature of the molded product during use are the temperatures that indicate the maximum heat shrinkage stress (the maximum heat shrinkage temperature). ) Is desirable. 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 shrinkage temperature is preferably in the range of 100 to 250 ° C, more preferably in the range of 150 to 240 ° C.

  Examples of a method for obtaining a carcass ply cord satisfying the above-described physical property values using the polyketone fiber include a method of adjusting temperature and tension during dipping. Specifically, for example, a carcass ply cord satisfying the conditions of the present invention can be obtained by processing at a temperature of 100 to 250 ° C. with a tension per cord of about 500 g to 4 kg.

（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／ｃｍ^３）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。カーカスプライコードの撚り係数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。 The carcass ply cord used in the present invention has the following formula (III),

(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. When the twist coefficient α of the carcass ply cord is less than 0.25, the heat shrinkage stress cannot be sufficiently ensured. On the other hand, when it exceeds 1.25, the elastic modulus cannot be sufficiently ensured and the reinforcing ability is reduced.

  The radial carcass 3 of the illustrated tire is composed of two carcass plies. However, in the present invention, the number of carcass plies constituting the radial carcass 3 is not limited to this, and is 1 to 3 or more. Also good. Further, the structure is not particularly limited. The locking structure of the radial carcass 3 in the bead portion is not limited to the structure in which the radial carcass 3 is wound around the bead core as shown in the drawing, and may be a structure in which the end portion of the carcass ply is sandwiched between two layers of bead cores (not shown). )

  In the present invention, the number and configuration of the belts 4 are not limited to the illustrated example, and may be a configuration in which no belt reinforcing layer is provided. The crossing belt layer is usually composed of a rubberized layer of cords, preferably a rubberized layer of steel cords, extending at an inclination with respect to the tire equatorial plane, and the two belt layers are composed of cords constituting each belt layer. The tires are stacked so as to cross each other across the equator plane. The belt reinforcing layer is usually composed of a rubberized layer of cords arranged substantially parallel to the tire circumferential direction.

  In the run flat tire of the present invention, it is only important to satisfy the conditions relating to the carcass ply and the reinforcing rubber layer, and the details and materials of the other tire structures are not particularly limited, and are not limited. It can be manufactured by the method. In the present invention, as the gas filled in the tire, normal or air having a changed oxygen partial pressure, or an inert gas such as nitrogen can be used.

Hereinafter, the present invention will be described in more detail with reference to examples.
<Preparation example of polyketone fiber>
A polyketone polymer with an intrinsic viscosity of 5.3, which is prepared by a conventional method and is completely alternatingly copolymerized with ethylene and carbon monoxide, is added to an aqueous solution containing 65% by mass of zinc chloride / 10% by mass of sodium chloride and stirred at 80 ° C. for 2 hours. It melt | dissolved and the dope with a polymer concentration of 8 mass% 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 spout diameter maintained at 80 ° C., and 5% by mass 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 a sulfuric acid aqueous solution having a concentration of 2 mass% 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 mass (based on 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 (mass% ratio).

  As described in Journal of Applied Polymer Science Vol 94, 446-452 (2004), the obtained undrawn yarn is appropriately changed in draw ratio and drying temperature to obtain a polyketone raw yarn having the physical properties shown in the following table. It was. For example, the obtained undrawn yarn is 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 fifth stage. A 5-stage drawing of 1.08 times (drawing tension 1.8 cN / dtex) at 200 ° C. is taken up by a winder, and the total draw ratio from undrawn yarn to 5-stage drawn yarn is 17.1. When doubled, the fiber yarn had high physical properties of a tensile strength of 15.6 cN / dtex, an elongation of 4.2%, and a tensile elastic modulus of 347 cN / dtex.

<Manufacture of tires>
As the reinforcing member for the carcass ply, a cord satisfying the conditions shown in the following table is used, and the area S2 of the portion 52 included in the region Y of the area 51 of the portion 51 included in the region X of the reinforcing rubber layer 5 is used. And the ratio S2 / S3 of the area S2 of the portion 52 included in the region Y of the reinforcing rubber layer 5 to the area S3 of the entire reinforcing rubber layer 5 was changed as shown in the table below. Each tire was prototyped. The size of each test tire was 245 / 45R19.

  About each obtained test tire, the spring constant was measured about the normal internal pressure state and the zero internal pressure state. The spring constant was measured by applying a load passing through a central axis in a plane perpendicular to the axial direction of the tire and measuring the deflection in the load direction. Here, as described above, the normal internal pressure state refers to a state in which the tire is mounted on a predetermined rim, is filled with the predetermined internal pressure, and a load of 75% of the predetermined load is applied. A state in which the internal pressure is zero (atmospheric pressure) and 75% of the predetermined load is applied. Therefore, the spring constant in the normal internal pressure state is a parameter that simulates the riding comfort during normal internal pressure travel, and the spring constant in the zero internal pressure state can be considered as a parameter that represents durability during run-flat travel. Here, the predetermined load is the maximum load (maximum load capacity) of the single wheel in the application size described in the predetermined industrial standard described above, and the predetermined internal pressure corresponds to the predetermined load. It is air pressure.

  The evaluation results of ride comfort and run-flat durability were both indicated by an index with Conventional Example 1 as 100. As for ride comfort, the lower the value, the better. Moreover, about run flat durability, it shows that durability is so high that a numerical value is high. These results are also shown in the table below.

＊１）一般的なディップ処理を施した加硫前のコードの、２５ｃｍの長さ固定サンプルを５℃／分の昇温スピードで加熱して、１７７℃時にコードに発生する最大応力（単位：ｃＮ／ｄｔｅｘ）である。

* 1) Maximum stress generated in the cord at 177 ° C when a 25 cm long fixed sample of the cord before vulcanization subjected to general dipping treatment is heated at a heating rate of 5 ° C / min. cN / dtex).

  As shown in the above table, it can be seen that the tires of the respective examples achieve both the ride comfort and the run-flat durability despite having the reinforcing rubber layer.

DESCRIPTION OF SYMBOLS 1 Tread rubber 2 Bead core 3 Radial carcass 4 Belt 4a Belt end 5 Reinforcement rubber layer 10 Run-flat tire 11 Tread part 12 Side wall part 13 Bead part 40 Cross belt layers 41 and 42 Belt ply 43 Belt reinforcement layer 51 Included in region X Part 52 Part included in region Y

Claims (2)

A tread portion, a pair of sidewall portions extending inward in the tire radial direction from both side portions of the tread portion, and a pair of bead portions continuous on the inner peripheral side of the pair of sidewall portions, A radial carcass made of one or more carcass plies extending between bead parts, a belt made of one or more belt plies disposed on the outer side in the tire radial direction of the radial carcass in the tread part, and at least the side In a run flat tire provided with a reinforcing rubber layer having a substantially crescent-shaped cross section disposed on the inner side in the tire width direction of the radial carcass at a portion corresponding to the wall portion,
In the cross section passing through the tire center axis C when the tire is mounted on a predetermined rim and the internal pressure is atmospheric pressure, the inner side in the tire width direction of the straight line L1 passing through the end face of the belt among the straight lines orthogonal to the tire center axis C The region X is called region X, the tire cross-section height is H, the length of half the rim diameter is RB, and the straight line L2 separated from the tire center axis C by RB + 0.65H and the straight line separated by RB + 0.45H. When the region sandwiched between L3 is referred to as region Y, the ratio S1 / S2 of the area S1 of the reinforcing rubber layer included in region X to the area S2 of the reinforcing rubber layer included in region Y is 0.1 or less. And
The reinforcing member of the carcass ply includes at least 50% by mass or more of polyketone fiber having a tensile strength of 10 cN / dtex or more and a tensile modulus of 200 cN / dtex or more, and a maximum heat shrinkage stress as a dip-treated cord is 0.1 A run-flat tire characterized by using a cord of ~ 1.8 cN / dtex.   The ratio of the area S2 of the reinforcing rubber layer included in the region Y to the area S3 of the entire reinforcing rubber layer in a cross section passing through the tire central axis C when the tire is mounted on a predetermined rim and the internal pressure is atmospheric pressure. The run-flat tire according to claim 1, wherein S2 / S3 is 0.5 to 0.65.

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