JP2007191154A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire improved in durability in run flat traveling without impairing ride comfort during normal traveling. <P>SOLUTION: In this pneumatic tire including a pair of side reinforcement rubber layers 7 having crescent sections inside a radial carcass 3 extending from a buttress part 5 to the side wall 6, a reinforcement cord layer 8 formed by coating a polyketone fiber cord with coating rubber is disposed at least in part of an area A extending from a belt end to a maximum width part of the tire side and an area B from the vicinity of a bead core to a bead filler. The polyketone fiber cord is formed by braiding a plurality of filament bundles made of polyketone, and satisfies a condition expressed by a formula:σ≥-0.01×E + 1.2 ; σ≥0.02 [wherein σ is heat contraction stress (dN/dtex) at 177°C, and E is an elastic modulus (cN/dtex) in the case of a 49N load at 25°C]. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  Conventionally, tires that can safely travel a certain distance without losing their load bearing capacity even when the internal pressure of the tire is reduced due to puncture, etc. The side reinforcing rubber layer is placed on the inner surface of the carcass with a relatively high modular crescent shape to improve the rigidity of the side wall. Various types of side-reinforced run-flat tires that can bear a load without significantly increasing the load have been proposed. (See Patent Documents 1 to 4).

  However, the conventional side-reinforced run-flat tire has a large deflection of the tire during run-flat running, and the sidewall portion becomes hot during run-flat running, and the rigidity of the sidewall portion is increased due to softening of rubber. Since the lowering and the bending become larger, the main cause of the failure at the end of the run-flat traveling is due to the crack of the side reinforcing rubber layer having a crescent cross section. Therefore, the conventional side reinforcement type run-flat tire has a problem that the durability distance in the run-flat running is 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 is deteriorated.

JP 2000-264012 A Special table 2002-500587 gazette Japanese translation of PCT publication No. 2002-500589 JP 2004-306658 A

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a pneumatic tire that solves the above-described problems of the prior art and has improved durability during run-flat running without impairing riding comfort during normal running.

  As a result of intensive studies to achieve the above object, the present inventors have found that a region A from the belt end of the side-reinforced type run-flat tire to the maximum width portion of the tire side portion and a region B from the vicinity of the bead core to the bead filler. By placing a reinforcing cord layer made of rubberized polyketone fiber cord having a specific heat shrinkage stress and elastic modulus on at least a part of the tire, it is possible to run flat without deteriorating the riding comfort of the tire during normal running. It has been found that the run-flat durability of the tire can be greatly improved by suppressing the deflection of the tire during traveling, and the present invention has been completed.

That is, the pneumatic tire according to the present invention includes a radial carcass composed of one or more carcass plies extending in a toroid shape between bead cores embedded in a pair of bead parts, and a tire radius of a crown part of the radial carcass. A tread portion disposed on the outer side in the direction, a pair of buttress portions located at both ends of the tread portion, a pair of sidewall portions connecting the buttress portion and the bead portion, and the buttress portion In a pneumatic tire provided with a pair of crescent-shaped side reinforcing rubber layers disposed inside the radial carcass over the sidewall portion,
A plurality of filament bundles made of polyketone are twisted in at least a part of the region A from the belt end to the maximum width portion of the tire side portion and the region B from the vicinity of the bead core to the bead filler. (II):
σ ≧ −0.01 × E + 1.2 (I)
σ ≧ 0.02 (II)
[Wherein σ is heat shrinkage stress (cN / dtex) at 177 ° C .; E is elastic modulus at 49 N load (cN / dtex) at 25 ° C.] The reinforcing cord layer formed by covering with rubber is provided.

  Here, the heat shrinkage stress σ at 177 ° C. of the polyketone fiber cord is obtained by heating a 25 cm long fixed sample of the polyketone fiber cord before vulcanization subjected to a general dip treatment at a heating rate of 5 ° C./min. The stress generated in the cord at 177 ° C, and the elastic modulus E at 49N load at 25 ° C of the polyketone fiber cord is a unit calculated from the tangent at 49N of the SS curve according to the JIS cord tensile test. Elastic modulus at cN / dtex.

  In the pneumatic tire of the present invention, it is preferable that the reinforcing cord layer is disposed in a region A from the belt end to the maximum width portion of the tire side portion.

  In a preferred example of the pneumatic tire of the present invention, an angle of the polyketone fiber cord in the reinforcing cord layer with respect to a tire radial direction is 0 to 85 °.

In the pneumatic tire of the present invention, the polyketone fiber cord has the following formula (III):
Nt = tan θ = 0.001 × N × (0.125 × D / ρ) ^1/2 (III)
Where N is the number of twists (times / 10 cm), ρ is the specific gravity of the cord (g / cm ³ ), and D is the total decitex number (dtex) of the cord. Is preferably 0.25 or more. Here, the number N of twists is the number of twists when a plurality of the filament bundles are twisted together.

  In a preferred example of the pneumatic tire of the present invention, the number of driving of the polyketone fiber cord in the reinforcing cord layer is 5 to 60 (lines / 50 mm).

  In the pneumatic tire of the present invention, the polyketone fiber cord is preferably formed by twisting two or three filament bundles made of polyketone having a fineness of 500 to 2000 dtex.

  In another preferred embodiment of the pneumatic tire of the present invention, the polyketone fiber cord shrinks at a high temperature and has a reversibility that expands when returned to room temperature.

［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。ここで、前記式（ＩＶ）中のＡがエチレン基であることが特に好ましい。 In another preferred embodiment of the pneumatic tire of the present invention, the polyketone is represented by the following general formula (IV):

[Wherein 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]. Here, it is particularly preferable that A in the formula (IV) is an ethylene group.

  According to the present invention, the polyketone fiber cord having specific heat shrinkage stress and elastic modulus is coated on at least a part of the region A from the belt end to the maximum width portion of the tire side portion and the region B from the vicinity of the bead core to the bead filler. It is possible to provide a pneumatic tire that is provided with a reinforcing cord layer that is covered with rubber and that has greatly improved durability during run-flat running without impairing riding comfort during normal running.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a partial cross-sectional view of one embodiment of the pneumatic tire of the present invention, and FIGS. 2, 3, 4 and 5 are partial cross-sectional views of other embodiments of the pneumatic tire of the present invention. is there.

  The illustrated tire includes a main body portion extending in a toroid shape between bead cores 2 embedded in a pair of bead portions 1 and a folded portion wound around the bead core 2 radially outward from the inside in the tire width direction to the outside. A radial carcass 3, a tread portion 4 disposed on the outer side in the tire radial direction of the crown portion of the radial carcass 3, a pair of buttress portions 5 located at both ends of the tread portion 4, and the buttress portion 5, A pair of sidewall portions 6 that connect the bead portion 1 and a pair of crescent-shaped side reinforcing rubber layers 7 that are disposed inside the radial carcass 3 extending from the buttress portion 5 to the sidewall portion 6. And at least part of the region A from the belt end to the maximum width portion of the tire side portion and the region B from the vicinity of the bead core to the bead filler And a pair of reinforcing cord layer 8 disposed outside of the radial carcass 3.

  In the illustrated tire, a bead filler 9 is disposed between the radial carcass 3 main body portion and the folded portion and outside the bead core 2 in the tire radial direction, and the radial carcass 3 has a crown portion. A belt 10 composed of two belt layers is disposed on the outer side in the tire radial direction, and a belt reinforcing layer 11A is further disposed on the outer side in the tire radial direction of the belt 10 so as to cover the entire belt 10. A pair of belt reinforcing layers 11B is disposed so as to cover only both ends of the reinforcing layer 11A. 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 10 is configured by laminating cords so as to cross each other with the tire equator plane interposed therebetween. The belt reinforcing layers 11A and 11B are usually made of rubberized layers of cords arranged substantially parallel to the tire circumferential direction.

  Note that the radial carcass 3 of the illustrated tire is composed of one carcass ply. However, in the pneumatic tire of the present invention, the number of carcass plies constituting the radial carcass 3 is not limited to this. It may be more than one, and the structure is not particularly limited. Moreover, although the belt 10 of the example of illustration consists of two belt layers, in the pneumatic tire of this invention, the number of the belt layers which comprise the belt 10 is not restricted to this. Furthermore, the belt reinforcement layers 11A and 11B in the illustrated example are composed of a single belt reinforcement layer 11A that covers the entire belt 10 and two belt reinforcement layers 11B that cover only both ends of the belt reinforcement layer 11A. However, in the pneumatic tire of the present invention, the belt reinforcing layers 11A and 11B are not necessarily provided, and a belt reinforcing layer having a different structure and the number of layers may be provided.

  Furthermore, the tire of the illustrated example includes a rim guard 12 having a substantially triangular cross section on the outer side in the tire width direction of the folded portion of the radial carcass 3 in the region extending from the sidewall portion 6 to the bead portion 1. In the tire, the rim guard 12 is not essential, and rim guards of other shapes can be provided. In the present invention, the maximum width portion of the tire side portion refers to the maximum width portion of the tire side portion when the rim guard 12 is not provided.

  Here, in the tire shown in FIG. 1, a single reinforcing cord layer 8 is disposed outside the radial carcass 3 in a region extending from the buttress portion 5 to the sidewall portion 6. As long as at least one reinforcing cord layer 8 is disposed in at least a part of the region A from the end portion of the belt 10 to the maximum width portion of the tire side portion and the region B from the vicinity of the bead core to the bead filler. The reinforcing cord layer 8 may be provided with two or more layers, or the reinforcing cord layer 8 may extend to a portion other than the region A and the region B.

  For example, in the pneumatic tire of the present invention, as shown in FIG. 2, the reinforcing cord layer 8 is disposed outside the radial carcass 3 in the region from the end portion of the belt 10 to the end portion of the folded portion of the carcass. As shown in FIG. 3, the reinforcing cord layer 8 extends from the end of the belt 10 along the outer side of the radial carcass 3 to the bead portion 1 through the space between the main body portion of the radial carcass 3 and the bead filler 9. 4, the reinforcing cord layer 8 extends from the end of the belt 10 along the outer side of the radial carcass 3. As shown in FIG. 4, the reinforcing cord layer 8 is folded and locked around the bead core 2 embedded in the bead portion 1. 5, a mode extending between the main body portion of the radial carcass 3 and the bead filler 9 and the vicinity of the bead core 2 embedded in the bead portion 1, as shown in FIG. 5, the reinforcing cord layer 8 is attached to the end of the belt 10. And outer radial carcass 3 in the region up to the end of the folded portion of the carcass from, also respectively arranged manner and between the main body and a bead filler 9 of the radial carcass 3 preferred.

In the pneumatic tire of the present invention, the reinforcing cord layer 8 disposed in at least a part of the region A and the region B is formed by twisting a plurality of filament bundles made of polyketone, and the following formulas (I) and ( II):
σ ≧ −0.01 × E + 1.2 (I)
σ ≧ 0.02 (II)
[Wherein σ is heat shrinkage stress (cN / dtex) at 177 ° C .; E is elastic modulus at 49 N load (cN / dtex) at 25 ° C.] It needs to be covered with rubber.

  Since the above polyketone fiber cord has a large thermal shrinkage stress at high temperatures, it exhibits high rigidity from the initial relatively small tire distortion during run-flat running where the tire is hot, and the diameter of the sidewall portion of the tire. The bending rigidity of the direction can be increased to suppress the bending of the tire, and as a result, the run flat durability of the tire can be improved. On the other hand, the polyketone fiber cord is low in rigidity when the tire strain in the cord extension direction during normal running is small, so the vertical spring of the tire during normal running is not raised, and the riding comfort of the tire is deteriorated. I will not let you.

  If the cord to be used does not satisfy the relationship of the above formula (I), the use of a cord having a large heat shrinkage stress σ but a low elastic modulus E sufficiently suppresses the deflection of the tire during run-flat running. If a cord with a high elastic modulus E but a small heat shrinkage stress σ is used, the vertical spring of the tire during normal running increases, and the tire during normal running The ride comfort is worse. Further, when the heat shrinkage stress σ at 177 ° C. of the cord to be used is less than 0.02 cN / dtex, the amount of deflection at the time of run-flat running becomes large and the run-flat durability distance becomes insufficient.

  Here, the polyketone fiber cord preferably has a heat shrinkage stress σ at 177 ° C. of 1.5 cN / dtex or less. When the heat shrinkage stress σ of polyketone fiber cords at 177 ° C exceeds 1.5 cN / dtex, the shrinkage force during vulcanization becomes too large, resulting in the damage of the cord inside the tire and the rubber placement, resulting in durability. It will cause deterioration of sex and uniformity. The polyketone fiber cord preferably has a heat shrinkage stress σ at 177 ° C. of 0.20 cN / dtex or more from the viewpoint of sufficiently suppressing deformation of the tire during run flat running. From the viewpoint of surely suppressing the deformation, the heat shrinkage stress σ at 177 ° C. is more preferably 0.30 cN / dtex or more, and further preferably more than 0.4 cN / dtex. In addition, the effect which suppresses the deformation | transformation of the tire at the time of run-flat driving | running | working is so high that heat contraction stress (sigma) is high. Further, the polyketone fiber cord preferably has an elastic modulus E at a load of 49 N at 25 ° C. of 30 cN / dtex or more from the viewpoint of sufficiently suppressing deformation of the tire during run flat running. From the viewpoint of reliably suppressing the deformation of the tire, the elastic modulus E at a load of 49 N is more preferably 80 cN / dtex or more. Furthermore, the polyketone fiber cord preferably has an elastic modulus E at a load of 49 N at 25 ° C. of 170 cN / dtex or less from the viewpoint of sufficiently ensuring fatigue resistance, and from the viewpoint of improving fatigue resistance. More preferably, the elastic modulus E at a load of 49 N is 150 cN / dtex or less.

  The angle of the polyketone fiber cord in the reinforcing cord layer 8 with respect to the tire radial direction is preferably in the range of 0 to 85 °. If the angle of the polyketone fiber cord with respect to the tire radial direction exceeds 85 °, it is not possible to sufficiently suppress the deflection of the tire during run-flat running, and the tire run-flat durability tends not to be sufficiently improved. There is.

The polyketone fiber cord used for the reinforcing cord layer 8 has the following formula (III):
Nt = tan θ = 0.001 × N × (0.125 × D / ρ) ^1/2 (III)
Where N is the number of twists (times / 10 cm), ρ is the specific gravity of the cord (g / cm ³ ), and D is the total decitex number (dtex) of the cord. Is preferably 0.25 or more. When the twist coefficient (Nt) of the polyketone fiber cord is less than 0.25, the fatigue property is lowered and the durability is insufficient.

  In the reinforcing cord layer 8 of the pneumatic tire of the present invention, the number of driven polyketone fiber cords is preferably in the range of 5 to 60 (lines / 50 mm). When the number of driven polyketone fiber cords in the reinforcing cord layer 8 is less than 5 (lines / 50 mm), the deflection of the tire during run-flat running cannot be sufficiently suppressed, and the run-flat durability of the tire is sufficiently improved. On the other hand, if it exceeds 60 (lines / 50 mm), the vertical spring of the tire during normal running tends to rise, and the riding comfort of the tire during normal running tends to deteriorate.

  The polyketone fiber cord used for the reinforcing cord layer 8 is preferably formed by twisting two or three filament bundles made of polyketone having a fineness of 500 to 2000 dtex. If the fineness of the filament bundle used for the polyketone fiber cord is less than 500 dtex, both the elastic modulus and the heat shrinkage stress are insufficient, and if it exceeds 2000 dtex, the cord diameter becomes thick and the driving cannot be made dense. In addition, even if the number of filament bundles made of polyketone is 4 or more, there is no particular limitation as long as the relationship of the above formulas (I) and (II) can be satisfied.

  The polyketone fiber cord used for the reinforcing cord layer 8 preferably has reversibility that shrinks at a high temperature and expands when returned to room temperature. In this case, the rigidity increases when the polyketone fiber cord in the reinforcing cord layer 8 is shrunk at a high temperature, that is, at the time of run flat running, and the bending of the sidewall portion of the tire can be suppressed. When the normal running, the polyketone fiber cord in the reinforcing cord layer 8 tends to expand, the rigidity is lowered, and the longitudinal spring of the tire is lowered, so that deterioration in riding comfort during normal running of the tire can be suppressed. Further, by using a reversible polyketone fiber cord having a difference in heat shrinkage stress between 20 ° C. and 177 ° C. of 0.20 cN / dtex or more, preferably 0.25 cN / dtex or more, during normal running and run flat running Both effects can be achieved.

The reinforcing cord layer 8 of the pneumatic tire of the present invention is formed by coating a polyketone fiber cord obtained by twisting a plurality of filament bundles made of polyketone with a coating rubber. The polyketone as a raw material of the polyketone fiber cord is represented by the above formula ( Polyketones consisting essentially of the repeating units represented by IV) are preferred. Among the polyketones, a polyketone in which 97 mol% or more of repeating units is 1-oxotrimethylene [—CH ₂ —CH ₂ —CO—] is preferable, and polyketone in which 99 mol% or more is 1-oxo trimethylene. Is more preferable, and a polyketone in which 100 mol% is 1-oxotrimethylene is most preferable.

  The polyketone as the raw material of the polyketone fiber cord may be partially bonded with ketone groups and with unsaturated compounds. However, the unsaturated compound-derived portions and ketone groups are alternately arranged. Is preferably 90% by mass or more, 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, methyl acrylate, methyl methacrylate, vinyl acetate, acrylamide, hydroxyethyl methacrylate, undecenoic acid, undecenol, 6-chlorohexene, N-vinylpyrrolidone, diethyl ester of sulphonylphosphonic acid , A compound containing an unsaturated bond, such as sodium styrenesulfonate, sodium allylsulfonate, vinylpyrrolidone, and vinyl chloride.

［式中、ｔ及びＴは、純度９８％以上のヘキサフルオロイソプロパノール及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の範囲にあることが好ましく、２〜１０ｄＬ／ｇの範囲にあることが更に好ましく、３〜８の範囲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、乾燥時及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及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、紡糸性及び物性に悪影響が出ることがある。 Furthermore, as the polymerization degree of the polyketone, the following formula:

[Wherein t and T are the flow times 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; The intrinsic viscosity [η] defined by the solute mass (g) is preferably in the range of 1 to 20 dL / g, more preferably in the range of 2 to 10 dL / g, More preferably, it is in the range of 8. 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.

  As the method for fiberizing the polyketone, (1) after spinning an unstretched yarn, performing multi-stage heat stretching, and stretching at a specific temperature and magnification in the final stretching step of the multi-stage heat 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 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 No., JP-A No. 2004-218189, JP-A No. 2004-285221, and the wet spinning method using an aqueous solution of zinc salt, calcium salt, thiocyanate, iron salt, etc., among these, A wet spinning method using an aqueous solution of is preferred.

  For example, in the 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 , N-hexane, isooctane, acetone, methyl ethyl ketone, etc., the solvent can be removed and washed in a non-solvent bath to obtain a polyketone undrawn yarn.

  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, followed by desalting and drying to obtain an undrawn polyketone yarn. 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 this heat drawing method, 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 (the melting point of the polyketone), and the total stretching ratio is preferably 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. Here, 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.

  The polyketone fiber cord is formed by twisting a plurality of filament bundles made of the polyketone, preferably two or three strands. For example, the filament bundle made of the polyketone is twisted, and then a plurality of the bundles are joined together. By applying an upper twist in the opposite direction, it can be obtained as a twisted cord having a double twist structure.

  A cord / rubber composite used for the reinforcing cord layer 8 can be obtained by coating the polyketone fiber cord obtained as described above with a coating rubber. Here, there is no restriction | limiting in particular as coating rubber of a polyketone fiber cord, The coating rubber used for the cord / rubber composite for the conventional tire can be used. Prior to coating the polyketone fiber cord with the coating rubber, the polyketone fiber cord may be subjected to an adhesive treatment to improve the adhesion to the coating rubber.

  In the pneumatic tire of the present invention, the reinforcing cord layer 8 formed by coating the above polyketone fiber cord with a coating rubber includes a region A from the belt end to the maximum width portion of the tire side portion and a region B from the vicinity of the bead core to the bead filler. It can arrange | position to at least one part and can manufacture by a conventional method. 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 described in more detail with reference to examples. However, the present invention is not limited to the following examples.

  A cord / rubber composite in which the material, structure, twist coefficient, elastic modulus, and heat shrink stress fiber cords shown in Tables 1 to 5 are arranged in parallel by the number of drivings shown in Tables 1 to 5 and coated with coating rubber Was made. Next, using the cord / rubber composite for the reinforcing cord layer 8 of the tire having the structure shown in FIGS. 1 to 5, a side-reinforcing type run-flat tire of size 215 / 45ZR17 was prototyped. The angles of the cords in the reinforcing cord layer 8 with respect to the tire radial direction are as shown in Tables 1 to 5. For comparison, a tire (Comparative Example 1) having the same structure except that the reinforcing cord layer 8 is not provided was manufactured as a prototype. Next, the longitudinal spring and run flat durability of the obtained tire were evaluated by the following methods, and the results shown in Tables 1 to 5 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 vertical spring constant of the tire was expressed as an index with the value being 100. 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 tire of Comparative Example 1 was taken as 100, and displayed as an index. The larger the index value, the longer the distance traveled until failure, and the better the run-flat durability.

＊１ ほぼ１００％が式（ＩＶ）で表される繰り返し単位からなり、繰り返し単位の９７モル％以上が１−オキソトリメチレンであるポリケトン．

* 1 Polyketone in which almost 100% is composed of repeating units represented by the formula (IV), and 97 mol% or more of repeating units are 1-oxotrimethylene.

＊１ ほぼ１００％が式（ＩＶ）で表される繰り返し単位からなり、繰り返し単位の９７モル％以上が１−オキソトリメチレンであるポリケトン．

* 1 Polyketone in which almost 100% is composed of repeating units represented by the formula (IV), and 97 mol% or more of repeating units are 1-oxotrimethylene.

＊１ ほぼ１００％が式（ＩＶ）で表される繰り返し単位からなり、繰り返し単位の９７モル％以上が１−オキソトリメチレンであるポリケトン．

* 1 Polyketone in which almost 100% is composed of repeating units represented by the formula (IV), and 97 mol% or more of repeating units are 1-oxotrimethylene.

＊１ ほぼ１００％が式（ＩＶ）で表される繰り返し単位からなり、繰り返し単位の９７モル％以上が１−オキソトリメチレンであるポリケトン．

* 1 Polyketone in which almost 100% is composed of repeating units represented by the formula (IV), and 97 mol% or more of repeating units are 1-oxotrimethylene.

＊１ ほぼ１００％が式（ＩＶ）で表される繰り返し単位からなり、繰り返し単位の９７モル％以上が１−オキソトリメチレンであるポリケトン．

* 1 Polyketone in which almost 100% is composed of repeating units represented by the formula (IV), and 97 mol% or more of repeating units are 1-oxotrimethylene.

  As apparent from Tables 1 to 5, at least part of the region A from the belt end of the side reinforcing type run-flat tire to the maximum width portion of the tire side portion and the region B from the vicinity of the bead core to the bead filler, By arranging the reinforcing cord layer using the polyketone fiber cord satisfying the conditions of the formula (I) and the formula (II), it is possible to suppress an increase in the vertical spring of the tire during normal running, that is, during normal running. The tire durability during run-flat driving can be greatly improved without impairing the tire comfort.

It is sectional drawing of the right half of an example of the pneumatic tire of this invention. It is sectional drawing of the right half of the other example of the pneumatic tire of this invention. It is sectional drawing of the right half of the other example of the pneumatic tire of this invention. It is sectional drawing of the right half of the other example of the pneumatic tire of this invention. It is sectional drawing of the right half of the other example of the pneumatic tire of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead part 2 Bead core 3 Radial carcass 4 Tread part 5 Buttress part 6 Side wall part 7 Side reinforcement rubber layer 8 Reinforcement cord layer 9 Bead filler 10 Belt 11A, 11B Belt reinforcement layer 12 Rim guard A Maximum width of tire side part from belt end Area B to the area from the bead core vicinity to the bead filler

Claims (9)

A radial carcass made of one or more carcass plies extending in a toroidal manner between bead cores embedded in a pair of bead portions, and a tread portion disposed on the outer side in the tire radial direction of the crown portion of the radial carcass. A pair of buttress portions located at both ends of the tread portion; a pair of sidewall portions connecting the buttress portion and the bead portion; and an inner side of the radial carcass extending from the buttress portion to the sidewall portion In a pneumatic tire provided with a pair of crescent-shaped side reinforcing rubber layers disposed in
A plurality of filament bundles made of polyketone are twisted in at least a part of the region A from the belt end to the maximum width portion of the tire side portion and the region B from the vicinity of the bead core to the bead filler. (II):
σ ≧ −0.01 × E + 1.2 (I)
σ ≧ 0.02 (II)
[Wherein σ is heat shrinkage stress (cN / dtex) at 177 ° C .; E is elastic modulus at 49 N load (cN / dtex) at 25 ° C.] A pneumatic tire comprising a reinforcing cord layer coated with rubber.   The pneumatic tire according to claim 1, wherein the reinforcing cord layer is disposed in a region A from the belt end to a maximum width portion of the tire side portion.   The pneumatic tire according to claim 1, wherein an angle of the polyketone fiber cord in the reinforcing cord layer with respect to a tire radial direction is 0 to 85 °. The polyketone fiber cord has the following formula (III):
Nt = tan θ = 0.001 × N × (0.125 × D / ρ) ^1/2 (III)
Where N is the number of twists (times / 10 cm), ρ is the specific gravity of the cord (g / cm ³ ), and D is the total decitex number (dtex) of the cord. The pneumatic tire according to claim 1, wherein the tire is 0.25 or more.   2. The pneumatic tire according to claim 1, wherein the number of driving of the polyketone fiber cord in the reinforcing cord layer is 5 to 60 (lines / 50 mm).   2. The pneumatic tire according to claim 1, wherein the polyketone fiber cord is formed by twisting two or three filament bundles made of polyketone having a fineness of 500 to 2000 dtex.   The pneumatic tire according to any one of claims 1 to 6, wherein the polyketone fiber cord contracts at a high temperature and has a reversibility that expands when returned to room temperature. The polyketone is represented by the following general formula (IV):

[Wherein 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], The pneumatic tire according to claim 1.   The pneumatic tire according to claim 8, wherein A in the formula (IV) is an ethylene group.

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