JP4966552B2 - Pneumatic radial tire - Google Patents

Description

  The present invention relates to a pneumatic radial tire, and more particularly, to a pneumatic radial tire that includes a side reinforcing layer on at least a part of a sidewall portion, is light and has excellent durability, and excellent steering stability.

  In recent years, as the speed of a vehicle increases, the force applied to each part of a running tire is also increasing, and against these forces, it is required to prevent tire deformation and improve steering stability. In response to this demand, it is conceivable to increase the thickness of the gauge on the sidewall portion of the tire. In this case, however, there is a problem that the weight of the tire increases and the fuel efficiency of the tire deteriorates.

  On the other hand, as a method for increasing the rigidity of the sidewall portion of the tire without increasing the weight of the tire, a side reinforcing layer formed by coating a steel cord or an organic fiber cord with a coating rubber is provided on at least one of the sidewall portions. The method of arrange | positioning to a part is taken (refer patent document 1).

JP 2001-191743 A

  However, when a steel cord is used as the reinforcing member of the side reinforcing layer, although the rigidity of the tire is improved and the steering stability is improved, there is a problem that the weight of the tire is increased and the rolling resistance is increased. .

  On the other hand, when an aramid fiber cord having a high elastic modulus is used as the reinforcing member of the side reinforcing layer, the steering stability can be improved while suppressing an increase in tire weight. Since the rate is very small, it is difficult to dispose the tire without slack, and there is a problem that the arrangement position, the cord length, and the cord angle are restricted. In addition, when sagging occurs in the disposed aramid fiber cord, not only the steering stability of the tire cannot be sufficiently improved, but also the durability of the tire due to the occurrence of buckling due to sagging. There is also a problem that is greatly reduced.

  In addition, cords made of polyester or nylon having moderate heat shrinkability are not difficult to manufacture as in the case of using the above-mentioned aramid fiber cords, but cords made of polyester or nylon are made of the above steel cords or aramids. Since the elastic modulus is smaller than that of the fiber cord, the rigidity of the tire cannot be sufficiently increased, and as a result, the steering stability of the tire cannot be sufficiently improved.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a pneumatic radial tire that solves the above-described problems of the prior art, is lightweight and has excellent durability, and excellent steering stability.

  As a result of intensive studies to achieve the above object, the present inventor uses a polyketone fiber cord having specific heat shrinkage stress, elastic modulus and total decitex for the side reinforcing layer in the pneumatic radial tire including the side reinforcing layer. As a result, it has been found that the occurrence of slack in the cord during manufacture can be prevented, and that the steering stability can be significantly improved without increasing the weight of the tire, and the present invention has been completed.

That is, the pneumatic radial tire of the present invention has a pair of bead portions and a pair of sidewall portions, and a tread portion connected to both sidewall portions, and extends in a toroidal shape between the pair of bead portions. A carcass made of at least one carcass ply that reinforces each of these parts, a belt made of at least two steel belt layers arranged on the outer side in the tire radial direction of the crown part of the carcass, and the side wall part from the bead part In a pneumatic tire provided with at least one side reinforcing layer disposed in at least a part of the region up to the shoulder portion of the tread portion through,
The side reinforcing layer is formed by coating multi-filament twisted polyketone fiber cords with a coating rubber, the total decitex per polyketone fiber cord is 1000 to 6000 dtex, and the polyketone fiber cord is represented by the following formula (I ) And formula (II):
σ ≧ -0.01 × E + 1.2 (I)
σ ≥ 0.02 (II)
[Wherein σ is a heat shrinkage stress (cN / dtex) at 177 ° C .; E is an elastic modulus at 49 N load (cN / dtex) at 25 ° C.] .

  Here, the heat shrinkage stress σ at 177 ° C of the above polyketone fiber cord is a 25 cm long fixed sample of polyketone fiber cord that has been subjected to general dip treatment and heated at a rate of 5 ° C / min. The elastic modulus E of the polyketone fiber cord at 49N load at 25 ° C is a unit calculated from the tangent at 49N of the SS curve according to the JIS cord tension test. Elastic modulus at cN / dtex.

［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ポリケトンの繊維からなる。ここで、前記式(III)中のＡがエチレン基であることが特に好ましい。 In a preferred example of the pneumatic radial tire of the present invention, the polyketone fiber cord has the following general formula (III):

[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], and consists of a polyketone fiber substantially consisting of a repeating unit represented by . Here, it is particularly preferable that A in the formula (III) is an ethylene group.

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

  According to the present invention, it has a side reinforcement layer formed by coating a polyketone fiber cord of a specific heat shrinkage stress, elastic modulus and total decitex with a coating rubber. An excellent pneumatic radial tire can be provided. Moreover, since the polyketone fiber cord does not sag during manufacture, the pneumatic radial tire of the present invention is excellent in manufacturing and can cope with various tire structures.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of the right half of one embodiment of the pneumatic radial tire of the present invention, and FIGS. 2, 3 and 4 are cross-sectional views of the right half of a modified example of the pneumatic radial tire of the present invention. It is.

  The radial tire shown in FIG. 1 has a pair of 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 comprising at least one carcass ply that reinforces each of these parts 1, 2 and 3, and a belt 5 comprising at least two steel belt layers arranged on the outer side in the tire radial direction of the carcass 4; A bead filler 7 disposed on the outer side in the tire radial direction of each of the ring-shaped bead cores 6 embedded in the bead portion 1, and at least one side reinforcing layer 8 disposed from the bead portion 1 to the sidewall portion 2; Is provided.

  The radial carcass 4 in the illustrated example is composed of a single carcass ply, and a main body portion 4a extending in a toroidal shape between a pair of bead cores 6 and around each bead core 6 from the inner side to the outer side in the tire width direction. However, in the pneumatic radial tire of the present invention, the number of plies and the structure of the radial carcass 4 are not limited to this.

  In the radial tire of the illustrated example, a belt 5 composed of two steel belt layers is disposed on the outer side in the tire radial direction of the crown portion of the radial carcass 4, and the steel belt layer is usually a tire equator. It consists of rubberized layers of steel cords that extend at an angle to the surface, and the two steel belt layers are laminated so that the steel cords constituting the steel belt layers intersect each other across the tire equatorial plane 5 is configured. Although the belt 5 in the drawing is composed of two steel belt layers, in the pneumatic radial tire of the present invention, the number of steel belt layers constituting the belt 5 may be three or more.

  Further, in the illustrated radial tire, the bead filler 7 is disposed between the carcass main body portion 4a and the carcass folded portion 4b. However, the pneumatic radial tire of the present invention does not include the bead filler 7. Also good. Here, in the radial tire shown in FIG. 1, one side reinforcing layer 8 is disposed between the bead filler 7 and the carcass folded portion 4 b in a region extending from the bead portion 1 to the sidewall portion 2. The pneumatic radial tire of the present invention is particularly limited as long as at least one side reinforcing layer 8 is disposed in at least a part of the region from the bead portion 1 through the sidewall portion 2 to the shoulder portion of the tread portion 3. It may be provided with two or more side reinforcing layers 8.

  For example, in the pneumatic radial tire of the present invention, as shown in FIG. 2, the side reinforcing layer 8 is disposed between the carcass main body portion 4 a and the bead filler 7 in a region extending from the bead portion 1 to the sidewall portion 2. As shown in FIG. 3, the side reinforcing layer 8 is disposed between the carcass body 4a and the bead filler 7 in the region extending from the bead part 1 to the side wall part 2 and between the bead filler 7 and the carcass folded part 4b. As shown in FIG. 4, the side reinforcing layer 8 has a tread portion between the bead filler 7 of the bead portion 1 and the folded portion 4 b of the carcass through the sidewall portion 2. The aspect extended to the shoulder part of 3 is also preferable.

In the pneumatic radial tire of the present invention, a cord / rubber composite formed by coating a multi-filament twisted polyketone fiber cord with a coating rubber is used for the side reinforcing layer 8. Here, the polyketone fiber cord used for the side reinforcing layer 8 has a total decitex per cord of 1000 to 6000 dtex, and the following formulas (I) and (II):
σ ≧ -0.01 × E + 1.2 (I)
σ ≥ 0.02 (II)
[Where σ is a heat shrinkage stress (cN / dtex) at 177 ° C .; E is an elastic modulus (cN / dtex) at a load of 49 N at 25 ° C.].

  Conventionally, the side reinforcing layer 8 has the advantage that the angle and width of the cord to be used can be set according to the required tire performance, but the shape of the raw tire before vulcanization and the product tire after vulcanization Because of the difference, there is a portion that is compressed during vulcanization, and therefore, when an organic fiber cord having a low thermal shrinkage rate, for example, an aramid fiber cord, is used for the side reinforcing layer 8, it can absorb compression strain during vulcanization. There is a problem that the cord is slack in the product tire and buckling occurs due to the slack. Especially, the cord angle is set to 0 ° (tire radial direction) or 90 ° (tire circumferential direction). In this case, this phenomenon is likely to occur. In addition, when steel cord is used for the side reinforcing layer 8, since the steel cord itself is straight, sagging and buckling are less likely to occur than when an organic fiber cord is used. There is a problem that the rolling resistance increases due to an increase in the weight of the tire.

  In contrast, the polyketone fiber cord has a high heat shrinkage stress at a high temperature, that is, at 177 ° C., that is, sufficiently heat shrinks at a high temperature, so that it can be disposed in the tire without sagging during the manufacture of the tire. it can. Therefore, in the pneumatic radial tire of the present invention, there is no occurrence of buckling due to the slack of the cord, and the durability of the tire can be sufficiently maintained. Here, it is preferable that the polyketone fiber cord has a reversibility that shrinks at a high temperature and expands when returned to room temperature. In this case, the steering stability of the tire can be sufficiently improved while reliably preventing the slack of the cord during tire manufacture. In addition, by using a reversible polyketone fiber cord with 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, it is effective for normal running and high-speed running. Can be compatible.

  In addition, the polyketone fiber cord satisfying the relationship of the above formulas (I) and (II) has an appropriate heat shrinkage and an elastic modulus close to that of an aramid fiber cord, so that the rigidity of the tire is sufficiently improved. As a result, the steering stability of the tire can be greatly improved. When the heat shrinkage stress σ at 177 ° C. of the polyketone fiber cord is less than 0.02 cN / dtex, the heat shrinkage is too small, so that the cord is slack during vulcanization, and buckling is likely to occur due to looseness. Therefore, the durability of the tire is reduced. Also, in the polyketone fiber cord that does not satisfy the relationship of the formula (I), if the cord has a high heat shrinkage stress (having sufficient heat shrinkability), the elastic modulus is too low, whereas if the elastic modulus is high, the heat shrinkage Since the stress is too small (insufficient heat shrinkability), in both cases, it is impossible to simultaneously achieve the prevention of sagging during production and the improvement of tire rigidity. It cannot be improved sufficiently.

  Here, the polyketone fiber cord preferably has a heat shrinkage stress σ at 177 ° C. of 1.5 cN / dtex or less. If the heat shrinkage stress σ of polyketone fiber cords at 177 ° C exceeds 1.5 cN / dtex, the shrinkage force during vulcanization will become too large, resulting in the damage of the cords inside the tire and the placement of the rubber, resulting in durability. Will worsen and uniformity. The polyketone fiber cord preferably has a heat shrinkage stress σ at 177 ° C. of 1.30 cN / dtex or less from the viewpoint of preventing the arrangement of the cord from being disturbed during vulcanization of the green tire, and 0.90 cN / dtex. More preferably, it is the following. Further, the polyketone fiber cord preferably has a heat shrinkage stress σ at 177 ° C. of 0.05 cN / dtex or more from the viewpoint of improving the steering stability by preventing deformation of the running tire, and 0.15 cN / dtex. More preferably, it is more preferably 0.4 cN / dtex. Furthermore, the polyketone fiber cord preferably has an elastic modulus E of 49 cN / dtex or more at a load of 49 N at 25 ° C. from the viewpoint of improving the driving stability by preventing deformation of the running tire, and 100 cN More preferably, it is at least / dtex.

  Furthermore, the above polyketone fiber cord has a total decitex of 1000 to 6000 dtex, so it has high rigidity and can sufficiently improve the steering stability of the tire, and is lighter than the steel cord and light in weight of the tire. Enable. Here, if the total decitex per polyketone fiber cord to be used is less than 1000 dtex, a highly rigid side reinforcing layer cannot be constructed with one sheet, and if it exceeds 6000 dtex, the gauge of the side reinforcing layer will be The tire becomes thicker and the tire cannot be reduced in weight.

The polyketone fiber cord used in the pneumatic radial tire of the present invention is preferably composed of polyketone multifilaments substantially composed of the repeating unit represented by the above formula (III). Among the polyketones substantially composed of the repeating unit represented by the formula (III), a polyketone in which 97 mol% or more of the repeating units is 1-oxotrimethylene [—CH ₂ —CH ₂ —CO—] is preferable. More preferred is a polyketone in which 99 mol% or more is 1-oxotrimethylene, and most preferred is a polyketone in which 100 mol% is 1-oxotrimethylene.

  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 (III), 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-vinyl pyrrolidone, 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; C is 100 mL of the diluted solution It is preferable that the intrinsic viscosity [η] defined by the mass (g) of the solute in the range is 1 to 20 dL / g, more preferably 2 to 10 dL / g, and 3 to Even more preferably in the range of 8. When the intrinsic viscosity is less than 1 dL / g, it is difficult to obtain a high-strength polyketone fiber cord because the molecular weight is too small, and troubles such as fluff and yarn breakage occur frequently during spinning, drying and drawing. 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 a wet spinning method using an organic solvent, a polyketone polymer is dissolved in hexafluoroisopropanol or m-cresol at a concentration of 0.25 to 20% by mass, extruded from a spinning nozzle to be fiberized, and then toluene, ethanol, isopropanol, n -Unstretched polyketone yarn can be obtained by removing the solvent in a non-solvent bath such as hexane, isooctane, acetone, methyl ethyl ketone, and washing.

  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, etc. at a concentration of 2 to 30% by mass, and a spinning nozzle is used 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 (melting point of polyketone), and the total stretching ratio is preferably 10 times or more.

  When polyketone fiberization is performed by the method of (1) above, the temperature in the final stretching step of the multistage thermal stretching is in the range of 110 ° C to (stretching temperature in the stretching step one step before the final stretching step-3 ° C). 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 (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 ° C / The cooling end temperature in the rapid cooling is preferably 50 ° C. or lower. 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 fibers (PK fibers) made of the polyketone, for example, applying a lower twist to the PK fibers, then combining a plurality of the fibers, and applying an upper twist in the opposite direction, It can be obtained as a twisted yarn cord. Here, it is preferable that the polyketone fiber cord has a double twist structure.

  A cord / rubber composite used for the side reinforcing 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, The coating rubber used for the conventional side reinforcement layer 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.

  The pneumatic radial tire of the present invention can be manufactured by a conventional method by applying a cord / rubber composite formed by rubber-drawing the above polyketone fiber cord to the side reinforcing layer 8. In the pneumatic radial tire of 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. However, the present invention is not limited to the following examples.

  A radial tire of size 205 / 65R15 having the structure shown in any of FIGS. 1 to 4 was manufactured according to a conventional method. The carcass of the test tire has a cord structure of 1670 dtex / 2 and a PET cord with a twist number of 40 × 40/10 cm arranged at a driving number of 100/10 cm and an angle of 0 ° (tire radial direction). It consists of a single carcass ply, and the belt consists of two steel belt layers in which steel cords with a structure of 1 x 5 x 0.25 mm are placed at a driving rate of 80/10 cm and an angle of 70 °.

  Also, as the heat shrinkage stress σ of the used cord at 177 ° C, a 25 cm long fixed sample of polyketone fiber cord that had been subjected to general dip treatment was heated at a heating rate of 5 ° C / min. Measure the stress generated in the cord at 177 ° C, and further calculate the elastic modulus E at 49N load at 25 ° C of the cord used from the tangent at 49N of the SS curve according to the JIS cord tension test cN The elastic modulus at / dtex was measured.

  The steering stability and durability of the radial tire obtained as described above were evaluated by the following methods. Further, the weight of the obtained tire was expressed in%, assuming that the weight of the tire of Comparative Example 1 was 100%. These results are shown in Table 1 together with the findings of the tires obtained.

(1) Steering stability Four test tires were mounted on an actual vehicle, the vehicle was driven, and evaluated by the driver's feeling. The evaluation criteria for steering stability are shown below.
+3: Level that can be recognized as better for general drivers than tires of Comparative Example 1 +2: Level that can be recognized as professional drivers better than tires of Comparative Example 1 +1: Pro drivers are slightly better than tires of Comparative Example 1 Recognition level ± 0: Equivalent to the tire of Comparative Example 1 −1: Level at which the professional driver can be recognized as slightly worse than the tire of Comparative Example 1 −2: Level at which the professional driver can be recognized as worse than the tire of Comparative Example 1 − 3: Level that can be recognized as being worse for general drivers than the tire of Comparative Example 1

(2) Durability The tire was run at 200% load, which is the maximum load condition of JATMA, and the tire that did not break down to 20,000km was judged as OK, and the tire that failed at less than 20,000km was judged as NG.

  From Table 1, the tires of the examples using the polyketone fiber cords satisfying the above formulas (I) and (II) and having a total decitex of 1000 to 6000 dtex are equal to or better than the comparative example 1 using the steel cords. Moreover, compared with the comparative example 1, it was lightweight and had sufficient durability.

  On the other hand, since the tire of Comparative Example 2 using an aramid fiber cord has slack, the steering stability is inferior, and because the tire of Comparative Example 3 has buckling, the steering stability is inferior. Tire durability was also poor. Furthermore, although the total decitex was 1000 to 6000 dtex, the tire of Comparative Example 4 using the polyketone fiber cord not satisfying the above formula (I) was inferior in handling stability to the tire of Comparative Example 1.

It is sectional drawing of the right half of one embodiment of the pneumatic radial tire of this invention. It is sectional drawing of the right half of the modification of the pneumatic radial tire of this invention. It is sectional drawing of the right half of the other modification of the pneumatic radial tire of this invention. It is sectional drawing of the right half of the other modification of the pneumatic radial tire of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tread part 4 Radial carcass 4a Carcass main-body part 4b Carcass folding | turning part 5 Belt 6 Bead core 7 Bead filler 8 Side reinforcement layer

Claims (4)

At least one carcass having a pair of bead portions, a pair of sidewall portions, and a tread portion continuous to both sidewall portions, extending in a toroidal shape between the pair of bead portions, and reinforcing these portions. A carcass made of ply, a belt made of at least two steel belt layers arranged on the outer side in the tire radial direction of the crown portion of the carcass, and an area from the bead portion to the shoulder portion of the tread portion through the sidewall portion In a pneumatic radial tire provided with at least one side reinforcing layer disposed on at least a part of
The side reinforcing layer is formed by coating multi-filament twisted polyketone fiber cords with a coating rubber, the total decitex per polyketone fiber cord is 1000 to 6000 dtex, and the polyketone fiber cord is represented by the following formula (I ) And formula (II):
σ ≧ -0.01 × E + 1.2 (I)
σ ≥ 0.02 (II)
[Wherein σ is a heat shrinkage stress (cN / dtex) at 177 ° C .; E is an elastic modulus at 49 N load (cN / dtex) at 25 ° C.] Pneumatic radial tire. The polyketone fiber cord has the following general formula (III):

[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], and consists of a polyketone fiber substantially consisting of a repeating unit represented by The pneumatic radial tire according to claim 1.   The pneumatic radial tire according to claim 2, wherein A in the formula (III) is an ethylene group.   The pneumatic radial tire according to any one of claims 1 to 3, wherein the polyketone fiber cord contracts at a high temperature and has a reversibility that expands when returned to room temperature.

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