JP4854013B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire (hereinafter, also simply referred to as “tire”), and more particularly to a pneumatic tire that achieves both high weight reduction and cut resistance without impairing running durability.

  The tires in recent years have been reduced in weight and flattened, and the curb and road holes and tires are sandwiched between the tires, and the plies on the side parts are cut, which can lead to air leakage and bursts in the worst case. Troubles due to phenomena have increased. Conventionally, in order to prevent troubles due to such a side cut phenomenon, the carcass ply is folded back around the bead core from the inner side to the outer side in the tire width direction, and the folded end is between the belt layer and the crown part of the carcass. By adopting a so-called envelope structure or a two-layer structure, a method of increasing the number of plies in the side part and preventing the tire side part from being broken has been mainly taken.

Further, in Patent Document 1, the carcass ply is aimed at improving the weather resistance against a cut edge of a tire and a weather resistance against ozone cracks during driving on a road curb or a rough road, and to achieve weight reduction of the tire. It has been reported that aromatic fiber fibers containing high-strength and high-modulus hetero rings are used as the fiber material of the cord.
JP-A-6-305303 (Claims etc.)

  In recent years when low rolling resistance due to weight reduction of tires is desired, the carcass ply having an envelope structure or a two-layer structure leads to an increase in rolling resistance due to an increase in weight, and other methods are required. In addition, the application of the aromatic ring-containing aromatic polymer fiber disclosed in Patent Document 1 to the carcass ply has made it possible to reduce the weight of the tire, but today it is desired to improve the performance with further weight reduction. ing.

  Accordingly, an object of the present invention is to provide a pneumatic tire that greatly improves the side cut resistance by a carcass ply having a single layer structure at the tire side portion, and achieves both high weight reduction and cut resistance as never before. It is to provide.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that the above object can be achieved by using an organic fiber cord satisfying a predetermined physical property value for the carcass layer, and completes the present invention. It came to.

That is, the pneumatic tire according to the present invention includes a carcass layer composed of one carcass ply extending in a toroidal shape between a pair of bead cores, and at least one belt ply arranged on the outer side in the crown portion radial direction of the carcass. In a pneumatic tire comprising a belt layer made of the carcass ply composed of an organic fiber cord and a coating rubber formed by coating the organic fiber cord,
The organic fiber cord contains at least 50% by mass of polyketone fiber, and the polyketone fiber has a single yarn fineness of 0.5 to 2 dtex, a crystallinity of 70 to 95%, a crystal orientation of 90% or more, and a density of 1. 25 g / cm ³ or more, the maximum heat shrinkage stress of the organic fiber cord containing at least 50% by mass of the polyketone fiber is in the range of 0.1 to 1.8 cN / dtex, and the polyketone fiber is 150 ° C. × The heat shrinkage ratio during 30 minutes of dry heat treatment is in the range of 1% to 5%.

  In the present invention, in the polyketone fiber, the tensile strength of the raw yarn is preferably 10 cN / dtex or more, and the elastic modulus is preferably 200 cN / dtex or more.

  According to the present invention, a pneumatic tire is provided which has a one-layer structure carcass ply at the tire side portion that significantly improves the side-cut resistance and achieves both high weight reduction and high cut resistance than ever before. can do.

Hereinafter, embodiments of the present invention will be specifically described.
FIG. 1 shows a schematic cross-sectional view of an example of a pneumatic tire according to the first embodiment of the present invention. The illustrated tire 10 includes a tread portion 1, a pair of sidewall portions 2 extending inward in the tire radial direction from both ends thereof, and a pair of bead portions 3 positioned at the inner ends thereof. A carcass layer made of the carcass ply 5 is extended toroidally between a pair of bead cores 4 embedded in the bead portion 3. Here, reference numeral 8 denotes a bead filler. The tire 10 is disposed on the outer side in the crown portion radial direction of the carcass layer, and is disposed on the outer side in the tire radial direction of the belt layer 6 including at least one belt ply (two in the illustrated example). And at least one (1 in the illustrated example) belt protective layer 7. In the illustrated tire, the belt protective layer 7 is disposed. However, in the present embodiment, the belt protective layer 7 may or may not be disposed as appropriate.

  The carcass ply 5 includes a fiber cord and a coating rubber that covers the fiber cord. That is, add a certain twist to the fiber, twist 2 to 3 strands, draw multiples of these as warp yarns, roughly smash thin and weak wefts into a sled, and then adhesive treatment to adhere to rubber I do. Thereafter, a topping rubber having a constant thickness is coated to obtain a rubber-coated cord.

  In the present invention, the cord of the carcass ply 5 desirably contains at least 50% by mass of polyketone fiber, preferably 70% by mass or more, and more preferably 100% by mass. If it is less than 50% by mass, the performance of any of the strength, heat resistance, and adhesion to rubber as a tire becomes insufficient.

In the present invention, to obtain a desired effect, the polyketone fiber has a single yarn fineness of 0.5 to 2 dtex, a crystallinity of 70 to 95%, a crystal orientation of 90% or more, and a density of 1. It is important that it is 25 g / cm ³ or more.

That is, when the single yarn fineness of the polyketone fiber is less than 0.5 dtex, the side cut resistance is not sufficient, while when it exceeds 2 dtex, it becomes difficult to produce the polyketone fiber. Preferably, it is in the range of 1.0 to 1.5 dtex. Further, if the crystallinity is less than 70%, the fiber structure is not sufficiently formed and sufficient strength cannot be obtained, and the shrinkage characteristics and dimensional stability during heating may be unstable. If it exceeds 95%, the desired effect cannot be obtained. Furthermore, in order to obtain the desired effect of the present invention, it is necessary that the degree of crystal orientation is 90% or more and the density is 1.25 g / cm ³ or more.

  The maximum heat shrinkage stress of the cord of the carcass ply 5 is in the range of 0.1 to 1.8 cN / dtex, preferably 0.4 to 1.6 cN / dtex, more preferably 0.6 to 1.4 cN / dtex. It is desirable to be in When the maximum heat shrinkage stress is less than 0.1 cN / dtex, the side cut resistance cannot be sufficiently improved. On the other hand, when the maximum heat shrinkage stress exceeds 1.8 cN / dtex, the cord is remarkably contracted by heating at the time of tire manufacture, so that there is a concern that the finished tire shape may be deteriorated.

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

  Furthermore, the tensile strength of the polyketone fiber contained in the cord of the carcass ply 5 is preferably 10 cN / dtex or more, more preferably 15 cN / dtex or more. When the tensile strength is less than 10 cN / dtex, the strength as a tire is insufficient.

  Furthermore, as a polyketone fiber contained in the cord of the carcass ply 5, the elastic modulus is preferably 200 cN / dtex or more, more preferably 250 cN / dtex or more. When this elastic modulus is less than 200 cN / dtex, the side cut resistance cannot be sufficiently improved.

（ｎは撚り数（回／１０ｃｍ）、Ｄはトータル表示デシテックス数、ρは繊維の比重（ｇ／ｃｍ^３）である）で定義される撚り係数Ｎが下記式（ＩＩ）、
０．６ ≦ Ｎ ≦ ０．９ ・・・ （ＩＩ）
を満たすことが好ましく、さらには下記式（ＩＩＩ）、
０．７ ≦ Ｎ ≦ ０．８５ ・・・ （ＩＩＩ）
を満たすことがより好ましい。この上撚り係数が０．６未満の場合にはカーカスプライコードに要求される耐疲労性が低下し、結果としてタイヤ耐久性が低下するという問題が生じる。一方、０．９より大きい場合には撚糸の撚り戻りが大きく、作業性が著しく悪化する。 Next, the following formula (I) of the cord of the carcass ply 5:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Subsequently, the coagulated yarn was washed with an aqueous sulfuric acid solution having a concentration of 2% by weight and a temperature of 25 ° C., and further washed with water at 30 ° C., and then the coagulated yarn was wound at a speed of 3.2 m / min.
After impregnating IRGANOX 1098 (manufactured by Ciba Specialty Chemicals) and IRGANOX 1076 (manufactured by Ciba Specialty Chemicals) into the coagulated yarn by 0.05% by weight (vs. polyketone polymer), the coagulated yarn was 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 stearyl sulfonate / dioctyllin Sodium acid = 30/30/10/5/23/1/1 (weight% ratio).

  The obtained undrawn yarn was drawn at 240 ° C. in the first stage, followed by the second stage at 258 ° C., the third stage at 268 ° C., the fourth stage at 272 ° C., and then the second stage at 200 ° C. The film was stretched five times at 1.08 times (stretching tension 1.8 cN / dtex) and wound with a winder. The total draw ratio from the undrawn yarn to the five-stage drawn yarn was 17.1 times.

In the following examples and comparative examples, in addition to the heat treatment conditions of the PK fibers in the above production examples, the PK fibers having the cord properties shown in Table 1 below by appropriately adjusting the twisting conditions and the dip treatment conditions of the cords according to ordinary methods Got. Each pneumatic radial tire (size: 215 / 45ZR17) was prototyped by a conventional method according to various conditions of the carcass ply cord shown in Table 1 below.
Each obtained tire was evaluated according to the following evaluation method.

(Rolling resistance)
A test tire adjusted to an internal pressure of 196 kPa was installed on a drum with an outer diameter of 1708 mm, and after applying the maximum load capacity specified by JATMA in 2000, it was preliminarily run at 80 km / h for 30 minutes to readjust the air pressure, After increasing the drum rotation speed to 200 km / h, the drum is coasted and the following equation is obtained from the moment of inertia until the drum rotation speed decreases from 185 km / h to 20 km / h:
Tire rolling resistance = ds / dt (ID / RD ² + It / Rt ² ) −Calculated according to the resistance of a single drum. In the formula, ID is a moment of inertia of the drum, It is a moment of inertia of the tire, RD is a drum radius, and Rt is a tire radius.
The rolling resistance at 50 km / h obtained by the above formula was obtained as a representative value, and the conventional tire was indicated as 100 as an index. Here, the smaller the value of rolling resistance is, the larger the index is. Therefore, the larger the index is, the better the fuel economy is.

(Side cut resistance)
Side-cut resistance is achieved by causing the test tire mounted on the actual vehicle to collide with a specific square steel material (110 mm x 110 mm x 1000 mm) at an entry speed of 10 km / h and an entry angle of 25 °, and gradually reducing the tire internal pressure. The internal pressure at which air leakage occurs was measured, and the conventional tire was indexed as 100. In addition, it has shown that cut resistance is so favorable that an index | exponent is large. The obtained results are shown in Table 1 below.

  From the test results shown in Table 1 above, the following was confirmed.

(Conventional example)
In the case of a rayon fiber carcass ply (single-layer structure) with an original yarn strength of 1.5 cN / dtex and a crystallinity of 50%, the side-cut resistance is not sufficient, and it can withstand the current trend toward low flatness and light weight. Is difficult.

Example 1
Polyketone fiber having a single yarn fineness of 1.2 dtex, a crystallinity of 90%, a crystal orientation of 91%, a density of 1.33 g / cm ³ , an original yarn strength of 15 cN / dtex, and an elastic modulus of 360 cN / dtex or more (1670 dtex / 2) As a result of applying the cord made of the above to the carcass ply and evaluating the side cut resistance with one carcass ply on the side portion, the contrast of the two-layer structure rayon fiber carcass ply and the one-layer envelope structure carcass ply is excellent. Side cut resistance could be secured. It also succeeded in reducing rolling resistance by reducing weight.

(Example 2)
Polyketone fiber having a single yarn fineness of 0.8 dtex, a crystallinity of 90%, a crystal orientation of 89%, a density of 1.30 g / cm ³ , an original yarn strength of 10.5 cN / dtex, and an elastic modulus of 175 cN / dtex (1670 dtex / 2) ) Is applied to the carcass ply and the side cut resistance is evaluated with one carcass ply on the side part. As a result, the two-layer structure rayon fiber carcass ply and the one-layer envelope structure carcass ply are excellent. A good side cut resistance could be secured. It also succeeded in reducing rolling resistance by reducing weight.

(Example 3)
From a polyketone fiber (1100 dtex / 2) having a single yarn fineness of 1.2 dtex, a crystallinity of 90%, a crystal orientation of 91%, a density of 1.33 g / cm ³ , an original yarn strength of 15 cN / dtex, and an elastic modulus of 360 cN / dtex. As a result of applying the cord to the carcass ply and evaluating the side cut resistance with one carcass ply on the side portion, the two-layer structure rayon fiber carcass ply and the one-layer envelope structure carcass ply are compared with each other. Side cut performance could be secured. It also succeeded in reducing rolling resistance by reducing weight.

Example 4
Polyketone fiber (1100 dtex / 2) having a single yarn fineness of 0.8 dtex, a crystallinity of 90%, a crystal orientation of 89%, a density of 1.30 g / cm ³ , an original yarn strength of 10.5 cN / dtex, and an elastic modulus of 175 cN / dtex. ) Is applied to the carcass ply and the side cut resistance is evaluated with one carcass ply on the side part. As a result, the two-layer structure rayon fiber carcass ply and the one-layer envelope structure carcass ply are excellent. A good side cut resistance could be secured. It also succeeded in reducing rolling resistance by reducing weight.

(Comparative Example 1)
When a rayon fiber ply with an increased strength is used (single-layer structure) by twisting three yarn strengths of 5.0 cN / dtex, the side cut resistance is higher than the conventional example, but it is sufficient. No, it is difficult to withstand the current low flatness and weight reduction. Moreover, rolling resistance also increased with the increase in ply mass.

(Comparative Example 2)
When a rayon fiber cord (1840 dtex / 2) having an original yarn strength of 5.0 cN / dtex is used for a carcass ply (two-layer structure) and the number of carcass plies in the side portion is two, the side cut resistance is improved. Although the side cut resistance is higher than the conventional example, it is not sufficient, and it is difficult to withstand the current low flatness and light weight. Moreover, rolling resistance also increased with the increase in ply mass.

(Comparative Example 3)
When a rayon fiber cord (1840 dtex / 3) ply having an original yarn strength of 5.0 cN / dtex is used in (one-layer envelope structure), and the number of plies in the side portion is two to improve the side cut resistance, Although the side cut resistance is higher than the conventional example, it is not sufficient, and it is difficult to withstand the current low flatness and light weight. Moreover, rolling resistance also increased with the increase in ply mass.

(Comparative Example 4)
When polyethylene terephthalate (PET) (1670 dtex / 2) ply having a yarn strength of 7.0 cN / dtex is used in a (single-layer structure), the side cut resistance is higher than the conventional example, but it is not sufficient. It is difficult to endure low flatness and light weight. Also, the rolling resistance was not much different from the conventional example.

1 is a cross-sectional view in the width direction of a pneumatic tire according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Bead core 5 Carcass layer 6 Belt layer 7 Belt protective layer 8 Bead filler 10 Pneumatic tire

Claims (2)

A carcass layer made of a single carcass ply extending in a toroidal shape between a pair of bead cores, and a belt layer made of at least one belt ply disposed outside the carcass in the crown portion radial direction, In a pneumatic tire in which a ply includes an organic fiber cord and a coating rubber formed by coating the organic fiber cord,
The organic fiber cord contains at least 50% by mass of polyketone fiber, and the polyketone fiber has a single yarn fineness of 0.5 to 2 dtex, a crystallinity of 70 to 95%, a crystal orientation of 90% or more, and a density of 1. 25 g / cm ³ or more der is, the maximum thermal shrinkage stress of the organic fiber cord of the polyketone fiber comprising at least 50 wt% or more is in the range of 0.1~1.8cN / dtex, and 0.99 ° C. of the polyketone fiber A pneumatic tire having a heat shrinkage ratio in the range of 1% to 5% during dry heat treatment for 30 minutes .   The pneumatic tire according to claim 1, wherein in the polyketone fiber, the tensile strength of the raw yarn is 10 cN / dtex or more and the elastic modulus is 200 cN / dtex or more.

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