JP4950516B2 - Heavy duty pneumatic radial tire - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a heavy duty pneumatic radial tire, and more particularly, a heavy load that is reduced in weight, improved in high-speed durability using organic fibers having excellent mechanical characteristics and high heat shrinkage characteristics, and improved handling stability. The present invention relates to a heavy duty pneumatic radial tire.

In the conventional carcass of a pneumatic tire, organic fiber cords such as rayon, nylon, and polyester are generally used as reinforcing cords. However, since these organic fiber cords have low initial tensile resistance, a tire using the cord for a carcass may be stretched and deformed during use of the tire. Therefore, such a tire has a possibility that running performance may be lowered and is difficult to use under severe conditions such as ultra high speed.
In addition, a cord made of polyketone fiber is known as a cord having a high initial tensile resistance, and it is known that it has a higher melting point and higher strength than conventional polyolefin fibers, and takes advantage of these excellent physical properties. It is expected to be used as a rubber reinforcing material for industrial materials, tires, belts and hoses.
In particular, pneumatic radius tires for light trucks and trucks / buses generally use steel cords as carcass cords, and therefore the tire weight is high.
In recent years, tire weight reduction has been strongly demanded especially from the viewpoint of environmental protection, and high-strength organic fibers that are lighter in weight than steel cords have attracted attention. Tires with polyketone fiber cords applied to carcass have high load durability. And steering stability are improved in a well-balanced manner (see, for example, Patent Documents 1 and 2). Recently, polyketone fibers having high heat shrinkage stress have been developed (for example, see Patent Document 3).

However, when a polyketone fiber having a high heat shrinkage stress is used, a tire having excellent characteristics as described above can be obtained, but on the other hand, the cord is significantly shrunk due to heating during tire manufacture, and the resulting tire shape is disturbed. In heavy-duty tires that deteriorate uniformity and require high durability, there is a concern that tire durability and steering stability may decrease.
In particular, when an organic fiber material is used as a rubber reinforcing material, the fiber is usually twisted and then an adhesive is applied to embed it in the rubber material as a woven fabric.
Recently, a technique related to a cocoon-shaped woven fabric using a polyketone cord as a warp has been disclosed (see, for example, Patent Document 4). (A) “A cord made of polyketone fiber and a polyketone fiber cord has a small friction coefficient, When used, slippage occurs between the wefts and the warp driving interval becomes non-uniform, so-called “missing” tends to occur. “(B)“ The cord made of polyketone fiber and polyketone fiber cord having high strength and high elasticity has high heat shrinkage stress, and the warp fabric is distorted by the heat shrinkage after weaving, and the flatness is impaired. ” As a means for solving this problem, increasing the fiber-to-fiber static friction coefficient (μs) of warp and weft is disclosed.

In addition, Patent Document 4 states that “they pass through a heat treatment step during application of an adhesive and rubber vulcanization during the manufacture of a koji fabric, which is mainly used for a rubber reinforcing material. The cords and strands made of a material exhibit very strong heat shrinkage stress, and are susceptible to wrinkle deformation and distortion of the molded product. For this reason, cords and strands made of polyketone fibers are preferably low in heat shrinkage stress. ing.
However, there is an increasing need to develop high-performance tires that are excellent in high-speed durability and handling stability along with the weight reduction of tires, and overcoming the above problems, polyketone fiber cords having very strong heat shrinkage stress Development of a technique for applying the polyketone fiber to a belt cord utilizing the characteristics has become necessary.

JP 2000-190705 A JP 2002-307908 A JP 2004-218189 A JP 2003-49339 A

  Under such circumstances, the present invention achieves a reduction in weight and a high-speed tire that suppresses excessive tire deformation and tire protrusion due to temperature rise using organic fibers having excellent mechanical properties and high heat shrinkage properties. It is an object of the present invention to provide a heavy-duty pneumatic radial tire with improved durability and handling stability.

［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、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上記（１）〜（４）の重荷重用空気入りラジアルタイヤ、
（６） 前記式（Ｉ）中のＡがエチレン基である上記（５）の重荷重用空気入りラジアルタイヤ、
（７） 前記ポリケトン繊維を少なくとも５０質量％コードの下記式（II）で定義される下撚り係数Ｎ₁が０．３５〜０．７０、下記式（III）で定義される上撚り係数Ｎ₂が、０．５０〜０．９５である上記（１）〜（７）の重荷重用空気入りラジアルタイヤ、
Ｎ₁＝ｎ₁×（０．１２５×Ｄ₁／ρ）^1/2×１０^-3 ・・・ （II）
Ｎ₂＝ｎ₂×（０．１２５×Ｄ₂／ρ）^1/2×１０^-3 ・・・ （III）
［式（II）及び（III）において、ｎ₁は下撚り数（回／１０ｃｍ）；ｎ₂は上撚り数（回／１０ｃｍ）；Ｄ₁は下撚り糸のｄｔｅｘ；Ｄ₂はトータルｄｔｅｘ；ρは上記ポリケトンコードの比重（ｇ／ｃｍ³）である。］
を提供するものである。 As a result of intensive studies to achieve the above object, the present inventor used a polyketone fiber cord having a maximum heat shrinkage stress in a specific range as a carcass cord of a radial tire, and in a form substantially orthogonal to the carcass cord. It has been found that the above problem can be solved by removing the weft cords arranged inside the tire. The present invention has been completed based on this finding.
That is, the present invention
(1) A pair of bead cores, a carcass layer including at least a carcass cord fixed to the bead core, an inner liner layer disposed on the inner side in the tire radial direction of the carcass layer, and a tire radius of a crown portion of the carcass layer A belt portion having at least two belt layers disposed on the outer side in the direction, a tread portion disposed on the outer side in the tire radial direction of the belt portion, and a pair of sidewall portions disposed on the left and right of the tread portion In the heavy load pneumatic radial tire, the carcass cord constituting the carcass layer includes at least 50 mass% of polyketone fiber, and the maximum heat shrinkage stress of the cord is 0.1 to 1.8 cN / dtex. And there is substantially no weft cord arranged inside the tire in a shape substantially perpendicular to the carcass cord. Heavy duty pneumatic radial tires,
(2) Tensile strength of polyketone fiber yarn contained in at least 50% by mass in the carcass cord is 10 cN / dtex or more, an elastic modulus is 200 cN / dtex or more, and a cord after adhesive treatment (Dip treatment) at 150 ° C. The pneumatic radial tire for heavy loads as described in (1) above, wherein the thermal shrinkage rate during dry heat treatment is 1 to 5%
(3) The heavy-duty pneumatic radial tire according to (1) or (2), wherein the minimum value of the interval (gap) between adjacent carcass cords is 0.4 mm,
(4) The heavy-duty pneumatic radial tire according to (1) to (3) above, wherein the fineness of the carcass cord is 3000 to 17000 dtex, and the elongation at 19.8 mN per 1 dtex of the cord is less than 5.0%,
(5) The polyketone constituting the polyketone fiber is represented by the following general formula (I)

[In the formula, A is a portion derived from an unsaturated compound polymerized by an unsaturated bond, and may be the same or different in the repeating unit]. 4) Heavy duty pneumatic radial tire,
(6) The heavy-duty pneumatic radial tire according to (5), wherein A in the formula (I) is an ethylene group,
(7) The lower twist coefficient N ₁ defined by the following formula (II) of at least 50% by mass of the polyketone fiber is 0.35 to 0.70, and the upper twist coefficient N ₂ defined by the following formula (III) Is a heavy-duty pneumatic radial tire according to the above (1) to (7), which is 0.50 to 0.95,
N ₁ = n ₁ × (0.125 × D ₁ / ρ) ^1/2 × 10 ⁻³ (II)
N ₂ = n ₂ × (0.125 × D ₂ / ρ) ^1/2 × 10 ⁻³ (III)
[In formulas (II) and (III), n ₁ is the number of twists (times / 10 cm); n ₂ is the number of twists (times / 10 cm); D ₁ is the dtex of the twisted yarn; D ₂ is the total dtex; ρ Is the specific gravity (g / cm ³ ) of the polyketone cord. ]
Is to provide.

  High-speed durability that suppresses tire protrusion and excessive deformation of the tire due to temperature rise using organic fibers containing at least 50% by mass of polyketone fiber having excellent mechanical properties and high heat shrinkage properties while reducing weight. A heavy-duty pneumatic radial tire with improved handling stability can be provided.

  First, in the heavy-duty pneumatic radial tire of the present invention, the carcass cord constituting the carcass layer includes at least 50% by mass of polyketone fibers, and the maximum heat shrinkage stress of the cord is 0.1 to 1.8 cN / dtex. In addition, it is necessary that there is substantially no weft cord arranged inside the tire in a shape substantially orthogonal to the carcass cord.

  In the present invention, the carcass cord constituting the carcass layer has high heat shrinkability, high strength, dimensional stability, heat resistance, and adhesiveness to rubber. It is necessary that at least 50% by mass of the fiber cord is polyketone fiber.

［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、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とが好ましい。
本発明に用いられるポリケトン繊維コードの原料であるポリケトンは、上記式（Ｉ）で表される繰り返し単位から実質的になるポリケトンが好ましい。また、該ポリケトンの中でも、繰り返し単位の９７モル％以上が１−オキソトリメチレン［−ＣＨ₂−ＣＨ₂−ＣＯ−］であるポリケトンが好ましく、９９モル％以上が１−オキソトリメチレンであるポリケトンがさらに好ましく、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。繰り返し単位中の１−オキソトリメチレンの割合が高いほど分子鎖の規則性が向上し、高結晶性で高配向度の繊維が得られる。 The polyketone constituting the polyketone fiber is represented by the following general formula (I)

[Wherein A is a portion derived from an unsaturated compound polymerized by an unsaturated bond, and may be the same or different in the repeating unit], and preferably substantially consists of a repeating unit.
The polyketone which is a raw material of the polyketone fiber cord used in the present invention is preferably a polyketone substantially consisting of the repeating unit represented by the above formula (I). 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. As the proportion of 1-oxotrimethylene in the repeating unit is higher, the regularity of the molecular chain is improved, and a fiber with high crystallinity and high degree of orientation can be obtained.

  The polyketone, which is the raw material of the polyketone fiber cord, may be partially bonded to each other and from the unsaturated compound, but the portion derived from the unsaturated compound and the ketone group are alternately arranged. The ratio is preferably 90% by mass or more, more preferably 97% by mass or more, and most preferably 100% by mass.

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

  As a method for fiberizing a polyketone obtained by a conventional method, (1) after preventing undrawn yarn, it is subjected to multistage hot drawing, and drawn at a specific temperature and magnification in the final drawing step of the multistage hot drawing. A method and (2) a method of performing unstretched yarn spinning, followed by heat stretching, and rapid cooling while applying high tension to the fiber after completion of the heat stretching are preferred. 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 hexafluorooisopropanol and m-cresol as described in JP-T-505344, WO 99/18143, WO 00/09611, JP 2001-164422, A wet spinning method using an aqueous solution of zinc salt, calcium salt, thiocyanate, iron salt or the like as described in JP-A Nos. 2004-218189 and 2004-285221 is preferable.

Further, as a method for drawing the obtained undrawn yarn, a hot drawing method in which the undrawn yarn is drawn by heating to a temperature higher than the glass transition temperature of the undrawn yarn is preferable. In the above method (2), it may be performed in one stage, but it is preferably performed 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 superheat plate, etc. 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 the polyketone fiber is fiberized by the method (1) above, the temperature in the final drawing step of the multistage hot drawing is in the range of 110 ° C. to (the drawing temperature of the drawing step one step before the final drawing step −3 ° C.). In addition, the draw ratio in the final drawing step of multi-stage heat drawing is such that when polyketone fiberization is carried out by the method of (2) above, the tension applied to the fiber after completion of heat drawing is 0.5 to 4 cN / dtex. The range is preferable, and the cooling rate in the rapid cooling is preferably 30 ° C./second or more, and 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 preferably has a crystal structure with a crystallinity of 50 to 90% and a crystal orientation of 95% or more. When the degree of crystallinity is less than 50%, the fiber structure is not sufficiently formed and sufficient strength cannot be obtained, and the shrinkage property and dimensional stability during heating may be unstable. For this reason, the crystallinity is preferably 50 to 90%, more preferably 60 to 85%.

  By cording the polyketone fiber cord obtained as described above, a cord / rubber composite used in the carcass ply layer can be obtained. Here, there is no restriction | limiting in particular as coating rubber of a polyketone fiber cord, The coating rubber used for the conventional belt and the carcass reinforcement layer can be used. Prior to rubberizing the polyketone fiber cord, an adhesive treatment may be applied to the polyketone fiber cord to improve the adhesion to the coating rubber.

The heat shrinkage stress of the polyketone fiber cord thus obtained is about 4 times that of a conventional fiber material such as nylon 6, 6, and 10 times that of polyethylene terephthalate.
Also, in order to make the most effective use of the high heat shrinkage characteristics of polyketone fibers, the processing temperature during processing and the temperature of the molded product during use are the temperature that indicates the maximum heat shrinkage stress (hereinafter referred to as the maximum heat shrinkage temperature). It is desirable that the temperature be close.
When used as a fiber material for reinforcing rubber such as tire cords and belts, the processing temperature such as the RFL treatment temperature and vulcanization temperature is 100 to 250 ° C, and the materials such as tires and belts are repeatedly used and rotated at high speed. The maximum heat shrinkage temperature is in the range of 100 to 250 ° C., more preferably 150 to 240 ° C., because the temperature when heat is generated becomes as high as 100 to 200 ° C.

Examples of the type of the carcass cord according to the present invention include (a) a cord composed only of polyketone fibers, and (b) a cord obtained by mixing or twisting polyketone fibers and fibers other than polyketone fibers. It is preferable that at least 50% by mass of the polyketone fiber is contained in one cord. Polyketone fibers are used at least 50% by weight, preferably at least 75% by weight, more preferably at least 90% by weight, and most preferably 100% by weight in the total warp in the knit fabric.
By setting the ratio of the polyketone fiber within the above range, excellent heat shrinkability, strength, dimensional stability, heat resistance, adhesion to rubber, and the like of the cord can be obtained.

  The fiber other than the polyketone fiber is not particularly limited as long as the ratio is less than 50% by mass, and known fibers such as polyamide fiber, polyester fiber, rayon fiber, and aramid fiber are used depending on the application and purpose. When the amount of fibers other than polyketone fibers exceeds 50% by mass, for example, in the case of warp made of polyester fiber or polyamide fiber, the strength and dimensional stability are impaired, and in the case of warp made of rayon fiber, the strength is greatly impaired. In the case of warp made of aramid fibers, the adhesiveness with rubber is greatly impaired.

  Furthermore, in the present invention, it is necessary that the maximum heat shrinkage stress of the cord containing at least 50% by mass of polyketone fiber is in the range of 0.1 to 1.8 cN / dtex. Preferably it is 0.4-1.6 cN / dtex, More preferably, it is 0.6-1.4 cN / dtex. By setting the maximum heat shrinkage stress within the above range, the tire has a stable shape that suppresses the reduction in carcass cord alignment efficiency due to heating during tire manufacture, ensures sufficient tire strength, and suppresses significant shrinkage of the carcass cord. Can be obtained.

In the pneumatic radial tire of the present invention, it is important that there is no weft cord arranged inside the tire in a shape substantially orthogonal to the carcass cord.
A cord warp containing at least 50% by weight of polyketone fiber having high heat shrinkage stress, high strength and high elastic modulus, and by removing the weft from the kite fabric having the weft, after being rubberized as the kite fabric, by heating during tire manufacture A pneumatic radial tire having improved tire performance and improved high-speed durability and steering stability without causing disturbance of the carcass cord arrangement derived from the weft due to the shrinkage of the polyketone fiber. Obtainable.
Specifically, wefts are removed before weaving with a weft processing device for textile cords disclosed in Japanese Patent Laid-Open No. 5-269890, or coating rubber is coated on one or a plurality of bonded cords. By arranging the cord-rubber composite material thus prepared on a tire molding machine, it is possible to manufacture a tire that is substantially free of the carcass ply weft.

In the present invention, it is preferable that the heat shrinkage stress of the polyketone fiber cord constituting the carcass ply layer is reversibly and repeatedly expressed corresponding to the tire temperature.
When the heat shrinkage stress of the polyketone fiber cord used in the present invention exceeds 110 ° C., it rapidly increases. As the tire temperature rises at high speeds, the heat shrinkage stress increases, preventing the shoulder from sticking out at high speeds and showing excellent handling stability at high speeds. That is, the heat shrinkage stress increases as the tire temperature rises.
The shrinkage of the polyketone fiber cord returns as the cord reaches room temperature, and reappears when the cord reaches a high temperature. This phenomenon occurs reversibly and is repeated every time the tire is driven.

  Moreover, in the heavy duty pneumatic radial tire of the present invention, the tensile strength of the polyketone fiber yarn contained in the carcass cord forming the carcass layer is at least 10 cN / dtex, more preferably 15 cN / dtex or more. Preferably there is. By setting the tensile strength within the above range, sufficient strength as a tire can be ensured. Although there is no restriction | limiting in particular about the upper limit of tensile strength, Usually, it is about 18 cN / dtex.

  The elastic modulus of the polyketone fiber base yarn contained in at least 50% by mass in the carcass cord is preferably 200 cN / dtex or more, more preferably 250 cN / dtex or more. By setting the elastic modulus within the above range, sufficient shape retention as a tire can be ensured. Although there is no restriction | limiting in particular about the upper limit of an elasticity modulus, Usually, it is about 350 cN / dtex.

  Furthermore, the heat shrinkage rate of the carcass cord after the adhesive treatment (Dip treatment) containing at least 50% by mass of the polyketone fiber at 150 ° C. for 30 minutes during the dry heat treatment is in the range of 1% to 5%, more preferably 2 It is preferable that it exists in the range of% -4%. By setting the heat shrinkage rate within the above range, it is possible to secure the alignment efficiency and the tire strength by heating at the time of manufacturing the tire, and to obtain a stable tire shape.

The polyketone fiber cord can be made by twisting filaments made of the polyketone, and the number of filament bundles to be twisted is not particularly limited, but a filament bundle having a fineness of 1000 to 8000 dtex is twisted by two or three. A code consisting of a combination is preferred. For example, it is possible to obtain a twisted yarn cord by applying a lower twist to the filament bundle, then combining two or three of them, and applying an upper twist in the opposite direction.
In the present invention, the cord containing at least 50% by mass of the polyketone fiber forming the carcass layer has a fineness of 3000 to 17000 dtex, preferably 6000 to 12000 dtex. By setting the fineness within the above range, the carcass strength necessary for a heavy-duty pneumatic radial tire can be ensured, and separation from the carcass end due to an excessively large cord diameter can be suppressed.
Further, it is desirable that the elongation at 19.8 mN per 1 dtex of the cord is less than 5.0%, more preferably less than 3.5%. By setting the elongation rate at 19.8 mN per 1 dtex of the cord within the above range, it is possible to suppress tire growth.

Furthermore, in the present invention, the polyketone fiber yarn is subjected to a lower twist with a lower twist coefficient N ₁ defined by the above general formula (II), and then a plurality of the lower twist yarns are aligned to reverse the lower twist. It consists of a twisted yarn in which the upper twist coefficient N ₂ defined by the general formula (III) is applied in the direction, and the lower twist coefficient N ₁ defined by the formula (II) of the polyketone fiber cord is 0.35 0.70, coefficient N ₂ twists defined by formula (III) is preferably in the range of 0.50 to 0.95.

  In the cord used in the present invention, a cord excellent in fatigue resistance, tensile rigidity and cord strength can be obtained by using a polyketone fiber cord in which the lower twist coefficient and the upper twist coefficient are set in the above ranges. Thus, a carcass ply cord in which the strength and fatigue resistance of the cord are highly balanced can be obtained.

  In the present invention, it is desirable that the minimum value of the distance between the carcass cord and the adjacent carcass cord is 0.4 mm or more, more preferably 0.6 mm or more. Usually, the distance between the carcass cord and the adjacent carcass cord is the smallest adjacent to the bead core (particularly the portion affected by the rim pressure). There is a concern that the adhesive strength between the cord and the coating rubber due to the friction and heat generation is lowered, and the drum durability is lowered.

  As described above, in the heavy-duty pneumatic radial tire of the present invention, the cord containing at least 50% by mass of the polyketone fiber is used for the carcass layer of the tire. Since the polyketone fiber cord has a high balance between the strength and fatigue resistance of the cord and has a high heat shrinkage stress at a high temperature, the cord is used for a carcass portion of a tire, thereby enabling high-speed running. Suppresses the shoulder protrusion, increases the rigidity of the tire side, and exhibits excellent handling stability at high speeds. Further, a heavy-duty pneumatic radial tire having improved tire performance and improved high-speed durability and steering stability without causing any disturbance in the carcass cord arrangement due to the substantial absence of wefts. Obtainable.

Next, embodiments of the tire of the present invention will be described with reference to the drawings. FIG. 1 is a left sectional view of a heavy duty pneumatic radial tire of the present invention. The tire shown in FIG. 1 includes a bead portion 1, a side portion 3, a tread portion 4, a carcass layer 5 that extends in a toroidal shape in a bead core 2 embedded in the bead portion 1, and a carcass layer 5. A belt 6 composed of at least two belt layers disposed on the outer side in the tire radial direction at the crown portion, and an inner liner layer 7 are disposed.
Here, in the present invention, a cord including at least 50 parts by mass of the above-described polyketone fiber is applied to a carcass cord (not shown) embedded in the carcass layer 5.

EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to the following Example at all. Various measurement methods were performed based on the following methods.
<Code property evaluation>
1. Tensile strength and tensile modulus Measured according to JIS-L-1013. As the tensile elastic modulus, an initial elastic modulus value calculated from a load at an elongation of 0.1% and a load at an elongation of 0.2% was adopted.
2. Dry heat shrinkage rate Dry heat treatment was performed in an oven at 150 ° C. for 30 minutes, and the fiber length before and after the heat treatment was measured by applying a load of 1/30 (cN / dtex) and obtained by the following equation. Dry heat shrinkage rate (%) = (Lb−La) / Lb × 100 (where Lb is the fiber length before heat treatment, and La is the fiber length after heat treatment)
3. Maximum heat shrinkage stress Adhesive treatment (Dip treatment), a sample obtained by fixing a polyketone fiber cord before vulcanization to a length of 25 cm, is heated at a heating rate of 5 ° C / min, and the stress generated in the cord is measured. It was measured. It is a value obtained by reading the maximum heat shrinkage stress from the obtained temperature-stress curve.

<Tire performance evaluation>
1. Drum endurance test Drum conditions: Based on JATMA conditions, internal pressure 700 kPa, step load [maximum load x (66%, 84%, 100%, 110%) x 6 hours], tire durability with a drum tester at a speed of 65 km / h A sex test was conducted. The distance traveled until the tire broke down was measured and expressed as an index with the distance traveled by the conventional tire as 100. Higher values indicate better tire durability.

<Manufacture of polyketone fibers>
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 mass% was obtained.
This dope is heated to 80 ° C., filtered through a 20 μm sintered filter, passed through a 10 mm air gap from a 50-hole nozzle with a diameter of 0.10 mmφ kept at 80 ° C., and 5% by weight of zinc chloride. Was extruded at a rate of discharge of 2.5 cc / min into water at 18 ° C. containing a coagulated yarn while being drawn at a speed of 3.2 m / min.
Subsequently, the coagulated yarn was washed with an aqueous sulfuric acid solution having a concentration of 2% by weight and a temperature of 25 ° C., and further washed with water at 30 ° C., and then the coagulated yarn was wound at a speed of 3.2 m / min.
The solidified yarn was impregnated with IRGANOX 1098 (manufactured by Ciba Specialty Chemicals) and IRGANOX 1076 (manufactured by Ciba Specialty Chemicals) in an amount of 0.05% by weight (with respect to polyketone polymer), and then dried at 240 ° C. A finishing agent was applied to obtain an undrawn yarn.
As the finishing agent, 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 / The one having a composition of sodium stearyl sulfonate / sodium dioctyl phosphate = 30/30/10/5/23/1/1 (mass% ratio) was used.

The obtained undrawn yarn was drawn at 240 ° C. in the first stage, followed by the second stage at 258 ° C., the third stage at 268 ° C., the fourth stage at 272 ° C., and then the second stage at 200 ° C. The film was stretched five times at 1.08 times (stretching tension 1.8 cN / dtex) and wound with a winder. The total draw ratio from the undrawn yarn to the five-stage drawn yarn was 17.1 times.
This fiber had high physical properties of strength 15.6 cN / dtex, elongation 4.2%, and elastic modulus 347 cN / dtex.

Examples 1-4 and Comparative Examples 1-4
The cords having the respective cord structures shown in Table 1 were prepared from the polyketone fibers produced as described above and used as carcass cords.
<Production of sample tires (tire size 225 / 80R17.5)>
After the coating rubber covering the cord is insulated into the cord made of 100% by mass of the polyketone fiber, the obtained material is cut into a necessary width and arranged on the tire molding machine so as to be almost parallel at each position of the tire cross section. And one carcass layer was formed.
A one-ply tire was manufactured using the carcass layer. For the belt layer, three steel cord belts with a (1 × 6) × 0.30 mm structure were placed, and the tires obtained were subjected to an indoor drum test to determine the distance traveled until the failure of the conventional tire. Expressed as 100 as an index. The larger the value, the better the tire durability performance. The results are shown in Table 1.
The tire of the conventional example used a steel cord (1 × 3 + 9 × 0.175 mm layer twist structure) as a carcass cord. Except for the carcass layer, it is the same as the sample tire. The steel cord is brass plated to ensure adhesion with the carcass coating rubber.
In addition, the carcass cord of Comparative Example 1 was a woven fabric using polyketone fibers as warps. As for the weft, a spun yarn made of cotton was used. (Fineness: 420 dtex, Tensile strength: 250 g, Cutting elongation: 5.5%, Cord interval: 30 mm)

As is apparent from Table 1, the tire of Comparative Example 1 has inferior tire durability compared to the conventional example due to the disorder of the arrangement of the carcass cord because wefts are present in the carcass cord.
In the tire of Comparative Example 2, the distance (gap) between the carcass cords around the bead core is 0, and the tire durability is greatly reduced compared to the conventional example due to the separation around the bead.
Further, the tire of Comparative Example 3 has a large carcass cord diameter, separation from the ply end, and the decrease in tire durability is considerably larger than that of the conventional example. Further, tires having a small upper twist coefficient and a lower twist coefficient both show a decrease in tire durability like the tire of Comparative Example 3.
On the other hand, it can be seen that the tire durability of the tires of the present invention shown in Examples 1 to 3 is significantly improved compared to the conventional example. Further, although the tire durability of the tire of Example 4 is equivalent to that of the conventional example, the tire durability is improved in comparison with the tire of Comparative Example 1 in which wefts are present in the carcass cord.

  According to the present invention, weight reduction and suppression of tire protrusion due to temperature rise and tire softening phenomenon using organic fibers containing at least 50% by mass of polyketone fibers having excellent mechanical properties and high heat shrinkage properties. It is possible to provide a heavy-duty pneumatic radial tire with improved high-speed durability and steering stability. This is particularly effective for heavy duty tires for light trucks.

It is a left sectional view showing one embodiment of the pneumatic tire of the present invention.

Explanation of symbols

1 Bead part 2 Bead core 3 Side part 4 Tread part 5 Carcass layer 6 Belt 7 Inner liner layer

Claims (7)

A pair of bead cores, a carcass layer including at least a carcass cord fixed to the bead core, an inner liner layer disposed on the inner side in the tire radial direction of the carcass layer, and on the outer side in the tire radial direction of the crown portion of the carcass layer A belt portion having at least two belt layers disposed; a tread portion disposed on the outer side in the tire radial direction of the belt portion; and a pair of sidewall portions disposed on the left and right sides of the tread portion. In the heavy-duty pneumatic radial tire, the carcass cord constituting the carcass layer includes at least 50 mass% of polyketone fibers, and the maximum heat shrinkage stress of the cord is 0.6 to 1.8 cN / dtex, and There is substantially no weft cord arranged inside the tire in a shape substantially orthogonal to the carcass cord. Pneumatic radial tire for heavy loads.   As a cord after the tensile strength of the polyketone fiber yarn contained at least 50% by mass in the carcass cord is 10 cN / dtex or more, the elastic modulus is 200 cN / dtex or more, and the adhesive treatment (Dip treatment) at 150 ° C. for 30 minutes. The pneumatic radial tire for heavy loads according to claim 1, wherein the thermal shrinkage rate during dry heat treatment is 1 to 5%.   The heavy-duty pneumatic radial tire according to claim 1 or 2, wherein a minimum value of an interval (gap) between adjacent carcass cords is 0.4 mm.   The pneumatic radial tire for heavy loads according to any one of claims 1 to 3, wherein the fineness of the carcass cord is 3000 to 17000 dtex, and the elongation at 19.8 mN per dtex of the cord is less than 5.0%. The polyketone constituting the polyketone fiber is represented by the following general formula (I)

[Wherein A is a portion derived from an unsaturated compound polymerized by an unsaturated bond, and may be the same or different in the repeating unit]. A heavy-duty pneumatic radial tire according to any one of the above.   The heavy-duty pneumatic radial tire according to claim 5, wherein A in the formula (I) is an ethylene group. The polyketone fiber has a lower twist coefficient N ₁ defined by the following formula (II) of at least 50 mass% cord of 0.35 to 0.70, and an upper twist coefficient N ₂ defined by the following formula (III) of 0. The heavy-duty pneumatic radial tire according to any one of claims 1 to 6, wherein the pneumatic radial tire is 50 to 0.95.
N ₁ = n ₁ × (0.125 × D ₁ / ρ) ^1/2 × 10 ⁻³ (II)
N ₂ = n ₂ × (0.125 × D ₂ / ρ) ^1/2 × 10 ⁻³ (III)
[In formulas (II) and (III), n ₁ is the number of twists (times / 10 cm); n ₂ is the number of twists (times / 10 cm); D ₁ is the dtex of the twisted yarn; D ₂ is the total dtex; Is the specific gravity (g / cm ³ ) of the polyketone cord. ]

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