JP2007283898A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve uniformity of a pneumatic tire applying a cord containing poly-ketone fiber having high strength and a high elastic modulus to it as a reinforcing cord of a belt layer or a belt protective layer. <P>SOLUTION: A carcass ply is reinforced by a cord made of twine finally twisted in a final twist coefficient N1 defined by an expression II in the opposite direction of primary twist by doubling a plurality of primary twisting yarns after primarily twisting fiber original yarn containing at least 50 mass% of the poly-ketone fiber, the final twist coefficient N1 and a primary twist coefficient N2 of which satisfy an expression III, the primary twist coefficient N2 of which satisfies an expression IV and the maximum heat contracting stress of which is in an area of 0.1 to 1.8 cN/dtex. The expression I is expressed as N1=nl×√(0.125×D1/ρ)×10<SP>-3</SP>, the expression II is expressed as N2=n2×√(0.125×D2/ρ)×10<SP>-3</SP>, the expression III is expressed as 0.81<N2/N1≤√(D2/D1), and the expression IV is expressed as 0.6≤N2≤1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire (hereinafter, also simply referred to as “tire”), and more specifically, a cord including polyketone fibers having high strength and high elastic modulus is applied as a reinforcing cord for a carcass layer, a belt layer, or a belt protective layer. The present invention relates to a pneumatic tire that exhibits excellent uniformity with little disturbance of the reinforcing cord during heating and expansion / contraction during manufacture of the tire.

  As a material that can replace conventional organic fiber materials, carbon monoxide and olefins such as ethylene and propene are polymerized using palladium or nickel as a catalyst, so that carbon monoxide and olefin are almost completely alternately copolymerized aliphatic. It has been found that a polyketone can be obtained (Non-patent Document 1), and today, research on making such a polyketone into a fiber is being conducted.

  Polyketone fibers are known to have a higher melting point than conventional polyolefin fibers, and have high strength and high elastic modulus. Utilizing these excellent physical properties, they are used for industrial materials, especially tires, belts, hoses. As such, it is expected to be developed as a rubber reinforcing material. From this viewpoint, various techniques have been proposed for polyketone fibers.

  For example, Patent Documents 1 to 9 disclose technologies related to polyketone fibers having high strength and high elastic modulus, respectively.

  On the other hand, Patent Document 10 discloses a technique regarding the number of lower twists, the number of upper twists, and the upper twist coefficient when an organic heat-shrinkable fiber cord is used for a carcass.

In addition, Patent Document 11 discloses an attempt to obtain a twisted yarn cord having a high utilization rate against raw yarn using polyketone fibers. Further, in Patent Document 12, a specific polyketone fiber is used as a raw yarn of an organic fiber cord, and further, the balance between the lower twist and the upper twist of the cord is defined within a specific range, whereby the strength and resistance of the organic fiber cord are determined. It has been reported that fatigue can be highly balanced. Furthermore, Patent Document 13 reports that, as a tire carcass cord, a double twisted yarn obtained by applying a lower twist of a predetermined twisting coefficient to an organic fiber yarn and then applying an upper twist in the opposite direction is reported. .
JP-A-1-124617 JP-A-2-112413 Japanese National Patent Publication No. 4-505344 JP-A-4-228613 Japanese National Patent Publication No. 7-508317 Japanese National Patent Publication No. 8-507328 US Pat. No. 5,955,019 WO99 / 18143 pamphlet International Publication No. 00/09611 Pamphlet etc. JP 2003-252005 A JP 2004-244742 A JP 2004-308024 A Japanese Patent No. 3118152 Industrial materials (December issue, page 5, 1997)

  However, it has been found that when the polyketone fiber cord disclosed in the above prior art is used as a tire reinforcing cord, the following problems may occur.

  That is, a cord made of polyketone fiber having high strength and high elastic modulus generates torsion torque when the cord is expanded or contracted due to heat shrinkage of the polyketone fiber, and this torsion torque adversely affects the treat or tire properties. It has been found.

  In the prior art, there is no description or suggestion regarding such problems, and moreover, means for solving these problems, i.e., cords containing polyketone fibers having high strength and high elastic modulus are used as tire reinforcing cords, and There is no description about obtaining a pneumatic tire excellent in uniformity.

  Accordingly, an object of the present invention is to increase the uniformity of a pneumatic tire in which a cord including polyketone fibers having high strength and high elastic modulus is applied as a reinforcing cord for a carcass layer, a belt layer, or a belt protective layer.

  As a result of intensive studies to solve the above problems, the present inventor has made the cords containing polyketone fibers having high strength and high elastic modulus to satisfy predetermined conditions in the carcass layer, belt layer or belt protective layer, respectively. It has been found that the above object can be achieved by application, and the present invention has been completed.

That is, the pneumatic tire of the present invention includes a tread portion, a pair of sidewall portions extending inward in the tire radial direction from both ends thereof, and a pair of bead portions positioned at the inner ends of the sidewall portions, A carcass layer composed of at least one carcass ply extending in a toroidal shape between a pair of bead cores embedded in the bead portion, and at least one belt ply disposed on the radially outer side of the crown portion of the carcass. In a pneumatic tire having a belt layer,
After at least one carcass ply of the carcass layer is applied to a fiber yarn containing at least 50% by mass or more of polyketone fiber with a lower twisting coefficient N1 defined by the following formula (I), the lower twisted yarn It consists of a twisted yarn that is twisted with an upper twist coefficient N2 defined by the following formula (II) in a direction opposite to the lower twist by aligning a plurality of yarns, and the lower twist coefficient N1 and the upper twist coefficient N2 are as follows: It is characterized in that it satisfies the formula (III), the upper twist coefficient N2 satisfies the following formula (IV), and is further reinforced by a cord having a maximum heat shrinkage stress in the range of 0.1 to 1.8 cN / dtex. It is what.
N1 = n1 × √ (0.125 × D1 / ρ) × 10 ⁻³ (I)
N2 = n2 × √ (0.125 × D2 / ρ) × 10 ⁻³ (II)
0.81 <N2 / N1 ≦ √ (D2 / D1) (III)
0.6 ≦ N2 ≦ 1 (IV)
(In the above formula, n1 is the number of lower twists (times / 10 cm), n2 is the number of upper twists (times / 10 cm), D1 is the indicated decitex number of the lower twisted yarn, D2 is the total indicated decitex number, and ρ is the specific gravity of the polyketone fiber. (G / cm ³ )

Another pneumatic tire of the present invention includes a tread portion, a pair of sidewall portions extending inward in the tire radial direction from both ends thereof, and a pair of bead portions positioned at the inner ends of the sidewall portions, A carcass layer composed of at least one carcass ply extending in a toroidal shape between a pair of bead cores embedded in the bead portion, and at least one belt ply disposed on the radially outer side of the crown portion of the carcass. In a pneumatic tire having a belt layer,
After at least one belt ply of the belt layer applies a lower twist to a fiber yarn containing at least 50% by mass of polyketone fiber with a lower twist coefficient N1 defined by the following formula (I), the lower twist yarn It is made of a twisted yarn with an upper twist coefficient N2 defined by the following formula (II) in a direction opposite to the lower twist by aligning a plurality of yarns, and the lower twist coefficient N1 and the upper twist coefficient N2 are as follows: The upper twist coefficient N2 satisfies the following formula (VI) that satisfies the formula (V), and is further reinforced by a cord having a maximum heat shrinkage stress in the range of 0.1 to 1.8 cN / dtex. It is what.
N1 = n1 × √ (0.125 × D1 / ρ) × 10 ⁻³ (I)
N2 = n2 × √ (0.125 × D2 / ρ) × 10 ⁻³ (II)
0.45 <N2 / N1 ≦ √ (D2 / D1) (V)
0.13 ≦ N2 ≦ 0.9 (VI)
(Where n1 is the number of lower twists (times / 10 cm), n2 is the number of upper twists (times / 10 cm), D1 is the indicated decitex number of the lower twisted yarn, D2 is the total indicated decitex number, and ρ is the specific gravity of the polyketone fiber. (G / cm ³ )

Still another pneumatic tire according to the present invention includes a tread portion, a pair of sidewall portions extending inward in the tire radial direction from both ends thereof, and a pair of bead portions positioned at the inner ends of the sidewall portions. A carcass layer composed of at least one carcass ply extending in a toroidal shape between a pair of bead cores embedded in the bead portion, and arranged on the outer side in the radial direction of the crown portion of the carcass, and from at least one belt ply A pneumatic tire having a belt layer and at least one belt protective layer disposed on the outer side in the tire radial direction of the belt layer,
The belt protective layer is applied to a fiber yarn containing at least 50% by mass of polyketone fiber with a lower twist coefficient N1 defined by the following formula (I), and then the plurality of lower twist yarns are aligned. It consists of a twisted yarn with an upper twist coefficient N2 defined by the following formula (II) in the opposite direction to the lower twist, and the lower twist coefficient N1 and the upper twist coefficient N2 satisfy the following formula (V) The upper twist coefficient N2 satisfies the following formula (VI), and the maximum heat shrinkage stress is reinforced by a cord in the range of 0.1 to 1.8 cN / dtex.
N1 = n1 × √ (0.125 × D1 / ρ) × 10 ⁻³ (I)
N2 = n2 × √ (0.125 × D2 / ρ) × 10 ⁻³ (II)
0.45 <N2 / N1 ≦ √ (D2 / D1) (V)
0.13 ≦ N2 ≦ 0.9 (VI)
(Where n1 is the number of lower twists (times / 10 cm), n2 is the number of upper twists (times / 10 cm), D1 is the indicated decitex number of the lower twisted yarn, D2 is the total indicated decitex number, and ρ is the specific gravity of the polyketone fiber. (G / cm ³ )

  In the tire according to the present invention, the polyketone fiber has a tensile strength of 10 cN / dtex or more, an elastic modulus of 200 cN / dtex or more, and a heat shrinkage ratio in the range of 1% to 5% at 150 ° C. × 30 minutes in the dry heat treatment. Is preferably used.

In the present invention, for the belt ply or the belt protective layer, the ratio (N2 / N1) between the lower twist coefficient N1 and the upper twist coefficient N2 of the cord satisfies the following formula (VII), and the upper twist coefficient N2 Preferably satisfies the following formula (VIII).
0.81 <N2 / N1 <1.4 (VII)
0.36 ≦ N2 ≦ 0.84 (VIII)

  According to the present invention, even when a cord including polyketone fiber having high strength and high elastic modulus is applied as a reinforcing cord for a carcass layer, a belt layer, or a belt protective layer, the heating or expansion / contraction at the time of manufacturing the tire It is possible to provide a pneumatic tire with less disturbance of the reinforcing cord and showing excellent uniformity.

Hereinafter, specific embodiments of the present invention will be described in detail.
(First embodiment)
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 5 composed of a single carcass ply (in the illustrated example) is extended between a pair of bead cores 4 embedded in the bead portion 3 in a toroidal shape. Here, the code | symbol 8 is a bead filler. Further, the tire 10 is disposed on the outer side in the radial direction of the crown portion of the carcass layer 5, 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 belt protective layer 7 (in the illustrated example).

In the present embodiment, the carcass ply of the carcass layer 5 in the illustrated tire 10 uses a fiber yarn containing at least 50% by mass or more of polyketone fibers, and the lower twist defined by the above formulas (I) and (II). The coefficient N1 and the upper twist coefficient N2 satisfy the formula (III), the upper twist coefficient N2 satisfies the formula (IV), and the maximum heat shrinkage stress is in the range of 0.1 to 1.8 cN / dtex. It is important to be reinforced by a certain cord (hereinafter referred to as “carcass ply cord”). Thereby, the uniformity of the tire can be increased.
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 cord of the carcass layer 5 desirably contains at least 50% by mass of polyketone fibers, 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.

  The maximum heat shrinkage stress of the carcass ply cord 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. When the maximum heat shrinkage stress is less than 0.1 cN / dtex, the alignment efficiency by heating at the time of tire manufacture is remarkably lowered, and the strength as a tire becomes insufficient. 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.

  Further, the tensile strength of the polyketone fiber contained in the carcass ply cord 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 carcass ply cord, 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, shape retention as a tire is insufficient.

  Furthermore, as the polyketone fiber contained in the carcass ply cord, the heat shrinkage rate at 150 ° C. for 30 minutes during the dry heat treatment is preferably in the range of 1% to 5%, more preferably in the range of 2% to 4%. 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.

  Next, the ratio N2 / N1 of the lower twisting coefficient N1 and the upper twisting coefficient N2 of the carcass ply cord is greater than 0.81, √ (D2 / D1) or less, preferably greater than 0.9 and less than 1.4 It is desirable. When this ratio is 0.81 or less, the twist torque generated by the lower twist becomes excessive, and the cord properties become extremely unstable. On the other hand, when the value is larger than the value of √ (D2 / D1), the twisting torque generated by the lower twist becomes large, and the cord properties are also unstable.

  The upper twist coefficient N2 of the carcass ply cord is 0.6 or more and 1 or less, preferably 0.68 or more and 0.90 or less. When this value 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, if it is greater than 1, the cord properties are extremely unstable, so that the fatigue resistance is also lowered.

  In addition, a weft cord can be appropriately arranged inside the tire so as to be substantially orthogonal to the carcass ply cord. As such a weft cord, known organic fiber cords such as nylon, ester, rayon, polynosic, lyocell, vinylon, etc. A fiber cord can be appropriately employed. The distance between the cords is preferably 5 to 50 mm, more preferably 20 to 35 mm. When this distance is less than 5 mm, the productivity of the woven fabric is deteriorated. On the other hand, when it exceeds 50 mm, the properties of the woven fabric are deteriorated.

(Second embodiment)
In the second embodiment, at least one belt ply of the belt layer 6 in the illustrated tire 10 uses a fiber yarn containing at least 50% by mass or more of polyketone fibers, and the above formulas (I) and (II) ) And the upper twist coefficient N2 satisfy the above formula (V), the upper twist coefficient N2 satisfies the above formula (VI), and the maximum heat shrinkage stress is 0.1 to 1 .. It is important to be reinforced by a cord in the range of 8 cN / dtex (hereinafter referred to as “belt ply cord”). Thereby, the uniformity of the tire can be increased.
In the second embodiment as well, the belt protective layer 7 may be appropriately disposed as necessary.

  The belt ply cord of the belt layer 6 desirably contains at least 50% by mass of polyketone fibers, preferably 70% by mass or more, and more preferably 100% by mass. If it is less than 50% by mass, any of the strength, heat resistance, and adhesion to rubber as a tire will be insufficient.

  The maximum heat shrinkage stress of the belt ply cord 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. When the maximum heat shrinkage stress is less than 0.1 cN / dtex, the alignment efficiency by heating at the time of tire manufacture is remarkably lowered, and the strength as a tire becomes insufficient. 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 tensile strength of the polyketone fiber contained in the belt ply cord 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 belt ply cord, 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, shape retention as a tire is insufficient.

  Furthermore, as the polyketone fiber contained in the belt ply cord, the heat shrinkage rate during dry heat treatment at 150 ° C. for 30 minutes is preferably in the range of 1% to 5%, more preferably in the range of 2% to 4%. 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.

  Next, the ratio N2 / N1 of the lower twist coefficient N1 and the upper twist coefficient N2 of the belt ply cord is larger than 0.45, √ (D2 / D1) or less, preferably larger than 0.81 and smaller than 1.4. It is desirable. When this ratio is 0.45 or less, the twisting torque generated by the lower twist becomes excessive, and the cord properties become extremely unstable. On the other hand, when the value is larger than the value of √ (D2 / D1), the twisting torque generated by the lower twist becomes large, and the cord properties are also unstable.

  Further, the belt ply cord has an upper twist coefficient N2 of 0.13 to 0.9, preferably 0.36 to 0.84. When this value is less than 0.13, the fatigue resistance required for the belt ply cord is lowered, resulting in a problem that the tire durability is lowered. On the other hand, if it is larger than 0.9, the cord properties become extremely unstable, so that the fatigue resistance is also lowered.

  In addition, a weft cord can be appropriately disposed inside the tire so as to be substantially orthogonal to the belt ply cord. As such a weft cord, known organic fiber cords such as nylon, ester, rayon, polynosic, lyocell, vinylon, etc. A fiber cord can be appropriately employed. The distance between the cords is preferably 5 to 50 mm, more preferably 20 to 35 mm. When this distance is less than 5 mm, the productivity of the woven fabric is deteriorated. On the other hand, when it exceeds 50 mm, the properties of the woven fabric are deteriorated.

(This third embodiment)
In the third embodiment, the belt protective layer 7 is essential. The belt protective layer 7 is a cord / rubber protective layer disposed on the upper side of the belt layer 6, and improves the rigidity and handling stability at high speed by reducing the rigidity of the belt part, and reduces road noise. It is used as a method for controlling tire performance. In the illustrated example, there is one layer, but two or more layers may be provided, or they may be arranged only at the belt end.

  In the third embodiment, the belt protective layer 7 in the illustrated tire 10 has a lower twist coefficient N1 and an upper twist coefficient N2 defined by the formula (I) and the formula (II), and the formula (V). A cord that satisfies the above formula (VI) and has a maximum heat shrinkage stress in the range of 0.1 to 1.8 cN / dtex (hereinafter abbreviated as “belt protective layer cord”). It is important to be reinforced. Thereby, the uniformity of the tire can be increased.

  The belt protective layer cord desirably contains at least 50% by mass of polyketone fibers, preferably 70% by mass or more, and more preferably 100% by mass. If it is less than 50% by mass, any of the strength, heat resistance, and adhesion to rubber as a tire will be insufficient.

  The maximum heat shrinkage stress of the belt protective layer cord 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. When the maximum heat shrinkage stress is less than 0.1 cN / dtex, the alignment efficiency by heating at the time of tire manufacture is remarkably lowered, and the function as a belt protective layer becomes insufficient. 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 tensile strength of the polyketone fiber contained in the belt protective layer cord 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 belt protective layer cord, 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, shape retention as a tire is insufficient.

  Furthermore, as the polyketone fiber contained in the belt protective layer cord, the heat shrinkage rate during dry heat treatment at 150 ° C. for 30 minutes is preferably in the range of 1% to 5%, more preferably in the range of 2% to 4%. 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.

  Next, the ratio N2 / N1 of the lower twist coefficient N1 and the upper twist coefficient N2 of the belt protective layer cord is greater than 0.45 and not more than √ (D2 / D1), preferably greater than 0.81 and less than 1.4. It is desirable to be. When this ratio is 0.45 or less, the twisting torque generated by the lower twist becomes excessive, and the cord properties become extremely unstable. On the other hand, when the value is larger than the value of √ (D2 / D1), the twisting torque generated by the lower twist becomes large, and the cord properties are also unstable.

  Further, the upper twist coefficient N2 of the belt protective layer cord is 0.13 or more and 0.9 or less, preferably 0.36 or more and 0.84 or less. When this value is less than 0.13, the fatigue resistance required for the belt protective layer cord is lowered, resulting in a problem that the tire durability is lowered. On the other hand, if it is larger than 0.9, the cord properties become extremely unstable, so that the fatigue resistance is also lowered.

  In addition, a weft cord can be appropriately arranged inside the tire so as to be substantially orthogonal to the belt protective layer cord. As such a weft cord, known organic fiber cords such as nylon, ester, rayon, polynosic, lyocell, vinylon, etc. These fiber cords can be used as appropriate. The distance between the cords is preferably 5 to 50 mm, more preferably 20 to 35 mm. When this distance is less than 5 mm, the productivity of the woven fabric is deteriorated. On the other hand, when it exceeds 50 mm, the properties of the woven fabric are deteriorated.

  Of course, in the present invention, in addition to the first to third embodiments, a tire appropriately combining these embodiments is also included.

  Next, polyketone fibers (hereinafter abbreviated as “PK fibers”) that can be used in the present invention will be described in detail.

  In the present invention, the fibers other than PK fibers of the fiber yarn containing at least 50% by mass or more of PK fibers can include nylon, ester, rayon, polynosic, lyocell, vinylon, and the like, and should be particularly limited. is not.

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 cord according to the present invention using the PK fiber is preferably a cord described in detail below. That is, it is a multifilament twisted PK fiber having a total decitex per cord of 3000 to 17000 dtex. If the total decitex per one cord is in the range of 3000 to 17000 dtex, it is possible to achieve high rigidity and light weight compared to steel cord, which is an advantage of organic fibers. If the total decitex is less than 3000 dtex, sufficient rigidity as a reinforcing cord cannot be obtained. On the other hand, if the total decitex exceeds 17000 dtex, the ply gauge becomes thick and the tire mass increases.

  The maximum heat shrinkage stress of the cord according to the present invention is determined by heating a 25 cm long fixed sample of the 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) generated in the cord at ° C.

（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［−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 PK fiber, the following general formula (IX),

(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). Among them, a polyketone in which 97 mol% or more of the repeating units is 1-oxotrimethylene [—CH ₂ —CH ₂ —CO—] is preferable, and a polyketone in which 99 mol% or more is 1-oxotrimethylene. 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 (IX), the unsaturated compound forming A is most preferably ethylene, but propylene, butene, pentene, cyclopentene, hexene, cyclohexene, heptene, octene, nonene, decene, dodecene, styrene, acetylene. , Unsaturated hydrocarbons other than ethylene such as allene, and methyl acrylate, methyl methacrylate, vinyl acetate, acrylamide, hydroxyethyl methacrylate, undecenoic acid, undecenol, 6-chlorohexene, N-vinylpyrrolidone, diethyl ester of sulphonylphosphonic acid Further, it may be a compound containing an unsaturated bond such as sodium styrene sulfonate, sodium allyl sulfonate, vinyl pyrrolidone and vinyl chloride.

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

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

  Furthermore, the PK fiber preferably has a crystal structure with a crystallinity of 50 to 90% and a crystal orientation of 95% or more. If the degree of crystallinity is less than 50%, the structure of the fiber is not sufficiently formed and sufficient strength cannot be obtained, and the shrinkage characteristics and dimensional stability during heating may be unstable. For this reason, the crystallinity is preferably 50 to 90%, more preferably 60 to 85%.

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

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

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

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

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

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

  In order to make the most effective use of the high heat shrinkage characteristics of 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 cord according to the present invention can have various shapes as long as the cord can be covered. Typically, it is a film, a sheet or the like. Moreover, if it is the belt protective layer 7, it can be made into ribbon shape. Furthermore, a known rubber composition can be appropriately employed as the coating rubber, and it is not particularly limited.

  The cord according to the present invention is coated with a rubber composition according to a known method such as dipping, coating, and bonding.

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

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

  Subsequently, the coagulated yarn was washed with an aqueous sulfuric acid solution having a concentration of 2% by mass and a temperature of 25 ° C., and further washed with water at 30 ° C., and then the coagulated yarn was wound at a speed of 3.2 m / min. The solidified yarn was impregnated with IRGANOX 1098 (manufactured by Ciba Specialty Chemicals) and IRGANOX 1076 (manufactured by Ciba Specialty Chemicals) in an amount of 0.05% by mass (based on polyketone polymer), and then dried at 240 ° C. A finishing agent was applied to obtain an undrawn yarn.

A finishing agent having the following composition was used.
Oleic acid lauryl ester / bisoxyethyl bisphenol A / polyether (propylene oxide / ethylene oxide = 35/65: molecular weight 20000) / polyethylene oxide 10 mol addition oleyl ether / polyethylene oxide 10 mol addition castor oil ether / sodium stearylsulfonate / dioctyllin Sodium acid = 30/30/10/5/23/1/1 (mass% ratio).

  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 yarn had high physical properties of strength 15.6 cN / dtex, elongation 4.2%, and elastic modulus 347 cN / dtex. In addition, it had high heat shrinkage characteristics of 150% at 30 ° C. for 30 minutes and heat shrinkage during heat treatment of 4.3% and maximum heat shrinkage stress of 0.92 cN / dtex. The PK fiber cord thus obtained (hereinafter also simply referred to as “PK”) was used in the following examples and the like.

(Examples 1-1 to 1-6, Comparative Examples 1-1 to 1-4, Conventional Example 1-1)
Each test tire (size: 225 / 45R17) having a single carcass ply structure having the cord properties shown in Tables 1 and 2 below was prototyped, and subjected to a strength test by hydraulic fracture and a uniformity measurement by a uniformity measuring machine. In the evaluation, a case where the uniformity was good was evaluated as ◯, and a case where the uniformity was poor was evaluated as x. In addition, as a durability evaluation, we compared the rate of decrease of cords dissected from tires pulled up after actual running from strong new ones. The evaluation was expressed as an index with the conventional example being 100. The higher the number, the better the result.
The obtained results are shown in Tables 1 and 2 below.

(Examples 2-1 to 2-9, Comparative Examples 2-1 to 2-4, Conventional Example 2-1)
Consists of a belt layer consisting of two belt plies (first belt ply: steel cord, second belt ply: second belt cord having cord properties shown in Tables 3 and 4 below), and further one layer of belt protection A test tire (size: 225 / 45R17) reinforced with a layer was made as a prototype, and a strength test by water pressure fracture and a uniformity measurement by a uniformity measuring machine were performed. In the evaluation, a case where the uniformity was good was evaluated as ◯, and a case where the uniformity was poor was evaluated as x. In addition, as a durability evaluation, we compared the rate of decrease of cords dissected from tires pulled up after actual running from strong new ones. The evaluation was expressed as an index with the conventional example being 100. The higher the number, the better the result.
The obtained results are shown in Tables 3 and 4 below.

(Examples 3-1 to 3-9, Comparative examples 3-1 to 3-4, Conventional example 3-1)
Test tires (size: 225 / 45R17) reinforced with a belt protective layer having cord physical properties shown in Tables 5 and 6 below were made as prototypes, and subjected to a strength test by water pressure fracture and a uniformity measurement using a uniformity measuring machine. In the evaluation, a case where the uniformity was good was evaluated as ◯, and a case where the uniformity was poor was evaluated as x. In addition, as a durability evaluation, we compared the rate of decrease of cords dissected from tires pulled up after actual running from strong new ones. The evaluation was expressed as an index with the conventional example being 100. The higher the number, the better the result.
The obtained results are shown in Tables 5 and 6 below.

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 (5)

A tread portion, a pair of sidewall portions extending inward in the tire radial direction from both ends thereof, and a pair of bead portions positioned at the inner ends of the sidewall portions, and a pair of bead cores embedded in the bead portion In a pneumatic tire having a carcass layer made of at least one carcass ply extending in a toroidal space, and a belt layer made of at least one belt ply disposed on the outer side in the crown portion radial direction of the carcass,
After at least one carcass ply of the carcass layer is applied to a fiber yarn containing at least 50% by mass or more of polyketone fiber with a lower twisting coefficient N1 defined by the following formula (I), the lower twisted yarn It is made of a twisted yarn with an upper twist coefficient N2 defined by the following formula (II) in a direction opposite to the lower twist by aligning a plurality of yarns, and the lower twist coefficient N1 and the upper twist coefficient N2 are as follows: It is characterized in that it satisfies the formula (III), the upper twist coefficient N2 satisfies the following formula (IV), and is further reinforced by a cord having a maximum heat shrinkage stress in the range of 0.1 to 1.8 cN / dtex. And pneumatic tires.
N1 = n1 × √ (0.125 × D1 / ρ) × 10 ⁻³ (I)
N2 = n2 × √ (0.125 × D2 / ρ) × 10 ⁻³ (II)
0.81 <N2 / N1 ≦ √ (D2 / D1) (III)
0.6 ≦ N2 ≦ 1 (IV)
(Where n1 is the number of lower twists (times / 10 cm), n2 is the number of upper twists (times / 10 cm), D1 is the indicated decitex number of the lower twisted yarn, D2 is the total indicated decitex number, and ρ is the specific gravity of the polyketone fiber. (G / cm ³ ) A tread portion, a pair of sidewall portions extending inward in the tire radial direction from both ends thereof, and a pair of bead portions positioned at the inner ends of the sidewall portions, and a pair of bead cores embedded in the bead portion In a pneumatic tire having a carcass layer made of at least one carcass ply extending in a toroidal space, and a belt layer made of at least one belt ply disposed on the outer side in the crown portion radial direction of the carcass,
After at least one belt ply of the belt layer applies a lower twist to a fiber yarn containing at least 50% by mass of polyketone fiber with a lower twist coefficient N1 defined by the following formula (I), the lower twist yarn It is made of a twisted yarn with an upper twist coefficient N2 defined by the following formula (II) in a direction opposite to the lower twist by aligning a plurality of yarns, and the lower twist coefficient N1 and the upper twist coefficient N2 are as follows: The upper twist coefficient N2 satisfies the following formula (VI) that satisfies the formula (V), and is further reinforced by a cord having a maximum heat shrinkage stress in the range of 0.1 to 1.8 cN / dtex. And pneumatic tires.
N1 = n1 × √ (0.125 × D1 / ρ) × 10 ⁻³ (I)
N2 = n2 × √ (0.125 × D2 / ρ) × 10 ⁻³ (II)
0.45 <N2 / N1 ≦ √ (D2 / D1) (V)
0.13 ≦ N2 ≦ 0.9 (VI)
(Where n1 is the number of lower twists (times / 10 cm), n2 is the number of upper twists (times / 10 cm), D1 is the indicated decitex number of the lower twisted yarn, D2 is the total indicated decitex number, and ρ is the specific gravity of the polyketone fiber. (G / cm ³ ) A tread portion, a pair of sidewall portions extending inward in the tire radial direction from both ends thereof, and a pair of bead portions positioned at the inner ends of the sidewall portions, and a pair of bead cores embedded in the bead portion A carcass layer made of at least one carcass ply extending in the toroidal space, a belt layer made of at least one belt ply arranged outside the carcass in the crown portion radial direction, and a tire radius of the belt layer In a pneumatic tire having at least one belt protective layer disposed on the outside in the direction,
The belt protective layer is applied to a fiber yarn containing at least 50% by mass of polyketone fiber with a lower twist coefficient N1 defined by the following formula (I), and then the plurality of lower twist yarns are aligned. It consists of a twisted yarn with an upper twist coefficient N2 defined by the following formula (II) in the opposite direction to the lower twist, and the lower twist coefficient N1 and the upper twist coefficient N2 satisfy the following formula (V) A pneumatic tire characterized in that the upper twist coefficient N2 satisfies the following formula (VI) and is further reinforced by a cord having a maximum heat shrinkage stress in a range of 0.1 to 1.8 cN / dtex.
N1 = n1 × √ (0.125 × D1 / ρ) × 10 ⁻³ (I)
N2 = n2 × √ (0.125 × D2 / ρ) × 10 ⁻³ (II)
0.45 <N2 / N1 ≦ √ (D2 / D1) (V)
0.13 ≦ N2 ≦ 0.9 (VI)
(Where n1 is the number of lower twists (times / 10 cm), n2 is the number of upper twists (times / 10 cm), D1 is the indicated decitex number of the lower twisted yarn, D2 is the total indicated decitex number, and ρ is the specific gravity of the polyketone fiber. (G / cm ³ )   4. The polyketone fiber having a tensile strength of 10 cN / dtex or more, an elastic modulus of 200 cN / dtex or more, and a heat shrinkage rate in the range of 1% to 5% at 150 ° C. for 30 minutes during dry heat treatment is used. The pneumatic tire according to any one of the above. The air according to claim 2 or 3, wherein the ratio (N2 / N1) of the lower twist coefficient N1 and the upper twist coefficient N2 of the cord satisfies the following formula (VII) and the upper twist coefficient N2 satisfies the following formula (VIII). Enter tire.
0.81 <N2 / N1 <1.4 (VII)
0.36 ≦ N2 ≦ 0.84 (VIII)

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