JP2009023567A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of securely improving many kinds of performance such as cut resistance, low rolling resistance or the like without increasing the weight of the tire by applying a reinforcing material formed into cord fabrics by using polyketone fibers to the tire. <P>SOLUTION: This pneumatic tire is provided with a carcass ply 5 composed of cord layers extended to both beads 1 through both buttress parts 3 and both side walls 2 sequentially from a crown, fixed in the beads 1, and arranged in a substantially radial direction. A carcass ply cord 5 includes at least 50 wt.% of polyketone fibers or more, maximum heat shrinkage stress as a dip treated cord is in a range of 0.1-1.8 cN/dtex, and a shrinkage percentage when treated by being dryed and heated at 150°C for 30 minutes is in a range of 1-5%. The carcass ply 5 includes wefts crossing the carcass ply cord arranged in a substantially radial direction, and the carcass ply 5 in the buttress part 3 satisfies a following relation; L≤0.25r. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire (hereinafter, also simply referred to as “tire”), and more particularly to a pneumatic tire according to an improvement of a carcass ply forming a skeleton.

  A pneumatic tire generally includes a bead core provided in a pair of left and right bead portions and a cord layer arranged in a substantially radial direction, extends from the crown portion to both bead portions via both side portions, and is moored to the bead portion. It includes a carcass ply, and a belt and a tread that are disposed radially outward of the crown portion.

  Of these, various reinforcing cords such as rayon, nylon, polyester (polyethylene terephthalate (PET), etc.) have been studied and used as a reinforcing cord used for a carcass ply forming a tire skeleton. Recently, as an alternative to these conventional organic fiber materials, carbon monoxide and olefins obtained by polymerizing carbon monoxide and olefins such as ethylene and propene using palladium or nickel as a catalyst are substantially completely alternate. Studies are also being conducted on fiberizing a polymerized aliphatic polyketone and using it as a cord material. Polyketone fibers are known to have a higher melting point than conventional polyolefin fibers, and to have high strength and high elastic modulus. Utilizing these excellent physical properties, they can be used for industrial materials, especially tires, belts, hoses, etc. Development as a rubber reinforcing material is expected.

Regarding the reinforcing material using such polyketone fibers, for example, in Patent Document 1, in a weft fabric composed of warps and wefts, 50% by mass or more of the fibers constituting the warps are used as polyketone fibers, and warp and wefts An interwoven fabric having a fiber-fiber static coefficient of friction (μs) of 0.2 or more is disclosed.
JP 2003-49339 A

  However, even if a conventional reinforcing cord or reinforcing material made of tinted fabric using polyketone fibers is applied to a tire, a sufficient improvement in performance cannot always be expected.

  Accordingly, an object of the present invention is to ensure various performances such as cut resistance and low rolling resistance without causing an increase in the weight of the tire by applying to the tire a reinforcing material made of a braided fabric using polyketone fibers. An object of the present invention is to provide a pneumatic tire that achieves a significant improvement.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the interwoven fabric using polyketone fibers has the following problems.
(B) Polyketone fiber itself having high strength and high elastic modulus, and a cord made of polyketone fiber using the same have high heat shrinkage stress, and the weave fabric is distorted by heat shrinkage after weaving and the flatness is lost. It is.
(B) Polyketone fibers having high strength and high elastic modulus and cords made of polyketone fibers are rubberized as tinted fabric and then heated during tire production, resulting in disturbance of the carcass cord arrangement due to shrinkage of the polyketone fibers. , Worsen tire uniformity.

  These problems are not mentioned at all in the prior art, so the inventors have solved this problem, and have further produced a high-performance, high-quality interwoven fabric and applied it to the tire carcass ply. As a result of intensive studies, the present inventors have found that the object can be achieved and have completed the present invention.

That is, the pneumatic tire according to the present invention includes a carcass ply formed of a cord layer that extends from a crown portion to both bead portions sequentially through both buttress portions and both sidewall portions and is anchored to the bead portions and arranged in a substantially radial direction. In a pneumatic tire comprising:
The carcass ply cord contains at least 50% by mass of polyketone fiber, the maximum heat shrinkage stress as a dip-treated cord is in the range of 0.1 to 1.8 cN / dtex, and heat at 150 ° C. for 30 minutes during dry heat treatment The shrinkage rate is in the range of 1% to 5%,
The carcass ply includes a weft that intersects with the carcass ply cord arranged in a substantially radial direction, and the carcass ply in the buttress portion has the following formula:
L ≦ 0.25r
(Wherein, r is the diameter (mm) of the carcass ply cord, L is the carcass ply between the two ends on the line connecting the cross-sectional centers of the carcass ply cords at both ends, among the cross-sectional centers of three adjacent carcass ply cords. The length of the perpendicular line drawn from the center of the cord section is satisfied.

In the pneumatic tire according to the present invention, it is preferable that the carcass ply is formed by a single piece, and the carcass ply cord is a cord obtained by twisting a fiber yarn and performing a dip treatment. Moreover, it is preferable that the said weft is cut | disconnected at the substantially constant space | interval in the multiple places of the tire circumferential direction, and it is preferable that the cutting pitch exists in the range of 5-30 mm. Further, after the carcass ply cord is subjected to a lower twist with a lower twist coefficient N1 defined by the following formula (1) to the fiber yarn, the plurality of the lower twist yarns are arranged in the opposite direction to the lower twist, It consists of a twisted yarn with an upper twist coefficient N2 defined by the following formula (2), and the lower twist coefficient N1 and the upper twist coefficient N2 satisfy the relationship represented by the following formula (3), And it is preferable that the upper twist coefficient N2 satisfies the relationship represented by the following formula (4).
N1 = n1 × √ (0.125 × D1 / ρ) × 10 ⁻³ (1)
N2 = n2 × √ (0.125 × D2 / ρ) × 10 ⁻³ (2)
0.81 <N2 / N1 ≦ √ (D2 / D1) (3)
0.3 ≦ N2 ≦ 0.9 (4)
(Where n1 is the number of lower twists (times / 10 cm), n2 is the number of upper twists (times / 10 cm), D1 is the number of display decitex of the lower twist yarn, D2 is the total number of decitex, and ρ is the specific gravity of the fiber yarn ( g / cm ³ ))

  Moreover, in the pneumatic tire of the present invention, the carcass ply is woven at a cord driving pitch of 50 to 130/100 mm after the dipping process, and the distance between the wefts substantially parallel to each other is 5 to 50 mm. It is preferable. Further, the polyketone fiber contained in the fiber cord forming the carcass ply preferably has a tensile strength of 10 cN / dtex or more.

Here, the maximum heat shrinkage stress of the cord means that a 25 cm long fixed sample of a carcass ply cord before vulcanization subjected to a general dip treatment is heated at a heating rate of 5 ° C./min. It is the maximum stress (unit: cN / dtex) generated in the cord at ° C. The heat shrinkage rate during dry heat treatment is the same dip-treated cord, which is subjected to a dry heat treatment at 150 ° C. for 30 minutes in an oven, and the cord length before and after the heat treatment is a load of 1/30 (cN / dtex). It is a value obtained by measuring with
Thermal shrinkage during dry heat treatment (%) = {(Lb−La) / Lb} × 100
However, Lb is the cord length before heat treatment, and La is the cord length after heat treatment. The tensile strength and tensile modulus of the polyketone fiber are values obtained by measurement according to JIS-L-1013. The tensile modulus is the load at an elongation of 0.1% and the elongation of 0.2%. It is the value of the initial elastic modulus calculated from the load at.

  According to the present invention, by greatly improving the uniformity of the tire, various performances such as cut resistance and low rolling resistance can be significantly improved without increasing the weight of the tire.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.
FIG. 1 is a partial cross-sectional view showing an example of the pneumatic tire of the present invention. The illustrated tire has a pair of left and right bead portions 1 and a pair of sidewall portions 2 in which bead cores 6 are embedded, and a tread portion 4 that is continuous from both sidewall portions 2 via a buttress portion 3. A carcass ply 5 is provided that extends in a toroidal shape between the portions 1 and consists of a single cord layer that reinforces the portions 1, 2, 3, and 4. A belt 7 composed of two belt layers is disposed on the outer side in the tire radial direction of the crown portion of the carcass ply 5. The buttress portion 3 is a portion having both ends of a ground contact end portion in contact with the road surface in the tread portion 4 and a central position from the ground contact end portion to the tire maximum width portion.

  In the illustrated example, the belt 7 includes two belt layers. However, in the tire of the present invention, the number of belt layers constituting the belt 7 is not limited to this. Here, the belt layer is usually composed of a rubberized layer of a cord extending obliquely with respect to the tire equatorial plane, preferably a rubberized layer of a steel cord, and the two belt layers each constitute a belt layer. The belt 7 is formed by laminating the cords so as to cross each other with the equator plane interposed therebetween.

  The carcass ply 5 is formed by coating a plurality of reinforcing cords arranged in parallel in a substantially radial direction with a coating rubber. That is, a plurality of carcass ply cords are drawn as warp yarns, and thin and weak weft yarns are roughly struck to form a suede-like adhesive treatment for further adhesion to rubber. Thereafter, a topping rubber having a certain thickness is coated to form a rubber-coated cord. Next, the warp yarn of the rubber-coated cord is cut so as to have a certain length, and both edge portions other than the cut surface are joined to obtain a carcass material. At the time of tire molding, the carcass material is cut in the same direction as the warp on a drum molding machine or similar equipment and joined to form a cylinder.

  In the illustrated example, the carcass ply 5 extends from the crown portion to both bead portions through both side wall portions, is wound around the bead core 6 and is moored to the bead portion 1. Of the carcass plies constituting the carcass, The at least one ply has a so-called envelope structure in which it is folded back around the bead core 6 from the inner side to the outer side in the tire width direction, and the folded end is located between the belt and the crown portion of the carcass. May be.

  In the present invention, it is necessary for the carcass ply cord to contain at least 50% by mass, preferably 70% by mass or more, more preferably 100% by mass of polyketone fiber. 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, and the desired effect of the present invention cannot be obtained.

  Further, the carcass ply cord used in the present invention has a maximum heat shrinkage stress as a dipped cord of 0.1 to 1.8 cN / dtex, preferably 0.4 to 1.6 cN / dtex, more preferably 0.8. It needs to be in the range of 6 to 1.4 cN / dtex. When the maximum heat shrinkage stress is less than 0.1 cN / dtex, the alignment efficiency due to heating during tire manufacture is significantly reduced, 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, and there is a concern that the finished tire shape may be deteriorated.

  Furthermore, the carcass ply cord used in the present invention 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 as a dip-treated cord. Is desirable. 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, in the present invention, the carcass ply 5 in the buttress portion 3 has the following formula:
L ≦ 0.25r
If this equation is not satisfied, tire uniformity will be significantly impaired. Here, r represents the diameter (mm) of the carcass ply cords 10, 11, and 12 shown in FIG. L is the cross-sectional center of the carcass ply cord 11 between the two ends on the line connecting the cross-sectional centers of the carcass ply cords 10 and 12 at both ends, among the cross-sectional centers of the three adjacent carcass ply cords 10, 11, and 12. This represents the length of the perpendicular drawn from.

  The carcass ply 5 includes wefts that intersect with the carcass ply cords arranged in a substantially radial direction. The number of the carcass plies 5 is not particularly limited, but it is preferable to configure the carcass with one carcass ply from the viewpoint of improving the uniformity of the tire and reducing the weight.

  The wefts in the carcass ply 5 are preferably cut at substantially constant intervals at a plurality of locations in the tire circumferential direction. As a means for cutting this weft, it can be performed by the known pick breaker processing described in JP-A-5-208458, but it goes without saying that the weft can be cut using other methods. is there.

  Furthermore, the weft cutting pitch is preferably in the range of 5 to 30 mm, more preferably in the range of 7 to 15 mm. If the cutting pitch is less than 5 mm, the carcass cord may be damaged in the cutting process. On the other hand, when it exceeds 30 mm, the uniformity in the tire circumferential direction cannot be sufficiently improved.

In addition, the carcass ply cord in the carcass ply 5 is obtained by applying a lower twist to the fiber yarn with a lower twist coefficient N1 defined by the following formula (1), and then drawing the plurality of lower twisted yarns together. In the reverse direction, the yarn is twisted with an upper twist coefficient N2 defined by the following formula (2), and the lower twist coefficient N1 and the upper twist coefficient N2 are expressed by the following formula (3). It is preferable that the upper twist coefficient N2 satisfies the relationship represented by the following formula (4).
N1 = n1 × √ (0.125 × D1 / ρ) × 10 ⁻³ (1)
N2 = n2 × √ (0.125 × D2 / ρ) × 10 ⁻³ (2)
0.81 <N2 / N1 ≦ √ (D2 / D1) (3)
0.3 ≦ N2 ≦ 0.9 (4)
In the 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 fiber yarn (g / Cm ³ ). By satisfying these relationships, flatness as a woven fabric is easily maintained, and the arrangement of the carcass ply cord is less disturbed.

  The carcass ply 5 is woven so that the cord driving pitch after the dip treatment is preferably 50 to 130/100 mm, and the distance between the wefts substantially parallel to each other is preferably 5 to 50 mm, more preferably 20 to 35 mm. It is. If the cord driving pitch is less than 50/100 mm, the strength as a tire will be insufficient. On the other hand, if it exceeds 130/100 mm, the tire weight will increase, fuel efficiency will decrease, and riding comfort will be impaired. It becomes. In addition, when the distance between the wefts is less than 5 mm, the productivity of the weave fabric is deteriorated. On the other hand, when it exceeds 50 mm, the properties of the interwoven fabric are deteriorated.

  Further, the weft has a fineness of preferably 60 dtex to 600 dtex, more preferably 100 dtex to 400 dtex. When the fineness is less than 60 dtex, there is a concern that weft breakage frequently occurs in the process from the manufacture of the interwoven fabric to the tire. On the other hand, when the fineness exceeds 600 dtex, there is a concern that the carcass cord arrangement is greatly disturbed in the expansion process of the tire manufacture, and the carcass cord arrangement is greatly disturbed.

  Further, the weft has a tensile strength of preferably 100 g to 2000 g, more preferably 200 g to 1500 g, and still more preferably 300 g to 1500 g. When the tensile strength is less than 100 g, there is a concern that weft breakage frequently occurs in the process from the blind manufacturing to the tire manufacturing. On the other hand, when the tensile strength exceeds 2000 g, there is a concern that the carcass code arrangement is greatly disturbed because the tire does not break uniformly in the expansion process of tire manufacture.

  Furthermore, the weft has a cutting elongation of preferably 3% to 30%, preferably 5% to 15%. When the cut elongation is less than 3%, there is a concern that weft breakage frequently occurs in the process from the blind manufacturing to the tire manufacturing. On the other hand, when the cut elongation exceeds 20%, there is a concern that the carcass cord arrangement may be disturbed because the carcass cord arrangement is not broken uniformly in the expansion process of tire manufacture.

  The polyketone fiber contained in the carcass ply cord has a tensile strength of 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, the polyketone fiber contained in the carcass ply cord preferably has an elastic modulus of 200 cN / dtex or more, more preferably 250 cN / dtex or more. When the elastic modulus is less than 200 cN / dtex, the shape retention as a tire is insufficient.

  Next, a carcass ply cord containing at least 50 mass% or more 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.

（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 (II),

(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 (II), 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 (III),

(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 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.

  The pneumatic tire of the present invention can be manufactured by a conventional method using the carcass ply described above as the radial carcass 4. In the pneumatic tire of the present invention, as the gas filled in the tire, normal or air with a changed oxygen partial pressure, or an inert gas such as nitrogen can be used.

Hereinafter, the present invention will be 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.
The coagulated 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 (based on polyketone polymer), and then dried at 240 ° C. or higher. A finishing agent was added to obtain an undrawn yarn. The heat shrinkage rate can be adjusted by appropriately controlling the drying temperature.

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 (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. This fiber yarn had high physical properties of strength 15.6 cN / dtex, elongation 4.2%, and elastic modulus 347 cN / dtex. In addition, the heat shrinkage rate during dry heat treatment at 150 ° C. for 30 minutes was 1.9%. The PK fiber thus obtained was used as a cord under the following conditions.

  The PK fiber obtained as described above was used as a cord under the following conditions.

(Examples 1-10, Comparative Examples 1-5, Conventional Examples)
Various carcass plies having a ply structure, a carcass ply cord, and a weft shown in Tables 1 to 6 below were produced by cutting the weft after coating with a coating rubber, etc., and tire sizes 215 / Various normal tires of 45 ZR17, 245/40 R18, and 305/30 R19 were prototyped.

In addition, 1-3 in a table | surface and a ply structure represent the following meaning.
2PH / L: It consists of two sheets of a carcass ply folded back from the inner side to the outer side in the tire width direction and a carcass ply folded back at the bead core.
1PH: It consists of one carcass ply folded back from the inner side in the tire width direction toward the outer side by a bead core.
1P-Env: a carcass ply returned from the inner side to the outer side in the tire width direction by the bead core, and folded back from the inner side to the outer side in the tire width direction around the bead core, and the folded end is a belt and a crown part of the carcass And a carcass ply having a so-called envelope structure.

  In Tables 4 to 6, among the presence / absence of cutting, “present” means that a pick break is applied, and “absent” means that a pick break is not applied.

(1) Tire weight The tire weight of the conventional example is shown as an index with the weight being 100. The larger the value, the greater the tire weight.
(2) Cut resistance The test tire was mounted on an actual vehicle and allowed to enter a curbstone (stepped portion) having a height of 100 mm at an angle of 45 °. The approach speed was gradually increased, and the speed at which the tire broke and the internal pressure was released was measured. The larger the value, the better the cut resistance and the better.
(3) Rolling resistance Rotate the drum while contacting the tire on a steel drum with a diameter of 2 m, raise to a constant speed, turn off the drum drive switch, rotate the drum freely, find the rolling resistance from the degree of deceleration, The rolling resistance of the tire of the conventional example is shown as an index with 100 as the rolling resistance. The smaller the index value, the smaller the rolling resistance and the better.
(4) Uniformity RFV (Radial Force Variation) and LFV (Lateral Force Variation) of a test tire filled with an internal pressure of 230 kPa were measured, and the value of the tire of the conventional example was represented as an index as 100. The smaller the index value, the better the uniformity.

  The following was confirmed from the evaluation results of the tire performance shown in Tables 4-6. First, in the conventional example, warp (carcass ply cord) is greatly disturbed and the uniformity is poor. On the other hand, in all of Examples 1 to 11, the warp (carcass ply cord) was less disturbed and the uniformity was good. On the other hand, in Comparative Examples 1 and 2, warp distortion was small and uniformity was good, but since the carcass cord strength was low compared to the examples, two carcass ply sheets were required, and reduction in tire weight could not be expected. . Further, in Comparative Examples 3 and 5, pick break was not performed, warp yarn was greatly disturbed, and uniformity was poor.

1 is a right half sectional view showing a pneumatic tire according to an embodiment of the present invention. It is sectional drawing which shows the state of disorder of the carcass ply cord in a carcass ply.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Buttress part 4 Tread part 5 Carcass ply 6 Bead core 7 Belt 10, 11, 12 Carcass ply cord

Claims (7)

In a pneumatic tire including a carcass ply made of a cord layer arranged in a substantially radial direction, extending from a crown portion to both bead portions sequentially through both buttress portions and both sidewall portions, and anchored to the bead portion.
The carcass ply cord contains at least 50% by mass of polyketone fiber, the maximum heat shrinkage stress as a dip-treated cord is in the range of 0.1 to 1.8 cN / dtex, and heat at 150 ° C. for 30 minutes during dry heat treatment The shrinkage rate is in the range of 1% to 5%,
The carcass ply includes a weft that intersects with the carcass ply cord arranged in a substantially radial direction, and the carcass ply in the buttress portion has the following formula:
L ≦ 0.25r
(Wherein, r is the diameter (mm) of the carcass ply cord, L is the carcass ply between the two ends on the line connecting the cross-sectional centers of the carcass ply cords at both ends, among the cross-sectional centers of three adjacent carcass ply cords. A pneumatic tire characterized by satisfying the length of a perpendicular line drawn from the center of the cord cross section.   2. The pneumatic tire according to claim 1, wherein the carcass ply is formed of a single sheet, and the carcass ply cord is a cord obtained by adding a twist to a fiber yarn and applying a dip treatment. 3.   The pneumatic tire according to claim 1 or 2, wherein the weft is cut at substantially constant intervals at a plurality of locations in the tire circumferential direction.   The pneumatic tire according to claim 3, wherein a cutting pitch of the weft yarn is in a range of 5 to 30 mm. After the carcass ply cord is subjected to a lower twist with a lower twist coefficient N1 defined by the following formula (1) to the fiber raw yarn, the plurality of the lower twisted yarns are aligned and in the opposite direction to the lower twist, the following formula It consists of a twisted yarn with an upper twist coefficient N2 defined in (2), the lower twist coefficient N1 and the upper twist coefficient N2 satisfy the relationship represented by the following formula (3), and The pneumatic tire according to any one of claims 1 to 4, wherein the upper twist coefficient N2 satisfies a relationship represented by the following formula (4).
N1 = n1 × √ (0.125 × D1 / ρ) × 10 ⁻³ (1)
N2 = n2 × √ (0.125 × D2 / ρ) × 10 ⁻³ (2)
0.81 <N2 / N1 ≦ √ (D2 / D1) (3)
0.3 ≦ N2 ≦ 0.9 (4)
(Where n1 is the number of lower twists (times / 10 cm), n2 is the number of upper twists (times / 10 cm), D1 is the number of display decitex of the lower twist yarn, D2 is the total number of decitex, and ρ is the specific gravity of the fiber yarn ( g / cm ³ ))   The carcass ply is woven as a cord driving pitch after dipping of 50 to 130/100 mm, and the distance between the wefts substantially parallel to each other is 5 to 50 mm. 6. The described pneumatic tire.   The pneumatic tire according to any one of claims 1 to 6, wherein the polyketone fiber contained in the fiber cord forming the carcass ply has a tensile strength of 10 cN / dtex or more.

Images