JP4986783B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire (hereinafter, also simply referred to as “tire”) having improved running fatigue resistance and road hazard resistance in normal times, and further, run flat without impairing riding comfort during normal running. The present invention relates to a side-reinforced run-flat tire that greatly improves the durability during traveling and further improves the durability of the carcass cord during normal traveling.

  Polyketone fiber has higher strength and higher elastic modulus than nylon fiber, polyester fiber, and rayon fiber, and has high heat resistance and good adhesiveness, so it can be used for various industrial materials. Is expected. Focusing on the excellent properties of such polyketone fibers, many attempts to use the polyketone fibers in tire cords have been studied and proposed (Patent Documents 1 to 4, etc.).

  On the other hand, as a so-called run-flat tire, the carcass in the sidewall portion of the tire can be safely run over a certain distance without losing the load supporting ability even when the internal pressure of the tire is reduced due to puncture or the like. A side-reinforcing rubber layer with a relatively high modulus is placed on the inner surface of the wall to improve the rigidity of the sidewall, and when the internal pressure decreases, the load can be borne without significantly increasing the deformation of the sidewall. Various types of side-reinforced run-flat tires such as the tires described above and tires whose sidewall portions are reinforced with various reinforcing members have been proposed (see Patent Documents 5 to 8).

  In this regard, cellulosic fibers such as rayon have been used as a reinforcing material for various rubber articles including tire reinforcement cords because of their high elasticity at room temperature and high adhesion to rubber. And since the Young's modulus at high temperature is higher than that of polyester such as polyethylene terephthalate (PET), the heat shrinkage rate at 177 ° C. is 0.65 to 1.0% and high thermal dimensional stability. It has also been used as a carcass reinforcing cord for the side reinforcing type run-flat tire.

  However, conventional side-reinforced type run-flat tires that use cellulosic fiber cords such as rayon as carcass reinforcement cords are not sufficiently high in the elastic modulus of cellulosic fibers, so that the tires are bent during run-flat running. When the tire becomes large due to the run-flat running and the temperature of the tire becomes high, the rigidity of the carcass ply is lowered and the deflection of the tire is further increased. For this reason, the main cause of tire failure at the end of run-flat driving is due to the cracking of the side-reinforcing rubber layer with a crescent-shaped cross section, and conventional side-reinforced run-flat tires have a long-running running distance. There was a problem of being short.

  On the other hand, if the sidewall is reinforced by increasing the gauge of the side reinforcing rubber layer, etc., in order to extend the durability distance of the tire during run-flat running, the tire weight increases or the tire runs during normal running. There is a problem that the vertical spring rises and the riding comfort during normal running deteriorates.

In order to solve such a problem, the applicant previously used a polyketone fiber cord having a specific heat shrinkage stress and elastic modulus as a carcass reinforcement cord of a side reinforcement type run-flat tire in Patent Document 9, It has been reported that tire deflection during run-flat driving can be suppressed without increasing tire weight, and as a result, tire run-flat durability can be greatly improved without deteriorating riding comfort during normal driving. ing.
JP-A-11-334313 JP 2002-309442 A JP 2002-307908 A JP 2006-123649 A JP 2000-264012 A Special table 2002-500587 gazette Japanese translation of PCT publication No. 2002-500589 JP 2004-306658 A JP 2006-224952 A

  As described above, the use of polyketone fibers for tire cords has been conventionally performed. However, in the conventionally proposed tire technology using polyketone fibers, the original excellent properties of polyketone fibers are not necessarily fully utilized. However, the current situation is that sufficient performance has not yet been achieved particularly from the viewpoint of improvement in normal running fatigue and road hazard resistance.

  Accordingly, an object of the present invention is to solve the above-described problems of the prior art and to provide a pneumatic tire excellent in running fatigue resistance and road hazard resistance in a normal state in a tire using polyketone fibers.

  Further, as described above, by applying the specific polyketone fiber cord to the carcass reinforcement cord of the side reinforcement type run-flat tire by the technique disclosed in Patent Document 9 by the present applicant, Although it became possible to significantly improve the run-flat durability of the tire without deteriorating the comfort, there was still room for improvement in the fatigue resistance of the carcass during normal driving.

  Accordingly, another object of the present invention is to solve the above-mentioned problems of the prior art, improve the durability during run-flat driving without impairing the riding comfort during normal driving, and further improve the fatigue resistance of the carcass during normal driving. An object of the present invention is to provide a run flat tire with improved performance.

  As a result of intensive studies to solve the above problems, the present inventors have used a polyketone fiber cord having specific heat shrinkage characteristics as a carcass reinforcing cord, and post-cure inflation (PCI) at a predetermined internal pressure or higher immediately after vulcanization. ), The occurrence of unevenness on the inner surface of the tire is suppressed, and as a result, the uniformity in the tire circumferential direction is increased, and it is possible to increase road hazard resistance as well as normal driving fatigue. As a result of the study, by applying the above configuration to run-flat tires of side reinforcement type, it is possible to suppress tire deflection during run-flat driving without increasing tire weight, resulting in worse ride comfort during normal driving. Without significantly reducing the run-flat durability of the tires, and further improving the fatigue resistance of the carcass during normal driving It has found to be able to improve, and have completed the present invention.

That is, the pneumatic tire of the present invention is a pneumatic tire provided with carcass plies extending from the crown portion to both bead portions via both side portions,
The carcass ply cord includes at least 50% by mass of polyketone fiber, and has a maximum heat shrinkage stress of 0.1 to 1.8 cN / dtex as a dip-treated cord, and the polyketone fiber is subjected to a dry heat treatment at 150 ° C. for 30 minutes. The thermal shrinkage is in the range of 0.3-3%,
Immediately after vulcanization, post-cure inflation (PCI) is performed at an internal pressure of 60 kPa or more.

  In the pneumatic tire of the present invention, it is preferable that the total width growth when the inner pressure is filled from no inner pressure to 30 kPa is 8 mm or less. Moreover, it is preferable that the polyketone fiber contained in the fiber cord forming the carcass ply has an original yarn tensile strength of 10 cN / dtex or more and an elastic modulus of 200 cN / dtex or more.

  Further, the carcass ply includes a weft that intersects a cord arranged in a substantially radial direction, and the weft is cut at a plurality of locations in the tire circumferential direction, and the cutting pitch A is in the range of 5 to 30 mm. Is preferred. Furthermore, it is preferable that the weft has a cutting elongation of 5 to 20% and a cutting strength of 200 to 1000 g. Furthermore, the weft is preferably made of cellulosic fiber or vinylon fiber, and the weft is preferably spun yarn.

  The present invention can be suitably applied to a run flat tire provided with a side reinforcing rubber layer having a crescent-shaped meridional shape over the entire or almost entire area of both side portions along the inner surface of the carcass ply.

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. In addition, the heat shrinkage rate of the polyketone fiber during the dry heat treatment was measured by measuring the fiber length before and after the heat treatment by applying a load of 1/30 (cN / dtex) in an oven at 150 ° C. for 30 minutes. It is a value obtained by the following formula.
Thermal shrinkage during dry heat treatment (%) = {(Lb−La) / Lb} × 100
However, Lb is the fiber length before heat treatment, and La is the fiber 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.

  Further, as a method of performing the post-cure inflation (PCI), a method in which the tire is taken out of the vulcanizer and then subjected to internal pressure to suppress the thermal contraction of the cord forming the carcass layer and to cool to near room temperature is preferable. However, PCI may be implemented using other methods and conditions.

  According to the present invention, the occurrence of unevenness on the inner surface of the tire is suppressed, and the uniformity in the tire circumferential direction is increased, thereby making it possible to realize a pneumatic tire excellent in normal running fatigue and road hazard resistance. . In addition, if the present invention is applied to a run-flat tire, the run-flat running durability is improved without impairing the riding comfort during normal running, and the carcass fatigue resistance during normal running is further improved. A flat tire can be realized.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a partial cross-sectional view of an example of the pneumatic tire of the present invention. The tire shown in FIG. 1 has a pair of left and right bead portions 1 and a pair of sidewall portions 2 in which bead cores 5 are embedded, and a tread portion 3 that is continuous with both sidewall portions 2. A carcass ply 4 is provided that includes two cord layers that extend in a toroidal shape and reinforce these portions 1, 2, and 3. A belt 6 composed of two belt layers is disposed on the outer side of the crown portion of the carcass ply 4 in the tire radial direction.

  FIG. 2 is a partial cross-sectional view showing an example of a run flat tire according to another preferred embodiment of the present invention. The tire shown in FIG. 2 has a pair of left and right bead portions 11 and a pair of sidewall portions 12, and a tread portion 13 connected to both sidewall portions 12, and extends in a toroidal shape between the pair of bead portions 11. A radial carcass 14 made of one or more carcass plies that reinforce each of these parts 11, 12, and 13, and a pair of crescent-shaped side reinforcing rubber layers 15 disposed inside the radial carcass 14 of the sidewall part 12. Prepare. A bead filler 17 is arranged on the outer side in the tire radial direction of the ring-shaped bead core 16 embedded in the bead part 11, and is composed of two belt layers on the outer side in the tire radial direction of the crown part of the radial carcass 14. In addition to the belt 18 being disposed, a belt reinforcing layer 19A is disposed on the outer side in the tire radial direction of the belt 18 so as to cover the entire belt 18, and only both ends of the belt reinforcing layer 19A are disposed. A pair of belt reinforcing layers 19B is disposed so as to cover.

  In the example shown in FIGS. 1 and 2, the belt is composed of two belt layers, but in the tire of the present invention, the number of belt layers constituting the belt is not limited to this. Further, the belt reinforcing layer is not limited to the illustrated example, and may be arranged in another structure. 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 is formed by laminating the cords so as to cross each other with the equator plane interposed therebetween. The belt reinforcing layer is usually composed of a rubberized layer of cords arranged substantially parallel to the tire circumferential direction.

  Further, the carcass ply is formed by covering a plurality of reinforcing cords arranged in parallel with a coating rubber, and in the illustrated example, a main body portion extending in a toroidal shape between a pair of bead cores embedded in the bead portion. And a folded portion wound radially outward from the inner side to the outer side in the tire width direction around each bead core. In the tire of the present invention, the number and structure of carcass plies are limited to this. is not.

  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 run flat running durability cannot be sufficiently improved. On the other hand, when the maximum heat shrinkage stress exceeds 1.8 cN / dtex, the cord is remarkably contracted by heating at the time of tire manufacture, so that there is a concern that the finished tire shape may be deteriorated.

  Furthermore, the polyketone fiber contained in the carcass ply cord used in the present invention has a heat shrinkage ratio in the range of 0.3% to 3%, preferably in the range of 1% to 2% at 150 ° C. for 30 minutes. is required. When the thermal shrinkage rate at 150 ° C. for 30 minutes during the dry heat treatment is less than 0.3%, 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, if the thermal shrinkage rate during dry heat treatment at 150 ° C. for 30 minutes exceeds 3%, the cord is significantly shrunk by heating at the time of manufacturing the tire, so that the finished tire shape may be deteriorated.

  Furthermore, the polyketone fiber contained in the carcass ply cord used in the present invention preferably has a tensile strength of the original yarn of 10 cN / dtex or more, more preferably 15 cN / dtex or more. When this 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 used in the present invention preferably has an elastic modulus of the raw yarn of 200 cN / dtex or more, more preferably 250 cN / dtex or more. When this elastic modulus is less than 200 cN / dtex, the run-flat running durability cannot be sufficiently improved.

  As shown in FIG. 3, the carcass ply according to the present invention includes a weft 22 intersecting with a carcass ply cord 21 arranged in a substantially radial direction, and the weft 22 is cut at a plurality of locations in the tire circumferential direction. It is preferable that As a means for cutting the weft 22, it can be performed by a known pick breaker process described in Japanese Patent Application Laid-Open No. 5-208458, but it goes without saying that the weft can be cut using other methods. It is.

  Moreover, it is preferable that the cutting pitch A of the weft 22 shown in FIG. 3 exists in the range of 5-30 mm, More preferably, it is the range of 7-15 mm. When the cutting pitch A 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.

  Furthermore, the weft 22 preferably has a cutting elongation of 5 to 20% and a cutting strength of 200 to 1000 g. If the cut elongation is less than 5% or the cut strength is less than 200 g, the weft 22 is unexpectedly cut before the step of topping the rubber, and the shape as a braided fabric cannot be maintained. On the other hand, when the cut elongation is greater than 20% or the cut strength exceeds 1000 g, it becomes difficult to cut the weft 22 in the cutting process, and the uniformity in the tire circumferential direction cannot be sufficiently improved.

  Furthermore, it is desirable that the weft yarn 22 is made of a cellulosic fiber or a vinylon fiber, and more preferably a spun yarn. Such a fiber can be designed to satisfy the above-described cutting elongation and cutting strength.

  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、Ｔは撚り数（回／１００ｍｍ）、Ｄはコードの総繊度（ｄｔｅｘ）、ρはコードに使用される繊維素材の密度（ｇ／ｃｍ^３）である）で定義される撚り係数αが０．２５〜１．２５の範囲であることが好ましい。ＰＫ繊維コードの撚り係数αが０．２５未満では、熱収縮応力が十分に確保できず、一方、１．２５を超えると、弾性率が十分に確保できず、補強能が小さくなる。 Further, the above code further includes the following formula (I),

(Where T is the number of twists (times / 100 mm), D is the total fineness of the cord (dtex), and ρ is the density of the fiber material used in the cord (g / cm ³ )) α is preferably in the range of 0.25 to 1.25. If the twist coefficient α of the PK fiber cord is less than 0.25, the heat shrinkage stress cannot be sufficiently ensured. On the other hand, if it exceeds 1.25, the elastic modulus cannot be sufficiently ensured and the reinforcing ability is reduced.

（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-vinyl pyrrolidone, diethyl ester of sulphonylphosphonic acid Further, it may be a compound containing an unsaturated bond such as sodium styrene sulfonate, sodium allyl sulfonate, vinyl pyrrolidone and vinyl chloride.

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

  In the pneumatic tire of the present invention, it is important that post-cure inflation (PCI) is performed immediately after vulcanization at an internal pressure of 60 kPa or more, preferably 100 kPa, more preferably 200 kPa or more. When the internal pressure of post-cure inflation (PCI) performed after vulcanization is less than 60 kPa, the heat shrinkage of the carcass cord after vulcanization cannot be sufficiently suppressed, and the intended purpose of the present invention is achieved. I can't do that.

  Furthermore, in the pneumatic tire of the present invention, the total width growth when filled from no internal pressure to 30 kPa is preferably 8 mm or less, more preferably 6 mm or less. By setting the total width growth to 8 mm or less, the circumferential distribution of the tension acting on the carcass cord can be made uniform. In addition to the above, it is preferable that the total width growth is 8 mm or less by appropriately selecting the cord diameter of the carcass cord in the range of 0.5 mm to 1.2 mm and the number of drivings in the range of 75 to 130/100 mm. It can be carried out.

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 (with respect to the polyketone polymer), and then the coagulated yarn was 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 stearyl sulfonate / dioctyllin Sodium acid = 30/30/10/5/23/1/1 (weight% ratio).

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

(Examples 1 to 6, Comparative Examples 1 and 2, Conventional Example 1)
The fiber cords having the carcass structure, material / thickness, tensile strength, heat shrinkage stress, and heat shrinkage rate during the dry heat treatment of the fibers shown in Table 1 below are arranged in parallel at 110 shots / 100 mm and covered with coating rubber A cord / rubber composite was produced by, for example, cutting the weft, and a pneumatic tire of size 225 / 60ZR17 having the structure shown in FIG. 1 was prototyped using the cord / rubber composite for a carcass ply. All carcass structures were two plies. Further, the inner surface irregularities, road hazard resistance and carcass cord fatigue resistance of the obtained tire were evaluated by the following methods, and the results shown in Table 2 were obtained.

(1) Tire inner surface unevenness The tire inner surface after vulcanization was evaluated by visual observation, and it was evaluated in three stages where there was almost no generation and some generation and remarkable generation.

(2) Road hazard resistance The test tire is filled with internal pressure, and an apparatus described in Japanese Patent Laid-Open No. 6-273299 (an arm rotatably supported in a certain direction and an impact attached to the tip of the arm). An evaluation method using a piece, an angle adjuster that regulates the arm swinging angle, and a tire side portion testing device provided with a load application mechanism on the arm), and the impact until air leakage occurs. The number of times was measured.

(3) Fatigue resistance of the carcass cord during normal running The test tire filled with an internal pressure of 230 kPa was subjected to a drum test, and after running a predetermined load at a predetermined speed for 50,000 km, the inner layer side carcass was removed from the tire. The cord was taken out, the cord strength was measured with an autograph manufactured by Shimadzu Corporation, and the retention rate from the new tire was determined. The larger the value, the better the fatigue resistance.

(Examples 7 to 11, Comparative Examples 3 and 4, Conventional Example 2)
Fiber cords having the material, thickness, heat shrinkage stress and dry heat shrinkage shown in Table 3 below are arranged in parallel by the number of driving (90 pieces / 100 mm), and the weft is cut after coating with the coating rubber. A cord / rubber composite was prepared, and using the cord / rubber composite for a carcass ply, a side-reinforcing type run-flat tire having a size 215 / 45ZR17 having a structure shown in FIG. All the carcass ply structures were one ply. Further, the longitudinal spring, run-flat durability of the obtained tire and fatigue resistance of the carcass cord during normal running were evaluated by the following methods, and the results shown in Table 4 were obtained.

(1) Longitudinal spring A load-deflection curve of a test tire filled with an internal pressure of 230 kPa is measured, and the inclination of a tangent at a certain load on the obtained load-deflection curve is defined as a longitudinal spring constant with respect to the load. The value of the vertical spring constant of the tire was expressed as an index with the value being 100. A larger index value indicates a larger longitudinal spring constant.

(2) Run-flat durability A drum test was performed in an environment with a load of 4.17kN, a speed of 89km / h, and a temperature of 38 ° C without filling the test tire with internal pressure. The distance measured until the failure of the tire of the conventional example 2 was taken as 100 and displayed as an index. The larger the index value, the longer the distance traveled until failure, and the better the run-flat durability.

(3) Fatigue resistance of the carcass cord during normal running The test tire filled with an internal pressure of 230 kPa is subjected to a drum test, and a predetermined load is applied and the carcass cord is run at a predetermined speed for 50,000 km. The cord strength was measured with an autograph manufactured by Shimadzu Corporation, and the retention rate from a new tire was determined. The larger the value, the better the fatigue resistance.

It is a right half sectional view showing an example of the pneumatic tire of the present invention. It is a right half sectional view showing other examples of the pneumatic tire of the present invention. It is a schematic sectional drawing which shows the part containing a carcass cord and the weft which cross | intersects it in a carcass ply.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,11 Bead part 2,12 Side wall part 3,13 Tread part 4,14 Carcass ply 5,16 Bead core 6,18 Belt 15 Side reinforcement rubber layer 17 Bead filler 19A, 19B Belt reinforcement layer 21 Carcass ply cord 22 Weft A Weft cutting pitch

Claims (8)

In a pneumatic tire having a carcass ply extending from the crown portion to both bead portions through both side portions,
The carcass ply cord includes at least 50% by mass of polyketone fiber, and has a maximum heat shrinkage stress of 0.1 to 1.8 cN / dtex as a dip-treated cord, and the polyketone fiber is subjected to a dry heat treatment at 150 ° C. for 30 minutes. The thermal shrinkage is in the range of 0.3-3%,
A pneumatic tire characterized in that post-cure inflation (PCI) is performed immediately after vulcanization at an internal pressure of 60 kPa or more.   2. The pneumatic tire according to claim 1, wherein the total width growth when the inner pressure is filled from the inner pressure to 30 kPa is 8 mm or less.   The pneumatic tire according to claim 1 or 2, wherein the polyketone fiber contained in the fiber cord forming the carcass ply has an original yarn tensile strength of 10 cN / dtex or more and an elastic modulus of 200 cN / dtex or more.   2. The carcass ply includes a weft that intersects a cord arranged in a substantially radial direction, and the weft is cut at a plurality of locations in the tire circumferential direction, and the cutting pitch A is in the range of 5 to 30 mm. The pneumatic tire according to any one of?   The pneumatic tire according to claim 4, wherein the weft has a cutting elongation of 5 to 20% and a cutting strength of 200 to 1000 g.   The pneumatic tire according to claim 4 or 5, wherein the weft is made of cellulosic fiber or vinylon fiber.   The pneumatic tire according to any one of claims 4 to 6, wherein the weft is a spun yarn.   The pneumatic tire according to any one of claims 1 to 7, further comprising a side reinforcing rubber layer having a crescent-shaped crescent shape along the inner surface of the carcass ply over the entire region or substantially the entire region of both side portions.

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