JP4683934B2 - Pneumatic safety tire - Google Patents

Description

  The present invention relates to a pneumatic safety tire, and more particularly to a pneumatic safety tire in which a side reinforcing rubber layer is disposed in a sidewall portion and durability in run-flat running is greatly improved.

  Conventionally, as a so-called run-flat tire that can safely travel a certain distance even when the internal pressure of the tire is reduced due to puncture etc., side reinforcement with a crescent cross section inside the carcass of the tire sidewall A side reinforcing type run flat tire is known in which a rubber layer is disposed to improve the rigidity of the sidewall portion. However, in the so-called run-flat running in a state where the internal pressure of the tire is reduced, the deformation of the side reinforcing rubber layer increases as the deformation of the sidewall portion of the tire increases. Heat generation proceeds and in some cases reaches a high temperature of 200 ° C. or higher. In such a state, the side reinforcing rubber layer exceeds its failure limit, and there is a risk that the tire will break down.

  As a means for delaying the time to failure, there is known a method of increasing the volume of the side reinforcing rubber layer by increasing the maximum thickness of the side reinforcing rubber layer. If such a method is adopted, the weight of the tire increases, and the rolling resistance of the tire increases, and the ride comfort and steering stability deteriorate.

  On the other hand, Japanese Patent Laid-Open No. 11-348512 (Patent Document 1) discloses a side reinforcing rubber layer as a tire having improved run flat durability while maintaining a normal running performance at the time of internal pressure filling at a high level. A tire is disclosed in which a short fiber-containing rubber composition is applied and the short fibers are arranged in the radial direction of the tire.

  JP 2004-136863 A (Patent Document 2) applies a rubber composition having a specific loss tangent (tan δ) to the side reinforcing rubber layer to improve riding comfort during normal driving, A tire with improved run-flat durability is disclosed.

JP 11-348512 A JP 2004-136863 A

  However, even the tires described in Japanese Patent Laid-Open Nos. 11-348512 and 2004-136863 still have insufficient room for durability during run-flat running, and there is still room for improvement.

  Accordingly, an object of the present invention is to solve the above-described problems of the prior art, and to maintain a conventional side-reinforced type safety tire while maintaining a high level of normal running performance (rolling resistance, steering stability, etc.) during filling with internal pressure. The object of the present invention is to provide a pneumatic safety tire that is lighter in weight, generates less heat from a side-reinforcing rubber layer, and has greatly improved run-flat running performance.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that a safety tire provided with a side-reinforced rubber layer contains a short rubber fiber made of polyketone having a specific heat shrinkage stress and elastic modulus. Is applied to the above-mentioned side reinforcing rubber layer, the rigidity of the sidewall portion during the run-flat running is maintained, and as a result, the run-flat running performance of the safety tire is significantly improved and the present invention is completed. It came to.

That is, the pneumatic safety tire of the present invention has a pair of bead portions and a pair of sidewall portions, and a tread portion connected to both sidewall portions, and extends in a toroidal shape between the pair of bead portions. In a pneumatic safety tire comprising a carcass that reinforces each of these parts, and a pair of cross-sectional crescent-shaped side reinforcing rubber layers disposed inside the carcass of the sidewall part,
For the rubber component in the side reinforcing rubber layer, the following formula (I) and formula (II):
σ ≧ -0.01 × E + 1.2 (I)
σ ≥ 0.02 (II)
[In the formula, σ is heat shrinkage stress (cN / dtex) at 177 ° C; E is elastic modulus at 49N load at 25 ° C (cN / dtex)] The rubber composition formed as described above is used.

  Here, the heat shrinkage stress σ at 177 ° C is the maximum heat shrinkage stress at 177 ° C. Specifically, when the sample length is fixed at 250 mm by an autograph manufactured by Shimadzu Corporation and left in a thermostat at 177 ° C. It can be determined by measuring the maximum stress obtained. The elastic modulus E at 49N load at 25 ° C is the slope of the tangential line at 49N load on the load-elongation curve. Specifically, the speed is 300mm / min with a sample length of 250mm by Shimadzu Autograph. It can be obtained by measuring the slope of the tangential line at a load of 49 N from the load-elongation curve obtained when pulled by.

［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ポリケトンの繊維であることが好ましい。ここで、前記式(III)中のＡとしては、エチレン基が特に好ましい。 In the pneumatic safety tire of the present invention, the polyketone short fiber has the following general formula (III):

[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], and is a polyketone fiber substantially consisting of a repeating unit represented by It is preferable. Here, as A in the formula (III), an ethylene group is particularly preferable.

  In the pneumatic safety tire of the present invention, it is preferable that the polyketone short fibers have a length of 0.1 mm to 15 mm and a diameter of 0.1 μm to 200 μm.

  Furthermore, in the pneumatic safety tire of the present invention, it is preferable that the polyketone short fiber has a reversibility that contracts at a high temperature and expands when returned to room temperature.

  In a preferred example of the pneumatic safety tire of the present invention, the rubber composition used for the side reinforcing rubber layer is formed by blending 2 to 20 parts by mass of the polyketone short fibers with respect to 100 parts by mass of the rubber component.

  According to the present invention, by using a rubber composition containing short fibers made of polyketone having a specific heat shrinkage stress and elastic modulus for the side reinforcing rubber layer, the normal running performance at the time of internal pressure filling is high, and the conventional side Compared to reinforced safety tires, the side reinforcement rubber layer generates less heat and the rigidity of the side wall during run-flat running can be maintained sufficiently. Safety tires can be provided.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of an example of the pneumatic safety tire of the present invention. The safety tire shown in FIG. 1 has a pair of left and right bead portions 1 and a pair of sidewall portions 2, and a tread portion 3 connected to both sidewall portions 2, and extends in a toroid shape between the pair of bead portions 1. A radial carcass 4 that reinforces each of the parts 1, 2, and 3, a belt 5 comprising two belt layers disposed on the outer side in the tire radial direction of the crown part of the carcass 4, and the sidewall part 2 A pair of crescent-shaped side reinforcing rubber layers 6 disposed inside the carcass 4, an inner liner 7 disposed on the inner surface of the tire, and a ring-shaped bead core 8 embedded in the bead portion 1, respectively, on the outer side in the tire radial direction. And the bead filler 9 arranged in the above.

  In the illustrated safety tire, the radial carcass 4 includes a folded carcass ply 4a and a down carcass ply 4b, and both end portions of the folded carcass ply 4a are folded around the bead core 8 to form folded ends. . The structure and the number of plies of the radial carcass 4 are not limited to this.

  In the safety tire shown in FIG. 1, a belt 5 composed of two belt layers is arranged on the outer side in the tire radial direction of the crown portion of the radial carcass 4, and the belt layer is usually a tire equatorial plane. The belt 5 is formed by laminating the two belt layers so that the cords constituting the belt layer intersect with each other across the equator plane. The belt 5 in FIG. 1 is composed of two belt layers, but in the safety tire of the present invention, the number of belt layers constituting the belt 5 is not limited to this.

In the pneumatic safety tire of the present invention, the side reinforcing rubber layer 6 has the following formula (I) and formula (II) with respect to the rubber component:
σ ≧ -0.01 × E + 1.2 (I)
σ ≥ 0.02 (II)
[In the formula, σ is heat shrinkage stress (cN / dtex) at 177 ° C; E is elastic modulus at 49N load at 25 ° C (cN / dtex)] It is necessary to use the rubber composition obtained. Since the polyketone short fibers have high heat shrinkage stress at high temperature, that is, at 177 ° C., the side reinforcing rubber layer 6 can sufficiently retain the rigidity during run-flat running. Therefore, by applying a rubber composition containing polyketone short fibers satisfying the above formulas (I) and (II) to the side reinforcing rubber layer 6, the run-flat durability of the safety tire can be greatly improved. . In addition, by applying the polyketone short fiber-containing rubber composition to the side reinforcing rubber layer 6, the run flat durability can be greatly improved, so that the side reinforcing rubber layer 6 is secured while ensuring sufficient run flat durability. As a result, it is possible to reduce the thickness of the safety tire and to suppress the heat generation of the side reinforcing rubber layer 6.

  In addition, if the heat shrinkage stress σ at 177 ° C of the polyketone short fiber is less than 0.02 cN / dtex, the rigidity of the side reinforcing rubber layer 6 during run flat running (at high temperature) cannot be secured. Decreases. In addition, when polyketone short fibers that do not satisfy the relationship of formula (I) are used, the rigidity of the side wall portion at room temperature becomes low, so that it is difficult to reduce the weight of the side reinforcing rubber.

  The rubber composition for the side reinforcing rubber layer 6 is formed by blending the polyketone short fibers with a rubber component. Examples of the rubber component of the rubber composition include natural rubber (NR) and diene synthetic rubbers such as styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), and polyisoprene rubber (IR). These rubber components may be used alone or in a blend of two or more. Of these rubber components, natural rubber and polybutadiene rubber are preferred.

The polyketone short fibers used in the rubber composition are preferably polyketone short fibers consisting essentially of repeating units represented by the formula (III). Of the polyketone as a raw material for short fibers, a polyketone in which 97 mol% or more of repeating units is 1-oxotrimethylene [—CH ₂ —CH ₂ —CO—] is preferable, and 99 mol% or more is 1-oxotrimethylene. More preferred is a polyketone that is methylene, and most preferred is a polyketone in which 100 mole percent is 1-oxotrimethylene.

  The polyketone as the raw material of the above polyketone short fiber may be partially bonded with ketone groups or with portions derived from unsaturated compounds, but with portions derived from unsaturated compounds and ketone groups alternately arranged. Is preferably 90% by mass or more, more preferably 97% by mass or more, and most preferably 100% by mass.

  In the formula (III), 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 , A compound containing an unsaturated bond, such as sodium styrenesulfonate, sodium allylsulfonate, vinylpyrrolidone, and vinyl chloride.

［式中、ｔ及びＴは、純度98％以上のヘキサフルオロイソプロパノール及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の範囲にあることが好ましく、2〜10dL/gの範囲にあることが更に好ましく、3〜8の範囲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を得ることが難しくなる上、紡糸時、乾燥時及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及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、紡糸性及び物性に悪影響が出ることがある。 Furthermore, as the polymerization degree of the polyketone, the following formula:

[Wherein, t and T are the flow times 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; C is 100 mL of the diluted solution It is preferable that the intrinsic viscosity [η] defined by the mass (g) of the solute in the range is 1 to 20 dL / g, more preferably 2 to 10 dL / g, and 3 to Even more preferably in the range of 8. When the intrinsic viscosity is less than 1 dL / g, it is difficult to obtain a high-strength polyketone fiber because the molecular weight is too small, 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.

  As the method for fiberizing the polyketone, (1) after spinning an unstretched yarn, performing multi-stage heat stretching, and stretching at a specific temperature and magnification in the final stretching step of the multi-stage heat 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. By performing polyketone fiberization by the method (1) or (2), a desired filament suitable for the production of the polyketone short fiber can be obtained.

  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 No., JP-A No. 2004-218189, JP-A No. 2004-285221, and the wet spinning method using an aqueous solution of zinc salt, calcium salt, thiocyanate, iron salt, etc., among these, A wet spinning method using an aqueous solution of is preferred.

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

  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, etc. at a concentration of 2 to 30% by mass, and a spinning nozzle is used at 50 to 130 ° C. Then, it is extruded into a coagulation bath and subjected to gel spinning, followed by desalting and drying to obtain an undrawn polyketone yarn. 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 this heat drawing method, 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 preferably 10 times or more.

  When polyketone fiberization is performed by the method of (1) above, the temperature in the final stretching step of the multistage thermal stretching is in the range of 110 ° C to (stretching temperature in the stretching step one step before the final stretching step-3 ° C). 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 (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 ° C / The cooling end temperature in the rapid cooling is preferably 50 ° C. or lower. Here, there is no restriction | limiting in particular as a rapid cooling method of the heat-stretched polyketone fiber, A conventionally well-known method can be employ | adopted, Specifically, the cooling method using a roll is preferable. In addition, since the polyketone fiber obtained in this way has a large residual elastic strain, it is usually preferable to perform relaxation heat treatment so that the fiber length is shorter than the fiber length after hot drawing. Here, the temperature of the relaxation heat treatment is preferably in the range of 50 to 100 ° C., and the relaxation ratio is preferably in the range of 0.980 to 0.999 times.

  The target polyketone short fiber can be obtained by cutting the polyketone fiber obtained by fiberization as described above in the yarn length direction. Here, the polyketone short fiber preferably has a length of 0.1 mm to 15 mm, and preferably has a diameter of 0.1 μm to 200 μm. If the length of the polyketone short fiber is less than 0.1 mm, the yield at the time of cutting is poor and the cost is high.On the other hand, if it exceeds 15 mm, the dispersibility in the rubber component at the time of blending becomes poor, so the polyketone short fiber is a fracture nucleus. Thus, the breaking characteristics of the side reinforcing rubber layer 6 are deteriorated. If the diameter of the polyketone short fiber is less than 0.1 μm, it is not preferable in terms of cost, and if it exceeds 200 μm, it is not preferable in terms of the strength of the side reinforcing rubber layer 6.

  The cross-sectional shape of the polyketone short fibers may be circular or different from a circular shape. In addition, the polyketone short fibers need not be subjected to an adhesive treatment in advance as long as the adhesiveness with the matrix rubber after vulcanization is sufficient, but if the adhesiveness is insufficient, Processing may be performed. Furthermore, the polyketone short fibers preferably have reversibility that shrinks at high temperatures and expands when returned to room temperature.

  The rubber composition for the side reinforcing rubber layer 6 is preferably formed by blending 2 to 20 parts by mass of the polyketone short fibers with respect to 100 parts by mass of the rubber component. If the blending amount of the polyketone short fiber is less than 2 parts by mass with respect to 100 parts by mass of the rubber component, the effect of blending the polyketone short fiber does not sufficiently appear, whereas if it exceeds 20 parts by mass, the dispersion of the polyketone short fiber is not achieved. The property deteriorates to become a fracture nucleus, and the fracture characteristics of the side reinforcing rubber layer 6 are lowered.

  The rubber composition for the side reinforcing rubber layer 6 includes, in addition to the rubber component and polyketone short fibers, compounding agents usually used in the rubber industry, such as fillers, softeners, anti-aging agents, and vulcanizing agents. Vulcanization aids, vulcanization accelerators, and the like can be appropriately selected and blended within a range that does not impair the object of the present invention. As these compounding agents, commercially available products can be suitably used. The rubber composition can be produced by blending polyketone short fibers and various compounding agents appropriately selected as necessary with respect to the rubber component, kneading, heating, extruding, and the like. it can.

  The pneumatic safety tire of the present invention can be manufactured by applying the above-mentioned polyketone short fiber-containing rubber composition to the side reinforcing rubber layer 6 and using a conventional method. In the pneumatic safety tire of the present invention, as the gas filled in the tire, normal or air having a changed oxygen partial pressure, or an inert gas such as nitrogen can be used.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

  A rubber composition having a formulation shown in Table 1 was prepared, and the rubber composition was applied to the side reinforcing rubber layer 6 to make a safety tire of size 265 / 35ZR18 with the structure shown in FIG. Moreover, run-flat durability was evaluated by the following method with respect to this safety tire. The results are shown in Table 1 together with the thickest gauge and weight of the side reinforcing rubber layer 6 of the test tire.

(1) Run flat durability Each prototype tire is assembled with rims at normal pressure, filled with 230kPa of internal pressure and left in a room at 38 ℃ for 24 hours, then the valve core is removed and the internal pressure is set to atmospheric pressure. A drum running test was conducted under conditions of 89km / h and temperature of 38 ℃. The distance traveled until the failure occurred at this time was measured, and the travel distance until the failure occurred in the tire of Comparative Example 1 was shown as an index. The larger the index value, the longer the distance traveled until the failure occurs, indicating better run-flat durability.

* 1 BR01 manufactured by JSR Corporation.
* 2 FEF.
* 3 N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine, "NOCRACK 6C" manufactured by Ouchi Shinsei Chemical Industry.
* 4 N-t-butyl-2-benzothiazolylsulfenamide, “Noxeller NS” manufactured by Ouchi Shinsei Chemical Industry.
* 5 Polyketone short fibers consisting almost 100% of repeating units represented by the formula (III), wherein 97 mol% or more of the repeating units is 1-oxotrimethylene, diameter = 10 μm, length = 2 mm.
* 6 Short fibers of polyketone (containing about 6% propylene) consisting of repeating units represented by formula (III), where A is mainly ethylene group, diameter = 10μm, length = 2mm.

  As is apparent from Table 1, the rubber composition containing the polyketone short fiber that satisfies the conditions of the above formulas (I) and (II) is applied to the side reinforcing rubber layer to greatly increase the laflat durability of the safety tire. Can be improved. Moreover, since the improvement width of the laflat durability is large, even when the thickness of the side reinforcing rubber layer is reduced to reduce the weight of the tire, excellent laflat durability can be obtained.

It is sectional drawing of one embodiment of the pneumatic safety tire of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tread part 4 Radial carcass 4a Folding carcass ply 4b Down carcass ply 5 Belt 6 Side reinforcement rubber layer 7 Inner liner 8 Bead core 9 Bead filler

Claims (6)

A carcass having a pair of bead portions and a pair of sidewall portions, and a tread portion connected to both sidewall portions, and extending in a toroidal shape between the pair of bead portions to reinforce these portions; and the sidewall In a pneumatic safety tire comprising a pair of cross-sectional crescent-shaped side reinforcing rubber layers disposed inside the carcass of a part,
For the rubber component in the side reinforcing rubber layer, the following formula (I) and formula (II):
σ ≧ -0.01 × E + 1.2 (I)
σ ≥ 0.02 (II)
[In the formula, σ is heat shrinkage stress (cN / dtex) at 177 ° C; E is elastic modulus at 49N load at 25 ° C (cN / dtex)] A pneumatic safety tire characterized by using a rubber composition. The polyketone short fiber has the following general formula (III):

[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], and is a polyketone fiber substantially consisting of a repeating unit represented by The pneumatic safety tire according to claim 1.   The pneumatic safety tire according to claim 2, wherein A in the formula (III) is an ethylene group.   The pneumatic safety tire according to any one of claims 1 to 3, wherein the polyketone short fibers have a length of 0.1 mm to 15 mm and a diameter of 0.1 µm to 200 µm.   The pneumatic safety tire according to any one of claims 1 to 4, wherein the polyketone short fibers have reversibility that contracts at a high temperature and expands when returned to room temperature.   The pneumatic safety tire according to claim 1, wherein the rubber composition used for the side reinforcing rubber layer is formed by blending 2 to 20 parts by mass of the polyketone short fibers with respect to 100 parts by mass of the rubber component. .

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