JP2009184562A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire in which rolling resistance and road noise are significantly reduced, and high-speed durability is improved. <P>SOLUTION: The pneumatic radial tire includes: a center part belt reinforcement layer 3 for covering only the center part of a main belt outside in a tire radial direction of the main belt 1; and a shoulder part belt reinforcement layer 4 for covering the end of the main belt. A twin-twisted cord comprised by twisting a plurality of filament bundles of polyhexamethylene adipamide (nylon 6, 6) is used in the center part belt reinforcement layer 3. A composite cord in which one or two filament bundles of aliphatic polyketone, and one filament bundle of polyhexamethylene adipamide (nylon 6, 6) are twisted is used in the shoulder part belt reinforcement layer 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire in which rolling resistance and road noise are greatly reduced and high-speed durability is improved.

  Along with the recent upgrades and quality of vehicles, especially in passenger cars, the reduction of vehicle vibration and the improvement of ride comfort are advancing rapidly, and tires are also required to have low noise and high ride comfort. It has been. In other words, it is desired to improve the riding comfort and reduce the noise generated inside the vehicle. As one of such noises, the running tire spreads the unevenness of the road surface and the vibration is transmitted to remove the air inside the vehicle. There has been a strong demand to reduce so-called road noise generated due to vibration. On the other hand, as vehicle fuel efficiency and pollution are advancing, there is a strong demand for low rolling resistance for tires.

  Various methods have been devised for reducing the road noise. One of them is a rubberized cord made of polyethylene-2,6-naphthalate, which is a high-rigidity fiber, and a cross belt layer (main belt). A method of suppressing the vibration of the belt portion by forming a belt reinforcing layer by spirally winding the upper portion of the belt) is known.

  However, if the cord that reinforces the center of the belt is made of fibers with excessively high rigidity, energy loss due to deformation that occurs in response to tire rolling increases, and when there is no belt reinforcement layer and when the low rigidity cord is used as a belt reinforcement layer It is known that the rolling resistance is increased as compared with the case used in the above.

  In contrast, by disposing a highly rigid belt reinforcement layer only at the belt end and not providing a belt reinforcement layer at the center of the belt, it is possible to prevent the deterioration of rolling resistance as described above. Further, since the radius of curvature of the tire crown portion becomes excessively small, it leads to a decrease in uneven wear resistance and steering stability, and an important road noise reduction effect cannot be obtained sufficiently.

  As a method for simultaneously solving such problems, that is, a method capable of simultaneously reducing road noise and rolling resistance, a highly rigid belt reinforcement layer such as polyethylene-2,6-naphthalate is disposed at the belt end. A method has been developed in which a low-rigidity belt reinforcing layer such as nylon 6,6 is installed in the center of the belt (see Patent Documents 1 to 3).

JP 11-208212 A JP-A-2003-320813 JP 2004-224074 A

  However, due to the recent trend toward high-grade automobiles and environmental regulations, the demand for quietness of tires is increasing, and the reduction of road noise obtained by applying polyethylene-2,6-naphthalate (PEN) cord to the belt reinforcement layer. Increasingly, the number of cases where the required performance cannot be sufficiently satisfied only by the effect. To solve this problem, by applying an aliphatic polyketone (PK) cord, which has about three times the rigidity of the PEN cord, to the belt reinforcement layer, belt vibration during tire rolling is suppressed and road noise is further reduced. can do. However, when the PK cord is applied to the belt reinforcing layer, as another problem, the cord constituting the belt reinforcing layer may bite into the belt layer, and the belt layer may be deformed to deteriorate the tire uniformity. This is because the PK cord expresses a much higher heat shrinkage stress during vulcanization than the PEN cord. In particular, in a tire in which soft rubber is applied to the belt reinforcing layer in order to improve riding comfort. Such a problem becomes prominent.

  Further, as described above, high-rigidity fibers such as polyethylene-2,6-naphthalate are arranged in the reinforcing layer at the belt end portion, and low-rigidity fibers such as nylon 6,6 are arranged in the reinforcing layer in the central portion of the belt. Example of producing tires of various sizes, and in many cases, there is a 5-10mm “gap” between the reinforcing layer at the belt end and the reinforcing layer at the center of the belt where the belt is not reinforced at all. Was scattered. In particular, in the process of expanding the raw tire during vulcanization and pressing it against the vulcanization mold, the stress generated in the belt reinforcing layer resisting expansion greatly differs between the belt end and the belt center. That is, since a highly rigid fiber is arranged in the reinforcing layer at the belt end, a large stress is generated during expansion, and as a result, the rubber around the fiber tends to flow during vulcanization, while the reinforcement at the center of the belt Since the low-rigidity fibers are arranged in the layer, the stress generated during expansion is relatively small, and the rubber does not flow and the arrangement is almost the same as that of the raw tire. As a result, such a “gap” is generated. It has been found that the tires produced in this manner have abnormally concentrated stress in the “gap” of the belt reinforcing layer during rolling, and as a result, the effect of reducing road noise cannot be obtained sufficiently.

  Accordingly, an object of the present invention is to provide a pneumatic radial tire that solves the above-described problems of the prior art, has a significantly reduced rolling resistance and road noise, and has improved high-speed durability. Another object of the present invention is to provide a pneumatic radial tire in which road resistance is reliably reduced in addition to low rolling resistance.

  As a result of intensive studies to achieve the above object, the present inventor has found that one or two filament bundles of aliphatic polyketone and one polyhexamethylene are used as the reinforcing element of the belt reinforcing layer for reinforcing the belt end. By using a composite cord twisted with adipamide (nylon 6,6), the spiral radius of the composite cord becomes large, the heat shrinkage behavior during tire vulcanization can be relaxed, and the composite cord during cord extension It has been found that road noise can be greatly reduced while maintaining tire uniformity, since the rigidity of the tire is not impaired.

  Further, as a result of further investigation, the inventor uses a cord in which a filament bundle of polyhexamethylene adipamide (nylon 6, 6) is twisted as a reinforcing element of the belt reinforcing layer that reinforces the belt central portion. Thus, the rolling resistance can be reduced, and in addition, the cord structure has a double twisted structure in which a plurality of filament bundles of polyhexamethylene adipamide (nylon 6, 6) are twisted together. It has been found that high-speed durability can be improved.

  Furthermore, the present inventor provides a width direction distribution of stress generated during expansion in the vulcanization process by providing a portion where the belt reinforcement layer that reinforces the belt center portion and the belt reinforcement layer that reinforces the belt end portion overlap each other. Because there are no parts that change rapidly, and there are overlapping parts, it is possible to reliably prevent the occurrence of the “gap” as described above in the vulcanization process, and to reliably reduce the road noise of the tire. I found.

That is, the pneumatic radial 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. A carcass, a main belt composed of at least two belt layers disposed on the outer side in the tire radial direction of the crown portion of the carcass, and disposed on the outer side in the tire radial direction of the main belt and substantially parallel to the tire circumferential direction. Comprising at least two belt reinforcing layers made of rubberized layers of arranged reinforcing elements,
The belt reinforcing layer comprises a pair of one or more center belt reinforcing layers covering only the central portion of the main belt and a pair of one or more shoulder belt reinforcing layers covering only the end portions of the main belt, The outer end of the shoulder belt reinforcing layer in the tire width direction is located on the outer side in the tire width direction of the main belt in the tire width direction outer end,
The reinforcing element constituting the center belt reinforcing layer is a cord of a double twist structure formed by twisting a plurality of filament bundles of polyhexamethylene adipamide (nylon 6, 6), and the shoulder belt reinforcing layer is The reinforcing element is a composite cord in which a filament bundle of one or two aliphatic polyketones and a filament bundle of one polyhexamethylene adipamide (nylon 6, 6) are twisted together .

  In a preferred example of the pneumatic radial tire of the present invention, the outer end in the tire width direction of the center belt reinforcing layer is the outer side in the tire width direction of the narrowest belt layer of the belt layers constituting the main belt. It is located inside the tire width direction from the end. In this case, the road noise of the tire can be sufficiently reduced.

  In another preferred embodiment of the pneumatic radial tire of the present invention, at least a part of the center portion belt reinforcing layer and the shoulder portion belt reinforcing layer adjacent to the center portion belt reinforcing layer overlap each other. In this case, there is no portion that changes suddenly in the width direction distribution of stress generated during expansion in the vulcanization process, and there is an overlapping portion, so that the above-mentioned “gap” is surely generated in the vulcanization process. As a result, tire road noise can be reliably reduced.

  Here, the width of the overlapping portion between the center belt reinforcing layer and the shoulder belt reinforcing layer adjacent to the center belt reinforcing layer is preferably in the range of 1 to 12 mm. In this case, it is possible to sufficiently prevent a gap from being generated between the center portion belt reinforcing layer and the shoulder portion belt reinforcing layer regardless of the section width of the tire.

  In another preferred embodiment of the pneumatic radial tire of the present invention, the total width of the belt reinforcing layer composed of the center belt reinforcing layer and the shoulder belt reinforcing layer is 2 to less than the total width of the main belt. 10mm wide. In this case, the road noise of the tire can be sufficiently reduced.

  In another preferred embodiment of the pneumatic radial tire of the present invention, the width of the shoulder belt reinforcing layer is 5 to 20% of the total width of the main belt. In this case, the road noise of the tire can be sufficiently reduced, and the rolling resistance is not deteriorated.

  In another preferred embodiment of the pneumatic radial tire of the present invention, the reinforcing element constituting the shoulder belt reinforcing layer is a composite cord having a total fineness of 1000 to 6000 dtex. In this case, the road noise of the tire can be sufficiently reduced, and the occurrence of a separation failure between the tread and the shoulder belt reinforcing layer can be prevented.

In the pneumatic radial tire of the present invention, the composite cord constituting the shoulder portion belt reinforcing layer has the following formula (I):
R = N × (0.125 × D / ρ) ^1/2 × 10 ^-3 (I)
[Where N is the number of twists of the cord (times / 10 cm), D is the total number of decitex of the cord (dtex), and ρ is the specific gravity of the cord (g / cm ³ )] R is preferably 0.20 to 1.05. In this case, road noise of the tire can be sufficiently reduced while preventing the occurrence of a separation failure between the tread and the shoulder belt reinforcement layer. The cord twist number N indicates the number of upper twists.

  In another preferred embodiment of the pneumatic radial tire of the present invention, the reinforcing element constituting the center portion belt reinforcing layer is a filament bundle of polyhexamethylene adipamide (nylon 6, 6) having a total fineness of 500 to 2000 dtex. It is a twisted cord. In this case, the rolling resistance and road noise of the tire can be sufficiently reduced, and the uneven wear resistance and steering stability of the tire can be prevented from being lowered.

In the pneumatic radial tire of the present invention, the cord of the double twist structure constituting the center portion belt reinforcing layer has the following formula (I):
R = N × (0.125 × D / ρ) ^1/2 × 10 ^-3 (I)
[Where N is the number of twists of the cord (times / 10 cm), D is the total number of decitex of the cord (dtex), and ρ is the specific gravity of the cord (g / cm ³ )] R is preferably 0.22 to 0.77. In this case, the occurrence of a separation failure between the tread and the center belt reinforcing layer can be prevented, the cord is not crimped, and the workability during tire production is good. The cord twist number N indicates the number of upper twists.

  In another preferred example of the pneumatic radial tire of the present invention, the number of cords constituting the center belt reinforcing layer and the shoulder belt reinforcing layer is 30/50 mm to 70/50 mm. In this case, the main belt can be sufficiently reinforced, and the occurrence of a separation failure between the tread and the center belt reinforcing layer and / or the shoulder belt reinforcing layer can be prevented.

  In the pneumatic radial tire of the present invention, each of the center belt reinforcing layer and the shoulder belt reinforcing layer is a ribbon-like shape obtained by rubberizing one or more reinforcing elements having a narrower width than the arrangement width. The sheet is preferably formed by spirally winding the sheet a plurality of times in the tire width direction until a predetermined width dimension is obtained. In this case, a joint part does not arise in the tire circumferential direction, and the main belt can be reinforced uniformly.

  According to the present invention, a cord in which a filament bundle of polyhexamethylene adipamide (nylon 6, 6) is twisted is used for the center belt reinforcing layer, and one or two aliphatic polyketones are used for the shoulder belt reinforcing layer. By using a composite cord in which a bundle of filaments and one polyhexamethylene adipamide (nylon 6, 6) are twisted together, tire rolling resistance and road noise can be greatly reduced. Moreover, the cord used for the center belt reinforcement layer is a double twisted structure cord formed by twisting a plurality of polyhexamethylene adipamide (nylon 6, 6) filament bundles, thereby improving high-speed durability. Can do. Furthermore, by providing a portion where the belt reinforcing layer that reinforces the belt center portion and the belt reinforcing layer that reinforces the belt end portion overlap each other, it is possible to reliably reduce tire road noise.

  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 a tread portion of a pneumatic radial tire according to the present invention. The pneumatic radial 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 a carcass extending in a toroidal shape between the pair of bead portions. A main belt 1 composed of at least two belt layers disposed on the outer side in the tire radial direction of the crown portion of the carcass, and disposed on the outer side in the tire radial direction of the main belt 1 and substantially parallel to the tire circumferential direction. And at least two belt reinforcing layers 2 made of rubberized layers of arranged reinforcing elements.

  In the pneumatic radial tire of the present invention, the belt reinforcing layer 2 includes one or more center belt reinforcing layers 3 covering only the central portion of the main belt 1 and one or more shoulders covering only the end portions of the main belt 1. It consists of a pair of partial belt reinforcement layers 4. Here, in the pneumatic radial tire of the present invention, it is preferable that the center portion belt reinforcing layer 3 is located on the inner side in the tire radial direction than the shoulder portion belt reinforcing layer 4 as in the illustrated example. In the illustrated tire, the center belt reinforcing layer 3 is composed of one layer, but the center belt reinforcing layer 3 of the tire of the present invention may be two or more layers. Furthermore, in the illustrated tire, the shoulder portion belt reinforcing layer 4 is composed of two layers, a layer 4a adjacent to the center portion belt reinforcing layer 3 and a layer 4b located on the outer side in the tire radial direction of the layer 4a. The tire belt reinforcing layer 4 of the tire of the present invention may be a single layer or three or more layers.

In the pneumatic radial tire of the present invention, the outer end portion P _{4 in} the tire width direction of the shoulder belt reinforcing layer 4 is located on the outer side in the tire width direction with respect to the outer end portion P _{1 in} the tire width direction of the main belt 1. Here, when the shoulder portion belt reinforcing layer 4 is composed of two or more layers, the outer end portion P _{4 in} the tire width direction of the shoulder portion belt reinforcing layer 4 is the most among the end portions of each layer of the shoulder portion belt reinforcing layer 4. An end located on the outer side in the tire width direction refers to an outer end P _{1 of} the main belt 1 in the tire width direction. The tire of the belt layer 1a having the widest belt layer constituting the main belt 1 It corresponds to the width direction outer side end. Incidentally, the shoulder portion the belt reinforcing layer 4 of each layer 4a of the tire in the illustrated example, 4b is a tire width direction outer end portion P ₄ are aligned, the pneumatic radial tire of the present invention, each layer of the shoulder portion the belt reinforcing layer The tire width direction outer side end portion may be uneven.

  The belt layers 1a and 1b constituting the main belt 1 are usually composed of a rubberized layer of a cord extending preferably inclining with respect to the tire equatorial plane, preferably a rubberized layer of a steel cord. Then, the two belt layers 1a and 1b are laminated so that the cords constituting the belt layers intersect with each other across the tire equatorial plane to constitute the main belt 1. The main belt 1 of the illustrated tire has two layers, a belt layer 1a having the widest width and a belt layer 1b that is positioned on the outer side in the tire radial direction of the belt layer 1a and narrower than the belt layer 1a. However, in the pneumatic radial tire of the present invention, the structure of the main belt 1 is not limited to this, and the number of belt layers constituting the main belt 1 may be three or more.

  On the other hand, the belt reinforcement layer 2 is composed of a rubberized layer of reinforcement elements arranged substantially parallel to the tire circumferential direction. The reinforcement element constituting the center belt reinforcement layer 3 is made of polyhexamethylene adipamide (nylon). 6, 6) a cord having a double twist structure in which a plurality of filament bundles are twisted together, while the reinforcing element constituting the shoulder belt reinforcing layer 4 is made of one or two aliphatic polyketones (PK). A composite cord in which a filament bundle and a filament bundle of one polyhexamethylene adipamide (nylon 6, 6) are twisted together. As a reinforcing element constituting the shoulder belt reinforcing layer 4, a composite cord in which one or two aliphatic polyketone filament bundles and one polyhexamethylene adipamide (nylon 6, 6) are twisted together is used. As a result, the spiral radius of the composite cord increases and the heat shrinkage behavior during tire vulcanization is alleviated, so that the composite cord can be prevented from biting into the belt layer, and the rigidity of the composite cord when the cord is extended can be reduced. High rigidity can be exhibited without any damage. For this reason, the pneumatic radial tire of the present invention can significantly reduce road noise while maintaining tire uniformity.

  Moreover, as a reinforcement element which comprises the center part belt reinforcement layer 3, rolling resistance is reduced by using the cord which twisted the filament bundle of the polyhexamethylene adipamide (nylon 6, 6) which has low rigidity. be able to. Further, since the cord constituting the center belt reinforcing layer 3 has a double twist structure in which a plurality of filament bundles of polyhexamethylene adipamide (nylon 6, 6), preferably two, are twisted together, Excellent adhesion to rubber compared to polyketone (PK) cords. As a result, the center part of the tire crown protrudes during high-speed driving, and even if continuous strain input or high temperature occurs, the tread rubber and center Peeling does not easily occur with the partial belt reinforcing layer, and high-speed durability can be improved. For example, the cord for the center portion belt reinforcing layer is obtained by applying a twist to a filament bundle made of the above polyhexamethylene adipamide (nylon 6, 6), and then combining a plurality, preferably two of them. By twisting in the direction, it can be obtained as a twisted cord.

In the pneumatic radial tire of the present invention, as shown in FIG. 1, the outer end portion P _{3 in} the tire width direction of the center belt reinforcing layer 3 is the widest of the belt layers 1 a and 1 b constituting the main belt 1. that is located inside the tire width direction than the tire width direction outer end portion P _1b of the narrow belt layer 1b of are preferred. In this case, since the end portion of the main belt 1 is reinforced by the composite cord constituting the shoulder portion belt reinforcing layer 4, the road noise of the tire can be sufficiently reduced.

  In the pneumatic radial tire of the present invention, the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4a adjacent to the center belt reinforcing layer 3 are at least partially overlapped as shown in FIG. Is preferred. In this case, there is no portion in which the distribution in the width direction of the stress generated during the expansion of the vulcanization process changes rapidly, and the stress generated during the expansion continuously changes in the tire width direction. Therefore, at the time of expansion of the vulcanization process, the degree of rubber flow continuously changes in the belt reinforcing layer 2 to prevent a gap from being generated between the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4. Can do. When the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4a adjacent to the center belt reinforcing layer 3 are overlapped, the center belt reinforcing layer 3 and the shoulder belt reinforcing layer are expanded when the vulcanization process is expanded. Even if it deviates somewhat from 4, the occurrence of a gap in which the main belt 1 is not reinforced at all can be reliably prevented by the presence of the overlap portion, so that a tire having a target structure can be easily manufactured.

  Here, the width W of the overlapping portion between the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4a adjacent to the center belt reinforcing layer 3 needs to be appropriately set according to the tire size and the expansion rate during vulcanization. Although not particularly limited, a range of 1 to 12 mm is preferable. If the tire has a small section width and a belt end expansion rate of 1% or less, the width W of the overlapping portion of the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4a adjacent to the layer 3 may be 1 mm. If the width W of the overlapping part between the center part belt reinforcing layer 3 and the shoulder part belt reinforcing layer 4a adjacent to the layer 3 is 12 mm, even if the tire is sufficient for an SUV or the like, the center part Generation of a gap between the belt reinforcing layer 3 and the shoulder belt reinforcing layer 4 can be sufficiently prevented.

In the pneumatic radial tire of the present invention, the total width W ₂ of the belt reinforcing layer 2 composed of the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4 is _{2 to} 10 mm than the total width W ₁ of the main belt 1. Wide is preferable. The total width W ₂ of the belt reinforcing layer 2 made larger than 2mm than the total width W ₁ of the main belt 1, by securely cover the end portion of the main belt 1 in the belt reinforcing layer 2 sufficiently reduce road noise can do. On the other hand, be increased beyond the 10mm than the total width W ₂ of the belt reinforcing layer 2 total width W ₁ of the main belt 1, it is impossible to further reduce the road noise.

In the pneumatic radial tire of the present invention, the width W ₄ of the shoulder portion belt reinforcing layer 4 is preferably 5 to 20% of the total width W ₁ of the main belt 1. If the width W _{4 of the} shoulder portion belt reinforcing layer 4 is less than 5% of the total width W ₁ of the main belt 1, the road noise of the tire may not be sufficiently reduced. On the other hand, if the width W _{4 of} the shoulder portion belt reinforcing layer 4 exceeds 20% of the total width W ₁ of the main belt 1, the rolling resistance of the tire may deteriorate. Here, when the shoulder portion belt reinforcing layer 4 is composed of two or more layers, the width W ₄ of the shoulder portion belt reinforcing layer 4 refers to the width of each layer of the shoulder portion belt reinforcing layer 4. The width W _4a of the layer 4a adjacent to the center belt reinforcing layer 3 and the width W _{4b of the} layer 4b located on the outer side in the tire radial direction of the layer 4a are indicated.

  In the pneumatic radial tire of the present invention, the reinforcing element constituting the shoulder belt reinforcing layer 4 includes one or two aliphatic polyketone (PK) filament bundles and one polyhexamethylene adipamide (nylon 6). , 6) is required to be a composite cord in which the filament bundle is twisted together. Here, the method for producing the composite cord is not particularly limited, and for example, one or two aliphatic polyketone (PK) filament bundles and one polyhexamethylene adipamide (nylon 6, 6). Each of these filament bundles is subjected to a lower twist, and these are then combined, and an upper twist is applied in the opposite direction to obtain a twisted yarn cord.

Examples of the aliphatic polyketone used for the composite cord constituting the shoulder belt reinforcing layer 4 include the following formula (II):
_{- (CH 2 -CH 2 -CO)} n - (R-CO) m - ··· (II)
[Wherein R is a portion derived from an unsaturated compound polymerized by an unsaturated bond, and may be the same or different in each repeating unit, provided that it is not an ethylene group; n and m are repeating It is substantially composed of a repeating unit represented by the following formula (III):
0.95 ≤ n / (n + m) ≤ 1 (III)
An aliphatic polyketone satisfying the above is preferable. Here, as the unsaturated compound forming R in the formula (II), unsaturated compounds other than ethylene such as propylene, butene, pentene, cyclopentene, hexene, cyclohexene, heptene, octene, nonene, decene, dodecene, Unsaturated hydrocarbons other than ethylene such as styrene, acetylene, and allene, methyl acrylate, methyl methacrylate, vinyl acetate, acrylamide, hydroxyethyl methacrylate, undecenoic acid, undecenol, 6-chlorohexene, N-vinyl pyrrolidone, and sulfonyl phosphonic acid And compounds containing unsaturated bonds such as diethyl ester, sodium styrene sulfonate, sodium allyl sulfonate, vinyl pyrrolidone and vinyl chloride.

  In the polyketone, the ketone groups may be partially bonded to each other and the unsaturated compound-derived portions may be bonded to each other, but the proportion of the unsaturated compound-derived portions and the ketone groups alternately arranged is 90% by mass. It is preferably at least 97% by mass, more preferably 100% by mass.

［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、3〜8dL/g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、高強度の複合コード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 More preferably, it is in the range of 8 dL / g. If the intrinsic viscosity is less than 1 dL / g, the molecular weight is too small, making it difficult to obtain a high-strength composite cord, and frequent troubles such as fluff and yarn breakage 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. A desired polyketone filament suitable for production of the composite 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 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.

  In the pneumatic radial tire of the present invention, the reinforcing element constituting the shoulder belt reinforcing layer 4 includes one or two aliphatic polyketone (PK) filament bundles having a total fineness of 1000 to 6000 dtex and one polyhexamethylene. A composite cord formed by twisting together a filament bundle of adipamide (nylon 6, 6) is preferable. If the total fineness of the composite cord is less than 1000 dtex, the rigidity of the shoulder belt reinforcing layer 4 becomes insufficient, and the road noise of the tire may not be sufficiently reduced. On the other hand, when the total fineness of the composite cord exceeds 6000 dtex, the amount of rubber existing between the cords decreases, and the peel resistance between the shoulder belt reinforcing layer 4 and the tread rubber deteriorates. There is a risk that a separation failure may occur with the belt reinforcing layer 4.

  In the pneumatic radial tire of the present invention, the composite cord constituting the shoulder portion belt reinforcing layer 4 preferably has a twist coefficient R defined by the above formula (I) of 0.20 to 1.05. When the twist coefficient R of the composite cord to be used is less than 0.20, the adhesion between the cord and the rubber is poor, and a separation failure is likely to occur between the tread and the shoulder belt reinforcing layer 4. On the other hand, when the twist coefficient R of the composite cord used exceeds 1.05, the stiffness of the cord is low, and the road noise of the tire may not be sufficiently reduced.

  In the pneumatic radial tire of the present invention, the reinforcing element constituting the center belt reinforcing layer 3 is a cord in which a filament bundle of polyhexamethylene adipamide (nylon 6, 6) having a total fineness of 500 to 2000 dtex is twisted. It is preferable. If a cord made of twisted filament bundle of polyhexamethylene adipamide (nylon 6, 6) with a total fineness of less than 500dtex is used, the rigidity of the center belt reinforcement layer 3 will be insufficient, and the radius of curvature of the tire crown will be reduced. The tire becomes excessively small, and the uneven wear resistance and steering stability of the tire are lowered, and further, the important road noise reduction effect may not be sufficiently obtained. On the other hand, if a cord twisted with a bundle of polyhexamethylene adipamide (nylon 6, 6) with a total fineness exceeding 2000dtex is used, the rigidity of the center belt reinforcement layer 3 will be too high, and the rolling resistance of the tire will be reduced. It may not be able to be reduced sufficiently.

  In the pneumatic radial tire of the present invention, the cord of the double twist structure constituting the center belt reinforcing layer 3 preferably has a twist coefficient R defined by the above formula (I) of 0.22 to 0.77. If the twist coefficient R of the cord of the double twist structure is less than 0.22, the adhesion between the cord and the rubber is poor, and a separation failure is likely to occur between the tread and the center belt reinforcing layer 3. On the other hand, when the twist coefficient R of the cord having the double twist structure exceeds 0.77, the cord is crimped, and the workability during tire production may be significantly deteriorated.

  In the pneumatic radial tire of the present invention, the number of cords constituting the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4 is preferably in the range of 30/50 mm to 70/50 mm. If the number of cords forming the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4 is less than 30/50 mm, the main belt 1 may not be sufficiently reinforced. On the other hand, when the number of cords constituting the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4 exceeds 70/50 mm, the amount of rubber existing between the cords decreases, and the center belt reinforcing layer 3 and the tread The peel resistance between the rubber and the peel resistance between the shoulder belt reinforcing layer 4 and the tread rubber deteriorates, and when running, the tread and the center belt reinforcing layer 3 and / or the shoulder belt reinforcing layer 4 Separation failure may occur.

  The pneumatic radial tire of the present invention is a cord formed by rubberizing a cord having a double twist structure in which a plurality of filament bundles of polyhexamethylene adipamide (nylon 6, 6) are twisted on the center belt reinforcing layer 3 / Apply rubber composite and twist one or two aliphatic polyketone filament bundles and one polyhexamethylene adipamide (nylon 6, 6) filament bundle on shoulder belt reinforcement layer 4 A cord / rubber composite formed by rubber-drawing the composite cord is applied, and the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4 are preferably partially overlapped and manufactured by a conventional method. it can. Here, there is no restriction | limiting in particular as a coating rubber of a code | cord, The coating rubber used for the conventional belt reinforcement layer can be used. Prior to rubberizing the cord, the cord may be treated with an adhesive to improve the adhesion to the coating rubber. In the pneumatic radial 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.

  In the production of the pneumatic radial tire of the present invention, a center belt obtained by rubberizing a cord of a double twisted structure formed by twisting a plurality of filament bundles of polyhexamethylene adipamide (nylon 6, 6) The center belt reinforcing layer 3 can be formed by spirally winding a ribbon-like sheet having a width smaller than the width of the reinforcing layer 3 in the tire width direction until a predetermined width is obtained. preferable. In the production of the pneumatic radial tire of the present invention, one or two aliphatic polyketone filament bundles and one polyhexamethylene adipamide (nylon 6, 6) filament bundle were twisted together. A ribbon-like sheet obtained by rubberizing the composite cord and having a width smaller than the width of the shoulder belt reinforcement layer 4 is spirally wound in the tire width direction a plurality of times until a predetermined width is obtained. Thus, it is preferable to form the shoulder portion belt reinforcing layer 4. By continuously spirally winding the ribbon-shaped sheet to form the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4, it is possible to reinforce the main belt 1 uniformly without generating a joint portion in the tire circumferential direction. it can.

  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 radial tire for passenger cars having a size of 255/55 R17 having the structure shown in FIG. 1 was produced according to a conventional method. In the tire of size: 255/55 R17, the width of the belt layer 1a on the inner side in the tire radial direction of the main belt 1 is 160 mm, and the width of the belt layer 1b on the outer side in the tire radial direction of the main belt 1 is 150 mm. The width of the center belt reinforcing layer 3 is 112 mm, the width of the shoulder belt reinforcing layer 4 on the inner side of the tire radial direction 4a is 38 mm, and the width of the shoulder belt reinforcing layer 4 on the outer side of the tire radial direction 4b. Is 26mm. The ratio of the shoulder portions belt reinforcing layer 4 having a width W ₄ for the difference (mm), the total width W ₁ of the main belt 1 between the total width W ₂ of the belt reinforcing layer 2 and the total width W ₁ of the main belt 1 (% ), The width W (mm) of the overlap portion between the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4a adjacent to the layer 3, and the center belt reinforcing layer 3 and the shoulder belt reinforcing layer 4 The material, fineness, twisting coefficient, and number of cords applied are as shown in Tables 1-3.

In the aliphatic polyketone used, 98% of the repeating units are (CH ₂ —CH ₂ —CO).

  Next, the vulcanized tire is dissected to expose the center belt reinforcement layer 3 and the shoulder belt reinforcement layer 4, and a gap is generated between the center belt reinforcement layer 3 and the shoulder belt reinforcement layer 4. It was confirmed whether or not the composite cord constituting the shoulder belt layer 3 was biting into the main belt 1. Moreover, road noise, rolling resistance, high-speed durability, and uniformity were evaluated for tires produced in the same manner as described below. The results are shown in Tables 1-3.

(1) Road noise The prototype tire is assembled to the rim, filled with 200kPa internal pressure, mounted on all four wheels of a sedan type passenger car with a displacement of 2000cc, and two people get on the road noise evaluation road test course for 60km While driving at a speed of / h, measure the total sound pressure (decibel) with a frequency of 100-500Hz through a sound collection microphone attached to the center of the backrest of the driver's seat, and evaluate and compare road noise from the measured value The road noise of the tire of Example 1 is shown as an index with 100 as the road noise. The larger the index value, the smaller the road noise and the better.

(2) Rolling resistance Using a rotating drum with a steel smooth surface with an outer diameter of 1707.6mm, a width that is greater than the maximum width of the test tire and a constant rotational speed, 0 to 180km under the action of a load of 400kgf The rolling resistance was measured by the coasting method when rotating at a speed of / h, the rolling resistance was evaluated from the measured value, and the rolling resistance of the tire of Comparative Example 1 was indicated as an index. It shows that rolling resistance is so small that index value is large.

(3) High speed durability The prototype tire is assembled to the rim, filled with 200kPa internal pressure, run at a speed of 150km / h for 30 minutes, and if there is no failure, the speed is increased by 6km / h. Measured, and indexed with the failure occurrence rate of Comparative Example 1 as 100. The larger the index value, the higher the endurance limit speed and the higher the high speed durability.

(4) Uniformity Based on JIS D4233, the primary component of RFV was measured, the uniformity was evaluated from this measured value, and the uniformity of Comparative Example 1 was displayed as an index. The larger the index value, the better the tire uniformity.

  The tires of Examples 1 to 6 can greatly improve tire road noise, rolling resistance, high-speed durability, and uniformity compared to tires using PEN cords as belt reinforcement layers (Comparative Examples 1 and 2). I understand.

  Further, the occurrence of biting into the main belt (Comparative Example 5), which is sometimes seen by using a PK cord for the belt reinforcing layer, is caused by one or two aliphatic polyketone filament bundles and one in the shoulder belt reinforcing layer. This was not observed in the tires of Examples 1 to 6 using a composite cord in which a filament bundle of polyhexamethylene adipamide (nylon 6, 6) was twisted.

  In addition, in comparison with the tire of Comparative Example 5, the tires of Examples 1 to 6 are formed by twisting two filament bundles of polyhexamethylene adipamide (nylon 6, 6) on the center belt reinforcing layer. It can be seen that high-speed durability can be greatly improved by using a cord with a twisted structure.

It is a fragmentary sectional view of an example of the tread part of the pneumatic radial tire of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main belt 1a The widest belt layer in the belt layer which comprises a main belt 1b The narrowest belt layer in the belt layer which comprises a main belt 2 Belt reinforcement layer 3 Center part belt reinforcement layer 4 Shoulder part Belt reinforcing layer 4a Layer adjacent to the center belt reinforcing layer 4b Layer positioned on the outer side in the tire radial direction of the layer adjacent to the center belt reinforcing layer P ₁ Outer end in the tire width direction of the main belt P _1b The narrowest belt Tire width direction outer end portion P ₃ center portion belt reinforcing layer tire width direction outer end portion P ₄ shoulder portion belt reinforcing layer tire width direction outer end portion W center portion belt reinforcing layer and shoulder portion belt reinforcement adjacent thereto Width of overlapping part with layer W ₁ Total width of main belt W ₂ Total width of belt reinforcement layer W ₄ Width of shoulder belt reinforcement layer W _4a Center belt reinforcement layer Width of the adjacent shoulder belt reinforcement layer W _4b Width of the layer located on the outer side in the tire radial direction of the shoulder belt reinforcement layer adjacent to the center belt reinforcement layer

Claims (12)

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 toroid shape between the pair of bead portions, and a tire radius of a crown portion of the carcass A main belt composed of at least two belt layers arranged on the outer side in the direction, and at least a rubberized layer of reinforcing elements arranged on the outer side in the tire radial direction of the main belt and arranged substantially parallel to the tire circumferential direction. In a pneumatic radial tire comprising two belt reinforcing layers,
The belt reinforcing layer comprises a pair of one or more center belt reinforcing layers covering only the central portion of the main belt and a pair of one or more shoulder belt reinforcing layers covering only the end portions of the main belt, The outer end of the shoulder belt reinforcing layer in the tire width direction is located on the outer side in the tire width direction of the main belt in the tire width direction outer end,
The reinforcing element constituting the center belt reinforcing layer is a cord of a double twist structure formed by twisting a plurality of filament bundles of polyhexamethylene adipamide (nylon 6, 6), and the shoulder belt reinforcing layer is The reinforcing element is a composite cord in which a filament bundle of one or two aliphatic polyketones and a filament bundle of one polyhexamethylene adipamide (nylon 6, 6) are twisted together Pneumatic radial tire.   The outer end portion in the tire width direction of the center belt reinforcing layer is located on the inner side in the tire width direction than the outer end portion in the tire width direction of the narrowest belt layer among the belt layers constituting the main belt. The pneumatic radial tire according to claim 1.   2. The pneumatic radial tire according to claim 1, wherein at least a part of the center part belt reinforcing layer and the shoulder part belt reinforcing layer adjacent to the center part belt reinforcing layer overlap each other.   The pneumatic radial tire according to claim 3, wherein a width of an overlapping portion between the center portion belt reinforcing layer and a shoulder portion belt reinforcing layer adjacent to the center portion belt reinforcing layer is 1 to 12 mm.   2. The pneumatic according to claim 1, wherein the total width of the belt reinforcing layer including the center belt reinforcing layer and the shoulder belt reinforcing layer is 2 to 10 mm wider than the total width of the main belt. Radial tire.   The pneumatic radial tire according to claim 1, wherein a width of the shoulder belt reinforcement layer is 5 to 20% of a total width of the main belt.   The pneumatic radial tire according to claim 1, wherein the reinforcing element constituting the shoulder belt reinforcing layer is a composite cord having a total fineness of 1000 to 6000 dtex. The composite cord constituting the shoulder belt reinforcing layer has the following formula (I):
R = N × (0.125 × D / ρ) ^1/2 × 10 ^-3 (I)
[Where N is the number of twists of the cord (times / 10 cm), D is the total number of decitex of the cord (dtex), and ρ is the specific gravity of the cord (g / cm ³ )] The pneumatic radial tire according to claim 1, wherein R is 0.20 to 1.05.   The reinforcing element constituting the center belt reinforcing layer is a cord formed by twisting a filament bundle of polyhexamethylene adipamide (nylon 6, 6) having a total fineness of 500 to 2000 dtex. The described pneumatic radial tire. The cord of the double twist structure constituting the center part belt reinforcing layer is represented by the following formula (I):
R = N × (0.125 × D / ρ) ^1/2 × 10 ^-3 (I)
[Where N is the number of twists of the cord (times / 10 cm), D is the total number of decitex of the cord (dtex), and ρ is the specific gravity of the cord (g / cm ³ )] The pneumatic radial tire according to claim 1, wherein R is 0.22 to 0.77.   2. The pneumatic radial tire according to claim 1, wherein the number of cords forming the center belt reinforcing layer and the shoulder belt reinforcing layer is 30/50 mm to 70/50 mm.   Each of the center belt reinforcing layer and the shoulder belt reinforcing layer has a predetermined width dimension obtained from a ribbon-like sheet obtained by rubberizing one or more reinforcing elements having a narrower width dimension than the arrangement width. The pneumatic radial tire according to claim 1, wherein the pneumatic radial tire is formed by spirally winding a plurality of times in the tire width direction.

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