Radial tires

Abstract

A radial tire comprising: a pair of parallel bead cores; at least one radial carcass ply wound around the bead core; at least one bias belt layer laminated to an outer periphery of the carcass ply; and at least one cap layer laminated to an outer periphery of the bias belt layer in a tire circumferential direction, wherein the cover layer comprises a dipped cord made using a yarn containing 90 mol% or more of polyethylene terephthalate, and wherein the dipped cord has a shrinkage rate of 3.0 to 4.0%, a strength at a modulus of elasticity of 5% of 2.5 to 3.0 g / d, a tear strength of 6.5 to 7.5 g / d and a dimensional stability index of 5.8 to 6.5, where the shrinkage rate is evaluated by applying an overload of 0.01 g / d using a normal test rite and measuring at 177 degrees for 2 minutes, where the strength at a modulus of elasticity of 5% is obtained by reading the load at the point with a strain rate of 5% on the SS curve in g units and dividing by the nominal denier (yarn denier for 1 ply and the product of yarn denier and number of plies for 2 or more plies), and wherein the dipped cord is formed by twisting 400 to 2200d yarns containing 90 mol% or more of polyethylene terephthalate in one or more layers, and wherein the twist coefficient thereof is 9,000 to 18,000 square root of [(twist / twist per meter) * nominal denier].

Description

[Technical field]

[0001] The present invention relates to a radial tire having a cover layer made of dipped polyethylene terephthalate cord. [State of the art]

[0002] In recent years, tire performance has been continuously improved in line with improvements in the road environment and vehicle performance. In particular, safety has been recognized as an important quality factor for tires due to the increasing vehicle weight and increasing top speed. Tire safety standards are also being revised in line with the increasing tire safety requirements. The tire industry is also actively researching methods to ensure tire safety.

[0003] The application of a cap layer on a passenger car tire is for the safety of the tire, and recently, a tire with such a cap layer has become commonplace. The cap layer is continuously wound without breakage in the circumferential direction of the tire between the tire tread portion and the steel cord layer for belt reinforcement, thereby maintaining the tire's dimensional stability and improving the tire's high-speed durability by suppressing tire expansion and deformation due to centrifugal force during high-speed driving. When the vehicle is traveling at high speed, the tire's air pressure increases with the increase in temperature inside the tire, corresponding to the increase in centrifugal force due to tire rotation, and a load is exerted in the longitudinal direction of the cap layer cord.In this way, when driving at high speed, the tire will become larger due to centrifugal force, temperature rise, and air pressure. When the load on the surface to the ground, which repeatedly comes into contact with the road surface during driving, decreases, and then the load on the surface not on the ground repeatedly returns, the amount of deformation exerted on the cord and the tire increases. In proportion to the increase in the amount of deformation, the work loss of the tire cord itself increases. This work loss, in turn, contributes to the temperature rise of the tire and the tire cord, resulting in a sudden temperature rise and deterioration of the tire's durability.

[0004] The cap cord serves to prevent the tire center and tread from expanding due to centrifugal force during vehicle travel, thereby reducing the extent of tire deformation, reducing the associated power loss, preventing tire temperature increases, and improving tire durability. Generally, a material that resists deformation due to its high elastic modulus is used. When the temperature rises, heat shrinkage is exerted, and the cap cord contracts, thus preventing tire expansion during travel.In this case, since the size of the tire is not increased, an increase in the rotational inertia of the tire is prevented, which leads to an increase in fatigue life and an increase in durability by reducing thermal wear and suppressing the heat generation of the tire.

[0005] Generally, the most commonly used material for cover ply material is nylon 66. This is due to the high shrinkage of nylon 66, and in particular, the section where the cover ply is reinforced is known to have the highest temperature on the tire during driving. Nylon 66, which has this property, is often used as a cover ply material because a material that has heat resistance in addition to heat shrinkage force and a material that has little decrease in adhesion due to heat should be used. Other materials that can be used as a cover ply material are aramids. Aramid has different properties than nylon 66. The aramid fiber is an aromatic polyamide fiber and is a polyamide fiber with a benzene ring in a repeating unit.When used for tire cover ply, as a material that exhibits stable properties even at high temperatures, it is unlikely to develop contraction force at high temperatures. However, since there is very little deterioration in properties even at high temperatures, deformation is suppressed, resulting in properties similar to those achieved with nylon cover ply. Although the use of such aramid fibers is increasing, there is a problem that aramid fibers have low fatigue strength, and at the same time, a cost problem arises because of their high price.

[0006] Research is also being conducted into using materials such as PET for cap materials, but since these materials are heat-sensitive, they have been difficult to use as cap materials. The present invention proposes using PET, which has been difficult to use as a cap material, as a cap material for a radial tire by limiting the properties of the PET cord.

[0007] US 2013 / 0302610 A1 relates to a drawn poly(ethylene terephthalate) fiber, a tire cord and manufacturing methods therefor.

[0008] US 2011 / 0024016 A1 discloses a non-drawn poly(ethylene terephthalate) fiber (PET fiber), a drawn PET fiber and a tire cord comprising them. [Revelation][Technical Problem]

[0009] An object of the present invention to solve the above problems is to provide a radial tire having a cover layer having an applied dipped cord of polyethylene terephthalate yarn.

[0010] In the case of the polyethylene terephthalate cover layer according to the invention, the polyethylene terephthalate fiber has a low elongation under specific load, has a high shrinkage rate, and has improved strength and elastic modulus. [Technical solution]

[0011] According to a corresponding embodiment of the present invention, a radial tire is provided, which comprises: a pair of parallel bead cores; at least one radial carcass ply wound around the bead core; at least one bias belt layer laminated on an outer periphery of the carcass ply; and at least one cover layer laminated on an outer periphery of the bias belt layer in a tire circumferential direction, wherein the cover layer comprises a dipped cord made using a yarn containing 90 mol% or more of polyethylene terephthalate, and wherein the dipped cord has a shrinkage rate of 3.0 to 4.0%, a strength at a modulus of elasticity of 5% of 2.5 to 3.0 g / d, a tear strength of 6.5 to 7.5 g / d and a dimensional stability index of 5.8 to 6.5, where the shrinkage rate is evaluated by applying an overload of 0.01 g / d using a normal test rite and measuring at 177 degrees for 2 minutes, where the strength at a modulus of elasticity of 5% is obtained by reading the load at the point with a strain rate of 5% on the SS curve in g units and dividing by the nominal denier (yarn denier for 1 ply and the product of yarn denier and number of plies for 2 or more plies), and wherein the dipped cord is formed by twisting 400 to 2200d yarns containing 90 mol% or more of polyethylene terephthalate in one or more layers, and wherein the twist coefficient thereof is 9,000 to 18,000 square root of [(twist / twist per meter) * nominal denier].

[0012] According to another suitable embodiment of the present invention, the dipped cord is characterized in that it has an intermediate elongation of 2.1 to 4.0% at 2.25 g / d and an elongation at break of 8.0 to 16.0%.

[0013] According to another suitable embodiment of the present invention, the cover layer is generally reinforced with one or two layers, and if necessary, it is reinforced throughout the tread, selectively only at the tread edge, or in two layers on the tread and additionally reinforced at the tread edge area. It is also possible to apply a reinforcing cord in a similar manner to the conventional cover layer, and this is not limited to a specific cover layer structure for application.

[0014] According to another suitable embodiment of the present invention, a tire for a passenger car including the cover layer is provided, and as with a general cover layer, the application is not limited to tire types such as runflat tires, general passenger car tires and light truck tires. [Beneficial effects]

[0015] Dipped cords made of high-strength polyethylene terephthalate yarns of the present invention can overcome the disadvantage of low adhesive force with conventional rubber, and the cords formed from this yarn have excellent adhesive force and strength and can be usefully used as a reinforcing material for rubber products such as tires and belts or other industrial uses.

[0016] According to the present invention, satisfactory results for tire durability at high speeds and the like can be achieved by using a polyethylene terephthalate dipped cord having specific properties according to the present invention for a cover ply of a radial tire for a passenger car. [Brief description of the drawings] Fig. 1 shows a spinning and drawing process of polyethylene terephthalate yarn according to the present invention. Fig. Figure 2 shows a force-deformation curve for the present invention and a conventional 1000d / 2 polyethylene terephthalate dip cord. Fig. Figure 3 shows the structure of a passenger car tire manufactured using a dipped cord according to the present invention in a cover ply. [Detailed Description of the Preferred Embodiments]

[0017] Preferred embodiments according to the present invention will be described in detail below. The embodiment described here does not limit the scope of the present invention, but is merely an example, and various changes may be made without departing from the technical concept of the present invention.

[0018] The cover ply cord for the radial tire according to the present invention is produced by the following method. A polyethylene terephthalate multifilament is prepared as a precursor for producing a cover ply cord. First, a polyethylene terephthalate chip with an intrinsic viscosity of 0.9 to 1.20 is melted and extruded while passing through a die to produce a discharged yarn.

[0019] The polyethylene terephthalate polymer may contain at least 85 mol% ethylene terephthalate units, but may optionally also contain only ethylene terephthalate units.

[0020] Optionally, the polyethylene terephthalate may contain a small amount of units derived from ethylene glycol and terephthalic acid or derivatives thereof, as well as one or more ester-forming components as copolymer units. Examples of other ester-forming components copolymerizable with polyethylene terephthalate units include glycols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, and the like, as well as dicarboxylic acids such as terephthalic acid, isophthalic acid, hexahydroterephthalic acid, stilbenedicarboxylic acid, diphenic acid, adipic acid, sebacic acid, and azelaic acid.

[0021] Terephthalic acid (TPA) and ethylene glycol as raw materials were melt-mixed in a ratio of 2.0 to 2.3 in the prepared polyethylene terephthalate chip. The melt mixture was subjected to transesterification and condensation polymerization to form a green chip. The green chip was then subjected to solid-state polymerization to obtain an intrinsic viscosity of 0.9 to 1.20 at a temperature of 240 to 260°C under vacuum.At this time, if the intrinsic viscosity of the raw chip is less than 0.9, the intrinsic viscosity of the final drawn yarn is reduced, so that it cannot have high strength as a treatment cord after heat treatment, and if the intrinsic viscosity of the chip exceeds 1.20, the spinning tension increases excessively and the cross section of the discharged yarn becomes uneven, resulting in a large number of filament breaks during drawing, resulting in poor processability in drawing.

[0022] In addition, an antimony compound, preferably antimony trioxide, can optionally be added as a polymerization catalyst during the condensation polymerization reaction, so that the amount of antimony metal remaining in the final polymer can be 180 to 300 ppm. If the residual amount is less than 180 ppm, the polymerization reaction rate becomes slow and the polymerization efficiency decreases. If the residual amount exceeds 300 ppm, antimony metal acts as a foreign material more than necessary, so that the strain deformability may be deteriorated.

[0023] The above-mentioned polyethylene terephthalate chip is melted and extruded while passing through a die to produce a discharged yarn. At this time, the die diameter is preferably 0.8 to 1.4 mm.

[0024] The discharged yarn is then rapidly cooled and solidified by passing through the cooling zone. At this point, if necessary, a heater of a specific length is installed in the section from the nozzle directly to the starting point of the cooling zone, i.e., in the length (L) section of the hood.

[0025] This zone is called delayed cooling zone or heating zone, which has a length of 50 to 300 mm and a temperature of 250 to 400°C (air contact surface temperature).

[0026] In the cooling zone, depending on the type of cooling air injection, open quenching, circular closed quenching, radial blow-out quenching, radial blow-in quenching, etc. can be used, but are not limited to these.

[0027] At this time, the temperature of the cooling air blown into the cooling zone is adjusted to 20 to 50°C for rapid cooling. Rapid cooling through a rapid temperature difference between the hood and the cooling zone is intended to increase the solidification point and spinning tension of the spun polymer, thereby increasing the orientation of the undrawn yarns and the formation of a connecting chain between crystals and crystals.

[0028] Subsequently, the friction coefficient between the single yarns and the bonded, discharged yarns is reduced as they pass through the cooling zone. At the same time, the discharged yarn can be oiled at 0.5 to 1.2 weight percent by the first spinning emulsion feeder, to which an emulsion with excellent drawability and thermal efficiency is supplied. The emulsion type used for the oil ring can be emulsion type, solvent type, or pure oil type, and the emulsion type does not limit the properties of the polyethylene terephthalate yarn used for the present invention.

[0029] It is preferable to form the undrawn yarn by spinning the oiled, spent yarn, and the orientation degree of the undrawn yarn is preferably 0.06 to 0.60. If the orientation degree of the undrawn yarn is below 0.06, the crystallinity and crystal density in the microstructure of the yarn cannot be increased, and if it is above 0.60, the draw formability will be reduced, which is undesirable. After that, the undrawn yarn is passed through a godet draw roll to be drawn multiple times at an appropriate draw ratio to produce a yarn.

[0030] In the present invention, the stretching is carried out by an apparatus in which the godet stretching roll is used in 5 stages.

[0031] Related to Fig.1, the PET chip is melt-spun at a low temperature of 290 to 310°C by an extruder 1, a gear pump 2, a nozzle 3, and a heater 4, thereby preventing a decrease in the viscosity of the polymer due to thermal decomposition and hydrolysis. The produced melt-extruded yarn is rapidly cooled and solidified by passing through the cooling zone 5. If necessary, a short heater can be installed at a distance up to the starting point of the cooling zone 5 immediately below the nozzle 3, i.e., in the length section L of the hood.

[0032] The length section (L) of the hood becomes a delayed cooling zone or a heating zone and has a length of 50 to 300 mm and a temperature of 250 to 400°C (air contact surface temperature). Depending on how the cooling air is blown out from the cooling zone 5, open quenching, circular closed quenching, and radial blowout quenching can be adopted, but are not limited to them. The present invention is characterized in that it is further controlled from the outside by an air conditioner to lower the cooling temperature from 20°C to 10-15°C, thus improving the cooling efficiency. The discharged yarn, which has passed through the cooling zone 5 and solidified, is oiled to 0.5 to 1.0% by the emulsion supply device 12 and is undrawn. The emulsion supply device 12 is characterized in that it is installed in a single stage before the godet draw roll 1(6).

[0033] The yarn that has passed the first godet draw roll is drawn into a drawn yarn by a spin-draw process as it passes through a series of draw rolls. The speed of godet draw roll 1 is set in the range of 2,000 to 3,500 m / min.

[0034] In the drawing process, the undrawn yarn may be drawn in several stages, and the temperature of each drawing roll may be lower than or equal to the glass transition temperature of the undrawn yarn, but the temperature is lower than 95°C, and the temperature of the last drawing roll 4(9) is preferably 200 to 250°C.

[0035] If the temperature of the final draw roll is below 200°C, the crystallinity and crystal size cannot be increased during the draw process, thus impairing the strength and thermal stability of the yarn, resulting in a decrease in morphological stability at high temperatures. If the temperature of the final draw roll exceeds 250°C, the problem is that the microstructure of the yarn becomes uneven, so the crystals decompose because the temperature is too close to the melting point, which may reduce the strength of the yarn.

[0036] In the present invention, the speed of the godet draw roll 1 is set in the range of 2,000 to 3,500 m / min. The winding is then carried out at a speed of 5,000 to 6,000 m / min onto the godet draw roll 4, and the temperature in the godet draw roll 4 is 200 to 250°C.

[0037] Furthermore, the total draw ratio of the yarn formed by winding as described above is preferably between 1.8 and 2.5. If the draw ratio is less than 1.8, the degree of orientation of the amorphous portion is insufficient, and a high-strength yarn cannot be obtained. As a result, the strength of the cover cord is low, resulting in a reduction in the high-speed durability of the tire. If the draw ratio is 2.5 or more, the degree of orientation is too high, and high cord strength can be achieved, but due to the high shrinkage rate, the processability in tire manufacturing is insufficient, resulting in a tire with poor uniformity and poor heat resistance.

[0038] To manufacture the radial tire according to the present invention, a dipped cord should be manufactured using the high-strength polyethylene terephthalate multifilament yarn. Furthermore, it is necessary to twist or ply the cord as a step prior to manufacturing the dipped cord.

[0039] In the present invention, in the production of a dipped cord using the high-strength polyethylene terephthalate yarn as a precursor for producing the dipped cords, the cord is twisted / twisted into a raw cord (twisting process).

[0040] The twisted yarn is produced by introducing a ply twist into a polyethylene terephthalate yarn, then applying a cable twist to it and twisting them together. Generally, the same or different twist ratios are used for the ply twist and the cable twist. The number of twists of the dipped cord depends on the thickness of the yarn used for the cord and the total denier. In the present invention, the twist coefficient, expressed as the square root of [(twist per meter) * nominal denier], is 9,000 to 18,000. A polyester carcass used in the carcass of tires typically has a twist coefficient of 19,000 to 21,000.In the present invention, by limiting the twist coefficient to the above-mentioned range, it is possible to demonstrate a better numerical value of the elastic modulus of the cord than the polyester cord for a carcass.

[0041] In the present invention, if the twist coefficient of the polyethylene terephthalate cord is less than 9000, the elongation at break is excessively reduced, thereby reducing the fatigue resistance of the cord itself and thus the tire life / durability. If it is above 18000, the strength and elastic modulus of the cord decrease, resulting in a reduction in the tire's high-speed durability due to increased heat generation due to increased tire expansion, which may make it difficult to improve the tire's high-speed durability, which is an objective of the invention.

[0042] The resulting raw cord is woven into a fabric using a loom. The resulting fabric is immersed in a dipping solution and heat-treated at an appropriate temperature and time to cure the adhesive solution on the surface of the fabric, thereby producing a dipped cord for tire cord with a resin layer applied to the surface of the cord. In the above process, the dipping solution is a one-bath solution that activates the surface of the polyethylene terephthalate fiber and a two-bath solution for introducing a resin layer called RFL (resorcinol formalin latex), which refers to the adhesive liquid applied to the surface of the fiber to impart the adhesive force between rubber and fiber.

[0043] In the present invention, an adhesive liquid for bonding cord and rubber can be prepared by the following method. Manufacturing process of 1-bath adhesive distilled water 950 parts by weight; 100% epoxy resin 5 parts by weight; 50% isocyanate 30 parts by weight

[0044] A solution containing the above elements is prepared and then stirred at 25°C for 3 hours. Manufacturing process for 2-bath adhesive 29.4 wt% resorcinol 45.6 parts by weight; distilled water 255.5 parts by weight; 37% formalin 20 parts by weight; and 10 wt.% sodium hydroxide 3.8 parts by weight

[0045] A solution containing the above elements is prepared and then reacted with stirring at 25°C for 2 hours to produce an RF resin condensate, and then the following components are added: 40 wt.% VP latex 300 parts by weight; distilled water 129 parts by weight; 28% ammonia water 23.8 parts by weight

[0046] After adding the ingredients, aging is carried out for 20 hours at 25°C and a solids concentration of 19.05% is maintained, with the adhesion amount of the adhesive preferably being 1.5 to 3.5% of the fiber weight based on the solids.

[0047] After passing through the single-bath and double-bath adhesive solutions, the dipped cord is dried and heat-treated. After passing through the single-bath adhesive solution, the hybrid dipped cords are dried at 120-170°C. The drying time can be 130-220 seconds, and during the drying process, the dipped cord can be stretched to approximately 2-6%. If the stretch ratio is low, the elongation at specific load and the elongation at break of the cords may increase, thereby exhibiting properties that make it difficult to use as tire cords. On the other hand, if the stretch ratio is higher than 6%, the amount of elongation at specific load is adequate, but the elongation at break may be too low, reducing fatigue resistance.

[0048] After drying, heat treatment is carried out in a temperature range of 200 to 245°C. The stretch ratio during heat treatment is maintained between 0.0 and 6.0%, and the heat treatment time is suitably between 50 and 90 seconds. If the heat treatment is carried out for less than 50 seconds, the reaction time of the adhesive solution is insufficient and the bond strength is reduced. If the heat treatment is carried out for more than 90 seconds, the hardness of the adhesive solution becomes high, and the fatigue resistance of the cord may be reduced.

[0049] After passing through the two-bath adhesive solution, the hybrid dipped cords are dried at 120-170°C. The drying time can be 80-150 seconds, and during the drying process, the dipped cord can be stretched by approximately 0-4%. If the stretch ratio is low, the elongation at specific load and the elongation at break of the cords may increase, thereby exhibiting properties that make their use as tire cords difficult. On the other hand, if the stretch ratio is more than 4%, the amount of elongation at specific load is adequate, but the elongation at break may be too low, reducing fatigue resistance.

[0050] After drying, heat treatment is performed in a temperature range of 200 to 245°C. The stretch ratio during heat treatment is maintained between -3 and 3.0%, and the heat treatment time is suitably between 50 and 120 seconds. If the heat treatment is performed for less than 50 seconds, the reaction time of the adhesive solution is insufficient and the bond strength is reduced. If the heat treatment is performed for more than 120 seconds, the hardness of the adhesive solution becomes high, and the fatigue resistance of the cord may be reduced.

[0051] Fig. Figure 2 shows a force-deflection curve for the present invention and a conventional 1000d / 2 polyethylene terephthalate dip cord.

[0052] According to the present invention, the stress-strain curve of the polyethylene terephthalate dipped cord can be adjusted to minimize the initial deformation caused by the external load on the polyethylene terephthalate dipped cord. The polyethylene terephthalate dipped cord of the present invention is characterized by having a strength of 2.5 to 3.0 g / d, a tensile strength of 6.5 to 7.5 g / d, and a dimensional stability index of 5.8 to 6.5 when the shrinkage rate is 3.0 to 4.0% and it is stretched by 5%.

[0053] The shrinkage rate is evaluated by applying an overload of 0.01 g / d using a standard Testrite and measuring at 177 degrees for 2 minutes. The strength at a 5% elastic modulus is obtained by reading the load at the point with a 5% deformation rate on the SS curve in g units and dividing by the nominal denier (yarn denier for 1 ply and the product of yarn denier and ply count for 2 or more plies). The ultimate tensile strength is obtained by reading the maximum load on the SS curve and dividing by the nominal denier. The dimensional stability index can be obtained as the sum of the elongation at a specific load at 2.25 g / d and the shrinkage rate (Testrite, 0.05 g / d, 177 degrees, 2 minutes) and is expressed by the ES index.

[0054] In the case of a conventional polyethylene terephthalate dipped cord, it is possible to have the shrinkage range according to the present invention, but in this case, with the reduction of the shrinkage ratio, the elastic modulus is also reduced, and the strength is 3.0 g / d or less at 5%, so the performance improvement of the tire is not enough, and it is common to have a dimensional stability index of 6.0 or more and a tear strength of 7.5 g / d or less.

[0055] Conversely, when the elastic modulus is increased to make the strength at 5% to the level of the present invention, the shrinkage rate becomes more than 3.5%, so that the workability in molding a tire becomes insufficient and, as a result, the uniformity is low, resulting in a reduction in high-speed durability due to tire unevenness.

[0056] According to another suitable embodiment of the present invention, the dipped cord is characterized in that it has an intermediate elongation of 2.1 to 4.0% at 2.25 g / d and an elongation at break of 8.0 to 16.0%.

[0057] According to the invention, the dipped cord is characterized in that the twist coefficient, which is represented by the square root of the number of twists (twist / meter) * nominal denier, is 9,000 to 18,000.

[0058] Polyethylene terephthalate dipped cords produced by the process described above can be used for the production of cover ply layers, and the high performance radial tire produced according to the present invention comprises such a cover ply layer.

[0059] Fig.3 is a partial cross-sectional view of the structure of a passenger car tire manufactured using a polyethylene terephthalate dipped cord according to the present invention as a cover layer.

[0060] With reference to Fig. 3, the bead region 35 of the tire 31 becomes an annular bead core 36 that is inextensible. The bead core 36 is preferably made of a continuously wound single-filament steel wire. In a preferred embodiment, a high-strength steel wire with a diameter of 0.95 to 1.00 mm forms a 4x4 structure or a 4x5 structure. In one embodiment of the tire cord according to the present invention, the bead region 35 may include a bead filler 37, and the bead filler 37 should have a hardness above a certain level, and preferably a Shore A hardness of 40 or more.

[0061] According to the present invention, the crown region of the tire 31 may be reinforced by the belt structure 38 and the cover ply 39. The belt structure 38 includes a cut belt ply 40 consisting of two belt cords 41 and 42, and the belt cord 41 of the cut belt ply 40 may be oriented at an angle of approximately 20 degrees with respect to the circumferential center plane of the tire. One belt cord 41 of the belt ply 40 may be arranged opposite to the direction of the belt cord 42 of the other belt ply 40 in a direction opposite to the circumferential center plane of the tire. However, the belt structure 38 may include any number of plies and may preferably be arranged in the range of 16 to 24 degrees. The belt structure 38 serves to provide transverse rigidity to minimize the rising of the tread 43 from the road surface during operation of the tire 31.The belt cords 41 and 42 of the belt structure 38 may be made of steel cords and have a 2+2 structure, but may be of any desired structure. The cover ply 39 and the edge ply 44 are reinforced on the upper side of the belt structure 38. The cords 45 of the cover ply 39 are reinforced parallel to the circumferential direction of the tire to suppress dimensional change in the circumferential direction due to high-speed rotation of the tire, and cords 45 of the cover ply 39 that have a large heat shrinkage stress at high temperatures are used. The cover ply cord 45 of the cover ply 39 may be formed with a dipped cord made of a high-strength yarn produced by the method of the present invention. One ply of the cover ply 39 and one ply of the edge ply 44 may be used, and preferably one or two plies of the cover ply and one or two plies of the edge ply may be reinforced.

[0062] Reference numbers 32 and 34 of Fig. 3 denotes a carcass ply 32 and a ply turn-up 34, and reference numeral 33 denotes a carcass ply reinforcing cord 33.

[0063] Examples and comparative examples, which do not limit the scope of the present invention, are described below. In the following examples and comparative examples, the evaluation of physical properties was based on measurement or evaluation as follows. (a) Shrinkage rate

[0064] After leaving at 25°C and 65% RH for 24 hours, the shrinkage ratio was expressed by using the ratio of the length (L0) measured at a static load of 0.01 g / d and the length (L1) after treatment at a static load of 0.01 g / d and 177°C for 2 minutes using Testrite. S(%)=(L0−L1) / L0×100 (b) Dipped cord strength (g / d) and percent intermediate elongation at 2.25 g / d, strength at 5%

[0065] It was measured at a specimen length of 250 mm and a tensile speed of 300 m / min using an Instron low-speed tensile tester. The intermediate strain at 2.25 g / d refers to the strain corresponding to a load of 2.25 g / d on the stress-strain rate curve, and the strength at 5% is measured by measuring the strain at 5% strain rate on the stress-strain rate curve and dividing it by the total denier of the cord. (c) Shape stability of the dipped cord (ES Index)

[0066] This represents the sum of the intermediate elongation and shrinkage rate (Testrite, 0.05 g / d, 177 degrees, 2 minutes) at 2.25 g / d, which corresponds to the elongation under the constant load of (b) above. [Example 1]

[0067] To produce the tire reinforcing fibers, polyethylene terephthalate fibers with raw cord were obtained by the method described above.

[0068] A 270 TPM bottom edge was added to the 1000D polyethylene terephthalate yarn, and a 270 TPM top edge was added and twisted together to produce a two-ply raw cord. The resulting raw cord was treated in a two-bath dipping process, and the single-bath dipping was performed by passing the raw cord through the adhesive solution prepared according to the following method and drying it at 160°C for 150 seconds, followed by a heat treatment at 240°C for 60 seconds. During drying, a 3% stretch was applied to prevent unevenness of the raw cord due to heat shrinkage.

[0069] A solution containing 950 parts by weight of distilled water, 5 parts by weight of 100% epoxy resin, 30 parts by weight of 50% isocyanate was prepared and stirred for 3 hours at 25°C.

[0070] The two-bath dipping process was performed by passing the raw cord through the adhesive solution prepared according to the following procedure and drying it at 160°C for 90 seconds, followed by a heat treatment at 240°C for 60 seconds. A stretch of -1% occurred during drying.

[0071] 45.6 parts by weight of 29.4 wt% resorcinol, 255.5 parts by weight of distilled water, 20 parts by weight of 37% formalin and 3.8 parts by weight of 10 wt% sodium hydroxide were prepared and reacted at 25°C for 5 hours with stirring, followed by the addition of the following elements: 300 parts by weight of 40 wt% VP latex, 129 parts by weight of distilled water, and 23.8 parts by weight of 28% ammonia water were added and aged at 25°C for 20 hours with stirring to maintain a solid concentration of 19.05%.

[0072] A two-bath immersion heat treatment was performed to complete the adhesive treatment. The properties of the resulting dipped cords were evaluated and are presented in Table 1. [Example 2]

[0073] A dipped cord was manufactured in the same manner as in Example 1 above, except that a 410 TPM ply twist was applied to the polyethylene terephthalate yarn (1300D), which was then twisted into a 410 TPM cable to produce a raw cord by twisting them together. A single-ply twist was used in the production of the raw cord. The properties of the thus-produced dipped cords were evaluated and are shown in Table 1. [Example 3]

[0074] A dipped cord was manufactured in the same manner as in Example 1 above, except that a 235 TPM layer twist was performed on polyethylene terephthalate yarn (1300D), which was then twisted together to form a raw cord. The properties of the dipped cords thus prepared were evaluated and are shown in Table 1. [Comparison example 1]

[0075] A 460 TPM layer twist was performed on nylon 66 (840D) yarns, which were then twisted together to form a 460 TPM cable. During production, the raw cord was twisted into two layers and passed through the prepared adhesive solution to impregnate the raw cord. Stretching was performed during drying to prevent unevenness in the raw cord due to heat shrinkage.

[0076] 45.6 parts by weight of 29.4 wt% resorcinol, 255.5 parts by weight of distilled water, 20 parts by weight of 37% formalin and 3.8 parts by weight of 10 wt% sodium hydroxide were prepared and reacted at 25°C for 5 hours with stirring, followed by the addition of the following elements: 300 parts by weight of 40 wt% VP latex, 129 parts by weight of distilled water, and 23.8 parts by weight of 28% ammonia water were added, and it was aged at 25°C for 20 hours with stirring to maintain a solid concentration of 19.05%.

[0077] An adhesive solution was used to perform a single-bath immersion heat treatment to complete the adhesive treatment. The properties of the resulting dipped cords were evaluated and are presented in Table 1. [Comparison example 2]

[0078] A dipped cord was prepared in the same manner as in Comparative Example 1 above, except that nylon 66 (1260D) was subjected to a 280 TPM layer twist, which was then twisted to a 280 TPM cable twist to produce a raw cord. The properties of the thus-prepared dipped cords were evaluated and are shown in Table 1. [Comparison example 3]

[0079] A dipped cord was prepared in the same manner as in Example 1 above, except that a 370 TPM ply twist was performed on the 1500D polyethylene terephthalate yarn, which was then twisted together to form a raw cord. The properties of the thus-prepared dipped cords were evaluated and are shown in Table 1. [Table 1] Example 1 Example 2 Example 3 Comparison example 1 Comparison example 2 Comparison example 3 material PET PET PET nylon nylon PET denier d 1000 1300 1300 840 1260 1500 Layers - 2 1 2 2 2 2 Power kgf 16.0 9.1 19.7 15.2 24.1 22.9 strength g / d 7.2 7.0 7.3 9.1 8.6 6.9 g / d, @ 5% 2.7 3.0 2.6 1.0 1.2 2.7 Elongation at specific load %, @2.25 g / d 3.3 3.1 3.4 7.9 7.9 4.2 Elongation at break % 13.4 11.3 13.9 20.1 23.1 17.0 shrinkage rate %, 0.01 g / day 3.4 3.6 3.5 6.5 5.9 3.3 %, 0.05 g / day 2.5 2.7 2.6 5.6 5.0 2.3 ES Index - 5.8 5.8 6.0 13.5 12.9 6.6 Number of twists TPM 270 410 235 460 280 370 Twist coefficient - 12075 14783 11983 18854 14056 20266 [Example 4]

[0080] A radial tire manufactured using the dipped cord prepared according to Example 1 of the present invention as a cover ply has a carcass ply with a radially outer ply turnup, and the carcass ply is provided to include one ply. At this time, the carcass cord was oriented at a 90-degree angle with respect to the tire's circumferential center surface. The ply turnup 34 has a height of 40 to 80% of the tire's maximum section height. The bead portion 35 includes a bead core 36 comprising 4 x 4 high-strength steel wires with a diameter of 0.95 to 1.00 mm and a bead filler 37 with a Shore A hardness of 40 or more. The belt structure 38 is reinforced by a belt reinforcing layer consisting of a layer of the cover ply 39 and a layer of the edge ply 44 on the upper side, so that the cover ply cords in the cover ply 39 run parallel to the circumferential direction of the tire.The properties of the dipped cords produced in this way were evaluated and are shown in Table 2. [Example 5]

[0081] A tire was manufactured in the same manner as in Example 4, except that the dipped cord prepared in Example 2 was used as the cord material for tire manufacturing. The properties of the thus-prepared dipped cords were evaluated and are shown in Table 2. [Example 6]

[0082] A tire was manufactured in the same manner as in Example 4, except that the dipped cord prepared in Example 3 was used as the cord material for tire manufacturing. The properties of the thus-prepared dipped cords were evaluated and are shown in Table 2. [Table 2] Area Example 4 carcass material PET Spec. (d / twisted yarn) 1500d / 2 Force (kg) 24 Elastic modulus (g / d) 72 Top layer material Diving cord from example 1 Spec. (d / twisted yarn) 1000d / 2 Force (kg) 16.0 Strength (g / d, @ 5%) 2.7 Tires Degree of flatness 0.6 Number of carcass plies 1 Number of cover layers 1 [Comparison example 4]

[0083] A tire was manufactured in the same manner as in Example 4, except that the dipped cord prepared in Comparative Example 1 was used as the cord material for tire production. The properties of the thus-prepared dipped cords were evaluated and are shown in Table 3. [Comparison Example 5]

[0084] A tire was manufactured in the same manner as in Example 4, except that the dipped cord prepared in Comparative Example 2 was used as the tire cord material. The properties of the thus-prepared dipped cords were evaluated and are shown in Table 3. [Comparison example 6]

[0085] A tire was manufactured in the same manner as in Example 4, except that the dipped cord prepared in Comparative Example 3 was used as the tire cord material. The properties of the thus-prepared dipped cords were evaluated and are shown in Table 3. [Table 3] Area Comparison example 4 Comparison example 5 Comparison example 6 carcass material PET PET PET Spec. (d / twisted yarn) 1500d / 2 1500d / 2 1500d / 2 Force (kg) 24 24 24 Elastic modulus (g / d) 72 72 72 Top layer material Diving cord from comparison example 1 Diving cord from comparison example 2 Diving cord from comparison example 3 Spec. (d / twisted yarn) 840d / 2 1260d / 2 1500d / 2 Force (kg) 15.2 24.1 22.9 Strength (g / d, @ 5%) 1.0 1.2 2.7 Tires Degree of flatness 0.6 0.6 0.6 Number of 1 1 1 Carcass plies Number of cover layers 1 1 1

[0086] The 205 / 65 R15 V tire manufactured according to Examples 5 and 6 and Comparative Example 3 was mounted on a 2000 cc class passenger car, and the noise generated inside the vehicle while traveling at 60 km / h was measured, and the values ​​in the audible frequency range were expressed in dB. Furthermore, the steering stability and ride comfort were evaluated in 5-point units of 100 points by a skilled driver's test course driving, and the results are shown in Table 4 below. The durability was measured according to the P-metric tire endurance test method of FMVSS 109 at a temperature of 38 (±3°C), tire loading of 85, 90, and 100%, and a vehicle was driven at a speed of 80 km / h for a total of 34 hours. The assessment was “okay” (OK) if there were no indications such as bead separation, cord cut, belt separation, etc.found in any part such as a tread, sidewall, carcass cord, inner liner and bead. [Table 4] Area Example 4 Example 5 Example 6 Comparison example 4 Comparison example 5 Comparison example 6 Tire weight (kg) 9.8 9.9 9.8 9.7 9.8 9.9 Driving comfort 100 99 100 97 98 95 Steering stability 100 100 100 100 100 98 resistance OK OK OK OK OK OK uniformity 100 100 100 98 98 99 Noise (dB) 61.2 61.4 61.0 61.7 61.5 62.3

[0087] Based on the test results of Table 4, the tires using the dipped cord according to the present invention (Examples 4, 5 and 6) were more effective in noise reduction and steering stability than Comparative Examples 4 and 5 in which the conventional nylon 66 yarn was used in the cover layer, and the tire uniformity was also improved.

[0088] In the above, the present invention has been described in detail only with reference to the described embodiments, but it will be apparent to those skilled in the art that various modifications and variations are possible within the technical scope of the present invention, and it is natural that such modifications are included within the scope of the appended claims. [Description of reference symbols] 1 extruder 2 gear pump 3 nozzles 4 Heating device 5 Cooling zone 6 to 10 stretching rollers 11 Winding roller 12 Emulsion feed device 31 tires 32 carcass ply 33 Reinforcing cord of the carcass ply 34 layer turnover 35 bulge region 36 bead core 37 Bead Fillers 38 Belt structure 39 Top layer 40 belt position 41, 42 belt cord 43 Tread 44 Peripheral location 45 cover cord

Claims

[1] A radial tire comprising: a pair of parallel bead cores; at least one radial carcass ply wound around the bead core; at least one bias belt layer laminated on an outer periphery of the carcass ply; and at least one cap layer laminated on an outer periphery of the bias belt layer in a tire circumferential direction, wherein the cover layer comprises a dipped cord made using a yarn containing 90 mol% or more of polyethylene terephthalate, and wherein the dipped cord has a shrinkage rate of 3.0 to 4.0%, a strength at a modulus of elasticity of 5% of 2.5 to 3.0 g / d, a tear strength of 6.5 to 7.5 g / d and a dimensional stability index of 5.8 to 6.5, where the shrinkage rate is evaluated by applying an overload of 0.01 g / d using a normal test rite and measuring at 177 degrees for 2 minutes, where the strength at a modulus of elasticity of 5% is obtained by reading the load at the point with a strain rate of 5% on the SS curve in g units and dividing by the nominal denier (yarn denier for 1 ply and the product of yarn denier and number of plies for 2 or more plies), and wherein the dipped cord is formed by twisting 400 to 2200d yarns containing 90 mol% or more of polyethylene terephthalate in one or more layers, and wherein the twist coefficient thereof is 9,000 to 18,000 square root of [(twist / twist per meter) * nominal denier]. [2] A radial tire according to claim 1, wherein the dipped cord has an intermediate elongation of 2.1 to 4.0% at 2.25 g / d and an elongation at break of 8.0 to 16.0%. [3] Radial tire according to claim 1 or 2, wherein the cover layer is reinforced with one or two layers.

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