KR102227154B1 - Polyester tire cord with improved heat resistance and tire comprising the same - Google Patents

Abstract

The present invention relates to a polyester tire cord, in a tire cord composed of a polyester yarn, wherein the tire cord has a cord strength of 4.3 g/d or more at 80°C after vulcanizing the tire cord at 177°C for 15 minutes, cord strength at 120°C is 4.0 g/d or more, and the toughness retention at 80°C and the toughness retention at 120°C after vulcanizing the tire cord at 177° C for 15 minutes are 60% or more. The tire cord of the present invention has the same strength and modulus as rayon even in a high temperature environment of 120°C or higher, and has excellent dimensional stability and heat resistance, so it can be advantageously applied to high-performance tires.

Description

Polyester tire cord with excellent heat resistance, and tires containing the same TECHNICAL FIELD {POLYESTER TIRE CORD WITH IMPROVED HEAT RESISTANCE AND TIRE COMPRISING THE SAME}

The present invention relates to a tire cord composed of polyester fibers and a tire including the same, and in particular, to a polyester tire cord having excellent heat resistance and dimensional stability, and a high performance tire constructed using the same.

Polyester, nylon, rayon, and the like are used as fibers for tire cords, and aramid fibers are also being developed for tire cords in recent years. Nylon fibers have long been used as fibers for tire cords because of their high strength and toughness. However, nylon fibers are not used as high-performance tire cords because of their high heat shrinkage and low modulus, and are used for bias tires of large vehicles.

Rayon fiber cord is used for high-performance tires because it has excellent thermal stability and very little deterioration in mechanical properties at high temperatures.However, it has a low strength level, high manufacturing cost, complicated manufacturing process, and environmental pollution problems due to the use of sulfur dioxide. As a result, its use is gradually decreasing.

Polyester fibers are widely used for tire cords because they have higher modulus and lower heat shrinkage than nylon fibers. However, polyester fiber has a problem of poor dimensional stability, such as a decrease in elastic modulus and an increase in shrinkage during molding (vulcanization process) of a tire due to a decrease in heat resistance according to temperature. In particular, the dimensional stability of the polyester fiber cord is far below the dimensional stability level of the rayon fiber cord, so there is a limitation that it is difficult to apply it to ultra-high performance tires. For polyester cords, high-speed spinning and spin draft increase technologies are applied to pursue dimensional stability comparable to that of rayon cords.

However, when such a technique is applied, there is a problem that the strength level of the yarn and the dip cord is lowered due to the decrease in the spinnability due to the increase in the crystallinity of the excessive undrawn yarn. On the other hand, when the stretchability is increased in order to improve the strength of the tire cord, poor fairness occurs, resulting in poor appearance of the yarn and a decrease in the strength utilization rate.

In addition, in order to use polyester fibers for tire cords, in addition to strength, it is required to improve dimensional stability so that shape deformation does not occur at high temperatures suitable for the driving environment of the tire. Even in the case of polyester tire cords, a flat spot phenomenon, which is a temporary geometrical deformation caused as a result of cooling the heated tire at high speed during parking, occurs, and this causes noise when mounted on a vehicle. In addition, even if the dimensional stability of the polyester tire cord is partially improved, there is a limitation in that it cannot be used as a substitute for rayon in an ultra-high performance tire because the elastic modulus is deteriorated in the high temperature environment of 120°C or higher that occurs during tire driving.

US 4101525 B US 5067538 B US 5472781 B EP 0423213 B

The present invention has been devised to solve the problems of the prior art as described above, one object of the present invention is a polyester tire cord having an elastic modulus equivalent to that of rayon even in a high temperature environment of 120°C or higher, and excellent in dimensional stability and heat resistance. Is to provide.

Another object of the present invention is a high-performance tire that can reduce weight, including a tire cord having excellent dimensional stability, improve driving performance, such as reducing noise during driving by reducing a flat spot phenomenon, and improving fuel economy performance by reducing rolling resistance Is to provide.

One aspect of the present invention for solving the above-described problem,

In the tire cord composed of polyester yarn, the tire cord has a cord strength of 4.3 g/d or more at 80° C. after vulcanizing the tire cord at 177° C. for 15 minutes (0.01 g/d), and at 120° C. The cord strength of is 4.0 g/d or more, and the toughness retention rate at 80° C. and the toughness retention rate at 120° C. calculated by the following Equation 1 after vulcanizing the tire cord at 177° C. for 15 minutes are 60% or more, respectively. It relates to a polyester tire cord, characterized in that.

[Equation 1]

Toughness retention rate (T ₂₅ -T ₈₀ ) = (Toughness value under _{T 80} condition/Toughness value under _{T 25 condition) X100}

Toughness retention rate (T ₂₅ -T ₁₂₀ ) = (Toughness value under _{T 120} condition/Toughness value under _{T 25 condition) X100}

(In the above formula, the polyester cord is a value measured after standing at 25°C and 65RH% for 24 hours _{, the toughness value under the T 25} condition is the toughness value measured under the 25°C ambient temperature, and the toughness under the T ₈₀ condition The value is the toughness value of the code measured under an atmosphere temperature of 80℃, and the toughness value _{under the condition T 120} is the toughness value of the code measured under an atmosphere temperature of 120℃)

In the present invention, the polyester tire cord has a 5% LASE of 0.8 g/d or more at 80° C., a median elongation (@2.25 g/d) of 9 to 11%, and a 5% LASE of 0.5 g/d at 120° C. d or more, and the median elongation (@2.25 g/d) may be 9-12%.

Another aspect of the present invention for solving the above-described problem relates to a tire comprising the polyester tire cord of the present invention.

Since the polyester tire cord of the present invention has an elastic modulus equal to that of rayon and has excellent heat resistance and dimensional stability, some standards of ultra high performance tires (UHPT) using rayon cords can be replaced with polyester tire cords. I can. According to the present invention, not only can the environmental pollution problem occurring during the manufacture of the rayon cord be solved, but also a remarkable effect of reducing the manufacturing cost of the ultra-high performance tire can be obtained by using a relatively inexpensive polyester tire cord.

In addition, since the polyester tire cord of the present invention has excellent heat resistance and dimensional stability, the elastic modulus of the cord is maintained even when the use of the cord is reduced during tire molding, thereby reducing tire weight and low rolling resistance without deteriorating tire performance, thereby improving fuel economy of automobiles. I can make it.

In addition, the high heat resistance and high elasticity polyester tire cord of the present invention is relatively high in cut and has good toughness, and has excellent toughness retention in high-temperature environments, improving the flat spot phenomenon due to the improvement of tire durability and high-temperature elastic modulus, and reducing running noise. , Improved ride comfort, improved handling, improved high-speed durability, and excellent tire driving performance.

1 schematically shows a six-stage spinning facility and a stretching process of a polyester yarn used in a polyester tire cord according to an embodiment of the present invention.
2 is a schematic cross-sectional view of a tire manufactured using a polyester tire cord according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

In describing the present invention, when it is determined that a detailed description of a related known technology may obscure the subject matter of the present invention, a detailed description thereof will be omitted. In the present specification, when a part "includes" a certain component (component), it does not exclude other components (components), but may further include other components, unless otherwise stated to the contrary. Means.

As used herein, "cord" is a reinforcing strand constituting a reinforcing structure of a tire, and refers to a product formed by twisting and blending several strands of yarn.

In the present specification, "LASE (Load at Specified Elongation)" means a load at a specific elongation.

In the present invention, "dimensional stability (E-S)" is expressed as the sum of intermediate elongation (E) and dry heat shrinkage (S). Since tires with a low dimensional stability (E-S) value have a small amount of deformation due to heat, tires using a cord with a low E-S value have higher tire uniformity and improved tire performance than a tire with a high cord.

In the present specification, "carcass" refers to a tire structure including a bead excluding a belt structure, a tread, an undertread, and sidewall rubber on a ply of a tire.

In the present specification, "specific draw ratio" means a ratio of a spin draft to a total draw ratio.

In the present specification, "spin draft" means the ratio of the linear speed (m/min) of the first drawing roller to the polymer discharge speed per unit area in the spinning nozzle.

In this specification, the term "flat spot" refers to a case where the glass transition temperature of the tire cord is low and the heat shrinkage rate is high, after shrinking in the footprint, cooling at this position, and when the cord reaches its glass transition temperature again. It means a phenomenon that maintains a flatspot up to.

The polyester tire cord of an embodiment of the present invention is a tire cord made of polyester yarn, and the tire cord has a cord strength at 80° C. after vulcanizing the tire cord at 177° C. for 15 minutes (0.01 g/d). 4.3 g/d or more, the cord strength at 120° C. is 4.0 g/d or more, and the toughness retention at 80° C. and 120° C. calculated by the following equation 1 after vulcanizing the tire cord at 177° C. for 15 minutes The retention rate of toughness in is 60% or more, respectively.

[Equation 1]

Toughness retention rate (T ₂₅ -T ₈₀ ) = (Toughness value under _{T 80} condition/Toughness value under _{T 25 condition) X100}

Toughness retention rate (T ₂₅ -T ₁₂₀ ) = (Toughness value under _{T 120} condition/Toughness value under _{T 25 condition) X100}

(In the above formula, the polyester cord is a value measured after standing at 25°C and 65RH% for 24 hours _{, the toughness value under the T 25} condition is the toughness value measured under the 25°C ambient temperature, and the toughness under the T ₈₀ condition The value is the toughness value of the code measured under an atmosphere temperature of 80℃, and the toughness value _{under the condition T 120} is the toughness value of the code measured under an atmosphere temperature of 120℃)

The polyester tire cord of the present invention has a 5% LASE of 0.8 g/d or more at 80° C., a median elongation (@2.25 g/d) of 9 to 11%, and a 5% LASE of 0.5 g/d at 120° C. It is above, and the median elongation (@2.25 g/d) is 9-12%. When the LASE and intermediate elongation values of the tire cord are out of the above ranges, the strength decreases at a high temperature and the shrinkage rate increases, thereby reducing the shape stability.

As the polyester fiber usable in the present invention, a polyester comprising a dicarboxylic acid and a glycol is preferably exemplified. Examples of the dicarboxylic acid component include terephthalic acid, 2,6-naphthalene dicarboxylic acid, isophthalic acid, and 1,4-cyclohexanedicarboxylic acid. Moreover, ethylene glycol, propylene glycol, tetramethylene glycol, 1, 4-cyclohexane dimethanol, etc. are mentioned as a glycol component. A part of the dicarboxylic acid component may be replaced with adipic acid, sebacic acid, dimer acid, sulfonic acid metal substituted isophthalic acid, or the like. In addition, some of the above glycol components may be replaced with diethylene glycol, neopentyl glycol, 1,4-cyclohexane diol, 1,4-cyclohexanedimethanol, polyalkylene glycol, or the like. Among these, polyethylene terephthalate, in which 90 mol% or more of the dicarboxylic acid component is composed of terephthalic acid, and 90 mol% or more of the glycol component is composed of ethylene glycol, is suitable. As the polyester yarn, in addition to polyethylene terephthalate (PET), polybutylene telephthalate (PBT), polyethylene naphthalate (PEN), or polytrimethylene terephthalate (PTT) may be used. The most preferred polyester polymer types are polyethylene terephthalate and polyethylene naphthalate.

Polyester includes various inorganic particles such as titanium oxide, silicon oxide, calcium carbonate, silicon thimide, mud, talc, kaolin, zirconic acid, and other particles such as crosslinked polymer particles and various metal particles, as well as conventional antioxidants and metals. Ion sequestering agents, ion exchangers, coloring inhibitors, waxes, silicone oils, various surfactants, and the like may be added.

The tire cord of the present invention has a strength of 5.0 g/d or more, a dry heat shrinkage of 3% or less after 2 minutes under a load of 0.05 g/d at 177°C, and a 5% LASE at room temperature of 2 g/d or more, The median elongation under 2.25 g/d load can be in the range of 4-6%. If the shrinkage ratio of the tire cord exceeds 3%, tire performance may deteriorate due to increased tire deformation during tire manufacturing.

The polyester yarn used in the tire cord of the present invention has intermediate elongation (@2.25 g/d): 2.5% to 3.0%, intermediate elongation (@4.5 g/d): 5.0% to 6.0% and intermediate elongation (@6.75 g /d): It satisfies the conditions of 7.5 ~ 9.0% at the same time. When the intermediate elongation does not meet the above requirements, when used for a tire cord, shape deformation due to a difference in the elastic modulus of the cord increases during the manufacture of tires, resulting in poor tire performance and poor performance.

In addition, the polyester yarn may simultaneously satisfy the following conditions (1) to (6).

(1) Intrinsic viscosity (I.V): 0.85 ~ 1.00

(2) Yarn strength: 7.0 g/d or more

(3) Amorphous Orientation Factor (AOF): 0.70 ~ 0.80

(4) Shrinkage: 4.0% or less

(5) Crystallinity: 50% or more

(6) Dimensional stability (E-S index) 8.5% or less

In the present invention, the dimensional stability (ES index) dimension is the sum of dry heat shrinkage (2 minutes elapsed under a load of 0.05 g/d at a temperature @ 177°C) and intermediate elongation (a load of @ 2.25 g/d), and the value is low. The more it is, the smaller the change in the shape of the tire cord is and the heat resistance is excellent.

In the present invention, the polyester yarn may be manufactured with a fineness of 1000 to 4000 denier, and thus it may meet the needs of the art to obtain a tire cord having a large fineness while exhibiting excellent physical properties. If the fineness of the polyester yarn is less than 1000 denier, sufficient strength as a tire cord cannot be secured, and if it exceeds 4000 denier, it is difficult not only to make stable spinning, but also it may hinder the weight reduction of the tire.

A method of manufacturing a polyester tire cord according to the present invention will be described as follows. First, the production of polyester yarn for tire cord in the present invention is to increase the spin-draft in the range of 1500-2500 through ultra-high-speed spinning at a spinning speed of 3,500 or more, and the intrinsic elongation coefficient in the range of 800-1400, Winding degree is improved heat resistance compared to conventional polyester high modulus low shrinkage (HMLS) yarn and dip cord by changing the microstructure of the final yarn by adjusting the total draw ratio of the yarn in the range of 1.6 to 1.9. Tire cords having dimensional stability can be manufactured.

First, a polyethylene terephthalate chip having an intrinsic viscosity of 1.0 to 1.15 is melted and extruded while passing through a nozzle to prepare a discharge yarn. Here, the polyethylene terephthalate polymer may contain at least 85 mol% of ethylene terephthalate units, but may optionally contain only ethylene terephthalate units.

Optionally, the polyethylene terephthalate may include, as a copolymer unit, a small amount of units derived from ethylene glycol and terephthalene dicarboxylic acid or derivatives thereof and one or more ester-forming components.

Examples of other ester-forming components copolymerizable with polyethylene terephthalate units include glycols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, terephthalic acid, isophthalic acid, hexahydroterephthalic acid, and stilbendica. Dicarboxylic acids such as carboxylic acid, dibenzoic acid, adipic acid, sebacic acid, and azelaic acid are included.

Terephthalic acid (TPA) and ethylene glycol raw materials are melt-mixed in a ratio of 2.0 to 2.3 in the prepared polyethylene terephthalate chip, and the melt mixture undergoes transesterification and condensation polymerization to form raw chips. Thereafter, the low chip is subjected to solid-phase polymerization to have an intrinsic viscosity of 1.00 to 1.15 at a temperature of 220° C. to 240° C. and a vacuum. At this time, if the intrinsic viscosity of the solid-phase polymerization chip is less than 1.00, the intrinsic viscosity of the final drawn yarn is lowered, so that it cannot exhibit high strength as a treated cord after heat treatment.If the intrinsic viscosity of the chip exceeds 1.15, the polymer melt phase is uneven and undissolved. Due to the increase in the crystalline material, the spinning tension and the cross section of the emitting yarn become uneven, causing a lot of filament cuts during stretching, resulting in poor spinning workability.

In addition, optionally, an antimony compound, preferably antimony trioxide, may be added as a polymerization catalyst during the condensation polymerization reaction so that the residual amount of antimony metal in the final polymer is 180 to 300 ppm. Polymerization when the residual amount is less than 180 ppm

The reaction rate is slow, the polymerization efficiency is lowered, and when the residual amount exceeds 300 ppm, more than necessary antimony metal acts as a foreign material, and the spinning and stretching workability may be deteriorated.

The polyethylene terephthalate chip as described above is melted and extruded while passing through a spinning nozzle to produce a discharge yarn. At this time, the diameter of the spinning nozzle is preferably 1.1 ~ 1.4 mm. Thereafter, the discharged sand is rapidly cooled and solidified by passing through a cooling zone. At this time, if necessary, a heating device of a certain length is installed in the distance from directly under the nozzle to the starting point of the cooling zone, that is, in the length (L) section of the hood. This zone is called a delayed cooling zone or a heating zone, which has a length of 50 to 150 mm and a temperature of 300 to 400°C (air contact surface temperature).

In the cooling zone, an open quenching method, a circular closed quenching method, a radial outflow quenching method, and a radial in flow quenching method are performed according to the method of blowing cooling air. ) Method may be applied, but is not limited thereto. At this time, the temperature of the cooling air injected for rapid cooling in the cooling zone is adjusted to 10°C to 30°C. The rapid cooling using such a rapid temperature difference between the hood and the cooling zone is to increase the solidification point and spinning tension of the spun polymer to increase the orientation of the undrawn yarn and the formation of a linking chain between the crystal and the crystal. Thereafter, the discharged yarn, which has been solidified while passing through the cooling zone, can be oiled at 0.3 to 1.0% by weight of the discharged yarn by an oil agent applying an oil agent having excellent stretchability and thermal efficiency while reducing the coefficient of friction between the single yarns.

The oiled discharged yarn is spun to form an undrawn yarn. At this time, the spin draft is 1500 to 2500, the spinning speed (first godet roller (GR1) speed) is preferably 3,000 m/min or more, preferably 3,500 m/min or more. When spinning at the spin draft and spinning speed in the above range, excellent strength of the yarn can be secured even at a low draw ratio. If the spin draft is less than 1500 or the spinning speed (the first godet roller (GR1) speed) is less than 3,000 m/min, the cross-sectional uniformity of the yarn deteriorates and the drawing workability decreases, and the degree of orientation of the undrawn yarn decreases, resulting in a decrease in crystallinity and crystallinity. Due to the lack of development, when stretching and dipping treatment, the thermal stability is lowered and the strength of the tire cord is lowered, and when high stretching is performed to improve strength and modulus, the dimensional stability may be deteriorated. When the spin draft exceeds 2500 or the spinning speed exceeds 4,000 m/min, the stretchability of the undrawn yarn is reduced, and the strength and the stretching workability of the yarn are deteriorated.

The undrawn yarn is passed through a draw roller and multi-stage stretched to produce a yarn. Yarn is formed by drawing the yarn that has passed through the first drawing roller while passing through a series of drawing rollers by a spin draw method. In the present invention, the undrawn yarn can be drawn in multiple stages by using a facility in which the drawing rollers are applied in 6 stages (GR1~GR6).

On the other hand, in the present invention, in the case of multistage stretching, the intrinsic stretching factor (spindraft/total stretching ratio) is maintained in the range of 800 to 1400. If the intrinsic elongation coefficient is less than 800, the dimensional stability may decrease due to an increase in the median elongation and shrinkage. On the contrary, when the intrinsic elongation coefficient exceeds 1500, the strength level of the yarn may decrease due to an excessive increase in crystallization. Further, as a stretching condition, the first stretching roller 6 can set its speed in the range of 3000 to 4000 m/min, and the fifth stretching roller 10 can wind up at 6000 to 7000 m/min.

The temperature of each drawing roller is higher than the glass transition temperature of the undrawn yarn and lower than 95° C., but the temperature in the fourth drawing roller and the fifth drawing roller 9, 10 is 200 to 250° C., more preferably 240. It can be set to ℃ ~ 250 ℃. If the temperature of the last drawing roller is less than 200°C, the crystallinity and the size of the crystal cannot be increased in the drawing process, and thus the strength and thermal stability of the yarn cannot be expressed, resulting in a decrease in dimensional stability at high temperatures, and the temperature of the last drawing roller is 250°C. If it is exceeded, it is too close to the melting point, and the microstructure of the yarn becomes uneven, such as crystal decomposition, and the strength of the yarn may decrease.

It is preferable that the winding speed of the stretched yarn is 6,000 m/min or more. If the winding speed is less than 6,000 m/min, productivity may decrease. The stretched yarn may preferably be wound at 6000 to 7000 m/min.

In addition, it is preferable that the total draw ratio of the yarn formed by winding as described above is 1.6 to 1.9 times. If the draw ratio is less than 1.6 times, productivity decreases and the strength and shape stability of the yarn and cord are lowered. If the draw ratio exceeds 1.9 times, the crystallization of the oriented amorphous part increases, resulting in a decrease in drawing workability and trimming. In the microstructure of the yarn, the molecular chain of the amorphous portion is broken, resulting in a decrease in the uniformity of the molecular chain, which is not preferable because the strong utilization rate may be reduced. In particular, in the case of ultra-high-speed spinning, it is preferable that the draw ratio is 1.9 times or less due to the restriction of the draw ratio adjustment according to the spinning equipment.

Thereafter, a dip cord is prepared by twisting, weaving, and dipping using the manufactured polyethylene terephthalate yarn. First, the polyethylene terephthalate yarn The three copies are twisted with a twisting machine in which false twisting and twisting are carried out in stages or a direct twisting machine in which simultaneous twisting is performed to produce a raw cord for tire cord. The twisted yarn is manufactured by applying a ply twist to the polyethylene terephthalate yarn and then applying a cable twist to twist it. .

The tire cord of the present invention has a fineness of 2000 to 8000 denier, and can be manufactured with 2 to 4 ply and soft water of 200 to 500 TPM. In the present invention, the softness of the polyethylene terephthalate dip cord is 200/200 TPM (Twist Per Meter) to 400/400 TPM with the same value for the upper and lower edges. When the upper and lower edges are set to the same value, the manufactured dip cord does not exhibit rotation or twist, and it is easy to maintain a straight line, thereby maximizing the expression of physical properties. At this time, if the number of years of the upper/lower edge is less than 200/200 TPM, it is easy to reduce the fatigue resistance due to the decrease in the cut of the raw cord, and if it exceeds 400/400 TPM, the strength decrease is large, and thus it is not suitable for tire cord.

Thereafter, the woven yarn is dipped in a dipping solution, dried, stretched and heat-set, then immersed in the dipping solution again, dried and heat-set to prepare a dip cord. The dipping solution is not particularly limited, but it is preferably an epoxy, parachlorophenol-based resorcinol/formalin mixed resin (Pexul). At this time, the drying should avoid rapid treatment at high temperatures, and is preferably carried out at 90°C to 180°C for 180 to 220 seconds. If the drying temperature is less than 90°C, drying may not be sufficiently performed, and when drying and heat treatment, gel due to the dipping solution resin may occur, and when it exceeds 180°C, gel due to the dipping solution resin may occur due to rapid drying. Non-uniform adhesion between the cord and the dip liquid resin may occur.

The heat setting is performed so that the cord impregnated with the dipping liquid has an appropriate adhesive strength with the tire rubber, and the heat setting temperature is preferably performed at 220° C. to 250° C. for 50 to 90 seconds. If heat setting is performed for less than 50 seconds, the adhesive strength is lowered due to insufficient reaction time of the adhesive solution, and when heat setting is performed for more than 90 seconds, the hardness of the adhesive solution decreases, and thus the fatigue resistance of the cord may be reduced.

Another aspect of the present invention relates to a tire in which a high-strength polyester cord having excellent heat resistance and dimensional stability is applied to a carcass. 2 is a schematic cross-sectional view of a tire for a passenger car manufactured by applying a polyethylene terephthalate cord according to the present invention to a carcass.

2, the tire of the present invention includes a carcass 14 extending from the tread portion 23 to the bead core 18 of the bead portion 17 facing each other through the sidewall portion 13, and the tread. In (23), it includes a belt portion 22 disposed radially outward of the carcass 14. The carcass 14 comprises at least one carcass ply 15 in which the polyester carcass cord of the present invention is arranged at an angle of, for example, 80° to 90° with respect to the equator of the tire. The carcass ply 15 extends from one bead core 18 to the opposite bead core 18 to pass through the crown area of the tire, and extends from both ends of the main body. As a result, it may be composed of a turnup portion 16 that is folded around the bead core 18 from the inside in the axial direction to the outside in the axial direction of the tire to fix the carcass ply. Reference numeral 19, which is not described in FIG. 2, denotes a bead filler, and reference numerals 20, 21, and 22 denote a belt structure, a cap ply, and a belt ply, respectively.

As described above, the polyester tire cord of the present invention has excellent other properties such as modulus, strength, and elongation, and exhibits high heat resistance and dimensional stability even in a high temperature environment to reduce the flat spot phenomenon, and adopt the cord of the present invention. One tire exhibits excellent performance with improved ride comfort and driving performance while also improving fuel efficiency.

Hereinafter, the present invention will be described in more detail with reference to examples, but these examples are for illustrative purposes only, and the scope of the present invention is not limited to these examples.

[Method of evaluating properties of polyester yarn and tire cord]

The evaluation of physical properties of the polyethylene terephthalate yarn and tire cord obtained in the following examples was measured or evaluated as follows.

(1) Tire cord strength (kgf)

After leaving for 24 hours at 25°C and 65% RH, an Instron's low-speed elongation type tensile tester was used. After adding 80 TPM of twist, the sample length was measured at 250 mm and a tensile speed of 300 m/min.

(2) Toughness retention rate after vulcanization of tire cord (%)

After vulcanizing the tire cord at 177°C for 15 minutes (0.01 g/d), leave it at 25°C and 65% RH for 24 hours, and then measure the toughness of the polyester cord and measured at each temperature of 80°C or 120°C. Using one toughness, the toughness retention was calculated according to Equation 1 below.

[Equation 1]

Toughness retention rate (T ₂₅ -T ₈₀ ) = (Toughness value under _{T 80} condition/Toughness value under _{T 25 condition) X100}

Toughness retention rate (T ₂₅ -T ₁₂₀ ) = (Toughness value under _{T 120} condition/Toughness value under _{T 25 condition) X100}

(In the above formula, the polyester tire cord is a property measured after leaving it at 25°C and 65RH% for 24 hours, _{and the toughness value under the T 25} condition is the toughness value of the cord measured under the 80°C ambient temperature, and under the T ₁₂₀ condition The toughness value of is the toughness value of the code measured under the ambient temperature of 120℃.)

(3) LASE (Load At Specified Elongation)

A load at elongation corresponding to 5% was taken from the elongation load curve obtained by the ASTM D885 measurement method. The sample before measurement was measured after leaving it for 24 hours in an atmosphere of 20°C and 65% RH.

(4) Median elongation of yarn and tire cord (%)

Elongation at specific load is measured on the elongation SS curve for yarn at 2.25 g/d, 4.5 g/d and 6.75 g/d, and tire cord at 2.25 g/d. Elongation was measured.

(5) Dry heat shrinkage rate of tire cord (%, Shrinkage)

The ratio of the length measured at 0.05 g/d static load (L ₀ ) and the length after treatment at 177° C. 2 minutes 0.05 g/d static load (L ₁ ) after leaving the tire cord at 25°C and 65% RH for 24 hours The dry heat contraction rate was calculated according to Equation 2 below.

[Equation 2]

S(%) = (L ₀ -L ₁ ) / L ₀ Х 100

(6) Intrinsic viscosity of yarn (I.V.)

0.1 g of a sample was dissolved in a reagent (90°C) in which phenol and 1,1,2,3-tetrachloroethanol were mixed in a weight ratio of 6:4 for 90 minutes to a concentration of 0.4 g/100ml, and then Ubbelohde (Ubbelohde) ) Transferred to a viscometer and held for 10 minutes in a 30°C constant temperature bath, and the number of seconds to fall of the solution was calculated using a viscometer and an aspirator. The number of seconds to fall of the solvent was also determined by the same method, and then the R.V. value and the I.V. value were calculated by the following Equations 3 and 4.

[Equation 3]

Relative viscosity (R.V.) = number of seconds to fall of sample/number of seconds to fall of solvent

[Equation 4]

Intrinsic viscosity (I.V.) = 1/4 Х (R.V.- 1)/concentration + 3/4 Х (ln R.V./concentration)

(7) Crystallinity of yarn (%)

The degree of crystalinity is measured using a density gradient tube by the density method. Assuming that the density of the crystalline region is ρc, the density of the amorphous region is ρa, and the density of the sample is ρ, the degree of crystallinity (X) is calculated according to Equation 5 below.

[Equation 5]

X(%)=(ρc-ρ)/(ρc-ρa)Х100

In the case of polyester, ρc=1.455 g/cm3 and ρa=1.355 g/cm3.

(8) Yarn's amorphous orietation function (Fa)

The amorphous orientation function was calculated through Equation 6 below using the birefringence index measured using a polarizing microscope and the crystal orientation function index measured from XRD.

[Equation 6]

Fa= (birefringence-crystal orientation functionx0.251x(crystallinity(%)/100))/(0.24x(1-crystallinity(%)/100))

(9) Dimensional stability index (ES)

In this embodiment, the dimensional stability index is calculated as the sum of the intermediate elongation (E) and dry heat shrinkage (S) at a load of 4.5 g/d for yarn and 2.25 g/d for processing cord.

[Equation 7]

Dimensional stability (E-S) = Medium elongation (E) + dry heat shrinkage (S)

(9) Spin draft

The spin draft is the ratio of the polymer speed in the spinning nozzle and the linear speed of the first drawing roller, and is calculated according to Equation 8 below.

[Equation 8]

Spindraft = V ₁ /V ₀

In the above formula, V ₁ : linear speed of the first stretching roller (m/min)

V ₀ : Discharge amount/sectional area=Q/(ðD ² /4Xρ)

Q: discharge amount (g/min), D: yarn diameter (mm), ρ: melt density (1.18 g/cm 3)

(10) Intrinsic elongation coefficient

[Equation 9]

Intrinsic Elongation Coefficient = Spin Draft/Total Elongation Ratio

Example 1

A solid-phase polymerization polyethylene terephthalate chip having an intrinsic viscosity (I.V.) of 1.08 and a moisture content of 10 ppm containing 250 ppm of an antimony metal was prepared. The prepared chips were melt-spun at a temperature of 300°C using an extruder at a discharge rate of 1500 g/min and a spin draft ratio of 1,800. Then, the discharged yarn is solidified by passing through a 100 mm long heating zone (atmosphere temperature 380°C) and a 530 mm long cooling zone (20°C, cooling air with a wind speed of 0.5 m/sec) under the nozzle to solidify. It was oiled with (containing 30% paraffin oil component). Wind up the POY yarn at a spinning speed (first godet roller speed) of 3,500m/min, the first step stretching is 1.3 times at 65℃, the second step stretching is 1.1 times at 70℃, and the third step stretching is 75℃. Performed at a rate of 1.2, heat-set at 250° C., loosened by 1.5%, and then wound to prepare a final drawn yarn (yarn) of 2040 denier.

After fabricating raw cord by twisting and twisting 3 strands of manufactured yarn at 276 TPM, the raw cord is immersed in epoxy resin and Pexul adhesive solution in a dipping tank, and then stretched 3.5% at 170℃ in a dry area. After drying for 150 seconds at 245℃ in a high-temperature drawing area, heat setting for 150 seconds under 3.0% stretching at 245℃, immersion in RFL again, drying at 170℃ for 100 seconds, and heat setting at 245℃ under -5.0% stretching for 40 seconds to dip The cord was prepared.

The physical properties of the polyester drawn yarn and dip cord thus prepared were evaluated and shown in Tables 1 and 2 below.

Examples 2 to 4 and Comparative Examples 1 to 3

Polyethylene terephthalate stretched yarns and dip cords of Comparative Examples 1 to 3 were prepared in the same manner as in Example 1 while changing spinning conditions such as spin draft, draw ratio, and intrinsic draw coefficient as shown in Table 1 below.

The properties of the polyethylene terephthalate drawn yarn and dip cord thus prepared were evaluated and shown in Tables 1 and 2 below.

Comparative example Example One 2 3 One 2 3 4 Sacrificial conditions Spinning equipment 5-speed 5-speed 5-speed 6-speed 6-speed 6-speed 6-speed Spinning speed
(GR1 speed, m/min) 2,500 4,000 4,400 3,500 3,800 3,900 4,000 Spin draft 690 2500 2800 1800 2000 2050 2400 Total draw ratio 2.04 1.58 1.50 1.80 1.72 1.70 1.75 Intrinsic Elongation Coefficient 338 1582 1867 1000 1163 1206 1371 Yarn
Properties Viscosity (dl/g) 0.92 0.92 0.92 0.92 0.92 0.92 0.92 Crystallinity (%) 44.1% 52.4% 56.5% 52.0% 54.5% 55.0% 54.8% Amorphous orientation function 0.78 0.65 0.78 0.75 0.74 0.74 0.71 Fineness (d) 2040 2040 2040 2040 2040 2040 2040 Strong (kg) 15.5 12.4 12.9 15.6 15.6 15.7 14.5 Strength (g/d) 7.6 6.1 6.3 7.6 7.6 7.7 7.1 Zhongshin (@2.25g/d) 3.2 3.1 2.9 2.8 2.7 2.7 2.9 Zhongshin (@4.5g/d) 6.3 7.5 5.8 5.7 5.6 5.6 5.9 Zhongshin (@6.75g/d) 9.3 Not measurable Measure
Impossible 8.2 8.1 8.0 8.8 Desperate (%) 13.0 20.0 15.2 14.2 14.0 13.9 16.8 Shrinkage (%) 5.0 0.8 2.4 2.7 2.7 2.6 2.3 E-S (%, @ 4.5g/d) 11.3 8.3 8.2 8.4 8.3 8.2 8.2

Comparative example Example One 2 3 One 2 3 4 Deep code 25℃ Structure (denier/ply) 2000d/3p 2000d/3p 2000d/3p 2000d/3p 2000d/3p 2000d/3p 2000d/3p Training (TPM) 276 276 276 276 276 276 276 Denier 6920 6920 6920 6920 6920 6920 6920 Strong (kg) 41.7 33.5 31.9 43.5 43.6 43.6 37.5 Strength (g/d) 6.0 4.8 4.6 6.3 6.3 6.3 5.4 LASE(g/d,@5%) 1.85 1.53 2.73 2.60 2.65 2.65 2.15 Jungshin(%,@2.25g/d) 6.2 7.7 3.7 4.2 4.2 4.1 5.8 Desperate (%) 21.4 26.0 14.0 16.8 16.3 16.0 22.5 Shrinkage (%) 2.3 0.3 2.4 2.0 2.0 2.0 0.4 E-S(%) 8.5 8.0 6.1 6.2 6.2 6.1 6.2 Toughness (kg-㎜) 1345 1483 885 1145 1121 1115 1245
After curing
Deep code 25℃ after curing Strong (kg) 42.2 33.4 31.0 43.5 43.6 43.6 37.5 Strength (g/d) 6.1 4.8 4.5 6.3 6.3 6.3 5.4 LASE(g/d,@5%) 1.1 0.9 1.8 1.4 1.4 1.5 1.1 Jungshin(%,@2.25g/d) 10.5 9.9 7.0 8.3 8.2 8.2 9.8 Desperate (%) 26.9 31.0 17.8 22.5 22.1 21.0 28.5 Toughness (kg-㎜) 1529 1730 1210 1420 1367 1352 1525 80℃ after curing Strong (kg) 29.5 26.6 24.5 34.7 34.9 35.0 31.1 Strength (g/d) 4.3 3.8 3.5 5.0 5.0 5.1 4.5 LASE(g/d,@5%) 0.8 0.8 1.2 1.0 1.0 1.0 0.8 Jungshin(%,@2.25g/d) 12.0 11.5 8.4 9.6 9.6 9.5 10.4 Desperate (%) 20.3 24.1 15.0 20.6 20.4 20.0 25.5 Toughness (kg-㎜) 707 868 552 965 935 918 1150 Toughness retention rate (%) 46.2% 58.5% 45.6% 68.0% 68.4% 67.9% 75.4% 120℃ after curing Strong (kg) 26.3 24.8 22.1 32.0 32.0 32.1 29.1 Strength (g/d) 3.8 3.6 3.2 4.6 4.6 4.6 4.2 LASE(g/d,@5%) 0.5 0.5 1.0 0.8 0.8 0.8 0.6 Jungshin(%,@2.25g/d) 13.1 12.5 9.6 10.1 10.0 10.0 11.6 Desperate (%) 20.4 21.5 13.1 21.5 21.1 20.0 21.0 Toughness (kg-㎜) 595 816 482 924 896 861 1045 Toughness retention rate (%) 38.9% 55.0% 39.8% 65.1% 65.6 63.7 68.5

As confirmed through the results of Table 2, the tire cords manufactured in Examples 1 to 4 of the present invention have toughness retention and dimensional stability index (ES) values compared to the tire cords manufactured in Comparative Examples 1 to 3 This is excellent. In particular, it can be seen that the tire cords manufactured in Examples 1 to 4 have excellent strength, toughness retention, intermediate elongation, and dimensional stability measured in a high temperature environment of 120°C.

In the above, the present invention has been described in detail only with respect to the described embodiments, but this description has been described for the purpose of illustrating the present invention, and various changes and changes can be made without departing from the scope of the present invention. It will be apparent to those of ordinary skill in the field. Accordingly, it should be understood that such changes are included in the protection scope of the present invention as defined by the following appended claims.

1: spinning pack 2: spinning nozzle
3: cooling zone 4: discharge yarn
5: emulsion application device 6: first drawing roller (GR1)
7: second drawing roller (GR2) 8: third drawing roller (GR3)
9: 4th drawing roller (GR4) 10: 5th drawing roller (GR5)
11: 6th drawing roller (GR6)
12: Polyester tire cord yarn
13: Sidewall 14: Carcass Fly
15: main body 16: turn-up portion
17: bead area 18: bead core
19: bead filler 20: belt structure
21: cap fly 22: belt fly
23: tread

Claims (9)

In the tire cord composed of polyester yarn, the tire cord has a cord strength of 4.3 g/d or more at 80° C. after vulcanizing the tire cord at 177° C. for 15 minutes (0.01 g/d), and at 120° C. The cord strength of is 4.0 g/d or more, and the toughness retention rate at 80°C and the toughness retention rate at 120°C calculated by the following equation 1 after vulcanizing the tire cord at 177°C for 15 minutes are 60% or more, respectively. Polyester tire cord, characterized in that.
[Equation 1]
Toughness retention rate (T ₂₅ -T ₈₀ ) = (Toughness value under _{T 80} condition/Toughness value under _{T 25 condition) X100}
Toughness retention rate (T ₂₅ -T ₁₂₀ ) = (Toughness value under _{T 120} condition/Toughness value under _{T 25 condition) X100}
(In the above formula, the polyester cord is a value measured after standing at 25°C and 65RH% for 24 hours, _{and the toughness value at the T 25} condition is the toughness value of the polyester cord measured at 25°C ambient temperature, and the T ₈₀ condition The toughness value at is the toughness value of the code measured under 80℃ atmosphere temperature, and the toughness value _{under the T 120} condition is the toughness value of the code measured under 120℃ atmosphere temperature)
The method of claim 1, wherein the polyester tire cord has a 5% LASE of 0.8 g/d or more at 80° C., a median elongation (@2.25 g/d) of 9 to 11%, and a 5% LASE at 120° C. Polyester tire cord, characterized in that it is 0.5 g/d or more and has a median elongation (@2.25 g/d) of 9 to 12%.
The polyester tire cord according to claim 1, wherein the tire cord has a strength of 5.0 g/d or more, and a dry heat shrinkage ratio of 3% or less after 2 minutes under a load of 0.05 g/d at 177°C.
The method of claim 1, wherein the polyester yarn has intermediate elongation (@2.25 g/d): 2.5% to 3.0%, intermediate elongation (@4.5 g/d): 5.0% to 6.0% and intermediate elongation (@6.75 g/d). d): Polyester tire cord, characterized in that it satisfies the conditions of 7.5 to 9.0% at the same time.
The polyester tire cord according to claim 3, wherein the polyester yarn satisfies the following conditions (1) to (6) at the same time.
(1) Intrinsic viscosity (IV): 0.85 ~ 1.00
(2) Strength: 7.0 g/d or more
(3) Amorphous Orientation Factor (AOF): 0.70 ~ 0.80
(4) Shrinkage: 4.0% or less
(5) Crystallinity: 50% or more
(6) Dimensional stability is less than 8.5%
The method of claim 1, wherein the polyester is polyethylene terephthalate, polybutylene telephthalate, polyethylene naphthalate or polytrimethylene terephthalate.
Polyester tire cord, characterized in that (PTT).
The polyester tire cord according to claim 1, wherein the tire cord has a cord fineness of 2000 to 8000 denier, 2 to 4 plies and 200 to 500 TPM.
A tire comprising the polyester tire cord of any one of claims 1 to 7.
The method of claim 8, wherein the tire includes a tread portion, a pair of sidewalls disposed on both sides of the tread portion, and a pair of bead portions disposed inside the tire radial direction of the sidewall, and between the pair of bead portions A tire in which a plurality of carcasses are disposed, wherein the carcasses are composed of the polyester tire cord.

Images