Tire cord and method for manufacturing the same

Abstract

This specification discloses a high-strength tire cord having a strength of 8.0 g / d or higher, a LASE@2% strength of 1.1 g / d or higher, a LASE@5% strength of 2.5 g / d or lower, and a toughness of 183 g / d·mm or higher, and satisfying a side wall indentation (SWI) value of 3.6% or lower, according to the ASTM D885 standard test method.

Description

Technical Field

[0001] The present invention relates to a tire cord using high-strength polyester raw yarn and a method for manufacturing the same.

Background Art

[0002] As the performance of automobiles gradually improves and road conditions are improved, it is required to maintain the stability and durability of tires during high-speed driving of automobiles. In addition, in consideration of environmental problems, energy problems, fuel efficiency, etc., tires that are light yet excellent in durability are required. As one measure to meet such requirements, research on tire cords used as rubber reinforcing materials for tires has been actively carried out.

[0003] The tire cord is manufactured using industrial raw yarns, for example, polyester raw yarns. Also, in order to improve the physical properties of the tire cord, research has been continuously conducted to improve the mechanical properties of the polyester raw yarns, such as tensile strength, elongation rate, etc.

[0004] Polyester raw yarn, which is a kind of industrial raw yarn, can generally be manufactured by melting polyester chips, forming filaments by discharging the melted polyester using a die, cooling the semi-solidified filaments discharged from the die, and then gathering, stretching, and winding the cooled filaments.

[0005] Research continues on methods to reduce the fineness of polyester tire cords (e.g., PET tire cords) in order to lighten tires. To achieve this tire weight reduction, three physical properties must be satisfied: modulus, toughness, and shrinkage. However, a method that satisfies all of these required properties for the tire cord has not yet been developed. In other words, lowering the fineness of the tire cord reduces the pressure at the spinning pack and die, which decreases the toughness of the tire cord, making it impossible to achieve all the desired properties. [Overview of the project] [Problems that the invention aims to solve]

[0006] This specification provides a tire cord that satisfies all of the following characteristics for tire cords using polyester with a wide range of fineness: high strength, high modulus, low shrinkage, and high elongation, thereby enabling weight reduction of the tire.

[0007] Furthermore, a method for manufacturing the tire cord may be provided in this specification. [Means for solving the problem]

[0008] This specification includes polyester yarn containing 90 mol% or more of polyethylene terephthalate. We can provide tire cords that meet the ASTM D885 standard test method, possessing a strength of 8.0 g / d (gf / D; grams / denier) or higher, a LASE (Load at specified elongation) @ 2% of 1.1 g / d or higher, a LASE @ 5% of 2.5 g / d or lower, and a toughness of 183 g / d·mm or higher, while satisfying a side wall indentation (SWI) value of 3.6% or lower.

[0009] In the physical properties of the tire cord, the sidewall indentation may be measured by the following formula 1:

[0010] [Formula 1] SWI(%)=[(D)-(C)]+[(A)-(B)]

[0011] In formula 1 above, (A) is the dry heat shrinkage rate measured after the dry heat shrinkage rate was measured using a shrinkage tester (measured with a test specimen length of 250 mm, at 180°C for 2 minutes, under an initial tensile load (20-45 g)), and then allowed to cool for 1 minute. (B) is the dry heat shrinkage rate measured after the dry heat shrinkage rate was measured using a shrinkage tester (measured with a test specimen length of 250 mm, at 180°C for 2 minutes, under an initial tensile load (40-90 g)), and then allowed to cool for 1 minute. (C) is the value of the intermediate elongation of the (A) specimen measured by the standard ASTM D885 test method under a load of 1.5 to 3.0 kg. (D) is the value of the intermediate elongation of the (B) specimen measured by the standard ASTM D885 test method under a load of 3.0 to 6.0 kg.

[0012] (A) may be 1.0-3.2%, (B) may be 0.7-2.8%, (C) may be 1.3-1.7%, and (D) may be 4.2-4.6%.

[0013] Furthermore, the tire cord can have a strong utilization rate of 88% or more according to the following formula 2.

[0014] [Formula 2] Strength utilization rate (%) = [Tensile strength of tire cord (g / d) / Tensile strength of polyester yarn (g / d)] × 100

[0015] The tire cord may include a high-strength polyester yarn manufactured from a polyester multifilament containing 200 to 2,000 polyester monofilaments having a fineness of 2.5 to 3.5 denier, and an adhesive layer impregnated into the high-strength polyester yarn.

[0016] The aforementioned polyester filament can be produced from a molten polyester resin containing 90 mol% or more of polyethylene terephthalate and having an intrinsic viscosity of 1.0 dl / g or more.

[0017] Such polyester filaments can have a tensile strength of 7.5 to 11.0 g / d and an elongation of 10 to 20%.

[0018] The tire cord may include a raw cord having a total fineness of 1000 to 6000 denier.

[0019] Furthermore, this specification provides a method for manufacturing tire cord, comprising the steps of: producing polyester filament by spinning molten polyester resin containing 90 mol% or more of polyethylene terephthalate and having an intrinsic viscosity of 1.0 dl / g or more using a spinning pack including a die with a nozzle; producing a plied yarn using the polyester filament; and heat-treating the plied yarn by immersing it in an adhesive solution.

[0020] More specifically, the step of producing the polyester yarn may include a step of discharging the molten polyester resin through a die that includes a nozzle section having a shear rate of 220 to 260 1 / sec (liters / second) and a polymer discharge rate of 2.0 m / min or less, under spinning pack pressure conditions of 1800 to 2500 psi (pound-force per square inch), thereby forming a polyester multifilament including a polyester monofilament having a fineness of 2.5 to 3.5 denier.

[0021] The tire cord provided by the method for manufacturing the tire cord has a strength of 8.0 g / d or more, LASE@2% (load at 2% elongation) of 1.1 g / d or more, LASE@5% (load at 5% elongation) of 2.5 g / d or less, and a toughness of 183 g / d·mm or more according to the standard test method of ASTM D885, and can satisfy a side wall indentation (SWI) value of 3.6% or less.

[0022] The polyester multifilament can include 200 to 2,000 polyester monofilaments having a fineness of 2.5 to 3.5 denier.

[0023] Also, the step of manufacturing the polyester raw yarn includes discharging a molten polyester resin having an intrinsic viscosity of 1.0 dl / g or more through a die including a nozzle part having a shear rate of 220 to 260 1 / sec and a polymer discharge rate of 2.0 m / min or less under a pressure condition of a spinning pack of 1800 to 2500 psi (pound-force per square inch) to manufacture a plurality of filaments, heating the plurality of discharged filaments by a heating part, cooling the plurality of heated filaments by a cooling part, converging the plurality of filaments to form a polyester multifilament, stretching the polyester multifilament, and winding the stretched multifilament.

[0024] The step of stretching the polyester multifilament can include stretching the polyester multifilament at a total draw ratio of 1.0 to 3.0 times.

Advantages of the Invention

[0025] According to the present invention, when manufacturing polyester raw yarn, while applying a low DPF (Denier per filament), the polymer discharge speed at the nozzle is adjusted to impart a high spinning tension and spinning draft. At the same time, the discharge pressure in the spinning pack is set high to maintain a high shear rate at the nozzle, so that excellent mechanical properties of the polyester raw yarn are maintained in the tire cord, and all physical properties required for weight reduction can be satisfied.

[0026] Therefore, the present invention can provide a lightweight tire cord that satisfies all of high strength, high modulus, low shrinkage, and high cut elongation.

Brief Description of the Drawings

[0027] [Figure 1] It is a schematic diagram of a raw yarn manufacturing apparatus according to an embodiment of the present invention.

Mode for Carrying Out the Invention

[0028] Hereinafter, the tire cord and its manufacturing method according to the embodiment of the present invention will be described in more detail.

[0029] Unless otherwise defined herein, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used in the description of the present invention are for the purpose of effectively describing specific examples only and are not intended to limit the present invention.

[0030] As used herein, the singular forms also include the plural forms unless the context clearly dictates otherwise.

[0031] As used herein, the meaning of "comprising" does not exclude the presence or addition of other specific features, regions, integers, steps, operations, elements, and / or components while embodying a specific feature, region, integer, step, operation, element, component, and / or group.

[0032] While the present invention can take on various forms through numerous modifications, specific embodiments are described in detail below. However, it should be understood that this is not intended to limit the invention to any particular disclosure, but rather to include all modifications, equivalents, or substitutions that fall within the aforementioned concept and technical scope.

[0033] In this specification, when the positional relationship between two parts is described using expressions such as "on top," "at the top," "at the bottom," or "to the side," one or more other parts may be located between the two parts unless the expressions "immediately" or "directly" are used.

[0034] In this specification, when temporal relationships are described using expressions such as "after," "following," "next," or "before," non-continuous events can be included, as long as the expressions "immediately" or "directly" are not used.

[0035] In this specification, the term "primarily twisted yarn" refers to a single yarn made by twisting a single filament in one direction.

[0036] In this specification, the term "plied yarn" refers to a yarn made by twisting two or more under-twisted yarns together in one direction, and is sometimes also called "raw-cord."

[0037] In this specification, the term "tire cord" refers to a twisted yarn containing adhesive so that it can be readily applied to rubber products for tires, and is also sometimes referred to as "dip-cord."

[0038] According to one embodiment of the invention, a tire cord can be provided that contains polyester yarn containing 90 mol% or more of polyethylene terephthalate, has a strength of 8.0 g / d or more, a LASE (Load at specified elongation) of 1.1 g / d or more at 2% LASE@5% LASE 2.5 g / d or less, and a toughness of 183 g / d·mm or more, as determined by the ASTM D885 standard test method, and satisfies a side wall indentation (SWI) value of 3.6% or less.

[0039] The inventors have devised a method to maintain excellent mechanical properties such as tensile strength and elongation of polyester filament by applying a high multifilament spinning method that satisfies spinning conditions of low denier per filament, low die extrusion speed, and low shear rate, and by including polyester filament produced by adjusting the pressure of the spinning pack. Through experiments, they have confirmed that including the polyester filament in this manner provides a high-strength tire cord that exhibits high modulus, high toughness, and stable shrinkage properties, thus completing the invention.

[0040] Herein, in this specification, DPF (Denier per filaments) refers to the denier value per polyester monofilament contained in the polyester yarn.

[0041] Tire cord is manufactured through a three-stage process: the production of raw yarn, the twisting process using the raw yarn, and heat treatment. However, a tire cord with superior performance can only be obtained by maintaining the physical properties of the raw yarn.

[0042] In other words, the raw yarn undergoes subsequent processes such as twisting and heat treatment, during which the properties of the yarn deteriorate and change. For example, strength and toughness may decrease, and shrinkage rate and intermediate elongation may change. Therefore, it is necessary to ensure that the properties of the raw yarn are maintained even after these subsequent processes.

[0043] Furthermore, in order to replace the existing fineness range, the required properties of tire cords for tire weight reduction must satisfy all three properties: large size, high modulus, high toughness, and low and stable shrinkage.

[0044] Here, the factor indicating the modulus is LASE (Load At Specific Elongation), and the factor indicating the shrinkage rate is Side Wall Indentation (SWI). Furthermore, in order to achieve high toughness, the modulus must be controlled to be low above a certain interval. In other words, even if the modulus is increased, it is necessary to prevent a decrease in other physical properties such as toughness. For example, in the elongation load curve obtained by the ASTM D885 measurement method, it is required to control the modulus to LASE@5%, which is defined as the load (g / d) at an elongation (stretch rate) corresponding to 5%.

[0045] However, while conventional tire cords that satisfy all three of the above physical properties have not been developed, the tire cord according to the above embodiment exhibits high strength even after post-processing of the raw yarn, and satisfies all of the excellent modulus, toughness, and shrinkage characteristics.

[0046] Such tire cords may be supplied with polyester filaments produced by adjusting the pressure of the spinning pack, along with a high multi-filament spinning method.

[0047] Specifically, the manufacturing conditions for the yarn involve using the high multifilament spinning method, which means applying a low DPF (Denier per filaments), a low extrusion speed at a low nozzle tip, and a low shear rate at the nozzle.

[0048] However, these manufacturing conditions can reduce the pressure at the spinning pack / die, which is linked to a decrease in the toughness of the tire cord.

[0049] In other words, the aforementioned high multi-filament spinning method can produce tire cords with high strength, high modulus, and stable shrinkage, but it is associated with a decrease in toughness (elongation at break). This is because each of these properties has an inverse relationship, and as a result, existing conventional spinning methods cannot achieve tire cords that satisfy all the desired properties.

[0050] Therefore, in this specification, we have devised an invention that applies a high multi-filament spinning method with specified spinning conditions, while simultaneously adjusting the pressure of the spinning pack to maintain high toughness.

[0051] Furthermore, the modulus range of the toughness at LASE@5% is limited to a specific range.

[0052] The tire cord manufactured using the above method can be used in tires that achieve weight reduction and improve rolling resistance by satisfying all of the aforementioned high strength, high modulus, low shrinkage, and high elongation, while maintaining the excellent inherent physical properties of the original yarn.

[0053] In other words, by reducing the gauge of the tire cord (from 2000De to 1500De, or from 3000De to 2000De), it is possible to improve rotational resistance.

[0054] Furthermore, according to the above embodiment, the physical properties of the tire, which tend to deteriorate, can be improved by lowering the fineness of the tire cord.

[0055] More specifically, the tire cord of the above embodiment can have a strength of 8.0 g / d or more, or 8.5 g / d or more, according to the ASTM D885 standard test method, and can also have a strength of 11 g / d or less, or 10 g / d or less.

[0056] Furthermore, the tire cord of the above embodiment may have a LASE@2% value of 1.1 g / d or more, or 1.15 g / d or more, or 1.20 g / d or more, as determined by the ASTM D885 standard test method for indicating the modulus. The LASE@2% value may also be 1.5 g / d or less, or 1.45 g / d or less, or 1.4 g / d or less.

[0057] The tire cord may have a LASE@5% value of 2.5 g / d or less, or 2.45 g / d or less, or 2.4 g / d or less, according to the ASTM D885 standard test method. Alternatively, the LASE@5% value may be 2.0 g / d or more, or 2.05 g / d or more, or 2.1 g / d or more.

[0058] The tire cord may have a toughness of 183 g / d·mm or more, or 200 g / d·mm or more, or 210 g / d·mm or more, according to the standard test method of ASTM D885. Furthermore, the tire cord may have a toughness of 300 g / d·mm or less, or 280 g / d·mm or less, or 250 g / d·mm or less, according to the standard test method of ASTM D885.

[0059] The tire cord may have a sidewall indentation (SWI) value of 3.6% or less, or 3.55% or less, or 3.4% or less, and may have a sidewall indentation (SWI) value of 3.0% or more, or 3.1% or more, or 3.2% or more, or 3.3% or more.

[0060] Furthermore, the tire cord may have a toughness of 300 g / d·mm or less, or 280 g / d·mm or less, or 250 g / d·mm or less, according to the standard test method of ASTM D885.

[0061] Therefore, a tire cord according to one embodiment can have a strength of 8.0-11 g / d, a toughness of 1.1-1.5 g / d for LASE@2%, a toughness of 183-300 g / d·mm, and a sidewall indentation (SWI) value of 3.0-3.6%, according to the standard test method of ASTM D885.

[0062] In this case, the sidewall indentation in the physical properties of the tire cord may be measured by the following formula 1:

[0063] [Formula 1] SWI(%)=[(D)-(C)]+[(A)-(B)]

[0064] In formula 1 above, (A) is the dry heat shrinkage rate measured after the dry heat shrinkage rate was measured using a shrinkage tester (measured with a test specimen length of 250 mm, at 180°C for 2 minutes, under an initial tensile load (20-45 g)), and then allowed to cool for 1 minute. (B) is the dry heat shrinkage rate measured after the dry heat shrinkage rate was measured using a shrinkage tester (measured with a test specimen length of 250 mm, at 180°C for 2 minutes, under an initial tensile load (40-90 g)), and then allowed to cool for 1 minute. (C) is the value of the intermediate elongation of the (A) specimen measured by the standard ASTM D885 test method under a load of 1.5 to 3.0 kg. (D) is the value of the intermediate elongation of the (B) specimen measured by the standard ASTM D885 test method under a load of 3.0 to 6.0 kg.

[0065] Furthermore, (A) may be 1.0-3.2%, (B) may be 0.7-2.8%, (C) may be 1.3-1.7%, and (D) may be 4.2-4.6%.

[0066] In this specification, the dry heat shrinkage rates before cooling in (A) and (B) above may be measured using a shrinkage tester as the ratio of the length (L0) measured under an initial tension selected from the above range after leaving a 250 mm long tire cord specimen at 25°C and 65% RH for 24 hours, to the length (L1) after treating it at 180°C for 2 minutes under the same initial tension. In other words, the dry heat shrinkage rate (L2) can be defined as the length change rate of the specimen {=[(L0-L1) / L0]×100}. L0 and L1 can each be measured five times.

[0067] Furthermore, the dry heat shrinkage rate after cooling can be expressed as the rate of change in length of L2 and L3 ({=[(L2-L3) / L2]×100}) by measuring the length of the test piece (L3) after cooling for 1 minute following the measurement of L2. The cooling may be performed at room temperature.

[0068] Furthermore, the initial tension loads in (A) and (B) and the loads in (C) and (D) can be measured by appropriately setting the load range within the range according to the fineness of the tire cord, regardless of the fineness classification.

[0069] In other words, the SWI is not limited to a range of tire cord denier, but can appropriately adjust its load range according to various denier range conditions and measure the average value. Specifically, it can be defined and set as a load corresponding to each tire cord denier.

[0070] In one embodiment of the invention, the fineness of the tire cord may include raw cord having a total fineness of 1000 to 6000 denier. Furthermore, the range of the initial load can be set according to the total fineness of the raw cord included in the tire cord, which is determined by the manufacturing conditions of the raw yarn.

[0071] Accordingly, according to the embodiments of this specification, when the total fineness of the tire cord is set in the range of 3000 denier and 4000 denier, the initial tension load of (A) may be 35 to 45 g, the initial tension load of (B) may be 70 to 90 g, the load of (C) may be 2.3 to 3.0 kg, and the load of (D) may be 4.6 to 6.0 kg.

[0072] More specifically, when the fineness of the tire cord is set to 2000 denier, 2600 denier, 3000 denier, and 4000 denier, the initial tensile load used to measure the dry heat shrinkage rate in (A) above may be 20g, 30g, 35g, and 45g, respectively.

[0073] The initial tensile load used to measure the dry heat shrinkage rate in (B) under each of the aforementioned denier conditions may be 40g, 60g, 70g, and 90g, respectively.

[0074] Furthermore, the load of (C) under each of the aforementioned denier conditions may be 1.5 kg, 2.0 kg, 2.3 kg, or 3.0 kg.

[0075] Furthermore, the load of (D) under each of the aforementioned denier conditions may be 3.0 kg, 4.0 kg, 4.6 kg, or 6.0 kg.

[0076] Furthermore, the dry heat shrinkage rate may be the average value of values ​​measured at least three times, four times or five times or more, within the specified load range.

[0077] The aforementioned tire cord may have a strip strength of 0.94 kg / dm / denier or higher.

[0078] Specifically, the reinforcing ability of a tire over a certain area is important in terms of tire performance. Furthermore, for tire weight reduction, strip strength corresponding to the fiber density is crucial, and high performance in this area indicates superior tire reinforcing ability.

[0079] Therefore, high-strength cords must be used to ensure superior tire reinforcement, and the distance between cords must be optimized to increase density.

[0080] Therefore, the tire cord of the present invention exhibits a high strip strength value of 0.94 kg / dm / denier or higher, thereby improving tire performance.

[0081] More specifically, the strip strength can be defined as the strength over a certain area, and in this invention, it can mean the performance in the tire's internal fabric.

[0082] The strip strength can be obtained by measuring the strength per 1 decimeter (10 cm) (kg / dm). Alternatively, the strip strength can be expressed as the strength obtained by converting the strength to a value per denier (kg / dm / denier).

[0083] Furthermore, in the present invention, the fabric may be a twisted yarn (i.e., a dip cord) obtained by immersing a polyester yarn (i.e., a raw cord) in an adhesive solution and heat-treating it.

[0084] According to one preferred embodiment of the invention, the strip strength of the tire cord may be 0.94 kg / dm / denier or greater, calculated taking into account the strength and density of the denier of the fabric contained within the cord.

[0085] The aforementioned tire cord may have a tensile strength of 7.5 to 9.5 g / d and an elongation of 14 to 22% according to the standard test method of ASTM D885.

[0086] Furthermore, the tire cord can have a strong utilization rate of 88% or more according to the following formula 2.

[0087] [Formula 2] Strength utilization rate (%) = [Tensile strength of tire cord (g / d) / Tensile strength of polyester yarn (g / d)] × 100

[0088] Specifically, the tire cord can exhibit a strength utilization rate of 88.5% or more, or 88.6% or more, or 88.7% or more, or 88.8% or more, or 88.9% or more; and 91.0% or less, or 90.8% or less, or 90.6% or less, or 90.4% or less. Therefore, the tire cord according to this specification can have excellent strength.

[0089] Preferably, the tire cord can exhibit a high utilization rate of 88.5% to 91.0%, or 88.5% to 90.8%, or 88.6% to 90.8%, or 88.6% to 90.6%, or 88.7% to 90.6%, or 88.7% to 90.4%, or 88.8% to 90.4%, or 88.9% to 90.4%.

[0090] More specifically, the strength utilization rate of the tire cord may be at a level of 90% or more in relation to the strength of the raw yarn.

[0091] Such tire cords may include a high-strength polyester yarn manufactured from a polyester multifilament comprising 200 to 2,000 polyester monofilaments having a fineness of 2.5 to 3.5 denier, and an adhesive layer impregnated into the high-strength polyester yarn.

[0092] Specifically, the polyester yarn containing the polyester multifilament may have a single yarn fineness of 2.5 to 3.5 denier and a total fineness of 500 to 3000 denier, or 1000 to 2000 denier.

[0093] The adhesive layer may be present in an amount of 0.5 to 10 parts by weight, 1 to 8 parts by weight, or 1.5 to 6 parts by weight relative to 100 parts by weight of the high-strength polyester yarn.

[0094] Furthermore, the polyester yarn can be produced from a molten polyester resin containing 90 mol% or more of polyethylene terephthalate and having an intrinsic viscosity of 1.0 dl / g or more.

[0095] According to one embodiment of the invention, the polyester filament can be produced as polyethylene terephthalate drawn yarn by a spinning process using chips made of 90 mol% or more polyethylene terephthalate (hereinafter referred to as PET).

[0096] Specifically, the PET drawn yarn is produced by melt-spinning the PET to produce an undrawn yarn, and then drawing this undrawn yarn. Furthermore, such PET drawn yarn can be twisted together and immersed in an adhesive to produce a dip cord-type tire cord.

[0097] Furthermore, the PET drawn yarn according to one embodiment of the above invention contains 90 mol% or more of PET in order to exhibit physical properties suitable for tire cords. If the PET drawn yarn contains less than 90 mol% of PET, it is difficult for the PET drawn yarn and the tire cord produced therefrom to exhibit desirable physical properties. Therefore, in the present invention, the term PET means 90 mol% or more of PET unless otherwise specified.

[0098] Such polyester filaments can have a tensile strength of 7.5 to 11.0 g / d and an elongation of 10 to 20%.

[0099] The tire cord comprises a raw cord made by twisting two or more polyester drawn yarns together in one direction, and an adhesive attached to the raw cord.

[0100] The polyester drawn yarn may have a single yarn fineness of 2.5 to 3.5 denier and a total fineness of 500 to 3000 denier.

[0101] The tire cord may include a raw cord having a total fineness of 1000 to 6000 denier.

[0102] Preferably, the tire cord may include the low cord having a total fineness of 1000 denier to 6000 denier, or 1000 denier to 5000 denier.

[0103] Furthermore, the tire cord may be a 2-ply yarn containing the polyester drawn yarn. As a non-limiting example, the low cord may have a total fineness of 1000 to 6000 denier by 2-twisting the polyester drawn yarn having a single fineness of 2.5 to 3.5 denier and a total fineness of 500 to 3000 denier.

[0104] Specifically, in one example, a low cord can be manufactured by feeding the polyester drawn yarn into a cable cord twisting machine and twisting it with a twist count of 200 TPM to 500 TPM. After immersing the low cord in an adhesive coating solution, it can be dried and heat-treated to produce a tire cord (dip cord).

[0105] On the other hand, according to another embodiment of the invention, a method for producing tire cord is provided, comprising the steps of: producing polyester filament by spinning molten polyester resin containing 90 mol% or more of polyethylene terephthalate and having an intrinsic viscosity of 1.0 dl / g or more using a spinning pack including a die with a nozzle; producing a plied yarn using the polyester filament; and heat-treating the plied yarn by immersing it in an adhesive solution, wherein the step of producing the polyester filament includes the step of extruding the molten polyester resin through a die including a nozzle having a shear rate of 220 to 260 1 / sec and a polymer extrusion rate of 2.0 m / min or less under a spinning pack pressure condition of 1800 to 2500 psi to form a polyester multifilament including a polyester monofilament having a fineness of 2.5 to 3.5 denier.

[0106] Specifically, to produce tire cords that satisfy all of the above-mentioned high strength, high modulus, low shrinkage, and high elongation, it is preferable to apply a low DPF (Denier per filament) to the polyester filament. However, as described herein, high spinning tension and spinning draft can be imparted not only by applying a low DPF to the polyester, but also by adjusting the polymer extrusion rate at the nozzle.

[0107] Furthermore, under the above-described yarn manufacturing conditions, the toughness of the yarn and tire cord may decrease due to the low nozzle discharge pressure. Therefore, this specification features a high discharge pressure in the spinning pack to maintain a high shear rate at the nozzle.

[0108] Therefore, this specification features that by adjusting the spinning conditions and simultaneously maintaining the pressure of the spinning pack within a certain range, the physical properties of the polyester yarn are maintained to be excellent in tire cord even after the yarn has undergone post-processing steps of twisting and heat treatment, thereby satisfying all the physical properties of tire cord required for weight reduction. Here, the tire cord can be manufactured by a normal method, except for adjusting the spinning method and the pressure conditions of the spinning pack during the production of the polyester yarn.

[0109] More specifically, as described above, high-strength polyester yarn for tire cords can be produced by spinning molten polyester resin having an intrinsic viscosity of 1.0 dl / g or more using a spinning pack that includes a die with a nozzle.

[0110] In one example, the molten polyester resin may contain 90 mol% or more of polyethylene terephthalate and may include molten polyethylene terephthalate resin having an intrinsic viscosity of 1.0 dl / g or more, or 1.1 dl / g to 1.9 dl / g. Preferably, the molten polyethylene terephthalate resin may have an intrinsic viscosity of 1.0 dl / g or more, or 1.1 dl / g or more. Furthermore, the molten polyethylene terephthalate resin may have an intrinsic viscosity of 1.7 dl / g or less, or 1.6 dl / g or less, or 1.5 dl / g or less, or 1.4 dl / g or less.

[0111] Furthermore, the molten polyethylene terephthalate resin may contain 90 mol% or more, 92 mol% or more, 95 mol% or more, 99 mol% or more, or 100 mol% of polyethylene terephthalate as its main component.

[0112] Furthermore, various known additives can be added during the preparation of the PET polymer constituting the undrawn yarn. Therefore, the type of additive is not limited.

[0113] Furthermore, the spinning may be carried out at 270-300°C, 275-300°C, or 275-290°C using a spinneret with 300-550 spinneret holes.

[0114] Furthermore, the step of manufacturing the polyester filament may include, after the step of manufacturing the plurality of filaments, a step of heating and cooling the discharged plurality of filaments, gathering the cooled filaments and then stretching them to manufacture a polyester stretched yarn, and then winding it up.

[0115] Preferably, the method for producing the polyester filament may include the steps of: producing a plurality of filaments by extruding molten polyester resin having an intrinsic viscosity of 1.0 dl / g or more through a die containing a nozzle having a shear rate of 220 to 260 1 / sec and a polymer extrusion rate of 2.0 m / min or less, under spinning pack pressure conditions of 1800 to 2500 psi; heating the extruded plurality of filaments with a heating unit; cooling the heated plurality of filaments with a cooling unit; bundling the plurality of filaments to form a polyester multifilament; stretching the polyester multifilament; and winding the stretched multifilament.

[0116] For example, the high-strength polyester filament can be manufactured by a manufacturing method that includes the steps of: melting a polyethylene terephthalate resin (e.g., PET chip) containing 90 mol% or more of polyethylene terephthalate and having an intrinsic viscosity of 1.0 dl / g or more, or 1.1 dl / g or more, or 1.5 dl / g or more, and extruding it into a plurality of filaments through a nozzle under the above-mentioned range conditions by adjusting the spinning conditions and the pressure of the spinning pack; heating the extruded plurality of filaments with a heating unit located around the nozzle; cooling the heated plurality of filaments with a cooling unit; bundling the plurality of filaments to form a polyester multifilament; stretching the polyester multifilament; and winding the stretched multifilament.

[0117] At this time, the spinning pack can adjust the discharge pressure range to 1800-2500 psi (approximately 126.55-175.8 kgf / cm2). However, if the discharge pressure of the spinning pack is 1800 psi or less, the polymer discharge rate at the nozzle will decrease, and the required performance may not be achieved. If it is 2500 psi or more, excessive pressure may cause equipment problems such as pack leaks.

[0118] Furthermore, when dispensing molten polyester resin through the die including the nozzle, the shear rate at the nozzle may be 220 to 260 1 / sec. If the shear rate is 220 1 / sec or less, the orientation of the polymer at the nozzle may decrease, reducing the toughness of the yarn. If the shear rate is 260 1 / sec or more, the decrease in spinning draft may affect the morphological stability of the yarn.

[0119] Furthermore, along with adjusting the shear rate at the nozzle, the polymer discharge speed at the nozzle can be adjusted to be 2.0 m / min or less. More specifically, the polymer discharge speed at the nozzle may be 0.1 to 2.0 m / min, or 0.5 to 2.0 m / min, or 1 to 2.0 m / min, or 1 to 1.9 m / min, or 1.3 to 1.9 m / min, or 1.5 to 1.9 m / min. If the polymer discharge speed is 2 m / min or higher, the polymer discharge speed at the nozzle may decrease, and the required performance may not be achieved.

[0120] This process makes it possible to form a polyester multifilament containing polyester monofilaments having a fineness of 2.5 to 3.5 denier. In other words, according to this specification, it means forming a polyester multifilament containing polyester monofilaments with a DPF of 2.5 to 3.5 De / ea (denier / strand).

[0121] Furthermore, the polyester multifilament may include 200 to 2,000 or 400 to 1,200 polyester monofilaments having a fineness of 2.5 to 3.5 denier. More specifically, the fineness of the polyester monofilament may be 2.6 to 3.5 denier or 2.7 to 3.4 denier.

[0122] The polyester yarn containing the aforementioned polyester multifilament may have a total fineness of 500 to 3000 denier, or 1000 to 2000 denier.

[0123] On the other hand, in the method for producing polyester filament, heating and cooling a plurality of extruded filaments, gathering the cooled filaments, and then stretching them to produce a polyester stretched yarn, and then winding it up, may be done in a conventional manner.

[0124] Furthermore, as shown in Figure 1, the polyester yarn manufacturing apparatus 1 according to an embodiment of the present invention includes an extruder 10, a spinning pack 20, a cooling unit 30, a bundling unit 40, a stretching unit 50, and a winder 60.

[0125] A hopper 12 is formed on the upper surface of the extruder 10, allowing for the supply of polymer chips. Inside the extruder 10 are a heating device and a transfer device, which melt the polymer chips supplied through the hopper 12 and transfer the molten resin to the spinning pack 20. The resin (polymer) is not limited to this, but polyester resin can be used. For the sake of explanation, a yarn manufacturing apparatus 1 capable of producing polyester yarn using polyester resin will be described below as one example. However, the yarn manufacturing apparatus 1 according to the embodiment of the present invention is not only used for the production of polyester yarn, but can also be used for the production of other yarns known in the industry.

[0126] Furthermore, the spinning pack 20 extrudes molten polyester resin transferred from the extruder 10 to form a plurality of filaments 2. The spinning pack 20 may include a spinning block, a pack body, a die, and a heating unit, and its form is not limited.

[0127] More specifically, the polyester filament manufacturing apparatus may include a spinning pack including a die that includes a nozzle section having a plurality of discharge holes for dispensing molten resin; a heating section located around the nozzle section that heats a plurality of filaments dispensed through the plurality of discharge holes; a cooling section that cools the plurality of filaments heated by the heating section; a bundling section that gathers the plurality of filaments cooled by the cooling section to form a multifilament; and a stretching section that stretches the multifilament. The plurality of discharge holes may be arranged in a circle in at least two or more rows. The distance between adjacent discharge holes on any one row, the distance between adjacent discharge holes on any other row, and the distance between discharge holes located close to each other on any one row and any other row adjacent to that row may be the same.

[0128] In this specification, the cooling unit 30 can use a general method for cooling filaments, and the method is not limited thereto.

[0129] For example, as shown in Figure 1, in this specification, a refrigerant may flow into the cooling chamber 32 through a refrigerant inlet 34 and out of the cooling chamber 32 through a refrigerant outlet 36.

[0130] Furthermore, the high-strength polyester yarn for tire cord may be manufactured by a manufacturing method that includes three or more godet rollers 52, 54, 56, and 58, and includes a step of stretching the unstretched multifilament 4 in at least two stages. In this case, the at least three godet rollers include first, second, and third godet rollers arranged sequentially with respect to the direction of movement of the multifilament, the rotation speed of the first godet roller may be 2000 to 4000 m / min, and the rotation speed of the third godet roller may be 5000 to 7000 m / min.

[0131] The step of stretching the polyester multifilament may include stretching the polyester multifilament with a total stretch ratio of 1.0 to 3.0 times, and polyester stretched yarn can be produced by the above method.

[0132] Preferably, the total stretch ratio may be 1.5 to 3.0 times, or 1.5 to 2.5 times. In other words, in order to increase the degree of orientation by stretching and to exhibit an appropriate level of strength, it is preferable that the total stretch ratio of the polyester stretched yarn be 1.0 times or more. However, in order to prevent yarn breakage due to excessive stretching, it is preferable that the total stretch ratio of the polyester stretched yarn be 3.0 times or less.

[0133] Furthermore, the multi-stage stretching speed ratio can be defined as the ratio of the difference between the rotational speed of the first godet roller and the rotational speed of the second godet roller to the difference between the rotational speed of the second godet roller and the rotational speed of the third godet roller, where the multi-stage stretching speed ratio may be 30:70 to 60:40.

[0134] Here, the spinning draft may be 1500 to 2000.

[0135] In the winder 60, the multifilament stretched in the stretching section 50 is wound up to produce polyester yarn 6.

[0136] The high-strength polyester yarn produced by the above method can have a tensile strength of 7.5 to 11.0 g / d and an elongation of 10 to 20%.

[0137] On the other hand, the step of producing a twisted yarn using the polyester filament may be a step of producing a raw cord by under-twisting and over-twisting the polyester drawn yarn under certain twisting conditions.

[0138] Specifically, in one example, the low cord can be manufactured by feeding the polyester drawn yarn into a cable cord twisting machine and performing under-twisting and over-twisting with a twist count of 200 TPM to 500 TPM.

[0139] Furthermore, the step of immersing the twisted yarn in an adhesive solution and heat-treating it may be a step of immersing the rocord in an adhesive solution, followed by drying and heat-treating it to produce a tire cord (dip cord).

[0140] Specifically, the plied yarn can be impregnated in a commonly known adhesive solution to form the adhesive layer. The adhesive solution can be one that is commonly used for the manufacture of tire cords, such as a resorcinol formaldehyde-latex (RFL) adhesive solution.

[0141] After impregnation with the adhesive solution, a heat treatment step may be carried out. The heat treatment step can be performed at a temperature of 220 to 260°C for 90 to 360 seconds, preferably at a temperature of 230 to 250°C for 90 to 240 seconds, and more preferably at a temperature of 240 to 245°C for 90 to 120 seconds.

[0142] By immersing the aforementioned high-strength polyester filament in an adhesive solution and heat-treating it under these conditions, the morphological stability of the tire cord can be further improved, and changes in the physical properties of the tire during vulcanization can be further reduced.

[0143] The present invention will be described in more detail below through examples and comparative examples. However, the following examples and comparative examples are for the purpose of understanding the present invention and do not limit the scope of the present invention.

[0144] [Examples and Comparative Examples: Production of Polyester Yarn] <Examples 1-3> Using the yarn manufacturing apparatus 1 shown in Figure 1, polyester yarn 6 made of polyethylene terephthalate (PET) was produced, with a monofilament single filament fineness of 2.7 to 3.4 denier (d) and a total fineness of 1500 denier (d).

[0145] Specifically, a molten polyester resin was produced by melting PET chips containing 90 mol% PET and having an intrinsic viscosity (IV) of 1.0 to 1.4 dl / g using a single-screw extruder. Subsequently, as shown in Table 1 below, the molten polyester resin was spun through a die 170 (L / D = 4.0 / 1.0, number of extrusion holes: 500) at a spinning speed of 3200 m / min to produce multiple filaments 2.

[0146] In this process, the conditions for manufacturing multiple filaments, including the nozzle passage speed, were adjusted as shown in Table 2 (DPF, Polymer discharge speed at nozzle, Shear rate at nozzle, Spinning pack pressure).

[0147] Subsequently, the multiple filaments 2 were heated by the heating section, cooled by the cooling section 30, and the cooled filaments 2 were bundled together to produce an undrawn multifilament 4 (undrawn yarn).

[0148] The molten material for spinning was extruded through a spinneret to obtain a polyester drawn yarn having a total fineness of 1000 denier (single filament fineness of approximately 4 denier). The process of obtaining the polyester drawn yarn was carried out under conditions of a spinning temperature of 290°C, a spinning speed of 3200 m / min, a total draw ratio of 1.5 times, and a relaxation rate of 1.5% (heat treatment at 180°C after drawing).

[0149] The stretched multifilament was wound up to produce polyester yarn (stretched yarn).

[0150] <Comparative Examples 1-2, Reference Example 1> Polyester filament was produced in the same manner as in Example 1, except that the diameter of the spindle, the number of holes, the spinning conditions, and the pressure of the spinning pack were changed as shown in Tables 1 and 2.

[0151] [Table 1]

[0152] [Table 2]

[0153] [Examples 4-6, Comparative Examples 3-4, and Reference Example 1: Manufacturing of Tire Cord] Using the polyester yarns produced in Examples 1-3, Comparative Examples 1-2, and Reference Example 1, tire cords for Examples 4-6, Comparative Examples 3-4, and Reference Example 2 were manufactured under the same conditions.

[0154] Specifically, polyester yarn was fed into a cable cord twisting machine to prepare two under-twisted yarns (Z-direction) with a twist count of 460 TPM. These two under-twisted yarns were then twisted together (S-direction) with a twist count of 460 TPM to produce a plied yarn (raw-cord). The plied yarn thus produced was immersed in an adhesive coating solution containing resorcinol-formaldehyde-latex (RFL), dried at 150°C for 100 seconds, and then heat-treated at 240°C for 100 seconds to produce a tire cord (dip cord). The tension applied to the raw cord during the immersion, drying, and heat-treatment processes was 0.5 kg / cord.

[0155] Furthermore, the total denier of the aforementioned low cord ranged from 1000 to 6000.

[0156] However, the tire cord of Comparative Example 6, which used Comparative Example 3, could not be manufactured, and its physical properties could not be measured.

[0157] [Experimental Example 1: Evaluation of Physical Properties of Polyester Yarn and Tire Cord] The tensile strength and elongation of the polyester yarn produced in the above-mentioned examples, comparative examples, and reference examples, as well as the tire cords using the same, were measured.

[0158] Tensile strength, elongation at break, and elongation in intermediate length (Growth rate) According to the ASTM D885 standard test method, the tensile strength (g / d), elongation, and strength utilization rate (Equation 2) of polyester drawn yarn and tire cord were measured using an Instron universal testing machine and are shown in Tables 3 and 4. The length of the test specimen was 250 mm, the tensile speed was 300 mm / min, and the initial load was set to 0.05 g / d.

[0159] In the stress-strain curve obtained in the aforementioned test, the elongation at a load of 4.5 g / d was expressed as "intermediate elongation (elongation rate)".

[0160] [Formula 2] Strength utilization rate (%) = [Tensile strength of tire cord (g / d) / Tensile strength of polyester yarn (g / d)] × 100

[0161] [Table 3]

[0162] [Table 4]

[0163] Referring to Tables 3 and 4 above, the polyester yarns of Examples 1 to 4 and the tire cords of Examples 4 to 6 using the same all exhibited excellent physical properties at or above the level of the comparative examples and reference examples.

[0164] [Experimental Example 2: Evaluation of the physical properties of tire cord] Strength, modulus, toughness, and SWI properties were measured for the tire cords manufactured in the above-mentioned examples, comparative examples, and reference examples. The results are shown in Table 5.

[0165] (1) Strength (Tenacity) and toughness The strength, tensile strength (g / d), elongation (%), and toughness of the tire cord were measured using an Instron universal testing machine according to the ASTM D885 standard test procedure. The test specimen length was 250 mm (cord length: 600 mm), the tensile speed was 300 mm / min, and the initial load was set to 0.05 g / d.

[0166] (2) Modulus (Lase@2%, Lase@5%) Stress-strain curves were obtained for each tire cord using the ASTM D885 standard test method. Using these stress-strain curves, the loads at length deformation rates of 2% and 5% were determined, and the Lase@2% and LASE@5% values ​​during elongation were measured.

[0167] The samples were left in an atmosphere of 20°C and 65% RH for 24 hours before being measured.

[0168] (3) Side wall indentation (SWI) The SWI was measured using equipment from Testrite, a British company, according to Equation 1 below.

[0169] [Formula 1] SWI(%)=[(D)-(C)]+[(A)-(B)]

[0170] In formula 1 above, (A) is the dry heat shrinkage rate measured after the dry heat shrinkage rate was measured using a shrinkage tester (measured with a test specimen length of 250 mm, at 180°C for 2 minutes, under an initial tensile load (20-45 g)), and then allowed to cool for 1 minute. (B) is the dry heat shrinkage rate measured after the dry heat shrinkage rate was measured using a shrinkage tester (measured with a test specimen length of 250 mm, at 180°C for 2 minutes, under an initial tensile load (40-90 g)), and then allowed to cool for 1 minute. (C) is the value of the intermediate elongation of the (A) specimen measured by the standard ASTM D885 test method under a load of 1.5 to 3.0 kg. (D) is the value of the intermediate elongation of the (B) specimen measured by the standard ASTM D885 test method under a load of 3.0 to 6.0 kg.

[0171] Furthermore, (A) is 1.0-3.2%, (B) is 0.7-2.8%, (C) is 1.3-1.7%, and (D) is 4.2-4.6%.

[0172] Specifically, a 2500 mm test specimen having a total fineness of 1000 to 6000 denier was left at 25°C and 65% RH for 24 hours, and then its length (L0) was measured under an initial tensile load of 0.01 g / d. Thereafter, using the shrinkage rate measuring device, the test specimen was treated at 180°C for 2 minutes under an initial tensile load of 0.01 g, and then its length (L1) was measured. Both L0 and L1 were measured three times each. The rate of change in the length of the test specimen {=[(L0-L1) / L0]×100} was defined as the dry heat shrinkage rate (L2) before cooling.

[0173] Furthermore, using the shrinkage rate measuring device, after measuring the dry heat shrinkage rate of the test piece, the test piece was removed from the device under the same load, left at room temperature (25°C) for 1 minute, and then the dry heat shrinkage rate was measured again when the cord had stabilized. In other words, the dry heat shrinkage rate after cooling is expressed as the rate of change in length of L2 and L3 ({=[(L2-L3) / L2]×100}) after measuring L2 and then measuring the length (L3) of the test piece after cooling for 1 minute.

[0174] [Table 5]

[0175] Referring to Table 5, the tire cords of Examples 4 to 6 have a strength of 8.0 g / d or more, a LASE@2% strength of 1.1 g / d or more, a LASE@5% strength of 2.5 g / d or less, and a toughness of 183 g / d·mm or more, satisfying all SWI values ​​of 3.6% or less. In other words, Examples 4 to 6 showed superior results compared to Comparative Examples 3 to 4 and Reference Example 2, with the tire cords maintaining excellent strength even after the post-processing step of the raw yarn, while exhibiting high modulus, low shrinkage, and high stretch effect.

[0176] In contrast, while Comparative Example 3 showed a certain level of strength, its modulus and toughness were lower than that of the Examples, and its SWI was 3.7%, indicating generally poor results.

[0177] Furthermore, it was impossible to manufacture tire cords using Comparative Example 4.

[0178] Furthermore, in Reference Example 2, the spinning draft was lower than the scope of the present application, the DPF was high at 3.9, and the toughness value was low at 175.0 g / d·mm. Also, in Reference Example 2, the LASE@2% value was 1.0%, which was lower than the example, limiting the improvement of the modulus.

[0179] (4) Strip strength For the tire cord of Example 6 described above, the strip strength was measured according to Table 6 below, based on a standard of 1500 De (denier) (warp density 118 ea / decimeter (threads / decimeter), load 26.1 kg).

[0180] Specifically, the tire cord, based on 1500 denier, can have a warp density of 118 ea / decimeter (threads / decimeter) when it has a strength of 8.0 g / d or more. Therefore, the strip strength can be calculated using the density value of the tire cord according to a certain load.

[0181] At this time, the strip strength was also measured when the tire cord strength (i.e., strength) was 8.0 g / d.

[0182] [Table 6]

[0183] As shown in Table 6 above, the strip strength of the tire cords in Example 6 (strength of 8.7 g / d) and 8.0 g / d satisfies the requirement of 0.94 kg / dm / denier or higher, and the strength of the woven fabric within the tire cord is excellent, making it possible to provide a high-strength tire.

[0184] Therefore, when manufacturing the yarn for providing tire cord, applying a high multi-filament spinning method with specified spinning conditions, while adjusting the spinning pack pressure, is essential to achieving excellent physical properties and, in particular, maintaining high toughness.

[0185] Although preferred embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above and includes all modifications that can be easily modified by a person with ordinary skill in the art to which the invention pertains and are considered equivalent. [Explanation of Symbols]

[0186] 1: Yarn manufacturing equipment 2: Multiple filaments 4: Unstretched multifilament 6: Polyester yarn 10: Extruder 12: Hoppa 20: Spinning pack 30: Cooling section 32: Cooling Chamber 34: Refrigerant inlet 36: Refrigerant outlet 40:Focusing part 50: Stretching part 52, 54, 56, 58: Godetlora 60: Winder

Claims

1. Contains polyester yarn containing 90 mol% or more of polyethylene terephthalate, It has a strongness of 8.0 g / d or higher, a LASE@2% strength of 1.1 g / d or higher, a LASE@5% strength of 2.5 g / d or lower, and a toughness of 183 g / d·mm or higher according to the ASTM D885 standard test method, and satisfies a side wall indentation (SWI) value of 3.6% or lower. Tire cord.

2. The sidewall indentation is measured by the following formula 1, according to the tire code of claim 1: [Formula 1] SWI (%) = [(D) - (C)] + [(A) - (B)] In the above formula 1, (A) is the dry heat shrinkage rate measured after the dry heat shrinkage rate was measured using a shrinkage tester (measured with a test specimen length of 250 mm, at 180°C for 2 minutes, under an initial tension load (20-45 g)), and then allowed to cool for 1 minute. (B) is the dry heat shrinkage rate measured after the dry heat shrinkage rate was measured using a shrinkage tester (measured with a test specimen length of 250 mm, at 180°C for 2 minutes, under an initial tensile load (40-90 g)), and then allowed to cool for 1 minute. (C) is the value of the intermediate elongation of the (A) specimen measured by the ASTM D885 standard test method under a load of 1.5 to 3.0 kg. (D) is the value of the intermediate elongation of the (B) specimen measured by the ASTM D885 standard test method under a load of 3.0 to 6.0 kg.

3. The above (A) is 1.0 to 3.2%, The aforementioned (B) is 0.7 to 2.8%, The aforementioned (C) is 1.3 to 1.7%, The tire code according to claim 2, wherein (D) is 4.2 to 4.6%.

4. The aforementioned tire cord has a strip strength of 0.94 kg / dm / denier or more. The tire cord according to claim 1.

5. The tire cord according to claim 1, wherein the tire cord has a strength utilization rate of 88% or more according to the following formula 2. [Formula 2] Strength utilization rate (%) = [Tensile strength of tire cord (g / d) / Tensile strength of polyester yarn (g / d)] × 100

6. The tire cord is a high-strength polyester yarn manufactured from a polyester multifilament containing 200 to 2,000 polyester monofilaments having a fineness of 2.5 to 3.5 denier; and The tire cord according to claim 1, comprising an adhesive layer impregnated into the high-strength polyester filament.

7. The tire cord according to claim 6, wherein the polyester filament is manufactured from a molten polyester resin containing 90 mol% or more of polyethylene terephthalate and having an intrinsic viscosity of 1.0 dl / g or more.

8. The tire cord according to claim 6, wherein the polyester yarn has a tensile strength of 7.5 to 11.0 g / d and an elongation of 10 to 20%.

9. The tire cord according to claim 1, wherein the tire cord includes a raw cord having a total fineness of 1,000 to 6,000 denier.

10. A step of producing polyester yarn by spinning a molten polyester resin containing 90 mol% or more polyethylene terephthalate and having an intrinsic viscosity of 1.0 dl / g or more using a spinning pack including a die with a nozzle, A step of manufacturing a twisted yarn using the aforementioned polyester filament, The process includes the step of immersing the aforementioned twisted yarn in an adhesive solution and heat-treating it, The step of producing the aforementioned polyester yarn is: The process includes the step of extruding the molten polyester resin through a die containing a nozzle having a shear rate of 220 to 260 1 / sec and a polymer extrusion rate of 2.0 m / min or less, under spinning pack pressure conditions of 1800 to 2500 psi, to form a polyester multifilament including a polyester monofilament having a fineness of 2.5 to 3.5 denier. A method for manufacturing a tire cord according to claim 1.

11. The method for manufacturing a tire cord according to claim 10, wherein the polyester multifilament comprises 200 to 2,000 polyester monofilaments having a fineness of 2.5 to 3.5 denier.

12. The step of producing the aforementioned polyester yarn is: A step of manufacturing multiple filaments by extruding molten polyester resin having an intrinsic viscosity of 1.0 dl / g or more through a die containing a nozzle having a shear rate of 220 to 260 1 / sec and a polymer extrusion rate of 2.0 m / min or less, under spinning pack pressure conditions of 1800 to 2500 psi, The steps include heating the multiple filaments that have been extruded by a heating unit, The steps include: cooling the heated plurality of filaments with a cooling unit; The steps include: gathering the aforementioned multiple filaments together to form a polyester multifilament; The steps include stretching the polyester multifilament, The steps include winding the stretched multifilament, A method for manufacturing a tire cord according to claim 10, including the method described in claim 10.

13. The step of stretching the polyester multifilament includes a step of stretching the polyester multifilament with a total stretch ratio of 1.0 to 3.0 times. A method for manufacturing a tire cord according to claim 10.

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