Eco-friendly tire cord and tire using same

Abstract

The present invention relates to an eco-friendly tire cord and a tire using the same, in which environmental burden is reduced by using regenerated polyethylene terephthalate fibers, and compared to tire cords produced using native polyethylene terephthalate fibers, the eco-friendly tire cord has physical properties equal to or higher than the same level, and in particular, the tire cord has excellent mechanical properties. Compared with a tire cord produced by using native polyethylene terephthalate, the excellent degree of heat resistance reaches the same level or more.

Description

Technical Field

[0001] The present invention relates to an environmentally friendly tire cord and a tire using the same, and more particularly to an environmentally friendly tire cord and a tire using the same, which reduce environmental load by using recycled polyethylene terephthalate fibers, and have physical properties that are at or above the same level as tire cords produced using virgin polyethylene terephthalate fibers. Background Art

[0002] Generally, tire reinforcement materials represented by polyethylene terephthalate (hereinafter referred to as "PET") have excellent mechanical strength, elastic modulus, dimensional stability, heat resistance and other important properties that rubber reinforcement materials should have, so they are widely used as rubber synthetic materials, for example, as reinforcement materials for tires, belts or hoses.

[0003] With the abuse of plastic materials, environmental pollution has intensified, and the international community's supervision has been continuously strengthened. Vehicles and related products are also required to meet environmentally friendly product standards, and this demand is gradually increasing.

[0004] In order to reduce environmental load or reuse resources, many attempts are being made, for example, regenerating polyester fibers from waste plastic bottles such as mineral water bottles and reusing them in clothing or industrial fields.

[0005] Compared with ordinary virgin PET tire cords, tire cords made of recycled PET have higher inherent viscosity and lower purity, which results in lower physical properties of tire cords and worse appearance than existing cords, especially poor heat resistance. As a result, the tire industry has limitations in using recycled PET and it has not been widely used. In addition, PET recycled resins recycled from waste plastic bottles have the problem of poor molding processability. Tire cords using recycled PET recycled resins are experiencing a problem of reduced commercial value due to poor physical properties such as impact resistance, heat resistance, dimensional stability, and poor appearance.

[0006] [Prior art literature]

[0007] [Patent Document]

[0008] Patent Document 1: JP 2004-100087 A

[0009] Patent Document 2: JP 2012-30737A Summary of the invention

[0010] Technical issues

[0011] The present invention aims to solve the problems of the prior art, and an object of the present invention is to provide a tire cord that reduces environmental load and enhances heat resistance by using recycled PET chips.

[0012] Another object of the present invention is to provide a tire cord and a tire using the same, which can achieve physical properties equal to or better than those of a product using only virgin PET even when using recycled PET chips.

[0013] Technical Solution

[0014] According to one embodiment of the present invention for achieving the above-mentioned purpose, the tire cord of the present invention is characterized in that it includes a dipped cord made by twisting and dipping recycled polyethylene terephthalate (PET) raw yarn made from recycled polyethylene terephthalate (PET), and after the tire cord is vulcanized at a temperature of 170°C for 15 minutes, the force at a normal temperature of 25°C reaches 18.5 kgf or more, and after vulcanization at a temperature of 170°C for 15 minutes, the force at a temperature of 80°C reaches 15.5 kgf or more, and after vulcanization at a temperature of 170°C for 15 minutes, the heat resistance retention rate at a temperature of 80°C calculated according to the following formula 1 reaches 85.0% or more, and the value of the fixed elongation load LASE (@5%) at an elongation of 5% measured at a high temperature of 80°C is 2.8 g / d or more.

[0015] [Formula 1]

[0016] Heat resistance retention rate (T 25 -T 80 )=(T 80 Force under conditions / T 25 force under conditions) × 100

[0017] The recycled polyethylene terephthalate (PET) has an intrinsic viscosity of 0.5 dl / g to 2.0 dl / g after solid phase polymerization and a weight distribution of 1.8 g / 100 ea to 2.5 g / 100 ea. The isophthalic acid content of the raw yarn made from the recycled polyethylene terephthalate (PET) is less than 1.5 mol percent.

[0018] The strength of the regenerated polyethylene terephthalate (PET) raw yarn is greater than 7.5 g / d, the raw yarn crystallinity is greater than 45%, and the dimensional stability ES% is less than 12.0%.

[0019] The fineness of the tire cord is in the range of 2000d to 7000d, the tire cord is a 2-layer to 4-layer recycled PET tire cord, and the twist number of the tire cord is 200TPM to 500TPM.

[0020] Another embodiment of the present invention relates to an environmentally friendly tire including a tire cord made of the recycled polyethylene terephthalate (PET).

[0021] Effects of the Invention

[0022] According to various embodiments of the present invention, the tire cord can reduce environmental load by using recycled PET chips, and can also show better heat resistance or physical properties of the same level compared with existing PET tire cords. Therefore, in the long run, the use of PET can be reduced and environmental protection and carbon reduction effects can be achieved by expanding the use of recycled PET.

[0023] Furthermore, compared with the existing common virgin PET polymerization process, since the present invention reuses the PET chips that have completed the polymerization process, there is no need to construct polymerization process equipment, which simplifies the process, thereby achieving the effect of saving costs and improving price competitiveness.

[0024] The tire using the tire cord of the present invention can achieve environmental protection by using recycled PET, and can also provide performance equal to or better than that of existing tires using PET (virgin PET) in terms of ride feel, handling stability, durability, uniformity and noise. DETAILED DESCRIPTION

[0025] Hereinafter, the present invention will be described in more detail.

[0026] In the present invention, terms such as "including" or "having" are used to indicate the existence of features, numbers, steps, operations, structural elements, components or their combinations recorded in the specification, and should not be understood as excluding the existence or additional possibilities of one or more other features, numbers, steps, operations, structural elements, components or their combinations in advance.

[0027] In this specification, the term "recycled polyethylene terephthalate (recycled PET)" can be used to include PET resin recycled for the purpose of reusing used waste PET or recycled PET chips containing the same.

[0028] In this specification, the term "virgin polyethyleneterephthalate" refers to unrecycled or recycled PET resin or PET chips containing the same.

[0029] In this specification, the term "recycled PET fiber" or "recycled PET yarn" refers to a fiber or yarn containing recycled PET.

[0030] As used herein, the term "cord" refers to a reinforcing belt constituting a reinforcing structure of a tire and is formed by bonding a plurality of strands of wire.

[0031] In this specification, "LASE (Load at Specified Elongation)" means a load at a specific elongation.

[0032] In this specification, "dimensional stability ES" is represented by the sum of the intermediate elongation E and the dry heat shrinkage S. A tire with a low dimensional stability ES value has a smaller deformation due to heat, so in the case of a tire using a cord with a low ES value, the uniformity of the tire is higher than that of a tire using a cord with a higher ES value, and the tire performance can also be improved.

[0033] According to one embodiment of the present invention, it relates to a tire cord, characterized in that it includes an impregnated cord made by twisting and impregnating recycled PET raw yarn made of recycled polyethylene terephthalate, after the tire cord is vulcanized at a temperature of 170°C for 15 minutes, the force at a normal temperature of 25°C reaches more than 18.5 kgf, after vulcanization at a temperature of 170°C for 15 minutes, the force at a temperature of 80°C reaches more than 15.5 kgf, after vulcanization at a temperature of 170°C for 15 minutes, the heat resistance retention rate at a temperature of 80°C calculated according to the following formula 1 reaches more than 85.0%, and the value of the fixed elongation load LASE (@5%) at an elongation of 5% measured at a high temperature of 80°C is more than 2.8 g / d.

[0034] [Formula 1]

[0035] Heat resistance retention rate (T 25 -T 80 )=(T 80 Force under conditions / T 25 force under conditions) × 100

[0036] After the tire cord of the present invention is vulcanized at a temperature of 170°C for 15 minutes, the force at a normal temperature of 25°C reaches 18.5kgf or more. And, the force can be 24kgf or less. After the tire cord of the present invention is vulcanized at a temperature of 170°C for 15 minutes, the force at a temperature of 80°C reaches 15.5kgf or more. Preferably, the force at a temperature of 80°C can be 22kgf or less. After vulcanization at a temperature of 170°C for 15 minutes, the heat resistance retention rate at a temperature of 80°C calculated according to the formula 1 reaches 85.0% or more. The heat resistance retention rate at a temperature of 80°C can reach 92.0% or less. The LASE (@5%) value measured at a high temperature of 80°C is 2.8g / d or more. Preferably, the LASE (@5%) value measured at a high temperature of 80°C can be 5.0g / d or less.

[0037] In the present invention, the intrinsic viscosity of the recycled polyethylene terephthalate (PET) after solid phase polymerization is 0.5 dl / g to 2.0 dl / g, preferably 0.9 dl / g to 1.5 dl / g, and has a weight distribution of 1.8 g / 100 ea to 2.5 g / 100 ea, and the isophthalic acid content of the precursor made from the recycled polyethylene terephthalate (PET) can be 1.5 mol% or less. The weight distribution is measured by measuring the total weight of 100 slices and dividing it by 100.

[0038] The polyethylene terephthalate multifilament constituting the tire cord of the present invention can be obtained by melting and spinning a resin composition containing recycled PET, and the obtained polyethylene terephthalate raw yarn is twisted, woven and impregnated to produce a dipped cord.

[0039] The recycled PET constituting the tire cord of the present invention has a weight distribution of 1.8-2.5 g / 100 ea. As the slice size decreases, the difference in the internal / external intrinsic viscosity (IV) of the slice decreases, the IV distribution becomes more uniform, and the increase in surface area makes it easier for the polymer to melt under the same heat, thereby reducing the IV drop and shortening the solid phase polymerization reaction time, thereby generating economic advantages. If the slices are of various sizes, when the polymer melts, the small slices will melt first, while the relatively large slices will not melt, and it is difficult to maintain a uniform state, which may lead to reduced heat resistance of the tire cord and poor appearance of the product.

[0040] In the present invention, if the inherent viscosity of the recycled PET chips is less than 0.5 dl / g, the inherent viscosity of the final drawn yarn will be reduced, and it will not be able to exert high-strength performance as a tire cord after heat treatment. If the inherent viscosity of the recycled PET chips is greater than 2.0 dl / g, the spinning tension and the cross-section of the spinning will be uneven due to the uneven melting of the polymer and the increase of unmelted crystalline materials, and the fiber breakage will be likely to occur during the drawing process, resulting in poor spinning workability.

[0041] The isophthalic acid content of the recycled PET used in the present invention is less than 1.5 mol%. If the isophthalic acid content is greater than 1.5 mol%, the crystallinity of the recycled PET will increase, thereby increasing the cost due to increased energy or the need for improved equipment, and the physical properties of the precursor may be reduced due to the thermal decomposition of PET. The tire cord of the present invention can also be composed of recycled PET that does not contain isophthalic acid. That is, the isophthalic acid content of the tire cord of the present invention can be 0 mol%.

[0042] In the present invention, the strength of the recycled polyethylene terephthalate (PET) precursor may be greater than 7.5 g / d, the crystallinity of the precursor may be greater than 45%, and the dimensional stability ES% may be less than 12.0%.

[0043] The crystallinity of the regenerated polyethylene terephthalate (PET) precursor is 45% or more, preferably 50% or less. The strength is 7.5 g / d or more, preferably 9.5 g / d or less. The strength of the regenerated PET precursor of the present invention is preferably 7.5 g / d or more. If it is less than 7.5 g / d, the strength is reduced, which may lead to a decrease in morphological stability. On the other hand, if the strength of the regenerated PET precursor of the present invention is greater than 9.5 g / d, the breakage of the tie-chain of the regenerated PET precursor and the orientation of the amorphous region may be less than those of the existing regenerated PET precursor.

[0044] The dimensional stability ES% of the recycled PET raw yarn of the present invention is 12% or less, and preferably 8.0% or more. In the present invention, the dimensional stability (ES index) refers to the sum of the dry heat shrinkage (@2 minutes at a temperature of 177°C and a load of 0.05g / d) and the intermediate elongation (@4.5g / d load). The lower the value, the smaller the morphological change of the tire cord and the better the heat resistance.

[0045] In the present invention, the fineness of the dipped cord ranges from 2000 to 7000 deniers, and may include 2 to 4 layers of twisted cords having a twist number per unit length of 200 to 500 TPM.

[0046] Hereinafter, the method for producing the recycled PET tire cord of the present invention will be described.

[0047] First, in the present invention, in the manufacture of recycled PET precursor for tire cord, the spinning speed (the speed of the first guide roller in the 6th section) is above 2000 m / min, preferably above 2300 m / min, and the spinning draft ratio (Spin-draft) is increased to the range of 1500 to 3000 by high-speed spinning, and the inherent tensile coefficient is adjusted to the range of 800 to 1400, and the winding degree is adjusted to the total stretch ratio of the precursor to the range of 2.0 to 2.5, thereby changing the microstructure of the final precursor, so that a tire cord with improved heat resistance and dimensional stability can be manufactured.

[0048] First, the recycled PET chips with an intrinsic viscosity of 0.5 to 2.0 dl / g are melted and extruded through a nozzle to produce spinning. The recycled polyethylene terephthalate chips as described above are melted and extruded through a nozzle to produce spinning. The recycled PET chips preferably use products with low IPA content and uniform weight distribution. If the IPA content is high, when manufacturing the precursor, the increase in crystallinity and crystal size will be suppressed, which may cause the strength and heat resistance stability of the precursor to decrease, and ultimately, in the tire cord manufacturing process, it may cause a decrease in force.

[0049] After that, the spinning is passed through the cooling zone for rapid cooling and solidification. In this case, a heating device of a certain length can be set in the distance from the nozzle to the starting point of the cooling zone, that is, in the length L interval of the rear cover according to the needs. The zone is called a delayed cooling zone or a heating zone, and the zone has a length of 50 mm to 150 mm and a temperature of 300° C. to 400° C.

[0050] In the cooling zone, according to the method of blowing cooling air, open quenching method, circular closed quenching method, radial outflow quenching method and radial inflow quenching method can be applied, but it is not limited to this. In this case, for rapid cooling, the temperature of the cooling air injected into the cooling zone is adjusted to 10°C to 30°C. Rapid cooling using the significant temperature difference between the rear cover and the cooling zone can increase the solidification point and spinning tension of the spun polymer, thereby increasing the orientation of the unstretched yarn and the formation of connecting chains between crystals and crystals. Afterwards, the spinning that passes through the cooling zone and solidifies can reduce the friction coefficient between the single yarns, and at the same time, the spinning can be oiled at 0.3 weight percent to 1.0 weight percent by applying an emulsion applying device with excellent stretchability and thermal efficiency.

[0051] The oil-coated filaments are spun to form undrawn filaments. In this case, the spinning draft ratio is 1500 to 3000, and the spinning speed is 2000 m / min or more for the first godet roller in the 6 sections, preferably 2300 m / min or more. The speed of the 4-section roller in the 6-section godet roller is 5200 to 5700 m / min. If the spinning is carried out at the spinning draft ratio and spinning speed in the above range, the excellent force of the precursor can be ensured under lower drawing. If the spinning draft ratio is less than 1500, the cross-sectional uniformity of the precursor will deteriorate, resulting in reduced drawing operability, reduced orientation of the undrawn filaments, and reduced crystallinity. Because the crystalline part is not developed, the thermal stability is reduced during the drawing and impregnation treatment, resulting in reduced force of the tire cord. In order to increase the force and modulus, if a high ratio drawing is performed, it may lead to reduced dimensional stability. If it exceeds 3000, the stretchability of the undrawn filaments is reduced, resulting in reduced strength and drawing operability of the precursor.

[0052] Afterwards, the unstretched filament is stretched in multiple stages through a stretching roller to produce a precursor. The filament passing through the first stretching roller is stretched while passing through a series of stretching rollers by a spin draw method to form a precursor. In the stretching process, the unstretched filament can be stretched in multiple stages, and the temperature of each stretching roller is higher than the glass transition temperature of the unstretched filament and lower than 95°C, but the temperature of the last stretching roller is preferably 200°C to 250°C. If the temperature of the last stretching roller is less than 200°C, the crystallinity and the size of the crystals cannot be increased in the stretching process, and the strength and thermal stability of the precursor cannot be fully utilized, resulting in reduced dimensional stability at high temperatures. If the temperature of the last stretching roller is greater than 250°C, it is too close to the melting point, which may cause the microstructure of the precursor to become uneven, such as crystal decomposition, thereby reducing the strength of the precursor.

[0053] In this case, the winding speed of the drawn raw yarn is preferably 5000 m / min or more. If the winding speed is less than 5000 m / min, the production efficiency may be reduced.

[0054] Furthermore, the total stretching ratio of the precursor formed by the winding method as described above is preferably 2.0 to 2.5 times. If the stretching ratio is less than 2.0 times, the production efficiency is reduced, and the strength and morphological stability of the precursor and the cord are reduced. If the stretching ratio is greater than 2.5 times, the crystallization of the oriented non-crystalline part increases, the stretching operability is reduced, and the wire breakage phenomenon occurs. In the microstructure of the precursor, the molecular chain of the non-crystalline part is broken, resulting in a decrease in the uniformity of the molecular chain, which may reduce the utilization rate of the force, and therefore, it is not ideal.

[0055] After that, the polyethylene terephthalate precursor yarn is twisted, woven and impregnated to produce a dipped cord. First, two strands of the polyethylene terephthalate precursor yarn are twisted using a twisting machine that performs single twisting and combined twisting in stages or a direct twisting machine that performs twisting at the same time, thereby producing a raw cord for a tire cord. The twisted yarn is produced by applying a ply twist to the polyethylene terephthalate precursor yarn and then applying a cable twist for combined twisting. Generally, the cable twist and the ply twist have the same twist number (winding level), or different twist numbers are applied according to requirements.

[0056] In the present invention, the twist number of the polyethylene terephthalate dipped cord is the same as the cable twist / ply twist, and its value is 200TPM / 200TPM (twist per meter) to 500TPM / 500TPM. If the cable twist and ply twist have the same value, the dipped cord produced is not easy to rotate or entangle, but is more likely to maintain a straight line shape, thereby maximizing its physical properties. In this case, if the twist number of the cable twist / ply twist is less than 200TPM / 200TPM, the breaking strength of the raw cord is reduced, resulting in easy reduction in fatigue resistance. If the twist number of the cable twist / ply twist is greater than 500TPM / 500TPM, the force is significantly reduced, and it is not suitable for use as a tire cord.

[0057] Afterwards, the braided yarn is immersed in the impregnation liquid, dried, stretched and heat-cured, and then immersed in the impregnation liquid again, dried and heat-cured, so as to manufacture the impregnated cord. The impregnation liquid is not particularly limited, and is preferably an epoxy resin, a parachlorophenol resorcinol / formalin mixed resin (Pexul). In this case, the drying process should avoid rapid treatment at high temperature, preferably, the drying process is carried out at a temperature of 90°C to 180°C for 180 seconds to 220 seconds. If the drying temperature is lower than 90°C, insufficient drying may result, and gel may be generated due to the impregnation liquid resin during drying and heat treatment. If it is greater than 180°C, the impregnation liquid resin may gel due to extreme drying, and uneven bonding may occur between the cord and the impregnation liquid resin.

[0058] The purpose of the thermal curing is to make the cord dipped in the impregnation liquid resin have appropriate adhesion to the tire rubber, and the thermal curing is preferably performed at a temperature of 220°C to 250°C for 50 seconds to 90 seconds. If the thermal curing time is less than 50 seconds, the reaction time of the adhesive liquid is insufficient, resulting in reduced adhesion, and if the thermal curing time is more than 90 seconds, the hardness of the adhesive liquid is reduced, which may lead to reduced fatigue resistance of the cord.

[0059] Another embodiment of the present invention relates to a tire including the tire cord made of the recycled PET. The tire of the present invention is not limited to radial tires for passenger cars, and may include various tires such as medium and heavy tires or motorcycle tires.

[0060] The tire cord composed of the recycled PET of the present invention is made of recycled PET, so it is environmentally friendly and has many other properties such as excellent modulus, strength and elongation. It exhibits high heat resistance and dimensional stability even at high temperatures, thereby reducing the flat spot phenomenon of the tire. The tire using the tire cord of the present invention has excellent ride feel and driving performance while also improving fuel economy.

[0061] Hereinafter, the present invention will be described in more detail through specific examples, but these examples are only for illustration and are not intended to limit the scope of the present invention.

[0062] Example

[0063] Example 1

[0064] The final drawn yarn (raw yarn) was produced by spinning recycled polyethylene terephthalate chips having an intrinsic viscosity of 1.08 dl / g using a radial inflow quenching device. The two strands of the produced raw yarn were cable twisted and ply twisted at 370 twist / meter to produce cord yarn.

[0065] Subsequently, the cord yarn is immersed in the epoxy resin adhesive liquid in the dipping tank, stretched 3.5% and dried for 150 seconds at a temperature of 170°C in the drying area, stretched 3.0% and thermally cured for 150 seconds at a temperature of 245°C in the high-temperature stretching area, and then immersed in resorcinol-formaldehyde emulsion (RFL) again, dried at a temperature of 170°C for 100 seconds, and then stretched 5.0% and relaxed at a temperature of 245°C, thereby manufacturing a dipped tire cord.

[0066] Example 2

[0067] The same method as in Example 1 was used to produce cord yarns and dipped cords except that the size of the chips was 2.0 to 2.4 g / ea and the uniformity of the chips was 65%. The physical properties of the dipped cords thus produced were evaluated. The results are shown in Table 1 below.

[0068] Example 3

[0069] The same method as in Example 1 was used to produce cord yarns and dipped cords except that the size of the chips was 1.8 to 2.5 g / ea and the uniformity of the chips was 92%. The physical properties of the dipped cords thus produced were evaluated. The results are shown in Table 1 below.

[0070] Example 4

[0071] The same method as in Example 1 was used to produce cord yarns and dipped cords except that the size of the chips was 1.8-2.5 g / ea and the uniformity of the chips was 88%. The physical properties of the dipped cords thus produced were evaluated and the results are shown in Table 1 below.

[0072] Comparative Example 1

[0073] The PET raw yarn and the dipped cord were manufactured in the same manner as in Example 1 except that virgin PET (RE-11) was used instead of recycled PET chips.

[0074] Comparative Example 2

[0075] The PET cord yarn and dipped cord were manufactured in the same manner as in Example 1 except that recycled PET chips produced by physical decomposition of PET bottles by Zhongxing Company were used. The physical properties of the dipped cord thus manufactured were evaluated and the results are shown in Table 1 below.

[0076] Comparative Example 3

[0077] PET cord yarn and dipped cord were manufactured in the same manner as in Comparative Example 1, except that the size of the recycled PET chips produced by physical decomposition of PET bottles by Zhongxing Company reached 1.0 g / ea-1.4 g / ea and the uniformity of the chips reached 50%. The physical properties of the dipped cords thus manufactured were evaluated, and the results are shown in the following Table 1.

[0078] Experimental Example 1: Physical Property Evaluation of Recycled PET Yarn and Tire Cord

[0079] The physical properties of the raw yarns, dipped cords, and tire cords produced in Examples 1 to 4 and Comparative Examples 1 to 3 were evaluated by the following methods, and the results are shown in Table 1 below.

[0080] (1) Intrinsic viscosity of PET chips

[0081] The intrinsic viscosity of r-PET and v-PET was calculated by the following method: as a pretreatment process, the slices were crushed using a Feezermill or pressed using a cable press, and then 0.1 g of the sample was dissolved in a reagent in which phenol and 1,1,2,3-tetrachloroethanol reagent (90°C) were mixed in a weight ratio of 6:4, and the concentration was 0.4 g / 100 ml. After 90 minutes of dissolution, the sample was transferred to an Ubbelohde viscometer and kept in a constant temperature bath at 30°C for 10 minutes. The falling seconds of the solution were obtained using a viscometer and an aspirator. After the falling seconds of the solvent were obtained in the same way, the RV value and IV value were calculated according to the following formula 2 and formula 3.

[0082] [Formula 2]

[0083] Relative viscosity (RV) = falling seconds of sample / falling seconds of solvent

[0084] [Formula 3]

[0085] Intrinsic viscosity (IV) = 1 / 4 × (RV-1) / concentration + 3 / 4 × (ln RV / concentration)

[0086] (2) Isophthalic acid (IPA) content

[0087] 1H-NMR was used. The pretreatment process before measurement was as follows: 0.012-0.015g of crushed PET slices were placed in a test tube, 0.1ml of deuterated trifluoroacetic acid (Trifluoroacetic acid-d) was added, and then allowed to stand for 2 hours to ensure that it was completely dissolved, and then 0.5ml of deuterated chloroform (CDCl3) was added and stirred to fully mix the two solvents. Subsequently, the pretreated test tube was used for analysis by 1H-NMR. After analysis, the IPA inherent peak and peak area were confirmed to obtain the IPA content.

[0088] (3) Weight distribution

[0089] Usually 3-5 repeated tests are performed, and the weight of 100 slices is measured and divided by 100 to record the weight distribution.

[0090] (4)LASE(Load At Specified Elongation)

[0091] In the tensile load curve obtained according to the ASTM D885 measurement method, the load corresponding to the elongation of 5% is taken. The sample before measurement is left to stand for 24 hours in an atmosphere of a temperature of 20° C. and a relative humidity (RH) of 65%, and then the measurement is performed.

[0092] (5) Tire cord force (kgf)

[0093] After the sample was left to stand at 25°C and 65% relative humidity for 24 hours, it was measured using an Instron slow elongation tensile tester. After winding at 80 TPM, the sample was measured at a sample length of 250 mm and a tensile speed of 300 m / min.

[0094] (6) Middle elongation of tire cord (%)

[0095] The intermediate elongation (Elongation at specific load) is measured on the strong elongation SS curve. The original yarn is measured for the elongation under a load of 4.5 g / d, and the treated cord is measured for the elongation under a load of 4.5 g / d.

[0096] (7) Dimensional stability index ES

[0097] In this embodiment, the dimensional stability index is obtained in the following manner: if it is a raw yarn, it is 4.5 g / d, and if it is a treated cord, the sum of the intermediate elongation E and the dry heat shrinkage under a load of 4.5 g / d is calculated.

[0098] [Formula 4]

[0099] Dimensional stability ES = intermediate elongation E + dry heat shrinkage S

[0100] (8) Crystallinity (%)

[0101] The degree of crystallinity is measured by a density method using a density gradient tube. If the density of the crystalline region is ρc, the density of the non-crystalline region is ρa, and the density of the sample is ρ, the degree of crystallinity X is calculated by the following formula 5.

[0102] [Formula 5]

[0103] X(%)=(ρc-ρ) / (ρc-ρa)×100

[0104] If it is polyester, then ρc=1.455g / cm 3 , ρa=1.355g / cm 3 .

[0105] (9) Heat resistance retention rate (%)

[0106] After the tire cord was vulcanized at 170° C. for 15 minutes, the heat resistance retention rate was calculated by the following Formula 1.

[0107] [Formula 1]

[0108] Heat resistance retention rate (T 25 -T80 )=(T 80 Force under conditions / T 25 force under conditions) × 100

[0109] [Table 1]

[0110]

[0111]

[0112] The results in Table 1 indicate that the tire cord using recycled PET of the present invention is made of recycled PET and can improve tire performance by improving tire durability, stability, and post-vulcanization force retention characteristics that affect flat spots at high temperatures while being environmentally friendly.

[0113] Example 5

[0114] The dipped cord prepared in Example 1 was applied to a tire carcass to produce a radial tire, and its characteristics were evaluated. The results are shown in Tables 2 and 3 below.

[0115] Example 6

[0116] A radial tire was manufactured in the same manner as in Example 5 except that the dipped cord prepared in Example 2 was used, and the characteristics thereof were evaluated. The results are shown in Tables 2 and 3 below.

[0117] Example 7

[0118] A radial tire was manufactured in the same manner as in Example 5 except that the dipped cord prepared in Example 3 was used, and its characteristics were evaluated. The results are shown in Tables 2 and 3 below.

[0119] Example 8

[0120] A radial tire was manufactured in the same manner as in Example 5 except that the dipped cord prepared in Example 4 was used, and the characteristics thereof were evaluated. The results are shown in Tables 2 and 3 below.

[0121] Comparative Example 4

[0122] A radial tire was manufactured in the same manner as in Example 5 except that the dipped cord prepared according to Comparative Example 1 was used, and its characteristics were evaluated. The results are shown in Tables 2 and 3 below.

[0123] Comparative Example 5

[0124] A radial tire was manufactured in the same manner as in Example 5 except that the dipped cord prepared according to Comparative Example 2 was used, and its characteristics were evaluated. The results are shown in Tables 2 and 3 below.

[0125] [Table 2]

[0126]

[0127] Test Example 2

[0128] A 205 / 65R15V tire made by applying the tire cords prepared in Examples 5 to 8, Comparison Examples 4 and 5 to the carcass was assembled on a 2000cc class vehicle. When the vehicle was traveling at a speed of 60km / h, the noise generated in the vehicle was measured and displayed as noise (dB) in the audible frequency range.

[0129] In terms of handling stability and ride quality, experienced drivers drove the car on a test track and evaluated it in 5-point increments on a 100-point scale. The results are shown in Table 3 below.

[0130] In terms of durability, according to the P-metric tire endurance test method of FMVSS109, the test is carried out at a temperature of 38°C, with 85%, 90%, and 100% of the tire's rated load, a driving speed of 80km / h, and a total driving time of 34 hours. Check whether there are signs of bead separation, cord breakage, belt separation, etc. on the tire tread or sidewall, carcass cord, inner liner, bead, etc. If no signs are found, it is judged to be qualified.

[0131] In terms of uniformity, each test tire was mounted on a wheel hub and assumed to be repaired. After filling the repair material, the radial force variation (RFV) was measured under the condition of an internal pressure of 320 kPa according to the uniformity test standard of JASO C607: 2000. The evaluation speed was 10 km / h.

[0132] The evaluation results were evaluated by an index with [Comparative Example 4] using virgin PET being 100. The larger the value, the smaller the RFV, and thus the better.

[0133] [Table 3]

[0134] Comparative Example 4 Comparative Example 5 Example 5 Example 6 Example 7 Example 8 Tire weight (kg) 9.6 9.9 9.7 9.6 9.7 10.3 Ride experience 100 97 100 100 99 100 Control stability 100 95 99 100 98 100 Durability qualified qualified qualified qualified qualified qualified Uniformity 100 96 100 100 100 100 Noise(dB) 61.4 64.0 61.9 61.4 61.8 61.1

[0135] Referring to the results in Table 3, it can be confirmed that the tire using the dipped cord of the present invention has lower noise and exhibits comparable performance to existing tires in terms of ride feel, handling stability, durability and uniformity, compared with the tires of Comparative Example 4 using existing virgin PET and Comparative Example 5 using existing recycled PET.

[0136] The above description is made with reference to the preferred embodiments of the present invention. It should be understood by those skilled in the art that various modifications and changes may be made to the present invention without departing from the scope of the concept and technical field of the present invention. Therefore, the true protection scope of the present invention should be determined by the protection scope of the attached invention claims.

Claims

1. A tire cord, characterized in that: The invention relates to a dipped cord made by twisting and dipping recycled polyethylene terephthalate raw yarn made from recycled polyethylene terephthalate, wherein after vulcanizing the tire cord at a temperature of 170°C for 15 minutes, the force at a normal temperature of 25°C reaches 18.5 kgf or more, after vulcanizing at a temperature of 170°C for 15 minutes, the force at a temperature of 80°C reaches 15.5 kgf or more, after vulcanizing at a temperature of 170°C for 15 minutes, the heat resistance retention rate at a temperature of 80°C calculated according to the following formula 1 reaches 85.0% or more, and the value of the fixed elongation load LASE at an elongation of 5% measured at a high temperature of 80°C is 2.8 g / d or more: [Formula 1] Heat resistance retention rate (T 25 -T 80 )=(T 80 Force under conditions / T 25 force under conditions)×100.

2. The tire cord according to claim 1, characterized in that: The recycled polyethylene terephthalate has an intrinsic viscosity of 0.5 dl / g to 2.0 dl / g after solid phase polymerization and a weight distribution of 1.8 g / 100 ea to 2.5 g / 100 ea. The isophthalic acid content of the raw yarn made from the recycled polyethylene terephthalate is less than 1.5 mol%.

3. The tire cord according to claim 1, characterized in that: The regenerated polyethylene terephthalate precursor has a strength of 7.5 g / d or more, a precursor crystallinity of 45% or more, and a dimensional stability ES% of 12.0% or less.

4. The tire cord according to claim 1, characterized in that: The fineness of the tire cord is in the range of 2000d to 7000d, the tire cord is a 2-layer to 4-layer recycled polyethylene terephthalate tire cord, and the twist number of the tire cord is 200 TPM to 500 TPM.

5. The tire cord according to claim 1, characterized in that: The regenerated polyethylene terephthalate raw yarn is regenerated polyethylene terephthalate that does not contain isophthalic acid.

6. A tire, characterized in that: Comprising the tire cord according to any one of claims 1 to 5.

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