Environmentally friendly tire cord and tire using same

Abstract

The present invention relates to an environmentally friendly tire cord that uses recycled polyethylene terephthalate fibers to reduce the environmental impact while providing physical properties at or above the level of tire cords produced using virgin polyethylene terephthalate fibers, particularly excellent heat resistance at or above the level of tire cords produced using virgin PET, and a tire using the same.

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 that reduces environmental impact by using recycled polyethylene terephthalate fibers, while having physical properties at the same level or higher than those of tire cords produced using virgin polyethylene terephthalate fibers, and a tire using the same. [Background technology]

[0002] Generally, tire reinforcement materials, such as polyethylene terephthalate (hereinafter abbreviated as "PET"), have excellent mechanical strength, elastic modulus, dimensional stability, and heat resistance, which are important properties that rubber reinforcement materials should have, and therefore are widely used as reinforcement materials for rubber composite materials, such as tires, belts, and hoses.

[0003] As environmental pollution caused by the indiscriminate use of plastic materials is accelerating, and regulations are being strengthened internationally, there is an increasing demand for environmentally friendly products for vehicles and related products.

[0004] In order to reduce the environmental impact and recycle resources, many attempts have been made to recycle recycled polyester fibers made from discarded PET bottles, such as drinking water bottles, into clothing and industrial use.

[0005] Compared to regular virgin PET tire cords, tire cords made from recycled PET have a high intrinsic viscosity and low purity, resulting in lower physical properties and a worse appearance than conventional tire cords, especially poor heat resistance, which has limited the use of recycled PET in the tire industry and has prevented it from being widely used. Furthermore, recycled PET resins made from PET bottles have the problem of poor moldability, and tire cords made from recycled PET resins have problems with reduced physical properties such as impact resistance, heat resistance, and dimensional stability, as well as poor appearance, resulting in reduced marketability. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-100087 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-30737 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention is intended to overcome the above-mentioned problems of the conventional technology, and one object of the present invention is to provide a tire cord that uses recycled PET chips and has reinforced heat resistance while having a low environmental impact.

[0008] Another object of the present invention is to provide a tire cord that uses recycled PET chips and has physical properties equivalent to or higher than those of products using only virgin PET, and a tire using the same. [Means for solving the problem]

[0009] In order to achieve the above object, one aspect of the present invention is to The tire cord includes a dipped cord produced by twisting and dipping recycled polyethylene terephthalate (PET) yarn produced from recycled polyethylene terephthalate (PET), and after vulcanization at 170°C for 15 minutes, the tire cord has a strength of 18.5 kgf or more at room temperature (25°C), a strength of 15.5 kgf or more at 80°C after vulcanization at 170°C for 15 minutes, a heat strength retention rate at 80°C calculated by the following formula 1 after vulcanization at 170°C for 15 minutes of 85.0% or more, and a LASE (@5%) value measured at high temperature (80°C) of 2.8 g / d or more.

[0010] (Number 1) Heat resistant strength maintenance rate (T 25 -T 80 )=(T 80 Strong in conditions / T 25 Powerful in the conditions) x 100

[0011] The recycled polyethylene terephthalate (PET) has an intrinsic viscosity of 0.5 to 2.0 dl / g after solid-state polymerization and a weight distribution of 1.8 to 2.5 g / 100 ea, and the raw yarn produced from the recycled polyethylene terephthalate (PET) has an isophthalic acid content of 1.5 mol% or less.

[0012] The recycled polyethylene terephthalate (PET) yarn has a strength of 7.5 g / d or more, a degree of crystallinity of 45% or more, and a dimensional stability (ES%) of 12.0% or less.

[0013] The tire cord has a fineness in the range of 2000-7000 d, is a 2-4 ply recycled PET tire cord, and has a twist of 200-500 TPM.

[0014] Another aspect of the present invention relates to an environmentally friendly tire that includes tire cord made from the above-described recycled polyethylene terephthalate (PET). [Effects of the Invention]

[0015] According to various embodiments of the present invention, tire cords can exhibit superior or equivalent heat resistance to conventional PET tire cords while reducing the environmental impact by using recycled PET chips. Therefore, in the long term, the reduction in PET use and the expansion of recycled PET use can achieve environmentally friendly and carbon-reducing effects.

[0016] In addition, compared to the conventional general virgin PET polymerization process, since the PET chips are recycled after the polymerization process has been completed, there is no need to build polymerization process equipment, simplifying the process and resulting in cost reduction and increased price competitiveness.

[0017] A tire using the tire cord of the present invention is environmentally friendly because it uses recycled PET, but can provide performance equal to or better than that of tires using conventional PET (virgin PET) in terms of ride comfort, handling stability, durability, uniformity, and noise. DETAILED DESCRIPTION OF THE INVENTION

[0018] The invention will be described in more detail below.

[0019] In this application, the terms "comprise" or "have" and the like are intended to specify the presence of any feature, number, step, operation, component, part, or combination thereof stated in the specification, but are to be understood as not precluding the possible presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0020] In this specification, the term "recycled polyethylene terephthalate (PET)" can be used to encompass PET resin obtained by regenerating used waste PET for the purpose of recycling, or recycled PET chips containing the same.

[0021] As used herein, the term "virgin polyethylene terephthalate" refers to PET resin or PET chips that contain the same that have not been regenerated or recycled.

[0022] As used herein, the terms "recycled PET fiber" or "recycled PET yarn" refer to a fiber or yarn that includes recycled PET.

[0023] As used herein, "cord" refers to a reinforcing belt that constitutes the reinforcing structure of a tire, and is a product formed by twisting and blending several threads.

[0024] In this specification, "LASE (Load at Specified Elongation)" means a load at a specific elongation rate.

[0025] In this specification, "dimensional stability (ES)" is expressed as the sum of intermediate elongation (E) and dry heat shrinkage (S). Tires with a low dimensional stability (ES) value have a small amount of deformation due to heat, so tires using cords with a low ES value have a higher degree of uniformity than tires using cords with a high ES value, which can also improve tire performance.

[0026] One aspect of the present invention relates to a tire cord that includes a dipped cord produced by twisting and dipping a recycled polyethylene terephthalate (PET) yarn made from recycled polyethylene terephthalate (PET), and that has a strength of 18.5 kgf or more at room temperature (25°C) after vulcanization at 170°C for 15 minutes, a strength of 15.5 kgf or more at 80°C after vulcanization at 170°C for 15 minutes, a heat strength retention rate at 80°C calculated by the following Equation 1 after vulcanization at 170°C for 15 minutes of 85.0% or more, and a LASE (@5%) value measured at high temperature (80°C) of 2.8 g / d or more.

[0027] (Number 1) Heat resistant strength maintenance rate (T 25 -T80 )=(T 80 Strong in conditions / T 25 Powerful in the conditions) x 100

[0028] The tire cord of the present invention has a strength of 18.5 kgf or more at room temperature (25°C) after vulcanization at 170°C for 15 minutes. The strength may be 24 kgf or less. The tire cord of the present invention has a strength of 15.5 kgf or more at 80°C after vulcanization at 170°C for 15 minutes, and preferably has a strength of 22 kgf or less at 80°C.

[0029] After vulcanization at 170°C for 15 minutes, the heat strength retention at 80°C calculated by the above formula 1 is 85.0% or more. The heat strength retention at 80°C may be 92.0% or less. The LASE (@5%) value measured at high temperature (80°C) is 2.8 g / d or more. Preferably, the LASE (@5%) value measured at high temperature (80°C) may be 5.0 g / d or less.

[0030] In the present invention, the recycled polyethylene terephthalate (PET) has an intrinsic viscosity after solid-state polymerization of 0.5-2.0 dL / g, preferably 0.9-1.5 dL / g, and a weight distribution of 1.8-2.5 g / 100 ea. The raw yarn produced from the recycled polyethylene terephthalate (PET) may have an isophthalic acid content of 1.5 mol% or less. Here, the weight distribution is determined by measuring the total weight of 100 chips and dividing by 100.

[0031] The polyethylene terephthalate multifilament constituting the tire cord of the present invention is obtained by melting and spinning a resin composition containing recycled PET. The produced polyethylene terephthalate yarn is then twisted, woven, and dipped to produce a dipped cord.

[0032] The recycled PET that makes up the tire cord of the present invention has a weight distribution of 1.8-2.5g / 100ea. As the chip size becomes smaller, the difference in IV (intrinsic viscosity) between the inside and outside of the chip decreases, resulting in a more uniform IV distribution. The increased surface area makes it easier to melt the polymer with the same amount of heat, thereby reducing IV drop and shortening the solid-state polymerization reaction time, resulting in economic benefits.

[0033] If the chips vary in size, the smaller chips melt first when the polymer is melted, while the larger chips do not, making it difficult to maintain a uniform state. This can result in a decrease in the heat resistance of the tire cord and poor product appearance.

[0034] In the present invention, if the intrinsic viscosity of the recycled PET chips is less than 0.5 dL / g, the intrinsic viscosity of the final drawn yarn will be low, making it impossible to achieve high strength as a tire cord after heat treatment. On the other hand, if the intrinsic viscosity of the recycled PET chips is more than 2.0 dL / g, the polymer melt phase will be non-uniform and the amount of undissolved crystalline material will increase, resulting in non-uniform spinning tension and non-uniform cross-section of the released yarn, and frequent filament breakage will occur during drawing, resulting in poor spinning workability.

[0035] The recycled PET used in the present invention has an isophthalic acid content of 1.5 mol% or less. If the isophthalic acid content exceeds 1.5 mol%, the crystallinity of the recycled PET will increase, resulting in increased costs due to increased energy consumption and equipment improvements, and the physical properties of the yarn may be reduced due to thermal decomposition of the PET. The tire cord of the present invention may be made from recycled PET that does not contain isophthalic acid. In other words, the tire cord of the present invention may have an isophthalic acid content of 0 mol%.

[0036] In the present invention, the recycled polyethylene terephthalate (PET) yarn may have a strength of 7.5 g / d or more, a degree of crystallinity of 45% or more, and a dimensional stability (ES%) of 12.0% or less.

[0037] The recycled polyethylene terephthalate (PET) yarn may have a crystallinity of 45% or more, preferably 50% or less. The strength may be 7.5 g / d or more, preferably 9.5 g / d or less. The strength of the recycled PET yarn according to the present invention is preferably 7.5 g / d or more, but if it is less than 7.5 g / d, the strength may decrease and the dimensional stability may also decrease.

[0038] On the other hand, if the strength of the recycled PET yarn according to the present invention exceeds 9.5 g / d, the tie-chain breakage and orientation of the amorphous region of the recycled PET yarn may be less than that of conventional PET yarn.

[0039] The recycled PET yarn according to the present invention may have a dimensional stability (ES%) of 12% or less, preferably 8.0% or more. In the present invention, the dimensional stability (ES index) value is the sum of the dry heat shrinkage (at 177°C under a load of 0.05 g / d for 2 minutes) and the intermediate elongation (at a load of 4.5 g / d). The lower the value, the smaller the change in shape of the tire cord and the better the heat resistance properties.

[0040] In the present invention, the dipped cord may have a fineness range of 2,000 to 7,000 denier and may contain 2 to 4 plies of plied yarn with a twist per unit length of 200 to 500 TPM.

[0041] The method for producing the recycled PET tire cord according to the present invention is as follows.

[0042] First, in the present invention, recycled PET yarn for tire cord is produced by high-speed spinning at a spinning speed (the speed of the first godet roller among the six stages) of 2,000 m / min or more, preferably 2,300 m / min or more, thereby increasing the spin draft in the range of 1,500 to 3,000, setting the intrinsic draw coefficient in the range of 800 to 1,400, and adjusting the take-up degree so that the total draw ratio of the yarn is in the range of 2.0 to 2.5, thereby changing the microstructure of the final yarn and producing a tire cord with improved heat resistance and dimensional stability.

[0043] First, recycled PET chips with an intrinsic viscosity of 0.5 to 2.0 dL / g are melted and extruded through a nozzle to produce a discharged yarn. The recycled polyethylene terephthalate chips are melted and extruded through a nozzle to produce a discharged yarn. It is recommended to use PET chips with a low IPA content and uniform weight distribution.

[0044] If the IPA content is high, it may inhibit the increase in crystallinity and crystal size during the production of raw yarn, resulting in a decrease in the strength and heat resistance stability of the raw yarn, which may result in a decrease in tenacity during the tire cord production process.

[0045] Next, the released yarn is passed through a cooling zone where it is rapidly cooled and solidified. If necessary, a heating device is installed along the length (L) of the hood from directly below the nozzle to the start of the cooling zone. This zone is called the delayed cooling zone or heating zone, and has a length of 50 to 150 mm and a temperature of 300 to 400°C.

[0046] In the cooling zone, the cooling air may be blown in by, but not limited to, open quenching, circular closed quenching, radial outflow quenching, and radial inflow quenching.

[0047] In this case, the temperature of the cooling air injected into the cooling zone for rapid cooling is adjusted to 10 to 30° C. Rapid cooling using such a sudden temperature difference between the hood and the cooling zone increases the solidification point and spinning tension of the spun polymer, and increases the orientation of the undrawn yarn and the formation of linking chains between crystals.

[0048] Next, the solidified released yarn is passed through a cooling zone, which reduces the coefficient of friction between the individual yarns, and the released yarn can be oiled at 0.3 to 1.0% by weight using an emulsion applicator that applies an emulsion with excellent stretchability and thermal efficiency.

[0049] The oiled released yarn is spun to form an undrawn yarn. In this case, the spin draft is 1500 to 3000, and the spinning speed is preferably 2000 m / min or more, preferably 2300 m / min or more, for the first godet roller among the six godet rollers. The speed of the fourth godet roller among the six godet rollers is 5200 to 5700 m / min. Spinning within these spin draft and spinning speed ranges ensures excellent tenacity of the raw yarn even at a low draw ratio.

[0050] If the spin draft is less than 1,500, the cross-sectional uniformity of the yarn deteriorates, resulting in poor drawing workability; the degree of orientation of the undrawn yarn is reduced, the crystallinity is lowered, and crystalline portions are developed, resulting in poor thermal stability during drawing and dipping treatments, resulting in a decrease in the strength of the tire cord; and if high drawing is performed to improve tenacity and modulus, dimensional stability may be reduced. If the spin draft exceeds 3,000, the drawability of the undrawn yarn is reduced, resulting in a decrease in the strength and drawing workability of the yarn.

[0051] Next, the undrawn yarn is passed through a drawing roller and drawn in an end stage to produce a raw yarn. The yarn that has passed through the first drawing roller is drawn by passing through a series of drawing rollers using a spin draw method to form the raw yarn. In the drawing process, the undrawn yarn may be drawn in multiple stages, and the temperature of each drawing roller is higher than the glass transition temperature of the undrawn yarn but lower than 95°C, with the temperature of the final drawing roller preferably being 200 to 250°C.

[0052] If the temperature of the final drawing roller is less than 200°C, the degree of crystallinity and crystal size do not increase during the drawing process, and the strength and thermal stability of the yarn cannot be achieved, resulting in a decrease in dimensional stability at high temperatures. If the temperature of the final drawing roller is more than 250°C, the temperature approaches the melting point, which can actually cause the crystals to decompose, resulting in an uneven microstructure of the yarn and a decrease in the strength of the yarn.

[0053] In this case, the winding speed of the drawn yarn is preferably 5,000 m / min or more. If the winding speed is less than 5,000 m / min, productivity may decrease.

[0054] In addition, the total draw ratio of the yarn formed by winding as described above is preferably 2.0 to 2.5. If the draw ratio is less than 2.0, productivity decreases and the strength and dimensional stability of the yarn and cord decrease, while if the draw ratio exceeds 2.5, crystallization of the oriented amorphous portion increases, reducing drawing workability and causing yarn breakage, and the molecular chains of the amorphous portion in the fine structure of the yarn are broken, reducing the uniformity of the molecular chains and, therefore, decreasing the tenacity utilization rate, which is undesirable.

[0055] Next, the produced polyethylene terephthalate yarn is used to twist, weave, and dip the yarn to produce a dipped cord. First, two polyethylene terephthalate yarns are twisted in a twisting machine that performs false twisting and plying in stages, or in a direct twisting machine that performs these processes simultaneously, to produce a raw cord for tire cords. The twisted yarn is produced by adding a ply twist to the polyethylene terephthalate yarn, then adding a cable twist and plying, and generally the ply twist and ply twist have the same number of twists (twist level), or different numbers of twists as needed.

[0056] In the present invention, the twist number of the polyethylene terephthalate dipped cord is set to 200 / 200 TPM (twist per meter) to 500 / 500 TPM, with the top and bottom twists being the same value. When the top and bottom twists are set to the same value, the manufactured dipped cord tends to maintain a straight line without rotation or twisting, maximizing the expression of physical properties. In this case, if the twist number of the top and bottom twists is less than 200 / 200 TPM, the raw cord's break elongation is reduced and fatigue resistance is likely to decrease. If it exceeds 500 / 500 TPM, the strength is significantly reduced, making it unsuitable for tire cords.

[0057] The woven yarn is then dipped in a dipping solution, dried, stretched, and heat-set, and then immersed in a dipping solution again, dried, and heat-set to produce a dipped cord. The dipping solution is not particularly limited, but is preferably an epoxy or parachlorophenol-based resorcinol / formalin mixed resin (Pexul). The drying should be avoided by rapid treatment at high temperatures, and is preferably carried out at 90 to 180°C for 180 to 220 seconds.

[0058] If the drying temperature is below 90°C, drying may not be sufficient, and gel may occur due to the dipping liquid resin during drying and heat treatment. If the temperature exceeds 180°C, rapid drying may cause gel to occur due to the dipping liquid resin, which may result in uneven adhesion between the cord and the dipping liquid resin.

[0059] The heat setting is performed so that the cord impregnated with the dipping liquid resin has an appropriate adhesive strength with the tire rubber, and is preferably performed at a temperature of 220 to 250°C for 50 to 90 seconds. If the heat setting is performed for less than 50 seconds, the adhesive liquid does not have enough time to react, resulting in a low adhesive strength, while if the heat setting is performed for more than 90 seconds, the hardness of the adhesive liquid decreases, resulting in a decrease in fatigue resistance of the cord.

[0060] Another aspect of the present invention relates to a tire including the tire cord made of the above-mentioned recycled PET. The tire of the present invention is not limited to a radial tire for a passenger car, but can be configured as a variety of tires, such as a heavy-duty tire and a motorcycle tire.

[0061] The tire cord made from the recycled PET of the present invention is environmentally friendly because it is produced using recycled PET, and yet has excellent other properties such as modulus, strength, and elongation. It also exhibits high heat resistance and dimensional stability even in high-temperature environments, reducing the flat spot phenomenon. Tires using the tire cord of the present invention exhibit excellent ride comfort and driving performance, as well as improved fuel economy.

[0062] The present invention will be described in more detail below with reference to specific examples, but these examples are merely illustrative and are not intended to limit the scope of the present invention.

[0063] Example Example 1 Recycled polyethylene terephthalate chips with an intrinsic viscosity of 1.08 dL / g were spun using a radial in-flow quenching system to produce the final drawn yarn (raw yarn). Two of the resulting raw yarns were twisted together at 370 twists / meter to produce a cord yarn.

[0064] Next, the cord yarn was immersed in an epoxy resin adhesive solution in a dipping tank, dried at 170°C for 150 seconds under 3.5% stretching in a dry area, and heat-set at 245°C for 150 seconds under 3.0% stretching in a high-temperature stretching area. Thereafter, the cord yarn was further immersed in resorcinol formalin latex (RFL), dried at 170°C for 100 seconds, and relaxed at 245°C for 5.0% stretching for 40 seconds to produce a tire cord, which is a dipped cord.

[0065] Example 2 A cord yarn and a dipped cord were produced in the same manner as in Example 1, except that the chip size was 2.0-2.4 g / ea and the chip uniformity was 65%. The physical properties of the dipped cord thus produced were evaluated, and the results are shown in Table 1 below.

[0066] Example 3 Cord yarns and dipped cords were produced in the same manner as in Example 1, except that the chip size was 1.8-2.5 g / ea and the chip uniformity was 92%. The physical properties of the dipped cords produced were evaluated, and the results are shown in Table 1 below.

[0067] Example 4 Cord yarns and dipped cords were produced in the same manner as in Example 1, except that the chip size was 1.8-2.5 g / ea and the chip uniformity was 88%. The physical properties of the dipped cords produced were evaluated, and the results are shown in Table 1 below.

[0068] Comparative Example 1 PET yarn and dipped cord were produced in the same manner as in Example 1, except that virgin PET (RE-11) was used instead of recycled PET chips.

[0069] Comparative Example 2 PET cord yarn and dipped cord were produced in the same manner as in Example 1, except that recycled PET chips produced by physically disassembling PET bottles at Zhongxing Company were used. The physical properties of the dipped cord thus produced were evaluated, and the results are shown in Table 1 below.

[0070] Comparative Example 3 PET cord yarn and dipped cord were produced in the same manner as in Comparative Example 1, except that the size of the recycled PET chips produced by physically disassembling PET bottles at Zhongxing Company was 1.0-1.4 g / ea and the uniformity of the chips was 50%. The physical properties of the dipped cords produced in this manner were evaluated, and the results are shown in Table 1 below.

[0071] Experimental Example 1: Evaluation of the physical properties of recycled PET yarn and tire cord The physical properties of the yarn, dipped cord, and tire cord produced in Examples 1-4 and Comparative Examples 1-3 were evaluated by the following methods, and the results are shown in Table 1 below.

[0072] (1) Intrinsic viscosity of PET chips The intrinsic viscosity of r-PET and v-PET was measured by either crushing chips using a Feezer mill or crimping them using a wire crimper during the pretreatment process. Then, 0.1 g of sample was dissolved in a 6:4 weight ratio mixture of phenol and 1,1,2,3-tetrachloroethanol (90°C) for 90 minutes to a concentration of 0.4 g / 100 ml. The sample was then transferred to an Ubbelohde viscometer and placed in a 30°C thermostatic bath for 10 minutes. The solution drop time was measured using the viscometer and an aspirator. The drop time of the solvent was also measured in the same way, and the RV and IV values ​​were calculated using Equations 2 and 3 below.

[0073] (Number 2) Relative viscosity (RV) = sample drop time / solvent drop time

[0074] (Number 3) Intrinsic viscosity (IV)=1 / 4×(RV-1) / concentration+3 / 4×(In RV / concentration)

[0075] (2) Isophthalic acid (IPA) content This was done using 1H-NMR. As a pretreatment step before measurement, 0.012-0.015g of crushed PET chips were placed in a sample tube, 0.1ml of trifluoroacetic acid-d was added, and the mixture was left for 2 hours. Once completely dissolved, 0.5ml of CDCl3 was added and stirred to ensure the two volumes were well mixed. 1H-NMR analysis was then performed using the pretreated sample tube. After analysis, the characteristic IPA peak and its area were confirmed to determine the IPA content.

[0076] (3) Weight distribution This is usually repeated 3-5 times, and the weight of 100 chips is measured, then divided by 100 and the weight distribution is recorded.

[0077] (4) LASE The load at 5% elongation was taken from the elongation load curve obtained by the ASTM D885 measurement method. Before measurement, the sample was left in an atmosphere of 20°C and 65% RH for 24 hours before measurement.

[0078] (5) Tire cord strength (kgf) After leaving the sample at 25°C and 65% relative humidity for 24 hours, the sample is twisted at 80 TPM using an INSTRON slow-extension tensile tester, with a sample length of 250 mm and a tensile speed of 300 m / min.

[0079] (6) Intermediate elongation of tire cord (%) The intermediate elongation (Elongation at specific load) was measured at a load of 4.5 g / d on the strength-elongation SS curve for the raw yarn, and at a load of 4.5 g / d for the treated cord.

[0080] (7) Dimensional stability index (ES) In this example, the dimensional stability index is determined as the sum of the intermediate elongation (E) and dry heat shrinkage at a load of 4.5 g / d for raw yarn and 4.5 g / d for treated cord.

[0081] (Number 4) Dimensional stability (ES) = Intermediate elongation (E) + Dry heat shrinkage (S)

[0082] (8) Crystallinity (%) The degree of crystallinity is measured using a density gradient tube by the density method. When the density of the crystalline region is ρc, the density of the amorphous region is ρa, and the density of the sample is ρ, the degree of crystallinity (X) is calculated using the following Equation 5.

[0083] (Number 5) X(%)=(ρc-ρ) / (ρc-ρa)×100 For polyester, ρc = 1.455 g / cm 3 , ρa=1.355g / cm 3 is.

[0084] (9) Heat resistance strength maintenance rate (%) The heat resistance strength retention rate is calculated by the following formula 1 after vulcanizing the tire cord at 170°C for 15 minutes.

[0085] (Number 1) Heat resistant strength maintenance rate (T 25 -T 80 )=(T 80 Strong in conditions / T 25 Powerful in the conditions) x 100

[0086] [Table 1]

[0087] As can be seen from the results in Table 1, the tire cord using recycled PET of the present invention is environmentally friendly because it is produced using recycled PET, and can also improve tire performance by improving the tenacity retention after vulcanization, which affects tire durability, stability, and flat spots at high temperatures.

[0088] Example 5 A radial tire was manufactured by applying the dipped cord manufactured in Example 1 to the carcass of the tire, and its properties were evaluated. The results are shown in Tables 2 and 3 below.

[0089] Example 6 A radial tire was manufactured in the same manner as in Example 5, except that the dipped cord manufactured in Example 2 was used, and its properties were evaluated. The results are shown in Tables 2 and 3 below.

[0090] Example 7 A radial tire was manufactured in the same manner as in Example 5, except that the dipped cord manufactured in Example 3 was used, and its properties were evaluated. The results are shown in Tables 2 and 3 below.

[0091] Example 8 A radial tire was manufactured in the same manner as in Example 5, except that the dipped cord manufactured in Example 4 was used, and its properties were evaluated. The results are shown in Tables 2 and 3 below.

[0092] Comparative Example 4 A radial tire was manufactured in the same manner as in Example 5, except that the dipped cord manufactured in Comparative Example 1 was used, and its properties were evaluated. The results are shown in Tables 2 and 3 below.

[0093] Comparative Example 5 A radial tire was manufactured in the same manner as in Example 5, except that the dipped cord manufactured in Comparative Example 2 was used, and its properties were evaluated. The results are shown in Tables 2 and 3 below.

[0094] [Table 2]

[0095] Test Example 2 The tire cords produced in Examples 5-8 and Comparative Examples 4 and 5 were applied to the carcass of 205 / 65R15V tires manufactured. The tires were mounted on a 2000cc vehicle, and the noise generated inside the vehicle was measured while driving at a speed of 60km / h, and the audible frequency range values ​​were expressed in terms of noise (dB).

[0096] The handling stability and ride comfort were evaluated by an experienced driver who drove the vehicle on a test course and rated it on a scale of 5 to 100 points. The results are shown in Table 3 below.

[0097] Durability was assessed according to the FMVSS109 P-metric tire endurance test, where the tire was driven for a total of 34 hours at a speed of 80km / h under conditions of 85%, 90%, and 100% of the tire's specified load at a temperature of 38°C. The tire was deemed to have passed the test if no signs of bead separation, cord breakage, or belt separation were found in any part of the tire, including the tread, sidewall, carcass cord, inner liner, or bead.

[0098] For uniformity, the tire provided for each test was mounted on a rim, filled with puncture repair material to simulate a puncture repair, and then radial force variation (RFV) was measured in accordance with the uniformity test conditions of JASO C607:2000 under a pressure of 320 kPa. The evaluation speed was 10 km / h.

[0099] The evaluation results were evaluated based on an index of 100, where [Comparative Example 4] using virgin PET is the standard, and the larger the index, the smaller the RFV and the better the product.

[0100] [Table 3]

[0101] Referring to the results in Table 3, it can be seen that the tire using the dipped cord according to the present invention exhibits reduced noise and comparable performance in terms of ride comfort, handling stability, durability, and uniformity compared to the tire of Comparative Example 4 using conventional virgin PET and the tire of Comparative Example 5 using conventional recycled PET.

[0102] Although the present invention has been described above with reference to preferred embodiments, it will be understood by those skilled in the art that various modifications and variations may be made to the present invention without departing from the spirit and scope of the present invention. Therefore, the true scope of protection of the present invention should be determined by the following claims.

Claims

1. The present invention includes a dipped cord manufactured by twisting and dipping a recycled polyethylene terephthalate (PET) yarn made from recycled polyethylene terephthalate (PET), After vulcanization at 170°C for 15 minutes, the strength at room temperature (25°C) is 18.5 kgf or more, and after vulcanization at 170°C for 15 minutes, the strength at 80°C is 15.5 kgf or more. After vulcanization at 170°C for 15 minutes, the heat strength retention rate at 80°C calculated by the following formula 1 is 85.0% or more, and the LASE (@5%) value measured at high temperature (80°C) is 2.8 g / d or more. Tire cord. (Number 1) Heat resistant strength maintenance rate (T 25 -T 80 ) = (T 80 Strong in Conditions / T 25 Powerful under these conditions) x 100

2. The recycled polyethylene terephthalate (PET) has an intrinsic viscosity after solid-state polymerization of 0.5 to 2.0 dl / g and a weight distribution of 1.8 to 2.5 g / 100 ea, and the raw yarn produced from the recycled polyethylene terephthalate (PET) has an isophthalic acid content of 1.5 mol% or less. The tire cord according to claim 1.

3. The recycled polyethylene terephthalate (PET) yarn has a strength of 7.5 g / d or more, a crystallinity of 45% or more, and a dimensional stability (E-S%) of 12.0% or less. The tire cord according to claim 1.

4. The tire cord has a fineness in the range of 2000-7000 d, and the tire cord is a 2-4 ply recycled PET tire cord, and the twist number of the tire cord is 200-500 TPM. The tire cord according to claim 1.

5. The recycled PET yarn is made from recycled PET that does not contain isophthalic acid. The tire cord according to claim 1.

6. A tire comprising the tire code name according to any one of claims 1 to 5.

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