KR101271586B1 - Poly(ethyleneterephthalate) tire cord and tire comprising the same - Google Patents

Abstract

The present invention relates to a polyethylene terephthalate tire cord and a tire comprising the same, which shows excellent shape stability and can be preferably applied to carcass cords of pneumatic tires.

The polyethylene terephthalate tire cord is 6.0-7.5 g / de strong, 3.8% -4.5% lean, 15% -25% lean under 2.25 g / de load, and heat treated for 10 minutes at 0.01 g / de load at 180 ° C. After that, the dry heat shrinkage is 1.5% or less.

PET, cord, dry heat shrinkage, strong, thin, medium, modulus, shape stability

Description

Polyethylene terephthalate tire cord and tire comprising same {POLY (ETHYLENETEREPHTHALATE) TIRE CORD AND TIRE COMPRISING THE SAME}

The present invention relates to a polyethylene terephthalate tire cord and a tire comprising the same. More specifically, the present invention relates to a polyethylene terephthalate tire cord and a tire comprising the same, which exhibits excellent shape stability and can be preferably applied to carcass codes of pneumatic tires.

The tire is a composite of fiber / steel / rubber and generally has a structure as shown in FIG. 1. In other words, steel and fiber cords serve to reinforce rubber and form a basic skeletal structure in the tire. In other words, compared to the human body is a bone-like role.

The performance required for the cord as a tire reinforcement is fatigue resistance, shear strength, durability, resilience and adhesion to rubber. Therefore, a cord of appropriate material is used according to the performance required for the tire.

Commonly used materials for the cord are rayon, nylon, polyester, steel, and aramid, and rayon and polyester are used for body ply (or also referred to as carcass, 6 in FIG. 1), and nylon is mainly capply. In Fig. 1 4, steel and aramid are mainly used for the tire belt portion (5 in Fig. 1).

The following briefly illustrates the tire structure and its characteristics shown in FIG. 1.

Tread (1): This part is in contact with the road surface. It should provide the necessary frictional force for braking and driving, has good abrasion resistance, can withstand external shocks and has low heat generation.

Body Ply or Carcass (6): A layer of cord inside the tire, which must support loads, withstand impacts and be resistant to flexing movements while driving.

Belt (5): Located between the body plies, most of them are made of steel wires to mitigate external shocks and maintain a wide tread ground to provide excellent driving stability.

Side Wall (3): refers to the rubber layer between the lower portion of the shoulder (2) from the bead (9) and serves to protect the inner body ply (6).

BEAD (9): A square or hexagonal wire bundle with rubber coating on the wire that seats and secures the tire to the rim.

Inner Liner (7): Located on the inside of the tire instead of the tube, it prevents air leakage and enables pneumatic tires.

CAP PLY (4): A special cord paper placed on the belt of some passenger radial tires that minimizes belt movement when driving.

Apex (8): This is a triangular rubber filler used to minimize the dispersion of beads, to mitigate external shocks, to protect the beads, and to prevent the inflow of air during molding.

The body ply in the tire, or carcass, is a key reinforcement that supports the load of the car and maintains the shape of the tire.In the early stages of tire development, natural materials such as cotton went through viscose rayon and nylon, which are then recycled fibers, and now polyester. Tire cords are mainly used. In addition, new materials such as polynaphthalene terephthalate (PEN), aramid, and steel are being used in small amounts, but the amount of use is minimal.

In particular, tire cords made of nylon and polyester contribute to the durability improvement of the tire with excellent price competitiveness and high strength compared to the conventional cotton or viscose rayon, and occupy much demand. However, such a synthetic fiber tire cord is low in form stability due to heat compared to a cellulose fiber fiber tire cord such as viscose rayon.

In order to compensate for this, in the tire manufacturing process, an additional process of applying heat under a constant load such as PCI (Post Cure Inflation) is applied to heat deformation in advance to minimize the shape of the tire during vulcanization. However, even if the PCI process is additionally performed, the shape deformation is much larger than that of viscose rayon or aramid, which makes it difficult to maintain a uniform tire shape. In addition, there is a problem that an increase in manufacturing process cost and process failure rate may increase according to the process addition.

Accordingly, the present invention is to provide a polyethylene terephthalate tire cord having excellent modulus and shape stability.

In addition, the present invention is to provide a pneumatic tire including the tire cord, not only having excellent high-speed driving performance, but also can further improve the controllability or ride comfort of the vehicle.

The present invention is a strong 6.0 to 7.5 g / de, a 3.8% to 4.5% medium, 15% to 25% lean under 2.25 g / de load, dry heat shrinkage after heat treatment for 10 minutes at 0.01 g / de load at 180 ℃ It provides a polyethylene terephthalate tire cord that is 1.5% or less.

The present invention also provides a pneumatic tire comprising the tire cord.

Hereinafter, a polyethylene terephthalate tire cord and a tire including the same according to a specific embodiment of the present invention will be described in detail. It will be apparent to those skilled in the art, however, that this is not intended to limit the scope of the invention, which is set forth as an example of the invention, and that various modifications may be made to the embodiments within the scope of the invention.

Additionally, unless otherwise indicated throughout this specification, "comprising" or "containing" refers to including any component (or component) without particular limitation, and refers to the addition of another component (or component). It cannot be interpreted as excluding.

According to one embodiment of the invention, there is provided a polyethylene terephthalate (hereinafter referred to as "PET") tire cord with certain properties. These PET tire cords are strongly 6.0 to 7.5 g / de under heavy load of 2.25 g / de, 3.8% to 4.5% for medium body, 15% to 25% for body length, and dry heat after heat treatment for 10 minutes at 0.01 g / de load at 180 ° C. This is solved through polyethylene terephthalate tire cords with shrinkage of less than 1.5%. As the PET tire cord exhibits various properties such as strength or elongation and dry heat shrinkage in this range, it can be preferably applied as a cord for carcass.

PET tire cord according to an embodiment of the present invention was confirmed that there is almost no deformation due to heat when showing excellent morphological stability at a high temperature between 150 ~ 180 ℃ that is given to the vulcanization process at the time of tire manufacturing. Here, even if the tire cord is introduced into the tire manufacturing process without a separate PCI process, the tire shape does not deform after the tire vulcanization. As a result, the PCI process, such as viscose rayon or aramid, can be omitted, thereby greatly reducing manufacturing costs and defects. In addition, the PET tire cord has a low modulus decrease rate due to a low shrinkage rate even after vulcanization, thereby maintaining a high modulus in the vulcanized tire. As a result, the resistance to the load of the vehicle and the load imposed by the sudden rotation is increased, so that the controllability and stability at the time of driving are improved, thereby expressing excellent performance as a carcass cord.

In addition, the PET tire cord may be heat treated at 0.01 ° C./de for 10 minutes at 180 ° C., and the core body under 2.25 g / de load may exhibit 6.5% or less, preferably 5.5% or less, wherein 2.25 g / The central body fluctuation value under de load may be 2.0% or less, preferably 1.5% or less.

In other words, the PET tire cord does not significantly increase elongation even after heat treatment at a load of 0.01 g / de at a high temperature of 180 ° C., as described above, under low temperature and high load (these high loads may be applied to high-speed running conditions of the tire). The difference value of elongation at the time of walking) is not big either. Accordingly, the PET tire cord has excellent modulus and shape stability, and thus, even if the running speed of the vehicle is suddenly increased and the temperature or load applied to the tire cord is suddenly increased, the appearance shape is hardly changed. Therefore, the tire cord can be suitably used as a carcass cord, and the like, and even when the running speed of the vehicle is suddenly increased, it is possible to suppress the deformation of the tire due to the deformation of the tire cord, so that the high-speed running performance of the tire The vehicle's adjustability and ride comfort can be further improved.

On the other hand, PET tire cord according to an embodiment of the present invention is not particularly limited in form, it may have a form equivalent to the conventional carcass code. More specifically, the PET tire cord is a deep cord having a total fineness of 1,000 to 5,000 deniers (d) per cord, a number of plies of 1 to 3, and a twist number of 200 to 500 TPM according to the form of a conventional carcass cord. It may have a form.

The tire cord may be applied as a carcass cord of the pneumatic tire. The tire to which the carcass cord is applied suddenly increases the running speed of the vehicle, but even if the temperature or load applied to the carcass cord suddenly increases, the appearance form of the carcass cord does not deform well and the tire itself is easily deformed. It doesn't work. Therefore, the tire not only exhibits high speed driving performance but also greatly improves the controllability and ride comfort of the vehicle. In addition, since the tire cord has various physical properties such as high modulus, shape stability, strength, or elongation that can be preferably used as a carcass cord, the tire to which the carcass cord is applied can exhibit excellent performance.

However, the above description mainly assumed the case in which the PET tire cord according to the embodiment of the invention is used as a carcass cord, but the use of such a PET tire cord is not limited to this, other such as a cap ply cord Of course, it can also be used for purposes.

On the other hand, the above-described PET tire cord is melt-spun PET to produce a non-drawn yarn, stretched the non-drawn yarn to prepare a stretched yarn, after the twisted yarns are twisted yarns immersed in an adhesive to form a tire cord in the form of a deep cord It may be prepared by the method of preparation. The specific conditions or the process of each of these steps can be directly or indirectly reflected on the physical properties of the final tire cord can be produced PET tire cord having the above-described physical properties.

In particular, the polyethylene terephthalate non-drawn yarn having a crystallinity of 25% or more and an amorphous Orientation Factor (AOF) of 0.15 or less is obtained by adjusting the melt spinning condition of the PET, and thus, a stretched yarn is manufactured and used therefrom. It has been found that the above-mentioned PET tire cords can be produced in which the elongation rate itself is not large and the elongation difference between them is not large at high or low loads under high temperature.

PET basically has a crystallized form, and is composed of a crystalline region and an amorphous region. However, the PET non-drawn yarn obtained under controlled melt spinning conditions has a higher degree of crystallization than previously known PET non-drawn yarn due to the orientation crystallization phenomenon, and thus exhibits a high degree of crystallinity of 25% or more, preferably 25 to 40%. Due to such a high degree of crystallinity, PET stretched yarns and tire cords prepared from the PET non-stretched yarns may exhibit high shrinkage stress and modulus.

At the same time, the PET non-drawn yarn exhibits an amorphous orientation index of 0.15 or less, preferably 0.08 to 0.15, which is significantly lower than previously known PET non-drawn yarn. At this time, the amorphous orientation index indicates the degree of orientation of the chains included in the amorphous region in the unstretched yarn, and has a lower value as the matting of the chains in the amorphous region increases. That is, in general, when the amorphous orientation index is lowered, the disorder is increased so that the chains of the amorphous regions become a relaxed structure rather than a tensioned structure, so that the drawn yarn and tire cords made from undrawn yarn have low shrinkage with low shrinkage rate. It will show stress. However, the PET non-drawn yarn obtained under controlled melt spinning conditions contains more crosslinks per unit volume, forming a fine network structure due to the molecular chains which make it slip during the spinning process. For this reason, the PET unstretched yarn can have a strained structure of the chains in the amorphous region while the amorphous orientation index is significantly lowered, thereby showing the developed crystal structure and excellent orientation characteristics.

Therefore, it is possible to manufacture PET stretched yarns and tire cords simultaneously exhibiting a low shrinkage rate and a high shrinkage stress using PET non-drawn yarns exhibiting such high crystallinity and low amorphous orientation index, and furthermore, according to one embodiment of the invention It has been found that it is possible to provide PET tire cords that exhibit excellent morphological stability and modulus with all the physical properties (e.g., optimized strength, stretch, severity, and low shrinkage, optimized by temperature or load described above).

The manufacturing method of such a PET tire cord will be described in each step as follows.

In the tire cord manufacturing method, PET unstretched yarn is first produced by melt spinning PET, which exhibits the above-described high crystallinity and low amorphous orientation index.

In this case, the melt spinning process may be performed under a higher spinning tension to obtain PET non-drawn yarn that satisfies such crystallinity and amorphous orientation index. For example, the melt spinning process may proceed under a spin tension of at least 0.85 g / d, preferably 0.85 to 1.25 g / d. In addition, for example, the rate of melt spinning the PET can be adjusted to 3,800 to 4,500 m / min, preferably 3,800 to 4,200 m / min can be adjusted.

As a result of the melt spinning process of PET under such high spinning tension and optionally high spinning speed, the crystallization degree is increased with the orientation crystallization phenomenon of PET, and the molecular chains forming the PET are slipped during the spinning process. It has been found that by forming a structure, PET undrawn yarn can be obtained that meets the above crystallinity and amorphous orientation index. However, adjusting the spinning speed to 5,000 m / min or more is difficult to realize in reality and it is difficult to proceed with the cooling process due to excessive spinning speed.

In the manufacturing process of such PET non-stretched yarns, chips having an intrinsic viscosity of 0.8 to 1.3 dl / g and composed of 90 mol% or more of polyethylene terephthalate can be used as the PET.

As described above, in the manufacturing process of the PET non-stretched yarn, conditions of higher spinning tension and optionally higher spinning speed can be imparted. In order to proceed the spinning step preferably under these conditions, the inherent characteristics of the chip It is preferable that a viscosity is 0.8 dl / g or more. In addition, it is preferable that the intrinsic viscosity is 1.3 dl / g or less in order to prevent the molecular chain cutting and the pressure increase due to the discharge amount in the spin pack due to the rise of the melting temperature of the chip.

In addition, the chip is preferably spun through a mold designed so that the fineness of the monofilament is 2.0 to 4.0 denier, preferably 2.5 to 3.0 denier. In other words, the monofilament should have a fineness of 2.0 denier or more in order to reduce the possibility of trimming due to interference between each other during the generation and trimming during spinning, and the fineness of the monofilament in order to give a sufficiently high spinning tension by increasing the radiation draft. Is preferably 4.0 denier or less.

In addition, after melt spinning the PET, the unstretched yarn may be manufactured by adding a cooling process. The cooling process may be performed by applying a cooling wind of 15 to 60 ° C., and each cooling wind temperature. It is preferable to adjust the cooling air volume to 0.4-1.5 m / s in conditions. Thereby, PET non-drawn yarn satisfying the above-mentioned crystallinity, amorphous orientation index, and the like can be produced more easily.

On the other hand, after manufacturing the PET non-drawn yarn that satisfies the above-described crystallinity and the like through the spinning step, the non-drawn yarn is stretched to produce a stretched yarn, the stretching step can be carried out under the draw ratio conditions of 1.3 to 1.7 or less. have. The PET non-drawn yarn has advanced crystal regions, and amorphous chains also have a low degree of orientation and form a fine network structure. Therefore, if the drawing step is carried out under high draw ratio conditions of more than 1.7, cutting or mourning may occur in the drawn yarns, and thus the final manufactured tire cord is also difficult to exhibit desirable physical properties. In addition, when the stretching process is performed under a relatively low draw ratio, the strength of the PET tire cord manufactured therefrom may be partially lowered. In particular, under a draw ratio of 1.3 or more, for example, PET tire cords exhibiting strengths of 6.0 g / de or more suitable for application to carcass codes or the like are possible, and thus, the drawing process is preferably performed under a draw ratio of 1.3 to 1.7. You can proceed.

After the drawn yarn is manufactured, the drawn yarn is fused and then immersed in an adhesive to prepare a dip cord, and such a twisted yarn process and immersion process follows a general method of processing a PET tire cord. However, in order to exhibit excellent shape stability suitable for application to carcass cord and the like, and to minimize physical property change during tire vulcanization, heat treatment may be performed at least 245 ° C., preferably between 245 and 250 ° C. for 1 minute and 30 seconds. have. The adhesive solution may be reacted through the heat treatment process, and crystallization may be performed according to the temperature range of the heat treatment process, thereby improving form stability.

The tire cords thus prepared may have a form with a total fineness of 1,000 to 5,000 denier, plies of 1 to 3, twist number of 200 to 500 TPM, and excellent morphological stability and modulus and tire process as described above. It may show the uniformity improvement of tire shape during vulcanization.

As described above, since the tire cord of the present invention can minimize the excellent shape stability and thermal deformation at high temperature, while maintaining a uniform tire appearance without a separate post-cure inflation (PCI) process, Even if the temperature and load increase sharply, deformation hardly occurs and high modulus can be expressed after the tire forming process.

Therefore, when the tire cord of the present invention is used, the tire cord and the tire including the tire can be prevented from being deformed even when the speed of the vehicle is suddenly increased, thereby further improving the controllability and riding comfort of the vehicle together with the high-speed running performance of the tire. You can.

Hereinafter, preferred examples are provided to help understanding of the present invention, but the following examples are merely to illustrate the present invention, and the scope of the present invention is not limited to the following examples.

Example  One

A PET polymer having an intrinsic viscosity of 1.05 dl / g was used, and a non-drawn yarn was prepared by melt spinning and cooling the PET polymer according to a conventional method at a spinning speed of 3,800 m / min under a spinning tension of 0.86 g / d. These undrawn yarns were drawn, heat-set and wound at a draw ratio of 1.54 to prepare PET drawn yarns.

At this time, the PET stretched yarn was 7.1 kg of yarn strength, the yarn core (@ 4.5kg) was 5.2%, yarn dry heat shrinkage was 7.6%.

PET drawn in Example 1 by twisting two strands of Z-bonded yarns with 430 TPM in the same twisted number of strands of S yarn with the same twisted number by immersing and passing through RFL adhesive solution, drying, and heat-treating them. Tire cords were prepared.

The RFL adhesive solution composition and drying and heat treatment conditions used a conventional PET cord treatment conditions, but the heat treatment process was performed at 248 ℃ for 1 minute 30 seconds to ensure better shape stability.

Example  2-7 and Comparative example  1-3

As shown in Table 1, the same as in Example 1, except that the spinning speed, the radial tension, the draw ratio, or the intrinsic viscosity conditions or tire cord manufacturing process in the manufacturing process of PET stretched yarn was changed PET tire cords were prepared by the method.

Condition Example Comparative example One 2 3 4 5 6 7 One 2 3 Spinning speed (m / min) 3800 4000 3800 3800 4200 4500 3800 3000 4800 3800 Radial tension (g / d) 0.86 0.92 0.82 0.91 0.98 1.07 0.86 0.52 1.17 0.86 Stretching cost 1.54 1.46 1.24 1.24 1.39 1.3 1.54 1.8 1.22 1.54 Intrinsic viscosity (dl / g) 1.05 1.05 0.9 1.2 1.05 1.05 1.05 1.05 1.05 1.05 Yarn strength (kg) 7.1 6.5 6.9 7.3 6.3 6.0 7.1 8.2 5.0 7.1 Yarn weight : 4.5 kg
(%) 5.2 5.4 5.2 5.3 5.7 6.2 5.2 4.5 6.7 5.2 Yarn yarn cutting (%) 15.3 19.1 14.9 16.2 20.3 22.5 15.3 11.2 23.5 15.3 Yarn Heat Shrinkage
(%) 7.6 7.1 7.3 7.9 6.5 6.2 7.6 12.3 5.8 7.6 Training (TPM) 430 430 430 430 430 430 260 430 430 430 Heat treatment temperature (캜) 248 248 248 248 248 248 248 248 248 235

The physical properties of the PET tire cords prepared according to Examples 1 to 7 and Comparative Examples 1 to 3 were measured by the following method, and the measured physical properties are summarized in Table 2 below.

1) strong and elongation measurement

After leaving the specimen in the standard state (25 ℃, 65 RH%) for more than 24 hours at the equilibrium state to reach the water equilibrium state, in accordance with the specification of ASTM D885 using an Instron low speed extension type tensile tester Cutting strength (g / de) and elongation at break (%) were measured under 250 mm sample length, 300 mm / min tensile speed, and 0.05 g / de loading conditions.

2) Dry heat shrinkage rate measurement

Dry shrinkage was measured for 10 minutes under a load of 0.01 g / de at a temperature of 180 ° C. using a shrinkage behavior tester (MK-V equipment manufactured by TestRite, UK).

Condition Example Comparative example One 2 3 4 5 6 7 One 2 3 Strong (g / de) 14.1 13.0 13.9 14.5 12.5 12.1 14.3 15.1 10.0 14.0 Chong (%) @ 4.5kg 4.2 4.1 4.2 4.3 4.0 4.0 4.1 4.5 4.3 4.2 Doubt (%) 17.5 20.3 17.2 17.7 22.5 23.7 17.0 16.4 26.3 17.5 Dry heat shrinkage (%) 1.3 1.1 1.2 1.5 1.0 0.9 1.4 3.2 0.7 1.7 After dry heat shrink
Chong (%) @ 4.5kg 5.9 5.6 5.8 6.4 5.4 5.2 6.1 8.4 5.6 6.6 After dry heat shrink
Neutral fluctuation (△%) 1.7 1.5 1.6 2.1 1.4 1.2 2.0 3.9 1.3 2.4

Manufacturing example  1 ~ 7 and comparison Manufacturing example  1-3

P195 / 70R14 tires were manufactured without a separate PCI process using PET tire cords prepared according to Examples 1 to 7 and Comparative Examples 1 to 3, except that the PCI process was not performed. The usual conditions were followed.

The physical properties of the P195 / 70R14 tires thus prepared were measured by the following method, and the measured physical properties are summarized in Table 3 below.

1) Bead Width Measurement

Each tire produced was cured at 177 ° C. for 10 minutes. After this, the cured tire was left without factory under factory condition (25 ° C., 65 RH%) without PCI for 24 hours, and then both beads of the tire as shown in FIG. 1 in an air-expanded state under room temperature conditions. The distance between (9) and the bead width was measured.

2) durability evaluation

Durability evaluation was carried out by applying ECER-30 regulation, which is the European tire durability standard test method. The durability progress results are expressed in time until the tire breakage.

Condition Manufacturing example Comparative Production Example One 2 3 4 5 6 7 One 2 3 Bead width (mm) 109 110 110 108 111 111 109 95 111 102 Durability rating (min) 102 91 105 107 92 94 101 95 65 98

As shown in Table 3, the tires of Preparation Examples 1 to 7 manufactured from PET tire cords manufactured from Examples 1 to 7 having low shrinkage and high modulus at high temperature have a bead width of 108 to 111 mm. It can be seen that the bead width is maintained without the PCI process and has excellent characteristics such as shape stability and uniformity. In addition, the tires of Manufacturing Examples 1 to 7 have a durability evaluation result of 91 min to 107 min, that is, all of them exceeding 1 hour and 30 minutes, it can be seen that excellent mechanical properties can be secured in actual use by automobile mounting or the like.

On the other hand, the tires of Comparative Preparation Examples 1 and 3 manufactured using the PET tire cords of Comparative Examples 1 and 3 had a bead width of less than 103 mm and were manufactured by shrinking the carcass cord after a tire curing process. It can be seen that the shape stability and uniformity of the remarkably inferior, and thus, it can be seen that problems such as high-speed running performance and adjustability of the tire may occur.

In addition, the tire of Comparative Preparation Example 2 manufactured using the PET tire cord of Comparative Example 2 was similar in the bead width measurement value, but it was confirmed that the durability evaluation results are remarkably inferior as PET tire cord strength is lowered. If the durability evaluation is not so good, there is a problem that may cause a very large risk, such as tire damage.

1 is a partial cutaway perspective view showing a configuration of a general tire.

Claims (10)

Strong 6.0-7.5 g / de under 2.25 g / de load, 3.8% to 4.5% in the middle body, 15% to 25% in the elongated body, Polyethylene terephthalate tire cord having a dry heat shrinkage of 1.5% or less after heat treatment at 0.01 ° C./de for 10 minutes at 180 ° C. The method of claim 1, Polyethylene terephthalate tire cord having a lean body of 6.5% or less under 2.25 g / de load after heat treatment at 0.01 ° C./de load at 180 ° C. for 10 minutes. The method of claim 1, Polyethylene terephthalate tire cord with heat transfer value under 2.25 g / de load not more than 2.0% after heat treatment at 0.01 g / de load at 180 ° C. for 10 minutes. The method of claim 1, Polyethylene terephthalate tire cord having a total fineness of 1,000 to 5,000 denier, 1 to 3 plies, and 200 to 500 TPM. 5. The method according to any one of claims 1 to 4, Polyethylene terephthalate tire cord that is a code for carcass. A pneumatic tire comprising the tire cord according to any one of claims 1 to 4. The method of claim 6, The pneumatic tire applying the cord to the carcass. Melting and spinning a polymer including 90 mol% or more of polyethylene terephthalate to prepare polyethylene terephthalate undrawn yarn having a crystallinity of 25% or more and an amorphous orientation index of 0.15 or less; Drawing a polyethylene terephthalate non-drawn yarn under a drawing ratio of 1.3 to 1.7 to prepare a polyethylene terephthalate drawn yarn; Plying the polyethylene terephthalate stretched yarn and immersing in an adhesive to prepare a dip cord; And Heat-treating the dipcode at 245 ° C. or higher; A method for producing a polyethylene terephthalate tire cord according to any one of claims 1 to 4, comprising a. 9. The method of claim 8, Wherein said polymer has an intrinsic viscosity of 0.8 to 1.3 dl / g. 9. The method of claim 8, Melt spinning of the polymer is a method of producing a polyethylene terephthalate tire cord proceeds with a spinning tension of 0.85 g / d or more and spinning speed of 3,800 to 4,500 m / min.

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