KR20090104613A - Polyethyleneterephthalate tire cord, and tire comprising the same - Google Patents

Abstract

PURPOSE: Polyethylene terephthalate tire cord and tire including the same are provided to offer stable high-speed driving without deformation of the cord for a cap ply even though the load applied on the tire cord is changed seriously. CONSTITUTION: Polyethylene terephthalate tire cord includes a shrinkage rate of 50% or greater when the load of 20g/cord is applied, comparing to the shrinkage rate of the load of 226g/cord at the temperature of 180 °C. The polyethylene terephthalate tire cord has the shrinkage rate of 60% or greater when the load of 20g/cord is applied in 180 °C comparing to the load of 226g/cord in the same temperature.

Description

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

The present invention relates to polyethylene terephthalate tire cords and pneumatic tires comprising the same. More specifically, the present invention is excellent in shape stability according to the external load change, it can be preferably applied to the cap ply cord of the pneumatic tire, etc., to suppress the deformation of the tire to improve the adjustment or ride comfort of the vehicle The present invention relates to a polyethylene terephthalate tire cord that can be made, and to a pneumatic tire comprising the same.

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.

Currently commonly used materials for the cord include rayon, nylon, polyester, steel, and aramid, and rayon and polyester are used for body ply (also called carcass) (6 in FIG. 1), and nylon is mainly used. In the cap ply (4 in FIG. 1), and 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 to be in contact with the road surface to provide the necessary frictional force for braking and driving, to have good abrasion resistance, to withstand external shocks, and to generate little heat.

Body Ply (or Carcass) (6): A layer of cord inside the tire, which must support loads, withstand impacts, and be resistant to fatigue during rolling.

Belt (5): Located between the body plies, consisting of steel wires in most cases 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 part of the shoulder (2) from the bead (9) and serves to protect the body ply (6) inside.

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

Inner Liner (7): Located on the inside of the tire instead of the tube, this 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): A triangular rubber filler used to minimize the dispersion of beads, to mitigate external impacts, to protect the beads, and to prevent the ingress of air during molding.

Recently, the development of tires suitable for high-speed driving is required with the advancement of passenger cars. Accordingly, high-speed driving stability and high durability of tires are recognized as very important characteristics. In addition, in order to satisfy the characteristics, the performance of the cap ply cord material is more important than ever.

The steel belts present in the tire are generally arranged in an oblique direction, but at high speeds, such steel belts tend to move in the circumferential direction by centrifugal force. At this point, the end of the pointed steel belt breaks rubber or generates cracks. Doing so may cause separation between belt layers and deformation of tire shape. Cap fly acts to increase the high speed durability and driving stability by catching the movement of the steel belt to suppress the separation between layers and form deformation of the tire.

In general, the cap fly cord is mainly made of nylon 66. By the way, in the case of such a nylon 66 code, it can exhibit an effect of suppressing the movement of the belt by wrapping the steel belt by expressing a high shrinkage force at a curing temperature of 180 ℃, but due to its low form stability, part of the tire and car's own load There is a disadvantage that the deformation may occur, which may cause a rattling while driving.

Moreover, as the nylon 66 cord has low shape stability, when the traveling speed of the vehicle is changed so that the load applied to the nylon 66 cord is changed, the appearance shape can be easily deformed and the tire can be deformed, thereby adjusting the vehicle. You may not be able to feel your sex or ride comfort.

In comparison, PET High Modulus Low Shrinkage (HMLS) fiber, which is widely used as a general polyethylene terephthalate (PET) fiber or an industrial fiber, has better shape stability than nylon 66, but has a lower shrinkage stress and a lower cappla. It is difficult to use preferably as a utilization code. Moreover, since these general PET fibers or HMLS fibers also do not have sufficient form stability, when the vehicle's traveling speed is changed and the load applied to the cords made of these materials changes, the appearance form can be relatively easily deformed to deform the tire. . Therefore, even when a cord made of these materials is used as a wet ply cord, the appearance of the cord may be relatively easily deformed and the tire may be deformed as the running speed of the vehicle is changed and the load applied to the cord is changed. The adjustment or ride comfort of the car is not enough.

Accordingly, the present invention is to provide a polyethylene terephthalate tire cord not only excellent in shape stability according to the external load changes, but also exhibits improved shrinkage stress.

In addition, the present invention is to provide a pneumatic tire including the tire cord, it is possible to improve the adjustability or ride comfort of the vehicle without deformation.

The present invention provides a polyethylene terephthalate tire cord having a shrinkage rate of 226 g / cord at 180 ° C. being 50% or more of a shrinkage rate of 20 g / cord at the same temperature.

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

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

The polyethylene terephthalate (hereinafter referred to as "PET") tire cord of the present invention has a shrinkage rate when a load of 226 g / cord is applied at 180 ° C., and a shrinkage rate when a load of 20 g / cord is applied at the same temperature. It is more than%.

At this time, the shrinkage (%) of the PET tire cord is a certain load (for example, 226g / cord (2000d) or 20g / cord using a shrinkage behavior tester (eg, Figure 2) according to the test method of ASTM D4974) After fixing the tire cord to be measured under a load (for example, 2000d) or the like, it can be determined, for example, by a value measured for 2 minutes under a constant temperature of 180 ° C.

The PET tire cord of the present invention exhibits a shrinkage rate that does not change significantly even if the load applied to itself changes significantly according to an external environment change. In particular, it has been found that the tire cord of the present invention has a small rate of change in shrinkage rate due to a change in load applied to itself, compared to a tire cord made of fibers such as nylon 66, general PET or HMLS. That is, the tire cord of the present invention not only has a large shrinkage rate but also a small change rate of the shrinkage rate due to the change in load, so that the deformation of the appearance form is suppressed even when the traveling speed of the vehicle is changed and the load applied to the tire cord is changed. (I.e., have good shape stability) and the tires containing them are not easily deformed. Therefore, the tire cord of the present invention can be applied to a cap ply cord or the like to improve the controllability or high-speed driving and ride comfort of the vehicle.

In addition, the tire cord of the present invention is 60% or more, preferably 70% or more of the shrinkage stress when a load of 226g / cord at a load of 180g / cord at a temperature of 20g / cord at the same temperature The shrinkage stress at the load of 20g / cord at 180 ° C may be 0.15g / d or more, and the shrinkage stress at the load of 226g / cord at 180 ° C is 0.09g / d or more Can be The tire cord of the present invention may have a shrinkage behavior index of 0.04 (g / d) /% or more defined by Equation 1 below when a load of 226 g / cord is applied at 180 ° C .:

[Calculation 1]

Shrinkage Behavior Index = Shrinkage Stress (g / d) / Shrinkage Rate (%)

At this time, the shrinkage stress (g / d) of the PET tire cord is a certain load (for example, 226g / cord (2000d) using a shrinkage behavior tester (eg, Figure 2) according to the test method of ASTM D5591 Alternatively, after fixing the tire cord to be measured with a load such as 20 g / cord (2000d) or the like, it may be determined, for example, by a value measured for 2 minutes under a constant temperature of 180 ° C. And, the shrinkage behavior index is measured under a certain load and temperature (for example, under a load of 180 ℃ and 226g / cord), the shrinkage measured by the test method of ASTM D4974 already described above and the test method of ASTM D5591 The shrinkage stress can be obtained by substituting the above formula (1).

As such, the tire cords of the present invention not only have excellent morphological stability, but also exhibit higher shrinkage stresses compared to nylon 66 cords, and these high shrinkage stresses can be maintained at any load on the tire cords. . In addition, the tire cord may exhibit an excellent shrinkage behavior index due to high shrinkage stress and low shrinkage rate. Therefore, the tire cord can be preferably applied as a cap fly cord, because, for example, the steel belt can be well wrapped in the pneumatic tire to effectively suppress the movement of the belt.

On the other hand, the tire cord of the present invention is not particularly limited in form, it may have a form equivalent to the conventional cap fly code. More specifically, the tire cord of the present invention has a total fineness of 1000 to 5000 denier (d) per cord, the number of plies is 1 to 3, and the number of twists is 200 to 500 TPM according to the form of a conventional cap ply cord. It may have the form of a dipcode.

In addition, the tire cord has a strength of 5 to 8 g / d, an elongation of 1.5 to 5.0%, preferably 2.0 to 5.0% (measured at 4.5 kg load), a stretch of 10 to 25% and a 0.5 to 5.0%, preferably Preferably a shrinkage of 2.0 to 5.0% (177 ° C., 30 g, 2 min). As the tire cord exhibits various physical properties such as strength or elongation in this range, it can be preferably applied as a capfly cord.

The tire cord may be applied as a cap ply cord of the pneumatic tire. The tire to which the cap ply cord is applied has a different driving speed, so that the load applied to the cap ply cord is largely changed, but the appearance of the cap ply cord is not easily deformed and the tire itself is not easily deformed. Therefore, the tire can improve the controllability or ride comfort of the vehicle. In addition, since the tire cord has various physical properties such as high shrinkage stress, strength, or elongation, which can be preferably used as a capfly cord, the tire to which the capfly cord is applied can exhibit stable high-speed driving performance.

In the above description, the tire cord of the present invention is mainly assumed to be used as a cap ply cord, but the use of the tire cord of the present invention is not limited thereto and may be used for other purposes such as body ply cord. Of course it can.

On the other hand, the tire cord of the present invention melt-spun PET to produce a non-drawn yarn, stretch the non-drawn yarn to prepare a stretched yarn, and after the twisted yarns are twisted yarns immersed in an adhesive to form a deep cord tire cord It may be prepared by the method of preparation. The specific conditions of the respective steps or the method of proceeding may be directly or indirectly reflected in the physical properties of the final manufactured tire cord, thereby producing the tire cord of the present invention 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 PET tire cord of the present invention can be produced with a smaller rate of change of shrinkage according to load change.

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 this high degree of crystallinity, PET drawn yarns and tire cords made from the PET non-drawn yarns can 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 greatly 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 low shrinkage and high shrinkage stress using PET non-drawn yarns exhibiting such high crystallinity and low amorphous orientation index, and furthermore, excellent physical properties according to the present invention. It has been found that it is possible to provide PET tire cords with.

When explaining the tire cord manufacturing method of the present invention for 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 1.2 g / d. In addition, for example, the rate of melt spinning the PET can be adjusted to 3800 to 5000 m / min, preferably 4000 to 4500 m / min can be adjusted.

As a result of the melt spinning process of PET under such a 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 slide during the spinning process to form a fine network structure. It has been found that PET non-drawn yarns can be obtained that satisfy the crystallinity and amorphous orientation index described above. However, adjusting the spinning speed to 5000 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 yarn, chips having an intrinsic viscosity of 0.8 to 1.3 and containing 90 mol% or more of polyethylene terephthalate can be melt spun as the PET.

As described above, in the manufacturing process of the PET non-stretched yarn, conditions of higher spinning tension and optionally high spinning speed can be imparted. In order to proceed the spinning step under these conditions, the intrinsic viscosity of the chip Is preferably 0.8 or more. However, it is preferable that the intrinsic viscosity is 1.3 or less in order to prevent the molecular chain cutting and the pressure increase due to the amount of discharge from 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. That is, in order to reduce the possibility of trimming due to interference between each other during the generation of trimming and cooling during spinning, the denier of the monofilament should be 2.0 denier or more, and the fineness of the monofilament in order to give a 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 is preferably 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. As a result, it is possible to more easily produce a tire cord exhibiting various physical properties according to the present invention.

On the other hand, after producing the PET non-drawn yarn that satisfies the above-described crystallinity and amorphous orientation index through this spinning step, the non-drawn yarn is drawn to prepare a drawn yarn. At this time, the stretching step may proceed under a draw ratio condition of 1.0 ~ 1.55. The PET non-drawn yarn has advanced crystal regions, and amorphous chains also have a low degree of orientation and form a fine network. Therefore, when the drawing process is carried out under a high draw ratio condition of more than 1.55, cutting or mousse may occur in the drawn yarn, 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. However, under an elongation ratio of 1.0 or more, for example, since it is possible to manufacture a PET tire cord having a strength of 6 g / d or more suitable for application to a capply cord or the like, the stretching process may be preferably performed under an elongation ratio of 1.0 to 1.55. Can be.

 After the drawn yarn is manufactured, the drawn yarn is fused and then immersed in an adhesive to prepare a dip cord. Such a twisted yarn process and an immersion process are in accordance with the conventional PET tire cord manufacturing process conditions and methods.

The tire cords thus prepared may have a form with a total fineness of 1000 to 5000 denier, plies of 1 to 3, twist of 200 to 500 TPM, and excellent overall physical properties as described above, for example, lower It can show the rate of change of shrinkage by load, high shrinkage stress and high strength.

As described above, the tire cord of the present invention not only shows a high shrinkage stress of nylon 66 or more, but also shows a good change in shrinkage rate due to a change in load applied to itself. Therefore, such a tire cord can be preferably applied as a cap ply cord of a pneumatic tire.

In addition, even if the tire to which the cap ply cord is applied is changed in the traveling speed of the vehicle so that the load applied to the cap ply cord is greatly changed, the cap ply cord is not deformed well, and thus the tire itself is not easily deformed and more stable. It enables high speed driving. Therefore, the tire can improve the controllability or ride comfort of the vehicle.

Hereinafter, the configuration and effects of the present invention will be described in more detail with reference to specific examples and comparative examples in order to help understanding of the present invention. However, the following examples are only intended to more clearly understand the present invention, and the present invention is not limited to the following examples.

Example  One

A PET polymer having an intrinsic viscosity of 1.05 was used, and a non-drawn yarn was prepared by melt spinning and cooling the PET polymer according to a conventional manufacturing method at a spinning speed of 4500 m / min under a spinning tension of 1.15 g / d. These undrawn yarns were drawn, heat-set and wound at a draw ratio of 1.24 to prepare PET drawn yarns.

PET twisted yarn of total fineness 1000 denier manufactured as described above, twisted and twisted two strands of low-stranded yarn Z-bonded with 430 TPM with S-strand of the same twist number, immersed and passed through RFL adhesive solution, and then dried and heat treated. PET tire cord was prepared.

The composition and drying and heat treatment conditions of the RFL adhesive solution were the same as those of conventional PET cords.

Example  2

During the manufacturing process of PET stretched yarn, unstretched yarn was prepared by melt spinning and cooling the PET polymer at a spinning speed of 4000 m / min under a spin tension of 0.92 g / d to draw, heat set, and stretch the undrawn yarn to a draw ratio of 1.46. The PET tire cord of Example 2 was prepared in the same manner as in Example 1 except that the PET stretched yarn was wound up.

Example  3-6

During the manufacturing process of PET stretched yarn, PET stretched yarn was prepared in the same manner as in Example 1 except that the spinning speed, the radial tension, the draw ratio or the intrinsic viscosity conditions were changed as shown in Table 1 below. PET stretched yarn was spliced together in the same manner as in Example 1, immersed in an adhesive solution, and then dried and heat-treated to prepare PET tire cords of Examples 3 to 6, respectively.

TABLE 1

Condition Example 3 Example 4 Example 5 Example 6 Spinning speed (m / min) Same as Example 1 Same as Example 1 3800 4800 Radial tension (g / d) 0.98 1.23 0.86 1.19 Elongation ratio Same as Example 1 Same as Example 1 1.54 1.16 Intrinsic viscosity 0.9 1.2 Same as Example 1 Same as Example 1

Example  7

A PET stretched yarn was prepared in the same manner as in Example 1, except that two twisted strands of Z-stranded at 260 TPM were twisted and twisted with S strands having the same twist number using the PET stretched yarn. The tire cord of Example 7 was prepared by the method.

Example  8

A PET stretched yarn was prepared in the same manner as in Example 2, except that two twisted strands of Z-stranded at 260 TPM were twisted and twisted with S strands having the same twist number using this PET stretched yarn. The tire cord of Example 8 was prepared by the method.

Example  9

A PET stretched yarn was prepared in the same manner as in Example 1, except that 2 strands of lower-twisted yarns Z-bonded at 360 TPM were twisted and twisted to S-strains of the same twist number using the PET stretched yarns. The tire cord of Example 9 was prepared by the method.

Example  10

A PET stretched yarn was prepared in the same manner as in Example 2, except that 2 strands of lower-twisted yarns Z-bonded at 360 TPM were twisted and twisted with S-yeons of the same twist number using the PET stretched yarns. The tire cord of Example 10 was prepared by the method.

Comparative Example 1 (Production of Tire Cord Using High Elasticity Low Shrinkage (HMLS) Fiber)

PET polymer with an intrinsic viscosity of 1.05 for the production of undrawn yarn was melt-spun at a spinning speed of 3000 m / min under a radial tension of 0.52 g / d, and an undrawn yarn was drawn at a draw ratio of 1.8 to produce a drawn yarn. The tire cord of Comparative Example 1 was prepared in the same manner as in Example 1.

Comparative Example 2 (Preparation of Tire Cord Using Nylon 66 Fiber)

According to a conventional manufacturing method, nylon 66 polymer having a relative viscosity of 3.3 is melt-spun and cooled at a spinning speed of 600 m / min to prepare an undrawn yarn, and the undrawn yarn is drawn, heat-set and wound at a draw ratio of 5.5 to nylon 66 fibers. The drawn yarn was prepared.

The twisted yarn of total fineness 840 denier manufactured as described above is twisted and twisted with 2 strands of lower twisted yarn Z-bonded with S T of the same twisted number, and immersed and passed through RFL adhesive solution, followed by drying and heat-treating nylon 66 fibers. The tire cord of Comparative Example 2 used was prepared.

The composition and drying and heat treatment conditions of the RFL adhesive solution were the same as those of conventional nylon 66 cord.

First, the crystallinity and amorphous orientation index (AOF) of PET undrawn yarn obtained in Examples 1 to 6 and Comparative Example 1 were measured by the following method, and the measurement results are summarized in Table 2 below (Examples 7 to 10, however. Since the PET non-drawn yarn and the drawn yarn of Example 1 or 2 were used as they are, the crystallinity and amorphous orientation index of the undrawn yarn were not separately measured.):

Crystallinity: After preparing a density gradient tube using CI ₄ , n-heptane, the density was measured and the crystallinity was measured using the following formula.

PET crystallinity (%) =

(At this time, PET is a constant of ρ _a = 1.336 and ρ _c = 1.457.

-AOF: AOF was calculated by the following equation using the birefringence measured using a polarizing microscope and the crystal orientation index (COF) measured from XRD.

AOF = (birefringence-crystallinity (%) * 0.01 * crystal orientation index (COF) * 0.275) / ((1-crystallinity (%) * 0.01) * 0.22)

TABLE 2

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Crystallinity (%) 36 30 34 36 28 38 9 AOF 0.009 0.093 0.015 0.012 0.120 0.002 0.245

For the tire cords prepared according to Examples 1 to 10 and Comparative Examples 1 and 2, shrinkage stress and shrinkage were measured by the following method using the shrinkage behavior tester of FIG. 2, and according to each load applied to the tire cord. The shrinkage stress is shown in Table 3, and the shrinkage rate is shown in Table 4.

-Shrinkage stress (g / d): After fixing the code with a constant load using the shrinkage behavior tester, in measuring the shrinkage stress for 2 minutes under a constant temperature of 180 ℃, the load on the code 20g / cord, 60g The respective shrinkage stresses were measured at / cord, 113g / cord, 160g / cord and 226g / cord.

TABLE 3

Unit: g / d 20g / cord 60g / cord 113g / cord 160g / cord 226 g / cord Example 1 0.312 0.307 0.310 0.308 0.241 Example 2 0.281 0.276 0.284 0.280 0.219 Example 3 0.301 0.282 0.256 0.247 0.205 Example 4 0.332 0.322 0.329 0.314 0.250 Example 5 0.247 0.260 0.245 0.226 0.194 Example 6 0.324 0.324 0.328 0.321 0.268 Example 7 0.317 0.314 0.311 0.307 0.246 Example 8 0.298 0.302 0.287 0.265 0.226 Example 9 0.309 0.312 0.312 0.312 0.253 Example 10 0.287 0.286 0.297 0.281 0.219 Comparative Example 2 0.123 0.076 0.062 0.065 0.004 Comparative Example 3 0.261 0.251 0.205 0.231 0.207

-Shrinkage rate (%): 20g / cord, 60g / cord, 113g / cord, 160g / cord for the load applied to the cord in measuring shrinkage rate under a constant load for 2 minutes under a constant temperature of 180 ° C using the shrinkage behavior tester. And 226 g / cord, each shrinkage was measured.

TABLE 4

unit: % 20g / cord 60g / cord 113g / cord 160g / cord 226 g / cord Example 1 2.8 2.5 2.1 1.8 1.5 Example 2 2.7 2.4 1.9 1.8 1.6 Example 3 2.5 2.4 2.1 1.8 1.6 Example 4 3.4 3.0 2.9 2.4 2.1 Example 5 3.1 2.8 2.5 2.3 2.3 Example 6 2.4 2.3 1.8 1.6 1.4 Example 7 2.6 2.3 2.2 1.8 1.7 Example 8 2.6 2.4 2.3 1.8 1.7 Example 9 2.6 2.5 2.1 2.0 1.7 Example 10 2.7 2.5 2.3 2.1 1.8 Comparative Example 2 3.0 2.2 1.3 1.1 0.7 Comparative Example 3 7.2 6.0 4.3 4.0 3.5

The shrinkage behavior index for each load was calculated from the measured shrinkage rate and the shrinkage stress, and the shrinkage behavior index according to the load change applied to the cord is summarized in Table 5 below.

TABLE 5

Unit: (g / d) /% 20g / cord 60g / cord 113g / cord 160g / cord 226 g / cord Example 1 0.11 0.12 0.15 0.17 0.16 Example 2 0.10 0.12 0.15 0.16 0.14 Example 3 0.12 0.12 0.12 0.14 0.13 Example 4 0.10 0.11 0.11 0.13 0.12 Example 5 0.08 0.09 0.10 0.10 0.08 Example 6 0.14 0.14 0.18 0.20 0.19 Example 7 0.12 0.14 0.14 0.17 0.15 Example 8 0.12 0.13 0.13 0.15 0.13 Example 9 0.12 0.13 0.15 0.16 0.15 Example 10 0.11 0.11 0.13 0.13 0.12 Comparative Example 2 0.12 0.03 0.05 0.06 0.01 Comparative Example 3 0.04 0.04 0.05 0.06 0.06

Referring to Tables 3 and 4 above, the tire cords of Examples 1 to 10 manufactured from PET non-drawn yarn exhibiting high crystallinity and low amorphous orientation index maintain high shrinkage stress and low shrinkage regardless of any load applied thereto. It is confirmed. On the other hand, the tire cord of Comparative Example 1 was confirmed that the shrinkage stress is significantly lowered as the load applied to itself changes, and the tire cord of Comparative Example 2 is confirmed that the shrinkage ratio changes significantly with the change of the load. do.

In addition, referring to Table 5, the tire cords of Examples 1 to 10 maintain a high shrinkage stress and a low shrinkage rate even if any load is applied to itself, thereby maintaining a high shrinkage behavior index. It is confirmed that the tire cord of 2 greatly changes the shrinkage stress, shrinkage rate or shrinkage behavior index as the load on the tire itself changes.

Thus, the tire cords of Examples 1 to 10 exhibit high shrinkage stress and low shrinkage ratio, as well as the shrinkage stress or shrinkage rate or the shrinkage behavior index calculated therefrom can be maintained at any load, so that the steel belt can be well maintained in the tire. It is confirmed that the wrapping can effectively suppress the movement of the belt and can be preferably applied as a capfly code.

In addition, the tire cords of Examples 1 to 10 exhibit high form stability, and even if the traveling speed of the vehicle is changed so that the load applied to the tire cord is changed, the deformation of the external form is suppressed and the tire including the tire is not easily deformed. This is confirmed. Therefore, the tire cords of Examples 1 to 10 may be applied as cap ply cords of pneumatic tires to enable stable high-speed driving and to improve vehicle maneuverability or ride comfort.

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

Figure 2 is a schematic diagram of the configuration of the shrinkage behavior tester used for the measurement of shrinkage and shrinkage stress.

Claims (10)

Polyethylene terephthalate tire cord with a shrinkage rate of 226 g / cord at 180 ° C. being 50% or more of a shrinkage rate when 20 g / cord is loaded at the same temperature. The method of claim 1, Polyethylene terephthalate tire cord having a shrinkage stress when a load of 226 g / cord is applied at 180 ° C. is 60% or more of a shrinkage stress when a load of 20 g / cord is applied at the same temperature. The method of claim 2, Polyethylene terephthalate tire cord with a shrinkage stress of at least 0.15 g / d when subjected to a load of 20 g / cord at 180 ° C. The method of claim 2, Polyethylene terephthalate tire cord with a shrinkage stress of at least 0.09 g / d when subjected to a load of 226 g / cord at 180 ° C. The method of claim 1, Polyethylene terephthalate tire cord having a shrinkage behavior index of 0.04 (g / d) /% or more, defined by the following formula 1 when loaded at 226 g / cord at 180 ° C: [Calculation 1] Shrinkage Behavior Index = Shrinkage Stress (g / d) / Shrinkage Rate (%) The method of claim 1, Polyethylene terephthalate tire cord with strength of 5 to 8 g / d, 1.5 to 5.0% of core (@ 4.5 kg) and 10 to 25% of elongation and 0.5 to 5.0% of shrinkage (177 ° C., 30 g, 2 min). The method of claim 1, Polyethylene terephthalate tire cord having a total fineness of 1000 to 5000 denier, 1 to 3 plies, and 200 to 500 TPM. The method according to any one of claims 1 to 7, Polyethylene terephthalate tire cord as a capfly cord. A pneumatic tire comprising the tire cord according to any one of claims 1 to 7. The method of claim 9, Air-injected tire applying the cord to the cap ply.

Images