KR101381970B1 - Poly(ethyleneterephthalate) tire cord, and tire comprising the same - Google Patents

Abstract

The present invention relates to a polyethylene terephthalate tire cord exhibiting excellent form stability and a tire comprising the same.
The polyethylene terephthalate tire cord satisfies the difference between the strain at the time of applying a constant load after repeating the tensile test under predetermined conditions and the initial strain at the time of applying the constant load before the tensile test.

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 tires. More specifically, the present invention relates to a polyethylene terephthalate tire cord and a tire comprising the same, which exhibits excellent form stability in the environment of use of the tire.

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 currently 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 a cap. In the ply (4 in FIG. 1), and steel and aramid are mainly used in the tire belt portion (5 in FIG. 1).

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

Tread (1): It is a part that comes into contact with the road surface, it should provide friction force necessary for braking and driving, good abrasion resistance, able to withstand external impact, and 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 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 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, development of a tire suitable for high-speed driving is required according to an advanced automobile, and accordingly, it is recognized that stability and high durability are very important characteristics during high-speed driving of the tire. In addition, in order to satisfy the characteristics, the performance of the cap ply cord material is important. In addition, since the body fly in the tire, that is, carcass, is a key reinforcing material that supports the overall load of the vehicle and maintains the shape of the tire, the performance of such a body fly cord material is equally important.

First, the cap fly serves to minimize the movement of the steel belt in the tire. More specifically, the steel belt existing in the tire is generally disposed in an oblique direction, but at high speeds, such a steel belt tends to move circumferentially by centrifugal force, at which point the end of the pointed steel belt breaks the rubber. Or cracking, causing separation between the belt layers and deformation of the 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 cord, 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 the modulus and shape stability is low in the process of driving and stopping the vehicle Partial deformation may occur due to a sudden temperature change in the tire or a self-load of the tire and the vehicle, which may increase the movement of the belt and cause breakage. In addition, since the environment in which the tire is used may cause the tire to be deformed continuously and repeatedly, the cap fly cord may serve to fix the belt without deformation even under the continuous and repetitive loads applied in such use environment. There is a need.

Accordingly, the present invention is to provide a polyethylene terephthalate tire cord that can be preferably used as a cap ply or body ply cord, etc. showing a better form stability.

The present invention also provides a tire that exhibits excellent stability and safety, including the polyethylene terephthalate tire cord.

The present invention provides a strain at a load of 1 kgf at 4 ° C. and a load of 2 g / de at 20 ° C. and / or 120 ° C., followed by 4 repeated tensile tests to remove and recover the load, and 1 kg f before the tensile test. A polyethylene terephthalate tire cord having a difference in initial strain of 0.5% or less when a load is applied is provided.

The present invention also provides a strain at the time of applying a load of 1 kgf after four repeated tensile tests that stretch and recover by 4% in the longitudinal direction at 20 ° C. and / or 120 ° C., and a load of 1 kgf before the tensile test. Provided is a polyethylene terephthalate tire cord having a difference in initial strain of 0.6% or less when is added.

The present invention also provides a pneumatic tire comprising the polyethylene terephthalate 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, a polyethylene terephthalate (hereinafter referred to as "PET") tire cord is provided. One embodiment of such a PET tire cord is repeated four times a tensile test at room temperature and / or high temperature, for example, 20 ° C. and / or 120 ° C., which is stretched by applying a load of 2 g / de and then removing and restoring the load. The difference between the strain at 1 kgf and the initial strain at 1 kgf before the tensile test is 0.5% or less, preferably 0.4% or less, and more preferably 0.2 to 0.4%. Can be.

In addition, another embodiment of the PET tire cord, after repeated four times the tensile test to stretch and recover by 4% in the longitudinal direction at room temperature and / or high temperature, for example, 20 ℃ and / or 120 ℃ The difference between the strain when a load of 1 kgf is applied and the initial strain when a load of 1 kgf is applied before the tensile test can be 0.6% or less, preferably 0.4 to 0.6%.

As will be described in more detail in the following examples, the difference between the strain and the initial strain can be measured and calculated by the following method.

First, at a constant temperature (at room temperature or high temperature described above), the tensile test for stretching and recovering the tire cord is repeated four times. At this time, the tensile test can be carried out using a universal tensile tester according to the standards of ASTM D885, etc., by applying a constant load (for example, 2g / de) to the tire cord to stretch and recover, or a constant strain rate (for example For example, it may proceed in a way of stretching in the longitudinal direction by 4%) and then recovering. After four iterations of this tensile test, a load-elongation curve can be derived by applying a load to the tire cord, and the strain of the tire cord when a 1 kgf load is applied under the load-elongation curve can be obtained. The difference between the strain of the tire cord thus obtained and the initial strain value at 1 kgf load obtained by deriving a load-elongation curve at the same temperature before repeating the tensile test is the main physical properties of the above-described PET tire cord in one or another embodiment. Can be a value.

PET tire cords exhibiting these physical property values exhibit excellent morphological stability in the environment of use of the tires, which can greatly improve performance, such as stability and safety of the tires, and can be very preferably used as cords for cap plies or body plies. This can be expected to be due to the technical principle described below.

The tires may be exposed to high temperatures or high pressures or corresponding inflated conditions during use of the vehicle, thereby placing a large load on the tire cords. In addition, a large temperature change or a load change may be applied to the tire and the tire cord included in the tire according to a stopped state or a running state of the tire, a change in the surrounding environment to which the tire is exposed, and the like. As such large temperature changes or load changes occur repeatedly and continuously, tire cords may be gradually deformed, and when such deformations become larger than a certain level, poor tire performance and breakage may occur. For example, when the tire cord is used as a capfly cord or a bodyfly cord, the modulus of the tire cord not only decreases due to temperature or load changes repeatedly and continuously, but also causes permanent deformation. Can be. As a result, the cap ply cord does not properly control the movement of the steel belt, or the body ply cord does not properly maintain the shape of the tire, thereby reducing the performance of the tire and further, the tire due to the movement of the steel belt. May cause damage.

However, the tire cord according to the embodiment of the present invention may exhibit a very small deformation rate and excellent shape stability even when repeated load changes are applied at room temperature and high temperature corresponding to the stationary state and the running state of the tire. . Therefore, even when the tire cord is used for a long time and subjected to repeated temperature change or load change, etc., the tire cord exhibits high modulus and stability, thereby effectively controlling the movement of the steel belt. In contrast, in the case of the conventional tire cord that does not meet the above-described physical properties, even if the initial performance is excellent, permanent deformation and modulus deterioration easily occurs by use for a certain period of time, it may cause the performance degradation and breakage of the tire have. Therefore, the tire cord according to an embodiment of the present invention can greatly improve the durability and lifespan of the tire, and can be very preferably used as a code for a cap ply.

In addition, the tire cord according to one embodiment of the present invention exhibits excellent morphological stability compared to previously known nylon or polyester-based tire cords, and in particular, exhibits excellent stability that does not cause morphological deformation even by rapid load or temperature change. . Therefore, the tire cord can maintain a uniform tire shape with little change in shape while supporting the overall load of the vehicle. Therefore, the tire cord according to the embodiment of the present invention is preferably applied as a body ply cord of an air-injected tire, so that it can exhibit a performance equivalent to or better than previously used viscose rayon cord, thereby improving tire performance. And economics can be greatly contributed.

The tire cord according to the embodiment of the present invention described above has a strain of 0.75 after applying a load of 1 kgf after repeating four times the tensile test to expand and apply a load of 2 g / de at 20 ° C. to remove and recover the load. It may be set to 0.95%, preferably 0.80 to 0.95%. In addition, the tire cord may be the strain at the time of applying a load of 1kgf after repeating the tensile test in the same manner at 120 ℃ 0.75 ~ 1.00%, preferably may be 0.80 ~ 0.97%.

The tire cord may have a strain rate of 1.00 to 1.20% when a load of 1 kgf is applied after repeating the tensile test 4 times in the longitudinal direction at 4 ° C. and then recovering it 4 times. For example, it may be 1.05 to 1.15%. In addition, the tire cord may be the strain at the time of applying a load of 1kgf after repeating the tensile test in the same manner at 120 ℃ 1.00 ~ 1.15%, preferably 1.00 ~ 1.10% can be.

As such, the tire cord exhibits excellent shape stability with little deformation even after repeated changes in load, and in particular, such properties can be maintained even at room temperature and high temperature. Therefore, the tire cord does not easily decrease modulus or permanent deformation even after long-term use, and can be preferably used as a cap ply cord or a body ply cord, and can greatly contribute to improving the stability and safety of the tire.

On the other hand, the above-described PET tire cord is not particularly limited in form, and may have a form equivalent to a conventional cap ply cord. More specifically, the PET tire cord is a deep cord having a total fineness of 1000 to 5000 denier (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 cap ply cord. It may have a form.

In addition, the tire cord is 5.0 to 8 g / d, preferably 5.5 to 7 g / d, 1.5 to 5.0%, preferably 2.0 to 5.0% of the core (@ 4.5 kg) and 10 to 25%, preferably Can represent 15 to 25% of the saline. As the tire cord exhibits various physical properties such as strength or elongation in this range, the tire cord can be suitably applied as a capfly code or a bodyfly code.

The above-described tire cord can be applied as a cap ply cord or a body ply cord of a pneumatic tire. Such tire cords can maintain stable initial performance and maintain a good initial modulus and hardly cause deformation even under repeated long-term and repetitive driving conditions of a vehicle, even if a large load change is repeatedly and continuously. This excellent morphological stability and initial modulus result in little noise, flat spots, etc., which were previously seen in capfly cords (e.g. nylon 66 cords), and can be used with long term performance. do.

In the above description, the case where the PET tire cord according to the embodiment of the present invention is used as a cap fly or body fly code is mainly assumed. However, the use of the PET tire cord is not limited thereto. Of course, it can also be used for other purposes, such as reinforcement of other rubber products such as tire cords or rubber belts.

On the other hand, the above-described PET tire cord may be prepared by melting spinning PET to produce an undrawn yarn, drawing the undrawn yarn to prepare a drawn yarn, fused and twisted the drawn yarn, and then immersing in an adhesive. It can take the form of deep code. At this time, the specific conditions or the progress method of each of these steps may be directly or indirectly reflected in the physical properties of the final tire cord can be produced PET tire cord having the above-described physical properties.

In particular, in order to satisfy the physical properties according to one embodiment of the invention, such as low strain difference after repeated tensile test, the conditions in the manufacturing process described below can be applied.

First, using the non-particles or particles having a particle size of 300ppm or less as the PET polymer, it is possible to proceed to the non-drawn yarn manufacturing process through the melt spinning. As melt spinning (particularly, high-speed melt spinning) is performed using such a PET polymer, even when the high-speed melt spinning proceeds, rapid orientation crystallization can be reduced to suppress trimming and sacrificial anxiety. You can get it.

In addition, in the manufacturing process of the non-drawn yarn through the melt spinning, the melt spinning process may be performed under a spinning tension of 0.85 g / d or more, preferably 0.85 to 1.25 g / d, and for this, the melt spinning speed may be 3800 to 5000 m. / min, preferably from 4000 to 4500m / min. After the unstretched yarn is manufactured by performing a melt spinning process under the conditions of such high spinning tension, the stretched yarn and the tire cord are manufactured, thereby producing a PET tire cord having physical properties according to the embodiment of the present invention. Its technical principles can be predicted as follows.

When the melt spinning process is carried out under the high spinning tension described above, for example, 0.85 to 1.25 g / d, the slippage of the PET polymer chain occurs in the unstretched yarn in the fluid state during spinning, which is amorphous. Tie chains or the like can be produced in the region so that undrawn yarn having a network structure can be obtained. When the undrawn yarn having such a network structure is drawn under predetermined conditions to produce a drawn yarn, the drawn yarn continues to have a network structure, so that a drawn yarn and a tire cord having better durability can be obtained, thereby the tire Even if the load is repeatedly and continuously loaded, modulus degradation and deformation can be greatly reduced. However, when the melt spinning process is performed under an excessively high spinning tension, trimming may occur, and thus physical properties of the finally manufactured tire cord may be lowered.

Hereinafter, the method of manufacturing the PET tire cord having the above characteristics will be described in more detail in each step.

In the tire cord manufacturing method, first, non-drawn yarn is produced by melt spinning a PET polymer having particles or particles of 300 ppm or less, and by using such a PET polymer, excessively rapid orientation crystallization is suppressed and high spinning tension and spinning Melt spinning under speed becomes possible. In particular, when using a PET polymer containing a large amount of particles that can act as crystal nuclei, since the rapid orientation crystallization is made according to the increase of the spinning speed or the spinning tension, the movement of the chain is suppressed. It's hard to expect.

In the melt spinning process using the PET polymer, melt spinning may be performed under higher spinning tension to increase the tie chains of the polymer chains in the amorphous region to obtain PET non-drawn yarn having a network structure. 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, as one means for achieving such a high spinning tension, the rate of melt spinning the PET polymer can be adjusted to 3800 to 5000 m / min, preferably to 4000 to 4500 m / min.

As a result of the melt spinning process of PET under such high spinning tension and optionally high spinning speed, it is found that the PET unstretched yarn having a fine network structure can be obtained as the molecular chains forming the PET slide during the spinning process. lost. 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 addition, even if a higher radial tension, etc., it is not preferable because the increase in the rigidity due to the crystallization and the occurrence of cutting and mourning may increase and the physical properties of the tire cord may be lowered.

In the manufacturing process of such PET non-stretched yarn, a chip having an intrinsic viscosity of 0.9 to 1.4 and containing 90 mol% or more of polyethylene terephthalate repeating units can be used as the PET polymer.

As described above, in the production process of the PET non-drawn yarn, a polymer having a particle content of 300 ppm or less is used to impart higher spinning tension and optionally higher spinning speed. In order to proceed with the spinning step preferably under these conditions, the intrinsic viscosity of the chip is preferably 0.9 or more. If it is lower than this, sufficient molecular chain length cannot be secured, and thus the strength is lowered, and the molecular chain is easily broken by repeated load and deformation, making it difficult to achieve physical properties according to one embodiment of the invention. . In addition, it is preferable that the intrinsic viscosity is 1.4 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 made of the PET polymer is preferably spun through the 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 to reduce the possibility of trimming due to interference with each other during the generation and trimming of the yarn during spinning. Is preferably 4.0 denier or less.

In addition, the spinneret is preferably a discharge diameter of 0.8 ~ 1.4mm. In the case of smaller than 0.8 mm, it is difficult to impart sufficient spinning tension, and the discharge pressure is increased due to the narrow detent hole area, which makes it difficult to melt spin the PET polymer having the inherent viscosity described above. In addition, it is difficult to ensure stable flow during spinning at 1.4mm or more due to excessive pressure drop.

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 one embodiment of the invention.

On the other hand, after manufacturing the PET non-drawn yarn having a network structure through this spinning step, the non-drawn yarn is drawn to prepare a stretched yarn, this stretching step can be carried out under the draw ratio conditions of 1.2 ~ 1.8 or less.

The PET non-drawn yarn has a crystalline region developed by high radial tension and the like, and the chains of the amorphous region also have a low degree of orientation and form a network structure. Therefore, if the drawing step is carried out under a high draw ratio condition of more than 1.8, cutting or mousse may occur in the drawn yarn, and thus the tire cord manufactured therefrom 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 the stretching ratio of 1.2 or more, for example, the production of PET tire cords having excellent strength suitable for being applied to the capply cord is possible, so that the stretching process may be preferably performed under the stretching ratio of 1.2 to 1.8.

In the stretching step, the undrawn yarn may be heat treated at a temperature of about 160 ° C. or more and less than 245 ° C., and preferably, the unstretched yarn is heat treated at a temperature of 180 ° C. to 230 ° C. for proper progress of the stretching step. 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. In addition to the above-described process conditions or methods, PET stretched yarns and tire cords can be produced according to conventional methods and conditions, which are obvious to those skilled in the art.

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, higher With modulus, it can exhibit low rate of change, good form stability and excellent durability even under constant and repeated load changes.

On the other hand, according to another embodiment of the invention, there is provided a pneumatic tire comprising the above-described PET tire cord. More specifically, the pneumatic tire may include the PET tire cord as a cap ply cord or a body ply cord, and the rest of the configuration depends on the configuration of a conventional pneumatic tire.

These tires not only have excellent shape stability while supporting the overall load of the vehicle stably, but also include tire cords having excellent long-term durability, which hardly causes form deformation even if a sudden and rapid change in speed and load is applied. Therefore, it is possible to further improve the riding comfort of the vehicle while exhibiting excellent high speed traveling performance.

As described above, according to the present invention, even if a sudden temperature change, a load change or a speed change is applied continuously or repeatedly, a tire cord showing excellent form stability and durability and stably supporting the overall load of the vehicle can be provided. have.

Therefore, such tire cords can be used for cap plies, body plies, and the like, which can greatly improve the life and durability of tires and contribute to the stability and safety of tires.

1 is a partial cutaway perspective view showing a configuration of a general tire.
2 and 3 show the tire cords of Example 1, Comparative Examples 1 and 2 at 20 ° C. and 120 ° C., respectively, when the tensile test was repeated four times according to the method of Test Example 1, and thereafter, a load was applied thereto. The load-elongation curve at the time of deformation is shown.
4 and 5 show the tire cords of Example 1, Comparative Examples 1 and 2, respectively, at 20 ° C. and 120 ° C., when the tensile test was repeated four times according to the method of Test Example 2, and thereafter, a load was applied thereto. The load-elongation curve at the time of deformation is shown.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. It should be noted, however, that the scope of the invention is not limited by these embodiments, but is merely given as an example.

Example 1

A PET polymer containing no particles and 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 method at a spinning speed of 4200 m / min under a spinning tension of 0.97 g / d. These undrawn yarns were drawn, heat-set and wound at a draw ratio of 1.38 to prepare PET drawn yarns.

The twisted yarns of the total fineness 1000 denier drawn yarns prepared as described above are twisted and twisted with two strands of the lower twisted yarns Z-bonded with 430 TPM with the same twisted number of S-strands, immersed and passed through the RFL adhesive solution, and then dried and heat treated. PET tire cords were prepared.

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

Example 2-5

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 twisted and twisted 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 2 to 5, respectively.

Condition Example One 2 3 4 5 Particle amount (ppm) 0 0 200 0 200 Spinning speed (m / min) 4200 4000 3800 4500 3800 Radial tension (g / d) 0.97 0.92 0.91 1.07 0.86 Stretching cost 1.38 1.46 1.48 1.3 1.52 Intrinsic viscosity (dl / g) 1.05 1.05 1.3 1.05 1.05 Drawer strength (kg) 6.3 6.5 7.0 6.0 6.7 Tenacity yarn central god @ 4.5kg (%) 5.7 5.4 5.3 6.2 5.2 Drawer's Body (%) 20.3 19.1 15.9 22.5 15.1

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

Melt-spun PET polymer with an intrinsic viscosity of 1.05 for the production of undrawn yarn at a spinning speed of 3300 m / min and a radial tension of 0.63 g / d, except that undrawn yarn was drawn with a draw ratio of 1.73 for the production of 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)

A non-drawn yarn was prepared by melt spinning and cooling a nylon 66 polymer having a relative viscosity of 3.3 m at a spinning speed of 600 m / min, and a non-drawn yarn was drawn, heat set, and wound at a draw ratio of 5.5 to prepare a drawn yarn using nylon 66 fibers. .

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.

Test Example 1: Measurement of strain difference after repeated tensile test under constant load

Tensile test to the tire cords prepared according to Examples 1 to 5 and Comparative Examples 1 and 2 were applied at a normal temperature (20 ℃) and high temperature (120 ℃) 2g / de and then removed to recover the load Was repeated 4 times. The tensile test was carried out after the tire cords of the Examples and Comparative Examples were prepared and left for 24 hours under conditions of 20 ° C. and 65% RH, which is a general laboratory environment, and based on a tensile property evaluation method based on ASTM D885. It proceeded using this attached universal tensile tester, Instron. The load-elongation curves during the four repeated tensile tests were obtained and shown in FIGS. 2 and 3.

After the repetition of the tensile test, the last 5th tensile evaluation was performed to obtain the load-elongation curve of each tire cord (see FIGS. 2 and 3), and from this, the tire strain at 1 kgf load was obtained. 2 is shown. In addition, the tire strain when the same load was applied before the above-described tensile test iteration was obtained and shown in Table 2 below, from which the strain difference was calculated.

Strain and difference at 1 kgf after tensile test under constant load (2 g / de) Room temperature (20 degrees) High temperature (120 degrees) Initial Strain @ 1kfg After 4 times
Strain rate @ 1kfg Strain difference Initial Strain @ 1kfg After 4 times
Strain Rate1kfg Strain difference Example 1 0.56 0.83 0.27 0.59 0.82 0.23 Example 2 0.54 0.87 0.33 0.58 0.89 0.31 Example 3 0.54 0.89 0.37 0.60 0.94 0.35 Example 4 0.60 0.85 0.25 0.62 0.85 0.23 Example 5 0.54 0.93 0.39 0.58 0.95 0.37 Comparative Example 1 0.70 1.45 0.75 0.84 1.57 0.73 Comparative Example 2 1.1 2.94 1.84 2.28 3.31 1.03

Test Example 2: Determination of strain difference after repeating tensile test to constant elongation

For the tire cords prepared according to Examples 1 to 5 and Comparative Examples 1 and 2, four tensile tests were performed at room temperature (20 ° C.) and high temperature (120 ° C.) to extend 4% in the longitudinal direction and then recover them. Repeated. The tensile test was carried out after the tire cords of the Examples and Comparative Examples were prepared and left for 24 hours under conditions of 20 ° C. and 65% RH, which is a general laboratory environment, and based on a tensile property evaluation method based on ASTM D885. It proceeded using this attached universal tensile tester, Instron. The load-elongation curves during the four repeated tensile tests were obtained and shown in FIGS. 4 and 5.

After the repetition of the tensile test, the last 5th tensile evaluation was performed to obtain the load-elongation curve of each tire cord (see FIGS. 4 and 5). From this, the tire strain at 1 kgf load was obtained. 3 is shown. In addition, the tire strain when the same load was applied before the above-described tensile test iterations were obtained and shown in Table 3 below, from which the strain difference was calculated.

Strain and difference at 1 kgf after tensile test to constant elongation (4%) Room temperature (20 degrees) High temperature (120 degrees) Initial Strain @ 1kfg After 4 times
Strain rate @ 1kfg Strain difference Initial Strain @ 1kfg After 4 times
Strain rate @ 1kfg Strain difference Example 1 0.58 1.08 0.5 1.59 1.0 0.41 Example 2 0.55 1.10 0.55 0.58 1.03 0.45 Example 3 0.54 1.06 0.52 0.61 1.04 0.43 Example 4 0.61 1.07 0.46 0.62 1.01 0.39 Example 5 0.55 1.14 0.59 0.59 1.08 0.49 Comparative Example 1 0.70 1.41 0.71 0.84 1.42 0.59 Comparative Example 2 1.10 2.13 1.03 2.13 2.51 0.38

Referring to Tables 2 and 3 of FIGS. 2 to 5, the tire cords of Examples 1 to 5 were manufactured under conditions such as high spinning tension using specific PET polymers, and thus the strain and the difference after repeated tensile test were very small. It is confirmed.

In comparison, the tire cords of Comparative Examples 1 and 2 do not satisfy these physical properties, and in particular, it is confirmed that the strain rate becomes significantly large after repeated tensile test.

From this, it is expected that the tire cords of Examples 1 to 5 have high morphological stability against repeated loads and deformations, and that excellent initial characteristics can be continuously improved even in long-term use, thereby greatly improving tire stability.

Claims (11)

Defines the initial strain was applied at the time a load of 1kgf in polyethylene terephthalate tire cord of a total fineness of 1000-5000 denier at 20 ℃ by S _0, and
Strain is defined as S when a load of 1 kgf is applied at 20 ° C. after four repeated tensile tests in which the polyethylene terephthalate tire cord is stretched by applying a load of 2 g / de at 20 ° C. and then removes and recovers the load. When, the polyethylene terephthalate tire cord that the difference of S-S ₀ is 0.5% or less.
The method according to claim 1,
Defines the initial strain was applied at the time a load of 1kgf in polyethylene terephthalate tire cord of a total fineness of 1000-5000 denier at 120 ℃ to S _'0, and
The polyethylene terephthalate tire cord was subjected to four times of tensile tests in which a load of 2 g / de was elongated at 120 ° C. and then removed to recover the load, and then a strain at 1 kgf at 120 ° C. was changed to S ′. When defined, the polyethylene terephthalate tire cord of which the difference of S'-S ' ₀ is 0.5% or less.
The polyethylene terephthalate tire cord according to claim 1, wherein a strain (S) after said tensile test at 20 ° C is 0.75 to 0.95%.
The polyethylene terephthalate tire cord according to claim 2, wherein the strain (S ') after the tensile test at 120 ° C is 0.75 to 1.00%.
Defines the initial strain was applied at the time a load of 1kgf in polyethylene terephthalate tire cord of a total fineness of 1000-5000 denier at 20 ℃ to L _0, and
When the polyethylene terephthalate tire cord was subjected to four times of tensile tests that stretched and recovered by 4% in the longitudinal direction at 20 ° C. and then recovered, four times, a strain at 1 kgf at 20 ° C. was defined as L.
The L - L ₀ is 0.6% or less of the polyethylene terephthalate tire cord difference.
6. The method of claim 5,
Initial strain rate when load of 1 kgf is applied to the polyethylene terephthalate tire cord of total fineness 1000-5000 denier at 120 degreeC is defined as L' ₀ ,
When the polyethylene terephthalate tire cord was subjected to four times of tensile tests which stretched and recovered by 4% in the longitudinal direction at 120 ° C. four times, the strain at the time of applying a load of 1 kgf at 120 ° C. was defined as L ′.
The L '- L' ₀ is 0.6% or less of polyethylene terephthalate tire cord difference.
The polyethylene terephthalate tire cord according to claim 5, wherein the strain (L) after the tensile test at 20 ° C is 1.00 to 1.20%.
The polyethylene terephthalate tire cord according to claim 6, wherein the strain (L ' ₀ ) after the tensile test at 120 ° C is 1.00 to 1.15%.
The polyethylene terephthalate tire cord according to claim 1, which exhibits a strength of 5 to 8 g / d, a torso of 1.5 to 5.0% (@ 4.5 kg) and a stretch of 10 to 25%.
The polyethylene terephthalate tire cord of claim 1, wherein the total fineness is 1000 to 5000 denier, 1 to 3 plies, and 200 to 500 TPM.
A pneumatic tire comprising the tire cord according to any one of claims 1 to 8.

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