KR20120001940A - Method for manufacturing poly(ethyleneterephthalate) drawn fiber, poly(ethyleneterephthalate) drawn fiber and tire-cord - Google Patents

Abstract

PURPOSE: A method for fabricating drawn yarn of polyethylene terephthalate is provided to improve comfortable property to drive in. CONSTITUTION: A method for fabricating drawn yarn of polyethylene terephthalate comprises: a step of spinning polymers by spinneret at 3500-4500m/min to prepare undrawn yarn; and a step of stretching the undrawn yarn in a ratio of 1.4-1.8. The polymer contains 90 mole% or more of polyethylene terephthalate. The crystallinity of the undrawn yarn is 20-35%.

Description

Manufacturing method of polyethylene terephthalate stretched yarn, polyethylene terephthalate stretched yarn and tire cord {METHOD FOR MANUFACTURING POLY (ETHYLENETEREPHTHALATE) DRAWN FIBER, POLY (ETHYLENETEREPHTHALATE) DRAWN FIBER AND TIRE-CORD}

The present invention relates to a process for the production of polyethylene terephthalate stretched yarn, which exhibits excellent strength and excellent morphological stability, which makes it possible to provide a tire cord which can be preferably used as a body fly cord, and a polyethylene terephthalate stretched yarn and tire cord obtained therefrom. .

The tire is a composite of fiber / steel / rubber and generally has a structure as shown in FIG. 1. Here, the body ply corresponding to 6 of FIG. 1 is a cord layer which is a core reinforcing material inside the tire, also called a carcass, and maintains the shape of the tire and withstands the impact while supporting the overall load of the vehicle. Strong fatigue resistance against flexion movement during driving is required.

In general, synthetic fiber materials such as polyester and polynaphthalene terephthalate are applied to such body plies, that is, tire cords.

The synthetic fiber cord has a great contribution to improving the durability of the tire due to its high strength, but has a disadvantage in that elasticity and form stability are degraded after vulcanization of the tire due to high shrinkage with respect to heat. In order to compensate for this, many studies have been conducted to improve the shape stability of the cord by applying an additional process such as PCI (Post Cure Inflation). In particular, in the case of high strength yarn for industrial use, it is possible to express high strength by increasing the draw ratio at low speed, but the PCI process is still required due to the high heat shrinkage rate and low elasticity.

Since the high-speed spinning technology is applied to the manufacturing process of the tire cord, it is possible to manufacture a polyester tire cord having high modulus low shrinkage (HMLS) properties without a PCI process.

In this case, in order to manufacture a tire cord having high elasticity and low shrinkage properties, unstretched yarn having high crystallinity should be used. Since the unstretched yarn having high crystallinity has a relatively narrow area that can be stretched, the unstretched yarn is manufactured using an ultrafast spinning equipment. In the case of stretching under conditions of high speed and high draw ratio, there is a problem that the cutting due to non-uniform stretching or friction can easily occur.

For this reason, in the ultra-fast spinning facility, there is a restriction on the application of the draw ratio to the undrawn yarn of high crystallinity, and a loss in which the tensile strength of the drawn yarn is greatly lowered due to insufficient drawing is achieved.

For this reason, it is a fact that there existed a limit in obtaining the polyester tire cord which shows the outstanding strength while showing the outstanding strength still.

Accordingly, the present invention provides a method for producing polyethylene terephthalate stretched yarn, which enables the provision of tire cords showing excellent strength and excellent form stability.

This invention also provides the polyethylene terephthalate stretched yarn obtained from the said manufacturing method.

The present invention also provides a polyethylene terephthalate tire cord and a method for producing the same, which exhibit excellent strength and excellent morphological stability.

According to the present invention, a polymer containing at least 90 mol% of polyethylene terephthalate and having an intrinsic viscosity of 1.1 to 1.5 dl / g has a ratio (L / D) of length (L) to diameter (D) of the spinning nozzle of 3.0 to 6.0. Manufacturing a non-drawn yarn by melt spinning through a spinneret at a speed of 3500 to 4500 m / min; And it provides a method for producing a polyethylene terephthalate stretched yarn comprising the step of stretching the undrawn yarn to a draw ratio of 1.4 to 1.8 times.

In addition, the present invention has an intrinsic viscosity of 1.0 to 1.2, has a tensile strength of 8.5 to 9.5 g / de, a polyethylene terephthalate having a middle body of 4.0 to 6.5% under a load of 4.5 g / de, and 10.0 to 15.0% of the elongation Provide drawing company.

The present invention also comprises the steps of forming a polyethylene terephthalate stretched yarn by the above-described method; Coalescing the stretched yarn; And it provides a method of producing a polyethylene terephthalate tire cord comprising the step of immersing the heat-treated yarn in an adhesive solution and heat treatment.

In addition, the present invention is an ES index, which is the sum of the dry heat shrinkage rate after heat treatment in an oven at 177 ° C. for 2 minutes under a load of 0.01 g / de, and the middle body under a load of 2.25 g / de, which is 5.5 to 6.5%. Provided are polyethylene terephthalate tire cords.

Hereinafter, a method for preparing polyethylene terephthalate stretched yarn, a method for preparing tire cords, a stretched yarn and tire cords obtained therefrom will be described. However, this is presented as an embodiment of the invention, whereby the scope of the invention is not limited, it will be apparent to those skilled in the art that various modifications to the various embodiments are possible within the scope of the invention.

In addition, unless otherwise stated throughout the present specification, the term "comprise" or "contains" means that a specific component (or component) is included without limitation, and excludes the addition of other components. It cannot be interpreted.

Polyethylene terephthalate (hereinafter referred to as 'PET') tire cord melt-spun PET, a polymer, to produce an undrawn yarn, and after drawing it to obtain a drawn yarn, the PET drawn yarn is twisted and immersed in an adhesive to dip It may be prepared in the form of a cord. Therefore, the properties of the undrawn yarn produced through melt spinning of PET and the drawn yarn produced by drawing them are directly and indirectly reflected in the physical properties of the PET tire cord.

The inventors of the present invention, in the course of repeating the research on the drawn yarn for the tire cord, when the non-drawn yarn manufactured by using the super-fast spinning technology for ultra-high spinning technology for PET having a high intrinsic viscosity, and manufactured the drawn yarn with the prepared non-drawn yarn, It has been found that the strength is excellent and the shape stability is excellent when the tire cord is manufactured using the same.

In particular, in the past, when the unstretched yarn is to be obtained from a polymer having a high intrinsic viscosity, cutting may occur due to the pressure increase of the Pack during spinning, and thus there is a limitation in applying a polymer having a high intrinsic viscosity. Moreover, there was a disadvantage in that the strength of the drawn yarn and the tire cord was lost because of limitations in the application of the draw ratio, and as a result, even with high intrinsic viscosity and ultrafast spinning technology, there was a limit in obtaining a tire cord having excellent strength and excellent form stability. there was.

However, the experimental results of the present inventors, in the melt spinning process for the production of undrawn yarn, using a spinneret in which the ratio (L / D) of the length (L) to the diameter (D) of the spinning nozzle meets a certain range Therefore, it was found that the problems caused by the pressure rise of the pack during spinning can be greatly reduced, and the limitation in the application of the draw ratio can be largely overcome.

Accordingly, it has been found that, by applying the manufacturing method described below, tire cords which can be preferably used as body ply cords of pneumatic tires can be produced by exhibiting excellent strength and excellent form stability.

According to one embodiment of the present invention, there is provided a method for producing PET stretched yarn. The method for producing PET stretched yarn includes a polymer having 90 mol% or more of polyethylene terephthalate and a polymer having an intrinsic viscosity of 1.1 to 1.5 dl / g, in which the ratio (L / D) of the length (L) to the diameter (D) of the spinning nozzle is Preparing undrawn yarn by melt spinning at a speed of 3500 to 4500 m / min through a spinneret of 3.0 to 6.0; And stretching the undrawn yarn to a draw ratio of 1.4 to 1.8 times.

Hereinafter, the manufacturing method of such PET stretch yarn will be described in detail for each step.

In the above production method, first, a non-drawn yarn is manufactured by melt spinning a polymer containing PET.

In particular, in the non-drawn yarn manufacturing step, by using ultra-fast spinning technology, an undrawn yarn having a high crystallinity can be obtained, and a tire cord showing excellent strength and form stability can be manufactured through the following process. In order to achieve a high degree of crystallization of such undrawn yarn, the polymer is melt spun under a spinning speed of 3500 to 4500 m / min. That is, it is preferable to apply a spinning speed of 3500 m / min or more in order to achieve the properties or productivity of the non-drawn yarn such as high crystallinity, the spinning speed is 4500 m to give the minimum cooling time required for the production of undrawn yarn It is appropriate to be less than / min.

It is also preferred that the melt spinning of the polymer proceed under a spin tension of 0.85 to 1.25 g / d. That is, in order to obtain undrawn yarn properties such as high crystallinity, the spin tension is preferably 0.85 g / d or more, and the spin tension is preferably 1.25 g / d or less in order to prevent the filament from being cut or the property deteriorated with more than necessary tension. .

On the other hand, as a raw material for producing the undrawn yarn may be used a polymer containing PET. The polymer containing PET may include various additives. According to one embodiment of the present invention, a polymer having a PET content of 90 mol% or more is used. Using such polymers, drawn yarns and tire cords having excellent physical properties described below can be produced. Therefore, hereinafter, 'PET polymer' means a polymer having a PET content of 90 mol% or more without any special explanation.

In addition, in order to manufacture the undrawn yarn under the spinning speed and spinning tension, the PET polymer preferably has an intrinsic viscosity of 1.1 to 1.5 dl / g, preferably 1.2 to 1.5 dl / g. That is, under the above-mentioned spinning tension and spinning speed, the melt spinning process may be performed using a polymer having an intrinsic viscosity of 0.8 dl / g or more. However, when a polymer having a low intrinsic viscosity is used, the strength of the stretched yarn and the tire cord may be reduced. have. Therefore, it is preferable to melt-spun a polymer having an intrinsic viscosity of 1.2 dl / g or more in order to obtain a tire cord having excellent strength and shape stability. However, in order to suppress cutting due to excessive pressure rise of the pack during spinning, it is preferable to melt spin the polymer having an inherent viscosity of 1.5 dl / g or less.

On the other hand, attempts have been made to obtain tire cords having excellent strength and shape stability by applying ultrafast spinning technology to polymers having high intrinsic viscosity. However, when melt spinning a polymer having an intrinsic viscosity below a certain level, the pressure may increase due to the discharge amount from the spinneret pack, which may cause the physical properties of the tire cord such as cutting off. In addition, in order to reduce the pack pressure, the melting temperature of the polymer must be increased. In this case, decomposition of the polymer may occur, thereby reducing the physical properties of the stretched yarn, and it becomes difficult to manufacture a tire cord having high strength and high form stability.

However, as a result of the experiments of the present inventors, as the melt spinning process proceeds through the spinneret having a ratio (L / D) of the length L to the diameter D of the spinning nozzle (L / D) of 3.0 to 6.0, the melt spinning temperature is drawn. It has been found that the spin pack pressure can be reduced without raising, allowing adequate melt spinning of polymers with high intrinsic viscosities up to 1.5 dl / g. Accordingly, the polymer having a high intrinsic viscosity can be appropriately melt spun without causing decomposition or the like of the polymer, whereby a drawn yarn and a tire cord having excellent strength can be obtained. In addition, by applying ultra-fast spinning technology to such polymers, undrawn yarns having high crystallinity and the like can be produced, and tire cords having excellent morphological stability can be produced therefrom. In this way, the melt spinning of the polymer having a high intrinsic viscosity by changing the L / D of the spinning nozzle to 3.0 to 6.0 is possible, such that the change of the elastic properties of the polymer in the state of Viscous by stress relaxation It seems to be due to the change.

In addition, in order to allow the melt spinning process to proceed properly under the above-mentioned conditions, the spinneret preferably has a hole area of 0.18 to 0.4 mm ² / De.

On the other hand, after melt spinning the PET polymer under the above-described conditions, a non-drawn yarn may be manufactured by adding a cooling process, and the cooling process is preferably performed by applying a cooling wind of 15 to 60 ° C., respectively. It is preferable to adjust the cooling air amount to 0.4-1.5 m / s in cooling wind temperature conditions. However, cooling unevenness may occur due to air drag phenomenon and discharge amount increase due to ultra-fast spinning, and interference phenomenon between monofilaments due to high multi-radiation. The method of plywood can be used.

The non-drawn yarn prepared through the above process may exhibit high crystallinity of 20 to 35% and low amorphous orientation factor of 0.08 to 0.15. Through the application of ultra-fast spinning technology and the like, the undrawn yarn having such crystal properties is obtained, and then the drawn yarn and the tire cord are manufactured, thereby producing a tire cord having excellent shape stability with excellent strength due to high intrinsic viscosity. have. The technical principle can be predicted as follows.

Unstretched PET polymer basically has a crystallized form, and is composed of a crystalline region and an amorphous region. However, the unstretched yarn obtained under the above melt spinning conditions has a higher degree of crystallization than previously known unstretched yarn (usually crystallized to less than 7%) due to the orientation crystallization phenomenon, so that it is 20% or more, preferably 20 to 35%. It shows high crystallinity. Due to this high degree of crystallinity, the drawn yarn and tire cords prepared using the undrawn yarn may exhibit high shrinkage stress and modulus.

At the same time, the undrawn yarn exhibits an amorphous orientation index of 0.15 or less, preferably 0.08 to 0.15, which is significantly lower than previously known undrawn 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. 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 strained structure, so that the drawn yarns and tire cords made from undrawn yarns have low shrinkage stresses with low shrinkage. Will be displayed. However, the undrawn yarn obtained under the melt spinning conditions described above contains more crosslinks per unit volume, forming a fine network structure due to the slipping of the molecular chains thereof during the spinning process. Because of this, the unstretched yarn can have a strained structure of the chains in the amorphous region while the amorphous orientation index is low, thereby showing the developed crystal structure and excellent orientation characteristics. Thus, as well as the unstretched yarn, the stretched yarn and tire cords obtained therefrom can exhibit high shrinkage stress and modulus with low shrinkage rate, and as a result, a tire cord exhibiting excellent shape stability can be produced.

On the other hand, after forming the unstretched yarn as described above, the unstretched yarn is stretched to produce polyethylene terephthalate stretched yarn. This stretching step can be carried out in a direct spinning stretching method (Direct Spinning & Drawing, hereinafter referred to as a 'DSD method') in which spinning and stretching are continuously performed in a single process according to a conventional drawing yarn manufacturing process.

In addition, the stretching step is preferably carried out so that the draw ratio is 1.4 to 1.8 times. That is, in order to manufacture a tire cord having excellent strength and form stability, it is preferable that the above-mentioned 1.4 times or more. The ratio is preferably 1.8 times or less.

The drawn yarns produced in this way not only have a relatively high intrinsic viscosity of 1.0 to 1.2, but also have a tensile strength of 8.5 to 9.5 g / de, a middle body under a load of 4.5 g / de of 4.0 to 6.5%, and elongate May be 10.0 to 15.0%. Due to the excellent physical properties of the stretched yarn, it is possible to produce a tire cord showing excellent strength and excellent shape stability using it.

On the other hand, according to another embodiment of the present invention, there is provided a method for producing a PET tire cord using the above-described method for producing PET stretched yarn. The method for producing a PET tire cord may include forming a polyethylene terephthalate stretched yarn by the above-described method; Coalescing the stretched yarn; And immersing the conjugated twisted yarn in an adhesive solution and performing heat treatment.

In this method of manufacturing a tire cord, the step of joining, for example, 'Z' with a twist number of 200 to 500 TPM (twist per meter) per unit length of the drawn yarn of the total fineness 800 to 1500 denier (Denier) It is soft, it can be carried out by the method of producing a twisted yarn by 'S' the 'Z' lead yarn 1 to 3 plies 200 to 500 TPM.

In addition, as the adhesive solution, one used for the production of a conventional tire cord, for example, Resorcinol Formaldehyde-Latex (RFL) adhesive solution can be used. And, the heat treatment process may proceed for 90 to 360 seconds at a temperature of 240 to 260 ℃, preferably 90 to 240 seconds under a temperature of 240 to 250 ℃, more preferably 90 under a temperature of 245 to 250 ℃ To 120 seconds. By immersing the conjugated twisted yarn in the adhesive solution and heat-treated under such conditions, the form stability of the tire cord can be further improved, and the change in physical properties can be further reduced when the tire is vulcanized.

The tire cords produced according to this process were defined as the sum of the dry heat shrinkage rate after heat treatment in an oven at 177 ° C. for 2 minutes under a load of 0.01 g / de, and the sum of the middle bodies under a load of 2.25 g / de (ES index). ) May be from 5.5 to 6.5%. In this case, the 'shape stability index (ES index)' is a sum of 'dry heat shrinkage rate (for 2 minutes under a load of 0.01 g / de in an oven at 177 ° C)' and 'heavy body (load of @ 2.25 g / de)'. The lower the value, the smaller the change in the shape of the tire cord and the better the tensile strength.

As described above, the tire cord manufactured according to the above-described process is obtained from an unstretched yarn having high crystallinity by applying a super fast spinning technique to a PET polymer having a high intrinsic viscosity, and may exhibit excellent tensile strength and excellent morphological stability. Accordingly, such tire cords are very preferably applied as body ply cords of pneumatic tires, so that the overall vehicle load can be supported very effectively. However, the use of the tire cord according to the present invention is not limited thereto, and may be applied to other uses such as a cap ply.

In particular, the tire cord may exhibit very excellent physical properties as a tire cord, such as tensile strength of 7.6 to 8.7 g / de, 3.5 to 5.5% of the middle body under a load of 2.25 g / de, and an elongation of 13.0% or more. have.

In addition, the tire cord has a total fineness of 1000 to 5000 denier (Denier), 1 to 3 ply, and twist number per unit length 200 to 500 twist per meter (TPM), it can take the form of a conventional tire cord.

According to the present invention, a tire cord having excellent strength with excellent shape stability and a manufacturing method thereof can be provided. This tire cord can minimize the deformation of the tire due to its excellent shape stability, and can effectively support the overall load of the vehicle.

Therefore, the tire cord is preferably used for applications such as body plying of pneumatic tires, so that the controllability and ride comfort of the vehicle can be improved.

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

Best Mode for Carrying Out the Invention Hereinafter, preferred embodiments are described to facilitate understanding of the present invention. However, the following examples are intended to illustrate the present invention without limiting it thereto.

      [Production of drawer]

Examples 1-7 (Ultrafast Spinning of High I.V.Polymers in L / D Modified Detentions)

In the spinneret where the ratio (L / D) of the length (L) to the diameter (D) of the spinning nozzle is as shown in Table 1 below, PET unburned in Examples 1 to 7 by melt spinning and cooling the PET polymer chip. A gentleman was produced. The conditions of the melt spinning used at this time was as shown in Table 1, the remaining conditions were in accordance with the conventional conditions for the production of PET non-drawn yarn. In addition, the unstretched yarn was stretched, heat fixed, and wound at a predetermined draw ratio shown in Table 1 to prepare a PET stretched yarn.

Comparative Examples 1 to 5 (Ultra High Speed Spinning Under Existing Conditions)

Unlike in Examples 1 to 7, PET stretch yarn was prepared through ultra-fast spinning under existing conditions of detention and intrinsic viscosity. The conditions of the melt spinning used at this time are shown in Table 1 below.

Intrinsic viscosity
(dl / g) Radiation tension
(g / d) Spinning speed
(m / min) Detention L / D Hole area
(mm ² / de) Stretching ratio Radiation temperature
(℃) Example 1 1.40 0.85 3500 5.0 0.35 1.80 295 Example 2 1.40 0.99 3800 5.0 0.35 1.66 295 Example 3 1.40 1.12 4200 5.0 0.35 1.50 295 Example 4 1.40 1.21 4500 5.0 0.35 1.40 295 Example 5 1.20 1.04 4200 5.0 0.35 1.50 293 Example 6 1.50 1.15 4200 5.0 0.35 1.50 297 Example 7 1.40 1.13 4200 4.0 0.25 1.50 297 Comparative Example 1 0.90 1.02 4200 2.0 0.12 1.50 287 Comparative Example 2 1.05 1.07 4200 5.0 0.35 1.50 290 Comparative Example 3 1.05 0.61 2800 2.0 0.12 2.25 290 Comparative Example 4 1.50 0.95 4200 2.0 0.12 1.50 295 Comparative Example 5 1.50 1.11 4200 2.0 0.12 1.50 303

[Measurement of physical properties of drawer]

Physical properties of the respective stretched yarns according to Examples 1 to 7 and Comparative Examples 1 to 5 were measured by the following method, and the measured physical properties are shown in Table 2 below.

1) Intrinsic viscosity of drawn yarn: After removal of oil from the drawn yarn sample and drying, the intrinsic viscosity of the drawn yarn was measured using an Oswald viscometer according to the OCP method.

2) Tensile Strength (g / de): According to the ASTM D885 standard, the yarn strength was measured using a universal tensile tester.

3) Critical (%) and Tensile (%): Elongation (heavy) and breaking elongation under a load of 4.5 g / de were measured using a universal tensile tester according to ASTM D885 standard.

Drawing company
Properties Intrinsic viscosity The tensile strength
(g / de) Serious
(%) Body
(%) Example 1 1.142 9.4 4.5 10.5 Example 2 1.140 9.1 4.8 11.1 Example 3 1.138 8.9 5.0 11.8 Example 4 1.139 8.6 6.0 13.0 Example 5 1.087 8.5 4.9 11.4 Example 6 1.208 8.7 5.4 12.2 Example 7 1.144 8.7 5.5 12.4 Comparative Example 1 0.811 7.7 4.9 11.3 Comparative Example 2 0.941 7.8 4.8 10.9 Comparative Example 3 0.935 8.8 4.2 9.8 Comparative Example 4 - - - - Comparative Example 5 1.211 7.9 5.5 13.1

As can be seen through Table 1 and Table 2, Comparative Examples 1 to 5 were prepared by applying the existing intrinsic viscosity and detention L / D of the drawn yarn, Comparative Examples 1 and 2 of the drawn yarn It was confirmed that the tensile strength was low. In addition, Comparative Example 3 is to apply a high elongation ratio to lower the radiation tension and spinning speed, it was confirmed that the shape stability is not sufficient due to the low middle body and the elongation. And, Comparative Examples 4 and 5 are applied to the intrinsic viscosity of the level of the example, and applied to the level of the embodiment of the radial tension, spinning speed and elongation ratio. However, at the spinning temperature of the embodiment level, spinning was impossible due to the trimming caused by the pack pressure increase (Comparative Example 4), and the spinning pressure was lowered to reduce the pack pressure by spinning the spinning temperature. It was confirmed that this was significantly reduced.

On the other hand, Examples 1 to 5 are in the range of the preferred tensile strength, core and elongation as the drawn yarn is prepared by drawing a non-drawn yarn produced by melt spinning a polymer having a high intrinsic viscosity in a L / D changed mold It was found to have excellent physical properties.

[Production of Tire Cord]

Examples 8-14

Two twisted yarns of 'Z' stretched to a predetermined total fineness, and twist per unit length (TPM), using the stretched yarn according to any one of Examples 1 to 7 After immersed in RFL adhesive solution, and dried and heat-treated to prepare a PET tire cord. At this time, the drawn yarn, drawn yarn fineness, the number of twists per unit length (TPM) and the code heat treatment conditions are shown in Table 3 below, and the composition and drying conditions of the RFL adhesive solution are typical production conditions of PET tire cord. Followed.

Comparative Examples 6-10

PET tire cords were prepared using the drawn yarns prepared under the conditions of Comparative Examples 1 to 5, wherein the used drawn yarns, drawn yarn fineness, number of twists per unit length (TPM) and cord heat treatment conditions are shown in the following table. 3 is shown.

Cord
Produce Used
Drawing company Yeonsinsa Island Island
(denier) TPM Ply Cord
Heat treatment condition Example 8 Example 1 1500 360 2 245 ~ 260 ℃, more than 90 seconds Example 9 Example 2 1500 360 2 245 ~ 260 ℃, more than 90 seconds Example 10 Example 3 1500 360 2 245 ~ 260 ℃, more than 90 seconds Example 11 Example 4 1500 360 2 245 ~ 260 ℃, more than 90 seconds Example 12 Example 5 1500 360 2 245 ~ 260 ℃, more than 90 seconds Example 13 Example 6 1500 360 2 245 ~ 260 ℃, more than 90 seconds Example 14 Example 7 1500 360 2 245 ~ 260 ℃, more than 90 seconds Comparative Example 6 Comparative Example 1 1500 360 2 245 ~ 260 ℃, more than 90 seconds Comparative Example 7 Comparative Example 2 1500 360 2 245 ~ 260 ℃, more than 90 seconds Comparative Example 8 Comparative Example 3 1500 360 2 245 ~ 260 ℃, more than 90 seconds Comparative Example 9 Comparative Example 5 1500 360 2 245 ~ 260 ℃, more than 90 seconds

[Measurement of physical properties of tire cord]

Physical properties of the tire cords according to Examples 8 to 14 and Comparative Examples 5 to 10 were measured by the following methods, and the measured physical properties are shown in Table 4 below.

1) Tensile Strength (g / de): According to the ASTM D885 standard, the cord strength was measured using a universal tensile tester.

2) Critical and% Elongation: Elongation (heavy) and breaking elongation under a load of 2.25 g / de were measured using a universal tensile tester according to ASTM D885 standard.

3) Dry heat shrinkage (%): Dry heat shrinkage was measured after 2 minutes with a load of 0.01 g / de in an oven at 177 ℃ using a dry heat shrinkage measuring device (manufacturer: TESTRITE, model name: MK-V).

4) Shape stability index (E-S index): The sum of the core and dry heat shrinkage rates measured by the above method.

Cord
Properties The tensile strength
(g / de) Serious
(%) Body
(%) Dry heat shrinkage
(%) ES Index Example 8 8.46 4.0 15.3 2.3 6.3 Example 9 8.19 4.0 15.7 2.1 6.1 Example 10 8.01 4.0 16.1 1.8 5.8 Example 11 7.74 4.0 16.5 1.7 5.7 Example 12 7.65 4.1 16.3 2.0 6.1 Example 13 7.83 4.1 16.0 2.1 6.2 Example 14 7.83 4.1 15.9 2.1 6.2 Comparative Example 6 6.93 4.0 16.3 2.4 6.4 Comparative Example 7 7.02 4.1 13.1 1.9 6.0 Comparative Example 8 7.92 4.0 15.4 3.5 7.5 Comparative Example 9 - - - - - Comparative Example 10 7.11 4.1 15.2 2.3 6.4

As can be seen through Table 3 and Table 4, Comparative Examples 6 to 10 is a preferred range of tensile strength or shape stability index using the drawn yarn prepared by applying the existing intrinsic viscosity and detention L / D Found out of the. In the case of Comparative Example 9, as described above, the spinning was not possible due to the trimming caused by the pack pressure increase, and thus, the tire cord was not manufactured.

On the other hand, Examples 8 to 14 showed that the tensile strength of the cord according to Examples 1 to 7, the elongation, the middle body, the dry heat shrinkage rate, and the shape stability index has a desirable range and excellent physical properties. In particular, it is expected to exhibit excellent morphological stability and tensile strength and to be preferably used as a tire cord for body plying of pneumatic tires.

Claims (10)

A polymer containing 90% by mol or more of polyethylene terephthalate and having an intrinsic viscosity of 1.1 to 1.5 dl / g was subjected to spinneret having a ratio (L / D) of length (L) to diameter (D) of the spinning nozzle (3.0 to 6.0). Preparing undrawn yarn by melt spinning at a speed of 3500 to 4500 m / min through; And
Method for producing a polyethylene terephthalate stretched yarn comprising the step of stretching the undrawn yarn to a draw ratio of 1.4 to 1.8 times.
The method of claim 1, wherein the spinneret has a confinement hole area of 0.18 to 0.4 mm ² / De.
The method of claim 1, wherein the melt spinning process is carried out under a radial tension of 0.85 to 1.25 g / d.
The method of claim 1, wherein the undrawn yarn has a crystallinity of 20 to 35%.
A polyethylene terephthalate stretched yarn having an intrinsic viscosity of 1.0 to 1.2, a tensile strength of 8.5 to 9.5 g / de, a 4.0 to 6.5% middle body under a load of 4.5 g / de, and a length of 10.0 to 15.0%.
Forming a polyethylene terephthalate stretched yarn by the method of any one of claims 1 to 4;
Coalescing the stretched yarn; And
The method of manufacturing a polyethylene terephthalate tire cord comprising the step of immersing the heat-treated yarn in an adhesive solution and heat treatment.
Polyethylene terephthalate tire cord with an ES index of 5.5 to 6.5%, which is the sum of dry heat shrinkage after heat treatment in an oven at 177 ° C. for 2 minutes under a load of 0.01 g / de and a heavy body under a load of 2.25 g / de .
8. The tire cord according to claim 7, wherein the tensile strength is 7.6 to 8.7 g / de, the central body under the load of 2.25 g / de is 3.5 to 5.5%, and the elongation is at least 13.0%.
The tire cord according to claim 7 or 8, having a total fineness of 1000 to 5000 denier, 1 to 3 plies, and a twist per meter (TPM) of 200 to 500 TPM per unit length.
The tire cord according to claim 7 or 8, which is used as a body fly cord of a pneumatic tire.

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