KR20150109731A

KR20150109731A - Poly(ethyleneterephthalate) Drawn Fiber, Method for Manufacturing The Same, and Tire Cord Manufactured Using The Same

Info

Publication number: KR20150109731A
Application number: KR1020140032917A
Authority: KR
Inventors: 정일; 전옥화; 박성호
Original assignee: 코오롱인더스트리 주식회사
Priority date: 2014-03-20
Filing date: 2014-03-20
Publication date: 2015-10-02

Abstract

Disclosed are a polyethylene terephthalate drawn yarn, a manufacturing method thereof, and a tire cord manufactured using the same, capable of manufacturing a tire cord having excellent strength and fatigue resistant properties while requiring a relatively small amount of rubber, by having excellent strength even with a relative low fineness. The polyethylene terephthalate drawn yarn of the present invention comprises 110-200 monofilaments having a fineness of 2.5- 4.5 deniers, having a strength of at least 8 g/d, 4-6% elongation at 4.5 kg load and 9-14% elongation.

Description

TECHNICAL FIELD [0001] The present invention relates to a polyethylene terephthalate stretched yarn, a method for producing the same, and a tire cord made using the same. BACKGROUND ART [0002] Polyethylene terephthalate (PET)

The present invention relates to a polyethylene terephthalate stretched yarn capable of producing a tire cord having excellent strength and endurance characteristics while requiring a relatively small amount of rubber by having an excellent strength despite having a relatively low fineness, And a tire cord made using the same.

The tire is a composite of fiber / steel / rubber, and generally has a structure as shown in Fig.

The body ply is a cord layer which is the core reinforcement material inside the tire. It is also called a carcass. It maintains the shape of the tire while supporting the overall load of the vehicle, and sustains the impact. The body ply has a high fatigue resistance This is the required part.

Synthetic fiber materials such as polyesters such as poly naphthalene terephthalate are generally applied to body fly tires.

Cap ply on top of Belt Plies is a reinforcing material that improves high-speed running by suppressing movement of stell belt due to centrifugal force when traveling at high speed of tire. It is a part where high modulus, shrinkage stress and excellent adhesion are required. Nylon 66 is generally used for cap-ply tire cords. Hybrid cords that use aramid and nylon 66 are used for high-performance tires. Polyethylene terephthalate (PET) is also increasingly used.

Such a synthetic fiber cord has a disadvantage in that it has a high strength and contributes greatly to improvement in the durability of the tire, but has a high shrinkage rate against heat, resulting in deterioration of elasticity and form stability after vulcanization of the tire. To overcome this problem, many studies have been conducted to improve the morphological stability of codes through the application of additional processes such as PCI (Post Cure Inflation). In particular, the high strength yarn for industrial use has been able to exhibit high strength by increasing the draw ratio at low speed, but the PCI process is still required because of high heat shrinkage and low elasticity.

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

On the other hand, interest in automobile fuel efficiency is increasing due to increasing oil prices and environmental concerns. Therefore, fuel economy has become one of the most important factors to consider when manufacturing tires. Among the many efforts to improve fuel efficiency, tire lightening has become a key development item, and automakers are demanding a reduction in tire weight by up to 50% in the future.

One of the methods for tire weight reduction is to reduce the amount of rubber used by manufacturing tire cords with fibers having a low fineness. However, even if the fibers are made of fibers having a low fineness, since the tire cord still has to satisfy a high level of strength and endurance characteristics, there is a problem that the kinds of fibers that can be used in this method are limited to expensive high-strength fibers . As a result, the practical application of this method is limited to high-performance tires for special purpose and advanced use.

Accordingly, the present invention relates to a polyethylene terephthalate stretching yarn capable of preventing problems that are unfavorable to the limitations and disadvantages of the related art, a method for producing the same, and a tire cord manufactured using the same.

One aspect of the present invention is to provide a tire cord made of polyethylene terephthalate yarn which enables production of a tire cord having excellent strength and endothelial property while requiring a relatively small amount of rubber by having an excellent strength even though having a relatively low fineness .

Another aspect of the present invention is to provide a tire cord made of polyethylene terephthalate yarn, which enables production of a tire cord having superior strength and endothelial property while requiring a relatively small amount of rubber by having an excellent strength despite having a relatively low fineness And a method for producing the same.

Another aspect of the present invention is to provide a tire cord which can be produced economically with superior strength and endothelial characteristics and which enables epoch-making tire weight reduction.

Other features and advantages of the invention, besides the above-mentioned aspects of the invention, will be described below, or may be apparent to those skilled in the art from the description.

In accordance with one aspect of the present invention as described above, it is preferred to use an elastomer composition comprising 110 to 200 monofilaments each having a fineness of 2.5 to 4.5 denier and having a strength of 8 g / d or more, an elongation at 4 to 6% 4.5 kg load), and a yarn count of 9 to 14%.

According to another aspect of the present invention, there is provided a process for producing a polymer comprising 90 mol% or more of polyethylene terephthalate having a terminal carboxyl group content of 15 to 30 eq / 10 ⁶ g and an intrinsic viscosity of 0.9 to 1.3 dl / g; Melting the polymer; Forming the plurality of monofilaments by spinning the melted polymer through a spinneret having 110 to 200 spinnerets at a spinning temperature of 280 to 300 캜; Cooling the monofilaments; Focusing the cooled monofilaments to form multifilaments; And stretching the multifilament so that the monofilaments have a fineness of 2.5 to 4.5 denier, respectively. The present invention also provides a method for producing a polyethylene terephthalate stretched yarn.

According to another aspect of the present invention, And an adhesive impregnated or coated on the composite yarn, wherein the composite yarn comprises: a first polyethylene terephthalate composite yarn formed by extruding a first polyethylene terephthalate yarn having a fineness of 450 to 550 denier; And a second polyethylene terephthalate subbing formed by casting a second polyethylene terephthalate stretching yarn having a fineness of 450 to 550 denier, wherein the first and second polyethylene terephthalate lower levers are stitched together, and 8 kgf Or more and a strength after fatigue of 7.5 kgf or more.

The foregoing general description of the present invention is intended to be illustrative of or explaining the present invention, but does not limit the scope of the present invention.

According to the present invention, a polyethylene terephthalate polymer which can be produced at a relatively low cost is used, and exhibits excellent tensile strength and shape stability while having a relatively low fineness, and is a harsh continuous yarn for high twist water development (for improving fatigue performance of a tire cord) PET yarns for tire cords that can withstand the conditions can be manufactured.

In addition, since the tire cord of the present invention manufactured using such a drawn yarn requires only a relatively small amount of rubber due to the low fineness of the drawn yarn, the tire cord can be realized not only to realize weight saving but also to have excellent strength and endurance characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
1 is a partially cutaway perspective view showing a configuration of a tire.

Hereinafter, embodiments of the present invention will be described in detail.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. Therefore, the present invention encompasses all changes and modifications that come within the scope of the invention as defined in the appended claims and equivalents thereof.

The term "comprising" or "comprising", unless otherwise stated explicitly throughout this specification, refers to the inclusion of a particular component (or component) without any limitations, and is to be interpreted as excluding the addition of another component I can not.

The present inventors have found that producing a tire cord with three fineness fibers is very advantageous for weight reduction of a tire. Specifically, a rolling process is performed to cover a thin rubber layer on the tire cord fabric during tire manufacturing. The amount of the rubber layer used varies depending on the thickness of the tire cord fabric. For example, a tire cord made of a PET stretcher having a fineness of 500 denier compared to a tire cord made of a PET stretcher having a fineness of 1500 denier is about 0.5 times thinner and therefore the amount of rubber used is about 0.5 It is only a ship.

Until now, tire cords for commercial use are made of PET stretchers of 1000, 1300, 1500, or 2000 denier. Thus, when a tire cord made from a PET stretch yarn of about three hundreds denier is used, a tire weight reduction of about 5% to about 10% compared to a conventional tire cord is possible.

However, the PET stretch yarn having a fineness of about 500 deniers has not been commercialized to date because of difficulty in production and difficulty in manifesting physical properties. That is, when the fineness of the PET stretch yarn is lowered to about 500 denier, it is difficult to satisfy the required strength level because the time for which the polymer is maintained at a high temperature is prolonged and the movement by the cooling wind becomes large.

The present invention overcomes these new problems. According to the present invention, a PET stretch yarn having excellent strength and shape stability can be produced in spite of having a low fineness, Not only enables a breakthrough tire weight reduction but also exhibits strength and endurance characteristics comparable to or better than conventional tire cords.

The PET stretchers of the present invention comprise 110 to 200 monofilaments each having a fineness of 2.5 to 4.5 denier and having a strength of 8 g / d or greater, elongation at 4.5 kg load at 4-6% 4.5 kg load, , And 9 to 14%.

The PET stretch yarn has a fineness of 450 to 550 denier. Thus, the tire cord fabric produced therefrom also has a relatively thin thickness and the amount of rubber used can be significantly reduced.

The PET stretch yarn may have an intrinsic viscosity of 0.85 to 1.1 dl / g.

Hereinafter, a method for producing the PET drawn yarn of the present invention will be described in detail.

First, a polymer containing 90 mol% or more of polyethylene terephthalate having a terminal carboxyl group (-COOH) content of 15 to 30 eq / 10 ⁶ g and an intrinsic viscosity (IV) of 0.9 to 1.3 dl / g ').

When producing PET drawn at a low fineness of 450 to 550 denier, the PET polymer is exposed to high temperature over 280 占 폚 for a long period of time in the step of melting the polymer and transferring it to the cage. Such prolonged exposure may cause thermal degradation of the polymer, which degradation may result in reduced radial pressure and reduced strength and heat resistance of the PET stretch yarn.

In order to avoid such problems, the present invention uses a PET polymer having a terminal carboxyl group (-COOH) content of 15 to 30 eq / 10 ⁶ g and an intrinsic viscosity (IV) of 0.9 to 1.3 dl / g.

If the intrinsic viscosity of the PET polymer is less than 0.9 dl / g, the length of the molecular chain is short and the stretchable level is reduced, so that the strength is lowered and the fatigue performance is also lowered, which is not preferable. Further, when a PET drawn yarn having a low fineness as in the present invention is produced, the strength and fatigue performance deterioration becomes more serious due to the long-term high-temperature stagnation of the polymer, and the performance as a tire cord becomes impossible.

On the other hand, if the intrinsic viscosity of the PET polymer exceeds 1.3 dl / g, the viscosity of the molten PET polymer becomes large and the manufacturing processability is deteriorated. If a high temperature exceeding 300 캜 is applied to reduce the viscosity, the decomposition of the PET polymer accelerates and the strength of the drawn yarn becomes poor.

On the other hand, since the decomposition reaction of the PET polymer begins at the carboxyl group, when the carboxyl group (-COOH) content of the PET polymer exceeds 30 eq / 10 ⁶ g, the decomposition of the polymer accelerates during a prolonged stay at a high temperature.

On the other hand, when the carboxyl group (-COOH) content of the PET polymer is less than 15 eq / 10 ⁶ g, the reaction with the adhesive is reduced due to the reduced reactivity and the adhesive strength with the rubber is reduced. Therefore, Inappropriate.

In order to control the terminal carboxyl group content of the PET polymer to 15 to 30 eq / 10 ⁶ g, a hindered phenol-based heat-resistant agent or a phenolic-amine heat-resistant agent The terminal carboxyl group content of the PET polymer can be controlled by addition. For example, a hindered phenol heat resistant agent or a phenolic amine with a content of 1000 to 3000ppm for the heat-resistant agent to the weight of the PET polymer by carrying out the polymerization, with the terminal carboxyl group content of 15 to 30 eq / 10 ⁶ g PET polymer may be provided. Examples of usable hindered phenolic resisting agents include tetrakis [methylene (3,5-di-t-butyl-4-hydroxyhydrocinnamate)] methane (trade name Irganox 1010), 1,3,5-trimethyl- (3,5-di-tert-butyl-4-hydroxy-benzyl) benzene (trade name Irganox 1330), 1,6- (Trade name IRGANOX 259), 2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl isocyanurate (trade name Songnox 1790), 4,4'-Butylidenebis (6-tert- 3-methylphenol) (trade name: Songnox 4425), and phenol amine heat resisting agents include N, N-hexane-1,6-diylbis (3- (3,5- di- tert.- butyl-4-hydroxyphenylpropionamide) (Irganox 1098) and N, N'-Propane-1,3-diylbis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionamide] (trade name Irganox 1019) And any phenolic heat resistant agent and phenol amine heat resistant agent known to those skilled in the art can be used.

The PET polymer of the present invention may contain at least one additive in addition to 90 mol% or more of PET, and the term " PET polymer " means a polymer having a PET content of 90 mol% or more unless otherwise stated.

After preparing the PET polymer as above, the polymer is melted and the molten polymer is melt extruded at a spinning temperature of 280 to 300 占 폚, preferably 280 to 290 占 폚, through a spinneret having 110 to 200 spinning holes at 2500 to 4000 m / min to form 110 to 200 monofilaments. The monofilaments are then cooled with a cooling wind at a temperature of 10 to 45 DEG C and a rate of 0.4 to 1 m / s, and the cooled monofilaments are converged to form multifilaments (i.e., unstretched fibers).

When PET yarn having a fineness of 450 to 550 denier is manufactured using a cage having more than 200 detention holes, the yarn and yarn quality are lowered due to an increase in the radial tension, The monofilaments are easily moved and the possibility of yarn breakage and damage due to the low fineness of the monofilaments in the drawing process and winding process is increased.

On the other hand, when a PET yarn having a fineness of 450 to 550 denier is manufactured using a cage having less than 110 cage holes, the shape stability of the PET stretch yarn is also lowered due to the low radiation tension, It may not meet.

However, when the melt spinning is carried out through the spinneret having 110 to 200 spinnerets, the fineness of the monofilaments is optimized, so that it is relatively easy to impart the spinning tension and the occurrence of problems in the drawing and winding processes can be minimized So that it is possible to manufacture a drawn yarn and a tire cord having superior properties and excellent physical properties.

On the other hand, according to the present invention, an undrawn yarn having a high degree of crystallinity can be obtained because an ultra-high speed spinning technique is used in an unstretched yarn manufacturing step, and a tire cord showing excellent strength and shape stability can be produced through subsequent processes.

In order to achieve high crystallinity of such an undrawn yarn, the PET polymer is melt-spun under a spinning speed of 2500 to 4000 m / min, preferably 3000 to 4000 m / min. That is, it is preferable to apply a spinning speed of 2500 m / min or more to achieve the physical properties or productivity of the non-drawn yarn such as high crystallinity. It is desirable to provide the minimum cooling time required for the non- Considering vibration and friction phenomena, the spinning speed should be less than 4000 m / min.

It is also preferred that the melt spinning of the PET polymer proceeds under a radiation tension of 0.6 to 1.2 g / d. That is, in order to obtain the undrawn properties required in the present invention, for example, high crystallinity, the spinning tension is preferably 0.6 g / d or more, and in order to prevent the filament from being cut or deteriorated due to a tension higher than necessary, The radiation tension is preferably 1.2 g / d or less.

According to the present invention, a PET polymer adjusted to have a relatively low terminal carboxyl group content of 15 to 30 eq / 10 ⁶ g is irradiated at a very high speed and the spinning temperature is set to 280 to 300 ° C, preferably 280 to 290 ° C, The hydrolysis of the PET polymer by heat and the decomposition of amines and the deterioration of the properties due to the degradation of the PET polymer are suppressed, so that PET stretch yarns and tire cords having better heat resistance and strength can be produced.

Optionally, it may be desirable to design the transfer pipe and pack of the molten polymer so that the hot holding time of the molten PET polymer (i.e., the residence time in the hot spinning facility) is shortened.

On the other hand, the cooling step is performed with a cooling wind at a temperature of 10 to 45 DEG C and a velocity of 0.4 to 1 m / s. If the velocity exceeds 1.0 m / s, the flow of monofilaments during spinning becomes undesirably undesirably 0.4 m < 2 > / s, not only sufficient cooling is not exhibited, but also external air flows into the closed spinning system due to the vacuum effect, resulting in uneven physical properties and poor workability.

After the non-drawn filament is formed, the non-drawn filament is drawn at a draw ratio of 1.5 to 2.5 to form a PET stretch yarn comprising monofilaments each having a fineness of 5 to 4.5 denier.

In order to produce a tire cord having excellent strength and shape stability, the stretching ratio is preferably 1.5 or more. However, in the case of the ultra-high-speed spinning of the present invention, in which the spinning speed is 2500 to 4000 m / min, the stretching ratio is 2.5 or less due to the restriction of the stretching ratio adjustment.

Such a stretching step may be carried out by a direct spinning and drawing method (hereinafter referred to as DSD method) in which spinning and drawing are continuously performed in a single process according to a conventional spinning process.

Optionally, further heat treatment / heat setting of the stretch yarn may be performed.

Then, the stretching yarn is wound by a winder.

The PET stretch manufactured according to the present invention has an intrinsic viscosity of 0.85 to 1.1 dl / g and has excellent strength and shape stability (i.e., strength of 8 g / d or more, 4 to 6% of midsole, at a 4.5 kg load, and 9 to 14% of the turnips).

Hereinafter, the tire cord manufactured from the PET stretch yarn of the present invention manufactured as described above and its manufacturing method will be described in detail.

The term " plied yarn " as used herein means a yarn formed by twisting primarily twisted yarns together.

As used herein, the term "twist number" refers to the number of twists per meter, and the unit is a twist per meter (TPM).

The tire cord of the present invention includes a composite yarn and an adhesive impregnated or coated with the composite yarn, and has a strength of 8 kgf or more and a strength after fatigue of 7.5 kgf or more.

Wherein the sintered body comprises a first polyethylene terephthalate base yarn formed by casting a first polyethylene terephthalate stretched yarn having a fineness of 450 to 550 denier and a second polyethylene terephthalate stretched yarn having a fineness of 450 to 550 denier And a second polyethylene terephthalate underfill formed.

Each of the first and second polyethylene terephthalate stretchers may comprise 110 to 200 monofilaments each having a fineness of 2.5 to 4.5 denier.

Each of the first and second polyethylene terephthalate stretchers may have a strength of at least 8 g / d, a shear strength of 4 to 6% at a load of 4.5 kg, and a slew of 9 to 14%.

The lower hearth may be performed by twisting each of the first and second polyethylene terephthalate stretchers in a counterclockwise (i.e., Z-direction) twist of 400-600 TPM.

The first and second polyethylene terephthalate lower levers are subjected to secondary twist to form a combined twist yarn. The uplift can be carried out by twisting the first and second polyethylene terephthalate lower levers in a clockwise (i.e., S-direction) twist with 400 to 600 TPM twist.

The lower and upper kinks should have an appropriate range to exhibit optimal strength and fatigue performance. For example, when a PET yarn having a fineness of 1000 denier is used, the tire cord shows the optimum strength and fatigue performance at around 470 TPM in both the lower and upper ends, and when the PET yarn having a fineness of 1500 deniers is used, The tire cord shows optimal strength and fatigue performance at around 360 TPM. The relationship between the number of kinks and the performance can be verified by the Twist Multiplier, and the optimal performance is shown at 13400 to 15000 in the number of connections calculated by Equation 1 below.

Equation 1: K = T *

Where K is the number of connections, T is the number of twists (TPM), and D is the fineness (denier)

Although the optimal twist number of 500 deniers calculated by this connection formula is 600 TPM, in the actual manufacturing process, the twist is loosened due to a too high twist number, or the threads are twisted to each other, And the deformation of the yarn causes a reduction in strength and damage of the yarn, which is undesirable. The inventors have performed an evaluation of several twist numbers and have found that the tire cord exhibits optimal strength and fatigue performance at 400 to 600 TPM (preferably 450 to 550 TPM) ] Reference).

The thus prepared composite yarn is immersed in a resorcinol-formaldehyde-latex (RFL) adhesive solution. In this case, 1-bath dipping or 2-bath dipping can be used. According to one embodiment of the present invention, the RFL adhesive solution comprises 2.0 wt% resorcinol, 3.2 wt% formalin (37%), 1.1 wt% sodium hydroxide (10%), 43.9 wt% styrene / butadiene / Vinyl pyridine (15/70/15) rubber (41%), and water.

According to one embodiment of the present invention, the pick-up rate of the adhesive is adjusted to be 3 to 12% by weight based on the polyester composite yarn. If the pick-up rate is less than 3% by weight, the adhesive strength of the tire cord with rubber decreases. If the pick-up rate exceeds 12% by weight, the strength and endothelial property of the tire cord are deteriorated.

(Optionally after drying for 10 to 400 seconds at 105 to 200 DEG C) at a temperature of 230 to 260 DEG C for 90 to 360 seconds, and preferably , The tire cord is completed by heat treatment at a temperature of 240 to 250 DEG C for 90 to 240 seconds, more preferably at a temperature of 245 to 250 DEG C for 90 to 120 seconds.

The shape stability of the tire cord can be further improved by immersing the composite yarn in an adhesive solution and heat treatment under the above conditions, so that it is possible to further reduce changes in properties of the tire during vulcanization.

The tire cord manufactured according to this process has excellent strength of 8 kgf and exhibits strength after fatigue of 7.5 kgf or more even after the fatigue test similar to the tire running condition, so that breakage and performance deterioration of the tire can be minimized. In addition, since it is made of a PET stretch yarn having a fineness of 450 to 550 denier, it is possible to realize a breakthrough tire light weight and slim tire production.

Hereinafter, the present invention will be described in detail with reference to examples and comparative examples. It should be noted, however, that the following examples are intended to assist the understanding of the present invention and should not limit the scope of the present invention thereby.

[ PET Stretcher Produce]

Example 1 to 6 (500 Denier Finnish Have PET A kite )

Hindered phenolic heat-resistant agent The content of terminal carboxyl groups was measured in the following table by changing the amount of tetrakis [methylene (3,5-di-t-butyl-4-hydroxyhydrocinnamate)] methane (trade name Irganox 1010) 1 and a controlled intrinsic viscosity of 1.20 dl / g.

The PET stretchers of Examples 1 to 6 were each produced by sequentially spinning, cooling, stretching, heat-setting and winding the PET polymer chips by applying ultra-high-speed spinning technology to such PET polymers. At this time, the applied spinning temperature, the number of spinnerets, the spinning speed, the stretching ratio, and the cooling wind (35 ° C) speed are as summarized in Table 1 below and the remaining spinning conditions are the same as those used in the production of PET polymer and PET stretch yarn .

Comparative Example 1-4

The PET stretchers of Comparative Examples 1 to 4 were fabricated by varying the spinning conditions as shown in Table 1 below.

[Table 1]

* -COOH content measurement

The pulverized polymer sample was dissolved in benzyl alcohol at 203 占 폚, phenol red indicator was added, and the resultant was neutralized with a caustic carbobenzyl alcohol solution to obtain a terminal carboxyl group content of the polymer.

[ Stretcher Measurement of physical properties]

The intrinsic viscosity, strength (tensile strength), midsole (intermediate elongation), and elongation (elongation at break) at a load of 4.5 kg of the PET stretch yarns prepared respectively in Examples 1 to 6 and Comparative Examples 1 to 4 were measured according to the following method And the operating performance was evaluated by the following methods. The results are shown in Table 2 below.

Intrinsic viscosity ( dl / g) measurement

After the oil of the PET drawn sample was removed and dried, the intrinsic viscosity of the drawn yarn was measured using an Oswald type viscometer according to the OCP method.

burglar( The tensile strength ) (g / d), 4.5 kg (%) In load, and Omission (%) Measure

According to ASTM D885, the tensile strength of the PET stretch yarn, the degree of sheathing at a load of 4.5 kg, and the yield were measured using a universal tensile tester.

Operability evaluation

The fishing performance was evaluated by calculating the percentage of the number of yarns normally produced with a volume of 10 kg without cutting off the total number of yarns that were attempted to be produced in 24 hours. That is, when the number of abnormal yarns due to truncation is 10, and the number of normally formed yarns is 90, the percentage of operation is 90%. If the above percentage of the above workability is above 95%, the workability is good. If it is below 95%, the workability is poor.

[Table 2]

As can be seen from the above Table 2, the stretch yarn of Comparative Example 1 made of a PET polymer having a low intrinsic viscosity of 0.8 dl / g had a low intrinsic viscosity of 0.775 dl / g and a melt viscosity of less than 8.0 g / d (i.e., 7.3 g / d), respectively.

In case of Comparative Example 2, although the high radiation temperature of 305 DEG C was applied due to the polymer intrinsic viscosity which was too high of 1.5 dl / g, the operation was poor due to the high pressure.

In Comparative Example 3, because of the high cooling wind speed of 1.4 m / s, the radiation resistance was poor and the operationability was poor.

In Comparative Example 4, due to the reduced monofilament fineness, the radiation resistance was very severe due to the presence of scattering, and the tensile strength was 7.3 g / d.

[Production of tire cord]

The PET stretch yarns of Example 1 or Example 5 were inferred in the Z-direction to make two strands of the lower strands, and the lower strands were stitched together in the S-direction to produce composite strands. The twist numbers of the lower and upper edges were the same. The types of PET stretch yarn used and the twist counts (TPM) of the outermost layer and the bottom layer were as shown in Table 3 below. The PET tire cords of Examples 7 to 12 and Comparative Examples 5 to 7 were prepared by immersing the composite yarns in an RFL adhesive solution, followed by drying and heat treatment. The composition and drying conditions of the RFL adhesive solution were in accordance with the conventional PET tire cord manufacturing conditions.

The tensile strengths of the tire cords of Examples 7 to 12 and Comparative Examples 5 to 7 thus prepared were measured according to the following methods, respectively, and the results are shown in the following Table 3 shows the results.

Strong (g / d), 4.5 kg (%) In load, and Omission (%) Measure

According to the ASTM D885 standard, the tensile strength of the tire cord, the tensile strength at a load of 4.5 kg, and the yield were measured using a universal tensile tester.

After fatigue Strong (g / d) measurement

After preparing the rubber specimens with tire cords, fatigue was applied to tire cords at 10% elongation and 10% compression at 2500 rpm at 80 ° C for 12 hours using a disk putigator. The detailed specification is JIS 1017 DISC TYPE TESTER (GOOD RICH METHOD). Then, after removing the rubber, the strength of the tire cord was measured in the same manner as above.

[Table 3]

As can be seen from Table 3, it is understood that the twisted number of less than 400 TPM and the twisted number of more than 600 TPM deteriorate the characteristics of the tire cord to the inner skin, and thus are not suitable for tire cords requiring long-term durability.

Claims

110 to 200 monofilaments each having a fineness of 2.5 to 4.5 denier,
A tensile strength of at least 8 g / d, an elongation at 4.5 kg load at a load of 4.5 kg of 4 to 6%, and an elongation of 9 to 14%.

The method according to claim 1,
Wherein the polyethylene terephthalate stretched yarn has a fineness of 450 to 550 denier.

The method according to claim 1,
Wherein the polyethylene terephthalate stretched yarn has an intrinsic viscosity of 0.85 to 1.1 dl / g.

Preparing a polymer comprising 90 mol% or more of polyethylene terephthalate having a terminal carboxyl group content of 15 to 30 eq / 10 ⁶ g and an intrinsic viscosity of 0.9 to 1.3 dl / g;
Melting the polymer;
Forming the plurality of monofilaments by spinning the melted polymer through a spinneret having 110 to 200 spinnerets at a spinning temperature of 280 to 300 캜;
Cooling the monofilaments;
Focusing the cooled monofilaments to form multifilaments; And
And stretching the multifilament so that the monofilaments have a fineness of 2.5 to 4.5 denier, respectively.

5. The method of claim 4,
The spinning speed in the spinning step is 2500 to 4000 m / min,
Wherein the stretching ratio in the stretching step is 1.5 to 2.5.

5. The method of claim 4,
Wherein the cooling step is performed at a temperature of 10 to 45 DEG C and a cooling wind at a rate of 0.4 to 1 m / s.

Combined twist; And
And an adhesive impregnated or coated on the composite yarn,
The above-
A first polyethylene terephthalate underfill formed by casting a first polyethylene terephthalate stretching yarn having a fineness of 450 to 550 denier; And
And a second polyethylene terephthalate underfill formed by casting a second polyethylene terephthalate stretching yarn having a fineness of 450 to 550 denier,
Wherein the first and second polyethylene terephthalate lower levers are stitched together,
A tire cord characterized by having a strength of at least 8 kgf and a strength after fatigue of at least 7.5 kgf.

8. The method of claim 7,
Wherein each of said first and second polyethylene terephthalate stretchers comprises 110 to 200 monofilaments each having a fineness of 2.5 to 4.5 denier.

8. The method of claim 7,
Wherein each of said first and second polyethylene terephthalate stretchers has a strength of at least 8 g / d, a flexural strength at a load of 4.5 kg of from 4 to 6%, and a slew of 9 to 14%.

8. The method of claim 7,
Wherein each of said first and second polyethylene terephthalate lower levers has a twist number of 400 to 600 TPM.

11. The method of claim 10,
Wherein the first and second polyethylene terephthalate lower levers are staged together with a twisted number of 400 to 600 TPM.

8. The method of claim 7,
Characterized in that the adhesive is a resorcinol-formaldehyde-latex adhesive.