KR20150104475A

KR20150104475A - Apparatus and Method for Manufacturing Polyester Yarn for Tire Cord

Info

Publication number: KR20150104475A
Application number: KR1020140026247A
Authority: KR
Inventors: 박성호
Original assignee: 코오롱인더스트리 주식회사
Priority date: 2014-03-05
Filing date: 2014-03-05
Publication date: 2015-09-15
Also published as: KR101956711B1

Abstract

Disclosed are an apparatus and a method for manufacturing polyester yarn for a tire cord. The apparatus for manufacturing polyester yarn for a tire cord, according to the present invention, comprises an insulating board arranged between a heating hood and a spinneret in order to prevent heat of the heating hood from being transferred to the spinneret.

Description

[0001] Apparatus and Method for Manufacturing Polyester Yarn for Tire Cord [0002]

The present invention relates to an apparatus and a method for producing polyester yarns for tire cords.

Generally, a method for producing a polyester yarn for a tire cord comprises the steps of melting a polyester chip, spinning the molten polyester through a spinneret, forming the molten polyester while discharging through the spinneret Cooling the monofilaments in the semi-solid state, collecting the cooled monofilaments to form multifilaments, stretching the multifilaments, and winding the drawn multifilaments.

On the other hand, tire cords are required to have high form stability (i.e., low moderate elongation and low dry shrinkage). Unlike conventional industrial polyester yarns that exhibit high strength by applying a high stretch ratio (e.g., 6 or more) after low speed spinning in order to impart good shape stability to the tire cord, polyester yarns for tire cords have high radiation Speed (for example, 2500 m / min or more). That is, by increasing the degree of orientation of the fibers before the stretching process, the shape stability of the tire cord as the final product can be improved.

However, the higher the spinning speed, the lower the stretching ratio. Accordingly, there has been a limit to improve the strength of the yarn for a tire cord due to a low stretching ratio (for example, 2.0 or less), and a tire cord made of a yarn having a relatively low strength has not exhibited satisfactory strength.

In order to produce a polyester yarn having a higher strength than that of a polyester yarn for a tire cord without deteriorating the shape stability of the tire cord, there has been proposed a method in which a molten polyester is discharged through the spinneret, A method of disposing a heating hood between the spinneret and the cooling section to retard the cooling of the monofilaments in the heated state has been suggested.

That is, by setting the temperature of the heating hood at a temperature that is equal to or slightly lower than the temperature of the spinneret (i.e., 200 to 300 ° C), the cooling of the monofilament is delayed and the degree of orientation of the non- Respectively.

However, the improvement in the strength of the polyester yarn, which can be achieved by such a delay cooling method, was only marginal.

Accordingly, the present invention relates to an apparatus and a method for producing a polyester yarn for a tire cord, which can prevent the problems due to the limitations and disadvantages of the related art as described above.

One aspect of the present invention is to provide an apparatus capable of producing a polyester yarn having a higher strength than that of a polyester yarn for a tire cord without deteriorating the shape stability of the tire cord.

Another aspect of the present invention is to provide a method for producing a polyester yarn having a higher strength than a conventional polyester cord for a tire cord without deteriorating the shape stability of the tire cord.

Other features and advantages of the invention will be set forth in the description which follows, or may be learned by those skilled in the art from the description.

According to one aspect of the present invention as described above, an extruder; A spinneret capable of spinning the melted polyester resin transferred through the extruder; A heating hood capable of heating a plurality of monofilaments formed as the molten polyester resin is discharged from the spinneret; A cooling unit capable of cooling the heated monofilaments; A focusing unit capable of focusing the cooled monofilaments to form multifilaments; A stretching unit capable of stretching the multifilament; A winder capable of winding the drawn multifilament; And a first heat insulating plate disposed between the heating hood and the spinneret to prevent the heat of the heating hood from being transferred to the spinneret. .

According to another aspect of the present invention, there is provided a method for producing a polyester resin, comprising spinning a molten polyester resin through a spinneret; Heating the plurality of monofilaments formed by discharging the polyester resin from the spinneret at 400 ° C or higher; Cooling the heated monofilaments; Collecting the cooled monofilaments to form multifilaments; Stretching the multifilament; And winding the elongated multifilament. The polyester yarn for a tire cord is produced by a method comprising the steps of:

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, by fixing the molecular arrangement of the polyester resin aligned in accordance with the die swelling phenomenon immediately after the molten polyester resin is discharged from the spinneret, the degree of strong expression of the multifilament under a predetermined stretching ratio can be maximized have.

That is, according to the present invention, even in an environment in which a relatively low stretching ratio is required to be applied due to a high spinning speed as in the case of producing a polyester yarn for a tire cord, the maximum strength that can be realized under such a low stretching ratio is expressed, Can be produced. By producing a tire cord using such a polyester yarn, a tire cord having high strength and excellent shape stability can be provided.

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.
Fig. 1 schematically shows the molecular structures immediately before and after the stretching of the polyester multifilament formed by the prior art,
Fig. 2 schematically shows the molecular structures immediately before and after the stretching of the polyester multifilament formed by one embodiment of the present invention,
3 schematically shows an apparatus for producing a polyester multifilament according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

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.

Generally, when a molten polyester resin is discharged into a spinneret, a sudden entropy increase causes a die swell phenomenon, also referred to as an extrudate swell. Due to such die swellability, the molecular chains and entanglement points of the polyester resin are regularly aligned.

However, as illustrated in FIG. 1, the regularly arranged monofilaments formed as the molten polymer is discharged from the spinneret pass through the heating hood and / or the cooling section, and such regular molecular arrangement state is somewhat deformed. As the molecular arrangement of the multifilament just before stretching is irregular, the stretchability of the multifilament is inevitably lowered (i. E., The degree of intensive development is inevitably reduced under a predetermined stretching ratio).

In the case of yarns for tire cords, which are subject to a relatively low draw ratio due to their high spinning speed, such low stretchability makes it impossible to achieve a satisfactory strength improvement of the polyester yarn.

Therefore, in order to realize a polyester yarn for tire cord of high strength, the stretchability of the radiated multifilament should be improved. To improve the extensibility of the spun multifilaments, the molecular arrangement of the polyester resin aligned with the die swell phenomenon immediately after being discharged from the spinneret is immediately fixed in that state so that the regular molecular arrangement is maintained until just prior to the drawing process do.

As a method for directly fixing the molecular arrangement of the polyester resin aligned in accordance with the die swell phenomenon immediately after being discharged from the spinneret, laser irradiation may be considered.

By intensively irradiating the polyester resin with a laser immediately after the molecular arrangement of the polyester resin discharged from the spinneret is aligned by the die swelling phenomenon (for example, by irradiating the monofilament passing through the spot 5 to 15 mm away from the spinneret By locally irradiating a portion of the molecular array), the molecular array can be anchored (i.e., in a regularly arranged state).

However, molecular alignment for lasers is disadvantageous in that it is not suitable for mass production of yarns composed of a plurality of monofilaments although it can be performed on one monofilament in laboratory scale, This is because there is no way for deviation.

Further, in order to manufacture a high-strength polyester yarn, a closed-type spinning system capable of precisely controlling the cooling process before stretching is required. The laser irradiation method is an open-type spinning system which makes precise control of the cooling process impossible. .

Therefore, according to the present invention, as shown in Fig. 2, a plurality of monofilaments in a semi-solid state emerging from the spinneret are heated at a high temperature of 400 DEG C or more in the heating hood for a relatively short time, The multifilament having the regular molecular arrangement is fixed in an aligned state and is stretched at a predetermined stretching ratio, thereby maximizing the strong expression.

The thus produced polyester yarn for tire cord of the present invention contains 300 to 1,000 monofilaments each having a fineness of 1 to 3 denier, and has a tensile strength of 9.7 g / d or more and a cut elongation of 9.6% or more.

In preferred embodiments, the polyester yarn has a tensile strength of at least 10 g / d.

Optionally, the monofilaments may be formed of polyethylene terephthalate (PET).

Hereinafter, with reference to FIG. 3, an apparatus and a method for producing a polyester yarn for a tire cord according to an embodiment of the present invention will be described in detail.

3, the apparatus according to one embodiment of the present invention includes an extruder 110, a spinneret 120 (not shown) capable of spinning melted polyester resin delivered through the extruder 110, A heating hood 140 capable of heating a plurality of monofilaments formed by discharging the melted polyester resin from the spinneret 120, a cooling unit 160 capable of cooling the heated monofilaments, A focusing unit 170 for focusing the cooled monofilaments to form multifilaments, a stretching unit 180 for stretching the multifilaments, a winder 190 for winding the stretched multifilaments 190 And a first heat insulating plate 130 disposed between the heating hood 140 and the spinneret 120 to prevent the heat of the heating hood 140 from being transferred to the spinneret 120 do.

Alternatively, the apparatus of the present invention may further include a second heat insulating plate 140 disposed between the heating hood 140 and the cooling unit 160 to prevent the heat of the heating hood 140 from being transferred to the cooling unit 160. [ (150).

A polyester (e.g., PET) chip having an intrinsic viscosity of 0.8 to 1.5 is put into the extruder 110 and melted. The temperature of the molten polyester may be between 290 and 310 ° C. When the temperature of the molten polyester is less than 290 ° C, the polymer is not uniformly dissolved and spinning is difficult. When the temperature exceeds 310 ° C, not only the viscosity of the polymer becomes too low but also pyrolysis due to high temperature is caused and high-

The melted polyester resin is radiated through the spinneret 120. L / D, which is the ratio of the hole length L to the hole diameter D of the spinneret, may be 2 to 5. When L / D is less than 2, radioactivity is poor, and when L / D exceeds 5, packing pressure increases and radioactivity is poor.

As soon as the polyester resin begins to solidify as it is discharged from the spinneret 120, a plurality of monofilaments in a semi-solid state are formed. At this time, as described above, the molecular arrangement of the polyester resin is regularly aligned by the die swellability.

According to the present invention, in order to fix the molecular arrangement of the polyester in an aligned state, the plurality of monofilaments in the semi-solid state are heated to a high temperature of 400 ° C or more in the heating hood 140. That is, the heating hood 140 of the present invention can heat the monofilaments at 400 ° C or higher.

The higher the temperature of the heating hood 140 for heating the monofilaments, the higher the strength of the final polyester yarn by increasing the molecular alignment effect. However, when the temperature is too high (for example, The thermal decomposition of the polymer may be caused, resulting in a decrease in the strength of the polyester yarn and a decrease in the quality of the yarn. Thus, the preferred temperature of the heating hood 140 for heating the monofilaments is 500 ° C to 600 ° C.

In addition, the heating time of the monofilaments in the heating hood 140 should be relatively short in order to minimize or prevent the pyrolysis of the polymer from occurring during fixation of the molecules. Accordingly, the heating hood 140 of the present invention preferably has a relatively short length (parallel to the traveling direction of the multifilament), for example, 20 to 50 mm.

On the other hand, the temperature of the spinneret 120 needs to be kept constant and stable in order to obtain stability of work and uniform fiber properties. If the surface temperature of the spinneret 120 is uneven, uniformity of the fiber properties is caused and the processability is deteriorated. When the heating hood 140 having a temperature higher than the temperature of the spinneret 120 is disposed below the spinneret 120 without any heat insulating plate, the heat of the heating hood 140 is transferred to the spinneret 120 The thermal decomposition of the molten polymer present in the spinneret 120 increases and temperature unevenness of the monofilaments discharged from the spinneret may be caused. This may cause the yarn manufacturing itself to be impossible, or at least the strength drop of the polyester yarn, Deg.] C, and severe physical property deviations.

Therefore, in order to prevent the heat of the heating hood 140 from being transferred to the spinneret 120, the first heat insulating plate 130 is interposed between the heating hood 140 and the spinneret 120, . That is, the transfer of the heat used during the heating step for fixing the molecular arrangement to the spinneret 120 is blocked.

The monofilaments heated while passing through the heating hood 140 are completely solidified by being cooled in the cooling unit 160. Blowing the cooling wind at a proper temperature and speed to the monofilaments for controlling the cooling process. The cooling behavior of the monofilaments has a great effect on the final properties of the fibers.

According to an embodiment of the present invention, the second heat insulating plate 150 is disposed between the heating hood 140 and the cooling unit 160 so that the heat of the heating hood 140 is transmitted to the cooling unit 160 It is prevented from being transferred.

The cooled and fully solidified monofilaments are collected by the focusing unit 170 to form the multifilament. The focusing unit 170 may apply an emulsion to the multifilament. That is, the multifilament forming step and the emulsion applying step may be performed simultaneously. The emulsifying agent may be carried out through a method of MO (Metered Oiling) or RO (Roller Oiling).

The multifilament formed through the focusing process is stretched in the stretching portion 180. [ The stretching unit 180 includes first and second godet rollers 181 and 182.

The first godet roller 181 determines a spinning rate and a draft ratio and determines a draw ratio by a ratio of the speed of the first godet roller 181 and the speed of the second godet roller 182, Is determined.

As described above, in order to impart excellent shape stability to the tire cord, the polyester yarn for tire cord needs to be produced at a high spinning speed. That is, by increasing the degree of orientation of the fibers before stretching, the shape stability of the tire cord as a final product can be improved. According to one embodiment of the present invention, the spinning speed (i.e., the speed of the first godet roller 181) is 2500 to 4000 m / min.

In the case of the present invention in which high-speed radiation is applied, there is a limit to setting the speed of the second godet roller 182 to be larger than the speed of the first godet roller 181. Therefore, according to an embodiment of the present invention, The stretching ratio is 1.5 to 2.0.

Optionally, the second godet roller 182 may be provided with heating means to perform heat treatment / heat setting of the drawn multifilament. By controlling the number of times the multifilaments are wound on the second godet roller 182, the time during which the multifilament stays on the second godet roller 182 can be adjusted, and the heat treatment / heat fixing for the drawn yarn can be performed.

The stretched and heat-treated multifilaments are wound by a winder 190 to complete a polyester yarn for a tire cord.

Hereinafter, a tire cord made of a polyester yarn for a tire cord of the present invention and a method for producing the same will be described in detail.

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

The term " tire cord " as used herein is defined to include the joint yarn itself as well as the joint yarn containing the adhesive so that it can be directly applied to the rubber product.

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 comprises a composite yarn and an adhesive impregnated or coated with the composite yarn, wherein the yarn has a tensile strength of 8.7 g / d or more, an intermediate elongation at a load of 2.25 g / d of 4.6% or less, And a dry heat shrinkage ratio.

The tire cord according to a particularly preferred embodiment of the present invention has a tensile strength of at least 9 g / d.

The combination yarn comprises a first polyester underfill formed by primary twist of a first polyester yarn and a second polyester underfill formed by inferring a second polyester yarn.

The first and second polyester yarns each have a tensile strength of at least 9.7 g / d, preferably at least 10 g / d.

The bottom yarn can be performed by twisting each of the first and second polyester yarns in a counterclockwise (i.e., Z-direction) twist number of 200 to 600 TPM.

The first and second polyester lower levers are secondary twisted together to form a combined twist yarn. The uplift can be performed by twisting the first and second polyester lower weaves together in a clockwise (i.e., S-direction) twisted number of 200 to 600 TPM.

If the twist count of the upper and / or lower tread is less than 200 TPM, the elongation of the tire cord, the endurance of the tire cord, and the adhesion deterioration with the rubber product fall outside the permissible range. If the tensile strength exceeds 600 TPM, There is a problem that the uniformity of the twist is lowered.

The polyester composite yarn prepared as described above is immersed in a resorcinol-formaldehyde-latex (RFL) 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.

The polyester sintered yarn containing the RFL adhesive solution by immersion is dried at 105 to 200 ° C for 10 to 400 seconds and then heat-treated at 105 to 300 ° C for 10 to 400 seconds to complete the tire cord. The drying process is for removing moisture present in the composite yarn, and the heat treatment process is for imparting adhesive force to the tire cord by reacting the RFL adhesive solution contained in the composite yarn.

On the other hand, if the drying and heat treatment times are shorter than the above range, respectively, and the drying and heat treatment temperatures are lower than the above ranges, the adhesive strength between the tire cord and the rubber is lowered. On the contrary, when the drying and heat treatment time are longer than the above ranges, or when the drying and heat treatment temperatures are higher than the upper range, the adhesion of the tire cord to the rubber is lowered due to excessive heat and the physical properties such as strength and fatigue resistance may be lowered have.

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.

Polyethylene terephthalate ( PET ) Manufacture of yarn

Example One

A polyethylene terephthalate (PET) yarn having a monofilament fineness of about 2.6 denier and a total fineness of 1000 denier was produced using the apparatus illustrated in Fig. Specifically, after melting a PET chip having an intrinsic viscosity of 1.2, the molten polymer was radiated at a spinning speed of 3500 m / min through spinneret (L / D = 4.0 / 1.0) , And a winding step were performed in this order. The length and temperature of the heating hood (H / H) were 30 mm and 400 deg. C, respectively, and the stretching ratio was 1.65.

Example 2

A PET yarn was produced in the same manner as in Example 1, except that the temperature of the heating hood (H / H) was 450 ° C.

Example 3

A PET yarn was produced in the same manner as in Example 1, except that the temperature of the heating hood (H / H) was 500 ° C.

Example 4

A PET yarn was produced in the same manner as in Example 1, except that the temperature of the heating hood (H / H) was 550 占 폚.

Example 5

A PET yarn was produced in the same manner as in Example 1 except that the temperature of the heating hood (H / H) was 600 占 폚.

Example 6

A PET yarn was produced in the same manner as in Example 1, except that the temperature of the heating hood (H / H) was 650 ° C.

Example 7

A PET yarn was produced in the same manner as in Example 1, except that the temperature of the heating hood (H / H) was 350 占 폚.

Comparative Example One

A PET yarn was produced in the same manner as in Example 1, except that an insulating plate between the spinneret and the heating hood (H / H) was omitted and the length and temperature of the heating hood (H / H) Respectively.

Comparative Example 2

Tensile strength, cut elongation and sanding of the PET yarns prepared respectively in Examples 1 to 7 and Comparative Examples 1 and 2 were respectively measured / evaluated by the following methods, and the results are shown in Table 1 below .

PET Yarn The tensile strength And Truncation Measure

The tensile strength (g / d) and elongation at break (%) of the PET yarn were measured using a universal tensile tester of Instron Engineering Corp. (Canton, Mass.) According to the ASTM D885 method.

PET Evaluation of yarn quality

The degree of occurrence of moth was visually observed to evaluate the yarn quality of the PET yarn relatively.

H / H Length
(mm) H / H temperature
(° C) Between spinning detention and H / H
Presence of insulation board The tensile strength
(g / d) Truncation
(%) Siliceous Example 1 30 400 U 9.7 10.2 ◎ Example 2 30 450 U 9.9 10.1 ◎ Example 3 30 500 U 10.1 9.8 ◎ Example 4 30 550 U 10.2 9.8 ○ Example 5 30 600 U 10.3 9.6 △ - ○ Example 6 30 650 U 9.8 9.2 × Example 7 30 350 U 9.3 11.0 ◎ Comparative Example 1 60 300 radish 9.0 11.8 ◎ Comparative Example 2 60 500 radish 8.6 12.2 ×

As shown in Table 1, when the temperature of the heating hood (H / H) was set to 400 ° C or higher, the PET yarn had a tensile strength of 9.7 g / d or more and a cutting elongation of 9.6% or more. Particularly, when the temperature of the heating hood (H / H) was set to 500 ° C to 600 ° C, the PET yarn exhibited a high tensile strength of 10 g / d or more.

On the other hand, when the temperature of the heating hood (H / H) was 300 ° C, the PET yarn exhibited unsatisfactory tensile strength of 9.0 g / d. This was due to the fact that, It is believed that the multifilament is stretched.

When the temperature of the heating hood (H / H) exceeded 600 ° C, the tensile strength of the PET yarn was reduced, the cutting elongation was lowered to less than 9.6%, and the yarn quality was deteriorated due to the excessively high temperature.

On the other hand, in the case of Comparative Example 2 in which there was no insulating plate between the heating hood (H / H) at 500 ° C and the spinneret, the tensile strength of the PET yarn was very low and the yarn was very bad, Likewise, the heat of the heating hood is transferred to the spinneret, which leads to an increase in the decomposition of the molten polymer present in the spinneret and to the unevenness of the physical properties of the monofilaments discharged from the spinneret.

Manufacture of tire cords

Example 8 to 14 and Comparative Example 3 and 4

Tire cords of Examples 8 to 14 and Comparative Examples 3 and 4 were respectively prepared under the same conditions in the same manner except that the PET yarns prepared in Examples 1 to 7 and Comparative Examples 1 and 2 were used respectively . Specifically, PET yarn was used to prepare two strands of twist yarn (Z-direction) having a twist number of 410 TPM, and the two twist yarns were stitched together (S-direction) with 410 TPM twisted yarn . Then, the combined yarn was passed through a resorcinol-formaldehyde-latex (RFL) adhesive solution, followed by drying and heat treatment to complete the tire cord.

The tensile strengths of the tire cords of Examples 8 to 14 and Comparative Examples 3 and 4, the intermediate elongation at break at 2.25 g / d load, the elongation at break and the dry heat shrinkage were measured respectively by the following methods, The results are shown in Table 2 below.

Tire cord The tensile strength , Intermediate elongation at 2.25 g / d load, and Truncation Measure

The tensile strength (g / d) of the tire cord, the elongation at break (%) at a load of 2.25 g / d, and the elongation at break (%) were measured using an Instron universal tensile tester according to the ASTM D885 method.

Tire cord Dry heat shrinkage Measure

(L1) of the sample after 2 minutes at a load of 0.01 g / d using a dry heat shrinkage ratio measuring device (TESTRITE, model name: MK-V) according to the ASTM D4974-04 method, and the length (L2) of the sample after 2 minutes with the load of d was measured. Next, the dry heat shrinkage ratio of the tire cord was calculated by applying L1 and L2 to the following equation.

Dry heat shrinkage ratio (%) = [(L1 - L2) / L1] × 100

Tensile strength (g / d) The elongation at break at 2.25 g / d load (%) Cutting Elongation (%) Dry heat shrinkage (%) Example 8 8.7 4.6 18.4 2.2 Example 9 8.9 4.5 16.9 2.3 Example 10 9.1 4.5 18.0 2.4 Example 11 9.2 4.6 18.1 2.5 Example 12 9.3 4.5 15.3 2.6 Example 13 8.8 4.6 13.6 3.1 Example 14 8.4 4.5 18.8 2.0 Comparative Example 3 8.1 4.5 18.2 2.3 Comparative Example 4 7.7 4.5 17.6 2.5

As shown in Table 2, the tire cords of Comparative Examples 3 and 4 made of PET yarn having a low tensile strength of 9.0 g / d or less have unsatisfactory tensile strengths of 8.1 g / d or less .

On the other hand, the tire cords of Examples 8 to 14, each made of PET yarn having a tensile strength of 9.3 g / d or more, had a high tensile strength of 8.4 g / d or more, especially PET yarn The tire cords of Examples 10 to 12, respectively, have very high tensile strengths of 9 g / d or more.

Further, it can be seen that the tire cords of Examples 8 to 12 and 14 all have excellent shape stability by showing moderate elongation at load of 2.25 g / d or less and dry heat shrinkage of 2.6% or less at 4.6% or less.

On the other hand, the tire cord of Example 13 made from the PET yarn of Example 6 in which the shrinkage occurred due to an excessively high heating hood (H / H) temperature (650 ° C) had a high dry shrinkage ratio of 3.1% Stability).

In addition, the tire cord of Comparative Example 4 made of the PET yarn of Comparative Example 2, which had low tensile strength and poor quality due to the absence of an insulating plate between the heating hood (H / H) at 500 ° C and the spinneret, g / d. < / RTI >

110: Extruder 120: spinning detention
130: first heat insulating plate 140: heating hood
150: second heat insulating plate 160: cooling part
170: focusing unit 180:
181: first godet roller 182: first godet roller
190: Winder

Claims

Extruder;
A spinneret capable of spinning the melted polyester resin transferred through the extruder;
A heating hood capable of heating a plurality of monofilaments formed as the molten polyester resin is discharged from the spinneret;
A cooling unit capable of cooling the heated monofilaments;
A focusing unit capable of focusing the cooled monofilaments to form multifilaments;
A stretching unit capable of stretching the multifilament;
A winder capable of winding the drawn multifilament; And
And a first heat insulating plate disposed between the heating hood and the spinneret to prevent the heat of the heating hood from being transferred to the spinneret.

The method according to claim 1,
Further comprising a second heat insulating plate disposed between the heating hood and the cooling unit to prevent the heat of the heating hood from being transferred to the cooling unit.

The method according to claim 1,
Wherein the length of the heating hood parallel to the traveling direction of the multifilament is 20 to 50 mm.

The method according to claim 1,
Wherein the heating hood is capable of heating the monofilaments at 400 DEG C or higher.

The method according to claim 1,
Wherein the converging section is capable of imparting an emulsion to the multifilament.

Radiating the molten polyester resin through a spinneret;
Heating the plurality of monofilaments formed by discharging the polyester resin from the spinneret at 400 ° C or higher;
Cooling the heated monofilaments;
Collecting the cooled monofilaments to form multifilaments;
Stretching the multifilament; And
And winding the stretched multifilament on the polyester yarn.

The method according to claim 6,
The spinning speed in the spinning step is 2500 to 4000 m / min,
And the stretching ratio in the stretching step is 1.5 to 2.0.

The method according to claim 6,
Wherein the heating step is performed by heating the monofilaments at 500 ° C to 600 ° C.

The method according to claim 6,
Further comprising the step of blocking the transition of the heat used during the heating step to the spinneret.

The method according to claim 6,
Further comprising the step of applying an emulsion to the multifilament. &Lt; RTI ID = 0.0 > 21. < / RTI >

11. The method of claim 10,
Wherein the emulsion application step is performed simultaneously with the multifilament formation step.