KR20170091968A

KR20170091968A - Manufacturing method of polyethylene terephthalate cord having excellent fatigue resistance

Info

Publication number: KR20170091968A
Application number: KR1020160012921A
Authority: KR
Inventors: 황수연; 주시환; 박진경; 김철
Original assignee: 주식회사 효성
Priority date: 2016-02-02
Filing date: 2016-02-02
Publication date: 2017-08-10

Abstract

The present invention provides a method for manufacturing a polyethylene terephthalate cord having an excellent fatigue resistance comprising the steps of: manufacturing undrawn yarns by melting polyethylene terephthalate chip having an intrinsic viscosity greater than or equal to 1.0, and extruding by means of a nozzle; multistage-stretching the undrawn yarns by making the undrawn yarns pass through a stretching roller, winding the same, and manufacturing yarns having a strength, formed by the winding, greater than or equal to 9.3 g/d and a dimensional stability index (the middle elongation + the dry shrinkage rate) less than or equal to 12.0; and manufacturing a raw cord by twisting the yarns by means of a twister, and heat treating the generated raw cord at a speed more than or equal to 20 m/min. Moreover, the present invention can manufacture a polyethylene terephthalate cord having a high strength, a low shrinkage and an excellent fatigue resistance which has a strength greater than or equal to 9.3 g/d based on 1,000 d/2ply, a dimensional stability index less than or equal to 6.0, and a fatigue resistance more than or equal to 90.0%. The present invention has a high stability against a repetitive stress, thereby utilizing as a tire cord and a rubber reinforcing material.

Description

Technical Field [0001] The present invention relates to a method of producing a polyethylene terephthalate cord having excellent fatigue resistance,

The present invention relates to a method for producing a polyethylene terephthalate cord having excellent fatigue resistance, and a method for producing a polyethylene terephthalate cord having improved fatigue resistance by improving a spinning and drawing process of a polyethylene terephthalate yarn constituting a cord.

In order to increase the strength of the polyester fiber used for industrial purposes, conventionally, after melting a high-viscosity chip having an intrinsic viscosity of 1.0 dl / g or more, the molten polymer temperature is sufficiently elevated to 300 ° C. and then melted and solidified. And the unstretched warp yarn obtained by winding at a low speed of 1,000 or less was directly stretched to a stretch ratio of 5.0 or more in one or two stages and relaxed and wound.

At this time, the degree of orientation of the undrawn yarn was lowered by low-speed winding, and high-strength characteristics were obtained by giving high-degree of extension.

However, since the yarn produced by the conventional method as described above has a high shrinkage ratio, when applied to a tire cord, the dimensional stability of the tire is deteriorated and shape distortion may occur.

In addition, the conventional method as described above is characterized in that the temperature of the heating hood and the cooling wind is appropriately adjusted so that the degree of orientation of the non-drawn filament is minimized and then the filament is drawn at a high magnification.

When the stretching magnification is increased to obtain fibers of higher strength by using the conventional spinning technique, the viscosity at the time of spinning, the shrinkage rate of the yarn due to high-rate stretching and the shape stability are lowered due to the high temperature of the heating hood during spinning. A large number of pin yarns and a problem in the process of causing a lot of spinning yarns due to high-magnification stretching lead to a decrease in post-processability. In addition, there is a problem in that the viscosity of the high viscosity polyethylene terephthalate resin is lowered during spinning, the shrinkage rate of the yarn is increased by high-rate stretching, and the shape stability is lowered. In the HMLS method for overcoming the above-mentioned problems, there is a problem that when the strength is taken in terms of strength and shape stability, the morphological stability is deteriorated, and when the morphological stability is improved, desired strength is not obtained.

U.S. Patent Nos. 4,101,525 and 4,491,657 disclose industrial polyethylene terephthalate yarns having high initial modulus and low shrinkage by manufacturing yarns by high speed spinning.

However, it is known that the yarns disclosed in these patents do not satisfy the characteristics required for tire cords due to their reduced strength when used as tire cords.

In order to produce a polyethylene terephthalate yarn which can be used for a tire cord, it is advantageous to increase the strength and strength of the yarn by increasing the non-crystallization in the microstructure of the yarn by the low radiation draft and the high stretching ratio in the spinning process. However, The shrinkage ratio is high and the strength utilization ratio (strength of the treated cord / strength of the yarn) is lowered. Therefore, there is a problem that a high-strength yarn must be manufactured to compensate.

On the other hand, the tire cord using the polyethylene terephthalate yarn having the orientation and crystal structure developed with high radiation draft and low stretching ratio has excellent modulus and strength utilization, but the strength is lowered after the heat treatment.

In addition, if the spinning draft and the stretching ratio condition of the spinning process are set to the middle of the above range, the microstructure and physical properties of the yarn are moderately exhibited, which makes it difficult to obtain the high strength required for the tire cord.

Korean Patent Publication No. 10-2013-0079257

In order to solve the above-mentioned problems, the present invention provides a method for producing a polyethylene terephthalate having a high fatigue resistance by conducting a heat treatment at a speed of 20 m / min or more at a raw cord twisted by using a polyethylene terephthalate yarn, And a cured polyethylene terephthalate cord.

In order to achieve the above-mentioned object, the present invention provides a method for producing a non-drawn filament, comprising: melting a polyethylene terephthalate chip having an intrinsic viscosity of 1.0 or more and extruding through a nozzle to produce an undrawn filament; The unstretched yarn is passed through a stretching roller to be multi-step stretched, and wound to produce a yarn having a strength of 9.3 g / d or more and a shape stability index (modulus of elongation + dry heat shrinkage) of 12.0 or less. And a step of preparing a raw cord by spinning the yarn with a twisted yarn and then subjecting the raw cord to heat treatment at a speed of 20 m / min or more to produce a polyethylene terephthalate cord having excellent fatigue resistance .

Wherein the raw cord has a twist per meter (TPM) of 390 to 430, wherein the polyethylene terephthalate cord has a tensile strength of 1000 d / 2ply of not less than 17.0 kg and a shape stability index of not more than 6.0, And a fatigue of 90% or more.

The present invention also provides a polyethylene terephthalate cord produced by the above process, and an industrial product selected from the group consisting of a tire cord, an industrial rope, a reinforcing material for civil engineering, a webbing and a seat belt.

The present invention relates to a process for producing a polyethylene terephthalate cord having a strength of at least 9.3 g / d based on 1000 d / 2ply, a morphological stability index of 6.0 or less and an internal fatigue of 90.0% or more and having high strength, low shrinkage and fatigue resistance And it has a high stability against repeated stress, so that it can be utilized as a tire cord and a rubber reinforcing material.

1 is a view showing the spinning and stretching process in the production of the polyethylene terephthalate yarn of the present invention.
FIG. 2 is a view showing a dipping process, a drying process, and a heat setting process in the production of the polyethylene terephthalate cord of the present invention.

Hereinafter, the present invention will be described in detail.

The present invention relates to a process for producing a non-drawn filament yarn by melting a polyethylene terephthalate chip having an intrinsic viscosity of 1.0 or more and extruding it through a nozzle; The unstretched yarn is passed through a stretching roller to be multi-step stretched, and wound to produce a yarn having a strength of 9.3 g / d or more and a shape stability index (modulus of elongation + dry heat shrinkage) of 12.0 or less. And a step of preparing a raw cord by spinning the yarn by a twin screw extruder, and conducting a heat treatment at a speed of 20 m / min or more at a temperature of 200 to 260 ° C. in the prepared raw cord. A method for producing a phthalate cord is provided.

The method for producing the polyethylene terephthalate cord according to the present invention will be described in detail as follows.

First, a polyethylene terephthalate chip having an intrinsic viscosity of 1.0 or more is melted and extruded while passing through a nozzle to produce a discharged yarn.

Here, the polyethylene terephthalate polymer may contain at least 85 mol% of ethylene terephthalate units, but may optionally contain only ethylene terephthalate units.

Optionally, the polyethylene terephthalate may comprise small amounts of units derived from ethylene glycol and terephthalenedicarboxylic acid or derivatives thereof and one or more ester-forming components in copolymer units. Examples of other ester forming components copolymerizable with the polyethylene terephthalate unit include glycols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol and the like, and glycols such as terephthalic acid, isophthalic acid, hexahydroterephthalic acid, Dicarboxylic acids such as dicarboxylic acid, dicarboxylic acid, dicarboxylic acid, dicarboxylic acid, dicarboxylic acid, dicarboxylic acid,

The terephthalic acid (TPA) and the ethylene glycol raw material are melt-mixed at a ratio of 2.0 to 2.3 to the polyethylene terephthalate chip thus prepared, and the molten mixture is transesterified and condensed to form a raw chip. Then, the low chip is subjected to solid phase polymerization so as to have an intrinsic viscosity of 1.0 to 1.15 at a temperature of 240 to 260 DEG C and a vacuum.

If the intrinsic viscosity of the raw chips is less than 1.0, the intrinsic viscosity of the final drawn yarn is lowered and the processed cord after heat treatment can not exhibit high strength. If the intrinsic viscosity of the chips exceeds 1.15, the radiation tension is excessively increased, The cross section becomes nonuniform, and many filament cuts occur during stretching, resulting in poor workability in stretching.

Alternatively, an antimony compound, preferably antimony trioxide, may be added as a polymerization catalyst in the course of the condensation polymerization reaction so that the residual amount of antimony metal in the final polymer is 180 to 300 ppm. If the residual amount is less than 180 ppm, the polymerization reaction rate is slowed to lower the polymerization efficiency. If the residual amount exceeds 300 ppm, unnecessary antimony metal acts as a foreign substance and the radiation-drawing workability may be lowered.

The polyethylene terephthalate chip is melted and extruded while passing through a nozzle to produce a discharged yarn.

Thereafter, the discharged yarn is quenched and solidified by passing through a cooling zone. At this time, if necessary, a heating device of a certain length is provided in a distance from the nozzle to the starting point of the cooling zone, that is, the length (L) of the hood.

This zone is referred to as the delayed cooling zone or heating zone, which has a length of 50 to 250 mm and a temperature of 250 to 400 ° C (air contact surface temperature).

In the cooling zone, an open quenching method, a circular closed quenching method, a radial outflow quenching method, and a radial in flow quenching ) Method, but the present invention is not limited thereto.

At this time, the temperature of the cooling air injected for quenching in the cooling zone is adjusted to 20 to 50 캜. Such quenching using the sudden temperature difference between the hood and the cooling zone is intended to increase the solidification point and the radiation tension of the radiated polymer to increase the orientation of the undrawn yarn and the formation of the connection chain between the crystal and the crystal.

Thereafter, the solidified yarn passing through the cooling zone can be oiled at 0.5 to 1.2% by weight with respect to the discharged yarn by reducing the coefficient of friction between the tweezers and applying an emulsion applying apparatus having excellent stretchability and thermal efficiency.

And the oiled discharged yarn is radiated to form an unstretched yarn. In this case, the spinning draft is preferably 1500 to 1800, and the spinning speed is preferably 3,000 to 3,200 m / min. When spinning at the spinning draft and spinning speed in the above range, excellent strength of the yarn can be secured even at a low stretching ratio.

If the radiation draft is less than 1,500 or the spinning speed is less than 3,000 m / min, the uniformity of the cross section of the yarn is deteriorated to deteriorate the drawing workability and the degree of orientation of the unstretched yarn is decreased to degrade the crystallization degree. , The thermal stability is lowered, the strength of the tire cord is lowered, and the shape stability may be lowered when the high stretching is performed to improve the strength and modulus. When the breaking strength is higher than 3,200 m / min, The strength and elongation workability are deteriorated.

Thereafter, the non-drawn yarn is passed through a stretching roller to be multi-step stretched to produce a yarn.

The yarn passed through the first stretching roller is stretched while passing through a series of stretching rollers by a spin draw method to form a yarn.

In the drawing step, the non-drawn filaments may be multi-filament drawn, and the temperature of each of the drawn filaments is preferably higher than the glass transition temperature of the unstretched filament and lower than 95 캜, but the final filament roller temperature is preferably 200 to 250 캜.

If the temperature of the last stretching roller is lower than 200 ° C, the crystallinity and the size of crystals do not increase in the stretching process, and the strength and thermal stability of the yarn are not exhibited, so that the morphological stability is deteriorated at high temperature. There is a problem that the microstructure of the yarn becomes uneven and the strength of the yarn is lowered.

Further, it is preferable that the total yarn m of the yarn formed by winding as described above is 2.14 to 2.22. When the stretching ratio is less than 2.14, the productivity is lowered and the strength of the yarn and the cord is lowered. When the stretching ratio exceeds 2.22, crystallization of the oriented non-gelling portion is increased, It is not preferable because the molecular chain of the noncrystalline chain is broken and the uniformity of the molecular chain is lowered and the strength utilization ratio may be lowered.

Thereafter, the produced polyethylene terephthalate yarn is used for twisting, weaving and dipping to produce a dipped cord.

First, the polyethylene terephthalate yarn is twisted with a direct twisted yarn in which twisting and twisting are simultaneously performed to produce a raw cord for a tire cord.

The twist yarns are produced by applying ply twist to a polyethylene terephthalate yarn followed by joining by applying a cable twist. Generally, the upper and lower yarns are subjected to the same softening (level of twist) or other softening as required .

In the present invention, the raw cord is heat-treated at a rate of 20 m / min or more at 200 to 260 ° C to produce a high-strength cord and improve fatigue resistance.

In the present invention, the polyethylene terephthalate dip cord has a softening point of 390/390 TPM to 430 TPM or 430 TPM. When the upper and lower edges are made to have the same numerical value, the manufactured dipped cords do not show any rotation or twist, and are easily maintained in a straight line, thereby maximizing physical property development. At this time, when the number of years of the upper / lower ends is less than 390/390 TPM, the yield of the cord is reduced and the fatigue is likely to decrease. When the upper limit is 430/450 TPM, the strength is deteriorated.

Thereafter, the woven yarn is loaded on a dipping solution, dried, stretched and heat-set, then immersed again in the dipping solution, dried and heat-set to produce a dipped cord.

The dipping solution is not particularly limited, but it is preferably epoxy resin, para-chlorophenol resorcinol / formalin mixed resin (Pexul).

At this time, the drying should be avoided at a high temperature, and the drying is preferably performed at 90 to 180 ° C for 180 to 220 seconds. If the drying temperature is lower than 90 ° C, drying may not be sufficiently performed, and gelation may occur due to the dipping resin when dried and heat treated. When the drying temperature is higher than 180 ° C, Uneven adhesion of the cord and the deep liquid resin may occur.

The hot fixation is performed so that the cord impregnated in the deep liquid resin has an appropriate adhesive strength with the tire rubber, and the heat fixation temperature is preferably from 220 to 250 DEG C for 50 to 90 seconds. When the heat fixation is performed in less than 50 seconds, the adhesive force is insufficient due to the short reaction time of the adhesive solution, and when the heat fixation is performed for 90 seconds or more, the hardness of the adhesive solution becomes low and the fatigue resistance of the cord may be reduced.

The cords thus prepared had a strength of 16 kgf or more, a morphology stability index (modulus of elongation + dry heat shrinkage) of 6.0% or less, a storage modulus of 9500 MPa or more, and creep (@ 80 ° C, 1800 sec) % Or less.

The cord manufactured as described above is excellent in fatigue resistance and can be utilized as an industrial product such as a tire cord, an industrial rope, a reinforcing material for civil engineering, a webbing, and a seat belt.

Hereinafter, the present invention will be described in detail with reference to examples. However, these examples are for illustrating the present invention specifically, and the scope of the present invention is not limited to these examples.

Examples 1 to 2 and Comparative Examples 1 to 3

A solid phase polymerized polyethylene terephthalate chip having an intrinsic viscosity (I.V.) of 1.10 and a water content of 10 ppm containing 220 ppm of antimony metal was prepared.

The prepared chip was passed through a spinning nozzle as shown in Table 1 at a temperature of 290 ° C using an extruder to form a discharged yarn. Thereafter, the blast furnace yarn was solidified by passing through a heating zone (atmosphere temperature 340 ° C) with a direct nozzle length of 60 nm and a cooling zone (blowing with cooling air having an air velocity of 0.5 m / s at 20 ° C) having a length of 500 mm, (Containing 70% paraffin oil component). The untreated yarn was wound up at the draw ratio and the speed shown in Table 1 to produce the final yarn.

Two strands of the fabric were wound up and down as shown in Table 1 to prepare a raw cord. The raw cord was immersed in a dipping tank of an epoxy resin and Pexul adhesive solution, and then dried in a drying zone at 170 DEG C under 4.0% , Heat-set at 245 ° C in a hot stretching zone at 150 ° C for 3.0 seconds, immersed in resorcinol formalin latex (RFL), dried at 170 ° C for 100 seconds, heat-set at 245 ° C for 40 seconds To prepare a dipped cord.

In Examples 1 and 2, the raw cord was subjected to a heat treatment at 230 ° C at a rate of 20m / min and 30m / min, respectively. In Comparative Examples 1 to 3, .

Evaluation example 1

The properties of the cords prepared in Examples 1 and 2 and Comparative Examples 1 to 3 were evaluated by the following methods. The results are shown in Table 1 below.

(1) Strength (kgf), medium elongation (%)

After standing at 25 ° C and 65% RH for 24 hours, a low tensile tensile tester of Instrong Co. was used. The tire cord was twisted at 80 TPM (Twist Per Meter) Measured at a speed of 300 m / min.

The applied elongation at this time represents the elongation at the point of load of 4.5 g / d.

(2) Dry Heat Shrinkage (%, Shrinkage)

(L0) measured at a constant load of 0.05 g / d and a ratio of the length (L1) after treatment at a constant load of 0.05 g / d for 2 minutes at 177 ° C, after being left at 25 ° C and 65% RH for 24 hours And shows the dry heat shrinkage ratio.

S (%) = (L0 - L1) / L0 100

(3) E-S

The elongation under a constant load is referred to as intermediate elongation (E) in the present invention, and the load at this time is 4.5 g / d. The term (S) means the dry heat shrinkage rate in the above (2), and the sum of the elongation modulus (E) and dry heat shrinkage rate (S) is referred to as E-S in the present invention.

Generally, when the tire is vulcanized, the shrinkage rate and modulus of elongation of the cord are changed. The sum of shrinkage and modulus of elongation is similar to the modulus concept of the code after the tire is fully fabricated.

That is, when the E-S value is low, a correlation is formed in which the modulus becomes high. If the modulus is high, it is easier to steer because of the large amount of force generated due to the deformation of the tire. On the other hand, it is possible to make a small deformation to produce the same tensile force. . Therefore, the E-S value is utilized as a property value for judging the superiority of the code performance in tire manufacturing.

In addition, since a deformation amount due to heat is small in a tire having a low E-S value in the manufacture of a tire, the uniformity of the tire is improved, thereby improving the uniformity of the tire as a whole. Therefore, in the case of a tire using a code having a low E-S value, it is possible to improve the tire performance because the uniformity of the tire is higher than that of a tire using a high code.

E-S = elongation at specific load + dry heat shrinkage

(4) My fatigue

The residual fatigue was measured by a Goodrich Disc Fatigue tester after fatigue test. The fatigue test conditions were 120 ° C, 2500rpm, compression 6%, and 12%, and 20 ° C for 72 hours. After the fatigue test, the residual strength was measured using a tester.

division Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Twist Per Meter (TPM) 350 470 510 390 430 Deep code Strong (kgf) 18.2 16.7 16.4 17.8 17.5 E-S 5.1 6.2 6.5 5.5 5.8 Fatigue test Strength after fatigue (kg) 14.6 16.3 15.9 16.9 16.8 My fatigue (%) 80.2 97.6 97.0 94.9 96.0

As can be seen from the above Table 1, the cords produced in Examples 1 and 2 of the present invention are superior in strength after fatigue as compared with the cords produced in Comparative Examples, and the cords produced in Examples 1 and 2 have an excellent fatigue resistance Was found to be superior.

1: Extruder 2: Gear pump
3: Nozzle 4: Heating device
5: cooling zone 6: drawn godet roller GR1
7: Drawing godet roller GR2 8: Drawing godet roller GR3
9: Drawing godet roller GR4 10: Drawing godet roller GR5
11: Winding roller 12: Emulsion feeder
13: Bobbin 14: Primary immersion zone
15: Primary drying zone 16: Primary heat-setting zone
17: Second immersion zone 18: Secondary drying zone
19: secondary heat fixing zone 20: winder

Claims

Melting a polyethylene terephthalate chip having an intrinsic viscosity of 1.0 or more and extruding through a nozzle to produce an undrawn yarn;
The unstretched yarn is passed through a stretching roller to be multi-step stretched and wound to produce a yarn having a strength of 9.3 g / d or more and a shape stability index (modulus of elongation + dry heat shrinkage) of 12.0 or less; And
The yarn is twisted with a twisted yarn to produce a raw cord, and the produced cord is subjected to heat treatment at a speed of 20 m / min or more at a range of 200 to 260 ° C. A method of manufacturing a cord.

The method according to claim 1,
Wherein the raw cord has a twist per meter (TPM) of 390 to 430. The method according to claim 1,

The method according to claim 2, wherein
Wherein the polyethylene terephthalate cord has a tensile strength of 1000 d / 2ply of not less than 17.0 kg, a shape stability index of not more than 6.0, and an internal fatigue of not less than 90%.

A polyethylene terephthalate cord produced by the method of any one of claims 1 to 3.

An industrial product comprising the polyethylene terephthalate cord of claim 4 and selected from the group consisting of tire cord, industrial rope, civil engineering reinforcement, webbing and seat belt.