JPS60162830A - Polyester dip code and its production - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polyester dipped cord, and more particularly to a polyester dipped cord that, when used in the carcass ply of a radial tire, improves the handling stability of the tire and completely reduces the rolling resistance.

Conventionally, tires have a crown section reinforced in the circumferential direction with an extremely rigid belt ply layer, and a sidewall section reinforced with a carcass ply layer arranged almost perpendicular to the tire's equatorial plane. In so-called radial tires, if the rigidity of the sidewall is small,
It has been reported that the unbalance between the rigidity of the crown and the rigidity of the crown significantly reduces steering stability.

Therefore, it is necessary to provide the sidewall with a degree of rigidity that does not impair riding comfort, so we use relatively high modulus organic fiber cord, especially high modulus rayon cord,
Alternatively, polyester cord was used in the carcass ply layer of radial tires.

However, rayon cord is highly hygroscopic and its strength and modulus decrease significantly due to moisture absorption.
When used, there is a problem that requires sufficient moisture content control, and it is a material with extremely poor productivity.

On the other hand, compared to rayon, polyester cord has almost no decrease in strength or modulus due to moisture absorption, and has many advantages such as high strength, no flat spots, and good heat resistance. However, compared to rayon cord, the modulus is slightly lower and the heat shrinkage rate is higher, which not only tends to cause problems with tire uniformity, but also causes the cord to shrink during tire vulcanization, which further reduces the modulus. There were few drawbacks that led to a decline.

In order to deal with these drawbacks, methods such as making the bead filler rubber higher9, increasing the folding height along the bead layer of the carcass ply, or using a high modulus bead filler rubber have been tried. However, this is not necessarily a preferable method from the viewpoint of reducing tire weight or rolling resistance.

In addition, in order to obtain polyester with higher modulus, there are methods to change the characteristics of the cord itself during the processing process, such as by reducing the number of cord twists or increasing the tension during heat treatment. In the latter case, the tire's uniformity properties are seriously deteriorated due to a significant increase in the heat shrinkage rate.

Another method is to use a low polymerization degree polyester cord, which has excellent thermal dimensional stability and is easy to impart high stiffness, for the carcass ply of a radial tire. It has been impossible to ensure sufficient tire durability performance because of the low fatigue resistance and poor fatigue resistance.

On the other hand, as a method for improving the dimensional stability without reducing the degree of polymerization of the polymer, there is a method of polyt-stretching as seen in US Pat. No. 4,195,032, but this method sacrifices toughness for improving the dimensional stability.

Therefore, the present invention has been developed to eliminate such conventional drawbacks, and it is possible to reduce the heat shrinkage rate of polyester dipped cord, improve fatigue resistance and toughness, and to apply it to carcass plies of radial tires. When used, it has characteristics such as improving the steering stability of the tire and reducing rolling resistance.

That is, the above purpose is (1) that the repeating structural unit of ethylene terephthalate is 8
Melt-spinning a polyester-based polymer with a dry polyester of 5 molti or more and a polyester having an intrinsic viscosity of 0.80 or more, preferably a high degree of polymerization of 0.80 to 1.20. Single thread denier is 30d
(3) After the yarn that has passed through the take-up roll is wound up continuously or once, the total stretching ratio is 5.0 times or more. , preferably 1, < is 6
．． (4) The quality of the drawn yarn satisfies the following conditions; (a) DT≧9.5p
/d.

Preferably DT≧11. Oj'/d C mouth) 12chi ≧ DE ≧ 5%, preferably 1
0%≧DE≧5% (c) Ta≧160°C More preferably, d) Birefringence of the fiber Δn≧195 X 1O-1 (e)
Long period LP by small-angle X-ray diffraction ≧1701 (f) Single yarn denier of fiber is 4 d or less (5) Twist coefficient of drawn yarn (multifilament yarn) 2000 to 1300, preferably 1800 to 1400
(Creating a raw cord by applying D lower twist and upper twist,
(6) The raw cord or the curtain fabric woven with the raw cord? This is achieved by 0-3% hot stretching followed by dip treatment to improve adhesion to the rubber.

According to this method, the repeating I2 structural unit of ethylene terephthalate is expressed from a polyester polymer of 85 moles or more, and a polyester fiber having an intrinsic viscosity of O, SO or more and a high degree of polymerization is produced. Dip liquid is applied to improve adhesion with 1. The twist coefficient is 2
A polyester dip cord having a twist of 000 to 1300, preferably 1800 to 1400, and a first twist, which has the following properties at the same time: high strength, high modulus, dimensional stability, and fatigue resistance. - A highly improved polyester dip cord can be obtained.

(a) Breaking strength of dip cord A≧7.5f/d preferred, <A≧8.0F/d (b) Intermediate elongation of dip cord B≦5chi (c3 ”'
Dry heat shrinkage rate of f' Lee Soashima cord C≦5% (d) C
≦-B + 8.5 This dipped cord is significantly different from conventional polyester dipped cords by 1-1 in terms of low shrinkage, high modulus, and high strength.

More specifically, the method of the present invention and the characteristics of the fibers obtained by the method will be described.

The polyester that is the raw material for the polyester cord intended in the present invention has an intrinsic viscosity of 0.80 or more, preferably 0.80 or more, as measured at 30°C in a solvent of p-chloroμ phenol/tetrachloroethane = 3/1 (weight ratio). 80 to 1.20,
More than 85 molar units, preferably d95 molar units or more of the structural units are made of ethylene terephthalate, and other structural units that can be mixed in small amounts include diethylene glycol, other polyethylene glycols having 1 to 10 carbon atoms, hexahydro- p-xylylene glycol,
Aromatic dicarboxylic acids such as isophthalic acid, cybenzoic acid, p-tart-phenyl-4,41-dicarboxylic acid, hexahydroterephthalic acid, aliphatic dicarboxylic acids such as adipic acid, human tetraoxyacids such as hydroxyacetic acid, etc. Such polyester materials are made into fibers by a conventional melt spinning method.

If necessary, matting agents, pigments, light stabilizers, heat stabilizers, antioxidants, antistatic agents, dyeability improvers, or adhesion improvers may be added to the outer polyester. All of them can be used, except those that have a serious adverse effect on the characteristics of the present invention depending on how they are blended.

Usually, the polyester is dried to a moisture content of 0.03% or less and spun using a melt spinning machine, preferably using an extruder type spinning machine.

The spinning take-off speed is volatilized when the single yarn denier of the yarn is 30
The birefringence is set to 0.002 to 0.010 below the denier. The spinning conditions corresponding to the yarn quality can be determined by optimizing not only the take-up speed but also a number of factors such as the nozzle hole diameter, the distance between the nozzle and the quench, the intrinsic viscosity of the polymer, and the spinning temperature.

In particular, it is preferable that the basic spinning factor parameters satisfy the following formula in order to realize the fibers used in the present invention, which have a high degree of polymerization and a small single filament denier.

(g)Q/FCD”≧23500 (f/ad 11
m1n) (a) Vw/Vo≦200 (su) LH: 30 ~ 200 [mII] (group TA
: 28 (1 to 330 ('Cal However, (g) to shi) In the formula, Q: Polymer discharge amount per single hole Cf/mim) D=
Nozzle hole diameter [pieces] vw: Spinning take-off speed (m/m1n) vo: Nozzle discharge linear velocity Cm/m1n) LH: Length of the heating zone directly under the nozzle [me] TA: Yarn atmosphere temperature in the heating zone directly below the nozzle [ °C]

When the birefringence index of the drawn yarn exceeds o, oio, the cutting strength DT is stably 9.5 F/d or more, preferably 11, o.
It does not become a high tenacity yarn with p/d or higher.

When the degree of polymerization of the polymer is constant, it is preferable that the birefringence of the drawn yarn is as small as possible in order to obtain a high-strength yarn. However, if the birefringence of the drawn yarn is set to less than 0.002,
This is not preferable because the spinning operation is impaired.

In addition, if the single yarn denier of the drawn yarn exceeds 30 deniers, it is difficult to draw it stably at a high draw ratio, and it is difficult to draw it stably at a high draw ratio as intended in the present invention. It becomes difficult to use.

The undrawn yarn obtained as described above is continuously spun,
Or, when stretching after winding, the pre-stretched tube under 1.10 times J-J between the undrawn yarn first supply roller and the undrawn yarn second supply roller maintained at 100° C. or lower. It is preferable to carry out a first stage drawing at a total stretching ratio of 40- or more between the undrawn yarn second supply roller and the first drawing roller, and if necessary, the undrawn yarn second supply roller and the undrawn yarn 1 A high temperature pressurized steam jet nozzle is thrown between the stretching roller and
The nozzle temperature is set to 200℃ or higher to eject high-temperature steam,
The stretching point is fixed near the hot pressurized steam jet nozzle. Furthermore, when performing the second stage drawing, a slit heater (heating device provided with a slit as a thread running path) with an ambient temperature of 170 to 420°C is provided between the first drawing roller and the second drawing roller. The yarn is heated while running through the slit in a non-contact state (atmospheric temperature refers to the temperature inside the slit). 2. Subjected to stretching rollers. At that time, a temperature gradient is provided in the slit heater, and the atmospheric temperature at the yarn inlet is 0°C or higher for all 1 time, and the calculated ambient temperature at the outlet is 420°C or lower.
It is preferable to allow the yarn to pass through so that it can remain there for more than a second. In addition, after the completion of two-stage stretching, continuous stretching is performed without winding once.
, or once rolled up, at 230-165℃ for 10
It is also possible to further improve the dimensional stability by performing a relaxation treatment of % or less.

The total stretching ratio is set to 5.0 times or more, preferably 6.0 times or more.

In order to obtain the high tenacity, low elongation yarn used in the present invention, it is drawn at a maximum draw ratio of 85 inches or more, preferably 90 inches or more, and the elongation at break is 5 to 12%. ,
The stretching ratio of each sample is basically determined by the degree of orientation of each drawn yarn.

In addition, the maximum stretching ratio refers to whether stretching is possible or the maximum stretching ratio f
Measured with n = 5, and refers to the average value.

The polyester fiber thus obtained has the following properties.

(b) DT≧9.5 f/d, preferably DT≧11
．． OF/d (b) 12%≧DI≧5ch, preferably 10%≧DE
≧5% Furthermore, mechanical loss tangent Tanδ measured at 110 C/S
The peak temperature Ta of the main dispersion appearing in the temperature dispersion of is 160
℃ or more indicates that the amorphous portion has been sufficiently elongated, and can be said to reflect the fiber quality of (a) and (b) in terms of microstructure.

Furthermore, these characteristics can be manufactured more stably by satisfying the following microstructural parameters.

) Δn≧195×10-” (e) Long period LP≧170X by small-angle X-ray diffraction)
(e) Δn represents the average orientation when viewed microscopically.
, and LP, which represents the degree of elongation in the fiber axis direction of the crystalline and amorphous portions, is large.

Furthermore, since the single filament denier of the drawn yarn is 4 d or less, the structural difference between the inner and outer layers of the filament is reduced, and the strength utilization rate is high, making it easier to develop high strength.

One feature of the present invention is that it enables the production of fibers with a high degree of polymerization and a small denier, thereby making it possible to use polyester fibers with a high degree of polymerization with high strength and low elongation for dipped cords. It's in 90.

The polyester multifilament yarn obtained above is twisted according to a conventional method to form a green cord.

Further, the raw cord or a blind fabric woven from the raw cord is subjected to a dipping liquid treatment to improve attachment properties to rubber, followed by hot stretching.

The inventors of the present invention have carefully studied the process from making these raw cords to dipping, and have been able to make the dip cords highly strong, have low intermediate elongation, and have a low shrinkage rate, which is not the case with conventional polyester dip cords. This led to the discovery of the ability to achieve superior performance that could not be achieved previously, leading to the present invention.

That is, in the case of the high strength, low elongation polyester fiber used in the present invention, the twist coefficient (TxvTf'') is usually often used.
000 to 2200 (for example, 47 for 840d/2 twist
turn/101'll), the strength utilization rate of the raw cord decreases, but when the twist coefficient is set in the range of 1300 to 2000, preferably 1400 to 1800, the strength utilization rate is very excellent, and it is By setting the hot stretch ratio as low as θ to 3, a dip cord with a low shrinkage rate and a low intermediate elongation can be obtained.

The intermediate elongation is a measure corresponding to the modulus of the cord, and the fact that the intermediate elongation of the dip cord is low indicates that the modulus of the cord is high.

The feature of the present invention is that a high strength, high modulus, and low elongation yarn is already created by elongating the molecular chain more than conventional polyester high strength yarn at the high strength yarn production stage, and after twisting, In the dipping process, the modulus of the dipped cord is increased by hot stretching. In other words, since there is no need to lower the intermediate elongation, the load on the cord during the dipping process is reduced, resulting in a highly strong polyester with a low shrinkage rate and low intermediate elongation (high modulus), which was previously unimaginable. The goal is to achieve a system dip chord.

Conventional polyester and dipped cords have a breaking strength A of 7.5 y/d or more, preferably 8.0.
P/d or more, there is no material whose intermediate elongation B and dry heat shrinkage coefficient C satisfy the following formulas, respectively. d) C≦-B + 8.5 These dip cord characteristics have a twist coefficient i of 2000 to 1
300, more preferably a low twist number range of 1800 to 1400, and a hot stretch ratio of 0 to 3% in the dipping process.
This can only be achieved under low stretch conditions.

Reducing the number of twists has the advantage of increasing the twisting speed and reducing costs, but according to conventional knowledge, it has the disadvantage of decreasing fatigue resistance.

However, since the dip cord of the present invention satisfies the formulas (a1 to (d)), even a low-twist cord has fatigue resistance that is higher than that of a cord with a conventional number of twists. This is evident from the high residual strength after the fatigue test.

The heat treatment temperature is generally in the range of 225-255°C, preferably in the range of 230-245°C. If the heat treatment temperature does not reach 225° C., the heat shrinkage rate of the treated cord will increase, making it impossible to obtain a sufficient set, increasing the growth of the tire, and worsening the uniformity of the tire. On the other hand, when the temperature exceeds 255°C, the strength of the treated cord decreases significantly. The heat treatment time is usually 1.0 to 4.0 minutes,
Preferably it is 2.0 to 3.0 minutes. Heat treatment time is 1.
If the heating time does not reach 0 minutes, the setting of the treatment cord will be insufficient as with the heat treatment temperature, and if it exceeds 4.0 minutes, the strength will decrease.

As described above, according to the present invention, a high modulus polyester dip cord can be obtained by lowering intermediate elongation without increasing heat shrinkability.

As a result, not only the handling stability of the tire is improved and the rolling b resistance is reduced, but also the uniformity of the tire can be improved.

The polyester tire cord of the present invention is particularly suitable for use in carcass plies of radial tires.When applied to carcass plies, as in the case of using conventional polyester cords, it adopts dimensions that increase the rigidity of the sidewall portion. Sufficient rigidity can be obtained without

Examples of the present invention will be described below, but characteristics and measurement methods not mentioned above are as follows.

Measuring method of birefringence (Δn) A Nikon polarizing microscope POH type Rhein Berek compensator was used, and a spectral light source activation device (Toshiba 5LS-8-B type) was used as a light source (Na light source). 5～
A 6 mm long sample cut at an angle of 45° to the fiber axis is placed on a glass slide with the cut side facing up. Place the sample slide glass on the rotating stage, adjust the rotating stage so that the sample is at 45 degrees to the polarizer, insert the analyzer to obtain a dark field, and then set the compensator to 30°. count the number of stripes (n pieces). The compensator scale a is the point at which the sample first becomes dark when the compensator is turned clockwise, and the compensator scale bt is the point at which the sample first becomes darkest when the compensator is turned counterclockwise. After that (read up to 1/10 scale in both cases), return the compensator to 30, remove the analyzer, measure the diameter d of the sample, and calculate the birefringence (Δn) t'' based on the following formula (number of measurements: 20). average value].

Δn=r/d (r=Bλ +6)λ. =58
9.3=Voice ε: C/10 of the compensator manual from Rait Co.
From 000 and l.

1=(a-b) (: Difference in continuation of compensator) Measuring method of intrinsic viscosity> Measurement is performed in a mixed solvent consisting of 75% by weight of p-chlorophenol and 25% by weight of tetrachloroethane.

Dissolve the polymer in a solvent at room temperature and measure the viscosity. The measurement is carried out at 30°C.

Intrinsic viscosity is the limit value at which the natural logarithm of the ratio of solution viscosity to solvent viscosity divided by the concentration of the polymer solution in grams of polymer per 100 ml of solution approaches zero concentration.

<Measurement method of strength and elongation properties of fibers and cords> JIS-L1
Based on fixed amount of 017. Take the sample in a skein shape and incubate at 20℃ for 6
After leaving it for 24 hours in a temperature and humidity controlled room at 5SRH, 1
The measurement was performed using a Tensilon °'UTM-4L type tensile tester (manufactured by Toyo Baldwin (KK)) at a section length of 20cII4 and a tensile rate of 20cg/min. However, the measurement was performed after conditioning the raw cord while it was wound around the ply-twisted pobbin.

<Formula for calculating twist coefficient> Twist coefficient = Number of twists x (denier) i Number of twists: turn/10cWI <Method for measuring disk fatigue> Using the normal disk fatigue test m'e, embedding a dip cord and vulcanizing. The prepared test piece was set and subjected to forced fatigue by rotation at a speed of 250° rpm for 48 hours under a compression ratio of 12.5% and an elongation ratio of 6.3%, and then the dip cord was removed from the rubber and the remaining All measurements were taken.

<Measurement method 1 of intermediate elongation> Based on the definition of JIS-L1017. The elongation rate under a constant load Wαf) is measured. The elongation measurement conditions are based on the measurement conditions of strength and elongation properties. The constant load W is defined by the following formula.

W=4.5Xmu1 d: Sample denier, d8: Standard denier, which is 1000 denier for raw yarn and 2000 denier for cord.

<Specific Gravity> Create a density gradient tube made of n-hebutane and carbon tetrachloride, place a sufficiently defoamed sample into the density gradient tube whose temperature is controlled to 30℃±0.1℃, and leave it for 5 hours. After determining the sample position in the density gradient tube, the value read on the scale of the density gradient tube was converted to a specific gravity value from the density gradient tube scale using a standard glass float - specific gravity calibration graph [1, measured with n = 4]. As a general rule, read specific gravity values to four decimal places.

<Constant length heating thermal stress peak temperature
/ d, measure the thermal contraction stress from room temperature to the continuous temperature, and determine the temperature W at which the thermal stress is maximum.

[For details, please refer to Textle Re5earch Jour.
See naL vol, 47+732 (197?).

] Single thread denier Measured according to JIS-L1073 <1977).

<Measurement method of dry heat shrinkage rate> Take a sample in the form of a skein, leave it in a temperature and humidity controlled room at 20°C and 65% RH for more than 24 hours, and then the 0. Length ll measured by applying a load corresponding to IP/d.

The sample was left in an oven at 150°C for 30 minutes under no tension, then taken out from the oven and placed in the above temperature/humidity room for 4 hours.
Leave it for 7 hours, then apply the above load again and measure.Length 41
It was calculated using the following formula.

Measuring method of fiber long period LP by small-angle X-ray diffraction
The measurement of the ray scattering pattern is performed using, for example, an X-ray generator (RU-aHu)' manufactured by Rigaku Denki Co., Ltd. For measurements, a tube voltage of 45 Kv, a tube current of 70 mA + copper anticathode, and CuKa (λx = 1.54) made monochromatic with a nickel filter were used.
181). Attach the fiber sample to the sample holder so that the single threads are parallel to each other. The thickness of the sample is 0.5-1. □It is appropriate to make it as high as iai. X perpendicular to the fiber axis of the fibers arranged in parallel
Inject H into Rigaku Denki HP S P C (Posit
ion 5intensive Proport-1o
nal Counter) system. An overview of this system can be found, for example, in (Polmer Jou
rnal, vol.

13, 501 (1981)).

The measurement conditions were: Q, 3miφ x 0.211φ medium pinhole collimator, 1ftk probe distance: 400ryu MCA (multi-channel analyzer) number of measurement channels: 256, measurement time = 600 seconds. Data processing is performed by subtracting the air scattering intensity from the measured scattering intensity by moving average processing, and by determining the maximum intensity position 'fM and μ, the fiber long period is calculated from the long period small angle scattering angle, 2α, according to the following formula. Calculate. [See Figure 2 (AI) - In the figure, 12 is the sample, 2I is pspc
Probe, 3' is positive VN analyzer, 4' is M
CA and 5' indicate the display section, respectively.λx = 1.5418
A Moving average processing is calculated according to the following formula.

However, [7, in the above equation, I (S)N and I(S)i are the measured scattering intensities (strong f minus air scattering intensity) of channel numbers N and l, respectively, and K is the number of adopted points of the moving average ( Here, = 7], N-K>0°N+≦256 <Mechanical temperature dispersion> Toyo Sokki Co., Ltd. Ill Rheovlbron is used, initial thread length is 4, heating rate is 2°C/min, sine at the time of measurement frequency 11
Measured under the condition of 0 Hz 1-1 Loss tangent tan δ = E'/
Find the temperature (Tα) at which El is maximum.

Example 1 Polyethylene terephthalate having the intrinsic viscosity shown in Table 1 was used as a raw material, and spinning was carried out under the conditions shown in Table 1 to obtain undrawn yarns having the birefringence shown in Table 1. During spinning, an appropriate amount of spinning oil was applied to the surface of the yarn before taking off the undrawn yarn.

The obtained undrawn yarn was drawn under the conditions shown in Table 2 to obtain drawn yarn having the quality shown in Table 3. Table 3 also shows the yarn quality of a commercially available high-strength grade polyester fiber for tire cord as Comparative Example 2.

Table 1 Table 2 Table 3 Next, the drawn yarns of Example 1 and Comparative Example 2 were combined,
A 1000 denier multifilament yarn was obtained.

The resulting yarns had 49T/10 an and 42 T/10 an, respectively.
T/10cN-71) t&37〒/1nljII 1
-fi 1ilf'-1k-h, u 11/MIJ/
It was made into a 2-ply 2-strand cord.

The raw cord thus obtained was immersed in a polyester dip solution consisting of a resorcinol-formalin-latex solution, and then dried with hot air at 120° C. for 3 minutes under a 1.5% stretch.

Subsequently, it was introduced into a hot stretch zone and heated at 240℃.
After 1% and 5% hot stretching in heated air at
A dipped cord was manufactured by performing heat treatment for a second.

The characteristics of the raw cord and dipped cord according to this example are as shown in Table 4.

The Tokuyu dip cord of the present invention has significantly improved strength compared to the dip cord obtained in the comparative example, and has low intermediate elongation and low dry heat shrinkage, which is a measure of dimensional stability, and has a low twist area. The fatigue resistance is far superior to that of the comparative example.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the dip code characteristics of the present invention,
The vertical axis shows the dry heat shrinkage rate, the horizontal axis shows the intermediate elongation, and the shaded area is the area showing the characteristics of the dip cord of the present invention. Figure 2 (4) is a schematic diagram showing the arrangement of the sample and film surface in the PSPC system used to measure the fiber long period by small-angle X-ray diffraction in the present invention.
This figure is a schematic diagram showing the small-angle X-ray diffraction pattern of the fiber of the present invention. Patent applicant Toyobo Co., Ltd. Figure → 1f Sekishin μC'/)

Claims (1)

[Claims] 1. The repeating structural unit of ethylene terephthalate is 85
A dip liquid cord made of polyester fibers having a high degree of polymerization of more than 10% and an intrinsic viscosity of 0.80 or more, and for improving adhesion to rubber, the following (a) to (d) A polyester dip cord with high strength and high modulus, as well as significantly improved dimensional stability and fatigue resistance. (a) Dip cord breaking strength A≧7.5P/d (υ
■ Intermediate elongation B≦5% (c) -? 'I\
・Dry heat shrinkage rate C60 ((to) C≦-B
+8.5 2. In claim 1, the breaking strength of the dip cord is 8.5. A polyester dipped cord whose polyester fiber has an intrinsic viscosity of 0.80 to 1.20. 3. The polyester dip cord according to claim 1 or 2, wherein the dip cord has a twist count of 1,800 to 1,400. 4. In claim 1, 2 or 3, 110 of the polyester fiber constituting the dipped cord
A polyester dip cord having a peak temperature Tα of the main dispersion appearing in the temperature dispersion of the mechanical loss tangent in C/S of 160° C. or higher. 5. Made of polyester polymer with a repeating structural unit of ethylene terephthalate of 85 moles or more, has a high degree of polymerization with an intrinsic viscosity of 0.80 or more, and has the following (a) to ())
Ply-twisted and ply-twisted high-strength polyester fibers with a twist coefficient of 2000 to 1300 that also have the properties shown in the formula? The method is characterized in that the raw cord or the blind fabric woven from the raw cord is subjected to a dip liquid treatment to improve adhesion to rubber, followed by hot stretching of 0 to 3%. A method for manufacturing a polyester dip cord with high strength, low shrinkage, and high modulus. ((a) DT≧9.5ri/d (b) 12%≧DE≧5% e Ta≧160°C (In the above, the twist coefficient is the number of twists (turn / 1
03) x yηtebow=-A-), where DT is the breaking strength, DE is the breaking elongation, and Ta is the temperature distribution of the mechanical loss tangent at 110C/S of the polyester fibers constituting the dip cord. The peak temperature of the main dispersion is shown. ) 6. A method for producing a polyester dip cord according to claim 5, wherein the birefringence Δn of the fiber is 195×10−” or more, and the fiber long period LP by small-angle X-ray diffraction is 170× or more. 7. Claim 5 or 6 provides a method for producing an alpolyester dipped cord in which the fibers have a DT of 11.OIF/d or more and a DE of 10 to 5%. 8. Claim 5, The method for manufacturing a polyester dip cord according to either of Item 6 or Item 7, using a raw cord subjected to first twisting and final twisting with a twist coefficient of 1800 to 14oO.