JPH11350249A - Polyester fiber for v-belt reinforcement and its production and cord for v-belt reinforcement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently obtain in stable grade the subject polyester fiber with excellent balance between mechanical strength and dimensional stability. SOLUTION: This polyester fiber for V-belt reinforcement comprises a polymer with ethylene terephthalate unit accounting for >=90 mol.% of the total repeating units of the molecular chain, satisfying the following characteristics: (1) intrinsic viscosity (IV): 0.90-1.05, (2) single fiber fineness: 1.0-4.5 denier, (3) yarn tenacity: >=6.5 g/d, (4) maximum thermal shrinkage stress: 0.2-0.5 g/d, (5) the sum of the dry heat shrinkage after left to stand at 150 deg.C for 30 min and the intermediate elongation at a stress of 4.5 g/d: <=9.7%. Using this polyester fiber, the other objective cord for V-belts with excellent dimensional stability, fatigue resistance and durability can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester fiber for reinforcing a V-belt, a method for producing the same, and a V-shaped fiber using the fiber.
The present invention relates to a belt reinforcing cord. More specifically, a polyester fiber for reinforcing a V-belt with an excellent balance between strength and dimensional stability, a method for efficiently producing this polyester fiber with stable quality, and excellent dimensional stability, fatigue resistance and durability. And a V-belt reinforcing cord.

[0002]

2. Description of the Related Art Synthetic fiber yarns made of polyester represented by polyethylene terephthalate are excellent in mechanical properties, dimensional stability and durability, so that they are used not only for clothing but also for industrial applications, especially for reinforcing rubber materials. Also widely used.

Among them, as a polyester fiber for reinforcing a V-belt, a high-strength raw yarn obtained by drawing a low-oriented undrawn yarn at a high draw ratio has been used.
Yarn obtained by stretching Y at a low magnification has come to be used. This is a technique born of a need to improve the properties of the belt, particularly the dimensional stability, at the expense of the strength of the cord. Here, the dimensional stability of the belt refers to a change in the belt length during or after the running of the belt and a belt tension maintenance rate.

[0004] On the other hand, as a spinning technique for improving the dimensional stability of a belt made of polyester fiber, a birefringence index of 1 is controlled by controlling an intrinsic viscosity and an atmosphere temperature under a die.
It can be reduced by a method of keeping the temperature within a range of 70 × 10 ^{−3 to} 195 × 10 ⁻³ (Japanese Patent Publication No. 2-46689) and a heat treatment after tensioning with a maximum heat shrinkage of 0.5 to 0.6 g / d. Method for obtaining shrinkable fiber (Japanese Patent Publication No. 1-44810)
In any of these methods, not only polyester fibers having a good balance between strength and dimensional stability useful as V-belt characteristics cannot be obtained, but spinning properties are poor. For this reason, there is a problem that it is not possible to obtain a qualitatively stable polyester fiber with less fluff.

Japanese Patent Laid-Open Publication No. Hei 8-121541 proposes a method of obtaining a power transmission belt that regulates the characteristics of an untreated cord. However, the shrinkage of the treated cord is high, and the dimensional stability is poor. Thus, there is a problem that the dimensional stability, fatigue resistance, durability and the like of the obtained V belt cannot be obtained.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art.

Accordingly, an object of the present invention is to provide a polyester fiber for reinforcing a V-belt having a good balance between strength and dimensional stability, a method for efficiently producing this polyester fiber with a stable quality, dimensional stability and resistance to dimensional stability. An object of the present invention is to provide a V-belt cord excellent in fatigue and durability.

[0008]

Means for Solving the Problems In order to solve the above problems, the polyester fiber for reinforcing a V-belt of the present invention comprises:
It mainly has the following configuration. That is, a polyester fiber for reinforcing a V-belt, comprising a polymer in which 90 mol% or more of all the repeating units of the molecular chain is ethylene terephthalate, and satisfying the following properties (a) to (e).

(A) Intrinsic viscosity (IV): 0.90 to 1.05 (B) Single fiber fineness: 1.0 to 4.5 d (C) Yarn strength: 6.5 g / d or more (D) Maximum Heat shrinkage stress: 0.2 to 0.5 g / d (e) Dry heat shrinkage after standing at 150 ° C. for 30 minutes and 4.5.
Sum of intermediate elongation at g / d: 9.7 or less.

[0010] In the V-belt reinforcing polyester fiber, the amount of -COOH terminal group of the polyester fiber is desirably 10 equivalent / 10 ⁶ g or less.

The method for producing a polyester fiber for reinforcing a V-belt of the present invention has the following constitution. That is, a polymer in which 90 mol% or more of all the repeating units of the molecular chain is ethylene terephthalate is melt-spun from a spinneret, and the spun yarn is passed through a heating zone, and then cooled and solidified by cold air to form a polyester fiber. In the method of spinning, the temperature of the heating area under the spinneret is 320 to 350 ° C. and the length is 6
5 to 75 cm, the birefringence of the undrawn yarn drawn at a spinning speed of 2700 to 3300 m / s is Δn _POY, and then one step at 1.1 to 1.5 times in a temperature range of 80 to 100 ° C. Eye stretching, 1.2 to 1.6 in a temperature range of 245 to 265 ° C.
And the birefringence of the drawn yarn when drawn so that the total draw ratio becomes 1.5 to 2.0 times is Δn _DY
And the difference between △ n _DY and △ n _POY (△ n _DY − △
n _POY ) in the range of 100 × 10 ^{−3 to} 120 × 10 ⁻³ .

Further, the V-belt cord of the present invention has the following configuration. That is, a cord obtained by the above-described method for producing a polyester fiber for reinforcing a V-belt, which is obtained by subjecting a polyester fiber having the above properties to twisting and twisting, further applying an adhesive, and heat-treating under tension. And a V-belt reinforcing cord characterized by satisfying the following characteristics (f) to (h).

[0013] (f) Strength: 5.5 g / d or more (g) intermediate elongation sum S _C and polyester for dry heat shrinkage after standing at 0.99 ° C. code 30 minutes and when code 2.67 g / d Sum S of dry heat shrinkage of fiber after standing at 150 ° C. for 30 minutes and intermediate elongation of polyester fiber at 4.5 g / d
Ratio to _F (S _C / S _F ): 50 to 70% (h) Ratio of maximum heat shrinkage stress of cord to maximum heat shrinkage stress of polyester fiber: 70 to 125%.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester fiber for reinforcing a V-belt of the present invention is made of a polymer in which 90 mol% or more of all repeating units of the molecular chain is ethylene terephthalate, that is, polyethylene terephthalate. The range is 0.9 to 1.05, preferably 0.92 to 1.0. If the intrinsic viscosity is less than 0.9, the durability of an industrial material, particularly a V belt, becomes insufficient. On the other hand, if the intrinsic viscosity exceeds 1.05, the workability deteriorates due to a remarkable increase in melt viscosity, and the toughness increases. The fiber with a high degree cannot be obtained.

The single fiber fineness (b) of the polyester fiber is 1.0 to 4.5 d, preferably 2 to 4.5 d.
The range is 3.5d. Monofilament fineness yarn is 1.
When it is smaller than 0d, the wear resistance between the single fibers constituting the cord in running of the V-belt is reduced, and the bending fatigue of the belt is reduced. On the other hand, if the single fiber fineness exceeds 4.5 d, the flexibility of the V-belt is impaired, which causes the bending fatigue property to be significantly reduced.

The polyester fiber for reinforcing a V-belt of the present invention has a yarn strength (C) of 6.5 g / d or more, preferably 6.6 g / d or more. If it is less than 6.5 g / d, the absolute value of the strength of the V-belt becomes low, and
This leads to a reduction in the life of the belt.

The polyester fiber for reinforcing a V-belt of the present invention has a maximum heat shrinkage stress (d) in the range of 0.2 to 0.5 g / d, preferably 0.25 to 0.4 g / d. . If the maximum heat shrinkage stress (d) is smaller than 0.2 g / d, the shrinkage of the belt becomes small and the tightening force of the pulley by the belt decreases. The tightening force is increased, and the calorific value is increased, resulting in greater damage to the belt.

Further, in the polyester fiber for reinforcing a V-belt of the present invention, 150 ° C., which is a measure of dimensional stability, is used.
The sum (e) of the dry heat shrinkage after standing for 30 minutes and the intermediate elongation at 4.5 g / d is 9.7 or less, preferably 9.5 or less. If the above sum (e) exceeds 9.7, the stress relaxation rate of the V-belt is high, that is, the V-belt tension maintenance rate is small, which causes slack of the V-belt and leads to a reduction in the life of the V-belt.

As described above, the polyester fiber for reinforcing a V-belt of the present invention is characterized by having an unprecedented effect of high strength and excellent dimensional stability. The polyester fiber for reinforcing a V belt of the present invention preferably has a -COOH terminal group of 10 equivalents / 10 ⁶ g or less, more preferably 6 equivalents / 10 ⁶ g or less. By adjusting the content of the terminal carboxyl group to this range, V
In the vulcanization process of the belt, the strength is prevented from dropping due to water.
The durability (fatigue life) of the belt can be improved.

Here, a specific method for obtaining a polyester fiber having a low carboxyl (—COOH) terminal group is as follows.
There is a method of reacting with a -COOH terminal group in a polymerization step and adding a compound that blocks the terminal group (blocking polymerization method). Examples of the -COOH blocking agent include a monoepoxy compound, a diepoxy compound, a carbonate compound, a monocarbodiimide compound, and a dicarbodiimide compound.

The V of the present invention having the above excellent characteristics
The belt reinforcing polyester fiber can be efficiently manufactured by the manufacturing method described below.

First, the polyester chips are supplied to an extruder type extruder to form molten chips, and subsequently, are spun from a spinneret. After the spun yarn passes through the slow cooling zone,
Cooled and solidified by chimney cold air. The cooling method here is preferably an annular cooling method.

Here, the temperature of the heating area under the base is 320 to 3
The temperature is set to 50 ° C, preferably 325 to 345 ° C. When the temperature of the heating area under the base is lower than 320 ° C., not only the yarn forming property is reduced and the yarn having many fluffs is formed but also the strength is reduced. If the temperature exceeds 350 ° C., the desired dimensional stability cannot be obtained.

The length of the heating zone under the base is 65 to 75 cm, preferably 68 to 73 cm. If the length of the heating zone below the base is less than 65 cm, the spinning property is deteriorated and the strength is reduced. If it exceeds 75 cm, the desired dimensional stability cannot be obtained.

In order to obtain more stable polyester fiber, it is preferable to provide a non-heating zone following the above-mentioned heating zone, that is, a heat-retaining area in a range of 5 to 15 cm in length.

This is not preferred.

The take-up speed (spinning speed) during melt spinning is 2
700 to 3300 m / min, preferably 2800 to 320
0 m / min. Below 2700 / min,
The desired dimensional stability of the yarn was not obtained, while 3300
If it exceeds m / min, the desired strength cannot be obtained.

In order to obtain a polyester fiber having a good balance between strength and dimensional stability, which is the object of the present invention, a combination of the above-described conditions of the heating zone under the die and the spinning speed is an important factor.

Next, the drawn semi-drawn yarn (undrawn yarn)
Is usually stretched without being wound once. Specifically, the above-mentioned semi-drawn (undrawn yarn) yarn is subsequently transferred to a drawing region, where the first-stage drawing is performed at 80 to 100 ° C, preferably 8 ° C.
At a temperature of 5 to 95 ° C., the film is stretched 1.1 to 1.5 times, preferably 1.1 to 1.3 times. Here, if the stretching temperature of the first-stage stretching is lower than 80 ° C., fluff is generated, and
When the temperature exceeds 00 ° C., the strength is reduced. On the other hand, if the first-stage stretching ratio is less than 1.1 times, the strength is reduced.
If it exceeds 5 times, it causes fluff.

Next, in the second stretching step, 245 to 265 is used.
° C, preferably at a temperature of 250-260 ° C,
It is stretched 1.6 times, preferably 1.3 to 1.5 times.

When the temperature in the second stretching is lower than 245 ° C.,
Not only do the fibers have a large amount of fluff and the yarn operability decreases significantly, but also the strength is reduced.
Yarn breakage occurs frequently, and the operability becomes extremely poor. When the second-stage stretching ratio is less than 1.2 times, the strength is reduced.
If the ratio exceeds 6 times, fluff is generated, and the contraction rate of the original yarn increases.

The total stretching ratio is 1.5 to 2.0 times,
Preferably, it is in the range of 1.6 to 1.9 times.
If the total stretching ratio is less than 1.5 times, the strength will be reduced, and if it exceeds 2.0 times, the stretchability will be poor and fluff will be generated.

Next, the film is usually wound around a non-heated roller and subjected to a relaxation treatment of about 2 to 4%.
It is wound by a winder at a speed of about m / min.

Accordingly, the above-mentioned range of the spinning conditions is preferable in view of the spinning operability and the strength of the obtained fiber.

In the above-described spinning and drawing, the birefringence of the polyester fiber undrawn yarn at the time of spinning-off is set to △.
n _POY and the birefringence of the drawn polyester fiber yarn after drawing as △ n _DY , the difference between these birefringences △ n _DY − △
n _POY and ^{100 × 10 -3 ~120 × 10 -3} , preferably those in the range of ^{105 × 10 -3 ~115 × 10 -3} .

If the difference in the birefringence is less than 100 × 10 ⁻³ , the strength of the obtained fiber is greatly reduced, and
When it exceeds 10 ^-3 , the dimensional stability of the obtained fiber is deteriorated, and the tension maintenance ratio of the belt tends to decrease.

By adopting such spinning / drawing conditions, a reduction in strength is minimized, and V is excellent in dimensional stability.
A polyester fiber for belt reinforcement can be obtained. As specific means for obtaining the above-mentioned birefringence, it is necessary to set the respective conditions of the intrinsic viscosity, the temperature of the heating area under the spinneret, the spinning speed, the draw ratio, and the relaxation treatment in the above-mentioned ranges.

That is, since the drawn polyester yarn thus produced has an excellent cord utilization ratio, it exhibits sufficient tenacity for a V-belt. Demonstrate excellent dimensional stability.

Therefore, according to the method of the present invention for producing a polyester fiber for reinforcing a V-belt, it is possible to stabilize the quality of the yarn and efficiently obtain a polyester fiber satisfying a good balance of strength and dimensional stability. Can be.

Next, the V-belt cord of the present invention will be described.

The cord for a V-belt of the present invention is obtained by the above-mentioned method, and at the same time, ply-twisting and ply-twisting a polyester fiber which simultaneously satisfies the above-mentioned properties (a) to (e) and further provides an adhesive And heat-treated under tension, and the cord has a strength (f) of 5.5 g / d or more, preferably 5.6 g / d or more.

Here, the strength (f) of the cord is 5.5 g /
Below d, the absolute value of the strength of the V-belt becomes low, which leads to a reduction in the life and durability of the V-belt.

[0043] Furthermore, (g) at 0.99 ° C. of the sum S _C and polyester fibers of the intermediate elongation at 2.67 g / d 0.99 ° C. in after standing for 30 minutes in dry heat shrinkage and the code in 30 minutes after standing Heat shrinkage of polyester and 4.5 g / d of polyester fiber
The ratio of the intermediate elongation at the time to the sum S _F (S _C / S _F ) is 50 to 70
%, Preferably in the range of 55 to 65%.
Here, when the ratio (g) is less than 50%, the stress relaxation rate of the V-belt is high, that is, the V-belt tension maintenance rate becomes small, causing not only slack of the V-belt but also shortening of the life of the V-belt. Connect. On the other hand, when the above ratio (g) exceeds 70%, the tension maintaining ratio of the V-belt is increased, the tightening of the pulley by the belt is increased, and the damage of the belt is increased.

Further, (h) the ratio of the maximum heat shrinkage stress of the cord to the maximum heat shrinkage stress of the polyester fiber is 70 to 12
5%, preferably in the range of 80 to 120%. If it is less than 70%, it causes slack of the V-belt during belt running. If it exceeds 125%, the tightening force of the V-belt on the pulley becomes large, As a result, the belt may be damaged.

Next, the adhesive treatment of the cord will be described.

Usually, it is desirable that the cord is first treated with an isocyanate-based or epoxy-based adhesive (first treatment), and then treated with RFL (resorcin, formaldehyde, latex) (second treatment).

In consideration of the adhesion to rubber or the fraying of the belt end surface when the belt is formed, it is more preferable that the first treatment is performed with a solvent system rather than a water system. The latex component of the RFL treatment agent in the second treatment is V
Latex that easily adheres to the rubber of the belt is selected, and generally the same type of latex as the rubber of the V-belt is used.
For example, CR rubbers include CR latex and H-NB.
H-NBR-based latex is more preferred for the R-based rubber.

The cord embedded in the V-belt receives heat or a load such as compression, extension, or bending during belt running, and the strength decreases with time.
The yarn produced by the method of the present invention has excellent strength after fatigue, that is, excellent residual strength, and exhibits favorable performance of extending the life of the belt.

Further, the cord thus obtained is excellent in bending fatigue resistance and chemical deterioration resistance when a V-belt is used.

Therefore, the V-belt cord of the present invention has excellent dimensional stability, fatigue resistance and durability, and can provide a V-belt having ideal performance.

[0051]

The present invention will be described below in more detail with reference to examples.

Each measured value in the examples was measured according to the following method. [Intrinsic viscosity (I
V)] Using an Ostwald viscometer, the relative viscosity η _rp of a solution in which 3 g of a sample was dissolved in 100 ml of orthochlorophenol was measured at 25 ° C., and the IV was calculated by the following approximate formula. IV = 0.0242η _rp +0.2634 where η _rp = (t × d) / (t ₀ × d ₀ ) t: Fall time of solution (second) t ₀ : Fall time of orthochlorophenol (second) d: Solution density (g / cc) d ₀ : density of orthochlorophenol (g / cc).

[Content of -COOH Terminal Group] 0.1 g / d of the sample filament was weighed, 5 ml of benzyl alcohol was added in a test tube, and the mixture was heated at 215 ° C. for 3 minutes to be dissolved. Thereafter, the mixture was quenched at 20 to 30 ° C. for several seconds and added to 10 ml of chloroform. Next, the test tube was washed with 5 ml of heated benzyl alcohol, cooled rapidly, and then the chloroform was added. The chloroform solution was titrated with a 0.1N caustic soda benzyl alcohol solution using a 0.1% alcohol solution of phenol red as an indicator, and -COOH terminal groups were measured.

[Strength, Elongation, Intermediate Elongation] Using a Tensilon tensile tester manufactured by Orientec Co., the strength was measured at a yarn length of 25 cm and a tensile speed of 30 cm / min. The intermediate elongation of the yarn is 4.5 g / d,
The cord shows an elongation at 2.67 g / d.

[Dry heat shrinkage: ΔSd] A sample was taken in a skein and left in a temperature-controlled room at 20 ° C. and 65 RH for 24 hours or more, and then measured by applying a load corresponding to 0.1 g / d of the sample. A sample having a length L ₀ was left in an oven at 150 ° C. for 30 minutes in a tensionless state, then taken out of the oven, left in the temperature control room for 4 hours, and measured again with the above weight applied.
It was calculated by the following formula from L _{1. △ Sd = (L 0 -L 1} ) / L 0 × 100 (%).

[Maximum heat shrinkage stress]
When the temperature is not lower than 150 ° C. and higher than 10 ° C.
When the temperature was not lower than ℃, the shrinkage stress was determined at a temperature rising rate of 3 ℃ / min.

[Birefringence index] The birefringence was determined by a normal Berek compensator method using a DOH light source with a POH type polarizing microscope manufactured by Nikon Corporation. The birefringence of the undrawn yarn was Δn _POY , and the birefringence of the drawn yarn was Δn _DY .

[Belt tension maintenance rate] 45.9
Apply a tension of 100 kg and pull a 100φ pulley for 1.5 hours.
22. After rotating at 3600 rpm at a temperature of 70 ° C.,
It was left to cool for 5 hours and calculated from the ratio of the belt tension.

[Examples 1 to 3 and Comparative Examples 1 to 3] A polyethylene terephthalate chip having an intrinsic viscosity of 1.23 was supplied to an extruder-type melt-spinning apparatus, and a discharge port diameter was 0.1 mm.
After spinning using a 6φ spinneret, and passing the spun fiber yarn through a heating zone (heating cylinder) having the atmospheric temperature and length shown in Table 1, cooling air is blown by the annular cooling cylinder at 30 m / min. After cooling by spraying at a high speed and applying a spinning oil with an oiling roller, the yarn is taken up at a speed shown in Table 1 by a take-up roller heated and controlled at 70 ° C., and the obtained undrawn yarn is continuously wound without being wound once. Then, it was drawn and wound up in two steps to obtain a drawn fiber yarn.

However, in Examples 1 and 2, -COOH was used during the polymerization.
As a terminal group blocking agent, 2,6-diisopropylphenyl-carbodiimide was polymerized and added in an amount of 1.8% by weight based on the weight of the chip.

The stretching ratio, temperature,
The total stretching ratio and Δn _{DY −Δn POY} were set to the conditions shown in Table 1.

Table 2 shows the results of evaluating the properties of the polyester fiber thus obtained.

[0063]

[Table 1]

[Table 2] Further, two polyester fibers each having a fineness of 1000 d and a single fiber number of 240 obtained as described above are drawn and twisted together, and then three twisted twists are twisted to give a total fineness of 6000 denier (1000 d // 2/3). , Twist 9.6t / 10cm ×
(17.0 t // 10 cm) and a 4% isocyanate solvent-based adhesive was applied to the cord.
After a heat treatment at a temperature of 20 ° C. for about 60 seconds, a 4% adhesive of RFL (resorcin, formaldehyde, latex) was applied, and then a heat treatment at a temperature of 220 ° C. for about 60 seconds.

At this time, tension was applied so that the intermediate elongation of each cord was almost constant (elongation at 2.67 g / d was 3%) to produce a core cord. Next, a standard belt A-35 using this core cord (6 embedded cords)
Was made.

Table 3 shows the results of evaluating various characteristics of the cord and V-belt thus obtained.

[0066]

[Table 3] As is clear from the results of Tables 1 to 3, the polyester fibers of Examples 1 and 2 obtained in the present invention are excellent in low shrinkage, and also have a high tension maintenance ratio which is a measure of V belt performance. It shows excellent values and is also excellent in V belt durability, and is most suitable as a fiber for V belt.

On the other hand, in Comparative Example 1, the intermediate elongation (4.
(Elongation at 5 g / d) and the dry heat shrinkage are high, so that the dimensional stability is deteriorated and the tension maintenance ratio of the V belt is also deteriorated.

In Comparative Example 2, Δn _{DY −Δn POY of the} yarn was used.
, The belt tension maintenance ratio is low, and the durability is inferior.

Further, in Comparative Example 3, the maximum heat shrinkage stress of the yarn was high, the ratio of the intermediate elongation to the dry heat shrinkage was small, and the tension maintenance rate and durability of the V-belt were the object of the present invention. Not satisfying.

[0070]

As described above, the polyester fiber for reinforcing a V-belt of the present invention has an excellent balance between strength and dimensional stability, and has ideal performance for reinforcing a V-belt. .

Further, according to the present invention, it is possible to efficiently produce a stable polyester fiber for reinforcing a V-belt with less fluff and the like.

Further, the cord for a V-belt of the present invention is excellent in dimensional stability, fatigue resistance and durability, and by using this cord, it is excellent in durability (fatigue resistance) and tension maintenance. And a V-belt having good dimensional stability can be provided.

Claims (4)

[Claims] 1. 90 mol% of all repeating units of a molecular chain
The above consists of a polymer that is ethylene terephthalate,
V satisfying the following characteristics (a) to (e)
Polyester fiber for belt reinforcement. (A) Intrinsic viscosity (IV): 0.90 to 1.05 (b) Single fiber fineness: 1.0 to 4.5 d (c) Yarn strength: 6.5 g / d or more (d) Maximum heat shrinkage stress : 0.2-0.5 g / d (e) Dry heat shrinkage after leaving at 150 ° C. for 30 minutes and 4.5
Sum of intermediate elongation at g / d: 9.7 or less 2. The polyester fiber for reinforcing a V-belt according to claim 1, wherein the amount of —COOH terminal group of the polyester fiber is 10 equivalents / 10 ⁶ g or less. 3. 90 mol% of all repeating units of the molecular chain
The above is a polymer that is ethylene terephthalate is melt spun from a spinneret, and after passing the spun yarn through a heating zone,
In the method of producing polyester fibers by cooling and solidifying with cold air, the temperature of the heating area under the base is set to 320 to
350 ° C, length 65-75cm, 2700-33
The birefringence of the undrawn yarn drawn at a spinning speed of 00 m / s is defined as Δn _POY, and then, in a temperature range of 80 to 100 ° C., 1.
The first stage is stretched to 1 to 1.5 times, and the second stage is stretched to 1.2 to 1.6 times in a temperature range of 245 to 265 ° C., so that the total stretch ratio becomes 1.5 to 2.0 times. The difference between Δn _DY and Δn _POY (Δn _{DY −Δn POY} ) when the birefringence of the drawn yarn is Δn _DY when drawn as described above is 100 × 10 ^{−3 to} 120 × 1
Method for manufacturing a V-belt reinforcing polyester fiber, characterized in that the 0 ^-3 range. 4. A polyester fiber obtained by the production method according to claim 3 and having the characteristics according to claim 1 or 2 is subjected to priming and plying, and is further subjected to a heat treatment under tension by applying an adhesive. A cord for reinforcing a V-belt, wherein the cord satisfies the following characteristics (f) to (h). (F) Strength: 5.5 g / d or more (g) of the intermediate elongation sum S _C and polyester fibers 150 ° C. in after standing 30 minutes dry heat shrinkage and code at 2.67 g / d code 150 Sum of dry heat shrinkage after standing at 30 ° C. for 30 minutes and intermediate elongation at 4.5 g / d of polyester fiber S
Ratio to _F (S _C / S _F ): 50 to 70% (h) Ratio of maximum heat shrinkage stress of cord to maximum heat shrinkage stress of polyester fiber: 70 to 125%.