JPH11323661A - Polyester filament and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyester filament having good yarn properties, capable of maintaining excellent wet heat resistant properties for a long period and capable of being industrially readily produced, and further to provide its production method. SOLUTION: This polyester filament consists of a composition obtained by adding 0.1-30 wt.% polymer having an ethylene component and a glycidyl methacrylate component, 0.01-10 wt.% polymer having the ethylene component and an acrylic ester component, and 0.3-2.0 wt.% carbodiimide compound to a polyethylene terephthalate or a polyester consisting essentially of the polyethylene terephthalate, and has >=1.4 relative viscosity and <=10 eq./t amount of a terminal carboxyl group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filament for industrial materials, in particular, a polyester filament having excellent moisture and heat resistance suitable for canvas yarn, belt cloth, filters and the like for papermaking, and a method for producing the same.

[0002]

2. Description of the Related Art Polyester filaments have excellent physical properties and are suitably used for filaments for industrial materials, especially for papermaking canvas, belt cloth and filters. However, the environment in which the filaments for industrial materials are used is severe, and the filaments may deteriorate in a relatively short period of time and become unusable. For example, a papermaking canvas using a polyester filament is exposed to a high-temperature and high-humidity state because it is used in processes such as a papermaking press zone and a subsequent drying zone. Therefore, water, heat,
It is known that the influence of water vapor causes polyester filaments to undergo thermal and hydrolytic degradation, making them unusable.

In the hydrolysis of polyester by water and water vapor, the polyester is decomposed by attacking an ester bond portion of a water molecule to form a carboxyl group and a hydroxyl group, and the polymer chain is split to cause hydrolysis degradation. Furthermore, the carboxyl terminal group formed thereby plays a catalytic role in the hydrolysis reaction of the polyester, and the hydrolysis rate is accelerated with an increase in the amount of the carboxyl terminal group. In particular, when heat is applied, hydrolysis is promoted.

Therefore, as a countermeasure against thermal hydrolysis, a method of improving the wet heat resistance of the filament by adopting a polyester having a small amount of carboxyl terminal groups has been adopted. For example, Japanese Patent Publication No. 1-15604,
No. 4-289221, a carbodiimide compound is added,
A method for obtaining a polyester filament having improved moist heat resistance by blocking a carboxyl terminal group is disclosed. However, it has been difficult to maintain the moist heat resistance for a long period of time only by reducing the amount of carboxyl terminal groups in the polyester filament.

Further, Japanese Patent Publication No. 58-22567 discloses a method of improving the wet heat resistance by adding a polyolefin to a polyester. However, since the polyolefin to be contained does not have a functional group, there is a problem that the phase separation from the polyester is caused and the yarn quality performance is reduced.

[0006] In order to solve the above-mentioned problems, the present inventors have previously disclosed in Japanese Patent Application No. 9-138191 a method in which a copolymer of ethylene and glycidyl methacrylate and a carbodiimide compound were added to polyester. A polyester filament was proposed. This filament had sufficient wet heat resistance and yarn quality performance. However, there is a disadvantage that the melt viscosity of the molten polymer stream is produced at the time of production, which may result in deterioration of the spinnability.

[0007] For this reason, the present inventors have disclosed in Japanese Patent Application No. 9-283386.
In the above item, a production method was proposed in which a copolymer of ethylene and glycidyl methacrylate and a polyolefin resin were melt-kneaded in advance, and the resulting mixture was kneaded with polyester to reduce the uneven viscosity of the molten polymer stream. By this method, the problem relating to the deterioration of the yarn-making property has been solved, but since a preliminary kneading step is required, problems such as industrial time loss, labor, and high cost arise. It became so.

[0008]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, and has excellent yarn quality performance, retains excellent moisture and heat resistance for a long period of time, and is industrially manufactured. It is intended to provide a polyester filament which is easy and a method for producing the same.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a polymer having an ethylene component and a glycidyl methacrylate component (hereinafter referred to as P [E-
GMA], a polymer containing an ethylene component and an acrylate component (hereinafter abbreviated as P [E-AE]) and a carbodiimide compound (hereinafter abbreviated as a CI compound) to form a filament. The present inventors have found that a filament having good quality performance and excellent moisture-heat resistance can be maintained for a long period of time, and that a high-quality filament having good spinning properties can be obtained without a preliminary kneading step, and the present invention has been achieved.

That is, the gist of the present invention is as follows. (A) Polyethylene terephthalate or a polyester mainly composed of polyethylene terephthalate, 0.1 to 30% by weight of P [E-GMA], 0.01 to 10% by weight of P [E-AE], and CI compound
A polyester filament comprising a composition to which 0.3 to 2.0% by weight is added, having a relative viscosity of 1.4 or more and a carboxyl terminal group amount of 10 eq / t or less. (B) The method for producing a polyester filament according to (a), wherein the following steps are sequentially performed. (1) Step of producing polyester (A) having a relative viscosity of 1.4 or more (2) P [E-GMA] (B) to polyester (A)
Step of adding P [E-AE] (C) and CI compound (D) and melt-spinning to obtain a filament having a relative viscosity of 1.4 or more and a carboxyl end group content of 10.0 eq / t or less (3) Filament Stretching process

The relative viscosity, the amount of carboxyl end groups and the content of the active CI compound contained in the filament in the present invention are measured by the following methods. [Relative viscosity] The relative viscosity was measured using an Ubbelohde viscometer under the conditions of an equal weight mixture of phenol and ethane tetrachloride as a solvent, a concentration of 0.5 g / dl and a temperature of 20 ° C. [Amount of carboxyl terminal group] The polyester was dissolved in benzyl alcohol and titrated with 0.1N methanolic potassium hydroxide solution. [Content of CI compound in active state] The filament was dissolved in a mixed solvent of heptafluoroisopropanol and chloroform, the polymer component was precipitated with acetonitrile, and the solution obtained by filtration was measured by HPLC.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The polyester in the present invention is polyethylene terephthalate (PET) or a polyester based on the same, and includes isophthalic acid, adipic acid, sebacic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,4 -Butanediol, neopentyl glycol, 1,
Those obtained by copolymerizing a small amount of 4-cyclohexanediol, 1,4-cyclohexanedimethanol or the like can also be used.

The filament of the present invention comprises a composition obtained by adding P [E-GMA], P [E-AE] and a CI compound to the above polyester. First, as P [E-GMA], a copolymer having a copolymerization ratio of a glycidyl methacrylate (hereinafter abbreviated as GMA) component in the main chain of polyethylene of 1 to 35 mol% is preferably used. In addition, as long as the effect is not impaired, a vinyl acetate component, a styrene component, or the like may be copolymerized as other components.

The reason for adding P [E-GMA] is as follows. By including a polyolefin component in the polyester main chain, the hydrolysis reaction of the ester portion can be suppressed, and the moist heat resistance can be improved.However, since the compatibility between the polyester and the olefin polymer is poor, phase separation occurs. This causes a decrease in yarn quality. Then, by introducing a GMA component that reacts with the polyester terminal group into the main chain, it becomes possible to reduce phase separation in the obtained filament.

The amount of P [E-GMA] must be 0.1 to 30% by weight. If the amount is less than 0.1% by weight, it is impossible to improve the wet heat resistance and reduce the phase separation as described above. If the amount exceeds 30% by weight, the reaction with the polyester proceeds excessively, and the melt viscosity is increased. , And unevenness in viscosity occurs to deteriorate the spinnability.

Further, as P [E-GMA], a copolymer having a copolymerization ratio of the GMA component of 1 to 35 mol% is preferable as described above, but if the copolymerization ratio of the GMA component is less than 1 mol%, If there is, the reaction with the polyester does not easily occur, phase separation occurs, and the obtained filament has low yarn quality performance, and also becomes fibrillated easily due to fatigue such as bending and friction. On the other hand, when the copolymerization ratio of the GMA component exceeds 35 mol%, the reaction with the polyester proceeds too much, the melt viscosity becomes remarkable, and the spinnability tends to deteriorate. Further, since the polyolefin component is reduced, the effect of improving the moist heat resistance is reduced.

As P [E-AE], a copolymer in which the copolymerization ratio of an acrylate (hereinafter abbreviated as AE) component in the main chain of polyethylene is 1 to 40 mol% is preferable. Other components may be copolymerized as long as the effects are not impaired.

The reason for adding P [E-AE] is as follows. As described above, the compatibility between the polyester resin and the polyolefin resin is poor, and in the present invention, in order to improve this point, a composition that is chemically reactive with polyester, such as P [E-GMA], is added. . The GMA component reacts with the polyester end groups to reduce phase separation,
The melt viscosity tends to increase, whereby the molten polymer stream has a melt viscosity unevenness, and the spinnability tends to deteriorate.

Therefore, the problem is solved by adding P [E-AE] containing a component having good compatibility with both. That is, P [E-AE] has good compatibility with P [E-GMA] because it contains an ethylene component, and also has good compatibility with polyester because it contains an acrylate component. And P [E-
When [AE] is added to a blend of polyester and P [E-GMA], the affinity is physically improved and the rise in melt viscosity can be reduced. In addition, in order to improve the dispersibility of the P [E-GMA] domain in the polyester matrix, it is possible to obtain a molten polymer having no spots, improve spinning operability, and improve the fiber properties of the obtained fiber. It becomes possible.

It is necessary that the amount of P [E-AE] added is 0.01 to 10% by weight. If the addition amount is less than 0.01% by weight, the increase in the melt viscosity of the polyester to which P [E-GMA] has been added as described above cannot be prevented.
If the amount is more than 10% by weight, the amount of the acrylate component increases, so that the ester bond portion increases, and as a result, the wet heat resistance decreases. Further, since P [E-AE] is not chemically bonded to the polyester, if the amount of P [E-AE] is increased, the spinnability deteriorates.

As P [E-AE], the copolymerization ratio of the AE component in the main chain of polyethylene is 1 to 40 mol%.
However, if the copolymerization ratio of the AE component is less than 1 mol%, the phase separation from the polyester cannot be reduced, resulting in a decrease in the yarn quality and a deterioration in the spinning property.
On the other hand, if the copolymerization ratio of the AE component exceeds 40 mol%, the olefin component is reduced, so that the ester bond portion is increased in the filament, and the moisture-heat resistance of the obtained filament is liable to decrease.

The CI compounds include N, N'-bis (2,6-dimethylphenyl) carbodiimide, N, N'-bis (2,6-diethylphenyl) carbodiimide, N, N'-bis (2,6 -Diisopropylphenyl) carbodiimide, N, N'-bis (2
-Isopropylphenyl) carbodiimide and the like. Among them, N, N'-bis (2,6-diisopropylphenyl) carbodiimide is preferred because of its heat resistance and its use on an industrial level.

The addition amount of the CI compound is 0.3 to 2.0% by weight.
It is necessary to If the amount is less than 0.3% by weight, the blocking of the carboxyl terminal group becomes insufficient, the fiber having a carboxyl terminal group amount of 10 eq / t or less cannot be obtained, and the fiber has insufficient wet heat resistance. On the other hand, when the content exceeds 2.0% by weight, the spinning property deteriorates.

The active CI compound is 20 to 1800
It is preferably contained at 0 ppm, more preferably 200 to 9000 ppm. The active state refers to a state capable of reacting with a carboxy group or a water molecule.If the content is 20 ppm or less, the effect of the CI compound is difficult to be exhibited. The upper limit of the amount is 2.
It is difficult because it is 0% by weight.

In the polyester of the present invention,
In addition to the three components described above, inorganic particles such as titanium oxide, a coloring agent, a plasticizer, a modifier, etc., in a range that does not affect the yarn performance, in order to suit various uses. It may be contained.

The polyester filament of the present invention has a relative viscosity of 1.4 or more and a carboxyl end group content of 10 or more.
It must be less than eq / t. If the carboxyl terminal group content of the filament is more than 10 eq / t, the filament quality will be significantly reduced due to long-term wet heat treatment, and the filament will not have sufficient wet heat resistance. If the relative viscosity is less than 1.4, the resistance to the deterioration due to the abrasion of the filament is deteriorated, and the abrasion resistance is deteriorated, so that it cannot be put to practical use.

The polyester filament of the present invention may be a monofilament or a multifilament.

Next, a method for producing the filament of the present invention will be described. First, a polyester having a relative viscosity of 1.4 or more is produced. The relative viscosity of the polyester before melt spinning is
If the molecular weight is less than 1.4, the spinnability deteriorates, the yarn quality performance of the obtained filament becomes insufficient, and the relative viscosity of the obtained filament cannot be increased to 1.4 or more.

The carboxyl end group content of the polyester is preferably 20 eq / t or less. If this condition is not satisfied, it may be difficult to reduce the carboxyl end group content of the filament obtained by melt spinning to 10 eq / t or less.

In order to obtain such a polyester, usually, a prepolymer having a relative viscosity of 1.2 to 1.4 is obtained by a melt polymerization method. Next, the prepolymer is heated in a solid state under reduced pressure or an inert gas flow to perform a solid-state polymerization reaction, thereby obtaining a polyester having a predetermined relative viscosity and a predetermined amount of carboxyl end groups. If the relative viscosity of the prepolymer is not appropriate, the total polymerization time becomes extremely long, or the relative viscosity of the polyester after solid phase polymerization cannot be increased to 1.4 or more.

It is preferable to select the conditions for the solid-state polymerization so that the relative viscosity of the polyester obtained by the solid-state polymerization is higher than that of the prepolymer by about 0.1 to 0.4. The solid-phase polymerization reduces the amount of carboxyl end groups of the polyester and removes impurities such as oligomers.

Next, P [E-
GMA], P [E-AE] and CI compounds are added, and melt spinning is performed. As a method for adding P [E-GMA] and P [E-AE], a method in which melt kneading is performed in advance and a master batch is formed can be employed. It is possible to obtain a polymer without spots. Therefore, it is preferable to employ a direct blending method since industrial production is easy and cost increase is small.

At this time, in order to suppress the phase separation between the polyester and the polyolefin component, it is preferable to incorporate a mixer capable of physically kneading such as a static mixer in the spinning line or the nozzle pack. .

The method of melt spinning is not particularly limited and can be carried out by a conventional method, but the spinning temperature is preferably 350 ° C. or lower, more preferably 300 ° C. or lower. If the spinning temperature is too high, the polyester and additives undergo thermal decomposition, making smooth spinning difficult and resulting in poor filament properties. Also,
A carboxyl end group is generated along with the thermal decomposition reaction of the polyester, and a large amount of the end group blocking agent is consumed during melt spinning, so that the amount of the carboxyl end group of the obtained filament tends to exceed 10 eq / t.

The spun filament is heated at 0 to 100 ° C.
Cooling is preferably carried out in a liquid at 20 to 90 ° C (for monofilament) or in air at 0 to 100 ° C, preferably 10 to 40 ° C (for multifilament). If the cooling temperature is too low, it becomes difficult to control the temperature and workability. If the cooling temperature is too high, the cooling becomes insufficient and the filament quality of the finally obtained filament is inferior.

Next, the cooled and solidified filament is stretched after winding once or without winding. Stretching can be performed in one stage or in two or more stages. The first-stage stretching is performed at a draw ratio of 3.0 to 6.5 times, and the second and subsequent stretches are performed at a higher temperature than the first-stage stretch so that the total draw ratio is 5.0 to 8.0 times. In the case of multifilament, the first-stage drawing is performed at a temperature of about 70 to 200 ° C.
It is performed at a temperature higher than the step stretching and at a temperature of about 150 to 300 ° C. In the case of a monofilament, the first-stage stretching is carried out in a liquid at a temperature of about 60 to 100 ° C. which does not cause the movement of the stretching point, and the second-stage stretching and thereafter are performed at a higher temperature than the first-stage stretching, and 130 to 300
Perform in a liquid or gas at a temperature of about ° C.

When the stretching temperature is lower than the above range, insufficient heating results in uneven drawing and yarn breakage. On the other hand, when the stretching temperature is too high, melting and thermal deterioration of the filament occur, which is not preferable. On the other hand, if the total draw ratio is less than 5.0, the quality of the obtained filament, particularly the linear strength, tends to be low. On the other hand, if the total draw ratio is larger than 8.0, the molecular orientation cannot respond to the plastic deformation in the fiber, so that microvoids are generated in the fiber, and a filament having satisfactory performance cannot be obtained.

Further, depending on the use of the filament, a relaxation heat treatment may be performed after the drawing. At this time, 150 to 50
It is preferably carried out in a gas at 0 ° C. with a relaxation rate of 1 to 15%. If the heat treatment temperature is lower than 150 ° C., the heat treatment effect on the filament tends to be insufficient, and if it is higher than 500 ° C., the thermal decomposition reaction of the polyester tends to occur on the fiber surface, although it depends on the heat treatment time. In addition, the relaxation rate is 1%
If it is less than 10, the resulting filament has too high a heat shrinkage rate, and in some cases, is not suitable for practical use. If the relaxation rate is more than 15%, the slackness of the yarn occurs in the relaxation heat treatment stage, and the operability deteriorates. At the same time, the yarn quality performance tends to decrease.

[0039]

In the present invention, a polyester compound containing a CI compound and a polyolefin-containing P [E-
Since GMA] and P [E-AE] are added, a filament having a low carboxyl end group content can be obtained, and a filament having wet heat resistance can be obtained. That is, G
By containing the MA component, it chemically bonds to the polyester terminal group, phase separation of the polyester and the polyolefin is suppressed, and further, by containing the AE component, the affinity is improved physically, No melt viscosity unevenness occurs. As a result, it is possible to obtain an excellent polyester filament exhibiting wet heat resistance for a long period of time and having no decrease in yarn quality performance, and not requiring a preliminary kneading step, and having high productivity and high quality.

[0040]

Next, the present invention will be described specifically with reference to examples. The measurement and evaluation of the characteristic values in the examples were performed as follows. The relative viscosity, the amount of carboxyl end groups, and the content of the active CI compound were measured by the above-described methods. [Strength and elongation] Measured according to JIS L 1013. [Wet heat resistance (strong retention)] The filament was treated with saturated steam at 120 ° C for 10 days, and then evaluated by the strength retention with respect to the untreated filament. [Yarn-making properties] The case where the spun yarn could not be collected was indicated by x, and the case where the sample could be collected was indicated by ○. [Drawn yarn surface irregularities] Measure the fiber diameter of the obtained filament with a micrometer, and the fluctuation rate of the fiber diameter value is 10%.
The above items were indicated by x, and the others were indicated by ○.

Example 1 A polycondensation reaction was carried out using PET oligomer and ethylene glycol as starting materials to obtain a polyester pellet (prepolymer) having a relative viscosity of 1.3 and a carboxyl end group content of 30 eq / t. Perform solid phase polymerization reaction of this pellet, relative viscosity 1.
6. A solid-phase polymerization pellet having a carboxyl end group content of 16 eq / t was obtained. 5.0% by weight of P [E-GMA]
(LOTADER AX-8840 manufactured by elf atochem), 0.5% by weight of P
[E-AE] (LOTRYL 28MA07 manufactured by elf atochem) and 1.
5% by weight of N, N'-bis (2.6-diisopropylphenyl)
The carbodiimide was added and melt spun. Melt spinning is
Using extruder type spinning device, spinning temperature 295 ℃
Performed using a spinneret having a spinning hole with a hole diameter of 2.0 mm,
The spun yarn was cooled in a water bath at 70 ° C. to obtain an undrawn yarn. This undrawn yarn is drawn at the first stage in a water bath at 90 ° C. (see 3.2.
), And then the second stage of stretching (1.7 times) was performed in a hot air atmosphere at 250 ° C., so that the total stretching ratio was 5.5 times.
Subsequently, a 10% relaxation heat treatment was performed in a hot air atmosphere at 400 ° C. to obtain a polyester monofilament (1600d). Table 1 shows various physical property values and evaluation results of the obtained monofilament.

Examples 2 to 4 and Comparative Examples 1 to 6 The same procedures as in Example 1 were carried out except that the addition amounts of P [E-GMA], P [E-AE] and CI compounds were changed as shown in Table 1. Thus, a polyester monofilament was obtained. Table 1 shows various physical property values and evaluation results of the obtained monofilament.

Example 5 A prepolymer pellet was obtained in the same manner as in Example 1. The pellet was subjected to a solid phase polymerization reaction to obtain a solid phase polymerization pellet having a relative viscosity of 1.5 and a carboxyl end group content of 18 eq / t. The amount of P [E-GM
A], P [E-AE], except that a CI compound was added,
A polyester monofilament was obtained in the same manner as in Example 1. Table 1 shows various physical property values and evaluation results of the obtained monofilament.

Comparative Example 7 A polyester monofilament was obtained in the same manner as in Example 5, except that a solid phase polymerization pellet having a relative viscosity of 1.39 was obtained by a solid phase polymerization reaction. Table 1 shows various physical property values and evaluation results of the obtained monofilament.

Example 6, Comparative Example 8 The same amount of P as shown in Table 1 was added to the same solid phase polymerization pellet as in Example 1.
[E-GMA], P [E-AE] and CI compounds were added and melt-spun. Melt spinning is performed using an extruder-type spinning device at a spinning temperature of 295 ° C using a spinneret having 48 spinning holes with a hole diameter of 0.4 mm to form a spun yarn.
It was cooled with air at 20 ° C. to obtain an undrawn yarn. This undrawn yarn
It is heated to 90 ° C., stretched 6.3 times between the first roller and the second roller heated to 230 ° C., then heated to 170 ° C. and subjected to a 6% relaxation heat treatment, and the polyester multifilament (300 d / 48f) was obtained. Table 1 shows various physical property values and evaluation results of the obtained multifilament.

[0046]

[Table 1]

As is clear from Table 1, the monofilaments obtained in Examples 1 to 5 and the multifilament obtained in Example 6 were excellent in strength and elongation, and also high in the strength retention after wet heat treatment. . In addition, since there was no unevenness on the yarn surface, high-quality fibers could be obtained with good productivity without causing unevenness in melt viscosity without going through the preliminary kneading step. On the other hand, the filaments of Comparative Examples 1 and 8
Since [E-AE] was not added, unevenness in the melt viscosity occurred in the molten polymer, and irregularities occurred on the fiber surface. In addition, fluffing due to single yarn breakage occurred, and the yarn could be wound up, but yarn breakage also occurred. Comparative Example 2
The filament No. did not have long-term wet heat resistance because P [E-GMA] was not added. The filament of Comparative Example 3 did not have the wet heat resistance because the CI compound was not added. In Comparative Example 4, the addition amount of P [E-GMA] was too large, in Comparative Example 5, the addition amount of P [E-AE] was too large, and in Comparative Example 6, the addition amount of the CI compound was too large. In both cases, the yarn-making properties were poor, and filaments could not be obtained. Further, the filament of Comparative Example 7 had a relatively low relative viscosity, and thus had low strength and poor heat and moisture resistance.

[0048]

The polyester filament of the present invention is
Excellent moisture and heat resistance can be maintained for a long period of time, and strength, elongation and other good yarn properties are good, and it is possible to obtain industrially high productivity, and filaments for industrial materials, especially It can be suitably used as a canvas thread for papermaking, a belt cloth, a filter, etc., which are industrial fabrics. Further, according to the production method of the present invention, such a polyester filament can be obtained industrially with high productivity.

Claims (5)

[Claims] 1. A polymer having an ethylene component and a glycidyl methacrylate component in an amount of 0.1 to 30% by weight and a polymer having an ethylene component and an acrylate component in a polyethylene terephthalate or a polyester mainly containing the same.
A polyester filament comprising a composition containing 0.01 to 10% by weight and 0.3 to 2.0% by weight of a carbodiimide compound, having a relative viscosity of 1.4 or more and a carboxyl terminal group amount of 10 eq / t or less. 2. The polyester filament according to claim 1, wherein the filament contains an active carbodiimide compound in an amount of 20 to 18000 ppm. 3. The method according to claim 1, wherein the carbodiimide compound is N, N′-bis
3. The polyester filament according to claim 1, which is (2,6-diisopropylphenyl) carbodiimide. 4. The method for producing a polyester filament according to claim 1, wherein the following steps are sequentially performed. (1) Step of producing polyester (A) having a relative viscosity of 1.4 or more (2) Polymer (B) having an ethylene component and a glycidyl methacrylate component in polyester (A), and a polymer having an ethylene component and an acrylate component in polyester (A) Step of adding the conjugate (C) and the carbodiimide compound (D) and melt-spinning to obtain a filament having a relative viscosity of 1.4 or more and a carboxyl terminal group amount of 10.0 eq / t or less (3) a step of drawing the filament 5. The method according to claim 5, wherein the carbodiimide compound (D) is N, N′-
The method for producing a polyester filament according to claim 4, which is bis (2,6-diisopropylphenyl) carbodiimide.