JP3784135B2 - Moist heat resistant polyester filament and its production method - Google Patents

Description

【００４４】
実施例７
実施例１と同じ固相重合ペレットに、実施例１と同じＥＭＧ 5.0重量％、ポリエチレン（ＰＥ） 3.0重量％及び実施例１と同じＣＤＩ 1.8重量％を添加し、実施例１と同様にして溶融紡糸、延伸、熱処理してポリエステルモノフィラメントを得た。
【００４５】
実施例８
ＥＭＧ、ＰＥ及びＣＤＩの添加量を表２のように変更した以外は実施例７と同様にしてポリエステルモノフィラメントを得た。
【００４６】
実施例９〜11
実施例３と同じ固相重合ペレットに、表２に示した量のＥＭＧ、ＰＥ及びＣＤＩを添加し、実施例１と同様な条件で溶融紡糸、延伸、熱処理してポリエステルモノフイラメントを得た。
【００４７】
比較例８〜13
ＥＭＧ、ＰＥ及びＣＤＩの添加量を表２のように変更した以外は実施例７と同様にしてポリエステルモノフィラメントを得た。
【００４８】
比較例14
ＥＭＧ、ＰＥ及びＣＤＩの添加量を表２のように変更した以外は実施例９と同様にしてポリエステルモノフィラメントを得た。
【００４９】
実施例12
実施例６と同じ固相重合ペレットに表２に示した量のＥＭＧ、ＰＥ及びＣＤＩを添加し、実施例６と同様にして溶融紡糸、延伸、熱処理してポリエステルマルチマルチフィラメントを得た。
【００５０】
比較例15
ＣＤＩを添加しない以外は実施例12と同様にしてポリエステルマルチフィラメントを得た。
【００５１】
上記の実施例及び比較例で得られたフィラメントの糸質性能等を表２に示す。
【００５２】
【表２】

【００５３】
【発明の効果】
本発明によれば、フィラメントがフィブリル化することがなく、糸質物性が良好で、かつ、優れた耐湿熱性能を長期間にわたって保持するポリエステルフィラメントが提供される。
そして、本発明のポリエステルフィラメントは、産業資材用フィラメント、特に抄紙用カンバス、ベルト布、フィルター等の工業用織物用として好適である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a filament for industrial materials, particularly a polyester filament having excellent moisture and heat resistance suitable for a papermaking canvas, a belt cloth, a filter and the like, and a method for producing the same.
[0002]
[Prior art]
Polyester filaments have excellent mechanical properties and are widely used as filaments for industrial materials, in particular as paper making canvases, belt fabrics or filters.
[0003]
However, the filament for industrial materials is used in a severe environment, and the filament may be deteriorated in a relatively short period of time, and may not be used. For example, a papermaking canvas using a polyester filament is exposed to a high temperature and high humidity condition because it is used in processes such as a papermaking press zone and a subsequent drying zone. For this reason, it is known that polyester filaments undergo heat and hydrolysis degradation due to the influence of water, heat, and water vapor, and cannot be used in a short period of time.
[0004]
In the hydrolysis of polyester by water or water vapor, this part is decomposed by attacking the ester bond part of the water molecule, a carboxyl group and a hydroxyl group are formed, the main chain is split, and the hydrolysis degradation proceeds. Furthermore, the carboxyl end groups formed thereby play a catalytic role in the hydrolysis reaction of the polyester, and as the amount of carboxyl end groups increases, the hydrolysis is accelerated, especially when heat is applied. Is done.
[0005]
Therefore, as a countermeasure against thermal hydrolysis, a method of improving the wet heat resistance of the filament by adopting polyester with a small amount of carboxyl end groups is employed. For example, Japanese Patent Publication No. 1-15604 and Japanese Patent Application Laid-Open No. 4-289221 disclose a method of obtaining a polyester filament having improved moisture and heat resistance by adding a carbodiimide compound and blocking carboxyl end groups. ing. However, it has been difficult to maintain the heat-and-moisture resistance performance for a long period only by reducing the amount of carboxyl end groups in the polyester filament.
[0006]
Here, Japanese Patent Laid-Open No. 7-258542 proposes a polyester filament in which a carbodiimide compound is added to block a carboxyl end group and polyolefin is contained.
However, when ordinary polyolefin is blended with polyester, there is a problem that phase separation is liable to occur, filaments are fibrillated, and yarn properties are deteriorated.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a polyester filament that does not fibrillate, has good yarn properties, and has excellent wet heat resistance over a long period of time, and a method for producing the same.
[0008]
[Means for Solving the Problems]
The present invention solves this problem, and the gist thereof is as follows.
1. It is obtained by melt spinning and stretching a composition prepared by blending 0.1 to 20% by weight of a copolymer of ethylene and glycidyl methacrylate and 0.3 to 2.0% by weight of a carbodiimide compound to a polyester produced through a solid phase polymerization reaction. A polyester filament characterized by having a relative viscosity of 1.40 or more and a carboxyl end group content of 10.0 eq / t or less.
2. The method for producing a polyester filament according to item 1, wherein the following steps are sequentially performed.
(A) A step of producing a prepolymer having a relative viscosity of 1.25 to 1.45 by a melt polymerization method, and then producing a polyester having a relative viscosity of 1.43 or more (but greater than the relative viscosity of the prepolymer) by solid-phase polymerization. ,
(B) A composition in which 0.1 to 20% by weight of a copolymer of ethylene and glycidyl methacrylate and 0.3 to 2.0% by weight of a carbodiimide compound is blended with polyester and melt-spun, has a relative viscosity of 1.40 or more, Obtaining a filament having a terminal group amount of 10.0 eq / t or less,
(C) A step of drawing a filament.
3. A composition comprising 75% by weight or more of a polyester produced through a solid phase polymerization reaction, 0.1 to 20% by weight of a copolymer of ethylene and glycidyl methacrylate, 0.1 to 20% by weight of a polyolefin, and 0.3 to 2.0% by weight of a carbodiimide compound. A polyester filament obtained by melt spinning and drawing, having a relative viscosity of 1.40 or more and a carboxyl end group amount of 10.0 eq / t or less.
4). 4. The method for producing a polyester filament according to item 3, wherein the following steps are sequentially performed.
(a) A step of producing a prepolymer having a relative viscosity of 1.25 to 1.45 by a melt polymerization method, and then producing a polyester having a relative viscosity of 1.43 or more (but greater than the relative viscosity of the prepolymer) by solid-phase polymerization. ,
(b) A composition comprising 75% by weight or more of polyester, 0.1 to 20% by weight of a copolymer of ethylene and glycidyl methacrylate, 0.1 to 20% by weight of polyolefin and 0.3 to 2.0% by weight of a carbodiimide compound was prepared and melt-spun. A step of obtaining a filament having a relative viscosity of 1.40 or more and a carboxyl end group amount of 10.0 eq / t or less,
(c) A step of drawing the filament.
[0009]
In addition, the relative viscosity in this invention, the amount of carboxyl terminal groups, and carbodiimide compound content are the values obtained by measuring with the following method.
(A) Relative viscosity Measured with an Ubbelohde viscometer using a mixture of equal weight of phenol and ethane tetrachloride in a solvent at a concentration of 0.5 g / dl and a temperature of 20 ° C.
(B) Carboxyl end group weight polyester is dissolved in benzyl alcohol and titrated with 0.1 N potassium hydroxide methanol solution.
(C) Carbodiimide compound content Filament was dissolved in an equal volume mixed solvent of hexafluoroisopropanol and trichloromethane, diluted with trichloromethane, acetonitrile was added to precipitate the polymer, and the filtered solution was subjected to liquid chromatography. Quantified by the method.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
[0011]
In the present invention, polyethylene terephthalate (PET) is preferred as the polyester, but it is mainly composed of PET, and is isophthalic acid, adipic acid, sebacic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1 , 4-butanediol, neopentyl glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and the like may be used in a small amount.
[0012]
In practicing the present invention, first, a prepolymer having a relative viscosity of 1.25 to 1.45 is obtained by an ordinary melt polymerization method. Next, the prepolymer pellets are heated in a solid phase under reduced pressure or in an inert gas flow to perform a solid phase polymerization reaction to obtain a polyester having a predetermined relative viscosity and a carboxyl end group amount. If the relative viscosity of the prepolymer is not appropriate, the total polymerization time will be remarkably increased, or the amount of carboxyl end groups of the polyester after solid-phase polymerization cannot be kept within a predetermined range. It is desirable that the relative viscosity be in the above range.
[0013]
The polyester after the solid-phase polymerization needs to have a relative viscosity of 1.43 or more (however, greater than the relative viscosity of the prepolymer). If this condition is not satisfied, the spinning property is deteriorated and the yarn performance is insufficient, and it is difficult to make the relative viscosity of the filament obtained by melt spinning 1.40 or more. When the relative viscosity of the filament is less than 1.40, resistance to deterioration due to wear is deteriorated and wear resistance is inferior, and cannot be put to practical use.
[0014]
In addition, it is preferable to select the conditions for the solid phase polymerization so that the relative viscosity is about 0.10 to 0.40 higher than that of the prepolymer by solid phase polymerization. This solid-state polymerization reduces the amount of carboxyl end groups of the polyester and removes impurities such as oligomers.
[0015]
The polyester after solid phase polymerization preferably has a carboxyl end group amount of 20.0 eq / t or less. If this condition is not satisfied, it is difficult to sufficiently reduce the amount of carboxyl end groups of the filament obtained by melt spinning. Temporarily, a large amount of a carbodiimide compound as an end group blocking agent that reduces the amount of carboxyl end groups is added. Thus, even if the amount of carboxyl end groups can be reduced, adding a large amount of the carbodiimide compound causes problems such as deterioration of the yarn forming property.
[0016]
The filament obtained by melt spinning must have a carboxyl end group content of 10.0 eq / t or less. When the amount of the carboxyl terminal group of the filament is larger than this, the yarn quality is significantly lowered by the long-term wet heat treatment, and the target wet heat resistance performance is not exhibited.
[0017]
In the present invention, when the polyester produced through such solid phase polymerization is melt-spun, a copolymer of ethylene and glycidyl methacrylate (referred to as EMG) or EMG and polyolefin, and a carbodiimide compound (referred to as CDI). Is blended.
[0018]
As the EMG, those obtained by copolymerizing 1 to 35 mol% of a glycidyl methacrylate component in the main chain of polyethylene are preferably used, but vinyl acetate, styrene, acrylate esters, etc. are used as long as the characteristics are not impaired. Copolymerized ones can also be used.
[0019]
Since EMG contains a glycidyl methacrylate component that reacts with the terminal group of the polyester, the EMG is excellent in compatibility with the polyester and contributes to the improvement of the moisture and heat resistance of the polyester without fibrillating the filament.
[0020]
If the content of the glycidyl methacrylate component in the EMG is too small, the compatibility with the polyester becomes insufficient. On the other hand, if the content is too large, the reaction with the polyester proceeds too much, resulting in a marked increase in melt viscosity and poor yarn production. To do.
[0021]
The amount of EMG added must be 0.1 to 20% by weight of the polyester composition. When this addition amount is less than 0.1% by weight, the heat-and-moisture resistance becomes insufficient.
[0022]
In addition, when polyolefin (homopolymer) is added together with EMG, the compatibility is improved by EMG, so that the fibrillation of the filament that occurs when only polyolefin is added is suppressed, and the yarn properties can be improved. Become. In addition, when only a relatively large amount of EMG is added, the melt viscosity increases and the operability during spinning may decrease, but when polyolefin is used in combination, the increase in melt viscosity is suppressed and the operability is improved.
[0023]
As the polyolefin, homopolymers such as polyethylene, polypropylene, polybutene and poly-4-methylpentene are used. Among these, polyethylene is particularly preferable, and polyethylene has particularly good compatibility with EMG containing a polyethylene component.
[0024]
When adding polyolefin, it is necessary to add 0.1 to 20% by weight. When this addition amount is less than 0.1% by weight, the effect of adding polyolefin is hardly reflected, and when it exceeds 20% by weight, the miscibility with polyester is lowered, resulting in a decrease in yarn physical properties.
[0025]
When EMG and polyolefin are added together, it is necessary to select the addition amount so that the ratio of the polyester is 75% by weight or more within the above range. When the proportion of the polyester is less than 75% by weight, it is difficult to obtain a filament having sufficient yarn physical properties.
[0026]
Specific examples of CDI include N, N′-bis (2,6-dimethylphenyl) carbodiimide, N, N′-bis (2,6-diethylphenyl) carbodiimide, N, N′-bis (2,6- And diisopropylphenyl) carbodiimide and N, N′-bis (2-isopropylphenyl) carbodiimide. Among these, N, N′-bis (2,6-diisopropylphenyl) carbodiimide is most preferable because it can be used at a heat resistance and industrial level.
[0027]
The amount of CDI added must be 0.3 to 2.0% by weight. If this condition is not satisfied, the target performance is not exhibited. That is, when the added amount is less than 0.3% by weight, the carboxyl end groups are not sufficiently blocked, and the heat-and-moisture resistance performance is not satisfied. When the added amount exceeds 2.0% by weight, the spinning property is deteriorated. The amount of CDI added should be such that the amount of carboxyl end groups in the filament obtained by melt spinning is 10.0 eq / t or less, and about 20 to 18000 ppm of active CDI remains. The active state means a state capable of reacting with a carboxy group or a water molecule, and if this content is less than 20 ppm, the effect of CDI is hardly expressed, and if it exceeds 18000 ppm, the amount of added CDI It is difficult because the upper limit is 2.0% by weight.
[0028]
Next, the manufacturing method of a filament is demonstrated.
Melt spinning can be carried out by a conventional method. However, in order to suppress phase separation of the polyester composition, it is preferable to carry out spinning by loading a stationary mixing element in a spinning line or a nozzle pack.
[0029]
The spinning temperature is 350 ° C. or lower, preferably 310 ° C. or lower. If the spinning temperature is too high, the polyester and additives undergo thermal decomposition, making smooth spinning difficult, and resulting filaments with poor physical properties. In addition, carboxyl end groups are generated along with the thermal decomposition reaction of the polyester, and a large amount of end group blocking agent is consumed during melt spinning, so that the desired performance cannot be exhibited. In melt spinning, it is necessary to adjust the spinning temperature and the residence time so that the relative viscosity of the filament obtained does not become less than 1.40.
[0030]
The spun filament is cooled in a liquid at 0-100 ° C, preferably 20-90 ° C or in air at 0-100 ° C, preferably 10-40 ° C. If the cooling temperature is too low, the temperature control and workability will be difficult, and if it is too high, the cooling will be insufficient, and the filament finally obtained will be inferior in yarn physical properties.
[0031]
Next, the cooled and solidified filament is drawn after being wound up or without being wound.
Stretching can be performed in a single stage or multiple stages including two or more stages, but is preferably performed in multiple stages. First, in the liquid at 65 to 95 ° C. or in the gas at 70 to 200 ° C. that does not cause the movement of the stretching point, the first stage stretching is performed 3.0 to 6.5 times, followed by 150 to 300 times higher than the first stage stretching. The second and subsequent stages are stretched so that the total stretching ratio is 5.0 to 8.0 times in a liquid or gas at ° C. At this time, the total draw ratio is set to be higher than the first stage draw ratio. If the stretching temperature is lower than the above range, heating is insufficient, and stretching spots and thread breakage occur. On the other hand, if the stretching temperature is too high, filament melting and thermal deterioration occur, which is not preferable. Further, when the total draw ratio is less than 5.0 times, the yarn quality, particularly the linear strength, of the obtained filament tends to be lowered. On the other hand, if the total draw ratio is larger than 8.0, the molecular orientation cannot cope with the plastic deformation in the fiber, so that microvoids are generated in the fiber and a filament having satisfactory performance cannot be obtained.
[0032]
Further, after stretching, it is preferable to perform relaxation heat treatment at a relaxation rate of 1.0 to 15.0% in a gas of 150 to 500 ° C. If the heat treatment temperature is lower than 150 ° C, the effect of heat treatment on the filament tends to be insufficient, and although it is related to the heat treatment time, if it is higher than 500 ° C, a thermal decomposition reaction of polyester occurs on the fiber surface, and a filament exhibiting the target performance is obtained. I can't. When the relaxation rate is less than 1.0%, the filament obtained has a high thermal shrinkage rate. In some cases, the filament is not suitable for practical use. When the relaxation rate exceeds 15.0%, slack in the yarn occurs at the relaxation heat treatment stage. The operability is poor and the target yarn quality performance is not exhibited.
[0033]
[Action]
In the present invention, polyester having a low carboxyl end group amount is used, and EMG or EMG and polyolefin and CDI are added to the polyester and melt-spun so that the filament has a low carboxyl end group amount and excellent moisture and heat resistance performance over a long period of time. Is obtained.
Because of the synergistic effect of EMG or EMG, polyolefin, and CDI, it exhibits excellent heat and moisture resistance and yarn properties, and EMG has a glycidyl group (and polyethylene component) that is chemically bonded to the end group of the polyester. (And polyolefin) have good compatibility, and the filament does not fibrillate.
[0034]
【Example】
Next, the present invention will be specifically described by way of examples.
The measurement and evaluation methods are as follows.
(a) High elongation
Measured according to JIS L 1013.
(b) The heat-resistant filament was evaluated by the strength retention rate against the untreated filament after being treated with saturated steam at 120 ° C. for 10 days.
(c) Applying a load of 0.2 g / d to the tip of the wear-resistant filament and reciprocating friction under the conditions of a stroke length of 70 mm and a speed of 40 times / minute while contacting a metal rod with a diameter of 0.8 mm at an angle of 90 degrees The state of the filament after 1000 reciprocating friction (the part in contact with the metal rod) was visually observed and evaluated in the following two stages.
○: No change is observed in the state of the filament.
X: Fibrilization or fluffing is observed in the filament.
[0035]
Example 1
A PET oligomer was melt polycondensed by a conventional method to prepare a prepolymer pellet having a relative viscosity of 1.34 and a carboxyl end group amount of 30.9 eq / t, and then a solid-phase polymerization reaction was performed to obtain a relative viscosity of 1.55 and a carboxyl end group amount of 15.8 eq / t. t solid phase polymerization pellets were obtained.
To this solid phase polymerization pellet, EMG: “LOTADER AX-8840” manufactured by ATOCHEM (with a glycidyl methacrylate component ratio of 8 mol%) 5.0% by weight and CDI: N, N′-bis (2,6-diisopropyl) 1.8% by weight of phenyl) carbodiimide was added and melt spun.
Melt spinning is performed using an extruder-type spinning device, using a spinning die having a spinning hole with a spinning diameter of 2.0 mm at a spinning temperature of 295 ° C., cooling the spun yarn in a 70 ° C. water bath, An undrawn yarn was obtained. The undrawn yarn was first-stage drawn in a 90 ° C. water bath at a draw ratio of 3.24, then in the hot air atmosphere at 250 ° C., the second-stage draw was carried out at a draw ratio of 1.67, and the total draw ratio was 5.40 times. did. Subsequently, relaxation heat treatment was performed at a relaxation rate of 10% in a hot air atmosphere at 400 ° C. to obtain a polyester monofilament.
[0036]
Example 2
A polyester monofilament was obtained in the same manner as in Example 1 except that the addition amounts of EMG and CDI were changed as shown in Table 1.
[0037]
Examples 3-5
Prepolymer pellets similar to those in Example 1 were subjected to solid phase polymerization to obtain solid phase polymerization pellets having a relative viscosity of 1.45 and a carboxyl end group amount of 17.5 eq / t.
After adding EMG and CDI in the amounts shown in Table 1 to this solid phase polymerization pellet and melt spinning under the same conditions as in Example 1, the first stage draw ratio was 3.32 times and the second stage draw ratio was 1.63 times. The polyester monofilament was obtained by stretching with a total stretching ratio of 5.40, followed by relaxation heat treatment.
[0038]
Comparative Examples 1-5
A polyester monofilament was obtained in the same manner as in Example 1 except that the addition amounts of EMG and CDI were changed as shown in Table 1.
[0039]
Comparative Example 6
A polyester monofilament was obtained in the same manner as in Example 3 except that the addition amounts of EMG and CDI were changed as shown in Table 1.
[0040]
Example 6
The amounts of EMG and CDI shown in Table 1 were added to the same solid phase polymerization pellets as in Example 1 and melt-spun.
Melt spinning is performed using an extruder-type spinning device, using a spinning die having 48 spinning holes with a spinning diameter of 295 ° C and a hole diameter of 0.4 mm, and the spinning yarn is cooled with air at 20 ° C. An undrawn yarn was obtained. This undrawn yarn is heated to 90 ° C, drawn at a draw ratio of 6.35 times between the first roller and the second roller heated to 230 ° C, and then heated to 170 ° C for relaxation heat treatment with a relaxation rate of 6%. To obtain a polyester multifilament.
[0041]
Comparative Example 7
A polyester multifilament was obtained in the same manner as in Example 6 except that CDI was not added.
[0042]
Table 1 shows the yarn quality and the like of the filaments obtained in the above examples and comparative examples. In the table, COOH represents the amount of carboxyl end groups, and the CDI content of the filament represents the amount of CDI present in the active state.
[0043]
[Table 1]

[0044]
Example 7
To the same solid phase polymerization pellet as in Example 1, 5.0% by weight of EMG, 3.0% by weight of polyethylene (PE) as in Example 1, and 1.8% by weight of CDI as in Example 1 were added and melted in the same manner as in Example 1. A polyester monofilament was obtained by spinning, stretching and heat treatment.
[0045]
Example 8
A polyester monofilament was obtained in the same manner as in Example 7 except that the addition amounts of EMG, PE and CDI were changed as shown in Table 2.
[0046]
Examples 9-11
To the same solid phase polymerization pellets as in Example 3, the amounts of EMG, PE and CDI shown in Table 2 were added, and melt spinning, stretching and heat treatment were performed under the same conditions as in Example 1 to obtain a polyester monofilament.
[0047]
Comparative Examples 8-13
A polyester monofilament was obtained in the same manner as in Example 7 except that the addition amounts of EMG, PE and CDI were changed as shown in Table 2.
[0048]
Comparative Example 14
A polyester monofilament was obtained in the same manner as in Example 9 except that the addition amounts of EMG, PE and CDI were changed as shown in Table 2.
[0049]
Example 12
EMG, PE and CDI in the amounts shown in Table 2 were added to the same solid phase polymerization pellets as in Example 6, and melt spinning, stretching and heat treatment were performed in the same manner as in Example 6 to obtain polyester multi-multifilaments.
[0050]
Comparative Example 15
A polyester multifilament was obtained in the same manner as in Example 12 except that CDI was not added.
[0051]
Table 2 shows the yarn quality and the like of the filaments obtained in the above Examples and Comparative Examples.
[0052]
[Table 2]

[0053]
【The invention's effect】
According to the present invention, there is provided a polyester filament that does not fibrillate, has good yarn properties, and retains excellent wet heat resistance over a long period of time.
The polyester filament of the present invention is suitable for industrial materials such as filaments for industrial materials, especially industrial textiles such as paper canvas, belt cloth, and filters.

Claims (9)

It is obtained by melt spinning and stretching a composition prepared by blending 0.1 to 20% by weight of a copolymer of ethylene and glycidyl methacrylate and 0.3 to 2.0% by weight of a carbodiimide compound to a polyester produced through a solid phase polymerization reaction. A polyester filament characterized by having a relative viscosity of 1.40 or more and a carboxyl end group content of 10.0 eq / t or less. The polyester filament according to claim 1, wherein the filament contains 20 to 18000 ppm of an active carbodiimide compound. The polyester filament according to claim 1 or 2, wherein the carbodiimide compound is N, N'-bis (2,6-diisopropylphenyl) carbodiimide. The method for producing a polyester filament according to claim 1, 2 or 3, wherein the following steps are sequentially performed.
(A) A step of producing a prepolymer having a relative viscosity of 1.25 to 1.45 by a melt polymerization method, and then producing a polyester having a relative viscosity of 1.43 or more (but greater than the relative viscosity of the prepolymer) by solid-phase polymerization. ,
(B) A composition in which 0.1 to 20% by weight of a copolymer of ethylene and glycidyl methacrylate and 0.3 to 2.0% by weight of a carbodiimide compound is blended with polyester and melt-spun, has a relative viscosity of 1.40 or more, Obtaining a filament having a terminal group amount of 10.0 eq / t or less,
(C) A step of drawing a filament. A composition comprising 75% by weight or more of a polyester produced through a solid phase polymerization reaction, 0.1 to 20% by weight of a copolymer of ethylene and glycidyl methacrylate, 0.1 to 20% by weight of a polyolefin, and 0.3 to 2.0% by weight of a carbodiimide compound. A polyester filament obtained by melt spinning and drawing, having a relative viscosity of 1.40 or more and a carboxyl end group amount of 10.0 eq / t or less. The polyester filament according to claim 5, wherein the filament contains 20 to 18000 ppm of a carbodiimide compound in an active state. The polyester filament according to claim 5 or 6, wherein the carbodiimide compound is N, N'-bis (2,6-diisopropylphenyl) carbodiimide. The polyester filament according to claim 5, 6 or 7, wherein the polyolefin is polyethylene. The method for producing a polyester filament according to claim 5, 6, 7, or 8, wherein the following steps are sequentially performed.
(a) A step of producing a prepolymer having a relative viscosity of 1.25 to 1.45 by a melt polymerization method, and then producing a polyester having a relative viscosity of 1.43 or more (but greater than the relative viscosity of the prepolymer) by solid-phase polymerization. ,
(b) A composition comprising 75% by weight or more of polyester, 0.1 to 20% by weight of a copolymer of ethylene and glycidyl methacrylate, 0.1 to 20% by weight of polyolefin and 0.3 to 2.0% by weight of a carbodiimide compound was prepared and melt-spun. A step of obtaining a filament having a relative viscosity of 1.40 or more and a carboxyl end group amount of 10.0 eq / t or less,
(c) A step of drawing the filament.