JP2003253100A - Polyester composition and fiber made therefrom - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polyester composition showing both high water absorption and thermal stability, and to provide a fiber made therefrom. <P>SOLUTION: The polyester composition is obtained by copolymerizing a special metal organic sulfate and a polyalkylene glycol on a polyester having an alkylene terephthalate as a major repeating unit and compounding the obtained product and a metal organic carboxylate. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester composition having both high water absorption and thermal stability, and a fiber comprising the same.

[0002]

2. Description of the Related Art Polyesters, especially polyethylene terephthalate, are widely used for various clothing applications because they have many excellent properties. However, compared to natural fibers such as cotton, silk and wool, and semi-synthetic fibers such as rayon and acetate, they have a drawback in that they have low water absorption and sweat absorption. In order to improve this task,
A water-absorbent polyester fiber having fine pores on the fiber surface, which are partially communicated to the hollow part, is proposed by treating hollow fiber made of polyester to which an organic sulfonic acid metal salt is added with an alkaline aqueous solution (Japanese Patent Publication No. 61- 60188
Japanese Patent Publication No. 62-44065).

However, the hollow polyester fiber having a microporous surface has a water absorption mechanism utilizing the capillary phenomenon, and therefore has a lower water absorption than natural fibers and semi-synthetic fibers, and is not necessarily at a satisfactory level. Had not arrived.

On the other hand, there has been proposed a polyester fiber (Japanese Patent Laid-Open No. 7-150468) having improved water absorption performance by copolymerizing a hydrophilic component such as a metal salt of organic sulfonic acid or polyalkylene glycol with polyester. In this method, the water absorption performance was significantly improved, but the organic sulfonic acid metal salt and the copolyester of polyalkylene glycol had a problem of low thermal stability.

[0005]

An object of the present invention is to provide a polyester composition having both high water absorption and thermal stability.

[0006]

The inventors of the present invention have completed the present invention as a result of intensive studies in view of the above-mentioned prior art.

That is, an object of the present invention is to use alkylene terephthalate as a main repeating unit, and to use the following formula (I)
And an organic sulfonic acid metal salt (A) represented by the following formula (I
A polyester composition obtained by blending a polyester copolymerized with the polyalkylene glycol (B) represented by I) with an organic carboxylic acid metal salt (C) represented by the following formula (III). it can.

[0008]

[Chemical 4]

[0009]

[Chemical 5]

[0010]

[Chemical 6]

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

In the present invention, the polyester in which the component (A) and the component (B) described later are copolymerized is a polyester having an alkylene terephthalate unit as a main repeating unit. The term "main" as used herein means copolymerization of repeating units other than alkylene terephthalate units in an amount of 20 mol% or less, preferably 15 mol% or less, and particularly preferably 10 mol% or less, based on all repeating units constituting the polyester. It means that the component may be contained. The glycol component of the alkylene terephthalate unit is preferably an alkylene glycol having 2 to 4 carbon atoms, and examples thereof include ethylene glycol, trimethylene glycol and tetramethylene glycol.

Examples of difunctional carboxylic acid components other than terephthalic acid that can be copolymerized include isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid, β-hydroxyethoxybenzoic acid and P-oxybenzoic acid. , Adipic acid, sebacic acid,
Aromatic such as 1,4-cyclohexanedicarboxylic acid,
Examples thereof include alicyclic and aliphatic bifunctional carboxylic acids.

As the diol component other than the alkylene glycol which can be copolymerized, for example, cyclohexane-1,4-dimethanol, neopentyl glycol, bisphenol A, bisphenol S, such as aliphatic, alicyclic and aromatic compounds. The diol compound can be mentioned.

Further, within the range where the achievement of the object of the present invention is not substantially impaired, trifunctional or higher polycarboxylic acid such as trimellitic acid and pyromellitic acid, glycerin, trimethylolpropane, penta A trifunctional or higher functional polyol such as erythritol may be used as a copolymerization component.

The component (A) to be copolymerized with the polyester is the organic sulfonic acid metal salt represented by the above formula (I), wherein R ¹ is an aromatic hydrocarbon group or an aliphatic hydrocarbon group, X ¹ is an ester-forming functional group, X ² is an ester-forming functional group or a hydrogen atom. The ester-forming functional group as referred to herein is a functional group capable of reacting and being bonded to the polyester via an ester bond, and is generally a hydroxyl group, a carboxyl group, or an ester thereof. M is an alkali metal such as Na, K, Li or M
Alkaline earth metals such as g and Ca, N among them
Preferred are a and K. Such an organic sulfonic acid metal salt can be used alone or as a mixture of two or more kinds, and preferable specific examples thereof include dimethyl 5-naphthylsulfoisophthalate, dimethyl 5-potassium sulfoisophthalate,
Dimethyl 5-lithium sulfoisophthalate, bis (β-hydroxyethyl) 5-sodium sulfoisophthalate
Ester, 5-potassium sulfoisophthalic acid bis (β-
Examples thereof include hydroxyethyl) ester and 5-lithium sulfoisophthalic acid bis (β-hydroxyethyl) ester.

The amount of the organic sulfonic acid metal salt copolymerized with the polyester is preferably 0.1 to 15 mol%, particularly 0.1 to 10 mol% based on the total dicarboxylic acid components constituting the polyester. Is preferred.

Next, the polyalkylene glycol as the component (B) represented by the above formula (II) is copolymerized for the purpose of improving the water absorption performance of the polyester, but based on the total dicarboxylic acid component constituting the polyester. 0.1 to 20% by weight, and particularly preferably 0.2 to 15% by weight.

Examples of such polyalkylene glycols include triethylene glycol, tetraethylene glycol, tripropylene glycol, polyethylene glycol (molecular weights of 1,000, 2000, 4000, 8000,
20,000, 50,000) and the like,
Polyethylene glycol having a molecular weight of 1000 to 8000 is particularly preferable.

Next, as the organic carboxylic acid metal salt as the component (C) represented by the formula (III) to be blended in the copolymerized polyester, sodium benzoate, potassium benzoate, magnesium benzoate, benzoate Lithium acid, zinc benzoate, sodium toluate, potassium toluate, lithium toluate and the like can be mentioned. Of these, sodium benzoate, potassium benzoate, and magnesium benzoate are particularly preferable, and the organic carboxylic acid metal salts may be used either individually or in combination of two or more. The amount of the organic carboxylic acid metal salt is preferably 0.01 to 5% by weight, more preferably 0.05 to 3% by weight, in the polyester composition.

If the amount is too small, the effect of promoting the crystallinity of the polyester composition and the effect of improving the water absorption performance are not exhibited. on the other hand,
Excessive compounding causes problems such as an increase in pack pressure and a decrease in polymer strength during spinning.

The intrinsic viscosity of the polyester composition of the present invention is usually in the range of 0.3 to 1.0, particularly 0.4 to 0.7.
Is preferred. When the intrinsic viscosity is less than 0.3,
The physical properties such as impact strength and stretch moldability tend to deteriorate, while the intrinsic viscosity is 1.0.
If it exceeds, the productivity tends to deteriorate and the formability such as stretching tends to decrease.

In the polyester composition of the present invention, the melt viscosity at 250 ° C. and a shear rate of 1000 sec ⁻¹ is adjusted by appropriately changing the above-mentioned three component ratios within the scope of the present invention and adjusting the intrinsic viscosity. 100 to 50
It is preferable to set 0 Pa · S. Within the above range, the spinnability at the time of melt spinning the composition and the continuous spinning stability can be compatible at a high level.

Next, a method for producing the polyester composition of the present invention will be described below by taking a polyester having an ethylene terephthalate unit as a main repeating unit as an example. First, dimethyl terephthalate and ethylene glycol are subjected to a transesterification reaction in the presence of a transesterification catalyst, a direct esterification reaction of terephthalic acid and ethylene glycol, or a reaction of terephthalic acid and ethylene oxide. , Bis (β-hydroxyethyl) terephthalate and / or an oligomer thereof are formed, and then melt polycondensation is performed under high temperature and reduced pressure in the presence of a polycondensation catalyst and a stabilizer to obtain polyethylene terephthalate. The following (I), (II) and (II
It is achieved by adding the component I) into the reaction system at any stage before the completion of the polyester synthesis. Preferably, the components (I) and (II) are bis (β-hydroxyethyl) terephthalate and / or oligomers thereof.
Prior to the formation of component (III), component (III) is preferably added during the polycondensation reaction.

[0025]

[Chemical 7]

[0026]

[Chemical 8]

[0027]

[Chemical 9]

Any catalyst may be used in these reactions, if necessary. Among them, the catalyst used in the transesterification reaction is an alkaline earth metal salt such as magnesium or calcium, titanium or zinc. , A metal compound such as manganese is preferably used, and a germanium compound, an antimony compound, a titanium compound, a cobalt compound, or a tin compound is preferably used as the polycondensation catalyst.

The amount of the catalyst used is not particularly limited as long as it is an amount necessary for proceeding the transesterification reaction and the polycondensation reaction, and a plurality of catalysts can be used in combination.

As the stabilizer, phosphoric acid esters such as trimethyl phosphate, triethyl phosphate and triphenyl phosphate, phosphorous acid esters such as triphenyl phosphite and trisdodecyl phosphate, methyl acid phosphate, dibutyl phosphate, It is preferable to use phosphorus compounds such as monobutyl phosphate acidic phosphoric acid ester, phosphoric acid, phosphorous acid, hypophosphorous acid and polyphosphoric acid.

The transesterification reaction catalyst can be supplied at the initial stage of the transesterification reaction in addition to the preparation of the raw materials. The stabilizer can be supplied before the initial polycondensation reaction, but it is preferable to add it at the end of the transesterification reaction. Further, the polycondensation catalyst can be supplied by the beginning of the polycondensation reaction step.

The reaction temperature during the transesterification reaction is usually 2
The reaction pressure is from 0 to 260 MPa, and the reaction pressure is from atmospheric pressure to 0.3 MPa.
Is. The reaction temperature during polycondensation is usually 250 to 3
It is 00 ° C., and the reaction pressure is usually 60 to 0.1 kpa. Such transesterification reaction and polycondensation reaction may be carried out in one step or in a plurality of steps.

The obtained polyester composition is made into chips by a conventional method. The average particle size of the chips is usually 2.0 to
It is set to 5.5 mm, preferably 2.2 to 4.0 mm.

The polyester composition of the present invention can be stably molded under a wide range of molding conditions, and a usual melt spinning method can be applied. The cross-sectional shape of the fiber is not limited to the round cross-section, and may be a modified cross-section such as a flat shape, a triangular cross section and a multi-lobed cross section.
There is no problem even if the hollow portion is provided. The temperature during melt spinning of the polyester composition of the present invention is 200 to 270.
C., preferably 220 to 250.degree. C. is suitable. Here, if the temperature is lower than 200 ° C, the temperature is too low and a stable molten state is hardly obtained. If the temperature is higher than 270 ° C, the polyester composition is thermally decomposed and the spun yarn is insufficiently cooled. Problems such as fusion occur. Next, the spun yarn may be taken up at a predetermined speed and then wound up once, and the resulting undrawn yarn may be drawn by a separate drawing machine. Alternatively, a direct spinning and drawing method may be applied in which the film is drawn and wound. As the direct spinning and drawing method, for example, spun yarn is 1000
~ 4000m / min pick up, then 1500 ~
Examples include a method of stretching and heat setting at a speed of 5000 m / min. Here, the heat set roller temperature is 130
The temperature is preferably 170 ° C to 170 ° C, and when it is in this range, the heat setting property is sufficient and the fiber is not melt-cut.
Further, it is possible to employ spinning conditions such as spinning at a high speed of 5000 m / min or more and omitting the drawing step depending on the application. Stable spinning can be performed by either method. The fiber obtained according to the method has a water absorption of 30 to 500% and a moisture absorption of 12 to 50% after being kept in a 35 ° C. 95% RH environment for 24 hours.

The yarn form of the fiber of the present invention thus obtained may be either filament or staple, and the total yarn fineness, the single yarn fineness, the number of twists, the number of entanglements, etc., depend on the purpose of use of the fiber. It can be set appropriately.

Further, in forming the fiber of the present invention into a cloth, the fiber of the present invention may be used 100% or may be used in combination with other fibers. Here, when used as a composite yarn when used in combination with other fibers, a mixed yarn or a composite false twisted yarn may be used. Examples of such fibers that can be used in combination include polyethylene terephthalate, polytrimethylene terephthalate, and polybutylene terephthalate. Polyesters such as nylon 6, polyamides such as nylon 6, nylon 66, polyolefins such as polyethylene and polypropylene, acrylics, para-type or meta-type aramids, and modified and / or composite fibers thereof, as well as natural fibers, regenerated fibers, semi-synthetic It can be freely selected and used from fibers and the like.

The polyester composition of the present invention may be formed into a film or sheet, and a method of imparting anisotropy by applying tension only in one direction after film formation, simultaneously or in any order in two directions. The desired conditions can be adopted without any problem in the method of stretching, the method of stretching in two or more stages.

[0038]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. The properties in the examples were measured by the following methods.

(1) Intrinsic viscosity (hereinafter abbreviated as IV): A certain amount of polymer was weighed and dissolved in o-chlorophenol at 35 ° C. to a concentration of 0.012 g / ml, and then
Obtained according to the usual method.

(2) Col-b: 160 ° C., 60 minutes,
The polymer subjected to dry heat treatment in a dryer was determined using a CR-200 type color difference meter manufactured by Minolta Co., Ltd.

(3) Terminal carboxyl group concentration: Makr
omol. chem. , 26, 226 (1958).

(4) Diethylene glycol (hereinafter referred to as DE
(Abbreviated as G) Content: The sample was decomposed with hydrazine and determined by gas chromatography.

(5) Tensile elongation and tensile strength: JIS L1
It was determined according to the method described in 070.

(6) Thermal stability (dry heat shrinkage): A sample knitted yarn was formed into a tubular knit and then dried by heating at 120 ° C. for 10 minutes to obtain the shrinkage of the tubular knitted fabric to determine the thermal stability. Was used as an index.

(7) Water absorption rate: A sample knitted yarn was formed into a tubular knit, and then scoured and preset according to a conventional method,
A weight reduction treatment was carried out at 120 ° C. using a sodium hydroxide aqueous solution. The tubular knitted fabric obtained in this way was heated to 105 ° C.
After being dried for 2 hours, the water absorption performance was evaluated by the water absorption method.

(8) Water absorption rate: 105 ° C. for the sample knitted fabric
After being dried for 2 hours in water, it was immersed in water for 1 hour and dehydrated for 5 minutes with a dehydrator of a domestic electric washing machine. The weight was determined according to the following formula from the weights of the dried tubular knitted fabric and the dehydrated tubular knitted fabric.

[0047]

[Equation 1] Water absorption rate (%) = (weight of tubular knitted fabric after dehydration-weight of tubular knitted fabric after drying) / weight of tubular knitted fabric after drying

(9) Moisture absorption rate: Sample tubular knitted fabric at 105 ° C.
After being dried for 2 hours at 35 ° C., it was left for 24 hours in a desiccator kept at 35 ° C. and 95% RH. The weight was determined according to the following formula from the weight of the tubular knitted fabric before and after standing.

[0049]

[Formula 2] Moisture absorption rate (%) = (weight of tubular knitted fabric after leaving-weight of tubular knitted fabric before leaving) / weight of tubular knitted fabric before leaving

(10) Melt viscosity: constant load extruded capillary rheometer flow tester (CFT-500D manufactured by Shimadzu Corporation, die diameter 0.5 mm, die length 1 mm) was used and tested at a temperature of 250 ° C. Pressure 0.98M
The melt viscosity was measured at Pa, 1.96 MPa, 2.94 MPa, and the melt viscosity was plotted against the shear rate. From this plot, an approximate expression of the melt viscosity with respect to the shear rate was calculated, and the melt viscosity at a shear rate of 1000 sec ⁻¹ was calculated from the approximate expression.

[Example 1] Dimethyl terephthalate 100
Parts by weight, ethylene glycol 64 parts by weight, 5-sodium sulfoisophthalic acid 10 parts by weight (component (A)) and polyethylene glycol (molecular weight: 4000) 5 parts by weight (component (B)) as a transesterification reaction catalyst. Using manganese acetate tetrahydrate, a transesterification reaction is carried out while distilling off by-produced methanol out of the system.

Furthermore, after adding germanium dioxide as a polymerization catalyst, an ester exchange reaction is carried out while heating up to 285 ° C., and when the distillation of methanol is almost completed, orthophosphoric acid as a stabilizer and crystallization acceleration. 1% by weight of sodium benzoate (component (C)) was added as an agent,
The transesterification reaction was completed.

Then, the reaction product was subjected to polycondensation reaction under high temperature and high vacuum to give an intrinsic viscosity of 0.40 and a Col-b value of 17.
8, terminal carboxyl group concentration 38eq / ton, DEG
A modified polyethylene terephthalate composition having 3.2 wt% and a melt viscosity of 140 Pa · S was obtained.

The obtained polyethylene terephthalate was dried in a dryer at 160 ° C. for 5 hours, and then, in a melt spinning device equipped with a 24-hole die, a polymer temperature of 280
Melt spinning was carried out at a discharge rate of 400 m / min at ℃, followed by 110 ℃ with a heating roller and 16 with a plate heater.
It was preheated to 0 ° C. and drawn with a small drawing machine at a draw ratio of 3.4 to obtain a drawn yarn of 93 dtex / 24 filament.

When the obtained drawn yarn was formed into a tubular knitted fabric, the dry heat shrinkage ratio at 120 ° C. was 20%, and the thermal stability was good. Further, the water absorption rate of the tubular knitted fabric of the drawn yarn is 28 mm / 10 minutes, the moisture absorption rate is 1.7%, and the water absorption rate is 0.
It was 6%, and the water absorption and hygroscopicity were good.

Example 2 In Example 1, the addition amount of 5-sodium sulfoisophthalic acid was changed from 10 parts by weight to 5 parts by weight.
The same operation was carried out except that the amount was changed to parts by weight. Intrinsic viscosity 0.54, Col-b value 16.9, terminal carboxyl group concentration 29 eq / ton, DEG 2.7 wt.
%, A modified polyethylene terephthalate composition having a melt viscosity of 135 Pa · S was obtained.

When the drawn yarn obtained by spinning and drawing was tubular knitted in the same manner as in Example 1, the dry heat shrinkage was 23% and the thermal stability was good. The water absorption rate is 75 mm / 1
At 0 minutes, the water absorption rate was 0.5%, the moisture absorption rate was 1.5%, and the water absorption and hygroscopicity were good.

Comparative Example 1 The same operation as in Example 1 was carried out except that polyethylene glycol was not added. Intrinsic viscosity was 0.33 and Col-b value was 1.
7.7, terminal carboxyl group concentration 39 eq / ton, D
A modified ethylene terephthalate composition having an EG of 3.2 wt% and a melt viscosity of 155 Pa · S was obtained.

When the drawn yarn obtained by spinning and drawing was tubular knitted in the same manner as in Example 1, the dry heat shrinkage at 120 ° C. was 45% and the thermal stability was insufficient. The water absorption rate of the tubular knitted fabric is 17 mm / 10 minutes, and the water absorption rate is 0.6.
%, The moisture absorption rate was 1.7%, which was not always sufficient.

[Comparative Example 2] In the same manner as in Example 2, except that polyethylene glycol and sodium benzoate were not added, an intrinsic viscosity of 0.4 was obtained.
3, Col-b value 5.0, terminal carboxyl group concentration 37
eq / ton, DEG4.0wt%, melt viscosity 150P
A modified ethylene terephthalate of a · S was obtained.

When the drawn yarn obtained by spinning and drawing was knitted in the same manner as in Example 1, the dry heat shrinkage at 120 ° C. was 78% and the thermal stability was insufficient. Also,
The water absorption rate of the tubular knitted fabric was 15 mm / 10 minutes, the water absorption rate was 0.4%, and the moisture absorption rate was 1.5%, which were not always sufficient.

Example 3 90 parts by weight of dimethyl terephthalate, 68 parts by weight of tetramethylene glycol, 20 parts by weight of ethylene glycol, 16 parts by weight of 5-sodium sulfoisophthalic acid (component (A)) and polyethylene glycol (molecular weight). : 4000) 120 parts by weight (component (B))
Using the manganese acetate tetrahydrate as a transesterification reaction catalyst, the transesterification reaction is carried out while distilling off by-produced methanol out of the system.

Further, after adding germanium dioxide as a polymerization catalyst, an ester exchange reaction was carried out while heating up to 285 ° C., and when the distillation of methanol was almost completed, orthophosphoric acid as a stabilizer and crystallization acceleration. 1% by weight of sodium benzoate (component (C)) was added as an agent,
The transesterification reaction was completed.

Then, the reaction product is subjected to polycondensation reaction under high temperature and high vacuum to give an intrinsic viscosity of 0.82 and a Col-b value of 4.
A modified polyethylene terephthalate composition having a terminal carboxyl group concentration of 45 eq / ton and a melt viscosity of 180 Pa · S was obtained.

The modified polyethylene terephthalate thus obtained was dried in a dryer at 160 ° C. for 5 hours, and then a spinning temperature of 230 was set in a melt spinning apparatus equipped with a 24-hole die.
After melt spinning at a temperature of 3,000 ° C. and a spinning speed of 3000 m / min,
It was cooled and solidified, oiled, and taken through a take-up roller to stably obtain fibers of 135 dtex / 36 filaments. The water absorption speed of the obtained tubular knitted fabric is 75 m.
m / 10 minutes, water absorption is 68%, moisture absorption is 14%,
The water absorption and hygroscopicity were good.

Example 4 In Example 3, the amount of 5-naphthylsulfoisophthalic acid was changed from 16 parts by weight to 7 parts.
A similar operation was carried out except that the amount was changed to parts by weight. As a result, modified polyethylene terephthalate having an intrinsic viscosity of 0.76, a Col-b value of 5.5, a terminal carboxyl group concentration of 35 eq / ton, and a melt viscosity of 140 Pa · S. A composition was obtained. Also,
The water absorption rate of the tubular knitted fabric is 70 mm / 10 minutes, and the water absorption rate is 59
%, The moisture absorption rate was 12%, and the water absorption and hygroscopicity were good.

[0067]

According to the present invention, it is possible to provide a polyester composition having both high water absorption and thermal stability, and further by melt spinning the composition, high water absorption and hygroscopicity can be obtained. Fibers having and can be provided.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Ryoji Tsukamoto             77, Kitayoshida-cho, Matsuyama-shi, Ehime Teijin Stock Association             Company Matsuyama Office (72) Inventor Shoji Makino             77, Kitayoshida-cho, Matsuyama-shi, Ehime Teijin Stock Association             Company Matsuyama Office F term (reference) 4J002 CF141 EG076 EW047 FD137                       GK01                 4J029 AA01 AB01 AB07 AC02 AE02                       BA03 BA05 BA08 BF17 BF25                       CB05 CB06 CH06 DB02 HA01                       HA02 HB02 JB17 JC54 JF02                       JF03 JF04 JF13 JF14 KE02                 4L035 BB77 BB89 BB91 EE02 EE05                       GG03 JJ15

Claims (6)

[Claims] 1. An organic sulfonic acid metal salt (A) represented by the following formula (I) and a polyalkylene glycol (B) represented by the following formula (II) are copolymerized with alkylene terephthalate as a main repeating unit. On polyester,
A polyester composition containing an organic carboxylic acid metal salt (C) represented by the following formula (III). [Chemical 1] [Chemical 2] [Chemical 3] 2. The polyester composition according to claim 1, wherein the copolymerization amount of the organic sulfonic acid metal salt is 0.1 to 15.0 mol% based on the total dicarboxylic acid components constituting the polyester. 3. The polyester composition according to claim 1, wherein the copolymerization amount of the polyalkylene glycol is 0.1 to 20% by weight based on the total dicarboxylic acid components constituting the polyester. 4. The compounding amount of the organic carboxylic acid metal salt is based on the total dicarboxylic acid component constituting the polyester.
The polyester composition according to claim 1, which is 0.01 to 5% by weight. 5. The polyester composition according to claim 1, which has a melt viscosity of 100 to 500 Pa · S at 250 ° C. and a shear rate of 1000 sec ⁻¹ . 6. A water absorption of 30 to 5, which is obtained by melt spinning the polyester composition according to claim 1.
A fiber having a moisture absorption rate of 12 to 50% after being kept in an environment of 00% and 35 ° C. and 95% RH for 24 hours.