JP2001172374A - Copolyester excellent in moisture absorption - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a copolyester having high moisture absorption properties and to obtain a material which comprises fibers containing the copolyester as the constituting component and is useful as woven and knitted fabrics, or the like, for underwear, sport wear, lining, and the like. SOLUTION: This copolyester is prepared by copolymerizing a hydrophilic compound, contains a polar group-containing compound and/or a crosslinking agent, and is excellent in moisture absorption.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copolyester having excellent hygroscopicity. The thermoplastic synthetic fiber obtained from the copolymerized polyester has excellent hygroscopicity, and can be particularly suitably used as a material for clothing such as innerwear, middle garment, and sports clothing.

[0002]

2. Description of the Related Art Thermoplastic synthetic fibers typified by polyester and polyamide are excellent in mechanical strength, chemical resistance, heat resistance and the like, and are therefore widely used mainly for apparel use and industrial use.

However, since these synthetic fibers have extremely low hygroscopicity, they are used in fields such as innerwear, inner garments, sports clothing, etc., which are directly in contact with the skin or worn near the skin side. In such a case, sweating from the skin causes stuffiness and stickiness, which is inferior to natural fibers in terms of comfort, and the actual use of clothing is limited. In order to solve this drawback, for example, as described in JP-B-60-475, JP-B-60-40612, or JP-A-60-215835, the equilibrium moisture content (moisture absorption) is high. Attempts have been made to obtain moisture-absorbing comfort as a fabric by blending, twisting, or drawing fibers and synthetic fibers. Although the comfort is certainly improved by using these methods, the effect is not sufficient, and contamination is caused by disperse dyes generally used when dyeing synthetic fibers, or poor homochromaticity. And the physical properties inherent in synthetic fibers are lost.

[0004] Also, a method is known in which acrylic acid or methacrylic acid is graft-polymerized on polyester fibers, and further, after the graft polymerization, their carboxyl groups are replaced with alkali metals to impart hygroscopicity.
That the polyester is difficult to graft polymerize,
It has not yet been put to practical use because it has potential deterioration in color fastness, light fastness, fiber physical properties, texture, and the like.

Japanese Patent Laid-Open Publication No. Sho 51-136924 proposes a core-sheath composite staple comprising a hydrophilic polyester as a core component and a non-hydrophilic polyester as a sheath component. As the hydrophilic polyester, a polyalkylene glycol copolymer alone or a mixture of a small amount of a polyalkylene glycol copolymer and a small amount of a sulfonic acid or acidic phosphate derivative is used.As a staple, both ends of the fiber are increased to absorb water. It is a proposal to improve the performance. However, in the study of the present inventors, although the staple can improve the water absorption,
It was found that it was difficult to improve the hygroscopicity.

Japanese Unexamined Patent Publication (Kokai) No. 53-111116 proposes a core-sheath type antistatic composite fiber containing a specific polyetherester as a core component. However, the effect of the fiber is antistatic, and there is a problem that the fiber physical properties (strong elongation characteristics) change with time because a polyester obtained by homopolymerizing a polyalkylene glycol is used as a core component. Further, there is a problem that the coloring of the polyetherester is intense and the quality of the obtained final product is impaired.

Japanese Patent Application Laid-Open No. 62-267352 discloses a polyester composition containing 50 to 70% by weight of a specific polyalkylene glycol. Fibers comprising this composition have low fiber properties (high elongation),
In addition, it is inferior in water resistance and color fastness, so that it is difficult to use it for clothing and industrial purposes.

Further, JP-A-6-123011 discloses a hygroscopic polyester fiber. This is a method in which a block polyether ester is blended with a polyester obtained by copolymerizing an alkylene sulfoisophthalate and a polyoxyalkylene glycol to form a fiber, but the copolymerization amount of the polyalkylene glycol in the fiber is small and sufficient moisture absorption is obtained. Not only is it difficult to obtain a fiber, but also there is a problem that the fiber properties change with time.

Further, JP-A-53-99296, JP-A-58-138753 and JP-A-6-1361.
No. 07 discloses a polyetherester using a bisphenol A-EO adduct. However, the hygroscopic properties of these copolymers are low, and synthetic fibers using these polymers easily change in physical properties over time, for example, decrease in elongation. I have not been able to.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to overcome the above-mentioned problems of the prior art and to obtain a copolymer polyester having a high moisture absorption rate. It is to provide a synthetic fiber of the nature.

[0011]

SUMMARY OF THE INVENTION The object of the present invention is to provide a hydrophilic compound (A) of 50 to 50 wt.
95% by weight of a copolymerized polyester, containing a polar group-containing compound (B) and / or a crosslinking agent (C),
It can be achieved by a copolymer polyester excellent in moisture absorption having a moisture absorption / desorption parameter (ΔMR) of 12.0% or more.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Copolyester is a component for imparting hygroscopicity to fibers, which is the object of the present invention, and it is essential that the polyester has higher hygroscopicity than the base fiber-forming polymer.

Examples of the acid component of the copolymerized polyester include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and naphthalene-2,6-dicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid. Particularly preferred is terephthalic acid. Examples of the glycol component include ethylene glycol, propylene glycol, tetramethylene glycol, diethylene glycol, neopentyl glycol and the like. Particularly preferred is ethylene glycol.

In order to impart hygroscopicity to the copolymerized polyester, it is essential to copolymerize the hydrophilic compound (A), and the polar group-containing compound (B) and / or the cross-linking agent (C) reduce the hygroscopicity. It is necessary to include it as an auxiliary component for further improving and as a component for stabilizing fiber properties.

The copolymerization amount of the hydrophilic compound (A) in the copolymerized polyester is from 50 to 95 from the viewpoint of hygroscopicity.
% By weight is required. Particularly preferably 55 to 90% by weight
It is.

The moisture absorption / desorption parameter (hereinafter referred to as ΔMR) indicating the moisture absorption properties of the copolymerized polyester is preferably as high as possible to increase the hygroscopicity of the synthetic fiber using the same, but 12.0% It is necessary to be above.
Preferably 15.0% or more, particularly preferably 18.0%
That is all.

Here, ΔMR is the difference between the moisture absorption rate (MR2) at 30 ° C. × 90% RH and the moisture absorption rate (MR1) at 20 ° C. × 65% RH (ΔMR (%) = MR2−
MR1).

Here, ΔMR is a driving force for obtaining comfort by releasing the moisture in the clothes when the clothes are worn to the outside air, and is a driving force of 30% when light to medium work or light to medium exercise is performed. This is the difference in moisture absorption between the temperature inside the clothes represented by ° C × 90% RH and the outside temperature and humidity represented by 20 ° C. × 65% RH. In the present invention, this ΔMR is used as a parameter as a scale for evaluating hygroscopicity. The larger the ΔMR, the higher the moisture absorption / desorption ability and the better the comfort when worn.

Further, the molecular weight of the hydrophilic compound (A) is preferably from 600 to 20,000, more preferably from 1,000 to 10,000, particularly preferably from 2,000, in view of compatibility with the polyester and dispersibility in the polyester.
~ 6000.

The hydrophilic compound (A) is not particularly limited as long as it contains at least one ester-forming group, but typical compounds include polyoxyalkylene compounds, polyoxazolines, polyacrylamide and derivatives thereof. , Polysulfoethyl methacrylate, poly (meth)
Acrylic acid and its salts, polyhydroxyethyl (meth) acrylate, polyvinyl alcohol, polyvinyl pyrrolidone and the like can be mentioned. Among them, polyoxyalkylene compounds are preferred. Examples of the polyoxyalkylene compound include a polyoxyethylene compound, a polyoxypropylene compound, and a polyoxytetramethylene compound. Among them, a polyoxyethylene compound is preferable, and polyethylene glycol is particularly preferable. Among polyethylene glycols, polyethylene glycol containing a crystallization inhibitor component is particularly preferred. Here, the crystallinity-suppressing factor component refers to an organic residue which is present in the molecular chain or at the terminal and disrupts the symmetry of the repeating unit of polyethylene glycol. Crystallization suppression means differential scanning calorimetry (DS
C, which means that the melting point obtained by heating conditions of 16 ° C./min) is lower than the melting point of polyethylene glycol having the same molecular weight. Specific compounds represented by the following general formula (III)

[0021]

Embedded image (Wherein X is -CR5R6- (R5 and R6 represents hydrogen or an alkyl _{group), - SO 2 -, -} O -, - S-,
-C (O)-, etc., and represents an integer of 10 ≦ n + m ≦ 450), and bisphenol A and bisphenol S
Compounds obtained by adding ethylene oxide (EO) to the above are particularly preferable.

Most of these compounds need to be copolymerized in the polyester, but some of them may be present in a dispersed state in the polymer.

The polar group-containing compound (B) contained in the copolymerized polyester is not particularly limited, but may be represented by the following general formula (I):

[0024]

Embedded image (Wherein R1 is an organic residue, X is an ester-forming group and n
Represents an integer of 1 or more, and Yi represents one or more polar groups selected from derivatives such as an amino group, a sulfonic acid group, a carboxyl group, a hydroxyl group, an amide group, and a phosphonic acid group (i
(Integer of ≧ 1)) is preferable. Here, “containing” refers to a state of being dispersed or copolymerized in the polyester, but it is particularly preferable that the copolymer is copolymerized. As the compound, a compound having a sulfonate group is particularly preferable. The inclusion of the polar group-containing compound not only further enhances the hygroscopicity of the polymer, but also has the effect of causing hydrogen bonds and ionic interactions in the polymer, making it difficult for the physical properties to change over time when formed into fibers. .

The content of the polar group-containing compound (B) in the copolymerized polyester is 0 with respect to the acid component constituting the whole polymer.
It is preferably from 50 to 50 mol%, more preferably from 2 to 30 mol%, particularly preferably from 2 to 15 mol%. By setting the content, the yarn is hardly broken, the fiber strength is increased, and the elongation does not easily change over time.

The crosslinking agent contained in the copolymerized polyester is not particularly limited as long as it reacts with the polyester to form a crosslinked structure.

[0027]

Embedded image (Wherein R2 is an organic residue of 3 to 6, R3 is hydrogen or an acetyl group, R4 is a hydrogen or alkyl group, 3 ≦ m + n
≦ 6) is preferably used. Here, “containing” includes dispersing in a polyester, but preferably has a crosslinked structure by copolymerization. The compound is preferably a polyfunctional carboxylic acid such as trimellitic acid or pyromellitic acid, or a polyol such as glycerin, trimethylolpropane, or pentaeristol, and particularly preferably trimellitic acid. The inclusion of the crosslinking agent (C) not only enhances the hygroscopicity of the polymer, but also has the effect that a crosslinked structure is formed in the polymer, and the physical properties of the fiber hardly change over time.

The proportion of the crosslinking agent in the copolymerized polyester is preferably from 0 to 30 mol%, more preferably from 1 to 15 mol%, particularly preferably from 2 to 10 mol%, based on the acid components constituting the whole polymer. . When the content is within the above range, it is preferable because the moisture absorption is kept high, the spinning properties are improved, and the fiber properties such as strength are improved.

In the present invention, at least one of the polar group-containing compound (B) and the crosslinking agent (C) must be contained in the copolymerized polyester.
It is particularly preferred to include both (B) and (C).

In the copolymerized polyester, pigments such as titanium oxide and carbon black, surfactants such as alkylbenzenesulfonate, conventionally known antioxidants, coloring inhibitors, and lightfastness are provided as long as the object of the present invention is not impaired. Of course, an agent, an antistatic agent or the like may be added.

By using the copolymerized polyester of the present invention as a component of the fiber-forming polymer, it is possible to obtain a synthetic fiber having an unprecedented high moisture absorption property and not impairing the fiber properties of the fiber-forming polymer. it can.

In the present invention, as the fiber-forming polymer, polyolefins such as polyethylene and polypropylene;
Examples include polyamides such as nylon 6 and nylon 66, and polyesters such as polyethylene terephthalate and polybutylene terephthalate, but are not limited thereto. Preferably, it is a polyester mainly composed of polyethylene terephthalate, which is the most versatile synthetic fiber for clothing.

As the form of the synthetic fiber, a core-sheath type composite fiber,
Core-sheath type composite hollow fiber, sea-island type composite fiber, laminated type composite fiber, blended fiber and the like can be mentioned, and the hygroscopic polyester of the present invention can be used as a component in any ratio.

In the case of synthetic fibers in which a copolymer polyester is blended with a fiber-forming resin, the blend ratio of the copolymer polyester is 3 to 80% by weight based on the total amount of the polymer. Preferably it is 5 to 35% by weight, more preferably 7 to 30% by weight. The lower limit of the mixing ratio is set for the purpose of imparting sufficient hygroscopicity, and the upper limit of the mixing ratio is set from the viewpoint of preventing a reduction in spinnability and a decrease in fiber properties.

In order to obtain practical wearing comfort, the ΔMR of the synthetic fiber is preferably as high as possible without causing a change with time, more preferably 1.0% or more, more preferably 1.5% or more, and particularly preferably 2% or more. 0.0% or more.

The fiber-forming polymer includes titanium oxide,
Other known antioxidants other than pigments such as carbon black,
Needless to say, a coloring prevention agent, a light resistance agent, an antistatic agent and the like may be added.

In the present invention, the copolyester fiber can be produced by a conventionally known method.

The cross-sectional shape of the synthetic fiber of the present invention is not limited to a circle, but may be a triangular, flat, multi-lobed or other irregular cross-section. The thread form of the synthetic fiber may be either filament or staple, and is appropriately selected depending on the application. The fabric form can be appropriately selected depending on the purpose, such as a woven fabric, a knitted fabric, or a nonwoven fabric.

[0039]

The present invention will be described in more detail with reference to the following examples. In addition, each characteristic value in an Example was calculated | required by the following method.

A. Intrinsic viscosity of polyester [η] Determined at 25 ° C as an orthochlorophenol solution.

B. Moisture Absorption and Desorption Parameters (ΔMR) of Copolyester and Fiber Using the Same In the case of a polymer, a chip of 1 g is cut into a cube of about 2 mm square.
Using 3 g, change in weight between the absolute dry weight and the weight after standing in a thermo-hygrostat (PR-2G manufactured by Tabai) for 24 hours in an atmosphere of 20 ° C. × 65% RH or 30 ° C. × 90% RH. From the following equation. Moisture absorption (%) = (weight after moisture absorption-weight when absolutely dry) /
Weight at absolute dryness × 100 20 ° C × 65% RH and 30 ° C × 90% measured above
From the moisture absorption rate under the condition of RH (referred to as MR1 and MR2, respectively), a moisture absorption rate difference ΔMR (%) = MR2-MR1 was obtained. The higher the ΔMR of the copolyester, the better,
As the evaluation, ΔMR ≧ 18 was evaluated as ○, and 12 ≦ ΔMR <18
△, ΔMR <12 as ×.

C. Strength and elongation Using a Tensilon tensile tester manufactured by Toyo Baldwin Co., values were obtained from a stress-strain curve under the conditions of a test length of 20 cm and a tensile speed of 10 cm / min.

D. Temporal change of fiber The drawn yarn was left for one month in an atmosphere of 20 ° C. and 70% RH, and the degree of decrease in elongation was measured by comparing the strength and elongation characteristics described in section C with those immediately after drawing. When the elongation is reduced by 8% or more immediately after stretching (for example, the elongation of 40%
The case where it is 2% or less was evaluated as Δ, and the case where the elongation was greatly reduced to 16% or more (for example, the elongation which was 40% and became 24% or less) was evaluated as ×.

Example 1 Dimethyl terephthalic acid 19 was used as the copolymerized polyester.
4 parts, 135 parts of ethylene glycol, 26.6 parts of dimethyl 5-sodium sulfoisophthalate (SSIA), 7.5 parts of trimethyl trimellitate (TMTM) and 0.1 part of tetrabutyl titanate, and 140 to 230
After transesterification while distilling off methanol at 0 ° C., a solution of 0.08 parts of trimethyl phosphate in ethylene glycol and polyethylene glycol 3 having a molecular weight of 4000 were prepared.
28 parts, 0.2 parts of Irganox 1010 (manufactured by Ciba-Gaiky) as an antioxidant, 0.2 parts of silicon as an antifoaming agent and 0.1 parts of tetrabutyl titanate were added to obtain 1.0 mm
The polymerization was carried out at 250 ° C. for 4 hours under reduced pressure to obtain a copolymerized polyester. The proportion of polyethylene glycol copolymerized with this copolymer was 60% by weight. The ΔMR of the obtained copolymerized polyester was 28.0% (MR
1 = 1.5%, MR2 = 29.5%).

The copolymerized polyester was used as a core component, and polyethylene terephthalate having an intrinsic viscosity of 0.70 was separately melted as a sheath component. The core / sheath ratio (weight ratio) was adjusted to 15/85 from a concentric core-sheath composite die. To obtain an undrawn yarn, followed by drawing and heat treatment to obtain a concentric core-sheath composite fiber of 75 denier and 24 filaments. When this fiber was made into a tubular knit and the moisture absorption / release characteristics were measured, ΔMR =
2.8%, and the elongation characteristics were also good. Further, the elongation did not decrease over time.

Examples 2 and 3, Comparative Example 1 The procedure of Example 1 was repeated, except that the amount of SSIA or TMTM was changed while the copolymerization ratio of polyethylene glycol in the copolymerized polyester was kept constant. A copolymerized polyester was obtained. In Comparative Example 1, the moisture absorption property was relatively low, and the elongation decreased with time.

[0047]

[Table 1] Examples 4 to 6, Comparative Example 2 In Examples 1 to 3 and Comparative Example 1, the molecular weight was 40 instead of polyethylene glycol in the copolymerized polyester.
00 bisphenol A ethylene oxide (EO)
Copolymer and polyester fibers were obtained in the same manner except that the adduct (BPA) was used. In Comparative Example 2, the moisture absorption property was relatively low, and the elongation decreased with time.

[0048]

[Table 2] Examples 7 to 9, Comparative Example 3 In Examples 1 to 3 and Comparative Example 1, a molecular weight of 40 was used instead of polyethylene glycol in the copolymerized polyester.
00 bisphenol sulfone (S) EO adduct (B
A copolymerized polyester and a synthetic fiber were obtained in the same manner except that PS) was used. In Comparative Example 3, the moisture absorption property was relatively low, and the elongation decreased with time.

[0049]

[Table 3] Examples 10 to 17, Comparative Examples 4 and 5 Same as Example 1 except that SSIA was fixed at 8 mol% and TMTM was constant at 3 mol% as in Example 1, and the molecular weight or copolymerization amount of polyethylene glycol was changed. A copolymerized polyester was obtained by the following method. Fibers were formed in the same manner as in Example 1 and the fiber properties are summarized in Table 4. PEG copolymerization amount of 4
When the amount is less than 0% by weight (Comparative Example 4), sufficient hygroscopicity cannot be obtained, and when the copolymerization amount of PEG is more than 99% by weight (Comparative Example 5), the hygroscopicity is low. In this case, the spinnability of the copolyester was low, the yarn breakage occurred frequently, and no conjugate fiber was obtained.

[0050]

[Table 4] Examples 18 to 27 Copolymerization was carried out in the same manner as in Example 1 except that PEG-4000 was used, the amount of copolymerization was changed to 60% by weight, and the amount of SSIA or TMTM was changed. Polyester was obtained. Fibers were formed in the same manner as in Example 1, and the fiber properties are summarized in Table 5. The change over time can be suppressed by SSIA and TMTM copolymerization, but a slight decrease in strength was observed as the amount of copolymerization increased.

Examples 28-35 Instead of using PEG-4000 as in Example 1,
EO adduct of bisphenol A or bisphenol S
A copolymerized polyester and a conjugate fiber using the same were obtained in the same manner as in Example 1 except that the EO adduct (both having a molecular weight of 4000) was used. Fibers were formed in the same manner as in Example 1, and the fiber properties are summarized in Table 5.

[0052]

[Table 5] Examples 36 to 40 Using the copolymerized polyester obtained in Example 1 as a core component,
In the same manner as in Example 1, polyethylene terephthalate having an intrinsic viscosity of 0.70 was separately melted as a sheath component, an unstretched yarn was obtained by changing the core-sheath composite ratio from a concentric core-sheath composite die, and then stretched and heat-treated. A concentric core-sheath composite fiber of 75 denier and 24 filaments was obtained. Table 6 summarizes the fiber properties. As the core ratio is increased, ΔMR is improved, but a decrease in strong elongation and a slight change with time are observed.

[0053]

[Table 6] Examples 41 to 45 In the same manner as in Examples 38 to 42, except that a die for forming a hollow portion at the core / sheath interface was used, a 75 denier 24 filament core / sheath composite hollow fiber (hollowness: 6%) was used.
I got The fiber properties are summarized in Table 7. As the core ratio is increased, ΔMR is improved, but a decrease in the elongation and a slight change with time are observed. In particular, a dyed fabric obtained by dyeing a tubular knitted fabric obtained from this fiber had good fastness.

[0054]

[Table 7] Examples 46 to 50 The copolymerized polyester obtained in Example 1 was used as an island component (18
Islands), and polyethylene terephthalate having an intrinsic viscosity of 0.70 was separately melted as a sea component, and an undrawn yarn was obtained by appropriately changing the island / sea ratio from a sea-island type composite die, and then drawing.
By heat treatment, a sea-island composite fiber of 75 denier and 9 filaments was obtained. Table 8 summarizes the fiber properties. As the island ratio is increased, ΔMR is improved, but a decrease in strong elongation and a slight change over time are observed.

[0055]

[Table 8] Examples 51 to 53 The copolymerized polyester (A) obtained in Example 1 and polyethylene terephthalate (B) having an intrinsic viscosity of 0.70 were separately melted, and a bonding ratio (weight ratio) A was obtained from a bonding type composite die. / B = 60/40, 50/50, 40 /
The unstretched yarn is obtained by discharging so as to be 60, and then stretched.
By heat treatment, a laminated composite fiber of 75 denier and 24 filaments was obtained. The fiber properties are summarized in Table 9, which has high ΔMR and high elongation properties.

[0056]

[Table 9] Examples 54 to 58 The copolymerized polyester (A) obtained in Example 1 was melt-mixed simultaneously with an extruder while appropriately changing the weight ratio to polyethylene terephthalate (B) having an intrinsic viscosity of 0.70, and this was mixed in a circular shape. An undrawn yarn was obtained by discharging from a die, followed by drawing and heat treatment to obtain a 75 denier 24-filament polyester fiber. Table 10 summarizes the fiber properties. As the blend ratio is increased, ΔMR is improved, but a decrease in strong elongation and a slight change with time are observed.

[0057]

[Table 10]

[0058]

The copolymer polyester obtained according to the present invention has a very high hygroscopic property, and the synthetic fiber obtained from the copolymer polyester has a sufficient hygroscopic property to obtain comfortable wearing. It has a dry touch texture and high color fastness and light fastness. Synthetic fibers obtained from the copolymerized polyester of the present invention include underwear, shirts / blouses, middle garments, sportswear, slacks, outer garments, linings, curtains, wallpapers, and even sheets, futon covers, and stuffed cotton. It is suitable for wear and extremely practical.

Claims (7)

[Claims] 1. A polyester obtained by copolymerizing a hydrophilic compound (A) with 50 to 95% by weight based on the total weight of a polymer,
A copolymer polyester containing a polar group-containing compound (B) and / or a cross-linking agent (C) and having a moisture absorption / desorption parameter (ΔMR) of 12.0% or more and excellent in hygroscopicity. 2. The molecular weight of the hydrophilic compound (A) is from 600 to 2
The copolymer polyester excellent in hygroscopicity according to claim 1, wherein the copolymer polyester has a molecular weight of 0000. 3. The copolyester excellent in hygroscopicity according to claim 1, wherein a polyoxyalkylene compound is used as the hydrophilic compound (A). 4. The copolyester excellent in hygroscopicity according to claim 1 or 2, wherein a polyoxyalkylene compound containing a crystallization inhibitor component is used as the hydrophilic compound (A). 5. A polar group-containing compound (B) in an amount of 0 to 50 mol% and a crosslinking agent (C) in an amount of 0 to 30 mol% (B + C ≠).
0) The copolyester excellent in hygroscopicity according to any one of claims 1 to 4, which is contained. 6. The polar group-containing compound (B) represented by the following general formula (I): (Wherein R1 is an organic residue, X is an ester-forming group and n
Represents an integer of 1 or more, and Yi represents one or more polar groups selected from derivatives such as an amino group, a sulfonic acid group, a carboxyl group, a hydroxyl group, an amide group, and a phosphonic acid group (i
The copolymer polyester excellent in hygroscopicity according to any one of claims 1 to 5, wherein a compound having a polar group represented by the formula (1) is used. 7. A crosslinking agent (C) represented by the following general formula (II): (Wherein R2 is a trivalent to hexavalent organic residue, R3 is hydrogen or an acetyl group, R4 is hydrogen or an alkyl group, 3 ≦ m +
The copolyester excellent in hygroscopicity according to any one of claims 1 to 6, wherein a polyfunctional compound represented by n ≦ 6) is used.