JP2009174063A - Normal atmosphere cation-dyeable polyester yarn and false twisted yarn comprising the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a normal atmosphere cation-dyeable polyester multifilament which can stably be dyed with cation dyes at normal atmosphere and has a high strength, and to provide a false-twisted yarn including the same. <P>SOLUTION: The cation-dyeable polyester multifilament having a single fiber fineness of ≤1.5 dtex, includes 10 or more bundled single fibers, having a strength of ≥1.5 cN/dtex, an elongation of ≤60%, characterized in that a sulfoisophthalic acid metal salt (A) and a specific compound (B) are contained in an acid component constituting the polyester in a specific ratio. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a normal pressure cationic dyeable polyester multifilament having fineness that is dyeable to a cationic dye under normal pressure, a false twisted yarn comprising the same, and a covering yarn using the same.

  Polyester fibers typified by polyethylene terephthalate have the disadvantage that, because of their chemical properties, they can be dyed only with disperse dyes and azoic dyes, and thus it is difficult to obtain a clear and deep hue. As a method for eliminating such drawbacks, a method in which a metal salt of sulfoisophthalic acid is copolymerized with 2 to 3 mol% of polyester has been proposed (see, for example, Patent Documents 1 and 2).

  However, the polyester fiber obtained by such a method can be dyed only under high temperature and high pressure, and if it is dyed after knitting or weaving with natural fiber or urethane fiber, natural fiber and urethane fiber are embrittled. There was a problem. If this is to be sufficiently dyed at normal pressure and at a temperature around 100 ° C., it is necessary to copolymerize a large amount of the metal salt of sulfoisophthalic acid. In this case, from the thickening effect due to the sulfonate group, There is a problem that the degree of polymerization of the polyester cannot be increased, the strength of the polyester fiber obtained by melt spinning is remarkably lowered, and the spinning operability is remarkably deteriorated. In particular, there has been a problem that it is difficult to produce an atmospheric pressure cationic dyeable yarn having a fineness of 1 d or less.

  On the other hand, in order to solve such a problem, a technique of copolymerizing a cationic dyeable monomer having a small ion binding intermolecular force has been disclosed (see, for example, Patent Documents 3 and 4). Examples of cationic dyeable monomers having a small ion-binding intermolecular force include 5-sulfoisophthalic acid tetrabutoxyphosphonate and the like, but these cationic dyeable monomer copolymer polyesters have poor thermal stability, and are used as atmospheric pressure cations. Even if an attempt was made to increase the amount of copolymerization for dyeing, thermal decomposition progressed during the polymerization reaction, making it difficult to increase the molecular weight. Furthermore, there is a drawback that the decomposition due to the thermal history during melt spinning is large, and the strength of the resulting yarn is weakened. Further, the 5-sulfoisophthalic acid tetrabutoxyphosphonate used is very expensive, and there is a problem that the cost of the resulting cationic dyeable polyester is greatly increased.

As a method for solving such a problem, a method of copolymerizing a metal salt of sulfoisophthalic acid and a polyethylene glycol having a molecular weight of 200 or more, and further copolymerizing a polyalkylene glycol having an average molecular weight of 400 to 1000 with a metal salt of sulfoisophthalic acid. A method has been proposed (see, for example, Patent Document 5). A method of copolymerizing a metal salt of sulfoisophthalic acid and adipic acid has been proposed. (For example, see Patent Document 6)
However, the strength of the normal pressure cationic dyeable polyester fiber obtained by melt spinning the polyester obtained by any of these methods is lowered, and thus the tear strength of the resulting fabric is lowered. There were problems such as low.

  Further, a core-sheath type composite fiber has been proposed in which a polyester copolymerized with 5-sodium sulfoisophthalic acid is disposed in the sheath part and a polyester comprising 95 mol% or more of a repeating unit of ethylene terephthalate is disposed in the core part (for example, a patent) Reference 7). However, the copolymerization amount of the sulfoisophthalic acid component in the copolymer polyester constituting the sheath part has a problem for the same reason as described above, and it is difficult to satisfy sufficient dyeability and strength. In addition, there are problems such as an increase in equipment cost in the spinning process due to the composite fiber, or a restriction in the fiber cross-sectional shape.

In addition, when using a normal pressure cationic dyeable polyester as a false twisted yarn, a conventional normal pressure cationic dyeable polyester cannot obtain a yarn that satisfies the strength and elongation enough to withstand the false twisting process. There was a big problem that the occurrence was large.
In view of the present situation, there has been a demand for a normal pressure cationic dyeable polyester false twisted yarn that satisfies fineness, strength, elongation, and satisfaction.

Japanese Patent Publication No.34-10497 JP-A-62-89725 JP-A-1-162822 JP 2006-176628 A JP 2002-284863 A JP 2006-200064 A Japanese Patent Laid-Open No. 7-126920

  The present invention solves the above-described problems, and is a normal pressure cationic dyeable polyester multifilament capable of stable cationic dyeing under normal pressure and having fine fineness and good elongation properties, and false twist thereof. Processed yarns and covering yarns using them are provided.

  A polyester multifilament in which the main repeating unit is composed of ethylene terephthalate, and a metal salt of sulfoisophthalic acid (A) and a compound represented by the following general formula (1) in all the acid components constituting the polyester (B) is included under the conditions satisfying the following formulas 1 and 2. The number of single yarns bundled with a single yarn fineness of 1.5 dtex or less is 10 and the strength is 1.5 cN / dtex. The cationic dyeable polyester multifilament having an elongation of 60% or less.

［上記式中、Ｒは水素または炭素数１〜１０のアルキル基を表し、Ｘは４級ホスホニウム塩、または４級アンモニウム塩を表す］
３．０≦Ａ＋Ｂ≦５．０ 数式１
０．２≦Ｂ／（Ａ＋Ｂ）≦０．７ 数式２
［ここで、Ａはスルホイソフタル酸の金属塩の共重合量（モル％）、Ｂは上記一般式（１）で表される化合物の共重合量（モル％）を表す。］

[In the above formula, R represents hydrogen or an alkyl group having 1 to 10 carbon atoms, and X represents a quaternary phosphonium salt or a quaternary ammonium salt.]
3.0 ≦ A + B ≦ 5.0 Formula 1
0.2 ≦ B / (A + B) ≦ 0.7 Formula 2
Here, A represents the copolymerization amount (mol%) of the metal salt of sulfoisophthalic acid, and B represents the copolymerization amount (mol%) of the compound represented by the general formula (1). ]

  ADVANTAGE OF THE INVENTION According to this invention, the dyeing | staining property by the cation dyeing under a normal pressure is favorable, and intensity | strength is higher than the conventional cation dyeable polyester, and false twist process tone can be improved significantly.

Hereinafter, the present invention will be described in detail.
The polyester used in the present invention is a polyester having ethylene terephthalate as a main repeating unit obtained by polycondensation reaction of terephthalic acid or an ester-forming derivative thereof and an ethylene glycol component. It is a copolyester containing an acid metal salt (A) and a compound (B) represented by the following general formula (1) in a state satisfying the following formula (1) and formula (2) simultaneously. The polyester is characterized in that the content of diethylene glycol in the polyester is 2.5% by weight or less and the intrinsic viscosity of the copolymerized polyester obtained is in the range of 0.55 to 1.0.

［上記式中、Ｒは水素または炭素数１〜１０のアルキル基を表し、Ｘは４級ホスホニウム塩、または４級アンモニウム塩を表す。］
３．０≦Ａ＋Ｂ≦５．０ （数式１）
０．２≦Ｂ／（Ａ＋Ｂ）≦０．７ （数式２）
［ここで、Ａはスルホイソフタル酸の金属塩の共重合量（モル％）、Ｂは上記一般式（１）で表される化合物の共重合量（モル％）を表す。］

[In the above formula, R represents hydrogen or an alkyl group having 1 to 10 carbon atoms, and X represents a quaternary phosphonium salt or a quaternary ammonium salt. ]
3.0 ≦ A + B ≦ 5.0 (Formula 1)
0.2 ≦ B / (A + B) ≦ 0.7 (Formula 2)
Here, A represents the copolymerization amount (mol%) of the metal salt of sulfoisophthalic acid, and B represents the copolymerization amount (mol%) of the compound represented by the general formula (1). ]

(Description of component A)
Examples of the sulfonate group-containing aromatic dicarboxylic acid component used in the present invention include a metal salt of 5-sulfoisophthalic acid (sodium salt, lithium salt, potassium salt), a quaternary phosphonium salt of 5-sulfoisophthalic acid, or 5 -Quaternary ammonium salts of sulfoisophthalic acid are exemplified. These ester-forming derivatives are also preferably exemplified. Among these groups, a metal salt of 5-sulfoisophthalic acid is preferably exemplified from the viewpoint of thermal stability, cost, etc., and in particular, a sodium salt of 5-sulfoisophthalic acid and a dimethyl ester thereof, 5-sulfoisophthalic acid. Particularly preferred is the sodium salt of dimethyl acid.

(Description of component B)
The compound (B) represented by the general formula (1) is quaternary phosphonium salt or quaternary ammonium salt of 5-sulfoisophthalic acid or a lower alkyl ester thereof. As the quaternary phosphonium salt, the quaternary ammonium salt is preferably a quaternary phosphonium salt or a quaternary ammonium salt substituted with an alkyl group, a benzyl group or a phenyl group, and particularly preferably a quaternary phosphonium salt. The four substituents may be the same or different. Specific examples of the compound represented by the chemical formula (1) include 5-sulfoisophthalic acid tetrabutylphosphonium salt, 5-sulfoisophthalic acid ethyltributylphosphonium salt, 5-sulfoisophthalic acid benzyltributylphosphonium salt, and 5-sulfoisophthalic acid. Acid phenyltributylphosphonium salt, 5-sulfoisophthalic acid tetraphenylphosphonium salt, 5-sulfoisophthalic acid butyltriphenylphosphonium salt, 5-sulfoisophthalic acid benzyltriphenylphosphonium salt, or dimethyl ester or diethyl ester of these isophthalic acid derivatives Preferably exemplified.

(Explanation of Formula 1)
In the present invention, the total of component A and component B copolymerized with the polyester needs to be within a range of A + B of 3.0 to 5.0 mol% based on the acid component. If it is less than 3.0 mol%, sufficient dyeing cannot be obtained by cationic dyeing under normal pressure. On the other hand, if it exceeds 5.0 mol%, the strength of the resulting polyester yarn is lowered, which is not suitable for practical use. Further, since the dye is consumed excessively, it is disadvantageous in terms of cost.

(Explanation of Formula 2)
The component ratio between component A and component B must be such that B / (A + B) is in the range of 0.2 to 0.7. When the ratio is 0.2 or less, that is, in a state where the proportion of component A is large, it is difficult to increase the degree of polymerization of the resulting polyester due to the thickening effect of the metal salt of sulfoisophthalic acid. On the other hand, when the ratio is 0.7 or more, that is, the ratio of the component B is large, the reaction is slow, and when the ratio of the component B is further increased, the decomposition proceeds and the degree of polymerization cannot be increased. Further, when the ratio of component B is increased, the thermal stability is deteriorated, and the decrease in molecular weight due to thermal decomposition when remelted in the melt spinning stage is increased, so that the strength of the resulting polyester yarn is decreased, which is not preferable.

(Description of DEG amount)
The diethylene glycol contained in the normal pressure cationic dyeable polyester in the present invention is preferably 2.5% by weight or less.
In general, when a cationic dyeable polyester is produced, in order to suppress the amount of diethylene glycol (DEG) by-produced in the production process of the polyester, a small amount of alkali metal salt, alkaline earth metal salt, hydroxide is used as a DEG inhibitor. 1 to 20 mol of the cationic dyeable monomer (compounds (A) and (B) in the case of the present invention) at least one of tetraalkylphosphonium, tetraalkylammonium hydroxide, trialkylamine and the like used. It is preferable to add about%.

(Explanation of intrinsic viscosity)
The intrinsic viscosity (solvent: orthochlorophenol, measurement temperature: 35 ° C.) of the polyester used in the present invention is preferably in the range of 0.55 to 1.0. When the intrinsic viscosity is 0.55 or less, the strength of the resulting polyester fiber is insufficient. On the other hand, when it is 1.0 or more, the melt viscosity becomes too high and melt molding becomes difficult. Since the production cost in the polycondensation step of the polymerized polyester is greatly increased by the solid phase polymerization method subsequent to the melt polymerization method, it is not preferable. The intrinsic viscosity of the normal pressure cationic dyeable polyester is more preferably in the range of 0.60 to 0.90.

(Production method of polyester resin)
The method for producing the copolyester in the present invention is not particularly limited, and a commonly known method for producing polyester is used. That is, a low polymer is produced by a direct polycondensation reaction between terephthalic acid and ethylene glycol, or an ester exchange reaction between an ester-forming derivative of terephthalic acid typified by dimethyl terephthalate and ethylene glycol. Subsequently, this reactive organism is produced by heating under reduced pressure in the presence of a polycondensation catalyst to carry out a polycondensation reaction until a predetermined polymerization degree is reached. As a method for copolymerizing an aromatic dicarboxylic acid containing sulfoisophthalic acid and / or an ester derivative thereof, a generally known production method can be used.

(Other additives)
In addition, the copolymer polyester in the present invention contains a small amount of additives as necessary, for example, antioxidants, fluorescent whitening agents, antistatic agents, antibacterial agents, ultraviolet absorbers, light stabilizers, heat stabilizers, and light-shielding agents. Or it may contain a matting agent. In particular, antioxidants and matting agents are particularly preferably added.

(Yarn making method)
There is no restriction | limiting in particular as a method of spinning said copolyester, A conventionally well-known method is employ | adopted. That is, it is preferable to produce the dried copolyester by melt spinning at a temperature in the range of 270 ° C. to 300 ° C., and the spinning speed of the melt spinning is preferably 400 to 5000 m / min. When the spinning speed is within this range, the strength of the obtained fiber is sufficient, and the winding can be stably performed. Furthermore, it is preferable that the undrawn yarn or the partially drawn yarn obtained by the above method is drawn in a range of about 1.2 times to 6.0 times in the drawing step. This stretching may be performed after winding the unstretched polyester fiber once, or may be performed continuously without winding. Moreover, there is no restriction | limiting in particular also about the shape of the nozzle | cap | die used at the time of spinning.

Cations that are adjusted within the range of the above-mentioned spinning method, the number of single yarns bundled with a single yarn fineness of 1.5 dtex or less, a strength of 1.5 cN / dtex or more, and an elongation of 60% or less are possible. It is preferable to use a dyeable polyester multifilament.
Here, it is necessary that the single yarn fineness is 1.5 dtex or less. When the single yarn fineness exceeds 1.5 dtex, the texture is hard as the fiber for clothing, and the synthetic fiber appearance is strong and preferable in the cationic dyed fabric. In addition, the number of bundled single yarns is required to be 5 or more, and if it is less than 5, it is not preferable because the weaving property is lowered or the texture becomes hard.

The fiber strength of the multifilament needs to be 1.5 cN / dtex or more. If the strength is less than 1.5 cN / dtex, yarn breakage and fluff are likely to occur in the false twisting process, and tearing when used as a fabric. The strength is lowered, which is not preferable. Preferably it is 2.0-5.0 cN / dtex.
Further, the elongation is 60% or less, and preferably 20 to 40% particularly for clothing. If the elongation is 60% or more, the shrinkage in the width direction at the time of heat setting when the fabric is set becomes too large, and the fabric surface may be wavy, which is not preferable in terms of fabric quality.

(False twisted yarn)
Although the above-mentioned multifilament is false twisted to obtain a normal pressure dyeable polyester false twisted yarn of the present invention, a false twisting method can be performed by a known method, for example, as shown in FIG. Using a false twisting machine equipped with a contact heater, the first false twisting heater is preferably stretched false twisting at a temperature of 200 to 500 ° C.

(Covering thread)
The elastic yarn as the core yarn used in the covering yarn of the present invention may be a conventionally used elastic yarn made of polyurethane elastomer, polyether / polyester block copolymer, polyether or synthetic rubber elastic body. preferable. Examples of polyurethane elastomers include diol components having a divalent hydroxyl group such as polyester diol, polyether diol, and polycarbonate diol, and polyisocyanates, preferably diisocyanates (such as diphenylmethane diisocyanate) and low molecular chain extenders (such as ethylene glycol). A low molecular weight diol) and a polyurethane elastomer obtained by reacting a terminal stopper if desired are exemplified. Examples of the polyether / polyester block copolymer include block copolymers having polybutylene terephthalate polyester as a hard segment and polyoxybutylene glycol as a soft segment. In addition, what added the ultraviolet absorber and antioxidant as needed is preferably used for said polyurethane elastomer or polyether * polyester block copolymer.
The method for producing the covering yarn of the normal pressure cationic dyeable polyester yarn in the present invention is not particularly limited by the examples, and a conventionally known method may be adopted.

As the covering means, there are a method using a twisted yarn using a hollow spindle while drafting (extending) the elastic yarn, or a method using air mixing. In general, the former having a large cover effect is superior in the quality of the fabric. Here, the number of twisted covering yarns is required to be 200 T / m or more. Below this, the covering effect is insufficient and the quality of the finished fabric is insufficient. In particular, 300 T / m or more is preferable for a multifilament not subjected to false twisting. If it is more than this, the necessary number of twisted yarns can be set arbitrarily, but the cost increases, so the upper limit is practically about 1000 T / m. On the other hand, the number of additional twists is 300 T / m or more, and the intended effect of the present invention is sufficiently expressed. However, there is an optimum number of twists depending on the type of yarn constituting the covering yarn, and it is not limited to the above range. Absent. Moreover, when performing additional twist, the same direction as a covering direction is good.
In the examples of the present invention, a 44 dtex polyether ester elastic yarn and a hollow spindle device were used as elastic yarns at 500 T / m.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not restrict | limited to these Examples. In addition, the analysis item etc. in an Example were measured by the method of the following description.
(A) Intrinsic viscosity:
A dilute solution obtained by dissolving the polyester composition in orthochlorophenol at 100 ° C. for 60 minutes was determined from a value measured at 35 ° C. using an Ubbelohde viscometer. The intrinsic viscosity of the tip is ηC, and the intrinsic viscosity of the undrawn yarn after spinning is ηF.
(A) Diethylene glycol (DEG) content:
The polyester composition chip was decomposed using hydrazine hydrate (hydrated hydrazine), and the content of diethylene glycol in the decomposition product was measured using gas chromatography (HP Hewlett-Packard (HP 6850)).
(C) Tensile strength, elongation and fineness of fiber:
Measurement was performed in accordance with the method described in JIS L1013.
(D) Cationic dyeability:
The tube knitting made of multifilament yarn is set at the temperature shown in the table in dyeing solution of Estrol Brilliant Blue N-RL 2% owf, sodium sulfate 3 g / L, acetic acid 0.5 g / L, bath ratio 1:50. Dyeing was performed for 1 hour to obtain a dyed fabric. For the dyed fabric, using the Macbeth COLOR-EYE model M-2020PL, the L * a * b * color display recommended by the International Commission on Illumination (CIE) as defined in JISZ 8729-1980 The brightness L * value represented by is measured. This lightness L * was used as a representative value of the intensity of staining.
(E) False twisting process:
The number of fluffs generated from false twisted yarn was evaluated.
Using a DT-104 type fluff counter device manufactured by Toray Industries, Inc., a polyester false twisted yarn sample is continuously measured at a speed of 500 m / min for 20 minutes to measure the number of fluffs generated, and the number per sample length of 10,000 m Expressed in
○ Less fuzz and good (less than 10 / 10,000m)
△ Slightly fluffy x Lots of fluff and poor product quality (10 / 10,000m or more)

[Example 1]
Add 0.03 parts by weight of manganese acetate and 0.12 parts by weight of sodium acetate trihydrate to a mixture of 100 parts by weight of dimethyl terephthalate, 4.1 parts by weight of dimethyl 5-sodium sulfoisophthalate and 60 parts by weight of ethylene glycol. Then, the temperature was gradually raised from 140 ° C. to 240 ° C., and the ester exchange reaction was performed while distilling out the methanol produced as a result of the reaction out of the system. Thereafter, 0.03 part by weight of orthophosphoric acid was added to complete the transesterification reaction.

  Thereafter, 0.05 parts by weight of antimony trioxide, 2.8 parts by weight of tetrabutoxyphosphonate 5-sulfoisophthalate, 0.3 parts by weight of tetraethylammonium hydroxide, and 0.003 parts by weight of triethylamine were added to the reaction product for polymerization. Move to a container, raise the temperature to 285 ° C., perform a polycondensation reaction at a high vacuum of 30 Pa or less, and terminate the reaction when the agitator power of the polymerization tank reaches a predetermined power or when a predetermined time has elapsed, According to the chip.

  After the polyester chip thus obtained was dried at 140 ° C. for 5 hours, a partially drawn yarn of 90 dtex / 72 filament was prepared at a spinning temperature of 285 ° C. and a winding speed of 3000 m / min, and the false twisting apparatus shown in FIG. Was used to obtain a 56 dtex / 72 filament false twisted yarn. The evaluation results of the obtained yarn are shown in Table 1.

[Examples 2 to 4, Comparative Examples 1 to 4]
In Example 1, it carried out like Example 1 except having changed the addition amount of sodium 5-sulfoisophthalate and 5-sulfoisophthalic acid tetrabutoxyphosphonate so that it might become Table 1. The results are shown in Table 1.

[Example 5]
In Example 4, the same procedure as in Example 1 was performed except that the number of die perforations used for spinning was changed as shown in Table 1. The results are shown in Table 1.

[Example 6]
Describe examples of covering yarn made using false twisted yarn of Example 3. Since the strength and elongation were good, the covering process was good, and the cation dyeability evaluation in the tube was also good.

[Comparative Example 5]
In Comparative Example 4, the same procedure as in Comparative Example 4 was performed except that the number of die perforations used for spinning was changed to 144. The results are shown in Table 1.

[Comparative Example 6]
Evaluation was made in the same manner as in Example 1 using only polyethylene terephthalate resin not containing Component A and Component B. The results are shown in Table 1. The cationic dyeability was poor and the appearance was poor.

[Comparative Example 7]
A covering yarn was prepared in the same manner as in Example 7 using the false twisted yarn of Comparative Example 1. Although the dyeability was good, the strength and elongation were not sufficient, and there were many yarn breaks and fluffs in the covering process, and the process condition was poor.

  The normal pressure cationic dyeable polyester multifilament of the present invention or false twisted yarn and covering yarn using the same have high strength and good atmospheric pressure cationic dyeability and fastness, and can be used in fine yarns. , A soft and dense fabric can be obtained.

It is the schematic of the false twist process yarn process of this invention.

Explanation of symbols

1 Cationic dyeable polyester yarn of the present invention
2 Thread guide
3, 3 'feed roller
4 Interlace nozzle
5 First heater
6 Cooling plate
7 False twist disk unit
8 1st Deliberry Roller
9 Second heater
10 Second deli berry roller
11 Winding roller
12 Polyester false twisted yarn cheese

Claims (4)

A polyester multifilament in which the main repeating unit is composed of ethylene terephthalate, and a metal salt of sulfoisophthalic acid (A) and a compound represented by the following general formula (1) in all the acid components constituting the polyester (B) is included under the conditions satisfying the following formulas 1 and 2. The number of single yarns bundled at a single yarn fineness of 1.5 dtex or less is 5 or more and the strength is 1.5 cN / dtex. The cationic dyeable polyester multifilament having an elongation of 60% or less.

[In the above formula, R represents hydrogen or an alkyl group having 1 to 10 carbon atoms, and X represents a quaternary phosphonium salt or a quaternary ammonium salt.]
3.0 ≦ A + B ≦ 5.0 Formula 1
0.2 ≦ B / (A + B) ≦ 0.7 Formula 2
Here, A represents the copolymerization amount (mol%) of the metal salt of sulfoisophthalic acid, and B represents the copolymerization amount (mol%) of the compound represented by the general formula (1). ]   The atmospheric pressure cationic dyeable polyester multifilament according to claim 1, wherein the metal salt of sulfoisophthalic acid is 5-sodium sulfoisophthalic acid and / or the compound (B) is 5-sulfoisophthalic acid tetrabutoxyphosphonate. A polyester multifilament in which the main repeating unit is composed of ethylene terephthalate, and a metal salt of sulfoisophthalic acid (A) and a compound represented by the following general formula (1) in all the acid components constituting the polyester (B) is included under the conditions satisfying the following mathematical formulas 1 and 2, the number of single yarns bundled at a single yarn fineness of 1.5 dtex or less is 5 or more, and the strength is 1.5 cN / dtex or more. Is a normal pressure cationic dyeable polyester multifilament obtained by false twisting a cationic dyeable polyester multifilament of 60% or less.

[In the above formula, R represents hydrogen or an alkyl group having 1 to 10 carbon atoms, and X represents a quaternary phosphonium salt or a quaternary ammonium salt.]
3.0 ≦ A + B ≦ 5.0 Formula 1
0.2 ≦ B / (A + B) ≦ 0.7 Formula 2
Here, A represents the copolymerization amount (mol%) of the metal salt of sulfoisophthalic acid, and B represents the copolymerization amount (mol%) of the compound represented by the general formula (1). ]   Using the atmospheric pressure cationic dyeable polyester multifilament according to any one of claims 1 to 3, an elastic yarn comprising at least one component selected from the group consisting of polyurethane, polyether, polyether ester and synthetic rubber is coated. A covering yarn characterized by comprising

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