JP6629657B2 - Flame retardant polyester fiber and method for producing the same - Google Patents

Description

  The present invention relates to a flame-retardant polyester fiber. More specifically, the present invention relates to a flame-retardant polyester fiber which has excellent flame retardancy even though it has a low phosphorus concentration, and which is superior in strength, elongation, and toughness as compared with conventional ones.

  Polyester is used for many purposes because of its usefulness, for example, for clothing, materials, and medical use. Among them, polyalkylene terephthalate is excellent in versatility and practicality, and is preferably used. Now, from the viewpoint of fire prevention, etc., it is required to impart flame retardancy to various polyester molded products. In particular, polyester fibers are widely used in clothing, bedding, curtains, carpets, and the like, but are insufficient in flame retardancy, and various efforts have been made to improve this point. A method of copolymerizing or blending, a method of kneading a flame retardant during the production of a molded article, a method of post-processing a molded article made of polyester, and attaching or impregnating the flame retardant to the surface or inside of the molded article have been proposed. These methods are also used for fibers.

  Among the above methods, the method of imparting flame retardancy by post-processing has the disadvantage that the texture becomes coarse, and the flame retardant drops off due to washing and friction, and the performance deteriorates. Further, in the method of kneading the flame retardant, the flame retardant exudes in the process of manufacturing a molded product, which causes a trouble. On the other hand, the method of copolymerizing a flame retardant during polymer production can overcome the above-mentioned disadvantages. As a method of copolymerizing the flame retardant, many methods have been proposed so far. For example, it is disclosed that a phosphoric acid ester as a phosphorus compound is copolymerized with a polyester (for example, Patent Document 1). 1)), a polymerization reaction is required to obtain a copolymerized polyester having the desired physical properties, and when the phosphorus compound is blended in an amount that imparts the desired flame retardancy, the physical properties of the fiber are remarkably increased. descend.

  Further, as a method of kneading a phosphorus-based flame retardant, it is disclosed that flame retardancy is exhibited by blending a specific organic phosphorus-containing compound into polyester fiber (for example, see Patent Documents 2 to 4). ). Specifically, an example is described in which a fiber is obtained by mixing a polyalkylene terephthalate and a specific organic phosphorus compound, and the fiber is used as a woven fabric, and the flame retardancy (for example, oxygen index) is slightly improved. The technique described in this publication teaches about flame retardation of polyalkylene terephthalate fiber, and there is no description about the yarn physical properties.

  Patent Literature 2 describes, as an example, a high-concentration flame-retardant fiber in which the concentration of a flame retardant added is 20 wt% and the content of phosphorus atoms is as high as 30,000 ppm. Generally, polyalkylene terephthalate containing an additive of as much as 20 wt% has large changes in physical properties such as fluidity and viscosity, and it is difficult to draw generally used yarns of around 10 tex or less. Is restricted. In fact, even in Patent Document 2, there is no description in Examples of only a yarn having a diameter as large as 100 tex, and no mention is made of the yarn physical properties at all.

Further, there is described an example of a resin composition which exhibits flame retardancy by using the flame retardant of the formula (1) (for example, see Patent Document 5). However, flame-retardant polyester fibers having high toughness required for applications requiring high elongation have not been proposed.
Patent Document 6 describes, as a method for producing a polyester fiber, melt-spinning a polyester composition in which the concentration of the flame retardant of the formula (1) is arbitrarily adjusted in advance. In order to determine the optimum flame retardant concentration, it was necessary to go back to the preparation of the polyester composition every time in order to determine the optimum flame retardant concentration, which was not efficient.

  In addition, depending on the manufacturing process of the yarn or nonwoven fabric and the type of equipment, conditions such as processing temperature and heating time do not match, so that the viscosity or IV of the polyester composition decreases, and the processability in processing such as spinning and drawing. In some cases, such as deterioration of the yarn strength and decrease in the yarn strength may occur (see, for example, Patent Document 6), and there has been a demand for a device capable of performing stable processing regardless of the type of equipment.

Japanese Patent Publication No. 55-041610 JP-A-52-012329 German Patent Application Publication No. 2630693 UK Patent Application No. 1515223 Japanese Patent No. 4653373 Japanese Patent Application No. 2014-249962

  The object of the present invention is to solve the above-mentioned conventional problems, obtain a flame-retardant polyester by melt-kneading a polyester with a flame retardant, have excellent flame retardancy at a low phosphorus concentration, and have a higher strength than conventional products. To provide a flame-retardant polyester fiber having high elongation and high toughness.

The present inventors have conducted intensive studies and found that polyester fibers obtained by melt-kneading a specific phosphorus compound and a chain extender so that the content of phosphorus atoms is 1000 to 16000 ppm are flame-retardant and yarn-resistant. The inventors have found that they have excellent physical properties, and have completed the present invention.
That is, according to the present invention, the object of the invention is achieved by the following.

<1> A phosphorus compound represented by the following general formula (1) such that the phosphorus atom content is 1000 to 16000 ppm with respect to the weight of the polyester fiber, and 0.005 wt with respect to the weight of the polyester resin before spinning. % To 1.5 wt%, a polyester fiber containing a chain extender having an intrinsic viscosity of 0.5 to 1.3 dL / g and a terminal carboxyl group content of 10 to 45 eq / T. Polyester fibers characterized by the following.

<2> The polyester fiber according to <1>, wherein the physical properties of the phosphorus compound represented by the following general formula (1) satisfy the following requirements.
(A) Organic purity of 97.0% or more and 100% or less (A) Chlorine content exceeds 0 ppm and 1000 ppm or less (C) pH fluctuation value (ΔpH) is 0 or more and 1.0 or less (D) Residual solvent amount is 0 ppm Over 1000ppm

<3> The tensile strength at break is 2.0 to 6.5 cN / dtex, the elongation at break is 20 to 80%, and the toughness expressed by (tensile strength at break) × (elongation at break) ^0.5 is 19 to 30. <1> The polyester fiber according to any one of <1> to <2>.
<4> Melt spinning of a polyester composition having an intrinsic viscosity of 0.5 to 1.3 dL / g in which a phosphorus compound represented by the following general formula (1) is blended so that the phosphorus atom compound becomes 1000 to 16000 ppm. A spinning speed of 800 to 4000 m / min by a spinning method, and a total draw ratio after spinning of 2.5 to 6.0 times, wherein the spinning speed is 2.5 to 6.0 times. Method for producing polyester fiber.
<5> A polyester composition of 0.4 to 0.6 dl / g in which a phosphorus compound represented by the general formula (1) is blended so that the phosphorus atom content is 7500 to 45000 ppm, and And a phosphorus atom content of 1,000 to 16000 ppm, and a melt-spinning method after adding a chain extender of 0.005 wt% to 1.5 wt% based on the total weight of the resin during melt spinning. The polyester fiber according to any one of <1> to <3>, wherein the spinning speed is 800 to 4000 m / min and the total elongation after spinning is 2.5 to 6.0 times. Manufacturing method.
<6> A phosphorus compound represented by the general formula (1) and a chain extender of 0.005 wt% to 1.5 wt% with respect to the total weight of the resin are blended so that the phosphorus atom content is 7500 to 45000 ppm. The polyester composition of 0.4 to 0.6 dlg / g is blended with an arbitrary polyester resin so that the phosphorus atom content becomes 1000 to 16000 ppm, and the spinning speed is set to 800 to 4000 m by a melt spinning method. The method for producing a polyester fiber according to any one of <1> to <3>, wherein the polyester fiber is drawn at a rate of / min and the total elongation after spinning is 2.5 to 6.0 times.

<7> A fiber structure comprising the polyester fiber according to any one of <1> to <3>.
<8> The fiber structure according to <7>, wherein the fiber structure is at least one type of structure selected from the group consisting of a yarn, a knit, a nonwoven fabric, a woven fabric, and another fiber structure. .

  According to the present invention, the melt-kneading of a phosphorus-based flame retardant has excellent flame retardancy even though it has a low phosphorus concentration, and is excellent in workability, excellent in thread properties such as strength, elongation, and toughness as compared with the related art. Flame retarded polyester fibers can be provided.

Hereinafter, the present invention will be described in detail.
(Polyester resin)
The polyester resin used in the production of the flame-retardant polyester fiber of the present invention is mainly a polyester obtained from an aromatic dicarboxylic acid or an ester-forming derivative thereof and a diol and an ester-forming derivative thereof as main starting materials. is there. As the dicarboxylic acid or its ester-forming derivative, specifically, phthalic acid, isophthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 4-diphenyldicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 5-tetra Butylphosphonium sulfoisophthalic acid, anthracene dicarboxylic acid, phenanthylene dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, benzophenone dicarboxylic acid, diphenoxyethane dicarboxylic acid, cyclohexane dicarboxylic acid, decalin dical Such as phosphate, dicarboxylic acids and their ester-forming derivatives such as tricyclodecane acid may be mentioned. Examples of the ester-forming derivatives include dimethyl ester, diethyl ester, dipropyl ester, dibutyl ester, dipentyl ester, dihexyl ester, diphenyl ester, and acid halides of dicarboxylic acid described above. One or more of these compounds may be used in combination, but it is preferable to use terephthalic acid or an ester-forming derivative thereof, and it is more preferable to use terephthalic acid or an ester-forming derivative thereof in a polyester from which a terephthalic acid or an ester-forming derivative thereof can be obtained. It is preferable to use 80 mol% or more based on the dicarboxylic acid component from the viewpoint of heat resistance.

Specific examples of diols and their ester-forming derivatives include ethylene glycol, trimethylene glycol, 1,2-propylene glycol, tetramethylene glycol, neopentyl glycol, hexamethylene glycol, cyclohexanedimethanol, octamethylene glycol, and decanediol. , Dodecanediol, tricyclo [5.2.1.0 ^2,6 ] decanedimethanol, polyethylene glycol, polypropylene glycol, 1,4-bis (β-hydroxyethoxy) benzene, 2,2-bis (p-β- Examples thereof include dihydroxy compounds of hydroxyethoxyphenyl) propane and bis (p-β-hydroxyethoxyphenyl) sulfone.

  Compounds other than the conventionally known dicarboxylic acid component and glycol component may be added as long as the constitutional requirements and objects of the present invention are not impaired. Examples of the third component to be added include an aliphatic oxycarboxylic acid (such as ω-hydroxycaproic acid) and an aromatic oxycarboxylic acid (such as p-hydroxybenzoic acid). Compounds having one or more ester-forming functional groups (alcohol, benzoic acid, etc. or glycerin, pentaerythritol, trimesic acid, trimellitic acid, etc.) are also within the range where the polymer is substantially linear. Can be used with

  It is preferable that the intrinsic viscosity (IV) of the polyester fiber be 0.5 to 1.3 dL / g in order to secure the tensile breaking strength and the breaking elongation of the polyester fiber or from the viewpoint of the productivity of the polyester fiber. If the polyester fiber is less than 0.5 dL / g, melt spinning is difficult, and high strength and high elongation physical properties are not compatible, so that a polyester fiber having high toughness cannot be obtained. In addition, when the viscosity exceeds 1.3 dL / g, the melt viscosity of the polyester is high, so that it is difficult to uniformly mix the phosphorus compound when melt-kneading the polyester with the phosphorus compound, or the melt spinning method is used. In the first various spinning methods, the spinnability is lowered, which may not be preferable.

The amount of the carboxyl terminal group (hereinafter referred to as CV amount) is set to 10 to 45 eq / T (equivalent / 10 ⁶ g) to suppress the IV reduction during spinning, and furthermore, the yarn in higher processing such as a dyeing step. It is preferable from the viewpoint of suppression of strength reduction and the like, more preferably 11 to 40 eq / T, still more preferably 12 to 39 eq / T, and still more preferably 15 to 38.5 eq / T.

  The content of phosphorus atoms used in the flame-retardant polyester fiber in the present invention must be 1,000 to 16,000 ppm based on the weight of the polyester fiber. If the content is less than 1,000 ppm, not only the flame retardancy is poor, but also the melting of the flame retardant. The effect of increasing the elongation (high toughness) by kneading becomes poor. On the other hand, if it exceeds 16000 ppm, it is necessary to increase the amount of the phosphorus compound containing a phosphorus atom. As a result, the IV of the polymer is lowered, and not only spinning becomes difficult but also the tensile strength at break and toughness of the obtained fiber. May also be unfavorable because it also decreases. It is preferably 1500 to 15300 ppm, more preferably 1800 to 15000 ppm, still more preferably 2000 to 14900 ppm, and most preferably 3500 to 8000 ppm.

(Organic phosphorus compound)
As the phosphorus-based flame retardant used for the flame-retardant polyester fiber of the present invention, a phosphorus compound represented by the following general formula (1) is used.

  The phosphorus compound represented by the formula (1) exhibits an extremely excellent flame retardant effect on the polyester fiber. As far as the present inventors know, it has been difficult to add a small amount of a flame retardant or to perform flame retardation by copolymerization in the conventional flame retardancy of halogen-free polyester fibers, and there are many practical problems. There was a point.

  However, according to the present invention, the phosphorus compound represented by the general formula (1) surprisingly easily achieves the flame retardancy of the polyester fiber by using a small amount of the phosphorus compound itself, and the inherent properties of the polyester fiber (Strength, elongation, knot strength, boiling water shrinkage, etc.) are not impaired. However, in the present invention, in addition to the phosphorus compound represented by the formula (1), another phosphorus compound, a fluorine-containing resin or another additive is used to reduce the use ratio of the phosphorus compound and to reduce the flame retardancy of the polyester fiber. Naturally, it can be incorporated for the purpose of improving, improving the physical properties of polyester fibers, improving the chemical properties of polyester fibers, or for other purposes. In the present invention, the phosphorus compound represented by the chemical structural formula of the above formula (1) needs to be blended so as to satisfy the above numerical range as the concentration of phosphorus atoms with respect to the weight of the polyester fiber. Indicates a state in which the phosphorus compound is dispersed in the polyester to form a composition, and the phosphorus compound itself or a partially decomposed phosphorus compound is copolymerized with the polyester main chain. It does not include the state that is being done.

  Next, a method for synthesizing the phosphorus compound in the present invention will be described. A typical production method of the phosphorus compound is shown below, but the phosphorus compound to be incorporated into the polyester fiber of the present invention may be one produced by a method other than the method described below. The phosphorus compound is obtained, for example, by reacting pentaerythritol with phosphorus trichloride, treating the oxidized reactant with an alkali metal compound such as sodium methoxide, and then reacting with benzyl halide.

  Further, it can also be obtained by a method of reacting aralkylphosphonic dichloride with pentaerythritol or a method of reacting benzyl alcohol with a compound obtained by reacting pentaerythritol with phosphorus trichloride and then performing Arbuzov transition at a high temperature. . The latter reaction is disclosed in, for example, U.S. Pat. No. 3,141,032, JP-A-54-157156 and JP-A-53-39698.

  The specific method of synthesizing the phosphorus compound will be described below. However, this synthesis method is merely for explanation, and the phosphorus compound used in the present invention includes not only these synthesis methods but also modifications and other synthesis methods. It may be synthesized by a method. A more specific synthesis method will be described in Preparation Examples described later.

(Method for synthesizing phosphorus compound of general formula (1))
The reaction product obtained by reacting pentaerythritol with phosphorus trichloride and then oxidizing with tert-butanol can be obtained by treating with sodium methoxide and reacting with benzyl bromide. Alternatively, it can be obtained by reacting pentaerythritol with phosphorus trichloride and subjecting the resulting product to a reaction product of benzyl alcohol with heat treatment in the presence of a catalyst.

  The phosphorus compound has an organic purity of preferably 97.0% or more and 100% or less, more preferably 98.0% or more and 99.99% or less, still more preferably 99.0% or more and 99.9% or less, as measured by HPLC. Less than 9% is used. By using the phosphorus compound having an organic purity in this range, it is possible to obtain a polyester fiber having both high flame retardancy and good physical properties. In particular, the organic purity affects the flame retardancy of the obtained polyester fiber, and when the organic purity is low, high flame retardancy cannot be obtained. Further, the phosphorus compound having a low organic purity may cause deterioration of the hue and physical properties of the polyester fiber obtained due to the influence of impurities, particularly, a reduction in heat resistance.

  Here, the measurement of the organic purity of the phosphorus compound by HPLC can be effectively performed by using the following method. The column used was Develosil ODS-7 300 mm × 4 mmφ manufactured by Nomura Chemical Co., Ltd., and the column temperature was 40 ° C. As a solvent, a mixed solution of acetonitrile and water 6: 4 (volume ratio) was used, and 5 μl was injected. The detector used UV-264 nm.

  As a method for removing impurities in the phosphorus compound and improving the organic purity, repulp washing (washing with a solvent, filtration with a solvent, such as water, an alcohol having 1 to 6 carbon atoms, or a ketone compound having 1 to 6 carbon atoms) can be used. Is the operation that is repeated several times.) Is the most effective and cost-effective. Here, examples of the alcohol having 1 to 6 carbon atoms include methanol, ethanol, isopropyl alcohol, normal propyl alcohol, butanol, pentyl alcohol, and hexyl alcohol. Examples of the ketone compound having 1 to 6 carbon atoms include acetone, Mention may be made of methyl ethyl ketone, diethyl ketone or ethyl propyl ketone. Among these compounds, water and ethanol, which are easily available, are more preferable. By performing the stirring while heating the mixture of the phosphorus compound and the solvent at the time of washing, more effective washing can be performed. It is difficult with a purification method such as ordinary recrystallization and distillation.

  The phosphorus compound preferably has a chlorine content of more than 0 ppm and 1000 ppm or less, more preferably 1 ppm or more and 500 ppm or less, and even more preferably 10 pm or more and 100 ppm or less. One of the objects of the present invention is to provide a halogen-free flame-retardant polyester fiber. Therefore, it is preferable to use the phosphorus compound having a chlorine content in this range. Further, by using the phosphorus compound having a chlorine content in this range, a polyester fiber having good heat stability and a polyester fiber having an excellent hue can be obtained. If the chlorine content exceeds this range, the thermal stability of the polyester fiber may be reduced, and the hue may be reduced due to the occurrence of burn during high-temperature molding. The chlorine content of the phosphorus compound can be effectively measured by performing analysis by a combustion method and detecting by a titration method in accordance with ASTM D5808.

  The phosphorus compound preferably has a pH variation value (ΔpH) of 0 to 1.0, more preferably 0.001 to 0.8, and still more preferably 0.01 to 0.5. Those, particularly preferably those of 0.05 or more and 0.3 or less, can be suitably used. Δ By using the phosphorus compound having a pH in this range, a polyester fiber having good heat stability can be obtained because the content of a trace amount of impurities such as a fluctuating pH is small, and the polyester fiber has excellent hue. Is obtained. Δ If the pH exceeds this range, the thermal stability of the polyester fiber may be reduced, and the hue may be reduced due to generation of burn during high-temperature molding.

The pH fluctuation value (ΔpH) of the phosphorus compound can be effectively measured by using the following method. That is, 99 g of distilled water and 1 g of a dispersant are mixed, stirred for 1 minute, and the pH is measured with a pH meter (the obtained pH value is set to pH 1). 1 g of the phosphorus compound is added to a mixed solution of the distilled water and the dispersant, and the mixture is stirred for 1 minute. The mixture after stirring is filtered, and the pH of the filtrate is measured with a pH meter (the obtained pH value is referred to as pH 2). The ΔpH of the present invention can be calculated by the following equation (α).
ΔpH = | pH1−pH2 | (α)
That is, the pH fluctuation value (△ pH) is the absolute value of the difference between the above pH1 and pH2.

  Further, the phosphorus compound preferably has a residual solvent amount of more than 0 ppm and 1000 ppm or less, more preferably 1 ppm or more and 800 ppm or less, still more preferably 5 ppm or more and 500 ppm or less, particularly preferably 10 ppm or more and 100 ppm or less. Can be suitably used. By using the phosphorus compound having a residual solvent amount in this range, a polyester fiber having high flame retardancy can be obtained. Polyolefin resins generally have low flame retardancy, and it is difficult to obtain desired flame retardancy when the phosphorus compound having a residual solvent amount exceeding this range is used. The amount of the residual solvent of the phosphorus compound can be effectively measured by a method similar to the method of measuring organic purity using HPLC.

  In order to keep the properties of the phosphorus compound such as the organic purity, chlorine content, pH fluctuation value, and residual solvent amount within a predetermined numerical range, it is preferable to sufficiently purify at the final stage of the above-mentioned synthesis method. Specifically, in a manufacturing process other than the final step, unreacted raw material compounds and by-products are sufficiently removed from the phosphorus compound generated by using a purification means such as washing, filtration, recrystallization, or distillation. Can be preferably selected. More preferably, the above-described repulp washing method is employed. However, in the final purification step, it is important to employ the above-described repulp washing method.

  The phosphorus compound is blended in an amount of 0.01 to 30% by weight, preferably 0.5 to 25% by weight, more preferably 1 to 20% by weight based on the weight of the polyester composition containing the phosphorus compound. The preferred range of the compounding ratio of the phosphorus compound is determined depending on the desired flame retardancy level, the type of the polyester resin, and the like. Even if other than the polyester resin and the phosphorus-based compound constituting these compositions, other components can be used as necessary as long as the object of the present invention is not impaired.Other flame retardants, flame retardant assistants, The compounding amount of the phosphorus compound can also be changed by using a fluorine-containing resin, and in many cases, the compounding ratio of the phosphorus compound can be reduced by using these compounds.

  When producing the polyester fiber of the present invention, the phosphorus compound represented by the above formula (1) is blended in an amount of 1000 to 16000 ppm based on the weight of the polyester composition, similarly to the polyester fiber degree. It is preferable to use a polyester composition.

(Chain extender)
Chain extenders are used to reduce the molecular chain of the polyester due to heat and external forces during the production and processing of the polyester, reducing the viscosity and reducing the processability and strength of the product. Is a substance added for the purpose of maintaining the apparent length of the polyester molecular chain by connecting. Since the terminal group of the polyester molecule is often a carboxyl group or a hydroxyl group, the chain extender used in the present invention must be a compound having a reactive functional group that reacts with the carboxyl group or the hydroxyl group. Is preferred. Specific examples include functional groups having reactivity with chain extension with the terminal functional groups of the polyester, such as isocyanate groups, epoxy groups, carbodiimide groups, oxazoline groups, melamine structures, and silane coupling agents.

  Epoxy group-containing compounds that can be used as chain extenders include glycidyl methacrylate, ethylene glycol diglycidyl ether, butanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, neopentyl glycol diglycidyl ether, Glycidyl ether compounds such as methylolpropane polyglycidyl ether, polypropylene glycol diglycidyl ether, allyl glycidyl ether, benzyl glycidyl ether, 9,9-bis (4-glycidyloxyphenyl) fluorene, glycidyl methacrylate, glycerin dimethacrylate, 2-hydroxy- 3-acryloyloxypropyl methacrylate, ethylene glycol dimethacrylate , Diethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, polypropylene glycol dimethacrylate, polypropylene glycol diacrylate, polytetramethylene glycol dimethacrylate, polytetramethylene glycol diacrylate, poly (ethylene glycol-tetramethylene glycol) dimethacrylate , Poly (ethylene glycol-tetramethylene glycol) diacrylate, poly (propylene glycol-tetramethylene glycol) dimethacrylate, poly (propylene glycol-tetramethylene glycol) diacrylate, polyethylene glycol-polypropylene glycol dimethacrylate, polyethylene glycol-poly Glycidyl esters such as Russia propylene glycol diacrylate and the like. The compound may contain a phosphorus atom.

  Examples of the chain extender, which is an epoxy group-containing compound, include ADR-4300-S (epoxy group-containing acrylic / styrene copolymer) manufactured by Allinco, DSM and BASF.

  The carbodiimide group-containing compound is a compound having at least one carbodiimide group (-N = C = N-) in a molecule. Specifically, dimethylcarbodiimide, diethylcarbodiimide, dipropylcarbodiimide, N, N′-dicyclohexylcarbodiimide, bis (trimethylsilyl) carbodiimide, bis (2,2-dimethyl-1,3-dioxolan-4-ylmethyl) carbodiimide, bis (2,6-diisopropylphenyl) carbodiimide can be mentioned. Further, a (co) polymer using a polyvalent isocyanate compound is preferable. Specific examples of the polyvalent isocyanate include, for example, hexamethylene diisocyanate, xylene diisocyanate, cyclohexane diisocyanate, pyridine diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4-diphenylmethane diisocyanate, p- Examples include phenylenediissocyanates, m-phenylenediissocyanates, and 1,5-naphthylene diisocyanate. Among them, cyclohexane diisocyanate and 2,4-tolylene diisocyanate are preferably used.

Examples of the chain extender include Carbodilite (registered trademark) HMV-8CA (trade name) and Carbodilite (same as above) LA-1 (trade name) manufactured by Nisshinbo Chemical Co., Ltd.
As the carbodiimide group-containing compound, a compound having a cyclic structure is also preferably used.

  The cyclic carbodiimide compound may have a plurality of cyclic structures. The cyclic structure has one carbodiimide group (-N = C = N-) and the primary nitrogen atom and the secondary nitrogen atom are bonded by a bonding group. One cyclic structure has only one carbodiimide group. The number of atoms in the cyclic structure is 8 to 50, preferably 10 to 30, more preferably 10 to 20, and most preferably 10 to 15. The cyclic structure is a structure represented by the following formula (5).

  In the above formula (5), Q is a divalent to tetravalent bonding group represented by the following formula (5-1), (5-2) or (5-3).

In the above formula, Ar ¹ and Ar ² are each independently a divalent to tetravalent C 5 to C 15 aromatic group which may contain a hetero atom and a substituent.
As an aromatic group, a C 5 -C 15 arylene group, a C 5 -C 15 arenetriyl group, or a C 5 -C 15 arene tetra group, each of which may have a heterocyclic structure containing a hetero atom. And an yl group. Examples of the arylene group (divalent) include a phenylene group and a naphthalenediyl group. Arenetriyl groups (trivalent) include a benzenetriyl group and a naphthalenetriyl group. Examples of the arenetetrayl group (tetravalent) include a benzenetetrayl group and a naphthalenetetrayl group. These aromatic groups may contain a substituent, and as the substituent, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 15 carbon atoms, a halogen atom, a nitro group, an amide group, a hydroxyl group, an ester Groups, ether groups, aldehyde groups and the like.
R ¹ and R ² each independently may contain a heteroatom and a substituent, and may have a divalent or tetravalent aliphatic group having 1 to 20 carbon atoms or a divalent or tetravalent aliphatic group having 3 to 20 carbon atoms. It is a cyclic group, a combination thereof, or a combination of an aliphatic group, an alicyclic group and a divalent to tetravalent aromatic group having 5 to 15 carbon atoms.

  Examples of the aliphatic group include an alkylene group having 1 to 20 carbon atoms, an alkanetriyl group having 1 to 20 carbon atoms, and an alkanetetrayl group having 1 to 20 carbon atoms. Examples of the alkylene group include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, a dodecylene group, and a hexadecylene group. As the alkanetriyl group, a methanetriyl group, an ethanetriyl group, a propanetriyl group, a butanetriyl group, a pentanetriyl group, a hexanetriyl group, a heptanetriyl group, an octanetriyl group, a nonanthryl group, a decanetriyl group, a dodecanetriyl group, And a hexadecanetriyl group. As alkanetetrayl groups, methanetetrayl group, ethanetetrayl group, propanetetrayl group, butanetetrayl group, pentanetetrayl group, hexanetetrayl group, heptanetetrayl group, octanetetrayl group, nonanetetrayl group , Decanetetrayl group, dodecanetetrayl group, hexadecanetetrayl group and the like. These aliphatic groups may contain a substituent, and as the substituent, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 15 carbon atoms, a halogen atom, a nitro group, an amide group, a hydroxyl group, an ester Groups, ether groups, aldehyde groups and the like.

  Examples of the alicyclic group include a cycloalkylene group having 3 to 20 carbon atoms, a cycloalkanetriyl group having 3 to 20 carbon atoms, and a cycloalkanetetrayl group having 3 to 20 carbon atoms. Examples of the cycloalkylene group include a cyclopropylene group, a cyclobutylene group, a cyclopentylene group, a cyclohexylene group, a cycloheptylene group, a cyclooctylene group, a cyclononylene group, a cyclodecylene group, a cyclododecylene group, and a cyclohexadecylene group. As the cycloalkanetriyl group, cyclopropanetriyl group, cyclobutanetriyl group, cyclopentanetriyl group, cyclohexanetriyl group, cycloheptanetriyl group, cyclooctanetriyl group, cyclononantriyl group, cyclodecanetriyl group Group, cyclododecanetriyl group, cyclohexadecanetriyl group and the like. As cycloalkanetetrayl groups, cyclopropanetetrayl group, cyclobutanetetrayl group, cyclopentanetetrayl group, cyclohexanetetrayl group, cycloheptanetetrayl group, cyclooctanetetrayl group, cyclononanetetrayl group, cyclodecanetetrayl group Yl group, cyclododecanetetrayl group, cyclohexadecanetetrayl group and the like. These alicyclic groups may contain a substituent, and as the substituent, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 15 carbon atoms, a halogen atom, a nitro group, an amide group, a hydroxyl group, Examples include an ester group, an ether group, and an aldehyde group.

As an aromatic group, a C 5 -C 15 arylene group, a C 5 -C 15 arenetriyl group, or a C 5 -C 15 arene tetra group, each of which may have a heterocyclic structure containing a hetero atom. And an yl group. Examples of the arylene group include a phenylene group and a naphthalenediyl group. Arenetriyl groups (trivalent) include a benzenetriyl group and a naphthalenetriyl group. Examples of the arenetetrayl group (tetravalent) include a benzenetetrayl group and a naphthalenetetrayl group. These aromatic groups may contain a substituent, and as the substituent, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 15 carbon atoms, a halogen atom, a nitro group, an amide group, a hydroxyl group, an ester group , An ether group, an aldehyde group and the like.
X ¹ and X ² each independently may contain a heteroatom and a substituent, and may have a divalent or tetravalent aliphatic group having 1 to 20 carbon atoms or a divalent or tetravalent aliphatic group having 3 to 20 carbon atoms. It is a cyclic group, a divalent to tetravalent aromatic group having 5 to 15 carbon atoms, or a combination thereof.

  Examples of the aliphatic group include an alkylene group having 1 to 20 carbon atoms, an alkanetriyl group having 1 to 20 carbon atoms, and an alkanetetrayl group having 1 to 20 carbon atoms. Examples of the alkylene group include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, a dodecylene group, and a hexadecylene group. As the alkanetriyl group, a methanetriyl group, an ethanetriyl group, a propanetriyl group, a butanetriyl group, a pentanetriyl group, a hexanetriyl group, a heptanetriyl group, an octanetriyl group, a nonanthryl group, a decanetriyl group, a dodecanetriyl group, And a hexadecanetriyl group. As alkanetetrayl groups, methanetetrayl group, ethanetetrayl group, propanetetrayl group, butanetetrayl group, pentanetetrayl group, hexanetetrayl group, heptanetetrayl group, octanetetrayl group, nonanetetrayl group , Decanetetrayl group, dodecanetetrayl group, hexadecanetetrayl group and the like. These aliphatic groups may contain a substituent. Examples of the substituent include an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 15 carbon atoms, a halogen atom, a nitro group, an amide group, a hydroxyl group, an ester group, an ether group, and an aldehyde group.

  Examples of the alicyclic group include a cycloalkylene group having 3 to 20 carbon atoms, a cycloalkanetriyl group having 3 to 20 carbon atoms, and a cycloalkanetetrayl group having 3 to 20 carbon atoms. Examples of the cycloalkylene group include a cyclopropylene group, a cyclobutylene group, a cyclopentylene group, a cyclohexylene group, a cycloheptylene group, a cyclooctylene group, a cyclononylene group, a cyclodecylene group, a cyclododecylene group, and a cyclohexadecylene group. As the alkanetriyl group, cyclopropanetriyl group, cyclobutanetriyl group, cyclopentanetriyl group, cyclohexanetriyl group, cycloheptanetriyl group, cyclooctanetriyl group, cyclononantriyl group, cyclodecanetriyl group , Cyclododecanetriyl group, cyclohexadecanetriyl group and the like. As the alkanetetrayl group, cyclopropanetetrayl group, cyclobutanetetrayl group, cyclopentanetetrayl group, cyclohexanetetrayl group, cycloheptanetetrayl group, cyclooctanetetrayl group, cyclononanetetrayl group, cyclodecanetetrayl Group, cyclododecanetetrayl group, cyclohexadecanetetrayl group and the like. These alicyclic groups may contain a substituent, and as the substituent, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 15 carbon atoms, a halogen atom, a nitro group, an amide group, a hydroxyl group, Examples include an ester group, an ether group, and an aldehyde group.

  As an aromatic group, a C 5 -C 15 arylene group, a C 5 -C 15 arenetriyl group, or a C 5 -C 15 arene tetra group, each of which may have a heterocyclic structure containing a hetero atom. And an yl group. Examples of the arylene group include a phenylene group and a naphthalenediyl group. Arenetriyl groups (trivalent) include a benzenetriyl group and a naphthalenetriyl group. Examples of the arenetetrayl group (tetravalent) include a benzenetetrayl group and a naphthalenetetrayl group. These aromatic groups may contain a substituent, and as the substituent, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 15 carbon atoms, a halogen atom, a nitro group, an amide group, a hydroxyl group, an ester Groups, ether groups, aldehyde groups and the like.

In the formulas (5-1) and (5-2), s and k are an integer of 0 to 10, preferably an integer of 0 to 3, and more preferably an integer of 0 to 1. If s and k exceed 10, the synthesis of the cyclic carbodiimide compound becomes difficult, and the cost may increase significantly. From this viewpoint, the integer is preferably selected from the range of 0 to 3. When s or k is 2 or more, X ¹ or X ² as a repeating unit may be different from other X ¹ or X ² .
X ³ may each contain a heteroatom and a substituent, and may have a divalent or tetravalent aliphatic group having 1 to 20 carbon atoms, a divalent or tetravalent alicyclic group having 3 to 20 carbon atoms, It is a tetravalent aromatic group having 5 to 15 carbon atoms, or a combination thereof.

  Examples of the aliphatic group include an alkylene group having 1 to 20 carbon atoms, an alkanetriyl group having 1 to 20 carbon atoms, and an alkanetetrayl group having 1 to 20 carbon atoms. Examples of the alkylene group include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, a dodecylene group, and a hexadecylene group. As the alkanetriyl group, a methanetriyl group, an ethanetriyl group, a propanetriyl group, a butanetriyl group, a pentanetriyl group, a hexanetriyl group, a heptanetriyl group, an octanetriyl group, a nonanthryl group, a decanetriyl group, a dodecanetriyl group, And a hexadecanetriyl group. As alkanetetrayl groups, methanetetrayl group, ethanetetrayl group, propanetetrayl group, butanetetrayl group, pentanetetrayl group, hexanetetrayl group, heptanetetrayl group, octanetetrayl group, nonanetetrayl group , Decanetetrayl group, dodecanetetrayl group, hexadecanetetrayl group and the like. These aliphatic groups may contain a substituent, and as the substituent, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 15 carbon atoms, a halogen atom, a nitro group, an amide group, a hydroxyl group, an ester group , An ether group, an aldehyde group and the like.

  Examples of the alicyclic group include a cycloalkylene group having 3 to 20 carbon atoms, a cycloalkanetriyl group having 3 to 20 carbon atoms, and a cycloalkanetetrayl group having 3 to 20 carbon atoms. Examples of the cycloalkylene group include a cyclopropylene group, a cyclobutylene group, a cyclopentylene group, a cyclohexylene group, a cycloheptylene group, a cyclooctylene group, a cyclononylene group, a cyclodecylene group, a cyclododecylene group, and a cyclohexadecylene group. As the alkanetriyl group, cyclopropanetriyl group, cyclobutanetriyl group, cyclopentanetriyl group, cyclohexanetriyl group, cycloheptanetriyl group, cyclooctanetriyl group, cyclononantriyl group, cyclodecanetriyl group , Cyclododecanetriyl group, cyclohexadecanetriyl group and the like. As the alkanetetrayl group, cyclopropanetetrayl group, cyclobutanetetrayl group, cyclopentanetetrayl group, cyclohexanetetrayl group, cycloheptanetetrayl group, cyclooctanetetrayl group, cyclononanetetrayl group, cyclodecanetetrayl Group, cyclododecanetetrayl group, cyclohexadecanetetrayl group and the like. These alicyclic groups may contain a substituent, and as the substituent, an alkyl group having 1 to 20 carbon atoms, an arylene group having 6 to 15 carbon atoms, a halogen atom, a nitro group, an amide group, a hydroxyl group, an ester Groups, ether groups, aldehyde groups and the like.

  As an aromatic group, a C 5 -C 15 arylene group, a C 5 -C 15 arenetriyl group, or a C 5 -C 15 arene tetra group, each of which may have a heterocyclic structure containing a hetero atom. And an yl group. Examples of the arylene group include a phenylene group and a naphthalenediyl group. Arenetriyl groups (trivalent) include a benzenetriyl group and a naphthalenetriyl group. Examples of the arenetetrayl group (tetravalent) include a benzenetetrayl group and a naphthalenetetrayl group. These aromatic groups may contain a substituent, and as the substituent, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 15 carbon atoms, a halogen atom, a nitro group, an amide group, a hydroxyl group, an ester Groups, ether groups, aldehyde groups and the like.

Ar ¹ , Ar ² , R ¹ , R ² , X ¹ , X ² and X ³ may contain a hetero atom. When Q is a divalent linking group, Ar ¹ , Ar ² , R ¹ , R ² , X ¹ , X ² and X ³ are all divalent groups. When Q is a trivalent linking group, one of Ar ¹ , Ar ² , R ¹ , R ² , X ¹ , X ² and X ³ is a trivalent group. When Q is a tetravalent linking group, one of Ar ¹ , Ar ² , R ¹ , R ² , X ¹ , X ² and X ³ is a tetravalent group, or two are trivalent groups. Group.

  Examples of the cyclic carbodiimide used in the present invention include the compounds represented by the formulas (5), (7) and (8).

<Cyclic carbodiimide (2)>

In the above formula, Q is a divalent linking group represented by the following formula (6-1), (6-2) or (6-3).

In the above formula, _Ar ^{a 1} and _Ar ^{a 2} are each independently a divalent aromatic group having 5 to 15 carbon atoms. The R _a ¹ and _R ^{a 2} are each independently a divalent aliphatic group having 1 to 20 carbon atoms, a divalent alicyclic group having 3 to 20 carbon atoms, and combinations thereof, or their aliphatic group, It is a combination of an alicyclic group and a divalent aromatic group having 5 to 15 carbon atoms. sa is an integer of 0 to 10. ka is an integer of 0-10. To X _a ¹ and _X ^{a 2} each independently, a divalent aliphatic C1-20 group, a divalent alicyclic group having 3 to 20 carbon atoms, divalent aromatic 5 to 15 carbon atoms Group, or a combination thereof. X _a ³ is a divalent aliphatic group having 1 to 20 carbon atoms, a divalent alicyclic group having 3 to 20 carbon atoms, a divalent aromatic group having 5 to 15 carbon atoms, or a combination thereof. is there. ^{_{However, Ar a 1, Ar a 2}} , R a 1, R a 2, X a 1, X a 2 , and _X ^{a 3} may contain a hetero atom. Examples of such a cyclic carbodiimide compound (2) include the following compounds.

<Cyclic carbodiimide (3)>

In the above formula, Q _b (b is a subscript, the same applies hereinafter) is a trivalent linking group represented by the following formula (7-1), (7-2) or (7-3), and Y is It is a carrier that carries a ring structure.

In the above _{^{formula, Ar b 1, Ar b 2}} , R b 1, R b 2, X b 1, X b 2, X b 3, s b and _{k b} are each formula (5-1) to (5- The same as Ar ¹ , Ar ² , R ¹ , R ² , X ¹ , X ² , X ³ , s and k in ³ ). However, one of these is a trivalent group.
Y is a single bond, a double bond, an atom, an atomic group, or a polymer. Y is a bonding portion, and a plurality of cyclic structures are bonded via Y to form a structure represented by Formula (7). Examples of such a cyclic carbodiimide compound (7) include the following compounds.

<Cyclic carbodiimide (4)>

In the above formula, Q _c (c is a subscript, hereinafter the same) is a tetravalent linking group represented by the following formula (8-1), (8-2) or (8-3), and Z ¹ And Z ² are carriers carrying a cyclic structure. Z ¹ and Z ² may combine with each other to form a cyclic structure.

^{_{Ar c 1, Ar c 2,}} R c 1, R c 2, X c 1, X c 2, X c 3, s c and _{k c} are each formula (5-1) to (5-3), The same as Ar ¹ , Ar ² , R ¹ , R ² , X ¹ , X ² , X ³ , s and k. ^{_{However, Ar c 1, Ar c 2}} , R c 1, R c 2, X c 1, X c 2 and _X ^{c 3} is either one of these is a tetravalent group, two trivalent Group.
Z ¹ and Z ² are each independently a single bond, a double bond, an atom, an atomic group or a polymer. Z ¹ and Z ² are bonding portions, and a plurality of cyclic structures are bonded via Z ¹ and Z ² to form a structure represented by Formula (8). Examples of such a cyclic carbodiimide compound (8) include the following compounds.

  Among the above carbodiimide compounds, it is preferable to use a compound having two or more rings containing a carbodiimide group per molecule of the compound from the viewpoint of a large chain elongation effect.

(Oxazoline compound)
As the oxazoline compound, a polymer containing an oxazoline group is preferable. Such a polymer can be prepared by polymerization of an addition-polymerizable oxazoline group-containing monomer alone or with another monomer. The addition-polymerizable oxazoline group-containing monomer is 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, Examples thereof include 2-isopropenyl-4-methyl-2-oxazoline and 2-isopropenyl-5-ethyl-2-oxazoline. One or a mixture of two or more of these can be used. Among these, 2-isopropenyl-2-oxazoline is easily available industrially and is suitable, and copolymerization at a ratio where the content of the oxazoline group in the polymer is 1 to 10 mmol / g is preferable. It is preferable from the point of view. The other monomer is not limited as long as it is a monomer copolymerizable with an addition-polymerizable oxazoline group-containing monomer, and examples thereof include an alkyl acrylate and an alkyl methacrylate (as the alkyl group, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a (meth) acrylic acid esters such as n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group and cyclohexyl group; acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, Unsaturated carboxylic acids such as styrenesulfonic acid and salts thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); unsaturated nitriles such as acrylonitrile, methacrylonitrile; acrylamide, methacrylamide, N-alkyl Acrylamide, N-alkyl methacrylamide , N, N-dialkylacrylamide, N, N-dialkylmethacrylate (alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl Amides, cyclohexyl group, etc.); vinyl esters, such as vinyl acetate and vinyl propionate; vinyl ethers, such as methyl vinyl ether and ethyl vinyl ether; α-olefins, such as ethylene and propylene; vinyl chloride, vinylidene chloride And α-, β-unsaturated monomers such as vinyl fluoride; α, β-unsaturated aromatic monomers such as styrene and α-methylstyrene; and one or more of these. Monomers can be used.

  As the melamine compound, a methylol melamine derivative obtained by condensing melamine and formaldehyde, a compound obtained by reacting these with lower alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol, and a mixture thereof are preferable. Examples of the methylol melamine derivative include monomethylol melamine, dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, hexamethylol melamine and the like.

  Examples of the isocyanate compound include tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate, metaxylylene diisocyanate, hexamethylene-1,6-diisocyanate, an adduct of tolylene diisocyanate and hexanetriol, and tolylene diisocyanate and trimethylol. Propane adduct, polyol-modified diphenylmethane-4,4'-diisocyanate, carbodiimide-modified diphenylmethane-4,4'-diisocyanate, isophorone diisocyanate, 1,5-naphthalenediisocyanate, 3,3'-vitrilen-4,4'-diisocyanate , 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, metaphenylene diisocyanate and the like.

Examples of the coupling agent include a silane coupling agent is indicated, for example, by general formula YRSiW _3. Here, Y is an organic functional group such as a vinyl group, an epoxy group, an amino group, and a mercapto group; R is an alkylene group such as a methylene, ethylene, and propylene group; W is a hydrolyzing group such as a methoxy group and an ethoxy group; An alkyl group (at least one X in the molecule is a hydrolyzable group). It is particularly preferred that the Y moiety is an epoxy group. Specific preferred silane coupling agents include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and the like. In addition, organometallic compounds containing metals such as zirconium, titanium, and aluminum are preferably classified into alkoxides, chelates, and acylates. Specific examples include zirconium tetraacetylacetonate, zirconium acetate, titanium acetylacetonate, triethanolamine titanate, titanium lactate, and the like, but are not limited thereto.

  It is necessary to blend the content of the chain extender so as to be 0.005 to 1.5 wt% based on the weight of the polyester fiber. It is preferably 0.01 to 1.2 wt%, more preferably 0.03 to 1.0 wt%, and still more preferably 0.004 to 0.8 wt%, based on the weight of the polyester fiber. When the content is less than 0.005 wt%, the effect of increasing the intrinsic viscosity of the polyester resin constituting the polyester fiber is extremely small, and no improvement in workability is observed. On the other hand, if it exceeds 1.5% by weight, the melt viscosity of the polyester composition will increase too much and the processing performance will worsen.

  In addition, when manufacturing the polyester fiber of the present invention, it is preferable to perform a melt spinning method and then to perform a drawing operation. For example, after the polyester, the phosphorus compound represented by the formula (1), and the chain extender are dry-blended, the mixture is melt-kneaded by an extruder at a temperature of 200 to 300 ° C. to obtain a polyester composition. It can be introduced into the spinning process. At this time, for example, a polyester composition having an intrinsic viscosity of 0.5 to 1.3 dL / g in which the phosphorus compound represented by the formula (1) is blended so that the phosphorus atom content is 1000 to 16000 ppm. Using, after spinning, a method of winding the undrawn yarn and drawing separately, a method of performing continuous drawing without winding the undrawn yarn once, and after cooling and solidifying the undrawn yarn in a coagulation bath after melt spinning. For example, a method of stretching in a heating medium or under contact heating such as a heating roller or by a non-contact type heater is employed.

Regarding the spinning speed, the spinning speed is 800 to 4000 m / min. When the spinning speed is less than 800 m / min, an undrawn yarn having a relatively high degree of orientation cannot be obtained, and when the spinning speed exceeds 4000 m / min, the oriented crystallization of the undrawn yarn is promoted and high strength is obtained. Not suitable for conversion.
Here, when the melt-spun undrawn yarn is drawn, if the total drawing ratio (total drawing ratio) is set to be in the range of 2.5 to 6.0 times, the fiber of the finally obtained fiber is obtained. The tensile strength can be achieved at a high level, the yarn breakage rate in the stretching step is low, and the productivity is further improved. The total stretching ratio is more preferably in the range of 2.8 to 5.5 times, and particularly preferably in the range of 3.0 to 5.0 times. The stretching step may be performed only in one-stage stretching or may be performed in two or more stages. For example, when a two-stage stretching method is adopted, the stretching ratio in the first stage is 2.0 to 5.5 times, and May be adjusted to about 1.0 to 2.0 times, and the total stretching ratio may be adjusted to 2.5 to 6.0 times.

As a method of adding the chain extender, a method of directly adding the chain extender to the polyester composition at the time of melt spinning, or in advance, when making a thick polyester resin having a concentration of 7500 to 45000 ppm, the chain extender is also added. There is also a method. In this case, it is necessary to determine the amount to be added in consideration of the dilution ratio so that the effect of the chain extender is obtained after dilution.
The polyester fiber of the present invention produced by such an operation has a breaking tensile strength of 2.0 to 6.5 cN / dtex, preferably 2.1 to 6.1 cN / dtex, more preferably 2.2 to 6.2 cN / dtex. It is 6.0 cN / dtex, more preferably 3.0 to 5.8 cN / dtex. The breaking elongation of the polyester fiber is 20 to 80%, preferably 22 to 75%, more preferably 24 to 73%, and still more preferably 25 to 50%. Further, the toughness calculated by (tensile strength at break) × (elongation at break) ^0.5 = (tensile strength at break) √ (elongation at break) is 19.0 to 30.0, preferably 19.5 to 29. 7, more preferably 19.6 to 29.5, even more preferably 20.5 to 28.0.

  The polyester fiber obtained in this manner may be used for woven or knitting as it is or after performing bulky processing, or may be used for woven or knitting after being mixed with or combined with other fibers. These polyester fibers may contain a small amount of other optional polymers, antioxidants, antistatic agents, dye improvers, dyes, pigments, matting agents and other additives.

  The polyester fiber in the present invention can be used as it is or after being subjected to the above-described processing, for various fiber structure applications including the polyester fiber. As the fibrous structure, any structure that can take fibers, such as yarn, fibrous, cord-like, woven, knitted, non-woven fabric, felt, papermaking, three-dimensional net-like, cotton-like, sheet-like material, can be preferably used. Among them, preferred is a fiber structure characterized by being at least one kind of fiber structure selected from the group consisting of a yarn, a string, a processed yarn, a net, a knit, a nonwoven fabric and a woven fabric. These fiber mulberry bodies can be arbitrarily selected according to the purpose from the production methods generally known to those skilled in the art.

  The polyester fiber of the present invention can be produced as described above, but the polyester composition containing the phosphorus compound represented by the above formula (1) need not be 1000 to 16000 ppm from the beginning. As another method, a polyester composition having a higher concentration of phosphorus atoms in the range of 7500 to 45000 ppm is prepared, and a predetermined amount is blended with the polyester composition and any kind of polyester during the production of polyester fiber. In addition, a method in which the total phosphorus compound concentration is adjusted to 1000 to 16000 ppm and then introduced into a spinning machine is also suitably used. This method has the advantage that the phosphorus content can be easily adjusted even if the required flame retardancy varies depending on the basis weight and shape of the polyester fiber product. In addition, since it is possible to avoid a situation where the phosphorus content is initially reduced by additives such as a pigment and a functional agent, the handleability is high. Furthermore, there is an advantage that the above-mentioned “any type of polyester” is less likely to be exposed to a molten state for a long time during melt spinning, and that the resulting fibers have good hue and the like. In the production of the polyester composition having a high phosphorus atom concentration, a chain extender may be added together with the phosphorus compound.

  The method for producing a polyester resin having a concentration of 7500 to 45000 ppm is not limited to one type. For example, using a twin-screw extruder equipped with a vent, the polyester resin is melted at 200 to 300 ° C. Then, there is a method in which a powdered phosphorus compound is charged and kneaded. However, the method is not limited to this. For example, a method in which a polyester resin and a phosphorus compound are dry-blended in advance and then charged into a twin-screw extruder is also used. The temperature at the time of melt-kneading is preferably from 201 to 250 ° C. More preferably, the temperature is set to 210 to 235 ° C.

  Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples. The evaluation was performed by the following method.

(A) Organic Purity The column used was Develosil ODS-7 300 mm × 4 mmφ manufactured by Nomura Chemical Co., Ltd., and the column temperature was 40 ° C. As a solvent, a mixed solution of acetonitrile and water 6: 4 (volume ratio) was used, and 5 μL was injected. The detector used UV-264 nm. Based on the measurement results, the area ratio was defined as the organic purity.

(B) Chlorine content According to ASTM D5808, analysis was performed by a combustion method and detected by a titration method.

(C) △ pH
99 g of distilled water and 1 g of a dispersant (ethanol) are mixed, stirred for 1 minute, and the pH is measured with a pH meter (the obtained pH value is referred to as “pH 1”). 1 g of the above organic phosphorus compound is added to the mixed solution of the distilled water and the dispersant, and the mixture is stirred for 1 minute. The mixture after stirring is filtered, and the pH of the filtrate is measured with a pH meter (the obtained pH value is referred to as “pH 2”). ΔpH was calculated by the following equation (α).
ΔpH = | pH1-pH2 | (α)

(D) Amount of residual solvent The column used was Develosil ODS-7 300 mm × 4 mmφ manufactured by Nomura Chemical Co., Ltd., and the column temperature was 40 ° C. As a solvent, a mixed solution of acetonitrile and water 6: 4 (volume ratio) was used, and 5 μL was injected. The detector used UV-264 nm. The amount of residual solvent was calculated using a separately prepared calibration curve.

(E) Oxygen index (LOI evaluation)
The measurement was performed according to JIS-K-7201. The higher the value, the better the flame retardancy.

(F) Intrinsic viscosity (IV)
The intrinsic viscosity number was determined by weighing a fixed amount of a chip or polyester fiber sample, dissolving it in o-chlorophenol at a concentration of 0.012 g / ml, cooling it once, and cooling the solution at 35 ° C using an Ubbelohde viscometer. It was calculated from the solution viscosity measured under temperature conditions.

(G) Concentration of Phosphorus Element Contained It was measured from a cylindrical knitted article by a fluorescent X-ray (Rataflex RU200, manufactured by Rigaku) by an ordinary method.

(H) Identification of Chemical Structure The primary structure of the polyester constituting the polyester fiber obtained according to the present invention is obtained by dissolving a polyester fiber sample in hexafluoroisopropanol and measuring ¹ H-NMR using JEOLA-600 manufactured by JEOL Ltd. And assigned from the obtained spectrum. The compounded phosphorus compound is obtained by dissolving a polyester fiber sample in a good solvent such as hexafluoroisopropanol and performing reprecipitation treatment with a poor solvent such as dimethylformamide (DMF) to extract the phosphorus compound from the solution component. In the same manner, ¹ H-NMR was measured, and it was assigned from the obtained spectrum, and the chemical structure was identified.

(I) Tensile strength, elongation, toughness, fineness The tensile strength at break and elongation (elongation at break) were measured according to the method described in Japanese Industrial Standards, JIS L1013: 1999 8.5. Further, the toughness was determined from the tensile strength at break and the elongation by the following formula. Toughness can be an index that simply represents the energy of the breaking strength of the polyester fiber. The fineness was measured according to the method described in JIS L1013: 1999 8.3.
(Toughness) = (Tensile strength at break: cN / dtex) × √ (Elongation at break:%) = (Tensile strength at break) × (Elongation at break) ^0.5

(J) Terminal carboxysyl group amount (CV amount)
After dissolving the polyester fiber comprising the obtained polyester composition in benzyl alcohol at 200 ° C. under a nitrogen atmosphere, the amount of terminal carboxyl groups (equivalents / 10 ⁶ g) is determined by titration as the number of equivalents per 1 t of polyester weight. = Eq / T).

(K) Evaluation of spinnability Spinnability can be evaluated by the number of yarn breaks during spinning.
The point at which the resin starts to come out from the pack in the form of a thread is defined as the starting point (0 minute), and the number of times of thread breakage during 60 minutes is counted. When the number of times of yarn breakage was 0 to 1, the spinning property was good (良好), the spinning property was unstable (△), 2 to 5 times, and spinning was impossible (X). The reason why the spinning property is unstable (△) for 2 to 5 times is that the spinning property may be improved by changing the spinning conditions.

(L) Method for quantifying the content of a chain extender When the chain extender has an isocyanate group, a carbodiimide group, an oxazoline group, or a melamine structure, a fluorescent X-ray measurement of the polyester fiber is performed to measure and evaluate the nitrogen atom content. When a silane coupling agent was used, the X-ray fluorescence of the polyester fiber was measured in the same manner, and the content was determined by measuring and evaluating the silicon atom content.
When the chain extender was an epoxy group-containing compound, a polyester fiber sample was dissolved in about 0.6 mL of a 1: 1 mixed solvent (volume ratio) of heavy trifluoroacetic acid and heavy chloroform, and ¹ H-NMR measurement was performed. . From the obtained spectrum, the abundance in the fiber was quantified from the integrated value of the peak group at δ = 0.6 to 2.0 ppm, which was assumed to be the alkyl group.

[Production Example 1] 2,4,8,10-tetraoxa-3,9-diphosphaspiro [5.5]
Production of undecane, 3,9-dibenzyl-3,9-dioxide (FR-1) 3,9-dibenzyloxy-2,4,8,10-tetraoxa-3 was placed in a reaction vessel having a stirrer, thermometer and condenser. , 9-Diphosphaspiro [5.5] undecane, 22.55 g (0.055 mol), benzyl bromide 19.01 g (0.11 mol) and xylene 33.54 g (0.32 mol) were charged and stirred at room temperature. While flowing, dry nitrogen was allowed to flow. Next, heating was started in an oil bath, and the mixture was heated and stirred at a reflux temperature (about 130 ° C.) for 4 hours. After the heating was completed, the mixture was allowed to cool to room temperature, 20 mL of xylene was added, and the mixture was further stirred for 30 minutes. The precipitated crystals were separated by filtration, and washed twice with 40 mL of xylene. The obtained crude product and 50 mL of methanol were placed in a reaction vessel equipped with a condenser and a stirrer and refluxed for about 3 hours. After cooling to room temperature, the crystals were separated by filtration, washed twice with 20 mL of methanol, and the obtained filtered material was dried at 120 ° C. and 1.33 × 10 ² Pa for 20 hours to obtain white flaky crystals. Was. The product was identified as bisbenzylpentaerythritol diphosphonate by mass spectrometry, ¹ H, ³¹ P nuclear magnetic resonance spectroscopy and elemental analysis. The yield was 19.76 g, the yield was 88%, and the ³¹ P-NMR purity was 99%. The organic purity measured by the method described in the text was 99.5%. The chlorine content was 51 ppm. ΔpH was 0.1. The residual solvent amount was 47 ppm.

[Production Example 2] Preparation of 2,4,8,10-tetraoxa-3,9-diphosphaspiro [5.5] undecane, 3,9-dibenzyl-3,9-dioxide (FR-2) The preparation was carried out in the same manner as in Preparation Example 1 except that the operations of washing once and washing with refluxing methanol were omitted.
The yield was 21.33 g, the yield was 95%, and the ³¹ P-NMR purity was 95%. The organic purity measured by the method described in the text was 94.0%. The chlorine content was 2500 ppm. ΔpH was 1.5. The residual solvent amount was 1100 ppm.
[Chain extender]
CE-1; an epoxy-containing acrylic-styrene copolymer manufactured by BASF, trade name: ADR4300-S
CE-2: Teijin Limited cyclic carbodiimide group-containing compound A compound represented by the following chemical structural formula. A cyclic carbodiimide compound was produced by the following operation, and the compound was identified by the following operation.

(M) Identification of Cyclic Carbodiimide Structure by NMR The synthesized cyclic carbodiimide compound was confirmed by ¹ H-NMR and ¹³ C-NMR. For NMR, JNR-EX270 manufactured by JEOL Ltd. was used. The solvent used was heavy chloroform.

(N) Identification of carbodiimide skeleton of cyclic carbodiimide by IR The presence or absence of the carbodiimide skeleton of the synthesized cyclic carbodiimide compound was confirmed by FT-IR at 2100 to 2200 cm ⁻¹ characteristic of carbodiimide. FT-IR used Magna-750 manufactured by Thermo Nicolay.

[Production Example 3] Production of cyclic carbodiimide CC1

Reaction of o-nitrophenol (0.11 mol), 1,2-dibromoethane (0.05 mol), potassium carbonate (0.33 mol), and 200 ml of N, N-dimethylformamide (DMF) equipped with a stirrer and a heater The apparatus was charged in an N ₂ atmosphere and reacted at 130 ° C. for 12 hours. After that, DMF was removed under reduced pressure. The obtained solid was dissolved in 200 ml of dichloromethane, and liquid separation was performed three times with 100 ml of water. The organic layer was dehydrated with 5 g of sodium sulfate, and dichloromethane was removed under reduced pressure to obtain an intermediate product A (nitro compound).

  Next, the intermediate product A (0.1 mol), 5% palladium carbon (Pd / C) (1 g), and 200 ml of ethanol / dichloromethane (70/30) were charged into a reactor equipped with a stirrer, and hydrogen exchange was performed for 5 hours. The reaction is repeated twice at 25 ° C. while hydrogen is always supplied, and the reaction is terminated when the decrease of hydrogen stops. When Pd / C was recovered and the mixed solvent was removed, an intermediate product B (amine) was obtained.

Next, triphenylphosphine dibromide (0.11 mol) and 150 ml of 1,2-dichloroethane are charged and stirred in a reactor equipped with a stirring device, a heating device, and a dropping funnel under an N ₂ atmosphere. A solution of the intermediate product B (0.05 mol) and triethylamine (0.25 mol) dissolved in 50 ml of 1,2-dichloroethane was gradually added dropwise at 25 ° C. After completion of the dropwise addition, the reaction was carried out at 70 ° C. for 5 hours. Thereafter, the reaction solution was filtered, and the filtrate was separated 5 times with 100 ml of water. The organic layer was dehydrated with 5 g of sodium sulfate, and 1,2-dichloroethane was removed under reduced pressure to obtain an intermediate product C (triphenylphosphine compound).

Next, under a N ₂ atmosphere, di-tert-butyl dicarbonate (0.11 mol), N, N-dimethyl-4-aminopyridine (0.055 mol), and dichloromethane were placed in a reactor equipped with a stirrer and a dropping funnel. 150 ml was charged and stirred. At 25 ° C., 100 ml of dichloromethane in which intermediate product C (0.05 mol) was dissolved was slowly dropped at 25 ° C. After the addition, the reaction was carried out for 12 hours. Thereafter, CC1 was obtained by purifying the solid obtained by removing dichloromethane. The structure of CC1 was confirmed by NMR and IR.

[Production Example 4] Production of cyclic carbodiimide CC2

o-Nitrophenol (0.11 mol), pentaerythrityltetrabromide (0.025 mol), potassium carbonate (0.33 mol), and 200 ml of N, N-dimethylformamide were mixed in a reactor equipped with a stirrer and a heating device to obtain N _2. After charging under an atmosphere and reacting at 130 ° C. for 12 hours, DMF was removed under reduced pressure. The obtained solid was dissolved in 200 ml of dichloromethane, and liquid separation was performed three times with 100 ml of water. The organic layer was dehydrated with 5 g of sodium sulfate, and dichloromethane was removed under reduced pressure to obtain an intermediate product D (nitro form).

  Next, the intermediate product D (0.1 mol), 5% palladium carbon (Pd / C) (2 g), and 400 ml of ethanol / dichloromethane (70/30) were charged into a reactor equipped with a stirrer, and hydrogen exchange was performed. The reaction was repeated twice at 25 ° C. while hydrogen was constantly supplied, and the reaction was terminated when the decrease in hydrogen was no longer observed. When Pd / C was recovered and the mixed solvent was removed, an intermediate product E (amine) was obtained.

Next, triphenylphosphine dibromide (0.11 mol) and 150 ml of 1,2-dichloroethane were charged and stirred in a reactor equipped with a stirring device, a heating device, and a dropping funnel under a N ₂ atmosphere. A solution of the intermediate product E (0.025 mol) and triethylamine (0.25 mol) in 50 ml of 1,2-dichloroethane was gradually added dropwise at 25 ° C. After completion of the dropwise addition, the reaction is carried out at 70 ° C. for 5 hours. Thereafter, the reaction solution was filtered, and the filtrate was separated 5 times with 100 ml of water. The organic layer was dehydrated with 5 g of sodium sulfate, and 1,2-dichloroethane was removed under reduced pressure to obtain an intermediate product F (triphenylphosphine compound).

Next, under a N ₂ atmosphere, di-tert-butyl dicarbonate (0.11 mol), N, N-dimethyl-4-aminopyridine (0.055 mol), and dichloromethane were placed in a reactor equipped with a stirrer and a dropping funnel. 150 ml is charged and stirred. At 25 ° C., 100 ml of dichloromethane in which the intermediate product F (0.025 mol) was dissolved was slowly dropped at 25 ° C. After the addition, the reaction is carried out for 12 hours. Thereafter, CC2 was obtained by purifying the solid obtained by removing dichloromethane. The structure of CC2 was confirmed by NMR and IR.

[Examples 1 to 3, 5 and Comparative Example 1]
Polyester having the type and IV (intrinsic viscosity) described in Table 1, a phosphorus compound, and a chain extender (CE-1, CE-2 (CC2 described above)) were used in an amount shown in Table 1 (100% by weight of polyester fiber). And melt-kneaded at 230 ° C. with a vented twin-screw extruder to obtain a polyester composition having an intrinsic viscosity shown in Table 1 (flame-retardant polyester composition). This polyester composition was spun from a die at an ambient temperature of 250 to 280 ° C, and was taken out at a take-up speed of 1000 m / min. Subsequently, the filament was stretched to 4.0 ± 0.5 times in one step or two steps to obtain a filament of 80 to 88 dtex. Table 2 shows the physical properties of the filament yarn. The results are shown in Tables 1 and 2. The LOI value in Example 1 was 25.5.

[Example 4]
Example 1 except that PET having an IV of 0.684 dL / g was used, titanium oxide was added at 0.3 wt% based on the weight of the polyester composition, and the amount of the chain extender was 0.1 wt%. A flame-retardant polyester composition was obtained in the same manner as described above to obtain fibers. The results are shown in Tables 1 and 2.

[Comparative Example 2]
A flame-retardant polyester composition was obtained and fibers were obtained in the same manner as in Example 1 except that the amount of the phosphorus compound was increased to 10% by weight and no chain extender was added. The properties are shown in Table 1, and the results are shown in Tables 1 and 2.

  As shown in Comparative Examples 1 and 2, when the amount of the chain extender was large (Comparative Example 1), or when the amount of the phosphorus compound was large (the phosphorus atom concentration was high), and no chain extender was used. In the case (Comparative Example 2), the spinnability was poor, and a drawn yarn sufficient for measuring the physical properties could not be obtained.

[Comparative Example 3]
A flame-retardant polyester composition was obtained and fibers were obtained in the same manner as in Comparative Example 2, except that the amount of the phosphorus compound was changed to 5% by weight. The properties are shown in Table 1, and the results are shown in Tables 1 and 2.

[Comparative Example 4]
In the same manner as in Example 1 except that PET having an IV of 0.600 dL / g was used, the amount of the phosphorus compound was increased to 10% by weight, and the amount of the chain extender was changed to 0.1% by weight. Thus, a flame-retardant polyester composition was obtained to obtain a fiber. The properties are shown in Table 1, and the results are shown in Tables 1 and 2.

[Comparative Example 5]
A flame-retardant polyester composition was obtained and fibers were obtained in the same manner as in Example 1 except that the phosphorus compound and the chain extender were not blended. The properties are shown in Table 1, and the results are shown in Tables 1 and 2.

[Reference Example 1]
A polyester shown in Table 1 and a polyester having an IV (intrinsic viscosity) of 0.900, a phosphorus compound and a chain extender were blended in the amounts shown in Table 1 (% by weight when the weight of the polyester composition was 100%). The mixture was melt-kneaded at 230 ° C. with a vented twin-screw extruder to obtain a polyester composition having an intrinsic viscosity of 0.572 as shown in Table 1 (flame-retardant polyester composition, referred to as master chip of Reference Example 1). ).

[Example 6]
The master chip described in Reference Example 1 and the polyester having the type and IV (intrinsic viscosity) described in Table 1 were dry-blended and spun from a die at an ambient temperature of 250 to 280 ° C, and a take-up speed of 1000 m / min. Picked up. Subsequently, the film was stretched to 4.0 ± 0.5 times in one or two steps to obtain a filament of 80 to 85 dtex. Table 2 shows the physical properties of this filament yarn. A tubular knit was prepared using this filament yarn, and the LOI value was measured. LOI was 25. The results are shown in Tables 1 and 2.

[Reference Example 2]
In Reference Example 1, a polyester composition having an intrinsic viscosity of 0.521 as shown in Table 1 was obtained in the same manner as in Reference Example 1 except that no chain extender was added (a flame-retardant polyester composition, This is referred to as the master chip of Example 2.)

[Example 7]
After dry-blending the master chip described in Reference Example 2, a polyester having the type and IV (intrinsic viscosity) described in Table 1, and a chain extender in an amount (parts by weight) shown in Table 1, the atmosphere temperature was reduced to 250 to It was spun from a die at 280 ° C. and was taken off at a take-off speed of 1000 m / min. Subsequently, the film was stretched to 4.0 ± 0.5 times in one or two steps to obtain a filament of 80 to 85 dtex. Table 2 shows the physical properties of this filament yarn. A tubular knit was prepared using this filament yarn, and the LOI value was measured. LOI was 25.0. The results are shown in Tables 1 and 2.

Example 8
Various fibers were manufactured from the fiber obtained in Example 1 in accordance with the following operation, and LOI evaluation was performed. The results are shown in Table 3.
(fabric)
The entire amount of the polyester fiber obtained in Example 1 was distributed to warps and wefts, and a plain weave fabric was obtained by a usual weaving method.
(knitting)
The polyester fiber obtained in Example 1 was used for a front reed, a middle reed, and a back reed, and a knitted fabric was obtained using an ordinary warp knitting machine.
(Non-woven fabric)
The flame-retardant polyester composition obtained in Example 1 was melt-spun at 250 to 280 ° C., and the long fibers picked up at a high speed by an ejector were continuously supplied and conveyed onto a moving net conveyor, and were embossed with an emboss roller. Thermocompression bonding (100 to 200 ° C) was performed to obtain a long-fiber nonwoven fabric.

  ADVANTAGE OF THE INVENTION According to this invention, while having low phosphorus density | concentration and having excellent flame retardance by melt-kneading a phosphorus-based flame retardant, it is possible to provide a flame-retardant polyester fiber having excellent yarn properties as compared with the related art.

Claims (8)

A phosphorus compound represented by the following general formula (1) so that the content of phosphorus atoms is 1000 to 16000 ppm with respect to the weight of the polyester fiber, and a chain extender so that the content is 0.005 wt% to 1.5 wt%. Wherein the polyester fiber has an intrinsic viscosity of 0.5 to 1.3 dL / g and a terminal carboxyl group content of 10 to 45 eq / T.

The polyester fiber according to claim 1, wherein the physical properties of the phosphorus compound represented by the following general formula (1) satisfy the following requirements.
(A) Organic purity of 97.0% or more and 100% or less (A) Chlorine content exceeds 0 ppm and 1000 ppm or less (C) pH fluctuation value (ΔpH) is 0 or more and 1.0 or less (D) Residual solvent amount is 0 ppm Over 1000ppm

Tensile strength at break is 2.0 to 6.5 cN / dtex, elongation at break is 20 to 80%, and toughness represented by (tensile strength at break) × (elongation at break) ^0.5 is 19.0 to 30.0. The polyester fiber according to claim 1, wherein   A polyester composition having an intrinsic viscosity of 0.5 to 1.3 dL / g, in which a phosphorus compound represented by the following general formula (1) is blended so as to have a phosphorus atom content of 1000 to 16000 ppm by a melt spinning method. The polyester fiber according to any one of claims 1 to 3, wherein the fiber is drawn at a spinning speed of 800 to 4000 m / min, and a total draw ratio after spinning is 2.5 to 6.0 times. Method.   A 0.4 to 0.6 dL / g polyester composition containing a phosphorus compound represented by the general formula (1) so that the phosphorus atom content is 7500 to 45000 ppm is mixed with an arbitrary polyester resin and phosphorus. Blend so that the atomic content becomes 1000-16000 ppm, and further add a chain extender of 0.005 wt% to 1.5 wt% based on the total weight of the resin at the time of melt spinning. The method for producing a polyester fiber according to any one of claims 1 to 3, wherein the polyester fiber is drawn at a rate of 800 to 4000 m / min and the total elongation after spinning is 2.5 to 6.0 times.   A phosphorus compound represented by the general formula (1) and a chain extender of 0.005 wt% to 1.5 wt% with respect to the total weight of the resin are blended so that the phosphorus atom content is 7500 to 45000 ppm. The polyester composition of 0.4 to 0.6 dL / g was blended with an arbitrary polyester resin so that the phosphorus atom content became 1000 to 16000 ppm, and then the spinning speed was adjusted to 800 to 4000 m / min by the melt spinning method. The method for producing a polyester fiber according to any one of claims 1 to 3, wherein a total elongation ratio after drawing and spinning is 2.5 to 6.0 times.   A fibrous structure comprising the polyester fiber according to claim 1.   The fiber structure according to claim 7, wherein the fiber structure is at least one kind of fiber structure selected from the group consisting of a yarn, a string, a processed yarn, a net, a knit, a nonwoven fabric, and a woven fabric.