JPH0329884B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a fiber in which polyarylphosphonate or/and polyarylphosphate is uniformly dispersed in a polyester polymer, and a method for producing the same. The purpose of the present invention is to easily break the ester bonds of polyester fibers by hydrolysis during dyeing without causing any problems in the process from spinning polyester to knitting and fabrics, and in the physical properties of the fibers, thereby causing a decrease in high elongation. This is intended to prevent pilling (pilling) when wearing clothes. Conventionally, synthetic fibers such as polyester and polyamide have excellent physical and chemical properties and have therefore been used in many applications, and are now largely replacing natural fibers such as cotton and wool. However, even such synthetic fibers have some disadvantages, one of which is the pilling that occurs while wearing clothes, and in terms of appearance and texture, anti-pilling fibers without pilling has been desired for a long time. At present, methods to prevent pill generation can be roughly divided into the following two types. That is, the first method is to reduce the strength and elongation of fibers, for example, low [η] fibers,
The second method is to make fibers with easily hydrolyzable fibers or fibers with defective structure such as cracks, or add post-treatment such as solvent or mechanical damage to achieve low strength and elongation. This is a method to suppress pilling by applying post-treatments such as resin or burning. However, the latter anti-pilling method does not provide a satisfactory anti-pilling effect when worn for a long time, and the post-treatment method has problems such as changes in the physical properties of the fabric and wash resistance. In addition, in the former method of lowering the strength and elongation of fibers, the formation of low [η] fibers and defect structure fibers are likely to cause fluff breakage during spinning and drawing, and furthermore, are likely to cause trouble during the spinning, knitting, and weaving processes. Poor operability. Further, when reducing the strength and elongation of fibers by post-treatment such as solvent or mechanical damage, a special process is required, which has disadvantages such as difficulty in controlling shrinkage and tear strength of the fabric. Therefore, it is considered that the optimal method for obtaining pill-resistant polyester fibers at present is to cause hydrolysis to occur easily and within an appropriate range during dyeing after fabric formation to reduce strength and elongation. For this purpose, it is necessary to add an appropriate amount of an easily hydrolyzable substance to the polyester fibers in advance, and examples of such easily hydrolyzable substances include phosphorus compounds found in JP-A-50-135331 and JP-A-50-123315. Copolymerization of silanol compounds disclosed in JP-A-51-133531 and JP-A-53-124562, or copolymerization of sulfone group-containing compounds disclosed in JP-A-54-46698. etc. have been proposed. By the way, in order to copolymerize these into polyester, it has been usual to add easily hydrolyzable substances between before the transesterification reaction and before the polymerization to polymerize the polyester. However, this method tends to cause problems such as a decrease in heat resistance due to the production of diethylene glycol and poor processability due to agglomeration of TiO ₂ , which is a matting agent, and problems such as loss and contamination due to switching of polymers. On the other hand, Tokko Akira
As seen in Publication No. 47-32297 and Japanese Patent Publication No. 47-32299, when polyarylphosphonate is P,
A method for obtaining flame-retardant fibers by blending with 0.4 to 4.0% by weight polyester is known, but as in the present invention, the specific viscosity (degree of polymerization) of the phosphorus compound, which is an easily hydrolyzable substance, and the [η] and phosphorus of the drawn polyester yarn are known. By regulating the content relationship, hydrolysis of the fiber occurs during hot water treatment such as dyeing, and when the hot water treatment time at 130℃ exceeds 60 minutes, the hydrolyzability decreases and the ester bond cleavage rate remains almost constant. As a result, there have been no polyester fibers or methods for producing the same that can easily pass through the process from polymer to knitting and weaving, and can easily maintain the optimum strength and elongation as anti-pill fibers after dyeing. Against this background, the present inventors have conducted extensive research in an effort to obtain a polyester fiber that has good processability, easily reduces strength and elongation during dyeing, and is anti-pilling due to pill shedding while taking advantage of conventional fiber physical properties. As a result, we have arrived at the present invention. That is, the present invention provides the following general formula (1) [a is 0 or 1, n is the degree of polymerization when the specific viscosity η _sp is 0.05≦η _sp ≦0.14 in a mixed solvent of tetrachloroethane/phenol = 1/1] Polyarylphosphonate or/and polyaryl represented by Phosphate exists in the polyester fiber, and the relationship between the intrinsic viscosity [η] of the polyester drawn yarn and the phosphorus content W (wt%) is expressed by the formula (2) W=[η] ^2.1 ±0.03 and 0.40≦[η]≦ 0.55... (2) is satisfied, and when the ester bond cleavage rates by hot water treatment at 130°C x 60 minutes and 130°C x 120 minutes are BC ₁ and BC ₂ , respectively (BC ₂ −
BC ₁ )/BC ₁ ≦0.3, and the single fiber dry strength DT (g/dr) and dry elongation DE of the final product after hot water treatment
The present invention relates to a pill-resistant polyester fiber characterized by having a product DT×DE (%) of 20 to 80, and a method for producing the same. The polyester fibers referred to in the present invention include, for example, terephthalic acid, isophthalic acid, naphthalene 2,
Aromatic dicarboxylic acids such as 6-dicarboxylic acid and phthalic acid, aliphatic dicarboxylic acids such as adipic acid and sebacic acid, or their esters, and diol compounds such as ethylene glycol, diethylene glycol, 1,4 dibutanediol, and neopentyl glycol. A polyester synthesized from polyethylene terephthalate, in which 85% or more of the repeating structural units are polyethylene terephthalate, is particularly preferred. In addition, the above polyester components include polyalkylene glycol, glycerin, pentaerythritol,
Copolymers of methoxypolyalkylene glycol, bisphenol A, sulfoisophthalic acid, silicon compounds, etc., or additives of up to 5% by weight, such as matting agents, heat stabilizers, ultraviolet absorbers,
A pigment or an antistatic property improver may also be included. In addition, the present invention uses conjugate fibers made of polyester polymers with [η] difference (polymerization degree difference) and those with modifying properties, circular, hollow, polygonal, surface unevenness, flat type, U
It may be a cross-sectional fiber such as a letter-shaped fiber, and any fiber form such as spun yarn, drawn yarn, false twisted yarn, interlaced yarn, taslan yarn, twisted yarn, knotted yarn, covering yarn, etc. may be used without any problem. As an easily hydrolyzable substance, the general formula is [a is 0 or 1, n is the degree of polymerization when specific viscosity η _sp is 0.05≦η _sp ≦0.14 in a mixed solvent of tetrachloroethane/phenol = 1/1] Polyarylphosphonate or/and polyaryl represented by Phosphate is advantageous in the following points (a) to (e), and may be one whose end is not capable of forming an ester, such as a phenoxy group or an alkoxy group. (a) Loss on heating in _N2 at 300℃ for 10 minutes is 5wt% or less,
Preferably, the amount is 3 wt% or less, and there is little discoloration or decomposition during the period after polymerization and spinning. (b) Solubility parameters similar to polyester, good compatibility with polyester, and melting point of 250°C.
In the following, the polyester is mixed in a solution form, (c) The viscosity of the polyester changes little during addition and mixing or after spinning and contains almost no water or impurities, (d) Bleed-out to the fiber surface The larger the molecular weight, the better, but an optimum molecular weight is required from the viewpoint of dispersibility in polyester and hydrolyzability. In the case of the polyaryl phosphonate or polyaryl phosphate of the present invention, the specific viscosity η _sp is 0.05≦η _sp ≦
It is preferable that the degree of polymerization is 0.14. The method for producing the polyaryl phosphonates and polyaryl phosphates of the present invention is one in which a nearly equimolar mixture of dihydroxydiphenyl sulfone and phenyl phosphonic dichloride or phenyl phosphonic dichloride is inert. A melt polymerization method in which polymerization is performed under gas at normal pressure and then at 150 to 280°C under reduced pressure with the addition of magnesium chloride or calcium chloride as a catalyst;
Alternatively, an interfacial polymerization method in which dihydroxydiphenyl sulfone is dissolved in water as an alkali metal salt and reacted with a methylene chloride solution of phenylphosphonic dichloride or phenylphosphate dichloride under stirring, or 1,1,2,2 tetrachloroethane Known methods such as a solution polymerization method in which polymerization is carried out using pyridine or calcium chloride as a catalyst and solidified in methanol as a non-solvent can be used. Also for terminal capping, during or after the polymerization of the polyarylphosphonate or polyarylphosphate, e.g.

【formula】

[Formula] R ₄ − OH (in the formula, X: Cl or Br, R ₁ to _{R 3} : alkyl group, aryl group, or alkoxy group, R ₄ : alkyl group or aryl group) can be used to react in a solvent solution. There is no problem. The present inventors have also found that when the specific viscosity η _sp representing the degree of polymerization of the phosphorus compound differs, the ester bond cleavage rate in hot water treatment follows different curves. That is, Fig. 1 is a model diagram showing the relationship between the time of hot water treatment at 130°C and the ester bond cleavage rate when polyarylphosphonate or polyarylphosphate is kneaded. Specific viscosity η _sp is 0.05≦η _sp ≦0.35
In the case of , curve B shows a typical trend when η _sp is higher than 0.35, and the difference between curves A and B is important in selecting the degree of polymerization of the phosphorus compound, as will be understood below. have meaning. When η _sp is less than 0.05, the viscosity changes greatly when added to the polyester polymer, which tends to impair spinning and drawing properties, and bleed-out to the fiber surface becomes large, which is not preferable. If η _sp exceeds 0.35, as shown in curve B in Figure 1, the temperature is 130℃×60
Ester bond cleavage rate in hydrothermal water treatment is 0.05≦η _sp
≦0.35, the hydrolyzability is lower than curve A, and the decrease in strength and elongation of the fiber is not constant between the case of dyeing once and the case of dyeing twice or more, such as re-dying, and there is a large difference in anti-pilling effect. Defects such as things that occur appear. The reason for this is that the phosphorus compound is uniformly dispersed in the polyester polymer with almost no alteration, and hot water decomposes the phosphorus compound and simultaneously cuts the polyester main chain, but the lower the degree of polymerization (specific viscosity) of the phosphorus compound It is thought that the higher the degree of polymerization, the more gradually the polymer is decomposed, resulting in the patterns shown by curves A and B in FIG. Therefore, in terms of hydrolytic stability, 0.05≦η _sp ≦0.35
The pattern of curve A seen in is better than curve B.
To put this numerically, 130℃ x 60 minutes and 130℃
If the ester bond cleavage rates of ×120 minute hot water treatment are BC ₁ and BC ₂ , respectively, (BC ₂ − BC ₁ )/BC ₁ ≦
0.3 is preferable, and (BC ₂ - BC ₁ )/BC ₁ ≦0.2 is more preferable. The specific viscosity η _sp referred to here is measured using a mixed solvent of tetrachloroethane/phenol = _1/1 (weight ratio) at 30°C using an Utspelode viscometer. Measure the η ₁ of the solution dissolved in . when falling, and η _sp = (η ₁ − η ₀ )/η ₀
More demanded. In addition, the present invention relates to a phosphorus compound, η _sp
=0.05 to 0.35 indicates a degree of polymerization ranging from about 3 to about 25. As mentioned above in the schematic diagram, the main objective of the present invention is to
In the first hot water treatment such as dyeing, hydrolysis of the fiber occurs and anti-pilling properties are developed due to a decrease in fiber strength and elongation.However, in the second and subsequent hot water treatments, the hydrolyzability decreases and the fiber strength and elongation decrease. The aim is to obtain fibers that do not significantly reduce the polymerization degree, and for this purpose, by lowering the η _sp (and therefore the polymerization degree n) of the phosphorus compound added, the hydrolyzability of the polyester increases, even when added in small amounts. Anti-pilling properties can be imparted with one heat treatment, and since the η _sp is low, it is easy to fall off during one heat treatment.
Most of the phosphorus compounds fall off, and during the second and subsequent heat treatments, there is less phosphorus compound remaining, resulting in lower hydrolyzability and less decrease in fiber strength and elongation. In other words, in that sense, the lower the η _sp of the phosphorus compound, the more likely it is to fall off during the first heat treatment.
In the present invention, the η _sp of the phosphorus compound is 0.05≦η _sp
≦0.14, and the degree of polymerization is specified in the range of 3≦n≦10. The ester bond cleavage rate BC is calculated from [η] before and after the hydrothermal treatment in the following order, and a cleavage rate of 0.5% means that all molecular chains are cleaved in half on average. Molecular weight from Griel's formula [η] = 1.27×10 ^{-4 Mn 0.86}
Find Mn. If the average number of molecular breaks/one molecular chain is m, then m = (Mn ₀ − Mn ₁ )/Mn ₁ Mn ₀ : Molecular weight before hydrothermal treatment Mn ₁ : Molecular weight after hydrothermal treatment BC = m×1/2Pn ₀ -1 x 100 = m x 192/2Mn ₀ -192 x 100 (%) In the present invention, the polyaryl phosphonate or/and polyaryl phosphate obtained as described above is processed into a melt or It must be added in powder form and mixed. It is not preferable to add the additive before polymerization of the polyester because it tends to change the viscosity of the polymer and cause side reactions such as decomposition of the additive. Further, in order to ensure that the additive is uniformly dispersed in the polyester polymer and to reduce troubles, it is more preferable to melt the additive and inject it into the polyester polymer immediately before spinning, then uniformly mix and disperse it using a static mixer or the like. Furthermore, if the melt viscosity of the additive is too high, mixing with the polyester polymer tends to be insufficient in the kneading method immediately before spinning, so the phosphorus compound
Melt the mixed additive at 200℃ by adding and mixing a heat-resistant thinning agent (such as a low-viscosity phosphorus compound or polyethylene glycol compound) with a heating loss of 20% or less under nitrogen gas for 10 minutes at 300℃. viscosity
It is desirable to keep it below 50 poise. However, the thinner is compatible with polyester and does not cause coloring, decomposition, or reaction, and the smaller the amount added, the better.
In addition, when melting additives, due to degradability, energy saving, temperature change when adding polyester, etc.
Preferably it is around 200°C. One of the requirements of the present invention is the intrinsic viscosity [η] of the drawn polyester yarn and the phosphorus content W for the drawn yarn.
(weight%), it is necessary that equation (2) W=[η] ^2.1 ±0.05 and 0.40≦[η]≦0.58...(2) hold true. Here we say [η]
means the intrinsic viscosity measured using a mixed solvent of equal amounts of tetrachloroethane and phenol in a constant temperature bath at 30°C using an Utsperohde viscometer, and the phosphorus content is determined by the colorimetric method of elemental analysis. It shows the weight percent of phosphorus in it. However, the phosphorus content includes polyarylphosphonate or polyarylphosphate alone or a mixture of both, and does not include a low-viscosity phosphorus compound used as a viscosity reducing agent. Note that the term "drawn yarn" includes yarns obtained by omitting the drawing step during high-speed spinning, partially drawn yarns, drawn false twisted yarns, spun yarns, and the like. Figure 2 shows the relationship between the intrinsic viscosity [η] of the drawn polyester yarn obtained by the present invention and the phosphorus content W (wt%), where the shaded area indicates W = [η] ^2.1 ±0.05 and 0.40≦
Indicates the range that satisfies [η]≦0.58. [η] of the drawn yarn is
When it is less than 0.40, there are problems such as fluff breakage during spinning and drawing, fiber damage during spinning and generation of white powder, and an increase in costs. In addition, when [η] exceeds 0.58, a large amount of phosphorus compound is required to cause easy hydrolysis, making it difficult to pass through the process from spinning to processing and controlling low strength and elongation due to hydrolysis, resulting in increased costs. This is undesirable as it causes contamination. As shown in FIG. 1, when the content of phosphorus compounds is high, it is almost easily hydrolyzed, but the content has an optimum range (the shaded area in FIG. 2) as shown in equation (2). If the content is lower than formula (2), the decrease in [η] will be small after hot water treatment such as dyeing, and as a result, the single fiber dry strength DT
When the product DT×DE of (g/dr) and dry elongation DE (%) exceeds 80, the fiber is too strong and does not exhibit a satisfactory anti-pilling effect. If the content is higher than the formula (2), [η] after hot water treatment is too low and DT×DE is less than 20, and pilling does not occur, but the fiber fuzz breaks off quickly and spoils the appearance of the fabric. The strength and elongation required to form a knitted fabric cannot be maintained, resulting in a fabric that is extremely susceptible to tearing, abrasion, bending, etc. As a result of intensive study by the present inventors, the product of single fiber strength and elongation, DT×DE, was determined from the viewpoint of pill shedding and fabric strength and elongation.
It has been found that 20 to 80 is preferable, and 30 to 50 is more preferable. Furthermore, various compounds are added to the polyester fiber for the purpose of achieving the specified strength and elongation according to the present invention during processing such as dyeing, which has no problem in strength and elongation (for example, DT x DE of 100 or more) up to the weaving and weaving process. As a result of kneading and studying, it was found that polyaryl phosphonate or/and polyaryl phosphate that satisfies heat resistance, dispersibility, hydrolyzability, etc. is kneaded into [η] of the polyester drawn yarn in the optimum range. They discovered that anti-pill fibers can be obtained. In addition, hydrolyzability changes depending on the temperature and time of hot water treatment such as dyeing, but in the present invention, after hot water treatment, for example, typically at 130℃ x 60 minutes, DT
must be in the range of 20 to 80. However, it is sufficient if the final product has a DT x DE of 20 to 80, and the hot water treatment conditions are not limited to 130°C x 60 minutes, and there will be no problem even if the processing conditions such as dyeing are changed. The present invention will be specifically explained below using Examples. Example 1 Polyethylene terephthalate chips containing -0.08% TiO ₂ were extruded using a 40φ extruder, and the following mixed additives having a viscosity of 10 poise, which had been heated and melted at 200°C in advance, were added to the polyester polymer in a stock solution tube of the polymer. Bisphenol sulfone phenyl phosphonate was injected to a concentration of 3.0% by weight (0.25% by weight of phosphorus), mixed with a static mixer, and spun from a nozzle. [(A) Polybisphenolsulfone phenylphosphonate η _sp = 0.11 (average degree of polymerization around 9.5) (B) Thinning agent: tristearyl phosphate (300℃
x Heating loss for 10 minutes: 5.1%) Mixing weight ratio: (A)/(B)] 4/1] The polyarylphosphonate was prepared by melt polymerization and purified using chloroform and methanol. Elemental analysis and NMR results revealed that the end was not blocked and chlorine remained. Next, the spun yarn was bundled into a tow of 500,000 dr, stretched 3.8 times by a two-stage water bath drawing method, and mechanically crimped and cut to produce a 3 dr x 76 mm staple. The [η] of the drawn yarn is 0.491 dl/g, and the phosphorus content determined by the colorimetric method is 0.26%. 0.23
%, which satisfies the relationship of equation (2) (the shaded area in Figure 2). When the obtained spun yarn and drawn yarn were observed using an electron microscope, no aggregation of the polyarylphosphonate was observed and the polyarylphosphonate was uniformly dispersed. Further, there was no fluff breakage during spinning and drawing, and no particular problems such as smoke generation, coloring, or viscosity change were observed. Furthermore, differential thermal analysis
NMR showed that less diethylene glycol was produced, and the melting point was 261°C, which was the same as normal polyester fiber. A 2/2 twill fabric was produced by using the obtained staples as spun yarn of 40 count cotton and used as warp and weft yarns, but no trouble occurred during the spinning and weaving processes. After relaxing and heat setting the fabric, it was lightly raised, dyed with disperse dye for 60 minutes at 130°C using a high-pressure winch, and sheared to obtain a wool-like polyester fabric for use in the winter. Table 1 shows the evaluation results for pilling, fiber properties, etc. of the polyester fabric. As Comparative Example 1, the polyarylphosphonate had a specific viscosity η _sp of 0.40 (average degree of polymerization of around 28), and as Comparative Example 2, the polyarylphosphonate was added in an amount of 1.5% by weight. Polyester fabrics were prepared in the same manner, and the evaluation results are also listed in Table 1.

[Table] The spun yarn obtained in Example 1 has DT×DE=144.3
It has a strength and elongation that does not cause problems up to the weaving process, and can be used at 130℃
DT× of textile unraveling yarn by hydrolysis with 60 minutes dyeing
It was found that the DE was 57.2, which caused a decrease in strength and elongation. Note that the decrease in strength and elongation due to heat setting at 180°C and slight napping was slight. In addition, the ester bond cleavage rate was 0.17 after hot water treatment at 130°C for 60 minutes.
%, 0.20% after 120 minutes treatment, and change in cutting rate (BC ₂ − BC ₁ )/BC ₁ between 60 minutes and 120 minutes treatment is 0.18, indicating that there is no big difference in fiber physical properties between one-time dyeing and two-time dyeing. I couldn't see it. In the pilling evaluation of the fabric, it passed the ICI method with a grade of 4-5 after 10 hours and a grade of 5 after 20 hours, and there were no particular problems such as tear strength or shedding of fuzz. Comparative Example 1 is a case where a polyarylphosphonate with a high specific viscosity (degree of polymerization) is used.
Curve B in the figure shows the pattern, and as BC ₁ was 0.11% in hot water treatment at 130°C for 60 minutes, there was less decrease in strength and elongation than in Example 1, and the pilling was grade 3-4, which was a rather bad result. . Further, double dyeing caused a large decrease in strength and elongation. Comparative Example 2 has a low phosphorus content of 0.12wt%, so there is little decrease in strength and elongation due to dyeing, and DT × DE = 122
Pilling was grade 2-3 in 10 hours and 1-2 in 20 hours.
I failed my grade. Example 2 Semidal polyethylene terephthalate polymer containing TiO ₂ = 0.45% has η _sp = 0.07 (polymerization degree 4 to
In 7), polybisphenol sulfone phenyl phosphate, which is not terminally blocked, is injected as a solution to the polyester polymer at a concentration of 4.0 wt% (0.31 wt% for phosphorus), mixed with a static mixer, and mixed through a nozzle. spun. The obtained spun yarn was bundled to 100,000 dr, and subjected to water bath drawing, crimping and cutting by conventional methods to obtain 1.5 dr x 38 mm.
Make 20 kg of staples and use 30 count cotton spun yarn to make 24
I created the Tenjikumaru version of the gauge. Thereafter, the sample was relaxed, heat set at 170°C, and then treated with hot water at 130°C for 60 minutes, and then used as a pilling test sample. Table 2 shows the physical property evaluation results.

【table】

[Table] There was only a small amount of fluff breakage during the spinning and drawing process, and there were no particular problems with smoking, coloring, viscosity changes, or filter clogging due to agglomeration of TiO ₂ during spinning. The drawn yarn has [η] = 0.55 dl/g and the phosphorus content =
It was 0.3wt% and satisfied formula (2). The single fiber strength and elongation of the spun yarn was 3.8 g/dr-41%, and there was no problem in the spinning and knitting processes, although the strength and elongation decreased significantly due to hot water treatment. The ester bond cleavage rate BC ₁ calculated from [η] before and after hot water treatment at 130°C for 60 minutes is as high as 0.27%, and after hot water treatment, [η] = 0.39 DT x DE = 72.5, and pilling was 4 in 5 hours. It was a satisfactory level of 4-5 in 10 hours. It was found that the pilling of the knitted fabric before hot water treatment was poor at 2nd grade for 5 hours and 1st grade for 10 hours, and that the anti-pilling effect was only exhibited when the strength and elongation were reduced by hydrolysis.

[Brief explanation of drawings]

Figure 1 is a model diagram showing the relationship between the time of hot water treatment at 130°C and the ester bond cleavage rate when a phosphorus compound is kneaded in the present invention, and Figure 2 is a model diagram showing the relationship between the intrinsic viscosity [η] and phosphorus bond cleavage rate of polyester drawn yarn. Content W (weight%)
In this figure, the shaded area is the range that satisfies equation (2).

Claims (1)

[Claims] 1 The following general formula (1) [In the formula, a is 0 or 1 and n is the degree of polymerization when the specific viscosity η _sp is 0.05≦η _sp ≦0.14 in a mixed solvent of tetrachloroethane/phenol = 1/1] or/and When polyaryl phosphate is present in the polyester fiber, the relationship between the intrinsic viscosity [η] of the drawn polyester yarn and the phosphorus content W (wt%) is expressed by the formula (2) W=[η] ^2.1 ±0.03 and 0.40≦[η ]≦0.55...(1) is satisfied, and when the ester bond cleavage rates by hot water treatment at 130°C x 60 minutes and 130°C x 120 minutes are BC ₁ and BC ₂ , respectively (BC ₂ −
BC ₁ )/BC ₁ ≦0.3 and single fiber dry strength DT (g/dr) and dry elongation DE of the final product after hot water treatment
An anti-pilling polyester fiber characterized in that the product DT x DE (%) is 20 to 80. 2 After the completion of polymerization of the polyester polymer and immediately before spinning, the following general formula (1) [a is 0 or 1, n is the degree of polymerization when the specific viscosity η _sp is 0.05≦η _sp ≦0.14 in a mixed solvent of tetrachloroethane/phenol = 1/1] Polyarylphosphonate or/and polyaryl represented by The intrinsic viscosity [η] and phosphorus content W (wt%) of the drawn polyester yarn after spinning are expressed by the formula (2): W=[η] ^2.1 ±0.03 and 0.40≦[η]≦0.55...(2 ) A method for producing anti-pilling polyester fibers, which comprises mixing the fibers so as to satisfy the following: and melt-spinning the mixture by a conventional method. 3. The method for producing anti-pilling polyester fiber according to claim 2, characterized in that the phosphorus compound is melted in advance, injected into the polyester polymer immediately before spinning, and mixed in a static mixer. 4. A patent characterized by adding and mixing a thinner with a heating loss of 20% or less under _N2 at 300°C for 10 minutes to reduce the melt viscosity of the mixed additive to 50 poise or less at 200°C. A method for producing a pill-resistant polyester fiber according to claim 3.