Reclaimed polyester fiber

Abstract

To provide a reclaimed polyester fiber having high tensile strength and good filament-producing property by utilizing reclaimed polyester B comprising a process end material of industrial materials as a coarse raw material.SOLUTION: A 3-layer composite polyester fiber comprises raw material polyester A and reclaimed polyester B, wherein the polyester fiber includes the innermost layer and an outer layer component comprising raw material polyester A and the middle layer component comprising reclaimed polyester B, the area ratio (A / B) of raw material polyester A to reclaimed polyester B is 80 / 20 to 50 / 50, the tensile strength is 5.0 to 9.0 cN / dtex, and the number of fuzzes per 10,000 m in length is 0 to 2.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a high-strength recycled polyester fiber made from recycled polyester, which is particularly suitable for use as an industrial material. [Background technology]

[0002] Polyester, especially polyethylene terephthalate, is inexpensive and has an excellent balance of chemical resistance, strength, etc., and is therefore widely used for fibers, films, molded products such as PET bottles, and packaging materials. When disposing of these polyester products, polyester is difficult to decompose and decompose, and even if it is incinerated, the high combustion heat creates a large load on the incinerator, which has been an issue.

[0003] Currently, a "bottle to bottle" recycling process has been established for some polyester products, such as PET bottles, in which they are returned to their raw materials through collection, cleaning, repelletization, melting, and molding. The above recycling process is called material recycling, and compared to chemical recycling, which chemically breaks down the material and returns it to its raw material stage, it consumes less energy and has been the subject of much study.

[0004] On the other hand, with material recycling, it is difficult to completely remove foreign matter contained in raw materials. Polyester products used as industrial materials such as narrow belts and fishing nets contain a large amount of foreign matter, such as pigments and dyes used to color the fibers that make up the products, as well as silicone treatment agents applied during the product manufacturing process. Therefore, even when using process scraps generated during the manufacturing process, it is difficult to recycle them into fibers for industrial materials, which require high raw yarn properties and quality.

[0005] For this reason, recycling of industrial materials as raw materials has been implemented so far for applications that do not require high physical properties such as staple fibers and nonwoven fabrics. In addition, for polyester fibers for industrial materials using recycled polyester, recycling has been implemented using recycled materials with relatively low amounts of foreign matter, such as PET bottles and film processing scraps.

[0006] For example, it has been proposed that high tensile strength can be obtained by using process waste materials of polyester products as a raw material and subjecting them to solid-state polymerization (Patent Document 1).

[0007] In addition, a technology has been proposed to suppress dye spots by producing composite fibers with a core-sheath structure in which recycled polyester is used as the core component and raw polyester material is used as the sheath component (Patent Document 2).

[0008] Furthermore, a technology has been proposed in which composite fibers having a core-sheath structure are produced using recycled polyester as the sheath component and raw polyester material as the core component, thereby obtaining higher raw yarn properties and better spinnability than when recycled polyester is used as the core component (Patent Document 3). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2004-100087 A [Patent Document 2] JP 2000-328369 A [Patent Document 3] JP 2001-172827 A Summary of the Invention [Problem to be solved by the invention]

[0010] Patent Document 1 describes that recycled polyester is solid-phase polymerized to improve the IV (intrinsic viscosity) of the recycled polyester, and as a result, a higher tensile strength can be obtained than fibers that are used as is without solid-phase polymerization. However, when using industrial process waste materials that contain a large amount of foreign matter such as pigments and dyes, the foreign matter contained in the raw material becomes an inhibitor during stretching, making it difficult to achieve high-ratio stretching to obtain high tensile strength.

[0011] In addition, the technology proposed in Patent Document 2 uses recycled polyester as the core component and raw polyester as the sheath component, which can suppress dye spots on the fiber surface. However, when recycled polyester is used as the core component, the layer thickness is greater than when recycled polyester is used as the sheath component, and there is a high probability that foreign matter contained in the recycled polyester will be present close to the direction perpendicular to the fiber axis in the cross section, and the locations where the foreign matter is concentrated will hinder stretching, making it difficult to achieve high-ratio stretching to obtain high tensile strength.

[0012] Furthermore, the technology proposed in Patent Document 3 discloses that by using recycled polyester as the sheath component and raw polyester as the core component, higher raw yarn properties and better spinnability can be obtained than when recycled polyester raw material is used as the core component. However, when using recycled polyester obtained from industrial material process waste materials in this method, there is a problem that foreign matter contained in the recycled polyester sheath component bleeds out during spinning, making high-ratio drawing difficult.

[0013] Therefore, an object of the present invention is to provide a polyester conjugate fiber having high tensile strength and good spinnability by utilizing recycled polyester obtained by recycling industrial materials as raw materials. [Means for solving the problem]

[0014] As a result of the inventors' investigations, they found that in order to obtain high tensile strength and good spinnability using recycled polyester, it is necessary to form a composite structure of recycled polyester and raw polyester, in which the recycled polyester is not a surface layer component, and the layer thickness of the recycled polyester is thin. Specifically, they came up with the idea of ​​forming a three-layer structure of raw polyester and recycled polyester, in which the raw polyester of the outer layer component reduces the bleed-out of foreign matter contained in the recycled polyester, and by making raw polyester A the innermost layer component with the greatest layer thickness, the layer thickness of the recycled polyester in the middle layer is small, and a configuration in which foreign matter is less likely to be aligned in a direction perpendicular to the fiber axis in the cross section is achieved.

[0015] Based on this knowledge, the present inventors conducted intensive research to achieve the above-mentioned object, and as a result, they discovered that a polyester fiber having high tensile strength and good spinnability can be obtained by setting the component ratio of raw material polyester A to recycled polyester B within a specific range and forming a three-layer conjugate fiber with raw material polyester A as the innermost layer component and outer layer component and recycled polyester B as the middle layer component, thereby completing the present invention.

[0016] Therefore, the present invention aims to solve the above problems, and mainly has the following configuration: A polyester three-layer conjugate fiber made of raw polyester A and recycled polyester B, the innermost and outer layer components being raw polyester A and the middle layer component being recycled polyester B, the area ratio (A / B) of raw polyester A to recycled polyester B being 80 / 20 to 50 / 50, the tensile strength being 5.0 to 9.0 cN / dtex, and the number of fluffs per 10,000 m of length being 0 to 2. Effect of the Invention

[0017] The polyester fiber of the present invention can suppress the bleeding out of foreign matter contained in the recycled polyester B and can make it difficult for the foreign matter to be aligned in the cross-sectional direction, and therefore exhibits high tensile strength and good spinnability. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The polyester fiber of the present invention is a polyester three-layer conjugated fiber made of raw polyester A and recycled polyester B, in which the innermost and outer layer components are raw polyester A and the middle layer component is recycled polyester B, the area ratio (A / B) of raw polyester A to recycled polyester B in the fiber cross section is 80 / 20 to 50 / 50, the tensile strength is 5.0 to 9.0 cN / dtex, and the number of fluffs per 10,000 m is 0 to 2.

[0019] The polyester fiber of the present invention will be described in detail below, but the present invention is not limited to the scope of the following description as long as it does not deviate from the gist of the present invention, and various modifications are possible within the scope of the present invention.

[0020] The polyester fiber of the present invention is a three-layer composite fiber made of raw polyester A and recycled polyester B. In the above three-layer composite, the innermost layer and outer layer components are raw polyester A, and the middle layer component is recycled polyester B, so that the bleeding out of foreign matter contained in recycled polyester B can be suppressed, and the foreign matter of recycled polyester B is less likely to be aligned in a direction perpendicular to the fiber axis in the cross section. In the above three-layer composite, the three-layer structure allows the innermost layer component and the outer layer component to be raw polyester A. On the other hand, a four-layer structure is not preferred because the outer layer or the innermost layer is recycled polyester B, and a five-layer or more structure is not preferred because it is difficult to form the layers.

[0021] In the polyester fiber of the present invention, the area ratio (A / B) of raw material polyester A to recycled polyester B fibers in the fiber cross section is 80 / 20 to 50 / 50. When the area ratio of the recycled polyester B is 20% or more, preferably 25% or more, a three-layer structure can be stably formed. On the other hand, when the upper limit of the area ratio of the recycled polyester B is 50% or less, preferably 40% or less, the raw material polyester A, which is a higher ratio, bears the drawing tension, and high-ratio drawing to obtain high raw yarn tensile strength is possible. The polyester fiber of the present invention preferably has an area ratio of the innermost layer, middle layer, and outer layer (innermost layer / middle layer / outer layer) of 75 / 20 / 5 to 30 / 50 / 20. The composite ratio of the raw material polyester A is 75 / 5 to 30 / 20, preferably 70 / 10 to 45 / 15, for the innermost layer / outer layer. When the innermost layer component ratio is 30% or less, or the outer layer component ratio is 20% or more, the recycled polyester B, which is the middle layer component, is configured near the center of the fiber cross section, and the layer thickness increases even with the same area ratio, making it difficult to obtain good spinnability during high-ratio drawing.

[0022] The raw polyester A in the present invention is a polyester (so-called virgin polyester and chemically recycled polyester) polymerized by a conventional method from a raw material obtained by depolymerizing a monomer or polymer. A small amount of recycled polyester B may be mixed in as long as the characteristics of the raw polyester A are not impaired. The IV (intrinsic viscosity) of the raw polyester A is preferably 1.0 to 1.5, more preferably 1.1 to 1.4. If it is 1.0 or less, the IV difference with the recycled polyester B is not obtained, and the raw polyester A cannot bear the tensile load. If it is 1.5 or more, the viscosity is high, which is undesirable because melt extrusion during spinning becomes difficult.

[0023] The recycled polyester B in the present invention is waste (including unreceived products) generated in the manufacturing process of polyester products, and may be remelted and pelletized. The polyester products are fibers and films, specifically, fishing nets, construction nets, civil engineering nets, narrow belts, wide belts, slings, canvas, ropes, hoses, etc., and particularly, fishing nets, construction nets, civil engineering nets, narrow belts, wide belts, slings, canvas, ropes, and hoses. The polyester products generally contain 1% to 10% by weight of components other than polyester, which become foreign matter during stretching. The IV of such recycled polyester B is preferably 0.5 to 0.8, more preferably 0.6 to 0.7. If it is 0.5 or less, stable melt extrusion becomes difficult, which is not preferable. If it is 0.8 or more, the viscosity is high, the IV difference with the raw material polyester A cannot be obtained, and the raw material polyester A is unlikely to bear the tension, which is not preferable. In addition, the pressure rise of the recycled polyester B in the present invention is preferably 0.15 to 0.5 MPa / 24 hr. If the pressure is less than 0.15 MPa / 24 hr, it is not preferable because it is outside the scope of the present invention. If the pressure is more than 0.5 MPa / 24 hr, it is not preferable because stable production becomes difficult due to an increase in filtration pressure. In the present invention, the pressure increase refers to a value measured and calculated by the method described in Example f.

[0024] The polyester fiber of the present invention has a tensile strength of 5.0 to 9.0 cN / dtex. By setting the lower limit of the tensile strength to 5.0 cN / dtex or more, preferably 5.5 cN / dtex or more, the fiber can be used as a high-strength polyester fiber suitable for industrial materials. On the other hand, by setting the upper limit of the tensile strength to 9.0 cN / dtex or less, preferably 8.5 cN / dtex or less, the stretching load can be suppressed, and a fiber with a small number of fluffs can be obtained.

[0025] The polyester fiber of the present invention has a fluff number per 10,000 m of length of 0 to 2. By setting the upper limit of the fluff number to 2 fluffs / 10,000 m, preferably 1 fluff / 10,000 m or less, and more preferably 0.5 fluff / 10,000 m or less, stable spinnability can be obtained.

[0026] The fineness of the polyester fiber of the present invention is not particularly limited, but is preferably 300 dtex to 3500 dtex, more preferably 500 dtex to 3300 dtex. If it is less than 300 dtex, the raw yarn strength is small, and the number of raw yarns required in the higher-order process increases, which is not preferable. If it exceeds 3500 dtex, the tensile load on the equipment increases in the higher-order process, which leads to equipment failure, which is not preferable.

[0027] The single fiber fineness of the polyester fiber of the present invention is not particularly limited, but is preferably 5 dtex to 30 dtex, more preferably 8 dtex to 25 dtex. If it is less than 5 dtex, it is not preferable because it is difficult to form a three-layer structure. If it exceeds 30 dtex, it is not preferable because it is difficult to obtain spinning stability.

[0028] The cross-sectional shape of the polyester fiber of the present invention is not particularly limited as long as it does not impair the effects of the present invention, and may be a circular cross section or a modified cross section such as a triangular, flat, or hexagonal cross section, but a circular cross section is preferred in terms of excellent productivity.

[0029] Next, the method for producing the polyester fiber of the present invention will be described.

[0030] The polyester fiber of the present invention is required to exhibit excellent mechanical properties for industrial material applications. The polyester used to satisfy such properties is not particularly limited, but polyethylene terephthalate having ethylene terephthalate as the main repeating unit is more preferable. In addition, these polyesters may be copolymerized with a third component as long as the object and effect of the present invention are not impaired, and may contain additives such as particles such as dulling agents, stabilizers such as antioxidants, light stabilizers, ultraviolet-resistant materials, antistatic agents, fillers, and crosslinking agents. Examples of copolymerization components include aromatic dicarboxylic acids such as isophthalic acid and naphthalenedicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, sebacic acid, and azelaic acid, diol compounds such as diethylene glycol and 1,4-butanediol, 5-sulfoisophthalic acid metal salts, and phosphorus-containing compounds.

[0031] Furthermore, the polyester fiber of the present invention may contain a colorant in the raw material polyester A and the recycled polyester B, and since the subsequent dyeing process can be omitted, this is advantageous in terms of production costs. The colorant is not particularly limited, and may be appropriately selected from inorganic colorants such as carbon black and iron oxide, and organic colorants such as cyanine, anthraquinone, azo, and perinone.

[0032] The three-layered conjugate polyester fiber of the present invention can be produced by a known conjugate fiber spinning and drawing method. That is, it may be produced by a two-step method in which the fiber is once spun and then wound and then drawn as a post-step, or it may be produced by a direct spinning and drawing method in which the fiber is continuously drawn without once being wound after spinning. The formation of the three-layer structure can also be produced by a known method, and an example is shown below, but the method is not limited thereto. After the raw material polyester A and the recycled polyester B are melted in a screw-type extruder, the innermost layer, middle layer, and outer layer components are fed to a spinning pack by their respective metering pumps. Inside the spinning pack, the innermost layer component is centered, and the middle layer component and the outer layer component are merged from the outside in this order to form a three-layered concentric conjugate flow, which is then discharged from a spinneret. The drawing method is not particularly limited, but in order to obtain a high-strength fiber, it is preferable to perform multi-stage drawing at least in two stages. EXAMPLES

[0033] The present invention will be described in more detail below with reference to examples and comparative examples.

[0034] The methods for measuring various properties in the present invention are as follows.

[0035] (a)IV (intrinsic viscosity) 100 ml of orthochlorophenol was added to 8.0 g of sample, and the solution was dissolved by heating at 160°C for 10 minutes. The relative viscosity ηr of the solution was measured using an Ostwald viscometer and calculated using the following approximate formula: IV (intrinsic viscosity)=0.0242ηr+0.2634 The calculation was made according to the following.

[0036] (B) Fineness Measured according to JIS L-1013 (2021) 8.3.1 Correct fineness a) Method A, with a specified load of 5 mN / tex x indicated tex number, and a specified yarn length of 90 m.

[0037] (c) Tensile strength The samples were placed in a temperature-controlled room with an air temperature of 20°C and humidity of 65%. Measurements were performed using the Tensilon UCT-100 manufactured by Orientec Co., Ltd. under the constant-speed elongation conditions specified in the standard test of JIS L-1013 (2021) 8.5.1. The gripping distance was 250 mm, the tensile speed was 300 mm / min, and the number of tests was 10.

[0038] (d) Frequency of fuzz generation The yarn obtained by spinning was unwound at a speed of 200 m / min, while the fuzz (single yarn breakage) contained in the fiber was detected using a photosensitive fuzz detection device manufactured by Daiko Co., Ltd., and the number of fuzz per 10,000 m of fiber length was evaluated according to the following criteria.

[0039] Number of fluffs (times / 10,000m) 0~0.1 pieces A (excellent) 0.1~0.5 pieces B (Good) 0.5 to 2 pieces C (fairly good) 2 or more D (defective).

[0040] (e) Area ratio The fiber was cut in a direction perpendicular to the fiber axis, and the cross section was photographed at 200x magnification using an optical microscope. From the photograph, the outer diameter R1 of the innermost layer component, the outer diameter R2 of the middle layer component, and the outer diameter R3 of the outer layer component were measured and calculated using the following formula: Innermost layer component ratio (%) = R1 2 / R3 2 Middle layer component ratio (%)=(R2 2 -R1 2 ) / R3 2 Outer layer component ratio (%)=(R3 2 -R2 2 ) / R3 2 The calculation was made as follows.

[0041] (f) Boost Using a pressure boosting tester including an extruder and a pressure sensor, a stainless steel filter with a filtering grain size of 20 μm was set at the discharge section from the extruder, polyester was melted in the extruder at 300°C, and the melt was extruded from the filter at a discharge rate of 4.0 g / min. The pressure value at the start of extrusion was taken as the "initial pressure value (MPa)" and the pressure value at the point of continuous extrusion for 24 hours was taken as the "final pressure value (MPa)." Based on these pressure values, the following calculation formula was used: Pressure increase (MPa / 24hr) = (final pressure value - initial pressure value) The pressure rise was calculated by the following formula.

[0042] [Example 1] Polyethylene terephthalate chips with an IV of 1.30 were used as raw polyester A, and polyethylene terephthalate chips with an IV of 0.67, which were made by crushing, melting, and repelletizing process waste materials generated during the fishing net manufacturing process, were used as recycled polyester B. Both components were melted in a screw-type extruder and then metered and fed to a spinning pack at 295°C so that the area ratio of raw polyester A to recycled polyester B was 70 / 30. Raw polyester A was the innermost and outer layer component, and recycled polyester B was the middle layer component. They were joined in the pack so that the area ratio of the innermost layer / middle layer / outer layer was 60 / 30 / 10, and extruded from an extrusion hole with a circular cross section and a hole diameter of 0.55 mm. The yarn was passed through an atmosphere heated to 300°C for 20 cm from the discharge hole directly below the spinneret face, and then cooled air was blown onto it to solidify it. An oil solution was then applied and the yarn was taken up at a speed of 500 m / min. The undrawn yarn obtained without being taken up was then drawn, heat set and relaxed under the conditions shown in Table 1 to obtain a three-layered composite polyester fiber of 1100 dtex / 90 filaments. The evaluation results of the fiber properties and spinnability are shown in Table 2. It was confirmed that the pressure rise of the recycled polyester B was 0.30 MPa / 24 hr, the fiber cross section formed a three-layered structure, the raw yarn tensile strength was 8.4 cN / dtex and the fuzz count was excellent.

[0043] [Table 1]

[0044] [Example 2] A polyester fiber was obtained in the same manner as in Example 1, except that the area ratio of raw polyester A and recycled polyester B was changed to 80 / 20, and the area ratio of the innermost layer / middle layer / outer layer was changed to 75 / 20 / 5. The evaluation results of the fiber properties and spinnability are shown in Table 2. It was confirmed that the fiber cross section formed a three-layer structure, the raw yarn tensile strength was 8.0 cN / dtex, and the fluff count was good.

[0045] [Example 3] A polyester fiber was obtained in the same manner as in Example 1, except that the area ratio of raw polyester A and recycled polyester B was changed to 80 / 20, and the area ratio of the innermost layer / middle layer / outer layer was changed to 60 / 20 / 20. The evaluation results of the fiber properties and spinnability are shown in Table 2. It was confirmed that the fiber cross section formed a three-layer structure, the raw yarn tensile strength was 7.5 cN / dtex, and the fluff count was good.

[0046] [Example 4] A polyester fiber was obtained in the same manner as in Example 1, except that the area ratio of raw polyester A and recycled polyester B was changed to 50 / 50, and the area ratio of the innermost layer / middle layer / outer layer was changed to 45 / 50 / 5. The evaluation results of the fiber properties and spinnability are shown in Table 2. It was confirmed that the fiber cross section formed a three-layer structure, the raw yarn tensile strength was 6.3 cN / dtex, and the fluff count was fairly good.

[0047] [Example 5] A polyester fiber was obtained in the same manner as in Example 1, except that the area ratio of raw polyester A and recycled polyester B was changed to 50 / 50, and the area ratio of the innermost layer / middle layer / outer layer was changed to 30 / 50 / 20. The evaluation results of the fiber properties and spinnability are shown in Table 2. It was confirmed that the fiber cross section formed a three-layer structure, the raw yarn tensile strength was 5.8 cN / dtex, and the fluff count was fairly good.

[0048] [Example 6] A polyester fiber was obtained in the same manner as in Example 1, except that recycled polyester B was changed to polyethylene terephthalate chips with an IV of 0.62, which were prepared by crushing, melting, and repelletizing process scraps of narrow belts. The evaluation results of the fiber properties and spinnability are shown in Table 2. It was confirmed that the pressure rise of recycled polyester B was 0.45 MPa / 24 hr, the fiber cross section formed a three-layer structure, the raw yarn tensile strength was 8.2 cN / dtex, and the fluff count was excellent.

[0049] [Table 2]

[0050] [Comparative Example 1] A polyester fiber was obtained in the same manner as in Example 1, except that the area ratio of raw polyester A and recycled polyester B was changed to 70 / 30, and the core component was raw polyester A and the sheath component was changed to a core-sheath structure of recycled polyester B. The evaluation results of the fiber properties and spinnability are shown in Table 3. The fiber cross section formed a two-layer structure, the raw yarn tensile strength was 5.8 cN / dtex, and the fluff count was poor.

[0051] [Comparative Example 2] A polyester fiber was obtained in the same manner as in Example 1, except that the area ratio of raw polyester A and recycled polyester B was changed to 70 / 30, the core component was recycled polyester B, and the sheath component was raw polyester A to form a core-sheath structure. The evaluation results of the fiber properties and spinnability are shown in Table 3. The fiber cross section formed a two-layer structure, the raw yarn tensile strength was 4.5 cN / dtex, and the fluff count was poor.

[0052] [Comparative Example 3] A polyester fiber was obtained in the same manner as in Example 1, except that the area ratio of raw polyester A to recycled polyester B was changed to 40 / 60, and the area ratio of the innermost layer / middle layer / outer layer was changed to 30 / 60 / 10. The evaluation results of the fiber properties and spinnability are shown in Table 3. The fiber cross section formed a three-layer structure, the raw yarn tensile strength was 4.3 cN / dtex, and the fluff count was poor.

[0053] [Comparative Example 4] A polyester fiber was obtained in the same manner as in Example 1, except that raw polyester A was used as the middle layer component and recycled polyester B was used as the innermost layer and outer layer components. The evaluation results of the fiber properties and spinnability are shown in Table 3. The fiber cross section formed a three-layer structure, the raw yarn tensile strength was 6.2 cN / dtex, and the fluff count was poor.

[0054] [Comparative Example 5] A polyester fiber was obtained in the same manner as in Example 1, except that the area ratio of raw polyester A and recycled polyester B was 70 / 30, the innermost layer component was changed to a four-layer structure of recycled polyester B / raw polyester A / recycled polyester B / raw polyester A, and the area ratio of the innermost layer / inner middle layer / outer middle layer / outer layer was changed to 20 / 60 / 10 / 10. The evaluation results of the fiber properties and spinnability are shown in Table 3. Stable spinnability was not obtained, and raw yarn could not be obtained.

[0055] [Table 3]

[0056] The fibers obtained in Examples 1 to 6 formed a three-layer structure, and were able to obtain high tensile strength and good spinnability. The fiber of Comparative Example 1 had a core-sheath two-layer structure, so foreign matter contained in the regenerated polyester B of the sheath component inhibited drawing, increasing the number of fluff, and the spinnability was poor. The fibers of Comparative Examples 2 to 3 had too high a ratio of the outer layer component and a regenerated ratio, so the spinnability and raw yarn tensile strength decreased with the increase in the number of fluff. The fiber of Comparative Example 4 used raw polyester A as the middle layer component, so the regenerated polyester B of the sheath inhibited drawing, increasing the number of fluff, and the spinnability was poor. The fiber of Comparative Example 5 had a difficult layer structure formation because the regenerated polyester B was the middle layer component, and raw yarn could not be obtained.

Claims

1. The regenerated polyester fiber is characterized in that the main repeating unit is composed of ethylene terephthalate, the polyester three-layer composite fiber being composed of raw material polyester A and recycled polyester B, the raw material polyester A is used as the innermost layer and the outer layer component, and the recycled polyester B is used as the middle layer component, the area ratio (A / B) of raw material polyester A to recycled polyester B is 80 / 20 to 50 / 50, the tensile strength is 5.0 to 9.0 cN / dtex, and the number of fuzz particles per 10,000 m is 0 to 2.

2. 2. The recycled polyester fiber according to claim 1, characterized in that the area ratio of the innermost layer, the middle layer and the outer layer is 75 / 20 / 5 to 30 / 50 / 20.

3. The regenerated polyester fiber according to claim 1 or 2, characterized in that the pressure rise of the regenerated polyester B is 0.15 to 0.5 MPa / 24 hr.

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