Full-recovery core-sheath type composite monofilament fiber and manufacturing method thereof

Abstract

The invention relates to a core-sheath type composite monofilament fiber, a core layer and a sheath layer of the core-sheath type composite monofilament fiber are made of regenerated raw materials obtained through physical recovery, the core layer comprises polyester macromolecules from textile waste, and the sheath layer comprises regenerated polyethylene glycol terephthalate (rPET). According to the monofilament fiber, raw materials obtained through chemical recovery are not used, the impact on the environment and the cost can be reduced to the minimum, the quality and the physical performance of the monofilament fiber can be better than those of original materials of recovered textiles, and therefore the same-level recovery of the textiles is achieved. The invention also relates to a method for manufacturing the core-sheath composite monofilament fiber.

Description

Technical Field

[0001] The present invention relates to a core-sheath type composite monofilament fiber, wherein both the core layer and the sheath layer are made of recycled raw materials obtained through physical recycling. The present invention also relates to a method for manufacturing the core-sheath type composite monofilament fiber. Background Art

[0002] The 18th-century Industrial Revolution began with technological changes in the textile industry, and the rapid development of the petrochemical industry further fueled innovation in textile materials. Today, with improved living standards, clothing has evolved beyond simply providing warmth and shelter to become a reflection of personal style and fashion. Textile materials used in clothing have also become more diverse, including natural fibers such as cotton, linen, wool, and silk; man-made fibers such as polyester, polyacrylonitrile, polyamide, and polypropylene; and blends combining two or more fibers. However, advances in textile technology and consumers' pursuit of fashion have also led to environmental problems of overproduction, overconsumption, and overdisposal. The recent surge in consumption driven by the fast fashion trend has generated a massive amount of out-of-season clothing and fashion waste, making the clothing industry a major source of global pollution. For example, in Taiwan Province of China, residents discarded 78,000 metric tons of used clothing in 2020, with a staggering 35% of that ending up in incinerators.

[0003] To promote the sustainability of the entire textile supply chain and achieve a circular economy focused on environmental protection, the textile industry has invested heavily in the recycling of textile and plastic waste. A successful example is the recycling of bottle flakes to produce recycled textiles. PET bottles are made of highly homogeneous polyethylene terephthalate (PET). Discarded PET bottles are recycled and cleaned into flakes, which are then crushed, melted, filtered, and granulated into polyester pellets. These pellets are then sent to chemical fiber mills to be drawn into yarn, which can then be woven into various polyester fabrics. Although polyester is also the most widely used material in the apparel industry, recycling clothing is technically much more difficult than recycling bottle flakes. These fibers are often blended with man-made and natural fibers, or even with several man-made fibers, resulting in complex compositions, mixed colors, and difficulty separating them. Furthermore, many garments are equipped with non-recyclable metal zippers, buttons, and other accessories, further complicating recycling efforts. Not to mention that commonly used polyester fibers are quite diverse and can be divided into those made from polyester materials such as polyethylene terephthalate (PET), polypropylene terephthalate (PTT), polybutylene terephthalate (PBT), or thermoplastic polyester elastomer (TPEE). Due to limitations in clothing sorting technology, less than 1% of recycled clothing is currently used to make new garments. In addition, current clothing recycling technology typically involves chemical recycling processes. This involves adding appropriate solvents to shredded clothing, causing them to depolymerize under specific reaction conditions into smaller molecules such as monomers or oligomers. After separation and purification, they are repolymerized into polyester particles for the production of recycled fibers. However, this type of chemical recycling process consumes a large amount of energy, and the subsequent waste disposal of chemicals such as solvents used in the process also increases environmental costs, which goes against the industry trend of energy conservation and carbon reduction.

[0004] Therefore, the relevant industries still have an urgent need for polyester recycled fibers and their manufacturing methods that can achieve the ideal circular economy of textile to textile (Textile to Textile). Summary of the Invention

[0005] In order to meet the above-mentioned industrial needs, the inventors of this case have worked hard on research and development, and thus obtained the invention applied for in this case. The materials used in this invention are completely made by physical recycling. The present invention involves the production of first regenerated ester particles as the internal core layer material from textile waste such as waste cloth, waste yarn or homogeneous waste containing polyester fibers after crushing, melting, filtering and granulation, and then using second regenerated ester particles of better quality and higher purity obtained by recycling bottle flakes as the external sheath material, and extruding them through a co-extrusion process to produce core-sheath type composite monofilament fibers. The quality and physical properties of the monofilament fibers in this case are comparable to those of virgin polyester fibers of the same grade, which is beneficial for downstream weaving and use, and achieves the goal of full recycling of polyester textiles.

[0006] Therefore, a first embodiment of the present invention provides a core-sheath composite monofilament fiber, which is produced by a coextrusion process and has a denier of 15 to 22,000, comprising:

[0007] a core layer extending in a longitudinal direction, comprising polyester waste obtained through physical recycling, wherein the polyester waste contains a polyester polymer selected from the group consisting of polyethylene terephthalate (PET), polypropylene terephthalate (PTT), polybutylene terephthalate (PBT), thermoplastic polyester elastomer (TPEE), and combinations thereof, wherein the core layer has an intrinsic viscosity in the range of 0.40 to 0.80 dL / g at a coextrusion temperature; and

[0008] a sheath layer substantially completely covering the core layer along the longitudinal direction, the sheath layer comprising recycled polyethylene terephthalate (rPET) obtained from bottle flake recycling, wherein the sheath layer has an intrinsic viscosity in the range of 0.64 dL / g to 1.05 dL / g at the coextrusion temperature;

[0009] Based on the total volume of the composite monofilament fiber, the core layer has a volume percentage ranging from 10% (v / v) to 90% (v / v).

[0010] A second embodiment of the present invention provides a method for manufacturing the core-sheath composite monofilament fiber, comprising the following steps:

[0011] Heating polyester waste obtained through physical recycling to produce a core layer melt stream, wherein the polyester waste comprises a polyester polymer selected from the group consisting of polyethylene terephthalate (PET), polypropylene terephthalate (PTT), polybutylene terephthalate (PBT), thermoplastic polyester elastomer (TPEE), and combinations thereof, wherein the core layer melt stream has an intrinsic viscosity in the range of 0.40 to 0.80 dL / g at a coextrusion temperature;

[0012] heating recycled polyethylene terephthalate (rPET) obtained by recycling bottle flakes to produce a sheath melt stream, wherein the sheath melt stream has an intrinsic viscosity in a range of 0.64 dL / g to 1.05 dL / g at the coextrusion temperature;

[0013] The core layer melt stream and the sheath layer melt stream are co-extruded at the co-extrusion temperature to obtain a core-sheath type composite monofilament fiber having a fineness of 15 to 22,000 deniers, wherein the core layer has a volume percentage in the range of 10% (v / v) to 90% (v / v) based on the total volume of the composite monofilament fiber.

[0014] The beneficial effects that can be achieved by the present invention include:

[0015] 1. The materials used for the core and sheath layers of the composite monofilament fibers in this invention are entirely recovered through physical recycling of polyester waste. Because this invention does not involve chemical recycling, not only is the recycling cost lower, but the chemical waste generated is also reduced, minimizing the environmental impact and costs of the overall recycling process.

[0016] 2. Conventional recycling and remanufacturing technology, in order to ensure the homogeneity and purity of raw materials, must first determine the type of plastic in the waste and classify it according to the material before subsequent corresponding processing can be carried out. For this reason, textile waste must first be sorted and classified manually or by expensive textile sorting machines, resulting in high costs and making the source of recycled materials almost limited to PET bottle recycling. The mechanical strength of the composite monofilament fiber in this case is mainly maintained by the sheath layer, and the sheath layer composed solely of PET can also mask the complex color of the core layer composed of polyester waste. Therefore, the present invention has lower requirements for the composition and quality of the core layer material, can accept a wider viscosity variation, and a higher content of impurities, dyes or additives, thereby reducing the textile waste screening process and reducing the classification process.

[0017] 3. The quality and physical properties of the composite monofilament fibers in this case are comparable to those of the original materials that constitute recycled textiles. Therefore, the present invention can achieve the same-level recycling of textiles and increase the recycling value of textile waste.

[0018] 4. The present invention can achieve the best benefits of textile recycling and is helpful to achieve the goal of 100% recycling of textiles. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a perspective schematic diagram of a core-sheath composite monofilament fiber produced according to one embodiment of the present invention;

[0020] Figure 2 is a schematic cross-sectional view of a core-sheath composite monofilament fiber according to one embodiment of the present invention;

[0021] Figure 3 is a schematic cross-sectional view of a core-sheath type composite monofilament fiber according to another embodiment of the present invention;

[0022] Figure 4A flow chart for manufacturing core-sheath composite monofilament fibers;

[0023] Figure 5A This is an image of a cross-section of a core-sheath composite monofilament fiber according to one embodiment of the present invention, comprising a sheath layer composed of 50±5% (v / v) recycled PET (rPET) from bottle flakes and a core layer composed of 50±5% (v / v) recycled polyethylene terephthalate (PET) waste yarn (T-rPET).

[0024] Figure 5B This is an image of a cross-section of a core-sheath composite monofilament fiber according to another embodiment of the present invention, comprising a sheath layer composed of 30±5% (v / v) recycled PET (rPET) from bottle flakes and a core layer composed of 70±5% (v / v) recycled polyethylene terephthalate (T-rPET) yarn.

[0025] Figure 5C This is an image of a cross-section of a core-sheath composite monofilament fiber according to another embodiment of the present invention, comprising a sheath layer composed of 50±5% (v / v) recycled PET (rPET) from bottle flakes and a core layer composed of 50±5% (v / v) recycled black polyethylene terephthalate waste (T-rPET).

[0026] Figure 5D This is an image of a cross-section of a core-sheath composite monofilament fiber according to another embodiment of the present invention, comprising a sheath layer composed of 30±5% (v / v) recycled PET (rPET) from bottle flakes and a core layer composed of 70±5% (v / v) recycled black polyethylene terephthalate waste (T-rPET).

[0027] Figure 6A This is an image of a cross-section of a core-sheath composite monofilament fiber according to another embodiment of the present invention, comprising a sheath layer composed of 35% (v / v) recycled PET (rPET) from bottle flakes, a middle layer composed of 20% (v / v) recycled PET (rPET) from bottle flakes, and a core layer composed of 45% (v / v) physically recycled black polyethylene terephthalate waste cloth (T-rPET); and

[0028] Figure 6B This is a cross-sectional image of a core-sheath composite monofilament fiber according to another embodiment of the present invention, which comprises a sheath layer composed of 55% (v / v) recycled PET bottles (rPET) from bottle flakes, a middle layer composed of 25% (v / v) recycled PET bottles (rPET) from bottle flakes, and a core layer composed of 20% (v / v) physically recycled polyethylene terephthalate black waste cloth (T-rPET).

[0029] Explanation of symbols:

[0030] 1.....monofilament fiber

[0031] 11.....Core layer

[0032] 12.....Sheath

[0033] 13.....Middle Layer

[0034] X....longitudinal direction. DETAILED DESCRIPTION

[0035] Figure 1 and Figure 2 This is a schematic diagram of an embodiment of the present application, showing a core-sheath type composite monofilament fiber 1 with a double-layer concentric structure, extending substantially along the longitudinal direction X. In this specification, the term "monofilament fiber" means a single continuously extending man-made fiber, as distinguished from a multifilament composed of dozens to hundreds of single fibers. The monofilament fiber generally has a fineness of 15 to 22,000 deniers, preferably a fineness of 50 to 6,500 deniers. Figure 1 and Figure 2 As shown, the monofilament fiber 1 comprises a core layer 11, and a sheath layer 12 that substantially completely covers the core layer 11 along the longitudinal direction X. "Substantially completely covered" herein means that the core layer 11 has at least 95% of its surface area, preferably at least 98% of its surface area, and more preferably at least 99% of its surface area along its entire length, covered by the sheath layer 12. The cross-section of the monofilament fiber 1 can be roughly circular, oval or dumbbell-shaped. According to the present invention, based on the total volume of the composite monofilament fiber 1, the core layer 11 has a volume percentage in the range of 10% (v / v) to 90% (v / v). In Figure 1 and Figure 2 In the first embodiment shown, the cross-sectional area ratio and volume ratio of the core layer 11 to the sheath layer 12 in the monofilament fiber 1 can be within a range of 90:10 to 10:90, preferably within a range of 70:30 to 50:50, for example, approximately 80:20. Various multifilament yarns, woven fabrics, and non-woven fabrics made using the monofilament fiber 1 of this embodiment also fall within the scope of the present invention.

[0036] According to the present application, the materials of the core layer 11 and the sheath layer 12 are obtained through physical recycling. "Physical recycling" as referred to herein means recycling waste containing plastic materials through mechanical processing methods such as crushing, washing, sorting, mixing, melting, filtering and granulation. Generally speaking, physical recycling does not significantly affect the chemical structure of the plastic materials contained in the waste. The material of the core layer 11 includes polyester waste. "Polyester waste" as referred to herein means textiles mainly composed of polyester polymers that are discarded during the production process or at the end of their service life, including but not limited to clothing, accessories, bedding, padding, scraps, waste cloth and waste yarn mainly composed of polyester polymers, and the polyester polymer is selected from the group consisting of polyethylene terephthalate (PET), polypropylene terephthalate (PTT) or polybutylene terephthalate (PBT), thermoplastic polyester elastomer (TPEE) and combinations thereof. In a preferred embodiment, the polyester waste contains at least 50% by weight, more preferably at least 80% by weight, for example at least 90% by weight of polyester polymers. The material of the sheath 12 comes from recycled polyethylene terephthalate (rPET) obtained by recycling bottle flakes. The "PET bottle recycling" referred to here means the process of obtaining rPET ester pellets by physically recycling PET bottles, and rPET ester pellets are commercially available. Since PET bottles are made of high-purity high-density PET, the intrinsic viscosity of the sheath 12 will be substantially higher than or equal to the intrinsic viscosity of the core layer 11. The "intrinsic viscosity" referred to here is used to describe the ability of polyester polymers to increase the viscosity of a solution in a solution, especially the intrinsic viscosity of recycled ester pellets containing polyester polymers at the co-extrusion temperature described later, which can be measured by ASTMD5225. As is well known to those skilled in the art, the intrinsic viscosity of a polymer is related to its molecular weight, and the relationship between the two can be expressed by the Mark-Houwink equation (Mark-Houwink Equation; [η] = K·Ma, where [η] is the intrinsic viscosity of the polymer in solution, M is the molecular weight of the polymer, and K and a are Mark-Houwink parameters, which are related to the type of polymer, the type of solvent, and temperature). According to the present invention, the core layer 11 can have an intrinsic viscosity in the range of 0.40 to 0.80 dL / g, preferably 0.50 to 0.66 dL / g, such as 0.45 to 0.50 dL / g. The sheath layer 12 can have an intrinsic viscosity in the range of 0.64 to 1.05 dL / g, preferably 0.66 to 0.85 dL / g, such as 0.74 to 0.80 dL / g.

[0037] The sheath layer 12 can be added with a masterbatch to give the sheath layer 12 a desired color. In order to prevent the color of the polyester waste contained in the core layer 11 from affecting the color performance of the monofilament fiber 1, Figure 1 and Figure 2 In the preferred embodiment shown, an appropriate amount of titanium white can be added to the core layer 11 to mask the color of the core layer 11 and make the monofilament fiber 1 present an ideal color.

[0038] Figure 3 This is a schematic diagram of a second embodiment of the present application, showing a core-sheath composite monofilament fiber 1 having a three-layer concentric structure. The monofilament fiber 1 typically has a fineness of 15 to 22,000 denier, preferably 50 to 6,500 denier. The materials of the core layer 11 and sheath layer 12 of the second embodiment are the same as those of the first embodiment, except that an intermediate layer 13 is included between the core layer 11 and the sheath layer 12, and the intermediate layer 13 can substantially completely cover the core layer 11 along the longitudinal direction X. The term "substantially completely covered" herein means that at least 95% of the outer surface area of ​​the core layer 11 along its entire length, preferably at least 98% of the outer surface area, and more preferably at least 99% of the outer surface area, is covered by the intermediate layer 13. The material used for the middle layer 13 is also rPET recycled from bottle flakes, and its intrinsic viscosity may also be in the range of 0.64 to 1.05 dL / g, preferably 0.66 to 0.85 dL / g, for example 0.74 dL / g to 0.80 dL / g. The intrinsic viscosities of the sheath layer 12 and the middle layer 13 may be substantially the same or different. A masterbatch may be added to the middle layer 13 to impart a desired color to the middle layer 13. In a preferred embodiment, the middle layer 13 is doped with titanium dioxide to serve as a masking layer for obscuring the color of the core layer 11, thereby achieving the desired color appearance of the monofilament fiber 1. In a second embodiment, the core layer 11 has a volume percentage in the range of 10% (v / v) to 90% (v / v), based on the total volume of the composite monofilament fiber 1. In a preferred embodiment, the core layer 11 has a volume percentage in the range of 20% (v / v) to 80% (v / v), the sheath layer 12 has a volume percentage in the range of 10% (v / v) to 60% (v / v), and the intermediate layer 13 has a volume percentage in the range of 10% (v / v) to 50% (v / v).

[0039] According to the present application, the monofilament fiber 1 is produced by a co-extrusion process. Figure 4 As shown, the method for manufacturing the above-mentioned core-sheath type composite monofilament fiber in this case includes the following steps: A. preparing a core layer melt flow from polyester waste; B. preparing a sheath layer melt flow from rPET; and C. co-extruding the core layer and sheath layer melt flows into a core-sheath type composite monofilament fiber.

[0040] Steps A and B involve heating the regenerated polyester pellets obtained through physical recycling to a coextrusion temperature, thereby producing core and sheath molten streams for forming the core layer 11 and sheath layer 12. The "coextrusion temperature" herein refers to the temperature at which the polyester polymer melts in the extruder and flows into the spinneret. Therefore, this temperature must be substantially above the melting point of the polyester polymer to melt the polyester polymer into a molten stream. In a preferred embodiment, the coextrusion temperature is within a range of 200°C to 300°C. In the embodiment of producing a core-sheath composite monofilament fiber with a three-layer concentric structure, step B further comprises heating rPET obtained from recycled bottle flakes to produce a molten stream for the intermediate layer. As previously mentioned, the core layer melt stream has an intrinsic viscosity at the coextrusion temperature within the range of 0.40 to 0.80 dL / g, for example, 0.45 to 0.50 dL / g, while the sheath layer melt stream and the middle layer melt stream have an intrinsic viscosity at the coextrusion temperature within the range of 0.64 to 1.05 dL / g, for example, 0.74 to 0.80 dL / g. If the intrinsic viscosity of the core layer melt stream, the sheath layer melt stream, or the middle layer melt stream is below the above range, the intrinsic viscosity can be increased by adding an appropriate amount of virgin PET or a chain extender.

[0041] Step C is a co-extrusion step, which involves allowing the core layer molten stream and the sheath layer molten stream to enter the spinneret of the extruder through a narrow channel, thereby forming a polyester stream in which the sheath layer molten stream covers the core layer molten stream. Subsequently, the polyester stream is extruded from the orifice of the spinneret and cooled (quenched) with cold water or cold air. During the cooling process, the polyester stream solidifies and forms a monofilament fiber 1 having a core layer 11 and a sheath layer 12, as shown in FIG. Figure 1 、 2 As shown. In the specific example of producing a core-sheath type composite monofilament fiber having a three-layer concentric structure, step C further includes allowing the intermediate layer molten flow to enter the spinneret of the extruder through a narrow channel, where a polyester flow is formed in which the sheath layer molten flow covers the intermediate layer molten flow and the intermediate layer molten flow covers the core layer molten flow. The polyester flow is then cooled to solidify and form a monofilament fiber 1 having a core layer 11, a sheath layer 12 and an intermediate layer 13, as shown. Figure 3 shown.

[0042] In a preferred embodiment, the method further comprises a heat-stretching step after step C, which involves heating and stretching the cooled monofilament. In one embodiment, the stretching and heating can be achieved by tensioning the monofilament using a set of godet rollers and passing it through a hot water bath and hot air. In another embodiment, both heating and stretching are performed by godet rollers. The heating temperature is within a range of 50°C to 300°C.

[0043] The following examples are only provided to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0044] Experiment 1: Preparation of fully recycled core-sheath composite monofilament fibers

[0045] Polyester pellets (T-rPET) obtained from physically recycled polyethylene terephthalate (PET) waste cloth or yarn (abbreviated as T-rPET) are placed in a core layer hopper. From there, they are fed into a screw extruder and melted at 220-300°C to produce a core layer melt stream. As shown in Table 1 below, the T-rPET used in Examples 1 and 2 was derived from yarn waste, and the resulting core layer melt stream had an intrinsic viscosity of 0.62 dL / g. The T-rPET used in Examples 3 and 4 was derived from cloth waste, and the resulting core layer melt stream had an intrinsic viscosity of 0.54 dL / g. Chain extenders can be added to the core layer melt stream to increase its intrinsic viscosity.

[0046] Recycled polyethylene terephthalate (rPET) pellets from recycled bottle flakes are placed in a sheath hopper, fed from the hopper into a screw extruder and melted at 200-300°C to produce a sheath melt stream. The resulting sheath melt stream has an intrinsic viscosity of 0.85 dL / g.

[0047] Metering pumps control the discharge rate of the core and sheath melt streams, in the volume ratios shown in Table 1. These two streams flow through a narrow channel into the extruder's spinneret, where they form a polyester stream with the sheath melt enveloping the core melt. The polyester stream is then extruded from the spinneret's orifice, cooled and solidified in a cold water environment, passed through a yarn guide, and then passed to the first roller (1GR). It is then stretched in hot water at 80-100°C and shaped with hot air at 110-220°C before passing to a winder to produce a monofilament fiber with a diameter of approximately 0.20mm. 5A to 5D The optical microscopic images of the cross sections of the core-sheath composite monofilament fibers prepared in Examples 1 to 4 show that the volume ratio of the core layer to the sheath layer is about 50:50 (Examples 1 and 3) or about 70:30 (Examples 2 and 4).

[0048] Table 1. Composition of fully recycled core-sheath composite monofilament fibers

[0049]

[0050] Experiment 2: Continuous Analysis of 1000 Points with a Single Longitudinal Laser

[0051] The core-sheath composite monofilament fibers prepared in Examples 1-4 were subjected to a single longitudinal laser analysis at 1000 points. First, the monofilament fibers were secured to a sample holder. The laser beam was then scanned along the longitudinal direction of the fibers, continuously measuring 1000 points. A detector recorded the change in reflected light intensity at each measurement point, allowing the change in longitudinal fiber diameter to be calculated. A black monofilament fiber extruded from virgin PET and having a diameter of 0.20 mm was subjected to the same analysis as a comparative example. The results are shown in Table 2.

[0052] As shown in Table 2, the yarn coefficient of variation (CV) of the fully recycled monofilament fibers prepared in Examples 1 to 4 is comparable to that of the comparative example, indicating that their longitudinal diameter uniformity is comparable to that of virgin PET fibers of the same grade.

[0053] Table 2. Composition of fully recycled core-sheath composite monofilament fibers

[0054]

[0055]

[0056] Experiment 3: Mechanical properties of fully recycled core-sheath composite monofilament fibers

[0057] The core-sheath composite monofilament fibers prepared in Examples 1-4 were subjected to fiber strength testing according to ASTM D3822 / D3822M. The core-sheath composite monofilament fibers prepared in Examples 1-4 were subjected to continuous 50-point longitudinal analysis to analyze the strength and elongation of the PET monofilament fibers. The monofilament fibers were secured in the fixture of a tensile testing machine, and the tensile test was then initiated. During the test, a 25 cm monofilament fiber was used. The 100 kg load cell of the tensile testing machine detected the tensile strength at break of the monofilament fiber, and the elongation was calculated based on the ratio of the length at break. This measurement system continuously measured the longitudinal direction of the fiber, recording data at 50 measurement points. Based on the force and displacement data recorded by the tensile testing machine, a stress-strain curve was plotted, and the maximum tensile strength (stress at break) and elongation at break (strain at break) of the fiber were calculated. A black monofilament fiber extruded from virgin PET and having a diameter of 0.20 mm was subjected to the same analysis as a comparative example. The results are shown in Table 3.

[0058] As shown in Table 3, the strength and elongation of the fully recycled monofilament fibers prepared in Examples 1-4 are comparable to those of the comparative example. Furthermore, the variation range of strength and elongation at 50 measurement points in the longitudinal direction is also quite narrow, indicating that their mechanical properties are comparable to those of virgin PET fibers of the same grade.

[0059] Table 3. Mechanical properties of fully recycled core-sheath composite monofilament fibers

[0060] Strength range (Kg) Average strength (Kg) Strength (g / Daniel) Elongation range (%) Average elongation (%) Example 1 1.78～2.00 1.91 4.6 32.0～39.6 36.2 Example 2 1.75～1.87 1.82 4.5 32.0～40.5 36 Example 3 1.76～1.90 1.83 4.4 32.0～38.4 35.3 Example 4 1.70～1.82 1.76 4.4 32.0～37.4 35.1 Comparative Example 1.79～1.90 1.85 4.5 35.3～44.0 39.7

[0061] In a separate experiment, the core-sheath composite monofilament fibers prepared in Examples 1-4 were heated in an oven at 200°C for 30 minutes to calculate their shrinkage (% shrinkage). Black monofilament fibers extruded from virgin PET and having a diameter of 0.20 mm were also subjected to the same test as a comparative example. The results are shown in Table 4.

[0062] As shown in Table 4, the thermal shrinkage of the fully recycled monofilament fibers prepared in Examples 1 to 4 is comparable to that of the comparative example, indicating that their mechanical properties are comparable to those of virgin PET fibers of the same grade.

[0063] Table 4. Mechanical properties of fully recycled core-sheath composite monofilament fibers

[0064] Shrinkage (%) Example 1 5.3 Example 2 4.9 Example 3 5.1 Example 4 4.3 Comparative Example 5.0±1.0

[0065] Experiment 4: Preparation of fully recycled core-sheath composite monofilament fibers

[0066] Experiment 1 was repeated, but rPET pellets from recycled bottle flakes were added to the intermediate layer hopper. From there, they were fed into a screw extruder and melted at 200-300°C to produce the intermediate layer melt stream. Metering pumps controlled the output of the core, sheath, and intermediate layer melt streams, directing these three streams through a narrow channel into the extruder's spinneret. This resulted in a polyester stream in which the sheath melt overwrapped the intermediate layer melt, and vice versa. The polyester stream was then extruded from the spinneret's orifice, cooled and solidified in a cold water environment, passed through a yarn guide, and then passed to the first roller (1GR). The fibers were then stretched using hot water at 80-100°C. After setting with hot air at 110-220°C, they were fed to a winder to produce monofilament fibers with a diameter of approximately 0.20 mm. Figure 6A and Figure 6B This is an optical microscopic image of the cross section of the core-sheath composite monofilament fiber prepared in Experiment 4, showing that the volume percentages of the core layer, the middle layer, and the sheath layer are approximately 45% (v / v), 20% (v / v), and 35% (v / v), respectively. Figure 6A ) or about 20% (v / v), 25% (v / v) and 55% (v / v) ( Figure 6B ).

Claims

1. A core-sheath composite monofilament fiber, characterized in that: Made by a co-extrusion process with a denier of 15 to 22,000, comprising: A core layer extending in a longitudinal direction, comprising polyester waste obtained through physical recycling, wherein the polyester waste contains a polyester polymer selected from the group consisting of polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, thermoplastic polyester elastomer and a combination thereof, wherein the core layer has an intrinsic viscosity in the range of 0.40 to 0.80 dL / g at a co-extrusion temperature; and a sheath layer substantially completely covering the core layer along the longitudinal direction, the sheath layer comprising recycled polyethylene terephthalate obtained from bottle flakes recycling, wherein the sheath layer has an intrinsic viscosity in the range of 0.64 dL / g to 1.05 dL / g at the coextrusion temperature; The core layer has a volume percentage ranging from 10% (v / v) to 90% (v / v) based on the total volume of the composite monofilament fiber.

2. The core-sheath type composite monofilament fiber according to claim 1, characterized in that: There is also an intermediate layer between the core layer and the sheath layer, which comprises recycled polyethylene terephthalate obtained from bottle flakes recycling, wherein the intermediate layer has a characteristic viscosity in the range of 0.64dL / g to 1.05dL / g at the co-extrusion temperature, and the intermediate layer is doped with masterbatch or titanium white to mask the color of the core layer.

3. The core-sheath type composite monofilament fiber according to claim 1, characterized in that: The volume ratio of the core layer to the sheath layer in the monofilament fiber is within a ratio range of 90:10 to 10:

90.

4. The core-sheath type composite monofilament fiber according to claim 2, characterized in that: The core layer has a volume percentage in the range of 20% (v / v) to 80% (v / v), the sheath layer has a volume percentage in the range of 10% (v / v) to 60% (v / v), and the middle layer has a volume percentage in the range of 10% (v / v) to 50% (v / v).

5. The core-sheath type composite monofilament fiber according to claim 1, characterized in that: The polyester waste contains at least 80% by weight of polyester polymers.

6. The core-sheath type composite monofilament fiber according to claim 5, characterized in that: The polyester waste contains at least 90% by weight of polyester polymers.

7. The core-sheath type composite monofilament fiber according to claim 1, characterized in that: The core layer is doped with titanium white to mask the color of the core layer.

8. A method for producing a core-sheath type composite monofilament fiber, characterized in that: It includes the following steps: Heating polyester waste obtained through physical recycling to obtain a core layer melt stream, wherein the polyester waste contains a polyester polymer selected from the group consisting of polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, thermoplastic polyester elastomer and a combination thereof, wherein the core layer melt stream has an intrinsic viscosity in the range of 0.40 to 0.80 dL / g at a coextrusion temperature; Heating recycled polyethylene terephthalate obtained by recycling bottle flakes to obtain a sheath layer melt stream, wherein the sheath layer melt stream has an intrinsic viscosity in the range of 0.64 dL / g to 1.05 dL / g at the coextrusion temperature; The core layer molten stream and the sheath layer molten stream are co-extruded at the co-extrusion temperature to obtain a core-sheath type composite monofilament fiber having a fineness of 15 to 22,000 deniers, wherein the core layer has a volume percentage in the range of 10% (v / v) to 90% (v / v) based on the total volume of the composite monofilament fiber.

9. The method for producing a core-sheath type composite monofilament fiber according to claim 8, characterized in that: The invention also comprises heating recycled polyethylene terephthalate obtained by recycling bottle flakes to obtain an intermediate layer melt stream, and co-extruding the intermediate layer melt stream with the core layer melt stream and the sheath layer melt stream at the co-extrusion temperature, wherein the intermediate layer melt stream has a characteristic viscosity in the range of 0.64 dL / g to 1.05 dL / g at the co-extrusion temperature.

10. The method for producing a core-sheath type composite monofilament fiber according to claim 8, characterized in that: The co-extrusion step includes cooling the extruded core layer molten stream and the sheath layer molten stream.

11. The method for producing a core-sheath type composite monofilament fiber according to claim 10, characterized in that: A heat stretching step is further included after the co-extrusion step, and the heat stretching step includes heating the monofilament fiber and stretching it.

12. The method for producing a core-sheath type composite monofilament fiber according to claim 11, characterized in that: The heat stretching step includes heating the monofilament fiber at a temperature in the range of 50°C to 300°C.

13. The method for producing a core-sheath type composite monofilament fiber according to claim 12, characterized in that: The heat-stretching step includes tensioning the monofilament fiber and passing it through a hot water bath at 50° C. to 300° C. and hot air.

14. The method for producing a core-sheath type composite monofilament fiber according to claim 8, wherein: The coextrusion temperature is in the range of 200°C to 300°C.

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