Method for preparing a polyester recycled fiber and an upper thereof

Abstract

The application discloses a polyester recycling fiber preparation method and a shoe upper thereof, and belongs to the field of polymer material recycling. The method takes white polyester waste in an industrial production process as raw material, and after pretreatment, the raw material is blended with special single-color masterbatch to obtain single-color regenerated chips through melt granulation. Single-color polyester filaments are prepared through melt spinning and drafting and setting. Finally, single-color shoe upper materials are directly prepared through a weaving process, and water dyeing is not needed in the whole process. Through the integrated coloring and spinning process, high-value recycling of polyester waste is realized, pollution and energy consumption problems in a traditional dyeing process are fundamentally avoided, the shoe upper material prepared has uniform and special color, excellent color fastness, and has environmental protection, excellent performance and cost advantages.

Description

Technical Field

[0001] This invention relates to a method for preparing polyester recycled fibers and its shoe upper, belonging to the field of polymer material recycling. Background Technology

[0002] With increasing global emphasis on sustainable development and resource recycling, the textile industry is gradually increasing its research and application of recycled materials. Polyester (polyethylene terephthalate, PET), as the most produced and widely used synthetic fiber, generates a large amount of pre-consumer waste during its production process, such as waste yarns with color differences and uneven fineness, and waste chips with substandard molecular weight. These industrial wastes usually have high purity and molecular weight, and their high-value utilization has significant economic and environmental benefits.

[0003] Currently, the recycling and reuse technology of polyester fibers is mostly concentrated in non-clothing or non-footwear fields, and there is a common bottleneck of poor color stability of recycled fibers. In order to obtain colored products, the industry generally relies on the subsequent water dyeing process (such as using disperse dyes or reactive dyes). This traditional process has many inherent defects: for example, it consumes a lot of water, chemicals and energy during the dyeing process, and generates dyeing wastewater that is difficult to treat, increasing the environmental burden and treatment costs. Dyeing can also easily lead to poor color fastness of fabrics (such as color fading after washing), uneven color (local graying or whitening), and color deviation, affecting the appearance and durability of products. In addition, the market demand for black shoe upper materials remains strong, accounting for more than 60%, but existing products are unable to achieve a balance between "environmental friendliness", "cost" and "blackness quality". The market is either high-cost products that rely on water dyeing and have poor environmental friendliness, or low-end recycled materials with poor blackness and lack of recognizability. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for preparing polyester recycled fibers and its shoe upper, so as to solve the long-standing technical problem in the field of polyester recycled shoemaking that cannot balance environmental protection, quality and cost.

[0005] To achieve the above objectives, the present invention provides a method for preparing polyester recycled fibers, comprising: S1. Pre-treatment of white polyester waste; S2. The pretreated white polyester waste is blended and melt-granulated with monochrome masterbatch to obtain monochrome recycled polyester chips. S3. The monochrome recycled polyester chips are melt-spun, and after cooling, stretching and heat setting, monochrome polyester filaments are obtained. Among them, white polyester waste refers to white polyester fiber waste filaments and waste chips (such as scraps and unqualified semi-finished products generated during the production process) that have not yet entered the consumption stage, and the chemical purity of the white polyester waste is ≥99%.

[0006] Further, in step S1, the pretreatment includes removing impurities from the white polyester waste, crushing and granulating it, and drying it to remove water, wherein the drying temperature is 80-120℃; Preferably, the white polyester waste after crushing and granulation is in the form of small particles of 3-10 mm.

[0007] Furthermore, in step S1, the moisture content of the pretreated white polyester waste is ≤0.5%.

[0008] Further, in step S2, the monochrome masterbatch is an environmentally friendly black polyester masterbatch with a carbon black content of 50%, the amount of monochrome masterbatch added is 1% of the total weight of the raw materials, and the melt granulation method includes melting using a screw extruder; Preferably, the screw speed in the screw extruder is 200-550 r / min; Preferably, the melting temperature of the screw extruder is 260-280℃.

[0009] Further, in step S3, the melt spinning includes pre-crystallizing and melting monochromatic recycled polyester chips to form a melt, which is then extruded through a spinneret and cooled and solidified by side blowing to form nascent fibers.

[0010] Preferably, the pre-crystallization temperature is 160-180℃; Preferably, the temperature at which the melt is formed is 270-290°C; Preferably, the orifice diameter of the spinneret is 0.2-0.3 mm; Preferably, the side-blowing air temperature is 25-30℃; Preferably, the side-blowing wind speed is 0.5-1m / s.

[0011] Furthermore, the process of conveying the melt to the spinneret also includes a step of filtering and homogenizing the melt.

[0012] Furthermore, the nascent fibers undergo at least three stages of drawing, with the temperature of each stage increasing in a stepwise manner; wherein, The first stretching section is configured as a uniform stress section to eliminate uneven stress inside the fiber. The second stretching section is configured as a stretching section, which further stretches the fiber, allowing the molecular chains inside the fiber to gradually align. The third stretching section is configured as a uniform diameter section, which ensures that the molecular chains inside the fiber are evenly oriented and arranged, thus ensuring that the fiber diameter is consistent.

[0013] Furthermore, the first stage drawing temperature is 80-90℃, the second stage drawing temperature is 120-130℃, and the third stage drawing temperature is 160-170℃.

[0014] Furthermore, the heat setting is carried out under conditions higher than the stretching temperature, and the heat-set fiber is texturing to form the monochrome polyester filament; Preferably, the heat setting temperature is 180-200℃.

[0015] A polyester recycled shoe upper is made by using a single-color polyester filament obtained by any of the polyester recycled fiber preparation methods according to claims 1-9 to form the shoe upper material through a weaving process; the weaving process includes knitting and / or weaving.

[0016] The beneficial effects of this invention are: This invention abandons the traditional water dyeing process and achieves internal coloring of fibers by adding special masterbatch at the raw material stage. No dyeing wastewater is generated throughout the process, completely avoiding the use of dye chemicals and the subsequent treatment problems. The production process is clean and environmentally friendly, meeting the requirements of green manufacturing and sustainable development. Furthermore, since the black masterbatch is uniformly dispersed in the polyester matrix during the melting stage, the resulting black fibers have uniform color, pure blackness, and specificity. This fundamentally solves the problems of color difference, color variation, poor color fastness, and color migration that are easily caused by traditional dyeing processes, resulting in stable and reliable material quality.

[0017] In addition, this application integrates the coloring, granulation, and spinning processes, eliminating the need for separate dyeing and finishing processes and related equipment investment, shortening the production process, saving water, electricity, steam, and dye consumption, and using low-priced pre-consumption industrial waste as the main raw material, thus achieving a significant reduction in costs from both the source and process aspects. Attached Figure Description

[0018] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the steps in a method for preparing polyester recycled fibers according to the present invention; Figure 2 This is a schematic diagram of the warp weave in Application Example 1 of the present invention; Figure 3 This is a schematic diagram of the weaving of the plain weave structure in Application Example 2 of the present invention; Figure 4 This is a schematic diagram of the weaving of the plain weave structure in Application Example 3 of the present invention. Detailed Implementation

[0019] This invention provides a method for preparing recycled polyester fibers and their shoe upper base, the method comprising the following steps: S1. Raw material selection and pretreatment: S11. Raw material selection: White polyester fiber waste filaments and polyester waste chips generated during industrial production are selected as core raw materials, wherein the chemical purity of the waste material is ≥99% to ensure the basic performance of the recycled materials. S12. Pretreatment: The pretreatment process includes impurity removal, crushing and granulation, and drying and dehydration. Impurity removal includes removing metal impurities such as iron filings using a magnetic separator and removing adhering dust using airflow cleaning or vibrating sieving. Crushing and granulation refers to feeding the waste filaments and waste chips after impurity removal, either separately or mixed, into a high-powered crusher to break them into uniform small segments or fragments with a length or particle size of 3-10 mm, so as to achieve rapid and uniform melting and mixing in the subsequent melting process. Drying and dehydration involves placing the crushed waste material in a hot air circulating drying device and drying it continuously at a temperature of 80-120℃ for 4-6 hours to completely remove the moisture adsorbed by the raw materials during storage and crushing, strictly controlling the moisture content of the final material to below 0.5%, preventing hydrolysis and degradation caused by moisture during subsequent high-temperature processing, and further ensuring the molecular weight stability of the polymer.

[0020] S2, Melt Coloring Granulation: S21. Ingredients and Mixing: The pretreated and fully dried waste fragments are premixed with an environmentally friendly black polyester masterbatch (the masterbatch is Guangdong Jiucai New Material PET8683) at a precise mass ratio of 99:1. The resin carrier of the masterbatch is homologous to the polyester waste and has excellent compatibility. S22. Melt Blending and Extrusion: The mixture is continuously and uniformly fed into a co-rotating twin-screw extruder. The process parameters are set as follows: the screw speed is adjusted according to the output and mixing requirements within the range of 200-550 r / min, and the temperature of each heating zone is controlled at 260-280℃ to ensure that the polyester is completely melted and does not overheat and decompose. Under the strong shearing, mixing and conveying action of the screw, the white polyester melt and the black masterbatch are uniformly dispersed and fused, and the carbon black particles are fully wrapped and dispersed in the polyester matrix. S23. Cooling and pelletizing: The uniformly colored melt is extruded from the die into continuous thin strips, and then immersed in a circulating water bath at 20-30℃ for rapid cooling and solidification. After water cooling, the material is introduced into a pelletizer by a traction device and cut into pellets of uniform length, thus obtaining black recycled polyester chips with uniform black color and which are ready to be used directly for spinning.

[0021] S3, Melt spinning: S31. Feeding and Melting: Black recycled polyester chips are fed into the drying hopper of the spinning machine via an automatic conveying system. They are pre-crystallized and dried at 160-180℃ to improve their crystallinity and heat resistance and prevent the chips from sticking together in the screw. Subsequently, the chips enter the spinning screw and are melted at a high temperature of 270-290℃ to form a uniform melt with good fluidity. S32. Melt transport and filtration homogenization: The melt passes through a component equipped with a high-precision metal filter to remove any trace amounts of unmelted gel or impurities. It then enters a static mixer for homogenization to eliminate local differences in temperature and viscosity, ensuring that the temperature and viscosity of each part of the melt are consistent. S33. Metering and Spinning: The homogenized melt is precisely metered by a high-precision metering pump at a constant pressure (10-15MPa) and delivered to the spinneret. The spinneret has a spinneret orifice diameter of 0.2-0.3mm and a number of orifices of 36-72, which is selected according to the required monofilament fineness. S34. Cooling and forming: After the molten fine stream is extruded from the spinneret, it immediately enters the side blowing chamber. The fine stream is cooled and solidified by uniform side blowing with a temperature between 25-30℃ and a wind speed between 0.5-1 m / s to form nascent fibers.

[0022] S35. Fiber post-treatment: Fiber post-treatment includes stretching, heat setting, and texturing. In this process, the nascent fibers are gradually stretched by passing them through three sets of hot rollers at different temperatures. The first stretching temperature is controlled at 80-90℃ for initial orientation. The second stretching temperature is 120-130℃ to further increase the stretch ratio and orientation degree. The third stretching temperature is 160-170℃ to complete the final high-ratio stretching, which makes the crystallization and orientation structure of the fibers more perfect. Heat setting refers to the process of placing the stretched fibers in a heat setting zone at 180-200℃ for 30-60 seconds under tension or partial relaxation to eliminate internal stress in the fibers, improve crystallization perfection, thereby fixing the fiber shape, improving dimensional stability and thermal stability, and enhancing color fastness. Texturing involves feeding the heat-set fibers into a texturing machine, where processes such as false twisting and hot box setting impart a certain degree of crimp elasticity and fluffiness to the fibers, improving the hand feel and coverage of the final fabric, and winding the fibers into standard-sized tube-packaged black polyester filaments.

[0023] S4, Weaving and shaping: The black polyester filaments prepared above are used as weaving yarns and wound into yarn bobbins that can be directly used by different weaving equipment (such as warp knitting machines, shuttle looms, and fly looms).

[0024] It should be noted that this application is not limited to environmentally friendly black polyester masterbatch with a carbon black content of 30%. Based on the same technical principle, that is, white waste in the industrial production process can be melt-colored with a specific color masterbatch to form an integrated spun yarn, those skilled in the art can understand and use polyester masterbatches of other colors such as red, blue, and green to prepare recycled fibers and shoe upper materials of the corresponding colors. These variations should all fall within the protection scope of this invention.

[0025] Example 1: like Figure 1 As shown, this embodiment provides a method for preparing a polyester recycled shoe upper base. This method achieves the direct conversion from waste materials in the industrial production process to high-quality black shoe materials through an integrated melt dyeing and spinning process. Specifically, it includes the following steps: S1. Raw material selection and pretreatment: S11. Raw material selection: White polyester fiber waste filaments and polyester waste chips generated during industrial production are selected as core raw materials, wherein the chemical purity of the waste material is ≥99% to ensure the basic performance of the recycled materials. S12. Pretreatment: The pretreatment process includes impurity removal, crushing and granulation, and drying and dehydration. Impurity removal includes removing metal impurities such as iron filings using a magnetic separator and removing adhering dust using airflow cleaning or vibrating sieving. Crushing and granulation refers to feeding the waste filaments and waste chips after impurity removal, either separately or mixed, into a high-powered crusher to break them into uniform small segments or fragments with a length or particle size of 6mm, so as to achieve rapid and uniform melting and mixing in the subsequent melting process. Drying and dehydration involves placing the crushed waste material in a hot air circulating drying device and drying it continuously at a temperature of 120℃ for 4 hours to completely remove the moisture adsorbed by the raw materials during storage and crushing, strictly controlling the moisture content of the final raw material to below 0.5%, preventing hydrolytic degradation caused by moisture during subsequent high-temperature processing, and further ensuring the stability of polymer molecular weight.

[0026] S2, Melt Coloring Granulation: S21. Ingredients and Mixing: The pretreated and fully dried waste fragments are premixed with an environmentally friendly black polyester masterbatch at a precise mass ratio of 99:1. The resin carrier of the masterbatch is homologous to the polyester waste and has excellent compatibility. S22. Melt Blending and Extrusion: The mixture is continuously and uniformly fed into a co-rotating twin-screw extruder. The process parameters are set as follows: the screw speed is 480 r / min and the temperature of each heating zone is controlled at 270℃ to ensure that the polyester is completely melted and does not overheat and decompose. Under the strong shearing, mixing and conveying action of the screw, the white polyester melt and the black masterbatch are uniformly dispersed and fused, and the carbon black particles are fully wrapped and dispersed in the polyester matrix. S23. Cooling and pelletizing: The uniformly colored melt is extruded from the die into continuous thin strips, and then immersed in a 20°C circulating water bath for rapid cooling and solidification. After water cooling, the material is introduced into a pelletizer by a traction device and cut into pellets of uniform length, thus obtaining black recycled polyester chips with uniform black color and which are ready to be used for spinning.

[0027] S3, Melt spinning: S31. Feeding and Melting: Black recycled polyester chips are fed into the drying hopper of the spinning machine via an automatic conveying system. They are pre-crystallized and dried at 170°C to improve their crystallinity and heat resistance and prevent the chips from sticking together in the screw. Subsequently, the chips enter the spinning screw and melt at a high temperature of 280°C to form a uniform melt with good fluidity. S32. Melt transport and filtration homogenization: The melt passes through a component equipped with a high-precision metal filter to remove any trace amounts of unmelted gel or impurities. It then enters a static mixer for homogenization to eliminate local differences in temperature and viscosity, ensuring that the temperature and viscosity of each part of the melt are consistent. S33, Metering and Spinning: The homogenized melt is precisely metered by a high-precision metering pump at a constant pressure (15MPa) and delivered to the spinneret, wherein the spinneret has a spinneret orifice diameter of 0.2mm and 36 orifices. S34. Cooling and forming: After the molten fine stream is extruded from the spinneret, it immediately enters the side blowing chamber. The fine stream is cooled and solidified by uniform side blowing at a temperature of 28℃ and a wind speed of 1m / s to form nascent fibers.

[0028] S35. Fiber post-treatment: Fiber post-treatment includes stretching, heat setting, and texturing. In this process, the nascent fibers are gradually stretched by passing them through three sets of hot rollers at different temperatures. The first stretching temperature is controlled at 85℃ for initial orientation. The second stretching temperature is 125℃ to further increase the stretch ratio and orientation degree. The third stretching temperature is 165℃ to complete the final high-ratio stretching, which makes the crystallization and orientation structure of the fibers more perfect. Heat setting refers to the process of placing the stretched fibers in a 190°C heat setting zone for 50 seconds under tension or partial relaxation to eliminate internal stress in the fibers, improve crystallization perfection, thereby fixing the fiber shape, improving dimensional stability and thermal stability, and enhancing color fastness. Texturing involves feeding the heat-set fibers into a texturing machine, where processes such as false twisting and hot box setting impart a certain degree of crimp elasticity and fluffiness to the fibers, improving the hand feel and coverage of the final fabric, and winding the fibers into standard-sized tube-packaged black polyester filaments.

[0029] S4, Weaving and shaping: The black polyester filaments prepared above are used as weaving yarns and wound into yarn bobbins that can be directly used by different weaving equipment (such as warp knitting machines, shuttle looms, and fly looms).

[0030] In summary, the preparation method provided in this embodiment completes the entire process from polyester waste to special black yarn. This yarn can be directly used to weave black shoe upper materials with various structures without the need for a dyeing process.

[0031] Comparative Example 1: This embodiment provides a method for preparing a polyester recycled shoe upper base. The only difference from Embodiment 1 is that the first stretching temperature is controlled at 100°C for preliminary orientation; the second stretching is carried out at 150°C to further increase the stretch ratio and orientation degree; and the third stretching is carried out at 190°C to complete the final high-ratio stretching, so that the crystallization and orientation structure of the fiber tends to be perfect. Other conditions are the same as in Embodiment 1.

[0032] Comparative Example 2: This embodiment provides a method for preparing a polyester recycled shoe upper base. The only difference from Embodiment 1 is that the content of the environmentally friendly black polyester masterbatch carbon black used in step S21, the ingredient mixing step, is 40%, while the other conditions are the same as in Embodiment 1.

[0033] Comparative Example 3: This embodiment provides a method for preparing a polyester recycled shoe upper base. The only difference from Embodiment 1 is that the content of the environmentally friendly black polyester masterbatch carbon black used in step S21, the ingredient mixing step, is 60%, while the other conditions are the same as in Embodiment 1.

[0034] Comparative Example 4: This embodiment provides a method for preparing a polyester recycled shoe upper base. The only difference from Embodiment 1 is that the environmentally friendly black polyester masterbatch used in step S21, the ingredient mixing step, is premixed at a precise mass ratio of 98:2. Other conditions are the same as in Embodiment 1.

[0035] Comparative Example 5: This embodiment provides a method for preparing a polyester recycled shoe upper base. The only difference from Embodiment 1 is that the moisture content of the final raw material is 1%, while the other conditions are the same as in Embodiment 1.

[0036] Comparative Example 6: This embodiment provides a method for preparing a shoe upper base based on recycled polyester. The only difference from Embodiment 1 is that the length or particle size of the white polyester fiber waste filaments and polyester waste chips used as the core raw materials are not uniform. Other conditions are the same as in Embodiment 1.

[0037] Comparative Example 7: This embodiment provides a method for preparing a polyester shoe upper base. The only difference from Embodiment 1 is that commercially available pure black polyester masterbatch is directly selected as the sole spinning raw material.

[0038] Comparative Example 8: This embodiment provides a method for preparing a shoe upper base. The only difference from Embodiment 1 is that commercially available pure white polyester masterbatch is directly selected as the sole spinning raw material.

[0039] To clarify the impact of raw material selection and specifications, carbon black content in masterbatch, and the effects of three drawing temperatures on the final sample's brightness value, this application designed a series of control groups. The specific schemes and results are shown in Table 1 below: Table 1 The comparative experimental data above show that in the polyester recycled fiber preparation process of the present invention, the carbon black content and addition amount of the black masterbatch are the most critical variables for controlling the final fiber blackness (brightness value). For example, under the condition of maintaining other process parameters, when the carbon black content increases from 30% to 60% (Example 1 → Comparative Example 2 → Comparative Example 3), or the addition amount increases from 1% to 2% (Example 1 → Comparative Example 4), the brightness value of the sample increases sequentially. This indicates that by precisely controlling the coloring system, the gradient and serialized production of fiber color can be achieved under the same process flow. Meanwhile, process stability also has a significant impact on color uniformity: when the raw material has uneven particle size (Comparative Example 6) or high moisture content after drying (Comparative Example 5), its brightness value increases to 2.7 and 3.0, respectively. This indicates that excessive moisture content can easily cause polyester hydrolysis during the melting process, damaging the integrity of the molecular chain; while uneven particle size will lead to differences in melting and mixing efficiency. Both of these will seriously affect the dispersion uniformity of the masterbatch, resulting in lighter color and mottled appearance. In addition, subsequent spinning process parameters also have a fine-tuning effect on color. For example, when the three-stage drawing temperature is increased from 85 / 125 / 165℃ in Example 1 to 100 / 150 / 190℃ in Comparative Example 1, the brightness value increases from 1.0 to 1.4. This indicates that excessively high drawing temperature may change the crystal morphology or surface structure of the fiber, which may have a certain weakening effect on the blackness of the color. Therefore, in actual production, it is necessary to further standardize the pretreatment process on the basis of ensuring the accurate proportion of the masterbatch system in order to ensure the uniformity and stability of color output.

[0040] Application Example 1: like Figure 2 As shown, this application example 1 illustrates the basic preparation method for the recycled polyester upper in Example 1, and its specific implementation scenario in the warp knitting process: The preparation process of this application example 1 is exactly the same as that of Example 1, with steps S1 to S3 (raw material selection and pretreatment, melt coloring and granulation, melt spinning) being identical. That is, black polyester filaments with the same properties are prepared according to the process parameters and methods described in Example 1. The core difference between this application example 1 and Example 1 lies in the S4 weaving and forming step, which is performed by the following steps in sequence: S41. Warping: The black polyester filaments from several bobbins are wound parallel and evenly onto the warp beam of the warp knitting machine according to the process requirements, ensuring that all yarns have consistent tension. S42. Knitting on the machine: The prepared warp beams are installed on a high-precision warp knitting machine with 28 needles / inch. The warp plain weave is used for knitting. This weave consists of alternating open and closed loops. The structure is stable and has moderate extensibility, which meets the requirements of the shoe upper material for stiffness and moderate elasticity. During the knitting process, the machine spindle speed is set to 1200 rpm to ensure a balance between production efficiency and fabric quality.

[0041] S43. Winding and Inspection: The woven fabric is drawn off the machine, and after tension adjustment and static elimination, it is evenly wound into a roll. The roll is then inspected to ensure that there are no obvious defects such as broken yarns, missed stitches, or horizontal stripes. Finally, a black warp-knitted shoe upper material with a thickness of about 1.2 mm is produced.

[0042] The shoe upper material obtained in Application Example 1 benefits from the structural characteristics of the warp weave and the uniform black color of the fiber itself. Its structure is stable and moderately elastic, making it easy to process and mold and comfortable to wear. Visually, it has a pure black color and a smooth surface, completely avoiding the color difference and color pattern problems of traditional dyeing processes.

[0043] Application Example 2: like Figure 3 As shown, this application example 2 illustrates the basic preparation method for the recycled polyester shoe upper described in Example 1, and its specific implementation scenario in the woven fabric field: The preparation process of Application Example 2 is exactly the same as that of Application Example 1, with steps S1 to S3 (raw material selection and pretreatment, melt coloring and granulation, melt spinning). That is, black polyester filaments with the same properties are prepared according to the process parameters and methods described in Application Example 1. The core difference between Application Example 2 and Application Example 1 is in the S4 weaving and forming step, and the weaving is carried out in the following steps: S41. Yarn Preparation: Several black polyester filament bobbins are placed on the warping frame, so that all yarns are wound parallel and under equal tension onto a large warp beam, forming the warp system required for weaving. The black polyester filaments serve as weft yarns, wound onto the weft feeder of the loom. Each warp yarn on the warp beam is then passed sequentially through the heddle holes and reed teeth according to a pre-set fabric weave pattern (e.g., plain weave, twill weave). This step determines the opening and closing sequence of the warp yarns and the warp and weft density of the fabric. S42. Loom Weaving: Install the prepared warp beams, heald frames, and reed onto the loom and weave using a plain weave structure. The warp and weft yarns interweave alternately, with the following parameters set during weaving: warp density 120 ends / inch, weft density 100 ends / inch. During loom operation, the warp yarns form the shed through the up-and-down movement of the heald frames, and the weft yarns are introduced into the shed by a jet of air or a rapier, then tightened by the reed. This cycle continues to form the fabric. S43. Unweaving and finishing: The woven fabric falls off the loom, undergoes simple inspection and winding, and finally produces a black woven shoe upper material with a thickness of about 1.5mm.

[0044] Through the woven process of this application example 2, the material fully integrates the tight and stable characteristics of plain weave with the advantages of recycled black fibers, enabling the production of a black shoe upper material that is structurally stable, wear-resistant, durable, has a high-end appearance, and is completely environmentally friendly.

[0045] Application Example 3: like Figure 4 As shown, this application example 3 illustrates the basic preparation method for the recycled polyester upper described in Example 1, and its specific implementation scenario in the field of flyknit (one-piece knitting) warp knitting machines: The preparation process of Application Example 3 is exactly the same as that of Application Example 1, with steps S1 to S3 (raw material selection and pretreatment, melt coloring and granulation, melt spinning), i.e., black polyester filaments with the same properties are prepared according to the process parameters and methods described in Application Example 11. The core difference between Application Example 3 and Application Example 1 lies in the S4 weaving and forming step, and the weaving is carried out in the following steps: S41. Programming and Yarn Configuration: Based on the three-dimensional digital model of the target shoe upper, the yarn feeder path, needle action, structure and knitting sequence are designed using professional knitting software. Black polyester filament is used as the main yarn and loaded onto multiple yarn feeders of the flying loom according to the design requirements. This process does not require traditional warping or heddle threading. S42. Machine Operation and High-Density Knitting: Import the programming file into an advanced 32-needle / inch high-precision flying warp knitting machine. Under program control, the machine runs at a high speed of 1500 rpm, making high-speed and complex movements between dozens of needles, knitting according to basic structures such as plain weave or their composite variations. S43, One-piece molding: According to the program instructions, the fabric is woven in one piece and seamlessly to be exactly the same shape as the shoe upper component. This greatly reduces material cutting waste (scraps) and improves material utilization. Through the integrated flyknit molding process described in Application Example 3, a black flyknit upper with a predetermined shape and structure is ultimately produced directly. This upper deeply integrates the technological advancements of flyknit technology with the material advantages of recycled black fibers, avoiding seams and making the upper lighter and more form-fitting, while also improving the overall aesthetics and wearing comfort.

[0046] Therefore, this application compares the black shoe upper material prepared in the above embodiments with that prepared in the comparative examples under the same conditions, and the comparison results are shown in the table below: Based on the color fastness test results shown in the table above, it can be found that the materials provided by the present invention (Application Examples 1-3) all achieve excellent levels of grade 4 or above in key indicators such as dry and wet rubbing color fastness, wash fastness (color change and staining), and migration resistance. Compared with Comparative Example 7, which directly uses commercially available pure black polyester masterbatch as the only spinning raw material, the color fastness performance of the present invention is comparable or close to that of Comparative Example 8, which directly uses commercially available pure white polyester masterbatch as the only spinning raw material. The present invention has significant advantages in wet rubbing color fastness and wash fastness, especially in wash fastness and wet rubbing.

[0047] In summary, this invention not only eliminates the water dyeing process, thus avoiding energy consumption, water consumption, and wastewater discharge, which aligns with the concepts of green manufacturing and resource recycling, but also produces a black shoe upper material with specific blackness, stable color, and excellent color fastness, meeting the application requirements of high-end shoe materials in terms of overall performance.

[0048] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0049] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing recycled polyester fibers, characterized in that: It includes: S1. Pre-treatment of white polyester waste; S2. The pretreated white polyester waste is blended and melt-granulated with monochrome masterbatch to obtain monochrome recycled polyester chips. S3. The monochrome recycled polyester chips are melt-spun, and after cooling, stretching and heat setting, monochrome polyester filaments are obtained.

2. The method for preparing recycled polyester fibers according to claim 1, characterized in that: In step S1, the pretreatment includes removing impurities from the white polyester waste, crushing and granulating it, and drying it to remove water. The drying temperature is 80~120℃. Preferably, the white polyester waste after crushing and granulation is in the form of small particles of 3-10 mm.

3. The method for preparing recycled polyester fibers according to claim 1, characterized in that, In step S1, the moisture content of the pretreated white polyester waste is ≤0.5%.

4. The method for preparing recycled polyester fibers according to claim 1, characterized in that, In step S2, the monochrome masterbatch is an environmentally friendly black polyester masterbatch with a carbon black content of 50%, and the amount of monochrome masterbatch added is 1% of the total weight of the raw materials. The melt granulation method includes melting using a screw extruder. Preferably, the screw speed in the screw extruder is 200-550 r / min; Preferably, the melting temperature of the screw extruder is 260-280℃.

5. The method for preparing recycled polyester fibers according to claim 1, characterized in that, In step S3, the melt spinning includes pre-crystallizing and melting monochromatic recycled polyester chips to form a melt, which is then extruded through a spinneret and cooled and solidified by side blowing to form nascent fibers. Preferably, the pre-crystallization temperature is 160-180℃; Preferably, the temperature at which the melt is formed is 270-290°C; Preferably, the orifice diameter of the spinneret is 0.2-0.3 mm; Preferably, the side-blowing air temperature is 25-30℃; Preferably, the side-blowing wind speed is 0.5-1m / s.

6. The method for preparing recycled polyester fibers according to claim 5, characterized in that: The process of conveying the melt to the spinneret also includes a step of filtering and homogenizing the melt.

7. The method for preparing recycled polyester fibers according to claim 5, characterized in that: The nascent fibers undergo at least three stages of drawing, with the temperature of each stage increasing in a stepwise manner; wherein, The first stretching section is configured as a uniform stress section to eliminate uneven stress inside the fiber. The second stretching section is configured as a stretching section, which further stretches the fiber, allowing the molecular chains inside the fiber to gradually align. The third stretching section is configured as a uniform diameter section, which ensures that the molecular chains inside the fiber are evenly oriented and arranged, thus ensuring that the fiber diameter is consistent.

8. The method for preparing recycled polyester fibers according to claim 7, characterized in that: The first stage drawing temperature is 80-90℃, the second stage drawing temperature is 120-130℃, and the third stage drawing temperature is 160-170℃.

9. The method for preparing recycled polyester fibers according to claim 1, characterized in that: The heat setting is carried out at a temperature higher than the stretching temperature, and the heat-set fibers are then texturing to form the monochrome polyester filaments. Preferably, the heat setting temperature is 180-200℃.

10. A polyester recyclable shoe upper, characterized in that, It includes: The monochromatic polyester filaments obtained by the polyester recycling fiber preparation method according to any one of claims 1-9 are used to make shoe upper materials through a weaving process; the weaving process includes knitting and / or weaving.

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