A method for producing regenerated fiber using waste polyester / nylon mixed fabric as raw material

Abstract

The present invention discloses a method for producing regenerated fiber using waste polyester / nylon hybrid fabric as raw material. The method first densifies the waste polyester / nylon hybrid fabric using a grinding disc granulator to produce waste polyester / nylon foam. The waste polyester / nylon foam is then mixed evenly with a certain amount of diol monomer and fed into a twin-screw extruder for alcoholysis and extrusion. Finally, the alcoholysis product is subjected to polycondensation and viscosity enhancement under the action of a catalyst, and then melt-pulled into yarn through a spinning machine to produce regenerated fiber. The regenerated fiber has a linear density of 50-500 dtex, a breaking strength of 2.5-10.0 cN / dtex, and an elongation at break of 5.0-100.0%. Using unscreenable waste polyester / nylon hybrid fabric as raw material, the method of the present invention produces regenerated fiber with excellent physical and mechanical properties through densification, alcoholysis, polycondensation, and spinning, achieving a closed-loop recycling process from fiber to fiber.

Description

Technical Field

[0001] This invention relates to the field of recycling and high-value utilization of waste textiles, specifically to a method for producing recycled fibers from waste polyester and nylon fabrics. Background Technology

[0002] With rapid social development and rising living standards, the demand for textiles is constantly increasing, leading to a surge in fiber production. Among these, chemical fibers far surpass natural fibers in production, dominating the market. Polyester, with its stable performance and good mechanical properties, is widely used and has become the highest-producing chemical fiber, accounting for over 80% of all chemical fibers. Nylon is the second highest, accounting for about 6%. Polyester is widely used in clothing fabrics, decorative materials, and industrial textiles, and is often blended with elastic nylon or spandex to improve comfort. When these mixed fabrics are recycled, simple sorting methods cannot separate the polyester and nylon, hindering proper classification and disposal. Direct melting and regeneration of waste polyester / nylon mixed fabrics without separation results in a significant reduction in the mechanical properties of the recycled products due to the biodegradability and incompatibility of nylon and polyester, making recycling difficult. Therefore, the recycling of polyester / nylon mixed fabrics is challenging. With the continuous growth of waste polyester / nylon mixed fabrics, the need for their recycling is urgent. Based on this, the present invention uses waste polyester / nylon blended fabrics as raw materials and obtains recycled fibers through densification treatment, alcoholysis, polycondensation, spinning and other processes, so as to realize the high-value closed-loop reuse of waste blended textiles.

[0003] Domestic and international scholars have also developed methods for recycling polyester / nylon blended fabrics. Patent CN113248705A discloses a method and application for the alcoholysis regeneration of waste polyester-polyamide 6 blended textiles. This patent uses waste polyester-polyamide 6 blended fabrics as raw materials, and its alcoholysis products and diacid monomers undergo sequential esterification, amidation, and transesterification reactions to obtain recycled polyesteramide, which can be melt-spun into recycled polyesteramide fibers. This process uses diacids for esterification, amidation, and transesterification reactions to improve the performance of recycled materials, but it requires a large amount of alcoholysis agent, has high energy consumption, and a long reaction process. In contrast, this invention uses alcoholysis and polycondensation to thicken fiber-derived recycled polyester / nylon materials, achieving high-value recycling of waste polyester / nylon fabrics. Publication No. CN101942708A discloses a polyester-polyamide copolymer fiber and its manufacturing method. This patent uses dimethyl terephthalate (DMT) and ethylene glycol as raw materials, performing a transesterification reaction at 200 °C for 2 hours. The temperature is then raised to 230 °C to add a nylon 6 intermediate prepolymer, followed by continuous heating and polycondensation under the catalysis of tetrabutyl titanate. The resulting polyester-polyamide chips are spun and drawn to obtain copolymer filaments. The production of this copolymer involves polycondensation and copolymerization of DMT and diol at different temperatures, a relatively complex process. In contrast, the main raw material of this invention is waste polyester-nylon blended fabric, which is recycled without separation. Summary of the Invention

[0004] The purpose of this invention is to address the increasing amount of textile waste and the difficulty in recycling and utilizing waste polyester / nylon blended fabrics. This invention provides a method for producing recycled fibers using waste polyester / nylon blended fabrics as raw materials. The method first involves feeding the waste polyester / nylon blended fabric into a grinding disc granulator for densification treatment to obtain polyester / nylon foam. The polyester / nylon foam is then mixed with diol and extruded under specific temperature, shear conditions, and residence time in a twin-screw extruder. After alcoholysis, the melt molecular chains of the blend break down, significantly improving its fluidity. This allows the melt to effectively filter out most solid impurities when passing through the twin-screw extruder die filter. Subsequently, the alcoholysis granules are mixed with a catalyst and fed into a high-temperature, high-pressure reactor, where the melt undergoes condensation at high temperatures. Small molecule products are then removed through vacuum degassing, resulting in molecular chain growth and a thickening effect. The thickened blend melt has increased strength, meeting spinning requirements. It is then fed into a spinning machine and drawn into filaments to obtain recycled fibers. This method provides a green, efficient, and high-value recycling approach for waste polyester / nylon blended fabrics.

[0005] Specifically, the purpose of this invention is to provide a method for producing recycled fibers from waste polyester / nylon blended fabrics, wherein the physical and mechanical properties of the recycled fibers meet the fiber usage standards (GB / T 14344-2008).

[0006] The present invention discloses a method for producing recycled fibers from waste polyester / nylon blended fabrics. This method is simple, low-cost, and environmentally friendly, and is suitable for industrial production.

[0007] To achieve the objectives of this invention, the following technical solution is adopted:

[0008] The specific steps of the method for producing recycled fibers from waste polyester / nylon 6 blended fabrics as described above are as follows:

[0009] (1) After the waste polyester / nylon mixed fabric is crushed, it is fed into a grinding disc granulator to agglomerate into granules, and then crushed to obtain polyester / nylon foam with a size of less than 40 mesh;

[0010] (2) The polyester / nylon foam obtained in step (1) is dried in a drum to reduce its moisture content to less than 100 ppm;

[0011] (3) The dried foam obtained in step (2) is mixed evenly with 0.2~10 phr of diol and then fed into a twin-screw extruder. The temperature of the twin-screw extruder is 100~280 ℃, the main screw speed is 100~400 rpm, the feed screw speed is 50~100 rpm, and the granulator speed is 80~200 rpm to obtain alcoholysis granules of waste polyester / nylon foam. It should be noted that the degree of alcoholysis of waste polyester / nylon foam needs to be controlled by controlling the amount of diol alcoholysis agent added.

[0012] (4) The alcoholysis granules obtained in step (3) are mixed with 50~450 ppm antimony-based catalyst and then added to a high-temperature and high-pressure reactor. The reaction temperature is 230~290 ℃, the stirring speed is 150~750 rpm, the vacuum degree is ≤200 Pa, and the reaction time is 1~3 h to obtain a thickened melt. First, the reaction temperature of the high-temperature and high-pressure reactor needs to be controlled so that the polycondensation process is carried out in the melt state of polyester / nylon blend. Second, the stirring efficiency of the stirring paddle and the vacuum degree need to be controlled so that the small molecules or oligomers generated in the polycondensation process are devolatilized and carried away, and the polycondensation reaction can proceed efficiently in the forward direction. Finally, the polycondensation time needs to be controlled so that the polycondensation process can reach the reaction equilibrium state as much as possible. It is worth noting that the viscosity of the thickened melt is closely related to the amount of diol added during the alcoholysis process. The viscosity of the polycondensation product needs to be controlled by controlling the amount of diol alcoholysis agent added. If the viscosity is too high, it may lead to a decrease in crystallization performance. If it is too low, it will lead to insufficient melt strength and poor spinning stability in the subsequent spinning process.

[0013] (5) The polyester / nylon blend after polycondensation is fed into a melt spinning machine. The process conditions of the melt spinning machine are as follows: main screw temperature 80~280 ℃, main screw speed 25~50 rpm, hot stretching temperature 75~120 ℃, stretching ratio 1.0~4.0, and the linear density of the resulting recycled fiber is 50~500 dtex.

[0014] Specifically, a method for producing recycled fibers from waste polyester / nylon blended fabrics includes the following steps:

[0015] Step 1: After crushing the recycled waste polyester / nylon mixed fabric, it is densified in a grinding disc pelletizer to obtain polyester / nylon foam.

[0016] Step 2: Mix the dried polyester / nylon foam with the diol hydrolysis agent evenly, put it into a twin-screw extruder, and hydrolyze and extrude it under certain temperature conditions, feed screw speed and main screw speed, and then granulate it through a granulator to obtain hydrolyzed granules;

[0017] Step 3: Mix the alcoholysis granules obtained in Step 2 with the catalyst in a certain proportion and put them into a high temperature and high pressure reactor. Polycondense and granulate them under certain temperature, vacuum degree, stirring speed and reaction time to obtain polyester / nylon recycled granules.

[0018] Step 4: The recycled polyester / nylon granules obtained in Step 3 are fed into a melt spinning machine and drawn into filaments under certain temperature conditions, main screw speed, and drawing speed to obtain recycled fibers.

[0019] The waste polyester / nylon blended fabric mentioned in step one above is any one, two or three of the following: a mixture of waste polyester fabric and waste nylon fabric, waste polyester / nylon blended fabric, waste polyester / nylon mixed fabric, and waste polyester / nylon interwoven fabric. The nylon content in the raw material is not higher than 10 wt%.

[0020] The polyester / nylon foam material mentioned in step two above has a moisture content ≤100 ppm after drying; the diol alcoholysis agent mentioned in step two includes, but is not limited to, ethylene glycol, diethylene glycol and propylene glycol, and the amount of diol alcoholysis agent added is 0.2~10 phr; the temperature of the twin-screw extruder mentioned in step two is 100~280 ℃, the main screw speed is 100~400 rpm, the feed screw speed is 50~100 rpm, and the granulator speed is 80~200 rpm.

[0021] The catalyst mentioned in step three above includes an antimony-based catalyst, with a catalyst dosage of 50~450 ppm. The antimony-based catalyst is selected from antimony glycolate and antimony trioxide. The reaction temperature of the high-temperature and high-pressure reactor is 230~290 ℃, the stirring speed is 150~750 rpm, the vacuum degree is ≤200 Pa, and the reaction time is 1~3 h.

[0022] In the process conditions of the melt spinning machine described in step four above, the main screw temperature is 80~280 ℃, the hot stretching temperature is 75~120 ℃, the main screw speed is 25~50 rpm, the draw ratio is 1.0~4.0, and the linear density of the resulting regenerated fiber is 50~500 dtex.

[0023] As a preferred technical solution:

[0024] A regenerated fiber produced from waste polyester / nylon blended fabric, wherein: the linear density of the regenerated fiber is 50~500 dtex, preferably 50~200 dtex, the breaking strength is 2.0~7.0 cN / dtex, preferably 3.0~6.0 cN / dtex, and the breaking elongation is 5.0~100.0%, preferably 10.0~30.0% (according to national standard GB / T 14344-2008).

[0025] The beneficial effects of this invention are as follows: 1) This invention uses waste polyester / nylon blended fabrics as raw materials, and obtains regenerated fibers through densification treatment, alcoholysis, polycondensation, spinning, and other processes. The regenerated fibers have a breaking strength greater than 3.0 cN / dtex and a breaking elongation greater than 10%, meeting the standards for the use of regenerated fibers; 2) This method can directly recycle waste polyester / nylon blended fabrics without separation and sorting steps. The process is simple, low-cost, and environmentally friendly, making it suitable for industrial production; 3) This method utilizes the in-situ esterification, amidation, and ester-amide exchange reactions of polyester and nylon during processing to promote molecular chain growth and two-phase compatibility, thereby obtaining regenerated fibers with excellent mechanical properties. This method realizes the high-value utilization of waste polyester / nylon fabrics and the closed-loop recycling from fiber to fiber, providing technical support for the establishment of a recycling system for waste blended textiles. Attached Figure Description

[0026] Figure 1 The infrared spectrum of the polyester / nylon regenerated fiber obtained in Example 1 of the present invention is shown. Detailed Implementation

[0027] The waste polyester / nylon blended fabrics used in the following embodiments of the present invention can be classified into mixtures of waste polyester and nylon fabrics, waste polyester / nylon blended fabrics, waste polyester / nylon mixed fabrics, and waste polyester / nylon interwoven fabrics, depending on the weaving conditions. Among them, the main component of the waste polyester / nylon blended fabric (purchased from Fujian Baichuan Resource Recycling Technology Co., Ltd., containing more than 90% polyester and less than 10% nylon) is polyester, accounting for more than 90%. The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Example 1

[0028] A method for producing recycled fibers from waste polyester / nylon blended fabrics is carried out according to the following steps:

[0029] (1) The collected waste polyester / nylon blended fabric was densified to obtain waste polyester / nylon foam, and the nylon content in the blended fabric component was 8.0%;

[0030] (2) After drying the waste polyester / nylon foam obtained in step (1), mix it evenly with 2 phr (Phr is the abbreviation for Parts per hundred parts of resin, which represents the amount of ethylene glycol to be added for every 100 parts of waste polyester / nylon foam) of ethylene glycol, and then put it into a twin-screw extruder for alcoholysis extrusion. Alcoholysis improves the melt fluidity and filters impurities in the melt to obtain polyester / nylon alcoholysis granules.

[0031] (3) The polyester / nylon alcoholysis granules obtained in step (2) are mixed with 250 ppm antimony glycolate and then fed into a high-temperature and high-pressure reactor for polycondensation. The polycondensation temperature is controlled between 265±5 ℃, the vacuum degree inside the reactor is ≤0.02 Mpa, the stirring speed inside the reactor is 750 rpm, and the polycondensation time is 3 h to obtain polyester / nylon thickening granules.

[0032] (4) The polyester / nylon thickening granules obtained in step (3) are fed into a melt spinning machine, the plasticizing temperature is controlled within the range of 240~270 ℃, the draw ratio is controlled at 3.1, and a regenerated fiber with a linear density of 130±20 dtex is obtained.

[0033] In step (2) above, the waste polyester / nylon foam is placed in a vacuum drying oven and dried for more than 10 hours under vacuum conditions ≤0.01 MPa and temperature (100 ℃±10 ℃) until the moisture content is less than 50 ppm. The main screw temperature of the twin-screw extruder is set sequentially from the feed port to the die head as 120 ℃, 150 ℃, 180 ℃, 210 ℃, 238 ℃, 250 ℃, 250 ℃, 253 ℃, 260 ℃, and 240 ℃, the main screw speed is 300±50 rpm, the feed screw speed is 50±10 rpm, and the granulator speed is 100±10 rpm. In step (4), the main screw temperature of the melt spinning machine is set sequentially from the feed port to the die head as 190 ℃, 220 ℃, 245 ℃, 260 ℃, and 258 ℃. The temperature is ℃, the hot stretching temperature is 85±2 ℃, and the main screw speed of the spinning machine is 40±10 rpm.

[0034] Three groups of regenerated fibers were obtained under the process conditions described in Example 1, with sample numbers 1, 2, and 3.

[0035] Mechanical property testing: The mechanical properties of recycled polyester fibers were tested according to GB / T 14344-2008 "Test Method for Tensile Properties of Chemical Fiber Filaments". The tensile strength and elongation at break of the recycled fibers are shown in the table below;

[0036] . Example 2

[0037] A method for producing recycled fibers from waste polyester / nylon blended fabrics is carried out according to the following steps:

[0038] (1) The collected waste polyester / nylon blended fabrics were densified to obtain waste polyester / nylon foam, and the nylon component content in the blended fabric was 6.1%;

[0039] (2) After drying the waste polyester / nylon foam obtained in step (1), mix it evenly with 1 phr propylene glycol and then put it into a twin-screw extruder for alcoholysis extrusion. Alcoholysis improves the melt fluidity and filters impurities in the melt to obtain polyester / nylon alcoholysis granules.

[0040] (3) The polyester / nylon alcoholysis granules obtained in step (2) were mixed with 250 ppm antimony trioxide and then fed into a high-temperature and high-pressure reactor for polycondensation. The polycondensation temperature was controlled between 268±4 ℃, the vacuum degree inside the reactor was ≤0.02 Mpa, the stirring speed inside the reactor was 700 rpm, and the polycondensation time was 2.5 h to obtain polyester / nylon thickening granules.

[0041] (4) The polyester / nylon thickening granules obtained in step (3) are fed into a melt spinning machine, and the plasticizing temperature is controlled within the range of 240~270 ℃ and the draw ratio is controlled within the range of 3.1 to obtain a regenerated fiber linear density of 130±10 dtex.

[0042] In step (2) above, the polyester / nylon foam is placed in a vacuum drying oven and dried for more than 12 hours under certain vacuum (≦0.02 Mpa) and temperature (100 ℃±10 ℃). The temperature of the main screw in the twin-screw extruder is set from the feed port to the die head as follows: 120 ℃, 150 ℃, 180 ℃, 210 ℃, 238 ℃, 250 ℃, 250 ℃, 253 ℃, 258 ℃, 240 ℃. The main screw speed is 300 rpm±25 rpm. In step (4), the temperature of the main screw in the melt spinning machine is set from the feed port to the die head as follows: 190 ℃, 220 ℃, 245 ℃, 260 ℃, 258 ℃. The hot stretching temperature is 95±2 ℃. The main screw speed of the spinning machine is 45±5 rpm.

[0043] Three groups of regenerated fibers were obtained under the process conditions described in Example 2, and the samples were numbered 1, 2, and 3.

[0044] Mechanical property testing: The mechanical properties of recycled polyester fibers were tested according to GB / T 14344-2008 "Test Method for Tensile Properties of Chemical Fiber Filaments". The tensile strength and elongation at break of the recycled fibers are shown in the table below;

[0045] . Example 3

[0046] A method for producing recycled fibers from waste polyester / nylon blended fabrics comprises the following steps:

[0047] (1) The collected waste polyester / nylon blended fabrics were densified to obtain polyester / nylon foam, and the nylon component content in the blended fabric was 7.2%;

[0048] (2) After drying the waste polyester / nylon foam obtained in step (1), mix it evenly with 5 phr of ethylene glycol and then put it into a twin-screw extruder for alcoholysis extrusion. Alcoholysis improves the melt fluidity and filters impurities in the melt to obtain polyester / nylon alcoholysis granules.

[0049] (3) The polyester / nylon alcoholysis granules obtained in step (2) are mixed with 280 ppm antimony glycolate and then fed into a high-temperature and high-pressure reactor for polycondensation. The polycondensation temperature is controlled between 265±4 ℃, the vacuum degree inside the reactor is ≤0.02 Mpa, the stirring speed inside the reactor is 800 rpm, and the polycondensation time is 3 h to obtain polyester / nylon thickening granules.

[0050] (4) The polyester / nylon thickening granules obtained in step (3) are fed into a melt spinning machine, the plasticizing temperature is controlled within the range of 240~270 ℃, the draw ratio is controlled at 3.3, and the linear density of the regenerated fiber is 125±10 dtex.

[0051] In step (2) above, the waste polyester / nylon blended foam is placed in a vacuum drying oven and dried for more than 10 hours under certain vacuum conditions (≤0.02Mpa) and temperature (100℃±5℃). The temperature of the twin-screw extruder main screw from the feed port to the die head is set to 120℃, 150℃, 170℃, 190℃, 218℃, 240℃, 253℃, 253℃, 255℃, and 245℃, and the main screw speed is 300 rpm±50 rpm. In step (4), the temperature of the melt spinning machine from the feed port to the die head is set to 190℃, 220℃, 245℃, 260℃, and 258℃, respectively. The hot stretching temperature is 90±2℃, and the main screw speed of the spinning machine is 40±5 rpm.

[0052] Three groups of regenerated fibers were obtained under the process conditions described in Example 3, and the samples were numbered 1, 2, and 3.

[0053] Mechanical property testing: The mechanical properties of recycled polyester fibers were tested according to GB / T 14344-2008 "Test Method for Tensile Properties of Chemical Fiber Filaments". The tensile strength and elongation at break of the recycled fibers are shown in the table below;

[0054] .

Claims

1. A method for producing recycled fibers from waste polyester / nylon blended fabrics, comprising the following steps: Step 1: After crushing the recycled waste polyester / nylon mixed fabric, it is densified in a grinding disc pelletizer to obtain polyester / nylon foam. Step 2: Mix the dried polyester / nylon foam with a moisture content ≤100 ppm evenly with the diol alcoholysis agent, and feed it into a twin-screw extruder. Extrude the mixture under the following conditions: twin-screw extruder temperature 100~280 ℃, main screw speed 100~400 rpm, feed screw speed 50~100 rpm, and granulator speed 80~200 rpm. Granulate the mixture using the granulator to obtain alcoholysis granules. The diol alcoholysis agent includes ethylene glycol, diethylene glycol, and propylene glycol, and the amount of diol alcoholysis agent added is 0.2~10 phr. Step 3: The alcoholysis granules obtained in Step 2 are mixed with the catalyst in a certain proportion and then put into a high-temperature and high-pressure reactor. Polycondensation is carried out under the conditions of reaction temperature of 230~290 ℃, stirring speed of 150~750 rpm, and vacuum degree ≤200 Pa. After reaction time of 1~3 h, granulation is performed to obtain polyester / nylon recycled granules. The catalyst includes antimony-based catalysts, and the catalyst dosage is 50~450 ppm. The antimony-based catalysts are selected from antimony glycolate and antimony trioxide. Step 4: The recycled polyester / nylon granules obtained in Step 3 are fed into a melt spinning machine. Under the conditions of a main screw temperature of 80~280 ℃, a hot stretching temperature of 75~120 ℃, a main screw speed of 25~50 rpm, and a draw ratio of 1.0~4.0, the fibers are drawn into filaments to obtain recycled fibers with a linear density of 50~500 dtex, a breaking strength of 2.5~10.0 cN / dtex, and a breaking elongation of 5.0~100.0%.

2. The method for producing recycled fibers from waste polyester / nylon blended fabrics according to claim 1, characterized in that, The waste polyester / nylon blended fabric mentioned in step one is any one, two or three of the following: a mixture of waste polyester fabric and waste nylon fabric, waste polyester / nylon blended fabric, waste polyester / nylon mixed fabric, and waste polyester / nylon interwoven fabric. The nylon content in the raw material is not higher than 10 wt%.

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