Method for preparing polyester industrial filament by recycling polyester chips from waste spinning products and polyester industrial filament

Abstract

The invention discloses a method for preparing polyester industrial filaments by recycling polyester chips from waste spinning products and the polyester industrial filaments, and belongs to the technical field of chemical fibers. The method comprises the following steps: by taking waste spinning product recycled materials as raw materials, carrying out solid-phase tackifying on the polyester chips recycled by a DMT method to obtain high-viscosity chips; extruding and melting the high-viscosity slices to obtain a spinning melt; extruding the spinning melt to obtain a melt trickle; carrying out slow cooling treatment on the melt trickles, and cooling through circular blowing or lateral blowing to obtain a strand body; the filament body is stretched and shaped, then low polymer blowing and winding are carried out, and the industrial polyester filament is obtained. According to the method, the waste spinning products are used for recycling raw materials, the production process is optimized, resources are saved, incineration is reduced, carbon emission is avoided, landfill is reduced, environmental protection is facilitated, land occupation is reduced, and human health is protected; and good performance and qualified rate of the product are ensured, so that the physical performance, broken filament performance and spinnability of the final product can meet the requirements.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical fibers. More specifically, it relates to a method for preparing polyester industrial filaments by recycling and regenerating polyester chips from waste textiles, and polyester industrial filaments. Background Art

[0002] With the rapid development of the automotive industry and continuous technological updates, the automotive scrap recycling industry has gradually emerged. The automotive scrap recycling industry refers to the industry that resourcefully utilizes scrapped automobiles through processes such as disassembling, classifying, and recycling. For the chemical fiber industry, we can fully recycle and reuse the airbags and seat belts in scrapped automobiles. Chemical fiber raw materials mainly come from petroleum. Recycling helps to save resources, reduce carbon emissions by avoiding incineration, and is beneficial to environmental protection by reducing landfill and land occupation, thus protecting human health.

[0003] Using waste automotive airbags and seat belts as the initial raw materials, through alcoholysis and transesterification to prepare refined DMT, and then the refined DMT undergoes transesterification reaction with ethylene glycol to remanufacture new regenerated polyester chips, which are then subjected to viscosity increase, melting, cooling, stretching and setting, and winding to obtain high-performance regenerated polyester industrial filaments.

[0004] Compared with the BHET method of regeneration, the DMT method of regeneration has lower requirements for raw material purity, can maximize the realization of closed-loop recycling and utilization, and reduce resource consumption. However, the DMT method of regeneration has a more complex process technology, a longer process flow line, a more complex catalyst system, and a large amount of methanol is used for transesterification in the DMT method, resulting in excessive impurities such as oligomers in the regenerated chips. The presence of impurities such as oligomers will affect the physical properties of polyester chips such as melting point and intrinsic viscosity, and further affect the fiber strength, stretching performance, and fiber uniformity during the spinning process. Excessive impurities such as oligomers may also cause problems such as broken ends and hairy filaments during the spinning process, reducing the spinning efficiency and product quality. Summary of the Invention

[0005] The purpose of the present invention is to address the above deficiencies and provide a method for preparing polyester industrial filaments by recycling and regenerating polyester chips from waste textiles. Using recycled and regenerated polyester chips from waste textiles as raw materials, through an optimized process matching the product, polyester industrial filaments with qualified physical properties, hairiness properties, and excellent performance are prepared.

[0006] To achieve the above object, the present invention is realized through the following technical solutions: In the first aspect, the present invention provides a method for preparing polyester industrial filaments by recycling and regenerating polyester chips from waste textiles, including: The DMT process recycled polyester chips are subjected to solid-phase viscosity increase to obtain high-viscosity chips with a viscosity of 1.0 dl / g to 1.3 dl / g; the DMT process recycled polyester chips are made from waste textile recycling materials; The obtained high-viscosity chips are extruded and melted to obtain a spinning melt; The obtained spinning melt is extruded to obtain a melt stream; After the obtained melt stream is subjected to slow cooling treatment, it is then cooled and formed in the form of ring blowing or side blowing to obtain a filament body; The obtained filament body is stretched and shaped, and after shaping, oligomer purging is carried out, and after winding, industrial polyester filaments are produced.

[0007] Preferably, the initial viscosity of the DMT process recycled polyester chips is 0.6 dl / g to 0.8 dl / g, and the end methyl content is 4% to 5%.

[0008] Preferably, the process conditions for the solid-phase viscosity increase are: rotating in an intermittent polymerization reaction vessel under a vacuum of 10 Pa to 20 Pa, uniformly heating to 140 °C to 180 °C and then holding for 8 hours to 15 hours to obtain pre-crystallized chips; then continuing to uniformly heat to 200 °C to 240 °C and then holding for 28 hours to 40 hours.

[0009] Preferably, the step of extruding and melting the obtained high-viscosity chips to obtain a spinning melt includes: The high-viscosity chips after solid-phase viscosity increase are extruded into a melt by a screw extruder and then distributed into the melt pipelines of the spinning box to form a spinning melt; Among them, the screw diameter of the screw extruder is 75 mm to 150 mm, the screw length-diameter ratio is 24 to 33, and the screw outlet temperature is ≥ 290 °C.

[0010] Preferably, the step of extruding the obtained spinning melt to obtain a melt stream includes: The spinning melt enters the spinning pack through a metering pump and is filtered through the filter screen in the spinning pack, and the melt is ejected from the spinneret to obtain a melt stream; Among them, the number of spinneret holes in the spinneret is 28 to 960, which is adjusted according to the specific product to be produced; the ratio of the microchannel length of the spinneret hole to the diameter of the spinneret hole is 1.0 to 3.0; the filter accuracy of the filter screen in the spinning pack is 20 μm to 30 μm.

[0011] Preferably, in the slow cooling device used for the slow cooling treatment, the height of the heat insulation cylinder is 80 mm to 500 mm, which is adjusted according to the specific product to be produced, and the temperature of the heating cover is 300°C to 350°C; the temperature of the ring blowing is 50°C to 70°C, the dynamic pressure is 0.02 kPa to 0.06 kPa, and the humidity is 50% to 70%; the temperature of the side blowing is 18°C to 25°C, the wind speed is 0.4 m / s to 0.6 m / s, and the humidity is 50% to 70%.

[0012] Preferably, the process conditions for the drawing and setting are as follows: The drawing speed is 300 m / min to 4000 m / min; the total draw ratio is 1.8 to 6.2; the setting temperature is 220°C to 260°C; the total relaxation rate is 2% to 9%.

[0013] Preferably, the network pressure for purging is 0.01 MPa to 0.15 MPa.

[0014] Preferably, the winding speed is 2000 m / min to 7000 m / min.

[0015] In a second aspect, the present invention also provides a polyester industrial filament, which is prepared by the method for preparing a polyester industrial filament by recycling and regenerating polyester chips from waste textiles described in the first aspect.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention uses recycled polyester chips by the DMT method as raw materials to prepare polyester industrial filaments, and optimizes the production process for this chip raw material. It not only utilizes waste textile recycling materials, helps to save resources, reduces incineration to avoid carbon emissions, and reduces landfilling which is beneficial to environmental protection and reduces land occupation, protecting human health; but also ensures the good performance and qualification rate of the products, enabling the physical properties, hairiness properties, and spinnability of the final products to meet the requirements; The fineness of the polyester industrial filament prepared by the method of the present invention is 100 dtex to 7000 dtex, the breaking strength is greater than or equal to 7.0 cN / dtex, the coefficient of variation of the breaking strength is less than or equal to 4.0%, the breaking elongation is 11% to 24%, and the intermediate elongation is 4.0% to 20%; The present invention uses recycled polyester chips by the DMT method. The terminal methyl groups therein can improve the wear resistance and weather resistance of the chips, making them more suitable for manufacturing various products; and because the DEG content of the recycled polyester chips by the DMT method is low, the heat strength loss of the polyester industrial filaments produced is smaller; at the same time, the bulk density of the recycled polyester chips by the DMT method is larger, which can not only reduce the crystallization temperature during solid-phase viscosity increase to achieve the purpose of increasing the chip crystallinity and reducing chip adhesion, but also make the chips melt more fully and uniformly during the spinning production process with continuous feeding, improving the spinnability; The present invention adopts optimized process conditions, which not only improve the convenience and efficiency of production, but also increase the degree of fiber orientation, reduce fiber defects, improve the stability of the crystal structure, enhance the mechanical properties of the product, and reduce the dyeing risk. Brief Description of the Drawings

[0017] Figure 1 It is a schematic diagram of the stretching, purging and winding process in the preparation method of the present invention; Figure 2 It is a comparison chart of S-S curves between Comparative Example 6 and Comparative Example 3 of the present invention; Figure 3 It is a comparison chart of S-S curves between Example 3 and Comparative Example 3 of the present invention. Detailed Embodiments

[0018] The preferred embodiments of the present invention will be described in more detail below in conjunction with the drawings and specific embodiments.

[0019] Using DMT method to regenerate polyester chips to prepare polyester industrial filaments, which can be used for the preparation of regenerated tire cord fabrics, regenerated sewing threads, regenerated airbags, and regenerated seat belts.

[0020] Example 1: This example provides a polyester industrial filament (regenerated tire cord fabric filament, which is a high modulus and low shrinkage filament) for use in regenerated tire cord fabrics, and its preparation method is as follows: Step 1: Place DMT method regenerated PET polyester chips with an average viscosity of 0.67 dl / g and an end methyl content of 4% - 5% in a rotary drum (batch solid-phase polymerization reactor), rotate under a vacuum of 15 pa, and then uniformly raise the temperature in the reactor to 160 °C by heating the heat conduction oil pipe and heat for 11 hours to obtain pre-crystallized chips. Then continue to uniformly raise the temperature in the reactor to 225 °C by heating the heat conduction oil pipe and continue to heat for 36 hours, so that the viscosity of the DMT method regenerated polyester chips after solid-phase viscosity increase is increased from 0.67 dl / g to 1.15 dl / g to form high-viscosity chips.

[0021] Step 2: Transport the high-viscosity chips after solid-phase viscosity increase to a screw extruder, and after extruding the melt through the screw extruder, distribute it to the melt pipelines of each spinning box through the melt main pipe to form spinning melt. Among them, the screw diameter of the screw extruder is 130 mm, the screw length-diameter ratio is 28, and the screw outlet temperature is 304.6 °C.

[0022] Step 3: The extruded melt is distributed to the melt pipelines of each spinning box through the main melt pipeline to form spinning melt. The spinning melt enters the spinning pack through a metering pump and is filtered through the filter screen in the spinning pack. The melt is ejected from the spinneret to obtain a melt stream. The rotational speed of the metering pump is 13.17 rpm, and the number of spinneret holes in the spinneret is 335; the ratio of the length of the microporous channel of the spinneret hole to the diameter of the spinneret hole is 1.3, and the length of the microporous channel refers to the length corresponding to the advancing direction of the melt in the spinneret hole; the pressure of the spinning pack is 18.2 Mpa, and the mesh accuracy of the filter screen in the spinning pack is 30 μm to improve the uniformity of the filament body; a diphenyl temperature of 298 °C is used to maintain good melt fluidity, uniformity, and pressure.

[0023] Step 4: After the melt streams of each group are subjected to slow cooling treatment, the melt streams are cooled and formed in the form of ring blowing to obtain a filament body. Among them, the ring blowing temperature is 60 °C, the dynamic pressure is 0.04 kPa, and the humidity is 60%. The temperature of the heating hood in the slow cooling device is 330 °C, and the height of the heat insulation cylinder is 80 mm, so that the spinning drawing is completed before the melt solidifies, which is beneficial to the formation of straight-chain macromolecules and the uniform orientation degree of each part.

[0024] Step 5: After the above-cooled filament body enters the spinning channel, it is subjected to stretching and setting and winding treatment to obtain polyester industrial filament prepared from DMT-process recycled polyester chips. Specifically, oiling is performed on the surface of the filament body, and then stretching, setting, purging, and winding are carried out; among them, the rotational speed of the oiling roller is 20 rpm, and the stretching and setting are completed by 6 pairs of rollers; the first pair of rollers: the temperature is 90 °C, and the speed is 3120 m / min, the second pair of rollers: the temperature is 95 °C, and the speed is 4050 m / min, the third, fourth, and fifth pairs of rollers: the temperature is 259 °C, and the speed is 5800 m / min, the sixth pair of rollers: not heated, and the speed is 5700 m / min; the parameters of the stretching and setting are: the total stretching multiple is 1.86; the total relaxation rate is 3.45%; the device used in this application is equipped with an air yarn guide after the setting hot roller, as Figure 1 shown, and the oligomers attached to the fiber surface due to migration are purged through the air yarn guide; the main network pressure is 0.45 Mpa, and the purging network pressure (2-network pressure) is 0.1 ± 0.05 Mpa; and winding and forming are carried out under the condition of a winding speed of 5600 m / min to obtain polyester industrial filament prepared from DMT-process recycled polyester chips (the parameters not described in detail are shown in Tables 2 and 3).

[0025] Example 2: This example provides a polyester industrial filament (recycled sewing thread filament) used for recycled sewing threads, and its preparation method is as follows: Step 1: Place the DMT-process recycled PET polyester chips with an average viscosity of 0.67 dl / g and a terminal methyl content of 4% - 5% in a rotating drum, rotate them under a vacuum of 15 Pa, and then uniformly raise the temperature in the reaction kettle to 160°C by heating the heat-conducting oil pipe and heat for 11 hours to obtain pre-crystallized chips. Then continue to uniformly raise the temperature in the reaction kettle to 220°C by heating the heat-conducting oil pipe and continue heating for 34 hours, so that the viscosity of the DMT-process recycled chips increases from 0.67 dl / g to 1.12 dl / g after solid-phase polymerization and form high-viscosity chips.

[0026] Step 2: Convey the high-viscosity chips after solid-phase polymerization to a screw extruder. After extruding the melt through the screw extruder, distribute it to the melt pipes of each spinning box through the melt main pipe to form spinning melt. Among them, the screw diameter of the screw extruder is 125 mm, the screw length-diameter ratio is 28, and the screw outlet temperature is 300.4°C.

[0027] Step 3: The extruded melt is distributed to the melt pipes of each spinning box through the melt main pipe to form spinning melt. The spinning melt enters the spinning pack through a metering pump and is filtered through the filter screen in the spinning pack. The melt is ejected from the spinneret to obtain a melt stream. Among them, the metering pump speed is 5.66 rpm, the number of spinneret holes in the spinneret is 48; the ratio of the microchannel length of the spinneret hole to the diameter of the spinneret hole is 2, and the microchannel length refers to the length corresponding to the forward direction of the melt in the spinneret hole; the filter screen accuracy of the filter screen in the spinning pack is 25 μm to improve the uniformity of the filament body. Use a diphenyl temperature of 298°C to maintain good melt fluidity, uniformity and pressure.

[0028] Step 4: After subjecting each group of melt streams to slow cooling treatment, cool and shape the melt streams in the form of side blowing to obtain a filament body. Among them, the side blowing temperature is 25°C, the wind speed is 0.5 m / s, and the humidity is 60%. The temperature of the heating hood in the slow cooling device is 310°C, and the height of the heat insulation cylinder is 150 mm, so that the spinning and stretching are completed before the melt solidifies, which is beneficial to the formation of straight-chain macromolecules and the uniform orientation degree of each part.

[0029] Step 5: After the above-mentioned cooled filament body enters the spinning channel, it is subjected to stretching and setting and winding treatment to obtain polyester industrial filament prepared from DMT-process recycled polyester chips. Specifically, oiling is performed on the surface of the filament body, and then stretching and setting, purging, and winding are carried out. Among them, the speed of the oiling wheel is 5.6 rpm, and the stretching and setting are completed by 5 pairs of rollers. The first pair of rollers: the temperature is 86°C, and the speed is 450 m / min; the second pair of rollers: the temperature is 123°C, and the speed is 460 m / min; the third pair of rollers: the temperature is 112°C, and the speed is 1484 m / min; the fourth pair of rollers: the temperature is 237°C, and the speed is 2515 m / min; the fifth pair of rollers: not heated, and the speed is 2460 m / min. Among them, the parameters of the stretching and setting are: the total stretching multiple is 5.59; the total relaxation rate is 4.57%. The device used in this application is equipped with an air guide wire device after the setting hot roller, as Figure 1 shown. The oligomers attached to the fiber surface due to migration are purged away through the air guide wire device; the main network pressure is 0.28 Mpa, and the purging network pressure (2-network pressure) is 0.05 ± 0.04 Mpa; and winding and forming are carried out under the condition that the winding speed is 2400 m / min to obtain polyester industrial filament prepared from DMT-process recycled polyester chips (the parameters not described in detail are shown in Table 2 and Table 3).

[0030] Example 3: This example provides a polyester industrial filament (regenerated airbag filament) used for a regenerated airbag, and its preparation method is as follows: Step 1: Place DMT-process recycled PET polyester chips with an average viscosity of 0.67 dl / g and an end methyl content of 4% - 5% in a rotary drum, rotate under a vacuum of 15 Pa, and then uniformly raise the temperature in the reaction kettle to 160°C and heat for 11 hours by heating the heat-conducting oil pipe to obtain pre-crystallized chips. Then, continue to uniformly raise the temperature in the reaction kettle to 220°C through the heat-conducting oil pipe and continue to heat for 34 hours so that the viscosity of the DMT-process recycled chips increases from 0.67 dl / g to 1.12 dl / g after solid-phase polymerization and form high-viscosity chips.

[0031] Step 2: Transport the high-viscosity chips after solid-phase polymerization to a screw extruder, and then extrude the melt through the screw extruder. After that, the melt is distributed to the melt pipes of each spinning box through the melt main pipe to form a spinning melt. Among them, the screw diameter of the screw extruder is 130 mm, the screw length-diameter ratio is 28, and the screw outlet temperature is 298.9°C.

[0032] Step 3: The extruded melt is distributed through the melt main pipe to the melt pipes of each spinning box to form spinning melt. The spinning melt enters the spinning pack through a metering pump and is filtered through the filter screen in the spinning pack. The melt is ejected from the spinneret to obtain a melt stream. The rotational speed of the metering pump is 11.6 rpm, and the number of spinneret holes in the spinneret is 144. The ratio of the microchannel length of the spinneret hole to the diameter of the spinneret hole is 2. The microchannel length refers to the length of the spinneret hole corresponding to the advancing direction of the melt. The filter screen accuracy of the filter screen in the spinning pack is 25 μm to improve the uniformity of the filament body. A diphenyl temperature of 296°C is used to maintain good melt fluidity, uniformity, and pressure.

[0033] Step 4: After the slow cooling treatment of each group of melt streams, the melt streams are cooled and formed by means of side blowing to obtain a filament body. Among them, the side blowing temperature is 25°C, the wind speed is 0.6 m / s, and the humidity is 60%. The temperature of the heating hood in the slow cooling device is 320°C, and the height of the heat insulation cylinder is 375 mm, so that the spinning drawing is completed before the melt solidifies, which is beneficial to the formation of straight-chain macromolecules and the uniform orientation degree of each part.

[0034] Step 5: After the above-cooled filament body enters the spinning channel, it is subjected to drawing and setting and winding treatment to obtain polyester industrial filament prepared from DMT method recycled polyester chips. Specifically, oiling is performed on the surface of the filament body, and then drawing and setting, purging, and winding are carried out. Among them, the rotational speed of the oiling wheel is 10.6 rpm, and the drawing and setting are completed by 6 pairs of rollers. The first pair of rollers: the temperature is 86°C, the speed is 460 m / min; the second pair of rollers: the temperature is 123°C, the speed is 469 m / min; the third pair of rollers: the temperature is 110°C, the speed is 1517 m / min; the fourth pair of rollers: the temperature is 241°C, the speed is 2614 m / min; the fifth pair of rollers: the temperature is 241°C, the speed is 2500 m / min; the sixth pair of rollers: not heated, the speed is 2400 m / min. Among them, the parameters of the drawing and setting are: the total draw ratio is 5.68; the total relaxation rate is 8.19%. The device used in this application is equipped with an air guide wire device after the setting hot roller. As Figure 1 shown, the oligomers attached to the fiber surface due to migration are purged through the air guide wire device; the main network pressure is 0.45 Mpa, and the purging network pressure (2-network pressure) is 0.1 ± 0.05 Mpa; and winding and forming are carried out under the condition that the winding speed is 2400 m / min to obtain polyester industrial filament prepared from DMT method recycled polyester chips (the parameters not described in detail are shown in Table 2 and Table 3).

[0035] Example 4: This example provides a polyester industrial filament (recycled safety belt filament) used for recycled safety belts, and its preparation method is as follows: Step 1: Place the DMT-process recycled PET polyester chips with an average viscosity of 0.67 dl / g and a terminal methyl content of 4% - 5% in a rotary drum, rotate them under a vacuum of 15 Pa, and then uniformly raise the temperature in the reaction kettle to 160 °C by heating the heat-conducting oil pipe and heat for 11 hours to obtain pre-crystallized chips. Then continue to uniformly raise the temperature in the reaction kettle to 220 °C by heating the heat-conducting oil pipe and continue to heat for 34 hours so that the viscosity of the DMT-process recycled chips increases from 0.67 dl / g to 1.12 dl / g after solid-phase polymerization and form high-viscosity chips.

[0036] Step 2: Convey the high-viscosity chips after solid-phase polymerization to a screw extruder. After extruding the melt through the screw extruder, distribute it to the melt pipelines of each spinning box through the melt main pipe to form a spinning melt. Among them, the screw diameter of the screw extruder is 130 mm, the length-diameter ratio of the screw is 28, and the temperature at the screw outlet is 301.3 °C.

[0037] Step 3: The extruded melt is distributed to the melt pipelines of each spinning box through the melt main pipe to form a spinning melt. The spinning melt enters the spinning pack through a metering pump and is filtered through the filter screen in the spinning pack. The melt is ejected from the spinneret to obtain a melt stream. Among them, the rotational speed of the metering pump is 14.12 rpm, and the number of spinneret holes in the spinneret is 144; the ratio of the length of the microporous channel of the spinneret hole to the diameter of the spinneret hole is 2, and the length of the microporous channel refers to the length corresponding to the advancing direction of the melt in the spinneret hole; the filter accuracy of the filter screen in the spinning pack is 30 μm to improve the uniformity of the filament body. Use a diphenyl temperature of 296 °C to maintain good melt fluidity, uniformity, and pressure.

[0038] Step 4: After subjecting each group of melt streams to slow cooling treatment, cool and form the melt streams in the form of side blowing to obtain a filament body. Among them, the side blowing temperature is 25 °C, the wind speed is 0.6 m / s, and the humidity is 60%. The temperature of the heating cover in the slow cooling device is 310 °C, and the height of the heat insulation cylinder is 400 mm, so that the spinning and stretching are completed before the melt solidifies, which is conducive to the formation of straight-chain macromolecules and the uniform orientation of each part.

[0039] Step 5: After the above-mentioned cooled filament body enters the spinning duct and undergoes stretching and setting and winding treatment, polyester industrial filament made from DMT-process recycled polyester chips is obtained. Specifically, oil is applied to the surface of the filament body, and then it is stretched and set, purged, and wound; among them, the speed of the oiling roller is 15.4 rpm, and the stretching and setting is completed by 5 pairs of rollers; the first pair of rollers: the temperature is 90°C, and the drawing speed is 403 m / min; the second pair of rollers: the temperature is 125°C, and the drawing speed is 413 m / min; the third pair of rollers: the temperature is 115°C, and the drawing speed is 1356 m / min; the fourth pair of rollers: the temperature is 225°C, and the drawing speed is 2457 m / min; the fifth pair of rollers: not heated, and the drawing speed is 2400 m / min; among them, the parameters of the stretching and setting are: the total stretching multiple is 6.10; the total relaxation rate is 2.32%; the device used in this application is equipped with an air yarn guide after the setting hot roller, as Figure 1 shown. The oligomers attached to the fiber surface due to migration are purged off through the air yarn guide; the main network pressure is 0.42 Mpa, and the purging network pressure (2-network pressure) is 0.1 ± 0.05 Mpa; and winding and forming are carried out under the condition that the winding speed is 2400 m / min to obtain polyester industrial filament made from DMT-process recycled polyester chips (the parameters not described in detail are shown in Tables 2 and 3).

[0040] The performance of the polyester industrial filament prepared in the above-mentioned examples was tested in this application, as shown in Table 1 specifically.

[0041] Table 1: Performance indicators of the polyester industrial filament prepared in each example

[0042] It can be seen from the table that the performance indicators of the polyester industrial filament prepared in Examples 1-4 all meet the standards, and even far exceed the index data.

[0043] Comparative Examples 1-4: In the present invention, virgin PET polyester chips with a viscosity of 0.67 dl / g were used to completely replace the DMT-process recycled PET polyester chips in Examples 1-4 as comparative examples, and the polyester industrial filaments used for different products were produced from virgin PET polyester chips by referring to the methods of Examples 1-4 respectively. The relevant parameters in each step of the comparative examples are shown in Tables 2 and 3, and there is no purging step in the comparative examples.

[0044] Table 2: Comparison of melt spinning process parameters between Comparative Examples 1-4 and Examples 1-4

[0045] Table 3: Comparison of qualitative winding process parameters between Comparative Examples 1-4 and Examples 1-4

[0046] The properties of the polyester industrial filaments prepared in the above comparative examples were tested, and the specific results are shown in Table 4.

[0047] Table 4: Performance indicators of the polyester industrial filaments prepared in Comparative Examples 1-4

[0048] As can be seen from the table, using recycled chips to prepare polyester industrial filaments in this application can reach the performance level of the polyester industrial filaments prepared from virgin chips, and the performance of some products can even exceed that of the polyester industrial filaments prepared from virgin chips.

[0049] The hairiness properties of the filaments in the above examples and comparative examples were tested and compared respectively, and the comparison results are shown in Table 5.

[0050] Table 5: Comparison of the hairiness properties of the filaments prepared in Examples 1-4 and Comparative Examples 1-4

[0051] Note: The products described in Examples 1 and 2 have no requirements for the amount of hairiness, and this index is not detected.

[0052] As can be seen from Table 5, the polyester industrial filaments produced from recycled polyester chips of waste imitations in this invention can meet the standards of the spinning conditions (number of broken ends) and hairiness conditions (amount of hairiness) of virgin polyester chips.

[0053] Comparative Example 5: In this comparative example, the BHET method recycled PET polyester chips were used to replace the DMT method recycled PET polyester chips in Example 3, and the BHET method recycled PET polyester chips were used to produce polyester industrial filaments with reference to the method of Example 3.

[0054] The raw materials and product properties of Example 3, Comparative Example 3 and Comparative Example 5 were compared, as shown in Table 6.

[0055] Table 6: Comparison of the raw materials and product properties of Example 3, Comparative Example 3 and Comparative Example 5

[0056] From the data shown in Table 6 above, it can be known that during the DMT method recycling process, the hydroxyl groups in the chips are converted into methyl groups. It was tested that the end methyl groups in the recycled chips by the DMT method are 4% - 5%. The end methyl groups can improve the wear resistance and weather resistance of the chips, making them more suitable for manufacturing various products; and because the DEG content of the DMT method recycled chips is low, the thermal strength loss of the polyester industrial filaments produced is smaller.

[0057] Comparative Example 6: Through experimental research, compared with the virgin chip, the weight of 100 grains of the recycled chip by the DMT method is about 90% of that of the virgin chip, and the bulk density is larger. It can not only reduce the crystallization temperature during solid-phase thickening to achieve the purpose of increasing the chip crystallinity and reducing chip adhesion, but also make the chip melt more fully and evenly during the continuous feeding spinning production process, improving the spinnability.

[0058] The unreacted DMT and other alcohol by-products will affect the molecular structure of the polyester chip, and then affect the microscopic structure parameters such as the crystallinity and orientation degree of the fiber. Compared with the spinning of virgin chips, the crystallinity and orientation degree of the products spun from the recycled chips by the DMT method are relatively small, which is likely to cause broken ends / hairs, affecting the physical-mechanical properties of the products.

[0059] After the melt is extruded from the spinneret holes, due to the speed difference between the spinning speed and the winding speed, the melt filament is gradually stretched and thinned along the running direction. The ratio of the spinning speed to the winding speed is the spinneret draw ratio, also called the draw rate. The draw rate is proportional to the speed of the first pair of rollers. If the draw speed is too fast, the stress is large, resulting in a necking zone with local overheating, and the fiber forms voids or even hairs and broken ends; if the draw speed is too slow, slow flow occurs, and the draw stress of the fiber is not sufficient to destroy the unstable structure and reconstruct it. The draw ratio may be very high, but the effective orientation is not large; if the draw speed is appropriate, the stress can destroy and reconstruct the unstable crystalline structure, establish the best thermal balance in the necking zone, without significant excessive tension, and the fiber defects are less.

[0060] Therefore, this comparative example provides a method for preparing polyester industrial filament. The 1GR speed, total draw, and relaxation rate in the method are the same as those in Comparative Example 3, and other raw materials and process steps are the same as those in Example 1.

[0061] The partial mechanical properties of the products prepared in this comparative example are compared with those of the products in Comparative Example 3 and Example 3 as shown in Table 7, and the comparison of crystallinity and orientation degree is shown in Table 8.

[0062] Table 7: Comparison of partial properties of the products of Comparative Example 6, Comparative Example 3, and Example 3

[0063] Table 8: Comparison of crystallinity and orientation degree of the products of Comparative Example 6, Comparative Example 3, and Example 3

[0064] During the fiber drawing process, the stress and strain change continuously. The draw curve, that is, the stress-strain curve (abbreviated as the S-S curve), reflects the internal relationship between stress and strain. Different as-spun fiber structures are different, and the stress-strain curves during drawing are also different. Figure 2 It is a comparison chart of the S-S curves of the products prepared in Comparative Example 6 and Comparative Example 3.Figure 3 S-S curve comparison diagram of the products prepared in Example 3 and Comparative Example 3

[0065] According to Table 7, Table 8, and Figure 2 and Figure 3 By comparison, it can be seen that increasing the drawing rate during the spinning of recycled polyester chips using the DMT method can disrupt the unstable crystalline structure formed and reconstruct a more stable crystalline structure to form an effective orientation to ensure subsequent drawing.

[0066] During the drawing process, the macromolecules in the fiber are oriented along the direction of the external force (fiber axis), increasing hydrogen bonds, dipole bonds, and other types of intermolecular forces. The number of molecular chains in the fiber that bear the external tension increases, thus significantly improving the breaking strength of the fiber, decreasing the elongation at break, and also significantly improving the wear resistance and fatigue strength against various different types.

[0067] Changes in crystallization: The as-spun fiber has an amorphous structure. Under the combined action of drawing stress and drawing temperature, significant crystallization can occur, the crystallinity increases, and the unstable crystalline structure is transformed into a stable crystalline structure.

[0068] Changes in orientation: The orientation degree of the as-spun fiber is very low. After drawing, not only an appropriate crystallinity is obtained, but also the orientation degree of the fiber is improved. The orientation degree of the fiber includes the orientation degree of the crystalline region and also the orientation degree of the non-crystalline region.

[0069] Comparative Example 7: This comparative example provides a method for preparing polyester industrial filament. In the preparation process of this comparative example, there is no 2-network (i.e., Figure 1 the air guide shown), and the rest of the raw materials, method steps, and process parameters are the same as those in Example 4.

[0070] Experiments have proved that during the transesterification reaction process of polyester, oligomers are easily generated in the form of polyester by-products. Especially for the polyester chips prepared by the DMT method, the chemical structure and properties of the oligomers are very stable and are easily adsorbed on the surface of the polyester. Increasing the dyeing temperature during the dyeing process can increase the migration of the oligomers. The higher the temperature, the greater the activity rate of the polyester molecular chains, and the faster the migration speed of the dye between the molecules. The longer the duration of the dye liquor circulation, the greater the probability of the oligomers migrating from the inside to the outside of the fiber. The cold and hot cycles and the presence of some auxiliaries and dyes will greatly exacerbate the migration, removal, and deposition of the oligomers.

[0071] The polyester industrial filaments prepared in Comparative Example 7 and Example 4 were respectively knitted into socks, dyed, and color judged. The proportion of color difference after dyeing is shown in Table 9.

[0072] Table 9: Comparison of the proportion of color difference after dyeing of the products in Comparative Example 7 and Example 4

[0073] As shown in Table 9, the proportion of color difference after dyeing of the products after purging is significantly reduced.

[0074] The fibers need to be heat-set. Heat setting affects the stiffness (i.e., dimensional stability), elongation at break, hand feeling, pilling and fuzzing of the fabric, etc. During the heat setting process, due to the migration of oligomers from the inside to the outside under heating conditions and adhesion to the fiber surface, color spot, stripe pattern and other color difference phenomena often occur, resulting in a significant decrease in the levelness and rubbing fastness of the fibers. In particular, the color difference of ultra-fine fibers is more obvious. Therefore, an air yarn guide is added after the setting roller to purge the oligomers adhering to the fiber surface due to migration, reduce the dyeing risk, and facilitate the spinnability.

[0075] The embodiments of the present invention have been described above. The above description is exemplary and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art in the technical field without departing from the scope and technical principle of the described embodiments. These modifications and variations should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing polyester industrial filament by recycling recycled polyester chips from waste textiles, characterized in that: include: The DMT recycled polyester chips were subjected to solid phase viscosity enhancement to obtain high viscosity chips with a viscosity of 1.0 dl / g to 1.3 dl / g; The DMT method regenerated polyester chips are made from recycled waste textiles; Extruding and melting the obtained high-viscosity slices to obtain a spinning melt; Extruding the obtained spinning melt to obtain a thin melt stream; After the obtained melt stream is subjected to a slow cooling treatment, it is cooled and formed by means of annular blowing or side blowing to obtain a wire strip body; The obtained filament body is stretched and shaped, and then the oligomer is blown after the shaping, and the polyester industrial filament is obtained after winding.

2. The method for preparing polyester industrial filament by recycling recycled polyester chips from waste textiles according to claim 1, characterized in that: The initial viscosity of the DMT recycled polyester chips is 0.6 dl / g to 0.8 dl / g, and the terminal methyl content is 4% to 5%.

3. The method for preparing polyester industrial filament by recycling recycled polyester chips from waste textiles according to claim 1, characterized in that: The process conditions of the solid phase viscosity enhancement are: rotating in an intermittent polymerization reaction container under a vacuum degree of 10Pa-20Pa, uniformly heating to 140°C-180°C and then keeping warm for 8 hours-15 hours to obtain pre-crystallized slices; then continuing to uniformly heat to 200°C-240°C and keeping warm for 28 hours-40 hours.

4. The method for preparing polyester industrial filament by recycling recycled polyester chips from waste textiles according to claim 1, characterized in that: The method of extruding and melting the obtained high-viscosity slice to obtain a spinning melt comprises: The high-viscosity chips after solid phase viscosity enhancement are extruded into melt by a screw extruder and then distributed to the melt pipe of the spinning manifold to form a spinning melt; Wherein, the screw diameter of the screw extruder is 75mm~150mm, the screw aspect ratio is 24~33, and the screw outlet temperature is ≥290℃.

5. The method for preparing polyester industrial filament by recycling recycled polyester chips from waste textiles according to claim 1, characterized in that: The step of extruding the obtained spinning melt to obtain a melt stream comprises: The spinning melt enters the spinning assembly through a metering pump and is filtered through a filter screen in the spinning assembly, and the melt is ejected from the spinneret to obtain a thin melt flow; The number of spinneret holes in the spinneret plate is 28 to 960; the ratio of the micropore channel length of the spinneret holes to the diameter of the spinneret holes is 1.0 to 3.0; and the filter mesh precision of the filter mesh in the spinning assembly is 20 μm to 30 μm.

6. The method for preparing polyester industrial filament by recycling recycled polyester chips from waste textiles according to claim 1, characterized in that: In the slow cooling device used for the slow cooling treatment, the height of the insulation tube is 80mm~500mm, and the temperature of the heating cover is 300℃~350℃; the temperature of the ring blowing is 50℃~70℃, the dynamic pressure is 0.02kPa~0.06kPa, and the humidity is 50%~70%; the temperature of the side blowing is 18℃~25℃, the wind speed is 0.4m / s~0.6m / s, and the humidity is 50%~70%.

7. The method for preparing polyester industrial filament by recycling recycled polyester chips from waste textiles according to claim 1, characterized in that: The process conditions of the stretching and shaping are: The pulling speed is 300m / min~4000m / min; the total stretching multiple is 1.8~6.2; the setting temperature is 220℃~260℃; The total relaxation rate is 2%~9%.

8. The method for preparing polyester industrial filament by recycling recycled polyester chips from waste textiles according to claim 1, characterized in that: The network pressure of the purge is 0.01MPa~0.15MPa.

9. The method for preparing polyester industrial filament by recycling recycled polyester chips from waste textiles according to claim 1, characterized in that: The winding speed is 2000m / min~7000m / min.

10. A polyester industrial filament, characterized in that: The polyester industrial filament is prepared by the method for preparing polyester industrial filament by recycling recycled polyester chips from waste textiles as described in any one of claims 1 to 9.

Images