A method for direct spinning of high-low viscosity PET two-component fiber melt

Abstract

A preparation method for direct spinning of high-low viscosity PET two-component fiber melt proposed by the present invention adopts a system containing three reaction kettles. Among them, the first esterification kettle, the second esterification kettle and the prepolymerization kettle are all carried out in the same reaction kettle, and the produced polyester enters different final polymerization kettles to obtain PET polyester melts with different viscosities. Compared with the five-kettle reaction system in the prior art, the reaction time required is shortened by about 40%. Moreover, the three-kettle system adopted by the present invention can also produce PET polyester melts with different viscosities simultaneously according to requirements, greatly improving the production flexibility. By adding fluorobenzene compounds during the production process of low-viscosity PET polyester, the orientation degree of the obtained high-low viscosity PET two-component fiber molecules is also improved, reducing the occurrence of phenomena such as broken filaments and floating filaments.

Description

Technical Field

[0001] The invention belongs to the technical field of polyester fibers, and in particular relates to a method for melt direct spinning of high- and low-viscosity PET bicomponent elastic fibers. Background Art

[0002] Elastic fiber plays an irreplaceable role in clothing fabrics, which makes it occupy a very important position in the textile industry. Among them, the fiber made by the parallel compounding of high- and low-viscosity PET has good spinnability and stable curling properties, and is a research hotspot for many domestic and foreign scholars.

[0003] At present, the production of elastic fibers with dual PET components is generally produced by chip spinning. The chips are extruded through a twin-screw extruder, and then enter the spinning box and components through different pipes for spinning to obtain dual PET component elastic fibers. The chip spinning production method has problems such as long production process, material loss, and high production cost. Although there is a process technology for PET elastic fibers using melt direct spinning, which shortens the production process and reduces the production cost, it is generally carried out through two sets of polyester production equipment, and enters the spinning box and components through different conveying pipeline systems for spinning. At present, PET polyester melt direct spinning generally adopts a five-reactor process, which is divided into two esterification reactors, two prepolymerization reactors and one final polycondensation reactor. A large amount of by-product ethylene glycol is generally produced in the prepolymerization reactor. In the existing process, this part of ethylene glycol is usually distilled and sent back to the esterification reactor for recycling. Although this operation improves the utilization rate of materials, the production cost is increased, and the reaction time is generally 6-10h, which is long, the initial construction cost is very high, and the cost recovery cycle is long.

[0004] In order to shorten the reaction time, DuPont has developed a three-kettle process, which includes an esterification kettle, a prepolymerization kettle and a final polycondensation reactor. In this process, ethylene glycol still needs to be distilled and collected from the prepolymerization kettle and then refluxed to the esterification kettle. At this time, the ethylene glycol in the recovery tank will enter the slurry mixing tank for slurry preparation, which will cause a large amount of water to enter the esterification kettle. The water entering the esterification kettle will absorb a large amount of heat and further enter the ethylene glycol and water separation tower from the esterification kettle gas-liquid separation tank. When the water is separated from the ethylene glycol in the tower, it also needs to absorb heat, which increases energy consumption.

[0005] In addition, in order to obtain high-viscosity PET polyester, in the existing production process, generally two methods are used to synthesize high-viscosity PET. One is to add a reaction viscosity-increasing kettle in the polymerization reaction equipment for synthesizing conventional polyester, and further carry out polycondensation reaction on the melt to obtain high-viscosity PET. The other method is to use solid-phase polycondensation to obtain high-viscosity PET. However, adding a reaction viscosity-increasing kettle will increase the manufacturing cost and make management more troublesome. Moreover, the reaction rate of the solid-phase viscosity-increasing method is low, and by-products are difficult to remove, resulting in low product yield. Finally, due to equipment errors and manual operation errors, the polyester melts with different viscosities produced by the two sets of polyester equipment cannot obtain the ideal intrinsic viscosity, and the tensile properties of the spun bicomponent fibers are extremely susceptible to the subsequent wire-drawing process conditions, and fiber breakage is likely to occur. Moreover, during the spinning process, in order to improve the mechanical properties of the fibers, stretching is usually carried out to increase the fiber orientation degree. In this case, more broken head filaments will appear on the fiber surface, ultimately resulting in insufficient fabric performance.

[0006] Therefore, exploring a set of polyester preparation methods that can save costs, can simultaneously produce PET polyester melts with different target viscosities, and have high orientation degrees of the obtained composite fibers is an important breakthrough in the field of manufacturing melt-spun PET bicomponent elastic fibers. Summary of the Invention

[0007] The present invention provides a method for direct melt spinning of high- and low-viscosity PET bicomponent fibers, aiming to reduce problems such as long production processes and high production costs existing in the existing processing technology, and can also simultaneously produce high-viscosity and low-viscosity PET polyester melts according to processing requirements, and finally spin high- and low-viscosity PET bicomponent fibers with good stability.

[0008] A method for direct melt spinning of high- and low-viscosity PET bicomponent fibers, wherein the first stage of esterification, the second stage of esterification, and the prepolymerization stage of the high- and low-viscosity PET polyester are all carried out in the same reaction kettle, and the final polymerization stage is carried out in two different reaction kettles.

[0009] In some embodiments of the present invention, the specific method for direct melt spinning of high- and low-viscosity PET bicomponent elastic fibers comprises the following steps:

[0010] A. Add terephthalic acid and ethylene glycol to the slurry mixing tank and prepare the slurry required for the esterification reaction;

[0011] B. Gradually add the slurry prepared in step A to the reaction kettle, carry out the first stage of esterification for 60 - 70 min; then carry out the second stage of esterification for 50 - 60 min; after the second stage of esterification reaction ends, adjust the temperature and absolute pressure in the reaction kettle, add catalytic aids and catalysts to carry out the prepolymerization reaction for 70 - 80 min to obtain a prepolymer;

[0012] C. The prepolymer is fed into different final polycondensation reactors. In one reactor, the reaction time is 120 - 130 min to obtain the high-viscosity PET polyester melt; in another reactor with the same temperature, a fluorinated benzene compound is added, and the reaction time is 50 - 60 min to obtain the low-viscosity PET polyester melt.

[0013] D. The obtained high-viscosity polyester melt and low-viscosity polyester melt are respectively extruded through a spinneret in a side-by-side manner, made into FDY filaments according to the FDY process, and then subjected to relaxation heat treatment to obtain the high-low viscosity PET bicomponent elastic fiber.

[0014] In some embodiments of the present invention, in step A, the catalytic promoter is one or more of trimethyl phosphate, triethyl phosphate, tripropyl phosphate, and triphenyl phosphate; the catalyst is one or more of antimony trioxide, antimony acetate, and antimony glycolate.

[0015] In some embodiments of the present invention, in step A, the molar ratio of terephthalic acid, ethylene glycol, catalytic promoter, and catalyst is 1:1.12 - 1.15:0.1 - 0.3:0.1 - 0.25.

[0016] In some embodiments of the present invention, in step B, the reaction conditions for the first stage of esterification are 260°C - 270°C and an absolute pressure of 0.05 MPa - 0.06 Mpa; the reaction conditions for the second stage of esterification are 270°C - 280°C and an absolute pressure of 0.009 MPa - 0.012 MPa; in step B, the reaction conditions for prepolymerization are 270°C - 280°C and an absolute pressure of 1.5 KPa - 2.0 KPa.

[0017] In some embodiments of the present invention, in step C, the reaction conditions in the reactor for preparing the high-viscosity PET polyester melt are 270°C - 280°C and an absolute pressure of 70 Pa - 120 Pa; the reaction conditions in the reactor for preparing the low-viscosity PET polyester melt are 270°C - 280°C and an absolute pressure of 200 Pa - 260 Pa.

[0018] In some embodiments of the present invention, in step C, the added fluorinated benzene compound is at least one of fluorinated benzene alkanoic acid, fluorinated phenol, and fluorinated alkylbenzene; the number of carbon atoms of the alkyl or alkylene group contained in the fluorinated benzene compound is 1 - 3. Among them, the fluorinated benzene alkanoic acid can be o-fluorobenzoic acid, m-fluorophenylacetic acid, p-fluoropropionic acid, p-fluorobutyric acid, p-fluorovaleric acid, difluorobenzoic acid, difluorophenylacetic acid, difluoropropionic acid, etc.; the fluorinated phenol can be o-fluorophenol, m-fluorophenol, p-fluorophenol, difluorophenol, trifluorophenol, etc.; the fluorinated alkylbenzene can be o-fluorotoluene, o-fluoroethylbenzene, m-fluoropropylbenzene, difluorotoluene, difluoroethylbenzene, difluoropropylbenzene, etc.

[0019] In some embodiments of the present invention, in step D, the obtained high-viscosity PET polyester melt and the low-viscosity PET polyester melt are compound-spun through a spinneret according to a mass ratio of 30-70:30-70.

[0020] Studies have shown that when the ratio of high-viscosity PET polyester to low-viscosity PET polyester changes from 70:30 to 30:70, the orientation of the side-by-side composite fiber decreases, the crystallinity increases, and the breaking strength, elongation at break, and boiling water shrinkage rate all gradually decrease. Therefore, in the general spinning process, the extrusion quality of the melt of different components is controlled by a metering pump to obtain better mechanical properties. In the present invention, the inventors surprisingly found that when preparing the low-viscosity PET polyester, a specific fluorobenzene compound is added thereto, and without strictly controlling the mass ratio of the subsequent spinning components, the obtained high- and low-viscosity PET bicomponent fibers still have good orientation degrees, and their breaking strength, elongation at break, and boiling water shrinkage rate all increase.

[0021] In some embodiments of the present invention, in step D, the parameters of the FDY process are as follows: the cooling temperature is 25-35°C, the network pressure is 0.10-0.15 MPa, the speed of the first roll is 1900-2100 m / min, and the temperature is 70-80°C; the speed of the second roll is 3200-3400 m / min, and the temperature is 120-145°C; the winding speed is 3300-3500 m / min.

[0022] In some embodiments of the present invention, the viscosity of the produced high-viscosity PET polyester melt is 0.700-0.850 dl / g, and the viscosity of the low-viscosity PET polyester melt is 0.400-0.550 dl / g.

[0023] Beneficial effects:

[0024] 1. In the present invention, a three-reactor system is used for the first time to prepare PET. The first esterification stage, the second esterification stage, and the prepolymerization stage of the PET polyester melt are all carried out in the same reaction kettle, which not only saves production costs, but also avoids the energy consumption caused by the reflux of ethylene glycol generated in the prepolymerization stage to the esterification section in the prior art, and also reduces the error caused by different reaction kettle systems, making the PET polyester melt have better composite properties during spinning;

[0025] 2. The PET polyester melt after the prepolymerization stage is divided into different reaction kettles for the final polycondensation reaction. By adjusting the temperature and pressure in different final polycondensation reaction kettles, high-viscosity PET polyester melt and low-viscosity PET polyester melt can be obtained simultaneously, overcoming the problems of high cost and low yield in the prior art for obtaining high-viscosity PET;

[0026] 3. Add fluorinated benzene compounds to the reactor for producing low-viscosity PET polyester melt, which can increase the molecular orientation degree of the low-viscosity PET polyester. Compared with the prior art method of increasing the orientation degree by controlling subsequent drawing process conditions, in the present invention, by adding fluorinated benzene compounds, on the one hand, the generation of broken filaments of the PET bicomponent fiber can be reduced; on the other hand, the presence of fluorine endows the PET bicomponent fiber with certain flame retardancy and low surface tension, and the presence of the benzene ring improves the rigidity of the PET bicomponent fiber, providing favorable conditions for the use of the PET bicomponent fiber in multiple fields. Detailed Embodiments

[0027] The present invention will be further described in detail below in conjunction with embodiments. It should be noted that the following embodiments and comparative examples are examples of the present invention, only used to illustrate the present invention, rather than to limit the present invention. Other combinations and various improvements within the concept of the present invention can be made without departing from the main idea or scope of the present invention.

[0028] Example 1

[0029] A. Add terephthalic acid and ethylene glycol to the slurry mixing tank to prepare the slurry required for the esterification reaction.

[0030] B. Gradually add the slurry prepared in step A to the reactor for the first stage of esterification, and react at 260 °C and an absolute pressure of 0.05 MPa for 60 min; then carry out the second stage of esterification, and react at 270 °C and an absolute pressure of 0.012 MPa for 50 min; after the second stage of esterification reaction ends, adjust the temperature in the reactor to 280 °C and the absolute pressure to 1.5 Kpa, add trimethyl phosphate and antimony trioxide for prepolymerization reaction, and the reaction time is 70 min to obtain a prepolymer; wherein, the molar ratio of terephthalic acid, ethylene glycol, trimethyl phosphate and antimony trioxide in the reactor is 1:1.12:0.3:0.1.

[0031] C. Feed the prepolymer into different final polycondensation reactors. React in one reactor at a temperature of 270 °C and an absolute pressure of 70 Pa for 120 min to obtain the high-viscosity PET polyester melt with a viscosity of 0.850 dl / g; in another reactor with the same temperature, adjust the absolute pressure to 200 Pa and add 3-fluorobenzoic acid accounting for 1% of the total mass of the contained PET polyester melt, and react for 50 min to obtain the low-viscosity PET polyester melt with a viscosity of 0.410 dl / g.

[0032] D. The obtained high-viscosity PET polyester melt and low-viscosity PET polyester melt are respectively extruded through a spinneret in a side-by-side manner with a mass ratio of 30:70, made into FDY yarn according to the FDY process, and then subjected to relaxation heat treatment: the cooling temperature is 25 °C, the network pressure is 0.10 MPa, the temperature of the first roller is 70 °C, the speed is 1900 m / min, the temperature of the second roller is 120 °C, the speed is 3200 m / min, and the winding speed is 3300 m / min, thus obtaining the high-low viscosity PET bicomponent elastic fiber.

[0033] Example 2

[0034] A. Add terephthalic acid and ethylene glycol to the slurry mixing tank to prepare the slurry required for the esterification reaction;

[0035] B. Gradually add the well-prepared slurry in step A to the reaction kettle for the first stage of esterification, reacting at 270 °C and an absolute pressure of 0.06 MPa for 70 min; then carry out the second stage of esterification, reacting at 280 °C and an absolute pressure of 0.009 MPa for 60 min; after the second stage of esterification reaction ends, adjust the temperature in the reaction kettle to 270 °C and the absolute pressure to 2.0 Kpa, add trimethyl phosphate and antimony trioxide for prepolymerization reaction, with a reaction time of 80 min, to obtain a prepolymer; among them, the molar ratio of terephthalic acid, ethylene glycol, trimethyl phosphate and antimony trioxide in the reaction kettle is 1:1.15:0.2:0.15;

[0036] C. Feed the prepolymer into different final polycondensation reaction kettles. React in one reaction kettle at a temperature of 280 °C and an absolute pressure of 90 Pa for 120 min to obtain the high-viscosity PET polyester melt with a viscosity of 0.800 dl / g; in another reaction kettle with the same temperature, adjust the absolute pressure to 230 Pa and add 4-fluorophenol accounting for 2% of the total mass of the contained PET polyester melt, and react for 60 min to obtain the low-viscosity PET polyester melt with a viscosity of 0.450 dl / g;

[0037] D. The obtained high-viscosity PET polyester melt and low-viscosity PET polyester melt are respectively extruded through a spinneret in a side-by-side manner with a mass ratio of 40:60, made into FDY yarn according to the FDY process, and then subjected to relaxation heat treatment: the cooling temperature is 30 °C, the network pressure is 0.15 MPa, the temperature of the first roller is 80 °C, the speed is 2000 m / min, the temperature of the second roller is 130 °C, the speed is 3300 m / min, and the winding speed is 3500 m / min, thus obtaining the high-low viscosity PET bicomponent elastic fiber.

[0038] Example 3

[0039] A. Add terephthalic acid and ethylene glycol to the slurry mixing tank to prepare the slurry required for the esterification reaction;

[0040] B. Gradually add the slurry prepared in step A to the reaction kettle to carry out the first stage of esterification. React for 70 min at 270 °C and an absolute pressure of 0.06 MPa; then carry out the second stage of esterification. React for 60 min at 280 °C and an absolute pressure of 0.009 MPa. After the second stage of esterification reaction ends, adjust the temperature in the reaction kettle to 270 °C and the absolute pressure to 2.0 KPa, add trimethyl phosphate and antimony trioxide to carry out the prepolymerization reaction, and the reaction time is 80 min to obtain a prepolymer; wherein, the molar ratio of terephthalic acid, ethylene glycol, trimethyl phosphate and antimony trioxide in the reaction kettle is 1:1.15:0.3:0.25;

[0041] C. Feed the prepolymer into different final polycondensation reaction kettles. React for 120 min in a reaction kettle with a temperature of 280 °C and an absolute pressure of 120 Pa to obtain the high-viscosity PET polyester melt with a viscosity of 0.746 dl / g; in another reaction kettle with the same temperature, adjust the absolute pressure to 260 Pa and add 2-fluoroethylbenzene accounting for 3% of the total mass of the contained PET polyester melt, and react for 60 min to obtain a low-viscosity PET polyester melt with a viscosity of 0.510 dl / g;

[0042] D. Extrude the obtained high-viscosity PET polyester melt and low-viscosity PET polyester melt through a spinneret in a side-by-side manner with a mass ratio of 50:50, and make FDY filaments according to the FDY process and then carry out relaxation heat treatment: the cooling temperature is 30 °C, the network pressure is 0.15 MPa, the temperature of the first roller is 80 °C, the speed is 2000 m / min, the temperature of the second roller is 130 °C, the speed is 3300 m / min, and the winding speed is 3500 m / min, thus obtaining the high- and low-viscosity PET bicomponent elastic fiber.

[0043] Example 4

[0044] A. Add terephthalic acid and ethylene glycol to the slurry mixing tank to prepare the slurry required for the esterification reaction;

[0045] B. Gradually add the slurry prepared in step A to the reaction kettle to carry out the first stage of esterification. React for 70 min at 270 °C and an absolute pressure of 0.06 MPa; then carry out the second stage of esterification. React for 60 min at 280 °C and an absolute pressure of 0.010 MPa. After the second stage of esterification reaction ends, adjust the temperature in the reaction kettle to 280 °C and the absolute pressure to 2.0 KPa, add trimethyl phosphate and antimony trioxide to carry out the prepolymerization reaction, and the reaction time is 80 min to obtain a prepolymer; wherein, the molar ratio of terephthalic acid, ethylene glycol, trimethyl phosphate and antimony trioxide in the reaction kettle is 1:1.15:0.3:0.25;

[0046] C. The prepolymer is fed into different final polycondensation reactors. In one reactor with a temperature of 280 °C and an absolute pressure of 120 Pa, the reaction time is 130 min to obtain the high-viscosity PET polyester melt with a viscosity of 0.715 dl / g. In another reactor with the same temperature, the absolute pressure is adjusted to 260 Pa and 3,5-difluoroethylbenzene accounting for 3.5% of the total mass of the low-viscosity PET polyester melt is added, and the reaction time is 60 min to obtain the low-viscosity PET polyester melt with a viscosity of 0.550 dl / g.

[0047] D. The obtained high-viscosity PET polyester melt and low-viscosity PET polyester melt are respectively extruded through a spinneret in a side-by-side manner with a mass ratio of 70:30, made into FDY filaments according to the FDY process, and then subjected to relaxation heat treatment: the cooling temperature is 35 °C, the network pressure is 0.15 MPa, the temperature of the first roller is 80 °C, the speed is 2100 m / min, the temperature of the second roller is 145 °C, the speed is 3400 m / min, and the winding speed is 3500 m / min, thus obtaining the high-low viscosity PET bicomponent elastic fiber.

[0048] Example 5

[0049] The operation is similar to that of Example 3, except that the fluorobenzene compound added is 3,5-difluoropentylbenzene.

[0050] Example 6

[0051] The operation is similar to that of Example 3, except that the 2-fluoroethylbenzene added accounts for 4% of the total mass of the low-viscosity PET polyester melt.

[0052] Example 7

[0053] The operation is similar to that of Example 3, except that 2-fluoroethylbenzene is not added.

[0054] The following performance tests are carried out on the obtained PET bicomponent fibers:

[0055] Tensile strength and elongation at break: Test on a YG023B-II type single yarn strength tester, and refer to the national standard GB / T14344-2008 "Test Method for Tensile Properties of Chemical Fiber Filaments". The pre-tension is 0.05 ± 0.005 cN / dtex, the clamping distance is 500 mm, and the tensile speed is 500 mm / min;

[0056] Boiling water shrinkage rate: Test according to the national standard GB / T6505-2008 "Test Method for Heat Shrinkage Rate of Chemical Fibers - Filaments" after treating in boiling water at 100 °C for 30 min.

[0057] Orientation degree: Test the orientation degree of the macromolecular chains of the obtained fibers by the sound velocity method using a SOM-π type sound velocity meter.

[0058] The above test results are shown in Table 1 as follows:

[0059] Table 1 Performance test results of PET bicomponent fibers obtained in Examples 1-7

[0060]

[0061]

[0062] From the viscosities in the examples and the data in Table 1, it can be seen that the method for direct spinning of PET bicomponent fiber melt provided by the present invention can obtain high-viscosity and low-viscosity PET polyester melts with different viscosities at the same time at a relatively low cost, and a fluorobenzene compound is added during the production of the low-viscosity PET polyester melt, which improves the orientation degree of the PET polyester molecular chain, and this orientation degree is not affected by the change of the spinning mass ratio of the high-viscosity and low-viscosity PET polyester components. Finally, the mechanical properties and boiling water shrinkage rate of the obtained PET bicomponent fiber are better than the corresponding properties of the high-viscosity and low-viscosity PET bicomponent fiber (Example 7) without adding fluorobenzene compounds. However, the data of Example 5 and Example 6 show that both the structure and the dosage of the fluorobenzene compound will affect the orientation degree and breaking strength of the obtained high-viscosity and low-viscosity PET bicomponent fiber. In addition, the high-viscosity and low-viscosity PET bicomponent fibers obtained in Examples 1-6 are very smooth during the spinning and drawing and setting processes, and there are no phenomena such as hairiness, floating filaments and broken ends (not shown in Table 1). This phenomenon indicates that the composite property of the obtained high-viscosity PET polyester melt and low-viscosity PET polyester melt during spinning is excellent.

[0063] Therefore, the method for direct spinning of high-viscosity and low-viscosity PET bicomponent fiber melt provided by the present invention has important reference value for reducing production costs and improving the properties of PET composite fibers.

Claims

1. A method for direct spinning of high-low viscosity PET two-component elastic fiber melt, characterized in that, The first stage of esterification, the second stage of esterification and the prepolymerization stage of PET polyester are all carried out in the same reaction kettle, and the final polymerization stage is carried out in two different reaction kettles; Specifically, the method for direct spinning of high and low viscosity PET two-component elastic fiber melt includes the following steps: A. Add terephthalic acid and ethylene glycol to the slurry mixing tank and prepare the slurry required for the esterification reaction; B. Gradually add the slurry prepared in step A to the reaction kettle, carry out the first stage of esterification for 60 - 70 min; then carry out the second stage of esterification for 50 - 60 min; after the second stage of esterification reaction ends, adjust the temperature and absolute pressure in the reaction kettle, add catalytic auxiliary agent and catalyst to carry out prepolymerization reaction for 70 - 80 min to obtain a prepolymer; C. Feed the prepolymer into different final polycondensation reaction kettles. React for 120 - 130 min in one reaction kettle to obtain the high viscosity PET polyester melt; add 1 - 3.5% of fluorobenzene compounds by mass fraction of the PET polyester melt in another reaction kettle with the same temperature and react for 50 - 60 min to obtain the low viscosity PET polyester melt; D. Extrude the obtained high viscosity polyester melt and low viscosity polyester melt through a spinneret in a side-by-side manner, make FDY filaments according to the FDY process and then carry out relaxation heat treatment to obtain the high and low viscosity PET two-component elastic fiber; In step C, the fluorobenzene compounds added are at least one of fluorobenzoic acid alkyl esters, fluorophenols, and fluoroalkylbenzenes, and the number of carbon atoms of the alkyl group contained in the fluorobenzene compounds is 1 - 3; The viscosity of the high viscosity PET polyester melt is 0.700 - 0.850 dl / g, and the viscosity of the low viscosity PET polyester melt is 0.400 - 0.550 dl / g.

2. The method for direct spinning of high-low viscosity PET two-component elastic fiber according to claim 1, characterized in that, In step A, the catalytic auxiliary agent is one or several of trimethyl phosphate, triethyl phosphate, tripropyl phosphate, and triphenyl phosphate; the catalyst is one or several of antimony trioxide, antimony acetate, and antimony glycolate.

3. The method for direct spinning of high-low viscosity PET two-component fiber melt according to claim 1, characterized in that, In steps A and B, the molar ratio of terephthalic acid, ethylene glycol, catalytic auxiliary agent, and catalyst is 1:1.12 - 1.15:0.1 - 0.3:0.1 - 0.

25.

4. The method for direct spinning of high-low viscosity PET two-component elastic fiber melt according to claim 1, characterized in that, In step B, the reaction conditions for the first stage of esterification are 260°C - 270°C and an absolute pressure of 0.05 MPa - 0.06 Mpa; the reaction conditions for the second stage of esterification are 270°C - 280°C and an absolute pressure of 0.009 MPa - 0.012 MPa; in step B, the reaction conditions for prepolymerization are 270°C - 280°C and an absolute pressure of 1.5 KPa - 2.0 KPa.

5. The method for direct spinning of high-low viscosity PET bicomponent elastic fiber melt according to claim 1, characterized in that, In step C, the reaction conditions in the reaction kettle for preparing the high viscosity PET polyester melt are 270°C - 280°C and an absolute pressure of 70 Pa - 120 Pa; the reaction conditions in the reaction kettle for preparing the low viscosity PET polyester melt are 270°C - 280°C and an absolute pressure of 200 Pa - 260 Pa.

6. The method for direct spinning of high-low viscosity PET two-component elastic fiber melt according to claim 1, characterized in that, In the step D, the obtained high-viscosity PET polyester melt and the low-viscosity PET polyester melt are compound-spun through a spinneret in a mass ratio of 30-70:30-70.

7. The method for direct spinning of high-low viscosity PET two-component elastic fiber melt according to claim 1, characterized in that In the step D, the parameters of the FDY process are as follows: the cooling temperature is 25-35°C, the network pressure is 0.10-0.15 MPa, the speed of the first roller is 1900-2100 m / min, and the temperature is 70-80°C; the speed of the second roller is 3200-3400 m / min, and the temperature is 120-145°C; the winding speed is 3300-3500 m / min.

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